JPH0678475B2 - Biodegradability control method for plastics - Google Patents

Description

Description: TECHNICAL FIELD The present invention uses an aliphatic polyester having biodegradability as a plastic material, and the biodegradability of the aliphatic polyester is arbitrarily controlled within the following range. It is about the method.

[Conventional technology and its problems]

To date, as a method of controlling the biodegradation rate of biodegradable plastics, (1) use a resin that is easily biodegradable, (2) add a resin and additives that are more easily biodegradable to the biodegradable resin, (3) By adding a large amount of powder to the biodegradable resin,
A method of increasing the biodegradation rate such as expanding the surface area of the biodegradable resin by making the blended body porous, and (4) using a resin with slow biodegradation, (5) difficult to biodegrade into biodegradable resin There is a method to reduce the biodegradation rate by adding resin, (6) adding antibacterial and enzyme inhibitors, (7) laminating biodegradable resin and non-biodegradable resin on the surface of biodegradable plastic. .

However, in the above methods (1), (2), (4), and (5), there are currently few resins that are said to be biodegradable, and among them, few are commercially available. There is little choice. In addition, when designing and synthesizing a biodegradable resin with biodegradability suitable for the purpose,
It costs a lot of money. In (6), there is concern that the biodegradation inhibitor as described above is stable during plastic processing, and is safe during processing, use, decomposition, and after decomposition. And in (7), there is a problem that the laminated film remains after the disassembly.

[Problems of the Invention]

Most preferably, the biodegradable plastic does not decompose during the period of use and decomposes rapidly after use. That is, the lower the initial biodegradation rate is than the subsequent biodegradation rate in the process of the microbial collapse of the shape of the plastic product, the more preferable.

Therefore, an object of the present invention is to provide a method for controlling biodegradability of a biodegradable plastic, which can suppress the biodegradation rate per unit volume to a range lower than that of the biodegradable plastic.

[Means for Solving the Problems]

As a result of repeated intensive studies to solve the above-mentioned problems, the present inventors have added 10 to 50 vol% of inorganic and / or organic filler to the biodegradable polyester, and the average volume of the filler (average of the dispersion layer). Volume) 4.2 × 10 ^{-3 to} 65.4 μm ³
By changing the range of the range, the biodegradation rate of the aliphatic polyester from the surface of the blend to a depth of about 20 μm, that is, the rate at which the blend begins to disintegrate due to biodegradation, Biodegradation rate per unit volume compared with biodegradation rate, 90-10%
The inventors have found that the adjustment can be made to the present invention and completed the present invention.

That is, according to the present invention, the biodegradable aliphatic polyester is mixed with an inorganic and / or organic filler in an amount of 10 to 50 vol%, and the average volume of the filler is 4.2 × 10 ^{−3 to} 65.4 μm ³
The method for controlling biodegradability of a plastic is provided by controlling the biodegradation rate per unit volume within a range of 90 to 10% of the aliphatic polyester.

The biodegradability in the present invention means that it is decomposed in a natural environment such as soil, and is also decomposed in a partial natural environment such as a landfill, and further, municipal waste, surplus sludge of a sewage treatment plant, pig excrement. It means that it is decomposed by a rapid composting process under aerobic conditions known as a treatment method, such as being decomposed by an aliphatic polyester-degrading enzyme-producing bacterium or a substance containing them. There is.

Examples of biodegradable aliphatic polyesters include polyhydroxybutyrate (PHB) and its derivatives, polycaprolactone (PCL), polyethylene adipate (PEA), polytetramethylene diadipate and other aliphatic polyesters and their derivatives, polycyclohexylenedimethyl. Examples thereof include alicyclic polyesters such as adipate and derivatives thereof, copolymers of thermoplastic synthetic resins with aliphatic polyesters having biodegradability, and blends of the above aliphatic polyesters with general resins. These are used alone or as a mixture of two or more kinds.

Examples of the inorganic filler include talc, calcium carbonate, clay, silica, alumina, glass powder, stainless steel, aluminum, copper, and magnetic iron. Examples of the organic filler include starch produced and refined from starch-containing substances such as potatoes, rice, and corn, as well as co-reacting starch with vinyl acetate, acrylic acid, acrylate, etc. Examples thereof include starch derivatives such as polymers, plant powders such as wood powder and cellulose powder, and thermoplastic resin powders that do not melt at the melting and processing temperature of thermosetting resin powders and biodegradable plastics.

In the present invention, an aliphatic polyester is blended with the inorganic and / or organic filler, and the average volume of the blended filler is changed to a specific range to obtain a plastic composition or a plastic molded article obtained. The rate of decomposition can be controlled. In this case, the blending ratio of the inorganic and / or organic filler is 10 to 50 vol%, preferably 20 to 50 vol% with respect to the blended composition,
Used at a relatively high rate. Also, the average volume of those fillers varies in the range of 4.2 × 10 ^{−3 to} 65.4 μm ³ ,
The filler having a smaller average volume has a greater effect of controlling the biodegradation rate of the obtained plastic composition or plastic molded product, and it is preferably specified in the range of 4.2 × 10 ^{−3 to} 40 μm ³ .

In order to control the biodegradability of the plastic molded product according to the present invention, the compounding amount and average volume of the inorganic and / or organic filler may be appropriately selected within the above range and melt molding may be carried out by a conventional method. In this way, the rate of biodegradation on the surface of the molded product is 90 to 10 times that of the aliphatic polyester alone.
Controlled plastic moldings in the range of% can be obtained. As a molding method, for example, extrusion molding, injection molding, blow molding, casting, vacuum molding, calender molding, foam molding, or the like can be used.

〔The invention's effect〕

According to the present invention, in a plastic molded article made of an aliphatic polyester, the biodegradation rate of the surface portion thereof can be adjusted within the range of 90 to 10% of the biodegradation rate of the raw material aliphatic polyester alone. Therefore, since such a plastic molded article is well suppressed during use, decomposition of the biodegradable resin, that is, collapse of the molded article, and easily decomposes and disintegrates in an environment where microorganisms exist after disposal, It is possible to overcome the drawbacks of biodegradable plastics in which biodegradation and disintegration occur.

The following is an example of a molded article to which the method of the present invention can be preferably applied. That is, everyday items such as textiles, films, packing, packaging materials such as cases and bottles,
Agricultural and forestry materials such as tree planting pots and tree planting sheets.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples.

(Physical property test, biodegradation test method) The tensile elastic modulus described in Examples and Comparative Examples is JIS K.
-7113, the biodegradation test was carried out according to the enzymatic method, and the polyester degrading enzyme used was lipase which is widely present in nature such as microorganisms and animals and plants. Enzymatic procedure 1
As an example, slice a cross section of a sheet of a PCL-calcium carbonate blend with a thickness of 0.5 mm, and use a sliced piece with a thickness of 0.1 mm (100 mg containing PCL) as a sample, and the reaction composition is PCL-degrading enzyme Rhizopus alizus. lipase (sigma) 34.9unit, buffer (pH = 7.0) 0.2M-KH 2 PO 4 -Na 2
HPO ₄ (Wako Pure Chemical Industries, Ltd.) 2.0 ml, surfactant 0.1% -Plysur
0.5 ml of f · A210G (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and a total volume of 20.0 ml were shaken at 30 ° C. for 16 hours for biodegradation. After the reaction was completed, the reaction solution was filtered through No. 2 filter paper, the water-soluble total organic carbon content of the filtrate was measured, and the difference between the water-soluble total organic carbon content in the system without enzyme and the PL The total carbon content (TOC) of the water-soluble PCL hydrolysis product eluted in the reaction composition by the hydrolysis of the enzyme with PC was determined as the index of biodegradability of PCL and the blend.

Regarding the raw materials, polycaprolactone (PCL) is H-7 manufactured by Daicel Chemical Co., Ltd., cornstarch is cornstarch W (average particle diameter 16 μm) manufactured by Nippon Food Processing Co., and calcium carbonate is Sunlight-100 (average particle diameter manufactured by Takehara Chemical Industry Co., Ltd.). 7.2
μm) and Sunlite-2500 (average particle size 1.5 μm) were used.

Example 1 High speed mixing mixer (Super mixer SMG1 manufactured by Kawata Co., Ltd.)
Part of (00) was changed so that the temperature of the mixing tank could be raised to 250 ° C.

PCL 10kg and Sunlight-2500 10kg are put into this tank and mixed and heated. After a lapse of about 20 minutes, when the load on the rotary motor suddenly increased, the load was discharged to a low rotation cooling tank, and the rotation was continued to blow air to cool and solidify to obtain a granular blend.

The blended body was formed into a sheet by an extruder SE-65 (65φ, bent type) manufactured by Toshiba Machine Co., Ltd., and each test was conducted as a sample for a physical property test and a biodegradation test. The results are shown in Table-1.

Example 2 Example 1 except that 12 kg of PCL and 8 kg of Sunlight-2500 were used.
The same experiment was performed. The results are shown in Table-1.

Comparative Example 1 Example 1 except that 16 kg of PCL and 4 kg of Sunlight 2500 were used.
The same experiment was performed. The results are shown in Table-1.

Comparative Example 2 Example 1 except that 10 kg of PCL and 10 kg of Sunlight-100 were used.
The same experiment was performed. The results are shown in Table-1.

Comparative Example 3 Example 1 except that PCL was 12 kg and Sunlight-100 was 8 kg.
The same experiment was performed. The results are shown in Table-1.

Example 3 PCL 10 kg, Sunlight-2500 6 kg, corn starch 4 k
An experiment was performed in the same manner as in Example 1 except that g was used.

The results are shown in Table-1. Comparative Example 4 The experiment was performed in the same manner as in Example 1 except that PCL was 12 kg and corn starch was 8 kg. The results are shown in Table-1.

Comparative Example 5 PCL alone was formed into a sheet by an extruder SE-65 (65φ) manufactured by Toshiba Machine Co., Ltd., and its physical property test and biodegradation test were conducted. The results are shown in Table-1.

Claims (1)

[Claims] 1. A biodegradable aliphatic polyester containing inorganic and / or
Or, with 10 to 50 vol% of an organic filler, the average volume of the filler is changed in the range of 4.2 × 10 ^{-3 to} 65.4 μm ³ , and the biodegradation rate per unit volume is 90 to 10% of the aliphatic polyester. A method for controlling biodegradability of plastics, which is characterized in that