JP2008239836A - Polylactic acid resin composition and molded product comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition that excels in heat resistance and does not lose its transparency even if placed under high temperature and high humidity over a long time, and to provide a molded article comprising the same. <P>SOLUTION: The polylactic acid resin composition is formulated with and composed of a polylactic acid resin with a weight ratio of L-lactic acid and D-lactic acid of 97/3-85/15 or 3/97-15/85 and a methacrylic resin. The molded article is composed of the above polylactic acid resin composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a polylactic acid resin composition and a molded product comprising the same, and more specifically, a polylactic acid resin that has excellent heat resistance and does not lose transparency even when exposed to a high temperature and high humidity environment for a long time. The present invention relates to a composition and a molded article comprising the composition.

  In recent years, biodegradable polymers that are decomposed in the natural environment by the action of microorganisms existing in soil or water have attracted attention from the viewpoint of global environmental conservation, and various biodegradable polymers have been developed. Of these, as a biodegradable polymer that can be melt-molded, for example, a fat comprising an aliphatic dicarboxylic acid component such as polyhydroxybutyrate, polycaprolactone, succinic acid or adipic acid, and a glycol component such as ethylene glycol or butanediol. Family polyesters and polylactic acid resins are well known. Among these, polylactic acid resin can be produced at low cost by fermentation using microorganisms, using lactic acid as a raw material for lactic acid as a raw material, and has transparency and a melting point of about 170. It is expected to be a biopolymer that can be melt-molded at a high temperature.

  However, the polylactic acid resin has a glass transition temperature of around 60 ° C., and has a large thermal deformation and rigidity reduction near this temperature. When used as various molded products, the polylactic acid resin is easily deformed under normal use conditions. Therefore, a polylactic acid material having excellent heat resistance is desired.

  In addition to heat resistance, molded products made of a blend of polylactic acid resin and polymethylmethacrylate resin are very transparent, and are environmentally friendly that can be diverted to applications that require optical use and design. It is attracting attention as a material.

  Non-Patent Document 1 describes that a glass transition temperature is improved by blending a polylactic acid resin and a polymethyl methacrylate resin, and a resin composition having an effect of improving heat resistance to some extent has been developed. However, further improvement in heat resistance is required.

  Patent Document 1 describes that a sheet containing a polylactic acid resin excellent in heat resistance and transparency can be prepared by blending a polylactic acid resin and a polymethyl methacrylate resin.

  However, although the resin composition mentioned above has excellent transparency and heat resistance at room temperature, there is a problem that it loses transparency when placed under high temperature and high humidity for a long time.

  Conventionally, the characteristics of polylactic acid resin greatly change depending on the weight ratio of L-lactic acid and D-lactic acid.

  In patent document 1, when heat resistance is considered, it is described that heat resistance can be improved by selecting a polylactic acid resin having an optical isomer content of less than 2%.

  However, it has been found that a molded article prepared using a polylactic acid resin having a polylactic acid optical isomer content of 2% loses transparency when placed under high temperature and high humidity for a long time.

  Therefore, such polylactic acid resin is difficult to be used as a component in a high-temperature and high-humidity environment, and is not suitable for use in products that are expected to be used at relatively high temperatures such as automobile parts. This is a major obstacle to the spread of environmentally friendly materials.

Under such circumstances, there has been a demand for a polylactic acid-based material that does not lose heat resistance and transparency even when placed under high temperature and high humidity for a long time.
Polymer, 39 (26), 6891 (1998) JP 2006-328368 A

  In view of the background of such prior art, the present invention does not provide a polylactic acid resin composition that is excellent in heat resistance and does not lose transparency even under high temperature and high humidity for a long time, and a molded product comprising the same. It is what.

  The present invention employs the following means in order to solve such problems.

That is, the polylactic acid resin composition of the present invention is
A polylactic acid resin and a methacrylic resin in which the weight ratio of the L-lactic acid component and the D-lactic acid component is 97/3 to 85/15, or 3/97 to 15/85, is a weight ratio (polylactic acid resin / methacrylic resin). Resin) 80/20 to 10/90, melted and kneaded.

A preferred embodiment of such a polylactic acid resin composition is:
(1) The methacrylic resin is a methacrylic resin having a weight average molecular weight of 50,000 to 450,000 and a syndiotacticity of 40% or more,
(2) The methacrylic resin contains at least one methacrylic resin having a glass transition temperature of 110 ° C. or higher,
(3) The methacrylic resin is composed of two or more methacrylic resins that satisfy one or more of the following conditions:
(A) Difference in glass transition temperature is 10 ° C. or more (b) Difference in syndiotacticity is 3% or more.

  Moreover, the molded article of the present invention is characterized by being composed of such a polylactic acid resin composition.

  According to the present invention, it retains transparency even when exposed to high temperature and high humidity for a long time, and has excellent heat resistance. Therefore, electrical / electronic parts, building parts, automobile parts, various containers, daily necessities, daily life miscellaneous goods In addition, materials suitable for various uses such as sanitary products can be provided.

  The present invention has intensively studied the polylactic acid resin composition which is excellent in the above-mentioned problem, that is, heat resistance and does not lose transparency even when kept under high temperature and high humidity for a long time. When a polylactic acid resin and a methacrylic resin in which lactic acid is blended at a specific weight ratio are blended, it has been found that this problem can be solved at once.

  The polylactic acid resin used in the present invention is a polylactic acid resin in which either the L-lactic acid component or the D-lactic acid component is the main constituent component, but contains other copolymer components other than the lactic acid component. Also good.

  Examples of such other copolymerizable component units include polycarboxylic acids, polyhydric alcohols, hydroxycarboxylic acids, and lactones. Specifically, oxalic acid, malonic acid, succinic acid, glutaric acid, Adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, 5-sodium sulfoisophthalic acid, 5- Polyvalent carboxylic acids such as tetrabutylphosphonium sulfoisophthalic acid, ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl Recall, glycerin, pentaerythritol, bisphenol A, aromatic polyhydric alcohol obtained by addition reaction of bisphenol with ethylene oxide, polyhydric alcohols such as diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycolic acid, Hydroxycarboxylic acids such as 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, hydroxybenzoic acid, and glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ Lactones such as -butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone can be used.

  The polylactic acid resin of the present invention is composed of L-polylactic acid containing a small amount of D-form or D-polylactic acid containing a small amount of L-form, and from the viewpoint of transparency and heat resistance, Among the total lactic acid components, it is necessary that 3% to 15% of L-form is contained in the case of D-polylactic acid, or 3% to 15% of D-form is contained in the case of L-polylactic acid.

  If a polylactic acid resin that uses less than 3% of L-form and less than 3% of D-form is used in the total lactic acid component, the crystallization of the polylactic acid resin proceeds when exposed to a high temperature environment for a long time. The component impedes the transmission of visible light, and the transparency is significantly reduced.

  If the L-form is contained in an amount of 15% or more, or the D-form is contained in an amount of 15% or more, the heat resistance and moldability are deteriorated, which is not suitable for use.

  The molecular weight and molecular weight distribution of the polylactic acid resin are not particularly limited as long as it can be substantially molded, but the weight average molecular weight of the polylactic acid resin is preferably 50,000 or more, particularly Preferably it is 100,000 or more. The upper limit is not particularly limited, but is preferably 500,000 or less, more preferably 300,000 or less, and particularly preferably 250,000 or less.

  The weight average molecular weight here is a weight average molecular weight in terms of polymethyl methacrylate (PMMA) measured by gel permeation chromatography (GPC) using hexafluoroisopropanol as a solvent.

  As a method for producing such a polylactic acid resin, a known polymerization method can be used, and it can be produced using a direct polymerization method from lactic acid or a ring-opening polymerization method via lactide.

  For example, in the ring-opening polymerization method, L-lactide and DL-lactide, which is an L-lactide dimer, are mixed at an arbitrary weight ratio, and ring-opening polymerization is performed, whereby any L-form and D-form can be obtained. A polylactic acid resin having a composition can be obtained.

  Alternatively, polylactic acid resins having different copolymerization ratios of D-form and L-form may be blended, and a polylactic acid resin having a copolymerization ratio of D-pair and L-form within the above range may be used.

  Next, as the methacrylic resin used in the present invention, the main component is a methyl methacrylate component unit, preferably 70% or more, and other vinyl monomer component units are preferably 30%. A copolymer copolymerized below may be used.

  As other vinyl monomers here, aromatic vinyl type such as α-methyl styrene, o-methyl styrene, p-methyl styrene, o-ethyl styrene, p-ethyl styrene, pt-butyl styrene, etc. Monomers, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, ethacrylonitrile, glycidyl itaconate, allyl glycidyl ether, styrene-p-glycidyl ether, p-glycidyl styrene, maleic anhydride, maleic acid N-substituted maleimides such as monoethyl ester, itaconic acid, itaconic anhydride, glutaric anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, acrylamide, methacrylamide, N- Methylacrylamide, butoxy Tylacrylamide, N-propylmethacrylamide, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, aminoethyl acrylate, propylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-acrylic acid 2- Hydroxypropyl, glycidyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, butanediol diacrylate, nonanediol diacrylate, polyethylene glycol diacrylate, methyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) ethyl acrylate, methacrylic acid, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, dimethylaminoethyl methacrylate, ethyl methacrylate Ruaminopropyl, phenylaminoethyl methacrylate, cyclohexylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate, methacrylic acid Pentamethylpiperidyl acid, tetramethylpiperidyl methacrylate, benzyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, polyethylene glycol dimethacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N -Methylallylamine, p-aminostyrene, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryloyl Oxazoline and 2-styryl - oxazoline etc. can be used, these vinyl monomers may be used alone or in combination. Among these, from the viewpoint of heat resistance, low hygroscopicity, and surface hardness, a copolymer containing a ring structural unit such as a lactone ring, maleic anhydride, glutaric anhydride, etc. in the main chain is preferably used. Furthermore, when a copolymer containing a ring structure in the main chain is used, it is more preferable to use a methacrylic resin not containing a ring structure.

  The methacrylic resin used in the present invention is preferably a methacrylic resin having a weight average molecular weight of 50,000 to 450,000 and a syndiotacticity of 40% or more. By using a methacrylic resin satisfying such conditions, the intermolecular interaction with the polylactic acid resin is increased and the affinity is improved, so that a resin composition excellent in transparency and heat resistance can be obtained. .

  The weight average molecular weight of the methacrylic resin is more preferably from 70,000 to 200,000, particularly preferably from 90,000 to 150,000, from the viewpoint of heat resistance and moldability.

  The weight average molecular weight here is a weight average molecular weight in terms of polymethyl methacrylate (PMMA) measured by GPC using hexafluoroisopropanol as a solvent.

  In addition, the syndiotacticity of the methacrylic resin is preferably 45% or more, more preferably 50% or more, still more preferably 65% or more, and particularly preferably 70% or more in terms of heat resistance. Although an upper limit is not specifically limited, 90% or less is preferable at the point of a moldability. Further, in terms of heat resistance, the heterotacticity is preferably 45% or less, more preferably 40% or less, even more preferably 35% or less, and particularly preferably 30% or less. preferable. In terms of heat resistance, isotacticity is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. preferable.

  As used herein, syndiotacticity, heterotacticity, and isotacticity are those directly observed at 0.9 ppm, 1.0 ppm, and 1.2 ppm in 1H-NMR measurement using deuterated chloroform as a solvent. The total integrated intensity ratio of the chain-branched methyl group peaks is 100%, and the ratio of the integrated intensity ratio of each peak is expressed as a percentage.

  The glass transition temperature of the methacrylic resin is not particularly limited, but is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, even more preferably 100 ° C. or higher, particularly preferably 110 ° C. or higher, from the viewpoint of heat resistance. Most preferred is ℃ or higher. Although an upper limit is not specifically limited, 150 degreeC or less is preferable at the point of a moldability.

  The glass transition temperature here is a value measured according to the method described in JIS K7121, and is a midpoint glass transition temperature when the temperature is raised at 20 ° C./min by DSC measurement. This is the temperature at which the change in specific heat capacity in the region is half the value.

  In the present invention, the methacrylic resin preferably contains at least one methacrylic resin having a glass transition temperature of 110 ° C. or higher. The melt flow rate (MFR) of the methacrylic resin used in the present invention is not particularly limited, but in terms of heat resistance, the MFR at a load of 230 ° C. and 37.2 N is 0.1 to 0.1 according to JIS K7210. It is preferably 40 g / 10 minutes, more preferably 1 to 30 g / 10 minutes, and particularly preferably 2 to 20 g / 10 minutes in terms of molding processability. If the MFR is less than 0.1 g / 10 minutes, the moldability tends to be lowered, and if it exceeds 40 g / 10 minutes, the heat resistance improving effect tends to be lowered.

  In the present invention, the blending ratio of the polylactic acid resin and the methacrylic resin is preferably 80:20 to 10:90 in terms of weight ratio (polylactic acid resin / methacrylic resin) in consideration of heat resistance and moldability. .

  If the weight ratio of the methacrylic resin is less than 10%, the moldability and heat resistance are remarkably lowered, so that it cannot be used. When the weight ratio of the polylactic acid resin is less than 10%, the significance as an environmentally conscious material is lost.

The methacrylic resin of the present invention is preferably composed of two or more methacrylic resins that satisfy one or more of the following conditions.
(A) Difference in glass transition temperature is 10 ° C. or more (b) Difference in syndiotacticity is 3% or more

  By using a methacrylic resin that satisfies such conditions, the intermolecular interaction with the polylactic acid resin is further increased and the affinity is improved, so that a resin composition excellent in transparency and heat resistance can be obtained. .

  In the present invention, in terms of heat resistance and moldability, the glass transition temperature is preferably composed of two or more methacrylic resins having a difference of 15 ° C. or more, and the difference is 20 ° C. or more. More preferred. If the difference in glass transition temperature between two or more methacrylic resins is less than 10 ° C., the effect of improving heat resistance is insufficient. Moreover, although the upper limit of the difference of glass transition temperature is not specifically limited, It is preferable that it is 60 degrees C or less at the point of transparency.

The glass transition temperature here is a value measured according to the method described in JIS K7121, and is a midpoint glass transition temperature when the temperature is raised at 20 ° C./min by DSC measurement.
It is a temperature at which the specific heat capacity change in the glass transition temperature region becomes a half value.

In the present invention, when two or more kinds of methacrylic resins are used, the glass transition temperature region, that is, the specific heat capacity change region tends to be wider than when used alone, and preferably the glass transition temperature ± 10. ° C, more preferably glass transition temperature ± 20 ° C, still more preferably glass transition temperature ± 30 ° C, particularly preferably glass transition temperature ± 40 ° C.
In the present invention, in terms of heat resistance and moldability, the syndiotactic difference is preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more. If the difference in syndiotacticity is less than 3%, the heat resistance improving effect is insufficient. Moreover, the upper limit of the difference of syndiotacticity is not particularly limited, but is preferably 50% or less from the viewpoint of transparency.

  In the present invention, the composition of each methacrylic resin when two or more methacrylic resins are used is not particularly limited, but the glass transition temperature or syndiotacticity is the highest value in terms of heat resistance and fluidity. The methacrylic resin 1 is methacrylic resin 1, the other is methacrylic resin 2, and the weight ratio of methacrylic resin 1 to methacrylic resin 2 (methacrylic resin 1 / methacrylic resin 2) is 10:90 to 90: 10 is preferable, and 60:40 to 40:60 is more preferable.

  As a method for producing such a methacrylic resin, known polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization and the like can be used. For example, by the method described in JP-A No. 58-13603 The methacrylic resin used in the present invention can be obtained. The temperature condition during the polymerization is not particularly limited, but is preferably 100 ° C. or lower, more preferably 70 ° C. or lower, even more preferably 30 ° C. or lower, and particularly preferably −10 ° C. or lower in terms of heat resistance of the methacrylic acid resin. .

  In the polylactic acid resin composition of the present invention, a filler (glass fiber, carbon fiber, metal fiber, natural fiber, organic fiber, glass flake, glass bead, ceramic fiber, ceramic bead is used as long as the object of the present invention is not impaired. , Asbestos, wollastonite, talc, clay, mica, sericite, zeolite, bentonite, dolomite, kaolin, finely divided silicic acid, feldspar powder, potassium titanate, shirasu balloon, calcium carbonate, magnesium carbonate, barium sulfate, calcium oxide, oxidation Including aluminum, titanium oxide, aluminum silicate, silicon oxide, gypsum, novaculite, dawsonite and clay), stabilizers (antioxidants, UV absorbers, etc.), lubricants, release agents, flame retardants, dyes and pigments Add agent, nucleating agent, antistatic agent, etc. Door can be. Especially, it is preferable to mix | blend a mold release agent from the point that the resin composition excellent in mechanical characteristics, a moldability, heat resistance, transparency, etc. is obtained.

  As such a release agent, those usually used as a release agent for thermoplastic resins can be used. Specifically, fatty acids, fatty acid metal salts, oxy fatty acids, fatty acid esters, partially aliphatic saponified esters, paraffin, low molecular weight polyolefins, fatty acid amides, alkylene bis fatty acid amides, aliphatic ketones, fatty acid lower alcohol esters, fatty acid polyhydric alcohols Examples thereof include esters, fatty acid polyglycol esters, and modified silicones.

  The amount of the release agent is preferably 0.01 to 3 parts by weight, more preferably 0.03 to 2 parts by weight, based on 100 parts by weight of the total of the polylactic acid resin and the methacrylic resin.

  Further, with respect to the polylactic acid resin composition used in the present invention, other thermoplastic resins (for example, polyethylene resin, polypropylene resin, polymethylpentene resin, cyclic olefin resin, Acrylonitrile / butanediene / styrene (ABS) resin, acrylonitrile / styrene (AS) resin, cellulose resin such as cellulose acetate, polyamide resin, polyacetal resin, polyester resin such as polyethylene terephthalate resin and polybutylene terephthalate resin, polycarbonate resin, polyphenylene oxide Resin, polyarylate resin, polysulfone resin, polyphenylene sulfide resin, polyether ether ketone resin, polyimide resin, polyetherimide resin, etc.) and thermosetting Fat (for example, phenol resin, melamine resin, polyester resin, silicone resin, epoxy resin) and soft thermoplastic resin (for example, ethylene / glycidyl methacrylate copolymer, polyester elastomer, polyamide elastomer, ethylene / propylene terpolymer, ethylene / butene- 1 copolymer or the like) can be further blended.

  In addition, a hydrolysis inhibitor may be added for the purpose of improving the durability of the polylactic acid resin composition of the present invention. Such hydrolysis inhibitors include carbodiimides, oxozalines, epoxy compounds, and the like.

  The addition amount is not particularly limited as long as it does not impair the effects of the present invention. However, when added in excess, the added additive inhibits visible light transmission, and thus transparency may be lost. Therefore, the amount is preferably 0.01% to 1.0% with respect to 100 parts by weight of the polylactic acid resin composition. Examples of the method for inhibiting hydrolysis include a method of dry blending a resin and a hydrolysis inhibitor in advance when the resin is supplied to an extruder, a method of supplying a hydrolysis inhibitor from a supply port in the middle of extrusion air, and the like. It is done.

  The method for producing the polylactic acid resin composition of the present invention is not particularly limited. For example, after pre-blending polylactic acid resin, methacrylic resin and other additives as necessary, at a melting point or higher, A method of uniformly melting and kneading with a single screw or twin screw extruder, a method of removing a solvent after mixing in a solution, etc. are used. From the viewpoint of productivity, a method of uniformly melting and kneading with a single screw or twin screw extruder is used. In view of heat resistance, a method of uniformly kneading with a twin screw extruder is more preferable.

  With respect to the polylactic acid resin composition of the present invention, the melt flow rate (MFR) is not particularly limited, but in terms of moldability, the MFR measured at 190 ° C. and 21.2 N load is 30 g / 10 according to JIS K7210. It is preferably not more than 20 minutes, more preferably not more than 20 g / 10 minutes, still more preferably not more than 10 g / 10 minutes, particularly preferably not more than 7 g / 10 minutes, and not more than 5 g / 10 minutes. Most preferably. When MFR exceeds 30 g / 10 min, the heat resistance tends to decrease. The lower limit is not particularly limited, but is preferably 0.1 g / 10 min or more from the viewpoint of moldability.

  For the polylactic acid resin composition of the present invention, the saturated water absorption is not particularly limited, but the saturated water absorption measured according to ASTM D570 is preferably 0.4% by weight or less, and 0.3% by weight or less. More preferably, it is more preferably 0.2% by weight or less, and particularly preferably 0.1% by weight or less. The lower limit is not particularly limited. If the saturated water absorption exceeds 0.4% by weight, deformation due to moisture absorption is likely to occur and the possibility of being unusable increases.

  The polylactic acid resin composition of the present invention can be processed into various molded products and used by methods such as injection molding and extrusion molding.

  Examples of the molded product comprising the polylactic acid resin composition of the present invention include injection molded products, extrusion molded products, blow molded products, films, and sheets. Further, these molded articles of the present invention can be used for various applications such as electric / electronic parts, building members, automobile parts, various containers, daily necessities, daily life goods and sanitary goods.

  The polylactic acid resin composition of the present invention and a molded product comprising the same can be recycled. For example, a polylactic acid resin composition and a molded product comprising the same are heat-treated at 80 ° C. or higher, preferably 100 ° C. or higher, pulverized, preferably powdered, and then methacrylic using a solvent such as acetone or tetrahydrofuran. The resin can be isolated and then the polylactic acid resin can be isolated from the residue using a solvent such as chloroform. The isolated resins can be used singly, and the resin composition obtained by further blending can be used in the same manner as the polylactic acid resin composition of the present invention, and can also be formed into a molded product.

  Hereinafter, the configuration and effects of the present invention will be described in more detail by way of examples. Here, the compounding ratio in an Example shows weight%. Moreover, the raw material used and the code | symbol in a table | surface are shown below.

(A) Polylactic acid resin (A-1) Poly L lactic acid resin (D 4%, Mw 210,000)
(A-2) Poly L lactic acid resin (D body 13%, Mw 210,000)
(A-3) Poly L lactic acid resin (D body 1.4%, Mw 130,000)

(B) Methacrylic resin (B-1) Methacrylic resin (Sumitomo Chemical “Sumipex LG21” Tg 105 ° C., Syndiotacticity 41%, Mw 80,000, MFR 21 g / 10 min (230 ° C., 37.2 N))
(B-2) Methacrylic resin (Kuraray “Parapet” HR-L, Tg 117 ° C., syndiotacticity 56%, Mw 90,000, MFR 2 g / 10 min (230 ° C., 37.2 N))
(B-3) Methacrylic resin (Sumitomo Chemical “Sumipex” LG35, Tg 90 ° C., Syndiotacticity 39%, Mw 100,000, MFR 35 g / 10 min (230 ° C., 37.2 N))

  The measurement method and determination method used in the present invention are shown below.

(1) Syndiotacticity A value measured by 1H-NMR measurement. 1H-NMR measurement was performed using JNM-AL400 manufactured by JEOL Ltd., using deuterated chloroform as a solvent, and a sample concentration of 20 mg / mL.

(2) Weight average molecular weight (Mw)
It is a value of weight average molecular weight in terms of standard PMMA measured by gel permeation chromatography (GPC). The GPC measurement uses a WATERS differential refractometer WATERS 410 as a detector, a MODEL510 high performance liquid chromatography as a pump, and a column with Shodex GPC K-806M and Shodex GPC K-G connected in series as a solvent. Hexafluoroisopropanol was used, the flow rate was 0.5 mL / min, and 0.1 mL of a solution having a sample concentration of 1 mg / mL was injected and measured.

(3) Transparency A plate-shaped molded product having a size of 5 cm × 5 cm × 3 mm was treated with a thermostatic PH (H) -101 type manufactured by ESPEC Corporation for 300 hours at a temperature of 65 ° C. and a humidity of 95%, and then Nippon Denshoku Industries Co., Ltd. Using a haze meter NDH-300A, the haze of the molded product was measured according to JIS-K7105.

(4) Heat resistance (deflection temperature under load)
Standard deflection value when a bending stress test piece with a thickness of 6.4 mm is used with a HDT tester S3-F type manufactured by Toyo Seiki Seisakusho and a bending stress of 0.45 MPa is generated on the test piece in accordance with ASTM standard D648. The temperature at which the temperature reaches the value is defined as the deflection temperature under load. When this temperature was higher, the heat resistance was higher, and when the deflection temperature under load was lower than 65 ° C., it was judged that it could not be used.

[Examples 1-5, Comparative Examples 1-3]
As shown in Table 1, a polylactic acid resin and a methacrylic resin are blended, and using a 30 mm diameter twin screw extruder, melt-kneading is performed under conditions of a cylinder temperature of 200 ° C. and a rotation speed of 200 rpm to obtain a pellet-shaped resin composition. It was.

  The obtained resin composition was injection-molded at a cylinder temperature of 220 ° C. and a mold temperature of 40 ° C. using an injection molding machine SG75H-MIV manufactured by Sumitomo Heavy Industries, Ltd. A plate-shaped molded product having a size of 3 mm was obtained.

  Table 1 shows the results of various evaluations using the obtained molded product.

  From the results in Table 1, the following is clear.

  From the comparison between Examples 1 to 5 and Comparative Examples 1 to 2, the ratio of D-lactic acid is 3% to 15%, and the weight average molecular weight is 50,000 to 450,000 and the syndiotacticity is 40% or more. It can be seen that a resin composition containing a methacrylic resin maintains heat resistance and maintains transparency even when exposed to a high temperature and high humidity environment for a long time.

Claims (5)

Weight ratio of polylactic acid resin and methacrylic resin in which the weight ratio of L-lactic acid component and D-lactic acid component is 97/3 to 85/15 or 3/97 to 15/85 (polylactic acid resin / methacrylic resin) A polylactic acid resin composition characterized by being blended at 80/20 to 10/90 and melt-kneaded. The polylactic acid resin composition according to claim 1, wherein the methacrylic resin is a methacrylic resin having a weight average molecular weight of 50,000 to 450,000 and a syndiotacticity of 40% or more. The polylactic acid resin composition according to claim 1 or 2, wherein the methacrylic resin contains at least one methacrylic resin having a glass transition temperature of 110 ° C or higher. The polylactic acid resin composition according to any one of claims 1 to 3, wherein the methacrylic resin is composed of two or more methacrylic resins satisfying at least one of the following conditions.
(A) Difference in glass transition temperature is 10 ° C. or more (b) Difference in syndiotacticity is 3% or more A molded article comprising the polylactic acid resin composition according to any one of claims 1 to 4.