JP2014169386A - Polylactic acid resin composition, molded article made of the same, and method for producing polylactic acid resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition which has high crystallization temperature and is superior in impact resistance.SOLUTION: The polylactic acid resin composition comprises: 100 pts.wt. of polylactic acid; (A) 0.01-5 pts.wt. of a specific hydrazide compound; (B) 0.01-5 pts.wt. of a specific carbodiimide compound; and (C) 0.01-2 pts.wt. of at least one impact resistance improving agent selected from an acrylonitrile-butadiene-styrene copolymer and silicone-acrylic-based rubber.

Description

  The present invention relates to a polylactic acid resin composition. More specifically, the present invention relates to a polylactic acid resin composition having a high crystallization rate and excellent heat resistance, molding processability, and impact resistance, and a molded article comprising the same.

  Currently, as part of countermeasures for environmental problems, development of technology for substituting plant raw materials for petroleum raw materials used as materials for industrial products is underway. An example of such a plastic material developed from plant-derived substances is polylactic acid (hereinafter sometimes abbreviated as PLA). Polylactic acid not only uses petroleum as a raw material but also has biodegradability, and thus has attracted attention as a plastic material that has a low environmental impact from production to disposal. However, since polylactic acid has a slow crystallization rate, it tends to be deformed when its glass transition temperature (about 60 ° C.) is exceeded, particularly in injection molding in which stretching is not performed. In order to suppress the deformation, in order to increase the degree of crystallinity, an attempt has been made to increase the mold temperature at the time of injection molding and extend the cooling time in the mold, but this method requires a long molding cycle. Therefore, it has a problem in productivity. Therefore, attempts have been made to improve the moldability and heat resistance by increasing the crystallization speed and crystallinity in order to produce a polylactic acid resin molded product with high productivity and use it in a wide range of applications.

  As a method for increasing the crystallization rate of polylactic acid resin, for example, a method of adding a crystal nucleating agent is often used. The crystal nucleating agent serves as a primary crystal nucleus of the crystalline polymer, promotes crystal growth, refines the crystal size, and increases the crystallization speed. Various crystal nucleating agents for polylactic acid resins are known. For example, inorganic particles composed of talc and / or boron nitride having a specific particle size or less (see Patent Document 1, etc.), amide compounds represented by a specific formula (see Patent Document 2, etc.), and a specific formula Metal phosphates (see Patent Document 3, etc.), phenylphosphonic acid metal salts represented by a specific formula (see Patent Document 4, etc.), urea compounds represented by a specific formula (see Patent Document 5, etc.), Oxamide derivatives and isocyanuric acid derivatives represented by a specific formula (see Patent Document 6, etc.), melamine compounds represented by a specific formula (see Patent Document 7, etc.), metal sulfonates represented by a specific formula (Patent Reference 8 etc.) are disclosed. Further, as a hydrazide-based organic nucleating agent for polylactic acid resin, N-benzoyl hydrazide represented by a specific formula (see Patent Document 9 etc.), hydrazide having a pyridine ring represented by a specific formula (see Patent Document 10 etc.) Sulfohydrazide represented by a specific formula (see Patent Document 11 etc.) and the like are shown. These crystal nucleating agents can increase the crystallization rate of polylactic acid and increase the degree of crystallinity, but in recent years, more effective crystals have been developed to achieve higher moldability and heat resistance. Development of nucleating agents is desired. On the other hand, improvement in impact resistance is also required for polylactic acid.

  In general, in order to improve the impact resistance of a resin, it is known to blend a rubbery polymer such as an olefin copolymer, and a method of adding a modified olefin compound in polylactic acid is also known ( (See Patent Document 12, etc.). In addition, a method of blending an acrylic rubber and / or silicon acrylic rubber with a graft copolymer obtained by grafting a vinyl monomer containing an alkyl acrylate and / or an aromatic vinyl monomer, etc. Is known (see, for example, Patent Document 13).

JP-A-8-3432 Japanese Patent Laid-Open No. 10-87975 JP 2003-192894 A International Publication No. 05/099784 Pamphlet JP 2005-187630 A Japanese Patent Laying-Open No. 2005-255806 JP 2005-272679 A JP 2010-150365 A JP 2007-332164 A JP 2009-144056 A JP 2009-249615 A JP 2001-123055 A JP 2006-56987 A

Panasonic Electric Works Technical Report (Vol.59, No.1) 55-59.

  Among the above patent documents, a nucleating agent that has a melting point higher by several tens of degrees Celsius than poly-L-lactic acid and is excellent in heat resistance is also reported to be effective in promoting crystallization of polylactic acid of stereocomplex. The effect of improving the temperature is not satisfactory, and it is still insufficient as a method for improving the molding processability and heat resistance of a large molded product.

Stereocomplex polylactic acid is known to have a reduced impact resistance as crystallization progresses (see Reference 1 etc.), and it is possible to achieve both high crystallinity and sufficient impact resistance. There is still a need for further expanding the industrial uses of polylactic acid.
Accordingly, an object of the present invention is to provide a polylactic acid resin composition having a high crystallization temperature and excellent impact resistance.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have (A) a hydrazide compound having a specific structure, (B) a carbodiimide compound having a specific structure, and (C) a specific impact resistance improvement. It has been found that the above object can be achieved by blending three of the agents with polylactic acid, and the present invention has been completed.

（式中、Ｒ^１，Ｒ^２，Ｒ^３，及びＲ^４は各々独立に、水素原子、炭素数１〜１０のアルキル基または炭素数６〜１２のアリール基を示す。）

（式中、Ａｒ^１，Ａｒ^２，Ａｒ^３，Ａｒ^４は、各々独立に炭素数１〜６のアルキル基または炭素数６〜１２のアリール基で置換されていてもよい芳香族基である。）
［２］次の（１）から（３）の昇温、降温過程を連続的に行うＤＳＣの測定条件において、溶融状態から降温したときの結晶化温度（ピークトップ温度：Ｔ_ｃｄ）が１５０℃以上であり、かつ結晶化に基づく発熱量（結晶化エンタルピー：Ｈ_ｃ）の値が４０Ｊ／ｇ以上である上記に記載のポリ乳酸樹脂組成物。
（１）３０℃から２６０℃まで２０℃／分で昇温
（２）２６０℃で１分間保持
（３）２６０℃から３０℃まで２０℃／分で降温
［３］ポリ乳酸が、ポリ−Ｌ−乳酸およびポリ−Ｄ−乳酸の混合物である、上記に記載のポリ乳酸樹脂組成物、
［４］上記に記載のポリ乳酸樹脂組成物からなる成形品、
［５］ポリ乳酸樹脂と（Ａ）ヒドラジド化合物と（Ｂ）カルボジイミド化合物とを溶融混練した後、（Ｃ）耐衝撃性改良剤を溶融混練する上記に記載のポリ乳酸樹脂組成物の製造方法、
［６］ポリ乳酸樹脂と（Ａ）ヒドラジド化合物と（Ｂ）カルボジイミド化合物とを溶融混練した後、（Ｃ）耐衝撃性改良剤を添加し、その後さらに（Ｂ）カルボジイミド化合物を添加し溶融混練する上記に記載のポリ乳酸樹脂組成物の製造方法。 That is, the present invention is as follows.
[1] 100 parts by weight of polylactic acid, (A) 0.01 to 5 parts by weight of a hydrazide compound represented by the following formula (I), (B) 0.01 to 5 parts by weight represented by the following formula (II) Polylactic acid resin composition containing 0.01 to 2 parts by weight of at least one impact modifier selected from (C) acrylonitrile-butadiene-styrene copolymer and silicone acrylic rubber object,

(In the formula, R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)

(In the formula, Ar ¹ , Ar ² , Ar ³ and Ar ⁴ are each independently an aromatic group which may be substituted with an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. )
[2] Under the DSC measurement conditions in which the following temperature increase and decrease processes (1) to (3) are continuously performed, the crystallization temperature (peak top temperature: T _cd ) when the temperature is decreased from the molten state is 150 ° C. The polylactic acid resin composition as described above, which has a calorific value based on crystallization (crystallization enthalpy: H _c ) of 40 J / g or more.
(1) Temperature rise from 30 ° C to 260 ° C at 20 ° C / min (2) Hold at 260 ° C for 1 minute (3) Temperature drop from 260 ° C to 30 ° C at 20 ° C / min [3] Polylactic acid is poly-L -A polylactic acid resin composition as described above, which is a mixture of lactic acid and poly-D-lactic acid,
[4] A molded article comprising the polylactic acid resin composition as described above,
[5] The method for producing a polylactic acid resin composition as described above, wherein the polylactic acid resin, (A) a hydrazide compound, and (B) a carbodiimide compound are melt-kneaded, and (C) the impact modifier is melt-kneaded.
[6] After melt-kneading the polylactic acid resin, (A) hydrazide compound, and (B) carbodiimide compound, add (C) impact resistance improver, and then add (B) carbodiimide compound and melt-knead. The manufacturing method of the polylactic acid resin composition as described above.

  According to the present invention, it is possible to provide a polylactic acid resin composition having a high crystallization temperature and excellent in not only molding processability and heat resistance but also impact resistance, and the obtained polylactic acid resin composition It is possible to obtain a molded article having high crystallinity and impact resistance by crystallizing the product by melt molding.

The polylactic acid resin composition of the present invention will be described in detail below.
(Polylactic acid)
The polylactic acid used in the polylactic acid resin composition of the present invention is a polymer composed of lactic acid units represented by the following formula. The polylactic acid is preferably a blend (mixture) of poly-L-lactic acid and poly-D-lactic acid. Poly-L-lactic acid is a polymer mainly containing L lactic acid units, and poly-D-lactic acid is a polymer mainly containing D lactic acid units. Here, “mainly” means that the repeating unit occupies 50 mol% or more based on all repeating units.

  The poly-L-lactic acid is preferably composed of 90 to 100 mol%, more preferably 95 to 100 mol%, and still more preferably 98 to 100 mol% L lactic acid units. Examples of other units include D-lactic acid units and copolymer component units other than lactic acid. The D lactic acid unit and the copolymer component unit other than lactic acid are preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and still more preferably 0 to 2 mol%. The poly-D-lactic acid is preferably composed of 90 to 100 mol%, more preferably 95 to 100 mol%, and still more preferably 98 to 100 mol% of D lactic acid units. Examples of other units include L lactic acid units and copolymer component units other than lactic acid. The L lactic acid unit and the copolymer component unit other than lactic acid are 0 to 10 mol%, preferably 0 to 5 mol%, more preferably 0 to 2 mol%.

  The copolymer component unit is a dicarboxylic acid having two or more functional groups capable of forming an ester bond, a polyhydric alcohol, a hydroxycarboxylic acid, a unit derived from a lactone, various polyesters composed of these various components, various polyethers, Examples are derived from various polycarbonates and the like.

  Examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid. Examples of polyhydric alcohols include aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, glycerin, sorbitan, neopentyl alcohol, diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol. Or aromatic polyhydric alcohol etc., such as what added ethylene oxide to bisphenol, etc. are mentioned. Examples of the hydroxycarboxylic acid include glycolic acid and hydroxybutyric acid. Examples of the lactone include glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone.

  The weight average molecular weight (Mw) of poly-L-lactic acid or poly-D-lactic acid is preferably 50,000 to 500,000, more preferably 150,000 to 350,000. Here, the weight average molecular weight is a weight average molecular weight in terms of standard polystyrene as measured by gel permeation chromatography (GPC) using chloroform as an eluent.

  Poly-L-lactic acid and poly-D-lactic acid can be produced by a known method. For example, it can be produced by heating and ring-opening polymerization of L-lactide or D-lactide in the presence of a metal polymerization catalyst. Moreover, after crystallizing low molecular weight polylactic acid containing a metal polymerization catalyst, it can be produced by solid phase polymerization by heating under reduced pressure or in an inert gas stream. Further, it can be produced by a direct polymerization method in which lactic acid is subjected to dehydration condensation in the presence / absence of an organic solvent.

  The polymerization reaction can be carried out in a conventionally known reaction vessel. For example, a vertical reaction vessel equipped with a high viscosity stirring blade such as a helical ribbon blade can be used alone or in parallel. Alcohol may be used as the polymerization initiator. Such alcohol is preferably non-volatile without inhibiting the polymerization of polylactic acid, for example, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol, ethylene glycol, triethylene glycol, benzyl alcohol and the like are suitable. Can be used.

  The polylactic acid preferably contains stereocomplex crystals. The polylactic acid containing this stereocomplex crystal is referred to as stereocomplex crystal polylactic acid. A stereocomplex crystal is formed by mixing poly-L-lactic acid and poly-D-lactic acid. In this case, the weight ratio of poly-L-lactic acid to poly-D-lactic acid is preferably (90:10) to (10:90), more preferably (75:25) to (25:75), Preferably it is (60:40)-(40:60).

  The weight average molecular weight of the stereocomplex polylactic acid is preferably 100,000 to 500,000, more preferably 100,000 to 300,000. The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene as measured by gel permeation chromatography (GPC) using chloroform as an eluent.

  The content of stereocomplex crystals is preferably 80 to 100%, more preferably 95 to 100%. The stereocomplex polylactic acid has a melting peak ratio of 195 ° C. or higher, preferably 80% or higher, more preferably 90% or higher, even more preferably, among melting peaks in the temperature rising process in differential scanning calorimetry (DSC) measurement. 95% or more. The melting point is preferably in the range of 195 ° C to 250 ° C, more preferably in the range of 200 to 220 ° C. Moreover, it is preferable that the value of the melting enthalpy derived from the melting peak in the heating process is 20 J / g or more.

  The polylactic acid in the present invention may be consumed by reacting part or all of the carboxy terminus with the carbodiimide compound, and the amount of the carboxy terminus in the polylactic acid is 12 eq. / Ton or less.

  Stereocomplex polylactic acid can be produced by mixing poly-L-lactic acid and poly-D-lactic acid at a predetermined weight ratio. Mixing can be performed in the presence of a solvent. The solvent is not particularly limited as long as it dissolves poly-L-lactic acid and poly-D-lactic acid. For example, chloroform, methylene chloride, dichloroethane, tetrachloroethane, phenol, tetrahydrofuran, N-methyl Preference is given to pyrrolidone, N, N-dimethylformamide, butyrolactone, trioxane, hexafluoroisopropyl alcohol or the like alone or in combination. Mixing can also be performed in the absence of a solvent. That is, a method of melting and kneading after mixing a predetermined amount of poly-L-lactic acid and poly-D-lactic acid, a method of adding and kneading one of them after melting one of them can be employed. When mixing poly-L-lactic acid and poly-D-lactic acid by melt-kneading, the composition of the present invention comprises a phosphoric acid ester metal salt represented by the following structural formula as an accelerator for stereocomplex crystallization. It may contain 0.03 part by weight or less based on 100 parts by weight of the object. Examples of such a phosphoric acid ester metal salt include “ADK STAB (registered trademark)” NA-11 (manufactured by ADEKA Corporation).

（式中、Ｍはアルカリ金属元素を表す。）

(In the formula, M represents an alkali metal element.)

(Metal polymerization catalyst)
In the composition of this invention, the metal polymerization catalyst used when manufacturing poly-L-lactic acid and poly-D-lactic acid may contain. The metal polymerization catalyst is preferably a compound containing at least one metal element selected from the group consisting of alkaline earth metals, rare earth metals, fourth-period transition metals, aluminum, zinc, germanium, tin, and antimony. Examples of the alkaline earth metal include magnesium, calcium, and strontium. Examples of rare earth elements include scandium and yttrium. Examples of the transition metal in the fourth period include iron, cobalt, nickel, and the like.

  The metal polymerization catalyst can be added to the composition, for example, as a carboxylate, alkoxide, aryloxide, or β-diketone enolate of these metals. In view of polymerization activity and hue, tin octylate, titanium tetraisopropoxide, and aluminum triisopropoxide are particularly preferable. The content of the metal polymerization catalyst is preferably 0.001 to 0.1 parts by weight, more preferably 0.005 to 0.05 parts by weight with respect to 100 parts by weight of polylactic acid. When the content of the metal polymerization catalyst is too small, the polymerization rate is remarkably lowered. On the other hand, if the amount is too large, coloring due to heat of reaction or depolymerization or transesterification reaction is accelerated, so that the hue and thermal stability of the resulting composition are deteriorated.

(Crystal nucleating agent)
The polylactic acid resin composition of the present invention contains a hydrazide compound represented by the following formula (I) and a carbodiimide compound represented by the following formula (II) as a crystallization accelerator for the polylactic acid resin. .

（式中、Ｒ^１，Ｒ^２，Ｒ^３，Ｒ^４は各々独立に、水素原子、炭素数１〜１０のアルキル基または炭素数６〜１２のアリール基を示す。）

(In the formula, R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms.)

（式中、Ａｒ^１，Ａｒ^２，Ａｒ^３，Ａｒ^４は、各々独立に炭素数１〜６のアルキル基または炭素数６〜１２のアリール基で置換されていてもよい芳香族基である。）

(In the formula, Ar ¹ , Ar ² , Ar ³ and Ar ⁴ are each independently an aromatic group which may be substituted with an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. )

(Hydrazide compound)
In the above formula (1), R ¹ , R ² , R ³ , and R ⁴ are each independently an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 12 carbon atoms. The alkyl group having 1 to 10 carbon atoms may have a branch, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, secondary butyl group, tertiary butyl group, isobutyl group, amyl group , Isoamyl group, tertiary amyl group, hexyl group, 2-hexyl group, 3-hexyl group, heptyl group, 2-heptyl group, 3-heptyl group, isoheptyl group, tertiary heptyl group, n-octyl group, isooctyl group , Tertiary octyl group, 2-ethylhexyl group, nonyl group, isononyl group, dodecyl group and the like. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a naphthalenyl group.

As the compound represented by the above formula (1), terephthalic acid dihydrazide, in which R ^{1 to} R ⁴ are all hydrogen atoms, is particularly preferable.
The content of the hydrazide compound is 0.01 to 5 parts by weight, preferably 0.2 to 2.0 parts by weight, more preferably 0.25 to 1.0 parts by weight with respect to 100 parts by weight of polylactic acid. It is. If it is less than 0.01 part by weight, the effect of promoting crystallization is insufficient, and if it is added more than 2 parts by weight, the production cost of the molded product of polylactic acid resin is reduced, which is not preferable.

(Carbodiimide compound)
In the above formula (2), Ar ¹ , Ar ² , Ar ³ , and Ar ⁴ are each independently independently substituted with an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. 1 to 30 aromatic groups. Examples of the aromatic group include a phenylene group and a naphthalenediyl group. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl, isobutyl, amyl, isoamyl, and tertiary amyl. Group, hexyl group, 2-hexyl group and 3-hexyl group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a naphthyl group.

The compounding amount of the carbodiimide compound is 0.01 to 5 parts by weight, preferably 0.4 to 4.0 parts by weight, more preferably 0.4 to 2.7 parts by weight with respect to 100 parts by weight of the polylactic acid resin. It is. If the amount is less than 0.01 parts by weight, the effect of addition is insufficient. If the amount is more than 5 parts by weight, a phenomenon such as a carbodiimide compound bleeding out on the surface of the polylactic acid resin composition occurs, and the appearance of the molded product May cause defects. Further, the molecular weight and content of the hydrazide compound represented by the above formula (1) are respectively M ₁ and x parts by weight, and the molecular weight and content of the carbodiimide compound represented by the above formula (2) are respectively M ₂ and y weight. The mixing ratio of these two components (molar ratio: (y / M ₂ ) / (x / M ₁ )) is preferably from 0.37 to 2.7, and from 0.6 More preferably, 1.2. When the value of this molar ratio exceeds 3.3, a sufficient nucleating agent effect may not be obtained even if the blending amount of the hydrazide compound and the carbodiimide compound is within the range of the above preferred values.

As the carbodiimide compound represented by the above formula (2), specifically, a compound represented by the following formula (III) in which all of Ar ^{1 to} Ar ⁴ are represented by ortho disubstituted benzene rings is particularly preferable. . Such a carbodiimide compound can be easily produced by referring to the production examples of the international publication WO2010 / 071213 pamphlet.

  In the polylactic acid resin composition of the present invention, a method of blending two components of the hydrazide compound and the carbodiimide compound represented by the above formulas (1) and (2) into the polylactic acid resin is performed by a conventionally known melt-kneading method. be able to. For example, the polylactic acid resin and the additive can be mixed by dry blending and then melt kneaded with a single screw or twin screw extruder. Further, the additive may be directly added to the polylactic acid resin melted in the kneader by using an automatic powder addition apparatus such as a disk feeder and melt-kneaded. Since the melting point of the stereocomplex crystal of polylactic acid is 200 ° C. or higher, melt kneading in the case of stereocomplex crystal polylactic acid is usually carried out in the range of 230 ° C. to 250 ° C. It is particularly preferable to simultaneously knead the two agents in the melted polylactic acid in order to develop a high crystallization promoting effect. First, one agent is added and kneaded, and then the other agent is added and kneaded. The method may not provide a sufficient crystallization promoting effect. Moreover, a sufficient crystallization promoting effect cannot be obtained only by blending only one of the agents into polylactic acid.

In addition, the crystal promotion effect of the compounds represented by the above formulas (I) and (II) having a nucleating agent effect in the stereocomplex polylactic acid composition which is a preferred embodiment of the present invention is evaluated by, for example, the following DSC measurement. be able to. That is, first, a part (5 to 10 mg) of a sample (stereo complex polylactic acid resin composition)
(1) The temperature is increased from 30 ° C. to 260 ° C. at a rate of temperature increase of 20 ° C./min
(2) After being held at 260 ° C. for 1 minute to melt,
(3) Cool from 260 ° C. to 30 ° C. at a cooling rate of 20 ° C./min,
At that time (first cycle), the crystallization temperature (crystallization peak temperature) and the calorific value (crystallization enthalpy) based on crystallization are determined. As the crystallization temperature (peak top temperature: hereinafter referred to as T _cd ) in the cooling process (temperature measurement) of (3) is observed on the higher temperature side, the crystallization rate becomes higher. calorific value based on (crystallization enthalpy:. to [Delta] H _c represent less) larger the crystallinity improvement effect is high.

In the present invention, when the two agents having a specific structure (hydrazide compound and carbodiimide compound) are simultaneously melt-kneaded with the polylactic acid in polylactic acid, polylactic acid having a particularly high crystallization promoting effect is obtained. Therefore, it is inferred that the reaction product of these two agents (the polycondensation product because they are bifunctional with each other) or the reaction product of these two agents with polylactic acid exhibits a high nucleating agent effect. In fact, it is known from the IR measurement of the resin after blending the two agents that the carbodiimide compound may be completely consumed when the blending amount of the hydrazide compound is increased. It has been suggested to react. Although it is not certain what type of product is formed after blending the two agents, it is known that the carboxyl end of polylactic acid reacts with the carbodiimide compound, and the end of the hydrazide —NH ₂ Considering that the group is nucleophilic and can react with polylactic acid, these two agents react with polylactic acid in multiple stages to give a product represented by the following formula: The present inventors consider whether this is the case.

（特に好適な２剤を組み合わせた場合の推定生成物の構造式を上記に示した。なお、上記式中の（波線）はポリ乳酸の主鎖を表している。また、上端にあったカルボジイミド基と同様に下端のカルボジイミド基が反応していてもよく、１分子内に４本のポリ乳酸の主鎖を持つ星型の生成物であってもよい。）

(The structural formula of the presumed product when combining two particularly suitable agents is shown above. (Wavy line) in the above formula represents the main chain of polylactic acid. Also, the carbodiimide at the upper end. The carbodiimide group at the lower end may be reacted in the same manner as the group, or it may be a star-shaped product having four polylactic acid main chains in one molecule.

(1) The partial structure of the nucleating agent represented by the above formula (I) is directly introduced into the main chain of polylactic acid, and
(2) The stereocomplex polylactic acid is crystallized by two points that the main chain of polylactic acid is easily entangled with each other by becoming a molecule having a maximum of four polylactic acid main chains in one molecule. I guess it was promoted.

(Impact resistance improver)
In the present invention, a commercially available acrylonitrile-butadiene-styrene copolymer (ABS resin) can be appropriately used. When the ABS resin is used, the content of the ABS resin in the polylactic acid resin composition is preferably in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the polylactic acid. If the content is less than 0.01 parts by weight, the impact resistance of the molded product cannot be improved so much. If the content exceeds 20 parts by weight, the ratio of the polylactic acid resin to the entire resin component is decreased, There is a possibility that biodegradability, which is a characteristic of lactic acid resin, is lowered.

  In the present invention, the silicon acrylic rubber is preferably a polyorganosiloxane / acrylic composite rubber containing a polyorganosiloxane and an alkyl (meth) acrylate rubber.

  The polyorganosiloxane / acrylic composite rubber containing the polyorganosiloxane and the alkyl (meth) acrylate rubber described above has a polyorganosiloxane component of 0.1 to 99.9 parts by weight and an alkyl (meth) acrylate rubber component of 99. It is preferable that it is in the range of .9 to 0.1 parts by weight (the total amount of both is 100 parts by weight). The polyorganosiloxane / acrylic rubber may be produced by any method, but the latex of the polyorganosiloxane is first prepared by emulsion polymerization, and then the monomer constituting the alkyl (meth) acrylate rubber is polyorgano It is preferred to polymerize the siloxane latex after impregnating it.

  The polyorganosiloxane rubber component constituting the composite rubber can be prepared by emulsion polymerization using the following organosiloxane and, if necessary, a crosslinking agent. In that case, a graft crossing agent can also be used together. Examples of the organosiloxane include various cyclic members having a 3-membered ring or more, and a 3- to 6-membered ring is preferably used. Examples include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, octaphenylcyclotetrasiloxane, and the like. These may be used alone or in combination of two or more. The amount of these used is 50 parts by weight or more, preferably 70 parts by weight or more in the polyorganosiloxane component.

  The alkyl (meth) acrylate rubber can be synthesized using the following alkyl (meth) acrylate, a crosslinking agent and a graft crossing agent. Examples of the alkyl (meth) acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, alkyl acrylate such as 2-ethylhexyl acrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, and n-lauryl methacrylate. And alkyl methacrylates.

  Examples of the crosslinking agent include ethylene glycol dimethacrylate, propylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, and the like. Examples of the graft crossing agent include allyl methacrylate, triallyl cyanurate, triallyl isocyanurate and the like. Allyl methacrylate can also be used as a crosslinking agent. These crosslinking agents and graft crossing agents may be used alone or in combination of two or more. The total amount of these crosslinking agents and grafting agents used is 0.01 to 20 parts by weight in the polyalkyl (meth) acrylate component.

  The silicon acrylic rubber used in the present invention is particularly preferably a graft copolymer obtained by grafting a (meth) acrylic acid ester monomer to the polyorganosiloxane / acrylic composite rubber described above. As the (meth) acrylic acid ester used for the graft polymerization, methyl methacrylate is preferably used.

  The amount of the monomer or monomer mixture used for the graft polymerization is not particularly limited, but may be 50 to 5 parts by weight with respect to 50 to 95 parts by weight of the polyorganosiloxane / acrylic composite rubber polymer. preferable. When the amount of the monomer or monomer mixture used in the graft polymerization exceeds 50 parts by weight, the impact resistance improving effect may be reduced. When the amount is less than 5 parts by weight, the powder characteristics of the graft copolymer May decrease.

  The graft copolymer used in the present invention is obtained by adding a (meth) acrylic acid ester monomer to a polyorganosiloxane / acrylic composite rubber polymer latex and polymerizing it in one or more stages by radical polymerization technology. The copolymer latex can be obtained by salting out and coagulating to separate and recover or by direct recovery by a spray drying method or the like. As the coagulant, a metal compound can be used, and in particular, an alkaline earth metal compound such as magnesium sulfate, calcium acetate, calcium chloride and the like can be used. Commercially available graft copolymers can be used as the graft copolymer thus obtained, and specific examples thereof include trade name Metabrene S-2001 manufactured by Mitsubishi Rayon Co., Ltd.

  The compounding quantity of the silicone acrylic rubber used in the present invention is 0.01 to 20 parts by weight with respect to 100 parts by weight of polylactic acid. If the content is less than 0.01 parts by weight, the impact resistance of the molded product cannot be improved so much. If the content exceeds 20 parts by weight, the ratio of the polylactic acid resin to the entire resin component is decreased, There is a possibility that biodegradability, which is a characteristic of lactic acid resin, is lowered.

  In the present invention, (C) the method for kneading the impact resistance improver to the polylactic acid resin is not particularly limited, but a method using a heat-melt kneading apparatus such as an extruder or a kneader is preferable. Examples of the extruder include a single-screw extruder, a twin-screw extruder, a multi-screw extruder of three or more axes, a twin-screw / single-screw composite extruder, etc., preferably from the viewpoint of kneadability and convenience. A single screw extruder or a twin screw extruder can be preferably used.

  In the present invention, as a method of melt-kneading using a single-screw or twin-screw extruder or the like, a polylactic acid resin, (A) a hydrazide compound, and (B) a carbodiimide are used in order to obtain a polylactic acid resin composition that is rapidly crystallized. A method in which (C) the impact modifier is melt-kneaded after the compound is melt-kneaded is preferred. As a specific manufacturing method, for example, after polylactic acid resin, (A) hydrazide compound, and (B) carbodiimide compound are melt-kneaded with an extruder in advance to form a chip, the chip and (C) improved impact resistance And a method of melt-kneading the agent with an extruder (two-stage kneading method). Also, polylactic acid resin, (A) hydrazide compound and (B) carbodiimide compound are supplied from the main feeder of the extruder, and (C) an impact resistance improver is supplied from the side feeder installed in the middle of the extruder, A method of melt kneading a polylactic acid resin and (C) an impact resistance improving agent (side feed kneading method) and the like are also included.

  In the present invention, the kneading temperature when kneading the (C) impact modifier to the polylactic acid resin is not particularly limited as long as it is equal to or higher than the melting point of the polylactic acid resin, but is preferably 220 ° C. from the viewpoint of moldability. It is -270 degreeC, More preferably, it is 220 degreeC-250 degreeC.

  In addition, as long as it does not impair the effects of the present invention, conventionally known plasticizers, antioxidants, heat stabilizers, hydrolysis inhibitors, light stabilizers, ultraviolet absorbers, pigments, and colorants, if necessary. , Various fillers, antistatic agents, release agents, fragrances, lubricants, flame retardants, silicic inorganic additives, foaming agents, fillers, antibacterial agents, antifungal agents, and the above formulas (1) and (2) You may mix | blend various additives, such as crystal nucleating agents other than the compound represented. The content of such additives is preferably 20% by weight or less in the polylactic acid resin composition of the present invention.

  Using the stereocomplex polylactic acid resin obtained by the present invention, injection molded products, extrusion molded products, vacuum pressure molded products, blow molded products, films, sheet nonwoven fabrics, fibers, fabrics, composites with other materials, agriculture Materials, fishery materials, civil engineering / architectural materials, stationery, medical supplies, or other molded articles can be obtained.

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, about the DSC measurement result (T _cd and ΔH _c values in Table 1) of the samples in the following examples and comparative examples, the conditions described in the above (1) to (3) are 3 cycles. Both the values of the first cycle and the third cycle when the measurement was performed continuously were shown.
Polylactic acid resin composition Charpy impact strength of a molded article obtained from the present invention (notched) is preferably 6 kJ / m ² or more, 7 kJ / m ² or more is more preferable. Furthermore, 8 kJ / m ² or more is preferable.

[Reference Example 1] Example of synthesis of homopolylactic acid by melt ring-opening polymerization of lactide Vertical stirring tank equipped with anchor blades equipped with vacuum piping, nitrogen gas piping, catalyst, L-lactide addition piping, and alcohol initiator addition piping ( 250 L) was purged with nitrogen, and 60 kg of L-lactide was charged, and the mixture was stirred and melted while heating to 140 ° C. This molten lactide is fed to a full-zone blade equipped stirring tank (120 L), stearyl alcohol 0.20 kg (0.012 mol / kg), and tin octylate 1.80 g (7.4 × 10 ⁻⁵ mol / kg). Was heated to 150 ° C. in a nitrogen gas atmosphere. Stirring was started when the contents were dissolved, and the internal temperature was raised from 185 ° C. to 190 ° C. and held. The viscosity of the reaction mixture increased with the progress of the reaction, and the power required for stirring gradually improved. Stirring was continued until this power value was saturated (several hours). After the stirring was stopped, the reaction vessel was degassed for 30 minutes at 39.9 kPa (300 Torr) and then allowed to stand, and the internal pressure was increased to 0.2 to 0.3 MPa (2 to 3 atmospheres) with nitrogen pressure. The polymer was extruded into a chip cutter and pelletized. Further, the pellets are melted with an extruder, charged into a non-axial vertical reactor at 30 kg / hr, depressurized to 1.5 kPa, and the residual lactide is reduced, and then the pellets are converted into chips again. -L-lactic acid has a weight average molecular weight of 160,000, polydispersity of 2.2, lactide content of 0.1 wt%, melting point of 179 ° C., carboxyl terminal amount of 6 eq. / Ton.
The same operation was performed except that D-lactide was used instead of L-lactide as a starting material, and the weight average molecular weight 150,000, polydispersity 2.1, lactide content 0.1 wt%, melting point 177 ° C, carboxyl end amount 8 eq. / Ton poly D-lactic acid was obtained.

[Reference Example 2] Example of synthesis of stereocomplex polylactic acid by melt-kneading poly-L-lactic acid and poly-D-lactic acid Chip of poly-L-lactic acid and poly-D-lactic acid produced in Reference Example 1 above Were mixed at a weight ratio of 1: 1 and dried at 50 ° C. for 5 hours in a dehumidifying dryer. With respect to 100 parts by weight of this mixed chip, 0.03 part by weight of “Adekastab (registered trademark)” NA-71 (manufactured by ADEKA), which is a phosphate metal salt, is represented by the above formula (III). After mixing 0.30 part by weight of the carbodiimide compound, the mixture was melt kneaded with a twin screw extruder at 270 ° C. and extruded to a chip cutter to obtain polylactic acid chips. As a result of DSC measurement of this chip, no crystal melting peak derived from homopolylactic acid was observed at all, and it was a stereocomplex polylactic acid having a melting point of 220 ° C. The reduced viscosity (IV) was 1.43, and the carboxyl end amount was 7.1 eq. / Ton.

  In the following Examples 1-5 and Comparative Examples 3-4, the compound sample was prepared by melt-kneading various additives with the stereocomplex polylactic acid prepared as mentioned above with a twin-screw extruder. Addition of the agent and kneading were performed in two steps as follows. That is, with respect to 100 parts by weight of the stereocomplex polylactic acid, the amount of terephthalic acid dihydrazide (China: manufactured by Jiangsu Yulin Chemical Co., Ltd.) is 0.30 parts by weight, and the amount of the carbodiimide compound represented by the above formula (III) is 0. The mixture of these two components was added simultaneously from the disc feeder to the twin screw extruder so that the amount was 96 parts by weight, and the polylactic acid melt was kneaded at 230 ° C. and rpm = 30 (retention time was about 3 minutes), first, a blended sample of these two agents was prepared. And after drying this mixing | blending sample of the 1st step with a hot air dryer at 100 degreeC for 5 hours, resistance to resistance as described in the following Examples 1-5 (Table 1) and Comparative Examples 3-4 (Table 2). The impact modifier is supplied from the first supply port of the extruder at the blending amount shown in Table 1 or 2 together with additives other than the carbodiimide compound represented by the above formula (III) to be additionally added. Only 5 parts by weight of the carbodiimide compound represented by the above formula (III) to be added is supplied from a side feeder installed in the middle of the extruder, and is made into chips by melt extrusion to create a second-stage blended sample. did. Here, the first supply port is a supply port at the root of the extruder. The melt extrusion was performed using a vent type twin screw extruder (TEX30XSST, manufactured by Nippon Steel Works, Ltd.) having a diameter of 30 mmφ. The extrusion temperature is C1 / C2 to C5 / C6 / C7 to C11 / D = 10 ° C./240° C./230° C./220° C./220° C., the main screw speed is 150 rpm, the discharge rate is 20 kg / h, The degree of vent pressure reduction was 3 kPa.

  After drying the blended sample in the second stage at 100 ° C. for 5 hours with a hot air dryer, using an injection molding machine (Toshiba Machine Co., Ltd .: IS-150EN), the cylinder temperature is 230 ° C., gold A test piece conforming to the ISO standard with a thickness of 4 mm was molded at a mold temperature of 100 ° C. and a molding cycle of 60 seconds, and allowed to stand in an environment of a temperature of 23 ° C. and a relative humidity of 50% for 24 hours. Charpy impact strength (notched) was measured.

Example 1
Addition and kneading of the above two steps using 6.0 parts by weight of silicon acrylic rubber (methabrene S-2001: manufactured by Mitsubishi Rayon Co., Ltd., grafting monomer is methacrylate) as impact modifier Samples of various additives were prepared by the method and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

(Example 2)
Using 8.0 parts by weight of silicon acrylic rubber (methabrene S-2001: the same lot as in Example 1) as an impact resistance improver, a sample of various additives in the above two-stage addition / kneading method Was prepared and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

(Example 3)
Using 6.0 parts by weight of acrylonitrile-butadiene-styrene copolymer (CH-T: manufactured by Chail) as an impact resistance improver, various additive compounding samples were prepared by the above-described two-stage addition / kneading method. Prepared and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

Example 4
By using 8.0 parts by weight of acrylonitrile-butadiene-styrene copolymer (CH-T: manufactured by Chail: the same lot as in Example 3) as an impact resistance improver, various kinds of the above two-stage addition and kneading methods are used. A blended sample of the additives was prepared and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

(Example 5)
Polylactic acid, terephthalic acid dihydrazide (China: manufactured by Jiangsu Yulin Chemical Co., Ltd.), and carbodiimide compound in the same amount as in Example 1 were added at the same time, and then 6.0 parts by weight of a silicon acrylic system as an impact modifier. A blended sample was prepared and molded using rubber (methabrene S-2001: manufactured by Mitsubishi Rayon Co., Ltd., graft monomer is methacrylic ester). The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

(Example 6)
A blended sample was prepared and molded in the same manner as in Example 1 except that ADR4300S (BASF) epoxy chain extender was not used. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 1 together with the composition of the added additive.

(Comparative Example 1)
Using the first-stage blended sample described above dried at 100 ° C. for 5 hours with a hot air dryer, a test piece compliant with the ISO standard was molded under the conditions described above. Table 2 summarizes the DSC measurement results and the Charpy impact strength (notched) of the obtained molded product.

(Comparative Example 2)
The amount of terephthalic acid dihydrazide (China: manufactured by Jiangsu Yulin Chemical Co., Ltd.) is 0.25 parts by weight and the amount of the carbodiimide compound represented by the above formula (III) is 0.80 with respect to 100 parts by weight of the stereocomplex polylactic acid. These two agents were added simultaneously so as to be parts by weight, and kneaded for 3 minutes at 230 ° C. and rpm = 30 with a lab plast mill to prepare a blended sample of these two agents. The DSC measurement results of the obtained sample are summarized in Table 2.

(Comparative Example 3)
By using 8.0 parts by weight of an acrylic rubber graft copolymer (methabrene W-341: manufactured by Mitsubishi Rayon Co., Ltd., the graft monomer is a methacrylic ester) as an impact resistance improver, the above two steps Samples of various additives were prepared by the above addition / kneading method and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 2 together with the composition of the added additive.

(Comparative Example 4)
Addition of the above two steps using 8.0 parts by weight of silicon acrylic rubber (methabrene SRK-200A: manufactured by Mitsubishi Rayon Co., Ltd., graft monomers are acrylate ester and styrene) as impact modifier -A blended sample was prepared by a kneading method and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 2 together with the composition of the added additive.

(Comparative Example 5)
1.0 part by weight of talc (fine talc P-3 manufactured by Nippon Talc Co., Ltd.) and 6.0 parts by weight of acrylonitrile-butadiene-styrene copolymer (CH—) with respect to 100 parts by weight of stereocomplex polylactic acid. T: the same lot as in Example 3) was fed from the first feed port of the twin screw extruder and melt-kneaded so as to be blended with polylactic acid together with the other additives listed in Table 2. The melt extrusion was performed using a vent type twin screw extruder (TEX30XSST, manufactured by Nippon Steel Works, Ltd.) having a diameter of 30 mmφ. The extrusion temperature is C1 / C2 to C5 / C6 / C7 to C11 / D = 10 ° C./240° C./230° C./220° C./220° C., the main screw speed is 150 rpm, the discharge rate is 20 kg / h, The degree of vent pressure reduction was 3 kPa. The obtained kneaded sample was dried at 100 ° C. for 5 hours with a hot air dryer, and then a test piece was molded in accordance with the ISO standard under the conditions described above. The DSC measurement results and Charpy impact strength (notched) of the obtained molded product are summarized in Table 2 together with the composition of the added additive.

(Comparative Example 6)
Samples containing various additives were prepared in the same manner as in Comparative Example 10 except that 6.0 parts by weight of silicon acrylic rubber (methabrene S-2001: the same lot as in Example 1) was used as the impact resistance improver. Prepared and molded. The DSC measurement results and Charpy impact strength (notched) of the obtained sample are summarized in Table 2 together with the composition of the added additive.

Since the rubber component that is an impact resistance improver is amorphous, the crystallinity of the crystalline resin generally decreases when the rubber component is added to the crystalline resin. This is no exception even when the organic nucleating agent system of the present invention is used, and the values of T _cd (crystallization rate) and ΔH _c (crystallinity) in the DSC measurement actually decrease (comparison). Examples 1 and 2 and Comparative Examples 3 and 4 and Examples 1 to 4). Moreover, it can be seen from the comparison between Examples 1 and 5 that there is a difference in the order of adding the nucleating agent.

When the organic nucleating agent system of the present invention is used, the impact resistance of the polylactic acid resin composition is improved by the addition of the rubber component, except when the impact resistance improver of Comparative Example 3 is used. 1 and the Charpy impact values in Table 2 (see Comparative Example 1 and Comparative Examples 3 to 4, and Examples 1 to 4). In addition, from the results of Examples 1 to 4 and Comparative Examples 3 to 4, as the rubber component to be used, in particular, a silicon acrylic rubber grafted with methyl methacrylate (methabrene S-2001: manufactured by Mitsubishi Rayon Co., Ltd.) is resistant. It can be said that it is excellent in improving impact. From the comparison between Example 1 and Comparative Example 6 and Example 3 and Comparative Example 5, when the organic nucleating agent system of the present invention and the rubber component are used in combination, the conventional nucleating agent (fine powder talc P-3) and the rubber component are used. It can be seen that the values of T _cd and ΔH _{c in} the 1st cycle are almost the same as in the case of using together. If the polylactic acid resin composition has the same crystallinity and the composition of the rubber component contained is the same, the impact resistance should be equivalent. Actually, the comparison between Example 3 and Comparative Example 5 shows that Charpy impact It can be seen that the values are equivalent. On the other hand, interestingly, from the comparison between Example 1 and Comparative Example 6, silicon acrylic rubber grafted with methyl methacrylate (methabrene S-2001: manufactured by Mitsubishi Rayon Co., Ltd.) despite the fact that the crystallinity is equivalent. When a specific rubber component is added, the impact resistance can be improved by using the organic nucleating agent system of the present invention as compared with the case of using conventional talc. The reason for this is not clear, but it is possible that the dispersibility of a specific rubber component is improved by blending the organic nucleating agent system of the present invention. Further, from the comparison between Example 1 and Example 2 and the comparison between Example 3 and Example 4, the impact resistance is not affected without increasing the crystallinity of the polylactic acid resin composition by increasing the addition amount of the rubber component. Can be improved. From the above results, it can be said that a stereocomplex polylactic acid resin composition having both high crystallinity and sufficient impact resistance can be suitably obtained by blending the organic nucleating agent of the present invention and a specific rubber component. In addition, unlike conventional nucleating agents such as talc, there is an advantage that the appearance of the molded product is good because no weld is generated in the molded product.

  As described above, according to the present invention, a hydrazide compound and a carbodiimide compound represented by a specific formula as a crystallization accelerator are added to a stereocomplex polylactic acid, and a rubber component having a specific structure is used as an impact resistance improver. By blending, a polylactic acid resin composition having a high crystallization temperature and excellent not only in molding processability and heat resistance but also in impact resistance is provided, and the polylactic acid resin composition is melt-molded and crystallized. As a result, it is possible to obtain a molded article having high crystallinity and impact resistance in a form having a good appearance.

  The molded product obtained from the polylactic acid resin composition of the present invention is a stereo complex and has excellent heat resistance, such as a bumper, radiator grill, side molding, garnish, wheel cover, aero parts, instrument panel, door trim, and seat. It is useful as automobile parts such as fabrics, door handles, floor mats, electrical / electronic parts, electrical equipment exterior parts OA exterior parts, product packaging films, waterproof sheets, various containers, bottles and the like. Moreover, when using the molded object of this invention as a sheet | seat, it may laminate | stack with paper or another polymer sheet, and may be used as a laminated body of a multilayer structure.

Claims (6)

100 parts by weight of polylactic acid, (A) 0.01 to 5 parts by weight of a hydrazide compound represented by the following formula (I), (B) 0.01 to 5 parts by weight of carbodiimide represented by the following formula (II) A polylactic acid resin composition comprising 0.01 to 2 parts by weight of a compound and (C) at least one impact modifier selected from acrylonitrile-butadiene-styrene copolymer and silicon acrylic rubber.

(In the formula, R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)

(In the formula, Ar ¹ , Ar ² , Ar ³ and Ar ⁴ are each independently an aromatic group which may be substituted with an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. ) In the DSC measurement conditions in which the following temperature increase and decrease processes (1) to (3) are continuously performed, the crystallization temperature (peak top temperature: T _cd ) when the temperature is decreased from the molten state is 150 ° C. or higher. The polylactic acid resin composition according to claim 1, wherein the calorific value based on crystallization (crystallization enthalpy: H _c ) is 40 J / g or more.
(1) Temperature increase from 30 ° C. to 260 ° C. at 20 ° C./min (2) Hold at 260 ° C. for 1 minute (3) Temperature decrease from 260 ° C. to 30 ° C. at 20 ° C./min   The polylactic acid resin composition according to claim 1 or 2, wherein the polylactic acid is a mixture of poly-L-lactic acid and poly-D-lactic acid.   The molded article which consists of a polylactic acid resin composition of any one of Claims 1-3.   The polylactic acid resin according to any one of claims 1 to 3, wherein a polylactic acid resin, (A) a hydrazide compound, and (B) a carbodiimide compound are melt-kneaded and then (C) an impact resistance improver is melt-kneaded. A method for producing the composition.   6. A polylactic acid resin, (A) a hydrazide compound, and (B) a carbodiimide compound are melt-kneaded, (C) an impact modifier is added, and then (B) a carbodiimide compound is further added and melt-kneaded. The manufacturing method of the polylactic acid resin composition as described in 2.