JPS5923545B2 - Method for producing open-celled ethylene polymer or copolymer cells - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an industrially easy-to-implement method for producing open-celled ethylene polymer or copolymer cells.

BACKGROUND ART Conventionally, as a method for manufacturing a foam having open cells, a method is known in which a closed cell foam is compressed to destroy the cell membrane. However, in the conventional method, when compressing a closed-cell foam, it was necessary to cool the foam to the glass transition temperature of the resin or lower (see, for example, Japanese Patent Publication No. 31695/1982).

Cooling the foam to the glass transition temperature of the resin or lower is industrially disadvantageous because the process is complicated. The present inventors have investigated various methods of manufacturing open-cell bodies by compressing closed-cell bodies of ethylene polymers or copolymers, and have found that the closed-cell bodies are compressively destroyed at around room temperature. The present invention was achieved by discovering a method capable of obtaining excellent open-celled foam.

That is, the present invention provides a first intermediate product which is made by heating a compound in which an ethylene polymer or copolymer is blended with a blowing agent and a crosslinking agent for a certain period of time, so that the decomposition rate of the blended blowing agent is 30Cf6 or less, and the compound is foamed and crosslinked. and heating the first intermediate product at a higher temperature than in the first step to decompose the residual foaming agent and crosslinking agent to generate a second intermediate product having closed cells that are easily destroyed. A second step,
This method includes a third step of compressing the second intermediate product at a temperature range of 0° C. to 40° C. to destroy the closed cells.

According to the method of the present invention, closed-cell cells of ethylene polymers or copolymers can be compressed and destroyed at temperatures around room temperature, and open-cell cells with excellent water absorption and air permeability can be obtained. The ethylene polymer or copolymer used in the present invention includes low density polyethylene, ethylene monovinyl acetate copolymer containing ethylene as a main component, ethylene-acrylic acid ester copolymer, and ethylene-propylene copolymer. etc.

The blowing agents used in the present invention include azodicarbonamide, N,N'-dinitrosopentamethylenetetramine, and the like.

The amount of blowing agent to be used is determined appropriately depending on the expansion ratio of the desired product, but generally it is 2 to 25 parts per 100 parts of resin.
It is about 100%.

In this way, a product with a foaming ratio of about 3 to 25 times can be obtained. These blowing agents can be used in combination with a blowing aid to adjust their decomposition temperature.

Examples of the foaming aid include urea compounds, organic acid salt compounds such as zinc stearate, and inorganic compounds such as basic zinc carbonate. The crosslinking agent used in the present invention is dicumyl peroxide, A,a'-
Bis(tert-butylperoxy)diisopropylbenzene, 1,15-bis(tert-butylperoxy)-3,5,5,1-trimethylcyclohexane, and the like.

The appropriate amount of the crosslinking agent used is about 0.5 to 5 parts, preferably about 0.5 to 3 parts, per 100 parts of the resin. In the present invention, it is desirable to select a crosslinking agent that has a lower decomposition temperature than the blowing agent. In the method of the present invention, first, an ethylene polymer or copolymer is blended with a blowing agent and a crosslinking agent, kneaded, and molded into a compound of a desired shape by a conventional method. The compound is then placed in a hermetically sealed mold and heated for a certain period of time to suppress decomposition of the blowing agent and carry out a crosslinking reaction. In this way, in the first step, a first intermediate product is produced in which the decomposition rate of the blowing agent is 30% or less, preferably 15% or less, and is crosslinked.

If the decomposition rate of the blowing agent exceeds 30%, the reason is not clear, but it may fail in the third step, making it difficult to destroy closed cells, or it may not be possible to obtain open cells with excellent water absorption. .

The first intermediate product must be crosslinked.

The degree of crosslinking can be selected from a wide range from low to high. The limit for low-grade products is the heating temperature in the first step that allows the product to be removed from the mold without being significantly deformed. ) If the range of crosslinking degree is expressed in terms of gel fraction, for example, 1 to 95
Weight % (ratio of the sample remaining in the basket to the amount charged when 0.3 g of the sample was placed in a 200-mesh wire basket and immersed in 100 cycles of xylene at 80° C. for 6 hours).

The first intermediate product taken out from the first mold is then heated under normal pressure or close to normal pressure in a mold of a desired size that can be closed but not airtight, to remove the remaining blowing agent and crosslinking agent. Let it break down.

The second intermediate product produced in the second step of the present invention is a closed cell, but the cell wall thickness is uneven, and it has a structure that is easily compressed and broken into an open cell. .

The second intermediate product cross-linked and foamed in the second step is cooled to around room temperature in the mold and then taken out.

The foaming ratio of the second intermediate product is suitably about 3 to 25 times. The second intermediate product taken out from the mold in the second step is then compressed at a temperature around room temperature of about 0 to 40°C to destroy closed cells and generate open cells.

Compression may be performed by either a processing press on a flat plate or a roll press. The open cell body obtained through the third step is subjected to secondary processing such as cutting into a desired shape.

Open-cell foams made of ethylene polymers or copolymers are not commercially available due to the high cost of conventional methods.

According to the method of the present invention, it can be manufactured at a relatively low cost, so
Industrialization is also easy.

Open-celled ethylene polymer or copolymer foam has better air permeability and water absorption than conventional closed-cell foam, and also has greater tear strength than conventional polyurethane open-cell foam. It has characteristics such as being resistant to discoloration.

The open-celled ethylene polymer or copolymer obtained by the method of the present invention can be used for cosmetic products (hubs, butts, maniyukia brush tips, etc.), daily household products (cooking scrubbers, window cleaning, toilets or baths, etc.). Scrubbers, cushioning materials for bedding or pillows, clothes brushes, shoe cream applicators, health scrubbers, etc.), medical devices (cushion materials in casts, liquid shoulder braces), adhesives for plasters, or topical medicines. base materials, etc.), industrial supplies (automotive supplies: packaging, cushions, air conditioner filters, etc.; light electrical supplies: refrigerator cold insulation materials, packaging, speaker cushions, microphone caps, etc.; water supplies: cold or heat insulation materials, filters, etc.) , vehicle supplies: door packing, etc.), office supplies (stamp pads, ink pads, brush tips, sponge finger wipes, printing rolls, etc.), sports supplies (protectors, supporters, cushion materials such as mats, gloves, gloves, etc.), clothing supplies. (
(anoratuku core, etc.), heavy supplies (diaper cover core, vehicle cushions, children's scrubbers, etc.), footwear supplies (shoe insoles, etc.), gardening supplies (water retaining material for the bottom of flower pots, etc.), packaging supplies. It has a wide range of uses (such as cushioning materials).

The present invention will be explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 70 parts of ethylene-vinyl acetate copolymer (trade name Evatate H2O2O, vinyl acetate content 15% by weight, manufactured by Sumitomo Chemical Co., Ltd.), ethylene-1a/olefin copolymer elastomer (trade name, Tabkanma-1A2OO9O)
, manufactured by Mitsui Petrochemical Industries, Ltd.) 30 parts, azodicarbonamide foaming agent (trade name, Vinyhole DW-6, manufactured by Eiwa Kasei Co., Ltd.) 11 parts, dicumyl peroxide (crosslinking agent) 1.5 parts , 0.4 parts of calcium hydroxide (cross-linking aid) and 0.6 parts of stearic acid (silica) at 70-100°C.
The mixture was kneaded using open rolls to form a compound.

Fill a rectangular mold with a thickness of 11C771 and a side of 12C771 with approximately the same size compound, and make a mold of 140~143
The mixture was heated under pressure at ℃ for a predetermined period of time to obtain a first intermediate product. Next, the first intermediate product was placed in a rectangular mold with a thickness of 2.8C771 and 25 cm on a side, heated at 190 to 210°C for a predetermined time, allowed to cool to room temperature, and a second intermediate product was taken out.

Next, the second intermediate product is rolled pressed (
A good open cell body was obtained through a gap of 0.2C77Z, 5 stages).

These results are shown in Table 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that the heating temperature and time of the first step were 145° C. and 20 minutes, respectively.

The results are shown in Table 2. With this method, virtually no open cells were obtained. That is, if the decomposition rate of the blowing agent in the first step exceeds 30%, it will be compressed and destroyed at room temperature, making it impossible to obtain a second intermediate product with a structure that easily forms open cells.
Even if roll pressing is performed in the third step, an open cell body cannot be obtained.Examples 2 to 7 Same conditions as in the method of Experimental Demon 1 of Example 1 except that the compounding formula and the foaming ratio of the second intermediate product were changed. I did it at

The results are shown in Table 3.

Example 8 100 parts by weight of low-density polyethylene (trade name Sumikasen G2Ol manufactured by Sumitomo Chemical Industries, Ltd.), azodicarbonamide foaming agent (trade name Vinihole AC-3M Eiwa Kasei Kogyo Co., Ltd.)
Co., Ltd.) 8 parts, dicumyl peroxide (linking agent 1.2
A compound was prepared by kneading 0.4 parts of calcium hydroxide (linking aid) and 0.6 parts of stearic acid (coating agent) using an open roll at 100-110°C.

The thickness of the compound is 1.1C77! , side 12C77
! The mixture was filled into a rectangular mold, and heated and pressed at 140 to 143°C for 25 minutes to obtain a first intermediate product. Next, the first intermediate product has a thickness of 3.0 CIn. Put it in a square mold with 20I on each side 1
It was heated at 90 to 210°C for 20 minutes, allowed to cool to room temperature, and the second intermediate product was taken out.

Next, the second intermediate product is rolled pressed (
Good open cells were obtained through a gap of 0.2 cm (5 stages).

These results are shown in Table 4.

Example 9 85 parts by weight of ethylene-propylene copolymer (trade name EPll manufactured by Nippon Gosei Rubber Co., Ltd.), ethylene monovinyl acetate copolymer (trade name Evatate H2O2O, vinyl acetate content 15% by weight, Sumitomo Chemical Co., Ltd.) Co., Ltd.) 15 parts by weight, azodicarbonamide blowing agent (trade name: Vinyhole AC-
3M, manufactured by Eiwa Kasei Kogyo Co., Ltd.) 11 parts, dicumyl peroxide (crosslinking agent) 1.5 parts, calcium hydroxide (crosslinking agent) 0.4 parts, and stearic acid (wei agent) 0.6 parts A compound was prepared by kneading with an open roll at 90 to 100°C.

The compound was filled into a rectangular mold with a thickness of 1.1 crrL and 120 mm on each side, and heated and pressed at 140 to 143° C. for 25 minutes to obtain a first intermediate product. Next, the thickness of the first intermediate product is 3C.
71, = put into a rectangular mold with 25 sides, 180~20
The second intermediate product was heated at 0° C. for 25 minutes, cooled with water to room temperature, and taken out. Next, the second intermediate product was passed through a roll press (gap 0.2C77!, 5 stages) at room temperature (25°C) to obtain a good open-celled product. These results are shown in Table 4.

Claims (1)

[Claims] 1 A compound prepared by blending an ethylene polymer or copolymer with a blowing agent and a crosslinking agent is heated for a certain period of time to produce a first intermediate product in which the decomposition rate of the blended blowing agent is 30% or less and is crosslinked. a second step of heating the first intermediate product at a higher temperature than the first step to decompose the remaining blowing agent and crosslinking agent to produce a second intermediate product having closed cells that are easy to break; Second intermediate product from 0℃
A method for producing an open-celled ethylene polymer or copolymer, which comprises a third step of destroying the closed cells by compression in a temperature range of 40°C.