JP2015063583A - Polylactic acid-based resin composition and molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid-based resin composition having excellent impact resistance (excellent in Charpy impact strength and falling weight resistance) while having sufficient transparency and heat resistance in a resin composition comprising a polylactic acid resin and an acrylic resin.SOLUTION: There is provided a polylactic acid-based resin composition which is a resin composition comprising a polylactic acid resin (A), a polymethyl methacrylate-based resin (B) having a deflection temperature of higher than 95°C under a load of 1.8 MPa and an acrylic polymer (C) having a weight average molecular weight of 700000 to 5000000, where the weight ratio [(A)/(B)] between the acrylic polymer (C) and the polymethyl methacrylate-based resin (B) is 20/80 to 70/30 and the content of the acrylic polymer (C) is 1 to 10 pts.mass based on the total 100 pts.mass of the polylactic acid resin (A) and the polymethyl methacrylate-based resin (B).

Description

  The present invention is a resin composition containing a polylactic acid resin and two kinds of acrylic resins, and has a low impact on the global environment and is excellent in transparency, heat resistance and impact resistance. It is about.

  In general, resins such as polypropylene (PP), acrylonitrile-butadiene-styrene resin (ABS), polyamide (PA6, PA66), polyester (PET, PBT), and polycarbonate (PC) are used as raw materials for molding. . However, molded articles produced from such resins are excellent in moldability and mechanical strength. However, when discarded, they increase the amount of dust and are hardly decomposed in the natural environment. Even if it remains in the ground semipermanently.

  On the other hand, in recent years, biodegradable polyester resins have attracted attention from the viewpoint of environmental conservation. Among biodegradable polyester resins, resins such as polylactic acid, polyethylene succinate, and polybutylene succinate are low in cost and highly useful because they can be mass-produced. Among them, polylactic acid resin can be produced from plants such as corn and sweet potato as raw materials, and even if incinerated after use, considering the carbon dioxide absorbed during the growth of these plants, the carbon balance is neutral. Therefore, it is considered as a resin having a particularly low load on the global environment.

  However, polylactic acid resin is inferior to various conventionally used molding resins in terms of moldability and mechanical properties. Therefore, by adding various additives to polylactic acid resin or mixing (alloying) various conventionally used resins, the moldability is improved while taking advantage of the low environmental impact of polylactic acid resin. The mechanical properties have been improved.

  Among various resins that have been used in the past, acrylic resins including polymethyl methacrylate (hereinafter sometimes abbreviated as PMMA) resins are widely used in various applications from the viewpoint of transparency. Yes. The acrylic resin has a very good compatibility with the polylactic acid resin, and has a great advantage in that the transparency is maintained even after mixing with the polylactic acid resin. In addition, the value in terms of use is great also in that the texture such as a feeling of hardness which is a characteristic of acrylic resin can be maintained.

  However, since both the polylactic acid resin and the acrylic resin have a hard and brittle property (high elastic modulus and low impact resistance), a resin composition obtained by mixing both resins also has this property. Therefore, it is difficult to directly apply a mixture of a polylactic acid resin and an acrylic resin to an application requiring impact resistance.

  Therefore, it is conceivable to add a material imparting impact resistance to the polylactic acid resin and the acrylic resin. Of course, the adverse effect on transparency due to the addition of these materials is inevitable. .

  Patent Document 1 contains a core-shell type impact-resistant agent having a refractive index equivalent to that of a substrate (matrix) in which a polylactic acid resin and an acrylic resin are mixed, thereby preventing the decrease in transparency as much as possible. It has been proposed to impart impact properties. However, since it is not easy to obtain a core-shell impact agent having a refractive index equivalent to that of the substrate, it has not been sufficient in terms of transparency. Furthermore, although impact resistance such as Charpy and Izod has been improved, it has sufficient impact resistance against falling ball impact and falling weight impact, which are a concern during normal use of molded products. It wasn't.

  Patent Document 2 describes that a resin composition having excellent flexibility is obtained by melt-mixing a polylactic acid resin and an acrylic elastomer such as methyl methacrylate / n-butyl acrylate copolymer. ing. According to this resin composition, it is possible to give a certain degree of flexibility, but the impact resistance is not sufficient.

International Publication No. 2005/085352 JP 2011-84654 A

  The present invention solves the above-mentioned problems, and in a resin composition containing a polylactic acid resin and an acrylic resin, it has excellent impact resistance while having sufficient transparency and heat resistance (Charpy impact). It is a technical problem to provide a polylactic acid-based resin composition that is excellent in both strength and weight drop resistance.

The inventors of the present invention have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the gist of the present invention is as follows.
(1) Polylactic acid resin (A), polymethyl methacrylate resin (B) having a deflection temperature under load of 1.8 MPa of 95 ° C. or higher, and an acrylic polymer having a weight average molecular weight of 700,000 to 5,000,000 ( C) -containing resin composition, wherein the mass ratio [(A) / (B)] of the polylactic acid resin (A) and the polymethyl methacrylate resin (B) is 20/80 to 70/30 The content of the acrylic polymer (C) is 1 to 10 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin (A) and the polymethyl methacrylate resin (B). Lactic acid resin composition.
(2) A molded product obtained by molding the polylactic acid resin composition according to (1).

The polylactic acid resin composition of the present invention specifies a polylactic acid resin (A), a polymethyl methacrylate resin (B) having specific heat resistance, and an acrylic polymer (C) having a specific molecular weight. By containing it in an amount, it is possible to have excellent impact resistance in which both Charpy impact strength and weight drop resistance are improved while maintaining transparency and heat resistance.
Among them, when a polylactic acid resin (A) having a low D-form content is used, not only heat resistance but also impact resistance can be further improved.
The polylactic acid-based resin composition of the present invention can be used for various applications, can greatly expand the range of use of the polylactic acid resin, which is a low environmental load material, and has a very high industrial utility value.

  Hereinafter, the present invention will be described in detail. The polylactic acid resin composition of the present invention (hereinafter sometimes simply referred to as a resin composition) comprises a polylactic acid resin (A), a polymethyl methacrylate resin (B) having specific heat resistance, and a specific molecular weight. It contains an acrylic polymer (C).

First, the polylactic acid resin (A) will be described. As the polylactic acid resin (A), poly (L-lactic acid), poly (D-lactic acid), and a mixture or copolymer thereof can be used. From the viewpoint of molding processability, heat resistance, and cost, It is preferable to mainly use poly (L-lactic acid).

  Among them, the polylactic acid resin (A) preferably has a D-form content of 0 to 2.0 mol%. The D-form content is further preferably 0 to 1.5 mol%, and most preferably 0 to 0.6 mol%. When the D-form content is within this range, the transparency of the polylactic acid resin itself is improved, and the resulting resin composition has good transparency. Furthermore, since the compatibility with the acrylic polymer (C) becomes higher, the impact resistance of the obtained resin composition is further improved. Moreover, since it is excellent in crystal performance, it becomes possible to obtain the molded object excellent in heat resistance.

  The D-form content of the polylactic acid resin (A) is a ratio (mol%) occupied by the D-lactic acid unit in the total lactic acid units constituting the polylactic acid resin (A). Therefore, for example, in the case of a polylactic acid resin (A) having a D-form content of 1.0 mol%, this polylactic acid resin (A) has a ratio of D-lactic acid units of 1.0 mol%, and L -The ratio which a lactic acid unit accounts is 99.0 mol%.

  In the present invention, the D-form content of the polylactic acid resin (A) is all methyl ester of L-lactic acid and D-lactic acid obtained by decomposing the polylactic acid resin (A), as described later in Examples. And is calculated by a method of analyzing the methyl ester of L-lactic acid and the methyl ester of D-lactic acid with a gas chromatography analyzer.

The polylactic acid resin (A) preferably has a weight average molecular weight of 30,000 to 500,000, more preferably 50,000 to 300,000, and even more preferably 70,000 to 200,000.
When the weight average molecular weight exceeds 500,000, not only the compatibility with the polymethyl methacrylate resin (B) is lowered, but also the extrusion becomes difficult because the viscosity is too high. On the other hand, when the weight average molecular weight is less than 30,000, the obtained molded product tends to have no physical properties that can be practically used.

  Furthermore, considering the moldability of the resin composition of the present invention, the polylactic acid resin (A) has a melt flow rate (measured at 190 ° C. under a load of 2.16 kg) of 0.1 to 50 g / 10 min. Among them, 0.2 to 40 g / 10 min is particularly preferable. When the melt flow rate exceeds 50 g / 10 min, the melt viscosity is too low, and the molded product obtained tends to be inferior in mechanical properties and heat resistance. When the melt flow rate is less than 0.1 g / 10 minutes, the load during the molding process becomes too high and the operability may be lowered.

The lactide content contained in the polylactic acid resin (A) is preferably in the range of 0 to 2500 ppm, more preferably 0 to 2000 ppm, and most preferably in the range of 0 to 1500 ppm.
When the lactide content exceeds 2500 ppm, it causes a decrease in stability at the time of melting, a decrease in the crystallization rate, and a decrease in the hydrolysis stability of the molded product.

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

  Next, the polymethyl methacrylate resin (B) will be described. The polymethyl methacrylate resin (B) refers to a copolymer having a methyl methacrylate component unit as a main component and other vinyl monomer component units copolymerized.

  Other vinyl monomer component units include aromatic vinyl monomers such as methyl styrene, ethyl styrene and butyl styrene, vinyl cyanide monomers such as acrylonitrile, methacrylonitrile and ethacrylonitrile, methacrylic monomers. Alkyl methacrylate ester monomers having 1 to 18 carbon atoms of alkyl groups (including cycloalkyl groups) such as methyl acid, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate, Methacrylic acid aryl ester monomers such as phenyl methacrylate, methacrylic acid aralkyl ester monomers such as benzyl methacrylate, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, acrylic An acid aminoethyl. These vinyl monomers may be used alone or in combination.

  In the present invention, the polymethyl methacrylate resin (B) needs to have a deflection temperature under load at 1.8 MPa of 95 ° C. or higher. When the deflection temperature under load at 1.8 MPa is less than 95 ° C., the resulting resin composition is inferior in heat resistance.

  In order to obtain the polymethyl methacrylate resin (B) having a deflection temperature under load as described above, the content of methyl methacrylate in the polymethyl methacrylate resin (B) is preferably 90% by mass or more. Especially, it is preferable to set it as 95 mass% or more. That is, it is preferable that 90% by mass or more of methyl methacrylate as a monomer component is contained in the polymer.

  The polymethyl methacrylate resin (B) preferably has a weight average molecular weight of 50,000 to 300,000, more preferably 70,000 to 150,000, and even more preferably 80,000 to 130,000. . If the weight average molecular weight exceeds 300,000, the fluidity is too low and processing becomes extremely difficult. On the other hand, when the weight average molecular weight is less than 50,000, it is difficult to obtain a resin composition having excellent heat resistance and mechanical strength.

  The polymethyl methacrylate resin (B) preferably has a melt flow rate at 230 ° C. and a load of 38 N of 0.1 to 50 g / 10 minutes, and preferably 0.5 to 50 g / 10 minutes. More preferably, it is particularly preferably 0.5 to 10 g / 10 min. When the melt flow rate is less than 0.1 g / 10 min, processing becomes extremely difficult due to low fluidity, and when it exceeds 50 g / 10 min, sufficient heat resistance and mechanical strength may not be obtained. is there.

  Examples of the polymethyl methacrylate resin (B) used in the present invention include “Acrypet VH” manufactured by Mitsubishi Rayon Co., Ltd. (load deflection temperature (1.8 MPa) 100 ° C.), “Sumipex MHF” manufactured by Sumitomo Chemical Co., Ltd. (load) Deflection temperature (1.8 MPa) 102 ° C.), “V825” manufactured by Arkema (load deflection temperature (1.8 MPa) 102 ° C.), and the like.

In the resin composition of the present invention, the mass ratio [(A) / (B)] of the polylactic acid resin (A) and the polymethyl methacrylate resin (B) is 20/80 to 70/30 as described above. In particular, it is preferably 20/80 to 50/50.
When the content of the polymethyl methacrylate resin (B) is below this range, it becomes difficult to sufficiently exhibit the performance inherent in the polymethyl methacrylate resin (B) such as transparency and heat resistance. . On the other hand, when the content of the polymethyl methacrylate resin (B) exceeds this range, the low environmental impact of the resin composition of the present invention due to the inclusion of the polylactic acid resin (A) is reduced, and the environment is reduced. The contribution degree of becomes smaller.

  Next, the acrylic polymer (C) will be described. The acrylic polymer (C) used in the present invention has a weight average molecular weight of 700,000 to 5,000,000. Among them, the weight average molecular weight is preferably 1 million to 5 million, and more preferably 2 million to 4.5 million. By containing a specific amount of the acrylic polymer (C) having a specific weight average molecular weight as described above, impact resistance can be remarkably improved while maintaining transparency and heat resistance.

  Generally, a rubbery polymer used as an impact resistance improving material often inhibits transparency and heat resistance when added to a resin composition. However, a resin composition containing a polylactic acid resin (A) and a polymethyl methacrylate resin (B) by containing a specific amount of the acrylic polymer (C) having a specific weight average molecular weight as described above. The impact resistance can be remarkably improved while maintaining the transparency and heat resistance of the. That is, as the impact resistance, the resulting resin composition is excellent in both Charpy impact strength and weight drop resistance.

  When the weight average molecular weight of the acrylic polymer (C) is less than 700,000, the resulting resin composition is inferior in both Charpy impact strength and weight drop resistance. On the other hand, when the weight average molecular weight exceeds 5,000,000, the resulting resin composition is deteriorated in compatibility due to the loss of compatibility, or the melt viscosity becomes too low and the molding processability is lowered.

  The acrylic polymer (C) is preferably composed of monomers such as acrylic acid and esters thereof, methacrylic acid and esters thereof, or a homopolymer of only one kind of these monomers, or two or more kinds. Any copolymer of these monomers may be used, and the copolymer may be a block copolymer, a random copolymer, a graft copolymer, or any copolymer thereof. Specific examples of such methacrylic acid and its ester monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, Examples include t-butyl methacrylate, neopentyl methacrylate, ethyl hexyl methacrylate, isodecyl acrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, benzyl methacrylate, tetrahydrofurfuryl methacrylate, methoxyethyl methacrylate, and the like. Moreover, monomers, such as substituted styrenes, such as styrene, (alpha) -methylstyrene, t-butylstyrene, and chlorostyrene, can also be copolymerized.

  Among these acrylic polymers (C), those commercially available include, for example, Metablene P series manufactured by Mitsubishi Rayon Co., Ltd., PARALOID K series manufactured by Rohm and Haas Co., and Kaneace PA Series manufactured by Kaneka Corporation. Is mentioned.

  The content of the acrylic polymer (C) needs to be 1 to 10 parts by mass with respect to a total of 100 parts by mass of the polylactic acid resin (A) and the polymethyl methacrylate resin (B). It is preferable that it is -8 mass parts, and it is most preferable that it is 3-7 mass parts. If the content of the acrylic polymer (C) is less than 1 part by mass, the effect of improving impact resistance cannot be obtained. On the other hand, when it exceeds 10 parts by mass, the fluidity is lowered, and the workability is deteriorated. Moreover, since it may become inferior to transparency, it is not preferable.

  Furthermore, the resin composition of the present invention preferably contains a carbodiimide compound. By containing the carbodiimide compound, the obtained resin composition can improve the wet heat durability of the resin composition while maintaining transparency, and can stably maintain its performance for a long period of time. As the carbodiimide compound, various compounds can be used, for example, aliphatic (alicyclic) carbodiimide, aromatic carbodiimide and the like, and those having various heterocyclic rings or various functional groups in the molecule may be used. .

It does not specifically limit as a method of manufacturing a carbodiimide compound, Many methods, such as the method of manufacturing an isocyanate compound as a raw material, are mentioned.
Specific examples of the monocarbodiimide compound include EN160 manufactured by Matsumoto Yushi Co., Ltd., Stavacsol I series manufactured by Rhein Chemie, and Fortezor HR, Chuo Kasei Co., Ltd.
On the other hand, specific examples of the polycarbodiimide compound include EN-180 manufactured by Matsumoto Yushi Co., Ltd., Stabuzol P manufactured by Rhein Chemie, and Carbodilite LA-1 manufactured by Nisshinbo Industries, Ltd.

  The content of the carbodiimide compound is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin (A) and the polymethyl methacrylate resin (B), and more preferably 0.2 to It is preferably 3 parts by mass. When the amount is less than 0.1 parts by mass, the effect of imparting wet heat durability as described above is poor. On the other hand, if the content of the monocarbodiimide compound exceeds 5 parts by mass, the transparency of the resulting resin composition may be impaired.

Moreover, it is preferable that the resin composition of this invention contains magnesium stearate. By containing magnesium stearate, the resin composition can improve the screw biting property of the pellets during molding, improve the workability, and improve the heat resistance while maintaining the transparency. A commercially available thing can be used as magnesium stearate.
The content of magnesium stearate is preferably 0.005 to 0.02 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin (A) and the polymethyl methacrylate resin (B). When the content of magnesium stearate exceeds 0.02 parts by mass, transparency may be impaired.

  In addition, although the resin composition of this invention contains the said component, from the point of transparency maintenance, components other than the said component, ie, polylactic acid resin (A), polymethyl methacrylate-type resin (B ), An acrylic polymer (C), magnesium stearate, and a monocarbodiimide compound.

  The resin composition of the present invention contains the polylactic acid resin (A), polymethyl methacrylate resin (B), and acrylic polymer (C). For example, by mixing them Can be manufactured. Although the method to mix is not specifically limited, The method of melt-kneading using a uniaxial or biaxial extruder can be mentioned. In order to improve the kneading state, it is preferable to use a twin screw extruder. The kneading temperature is preferably in the range of [melting point of polylactic acid resin (A) + 5 ° C.] to [melting point of polylactic acid resin (A) + 100 ° C.], and the kneading time is preferably in the range of 20 seconds to 30 minutes. When the temperature is lower than this range or for a short time, kneading or reaction may be insufficient. Conversely, when the temperature is high or for a long time, the resin may be decomposed or colored.

  In addition, when magnesium stearate is included in the resin composition, it is preferable to adhere on the surface of the pellet prepared by melt kneading as described above, from the viewpoint of the effect on the bite of the pellet into the screw. . This is a so-called external addition method.

  The resin composition of the present invention can be formed into various molded products by molding methods such as injection molding, blow molding, extrusion molding, inflation molding, and vacuum molding, pressure molding, and vacuum / pressure molding after sheet processing. In particular, it is preferable to adopt an injection molding method, and in addition to a general injection molding method, gas injection molding, injection press molding, and the like can be employed. As an example of injection molding conditions suitable for the resin composition of the present invention, the cylinder temperature is not less than the melting point or flow start temperature of the resin composition, preferably 190 to 270 ° C., and the mold temperature is that of the resin composition. (Melting point-20 ° C.) or less is appropriate. If the molding temperature is too low, the operability becomes unstable, such as short-circuiting in the molded body, and it tends to be overloaded. Conversely, if the molding temperature is too high, the resin composition will decompose and the resulting molded body Problems such as reduction in strength and coloration are likely to occur, and both may be undesirable.

  The molded article of the present invention is obtained by molding the polylactic acid resin composition of the present invention, and can be obtained by the molding method as described above. Specific examples of the molded article of the present invention include various transparent molded articles, including many articles such as daily necessities, various miscellaneous goods, peripheral devices for electronic devices, and interior and exterior parts of automobiles. Among them, the resin composition and molded product of the present invention are useful in parts and applications that require sufficient impact resistance, heat resistance and transparency.

  Hereinafter, the present invention will be described more specifically with reference to examples. The characteristic values and evaluation methods of the resin compositions of Examples and Comparative Examples are as follows.

(1) D-form content of polylactic acid resin 0.3 g of polylactic acid resin was weighed and added to 6 mL of 1N potassium hydroxide / methanol solution and sufficiently stirred at 65 ° C. Subsequently, 450 μL of sulfuric acid was added and stirred at 65 ° C. to decompose polylactic acid, and 5 mL was measured as a sample.
To this sample, 3 mL of pure water and 13 mL of methylene chloride were mixed and shaken. After stationary separation, about 1.5 mL of the lower organic layer was collected, filtered through a HPLC disk filter having a pore size of 0.45 μm, and then subjected to gas chromatography measurement using HP-6890 Series GC system manufactured by Hewlett Packard. The ratio (%) of the peak area of D-lactic acid methyl ester to the total peak area of lactic acid methyl ester was calculated, and this was defined as the D-form content (mol%) of the polylactic acid resin (A).

(2) Melt flow rate (MFR) of polylactic acid resin
According to JIS K-7210, it measured in the load of 190 degreeC and 21.2N.

(3) Melt flow rate (MFR) of polymethyl methacrylate resin
According to JIS K-7210, it measured at 230 degreeC and the load of 38N.
(4) Weight average molecular weight measurement of polylactic acid resin, polymethyl methacrylate resin, and acrylic polymer Tetrahydrofuran or chloroform using a gel permeation chromatography (GPC) apparatus (manufactured by Shimadzu Corporation) equipped with a differential refractive index detector Was obtained in terms of standard polystyrene in 40 ° C.

(5) Melt flow rate (MFR) of resin composition
According to JIS K-7210, it measured at 230 degreeC and the load of 38N. The melt flow rate of the resin composition is preferably between 3 and 15 g / 10 minutes, more preferably between 5 and 10 g / 10 minutes.
(6) Transparency (haze)
Using the obtained 2 mm thick plate, the haze was measured according to JIS K-7105 to evaluate the transparency. The haze is preferably 6.0 or less, and more preferably 5.8 or less.

(7) Impact resistance (Charpy impact strength)
The obtained test piece for general physical property measurement (ISO type) having a V-shaped cut was used as a test sample. And according to ISO 179-1, Charpy impact strength was measured using the obtained test piece. Preferably Charpy impact strength is 3 kJ / ^{m 2} or more, more preferably 4 kJ / ^{m 2} or more, and most preferably 6 kJ / ^{m 2} or more.

(8) Impact resistance (weight drop resistance)
Using the obtained 2 mm thick plate, impact resistance (weight drop resistance) was measured according to “6. DuPont type” of JIS K5600-5-3. The impact resistance was evaluated based on the value of 50% fracture energy obtained by the measurement. The fracture energy is preferably 0.60 J or more.

(9) Heat resistance Using the obtained test piece for general physical property measurement (ISO type), the deflection temperature under load was measured at a load of 0.45 MPa according to ISO75, and the heat resistance was evaluated. The deflection temperature under a load of 0.45 MPa is more preferably 69 ° C. or higher.

(10) Wet heat durability The obtained test specimen for general physical property measurement (ISO type) was subjected to wet heat treatment by exposure to a high temperature and high humidity environment of 60 ° C. and 95% RH for 500 hours. The bending strength of each of the test piece subjected to the wet heat treatment and the test piece not subjected to the wet heat treatment was measured according to ISO178. And based on the following formula | equation, the bending fracture strength retention was computed. The bending strength retention is preferably 60% or more, particularly preferably 90% or more.
Bending strength retention (%) = [(Bending strength after wet heat treatment) / (Bending strength before wet heat treatment)] × 100

The raw materials used are shown below.
[Polylactic acid resin]
A-1: “U'Z S-12” manufactured by Toyota Motor Corporation (D-form content = 0.1 mol%, MFR = 8 g / 10 min, weight average molecular weight 120,000, lactide content 1000 ppm)
A-2: “PLA-3001D” manufactured by NatureWorks (D-form content = 1.4 mol%, MFR = 10 g / 10 min, weight average molecular weight 130,000, lactide content 2000 ppm)
A-3: “PLA6302D” manufactured by NatureWorks (D-form content = 10 mol%, MFR = 11 g / 10 min, weight average molecular weight 130,000, lactide content 2000 ppm)

[Polymethyl methacrylate resin]
B-1: “Acrypet VH” manufactured by Mitsubishi Rayon Co., Ltd. (deflection temperature under load (1.8 MPa) = 100 ° C., methyl methacrylate content = 95 mass% or more, MFR = 2 g / 10 min, weight average molecular weight 100,000 )
B-2: “Acrypet MD” manufactured by Mitsubishi Rayon Co., Ltd. (deflection temperature (1.8 MPa) = 87 ° C., methyl methacrylate content = less than 95% by mass, MFR = 6 g / 10 min, weight average molecular weight 80,000 5,000)

[Acrylic polymer]
C-1: “Metabrene P550A” (weight average molecular weight 950,000) manufactured by Mitsubishi Rayon Co., Ltd.
-C-2: "Metablene P551A" manufactured by Mitsubishi Rayon Co., Ltd. (weight average molecular weight 1,450,000)
C-3: “Paralloid K-400P” manufactured by Rohm and Haas (weight average molecular weight 2.3 million)
C-4: “Metabrene P530A” manufactured by Mitsubishi Rayon Co., Ltd. (weight average molecular weight 3.1 million)
-C-5: “Metabrene P531A” manufactured by Mitsubishi Rayon Co., Ltd. (weight average molecular weight 4.5 million)
C-6: “Kaneace PA-60” manufactured by Kaneka Corporation (weight average molecular weight: 8 million)
-C-7: “Metabrene P700” manufactured by Mitsubishi Rayon Co., Ltd. (weight average molecular weight 500,000)

〔Magnesium stearate〕
・ D-1: “SMO” manufactured by Dainichi Chemical Co., Ltd.
[Monocarbodiimide compound]
E-1: N, N′-bis (2,6-diisopropylphenyl) carbodiimide “Stavaxol I” manufactured by Rhein Chemie

Example 1
Using a twin screw extruder (TEM37BS type manufactured by Toshiba Machine Co., Ltd.), 30 parts by mass of polylactic acid resin (A-1), 70 parts by mass of polymethyl methacrylate resin (B-1), and acrylic polymer (C -1) 5 parts by mass were dry-blended and supplied from the root supply port of the extruder, and extrusion was carried out while venting under the conditions of a kneading temperature of 230 ° C., a screw rotation speed of 150 rpm, and a discharge of 20 kg / h. The resin discharged from the tip of the extruder was cut into pellets to obtain pellets of the resin composition. The pellets of the obtained resin composition were dried with hot air at 85 ° C. for 10 hours, and used for measuring general physical properties at a cylinder temperature of 220 ° C. and a mold surface temperature of 40 ° C. using an IS-80G injection molding machine manufactured by Toshiba Machine. A test piece (ISO type) and a 2 mm thick plate (length 90 mm, width 50 mm) were prepared and subjected to various measurements.

Examples 2 to 17 and Comparative Examples 1 to 11
As shown in Table 1, pellets of the resin composition were obtained in the same manner as in Example 1 except that the content and type of each component were changed. Then, this was injection molded in the same manner as in Example 1 to prepare a test piece for measuring general physical properties (ISO type) and a 2 mm thick plate (length 90 mm, width 50 mm) and subjected to various measurements. In Example 17, after obtaining pellets of the resin composition, magnesium stearate (D-1) was added to a total of 100 parts by mass of the polylactic acid resin (A) and the polymethyl methacrylate resin (B). On the other hand, it was dried in hot air after blending an amount of 0.010 parts by mass. This was injection-molded in the same manner as in Example 1 to prepare a test piece for general physical property measurement (ISO type) and a 2 mm thick plate (length 90 mm, width 50 mm), which were subjected to various measurements.

  Table 1 shows the evaluation results of the resin compositions and molded bodies obtained in Examples 1 to 17 and Comparative Examples 1 to 11.

As is clear from Table 1, the polylactic acid resin compositions of Examples 1 to 17 have excellent impact resistance while having sufficient transparency and heat resistance (Charpy impact strength and weight resistance). A molded article having excellent dropability) was obtained.
On the other hand, since the polylactic acid resin compositions of Comparative Examples 1 to 4 did not contain an acrylic polymer (C) having a weight average molecular weight of 700,000 to 5,000,000, the polylactic acid of Comparative Example 5 Since the content of the acrylic polymer (C) having a weight average molecular weight of 700,000 to 5,000,000 was too small, the obtained molded products had impact resistance (Charpy impact strength and weight resistance). The dropability was inferior. Since the polylactic acid-based resin composition of Comparative Example 6 was an acrylic polymer having a weight average molecular weight exceeding 5 million, transparency was lowered due to the loss of compatibility, and the resin composition The MFR was too low and the molding processability was poor. Since the polylactic acid resin composition of Comparative Example 7 was an acrylic polymer having a weight average molecular weight of less than 700,000, the resulting molded article was inferior in both Charpy impact strength and weight drop resistance. It became. The polylactic acid-based resin composition of Comparative Example 8 was obtained because the polylactic acid resin (A) had a too high ratio, so that the performance inherent in the polymethyl methacrylate resin (B) could not be sufficiently exhibited. The molded product was inferior in transparency and heat resistance. Since the polylactic acid resin composition of Comparative Example 9 contained too much acrylic polymer (C), it became inferior in fluidity and deteriorated in molding processability. And the obtained molded object became inferior to transparency. Since the polylactic acid resin composition of Comparative Examples 10 and 11 used a polymethyl methacrylate resin having a deflection temperature under load of 1.8 MPa of less than 95 ° C., the obtained molded article was inferior in heat resistance. became.

Claims (2)

A polylactic acid resin (A), a polymethyl methacrylate resin (B) having a deflection temperature under load of 1.8 MPa of 95 ° C. or higher, and an acrylic polymer (C) having a weight average molecular weight of 700,000 to 5,000,000. A resin composition comprising: a polylactic acid resin (A) and a polymethyl methacrylate resin (B) having a mass ratio [(A) / (B)] of 20/80 to 70/30, an acrylic resin The content of the polymer (C) is 1 to 10 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin (A) and the polymethyl methacrylate resin (B). Composition. The molded object obtained by shape | molding the polylactic acid-type resin composition of Claim 1.