JP2000017094A - Open cell foam and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for preparing an open cell foam which can afford a highly expanded open cell foam having a specific gravity of 0.25 or less and is advantageous from a cost standpoint and excellent in processibility and workability owing to simultaneous formation of an open cell with continuous extrusion vulcanization molding. SOLUTION: A compound comprising a polymer blend consisting of an EPDM (ethylene-propylene-diene copolymer rubber) and 20-60 pts.wt., based on 100 pts.wt. of the EPDM, of a blowing agent is molded at a vulcanizing temperature of 150-250 deg.C by means of a continuous extrusion vulcanization molding method. As the PE is employed a low density PE, the Mooney viscosity (ML1+4, 100 deg.C) of the EPDM is adjusted to 5-50, and the compound is adjusted such that it has a Mooney viscosity (Vm, 125 deg.C) of 5-30 and a Mooney scorch (t5) of 2-7 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an open-cell foam and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing an open-cell high-foam sponge, a closed-cell foam previously extruded and vulcanized or molded and vulcanized is pressed with a roll or the like to crush the air bubbles. 2. Description of the Related Art There is known a method of producing a highly foamed sponge having continuous cells by making the cells continuous with each other.

[0003]

However, in the prior art, it is necessary to lower the viscosity of the compound by compounding a large amount of a plasticizer and compounding a non-reinforcing filler when compounding the compound. And the workability is poor. In addition, since the foamed material must be further crushed by applying pressure with a roll or the like through the once foamed foam, the process becomes longer, which is economically disadvantageous. An object of the present invention is to provide an open-cell high-foamed material which overcomes these problems and a method for producing the same.

[0004]

Means for Solving the Problems The present inventor has made intensive studies to achieve the above object, and as a result, used a compound in which a specific polymer blend was used as a polymer and a blowing agent was compounded in a specific ratio, The present inventors have found that by directly molding the kneaded compound by a continuous extrusion vulcanization molding method, it is possible to obtain a highly foamed foam having a specific gravity of 0.25 or less, and completed the present invention.

That is, the high-open-cell foam having a specific gravity of 0.25 or less according to the present invention comprises, as polymers, ethylene-propylene-diene copolymer rubber (hereinafter referred to as “EPDM”) and polyethylene (hereinafter “PE”). Manufactured by a continuous extrusion vulcanization molding method from a compound obtained by blending 20 to 60 parts by weight of a foaming agent with 100 parts by weight of EPDM.

BEST MODE FOR CARRYING OUT THE INVENTION

[0006] EPDM, one component of the polymer blend used in the compound of the present invention, is a copolymer comprising ethylene, propylene and a diene compound,
Examples of the diene compound include 1,4-hexadiene, dicyclopentadiene, and ethylidene norbornene. E
It is desirable to use a PDM having a Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 50. The reason is that if the Mooney viscosity (ML1 + 4, 100 ° C.) is less than 5, workability and workability are difficult, while if it exceeds 50, the cell structure tends to become closed cells.

The reason why PE is used as the other component of the polymer blend is that the cell structure tends to become closed cells without the addition of PE, and the compound viscosity at room temperature is high due to the addition of PE. This is because the viscosity can be reduced. As the type of PE, a density obtained by polymerizing ethylene at a high pressure (500 to 7000 atm) is 0.910 to 0.935 g / cm.
Preferably, a low density polyethylene of 3 is used.

[0008] E in a polymer blend of EPDM and PE (hereinafter referred to as "EPDM / PE blend")
Although there is no particular limitation on the weight ratio of PDM to PE, it is generally preferred that EPDM / PE = 100/10 to 30.

The compound of the present invention contains a foaming agent in addition to the above polymer blend. Any foaming agent can be used, and specific examples thereof include sodium bicarbonate, sodium carbonate, ammonium bicarbonate, inorganic foaming agents such as ammonium carbonate, and nitroso compounds such as dinitrosopentamethylenetetramine as an organic foaming agent, Examples include azo compounds such as azodicarbonamide and azodicarboxylic acid metal salts, and azide compounds such as benzenesulfonylhydrazide and toluenesulfonylhydrazide.

It is necessary that the amount of the foaming agent is 20 to 60 parts by weight based on 100 parts by weight of EPDM. The reason is that if the amount is less than 20 parts by weight, the specific gravity is high and the cells tend to be closed cells, whereas if it exceeds 60 parts by weight, outgassing precedes and the cells do not grow and the cells are hardly foamed.

[0011] In the above compound, in addition to the EPDM / PE blend and the foaming agent, a foaming auxiliary, if necessary,
Additives such as a vulcanizing agent, a vulcanization accelerator, a filler, an antioxidant, and a coloring agent can be appropriately compounded.

The above compound has a Mooney viscosity (V
m, 125 ° C.) of 5 to 30 and a Mooney scorch (t5) of 2 to 7 minutes is preferred. The reason for this is that if the Mooney viscosity (Vm, 125 ° C.) is less than 5, workability and workability are difficult, while if it exceeds 30, the cell structure tends to become closed cells. If the Mooney scorch (t5) is less than 2 minutes, initial vulcanization occurs during work such as roll kneading, and it is difficult to obtain stable quality, while if it exceeds 7 minutes, outgassing precedes and bubbles grow. This is because high foaming is unlikely to occur.

In molding the compound by continuous extrusion vulcanization, the vulcanization temperature is preferably controlled in the range of 150 to 250 ° C.

[0014]

The open cell is formed simultaneously with the continuous extrusion vulcanization molding.

[0015]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples.

(Example 1) A compound of the present invention was prepared by kneading the following components in the mixing ratio. The physical properties of the unvulcanized product of this compound are based on Mooney viscosity (Vm, 125
° C) is 12 and Mooney scorch (t5) is 4.4.
Minutes.

Ingredients (trade name) parts by weight EPDM / PE blend (Mitsui Chemicals Eptalloy) 100/20 Zinc oxide (Seido Kagaku Zinhua No. 3) 5 Stearic acid (Shin Nippon Rika ST150) 2 Polyethylene glycol (Lion PEG 4000) 1 Carbon black (Asahi Carbon 50HG) 30 White filler (Nitto Powdered Nobelite A) 30 Paraffin oil (Idemitsu Kosan PW380) 30 Vulcanizing agent (powder sulfur) 2 MBT (Ouchi M) 1 (2-mercaptobenzothiazo) -B) ZnBDC (Ouchi BZ) 4 (Zinc di-n-butyldithiocarbamate) DBU (Kawaguchi BUR) 2 (Dibutylthiourea) Dehydrating agent (Inoue Lime VST18) 15 Blowing agent (Eiwa Chemical Co., Vinyl Hole AC3SW) 30

The above compound was molded at a vulcanization temperature of 230 ° C. by a continuous extrusion vulcanization molding method to obtain a foam. This foam has an open cell structure with an expansion ratio of 23 times,
The specific gravity was 0.05.

Example 2 A foam was produced in the same manner as in Example 1 except that the amount of the foaming agent was changed to 50 parts by weight. This foam had an open cell structure and a specific gravity of 0.09.

(Example 3) A foam was produced in the same manner as in Example 1 except that the vulcanization system was varied by changing the Mooney scorch (t5) of the unvulcanized compound as follows. The foam structure of each foam was open cells, and the specific gravity changed as follows.

T5 (min) 3.6 4.4 5.1 5.7 6.9 Specific gravity 0.06 0.05 0.05 0.17 0.25

Example 4 A foam was produced in the same manner as in Example 1 except that the temperature was changed as follows while adjusting the vulcanization. The foam structure of the foam was an open cell. The specific gravity changed as follows.

Vulcanization temperature (° C.) 150 180 200 220 250 Specific gravity 0.13 0.07 0.06 0.05 0.06

Comparative Example EPDM / PE as polymer
EPDM alone was used instead of the blend (ie PE
A foam was manufactured in the same manner as in Example 1 except that no foam was added, and the foam had a closed cell structure and a specific gravity of 0.19.

[0025]

As described above, according to the present invention, it is possible to obtain a high foam of open cells having a specific gravity of 0.25 or less, and open cells are formed simultaneously with continuous extrusion vulcanization. It is advantageous in terms of cost, and is excellent in workability and workability.

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Claims (5)

[Claims] 1. A polymer blend of ethylene-propylene-diene copolymer rubber and polyethylene was used as a polymer, and a foaming agent of 20 to 60 parts by weight was blended with 100 parts by weight of ethylene-propylene-diene copolymer rubber. An open-cell foam having a specific gravity of 0.25 or less, produced from the compound by a continuous extrusion vulcanization molding method. 2. The open cell foam according to claim 1, wherein the polyethylene is a low density polyethylene. 3. The open-cell foam according to claim 1, wherein the ethylene-propylene-diene copolymer rubber has a Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 50. 4. The compound has a Mooney viscosity (Vm, 12
The open-cell foam according to any one of claims 1 to 3, wherein (5 ° C) is 5 to 30 and Mooney scorch (t5) is 2 to 7 minutes. 5. A polymer blend of ethylene-propylene-diene copolymer rubber and polyethylene as a polymer, and a foaming agent of 20 to 60 parts by weight based on 100 parts by weight of ethylene-propylene-diene copolymer rubber. A method for producing an open-cell foam having a specific gravity of 0.25 or less, wherein the compound is molded by a continuous extrusion vulcanization molding method at a vulcanization temperature of 150 to 250 ° C.