JPH05117507A - Biodegradable plastic product - Google Patents

Abstract

PURPOSE:To obtain a plastic product non-biodegradable usually, but developing adequate biodegradability only in its disposal by molding a biodegradable plastic composition containing an inorganic antibacterial agent capable of dissolving out antibacterial metal ion. CONSTITUTION:The objective plastic product can be obtained by molding, through extrusion or injection, a biodegradable plastic composition produced by incorporating (A) a raw material for the biodegradable plastics (e.g. a polyester producible by the action of microorganisms, chitin, starch polymer) with (B) a required amount of an inorganic antibacterial agent prepared by bearing the aqua ion or complex ion of an antibacterial heavy metal (e.g. silver, copper, zinc, lead) on an inorganic carrier (e.g. phosphate, hydroxyapatite, zeolite, inorganic laminar compound). This plastic product, which is non- biodegradable usually, is controllable in its biodegradability so as to develop biodegradability only in its disposal through gradual dissolution, due to the moisture in the soil, of the antibacterial metal ion contained therein, resulting in losing its antibacterial ability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable plastic product which is not always biodegradable and whose biodegradability can be controlled so that it exhibits sufficient biodegradability only at the time of disposal. is there.

[0002]

2. Description of the Related Art Recently, various biodegradable plastics products, which are decomposed by microorganisms such as bacteria, actinomycetes, and filamentous fungi in the soil when discarded, have been proposed due to problems in disposal of plastics products. .. (For example, Japanese Patent Laid-Open No. 53-
(See JP-A-130788, JP-A-54-140792, and JP-A-55-90518)

However, conventional biodegradable plastics products of this type are not kept in a sterile state during use and storage of the product, but are always exposed to attack from microorganisms. There is a fatal problem that it is biodegraded and deteriorates during use or storage. In particular, the better the biodegradability is, the more the deterioration phenomenon is remarkable, and the improvement of biodegradability and the prevention of biodegradability deterioration during use are contradictory. Product development was desired.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems and suppresses biodegradation during use or storage to prevent deterioration of biodegradable plastics products. It can be used and stored with a sense of security, and its biodegradability can be properly controlled so that it will not be rapidly biodegraded when it is disposed of in the soil and will not cause disposal problems. It was completed for the purpose of providing degradable plastics products.

[0005]

The biodegradable plastics product of the present invention made to solve the above problems is
It is characterized by being molded with a biodegradable plastics composition containing an inorganic antibacterial agent which elutes antibacterial metal ions.

The antibacterial metal ion used in the present invention is an aqua ion or complex ion of a heavy metal having antibacterial properties, and the heavy metal having antibacterial properties is, for example, silver,
Copper, zinc, etc. can be mentioned. Such an antibacterial metal ion generally has a broad antibacterial spectrum, exerts an antibacterial effect on biodegradable bacteria, actinomycetes, and filamentous fungi, and is resistant to biodegradable plastics products. Is given.

As the inorganic antibacterial agent capable of eluting the above antibacterial metal ions, known antibacterial agents are used for inorganic carriers such as phosphate, hydroxyapatite, zeolite, aluminosilicate, inorganic layered compound and soluble glass. One that holds metal ions and one of metal compounds such as silver, copper and zinc
One kind or two or more kinds can be selected. And, when this inorganic antibacterial agent is made to coexist with water, a minute amount of the antibacterial metal ion is eluted in water.

On the other hand, the biodegradable plastic containing the inorganic antibacterial agent is decomposed by microorganisms such as bacteria, actinomycetes or filamentous fungi when it is discarded in the soil. Polyesters, polysaccharides produced by microorganisms, natural polymers, chitins, protein-modified resins, polymers using starch, synthetic polymers such as polylactic acid, and blends of biodegradable plastics with other polymers ..

In order to mold a biodegradable plastics product with a biodegradable plastics composition containing an inorganic antibacterial agent that elutes antibacterial metal ions as described above, for example, biodegradable plastics can be molded. When a required amount of the powder of the inorganic antibacterial agent is kneaded into the raw material to form a biodegradable plastic composition and then molded by an extrusion molding method or an injection molding method, or when the molding method cannot be used like pullulan, The film may be formed by mixing powder of an inorganic antibacterial agent in the solution.

In the present invention thus molded, the biodegradable plastics product contains the above-mentioned inorganic antibacterial agent, and is provided with biodegradability during use or storage. Therefore, biodegradation does not occur even when exposed to attack from microorganisms, and biodegradability is effectively prevented. In particular, in the case of crystalline plastic, since the inorganic antibacterial agent gathers in the amorphous part where biodegradation first proceeds, even if the content of the inorganic antibacterial agent is small, its action and effect are sufficiently exerted. To be demonstrated.

When the biodegradable plastics product is buried in soil and disposed of, it is hardly biodegradable by the action of the inorganic antibacterial agent even by a large number of microorganisms present in the soil, but When it begins to be decomposed, it progresses rapidly. The reason for this is that the antibacterial metal ions gradually elute due to the water content in the soil, and the eluted ions react with the constituents in the soil to become insolubilized substances and lose their antibacterial properties. It is considered that the ions are likely to bind to the protein of the microorganism and gradually lose the active antibacterial metal ion due to the attack of the microorganism.

[0012] As described above, the biodegradable plastic product molded from the biodegradable plastic composition of the present invention whose biodegradability is controllable has excellent biodegradability at the initial stage of attack by microorganisms. The plastic can be used safely in packaging materials, containers, agricultural sheets, etc. without being significantly weakened by the attack of microorganisms, and no special consideration is required for long-term storage. Is also not biodegradable, thus greatly expanding the applications of biodegradable plastics. In addition, upon disposal, the rate of biodegradation is slow at the initial stage, but finally it is acceleratedly decomposed, so that the contradictory requirements of biodegradability and strength during use are satisfied at the same time.

[0013]

【Example】

(Example 1) 40% phosphoric acid aqueous solution 10 heated to 50 ° C.
Gradually add 53.3 g of calcium hydroxide and 280.8 g of aluminum hydroxide to 00 g and react at 60 ° C.
After holding for 5 hours at 30 ° C., the obtained slurry was cooled to 30 ° C., transferred to a ball mill, and 12 g of silver nitrate was added to the slurry.
The reaction was completed by kneading for a period of time. Then, the reaction slurry was filtered and the obtained filter cake was dried at 300 ° C. for 12 hours to obtain an antibacterial phosphate compound powder. The antibacterial phosphate compound powder thus obtained was added to a 3-hydroxybutyrate / 3-hydroxycivalate copolymer (manufactured by ICI, trade name: Biopol) to injection-mold a plate material, Test piece (1 x 1 x 40 mm)
The filamentous fungus that was prepared and cultured from the soil was contacted and cultured at 28 ° C., and the strength reduction rate (%) of the test piece after a predetermined period of time was measured, and the results shown in Table 1 were obtained. Comparing this result with the one without addition of the antibacterial phosphate compound powder, the one without addition of the antibacterial phosphate compound powder had a strength reduction rate of 80% after 30 days, 4
As shown in Table 1, the antibacterial phosphate compound powders added in Example 1 showed significant reductions of 90% after 0 days and 100% after 50 days. It was confirmed that the strength reduction rate can be controlled and arbitrarily delayed according to the addition amount of the phosphate compound powder.

[0014]

[Table 1] (Example 2) Similar to Example 1, silver nitrate powder was added to a 3-hydroxybutyrate / 3-hydroxycivalate copolymer (trade name: Biopol, manufactured by ICI) to measure the strength reduction rate of the test piece. The results obtained are as shown in Table 2, and it was confirmed that the strength reduction rate can be arbitrarily controlled according to the addition amount.

[0015]

[Table 2]

[0016]

As is apparent from the above description, the present invention suppresses biodegradation during use and storage and prevents deterioration of biodegradable plastics products, so that they can be used and stored at ease. The biodegradability can be appropriately controlled so that the biodegradability does not occur rapidly when the soil is disposed of in the soil and the disposal problem is not caused. Therefore, the present invention contributes greatly to industrial development as a biodegradable plastics product that eliminates the conventional problems.

Claims (3)

[Claims] 1. A biodegradable plastics product, characterized by being molded with a biodegradable plastics composition containing an inorganic antibacterial agent which elutes antibacterial metal ions. 2. The biodegradable plastics product according to claim 1, wherein the inorganic antibacterial agent is an inorganic carrier in which antibacterial metal ions are held. 3. The biodegradable plastics product according to claim 1, wherein the inorganic antibacterial agent is an antibacterial metal compound.