JPH08259788A - Biodegradable plastic composition - Google Patents

Abstract

PURPOSE: To obtain a plastic compsn. which is excellent bath in three- dimensional structural properties and in biodegradability and is useful for a molded item used for a short time, such as a one-way container for food packaging. CONSTITUTION: This compsn. comprises 30-78wt.% biodegradable aliph. polyester resin, 20-60wt.% inorg. filler, and 2-10wt.% elastomer having a 100% tensile stress of 5-100kgf/cm<2> and has a tensile elastic modulus of 20,000kgf/cm<2> or higher and a 50% breaking strength (by du Pont impact test using a 0.43mm- thick sheet) of 0.4J or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable plastic composition which can be processed into a molded product having excellent structural properties, and more particularly, to various molded products, particularly packaging containers and other disposable containers. The present invention relates to a biodegradable plastic composition suitable for vacuum molding, injection molding and the like.

[0002]

2. Description of the Related Art Conventionally, various so-called biodegradable plastics which are biodegradable in soil have been known. Among these plastics, aliphatic polyester is relatively excellent in biodegradability, but polycaprolactone resin and polytetramethylene succinate are too flexible, and the resin alone requires three-dimensional structural properties. It is not suitable as a material for one-way food packaging containers such as trays and lunch boxes. On the other hand, resins such as polyhydroxybutyric acid and polylactic acid have low flexibility and high structural strength, but since they have low impact resistance, they tend to crack when they are dropped or collided with impact, so Is still inappropriate.

In order to make up for these drawbacks, a flexible polycaprolactone (PCL), which has a rigidity of poly-β-hydroxybutyric acid (reported in the Proceedings of the Polymer Society of Japan ('93 vol. 42 No 9, page 3712)), has been reported. Technology to improve impact resistance by adding PHB [Polymer Preprint
s, Vol.42 No9 (1993), page 3712], and other techniques for blending a highly biodegradable resin with a highly flexible biodegradable resin to obtain practical strength. Various reports have been made in recent years. However, even if we could solve the problem of physical properties by mixing the above two resins with high unit price of more than 5 times that of general-purpose resin, which is currently the cause of the plastic waste problem, the cost is still high and the original purpose is It seems that it cannot solve a certain waste problem.

[0004] Further, JP-A-6-172620, JP-A-6-172621 and US Pat. No. 3,921,
No. 333 proposes that rigidity is improved by adding a filler such as inorganic fine particles to a biodegradable resin component that is flexible and has good impact resistance. As the amount of the filler in the composition increases, the impact resistance decreases, and the amount of the filler increases until the rigidity equal to or higher than that of polypropylene or polystyrene currently used as a general-purpose resin is obtained. If this is done, the impact resistance will drop to such an extent that it cannot be used practically. Therefore, if it is attempted to obtain practical rigidity strength and structural strength with a composition containing a sufficient amount of filler to maintain appropriate impact resistance, the rigidity will be insufficient. In the case of a rod-shaped or thick-walled structure, its diameter and thickness must be further increased. However, if such a measure is taken, a large amount of expensive resin raw material will be used, resulting in deterioration of molding efficiency, increase in problems in product design, deterioration of transportation efficiency, waste of resources, and waste amount. There is a high risk that biodegradable plastics will adversely affect the environmental protection originally intended, such as increase.

On the other hand, as an example of adding an elastomer to a biodegradable resin, Japanese Patent Laid-Open No. 6-166782 proposes to add a styrene elastomer to polycaprolactone. The purpose of is not to improve impact resistance but to improve processability such as peeling properties, and since the compounding amount of the elastomer can be up to 80% by weight in the composition, a molded article made of this composition is biodegradable. When used as a plastic molded product, there remains concern about biodegradability and environmental protection.

Although it is already known to use an elastomer for such a brittle material, at present, an effective impact modifier for improving the impact resistance of biodegradable plastics is used. Alternatively, the reality is that no biodegradable impact modifier has been found.

However, a low-cost biodegradable or biodegradable plastic composition having high structural strength and high impact resistance is an indispensable situation in view of the current waste disposal problem. For example, considering golf tees, pins, piles, etc., they are stabbed or driven into the ground during use, so they must be rigid enough to be able to penetrate into hard soil to some extent. It is necessary to endure without crushing to some extent and be recovered without being left in the natural world, and piles and the like are also required to have impact resistance such that they are not cracked, broken, or shattered by the impact of a hammer or the like. Also,
Even for packaging materials such as food packaging containers, if the containers that contain the contents fall or are deformed significantly when piled up, or if they break or break, the product value will be significantly reduced. And the like. Furthermore,
Even in an automatic wrapping machine using a wrap, which is usually used for one-way food packaging containers, a comparatively large force is applied to an extremely thin container at the time of packaging, so if the rigidity and impact resistance are not well balanced, it will crack. Problems such as crushing and deformation will occur.

[0008] As described above, a biodegradable or biodegradable plastic composition having low cost, good structural strength and high impact resistance is still realized despite the socially urgent demand. Has not yet reached.

Therefore, a main object of the present invention is to provide a low-cost biodegradable plastic composition having a good balance of excellent structural strength and high impact resistance. In the present specification, "biodegradable plastic" means
At least a part of the plastic is decomposed by the microorganisms existing in the natural environment and / or the enzyme produced by the microorganisms to cause the collapse of the shape of the molded article made therefrom.

[0010]

[Means for Solving the Problems] As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a biodegradable aliphatic polyester resin, together with a specific amount of an inorganic filler, is specified. It was found that the above object can be achieved by compounding a specific amount of an elastomer having a tensile stress of, and the present invention has been completed.

Thus, the present invention provides: (A) biodegradable aliphatic polyester resin 30-78% by weight (B) inorganic filler 20-60% by weight and (C) 100% tensile stress 5-100 kgf / cm. ^A composition comprising 2 to 10% by weight of an elastomer having a tensile modulus of at least 2
Disclosed is a biodegradable plastic composition having a 50% puncture strength of at least 0.4 J according to a DuPont impact test in a sheet form having a thickness of 4,000 kgf / cm ² and a thickness of 0.43 mm. is there.

Hereinafter, the biodegradable plastic composition of the present invention
The thing will be described in more detail. Aliphatic polyester resin (A) : Plastic of the present invention
As an aliphatic polyester resin used in the composition
The one having biodegradability is used. Here "live
A "degradable" polyester resin exists in the natural environment
Polyester that is decomposed into low molecular weight substances by the involvement of microorganisms
A resin is used in the present invention.
The oil is JIS K6950-1994 "Plastic-
Aerobic biodegradability test method using activated sludge "
When activated sludge A or B has a biodegradability of at least
20%, preferably 50% or more is suitable. one
However, regarding anaerobic bacteria-degrading resin, it is still JIS standard.
Although it does not exist, it is equivalent to the aerobic bacterium-degrading resin.
It is desirable to have a degree of decomposition.

Examples of such biodegradable aliphatic polyester resin (A) are hydroxyalkanecarboxylic acids having 2 to 6 carbon atoms or lactone (co) which is a cyclic compound thereof.
A polymer, a polycondensation product of an aliphatic dicarboxylic acid having 2 to 8 carbon atoms and an alkylene glycol having 2 to 8 carbon atoms, and the like are included, and more specifically, for example, polylactic acid, polyhydroxybutyric acid, polyhydroxy Valeric acid, polycaprolactone or a copolymer composed of two or more kinds of monomers constituting these homopolymers; polytetramethylene succinate, polyethylene succinate, polytetramethylene adipate or monomers constituting these polymers And two or more types of copolycondensates thereof and the like.

These polyester resins are, for example, within a range that does not substantially affect the above-mentioned biodegradability,
Introduction of trifunctional compounds (eg: glycerin, trimethylolpropane, etc.), isocyanate compounds (eg: tolylene diisocyanate, isophorone diisocyanate, etc.), aromatic rings (eg: terephthalic acid, isophthalic acid, bisphenol, etc.), etc. May be modified by

The molecular weight of the aliphatic polyester resin used in the present invention is not particularly limited and can be selected from a wide range, but usually the number average molecular weight is about 30,000.
0 to about 1,000,000, especially about 50,000 to about 30
Those in the range of 0000 are preferred.

A resin composition obtained by melt-kneading 60 g of talc (average particle size 8 μ) with 40 g of resin with a high-speed mixing mixer or the like until it becomes uniform has a tensile elastic modulus of 20,0.
An aliphatic polyester resin having a pressure of not less than 00 kgf / cm ² is particularly suitable.

In the present specification, "tensile modulus" means AST.
It is a value when measured by the method described in MD882.

Inorganic filler (B) : In the present invention, the inorganic filler is the above-mentioned aliphatic polyester resin (A).
Is added to the resin for the purpose of improving the rigidity of
Therefore, as long as the object can be achieved, the kind thereof is not particularly limited, and those generally used in the art as a filler for the resin can be similarly used.

However, since the composition of the present invention has one purpose to solve the waste problem, in general, fine particles of inorganic substances derived from natural products are suitable, for example, talc,
Examples include mica, chlorite, wollastonite,
These may be used alone or in combination of two or more.

The shape of the inorganic fine particles is not particularly limited, and those having a shape usually used as a resin filler can be used as well. Among them, the aspect ratio of plate-like or needle-like is particularly preferable. A shape having a relatively large value is generally preferable because it has a large effect of improving rigidity. The inorganic fine particles are usually 0.5 to 20 μm, preferably 1 to 1
It is desirable to have an average particle size within the range of 0 μm.
Further, the inorganic fine particles may be fired or treated with a coupling agent such as a silane coupling agent, if necessary.

In the present invention, a part of the inorganic filler used is starch, within the range that does not substantially affect the physical properties (tensile modulus and impact resistance) of the composition of the present invention. Natural polysaccharide fine particles such as cellulose; wood flour; animal proteins such as casein and gluten may be substituted, but the amount should be 50% by weight or less at the maximum. Therefore, it should be understood that the inorganic filler referred to in the present invention includes those in which such a part is substituted with organic fine particles.

Elastomer (C) : In the present invention, the elastomer is the above-mentioned aliphatic polyester resin (A).
The main purpose of the resin composition is to improve the impact resistance of the resin composition whose rigidity is increased by adding the inorganic filler (B) to the resin composition.

However, the elastomer (C) used for this purpose has a tensile stress of 5 to 100 kgf / c when measured by the method of JIS 6301.
Those in the range of m ² , preferably 5 to 80 kgf / cm ² , and more preferably 5 to 50 kgf / cm ² are suitable. Further, the elastomer is generally JIS 63
It is desirable that the elongation as measured by the method No. 01 is 100% or more, preferably 300% or more, more preferably 500% or more.

Thus, in the present invention, diene rubbers such as polybutadiene and polyisoprene; thermoplastic rubbers such as styrene-based, urethane-based and polyester-based rubbers and hydrogenated rubbers thereof, as long as they satisfy the above physical properties.
Copolymer rubbers such as styrene / butadiene rubber and ethylene / propylene / diene copolymer; epichlorohydrin rubber and the like; further, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid random copolymer, and aliphatic ester -Any elastomer such as a biodegradable rubber such as a diene radical copolymer can be used, but generally, one having good compatibility with the above-mentioned aliphatic polyester resin (A) is used. desirable.

Particularly in the present invention, the elastomer (C) is 40 to 90% by weight, preferably 55 to 8%.
5% by weight of soft segment (S) and 10 to 60% by weight, preferably 15 to 45% by weight of hard segment (H), wherein the hard segment (H) is 8.5 to 1
1, preferably having a solubility parameter (SP value) within the range of 8.5 to 10.5 and bound to the end of the hard segment (H) in a form conceptually represented by H—S—H. Thermoplastic elastomers that are present are preferred. Examples of such a soft segment (S) of the thermoplastic elastomer include:
Examples thereof include polybutadiene, polyisoprene, styrene-butadiene rubber, multi-component copolymerized polyester rubber, uratan rubber and polyether rubber. Examples of the hard segment (H) include styrene oligomer and biodegradable aliphatic polyester resin ( Examples of A) include the above-mentioned oligomers of the aliphatic polyester.

Specific examples of the thermoplastic elastomer include styrene / butadiene / styrene copolymer (SBS rubber) and its hydrogenated copolymer, styrene / isoprene / styrene copolymer (SIS rubber), and radial. Styrene / butadiene / styrene copolymer, ethylene /
Examples thereof include propylene / diene copolymer.

Other suitable examples of the elastomer (C) include butadiene rubber, random styrene-butadiene rubber, isoprene rubber and the like.

Biodegradable plastic composition : In the biodegradable plastic composition of the present invention, the aliphatic polyester resin (A), the inorganic filler (B) and the elastomer (C) described above are hot melt mixed and dispersed. It can be manufactured. The compounding ratio of each component of (A), (B) and (C) at that time can be as follows. The numerical values are% by weight based on the total weight of the three components (A), (B) and (C).

General range Preferred range More preferred range Aliphatic polyester resin (A) 30-78 30-73 30-68 Inorganic filler (B) 20-60 25-60 30-60 Elastomer (C) 2-10 2 If the elastomer (C) is biodegradable by itself, the resin composition of the present invention is biodegraded of all the resin components and does not remain in the natural environment, which is desirable. However, when the elastomer (C) is not biodegradable, it is preferable to minimize the amount of the elastomer (C) to be mixed with the natural environment. However, if the compounding amount of the elastomer (C) is reduced, the impact resistance of the obtained composition tends to decrease, so the compounding amount is reduced while paying attention to practical strength depending on the intended use of the final composition. Preferably,
Particularly, when the blending ratio of the aliphatic polyester resin (A) in the composition of the present invention is a% by weight and the blending ratio of the elastomer (C) is b% by weight, the ratio of b / a + b is 0.1 or less, preferably It is desirable to set it within the range of 0.03 to 0.07.

The plastic composition of the present invention can be produced by hot melt mixing and dispersing the aliphatic polyester resin (A), the inorganic filler (B) and the elastomer (C). , For example, kneader,
It can be carried out by using an ordinary dispersion / mixing processing method using a Banbury mixer, a mixing roll or the like. However, when the processing by these methods is carried out at a temperature equal to or higher than the melting temperature of the compound for a long time in an air atmosphere containing moisture and oxygen, the aliphatic polyester resin (A) is decomposed and the composition is deteriorated. , It may deteriorate,
When processing requires a long time, it is desirable to carry out the processing in a dry inert gas atmosphere.

Alternatively, it is preferable to use the mixing and dispersing method disclosed in Japanese Patent Publication No. 29126/1989, and to carry out the treatment in a short time such that the high temperature holding time of the mixture is within 10 to 30 seconds. Further, by directly dispersing the inorganic filler (B) and the elastomer (C) in the aliphatic polyester resin (A) using a twin-screw extruder, it is possible to obtain a composition with less characteristic deterioration.

The plastic composition of the present invention produced as described above has at least 20,000 kgf /
cm ² or more, preferably 20,000 to 40,000 kg
f / cm ² , more preferably 20,000 to 35,000
It has a tensile elastic modulus in the range of 0 kgf / cm ² and a 50% breaking strength by a DuPont impact test in a sheet having a thickness of 0.43 mm is 0.4 J or more, preferably 0.5-5.
J, and more preferably within the range of 0.5-3J.

For the 50% breaking strength according to the DuPont impact test in this specification, a tip having a tip radius of 4.7 mm was used, and the four sides of the sheet were fixed so that the tip could punch through the sheet at the time of impact. Adjust and measure the drop height of
It is the value obtained using the calculation method of IS K7211.

The composition of the present invention can be used to process various plastic moldings. Molded articles can be produced from the composition of the present invention by using a usual plastic molding method. For example, a single-layer or multi-layer extrusion molding method, an injection molding method, or a calendar molding method is applied. It can be made into a foamed structure if necessary. Further, when the product obtained by these moldings is in the form of a sheet, secondary processing such as vacuum molding or pressure molding can be added to this to give a desired shape such as a food packaging container.

In the processing, various additives which are usually used for resin processing, such as antioxidants, surfactants and colorants, may be added, if necessary.

[0036]

The composition of the present invention and the biodegradable molded article produced using the same have a high tensile modulus (rigidity).
With high impact strength. This high rigidity means that the strength required for a molded product can be obtained with a small amount of raw materials, and it indicates that the target molded product can be economically manufactured. Therefore, it becomes possible to practically design a food packaging container and various injection molded products.

Since the composition of the present invention has excellent rigidity and impact resistance as described above, it is also useful when used as a layer for supporting the structure of a laminated molded article.

Articles molded from the composition of the present invention are essentially natural, and most of the resin component excluding inorganic fine particles, which does not adversely affect the environment, is biodegraded, and some non-biodegradable polymers are Even if it remains, it is 10% or less of the entire composition, and therefore, for example, even after landfill treatment, it loses its shape and collapses after a certain period of time, and the load on the environment can be suppressed to a small level, and the disposal characteristics are extremely good. Can be treated as waste.

Thus, the composition of the present invention can be used, for example, in one-way food packaging containers such as food trays and bento containers; cups, plates, spoons, forks, partitioning of packaging boxes used in the field, and one-way use such as guesswork. Supplies: Further, it can be widely used for flower pots, piles and pins for agriculture and forestry, golf tees, baskets for seed dispersal, cards, and other molded products having a relatively short period of use.

[0040]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The physical properties of the sheets and molded articles obtained in Examples and Comparative Examples are evaluated and measured as follows.

Evaluation of Physical Properties and Measuring Method : (1) 100% Tensile Stress of Elastomer 100% tensile stress is used to evaluate the properties of the elastomer (JIS K6301).

Shimazu Seisakusho Autograph AGS-500S is used as the tensile tester. (2) Tensile Elastic Modulus Tensile elastic modulus is used to evaluate the rigidity of the sheet (AST
M D882).

The test equipment is Autograph AG manufactured by Shimadzu Corporation.
Use S-500S.

(3) Impact test 50% breaking energy is determined using a DuPont impact tester as an evaluation of the impact property of the sheet (JIS K7211).
Calculated according to the falling weight impact test law for hard plastics). Room temperature 20 ° C, hammer radius 4.7 mm, weight 200 g
Is. The sheet was fixed on all sides.

(4) Waist / Bending Strength As an evaluation of the rigidity of a molded product, a food container is molded, and its waist strength (see FIG. 1) and bending strength (see FIG. 2) are used. If the waist strength is low, there is a problem that the container is deformed when the wrap is hung on the container, especially when it is hung on an automatic wrapper. Also, if the bending strength is weak, it will be crushed when trying to pack the contents into the container, or it will be deformed when holding the container with the contents inside because it is strength related to the deflection of the container, It will be deformed when you wrap the wrap. As described above, both strengths are important strengths for a container-shaped molded article and are preferably high. Testing equipment is Shimadzu Autograph AGS-50
Use 0S. However, the head speed is 50 mm /
min. And

Example 1 High-speed mixing mixer (Super mixer SM, manufactured by Kawata Co., Ltd.)
G100) was partially modified so that the temperature of the mixing tank could be raised to 250 ° C. To Union Carbide Polycaprolactone (TONE P787; hereinafter PCL) 9.5k
g, and 10 kg of talc (FVS) manufactured by Wandou Kogyo Co., Ltd., and mixed and heated. After about 20 minutes, when the load on the rotary motor suddenly increased, the content was discharged to a low rotation cooling tank, and rotation was continued to blow air to solidify by cooling to obtain a granular blend.

Toughprene A (soft segment 60), which is a styrene-butadiene-styrene copolymer (SBS) manufactured by Asahi Kasei, is used for 19.5 kg of the above blend.
%; 100% Tensile stress 20 kgf / cm ² ) 0.5 kg was added and premixed with a mixer, and the mixture was kneaded with a Toshiba Machine Extruder SE-65 (65φ vent type) (setting 160 ° C., resin temperature 162). ℃), extruded from T die.
A 43 mm thick sheet was obtained. The sheet was heated by a single-shot vacuum forming machine at a heater temperature of 200 ° C. for a heating time of 4 seconds,
With a total shot time of 10 seconds, length 18 cm, width 12 cm,
It was molded into a food tray having a depth of 2.5 cm and subjected to a strength test and a DuPont impact test. Table 1 shows the measurement results of the physical properties of the sheet and the container. In addition, a packaging test and a biodegradation test were performed as follows.

(Packaging test) After putting 200 g of the content in the obtained test tray, wrapping was carried out at a speed of 50 pieces / minute with an automatic wrapping machine (Omori Machinery, model 8000), but wrapping was carried out without any problem. I was able to wrap it.

(Biodegradation test) Further, the obtained food tray was put in a nylon net bag having 5 mm holes, and it was put into raw garbage 5
00 kg and 100 kg of rice husk were put into a mixture that had been pulverized and mixed, and gently stirred for 2 weeks so that the bag was not damaged. Thereafter, 500 kg of beef compost per 200 kg of the mixture was added, stirred and allowed to stand for 2 months. After that, when the tray in the net bag was observed, the shape completely disappeared and it was barely 1
It was decomposed to the extent that some 0 mm square fragments could be confirmed.

Example 2 0.5 kg of Toughprene A was added to Toughprene 315 (soft segment 80%; 100, SBS manufactured by Asahi Kasei Corporation).
The same operation as in Example 1 was performed except that the% tensile stress was changed to 20 kgf / cm ² . Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Example 3 0.5 kg of Toughprene A was added to Radial S manufactured by Asahi Kasei Corporation.
BR Sorprene T414 (soft segment 60
%; 100% tensile stress 39 kgf / cm ² ) was changed to the same operation as in Example 1. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Example 4 9.5 kg of polycaprolactone was used as 9.5 kg of Bionore (# 3010) manufactured by Showa High Polymer Co., Ltd., and 0.5 kg of Toughprene A was used as a styrene-isoprene-styrene copolymer manufactured by Nippon Synthetic Rubber Co., Ltd. SIS5002 (78% soft segment; 100% tensile stress 9.6kgf / c
m ² ) The same operation as in Example 1 was performed except that the amount was changed to 0.5 kg. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Example 5 Takg 10 kg to 12 kg, polycaprolactone 9.
5kg to 7.6kg, and Toughprene A 0.5kg
E-SBR which is a random SBR manufactured by Japan Synthetic Rubber Co., Ltd.
No. 0202 (100% tensile stress 35 kgf / cm ² ) 0.
The same operation as in Example 1 was performed except that the amount was changed to 4 kg. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Example 6 0.5 kg of Toughprene A was added to Lavalon SE5400BN (100% of hydrogenated SBS type elastomer manufactured by Mitsubishi Chemical Corporation).
The same operation as in Example 1 was performed except that the tensile stress was changed to 28 kgf / cm ² ) 0.5 kg. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Example 7 The same as Example 1 except that 0.5 kg of Toughprene A was changed to 0.5 kg of Thermolane 3650 (100% tensile stress 21 kgf / cm ² ) which is an olefinic elastomer manufactured by Mitsubishi Chemical Corporation. The operation was performed. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Reference Example 1 (Production of Biodegradable Elastomer) (a) Separation and Identification of Strains Activated sludge was spread on a yeast extract medium to allow colonies to appear (30 ° C., 3 days). Each of the colonies has sodium 4-hydroxybutyrate as its sole carbon source,
Culturing in a nitrogen-limited inorganic salt medium (30 ° C., 4 days) and selecting colonies stained blue with Sudan Black B and colonies stained red with Neil Blue A (ultraviolet light of 254 nm) that emitted red light I got it. Each of the strains selected above was identified with the AP120 NE test kit to obtain a strain identified as Comamonas acidvorans .

(B) Proliferation of bacterial cells The obtained bacterial strain was cultured in a nutrient liquid medium (30 ° C.,
The cells were cultured for 1 day) to grow the cells.

(C) Fermentation Synthesis of Polyester Elastomer Using the obtained bacterial cells, 1 g of 1-pentanol was added to an inorganic salt medium containing no nitrogen source per liter of the medium,
10 g of 1,4-butanediol per liter of medium
The cells were added and cultured (30 ° C., 2 days).

(D) Purification and Identification of Polyester The cultured bacterial cells were collected by a centrifuge and dried by a freeze dryer. The dried cells were refluxed with hot chloroform for 5 hours using a Soxhlet extractor, the extract was filtered through a glass filter, concentrated, and reprecipitated in methanol to obtain polyester. The obtained polyester was decomposed with methanolic sulfuric acid to obtain a methyl ester of a monomer. By the gas chromatography method (column is a capillary column Neutra bond-1 manufactured by GL Science Co., Ltd.), the identification and composition ratio of the monomer are measured, and further the H-NMR of the polyester is measured. 18% by weight, 4-hydroxybutyric acid unit 62% by weight, 3-hydroxyvaleric acid unit 2
It was confirmed to be a 0-wt% 3-hydroxybutyric acid-4-hydroxybutyric acid-3-hydroxyvaleric acid copolymer.

Example 8 0.5 kg of tufprene A was mixed with 3-hydroxybutyric acid-4-hydroxybutyric acid-3-hydroxyvaleric acid copolymer obtained in Reference Example 1 (100% tensile stress 10 kgf / cm ² ).
The same operation as in Example 1 was performed except that the amount was changed to 0.5 kg. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

As is clear from Table 1, the molded article made of the composition of the present invention exhibited a sufficiently high impact strength even though the sheet had a high tensile elastic modulus. Further, the above container also exhibited high resistance to impact force. Furthermore, the container was applicable to automatic packaging machines.

Comparative Example 1 PCL was formed into a sheet with a thickness of 0.43 mm by an extruder, and the physical properties were evaluated as in Example 1. Table 1 shows the results of measuring the physical properties of the sheet and the container and the results of the biodegradation test. As can be seen from Table 1, PCL alone has good impact resistance, but its rigidity is inferior, so the container is deformed and it cannot be applied to an automatic wrap packaging machine.

Comparative Example 2 The same operation as in Example 1 was carried out except that the amount of PCL charged to the high speed mixing mixer was increased by 0.5 kg instead of 0.5 kg of Tuffrene A. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

Comparative Example 3 The same operation as in Example 4 was carried out except that the amount of bionole charged to the high speed mixing mixer was increased by 0.5 kg instead of 0.5 kg of Tuffprene A. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

As can be seen from the physical properties of the sheets shown in Table 1, the molded products of Comparative Examples 2 to 3 had sufficient rigidity but were inferior in impact resistance. When these were placed in an automatic packaging machine, damage to the container was recognized.

Comparative Example 4 0.5 kg of Tufrene A was mixed with ABS10, which is an acrylonitrile butadiene styrene copolymer manufactured by Japan Synthetic Rubber Co., Ltd.
(Soft segment 22.5%; 100% tensile stress is 1
The same operation as in Example 1 was performed except that the amount was changed to 0.5 kg because the elongation did not increase by 0% or more. The results of physical properties and biodegradation test results of the obtained sheets and containers are first
Shown in the table.

Comparative Example 5 0.5 kg of Tuffrene A was used as B-2, which is a methyl methacrylate butadiene styrene copolymer manufactured by Kaneka Corporation.
2M (soft segment 40%; 100% tensile stress 80
The same operation as in Example 1 was performed except that the amount was changed to 0.5 kg. Table 1 shows the results of measuring the physical properties of the obtained sheets and containers and the results of biodegradation tests.

[0068]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a waist strength test method for evaluating the rigidity of a container.

FIG. 2 is a schematic diagram showing a method of measuring bending strength for evaluating the rigidity of a container.

Claims (4)

[Claims] 1. (A) Biodegradable aliphatic polyester resin 30 to 78% by weight (B) Inorganic filler 20 to 60% by weight and (C) 100% tensile stress in the range of 5 to 100 kgf / cm ² . 2 to 10% by weight of an elastomer according to claim 1, having a tensile modulus of at least 2.
A biodegradable plastic composition having a 50% breaking strength of at least 0.4 J according to a DuPont impact test in a sheet form having a weight of 4,000 kgf / cm ² and a thickness of 0.43 mm. 2. The elastomer (C) is 40 to 90% by weight.
Of 10 to 60% by weight of a hard segment, the hard segment having a solubility parameter in the range of 8.5 to 11 and bonded to the ends of the soft segment. The composition of claim 1. 3. An elastomer (C) is butadiene rubber,
The composition of claim 1 selected from random styrene-butadiene rubber and isoprene rubber. 4. A molded article made from the composition according to claim 1.