JP5857263B2 - Polylactic acid resin composition, method for producing injection molded product, injection molded product, and holder for electronic device - Google Patents

Description

  The present invention relates to a polylactic acid resin composition used for injection molding, a method for producing an injection molded article using the polylactic acid resin composition, an injection molded article formed from the polylactic acid resin composition, and the polylactic acid resin composition The present invention relates to a holder for an electronic device formed from an object.

  In recent years, an increase in the concentration of carbon dioxide in the atmosphere has been pointed out as a cause of global warming, and the need for carbon dioxide emission regulations on a global scale has been advocated. Causes of carbon dioxide generation include respiration of organisms, rot and fermentation by bacteria, etc., but the amount of carbon dioxide generated by combustion of substances derived from petroleum resources is large, and it is due to carbon dioxide in the current atmosphere It is no exaggeration to say that the temperature rise phenomenon is caused by economic activity that wasted oil resources after human revolution. Furthermore, petroleum resources are limited resources and are expected to be depleted in the future.

  On the other hand, in recent years, the effective use of plant resources that absorb and fix carbon dioxide in the atmosphere during growth has attracted attention as a carbon neutral material. When obtaining plant resources, carbon dioxide in the atmosphere is absorbed by plant vegetation, and attempts have been made to replace petroleum resources with these plant resources.

  Also in the field of plastic materials, attempts are being made to switch from conventional materials based on petroleum to materials using biomass. Plastic materials using biomass initially attracted attention as biodegradable plastics, but recently they have been re-evaluated as carbon-neutral plant plastics and have been put into practical use in some areas. One type of typical plant plastic is polylactic acid resin. By injection-molding the polylactic acid resin composition, it is expected to obtain various molded articles such as an electronic device holder, an electronic device internal chassis component, an electronic device casing, and an electronic device internal component.

  However, polylactic acid is poor in durability, and particularly from the viewpoint of obtaining an injection molded product, the injection molded product thermally shrinks over time in a high temperature environment, which makes it difficult to withstand long-term use. . It is considered that the heat shrinkage of the injection molded product is due to the progress of crystallization of polylactic acid in the injection molded product over time.

  If the crystallization of polylactic acid is sufficiently advanced at the time of molding, the thermal shrinkage of the injection molded product is suppressed to some extent. For example, in Patent Document 1, in obtaining a polylactic acid resin injection-molded article, a polylactic acid resin, (a) a cyclic compound having in its molecule a functional group selected from C═O and NH and O, (b) A mixture of a cyclic compound having C═O in the molecule and a cyclic compound having a functional group selected from NH, S and O in the molecule, (c) may be substituted or may contain a metal A polylactic acid resin composition containing a phthalocyanine compound and (d) an organic crystal nucleating agent containing at least one organic pigment selected from the group consisting of optionally substituted porphyrin compounds is contacted with a supercritical fluid. It is disclosed that the mixture is melt-kneaded and then the melt is injection molded. By using the organic crystal nucleating agent, crystallization of the polylactic acid resin during molding is promoted.

  However, it is difficult to sufficiently suppress the heat shrinkage of the injection-molded product even if the crystallization of polylactic acid has sufficiently progressed at the time of molding. Furthermore, in this case, special polylactic acid such as a stereocomplex type polylactic acid which requires an additive such as a nucleating agent for promoting crystallization at the time of molding, a molding cycle becomes long, or in some cases is easily crystallized. Is necessary. In the case where a nucleating agent is used, there is also a problem that the durability of the injection molded product is lowered due to the accelerated hydrolysis of polylactic acid. For this reason, it complicates the manufacturing process, decreases the manufacturing efficiency, and increases the cost, which hinders the spread of polylactic acid resin.

JP 2010-6041 A

  The present invention has been made in view of the above-mentioned reasons, and is a polylactic acid resin composition containing polylactic acid, which does not cause complicated manufacturing process and high cost, and does not cause high cost of the injection molded product. It is an object of the present invention to provide a polylactic acid resin composition in which thermal shrinkage over time is greatly suppressed, and an injection molded product produced from this polylactic acid resin composition for injection molding.

  The polylactic acid resin composition according to the present invention contains polylactic acid, a polymethyl methacrylate resin, and an ABS resin, wherein the ratio of the polylactic acid is in the range of 3 to 40% by mass, and the ratio of the polymethyl methacrylate resin is The range is 0.5 to 17% by mass, and the polylactic acid contains D-lactic acid units in a proportion of 8 to 15 mol%.

  The polylactic acid composition according to the present invention contains polylactic acid, a polymethyl methacrylate resin, and an ABS resin, the ratio of the polylactic acid is in the range of 3 to 40% by mass, and the ratio of the polymethyl methacrylate resin is 0. The polylactic acid may be a polylactic acid that does not crystallize even when heated at 100 ° C. for 2 hours.

  In the polylactic acid resin composition according to the present invention, the ratio of the polylactic acid is preferably in the range of 5 to 40% by mass.

  In the polylactic acid resin composition according to the present invention, the ratio of the polymethyl methacrylate resin is preferably in the range of 2 to 17% by mass.

  In the polylactic acid resin composition which concerns on this invention, it is also preferable that the ratio of the said polylactic acid is the range of 23-35 mass%, and the ratio of the said polymethyl methacrylate resin is the range of 3-17 mass%.

  In the polylactic acid resin composition which concerns on this invention, it is also preferable that the ratio of the said polylactic acid is the range of 8-15 mass%, and the ratio of the said polymethyl methacrylate resin is the range of 1-17 mass%.

In the polylactic acid resin composition according to the present invention, the ratio of the polylactic acid is in the range of 3 to 8% by mass, and the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 3% by mass. In the polylactic acid resin composition which concerns on invention, it is preferable that content of the said ABS resin is 50 mass% or more with respect to the total amount of the said polylactic acid, the said polymethyl methacrylate resin, and the said ABS resin.

  In the polylactic acid resin composition which concerns on this invention, it is preferable that the ratio of the styrene unit which comprises the said ABS resin is the range of 55-70 mass%, and the ratio of a butadiene unit is the range of 8-23 mass%.

  The polylactic acid resin composition according to the present invention preferably further contains a carbodiimide compound.

  The polylactic acid resin composition according to the present invention preferably further contains a copolymer of alkyl methacrylate and alkyl acrylate.

  The polylactic acid resin composition according to the present invention preferably further contains a core-shell rubber.

  In the method for producing an injection molded product according to the present invention, the polylactic acid resin composition is prepared, and the polylactic acid resin composition is injection molded.

  The injection molded product according to the present invention is formed by injection molding the polylactic acid resin composition.

  The electronic device holder according to the present invention is formed by injection molding the polylactic acid resin composition.

  In the present invention, the polylactic acid resin composition containing polylactic acid is injection-molded, so that thermal shrinkage over time in a high-temperature environment is greatly suppressed without complicating the manufacturing process and increasing costs. An injection molded product is manufactured.

It is a perspective view which shows the external appearance of the holder for electronic devices in one Embodiment of this invention. It is a graph which shows the result of having performed the heat processing for 2 hours at 100 degreeC to polylactic acid AE used in the Example, and having performed differential scanning calorimetry about polylactic acid AE after processing.

[Ingredients in polylactic acid resin composition]
The component which the polylactic acid resin composition by this embodiment can contain is demonstrated.

(Polylactic acid)
Examples of polylactic acid include a homopolymer of lactic acid and a copolymer of lactic acid and a hydroxycarboxylic acid other than lactic acid. Polylactic acid is obtained by polymerizing lactic acid. Lactic acid is obtained, for example, by fermenting starch derived from plants such as corn.

  Examples of lactic acid include L-lactic acid, D-lactic acid, and a lactone that is a dimer of lactic acid.

  Examples of hydroxycarboxylic acids other than lactic acid that can be copolymerized with lactic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, and hydroxycaproic acid. These hydroxycarboxylic acids may be used alone or in combination of two or more.

  Polylactic acid substantially consists of an L-lactic acid unit and a D-lactic acid unit represented by the following formula [Chemical Formula 1].

  The polylactic acid used in the present embodiment is a polylactic acid in which the proportion of D-lactic acid units is in the range of 8 to 15 mol% with respect to all units (monomer units) constituting the polylactic acid, at 100 ° C. for 2 hours. Polylactic acid that does not crystallize even when heated, or the proportion of D-lactic acid units is in the range of 8 to 15 mol% with respect to all units constituting polylactic acid and does not crystallize even when heated at 100 ° C. for 2 hours. Polylactic acid. Whether or not polylactic acid is crystallized is confirmed from the measurement result by differential scanning calorimetry (DSC). When polylactic acid is crystallized, an endothermic peak due to melting is observed at around 160 ° C. by differential scanning calorimetry (DSC), but such an endothermic peak is not observed when it is not crystallized.

  Use of such polylactic acid is important for suppressing thermal shrinkage of the injection molded product. These polylactic acids have the property that crystallization is very difficult to proceed. For this reason, it becomes difficult for crystallization of polylactic acid to proceed in an injection-molded product formed from the polylactic acid resin composition, and therefore, thermal shrinkage of the injection-molded product due to crystallization of polylactic acid is greatly suppressed. The proportion of D-lactic acid units in the polylactic acid is preferably in the range of 8 to 15 mol% as described above, more preferably in the range of 8 to 13 mol%, and further in the range of 8 to 12 mol%. The range is preferable, and the range of 8.6 to 11.6 mol% is particularly preferable.

  The ratio of D-lactic acid units in polylactic acid is measured by an optical rotation method. For example, a 1% by mass trichloromethane solution of polylactic acid to be measured is prepared, and the ratio of D-lactic acid units in the polylactic acid in this solution is measured by a digital polarimeter (for example, manufactured by SHANGHAI CHANGFANG OPTICAL INSTRUMENT CO., LTD. , Model number WZZ-2S).

  The proportion of units other than the lactic acid units constituting the polylactic acid is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, still more preferably 0 to 1 mol%. Units other than lactic acid constituting polylactic acid are composed of units derived from dicarboxylic acid, polyhydric alcohol, hydroxycarboxylic acid, lactone, etc. having a functional group capable of forming two or more ester bonds, and these various components. Examples are units derived from various polyesters, various polyethers, various polycarbonates and the like. Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid. Polyhydric alcohols include ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, hexanediol, octanediol, glycerin, sorbitan, neopentyl glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol And aliphatic polyhydric alcohols such as those obtained by adding ethylene oxide to bisphenol. Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, 4-hydroxybenzoic acid and the like. Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, and the like.

  Polylactic acid can be produced by a known method. For example, L- and D-lactide is produced by heating and ring-opening polymerization in the presence of a metal polymerization catalyst. Furthermore, polylactic acid is also produced by a direct polymerization method in which lactic acid is dehydrated and condensed in the presence / absence of an organic solvent.

  The polymerization reaction can be carried out using a conventionally known reaction vessel. As the reaction vessel, for example, a vertical reactor or a horizontal reactor equipped with a high-viscosity stirring blade such as a helical ribbon blade is used alone, or a plurality of them are used in combination. The reaction vessel may be a batch type, a continuous type or a semi-batch type, or a combination of these methods.

  Alcohol may be used as a polymerization initiator. This alcohol preferably does not inhibit the polymerization of polylactic acid and is non-volatile. As the alcohol, for example, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol and the like are preferably used.

  In the solid phase polymerization method, a relatively low molecular weight lactic acid polyester obtained by the ring-opening polymerization method or the direct polymerization method of lactic acid described above is used as a prepolymer. The prepolymer is preferably crystallized in advance by being kept in a temperature range of the glass transition temperature (Tg) or higher and lower than the melting point (Tm) from the viewpoint of preventing fusion. The crystallized prepolymer is filled in a fixed vertical or horizontal reaction vessel, or a reaction vessel (rotary kiln or the like) that rotates itself like a tumbler or kiln, and the glass transition temperature (Tg) of the prepolymer. ) It is heated to a temperature range above the melting point (Tm). There is no problem even if the polymerization temperature is raised stepwise as the polymerization proceeds. In addition, for the purpose of efficiently removing water generated during solid phase polymerization, a method of reducing the pressure inside the reaction vessels or circulating a heated inert gas stream is also preferably used.

  The weight average molecular weight of polylactic acid is preferably in the range of 100,000 to 500,000, more preferably in the range of 100,000 to 300,000. This weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography using chloroform as a solvent (mobile phase).

  Furthermore, it is preferable that the molecular weights of polylactic acid are uniform, that is, it is preferable that the molecular weight distribution is not broad or that there are multiple peaks in the molecular weight distribution. In this case, the moldability of the polylactic acid resin composition is particularly improved, the molding cycle is shortened, and welds and flow marks are less likely to occur in the injection molded product, and the appearance of the injection molded product is further improved. .

  It is preferable that the melt flow rate (190 degreeC 2.16kg) of polylactic acid prescribed | regulated to ISO ASTM D1238 is 1-16g / 10min. In this case, the moldability (fluidity) of the polylactic acid resin composition is particularly improved.

  The ratio of polylactic acid to the whole polylactic acid resin composition is in the range of 3 to 40% by mass, and particularly preferably in the range of 5 to 40% by mass. In particular, from the viewpoint of improving the mechanical strength of the molded product and reducing the amount of petroleum resources used, the polylactic acid content in the polylactic acid resin composition is preferably 20% by mass or more, and more preferably 25% by mass. The above is preferable. On the other hand, from the viewpoint of maintaining the durability (hydrolysis resistance) of the molded product, the content of polylactic acid in the polylactic acid resin composition is particularly preferably 30% by mass or less. In particular, the polylactic acid content is preferably in the range of 20 to 35% by mass.

  Moreover, it is also preferable that the ratio of polylactic acid is in the range of 23 to 35% by mass. In this case, a polylactic acid resin composition in which good mechanical properties and durability are maintained while greatly reducing the amount of petroleum resources used can be obtained.

  Moreover, it is also preferable that content of the polylactic acid in a polylactic acid resin composition is the range of 8-15 mass%. In this case, the moldability of the polylactic acid resin composition is particularly good, the appearance defect of the molded product is further suppressed, and the durability of the molded product is further improved.

  Moreover, it is also preferable that the ratio of polylactic acid is in the range of 3 to 8% by mass. In this case, the moldability of the polylactic acid resin composition is remarkably improved, the appearance defect of the molded product is further suppressed, and the durability of the molded product is remarkably improved.

  Such polylactic acid having a D-lactic acid unit ratio of 8 to 15 mol% has a low melting point, and is not suitable for injection molding alone, but in this embodiment, polymethyl methacrylate resin and ABS described later are used. By using resin or core-shell rubber, a polylactic acid resin composition suitable for injection molding can be obtained, and welds and flow marks are less likely to occur in injection-molded products, while maintaining high impact resistance. obtain.

  Thereby, even if it is a case where it exposes for 48 hours, for example in an 80 degreeC atmosphere, it also becomes possible to obtain the injection molded product with a very small heat shrink.

(Polymethyl methacrylate resin)
When the polylactic acid resin composition contains a polymethyl methacrylate resin (PMMA resin), the dimensional stability, impact resistance, and heat resistance of the injection molded product are improved.

  A part or all of the polymethyl methacrylate resin (PMMA resin) may be a polymethyl methacrylate resin elastomer (PMMA resin elastomer).

  It is preferable that the melt flow rate (230 degreeC 3.8 kg) prescribed | regulated to ISO ASTM D1238 of a PMMA resin is 1.5 g / 10min or more. Furthermore, the melt flow rate is preferably 5 g / 10 min or more. When the melt flow rate is 1.5 g / 10 min or more, the compatibility of the PMMA resin with polylactic acid is increased in the polylactic acid resin composition, thereby further improving the appearance of the injection molded product and impact resistance. Is further improved.

  The weight average molecular weight of the PMMA resin is preferably in the range of 60,000 to 80,000, and more preferably in the range of 65,000 to 75,000. In this case, in the polylactic acid resin composition, the compatibility of the PMMA resin with the polylactic acid is increased, whereby the appearance of the injection-molded product is further improved and the impact resistance is further improved. This weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography using chloroform as a solvent (mobile phase).

  The content of the PMMA resin in the polylactic acid resin composition is preferably in the range of 0.5 to 17% by mass, and more preferably in the range of 2 to 17% by mass. When the content is 2% by mass or more, the dimensional stability, impact resistance, and heat resistance of the injection molded product are particularly improved. Further, when the content is 17% by mass or less, the high fluidity of the polylactic acid resin composition is maintained, and the high moldability of the polylactic acid resin composition and the good appearance of the injection molded product are maintained. The content of this PMMA resin is preferably in the range of 3 to 12% by mass.

  Moreover, when the ratio of polylactic acid is in the range of 23 to 35% by mass, the content of the PMMA resin is preferably in the range of 3 to 17% by mass. In this case, a polylactic acid resin composition in which good mechanical properties and durability are maintained while greatly reducing the amount of petroleum resources used can be obtained.

  Moreover, when the content of polylactic acid in the polylactic acid resin composition is in the range of 8 to 15% by mass, the content of the PMMA resin is preferably in the range of 1 to 17% by mass. In this case, the moldability of the polylactic acid resin composition is particularly good, the appearance defect of the molded product is further suppressed, and the durability of the molded product is further improved.

  Moreover, when the ratio of polylactic acid is in the range of 3 to 8% by mass, the content of the PMMA resin is preferably in the range of 0.5 to 3% by mass. In this case, the moldability of the polylactic acid resin composition is remarkably improved, the appearance defect of the molded product is further suppressed, and the durability of the molded product is remarkably improved.

(ABS resin)
The polylactic acid resin composition contains ABS resin (acrylonitrile / butadiene / styrene copolymer resin), so that the dimensional stability, impact resistance and heat resistance of the injection molded product are maintained, and the polylactic acid resin composition is molded. The weldability and flow mark are less likely to occur in the injection molded product.

  In order to sufficiently improve the mechanical properties such as impact resistance of the injection-molded product, the ratio of the styrene unit constituting the ABS resin is preferably 72% by mass or less, and more preferably 70% by mass or less. Particularly preferred is 62% by mass or less. Furthermore, the proportion of styrene units is preferably 40% by mass or more, more preferably 55% by mass or more, and particularly preferably 58% by mass or more. That is, the proportion of styrene units is preferably in the range of 40 to 72 mass%, more preferably in the range of 55 to 70 mass%, and still more preferably in the range of 58 to 62 mass%.

  In order to sufficiently suppress the weld and the flow mark of the injection molded product, the ratio of the butadiene unit constituting the ABS resin is preferably in the range of 8 to 23% by mass, and may be in the range of 8 to 16% by mass. More preferred. When an ABS resin having a low butadiene ratio is used, the butadiene component in the ABS resin is hardly squeezed out from the matrix of the injection molded product even if the injection molded product is subjected to heat treatment. For this reason, the butadiene component is suppressed by floating on the surface of the injection-molded product, and the flow mark due to such lifting is suppressed, so that the appearance of the injection-molded product is well maintained.

  The proportion of acrylonitrile units in the ABS resin depends on the proportion of styrene units and butadiene units, but is preferably in the range of 1.5 to 30% by mass, more preferably in the range of 15 to 30% by mass. In particular, when the ABS resin is substantially composed only of acrylonitrile units, butadiene units, and styrene units, the ratio of acrylonitrile units is preferably in the range of 15 to 30% by mass.

  The structural unit of the ABS resin may include a structural unit other than the acrylonitrile unit, the butadiene unit, and the styrene unit. For example, the structural unit of the ABS resin may include a methyl methacrylate unit.

  The proportion of constituent units such as acrylonitrile units, styrene units, butadiene units, and methyl methacrylate units in the ABS resin is measured by the NMR measurement results of the ABS resin, and by the gradient polymer elution chromatography (GPEC) of the ABS resin. Derived based on the result.

  The particle size of the ABS resin is not particularly limited, but it is preferable that the particle size is smaller from the viewpoint of maintaining the appearance of the injection molded product well over a long period of time. When the particle size of the ABS resin is small, even if the injection molded product is exposed to a high temperature for a long period of time, whitening of the injection molded product is difficult to occur. Such suppression of whitening is considered to be due to the fine dispersion of the components in the injection-molded product due to the small particle size of the ABS resin and the reduction of the squeeze effect. In order to sufficiently suppress the whitening of the injection molded article, the average particle diameter of the ABS resin is preferably 0.4 μm or less, more preferably 0.35 μm or less, and particularly 0.3 μm or less. Is preferred. The lower limit of the average particle diameter is not particularly limited, but is preferably 0.1 μm or more. The average particle diameter is evaluated by, for example, staining ABS resin particles, photographing the particles with a transmission electron microscope (TEM), and analyzing the photographed image.

  The method for synthesizing the ABS resin is not particularly limited, but it is preferably produced by an emulsion polymerization method or a bulk polymerization method. Furthermore, in order to improve the appearance of the injection molded product when heat treatment is performed on the injection molded product, it is preferable to use an ABS resin produced by an emulsion polymerization method.

  By using such an ABS resin, the occurrence of welds and flow marks during the injection molding of the polylactic acid resin composition is suppressed, and the appearance of the injection molded product is improved. Furthermore, by using such an ABS resin, the color developability when the injection molded product is colored is excellent.

  In order to sufficiently suppress the occurrence of welds and flow marks in the injection molded product, the ratio of the polylactic acid, the polymethyl methacrylate resin and the ABS resin in the polylactic acid resin composition is 50% by mass or more. It is preferable. Within this range, the injection moldability of the polylactic acid resin composition is particularly excellent, and the occurrence of welds and flow marks in the injection molded product is remarkably suppressed. The upper limit of the ABS resin content is not particularly limited, and is regulated according to the content of other components in the polylactic acid resin composition.

(Carbodiimide compound)
The polylactic acid resin composition also preferably contains a carbodiimide compound such as a polycarbodiimide compound or a monocarbodiimide compound. In this case, these compounds react with some or all of the carboxyl group ends of the polylactic acid to block them, thereby improving the durability of the injection-molded product in a high-temperature and high-humidity environment.

  Examples of the polycarbodiimide compound include poly (4,4′-diphenylmethanecarbodiimide), poly (4,4′-dicyclohexylmethanecarbodiimide), poly (1,3,5-triisopropylbenzene) polycarbodiimide, and poly (1,3 , 5-triisopropylbenzene and 1,5-diisopropylbenzene) polycarbodiimide. Examples of the monocarbodiimide compound include N, N′-di-2,6-diisopropylphenylcarbodiimide.

  As such a carbodiimide compound, a commercially available product can be used as appropriate. Specific examples of the carbodiimide compound include trade name carbodilite LA-1 (poly (4,4'-dicyclohexylmethanecarbodiimide)) manufactured by Nisshinbo Industries, Inc., HCV-15CA, and the like.

  When a carbodiimide compound is used, the content of the carbodiimide compound in the polylactic acid resin composition is preferably in the range of 0.1 to 5% by mass. When the content is 0.1% by mass or more, the durability of the injection molded product is further improved, and when the content is 5% by mass or less, the high mechanical strength of the injection molded product is maintained. The content of the carbodiimide compound is preferably 3% by mass or less.

  When a carbodiimide compound is used, when the master batch is prepared by premixing only polylactic acid and a carbodiimide compound during the preparation of the polylactic acid resin composition, the above-mentioned action due to the use of the carbodiimide compound is particularly effective. Is demonstrated.

(Copolymer of alkyl methacrylate and alkyl acrylate)
The polylactic acid resin composition preferably contains a copolymer of alkyl methacrylate and alkyl acrylate. In this case, mechanical properties such as impact resistance of the injection molded product are further improved.

  Examples of the alkyl methacrylate include methyl methacrylate and ethyl methacrylate. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate and the like. The polymerization molar ratio of alkyl methacrylate to alkyl acrylate is preferably in the range of 40:60 to 95: 5. The weight average molecular weight of the copolymer of alkyl methacrylate and alkyl acrylate is preferably in the range of 1 million to 5 million. This weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography using chloroform as a solvent (mobile phase).

  A specific example of such a copolymer of an alkyl methacrylate and an alkyl acrylate is trade name Metabrene P530 manufactured by Mitsubishi Rayon Co., Ltd.

  When a copolymer of alkyl methacrylate and alkyl acrylate is used, the content of the copolymer of alkyl methacrylate and alkyl acrylate in the polylactic acid resin composition is 0.5 mass% to 5 mass%. It is preferable to be within the range. When the content is 1.0% by mass or more and 3.0% by mass or less, the impact resistance of the injection molded product is particularly improved. The reason is that the melt viscosity of the polylactic acid resin composition is sufficiently increased within the above range, thereby forming an amorphous sea-island structure in the microstructure of the injection molded product, which improves the impact resistance of the injection molded product. It is thought to bring about.

(Core shell rubber)
The polylactic acid resin composition may contain a core-shell rubber. In this case, mechanical properties such as impact resistance of the injection molded product are further improved. The core-shell rubber is a polymer having a multilayer structure, and an innermost layer (core layer) made of the polymer and one or more layers (shell layer) covering the core layer and made of a polymer different from the core layer. ). Examples of the core-shell rubber include a resin obtained by polymerizing a monomer such as a styrene monomer or a vinyl cyanide monomer in the presence of a rubbery polymer.

  When the core-shell rubber is used, the content of the polylactic acid resin composition as a whole is not limited, but from the viewpoint of improving the durability of the molded product, this content is preferably 1% by mass or more, If it is 3 mass% or more, it is still more preferable. From the viewpoint of improving the flowability of the polylactic acid resin composition and improving the moldability, workability, handling, etc. of the polylactic acid resin composition, the content of the core-shell rubber is preferably 12% by mass or less.

  The core shell rubber will be described in more detail.

  An example of the core-shell rubber is Si-containing core-shell rubber. When the core-shell rubber containing Si is used, the flame retardancy of the molded product is further improved. The core-shell rubber containing Si may contain at least one of a polyorganosiloxane-containing graft copolymer whose core layer is composed of a polymer containing Si and an epoxy-modified silicone / acrylic rubber. It is particularly preferable that a polyorganosiloxane-containing graft copolymer is contained.

  Examples of the core-shell rubber containing Si include polyorganosiloxane-containing graft copolymers and epoxy-modified silicone / acrylic rubber.

When the polylactic acid resin composition contains a polyorganosiloxane-containing graft copolymer, the flame retardancy and impact resistance of the molded product are particularly improved. The polyorganosiloxane-containing graft copolymer is obtained from the following components (X) to (Z);
(X) polyorganosiloxane particles;
(Y) a first vinyl monomer;
(Z) A second vinyl monomer.

(Y) component consists only of the following (Y-1) component, or consists of the following (Y-1) component and (Y-2) component, and contains these components in the following ratio;
(Y-1) 100 to 50% by mass of a polyfunctional monomer;
(Y-2) 0-50 mass% of other copolymerizable monomers.

  In the presence of 40 to 90 parts by mass of the (X) component, the polyorganosiloxane-containing graft copolymer polymerizes 0.5 to 10 parts by mass of the (Y) component, and further 5 to 50 parts by mass of the (Z) component. It is obtained by polymerizing. The amount of each component is a value when the total amount of the components (X) to (Z) is 100 parts by mass.

  Component (X) has a toluene insoluble content (a toluene insoluble content when 0.5 g of (X) component is immersed in 80 ml of toluene at room temperature for 24 hours) of 95% by mass or less, further 50% by mass or less, particularly 20% by mass. % Or less is preferable for improving the flame retardancy and impact resistance of the molded product.

  Specific examples of the component (X) include polydimethylsiloxane particles, polymethylphenylsiloxane particles, dimethylsiloxane-diphenylsiloxane copolymer particles, and the like. Among these, only 1 type may be used or 2 or more types may be used together.

  Part or all of the component (X) may be modified polyorganosiloxane particles containing a polymer other than polyorganosiloxane. Specific examples of the polymer other than polyorganosiloxane include polybutyl acrylate, butyl acrylate-styrene copolymer, and the like. The content of the polymer other than the polyorganosiloxane in the component (X) is preferably low, and the content is particularly preferably 5% by mass or less. In particular, it is preferable for the component (X) to be particles composed essentially of polyorganosiloxane in order to improve the flame retardancy of the molded product.

  The average particle diameter of the component (X) is not particularly limited, but the number average particle diameter obtained from light scattering or electron microscope observation is preferably 0.008 to 0.6 μm, preferably 0.01 to 0.2 μm. It is more preferable if it is 0.01 to 0.15 μm. If the number average particle size is too small, it is difficult to produce the component (X). Conversely, if the number average particle size is too large, the flame retardancy of the molded product may not be sufficiently improved. In order to improve the appearance of the molded product, it is preferable that the variation coefficient (100 × standard deviation / number average particle size (%)) of the particle size distribution of the component (X) is in the range of 10 to 100%. More preferably, it is ˜60%.

  (X) Monomers of organosiloxane; homopolymerization of bifunctional silane compound; copolymerization of organosiloxane and bifunctional silane compound; organosiloxane and vinyl polymerizable group-containing silane Copolymerization with a compound; copolymerization of a bifunctional silane compound and a vinyl-based polymerizable group-containing silane compound; organosiloxane, bifunctional silane compound and vinyl-based polymerizable group-containing silane compound, or further, these compounds and trifunctional or more And the like, and the like.

  Among the above compounds, the organosiloxane or the bifunctional silane compound is a component constituting the main skeleton of the polyorganosiloxane chain.

  Examples of the organosiloxane include hexamethylcyclotrisiloxane (a), octamethylcyclotetrasiloxane (b), decamethylcyclopentasiloxane (c), dodecamethylcyclohexasiloxane (d), and tetradecamethylcycloheptasiloxane (e). , Hexadecamethylcyclooctasiloxane (f) and the like.

  Difunctional silane compounds include diethoxydimethylsilane, dimethoxydimethylsilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, heptadecafluorodecylmethyldimethoxysilane , Trifluoropropylmethyldimethoxysilane, octadecylmethyldimethoxysilane and the like.

  In particular, from the viewpoint of improving economic efficiency and flame retardancy of molded products, (b) component, a mixture of components (a) to (e), or (a) to (a) in the monomer used for the production of component (X) (F) It is preferable that the ratio of the mixture of a component is 70-100 mass%, and it is still more preferable that it is 80-100 mass%. It is preferable that diphenyldimethoxysilane, diphenyldiethoxysilane, etc. occupy 0-30 mass%, and it is still more preferable that the remaining part occupies 0-20 mass%.

  The vinyl polymerizable group-containing silane compound is copolymerized with an organosiloxane, a bifunctional silane compound, a trifunctional or higher functional silane compound, and the like, thereby introducing a vinyl polymerizable group into the side chain or terminal of the copolymer. . This vinyl-based polymerizable group acts as a graft active site when chemically bonding to a vinyl-based (co) polymer formed from the (Y) component or the (Z) component described later. Furthermore, this vinyl polymerizable group-containing silane compound can be cross-linked by radical reaction between graft active sites in the presence of a radical polymerization initiator. That is, the vinyl polymerizable group-containing silane compound can also function as a crosslinking agent. As the radical polymerization initiator, the same ones that can be used in graft polymerization described later can be used. In addition, even when the vinyl polymerizable group-containing silane compound functions as a crosslinking agent, a part of the silane compound remains as a graft active point, so that grafting is possible.

  Specific examples of the vinyl polymerizable group-containing silane compound include γ-methacryloyloxypropyldimethoxymethylsilane, γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropyltriethoxysilane, and γ-methacryloyloxypropyldiethoxymethylsilane. (Meth) acryloyloxy group-containing silane compounds such as γ-acryloyloxypropyldimethoxymethylsilane and γ-acryloyloxypropyltrimethoxysilane; vinylphenyl groups such as p-vinylphenyldimethoxymethylsilane and p-vinylphenyltrimethoxysilane -Containing silane compounds; vinyl group-containing silane compounds such as vinylmethyldimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane; mercaptopropylto Silane, and mercapto group-containing silane compounds such as mercaptopropyl dimethoxymethyl silane, and the like.

  Among these, at least one selected from a (meth) acryloyloxy group-containing silane compound, a vinyl group-containing silane compound, and a mercapto group-containing silane compound is preferable from the viewpoint of economy. In addition, when the said vinyl polymerizable group containing silane compound is a trialkoxysilane type | mold, it also has a role of the silane compound more than trifunctional shown below.

  A trifunctional or higher functional silane compound is copolymerized with the organosiloxane, bifunctional silane compound, vinyl polymerizable group-containing silane compound, etc. to introduce a cross-linked structure into the polyorganosiloxane, and the component (X) is a rubber. Elasticity can be imparted. That is, a trifunctional or higher functional silane compound is used as a crosslinking agent for polyorganosiloxane.

  Examples of the trifunctional or higher functional silane compounds include tetraethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, trifluoropropyltrimethyl. Examples thereof include tetrafunctional and trifunctional alkoxysilane compounds such as methoxysilane and octadecyltrimethoxysilane. Of these, at least one of tetraethoxysilane and methyltriethoxysilane is preferably used from the viewpoint of high crosslinking efficiency.

  The proportion of the organosiloxane, bifunctional silane compound, vinyl polymerizable group-containing silane compound, and trifunctional or higher functional silane compound used during polymerization is appropriately determined. In particular, the ratio of the total amount of the organosiloxane and the bifunctional silane compound is preferably 50 to 99.9% by mass, and more preferably 60 to 99.5% by mass. In addition, it is preferable that the ratio of organosiloxane and a bifunctional silane compound is 100 / 0-0 / 100 by weight ratio, and if it is 100 / 0-70 / 30, it is still more preferable. The proportion of the vinyl polymerizable group-containing silane compound is preferably 0 to 40% by mass, and more preferably 0.5 to 30% by mass. The proportion of the trifunctional or higher functional silane compound is preferably 0 to 50% by mass, and more preferably 0 to 39% by mass. At least one of the vinyl polymerizable group-containing silane compound and the trifunctional or higher silane compound is preferably used, and in particular, the ratio of at least one of the vinyl polymerizable group containing silane compound and the trifunctional or higher functional silane compound. Is preferably 0.1% or more. When the proportion of the organosiloxane and the bifunctional silane compound used is too small, the molded product tends to become brittle. On the other hand, if the amount is too large, the amount of the vinyl polymerizable group-containing silane compound and the tri- or higher functional silane compound is too small, and the effect of using these tends to be difficult to be expressed. Further, if the ratio of the vinyl polymerizable group-containing silane compound or the trifunctional or higher functional silane compound is too small, the flame retardancy of the molded product may not be sufficiently improved. On the other hand, if it is too much, the molded product tends to be brittle.

  The component (X) is preferably produced by emulsion polymerization of the above monomer. Emulsion polymerization is performed, for example, when the monomer and water are emulsified and dispersed in water by mechanical shearing in the presence of an emulsifier and become an acidic state. In this case, when emulsion droplets of several μm or more are prepared by mechanical shearing, the average particle size of the component (X) obtained after polymerization is controlled in the range of 0.02 to 0.6 μm depending on the amount of the emulsifier. Is done. In addition, the coefficient of variation (100 × standard deviation / average particle size) (%) of the particle size distribution of the component (X) is controlled in the range of 20 to 70%.

  When the component (X) having an average particle size of 0.1 μm or less and a narrow particle size distribution is produced, the component (X) is preferably produced by multistage polymerization. For example, 1 to 20% of an emulsion composed of emulsion droplets of several μm or more obtained by emulsifying the monomer, water, and emulsifier by mechanical shearing was obtained by emulsion polymerization in an acidic state first. It is preferred that the remaining emulsion additionally polymerizes in the presence of component X) as a seed. The component (X) obtained from this is controlled in the range of the average particle size of 0.02 to 0.1 μm and the variation coefficient of the particle size distribution of 10 to 60% according to the amount of the emulsifier. In a more preferable method, in the multistage polymerization, instead of using the component (X) as a seed, a vinyl monomer (for example, styrene, butyl acrylate, methyl methacrylate, etc.) used during graft polymerization described later is used in a conventional emulsion weight. By using a vinyl-based (co) polymer obtained by (co) polymerization by a legal method, polyorganosiloxane (modified polyorganosiloxane) particles can be obtained by multistage polymerization as described above. In this case, the average particle size of the resulting polyorganosiloxane (modified polyorganosiloxane) particles is in the range of 0.008 to 0.1 μm depending on the amount of the emulsifier, and the variation coefficient of the particle size distribution is in the range of 10 to 50%. Be controlled. The emulsified droplets of several μm or more can be prepared by using a high-speed stirrer such as a homomixer.

  In the emulsion polymerization, an emulsifier that does not lose emulsification ability under an acidic state is used. Specific examples include alkylbenzene sulfonic acid, sodium alkylbenzene sulfonate, alkyl sulfonic acid, sodium alkyl sulfonate, sodium (di) alkyl sulfosuccinate, sodium polyoxyethylene nonylphenyl ether sulfonate, sodium alkyl sulfate, and the like. These may be used alone or in combination of two or more. In particular, it is preferable to use at least one selected from alkylbenzene sulfonic acid, sodium alkylbenzene sulfonate, alkyl sulfonic acid, sodium alkyl sulfonate, and sodium (di) alkyl sulfosuccinate since the emulsion stability is relatively high. Furthermore, alkylbenzenesulfonic acid and alkylsulfonic acid are particularly preferable because they also act as a polymerization catalyst for the monomer.

  The acidic state of the reaction system is achieved by adding an inorganic acid such as sulfuric acid or hydrochloric acid or an organic acid such as alkylbenzene sulfonic acid, alkyl sulfonic acid, or trifluoroacetic acid to the reaction system. The pH of the reaction system is preferably adjusted to 1 to 3 and more preferably adjusted to 1.0 to 2.5 in consideration of corrosion inhibition of production facilities and achievement of an appropriate polymerization rate. The heating for the polymerization is preferably 60 to 120 ° C., more preferably 70 to 100 ° C. in order to achieve an appropriate polymerization rate.

  In an acidic state, the Si—O—Si bond forming the polyorganosiloxane skeleton is in an equilibrium state of cleavage and generation, and this equilibrium changes with temperature. For this reason, in order to stabilize the polyorganosiloxane chain, it is preferable to neutralize the reaction system by adding an alkaline aqueous solution such as sodium hydroxide, potassium hydroxide or sodium carbonate to the reaction system. Further, the equilibrium becomes closer to the production side as the temperature becomes lower, and a product having a high molecular weight or a high degree of crosslinking is easily obtained. For this reason, in order to obtain a product having a high molecular weight or a high degree of crosslinking, after the polymerization of the monomer proceeds at 60 ° C. or higher, the reaction system is cooled to room temperature or lower and held for about 5 to 100 hours. It is preferable to be neutralized.

  The component (X) thus obtained is, for example, an organosiloxane or a bifunctional silane compound, and further when a vinyl-based polymerizable group-containing silane compound is added to polymerize them, usually by random copolymerization. A polymer having a vinyl polymerizable group is obtained. When a trifunctional or higher functional silane compound is copolymerized, a copolymer having a network structure by crosslinking is obtained. Further, when the vinyl polymerizable groups are cross-linked by a radical reaction by a radical polymerization initiator used at the time of graft polymerization described later, a cross-linked structure is formed due to a chemical bond between the vinyl polymerizable groups, and a part thereof is not yet formed. The vinyl polymerizable group of the reaction remains.

  (Y) component consists of (Y-1) component, or consists of (Y-1) component and (Y-2) component. The (Y-1) component is a polyfunctional monomer containing two or more polymerizable unsaturated bonds in the molecule, and the ratio in the (Y) component is 100 to 50% by mass. (Y-2) component is vinyl monomers other than (Y-1) component, and the ratio in (Y) component is 0-50 mass%. By using the component (Y), the flame retardancy and impact resistance of the molded product are improved.

  The ratio of the component (Y-1) in the component (Y) is 50% by mass or more, and the ratio of the component (Y-2) in the component (Y) is 50% by mass or less. Impact properties are further improved. The ratio of the (Y-1) component in the (Y) component is particularly preferably 100 to 80% by mass, and more preferably 100 to 90% by mass. The proportion of the component (Y-2) in the component (Y) is particularly preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.

  Examples of the component (Y-1) include allyl methacrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, and divinylbenzene. Among these compounds, only one kind may be used or two or more kinds may be used in combination. In these, it is preferable that allyl methacrylate is used especially at the point of economical efficiency and an effect.

  As component (Y-2), aromatic vinyl monomers such as styrene, α-methylstyrene, paramethylstyrene and parabutylstyrene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; acrylic acid Methyl, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, hydroxyethyl acrylate, hydroxybutyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, lauryl methacrylate (Meth) acrylic acid ester monomers such as glycidyl methacrylate and hydroxyethyl methacrylate; carboxyl group-containing vinyl monomers such as itaconic acid, (meth) acrylic acid, fumaric acid and maleic acid . These may be used alone or in combination of two or more.

  The component (Z) ensures compatibility between the polyorganosiloxane-containing graft copolymer and the components (A) and (D), and contributes to improving the dispersibility of the polyorganosiloxane-containing graft copolymer.

  As the (Z) component, the same compounds as the above (Y-2) component such as methyl methacrylate, butyl methacrylate, styrene, acrylonitrile and the like can be used. Among these compounds, only one kind may be used, or two or more kinds may be used in combination.

The solubility parameter of the component (Z) is preferably 9.15 to 10.15 [(cal / cm ³ ) ^1/2 ], and 9.17 to 10.10 [(cal / cm ³ ) ^1/2 ], More preferably 9.20 to 10.05 [(cal / cm ³ ) ^1/2 ]. When the solubility parameter is within the above range, the flame retardancy of the molded product is further improved. The solubility parameter is a value calculated by using the group parameter of Small in the group contribution method described in “Polymer Handbook”, 1999, 4th edition, pages 682 to 685, published by John Wiley & Son, Inc.).

  In the presence of 40 to 90 parts by mass of the (X) component, the polyorganosiloxane-containing graft copolymer is polymerized in an amount of 0.5 to 10 parts by mass of the (Y) component, and further 5 to 50 parts by mass of the (Z) component. Is obtained by polymerization. The total amount of components (X) to (Z) is 100 parts by mass. In particular, the proportion of the component (X) is preferably 60 to 80 parts by mass, and more preferably 60 to 75 parts by mass. The proportion of the component (Y) is preferably 1 to 5 parts by mass, and more preferably 2 to 4 parts by mass. The proportion of component (Z) is preferably 15 to 39 parts by mass, more preferably 21 to 38 parts by mass.

  When the proportion of the component (X) is too small or too large, the flame retarding effect of the molded product is low. When the component (Y) is too small, the flame retardancy effect and impact resistance improving effect of the molded product are lowered, and when it is too much, the impact resistance improving effect of the molded product is lowered. (Z) When there are too few components and there are too many components, the flame-retardant effect of a molded article will become low.

  The polyorganosiloxane-containing graft copolymer can be produced by known seed emulsion polymerization. For example, the (Y) component undergoes radical polymerization in the (X) component latex, and further, the (Z) component undergoes radical polymerization, whereby a polyorganosiloxane-containing graft copolymer is obtained. Both the component (Y) and the component (Z) may be polymerized in one stage or in two or more stages.

  In the radical polymerization, an appropriate method such as a method of advancing the reaction by thermally decomposing a radical polymerization initiator or a method of advancing the reaction in a redox system using a reducing agent can be adopted. The reaction temperature during the polymerization is preferably 30 to 120 ° C.

  As radical polymerization initiators, cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, di-t-butyl peroxide, t-butyl peroxide are used because of their high reactivity. Organic peroxides such as oxylaurate, lauroyl peroxide, succinic acid peroxide, cyclohexanenon peroxide, acetylacetone peroxide; inorganic peroxides such as potassium persulfate and ammonium persulfate are preferably used. The amount of the radical polymerization initiator used is 0.005 to 20 parts, further 0.01 to 10 parts, particularly 0.03 to 5 parts, with respect to 100 parts of the (Y) component or the (Z) component. Preferably there is.

  On the other hand, as the reducing agent used in the redox system, ferrous sulfate / glucose / sodium pyrophosphate, ferrous sulfate / dextrose / sodium pyrophosphate, ferrous sulfate / sodium formaldehyde sulfoxylate / ethylenediamine acetate, etc. And the like.

  A chain transfer agent may be used during radical polymerization. Specific examples of the chain transfer agent include t-dodecyl mercaptan, n-octyl mercaptan, n-tetradecyl mercaptan, n-hexyl mercaptan and the like. When the chain transfer agent is used, the amount used is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (Y) or the component (Z).

  In the polymerization, when the component (X) contains a vinyl polymerizable group, when the component (Y) is polymerized by a radical polymerization initiator, the component (X) is a vinyl polymerizable group of the component (X). By reacting with, a graft is formed. In the absence of a vinyl polymerizable group in component (X), when a specific radical initiator such as t-butyl peroxylaurate is used, hydrogen is extracted from an organic group such as a methyl group bonded to a silicon atom. In this way, the (Y) component is polymerized by the radicals generated to form a graft. Further, when the (Z) component is polymerized by the radical polymerization initiator, it not only reacts with the (X) component in the same manner as the (Y) component, but also exists in the polymer formed by the (Y) component. The graft by the (Z) component is formed by reacting with the saturated bond.

  The polyorganosiloxane-containing graft copolymer obtained by emulsion polymerization or the like may or may not be separated from the latex. As a method for separating the polyorganosiloxane-containing graft copolymer from the latex, a usual method, for example, by adding a metal salt such as calcium chloride, magnesium chloride, magnesium sulfate to the latex, the latex is coagulated, separated, washed with water, A method of dehydrating and drying can be employed. A spray drying method may be employed.

  In the polymerization of the (Y) component and the (Z) component in the presence of the (X) component, the portion corresponding to the branch of the graft copolymer (here, the polymer of the (Y) component and the (Z) component) A so-called free polymer obtained by polymerizing only the branch component alone without grafting to the trunk component (here (X) component) is also produced as a by-product, and a mixture of the polyorganosiloxane-containing graft copolymer and the free polymer is obtained. . Both of these are referred to as a polyorganosiloxane-containing graft copolymer.

  In the polyorganosiloxane-containing graft copolymer, the (Y) component is grafted to the (X) component, and the (Z) component is also grafted to the polymer formed by the (Y) component as well as the (X) component. Therefore, the amount of free polymer is reduced. Acetone insoluble content of this polyorganosiloxane-containing graft copolymer (acetone insoluble content when 1 g of polyorganosiloxane-containing graft copolymer is immersed in 80 ml of acetone at room temperature for 48 hours) is 80% or more, and more than 85% It is preferable for improving the flame retardancy of the molded product.

  Such a polyorganosiloxane-containing graft copolymer is commercially available. Examples of commercially available polyorganosiloxane-containing graft copolymers include Kane Ace MR01 and Kane Ace MR02 manufactured by Kaneka Corporation.

  When the polylactic acid resin composition contains an epoxy-modified silicone / acrylic rubber, the content is preferably in the range of 3 to 12% by mass.

  Examples of the epoxy-modified silicone / acrylic rubber include polymers of alkyl acrylate, silyl group-terminated polyether, and glycidyl group-containing vinyl compounds. This epoxy-modified silicone / acrylic rubber is a composite of a copolymer of an alkyl acrylate and a silyl group-terminated polyether (silicone acrylic composite rubber) and a polymer of a glycidyl group-containing vinyl compound such as glycidyl methacrylate. May be. In this case, all or part of the copolymer of alkyl acrylate and silyl group-terminated polyether and the polymer of the glycidyl group-containing vinyl compound may be copolymerized.

  The core layer of the epoxy-modified silicone / acrylic rubber is composed of a copolymer of an alkyl acrylate and a silyl group-terminated polyether, and the shell layer is composed of a polymer of a glycidyl group-containing vinyl compound. This multilayer structure polymer can be obtained by, for example, graft polymerization by adding a glycidyl group-containing vinyl compound to a latex of a copolymer of an alkyl acrylate and a silyl group-terminated polyether.

  The structural formula of a typical example of a copolymer (silicone acrylic composite rubber) of an alkyl (meth) acrylate and a silyl group-terminated polyether is shown in the following formula [Chemical Formula 2]. The left part of this structural formula is an alkyl (meth) acrylate unit derived from an alkyl (meth) acrylate, and the right part is a silyl group-terminated polyether unit derived from a silyl group-terminated polyether.

  A structural example of a typical example of a vinyl compound containing a glycidyl group is shown in the following formula [Chemical Formula 3].

  Specific examples of the alkyl (meth) acrylate include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and n-methacrylate. Hexyl, 2-ethylhexyl methacrylate; cyclohexyl methacrylate, stearyl methacrylate, octadecyl methacrylate, phenyl methacrylate, benzyl methacrylate, chloromethyl methacrylate, 2-chloroethyl methacrylate, methacrylic acid 2-hydroxyethyl; 3-hydroxypropyl methacrylate, 2,3,4,5,6-pentahydroxyhexyl methacrylate, 2,3,4,5-tetrahydroxypentyl methacrylate, aminoethyl acrylate, Propylaminoacrylate Le; dimethylaminoethyl methacrylate, ethyl methacrylate aminopropyl, and the like phenyl methacrylate aminoethyl or cyclohexyl aminoethyl methacrylate. Among these compounds, only one kind may be used or two or more kinds may be used in combination.

  As the silyl group-terminated polyether, a polyether such as polyethylene or polypropylene having a silyl group at the terminal is used. Specific examples of the silyl group include halogens such as alkylsilyl groups such as methylsilyl group, ethylsilyl group, propylsilyl group, and butylsilyl group, 3-chloropropylsilyl group, and 3,3,3-trifluoropropylsilyl group. Alkylsilyl group, vinylsilyl group, allylsilyl group, alkenylsilyl group such as butenylsilyl group, arylsilyl group such as phenylsilyl group, tolylsilyl group, naphthylsilyl group, cycloalkylsilyl group such as cyclopentylsilyl group, cyclohexylsilyl group, benzyl Examples thereof include aryl-alkylsilyl groups such as silyl group and phenethylsilyl group. Among such silyl group-terminated polyethers, only one type may be used, or two or more types may be used in combination.

  Examples of the glycidyl group-containing vinyl compound include glycidyl methacrylate, glycidyl itaconate, diglycidyl itaconate, allyl glycidyl ether, styrene-4-glycidyl ether, and 4-glycidyl styrene. Among these compounds, only one kind may be used or two or more kinds may be used in combination.

  As such an epoxy-modified silicone / acrylic rubber, commercially available products can be used as appropriate. Specific examples thereof include trade name METABRENE S2200 manufactured by Mitsubishi Rayon Co., Ltd., which is a core-shell structure containing glycidyl methacrylate in the shell.

  The polylactic acid resin composition may contain core-shell rubber other than Si-containing core-shell rubber, that is, core-shell rubber not containing Si. Examples of the core-shell rubber not containing Si include an unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer.

  When an unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer is used, the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer is a core-shell rubber containing Si. All or part of these functions can be exhibited in place of the core-shell rubber containing Si. In this case, the cost is advantageous.

  The unsaturated carboxylic acid alkyl ester used to obtain the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer includes methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate. Etc. Examples of the diene rubber component include rubbers having a glass transition point of 10 ° C. or less, such as polybutadiene, styrene-butadiene copolymer, and acrylonitrile-butadiene. Examples of the aromatic vinyl include nuclei substituted styrene such as styrene, α-methylstyrene and p-methylstyrene. These unsaturated carboxylic acid alkyl esters, diene rubbers, and aromatic vinyls can be used alone or in combination of two or more.

  A representative example of the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer is a methyl methacrylate-butadiene-styrene copolymer (MBS resin). The methyl methacrylate-butadiene-styrene copolymer is preferably a multilayer structure polymer including a core layer composed of a butadiene / styrene polymer and a shell layer composed of a methyl methacrylate polymer.

  The structural formula of the butadiene / styrene polymer is shown in the following formula [Chemical Formula 4]. The left part of this structural formula is a butadiene unit derived from butadiene, and the right part is a styrene unit derived from styrene.

  The structural formula of the methacrylic polymer constituting the shell layer is shown in the following formula [Chemical Formula 5].

  Examples of the method for producing the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer include various methods such as bulk polymerization, suspension polymerization, and emulsion polymerization, and the emulsion polymerization method is particularly preferable. is there. The core-shell type graft rubber-like elastic body thus obtained preferably contains 50% by mass or more of the diene rubber component.

  As such a methyl methacrylate-butadiene-styrene copolymer, a commercially available product may be used as appropriate. As a suitable specific example of a methyl methacrylate-butadiene-styrene copolymer, Mitsubishi Rayon Co., Ltd. trade names, Metabrene C-223A, Metabrene C-323A, Metabrene C-215A, Metabrene C-201A, Metabrene C-202, Examples include METABLEN C-102, METABLEN C-140A, METABLEN C-132, etc., trade name Kane Ace M-600 manufactured by Kaneka Corporation, and trade name Paraloid EXL-2638 manufactured by Rohm & Haas Co., Ltd.

(Polycarbonate resin)
The polylactic acid resin composition may contain a polycarbonate resin. In this case, the durability of the injection molded product is further improved. The content of the polycarbonate resin in the polylactic acid resin composition is appropriately set, but is preferably in the range of 1 to 20% by mass. When the content is 1% by mass or more, the durability of the molded product is improved. This content is preferably 10% by mass or more. Moreover, if this content is 20 mass% or less, the ratio of the polylactic acid resin with respect to the whole resin component will not fall too much, and the biodegradability which is the characteristic of polylactic acid resin will fully be exhibited.

  Examples of the polycarbonate resin include aromatic polycarbonate resins obtained by reacting a dihydric phenol and a carbonate precursor. Examples of the reaction method include an interfacial polycondensation method, a melt transesterification method, a solid phase transesterification method of a carbonate prepolymer, and a ring-opening polymerization method of a cyclic carbonate compound.

  Representative examples of dihydric phenols include hydroquinone, resorcinol, 4,4'-biphenol, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol) A), 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4 '-(P-phenylenediisopropylidene) diphenol, 4,4'-(m-phenylenediisopropylidene) diph 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, bis (4- Hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) ketone, bis (4-hydroxyphenyl) ester, bis (4-hydroxy-3-methylphenyl) sulfide, 9,9-bis (4-hydroxyphenyl) fluorene, 9 , 9-bis (4-hydroxy-3-methylphenyl) fluorene. A preferred dihydric phenol is bis (4-hydroxyphenyl) alkane, and bisphenol A (BPA) is particularly preferred because it can improve the toughness of the molded product.

  Examples of the carbonate precursor include carbonyl halide, carbonic acid diester, and haloformate. Specific examples include phosgene, diphenyl carbonate, and dihaloformate of dihydric phenol.

  When an aromatic polycarbonate resin is produced from a dihydric phenol and a carbonate precursor by an interfacial polymerization method, a catalyst, a terminal terminator, an antioxidant for the oxidation of the dihydric phenol, etc. are used as necessary. May be.

  As polycarbonate resin, branched polycarbonate resin copolymerized with trifunctional or higher polyfunctional aromatic compound, polyester carbonate resin copolymerized with aromatic or aliphatic (including alicyclic) difunctional carboxylic acid, bifunctional A copolymer polycarbonate resin obtained by copolymerizing a functional alcohol (including an alicyclic), and a polyester carbonate resin obtained by copolymerizing the bifunctional carboxylic acid and the difunctional alcohol together may be used. Two or more kinds of polycarbonate resins may be used as the polycarbonate resin.

  When a branched polycarbonate resin is used, the melt tension of the polylactic acid resin composition increases, thereby improving the moldability in extrusion molding, foam molding, blow molding and the like. As a result, a molded product having superior dimensional accuracy can be obtained. Examples of the trifunctional or higher polyfunctional aromatic compound used for obtaining the branched polycarbonate resin include 4,6-dimethyl-2,4,6-tris (4-hydroxydiphenyl) heptene-2, 2,4, 6-trimethyl-2,4,6-tris (4-hydroxyphenyl) heptane, 1,3,5-tris (4-hydroxyphenyl) benzene, 1,1,1-tris (4-hydroxyphenyl) ethane, , 1,1-tris (3,5-dimethyl-4-hydroxyphenyl) ethane, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 4- {4- [1,1 A preferred example is trisphenol such as -bis (4-hydroxyphenyl) ethyl] benzene} -α, α-dimethylbenzylphenol. Other polyfunctional aromatic compounds include phloroglucin, phloroglucide, tetra (4-hydroxyphenyl) methane, bis (2,4-dihydroxyphenyl) ketone, 1,4-bis (4,4-dihydroxytriphenylmethyl) Examples include benzene, trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, and acid chlorides thereof. Of these, 1,1,1-tris (4-hydroxyphenyl) ethane and 1,1,1-tris (3,5-dimethyl-4-hydroxyphenyl) ethane are preferable, and 1,1,1-tris (4 -Hydroxyphenyl) ethane is preferred.

The proportion of the structural unit derived from the polyfunctional aromatic compound in the branched polycarbonate resin is 100% by mole in total of the structural unit derived from the dihydric phenol and the structural unit derived from the polyfunctional aromatic compound. 0.03 to 1 mol%, preferably 0.07 to 0.7 mol%, particularly preferably 0.1 to 0.4 mol%. The branched structural unit is not only derived from a polyfunctional aromatic compound, but also derived from a side reaction during a melt transesterification reaction without using a polyfunctional aromatic compound. Also good. Note that the proportion of the branched structure can be calculated by ^{1 H-NMR} measurement.

  On the other hand, the aliphatic bifunctional carboxylic acid is preferably α, ω-dicarboxylic acid, and specific examples thereof include sebacic acid (decanedioic acid), dodecanedioic acid, tetradecanedioic acid, octadecanedioic acid, icosane diacid. Examples thereof include linear saturated aliphatic dicarboxylic acids such as acids and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. As the bifunctional alcohol, an alicyclic diol is suitable, and examples thereof include cyclohexanedimethanol, cyclohexanediol, and tricyclodecane dimethanol. Further, a polycarbonate-polyorganosiloxane copolymer obtained by copolymerizing polyorganosiloxane units can also be used.

  As the polycarbonate resin, two or more kinds of polycarbonates having different dihydric phenol components, polycarbonates containing branched components, various polyester carbonates, polycarbonate-polyorganosiloxane copolymers, and the like may be used. Further, two or more kinds of polycarbonates having different production methods, polycarbonates having different end stoppers, and the like may be used.

  Reaction methods such as interfacial polymerization, molten transesterification, solid phase transesterification of carbonate prepolymers, and ring-opening polymerization of cyclic carbonate compounds, which are polycarbonate resin production methods, are well known in various documents and patent publications. It is the method that has been.

  As the polycarbonate resin, not only a virgin raw material but also a polycarbonate resin regenerated from a used product, a so-called material recycled aromatic polycarbonate may be used. Used products include soundproof walls, glass windows, translucent roofing materials, various glazing materials such as automobile sunroofs, transparent members such as windshields and automobile headlamp lenses, containers such as water bottles, optical recording media, etc. Is preferred. These do not contain a large amount of additives or other resins, and the desired quality is easily obtained stably. In particular, an automotive headlamp lens, an optical recording medium, and the like are preferred as preferred embodiments because they satisfy the more preferable conditions of the viscosity average molecular weight described below. In addition, said virgin raw material is a raw material which is not yet used in the market after the manufacture.

The viscosity average molecular weight of the polycarbonate resin is preferably 1 × 10 ^{4 to} 5 × 10 ⁴ , more preferably 1.4 × 10 ^{4 to} 3 × 10 ⁴ , and still more preferably 1.8 × 10 ^{4 to} 2.5 × 10. ⁴ . When the viscosity average molecular weight is in the range of 1.8 × 10 ^{4 to} 2.5 × 10 ⁴ , the polylactic acid resin composition is particularly excellent in both good fluidity and impact resistance of the molded product. Most preferably, the viscosity average molecular weight is in the range of 1.9 × 10 ^{4 to} 2.4 × 10 ⁴ . The viscosity average molecular weight only needs to satisfy the entire polycarbonate resin, and a mixture of two or more polycarbonate resins having different molecular weights may satisfy this range.

In calculating the viscosity average molecular weight, first, the specific viscosity calculated by the following formula (a) was measured using an Ostwald viscometer for a sample solution prepared by dissolving 0.7 g of a polycarbonate resin in 100 ml of methylene chloride at 20 ° C. Obtained from measurement results. Next, the viscosity average molecular weight M is determined from the specific viscosity obtained using the following formulas (b) to (d).
Specific viscosity (ηSP) = (t−t0) / t (a)
[T0 is the drop time of methylene chloride, t is the drop time of the sample solution]
ηSP / c = [η] + 0.45 × [η] ² c (where [η] is the intrinsic viscosity) (b)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83 (c)
c = 0.7 (d)
(Other thermoplastic resins)
In the polylactic acid resin composition, various thermoplastic resins other than the above may be contained. For example, the polylactic acid resin composition is made of polyethylene terephthalate resin (PET resin), polybutylene terephthalate resin (PBT resin), cyclohexanedimethanol copolymerized polyethylene terephthalate resin (so-called PET-G resin), polyethylene naphthalate resin, polybutylene naphthalate. Aromatic polyester resins such as resins; cyclic polyolefin resins; polycaprolactone resins; thermoplastic fluororesins typified by polyvinylidene fluoride resins; polyethylene resins, ethylene- (α-olefin) copolymer resins, polypropylene resins, propylene- ( (alpha-olefin) copolymer resin etc. may be contained. The polylactic acid resin composition may contain only one kind of resin as described above, or may contain two or more kinds. Such various thermoplastic resins can further improve the impact resistance of the injection molded product. When these thermoplastic resins are used, the content thereof is preferably in the range of 3 to 12% by mass with respect to the polylactic acid resin composition.

(Fillers, etc.)
The polylactic acid resin composition may contain a filler. As the filler, for example, talc, wollastonite, mica, clay, montmon lilonite, smectite, kaolin, zeolite (aluminum silicate), anhydrous amorphous aluminum silicate obtained by acid treatment and heat treatment of zeolite, etc. An inorganic filler is mentioned. Talc and wollastonite are particularly preferable. Among these fillers, only one type may be used, or two or more types may be used in combination.

  Examples of talc include talc that is generally used as a filler material for resin molding materials. Any appropriate commercially available talc can be used. The average particle diameter of talc is usually preferably in the range of 0.1 to 10 μm. This average particle diameter is a value measured by a laser diffraction / scattering method using a laser diffraction / scattering particle size analyzer (such as Microtrack MT3000II series manufactured by Nikkiso Co., Ltd.).

  Although the content of talc in the polylactic acid resin composition is not particularly limited, it is preferably in the range of 1 to 30% by mass. If this content is 1% by mass or more, the tensile modulus of the molded product is improved, and if this content is 30% by mass or less, the penetration of talc into the screw during kneading of the polylactic acid resin composition is suppressed. Thus, good workability and moldability are maintained. The content of this talc is preferably in the range of 1 to 15% by mass, and more preferably in the range of 3 to 8% by mass. When this content is 8% by mass or less, the occurrence of welds and flow marks is sufficiently suppressed even when a molded product having a complicated shape is obtained, and when this content is 3% by mass or more, talc The effect of addition is particularly demonstrated.

  The polylactic acid resin composition may contain a dye or a pigment as a colorant. As dyes, coumarin fluorescent dyes, benzopyran fluorescent dyes, perylene fluorescent dyes, anthraquinone fluorescent dyes, thioindigo fluorescent dyes, xanthene fluorescent dyes, xanthone fluorescent dyes, thioxanthene fluorescent dyes, thioxanthone fluorescent dyes , Thiazine fluorescent dyes, diaminostilbene fluorescent dyes, fluorescent dyes (including fluorescent brighteners); perylene dyes; coumarin dyes; thioindigo dyes; anthraquinone dyes; thioxanthone dyes; Peranone dyes; quinoline dyes; quinacridone dyes; dioxazine dyes; isoindolinone dyes; phthalocyanine dyes. Of the fluorescent dyes, coumarin fluorescent dyes, benzopyran fluorescent dyes, and perylene fluorescent dyes that have good heat resistance and little deterioration during molding of the polycarbonate resin are suitable. As the pigment, metallic pigments such as various plate fillers having a metal film or a metal oxide film, carbon, and the like can be used.

  The content of the colorant in the polylactic acid resin composition is preferably 2% by mass or less, more preferably 1.5% by mass or less, with respect to 100 parts by mass of the total amount of the resin components. Furthermore, the content of the colorant is preferably 0.00001 parts by mass or more, more preferably 0.00005 parts by mass or more, and 0.5 parts by mass or more with respect to 100 parts by mass of the total amount of the resin components. If it is more preferable.

(Other)
The polylactic acid resin composition is not contrary to the object of the present invention and, as long as the effect is not impaired, an antioxidant, a stabilizer, an ultraviolet absorber, a lubricant, a mold release agent, a plasticizer, an antistatic agent, if necessary. Known additives such as agents, inorganic and organic antibacterial agents may be contained. Antioxidants include 2,2-methylenebis- (4-methyl-6-tert-butylphenol), octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, and bis (3 -T-butyl-4-hydroxy-5-methyl-phenyl) dicyclopentadiene and the like. These additives may be added at the time of kneading the polylactic acid resin composition, or may be added at the time of molding or the like.

[Polylactic acid resin composition and injection molded product]
The polylactic acid resin composition is prepared by mixing and kneading the raw materials of the polylactic acid resin composition as described above by an arbitrary method. In the mixing and kneading, for example, a twin screw extruder, a Banbury mixer, a heating roll, or the like is used. Among them, melt kneading using a twin screw extruder is preferable.

  For example, in preparing the polylactic acid resin composition, a method of supplying the raw materials of the polylactic acid resin composition independently to a melt kneader represented by a vent type twin screw extruder, or a part of the raw materials was premixed Thereafter, a method of supplying to the melt kneader independently of the remaining components may be employed. Moreover, after supplying a part of raw material to a melt kneader, the method of supplying the remaining raw material from the middle of a melt extruder may be employ | adopted. The heating temperature at the time of melt kneading is preferably in the range of 200 to 260 ° C.

  In addition, when there is a liquid component in the raw material, a so-called liquid injection device, a liquid addition device, or the like may be used when supplying the liquid component to the melt extruder. Such a liquid injection device or a liquid addition device is preferably provided with a heating device. Therefore, the melt extruder preferably has a raw material supply port for liquid injection. For example, when a liquid component is supplied to a melt extruder, the liquid component is fed into a press melt extruder from a feed port formed in a barrel of a normal melt extruder by a known liquid conveying device such as a gear pump. It is preferable to supply at a pressure equal to or higher than the discharge pressure.

  The polylactic acid resin composition may be formed into pellets as necessary. For example, a polylactic acid resin composition extruded by a melt extruder is directly cut and pelletized, or after a strand of the polylactic acid resin composition is formed, the strand is cut by a pelletizer or the like and pelletized. Thus, a pellet-shaped polylactic acid resin composition may be obtained. When the influence of external dust or the like needs to be reduced during pelletization, it is preferable that the atmosphere around the melt extruder is cleaned. The shape of the pellet-like polylactic acid resin composition may be a general shape such as a cylinder, a prism, or a sphere, but is more preferably a cylinder. The diameter of the columnar polylactic acid resin composition is preferably 1 to 5 mm, more preferably 1.5 to 4 mm, and still more preferably 2 to 3.3 mm. On the other hand, the length of the columnar polylactic acid resin composition is preferably 1 to 30 mm, more preferably 2 to 5 mm, and still more preferably 2.5 to 3.5 mm.

  An injection-molded product is obtained by injection molding of the polylactic acid resin composition. In injection molding, not only ordinary molding methods, but also injection compression molding, injection press molding, gas-assisted injection molding, foam molding (including the method of injecting supercritical fluid), insert molding, in-mold coating molding, bicolor Molding, sandwich molding, ultra-high speed injection molding or the like may be employed.

  In the injection molding of the polylactic acid resin composition, an appropriate injection molding apparatus can be used. In particular, in order to control the cavity surface temperature of the mold at the time of injection as described above, it is preferable to use a mold including an electric heater. In this case, when the polylactic acid resin composition is injected, the temperature of the cavity surface is accurately and quickly adjusted by an electric heater.

  Since the polylactic acid in the injection-molded product thus obtained does not easily crystallize, thermal shrinkage over time in the high-temperature environment of the injection-molded product is greatly suppressed. Moreover, since it is not necessary to advance crystallization of polylactic acid during injection molding, the molding cycle is shortened, and welds and flow marks are less likely to occur in the injection molded product. Furthermore, the injection molded product has characteristics required for the molded product such as sufficiently high durability, impact resistance, and heat resistance. For this reason, the injection-molded product can be used in a wide range of fields such as the home appliance field, the building material, and the sanitary field that are expected to be used for a long period of time.

  As a particularly preferable specific example of the injection-molded product, an internal part such as a casing for an electronic device such as an exterior of a holder for an electronic device such as a mobile phone or a smartphone, or an internal chassis component in an electronic device such as a mobile phone can be given. .

  FIG. 1 shows an electronic device holder 2 as an example of an injection-molded product 1. The electronic device holder 2 has a function of holding and fixing an electronic device such as a mobile phone on a desktop or the like, or further has a function as a charger for charging a battery in the electronic device. In the electronic device holder 2, a region (mounting region 3) on which the electronic device is placed and a holding rib 4 protruding from the outer edge of the placement region 3 are formed. The electronic device placed on the placement region 3 is further supported by the holding rib 4, whereby the electronic device is held and fixed to the electronic device holder 2. For this reason, the electronic device holder 2 is formed to match the shape and dimensions of the electronic device. The electronic device holder 2 is not limited to such a structure, and may have an appropriate structure capable of holding the electronic device. For this purpose, the electronic device holder 2 is formed to match the shape and dimensions of the electronic device.

  When the electronic device holder 2 is exposed to a high temperature and thermally contracted over time, the electronic device holder 2 is deformed and the electronic device is not held and fixed. For example, when the electronic device holder 2 is left in an automobile, it may be exposed to a high temperature for a long time. In such a case, if heat shrinkage occurs, the electronic device is held and fixed in the electronic device holder. It will disappear. However, when the electronic device holder 2 is an injection-molded product 1 formed by injection molding from the polylactic acid resin composition according to the present embodiment, the electronic device holder 2 is less likely to undergo thermal shrinkage, and can be used for a long time. It becomes possible. In particular, it is preferable that thermal shrinkage is sufficiently suppressed even when exposed to an electronic device holder at 280 ° C. for 48 hours. Further, it is preferable that the occurrence of whitening is sufficiently suppressed when the electronic device holder 2 is exposed to an atmosphere of 80 ° C. for 48 hours.

  Various types of surface treatment may be applied to the injection molded product. Surface treatment includes forming a new layer on the surface of the molded product, such as vapor deposition (physical vapor deposition, chemical vapor deposition, etc.), plating (electroplating, electroless plating, hot dipping, etc.), painting, coating, printing, etc. Is mentioned. Specific examples of the surface treatment include hard coat, water / oil repellent coat, ultraviolet absorption coat, infrared absorption coat, metalizing (evaporation, etc.) and the like.

[Production example]
The mixture of L-lactide and D-lactide is reacted by heating in a reactor equipped with a stirring blade in a nitrogen atmosphere in the presence of a metal polymerization catalyst and alcohol, and then the pressure in the reactor is reduced to remain in the mixture. Lactide was removed. Furthermore, polylactic acid was prepared by chipping this mixture. In preparing this polylactic acid, the ratio of D-lactic acid units is 11.6 mol%, the weight average molecular weight is 101,000, and is defined in ISO ASTM D1238 by changing the blending ratio of L-lactide and D-lactide. Polylactic acid (polylactic acid A) having a melt flow rate (190 ° C. 2.16 kg) of 10.8 g / 10 min, a ratio of D-lactic acid units of 8.6 mol%, a weight average molecular weight of 114,000, ISO Polylactic acid (polylactic acid B) having a melt flow rate (190 ° C., 2.16 kg) as defined in ASTM D1238 of 7.0 g / 10 min was obtained.

[Examples and Comparative Examples]
For each Example and Comparative Example, the components shown in the following table were used, and the resin components were dried in advance, and then these components were mixed with a tumbler for 10 minutes. The obtained mixture was extruded with a twin-screw extruder under conditions of a die vicinity temperature of 190 ° C. and an inlet vicinity temperature of 200 ° C. to obtain a strand.

  The strand was quickly cooled in a cooling tank and then cut with a cutter to obtain a pellet-shaped resin composition having a length of 2 to 4 mm.

  The resin composition was dried by heating at 80 ° C. for 4 hours in a dehumidifying dryer, and then a 100-ton injection molding machine and an ISO-compliant test piece mold (color plate, 60 mm × 60 mm × 2 mm, 2 The cylinder temperature was set to 230 ° C. near the head and 220 ° C. near the material inlet, and the mold temperature was set to 70 ° C. and injection molding was performed to obtain a molded product.

[Evaluation of crystallization of polylactic acid]
Polylactic acid A to E used in each Example and Comparative Example was heated at 100 ° C. for 2 hours. Differential scanning calorimetry (DSC) of polylactic acid after heating was performed. The result is shown in FIG. In the figure, A represents the result for polylactic acid A, B represents the result for polylactic acid B, C represents the result for polylactic acid C, D represents the result for polylactic acid D, and E represents the result for polylactic acid E. The results are shown respectively. As shown in this result, in polylactic acid D and polylactic acid E, an endothermic peak (symbol P in the figure) due to melting was observed around 160 ° C., whereas in polylactic acid A to C, such an endothermic peak was I was not able to admit. Thereby, it was confirmed that polylactic acid D and polylactic acid E were crystallized by heating, whereas polylactic acids A to C were not crystallized even when heated.

[Molding cycle evaluation]
For each example and comparative example, a single-point gate mold was used during injection molding of the resin composition, and the dimensions of the molded product were 60 mm × 60 mm × 2 mm. The mold temperature during injection molding was set to 70 ° C. In this case, after the injection of the resin composition into the mold, the holding time (cooling time) required until the molded product can be taken out from the mold without deformation is measured, and this is measured in the molding cycle. It was used as an index.

[Appearance evaluation]
For each example and comparative example, a two-point gate mold was used during the injection molding of the resin composition, and the dimensions of the molded product were 60 mm × 60 mm × 1 mm. In this case, the presence or absence of welds at the center of the molded product was confirmed. In each example and comparative example, 100 samples were tested and evaluated by the number of samples (number of defects) in which welds or flow marks were recognized.

[Thermal stability]
In each Example and Comparative Example, injection molding was performed continuously for 200 shots in obtaining a molded product. In this case, the number of molded products in which dirt was observed on the surface was confirmed, and this was used as an index of thermal stability.

[Impact resistance evaluation]
The notched Charpy impact value of the molded product obtained in each example and comparative example was measured according to ISO 179.

[Heat resistance evaluation]
The deflection temperature under load of the molded article in each example and comparative example was measured according to ISO 75-1 and 75-2. The measurement load was 0.45 MPa.

[Durability evaluation]
After the molded products obtained in each Example and Comparative Example were exposed to an atmosphere of 60 ° C. and 95% RH, the tensile strength of the molded products was measured according to ISO 179. By performing this test with varying exposure times, the shortest exposure time at which the tensile strength of the molded article after exposure reaches 90% or less of the tensile strength of the molded article before exposure is identified and this is determined as the durability. It was used as an index.

[Dimensional stability evaluation]
The mold shrinkage was calculated by the following equation by comparing the dimension (a) of the mold used for molding of each Example and Comparative Example with the dimension (b) of the molded product.

{(B−a) / b} × 100 (%)
[Appearance after 80 ° C treatment]
The molded article was subjected to a treatment for 48 hours in an atmosphere at 80 ° C. The appearances of the molded product before treatment and the molded product after treatment were visually observed and compared.

  As a result, the case where no change was observed in the appearance was evaluated as ◯, and the case where whitening occurred on the surface of the molded body after the treatment was evaluated as ×.

[Post-shrinkage]
The molded article was subjected to a treatment for 48 hours in an atmosphere at 80 ° C. From the dimension (a) of the molded product before the treatment and the dimension (b) of the molded product after the treatment, the molding shrinkage rate was calculated by the following formula.

{(B−a) / b} × 100 (%)
[Evaluation results]
The result of the above evaluation test is shown in the following table together with the blending composition in each example and comparative example. As shown in the results below, in each Example, an injection molded product having a small post-shrinkage and a small thermal shrinkage with time was obtained although the molding cycle was short.

Details of each component shown in Table 1 are as follows.
Polylactic acid A: Polylactic acid A obtained in Production Example, D-lactic acid unit ratio 11.6 mol%, and molecular weight distribution has only one peak.
Polylactic acid B: Polylactic acid B obtained in Production Example, D-lactic acid unit ratio 8.6 mol%, molecular weight distribution has only one peak.
Polylactic acid C: manufactured by Nature Works LLC, trade name: NatureWorks 4060D, D-lactic acid unit ratio: 12 mol%, molecular weight distribution has three peaks.
-Polylactic acid D: manufactured by Zhejiang Haisei Biological Materials Co., Ltd., trade name REVODE101, D-lactic acid unit ratio of 5 mol%.
Polylactic acid E: manufactured by Zhejiang Haisho Biological Materials Co., Ltd., trade name REVODE110, 3 mol% of D-lactic acid unit.
ABS resin A: Acrylonitrile unit ratio 23 mass%, styrene unit ratio 60 mass%, butadiene unit ratio 17.5 mass%, synthetic product by emulsion polymerization, average particle size 0.30 μm.
ABS resin B: 23% by mass of acrylonitrile unit ratio, 60% by mass of styrene unit, 17.5% by mass of butadiene unit, synthetic product by emulsion polymerization, mixed product having average particle diameters of 0.30 μm and 0.1 μm.
ABS resin C: Acrylonitrile unit ratio 23 mass%, styrene unit ratio 62 mass%, butadiene unit ratio 14.5 mass%, synthetic product by emulsion polymerization, average particle size 0.30 μm.
ABS resin D: acrylonitrile unit ratio 20.5% by mass, styrene unit ratio 69.0% by mass, butadiene unit ratio 10.5% by mass, synthetic product by bulk polymerization, average particle size 0.46 μm.
PMMA1: Polymethylmethacrylate, melt flow rate (230 ° C., 3.8 kg) defined by ISO ASTM D1238, 16 g / 10 min, weight average molecular weight 70,000, load deflection temperature defined by ISO 306, 78 ° C.
PMMA 2: Polymethylmethacrylate, melt flow rate (230 ° C., 3.8 kg) defined by ISO ASTM D1238, 8.0 g / 10 min, weight average molecular weight 80,000, load deflection temperature defined by ISO 306, 82 ° C.
PMMA3: Polymethyl methacrylate, melt flow rate (230 ° C., 3.8 kg) defined by ISO ASTM D1238, 1.8 g / 10 minutes, weight average molecular weight 100,000, load deflection temperature defined by ISO 306, 87 ° C.
-Carbodiimide compound A: Poly (4,4'-dicyclohexylmethanecarbodiimide).
-Carbodiimide compound B: Diisopropylphenylcarbodiimide.
-Elastomer: Copolymer of alkyl methacrylate and alkyl acrylate, trade name Metabrene P530A manufactured by Mitsubishi Rayon Co., Ltd.
Core shell rubber: Trade name Metabrene S2200 manufactured by Mitsubishi Rayon Co., Ltd.

Claims (20)

Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
The ratio of the polylactic acid is in the range of 8 to 15 % by mass, the ratio of the polymethyl methacrylate resin is in the range of 1 to 17% by mass,
A polylactic acid resin composition, wherein the polylactic acid contains D-lactic acid units in a proportion of 8 to 15 mol%.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 8% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 3% by mass,
  A polylactic acid resin composition, wherein the polylactic acid contains D-lactic acid units in a proportion of 8 to 15 mol%.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 40% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 17% by mass,
  The polylactic acid contains D-lactic acid units in a proportion of 8 to 15 mol%,
  A polylactic acid resin composition further comprising a copolymer of an alkyl methacrylate and an alkyl acrylate.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 40% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 17% by mass,
  The polylactic acid contains D-lactic acid units in a proportion of 8 to 15 mol%,
  A polylactic acid resin composition further containing a core-shell rubber. Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
The ratio of the polylactic acid is in the range of 8 to 15 % by mass, the ratio of the polymethyl methacrylate resin is in the range of 1 to 17% by mass,
A polylactic acid resin composition, wherein the polylactic acid is polylactic acid that does not crystallize even when heated at 100 ° C. for 2 hours.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 8% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 3% by mass,
  A polylactic acid resin composition, wherein the polylactic acid is polylactic acid that does not crystallize even when heated at 100 ° C. for 2 hours.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 40% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 17% by mass,
  The polylactic acid is a polylactic acid that does not crystallize even when heated at 100 ° C. for 2 hours,
  A polylactic acid resin composition further comprising a copolymer of an alkyl methacrylate and an alkyl acrylate.   Containing polylactic acid, polymethyl methacrylate resin, and ABS resin,
  The ratio of the polylactic acid is in the range of 3 to 40% by mass, the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 17% by mass,
  The polylactic acid is a polylactic acid that does not crystallize even when heated at 100 ° C. for 2 hours,
  A polylactic acid resin composition further containing a core-shell rubber. The ratio of the said polylactic acid is the range of 5-40 mass%, The polylactic acid resin composition as described in any one of Claim 3, 4, 7, 8 . The polylactic acid resin composition according to any one of claims 1 , 3, 4, 5, 7 , and 8 , wherein a ratio of the polymethyl methacrylate resin is in a range of 2 to 17% by mass. The ratio of the polylactic acid is in the range of 23 to 35% by mass,
The polylactic acid resin composition according to any one of claims 3, 4, 7, and 8, wherein a ratio of the polymethyl methacrylate resin is in a range of 3 to 17% by mass. The ratio of the polylactic acid is in the range of 8 to 15% by mass,
The polylactic acid resin composition according to any one of claims 3, 4, 7, and 8, wherein a ratio of the polymethyl methacrylate resin is in a range of 1 to 17% by mass. The ratio of the polylactic acid is in the range of 3 to 8% by mass,
The polylactic acid resin composition according to any one of claims 3, 4, 7, and 8, wherein the ratio of the polymethyl methacrylate resin is in the range of 0.5 to 3 mass%. The polylactic acid according to any one of claims 1 to 13 , wherein a content of the ABS resin is 50% by mass or more based on a total amount of the polylactic acid, the polymethyl methacrylate resin, and the ABS resin. Resin composition. The ratio of the styrene unit which comprises the said ABS resin is the range of 55-70 mass%, and the ratio of a butadiene unit is the range of 8-23 mass%, The polylactic acid resin composition as described in any one of Claims 1 thru | or 14 object. The polylactic acid resin composition according to any one of claims 1 to 15 , further comprising a carbodiimide compound. The polylactic acid resin composition according to any one of claims 1, 2 , 4 , 5 , 6 , and 8 , further comprising a copolymer of an alkyl methacrylate and an alkyl acrylate. The polylactic acid resin composition according to any one of claims 1, 2 , 3 , 5 , 6 , and 7 , further containing a core-shell rubber. The manufacturing method of the injection molded product which prepares the polylactic acid resin composition as described in any one of Claims 1 thru | or 18 , and injects the said polylactic acid resin composition. An injection molded product formed by injection molding the polylactic acid resin composition according to any one of claims 1 to 18 .

Images