JP2000302855A - Method for crystallizing aliphatic polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for crystallizing an aliphatic polyester at a lower temperature and within a shorter time compared to the conventional crystallization method and without any problem of fusion or breakage. SOLUTION: A solid aliphatic polyester is crystallized by bringing it into contact with a liquid. Alternatively, a melt aliphatic polyester is solidified and crystallized by bringing it into contact with a liquid. Further alternatively, an aliphatic polyester solution wherein an aliphatic polyester is dissolved in a solvent is solidified and crystallized by bringing it into contact with a liquid. An aliphatic polyester is crystallized with no limit of its molecular weight or relative viscosity ηrel and without any problem of fusion, breakage, etc. The crystallization of the aliphatic polyester enables stable operation without any problem such as a fusion between particles, a breakage of particles, a blocking inside the device, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for crystallizing an aliphatic polyester. The present invention relates to an improved crystallization method for aliphatic polyesters. The present invention relates to a method for crystallizing polylactic acid. The present invention relates to an improved method for crystallizing polylactic acid.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 8-34843
No. 34843 discloses a technique relating to a method for producing a high molecular weight aliphatic polyester. That is, an aliphatic polyester having a specific relative viscosity η _rel (1.5) or more is crystallized and then subjected to solid-phase polymerization under specific conditions to obtain a high-molecular-weight and high-melting-point product that can be formed as fishing line or the like. It is said that an aliphatic polyester can be obtained. However, regarding the crystallization technique, it is said that various conventionally known methods such as crystallization at room temperature and crystallization such as cooling with water can be used, and it can be used only in contact with a liquid. There is no suggestion or disclosure about possible crystallization.

[0003] Japanese Patent Application Laid-Open No. 8-165339
165339 discloses a technique relating to a method for producing lactic acid-based copolymerized polyester granules. That is,
A lactic acid-based copolymerized polyester comprising a lactic acid component, a dicarboxylic acid component, and a diol component, a glass transition temperature or higher,
It is said that the crystallization at a temperature lower than the melting point can solve the fusion problem. JP-A-8-165
No. 339 includes paragraphs [0014] to
As described in [0016], a lactic acid-based copolymerized polyester is extruded from a die in a molten state to form a strand, and the molten strand is crystallized while being cooled at a constant cooling rate, and the crystallized strand is cut. A technique for granulating is disclosed. However, there is no suggestion or disclosure about crystallization by contact with a liquid.

[0004]

When a low-molecular-weight aliphatic polyester is to be crystallized by heating in a solid state by a conventional technique, it is fused due to its low melting point.
As described in paragraph No. [0021] of Japanese Patent Publication No. 34843, the low molecular weight aliphatic polyester is brittle, and thus has a problem that breakage of pellets, powderization of pellets, and the like occur. The problem to be solved by the present invention, when crystallizing a solid state aliphatic polyester,
An object of the present invention is to provide a method for crystallizing an aliphatic polyester, which can be crystallized without causing problems such as fusion, breakage, and powdering. Another object of the present invention is to provide a novel method for crystallizing an aliphatic polyester, which comprises simultaneously solidifying and crystallizing an aliphatic polyester melt or an aliphatic polyester solution. Also,
To provide an improved aliphatic polyester crystallization method capable of crystallizing an aliphatic polyester at a lower temperature and in a shorter time than conventional crystallization methods without fusing, breaking, or powdering. It is in.

[0005]

Means for Solving the Problems The present inventors have described the above-mentioned.
Considering the situation, the molecular weight and relative viscosity η of the aliphatic polyester
_relAs a result of intensive studies on crystallization independent of
Ming has been completed. That is, the present invention provides the following [1]
To [20]. [1] Contacting a solid state aliphatic polyester with a liquid
Characterized by being crystallized by causing
For crystallization of aromatic polyesters. [2] Contacting molten aliphatic polyester with liquid
Is characterized by solidification and crystallization
A method of crystallizing an aliphatic polyester. [3] An aliphatic polyester obtained by dissolving an aliphatic polyester in a solvent.
The ester solution is solidified by contact with a liquid.
Aliphatic polyester characterized by being crystallized by
Tell crystallization method.

[4] The method for crystallizing an aliphatic polyester according to any one of [1] to [3], wherein the liquid does not dissolve the aliphatic polyester. [5] The method for crystallization of an aliphatic polyester according to any one of [1] to [4], wherein the liquid at least partially contains water. [6] The method for crystallizing an aliphatic polyester according to any of [1] to [5], wherein the contact temperature is in a temperature range from the freezing point of the liquid to the melting point of the aliphatic polyester.

[7] The contact temperature is in a temperature range from the glass transition point of the aliphatic polyester to the melting point and lower than the melting point, [1].
The method for crystallizing an aliphatic polyester according to any one of claims 1 to 5. [8] The method for crystallizing an aliphatic polyester according to any one of [1] to [5], wherein the contact temperature is in a temperature range of 30 ° C. or more and 100 ° C. or less. [9] The amount of the aliphatic polyester to be subjected to crystallization is from 0.1% by weight to 99% by weight based on the total weight of the liquid and the aliphatic polyester to be treated per unit time, [1] to [1]. 8] The method for crystallizing an aliphatic polyester according to any one of [1] to [8].

[10] The amount of the aliphatic polyester to be subjected to crystallization is not less than 1% by weight based on the total weight of the liquid and the aliphatic polyester to be treated per unit time.
The method for crystallizing an aliphatic polyester according to any one of [1] to [8], which is not more than weight%. [11] The method for crystallizing an aliphatic polyester according to any one of [1] to [10], wherein the time required for crystallization is 1 second to 180 minutes. [12] The method for crystallizing an aliphatic polyester according to any one of [1] to [10], wherein the time required for crystallization is 1 minute to 60 minutes.

[13] The method according to any one of [1] to [12], wherein the crystallized aliphatic polyester obtained has a heat of crystallization of 0 to 30 [J / g]. A method for crystallizing an aliphatic polyester. [14] The aliphatic polyester according to any one of [1] to [12], wherein the obtained crystallized aliphatic polyester has a heat of crystallization of 0 to 10 [J / g]. Crystallization method. [15] The aliphatic polyester to be subjected to crystallization has a relative viscosity ηrel of 0.1 or more and less than 1.5. [1]
The method for crystallizing an aliphatic polyester according to any one of claims 1 to 14.

[16] The method for crystallizing an aliphatic polyester according to any one of [1] to [15], wherein the aliphatic polyester to be subjected to crystallization has a glass transition point of 20 ° C. or more and 60 ° C. or less. . [17] The method for crystallizing an aliphatic polyester according to any one of [1] to [16], wherein the aliphatic polyester to be subjected to crystallization has a weight average molecular weight Mw of 0.020,000 to 50,000. [18] the aliphatic polyester is polylactic acid;
The method for crystallizing polylactic acid according to any one of [1] to [17].

[19] The method for crystallizing polylactic acid according to [18], wherein the polylactic acid is obtained by directly polymerizing lactic acid. [20] The method for crystallizing polylactic acid according to [18], wherein the polylactic acid is obtained by ring-opening polymerization of lactide.

[0012]

Embodiments of the present invention will be described below in detail. [Aliphatic polyester] In the present invention, the aliphatic polyester includes the following aliphatic polyhydroxycarboxylic acids, aliphatic polyesters, and mixtures thereof, as long as it is a polymer that crystallizes.

Specifically, for example, an aliphatic polyhydroxycarboxylic acid such as a homopolymer such as polylactic acid and polyhydroxycaproic acid and a copolymer of lactic acid and another aliphatic hydroxycarboxylic acid, a lactic acid unit, an aliphatic polyvalent Aliphatic polyesters composed of carboxylic acid units and aliphatic polyhydric alcohol units, aliphatic polyesters containing lactic acid units and polyfunctional polysaccharides, aliphatic polycarboxylic acids such as polybutylene succinate and aliphatic polyhydric alcohols Polyesters, and mixtures of the above-mentioned aliphatic polyhydroxycarboxylic acids and aliphatic polyesters. When the aliphatic polyhydroxycarboxylic acid and the aliphatic polyester are copolymers, they include random copolymers, alternating copolymers, block copolymers, and graft copolymers. The concept of a mixture includes the concepts of a polymer blend and a polymer alloy.

The polylactic acid includes poly (L-lactic acid) whose structural unit is composed only of L-lactic acid and poly (D-lactic acid) whose structural unit is composed only of D-lactic acid.
-Lactic acid), and poly (DL-lactic acid) in which L-lactic acid units and D-lactic acid units are present in various ratios. Examples of the aliphatic hydroxycarboxylic acid other than lactic acid constituting the aliphatic polyhydroxycarboxylic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, and 6-hydroxy Caproic acid and the like. These aliphatic hydroxycarboxylic acids are used alone as homopolymers, or as a mixture of them or as a copolymer by mixing with lactic acid.

Polylactic acid can be produced by a method of directly dehydrating and polycondensing L-lactic acid, D-lactic acid or DL-lactic acid, for example, a method described in JP-A-6-65360. Further, it can also be produced by a method in which lactide which is a cyclic dimer ester of lactic acid is subjected to ring-opening polymerization.
The ring-opening polymerization may be performed in the presence of a compound having a hydroxyl group such as a higher alcohol or hydroxycarboxylic acid. Lactic acid has stereoisomers, and lactide has stereoisomers. That is, L-lactic acid and D-lactic acid are used for lactic acid, L-lactide composed of two L-lactic acids is used for lactide, and two D-lactic acids are used for lactide.
There are D-lactide composed of lactic acid and MESO-lactide composed of L-lactic acid and D-lactic acid. In the present invention, any raw material can be used, and the composition thereof is not particularly limited. However, in order to exhibit crystallinity, the lactic acid component contains 75% or more of the L-lactic acid component in the total lactic acid component. More preferably, the lactic acid component contains 90% or more of the L-lactic acid component in the total lactic acid component, and more preferably, the lactic acid component contains 95% or more of the L-lactic acid component in the total lactic acid component. More preferably, the lactic acid component contains 97% or more of the L-lactic acid component in the total lactic acid component.

Lactic acid and other aliphatic hydroxycarboxylic acid copolymers can be produced by a method of dehydrating polycondensation of lactic acid and the above-mentioned hydroxycarboxylic acid, for example, a method disclosed in JP-A-6-65360. Further, it can also be produced by a method of ring-opening copolymerizing lactide, which is a cyclic dimer ester of lactic acid, with cyclic esters of the above aliphatic hydroxycarboxylic acids. It may be manufactured by any method.

An aliphatic polyester containing a lactic acid unit, an aliphatic polycarboxylic acid unit and an aliphatic polyhydric alcohol unit, or an aliphatic polyhydric ester used for producing an aliphatic polyester of an aliphatic polycarboxylic acid and an aliphatic polyhydric alcohol. Examples of the carboxylic acid include oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, undecandioic acid, dodecandioic acid, and anhydrides thereof. These may be an acid anhydride or a mixture with an acid anhydride.

Examples of the aliphatic polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-
Butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol and the like.

The aliphatic polyester comprising a lactic acid unit, an aliphatic polycarboxylic acid unit and an aliphatic polyhydric alcohol unit can be obtained by mixing the above-mentioned aliphatic polycarboxylic acid and the above-mentioned aliphatic polyhydric alcohol with polylactic acid and lactic acid. It can be produced by a method of reacting a hydroxycarboxylic acid copolymer or the like, or a method of reacting lactic acid with the aliphatic polycarboxylic acid and the aliphatic polyhydric alcohol. Further, it can also be produced by a method of reacting the aliphatic polycarboxylic acid and the aliphatic polyhydric alcohol with lactide, which is a cyclic dimer ester of lactic acid, and the above-mentioned cyclic ester of hydroxycarboxylic acid. It may be manufactured by any method. The aliphatic polyester of an aliphatic polycarboxylic acid and an aliphatic polyhydric alcohol can be produced by a method of reacting the aliphatic polycarboxylic acid and the aliphatic polyhydric alcohol.

Examples of the polyfunctional polysaccharide used for producing an aliphatic polyester containing a lactic acid unit and a polyfunctional polysaccharide include, for example, cellulose, cellulose nitrate, cellulose acetate, methyl cellulose, ethyl cellulose, CMC (carboxymethyl cellulose), nitrocellulose and cellophane. ,
Regenerated cellulose such as viscose rayon and cupra, hemicellulose, starch, amylopectin, dextrin, dextran, glycogen, pectin, chitin,
Chitosan and the like, and mixtures thereof and derivatives thereof. Of these, cellulose acetate and ethyl cellulose are particularly preferred.

The aliphatic polyester containing a lactic acid unit and a polyfunctional polysaccharide can be produced by a method in which the above polyfunctional polysaccharide is reacted with lactic acid or polylactic acid, a copolymer of lactic acid and another hydroxycarboxylic acid, or the like. Further, it can also be produced by a method of reacting the above-mentioned polyfunctional polysaccharide with lactide, which is a cyclic dimer ester of lactic acid, or the above-mentioned cyclic ester of hydroxycarboxylic acid. It may be manufactured by any method.

When the aliphatic polyester used in the present invention is produced, an organic solvent can be used as a reaction solvent, but need not be used. When an organic solvent is used, the concentration of the organic solvent in the aliphatic polyester solution used for crystallization is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 10% by weight or less. Also,
Commonly known nucleating agents such as talc, clay and titanium oxide may be added. Therefore, the aliphatic polyester provided for crystallization in the present invention may contain a monomer, a low molecular weight oligomer, an organic solvent, a nucleating agent, and the like.
The crystallization method of the present invention can be applied to the above-mentioned various aliphatic polyesters, but in particular, polylactic acid, polybutylene succinate, homopolymers such as polyhydroxycaproic acid, and aliphatic acids other than lactic acid and lactic acid. Copolymers with hydroxycarboxylic acids (when transparency is required, those containing 50% or more by weight of a lactic acid component are preferred), polyesters composed of lactic acid and aliphatic polycarboxylic acids and aliphatic polyhydric alcohols (transparency Is preferred, the lactic acid component preferably contains 50% or more by weight)).

[Weight average molecular weight M of aliphatic polyester]
w] The weight average molecular weight Mw of the aliphatic polyester is determined, for example, by gel permeation chromatography (GP
The value measured according to C) can be used. For example,
The weight average molecular weight Mw of polylactic acid can be measured by GPC under the following measurement conditions. Column temperature = 40
° C, solvent = chloroform, standard sample = polystyrene. Although the molecular weight of the aliphatic polyester used in the present invention is not particularly limited, containers, films,
When molded into a molded product such as a sheet or a plate, a material exhibiting substantially sufficient mechanical properties is preferable. In this case, if the molecular weight is low, the strength of the obtained molded product is reduced, and the decomposition rate is increased. Conversely, if it is too high, the workability decreases, and molding becomes difficult. The weight average molecular weight Mw of the aliphatic polyester used in the present invention is 0.02 to 5,000,000.
020,000 to 3,000,000 are preferred, 0.02 to 2,000,000 are more preferred, 0.0000 to 1,000,000 are more preferred,
0.0000 to 500,000 is more preferable, 0.020,000 to 50,000 is more preferable, 0.1000 to 50,000 is more preferable, and
20,000 to 50,000 are more preferable, 40,000 to 40,000 are more preferable, and 50,000 to 30,000 are more preferable.

[Relative viscosity of aliphatic polyester η _rel ]
As the relative viscosity η _rel of the aliphatic polyester, for example, a value measured using an Ubbelohde viscometer or the like can be used. For example, the relative viscosity η _rel of polylactic acid can be measured using an Ubbelohde viscometer under the following measurement conditions. Solvent = dichloromethane, concentration = 0.5 g / deciliter, measurement temperature = 20 ° C. The relative viscosity η _rel of the aliphatic polyester used in the present invention is not particularly limited. For example, in a preferred embodiment, the relative viscosity η _rel of the polylactic acid used in the present invention is preferably from 0.2 (corresponding to Mw of 2,000) to 0.74 (Mw).
Equivalent to 50,000. ), More preferably 0.22 (Mw 0.4
Equivalent to ten thousand. ) To 0.62 (corresponding to Mw 40,000), more preferably 0.23 (corresponding to Mw 50,000) to 0.51.
(Equivalent to 30,000 Mw).

[Glass transition point T of aliphatic polyester]
g] The glass transition point Tg of the aliphatic polyester is determined by a differential scanning calorimeter (DSC) (sample weight = about 5 mg, temperature condition =
-20 ° C to 100 ° C, heating rate = 10 ° C / min). The glass transition point Tg of the aliphatic polyester used in the present invention is not particularly limited. For example, in a preferred embodiment, the glass transition point Tg of the polylactic acid used in the present invention is preferably from 26 ° C. (corresponding to Mw of 0.2000) to 55 ° C. (Mw5).
Equivalent to ten thousand. ), More preferably 37 ° C (corresponding to Mw 40,000) to 54 ° C (corresponding to Mw 40,000), more preferably 40 ° C (corresponding to Mw 50,000) to 52 ° C (corresponding to Mw 30,000). ).

[Form of Aliphatic Polyester] The aliphatic polyester used in the present invention may be in any of a solid state, a molten state and a solution state. In the solid state, the shape is not particularly limited, plate-like, lump-like, string-like,
Pellets, granules and the like can be used. Pellets or granules are preferred from the viewpoint of uniform crystallization and ease of handling. The method of forming the aliphatic polyester into pellets or granules is not particularly limited, and a known method is used.

In the molten state or the solution state, the method of contacting with the liquid is not limited at all. For example, an aliphatic polyester melt, or an aliphatic polyester solution obtained by dissolving an aliphatic polyester in a solvent, may be dropped into a liquid such as water to be solidified and crystallized.
Spherical pellets can be obtained. The shape of the pellets and the shape of the particles are not particularly limited. The pellet shape or the grain shape does not need to be a specific shape such as a crushed shape, a chip shape, a spherical shape, a cylindrical shape, a marble shape, a tablet shape, but generally, a spherical shape, a cylindrical shape, or a marble shape is preferable. Pellet production equipment is not particularly limited, for example, a Sandvik strip former, a rotoformer, a double roll feeder, a Kaiser rotary dropformer, and a piston type dropformer, Mitsubishi Examples include a drum cooler manufactured by Kasei Engineering Co., Ltd., a steel belt cooler manufactured by Nippon Belding Co., Ltd., and a hybrid former. The polylactic acid molten droplet generator and the polylactic acid solution droplet generator are not particularly limited, and specific examples thereof include a Kaiser pastilator.
The size of the pellets and grains is not particularly limited, but is preferably 0.1 mm to 10 mm, more preferably 1 mm to 5 mm, in consideration of handling in the manufacturing process and handling during secondary molding.

[Crystallization] In the present specification, crystallization means measurement by a differential scanning calorimeter (DSC) (measurement conditions; sample weight = 5 mg, temperature conditions = 20 ° C. to 200 ° C., heating rate =
10 ° C./min) and the measured heat of crystallization is 30 [J /
g] means the following: In the present invention, the method of contacting the aliphatic polyester with the liquid is not particularly limited.

When the aliphatic polyester is in a solid state, it can be charged into a liquid and brought into contact with the liquid, or the liquid can be poured into the aliphatic polyester solid and brought into contact with the liquid. The method for charging the solid aliphatic polyester into the liquid is not particularly limited, and specific examples thereof include a method using a tank and a method using a tower. When using a tank, stirring may or may not be performed,
Preferably, it is better to stir. When a column is used, the aliphatic polyester solid can be brought into contact with the liquid in countercurrent or cocurrent. It is also possible to charge aliphatic polyester solids into the flowing liquid. The method of pouring the liquid into the aliphatic polyester solid and bringing it into contact may be a method of spraying the liquid on the aliphatic polyester solid, or flowing the liquid through a tower filled with the aliphatic polyester solid. When the aliphatic polyester is in a molten state or a solution state, it can be charged into a liquid and brought into contact with the liquid. As a typical method, there is a method of dripping into a liquid.

Also, once dropped and solidified in a liquid, it can be crystallized by bringing it into contact with a liquid as a solid aliphatic polyester by the method described above. The amount of the aliphatic polyester to be subjected to crystallization may be 0.1% by weight or more and less than 100% by weight based on the total weight of the liquid and the aliphatic polyester to be treated per unit time.
If used effectively, the content is preferably 1% by weight or more and 80% by weight or less. 80% by weight of aliphatic polyester
If it exceeds the range, the fusibility will be high.

The contact temperature may be at least the freezing point of the liquid used but less than the melting point of the aliphatic polyester. However, if the temperature is too low, it takes a long time for crystallization, which is not practical. If the temperature is too high, the decomposition rate of the aliphatic polyester increases, which is not preferable. Therefore, practically 10 ° C
The temperature is preferably from 100C to 100C, more preferably from 30C to 100C. Further, the temperature is preferably from the glass transition point of the aliphatic polyester to 100 ° C. or lower. Further, in order to prevent fusion, the aliphatic polyester may be brought into contact with the liquid at a temperature equal to or lower than the glass transition point, and then the temperature may be increased to cause crystallization. The relationship between the liquid to be used and the contact temperature is not particularly limited. For example, when the temperature is equal to or higher than the boiling point of the liquid, a reflux pipe may be provided. The contact temperature may be gradually increased as long as it is within the range, or may be gradually cooled,
Preferably, it is kept at a constant temperature. The rate of temperature rise when the temperature is gradually increased and the rate of cooling when the temperature is gradually cooled are not particularly limited, but are preferably 0.1 to 20 [° C./min].

The liquid is not particularly limited as long as the aliphatic polyester does not dissolve at the contact temperature. As a specific example of the liquid, for example, a commonly used general-purpose solvent can be used. As a more detailed example,
For example, water, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, esters and the like,
These may contain organic acids. These may have a single composition or may be used as a mixture. Examples of the alcohol include methanol, ethanol, propanol, is
o-propanol, butanol, iso-butanol,
sec-butanol, tert-butanol, pentanol, iso-pentanol, tert-pentanol, hexanol, iso-hexanol, tert-
Hexanol and cyclohexanol. As the aliphatic hydrocarbon, hexane, cyclohexane, n-
Heptane, n-octane, n-nonane, n-decane, n
-Undecane, n-dodecane, n-tridecane, n-tetradecane. Examples of the aromatic hydrocarbon include benzene, toluene, xylene, mesitylene, cumene, cymene, styrene, and ethylbenzene. Examples of ketones include acetone and methyl ethyl ketone,
Examples of the ether include methyl-t-butyl ether, dibutyl ether, and anisole, and examples of the esters include ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and butyl lactate.

After the aliphatic polyester is crystallized by contact with a liquid, the crystallized aliphatic polyester and the liquid can be separated by a known method. After separating from the liquid, it is dried by a known method to obtain a crystallized aliphatic polyester.

[0034]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to the following examples. In the examples, description will be made focusing on polylactic acid which is a typical specific example of the aliphatic polyester. Example 1 90 ml in a 2000 ml glass round bottom flask
% L-lactic acid 1070 g and tin 0.75 g were charged. After purging with nitrogen, the temperature was gradually raised and reduced. Finally, the reaction was performed at a reaction temperature of 160 ° C. and a reaction pressure of 10 Torr for 15 hours. The relative viscosity ηrel of the obtained polylactic acid was 0.29. This polylactic acid was made into rice-sized pellets by a granulator. Charge 20 g of pellets into 80 g of water at 50 ° C.
Let stand for minutes. No fusion or breakage of the pellets was observed. The pellet was taken out, dried under reduced pressure at room temperature, and measured by a differential scanning calorimeter. As a result, no heat of crystallization was detected.

Example 2 Polylactic acid 20 obtained in Example 1
g of the molten solution was dropped into 80 g of water at 50 ° C. with stirring. Solidification was observed upon dropping and the condition was maintained for 60 minutes. No fusion or breakage of the particles was observed. The particles were taken out, dried under reduced pressure at room temperature, and measured with a differential scanning calorimeter. As a result, no heat of crystallization was detected.

Example 3 Polylactic acid 20 obtained in Example 1
Then, 10 g of dichlorobenzene was added to g, to prepare a polylactic acid solution. This polylactic acid solution is placed in 270 g of water at 50 ° C.
It was added dropwise with stirring. It is observed that it solidifies simultaneously with the dropping,
The state was maintained for 60 minutes. No fusion or breakage of the particles was observed. The particles were taken out, dried under reduced pressure at room temperature, and measured with a differential scanning calorimeter. As a result, no heat of crystallization was detected.

Comparative Example 1 The polylactic acid pellets obtained in Example 1 were placed in an oven at 50 ° C. and crystallized. 6
After 0 minute, the pellet was still transparent, and the heat of crystallization was 40 [J / g] as measured by a differential scanning calorimeter. The polylactic acid pellets obtained in Example 1 were placed in a 60 ° C. oven and crystallized. After 30 minutes, the pellets were fused.

[0038]

According to the method of the present invention, when the aliphatic polyester is crystallized, it can be crystallized without being restricted by the molecular weight or the relative viscosity ηrel and without causing problems such as fusion and breakage. Can be. Therefore, by crystallizing the aliphatic polyester by the method of the present invention, stable operation can be performed without causing problems such as fusion of particles, breakage of particles, and blockage in the device. Further, according to the method of the present invention, there is provided a novel method for crystallizing an aliphatic polyester, which comprises solidifying and simultaneously crystallizing an aliphatic polyester melt or an aliphatic polyester solution. be able to. Further, according to the method of the present invention, in the crystallization of the aliphatic polyester, the crystallization can be performed at a lower temperature and in a shorter time than the conventional crystallization method without fusion or breakage.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Kotaki 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsui Chemicals Co., Ltd. 72) Inventor Masanobu Ajioka 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa F-term (reference) 4F201 AA01 AA24 AR06 BA04 BC01 BC12 BC15 BN03 BN12 BN15 BN44 4J029 AA02 AB07 AD08 AE02 BA03 BA04 BA05 BA09 BD04A CA01 CA03 CA05 CA06 EA05 EH03 KH03

Claims (8)

[Claims] 1. A method for crystallizing an aliphatic polyester, comprising bringing an aliphatic polyester in a solid state into contact with a liquid to crystallize the aliphatic polyester. 2. A method for crystallizing an aliphatic polyester, comprising bringing an aliphatic polyester in a molten state into contact with a liquid to solidify and crystallize the aliphatic polyester. 3. An aliphatic polyester solution obtained by dissolving an aliphatic polyester in a solvent is brought into contact with a liquid,
A method for crystallizing an aliphatic polyester, comprising solidifying and crystallizing. 4. The method for crystallizing an aliphatic polyester according to claim 1, wherein the liquid does not dissolve the aliphatic polyester. 5. The method for crystallization of an aliphatic polyester according to claim 1, wherein the liquid contains water at least partially. 6. The method for crystallization of an aliphatic polyester according to claim 1, wherein the contact temperature is in a temperature range from the freezing point of the liquid to the melting point of the aliphatic polyester. 7. The method for crystallizing an aliphatic polyester according to claim 1, wherein the contact temperature is in a temperature range from the glass transition point of the aliphatic polyester to the melting point and lower than the melting point. 8. The method for crystallizing an aliphatic polyester according to claim 1, wherein the aliphatic polyester is polylactic acid.