JP2012126871A - Polylactic acid resin composition and molded article using the same - Google Patents

Abstract

Disclosed is a polylactic acid resin composition which has heat resistance due to crystallization of polylactic acid resin and which can also improve weather resistance and impact resistance, and a molded article using the same.
It is characterized by containing a polylactic acid resin, a carbodiimide compound, a phenylphosphonic acid metal salt, and a core-shell rubber.
[Selection figure] None

Description

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

  Polylactic acid resin, which is a biodegradable resin, is currently expected to be used against the background of the fact that a large amount of L-lactic acid has been produced by fermentation from sugars derived from corn, straw, etc. ing. In addition, it is attracting attention as an environmentally conscious molding resin because it has high rigidity and good transparency, because the raw material is a natural crop, the total carbon oxide emissions are extremely low, and it has biodegradability. .

  For example, polylactic acid resins are expected to be used as plant-derived plastics, that is, petroleum-saving plastics, in the fields of home appliances, OA equipment and the like in which conventional general-purpose resins have been used.

  A polylactic acid resin has a slow crystallization rate and is in an amorphous state after molding unless a mechanical process such as stretching is performed. However, since the glass transition temperature (Tg) of polylactic acid resin is as low as 60 ° C. and poor in heat resistance, there is a problem that it cannot be used in an environment where the temperature is 55 ° C. or higher.

  One method for improving the heat resistance of the polylactic acid resin is to increase the crystallization of the polylactic acid resin. That is, by increasing the crystallization rate of polylactic acid, a high crystallinity can be obtained and the heat resistance can be improved.

  When polylactic acid resin is crystallized, for example, the mold temperature is set in the vicinity of the crystallization peak temperature of polylactic acid resin during molding, and the mold is held for a long time, or the molded product is heat-treated after molding Can be used.

  However, a long cooling process at the time of molding is not practical and crystallization tends to be insufficient. In addition, crystallization by heat treatment after molding is deformed in the process of crystallizing the molded product, so that dimensional stability cannot be obtained, and cracks, cracks, etc. are likely to occur in practical use. Further, there is a problem that transparency is remarkably deteriorated by crystallization.

  Thus, as a method for increasing the crystallization rate of polylactic acid resin, a method of blending an inorganic or organic crystal nucleating agent has been studied (see Patent Document 1).

International Publication No. 2005/108501 Pamphlet

  However, although heat resistance can be improved by accelerating crystallization of polylactic acid resin with a crystal nucleating agent, there are problems in durability, particularly weather resistance and impact resistance. That is, even if the polylactic acid resin is crystallized, deterioration due to hydrolysis cannot be suppressed, and the heat resistance temperature and rigidity are improved while flexibility is lost.

  Due to the brittle, hard and inflexible properties of such polylactic acid resins, its use has been limited to the field of hard molded products. For example, when it is molded into an injection-molded product, there are problems such as lack of flexibility and impact resistance, whitening and deterioration of hinge characteristics when bent, and it is not used in soft and semi-rigid fields is the current situation.

  For example, packaging containers have problems such as deformation during transportation and storage, development in high-temperature use fields such as heat sterilization and microwave ovens, molding cycleability, etc., which are major obstacles in promoting the market for polylactic acid. It has become. Therefore, there is a strong demand for improving the above-mentioned problems without impairing the excellent rigidity inherent in polylactic acid.

  The present invention has been made in view of the circumstances as described above, and has a heat resistance due to crystallization of a polylactic acid resin, and can also improve the weather resistance and impact resistance, and An object is to provide a molded product using the same.

  In order to solve the above problems, the polylactic acid resin composition of the present invention is characterized by containing a polylactic acid resin, a carbodiimide compound, a phenylphosphonic acid metal salt, and a core-shell rubber.

  In this polylactic acid resin composition, the phenylphosphonic acid metal salt is preferably zinc phenylphosphonate.

  In this polylactic acid resin composition, the core-shell rubber is composed of a rubber polymer having a core structure obtained by polymerizing a diene monomer, an acrylic monomer, an aromatic vinyl monomer, an unsaturated nitrile monomer, In addition, a copolymer in which at least one unsaturated compound selected from polymers obtained by polymerizing at least one monomer among them is grafted to form a shell structure is preferable.

  In this polylactic acid resin composition, the content of the carbodiimide compound is 0.1 to 4 parts by mass with respect to 100 parts by mass of the polylactic acid resin, and the content of the phenylphosphonic acid metal salt is with respect to 100 parts by mass of the polylactic acid resin. The content of the core-shell rubber is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid resin.

  The molded product of the present invention is characterized in that it is obtained by injection molding the above-mentioned polylactic acid resin composition.

  According to the present invention, heat resistance due to crystallization of polylactic acid resin can be obtained, and weather resistance and impact resistance can be improved.

  The present invention is described in detail below.

  The polylactic acid resin used in the polylactic acid resin composition of the present invention is a polyester-based resin produced by condensation polymerization using lactic acid obtained by decomposing sugar derived from corn, straw, etc. as a monomer.

  As the polylactic acid resin, a polylactic acid resin obtained by condensation polymerization of only a lactic acid component can be used as a raw material monomer. Alternatively, a polylactic acid resin obtained by polycondensation of a lactic acid component and a hydroxycarboxylic acid component other than lactic acid (hereinafter simply referred to as “hydroxycarboxylic acid component”) as a raw material monomer may be used.

  In lactic acid, there are optical isomers of L-lactic acid (L form) and D-lactic acid (D form). In the present invention, either one of the optical isomers or both of them may be used as the lactic acid component. However, in consideration of moldability, the optical purity having one of the optical isomers as a main component is high. It is preferable to use lactic acid.

  Here, the “main component” refers to a component whose content in the lactic acid component is 50 mol% or more.

  The content of L-form or D-form in the lactic acid component in the case of condensation polymerization of only the lactic acid component, that is, the content of the larger of the optical isomers is preferably 80 to 100 mol%, preferably 90 to 100 mol. % Is more preferable, and 99 to 100 mol% is more preferable.

  On the other hand, as the hydroxycarboxylic acid component, glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid and the like can be used. These may be used alone or in combination of two or more. Among these, glycolic acid and hydroxycaproic acid are preferable.

  Moreover, in this invention, the dimer of the said lactic acid and the hydroxycarboxylic acid compound may be contained in each component.

  As the lactic acid dimer, for example, lactide, which is a cyclic dimer of lactic acid, can be used. As a dimer of a hydroxycarboxylic acid compound, for example, glycolide which is a cyclic dimer of glycolic acid can be used.

  The lactide includes L-lactide, which is a cyclic dimer of L-lactic acid, D-lactide, which is a cyclic dimer of D-lactic acid, meso-lactide obtained by cyclic dimerization of D-lactic acid and L-lactic acid, And DL-lactide, which is a racemic mixture of D-lactide and L-lactide. Although any lactide can be used in the present invention, D-lactide and L-lactide are preferable in consideration of the balance between strength and flexibility of the polylactic acid resin composition, heat resistance, and transparency.

  In addition, the dimer of lactic acid can be contained in both the lactic acid component in the case of polycondensation of only the lactic acid component and the lactic acid component in the case of polycondensation of the lactic acid component and the hydroxycarboxylic acid component.

  The content of the dimer of lactic acid is preferably 80 to 100 mol%, more preferably 90 to 100 mol% in the lactic acid component, considering both the strength and flexibility of the polylactic acid resin composition.

  The content of the dimer of the hydroxycarboxylic acid compound is preferably 80 to 100 mol%, and preferably 90 to 100 mol% in the hydroxycarboxylic acid component, considering both the strength and flexibility of the polylactic acid resin composition. More preferred.

  The condensation polymerization reaction of only the lactic acid component and the condensation polymerization reaction of the lactic acid component and the hydroxycarboxylic acid component are not particularly limited, and can be performed using, for example, a known method. The condensation polymerization reaction of lactic acid is a method in which a carboxyl group and a hydroxyl group of lactic acid are esterified. For example, a method of azeotropic dehydration of L-lactic acid, D-lactic acid, or a mixture thereof in the presence of a high-boiling solvent under reduced pressure can be used.

  Moreover, as a ring-opening polymerization method using lactide, a method of esterifying a ring-opened lactide, for example, a method of ring-opening L-lactide, D-lactide, etc. in the presence of a polymerization regulator and a polymerization catalyst. Can be used.

  The molecular weight and molecular weight distribution of the polylactic acid resin are not particularly limited as long as it can be molded, but the molecular weight is determined by gel permeation chromatography (GPC) in consideration of maintaining good molding processability and mechanical properties. The weight average molecular weight is preferably in the range of 50,000 to 400,000, more preferably in the range of 100,000 to 400,000.

  Moreover, in this invention, you may use the stereocomplex which consists of two types of polylactic acid resin obtained using the lactic acid component which has a different isomer as a main component as a polylactic acid resin.

  One polylactic acid (hereinafter referred to as “polylactic acid (A)”) constituting the stereocomplex contains 90 to 100 mol% of L isomer and 0 to 10 mol% of other components including D isomer. The other polylactic acid (hereinafter referred to as “polylactic acid (B)”) contains 90 to 100 mol% of D isomer and 0 to 10 mol% of other components including L isomer. As other components other than L-form and D-form, dicarboxylic acid, polyhydric alcohol, hydroxycarboxylic acid, lactone and the like having a functional group capable of forming two or more ester bonds can be used. Moreover, polyester, polyether, polycarbonate, etc. which have two or more of the said unreacted functional groups in a molecule | numerator may be sufficient.

  The mass ratio of polylactic acid (A) to polylactic acid (B) in the stereo complex (polylactic acid (A) / polylactic acid (B)) takes into account both strength and flexibility, heat resistance, and transparency. Then, 10 / 90-90 / 10 are preferable, 20 / 80-80 / 20 are more preferable, and 40 / 60-60 / 40 are more preferable.

  A carbodiimide compound is blended in the polylactic acid resin composition of the present invention. By mix | blending a carbodiimide compound, the hydrolysis resistance of a polylactic acid resin composition can be improved, and a weather resistance can be improved.

  The carbodiimide compound is not particularly limited as long as it has one or more carbodiimide groups in the molecule. For example, a monocarbodiimide compound, a polycarbodiimide compound, or the like can be used.

  As the monocarbodiimide compound, for example, aliphatic monocarbodiimide, aromatic monocarbodiimide and the like can be used. As the polycarbodiimide compound, for example, aliphatic polycarbodiimide, alicyclic polycarbodiimide and the like can be used. These may have various heterocyclic rings or functional groups in the molecule.

  As the carbodiimide compound, any of a carbodiimide compound having an isocyanate group in the molecule and a carbodiimide compound having no isocyanate group in the molecule can be used.

  Examples of the carbodiimide skeleton of the carbodiimide compound include N, N′-di-o-triylcarbodiimide, N, N′-dioctyldecylcarbodiimide, N, N′-di-2,6-dimethylphenylcarbodiimide, and N-triyl. -N'-cyclohexylcarbodiimide, N-triyl-N'-phenylcarbodiimide, N, N'-di-p-nitrophenylcarbodiimide, N, N'-di-p-hydroxyphenylcarbodiimide, N, N'-di- Cyclohexylcarbodiimide, N, N'-di-p-triylcarbodiimide, p-phenylene-bis-di-o-triylcarbodiimide, 4,4'-dicyclohexylmethanecarbodiimide, tetramethylxylylenecarbodiimide, N, N-dimethyl Phenylcarbodiimide, N, N'- 2,6-diisopropylphenyl carbodiimide and the like.

  As the alicyclic monocarbodiimide, for example, dicyclohexylcarbodiimide can be used.

  As the aromatic monocarbodiimide, for example, N, N′-diphenylcarbodiimide, N, N′-di-2,6-diisopropylphenylcarbodiimide and the like can be used.

  As the alicyclic polycarbodiimide, for example, polycarbodiimide derived from 4,4′-dicyclohexylmethane diisocyanate can be used, and more specifically, for example, poly (4,4′-dicyclohexylmethanecarbodiimide) etc. Can be used.

  As the aromatic polycarbodiimide, for example, polycarbodiimide derived from phenylene-p-diisocyanate, polycarbodiimide derived from 1,3,5-triisopropyl-phenylene-2,4-diisocyanate can be used. Specifically, for example, poly (4,4′-diphenylmethanecarbodiimide), poly (1,3,5-triisopropylbenzene) polycarbodiimide, poly (1,3,5-triisopropylbenzene and 1,5-diisopropylbenzene) ) Polycarbodiimide or the like can be used.

  Polycarbodiimide may have a molecular structure different from other parts such as a molecular chain branched such that both ends of the molecule or any part in the molecule may have a functional group such as an isocyanate group. It may be.

  It does not specifically limit as a method to manufacture a carbodiimide compound, For example, it can carry out using well-known methods, such as the method of manufacturing an isocyanate compound from a raw material.

  0.1-4 mass parts is preferable with respect to 100 mass parts of polylactic acid resins, and, as for content of the carbodiimide compound in the polylactic acid resin composition of this invention, 1-3 mass parts is more preferable. When there is too little content of a carbodiimide compound, hydrolysis resistance may fall. When there is too much content of a carbodiimide compound, reaction with polylactic acid resin may increase, it may become high viscosity and pelletization may become difficult.

  The polylactic acid resin composition of the present invention contains a phenylphosphonic acid metal salt. By compounding a phenylphosphonic acid metal salt, the crystallization speed of the polylactic acid resin composition can be improved, and the heat resistance and rigidity can be improved.

The phenylphosphonic acid metal salt is a metal salt of phenylphosphonic acid having a phenyl group which may have a substituent and a phosphonic group (—PO (OH) ₂ ). Examples of the substituent for the phenyl group include an alkyl group having 1 to 10 carbon atoms and an alkoxycarbonyl group having 1 to 10 carbon atoms in an alkoxy group. As phenylphosphonic acid, for example, unsubstituted phenylphosphonic acid, methylphenylphosphonic acid, ethylphenylphosphonic acid, propylphenylphosphonic acid, butylphenylphosphonic acid, dimethoxycarbonylphenylphosphonic acid, diethoxycarbonylphenylphosphonic acid, etc. Can do. Among these, unsubstituted phenylphosphonic acid is preferable in view of improvement in heat resistance and the like.

  Examples of the phenylphosphonic acid metal salt include salts of lithium, sodium, magnesium, aluminum, potassium, calcium, barium, copper, zinc, iron, cobalt, nickel, and the like. Among these, zinc salts are preferable, and zinc phenylphosphonate is particularly preferable. Heat resistance can be greatly improved by using zinc phenylphosphonate.

  0.1-5 mass parts is preferable with respect to 100 mass parts of polylactic acid resins, and, as for content of the phenylphosphonic acid metal salt in the polylactic acid resin composition of this invention, 1-3 mass parts is more preferable. If the phenylphosphonic acid metal salt content is too small, the crystallization rate may be slow. If the content of the phenylphosphonic acid metal salt is too large, the molded product may be softened and mechanical properties, particularly impact resistance, heat resistance, and the like may be deteriorated.

  A core-shell rubber is blended with the polylactic acid resin composition of the present invention. By blending the core shell rubber, the impact resistance of the molded product can be improved.

  Examples of the core-shell rubber include a rubber polymer having a core structure obtained by polymerizing at least one monomer selected from a diene monomer, an acrylic monomer, and a silicone monomer. Grafted with at least one unsaturated compound selected from a polymer, an aromatic vinyl monomer, an unsaturated nitrile monomer, and a polymer obtained by polymerizing at least one of these monomers. A core-shell copolymer having a shell structure can be used.

  As the diene monomer, for example, a diene monomer having 4 to 6 carbon atoms can be used, and butadiene, isoprene and the like can be used. Of these, butadiene is preferred. Examples of rubber polymers obtained by polymerizing diene monomers include butadiene rubber, acrylic rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, ethylene-propylene-diene terpolymer (EPDM), and the like. Is mentioned.

  Examples of acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and hexyl (meth). An acrylate etc. are mentioned. In this case, for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, allyl (meth) acrylate Triallyl cyanurate or the like can be used.

  Examples of silicone monomers include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, octamethyl Phenylcyclotetrasiloxane and cyclosiloxane compounds of at least one of these can be used.

  The average particle diameter of the rubbery polymer is preferably 0.4 to 1 μm in consideration of impact resistance and the like.

  Among the unsaturated compounds that can be grafted to the rubbery polymer, examples of the acrylic monomer include (meth) acrylic acid alkyl ester, (meth) acrylic acid ester, anhydride, alkyl, and phenyl N-substituted maleimide. Can be used. Here, the alkyl preferably has 1 to 10 carbon atoms, and examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and the like. Can be used. Of these, methyl (meth) acrylate is preferred. Moreover, as an anhydride, an acid anhydride etc. can be used, for example, carboxylic acid anhydrides, such as maleic anhydride and itaconic anhydride, can be used.

  As an aromatic vinyl monomer, styrene, a C1-C10 alkyl substituted styrene, a halogen substituted styrene etc. can be used, for example. As the alkyl-substituted styrene, for example, o-ethyl styrene, m-ethyl styrene, p-ethyl styrene, α-methyl styrene and the like can be used.

  As the unsaturated nitrile monomer, for example, acrylonitrile, methacrylonitrile, ethacrylonitrile and the like can be used.

  As a core-shell rubber, a rubber polymer having a core structure obtained by polymerizing a diene monomer, an acrylic monomer, an aromatic vinyl monomer, an unsaturated nitrile monomer, and at least one kind of these monomers are used. A copolymer in which at least one unsaturated compound selected from polymers obtained by polymerizing a monomer is grafted to form a shell structure can be preferably used. Among these, a core-shell rubber having a diene rubber such as butadiene rubber as a core and a copolymer of an acrylic monomer and an aromatic vinyl monomer as a shell is preferable. Such a core shell rubber is excellent in compatibility with the polylactic acid resin and shock absorption by the rubber, and can improve impact resistance.

  It does not specifically limit as a method to manufacture a core shell copolymer, For example, it can carry out using a well-known method.

  The unsaturated compound that can be grafted is preferably contained in an amount of 40 parts by mass or less, more preferably 5 to 30 parts by mass with respect to 100 parts by mass of the core-shell rubber. By setting it as such a range, it can be excellent in compatibility with a polylactic acid resin, and impact resistance can be improved.

  1-10 mass parts is preferable with respect to 100 mass parts of polylactic acid resins, and, as for content of the core-shell rubber in the polylactic acid resin composition of this invention, 3-9 mass parts is more preferable. If the content of the core-shell rubber is too small, the impact resistance may be lowered. When the content of the core-shell rubber is too large, the molded product may be softened or the heat resistance may be lowered.

  The polylactic acid resin composition of the present invention may further contain other components within a range that does not impair the effects of the present invention. Examples of such other components include pigments, lubricants, antioxidants, heat stabilizers, ultraviolet absorbers, hindered amine light stabilizers, antistatic agents, flame retardants, tackifiers, plasticizers, fillers, Internal mold release agents, antibacterial antifungal agents, and the like can be used.

  The polylactic acid resin composition of the present invention can contain other resins and the like as necessary. For example, general-purpose resins such as polyethylene, polypropylene, polyethylene, polystyrene, biodegradable resins such as polycaprolactone, polybutylene succinate, cellulose acetate, polyethylene oxide, methacrylbutylene styrene resin (MBS resin), acrylonitrile butylene styrene resin (ABS resin) ) Etc. can be used.

  The polylactic acid resin composition of the present invention can be produced by kneading the above components. The kneading of each component is not particularly limited and can be performed by various methods. For example, the dry blend method in which each component is charged and kneaded in a tumbler, V-type blender, ribbon blender, Hellshell mixer, tumbler mixer, etc., and the dry blend is melt-kneaded with a single or twin screw extruder, kneader, roll, etc. and cooled. Further, a pelletizing method, a solution blend method in which each resin is dissolved in a solvent, and the solvent is removed after mixing can be used.

  Since the polylactic acid resin composition of the present invention is excellent in molding processability, various molded products can be obtained. The method for producing the molded product is not particularly limited. For example, injection molding, extrusion molding, blow molding, inflation molding, inflation blow molding, foamed sheet molding, and vacuum molding after sheet processing, compressed air, similar to general plastics. Molding, vacuum / pressure forming and the like can be used.

  By such a method, as a molded product, for example, an injection molded product, a film or sheet by extrusion molding, a molded product by processing these films or sheets, a hollow body by blow molding, a molded product by processing this hollow body, etc. are obtained. be able to.

  In the present invention, injection molding is particularly preferable, and in addition to a general injection molding method, a gas injection molding method, an injection press molding method, or the like can also be used. As the injection molding conditions, the cylinder temperature is set to the melting point or flow start temperature of the polylactic acid resin composition or more, preferably 170 to 250 ° C., more preferably 200 to 230 ° C., and the mold temperature is (resin composition (Melting point of -40 ° C) or less. If the cylinder temperature is too low, the operability may become unstable, such as a short circuit in the molded product, or an overload may occur. If the cylinder temperature, that is, the molding temperature is too high, the strength of the molded product obtained by decomposing the polylactic acid resin composition may be reduced or colored.

  The polylactic acid resin composition of the present invention can further increase its heat resistance by promoting crystallization during molding.

  For example, crystallization can be promoted by heat-treating the molded product taken out from the mold again at a temperature not lower than the glass transition temperature and not higher than (melting point−40 ° C.).

  It is also possible to promote crystallization in the mold during injection molding. In that case, it is preferable to hold the molded product for a certain period of time in a mold maintained at a temperature not lower than the glass transition temperature and not higher than (melting point−40 ° C.) of the polylactic acid resin composition, and then remove from the mold.

  When crystallization is promoted by these methods, the range of the glass transition temperature of the polylactic acid resin composition to 140 ° C is preferable, and 80 to 120 ° C is more preferable.

  As the polylactic acid resin composition of the present invention, for example, using a differential scanning calorimeter “DSC220C” manufactured by Seiko Instruments Inc., 10 mg of the polylactic acid resin composition is put in a measurement container, and a nitrogen gas flow rate of 50 mL / The crystallization peak temperature observed when the temperature is raised from 20 ° C. to 210 ° C. at a heating rate of 10 ° C./min is observed in the range of 110 ° C. to the melting point of the polylactic acid resin composition. It is preferable because of its excellent resistance.

In addition, the polylactic acid resin composition of the present invention uses DSC to put 10 mg of the polylactic acid resin composition into a measurement container, and from 20 ° C. to 210 ° C. at a nitrogen gas flow rate of 50 mL / min and a heating rate of 10 ° C./min. The temperature is raised and then held at 210 ° C. for 3 minutes, then the temperature is lowered to −100 ° C. at a cooling rate of 20 ° C./min, and the second temperature rise is again carried out to 200 ° C. At this time, using the melting calorie peak area (ΔHm) of the DSC curve drawn at the time of secondary heating and the crystallization calorie peak area (ΔHc) of the DSC curve drawn at the time of primary heating, it is calculated from the following formula: The crystallinity α is preferably in the range of 20 to 100%.
Crystallinity α = [(ΔHm−ΔHc) / ΔHm] × 100 (%)

  The polylactic acid resin composition of the present invention is capable of improving the crystallization speed and crystallinity of the polylactic acid resin, has high heat resistance, and maintains excellent transparency, weather resistance, impact resistance, molding Since it is excellent in workability, it can be suitably used for various applications.

  Specific examples of the molded product of the present invention include personal computer casing parts and casings, mobile phone casing parts and casings, other OA equipment casing parts, resin parts for electrical appliances such as connectors; bumpers, instrument panels Automotive parts such as console boxes, garnishes, door trims, ceilings, floors, panels around engines, etc .; Resin parts for agricultural materials such as containers and cultivation containers, and agricultural machinery; Resin for marine products such as floats and processed fishery products containers Parts; Plates, cups, spoons and other tableware and food containers; Medical resin parts such as syringes and infusion containers; Drain materials, fences, storage boxes, resin distribution parts for construction, distribution boards, etc .; for flower beds Resin parts for greening materials such as bricks and flower pots; Resin parts for leisure and miscellaneous goods such as cooler boxes, fan fans and toys; sentences such as ballpoint pens, rulers and clips Ingredients for resin parts, and the like.

  The polylactic acid resin composition of the present invention can be formed into an extruded product such as a film, a sheet, or a pipe, or a hollow molded product. Specific examples of such molded articles include agricultural multi-films, construction sheets, various blow molded bottles, and the like.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In addition, the compounding quantity of Table 1 shows a mass part.

As the blending components shown in Table 1, the following were used.
(Polylactic acid resin)
Pellets (carbodiimide compound) of a lactic acid polymer having a weight average molecular weight of 160,000 to 180,000 ("3001D" manufactured by Nature Works, USA, L-form content 98.5%, D-form content 1.5%)
Poly (1,3,5-triisopropylbenzene) polycarbodiimide (“Stavaxol P” manufactured by Rheim Chemie Rheinau GmbH / Germany)
(Phenylphosphonic acid metal salt)
Unsubstituted zinc phenylphosphonate (Eco Promote manufactured by Nissan Chemical Industries, Ltd.)
(Core shell rubber)
Core shell rubber with butadiene rubber as the core and methyl methacrylate / styrene copolymer as the shell ("C223A" manufactured by Mitsubishi Rayon Co., Ltd.)

  A polylactic acid resin, a carbodiimide compound, a metal salt of phenylphosphonic acid, and a core shell rubber were blended and dry blended with a tumbler. This is supplied from the base supply port of the twin screw extruder, extruded at a barrel temperature of 210 ° C, heated and kneaded, extruded into a strand shape, cooled until the strand reaches 50 ° C in water, and then cut into 2 to 4 mm with a pelletizer. Thus, a pellet-shaped polylactic acid resin composition was obtained.

  The obtained pellets were sufficiently dried to remove moisture and then injection molded to produce general physical property measurement test pieces (ISO type). The molding conditions were such that the molten resin temperature was in the range of 200 to 230 ° C. and the mold temperature was 40 ° C. in order to avoid thermal decomposition of the resin in the injection cylinder.

  Next, the test piece taken out from the mold was heat-treated at a temperature of 100 ° C. for a treatment time of 10 minutes for crystallization treatment.

  The test piece was evaluated as follows.

[Tensile strength]
Tensile strength (MPa) was measured according to ISO 525. A part of the test piece was measured after being exposed to a high temperature and high humidity environment of 60 ° C. and 95% RH for 300 hours.

[Load deflection temperature]
The deflection temperature under load (0.46 MPa) was measured according to ISO 75. The temperature of the test piece in the liquid heat transfer medium was increased under bending stress, and the temperature (° C.) when the softening started and the specified deflection amount was reached was measured.

[Charpy impact strength]
Charpy impact strength was measured according to ISO 179. The impact strength was evaluated by hammering the back of the notch of the test piece and using the energy (kJ / m ² ) required for breaking.

  The evaluation results are shown in Table 1.

  From Table 1, in Examples 1-4, crystallization of the polylactic acid resin was promoted and the heat resistance could be improved. Even after exposure to a high temperature and high humidity environment, the tensile strength did not decrease and the weather resistance was high, and the impact resistance was also high.

  On the other hand, in Comparative Example 1 in which no carbodiimide compound was blended, the tensile strength decreased greatly and the weather resistance decreased after exposure to a high temperature and high humidity environment. In Comparative Example 2 in which the phenylphosphonic acid metal salt was not blended, the crystallization was slow and the heat resistance was lowered. In Comparative Example 3 in which the core shell rubber was not blended, the impact resistance was lowered.

Claims (5)

  A polylactic acid resin composition comprising a polylactic acid resin, a carbodiimide compound, a metal salt of phenylphosphonic acid, and a core-shell rubber.   The polylactic acid resin composition according to claim 1, wherein the phenylphosphonic acid metal salt is zinc phenylphosphonate.   The core shell rubber is a rubber polymer having a core structure obtained by polymerizing a diene monomer, an acrylic monomer, an aromatic vinyl monomer, an unsaturated nitrile monomer, and at least one of them. The polylactic acid according to claim 1 or 2, wherein the polylactic acid is a copolymer in which at least one unsaturated compound selected from polymers obtained by polymerizing monomers is grafted to form a shell structure. Resin composition.   The content of the carbodiimide compound is 0.1 to 4 parts by mass with respect to 100 parts by mass of the polylactic acid resin, and the content of the phenylphosphonic acid metal salt is 0.1 with respect to 100 parts by mass of the polylactic acid resin. The polylactic acid resin according to any one of claims 1 to 3, wherein the content of the core-shell rubber is 1 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid resin. Composition.   A molded article, wherein the polylactic acid resin composition according to any one of claims 1 to 4 is injection-molded.