JPH04202544A - Resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition having bio-degradability as well as excellent physical properties by dispersing graft-modified starch in a synthetic resin. CONSTITUTION:The objective resin composition having bio-degradability as well as excellent physical properties can be produced by compounding (A) a graft-modified starch having a grafting ratio of 0.1-150% (preferably 5-100%) and produced by reacting starch (preferably starch having a polyhedral granular form with small diameter, e.g. corn starch and rice starch) with a monomer (e.g. vinyl acetate and ethyl acrylate) in an organic solvent, water or their mixture in the presence of a graft-initiation agent such as redox agent at 10-100 deg.C (preferably 15-75 deg.C) to (B) a synthetic resin in an amount to get a resin composition having the concentration of A of 5-60% and, as necessary, adding plasticizers, unmodified starches, sugars, cellulose derivatives, proteins, fatty acids, oil and fat, etc.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a resin composition that imparts biodegradability to a synthetic resin and does not impair its physical properties. Biodegradation is the process of decomposition through the action of microorganisms (bacteria, fungi, etc.) or enzymes, and ultimately leads to complete disintegration. (1) Occurs due to partial contact with soil.

(Prior Art) As a method for imparting biodegradability to synthetic resins, Japanese Patent Application Laid-Open No. 49-55740 discloses that thermoplastic synthetic resins or thermosetting elastane resins dispersed in Biodegradable compositions that are easily susceptible to biological attack, including starch granules, and unsaturated fatty acids or derivatives thereof that have at least one double bond in one molecule as disclosed in Japanese Patent Publication No. 52-42187. characterized by the existence of
Biodegradable compositions have been proposed that include synthetic resins based on carbon-to-carbon bonds and small, regularly sized biodegradable particles such as natural starch granules.

(Problems to be Solved by the Invention) Although the method of dispersing starch granules in a synthetic resin exhibits biodegradability, the compatibility between the synthetic resin and starch is poor, and the physical properties of the synthetic resin are inferior.

In addition, in the method of blending unsaturated fatty acids with double bonds or their derivatives into natural starch, the compatibility between the synthetic resin and starch may be improved to some extent, or the unsaturated fatty acids may be absorbed by the bamboo shoots adsorbed to the starch. The compatibility cannot be said to be sufficient.

Therefore, there is currently no resin composition that is biodegradable and satisfies physical properties.

(Means for solving the problem) As a result of intensive studies to solve the above problem, it was discovered that by blending graft-modified starch with synthetic resin, it can be biodegradable and have physical properties. The invention was completed.

Examples of starch raw materials used to produce the modified starch of the present invention include wheat starch, corn starch, waxy corn starch, high amylose-containing corn starch,
Unmodified starch such as rice starch, potato starch, sweet potato starch, tapioca starch, sago starch, or starch-containing substances such as wheat flour, tapioca powder, corn flour, rice flour, or dextrinization, oxidation, acid treatment, pregelatinization treatment, Etherified, esterified, and crosslinked compounds can also be used. Preferably, starches stored above ground, such as corn starch and rice starch, which have small particle diameters and polyhedral shapes, or those obtained by classifying or crushing the above-mentioned starches and making them fine, are suitably used.

The graft-modified starch of the present invention includes vinyl acetate, vinyl formate, vinyl propionate, vinyl trifluoroacetate, t-
Butyl vinyl ether, vinyl trimethylsilyl ether, acrylamide, methacrylamide, acrylic acid,
Methacrylic acid, acrylic acid alkyl ester, methacrylic acid alkyl ester, acrylic acid hydroxyalkyl ester, methacrylic acid hydroxyalkyl ester,
Methoxyalkyl acrylate, methoxyalkyl methacrylate, ethoxyalkyl acrylate, ethoxyalkyl methacrylate, butoxyalkyl acrylate, butoxyalkyl methacrylate, methoxypolyethylene glycol acrylate, methoxypolyethylene glycol methacrylate, Acrylic acid polypropylene glycol ester, methacrylic acid polypropylene glycol ester, acrylic acid 2-hydroxy-3-chloropropyl ester, methacrylic acid 2-hydroxy-
3-chloropropyl ester, acrylic acid dimethylaminoethyl ester, methacrylic acid dimethylaminoethyl ester, acrylic acid diethylaminoethyl ester,
Diethylaminoethyl methacrylate, 2-hydroxy-3-trimethylammonium chloride propyl acrylate, 2-hydroxy-3-trimethylammonium chloride propyl acrylate, ethyltrimethylammonium acrylate chloride ester, ethyltrimethylammonium methacrylate chloride Ester, methacrylic acid glycidyl ester, acrylic acid tetrahydrofurfuryl ester, methacrylic acid tetrahydrofurfuryl ester, acrylic acid propyltrimethoxysilane ester, methacrylic acid propyltrimethoxysilane ester, acrylic acid chloride, methacrylic acid chloride, acrylic acid-
2-chloroethyl ester, methacrylic acid-2-chloroethyl ester, acrylic acid-2,3-dibromopropyl ester, methacrylic acid-2,3-dibromopropyl ester, acrylic acid tribromphenyl ester,
It is obtained by graft polymerization of monomers such as tribromphenyl methacrylate, acrylonitrile, styrene, maleic anhydride, and itaconic acid.

These graft polymerization reactions of starch and monomers are carried out by combining ceric salts, persulfates, persulfates and sulfites, or hydrogen peroxide and mole using organic solvents such as methanol, acetone, water, or mixed solutions thereof. Using a graft initiator such as a salt-based redox system, at 10-100℃
, preferably at 15 to 75°C according to a conventional method. It can also be performed using radiation or electron beams.

Grafting rate is 0.1-150%, preferably 5-100%
%. When the grafting rate is less than 0.1%, sufficient compatibility with the synthetic resin cannot be obtained, and when it is more than 150%, the biodegradability of starch is slightly reduced. Incidentally, the graft ratio referred to herein means the percentage of weight increase due to graft polymerization based on the raw material starch used.

The synthetic resins used in the present invention include polyethylene,
polyolefins such as polyisobutylene, polypropylene, vinyl polymers such as polyvinyl chloride, polyvinyl acetate, polystyrene: polyacrylic nitrile: polyvinyl rubber: substantially water-insoluble polyacrylic ester or polymethacrylic ester polyacetal polyamide, thermal Polycondensates and polyarylethers such as plastic polyesters, polycarbonates, and polyalkylene terephthalates: Thermoplastic polyimides, polyhydroxybutyrates: High molecular weight, substantially water-insoluble polyalkylene oxides, such as polymers of ethylene oxide or propylene oxide; Examples include copolymers and the like.

Furthermore, different types of known substantially water-insoluble thermoplastic copolymers and mixtures thereof may also be used; furthermore, polymers having polar groups such as ether, acid or ester groups are preferred.

The starch concentration of the graft-modified starch in the resin composition of the present invention is preferably 5 to 60%. If the starch concentration is less than 5%, good biodegradability cannot be obtained. Further, if the starch concentration is 60% or more, sufficient physical restraint cannot be obtained.

Additives other than the modified starch of the present invention may be added to the resin composition of the present invention. Examples of these include plasticizers, unmodified starches, sugars such as oligosaccharides and monosaccharides, cellulose derivatives such as carboxydimethylcellulose and alkylcellulose,
Examples include proteins such as casein, fatty acids, fats and oils, and the like.

Since the resin composition of the present invention is not subject to many restrictions during kneading, it can be mixed and molded by extrusion molding, injection molding, and calender molding.

(Function) The resin composition of the present invention is biodegradable and has physical properties because it contains graft-modified starch in which various polymers are graft-bonded to starch in a synthetic resin.

(Examples and Effects of the Invention) Preparation Example 1 2.5 kg of corn starch, 51 kg of water. Mohr salt 2.5g
, 13 ml of 1N sulfuric acid was mixed, and after stirring for 10 minutes, 625 g of vinyl acetate and 10 g of hydrogen peroxide were added.
After stirring and reacting at 40°C for 4 hours, washing with water, dehydration,
It was dried to obtain a polyvinyl acetate graft modified starch with a graft ratio of 18%.

Preparation Example 2 2.5 kg of corn starch, 51 kg of water. Mohr salt 2.5g
, 13ml of 1N sulfuric acid was mixed, and after stirring for 10 minutes, 625g of ethyl acrylate and 10g of hydrogen peroxide were mixed.
was added and stirred at 40°C for 4 hours to react, then washed with water,
It was dehydrated and dried to obtain polyethyl acrylate graft modified starch with a grafting rate of 20%.

Preparation Example 3 2.5 kg of corn starch, 51 kg of water. Mohr salt 2.5g
, mixed 13 ml of 1N sulfuric acid, stirred for 10 minutes, added 625 g of acrylonitrile and 10 g of hydrogen peroxide, stirred at 40°C for 4 hours to react, and washed with water.
It was dehydrated and dried to obtain polyacrylonitrile graft-modified starch with a graft ratio of 21%.

Example 1 The modified starch and unmodified corn starch obtained in Preparation Examples 1 to 3 were mixed in linear low-density polyethylene in an amount of 40% by weight, and then heat blended in a twin-roll mill. The kneaded dough was cooled and cut to obtain a masterbatch.

This masterbatch and linear low-density polyethylene were mixed to have various starch contents, and the cylinder diameter was 25mm5.
The mixture was supplied to a single screw extruder with L/D=24, and extrusion molded at a temperature of 160°C.

Example 2 The molded piece obtained in Example 1 was punched into a shape suitable for a tensile test using a punching die, and after conditioning in a constant temperature and humidity chamber, a tensile test was performed using a tensile tester to determine yield strength, breaking strength, Physical properties such as elongation at break were measured. The results are shown in Table 1.

Example 3 The test piece used in Example 2 was buried in activated sludge at 40°C for 1
After being left for 00 days, the condition was observed and the results are shown in Table 1.

The evaluation of the activated sludge test was as follows: Completely disintegrated - ○ Cracks occurred: △ No change: × From the results in Table 1, the resin composition of the present invention has both biodegradability and physical properties. I understand.

Claims (1)

[Claims] (1) A biodegradable resin composition in which graft-modified starch is dispersed in a synthetic resin.