JP2001049099A - Polyhydroxycarboxylic acid pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellet of a polyhydroxycarboxylic acid which can effectively be subjected to crystallization and polycondensation reaction in a solid state without causing blocking. SOLUTION: A pellet of a polyhydroxycarboxylic acid is composed of a core portion 1 and a skin portion 2 covering the core portion 1, the core portion is composed of a resin containing a polyhydroxycarboxylic acid having weight average molecular weight(MW) of 2,000 to 30,000, and the skin portion is composed of a resin containing a polyhydroxycarboxylic acid having weight average molecular weight(MW) of 30,000 to 200,000, the resin forming the core has a melting point lower than the resin forming the skin portion, or it does not show a melting point.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to polyhydroxycarboxylic acid pellets. More specifically, crystallization,
The present invention relates to polyhydroxycarboxylic acid pellets having a specific shape suitable for solid-state polymerization.

[0002]

2. Description of the Related Art [Technical Background] In recent years, waste disposal has become a problem in connection with environmental protection. In particular, molded products and processed products of general-purpose general-purpose polymer materials are not degradable and disintegratable by microorganisms when landfilled as waste.
There is a problem that they remain semi-permanently as foreign matter, and that an additive such as a plasticizer elutes and pollutes the environment. Also, when incinerated as waste, the high heat generated by combustion can damage the furnace, and the smoke and exhaust gas generated by combustion can cause air pollution, ozone depletion, global warming, acid rain, etc. In recent years, what can be the cause has become more and more up-close.

[0003] From such a background, there is an increasing demand for a polymer material which is tough but has a low combustion heat and does not damage the furnace even when it is to be decomposed or burned after being used as a waste after use. In spite of this, it cannot be said that polymer materials that can meet such demands are always supplied.

[0004] By the way, those satisfying the above requirements include, for example, polyhydroxycarboxylic acid and the like.
Among them, polylactic acid, which is a kind of the polyhydroxycarboxylic acid, is highly transparent, tough, and in the presence of water,
It is easily hydrolyzed, and when used as a general-purpose resin, decomposes without disposing of the environment after disposal, so it is environmentally friendly. The excellent property of being friendly to the living body was already noticed before the present application because it is decomposed and absorbed in the living body without causing toxicity to the living body later. For example, Japanese Patent Application Laid-Open No. 05-255488 discloses a production method using a so-called solid-phase polymerization in which a polyhydroxycarboxylic acid (a so-called low molecular weight polymer) is subjected to a polycondensation reaction below its melting point.

As a method for producing polyhydroxycarboxylic acid using solid-phase polycondensation, the polyhydroxycarboxylic acid is produced through a liquid-phase polycondensation reaction step and a solid-phase polycondensation reaction step. However, the polyhydroxycarboxylic acid obtained in the liquid phase polycondensation reaction step is a relatively low molecular weight substance, has a low melting point,
If the molecular weight is low, the crystallinity is low, so that if it is directly subjected to a solid-phase polycondensation reaction step, blocking may occur. For this reason, a crystallization step is provided before the solid-phase polycondensation reaction step, and the polyhydroxycarboxylic acid that has passed through the liquid-phase polycondensation reaction step is heated and crystallized, and then subjected to the solid-phase polycondensation reaction step. ing.

[0006] However, if the crystallization step is carried out rapidly and the temperature is raised rapidly or heated at a high temperature, polyhydroxycarboxylic acid is blocked in the system. I had to take it. As a result, productivity could not be improved as expected, and a more economical and more efficient production method was required.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a polyhydroxycarboxylic acid pellet capable of efficiently crystallizing and solid-phase polycondensation reaction of the polyhydroxycarboxylic acid. The purpose is to provide.

[0008]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of intensive studies to solve the above problems, as a pellet of polyhydroxycarboxylic acid, by forming a pellet having a specific layer structure, a polyhydroxycarboxylic acid capable of efficiently crystallizing and solid-phase polycondensation reaction of polyhydroxycarboxylic acid can be obtained. The present inventors have found a hydroxycarboxylic acid pellet and a method for producing the same, and have completed the present invention.

The polyhydroxycarboxylic acid pellet of the present invention is a polyhydroxycarboxylic acid pellet comprising (I) a core portion and (II) a jacket covering the core portion. The core has a weight average molecular weight (Mw) of 2.0
(II) a polyhydroxycarboxylic acid having a weight average molecular weight (Mw) in the range of 30,000 to 200,000 comprising a resin containing a polyhydroxycarboxylic acid in the range of 00 to 30,000; The resin comprising an acid-containing resin, wherein the resin constituting the core portion has a lower melting point than the resin constituting the jacket portion, or has no melting point.

[0010] In the present invention, the hydroxycarboxylic acid is preferably an aliphatic hydroxycarboxylic acid. Further, the aliphatic hydroxycarboxylic acid preferably contains lactic acid.

It is preferable that the polyhydroxycarboxylic acid pellet is a raw material for crystallization and / or solid phase polymerization in the crystallization step and / or solid phase polymerization step. That is, the present invention provides the following (1) to (4). (1) A polyhydroxycarboxylic acid pellet comprising (I) a core portion and (II) a jacket covering the core portion, wherein (I) the core portion has a weight average molecular weight (Mw). Is 2,0
(II) a polyhydroxycarboxylic acid having a weight average molecular weight (Mw) in the range of 30,000 to 200,000 comprising a resin containing a polyhydroxycarboxylic acid in the range of 00 to 30,000; Polyhydroxycarboxylic acid comprising a resin containing an acid, wherein the resin constituting the core portion has a lower melting point than the resin constituting the jacket portion or does not show a melting point. pellet. (2) The polyhydroxycarboxylic acid pellet according to (1), wherein the hydroxycarboxylic acid is an aliphatic hydroxycarboxylic acid. (3) The polyhydroxycarboxylic acid pellet according to (2), wherein the aliphatic hydroxycarboxylic acid contains lactic acid. (4) The polyhydroxycarboxylic acid pellet according to any one of (1) to (3) is a raw material for crystallization and / or solid phase polymerization in a crystallization step and / or a solid phase polymerization step. A method for producing a polyhydroxycarboxylic acid, which is characterized by the following.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the polyhydroxycarboxylic acid pellet according to the present invention will be specifically described.

The polyhydroxycarboxylic acid pellet according to the present invention comprises (I) a core portion and (II) a jacket covering the core portion, and is shown, for example, in FIG. FIG. 1 is a schematic perspective view of one embodiment of a polyhydroxycarboxylic acid pellet according to the present invention. In FIG.
Reference numeral 2 indicates a jacket. In addition, the sheath part may be referred to as a sheath part.

The shape of the pellet is arbitrary, and preferably
It has a columnar or prismatic shape as shown in FIG.

The length of such pellets in the axial direction is generally in the range of 0.5 to 5.0 mm, preferably 1.5 to 4.5 mm.

The diameter of such polyhydroxycarboxylic acid pellets is usually in the range of 0.5 to 5.0 mm, preferably 1.5 to 4.5 mm.

The weight ratio of the jacket portion to the core portion is arbitrary, but the weight of the core portion is 40 to 98% by weight of the pellet weight,
Preferably, it is in the range of 50 to 95% by weight. [Coat part] In the polyhydroxycarboxylic acid pellets according to the present invention, the coat part has a weight average molecular weight (Mw) of 30,
It is composed of a resin containing polyhydroxycarboxylic acid in the range of 000 to 200,000. The resin containing the polyhydroxycarboxylic acid that constitutes the outer cover portion refers to a polyhydroxycarboxylic acid containing 50 to 100% by weight, preferably 65% by weight.
Consists of resin containing in an amount of １００100% by weight. Polyhydroxycarboxylic acid The hydroxycarboxylic acid used in the present invention may be any carboxylic acid having a hydroxyl group,
There is no particular limitation.

Specifically, for example, 2-hydroxyethanolic acid, 2-hydroxypropanoic acid, 2-hydroxybutanoic acid, 2-hydroxypentanoic acid, 2-hydroxyhexanoic acid, -Hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxy-2-methylpropanoic acid, 2-hydroxy-2-methylbutanoic acid, 2-hydroxy-2-ethylbutanoic acid 2-hydroxy-2-methylpentanoic acid, 2-hydroxy-2-ethylpentanoic acid, 2-hydroxy-2-propylpentanoic acid, 2-hydroxy-2-butylpentanoic acid, 2 -Hydroxy-2-methy Hexanoic acid, 2-hydroxy-2-ethylhexanoic acid, 2-hydroxy-2-propylhexanoic acid, 2-hydroxy-2-butylhexanoic acid, 2-hydroxy-2-pentylhexano Ic Acid, 2-
Hydroxy-2-methylheptanoic acid, 2-
Hydroxy-2-ethylheptanoic acid, 2-
Hydroxy-2-propylheptanoic acid, 2
-Hydroxy-2-butylheptanoic acid, 2
-Hydroxy-2-pentylheptanoic acid,
2-hydroxy-2-hexylheptanoic acid, 2-hydroxy-2-methyloctanoic acid, 2-hydroxy-2-ethyloctanoic acid, 2-hydroxy-2-propyloctanoic acid, 2- Hydroxy-2-butyl octanoic acid, 2-hydroxy-2-pentyl octanoic acid, 2-hydroxy-2-hexyl octanoic acid, 2-hydroxy-2-heptyl octanoic acid, 3-hydroxypropa Neuk Acid,
3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-hydroxyheptanoic acid,
3-hydroxyoctanoic acid, 3-hydroxy-3-methylbutanoic acid, 3-hydroxy-3-methylpentanoic acid, 3-hydroxy-3-ethylpentanoic acid, 3-hydroxy-3- Methylhexanoic acid, 3-hydroxy-3-ethylhexanoic acid, 3-hydroxy-3-propylhexanoic acid, 3-hydroxy-3-methylheptanoic acid, 3-hydroxy-3-ethylhepta Neuic acid, 3-hydroxy-3-propylheptanoic acid, 3-hydroxy-3-butylheptanoic acid, 3-hydroxy-3-methyloctanoic acid, 3-hydroxy-3-ethyloctanoic Acid, 3-hydroxy-3-propyl Octanoic acid, 3-hydroxy-3-butyloctanoic acid, 3-hydroxy-3-pentyloctanoic acid, 4-hydroxybutanoic acid, 4-hydroxypentanoic acid, 4-hydroxyhexano Ic acid, 4-hydroxyheptanoic acid, 4-hydroxyoctanoic acid, 4-hydroxy-4
-Methylpentanoic acid, 4-hydroxy-4
-Methylhexanoic acid, 4-hydroxy-4
-Ethylhexanoic acid, 4-hydroxy-4
-Methylheptanoic acid, 4-hydroxy-4
-Ethylheptanoic acid, 4-hydroxy-4
-Propylheptanoic acid, 4-hydroxy-
4-methyloctanoic acid, 4-hydroxy-
4-ethyloctanoic acid, 4-hydroxy-
4-propyl octanoic acid, 4-hydroxy-4-butyl octanoic acid, 5-hydroxypentanoic acid, 5-hydroxyhexanoic acid, 5-hydroxyheptanoic acid,
5-hydroxyoctanoic acid, 5-hydroxy-5-methylhexanoic acid, 5-hydroxy-5-methylheptanoic acid, 5-hydroxy-5-ethylheptanoic acid, 5-hydroxy-5 Methyloctanoic acid, 5-hydroxy-5-ethyloctanoic acid, 5-hydroxy-5-propyloctanoic acid, 6-hydroxyhexanoic acid, 6-hydroxyheptanoic acid, 6-hydroxyocta Neuk acid, 6-hydroxy-6-methylheptanoic acid, 6-hydroxy-6-methyloctanoic acid, 6-hydroxy-6-ethyloctanoic acid, 7-hydroxyheptanoic acid, 7- Hydroxyoctanoy Kuashiddo, 7-hydroxy-7
Aliphatic hydroxycarboxylic acids such as methyloctanoic acid and 8-hydroxyoctanoic acid and oligomers or glycolides derived therefrom,
Cyclic dimers such as lactide; Also,
As the above-mentioned glycolide and lactide cyclic dimer,
Specifically, for example, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide which is a cyclic dimer of lactic acid, glycolide which is a cyclic dimer of glycolic acid,
Examples thereof include ε-caprolactone, which is a cyclic ester of 6-hydroxycaproic acid, and β-propiolactone, γ-butyrolactone, δ-valerolactone, and the like.

Among them, preferred specific examples include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid and 6-hydroxycaproic acid. But,
Among them, lactic acid is preferred from the viewpoint of transparency of the obtained polyhydroxycarboxylic acid. These hydroxycarboxylic acids may be used in combination of two or more.

In the case where lactic acid has an asymmetric carbon in the molecule, such as lactic acid, there are D-form, L-form and an equivalent mixture thereof (racemic form), and any of them can be used. Among them, L-lactic acid is preferable. In the present invention, polyhydroxycarboxylic acid is produced using hydroxycarboxylic acid as a raw material, but 20 mol% or less of dicarboxylic acid and / or glycol may be used.
The dicarboxylic acid used in the present invention is not particularly limited. For example, succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecanediacid Acids, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and aliphatic dicarboxylic acids such as 3,3-dimethylpentanedioic acid, terephthalic acid, isophthalic acid, phthalic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid,
And aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid.

These dicarboxylic acids can be used alone or in combination of two or more.

When the compound has an asymmetric carbon in the molecule, there are D-form, L-form and an equivalent mixture thereof (racemic form), and any of them can be used.
The glycol used in the present invention is not particularly limited. For example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1 , 5-pentanediol, 1,6-hexanediol, 1,7-
Heptanediol, 1,8-octanediol, 1,9
-Nonanediol, neopentyl glycol, polytetramethylene glycol, 1,4-hexanediol,
1,4-cyclohexanedimethanol and the like can be mentioned.

These glycols can be used alone or in combination of two or more.

When the compound has an asymmetric carbon in the molecule, there are D-form, L-form and an equivalent mixture thereof (racemic form), and any of these can be used.
In the present invention, the production of polyhydroxycarboxylic acid is carried out using hydroxycarboxylic acid as a raw material.For example, monofunctional compounds such as benzoylbenzoic acid, diphenylsulfonemonocarboxylic acid, stearic acid, methoxypolyethylene glycol, and phenoxypolyethylene glycol are used. And other compounds such as trimesic acid, polyfunctional compounds such as trimethylolethane, trimethylolpropane, and pentaerythritol. These other compounds are used in an amount of 0.01 to 2 with respect to the hydroxycarboxylic acid.
It is desirably added in an amount of 0 mol%, preferably 0.05 to 10 mol%. The catalyst used in the present invention is not particularly limited as long as it substantially promotes the progress of the dehydration polycondensation reaction.

Specific examples of the catalyst include, for example, a periodic table
Group II, III, IV and V metals, oxides and salts thereof.

More specifically, metals such as zinc powder, tin powder, aluminum, magnesium, and germanium, tin (II) oxide, antimony (III) oxide, zinc oxide, aluminum oxide, magnesium oxide, and titanium (IV) oxide , Metal oxides such as germanium (IV) oxide, tin (II) chloride,
Metal halides such as tin (IV) chloride, tin (II) bromide, tin (IV) bromide, antimony (III) fluoride, antimony (V) fluoride, zinc oxide, magnesium chloride, aluminum chloride, etc., tin sulfate (II), sulfates such as zinc sulfate and aluminum sulfate, carbonates such as magnesium carbonate and zinc carbonate, borates such as zinc borate, tin acetate (II), tin (II) octoate, tin lactate ( II), organic carboxylate salts such as zinc acetate and aluminum acetate, tin (II) trifluoromethanesulfonate, zinc trifluoromethanesulfonate, magnesium trifluoromethanesulfonate,
Organic sulfonates such as tin (II) methanesulfonate, tin (II) p-toluenesulfonate, methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 1-
Butanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-xylene-2-sulfonic acid, naphthalene-1-sulfonic acid,
Organic sulfonic acids such as naphthalene-2-sulfonic acid, and acids such as sulfuric acid and hydrochloric acid.

Other examples include metal alkoxides of the above metals such as dibutyltin oxide, and alkyl metals of the above metals such as diethyl zinc. Among these, tin powder (metal powder), tin oxide (II), p
-Toluenesulfonic acid and methanesulfonic acid are preferred.

These can be used alone or in combination of two or more.

The amount of the catalyst to be used is not particularly limited as long as it substantially accelerates the reaction rate. The amount of the catalyst used depends on the type of the catalyst used, but is generally preferably in the range of 0.00005 to 5% by weight of the obtained polyhydroxycarboxylic acid. A range of weight% is preferred. The polyhydroxycarboxylic acid of the present invention is produced by a direct polymerization method and a lactide method of hydroxycarboxylic acid, and is produced by a liquid phase polymerization and / or a solid phase polymerization as a reaction mode. Hereinafter, the liquid phase polymerization step will be described. The liquid phase polymerization step is a step of producing a polyhydroxycarboxylic acid by subjecting a hydroxycarboxylic acid as a monomer to a dehydration polycondensation reaction in a liquid state, that is, a solution state or a molten state. The method of performing the dehydration polycondensation reaction in the liquid phase polymerization step is not particularly limited, but generally, the dehydration polycondensation reaction is performed under an inert gas atmosphere, a flowing gas atmosphere, and / or under reduced pressure. The reaction system of the dehydration polycondensation reaction is preferably a melt polymerization system or a solution polymerization system using an organic solvent. Further, the dehydration polycondensation reaction can be carried out by appropriately selecting conditions such as using an organic solvent (solution polymerization reaction method) depending on the desired weight average molecular weight (Mw) and the simplicity of the operation. Generally, when an organic solvent is used (solution polymerization reaction system), the weight average molecular weight (M
w) can be efficiently obtained,
When an organic solvent is not used (melt polymerization reaction method), there is a feature that the operation is simple because the trouble of distilling off the organic solvent in the prepolymer solidification step can be omitted.

In the liquid phase polymerization step, when an organic solvent is used, the organic solvent is not particularly limited as long as it can substantially maintain the progress of the dehydration polycondensation reaction.
One type or a combination of two or more types may be used. Specific examples of such organic solvents include, for example, hydrocarbon solvents such as toluene, xylene and mesitylene, chlorobenzene, bromobenzene, iodobenzene, p-
Halogen solvents such as dichlorobenzene, 1,1,2,2-tetrachloroethane and p-chlorotoluene; ketone solvents such as 3-hexanone, acetophenone and benzophenone; dibutyl ether, anisole and phenetole;
o-dimethoxybenzene, p-dimethoxybenzene, 3
-Methoxy toluene, dibenzyl ether, benzyl phenyl ether, ether solvents such as methoxy naphthalene, phenyl sulfide, thio ether solvents such as thioanisole, methyl benzoate, methyl phthalate, ester solvents such as ethyl phthalate, diphenyl ether, 4
Alkyl-substituted diphenyl ethers such as -methylphenyl ether, 3-methylphenyl ether and 3-phenoxytoluene, or 4-bromophenyl ether;
Halogen-substituted diphenyl ethers such as -chlorophenyl ether, 4-bromodiphenyl ether, 4-methyl-4'-bromophenyl ether, or 4-methoxydiphenyl ether, 4-methoxyphenyl ether, 3-methoxyphenyl ether, 4-methyl-4 '
Examples thereof include diphenyl ether solvents such as alkoxy-substituted diphenyl ethers such as -methoxydiphenyl ether and the like, and cyclic diphenyl ethers such as dibenzofuran and xanthene. Among them, hydrocarbon solvents, halogen solvents and alkyl-substituted diphenyl ether solvents are preferable. Among them, toluene, xylene, o-dichlorobenzene and diphenyl ether are particularly preferred.

The solvent which can be used in the liquid phase polymerization step preferably has a boiling point of 100 ° C. or higher,
The temperature is more preferably at least 135 ° C, even more preferably at least 170 ° C. When using an organic solvent in the liquid phase polymerization step, the reaction temperature can be substantially maintained in the liquid phase state of the organic solvent of the reaction system, taking into account the rate of formation and thermal decomposition of the polyester, It is sufficient that the progress of the dehydration polycondensation reaction can be maintained, and there is no particular limitation.

The reaction temperature in the liquid phase polymerization step is 100 to 20
A range of 0 ° C is preferable, and a range of 110 to 180 ° C is more preferable.

When the reaction is carried out at normal pressure (atmospheric pressure) using an organic solvent in the liquid phase polymerization step, the distillation temperature of the organic solvent at normal pressure (atmospheric pressure) is usually defined as the reaction temperature. adopt.

An organic solvent is used in the liquid phase polymerization step,
When the reaction is carried out under a specific pressure, the distillation temperature of the organic solvent at the pressure of the reaction system is usually employed as the reaction temperature.

When an organic solvent having a boiling point under normal pressure (atmospheric pressure) higher than the preferable reaction temperature is used,
In order to carry out the reaction at a preferable reaction temperature, the pressure of the reaction system may be reduced.

In the liquid phase polymerization step, by performing the dehydration polycondensation reaction under a low temperature and a high vacuum, the dehydration polycondensation reaction can proceed efficiently without undesired side reactions.

The amount of the organic solvent used in the liquid phase polymerization step is not particularly limited as long as the progress of the reaction can be substantially maintained.

The amount of the organic solvent used in the liquid phase polymerization step is generally set from the industrial point of view in consideration of the reaction rate, the purity of the reaction product (polyester), the volumetric efficiency, the solvent recovery and the like. Usually, the concentration of the obtained polyhydroxycarboxylic acid is 10% by weight or more,
It is preferably at least 0% by weight, more preferably at least 80% by weight.

The reaction temperature in the case where an organic solvent is not used in the liquid phase polymerization step is not particularly limited as long as the progress of the dehydration polycondensation reaction can be maintained. Specifically, the reaction temperature is determined in consideration of the rate of polyester formation and the rate of thermal decomposition. To react at a temperature equal to or higher than the melting point of the polymer present in the reaction system.
The reaction is preferably performed in a temperature range of not more than ℃. Above all, a range of 100 to 200 ° C. is preferable, and 110 to 180 ° C.
Is more preferable.

The weight average molecular weight (Mw) of the polyhydroxycarboxylic acid obtained in the liquid phase polymerization step is 2,000
0-100,000, preferably 5,000
More preferably, it is from 30,000 to 30,000.

The liquid phase polymerization step may be carried out by either a continuous type or a batch type polymerization method. The polyhydroxycarboxylic acid produced by the liquid phase polymerization step is supplied to the granulation step.

When the polyhydroxycarboxylic acid is supplied from the liquid phase polymerization step to the granulation step, the polyhydroxycarboxylic acid may be supplied in a liquid state as it is after completion of the liquid phase polymerization, or may be cooled, solidified, pulverized once. After that, it may be supplied again after being plasticized and melted again by a melting drum, an extruder or the like. Although the polyhydroxycarboxylic acid of the present invention can be used as it is even in the state of particles granulated by the above-described method, it is preferable to further carry out solid phase polymerization from the viewpoint of strength. When performing solid phase polymerization, it is desirable to crystallize the polyhydroxycarboxylic acid as a step before the solid phase polymerization step in order to prevent fusion of particles. Hereinafter, the crystallization step will be described first. In the present invention, crystallization is performed mechanically and / or
Alternatively, the heating is performed while stirring and flowing with a gas.

More specifically, the crystallization is carried out by maintaining the polyhydroxycarboxylic acid at a temperature not lower than the glass transition temperature and not higher than the melting point for 1 minute to 10 hours, preferably 2 minutes to 1 hour.

The crystallization can be carried out by either a batch method or a continuous method. Next, the solid-state polymerization step of the present invention will be described. As the reaction temperature of solid-state polymerization,
The polymer (prepolymer and polyhydroxycarboxylic acid as a reaction product) existing in the reaction system may be substantially maintained in a solid state, and is not particularly limited, but specifically, 100 ° C. or higher and melting point or lower. It is preferred that
In general, the higher the reaction temperature, the faster the polymerization rate,
It is preferable to carry out at around the melting point of the polyhydroxycarboxylic acid.

As the gas that can be used in the solid phase polymerization step, specifically, nitrogen gas, helium gas,
Examples thereof include an argon gas, a xenon gas, a krypton gas, and a carbon dioxide gas.

The water content in the gas used in the solid-state polymerization step is as low as possible and is preferably substantially anhydrous. If the water content is high, the water generated by the dehydration polycondensation reaction tends to be unable to be removed efficiently, so that the polymerization rate may be slow, which is not preferable. In the above case, the gas is used after being dehydrated by previously passing a gas through a layer filled with molecular sieves, ion exchange resins and the like.

When the water content in the gas is indicated by the dew point, the dew point of the gas is preferably -20 ° C or lower, more preferably -50 ° C or higher.

The flow rate of the gas used in the solid phase polymerization step is determined in consideration of the polymerization rate, the type and amount of the catalyst, and the weight average molecular weight of the polyhydroxycarboxylic acid to the polyhydroxycarboxylic acid in the dehydration polycondensation reaction. In the dehydration / polycondensation reaction, it is only necessary to remove generated water to such an extent that a polyhydroxycarboxylic acid having a sufficiently high weight average molecular weight can be obtained, and there is no particular limitation.

The solid phase polymerization step may be carried out by either a continuous or batch polymerization method.

The weight average molecular weight (Mw) of the polyhydroxycarboxylic acid produced in the solid phase polymerization step is as follows:
Generally, those having a range of 30,000 to 200,000 are preferable, and those having a range of 50,000 to 180,000 are more preferable. The resin constituting the jacket portion of the polyhydroxycarboxylic acid pellets of the present invention may be polyhydroxycarboxylic acid alone, or may be a resin composition of polyhydroxycarboxylic acid and a resin other than polyhydroxycarboxylic acid. Good.

The amount of the resin other than polyhydroxycarboxylic acid is 0 to 50% by weight, preferably 0 to 35% by weight, based on the resin constituting the outer cover. Examples of such resins other than polyhydroxycarboxylic acid include polyethylene terephthalate, polyester containing a comonomer such as 20% by mole or more of isophthalic acid and cyclohexanedimethanol, 20% by mole or more of isophthalic acid, and 1% by mole or more of 1,3 or more. Polyester containing bis (hydroxyethoxy) benzene, polyester containing aliphatic carboxylic acid such as adipic acid and sebacic acid as a comonomer.
Examples include polyester block copolymers, polyester / polyether block copolymers having a soft segment of polyether such as polybutylene glycol as a soft segment, and polyesters such as polybutylene terephthalate and polyethylene naphthalate. Further, as a resin other than polyhydroxycarboxylic acid, a polyolefin containing a structural unit derived from an olefin monomer having 2 to 6 carbon atoms can be used. Such polyolefins include low density polyethylene, high density polyethylene,
Examples thereof include linear low-density polyethylene, polypropylene, prebutene, polypentene, and polymethylpentene. The compounding amount of such a resin is 0 to 10% by weight, preferably 0 to 5% by weight, based on the resin constituting the outer cover. Further, as a resin other than polyhydroxycarboxylic acid, an ethylene- (meth) acrylic acid copolymer can also be used. Examples of such an ethylene- (meth) acrylic acid copolymer include an ethylene-methacrylic acid copolymer, an ethylene-acrylic acid copolymer, and an ethylene-acrylic acid-methacrylic acid terpolymer. The ethylene- (meth) acrylic acid copolymer may contain a small amount of a component other than ethylene and (meth) acrylic acid copolymerized.
Examples of components other than acrylic acid include unsaturated carboxylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, and isobutyl (meth) acrylate, and vinyl esters such as vinyl acetate.

The compounding amount of such a resin is from 0 to 10% by weight, preferably from 0 to 5% by weight, based on the resin constituting the jacket.
% By weight. The content of (meth) acrylic acid in the ethylene- (meth) acrylic acid copolymer is preferably 0.5 to 8% by weight, particularly preferably 1 to 6% by weight. (Meta)
When the acrylic acid content is within such a range, it is possible to improve the crystallization rate at the time of temperature rise while maintaining the transparency of the polyhydroxycarboxylic acid resin composition obtained by blending with the polyhydroxycarboxylic acid. it can. This ethylene
(Meth) acrylic acid copolymer is ASTM D1238
MFR (190 ° C.) is usually 0.05 to 100 g
/ 10 minutes, preferably 0.1 to 50 g / 10 minutes.
Such an ethylene- (meth) acrylic acid copolymer is
In addition to those in which the carboxyl group in the side chain is not bonded to a metal, those in which at least a part is present in the form of a metal salt of a carboxylic acid (ionomer) may be included. This metal salt includes sodium salt, lithium salt,
Alkali metal salts such as potassium salts, zinc salts, cobalt salts, nickel salts, manganese salts, divalent transition metal salts such as lead salts and copper salts, and alkaline earth metal salts such as calcium salts and magnesium salts are preferred, and zinc is particularly preferred. Salts are desirable because they can maintain the transparency of the polyhydroxycarboxylic acid resin composition. When the ethylene- (meth) acrylic acid copolymer is an ionomer, the ratio of the carboxyl group bonded to the metal to all carboxyl groups is not particularly limited, but is usually in the range of 3 to 100%. Such an ethylene- (meth) acrylic acid copolymer is, for example,
It is produced by a method in which ethylene, (meth) acrylic acid and, if necessary, other comonomers are copolymerized by a high-pressure radical polymerization method, and if necessary, a neutralization treatment is carried out with ions of the metal. Furthermore, in addition to the above, examples of resins other than polyhydroxycarboxylic acid include polyamides such as nylon 6, nylon 66, and nylon 12, and polycarbonates such as polyester carbonate and polycarbonate.

The amount of such a resin is from 0 to 10% by weight, preferably from 0 to 5% by weight, based on the resin constituting the outer cover.
% By weight. Among these, in particular, a polyester containing a comonomer such as 20% by mole or more of isophthalic acid and cyclohexanedimethanol, a polyester containing a comonomer such as 20% by mole or more of isophthalic acid and cyclohexanedimethanol, and 1% by mole or more of 1,3 A polyester comprising -bis (hydroxyethoxy) benzene,
Polyolefins and ethylene- (meth) acrylic acid copolymers are preferred.

If necessary, ordinary additives such as coloring agents, antioxidants, oxygen absorbers, ultraviolet absorbers, antistatic agents, flame retardants, bluing agents, etc. (External) A lubricant, a heat stabilizer and the like may be contained. [Core] In the polyhydroxycarboxylic acid pellets according to the present invention, the core has a weight average molecular weight (Mw) of 2,0.
It is composed of a resin containing polyhydroxycarboxylic acid in the range of 00 to 30,000.

The resin containing a polyhydroxycarboxylic acid constituting the core portion is a polyhydroxycarboxylic acid having a content of 50 to 50%.
It consists of a resin containing 100% by weight, preferably 65-100% by weight. The resin forming the core portion has a lower or lower melting point than the resin forming the jacket portion. In the case of indicating the melting point, the difference between the melting point of the resin constituting the core portion and the melting point of the resin constituting the jacket portion is 5 ° C to 40 ° C, particularly 8 ° C.
It is preferably in the range of 30C to 30C. The polyhydroxycarboxylic acid constituting the core portion is produced by the same method as that for the above-mentioned outer portion polyhydroxycarboxylic acid, but it is preferable to use only the liquid phase polymerization. Further, within the range not impairing the object of the present invention, the other resin exemplified as the resin constituting the outer cover portion is set to 50% by weight or less, preferably 35% by weight or less of the whole resin constituting the core portion. Can also be blended. [Production of Pellets] The polyhydroxycarboxylic acid pellets of the present invention are obtained by melt-kneading the resin constituting the jacket portion and the resin constituting the core portion with separate extruders, and then joining them with a die. It can be manufactured by a conventional method, for example, a method of cutting in air and dropping it in water to cool it, or a method of introducing molten resin into water and then pelletizing.

The extruder may be a single-screw extruder or a twin-screw extruder, and a vacuum vent line may be arbitrarily provided in the middle of the extruder.

The polyhydroxycarboxylic acid resin used for the jacket and the polyhydroxycarboxylic acid resin used for the core may or may not be dried before being charged into the extruder.

The obtained pellet is usually in the shape of a column or a prism. The cross-sectional shape is arbitrary, and a desired shape can be obtained by selecting an appropriate die.

Further, depending on the cooling conditions of the strand, the shape of the cutter blade, the take-up speed, the number of revolutions of the cutter blade, etc., the pellets can be deformed or the cut surface shape can be deformed during cutting.

Further, by changing the cutting conditions such as the take-up speed and the number of revolutions of the cutter blade, the height and the diameter of the pellet can be arbitrarily changed. The polyhydroxycarboxylic acid pellets produced as described above are preferably raw materials for crystallization and / or solid phase polymerization.

By using the above polyhydroxycarboxylic acid pellets for crystallization and solid phase polymerization, a polyhydroxycarboxylic acid having a higher molecular weight can be produced more efficiently.

At this time, the above-mentioned crystallization and solid-phase polymerization are carried out in the same manner as in the case of the above-mentioned polyhydroxycarboxylic acid pellet casing. That is, first, crystallization is performed by heating while stirring and flowing with mechanical and / or gas. More specifically, crystallization is performed at a temperature equal to or higher than the glass transition temperature of the polyhydroxycarboxylic acid and the melting point. It is carried out by holding at the following temperature for 1 minute to 10 hours, preferably 2 minutes to 1 hour.

The crystallization can be carried out by either a batch method or a continuous method. Next, in the solid-phase polymerization step, the reaction temperature of the solid-phase polymerization is such that the polymer (prepolymer and polyhydroxycarboxylic acid, which is a reaction product) present in the reaction system substantially maintains a solid state. Although not particularly limited, it is specifically preferable that the temperature is 100 ° C. or higher and the melting point or lower. Generally, the higher the reaction temperature, the faster the polymerization rate. Therefore, it is preferable to carry out the reaction at around the melting point of the polyhydroxycarboxylic acid.

As the gas that can be used in the solid phase polymerization step, specifically, nitrogen gas, helium gas,
Examples thereof include an argon gas, a xenon gas, a krypton gas, and a carbon dioxide gas.

The water content in the gas used in the solid-state polymerization step is as low as possible and preferably substantially anhydrous. If the water content is high, the water generated by the dehydration polycondensation reaction tends to be unable to be removed efficiently, so that the polymerization rate may be slow, which is not preferable. In the above case, the gas is used after being dehydrated by previously passing a gas through a layer filled with molecular sieves, ion exchange resins and the like.

When the water content in the gas is indicated by the dew point, the dew point of the gas is preferably -20 ° C. or lower, more preferably -50 ° C. or higher.

The flow rate of the gas used in the solid-state polymerization step is determined in consideration of the polymerization rate, the type and amount of the catalyst, and the weight average molecular weight of the polyhydroxycarboxylic acid to the polyhydroxycarboxylic acid in the dehydration polycondensation reaction. In the dehydration / polycondensation reaction, it is only necessary to remove generated water to such an extent that a polyhydroxycarboxylic acid having a sufficiently high weight average molecular weight can be obtained, and there is no particular limitation.

The solid-phase polymerization step may be carried out by either a continuous or batch polymerization method.

The weight average molecular weight (Mw) of the higher molecular weight polyhydroxycarboxylic acid produced by the above-mentioned crystallization and / or solid phase polymerization step is generally about 50,000 to 1,000,000. 000 is preferable, and 100,000 to 500,000 is more preferable. The polyhydroxycarboxylic acid produced in the present invention can be suitably used as a substitute for a resin used for medical use, food packaging and general use which have been known and used before the present application. The method for processing the polyhydroxycarboxylic acid according to the present invention is not particularly limited, but specifically, injection molding, extrusion molding, inflation molding, extrusion hollow molding, foam molding, calender molding, blow molding, balloon molding, vacuum molding Molding, forming methods such as spinning, among which inflation molding,
Blow molding, extrusion hollow molding, foam molding, spinning and the like are more preferable.

The polyhydroxycarboxylic acid can be prepared by an appropriate molding method, for example, a member of a writing implement such as a ball-point pen, a mechanical pen, a pencil, etc., a member of a stationary, a golf tee, and a member of a smoked golf ball for a starting ball type. Capsules for oral medicine, carriers for suppositories for anal and vagina, carriers for suppositories for skin and mucous membranes, capsules for agricultural chemicals, capsules for fertilizer, capsules for seedlings, compost bags, fishing line spools, fishing floats, fishing baits, lures , Fishing buoys,
Hunting decoys, hunting shot capsules, tableware and other camping equipment, nails, piles, binding materials, muddy / slippery materials for snowy roads,
It can be suitably used as a block or the like. In addition, by an appropriate molding method, for example, a lunch box, tableware,
Bento and side dish containers sold at convenience stores, chopsticks, split chopsticks, forks, spoons, skewers, toothpicks, cups of ramen, cups used in beverage vending machines, fresh fish, meat, fruits and vegetables, Containers and trays for food products such as tofu and prepared foods, toro boxes used in the fresh fish market, bottles for dairy products such as milk, yogurt and lactic acid bacteria drinks, and bottles for soft drinks such as carbonated drinks and soft drinks , Bottles for liquor drinks such as beer and whiskey, bottles with or without pumps for shampoo and liquid soap, tubes for toothpaste, cosmetic containers, detergent containers, bleach containers, cool boxes, flowerpots, casings for water purifier cartridges For transporting casings such as artificial kidneys and artificial livers, components for syringes, and home appliances such as televisions and stereos.衝材, computer printer clock or the like precision machine during transportation cushioning material for use in the, can be suitably used as a cushioning material or the like for use when transporting ceramic products such as glass and ceramics. The film or sheet containing the polyhydroxycarboxylic acid of the present invention may be used for shopping bags, garbage bags, compost bags, cement bags, fertilizer bags, sandbag bags, food / confectionery packaging films, food wrap films, agricultural / Horticultural films, greenhouse films, films for magnetic tape cassette products such as video and audio, films for floppy disk packaging, fences, oil fences for marine, river, and lakes, adhesive tapes, tapes, binding materials, waterproof sheets , Bulk, tent, etc.

The foam containing the polyhydroxycarboxylic acid of the present invention can be used, for example, in a lunch box, tableware, a container for lunches and prepared dishes, a cup of cup ramen, and a vending machine for beverages, which are sold at convenience stores. Used cups, containers and trays for foodstuffs such as fresh fish, meat, fruits and vegetables, tofu, natto, prepared foods, and dairy products such as torobaco, milk, yogurt, and lactic acid beverages used in the fresh fish market. Containers, containers for carbonated drinks and soft drinks, containers for alcoholic drinks such as beer and whiskey, cosmetic containers, detergent containers,
Bleaching containers, cool boxes, flower pots, tapes, cushioning materials for use in transporting home appliances such as TVs and stereos,
Cushioning material for transportation of precision machines such as computers, printers, clocks, etc., Cushioning material for transportation of optical machines such as cameras, glasses, microscopes, telescopes, etc., and transportation of ceramic products such as glass and ceramics It can be suitably used as a cushioning material, a light shielding material, a heat insulating material, a soundproofing material and the like for use.

The foam containing the polyhydroxycarboxylic acid of the present invention can be suitably used for medical or hygienic purposes. For example, bandages, carriers for patches for skin and mucous membranes,
Triangular bandage, bandage, towel, disposable towel, disposable wet towel, towel, rag, tissue, cleaning / disinfecting wet tissue, Aka's wet wipe, tissue napkin, sanitary napkin, sanitary tampon, surgery It can be suitably used for blood absorption tampon for business use and childbirth, hygiene cover stock material, sterilization bag and the like. Furthermore, it can be suitably used for general industrial use including agriculture, fishing, forestry, industry, construction and civil engineering, transportation and transportation, and recreational use including leisure and sports. For example, agricultural cold gauze, oil absorbing material, soft ground reinforcement, artificial leather, floppy disk lining, cement bag, fertilizer bag, sandbag bag, heat insulating material, soundproofing material, cushioning material, cushion for furniture such as bed and chair It can be suitably used as a material, floor cushion material, packaging material, binding material, non-slip material for muddy or snowy roads, and the like.

[0073]

The polyhydroxycarboxylic acid pellet having a core-sheath structure as in the present invention comprises a core portion and a jacket covering the core portion. For this reason, even if the core resin is amorphous or polyhydroxycarboxylic acid having a low melting point, the outer periphery thereof is covered with a polyhydroxycarboxylic acid having a high molecular weight and a high melting point. It can be handled in the same way as hydroxycarboxylic acid pellets. In other words, even if crystallization at high temperature or solid-phase polymerization at high temperature, pellets are hardly fused to each other in the process or to the inner wall or piping in the dryer to form lumps, so that resin molding of a certain quality is performed. Products can be manufactured stably. Also, even if dry blended with other resin and dried at high temperature, or contacted with resin dried at high temperature, the resin is fused to each other in the dryer, Therefore, it is possible to stably produce a resin molded product of a constant quality.

[0074]

The present invention will be described below in more detail with reference to examples.

The description of the synthesis examples, embodiments, and examples in the specification of the present application is for the purpose of assisting the understanding of the contents of the present invention, and these descriptions narrow the technical scope of the present invention. It is not of a nature to be interpreted.

The evaluation method used in this example is as follows. 1. Weight average molecular weight Weight average molecular weight (Mw) of polyhydroxycarboxylic acid
Is a gel permeation chromatography (GP
C, column temperature 40 ° C., chloroform solvent). 2. Melting point The melting point of polyhydroxycarboxylic acid is determined by a differential scanning calorimeter.
(Pyris 1 type differential scanning calorimeter manufactured by PerkinElmer). Measurement conditions are 60 ° C and 5mmH
5 mg of a sample from the center of the polyhydroxycarboxylic acid pellets dried for about 5 hours or more under a pressure of 5 g was sealed in a liquid aluminum pan under a nitrogen atmosphere.
The temperature of an endothermic peak detected when the temperature is raised at a temperature rising rate of 0 ° C. to 10 ° C. is determined. [Example 1] Inner core 88% L-lactic acid 102.3 kg, stannous oxide 410
g into a drum with a stirrer having an internal volume of 0.5 m ³ , and the temperature was raised from room temperature to 160 ° C. over 1 hour under a normal pressure nitrogen atmosphere, and the temperature was maintained at 160 ° C. for 1 hour. The pressure was gradually reduced from normal pressure to 10 mmHg over 2 hours, and the reaction was finally performed at 160 ° C./10 mmHg for 10 hours. The weight average molecular weight of this polylactic acid is 10.0
00, melting point 145 ° C. Outer part 88% L-lactic acid 102.3kg, stannous oxide 410
g into a drum with a stirrer having an internal volume of 0.5 m ³ , and the temperature was raised from room temperature to 140 ° C. over 1 hour under a normal pressure nitrogen atmosphere, and heated at 140 ° C. for 3 hours while distilling water out of the system. Stirred. Thereafter, a Dean-Stark trap containing 72 kg of o-dichlorobenzene was installed, and 72 kg of o-dichlorobenzene was further added to the reaction mass.
It was azeotropically dehydrated at 270 mmHg for 4 hours. Remove the Dean Stark trap and remove 30 molecular sieves.
g, filled with a tube containing 54 kg of o-dichlorobenzene having a water content of 10 ppm or less. -Dichlorobenzene was added, and the mixture was heated and stirred at 140 ° C / 270 mmHg for 8 hours while preventing water from being mixed into the system. Thereafter, the reaction solution was cooled to 30 ° C. to crystallize the polymer, and o-dichlorobenzene was distilled off at 60 ° C./10 mmHg to dry the polymer under a nitrogen atmosphere. This polylactic acid has a weight average molecular weight of 66,000 and a melting point of 15
6 ° C. Manufacture of pellets The resin for the jacket part is melted with a twin-screw extruder with a cylinder temperature of 180 ° C, and the resin for the core part is melted with a single-screw extruder with a cylinder temperature of 172 ° C. The extruder was extruded into the form of a strand into the air by joining the discharge ports, cooled in water, and then pelletized with a strand cutter to obtain a pellet of polylactic acid. In addition, the feed rate of the extruder was adjusted so that the weight ratio of the polylactic acid in the jacket portion and the inner core portion was 20:80. Crystallization / Solid State Polymerization Such polylactic acid pellets are continuously supplied to a reactor equipped with a horizontal continuous heating tank 2, a horizontal continuous heating tank 3, and a solid state polymerization reaction tank 4 as shown in FIG. And solid phase polycondensation. In FIG. 2, 1 is a supply hopper, 5
Denotes a nitrogen purifier, 6 denotes a blower, and 7 denotes a heater. In this reactor, in the horizontal continuous heating tank 2, a step (A) of supplying pellets of polyhydroxycarboxylic acid from one of the heating tanks and discharging the pellets of polyhydroxycarboxylic acid from the other while heating and stirring is performed. Will be In the horizontal continuous heating tank 3, a step (B) of supplying pellets of the polyhydroxycarboxylic acid having undergone the step (A) from one of the heating tanks and discharging the pellets of the polyhydroxycarboxylic acid from the other while heating and stirring the same. Done.

The polylactic acid liquid phase polycondensate pellets produced by the above-described method are supplied from one of the horizontal continuous heating tanks 2 to 70.
The mixture was stirred while being heated to ° C. The residence time in this step (A) was 40 minutes. Next, the polylactic acid pellets produced in the step (A) are supplied to the horizontal heating tank 3,
And stirred while heating. The residence time in this step (B) was 20 minutes.

The polylactic acid pellets obtained by the crystallization step as described above are supplied to a solid-state polycondensation reaction tank 4 and heated in the reaction tank under a nitrogen atmosphere at 140 ° C. for 40 hours.
Solid phase polycondensation was performed.

The weight average molecular weight of the polylactic acid obtained in the solid phase polycondensation step was 140,000.

In each of the above steps, polylactic acid did not cause fusion and could be produced efficiently. Comparative Example 1 A solid-state polycondensation reaction was carried out using the same reaction apparatus as in Example 1 except that pellets of polyhydroxycarboxylic acid comprising only the inner core portion of Example 1 were used.

That is, the polylactic acid polycondensate pellets were supplied to the horizontal continuous heating tank 2 and stirred while heating to 70 ° C. The supply amount was adjusted so that the residence time in this step (A) was 40 minutes. However, since the pellets were melted in this step, heating in the subsequent steps became impossible.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a polyhydroxycarboxylic acid pellet according to the present invention.

[Explanation of symbols]

 1 ... core part 2 ... ... jacket part

FIG. 2 is a conceptual diagram illustrating a heating device used in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Supply hopper 2 ... Horizontal continuous heating tank 3 ... Horizontal continuous heating tank 4 ... Solid-state polycondensation reaction tank 5 ... Nitrogen purification apparatus 6 ... Blower 7 ... Heater

Continued on the front page F term (reference) 4F201 AA24 AH01 AH02 AH53 AH54 AH55 AH56 AH59 BA02 BC02 BC12 BC19 BC37 BL12 BL42 BL43 4J002 CF18W CF18X CF19W CF19X GB00 GC00 GG01 GG02 GL00 4J029 AA02 AA05 EA02 EA02 EA02 EH03 JA011 JA051 JA061 JA091 JA121 JA191 JA201 JB013 JB063 JB143 JB153 JB171 JB183 JC343 JC361 JC371 JF131 JF181 JF211 JF221 JF321 JF361 JF371 JF471 KB05 KC01 KD01 KD02 KD07 K04 KD09 KD17 K05 KD09 KD17 K05 KD09 KD17

Claims (4)

[Claims] 1. A polyhydroxycarboxylic acid pellet comprising (I) a core part and (II) a jacket covering the core part, wherein (I) the core part has a weight average molecular weight ( Mw) is 2,000-
And (II) the jacket portion has a weight average molecular weight (Mw) of 30,000.
A resin comprising a polyhydroxycarboxylic acid in the range of ~ 200,000, wherein the resin constituting the core portion has a lower or lower melting point than the resin constituting the outer cover portion A polyhydroxycarboxylic acid pellet, characterized in that: 2. The polyhydroxycarboxylic acid pellet according to claim 1, wherein the hydroxycarboxylic acid is an aliphatic hydroxycarboxylic acid. 3. The polyhydroxycarboxylic acid pellet according to claim 2, wherein the aliphatic hydroxycarboxylic acid contains lactic acid. 4. The polyhydroxycarboxylic acid pellet according to claim 1, which is a raw material for crystallization and / or solid phase polymerization in a crystallization step and / or solid phase polymerization step. A method for producing a polyhydroxycarboxylic acid, which is characterized by the following.