JPH0834843A - Production of high-molecular aliphatic polyester - Google Patents

Abstract

PURPOSE:To obtain a high-molecular high-melting aliph. polyester which is moldable, e.g. into fishing lines by crystallizing an aliph. polyester having a specified relative viscosity and then subjecting it to solid-phase polymn. under specified conditions. CONSTITUTION:An aliph. polyester having a relative viscosity of 1.5 or higher is crystallized and then subjected to solid-phase polymn. at a temp. lower than its m.p. in an inert gas atmosphere or under a reduced pressure, providing the objective polyester. The polyester having a relative viscosity of 1.5 or higher can be produced by reacting a diol with a dicarboxylic acid and subjecting the resulting oligomer to glycol removal reaction in the presence of a catalyst. The mol.wt. and m.p. are thus increased without detriment to the inherent biodegradability. The polyester with an increased mol.wt. can be applied to fishing lines and to fibers, films, etc., requiring high strengths.

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 article, and more specifically to a method for producing a high molecular weight aliphatic polyester by solid phase polymerization. The present invention relates to a method for producing an aliphatic polyester.

[0002]

2. Description of the Related Art Synthetic fibers, films, and other plastics used as moldings have the advantages of being light and durable, and of being inexpensive and capable of being stably supplied in large quantities.
It brings richness and convenience to our lives, and has built a modern society that can be called a plastic civilization. However, in recent years, there has been a demand for the development of polymer materials that decompose in the natural environment in response to environmental problems on a global scale. Among them, plastics that are decomposed by microorganisms are especially environmentally friendly materials. There is great expectation as a new type of functional material.

It is well known that aliphatic polyesters are biodegradable, and among them, poly-3-hydroxybutyric acid (PH) produced by microorganisms is particularly well known.
B) and synthetic polymer poly-ε-caprolactone (P
CL) and polyglycolic acid (PGA) are typical ones.

[0004] PHB-based biopolyesters are industrially produced because they have excellent environmental compatibility and physical properties. However, they are poor in productivity and are costly in view of polyethylene. There is a limit to the possible substitution as a plastic for use [see Textile and Industry, Vol. 47, p. 532 (1991)]. For PCL, fiber,
A high degree of polymerization that can be formed into a film has been obtained, but it has a melting point of 65 ° C or less and poor heat resistance, making it unsuitable for a wide range of applications [Polymer Science Technology (Polym. Sci. Technol.), 3 volumes, Page 61 (1973)
reference〕. Furthermore, PGA and glycolide-lactide (9: 1) copolymers, which have been put into practical use as biocompatible sutures, are metabolically absorbed in vivo after undergoing abiotic hydrolysis, It is not suitable for use as a general-purpose plastic because it is expensive and has poor water resistance.

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 well known polymers at low cost. It has been confirmed that it can be produced and that it is biodegraded by microorganisms even in a soil burial test [Int. Biodetetn. Bull.], Vol. 11, 127.
P. (1975) and Polymer Science Technology (Polym. Sci. Technol.), Vol. 3, p. 61 (197).
3)], but these polymers have poor thermal stability,
Since the decomposition reaction occurs at the time of polycondensation, it is usually 2,000
Only those having a molecular weight of about 6,000 were obtained, which was not sufficient for processing into fibers or films.

[0006]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention As a result of previous investigations to increase the molecular weight of such aliphatic polyesters, the present inventors have found that titanium, antimony and germanium compounds are used as catalysts 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 a fiber, and it has been already proposed, for example, in Japanese Patent Application Nos. 5-98851 and 5-297330. The aliphatic polyester produced in this manner can be molded and processed into various films by itself as a film or fiber, but when considering applications such as fishing lines that are highly demanded 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. 5-98851 and Japanese Patent Application No. 5-29733.
Although the method presented in No. 0 can be used for melt polymerization to increase the molecular weight, a very large rotational power was required during the production.

The present invention does not impair the original property of biodegradability and uses no special device,
Moreover, it is an object of the present invention to provide a method for producing an aliphatic polyester having a high molecular weight and a high melting point that can be molded as a fishing line or the like.

[0008]

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

That is, according to the present invention, after the aliphatic polyester having a relative viscosity of 1.5 or more is crystallized, solid phase polymerization is carried out at a temperature lower than its melting point under an inert gas atmosphere or under reduced pressure. The gist is a method for producing a characteristic high molecular weight aliphatic polyester.

The present invention will be described in detail below. In the present invention, it is first necessary to produce an aliphatic polyester having a relative viscosity of 1.5 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 is
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, cyclohexanedimethanol and the like, and mixtures thereof. Among these, those having an even number of carbon atoms, such as ethylene glycol, 1,4-butanediol, 1,6-
Use of hexanediol or the like is preferable in that an aliphatic polyester having a high melting point can be obtained, and use of ethylene glycol, 1,4-butanediol and succinic acid in combination produces an aliphatic polyester having a melting point of 100 ° C. or higher. It is the best because it can be obtained. Furthermore, polyhydric alcohols such as glycerin, trimethylolpropane and pentaerythritol can be used together.

Examples of the dicarboxylic acid used at this time include oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid and their acid anhydrides. And alkyl ester compounds such as succinic anhydride, glutaric anhydride, dimethyl succinic acid, dimethyl adipic acid and the like and mixtures thereof. Of these, 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 It is optimal to use in combination with -butanediol or the like in that an aliphatic polyester having a melting point of 100 ° C or higher can be obtained. In addition, an aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid can be used in combination as long as biodegradability is not impaired. Further, an oxycarboxylic acid such as malic acid, citric acid and tartaric acid, and a polyvalent carboxylic acid such as trimellitic anhydride, pyromellitic anhydride and trimesic acid can be used in combination.

The charging ratio of these dicarboxylic acid and diol is preferably 1: 1 to 1: 2.5, and more preferably 1: 1.01 to 1: 2, in terms of molar ratio. Optimally, it is 1: 1.05 to 1: 1.8.

The reaction conditions for synthesizing the oligomer are preferably 120 to 250 ° C. and 1 to 10 hours, 150 to 220 ° C. and 2 to 5 hours, under atmospheric pressure and in an inert gas atmosphere. It is more preferable to carry out under a nitrogen gas stream.

Next, a metal compound may be used as a catalyst used for polycondensing the oligomer, and examples of the metal compound include titanium, germanium, antimony,
Magnesium, calcium, zinc, iron, zirconium,
Vanadium, lithium, cobalt, manganese, etc. are mentioned. These metal compounds are used in the form of their 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.
-Butoxy germanium, tetraethoxy germanium, tetrabutyl germanium, germanium oxide (I
V), tributoxyantimony, triethoxyantimony, antimony trioxide, antimony acetate, zinc acetate, calcium acetylacetonate, magnesium acetylacetonate, zinc acetylacetonate, tetrabutoxyzirconium, etc., and these catalysts may be used alone or Two
More than one species may be used.

The amount of catalyst used at that time is
Per 100 parts by weight of the produced aliphatic polyester, 0.
The amount is preferably 01 to 5 parts by weight, more preferably 0.05 to 2 parts by weight. If the amount of the catalyst is less than 0.01 parts by weight, the effect as a catalyst becomes weak, and it is difficult to obtain a polymer having a target molecular weight. Even if it is used in excess of 5 parts by weight, the effect does not change significantly. On the contrary, the polymer produced is colored, which is not preferable. These catalysts need only be present at the time of polycondensation, and may be added immediately before deglycolization or may be added before esterification.

Further, when deglycolized and polymerized, a phosphorus compound can be added as a coloring preventing agent. 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 diester. Spirophosphorus compounds and the like represented by phosphates and their metal salts, ammonium salts, chlorides, bromides, sulfides, esterified compounds and the like can be mentioned, but particularly preferably, phosphoric acid, polyphosphoric acid, metaphosphoric acid, Examples thereof include bis (2,4-dibutylphenyl) pentaerythritol diphosphate. These phosphorus compounds may be used alone or in combination of two or more.

The amount of the phosphorus compound used at that time is preferably 0.001 to 1 part by weight, and 0.01 to 0.5 part by weight, per 100 parts by weight of the aliphatic polyester produced.
More preferably parts by weight. 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 a reduced pressure of 0.01 to 10 mmHg.
It is preferably carried out at 1 ° C for 1 to 10 hours, and 0.1 to 5 mmH
More preferably, it is carried out under a reduced pressure of g at 220 to 260 ° C. for 1 to 5 hours.

The aliphatic polyester thus obtained has a relative viscosity of 1.5 or more, but it is not sufficient in terms of molecular weight and melting point and needs to be further increased. For that purpose, it is necessary to solid-phase polymerize 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 first necessary to crystallize the above-mentioned aliphatic polyester synthesized by melt polymerization.

No specific method is used as a method for crystallizing the above aliphatic polyester,
Crystallization may be performed at room temperature, or various conventionally known methods for promoting crystallization such as water cooling may be used. At this time, the relative viscosity of the aliphatic polyester needs to be 1.5 or more. If it is less than 1.5, not only is it easily broken during melt pelletizing, but also it is brittle, so that the pre-crystallization step of solid phase polymerization is performed. However, a large amount of powder is generated, which is not preferable. The upper limit is not particularly limited, but is usually 3.0 from the viewpoint of torque during melt polymerization and payout time.
Is preferred. Next, it is necessary to solid-phase polymerize the crystallized aliphatic polyester at a temperature lower than the melting point of each aliphatic polyester, preferably 1 to 50 ° C lower temperature, particularly 5 to 30 ° C lower temperature. Solid phase polymerization is preferred. At this time, at a temperature of 1 ° C. or lower lower than the melting point, some of the polymers are melted and fusion of the polymers occurs, which is not preferable. Further, at a temperature lower than the melting point by 50 ° C. or less, polycondensation does not proceed in a substantially short time, which is not preferable. The melting point at this time is
It refers to the endothermic peak temperature of the melting point of the polymer as measured by a thermal analysis device (DSC) at a heating rate of 20 ° C./min.

In the solid phase polymerization in the present invention, the diffusion of the glycol component and the water component from the surface of the polymer is a rate-determining step. Therefore, the larger the surface area of the polymer, the faster the polymerization. Therefore, the shape of the polymer is most preferably in the form of fine powder, but it is preferable that the shape of the polymer is granular or powder from the viewpoint of handling and using a conventional device. The block (lump) shape is not preferable because the surface area of the polymer becomes small and the polycondensation rate becomes slow. Further, as the conditions for the solid phase polymerization, various conventionally known methods used when solid phase polymerizing polyethylene terephthalate or the like can be used. For example, a method of polycondensation under 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 mentioned.

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

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples. Each value was obtained as follows.

(1) Relative Viscosity (ηrel) Using a Ubbelohde viscometer, the viscosity of the polymer solution at a concentration of 0.5 g / deciliter was measured and used as a measure of the molecular weight. As the solvent, a phenol / tetrachloroethane (1: 1, weight ratio) mixed solvent was used, and
It was measured at ° C.

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

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

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

The relative viscosity (ηrel) of this polymer is 2.
00 and the melting point was 116 ° C. After cooling this polymer to room temperature and completely crystallizing, 4 mm x 3 m
It was cut into a size of m × 1 mm, left standing in a vacuum dryer, and subjected to solid phase polymerization at a temperature of 105 ° C. under a reduced pressure of 1 mmHg for 7 days.

The polymer thus obtained has a relative viscosity (ηrel) greatly increased to 4.87 and a melting point of 131.
It rose to ℃.

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

The polymer thus obtained has a greatly increased relative viscosity (ηrel) of 3.80 and a melting point of 130.
It rose to ℃.

Example 3 47.2 g (0.4 mol) of succinic acid was placed in a three-necked flask equipped with a stirrer, a Wiggle 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 this hot water bath was raised to 200 ° C., nitrogen was slowly poured into the melt, and the water and excess glycol produced at a temperature of 200 ° C. for 3 hours were distilled off to obtain an oligomer.

Then, 0.05 g of polyphosphoric acid and 0.15 g of tetrabutoxy germanium (4.0 × 10 ^-4 mol)
Was added, and the temperature was maintained at 220 ° C., and the mixture was heated at a reduced pressure of 0.5 mmHg for 1 hour, and further at 240 ° C. and 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.
The melting point was 12 and the melting point was 103 ° C. After cooling this polymer to room temperature and completely crystallizing, 4 mm x 3 m
It was cut into a size of m × 1 mm and left standing in a vacuum dryer, and solid phase polymerization was carried out at a temperature of 95 ° C. under a reduced pressure of 1 mmHg for 5 days.

The polymer thus obtained has a greatly increased relative viscosity (ηrel) of 3.77 and a melting point of 114.
It rose to ℃.

Example 4 40.0 g (0.4 mol) of succinic anhydride and 37.5 g (0) of 1,4-butanediol were placed in a three-necked flask equipped with a stirrer, a Wigley fractionating tube and a gas introducing tube. 0.42 mol) and 6.5 g (0.10 mol) of ethylene glycol were added and immersed in a hot water bath. Raise the temperature of this water bath to 200 ° C,
Nitrogen was slowly flowed into the melt, and the water and excess glycol produced over a period of 3 hours at a temperature of 200 ° C. were distilled off to obtain an oligomer.

Then, 0.025 g of polyphosphoric acid and 0.27 g of tributoxyantimony (8.0 × 10 ⁻⁴ mol) were added, the temperature was kept at 220 ° C., and further reduced pressure of 0.5 mmHg was applied for 2 hours, and further. A viscous polymer liquid was obtained by heating at 240 ° C. under a reduced pressure of 0.5 mmHg for 1 hour.

The relative viscosity (ηrel) of this polymer is 2.
27 and the melting point was 101 ° C. After cooling this polymer to room temperature and completely crystallizing, 4 mm x 3 m
Cut into a size of mx 1 mm, put in a two-necked flask, pass nitrogen gas heated to 95 ° C through one port, and discharge glycols produced from the other port while solid phase polymerization is performed. I went there for 7 days.

The polymer thus obtained has a relative viscosity (ηrel) greatly increased to 3.63 and a melting point of 112.
It rose to ℃.

Example 5 In a three-necked flask equipped with a stirrer, a Wiggle fractionating tube and a gas introduction 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 this hot water bath was raised to 200 ° C., nitrogen was slowly poured into the melt, and the water and excess glycol produced at a temperature of 200 ° C. for 3 hours were distilled off to obtain an oligomer.

Then, 0.025 g of polyphosphoric acid and 0.17 g (6.0 × 10 ⁻⁴ mol) of tetraisopropoxy titanium were added, and the temperature was maintained at 220 ° C. to give 0.5 mmHg.
Under reduced pressure of 2 hours, further 240 ℃, 0.5mmHg
A viscous polymer liquid was obtained by heating under reduced pressure for 1 hour.

The relative viscosity (ηrel) of this polymer is 2.
And the melting point was 109 ° C. After cooling this polymer to room temperature and completely crystallizing, 4 mm x 3 m
It was cut into a size of m × 1 mm and left standing in a vacuum dryer, and solid phase polymerization was carried out at a temperature of 100 ° C. under a reduced pressure of 1 mmHg for 5 days.

The polymer thus obtained has a relative viscosity (ηrel) greatly increased to 3.45 and a melting point of 121.
It rose to ℃.

[0045]

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

Claims (1)

[Claims] 1. A high-characterizing method, which comprises crystallizing an aliphatic polyester having a relative viscosity of 1.5 or more and then performing solid-phase polymerization at a temperature lower than its melting point under an inert gas atmosphere or under reduced pressure. Method for producing a molecular weight aliphatic polyester.