JP4788145B2 - Polylactic acid resin composition and molded product obtained by molding the same - Google Patents

Description

  The present invention relates to a polylactic acid resin composition excellent in impact resistance while maintaining a good appearance, and a molded body obtained by molding the same.

In recent years, the consumption of plastic products such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride has been increasing year by year. Along with this, these waste treatments are attracting attention as one of the environmental problems.
The current waste disposal methods are mainly incineration or buried in the soil. For example, in the case of incineration, there is a problem that polyvinyl chloride generates toxic gas. In addition, polyethylene has a high calorie burn and has a problem of shortening the life of the incinerator because the speed of damaging the incinerator is high. On the other hand, in the case of buried in the soil, the land to be buried is limited. In addition, when disposed in the natural environment, these resins have extremely high chemical stability and are hardly decomposed by microorganisms, so they remain permanently, causing problems such as environmental pollution. Yes.
Under such circumstances, recycling of resins represented by PET bottles has been promoted, but in reality the recovery rate is still low, and advanced technology and expensive equipment are required to separate the resins. And In addition, there is a drawback that the use is limited even when these recycled resins are reused.

Recently, biodegradable polymers or biodegradable polymers that decompose under natural environments have been actively developed. Among these biodegradable polymers, examples of biodegradable polymers that can be melt-molded that are expected to be versatile include, for example, polyhydroxybutyrate, polycaprolactone, aliphatic dicarboxylic acid components such as succinic acid and adipic acid, ethylene glycol, and the like. Aliphatic polyesters composed of glycol components such as butanediol, polylactic acid and the like are known. Among them, polylactic acid resin is attracting attention as an alternative to medical materials and general-purpose resins because it can be molded in various ways such as injection, fiberization, and foaming.
However, this polylactic acid resin has a drawback of being hard and brittle because of its high crystallinity. For this reason, resin molded bodies using polylactic acid resin have problems such as low impact resistance and easy breakage, and various studies have been made.
For example, Patent Document 1 and the like include a thermoplastic resin composition comprising a polylactic acid polymer and an acrylic polymer, and attempts to improve heat resistance while making use of the transparency of the polylactic acid resin. ing.
JP 2004-269720 A

However, the method described in Patent Document 1 or the like cannot obtain a sufficient effect, and further improvement has been desired.
Accordingly, an object of the present invention is to provide a polylactic acid resin composition and a molded article that are excellent in impact resistance while eliminating the problems associated with the polylactic acid resin and maintaining a good appearance.

In order to achieve the above object, the polylactic acid resin composition of the first invention of the present invention comprises 50-99.9% by mass of polylactic acid resin (A) and 0.1-50% by mass of the following ( B) It is characterized by comprising only the component.
(B) Ethylene / α-olefin copolymer rubber, ethylene / α-olefin / non-conjugated polyene copolymer rubber, ethylene / (meth) acrylic acid alkyl ester copolymer, ethylene / vinyl acetate copolymer, or acid One segment comprising a thermoplastic resin segment (a) selected from modified olefin rubbers as a trunk component and a vinyl polymer segment (b) formed from at least one vinyl monomer as a branch component. In which the dispersed phase is formed as fine particles having a particle diameter of 0.001 to 10 μm in the other segment

  The molded product of the second invention of the present invention is obtained by molding the polylactic acid resin composition of the first invention.

The polylactic acid resin composition of the first invention of the present invention is a specific product comprising a polylactic acid resin (A), a thermoplastic resin segment (a) as a trunk component, and a vinyl polymer segment (b) as a branch component. It is composed of a multiphase structure type graft copolymer (B), can have a good appearance without causing interfacial peeling, and can have excellent impact resistance.
That is, the thermoplastic resin segment (a) can have a high impact resistance effect because of its excellent elastic recovery property, but it cannot be introduced because it is generally incompatible with a polylactic acid resin alone. The vinyl polymer segment (b) is excellent in compatibility with the polylactic acid resin, but the effect of improving the impact resistance cannot be obtained even if it is usually added alone. However, in the present invention, since the graft copolymer (B) composed of these two segments (a) and (b) is used, it is well compatible with the polylactic acid resin (A), and no interfacial peeling occurs. It can have a good appearance. Moreover, the effect of improving impact resistance is obtained by the fine dispersion of the graft copolymer (B) in the polylactic acid resin (A).

The molded product of the second invention of the present invention is obtained by molding the polylactic acid resin composition of the first invention, and has a high impact resistance while maintaining a good appearance. It becomes.
The molded article of the present invention is expected to be used as a biodegradable or biodegradable polymer that decomposes in a natural environment, specifically as a substitute for various medical materials and general-purpose resins.

  Hereinafter, embodiments of the present invention will be described in detail.

First, the polylactic acid resin (A) used in the present invention will be described.
Polylactic acid has three types of optical isomers, L-form, D-form and DL (racemic) -form, any of which may be used, and a copolymer of these optical isomers is also used.
Moreover, other copolymerization components other than lactic acid may be included. Other copolymerization components include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentaerythritol, Glycol compounds such as bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, Phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid Dicarboxylic acids such as 5-sodium sulfoisophthalic acid and 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, and caprolactone, valero Examples include lactones such as lactone, propiolactone, undecalactone, and 1,5-oxepan-2-one.
As such a copolymer component, it is preferable to set it as content of 30 mol% or less normally in all the monomer components, and it is preferable that it is 10 mol% or less.

  In the present invention, it is preferable to use a polylactic acid resin having a high optical purity of the lactic acid component from the viewpoint of compatibility. That is, among the total lactic acid components of the polylactic acid resin, it is preferable that the L-form is contained at 80% or more, or the D-form is contained at 80% or more, the L-form is contained at 90% or more, or the D-form is 90% or more It is particularly preferable that the L-form is contained at 95% or more, or the D-form is contained at 95% or more.

  The molecular weight and molecular weight distribution of the polylactic acid resin are not particularly limited as long as it can be substantially molded, but the weight average molecular weight is usually 10,000 to 1,000,000, preferably 40,000 to 600,000. More preferably, it is desirably 80,000 to 400,000. When the weight average molecular weight of the polylactic acid resin is less than the lower limit, mechanical properties such as strength and elastic modulus tend to be insufficient. Moreover, when the said upper limit is exceeded, it exists in the tendency for shaping | molding workability to become inadequate.

  The melting point of the polylactic acid resin is not particularly limited, but is preferably 120 ° C. or higher, and more preferably 150 ° C. or higher.

  As a method for producing such a polylactic acid resin, a known polymerization method can be used, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

Next, the graft copolymer (B) used in the present invention will be described.
The graft copolymer (B) has a thermoplastic resin segment (a) as a trunk component and a vinyl polymer segment (b) as a branch component, and one segment has a particle size of 0.001 to 10 μm in the other segment. A specific multiphase structure type graft copolymer forming a dispersed phase as fine particles.

Examples of the thermoplastic resin used for the thermoplastic resin segment (a) as a main component of the graft copolymer (B) include ethylene / α-olefin copolymer rubber and ethylene / α-olefin / non-conjugated polyene copolymer. rubber, ethylene-alkyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, and acid-modified olefin-based rubber. These may be used alone or in combination of two or more.

  Examples of the α-olefin other than ethylene of the ethylene / α-olefin copolymer rubber and the ethylene / α-olefin / non-conjugated polyene copolymer rubber include propylene, 1-butene, 1-pentene, 1-hexene, 1- Examples include octene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene. These α-olefins are used alone or in combination of two or more. Non-conjugated polyenes include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, ethylidene norbornene, vinyl norbornene and the like.

  Specific examples of the ethylene / α-olefin copolymer rubber include ethylene / propylene copolymer rubber, ethylene / butene copolymer rubber, ethylene / hexene copolymer rubber, ethylene / octene copolymer rubber and the like. .

  Specific examples of the ethylene / α-olefin / non-conjugated polyene copolymer rubber include ethylene / butene / non-conjugated polyene copolymer rubber and ethylene / propylene / non-conjugated polyene copolymer rubber. More specifically, an ethylene / propylene / ethylidene norbornene copolymer rubber and an ethylene / propylene / dicyclopentadiene copolymer rubber may be mentioned.

  Specific examples of the ethylene / (meth) acrylic acid alkyl ester copolymer include ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / n-butyl acrylate copolymer, ethylene / acrylic. Examples thereof include an isobutyl acid copolymer, an ethylene / 2-ethylhexyl acrylate copolymer, and an ethylene / methyl methacrylate copolymer. In this specification, acrylic and methacryl are collectively referred to as (meth) acrylic.

  Specific examples of the acid-modified olefin rubber include acid-modified products of ethylene / butene copolymer rubber, acid-modified products of ethylene / propylene copolymer rubber, acid-modified products of ethylene / hexene copolymer rubber, ethylene / octene. Acid-modified products of copolymer rubber, acid-modified products of ethylene / butene / non-conjugated polyene copolymer rubber, acid-modified products of ethylene / propylene / non-conjugated polyene copolymer rubber, ethylene / acrylic acid copolymer, ethylene -Ethyl acrylate / maleic anhydride copolymer, ethylene / ethyl acrylate / acrylic acid copolymer and the like.

Among these thermoplastic resins, ethylene / propylene copolymer rubber or acid-modified products thereof, ethylene / octene copolymer rubber or acid-modified products thereof, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer are used. Polymer, ethylene / n-butyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / propylene / non-conjugated polyene copolymer rubber or acid-modified product thereof, ethylene / ethyl acrylate / maleic anhydride copolymer Since a polymer has the high elastic recovery property, since it is excellent in the impact resistance improvement effect as a result, it is preferable.

  Examples of the vinyl monomer forming the vinyl polymer segment (b) serving as a branch component of the graft copolymer (B) include (meth) acrylic acid alkyl esters having 1 to 20 carbon atoms in the alkyl chain length, and acids. It is at least one monomer selected from a vinyl monomer having a group, a vinyl monomer having a hydroxyl group, a vinyl monomer having an epoxy group, a vinyl monomer having a cyano group, and styrene. In this specification, acrylic and methacryl are collectively referred to as (meth) acrylic.

  More specifically, this vinyl monomer includes methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ( Lauryl (meth) acrylate, stearyl (meth) acrylate, (meth) acrylic acid, maleic acid, maleic anhydride, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic Examples include glycidyl acid, (meth) acrylonitrile, and styrene. Among these, from the high affinity with the polylactic acid resin (A), methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic acid, (meth) acrylic acid 2 -Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, acrylonitrile and styrene are preferred.

  The mass average molecular weight of the vinyl polymer forming the vinyl polymer segment (b) [measured by gel permeation chromatography (GPC) in terms of styrene in tetrahydrofuran (THF)] is usually 1,000 to The range is 2,000,000, preferably 5,000 to 1,200,000. When the mass average molecular weight is less than 1,000, the heat resistance of the graft copolymer (B) tends to decrease, and when the mass average molecular weight exceeds 2,000,000, the graft copolymer (B). The melt viscosity of the resin tends to increase, and the moldability tends to decrease.

  The melt flow rate (MFR) or melt index (MI) of the graft copolymer (B) is preferably 0.01 to 500 g / 10 minutes, more preferably 0.1 to 300 g / 10 minutes, most preferably 1 to 200 g / 10 minutes. This MFR is measured under the conditions of a resin temperature of 230 ° C. and a measurement load of 21 N (2.16 kg · f) in accordance with a method defined in JIS 7210. When the MFR is less than 0.01 g / 10 minutes or exceeds 500 g / 10 minutes, the affinity between the graft copolymer (B) and the polylactic acid resin (A) is reduced, or the appearance of the obtained molded article is deteriorated. It is not preferable because it is in a tendency.

  As described above, the graft copolymer (B) is of a multiphase structure type, and one segment of the thermoplastic resin segment (a) and the vinyl polymer segment (b) has a particle size of 0 in the other segment. A dispersed phase is formed as fine particles of .001 to 10 μm. In both cases where the thermoplastic resin segment (a) or the vinyl polymer segment (b) has a particle diameter of less than 0.001 μm or more than 10 μm, the graft copolymer (B) is converted into a polylactic acid resin (A). When mixed, the dispersibility is poor, and the appearance of the resulting molded article tends to deteriorate, or the mechanical properties tend to deteriorate.

  In the graft copolymer (B), the thermoplastic resin segment (a) is usually 5 to 99% by mass, preferably 20 to 95% by mass, and the vinyl polymer segment (b) is usually 1 to 95% by mass, Preferably it is 5-80 mass%. When the thermoplastic resin segment (a) is less than 5% by mass or the vinyl polymer segment (b) is more than 95% by mass, the dispersibility of the graft copolymer (B) to the polylactic acid resin (A) decreases. The appearance of the resulting molded product tends to be lowered. On the contrary, when the thermoplastic resin segment (a) exceeds 99% by mass or the vinyl polymer segment (b) is less than 1% by mass, the improvement effect on the polylactic acid resin (A) tends to be insufficient. is there. Based on such a tendency, the ratio of the thermoplastic resin segment (a) and the vinyl polymer segment (b) is adjusted to change the polarity of the graft copolymer (B). The interaction between (A) and the graft copolymer (B) can be adjusted.

  The grafting method for producing the graft copolymer (B) may be any generally known chain transfer method or ionizing radiation irradiation method, but the method shown below is most preferred. This is because the production method is simple, the grafting efficiency is high, the secondary aggregation of the vinyl polymer segment (b) due to heat does not occur, and the graft copolymer (B) is mixed with the polylactic acid resin (A). This is because it becomes easy and the interaction between the two is excellent.

For example, a specific example of producing the graft copolymer (A) in a mode in which the vinyl polymer segment (b) forms a dispersed phase as fine particles in the thermoplastic resin segment (a) is shown below.
First, 100 parts by mass of thermoplastic resin pellets are suspended in water. 1 to 400 parts by weight of vinyl monomer, 0.01 to 20 parts by weight of radically polymerizable organic peroxide with respect to 100 parts by weight of vinyl monomer, and decomposition temperature for obtaining a 10-hour half-life A mixed solution comprising 0.01 to 8 parts by mass of a radical polymerization initiator at 40 to 90 ° C. with respect to 100 parts by mass in total of the vinyl monomer and the radical polymerizable organic peroxide is added. Here, the radical polymerizable organic peroxide refers to a compound having a peroxide bond and a radical polymerizable functional group in one molecule. As this radically polymerizable organic peroxide, for example, one or a mixture of two or more compounds represented by the following general formula (1) or general formula (2) is used. It is preferable that the usage-amount of a radically polymerizable organic peroxide is 0.01-15 mass parts with respect to 100 mass parts of vinylic monomers.

  Next, the mixture is heated under conditions where decomposition of the radical polymerization initiator does not substantially occur, and a mixed solution composed of the vinyl monomer, the radical polymerizable organic peroxide, and the radical polymerization initiator having the above-described blending composition is submerged in water. It is impregnated in the pellets of the thermoplastic resin suspended in the solution. When the impregnation rate reaches 20% by mass or more, preferably 30% by mass or more of the addition amount, the temperature of the aqueous suspension is raised, and the vinyl monomer and the radical polymerizable organic peroxide are added. A grafted precursor is obtained by copolymerization in the thermoplastic resin pellets. By melting and mixing this grafting precursor at 100 to 300 ° C., a graft copolymer (B) comprising a thermoplastic resin segment (a) and a vinyl polymer segment (b) is obtained.

The radical polymerizable organic peroxide represented by the general formula (1) or the general formula (2) is the following compound.

  Specific examples of the radical polymerizable organic peroxide represented by the general formula (1) or the general formula (2) include t-butylperoxyacryloyloxyethyl carbonate and t-butylperoxymethacryloyloxyethyl. Carbonate, t-butylperoxyallyl carbonate, and t-butylperoxymethacrylic carbonate are preferred.

  In the polylactic acid resin composition of the first invention of the present invention, the polylactic acid resin (A) and the graft copolymer (B) having the above constitution are melted at 120 to 300 ° C., more preferably 140 to 280 ° C., Manufactured by mixing. When this temperature is less than 120 ° C., the melting is incomplete or the melt viscosity is high, so that the mixing becomes insufficient and phase separation or delamination tends to appear, which is not preferable. On the other hand, when it exceeds 300 degreeC, since polylactic acid resin (A) and a graft copolymer (B) decompose | disassemble, it is unpreferable. As a method of melting and mixing, a known method such as a kneading method using a single screw extruder, a twin screw extruder, a Banbury, a kneader, a roll or the like is employed.

  Further, the graft copolymer (B) may not necessarily be mixed after it is prepared as a graft copolymer, and may be mixed with the polylactic acid resin (A) in the state of a grafted precursor. This is because the grafting precursor is converted into the graft copolymer (B) by melting and mixing. In addition, when melted and mixed with the grafting precursor, there is a possibility that a part thereof may be copolymerized with the polylactic acid resin (A) to become a graft copolymer.

  As for the ratio of the polylactic acid resin (A) and the graft copolymer (B) in the present invention, the polylactic acid resin (A) is preferably 50 to 99.9% by mass, and more preferably 60 to 99% by mass. Therefore, the proportion of the graft copolymer (B) is preferably 0.1 to 50% by mass, and more preferably 1 to 40% by mass. If the proportion of the graft copolymer (B) is less than 0.1% by mass, the resulting molded product is insufficiently developed in impact resistance, and if it exceeds 50% by mass, the resulting molded product is biodegradable. Is unfavorable because of lowering.

  Moreover, you may mix | blend other resin, rubber | gum, or an inorganic filler with the polylactic acid resin composition of this invention in the range which does not impair the objective of this invention. Examples of such resins and rubbers include general-purpose plastics such as polypropylene, polyethylene, polystyrene, and polyvinyl chloride, ethylene / methyl acrylate / glycidyl methacrylate copolymer, ethylene / glycidyl methacrylate copolymer, and ethylene / acetic acid. Epoxy group-containing olefin resins such as vinyl glycidyl methacrylate copolymer, engineering plastics such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyamide, butyl rubber, polyisobutylene rubber, nitrile rubber (NBR), natural rubber, acrylic Examples thereof include elastomers such as rubber, silicon rubber, polyamide-based elastomer, and polyester-based elastomer. Examples of the inorganic filler include calcium carbonate, calcium silicate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, and disulfide. Examples include molybdenum, graphite, glass fiber, glass sphere, shirasu balloon, basic magnesium sulfate whisker, calcium titanate whisker, and aluminum borate whisker.

  Further, the polylactic acid resin composition of the present invention is a known heat stabilizer, anti-aging agent, weathering stabilizer, antistatic agent, dispersant, foaming agent, ultraviolet light inhibitor, and colorant as long as the object of the present invention is not impaired. , Plasticizers, mineral oil softeners and the like can be blended.

  The molded body of the present invention can be obtained by molding the polylactic acid resin composition described above. The shape of the molded product of the present invention is not particularly limited, and may be any of injection molded products, compression molded products, blow molded products, sheets, films, yarns, fabrics, and the like. More specifically, automobile parts, home appliance parts, product packaging films, waterproof sheets, various containers, bottles and the like can be mentioned. Moreover, when using the molded object of this invention as a sheet | seat, you may laminate | stack with a sheet | seat with paper or resin, and may use it as a laminated body of a multilayer structure.

  In addition, the method for producing the molded body of the present invention is not particularly limited, and any of injection molding, extrusion molding, blow molding, inflation molding, profile extrusion molding, injection blow molding, vacuum pressure molding, spinning, etc. Also, it can be suitably used.

  The molded body formed by molding the polylactic acid resin composition of the present invention can be molded with a normal thermoplastic resin molding machine, for example, substitutes for medical materials and general-purpose resins, automobile parts, household appliance parts, It can be used in a wide range of fields including miscellaneous goods.

The embodiment will be described more specifically below with reference examples, examples and comparative examples, but the present invention is not limited to these examples. Unless otherwise indicated, the part and% in each example show a mass part and mass%. In addition, the test method used for the physical-property measurement in these reference examples, an Example, and a comparative example is as follows.
(1) Izod impact test: Using a granulated resin, a test piece was prepared by an injection molding machine (manufactured by Tabata Machinery Co., Ltd.). The size of the test piece is as follows.
Izod impact test piece 64mm x 12.7mm x 3.2mm (with notch)
The test was performed according to JIS7110.
(2) Molded body appearance: The molded body appearance of the test piece used in the Izod impact test was evaluated according to the following evaluation criteria.
A: A state in which no interfacial peeling is observed. X: State where interface peeling is observed.

The following reference examples and abbreviations in the table represent the following substances.
Polylactic acid resin 1: Terramac TE-4000, manufactured by Unitika Ltd. Polylactic acid resin 2: Terramac TE-7000, manufactured by Unitika Ltd. EPR: Ethylene / propylene copolymer rubber (trade names: EP07P, manufactured by JSR Corp.) )
EOR: Ethylene / octene copolymer rubber (trade name: Engage 8100, DuPont Dow Elastomer Co., Ltd.)
EEA: Ethylene / ethyl acrylate copolymer (trade name: NUC Copolymer-NUC6570, manufactured by Nippon Unicar Co., Ltd.)
MMA: methyl methacrylate EA: ethyl alkylate BA: butyl acrylate St: styrene MAA: HPMA methacrylate: 2-hydroxypropyl methacrylate GMA: glycidyl methacrylate AN: acrylonitrile

[Reference Example 1, Production of Graft Copolymer]
In a 5 liter stainless steel autoclave, 2500 g of pure water was added, and 2.5 g of polyvinyl alcohol was dissolved as a suspending agent. 500 g of EPR was put into this and stirred and dispersed. Separately, 1.5 g of di-3,5,5-trimethylhexanoyl peroxide as a radical polymerization initiator, 9 g of t-butylperoxymethacryloyloxyethyl carbonate as a radical polymerizable organic peroxide, and 200 g of MMA as a vinyl monomer , Dissolved in a mixed solution of 250 g of BA and 50 g of GMA. This mixed solution was put into the autoclave and stirred.

  Next, the autoclave was heated to 60 to 65 ° C. and stirred for 3 hours to impregnate EPR with a radical polymerization initiator, a radical polymerizable organic peroxide and a vinyl monomer. Subsequently, it was confirmed that the total amount of the impregnated vinyl monomer, radical polymerizable organic peroxide and radical polymerization initiator was 30% by weight or more of the addition amount. Thereafter, the temperature was raised to 70 to 75 ° C., maintained at that temperature for 6 hours to complete the polymerization, washed with water and dried to obtain a grafted precursor.

  The MMA / BA / GMA copolymer was extracted from this grafted precursor with tetrahydrofuran (THF), and the weight average molecular weight (in THF, in terms of styrene) was measured by GPC. As a result, it was 800,000.

  Next, this grafting precursor was extruded at 180 ° C. with a Laboplast Mill single screw extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and grafted to obtain a graft copolymer (B).

  When this graft copolymer (B) was observed with a scanning electron microscope (manufactured by Hitachi, Ltd.), heat of a multiphase structure type in which a true spherical resin having a particle size of 0.3 to 0.4 μm was uniformly dispersed. The MMA / BA / GMA copolymer, which is a plastic resin and is a vinyl polymer segment (b), forms an dispersed phase as fine particles in the EPR that is the thermoplastic resin segment (a). The graft efficiency of the MMA / BA / GMA copolymer was 70%.

[Reference Examples 2-3 ]
The graft copolymer (B) was obtained in the same manner as in Reference Example 1 except that the components and blending ratios shown in Table 1 were used.

[Examples 1 to 3 , Comparative Examples 1 to 4 , Production of Polylactic Acid Resin Composition]
After dry blending with the components and blending ratios shown in Table 2, the mixture was melted and mixed with a coaxial twin screw extruder having a screw diameter of 30 mm set at a cylinder temperature of 190 ° C. to obtain polylactic acid resin composition pellets.

[Summary of Examples and Comparative Examples]
As shown in Table 1, it was confirmed that the polylactic acid resin composition and molded body of the present invention have good impact resistance and molded body appearance as seen in the results of Examples 1 to 3. It was done.
On the other hand, Comparative Examples 1 and 2 were inferior in impact resistance because they were polylactic acid resins alone. In Comparative Examples 3 and 4, only the thermoplastic resin alone was added to the polylactic acid resin, so that the impact resistance and the appearance of the molded product were inferior. Further, Comparative Example 5 was inferior in impact resistance because only the vinyl segment polymer was added to the polylactic acid resin.

  Biodegradable or biodegradable polymers that decompose under natural conditions, specifically various medical materials and substitutes for general-purpose resins, automobile parts, home appliance parts, miscellaneous goods, etc. It is.

Claims (2)

A polylactic acid resin composition comprising only 50 to 99.9% by mass of a polylactic acid resin (A) and 0.1 to 50% by mass of the following component (B).
(B) Ethylene / α-olefin copolymer rubber, ethylene / α-olefin / non-conjugated polyene copolymer rubber, ethylene / (meth) acrylic acid alkyl ester copolymer, ethylene / vinyl acetate copolymer, or acid One segment comprising a thermoplastic resin segment (a) selected from modified olefin rubbers as a trunk component and a vinyl polymer segment (b) formed from at least one vinyl monomer as a branch component. In which the dispersed phase is formed as fine particles having a particle diameter of 0.001 to 10 μm in the other segment   A molded article obtained by molding the polylactic acid resin composition according to claim 1.