JP3344762B2 - Method for producing biodegradable resin 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 biodegradable resin foam, and more particularly, to a sheet, a film, a packaging material (for example, a cup tray, a cushion material) comprising starch and vinyl alcohol resin particles as main components. , A protective sheet, a protective film, etc.).

[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. Also,
Raw starch contains water, and when kneaded under high pressure by an extruder, the starch becomes gelatinized and melts, and expands when the melt is left under normal pressure. When such a foam is used as an industrial material for buffering, the water resistance and strength are significantly insufficient.

[0005]

An object of the present invention is to provide a biodegradable resin foam using hydrated starch and hydrated vinyl alcohol resin, which has sufficient water resistance and strength even at a high expansion ratio. It is.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have made intensive studies. As a result, it is manufactured by a method of melting and foaming a composition in which a starch-based polymer containing water, a vinylic resin containing water, a nonionic surfactant, and an organic filler are further added with a thickener as required. The present inventors have found that the above-mentioned problems can be solved by the obtained foam, and have completed the present invention.

[0007] That is, the present invention is manufactured by mixing a starch-based polymer having a water content of 5 to 30% by weight, a vinyl alcohol-based resin having a water content of 5 to 30% by weight, a nonionic surfactant, and an organic filler. And the total water content is 5 to 30
The present invention provides a biodegradable resin foam characterized by melting and foaming a composition of which weight percent is contained. More specifically, in the present invention, as described above, a starch-based polymer having a water content of 5 to 30% by weight and a vinyl alcohol-based resin having a water content of 5 to 30% by weight are used as starting materials, and a nonionic surfactant is added thereto. A biodegradable resin foam, which is produced by further mixing a thickener as required with an organic filler, and melts and foams a composition whose total water content is controlled to 5 to 30% by weight. Is the gist. Hereinafter, the present invention will be described in detail.

In the foam of the present invention, a starch-based polymer and a vinyl alcohol-based resin are used as the biodegradable resin. The weight ratio of the starch-based polymer to the vinyl alcohol-based resin is usually from 2: 8 to 8: 2. When the proportion of the starch-based polymer is too small, the biodegradability or the disintegration property is impaired, while when the proportion is too large, the mechanical properties of the foam become insufficient. The ratio of the biodegradable resin, that is, the starch-based polymer and the vinyl alcohol-based resin in the composition is 40 to 95% by weight, preferably 50 to 9% by weight.
0% by weight.

[0009] Starch-based polymers include raw starch (corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tapioca starch, sorghum starch, rice starch, mame starch, kuzu starch, warabi starch. Hishi starch, etc.): Physically modified starch (α-starch, fractionated amylose, wet heat-treated starch, etc.): Enzymatically modified starch (hydrolyzed dextrin, enzymatically decomposed 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, crosslinked starch, etc.), and mixtures of two or more thereof are used. Among the chemically modified starch derivatives, the esterified starches include acetate esterified starch, succinic esterified starch, nitrated esterified starch, phosphorylated esterified starch, urea phosphorylated esterified starch, xanthated esterified starch, and acetoacetated starch. Examples of etherified starch such as acetic acid-esterified starch include allyl etherified starch, methyl etherified starch, carboxymethyl etherified starch, hydroxyethyl etherified starch, and hydroxypropyl etherified starch. Reaction product of -diethylaminoethyl chloride, and reaction product of starch and 2,3-epoxypropyltrimethylammonium chloride.

The vinyl alcohol resin used in the present invention includes a partially or completely saponified polyvinyl acetate, that is, a polyvinyl alcohol (PVA) resin or a saponified ethylene-vinyl acetate copolymer (EVOH). No. In PVA-based resins, vinyl esters and monomers copolymerizable therewith, such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-
Olefins such as octadodecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and salts thereof or mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, and acrylamide , Amides such as methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, N-
Compounds having a cationic group such as acrylamidomethylammonium chloride, allyltrimethylammonium chloride, dimethyldiallylammonium chloride, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, polyoxyethylene group, polyoxypropylene group, polyoxybutylene group, etc. However, the present invention is not limited thereto, but includes saponified copolymers of unsaturated monomers having an oxyalkylene group. Further, it may be what has been so-called "post-modified" such as oxyalkylene etherification, cyanoethylation, acetalization, urethanization, and esterification. The saponification degree of the PVA-based resin is 50 to 100 mol%, preferably 70 to 100 mol%.
It is necessary to select from 100 mol% and the degree of polymerization from 300 to 5000, preferably from 700 to 3000.

In EVOH, the proportion of ethylene is 10
６０60 mol%, preferably 20-60 mol%. The saponification degree is at least 60 mol%, preferably at least 90 mol%. EVOH, unless it impairs the spirit of the present invention,
Other copolymerizable monomers, for example, other α-olefins, ethylenically unsaturated carboxylic compounds (acids, anhydrides, salts, esters, amides, nitriles, etc.), vinyl ethers, vinyl esters other than vinyl acetate, ethylene It may be modified with an unsaturated sulfonic acid compound (acid, salt, etc.), an oxyalkylene group-containing monomer, or the like. Moreover, what is called "post-modified" such as oxyalkylene etherification, cyanoethylation, acetalization, urethanization and the like may be used.

The reasons for controlling the water content of the starch-based polymer and the vinyl alcohol-based resin to 5 to 30% by weight and the water content of the whole composition to 5 to 30% by weight, preferably 10 to 20% by weight are as follows. It is. The water contained in the starch has an effect on melt plasticization, and the water in the vinyl alcohol-based resin has an action of disturbing its crystallinity, so that the plasticization can be carried out immediately. When mixing the hydrated starch-based polymer with the hydrated vinyl alcohol-based resin, the water is more pre-hydrated than the starch or vinyl alcohol, which is added later to the anhydrous or low-hydrated powder of the starch polymer or vinyl alcohol-based resin. Mixing the system resin has better miscibility, and a foam having excellent physical properties can be obtained. As the water-containing method, any method such as directly spraying water on anhydrous or low-water-containing powder, or once melting the powder and mixing the water under pressure can be adopted. Some PVAs are dissolved in water depending on the varieties, but they are practically acceptable. However, in the present invention, it is advantageous to control the water content, the degree of saponification, the degree of polymerization, the particle size, etc., so that the water-containing PVA maintains the particle shape. In a system without an organic filler, the foamability of the composition is poor, and a foam is produced in a system in which an organic filler coexists as in the present application. If the water content is too high, the foam tends to shrink, so it is desirable to control a relatively small water content. If the water content is lower than the lower limit, uniform foaming becomes difficult in any case, while if the water content is higher than the upper limit, the foam density decreases.

Known nonionic surfactants can be used. Among them, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene block polymer, polyoxyethylene alkyl amine ether, ether type nonionic surfactant such as polyoxyethylene lanolin alcohol ether, Particularly preferred for the production method of the present invention. Nonionic surfactants are
0.5 to 10% by weight of the composition, preferably 2 to 5% by weight
It is. If the content is less than 0.5% by weight, bubbles are destroyed,
Since water vapor escapes, it is difficult to obtain a product having a small density. If the content exceeds 10% by weight, the viscosity of the composition decreases,
Insufficient stabilization of the bubbles results in non-uniform bubble sizes.

As the organic filler, a natural animal or plant material is useful, and any shape of a fibrous material, a powder, or a particle may be used. Examples thereof include cotton, hemp, pulp, husk, and sawdust. The use ratio of the organic filler is 1 to 50% by weight, preferably 5 to 30% by weight of the whole composition. The thickening agent to be added to the composition used for producing the foam of the present invention is used to maintain the melt viscosity of the composition at the time of melting at a certain level or more. Alternatively, those having an action of crosslinking a vinyl alcohol resin can be used. For example, boric acid; borax; glyoxal, malonaldehyde, succinaldehyde, glutaraldehyde, adipaldehyde, malealdehyde, 2-pentene-1,5-dialdehyde, o-phthaldialdehyde, isophthaldialdehyde, terephthaldi Dialdehydes such as aldehydes; formaldehyde; epichlorohydrin; acrolein; phosphorus oxychloride; trimetaphosphoric acid; It is practical that the compounding amount of the thickener is in the range of 0.05 to 5% by weight in the composition.

The effect of the present invention can be achieved when the molten composition at the time of molding, particularly at the time of injection molding, has a certain viscosity or more. The composition used in the present invention is 5 ° C at 160 ° C.
The melt viscosity after separation is 10,000 poise or more. Therefore, the amount of the thickener is adjusted so that the mixture exhibits the above-mentioned melt viscosity under the above-mentioned conditions.

[0016] In addition to the above components, the foaming composition used in the present invention may contain, depending on the desired properties and use of the foamed molded article,
Various additives such as an ultraviolet stabilizer, a flame retardant, an antibacterial agent, an antioxidant, a lubricant, a crosslinking aid, and the like can be added.

In the present invention, the composition can be foamed in the same manner as in the conventional foaming method, and a polyolefin or polystyrene extrusion or injection foaming apparatus can be used. It is also possible to mix all the components of the composition of the present invention, supply them to an extrusion or injection foaming apparatus, melt them, and extrude them directly to obtain a foam, but all or a part of the composition is fed to an extruder. A method of supplying and performing melt-kneading, once forming compound pellets, then mixing the compound pellets and the remaining components of the composition, and supplying the resulting mixture to an extrusion or injection foaming apparatus to obtain a foam is suitably adopted. .

[0018]

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

[0019]

Next, the present invention will be described more specifically with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 Potato starch having a water content of 15.2% 82.5 parts, PVA having a water content of 20.0% (saponification degree 98.5 mol%, polymerization degree 1100, average particle diameter 1 mm) 37,5 parts and Moisture content 1
2.3% recycled newspaper pulp (average particle size 2 mm) 20
Parts of a nonionic surfactant [polyoxyethylene nonyl phenyl ether (HLB = 17)] (part ratio: 15.8%) with a twin-screw extruder (30 mm in diameter,
(L / D = 30) at a temperature of 160 ° C. from a strand die having a nozzle having a diameter of 5 mm to obtain a foam by extrusion molding. The properties of the foam are shown in Table 1. Example 2 The same experiment as in Example 1 was performed except that EVOH (ethylene content: 44 mol%, saponification degree: 99.4 mol%, average particle size: 3 mm) was used instead of PVA. The results are shown in Table 1.

[0020]

[Table 1] Foam quality Example 1 Example 2 Foaming state ○ ○ Cell structure Independent Cell size (mm) 0.7 0.7 Density (g / cc) 0.06 0.06

Examples 3-5, Comparative Examples 1-2 Constarch having a water content of 12.8%, EVOH having a water content of 20.0% (ethylene content 38 mol%, saponification degree 99.4)
Mol%), a nonionic surfactant [polyoxyethylene nonylphenyl ether (HLB = 17)], and boric acid were charged into a Henschel mixer at the ratios shown in Table 2 and mixed. In the mixture, rice flour of 200 mesh under (moisture content 9.5%), hemp fiber of cut length 2mm (moisture content of 10.0%), pulp powder of 300 mesh under (moisture content of 8.0%) Were tumbled at the ratios shown in Table 2. The mixture was fed to a twin-screw extruder (diameter 30 mm, L / D
= 30) using a strand die having a nozzle of 5 mm in diameter at a temperature of 160 ° C to produce a foam. The properties of the foam are shown in Table 2. As a comparative example, a case where no organic filler was added was shown.

[0022]

Composition: (parts) Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Hydrous corn starch 68.8 91.7 68.8 68.8 91.7 Hydrous EVOH 50.0 25.0 50.0 50.0 25.0 Nonionic surfactant 2 2 2 2 2 Bor Acid 0.5 0.5 0.5 0.5 0.5 Rice flour 20.0 Hemp fiber 10.0 Pulp powder 30.0 Moisture content (%) of the entire composition 14.6 13.7 14.0 15.5 14.0 Quality of foam: Foaming state ○ ○ ○ × × Cellular structure Independent Independent--Air bubbles Size (mm) 0.6 1.0 0.5 − − Density (g / cc) 0.07 0.08 0.07 − − ○: Good foaming state ×: Poor foaming state There are some places where foaming occurs but no foaming.

Examples 6-8, Comparative Examples 3-4 Potato starch having a water content of 15.2%, water content of 25.0%
EVOH (ethylene content 44 mol%, saponification degree 99.
4 mol%), PVA having a water content of 30.0% (a saponification degree of 9)
8.2 mol%, degree of polymerization 1400), nonionic surfactant [polyoxyethylene nonyl phenyl ether (HL
B = 17)] and boric acid were charged into a Henschel mixer at the ratios shown in Table 3 and mixed. The mixture is melt-kneaded using a twin-screw extruder (diameter 30 mm, L / D = 30) at a cylinder temperature of 110 ° C., a die temperature of 110 ° C., and a screw rotation speed of 100 rpm, and extruded from a strand die to form an unfoamed compound. A pellet was obtained. The pellets were dried with a hot air drier to adjust the water content.

The thus obtained compound pellets were dry-blended with a 200-mesh undersized rice flour (water content: 9.5%) in the ratio shown in Table 3 and injection-molded under the following conditions to obtain a rod-shaped foam. Obtained. Injection molding machine: PS60E12AS manufactured by Nissei Plastic Industry Co., Ltd.
Type E Injection temperature; 170 ° C. Nozzle shear rate; Example 6 1.6 × 10 ⁴
sec- ¹ Example 7 13.3 × 10 ⁴ sec ^-1 Example 8 1.6 × 10 ⁴ sec ^-1 Comparative Examples 1 and 2 3.3 × 10 ⁴ sec ^-1 Injection pressure; 900 kg / cm ² compound Table 3 summarizes melt viscosity and foam quality.
It was shown to.

[0025]

Composition: (parts) Example 6 Example 7 Example 8 Comparative Example 3 Comparative Example 4 Water-containing potato starch 70.7 94.3 82.5 94.3 82.5 Water-containing EVOH 53.3 26.7 26.7 Water-containing PVA 28.5 14.3 28.5 14.3 Non-ionic surfactant 2 2 2 2 2 Boric acid 0.3 0.3 0.3 Rice flour 20.0 10.0 10.0 Melt viscosity of compound 1.1 1.5 1.3 1.5 1.3 (× 10 ⁴ poise) Moisture content (%) of compound 16.2 16.5 16.1 16.5 16.1 Quality of foam Foaming state ○ ○ ○ × × Bubble Structure Independent Independent Independent Independent Independent Bubble Size (mm) 0.3 0.3 0.3 5 5 Density (g / cc) 0.02 0.03 0.03 0.06 0.06 Elasticity Flexible Flexible Flexible Brittle Load 50k
g, L / D = 10/1 mm orifice, measured at 160 ° C. for 5 minutes

Examples 9 to 10, Comparative Example 5 Corn starch having a water content of 12.8%, water content of 25.0%
EVOH (ethylene content 44 mol%, saponification degree 99.
4 mol%) nonionic surfactant [polyoxyethylene nonylphenyl ether (HLB = 17)], boric acid and 200-mesh under rice flour (water content 9.5)
%) And recycled pulp from old newspaper (moisture content: 12.3%) were mixed in a Henschel mixer at the ratio shown in Table 4. The mixture was heated at a cylinder temperature of 110 ° C. and a die temperature of 110 using a twin-screw extruder (diameter: 30 mm, L / D = 30).
The mixture was melt-kneaded at 100 ° C. at a screw rotation speed of 100 rpm and extruded from a strand die to obtain unfoamed compounded pellets. The compound obtained above was subjected to injection foam molding under the following conditions to obtain a rod-shaped foam. Injection molding machine: PS60E12AS manufactured by Nissei Plastic Industry Co., Ltd.
E type Injection temperature; 170 ° C. Shear rate at nozzle; 3.3 × 10 ⁴ sec ^-1 Injection pressure; Melt viscosity of 900 kg / cm ² compound, quality of foam
It was shown to. A foam was produced by extrusion molding from a strand die having a nozzle of 5 mm in diameter at a temperature of 160 ° C. The properties of the foam are shown in Table 4. In addition, a case where no organic filler was added was shown as a comparative example.

[0027]

Table 4 Composition: (parts) Example 9 Example 10 Comparative Example 5 Hydrous cornstarch 68.8 68.8 68.8 Hydrous EVOH 53.3 53.3 53.3 Nonionic surfactant 2 2 2 Boric acid 0.5 0.5 0.5 Rice cake 10 old newspaper Recycled pulp 10 Melt viscosity 1.4 1.5 0.8 (× 10 ⁴ poise) Compound moisture content (%) 13.3 13.9 13.5 Foam quality Foaming state ○ ○ × Bubble structure Independent independent Non-uniform foam Bubble size (mm) 0.4 0.4 Density (g / Cc) 0.03 0.03

[0028]

According to the present invention, it is possible to obtain a low-density biodegradable resin foam having fine closed cells and a good condition of the surface of the molded body.

Claims (3)

(57) [Claims] 1. A starch-based polymer having a water content of 5 to 30% by weight, a vinyl alcohol-based resin having a water content of 5 to 30% by weight, a nonionic surfactant, and an organic filler are mixed and produced. A method for producing a biodegradable resin foam, comprising melting and foaming a composition having a water content of 5 to 30% by weight. 2. The method according to claim 1, wherein the organic filler is a vegetable fibrous material. 3. A starch polymer having a water content of 5 to 30% by weight, a vinyl alcohol resin having a water content of 5 to 30% by weight, a nonionic surfactant, an organic filler, and a thickener are mixed. A method for producing a biodegradable resin foam, comprising melting and foaming a composition produced and having a total water content of 5 to 30% by weight.