JP3357188B2 - Method for producing high molecular weight aliphatic polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high molecular weight aliphatic polyester which can be decomposed by microorganisms in soil and used as a molded product. The present invention relates to a method for producing an aliphatic polyester.

[0002]

2. Description of the Related Art Plastics used as synthetic fibers, films and other molded products can be supplied stably at low cost and in large quantities in addition to the advantages of being light and durable.
It has brought richness and convenience to our lives and built a modern society that can be called a plastic civilization. However, in recent years, there has been a demand for the development of a polymer material that can be decomposed in the natural environment in response to environmental problems on a global scale. And high expectations as a new type of functional material.

[0003] It is well known that aliphatic polyesters are biodegradable, and among them, poly-3-hydroxybutyric acid (PH
B) or synthetic polymer poly-ε-caprolactone (P
CL) and polyglycolic acid (PGA) are representative thereof.

[0004] Biopolyesters mainly composed of PHB are produced industrially because of their excellent environmental compatibility and physical properties. However, they are poor in productivity and are generally represented by polyethylene in view of cost. There is a limit to be able to substitute as a plastic for use (Fiber and Industry, vol. 47, p. 532 (1991)). For PCL, fibers,
Although a polymer with a high degree of polymerization that can be formed into a film is obtained, its melting point is less than 65 ° C and its heat resistance is poor, so it cannot be applied to a wide range of applications [Polym. Sci. Technol. 61 pages (1973)
reference〕. Furthermore, PGA and glycolide-lactide (9: 1) copolymers that have been put into practical use as biocompatible sutures are metabolically absorbed in vivo after undergoing abiotic hydrolysis. Since it is expensive and has poor water resistance, it is not suitable for use as ordinary plastic.

On the other hand, α, ω-aliphatic diols and α, ω-
Aliphatic polyesters produced by melt polycondensation with aliphatic dicarboxylic acids, such as polyethylene succinate (PES), polyethylene adipate (PEA) and polybutylene succinate (PBS) are long-known polymers that are inexpensive. It has been confirmed that it can be produced and is biodegraded by microorganisms in soil burial tests [Intert. Biodetetn. Bull., Vol. 11, 127].
(1975) and Polymer Science Technology (Polym. Sci. Technol.), Vol. 3, p. 61 (197)
However, these polymers have poor thermal stability,
Since a decomposition reaction occurs at the time of polycondensation, it is usually 2,000.
Only a molecular weight of about 6,000 was obtained, which was not sufficient for processing as a fiber or film.

[0006]

SUMMARY OF THE INVENTION The present inventors have previously studied to increase the molecular weight of such aliphatic polyesters. As a result, when titanium, antimony or germanium compounds are used as catalysts, they can be used in a short time. It has been found that the molecular weight can be increased to such an extent that it can be formed into a film or fiber, and has been already proposed in, for example, Japanese Patent Application Nos. 5-98851 and 5-297330. The aliphatic polyester produced in this way can be formed into various applications as a film or a fiber by itself, but when considered for applications such as fishing lines, which are often required for biodegradability, the strength is sufficient. Instead, it is necessary to further increase the molecular weight and melting point. Of course, Japanese Patent Application No. Hei 5-98885 and Japanese Patent Application No. Hei 5-29733.
Although the molecular weight can be increased by melt polymerization using the method presented in No. 0, very high rotational power was required during manufacture.

[0007] The present invention provides a biodegradable material without impairing its original property and without using any special equipment.
It is another object of the present invention to provide a method for producing a high-molecular-weight, high-melting-point aliphatic polyester that can be molded as a fishing line or the like.

[0008]

Means for Solving the Problems The present inventors have conducted various studies in order to solve the above-mentioned problems, and as a result, have found that polycondensation in a solid state increases the molecular weight and the melting point. As a result, the present invention has been achieved based on this finding.

That is, the present invention relates to a method of crystallizing an aliphatic polyester having a relative viscosity of 1.5 or more, followed by solid-phase polymerization at a temperature lower than the melting point in an inert gas atmosphere or under reduced pressure. The gist of the invention is a method for producing a high-molecular-weight aliphatic polyester.

Hereinafter, the present invention will be described in detail. In the present invention, it is necessary to first produce an aliphatic polyester having a relative viscosity of 2.00 or more . Such an aliphatic polyester can be produced by reacting a diol with a dicarboxylic acid to obtain an oligomer, and then subjecting the obtained oligomer to a deglycol reaction in the presence of a catalyst.

The diol used at this time includes:
For example, ethylene glycol, trimethylene glycol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,10-decanediol, propylene glycol, neopentyl glycol,
Examples thereof include diethylene glycol, dipropylene glycol, cyclohexane dimethanol and the like, and mixtures thereof. Among them, those having an even number of carbon atoms, for example, ethylene glycol, 1,4-butanediol, 1,6-
The use of hexanediol or the like is preferable in that an aliphatic polyester having a high melting point can be obtained, and the use of ethylene glycol, 1,4-butanediol, and succinic acid in combination with an aliphatic polyester having a melting point of 100 ° C. or more It is optimal in that it can be obtained. Further, polyhydric alcohols such as glycerin, trimethylolpropane and pentaerythritol can be used in combination.

The dicarboxylic acids used at this time include, for example, oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecane diacid, eicosane diacid and their acid anhydrides. And alkyl esterified compounds such as succinic anhydride, glutaric anhydride, dimethylsuccinic acid, dimethyladipic acid and the like, and mixtures thereof. Among them, those having an even number of carbon atoms, such as succinic acid, adipic acid, and succinic anhydride, are preferable in that an aliphatic polyester having a high melting point can be obtained, and succinic acid, succinic anhydride, and 1,4 are preferable. When -butanediol or the like is used in combination, it is optimal in that an aliphatic polyester having a melting point of 100 ° C or more can be obtained. An aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid can be used in combination as long as the biodegradability is not hindered. Further, oxycarboxylic acids such as malic acid, citric acid, tartaric acid and the like, and polyvalent carboxylic acids such as trimellitic anhydride, pyromellitic anhydride and trimesic acid can be used in combination.

The charge ratio of these dicarboxylic acids and diols is preferably from 1: 1 to 1: 2.5, more preferably from 1: 1.01 to 1: 2, by mole ratio. It is optimal to set the ratio to 1: 1.05 to 1: 1.8.

The reaction conditions for synthesizing the oligomer are preferably in the range of 120 to 250 ° C. for 1 to 10 hours, and in the range of 150 to 220 ° C. for 2 to 5 hours under atmospheric pressure and inert gas atmosphere. More preferably, it is performed under a nitrogen gas stream.

Next, a metal compound may be used as a catalyst used in the polycondensation of the oligomer, and titanium, germanium, antimony,
Magnesium, calcium, zinc, iron, zirconium,
Vanadium, lithium, cobalt, manganese and the like can be mentioned. These metal compounds are used in the form of metal alkoxides, metal acetylacetonates, metal oxides, metal complexes, metal hydroxides, organic acid salts and the like. Examples of particularly preferred catalysts include tetra-n-butyl titanate, tetraisopropyl titanate, tetraethyl titanate, titanium oxyacetylacetonate, dibutoxydiacetacetoxytitanium, titanium acetate, tetra-n
-Butoxygermanium, tetraethoxygermanium, tetrabutylgermanium, germanium oxide (I
V), tributoxyantimony, triethoxyantimony, antimony trioxide, antimony acetate, zinc acetate, calcium acetylacetonate, magnesium acetylacetonate, zinc acetylacetonate, tetrabutoxyzirconium and the like. 2
More than one species may be used.

The amount of the catalyst used at that time is as follows:
0.1 parts by weight per 100 parts by weight of the aliphatic polyester produced.
The amount is preferably from 01 to 5 parts by weight, more preferably from 0.05 to 2 parts by weight. When the amount of the catalyst is less than 0.01 part by weight, the effect as a catalyst is weakened, and it is difficult to obtain a polymer having a target molecular weight. Even when the amount exceeds 5 parts by weight, the effect is not largely changed. Conversely, the formed polymer is undesirably colored. These catalysts need only be present at the time of polycondensation, and may be added immediately before deglycolization or may be added before esterification.

In the course of deliquorization and polymerization, a phosphorus compound may be added as a coloring inhibitor. Examples of the phosphorus compound include phosphoric acid, phosphoric anhydride, polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphorous acid, tripolyphosphoric acid, bis (2,4-dibutylphenyl) pentaerythritol diphosphate. Spirophosphorus compounds represented by phosphates and their metal salts, ammonium salts, chlorides, bromides, sulfides, esterified compounds and the like are particularly preferred, and phosphoric acid, polyphosphoric acid, metaphosphoric acid, Bis (2,4-dibutylphenyl) pentaerythritol diphosphate and the like can be mentioned. These phosphorus compounds may be used alone or as a mixture of two or more.

The amount of the phosphorus compound used at this time is preferably 0.001 to 1 part by weight, preferably 0.01 to 0.5 part by weight, per 100 parts by weight of the aliphatic polyester to be produced.
Parts by weight are more preferred. Further, these phosphorus compounds may be added immediately before deglycolization or may be added before esterification.

The reaction conditions for the polycondensation are 200 to 280 under reduced pressure of 0.01 to 10 mmHg.
C. for 1 to 10 hours, preferably 0.1 to 5 mmH
More preferably, the reaction is performed at 220 to 260 ° C. for 1 to 5 hours under a reduced pressure of g.

The aliphatic polyester thus obtained has a relative viscosity of 2.00 or more , but is not sufficient in terms of molecular weight and melting point and needs to be further increased.
For that purpose, it is necessary to carry out solid phase polymerization of the aliphatic polyester obtained above at a temperature lower than the melting point under an inert gas atmosphere or under reduced pressure. For that purpose, it is necessary to first crystallize the aliphatic polyester synthesized by melt polymerization.

As a method of crystallizing the above aliphatic polyester, no special method is used.
Crystallization may be performed at room temperature, or various conventionally known methods for promoting crystallization, such as cooling with water, may be used. The relative viscosity of the aliphatic polyester at this time is
It is necessary to have 2.00 or more, and if it is less than 2.00 , not only is it easy to break during melt pelletization, but also because of brittleness, a large amount of powder is generated in the pre-crystallization stage of solid phase polymerization. Is not preferred. Although the upper limit is not particularly limited, it is usually preferably up to 3.0 from the viewpoint of torque during melt polymerization and payout time. Next, it is necessary to carry out solid-phase polymerization of the crystallized aliphatic polyester at a temperature lower than the melting point of each aliphatic polyester.
A low temperature is preferable, and it is particularly preferable to carry out the solid phase polymerization at a temperature lower by 5 to 30C. At this time, if the temperature is lower than the melting point by 1 ° C. or higher, the polymer partially melts, and fusion between the polymers occurs, which is not preferable. In addition, 5
A temperature of 0 ° C. or lower is not preferable because the polycondensation does not substantially proceed in a short time. The melting point at this time indicates an endothermic peak temperature of the melting point of the polymer when measured at a heating rate of 20 ° C./min with a thermal analyzer (DSC).

In the solid-phase polymerization of the present invention, the diffusion of the glycol component and the water component from the polymer surface is a rate-determining step. Therefore, the larger the surface area of the polymer, the faster the polymerization proceeds. Thus, the polymer is optimally in the form of a fine powder, but is preferably in the form of granules or powder from the viewpoint of handling and use of a conventional apparatus. In the case of a block (mass) shape, the surface area of the polymer becomes small, so that the rate of polycondensation decreases, which is not preferable. As the conditions for the solid-phase polymerization, various conventionally known methods used for solid-phase polymerization of polyethylene terephthalate or the like can be used. For example, a method of performing polycondensation under a reduced pressure at a predetermined temperature, a method of flowing an inert gas heated to a predetermined temperature to increase the degree of polymerization, and the like can be given.

The high-molecular-weight aliphatic polyester produced as described above is thermoplastic and has moldability, so that it can be applied to various uses. In addition to being used to impart biodegradability to fishing lines, fishing nets, and the like that require high strength, they can be used after being processed into films, fibers, nonwoven fabrics, sheets, and the like.

[0024]

The present invention will be specifically described below with reference to examples. In addition, each value was calculated | required as follows.

(1) Relative viscosity (ηrel) The molecular weight was measured by using an Ubbelohde viscometer to measure the viscosity of the polymer solution at a concentration of 0.5 g / deciliter. As a solvent, a phenol / tetrachloroethane (1: 1, weight ratio) mixed solvent was used, and 30
Measured in ° C.

(2) Melting Point The melting point was measured at a heating rate of 20 ° C./min using a thermal analyzer (DSC-7) manufactured by Perkin Elmer.

Example 1 A succinic acid (47.2 g, 0.4 mol) was placed in a three-necked flask equipped with a stirrer, a Wigrew fractionating tube, and a gas introducing tube.
54.1 g (0.6 mol) of 1,4-butanediol was added and immersed in a hot water bath. The temperature of the water bath was raised to 200 ° C., nitrogen was slowly flowed into the melt, and water and excess glycol generated at 200 ° C. for 2 hours were distilled off to obtain oligomers.

Then, tetrabutyl titanate 0.14
g (4.0 × 10 ⁻⁴ mol) and bis (2,4-dibutylphenyl) pentaerythritol diphosphate 0.1 g.
Add 0.5 g, keep the temperature at 220 ° C, and add 0.5 mmH
g under reduced pressure for 2 hours, 240 ° C., 0.5 mmH
By heating under reduced pressure of 20 g for 20 minutes, a viscous polymer liquid was obtained.

The relative viscosity (ηrel) of this polymer is 2.
The melting point was 116 ° C. After cooling the polymer to room temperature and completely crystallizing, 4 mm × 3 m
The resultant was cut into a size of mx 1 mm, and allowed to stand in a reduced-pressure drier. Solid-state polymerization was performed at a temperature of 105 ° C under a reduced pressure of 1 mmHg for 7 days.

The relative viscosity (η rel) of the polymer thus obtained was greatly increased to 4.87, and the melting point was 131.
° C.

Example 2 A polymer having a relative viscosity of 2.00 melt-polymerized in Example 1 was completely crystallized, cut into a size of 4 mm × 3 mm × 1 mm, and placed in a two-necked flask. The solid phase polymerization was carried out for 5 days while passing nitrogen gas heated to 105 ° C. through the other port and discharging formed glycol and the like from the other port.

The relative viscosity (η rel) of the polymer thus obtained was greatly increased to 3.80 and the melting point was 130
° C.

Example 3 47.2 g (0.4 mol) of succinic acid was placed in a three-necked flask equipped with a stirrer, a Wiggrew fractionating tube and a gas introducing tube.
32.3 g (0.52 mol) of ethylene glycol was added and immersed in a hot water bath. The temperature of the water bath was raised to 200 ° C., nitrogen was slowly flowed into the melt, and water and excess glycol generated at the temperature of 200 ° C. for 3 hours were distilled off to obtain oligomers.

Next, 0.05 g of polyphosphoric acid and 0.15 g of tetrabutoxygermanium (4.0 × 10 ^-4 mol)
Was added, and the mixture was heated at 220 ° C. for 1 hour under a reduced pressure of 0.5 mmHg, and further heated at 240 ° C. for 1 hour under a reduced pressure of 0.5 mmHg to obtain a viscous polymer liquid.

The relative viscosity (ηrel) of this polymer is 2.
The melting point was 103 ° C. After cooling the polymer to room temperature and completely crystallizing, 4 mm × 3 m
The resultant was cut into a size of mx 1 mm, allowed to stand in a vacuum drier, and subjected to solid-state polymerization at a temperature of 95 ° C under a reduced pressure of 1 mmHg for 5 days.

The relative viscosity (η rel) of the polymer thus obtained was greatly increased to 3.77, and the melting point was 114.
° C.

Example 4 In a three-necked flask equipped with a stirrer, a Wigrew fractionating tube, and a gas introducing tube, 40.0 g (0.4 mol) of succinic anhydride and 37.5 g (0,0) of 1,4-butanediol were added. .42 mol) and 6.5 g (0.10 mol) of ethylene glycol, and immersed in a hot water bath. The temperature of this hot water bath was raised to 200 ° C,
Nitrogen was slowly flowed into the melt, and the generated water and excess glycol were distilled off at 200 ° C. for 3 hours to obtain an oligomer.

Next, 0.025 g of polyphosphoric acid and 0.27 g (8.0 × 10 ⁻⁴ mol) of tributoxyantimony were added, and the temperature was maintained at 220 ° C. under a reduced pressure of 0.5 mmHg for 2 hours. At 240 ° C. under a reduced pressure of 0.5 mmHg for 1 hour to obtain a viscous polymer liquid.

The relative viscosity (ηrel) of this polymer is 2.
27 and the melting point was 101 ° C. After cooling the polymer to room temperature and completely crystallizing, 4 mm × 3 m
mx 1 mm, put into a two-necked flask, pass nitrogen gas heated to 95 ° C through one port, and discharge glycol and the like generated from the other port while solid-phase polymerization was performed. I went for seven days.

The relative viscosity (η rel) of the polymer thus obtained was greatly increased to 3.63, and the melting point was 112.
° C.

Example 5 In a three-necked flask equipped with a stirrer, a Wigrew fractionating tube and a gas introducing tube, 42.5 g (0.36 mol) of succinic acid, 5.8 g (0.04 mol) of adipic acid, 1,4-
54.1 g (0.6 mol) of butanediol was added and immersed in a hot water bath. The temperature of the water bath was raised to 200 ° C., nitrogen was slowly flowed into the melt, and water and excess glycol generated at the temperature of 200 ° C. for 3 hours were distilled off to obtain oligomers.

Next, 0.025 g of polyphosphoric acid and 0.17 g (6.0 × 10 ⁻⁴ mol) of titanium tetraisopropoxy were added, and the temperature was maintained at 220 ° C. to obtain 0.5 mmHg.
For 2 hours under reduced pressure of 240 ° C., 0.5 mmHg
The mixture was heated under reduced pressure for 1 hour to obtain a viscous polymer liquid.

The relative viscosity (ηrel) of this polymer is 2.
07 and the melting point was 109 ° C. After cooling the polymer to room temperature and completely crystallizing, 4 mm × 3 m
The resultant was cut into a size of mx 1 mm, and allowed to stand in a reduced-pressure drier. Solid-state polymerization was performed at a temperature of 100 ° C under a reduced pressure of 1 mmHg for 5 days.

The relative viscosity (ηrel) of the polymer thus obtained was greatly increased to 3.45, and the melting point was 121.
° C.

[0045]

According to the present invention, it is possible to increase the molecular weight and the melting point without impairing the original property of biodegradability. Therefore, it can be used for applications such as fishing lines, fibers and films that require high strength.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (1)

(57) [Claims] 1. A method of crystallizing an aliphatic polyester having a relative viscosity of 2.00 or more , followed by solid-phase polymerization at a temperature lower than its melting point in an inert gas atmosphere or under reduced pressure. A method for producing an aliphatic polyester having a molecular weight.