JP2011006638A - Thermoplastic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel polylactic acid-based thermoplastic resin composition improving hydrolysis resistance and having well-balanced hydrolysis resistance and stiffness such as tensile strength and tensile elastic modulus.SOLUTION: The composition includes: (A) 50-98 mass% of a polylactic acid resin, (B) 1-20 mass% of a complex comprising glycidyl methacrylate and a silicone-acryl composite rubber, and (C) 1-30 mass% of talc.

Description

  The present invention relates to a thermoplastic resin composition.

  With the recent increase in interest in global environmental problems, it is desired to realize a plastic that does not depend excessively on petroleum resources and has biodegradability. One of such plastic candidates is polylactic acid resin.

  However, the polylactic acid resin is easily hydrolyzed and needs to have hydrolysis resistance to such a degree that it can be put into practical use. Moreover, it is generally a hard and brittle material, and practical improvements have been required in terms of rigidity such as tensile strength and tensile elastic modulus.

  Therefore, various measures for solving such problems have been studied.

  For example, in order to increase water resistance and maintain mechanical strength, a graft copolymer of an ethylene-glycidyl methacrylate copolymer and an acrylonitrile-styrene copolymer and a thermoplastic resin are used as a fat represented by polylactic acid. A method of adding a carbodiimide after chemically bonding to a group polyester resin and adding a carbodiimide (Patent Document 1) or a rubber component containing an epoxy group and a fibrillated fluorine to improve the impact resistance of a polylactic acid resin A method of adding a resin (Patent Document 2) has been proposed.

  However, even in such conventional improvement measures, hydrolysis resistance is not always practically sufficient, and polylactic acid is excellent in balance between hydrolysis resistance and rigidity such as tensile strength and tensile elastic modulus. A thermoplastic resin composition has not been realized.

JP 2007-145937 A JP 2008-291107 A

  The present invention solves the problems of the prior art from the background as described above, and is expected to be practically 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. An object of the present invention is to provide a new polylactic acid-based thermoplastic resin composition which is improved in hydrolyzability and has an excellent balance between hydrolysis resistance and rigidity such as tensile strength and tensile elastic modulus.

  The thermoplastic resin composition of the present invention is characterized by the following.

First, the following formulation:
(A) Polylactic acid resin: 50 to 98% by mass
(B) Composite of glycidyl methacrylate and silicone acrylic composite rubber: 1 to 20% by mass
(C) Talc: 1-30% by mass
Have

  Secondly, the first thermoplastic resin composition contains a carbodiimide compound.

  Third, the first or second thermoplastic resin composition contains a polycarbonate resin.

  According to the first invention, the hydrolysis resistance of the polylactic acid resin composition can be improved, and the balance between the hydrolysis resistance and rigidity such as tensile strength and tensile elastic modulus is excellent. can do. As a result, it can be widely used in home appliance fields, building materials, sanitary fields, etc. that are expected to be used for a long time.

  According to the second invention, by further containing a carbodiimide that reacts with a terminal group of polylactic acid, in addition to the effects of the first invention, the durability in a high-temperature and high-humidity environment can also be improved. become.

  According to the third invention, by further containing the polycarbonate resin, in addition to the effects of the first or second invention, the hydrolysis resistance of the entire molded product can be further improved.

  The (A) polylactic acid resin contained in the thermoplastic resin composition of the present invention means polylactic acid and a copolymer of lactic acid and hydroxycarboxylic acid. Starch obtained from plants such as corn is fermented into lactic acid and polymerized by chemical synthesis.

  Examples of lactic acid include L- and / or D-lactic acid, lactone which is a dimer of lactic acid, and the like. Furthermore, examples of the hydroxycarboxylic acid copolymerizable with lactic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, and hydroxycaproic acid, and one or more can be used.

  In the present invention, commercially available poly L-lactic acid is preferred.

  The molecular weight of polylactic acid is not particularly limited, but it is considered that the weight average molecular weight is 10,000 or more, more preferably 30,000 or more from the viewpoint of physical and thermal properties.

  In addition, as polylactic acid, about the above polylactic acid resin, the mixture ratio shall be in the range of 50-98 mass%. When the amount is less than 50% by mass, it is difficult to realize the rigidity such as tensile strength and tensile modulus as a polylactic acid resin, and when it exceeds 98% by mass, it is difficult to realize high hydrolysis resistance. Become.

  In the present invention, the composite of (B) glycidyl methacrylate and silicone acrylic composite rubber is a mixture of glycidyl methacrylate and silicone acrylic composite rubber, and all or a part of the composite is glycidyl methacrylate and silicone acrylic composite rubber. And may be present as a copolymerized copolymer. This polymer may have a multilayer structure.

  The silicone acrylic composite rubber is a polymer of an acrylic component composed of an alkyl acrylate unit and a silicone component composed of a silyl group-terminated polyether.

  Specifically, as the alkyl acrylate unit, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, stearyl methacrylate, octadecyl methacrylate, phenyl methacrylate, benzyl methacrylate, chloromethyl methacrylate, 2-chloroethyl methacrylate, 2-methacrylic acid 2- Hydroxyethyl, 3-hydroxypropyl methacrylate, 2,3,4,5,6-pentahydroxyhexyl methacrylate, 2,3,4,5-tetrahydroxypentyl methacrylate, aminoethyl acrylate, acrylic acid Propylaminoethyl Dimethylaminoethyl methacrylate, ethyl methacrylate aminopropyl, and the like phenyl methacrylate aminoethyl or cyclohexyl aminoethyl methacrylate. One to two or more of these units can be used.

  Specific examples of the silyl group of the silyl group-terminated polyether include alkylsilyl such as methyl, ethyl, propyl and butyl, alkylsilyl halide such as 3-chloropropyl and 3,3,3-trifluoropropyl, and vinyl. Alkenylsilyl such as allyl and butenyl, arylsilyl such as phenyl, tolyl and naphthyl, cycloalkylsilyl such as cyclopentyl and cyclohexyl, and aryl-alkylsilyl such as benzyl and phenethyl. Moreover, polyethylene, polypropylene, etc. are used for polyether. These can use 1 type, or 2 or more types.

  The multilayer structure polymer is composed of an innermost layer (core layer) and one or more layers (shell layer) covering the innermost layer (core layer), and a so-called core-shell type in which adjacent layers are composed of different polymers. It is a polymer having a structure called.

  (B) A commercially available product can also be used for the composite of glycidyl methacrylate and silicone acrylic composite rubber. As a specific example, Mitsubishi Rayon Co., Ltd. Metabrene S2200 can be mentioned.

  (B) The compounding ratio of the composite of glycidyl methacrylate and silicone acrylic composite rubber is in the range of 1 to 20% by mass. When the amount is less than 1% by mass, the hydrolysis resistance cannot be improved, and when it exceeds 20% by mass, it becomes difficult to form a resin composition by gelation during kneading. Occurs.

  Furthermore, in the present invention, (C) talc is blended. This talc is well known as a commercially available filler material. About the magnitude | size, it is normally preferable to set it as the thing within the range of a particle size of 0.5 micrometer-12 micrometers.

  The blending ratio of talc is in the range of 1 to 30% by mass. When the amount of talc is less than 1% by mass, the tensile elastic modulus cannot be improved, and when it exceeds 30% by mass, part of the talc does not bite into the screw during kneading, making it difficult to pelletize the resin composition. For example, the workability decreases.

  And in the thermoplastic resin composition of this invention, it is effective to contain carbodiimide compounds, such as a polycarbodiimide compound and a monocarbodiimide compound, in addition to the said component. This exhibits a function of blocking by reacting with part or all of the carboxyl group terminals of the polylactic acid resin in the thermoplastic resin composition of the present invention, and has practically sufficient hydrolysis resistance. A molded product can be obtained, and the durability under a high temperature and high humidity environment can be improved.

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

  A commercially available carbodiimide compound can also be used. Specific examples thereof include Carbodilite LA-1 (poly (4,4′-dicyclohexylmethanecarbodiimide)) manufactured by Nisshinbo Industries, Ltd.

  For example, the blending ratio of the carbodiimide compound is preferably in the range of 0.1 to 5% by mass in the total amount of the thermoplastic resin composition of the present invention. If the amount is less than 0.1% by mass, the improvement in the durability cannot be expected so much. If the amount exceeds 5% by mass, gelling occurs during kneading and it becomes difficult to pelletize the resin composition. This is not preferable.

  Furthermore, it is effective to contain a polycarbonate resin in the thermoplastic resin composition of the present invention. As a result, the hydrolysis resistance of the entire molded product can be further improved.

  A commercially available polycarbonate resin can be used, and the blending ratio thereof is preferably in the range of 1 to 20% by mass in the total amount of the thermoplastic resin composition of the present invention, for example. If it is less than 1% by mass, improvement in hydrolysis resistance cannot be expected so much. If it exceeds 20% by mass, the ratio of polylactic acid resin is lowered, and the use ratio of non-petroleum resin, which is characteristic of polylactic acid resin, is not preferable. .

  Furthermore, the thermoplastic resin composition of the present invention may contain a crystal nucleating agent. Usually, polylactic acid resin molding materials improve heat resistance, elastic modulus, etc. by crystallization in the mold, but the crystallization speed is slow and the holding time in the mold is considerably lengthened to promote crystallization. There is a need. The crystal nucleating agent can increase the crystallization rate and shorten the holding time in the mold. Examples of such a crystal nucleating agent include zinc phenylphosphonate having an average particle diameter of 3 μm or less. A commercially available product can be used for this product, and specific examples thereof include Eco Promote manufactured by Nissan Chemical Industries, Ltd.

  Furthermore, in the thermoplastic resin composition of the present invention, a stabilizer, a pigment, a dye, a reinforcing agent (mica) can be used at the time of resin mixing or molding depending on the purpose, as long as the object and effect of the present invention are not impaired. , Clay, glass fiber, etc.), colorants, ultraviolet absorbers, antioxidants, lubricants, mold release agents, plasticizers, antistatic agents, inorganic and organic antibacterial agents, and the like can be blended. .

  The thermoplastic resin composition of the present invention as described above can be produced by mixing and kneading each component. In the case of producing as pellets, there is no particular limitation, and for example, a twin screw extruder, a Banbury mixer, a heating roll or the like can be used. Among them, melt kneading by a twin screw extruder is preferable, and if necessary, side Resins and other additives can be blended by feeding or the like.

  The polylactic acid-based thermoplastic resin composition of the present invention can be molded into various molded articles by a usual molding method such as injection molding, blow molding, sheet molding, vacuum molding and the like.

  Therefore, an example will be shown below and will be described in more detail. Of course, the present invention is not limited to the following examples.

<Manufacture of resin composition>
Each component was blended at the blending ratio (unit: mass%) shown in Table 1.

The resin component was previously dried and then the blend was mixed for 10 minutes with a tumbler and passed through a twin screw extruder. The temperature of the twin screw extruder was set to 190 ° C. near the die and 200 ° C. near the inlet. The strand coming out of the twin screw extruder was immediately cooled in a cooling bath, and then cut into 2 to 4 mm pellets with a cutter.
<Molding>
Prior to molding, the pellets were dried. Drying was performed with a dehumidifying dryer at 120 ° C. for 4 hours, and molding was performed with a 100-ton injection molding machine.

The cylinder temperature was set to 200 ° C. near the head and 190 ° C. near the material inlet. The mold temperature was 110 ° C. and the holding time in the mold was 100 s. In Example 13, the in-mold holding time was 300 s.
<Evaluation>
1) The obtained molded product samples were evaluated for tensile strength, tensile elastic modulus, and durability. The method at that time was as follows.
(Evaluation methods)
Tensile strength Tensile strength was measured according to ISO 527.

Tensile elastic modulus The tensile elastic modulus was measured according to ISO 527.

Durability A wet heat test was performed at 60 ° C. and 95 RH, and the time when the tensile strength retention was 80% or less was measured.

2) As is clear from the comparison between Examples 1 to 13 and Comparative Examples 1 to 4 shown in Table 1, according to the examples of the present invention,
Tensile strength: 50 MPa or more Tensile modulus: 2.8 GPa or more Durability: Excellent characteristics in a balance of 250 hours or more. In particular, Examples 5 to 7 using carbodiimide and Examples 8 to 10 using polycarbonate resin all have a durability of 500 hr or more, and it was confirmed that the durability was improved.

Claims (3)

The following formulation:
(A) Polylactic acid resin: 50 to 98% by mass
(B) Composite of glycidyl methacrylate and silicone acrylic composite rubber: 1 to 20% by mass
(C) Talc: 1-30% by mass
A thermoplastic resin composition characterized by comprising:   The thermoplastic resin composition according to claim 1, comprising a carbodiimide compound.   The thermoplastic resin composition according to claim 1, comprising a polycarbonate resin.