JP2014065794A - Polylactic acid-based resin composition and molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid-based resin composition which is excellent in each of transparency, impact resistance, and flexibility, and can be used as a film for a food product or the like.SOLUTION: A polylactic acid-based resin composition contains a polylactic acid resin (A), a multilayer structure polymer (B), and a (meth)acrylate-based polymer (C), and satisfies following conditions (I) to (III): (I) the multilayer structure polymer (B) is composed of a core layer and a shell layer, the core layer contains acrylic rubber, and the shell layer is obtained by graft-polymerizing one or more vinyl monomers onto the acrylic rubber of the core layer in the presence of the acrylic rubber of the core layer, (II) the weight average molecular weight of the (meth)acrylate-based polymer (C) is 1,000,000 or more and less than 15,000,000, and (III) the content of (B) is 0.5 to 15 pts.mass based on 100 pts.mass of the polylactic acid resin (A), and the content of (C) is 0.1 to 10 pts.mass based on 100 pts.mass of the polylactic acid resin (A).

Description

  The present invention relates to a polylactic acid resin composition excellent in transparency, flexibility, and impact resistance, and a molded article made of the resin composition.

  Films used as packaging materials for newspapers, magazines, foods, etc. are desired to be formed of biodegradable resins in accordance with the recent increase in social demand for environmental protection. Among biodegradable resins, polylactic acid is widely present in nature, has little harm to animals, plants and animals, has a melting point of 140-175 ° C, has sufficient heat resistance, and has very high transparency. At the same time, it is a relatively inexpensive thermoplastic resin and can be produced from plant-derived raw materials, and thus has attracted a great deal of attention.

  However, since sheets and films made of polylactic acid have very hard and brittle properties as they are, it has been difficult to use them in fields where flexibility and impact resistance are required.

  Various studies have been conducted to improve the impact resistance and flex resistance of polylactic acid. For example, Patent Document 1 discloses a composition comprising polylactic acid mixed with polycarbonate, which is a transparent resin having excellent impact resistance, and containing an organic polysiloxane-polycarbonate copolymer and an acrylic core-shell impact modifier. It is disclosed. Patent Document 2 discloses a heat shrink film made of a mixed resin containing polylactic acid and silicone-acrylic composite rubber. Furthermore, Patent Document 3 discloses that impact resistance at low temperatures is improved by adding epoxidized natural rubber to polylactic acid.

  However, the resin compositions described in Patent Documents 1, 2, and 3 improve the impact resistance, but the transparency, which is an advantage of polylactic acid, is impaired. Therefore, food films and industrial films that require transparency are required. It was difficult to use for this purpose.

  Patent Document 4 discloses a resin composition containing an acrylic polymer having good compatibility with polylactic acid, polylactic acid, and a graft copolymer obtained by grafting a vinyl monomer to a rubbery polymer. It is disclosed. However, although this resin composition has good transparency, it has poor flexibility, poor texture, and insufficient impact resistance and flex resistance.

  Furthermore, Patent Document 5 discloses a resin composition containing polylactic acid and a multilayer structure polymer. However, in these patent documents, in order to obtain a resin composition excellent in impact resistance, flexibility, and bending resistance, a resin composition in which at least about 10% by mass of one kind of multilayer structure polymer is substantially added. Things are shown. That is, unless about 10% by mass of one kind of multilayer structure polymer is added to the resin composition, the effect of improving impact resistance and flex resistance is not exhibited, but it is obtained when the amount of addition of the multilayer structure polymer is increased. There was a problem that transparency of a resin composition fell.

  Patent Document 6 discloses a resin composition containing polylactic acid, epoxy-modified silicone / acrylic rubber, and methyl methacrylate / butadiene / styrene copolymer rubber. By using the two specific rubber components, the resin composition has improved impact resistance as compared to the case where the same amount of other rubber components are used.

  However, epoxy-modified silicone / acrylic rubber reacts with polylactic acid and is easily gelled. Therefore, when a resin composition containing this resin is molded into a sheet or film, the gelled part is noticeable in the molded product. In addition, there is a problem that only inferior transparency can be obtained. Further, the methyl methacrylate / butadiene / styrene copolymer rubber has a problem in that the core layer of the core-shell structure is a butadiene / styrene polymer, so that the transparency of the resulting resin composition or molded article is impaired.

  As described above, although the resin composition disclosed in Patent Document 6 has improved impact resistance, it has a problem that it is easily gelled and the excellent transparency unique to polylactic acid is also impaired, and transparency is required. It was difficult to use for sheet and film applications.

US Pat. No. 7,309,730 JP 2007-177140 A US Pat. No. 6,456,631 International Publication No. 2005/85352 JP 2003-286396 A JP 2009-263526 A

  The present invention provides a polylactic acid-based resin composition that solves the above-mentioned problems and is excellent in all of transparency, impact resistance, and flexibility, and can be used for a food film or the like. This is a technical issue.

  As a result of repeated researches to solve the above problems, the present inventors have found that a polylactic acid resin (A) has a core-shell multilayer polymer (B) composed of specific components and a high molecular weight (meth) acrylic. By adding the acid ester polymer (C), the effects of both polymers (improvement of impact resistance and flexibility) are exhibited synergistically, and even when added in small amounts, sufficient effects can be achieved. As a result, it has been found that a polylactic acid resin composition excellent in impact resistance and flexibility can be obtained without impairing transparency, and the present invention has been achieved.

That is, the gist of the present invention is as follows.
(1) It contains a polylactic acid resin (A), a multilayer structure polymer (B), and a (meth) acrylic acid ester polymer (C), and satisfies the following conditions (a) to (c): A polylactic acid resin composition.
(A) The multilayer structure polymer (B) is composed of a core layer and a shell layer, the core layer contains an acrylic rubber, and the shell layer is one or more in the presence of the acrylic rubber of the core layer. This vinyl monomer is obtained by graft polymerization to the acrylic rubber of the core layer.
(B) The (meth) acrylic acid ester polymer (C) has a weight average molecular weight of 1 million or more and less than 15 million.
(C) The content of the multilayer structure polymer (B) is 0.5 to 15 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A), and the (meth) acrylate polymer (C) Is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A).
(2) A molded article comprising the polylactic acid resin composition according to (1).

The polylactic acid resin composition of the present invention comprises a polylactic acid resin (A), a core-shell structure multilayer polymer (B) comprising a specific component, and a high molecular weight (meth) acrylate polymer (C). ), The effects of both polymers (improvement of impact resistance and flexibility) are exhibited synergistically, and a sufficient effect can be achieved even with small additions. For this reason, the polylactic acid-based resin composition of the present invention has improved impact resistance and flexibility while maintaining the high transparency inherent in the polylactic acid resin.
Therefore, the polylactic acid resin composition of the present invention can be molded into various molded products such as films, sheets, injection molded products, and foamed products, and can be widely used for various applications.

Hereinafter, the present invention will be described in detail.
First, the polylactic acid resin (A) will be described. Examples of the polylactic acid resin (A) in the present invention include poly-L-lactic acid in which the structural unit of lactic acid is L-lactic acid, poly-D-lactic acid in which the structural unit is D-lactic acid, and a combination of L-lactic acid and D-lactic acid. Examples thereof include poly DL-lactic acid which is a polymer, or a mixture thereof.

  The weight average molecular weight of the polylactic acid resin (A) is preferably 100,000 to 300,000, and more preferably 120,000 to 200,000. When the weight average molecular weight of the polylactic acid resin (A), which is the main component of the resin composition, is less than 100,000, the resulting molded product tends to be inferior in mechanical properties. On the other hand, if the weight average molecular weight exceeds 300,000, the melt viscosity becomes too high, and melt extrusion tends to be difficult when obtaining a molded product.

As the polylactic acid resin (A) used in the present invention, either crystalline polylactic acid or amorphous polylactic acid may be used, but in consideration of ensuring stability and heat resistance when forming a molded body, It is preferable to use a functional polylactic acid.
Here, crystalline polylactic acid refers to polylactic acid having a melting point in the range of 140 to 175 ° C., and amorphous polylactic acid refers to polylactic acid having substantially no melting point.

  In order for the polylactic acid resin (A) to be crystalline polylactic acid, the D-form content in the polylactic acid resin (A) is preferably 5 mol% or less, more preferably 2 mol% or less. More preferably, it is 1 mol% or less. When the D-form content exceeds 5 mol%, the crystallinity of polylactic acid is lowered, and even when a crystal nucleating agent is added or a specific heat treatment is performed, the crystal is not sufficiently crystallized, and an operation for obtaining a molded product is performed. The resulting molded product tends to be inferior in heat resistance.

  As the polylactic acid resin (A) used in the present invention, various commercially available polylactic acid resins can be used, and different types can also be used in combination. Also, lactide, which is a cyclic dimer of lactic acid, is used as a raw material, and a product produced by a known melt polymerization method or further using a solid phase polymerization method can be used.

The amount of residual lactide in the polylactic acid resin (A) is preferably 0.5% by mass or less, more preferably 0.3% by mass, and most preferably 0.1% by mass or less. preferable. When the amount of residual lactide exceeds 0.5% by mass, when obtaining a molded product, for example, when forming a sheet or film, smoke is significantly generated, equipment near the die is contaminated, product quality is lowered, and operability is reduced. It is easy to fall. Furthermore, since the durability of the molded article is inferior, it is not preferable.
As a method for reducing the amount of residual lactide, when the polylactic acid resin (A) is polymerized, it is removed by reducing the pressure at a temperature equal to or higher than the melting point, or the pellet after polymerization of the polylactic acid resin (A) is heated to a high temperature (60 to 160). C.) a method of removing by treatment under reduced pressure, and a method of extracting and removing by immersion in warm water.

  The polylactic acid resin composition of the present invention is mainly composed of the polylactic acid resin (A), and the content of the polylactic acid resin (A) is 80 to 99% by mass of the entire resin composition. Is more preferable, 85 to 98% by mass is more preferable, and 90 to 96% by mass is most preferable. If the content of the polyresin resin (A) is too large, the contents of the multilayer polymer (B) and the (meth) acrylic acid ester polymer (C) will be too small, and the impact resistance and flexibility will be reduced. The improvement effect is poor. On the other hand, if the content of the polylactic acid resin (A) is small, the content of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) increases, so that the transparency of the resin composition is high. descend.

  In addition, in the polylactic acid-type resin composition of this invention, if it is a range which does not impair an effect, you may contain other resins other than a polylactic acid resin (A).

Examples of such other resins include polyolefin, polyester, polyamide, polycarbonate, polystyrene, polymethyl (meth) acrylate, poly (acrylonitrile-butadiene-styrene) copolymer, liquid crystal polymer, and polyacetal.
Examples of the polyolefin include polyethylene and polypropylene.
Examples of the polyamide include polyamide 6, polyamide 66, polyamide 610, polyamide 11, polyamide 12, and polyamide 6T. Examples of the polyester include various aromatic polyesters and various aliphatic polyesters. Specific examples of the aromatic polyester include polyethylene terephthalate, polybutylene terephthalate, polyarylate, and polybutylene adipate terephthalate. Specific examples of the aliphatic polyester include polybutylene succinate and poly (butylene succinate). (Nate-lactic acid) copolymer, polyhydroxybutyric acid and the like.

  Other polyesters include polycyclohexylene dimethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate terephthalate, polybutylene isophthalate terephthalate, polyethylene terephthalate / cyclohexylene dimethylene terephthalate, cyclohexyl. Examples include dimethylene isophthalate choterephthalate, copolyester composed of p-hydroxybenzoic acid residue and ethylene terephthalate residue, polytrimethylene terephthalate composed of 1,3-propanediol which is a plant-derived raw material, and the like. The method for mixing the polylactic acid resin (A) and these resins is not particularly limited.

Next, the multilayer structure polymer (B) will be described.
The multilayer structure polymer (B) in the present invention is composed of a core layer and a shell layer covering the core layer, and adjacent layers are composed of different types of polymers and have a so-called core-shell type structure. It is a polymer having. The number of layers in both the core layer and the shell layer is 1 or more, and the core layer and the shell layer may have two or more layers.

The core layer of the multilayer structure polymer (B) contains an acrylic rubber, and among them, the core layer is preferably formed of an acrylic rubber. The shell layer is obtained by graft polymerization of one or more vinyl monomers on the acrylic rubber of the core layer in the presence of the acrylic rubber of the core layer.
By including such a multilayer structure polymer (B) in the polylactic acid resin (A), the impact resistance and flexibility of the resulting resin composition can be improved.

  The acrylic rubber contained in the core layer of the multilayer structure polymer (B) preferably contains an alkyl acrylate as a monomer. The content of the acrylic acid alkyl ester monomer is preferably 50 to 100 mass%, more preferably 60 to 95 mass%, more preferably 65 to 95 mass% of the total mass of the monomers constituting the acrylic rubber. More preferably, it is mass%. When the content of the acrylic acid alkyl ester monomer is less than 50% by mass, the impact resistance and flexibility of the finally obtained molded article are not sufficiently improved, and the transparency of the molded article may be lowered. .

  Specific examples of the acrylic acid alkyl ester include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, tridecyl acrylate, ethoxyethoxyethyl acrylate, methoxytripropylene glycol acrylate 4-hydroxybutyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, butyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like, among which n-butyl acrylate is preferable.

  Except for the case where only the acrylic acid alkyl ester monomer is used as the monomer constituting the acrylic rubber, the acrylic rubber is obtained by polymerizing a mixture of the acrylic acid alkyl ester monomer and other monomers. Examples of other monomers include aromatic vinyl monomers, acrylic acid alkyl ester monomers and / or vinyl monomers copolymerizable with aromatic vinyl monomers. Further, if necessary, a polyfunctional monomer may be included if it is about 5% by mass or less.

In the present invention, the shell layer of the multilayer structure polymer (B) is graft-polymerized with one or more vinyl monomers on the acrylic rubber of the core layer in the presence of the acrylic rubber of the core layer. It is obtained by making it. Thus, the multilayer structure polymer (B) is an acrylic rubber graft copolymer.
As the vinyl monomer, methyl methacrylate is used alone, or methyl methacrylic ester such as styrene, α-methylstyrene, vinyltoluene, etc .; methacrylic acid ester such as 2-ethylhexyl methacrylate; methyl acrylate, Acrylic esters such as ethyl acrylate and n-butyl acrylate; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile can be used in combination. The amount of these monomers used is preferably 20% by mass or less of the acrylic rubber graft copolymer.

  Examples of the above-mentioned multilayer polymer (B) commercially available include “Paraloid BPM-500” manufactured by Rohm and Haas, “Paraloid BPM-515” manufactured by Rohm and Haas, and “Metablene W-” manufactured by Mitsubishi Rayon Co., Ltd. 450A "," Maybrene W-600A "manufactured by Mitsubishi Rayon Co., Ltd., and the like. These can be used alone or in combination of two or more.

  The content of the multilayer structure polymer (B) is required to be 0.5 to 15 parts by mass, particularly 0.5 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). It is preferable and it is more preferable that it is 1.0-6 mass parts. When content of a multilayer structure polymer (B) is less than the said range, it will become difficult to obtain the resin composition excellent in impact resistance and a softness | flexibility. On the other hand, when the content of the multilayer structure polymer (B) exceeds the above range, the excellent transparency characteristic of the polylactic acid resin (A) is impaired, and the resulting resin composition is inferior in transparency. .

Next, the (meth) acrylic acid ester polymer (C) will be described.
The (meth) acrylic acid ester polymer (C) in the present invention is preferably composed of monomers such as acrylic acid and its ester, methacrylic acid and its ester, and only one of these monomers is used alone. Either a polymer or a copolymer of two or more monomers may be used, and in the copolymer, any copolymer obtained by a block copolymer, a random copolymer, a graft copolymer, or a combination thereof. It may be. Specific examples of the monomer of such (meth) acrylic acid and its ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, ( N-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, neopentyl (meth) acrylate, ethylhexyl (meth) acrylate, isodecyl acrylate , Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, benzyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, methoxyethyl (meth) acrylate, (meth) acrylic Dimethylaminoethyl acid, chloroethyl (meth) acrylate, (meth) a Trifluoroethyl acrylic acid, (meth) heptadecafluorooctyl acrylate, (meth) acrylic acid isobornyl, and the like (meth) adamantyl acrylate and (meth) tricycloalkyl Desi sulfonyl acrylate. Moreover, monomers, such as substituted styrenes, such as styrene, (alpha) -methylstyrene, t-butylstyrene, and chlorostyrene, can also be copolymerized.

  There is no restriction | limiting in particular as a polymerization method of the said (meth) acrylic-ester type copolymer (C), Well-known methods, such as solution polymerization, suspension polymerization, and block polymerization, are used.

  The (meth) acrylic acid ester polymer (C) needs to have a weight average molecular weight of 1,000,000 or more and less than 15 million, preferably 1.5 million to 12 million, more preferably 3 million. It is preferably ˜10 million. When the weight average molecular weight of the (meth) acrylic acid ester polymer (C) is less than 1,000,000, the impact resistance and the flexibility improving effect are not sufficient. On the other hand, if the weight average molecular weight exceeds 15 million, the compatibility of the resulting resin composition is impaired, or the melt viscosity becomes too high and handling becomes difficult.

  Among such (meth) acrylic acid ester polymers (C), commercially available products include, for example, the Metabrene P series manufactured by Mitsubishi Rayon Co., Ltd., the PARALOID K series manufactured by Rohm and Haas Co., and Kaneka. Kane Ace PA series made by the company.

  Content of said (meth) acrylic-ester type polymer (C) is 0.1-10 mass parts with respect to 100 mass parts of polylactic acid resin (A), and 0.3-8 mass parts especially It is preferable that it is 0.5-6 mass parts. When the content of the (meth) acrylic acid ester polymer (C) is less than 0.1 parts by mass, it is difficult to obtain a resin composition excellent in impact resistance and flexibility. On the other hand, when the content of the (meth) acrylic acid ester polymer (C) exceeds 10 parts by mass, the resulting resin composition is not only inferior in transparency, but also has a great fluidity when producing a molded product. It is not preferable because it is lowered.

The polylactic acid resin composition of the present invention is a resin composition containing the polylactic acid resin (A) as described above, a multilayer structure polymer (B), and a (meth) acrylic acid ester polymer (C). It is a thing. In the present invention, it is an important point to select and use a core-shell multilayer polymer (B) composed of specific components and a high molecular weight (meth) acrylate polymer (C) in combination. is there.
By using such a multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) in combination, the respective effects (impact of improving impact resistance and flexibility) are exhibited synergistically, Even if the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) are added in small amounts to the resin composition, the respective effects are sufficiently exhibited. As a result, it is possible to obtain a polylactic acid resin composition having excellent impact resistance and flexibility without impairing the transparency of the polylactic acid resin (A).

In the present invention, the total content of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) is 1 to 16 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). It is preferable that it is 2-10 mass parts among them, and it is more preferable that it is 2-8 mass parts.
When the total content of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) is less than 1 part by mass, the effect of improving impact resistance and flexibility becomes poor. On the other hand, when the total content of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) exceeds 16 parts by mass, the resulting resin composition is not only inferior in transparency. In addition, the operability in producing the molded body is deteriorated, and the heat resistance of the obtained molded body is lowered.

  Moreover, it is preferable that the mass ratio of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) in the polylactic acid resin composition of the present invention is 90/10 to 50/50. . By containing both polymers in such a ratio, impact resistance and flexibility are more effectively imparted.

  As described above, when the polylactic acid resin composition of the present invention is used, a molded article excellent in transparency, impact resistance and flexibility can be obtained. The molded body obtained from the resin composition of the present invention will be described later. As an index indicating the transparency, the haze value can be 10% or less in the case of a sheet having a thickness of 100 to 500 μm. Among them, the haze value is preferably less than 7%, and more preferably less than 6%. When the film has a haze value of 10% or more, the transparency is lowered. For example, when used in a packaging material, it is difficult to confirm the contents.

  Moreover, both impact resistance and flexibility in the present invention are mutually related performances. As an index indicating impact resistance, in the case of a sheet having a thickness of 100 to 500 μm, the impact strength (described in the examples described later) can be set to 5 kgf · cm / 100 μm or more, and in particular, 8 kgf It is preferably cm / 100 μm or more, and more preferably 10 kgf · cm / 100 μm or more.

  It has been difficult to obtain a polylactic acid-based resin composition excellent in both performance such as transparency and impact resistance by conventional techniques. However, in the study by the present inventors, the multilayer structure polymer (B) which is an acrylic rubber graft copolymer in which the core layer and the shell layer are composed of specific components, and a high weight average molecular weight of 1 million or more. By selecting the (meth) acrylic acid ester polymer (C) with a molecular weight, using both in combination, and including a specific amount, both performances such as transparency and impact resistance of polylactic acid resin can be obtained. It was found to improve. Although the mechanism is unknown, the polylactic acid resin (A), the multilayer structure polymer (B), and the (meth) acrylic acid ester polymer (C) are excellent in compatibility, and these in the resin composition It is assumed that it is involved in the excellent dispersibility of

  In the polylactic acid resin composition of the present invention, the polylactic acid resin (A), the multilayer polymer (B), and the (meth) acrylic acid ester heavy polymer are within a range that does not impair the effects of the present invention. In addition to the three components of the coalescence (C), additives as shown below may be contained. For example, end-capping agents, UV inhibitors, light stabilizers, anti-fogging agents, anti-fogging agents, antistatic agents, plasticizers, flame retardants, anti-coloring agents, antioxidants, fillers, pigments, mold release agents, moisture-proofing agents And various additives such as an oxygen barrier agent and a crystal nucleating agent. However, a component containing a reactive functional group (such as an epoxy group or an allyl group) is not preferable. When the resin composition contains a reactive functional group (such as an epoxy group or an allyl group), the functional group reacts with polylactic acid and the polylactic acid is easily gelled. When polylactic acid is gelled, a gelled portion is formed in the resulting molded product, and the quality is lowered and the transparency is easily lowered.

Next, the manufacturing method of the polylactic acid-type resin composition of this invention is demonstrated.
The multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) are often in a powder state, and contamination of the supply line in the production process tends to be a problem. Therefore, in the production of the polylactic acid resin composition of the present invention, the polylactic acid resin (A) has a high concentration of the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C). It is preferable to employ a method of preparing a added master batch pellet and diluting the master batch pellet with the polylactic acid resin (A) to obtain a polylactic acid resin composition.

  In such a master batch pellet, the content of the multilayer structure polymer (B) is preferably 10 to 50 parts by mass, more preferably 15 to 50 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). It is preferable that it is 20-50 mass parts. When the content of the multilayer structure polymer (B) is less than 10 parts by mass, the amount of master batch pellets used in obtaining the resin composition of the present invention increases, and the master containing the multilayer structure polymer in a high concentration. This is not a batch pellet. On the other hand, when the content exceeds 50 parts by mass, the operability at the time of preparing the master batch pellet is lowered, the dispersibility of the multilayered polymer is lowered, and the resulting master batch pellet has uneven concentration.

  The content of the (meth) acrylic acid ester polymer (C) in such a master batch pellet is preferably 3 to 20 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). It is preferable that it is -20 mass parts, and it is more preferable that it is 7-15 mass parts. When the content of the (meth) acrylic ester polymer (C) is less than 3 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A), a master batch pellet is obtained when the resin composition of the present invention is obtained. Therefore, it cannot be said to be a master batch pellet containing the multilayer structure polymer in a high concentration. On the other hand, if the content of the (meth) acrylic acid ester polymer (C) exceeds 20 parts by mass, the viscosity becomes too high and the operability at the time of preparing the master batch pellet is lowered, and the dispersibility of the multilayer structure polymer is reduced. And the resulting master batch pellets have uneven concentration.

Next, after manufacturing the masterbatch pellet of the present invention as described above, a method of manufacturing the polylactic acid resin composition of the present invention by diluting with the polylactic acid resin (A) will be described.
First, the manufacturing method of the masterbatch pellet of this invention is demonstrated. In an extruder, a polylactic acid resin (A), a multilayer structure polymer (B), and a (meth) acrylic acid ester polymer (C) are added and melt-kneaded. At this time, melt kneading is performed with a single screw extruder or a twin screw extruder, the cylinder temperature is 180 to 230 ° C., the die temperature is 190 to 240 ° C., the resin composition is melt kneaded and extruded, and the strand is cooled. The method of cutting into pellet size is preferable. The extruder to be used is preferably a twin screw extruder because of the kneading ability. The addition method is not particularly limited, such as a method of adding the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) from a separate feeder, a method of dry blending and adding from a hopper. However, since the multilayer structure polymer (B) and the (meth) acrylic acid ester polymer (C) have different particle diameters and are added in a large amount, it is preferable to add them by weighing with separate feeders.

  And the polylactic acid-type resin composition of this invention uses the masterbatch pellet obtained as mentioned above, and a multilayer structure polymer (B) and a (meth) acrylic acid ester-type polymer (C) are desired. It can obtain by diluting with a polylactic acid resin (A) so that it may become a density | concentration. Specifically, after the master batch pellet and the polylactic acid resin (A) are dry blended, it is preferable to perform melt kneading with a single screw extruder or a twin screw extruder.

Next, the molded product of the present invention will be described.
The molded body of the present invention is composed of the polylactic acid resin composition of the present invention, and the polylactic acid resin composition of the present invention is extruded, injection molded, blow molded, inflation molded, injection blow molded, foamed. It is formed by a method such as sheet forming, vacuum forming after processing the sheet, pressure forming, or vacuum / pressure forming.

  That is, the molded body of the present invention is a film, sheet formed by extrusion molding, a molded body processed from these films and sheets, a molded body formed by injection molding, or bead foaming or extrusion foaming. Examples thereof include a molded body, a hollow body formed by blow molding, and a molded body processed from the hollow body. Among them, the molded article of the present invention is preferably a sheet formed by extrusion molding or a film obtained by stretching the sheet, taking advantage of the excellent transparency of the polylactic acid resin composition of the present invention.

Next, the manufacturing method of a sheet | seat and a film is demonstrated as a manufacturing method of the molded object of this invention.
Examples of the sheet manufacturing method include a T-die method, an inflation method, and a calendar method. Of these, a T-die method and an inflation method in which a material is melt-kneaded and extruded using a T-die are preferable. When producing a polylactic acid-based sheet by the T-die method, the master batch pellet as described above is prepared in advance, and the master batch pellet and the polylactic acid resin (A) are supplied to the extruder hopper of the film forming apparatus. It is preferable to do. In melt kneading, a general kneader such as a single screw extruder, a twin screw extruder, a roll kneader, or a Brabender can be used.

  As temperature conditions during film formation, the cylinder temperature is preferably 150 to 250 ° C., and the T die temperature is preferably 160 to 250 ° C. Moreover, it is preferable that the cast roll is controlled at 20-50 degreeC. According to this method, a polylactic acid sheet having a thickness of 50 to 2000 μm can be obtained.

  Next, as a method for producing the film, it is preferable to uniaxially or biaxially stretch the polylactic acid-based sheet produced by the above production method. Examples of the stretching method include a roll method and a tenter method, and it is preferable to employ any one of a uniaxial stretching method, a sequential biaxial stretching method, and a simultaneous biaxial stretching method. The surface magnification in stretching is preferably 4 to 16 times. If the surface magnification is less than 4, the mechanical properties of the resulting film, particularly the tensile strength, may be low and may not be practical. On the other hand, if the surface magnification exceeds 16 times, the film may not be able to withstand the stretching stress during stretching and may be broken.

  The sheet temperature during stretching is preferably 50 to 110 ° C, more preferably 60 to 90 ° C. When the stretching temperature is less than 50 ° C., the film is broken at the initial stage of stretching due to insufficient heat for stretching. Moreover, when it exceeds 110 degreeC, there exists a tendency which heat | fever adds to a film too much and becomes draw extending | stretching and stretched spots occur frequently.

  Moreover, you may give a thermal relaxation process after extending | stretching in order to provide dimensional stability to a stretched film. As a method of thermal relaxation treatment, a method of blowing hot air, a method of irradiating infrared rays, a method of irradiating microwaves, a method of contacting on a heat roll, etc. can be selected, and a method of blowing hot air in that it can be heated uniformly and accurately Is preferred. In that case, it is preferable that it is 1 second or more in the range of 80-160 degreeC, and it is preferable to implement on the conditions of a 2-8% relaxation rate.

  Next, the present invention will be described specifically by way of examples. The measurement and evaluation of various characteristic values in the examples were performed as follows.

(1) Weight average molecular weight (Mw) of polylactic acid resin (A)
Using a gel permeation chromatography apparatus (manufactured by Shimadzu Corp.) equipped with a differential refractive index detector (manufactured by Shimadzu Corp., RID-10A), tetrahydrofuran (THF) as an eluent and a flow rate of 1.0 ml / min at 40 ° C. It was measured. As the column, SHODEX KF-805L and KF-804L (manufactured by Showa Denko KK) were connected and used. The sample was dissolved in 0.5 ml of chloroform after dissolving 10 mg of the polylactic acid resin (A), diluted with 5 ml of THF, filtered through a 0.45 μm filter, and then used for measurement. The molecular weight was converted using polystyrene (manufactured by Waters) as a standard sample.

(2) D-form content (mol%) of polylactic acid resin (A)
Add about 0.3 g of polylactic acid resin (A) to 6 ml of 1N potassium hydroxide / methanol solution, stir well at 65 ° C. to decompose polylactic acid, add 450 μl of sulfuric acid, and stir at 65 ° C. And lactate methyl ester. 5 ml of this sample, 3 ml of pure water, and 13 ml of methylene chloride were mixed and shaken. After stationary separation, about 1.5 ml of the lower organic layer was collected, filtered through a disk filter for HPLC having a pore size of 0.45 μm, and subjected to GC measurement using HP-6890 Series GC system manufactured by Hewlett Packard. The ratio (%) of the peak area of D-lactic acid methyl ester to the total peak area of lactate methyl ester was calculated, and this was used as the D-form content (mol%).

(3) Residual lactide amount of polylactic acid resin (A) 10 ml of dichloromethane and 0.5 ml of 2,6-dimethyl-γ-pyrone internal standard solution were added to 0.5 g of polylactic acid resin (A) and shaker (150 rpm × 40 minutes) and dissolved by stirring to prepare a sample solution for measurement. Cyclohexane was added thereto to precipitate a polymer, which was filtered through a disk filter for HPLC (pore size: 0.45 μm) and measured by gas chromatography. As the standard substance, L-lactide manufactured by Tokyo Chemical Industry was used.
Gas chromatography (Hewlett Packard, HP-6890) uses helium (He) as a carrier gas at a flow rate of 2.5 ml / min, an oven program held at 80 ° C. for 1 minute, and 20 ° C./min at 200 ° C. The temperature was raised to 280 ° C. at 30 ° C./min, and the conditions were maintained for 5 minutes. The column was DB-17 (30 m × 0.25 mm × 0.25 μm) manufactured by J & W, and the detector was measured by FID (temperature 300 ° C.) and the internal standard method.

(4) Melting point of polylactic acid resin (A) Using a differential scanning calorimeter (DSC device DSC7 manufactured by PerkinElmer), the polylactic acid resin (A) was heated from 20 ° C to 250 ° C at 20 ° C / min, Melting measured after holding for 5 minutes, cooling from 250 ° C. to 0 ° C. at 20 ° C./minute, holding at 0 ° C. for 5 minutes, and then re-heating from 0 ° C. to 250 ° C. at 20 ° C./minute The peak temperature (Tm) was taken as the melting point.

(5) Haze (transparency)
About the obtained sheet | seat and the stretched film, it measured using Nippon Denshoku Industries Co., Ltd. haze meter NDH2000 by JIS-K7105. At this time, the number of samples was set to 5, and the average value of these measured values was taken as the measured value.

(6) Impact resistance of sheet Using the obtained sheet having a thickness of 250 μm and using a film impact tester manufactured by Toyo Seiki Seisakusho, the pendulum capacity is fixed to the sheet fixed under tension in an atmosphere of 20 ° C. and 65% RH. A 30 kgf · cm impact head (0.5 inch hemispherical shape) was struck and the energy required to penetrate the sheet was measured.

(7) Flexibility of stretched film The texture of the obtained stretched film was evaluated in the following two stages by touch.
○: With flexibility ×: Without flexibility

(8) Impact resistance of injection molded products [Charpy impact test]
Using the obtained bending specimen (X), a notched specimen was prepared according to ISO 179-1, and the Charpy impact strength was measured.
[Falling weight impact test]
Using the obtained injection-molded product [color plate (Y)], impact strength was measured according to ASTM-2794. The striker R used for the evaluation is 1/8 inch, and the fracture state after every five tests is visually observed. The impact strength (J) is calculated from the height of the falling weight (cm) when it is not destroyed at all. Calculated.

Next, various raw materials used in Examples and Comparative Examples are shown.
[Polylactic acid resin (A)]
(A-1): manufactured by Nature Works, product number: 4032D, D-form content: 1.4 mol%, residual lactide content: 0.2 mass%, weight average molecular weight (Mw): 160,000, melting point: 165 ° C.
(A-2): Nature Works, product number: 4042D, D-form containing 4.0 mol%, residual lactide amount 0.2 mass%, weight average molecular weight (Mw) 160,000, melting point 150 ° C.

[Multilayer structure polymer (B)]
(B-1): Rohm and Haas “Paraloid BPM-500”, core-shell type, core layer... Acrylic rubber, shell layer... Methyl methacrylate grafted onto acrylic rubber (B-2) : Rohm and Haas “Paraloid BPM-515”, core shell type, core layer: acrylic rubber, shell layer: methyl methacrylate grafted onto acrylic rubber (B-3): manufactured by Mitsubishi Rayon Co., Ltd. "Metablene W-600A", core-shell type, core layer ... acrylic rubber, shell layer ... methyl methacrylate copolymer graft polymerized to acrylic rubber [other multilayer polymers]
(X-1): “Maybrene C-223A” manufactured by Mitsubishi Rayon Co., Ltd., core-shell type, core layer: butadiene rubber, shell component: (meth) methyl acrylate polymer

[(Meth) acrylic acid ester polymer (C)]
(C-1): METABRENE P-531A manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 4.5 million (C-2): METABRENE P-530A manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 3.1 million [low molecular weight (meth) acrylic acid ester Polymer)
(Y-1): METABRENE P-501A manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 800,000 (Y-2): METABRENE P-570A manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 250,000

Production Examples 1-3
Using a twin screw extruder (TEM26SS type manufactured by Toshiba Machine Co., Ltd.), polylactic acid resin (A), multilayer structure polymer (B), (meth) acrylic acid ester polymer (C) as shown in Table 1 Were measured with separate feeders and added from the root supply port so as to have the ratio shown in Table 1, and melt kneaded under conditions of barrel temperature 190 ° C., screw rotation speed 150 rpm, discharge 15 kg / h. After melt-kneading, strands were extruded from a 0.4 mm diameter × 3 hole die and cut into pellets to obtain pellets. The obtained pellets were dried at a temperature of 60 ° C. for 48 hours in a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Kagaku Co., Ltd.) to obtain master batch pellets M-1 to M-3.

Example 1
(Resin composition)
The master batch pellet (M-1) obtained in Production Example 1 and the polylactic acid resin (A-1) were dry blended at a mass ratio [(M-1) / (A-1)] 10/90. The following sheet, stretched film, and injection molded article were produced.
[Sheet]
The master batch pellet (M-1) dry-blended as described above and the polylactic acid resin (A-1) are melt-extruded at a T-die temperature of 230 ° C with a single-screw extruder having a diameter of 90 mm, and the temperature is controlled to 35 ° C. The polylactic acid-based sheet having a thickness of 250 μm made of the resin composition of the present invention was obtained by closely contacting the cast roll and cooling.
[Stretched film]
The end part of the obtained polylactic acid-based sheet was held by a clip of a tenter type simultaneous biaxial stretching machine, and after running in a preheating zone at 81 ° C., the temperature was 79 ° C., 3.0 times the MD, and 3 times the TD. .3 simultaneous biaxial stretching. Thereafter, after a heat treatment for 4 seconds at a temperature of 140 ° C. with a TD relaxation rate of 5%, the film was cooled to room temperature and wound to obtain a 25 μm thick polylactic acid-based stretched film.
[Injection molded body]
The master batch pellet (M-1) dry-blended as described above and the polylactic acid resin (A-1) were subjected to a cylinder temperature of 200 ° C. and a mold surface temperature using a NEX110 type injection molding machine manufactured by Nissei Resin Co., Ltd. While adjusting to 25 ° C., an ISO bending test piece (X) having a length of 80 mm, a width of 10 mm, and a thickness of 4 mm, and an ASTM color plate (Y) having a length of 85 mm, a width of 50 mm, and a thickness of 2 mm were prepared.

Example 2
In the same manner as in Example 1 except that the master batch pellet (M-2) obtained in Production Example 2 was used instead of the master batch pellet (M-1), a resin composition, a sheet, a stretched film, An injection molded body was produced.

Example 3
In the same manner as in Example 1 except that the master batch pellet (M-3) obtained in Production Example 3 was used instead of the master batch pellet (M-1), a resin composition, a sheet, a stretched film, An injection molded body was produced.

Examples 4-17, Comparative Examples 1-14
A polylactic acid resin (A), a multilayer structure polymer, and a (meth) acrylic acid ester polymer were dry blended in the composition (ratio) shown in Tables 2 and 3 and a twin screw extruder (TEM26SS type manufactured by Toshiba Machine Co., Ltd.) The mixture was supplied from the root supply port, and melt kneaded under the conditions of a barrel temperature of 190 ° C., a screw rotation speed of 150 rpm, and a discharge of 15 kg / h. After melt-kneading, a strand is extruded from a 0.4 mm diameter × 3 hole die, cut into a pellet, and heated at 60 ° C. in a vacuum dryer (trade name “Vacuum Dryer DP83” manufactured by Yamato Kagaku Co., Ltd.). And dried for 48 hours to obtain a resin composition. Using the obtained pellets, the following sheet, stretched film, and injection molded article were produced.
[Sheet]
The pellet obtained above is melt-extruded at a T-die temperature of 230 ° C. with a single-screw extruder having a diameter of 90 mm, and is cooled by being brought into close contact with a cast roll whose temperature is controlled at 35 ° C. The resin composition of the present invention. A polylactic acid-based sheet having a thickness of 250 μm was obtained.
[Stretched film]
The end part of the obtained polylactic acid-based sheet was held by a clip of a tenter type simultaneous biaxial stretching machine, and after running in a preheating zone at 81 ° C., the temperature was 79 ° C., 3.0 times the MD, and 3 times the TD. .3 simultaneous biaxial stretching. Thereafter, after a heat treatment for 4 seconds at a temperature of 140 ° C. with a TD relaxation rate of 5%, the film was cooled to room temperature and wound to obtain a 25 μm thick polylactic acid-based stretched film.
[Injection molded body]
Using the NEX110 type injection molding machine manufactured by Nissei Resin Co., Ltd., the pellets obtained above were subjected to ISO bending with a cylinder temperature of 200 ° C. and a mold surface temperature of 25 ° C. with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm. A test piece (X) and an ASTM color plate (Y) having a length of 85 mm, a width of 50 mm, and a thickness of 2 mm were prepared.

  The composition of the resin compositions obtained in Examples 1 to 17 and the characteristic values of various molded bodies are shown in Table 2, and the composition of the resin compositions obtained in Comparative Examples 1 to 14 and the characteristic values of various molded bodies are shown in Table 3. Shown in

As is clear from Table 2, the polylactic acid-based resin compositions obtained in Examples 1 to 17 were polylactic acid resin (A), multilayer structure polymer (B), (meth) acrylic acid ester polymer (C ) Was within the scope of the present invention, and thus the various molded articles obtained had high transparency, and were excellent in impact resistance and flexibility.
On the other hand, as is clear from Table 3, the resin composition of Comparative Example 1 does not contain the multilayer structure polymer (B) or the (meth) acrylic acid ester polymer (C), so that it has impact resistance and flexibility. It was inferior in nature. Since the resin composition of Comparative Example 2 did not contain the (meth) acrylic acid ester polymer (C), the resin composition was inferior in impact resistance and flexibility. The resin composition of Comparative Example 3 was inferior in transparency because the content of the multilayer structure polymer (B) was larger than the range of the present invention. Since the resin composition of Comparative Example 4 did not contain the multilayer structure polymer (B), the resin composition was inferior in impact resistance and flexibility. Since the resin composition of Comparative Examples 5-9 used the (meth) acrylic acid ester polymer with a low degree of polymerization, it was inferior to impact resistance and a softness | flexibility. The resin compositions of Comparative Examples 10 and 11 were inferior in transparency because the multilayer structure polymer defined in the present invention was not used. Since the resin composition of Comparative Example 12 did not use the multilayer structure polymer defined in the present invention and the (meth) acrylic acid ester polymer having a high degree of polymerization, the transparency, impact resistance, and flexibility were inferior. there were. Since the resin compositions of Comparative Examples 13 and 14 contained too much (meth) acrylic acid ester polymer (C), the resin composition was inferior in transparency, and the fluidity was greatly increased when various molded articles were produced. However, it was inferior in operability.

Claims (2)

A polylactic acid comprising a polylactic acid resin (A), a multilayer structure polymer (B), and a (meth) acrylic acid ester polymer (C) and satisfying the following conditions (a) to (c) -Based resin composition.
(A) The multilayer structure polymer (B) is composed of a core layer and a shell layer, the core layer contains an acrylic rubber, and the shell layer is one or more in the presence of the acrylic rubber of the core layer. This vinyl monomer is obtained by graft polymerization to the acrylic rubber of the core layer.
(B) The (meth) acrylic acid ester polymer (C) has a weight average molecular weight of 1 million or more and less than 15 million.
(C) The content of the multilayer structure polymer (B) is 0.5 to 15 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A), and the (meth) acrylate polymer (C) Is 0.1 to 10 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). The molded object which consists of a polylactic acid-type resin composition of Claim 1.