JP3344760B2 - Collapsed molded foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collapsible foamed molded product, and more particularly to a sheet, a film, a packaging material (for example, a cup tray, a cushioning material, a protective material) mainly comprising starch and a polyvinyl alcohol resin. Disintegrable foamed molded articles such as sheets and protective films).

[0002]

2. Description of the Related Art In recent years, interest in environmental issues has increased,
For example, there is an increasing demand for the development of technology relating to disposal of synthetic polymer materials such as plastics. As one of them, attention has been focused on biodegradable plastics that can replace conventional petroleum plastics.

As a biodegradable plastic, US Pat. No. 4,138,784 discloses a composition comprising starch and an ethylene / acrylic acid copolymer (EAA) disclosed in JP-A-3-3.
No. 1333 discloses a composition comprising an ethylene / vinyl alcohol copolymer (EVOH) and a modified starch. A foamable material using a biodegradable plastic is disclosed in JP-A-2-298525. The foamable material described in this patent uses water as a foaming agent, but is insufficient in elasticity and compressive strength, for example, as a packing. Also, Japanese Patent Application Laid-Open No. 2-1
No. 4228 discloses a foamable material comprising a starch containing water and a synthetic thermoplastic polymer which is substantially insoluble in water. In Japanese Patent Publication No. 4-500833,
A biodegradable plastic foam article comprising starch and EAA and / or EVOH is disclosed.

[0004] Such a biodegradable plastic foam is produced by adding a plasticizer such as glycerin and a foaming agent to a starch / EVOH composition, melt-mixing and extrusion molding.
Although a foam having a low density, for example, 0.6 g / cc, is obtained, open cells and closed cells are mixed, the size of the cells is not uniform, and the holes through which the cells are removed are formed on the surface of the molded body. And only a molded article whose surface is uneven and rough can be obtained.

[0005]

SUMMARY OF THE INVENTION According to the present invention, even when a plasticizer such as glycerin is used, the cells are closed cells, the expansion ratio is high and the state of the surface of the molded article is good. It is intended to provide the body.

[0006]

Means for Solving the Problems The above-mentioned problems are attributable to starch, polyvinyl alcohol-based resin (hereinafter abbreviated as PVA),
Foaming agents, set comprising a plasticizer and dialdehyde compounds
Product and dialdehyde compound in terms of solid content,
0.2 to 3.0 parts by weight per 100 parts by weight of the composition
The problem is solved by a disintegrable foam molded article obtained by foaming the composition. In the molded article of the present invention, starch and PVA are used as biodegradable plastics. The weight ratio of starch to PVA is usually 10:90 to 90:10, preferably 2
0:80 to 80:20.

Various starches can be used, for example, corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch, rice starch, mame starch, kudzu starch, warabi starch Has starch, sis starch, etc .: physically modified starch (α-starch, fractionated amylose, heat-moisture treated starch, etc.): enzyme-modified starch (hydrolyzed dextrin, enzymatically decomposed dextrin, amylose, etc.): chemically degraded starch (acid-treated starch, hypochlorite) Chlorate oxidized starch, dialdehyde starch, etc.): Chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, crosslinked starch, etc.) and the like can be exemplified.

The PVA of the present invention includes not only partially saponified or completely saponified polyvinyl acetate but also vinyl esters and monomers copolymerizable therewith, such as ethylene, propylene, isobutylene, α-octene, α −
Dodecene, olefins such as α-octadodecene, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, unsaturated acids such as itaconic acid or its salts or mono- or dialkyl esters, acrylonitrile, methacrylonitrile, etc. Nitriles, amides such as acrylamide and methacrylamide, olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid or salts thereof, alkyl vinyl ethers, N-acrylamidomethylammonium chloride, allyltrimethylammonium chloride, dimethyl Compounds having a cationic group such as diallyl ammonium chloride, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene group, polyoxypro Ren group, but the copolymer saponified unsaturated monomer having a polyoxyalkylene group such as polyoxyethylene butylene group, not necessarily limited thereto. The degree of saponification of PVA is 60 to 100 mol%, preferably 80 to 100 mol%, and the degree of polymerization is 5 to 5.
It is necessary to select from the range of 00 to 4000, preferably 1000 to 3000.

As the plasticizer, polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, mannitol and sorbitol can be used. . The ratio of the plasticizer is 5 to 30 parts by weight, preferably 15 to 25 parts by weight based on 100 parts by weight of the total amount of starch and / PVA. Water may be used together with the plasticizer, and in this case, the total weight of water and the plasticizer is used in the above range.

Examples of the dialdehyde compound include glyoxal, glutaraldehyde, malonaldehyde and terephthalaldehyde. The amount of the dialdehyde compound was 0.2% in terms of solid content per 100 parts by weight of the composition.
To 3.0 parts by weight, preferably 1.0 to 2.0 parts by weight. By adding the dialdehyde, the starch and / or PVA are cross-linked, and the composition is thickened. As a result, a foam molded article having closed cells, a low density, and a good surface state can be obtained. It is considered something. If the dialdehyde compound is used in an amount exceeding the above range, the viscosity of the composition becomes too high and foam molding cannot be performed.

Known foaming agents can be used.
For example, azodicarbonamide, azobisisobutyronitrile, p-toluenesulfonyl hydrazide, and benzenesulfonyl hydrazide are suitable, and the addition amount thereof is preferably 1 to 3 parts by weight based on 100 parts by weight of the foaming composition. In the foaming composition used in the present invention, in addition to the above-mentioned components, various additives such as an ultraviolet stabilizer, a flame retardant, an antibacterial agent, an antioxidant, and Agents and the like can also be added.

[0012]

According to the present invention, a foam having a high foaming ratio and good surface condition having closed cells can be obtained.

[0013]

Next, the present invention will be described more specifically with reference to examples. Examples 1 and 2 and Comparative Examples 1 and 2 80% by weight of 12% water-containing constarch, PVA (degree of saponification 81.0 mol%, degree of polymerization 1700, particle size 2 mm or less) 2
A mixture of 0 parts by weight and 20 parts by weight of glycerin was compounded with a twin screw extruder to obtain a granular material. 100 parts by weight of the compound was dry-blended with 1 part by weight and 1.5 parts by weight of a 40% aqueous solution of glyoxal in terms of solid content, cross-linked with a ruder, and compounded again. Azodicarbonamide (a foaming agent) and calcium stearate were dry-blended to the crosslinked compound in the amounts shown in Table 1, extruded into a sheet, and foamed.

The conditions of each step are as follows. Compounded co-rotating twin screw extruder (diameter 30 mm, L / D = 30)
Processing temperature: 170 ° C Ruder cross-linking co-rotating twin-screw extruder (diameter 30 mm, L / D = 30)
Processing temperature: 150 ° C Extruded sheet foaming single-screw extruder (40 mm diameter) used Foam sheet die: width 150 mm, lip opening 1.0 mm Melt viscosity after crosslinking, foam sheet density, foam type, surface condition are shown in Table 1. Show. As comparative examples, examples in which the use of glyoxal is omitted and cases in which a large amount of glyoxal is blended are also shown.

[0015]

[Table 1]

Examples 3 to 4 70 parts by weight of a 12% aqueous constarch, 30 parts by weight of PVA (degree of saponification 96.5 mol%, degree of polymerization 1100, particle size under 10 mesh) and 20 parts by weight of glycerin were twin-screw extruder. Compound pelletized. To 100 parts by weight of the compound pellets, the dialdehyde shown in Table 2 was dry-blended at a solids content, crosslinked with a ruder, and again compound pellets were dry-blended at a solids content, crosslinked with a ruder, and again compounded. Azodicarbonamide and calcium stearate (StaCa) were dry blended in the amounts shown in Table 2,
It was extruded into a sheet and foamed. Table 2 shows the results.

[0017]

[Table 2]Example 3 Example 4 Glutardialdehyde 1.5(50% aqueous solution) Terephthalaldehyde (powder) 1.5(Weight part) Melt viscosity (poise) 7.5 × 1.0^Five 9.0 × 10^Five (160 ° C) Blowing agent (parts by weight) 2.0 2.0 StaCa * (parts by weight) 0.2 0.2 Foam sheet density 0.30 0.35(G / cc) Bubble type Independent Independent Bubble size uniformity Good Good Surface condition good goodSmooth smooth

Claims (2)

(57) [Claims] 1. A composition comprising starch, a polyvinyl alcohol resin, a foaming agent, a plasticizer, and a dialdehyde compound.
Product and the dialdehyde compound in terms of solid content
A disintegratable foamed molded article obtained by foaming a composition containing 0.2 to 3.0 parts by weight per 100 parts by weight of a product. 2. The disintegratable foamed molded article according to claim 1, wherein the dialdehyde compound is glyoxal.