JP2006291214A - Injection-molded article, process for producing the same, and pellet used for injection molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection-molded article mainly comprising a plant-derived raw material, having heat resistance and exhibiting a rapid crystallization speed. <P>SOLUTION: This injection-molded article is obtained by the use of a resin composition comprising a lactic acid-based resin (A) and a natural fiber (B) comprising 40-60 mass% of cellulose and 10-30 mass% of lignin, where the mass ratio of the lactic acid-based resin (A) to the natural fiber (B) is 99:1 to 70:30, and the lactic acid based resin (A) has the ratio of an L-lactic acid to a D-lactic acid of 100:0 to 97:3, or 0:100 to 3:97. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an injection-molded article comprising a plant-derived raw material as a main component, a high crystallization rate, and heat resistance.

  Plastics are now widely used in every field such as daily life and industry, and the annual production of plastics around the world has reached about 100 million tons. Most of the plastic produced is discarded after use, and this has been recognized as one of the causes of the global environment. Therefore, there is a demand for materials that do not adversely affect the global environment even when discarded.

  In addition, since petroleum, which is a raw material for ordinary plastics, is a depleting resource, the use of renewable resources is required. For example, plant-derived plastics can be obtained by using renewable non-depleting resources, so it is possible to conserve petroleum-depleting resources such as oil, and after use, they are biodegraded and return to nature. Recyclable.

  Among plant raw material plastics, lactic acid resins are lactic acid obtained by fermentation of starch, can be mass-produced by chemical engineering, and are excellent in transparency, rigidity, heat resistance and the like. Therefore, in particular, lactic acid-based resins are attracting attention as an alternative material for polystyrene and polyethylene terephthalate in the field of injection molding for film packaging materials, home appliances, OA equipment, automobile parts, and the like.

  An injection molded body used for applications such as home appliances, OA equipment, and automobile parts is required to have heat resistance to prevent fire. However, lactic acid-based resins have a low glass transition temperature and are poor in heat resistance as compared with ABS resins, filler-filled polypropylene resins, and the like. For this reason, it has been difficult to use in applications such as home appliances, OA equipment, and automobile parts.

In order to improve the heat resistance of the biodegradable resin, a composite material in which the biodegradable resin and natural fiber are combined is known. For example, Japanese Patent Laid-Open No. 9-169897 discloses a biodegradable fiber reinforced molded body in which natural fibers and the like are bonded to an aliphatic polyester resin in a dispersed state, and Japanese Patent Laid-Open No. 2002-146219. Further, it is disclosed that a natural fiber and a particulate biodegradable resin are mixed and a biodegradable composite material is produced by hot press molding.
However, these composite materials still have insufficient heat resistance, which may cause problems in practical use.

JP-A-9-169897 JP 2002-146219 A

  The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an injection-molded article having a plant-derived raw material as a main component, excellent heat resistance, and high crystallization speed. It is in.

As a result of intensive studies in view of such a current situation, the present inventors have completed the present invention with high effects.
The injection-molded article of the present invention is a resin composition comprising (A) a lactic acid resin and (B) natural fibers containing 40% by mass to 60% by mass of cellulose and 10% by mass to 30% by mass of lignin. And (A) lactic acid-based resin and (B) natural fiber in a mass ratio of 99: 1 to 70:30, and (A) the lactic acid-based resin is L lactic acid: D lactic acid = The resin composition is 100: 0 to 97: 3 or L lactic acid: D lactic acid = 0: 100 to 3:97.

Here, the crystallization calorific peak temperature (Tc) of the resin composition is preferably 100 ° C. or higher.
Further, the deflection temperature under load of the injection molded body can be 133 ° C. or higher.

The injection-molded article of the present invention can be formed after kneading (A) a coating obtained by impregnating (immersing) a natural fiber in (A) a lactic acid resin and (A) a lactic acid resin. .
Alternatively, it may be formed after kneading (A) a lactic acid resin-impregnated (B) natural fiber impregnated (immersed) (B) natural fiber with the lactic acid resin.

  The pellet of the present invention is a resin composition comprising (A) a lactic acid resin and (B) natural fibers containing 40% by mass to 60% by mass of cellulose and 10% by mass to 30% by mass of lignin. , (A) lactic acid-based resin and (B) natural fiber in a mass ratio of 99: 1 to 70:30, and (A) the lactic acid-based resin is L lactic acid: D lactic acid = 100: The resin composition is 0 to 97: 3 or L lactic acid: D lactic acid = 0: 100 to 3:97.

  Here, the components of the pellet can be uniformly dispersed in appearance.

  The pellet of the present invention can be formed by kneading (A) a lactic acid resin with a coating obtained by impregnating (immersing) the (B) natural fiber in (A) a lactic acid resin by pultrusion molding. .

  The method for producing pellets of the present invention includes (B) a lactic acid resin further obtained by (B) impregnating (immersing) natural fibers in (A) lactic acid resin, and (A) lactic acid resin. And a kneading step.

  Another method for producing the pellets of the present invention includes: (B) impregnating (immersing) natural fibers in (A) lactic acid-based resin by pultrusion, and then forming a coated pellet; (A) adding a lactic acid resin and kneading.

  The method for producing an injection-molded article of the present invention comprises a step of forming a coating pellet after impregnating (immersing) (B) natural fibers in (A) a lactic acid-based resin by pultrusion molding; (A) A step of adding a lactic acid-based resin and kneading to form pellets, and a step of forming an injection-molded body using the pellets are provided.

  According to the present invention, by using a resin composition in which a natural fiber containing a predetermined amount of lignin is mixed with a lactic acid-based resin or the like, a plant-derived raw material is a main component, heat resistance is high, and crystallization speed is high. An early injection molded body can be provided.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described below.
The injection-molded article of the present invention comprises a resin composition comprising (A) a lactic acid resin and (B) natural fibers containing 40% to 60% by mass of cellulose and 10% to 30% by mass of lignin. Use. However, it is necessary to contain (A) lactic acid resin and (B) natural fiber in a mass ratio of (A) lactic acid resin: (B) natural fiber = 99: 1 to 70:30. , 95: 5 to 80:20. (B) If the content of the natural fiber is less than 1% by mass, the effect of improving the heat resistance and the crystallization speed is poor, whereas if it exceeds 30% by mass, the impact resistance of the resulting injection-molded product is reduced. Practical problems occur.

  Examples of natural fibers containing 40% to 60% by weight of cellulose and 10% to 30% by weight of lignin used in the present invention include, for example, 40% to 60% by weight of cellulose and 10% to 30% by weight of lignin. And natural fibers such as kenaf, bamboo, bagasse, etc. By blending natural fibers containing cellulose and lignin as described above, excellent heat resistance can be exhibited by the crystallization promoting effect by cellulose and lignin, and the synergistic effect of the elastic modulus improvement and fiber reinforcement by crystallization. . When cellulose is less than 40% by mass or lignin is less than 10% by mass, the effect of improving heat resistance by fiber reinforcement can be expected, but crystallization cannot be promoted, and practically sufficient heat resistance cannot be obtained. . Further, when the cellulose exceeds 60% by mass, the fiber undergoes thermal degradation in the extruder, causing discoloration and strength reduction. When the lignin exceeds 30% by mass, the low molecular weight product is blown out. Appearance defects occur.

  The (A) lactic acid-based resin used in the present invention is composed of poly (L-lactic acid) having a structural unit of L-lactic acid, poly (D-lactic acid) having a structural unit of D-lactic acid, a structural unit of L-lactic acid, and Poly (DL-lactic acid) which is D-lactic acid, or a mixture thereof. Here, the constituent ratio of D-lactic acid (D-form) and L-lactic acid (L-form) of the lactic acid resin is L-form: D-form = 100: 0 to 97: 3, or L-form: D-form = 0: 100. ~ 3: 97. Outside the range where the composition ratio of the L body and the D body is outside the range, the heat resistance of the molded body is difficult to obtain, and the application may be limited. In consideration of availability, etc., L-form: D-form = 99.5: 0.5 to 97: 3, or L-form: D-form = 0.5: 99.5 to 3:97. It is preferable.

  As a polymerization method for the lactic acid-based resin, known methods such as a condensation polymerization method and a ring-opening polymerization method can be employed. For example, in the condensation polymerization method, L-lactic acid or D-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid resin having an arbitrary composition.

  In the ring-opening polymerization method, a lactic acid-based resin can be obtained from lactide, which is a cyclic dimer of lactic acid, by selecting an appropriate catalyst and using a polymerization regulator as necessary. Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. Accordingly, by mixing and polymerizing, a lactic acid resin having an arbitrary composition and crystallinity can be obtained.

Furthermore, a small amount of a copolymer component can be added as required to improve heat resistance, etc., and as a small amount of the copolymer component, a non-aliphatic dicarboxylic acid such as terephthalic acid and / or ethylene of bisphenol A can be used. Non-aliphatic diols such as oxide adducts can be used.
Furthermore, for the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, or an acid anhydride can be used.

Even if the lactic acid-based resin is a copolymer with other hydroxycarboxylic acid units such as lactic acid and / or α-hydroxycarboxylic acid other than lactic acid, it is a copolymer with an aliphatic diol and / or an aliphatic dicarboxylic acid. It may be a polymer.
As other hydroxycarboxylic acid units, optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid 2-hydroxy-carboxylic acid such as 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxycaproic acid, caprolactone, butyrolactone, valero Examples include lactones such as lactones.

  Examples of the aliphatic diol copolymerized with the lactic acid resin include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  Examples of the structure of the copolymer include a random copolymer, a block copolymer, and a graft copolymer. Any structure may be used, but the block copolymer is particularly effective in terms of impact resistance improvement effect and transparency. preferable. When the polylactic acid segment is A, for example, the diol dicarboxylic acid segment is B, a polymer having transparency and impact resistance can be obtained by forming a typical ABA block copolymer. In this case, the glass transition temperature (Tg) of the B segment is preferably 0 ° C. or less from the viewpoint of the development of impact resistance.

  The lactic acid resin used in the present invention preferably has a weight average molecular weight in the range of 50,000 to 400,000, more preferably 100,000 to 250,000. When the weight average molecular weight of the lactic acid-based resin is smaller than 50,000, practical physical properties such as mechanical properties and heat resistance are hardly expressed. When it is larger than 400,000, the melt viscosity is too high and the molding processability is poor. Sometimes.

  Typical examples of the lactic acid-based resin preferably used in the present invention include “Nature Works” series manufactured by Cargill Dow, and the like.

  In the present invention, an aliphatic polyester and / or an aromatic aliphatic polyester having a glass transition temperature (Tg) of 0 ° C. or lower can be mixed with the lactic acid resin. These mixing amounts are preferably in the range of 5 to 50 parts by mass with respect to 100 parts by mass of the lactic acid resin. Thus, impact resistance can be imparted to the lactic acid resin by mixing an aliphatic polyester or the like having a Tg of 0 ° C. or less. In addition, when the glass transition temperature of the mixed aliphatic polyester exceeds 0 ° C., the impact resistance improving effect becomes poor.

  Examples of the aliphatic polyester having a Tg of 0 ° C. or lower used in the present invention include, for example, an aliphatic polyester excluding a lactic acid resin, for example, an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, and a cyclic polyester Examples include aliphatic polyesters obtained by ring-opening polymerization of lactones.

  As the above “aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid”, one or more of the following aliphatic diols and aliphatic dicarboxylic acids are selected and condensed. Can be obtained. If necessary, a desired polymer (polymer) can be obtained by jumping up with an isocyanate compound, an epoxy compound, or the like. In the present invention, such aliphatic polyester is preferably biodegradable. Examples of the aliphatic diol used here include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like, and examples of the aliphatic dicarboxylic acid include succinic acid. Typical examples include acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid.

  As the above “aliphatic polyester obtained by ring-opening polymerization of cyclic lactone”, one or more kinds of cyclic monomers such as ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like are used. Those obtained by selective polymerization are listed.

  As the aromatic aliphatic polyester used in the present invention, those having crystallinity lowered by introducing an aromatic ring between aliphatic chains can be used. For example, it can be obtained by condensing an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, and an aliphatic diol component.

  Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, and naphthalenedicarboxylic acid. Examples of the aliphatic dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. Is mentioned. Examples of the aliphatic diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Two or more types of aromatic dicarboxylic acid components, aliphatic dicarboxylic acid components, and aliphatic diol components may be used.

  In the present invention, the aromatic dicarboxylic acid component most preferably used is terephthalic acid, the aliphatic dicarboxylic acid component is adipic acid, and the aliphatic diol component is 1,4-butanediol.

  As aliphatic polyesters other than the above lactic acid resins, copolymers of succinic acid, 1,4-butanediol and adipic acid, and as aromatic aliphatic polyesters, copolymers of tetramethylene adipate and terephthalate, polybutylene adipate And a copolymer of terephthalate and the like. As specific examples of aliphatic polyesters and aromatic aliphatic polyesters other than lactic acid-based resins, “Bionole” manufactured by Showa Polymer Co., Ltd., obtained by polymerizing succinic acid, 1,4-butanediol, and adipic acid. ”Series,“ Cell Green ”series manufactured by Daicel Chemical Industries, Ltd. obtained by ring-opening condensation of ε-caprolactone,“ Enpole ”manufactured by Ile Chemical Co., Ltd., Eastman Chemicals as a copolymer of tetramethylene adipate and terephthalate “Estarx Bio” manufactured by BASF Corporation, “Ecoflex F” manufactured by BASF, etc. can be commercially obtained as a copolymer of polybutylene adipate and terephthalate.

  As described above, the resin composition used for forming the injection molded article of the present invention may contain a copolymer of a lactic acid-based resin, a diol and a dicarboxylic acid, etc., an aliphatic polyester other than the lactic acid-based resin, and An aromatic aliphatic polyester may be included.

  In the present invention, it is necessary to mix (A) lactic acid-based resin and (B) natural fiber in a mass ratio within a range of 99: 1 to 70:30. The above copolymer, aliphatic polyester and / or aromatic aliphatic polyester are also considered. That is, when an aliphatic polyester having a glass transition temperature of 0 ° C. or less and / or an aromatic aliphatic polyester is mixed, the mass including these masses becomes the mass of the lactic acid resin, and this mass is (A ) It is necessary to be within the range of the mixing amount of the lactic acid resin.

  In the present invention, it is preferable that the coating obtained by impregnating a natural fiber with a lactic acid resin by pultrusion is further mixed with a lactic acid resin, kneaded, and then subjected to injection molding. Here, it is preferable that the coating obtained by impregnating a natural fiber with a lactic acid resin is pelletized to form a coating pellet. Further, here, it is preferable that the coating pellets and the lactic acid resin are kneaded and then pelletized to form pellets. The pellets are visible to the naked eye as the components are uniformly dispersed. The kneading can be performed by, for example, the same direction twin screw extruder.

By the way, when the injection molded product is stored for a long period of time, it may be hydrolyzed by water vapor in the air or moisture from the outside, resulting in a decrease in mechanical properties.
In the present invention, a hydrolysis inhibitor (C) can be further blended in order to improve the durability of the injection molded article. Here, as for the compounding quantity of a hydrolysis inhibiting agent (C), the total mass of lactic acid-type resin (A) and a natural fiber (B) is 0.1-5.0 mass parts with respect to 100 mass parts. Is preferred. If the addition amount of the hydrolysis inhibitor is 0.1 parts by mass or more and 5.0 parts by mass or less, sufficient durability can be imparted, biodegradability is not impaired, and hydrolysis is not performed. The inhibitor does not bleed out, and appearance defects and deterioration of mechanical properties due to plasticization do not occur.

  Examples of the hydrolysis inhibitor used in the present invention include epoxy compounds, isocyanate compounds, acid anhydrides, oxazoline compounds, melamine compounds, etc. Among them, it is preferable to use carbodiimide compounds.

As the carbodiimide compound used in the present invention, those having a basic structure represented by the following general formula are particularly preferable.

-(N = C = N-R-) n-

However, in the formula, R represents an organic bond unit, and may be, for example, aliphatic, alicyclic or aromatic. n represents an integer of 1 or more, and is usually appropriately determined between 1 and 50. When n is 2 or more, two or more R may be the same or different.

  Specifically, for example, bis (dipropylphenyl) carbodiimide, poly (4,4′-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), poly ( Examples of the carbodiimide compound include diisopropylphenylenecarbodiimide), poly (methyl-diisopropylphenylenecarbodiimide), poly (triisopropylphenylenecarbodiimide), and the like. These carbodiimide compounds may be used alone or in combination of two or more.

The carbodiimide compound used in the present invention is preferably an aromatic carbodiimide compound. Even an aliphatic carbodiimide compound has a sufficient hydrolysis resistance imparting effect, but an aromatic carbodiimide compound can impart hydrolysis resistance more effectively.
Specific examples of the carbodiimide compound include “STABAXOL” manufactured by Rhein Chemie, “Carbodilite” manufactured by Nisshinbo Co., Ltd., and the like.

  In the present invention, additives such as a heat stabilizer, a nucleating agent, an antioxidant, a UV absorber, a light stabilizer, a lubricant, a pigment, a dye, and a plasticizer are prescribed within a range that does not impair the effects of the present invention. Can do.

  In the present invention, the crystallization calorific value peak temperature (Tc) is a value determined by differential scanning calorimetry when a sample is held at 200 ° C. for 2 minutes and then cooled down to 40 ° C. at 10 ° C./min. The temperature at which the chemical peak appears. In the present invention, the crystallization heat amount peak temperature (Tc) of the resin composition forming the injection-molded body is preferably 100 ° C. or higher, and more preferably 110 ° C. or higher. If the crystallization calorie peak temperature is 100 ° C. or higher, the crystallization speed is high, and crystallization can be performed in a short time in the mold during injection molding, and crystallization is performed after taking out from the mold after molding. Even in this case, it can be performed in a short time, and an injection-molded product can be obtained efficiently.

  In the present invention, the deflection temperature under load is preferably 133 ° C. or higher, and more preferably 140 ° C. or higher. If the deflection temperature under load is 133 ° C. or higher, it can be preferably used for daily necessities and food containers where heat resistance is desired, and if it exceeds 140 ° C., it can be suitably used for electric and electronic parts, automobile parts, etc. it can.

  The injection molded product of the present invention preferably has a flexural modulus at 80 ° C. of 800 MPa or more, and more preferably 860 MPa or more. (A) The bending elastic modulus of an injection-molded article is improved by blending an appropriate amount of (B) component, that is, natural fibers containing 40 to 60% by mass of cellulose and 10 to 30% by mass of lignin into the lactic acid-based resin. And can be used for applications requiring heat resistance.

Next, the molding method of the injection molded body of the present invention will be described.
The injection molded article of the present invention is formed by first forming a coated pellet from a material in which a natural fiber is impregnated with a lactic acid resin by pultrusion molding, and the coated pellet, the lactic acid resin, and, if necessary, other These additives and the like are extruded into a strand shape using a twin-screw extruder to produce pellets, and the pellets are again put into an injection molding machine and injection molded. Alternatively, an injection molded article can be obtained by charging a lactic acid resin and natural fiber into a twin screw extruder and directly kneading and injection molding. In the present invention, it is preferable to use the former method, that is, the method of forming a coated pellet by pultrusion and then kneading and molding with a lactic acid resin. By impregnating natural fiber with lactic acid resin by pultrusion molding, poor feed due to high fiber bulk density is alleviated, and dispersibility of natural fiber is further improved when kneading with a twin screw extruder. The effect of improving heat resistance and crystallization speed can be maximized. In addition, since lactic acid-type resin is easy to raise | generate a hydrolysis at the time of melt molding, it is preferable to dry beforehand or pass through a vacuum vent extrusion process.

  As the injection molding method, for example, an injection molding method such as an injection molding method, a gas assist molding method, or an injection compression molding method that is generally employed when molding a thermoplastic resin can be employed. In addition to the above methods, an in-mold molding method, a gas press molding method, a two-color molding method, a sandwich molding method, PUSH-PULL, SCORIM, or the like can also be employed in accordance with other purposes. However, the injection molding method is not limited to these.

  The injection molding apparatus used is a general injection molding machine, gas assist molding machine, injection compression molding machine, etc., molding molds and incidental equipment used in these molding machines, mold temperature control device, raw material drying device Etc. Molding conditions are preferably such that the molten resin temperature is in the range of 170 ° C. to 210 ° C. in order to avoid thermal decomposition of the resin in the injection cylinder.

  When the injection molded body is obtained in an amorphous state, the mold temperature is preferably as low as possible in order to shorten the cooling time of the molding cycle (mold closing to injection to holding pressure to cooling to mold opening to taking out). . In general, the mold temperature is preferably 15 ° C to 55 ° C, and it is also desirable to use a chiller. However, in order to suppress shrinkage, warpage, and deformation of the molded body during post-crystallization, it is advantageous to set the mold temperature on the high temperature side even in this range.

  The molded body obtained by injection molding may be crystallized by heat treatment. Thus, by crystallizing a molded object, the heat resistance of a molded object can further be improved. The crystallization treatment can be performed in the mold during molding and / or after taking out from the mold. From the viewpoint of productivity, when the crystallization speed of the resin composition forming the injection-molded body is low, it is preferable to perform the crystallization treatment after taking out from the mold, while when the crystallization speed is high. May be crystallized in a mold. In the case of crystallizing in the mold, the molten resin is filled in the heated mold and then held in the mold for a certain time. The mold temperature is preferably 80 to 130 ° C, more preferably 90 to 120 ° C, and the cooling time is preferably 1 to 300 seconds, more preferably 5 to 30 seconds. By performing the crystallization treatment within the temperature range and the cooling time, the heat resistance of the injection-molded product can be further improved.

  When the crystallization treatment is performed after taking out the molded body from the mold, the heat treatment temperature is preferably in the range of 60 to 130 ° C, and more preferably in the range of 70 to 90 ° C. When the heat treatment temperature is less than 60 ° C., crystallization may not proceed in the molding step, and when it is higher than 130 ° C., deformation or shrinkage may occur when the molded body is cooled. The heating time is appropriately determined depending on the composition of the resin constituting the injection molded body and the heat treatment temperature. For example, when the heat treatment temperature is 70 ° C., the heat treatment is performed for 15 minutes to 5 hours. When the heat treatment temperature is 130 ° C., the heat treatment is performed for 10 seconds to 30 minutes.

  As a method of crystallization, a method of injection molding using a mold heated to a predetermined temperature in advance and crystallizing in the mold as it is, a method of increasing the temperature of the mold after injection molding and crystallizing in the mold Alternatively, after the injection molded body is taken out of the mold in an amorphous state, it is crystallized with hot air, steam, hot water, far infrared heater, IH heater or the like. During crystallization, the injection-molded body does not have to be fixed. However, in order to prevent deformation of the molded body, it is preferably fixed with a mold, a resin mold or the like. Further, in consideration of productivity, heat treatment can be performed in a packed state.

  As described above, the injection-molded article of the present invention has excellent heat resistance and crystallization speed, and is required for electric and electronic equipment parts, automobile parts, daily necessities, food containers, etc., which require heat resistance. Suitable as an injection-molded product.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples, and various applications are possible without departing from the technical scope of the present invention. In addition, each Example and each comparative example evaluated by the method shown below.

(1) Deflection temperature under load (heat resistance)
Based on Japanese Industrial Standards JIS K-7191, a test piece having a length (L) of 120 mm, a width (W) of 11 mm, and a thickness (t) of 3 mm was prepared. About this test piece, Toyo Seiki Co., Ltd. The deflection temperature under load (HDT) was measured using “S-3M” manufactured by Seisakusho. However, the measurement was performed in the flatwise direction and the bending stress applied to the test piece was 45.1 N / cm ² .

(2) Flexural modulus (rigidity)
Based on Japanese Industrial Standards JIS K-7171, a test piece having a length (L) of 80 mm, a width (W) of 10 mm, and a thickness (t) of 4 mm was prepared, and this test piece was manufactured by Intesco Corporation. The bending elastic modulus at 80 ° C. was measured using a precision universal material testing machine “MODEL2010”.

(3) Crystallization calorific value peak temperature About 10 mg of scaly pieces were cut out from the injection-molded product to prepare test pieces. The test piece was measured for temperature drop based on Japanese Industrial Standard JIS K-7121 using a differential scanning calorimeter “DSC-7” manufactured by PerkinElmer. The injection molded body test piece was melted by heating at 200 ° C. for 2 minutes, and then the temperature was lowered under the condition of 10 ° C./min. The temperature at which the crystallization peak appeared during this temperature lowering process was defined as the crystallization heat amount peak temperature.

Example 1
Nature Works 4032D (L-lactic acid / D-lactic acid = 99/1, weight average molecular weight 200,000) manufactured by Cargill Dow as a lactic acid resin, and kenaf fiber (containing cellulose) as natural fiber The amount was 53 mass%, the lignin content was 18 mass%, and the average diameter was 17 mm). The lactic acid-based resin was supplied to a 30 mmφ single screw extruder manufactured by Silico-Pura Kogyo Co., Ltd., to which a pultrusion crosshead die was connected. On the other hand, the kenaf fiber is passed through the hole of the crosshead die of this single screw extruder, the resin temperature is 180 ° C. and impregnated with lactic acid resin, the resin coating is performed, and after cooling in the water tank, the pellet cutter A coated pellet was made through. The average diameter of the resulting coated pellets was 1.5 mm and the average length was 3 mm. Moreover, the ratio of the kenaf fiber with respect to the lactic acid-type resin in a coating material pellet was (A) lactic acid-type resin: (B) kenaf fiber = 70: 30 (mass%).

Next, the obtained coating pellets and the lactic acid resin (Nature Works 4032D) were mixed in such a ratio that the ratio of the lactic acid resin to the kenaf fiber was (A) lactic acid resin: (B) kenaf fiber = 95: 5 was compounded at 180 ° C. using a 25 mmφ small-sized same-direction twin screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., and formed into a pellet shape. The obtained pellets were injection molded using an injection molding machine “IS50E” (screw diameter 25 mm) manufactured by Toshiba Machine Co., Ltd. to obtain a plate material. The plate materials were L100 mm × W100 mm × t3 mm plate material, L120 mm × W11 mm × t3 mm plate material, L100 mm × W100 mm × t4 mm plate material, and L80 mm × W10 mm × t4 mm plate material. That is, two types of plate materials having different thicknesses were produced. However, main molding conditions are as follows.
1) Temperature conditions: Cylinder temperature (195 ° C) Mold temperature (20 ° C)
2) Injection conditions: Injection pressure (115 MPa) Holding pressure (55 MPa)
3) Measurement conditions: Screw rotation speed (65 rpm) Back pressure (15 MPa)

  The obtained injection-molded body (plate material) was allowed to stand in a baking test apparatus (DKS-5S) manufactured by Daiei Kagaku Seisaku Seisakusho and subjected to heat treatment at 70 ° C. for 3.5 hours to promote crystallization. The obtained injection-molded body (plate material) was subjected to measurement (evaluation) of the deflection temperature under load, the flexural modulus (bending strength), and the crystallization calorific value peak temperature. Moreover, comprehensive evaluation was also performed based on the obtained evaluation. However, the symbol “◎” indicates that it is particularly excellent, the symbol “◯” indicates that all evaluation items are well-balanced and excellent, and the symbol “×” is inferior, This indicates that it cannot be applied to injection molded products that require sufficient heat resistance and rigidity. The results are shown in Table 1.

(Example 2)
In Example 1, the content ratio of (A) lactic acid-based resin and (B) natural fiber in the pellets used for forming the injection-molded product is set to Nature Works 4032D: Kenaf fiber = 90: 10 (mass%). An injection molded body (plate material) was produced in the same manner as in Example 1 except that it was changed to.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
In Example 1, the content ratio of (A) lactic acid-based resin and (B) natural fiber in the pellets used for forming the injection-molded product is set to Nature Works 4032D: Kenaf fiber = 80: 20 (mass%). An injection molded body (plate material) was produced in the same manner as in Example 1 except that it was changed to.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

Example 4
In Example 1, natural fibers were changed to bamboo fibers manufactured by Aussie Co., Ltd. (cellulose content 53%, lignin content 27%, average diameter 10 mm), and (A) lactic acid resin and (B) natural An injection-molded body (plate material) was produced in the same manner as in Example 1 except that the ratio with respect to the fiber was changed to Nature Works 4032D: bamboo fiber = 90: 10 (mass%).
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
In Example 1, in place of Nature Works 4032D, Nature Works 5040D (L-lactic acid / D-lactic acid = 97.7 / 2.3, weight average molecular weight of 200,000) was used as the lactic acid resin, instead of Nature Works 4032D. In the same manner as in Example 1, an injection molded body (plate material) was produced.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, an injection-molded body (plate material) was produced in the same manner as in Example 1 except that (B) only the Nature Works 4032D, which is a lactic acid resin, was used without using natural fibers.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In Example 1, instead of (B) natural fiber, glass fiber (average thickness 5 mm, average length 2 mm) manufactured by Nippon Sheet Glass Co., Ltd. was used, and the ratio of lactic acid resin to glass fiber was Nature Works. 4032D: Glass fiber = 90: 10 (mass%) Except having changed so that it might become, it produced the injection-molded body (plate material) like Example 1.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In Example 1, instead of natural fiber (B), flax fiber (cellulose content is 80 mass%, lignin content is 1 mass%, average diameter is 20 mm) manufactured by Teikoku Fibers Co., Ltd. An injection-molded body (plate material) was produced in the same manner as in Example 1 except that the ratio of the resin and the flax fiber was changed to be Nature Works 4032D: flax fiber = 90: 10 (mass%). .
About the obtained board | plate material, evaluation (measurement) similar to Example 1 was performed. The results are shown in Table 1.

(Comparative Example 4)
The kenaf fiber used in Example 1 was heated and refluxed at 70 to 80 ° C. using a mixed solution of sodium chlorite, glacial acetic acid and distilled water (lignin content of 8.5 mass) as a natural fiber. It was. That is, in Example 1, as a natural fiber, a cellulose content of 58% by mass and a lignin content of 8.5% by mass) were used, and the ratio between the lactic acid resin and the natural fiber was Nature Works 4032D: Natural fiber = An injection molded body (plate material) was produced in the same manner as in Example 1 except that the ratio was changed to 90:10 (mass%).
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)
In Example 1, it implemented except having used Nature Works 4050D (L-lactic acid / D-lactic acid = 95.0 / 5.0, weight average molecular weight 180,000) instead of Nature Works 4032D as lactic acid-type resin. In the same manner as in Example 1, an injection molded body (plate material) was produced.
The obtained injection-molded body (plate material) was evaluated (measured) in the same manner as in Example 1. The results are shown in Table 1.

As is apparent from Table 1, the injection-molded articles of Examples 1 to 5 have a deflection temperature under load of 133 ° C. or more and excellent heat resistance, and have a large bending elastic modulus at 80 ° C. and excellent rigidity. It turned out to be a thing. Furthermore, it was found that the injection molded articles (resin compositions) of Examples 1 to 5 had a crystallization heat amount peak temperature of 100 ° C. or higher and a high crystallization rate.
On the other hand, it was found that the injection molded articles of Comparative Examples 1 to 5 had a deflection temperature under load of 132 ° C. or lower, a low flexural modulus, and a crystallization heat amount peak temperature of 96 ° C. or lower.
That is, by blending a natural fiber having a cellulose content of 40 to 60% by mass and a lignin content of 10 to 30% by mass into a predetermined lactic acid-based resin, the crystallization promoting effect is excellent and At the same time, the heat resistance was improved by the synergistic effect of fiber reinforcement.

Claims (11)

  (A) A lactic acid resin, and (B) a natural fiber containing 40% by mass to 60% by mass of cellulose and 10% by mass to 30% by mass of lignin. Resin and (B) natural fiber in a mass ratio of 99: 1 to 70:30, and the (A) lactic acid resin is L lactic acid: D lactic acid = 100: 0 to 97: 3, Alternatively, an injection-molded article comprising a resin composition having L lactic acid: D lactic acid = 0: 100 to 3:97.   2. The injection-molded article according to claim 1, wherein the resin composition has a crystallization calorific peak temperature (Tc) of 100 ° C. or higher.   The injection-molded article according to claim 1 or 2, wherein the deflection temperature under load of the injection-molded article is 133 ° C or higher.   4. The method according to claim 1, wherein the coating is formed after kneading (A) a lactic acid resin impregnated with (B) a natural fiber and (A) a lactic acid resin. 5. The injection-molded article described in the item.   The injection according to claim 4, wherein the coating is formed by kneading (A) a lactic acid-based resin and (A) a lactic acid-based resin impregnated with the (B) natural fiber by pultrusion molding. Molded body.   (A) A lactic acid resin, and (B) a natural fiber containing 40% by mass to 60% by mass of cellulose and 10% by mass to 30% by mass of lignin. Resin and (B) natural fiber in a mass ratio of 99: 1 to 70:30, and the (A) lactic acid resin is L lactic acid: D lactic acid = 100: 0 to 97: 3, Or the pellet characterized by using the resin composition which is L lactic acid: D lactic acid = 0: 100-3: 97.   7. The pellet according to claim 6, wherein the constituent components are uniformly dispersed in appearance.   8. The coating according to claim 6 or 7, wherein (A) a lactic acid resin impregnated with (B) natural fibers is kneaded with (A) a lactic acid resin by pultrusion molding. pellet.   (B) A step of impregnating a natural fiber with (A) a lactic acid resin, and a step of further adding (A) a lactic acid resin to the product obtained by the impregnation step and kneading. A method for manufacturing pellets.   (B) a step of impregnating (A) lactic acid-based resin with natural fibers by pultrusion and then forming a coating pellet; and (A) adding a lactic acid-based resin to the coating pellet and kneading the coating pellet; A method for producing pellets, comprising: (B) natural fiber is impregnated with (A) lactic acid resin by pultrusion, and then a coating pellet is formed, and (A) lactic acid resin is further added to the coating pellet and kneaded to form a pellet. And a method of forming an injection molded body using the pellet. A method for manufacturing an injection molded body.