JP3420794B2 - Biodegradable resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a biodegradable resin composition. More specifically, it relates to a composition for producing a biodegradable plastics molded product having a high decomposition rate.

[0002]

2. Description of the Related Art Conventional synthetic plastics such as food packaging films, packaging containers, agricultural films, civil engineering sheets, etc.
It does not decompose in the natural environment for a long time, which adversely affects the environment. In recent years, research has been conducted to provide new biodegradable plastics that replace these synthetic plastics. For example, those derived from so-called biosynthesis such as polyhydroxybutyrate / polyhydroxyvallate copolymer, polycaprolactone,
Examples thereof include synthetic polymers such as aliphatic polyester, thermoplastic resin-starch mixture, thermoplastic resin-chitin or chitosan mixture.

However, some of these biodegradable plastics may take several years to decompose, and during that period, if the animals eat the discarded undegraded plastics, the animals will be damaged. However, it is not always satisfactory in terms of decomposition rate, and the development of biodegradable plastics having a high decomposition rate has been desired. In addition, previously, the inventors of the present invention reacted an ethylene / vinyl alcohol copolymer having a specific ethylene content and a specific melt index with a natural protein such as gelatin, collagen and casein and a polyfunctional alcohol. A patent application was filed for a biodegradable resin composition obtained by mixing an esterified product or an esterified protein derivative of the obtained protein (Japanese Patent Application No. 4-297724). However, even with this resin composition, the rate of decomposition of the molded product obtained in soil is not yet sufficiently satisfactory, and there is room for further improvement. Therefore, an object of the present invention is to provide a biodegradable resin composition having a high decomposition rate.

[0004]

The inventors of the present invention have made extensive studies in order to solve the above problems in view of the above situation.
As a result, they have found that a composition obtained by further mixing a water-soluble thermoplastic resin with a resin known as biodegradable plastics meets the above-mentioned object. That is, when the composition is discarded in water or soil, the water-soluble thermoplastic resin in the plastics dissolves or swells in water, in some cases the plastics collapse, and further bacteria that cause biodegradation It was found that it is possible to create an atmosphere that is easy to live in, and to increase the space where bacteria are inhabited by forming voids in the plastics, which can accelerate the biodegradation rate of the plastics, and thus the biodegradability of the present invention. The resin composition was completed.

That is, the gist of the present invention is that 20 to 80 parts by weight of biodegradable plastic and 80 to 2 of water-soluble thermoplastic resin are used.
A biodegradable resin composition obtained by mixing 0 parts by weight.

The biodegradable plastics used in the present invention is not particularly limited, and for example, the above-mentioned biosynthesis-derived polyhydroxybutyrate / polyhydroxyvallate copolymer, chemical synthesis-derived polycaprolactone, Examples include aliphatic polyesters, thermoplastic resin-starch mixtures, thermoplastic resin-chitin or chitosan mixtures, and thermoplastic resin-esterified protein mixtures.

The esterified protein used in the present invention is a carboxyl group of the side chain of the protein, which is obtained by reacting a natural protein such as plant-derived gluten, animal-derived collagen or gelatin with a polyfunctional alcohol. Examples thereof include an esterified product of a chain-extended protein, or an esterified protein derivative obtained by further reacting a functional group derived from a polyfunctional alcohol present in the side chain of the esterified product of the protein. Of these, esterified gelatin in which the protein is gelatin and derivatives thereof are preferably used.

Specific examples of the esterified protein derivative in the present invention include the following (Japanese Patent Application No. 4-297724). (1) A protein aqueous solution, a fine powder or a suspension thereof is reacted with an excess of a polyfunctional alcohol for esterification, and an esterified product of a protein in which a carboxyl group of a protein side chain is extended, (2) a polyfunctional compound Using a polyhydric alcohol as the alcohol, a protein derivative urethanized by reacting a compound having an isocyanate group with a hydroxyl group derived from a polyhydric alcohol present in a chain-extended side chain,
(3) A polyhydric alcohol is used as a polyfunctional alcohol, a compound having an epoxy group is reacted with a hydroxyl group derived from a polyhydric alcohol present in a chain-extended side chain, and then a resin derivative, and (4) ) An alcohol having an unsaturated bond is used as the polyfunctional alcohol, and a vinyl monomer is subjected to addition polymerization in the presence of a polymerization initiator in the unsaturated group derived from the alcohol present in the chain-extended side chain, or a synthetic high It is a protein derivative in which a molecule is graft-polymerized or an esterified product of a protein having the unsaturated group is graft-polymerized in a synthetic polymer.

In order to synthesize such an esterified protein, the first step is to react the carboxyl group of the side chain of the amino acids constituting the protein with a polyfunctional alcohol to extend the chain by esterification to give a protein. An esterified product of a protein having a polyfunctional alcohol-derived functional group in its side chain is prepared. Then, as a second step, an organic solvent such as toluene, dimethylformamide, ethyl acetate, tetrahydrofuran, cyclohexane, dimethylsulfoxide, etc., which has been used in the first step in a solvent which has conventionally been poor in affinity and used in the protein itself, was obtained. The resulting esterified product is combined with so-called conventional polymerization technology such as addition polymerization of raw material compound of epoxy resin or urethane resin or other polymerizable vinyl monomer, or graft polymerization with synthetic polymer to produce a protein derivative. .

In the present invention, examples of the thermoplastic resin which is mixed with starch, chitin or chitosan or esterified protein to form biodegradable plastics include polyethylene and ethylene / vinyl alcohol copolymers, preferably ethylene. / Vinyl alcohol copolymer. Particularly, in the ethylene / vinyl alcohol copolymer, the ethylene content is 10 to 70 mol%,
The saponification degree is 30% or more, preferably 80% or more. If the ethylene content is less than 10 mol%, the film moldability will be poor, and if it exceeds 70 mol%, the biodegradability will be poor. If the degree of saponification is less than 30%, the gas barrier property may be poor when formed into a film, and the application may be limited. Further, a material having a melt index of 0.2 to 30 under a load of 230 ° C. and 2160 g is an excellent material as a thermoplastic resin in the biodegradable resin composition of the present invention. If the melt index is less than 0.2 or exceeds 30, the film moldability is poor, which is not preferable. The mixing ratio of these thermoplastic resins with starch, chitin, chitosan, and esterified protein is usually 1 to 3 parts by weight of the thermoplastic resin, and starch, chitin, chitosan, esterified protein 1 to 3 are added.
0 parts by weight.

The water-soluble thermoplastic resin mixed for the purpose of increasing the rate of biodegradability is not particularly limited, but examples thereof include polyethylene oxide, polyvinylpyrrolidone resin and acrylic acid copolymer. As the acrylic acid-based copolymer, acrylic acid / acrylic acid ester copolymer, acrylic acid / methacrylic acid ester copolymer, methacrylic acid / acrylic acid ester copolymer,
Examples thereof include methacrylic acid / methacrylic acid ester copolymers. Among them, the weight average molecular weight is 50,000 to 10,000,000,
Preferably 100,000 to 3,000,000 polyethylene oxide,
A polyvinylpyrrolidone resin having a weight average molecular weight of 10,000 to 700,000 or the acrylic acid-based copolymer having a weight average molecular weight of 10,000 to 1,500,000, preferably 20,000 to 500,000 is preferably used. The combination of monomers in the acrylic acid-based copolymer and the composition ratio thereof are not uniquely determined because they differ depending on the intended use of the molded article, but for example, in the case of acrylic acid / acrylic acid ester copolymer, the composition ratio Is 1/9 to 5/5 (molar ratio).

The mixing ratio of the biodegradable plastics and the water-soluble thermoplastic resin is such that the biodegradable plastics 20 to 8 are mixed.
0 parts by weight and 80 to 20 parts by weight of the water-soluble thermoplastic resin are mixed to make 100 parts by weight. If the amount of the water-soluble thermoplastic resin exceeds 80 parts by weight, it will not function as the original biodegradable plastics, and the strength of the molded product will be deteriorated, so that favorable results cannot be obtained. In addition, the water-soluble thermoplastic resin is 20
If the amount is less than parts by weight, the feature of the present invention of increasing the rate of biodegradability becomes unclear. By appropriately adjusting the mixing ratio of the water-soluble thermoplastic resin to 20 to 80 parts by weight, the biodegradability rate can be increased to several weeks to several months.

According to this mechanism, when the biodegradable plastics obtained by molding the biodegradable resin composition of the present invention is discarded in water or soil, first, the water-soluble thermoplastic resin in the plastics becomes water. This is due to the fact that it dissolves or swells in, creates an atmosphere in which biodegradable bacteria are likely to live, and creates voids in the biodegradable plastics, increasing the space in which bacteria live. Further, even if the plastics are not biodegraded, the water-soluble thermoplastic resin in the molded article such as a film or sheet produced using the composition of the present invention dissolves or swells in water,
A molded product such as a film or a sheet is broken, and in some cases, it is disintegrated into granules and becomes smaller, and thus the biodegradability rate can be accelerated.

In the present invention, a mixing method which is usually used is adopted for mixing the biodegradable plastics and the water-soluble thermoplastic resin. For example, both may be mixed with a kneading machine such as a Banbury mixer, a multi-screw roll, and a screw type extruder. When a mixture of a thermoplastic resin and starch, chitin, chitosan or esterified protein is used as the biodegradable plastics, a water-soluble mixture is used when mixing the thermoplastic resin, starch, chitin, chitosan and esterified protein. A thermoplastic resin can also be kneaded.

In the composition of the present invention, if necessary, a plasticizer such as glycols, glycerins, ureas, a heat stabilizer, an ultraviolet absorber, a pigment and water can be appropriately mixed. The composition of the present invention is molded into a film or sheet by a method such as inflation, or formed into a molded product by a method such as injection and used for various purposes. Molded products such as films and sheets obtained from the composition of the present invention can have a faster decomposition rate in a natural environment such as water or soil than conventional biodegradable plastics. Therefore, for example, even after being used for fishing bait containers, food packaging materials, and other various packaging materials and then discarded, they can be naturally acclimated without adversely affecting the environment.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The biodegradability of the films obtained in Examples and the like in water or soil was evaluated by immersing three 50-micron-thick films cut into 10 cm × 10 cm in activated sludge water, or in the soil surface layer. The one embedded in a lower portion of about 10 cm was taken out every predetermined number of days, and the appearance thereof was visually observed and evaluated according to the following four grades. A. A film whose damage is over 80% of the film and does not retain its original shape. B. The degree of damage is 30 to 80% of the film, but the original shape is retained. C. The degree of damage is less than 30 of the film. D. Almost no damage.

Example 1 80 parts by weight of 3-hydroxybutyrate / 3-hydroxyvalerate copolymer (trade name: manufactured by Biopol ICI) and polyethylene oxide (weight average molecular weight 300,000)
20 parts by weight were mixed with a Henschel mixer to obtain a biodegradable resin composition of the present invention. Next, this composition was melt-mixed with a Banbury mixer, and a film having a thickness of 50 μm was obtained by inflation. Table 1 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

Comparative Example 1 A film having a thickness of 50 μm was obtained in the same manner as in Example 1 except that polyethylene oxide was not added. Table 1 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

[0019]

[Table 1]

Example 2 The present invention was prepared by mixing 30 parts by weight of an ethylene / vinyl alcohol copolymer-starch mixture (trade name: manufactured by Matabi Novamont) with 70 parts by weight of polyethylene oxide (weight average molecular weight 700,000) with a Henschel mixer. A biodegradable resin composition of was obtained. Then, in the same manner as in Example 1, a film having a thickness of 50 μm was obtained. Table 2 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

Comparative Example 2 A film having a thickness of 50 μm was obtained in the same manner as in Example 2 except that polyethylene oxide was not added. Table 2 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

[0022]

[Table 2]

Example 3 40 parts by weight of an aliphatic polyester (trade name: Bionole Showa High Polymer Co., Ltd.) and 60 parts by weight of polyethylene oxide (weight average molecular weight of 1.5 million) were mixed in a Henschel mixer to obtain the biodegradable resin of the present invention. A composition was obtained. Then, in the same manner as in Example 1, a film having a thickness of 50 μm was obtained. Table 3 shows the evaluation results of the disintegration property and biodegradability of the film in the activated sludge water.

Comparative Example 3 A film having a thickness of 50 μm was obtained in the same manner as in Example 3 except that polyethylene oxide was not added. Table 3 shows the evaluation results of the disintegration property and biodegradability of the film in the activated sludge water.

[0025]

[Table 3]

Examples 4 to 8 Table 4 shows biodegradable plastics and water-soluble thermoplastic resins.
The biodegradable resin composition of the present invention was obtained by mixing in the proportions shown in. Then, in the same manner as in Example 1, a film having a thickness of 50 μm was obtained. Table 4 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

[0027]

[Table 4]

Example 9 (Production of esterified gelatin) 45 parts by weight (dry weight) of alkali-treated gelatin (Konica Gelatin Co., Ltd., α gelatin having a molecular weight of about 100,000) was placed in a reactor equipped with a stirrer.
This was dissolved in 100 parts by weight of distilled water. Next, 50 parts by weight of allyl alcohol was added and reacted at 50 ° C. for 24 hours. In order to recover the esterified product, water as a solvent and excess allyl alcohol which did not participate in the reaction were evaporated under reduced pressure at 50 ° C., and subsequently, at 24 ° C. at 24 ° C.
It was completely dried and removed under reduced pressure for an hour. The obtained esterified product was again dissolved in 100 parts by weight of distilled water, and the same operation as above was repeated 3 times. As a result, about 91% of the carboxyl groups of 48 parts by weight of gelatin were gelatinized / allyl alcohol ester. A compound (esterified gelatin) was obtained.

(Production of Thermoplastic Resin-Esterified Gelatin Mixture) Ethylene / vinyl alcohol copolymer (ethylene content 25 mol%, saponification degree 99%, melt index (230 ° C., 2160 g load) 1.5 g / 10
Min) 100 parts by weight and esterified gelatin 20 obtained above
3 parts by weight of urea and 5 parts by weight of water were added, and the mixture was mixed a second time to obtain a biodegradable plastics composed of a thermoplastic resin-esterified gelatin mixture. .

(Production of Biodegradable Plastics Film) 60 parts by weight of the above biodegradable plastics and 40 parts by weight of polyethylene oxide (weight average molecular weight 300,000) are mixed in a Henschel mixer to obtain the biodegradable resin of the present invention. A composition was obtained. Next, this composition was melt-mixed with a Banbury mixer, and a film having a thickness of 50 μm was obtained by inflation. Disintegration of film in soil,
The results of evaluation of biodegradability are shown in Table 5.

Comparative Example 4 A film having a thickness of 50 μm was obtained in the same manner as in Example 9 except that polyethylene oxide was not added in the production of the biodegradable plastics film of Example 9. Table 5 shows the evaluation results of the disintegration property and biodegradability of the film in soil.

[0032]

[Table 5]

Example 10 The biodegradable resin of the present invention was prepared by mixing 50 parts by weight of the thermoplastic resin-esterified gelatin mixture obtained in Example 9 and 50 parts by weight of polyethylene oxide (weight average molecular weight 300,000) with a Henschel mixer. A composition was obtained. Then, in the same manner as in Example 1, a film having a thickness of 50 μm was obtained. Table 6 shows the evaluation results of the disintegration property and biodegradability of the film in the activated sludge water.
Shown in.

Comparative Example 5 A film having a thickness of 50 μm was obtained in the same manner as in Example 10 except that polyethylene oxide was not added. Table 6 shows the evaluation results of the disintegration property and biodegradability of the film in the activated sludge water.

[0035]

[Table 6]

[0036]

EFFECTS OF THE INVENTION Molded products such as films and sheets obtained by using the biodegradable resin composition of the present invention have a decomposition rate higher than that of conventional biodegradable plastics in a natural environment such as water or soil. Can be made faster. Therefore, for example, even after being used for fishing bait containers, food packaging materials, and various other packaging materials and then discarded, they can be naturally and quickly acclimated without adversely affecting the environment.

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Claims (8)

(57) [Claims] 1. A biodegradable resin composition obtained by mixing 20 to 80 parts by weight of biodegradable plastic and 80 to 20 parts by weight of a water-soluble thermoplastic resin. 2. The water-soluble thermoplastic resin has a weight average molecular weight of 5.
1 to 10 million polyethylene oxide.
The biodegradable resin composition described. 3. The biodegradable resin composition according to claim 1, wherein the water-soluble thermoplastic resin is a polyvinylpyrrolidone resin. 4. The biodegradable resin composition according to claim 1, wherein the water-soluble thermoplastic resin is an acrylic acid / acrylic acid ester copolymer or an acrylic acid / methacrylic acid ester copolymer. 5. The biodegradable resin composition according to claim 1, wherein the biodegradable plastic is a polyhydroxybutyrate / polyhydroxyvallate copolymer or polycaprolactone. 6. The biodegradable resin composition according to claim 1, wherein the biodegradable plastic is an aliphatic polyester. 7. The biodegradable resin composition according to claim 1, wherein the biodegradable plastic is a thermoplastic resin-starch mixture or a thermoplastic resin-esterified protein mixture. 8. The thermoplastic resin has an ethylene content of 10 to 7
The biodegradable resin composition according to claim 7, which is an ethylene / vinyl alcohol copolymer having a melt index of 0 mol% and a melt index under a load of 2160 g at 230 ° C.