JP2005096120A - Method for accelerating crystallization of injection-molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for accelerating the crystallization of an injection-molded product based on a lactic acid resin, capable of still more accelerating the crystallization of the injection-molded product as compared with a method for adding an inorganic crystallization accelerator. <P>SOLUTION: The inorganic crystallization accelerator and an organic crystallization accelerator, of which the amount is 0.1-20 mass% of the inorganic crystallization accelerator, are compounded with a resin composition based on the lactic acid resin and the obtained compound is injection-molded to be crystallized at 60-130°C in a mold. By this constitution, the crystallization of the injection-molded product can be still more accelerated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for accelerating crystallization of an injection molded body made of a lactic acid resin.

  Plastics are now pervasive in every field of life and industry, with annual production of around 100 million tons worldwide. However, most of them are discarded after use, and this is recognized as one of the causes that disturb the global environment. For this reason, effective use of exhaustible resources has been emphasized in recent years, and the use of renewable resources has become an important issue.

  Currently, one of the means attracting attention as a solution is the use of plant raw material (biodegradable) plastic. Plant-based plastics not only use non-depleted resources, but can save exhaustible resources during plastic production, and also have excellent recyclability. In particular, lactic acid resins are made from lactic acid obtained by fermentation of starch, can be mass-produced by chemical engineering, and have excellent transparency, rigidity, heat resistance, etc., so they can replace polystyrene and polyethylene terephthalate. Its use is attracting attention as a material in the field of film packaging and injection molding.

  However, lactic acid resins are poor in heat resistance, and as such are difficult to use in applications that require heat resistance. As means for improving this, there is known a method for improving heat resistance by crystallizing a molded product containing a lactic acid resin as a main component. However, since the lactic acid resin has a very low crystallization rate, the crystallization treatment has a problem that it is difficult to introduce it into an actual production process.

Conventionally, as a technique for improving the crystallization speed of a lactic acid-based resin, Patent Document 1 (Japanese Patent Laid-Open No. 9-278991) includes blending an aliphatic carboxylic acid amide, a salt, an ester, and an aliphatic alcohol with a lactic acid-based resin. A technique for improving the crystallization rate is disclosed.
Further, in Patent Document 2 (Japanese Patent Laid-Open No. 11-5849), an organic compound having a melting point or softening point of 80 to 300 ° C. and a melting entropy of 10 to 100 cal / K / mol is blended. A technique for improving the conversion speed is disclosed.
Patent Document 3 (Japanese Patent Laid-Open No. 11-116784) discloses a technique for improving the crystallization speed and heat resistance by blending a clarifying agent, and Patent Document 4 (Japanese Patent Laid-Open No. 11-116784) describes an impact resistance improver. A technique for improving impact resistance and heat resistance by blending is disclosed.
Furthermore, Patent Document 5 (Japanese Patent Laid-Open No. 8-3432) discloses a technique for improving the crystallization speed by blending talc and boron nitride.
JP-A-9-278991 JP-A-11-5849 Japanese Patent Laid-Open No. 11-116783 JP-A-11-116784 JP-A-8-3432

  The present invention relates to a method for accelerating crystallization of an injection-molded body containing a lactic acid resin as a main component, and is intended to provide a method that can promote crystallization more than the conventionally disclosed methods.

  As a result of intensive studies in view of such problems, the present inventors have completed the highly effective present invention and propose the following invention.

  That is, the present invention is a method for further promoting crystallization of an injection-molded product obtained by blending an inorganic crystallization accelerator with a resin composition containing a lactic acid resin as a main component. Further, 0.1 to 20% by mass of an organic crystallization accelerator is further blended, and after injection molding, it is crystallized as it is in a mold at 60 to 130 ° C. Suggest a method.

Further, the present invention is an injection-molded product comprising an inorganic crystallization accelerator blended with a resin composition containing a lactic acid resin as a main component,
Further blending 0.1 to 20% by weight of organic crystallization accelerator with respect to the inorganic crystallization accelerator,
Relative crystallinity of the lactic acid resin portion determined from the following formula based on the heat of crystallization (ΔHc) and the heat of crystal fusion (ΔHm) when the temperature is raised from 30 ° C. to 200 ° C. at a rate of 10 ° C./min ( We propose an injection molded body in which χc) is increased to 90% or more.
χc (%) = (ΔHm−ΔHc) / ΔHm × 100

  When the present inventors blended an inorganic crystallization accelerator with a resin composition containing a lactic acid resin as a main component to promote crystallization, the blending amount of the inorganic crystallization accelerator exceeds a certain level. There is a limit to the degree of crystallinity that can be promoted even if it is increased, and the combination of an inorganic crystallization accelerator and an organic crystallization accelerator can promote crystallization beyond the above-mentioned limit. It has been found that it is effective to carry out the crystallization treatment in the mold instead of taking out the molded body from the mold and carrying out the crystallization treatment. Therefore, according to the crystallization promotion method of the present invention, crystallization can be promoted more than the conventionally disclosed method, and the time required for crystallization can be shortened. Moreover, if it is the injection molded object of this invention, compared with the injection molded object which has the lactic acid resin as a main component, the injection molded object whose relative crystallinity degree is still higher can be obtained.

In the present invention, the “resin composition containing a lactic acid resin as a main component” means a resin composition containing a lactic acid resin in an amount of 50 to 100% by mass, particularly 70 to 100% by mass. It is.
In the present invention, the “inorganic crystallization accelerator” is a substance that has an action of accelerating crystallization of an injection-molded product and shortening the crystallization time. A substance occupying 50% by mass or more.
The “organic crystallization accelerator” is a substance that has an action of promoting crystallization of the injection-molded product and shortening the crystallization time. A substance occupying more than mass%.
It should be noted that the upper limit and lower limit of the numerical range specified by the present invention are not limited as long as they have the same operational effects as those within the numerical range even if they are slightly outside the numerical range specified by the present invention. It is intended to include within the scope of the invention.

  Embodiments of the present invention will be described below, but the scope of the present invention is not limited to the embodiments described below.

  An injection molded product according to the present invention includes a resin composition containing a lactic acid resin as a main component, an inorganic crystallization accelerator, a certain amount of an organic crystallization accelerator with respect to the inorganic inorganic crystal accelerator, and Other additives can be blended, which can be obtained through injection molding and crystallization treatment. Other steps may be added.

(Resin composition)
The resin composition that is a constituent component of the injection-molded article of the present invention contains a lactic acid resin as a main component, but if necessary, other resin components having biodegradability are blended (polymer blend). It may be made.

[Lactic acid resin]
The lactic acid-based resin used in the present invention includes poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, or structural units whose L-lactic acid and D are structural units. -Poly (DL-lactic acid) which is lactic acid, or a mixture of two or more of these can be used. At this time, the DL composition ratio of the lactic acid-based resin is preferably L-form: D-form = 100: 0 to 90:10, or L-form: D-form = 0: 100 to 10:90. Preferably, L-form: D-form = 99.5: 0.5 to 94: 6, or L-form: D-form = 0.5: 99.5 to 6:94. Within such a range, the heat resistance of the component can be easily obtained and can be used for a wide range of applications.

  In addition, the lactic acid resin used in the present invention may be a copolymer of any of the above lactic acids and an α-hydroxycarboxylic acid, an aliphatic diol, or an aliphatic dicarboxylic acid. At this time, as the “α-hydroxycarboxylic acid” copolymerized with the lactic acid resin, optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), Glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyn-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, etc. Examples of the “aliphatic diol” copolymerized with a lactic acid resin include ethylene glycol, 1,4-butanediol, 1 and lactones such as bifunctional aliphatic hydroxy-carboxylic acid, caprolactone, butyrolactone, and valerolactone. , 4-cyclohexanedimethanol and the like, and examples of the “aliphatic dicarboxylic acid” include succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid. That.

  As a polymerization method for the lactic acid-based resin, a condensation polymerization method, a ring-opening polymerization method, and other known polymerization methods can be employed. For example, in the condensation polymerization method, L-lactic acid or D-lactic acid, or a mixture thereof can be directly dehydrated and condensation polymerized to obtain a lactic acid resin having an arbitrary composition. In the ring-opening polymerization method, a polylactic acid-based polymer can be obtained using lactide, which is a cyclic dimer of lactic acid, using a selected catalyst while using a polymerization regulator or the like as necessary. At this time, L-lactide which is a dimer of L-lactic acid, D-lactide which is a dimer of D-lactic acid, or DL-lactide composed of L-lactic acid and D-lactic acid is used as the lactide. It is possible to obtain a lactic acid resin having an arbitrary composition and crystallinity by mixing and polymerizing these as necessary.

It should be noted that the lactic acid resin used in the present invention may be a non-aliphatic dicarboxylic acid such as terephthalic acid or an ethylene oxide adduct of bisphenol A as a small amount of a copolymer component as required for improving heat resistance. Non-aliphatic diols and the like may be added.
A small amount of a chain extender such as a diisocyanate compound, an epoxy compound, or an acid anhydride may be added for the purpose of increasing the molecular weight.

The preferred range of the weight average molecular weight of the lactic acid resin used in the present invention is 50,000 to 400,000, more preferably 100,000 to 250,000. If the molecular weight is 50,000 or more, suitable practical physical properties can be expected, and if it is 400,000 or less, there is no problem that the melt viscosity is too high and the molding processability is inferior.
Typical examples of lactic acid resins include the Laissia series made by Mitsui Chemicals, and the Nature Works series made by Cargill Dow.

[Resin components other than lactic acid resins]
As described above, the resin composition forming the injection-molded article of the present invention has an aliphatic polyester having biodegradability, an aromatic polyester having biodegradability, or biodegradability as necessary. Aromatic aliphatic polyester can be blended (polymer blend).

[Aliphatic polyester with biodegradability]
Examples of aliphatic polyesters having biodegradability other than lactic acid resins include aliphatic polyesters obtained by condensing aliphatic diols and aliphatic dicarboxylic acids, and aliphatic polyesters obtained by ring-opening polymerization of cyclic lactones. Group polyester, synthetic aliphatic polyester, and the like.

The “aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid” includes any one of ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol, which are aliphatic diols, or these A mixture of two or more of these, and an aliphatic dicarboxylic acid such as succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid, or a combination of two or more of these An aliphatic polyester obtained by condensation polymerization with a mixture can be used. If necessary, a polymer obtained by jumping up with an isocyanate compound or the like can also be used.
The preferable range of the weight average molecular weight of the aliphatic polyester is 50,000 to 400,000, more preferably 100,000 to 250,000.
Specific examples include Bionole series manufactured by Showa Polymer Co., Ltd. and Enpole manufactured by Ile Chemical Co., Ltd.

The “aliphatic polyester obtained by ring-opening polymerization of cyclic lactones” includes any of cyclic monomers such as ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone, or two or more of them. What polymerized the component which consists of these can be used.
The preferable range of the weight average molecular weight of the aliphatic polyester is 50,000 to 400,000, more preferably 100,000 to 250,000.
Specific examples include Cell Green Series manufactured by Daicel Chemical Industries.

As the “synthetic aliphatic polyester”, cyclic acid anhydrides and oxiranes, for example, copolymers of succinic anhydride with ethylene oxide, propylene oxide and the like can be used.
The preferable range of the weight average molecular weight of the aliphatic polyester is 50,000 to 400,000, more preferably 100,000 to 250,000.

[Aromatic polyester with biodegradability]
As the aromatic polyester having biodegradability other than the lactic acid-based resin, for example, an aromatic aliphatic polyester having a biodegradability composed of an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, and an aliphatic diol component is used. Can do.

In this case, examples of the “aromatic dicarboxylic acid component” include isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic dicarboxylic acid component include succinic acid, adipic acid, and suberin. Examples of the “aliphatic diol” include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like.
Two or more types of aromatic dicarboxylic acid components, aliphatic dicarboxylic acid components, or aliphatic diol components can be used.

  In the present invention, the aromatic dicarboxylic acid component most preferably used is terephthalic acid, the aliphatic dicarboxylic acid component is adipic acid, and the aliphatic diol component is 1,4-butanediol.

[Aromatic aliphatic polyester with biodegradability]
Examples of aromatic aliphatic polyesters having biodegradability other than lactic acid resins include biodegradable aromatic aliphatic polyesters comprising an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, and an aliphatic diol component. be able to.
Examples of the aromatic dicarboxylic acid component include isophthalic acid, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic dicarboxylic acid component include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanoic acid. Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and the like. Two or more types of aromatic dicarboxylic acid components, aliphatic dicarboxylic acid components, and aliphatic diol components can be used.
Among the above, the aromatic dicarboxylic acid component that can be most suitably used is terephthalic acid, the aliphatic dicarboxylic acid component is adipic acid, and the aliphatic diol component is 1,4-butanediol.
It is known that an aliphatic polyester composed of an aliphatic dicarboxylic acid and an aliphatic diol has biodegradability. However, in order to develop biodegradability in an aromatic aliphatic polyester, an aliphatic polyester is used between aromatic rings. There must be a family chain. Therefore, the aromatic dicarboxylic acid component of the aromatic aliphatic polyester having biodegradability used in the present invention is preferably 50 mol% or less.
Typical examples of aromatic aliphatic polyesters having biodegradability other than lactic acid-based resins include copolymers of polybutylene adipate and terephthalate (BASF Ecoflex), and copolymers of tetramethylene adipate and terephthalate. (Easman Chemicals EastarBio).

  In addition, it is preferable that the glass transition temperature (Tg) of said aliphatic polyester, aromatic polyester, and aromatic aliphatic polyester is 0 degreeC or less from the impact-resistant improvement effect.

[Inorganic crystallization accelerator]
As the inorganic crystallization accelerator in the present invention, talc, kaolin, calcium carbonate, bentonite, mica, sericite, glass flake, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, Hydrous calcium borate, alumina, magnesia, wollastonite, zonotlite, sepiolite, whisker, glass fiber, glass flake, metal powder, beads, silica balloon, shirasu balloon, etc., or a combination of two or more of these Mention may be made of mixtures. In addition, the surface of the inorganic crystallization accelerator can be treated with titanic acid, fatty acid, silane coupling agent, etc. to improve the adhesion with the resin, and the effect of the inorganic crystallization accelerator can be improved. It is.

The average particle size of the inorganic crystallization accelerator is preferably 0.1 to 5 μm, and more preferably 1 to 3 μm. When the average particle size is smaller than 5 μm, the inorganic crystallization accelerator becomes a starting point of destruction and the strength of the injection molded article is hardly lowered. On the other hand, if the average particle size is larger than 0.1 μm, poor dispersion of the inorganic crystallization accelerator hardly occurs.
In addition, the average particle diameter in this invention shows the value measured by the laser diffraction method.

  The blending amount of the inorganic crystallization accelerator is preferably 0.1 to 25 parts by mass, and 0.5 to 10 parts by mass with respect to 100 parts by mass of the resin composition containing a lactic acid resin as a main component. More preferably. If it is the range of 0.1-25 mass parts, crystallization of lactic acid-type resin can be accelerated | stimulated, and an inorganic filler becomes a starting point of destruction and does not produce the strength fall of lactic acid-type resin easily.

[Organic crystallization accelerator]
Examples of the organic crystallization accelerator in the present invention include dibutyl adipate, diisobutyl adipate, diisononyl adipate, diisodecyl adipate, di (2-ethylhexyl) adipate, di (n-octyl) adipate, di (adipate) ( n-decyl), dibutyl diglycol adipate, dibutyl sebacate, di (2-ethylhexyl) sebacate, di (n-hexyl) azelate, di (2-ethylhexyl) azelate, di (2-ethylhexyl) dodecanedioate ), Fatty acid esters such as acetyl tributyl citrate, phthalic acid esters such as diisononyl phthalate, diisodecyl phthalate, di (2-ethylhexyl) phthalate, or trimellitic acid esters such as trimellitic acid tri (2-ethylhexyl) One of There can be mentioned a mixture of two or more of these combinations.

The solubility parameter (SP value) of the organic crystallization accelerator is preferably in the range of 8.5 to 10.0 (cal / cm ³ ) ^1/2 . If the SP value of the organic crystallization accelerator is 8.5 (cal / cm ³ ) ^1/2 or more, bleeding out to the surface of the lactic acid resin does not occur, which is practically preferable. When the SP value is 10.0 (cal / cm ³ ) ^1/2 or less, the compatibility with the lactic acid resin is high, and the lactic acid resin is plasticized and hardly has heat resistance. The SP value of the present invention is the Fedors method [Polym. Eng. Sci. 14 (2) 152, (1974)].

As a compounding quantity of the said organic type crystallization accelerator, 0.1-20 mass% is mix | blended with respect to the compounding quantity of an inorganic type crystallization accelerator. Preferably 1-15 mass% is mix | blended, Furthermore, it is more preferable to mix | blend 5-10 mass%. When blended in an amount of 0.1 to 20% by mass, the crystallization promoted by the organic crystallization accelerator can be further promoted, and the crystallization promotion limit by the organic crystallization accelerator is greatly exceeded. Can be made.
In addition, it is preferable to mix | blend 0.1-5 mass parts of organic type crystallization promoter with respect to 100 mass parts of resin compositions which have lactic acid-type resin as a main component, 0.5-3 mass parts is mix | blended. Is preferred. If it is in the range of 0.1 to 5 mass, not only the crystallization promoting effect can be obtained, but also the plasticization of the resin composition mainly composed of a lactic acid resin, and the organic crystallization accelerator on the surface of the molded body No bleed out occurs.

(Carbodiimide compound)
In order to mainly impart hydrolysis resistance to the injection-molded product, a carbodiimide compound can be added. A preferable addition amount is 0.1 to 5 parts by mass of the carbodiimide compound with respect to 100 parts by mass of the resin forming the injection molded body. If it is in the range of 0.1 to 5 parts by mass, the hydrolysis resistance improving effect is exhibited, and the appearance of the molded product due to bleedout of the carbodiimide compound and the deterioration of mechanical properties due to plasticization do not occur. .

Examples of the carbodiimide compound include those having a basic structure represented by the following general formula.
-(N = C = N-R-) n-
In the above formula, n represents an integer of 1 or more. R represents another organic bond unit. In these carbodiimide compounds, the R portion may be aliphatic, alicyclic, or aromatic. Moreover, what is necessary is just to set n suitably between 1-50 normally.

Specific examples include bis (dipropylphenyl) carbodiimide, poly (4,4′-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), poly (diisopropylphenylene). Carbodiimide), poly (methyl-diisopropylphenylene carbodiimide), poly (triisopropylphenylene carbodiimide), and the like, and monomers thereof. These carbodiimide compounds can be used alone or in combination of two or more.
0.1-5 mass parts is preferable with respect to 100 mass parts of resin which forms an injection molded body, and, as for the compounding quantity of a carbodiimide compound, it is more preferable to add 0.5-3 mass parts. If it is blended within the range of 0.1 to 5 parts by mass, an effect of improving hydrolysis resistance can be obtained, and the appearance of the molded body due to bleed-out of the carbodiimide compound and deterioration of mechanical properties due to plasticization also occur. hard.

(Other additive substances)
Additives such as a plasticizer, a heat stabilizer, an antioxidant, a UV absorber, a light stabilizer, a pigment, a colorant, and a lubricant can be formulated within a range not impairing the effects of the present invention.

(Injection molded body crystallization promotion method and production method)
According to the present invention, the resin composition, the inorganic crystallization accelerator, the organic crystallization accelerator, and other additives are mixed and melted and injection-molded so as to have the above composition, followed by crystallization by heat treatment. An injection molded body can be obtained. Hereinafter, the manufacturing method will be described in more detail.

First, a resin composition containing a predetermined amount of a lactic acid resin as a main component, an inorganic crystallization accelerator, an organic crystallization accelerator, and other additives are added to the same injection molding machine. Add raw materials and mix. Specifically, the raw material is directly mixed using an injection molding machine and injection molded, or the dry blended raw material is extruded into a strand shape using a twin-screw extruder to produce pellets and then injected again. A method of creating an injection-molded body using a molding machine can be employed. In any method, it is necessary to consider a decrease in molecular weight due to decomposition of the raw material, and the latter is preferably selected for uniform mixing. For example, a resin component mainly composed of a lactic acid resin may be sufficiently dried to remove moisture, then melt mixed using a twin screw extruder, and extruded into a strand shape to produce pellets.
Regarding the melt extrusion temperature, the melting point changes depending on the composition ratio of the L-lactic acid structure and the D-lactic acid structure, and the melting point of the mixed resin changes depending on the mixing ratio of the aromatic aliphatic polyester. It is preferable to do. In practice, a temperature range of 100 to 250 ° C. may be usually selected.

  The pellets produced by the above method may be sufficiently dried to remove moisture and then injection molded by the following method.

  The injection molding method is not particularly limited, but typically, an injection molding method such as a general injection molding method for a thermoplastic resin, a gas assist molding method, and an injection compression molding method may be employed. In addition to the above methods, an in-mold molding method, a gas press molding method, a two-color molding method, a sandwich molding method, PUSH-PULL, SCORIM, or the like can also be employed according to other purposes.

The injection molding apparatus is composed of a general injection molding machine, a gas assist molding machine, an injection compression molding machine, and the like, and a molding die used for these, ancillary equipment, a mold temperature control device, a raw material drying device, and the like. However, the present invention is not limited to such a configuration.
Molding conditions are preferably such that the molten resin temperature is in the range of 170 ° C. to 210 ° C. in order to avoid thermal decomposition of the resin in the injection cylinder.

  When the injection molded body is obtained in an amorphous state, the mold temperature is preferably as low as possible from the viewpoint of shortening the cooling time of the molding cycle (mold closing-injection-holding pressure-cooling-mold opening-removing). In general, it is preferable to use a chiller at 15 to 55 ° C., but it is advantageous to set the temperature in the range of 20 to 40 ° C. in order to suppress shrinkage, warpage and deformation of the molded body during post-crystallization.

In the present invention, after injection molding, crystallization (crystallization treatment) is performed by heat treatment in order to increase the heat resistance of the injection molded body.
As a method of crystallization treatment, (1) a method in which injection molding is performed on a mold whose temperature has been raised in advance and crystallization is performed in the mold, or (2) the temperature of the mold is increased after injection molding in the mold. (3) After the injection molded body is taken out of the mold in an amorphous state, it can be crystallized with hot air, steam, hot water, far infrared heater, IH heater, etc. In order to obtain the crystallization promoting effect of the present invention, it is preferable to employ the methods (1) and (2) in which the treatment is performed in a mold.

A more preferable crystallization method is the method (1) described above, that is, a method in which a molten resin is filled in a heated mold, and is maintained in the mold for a certain period of time for crystallization. At this time, the mold temperature is preferably 60 ° C to 130 ° C, particularly preferably 70 ° C to 90 ° C. When the temperature is in the range of 60 ° C. to 130 ° C., crystallization does not take a long time, the cycle does not become too long, and deformation does not occur during release.
The time for holding in the mold is appropriately determined depending on the composition and the heat treatment temperature. For example, in the case of 70 ° C., the heat treatment is preferably performed for 15 minutes to 5 hours. When the heat treatment temperature is 130 ° C., it is preferable to perform the heat treatment for 10 seconds to 30 minutes.

  Since the injection-molded article of the present invention has excellent discoloration resistance and colorability, it can be used as building materials, home appliances, automobile parts, and other general molded products.

  Examples are shown below, but the present invention is not limited by these. In addition, the result shown in an Example evaluated by the following method.

(1) Crystallization speed Based on JIS K7121, the heat-treated molded body is cut out to about 10 mg, and DSC-7 manufactured by Perkin Elmer is used, from 30 ° C. to 200 ° C. at a rate of 10 ° C./min. The temperature rise was measured, and the heat of crystallization (ΔHc) and the heat of crystal fusion (ΔHm) were read from the obtained thermogram. From the obtained value, the relative crystallinity was calculated by the following formula, and a sample having a relative crystallinity (χc) exceeding 90% by heat treatment at 70 ° C. for 60 minutes was regarded as acceptable.
χc (%) = (ΔHm−ΔHc) / ΔHm × 100

(2) Heat resistance A test piece of L120 mm × W11 mm × t3 mm was prepared based on JISK-7191, and the deflection temperature under load (HDT) was measured using S-3M manufactured by Toyo Seiki Co., Ltd. The measurement was performed in the edgewise direction and the bending stress applied to the test piece of 1.80 MPa. A weighted deflection temperature of 50 ° C. or higher was regarded as acceptable.

(3) Impact resistance No. 2A test piece (with notch, L64mm x W12.7mm x t4mm) was prepared based on JISK-7110, and Izod impact strength at 23 ° C was measured using JISL-D manufactured by Toyo Seiki Seisakusho. Measurements were made. The Izod impact strength was determined to be 5 kJ / m ² .

(Example 1)
NatureWorks 4031D (L-lactic acid / D-lactic acid = 98.5 / 1.5, weight average molecular weight 200,000) manufactured by Cargill Dow as a lactic acid-based resin, SG-95 (talc manufactured by Nippon Talc Co., Ltd. as an inorganic crystallization accelerator) , Average particle diameter: 2.5 μm), DOZ (dioctyl azelate, SP value: 8.96) manufactured by Taoka Chemical Co., Ltd. as an organic crystallization accelerator, and NatureWorks 4031D, SG-95 and DOZ in a mass ratio of 100: 10 : 2 in a ratio, and 2 parts by mass of plasticizer (CITROFLEX A-2 (acetyltriethyl citrate, SP value: 10.23) manufactured by Morimura Shoji Co., Ltd.) with respect to 100 parts by mass of lactic acid resin After blending, it was compounded at 180 ° C. using a 40 mmφ small-size co-directional twin screw extruder manufactured by Mitsubishi Heavy Industries, and made into a pellet shape. The pellets thus obtained were injection-molded with a plate material of L200 mm × W30 mm × t3 mm and 4 mm using an injection molding machine IS50E (screw diameter 25 mm) manufactured by Toshiba Machine (main molding conditions are shown below). The sample was left in a baking test apparatus (DKS-5S manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), heat-treated at 70 ° C. for 2 hours, and evaluated for the deflection temperature under load and the Izod impact strength. .

1) Temperature conditions: Cylinder temperature (195 ° C) Mold temperature (20 ° C)
2) Injection conditions: Injection pressure (115 MPa) Holding pressure (55 MPa)
3) Measurement conditions: Screw rotation speed (65 rpm) Back pressure (15 MPa)

On the other hand, after dry blending with the above composition, an amorphous molded body of L100 mm × W100 mm × t2 mm is injection molded by IS50E manufactured by Toshiba Machine. The molding conditions at this time were a cylinder temperature of 195 ° C., a mold temperature of 20 ° C., an injection pressure of 115 MPa, an injection time of 1.5 sec, a holding pressure of 115 MPa, a holding time of 3.0 sec, a back pressure of 15 MPa, and a screw rotation speed of 65 rpm.
Next, the injection-molded product obtained by the above method is left still in a baking test apparatus (DKS-5S manufactured by Daiei Kagaku Seiki Seisakusho), heat-treated at 70 ° C. for 60 minutes, and the crystallization rate is evaluated. went. The results are shown in Table 1.

(Example 2)
NatureWorks4031D, SG-95, and DOZ were dry blended at a mass ratio of 100: 15: 2, and injection molded products were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
NatureWorks4031D, SG-95, and DOZ were dry blended at a mass ratio of 100: 20: 2, and injection molded articles were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
NatureWorks 4031D, SG-95, and DOZ were dry blended at a mass ratio of 100: 30: 2, and injection molded articles were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 5)
As an inorganic crystallization accelerator, KAP-150 (wollastonite, average particle diameter: 4.9 μm) manufactured by Kansai Matec Co., Ltd. is used, and the ratio of NatureWorks 4031D, KAP-150, and DOZ is 100: 10: 2. Then, an injection molded product was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 6)
DIDA (diisodecyl adipate, SP value: 8.95) manufactured by Taoka Chemical Co., Ltd. was used as an organic crystallization accelerator, and NatureWorks 4031D, SG-95, and DIDA were dry blended at a mass ratio of 100: 10: 2. Then, an injection molded product was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
An injection molded product was prepared and evaluated for NatureWorks 4031D in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 2)
NatureWorks4031D and SG-95 were dry blended at a mass ratio of 100: 10, and injection molded articles were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 3)
NatureWorks4031D and SG-95 were dry blended at a mass ratio of 100: 15, and injection molded articles were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 4)
NatureWorks4031D and SG-95 were dry blended at a mass ratio of 100: 20, and injection molded articles were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

(Comparative Example 5)
NatureWorks4031D and SG-95 were dry blended at a mass ratio of 100: 30, and injection molded products were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 2.

As is apparent from Table 2 and FIG. 1, the injection molded articles of Comparative Examples 1 to 5 are excellent in heat resistance, but even if the amount of the inorganic crystallization accelerator (SG-95) is increased, it is 70. The relative crystallinity after heat treatment at 60 ° C. for 60 minutes did not increase beyond 82%, and it was found that the inorganic crystallization accelerator alone had a limit. In addition, the injection molded articles of Comparative Examples 1 to 5 had an Izod impact strength of less than 5 kJ / m ² , and were insufficient in physical properties as a practical product in terms of crystallization speed and impact resistance.
On the other hand, the injection molded articles of Examples 1 to 6 have a relative crystallinity of 97 to 98% far exceeding the limit value of 82% of the relative crystallinity when only the inorganic crystallization accelerator is blended. Have been gained. Moreover, the deflection temperature under load was 50 ° C. or more, the Izod impact strength was 5 kJ / m ² or more, and it was found that the crystallization speed, heat resistance, and impact resistance were all excellent.

The graph which showed the relationship between the compounding quantity (mass part with respect to 100 mass parts of resin compositions) of an inorganic type crystallization accelerator, and relative crystallinity degree (%) regarding the injection molded body obtained by the Example and the comparative example. It is.

Claims (3)

A method of further promoting the crystallization of an injection molded article obtained by blending an inorganic crystallization accelerator in a resin composition containing a lactic acid resin as a main component,
Injection characterized by further blending an organic crystallization accelerator of 0.1 to 20% by mass with respect to the inorganic crystallization accelerator, and crystallizing at 60 to 130 ° C. directly in the mold after injection molding. Method for promoting crystallization of molded article. An injection-molded product obtained by blending a resin composition containing a lactic acid resin as a main component with an inorganic crystallization accelerator,
Further blending 0.1 to 20% by weight of organic crystallization accelerator with respect to the inorganic crystallization accelerator,
Relative crystallinity of the lactic acid resin portion determined from the following formula based on the heat of crystallization (ΔHc) and the heat of crystal fusion (ΔHm) when the temperature is raised from 30 ° C. to 200 ° C. at a rate of 10 ° C./min ( An injection molded article in which χc) is increased to 90% or more.
χc (%) = (ΔHm−ΔHc) / ΔHm × 100 The resin composition containing a lactic acid resin as a main component contains 5 to 30% by mass of an aliphatic polyester other than the lactic acid resin and 5 to 20% by mass of an aromatic aliphatic polyester. Item 3. An injection-molded article according to Item 2.

Images