JP2006328163A - Polylactic acid-based resin composition, molding of the same and method for molding the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition containing polylactic acid-based resin increased in crystallization kinetic, improved in hard and brittle properties and increased in stability especially stability at a high temperature and in a high humidity. <P>SOLUTION: The resin composition comprises a polylactic acid-based resin, an organic nucleating agent, a plasticizer and a stabilizer, wherein 0.1-10 pts.wt. plasticizer is contained based on 100 pts.wt. polylactic acid-based resin. The nucleating agent is preferably a trimesic triamide compound and the trimesic triamide compound is preferably at least one selected from a group consisting of trimesic tricyclohexylamide and trimesic tri(2-methylcyclohexyl amide). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polylactic acid resin composition, a molded body thereof, and a molding method thereof.

  In recent years, environmentally friendly plastics for resource recycling have attracted attention. One of them is polylactic acid resin. Since polylactic acid-based resins can be obtained from plants, carbon-neutral materials that do not use petroleum resources and sustainable resources that can contribute to the establishment of a recycling-oriented society are in the spotlight. Polylactic acid-based resins have higher biodegradability than other resins and are expected to be widely used in a wide range of fields as environmentally friendly resins.

  Incidentally, polylactic acid resins generally have a slow crystallization rate. Therefore, it takes a long time to crystallize the polylactic acid resin for the purpose of improving heat resistance, and the productivity is poor. When forming into a product exposed to a relatively high temperature, such as tableware, a cup or a home appliance without performing sufficient crystallization, the product (molded product) has a problem of causing thermal deformation and the like. As means for solving such problems, there are known techniques for blending polylactic acid resins with inorganic nucleating agents such as mica and calcium carbonate, and blending organic nucleating agents to improve the crystallization speed. (See Patent Documents 1 and 2). However, the addition of an inorganic nucleating agent has a problem that the fluidity of the resin is lowered during molding and the moldability is deteriorated.

  In addition, polylactic acid resins generally have hard and brittle physical properties. A technique of adding a plasticizer to a polylactic acid resin for the purpose of improving such physical properties is known. However, in order to improve the crystallization speed of the polylactic acid resin as described above, when a plasticizer is further added to the composition in which the organic nucleating agent is mixed with the polylactic acid resin, the heat of the resulting resin composition is increased. It has been found that stability, particularly strength at high temperatures and high humidity, may be significantly reduced.

Japanese Patent Laid-Open No. 10-87975 International Publication No. 03/042302 Pamphlet

  In view of the above circumstances, the problem to be solved by the present invention is that the crystallization speed is fast, the moldability is good, the hard and brittle properties are improved, and high strength and heat stability are achieved by normal molding. A polylactic acid resin composition capable of obtaining an excellent molded article (particularly excellent in stability at high temperature and high humidity), and high strength and excellent thermal stability using the polylactic acid resin composition It is to provide a method for producing a molded product having high strength and excellent thermal stability.

  As a result of diligent research to solve the above problems, the present inventors have blended a stabilizer together with an organic nucleating agent and a plasticizer in a polylactic acid resin, and further specify the blending amount of the plasticizer at that time By setting the amount, a resin composition that exhibits good moldability, has a high crystallization speed, improves the hard and brittle properties unique to polylactic acid resins, and greatly improves the thermal stability of the molded body. Furthermore, by molding in a state where the organic nucleating agent in the resin composition is completely dissolved, the resin has a higher crystallization speed and excellent thermal stability of the molded body. The present inventors have found that a molded body can be obtained and have completed the present invention.

That is, the present invention is as follows.
[1] A resin composition comprising a polylactic acid resin, an organic nucleating agent, a plasticizer and a stabilizer, the resin comprising 0.1 to 10 parts by weight of the plasticizer with respect to 100 parts by weight of the polylactic acid resin Composition.
[2] The ratio of the structural unit consisting of L-lactic acid residues in the polylactic acid resin is 80 to 99.5 mol% with respect to all the structural units constituting the polylactic acid resin, or the polylactic acid resin The resin composition according to the above [1], wherein the proportion of structural units composed of D-lactic acid residues with respect to all structural units constituting the resin is 80 to 99.5 mol%.
[3] The organic nucleating agent is represented by the general formula (1)

[Wherein R ¹ represents a residue obtained by removing all carboxyl groups from trimesic acid. Three R ^{2 s} are the same or different and are a cyclohexyl group optionally having a linear or branched alkyl group having 1 to 4 carbon atoms, or a straight chain having 1 to 4 carbon atoms or Represents a branched alkyl group. ]
The resin composition according to the above [1] or [2], which is a trimesic acid triamide compound represented by the formula:
[4] The resin composition according to [3], wherein the trimesic acid triamide compound is at least one selected from the group consisting of trimesic acid tricyclohexylamide and trimesic acid tri (2-methylcyclohexylamide).
[5] The resin composition as described in [3] or [4] above, wherein the trimesic acid triamide compound has a particle shape having an average particle size of 10 μm or less and a maximum particle size of 30 μm or less.
[6] By melt-kneading a polylactic acid resin, an organic nucleating agent, a plasticizer and a stabilizer at a ratio of 0.1 to 10 parts by weight of the plasticizer with respect to 100 parts by weight of the polylactic acid resin. In the above [3] or [4], the obtained resin composition, wherein the organic nucleating agent is a trimesic acid triamide compound having a particle shape having an average particle size of 10 μm or less and a maximum particle size of 30 μm or less. The resin composition as described.
[7] The resin according to any one of [1] to [6], wherein the content of the organic nucleating agent is 0.05 to 5 parts by weight with respect to 100 parts by weight of the polylactic acid resin. Composition.
[8] The resin composition according to any one of [1] to [7], wherein the plasticizer is polyethylene glycol dibenzoate.
[9] The resin composition according to any one of [1] to [8] above, wherein the stabilizer comprises a compound capable of undergoing a crosslinking reaction with a polylactic acid resin.
[10] The resin composition according to [9] above, wherein the compound capable of undergoing a crosslinking reaction with the polylactic acid resin is a carbodiimide compound.
[11] The resin composition according to any one of [1] to [10], wherein the content of the stabilizer is 0.2 to 10 parts by weight with respect to 100 parts by weight of the polylactic acid resin.
[12] The resin composition according to any one of [1] to [11], wherein the glass transition temperature (Tg) is 40 to 70 ° C.
[13] The resin composition according to any one of [1] to [12], wherein the acid component content is 5 equivalents / ton or less.
[14] The resin composition according to any one of [1] to [13], wherein the crystallization completion time is 300 seconds or less.
[15] A molded article obtained by molding the resin composition according to any one of [1] to [14].
[16] A method for producing a molded body from the resin composition according to any one of [1] to [14], wherein the resin composition is a molten polylactic acid based organic nucleating agent. Kneading until the organic nucleating agent is dissolved in the molten polylactic acid resin at a temperature equal to or higher than the melting temperature of the resin, and in the molding process, the organic nucleating agent is dissolved in the molten polylactic acid resin A method for producing a molded article, characterized by comprising:
[17] Production of molded article according to [16], wherein the molding step is injection molding, extrusion molding, injection blow molding, injection extrusion blow molding, injection compression molding, extrusion blow molding, extrusion thermoform molding or melt spinning. Method.

  The polylactic acid-based resin composition of the present invention has good moldability, has a high crystallization speed, and improves the hard and brittle properties unique to the polylactic acid-based resin. A molded article having good strength and heat resistance can be obtained in a short time. The molded body thus obtained is excellent in thermal stability (particularly, stability under high temperature and high humidity), and achieves a molded body in which strength reduction under high temperature and high humidity is suppressed.

The following is a detailed description of the present invention.
The resin composition of the present invention contains a polylactic acid resin. In the present invention, the polylactic acid-based resin is not particularly limited, and polylactic acid-based resins having lactic acid units having various optical purities can be used, but a structural unit composed of an L-lactic acid residue (so-called L-lactic acid unit). Or it is preferable that the structural unit (what is called D-lactic acid unit) which consists of D-lactic acid residues exists in the range of 80-99.5 mol% with respect to all the structural units which comprise polylactic acid-type resin. Such a polylactic acid resin is relatively easy to obtain and has a high melting point, so that it becomes easy to obtain a resin composition having better heat resistance. The structural unit consisting of L-lactic acid residue or D-lactic acid residue is more preferably in the range of 90 to 99.2 mol%, and 93 to 99 mol, based on all structural units constituting the polylactic acid resin. More preferably, it is in the range of%.

  Moreover, what is derived from L-lactic acid, D-lactic acid, DL-lactic acid, L-lactide, D-lactide, meso-lactide alone or a mixture thereof can be used as the polylactic acid resin. That is, it may be produced by direct dehydration condensation of lactic acid or by lactide ring-opening method.

In addition, the polylactic acid-based resin may have other structural units other than lactic acid residues as long as the effects of the present invention are not impaired (the range is preferably 50 mol% or less, more preferably Is 20 mol% or less.). Examples of such other structural units include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, and aliphatic glycols such as ethylene glycol, propylene glycol, and 1,4-butanediol. Hydroxycarboxylic acid units derived from the above; units of hydroxycarboxylic acids such as glycolic acid, β-hydroxybutyric acid, hydroxypivalic acid, and hydroxyvaleric acid.
In addition, when the polylactic acid-based resin includes a structural unit derived from a hydroxycarboxylic acid other than lactic acid, the “all structural units constituting the polylactic acid-based resin” in the present invention refers to a structural unit derived from lactic acid (lactic acid Residues) and structural units derived from hydroxycarboxylic acids other than lactic acid.

  In the present invention, the molecular weight of the polylactic acid resin is not particularly limited, but the number average molecular weight (Mn) is preferably in the range of 5,000 to 400,000, and preferably 10,000 to 200,000. More preferred. When the number average molecular weight (Mn) is smaller than 5,000, when a molded product is produced using the obtained resin composition, the strength thereof decreases, the acid component content increases, the hydrolyzability increases, etc. This tends to reduce the stability. On the other hand, when it is larger than 400,000, the moldability tends to deteriorate when the resulting resin composition is molded. In the present invention, the number average molecular weight is a value in terms of polymethyl methacrylate (PMMA) measured by GPC (gel permeation chromatography). As GPC measurement conditions, 150C ALC / GPC manufactured by Waters as a GPC device, Shodex (registered trademark) HFIP806M manufactured by Showa Denko KK as a column, RI detector as a detector, hexafluoro of 20 mM sodium trifluoroacetate as a developing solvent An isopropanol solution is used, the column temperature is 40 ° C., and the flow rate is 1.0 mL / min. Standard PMMA used for PMMA conversion is PM1 manufactured by Polymer Laboratories.

  In addition, the polylactic acid-type resin used by this invention may use what was induced | guided | derived from a plant from the point of availability, L- or D-methyl lactate, L- or D-ethyl lactate. It is also possible to use a product produced from a lactic acid derivative such as a raw material (monomer) or a product produced by a microorganism.

  The resin composition of the present invention contains an organic nucleating agent. In the present invention, the organic nucleating agent can be used without limitation as long as it has a nucleating action on the thermoplastic resin, such as trimesic acid triamide compound; higher fatty acid metal salts such as sodium montanate and calcium montanate, etc. Among them, a trimesic acid triamide compound is preferable. By using a trimesic acid triamide compound, a great effect is shown in improving the crystallization speed of the resin composition. In the present invention, the organic nucleating agent may be one or more compounds.

  The trimesic acid triamide compound has the general formula (1)

[Wherein R ¹ represents a residue obtained by removing all carboxyl groups from trimesic acid. Three R ^{2 s} are the same or different and are each a cyclohexyl group optionally having a linear or branched alkyl group having 1 to 4 carbon atoms, or a straight chain having 1 to 4 carbon atoms or Represents a branched alkyl group. ]
And cyclohexylamine optionally having trimesic acid or acid chloride thereof and a linear or branched alkyl group having 1 to 4 carbon atoms, or linear or branched having 1 to 4 carbon atoms It is a compound obtained by amidating a chain alkylamine.
Specific examples of the cyclohexylamine optionally having a linear or branched alkyl group having 1 to 4 carbon atoms include cyclohexylamine, 2-methylcyclohexylamine,
3-methylcyclohexylamine, 4-methylcyclohexylamine, 2-ethylcyclohexylamine, 3-ethylcyclohexylamine, 4-ethylcyclohexylamine, 2-n-propylcyclohexylamine, 3-n-propylcyclohexylamine, 4-n- Propylcyclohexylamine, 2-iso-propylcyclohexylamine, 3-iso-propylcyclohexylamine, 4-iso-propylcyclohexylamine, 2-n-butylcyclohexylamine, 3-n-butylcyclohexylamine, 4-n-butylcyclohexyl Amine, 2-iso-butylcyclohexylamine, 3-iso-butylcyclohexylamine, 4-iso-butylcyclohexylamine, 2-sec-butylcyclohexylamine 3-sec-butylcyclohexylamine, 4-sec-butylcyclohexylamine, 2-tert-butylcyclohexylamine, 3-tert-butylcyclohexylamine, 4-tert-butylcyclohexylamine, 2,3-dimethylcyclohexylamine, 2, 4-dimethylcyclohexylamine, 2,5-dimethylcyclohexylamine, 2,6-dimethylcyclohexylamine, 2,3,4-trimethylcyclohexylamine, 2,3,5-trimethylcyclohexylamine, 2,3,6-trimethylcyclohexyl Examples include amine, 2,4,6-trimethylcyclohexylamine, 3,4,5-trimethylcyclohexylamine and the like. Specific examples of the linear or branched alkylamine having 1 to 4 carbon atoms include methylamine, ethylamine, n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, tert -Butylamine is mentioned.

  Among the trimesic acid triamide compounds, trimesic acid tricyclohexylamide, trimesic acid tri (2-methylcyclohexylamide), trimesic acid tri (3-methylcyclohexylamide) are particularly excellent in improving the crystallization speed of polylactic acid-based resins. ), Trimesic acid tri (4-methylcyclohexylamide) and trimesic acid tri (2,3-dimethylcyclohexylamide) are preferable, and trimesic acid tricyclohexylamide and trimesic acid tri (2-methylcyclohexylamide) are particularly preferable.

The shape of the organic nucleating agent in the resin composition of the present invention is not particularly limited. However, when a trimesic acid triamide compound is used as the organic nucleating agent, the average particle size is 10 μm or less and the maximum particle size is 30 μm. The following particle shape is preferable, and a particle shape having an average particle diameter of 5 μm or less and a maximum particle diameter of 20 μm or less is particularly preferable. When the average particle size is larger than 10 μm or the maximum particle size is larger than 30 μm, the dissolution of the trimesic acid triamide compound in the polylactic acid resin is insufficient, and the nucleation action on the polylactic acid resin tends to be reduced. There is. As a result, the relative crystallinity of the obtained molded product is lowered, and the heat resistance tends to be lowered.
The resin composition of the present invention in which the trimesic acid triamide compound has the average particle size and the maximum particle size as described above can be produced by using the trimesic acid triamide compound having the average particle size and the maximum particle size.

  The amount of the organic nucleating agent used can be appropriately changed according to the specific use of the resin composition, but generally 0.05 to 5 parts by weight with respect to 100 parts by weight of the polylactic acid resin. Is preferable, 0.1 to 2 parts by weight is more preferable, and 0.2 to 1.5 parts by weight is particularly preferable. When the amount used is less than 0.05 parts by weight, the effect of improving the crystallization speed tends to be small. On the other hand, when the amount exceeds 5 parts by weight, the effect corresponding to the amount added is not increased, and the cost tends to increase.

  Moreover, you may further add inorganic type nucleating agents, such as a talc, a mica, and a calcium carbonate, as needed within the range which does not impair the effect of this invention. The amount of the inorganic nucleating agent added is preferably 3 to 30 parts by weight with respect to 100 parts by weight of the polylactic acid resin.

  The resin composition of the present invention contains a plasticizer. In the present invention, as the plasticizer, those used as a plasticizer for thermoplastic resins can be used. For example, polyhydric alcohol derivatives such as glycerin triacetate, glycerin tri-2-ethylhexanoate, glycerin triisostearate; triethyl acetyl citrate, tripropyl acetyl citrate, tri (2-ethylhexyl) citrate, acetyl citric acid Hydroxycarboxylic acid derivatives such as triisostearyl, triethyl citrate, tripropyl citrate, tri (2-ethylhexyl) citrate, triisostearyl citrate; butyl oleate, isostearyl oleate, isobutyl adipate, diadipate Aliphatic carboxylic acid esters such as (2-ethylhexyl); Aromatic carboxylic acid esters such as di (2-ethylhexyl) phthalate and diisononyl phthalate; Polyethylene glycol diacetate Polyethylene glycol dipropionate, polyethylene glycol di-2-ethylhexanoate, polyethylene glycol dibenzoate, polypropylene glycol diacetate, polypropylene glycol dipropionate, polypropylene glycol di-2-ethylhexanoate, polypropylene glycol dibenzoate, etc. And polyether polyol derivatives; phosphoric acid derivatives such as tributyl phosphate, tri (2-ethylhexyl) phosphate, triphenyl phosphate, triisostearyl phosphate, and the like. Among these, it is possible to produce a molded article which is excellent in stability over time and flexibility under daily use conditions, and has no plasticizer bleed-out, and has low volatility. Therefore, polyether polyol derivatives are preferable, and among them, polyethylene glycol dibenzoate is particularly preferable. In the present invention, the plasticizer can be one or more compounds.

  The amount of the plasticizer used is 0.1 to 10 parts by weight, preferably 0.5 to 7 parts by weight, based on 100 parts by weight of the polylactic acid resin. When the amount of the plasticizer used is more than 10 parts by weight, the glass transition temperature (Tg) is lowered and the strength retention is lowered. On the other hand, when the amount is less than 0.1 parts by weight, a molded product molded from the resulting resin composition becomes brittle.

  The resin composition of the present invention contains a stabilizer. In the present invention, various compounds can be used without limitation as long as the stabilizer is a compound capable of undergoing a crosslinking reaction with a polylactic acid resin, but carbodiimide compounds and epoxy compounds are preferred, and carbodiimide compounds are particularly preferred. As an epoxy compound, 2-phenylphenyl glycidyl ether etc. can be illustrated, for example. The carbodiimide compound is not particularly limited as long as it has one or more carbodiimide groups in the molecule. For example, a carbodiimide compound synthesized by a decarboxylation reaction from an isocyanate compound according to a conventionally known method may be used. it can. Moreover, you may use what is marketed. Examples of the monocarbodiimide compound having one carbodiimide group in the molecule include aliphatic or alicyclic monocarbodiimides such as diisopropylcarbodiimide, dicyclohexylcarbodiimide and dioctylcarbodiimide, and aromatic monocarbodiimides such as diphenylcarbodiimide. As an isocyanate compound in the synthesis of a polycarbodiimide having two or more carbodiimide groups in the molecule, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2 Aromatic diisocyanates such as 1,4-tolylene diisocyanate, tetramethylxylylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyldimethylmethane diisocyanate; Nert, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, etc. The aliphatic Alicyclic diisocyanate and the like are. The polycarbodiimide may have all or part of the isocyanate group remaining at the end sealed, and as such a sealing agent, monoisocyanate such as cyclohexyl isocyanate, phenyl isocyanate, tolyl isocyanate, etc. Compound: Compounds having active hydrogen such as hydroxyl group and amino group are exemplified. Among the carbodiimide compounds, polycarbodiimide having two or more carbodiimide groups in the molecule is preferable from the viewpoint of improving hydrolysis resistance of a molded product molded from the obtained resin composition. Polycarbodiimide obtained from aliphatic or alicyclic carbodiimide, aliphatic or alicyclic diisocyanate is preferable from the viewpoint of the compatibility of the above and the hydrolysis resistance of a molded product molded from the resulting resin composition. In the present invention, one or more compounds can be used as the stabilizer.

  The amount of the stabilizer used can be appropriately changed according to each application, but is preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the polylactic acid resin used. More preferably, it is 5 to 5 parts by weight.

  The resin composition of the present invention contains an inorganic additive such as dibasic sulfate, dibasic lead stearate, calcium hydroxide, calcium silicate, etc., as necessary within the range not impairing the effects of the present invention; , Pigments, impact resistance improvers, processing aids, reinforcing agents, colorants, flame retardants, weather resistance improvers, UV absorbers, antioxidants, hydrolysis resistance improvers, fungicides, antibacterial agents, light Various additives such as stabilizers, anti-static agents, silicone oil, anti-blocking agents, mold release agents, foaming agents, and fragrances; various fibers such as glass fibers and polyester fibers; fillers such as silica and wood flour; various couplings Arbitrary components, such as an agent, can be mix | blended as needed.

  Furthermore, the resin composition of the present invention can be used as necessary within the range not impairing the effects of the present invention. Polyurethane resin; Polyamide resin; Polyester resin; Polyvinyl chloride resin; Polyvinylidene chloride resin; Polycarbonate resin; Resin; Saponified ethylene-vinyl acetate copolymer; Acrylic resin such as polyacrylate, polymethacrylate, polymethyl methacrylate, methyl methacrylate-acrylic ester copolymer; Copolymerization of aromatic vinyl compound and vinyl cyanide compound Polymer; aromatic vinyl compound-vinyl cyanide compound-olefin compound copolymer; methyl methacrylate-styrene-butylene copolymer; other resins such as styrene polymer and olefin polymer may be contained. .

  Although the glass transition temperature (Tg) of the resin composition of this invention can be suitably changed according to each use, it is preferable that it is 40-70 degreeC, and it is more preferable that it is 50-60 degreeC. A molded product obtained from a resin composition having a glass transition temperature (Tg) in such a range is preferable because problems such as deformation are less likely to occur during use, and brittleness is improved. The glass transition temperature (Tg) of the resin composition can be adjusted to a desired temperature by adjusting the amount of plasticizer used, for example.

Although the acid component content of the resin composition of the present invention can be appropriately changed according to each application, it becomes easy to obtain a resin composition having higher stability. Or less, more preferably 0 equivalent / ton or more and 1 equivalent / ton or less. The acid component content can be adjusted, for example, by changing the amount and type of stabilizer described above.
The acid component content is determined based on the carboxyl group terminal concentration of the polylactic acid resin in the resin composition of the present invention, the acidic functional group contained in the organic nucleating agent, plasticizer, stabilizer, optional component, and the like. It varies depending on the concentration. The acid component content can be determined by a titration method as described in Examples described later.

The crystallization completion time of the resin composition of the present invention is preferably in the range of 0 to 300 seconds, and more preferably in the range of 0 to 200 seconds. When the crystallization completion time is within this range, a molded product having high heat resistance can be easily obtained by a normal molding method when molding the resin composition. The crystallization completion time of the resin composition can be adjusted by increasing or decreasing the amount of the organic nucleating agent used.
In the present specification, the crystallization completion time is a time until completion of heat generation due to crystallization, which is measured by a differential scanning calorimeter (DSC).

  The resin composition of the present invention can be obtained by kneading the above components. There is no restriction | limiting in particular as the kneading | mixing method of each component, It can mix by a conventionally well-known method. For example, a dry blend method in which each component is charged and kneaded in a tumbler, V-type blender, ribbon blender, Hellshell mixer, tumbler mixer, etc., and the dry blend product is melt-kneaded with a single or twin screw extruder, kneader, roll, etc. And then cooling and pelletizing, or a solution blending method in which each resin is dissolved in a solvent and mixed and then the solvent is removed.

  The resin composition of the present invention can be easily molded into molded products having various shapes by known molding methods such as extrusion molding, injection molding, calendar molding, vacuum molding, and pressure molding, and the resulting molding. The body can be high strength and excellent in thermal stability. It can also be formed into a fiber by melt spinning.

  Furthermore, by molding the resin composition of the present invention in accordance with the method for producing a molded article of the present invention, a molded article particularly excellent in heat resistance and strength retention can be obtained. The method for producing such a molded article is to set the resin temperature at a temperature equal to or higher than the melting temperature of the organic nucleating agent in the molten polylactic acid resin, and knead until the organic nucleating agent is dissolved in the molten polylactic acid resin. The organic nucleating agent is characterized in that it is subjected to a molding step in a state dissolved in a molten polylactic acid resin, whereby a high relative crystallinity can be obtained in a molded body in a short molding time. It is possible to give excellent heat resistance temperature and strength retention. The relative degree of crystallinity is a value measured by the method described in Examples described later.

Since organic nucleating agents, especially trimesic acid triamide compounds, generally have a high melting point of about 180 ° C. to 380 ° C., they are higher than the melting point of polylactic acid resins (generally 145 ° C. to 180 ° C.). When heated together, the polylactic acid resin dissolves first, and then the organic nucleating agent dissolves in the molten polylactic acid resin. Therefore, in this specification, the “dissolution temperature” of the organic nucleating agent in the molten polylactic acid resin is determined by using a resin composition (pellet or dry blend) containing the organic nucleating agent under an optical microscope. It is the temperature at which the organic nucleating agent is dissolved in the molten polylactic acid resin and no solid is observed. In addition, in the case of injection molding, whether or not the organic nucleating agent is dissolved in the molten polylactic acid resin is easily determined by visually observing the molten resin composition coming out from the nozzle tip of the heating cylinder. be able to. That is, when the organic nucleating agent is not completely dissolved in the molten polylactic acid resin and any solid remains, the molten resin composition is cloudy but completely dissolved. It is transparent without turbidity. Similarly, in extrusion molding, it can be confirmed whether or not the molten resin composition is completely dissolved by visual observation of the transparency of the molten resin composition discharged from the die. In the case of other molding methods, it can be confirmed in the molding step whether the molten resin composition discharged from the cylinder nozzle or the die is completely dissolved by visual observation.
The dissolution temperature depends on the type of organic nucleating agent, the particle size and the amount used, the type of polylactic acid resin, the type and amount of stabilizer, and the type of plasticizer and the amount used. However, in the range of 0.05 to 5 parts by weight of the organic nucleating agent with respect to 100 parts by weight of the polylactic acid resin, it is usually in the range of 210 ° C. to 250 ° C. 220 to 245 degreeC is preferable from the balance of the melt | dissolution rate to polylactic acid-type resin, and the thermal decomposition suppression of polylactic acid-type resin.
Further, kneading so that no solid organic nucleating agent is present can be carried out by adjusting the residence time of the resin composition during heating and melting, the screw rotation speed, and the like. Next, while maintaining this molten state, the resin composition is subjected to a molding step to cool and crystallize the resin composition. The temperature during cooling (for example, the mold temperature in injection molding) is preferably 60 to 120 ° C, particularly 90 to 110 ° C.
By using such a molding method, it is possible to obtain a molded article having a high crystallization speed and excellent moldability, and a high relative crystallinity and strength retention.

  The molded body of the present invention is, for example, a vehicle part, a housing such as a body of a household appliance, a gear, general goods, clothing, a bag, a latch member such as a fastener or a button, agricultural material, building material, civil engineering material, tableware. It can be suitably used as a kind or toy.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. Measurement methods and chemicals used in the following examples and comparative examples are as follows.

<Measurement method>
Particle size of organic nucleating agent: Non-ionic surfactant (Triton X-100) was dissolved using a laser diffraction scattering method particle size distribution measuring device (Microtrac particle size distribution device FRA). After dispersing the organic nucleating agent in water and ultrasonically dispersing for 3 minutes, the particle size distribution was measured.

  Glass transition temperature: When the resin composition was heated to 10 ° C./min using a differential scanning calorimeter (Perkin Elmer, DSC7), when the resin composition changed to a rubbery state The temperature at was taken as the glass transition temperature.

  Acid component content: A 100 mL Erlenmeyer flask was dissolved in a resin composition (0.5 g) and chloroform (50 mL) after blast drying at 100 ° C. for 12 hours. To this was further added benzyl alcohol (50 mL). The solution was titrated with a 0.005N potassium hydroxide / ethanol solution using phenolphthalein as an indicator to obtain a titer. Separately, a blank test without using a resin composition was performed to obtain a titer. The acid component content was calculated from both titration amounts.

  Crystallization completion time: Using a differential scanning calorimeter (Perkin Elmer, DSC7), the resin composition (10 mg) was melted at 200 ° C. for 2 minutes, and further, 100 ° C. at a rate of −70 ° C./minute. Then, the temperature was kept at 100 ° C., and the calorific value with respect to time was measured. Based on the time when the temperature reached 100 ° C., the time to complete the exotherm (the time until the exothermic peak returned to the baseline) was defined as the crystallization completion time.

Relative crystallinity: Using a differential scanning calorimeter (Perkin Elmer, DSC7), the test pieces obtained in the following examples and comparative examples were cut to obtain evaluation samples. When about 10 mg of the evaluation sample was heated from 20 ° C. to 200 ° C. at a rate of 10 ° C./min, the heat of crystallization ΔHc (J / g) and the heat of fusion ΔHm (J / g) were measured, and the relative crystal The degree of conversion was calculated from the following formula.
Relative crystallinity (%) = (ΔHm−ΔHc) / ΔHm × 100

Formability: Formability when producing test pieces in the following examples and comparative examples was evaluated according to the following criteria.
A: Good releasability and easy molding.
○: Slightly attached to the mold, but relatively easy to mold.
X: Molding is difficult due to poor releasability from the mold.

  Heat-resistant temperature: The deflection temperature under load (HDT) was measured according to JIS K-7191. The temperature obtained by this was defined as the heat resistant temperature.

Strength retention: Test pieces obtained in the following examples and comparative examples were left for 30 hours under conditions of a temperature of 80 ° C. and a humidity of 95% Rh. Tensile strength (measurement conforms to JIS K-7113) was measured before and after standing, and the strength retention was calculated by the following formula.
Strength retention (%) = (Tensile strength after leaving) / (Tensile strength before leaving) × 100

<Used chemicals>
(Polylactic acid resin)
Polylactic acid resin: Cargill Dow (# 3001D) (content of structural unit consisting of L-lactic acid residue: 98.5 mol%, number average molecular weight (Mn: 150,000))
(Organic nucleating agent)
Organic nucleating agent A: trimesic acid tricyclohexylamide (average particle size 1.6 μm, maximum particle size 10 μm): Shin Nippon Rika Co., Ltd. Organic nucleating agent B: trimesic acid tri (2-methylcyclohexylamide) ( (Average particle size 1.5 μm, maximum particle size 10 μm): manufactured by Shin Nippon Rika Co., Ltd. (plasticizer)
Polyethylene glycol (average molecular weight 200) dibenzoate: manufactured by Shin Nippon Rika Co., Ltd. (Likaflow LA-100)
(Stabilizer)
Polycarbodiimide: Nisshinbo Co., Ltd. (carbodilite LA-1)

<Example 1>
Polylactic acid resin (100 parts by weight), organic nucleating agent A (1 part by weight), polyethylene glycol (average molecular weight 200) dibenzoate (5 parts by weight) and polycarbodiimide (1 part by weight) are dry blended to form a resin. A composition was obtained. The resin composition (dry blend) is melt-kneaded at 220 to 250 ° C., and when the acid component content becomes 1.0 equivalent / ton or less, it is extruded into water in a strand shape and cut with a pelletizer, Pellets of the resin composition (melt kneaded product) were obtained. Next, the pellets were dried in a vacuum dryer at 80 ° C. for 12 hours, and then a test piece having a thickness of 4 mm was molded with an injection molding machine set at a resin temperature of 235 ° C. and a mold temperature of 100 ° C. with a cooling time of 60 seconds. did. Table 1 below summarizes the moldability during molding of the test piece, the heat-resistant temperature, the relative crystallinity, and the strength retention of the test piece. Note that the organic nucleating agent A is completely dissolved in the molten polylactic acid resin when the test piece is manufactured, because the molten resin coming out from the nozzle tip of the heating cylinder of the injection molding machine is transparent. This was confirmed by visual observation.

<Examples 2 and 3>
A test piece was produced in the same manner as in Example 1 except that the resin composition shown in Table 1 was used. Table 1 below summarizes the moldability during molding of the test piece, the heat-resistant temperature, the relative crystallinity, and the strength retention of the test piece.
In any test piece production, the organic nucleating agent is completely dissolved in the molten polylactic acid resin because the molten resin coming out from the nozzle tip of the heating cylinder of the injection molding machine is transparent. It was confirmed by visual observation.

<Examples 4 and 5>
A test piece was prepared in the same manner as in Example 1 except that the resin composition shown in Table 1 was used and the resin temperature during injection molding was 195 ° C. Table 1 below summarizes the moldability during molding of the test piece, the heat-resistant temperature, the relative crystallinity, and the strength retention of the test piece.
In any test piece production, the organic nucleating agent is not completely dissolved in the molten polylactic acid resin, and the molten resin coming out from the nozzle tip of the heating cylinder of the injection molding machine is slightly cloudy. It was confirmed by visual observation.

<Comparative Example 1>
A test piece was prepared in the same manner as in Example 1 except that the amount of polyethylene glycol (average molecular weight 200) dibenzoate was changed from 5 parts by weight to 15 parts by weight. Table 1 below summarizes the moldability during molding of the test piece, the heat-resistant temperature, the relative crystallinity, and the strength retention of the test piece.

<Comparative Example 2>
Using only a polylactic acid resin, a test piece having a thickness of 4 mm was produced by an injection molding machine set at a mold temperature of 100 ° C. with a cooling time of 60 seconds. The mold releasability from the mold during molding was poor, and deformations such as protrusions were observed in the obtained test piece. The heat resistant temperature and strength retention of the test piece are summarized in Table 1 below.

<Comparative Example 3>
A test piece made of only a polylactic acid resin was produced in the same manner as in Comparative Example 2 except that the mold temperature was changed from 100 ° C. to 30 ° C. Table 1 below shows the moldability at the time of molding the test piece, the heat-resistant temperature and the strength retention of the test piece.

<Comparative example 4>
A test piece was produced according to the same method as in Example 1 except that polycarbodiimide was not used. Table 1 below shows the moldability at the time of molding the test piece, the heat-resistant temperature and the strength retention of the test piece.

  Since the resin composition of the present invention has a high crystallization rate, a molded product having high heat resistance can be obtained by a normal molding method. Further, while improving the hard and brittle property, the stability, particularly high temperature, Excellent stability under high humidity and excellent moldability, so chassis for vehicle parts, home appliances, gears, general goods, clothing, bags, fasteners such as fasteners and buttons, agricultural materials, It can be used as a molded product for building materials, civil engineering materials, tableware, toys, etc.

Claims (17)

  A resin composition comprising a polylactic acid resin, an organic nucleating agent, a plasticizer and a stabilizer, the resin composition comprising 0.1 to 10 parts by weight of a plasticizer with respect to 100 parts by weight of the polylactic acid resin.   The ratio of the structural unit consisting of L-lactic acid residues to the total structural units constituting the polylactic acid resin is 80 to 99.5 mol%, or the polylactic acid resin constitutes the polylactic acid resin The resin composition of Claim 1 whose ratio of the structural unit which consists of D-lactic acid residues with respect to all the structural units to perform is 80-99.5 mol%. The organic nucleating agent has the general formula (1)

[Wherein R ¹ represents a residue obtained by removing all carboxyl groups from trimesic acid. Three R ^{2 s} are the same or different and are a cyclohexyl group optionally having a linear or branched alkyl group having 1 to 4 carbon atoms, or a straight chain having 1 to 4 carbon atoms or Represents a branched alkyl group. ]
The resin composition of Claim 1 or 2 which is a trimesic acid triamide compound represented by these.   The resin composition according to claim 3, wherein the trimesic acid triamide compound is at least one selected from the group consisting of trimesic acid tricyclohexylamide and trimesic acid tri (2-methylcyclohexylamide).   The resin composition according to claim 3 or 4, wherein the trimesic acid triamide compound has a particle shape having an average particle size of 10 µm or less and a maximum particle size of 30 µm or less.   Resin obtained by melt-kneading polylactic acid resin, organic nucleating agent, plasticizer and stabilizer at a ratio of 0.1 to 10 parts by weight of plasticizer with respect to 100 parts by weight of polylactic acid resin The resin composition according to claim 3 or 4, wherein the organic nucleating agent is a trimesic acid triamide compound having a particle shape having an average particle size of 10 µm or less and a maximum particle size of 30 µm or less.   The resin composition according to any one of claims 1 to 6, wherein the content of the organic nucleating agent is 0.05 to 5 parts by weight with respect to 100 parts by weight of the polylactic acid resin.   The resin composition according to any one of claims 1 to 7, wherein the plasticizer is polyethylene glycol dibenzoate.   The resin composition according to any one of claims 1 to 8, wherein the stabilizer comprises a compound capable of undergoing a crosslinking reaction with a polylactic acid resin.   The resin composition according to claim 9, wherein the compound capable of undergoing a crosslinking reaction with the polylactic acid resin is a carbodiimide compound.   The resin composition according to any one of claims 1 to 10, wherein the content of the stabilizer is 0.2 to 10 parts by weight with respect to 100 parts by weight of the polylactic acid resin.   The resin composition of any one of Claims 1-11 whose glass transition temperature (Tg) is 40-70 degreeC.   The resin composition according to any one of claims 1 to 12, wherein the acid component content is 5 equivalents / ton or less.   The resin composition according to any one of claims 1 to 13, wherein the crystallization completion time is 300 seconds or less.   The molded object formed by shape | molding the resin composition of any one of Claims 1-14.   It is a method of manufacturing a molded object from the resin composition of any one of Claims 1-14, Comprising: This resin composition is temperature more than the melting temperature with respect to molten polylactic acid-type resin of an organic nucleating agent. The organic nucleating agent is kneaded until dissolved in the molten polylactic acid resin, and the organic nucleating agent is dissolved in the molten polylactic acid resin and subjected to a molding step. Body manufacturing method.   The method for producing a molded article according to claim 16, wherein the molding step is injection molding, extrusion molding, injection blow molding, injection extrusion blow molding, injection compression molding, extrusion blow molding, extrusion thermoform molding or melt spinning.