JP2003113233A - Method for producing glycolic acid copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently produce a glycolic acid copolymer having high molecular weight and slight discoloration by a direct polycondensation method. SOLUTION: In this method for producing a glycolic acid copolymer comprising >=75 mol% of a glycolic acid unit by subjecting a raw material comprising >=69 mol% of glycolic acid to polycondensation, the method for producing a glycolic acid copolymer comprises previously dissolving an oxide of at least one metal second from the group consisting of magnesium, iron, cobalt, hafnium, lanthanum and samarium and in an aqueous solution containing a hydroxycarboxylic acid and >=3 mass % of water and using the aqueous solution as a polycondensation catalyst.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a glycolic acid copolymer. Specifically, it relates to a method for easily and efficiently producing a high-molecular weight glycolic acid copolymer.

[0002]

2. Description of the Related Art Aliphatic polyesters produced from hydroxycarboxylic acids represented by polylactic acid, polyglycolic acid or copolymers thereof have attracted attention as biodegradable polymers, and are used for medical applications such as sutures. It is used in various fields such as materials and sustained-release materials such as pharmaceuticals, agricultural chemicals, and fertilizers.
As a method for obtaining a polymer for these uses, conventionally, lactic acid or glycolic acid is once polycondensed to form a prepolymer, and then lactide or glycolide is produced by depolymerization, and ring-opening polymerization is performed using these to produce polylactide. Alternatively, polyglycolide was produced. According to this method, a polymer having a high molecular weight can be obtained, but a large number of steps are required, a great deal of labor is required to obtain polylactide and polyglycolide, and it is not economical.

The method of directly subjecting lactic acid or glycolic acid to a polycondensation reaction is economical, but on the other hand, it has the drawback that it cannot be made into a high molecular weight compound and has not been industrialized. For example, as an attempt to increase the molecular weight, JP-A-5-43665 is used.
In the publication, a method of directly polycondensing an oxyacid in the presence of a germanium compound, that is, a method of performing melt polycondensation by adding germanium oxide to glycolic acid, is described in a wide range of applications. No polyglycolic acid having a molecular weight high enough to be available has been obtained.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to carry out a polycondensation reaction of glycolic acid directly, so that glycolic acid copolymerization of efficient, high molecular weight and less coloring is carried out. To produce a coalesce.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a specific metal oxide is once dissolved in an aqueous solution containing hydroxycarboxylic acid, and lactic acid, The inventors have found that by directly polycondensing a hydroxycarboxylic acid such as glycolic acid, a glycolic acid copolymer having a high molecular weight and less coloring can be efficiently obtained, and the present invention has been completed.

That is, the present invention is as follows. (1) When polycondensing a raw material containing 69 mol% or more of glycolic acid to produce a glycolic acid copolymer containing 75 mol% or more of glycolic acid units, in advance, from magnesium, iron, cobalt, hafnium, lanthanum, and samarium, A glycolic acid copolymer, characterized in that at least one metal oxide selected from the group consisting of: is dissolved in an aqueous solution containing hydroxycarboxylic acid and 3% by mass or more of water and is used as a polycondensation catalyst. Manufacturing method. (2) The method for producing a glycolic acid copolymer according to (1), wherein the oxide of the metal is magnesium oxide. (3) The oxides of the above metals are (a) magnesium oxide, (b) iron, cobalt, hafnium, germanium,
The method for producing a glycolic acid copolymer according to (1), which is an oxide of at least one metal selected from the group consisting of lanthanum and samarium.

The present invention is described in detail below. The content of the glycolic acid unit contained in the polyglycolic acid copolymer of the present invention is 75 mol% or more, preferably 7
5 to 99 mol%, more preferably 80 to 95 mol%
%, Most preferably 82 to 90 mol%. When the content of glycolic acid units is less than 75 mol%, mechanical properties such as strength and elastic modulus of the resulting copolymer, thermal properties such as softening temperature, and gas barrier properties deteriorate. If the content of glycolic acid units exceeds 99 mol%,
The thermal stability of the copolymer is not sufficient, and it tends to be easily decomposed by heat during melt molding.

The content of the glycolic acid unit contained in the glycolic acid-based copolymer depends on the ratio of glycolic acid contained in the raw materials, the reactivity between the glycolic acid and the copolymerization component used, and the polycondensation conditions. Although varying, generally, a glycolic acid and a copolymerization component at a ratio substantially equal to the content of the glycolic acid unit in the target glycolic acid-based copolymer are used as raw materials. However, some copolymerization components are inferior in polycondensation property to glycolic acid. In that case, the ratio of the glycolic acid unit in the raw material can be used at a ratio lower than the content ratio of the glycolic acid unit in the target glycolic acid-based copolymer. When the ratio of glycolic acid in the raw material is too low, the catalyst of the present invention does not exhibit excellent catalytic performance and does not achieve the object of the present invention.
Therefore, the proportion of glycolic acid in the raw material was 69 mol.
% Or more, preferably 72 mol
% Or more, more preferably 75 mol% or more.

Examples of copolymerization components other than glycolic acid units include hydroxycarboxylic acids other than glycolic acid, dicarboxylic acids, diols, trivalent or higher polyvalent compounds, and polysaccharides. It is not limited to these as long as they are copolymerizable. Examples of hydroxycarboxylic acids other than glycolic acid include:
L-lactic acid, D-lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid and 6-hydroxycaproic acid can be mentioned. Examples of dicarboxylic acids include succinic acid, oxalic acid, malonic acid,
Aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, diglycolic acid and the like can be mentioned. Examples of diols include ethylene glycol, diethylene glycol,
Triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,
Examples include 3-butanediol and 1,4-butanediol. Examples of trivalent or higher polyfunctional compounds include glycerin, trimethylolpropane, pentaerythritol,
Examples include malic acid, trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, and gallic acid. Examples of polysaccharides include cellulose, cellulose nitrate, cellulose acetate, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, hemicellulose, starch,
Examples include amylopectin, dextrin, dextran, glycogen, pectin, chitin, chitosan, mixtures thereof, and derivatives thereof.

Among these, preferred examples of the copolymerization component include D- and L-lactic acid. A more preferable example is L-lactic acid, and most preferable is L-lactic acid produced by a fermentation method having an optical purity of 95% or more, and further preferably 98% or more. If desired, in addition to the above copolymerization components, oligomers containing glycolic acid units can be used together.

Magnesium, iron, used in the present invention,
The oxides of at least one metal selected from the group consisting of cobalt, hafnium, germanium, lanthanum, and samarium can be used alone or in combination of two or more in the form of a composite oxide. As the metal oxide, preferred is magnesium oxide, more preferably magnesium oxide and at least one metal oxide selected from the group consisting of iron, cobalt, hafnium, germanium, lanthanum, and samarium. It is a combination with.

The amount of the above metal oxide added is usually 1 × 10 ⁻⁷ as the metal atom per 1 g of the monomer.
˜1 × 10 ⁻² mol, preferably 3 × 10 ⁻⁷ to 1 × 10 ⁻³
It is a mole. When the addition amount is less than 1 × 10 ⁻⁷ mol,
The polycondensation rate cannot be increased and the addition amount is 1 × 10 ^-2
If it exceeds the molar amount, the polymer may be easily colored. The method of dissolving the oxide of the above metal in an aqueous solution containing hydroxycarboxylic acid and 3% by mass or more of water and using this as a polycondensation catalyst is not limited. Is added to a polymerization raw material aqueous solution containing 3% by mass or more of water and glycolic acid,
After being dissolved, there is a method of supplying it to the polymerization step.

The amount of the hydroxycarboxylic acid in the aqueous solution containing the hydroxycarboxylic acid used for dissolving the metal oxide is preferably 5 to 97% by mass, more preferably 10 to 80% by mass. The amount of water in the aqueous solution must be 3% by mass or more, and preferably 3% by mass.
˜95% by mass, more preferably 5 to 80% by mass, most preferably 10 to 70% by mass. When the amount of water in the aqueous solution is less than 3% by mass, the oxide of the above metal is not uniformly dissolved and sufficient catalytic activity cannot be exhibited. If it exceeds 95% by mass, the dissolution rate of the oxide of the above metal tends to be slow. The temperature at which the metal oxide is dissolved is preferably 10 to 150 ° C, more preferably 20 to 130 ° C.

A method for producing a glycolic acid copolymer by polycondensing a raw material containing glycolic acid includes a step of dehydrating and concentrating an aqueous solution of the raw material, a step of melt polycondensing after the dehydrating and concentrating step, and further, if necessary, melting. The step of performing solid-phase polymerization using the polymer obtained by polycondensation as a prepolymer is included. The method for producing the glycolic acid copolymer includes (A)
At any time from the dehydration / concentration step of the raw material aqueous solution containing water and glycolic acid to the subsequent melt polycondensation step, the metal oxide is previously contained with a hydroxycarboxylic acid such as glycolic acid and 3% by mass or more of water. A method for producing a glycolic acid copolymer by adding what is dissolved in an aqueous solution and performing melt polycondensation, (B) adding the above metal oxide to a polymerization raw material aqueous solution containing 3% by mass or more of water and glycolic acid Then, a method of producing a glycolic acid copolymer by dissolving the oxide of the above metal and then performing melt polycondensation.

In the case of producing a high molecular weight polyglycolic acid copolymer having less coloration and a weight average molecular weight of more than 100,000, a method of carrying out solid phase polymerization after the melt polycondensation step is preferable. The method for producing the glycolic acid copolymer will be described in more detail below. The conditions of dehydration concentration in the step of dehydrating and concentrating the raw material aqueous solution are not limited, but usually, in an atmosphere of an inert gas such as nitrogen, under an inert gas flow or under reduced pressure, the temperature is preferably 100 to 150. C, more preferably 100-13
0 ° C., degree of reduced pressure is preferably 13.3 to 101.3
It is preferable to carry out each step in kPa in multiple stages.

In the melt polycondensation step, polycondensation is usually carried out in an atmosphere of an inert gas such as nitrogen, under an inert gas flow, or under reduced pressure, with the reaction temperature changing from 130 to 220 ° C. in multiple stages. The melt polycondensation is preferably performed at 150 to 200 ° C. When the melt polycondensation temperature is lower than 130 ° C, the reaction rate tends to be slow. When the temperature exceeds 220 ° C, the coloring or decomposition of the polymer or the distillation of by-products such as cyclic dimers tends to increase. The degree of pressure reduction during the melt polycondensation reaction is preferably 13.3 Pa to 6.7 kPa, more preferably 66.7 Pa to 6.0 kPa, and most preferably 0.4 to 5.3 kPa in multiple stages and melted. Carry out polycondensation. If the pressure exceeds 6.7 kPa, water generated during polycondensation cannot be efficiently removed, and if it is less than 13.3 Pa, the problem of by-product formation tends to occur. The time for the melt polycondensation reaction is preferably 2 to 20 hours, more preferably 4 to 15 hours. If it is carried out for more than 20 hours, a problem of coloring the polymer may occur.

By carrying out solid-phase polymerization subsequently using the polymer produced by the melt polycondensation as a prepolymer, a glycolic acid copolymer having less coloring and a weight average molecular weight of more than 100,000 can be obtained. It is necessary that the prepolymer be cooled and solidified before being subjected to solid phase polymerization, shaped into particles or pellets, and then crystallized. There is no limitation on the shaping method in the shaping step, but usually, the molten prepolymer is brought into contact with a liquid such as an inert gas or water to form a lump, and then crushed into particles. And a method in which the molten prepolymer is transferred to an extruder and pelletized. The particle size of the prepolymer shaped into particles or pellets is not limited as long as it is set in consideration of the easiness of handling in the crystallization step or the solid phase polymerization step and the polymerization rate in the solid phase polymerization, Usually, the average particle size is 0.1 to 10 mm.

There is no limitation on the crystallization method in the crystallization step, and a known method can be used. Usually, it is a method of heating the cooled and solidified prepolymer in a gas phase, or a method of heating at a crystallization temperature in a liquid in which the prepolymer is not dissolved. The crystallization conditions are not limited, but usually under an inert gas atmosphere such as nitrogen, under an inert gas flow or under reduced pressure, the crystallization treatment temperature is not less than the glass transition temperature of the prepolymer and less than the melting point. The crystallization time is usually 10 to 360 minutes.

As specific crystallization treatment conditions, the pressure is preferably 13.3 Pa to 101.3 kPa, and 0.4 to
6.7 kPa is more preferable. Crystallization temperature is 100
-160 degreeC is preferable, More preferably, it is 120-15.
The crystallization time at 0 ° C. is preferably 30 minutes to 300 minutes. If the crystallization temperature is lower than 100 ° C, fusion of the prepolymer particles tends to occur during solid-phase polymerization, and if it exceeds 160 ° C, fusion of the prepolymers tends to occur during heat treatment. This crystallization treatment can be carried out in multiple steps within the above temperature range.

In the solid phase polymerization step, the molecular weight of the prepolymer used for the solid phase polymerization step is not limited, but the weight average molecular weight is 3,
000-80,000, preferably 8,000-50,
It is 000. When the weight average molecular weight is less than 3,000, the time required for the solid phase polymerization step until the desired weight average molecular weight is achieved becomes enormous. In addition, also in the crystallization process or the solid-phase polymerization process, problems such as fusion and crushing may occur. Weight average molecular weight of 80,
It is inefficient to produce more than 000 prepolymers by melt polymerization and coloration may occur.

The reaction temperature in the solid phase polymerization step is preferably not less than the midpoint glass transition temperature of the crystallized prepolymer and less than the melting peak temperature, more preferably not less than the extrapolation melting start temperature of the crystallized prepolymer, Below the melting peak temperature. The reaction temperature in solid state polymerization is JISK7
Below the midpoint glass transition temperature described in 121, almost no high molecular weight can be achieved, and above the melting peak temperature, particles may be fused to each other during solid phase polymerization, and solid phase polymerization may not be able to continue.

Solid phase polymerization can be carried out under an atmosphere of an inert gas such as nitrogen, under reduced pressure or under pressure. The degree of reduced pressure in the reaction system and the pressure in the reaction system are not limited as long as a glycolic acid copolymer having a sufficiently high weight average molecular weight is obtained, but in the case of carrying out under reduced pressure,
The pressure is preferably 13.3 Pa to 6.7 kPa, and is 0.3.
~ 1.3 kPa is more preferable. In the case of producing a glycolic acid copolymer having a higher molecular weight, for example, a weight average molecular weight of more than 100,000, it is more preferable to carry out solid phase polymerization under an inert gas flow atmosphere.

Specific examples of the inert gas used in the solid phase polymerization, that is, the gas to be circulated in the reaction system, include nitrogen gas, helium gas, argon gas, xenon gas, krypton gas and the like. The amount of water contained in the inert gas to be circulated is as low as possible, and it is preferable that the gas is substantially anhydrous. If the water content is high, the water generated in the solid-state polymerization reaction cannot be removed efficiently, and the polymerization rate tends to be slow. In order to obtain an anhydrous gas, it is advisable to pass it through a layer filled with molecular sieves, ion exchange resins and the like. When showing the water content of the circulating gas as a dew point, the dew point of the gas is preferably −20 ° C. or lower, and more preferably −50 ° C. or lower.

Regarding the flow rate of the inert gas to be circulated,
Considering the particle size and crystallinity of the prepolymer, it suffices to be able to remove the generated water to the extent that a glycolic acid copolymer having a sufficiently high weight average molecular weight can be obtained. Generally, the higher the flow rate of the inert gas to be circulated, the more efficiently the water generated in the solid phase polymerization reaction can be removed, and the case where a polyglycolic acid copolymer having a weight average molecular weight of more than 100,000 is produced. In addition, the flow rate of the inert gas per 1 g of the prepolymer is preferably 0.02 to 200 ml / min, more preferably 0.5 to 150 ml / min.
Most preferred is 0-100 ml / min. 1g of prepolymer
If the flow rate of the inert gas per unit is less than 0.02 ml / min, the efficiency of removing the produced water in the solid-state polymerization reaction decreases, and it is difficult to obtain polyglycolic acid having a high molecular weight. At flow rates above 200 ml / min no further improvement in the efficiency of water removal is observed. The solid-phase polymerization reaction time is preferably 5 to 200 hours, and 10
-120 hours are more preferable. When it is carried out for more than 200 hours, problems such as coloration of the polymer and a decrease in yield due to side reactions may occur.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to Examples. Each characteristic value in the present invention is measured by the following methods. (1) Weight average molecular weight It is determined under the following conditions using a gel permeation chromatography (GPC) analyzer 8020 GPC system manufactured by Toso Co., Ltd. Hexafluoroisopropanol (HFIP) in which 80 mmol / l sodium trifluoroacetate was dissolved was used as a solvent, and 40 ° C., 1 ml.
/ Min as column, Tskgel® G5000HHR + T
skgel (registered trademark) G3000HHR (both Tosoh Corporation)
A calibration curve obtained from the elution time by RI detection using a polymethylmethacrylate standard substance is prepared in advance, and the weight average molecular weight is obtained from the elution time. As a polymer sample solution for evaluation, 20 mg of the sample was precisely weighed and then the above-mentioned sodium trifluoroacetate-containing HFI was used.
What was melt | dissolved in P3g and filtered with a 0.2 micron filter after that is used.

(2) Coloring degree of polymerized polymer When determining the weight average molecular weight by the above method, a UV detector set to a wavelength of 350 nm is connected as a detector,
At that time, the degree of coloring is evaluated by the total number of detected counts.
When the count number is less than 50, the obtained polymer visually corresponds to white to pale yellow, and the count number is 50 to 10
A value of 0 corresponds to yellow, and a count of more than 100 corresponds to brown to black brown. (3) was precisely weighed and content samples 70mg of glycolic acid units of polyglycolic acid copolymer, dissolved in d of trifluoroacetic acid 1 ml, using tetramethylsilane as a reference substance, ¹
Measured by 1 H-NMR. (4) Thermal properties of prepolymer before solid-state polymerization Differential scanning calorimetry (DSC measurement) was performed using DSC-7 manufactured by Perkin Elmer Co., Ltd. The crystallized prepolymer is heated from 0 ° C to 10 ° C / min at a heating rate of 25 ° C.
From the DSC curve obtained by raising the temperature to 0 ° C, JISK
According to 7121 (Plastic transition temperature measuring method), the extrapolation melting start temperature and the melting peak temperature are determined.

[0027]

Example 1 100 m equipped with a stirrer and a nitrogen introducing pipe
High purity glycolic acid (65 mass% aqueous solution; DuPont KK Gripia (registered trademark) 7 was placed in a reaction vessel.
0) 93 g and L-lactic acid (90% aqueous solution; manufactured by Wako Pure Chemical Industries, Ltd.) 11 g, and the total amount of glycolic acid and lactic acid 1
0.008 mmol of magnesium oxide was charged per g. After the magnesium oxide was dissolved, nitrogen substitution was carried out, the temperature was raised to 130 ° C. under normal pressure and stirring under a nitrogen stream, and dehydration concentration was carried out for 1 hour. Then, the temperature was raised to 180 ° C. and kept for 30 minutes under normal pressure to complete the concentration. Then, the pressure reduction is started, and it is 20 minutes at 27 kPa, 20 minutes at 6.7 kPa, and 2 minutes at 0.07 kPa.
After holding for 0 minutes to continue the reaction, the temperature was raised to 200 ° C. and the polycondensation reaction was continued for 4 hours. The content of glycolic acid unit in the obtained polyglycolic acid copolymer was 8
It was 8 mol%.

The resulting prepolymer had a weight average molecular weight of 21,000 and a total count of 7 by UV detector, which is an index of the coloring degree of the polymer. The obtained prepolymer was heat-treated in a nitrogen atmosphere at 130 ° C. for 24 hours, then pulverized and subjected to solid phase polymerization. The extrapolation melting onset temperature of the prepolymer before the solid phase polymerization was 135 ° C, and the melting peak temperature was 190 ° C. 0.5 g of the crystallized prepolymer was charged in advance in a glass U tube filled with glass wool. Furthermore, after filling the upper part with glass wool, solid phase polymerization was carried out at a solid phase polymerization temperature of 170 ° C. and a nitrogen gas flow rate of 1.5 ml / min for 20 hours. The polymer obtained by solid phase polymerization has a weight average molecular weight of 10
The total number of counts by the UV detector was 14 at 6,000.

[0029]

Comparative Example 1 The procedure of Example 1 was repeated except that magnesium oxide was not added. The prepolymer obtained by melt polycondensation has a glycolic acid unit content of 88 mol%,
The weight average molecular weight was 8000 and the total count number by the UV detector was 5. The polymer obtained by solid phase polymerization had a weight average molecular weight of 29,000 and a total count of 36 by UV detector.

[0030]

Example 2 Polymerization was carried out in the same manner as in Example 1 except that 0.008 mmol of magnesium oxide was replaced with 0.004 mmol of magnesium oxide and 0.004 mmol of germanium oxide. The prepolymer obtained by melt polycondensation has a glycolic acid unit content of 88 mol%,
The weight average molecular weight was 22,000 and the total count number by the UV detector was 20. The polymer obtained by solid-phase polymerization had a weight average molecular weight of 136,000 and a total count of 25 by a UV detector.

[0031]

[Comparative Example 2] 100 m equipped with a stirrer and a nitrogen introducing pipe
High purity glycolic acid (65 mass% aqueous solution; DuPont KK Gripia (registered trademark) 7 was placed in a reaction vessel.
0) 93 g and L-lactic acid (90% aqueous solution; manufactured by Wako Pure Chemical Industries, Ltd.) 11 g were charged, and after nitrogen substitution, the temperature was raised to 130 ° C. under atmospheric pressure and stirring under a nitrogen stream to obtain water. After concentrating the raw material aqueous solution until the amount became less than 1% by mass, polymerization was carried out in the same manner as in Example 1 except that 0.008 mmol of magnesium oxide was charged per 1 g of the total amount of glycolic acid and lactic acid. .

The prepolymer obtained by melt polycondensation had a glycolic acid unit content of 88 mol%, a weight average molecular weight of 10,000, and a total count of 7 by a UV detector. The polymer obtained by solid phase polymerization has a weight average molecular weight of 33,000, and the total number of counts by UV detector is 1
It was 5. Thus, when magnesium oxide was added to a system having a water content of less than 1% by mass, the dissolution of magnesium oxide was insufficient and sufficient catalytic activity was not expressed.

[0033]

Comparative Example 3 65 g of high-purity glycolic acid (65% by mass aqueous solution; Gripia (registered trademark) 70 manufactured by Du Pont Co., Ltd.) as raw materials, and 43 g of L-lactic acid (90% aqueous solution; manufactured by Wako Pure Chemical Industries, Ltd.) Polymerization was performed in the same manner as in Example 1 except that was used. In the solid phase polymerization, the polymer particles were fused to each other and it was difficult to continue the solid phase polymerization. Therefore, the melt polymerization time was extended by 10 hours.
The prepolymer obtained by melt polycondensation has a glycolic acid unit content of 57 mol% and a weight average molecular weight of 37,000.
It was 0, and the total count number by the UV detector was 60.

If the content of glycolic acid units in the polyglycolic acid copolymer is outside the scope of the present invention, it is difficult to increase the molecular weight by solid-state polymerization, and the melt polymerization time is lengthened. Thus, even if an attempt is made to obtain a high molecular weight product, the molecular weight is not sufficiently increased, and the obtained polymer is colored.

[0035]

Comparative Example 4 Polymerization was carried out in the same manner as in Example 1 except that tin dichloride was used instead of magnesium oxide. The prepolymer obtained by melt polycondensation has a glycolic acid unit content of 89 mol%, a weight average molecular weight of 17,000, and UV.
The total number of counts by the detector was 134.

The polymer obtained by solid phase polymerization had a weight average molecular weight of 53,000 and a total count of 150 by UV detector. Although tin dichloride showed a relatively high performance as a polycondensation catalyst, the coloring of the polymer was remarkable, and the final polymer yield was reduced at the initial 30%, which was not practical.

[0037]

Example 3 Magnesium oxide was added to L-lactic acid 90% in advance.
% Polymerization was performed in the same manner as in Example 1 except that it was dissolved in an aqueous solution. The prepolymer obtained by melt polymerization has a glycolic acid unit content of 88 mol% and a weight average molecular weight of 1.
It was 1,000 and the total number of counts by the UV detector was 15.

The polymer obtained by solid phase polymerization had a weight average molecular weight of 76,000 and a total count of 20 by UV detector. When glycolic acid was included as the hydroxycarboxylic acid in the aqueous solution containing the hydroxycarboxylic acid that dissolves the metal oxide, a polyglycolic acid copolymer having a higher molecular weight was obtained.

[0039]

Examples 4 to 8 Instead of magnesium oxide,
Polymerization was performed in the same manner as in Example 1 except that hafnium oxide, ferric trioxide, cobalt oxide, lanthanum oxide, and samarium oxide were used. The content of glycolic acid units in the prepolymer obtained by melt polymerization is 88 in all cases.
It was mol%.

[0040]

[Example 9] Except that the amounts of glycolic acid aqueous solution and L-lactic acid aqueous solution used were changed to 97 g and 6 g, respectively.
Polymerization was carried out in the same manner as in Example 1. The glycolic acid unit content in the prepolymer obtained by melt polymerization is 94 m.
It was ol%.

[0041]

Example 10 93 g of high-purity glycolic acid (65 mass% aqueous solution; Gripia (registered trademark) 70 manufactured by Du Pont Co., Ltd.) as raw materials and 10 g of L-lactic acid (90% aqueous solution; manufactured by Wako Pure Chemical Industries, Ltd.) In addition, polycondensation was performed in the same manner as in Example 1 except that 1 g of succinic acid and 1 g of ethylene glycol were used. The prepolymer obtained by melt polymerization had a glycolic acid unit content of 89 mol%, a weight average molecular weight of 25,000, and a total count of 18 by a UV detector.
Met. The polymer obtained by solid phase polymerization had a weight average molecular weight of 176,000 and a total count of 29 by UV detector.

[0042]

Example 11 Instead of magnesium oxide, 0.004 mmol of magnesium oxide and 0.004 of hafnium oxide were used.
Polymerization was carried out in the same manner as in Example 1 except that 1 mmol was used. The glycolic acid unit content in the prepolymer obtained by melt polymerization was 88 mol%. By using magnesium oxide and germanium oxide together, it was possible to obtain a glycolic acid copolymer having less coloration and a higher molecular weight even in the case of polymerization for a relatively long time.

[0043]

[Example 12] Instead of magnesium oxide, 0.004 mmol of magnesium oxide and 0.004 of samarium oxide were used.
Polymerization was carried out in the same manner as in Example 1 except that 1 mmol was used. The glycolic acid unit content in the prepolymer obtained by melt polymerization was 88 mol%. By using magnesium oxide and samarium oxide in combination, it was possible to obtain a glycolic acid copolymer having a higher molecular weight with less coloring even after the polymerization for a relatively long time.

The above results are summarized in Table 1.

[0045]

[Table 1]

[0046]

EFFECTS OF THE INVENTION According to the present invention, a polyglycolic acid copolymer having a high molecular weight and little coloring can be efficiently produced by a method of directly polycondensing a raw material containing glycolic acid.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4J029 AA02 AC02 AD01 AD08 AD10                       AE06 AE18 BA03 BA04 BA05                       BA08 BF09 BF10 BF18 CA02                       CA03 CA04 CA05 CA06 EA02                       EA03 EA05 FC03 FC04 FC05                       FC08 FC35 FC36 JA091                       JF131 JF271 JF281 JF341                       JF361 JF561 JF571 KB03                       KB05 KD02 KD07 KD09 KF02                       KF07

Claims (3)

[Claims] 1. When producing a glycolic acid copolymer containing 75 mol% or more of glycolic acid units by polycondensing a raw material containing 69 mol% or more of glycolic acid,
Magnesium, iron, cobalt, hafnium, lanthanum,
And at least one metal oxide selected from the group consisting of samarium and hydroxycarboxylic acid and 3% by mass.
A method for producing a glycolic acid copolymer, characterized by being dissolved in an aqueous solution containing the above water and used as a polycondensation catalyst. 2. The method for producing a glycolic acid copolymer according to claim 1, wherein the metal oxide is magnesium oxide. 3. The combination of (a) magnesium oxide and (b) an oxide of at least one metal selected from the group consisting of (b) iron, cobalt, hafnium, germanium, lanthanum and samarium, as the metal oxide. The method for producing a glycolic acid copolymer according to claim 1, wherein