JP4654737B2 - Resin composition, molded article and method for producing molded article - Google Patents

Description

  The present invention relates to a resin composition composed of a polymer capable of having a crystal structure, and a molded article obtained by molding such a resin composition, and is particularly characterized by a nucleating agent for promoting crystallization of a biodegradable resin. It is what you have.

2. Description of the Related Art In recent years, the use of resin materials that have a so-called biodegradability that can be decomposed in a natural environment has attracted attention due to an increase in environmental awareness.
Unlike conventional general-purpose synthetic resins, biodegradable resins are produced from, for example, non-fossil fuels, so that there is no problem of resource depletion. It has advantages such as being able to contribute, being able to be produced from natural resources such as corn, and being able to suppress the amount of CO ₂ gas generation that is the cause of global warming overall. It is a material that is expected to receive more attention.
Among biodegradable resins, for example, aliphatic polyesters, particularly polylactic acid, has a high melting point (170 to 180 ° C.), and the material produced thereby can be made transparent. As a result, it is expected to be widely practical.

Such biodegradable resins include, for example, materials for agriculture, forestry and fisheries (films, planting pots, fishing lines, fish nets, etc.), civil engineering materials (water retention sheets, plant nets, etc.), packaging / container fields (soil, food, etc.) It is said that disposable products such as daily necessities, sanitary goods, and play goods are the main uses, but in the future, the use will be further expanded from the viewpoint of environmental protection. It is being considered.
For example, application to electric products and electronic products such as a television housing and a personal computer housing has been studied.
Considering applications such as housings and structural materials for electrical products, heat resistance of about 80 ° C. is generally required.

By the way, in recent years, in order to maintain high characteristics as a practical material, it is important to increase the crystallinity of the material.
Examples of the polymer having a crystal structure include polyolefin polymers such as polypropylene, polyester polymers such as polyethylene terephthalate, polyamide polymers, and the like.

However, polylactic acid, which is a typical biodegradable polyester, has poor heat resistance and has a glass transition temperature (Tg) of around 60 ° C. However, there is a problem in practical use that it is deformed.
Here, the practical heat resistance means that a rigidity (elastic modulus) in the vicinity of 80 ° C. is obtained at about 100 MPa.

In order to raise the heat resistance of biodegradable polyester, the method of adding inorganic fillers, such as talc and mica which have heat resistance, is mentioned, for example.
That is, by adding an inorganic filler having high heat resistance to the resin, the effect of improving and hardening the mechanical properties can be obtained.
However, it is difficult to ensure sufficient heat resistance in practical use only by adding an inorganic filler to the resin.

In view of this point, conventionally, there has been proposed a technique for improving the heat resistance of polylactic acid by performing a heat treatment during or after molding.
Polylactic acid is a material that can have a crystal structure, but it is a polymer that is difficult to crystallize. Therefore, if polylactic acid is molded in the same way as ordinary general-purpose resins, the molded product becomes amorphous. It is inferior in mechanical strength and is likely to cause thermal deformation.
In contrast, by performing heat treatment during or after molding, polylactic acid can be crystallized, and the heat resistance of the molded product can be improved.

However, such a crystallization method by heat treatment has a practical problem that a long time is required for crystallization.
For example, an injection molding process using a general-purpose resin is usually performed in a molding cycle of about 1 minute. However, in order to complete the crystallization of a molded product of polylactic acid through a heat treatment process in a mold, a considerable amount of time is required. It was confirmed that it takes time.
In addition, when crystallizing with polylactic acid alone without adding a substance that becomes a crystal nucleus of polylactic acid, the crystal nuclei are generated on the order of microns because the frequency of free generation of crystal nuclei is small. The crystal itself becomes a factor of light scattering and becomes cloudy, the transparency is lost, and the effectiveness in practical use is reduced.

With respect to polymers that can take a crystal structure, a technique of adding a nucleating agent has been studied in order to solve the various problems as described above, that is, to promote crystallization of a polymer that can take a crystal structure.
The nucleating agent is a primary crystal nucleus of the crystalline polymer and promotes crystal growth of the crystalline polymer. Also, in a broad sense, a nucleating agent is a substance that promotes crystallization of a crystalline polymer, that is, increases the crystallization rate of the polymer itself.
When the nucleating agent is added to the resin, the polymer crystals can be refined, and the rigidity can be improved or the transparency can be improved.
Further, when crystallization is performed during molding, there is also an advantage that the molding cycle can be shortened because the overall speed (time) of crystallization is increased.

The effect as described above can be seen in other crystalline resins.
For example, polypropylene (hereinafter also referred to as PP) has improved rigidity and transparency by adding a nucleating agent, and PP with improved physical properties has been put to practical use in many molded products.
As a nucleating agent in this case, for example, a sorbitol-based substance can be mentioned, and it is considered that a three-dimensional network formed by this nucleating agent acts effectively.
Also, a metal salt type nucleating agent has been put into practical use for PP.
Examples of metal salt type nucleating agents include hydroxy-di (t-butylbenzoate) aluminum, sodium bis (4-t-butylphenyl) phosphate, and sodium methylenebis (2,4-di-t-butylphenyl) phosphate. Examples include salts.

However, when talc is applied as a nucleating agent to a polyester such as polylactic acid, a sufficient effect cannot be obtained unless the amount added is several tens of percent. If the amount added is increased in this way, the resin composition becomes brittle. The problem of end up.
Moreover, if it is such an addition amount, the resin composition obtained will become white and the problem in the practical use that transparency will be lost will be produced.

As a nucleating agent applied to aliphatic polyester, for example, a sorbitol-based substance has been studied. This substance is effective as a crystallization nucleating agent in PP and has also been disclosed as a technique effective against polylactic acid (see, for example, Patent Document 1).
Other methods for promoting crystallization by adding a nucleating agent to polyester include, for example, aliphatic carboxylic acid amides, aliphatic carboxylates, aliphatic alcohols, and aliphatic carboxylic acids as transparent nucleating agents. A technique of adding at least one selected from a group of compounds consisting of acid esters and having a melting point of 40 to 300 ° C. has been proposed (for example, see Patent Document 2).
Further, for example, at least one selected from the group consisting of aliphatic polyesters and organic compounds having a melting point or softening point of 80 to 300 ° C. and a melting entropy of 10 to 100 cal / K / mol as a transparent nucleating agent Techniques for adding organic compounds (for example, see Patent Document 3 below), techniques for adding fatty acid esters having a specific structure as a clarifying agent to polylactic acid resins, and the like have been proposed (for example, Patent Documents below). 4).

JP-A-10-158369 JP-A-9-278991 JP-A-11-5849 Japanese Patent Laid-Open No. 11-116783

However, even when any of the nucleating agents disclosed in the above prior art is used, a practically sufficient crystallization promoting effect has not yet been realized, and the heat resistance of the produced molded product is insufficient practically. This is the current situation.
Moreover, a nucleating agent that can greatly accelerate the crystallization of polyester when combined with polyester has not yet been obtained.

  Therefore, in the present invention, in view of the conventional situation as described above, the crystallization of a polymer capable of taking a crystal structure is promoted, and it has practical heat resistance and mechanical strength, and further biodegradability. And a resin molded product obtained by molding the resin composition.

  In the present invention, a resin composition comprising at least a polymer capable of having a crystal structure and one or more amino acids, and a resin molded article using the same are provided.

  By including an amino acid in a polymer capable of taking a crystal structure, the amino acid functions as an effective nucleating agent, and the crystallization of the polymer is greatly promoted.

According to the present invention, crystallization of a polymer capable of forming a crystal structure with an amino acid functioning as a nucleating agent is promoted, and a resin composition exhibiting excellent rigidity, moldability and heat resistance can be provided.
In particular, when polylactic acid was applied as a polymer, a resin composition having transparency and excellent practical use was obtained.
Further, according to the present invention, when a resin molded product is molded with the resin composition, the degree of crystallinity of the polymer capable of taking a crystal structure in the resin composition is increased, so that excellent rigidity, moldability and heat resistance are obtained. It was possible to provide a resin molded product showing

The resin composition according to the present invention and a molded product using the same will be specifically described below.
The resin composition of the present invention comprises at least a polymer that can have a crystal structure and an amino acid that promotes crystallization of the polymer.

First, a polymer that can take a crystal structure will be described.
As the polymer, any conventionally known polymer can be applied as long as it has a property capable of taking a crystal structure.
What can take a crystal structure should just be what can take even a part of crystal structure, and does not need to be able to arrange all the molecular chains regularly. Furthermore, even if all the molecular chains are not regular, it is only necessary that some molecular chain segments can be oriented.

Examples of the polymer having a crystal structure include polyolefin polymers such as polypropylene, polyester polymers such as polyethylene terephthalate, polyamide polymers, and the like.
The polyester polymer (hereinafter simply referred to as “polyester”) is a high molecular compound having at least one ester bond, and any polymer can be used as long as it can take a crystal structure, and any known one can be applied.
The polyester capable of taking a crystal structure is preferably linear, but may be branched.

Moreover, as a suitable example of polyester that can take a crystal structure, it can be produced from natural resources that can be decomposed in nature without using petroleum resources, such as corn, and suppresses the emission of carbon dioxide. Examples include biodegradable polyesters that can contribute to prevention.
Examples of the biodegradable polyester include polyester resins that are metabolized by microorganisms, and aliphatic polyesters that are excellent in moldability, heat resistance, and impact resistance are particularly suitable.

Examples of the aliphatic polyesters include oxalic acid, polysuccinic acid, polyhydroxybutyric acid, polydiglycolic acid, polycaprolactone, polydioxanone, and polylactic acid aliphatic polyester.
Among these, polylactic acid-based aliphatic polyester is particularly preferable. Examples of polylactic acid-based aliphatic polyesters include polymers of oxyacids such as lactic acid, malic acid, and glycolic acid, and copolymers thereof, among which hydroxycarboxylic acid-based aliphatic polyesters are preferably used. Further, among the hydroxycarboxylic acid-based aliphatic polyesters, polylactic acid is most preferable.

Various biodegradable polyesters can be produced by a conventionally known method.
Specific examples include lactide method, polycondensation of polyhydric alcohol and polybasic acid, or intermolecular polycondensation of hydroxycarboxylic acid having a hydroxyl group and a carboxyl group in the molecule.

In particular, polylactic acid-based aliphatic polyesters can be generally produced by a ring-opening polymerization method of lactide which is a cyclic diester and a corresponding lactone, so-called lactide method. In addition to the lactide method, direct dehydration condensation method of lactic acid Can be produced.
Examples of the catalyst for producing the polylactic acid-based aliphatic polyester include metal compounds such as tin, antimony, zinc, titanium, iron, and aluminum. Tin-based catalysts and aluminum-based catalysts are preferable, and it is particularly preferable to use tin octylate and aluminum acetylacetonate.

In particular, poly L-lactic acid that can be prepared by lactide ring-opening polymerization is preferable among polylactic acid-based aliphatic polyesters. This is because poly-L-lactic acid is hydrolyzed to become L-lactic acid, and its safety has been confirmed.
However, in the present invention, the polylactic acid-based aliphatic polyester is not limited to the L-form, and the lactide used is not limited to the L-form.
As an example of polyester that can take a specific crystal structure, biodegradable polyester (product name: Lacia) manufactured by Mitsui Chemicals, Inc. can be applied.

The resin composition of the present invention may contain, as a resin component, polyester or other biodegradable resin that does not necessarily have a crystal structure, in addition to the polymer that can have the crystal structure.
For example, biodegradable resins include polysaccharide derivatives such as cellulose, starch, dextran or chitin, peptides such as collagen, casein, fibrin or gelatin, polyamino acids, polyvinyl alcohol, nylon 4 or nylon 2 / nylon 6 copolymers. Polyamides such as polyglycolic acid, polylactic acid, polysuccinic acid ester, polyoxalic acid ester, polyhydroxybutyric acid, butylene polydiglycolate, polycaprolactone or polydioxanone, which are known not to have a crystal structure .
These may be contained alone or a plurality of types may be mixed.

  That is, the biodegradable polymer to be applied is an organic material that is decomposed and assimilated by the action of the natural world or a living body, and conventionally known materials can be appropriately used as long as they are ideal materials suitable for the environment. .

  The biodegradable resin can be produced by a known method, but other known commercial products can also be applied. For example, Toyota Motor Corporation, trade name Rakuti, Mitsui Chemicals, trade name Lacia, or Cargill Dow Polymer LLC shares The product name, Nature Works, etc., are available.

The biodegradable polymer constituting the resin composition of the present invention may be only one of those exemplified above, or may be a combination of two or more.
When two or more types of biodegradable resins are contained, these resins may form a copolymer or may be in a mixed state.
Further, the resin composition may contain a resin other than the biodegradable resin described above.
Examples thereof include polylactic acid and polybutylene succinate with a reduced decomposition rate.

Next, an amino acid that is a nucleating agent that promotes crystallization of a polymer that can take a crystal structure will be described.
An amino acid is a compound having an amino group (—NH ₂ ) and a carboxyl group (—COOH) in the molecule.
In addition, imino acid can be similarly applied.

Specific examples of amino acids that are nucleating agents include glycine, alanine, and valine (the following formula (1)), leucine, isoleucine, serine, threonine, cysteine, and methionine (the following formula ( 2)), phenylglycine (following formula (3)), tryptophan, proline (following formula (4)), o-tyrosine (following formula (5)), glutamic acid, aspartic acid, glutamine, asparagine, lysine, arginine, histidine Is mentioned.
In addition, * in Formula (1)-(10) is an asymmetric carbon atom.

The various amino acids are classified as α-amino acids and have a structure in which a carboxyl group and an amino group are bonded to the same carbon atom.
The present invention is not limited to these, and various amino acids such as β-amino acids, γ-amino acids, and δ-amino acids can also be applied.
Depending on the ratio of the number of carboxyl groups and amino groups contained in the molecule, monoamino monocarboxylic acid (neutral amino acid), monoamino dicarboxylic acid (acidic amino acid), diamino monocarboxylic acid (basic amino acid) Although these are classified, the same applies to these.
Among the above-mentioned various amino acids, α-amino acid is a material with excellent biodegradability, and in the resin composition finally obtained, excellent transparency can be ensured, so a practically excellent composition as a material. It has the advantage that a product is obtained.

In addition, since many α-amino acids have asymmetric carbon atoms, optical isomers exist.
Most of the constituents of proteins contained in living organisms are L-form α-amino acids.
In general, an amino acid often means an L-α-amino acid constituting a protein of a living body, but in the present invention, the amino acid is not limited to such an amino acid, and an amino group and a carboxyl group are formed in the molecule. You can apply what you have.
Various forms of amino acid optical isomers can also be applied.

In addition to the functional group consisting of at least an amino group and a carboxyl group, the amino acid has an aliphatic or aromatic structure.
Aliphatic or aromatic structures can be considered as substituents to the basic amino acid structure. A functional group or a substituent may be further introduced into the substituent.
Specifically, for example, a halogen atom (for example, fluorine, chlorine, bromine or iodine), nitro group, cyano group, hydroxy group, thiol group, sulfo group, sulfino group, mercapto group, phosphono group, for example, linear or branched Alkyl groups (for example, methyl group, ethyl group, isopropyl group, n-propyl group, n-butyl group, isobutyl group, second butyl group, third butyl group, pentyl group, hexyl group, heptyl group, octyl group, Nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group or eicosyl group, etc.), hydroxyalkyl group (for example, hydroxymethyl group, hydroxyethyl group, 1-hydroxyisopropyl group, 1-hydroxy-n-propyl group 2-hydroxy-n-butyl group or 1-hydroxy-isobutyl group), halogenoalkyl group (for example, chloromethyl, dichloromethyl, trichloromethyl, fluoromethyl, difluoromethyl, trifluoromethyl, 2-bromoethyl, 2,2, 2-trifluoroethyl, pentafluoroethyl, 3,3,3-trifluoropropyl, 4,4,4-trifluorobutyl, 5,5,5-trifluoropentyl, 6,6,6-trifluorohexyl, etc. ), A cycloalkyl group (such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl or cycloheptyl), an alkenyl group (such as vinyl, crotyl, 2-pentenyl or 3-hexenyl), a cycloalkenyl group (such as 2-cyclopentenyl, 2 -Cyclohexenyl, 2- Clopentenylmethyl or 2-cyclohexenylmethyl), alkynyl groups (eg ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-pentynyl or 3-hexynyl), oxo groups, thioxo groups, amidino groups, imino groups Group, alkylenedioxy group (eg methylenedioxy or ethylenedioxy), aromatic monocyclic or aromatic condensed cyclic hydrocarbon group such as phenyl or biphenyl, bridged ring such as 1-adamantyl group or 2-norbornanyl Aromatic hydrocarbon groups such as formula hydrocarbon groups, alkoxy groups (eg methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, neopentyloxy or hexyloxy), alkylthio Groups (eg methylthio) , Ethylthio, propylthio, isopropylthio, butylthio, isobutylthio, pentylthio or hexylthio), carboxyl group, alkanoyl group (eg formyl; acetyl, propionyl, butyryl or isobutyryl etc.), alkanoyloxy group (eg formyloxy; acetyloxy, propionyl) Alkyl-carbonyloxy groups such as oxy, butyryloxy or isobutyryloxy), alkoxycarbonyl groups (eg methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl or butoxycarbonyl etc.), aralkyloxycarbonyl groups (eg benzyloxycarbonyl etc.), thio A carbamoyl group, an alkylsulfinyl group (such as methylsulfinyl or ethylsulfinyl), an alkylsulfonyl group ( For example, methylsulfonyl, ethylsulfonyl or butylsulfonyl), sulfamoyl group, monoalkylsulfamoyl group (for example, methylsulfamoyl or ethylsulfamoyl), dialkylsulfamoyl group (for example, dimethylsulfamoyl or diethylsulfamoyl) Moyl etc.), arylsulfamoyl groups (eg phenylsulfamoyl or naphthylsulfamoyl etc.), aryl groups (eg phenyl or naphthyl etc.), aryloxy groups (eg phenyloxy or naphthyloxy etc.), arylthio groups (eg Phenylthio or naphthylthio etc.), arylsulfinyl group (eg phenylsulfinyl or naphthylsulfinyl etc.), arylsulfonyl group (eg phenylsulfonyl or naphthylsulfonyl etc.), aryl A carbonyl group (such as benzoyl or naphthoyl), an arylcarbonyloxy group (such as benzoyloxy or naphthoyloxy), an alkylcarbonylamino group which may be halogenated (such as acetylamino or trifluoroacetylamino), a substituent A carbamoyl group (for example, a group represented by the formula -CONR1R2). However, in the formula, R 1 and R 2 are each a hydrogen atom, a hydrocarbon group which may have a substituent, or a heterocyclic group which may have a substituent. R1 and R2 may form a ring together with the adjacent nitrogen atom. ), An amino group which may have a substituent (for example, amino, alkylamino, tetrahydropyrrole, piperazine, piperidine, morpholine, thiomorpholine, pyrrole or imidazole), an ureido group which may have a substituent ( For example, a group represented by the chemical formula —NHCONR 1 R 2, where R 1 and R 2 are each a hydrogen atom, a hydrocarbon group which may have a substituent, or a heterocyclic group which may have a substituent. R1 and R2 may form a ring together with the adjacent nitrogen atom), and a carboxamide group (for example, a group represented by the formula -NR1COR2, wherein R1 And R2 are each a hydrogen atom, a hydrocarbon group which may have a substituent, or a heterocyclic group which may have a substituent, and R1 and R2 are adjacent to each other. May form a ring together with that nitrogen atom.), A group represented which may have a substituent sulfonamide group (e.g., by chemical formula -NR1SO ₂ R2. In the formula, each of R1 and R2 a hydrogen atom, A hydrocarbon group which may have a substituent, or a heterocyclic group which may have a substituent, and R 1 and R 2 may form a ring together with the adjacent nitrogen atom). A hydroxyl group or a mercapto group which may have a substituent, a heterocyclic group which may have a substituent (for example, as an atom (ring atom) constituting a ring system, in addition to a carbon atom, an oxygen atom, a sulfur atom, and Aromatic heterocyclic groups containing at least one hetero atom selected from nitrogen atoms, etc., specifically pyridyl, furyl, thiazolyl, saturated or unsaturated aliphatic heterocyclic groups, etc.), or substitution thereof Group is chemically acceptable Substituent or the like is substituted Ri and the like.

The amino acid applied in the present invention preferably has an aromatic substituent.
The aromatic substituent may be a heterocyclic ring.
Specifically, tryptophan (following formula (6)), phenylalanine (following formula (7)), etc. are mentioned. Phenyl glycine in which a phenyl group is introduced into glycine can also be applied.
An amino acid in which a substituent is further introduced into the aromatic substituent is also effective in the present invention.
Specific examples include tyrosine in which a hydroxyl group is introduced at the para position of the phenyl group of phenylalanine. M-tyrosine having a hydroxyl group introduced at the meta position (the following formula (8)) can also be applied, and o-tyrosine having a hydroxyl group introduced at the ortho position can also be applied.
Moreover, p-chloro-phenylalanine (following formula (9)) in which chlorine is introduced into the phenyl group of phenylalanine is also applicable. The introduction position of chlorine is not limited to the para position, and may be either the meta position or the ortho position.
In addition, p-hydroxyphenylglycine (the following formula (10)) can also be applied. This can be applied to either L-form or D-form, or a mixture thereof, or a racemate.

As the amino acid applied in the present invention, commercially available materials can be applied, and the amino acid may be synthesized by a conventionally known chemical synthesis method.
Examples of commercially available amino acids include those sold by Ajinomoto Takara Corporation, Kyowa Hakko Co., Ltd.
Moreover, you may synthesize | combine an amino acid by amino acid fermentation which is a biochemical manufacturing method.
Amino acid fermentation is aerobic fermentation using amino acids as products.
In addition, lysine fermentation, ornithine fermentation and the like are known.
Unlike chemical synthesis, amino acid fermentation has the advantage that only one of the enantiomers is synthesized.
An amino acid may be obtained by known amino acid fermentation, and the amino acid may be chemically modified to introduce the aforementioned substituent.

The amino acid applied in the present invention is preferably in the form of powder under room temperature conditions.
Furthermore, it is preferable that the powder particles are amino acid crystals.
The particle size of the amino acid crystal particles is preferably 10 μm or less, and more preferably 1 μm or less.
Further, in the resin composition, the mixing ratio of the amino acid in the composition is preferably in the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the polymer capable of taking a crystal structure. It is desirable to set it in the range of 0.01 parts by weight to 1 part by weight.
The particle size and content of amino acid crystal particles influence each other, and it is necessary to determine the particle size and content so as to be effective as a nucleating agent that promotes crystallization of the polymer.

Hereinafter, the content of the amino acid serving as a nucleating agent and the optimum range of the particle diameter will be described with respect to a polymer that can take a crystal structure.
When there are two resin compositions here and the contents of the nucleating agent are substantially the same, the smaller the nucleating agent particle size, the higher the crystallization effect. This is because the smaller the particle size of the nucleating agent, the larger the number of nucleating agent particles in the resin composition, and the number of nuclei increases to make the crystals finer.
In this case, when the particle size of the nucleating agent is halved, the volume of one nucleating agent particle is ８, so the number of particles is 8 times. That is, if the particle size is halved, the same effect can be expected even if the addition amount is 1/8.
In addition, when the nucleating agent of the same particle diameter is contained, it is clear that the effect as a nucleating agent becomes higher when the addition amount is increased.

Based on the above, the particle size of the nucleating agent and the optimum range of the content will be described in detail.
Here, a simple model is considered and the following is assumed.
(1) For simplification of calculation, the density of the polymer capable of taking a crystal structure and the density of the nucleating agent are substantially the same.
(2) The nucleating agent particles are not aggregated at all and are completely uniformly dispersed in the resin composition, that is, the nucleating agent is present in a cubic lattice form in the composition.
(3) The polymer crystal that can take a crystal structure is a cube.
(4) Similarly, the nucleating agent particles are also cubic.
(5) One resin crystal is generated from one nucleating agent.
(6) Here, the polymer capable of taking a crystal structure is specifically polylactic acid.
Based on the above assumption, the crystal size of polylactic acid can be determined by volume calculation from the content (%) of the nucleating agent and the particle size of the nucleating agent.
The results are shown in Table 1 below.

Specifically, when polylactic acid, which is a polymer that can take a crystal structure, contains a nucleating agent, for example, the size (length of one side) of the nucleating agent is 0.05 μm, and the addition amount of the nucleating agent is 0.5. % (0.005) and the size of the polylactic acid crystal is X μm, X ³ × 0.005 = 0.05 ³ , so the polylactic acid crystal size is calculated to be 0.29 μm. .
When the nucleating agent is actually contained in the resin molded product, the particle size and content of the nucleating agent may be selected so that the required crystal size is obtained according to the purpose with reference to the volume calculation as described above. .

For example, let us consider a case where the polymer that can take a crystal structure is polylactic acid, the crystallization temperature is 120 ° C., and the crystallization time is about 1 minute or less.
The growth rate (dr / dt) of the spherulite radius (r) of polylactic acid at 120 ° C. was confirmed to be about 2 μm / min.
Here, specifically, when the growth rate of the radius of the spherulite is substantially the same as the growth rate of the cubic-shaped crystal assumed above, the time required for crystallization can be calculated. The results are shown in Table 2 below.

For example, when the particle size of the nucleating agent is 1 μm and the addition amount is 1%, the crystallization time is calculated as 70 seconds.
In the resin composition, it was confirmed that the nucleating agent was preferably contained in an amount of 0.001 to 10 parts by weight with respect to 100 parts by weight of the polymer capable of taking a crystal structure.
When the content of the nucleating agent with respect to 100 parts by mass of the polymer is less than 0.001 part by mass, the content of the nucleating agent is too small and the crystallization of the polymer is promoted by containing the nucleating agent. Becomes difficult.
On the other hand, when the content of the nucleating agent is more than 50 parts by mass with respect to 100 parts by mass of the polymer, the content of the nucleating agent is too much, and mechanical properties such as rigidity of the finally obtained resin composition deteriorate. There is a problem that it ends up.
Therefore, by adding the nucleating agent in the range of 0.001 to 10 parts by mass with respect to 100 parts by mass of the polymer, crystallization of the polymer can be promoted and deterioration of the mechanical properties of the resin composition can be prevented. Was confirmed.

For example, when polylactic acid contains 10 parts by mass of a nucleating agent having a particle size of 10 μm and is crystallized under a temperature condition of 120 ° C., the time required for crystallization is about 5 minutes from Table 2 above. .
That is, when polylactic acid is crystallized in a mold having a mold temperature set to about 120 ° C. with an injection molding machine, the time required for crystallization is estimated to be about 5 minutes.
On the other hand, the resin stays in a molten state at a high temperature in the cylinder of the molding machine, but polylactic acid may be thermally decomposed, so the residence time in the mold is set to 5 minutes or less. Therefore, the inclusion of 10 parts by mass of a nucleating agent having a particle size of 10 μm with respect to polylactic acid is a boundary condition that satisfies the optimum range of the nucleating agent content described above.

In the nucleating agent, if the particle size is too small, aggregation occurs, the dispersibility in the polymer capable of forming a crystal structure deteriorates, and it is unevenly distributed in the polymer, so that the substantial particle size may increase. .
In view of this point, the particle size of the nucleating agent is preferably about 0.5 μm or less, whereby aggregation is suppressed and good dispersibility in the resin can be ensured.
When polylactic acid is crystallized using a nucleating agent having a particle size of 0.5 μm, the lower limit of the content of the nucleating agent is set as the lower limit of the nucleating agent content in order to keep the time required for crystallization from about 2 minutes as shown in Table 2 above. It turns out that it is 0.001 mass part with respect to 100 mass parts of lactic acid.
Depending on the kind of the nucleating agent, even if the particle size is smaller than 0.5 μm, the aggregation may be reduced. In this case, the content can be further reduced. Or when using a nucleating agent of a smaller size, dispersion | distribution of the nucleating agent to resin can be improved by using some aggregation preventing agent, and content can also be decreased.

In order to provide practical versatility with respect to the intended resin composition, so-called spherulites of the polymer must be smaller than the wavelength of visible light in order to ensure transparency.
For this reason, the size of the nucleating agent particles in the polymer must be smaller than the wavelength of visible light.
Here, it is assumed that the wavelength of visible light is 1 μm, and the particle size of the nucleating agent is at least 0.5 μm or less in the range of the particle size of the nucleating agent and the addition amount of the nucleating agent described in Table 1. The amount of agent added must be 10% or more.
In order to sufficiently secure the transparency of the resin composition, it is desirable that the particle size of the nucleating agent is 0.15 μm or less and the addition amount of the nucleating agent is 1% or more. More desirably, the particle size of the nucleating agent is 0.05 μm or less, and the addition amount of the nucleating agent is preferably 1% or more.
More desirably, the particle size of the nucleating agent is preferably 0.01 μm or less, and the addition amount of the nucleating agent is preferably 0.1% or more.

In the above, “transparency” is determined to have practical transparency even in a slightly cloudy state such as so-called glass or amorphous polymer polystyrene. .
Haze is known as an indicator of turbidity. The measuring method is defined by Japanese Industrial Standard JIS K 7105 and the like.
Specifically, the transparency is expressed by the haze value of a 1 mm thick plate made of resin. The smaller the haze value, the higher the transparency.
For example, a known resin composition in which a sorbitol-based substance is added to polypropylene has high transparency, and a container made of the polypropylene resin composition has transparency enough to recognize the contents of food or the like contained therein. In this case, the haze value is about 30%.
In addition, also in the resin composition of this invention, a haze value can be made small and transparency can be improved by optimizing the particle size of the amino acid added with respect to the polymer which can take a crystal structure.

By the way, it is practically difficult to configure the powder of the nucleating agent particles only with particles having a single particle size. That is, the particle size of the nucleating agent particles has a certain distribution. That is, particles having a larger particle size are also included.
However, if particles having a wavelength larger than the wavelength of light are contained in the polymer and their refractive indexes are different from each other, the particles become optical foreign matters and the transparency is lowered.
At this time, it is more desirable that the refractive index of the polymer capable of forming a crystal structure is as close as possible to the refractive index of the amino acid. Specifically, it is desirable that they are within about ± 0.05 of each other. This prevents the amino acid particles from becoming an optical foreign material to the polymer.

The optimal range of nucleating agent content and particle size explained above is a calculation estimate based on a number of assumptions. Actually, the nucleating agent aggregates or does not disperse substantially uniformly in the polymer. The particle size of the nucleating agent is distributed.
For this reason, it is thought that it is necessary to increase the content of the nucleating agent relative to the polymer. However, the content of the nucleating agent is preferably about 1% in consideration of a decrease in mechanical properties of the resin composition.
Therefore, in a resin composition, the effect by a nucleating agent can further be heightened by making the addition amount of a nucleating agent into the range of 0.01 mass part-1 mass part with respect to 100 mass parts of polymers.

A conventionally known method can be applied to the method of processing the amino acid as the nucleating agent into the above-described particle size.
For example, either a mechanical grinding method or a chemical method may be used.
Examples of the mechanical pulverization method include a ball mill method and freeze pulverization. Alternatively, a pulverization method called a jet mill or an air hammer can also be applied.
These methods are methods in which particles are collided with airflow from two directions and pulverized.
Chemical methods include recrystallization and spray drying.
Amino acids can be dissolved in a predetermined solvent and fine particles can be obtained by recrystallization.
That is, by utilizing the difference in solubility depending on the temperature, cooling a hot amino acid saturated solution, evaporating and concentrating the solvent, or adding another suitable solvent to the solution to reduce the solubility, etc. Fine particles are obtained.
Alternatively, spray drying in which fine particles are obtained by spraying a solution in which an amino acid is dissolved to vaporize a solvent can also be applied.
In addition, any conventionally known fine particle manufacturing method can be applied.

If the amino acid particles are made smaller by micronization, aggregation tends to occur.
In the stage before addition to the polymer capable of taking a crystal structure, it is not considered in the present invention whether the amino acid powder, that is, the particles are aggregated, little aggregated or not aggregated. When the resin composition is added to form a resin composition, it is not preferable that the amino acid particles aggregate in the polymer as described above, and it is desirable that the resin composition be uniformly dispersed. In order to achieve this state, it is desirable to suppress aggregation of amino acid particles in the stage before addition to the polymer.
As a method for suppressing aggregation, a conventionally known method can be used.
For example, a method of adding an aggregation inhibitor to an amino acid before the atomization processing, adding during the processing, or adding after the processing.
As the anti-aggregation agent, conventionally known materials can be applied, and examples thereof include low molecular weight polyethylene and nonionic surfactants.

Although uniform dispersion of amino acids in the polymer may be achieved only by adding an anti-aggregation agent, the method of mixing the polymer and amino acids is equally important.
The mixing method will be described later.

In the resin composition, for example, an inorganic filler may be added in addition to the polymer and amino acid described above. Thereby, heat resistance, rigidity, etc. are improved.
As the inorganic filler, known materials can be applied, and examples thereof include talc, alumina, silica, magnesia, mica, kaolin, and the like, and any one of them may be used, or a plurality of types may be combined.
When polylactic acid or polypropylene is applied as a polymer that can have a crystal structure, talc, an inorganic filler, has the effect of promoting crystallization of the polymer without canceling the action of each other even when used in combination with an amino acid. Therefore, it is a preferable material.
Here, the inorganic filler is preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the polymer that can take a crystal structure.
If the addition amount of the inorganic filler is less than 1 part by mass with respect to 100 parts by mass of the polymer, the addition amount of the inorganic filler is too small, and the effect of improving the heat resistance and rigidity of the resin composition cannot be obtained sufficiently.
On the other hand, when the addition amount of the inorganic filler is more than 50 parts by mass with respect to 100 parts by mass of the polymer, the addition amount of the inorganic filler is too much, and the resin composition finally obtained may be weakened.
Therefore, adding an inorganic filler in the range of 1 to 50 parts by mass with respect to 100 parts by mass of the polymer can increase the heat resistance and rigidity of the resin composition and prevent the resin composition from becoming brittle. .

When the resin composition of the present invention is molded into a product, and the product is used for a short period of time and discarded, it is desirable that the polymer is easily decomposed.
For example, in recent years, it has been proposed to use a degradable polymer, that is, a biodegradable polyester, for applications such as shopping bags that have a short use period.
Further, for this purpose, research and development for accelerating the degradation of the polymer has been carried out. In the case of polyester, a substance that accelerates the hydrolysis may be added.
When the polymer that can take a crystal structure is a polyester, an amino acid may promote the hydrolysis of the polymer, and in this case, the resin composition of the present invention can be said to be suitable for applications with a short use period as described above. .
Of course, you may add the substance which accelerates | stimulates decomposition | disassembly of another polymer.

On the other hand, when the resin composition of the present invention is molded into a product and the product is used for a relatively long period of time, for example, when used for a casing of an electrical product, the polymer is not significantly decomposed during the period of use. It is good to make it.
In order to achieve this object, a substance that suppresses the decomposition of the polymer is added as necessary.
When the polymer capable of taking a crystal structure is polyester, it is preferable to add, for example, a hydrolysis inhibitor in addition to the polyester and amino acid described above.
Thereby, in the resin composition of this invention, hydrolysis of polyester is suppressed and the long-term reliability in use of a molded article can be improved.

The hydrolysis inhibitor is not particularly limited as long as it is a material that can suppress hydrolysis of polyester, particularly biodegradable resin. For example, it is reactive with active hydrogen in the biodegradable resin. And the like.
By adding such a compound as a hydrolysis inhibitor, the amount of active hydrogen in the biodegradable resin is reduced in the resin composition, and the active hydrogen hydrolyzes the polymer chain constituting the biodegradable resin catalytically. Can be prevented.
The active hydrogen here means hydrogen in a bond (N—H bond or O—H bond) of oxygen, nitrogen or the like and hydrogen, and this active hydrogen is a bond of carbon and hydrogen (C—H). Reactivity is higher than hydrogen in bond).
Specifically, for example, hydrogen in a carboxyl group (—COOH), a hydroxyl group (—OH), an amino group (—NH ₂ ), an amide bond (—NHCO—) or the like in the biodegradable resin is an active hydrogen.

As a hydrolysis inhibitor, a carbodiimide compound, an isocyanate compound, an oxazoline type compound etc. are mentioned, for example, These 1 type may be used and may be used in combination of multiple types.
In particular, a carbodiimide compound is a suitable material because it can be easily melt-kneaded with a biodegradable resin and a hydrolysis inhibiting effect can be obtained by adding a small amount.

The carbodiimide compound used as a hydrolysis inhibitor is a compound having one or more carbodiimide groups in the molecule, and includes a polycarbodiimide compound and the like.
Examples of the monocarbodiimide compound contained in this carbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, naphthylcarbodiimide, and among them, it is particularly easily industrially available. Dicyclohexylcarbodiimide, diisopropylcarbodiimide and the like are preferable.

  Examples of the isocyanate compound that serves as a hydrolysis inhibitor include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and 2,4 ′. -Diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4 , 4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecame Range isocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4 ' -Dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, etc. are mentioned.

  Examples of the oxazoline compound that serves as a hydrolysis inhibitor include 2,2′-o-phenylenebis (2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), and 2,2′-p-. Phenylenebis (2-oxazoline), 2,2′-p-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2 ′ -P-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'-ethylenebis (2- Oxazoline), 2,2'-tetramethylenebis (2-oxazoline), 2,2'-hexamethylenebis (2-oxazoline), 2,2'-octamethylenebis (2-oxazoline), 2 2'-ethylene bis (4-methyl-2-oxazoline), 2,2'-diphenylenebis (2-oxazoline).

The said hydrolysis inhibitor can be easily manufactured in accordance with a well-known method, and a commercial item can be used suitably.
In the hydrolysis inhibitor, since the biodegradation rate of the resin composition can be adjusted depending on the type and addition amount, the type and addition amount to be added may be determined according to the target product.
Specifically, the addition amount of the hydrolysis inhibitor is about 5% by mass or less, preferably about 1% by mass or less with respect to the total mass of the resin composition.

  In the resin composition of the present invention, for example, an antioxidant, a light stabilizer, an ultraviolet absorber, a pigment, a colorant, an antistatic agent, and a release agent, as long as the above-described nucleating agent does not significantly prevent crystallization. A fragrance, a lubricant, a flame retardant, a filler, an antibacterial and antifungal agent and the like can be added as necessary.

The resin composition of this invention can be manufactured by mixing the polymer which can take the crystal structure mentioned above, the amino acid used as the nucleating agent mentioned above, and the other material mentioned above.
Examples of the production method include a method in which a raw material polymer is mixed with a nucleating agent, an inorganic filler, a hydrolysis inhibitor, and the like and melt-kneaded using an extruder.
As another method, for example, it can be produced by a solution method or the like.
The solution method is a method in which an arbitrary solvent capable of dispersing and dissolving each component is used, and each component and solvent as raw materials are well stirred to form a slurry, and the solvent is removed by a known method such as drying. In addition, as a method of manufacturing a resin composition, it is not restrict | limited to these methods, The conventionally well-known methods other than these can also be used.

That is, in the resin composition, it is important that the compound serving as the nucleating agent is finely dispersed substantially uniformly in the polymer capable of taking a crystal structure. In order to disperse substantially uniformly, a conventionally known method may be used. For example, a method of dispersing and coloring a pigment in a resin, a method of using three rolls, a method of repeating simple heat-kneading a plurality of times, and the like can be mentioned.
Specifically, in order to disperse the compound serving as the nucleating agent in the polymer substantially uniformly, first, pellets made of a polymer capable of taking a crystal structure such as polylactic acid are dried under reduced pressure at 60 ° C. for 5 hours, for example.
Next, a predetermined amount of the polymer pellet and the compound serving as the nucleating agent are weighed and mixed with a mixer or the like.
Next, the mixture is heated and kneaded using, for example, a twin-screw kneader, and after the heating and kneading, the kneaded product is cut into pellets and dried with hot air.
As described above, it is possible to obtain a resin composition in which a compound serving as a nucleating agent is dispersed substantially uniformly in a polymer.
It should be noted that pellets made of a polymer having a crystal structure such as polylactic acid are not limited to drying under reduced pressure as described above, and for example, hot air drying at a temperature of 80 ° C. for 12 hours may be performed. It is preferable to perform drying.

In the resin composition mentioned above, it becomes the resin molded product which consists of a polymer and amino acid which can take a crystal structure by attaching | subjecting to a heating process and a filling holding process.
The heating process performed when producing a resin molded product from the resin composition may be any process as long as the resin composition can be heated and melted.
Examples of the heating means used in the heating step include known means using a heater or the like.
The heating temperature is usually about + 10 ° C. to + 50 ° C. of the melting point of the resin composition, and preferably about + 15 ° C. to + 30 ° C. higher than the melting point of the resin composition.
The melting point is a value measured by a differential scanning calorimeter (DSC) or the like.
Specifically, when the melting point is determined, for example, when the polymer capable of taking a crystal structure is polylactic acid, 3 to 4 mg of the resin composition is cut out, placed in an aluminum pan, used as a sample, and the sample is heated to 200 ° C. once. Then, the temperature is decreased at a rate of 50 ° C./min and cooled to 0 ° C., and then DSC measurement is performed while the temperature is increased at a rate of temperature increase of 20 ° C./min. Calculated as temperature.

A conventionally well-known process can be applied to the filling and holding process as long as the melt of the resin composition after the heating process is filled and held in the mold.
The mold may be any mold as long as it is kept at a temperature within a temperature range of about −50 to + 30 ° C. of the crystallization temperature of the resin composition. There is no particular limitation.
The mold heat retaining means may be a known means, and examples of the heat retaining means include a means using a heater and a thermostat.

In producing a resin molded product from the resin composition, the temperature of the mold is usually about -50 of the crystallization temperature of the resin composition from the viewpoint of crystallization of the resin composition and prevention of thermal deformation of the molded product. Within the temperature range of ˜ + 30 ° C., preferably about 90-140 ° C.
As described above, the crystallization temperature can be measured by DSC measurement.
Specifically, when the crystallization temperature is determined, for example, when the polymer capable of taking a crystal structure is polylactic acid, 3 to 4 mg of the resin composition is cut out, put into an aluminum pan, and used as a sample. The temperature of the exothermic peak near 120 ° C. is obtained, for example, by performing DSC measurement while cooling to 0 ° C. at 20 ° C./min.

When the resin composition is composed of a plurality of types of polymers, a plurality of endothermic peaks and a plurality of exothermic peaks due to their origin may be measured in DSC measurement.
In this case, the melting point as the resin composition is the endothermic peak temperature derived from the main one of those polymers (the polymer with the highest content), and similarly the crystallization temperature is the exothermic peak temperature derived from the main polymer. And
In the filling and holding step, the melt of the resin composition is filled into the mold, and the melt of the resin composition is higher than the heat retention temperature of the mold, but approaches the heat retention temperature as time passes.
The filling means may be any means as long as the mold can be filled with the melt of the resin composition, and may be a known means.
For example, a means for injecting a melt into a mold by pressure can be used.
The cooling means may be any means as long as it can cool the melt of the resin composition, and known means can be applied.
As the cooling method, a known method can be applied as long as the melt of the resin composition can be cooled, and the cooling time is not particularly limited. Rapid cooling or slow cooling may be used.
Examples of the cooling step include a cooling means or a rapid cooling means using water, ice, ice water, dry ice, liquid nitrogen, or the like.

From the viewpoint of crystallization and productivity of the resin composition, the filling and holding time is more preferably about 10 seconds to 4 minutes, and most preferably about 20 seconds to 1 minute.
Then, as soon as the crystallization of the resin composition is completed, the molded product is removed from the mold.
Further, the molded product may be taken out from the mold even when crystallization is in progress.
This is because if the crystallization proceeds to some extent, the elastic modulus is improved, and the molded product of the resin composition may be taken out of the mold without deformation. At this time, crystallization of the molded product after the mold release further proceeds due to the residual heat, and the crystallization is almost saturated before being cooled to room temperature.

  After the filling and holding step, the temperature of the molded product when taking out the molded product from the mold is preferably as low as possible. As a means for lowering the temperature of the molded product, for example, a means for spraying cold air on the molded product when the mold is opened may be mentioned. Thus, the deformation | transformation risk of a molded article is improved by making the temperature of a molded article low.

Examples of the method for producing a resin molded product from the resin composition include casting method, compression method, transfer method, injection method, extrusion method, inflation method, calendering method, blowing method, vacuum method, laminating method, spraying method. Known molding methods such as the up method, the foaming method, the matched die method, and the SMC method can be applied.
When forming a resin molded product by such a molding method, it is preferable to use a known molding machine such as an injection molding machine.

Next, a method for producing a resin molded product from the resin composition will be described more specifically.
First, the resin composition is heated and melted at a temperature about +15 to + 30 ° C. higher than the melting point of the resin composition using a known injection molding machine.
Next, the melt of the resin composition is injected into a mold kept at a temperature in the temperature range of −50 to + 30 ° C. of the crystallization temperature of the resin composition.
Next, after injection, pressure is continuously applied to the melt in the mold as desired to compensate for so-called “sinks”.
Then release the pressure and let it stand. This standing time is called normal cooling time. During this holding time, heat is gradually taken away from the resin to the mold, and the temperature of the resin in the mold gradually decreases.
Therefore, in actuality, the holding time may be included in the cooling time.
Here, the standing time after releasing the holding pressure is referred to as cooling.
The injection pressure speed, injection pressure, injection time, holding pressure, holding time, etc. are appropriately set depending on the type of resin of the resin composition, the shape of the mold, and the like.
The cooling time may be a cooling time sufficient for the crystallization of the resin molded into the mold shape to be almost saturated, and is usually about 1 minute or less, preferably about 20 seconds to 1 minute.
In addition, a polymer that can take a crystal structure by filling and holding a melt of the resin composition in a mold kept at a temperature in the temperature range of −50 to + 30 ° C. of the crystallization temperature of the resin composition is molded. Can be rapidly crystallized. As a result, the molding cycle can be shortened, the productivity can be improved, and the yield can be improved.

The above description focuses on crystallizing the resin at the time of molding. However, the other two problems can be solved, and these problems will be described in more detail below.
Normally, the temperature of the mold is kept at a temperature equal to or lower than the Tg of the resin. When the resin is injected into the mold at such a temperature, the heat of the injected resin is quickly taken away into the mold, It becomes difficult to flow in the mold. For this reason, a flow mark is generated in the molded product, and the weld becomes very conspicuous.
Also, since the resin does not flow easily, when molding with a complicated mold, the number of gates must be increased to ensure that the resin is filled into the mold.
For this reason, runners are generated by the number of gates, and the resin is wasted correspondingly.
On the other hand, the mold temperature in the above method is higher than the mold temperature of the prior art.
Therefore, the method of removing heat from the resin injected into the mold is smaller than that of the prior art, and the flowability of the resin in the mold is better than that of the prior art.
For this reason, problems of flow marks and welds are less likely to occur.
In addition, the number of gates can be reduced as compared with the prior art, and less resin is wasted on the runner.
In addition, the method of manufacturing the resin molded product from the resin composition is not limited to the above-described method, and the mold may be molded at a temperature lower than the temperature according to a normal method.
For example, when the polymer capable of taking a crystal structure is polylactic acid, it may be molded by a usual method such as setting the mold temperature of Tg of 60 ° C. or lower to 50 ° C., for example.
In this case, in order to ensure heat resistance, it is necessary to crystallize the polymer by heat treatment after molding. However, in the resin composition, crystallization can be promoted by a nucleating agent, so that the conventional resin composition is crystallized. The heat treatment time required for this is shorter and the yield can be improved.
In addition, when it is not necessary to focus on crystallization of the polymer which can take a crystal structure, it is not necessary to heat-process.

The resin composition described above can be widely used for various molded articles.
In addition, the resin molded product according to the present invention is excellent in rigidity because of the high crystallinity of the resin composition, and can be further improved in transparency, so it is suitable for use in products with high demands such as rigidity and transparency. It is.
Specifically, resin molded products include, for example, generators, motors, transformers, current transformers, voltage regulators, rectifiers, inverters, relays, power contacts, switches, machine breakers, knife switches, etc. Electric rod parts, electrical parts cabinets, light sockets, various terminal boards, plugs, power modules and other electrical equipment parts, sensors, LED lamps, connectors, resistors, relay cases, small switches, coil bobbins, capacitors, variable capacitor cases, optical pickups, Oscillator, transformer, printed circuit board, tuner, speaker, microphone, headphones, floppy disk (registered trademark) disk or MO disk storage device, small motor, magnetic head base, semiconductor, liquid crystal, FDD carriage, FDD chassis, inkjet printer Or thermal transfer printer etc. Printers, printer ink cases, motor brush holders, parabolic antennas, electronic parts represented by parabolic antennas or computer-related parts, VTR parts, TV parts, housings for electrical or electronic devices such as TVs or PCs, irons, hair dryers, Rice cooker parts, microwave oven parts, audio products, audio equipment parts such as audio / laser discs / compact discs, lighting parts, freezer parts, air conditioner parts, typewriter parts, word processor parts, etc. ; Office computer related parts, telephone equipment related parts, facsimile related parts, copier related parts, cleaning jigs, motor parts, machine related parts such as lighters or typewriters, microscopes, binoculars, cameras or watches Representative light Equipment, precision machinery-related parts, alternator terminals, alternator connectors, IC regulators, various valves such as potentiometer bases or exhaust gas valves for light day, fuel-related / exhaust / intake system pipes, air intake nozzle snorkel, intake manifold , Fuel pump, engine coolant joint, carburetor main body, carburetor spacer, exhaust gas sensor, coolant sensor, oil temperature sensor, brake pad wear sensor, throttle position sensor, crankshaft position sensor, air flow meter, brake pad wear sensor , Thermostat base for air conditioner, wind flow control valve for heating, brush holder for radiator motor, water Pump impeller, turbine vane, wiper motor related parts, detributor, starter switch, starter relay, transmission wire harness, window washer nozzle, air conditioner panel switch base, fuel related electromagnetic valve coil, fuse connector, horn terminal, electrical equipment Examples thereof include parts insulating plates, step motor rotors, lamp sockets, lamp reflectors, lamp housings, brake pistons, solenoid bobbins, engine oil filters, parts for automobiles such as an ignition device case, and packaging materials.
It can also be applied to gears, rotating shafts of gears, bearings, racks, pinions, cams, cranks, crank arms, and other mechanical mechanism parts, and wheels, wheels, and the like.

In particular, since the resin molded product of the present invention has improved crystallinity, it is suitable as a housing for electric or electronic equipment such as a television or a personal computer that requires high heat resistance.
In addition, if this resin molded product is mainly composed of aliphatic polyester, especially polylactic acid, it can be disposed of after biodegradation after use, and there is an advantage that no extra energy is consumed for disposal. Yes.

About the resin composition of this invention, the specific sample was produced and the characteristic evaluation was performed.
[Example 1]
As a polymer capable of taking a crystal structure, 90 parts by mass of polylactic acid (trade name: H100J) manufactured by Mitsui Chemicals, Inc. and 10 parts by mass of DL-m-Tyrosine manufactured by Tokyo Chemical Industry Co., Ltd. as an amino acid as a nucleating agent are contained. And mixed. This was kneaded while heating at a heating temperature in the range of 160 ° C. to 180 ° C. and then pelletized. This is designated as the resin composition sample of Example 1.

[Example 2]
L (+)-2-phenylglycine manufactured by Wako Pure Chemical Industries, Ltd. was used as an amino acid that is a nucleating agent.
The other conditions were the same as in Example 1, and the resin composition sample of Example 2 was produced.

Example 3
L-methionine manufactured by Kanto Chemical Co., Ltd. was used as the nucleating agent amino acid.
Other conditions were the same as in Example 1, and a resin composition sample of Example 3 was produced.

Example 4
DL-methionine manufactured by Kanto Chemical Co., Inc. was used as the nucleating agent amino acid.
The other conditions were the same as in Example 1, and a resin composition sample of Example 4 was produced.

[Comparative Example 1]
The mixture was heated and kneaded in the same manner as in Example 1 above, using only polylactic acid without containing an amino acid as a nucleating agent, and pelletized. This is the resin composition sample of Comparative Example 1.

[Comparative Example 2]
Instead of amino acid, calcium stearate manufactured by Kanto Chemical Co., Inc. was used.
Other conditions were the same as in Example 1, and a resin composition sample of Comparative Example 2 was produced.

[Comparative Example 3]
Instead of amino acids, talc (trade name: LMS-200) manufactured by Fuji Talc was used.
Other conditions were the same as in Example 1, and a resin composition sample of Comparative Example 3 was produced.

[Evaluation]
For the resin composition samples of [Examples 1 to 4] and [Comparative Examples 1 to 3] described above, the crystallization temperature was measured by a differential scanning calorimetry (DSC) measurement method.
Specifically, first, each resin composition sample was used as a cut test piece in an amount of 3 mg to 4 mg.
A test specimen was prepared by placing the test piece in an aluminum pan.
This test sample was once heated to 200 ° C. and then cooled so as to decrease the temperature by 20 ° C. per minute. At that time, an exothermic peak temperature due to crystallization near 120 ° C. was measured as a crystallization temperature.
The measurement results of the crystallization temperatures of the resin compositions of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 3 below.

From the evaluation results in Table 3, in Examples 1 to 4 in which an amino acid was added as a nucleating agent, the crystallization temperature was higher and the degree of crystallinity was higher than in Comparative Examples 1 to 3 in which no amino acid was contained. I understand that it is.
Thereby, the crystallinity of the resin composition was increased, and practically sufficient heat resistance and mechanical strength were obtained.
On the other hand, in Comparative Example 1, since a resin composition composed only of polylactic acid was prepared without containing a nucleating agent, polylactic acid did not crystallize and solidified in an amorphous state. This was confirmed by the fact that no exothermic peak was observed by the DSC measurement method.
In Comparative Example 2, polylactic acid contained calcium stearate as a nucleating agent, so that the crystallization temperature could be increased as compared with Comparative Example 1, but an amino acid was contained as a nucleating agent. Compared with Examples 1 to 4, a sufficiently high crystallization temperature could not be obtained, and the resin composition had many amorphous portions, and practically sufficient heat resistance and mechanical strength could not be obtained.
In Comparative Example 3, the crystallization temperature could be increased as compared with Comparative Example 1 by adding talc as a nucleating agent to polylactic acid, but an example in which an amino acid was added as a nucleating agent. Compared with 1 to 4, a sufficiently high crystallization temperature could not be obtained, and the resin composition had many amorphous portions, and practically sufficient heat resistance and mechanical strength could not be obtained.
In addition, in the case of using talc, in order to sufficiently increase the crystallinity, the content must be increased considerably, resulting in a decrease in fluidity when molding the resin composition, and finally There exists a possibility that the molded article of the resin composition obtained may become weak. That is, when talc is used as a nucleating agent, severe restrictions are imposed on the amount added, and thus there is a problem that the effect of improving the crystallinity of the resin composition cannot be obtained sufficiently. .

From the above, by adding an amino acid as a nucleating agent to a polymer that can take a crystal structure, the crystallization temperature can be effectively increased, the crystallinity is high, and practically sufficient heat resistance and mechanical strength. It became clear that the resin composition which has this was obtained.
Moreover, it was confirmed that the nucleating agent amino acid is a very suitable material when the resin composition finally produced has biodegradability.

Claims (8)

A resin composition comprising polylactic acid and at least one of methionine, proline, m-tyrosine, o-tyrosine and valine. A resin composition comprising polylactic acid and any one of L-methionine, DL-methionine and DL-m-tyrosine. The resin composition according to claim 1 or 2, wherein the polylactic acid is poly L-lactic acid. A molded article produced from a resin composition comprising polylactic acid and at least one of methionine, proline, m-tyrosine, o-tyrosine and valine. A molded product produced from a resin composition comprising polylactic acid and any one of L-methionine, DL-methionine and DL-m-tyrosine. The molded product according to claim 4 or 5, wherein the polylactic acid is poly-L-lactic acid. A resin composition comprising polylactic acid and any one or more of methionine, proline, m-tyrosine, o-tyrosine and valine is heated and melted at a temperature +15 to + 30 ° C. higher than the melting point of the resin composition,
Injecting the melt of the resin composition after the heat melting into a mold kept at a temperature in the temperature range of −50 to + 30 ° C. of the crystallization temperature of the resin composition,
A method for producing a molded product, in which a pressure is continuously applied to the melt in the mold, and then the pressure is released and left standing. A resin composition comprising polylactic acid and any one of L-methionine, DL-methionine, and DL-m-tyrosine is heated and melted at a temperature +15 to + 30 ° C. higher than the melting point of the resin composition;
Injecting the melt of the resin composition after the heat melting into a mold kept at a temperature in the temperature range of −50 to + 30 ° C. of the crystallization temperature of the resin composition,
A method for producing a molded product, in which a pressure is continuously applied to the melt in the mold, and then the pressure is released and left standing.