WO1999019378A1

WO1999019378A1 - Processes for producing polyhydroxy carboxylic acid and glycolide

Info

Publication number: WO1999019378A1
Application number: PCT/JP1998/004618
Authority: WO
Inventors: Mitsuru Hoshino; Kazuyuki Yamane; Yukichika Kawakami; Yasushi Okada
Original assignee: Kureha Kagaku Kogyo K.K.
Priority date: 1997-10-13
Filing date: 1998-10-13
Publication date: 1999-04-22

Abstract

A process for producing a polyhydroxy carboxylic acid which comprises condensation-polymerizing either an alkyl hydroxy carboxylate or a hydrolyzate containing a hydroxy carboxylic acid and obtained by hydrolyzing at least part of the alkyl hydroxy carboxylate to yield a prepolymer and polymerizing the resultant prepolymer by solid state polymerization; and a process for producing a glycolide which comprises subjecting the resultant glycolic acid prepolymer or polyglycolic acid to solid state depolymerization.

Description

Description Technical field of producing polyhydroxycarboxylic acid and glycolide>

The present invention relates to a method for producing polyhydroxycarboxylic acid such as polyglycolic acid, and more particularly, to economically produce polyhydroxycarboxylic acid having excellent melt moldability and mechanical properties. On how to do it. Polyhydroxycarboxylic acid obtained by the production method of the present invention is a polymer having a high molecular weight, has biodegradability, and can be obtained as a high-quality polymer. It is useful as a substitute for medical materials and general-purpose resins, for example.

Polyhydroxycarboxylic acid, typified by polyglycolic acid and polylactic acid, is degraded in the natural environment and eventually has the biodegradability of being converted into water and carbon dioxide by microorganisms . For this reason, polyhydroxycarboxylic acids are receiving attention in fields such as medical materials and general-purpose resin substitutes. In particular, at present, when environmental issues are being closed up, biodegradable polyhydroxycarboxylic acid can be said to meet the needs of the times. However, conventionally, it has been very difficult to economically obtain a high-molecular-weight, high-quality polyhydroxycarboxylic acid.

Conventionally, poly (hydroxycarboxylic acid) production methods include cyclic dimers such as lactide (a cyclic dimer of lactic acid) and glycolide (a cyclic dimer of glycolic acid). After synthesis, the cyclic dimer is catalyzed (eg, A method of performing ring-opening melt polymerization in the presence of tin stannate) is known. According to this method, a polymer having a high molecular weight can be obtained. However, in this method, it is difficult to obtain a high-purity cyclic dimer at a low cost, and the obtained polymer tends to be expensive. In addition, this method has complicated reaction steps and operations.

JP-A-6-635360 describes that a hydroxycarboxylic acid or an oligomer thereof is subjected to a dehydration polycondensation reaction in a reaction mixture containing an organic solvent in the substantial absence of water. Then, a method for producing a polyhydroxycarponic acid having a weight average molecular weight of not less than 1500 is described. The examples in this publication show that polylactic acid having a high molecular weight of up to about 180,000 was obtained. However, in this method, since an organic solvent is used, complicated equipment is required for dehydration, drying, and recovery of the organic solvent. In addition, the publication does not describe any examples relating to polyglycolic acid. Polyglycolic acid does not dissolve in chloroform-methylene chloride. Therefore, the average molecular weight measurement method described in the official gazette (that is, gel partitioning in a crotch-form solution) is used. Chromatography) and the method of measuring logarithmic viscosity using a Ubbelohde viscometer with a methylene chloride solution cannot be applied to polyglycolic acid. Therefore, according to the content of this publication, it can be said that polyglycolic acid can be obtained as a polymer having a weight average molecular weight of 150,000 or more necessary for exhibiting sufficient mechanical properties by the above method. It cannot be estimated.

Japanese Patent Application Laid-Open No. 7-173264 discloses that a hydroxycarboxylic acid ester or a mixture thereof or an oligomer thereof is subjected to a condensation reaction in the presence of a catalyst to give a weight average molecular weight of about 15 A process for producing polyhydroxycarboxylic acids of at least 2,000 is disclosed. However, the gazette It is described that the weight average molecular weight of the poly (hydroxycarboxylic acid) obtained by the method is as low as about 15,500 to 100,000. Therefore, this production method cannot obtain a high molecular weight polyhydroxycarboxylic acid having sufficient mechanical properties.

Conventionally, as a method for obtaining a high molecular weight polyhydroxycarboxylic acid in a short time, a low molecular weight polymer is prepared by polycondensation of a hydroxycarboxylic acid, and the low molecular weight polymer is prepared. There is known a method of prolonging quenching by reacting with a binder. Specifically, Japanese Patent Application Laid-Open No. 62-280220 discloses that (co) polycondensation of lactic acid and glycolic acid is carried out to obtain low molecular weight polylactide, polyglycolide, Alternatively, a copolycondensate thereof is prepared and then reacted with an oxychloride selected from a dichloride compound or thionyl chloride, and then subjected to a melt polycondensation reaction, or an amine compound is added. It describes a method for producing high molecular weight polylactide, polyglycolide, or a copolycondensate thereof by reacting. However, the examples in the publication show that the obtained polymer has a molecular weight of less than 20,000, and its mechanical properties are insufficient, so that its use is limited. With this method, it is not possible to obtain polyhydroxycarboxylic acid exhibiting sufficient mechanical properties.

Japanese Patent Application Laid-Open No. H11-156319 discloses that when glycolic acid and Z or lactic acid are polycondensed to produce an aliphatic polyester, ethylene glycol, 1,2-propylene glycol and the like are used. A method for producing an aliphatic polyester which is added to glycols to increase the molecular weight by solid phase polymerization is disclosed. However, this method has a problem that an undesirable heterogeneous structure is introduced into the formed polymer.

In other words, as described in JP-T-6-501128, a typical sample component of an industrial-grade 70% aqueous solution of glycolic acid is used. Is as shown below.

Glycolic acid 62.4% by weight

Glycolic acid dimer 8.8% by weight

Diglycolic acid 2.2% by weight

2.2% by weight of methoxyacetic acid

Formic acid 0.2 4 wt ^_0/0 When you produce polycondensate (co) with glycol acid of Yo I Do composition, diglycidyl cholic acid contained as a impurity in the glycol acid, main butoxy Acetic acid and formic acid not only introduce a heterogeneous structure into the resulting polymer, but also make the amount of carboxyl groups in the reaction system excessive compared to the amount of hydroxyl groups. In the invention described in Japanese Patent Application Laid-Open No. H11-156319, it is presumed that the reason for adding glycols during the polycondensation is to make up for the insufficient amount of hydroxy groups. However, the polyglycolic acid synthesized by this method must have a structure containing a considerable amount of undesired heterogeneous bonds other than the glycolic acid binding unit.

On the other hand, hydroxycarboxylic acids such as glycolic acid are difficult to isolate and purify using general-purpose purification methods such as distillation, so complicated operations are required to obtain high-purity substances. In addition, there was a problem that the yield was low. Therefore, high-purity hydroxycarboxylic acids are very expensive and their industrial use is very limited.

As described above, all of the conventional methods for producing polyhydroxycarboxylic acid, including the method using a binder, have advantages and disadvantages. In general, when polyhydroxycarboxylic acid is applied to films and molded articles, its weight average molecular weight must be 15 to stably exhibit the mechanical strength required for these uses. Desirably, it is a high molecular weight substance having a molecular weight of at least 0,000, and more than 200,000 depending on the use. Also, the binder component A production method which can obtain a polyhydroxycarboxylic acid containing no or a small amount thereof in a short time is desirable. However, a high molecular weight and high quality polyhydroxycarboxylic acid can be economically obtained, and no industrially suitable production method has been proposed yet.

An object of the present invention is to provide a method for economically producing a high molecular weight polyhydroxycarboxylic acid having excellent melt moldability and mechanical properties.

Another object of the present invention is to provide a method for economically producing high-quality, high-molecular-weight polyhydroxycarboxylic acid with reduced coloring.

The present inventors have made intensive studies to overcome the problems of the prior art, and as a result, polycondensation of an alkyl glycolate to produce a glycolic acid prepolymer was performed. It has been found that high-molecular-weight polyglycolic acid can be obtained by solid-phase polymerization of poly (glycolic acid). According to this method, a high-molecular-weight polyglycolic acid having a weight-average molecular weight of 150,000 or more can be obtained at relatively low cost. The ease of purification eliminates the problem of introducing unwanted heterologous structures into the resulting polymer. The method of the present invention can be extended to a method for producing polyhydroxycarboxylic acid using a hydroxycarboxylic acid alkyl ester.

When a catalyst is used during the polycondensation of the glycolic acid alkyl ester or during the solid phase polymerization, the produced polymer tends to be colored, and there is also a problem in treating the catalyst remaining in the polymer. On the other hand, when no catalyst is used, There is a problem that it takes a long time for polycondensation and solid-phase polymerization of alkyl glycolate.

Thus, the present inventors have further studied and found that at least a part (that is, part or all) of the hydroxycarboxylic acid alkyl ester is hydrolyzed to give the hydroxycarboxylic acid. By subjecting the hydrolysis product to polycondensation to form a prepolymer, and then subjecting the produced prepolymer to solid-state polymerization to obtain a high molecular weight High-quality polyhydroxycarboxylic acid was obtained.

According to the production method using this hydrolysis product as a raw material, the purification of the hydroxycarboxylic acid ester is easy, so that a high-purity hydroxycarboxylic acid ester can be used. Hydroxycarboxylic acids in the product also have high purity. According to the production method using a hydrolysis product as a raw material, similarly to the case where a hydroxycarboxylic acid ester is used as a raw material, a high molecular weight polyglycolic acid having a weight average molecular weight of 150,000 or more is used. Can be obtained at relatively low cost, and the problem of introducing an undesirable heterogeneous structure into the formed polymer is eliminated. Further, according to the production method using the hydrolysis product, it is possible to obtain high-quality polyhydroxycarboxylic acid with little coloring. This production method is particularly suitable as a method for producing high-quality, high-molecular-weight polyglycolic acid.

In the course of studying the solid-state polymerization reaction, the present inventors have found that, when crystalline glycolic acid prepolymer and poly (vinyl alcohol) are heated under solid-phase polymerization conditions, The part was depolymerized (solid phase depolymerization), and glycoside was found to be produced as a by-product. As a result of further study on the heating temperature, it was found that the heating temperature was more than 220 ° C and less than 245 ° C. We have found that solid-phase depolymerization can efficiently produce high-purity dali-cholide. In solid phase depolymerization, the glycol sublimes and can be collected outside the system.

Conventionally, the glycolic acid prepolymer is ground into a powder and supplied to the reactor in a very small amount (approximately 20 g Zh) while being reduced in pressure (12 to 15 torr) to 270 to 28 A method has been proposed in which depolymerization is carried out by heating to a high temperature of 0 ° C. and the generated glycol is collected in a trap (US Pat. No. 2,668,162). However, this method is difficult to scale up, and the prepolymer becomes heavy during heating and remains in the reactor as a large amount of residue. Cleaning is also complicated. On the other hand, according to the method found by the present inventors, the temperature and time of solid-phase depolymerization, the conditions for recovering sublimed glycolide, and the like are controlled, as necessary. The yield of glycolide can be increased, and high-molecular-weight polyglycolic acid can be obtained at the same time without producing a heavy residue. Therefore, another object of the present invention is to provide a novel method for economically producing high-purity glycolide.

The present invention has been completed based on these findings.

According to the present invention, (1) an alkyl ester of hydroxycarboxylic acid

(A) or a hydroxycarboxylic acid-containing hydrolysis product (B) obtained by hydrolyzing at least a part of the hydroxycarboxylic acid alkyl ester to form a prepolymer. Then, (2) a method for producing polyhydroxycarboxylic acid by solid-phase polymerization of the produced prepolymer is provided.

According to the present invention, preferably, the hydroxycarboxylic acid alkyl ester is used. The stele is an alkyl glycolate, the prepolymer is a prepolymer of glycolic acid, and the polyhydroxycarboxylic acid is polyglycolic acid. Is provided.

Further, according to the present invention, at least one kind of glycolic acid polymer selected from the group consisting of crystalline preglycolic acid and polyglycolic acid , A solid phase depolymerization at a temperature of not less than 220 ° C. and less than 245 ° C. is provided.

BEST MODE FOR CARRYING OUT THE INVENTION>

Alkyl hydroxycarbonate and

The hydrolysis product

In the present invention, as a starting material, a hydroxycarboxylic acid alkyl ester (A) or a hydroxycarboxylic acid-containing product obtained by hydrolyzing a part or all of the hydroxycarboxylic acid alkyl ester is used. Use the hydrolysis product (B).

Examples of the hydroxycarboxylic acids include lactic acid, glycolic acid, 2-hydroxyisobutanoic acid, 3-hydroxybutanoic acid, 4-hydroxybutanoic acid, and 6-hydroxycabronate. Acids etc. can be mentioned. Among these, lactic acid and glycolic acid are preferred, and glycolic acid is particularly preferred.

As the hydroxycarboxylic acid alkyl ester used in the present invention, an ester of hydroxycanolevonic acid and a lower alcohol is preferable. Lower alcohols include methanol, ethanol, phenol, and isopro. Examples include Knoll, Butanol, Pennell, Hexanol, Heptanol, and Octanol. Among the lower alcohols, methanol, ethanol, phenol and isop Alcohols having 1 to 4 carbon atoms, such as lopanol and butanol, are particularly preferred. This is because the use of a hydroxycarboxylic acid alkyl ester having 1 to 4 carbon atoms in the alkyl group facilitates dealcoholization during polycondensation and hydrolytic decomposition. Since these hydroxycarboxylic acid alkyl esters can be isolated by distillation or the like, high-purity products can be obtained relatively easily.

Preferred specific examples of the hydroxycarboxylic acid esters include, for example, methyl glycolate, ethyl glycolate, ethyl glycolate n-propyl, and glycolate. Examples include isopropyl, n-butyl glycolate, isobutyl glycolate, and t-butyl glycolate. Of these, methyl glycolate and ethyl glycolate are particularly preferred because of their ease of dealcoholization.

The purity of the alkyl ester of hydroxycarboxylic acid is not particularly limited.However, in order to obtain a high-molecular-weight polymer, the content of a low-molecular-weight compound serving as an impurity that stops the polymerization reaction is reduced as much as possible. It is desirable to keep it. Such impurities include, for example, when methyl glycolate is used as the alkyl ester of hydroxycarboxylic acid, methyl methoxyacetate, diglycol And methyl oleate. The content of these impurities is usually less than 1% by weight, preferably less than 0.3% by weight, and more preferably less than 0.1% by weight, which is sufficient for increasing the molecular weight. It is desirable in doing.

These azoalkylyl hydroxycarboxylates are usually used alone, but may be used in combination of two or more as required. However, when a mixture of two or more alkyl hydroxycarbonates is used, it is desirable for the solid phase polymerization to be performed so that the crystallinity of the resulting prepolymer is not hindered. Other monomers include, for example, lactic acid, glycolic acid, 2—hydroxyisobutanoic acid, 3—hydroxybutanoic acid, 4-hydroxybutanoic acid, 6—hydroxycabronic acid, and the like. Hydroxycarboxylic acid; Ethylene oxalate, Lactide, Lactones (eg, / 3-propiolactone, / 3-Butyrolactone, Pinoclorola Cuton, arbutyrolactone, (5—valerolactone, / 3—methyl-1 5—norrerolactone, £ 1 liter prolactone), trittle Methylene carbonate, and cyclic monomers such as 1,3-dioxane; fats such as ethylene glycol, propylene glycol, and 1,4-butanediol Aliphatic dicarbonates and aliphatic dicarbonates such as succinic acid and adipic acid Or a mixture of substantially equimolar amounts thereof with an alkyl ester; etc. The other monomers may be used alone or in combination of two or more. The amount of other monomers used is desirably within a range that does not inhibit the crystallinity of the prepolymer.

Hydrolysis of the hydroxycarboxylic acid alkyl ester can be easily carried out by adding water to the hydroxycarboxylic acid alkyl ester and heating. Water may be added to the reaction system in its entirety at the start of the hydrolysis reaction, but may be added in several portions if necessary, or may be added continuously.

When hydrolyzing the hydroxycarboxylic acid alkyl ester, a solid catalyst may be used, if necessary. Examples of the solid catalyst include sulfonate-based ammonium salt-based ion exchange resins. After the completion of the hydrolysis reaction, these solid catalysts can be easily removed by filtration or the like. In addition, a solid catalyst is filled in a column, and the mixture can be hydrolyzed by passing a mixture of a hydroxycarboxylic acid alkyl ester and water. Hydrolysis of hydroxycarboxylic acid alkyl esters produces hydroxycarboxylic acids and alcohols. Removal of the formed alcohol gives the hydroxycarboxylic acid. Partial hydrolysis of the hydroxycarboxylic acid alkyl ester results in a mixture of hydroxycarboxylic acid and hydroxycarboxylic acid alkyl ester. In the present invention, such a hydrolysis product is referred to as a hydroxycarboxylic acid-containing hydrolysis product (B).

Since the hydrolysis reaction is an elimination equilibrium reaction between the ester group and the hydroxyl group of the hydroxycarboxylic acid alkyl ester, it is necessary to increase the amount of water added and to remove Z or the produced alcohol out of the system. And can proceed efficiently.

The amount of water added in the hydrolysis reaction is not particularly limited as long as it is at least an amount sufficient to hydrolyze at least a part of the hydroxycarboxylic acid ester. Usually, it is not less than equivalent (more than equimolar), preferably not less than 2 equivalents and not more than 20 equivalents. If the amount of water added is too small, the reaction rate of the hydrolysis reaction becomes extremely slow, and it is difficult to increase the hydrolysis reaction rate to a desired level. Even if the amount of water added is too large, the effect of increasing the efficiency of the hydrolysis reaction is saturated, so that it is not economical.

The hydrolysis of the alkyl hydroxycarbonate need not necessarily be carried out quantitatively, but is usually at least 50 mol%, preferably at least 80 mol%, of the charged hydroxycarboxylic acid alkyl ester. More preferably, at least 99 mol% is hydrolyzed to hydroxycarboxylic acid. The upper limit of the hydrolysis reaction rate is 100 mol%.

The hydrolysis product (B) is produced when the hydrolysis reaction rate is more than 99 mol%. Is substantially all hydroxycarboxylic acid. The hydrolysis product (B) is a mixture in which, when the hydrolysis reaction rate is, for example, 80 mol%, 80 mol% is hydroxycarboxylic acid and the remaining 20 mol% is alkyl hydroxycarbonate. is there.

Hydroxycarboxylic acid alkyl ester (A) has a too low rate of hydrolysis because of the low rate of polycondensation and solid-state polymerization in the absence of a catalyst. Under this condition, it becomes difficult to shorten the reaction time or to improve the yield of the polycondensate or the solid-phase polymer. On the other hand, hydroxycarboxylic acid alkyl esters tend to be colored when polycondensation or solid-phase polymerization is carried out using a catalyst. Therefore, if a hydrolysis product (B) having a hydrolysis reaction rate that is too low is used, It becomes difficult to prevent coloring in the presence of a catalyst. However, according to the production method of the present invention, even if the hydroxycarboxylic acid alkyl ester (A) is used, a sufficiently high molecular weight polyhydroxycarboxylic acid can be obtained. Even when the hydrolysis product (B) in which at least 10 mol%, and in many cases at least 30 mol% of the hydroxycarboxylic acid alkyl ester is hydrolyzed to hydroxycarboxylic acid, the reaction rate and the prevention of discoloration can be improved. Some improvement effects can be obtained.

The hydrolysis reaction and the dehydration reaction can proceed simultaneously. Alkyl hydroxycarbonate remaining unreacted during the hydrolysis reaction may be removed from the reaction system before the polycondensation reaction and during the Z or polycondensation reaction. After the hydrolysis reaction, water or produced alcohol may remain in the reaction system. The operation of dehydration and dealcoholation during the hydrolysis reaction may involve a polycondensation reaction of hydroxycarboxylic acid ester and / or hydroxycarboxylic acid. May not always be clearly distinguished in stages. Therefore, in the present invention, when the hydrolysis product (B) is used, at least a part of the polycondensation reaction may proceed during the hydrolysis reaction. That is, a polycondensation reaction product may be contained in the hydrolysis product.

In the present invention, the step of hydrolyzing the hydroxycarboxylic acid alkyl ester (A) to produce the hydroxycarboxylic acid-containing hydrolysis product (B) is carried out by the following pre-polymerization reaction by polycondensation reaction. This corresponds to the first step of (1).

Synthesis of prepolymer

In the present invention, in the step (1), a hydroxycarboxylic acid-containing hydrolysis product obtained by hydrolyzing at least a part of the hydroxycarboxylic acid alkyl ester (A) or the hydroxycarboxylic acid alkyl ester is obtained. The product (B) is polycondensed to form a hydroxycarboxylic acid prepolymer (hereinafter simply referred to as “prepolymer”). In the prepolymer synthesis step, a polycondensation reaction involving a dealcoholization reaction and a Z or dehydration reaction proceeds.

When the hydrolysis product (B) containing a hydroxycarboxylic acid is polycondensed, a polycondensation reaction may be performed subsequently in a reactor in which the hydroxycarboxylic acid alkyl ester is hydrolyzed, The hydrolysis reaction and the polycondensation reaction may be performed in separate apparatuses. When the hydroxycarboxylic acid alkyl ester (A) or the hydrolysis product (B) is polycondensed, an inert gas such as nitrogen gas is added to the reaction system to facilitate the dealcoholization reaction and the Z or dehydration reaction. The flow may be continued, or the pressure of the reaction system may be reduced.

The polycondensation reaction is usually above 80 ° C, preferably 100 to 230 ° C, more preferably 110 to 220 ° C, most preferably 120 ~ 2 1 0 Performed in a temperature range of ° C. If the reaction temperature is too low, the reaction rate will increase significantly. If the reaction temperature is too high, the thermal stability of the formed prepolymer is impaired, and the prepolymer is easily colored. The reaction temperature does not need to be kept constant during the polycondensation reaction, but may be varied as needed.

In the production method of the present invention, the hydroxycarboxylic acid alkyl ester

The polycondensation of (A) or the hydrolysis product containing hydroxycarboxylic acid (B) produces prepolymers of relatively low molecular weight, often crystalline. If the prepolymer is not crystalline, it tends to be in a molten state during the solid-state polymerization reaction, and as a result, side reactions are likely to occur. The weight average molecular weight of the prepolymer is usually from 5,000 to 5,000, preferably less than 50,000, and preferably from 8,000 to 100,000. If the weight average molecular weight of the prepolymer is too low, it takes a long time to obtain a high molecular weight polyhydroxycarboxylic acid by the subsequent solid-phase polymerization, which is not economical. On the other hand, the weight average molecular weight is not less than 150,000 or more depending on the polycondensation of the hydroxycarboxylic acid alkyl ester (A) or the hydrolysis product (B) alone without combining with solid-state polymerization. It is difficult to obtain high molecular weight polymers.

The glass transition temperature of the prepolymer is usually 100 ° C or lower, and is usually about 20 to 50 ° C. Since the prepolymer has an appropriate glass transition temperature and is crystalline, solid-state polymerization can be easily performed. The melting point of the prepolymer is preferably in the range of 130 to 230, more preferably in the range of 150 to 225 ° C. If the melting point of the prepolymer is too low, it is difficult to shorten the reaction time by setting the solid-state polymerization temperature high.

Hydroxycarboxylic acid alkyl ester (A) or hydrolysis product

The polycondensation of (B) is reversed when the resulting prepolymer reaches a predetermined molecular weight. End point. When the produced prepolymer has a relatively low molecular weight, it is liquid at the end of the polycondensation reaction, and solidifies and crystallizes upon cooling. If the resulting prepolymer has a relatively high molecular weight, the solidification stage is the end point of the polycondensation reaction. After the completion of the reaction, solid-phase polymerization may be performed as it is.However, in order to increase the total surface area, it is preferable that the prepolymer is granulated by a treatment such as pulverization and then solid-phase polymerization is performed. It is more efficient.

Preferably, the prepolymer has a crystallinity of at least 10% when determined by the amount of molten enthalpy. If the crystallinity is too low, solid-state polymerization becomes difficult and side reactions are likely to occur. The crystallinity of the prepolymer is preferably greater than or equal to 20%, more preferably greater than or equal to 30%, and often greater than or equal to 40%. The upper limit of the crystallinity is usually about 70%, and in many cases about 60%.

The synthesis of the prepolymer can be carried out without a catalyst, but a catalyst may be used to shorten the polymerization time. Catalysts include stannous chloride, stannic chloride, stannous sulfate, stannous oxide, stannic oxide, tetraphenyltin, stannous octoate, and stannous acetate. Tin-based catalysts such as monoacid and stannic acetate; Titanium-based catalysts such as titanium tetrachloride, isopropionate titanate, and butyl titanate; metal germanium, germanium tetrachloride, and germanium oxide Germanium-based catalysts such as rumanium; and metal oxide-based catalysts such as zinc oxide, antimony trioxide, lead oxide, aluminum oxide, and iron oxide. These polycondensation catalysts can be used alone or in combination of two or more.

In the case of using a polycondensation catalyst, a polycondensation catalyst, referenced to the metal atom, of the monomer 1 mole, preferable to rather the ^{1 X 1 0- 5 ~ 1 X} 1 0 2 eq, favored more properly it is added at a rate of 3 X 1 0 one ^⁵ ~ ⁵ X 1 0 ^ύ equivalent. Here, the monomer means a hydroxycarboxylic acid alkyl ester and Z or hydroxycarboxylic acid. If the addition amount of the polycondensation catalyst is too small, the polymerization time becomes long, and the purpose of adding the catalyst cannot be sufficiently achieved. If the addition amount of the polycondensation catalyst is too large, the color of the produced polymer becomes large, and the commercial value may be impaired. The polycondensation catalyst is added to the reaction system as it is, or dissolved or mixed in an appropriate liquid. The addition may be made at once or in portions. The polycondensation catalyst may be added to the reaction system at any time until the polycondensation reaction is substantially completed.

The synthesis of the prepolymer is preferably carried out without a catalyst in consideration of the suppression of coloring of the polyhydroxycarboxylic acid and the handling of the remaining catalyst. When performing the polycondensation reaction, a coloring inhibitor may be added if necessary. As a coloring inhibitor, a phosphorus compound can be suitably used. Examples of the phosphorus compound include phosphoric acid, trimethyl phosphinate, triethyl phosphinate, triphenyl phosphite, monomethyl polyphosphate, and polymethyl phosphate. Getyl linoleate, pyrrolic acid, triethyl pyrophosphate, hexamyl pyramide phosphite, phosphorous acid, triethyl phosphite, triethyl phosphite Examples include fuel. These phosphorus compounds can be used alone or in combination of two or more.

The phosphorus compound is preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the product theoretically obtained by the polycondensation reaction. 0 3 to 3 parts by weight are added. If the amount is too small, the effect of preventing coloration is small. If the amount is too large, the reaction rate of polycondensation may be reduced. The phosphorus compound is added to the reaction system as it is, or dissolved or mixed in an appropriate liquid. Additions can be made in batches or split Is also good. The phosphorus compound may be added to the reaction system at any time until the polycondensation reaction is substantially completed.

Solid state polymerization

In the present invention, a high molecular weight polyhydroxycarboxylic acid is produced by subjecting the prepolymer obtained by the above method to solid phase polymerization.

When solid-phase polymerization is performed, the shape of the prepolymer may be any of a lump, a pellet, a granule, a powder, and the like, and is not particularly limited. If the prepolymer is made finer by pulverization or the like, the total surface area increases, so that the solid phase reaction can be promoted.

The solid phase polymerization is usually carried out by heating to a temperature equal to or higher than the glass transition temperature of the prepolymer in an inert gas atmosphere, under reduced pressure, or in an inert solvent. In solid-state polymerization, the polymerization reaction is performed in a solid state literally. Therefore, the upper limit of the reaction temperature of solid-state polymerization is determined by the melting point of the prepolymer and the solid-state polymerization reaction product.

At the start of the solid-state polymerization, the reaction temperature is lower than the melting point of the prepolymer, preferably 5 ° C or less of the melting point of the prepolymer, more preferably 10 ° C. The following is assumed. If solid-state polymerization is started by heating to a temperature equal to or higher than the melting point of the pre-polymer, the pre-polymer is melted, so it can no longer be called solid-state polymerization, and it becomes melt polymerization. U. In melt polymerization, side reactions become very likely to occur and it is difficult to increase the molecular weight. In addition, if the prepolymer is heated to a temperature very close to the melting point and solid-state polymerization is initiated, side reactions are likely to occur, which tends to cause a decrease in molecular weight, generation of gas, coloring, and the like. Not good. After the start of solid-state polymerization, the pre-polymer or the product during the solid-state polymerization reaction (hereinafter, both are called `` solid-state polymerization reaction The melting point of In such a case, the reaction temperature of solid-state polymerization can be gradually increased. Therefore, if the melting point of the solid-phase polymerization reaction product is higher than the melting point of the raw material prepolymer during the solid-state polymerization, the reaction temperature is increased during the solid-state polymerization at the start of the solid-state polymerization described above. The temperature can be raised to a temperature exceeding the temperature, thereby increasing the reaction rate of solid-state polymerization. Therefore, for example, during the solid phase polymerization, the reaction temperature can be raised to a temperature higher than the melting point of the prepolymer produced in step (1), and the solid phase polymerization reaction can be continued. However, even in that case, the reaction temperature must be controlled to a temperature at which the solid-state polymerization reaction product maintains a solid state, and the melting point of the solid-state polymerization reaction product at that point should be 5 ° C or less. Preferably, it should be 1 o ° c or less.

The reaction temperature of solid-state polymerization is a temperature higher than the glass transition temperature of the prepolymer, from the viewpoints of the reaction rate, maintenance of the solid state, and the physical properties of the formed polymer. It is preferable that the temperature is appropriately determined within a temperature range at which the material can maintain a solid state. The reaction temperature is often between 100 and 230. Preferably, it is determined within the range of C. More specifically, the temperature is higher than the glass transition temperature of the prepolymer, preferably 100 ° C or higher, and the melting point of the immediately preceding prepolymer obtained in step (1). At lower temperatures, solid state polymerization can be initiated and the reaction temperature can be raised as the melting point of the solid state polymerization reaction product increases during solid state polymerization. Even when the reaction temperature is increased during solid-state polymerization, the temperature is controlled to a temperature of 230 ° C or lower and the temperature at which the solid-state polymerization reaction product maintains a solid state. It is preferable to continue the phase polymerization.

Solid-phase polymerization is usually carried out under the following conditions: (1) under an atmosphere of an inert gas such as nitrogen or argon, (2) under reduced pressure, or (3) under an inert solvent such as liquid paraffin. This is done by heating the polymer. At the start of and during solid state polymerization, the reaction temperature is controlled to a temperature at which the prepolymer and the solid state polymerization reaction product maintain a solid state. By this solid-state polymerization, high-molecular-weight polymers can be obtained by avoiding undesired side reactions.

The molecular weight of the polymer produced by solid-state polymerization is 150,000 in order to exhibit stable and sufficient mechanical properties for applications such as films and molded products. As described above, more preferably, it is more preferably 200,000 or more.

Solid phase polymerization can be carried out without a catalyst, but a catalyst may be used to shorten the polymerization time. Catalysts include stannous chloride, stannic chloride, stannous sulfate, stannous oxide, stannic oxide, tetraphenyltin, stannous octoate, and stannous acetate. Tin-based catalysts such as acid and stannic acetate; Titanium-based catalysts such as titanium tetrachloride, isopropionate titanate and butyl titanate; metal germanium, germanium tetrachloride, and germanium oxide And a metal oxide catalyst such as zinc oxide, antimony trioxide, lead oxide, aluminum oxide, iron oxide, and the like. These catalysts can be used alone or in combination of two or more.

When a catalyst is used in the solid phase polymerization, the catalyst is usually used in an amount of 0.001 to 2 parts by weight, preferably 0.005 to 0 parts by weight, per 100 parts by weight of the prepolymer. . Add 5 parts by weight. If the amount of the catalyst is too small, the effect of shortening the solid-state polymerization time is small, and the purpose of adding the catalyst cannot be sufficiently achieved. If the amount of catalyst added is too large, the color of the formed polymer becomes too large, which may impair the commercial value. The catalyst is added to the reaction system as it is or after being dissolved or mixed in an appropriate liquid. The catalyst may be added all at once or in portions. The catalyst is substantially Any time may be added to the reaction system until the solid-phase polymerization reaction is completed. However, in the solid-state polymerization reaction, it is preferable to carry out the reaction without a catalyst in consideration of suppressing the coloring of the produced polymer and handling the remaining catalyst.

When performing solid phase polymerization, a coloring inhibitor can be added if necessary. As a coloring inhibitor, a phosphorus compound can be suitably used. Examples of the phosphorus compound include phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, monoethyl polyester polyphosphate, and polyethyl phosphate. Getyl ester, pyrrolinic acid, triethylpyrrolineate, hexamethylpyrrolineate, phosphite, triethyl phosphite, triphenyl phosphite And so on. These phosphorus compounds can be used alone or in combination of two or more. The phosphorus compound is usually added in an amount of 0.001 to 10 parts by weight, preferably 0.003 to 3 parts by weight, based on 100 parts by weight of the prepolymer. If the amount is too small, the effect of preventing coloring is small, and if it is too large, the polymerization rate may be slow. The phosphorus compound is added to the reaction system as it is, or dissolved or mixed in an appropriate liquid. The addition may be made at once or in portions. The phosphorus compound may be added to the reaction system at any time as long as the solid-state polymerization reaction is practically completed. In the case where a coloring inhibitor has already been added during the synthesis of the prepolymer, it is not necessary to add the coloring inhibitor again during the solid phase polymerization, but it may be added if desired.

The solid-phase polymerization can be terminated preferably at any time when a polyhydroxycarboxylic acid having a weight average molecular weight of 150,000 or more is produced. It is more preferable to produce a polymer having a weight average molecular weight of 200,000 or more by solid phase polymerization. Manufacturing method of glycolide

In the solid-state polymerization step of the present invention, since the glycol may sublime, by collecting the by-product glycolide, it is possible to obtain a high-purity glycolide. it can.

Glycolide has been used as a raw material for polyglycolic acid (polyglycolide) and glycolic acid copolymer, but it is economically efficient. It was very difficult to mass-produce the glycol.

On the other hand, at least one type of glycolic acid polymer selected from the group consisting of crystalline glycolic acid prepolymer and polyglycolic acid was added at 220 ° C or higher. By performing solid-phase depolymerization at a temperature of less than 45 ° C, high-purity glycolide can be efficiently obtained. The solid-phase depolymerization is preferably performed at a temperature in the range of 220 ° C or more and less than 245 ° C. The solid-phase depolymerization is performed under a temperature condition in which the glycolic acid polymer maintains a solid state.

It is preferable that the glycolic acid polymer has a melting point of 220 ° C. or more. If the melting point of the glycolic acid polymer is lower than 220 ° C before the solid phase depolymerization reaction, it is desirable to increase the melting point by heat treatment or the like. If the solid phase depolymerization temperature is higher than 245 ° C, the glycolic acid polymer is easily decomposed.

The glycolic acid polymer is obtained by polycondensing a glycolic acid alkyl ester or a glycolic acid-containing hydrolysis product obtained by hydrolyzing at least a part of the glycolic acid alkyl ester. Prepolymers or polymers have a relatively high melting point, which allows for solid-state depolymerization at high temperatures, and high yields of glycosides. You.

Glycolic acid polymers include flakes, pellets, powders, particles, etc. Any shape can be used, but it is preferable to reduce the size by grinding to increase the reaction rate.

The conditions of the solid-phase depolymerization are the same as those of the solid-phase polymerization described above, except for the above temperature conditions. That is, in the solid phase depolymerization, when a glycolic acid prepolymer or a solid phase polymerization reaction product during the solid phase polymerization reaction of the prepolymer is used as a raw material, Compete with The solid-phase depolymerization is preferably carried out under a normal pressure under an inert gas stream or under reduced pressure. Glycoride generated by the solid-phase depolymerization sublimates, so that it can be recovered by collecting it outside the system. In a pressurized system, the glycol is not discharged out of the system, so the equilibrium reaction between solid-phase depolymerization and solid-phase polymerization is likely to occur, and glycol is not easily generated. Isolation is often difficult and is not preferred. The sublimated glycol can be recovered by a conventional method. Although the solid phase depolymerization occurs even at a temperature lower than 220 ° C, the reaction rate is slow. Therefore, in order to obtain a good yield of the glycol, the reaction temperature is set to 220 ° C or higher. On the other hand, when the reaction temperature exceeds 245 ° C, it becomes difficult to maintain the glycolic acid polymer in a solid state, and the glycolic acid polymer becomes heavy. Residue easily.

According to this solid-phase depolymerization method, by controlling the temperature and time of the solid-phase depolymerization and the conditions for collecting the sublimated glycolide, the yield of glycolide can be increased. In addition, high-molecular-weight polyglycolic acid can be obtained at the same time without producing a heavy residue. The glycol obtained by solid phase depolymerization can be used as it is, but if necessary, the purity can be further increased by a purification operation such as recrystallization.

The recovery of glycol by this solid phase depolymerization method is based on glycol It can also be applied to chemical recycling of products composed of acid polymers. Therefore, when solid-phase depolymerization is applied, there is no particular restriction on the molecular weight of the glycolic acid polymer, as long as solid-phase depolymerization is possible.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The methods for measuring physical properties are as follows.

(1) Weight average molecular weight

The weight average molecular weight was determined under the following conditions using a GPC (gel permeation chromatography) analyzer.

Using HFIP (Hexafluoroy Sopronol) as a solvent and passing through a column (HFIP—LG + HFIP—806 MX: 2 pieces: SHODEX) at 40 ° C and lm LZ, the molecular weight is 8 2 Elution of 70,000, 101,000, 34,000, 100,000, and 0.2000 known molecular weight PMMA (methyl polymethacrylate) standards by RI detection A calibration curve obtained from the time was prepared in advance, and the weight average molecular weight was calculated from the elution time.

(2) Melting point

The melting point was determined using a DSC (differential scanning calorimeter) under the following conditions.

Approximately 10 mg of the sample was packed in an aluminum pan, and the sample was dried at 30 ° C for 10 minutes under a nitrogen atmosphere of 50 mLZ using a Mettler DSC 25. The temperature was raised to ° C, and the temperature of the endothermic peak was determined as the melting point.

(3) Glass transition temperature The glass transition temperature in the present invention is defined as the starting temperature of the second-order transition of the temperature change curve of the amount of heat in the transition region from the glass state to the rubber state using a differential scanning calorimeter (DSC). In the examples, since the degree of crystallinity of the formed prepolymer was high, it was made to be in an amorphous state once, and was determined from the change in calorific value using DSC according to the following method.

The prepolymer was sandwiched between aluminum sheets, melt-pressed at a temperature of the obtained melting point plus 10 ° C, and rapidly cooled with ice water to obtain a sheet-like amorphous polymer. Cut out this, pack about 10 mg into aluminum, and use DSC 25 manufactured by METTLER ONE, Inc. under nitrogen atmosphere of 50 mL / min. The temperature rises to 260 ° C at a rate of one minute, and the transition temperature of the temperature change curve of the amount of heat in the secondary transition region corresponding to the transition region from the glassy state to the rubbery state is the glass transition temperature. And

(4) Raw material purity

Low-molecular-weight compounds in the hydroxycarboxylic acid alkyl ester, which are impurities that stop the polymerization, were quantitatively analyzed by gas chromatography. The content of impurities in the methyl glycolate used in this example was 0.01 wt.% Or less, which was below the detection limit of gas chromatography.

%. As the glycolic acid, a special-grade reagent manufactured by Kanto Chemical Industry Co., Ltd. was used.

(5) Crystallinity

The crystallinity of the prepolymer was determined from the enthalpy of fusion according to the following method using DSC.

Fill an aluminum pan with about 10 mg of prepolymer, and use METTLER DSC 25 in a nitrogen atmosphere of 5 OmL for ⁷ minutes at a temperature of 30 ° C to 10 ° C for 26 minutes. The temperature was raised to ° C, and the melting enthalpy of the crystal melting part was determined. In the case of glycolic acid prevolima, J ournalof Ap plied 26, 1727-1734 (19981), the melting of the polyglycolic acid crystal part reported in Polymer Science, Vol. Based on .5 J / g, it was determined from the amount of molten enthalpy (unit: JZ g) of the obtained prepolymer by the following formula. Crystallinity (%) =

[Melting of prepolymers: Ruby Z26.5] XI00 [Example 1]

Synthesis example 1 of pre-polymer

500 g of methyl glycolate and 0.1 g of stannic chloride were charged into a 1-liter titanium autoclave, and the temperature was gradually raised from 130 ° C to 150 ° C. While heating, the methanol generated by the polycondensation reaction was removed. After reacting for 3 hours, the temperature was raised to 180 ° C., and the alcohol-free polycondensation reaction was further continued under reduced pressure of 5 kPa (50 mbar) for 2 hours. After cooling to room temperature, 265 g of a white solid was removed.

The prepolymer obtained in this way has a crystallinity of 52%, a weight average molecular weight of 620,000, a melting point of 207 ° C, and a glass transition temperature of 38 ° C. Met.

Solid state polymerization

After crushing the prepolymer obtained in the above Synthesis Example 1 in a mortar, 20 g of the prepolymer was charged into an eggplant-shaped flask, and the mixture was subjected to a pressure reduction of 10 Pa (0.1 mbar). Solid-state polymerization was performed at 00 ° C for 2 hours and at 215 ° C for 38 hours. The polymer obtained after the reaction had a weight-average molecular weight of 268,000 and a melting point of 228 ° C.

[Example 2]

Synthesis example 2 of prepolymer

Add 500 g of methyl glycolate and 0.1 g of stannic chloride to 1 L The mixture was charged in an autoclave and heated to 130 ° C. to remove methanol formed by the polycondensation reaction. After the reaction for 3 hours, the temperature was raised to 180 ° C., and dry nitrogen was introduced at a flow rate of 1 L / min for 5 hours to continue the dealcohol-free polycondensation reaction. After cooling to room temperature, 2488 g of a white solid was removed.

The prepolymer obtained in this way has a crystallinity of 49%, a weight average molecular weight of 10,000,000, a melting point of 1950 ° C, and a glass transition temperature of 37. there were.

Solid state polymerization

After pulverizing the prepolymer obtained in the above Synthesis Example 2 in a mortar, 20 g of the prepolymer was charged into an eggplant-shaped flask, and 100 ml of dry nitrogen gas was passed through for Z minutes. Solid phase polymerization was performed at 200 ° C for 1 hour, 210 ° C for 1 hour, 220 ° C for 18 hours, and 225 ° C for 10 hours. The polymer obtained after the reaction had a weight average molecular weight of 451,000 and a melting point of 23.6 ° C.

[Example 3]

After pulverizing the prepolymer obtained in the above Synthesis Example 2 in a mortar, 20 g of the prepolymer and 50 g of liquid paraffin were charged into an eggplant-shaped flask, and the mixture was stirred with stirring. The mixture was heated at 190 ° C for 1 hour and at 210 ° C for 4 hours to perform solid phase polymerization. The resulting polymer was separated by filtration, washed with hexane, and dried. The dried polymer had a weight average molecular weight of 163,000 and a melting point of 226 ° C.

[Example 4]

Synthetic example 3 of prepolymer

Transfer 500 g of methyl glycolate, 1.0 g of antimony trioxide, and 1.0 g of triphenyl phosphite into a 1-liter titanium autoclave. The methanol produced by the polycondensation reaction was removed while charging and heating to 150 ° C. After the reaction for 3 hours, the temperature was raised to 200 ° C., and the alcohol removal polycondensation reaction was further continued under a reduced pressure of 0.5 kPa (5 mbar). When the reaction started to solidify, the stirring was stopped and the reaction was continued until the reaction completely solidified.

The prepolymer obtained in this manner had a crystallinity of 56%, a weight average molecular weight of 16,000, a melting point of 21.5 ° C, and a glass transition temperature of 37 ° C. Was.

Solid state polymerization

After pulverizing the prepolymer obtained in the above Synthesis Example 3 in a mortar, 50 g of the micronized prepolymer was flown into a dry nitrogen gas at 100 m1Z while flowing. Solid-state polymerization was performed at 200 ° C for 10 hours, at 210 ° C for 1 hour, and at 220 ° C for 3 hours. The polymer obtained after the reaction had a weight average molecular weight of 208,000 and a melting point of 23 ° C. In addition, this polymer is mixed with a phenol / 0.5,4,5—trichlorophenol mixed solvent with a concentration of 0.5 g / dl [10Z7 (weight ratio)]. The solution was used at 30.0 ± 0.1 ° C. using a Ube-mouth 1-D viscometer. _{When n} / C was determined, it was 0.41.

[Comparative Example 1]

When 20 g of the prepolymer obtained in Synthesis Example 1 was charged into an eggplant-shaped flask and heated to 235 ° C, the prepolymer melted and was colored brown. After reacting under reduced pressure at 30 Pa (0.3 mbar) for 10 hours, the resulting polymer was taken out.The weight average molecular weight was 420,000 and the melting point was 2 17 ° C.

[Comparative Example 2]

Synthesis of prepolymers: ^ 4 A dehydration polycondensation reaction was carried out in the same manner as in Synthesis Example 3 except that 500 g of methyl glycolate was replaced with 42 g of glycolic acid (special grade reagent manufactured by Kanto Chemical Industry Co., Ltd.). I got it. The obtained prepolymer had a crystallinity of 44%, a weight average molecular weight of 37,000, a melting point of 21 ° C and a glass transition temperature of 38 ° C.

Solid state polymerization

Solid phase polymerization was carried out in the same manner as in Example 4, except that the prepolymer obtained in Synthesis Example 4 was used. The polymer obtained after the reaction had a weight average molecular weight of 86,000 and a melting point of 214 ° C and 2229 ° C. Furthermore, a solution of a mixture of phenol / 2,4,5—trichlorophenol [0.5 / 10 (weight ratio)] having a concentration of 0.5 g Zdl was prepared. When _en / C was determined at 0.0 ± 0.1 ° C. using an Ubbelohde viscometer, it was 0.26.

Table 1 shows the results of Examples 1 to 4 and Comparative Examples 1 and 2.

C7) o ΟΊ

0T A 7 V

■ X

CO t Prebolimer Polymer

Deer Crystallinity Molecular weight Melting point Polymerization method Molecular weight Melting point

(% U) Vnirt V Example 1 Methyl glycolate 52 62,000 207 Solid phase 268,000 228 Example 2 Ge II Methinocholate 49 10,000 195 Solid phase * ² 451,000 236

Example 3 Methyl glycolate 49 10,000 195 Solid phase ' ³ 163,000 226

Example 4 Methyl glycolate 56 16,000 215 Solid phase * ⁴ 208,000 232

O

Comparative Example 1 Methyl glycolate 52 62,000 207 Melt ' ⁵ 42,000 217

214

Comparative Example 2 Glycolic acid 44 37,000 214 Solid phase ' ⁶ 86,000

* 5: Under reduced pressure

* 6: Under reduced pressure.

[Example 5]

Hydrolysis

500 g (5.56 mol) of methyl glycolate and 300 g (16.

(67 moles) was charged into a 1-liter titanium autoclave, heated to 120 ° C, and produced by a condenser through circulating water at 65 to 85 ° C. The toluene was removed. After 7 hours, about 15 mol% of the methyl glycolate remained in the autoclave (hydrolysis reaction rate = about 85.0 mol%).

Synthesis example 5 of prepolymer

The capacitor was removed from the autoclave and heated gradually to 150 ° C to perform dehydration (dehydration and dealcoholation). When the distillation of water almost disappeared, the temperature was raised to 180 ° C., and the removal of the condensed water was continued under a reduced pressure of 5 kPa (50 mbar) for 2 hours. Further, the temperature was raised to 200 ° C., and the removal of the condensed water was continued under a reduced pressure of 0.1 lkPa (lmbar) for 2 hours. After cooling to room temperature, 3885 g of a white solid was removed. The obtained prepolymer had a crystallinity of 52%, a weight average molecular weight of 220,000, a melting point of 205 ° C, and a glass transition temperature of 37 ° C.

Solid state polymerization

After pulverizing the prepolymer obtained in the above Synthesis Example 5 in a mortar, 20 g was charged into an eggplant-shaped flask, and at 200 ° C. for 2 hours under a reduced pressure of 10 Pa (0.1 lmbar), Solid-state polymerization was performed at 215 ° C for 38 hours. The polymer formed after the reaction was almost white, had a weight average molecular weight of 268,000 and a melting point of 228 ° C. [Example 6]

Hydrolysis

500 g (5.56 mol) of methyl glycolate and 900 g (50 mol) of water were charged into a 2 L titanium autoclave, heated to 120 ° C, The formed methanol was removed by a condenser through circulating water at 65 to 85 ° C. After 7 hours, about 0.5 mol% of the charged amount of methyl glycolate remained in the autocrepe (hydrolysis reaction rate = about 99.5 mol%).

Synthetic example of prepolymer 6

The capacitor was removed from the autoclave and heated gradually to 150 ° C to perform a dehydration operation. The temperature was raised to 180 ° C. when almost no water distilled, and the removal of condensed water was continued under reduced pressure of 5 kPa (50 mbar) for 2 hours. Further, the temperature was raised to 200 ° C., and the removal of the condensed water was continued under a reduced pressure of 0.1 kPa (lmbar) for 2 hours. After cooling to room temperature, 393 g of a white solid were removed. The obtained prepolymer had a crystallinity of 49%, a weight average molecular weight of 188,000, a melting point of 204 ° C and a glass transition temperature of 37 ° C.

Solid state polymerization

After pulverizing the prevolima obtained in the above Synthesis Example 6 in a mortar, 20 g of the prevolima was charged into an eggplant-shaped flask, and while flowing dry nitrogen at 100 mL / min, 200 g was poured. Solid-state polymerization was performed at 1 ° C. for 1 hour, 1 hour at 210 ° C., 18 hours at 220 ° C., and 10 hours at 225 ° C. The polymer formed after the reaction was almost white, had a weight average molecular weight of 451,000 and a melting point of 2336 ° C.

[Example 7]

Solid state polymerization After pulverizing the prepolymer obtained in the above Synthesis Example 6 in a mortar, 50 g of a fluid paraffin and 20 g of the prepolymer were charged into an eggplant-shaped flask and stirred. While heating at 190 ° C for 1 hour and at 210 ° C for 4 hours, solid-state polymerization was performed. After the polymer was filtered off, it was washed with hexane and dried. The polymer formed after drying was almost white, had a weight average molecular weight of 163,000 and a melting point of 226 ° C.

[Example 8]

Hydrolysis

500 g (5.56 mol) of methyl glycolate and 900 g (50 mol) of water were charged into a 2 L titanium autoclave, heated to 120 ° C, The generated methanol was removed by a condenser through circulating water at 65 to 85 ° C. After 7 hours, about 0.5 mol% of the methyl glycolate remained in the autoclave (hydrolysis reaction rate: about 95.5 mol%).

Synthetic example of prepolymer 7

The capacitor was removed from the autoclave and heated gradually to 150 ° C to perform a dehydration operation. When almost no water distills off, add 0.05 g of stannic chloride, raise the temperature to 180 ° C, and reduce the pressure to 5 kPa (50 mbar) for 2 hours. The removal of the condensed water was continued. Further, the temperature was raised to 200, and the removal of condensed water was continued under a reduced pressure of 0.1 lkPa (lmbar) for 1 hour. After cooling to room temperature, 390 g of a white solid was removed. The obtained prepolymer had a crystallinity of 56%, a weight average molecular weight of 48,000, a melting point of 206 ° C, and a glass transition temperature of 38 ° C. Solid state polymerization

After pulverizing the prepolymer obtained in the above Synthesis Example 7 in a mortar, 20 g of the prepolymer was charged into an eggplant type flask, and dried nitrogen was flowed at 10 OmL / min. Solid-state polymerization was performed at 200 ° C. for 1 hour, 210 ° C. for 1 hour, 220 ° C. for 18 hours, and 225 ° C. for 10 hours. The polymer formed after the reaction was almost white, had a weight average molecular weight of 432,000 and a melting point of 234.

[Example 9]

Synthetic example of prepolymer 8

500 g of methyl glycolate and 0.5 g of stannic chloride were charged into a 1 L titanic autoclave and heated while gradually heating from 130 ° C to 150 ° C. Then, the condensation methanol was removed. After 3 hours, the temperature was raised to 180 ° C, and the removal of the condensed alcohol was continued under a reduced pressure of 5 kPa (50 mbar) for 2 hours. Further, the temperature was raised to 200 ° C., and the removal of the condensed alcohol was continued under a reduced pressure of 0.1 lkPa (1 mbar) for 2 hours. After cooling to room temperature, 265 g of a white solid was removed. The obtained prepolymer had a crystallinity of 48%, a weight average molecular weight of 620,000 and a melting point of 207. C, the glass transition temperature was 38 ° C.

Solid state polymerization

After pulverizing the prepolymer obtained in the above Synthesis Example 8 in a mortar, 20 g was charged into an eggplant-shaped flask and dried at 200 ° C. while flowing dry nitrogen for 100 ml LZ. Solid phase polymerization was carried out for 1 hour, 1 hour at 210 ° C, 18 hours at 220 ° C, and 10 hours at 225 ° C. The polymer formed after the reaction had a weight-average molecular weight of 448,000, a high molecular weight and a melting point of 234, but was colored brown.

[Comparative Example 3]

20 g of the prepolymer obtained in Synthesis Example 6 above was charged into an eggplant-shaped flask, and heated to 235 ° C, whereupon the prepolymer melted and was colored deep brown. Decompression at 30 Pa (0.3 mbar) for 10 hours After the lower reaction was carried out, the polymer was taken out and found to have a weight average molecular weight of 420,000 and a melting point of 2117 ° C.

[Comparative Example 4]

Synthetic example of prepolymer 9

70% glycolic acid (special grade reagent manufactured by Kanto Chemical Industry Co., Ltd.) 700 g of an aqueous solution was charged into a 1-liter titanium autoclave, and the temperature was gradually raised from 130 to 150 ° C. Heating was performed while heating to remove the condensed water. After 3 hours, the temperature was raised to 180 ° C, and the removal of the condensed water was continued under reduced pressure of 5 kPa (50 mbar) for 2 hours. Further, the temperature was raised to 200 ° C., and the removal of the condensed water was continued under a reduced pressure of 0.1 kPa (lmbar) for 2 hours. After cooling to room temperature, 275 g of a white solid was removed. The resulting prepolymer had a crystallinity of 44%, a weight average molecular weight of 46,000, a melting point of 208 and a glass transition temperature of 36 ° C.

Solid state polymerization

After pulverizing the prevolimer obtained in the above Synthesis Example 9 in a mortar, 20 g of the prebolimer was charged into an eggplant-shaped flask, and dried at 200 ° C. while flowing dry nitrogen for 100 ml LZ. The solid-state polymerization was performed for 1 hour at 210 ° C, 18 hours at 220 ° C, and 10 hours at 225 ° C. The polymer formed after the reaction was almost white, had a weight average molecular weight of 108,000 and a melting point of 2 16 ° C.

[Comparative Example 5]

500 g of methyl glycolate and 0.5 g of stannic chloride were charged into a 1 L titanium autoclave, and the temperature was gradually raised from 130 ° C to 150 ° C. Heat was applied to remove the methanol formed by the condensation reaction. Even after 30 hours of reaction, the amount of methanol removed was less than half the theoretical amount, so the reaction was stopped. CO

cn o

Mill M

Table 2

Prepolymer Polymer

Hydrolysis

Raw material Conclusion Molecular weight Melting point Polymerization method Molecular weight Color

(Mol ¾) ^Λη (° C) Example 5 Cryconoleic acid menolee 85.0 52 22,000 205 Solid phase 268,000 228 White Solid example 6 7 Lyco-norre menolere 99.0 49 18,000 204 Solid phase * ² 451,000 236 White Example 7 Glycolic acid Methyl 99.5 49 18,000 204 Solid phase ³ 163,000 226 White Difficult 8 Methyl glycolate 99.5 56 48,000 206 Solid phase ' ⁴ 432,000 234 White Example 9 Methyl glycolate None 48 62,000 207 Solid phase * ⁵ 448,000 234 Brown Comparative example 3 Glycolic acid Methyl 99.5 49 18,000 204 Melted "42,000 217 Brown Comparative Example 4 No glycolic acid 44 46,000 208 Solid phase ' ⁷ 108,000 216 White

Comparative Example 5 Methyl glycolate None Polycondensation reaction of methyl glycolate (non-solid-state polymerization): Reaction stopped

2 ^ 9 ~ (footnote)

* 1: Under reduced pressure

* 2: Under nitrogen,

* 3: Under liquid paraffin,

* 4: Under nitrogen,

* 5: Under nitrogen,

* 6: Under reduced pressure

* 7: Under nitrogen.

[Example 10]

Hydrolysis

Example of synthesis of prepolymer 10

The capacitor was removed from the above autoclave, heated gradually to 150 ° C, and dewatered. The temperature was raised to 180 ° C. when almost no water was distilled off, and the removal of condensed water was continued under reduced pressure of 5 kPa (50 mbar) for 2 hours. Further, the temperature was raised to 215 ° C, and the removal of the condensed water was continued under a reduced pressure of 0.1 kPa (lmbar) for 2 hours. After cooling to room temperature, 390 g of a white solid was removed. The resulting prepolymer had a crystallinity of 50%, a weight-average molecular weight of 200000, a melting point of 211 ° C, and a glass transition temperature of 38 ° C.

Solid-phase weight and solid-state light polymerization 20 g of the prepolymer (melting point: 22.degree. C.) obtained in Synthesis Example 10 above was poured into an eggplant-shaped flask, and the solution was heated to 220.degree. C. under reduced pressure of OPa (0.1 lmbar). For 3 hours, at 225 ° C for 3 hours, at 230 ° C for 3 hours, and at 235 ° C for 3 hours to perform solid-state polymerization and solid-state depolymerization. I went.

Glycoride sublimated to the decompression line was trapped and collected. The obtained glycol was 15 g (75% yield).

On the other hand, the polymer remaining in the flask due to solid-state polymerization remained in a solid state, and could be easily removed by tilting the flask. After removing the polymer, no deposits were found on the flask, and cleaning of the flask was easy. The extracted polymer had a weight average molecular weight of 492,000 and a melting point of 238 ° C.

[Example 11]

Example of synthesis of prepolymer 1 1

500 g of methyl glycolate and 0.1 g of stannic chloride were charged into a 1-liter titanium autoclave and heated to 130 ° C by polycondensation reaction. The generated methanol was removed. Thereafter, the removal of the produced alcohol was continued under reduced pressure at 200 ° C. for 5 hours and at 214 ° C. for 3 hours. After cooling to room temperature, 235 g of a pale yellow solid was removed.

The prepolymer obtained in this manner had a crystallinity of 53%, a weight average molecular weight of 650,000, a melting point of 220 ° C, and a glass transition temperature of 38 ° C. there were.

Solid state polymerization and solid state depolymerization

Solid phase polymerization and solid phase depolymerization were carried out in the same manner as in Example 10 except that the prepolymer (melting point: 220 ° C.) obtained in Synthesis Example 11 above was used. The obtained glycol was 14 g (70% yield). On the other hand, the polymer remaining in the flask due to solid-state polymerization remained in a solid state and could be easily removed by tilting the flask. After removing the polymer, no deposits were found on the flask, and the cleaning of the flask was easy. The removed polymer had a weight average molecular weight of 31,000 and a melting point of 2336 ° C.

[Comparative Example 6]

20 g of the prepolymer (melting point: 22.degree. C.) obtained in the above Synthesis Example 10 was thrown into an eggplant-shaped flask, and the pressure was reduced to 220.degree. C. under reduced pressure of OPa (0.1 lmbar). 3 hours, heating at 225 ° C for 3 hours, heating at 230 ° C for 3 hours, heating at 235 ° C for 3 hours, heating at 250 ° C for 1 hour Solid state polymerization and solid state depolymerization were performed.

Glycoride sublimated to the decompression line was trapped and collected. The obtained glycol was 16 g (80% yield). However, in the flask, a black-brown mass in which the prepolymer became heavy under high temperature conditions was firmly attached.

According to the present invention, there is provided a method for economically producing a high molecular weight polyhydroxycarboxylic acid having excellent melt moldability and mechanical properties. The polyhydroxycarboxylic acid obtained by the production method of the present invention has a high molecular weight, has biodegradability, and can be obtained as a high-quality polymer. Therefore, they are useful in a wide range of fields, for example, as substitutes for medical materials and general-purpose resins. Further, according to the present invention, high-purity glycolide useful as a raw material such as polyglycolide (polyglycolic acid) can be efficiently obtained.

Claims

The scope of the claims

1. (1) Hydroxycarboxylic acid alkyl ester (A) or a hydroxycarboxylic acid-containing hydrolysis product obtained by hydrolyzing at least a part of the hydroxycarboxylic acid alkyl ester ( (B) polycondensation to produce a prepolymer, and then (2) a method for producing a polyhydroxycarboxylic acid by solid-phase polymerization of the produced prepolymer.

2. The process according to claim 1, wherein the hydroxycarboxylic acid alkyl ester (A) is an alkyl group having 1 to 4 carbon atoms.

3. Hydroxycarboxylic acid-containing hydrolysis product (B) is a hydrolysis product containing hydroxycarboxylic acid obtained by hydrolyzing at least 50 mol% of hydroxycarboxylic acid alkyl ester. The production method according to claim 1, which is a product.

4. The production method according to claim 1, wherein the hydroxycarboxylic acid alkyl ester (A) is a glycolic acid alkyl ester.

5. The process according to claim 1, wherein the hydrolysis product (B) is a glycolic acid-containing hydrolysis product obtained by hydrolyzing at least a part of an alkyl glycolate. Method.

6. In the step (1), the polycondensation of the alkyl ester of hydroxycarboxylic acid (A) or the hydrolysis product (B) is carried out at 100 to 230 ° C. The production method according to claim 1, wherein the pre-polymer is produced by performing the following steps.

7. The production method according to claim 1, wherein in the step (1), the hydroxycarboxylic acid alkyl ester (A) or the hydrolysis product (B) is polycondensed in the absence of a catalyst to produce a prepolymer. .

8. The production method according to claim 1, wherein, in the step (1), a prepolymer having a weight average molecular weight of 5,000 or more and less than 150,000 is produced. (

9. The production method according to claim 1, wherein, in the step (1), a prepolymer having a glass transition temperature of 100 ° C or lower is produced.

10. The method according to claim 1, wherein in the step (1), a crystalline prepolymer having a crystallinity of at least 10% is formed.

11. The production method according to claim 1, wherein, in the step (2), the prepolymer is subjected to solid-state polymerization under an inert gas atmosphere, under reduced pressure, or under an inert solvent.

12. The production method according to claim 1, wherein in the step (2), the solid-phase polymerization is performed at a temperature equal to or higher than a glass transition temperature of the prepolymer.

13. The method according to claim 1, wherein in the step (2), the solid phase polymerization is carried out at a temperature at which the prepolymer keeps a solid state.

14. The method according to claim 13, wherein in the step (2), solid-state polymerization is performed at a temperature of 5 V or less of the melting point of the prepolymer.

15. In the above step (2), solid-phase polymerization is started at a reaction temperature at which the prepolymer maintains a solid state, and during the solid-state polymerization, the melting point of the generated solid-phase polymerization reaction product increases. The method according to claim 1, wherein the solid-state polymerization is continued within a temperature range in which the solid-state polymerization reaction product can maintain a solid state.

16. The production method according to claim 15, wherein during the solid-phase polymerization, the reaction temperature is increased within a temperature range of 5 ° C or lower of the melting point of the solid-phase polymerization reaction product to continue the solid-phase polymerization.

17. The production method according to claim 13, wherein in the step (2), the solid phase polymerization is performed at a temperature within a temperature range of 100 to 230 and a temperature at which the prepolymer maintains a solid state. .

18. In the step (2), the solid-state polymerization is performed within a temperature range of 100 to 230 ° C. and a temperature at which a solid-state polymerization reaction product can maintain a solid state. The production method according to claim 15, wherein the method is continued.

19. The method according to claim 1, wherein in step (2), the prepolymer is subjected to solid-phase polymerization without a catalyst.

20. In the step (2), a polyhydroxycarboxy having a weight average molecular weight of 150,000 or more is obtained by solid phase polymerization of a prepolymer. 2. The production method according to claim 1, wherein the acid is produced.

21. At least one glycolic acid polymer selected from the group consisting of crystalline glycolic acid prepolymer and polyglycolic acid, at a temperature of 220 ° C or higher and 2450 ° C A method for producing glycolide that undergoes solid phase depolymerization at temperatures below C.

22. The method according to claim 21, wherein the glycolic acid polymer is subjected to solid-phase depolymerization in an inert gas stream or under reduced pressure, and the sublimated glycol is recovered outside the system.

23. The production method according to claim 21, wherein the melting point of the glycolic acid polymer is 220 ° C or higher.

24. Glycolic acid polymer is obtained by hydrolyzing at least a part of alkyl glycolate or alkyl glycolate. The production method according to claim 21, which is a glycolic acid prepolymer or polyglycolic acid obtained by polycondensing an acid-containing hydrolysis product.