JP5348161B2 - Polylactic acid-based thermoplastic resin composition and molded article thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid thermoplastic resin composition excellent in mechanical strengths such as impact resistance, heat resistance, etc. by giving mechanical strengths such as practically sufficient impact-resistant strength etc. to the polylactic acid resin. <P>SOLUTION: This polylactic acid thermoplastic resin composition contains 20-95 pts.wt. polylactic acid resin (A) and 5-80 pts.wt. rubber reinforced resin (B) (wherein the total of the polylactic acid resin (A) and the rubber reinforced resin (B) is 100 pts.wt.), and the rubber reinforced resin (B) contains 30-95 wt.% rubber-containing graft copolymer (b-1) and 5-70 wt.% hard (co)polymer (b-2) and the hard (co)polymer (b-2) contains a (meth)acrylic resin component. For a monomer constituting the (meth)acrylic resin component, methacrylate and/or acrylate are preferable. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a polylactic acid-based thermoplastic resin composition capable of providing a molded article excellent in mechanical properties such as impact resistance and heat resistance, and a molding formed by molding this polylactic acid-based thermoplastic resin composition. It is about goods.

  Recently, an increase in the concentration of carbon dioxide in the atmosphere has been pointed out as a cause of global warming, and the need for regulation of carbon dioxide emissions on a global scale has been advocated. Carbon dioxide emission sources include respiration of organisms, spoilage and fermentation by bacteria, etc., but the part due to combustion is large, and the current phenomenon of rising carbon dioxide concentration in the atmosphere wasted oil resources after the industrial revolution by humans It is no exaggeration to say that it was brought about by economic activities.

  By the way, in recent years, effective utilization of plant resources that absorb and fix carbon dioxide has attracted attention as carbon neutral. In other words, vegetation is intended to absorb carbon dioxide while replacing petroleum resources that are expected to be depleted in the future.

  In the field of plastics, biomass-based plastics were developed from those based on conventional petroleum as a basic raw material. At first, they attracted attention as biodegradable resins, but recently their significance has been reviewed as plant-based plastics. ing.

  Among these biodegradable resins, polylactic acid resin (PLA) has been expected to be put into practical use because of its physical properties and possibility of mass production. However, polylactic acid resin is mechanical compared to existing petroleum plastics. There is a drawback that it is inferior in strength, particularly impact strength, and its improvement has been desired from an early stage.

  In general, in order to improve the impact strength strength of plastics, a method of blending a rubbery polymer has been performed, and similar efforts have been made for polylactic acid resins.

  For example, Patent Document 1 “Japanese Patent Laid-Open No. 9-316310” and Patent Document 2 “Japanese Patent Laid-Open No. 2001-123055” disclose a method of adding a modified olefin compound to Japanese Patent Laid-Open No. 11-140292. ”Shows a method of blending a cross-linked polycarbonate, but none of them can be said to have a sufficient effect of improving physical properties as compared with existing general-purpose plastics.

  Patent Document 4 “Japanese Patent Laid-Open No. 2002-37987” shows the blending of a graft polymer (AES resin) to ethylene-propylene-diene rubber (EPDM), but the impact strength indicated by Izod impact strength. The improvement effect is not sufficient.

  Patent Document 5 “Japanese Patent Application Laid-Open No. 2003-286396” shows a blending effect of a graft polymer as a multilayer structure polymer. Here, the outermost layer of the multilayer polymer is defined as a polymer containing an unsaturated carboxylic acid alkyl ester-based unit. Specifically, a polymer grafted to a rubbery polymer such as methyl methacrylate is suggested. ing. In this technique, the reforming effect is certainly highly evaluated, but since these modifiers are all expensive, they are not suitable for industrial production.

JP 9-316310 A JP 2001-123055 A JP-A-11-140292 JP 2002-37987 A JP 2003-286396 A

  The present invention solves the above-described problems in the prior art, and gives mechanical strength such as practically sufficient impact strength to the polylactic acid resin, thereby being excellent in mechanical properties such as impact resistance, heat resistance and the like. It is an object of the present invention to provide a polylactic acid-based thermoplastic resin composition capable of obtaining a molded product, and a molded product formed by molding the polylactic acid-based thermoplastic resin composition.

  As a result of diligent efforts to verify and improve the conventional technology, the present inventors have obtained a very high impact strength strength by blending a rubber-reinforced resin containing a (meth) acrylic resin component with a polylactic acid resin. The present invention has been discovered.

That is, the gist of the present invention is that a polylactic acid-based thermoplastic resin composition containing 40 to 90 parts by weight of a polylactic acid resin (A) and 10 to 60 parts by weight of a rubber-reinforced resin (B) (however, a polylactic acid resin ( A) and the rubber-reinforced resin (B) in total 100 parts by weight), and the rubber-reinforced resin (B) is in the presence of a rubbery polymer having a gel content of 60 to 95% by weight, Obtained by graft polymerization of vinyl cyanide monomer and aromatic vinyl monomer having a weight composition ratio of vinyl cyanide monomer and aromatic vinyl monomer of 25/75 to 30/70. The rubber-containing graft copolymer (b-1) 30 to 95% by weight and the hard (co) polymer (b-2) 5 to 70% by weight, and the hard (co) polymer (b-2) ) Contains 20 to 100% by weight of a (meth) acrylic resin component. Polylactic acid thermoplastic resin composition which consists in.

In the present invention, the monomers constituting the (meth) acrylic resin component in said rigid (co) polymer (b-2), methacrylic acid esters and / or acrylic acid esters are preferred.

  In the present invention, “(meth) acrylic acid” is a general term for “acrylic acid” and “methacrylic acid”, and “hard (co) polymer” means “hard polymer (homopolymer)” and “hard copolymer”. It is a general term for “polymer”.

  Another gist of the present invention resides in a molded article formed by molding the polylactic acid-based thermoplastic resin composition of the present invention.

  In the present invention, the later-described polylactic acid resin (A), the hard (co) polymer (b-2), the acetone-soluble component of the rubber-containing graft copolymer (b-1), and the hard (co) polymer The weight average molecular weight (Mw) of the acetone-soluble component of (b-2) is measured by dissolving in tetrahydrofuran (THF) with gel permeation chromatography (GPC) and converted to polystyrene (PS). It is shown by.

  The polylactic acid-based thermoplastic resin composition of the present invention has a good balance of mechanical strength such as impact strength, rigidity, and heat resistance of a molded product obtained by molding the composition, and is used as various cases and structural members. It is a material suitable for.

  According to the present invention, by providing a practical polylactic acid-based thermoplastic resin composition as described above, the use of a polylactic acid resin that is a plant-based resin is expanded, and the practice of the philosophy of carbon neutral is promoted. It can contribute to reduction of environmental load.

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

[Polylactic acid resin (A)]
The polylactic acid resin (A) applied to the resin composition of the present invention can be obtained by known means such as a method of directly dehydrating condensation polymerization of lactic acid or a method of ring-opening polymerization of lactide.

  There are three types of optical isomers, L-form, D-form, and DL-form, in the polylactic acid resin, and commercially available polylactic acid resins have L-form purity close to 100%. The polylactic acid resin (A) used in (1) does not particularly define its purity, and may be a copolymer containing other copolymerization components as long as the effects of the present invention are not impaired.

  Other copolymerization components contained in the polylactic acid resin (A) include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethano -Glycol compounds such as diol, neopentyl glycol, glycerin, pentaerythritol, bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; oxalic acid, succinic 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, Dicarboxylic acids such as' -diphenyl ether dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium isophthalic acid; hydroxycarboxylic acids such as glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid Examples include acids; lactones such as caprolactone, valerolactone, propiolactone, undecalactone, and 1,5-oxepan-2-one. The content of such a copolymer component is usually preferably 30 mol% or less and more preferably 10 mol% or less in all monomer components in the polylactic acid resin (A).

  The molecular weight and molecular weight distribution of the polylactic acid resin (A) is not particularly limited as long as it can be practically processed, but the weight average molecular weight is usually 10,000 or more, preferably 50,000 or more, Furthermore, it is desirable that it is 100,000 or more. Although there is no restriction | limiting in particular about the upper limit of the weight average molecular weight of a polylactic acid resin (A), Usually, it is 400,000 or less.

  The molecular weight can be measured by GPC (solvent THF: tetrahydrofuran), but when polylactic acid is in the form of pellets, it may be difficult to dissolve in THF. In that case, after dissolving in chloroform, The polymer component is precipitated using methanol, and the dried polymer component is dissolved in THF, and the molecular weight of the soluble component can be measured. Further, it can be dissolved by heating as necessary.

In the present invention, the amount of the polylactic acid-based thermoplastic polylactic acid resin in the resin composition (A) is 100 parts by weight of the total of the polylactic acid resin (A) and the rubber-reinforced resin (B) 4 0 to 90 parts by weight is preferable from the viewpoint of carbon neutral and improvement of impact resistance. If the blending amount of the polylactic acid resin (A) is less than this range, the object of the present invention for effectively using the polylactic acid resin cannot be achieved. If the blending amount is large, a polylactic acid-based thermoplastic resin molded article having excellent impact resistance is obtained. Cannot be obtained.

In addition, a polylactic acid resin (A) may be used individually by 1 type, and 2 or more types may be mixed and used for it.
Specific examples of such a polylactic acid resin include, for example, “Lacia” manufactured by Mitsui Chemicals, Inc., “Nature Works” manufactured by Cargill-Dow, “Ecology” manufactured by Mitsubishi Plastics, Inc., and the like. Can be used.

[Rubber reinforced resin (B)]
The rubber-reinforced resin (B) used in the present invention is composed of 30 to 95% by weight of a rubber-containing graft copolymer (b-1) obtained by graft polymerization of a hard (co) polymer to a rubbery polymer, and a hard (co) weight. (B-2) 5 to 70% by weight (total of 100% by weight of (b-1) and (b-2)), and at least in the hard (co) polymer (b-2) (meth) It contains an acrylic resin component.

<Rubber-containing graft copolymer (b-1)>
The rubber-containing graft copolymer (b-1) used in the present invention is generally expressed by ABS, ASA, AES, MBS, etc., and has a structure in which a hard (co) polymer is graft-polymerized to a rubbery polymer. It is what you have.

  Examples of the rubbery polymer forming the rubber-containing graft copolymer (b-1) include butadiene rubbers such as polybutadiene, styrene / butadiene copolymer, acrylate ester / butadiene copolymer, and styrene / isoprene. Conjugated diene rubbers such as copolymers; Acrylic rubbers such as polybutyl acrylate; Olefin rubbers such as ethylene / propylene copolymers; Silicone rubbers such as polyorganosiloxane, etc. It can be used alone or in admixture of two or more. These rubbery polymers can be used from monomers, and the structure of the rubbery polymer may take a core / shell structure. For example, a rubbery polymer having polybutadiene as the core and acrylic acid ester as the shell can be used.

Gel content of the rubber polymer described above, 6 0-95 wt%, good Mashiku is 70 to 85 wt%. When the gel content is within this range, the properties of the resulting polylactic acid-based thermoplastic resin composition, particularly the impact strength, can be improved.

  In order to measure the gel content of the rubber polymer, specifically, the weighed rubber polymer was dissolved in an appropriate solvent at room temperature (23 ° C.) over 20 hours, and then 100 mesh. After separating with a wire mesh, the insoluble matter remaining on the wire mesh is dried at 60 ° C. for 24 hours and then weighed. The ratio (% by weight) of the insoluble matter with respect to the rubber polymer before fractionation is determined and used as the gel content of the rubber polymer. As the solvent used for dissolving the rubbery polymer, for example, toluene is used for polybutadiene and acetone is used for polybutyl acrylate.

  The particle size of the rubbery polymer is not particularly limited, but is preferably 0.1 to 1 μm, and more preferably 0.2 to 0.5 μm. The average particle size of the rubbery polymer can be measured by an optical method before graft polymerization. Further, after graft polymerization, the average particle diameter can be calculated using a transmission electron microscope (TEM) after dyeing the rubber polymer with a dyeing agent.

  The rubber-containing graft copolymer (b-1) is preferably obtained by graft polymerization of 60 to 20% by weight of the graft-polymerizable monomer component in the presence of 40 to 80% by weight of the above rubbery polymer. (However, the total of the rubbery polymer and the monomer mixture is 100% by weight). Here, if the rubber polymer is less than 40% by weight, the impact resistance of the obtained polylactic acid-based thermoplastic resin molded article cannot be obtained, and if it exceeds 80% by weight, the impact resistance and fluidity are lowered. May be incurred.

  Examples of monomer components capable of graft polymerization include vinyl cyanide monomers, aromatic vinyl monomers, methacrylic acid ester monomers, acrylic acid ester monomers, and maleimide compounds. Each monomer can be used alone or in combination of two or more.

Examples of the vinyl cyanide monomer include acrylonitrile and methacrylonitrile, and acrylonitrile is particularly preferable.
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, bromostyrene, and the like, and styrene and α-methylstyrene are particularly preferable.
Examples of the methacrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and derivatives thereof. Among these, methyl methacrylate is particularly preferable.
Examples of the acrylate monomer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and derivatives thereof. Among these, methyl acrylate is particularly preferable.
Examples of the maleimide compound include N-phenylmaleimide, N-cyclohexylmaleimide and the like.

  Moreover, the monomer modified | denatured by the functional group by the case may be included, for example, acrylic acid, methacrylic acid, itaconic acid, fumaric acid etc. are mentioned as unsaturated carboxylic acid. These can be used individually by 1 type or in mixture of 2 or more types. The proportion of use is preferably 30% by weight or less, particularly preferably 10% by weight or less, based on 100% by weight in the monomer mixture.

The monomer component to be grafted of the rubber-containing graft copolymer (b-1) is preferably a vinyl cyanide monomer or an aromatic vinyl monomer among the above exemplified monomers. As the vinyl monomer, acrylonitrile is preferable, and as the aromatic vinyl monomer, styrene is particularly preferable from the viewpoint of further improving the impact resistance of the obtained polylactic acid-based thermoplastic resin molded article. In this case, the weight composition ratio of the vinyl cyanide monomer and the aromatic vinyl monomer is 2 5 / 75-30 / 70. Outside this range, dispersibility and thermal stability decrease.

  The weight-average molecular weight of the acetone-soluble component of the rubber-containing graft copolymer (b-1) is preferably in the range of 50,000 to 600,000, more preferably 50,000 to 550,000, and still more preferably. It is in the range of 100,000 to 450,000. When the weight-average molecular weight of acetone-soluble component is lower than this range, the resulting polylactic acid-based thermoplastic resin molded article has insufficient impact resistance, and when it exceeds this range, polylactic acid-based thermoplasticity The moldability of the resin composition is reduced. The acetone-soluble component corresponds to a polymer product of a monomer that is not graft-polymerized to the rubbery polymer that is generated when the monomer is graft-polymerized to the rubbery polymer.

  The graft ratio of the rubber-containing graft copolymer (b-1) ((acetone insoluble matter weight / rubber polymer weight-1) × 100) is preferably 15 to 120% by weight, more preferably 20 to 85% by weight. Is more preferable. When the graft ratio is lower than 15% by weight, the dispersibility of the rubbery polymer is lowered and the impact strength is lowered. When the graft ratio is higher than 120% by weight, the impact strength and molding are reduced. Tend to decrease. The grafted copolymer may have a structure occluded not only inside but also inside the rubbery polymer.

  Graft polymerization can be performed by known emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization, and may be a method combining these polymerization methods. As the rubber-containing graft copolymer (b-1), two or more kinds of rubber-containing graft copolymers having different polymerization methods and component compositions may be mixed and used.

<Hard (co) polymer (b-2)>
As a monomer component used for the hard (co) polymer (b-2) of the present invention, one or more monomers introduced in the above rubber-containing graft copolymer (b-1) are used. Can be used.
The weight average molecular weight of the hard (co) polymer (b-2) is preferably in the range of 30,000 to 300,000, and more preferably in the range of 50,000 to 250,000. When the weight average molecular weight of the hard copolymer (b-2) is lower than this range, the resulting polylactic acid-based thermoplastic resin molded article has insufficient impact resistance, and when this range is exceeded. In this case, the moldability is lowered.

  By blending the hard (co) polymer (b-2), characteristics such as heat resistance and fluidity can be improved, but the blending amount of the hard (co) polymer (b-2) is rubber-containing. If it exceeds 70% by weight with respect to the total of 100% by weight of the graft copolymer (b-1) and the hard (co) polymer (b-2), the rubber content in the rubber-reinforced resin (B) is reduced. As a result, the impact strength is reduced. For this reason, the compounding amount of the hard (co) polymer (b-2) is 100% by weight in total of the rubber-containing graft copolymer (b-1) and the hard (co) polymer (b-2). 5 to 70% by weight, preferably 5 to 60% by weight, more preferably 5 to 50% by weight.

  Moreover, when mix | blending hard (co) polymer (b-2), the weight of acetone soluble part which match | combined the rubber-containing graft copolymer (b-1) and hard (co) polymer (b-2). The average molecular weight is in the range of 50,000 to 600,000, particularly in the range of 50,000 to 550,000, in particular 100,000, as shown in the description of the rubber-containing graft copolymer (b-1). A range of 450,000 is preferred. When the weight-average molecular weight of acetone-soluble component is lower than this range, the resulting polylactic acid-based thermoplastic resin molded article has insufficient impact resistance, and when it exceeds this range, polylactic acid-based thermoplasticity The moldability of the resin composition is reduced.

  In addition, a hard (co) polymer (b-2) may be used individually by 1 type, and may mix and use 2 or more types of a different composition and molecular weight.

<Rubber content>
In the present invention, the rubber content in the rubber-reinforced resin (B), that is, the rubber weight in the mixture of the rubber-containing graft copolymer (b-1) and the hard (co) polymer (b-2). It is preferable to adjust the coal content to be in the range of 5 to 80% by weight, particularly 10 to 70% by weight. If the content of the rubbery polymer in the rubber reinforced resin (B) is lower than this range, sufficient impact resistance cannot be obtained, and if it exceeds this range, the impact strength is reduced. . The content of the rubbery polymer in the rubber reinforced resin (B) can be measured by using an infrared spectrometer.

<(Meth) acrylic resin component>
The (meth) acrylic resin component is contained in the hard (co) polymer (b-2) in the rubber-reinforced resin (B) used in the present invention in a proportion of 20 to 100% by weight. In addition, the (meth) acrylic resin component is included in the hard (co) polymer (b-2) rather than the graft component of the rubber-containing graft copolymer (b-1), thereby improving impact resistance. The effect is exhibited even more effectively.

  Thus, by using the hard (co) polymer (b-2) containing a (meth) acrylic resin component, the rubber-reinforced resin (B) used in the present invention contains a (meth) acrylic resin. It is preferable that the component is contained in an amount of 5 to 70% by weight, particularly 5 to 60% by weight, particularly 5 to 50% by weight. If the content of the (meth) acrylic resin component in the rubber reinforced resin (B) is less than 5% by weight, the effect of improving the impact resistance by blending the rubber reinforced resin (B) can be sufficiently exerted. Can not. Further, if the (meth) acrylic resin component in the rubber-reinforced resin (B) exceeds 70% by weight, impact resistance and moldability are lowered, which is not preferable.

  As the (meth) acrylic resin component, a polymerization component of a methacrylic ester monomer such as methyl methacrylate, or an acrylate monomer such as methyl methacrylate monomer and methyl acrylate and / or A copolymerization component with other copolymerizable monomers is preferable, but the weight ratio of each monomer of methacrylic acid ester and acrylic acid ester is preferably 100/0 to 50/50, and more preferably 99/1 to A range of 80/20 is preferred. When the amount of acrylic ester exceeds this range, the thermal stability and heat resistance of the resulting polylactic acid-based thermoplastic resin composition tend to be impaired.

  Specific examples of the copolymer of methyl methacrylate and methyl acrylate include, for example, “Parapet G” manufactured by Kuraray Co., Ltd., “Acrypet VH”, “Acrypet” manufactured by Mitsubishi Rayon Co., Ltd. MD ”and the like. Therefore, by blending these in the polylactic acid-based thermoplastic resin composition of the present invention as a hard (co) polymer (b-2), (meta) ) An acrylic resin component can be contained.

[Other ingredients]
In the polylactic acid-based thermoplastic resin composition of the present invention, the polylactic acid resin (A), the rubber-reinforced resin (B), that is, the rubber-containing graft copolymer (b-1) and, if necessary, are blended. In addition to the hard (co) polymer (b-2), various additives and other resins can be further blended. In this case, various additives include known antioxidants, ultraviolet absorbers, lubricants, plasticizers, stabilizers, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), carbon fibers and glass fibers, Fillers such as talc, wollastonite, calcium carbonate, silica, flame retardants (halogen flame retardants, phosphorus flame retardants, antimony compounds, etc.), anti-drip agents, antibacterial agents, fungicides, silicone oil, couplings 1 type or 2 types or more, such as an agent, is mentioned.

  Other resins include rubber-reinforced styrene resins such as HIPS resin, ABS resin, ASA resin, AES resin, AS resin, polystyrene resin, polycarbonate resin, nylon resin, methacrylic resin, polyvinyl chloride resin, Examples include polybutylene terephthalate resin, polyethylene terephthalate resin, and polyphenylene ether resin. Moreover, what blended these 2 or more types may be sufficient, and you may mix | blend the said resin modified | denatured with the compatibilizing agent, the functional group, etc. further.

[Production and molding of polylactic acid-based thermoplastic resin composition]
There is no restriction | limiting in particular as a method of pelletizing the polylactic acid-type thermoplastic resin composition of this invention, For example, a twin-screw extruder, a Banbury mixer, a heating roll, etc. can be used, Among these, a twin-screw extruder is used. Melt kneading by is preferable, and if necessary, resin and other additives can be blended by side feed or the like.

  The polylactic acid-based resin composition of the present invention can be molded into various molded products by ordinary molding methods such as injection molding, blow molding, sheet molding, and vacuum molding. Is preferred.

  Although there is no restriction | limiting in particular as a use of the molded product obtained, In an automobile connection, it can use suitably especially for interior parts, such as a floor board in a trunk, a tire cover, and a floor box.

  In addition, when preparing each component of the polylactic acid-based thermoplastic resin composition of the present invention, or when mixing, kneading, or molding these components, the resin waste, etc. generated as it is or in some cases is crushed. Thus, it can be subjected to a melt regeneration process. In this case, it can be recovered during molding, but it can also be recovered separately and used as a raw material in the above-described pellet manufacturing process.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In the following, “part” means “part by weight”.

The weight average molecular weight was measured by a standard PS (polystyrene) conversion method using Tosoh Co., Ltd. product: GPC (gel permeation chromatography, solvent; THF).
The average particle diameter of the rubber polymer was determined by a dynamic light scattering method using Nikkiso Co., Ltd .: Microtrac Model: 9230UPA.
The weight composition ratio of the monomer was determined using FT-IR manufactured by Horiba Ltd.

[Polylactic acid resin]
Polylactic acid resin (a-1): biodegradable polymer (L-form / D-form = 98/2 (weight ratio),
(Weight average molecular weight = 140,000, melting point = 171 ° C.)

[Rubber reinforced resin]
[Rubber-containing graft copolymer (b-1)]
Synthesis Example 1: Production of rubber-containing graft copolymer (b-1-1) A rubber-containing graft copolymer was synthesized by the emulsion polymerization method with the following composition.
[Combination]
Styrene (ST) 25 parts Acrylonitrile (AN) 10 parts Polybutadiene latex 65 parts (as solids)
Disproportionated potassium rosinate 1 part Potassium hydroxide 0.03 part Tertiary decyl mercaptan (t-DM) 0.04 part Cumene hydroperoxide 0.3 part Ferrous sulfate 0.007 part Sodium pyrophosphate 0.1 Part Crystalline glucose 0.3 part Distilled water 190 part

  An autoclave is charged with distilled water, disproportionated potassium rosinate, potassium hydroxide and polybutadiene latex (gel content 80% by weight, average particle size 0.3 μm), heated to 60 ° C., ferrous sulfate, sodium pyrophosphate Crystalline glucose was added and ST, AN, t-DM and cumene hydroperoxide were continuously added over 2 hours while maintaining the temperature at 60 ° C., and then the temperature was raised to 70 ° C. and maintained for 1 hour to complete the reaction. . An antioxidant was added to the ABS latex obtained by this reaction, then coagulated with sulfuric acid, sufficiently washed with water, and dried to obtain an ABS graft copolymer (b-1-1).

Synthesis Example 2: Production of rubber-containing graft copolymer (b-1-2) In the raw material formulation of Synthesis Example 1, polybutadiene (average particle size 0.3 μm) 50 having a gel content of 97% by weight as a rubbery polymer. The graft polymerization was carried out in the same manner as in Synthesis Example 1 except that 37 parts of styrene and 13 parts of acrylonitrile were reacted as a monomer using a part (as a solid content), and an ABS graft copolymer (b-1- 2) was obtained.

Synthesis Example 3: Production of rubber-containing graft copolymer (b-1-3) In the raw material formulation of Synthesis Example 1, polybutyl acrylate (gel content 65%, average particle size 0.34 μm) 60 was used as the rubbery polymer. Graft polymerization was performed in the same manner as in Synthesis Example 1 except that 36 parts of methyl methacrylate (MMA) and 4 parts of methyl acrylate (MA) were reacted as a monomer. A polymer (b-1-3) was obtained.

The rubber content, the weight composition ratio of the monomer, the graft ratio, and the weight-average molecular weight of the acetone-soluble component of the rubber-containing graft copolymer produced in Synthesis Examples 1, 2, and 3 were measured. there were.
Rubber-containing graft copolymer (b-1-1): rubber content = 66.2% by weight
AN / ST = 28/72
Graft ratio = 40% by weight
Weight average molecular weight (Mw) = 154,000
Rubber-containing graft copolymer (b-1-2): rubber content = 52.4% by weight
AN / ST = 26/74
Graft ratio = 57% by weight
Weight average molecular weight (Mw) = 145,000
Rubber-containing graft copolymer (b-1-3): rubber content = 62.3 wt%
MMA / MA = 90/10
Graft ratio = 35% by weight
Weight average molecular weight (Mw) = 70,000

The following commercially available products were used as the rubber-containing graft copolymer (b-1-4).
Rubber-containing graft copolymer (b-1-4): “Metablene S-20” manufactured by Mitsubishi Rayon Co., Ltd.
01 "(rubber polymer (made of silicone / butyl acrylate
Composite rubber) is graft polymerized with methyl methacrylate, etc.
Copolymer. Rubber content = approx. 65% by weight)

[Hard (co) polymer]
Synthesis Example 4: Production of Rigid (Co) polymer (b-2-1) A rigid (co) polymer was synthesized by suspension polymerization as follows.
In a nitrogen-substituted reactor, 120 parts of water, 0.002 part of sodium alkylbenzene sulfonate, 0.5 part of polyvinyl alcohol, 0.3 part of azoisobutylnitrile, 0.5 part of t-DM, 25 parts of acrylonitrile, 25 parts of styrene, A monomer mixture consisting of 50 parts of methyl methacrylate was used and heated at a starting temperature of 60 ° C. for 5 hours and then reached 120 ° C. while sequentially adding a portion of styrene. Furthermore, after reacting at 120 ° C. for 4 hours, the polymer was taken out to obtain a hard (co) polymer (b-2-1).

Synthesis Example 5 Production of Rigid (Co) polymer (b-2-2) Monomer comprising 25 parts of acrylonitrile, 20 parts of styrene, 35 parts of α-methylstyrene (AMST), and 20 parts of N-phenylmaleimide (NPMI) Polymerization was carried out in the same manner as in Synthesis Example 4 except that a part of styrene, α-methylstyrene, and N-phenylmaleimide was sequentially added, and a hard (co) polymer (b-2- 2) was obtained.

Synthesis Example 6 Production of Hard (Co) polymer (b-2-3) Polymerization was conducted in the same manner as in Synthesis Example 4 except that a monomer mixture consisting of 98 parts of methyl methacrylate and 2 parts of methyl acrylate was added. To obtain a hard (co) polymer (b-2-3).

The weight composition ratio and weight average molecular weight (Mw) of the monomers of the hard (co) polymer produced in Synthesis Examples 4, 5, and 6 were measured and were as follows.
Hard (co) polymer (b-2-1): AN / ST / MMA = 23/28/49
Weight average molecular weight (Mw) = 113,000
Hard (co) polymer (b-2-2): AN / (ST + AMST) / NPNI
= 24/57/19
Weight average molecular weight (Mw) = 150,000
Hard (co) polymer (b-2-3): MMA / MA = 98/2
Weight average molecular weight (Mw) = 136,000

[Production and evaluation of polylactic acid-based thermoplastic resin composition pellets]
Each of the above components was mixed at the blending ratio shown in Table 1, and further mixed with 0.3 part of “Carbodilite HMV-8CA” manufactured by Nisshinbo Co., Ltd. as a stabilizer, followed by biaxial extrusion at 200 to 240 ° C. A pellet of a polylactic acid-based thermoplastic resin composition was prepared by melting and mixing with a machine (“TEX-30α” manufactured by Nippon Steel Works) and pelletizing.

These resin pellets are molded at 220 to 250 ° C. with a 2 ounce injection molding machine (manufactured by Toshiba Corporation), impact resistance (Charpy impact strength), bending strength, bending elastic modulus, heat resistance (deflection temperature under load). ) Was measured by the following method.
Charpy impact strength (KJ / m): ISO 179 (normal temperature)
Bending strength (MPa): ISO 178 (normal temperature)
Flexural modulus (MPa): ISO 178 (normal temperature)
Deflection temperature under load (° C): ISO 75 (measurement load 0.45 MPa)

[Examples and Comparative Examples]
Table 1 shows Examples 1 to 3, 6 and Comparative Examples 1 to 7 .

[Discussion]
As is apparent from Table 1 , the polylactic acid-based thermoplastic resin compositions of Examples 1 to 3 and 6 that satisfy the requirements of the claims of the present invention are excellent in impact resistance, bending characteristics, and heat resistance physical property balance, In particular, the impact resistance is excellent.
In contrast, the polylactic acid resin alone of Comparative Example 1 has low impact strength. Even if a rubber-containing graft copolymer is blended, even if it contains Comparative Example 2 that does not contain a (meth) acrylic resin component, or contains a (meth) acrylic resin component, only a hard (co) polymer can be used. In Comparative Example 3 containing no rubber-containing graft copolymer, although the impact strength is slightly improved, the improvement effect is remarkably low.
Moreover, even if it contains the (meth) acrylic-type resin component, even in Comparative Examples 4 and 5 which do not contain a hard (co) polymer, the effect of improving impact strength is obtained, but Examples 1 to 3, 6 It is inferior to.

  A molded product formed by molding the polylactic acid-based thermoplastic resin composition of the present invention has excellent mechanical strength such as impact resistance and excellent balance of mechanical properties and heat resistance. In terms of applications, it can be used for various purposes according to market needs, such as floorboards in the trunk, tire covers, floor boxes, especially interior parts for vehicles and ships, etc., and its industrial utility is very high In addition, it is also effective in reducing environmental impact.

Claims (5)

A polylactic acid-based thermoplastic resin composition containing 40 to 90 parts by weight of a polylactic acid resin (A) and 10 to 60 parts by weight of a rubber-reinforced resin (B) (however, the polylactic acid resin (A) and the rubber-reinforced resin (B) And 100 parts by weight in total)
The rubber-reinforced resin (B) has a weight composition ratio of vinyl cyanide monomer to aromatic vinyl monomer in the presence of a rubbery polymer having a gel content of 60 to 95% by weight. Rubber-containing graft copolymer (b-1) obtained by graft polymerization of vinyl cyanide monomer and aromatic vinyl monomer of / 75 to 30/70 and hard (copolymer ) Polymer (b-2) 5 to 70% by weight, and the hard (co) polymer (b-2) contains 20 to 100% by weight of a (meth) acrylic resin component. A polylactic acid-based thermoplastic resin composition characterized by the above.   2. The polylactic acid-based thermoplastic resin according to claim 1, wherein the rubber-containing graft copolymer (b-1) has a weight-average molecular weight of acetone-soluble components in the range of 50,000 to 600,000. Composition.   The polylactic acid thermoplastic resin composition according to claim 1 or 2, wherein the monomer constituting the (meth) acrylic resin component is a methacrylic acid ester and / or an acrylic acid ester.   The monomers constituting the (meth) acrylic resin component are methacrylic acid ester and acrylic acid ester, and the weight ratio of each monomer of methacrylic acid ester and acrylic acid ester is 99/1 to 80/20. It is a range, The polylactic acid-type thermoplastic resin composition of Claim 3 characterized by the above-mentioned.   A molded product obtained by molding the polylactic acid-based thermoplastic resin composition according to any one of claims 1 to 4.