JPH09169835A - Biodegradable polyester and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable polyester which retains sufficient strengths during its use and, when disposed of, decomposes in the natural environment into carbon dioxide and water without loading the environment by producing a polyester comprising specific structural units and having a specified number average mol.wt. SOLUTION: A biodegradable polyester comprising structural units represented by the formula (wherein R is a 0-18C alkylene) and having a number average mol.wt. of 25,000 or higher is obtd. by subjecting a dicarboxylic acid component comprising an aliph. dicarboxylic acid (e.g. oxalic, succinic. or glutaric acid) or its anhydride or a dialkyl ester, if necessary together with an arom. dicarboxylic acid or a tri or higher carboxylic acid, and cyclohexanedimethanol (1,4-cyclohexanedimethanol being the most suitable) to esterification or transesterification and subjecting the resultant oligomer to polycondensation in the presence of at least one polymn. catalyst selected from among titanium-, antimony-, tin-, zinc-, and germanium-based catalysts in an amt. of 1×10<-4> -1×10<-2> mol per mol of the dicarboxylic acid component.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high molecular weight polyester which is decomposed by microorganisms in soil and can be used as a molded article, and a method for producing the same.

[0002]

2. Description of the Related Art Plastics used as moldings such as synthetic fibers, films and the like have the advantages that they are light and durable and that they can be supplied inexpensively and stably in large quantities. Has brought about richness and convenience to the modern society, which can be called a plastic civilization.
As the plastic used, synthetic resins such as aromatic polyester and nylon are mainly used, but since they retain their shape for a long period of time and are not decomposed, they have caused great environmental problems.

Therefore, in recent years, in response to global environmental problems, plastics that are decomposed in the natural environment have become
There are great expectations in the industry as environmentally compatible materials and new types of functional materials. Then, an aliphatic polyester produced by melt polycondensation of α, ω-aliphatic diol and α, ω-aliphatic dicarboxylic acid, for example, polyethylene succinate (PES), polyethylene adipate (PEA) and polybutylene succinate ( PBS) is a polymer that has been known for a long time, but it has been confirmed that it can be manufactured at low cost and that it is biodegraded by microorganisms in the soil burial test [International Biodeterioration Bulletin (Int .Biodetet
n.Bull.), Vol. 11, p. 127 (1975) and Polymer Science Technology (Polym.Sci.Techno)
l.), Vol. 3, p. 61 (1973)].

[0004]

However, since aliphatic polyesters typified by polyethylene succinate are excellent in biodegradation rate, the strength is reduced within a year, and after almost a few years, almost all of the strength is reduced. Disappears. Therefore, when it is used in an environment such as soil or water, the strength decreases before it is used, and use under such conditions is restricted.
It is not used in fields that require stability in the period until the purpose of use is fulfilled, and synthetic fibers such as aromatic polyester and nylon are still used in such fields at present. is there.

The present invention solves the above-mentioned problems,
Provided is a polyester which has sufficient strength within a period in which it should be used, and is decomposed into carbon dioxide and water in the environment after use and does not exert a load on the natural environment. The purpose is to do.

[0006]

Means for Solving the Problems The present invention achieves the above object. First, it comprises a structural unit represented by the following formula (I) and has a number average molecular weight of at least 25,
The gist is a biodegradable polyester characterized in that it is 000.

Embedded image (However, R represents an alkylene group having 0 to 18 carbon atoms.)

Secondly, according to the present invention, an aliphatic dicarboxylic acid and cyclohexanedimethanol are transesterified to form an oligomer, and then titanium is used as a polymerization catalyst.
One or more catalysts selected from antimony, tin, zinc and germanium catalysts are used for polycondensation using 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol of 1 mol of dicarboxylic acid. The gist is a method for producing a biodegradable polyester.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The polyester of the present invention is an alicyclic polyester composed of the structural unit represented by the formula (I), and has a number average molecular weight of at least 2 in terms of polymethylmethacrylate calculated by gel filtration chromatography (GPC).
It is 5,000 or more. When the number average molecular weight is less than 25,000, the moldability is poor and the strength of the molded product is low. This alicyclic polyester having a high molecular weight cannot be obtained by conventional methods at all, and it is sufficient to have a molecular weight of 25,000 or more without complicated treatment using a chain extender such as diisocyanates. It has a high molecular weight.

In order to obtain the alicyclic polyester of the present invention, various production methods can be used. The alicyclic polyester of the present invention includes, for example, an aliphatic dicarboxylic acid and cyclohexanedimethanol under nitrogen at 120 to 25.
After transesterification at a temperature of 0 ° C. to obtain an oligomer,
It can be obtained by adding a polymerization catalyst and polycondensing by a deglycol reaction.

The aliphatic dicarboxylic acid used in the present invention is a dicarboxylic acid having 2 to 20 carbon atoms such as oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, Dodecanedioic acid, eicosanedioic acid, and their acid anhydrides and dialkyl ester compounds such as succinic anhydride, glutaric anhydride, adipic acid anhydride, dimethyl succinate, and dimethyl adipate, and mixtures thereof can be mentioned. Of these, for example, succinic acid, adipic acid, and succinic anhydride are preferable because a polyester having a high melting point 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 acid anhydride, pyromellitic acid anhydride and trimesic acid can be used in combination.

The cyclohexanedimethanol used in the present invention is most preferably 1,4-cyclohexanedimethanol, and in order to produce a polyester having a high melting point, a higher trans-form content is preferable. Also,
Ethylene glycol, 1,4 as long as the physical properties are not impaired
-Butanediol, neopentyl glycol, diethylene glycol, propylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. may be used alone or in combination of two or more. Furthermore, polyhydric alcohols such as glycerin and pentaerythritol can be used together.

As a catalyst for synthesizing an oligomer by transesterifying the aliphatic dicarboxylic acid with the cyclohexanedimethanol, titanium, tin, and zinc catalysts may be used. The metal of these metal catalysts is in the form of its organometallic compound, organic acid salt, metal complex, metal alkoxide, metal oxide, metal hydroxide, carbonate, phosphate, sulfate, nitrate, chloride and the like. Of these, acetate, metal acetylacetone complex, metal alkoxide and metal oxide are preferred. Specific examples of particularly preferable catalysts include titanium (IV) oxyacetylacetonate, stannous acetate, di-n-butyltin (IV) oxide, tetra-n-butyl titanate,
Zinc acetate, etc., and these catalysts may be used alone or in combination of two or more. At that time, the amount of the catalyst used is 1 × 10 ⁻⁴ to 1 with respect to 1 mol of the aliphatic dicarboxylic acid.
It is preferably ^{x10 -2} mol, more preferably 2 x 10 ^-4 to 2 x 10 ^-3 mol.

As the polymerization catalyst for deglycolization and polycondensation, titanium, antimony, tin, zinc or germanium catalysts are used.
The metal alkoxide, metal oxide, metal complex, metal hydroxide, carbonate, sulfate, nitrate, chloride and the like are used. Specific examples of particularly preferable catalysts include tetra-n-butyl titanate, tetraisopropyl titanate, titanium oxyacetylacetonate, dibutoxy diacetoacetoxy titanium, tributoxy antimony,
Antimony trioxide, antimony acetate, tetra-n-butoxy germanium, germanium (IV) oxide, etc.,
These catalysts may be used alone or in combination of two or more. The amount of catalyst used in this case is 1 × 10 ⁻⁴ to 1 × 10 ⁻² mol per 1 mol of aliphatic dicarboxylic acid, and 2 × 10 ^{−4 to} 5 × 10 ⁻³ mol. It is more preferable to use the above range. These catalysts may be present at the time of polycondensation, and may be added immediately before polycondensation or before esterification.

A phosphorus compound may be added during the polycondensation reaction. Typical phosphorous compounds added here include phosphoric acid, phosphoric anhydride, polyphosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, hypophosphorous acid, tripolyphosphoric acid and their metals. Examples thereof include salts, ammonium salts, chlorides and esterified products. In addition, bis (2,4-
Dibutylphenyl) pentaerythritol diphosphate (Ultrachemical 626 manufactured by GE Chemicals)
A spirophosphorus compound typified by and the like can also be used. Particularly preferred are phosphoric acid, polyphosphoric acid, metaphosphoric acid, bis (2,4-dibutylphenyl) pentaerythritol diphosphate, phosphorous acid and the like. 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 1 × 10 6 relative to 1 mol of the aliphatic dicarboxylic acid.
^-6 to 1 × 10 ^-2 mol is preferable, and 1 × 10 ^-4 to 1 × 10 is preferable.
^-2 mol is more preferred. These phosphorus compounds may be present at the time of polycondensation, and may be added immediately before polycondensation or before esterification.

In the present invention, the molar ratio of the aliphatic dicarboxylic acid and cyclohexanedimethanol to be used when synthesizing the oligomer by transesterification is preferably 1: 1 to 1: 3, and is preferably 1: 1. 1.05-
Optimal is 1: 2.

Further, the reaction conditions for synthesizing the oligomer by transesterification are 120 to 250 ° C.
A range of 10 hours is preferable, and 2 to 5 at 150 to 240 ° C.
More preferably, it is carried out under atmospheric pressure and a nitrogen stream within a range of time.

Regarding polycondensation, 0.01 to 10
It is preferable to carry out under reduced pressure of mmHg at 190 to 350 ° C. for 1 to 15 hours, under reduced pressure of 0.1 to 1 mmHg, 220
It is more preferable to carry out at 290 ° C. for 2 to 10 hours. Further, if necessary, the molecular weight can be increased by solid phase polymerization after completion of the melt polymerization.

Since the polyester of the present invention has a high melting point and is thermoplastic and has excellent moldability, it can be applied to various uses. For example,
As a biodegradable polymer, it can be processed into a film, a fiber or a sheet and used as various bottles, shopping bags, packaging materials, synthetic threads, fishing lines, fishing nets, non-woven fabrics, agricultural mulch films, and the like.

The microbial selectivity for which the polyester of the present invention can be used as a biodegradable polymer is not particularly clear, but it is immersed in a normal soil burial test or immersed in an activated sludge aeration tank used in a sewage treatment plant. Depending on the method, biodegradability can be easily confirmed. That is, it can be confirmed by immersing the molded product in soil for a predetermined period of time and then measuring the molecular weight of this molded product or by comparing its surface morphology with that before burial.

[0020]

The present invention will be specifically described below with reference to examples. In addition, each measured value in this example was obtained as follows. (1) Number average molecular weight (Mn) calculated from GPC in terms of polymethylmethacrylate Using a GPC measuring device 8010 manufactured by Tosoh Corporation, TSKge
l 7.8mmφ × 30cm with two GMH _HR- H connected
Measured at 40 ° C. using a long column and using HFIP (hexafluoroisopropanol) / 10 mM sodium trifluoroacetate as eluent. In addition, polymethylmethacrylate was used as a standard.

(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. (3) Biodegradability After the molded article was embedded in soil for a predetermined period, the surface morphology of this molded article was judged by visual observation or optical microscope observation. A: I can't find any fragments. B: The shape collapsed and fell apart. C: Decomposition is clearly observed. D: Small holes are seen. E: No change.

Example 1 35.4 g (0.30 mol) of succinic acid and 47.6 g of 1,4-cyclohexanedimethanol were placed in a three-necked flask equipped with a stirrer, a Wigley fractionation pipe and a gas introduction pipe.
(0.33 mol) was added and immersed in an oil bath. The oil bath is heated to 240 ° C. and nitrogen is slowly flushed into the melt and 2
The water and the excess cyclohexanedimethanol which were formed over 2 hours at a temperature of 40 ° C. were distilled off to obtain an oligomer.

[0023] Then, tetra -n- butyl titanate 0.10g (3.0 × 10 ^-4 mol), tetra -n- butoxy germanium 0.11g (3.0 × 10 ^-4 mol) and phosphoric acid 0.02g And the temperature is 280 over 1 hour.
At the same time, the pressure is reduced to 0.5 mmHg and the temperature is raised to 2.
Polymer was obtained by polycondensation at 80 ° C. for 7 hours.

The melting point of this polymer is 120 ° C. and G
The number average molecular weight (Mn) in terms of polymethylmethacrylate calculated from PC was 38,000. A film with a thickness of about 100 μm is formed from the obtained polyester by heat pressing, and the film is embedded in soil of about 5 cm from the surface layer and biodegraded after 3 months, 6 months, 1 year and 2 years. It was evaluated by observing the degree. Table 1 shows the results.
Shown in

Example 2 35.4 g (0.30 mol) of succinic acid and 64.9 g of 1,4-cyclohexanedimethanol were placed in a three-necked flask equipped with a stirrer, a Wigley fractionating tube and a gas introducing tube.
(0.45 mol), zinc acetate (dihydrate) 0.03 g
The (1.5 × 10- ⁴ mol) was placed, was immersed in an oil bath. The temperature of this oil bath was raised to 240 ° C., nitrogen was slowly flowed into the melt, and the water and excess cyclohexanedimethanol which were produced at 240 ° C. for 3 hours were distilled off to obtain an oligomer.

Then, tributoxy antimony 0.10
g (3.0 × 10 ^-4 mol), tetra-n-butoxygermanium 0.11 g (3.0 × 10 ^-4 mol) and polyphosphoric acid 0.01 g were added, and the temperature was raised to 280 ° C. over 1 hour. At the same time, raise the pressure to 0.5 mmHg and reduce the pressure to 280
Polymer was obtained by polycondensation at a temperature of ° C for 8 hours.

This polymer was extruded into water through a small hole at the bottom of the flask, cooled and cut to prepare a pellet of about 4 mm. This pellet is 110 ℃, 1mmHg
Solid state polymerization was carried out for 5 days under reduced pressure.

The melting point of this polymer is 132 ° C.
The number average molecular weight (Mn) in terms of polymethylmethacrylate calculated from PC was 56,000.

Comparative Example 1 (Synthesis of polyethylene succinate) 47.2 g of succinic acid and 49.7 g of ethylene glycol were placed in a three-necked flask equipped with a stirrer, a Wigley fractionation pipe and a gas introduction pipe, and placed in an oil bath. Soaked 20 this oil bath
The temperature was raised to 0 ° C., nitrogen was slowly poured into the melt, and 200
The esterification was carried out at a temperature of ° C for 3 hours.

Then, polyphosphoric acid (0.05 g) and germanium oxide (0.0084 g) were added, and the temperature was raised to 280 ° C. over 1 hour and 30 minutes, and at the same time, a reduced pressure of 0.5 mmHg was applied, and the temperature was set at 280 ° C. for 1 hour. Condensation gave a polymer.

The melting point of this polymer is 104 ° C. and G
The number average molecular weight (Mn) in terms of polymethylmethacrylate calculated from PC was 44,000.

The polyester obtained was evaluated by observing the degree of biodegradation in the same manner as in Example 1. Table 1 shows the results.

[0033]

[Table 1]

[0034]

INDUSTRIAL APPLICABILITY The polyester of the present invention has sufficient strength within a certain period of time to be used, and is decomposed into carbon dioxide and water after use. Further, according to the production method of the present invention, such polyester can be easily obtained.

Claims (2)

[Claims] 1. A biodegradable polyester comprising a structural unit represented by the following formula (I) and having a number average molecular weight of at least 25,000. Embedded image (However, R represents an alkylene group having 0 to 18 carbon atoms.) 2. An aliphatic dicarboxylic acid and cyclohexanedimethanol are transesterified to form an oligomer, and then, as a polymerization catalyst, at least one catalyst selected from titanium, antimony, tin, zinc and germanium catalysts is used. 1 × 10 ⁻⁴ to 1 × 10 1 mol of dicarboxylic acid
^-A method for producing a biodegradable polyester, which comprises polycondensing using ² mol.