JPS58118833A - Preparation of reprocessed synthetic resin foam - Google Patents

Abstract

PURPOSE:To prepare a reprocessed resin foam with low cost from a scrap of ethylene/vinyl acetate copolymer resin foam, by a method wherein a crosslinker and a foaming agent are added to fragments of a resin foam crushed within a kneader, and the mixt. is introduced into a mold and heated. CONSTITUTION:Scraps and rejects of ethylen/vinyl acetate copolymer resin foam (those with low density are preferred) are kneaded and crushed by a kneader such as roller, to form a viscous resin material. Then, 100pts.wt. above resin material, 0.5-5pts.wt. crosslinker (e.g., dicumyl peroxide), and 3-10pts.wt. foaming agent (e.g., azodicarbonamide) are kneaded to give a compd. After filled and closed into a mold, the compd. is crosslinked and foamed with heat to yield a high density reprocessed synthetic resin foam on removing from the mold. In the above method, when the amt. of a foaming agent is 10-50pts.wt. and the removing temp. from the mold is 50-80 deg.C lower than the heating temp. after crosslinking and foaming, a low-density foamed product can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing recycled synthetic resin foam, and in particular,
The present invention relates to a method for producing a recycled synthetic resin foam having a bulk density or a low density using shredded pieces or defective products of an ethylene-vinyl acetate copolymer resin foam as a raw material.

Synthetic resin foams are used in an extremely wide range of applications as industrial materials such as building materials and cushioning materials. A considerable amount of these synthetic resin foams have no use and are discarded as they are, such as fragments and defective products that are generated when they are cut into predetermined dimensions. Moreover, these must be disposed of as industrial waste by incineration, etc., which poses a major problem due to the cost and pollution caused by this process.
From the viewpoints of resource saving, cost reduction, and prevention of separate documents, there is a strong demand for a method of recycling these synthetic resin foam wastes into new synthetic resin foams as raw materials.

In view of these circumstances, the inventors of the present application have conducted intensive research on a method for producing recycled synthetic resin foam from waste synthetic resin foam, and as a result, they have developed an ethylene-vinyl acetate copolymer resin (hereinafter referred to as EVA). We have discovered a method for producing the above-mentioned recycled synthetic resin foam.

That is, in the first invention of the present application, a resin raw material is obtained by crushing EvA foam pieces with a mixer such as a roll, and 05 to 5.0 parts by weight of a crosslinking agent and 3 parts by weight of a blowing agent are added to 100 parts by weight of the resin raw material. ~10 parts by weight of the compound II powder raw material added and kneaded is filled into a molded mold and tightly closed with a cover, and then the filled raw material is heated to the temperature at which it is filled into the mold to cause foaming and crosslinking reactions. This is a method for producing a high-density recycled synthetic resin foam, which is characterized in that after the molding process is completed, the lid of the mold is opened to obtain the final foam all at once.

Further, in the second invention of the present application, a resin raw material is obtained by crushing EVA foam pieces with a kneader such as a roll, and 05 to 5.0 parts by weight of a crosslinking agent and 10 parts by weight of a blowing agent are added to 100 parts by weight of the resin raw material. ~50 parts by weight is added and kneaded, and the mold is filled with the nenkonno or land raw material, which is tightly closed with a cover, and then the foaming agent is decomposed by heating while the filling raw material is filled in the mold, Next, the filling material is held in the mold and cooled to a temperature 50 to 80 degrees Celsius lower than the heating temperature, and then the cover of the mold is opened to obtain the final foam at once. This is a method for producing a low-density recycled synthetic resin foam.

Next, these two inventions will be explained in detail.

As the EVA foam piece used in the present invention, a high-density or low-density EVA foam manufactured by a conventional manufacturing method can be used. This EvAllfli may be arbitrary, but it is usually 10 to 40 parts of vinyl acetate per 100 parts of ethylene. When these EVA foam pieces are crushed and kneaded using a common mixer, a viscous resin raw material is obtained. In this case, any EVA foam piece can be used, but it is preferable to use a low-density EVA foam piece obtained by the method disclosed in Japanese Patent Application No. 54-65843.

Examples of the crosslinking agent used in the present invention include dicumyl/9-oxide, 2,5-dimethyl-2,5-no(t-butyl)
These are organic peroxides such as monooxide, 1,3-bis(t-butylno-9-oxyisopropyl)benzene, m-octadecylazidoformate, and t-butylperoxycumene.

The amount of crosslinking agent added is also related to the amount of blowing agent used,
The amount is 0.5 to 5.0 parts by weight per 100 parts by weight of the raw material obtained by crushing the EVA foam. If the amount is less than 0.5 parts by weight, sufficient crosslinking will not occur, and if it exceeds 5.0 parts by weight, the balance with the foaming agent will be lost and unstable foaming will occur.

Examples of the blowing agent in the present invention include azodicagenamide, dinitrosopentamethylenetetramine, p-
) Luenesulfonylhydrazine, azobisisobutyronitrile, diazoaminoisobenzene, toluenesulfonyl semicarbazide can be used. In the first invention, the amount of these blowing agents used is 3 to 10 parts by weight based on 100 parts by weight of the resin and raw material obtained by crushing EVA foam pieces, while in the second invention, it is 10 to 50 parts by weight. Department “.

The reason why the amount of blowing agent used is different between the first invention and the second invention is that the first invention obtains a high-density foam with a density of 0605 to 0.3, whereas the second invention has a density of 0.
This is because a low density foam with a density of 0.02 to 0.05 is obtained.

In the present invention, additives other than those mentioned above, such as foaming aids, colorants, fillers, etc., are used as necessary.

When using another resin as a filler, a polyolefin resin such as polyethylene or polystyrene is used because of its compatibility with the main raw material, and the amount added is 30 inches or less. Also, if 15 inches or less of synthetic rubber or natural rubber is added,
This acts as a so-called binder, and when processed by rolls, the processability is good and it becomes easy to form a sheet.

In the present invention, after the above amount of the mixture is sufficiently kneaded, it is filled into a mold. The mold used here may be of any shape, but it is preferable that the mold has a wide opening at the top, since the product will jump out of the mold all at once when the foamed product is demolded. The foaming raw material is filled into the mold by substantially filling it or pressing it slightly, and then the mold trap is covered and the mold is tightly closed and fixed. The cover can be fixed in any way you like, but a convenient way to open and close the cover freely and to securely close the cover is to attach a mold cover to the tip using a press. , this is how to open and close the mold.

When the preparations are completed in this way, a foaming operation is carried out, but this foaming process is slightly different between the first invention and the second invention. First, in the case of the first invention, as in the production of ordinary resin foam,
After foaming and crosslinking reactions are caused by heating the mixture while it is filled in the mold, the lid of the mold is opened to obtain the final foam at once. The heating temperature at this time depends on the decomposition temperature of the blowing agent used, but is generally around 160 to 170°C.

On the other hand, in the case of the second invention, the foaming agent is sufficiently decomposed by heating at the same temperature as in the wc1 invention, and then the product is cooled as it is. The cooling temperature at this time is determined by the raw materials used, the type and amount of additives, etc.
Although it cannot be determined by law, the temperature is generally 60 to 110°C, which is about 50 to 80°C lower than the temperature during heating. This cooling is performed as forced cooling, for example, by sending cooling water to the nozzle of the mold. After this cooling, the lid of the mold is opened and the final foam is obtained all at once. In this way, cooling once after heating is the second invention with a density of 0.0.
This is due to the following reasons: 2 to 0.05% low density foam is obtained.

That is, in the second invention, a larger amount of blowing agent is used than in the first invention to obtain a low-density foam, and in this case, if foaming is attempted in the same foaming process as in the first invention, heating This is because the foaming pressure in the molding room becomes abnormally high, and when demolding, the foam explodes and scatters due to this high pressure, making it impossible to obtain the desired foam. On the other hand, in the second invention of the present application, it is considered that the vapor pressure of the gas generated by decomposing the blowing agent in the mold decreases as the temperature decreases due to cooling, and the internal pressure decreases. As a result, when the mold is released after cooling, foaming occurs all at once without scattering of air bubbles, resulting in a low-density foam.

According to the present invention described above, E
It is possible to use the loaded pieces and defective products of VA foam as raw materials and recycle them into new synthetic resin foams with high density or low density, thus greatly contributing to resource saving, pollution prevention, and cost reduction. It is something. Furthermore, the recycled synthetic resin foam obtained by the present invention has approximately the same physical properties as the conventionally produced EVA foam, as shown in the examples below.

The present invention will be explained in detail below.

Example 1 An EVA foam with a specific gravity of 0071 was crushed with an open roll, and 27.5 parts by weight of the blowing agent AK, 0.75 parts by weight of crosslinking agent peroxide, and 15 parts by weight of isogrene rubber were kneaded with 100 parts by weight of the foam. 1 under pressure in a press
Heated at 58℃ for 20 minutes, foamed and molded to specific gravity O1
Obtained EVA foam with Vd Example 2 100 parts by weight of EVA foam with specific gravity 0071 crushed with an open roll, 212 parts by weight of blowing agent AKφ, 1.1 parts by weight of crosslinking agent, 15 parts by weight of isogrene rubber. The mixture was heated under press pressure at 158°C for 20 minutes, then foamed and molded to form an EV with a specific gravity of 0.0721r/ai.
Foam A was obtained.

Example 3 A specific gravity of 0.1141 r/- was obtained at IB 8° C. for 20 minutes using 100 phr of crushed material, 7.5 phr of EVA resin, 7.5 phr of foaming agent, and 0.75 phr of crosslinking agent.

Claims (2)

[Claims] (1) A resin raw material is obtained by crushing ethylene vinyl acetate copolymer resin foam pieces with a mixer such as a roll, and 0.5 parts of a crosslinking agent is added to 100 parts by weight of the resin raw material. ~5.0
A compound raw material prepared by adding and kneading 3 to 10 parts by weight of a blowing agent and a foaming agent is filled into a mold, tightly closed with a cover, and then heated while the filled raw material is filled with the mold's internal pressure to cause foaming and 1. A method for producing a recycled synthetic resin foam, which is characterized in that after a crosslinking reaction occurs, the lid of a mold is opened to obtain a final foam all at once. (2) A resin raw material is obtained by crushing ethylene vinyl acetate copolymer resin foam pieces with a mixer such as a roll, and 05 to 50 parts by weight of a crosslinking agent and 10 to 50 parts by weight of a blowing agent are prepared for 100 parts by weight of the resin raw material. The compound raw material added and kneaded is filled into the mold and tightly closed with a cover, and then the foaming agent is decomposed by heating the filled raw material while it is filled in the disk. A method of recycling a merchandising bond, which is characterized in that the foam is cooled to a temperature 50 to 80°C lower than the heating temperature while it is held in the mold, and then the molding cover is opened to obtain the final foam at once. Manufacturing method of synthetic resin foam 0