JPH0594247U - Degradable foam sheet - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a decomposable foam sheet 1 which has functions such as packaging of articles, lining of greenhouses, and paddy rice raising seedlings, and decomposes after disposal to reduce the volume and naturally return. [Structure] A mixture of polyethylene resin 4 = 55 to 90% by weight, styrene resin 5 = 5 to 20% by weight, starch 6 = 5 to 25% by weight, and surfactant 7 = 0.1 to 0.2% by weight. Foam 10 to 30 times.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 INDUSTRIAL APPLICABILITY The present invention relates to materials for packaging articles, linings of greenhouses, paddy rice raising seedlings, and the like.

[0002]

[Prior Art]

 Non-crosslinked expanded polyethylene sheet made from non-degradable polyethylene is well known. The foamed sheet has been improved in physical properties and stability in physical properties, but it is hard to say that much effort was made in the deterioration accelerating treatment. It would take at least 3 years, and perhaps 100 years or more, for the foam sheet to deteriorate to a pollution-free state without actively adding a UV stabilizer.

[0003]

[Problems to be solved by the device]

 When used for packaging of articles, the foamed sheet after use was sometimes scattered. Even in agricultural applications such as linings of greenhouses and rice seedlings, foamed sheets were sometimes scattered after use.

In these cases, since the scattered foamed sheet does not spontaneously decompose, there is a problem in that the environment is semipermanently contaminated unless it is collected and incinerated. In addition, even if collected and incinerated, there was a problem that carbon dioxide was generated, which promotes global warming.

[0005]

[Means for Solving the Problems]

 Polyethylene resin 4 suitable for the application field of the present invention is used as a main component. Starch 6 for imparting decomposability, and a mixture of styrene resin 5 and surfactant 7 for improving the characteristics of the foam are used as raw materials.

The polyethylene resin 4 includes low density polyethylene, high density polyethylene and the like, and there are various brands such as crosslinked, non-crosslinked and non-crosslinked, and any brand can be used. From the viewpoint of price, foaming conditions and the like, non-crosslinked polyethylene resin 4 is preferable.

As the styrene resin 5, any of polystyrene resin, acrylonitrile-styrene copolymer resin, and acrylonitrile-butadiene-styrene copolymer resin may be used.

The styrene resin 5 is contained in an amount of 5 to 20% by weight.

As the starch 6, starch alone or a mixture of starch and fatty acid is used. The starch is a raw material starch having an average particle size of 5, 10 or 80 μm, which is either rice, corn or potato, and is subjected to a dehydration treatment to obtain a hydrophobic modified starch. The following is used. Regarding the master batch, 25 to 5% by weight of the modified starch described above is kneaded with respect to the total of 75 to 95% by weight of the polyethylene resin and the styrene resin to obtain a master batch having a water content of 1% or less. Fatty acid 2 to 20% may be mixed into the modified starch. As the photodegradation accelerator, an organic metal salt that is activated by ultraviolet rays may be added in an amount of 0.1 to 10% based on the modified starch.

Starch 6 is contained in an amount of 5 to 25% by weight.

As the surfactant 7, any of an anionic surfactant, a cationic surfactant and a nonionic surfactant may be used.

The surfactant 7 is contained in an amount of 0.1 to 0.2% by weight.

The polyethylene resin 4 is in the range of 55 to 90% by weight, the styrene resin 5 is in the range of 5 to 20% by weight, the starch 6 is in the range of 5 to 25% by weight, and the surfactant 7 is in the range of 0.1 to 2. The degradable foam sheet 1 of the present invention is obtained by foaming the mixture of 0 wt% in the range of 10 to 30 times.

As shown in FIG. 1, the cells 3 of the decomposable foam sheet 1 of the present invention are minute. This is due to the nucleating agent effect of starch 6.

[0015]

[Action]

 When used for wrapping articles, lining greenhouses, and for raising rice seedlings, the decomposable foam sheet 1 has the same function as a non-crosslinked foam polyethylene sheet made of non-decomposable polyethylene.

After use, the decomposable foam sheet 1 is discarded, and the decomposable foam sheet 1 is reduced in volume due to erosion and crushing of the starch 6 by microorganisms in the soil and water having the starch 6 as a nutrient source. One becomes a strip.

After use, in the decomposable foam sheet 1 that has been discarded, the Mg-based or Ca-based substance in the soil reacts with the added fatty acid 6 to generate peroxide. The C—C bonds of the polyethylene resin 4 and the styrene resin 5 are oxidized due to the peroxide, and the C—C bonds are broken, so that the decomposable foam sheet 1 has a reduced volume and becomes a strip.

In the decomposable foam sheet 1 which has been disposed of after use, the decomposable foam sheet 1 is reduced in volume by the activated organometallic salt 6 when the organometal salt 6 is excited by sunlight, especially its ultraviolet rays. And it becomes a strip.

The styrenic resin 5 strengthens the bending rigidity of the walls of the cells 3 and prevents the decomposable foam sheet 1 from shrinking.

When the content of the styrene resin 5 is too high, the decomposable foam sheet 1 is likely to tear. If the content of the styrene resin 5 is too low, the effect of preventing the decomposable foam sheet 1 from shrinking will not be obtained.

The surfactant 7 forms a film on the inner surface of the cell 3 of the decomposable foam sheet 1, hinders gas exchange, and eventually prevents shrinkage. Furthermore, it also has an antistatic function.

If the content of the surfactant 7 is too low, it becomes impossible to prevent the decomposable foam sheet 1 from shrinking. Even if the content is 2.0% by weight or more, there is no difference in the decomposable foam sheet 1 shrinkage prevention performance, and the cost only increases.

If the expansion ratio is too low, the basic functions of the decomposable foam sheet 1, such as the cushioning property and the heat retaining property, are impaired. If the expansion ratio is too high, the wall forming the cells 3 becomes thin and the gas permeability increases, so that the decomposable foam sheet 1 cannot be prevented from shrinking.

[0024]

Example 1 High-pressure polyethylene resin 4 = 84.85% by weight, polystyrene resin 5 = 8.0% by weight, starch 6 = 7.0% by weight, nonionic surfactant 7 = 0.15% by weight were mixed. Then, the mixture was supplied from the hopper of the extruder. The extruder is sequentially heated to about 200 ° C. from this supply part, and is further discharged to the tip of the extruder by a screen. On the other hand, Freon 22 = 40 PHR as a foaming agent was pressed into the extruder and kneaded well. From the circular die at the tip of the extruder, the temperature of which was controlled to about 100 ° C., was extruded into the air to obtain a foam having a thickness of 1.2 mm, and the degradable foam sheet 1 of the present invention having a width of 450 mm was obtained.

When the shrinkability of the decomposable foam sheet 1 of Example 1 was examined, the thickness of 1.2 mm showed no change in the thickness even after 1 week.

The decomposable foam sheet 1 of Example 1 was embedded in soil and the change in elongation rate before and after the embedding was measured to evaluate the decomposability. After 50 days of burial in soil, the residual elongation was about 50%, and after 100 days of burial in soil, the residual elongation was about 45%.

[0027]

[Effect of the device]

 1. A decomposable foam sheet 1 that does not pollute the environment is obtained. 2. It is possible to prevent the decomposable foam sheet 1 from shrinking. 3. Starch 6 acts not only as a degradability promoter but also as a foam nucleating agent. 4. The surfactant 7 acts as an antistatic agent and at the same time as an antistatic agent.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a decomposable foam sheet of the present invention cut in the thickness direction.

[Explanation of symbols]

 1 Decomposable foam sheet 2 Skin 3 Cell 4 Polyethylene resin 5 Styrene resin 6 Starch 7 Surfactant

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Claims (1)

[Scope of utility model registration request] 1. Polyethylene resin = 55 to 90% by weight,
Styrene resin = 5 to 20% by weight, starch = 5 to 25% by weight, surfactant = 0.1 to 0.2% by weight, and the expansion ratio is in the range of 10 to 30 times. Degradable foam sheet characterized by.