JP5958857B2 - Polylactic acid resin composition, method for producing molded product, and molded product - Google Patents

Description

  The present invention relates to a polylactic acid resin composition, a method for producing a molded article using the polylactic acid resin composition, and a molded article formed from the polylactic acid resin composition.

  In recent years, an increase in the concentration of carbon dioxide in the atmosphere has been pointed out as a cause of global warming, and the need for carbon dioxide emission regulations on a global scale has been advocated. Causes of carbon dioxide generation include respiration of organisms, rot and fermentation by bacteria, etc., but the amount of carbon dioxide generated by combustion of substances derived from petroleum resources is large, and it is due to carbon dioxide in the current atmosphere It is no exaggeration to say that the temperature rise phenomenon is caused by economic activity that wasted oil resources after human revolution. Furthermore, petroleum resources are limited resources and are expected to be depleted in the future.

  On the other hand, in recent years, the effective use of plant resources that absorb and fix carbon dioxide in the atmosphere during growth has attracted attention as a carbon neutral material. When obtaining plant resources, carbon dioxide in the atmosphere is absorbed by plant vegetation, and attempts have been made to replace petroleum resources with these plant resources.

  Also in the field of plastic materials, attempts are being made to switch from conventional materials based on petroleum to materials using biomass. Plastic materials using biomass initially attracted attention as biodegradable plastics, but recently they have been re-evaluated as carbon-neutral plant plastics and have been put into practical use in some areas. One type of typical plant plastic is polylactic acid resin. By injection-molding the polylactic acid resin composition, it is expected to obtain various molded articles such as an electronic device holder, an electronic device internal chassis component, an electronic device casing, and an electronic device internal component.

  For example, Patent Document 1 discloses that polylactic acid is 25 to 45% by mass, Si-containing core-shell rubber is 3 to 12% by mass, organophosphorous flame retardant is 1 to 15% by mass, and fluorine-containing anti-dripping agent is 0.2 to 3% by mass. And the use of a polylactic acid resin composition containing 15 to 70.8% by mass of a thermoplastic resin such as a polycarbonate resin.

  Further improvement in durability is desired for molded articles formed from a polylactic acid resin composition containing polylactic acid and a polycarbonate resin as described above.

  However, when polylactic acid is used, it has been difficult to improve the durability of the molded product. In particular, when polylactic acid and polycarbonate resin are used in combination, if an elastomer such as core-shell rubber is used to improve the mechanical strength of the molded product, the durability of the molded product tends to be further reduced. was there. Such a problem has hindered the spread of polylactic acid.

JP 2011-168756 A

  The present invention has been made in view of the above reasons, and a polylactic acid resin composition capable of forming a highly durable molded product while containing polylactic acid, a polycarbonate resin, and an elastomer, and the polylactic acid resin composition It aims at providing the manufacturing method of a molded article from a thing, and the molded article formed from this polylactic acid resin composition.

  The polylactic acid resin composition according to the first embodiment of the present invention contains polylactic acid in a proportion of 4% by mass or more and less than 15% by mass, contains a polycarbonate resin, has an Na content of 15 ppm or less, and a K content of 15 ppm or less. Further, an elastomer having an S content of 13 ppm or less is contained in a proportion of 1% by mass or more.

  In the second aspect of the present invention, in the first aspect, the pH of the elastomer is in the range of 6-8.

  In the 3rd form of this invention, the melt flow rate (300 degreeC 1.2kg) prescribed | regulated to ISO ASTM D1238 of the said polycarbonate resin in the 1st or 2nd form is the range which is 10-25 g / 10min. It is.

  The polylactic acid resin composition according to the fourth aspect of the present invention further contains a flame retardant in any one of the first to third aspects.

  The polylactic acid resin composition according to the fifth aspect of the present invention, in any one of the first to fourth aspects, has a tensile strength retention when exposed to an atmosphere of 60 ° C. and 95% RH for 1000 hours. A molded product that is 80% or more is formed.

  In the method for producing a molded product according to the sixth aspect of the present invention, the polylactic acid resin composition according to any one of the first to fifth aspects is molded.

  The molded product according to the seventh aspect of the present invention is formed by molding the polylactic acid resin composition according to any one of the first to fifth aspects.

  The molded product according to the eighth aspect of the present invention has a tensile strength retention of 80% or more when exposed in an atmosphere of 60 ° C. and 95% RH for 1000 hours in the seventh embodiment.

  According to the present invention, although the polylactic acid resin composition contains polylactic acid, a polycarbonate resin, and an elastomer, a molded article having high durability can be obtained by molding the polylactic acid resin composition. it can.

It is a perspective view which shows the external appearance of the holder for electronic devices in one Embodiment of this invention.

[Ingredients in polylactic acid resin composition]
The polylactic acid resin composition according to the present embodiment contains polylactic acid in a proportion of 4% by mass or more and less than 15% by mass, contains a polycarbonate resin, further contains an Na content of 15 ppm or less, a K content of 15 ppm or less, and an S content. An elastomer having a content of 13 ppm or less is contained in a proportion of 1% by mass or more. Hereinafter, components that can be contained in the polylactic acid resin composition according to the present embodiment will be described in more detail.

(Polylactic acid)
The polylactic acid contained in the polylactic acid resin composition preferably has a weight average molecular weight (Mw) of 70,000 or more. In this case, the fluidity of the polylactic acid resin composition and the durability of the molded product become more suitable as an injection molding material. The polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 4.0 or less. Furthermore, the content of polylactic acid in the polylactic acid resin composition is in the range of 4 to 15% by mass, preferably in the range of 4 to 12% by mass, more preferably in the range of 4 to 10% by mass. The range is particularly preferably 4-7% by mass.

  By satisfying such conditions, moderate flowability is imparted to the polylactic acid to ensure good moldability of the polylactic acid resin composition, and gas is hardly generated from the polylactic acid during molding. Thereby, sink marks and unevenness are less likely to occur in the molded product, and the appearance is improved. Further, even when the molded product is heated, it is difficult to cause appearance defects such as whitening. Furthermore, mold stains are less likely to occur during mold molding, so that the polylactic acid resin composition can be continuously molded and the mass productivity of the molded product is improved. Furthermore, despite the use of polylactic acid, the durability of the molded article is unlikely to decrease. In addition, this invention does not prevent that a polylactic acid resin composition contains a hydrolysis inhibiting agent from a viewpoint of a durable improvement. However, even if no hydrolysis inhibitor is used, the durability of the molded product is unlikely to decrease as described above. For this reason, it is also possible to obtain a molded article having good durability while reducing the production cost without using a hydrolysis inhibitor or suppressing the amount used.

  The weight average molecular weight of polylactic acid is more preferably in the range of 70,000 to 500,000, more preferably in the range of 70,000 to 300,000, and in the range of 70,000 to 100,000. Particularly preferred. Further, the polylactic acid dispersity (Mw / Mn) is preferably 4 or less, more preferably 3.5 or less, further preferably 3.0 or less, and further preferably 2.5 or less. preferable.

  The weight average molecular weight (Mw) and number average molecular weight (Mn) of polylactic acid are calculated by converting the measurement results by gel permeation chromatography using hexafluoroisopropanol as a solvent (mobile phase) by a calibration curve using standard polystyrene. Calculated. In measuring the weight average molecular weight and number average molecular weight of polylactic acid, 0.036 g of polylactic acid was dissolved in 9 mL of HFIP (hexafluoroisopropanol) over 48 hours, and the resulting solution was filtered with a filter. A sample for measurement is obtained. When this sample is measured with a high-speed GPC device (model number HLC-8220) manufactured by Tosoh Corporation, the weight average molecular weight and number average molecular weight of polylactic acid are calculated based on the measurement result.

  Examples of polylactic acid include a homopolymer of lactic acid and a copolymer of lactic acid and a hydroxycarboxylic acid other than lactic acid. Polylactic acid is obtained by polymerizing lactic acid. Lactic acid is obtained, for example, by fermenting starch derived from plants such as corn.

  Examples of lactic acid include L-lactic acid, D-lactic acid, and a lactone that is a dimer of lactic acid.

  Examples of hydroxycarboxylic acids other than lactic acid that can be copolymerized with lactic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, and hydroxycaproic acid. These hydroxycarboxylic acids may be used alone or in combination of two or more.

  The polylactic acid preferably contains at least one of poly-L-lactic acid, which is a polymer of L-lactic acid, and stereocomplex polylactic acid. In particular, when the polylactic acid is composed solely of stereocomplex type polylactic acid, or is composed only of poly-L-lactic acid and stereocomplex type polylactic acid, the molded product has very excellent appearance, water resistance, impact resistance and other properties. Is obtained.

  Polylactic acid substantially consists of an L-lactic acid unit and a D-lactic acid unit represented by the following formula [Chemical Formula 1].

  The poly-L-lactic acid is preferably composed of 90 to 100 mol%, more preferably 95 to 100 mol%, and still more preferably 99 to 100 mol% L-lactic acid units. When the ratio of the L-lactic acid unit is high, the durability of the molded product is further improved. Examples of units other than L-lactic acid include D-lactic acid units and units other than lactic acid.

  Polylactic acid may contain units other than lactic acid. Units other than lactic acid include units derived from dicarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, lactones and the like having functional groups capable of forming two or more ester bonds, and various polyesters and various polyesters composed of these various components. Examples are units derived from ether, various polycarbonates and the like.

  Polylactic acid is produced by a known method. For example, L- or D-lactide is produced by heating and ring-opening polymerization in the presence of a metal polymerization catalyst. Polylactic acid can also be produced by crystallizing a low molecular weight polylactic acid containing a metal polymerization catalyst, followed by solid phase polymerization by heating under reduced pressure or in an inert gas stream. Furthermore, polylactic acid is also produced by a direct polymerization method in which lactic acid is dehydrated and condensed in the presence / absence of an organic solvent.

  The melt flow rate (190 ° C. 2.16 kg) of polylactic acid is preferably in the range of 1 to 16 g / 10 min. In this case, the moldability (fluidity) of the polylactic acid resin composition is particularly improved.

(Polycarbonate resin)
When the polylactic acid resin composition contains a polycarbonate resin, the heat resistance and impact resistance of the molded product are improved.

  The content of the polycarbonate resin in the polylactic acid resin composition is appropriately set, but is preferably in the range of 20 to 97% by mass with respect to the entire polylactic acid resin composition. When the polylactic acid resin composition contains a thermoplastic resin other than polylactic acid and polycarbonate resin, the content of the polycarbonate resin is appropriately set according to the type of the thermoplastic resin in the polylactic acid resin composition. For example, depending on the type of thermoplastic resin in the polylactic acid resin composition, the content of the polycarbonate resin is preferably in the range of 80 to 95% by mass, and preferably in the range of 20 to 80% by mass.

  Examples of the polycarbonate resin include aromatic polycarbonate resins obtained by reacting a dihydric phenol and a carbonate precursor. Examples of the reaction method include an interfacial polycondensation method, a melt transesterification method, a solid phase transesterification method of a carbonate prepolymer, and a ring-opening polymerization method of a cyclic carbonate compound.

  Representative examples of the dihydric phenol include hydroquinone, resorcinol, 4,4′-biphenol, 1,1-bis (4-hydroxyphenyl) ethane, bisphenol A, 2,2-bis (4-hydroxy-3- Methylphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1, 1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 2,2-bis (4-hydroxyphenyl) pentane, 4,4 ′-(p-phenylenediisopropylidene) diphenol, 4, 4 ′-(m-phenylenediisopropylidene) diphenol, 1,1-bis (4-hydroxyphenyl) -4- Sopropylcyclohexane, bis (4-hydroxyphenyl) oxide, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxyphenyl) ketone, bis (4-hydroxyphenyl) ester, bis (4-hydroxy-3-methylphenyl) sulfide, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene And so on. A preferable dihydric phenol is bis (4-hydroxyphenyl) alkane, and bisphenol A is particularly preferable in that the toughness of the molded product can be improved.

  Examples of the carbonate precursor include carbonyl halide, carbonic acid diester, and haloformate. Specific examples include phosgene, diphenyl carbonate, and dihaloformate of dihydric phenol.

  When an aromatic polycarbonate resin is produced from a dihydric phenol and a carbonate precursor by an interfacial polymerization method, a catalyst, a terminal terminator, an antioxidant for the oxidation of the dihydric phenol, etc. are used as necessary. May be.

  As polycarbonate resin, branched polycarbonate resin copolymerized with trifunctional or higher polyfunctional aromatic compound, polyester carbonate resin copolymerized with aromatic or aliphatic (including alicyclic) difunctional carboxylic acid, bifunctional A copolymer polycarbonate resin obtained by copolymerizing a functional alcohol (including an alicyclic), and a polyester carbonate resin obtained by copolymerizing the bifunctional carboxylic acid and the difunctional alcohol together may be used. Two or more kinds of polycarbonate resins may be used.

  When a branched polycarbonate resin is used, the melt tension of the polylactic acid resin composition increases, thereby improving the moldability in extrusion molding, foam molding, blow molding and the like. As a result, a molded product having superior dimensional accuracy can be obtained. Examples of the trifunctional or higher polyfunctional aromatic compound used for obtaining the branched polycarbonate resin include 4,6-dimethyl-2,4,6-tris (4-hydroxydiphenyl) heptene-2, 2,4, 6-trimethyl-2,4,6-tris (4-hydroxyphenyl) heptane, 1,3,5-tris (4-hydroxyphenyl) benzene, 1,1,1-tris (4-hydroxyphenyl) ethane, , 1,1-tris (3,5-dimethyl-4-hydroxyphenyl) ethane, 2,6-bis (2-hydroxy-5-methylbenzyl) -4-methylphenol, 4- {4- [1,1 A preferred example is trisphenol such as -bis (4-hydroxyphenyl) ethyl] benzene} -α, α-dimethylbenzylphenol. Other polyfunctional aromatic compounds include phloroglucin, phloroglucide, tetra (4-hydroxyphenyl) methane, bis (2,4-dihydroxyphenyl) ketone, 1,4-bis (4,4-dihydroxytriphenylmethyl) Examples include benzene, trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, and acid chlorides thereof. Of these, 1,1,1-tris (4-hydroxyphenyl) ethane and 1,1,1-tris (3,5-dimethyl-4-hydroxyphenyl) ethane are preferable, and 1,1,1-tris (4 -Hydroxyphenyl) ethane is preferred.

The proportion of the structural unit derived from the polyfunctional aromatic compound in the branched polycarbonate resin is 100% by mole in total of the structural unit derived from the dihydric phenol and the structural unit derived from the polyfunctional aromatic compound. 0.03 to 1 mol%, preferably 0.07 to 0.7 mol%, particularly preferably 0.1 to 0.4 mol%. The branched structural unit is not only derived from a polyfunctional aromatic compound, but also derived from a side reaction during a melt transesterification reaction without using a polyfunctional aromatic compound. Also good. In addition, the ratio of this branched structure can be calculated by ¹ H-NMR measurement.

  On the other hand, the aliphatic bifunctional carboxylic acid is preferably α, ω-dicarboxylic acid, and specific examples thereof include sebacic acid (decanedioic acid), dodecanedioic acid, tetradecanedioic acid, octadecanedioic acid, icosane diacid. Examples thereof include linear saturated aliphatic dicarboxylic acids such as acids and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. As the bifunctional alcohol, an alicyclic diol is suitable, and examples thereof include cyclohexanedimethanol, cyclohexanediol, and tricyclodecane dimethanol. Further, a polycarbonate-polyorganosiloxane copolymer obtained by copolymerizing polyorganosiloxane units can also be used.

  As the polycarbonate resin, two or more kinds of polycarbonates having different dihydric phenol components, polycarbonates containing branched components, various polyester carbonates, polycarbonate-polyorganosiloxane copolymers, and the like may be used. Further, two or more kinds of polycarbonates having different production methods, polycarbonates having different end stoppers, and the like may be used.

  Reaction methods such as interfacial polymerization, molten transesterification, solid phase transesterification of carbonate prepolymers, and ring-opening polymerization of cyclic carbonate compounds, which are polycarbonate resin production methods, are well known in various documents and patent publications. It is the method that has been.

  As the polycarbonate resin, not only a virgin raw material but also a polycarbonate resin regenerated from a used product, a so-called material recycled aromatic polycarbonate may be used. Used products include soundproof walls, glass windows, translucent roofing materials, various glazing materials such as automobile sunroofs, transparent members such as windshields and automobile headlamp lenses, containers such as water bottles, optical recording media, etc. Is preferred. These do not contain a large amount of additives or other resins, and the desired quality is easily obtained stably. In particular, an automobile headlamp lens, an optical recording medium, and the like are preferable as the preferred embodiment because they satisfy the more preferable conditions of the viscosity average molecular weight described below. In addition, said virgin raw material is a raw material which is not yet used in the market after the manufacture.

The viscosity average molecular weight of the polycarbonate resin is preferably 1 × 10 ^{4 to} 5 × 10 ⁴ , more preferably 1.4 × 10 ^{4 to} 3 × 10 ⁴ , and still more preferably 1.8 × 10 ^{4 to} 2.5 × 10. ⁴ . When the viscosity average molecular weight is in the range of 1.8 × 10 ^{4 to} 2.5 × 10 ⁴ , the polylactic acid resin composition is particularly excellent in both good fluidity and impact resistance of the molded product. Most preferably, the viscosity average molecular weight is in the range of 1.9 × 10 ^{4 to} 2.4 × 10 ⁴ . The viscosity average molecular weight only needs to satisfy the entire polycarbonate resin, and a mixture of two or more polycarbonate resins having different molecular weights may satisfy this range.

In calculating the viscosity average molecular weight, first, the specific viscosity calculated by the following formula (a) was measured using an Ostwald viscometer for a sample solution prepared by dissolving 0.7 g of a polycarbonate resin in 100 ml of methylene chloride at 20 ° C. Obtained from measurement results. Next, the viscosity average molecular weight M is determined from the specific viscosity obtained using the following formulas (b) to (d).
Specific viscosity (ηSP) = (t−t0) / t (a)
[T0 is the drop time of methylene chloride, t is the drop time of the sample solution]
ηSP / c = [η] + 0.45 × [η] ² c (where [η] is the intrinsic viscosity) (b)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83 (c)
c = 0.7 (d)
It is preferable that the melt flow rate (300 degreeC 1.2kg) prescribed | regulated to ISO ASTM D1238 of a polycarbonate resin is the range of 10-25 g / 10min. In this case, the durability of the molded product is further improved. The melt flow rate (300 ° C., 1.2 kg) is preferably in the range of 10 to 20 g / 10 minutes.

(Carbodiimide compound)
The polylactic acid resin composition also preferably contains a carbodiimide compound such as a polycarbodiimide compound or a monocarbodiimide compound. In this case, these compounds react with some or all of the carboxyl group ends of polylactic acid to exert a blocking action, thereby further improving the durability of the molded product in a high-temperature and high-humidity environment.

  Examples of the polycarbodiimide compound include poly (4,4′-diphenylmethanecarbodiimide), poly (4,4′-dicyclohexylmethanecarbodiimide), poly (1,3,5-triisopropylbenzene) polycarbodiimide, and poly (1,3 , 5-triisopropylbenzene and 1,5-diisopropylbenzene) polycarbodiimide. Examples of the monocarbodiimide compound include N, N′-di-2,6-diisopropylphenylcarbodiimide.

  As such a carbodiimide compound, a commercially available product can be used as appropriate. Specific examples of the carbodiimide compound include trade name carbodilite LA-1 (poly (4,4'-dicyclohexylmethanecarbodiimide)), carbodilite HMV-8CA, carbodilite HMV-15CA, etc., manufactured by Nisshinbo Chemical Co., Ltd.

  The carbodiimide compound preferably does not have an isocyanate group. That the carbodiimide compound does not have an isocyanate group means that the compound having an isocyanate group is not mixed in the carbodiimide compound. That is, in the carbodiimide compound, a compound having an isocyanate group may be mixed, but it is preferable that such a compound having an isocyanate group is not contained in the polylactic acid or the resin composition. In this case, the durability of the molded product is further improved. This is considered because the reactivity of an isocyanate group is too high compared with a carbodiimide group. That is, it is considered that the isocyanate group reacts and is consumed quickly in the molded product, and therefore, the function of blocking the carboxyl group terminal of polylactic acid is quickly lost.

  Examples of the polycarbodiimide compound having no isocyanate group include trade name Carbodilite HMV-15CA manufactured by Nisshinbo Chemical Co., Ltd.

  When a carbodiimide compound is used, the content of the carbodiimide compound in the polylactic acid resin composition is preferably in the range of 0.1 to 5% by mass. When the content is 0.1% by mass or more, the durability of the molded product is further improved, and when the content is 5% by mass or less, high mechanical strength of the molded product is maintained. The content of the carbodiimide compound is preferably 3% by mass or less. The content of the carbodiimide compound is particularly preferably in the range of 0.1 to 1.0% by mass, and more preferably in the range of 0.1 to 0.5% by mass.

  When a carbodiimide compound is used, when the master batch is prepared by premixing only polylactic acid and a carbodiimide compound during the preparation of the polylactic acid resin composition, the above-mentioned action due to the use of the carbodiimide compound is particularly effective. Is demonstrated.

(Copolymer of alkyl methacrylate and alkyl acrylate)
The polylactic acid resin composition preferably also contains a copolymer of alkyl methacrylate and alkyl acrylate. In this case, mechanical properties such as impact resistance of the molded product are further improved.

  Examples of the alkyl methacrylate include methyl methacrylate and ethyl methacrylate. Examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, butyl acrylate and the like. The polymerization molar ratio of alkyl methacrylate to alkyl acrylate is preferably in the range of 40:60 to 95: 5. The weight average molecular weight of the copolymer of alkyl methacrylate and alkyl acrylate is preferably in the range of 1,000,000 to 5,000,000. This weight average molecular weight is a standard polystyrene equivalent weight average molecular weight determined by gel permeation chromatography using chloroform as a solvent (mobile phase).

  A specific example of such a copolymer of an alkyl methacrylate and an alkyl acrylate is trade name Metabrene P530 manufactured by Mitsubishi Rayon Co., Ltd.

  When a copolymer of alkyl methacrylate and alkyl acrylate is used, the content of the copolymer of alkyl methacrylate and alkyl acrylate in the thermoplastic resin composition is 0.5 mass% to 5 mass%. It is preferable to be within the range. When the content is 1.0% by mass or more and 3.0% by mass or less, the impact resistance of the molded product is particularly improved. The reason is that the melt viscosity of the thermoplastic resin composition is sufficiently increased within the above range, thereby forming an amorphous sea-island structure in the microstructure of the molded product, which leads to an improvement in impact resistance of the molded product. For this reason.

(Polybutylene adipate terephthalate)
The polylactic acid resin composition preferably further contains polybutylene adipate terephthalate. Polybutylene adipate terephthalate is a copolymer of 1,4-butanediol, adipic acid and terephthalic acid. Specific examples thereof include trade name Ecoflex manufactured by BASF.

  When the polylactic acid resin composition contains polybutylene adipate terephthalate, when the polylactic acid resin composition is molded, the polylactic acid is cross-linked by polybutylene adipate terephthalate by the reaction between polylactic acid and polybutylene adipate terephthalate. . This strengthens the structure in the molded product, and as a result, the durability and mechanical properties of the molded product are further improved.

  When polybutylene adipate terephthalate is used, the content in the polylactic acid resin composition is preferably 0.1 to 10% by mass.

  When the polylactic acid resin composition contains polybutylene adipate terephthalate, it is preferable that the polylactic acid resin composition further contains an organic peroxide. In this case, free radicals are generated from the organic peroxide when the polylactic acid resin composition is molded, so that the radical reaction between polylactic acid and polybutylene adipate terephthalate is promoted, and the durability and mechanical properties of the molded product are increased. The characteristics are further improved. As the organic peroxide, for example, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane (trade name Perhexa 25B manufactured by NOF Corporation) is used. The content of the organic peroxide in the polylactic acid resin composition is not particularly limited, but is preferably 0.01 to 1% by mass, for example.

(Elastomer)
When the polylactic acid resin composition contains an elastomer, mechanical properties such as impact resistance of the molded product are improved.

  Furthermore, the Na content of the elastomer is 15 ppm or less, the K content is 15 ppm or less, the S content is 13 ppm or less, and the proportion of this elastomer is 1% by mass or more based on the entire polylactic acid resin composition. The durability of the product is improved and discoloration of the molded product is suppressed. This is because the content of Na and K with a small atomic number in the elastomer is small, hydrolysis of polylactic acid and polycarbonate resin is suppressed, and further, the discoloration of the polycarbonate resin is suppressed by low content of sulfur component in the elastomer. It is thought that it is to be done. The ratio of the elastomer in the polylactic acid resin composition is particularly preferably in the range of 2 to 9% by mass.

  The Na content, K content, and S content of the elastomer are measured by fluorescent X-ray analysis. As the measuring device, for example, a fluorescent X-ray analyzer (product number XEPOS) manufactured by Spectro Corporation is used.

  Moreover, it is preferable that pH of this elastomer is the range of 6-8. In this case, hydrolysis of polylactic acid is further suppressed. For this reason, the durability of the molded product is further improved.

  The elastomer preferably has a functional group that reacts with an ester bond. In this case, the appearance of the molded product is improved. The reason is considered as follows. When a polycarbonate resin and polylactic acid are used in combination, the difference in fluidity between the two is usually large, so that a sea-island structure of polylactic acid and the polycarbonate resin is easily formed in the molded product. This sea-island structure causes flow marks in the molded product. However, when the elastomer has a functional group that reacts with an ester bond as described above, the polylactic acid is thickened, thereby reducing the difference in fluidity between the polylactic acid and the polycarbonate resin. For this reason, it is considered that the compatibility between the polylactic acid and the polycarbonate resin is improved, thereby improving the appearance of the molded product.

  Moreover, when such an elastomer is used, when a polylactic acid resin composition contains a flame retardant, high flame retardancy can be imparted to the molded product while reducing the ratio of the flame retardant. This is also considered to be because hydrolysis of polylactic acid is suppressed.

  A core shell rubber is preferably used as the elastomer. The core-shell rubber is a polymer having a multilayer structure, and an innermost layer (core layer) made of the polymer and one or more layers (shell layer) covering the core layer and made of a polymer different from the core layer. ). Examples of the core-shell rubber include a resin obtained by polymerizing a monomer such as a styrene monomer or a vinyl cyanide monomer in the presence of a rubbery polymer.

  The ratio of the core shell rubber to the entire polylactic acid resin composition is 1% by mass or more. This ratio is more preferably 3% by mass or more. From the viewpoint of improving the flowability of the polylactic acid resin composition and improving the moldability, workability, handling, etc. of the polylactic acid resin composition, the content of the core-shell rubber is preferably 12% by mass or less.

  The core shell rubber will be described in more detail. As the core-shell rubber, an unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer is preferably used. The unsaturated carboxylic acid alkyl ester used to obtain the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer includes methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate. Etc. Examples of the diene rubber component include rubbers having a glass transition point of 10 ° C. or less, such as polybutadiene, styrene-butadiene copolymer, and acrylonitrile-butadiene. Examples of the aromatic vinyl include nuclei substituted styrene such as styrene, α-methylstyrene and p-methylstyrene. These unsaturated carboxylic acid alkyl esters, diene rubbers, and aromatic vinyls can be used alone or in combination of two or more.

  A representative example of the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer is a methyl methacrylate-butadiene-styrene copolymer (MBS resin). The methyl methacrylate-butadiene-styrene copolymer is preferably a multilayer structure polymer including a core layer composed of a butadiene / styrene polymer and a shell layer composed of a methyl methacrylate polymer.

  The structural formula of the butadiene / styrene polymer is shown in the following formula [Chemical Formula 2]. The left part of this structural formula is a butadiene unit derived from butadiene, and the right part is a styrene unit derived from styrene.

  The structural formula of the methacrylic polymer constituting the shell layer is shown in the following formula [Chemical Formula 3].

  Examples of the method for producing the unsaturated carboxylic acid alkyl ester-diene rubber-aromatic vinyl graft copolymer include various methods such as bulk polymerization, suspension polymerization, and emulsion polymerization, and the emulsion polymerization method is particularly preferable. is there. The core-shell type graft rubber-like elastic body thus obtained preferably contains 50% by mass or more of the diene rubber component.

  As such a methyl methacrylate-butadiene-styrene copolymer, a commercially available product may be used as appropriate.

(Plant-derived PET)
It is also preferable that the polylactic acid resin composition contains PET (plant-derived PET) synthesized from a raw material including a plant-derived raw material. In such plant-derived PET, for example, terephthalic acid and monoethylene glycol containing monoethylene glycol (biomonoethylene glycol) produced from plant-derived ethanol such as sugar cane (so-called bioethanol) undergo dehydration condensation. Is synthesized.

  By using such plant-derived PET, the amount of petroleum-derived resources used in the polylactic acid resin composition and its molded product is reduced, which makes it possible to reduce petroleum-derived resources, which is an environmental problem. Contribute to the solution.

  The ratio of biomonoethylene glycol to the whole monoethylene glycol in the raw material of plant-derived PET is not particularly limited, but is preferably in the range of 1 to 100% by mass, and more preferably in the range of 5 to 100% by mass. In addition, regarding plant origin PET, the ratio of the biomonoethylene glycol with respect to the whole monoethylene glycol in the raw material is measured by ASTM D6866-11 METHOD B.

  When plant-derived PET is used, the proportion of plant-derived PET in the polylactic acid resin composition is not particularly limited, but is preferably in the range of 1 to 30% by mass.

(Other thermoplastic resins)
In the polylactic acid resin composition, various thermoplastic resins other than the above may be contained. For example, a polylactic acid resin composition is composed of ABS resin (acrylonitrile / butadiene / styrene copolymer resin), PMMA resin (polymethyl methacrylate resin), PP resin (polypropylene resin), LDPE resin (low density polyethylene resin), polyethylene terephthalate resin ( PET resin), polybutylene terephthalate resin (PBT resin), cyclohexanedimethanol copolymerized polyethylene terephthalate resin (so-called PET-G resin), polyethylene naphthalate resin, polybutylene naphthalate resin, and other aromatic polyester resins; cyclic polyolefin resins; Polycaprolactone resin; thermoplastic fluororesin represented by polyvinylidene fluoride resin; polyethylene resin, ethylene- (α-olefin) copolymer resin, and the like may be contained. The polylactic acid resin composition may contain only one kind of resin as described above, or may contain two or more kinds. Such various thermoplastic resins can further improve the impact resistance of the molded product. When these thermoplastic resins are used, the content thereof is preferably in the range of 3 to 12% by mass with respect to the polylactic acid resin composition.

(Antioxidant)
The polylactic acid resin composition preferably contains an antioxidant. In this case, the durability of the molded product is further improved by further suppressing hydrolysis of polylactic acid in the molded product. Antioxidants include 2,2-methylenebis- (4-methyl-6-tert-butylphenol), octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanoate, and bis (3 It is preferable to use at least one selected from the group consisting of (t-butyl-4-hydroxy-5-methyl-phenyl) dicyclopentadiene.

(Fillers, etc.)
The polylactic acid resin composition may contain a filler. As the filler, for example, talc, wollastonite, mica, clay, montmon lilonite, smectite, kaolin, zeolite (aluminum silicate), anhydrous amorphous aluminum silicate obtained by acid treatment and heat treatment of zeolite, etc. An inorganic filler is mentioned. Talc and wollastonite are particularly preferable. Among these fillers, only one type may be used, or two or more types may be used in combination.

  The average particle diameter of talc is usually preferably in the range of 0.1 to 10 μm. This average particle diameter is a value measured by a laser diffraction / scattering method using a laser diffraction / scattering particle size analyzer (such as Microtrack MT3000II series manufactured by Nikkiso Co., Ltd.).

  Although the content of talc in the polylactic acid resin composition is not particularly limited, it is preferably in the range of 1 to 30% by mass. If this content is 1% by mass or more, the tensile modulus of the molded product is improved, and if this content is 30% by mass or less, the penetration of talc into the screw during kneading of the polylactic acid resin composition is suppressed. Thus, good workability and moldability are maintained. The content of this talc is preferably in the range of 1 to 15% by mass, and more preferably in the range of 3 to 8% by mass. When this content is 8% by mass or less, the occurrence of welds and flow marks is sufficiently suppressed even when a molded product having a complicated shape is obtained, and when this content is 3% by mass or more, talc The effect of addition is particularly demonstrated.

  The polylactic acid resin composition may contain a dye or a pigment as a colorant. As dyes, coumarin fluorescent dyes, benzopyran fluorescent dyes, perylene fluorescent dyes, anthraquinone fluorescent dyes, thioindigo fluorescent dyes, xanthene fluorescent dyes, xanthone fluorescent dyes, thioxanthene fluorescent dyes, thioxanthone fluorescent dyes , Thiazine fluorescent dyes, diaminostilbene fluorescent dyes, fluorescent dyes (including fluorescent brighteners); perylene dyes; coumarin dyes; thioindigo dyes; anthraquinone dyes; thioxanthone dyes; Peranone dyes; quinoline dyes; quinacridone dyes; dioxazine dyes; isoindolinone dyes; phthalocyanine dyes. Of the fluorescent dyes, coumarin fluorescent dyes, benzopyran fluorescent dyes, and perylene fluorescent dyes that have good heat resistance and little deterioration during molding of the polycarbonate resin are suitable. As the pigment, metallic pigments such as various plate fillers having a metal film or a metal oxide film, carbon, and the like can be used.

  The content of the colorant in the polylactic acid resin composition is preferably 2% by mass or less, more preferably 1.5% by mass or less, with respect to 100 parts by mass of the total amount of the resin components. Furthermore, the content of the colorant is preferably 0.00001 parts by mass or more, more preferably 0.00005 parts by mass or more, and 0.5 parts by mass or more with respect to 100 parts by mass of the total amount of the resin components. If it is more preferable.

(Flame retardants)
The polylactic acid resin composition preferably further contains a flame retardant. In this case, the flame retardancy of the molded product is improved. As the flame retardant, a Br flame retardant, an organic phosphorus flame retardant, or antimony oxide is preferably used.

  In this embodiment, since the polylactic acid resin composition contains an elastomer having an Na content of 15 ppm or less, a K content of 15 ppm or less, and an S content of 13 ppm or less in a proportion of 1% by mass or more, the amount of flame retardant used is At least, high flame retardancy is imparted to the molded product. In particular, when an organic phosphorus flame retardant is used, a preferable ratio of the organic phosphorus flame retardant is in the range of 5 to 10% by mass with respect to the total amount of the polylactic acid resin composition.

  As the organic phosphorus flame retardant, a cyclic phosphazene compound represented by the following [Chemical Formula 4] is preferably used.

R ¹ and R ² are each independently an aryl group or a (meth) acrylic acid ester group having an unsaturated bond at the terminal, and R ¹ and R ² may be the same or different. n is an integer of 3 to 25.

  As the cyclic phosphazene compound represented by [Chemical Formula 4], appropriate commercially available products may be used. For example, product numbers SPB100 and SPB100L manufactured by Otsuka Chemical Co., Ltd., trade name Ravitor FP-100 manufactured by Fushimi Pharmaceutical Co., Ltd. May be used.

  The cyclic phosphazene compound represented by [Chemical Formula 4] is particularly preferably liquid. In this case, the dispersibility of the cyclic phosphazene compound in the polylactic acid resin composition is improved, and the flame retardancy of the molded product is particularly improved. Moreover, the flame retardance of a molded article can be improved while reducing the content of the cyclic phosphazene compound represented by [Chemical Formula 4]. In particular, as the cyclic phosphazene compound represented by the liquid [Chemical Formula 4], it is preferable to use a product number SPB100L manufactured by Otsuka Chemical Co., Ltd.

  It is also preferable that the organophosphorous flame retardant contains a phosphate ester compound represented by the following formula [Chemical Formula 5]. When this phosphoric ester compound is used, the flame retardancy of the molded product is greatly improved while maintaining high impact resistance of the molded product.

  N in the formula [Chemical Formula 5] represents an integer of 0 to 5. The phosphate ester compound represented by the formula [Chemical Formula 5] may be a mixture of compounds having different n numbers. When the phosphate ester compound is a mixture as described above, the average n number is preferably 0.5 to 1.5, more preferably 0.8 to 1.2, and still more preferably 0.95 to 1.15. Especially preferably, it is the range of 1-1.14.

  X in the formula [Chemical Formula 5] represents a divalent group in which a hydroxyl group is removed from a dihydroxy compound selected from the group consisting of hydroquinone, resorcinol, bisphenol A, and dihydroxydiphenyl. X is particularly preferably a divalent group derived from resorcinol, bisphenol A, or dihydroxydiphenyl.

R ¹ , R ² , R ³ , and R ⁴ in the above formula [Chemical Formula 5] each independently represent an aryl group having 6 to 12 carbon atoms. Specific examples of R ¹ , R ² , R ³ , and R ⁴ include monovalent groups derived from hydroxy compounds such as phenol, cresol, xylenol, isopropylphenol, butylphenol, and p-cumylphenol. Illustrated. Among these, it is preferable that R ¹ , R ² , R ³ , and R ⁴ are a phenyl group or a 2,6-dimethylphenyl group.

  The phenyl group may have a substituent having a halogen atom. Specific examples of the phosphate compound having a group derived from this phenyl group include tris (2,4,6-tribromophenyl) phosphate, tris (2,4-dibromophenyl) phosphate, and tris (4-bromophenyl). Examples include phosphate.

  On the other hand, specific examples of the phosphate compound having a halogen atom-free substituent include monophosphate compounds such as triphenyl phosphate and tri (2,6-xylyl) phosphate; resorcinol bisdi (2,6-xylyl) phosphate) A phosphate oligomer mainly composed of bisphenol A; a phosphate oligomer mainly composed of 4,4-dihydroxydiphenyl bis (diphenyl phosphate); a phosphate ester oligomer mainly composed of bisphenol A bis (diphenyl phosphate). Here, “mainly” means that a small amount of other components having different degrees of polymerization may be included. More preferably, the component of n = 1 in the above formula [Chemical Formula 5] is 80% by mass or more, more preferably 85% by mass. % Or more, more preferably 90% by mass or more.

  The acid value of the phosphate ester compound is preferably 0.2 mgKOH / g or less, more preferably 0.15 mgKOH / g or less, still more preferably 0.1 mgKOH / g or less, and particularly preferably 0.05 mgKOH / g. It is as follows. The lower limit of the acid value can be substantially 0, and is preferably 0.01 mgKOH / g or more practically. When the polylactic acid resin contains a phosphate ester compound represented by the formula [Chemical Formula 5] and having an acid value of 0.2 mgKOH / g or less, the thermal stability of the polylactic acid resin composition is particularly high, and the polylactic acid resin composition The hydrolysis resistance of the product is improved and the water resistance of the molded article is increased. The content of the half ester in the phosphate ester compound is more preferably 1.1% by mass or less, and still more preferably 0.9% by mass or less. As a minimum, 0.1 mass% or more is preferable practically, and 0.2 mass% or more is more preferable. When the acid value exceeds 0.2 mg KOH / g, or when the half ester content exceeds 1.5 mg, the thermal stability at the time of molding becomes inferior, and the polylactic acid resin composition accompanying the decomposition of the aromatic polycarbonate The hydrolysis resistance of the product decreases.

  As a specific example of such a phosphate ester compound, product number PX202 manufactured by Daihachi Chemical Industry Co., Ltd. may be mentioned.

  The organophosphorus flame retardant is a compound represented by the following structural formula (1-1) (resorcinol dixylenyl phosphate) and the following structural formula (1-2) as the phosphoric ester compound represented by [Chemical Formula 5]. It is preferable to contain at least one of the compounds (bisphenol A bis (diphenyl phosphate)).

  In particular, when the organic phosphorus compound contains the compound represented by the structural formula (1-1), not only the flame retardancy of the molded product is improved, but also the heat resistance and durability of the molded product are improved.

  Examples of the organic phosphorus flame retardant include ammonium phosphate. As a specific example of ammonium phosphate, product number AP422 manufactured by Clariant Japan Co., Ltd. may be mentioned. Even when such an ammonium phosphate is used, the flame retardancy of the molded product is greatly improved while maintaining high impact resistance of the molded product.

(Fluorine-containing anti-dripping agent)
The polylactic acid resin composition preferably further contains a fluorine-containing anti-dripping agent. The fluorine-containing anti-drip agent is used in order to prevent melting and dropping at the time of combustion of the molded product and further improve the flame retardancy.

  The content of the fluorine-containing anti-dripping agent in the polylactic acid resin composition is preferably in the range of 0.2 to 3% by mass, and more preferably in the range of 0.2 to 1% by mass. In such a range, it is possible to achieve both high mechanical strength and high flame resistance of the molded product.

  As the fluorine-containing anti-drip agent, polytetrafluoroethylene (PTFE) having fibril forming ability is preferably used. PTFE having a fibril-forming ability has a very high molecular weight and tends to form a fibrous form by bonding PTFE to each other by an external action such as shearing force. The number average molecular weight obtained from the standard specific gravity of PTFE is preferably in the range of 1 million to 10 million, and more preferably in the range of 2 million to 9 million. This PTFE may be in solid form or in the form of an aqueous dispersion. A PTFE mixture may be constituted by mixing PTFE with other resins for the purpose of improving dispersibility and further improving flame retardancy and mechanical properties of the molded product. Examples of commercially available PTFE having fibril forming ability include Teflon (registered trademark) 6J manufactured by Mitsui DuPont Fluorochemical Co., Ltd., and Polyflon MPA FA500, F-201L manufactured by Daikin Chemical Industries, Ltd. Commercially available PTFE aqueous dispersions include Asahi IC Fluoropolymers' Fullon AD-1, AD-936, Daikin Industries, Ltd., Fullon D-1, D-2, Mitsui DuPont Fluorochemical Co., Ltd. A typical example is Teflon (registered trademark) 30J manufactured by the company.

  Commercially available products of PTFE in a mixed form include “Metablene A3800” (trade name) manufactured by Mitsubishi Rayon Co., Ltd. and “BLENDEX B449” (trade name) manufactured by GE Specialty Chemicals.

  In the case of PTFE in a mixed form, the proportion of PTFE in 100% by mass of the PTFE mixture is preferably 1 to 60% by mass, more preferably 5 to 55% by mass. When the ratio of PTFE is in the above range, good dispersibility of PTFE can be achieved.

  The particle diameter of PTFE is preferably small. In this case, the dispersibility of PTFE in the polylactic acid resin composition is improved, thereby further improving the durability and flame retardancy of the molded product. In particular, the average particle size of PTFE is preferably in the range of 20 to 100 μm. The average particle diameter of this PTFE is a value measured by ASTM D4895.

(Other)
As long as the polylactic acid resin composition does not contradict the purpose of the present invention and does not impair the effect thereof, the stabilizer, the ultraviolet absorber, the lubricant, the release agent, the plasticizer, the antistatic agent, the inorganic and the You may contain well-known additives, such as an organic type antibacterial agent. These additives may be added at the time of kneading the polylactic acid resin composition, or may be added at the time of molding or the like.

[Polylactic acid resin composition and molded product]
The polylactic acid resin composition is prepared by mixing and kneading the raw materials of the polylactic acid resin composition as described above by an arbitrary method. In the mixing and kneading, for example, a twin screw extruder, a Banbury mixer, a heating roll, or the like is used. Among them, melt kneading using a twin screw extruder is preferable.

  For example, in preparing the polylactic acid resin composition, a method of supplying the raw materials of the polylactic acid resin composition independently to a melt kneader represented by a vent type twin screw extruder, or a part of the raw materials was premixed Thereafter, a method of supplying to the melt kneader independently of the remaining components may be employed. Moreover, after supplying a part of raw material to a melt kneader, the method of supplying the remaining raw material from the middle of a melt extruder may be employ | adopted. Although the heating temperature at the time of melt kneading is appropriately set according to the composition of the polylactic acid resin composition, it is preferably in the range of 200 to 260 ° C.

  In addition, when there is a liquid component in the raw material, a so-called liquid injection device, a liquid addition device, or the like may be used when supplying the liquid component to the melt extruder.

  The polylactic acid resin composition may be formed into pellets as necessary. For example, a polylactic acid resin composition extruded by a melt extruder is directly cut and pelletized, or after a strand of the polylactic acid resin composition is formed, the strand is cut by a pelletizer or the like and pelletized. Thus, a pellet-shaped polylactic acid resin composition may be obtained.

  As a molding method of the polylactic acid resin composition, an appropriate molding method such as injection molding, rotational molding, blow molding, vacuum molding or the like can be adopted. In particular, injection molding is preferred. In injection molding, not only ordinary molding methods, but also injection compression molding, injection press molding, gas-assisted injection molding, foam molding (including the method of injecting supercritical fluid), insert molding, in-mold coating molding, bicolor Molding, sandwich molding, ultra-high speed injection molding or the like may be employed.

  In the injection molding of the polylactic acid resin composition, an appropriate injection molding apparatus can be used. In particular, in order to control the cavity surface temperature of the mold at the time of injection, it is preferable to use a mold having an electric heater. In this case, when the polylactic acid resin composition is injected, the temperature of the cavity surface is accurately and quickly adjusted by an electric heater.

  The molded product thus obtained can be used in a wide range of fields such as home appliances, building materials and sanitary fields that are expected to be used for a long time.

  The molded product according to the present embodiment is less likely to be deteriorated in durability despite the use of polylactic acid, polycarbonate resin, and elastomer. In particular, by molding the polylactic acid resin composition, it is preferable to form a molded product having a tensile strength retention of 80% or more when exposed to an atmosphere of 60 ° C. and 95% RH for 1000 hours. More preferably, a molded article having a tensile strength retention of 80% or more when exposed to an atmosphere of 60 ° C. and 95% RH for 3000 hours is formed. That is, it is preferable that the retention rate of the tensile strength when the molded article formed from the polylactic acid resin is exposed for 1000 hours in an atmosphere of 60 ° C. and 95% RH is 80% or more. More preferably, the molded article has a tensile strength retention of 80% or more when exposed to an atmosphere of 60 ° C. and 95% RH for 3000 hours. The tensile strength retention is the ratio of the tensile strength of the molded article after the exposure treatment under the above conditions to the tensile strength of the molded article before the exposure treatment under the above conditions. Tensile strength is measured according to ISO 179.

  The use of the molded product is not particularly limited, and examples thereof include in-vehicle components, electronic components, and home appliance housings. In particular, when a flame retardant is used, the molded product is suitable as a battery pack housing, a personal computer housing, a multifunction device part, or the like.

  FIG. 1 shows an electronic device holder 2 as an example of a molded product 1. The electronic device holder 2 has a function of holding and fixing an electronic device such as a mobile phone on a desktop or the like, or further has a function as a charger for charging a battery in the electronic device. In the electronic device holder 2, a region (mounting region 3) on which the electronic device is placed and a holding rib 4 protruding from the outer edge of the placement region 3 are formed. The electronic device placed on the placement region 3 is further supported by the holding rib 4, whereby the electronic device is held and fixed to the electronic device holder 2. For this reason, the electronic device holder 2 is formed to match the shape and dimensions of the electronic device. The electronic device holder 2 is not limited to such a structure, and may have an appropriate structure capable of holding the electronic device. For this purpose, the electronic device holder 2 is formed to match the shape and dimensions of the electronic device.

  Various surface treatments may be applied to the molded article. Surface treatment includes forming a new layer on the surface of the molded product, such as vapor deposition (physical vapor deposition, chemical vapor deposition, etc.), plating (electroplating, electroless plating, hot dipping, etc.), painting, coating, printing, etc. Is mentioned. Specific examples of the surface treatment include hard coat, water / oil repellent coat, ultraviolet absorption coat, infrared absorption coat, metalizing (evaporation, etc.) and the like.

[Production Example 1]
The mixture of L-lactide and D-lactide is reacted by heating in a reactor equipped with a stirring blade in a nitrogen atmosphere in the presence of a metal polymerization catalyst and alcohol, and then the pressure in the reactor is reduced to remain in the mixture. Lactide was removed. Furthermore, polylactic acid was prepared by chipping this mixture. In preparing this polylactic acid, polylactic acid D and polylactic acid F having the composition described later were prepared by changing the blending ratio of L-lactide and D-lactide.

[Examples and Comparative Examples]
For each Example and Comparative Example, the components shown in the following table were used, and the resin components were dried in advance, and then these components were mixed with a tumbler for 10 minutes. The obtained mixture was extruded with a twin-screw extruder under conditions of a die vicinity temperature of 190 ° C. and an inlet vicinity temperature of 200 ° C. to obtain a strand.

  The strand was quickly cooled in a cooling tank and then cut with a cutter to obtain a pellet-shaped resin composition having a length of 2 to 4 mm.

  The resin composition was dried by heating at 80 ° C. for 4 hours in a dehumidifying dryer, and then a 100-ton injection molding machine and an ISO-compliant test piece mold (color plate, 60 mm × 60 mm × 2 mm, 2 The cylinder temperature was set to 230 ° C. near the head and 220 ° C. near the material inlet, and the mold temperature was set to 70 ° C. and injection molding was performed to obtain a molded product.

[Molding cycle evaluation]
For each example and comparative example, a single-point gate mold was used during injection molding of the resin composition, and the dimensions of the molded product were 60 mm × 60 mm × 2 mm. In this case, after the injection of the resin composition into the mold, the holding time (cooling time) required until the molded product can be taken out from the mold without deformation is measured, and this is measured in the molding cycle. It was used as an index.

[Evaluation of appearance and mold contamination]
For each example and comparative example, a single-point gate mold was used during injection molding of the resin composition, and the dimensions of the molded product were 60 mm × 60 mm × 2 mm. In each example and comparative example, 100 samples were tested.

  The presence or absence of wrinkles and sink marks in this sample was confirmed, and the number of moldings (number of defects) in which wrinkles or sink marks had occurred was confirmed.

  Furthermore, the presence or absence of welds and flow marks at the center of the sample was confirmed, and the number of samples (number of defects) in which welds or flow marks were observed was confirmed.

  Further, every time the sample was molded, the presence or absence of mold contamination was confirmed, and the number of times mold contamination was observed was confirmed.

[Color development evaluation]
In each Example, carbon black (carbon black MA600B manufactured by Mitsubishi Chemical Corporation) was blended at a ratio of 1 part by mass with respect to 100 parts by mass of the total amount of raw material components shown in the following table when the composition was prepared.

The resin composition containing the carbon black was molded by an injection molding machine to obtain a molded product having a size of 90 mm × 150 mm × 3 mm. The L ^* value of the surface of the molded product was measured using a spectrophotometer (Murakami Color Research Laboratory).

As a result, the case where the L ^* value was 10 or less was evaluated as A, the case of 11 to 15 as B, and the case of 16 or less as C.

[Impact resistance evaluation]
The notched Charpy impact value of the molded product obtained in each example and comparative example was measured according to ISO 179.

[Heat resistance evaluation]
The deflection temperature under load of the molded article in each example and comparative example was measured according to ISO 75-1 and 75-2. The measurement load was 0.45 MPa.

[Durability evaluation]
The molded products obtained in each Example and Comparative Example were exposed to an atmosphere of 60 ° C. and 95% RH for 1000 hours, and then the tensile strength of the molded products was measured according to ISO 179. The ratio (tensile strength retention ratio) of the molded product after the exposure treatment to the tensile strength of the molded product before the exposure treatment was derived, and this was used as an index of durability.

[Appearance after 80 ° C treatment]
The molded article was subjected to a treatment for 48 hours in an atmosphere at 80 ° C. The appearances of the molded product before treatment and the molded product after treatment were visually observed and compared.

  As a result, A was evaluated when no change was observed in the appearance, and B was evaluated when whitening occurred on the surface of the molded article after the treatment.

[Flame retardance]
The flame retardant class was evaluated by performing a combustion test according to UL94 on the molded product. The following table shows the thickness of the molded article subjected to the test and the flame retardance class.

[Evaluation results]
The result of the above evaluation test is shown in the following table together with the blending composition in each example and comparative example.

  In addition, according to the said result, when polycarbonate resin was used, when the ratio of the elastomer A was 1 mass% or more, the external appearance evaluation became especially favorable. This is considered to be because the compatibility between the polylactic acid and the polycarbonate resin was improved because the elastomer A has a functional group that reacts with an ester bond.

  Moreover, in each Example, the holder for electronic devices which has the external shape shown in FIG. 1 was formed by injection-molding the resin composition. Thereby, the holder for electronic devices with a favorable external appearance was obtained.

The details of each component shown in the table are as follows.
Polylactic acid A: manufactured by Nature Works LLC, trade name: NatureWorks 4032D, D-lactic acid unit ratio of 1.9 mol%, dispersity of 4.0 or less.
Polylactic acid B: polylactic acid obtained in Production Example 1, ratio of D-lactic acid unit 1.9 mol%, weight average molecular weight 75,000, number average molecular weight 31,000, dispersity 2.4, ISO Melt flow rate as defined in ASTM D1238 (190 ° C. 2.16 kg) 5.0 g / 10 min.
Polycarbonate resin A: Melt flow rate specified in ISO ASTM D1238 (300 ° C., 1.2 kg) 15 g / 10 min, load deflection temperature specified in ISO 306, 128 ° C.
Polycarbonate resin B: Melt flow rate (300 ° C., 1.2 kg) defined by ISO ASTM D1238 22 g / 10 min, load deflection temperature defined by ISO 306, 128 ° C.
Carbodiimide compound A: Carbodiimide compound having an isocyanate group, poly (4,4′-dicyclohexylmethanecarbodiimide), carbodiimide equivalent 248, carbodiimide group: isocyanate group molar ratio 15: 2, LA-1 manufactured by Nisshinbo Chemical Co., Ltd.
-Carbodiimide compound B: Carbodiimide compound having no isocyanate group, carbodiimide equivalent 262, Nisshinbo Chemical Co., Ltd., HMV-15CA.
Elastomer A: Core shell rubber (MBS resin), pH 7.1, electric conductivity 47 mS / m, Na content 15 ppm, K content 15 ppm, S content 13 ppm.
Elastomer B: Core shell rubber (MBS resin), pH 6.0, electric conductivity 7 mS / m, Na content 15 ppm, K content 15 ppm, S content 13 ppm.
-Elastomer C: Copolymer of alkyl methacrylate and alkyl acrylate, trade name Metabrene C223A manufactured by Mitsubishi Rayon Co., Ltd., pH 4.6, electric conductivity 47 mS / m, Na content 95 ppm, K content 85 ppm, S Content 1610ppm.
PTFEA: polytetrafluoroethylene, average particle size 470 μm, apparent density 470 g / l, manufactured by Mitsui DuPont Fluorochemical Co., Ltd., product number PTFE 6-J
PTFEB: polytetrafluoroethylene, average particle size 28 μm, melting point 327 ° C.

  In calculating the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polylactic acid, 0.036 g of polylactic acid is first dissolved in 9 mL of HFIP (hexafluoroisopropanol) over 48 hours, and thereby obtained. A sample for measurement was prepared by filtering the solution through a filter. This sample was measured with a high-speed GPC apparatus (model number HLC-8220) manufactured by Tosoh Corporation using hexafluoroisopropanol as a mobile phase. The measurement results were converted by a calibration curve using standard polystyrene, and the weight average molecular weight (Mw) and number average molecular weight (Mn) of polylactic acid were calculated.

Claims (8)

Polylactic acid is contained in a proportion of 4 to 15% by mass, polycarbonate resin is contained in a proportion of 72.5 to 79.5% by mass , Na content is 15 ppm or less, K content is 15 ppm or less, S content A polylactic acid resin composition comprising a methyl methacrylate-butadiene-styrene copolymer having a content of 13 ppm or less in a proportion of 2 to 9% by mass . The polylactic acid resin composition according to claim 1, wherein the methyl methacrylate-butadiene-styrene copolymer has a pH in the range of 6-8. The polylactic acid resin composition according to claim 1 or 2, wherein the polycarbonate resin has a melt flow rate (300 ° C, 1.2 kg) as defined in ISO ASTM D1238 in the range of 10 to 25 g / 10 min. The polylactic acid resin composition according to any one of claims 1 to 3, further comprising a flame retardant. The polylactic acid resin composition according to any one of claims 1 to 4, wherein a molded article having a tensile strength retention of 80% or more when exposed to an atmosphere of 60 ° C and 95% RH for 1000 hours is formed. . The manufacturing method of the molded article which shape | molds the polylactic acid resin composition as described in any one of Claims 1 thru | or 5. A molded article formed by molding the polylactic acid resin composition according to any one of claims 1 to 5. The molded article according to claim 7, wherein the tensile strength retention when exposed to an atmosphere of 60 ° C. and 95% RH for 1000 hours is 80% or more.

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