JPH08157705A - Biodegradable resin composition - Google Patents

Abstract

PURPOSE: To obtain a biodegradable resin composition excellent in moldability, mechanical properties and heat resistance by mixing a specified aliphatic polyester with poly-3-hydroxybutyrate. CONSTITUTION: This resin composition comprises an aliphatic polyester prepared from a glycol, an aliphatic dicarboxylic acid or its derivative and poly-3- hydroxybutyrate. It is desirable that the poly-3-hydroxybutyrate has a weight- average molecular weight of 400000 or above. If it has a molecular weight below that, it can not give a satisfatory molding.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention has excellent moldability and mechanical performance, and is used as a packaging member for medicines, cosmetics, foods and industrial materials / machines, machine parts, fibers, monofilaments, clothing and the like. The present invention relates to a resin composition having excellent biodegradability.

[0002]

2. Description of the Related Art Many plastics have hitherto been used in various industries as molding materials for packaging materials, clothing, fibers, monofilaments and industrial machine parts. However, in recent years, from the standpoint of environmental protection, the reuse of plastics has been exclaimed, and in fields of application where reuse is not possible, the use of biodegradable resins that decompose due to the action of microorganisms or hydrolysis is strongly socially strong. It has been requested. Polyesters using aromatic compounds are generally known to have a high melting point or a high glass transition point and thus can be used as molded articles, but they are generally not biodegradable. On the other hand, aliphatic polyester is
It is known to be decomposed by microorganisms.

Poly-3-hydroxybutyric acid (hereinafter abbreviated as PHB) is generally produced by a fermentation method using a microorganism. PHB has biodegradability that is completely decomposed by the action of microorganisms widely distributed in nature, and is thermoplastic, so its use for various purposes by existing molding methods is being actively investigated. is there. However, it is known that PHB lacks thermal stability in a molten state and is difficult to mold, and the molded product obtained has a small elongation and is hard and brittle. Further, PHB has a high crystallinity and an excellent gas barrier property, but a sufficiently crystallized PHB is difficult to draw, and it is difficult to produce a yarn having practical mechanical performance by melt spinning or drawing. .

Aliphatic polyesters synthesized from glycols and aliphatic dicarboxylic acids generally have a low elastic modulus and a melting point of about 100 ° C., and therefore the heat resistance is not sufficient. Therefore, although these synthesized aliphatic polyesters and PHBs have excellent biodegradability to meet social demands for environmental protection, they have not yet been fully utilized. .

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above problems found in the prior art and provides a biodegradable resin composition having excellent moldability, mechanical performance and heat resistance and having high practicality. That is the subject.

[0006]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, a biodegradable resin composition comprising an aliphatic polyester synthesized from glycols and an aliphatic dicarboxylic acid or its derivative and PHB was found to be a material having mechanical performance and heat resistance, and the present invention was completed. Let

The aliphatic polyester shown in the present invention is mainly composed of polyester chemically synthesized from glycols and an aliphatic dicarboxylic acid, its acid anhydride or an acid derivative such as a lower alkyl ester. Alternatively, a compound having a sufficiently high molecular weight is also included by reacting a compound capable of forming a carbonate bond with an oligoester or polyester of the above aliphatic polyester.

Examples of glycols used in the present invention include ethylene glycol, 1,3 and 1,4-
Examples are butanediol and trimethylene glycol. These glycols may be used in combination.

Aliphatic dicarboxylic acids or acid derivatives thereof which react with glycols to form aliphatic polyesters include succinic acid, adipic acid, malonic acid, glutaric acid,
Azelaic acid and the like are exemplified, and esters or acid anhydrides thereof can also be used. The dicarboxylic acid and its acid derivative may be used in combination.

PHB which is another constituent of the composition of the present invention may be chemically synthesized or may be produced by a microorganism. For example, the genus Alcaligenes, Azotobacter
Genus, Methylobacterium, Nocardia, Pseudomona
s) It can be produced by a known fermentation method using a bacterium of the genus or the like. Regarding the method for separating and purifying PHB from the bacterial cells containing PHB obtained by the fermentation method, for example,
U.S. Pat. Or, Japanese Patent Application No. 5-323
For 019, the bacterial cells were crushed with a high pressure homogenizer, and then P
A method for separating HB and treating the separated PHB with an oxygen-based bleach is described. The PHB used in the present invention is
PHB having a weight average molecular weight of 40,000 or more is preferable. The reason is that since PHB is poor in thermal stability, if PHB having a molecular weight lower than that is used, the melt viscosity becomes too low at the time of melt molding, and a satisfactory molded product cannot be obtained, or the mechanical performance of the molded product is insufficient This is because inconveniences such as not occurring occur.

The resin composition of the present invention may contain conventional auxiliary additives such as inorganic fillers, pigments, antioxidants and plasticizers. The composition of the present invention includes injection molding, injection blow molding, injection stretch blow molding, extrusion, extrusion blow molding, extrusion stretch blow molding, stretching, rolling, thermoforming, spinning,
By a molding processing method that can be generally applied to thermoformable resins such as spinning accompanied by stretching, spinning, and weaving, sheets, films, soft and hard containers / bottles, tubes, monofilaments, fibers, nonwoven fabrics, woven fabrics, machine parts, It can be converted into sports equipment parts products.

As a particularly specific use of these molded products, materials that cannot be collected or reused after use or are difficult, such as medical instruments and equipment, containers for foods, drugs, fragrances, garbage bags, fishing lines. , Yarn such as fishing nets, nets, medical and industrial cloths, and other industrial and agricultural materials.

[0013]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. The tensile properties shown below were measured as follows. Apparatus: Tensile tester Test piece shape: Strip length 100 mm, width 10 mm, chuck distance 50 mm Peeling speed: 50 mm / min Measuring conditions: temperature 23 ° C or 80 ° C, relative humidity 50%

Examples 1 to 3, Protomonas e, a bacterium, which has been deposited at the Institute of Biotechnology, Institute of Biotechnology, AIST.
xtorquens) K (consignment number: FERM BP-354
Using 8), continuous culture was performed aerobically using methanol as a carbon source. The culture conditions are a culture temperature of 32 ° C. and a culture pH of 6.
5, the average residence time was 40 hours, and continuous culture was performed so that the nitrogen supply rate was the rate-determining factor for bacterial growth. According to recent literature, this bacterium is Methylobacter
(Iium Bousfield and PN)
Green; Int.J.Syst.Bacteriol., 35,209 (1985), T. Urak
ami et al .; Int.J.Syst.Bacteriol., 43,504-513 (1993))
. The bacterial cells obtained by continuous culturing are described in Japanese Patent Application No. 5-32 mentioned above.
According to the method for separating and purifying PHB described in 3019, after crushing with a high-pressure homogenizer, PHB was centrifuged, and the separated PHB was first treated with protease and then treated with hydrogen peroxide to obtain high-purity PHB. The molecular weight of this purified PHB was 1,000,000. The PHB was pelletized using a screw type extruder. The molecular weight at the time of pelletization was 700,000. The PHB pellets thus obtained and the aliphatic polyester (“Bionore # 1010” manufactured by Showa High Polymer Co., Ltd.) were mixed so that the PHB parts by weight were 30%, 60% and 80%, respectively, and a single screw extruder was used. [Toyo Seiki Co., Ltd., Labo Plastomill, screw diameter: 20 mm] is used, and the cylinder temperature is set to 170 to 190 ° C. by the T-die / cooling roll method (cooling roll temperature: 25 to 55 ° C.), thickness approximately. A 200 μm sheet was prepared.

From the obtained sheet, length 100 mm, width 1
A 0 mm strip-shaped test piece was cut out and a tensile test was performed at 23 ° C. Table 1 shows the results. Comparative Example 1 Aliphatic polyester (“Bionore # 1” manufactured by Showa High Polymer Co., Ltd.
010 ") using a single-screw extruder [manufactured by Toyo Seiki Co., Ltd., Labo Plastomill, screw diameter: 20 mm] with a cylinder temperature of 170 to 190 ° C. and a T-die / cooling roll method (cooling roll temperature: 25 A sheet having a thickness of about 200 μm was prepared. A strip type test piece having a length of 100 mm and a width of 10 mm was cut out from the obtained sheet,
A tensile test was performed at 23 ° C. Table 1 shows the results.

Examples 4 to 7 The sheets obtained in Examples 1 to 4 were subjected to a tensile test at 80 ° C. The results are shown in Table 2. Comparative Example 2 The sheet obtained in Comparative Example 1 was subjected to a tensile test at 80 ° C. The results are shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

INDUSTRIAL APPLICABILITY The composition of the present invention provides a molded product having excellent moldability and mechanical properties, heat resistance, gas barrier properties and biodegradability.

Claims (2)

[Claims] 1. A biodegradable resin composition comprising an aliphatic polyester synthesized from glycols and an aliphatic dicarboxylic acid or a derivative thereof and poly-3-hydroxybutyric acid. 2. The biodegradable resin composition according to claim 1, wherein poly-3-hydroxybutyric acid having a weight average molecular weight of 400,000 or more is used.