JP6249129B1 - Polylactic acid-based thermoplastic resin composition and molded article thereof - Google Patents

Abstract

The present invention provides a polylactic acid-based thermoplastic resin composition in which the impact resistance and heat resistance of a molded product obtained are improved and the weld appearance and weld strength of the molded product are remarkably improved, and the molded product thereof. A resin composition comprising a polylactic acid resin (A), a graft copolymer (B), a copolymer (C-1) and a copolymer (C-2), wherein the copolymer ( C-1) is a copolymer containing a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit, and the copolymer (C-2) is It is a copolymer containing methyl methacrylate units, and the content weight ratio of the copolymer (C-1) and the copolymer (C-2) is such that the copolymer (C-1) / copolymer (C- 2) A polylactic acid-based thermoplastic resin composition in which 10/90 to 90/10. A polylactic acid-based thermoplastic resin molded article formed by molding this polylactic acid-based thermoplastic resin composition. [Selection figure] None

Description

  The present invention relates to a polylactic acid-based thermoplastic resin composition excellent in heat resistance, impact resistance, weld strength, and weld appearance of a molded article to be obtained. The present invention also relates to a molded article formed by molding this polylactic acid-based thermoplastic resin composition.

  Rubber-reinforced styrene-based resins such as acrylonitrile-butadiene-styrene (ABS) resin and rubber-reinforced polystyrene (HIPS) are excellent in appearance of molded products, impact resistance, heat resistance, and molding processability. Widely used in the automotive field. In recent years, resin compositions derived from plant-derived biomass resins such as polylactic acid resin have been reduced for these petroleum-derived resins in order to reduce environmental impact. It has been.

  However, polylactic acid resin generally has low impact resistance and heat resistance compared to ABS resin, and is incompatible with alloying with ABS resin. There is a problem that performance such as heat resistance and molding processability is impaired. Moreover, since both are incompatible, there is a problem that the strength and appearance of the obtained molded product, particularly the strength and appearance of the welded portion are impaired. Thus, the following has been proposed as a technique for improving the impact resistance, heat resistance, weld strength and appearance of a polylactic acid resin molded product.

  For example, Patent Document 1 proposes a combination of a polycarbonate resin excellent in heat resistance and impact resistance and a polylactic acid resin. However, although heat resistance and impact resistance are improved due to the inherent properties of polycarbonate resin, polylactic acid resin and polycarbonate resin are incompatible, so the overall appearance and strength of the molded product, especially weld appearance and weld strength, are improved. It will be inferior.

  Patent Document 2 describes that impact resistance and heat resistance are improved by blending polymethyl methacrylate and an acrylic polymer in a polylactic acid resin. Here, it is said that the impact resistance is improved by the acrylic polymer and the heat resistance is improved by the polymethyl methacrylate, but the effect of improving the heat resistance by the polymethyl methacrylate is not sufficient, and the weld strength -There has been no study on improving the appearance.

  Patent Document 3 proposes to improve compatibility and improve weld strength by blending a modified polyolefin resin with a polylactic acid resin and a polypropylene resin. However, the resin of Patent Document 3 does not have sufficient heat resistance and impact resistance, although the weld strength is improved.

JP 2015-42735 A Japanese Patent Laying-Open No. 2015-63583 JP 2016-47874 A

  It is an object of the present invention to provide a polylactic acid-based thermoplastic resin composition in which the impact resistance and heat resistance of a molded product to be obtained are improved and the weld appearance and weld strength of the molded product are remarkably improved, and the molded product thereof. Let it be an issue.

  As a result of diligent efforts to verify and improve the prior art, the present inventors have found that the polylactic acid resin (A) and the graft copolymer (B) include a specific copolymer such as a styrene / acrylonitrile / maleimide copolymer. A polylactic acid-based thermoplastic resin having practically sufficient characteristics in heat resistance, impact resistance, weld strength and appearance by blending (C-1) and methyl methacrylate-based copolymer (C-2) The present inventors have found that a composition can be obtained and have reached the present invention.

  That is, the gist of the present invention is as follows.

[1] A resin composition comprising a polylactic acid resin (A), a graft copolymer (B), a copolymer (C-1) and a copolymer (C-2), wherein the copolymer (C -1) is a copolymer containing a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit, and the copolymer (C-2) is a methacrylic monomer It is a copolymer containing acid methyl units, and the content weight ratio of the copolymer (C-1) to the copolymer (C-2) is such that the copolymer (C-1) / copolymer (C- 2) A polylactic acid-based thermoplastic resin composition in which 10/90 to 90/10 , wherein the copolymer (C-1) is a vinyl cyanide monomer unit, an aromatic vinyl monomer 20 to 40 parts by weight of vinyl cyanide monomer unit, aromatic vinyl single unit with respect to 100 parts by weight of the total body unit and maleimide monomer unit A copolymer containing 25 to 45 parts by weight of a monomer unit and 25 to 45 parts by weight of a maleimide monomer unit and having a weight average molecular weight (Mw) of 30,000 to 300,000, C-2) is methyl methacrylate unit, maleimide monomer unit and aromatic vinyl monomer unit, and 100 to 100 parts by weight of methyl methacrylate unit, 70 to 90 parts by weight, maleimide monomer A copolymer comprising 8 to 25 parts by weight of a body unit and 2 to 10 parts by weight of an aromatic vinyl monomer unit and having a weight average molecular weight (Mw) of 30,000 to 300,000 Lactic acid-based thermoplastic resin composition.

[ 2 ] With respect to 100 parts by weight of the total of the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1) and the copolymer (C-2), the polylactic acid resin (A ) Is 5 to 40 parts by weight, the content of the graft copolymer (B) is 5 to 30 parts by weight, the content of the copolymer (C-1) is 5 to 40 parts by weight, The polylactic acid thermoplastic resin composition according to [1 ], wherein the content of C-2) is 5 to 40 parts by weight.

[ 3 ] The graft copolymer (B) is obtained by graft-polymerizing 50 to 90% by weight of a vinyl-based monomer mixture with 50 to 90% by weight of a rubbery polymer (however, the rubbery polymer and vinyl-based polymer). 100% by weight in total with the monomer mixture), the rubbery polymer is a polybutadiene rubber or acrylic rubber having a gel content of 40 to 99% by weight and an average particle size of 0.1 to 1 μm, and the vinyl The monomer mixture is a mixture containing a vinyl cyanide monomer and an aromatic vinyl monomer, or a mixture containing a methacrylate ester monomer and an acrylate ester monomer, The graft copolymer (B) has a graft ratio of 15 to 120% by weight and a weight-average molecular weight (Mw) of acetone-soluble component of 50,000 to 600,000 [1] or [ 2 polylactic acid based heat according to] Plastic resin composition.

[ 4 ] A polylactic acid-based thermoplastic resin molded article obtained by molding the polylactic acid-based thermoplastic resin composition according to any one of [1] to [ 3 ].

According to the present invention, it is possible to provide a polylactic acid-based thermoplastic resin composition capable of obtaining a molded article having improved heat resistance and impact resistance, and further improved weld appearance and weld strength.
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-derived resin is expanded, and the practice of the philosophy of carbon neutral is promoted. It can contribute to reduction of environmental load.

  The molded product formed by molding the polylactic acid-based thermoplastic resin composition of the present invention is suitable for the design of a wide variety of products due to its excellent heat resistance, impact resistance, weld appearance, and weld strength. is there.

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

In the following description, the “molded body” is obtained by molding the polylactic acid-based thermoplastic resin composition of the present invention.
Further, “unit” refers to a structural portion derived from a monomer compound (monomer) before polymerization, and for example, “methyl methacrylate unit” refers to “structural portion derived from methyl methacrylate”. The content ratio of each monomer unit in the polymer corresponds to the content ratio of the monomer in the monomer mixture used for producing the polymer.
“(Meth) acryl” means one or both of “acryl” and “methacryl”.
In the present invention, the weight average molecular weight (Mw) of the polylactic acid resin (A), the weight average molecular weight (Mw) of the acetone-soluble component of the graft copolymer (B), and the weight average of the copolymer (C) All molecular weights (Mw) are those measured by dissolving in tetrahydrofuran (THF) with gel permeation chromatography (GPC) in terms of polystyrene (PS).
In the present invention, “resin component” means polylactic acid resin (A), graft copolymer (B), copolymer (C-1), copolymer (C-2), and as necessary. Furthermore, it indicates the total of other resins that may be contained.

[Polylactic acid-based thermoplastic resin composition]
The polylactic acid-based thermoplastic resin composition of the present invention (hereinafter sometimes referred to as “the resin composition of the present invention”) includes a polylactic acid resin (A), a graft copolymer (B), a copolymer ( C-1) and a resin composition containing a copolymer (C-2), wherein the copolymer (C-1) is a vinyl cyanide monomer unit or an aromatic vinyl monomer unit. And a copolymer containing a maleimide monomer unit, and the copolymer (C-2) is a copolymer containing a methyl methacrylate unit.

[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%. From the viewpoint of crystallization, the polylactic acid resin (A) used in is preferably 98% or higher in optical purity of L-form or D-form. In addition, the polylactic acid resin (A) may be a copolymer containing other copolymer 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) are not particularly limited as long as it can be substantially molded, but the weight average molecular weight (Mw) is usually 10,000 or more, preferably 5 It is desirable that it is 10,000 or more, and 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), The weight average molecular weight of the polylactic acid resin which exists in a market normally is 400,000 or less.

  The weight average molecular weight (Mw) of the polylactic acid resin (A) can be measured by GPC (solvent THF) as described above. However, when the polylactic acid resin is in a pellet form, it is difficult to dissolve in THF. In this case, after dissolving in chloroform, the polymer component is precipitated using methanol, and the dried polymer component is dissolved in THF, and the weight average molecular weight (Mw) of the soluble component is measured. can do. Further, it can be dissolved by heating as necessary.

  Said 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 “INGEO” manufactured by Nature Works, “Levoda” manufactured by China Marine Biomaterials Co., Ltd., and any of these can be used in the present invention.

  The content ratio of the polylactic acid resin (A) in the resin composition of the present invention is not particularly limited, but the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1), and the copolymer The amount is preferably in the range of 5 to 40 parts by weight, more preferably 7 to 37 parts by weight, and still more preferably 10 to 35 parts by weight with respect to 100 parts by weight of the combined (C-2). When the content ratio of the polylactic acid resin (A) is within this range, it is preferable from the viewpoint of physical properties such as heat resistance and impact resistance and environmental problems such as carbon neutral.

[Graft Copolymer (B)]
The graft copolymer (B) used in the present invention is preferably a rubbery polymer, a vinyl cyanide monomer, an aromatic vinyl monomer, a (meth) acrylic acid ester monomer, It is formed by graft polymerization of at least two kinds of vinyl monomers such as maleimide monomers.

<Rubber polymer>
Examples of the rubbery polymer forming the graft copolymer (B) include butadiene rubbers such as polybutadiene, styrene / butadiene copolymer, acrylate ester / butadiene copolymer, and styrene / isoprene copolymer. Conjugated diene rubbers; acrylic rubbers such as polybutyl acrylate, and olefin rubbers such as ethylene / propylene copolymers. Among these, from the viewpoint of impact resistance, polybutadiene rubbers, conjugated diene rubbers, Olefin rubber and acrylic rubber are preferable, and polybutadiene rubber and acrylic rubber are particularly preferable. These rubbery polymers can be used singly or in combination of two or more.

  These rubbery polymers may have a core / shell structure. For example, a rubbery polymer having polybutadiene as a core and an acrylic acid ester such as butyl acrylate as a shell can be used.

  The gel content of the rubbery polymer is preferably 40 to 99% by weight, more preferably 50 to 95% by weight, and particularly preferably 60 to 85% by weight. When the gel content is within this range, the properties of the resulting polylactic acid-based thermoplastic resin composition, particularly the impact resistance, 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 a solvent used for dissolving the rubbery polymer, for example, toluene is used for polybutadiene, and acetone is used for polybutyl acrylate.

  The average particle size of the rubber 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.

<Graft component>
The graft copolymer (B) is preferably obtained by graft polymerization of 50 to 10% by weight of a graft-polymerizable vinyl monomer mixture in the presence of 50 to 90% by weight of the rubbery polymer. (However, the total of the rubber polymer and the monomer mixture is 100% by weight.) Here, when the rubbery polymer is not less than the above lower limit, the resulting polylactic acid-based thermoplastic resin molded article has good impact resistance, and when it is not more than the above upper limit, the impact resistance is prevented from being lowered. can do.

  As described above, the vinyl monomer component that can be graft-polymerized to the rubber polymer includes a vinyl cyanide monomer, an aromatic vinyl monomer, a (meth) acrylic acid ester monomer, and a maleimide. The above-mentioned vinyl monomers can be used by selecting two or more kinds.

  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 monomer include N-phenylmaleimide and N-cyclohexylmaleimide.

  These monomer components may optionally contain a monomer modified with a functional group. Examples of such monomers include unsaturated carboxylic acids such as acrylic acid and methacrylic acid. , Itaconic acid, fumaric acid and the like. 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 of the total monomer components.

  As the vinyl monomer component grafted to the rubbery polymer of the graft copolymer (B), among the above exemplified monomers, in particular, a combination of a vinyl cyanide monomer and an aromatic vinyl monomer And a combination of a methacrylic acid ester monomer and an acrylic acid ester monomer. As a combination of a vinyl cyanide monomer and an aromatic vinyl monomer, acrylonitrile is used as the vinyl cyanide monomer, styrene is used as the aromatic vinyl monomer, and polylactic acid-based heat is obtained. This is preferable from the viewpoint of further improving the impact resistance of the plastic resin molded product. In this case, the weight composition ratio of the vinyl cyanide monomer and the aromatic vinyl monomer is preferably in the range of 20/80 to 35/65, more preferably 25/75 to 30/70. By being in this range, the dispersibility becomes good. Further, as a combination of a methacrylic ester monomer and an acrylate ester monomer, methyl methacrylate as a methacrylic ester monomer, methyl acrylate as an acrylate ester monomer, It is preferable from a compatible viewpoint with the polylactic acid resin (A) in the resin composition obtained. In this case, the weight composition ratio of the methacrylic ester monomer and the acrylate ester monomer is preferably 100/0 to 50/50, more preferably 99/1 to 80/20. By being in this range, the compatibility with the polylactic acid resin (A) becomes good.

<Weight average molecular weight (Mw) of acetone-soluble matter>
The weight average molecular weight (Mw) of the acetone-soluble component of the graft copolymer (B) is preferably in the range of 50,000 to 600,000, more preferably 50,000 to 550,000, and even more preferably 50,000. It is in the range of ~ 450,000. When the weight-average molecular weight (Mw) of the acetone-soluble component of the graft copolymer (B) is at least the above lower limit, the resulting polylactic acid-based thermoplastic resin molded article has sufficient impact resistance, By being below the upper limit value, the moldability of the resin composition of the present invention is improved. The acetone-soluble component corresponds to a polymer product of a vinyl monomer that is not graft-polymerized to a rubber polymer that is produced when a vinyl monomer is graft-polymerized to a rubber polymer. It is.

<Graft ratio>
The graft ratio of the graft copolymer (B) ((acetone insoluble matter weight / rubber polymer weight-1) × 100) is preferably 15 to 120% by weight, and preferably 20 to 85% by weight. More preferred. When the graft ratio of the graft copolymer (B) is at least the above lower limit, the dispersibility of the graft copolymer (B) and the impact resistance of the resulting polylactic acid-based thermoplastic resin molded article are improved. Moreover, impact resistance becomes favorable because a graft ratio is below the said upper limit. The copolymer grafted on the rubber polymer may have a structure occluded not only inside but also inside the rubber polymer.

<Manufacturing method>
Graft polymerization at the time of producing the graft copolymer (B) can be carried out by known emulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization, and may be a method combining these polymerization methods.

<Content ratio>
As a graft copolymer (B), only 1 type may be used and 2 or more types of the graft copolymers (B) from which a polymerization method and a component composition differ may be mixed and used.

  The content ratio of the graft copolymer (B) in the resin composition of the present invention is such that the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1), and the copolymer (C- It is preferable that it is the range of 5-30 weight part with respect to a total of 100 weight part of 2), More preferably, it is the range of 8-28 weight part, More preferably, it is the range of 10-25 weight part. When the content ratio of the graft copolymer (B) is within this range, it is preferable from the viewpoint of impact resistance and heat resistance. If the proportion of the graft copolymer (B) is less than the above range, sufficient impact resistance cannot be exhibited, and the object of the present invention may not be achieved. On the other hand, if the amount of the graft copolymer (B) is larger than the above range, the heat resistance is inferior, particularly the compatibility is deteriorated, and it may be impossible to obtain a polylactic acid-based thermoplastic resin molded article having an excellent appearance. .

[Copolymer (C-1)]
The vinyl monomer component forming the copolymer (C-1) is a vinyl cyanide monomer, an aromatic vinyl monomer, and a maleimide monomer. Two or more types can be selected and used.

  The copolymer (C-1) contains a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit, so that heat resistance, compatibility, particularly weld strength, weld Appearance can be improved.

  Examples of the vinyl cyanide monomer constituting the copolymer (C-1) include acrylonitrile and methacrylonitrile, with acrylonitrile being particularly preferred. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, bromostyrene, and the like, and styrene and α-methylstyrene are particularly preferable. As maleimide monomers, maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-toluylmaleimide, N-xylylmaleimide N-naphthylmaleimide, Nt-butylmaleimide, N-orthochlorophenylmaleimide, N-orthomethoxyphenylmaleimide and the like, among which N-cyclohexylmaleimide, N-phenylmaleimide, N-toluylmaleimide, N-orthochlorophenylmaleimide and N-orthomethoxyphenylmaleimide are preferable, and N-phenylmaleimide is particularly preferable.

  As a combination of vinyl cyanide monomer, aromatic vinyl monomer, and maleimide monomer in copolymer (C-1), acrylonitrile is aromatic vinyl as the vinyl cyanide monomer. Styrene and α-methylstyrene are preferred as the monomer and N-phenylmaleimide is preferred as the maleimide monomer from the viewpoint of further improving the heat resistance and compatibility of the resulting polylactic acid-based thermoplastic resin molded product. . Furthermore, acrylonitrile is used as the vinyl cyanide monomer, styrene is used as the aromatic vinyl monomer, N-phenylmaleimide is used as the maleimide monomer, and the resulting polylactic acid-based thermoplastic resin molded product This is preferable from the viewpoint of further improving the tensile nominal strain associated with heat resistance, particularly compatibility.

  The content ratio of each monomer unit contained in the copolymer (C-1) is 100 parts by weight in total of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit. On the other hand, the range of 20 to 40 parts by weight of vinyl cyanide monomer units, 25 to 45 parts by weight of aromatic vinyl monomer units, and 25 to 45 parts by weight of maleimide monomer units is preferable. When the content ratio of each monomer unit is within the above range, heat resistance, particularly weld strength and weld appearance are improved.

  The copolymer (C-1) is a vinyl monomer unit other than a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit, such as (meth). Although it may contain an acrylic ester monomer unit, it is a copolymer composed of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit (C -1) In order to effectively obtain the above effect, the proportion of the other vinyl monomer units in the copolymer (C-1) is preferably 30% by weight or less, particularly 0 to 25% by weight. %, Especially 0 to 20% by weight, preferably not contained.

  The weight average molecular weight (Mw) of the copolymer (C-1) 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 copolymer (C-1) is lower than this range, the resulting polylactic acid-based thermoplastic resin molded article has insufficient impact resistance, and when it exceeds this range, There is a risk that molding processability is lowered.

  There is no restriction | limiting in particular in the manufacturing method of a copolymer (C-1), It can obtain by the well-known emulsion polymerization method, suspension polymerization method, block polymerization method, solution polymerization method, etc.

  As the copolymer (C-1), only one type may be used, or two or more types having different vinyl monomer compositions and physical properties may be mixed and used.

  The content ratio of the copolymer (C-1) in the resin composition of the present invention is such that the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1), and the copolymer (C -2) is preferably in the range of 5 to 40 parts by weight, more preferably in the range of 7 to 37 parts by weight, and still more preferably in the range of 10 to 35 parts by weight. When the content ratio of the copolymer (C-1) is within this range, it is preferable from the viewpoint of impact resistance, heat resistance, particularly weld strength and weld appearance. If the content ratio of the copolymer (C-1) is less than the above range, sufficient heat resistance, weld strength and weld appearance cannot be expressed, and the object of the present invention may not be achieved. On the other hand, when the content ratio of the copolymer (C-1) is larger than the above range, the impact resistance is inferior, and in particular, it is not possible to obtain a polylactic acid-based thermoplastic resin molded article excellent in weld strength and weld appearance. There is.

[Copolymer (C-2)]
The vinyl monomer component forming the copolymer (C-2) has at least an essential component of methyl methacrylate, and other than aromatic vinyl monomers, maleimide monomers, and methyl methacrylate. A (meth) acrylic acid ester monomer may be included. Two or more of the above monomers can be selected and used.

  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 (meth) acrylate monomers other than methyl methacrylate include methacrylate monomers such as ethyl methacrylate, propyl methacrylate, butyl methacrylate and derivatives thereof, methyl acrylate, ethyl acrylate Acrylate monomers such as propyl acrylate, butyl acrylate, and derivatives thereof. Examples of maleimide monomers include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-toluylmaleimide, N-xy Reel maleimide, N-naphthylmaleimide, Nt-butylmaleimide, N-orthochlorophenylmaleimide, N-orthomethoxyphenylmaleimide, etc., among which N-cyclohexylmaleimide, N-phenylmaleimide, N-toluyl Maleimide, N-orthophenylphenylmaleimide and N-orthomethoxyphenylmaleimide are preferred, and N-phenylmaleimide and N-cyclohexylmaleimide are preferred.

  Among these, the copolymer (C-2) contains a methyl methacrylate unit, a maleimide monomer unit, and an aromatic vinyl monomer unit. It is preferable from the viewpoint of improving the compatibility between the graft copolymer (B) and the copolymer (C-1) and improving the weld strength and weld appearance associated therewith.

  The content ratio of each monomer unit contained in the copolymer (C-2) is 100 parts by weight in total of the methyl methacrylate unit, the maleimide monomer unit, and the aromatic vinyl monomer unit. The range of 70 to 90 parts by weight of methyl methacrylate units, 2 to 10 parts by weight of aromatic vinyl monomer units, and 8 to 25 parts by weight of maleimide monomer units is preferred. When the content ratio of each monomer unit is within the above range, the heat resistance of the obtained polylactic acid-based thermoplastic resin molded article is improved, and in particular, the compatibility by blending the copolymer (C-2). By increasing the tension and the nominal tensile strain, it is possible to effectively obtain the effect of preventing the sharp edge due to the brittle fracture of the shape of the fractured portion when the product is broken.

  Copolymer (C-2) is a vinyl monomer unit other than methyl methacrylate unit, aromatic vinyl monomer unit, and maleimide monomer unit, such as vinyl cyanide monomer. It may contain (meth) acrylic acid ester monomer units other than units and methyl methacrylate, but is composed of methyl methacrylate units, aromatic vinyl monomer units, and maleimide monomer units. In order to effectively obtain the above effect of the copolymer (C-2), the proportion of the other vinyl monomer units in the copolymer (C-2) is preferably 20% by weight or less. In particular, it is preferably 0 to 18% by weight, particularly 0 to 15% by weight, and preferably not contained.

  The weight average molecular weight (Mw) of the copolymer (C-2) is preferably in the range of 30,000 to 300,000, more preferably in the range of 50,000 to 250,000. When the weight average molecular weight of the copolymer (C-2) is lower than this range, the resulting polylactic acid-based thermoplastic resin molded article has insufficient impact resistance, and when it exceeds this range, There is a risk that molding processability is lowered.

  There is no restriction | limiting in particular in the manufacturing method of a copolymer (C-2), It can obtain by the well-known emulsion polymerization method, suspension polymerization method, block polymerization method, solution polymerization method, etc.

  A copolymer (C-2) may use only 1 type, and may mix and use 2 or more types of things from which a vinyl-type monomer composition, physical properties, etc. differ.

  The content ratio of the copolymer (C-2) in the resin composition of the present invention is such that the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1), and the copolymer (C -2) is preferably in the range of 5 to 40 parts by weight, more preferably in the range of 7 to 37 parts by weight, and still more preferably in the range of 10 to 35 parts by weight. When the content ratio of the copolymer (C-2) is within the above range, the resulting polylactic acid-based thermoplastic resin molded article is improved in impact resistance and heat resistance, particularly polylactic acid (A) and a graft copolymer ( It is preferable from the viewpoint of improving the compatibility between B) and the copolymer (C-1) and improving the weld strength and weld appearance associated therewith. When the content of the copolymer (C-2) is less than the above range, the impact resistance and the compatibility between the polylactic acid (A), the graft copolymer (B) and the copolymer (C-1) are reduced. In some cases, the weld strength and weld appearance improvement effect associated therewith cannot be expressed, and the object of the present invention cannot be achieved. On the contrary, if the content of the copolymer (C-2) is larger than the above range, the effect of improving the heat resistance, particularly the impact resistance cannot be exhibited, and the object of the present invention may not be achieved. .

[Content Ratio of Copolymer (C-1) and Copolymer (C-2)]
The content ratio of the copolymer (C-1) and the copolymer (C-2) contained in the resin composition of the present invention is copolymer (C-1) / copolymer (C- 2) = 10/90 to 90/10, particularly preferably 15/85 to 85/15, particularly preferably 20/80 to 80/20. When the content weight ratio of the copolymer (C-1) and the copolymer (C-2) is within the above range, in particular, the polylactic acid (A), the graft copolymer (B), and the copolymer (C -1) improved compatibility, improved weld strength and weld appearance, and improved compatibility and improved tensile nominal strain, resulting in brittle fracture when the product breaks. The effect of preventing sharp edges can be obtained, which is preferable. If the content weight ratio of the copolymer (C-1) and the copolymer (C-2) is out of the above range, the impact resistance of the polylactic acid-based thermoplastic resin molded article becomes inferior, and the tensile nominal strain In some cases, the weld strength and weld appearance are not improved.

[Other ingredients]
In addition to the polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1) and the copolymer (C-2), the resin composition of the present invention further includes various additives. And other resins can be blended. In this case, various additives include known antioxidants, ultraviolet absorbers, lubricants, plasticizers, stabilizers, mold release agents, antistatic agents, colorants (pigments, dyes, etc.), flame retardants (halogen-based flame retardants). 1 type, or 2 or more types, such as a flame retardant, a phosphorus flame retardant, an antimony compound), a drip inhibitor, an antibacterial agent, a fungicide, a coupling agent, and an anti-hydrolysis agent.

  Other resins include HIPS resin, AS resin, polystyrene resin, polycarbonate resin, nylon resin, methacrylic resin, polyvinyl chloride resin, polybutylene terephthalate resin, polyethylene terephthalate resin, polyphenylene ether resin, polyethylene resin, polyethylene naphthalate. Examples of the resin include polypropylene resin, polypropylene terephthalate resin, polyphenylene sulfide resin, polyacetal resin, polyimide resin, phenol resin, melamine resin, silicone resin, unsaturated polyester resin, and epoxy 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.

  However, when the resin composition of the present invention contains the above-mentioned other resin, the above-mentioned other resin is 50 parts by weight or less, particularly 30 parts by weight or less based on 100 parts by weight of the resin component. It is preferable in terms of effective use of the resin (A) and improvement of characteristics by the graft copolymer (B) and the copolymers (C-1) and (C-2).

[Production and molding of polylactic acid-based thermoplastic resin composition]
The resin composition of this invention is mix | blended with a polylactic acid resin (A), a graft copolymer (B), a copolymer (C-1), and a copolymer (C-2) as needed. It can manufacture by mixing another additive etc. by the well-known method using a well-known apparatus.
The method for pelletizing the resin composition of the present invention is not particularly limited, and for example, a twin screw extruder, a Banbury mixer, a heating roll, and the like can be used, among which melt kneading with a twin screw extruder is preferable, If necessary, resins and other additives can be blended by side feed or the like.

  The resin composition of the present invention can be molded into various molded products by a normal molding method such as injection molding, blow molding, sheet molding, vacuum molding, etc., and injection molding is particularly suitable as the molding method. .

  In addition, when preparing each component of the resin composition of the present invention, or when mixing, kneading, or molding these components, the resin waste, etc., is crushed as it is or in some cases and melt-recycled. Can be used. 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.

〔Molding〕
The use of the polylactic acid-based thermoplastic resin molded product of the present invention formed by molding the resin composition of the present invention is not particularly limited, but due to its excellent heat resistance, impact resistance, weld strength, and weld appearance, In the case of housing components of white goods such as refrigerators and washing machines, OA equipment internal parts, and automobiles, it can be suitably used for switch parts, vibrating equipment, vehicle car audio fitting parts, and the like.

Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, reference examples, and comparative examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded. Absent.
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 (A)]
Polylactic acid resin (A): Polylactic acid resin (L-form / D-form = 98/2 (weight ratio),
Weight average molecular weight (Mw) = 140,000, melting point = 171 ° C.)

[Graft Copolymer (B)]
<Synthesis Example 1: Production of Graft Copolymer (B-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).

<Synthesis Example 2: Production of Graft Copolymer (B-2)>
In the raw material formulation of Synthesis Example 1, 60 parts (as solid content) of polybutyl acrylate (gel content 65% by weight, average particle size 0.34 μm) was used as the rubbery polymer, and methyl methacrylate ( Graft copolymerization was performed in the same manner as in Synthesis Example 1 except that 36 parts of MMA and 4 parts of methyl acrylate (MA) were reacted to obtain a graft copolymer (B-2).

The rubber-containing graft copolymers (B-1) and (B-2) produced in Synthesis Examples 1 and 2, the rubber content, the weight composition ratio of the monomers, the graft ratio, and the weight-average molecular weight of the acetone-soluble component Was measured and was as follows.
Graft copolymer (B-1): rubber content = 66.2 wt%
AN / ST = 28/72
Graft ratio = 40% by weight
Weight average molecular weight (Mw) = 154,000
Graft copolymer (B-2): rubber content = 62.3 wt%
MMA / MA = 90/10
Graft ratio = 35% by weight
Weight average molecular weight (Mw) = 70,000

[Copolymer (C-1)]
<Synthesis Example 3: Production of Copolymer (C-1-1)>
A copolymer was synthesized by a suspension polymerization method 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, 28 parts of acrylonitrile, 26 parts of styrene, Using a monomer mixture consisting of 10 parts of α-methylstyrene and 36 parts of N-phenylmaleimide, the mixture was heated at a starting temperature of 60 ° C. for 5 hours and then reached 120 ° C. while sequentially adding a part of styrene. . Furthermore, after making it react at 120 degreeC for 4 hours, polymer was taken out and the copolymer (C-1-1) was obtained.

<Synthesis Example 4: Production of Copolymer (C-1-2)>
A copolymer was synthesized by a suspension polymerization method 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, 14 parts of acrylonitrile, 55 parts of styrene, A monomer mixture consisting of 31 parts of N-phenylmaleimide was used, and the mixture was heated at a starting temperature of 60 ° C. for 5 hours and then reached 120 ° C. while sequentially adding a part of styrene. Furthermore, after making it react at 120 degreeC for 4 hours, polymer was taken out and the copolymer (C-1-2) was obtained.

The weight composition ratio of the monomers of the copolymers (C-1-1) and (C-1-2) produced in Synthesis Examples 3 and 4 and the weight average molecular weight (Mw) were measured. Met.
Copolymer (C-1-1): AN / ST / α-methylstyrene / N-phenylmaleimide
= 28/26/10/36
Weight average molecular weight (Mw) = 120,000
Copolymer (C-1-2): AN / ST / N-phenylmaleimide = 14/55/31
Weight average molecular weight (Mw) = 170,000

[Copolymer (C-2)]
<Synthesis Example 5: Production of copolymer (C-2-1)>
In a stainless polymerization tank equipped with a stirrer, 150 parts of ion exchange water, 75 parts of methyl methacrylate, 18 parts of N-phenylmaleimide, 7 parts of α-methylstyrene, 0.2 part of 2,2′-azobis (isobutyronitrile), 0.25 parts of n-octyl mercaptan and 0.7 parts of polyvinyl alcohol were charged. The internal temperature of the polymerization tank was set at 75 ° C. for 3 hours, and the temperature was raised to 90 ° C. for 1 hour. The contents were extracted, washed with a centrifugal dehydrator, and dried to obtain a powdery copolymer (C-2-1).

When the weight composition ratio and weight average molecular weight (Mw) of the monomer of this copolymer (C-2-1) were measured, it was as follows.
Copolymer (C-2-1): Methyl methacrylate / N-phenylmaleimide
/ Α-methylstyrene = 75/18/7
Weight average molecular weight (Mw) = 130,000

In addition, the following raw materials were used.
Copolymer (C-2-2): “Polyimilex PML203” manufactured by Nippon Shokubai Co., Ltd.
Methyl methacrylate / styrene / N-phenylmaleimide copolymer
Weight average molecular weight (Mw) = 200,000
Copolymer (X): “Acrypet VH” manufactured by Mitsubishi Chemical Corporation
Methacrylic resin
Weight average molecular weight (Mw) = 150,000

[Production and evaluation of polylactic acid-based thermoplastic resin composition pellets]
Each of the above components is mixed at a blending ratio shown in Tables 1 to 3, and melt-mixed with a twin-screw extruder (“TEX-30α” manufactured by Nippon Steel Works) at 200 to 240 ° C. A pellet of a lactic acid thermoplastic resin composition was prepared.

  Using these resin pellets, various test pieces were molded at 200 to 250 ° C. with a 2 ounce injection molding machine (manufactured by Toshiba Corporation), and impact resistance, heat resistance, and tensile nominal strain were measured by the following methods.

Impact resistance: Charpy impact value (KJ / m ² ): Performed according to ISO 179-1 (notched, 23 ° C.), passed: 10 KJ / m ² or more, reject: less than 10 KJ / m ² .

  Heat resistance: Deflection temperature under load (° C.): Performed in accordance with ISO 75 (measurement load 0.45 MPa), pass: 90 ° C. or higher, reject: less than 90 ° C.

  Compatibility: Tensile nominal strain (%): Performed according to ISO 527. A large tensile nominal strain indicates that the interface between the compositions is high and the compatibility is excellent, and the pass: 10% or more, and the failure is less than 10%.

  In the present invention, it is essential to pass all of the above measurements of impact resistance, heat resistance and tensile nominal strain.

  Further, the weld strength retention rate and the weld appearance were evaluated by the following methods.

  Weld strength retention rate (%): Using an autograph tensile tester manufactured by Shimadzu Corporation, the tensile yield strength retention rate (%) of the welded test piece relative to the test piece without weld was calculated. The test was conducted in accordance with ASTM D638, and the pass was determined to be 90% or higher and the rejection was determined to be lower than 90%.

Weld appearance: The weld part of the molded product was visually observed and judged according to the following evaluation criteria.
<Evaluation criteria>
○: The weld part of the molded product is not conspicuous, and it can be judged that the product has practicality when used as a product. ×: The weld part of the molded product is clearly noticeable, resulting in poor product value

[Examples , Reference Examples and Comparative Examples]
Tables 1 to 3 show the results of Examples 1 to 3, 5 to 18 , Reference Example 4 and Comparative Examples 1 to 7.

[Discussion]
The following can be understood from Tables 1 and 2.
With the polylactic acid-based thermoplastic resin compositions of Examples 1 to 3, 5 to 18 that satisfy the requirements of the claims of the present invention, impact resistance, heat resistance, and further improved compatibility, tensile nominal strain, weld strength, A molded product having an excellent weld appearance can be obtained.

Table 3 shows the following.
Comparative Example 1, which is a general ABS resin that does not contain the polylactic acid resin (A) and uses the copolymer (X), has low heat resistance and is inferior in weld strength and weld appearance. Comparative Example 2 using only the polylactic acid resin (A) has extremely low impact resistance and heat resistance, and is inferior in tensile nominal strain, weld strength, and weld appearance. Since Comparative Example 3 does not contain the copolymer (C-1), impact resistance and heat resistance are low, and tensile nominal strain, weld strength, and weld appearance are inferior. Since Comparative Examples 4 and 5 include only one of the copolymer (C-1) and the copolymer (C-2) and do not include the other, impact resistance, tensile nominal strain, weld strength, weld Appearance is inferior. In Comparative Examples 6 and 7, since the ratio of the copolymer (C-1) to the copolymer (C-2) is outside the range of 10/90 to 90/10, it is also caused by impact resistance and compatibility. The tensile nominal strain, weld strength, and weld appearance are low.

  The polylactic acid-based thermoplastic resin composition of the present invention is superior in impact resistance and heat resistance even when blended with plant-derived components, and also has excellent tensile nominal strain, weld strength, and weld appearance due to increased compatibility. The surface appearance of the obtained molded product can also be made excellent. The molded product formed by molding the polylactic acid-based thermoplastic resin composition of the present invention can be widely used for products used indoors, such as ABS resin and PS resin, for example, in accordance with market needs. It can be used for various purposes, and its industrial usefulness is very high, and it is also effective for reducing the environmental load.

Claims (4)

A resin composition comprising a polylactic acid resin (A), a graft copolymer (B), a copolymer (C-1) and a copolymer (C-2), wherein the copolymer (C-1) Is a copolymer containing a vinyl cyanide monomer unit, an aromatic vinyl monomer unit, and a maleimide monomer unit, and the copolymer (C-2) is a methyl methacrylate unit. The content weight ratio of the copolymer (C-1) to the copolymer (C-2) is copolymer (C-1) / copolymer (C-2) = A polylactic acid-based thermoplastic resin composition that is 10/90 to 90/10 ,
The copolymer (C-1) is a vinyl cyanide monomer based on a total of 100 parts by weight of a vinyl cyanide monomer unit, an aromatic vinyl monomer unit and a maleimide monomer unit. 20 to 40 parts by weight of a body unit, 25 to 45 parts by weight of an aromatic vinyl monomer unit, 25 to 45 parts by weight of a maleimide monomer unit, and a weight average molecular weight (Mw) of 30,000 to 300 , 000 copolymer, and the copolymer (C-2) is a methacrylic acid copolymer based on a total of 100 parts by weight of methyl methacrylate unit, maleimide monomer unit and aromatic vinyl monomer unit. 70 to 90 parts by weight of methyl acid unit, 8 to 25 parts by weight of maleimide monomer unit, 2 to 10 parts by weight of aromatic vinyl monomer unit, and weight average molecular weight (Mw) of 30,000 to a copolymer of 300,000 Polylactic acid thermoplastic resin composition according to symptoms. The polylactic acid resin (A), the graft copolymer (B), the copolymer (C-1) and the copolymer (C-2) are contained in a total of 100 parts by weight of the polylactic acid resin (A). The amount is 5 to 40 parts by weight, the content of the graft copolymer (B) is 5 to 30 parts by weight, the content of the copolymer (C-1) is 5 to 40 parts by weight, and the copolymer (C-2 The polylactic acid-based thermoplastic resin composition according to claim 1, wherein the content of) is 5 to 40 parts by weight. The graft copolymer (B) is obtained by graft-polymerizing 50 to 90% by weight of a vinyl-based monomer mixture with 50 to 90% by weight of a rubbery polymer (provided that the rubbery polymer and vinyl-based monomer are mixed). 100% by weight in total with the mixture), the rubbery polymer is a polybutadiene rubber or acrylic rubber having a gel content of 40 to 99% by weight and an average particle size of 0.1 to 1 μm, and the vinyl monomer The body mixture is a mixture containing a vinyl cyanide monomer and an aromatic vinyl monomer, or a mixture containing a methacrylate ester monomer and an acrylate ester monomer, and the graft copolymer The polymer according to claim 1 or 2 , wherein the graft ratio of the polymer (B) is 15 to 120% by weight, and the weight-average molecular weight (Mw) of the acetone-soluble component is 50,000 to 600,000. Lactic acid based thermoplastic resin Narubutsu. The polylactic acid-type thermoplastic resin molded product formed by shape | molding the polylactic acid-type thermoplastic resin composition of any one of Claim 1 thru | or 3 .