JPH06336519A - Poly(ethylene succinate) and its production - Google Patents

Abstract

PURPOSE:To obtain the subject compound which has excellent biodegradability and is usable as various moldings by polymerizing specific monomers in a specific manner to a given number-average mol.wt. CONSTITUTION:This compound comprises structural units represented by the formula and has a number-average mol.wt., in terms of PS. as measured by gel permeation chromatography of 25,000 or higher. The compound is obtained preferably by reacting succinic acid with ethylene glycol in the presence of at least one member selected from Ti, Sn, Mn, and Co catalysts (e.g. manganese acetate tetrahydrate) to obtain an oligomer and condensation-polymerizing the oligomer in the presence of at least either a Ti catalyst or a Ge catalyst (e.g. tetra-n-butyl titanate).

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Plastics, which are used as synthetic fibers, films, and other molded products, have the advantages of being light and durable, and of being inexpensive and capable of being stably supplied in large quantities. It has brought convenience and built a modern society that can be called a plastic civilization. However, in recent years, in response to environmental problems on a global scale, there has been a demand for the development of polymer materials that decompose in the natural environment. Among them, plastics that are decomposed by microorganisms are especially environmentally friendly. There are great expectations in the industry as materials and new types of functional materials.

It is well known that aliphatic polyesters are biodegradable, and among them, poly-3-hydroxybutyric acid ester (PHB) produced by microorganisms and poly-ε which is a synthetic polymer are known. Caprolactone (PCL) and polyglycolic acid (PGA) are the typical ones.

[0004] PHB-based biopolyesters are industrially produced because they have excellent environmental compatibility and physical properties, but they are poor in productivity and are generally used from the viewpoint of cost as represented by polyethylene. There are limits to what can be substituted as plastics (Fiber and Industry, 47, 532)
Page (1991)). Regarding PCL, although a high degree of polymerization that can be formed into fibers and films has been obtained, it has a melting point of 65 ° C or less and poor heat resistance, and cannot be used for a wide range of applications [Polymer Science Technology (Polym. . Technol., Volume 3, p. 61 (19
73)]. Furthermore, PGA and glycolide-lactide (9: 1) copolymers, which have been put into practical use as bioabsorbable sutures, are metabolized and absorbed in vivo after undergoing abiotic hydrolysis, but are expensive. In addition to being poor in water resistance, it is not suitable for use as general-purpose plastics.

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 and are inexpensive. It has been confirmed that it can be produced and that it is biodegraded by microorganisms even when it is buried in the soil [Int. Biodetetn. Bull., Vol. 11, p. 127 (1975) and Polymer Science Technology. (See Polym. Sci. Technol.), Vol. 3, p. 61 (1973)], these polymers have poor thermal stability.
Decomposition reaction occurs at the time of polycondensation, so it is usually 2,000-
Molecular weight of about 6,000 (concentration of 0.5 using chloroform)
g / deciliter, reduced specific viscosity ηsp measured at 30 ° C.
/ C was less than 0.3), which was not sufficient for processing into fiber or film. Among them, especially polyethylene succinate had a melting point of 100 ° C. or higher, and although its excellent biodegradability was reported, it had poor thermal stability at the time of polymerization. However, it is impossible to obtain a resin having a molecular weight sufficient for molding, and for example, the above-mentioned literature (Int. Biodetetn. Bull.,
Vol. 11, p. 127 (1975)) makes commercially available low molecular weight polyethylene succinate capable of forming a film by heating under reduced pressure, but still the molecular weight is at most about 20,000. It was not possible to express sufficient performance.

Therefore, in order to increase the molecular weight of these aliphatic polyesters, it has been reported to treat them with diisocyanates such as hexamethylene diisocyanate and toluene diisocyanate [Polymer Journal
(Polymer J.), Vol. 2, p. 387 (1971) and Japanese Patent Application Laid-Open No. 4-189822], these methods have the effect of increasing the molecular weight, but the reaction step is usually performed in two steps. And the process becomes complicated,
The obtained polyester has a problem that its biodegradability is somewhat inferior because its crystallinity and melting point are slightly lowered and urethane bonds are included in the molecule.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a high molecular weight polyethylene succinate and a method for producing the same, which does not impair the original property of biodegradability and has an increased molecular weight such that it can be used as a molded article. It is intended to be provided.

[0008]

As a result of various investigations to solve the above problems, the present inventors have found that polyethylene succinate produced from succinic acid and ethylene glycol using a specific catalyst solves the above problems. Based on this finding, the inventors arrived at the present invention.

That is, first, the present invention comprises a constitutional unit represented by the following formula (I), and has a polystyrene-reduced number average molecular weight of at least 25,000 as determined by gel filtration chromatography (GPC). The main point is polyethylene succinate.

[0010]

[Chemical 2]

Secondly, succinic acid and ethylene glycol are reacted in the presence of at least one catalyst selected from titanium, tin, manganese and cobalt type catalysts to obtain an oligomer, which is then obtained. The gist is a method for producing polyethylene succinate, which comprises polycondensing an oligomer in the presence of one or two catalysts selected from titanium and germanium catalysts.

The present invention will be described in detail below. The polyethylene succinate of the present invention comprises a constitutional unit represented by the formula (I), and has a polystyrene-reduced number average molecular weight of at least 25,000 as determined by gel filtration chromatography (GPC). When the number average molecular weight is less than 25,000, the moldability and the strength of the molded product will be low. The polyethylene succinate of the present invention has a sufficient molecular weight without being treated with a chain extender such as diisocyanates. This high molecular weight polyethylene succinate cannot be obtained by conventional methods at all, and this is the feature of the present invention.

To obtain the polyethylene succinate of the present invention, various known production methods can be used except that a specific catalyst is used. For example, J. Am. Chem. S
oc. 52, p. 718 (1930), transesterification of succinic acid and ethylene glycol in the presence of a specific catalyst under nitrogen at a temperature of 120 to 250 ° C. to give an oligomer. After obtaining the poly (ethylene succinate), a polymerization catalyst is added and polycondensation is performed by deglycolization to obtain the desired polyethylene succinate.

In the present invention, titanium, tin, manganese and cobalt type catalysts are used as catalysts for transesterification to synthesize oligomers. These metals are used as their organometallic compounds, organic acid salts, metal complexes, metal alkoxides, metal oxides, metal hydroxides, carbonates, phosphates, sulfates, nitrates, chlorides, etc.
Among them, it is preferable to use them in the form of acetate, acetylacetone metal complex and metal oxide. Specific examples of particularly preferable catalysts include titanium (IV) oxyacetylacetonate, stannous acetate, di-n-butyltin (IV) oxide, manganese acetate (II) tetrahydrate, manganese (I
I) acetylacetonate, cobalt (II) acetate tetrahydrate, cobalt (II) acetylacetonate, etc.,
You may use these catalysts 1 type (s) or 2 or more types. Further, in that case, the amount of the catalyst used is preferably 1 × 10 ^{−4 to} 5 × 10 ⁻³ mol per 1 mol of succinic acid, and 2 ×
It is more preferably used in the range of 10 ^{−4 to} 2 × 10 ⁻³ mol.

As the polymerization catalyst for deglycolization and polymerization, titanium or germanium catalysts are used. These are metal alkoxides, metal oxides, metal complexes, metal hydroxides, carbonates, Used in the form of sulfates, nitrates, chlorides, etc. Specific examples of particularly preferable catalysts include tetra-n-butyl titanate,
Tetraisopropyl titanate, tetra-n-butoxy germanium, germanium (IV) oxide, etc. may be used, and these catalysts may be used alone or in combination. The amount of catalyst used in this case is 1 mol per 1 mol of succinic acid.
X10 ^{-4 to} 5 x 10 ^-3 mol is preferable, and 2 x 10 ^-4 to 2
It is more preferable to use it in a range of × 10 ^-3 mol.

In the present invention, the molar ratio of succinic acid and ethylene glycol used when synthesizing an oligomer by transesterification is preferably 1: 1 to 1: 2.2, preferably 1: 1. It is more preferably 0.05 to 1: 1.6, and most preferably 1: 1 to 1: 1.5.

Further, the reaction conditions for transesterification to produce an oligomer are 120 to 250 ° C. and 1 to 1
The heating time is preferably 0 hour, more preferably 150 to 220 ° C. for 2 to 5 hours, and more preferably under atmospheric pressure and nitrogen stream.

For polycondensation, 0.01 to 10 mm
It is preferable to carry out under reduced pressure of Hg at 150 to 250 ° C. for 1 to 10 hours, under reduced pressure of 0.1 to 1 mmHg, 190 to 2
More preferably, it is carried out at 40 ° C. for 2 to 7 hours.

Since the polyethylene succinate of the present invention has a melting point of 100 ° C. or higher and is thermoplastic and has 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. Besides this, the polyethylene succinate of the present invention can be used as a base resin for hot melt adhesives, paints, and urethane elastomers.

When the polyethylene succinate of the present invention is used as a biodegradable polymer, the microbial selectivity is not particularly clear, but it is an activated sludge aeration tank used in ordinary soil burial tests and sewage treatment plants. The biodegradability can be easily confirmed by the method of immersing in. 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.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples. Each value was obtained as follows. (1) polystyrene-reduced number average molecular weight (Mn) obtained from GPC Using a GPC measuring device manufactured by Waters,
Waters ultrastyragel having an average pore diameter of 10 ³ and 10 ⁴ Å was used at a temperature of 35 ° C. by using chloroform as an eluent, using a column having a total length of 7.8 mmφ × 30 cm, in which two pipes were connected in total. In addition, polystyrene was used as a standard. (2) Reduced specific viscosity (ηsp / c) The polymer solution viscosity at a concentration of 0.5 g / deciliter was measured using an Ubbelobe viscometer and used as a measure of the molecular weight. Chloroform was used as the solvent,
It was measured at 30 ° C. (3) Melting point Using a minute melting point measuring device MP-S3 manufactured by Yanaco Co., Ltd., the melting point was measured at a temperature rising rate of 1 to 2 ° C./min. (4) Appearance It was judged by visual observation or optical microscope observation. A: Severe damage B: Significant damage C: Some damage
D: Invariant (5) Film strength A sample of a predetermined size was prepared in accordance with JIS K-7327 and measured using an Intesco precision universal testing machine 2020 type.

Example 1 First, 47.2 g (0.400 mol) of succinic acid and 32.3 g (0.520 mol) of ethylene glycol were placed in a three-necked flask equipped with a stirrer, a Wigley fractionation pipe and a gas introduction pipe. And manganese (II) acetate tetrahydrate 0.029 g (1.2 x 1
0 ^-4 mol) and put into an oil bath. 200 this oil bath
The temperature is raised to ℃, nitrogen is slowly flowed into the melt, 200 ℃
The water and the excess ethylene glycol that were formed over 2 hours at the above temperature were distilled off to obtain an oligomer.

Then, tetra-n-butyl titanate 0.
14 g (4.0 × 10 ⁻⁴ mol) was added, the temperature was kept at 200 ° C., and under a slight amount of nitrogen, under a reduced pressure of 2 mmHg for 2 hours,
Furthermore, 57.6 g of a viscous polymer liquid was obtained by heating for 2 hours under reduced pressure of 1 mmHg or less.

The ηsp / c of this polymer is 0.68 (concentration
0.5 g / deciliter, 30 ° C, in chloroform), and the melting point was 107 ° C. The number average molecular weight (Mn) in terms of polystyrene determined by GPC is 34,000.
It was 0.

Example 2 0.032 g of titanium (IV) oxyacetylacetonate (1.0. G) instead of 0.029 g of manganese (II) acetate tetrahydrate.
27.6 g of the target polymer was obtained in exactly the same manner as in Example 1 except that 2 × 10 ⁻⁴ mol) was used. The ηsp / c of this polymer is 0.76 (concentration: 0.5 g / deciliter, 30 ° C, in chloroform), melting point is 107 ° C.
Met. The polystyrene-reduced number average molecular weight (Mn) determined by GPC was 35,000.

Example 3 In place of 0.029 g of manganese (II) acetate tetrahydrate, 0.030 g (1.2 × 10 ⁻⁴ ) of cobalt (II) acetate tetrahydrate was used.
The desired polymer (57.6 g) was obtained in exactly the same manner as in Example 1 except that (mol) was used. Η of this polymer
sp / c is 0.75 (concentration 0.5 g / deciliter, 30
℃, in chloroform), the melting point was 107 ℃. The polystyrene-reduced number average molecular weight (Mn) determined by GPC was 35,000.

Example 4 118 g (1.00 mol) of succinic acid, 80.7 g (1.30 mol) of ethylene glycol and di-n were placed in a three-necked flask equipped with a stirrer, a Wiggle fractionation pipe and a gas introduction pipe. −
Butyltin (IV) oxide (0.075 g, 3.0 × 10 ^-4 mol) was added and immersed in an oil bath. The temperature of this oil bath was raised to 200 ° C., nitrogen was slowly flowed into the melt, and the water and excess ethylene glycol that were produced over 3 hours at a temperature of 200 ° C. were distilled off to obtain an oligomer.

Next, 0.325 g (1.3 × 10 ^-3 mol) of tetra-n-butoxygermanium was added, and the temperature was adjusted to 20.
Keep it at 0 ℃ and under a reduced pressure of 2mmHg under a very small amount of nitrogen.
By heating for 5 hours and further under reduced pressure of 1 mmHg or less for 4.5 hours, 144 g of a viscous polymer liquid was obtained.

Ηsp / c of this polymer is 0.61 (concentration
0.5 g / deciliter, 30 ° C, in chloroform), and the melting point was 107 ° C. The number average molecular weight (Mn) in terms of polystyrene determined by GPC is 30,000.
It was 0.

Example 5 0.28 g of tetraisopropyl titanate (1.0 x 10) was used instead of 0.325 g of tetra-n-butoxygermanium.
⁽³ mol) was obtained in exactly the same manner as in Example 4 to obtain 144 g of the intended polymer. Ηsp / c of this polymer is 0.61 (concentration 0.5 g / deciliter, 30
℃, in chloroform), the melting point was 107 ℃. The polystyrene-reduced number average molecular weight (Mn) determined by GPC was 30,000.

Comparative Example 1 Example 1 except that 0.026 g of zinc acetate tetrahydrate was used in place of 0.029 g of manganese (II) acetate tetrahydrate.
In the same manner as described above, 57.6 g of a polymer was obtained. The ηsp / c of this polymer is 0.44 (concentration 0.5 g / deciliter,
30 ° C. in chloroform), and the number average molecular weight (Mn) in terms of polystyrene determined by GPC is 12,000.
Met.

Comparative Example 2 57.0 g of a polymer was obtained in the same manner as in Example 1 except that 0.029 g of manganese (II) acetate tetrahydrate was not used. Ηsp / c of this polymer is 0.48
The number average molecular weight (Mn) in terms of polystyrene determined by GPC was 17,000 (concentration: 0.5 g / deciliter, 30 ° C., in chloroform).

Reference Examples 1-5 The polymers obtained in Examples 1-5 were heated using a hot press machine.
Melt and press at a temperature 30 to 40 ° C higher than its melting point,
A μm film was made. Then, this film is 5
Cut into cm x 5 cm, and in the soil (garden of private house, surface 5-10
It was embedded in cm) and the state of the film was examined after 3 months and 6 months in the initial stage, and biodegradability was evaluated. The results are shown in Table 1.

As a comparative example, commercially available polyethylene film and polyester film (both having a thickness of 50 μm) are used.
Thickness), but no change in appearance or film strength was observed.

[0035]

[Table 1]

From Table 1, it is clear that the polyethylene succinate of the present invention has excellent biodegradability despite its high molecular weight.

[0037]

The polyethylene succinate of the present invention is
Despite its high molecular weight, it has excellent biodegradability. Therefore, it can be processed into various shapes and used as a biodegradable film, fiber or sheet.
Further, according to the production method of the present invention, such polyethylene succinate can be easily obtained.

Claims (2)

[Claims] 1. A constitutional unit represented by the following formula (I), which has a polystyrene-reduced number average molecular weight of at least 25,0 as determined by gel filtration chromatography (GPC).
A polyethylene succinate that is 00. [Chemical 1] 2. An oligomer is obtained by reacting succinic acid and ethylene glycol in the presence of at least one catalyst selected from titanium, tin, manganese and cobalt catalysts, and then the obtained oligomer is converted to titanium and titanium. The method for producing polyethylene succinate according to claim 1, wherein the polycondensation is carried out in the presence of one or two catalysts selected from germanium-based catalysts.