JPH0570697A - Resin composition - Google Patents

Abstract

PURPOSE:To provide a resin composition, excellent in melt-moldability and strength and capable of naturally degrading the shape when allowed to stand in the open air and providing degradable resin molded products excellent in shape retaining properties even when polymer contained in a molded product absorbs moisture. CONSTITUTION:A resin composition is obtained by blending (A) 100 pts.wt. thermoplastic resin (e.g. a 2-20C olefinic polymer or a polystyrene-based polymer) with (B) 0.2-50 pts.wt. polyvinyl alcoholic resin having 4-50C alkyl group in the terminals and 50-3000, preferably 200-1000 viscosity-average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition having properties such as biodegradability in which it is slowly biodegraded when left outdoors and naturally disintegrates.

[0002]

2. Description of the Related Art Among various molding materials, water-soluble polymers such as polyvinyl alcohol are well known as materials having a disintegrating property that naturally collapses when left in the open after being molded into a predetermined shape. However, molded products of these water-soluble polymers have generally been molded from an aqueous solution because of poor melt moldability of the water-soluble polymers. In fields where molding accuracy is required, it has hardly been put to practical use. With respect to this drawback of poor melt moldability, various water-soluble polymers having heat-meltability while maintaining water-solubility have already been proposed. However, a single molded product of these water-soluble polymers has a drawback that when exposed to an environment containing water, the polymer constituting the molded product absorbs moisture and plasticizes, and its shape is easily changed. It was Further, it has been widely tried to knead a substance such as starch having biodegradability into a thermoplastic resin,
The compatibility of the thermoplastic resin and starch is poor, and the strength of the obtained molded product is remarkably reduced as compared with the original thermoplastic resin.

[0003]

DISCLOSURE OF THE INVENTION The present invention has good hot-melt moldability and strength, and has the characteristic of spontaneously degrading its shape when left outdoors, and the polymer constituting the molded article absorbs moisture. Even so, it is an object of the present invention to provide a disintegrating molded product excellent in shape retention.

[0004]

As a result of intensive studies to solve the above problems, the present inventors have found that the number of carbon atoms is 4-5.
It is composed of a polyvinyl alcohol-based resin (A) having a 0 (zero) alkyl group at its end (preferably at one end) and a thermoplastic resin (B), and the mixing ratio is 100 (B).
Polyvinyl alcohol-based resin (A) 0.
The resin composition, which is 2 to 50 parts by weight, has good hot melt moldability and strength, and has the property that it naturally collapses when left outdoors, and the polymer constituting the molded product absorbs moisture. It was found that the above object of excellent shape retention can be achieved, and the present invention has been completed.

The form of the resin composition of the present invention is that the polyvinyl alcohol resin (A) dispersed in the resin composition in the form of uniform and fine particles is first biodegraded by microorganisms in nature. It becomes porous, and as a result, the thermoplastic resin (B) is more likely to be decomposed, and as a result, it has a characteristic of spontaneously disintegrating when left outdoors, and each component constituting the composition is suitable for the purpose. To be selected.

The number of carbon atoms of the terminal alkyl group of the polyvinyl alcohol-based resin having an alkyl group at the terminal used in the present invention is preferably 4 to 50, more preferably 6 to 30, and most preferably 8 to 20. Are even more preferred. When the carbon number is less than 4, it is not so different from the unmodified polyvinyl alcohol and the dispersibility in the thermoplastic resin (B) is not good. Further, those having more than 50 carbon atoms are not preferable because the biodegradability of the polyvinyl alcohol resin is lowered and the time required for the intended morphological collapse is too long. Examples of the alkyl group used in the present invention include an alkyl group having 4 to 50 carbon atoms, a branched alkyl group, an alkylaryl group, and the like, which has a connecting group composed of oxygen, nitrogen or sulfur atoms. Is also included. The content of the vinyl alcohol unit in the molecule of the polyvinyl alcohol resin (A) used in the present invention is preferably 20 to 100 mol%, more preferably 30 to 99.5 mol%, and 40
˜99 mol% is even more preferred. The content of vinyl alcohol unit in the polyvinyl alcohol resin (A) is 2
If it is less than 0 mol%, the biodegradability of the molded product tends to decrease. The viscosity average degree of polymerization of the polyvinyl alcohol resin (A) of the present invention is preferably 50 to 3000, and 100 to
2000 is more preferable, and 200 to 1000 is even more preferable. If the viscosity average degree of polymerization of the polyvinyl alcohol resin (A) is more than 3000, the melt viscosity tends to be too high and the moldability tends to be lowered.

The polyvinyl alcohol resin (A) of the present invention may contain a copolymerized unit other than a terminal alkyl group and a vinyl alcohol unit. These copolymerized units are not particularly limited as long as they can be copolymerized with vinyl ester, and for example, α such as ethylene, propylene, n-butene, isobutene, 1-hexadecene, etc.
-Olefins, styrene, styrenes such as α-methylstyrene, vinyl chloride, vinylidene chloride, halogen-containing monomers such as tetrafluoroethylene, (meth) acrylic acid, fumaric acid, itaconic acid, crotonic acid, maleic acid,
Carboxylic acid-containing monomers such as maleic anhydride and salts thereof, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth ) 2-Ethylhexyl acrylate, (meth) acrylic acid esters such as stearyl (meth) acrylate, dimethyl fumarate, dimethyl itaconic acid, dimethyl maleate, monomethyl maleate, dimethyl crotonate, etc., methyl vinyl ether, Vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, lauryl vinyl ether and stearyl vinyl ether, sulfonic acid group-containing monomers such as vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid and the like , (Meth) acrylamide, N,
Amide group-containing monomers such as N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, Nt-butoxy (meth) acrylamide, Nt-octyl (meth) acrylamide and N-vinylpyrrolidone, dimethyl Amino group-containing monomer such as aminoethyl (meth) acrylamide, quaternary ammonium salt-containing monomer such as (meth) acrylamide-propyl-trimethylammonium chloride, vinylhydroxysilane, (meth) acrylic acid-3-trimethoxy Silyl group-containing monomers such as silylpropyl, allyl alcohol, dimethylallyl alcohol, hydroxyl group-containing monomers such as isopropenyl alcohol,
Examples thereof include copolymerized units derived from acetyl group-containing monomers such as allyl acetate, dimethylallyl acetate, and isopropenyl acetate. The content of these copolymerized units is not particularly limited, depending on the use of the molded product,
It is appropriately selected from 0 to 10 mol%.

Further, a plasticizer may be used in the polyvinyl alcohol resin (A) of the present invention to improve its moldability. As these plasticizers, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having a molecular weight of 600 or less, trimethylene glycol, tetramethylene glycol, pentamethylene glycol,
Hexamethylene glycol, glycols such as propylene glycol, glycerin, 1,3-butanediol,
Examples include, but are not limited to, diols such as 2,3-butanediol, trimethylolbropan, diglycerin, 3-methyl-1,3,5pentanetriol, and a small amount (10% or less) of water. Not a thing. Of these plasticizers, glycerin, ethylene glycol and the like are particularly preferable. The addition amount of these plasticizers is 30 parts by weight or less, preferably 20 parts by weight or less, and more preferably 10 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin (A).

As the thermoplastic resin (B) of the present invention, any thermoplastic resin which can be molded at a usual molding temperature of 270 ° C. or lower can be preferably used. Examples of these thermoplastic resins include olefin polymers having 2 to 20 carbon atoms, polystyrene polymers, polyvinyl chloride polymers, and the like. A thermoplastic resin having a molding temperature higher than 270 ° C. is not preferable because the polyvinyl alcohol resin (A) to be blended at the time of molding causes thermal decomposition.

As a method for blending the polyvinyl alcohol resin (A) and the thermoplastic resin (B) in the present invention, the polyvinyl alcohol resin (A) and the thermoplastic resin (B) are blended by melt-kneading. , A method of powder dry blending, a method of previously blending all of the thermoplastic resin (B) and a part of the polyvinyl alcohol resin (A), and a method of blending the remaining polyvinyl alcohol resin, polyvinyl alcohol resin (A )
Any of the methods in which the solvent is removed after blending and the thermoplastic resin (B) in a solution state can be used. Examples of the method for molding the resin composition of the present invention include press molding, extrusion molding, injection molding and blow molding. Examples of the shape of the blend used in the present invention include pellets, chips, flakes, and pulverized particles, but if troubles such as defective biting do not occur when charged into a molding machine, these shapes can be used. Other shapes do not matter. In addition, an antioxidant, an ultraviolet absorber, a lubricant, a colorant, a heat stabilizer and the like can be added to the resin composition of the present invention, if necessary. Further, other polymer compounds may be blended to the extent that the effects of the present invention are not impaired. The resin composition of the present invention is a resin composition which, when left outdoors, is slowly biodegraded and spontaneously disintegrates, and has uses as agricultural equipment such as agricultural mulch film, disposable shopping bags, disposable bottles and the like. Examples include molded products.

[0011]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following, "parts" and "%" mean "parts by weight" and "% by weight", respectively, unless otherwise specified. The tensile strength / elongation of the film shown in this Example is 50 mm for the distance between chucks, and 500 mm for the tensile speed in the direction perpendicular to the film-forming direction, for the film whose humidity was adjusted at 20 ° C. and 65% RH for 10 days. It is measured by a method of pulling at min.

Example 1 Commercially available low density polyethylene (melt index 7.2)
g / 10 min) 100 parts of a polyvinyl alcohol resin having an n-dodecyl group at one end and a degree of polymerization of 500 and a degree of saponification of 60 mol% is mixed and melt-extruded at 160 ° C. to form a film having a thickness of 100 μm. I got a film. Even when the obtained film was allowed to stand for 2 weeks under the conditions of a temperature of 20 ° C. and a relative humidity of 100% RH, no remarkable change in morphology was observed. Table 1 shows the tensile strength / elongation of the film and the morphological change after the film was buried in 30 cm underground for 6 months.

Example 2 20 parts of a polyvinyl alcohol resin having an n-dodecyl group at one end and a polymerization degree of 500 and a saponification degree of 88 mol% was blended with 2 parts of glycerin and a commercially available low density polyethylene (melt index). 7.2g / 10mi
n) 100 parts are mixed and melt-extruded into a film at 160 ° C.,
A film with a thickness of 100 μ was obtained. Even when the obtained film was allowed to stand for 2 weeks under the conditions of a temperature of 20 ° C. and a relative humidity of 100% RH, no remarkable change in morphology was observed. Table 1 shows the tensile strength / elongation of the film and the morphological change after being buried in a 30 cm underground for 6 months.

Comparative Example 1 Instead of the polyvinyl alcohol resin having an n-dodecyl group at one end and a degree of polymerization of 500 and a degree of saponification of 60 mol% used in Example 1, a polyvinyl alcohol resin having a degree of polymerization of 500 and a degree of saponification of 60 mol% was used. Example 1 using modified polyvinyl alcohol
Melt extrusion film formation was performed at 160 ° C. in the same manner as in 1. to obtain a film having a thickness of 100 μm. When the obtained film was allowed to stand for 2 weeks under the conditions of a temperature of 20 ° C. and a relative humidity of 100% RH, no remarkable morphological modification was observed. Tensile strength and elongation of the film,
Table 1 shows the changes in morphology after being buried in 30 cm underground for 6 months. Comparative Example 2 Instead of the polyvinyl alcohol resin having an n-dodecyl group at one end and a polymerization degree of 500 and a saponification degree of 60 mol% used in Example 2, a commercially available polymerization degree of 500 and a saponification degree of 8 were used.
Using 8 mol% of unmodified polyvinyl alcohol, melt extrusion film formation was performed at 160 ° C. in the same manner as in Example 1, and the thickness was 100.
A film of μ was obtained. The obtained film is heated at a temperature of 20 ° C.
No significant change in morphology was observed even after standing for 2 weeks under the condition of relative humidity of 100% RH. The tensile strength and elongation of the obtained film were significantly inferior to those of Example 1. Comparative Example 3 A film having a thickness of 90 μm was obtained by an aqueous solution casting method using only commercially available unmodified polyvinyl alcohol having a polymerization degree of 500 and a saponification degree of 88 mol%. When the obtained film was left for 2 weeks under the conditions of a temperature of 20 ° C. and a relative humidity of 100% RH, fusion between the films occurred. Comparative Example 4 Using only the commercially available low density polyethylene used in Example 1, melt extrusion film formation was performed at 160 ° C. in the same manner as in Example 1,
A film with a thickness of 100 μ was obtained. Even when the obtained film was allowed to stand for 2 weeks under the conditions of a temperature of 20 ° C. and a relative humidity of 100% RH, no remarkable change in morphology was observed. Table 1 shows the tensile strength / elongation of the film and the morphological change after the film was buried in 30 cm underground for 6 months.

[0015]

[Table 1]

[0016]

EFFECT OF THE INVENTION The resin composition of the present invention has good hot melt moldability and strength. When left outdoors, it naturally biodegrades and collapses in shape, and the polymer constituting the molded article absorbs moisture. Also has an extremely high industrial value in terms of excellent shape retention.

Claims (1)

[Claims] 1. A polyvinyl alcohol-based resin (A) having an alkyl group having 4 to 50 carbon atoms at the end and a thermoplastic resin (B), the blending ratio of which is thermoplastic resin (B) 10.
A resin composition containing 0.2 to 50 parts by weight of the polyvinyl alcohol-based resin (A) with respect to 0 cut parts by weight.