JP2009242520A - Polylactic acid resin composition and molded article obtained by molding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid resin composition which allows an increase in crystallization rate, hardly causes deformation even when molded in a short time and gives a molded article having high heat resistance, and the molded article molded from the same. <P>SOLUTION: The polylactic acid resin composition comprises a polylactic acid resin, a crystallization nucleating agent and a glycerin fatty acid ester or a polyglycerin fatty acid ester, wherein the crystallization nucleating agent is at least one kind selected from clay minerals, fatty acid amides and a compound group of organometallic complex. The molded article molded from the same is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a polylactic acid resin composition having an improved crystallization rate and a molded body formed by molding the same.

In recent years, with the growing awareness of the environment, the use of so-called plant-derived plastic materials using biomass as a raw material has attracted attention, one of which is polylactic acid. Unlike known general-purpose resins, polylactic acid can be produced from natural materials such as corn, so it does not cause fossil resource depletion and can suppress the amount of carbon dioxide gas that is one cause of global warming. And so on. In addition, these are materials that can be decomposed in the natural environment, so-called biodegradability, and can contribute to the solution of problems related to waste treatment. .

However, since polylactic acid is slowly crystallized, crystallization does not proceed sufficiently in a short time molding, which may cause deformation of the molded body or decrease in heat resistance. Therefore, as a method for improving the moldability and heat resistance of polylactic acid, Patent Document 1 proposes a method of adding amide compound or talc to polylactic acid to promote crystallization. Various methods for adding a thermoplastic polyester to promote crystallization have been proposed.

However, although the physical properties are improved by the method described in the above publication as compared with a molded product of polylactic acid alone, it is not sufficient to obtain physical properties equivalent to those of other general-purpose resins.
JP 2004-51666 A JP 2006-36818 A

The present invention is a polylactic acid-based polylactic acid that can shorten the molding time, is less likely to deform the molded body even at a low mold temperature, has excellent releasability from the mold, and has a high heat resistance. It aims at providing a resin composition and a molded object consisting thereof.

In order to achieve the above object, the present invention has the following configuration.
1. A polylactic acid resin composition, comprising a crystal nucleating agent and a glycerin fatty acid ester or a polyglycerin fatty acid ester.
2. 2. The polylactic acid resin composition according to 1 above, containing 0.1 to 10% by mass of a crystal nucleating agent and 0.1 to 10% by mass of glycerin fatty acid ester or polyglycerin fatty acid ester.
3. 3. The polylactic acid resin composition as described in 1 or 2 above, wherein the crystal nucleating agent is at least one selected from clay minerals, fatty acid amides, and organometallic complexes.
4). The molded object formed by shape | molding the polylactic acid resin composition in any one of said 1-3.

According to the present invention, the molding time can be shortened and the mold temperature can be lowered, so that productivity can be improved and energy can be saved.

Hereinafter, the present invention will be described in detail according to the best mode for carrying out the invention. The polylactic acid of the present invention is a polymer obtained by polymerizing lactic acid. The mass average molecular weight of the polylactic acid is not particularly limited, but is desirably 10,000 or more and 400,000 or less. When the mass average molecular weight of polylactic acid is less than the lower limit, mechanical properties such as strength and elastic modulus tend to be insufficient, and when the upper limit is exceeded, fluidity during molding tends to decrease.

The polymerization method of polylactic acid is not particularly limited, and may be direct polymerization of D-lactic acid and L-lactic acid, and ring-opening polymerization of D-lactide, L-lactide, and meso-lactide, which are cyclic dimers of lactic acid. It may be. When polylactic acid is a copolymer of the D-form material and the L-form material, the content of one of the D-form material and the L-form material is 90 mol% or more, more preferably 95 mol%. It is more preferable that the content is 98 mol% or more. When one of the D-form and the L-form is less than 90 mol%, crystallization is inhibited due to a decrease in stereoregularity, and the effects of the present invention tend not to be sufficiently exhibited. The polylactic acid thus obtained exhibits optical isomerism, and the polylactic acid may be any of D-form, L-form and DL-form. Also, a blend of polylactic acid whose main constituent is D-form and polylactic acid whose main constituent is L-form may be used.

The polylactic acid resin composition used in the present invention is obtained by adding a crystal nucleating agent and a dispersant to polylactic acid.

Examples of the crystal nucleating agent used in the present invention include clay minerals, fatty acid amides, and organometallic complexes. Examples of the clay mineral include talc, mica, montmorillonite, beidellite, saponite, hectorite, and kaolinite. Among them, talc is a chemically stable mineral and can be preferably used as a crystal nucleating agent.

As fatty acid amides, lauric acid amide, palmitic acid amide, oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, ricinoleic acid amide, hydroxystearic acid amide, methylene bis stearic acid amide, ethylene bis lauric acid amide, ethylene Bisoleic acid amide, ethylene bisstearic acid amide, ethylene biserucic acid amide, ethylene bisbehenic acid amide, methylene bishydroxystearic acid amide, hexamethylene bishydroxystearic acid amide, ethylene bishydroxystearic acid amide, butylene bisstearic acid amide Examples include acid amide, hexamethylene bishydroxystearic acid amide, hexamethylene bisbehenic acid amide, and the like. Among these, it is particularly preferable to use ethylenebis-12-hydroxystearic acid amide.

Examples of the organometallic complex include various organic pigments such as copper phthalocyanine and zinc phenylphosphonate.

The polylactic acid resin composition of the present invention contains glycerin fatty acid ester or polyglycerin fatty acid ester as a dispersant for the crystal nucleating agent. The glycerin fatty acid ester or the polyglycerin fatty acid ester may be used alone or in combination of two or more.
Examples of the glycerol fatty acid ester used in the present invention include glycerol stearate, glycerol palmitate, glycerol behenate, glycerol-12-hydroxystearate, glycerol oleate, glycerol caprylate, glycerol caprate, glycerol laurate and the like. be able to.

  Examples of the polyglycerol fatty acid ester used in the present invention include diglycerol stearate, diglycerol palmitate, diglycerol behenate, diglycerol-12-hydroxystearate, diglycerin oleate, diglycerol caprylate, and diglycerol caprate. , Diglycerin laurate, triglycerin laurate, triglycerin oleate, triglycerine palmitate, triglyceryl stearate, tetraglyceryl stearate, decaglycerin stearate, decaglycerin laurate, decaglycerin oleate, tetraglycerin polyricinolate, Examples include hexaglycerin polyricinoleate.

The glycerin fatty acid ester or polyglycerin fatty acid ester used in the present invention can be produced by a conventionally known method. As an example, it can be obtained by esterifying glycerin or polyglycerin with a fatty acid. Commercial products can also be used.

In the present invention, the compounding amount of the crystal nucleating agent is preferably 0.1 to 10% by mass, and the compounding amount of the glycerin fatty acid ester or the polyglycerol fatty acid ester is desirably 0.1 to 10% by mass. More preferably, the compounding amount of the crystal nucleating agent is 0.5 to 5% by mass, and the compounding amount of the monoglycerol fatty acid ester or the polyglycerol fatty acid ester is 0.5 to 5% by mass. When it is below this range, the performance is insufficient, and when it is above this range, the melt viscosity is lowered, and molding becomes difficult or physical properties such as bleed out are reduced.

The resin composition of the present invention can be produced by a conventionally known method. As an example, a method of uniformly premixing a resin and an additive, melt-kneading, and pelletizing can be mentioned. As a premixing method, various powder blenders, Henschel mixers, and the like can be used. After premixing, the strand is extruded by a twin screw extruder equipped with a strand die, and the strand can be cut and pelletized to obtain a high concentration master batch. Furthermore, it can be set as the molded object of a desired additive density | concentration by mixing a high concentration masterbatch with a polylactic acid resin.

In addition, a method of supplying the resin and the additive to the twin screw extruder without premixing can be used. After the resin is supplied to the twin screw extruder and melted, the additive can be supplied to the twin screw extruder using a side feeder and a liquid addition device and kneaded. Moreover, it is also possible to use a combination of the above-described premixing method and a method using a side feeder and a liquid addition device.

Examples of the method for producing the molded body of the present invention include injection molding, extrusion molding, blow molding, inflation molding, profile extrusion molding, injection blow molding, vacuum pressure molding, and spinning. Particularly in injection molding, the conventional polylactic acid resin has low productivity due to slow crystallization, and the target molded product may not be obtained due to deformation or the like. By using a lactic acid resin composition, it is possible to efficiently produce a molded body.

Hereinafter, the present invention will be described in detail with reference to examples, but the embodiment of the present invention is not limited thereto.

[Evaluation methods]
Vicat softening point: Vicat softening point was measured using HDT TESTER (manufactured by Toyo Seiki Co., Ltd.).
Formability: ○ ・ ・ ・ Moldable with almost no deformation △ ・ ・ ・ Can be taken out from the mold, but some deformation is seen × ・ ・ ・ Not released due to protrusion from the mold, but greatly deformed when taken out

Examples 1-6 Comparative Examples 1-2
An experiment was conducted in which the mold temperature was constant and the cooling time was changed.
Table 1 shows the crystal nucleating agent and glycerin fatty acid ester or polyglycerin fatty acid ester in polylactic acid (Mitsui Chemicals "Lacia H-100" mass molecular weight 150,000, D-form content 1.2 to 1.6%). The mixture blended with the content was melt kneaded and extruded at 180 ° C. using a twin screw extruder equipped with a strand die, and the strand was cut to prepare a pellet-like polylactic acid resin composition.
For the prepared polylactic acid resin composition, a sheet having a thickness of 3 mm was prepared using an injection molding machine equipped with a test piece mold at a mold temperature of 105 ° C. and a cooling time of 60, 90, 120, and 150 seconds. Then, the moldability and Vicat softening point were measured. The measurement results are shown in Table 2.

結晶核剤１：タルク（商品名 ハイトロンA 竹原化学工業社製）
結晶核剤２：エチレンビスー１２ヒドロキシステアリン酸アミド（商品名 スリパックスH 日本化成社製）
（ポリ）グリセリン脂肪酸エステル１：グリセリンステアレート （商品名リケマールS-100A 理研ビタミン社製）
（ポリ）グリセリン脂肪酸エステル２：ジグリセリンステアレート （商品名リケマールＳ−７１−Ｄ 理研ビタミン社製）

Crystal nucleating agent 1: Talc (Brand name Hytron A Takehara Chemical Industry Co., Ltd.)
Crystal nucleating agent 2: Ethylene bis-12 hydroxystearic acid amide (trade name Sripacks H Nippon Kasei Co., Ltd.)
(Poly) glycerin fatty acid ester 1: glyceryl stearate (trade name Riquemar S-100A manufactured by Riken Vitamin Co., Ltd.)
(Poly) glycerin fatty acid ester 2: diglyceryl stearate (trade name Riquemar S-71-D manufactured by Riken Vitamin Co., Ltd.)

Examples 7-12 Comparative Examples 3-4
An experiment was conducted in which the mold temperature was changed at a constant cooling time.
Table 1 shows the crystal nucleating agent and glycerin fatty acid ester or polyglycerin fatty acid ester in polylactic acid (Mitsui Chemicals "Lacia H-100" mass molecular weight 150,000, D-form content 1.2 to 1.6%). The mixture blended with the content was melt kneaded and extruded at 180 ° C. using a twin screw extruder equipped with a strand die, and the strand was cut to prepare a pellet-like polylactic acid resin composition.
For the prepared polylactic acid resin composition, a sheet having a thickness of 3 mm was prepared under conditions of a mold temperature of 90, 95, 100, and 105 ° C. with a cooling time of 90 seconds using an injection molding machine equipped with a test piece mold. The moldability and Vicat softening point were measured. The measurement results are shown in Table 3.

As shown in Table 2, when the mold temperature is constant, Comparative Examples 1 and 2 show an improvement in heat resistance in the vicinity of 120 seconds, whereas Examples 1 to 6 have a heat resistance in the vicinity of 90 seconds. An improvement is seen. Moreover, as shown in Table 3, when the cooling time is fixed, the heat resistance is not improved in Comparative Examples 3 and 4, whereas the heat resistance is improved by a mold of about 90 ° C. in Examples 7 to 12. Is seen. Therefore, according to the production method of the present invention, crystallization proceeds rapidly even in a short molding cycle or molding at a low mold temperature, and the molded body is hardly deformed and a molded body having excellent heat resistance is obtained. be able to.

Claims (4)

A polylactic acid resin composition, comprising a crystal nucleating agent and a glycerin fatty acid ester or a polyglycerin fatty acid ester. 2. The polylactic acid resin composition according to claim 1, comprising 0.1 to 10% by mass of a crystal nucleating agent and 0.1 to 10% by mass of glycerin fatty acid ester or polyglycerin fatty acid ester. The polylactic acid resin composition according to claim 1 or 2, wherein the crystal nucleating agent is at least one selected from clay minerals, fatty acid amides, and organometallic complexes. The molded object formed by shape | molding the polylactic acid resin composition of any one of Claims 1-3.