JPH08120060A - Production of polyhydroxycarboxylic acid - Google Patents

Abstract

PURPOSE: To produce a solid high-mol.-wt. polyhydroxycarboxylic acid easily at a low cost by an industrially advantageous process which can easily be made continuous and in which an org. solvent soln. of a polyhydrocarboxylic acid is solidified by cooling and then ground. CONSTITUTION: An org. solvent soln. of a polyhydroxycarboxylic acid is solidified by cooling and then ground, giving a solid polyhydroxycarboxylic acid. For instance, one of the following two processes can be used: a process wherein the solvent soln. is charged into a kneader and kneaded under cooling while a solid mixture of the polymer and the solvent is being taken out; and a process wherein after the solvent soln. is solidified by cooling, the resultant solid mixture of the polymer and the solvent is ground. There is no limitation on the method for preparing the solvent soln.; however, it is conveniently prepd. by subjecting a hydroxycarboxylic acid compd. or its oligomer to condensation by dehydration in an org. solvent in the presence or absence of a catalyst (e.g. a divalent tin compd.).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polyhydroxycarboxylic acid useful as a biodegradable polymer as an alternative to medical materials and general-purpose resins.

[0002]

2. Description of the Related Art Polyhydroxycarboxylic acid is not only excellent in mechanical, physical and chemical properties, but is also decomposed in a natural environment without harming others, and finally it is decomposed by microorganisms into water. It has a biodegradable function of becoming carbon dioxide gas, and has recently become a substitute for medical materials and general-purpose resins.
It is a plastic that has attracted particular attention in various fields.

Generally, as a method for producing a polyhydroxycarboxylic acid, in the case of a hydroxycarboxylic acid such as lactic acid or glycolic acid, it is dehydrated and dimerized to obtain a cyclic dimer, and then a catalyst (Sn catalyst) is used. It is known that a high molecular weight polymer can be obtained by ring-opening melt polymerization in the presence (hereinafter, referred to as indirect polymerization method). However, in this method, the operation of the reaction is complicated, the obtained polymer is not only expensive, and since the production method is a method of directly obtaining a product as pellets after melt polymerization, the obtained polymer form is Limited to pellets. Further, some hydroxycarboxylic acids do not form a cyclic dimer, and in this case, this method cannot be used.

On the other hand, several methods for obtaining polyhydroxycarboxylic acid by direct dehydration condensation from hydroxycarboxylic acid or its oligomer (hereinafter referred to as direct polymerization method) have been disclosed (JP-A-59-096).
123, JP-A-61-028521). With this method, it is possible to produce various polyhydroxycarboxylic acid homopolymers and copolymers without the above-mentioned restrictions on the raw materials. Furthermore, the production method is a very simplified production method of directly polymerizing the hydroxycarboxylic acid to obtain the polymer, which is an industrially useful production method. However, there are several methods for extracting the polymer from a solution of polyhydroxycarboxylic acid in an organic solvent, but no industrially satisfactory method has been known yet.

For example, in general, in order to obtain a solid polymer, a method is known in which the polymer is once dissolved in a good solvent and then contacted with a non- or poor solvent to precipitate and take out the polymer. Even when this method is applied to a polymer, there are some problems such as a problem that the polymer that precipitates becomes a gel-like substance, which makes stirring difficult and adheres to a pot.

In order to solve such a problem, a method of simultaneously purifying and isolating the polymer by contacting the polymer solution with a precipitant under the influence of turbulent shearing force so that the precipitated polymer is divided into fine particles Is disclosed (Japanese Patent Laid-Open No. 63-
254128). However, in this method, a special device has to be used, and there is a drawback that an excessive equipment cost is required.

In addition, a method has been disclosed in which polyhydroxycarboxylic acid is dissolved in a solvent of xylene or diethyl phthalate by heating and then cooled to remove the solvent (Japanese Patent Laid-Open Nos. 58-206637 and 58-206637). 61-0425
No. 31). Although it is possible to easily obtain a powder of the polymer by this method, for example, JP-A-04-337
In the case of the polymer solution obtained by the direct polymerization method as disclosed in No. 321, since a solvent different from the solvent used at the time of polymerization is newly used, the polyhydroxycarboxylic acid and the solvent as described are also used. When the solvent is separated, a large amount of the oligomer of the polymer is contained in the separated solvent, so that the step of separating and recovering the solvent and the oligomer becomes complicated, and an excessive equipment cost is required. Furthermore, in a high-molecular-weight and high-concentration polyhydroxycarboxylic acid solution, there is a problem that the method of separating the polymer and the solvent by filtration as described above is impossible because the entire solution solidifies when cooled. .

Further, the inventors of the present invention obtained a high molecular weight polymer of hydroxycarboxylic acid by a direct polymerization method using a special solvent, and further controlled the reaction mass to a specific concentration to perform cooling crystallization. It was found that a solid polymer product was obtained (JP-A 06-172502). However, in this method, depending on the molecular weight of the polymer at the time of crystallization and the concentration conditions, the resulting solid material will be in the form of powder, granules, blocks, or lumps, so that a powdery or granular polymer that is easy to handle is obtained. In order to achieve this, it is necessary to extremely reduce the concentration during crystallization, and in order to separate the polymer and solvent by filtration, it is necessary to provide a separation and recovery step for the solvent and oligomer as described above, It has been desired to develop a technique for taking out a solid substance of the polymer.

[0009]

An object of the present invention is to provide an industrially useful method for producing a solid polyhydroxycarboxylic acid from an organic solvent solution of polyhydroxycarboxylic acid, which can be easily continuous. is there. Another object of the present invention is to provide a method for easily and inexpensively extracting solid polyhydroxycarboxylic acid even if it has a high molecular weight and a high concentration.

Means for Solving the Problems The inventors of the present invention have made earnest studies on a production method capable of producing a polyhydroxycarboxylic acid industrially efficiently and at low cost, and as a result, have conducted a specific treatment on an organic solvent solution of the polymer. The present invention has been completed by discovering that the solid mixture of the polymer can be easily and inexpensively taken out even if the polymer has a high molecular weight and a high concentration. That is, the present invention is a method for producing a solid polyhydroxycarboxylic acid, which comprises cooling and solidifying and pulverizing an organic solvent solution of polyhydroxycarboxylic acid.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. Specific examples of the polyhydroxycarboxylic acid in the method of the present invention include 2-hydroxyethanoic acid, 2-hydroxypropanoic acid, 2-hydroxybutanoic acid, 2-hydroxypentanoic acid, and 2-hydroxypentanoic acid. Hydroxyhexanoic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxy-2-
Methyl propanoic acid, 2-hydroxy-2-
Methylbutanoic acid, 2-hydroxy-2-ethylbutanoic acid, 2-hydroxy-2-methylpentanoic acid, 2-hydroxy-2-ethylpentanoic acid, 2-hydroxy-2-propylpenta Noic acid, 2-hydroxy-2-butylpentanoic acid, 2-hydroxy-2-methylhexanoic acid, 2-hydroxy-2-ethylhexanoic acid, 2-hydroxy-2-propylhexanoic acid Acid, 2-hydroxy-2-
Butyl hexanoic acid, 2-hydroxy-2-
Pentyl hexanoic acid, 2-hydroxy-2
-Methylheptanoic acid, 2-hydroxy-2
-Ethyl heptanoic acid, 2-hydroxy-2
-Propyl heptanoic acid, 2-hydroxy-
2-butyl heptanoic acid, 2-hydroxy-
2-pentyl heptanoic acid, 2-hydroxy-2-hexyl heptanoic acid, 2-hydroxy-2-methyl octanoic acid, 2-hydroxy-2-ethyl octanoic acid, 2-hydroxy-2- Propyl octanoic acid, 2-hydroxy-2-butyl octanoic acid, 2-hydroxy-2-pentyl octanoic acid, 2-hydroxy-2-hexyl octanoic acid, 2-hydroxy-2-heptyl octa Noic Acid, 3-
Hydroxypropanoic acid, 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexanoic acid, 3-
Hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxy-3-methylbutanoic acid, 3-hydroxy-3-methylpentanoic acid, 3-hydroxy-3-ethylpentanoic acid, 3-hydroxy-3-methylhexanoic acid, 3-hydroxy-3-ethylhexanoic acid, 3-hydroxy-3-propylhexanoic acid, 3-hydroxy-3-methylheptanoic acid, 3- Hydroxy-3-ethyl heptanoic acid, 3-hydroxy-3-propyl heptanoic acid, 3-hydroxy-3-butyl heptanoic acid, 3-hydroxy-3-methyl octanoic acid, 3-hydroxy- 3-ethyl octanoic acid Acid, 3-hydroxy-3-propyloctanoic acid, 3-hydroxy-3-butyloctanoic acid, 3-hydroxy-3-pentyloctanoic acid, 4-hydroxybutanoic acid, 4-hydroxy Pentanoic acid, 4-hydroxyhexanoic acid, 4-hydroxyheptanoic acid, 4-hydroxyoctanoic acid, 4-hydroxy-4-methylpentanoic acid, 4-hydroxy-4-methylhexano Ic acid, 4-hydroxy-4-ethylhexanoic acid, 4-hydroxy-4-methylheptanoic acid, 4-hydroxy-4-ethylheptanoic acid, 4-hydroxy-4-propylheptanoic acid , 4-hydroxy 4-methyloctanoic acid, 4-hydroxy-4-ethyloctanoic acid, 4-hydroxy-4-propyloctanoic acid, 4-hydroxy-4-butyloctanoic acid, 5-hydroxypentanoic acid Acid, 5-hydroxyhexanoic acid, 5
-Hydroxyheptanoic acid, 5-hydroxyoctanoic acid, 5-hydroxy-5-methylhexanoic acid, 5-hydroxy-5-methylheptanoic acid, 5-hydroxy-5-ethylheptanoic acid , 5-hydroxy-5-methyloctanoic acid, 5-hydroxy-5-ethyloctanoic acid, 5-hydroxy-5-propyloctanoic acid, 6-hydroxyhexanoic acid, 6-hydroxyheptano Ic acid, 6-hydroxyoctanoic acid, 6-hydroxy-6-methylheptanoic acid, 6-hydroxy-6-methyloctanoic acid, 6-hydroxy-6-ethyloctanoic acid, 7-hydroxy Heptano Obtained by direct dehydration polymerization of aliphatic hydroxycarboxylic acids such as acid, 7-hydroxyoctanoic acid, 7-hydroxy-7-methyloctanoic acid, 8-hydroxyoctanoic acid and oligomers derived therefrom. It may be a polymer obtained by melt-polymerizing a cyclic dimer such as glycolide or lactide, a copolymer of one kind or a mixture of two or more kinds, or a mixture. Further, there is no limitation on the manufacturing method thereof. Furthermore, these hydroxycarboxylic acids and their oligomers or cyclic dimers have optically active carbons, and are D-form and L-form, respectively.
Although it may take the form of a body or a D / L body, the form is not limited in the method of the present invention. That is, there is no limitation on the form of the polyhydroxycarboxylic acid.

When the polymer is obtained by direct dehydration polymerization, the polymerization catalyst may be added or not added depending on the degree of polymerization (logarithmic viscosity) of the desired polymer. When producing a low molecular weight polymer (logarithmic viscosity of less than about 0.3 dl / g), the target polymer can be easily obtained with or without addition of a catalyst.
When producing a polymer having a high molecular weight (logarithmic viscosity of about 0.3 dl / g or more), it is preferable to use a catalyst in view of reaction time (reaction rate).

As the catalyst, the periodic table of elements I, I
Examples thereof include metals of groups I, III, IV and V, or salts thereof. For example, metals such as zinc, tin, aluminum and magnesium, tin oxide, antimony oxide, zinc oxide,
Metal oxides such as aluminum oxide, magnesium oxide, and titanium oxide; metal halides such as zinc chloride, stannous chloride, stannic bromide, antimony fluoride, magnesium chloride, and aluminum chloride; tin sulfate, zinc sulfate, and sulfuric acid. Sulfates such as aluminum, hydroxides such as tin hydroxide and zinc hydroxide,
Carbonates such as magnesium carbonate, zinc carbonate and calcium carbonate, organic carboxylates such as tin acetate, tin octoate, tin lactate, zinc acetate and aluminum acetate, organics such as tin trifluoromethanesulfonate and tin p-toluenesulfonate Examples thereof include sulfonates and the like.

In addition, organic metal oxides of the above metals such as dibutyltin oxide, metal alkoxides of the above metals such as titanium isopropoxide, alkyl metals of the above metals such as diethylzinc, or ion exchange resins such as Dowex and Amberlite. Etc. The amount used is preferably 0.0001 to 10% by weight of the hydroxycarboxylic acid or the oligomer thereof.

In the direct dehydration polymerization, a polycondensation reaction may be carried out by adding a coloring inhibitor in order to suppress coloring due to thermal deterioration during the polymerization. As the coloring inhibitor used, phosphorus compounds such as phosphoric acid, triphenyl phosphate, pyrophosphoric acid, phosphorous acid and triphenyl phosphite are preferable. The amount added is preferably 0.01 to 5% by weight, more preferably 0.5 to 2% by weight, based on the polymer. 0.01
If it is less than 5% by weight, the effect of the anti-coloring agent becomes small, and if it exceeds 5% by weight, no further effect can be expected in the effect of the anti-coloring agent and the degree of polymerization may not be increased.

In the direct dehydration polymerization, the polymerization conditions may be either normal pressure or reduced pressure, and the range up to the reflux temperature of the solvent used can be employed, preferably 50 to 220.
C., more preferably 100 to 170.degree. If the temperature is lower than 50 ° C., the efficiency of removing the water generated by the reaction from the reaction system is deteriorated, and the reaction rate is significantly reduced. Also 2
At a temperature above 20 ° C., deterioration of the polymer may occur, which may cause coloration of the reaction solution and deteriorate the quality of the obtained product.

Organic solvents used in the direct dehydration polymerization include aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, halogenated hydrocarbon compounds, ether compounds,
Although a ketone compound or the like can be used, a solvent having a high polymerization rate during dehydration polycondensation is preferable, and examples thereof include tetradecane, dodecene, diphenyl, naphthalene, dichlorobenzene, chloronaphthalene, hexyl ether, anisole, ethoxybenzene, and 2 , 4-dichloromethoxybenzene, diphenyl ether, cyclohexyl ketone, acetophenone and the like. These may be one kind or a mixture of two or more kinds, and there is no limitation on the composition thereof.

The amount used is such that the polymer concentration is usually 3-9.
The range is 0% by weight, preferably 15 to 8
The range is 0% by weight, more preferably 30 to 70% by weight. If it exceeds 90% by weight, the viscosity of the polymer when heated and dissolved becomes extremely high, which may make it difficult to handle such as liquid transfer and operations such as stirring. Conversely 3
When the content is less than wt%, there is no problem in reaction and post-treatment, but there is a problem in volume efficiency.

Regarding the apparatus used for the reaction in the direct dehydration polymerization, since the reaction is dehydration polycondensation, in order to obtain a polymer having a high molecular weight, water produced as the reaction proceeds can be removed to the outside of the system. Need to be a device. As a method of removing the produced water, a method of removing a mixture of refluxing solvent and water from the system as it is, a method of passing the mixture through a dehydrator and returning the dried solvent to the system again can be used.

When a dehydrator is used, molecular sieves (3A, 4A, 5A, etc.), inorganic desiccants such as silica gel; diphosphorus hydroxide, phosphorus pentoxide, calcium hydride, sodium hydride, lithium hydride, etc. The hydride can be dried using a dehydration tower packed with a dehydrating agent such as an alkali metal such as sodium, lithium, potassium and calcium and an alkaline earth metal. In addition, a method of separating and removing water in the solvent to be distilled off by using an apparatus equipped with a distillative separation capacity may be used, or the distillate from the distillate may be once allowed to flow out of the reaction system, and then distilled and separated for dehydration. A method of returning the solvent to the reaction system may be used, and it is sufficient that water in the solvent to be returned to the reaction system is substantially removed, and there is no limitation on the method.

The present invention is a method for producing a solid polyhydroxycarboxylic acid, which comprises cooling, solidifying and pulverizing an organic solvent solution of polyhydroxycarboxylic acid. Therefore, in the case of an organic solvent solution of polyhydroxycarboxylic acid obtained by polymerization by direct dehydration polymerization method, after appropriately adjusting the solution concentration, it is directly applied to the method of the present invention to obtain a solid mixture of the polymer and the organic solvent. Although it can be obtained, in the case of a polyhydroxycarboxylic acid obtained by an indirect polymerization method, since it is in the form of pellets, it is redissolved in the organic solvent as described above,
It is necessary to apply the method of the present invention after making the polymer solution in an organic solvent.

The polyhydroxycarboxylic acid used in the present invention preferably has an inherent viscosity of 0.3 to 5.0 dl / g. If it is less than 0.3 dl / g, it may not be sufficiently solidified when the organic solvent solution is cooled. Also 5.0 dl
If it exceeds / g, the load on the apparatus increases and the concentration of the organic solvent solution must be reduced.

The concentration of the polymer solution at the time of solidification by cooling and pulverization varies slightly depending on the kind and molecular weight of the polymer, but is usually in the range of 15 to 95% by weight, preferably 2
It is 0 to 80% by weight, more preferably 30 to 70% by weight. When the concentration is lower than 15 wt%, there is no problem in polymer precipitation, but there are problems in volume efficiency and processing capacity. On the other hand, when the content is higher than 95% by weight, the solution viscosity becomes higher as the molecular weight of the polymer becomes higher, and the load on the apparatus becomes large and the operation becomes impossible in some cases.

As a method for taking out a solid mixture of polyhydroxycarboxylic acid and an organic solvent in the method of the present invention, cooling solidification and pulverization may be carried out at the same time. Once the solid mixture is cooled and solidified, the obtained polymer and organic solvent are obtained. Alternatively, the solid mixture of and may be crushed.

As a method for simultaneously performing the cooling solidification and the pulverization treatment, there is a method in which an organic solvent solution of polyhydroxycarboxylic acid is charged into a kneading machine and the solid mixture of the polymer is taken out while cooling and kneading. In this case, the polymer solution charged into the kneader increases in viscosity as it is cooled, and a solid mixture of the polymer and the organic solvent is gradually precipitated and simultaneously pulverized by kneading.

On the other hand, examples of the method of once cooling and solidifying and then pulverizing include a method of chilling and solidifying an organic solvent solution of polyhydroxycarboxylic acid and then pulverizing the obtained solid mixture of the polymer and the organic solvent. . In this case, for example, a method using a flaker and a crusher can be mentioned,
A solid mixture of the polymer solution cooled and solidified by a breaker is once produced and then pulverized by a pulverizer or the like.

In any of the methods, a solid mixture of the polymer can be taken out from the polymer solution having a high molecular weight and a high concentration in a form that is easy to handle, and continuation can be easily made by selecting an apparatus to be used.

The kneading machine which can be used in the method of the present invention is generally called a kneading machine, and it is preferable that two or more stirring blades have good clearance so that one of them cannot be stirred. The type and shape are not particularly limited as long as the solution of the polyhydroxycarboxylic acid in an organic solvent can be cooled and kneaded until a solid mixture of the polymer and the organic solvent is precipitated, and conventionally known ones can be used. .

For example, as a batch type kneader, a double-arm type kneader (also called a Warner type kneader or simply a kneader), a double planetary mixer, an internal type kneader (also called an internal mixer), a muller type kneader There are Japanese-style machines (also called edge runners), roll mixers, etc., and continuous kneaders include roll mills, botters, and K.K. R. C. A kneader (self-cleaning type reactor) and the like can be mentioned. In addition to this, a screw type extruder such as a screw extruder or a mixed extruder,
Gear compounders, cork kneaders, plastomills and the like can be mentioned. Examples of product names include table type kneaders (PN-1, PN-5, PNV-1, PNV, manufactured by Irie Shokai).
-5, PBV, etc.), Mitsubishi Heavy Industries self-cleaning reactor (SCR, N-SCR, HVR, etc.), Kurimoto Tekko SC processor (SCP-100), Kurimoto Tekko K
An RC kneader, KEX extruder made by Kurimoto Tekko Co., Ltd., an eyeglass blade polymerization machine made by Hitachi, Ltd., and the like can be mentioned.

When the solution of polyhydroxycarboxylic acid in an organic solvent is solidified by cooling and then the solid mixture of the polymer and the organic solvent is crushed, a cooling device or a crushing device is used.
Any apparatus can be used as long as it can be crushed after cooling and solidifying the organic solvent solution of the polymer, and there is no limitation on the shape and model, the cooling method and the crushing method. As an apparatus for cooling and solidifying, a cooling and solidifying apparatus having a thin film forming function is preferable, and an apparatus having a function of simultaneously crushing a solid mixture of the cooled and solidified polymer and an organic solvent is more preferable. Generally, single-belt flakers, double-belt flakers, drum flakers, etc. are known as cooling and solidifying devices having a thin film forming function, and flakers (manufactured by Tamagawa Machinery Co., Ltd.) and rotary coolers are known as drum flakers. (Manufactured by Nippon Vacuum Technology KK) and the like. Further, examples of the drum flaker having a crushing function include a drum cooler (manufactured by Mitsubishi Kasei Techno Engineers Co., Ltd.).

When treating a solution of polyhydroxycarboxylic acid in an organic solvent with these apparatuses, the temperature inside the apparatus or at the receiving part of the polymer solution is usually from 150 ° C to -10 ° C.
And preferably in the range of 100 to 0 ° C, more preferably 80 to 10 ° C. At a temperature above 150 ° C., problems such as deterioration of the polymer and quality problems, and precipitation defects due to dissolution of the polymer in an organic solvent occur.
On the other hand, if the temperature is lower than -10 ° C, excessive labor is required for cooling.

The cooling rate for cooling and solidifying the organic solvent solution of the polymer and the organic solvent is usually 0.01 to
200 ° C./min, preferably 0.01 to 100 ° C./min, more preferably 0.01 to 20 ° C./min. 200 ° C /
If it exceeds the minute, excessive labor is required for cooling.

The shape of the solid mixture of the polyhydroxycarboxylic acid and the organic solvent obtained in the present invention is the shape of the kneading device used (clearance with the stirring blade), the shape of the crusher for cooling, solidifying and crushing. And has a shape such as powder, granules, granules, flakes, and blocks, depending on the molecular weight and concentration of the polymer, the cooling rate, etc., and its bulk density is in the range of about 0.05 to 0.60 g / ml. Have.
Therefore, when it is desired to obtain a solid mixture having a well-handled shape, an appropriate blade shape of a kneader or a crusher is selected, or the polymer obtained by the kneader or the crusher is treated. The solid mixture can be further adjusted to a desired particle size with a grinder or the like.

Further, in the case of pulverizing with a pulverizer, it is possible to carry out dry pulverizing for pulverizing as it is, or wet pulverizing for pulverizing in a liquid medium such as an organic solvent or water. Examples of the dry crusher include Rotoplex (manufactured by Hosokawa Micron Co., Ltd.) and Hammer Mill (Hosokawa Micron Co., Ltd.).
Manufactured by Hosokawa Micron Co., Ltd., and wet pulverizers include a disintegrator (manufactured by Komatsu Zenoa Co., Ltd.) and a golatol pump (manufactured by Tosho Co., Ltd.). It suffices to be able to pulverize the mixture of shapes, and there is no limitation on its shape or model.

From the thus obtained solid mixture of the polymer and the solvent, the solvent is removed by a known method such as sludging and filtering using a solvent mixed with the solvent and then drying, A solid product of the polymer can be easily obtained. Examples of the solvent that can be used during sludging include alcohols such as methanol, ethanol, n-propanol, and isopropanol, ketones such as acetone, methylacetone, and methylethylketone, methylethylether, diethylether, isopropylether, and the like. n-butyl ether, methyl-t-
Examples include ethers such as butyl ether, hydrocarbons such as n-pentane, n-hexane, isohexane, n-heptane, and n-octane, provided that the solvent can be removed without dissolving the polymer. Any solvent may be used. The cake after sludge and filtration can be dried at a temperature at which the polymer does not dissolve in the solvent to obtain the desired solid polyhydroxycarboxylic acid.

[0035]

EXAMPLES Examples of the method of the present invention will be described below, but the present invention is not limited to the methods and apparatuses described below. The logarithmic viscosity (ηinh) is represented by the following formula (Equation 1) ηinh = ln (t / t.) / C, where t. = Flow-down time of the solvent in the viscometer t = Flow-down time of a dilute polymer solution of the same solvent in the same viscometer c = Concentration of polymer solids in 100 ml of solvent expressed in grams 0.1 g polymer solids / dichloromethane 20 ml Was measured at a temperature of 20 ° C. Weight average molecular weight (Mw) It measured using Shodex GPC system-11 (made by Showa Denko). The Mw value was calculated in terms of polystyrene.

Example 1 104.2 g of 90% L-lactic acid was added at 130 ° C./50 mmHg.
After stirring with heating for 3 hours while removing water to the outside of the system, 75 g of diphenyl ether and 0.4 g of tin powder were added, and a Dean stack filled with 30 g of molecular sieves 3A was attached to the reactor, and the refluxing solvent passed through the molecular sieves. I tried to return to the system. 130 ° C / 15mm
The reaction was carried out at Hg for 30 hours. After the reaction is completed,
The mixture was charged into a type kneader (PNV-1H manufactured by Irie Shokai) and cooled to 20 ° C. for 1 hour while kneading. At this time, the polymer liquid was gradually solidified and pulverized into a white powder.
The powder of the polymer and diphenyl ether mixture (polymer concentration: 50% by weight) was washed and filtered with 300 g of methanol three times and then dried under reduced pressure at 60 ° C. and 100 mmHg to obtain white powdery L-polylactic acid. Yield 93.1
%, Mw 212,000, logarithmic viscosity 1.51 dl / g,
The bulk density was 0.25 g / ml.

Example 2 The same procedure as in Example 1 was carried out except that the reaction time was changed to 8 hours. As a result, the obtained polylactic acid was a white powder and the yield was 89.4% and Mw was 5. 20,000, logarithmic viscosity 0.61d
The volume density was 1 / g and the bulk density was 0.26 g / ml.

Example 3 Instead of 90% L-lactic acid, 75 g of 90% L-lactic acid and 90 g were used.
% D / L-lactic acid was used in the same manner as in Example 1 except that 15 g of D / L-lactic acid was used. As a result, white powdery L-lactic acid and D / L were obtained.
A copolymer of lactic acid was obtained. Yield 94.2%, weight average molecular weight Mw 231,000, logarithmic viscosity 1.60 dl /
and the bulk density was 0.21 g / ml.

Example 4 Instead of 90% L-lactic acid, 75 g and 70% of 90% L-lactic acid were used.
% -Glycolic acid Example -1 except using 9.6 g
As a result of the same method as described above, a white powdery copolymer of L-lactic acid and glycolic acid was obtained. Yield 87.2%,
Weight average molecular weight Mw 182,000, logarithmic viscosity 1.30
It was dl / g and the bulk density was 0.22 g / ml.

Example-5: 90% L-lactic acid 75 g and DL instead of 90% L-lactic acid
As a result of performing the same method as in Example 1 except that 6.8 g of 4-hydroxybutanoic acid was used, a white powdery copolymer of L-lactic acid and DL-4-hydroxycarboxylic acid was obtained. It was The yield was 89.6%, the weight average molecular weight Mw was 165,000, the logarithmic viscosity was 1.22 dl / g, and the bulk density was 0.19 g / ml.

Example 6 Instead of 90% L-lactic acid, 75 g of 90% L-lactic acid and DL
As a result of performing the same method as in Example 1 except that 6.8 g of 3-hydroxybutanoic acid was used, a white powdery copolymer of L-lactic acid and DL-3-hydroxybutanoic acid was obtained. Got Yield 88.3%, weight average molecular weight Mw 152,000, logarithmic viscosity 1.12d.
It was 1 / g and the bulk density was 0.19 g / ml.

Example 7 Example 7 except that anisole was used instead of diphenyl ether and the polymerization conditions were 130 ° C./350 mmHg.
As a result of carrying out in the same manner as in No. 1, the obtained L-polylactic acid was a white powder, yield 88.6%, weight average molecular weight M.
The w was 152,000, the inherent viscosity was 1.12 dl / g, and the bulk density was 0.25 g / ml.

Example-8 An anisole solution of L-polylactic acid obtained by the same method as in Example-7 was charged into a kneader equipped with a Dean stack and a condenser, and the solvent was extracted at 130 ° C./350 mmHg. After concentrating to 75% by weight, Example-1
The same process was carried out. The obtained L-polylactic acid was a white powder and had a yield of 88.5% and a weight average molecular weight Mw of 15.5.
10,000, logarithmic viscosity 1.14 dl / g, bulk density 0.23 g
/ Ml.

Example-9 As a result of carrying out in the same manner as in Example-7 except that 225 g of anisole was used, the obtained L-polylactic acid was a white powder and the yield was 88.5% and the weight average molecular weight was Mw 15.5
10,000, logarithmic viscosity 1.14 dl / g, bulk density 0.24 g
/ Ml.

Example 10 The procedure of Example 1 was repeated, except that o-dichlorobenzene was used instead of diphenyl ether and the polymerization conditions were 140 ° C./250 mmHg. The obtained L-polylactic acid was a white powder and had a yield of 91.1%, a weight average molecular weight Mw of 172,000, an inherent viscosity of 1.25 dl / g, and a bulk density of 0.26 g / ml.

Example-11 The procedure of Example-8 was repeated except that o-dichlorobenzene was used instead of anisole and the polymerization conditions were 140 ° C / 250 mmHg. The obtained L-polylactic acid was a white powder and the yield was 90.8% and the weight average molecular weight was M.
The w was 174,000, the inherent viscosity was 1.26 dl / g, and the bulk density was 0.25 g / ml.

Example-12 1500 g of 90% L-lactic acid was placed in a 2000 ml three-necked flask equipped with a Dean stack, a condenser, a thermometer and a stirrer, and gradually lowered from atmospheric pressure to 30 mmHg at 150 ° C. The dehydration reaction was performed for 8 hours. Zn powder was added thereto, and a cyclic dimer of lactic acid (lactide) that distilled at 200 ° C./5 mmHg / 4Hr was collected. The yield at this time was 85 mol% with respect to lactic acid. The lactide was recrystallized in ethyl acetate and dried. 1% by weight and 2% by weight of lauryl alcohol / lactide as a molecular weight modifier were added and the mixture was stirred at 180 ° C. for 4 hours in a nitrogen atmosphere. After the reaction was completed, the reaction product was extracted from the extraction port at the bottom of the reactor, and the obtained strand was cooled and cut with a pelletizer. The obtained L-
The polylactic acid had a weight average molecular weight Mw of 165,000 and an inherent viscosity of 1.21 dl / g. 200 g of the pellets of L-polylactic acid and 100 g of diphenyl ether were charged into a kneader, heated and stirred at 130 ° C. for 1 hour to dissolve, and then gradually cooled while kneading and cooled to 20 ° C. in 1 hour. The solid mixture of polylactic acid and diphenyl ether thus obtained was washed with 800 g of methanol three times and filtered,
It was dried under reduced pressure at 0 ° C. The obtained L-polylactic acid was in the form of white powder, the yield was 98.7%, and the weight average molecular weight Mw was 16.
50,000, logarithmic viscosity 1.23 dl / g, bulk density 0.20
It was g / ml.

Example 13 100 g of pellets of L-polylactic acid charged in a kneader
150 g of xylene instead of diphenyl ether
The same method as in Example-12 was carried out except that was used.
The obtained polylactic acid was a white powder, and the yield was 98.5%.
Weight average molecular weight Mw 165,000, logarithmic viscosity 1.21
It was dl / g and the bulk density was 0.22 g / ml.

Example 14 Purchased polylactic acid pellets (manufactured by Boehringer, Lo
t. No. L-210, Mw 740,000, logarithmic viscosity 3.
The same procedure as in Example 13 was carried out except that 62 dl / g) was used, and as a result, the obtained polylactic acid was a white powder and the yield was 94.2% and the weight average molecular weight Mw was 720,000.
Logarithmic viscosity 3.60 dl / g, bulk density 0.24 g / m
It was l.

Example 15 104.2 g of 90% L-lactic acid was added at 130 ° C./50 mmHg.
After stirring with heating for 3 hours while removing water to the outside of the system, 75 g of diphenyl ether and 0.4 g of tin powder were added, and a Dean stack filled with 30 g of molecular sieves 3A was attached to the reactor, and the refluxing solvent passed through the molecular sieves. I tried to return to the system. 130 ° C / 15mm
The reaction was carried out at Hg for 30 hours. 70 g of the obtained diphenyl ether solution of L-polylactic acid was charged into a flat-bottomed flask having an inner diameter of 12 cm, and gradually cooled to room temperature. At this time, as the temperature of the reaction solution decreased, L-polylactic acid was precipitated and finally became a uniform solid thin film. A thin film of this solid mixture of L-polylactic acid and diphenyl ether (polymer concentration 50% by weight) was scraped off, pulverized with a homogenizer in 300 g of methanol, and then sludge,
Filtration was repeated 3 times and dried under reduced pressure at 60 ° C. to obtain white powdery L-polylactic acid. Yield 92.1%, weight average molecular weight Mw 214,000, logarithmic viscosity 1.54 dl / g,
The bulk density was 0.24 g / ml.

Example 16 As a result of the same procedure as in Example 15 except that the reaction time was 8 hours, the obtained polylactic acid was a white powder and the yield was 88.9% and Mw was 5. 20,000, logarithmic viscosity 0.61d
It was 1 / g and the bulk density was 0.24 g / ml.

Example 17 Instead of 90% L-lactic acid, 90% L-lactic acid 75 g and 90
% D / L-lactic acid was used in the same manner as in Example 15 except that 15 g of D / L-lactic acid was used. As a result, white powdery L-lactic acid and D / L were obtained.
A copolymer of lactic acid was obtained. Yield 92.8%, weight average molecular weight Mw 22.9 million, logarithmic viscosity 1.59 dl /
and the bulk density was 0.23 g / ml.

Example 18 Instead of 90% L-lactic acid, 75% and 70% of 90% L-lactic acid were used.
% -Glycolic acid Example -1 except using 9.6 g
As a result of performing the same method as in Example 5, a white powdery copolymer of L-lactic acid and glycolic acid was obtained. Yield 86.3%,
Weight average molecular weight Mw 186,000, logarithmic viscosity 1.30
It was dl / g and the bulk density was 0.26 g / ml.

Example-19 90 g L-lactic acid 75 g and DL instead of 90% L-lactic acid
A procedure similar to that in Example-15 was carried out except that 6.8 g of 4-hydroxybutanoic acid was used. As a result, a white powdery copolymer of L-lactic acid and DL-4-hydroxycarboxylic acid was obtained. It was Yield 88.7%, weight average molecular weight Mw 165,000, logarithmic viscosity 1.22 dl / g,
The bulk density was 0.21 g / ml.

Example-20 75 g of 90% -L lactic acid and DL instead of 90% L-lactic acid
As a result of carrying out in the same manner as in Example-15, except that 6.8 g of 3-hydroxybutanoic acid was used, a white powdery lactic acid-DL-3-hydroxybutanoic acid copolymer was obtained. It was Yield 90.1%, weight average molecular weight Mw 151,000, logarithmic viscosity 1.13dl /
and the bulk density was 0.23 g / ml.

Example-21 69.5 kg of 90% L-lactic acid was charged into a 200 L reactor, and the mixture was heated with stirring at 130 ° C./50 mmHg for 3 hours while removing water to the outside of the system, and then 50 kg of anisole, 133 g of tin powder was added, and the distilled anisole was allowed to return to the system through a dehydrator filled with molecular sieves 3A, and a reaction was carried out at 130 ° C./350 mmHg for 30 hours. The obtained anisole solution of polylactic acid was cooled and solidified with a drum flaker. Using a Rotoplex R-20 / 10 (manufactured by Hosokawa Micron), a coarsely pulverized product of the solid mixture of the polymer solution taken out at a drum temperature of 0 to 10 ° C., a rotation speed of 1 rpm, and a treatment amount of 2.2 kg / Hr was used.
Dry pulverization was performed with a screen diameter of 1 mm. The obtained pulverized product was sludged with 200 kg of methanol and filtered three times, and dried under reduced pressure at 60 ° C. The obtained polylactic acid was in the form of white flakes with a yield of 89.2% and a weight average molecular weight Mw.
155,000, logarithmic viscosity 1.12 dl / g, bulk density 0.
It was 16 g / ml.

Example-22 Example-2 except that diphenyl ether was used instead of anisole and the polymerization conditions were 130 ° C./15 mmHg.
Synthesis and solidification by cooling in the same manner as in 1 gave a solid mixture coarsely pulverized product of polylactic acid and diphenyl ether. 25 kg of this solid mixture was added to 100 parts of isopropyl alcohol.
The mixture was charged into a 200 L reactor together with kg, stirred at 200 rpm, and wet pulverized while circulating the slurry from the bottom of the reactor with a Gorator pump (manufactured by Tosho Co., Ltd.). After crushing, sludge and filtration were repeated twice, and dried under reduced pressure at 60 ° C. The obtained polylactic acid was a white powder, and the yield was 86.7%, the weight average molecular weight Mw was 198,000, the logarithmic viscosity was 1.52 dl / g, and the bulk density was 0.14 g / ml.

Example-23 The procedure of Example-21 was repeated except that o-dichlorobenzene was used instead of anisole and the polymerization conditions were 140 ° C / 250 mmHg. The obtained polylactic acid was in the form of white flakes, the yield was 87.0%, and the weight average molecular weight was Mw.
182,000, logarithmic viscosity 1.39 dl / g, bulk density 0.
It was 16 g / ml.

Example-24 37 g of L-polylactic acid pellets obtained in the same manner as in Example-12 and 37 g of o-dichlorobenzene were used to obtain an inner diameter of 12
It was charged in a flat-bottom flask having a diameter of 0.1 cm, the pellet was dissolved at 130 ° C., and then gradually cooled to obtain a solid mixture of polylactic acid and o-dichlorobenzene. The solid mixture was scraped out, pulverized in 300 g of methanol with a homogenizer, sludge and filtered three times, and dried under reduced pressure. The polylactic acid obtained was a white powder and had a yield of 92.1% and a weight average molecular weight M.
The w was 164,000, the inherent viscosity was 1.19 dl / g, and the bulk density was 0.24 g / ml.

Example-25 Purchased Polylactic Acid Pellets (Boehringer, Lo
t. No. L-210, Mw 740,000, logarithmic viscosity 3.
The same procedure as in Example-24 was carried out, except that 62 dl / g) was used. The obtained polylactic acid was in the form of white powder, the yield was 94.1%, the weight average molecular weight Mw was 700,000, the logarithmic viscosity was 3.59 dl / g, and the bulk density was 0.23 g / ml.

[0061]

INDUSTRIAL APPLICABILITY By carrying out the method of the present invention, a high molecular weight solid polyhydroxycarboxylic acid can be easily and inexpensively taken out, and an industrially useful method for producing a polyhydroxycarboxylic acid which can be easily continuous. Can be provided.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 6-203135 (32) Priority date Hei 6 (1994) August 29 (33) Priority claim country Japan (JP)

Claims (8)

[Claims] 1. A method for producing a solid polyhydroxycarboxylic acid, which comprises cooling and solidifying and pulverizing an organic solvent solution of polyhydroxycarboxylic acid. 2. A method comprising charging a kneader with an organic solvent solution of polyhydroxycarboxylic acid, and taking out a solid mixture of the polymer and the organic solvent while cooling and kneading.
The described method. 3. The method according to claim 1, which comprises cooling and solidifying a solution of polyhydroxycarboxylic acid in an organic solvent, and then pulverizing the obtained solid mixture of the polymer and the organic solvent. 4. The method according to claim 1, wherein the solution of polyhydroxycarboxylic acid in an organic solvent is obtained by dehydration condensation of hydroxycarboxylic acids and their oligomers in an organic solvent solution in the presence or absence of a catalyst. . 5. The method according to claim 1, wherein the polyhydroxycarboxylic acid has an inherent viscosity of 0.3 to 5.0 dl / g. 6. The method according to claim 1, wherein the concentration of the organic solvent solution of polyhydroxycarboxylic acid is 15 to 95% by weight. 7. The method according to claim 4, wherein the catalyst is a divalent tin compound or tin powder. 8. The method according to claim 7, wherein the divalent tin compound is selected from stannous chloride, stannous hydroxide, tin sulfate and stannous oxide.