JPH0490339A - Biodegradable laminated molding - Google Patents

Abstract

PURPOSE:To obtain biodegradability and oxygen barrier properties by providing a thin layer composed of a saponified ethylene/vinyl acetate copolymer to at least the single surface of a molding composed of a composition of a thermoplastic resin and a starch type polymer. CONSTITUTION:A thin layer (B) composed of a saponified ethylene/vinyl acetate copolymer wherein ethylene content is 20-60mol.% and the saponification degree of a vinyl acetate unit is 60mol.% or more is provided to at least the single surface of a molding (A) composed of a composition wherein the wt. ratio of a thermoplastic resin to a starch type polymer is 80:20-20:80. The thermoplastic resin is a vinyl alcohol type resin. In this case, when the content of the starch type polymer in the composition constituting the molded article (A) is less than the abovementioned ratio, biodegradability is damaged and, when said content is more than said ratio, the mechanical properties of the composition become insufficient. When the ethylene content of the saponified ethylene/vinyl acetate copolymer used in the formation of the thin layer (B) is below 20mol.%, water resistance is lowered and, when the ethylene content exceeds 60mol.%, oxygen barrier properties become inferior. When the saponification degree of said copolymer is below 60mol.%, oxygen barrier properties also become inferior.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laminate molded product having both biodegradability and oxygen barrier properties.

Conventional technology Plastic molded products, including packaging materials such as plastic films and containers, are often discarded through other than regular disposal routes.In this case, the molded products maintain their shape for many years. As a result, serious waste pollution is occurring. Therefore, it is desirable that molded products that are likely to be discarded outdoors or in rivers are quickly decomposed by microorganisms in the soil or water after the purpose of use is achieved.

Against this background, development of biodegradable molded products has recently become active.

It is known that blending starch-based polymers is effective in making molded products biodegradable.

For example, JP-A-2-14228 discloses a compounded polymeric material obtained from a melt containing a water-containing decomposed starch and at least one substantially water-insoluble synthetic thermoplastic polymer. Examples of synthetic thermoplastic polymers include polyethylene, polyisobutylene, polypropylene, polyvinyl chloride, polyvinyl acetate, polystyrene, polyacrylonitrile, polyvinylcarbazole, polyamide, polyacrylic ester, polymethacrylic ester, ethylene-vinyl acetate copolymer, Ethylene-vinyl alcohol copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ABS copolymer, styrene-acrylonitrile copolymer polyacetal, etc. are used.

U.S. Patent No. 3,949,145 describes saponification degree of 85
1 to 4 parts by weight of polyvinyl alcohol with ~lOO mol%,
A film consisting of 8 parts by weight of starch and 1 to 5 parts by weight of glycerin, comprising a polyol-toluene diisocyanate prepolymer 0,1 containing free isocyanate-1 groups.
A degradable agricultural mulch coated with a water-resistant coating composition consisting of a mixture of 0.02 parts by weight and 1 part by weight of polyvinylidene chloride-acronitrile copolymer or 1 part by weight of polyvinylidene chloride containing a plasticizer. Film is shown.

The present applicant has also filed a patent application for a polyvinyl alcohol/starch film containing polyvinyl alcohol and starch with a degree of saponification of 93 mol% or more and stretched at least in the l-axis direction (patent application 6
3-307225).

Although it is not related to biodegradable molded products, Japanese Patent Publication No. 46-23911 discloses that a saponified ethylene-vinyl acetate copolymer dissolved in a solvent or dispersed in water is used for packaging materials to be treated. A method is shown for improving the gas permeation resistance of packaging materials by surface coating. Examples of packaging materials include polyethylene, polypropylene, polystyrene, polyvinyl chloride, paper, cellophane, and cellulose acetate.

Japanese Patent Publication No. 47-48489 discloses a method in which a saponified ethylene-vinyl acetate copolymer is dissolved in a specific alcohol/water solvent to prepare a coating solution, and the coating solution is applied to a substrate and dried. has been done. Examples of the base material include polyolefin, polyester, vinyl resin, cellulose natural polymer, metal, paper, and wood.

Problems to be Solved by the Invention A molded article made by blending a starch-based polymer with a thermoplastic resin exhibits biodegradability, so it can be employed as a waste countermeasure. However, the molded product is food (including beverages)
In the case of packaging materials for pharmaceutical products, packaging materials are required to have oxygen barrier properties, and even if thermoplastic resins such as saponified ethylene-vinyl acetate copolymers or polyvinyl alcohol are used, oxygen barrier properties are required. However, there is a problem in that when a starch-based polymer is blended into this and molded, the oxygen barrier properties are greatly reduced.

The film described in U.S. Pat. No. 3,949,145 is limited to use as an agricultural mulch film, and the water-resistant coating composition coated on the film consisting of polyvinyl alcohol, starch, and glycerin contains free isocyanate groups. Since it contains , it is not suitable for use in food packaging due to toxicity. In addition, a water-resistant coating composition consisting of a mixture of a polyol-toluene diisocyanate prepolymer containing free incyanate groups and a polyvinylidene chloride-acrylonitrile copolymer or a plasticizer-containing polyvinyl chloride inhibits biodegradability. In addition, the use of coating agents containing chlorine has a negative effect on incineration.

In view of these circumstances, the present invention was made with the object of providing a laminate molded product having both biodegradability and oxygen barrier properties.

Means for Solving the Problems The biodegradable laminate molded product of the present invention has an ethylene-vinyl acetate copolymer resin on at least one side of the molded product (A) made of a composition of a thermoplastic resin and a starch polymer. A thin layer (B) of a chemical compound is provided.

The present invention will be explained in detail below.

As the thermoplastic resin, vinyl alcohol resin is important. Vinyl alcohol resins include polyvinyl alcohol with various degrees of polymerization and saponification: vinyl acetate, short-chain or long-chain α-olefins, ethylenically unsaturated carboxylic acids, their salts, anhydrides, esters, amides, and nitriles. , vinyl ether, vinyl ester other than vinyl acetate, ethylenically unsaturated sulfonic acid, oxyalkylene group-containing monomer, etc. "Copolymerized" polyvinyl alcohol obtained by saponifying a copolymer: polyvinyl alcohol or "copolymerized""Post-modified" polyvinyl alcohol obtained by urethanization, acetalization, cyanethylation, oxyalkylene etherification, etc. of polyvinyl alcohol.

Among vinyl alcohol resins, the ethylene content is 20
~60 mol%, degree of saponification of vinyl acetate unit is 60 mol%
or more (especially 80 mol% or more, even 90 mol% or more)
saponified ethylene-vinyl acetate copolymer, degree of polymerization 50
Polyvinyl alcohol having a saponification degree of 0 to 2,000 (particularly 1,800 or less) and a saponification degree of 60 mol% or more is particularly important.

In addition to vinyl alcohol resins, thermoplastic resins include polyolefin resins, acrylic resins, polyamide resins, polyester resins, polyurethane resins, polystyrene resins, polyacetal resins, polycarbonate resins, diene resins, and cellulose. Other resins may also be used.

Examples of starch-based polymers include raw starches such as corn starch, potato starch, sweet potato starch, rice starch, kissaba starch, sago starch, kubioka starch, sorghum starch, rice starch, bean starch, arrowroot starch, bracken starch, lotus starch, and water chestnut starch: physical Modified starch (α-starch, fractionated amylose, heat-treated starch, etc.), enzyme-modified starch (
Hydrolyzed dextrin, enzymatically degraded dextrin, amylose, etc.), chemically modified starch (acid-treated starch, hypochlorite oxidized starch, dialdehyde starch, etc.), chemically modified starch derivatives (esterified starch, etherified starch, cationized starch) , cross-linked starch, etc.) Among chemically modified starch derivatives, esterified starches include acetate-esterified starch,
Etherified starches include allyl etherified starch, methyl ether, succinate starch, nitrate starch, phosphate starch, urea phosphate starch, xanthate starch, acetoacetate starch, etc. Examples of cationized starch include cationized starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, and reaction products of starch and 2-diethylaminoethyl chloride, starch and 2.3-epoxypropyltrimethylammonium. Examples of crosslinked starches such as chloride reactants include formaldehyde crosslinked starch, epichlorohydrin crosslinked starch, phosphoric acid crosslinked starch, and acrolein crosslinked starch.

In addition to thermoplastic resins and starch polymers, cellulose polymers, other polysaccharide polymers, protein polymers, and the like may be used in combination.

Examples of cellulose-based polymers include methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, hydroxybutylmethylcellulose, carboxymethylcellulose, acetylcellulose, and the like.

Other polysaccharide polymers include mannans such as elephant mannan, salep mannan, wood mannan, seaweed mannan, and yeast mannan, fructans such as inunone and levan, glycogen, caronin, laminaran, xylan, chitin, and chitosan. , pectic acid, hyaluronic acid, agarose, alginic acid, heparin, chondroitin sulfate, carrageenan, gum arabic, gum tragacanth,
Examples include karaya gum, guar gum, locust bean gum, meskit gum, gatchi gum, funori, and agar.

Examples of protein polymers include collagens such as gelatin and glue, casein, zein, gluten, blood albumin, and soybean protein.

From the composition of the above-mentioned thermoplastic resin and starch-based polymer, by any molding method including melt molding method (extrusion molding method, injection molding method, extrusion coating method, etc.), casting film forming method, A molded article iA) is molded. In this case, plasticizers, stabilizers, fillers, colorants,
A waterproofing agent or the like may also be added.

The ratio of the thermoplastic resin and starch polymer in the composition constituting the molded article (A) is 80.20 to 208 by weight.
0, especially 70: 30 to 30 near 0. If the ratio of starch-based polymer is too low, biodegradability will be impaired, while if it is too high, the mechanical properties of the molded product will be insufficient. do. However, depending on the application, it may be acceptable to deviate slightly from the above blending ratio.

The shape of the molded product FA+ is arbitrary, such as a film, sheet, tape, tube, bottle, training vibrator, or strand. After forming, secondary processing such as vacuum forming, stretching, bag making, rolling, embossing, and splitting can be performed.

In the present invention, a thin layer of saponified ethylene-vinyl acetate copolymer (
Provide Bl.

The saponified ethylene-vinyl acetate copolymer used to form the thin layer (B) desirably has an ethylene content of 20 to 60 mol%, a degree of saponification of vinyl acetate units of 60 mol% or more, and an ethylene content of 20 to 60 mol%. If it is less than mol %, water resistance will be insufficient, and if it exceeds 60 mol %, oxygen barrier property will be insufficient. When the degree of saponification is less than 60 mol%, oxygen barrier properties are also insufficient.

The thickness of the thin layer (B) is 0.5 to 15 μm, especially 1 to 10 μm.
μm, more preferably 1 to 8 Ltrn,
If the film thickness is too thin, oxygen barrier properties will be insufficient, while IS
When it exceeds .mu.m, even though it is advantageous in terms of oxygen barrier properties, biodegradability decreases.

Since the film thickness is thin, the thin layer (B) can be formed by applying a solution of a saponified ethylene-vinyl acetate copolymer dissolved in a solvent to the molded product (A) by coating, dipping, spraying, or other means. conduct.

The biodegradable laminate molded product of the present invention is particularly useful as a packaging material for foods (including drinks and seasonings) or pharmaceuticals,
It is also useful as a packaging material for industrial chemicals, fertilizers, fragrances, and other products that require oxygen barrier properties and aroma retention properties. Moreover, it can be used not only as a packaging material but also for various purposes.

Function Molded product (Al is made of a composition of a thermoplastic resin and a starch-based polymer, so while ensuring the necessary strength, it exhibits favorable biodegradability due to the presence of the starch-based polymer.

The thin layer (B) of the saponified ethylene-vinyl acetate copolymer provided on at least one side of the molded product (A)
It imparts oxygen barrier properties to the molded product (Al) without impairing its biodegradability.In addition to oxygen barrier properties, it also has properties such as fragrance retention, oil resistance, chemical resistance, antistatic properties, and heat retention. When the molded product (Al) itself does not have water resistance, the thin layer (B) also plays the role of improving water resistance.

Example Next, the present invention will be further explained with reference to Examples.

Hereinafter, "parts" refer to parts by weight.

Example 1 "Ki" 4th Section" Phantom - Ethylene content 44 mol%, degree of saponification of vinyl acetate unit 9
40 parts of 9.0 mol% saponified ethylene-vinyl acetate copolymer, 55 parts of corn starch and 20 parts of serine
The mixture was mixed in a Henschel mixer, then fed into a twin-screw extruder and extruded linearly at a temperature of 170°C to form pellets.

The pellets were then fed into a single-screw extruder and extruded from a T-die at a cylinder temperature of 160°C and a goose temperature of 150°C to obtain a molded product (A) consisting of a film with a thickness of 50 μm.
I got it.

Book 1"l- Ethylene content 29 mol%, degree of saponification of vinyl acetate unit 9
9.6 mol% of saponified ethylene-vinyl acetate copolymer was dissolved in a mixed solvent of water/isopropanol at a weight ratio of 50,150 to prepare a solution having a concentration of 15% by weight.

Apply this solution to the above molded product (A) using an applicator.
It was coated on both sides of the film and dried with hot air to form a thin layer (Bl).

The thickness of each thin layer (Bl) was 5 μm on a dry basis.

The oxygen permeability of the resulting laminated molded product was measured, and the product was buried in soil and its condition was examined after 3 months, 6 months, and 1 year.

Example 2 A laminate molded product was obtained by repeating the thin layer (Example except that the thickness of B+ was 2 μm on a dry basis) and evaluated.

Comparative Example 1 The molded article (A) in Example 1 (without the thin layer (B)) was evaluated.

Comparative Example 2 Molded product of Example 1 [Both sides of Al were coated with polyvinylidene chloride emulsion to a thickness of 5 μm each on a dry basis]
A coating layer was formed and evaluated.

Table 1 shows the results of Examples 1 and 2 and Comparative Examples 1 and 2 described above.

Table 1 Note 1. The unit of thickness of thin layer (B) is μm.

Note 2. Oxygen permeability is measured at 25°C and 75%RH. Is the unit cc/rr? -24hr-atm.

Note 3. The meanings of the symbols in the biodegradable tank are as follows.

0: No pitting change A: Cracks B: Many cracks C: Numerous holes and cracks Example 3 - Ethylene content 38 mol%, degree of saponification of vinyl acetate unit 9
40 parts of 9.0 mol% saponified ethylene-vinyl acetate copolymer, 60 parts of tapioca starch, and 15 parts of glycerin
After mixing in a Henschel mixer, the mixture was fed to a twin-screw extruder and extruded linearly at a temperature of 180°C to form pellets.

This pellet was then fed to a single screw extruder and extruded from a T-die at a cylinder temperature of 170°C and a goose temperature of 160°C to obtain a molded product [A] consisting of a film with a thickness of 50 μm.
I got it.

[Ethylene content 38 mol%, saponification degree of vinyl acetate unit 9
9.6 mol% of saponified ethylene-vinyl acetate copolymer was dissolved in a mixed solvent of water/n-propertool at a weight ratio of 40/60 to prepare a solution with a concentration of 10% by weight.

This solution was applied to the above molded article (Al
was coated on both sides of the film and dried with hot air to form a thin layer (B).

The thickness of each thin layer (Bl was 3 μm on a dry basis).

The oxygen permeability of the resulting laminated molded product was measured, and the product was buried in soil and its condition was examined after 3 months, 6 months, and 1 year.

Comparative Example 3 The molded article (A) in Example 3 (without the thin layer (B)) was evaluated.

Example 4 80 parts of low-density polyethylene (F-161 manufactured by Mitsubishi Kasei Corporation) with a melt index of 6 g/lo and 20 parts of oxidized starch were mixed in a Henschel mixer and then transferred to an extruder. Once supplied, the pellets are made into pellets, and then the pellets are supplied to an extruder and extruded from a T-die at a cylinder temperature of 190°C and a goose temperature of 180°C to a thickness of 50 LL.
A molded article (A) consisting of a film of m was obtained.

! The saponified ethylene-vinyl acetate copolymer solution of Example 1 was applied to both sides of the molded product (Al) and dried with hot air to form a thin layer (B). The thickness of each was 5 μm on a dry basis.

艷I The oxygen permeability of the obtained laminated molded product was measured, and the product was buried in the soil and its condition was examined after 3 months, 6 months, and 1 year.

The results are shown in Table 2.

Comparative Example 4 The molded article (A) in Example 4 (without the thin layer (B)) was evaluated.

The results of Examples 3 and 4 and Comparative Examples 3 and 4 described above are shown in Table 2.

Table 2 Note 1. Thin layer (B+thickness unit is μm.

Note 2. Oxygen permeability is measured at 25°C and 75%RH. The unit is cc/rn”・24hr-atll.

Note 3. The meaning of the biodegradable width symbol is as follows.

0 No change A, cracks B Many cracks C: Innumerable holes and cracks Example 5 Polymerization degree 1700, saponification degree 99 mol% polyvinyl alcohol 40 parts, corn starch 60 parts part, glycerin 20
A molded product (A) consisting of a film having a thickness of 50 parts was obtained by casting a composition consisting of 500 parts of water and 500 parts of water onto a drum, drying and peeling.

LIL The saponified ethylene-vinyl acetate copolymer solution of Example 1 was applied to both sides of the molded article (A) and dried with hot air to form a thin layer (B). The thickness of the thin layers CB) was in each case 4 μm on a dry basis.

j Oxygen permeability of the obtained laminate molded product (25°C, 75%RH
) is 2 ce/m' -24hr-atll
Met. When this was buried in the ground, countless holes and cracks were found within a year.

Effects of the Invention The biodegradable laminate molded product of the present invention not only exhibits excellent oxygen barrier properties, but also has sufficient strength and other properties when used, but after the purpose of use is achieved, it does not disintegrate into soil or water. It is quickly decomposed by microorganisms.

In addition, the biodegradable laminate molded product of the present invention also has properties such as aroma retention, oil resistance, chemical resistance, antistatic property, and heat retention.

Claims (1)

[Claims] 1. A thin layer (B) of a saponified ethylene-vinyl acetate copolymer is provided on at least one side of a molded article (A) made of a composition of a thermoplastic resin and a starch polymer. A biodegradable laminate molded product. 2. The biodegradable laminate molded product according to claim 1, wherein the thin layer (B) has a thickness of 0.5 to 15 μm. 3. The weight ratio of thermoplastic resin and starch polymer in the composition constituting the molded article (A) is 80:20 to 2.
The biodegradable laminate molded product according to claim 1, wherein the ratio is 0:80. 4. The biodegradable material according to claim 1, wherein the saponified ethylene-vinyl acetate copolymer constituting the thin layer (B) has an ethylene content of 20 to 60 mol% and a degree of saponification of vinyl acetate units of 60 mol% or more. Laminated molded product. 5. The biodegradable laminate molded product according to claim 1, wherein the thermoplastic resin is a vinyl alcohol resin. 6. The biodegradable laminate molded product according to claim 1, which is a packaging material for food or medicine.