JP4596125B2 - Polylactic acid resin composition and molded article using the same - Google Patents

Description

  The present invention relates to a colored polylactic acid resin composition and a molded article using the same.

  When plastic is used as a molding material, it is routinely performed to disperse and color the pigment in order to enhance its design. However, even when trying to disperse pigments in poly-L lactic acid resin, which is going to be used as an environmentally friendly material in recent years, it is difficult to disperse and color irregularities of molded products are likely to occur. Therefore, there is a prescription that can disperse pigments uniformly. It was sought after. In such a case, it is generally colored by preparing a resin composition called a master batch in which a pigment is dispersed in a polylactic acid resin at a high concentration in advance, and blending and molding this master batch in a small amount to a polylactic acid resin. A technique for producing a molded product is often used. However, even when trying to make a master batch of poly L lactic acid resin, it is difficult to uniformly disperse even if it is simply melt-kneaded using a well-known twin screw extruder or the like. Even when blended with poly-L lactic acid and melt-molded using this, color unevenness of the molded product tends to occur.

  For example, Patent Document 1 discloses a technique in which a masterbatch made of polycaprolactone and a pigment is pre-manufactured in a biodegradable resin, this is mixed with an aliphatic polyester, pelletized, and further injection molded. Excluding the process of kneading and pelletizing, trying to disperse pigments with very fine particles, or trying to disperse a large amount of pigments may result in uneven color and poor gloss, and adjustment of injection molding conditions It was difficult to improve.

  As described above, a resin composition and a pigment master batch suitable for a melt-colored molded product of a polylactic acid resin have not yet been found.

Japanese Patent Laid-Open No. 10-268573

  An object of the present invention is to obtain a resin composition that is excellent in pigment dispersibility and greatly improved in production efficiency when producing a polylactic acid molded article.

  In order to solve the above problems, the present inventors have found that the following polylactic acid resin composition is particularly excellent in pigment dispersibility in a melt-molded product, and have reached the present invention. That is, this invention is the following polylactic acid resin-type resin compositions and a molded article using the same.

(1) A polylactic acid resin (A) having a molar ratio (L / D) of L-lactic acid residue to D-lactic acid residue of 100/0 to 90.9 / 10.1 and a number average molecular weight of 50,000 to 300,000. ) 40 to 99.98% by mass, the molar ratio (L / D) of L-lactic acid residue to D-lactic acid residue is 90.8 / 10.2 to 10.2 / 90.8, and the number average molecular weight is A polylactic acid resin composition comprising 0.01 to 60% by mass of a polylactic acid resin (B) of 500 to 49999 and 0.01 to 70% by mass of an inorganic pigment and / or an organic pigment.

(2) The polylactic acid resin composition according to (1), wherein the polylactic acid resin (A) has an acid value of 10 to 80 equivalents / 10 ⁶ g.

(3) The polylactic acid resin composition according to (1) or (2), wherein the acid value of the polylactic acid resin (B) is 10 to 80 equivalents / 10 ⁶ g.

(4) The polylactic acid resin composition according to any one of (1) to (3), wherein the polylactic acid resin (B) includes a polyglycerin segment.

(5) The polylactic acid resin composition according to (4), wherein the degree of polymerization of polyglycerol is in the range of 3-20.

(6) The polylactic acid resin composition according to any one of (1) to (5), wherein the polylactic acid resin (B) has a sulfonic acid metal base.

(7) The polylactic acid resin composition according to (6), wherein the concentration of sulfur atoms derived from the sulfonic acid metal base is 2500 ppm or less.

(8) A molded article using the polylactic acid resin composition according to any one of (1) to (7).

  The present invention can suppress color unevenness and surface gloss reduction of a colored polylactic acid molded product, and further increase the production efficiency of the molded product.

  The polylactic acid resin composition of the present invention comprises polylactic acid (A), polylactic acid (B), and a pigment as essential components. Hereinafter, the best mode will be described in order.

  The polylactic acid (A) used in the present invention preferably has a molar ratio (L / D) of L-lactic acid residue to D-lactic acid residue of 100/0 to 90.9 / 10.1. A preferable molar ratio is 100/0 to 93/7, and a more preferable molar ratio is 99.5 to 94/6. Polylactic acid (A) is an indispensable component for maintaining heat resistance as a molded product. When the above molar ratio is deviated, the heat resistance of the resin is lowered, and for example, there may be a problem of deformation or blocking at high temperatures in summer.

  The polylactic acid (A) used in the present invention preferably has a number average molecular weight of 50,000 to 300,000. If the number average molecular weight is less than 50000, problems may occur in the strength and durability of the molded product. On the other hand, if it exceeds 300,000, the melt viscosity at the time of melting increases, so the dispersibility of the pigment may decrease particularly. Preferably it is 60000-200000. The number average molecular weight referred to in the present invention is a value measured using gel permeation chromatography.

  The compounding ratio of the polylactic acid (A) used in the present invention is 40 to 99.98% by mass. If it is less than 40% by mass, the heat resistance and strength of the molded product may be lowered, and if it exceeds 99.98% by mass, the effect of pigment dispersibility may be diminished. Preferably it is 50-99 mass%, More preferably, it is 60-97 mass%.

The acid value of the polylactic acid (A) used in the present invention is preferably 10 to 80 equivalents / 10 ⁶ g. This is because the pigment dispersibility can be stably exhibited by having an appropriate acid value. That is, if it is less than 10 equivalents / 10 ⁶ g, the effect of pigment dispersibility may be diminished. Conversely, if it exceeds 80 equivalents / 10 ⁶ g, the hydrolyzability may be reduced, and the durability of the molded product may be reduced. .

  The molar ratio (L / D) of the L-lactic acid residue to the D-lactic acid residue of the polylactic acid (B) used in the present invention is preferably 90.8 / 10.2 to 10.2 / 90.8. . This is because, even if the molar ratio of the L-lactic acid residue exceeds 90.8 or less than 10.2, the pigment dispersibility decreases. In the present invention, the main polylactic acid (A) is an L-lactic acid residue, a D-lactic acid residue, and a polylactic acid (B) having a different number average molecular weight, which will be described later, in combination for increasing pigment dispersibility. It is. Although the reason is not clear, it is out of the above range, and when the difference from polylactic acid (A) is eliminated, the pigment dispersibility tends to be lowered.

  The number average molecular weight of the polylactic acid (B) used in the present invention is desirably 500 to 49999. When the number average molecular weight is less than 500, the strength of the molded product may decrease, and the heat resistance tends to decrease. If it exceeds 49999 and there is no difference from polylactic acid (A), the pigment dispersibility tends to decrease. Preferably it is 3000-35000.

  The polylactic acid resin (B) used in the present invention preferably has polyglycerol as its copolymer segment. The polyglycerin used preferably has a degree of polymerization of 3 or more. In the case of glycerin or a dimer of glycerin, a high-molecular-weight lactic acid-based polyester may not be obtained with a sufficient hydroxyl group concentration. On the other hand, if the degree of polymerization exceeds 20, the water resistance of the resin may decrease.

  The polyglycerin segment is contained in the polylactic acid resin (B) in an amount of preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 7% by mass or less, and particularly preferably 5% by mass or less. The lower limit is not particularly defined, but is preferably 0.01% by mass or more, and more preferably 0.02% by mass or more.

  As a method for producing a polylactic acid resin containing polyglycerin as a copolymerization component, for example, a method in which polyglycerin is collectively charged as a polymerization initiator at the time of ring-opening polymerization of lactide and melted in a nitrogen atmosphere to perform ring-opening polymerization, There is a method of depolymerizing molecular weight polylactic acid with polyglycerin and the like, and the former method is preferred in order to stably obtain a polylactic acid resin having a desired reduced viscosity. Moreover, after manufacturing a polylactic acid segment part, you may make it react with polyglycerol, or you may make it combine. As a method for bonding the polylactic acid segment portion to the polyglycerin after production, a method such as a method using a urethane bond or a method using an epoxy group can be used.

The hydroxyl group concentration of the polylactic acid resin (B) used in the present invention is preferably 100 equivalents / 10 ⁶ g or more. If it is less than 100 equivalents / 10 ⁶ g, good pigment dispersibility may not be obtained. If the concentration exceeds 1000 equivalent / 10 ⁶ g, the water resistance of the resin may deteriorate. More preferably, it is 130 equivalents / 10 ⁶ g or more, more preferably 150 equivalents / 10 ⁶ g or more, and the upper limit is more preferably 800 equivalents / 10 ⁶ g or less, still more preferably 600 equivalents / 10 ⁶ g or less, Particularly preferred is 400 equivalents / 10 ⁶ g or less, and most preferred is 300 equivalents / 10 ⁶ g or less.

  The polylactic acid resin (B) used in the present invention preferably has a glass transition temperature of 40 ° C. or higher, and preferably 60 ° C. or lower. By making it within this range, pigment dispersibility is improved. As a method of bringing the glass transition temperature into the range of 40 to 60 ° C., it can be adjusted by adjusting the polyglycerin segment, selecting other copolymerization monomers, and optimizing these amounts.

  In the polylactic acid resin (B) used in the present invention, pigment dispersibility can be remarkably improved by introducing a sulfonic acid metal base into the molecule. In that case, it is preferable to carry out copolymerization in a concentration range where the concentration of sulfur atoms derived from the metal sulfonate group is 2500 ppm or less. More preferably, it is 2000 ppm or less, More preferably, it is 1500 ppm or less. Although a minimum is not specifically limited, If the sulfonic acid metal base is not copolymerized, dispersibility, such as an inorganic pigment and an organic pigment, may fall. Moreover, when the density | concentration of a sulfur atom exceeds 2500 ppm, resin melt viscosity will become high too much, compatibility with a polylactic acid resin (A) may worsen, and also pigment dispersibility may worsen.

  As a method of introducing a sulfonic acid metal salt as the polylactic acid resin (B) used in the present invention, a method of copolymerizing a compound having a sulfonic acid metal base copolymerizable with polylactic acid, and the obtained polylactic acid resin Is a method of sulfonating by a known method. Although it does not specifically limit, the method of copolymerizing the compound with the sulfonic acid metal base copolymerizable with polylactic acid is preferable.

  Preferable compounds having a sulfonic acid metal base include compounds exemplified by the following formula (I) or (II).

(However, R ¹ and R ² are alkyl groups having 20 or less carbon atoms and may be the same or different. M represents Li, Na or K.)

HO—R ³ —SO ₃ M Formula (II)
(However, R ³ represents an alkyl group having 20 or less carbon atoms, and M represents Li, Na, or K.)

  As the lactic acid used as the raw material for the polylactic acid resins (A) and (B), either L-lactic acid or D-lactic acid can be used. Further, L-lactide, D-lactide, and DL-lactide may be used. The number average molecular weight is arbitrarily adjusted by changing the polymerization time and temperature of the polyester, the degree of reduced pressure during polymerization (in the case of reduced pressure polymerization), or changing the amount of polyalcohol component to be copolymerized. be able to. In the present invention, the L / D ratio is determined by measuring the optical rotation of the lactic acid monomer after the methanolysis decomposition of the polylactic acid resin.

  As the ring-opening polymerization catalyst of lactide, ring-opening polymerization catalysts such as tin octylate and aluminum acetylacetonate can be used, and there is no particular limitation.

Polylactic acid resins used in the present invention (B) has a melt viscosity of 200 ° C. to 220 ° C. at a shear rate of ^{1.0 × 10 3 ~1.0 × 10 5} sec -1 is 1.0 to 1.0 × 10 ² dPa · s is desirable. A more preferable melt viscosity is 3.0 to 5.0 × 10 ¹ dPa · s. When the melt viscosity at 200 ° C. to 220 ° C. at a shear rate of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ sec ⁻¹ is lower than 1.0 dPa · s, the heat resistance is insufficient and the fluidity is too high. There is a risk of poor biting into the hopper or the like during the molding process. In addition, when the melt viscosity is higher than 1.0 × 10 ³ dPa · s, the melt viscosity of the resin becomes high, and the fluidity balance between the main resin and the pigment master batch at the time of melt molding is lost, resulting in poor dispersion. There is.

  In addition to lactic acid, the polylactic acid resins (A) and (B) used in the present invention include glycolic acid, malic acid, citric acid, gluconic acid, 3-hydroxybutyric acid and 4-hydroxybutyric acid for controlling other properties. Oxyacids such as, lactones such as caprolactone, valerolactone, butyrolactone, aliphatic dibasic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, ethylene glycol, diethylene glycol, neopentyl glycol, propylene glycol, 1,4 Aliphatic glycols such as butanediol, 1,6-hexanediol, and 1,9-nonanediol can be copolymerized, but are not limited to these copolymer components. Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and orthophthalic acid, and aromatic diols such as bisphenol A and alkylene oxide adducts of bisphenol A may be copolymerized as long as they are in small amounts, but are biodegradable. It is preferably not included from the aspect. The amount of other monomers to be copolymerized is preferably less than 30 mol% when the total amount of lactic acid and other monomers is 100 mol.

  The resin composition of the present invention can be obtained by using a polylactic acid resin and a pigment as essential components and, if necessary, other inorganic particles, organic particles, waxes, and a solvent. In this case, the pigment concentration varies depending on the type of pigment, but is usually 0.01 to 70% by mass in the resin composition. Examples of the pigment include inorganic pigments (carbon black, iron oxide, titanium oxide, calcium carbonate, yellow lead, sub-pencil, bitumen, etc.), organic pigments (nitroso pigments, nitro pigments, azo pigments, phthalocyanine pigments, etc.), and these A mixture is mentioned.

  Examples of inorganic particles include inorganic particles containing metal oxides such as magnesium, calcium, barium, zinc, zirconium, molybdenum, silicon, antimony, and titanium, hydroxides, sulfates, carbonates, and silicates. Is mentioned. Among these inorganic particles, silica is particularly preferable from the viewpoint of environmental addition in soil. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and needle, and is not limited.

  Examples of the organic particles include polymethyl methacrylate resin, polystyrene resin, nylon resin, melamine resin, benzoguanamine resin, phenol resin, urea resin, silicone resin, methacrylate resin, acrylate resin, terpene resin and other polymer particles, or cellulose powder, Examples include nitrocellulose powder, wood powder, waste paper powder, rice husk powder, and starch. The polymer particles can be obtained by a polymerization method such as emulsion polymerization, suspension polymerization, dispersion polymerization, soap-free polymerization, or microsuspension polymerization. The organic particles can be used to such an extent that the characteristics are not impaired and the environmental load is not a problem. The shape of the particles may be any shape such as powder, granule, granule, flat plate, and needle, and is not limited.

  Specific examples of waxes include liquid paraffin, natural paraffin, micro wax, synthetic paraffin, hydrocarbon wax such as polyethylene wax, fatty acid wax such as stearic acid, stearic acid amide, palmitic acid amide, and methylene bisstearo. Fatty acid amide waxes such as amide, ethylenebisstearoamide, oleic acid amide, esylic acid amide, lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, fatty acid polyglycol esters, etc. waxes, cetyl alcohol, stearyl alcohol And other natural waxes such as alcohol waxes, olefin waxes, caster waxes and carnauba waxes, and metal soaps derived from fatty acids having 12 to 30 carbon atoms. Among these waxes, natural waxes such as castor wax and carnauba wax are particularly preferable because of excellent biodegradability. These waxes may be blended for the purpose of a lubricant.

  Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene, xylene, and solvesso, ester solvents such as ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate, and ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone. Alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, Further examples include glycol ether ester solvents obtained by acetylating these, and lactic acid ester solvents such as ethyl lactate and methyl lactate. It is. The solvent can be used alone or in combination of two or more.

  If necessary, the resin composition of the present invention includes an antioxidant, a heat stabilizer, an ultraviolet absorber, a lubricant, a tackifier, a plasticizer, a crosslinking agent, a viscosity modifier, an antistatic agent, a fragrance, an antibacterial agent, and a dispersion. Various additives such as an agent and a polymerization inhibitor can be added as long as the effects of the present invention are not impaired.

  As a method for producing the resin composition of the present invention, a pigment dispersion resin, an inorganic pigment, an organic pigment and the like are ordinary dispersing machines such as a roll mill dispersing machine, a sand grind mill dispersing machine, a planetary mixer, a high speed disperser dispersing machine, Using a uniaxial kneader, a biaxial kneader, or the like, temperature conditions and the like according to the resin characteristics can be set and mixed and dispersed.

  Specifically, since it is necessary to mix a polylactic acid resin, an inorganic pigment, an organic pigment, and other compounds in a molten state, a resin having a mixing effect of the melt is required. Preferably, there are a single screw extruder, a twin screw extruder, and the like, but these resins may be mixed sufficiently.

  As the temperature condition at that time, any temperature may be used as long as the polylactic acid resin and inorganic pigment, organic pigment, and other compounds used for extrusion can be melt-flowed. It is considered that the temperature is 350 ° C. or lower, and more preferably 150 ° C. or higher and 300 ° C. or lower. If the temperature is too low, the polymer cannot be fed out or an excessive load is applied to the extruder. Conversely, if the temperature is too high, the polymer may be thermally deteriorated. The discharge amount and other conditions for producing the resin composition can be set by appropriately adjusting to the appropriate conditions of the machine base.

  The resin composition of the present invention is prepared by melting and kneading all the components of the polylactic acid resin (A), polylactic acid resin (B), pigments, and other additives to be added as necessary. It is possible to carry out melt molding using the above, or to melt and knead a part of it first, and blend and mold the remaining components before molding. In particular, a polylactic acid resin (B) and a pigment are used as master pellets, or a polylactic acid resin (B) and a part of the polylactic acid resin (A) and a pigment are used as master pellets. It is preferable to simply mix the pellets of A) (or the remaining polylactic acid resin (A)) with each other and melt-mold them as they are to increase the production efficiency.

  The melt molding method for the polylactic acid resin composition of the present invention is not particularly limited in methods other than injection molding, extrusion molding, and profile extrusion molding. Injection blow molding, direct blow molding, blow compression molding, stretch blow molding , Calender molding, thermoforming (including vacuum and pressure molding), reaction injection molding, foam molding, compression molding, powder molding (including rotation / stretch molding), laminate molding, casting, melt spinning, etc. .

  Since the resin composition of the present invention can efficiently disperse a very high concentration of pigment, it can be expected to be applied to coloring of solvent-soluble or water-dispersed polylactic acid resins.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Synthesis Example a>
DL-lactide 500 parts by mass, ethylene glycol diester of 5-sodiumsulfoisophthalic acid 3.6 parts by mass, and 0.1 part by mass of tin octylate as a ring-opening polymerization catalyst were charged into a four-necked flask. For 1 hour to proceed with ring-opening polymerization, and then the residual lactide was distilled off under reduced pressure to obtain a polylactic acid resin (a) corresponding to the polylactic acid resin (B). The resin properties and composition are shown in Table 1.

<Synthesis Example b>
By charging 250 parts by mass of L-lactide, 250 parts by mass of DL-lactide, 1 part by mass of lactic acid and 0.5 parts by mass of aluminum acetylacetonate into a four-necked flask and heating and melting at 180 ° C. for 3 hours in a nitrogen atmosphere. The ring-opening polymerization was advanced, and then the residual lactide was distilled off under reduced pressure to obtain a polylactic acid resin (b) corresponding to the polylactic acid resin (B). The resin properties and composition are shown in Table 1.

<Synthesis Example c>
250 parts by mass of L-lactide, 250 parts by mass of DL-lactide, 75 parts by mass of caprolactone and 0.125 parts by mass of tin octylate are added to a four-necked flask and heated and melted at 190 ° C. for 20 minutes in a nitrogen atmosphere. The ring polymerization was advanced, and then the residual lactide and caprolactone were distilled off under reduced pressure to obtain a polylactic acid resin (c) corresponding to the polylactic acid resin (B). The resin properties and composition are shown in Table 1.

<Synthesis Example d>
250 parts by mass of L-lactide, 250 parts by mass of DL-lactide, 13 parts by mass of polyglycerin having a polymerization degree of 10 (Daicel Chemical PGL10: hydroxyl group concentration 850 mgKOH / g) and 0.5 parts by mass of aluminum acetylacetonate in a four-necked flask The ring-opening polymerization was advanced by charging and heating and melting at 180 ° C. for 3 hours under a nitrogen atmosphere, and then the residual lactide was distilled off under reduced pressure to obtain a polylactic acid resin (d) corresponding to the polylactic acid resin (B). . The resin properties and composition are shown in Table 1.

<Synthesis Example e>
480 parts by mass of L-lactide, 20 parts by mass of DL-lactide, 0.5 parts by mass of tin octylate were charged into a four-necked flask, and the ring-opening polymerization was advanced by heating and melting at 180 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, residual lactide was distilled off under reduced pressure to obtain a polylactic acid resin (e) corresponding to the polylactic acid resin (A). The resin properties and composition are shown in Table 1.

<Measurement method of resin characteristic value>
The characteristic value of the resin was measured by the following method. The results are shown in Table 1.

(1) Resin composition Using a 200 MHz nuclear magnetic resonance spectrometer, lactic acid residues of polylactic acid polyester and other components were quantified.

(2) Number average molecular weight Using Hitachi high performance liquid chromatograph LaChrom D-7000 manufactured by Hitachi, Ltd., it was measured at a temperature of 30 ° C. using chloroform as a solvent. From the measurement data, polystyrene conversion was performed to obtain the number average molecular weight. The column used was Showa Denko Shodex KF series.

(3) Melt viscosity The melt viscosity of 200-230 degreeC of polylactic acid resin was measured with the Toyo Seiki capillograph apparatus. The data on the relationship between the shear rate and the melt viscosity was organized.

(4) Glass transition temperature 5 mg of sample was placed in an aluminum sample pan and sealed, and the temperature was increased to 200 ° C. using a differential scanning calorimeter (DSC) DSC-220 manufactured by Seiko Instruments Inc. Measured in minutes. The glass transition temperature was determined by the temperature at the intersection of the base line extension below the glass transition temperature and the tangent that indicates the maximum slope at the transition.

(5) Hydroxyl concentration After the polylactic acid resin is dissolved in toluene, water is removed by azeotropy with water, and then excess phenyl isocyanate is added to react the resin hydroxyl group. The unreacted phenyl isocyanate is then reacted with excess diethylamine and the amount of unreacted diethylamine is titrated with acid. The amount of reactive amine is calculated from the measured value, and the amount of unreacted isocyanate and the amount of reactive isocyanate are calculated from the amount of reactive amine. The amount of reactive isocyanate was calculated as the resin hydroxyl group concentration.

(6) Sulfur atom concentration in sulfonic acid metal base It calculated | required from the sulfur atom concentration which is a metal component. That is, 0.1 g of a sample was carbonized and dissolved in an acid, and then obtained by atomic absorption analysis.

(7) Measurement of Acid Value 0.8 g of polylactic acid resin was dissolved in 20 ml of chloroform / methanol (3/1), and titrated with 0.1N sodium methoxide methanol solution using phenolphthalein as an indicator. equivalents per ⁶ g of (eq / 10 ⁶ g) was obtained.

<Example 1>
80 parts by mass of polylactic acid resin (a), 10 parts by mass of carbon black, and 10 parts by mass of titanium oxide were mixed, and the mixture was set to an extruder (L / D = 30, rotation speed 30 rpm, total barrel temperature 200 ° C.). A pigment master batch was obtained by melt-kneading with a screw diameter of 20 mm, full flight, compression ratio of 2.0), extruding into a string from a nozzle, and cutting into pellets by cutting with a cutter in water.

  Next, 5 parts by mass of the pigment master batch obtained by kneading and 95 parts by mass of the polylactic acid resin (e) were mixed, and the mixture was an extruder (L / D) set at a rotation speed of 30 rpm and a total barrel temperature of 200 ° C. = 30, screw diameter = 20 mm, full flight, compression ratio 2.0), the mixture was extruded into a string from a nozzle, cut into a pellet after passing through water and then pelletized by molding.

Using the colored pellets for molding obtained here, with an injection molding machine (Toshiba IS-100E: mold clamping force 100 tons) at a cylinder temperature of 200 ° C., a mold temperature of 30 ° C., and a back pressure of 20 kg / cm ² , An ISO75 standard test piece was prepared. Using this, the pigment dispersion state, presence / absence of color unevenness, and gloss state were determined using the following indices. The evaluation results are shown in Table 2.

Pigment dispersion state: ISO75 Dumbbell test piece ○: Pigment dispersion state good Δ: Pigment dispersion failure of 2 mm or less is small in dumbbell test piece ×: Pigment dispersion failure larger than 2 mm is many in dumbbell test piece

Presence / absence of color irregularity: Press-molded into a 1 mm thick flat plate, and visually judged the degree of color irregularity.
○: No color unevenness ×: Color unevenness

  Also, the cylinder temperature was set to 200 ° C., a die lip for producing the molded product shown in FIG. 1 was attached to a single screw extruder (L / D = 25, full flight screw, screw diameter 65 mm), and then the tip of the cooling water tank A sizing mold for determining the final dimensions of the profile extruded product was attached to the molded product, and the molded product was molded by a profile extrusion molding equipment equipped with a take-up machine via a water tank, and the surface smoothness of the molded product was evaluated.

Surface smoothness: The outer surface unevenness state of the molded product was measured using an ultra-deep surface shape measuring microscope (VK-8500 manufactured by Keyence), and the following evaluation was performed.
○: Maximum height of uneven surface is less than 100 μm Δ: Maximum height of uneven surface is 100 μm or more and less than 200 μm ×: Maximum height of uneven surface is 200 μm or more

<Example 2>
21 parts by mass of polylactic acid resin (a), 78 parts by mass of polylactic acid resin (e), 0.5 parts by mass of carbon black, and 0.5 parts by mass of titanium oxide were mixed. Melt and knead with an extruder (L / D = 30, screw diameter = 20 mm, full flight, compression ratio 2.0) set at 200 ° C., extrude into a string from a nozzle, cut through a water cutter and then pelletized A resin composition was obtained.
Next, an ISO75 standard test piece was produced with an injection molding machine (Toshiba IS-100E: mold clamping force 100 tons) at a cylinder temperature of 200 ° C., a mold temperature of 30 ° C., and a back pressure of 20 kg / cm ² . Using this, the pigment dispersion state, presence / absence of color unevenness, and gloss state were similarly determined.

  Also, the above resin composition pellets are put into a hopper, the cylinder temperature is set to 200 ° C., and the molded product shown in FIG. 1 is manufactured with a single screw extruder (L / D = 25, full flight screw, screw diameter 65 mm). Attach a die lip to the cooling water tank, and then attach a sizing die that determines the final dimensions of the profile extrusion product to the end of the cooling water tank. The surface smoothness was evaluated. The evaluation results are shown in Table 2.

<Example 3>
80 parts by mass of polylactic acid resin (a), 10 parts by mass of carbon black, and 10 parts by mass of titanium oxide were mixed, and the mixture was set to an extruder (L / D = 30, rotation speed 30 rpm, total barrel temperature 200 ° C.). The mixture was melt-kneaded with a screw diameter of 20 mm, full flight, and a compression ratio of 2.0), extruded from a nozzle in a string shape, passed through water, cut with a cutter, and pelletized to obtain a pigment master batch.

  Next, 5 parts by mass of the pigment masterbatch obtained by kneading and 95 parts by mass of the polylactic acid resin (e) were mixed with each other and evaluated by injection molding and profile extrusion molding as they were in the same manner as in Example 1. . The evaluation results are shown in Table 2.

<Example 4>
40 parts by mass of polylactic acid resin (a), 40 parts by mass of polylactic acid resin (e), 10 parts by mass of carbon black, and 10 parts by mass of titanium oxide were mixed, and the mixture was set at a rotation speed of 30 rpm and a total barrel temperature of 250 ° C. Pigment master batch that was melt-kneaded with an extruded extruder (L / D = 30, screw diameter = 20 mm, full flight, compression ratio 2.0), extruded into a string from a nozzle, cut through a cutter after passing through water, and pelletized Got.

  Next, 5 parts by mass of the pigment masterbatch obtained by kneading and 95 parts by mass of the polylactic acid resin (e) were mixed with each other and evaluated by injection molding and profile extrusion molding as they were in the same manner as in Example 1. . The evaluation results are shown in Table 2.

<Examples 5 to 9, Comparative Example 1>
Various evaluations were performed by the same methods as in Example 2 using the raw materials listed in Table 2. The results are shown in Table 2.

<Comparative example 2>
80 parts by mass of polylactic acid resin (e), 10 parts by mass of carbon black, and 10 parts by mass of titanium oxide were mixed, and the mixture was set to an extruder (L / D = 30, The mixture was melt-kneaded with a screw diameter of 20 mm, full flight, and a compression ratio of 2.0), extruded from a nozzle into a string shape, passed through water, cut with a cutter, and pelletized to obtain a pigment master batch.

Next, 5 parts by mass of the pigment master batch obtained by kneading and 95 parts by mass of the polylactic acid resin (e) were mixed, and the mixture was an extruder (L / D) set at a rotation speed of 30 rpm and a total barrel temperature of 200 ° C. = 30, screw diameter = 20 mm, full flight, compression ratio 2.0), the mixture was extruded into a string from a nozzle, cut into a pellet after passing through water and then pelletized by molding.
Using the colored pellets, molding was performed in the same manner as in Example 1 and evaluated. The evaluation results are shown in Table 2.

<Comparative Example 3>
500 parts by mass of caprolactone and 0.125 parts by mass of tin octylate are added to a four-necked flask, and the mixture is heated and melted at 190 ° C. for 30 minutes in a nitrogen atmosphere to proceed with ring-opening polymerization. As a result, a polycaprolactone resin (f) was obtained. The number average molecular weight of the polycaprolactone resin (f) was 8300.
Next, 78 parts by mass of polylactic acid resin (e), 12 parts by mass of caprolactone resin (f), 5 parts by mass of carbon black, and 5 parts by mass of titanium oxide were mixed, and the mixture was set at a rotation speed of 30 rpm and a total barrel temperature of 200 ° C. The resin composition was melt-kneaded with an extruded machine (L / D = 30, screw diameter = 20 mm, full flight, compression ratio 2.0), extruded from a nozzle into a string shape, passed through water, cut by a cutter and pelletized. Got.
Using this resin composition, injection molding and profile extrusion molding were performed in the same manner as in Example 1, and various evaluations were performed. The evaluation results are shown in Table 2.

  As can be seen from Table 2, Examples 1 to 9 have achieved pigment dispersibility, prevention of uneven color, and glossiness from the production of injection molded specimens, and can improve the surface smoothness of the shaped extrusions. Yes.

  On the other hand, Comparative Examples 1 to 3 do not contain the polylactic acid resin (B), and thus are outside the scope of the present invention. All were inferior in pigment dispersibility, color unevenness, and surface smoothness.

  The present invention can suppress color unevenness and surface gloss reduction of a colored polylactic acid molded product, and further increase the production efficiency of the molded product.

It is sectional drawing of a profile extrusion molded product.

Claims (6)

Molar ratio (L / D) Number average molecular weight be 100 / 0-94 / 6 of L- lactic acid residue and D- lactic acid residues Ri from 60,000 to 300,000 der, acid value 10 to 80 equivalent / 10 ⁶ g der Ru polylactic acid resin (A) 40 to 99.98 wt%,
The molar ratio of L-lactic acid residue to D-lactic acid residue (L / D) is 90.8 / 10.2 to 50/50 , the number average molecular weight is 3000 to 35000 , and the acid value is 10 to 80 equivalents. / 10 ⁶ g, and the melt viscosity at 200 ° C. to 220 ° C. at a shear rate of 1.0 × 10 ^{3 to} 1.0 × 10 ⁵ sec ⁻¹ is 1.0 to 1.0 × 10 ² dPa · s. 0.01 to 60% by mass of polylactic acid resin (B),
0.01 to 70% by mass of an inorganic pigment and / or an organic pigment ,
A colored polylactic acid resin composition for melt molding comprising: The polylactic acid resin composition according to claim 1, wherein the polylactic acid resin (B) contains a polyglycerin segment. The polylactic acid resin composition according to claim 2 , wherein the degree of polymerization of polyglycerol is in the range of 3-20. The polylactic acid resin composition according to any one of claims 1 to 3 , wherein the polylactic acid resin (B) has a sulfonic acid metal base introduced into the molecule . The polylactic acid resin composition according to claim 4 , wherein the concentration of sulfur atoms derived from the sulfonic acid metal base is 2500 ppm or less. A molded article using the polylactic acid resin composition according to any one of claims 1 to 5 .