JP5329690B2 - Ethylene / propylene / diene rubber foam - Google Patents

Description

  TECHNICAL FIELD The present invention relates to an ethylene / propylene / diene rubber foam, and more particularly to an ethylene / propylene / diene rubber foam suitably used as a sealing material for various industrial products.

  Conventionally, EPDM foams obtained by foaming ethylene / propylene / diene rubber (hereinafter sometimes abbreviated as EPDM) are known as sealing materials for various industrial products.

  EPDM foam is generally produced by foaming with a foaming agent and crosslinking with sulfur (see, for example, Patent Document 1).

  It is also known to produce an EPDM foam by foaming with a foaming agent and crosslinking with an organic peroxide (see, for example, Patent Document 2).

JP 2006-182796 A JP 2002-179825 A

  However, when EPDM is crosslinked with sulfur, depending on the type of member to be sealed, the member may be corroded by sulfur remaining in the EPDM foam.

  Further, when EPDM is crosslinked with an organic peroxide-based crosslinking agent in the presence of oxygen, crosslinking on the surface of the EPDM foam may be insufficient, resulting in stickiness on the surface.

  An object of the present invention is to provide an EPDM foam which has reduced corrosivity, reduced surface stickiness, and is highly foamed and excellent in flexibility.

To achieve the above object, an ethylene-propylene-diene rubber foamed material of the present invention are ethylene-propylene-diene rubber, Ri Na and a quinoid crosslinking agent and a rubber composition containing an organic peroxide crosslinking agent is foamed, The quinoid crosslinking agent contains p-quinone dioxime and p, p′-dibenzoylquinone dioxime, and the p-quinone dioxime is 0.05 to 2 with respect to 100 parts by weight of ethylene / propylene / diene rubber. It is characterized by containing 0.05 to 10 parts by weight of p, p′-dibenzoylquinonedioxime with respect to 100 parts by weight of ethylene / propylene / diene rubber .

  In the ethylene / propylene / diene rubber foam of the present invention, it is preferable that the content of dienes in the ethylene / propylene / diene rubber is 3 to 20% by weight.

  In the ethylene / propylene / diene rubber foam of the present invention, it is preferable that the organic peroxide-based crosslinking agent contains an organic peroxide-based crosslinking agent having a one-minute half-life temperature exceeding 160 ° C.

  In the ethylene / propylene / diene rubber foam of the present invention, the organic peroxide crosslinking agent is preferably contained in an amount of 0.05 to 20 parts by weight with respect to 100 parts by weight of the ethylene / propylene / diene rubber.

  In the ethylene / propylene / diene rubber foam of the present invention, it is preferable that the rubber composition further contains thiazoles and thioureas as a crosslinking aid.

  In the EPDM foam of the present invention, a quinoid crosslinking agent and an organic peroxide crosslinking agent are used in combination as a crosslinking agent. Therefore, corrosivity can be reduced compared with the case where sulfur is used as a crosslinking agent. Moreover, the combined use of the quinoid crosslinking agent and the organic peroxide crosslinking agent can sufficiently ensure crosslinking on the surface of the EPDM foam, and can reduce the occurrence of stickiness on the surface. And the EPDM foam of this invention can ensure the high foaming and the softness | flexibility equivalent to the case where it bridge | crosslinks with sulfur.

  The EPDM foam of the present invention can be obtained by foaming a rubber composition containing EPDM, a quinoid crosslinking agent and an organic peroxide crosslinking agent.

  EPDM is a rubber obtained by copolymerization of ethylene, propylene and dienes. In addition to ethylene and propylene, dienes are further copolymerized to introduce unsaturated bonds and enable crosslinking with a crosslinking agent. It is said.

  Examples of dienes include 5-ethylidene-2-norbornene, 1,4-hexadiene, dicyclopentadiene, and the like.

  In this invention, content (diene content) of dienes in EPDM is 3-20 weight%, for example, Preferably, it is 9-20 weight%, More preferably, it is 9-12 weight%. If the diene content is less than this, surface shrinkage of the resulting EPDM foam may occur. Moreover, when more than this, a crack may arise in an EPDM foam.

  Moreover, the Mooney viscosity (ML1 + 4, 100 degreeC) of EPDM is 20-150, for example, Preferably, it is 30-80.

  The quinoid crosslinking agent is an organic compound having a quinoid structure, and examples thereof include p-quinone dioxime, p, p′-dibenzoylquinone dioxime, and poly-p-dinitrosobenzene. Preferred examples of the quinoid crosslinking agent include p-quinone dioxime and p, p′-dibenzoylquinone dioxime, and more preferred is p-quinone dioxime.

  These quinoid crosslinking agents may be used alone or in combination of two or more. Preferably, p-quinone dioxime and p, p′-dibenzoylquinone dioxime are used in combination. When p-quinonedioxime and p, p′-dibenzoylquinonedioxime are used in combination, a good foam shape of the obtained EPDM foam can be secured.

  The mixing ratio of the quinoid crosslinking agent is, for example, 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight, and more preferably 0.1 to 12 parts by weight with respect to 100 parts by weight of EPDM. . Specifically, when p-quinonedioxime is used, the blending ratio of the p-quinonedioxime is, for example, 0.05 to 2 parts by weight, preferably 0.1 to 100 parts by weight of EPDM. -1 part by weight. Moreover, when using p, p'-dibenzoylquinone dioxime, the compounding ratio of the p, p'-dibenzoylquinone dioxime is, for example, 0.05 to 10 parts by weight with respect to 100 parts by weight of EPDM. The amount is preferably 0.5 to 7 parts by weight.

  In the case where p-quinone dioxime and p, p′-dibenzoylquinone dioxime are used in combination, the weight ratio of p, p′-dibenzoylquinone dioxime to p-quinone dioxime (p, p′-di (Benzoylquinonedioxime / p-quinonedioxime) is, for example, 0.25 to 50, preferably 1.1 to 40, and more preferably 5 to 30.

  The organic peroxide-based crosslinking agent is an organic compound having a peroxide structure, and preferably includes an organic peroxide-based crosslinking agent having a 1-minute half-life temperature exceeding 160 ° C., more preferably 1 minute. An organic peroxide crosslinking agent having a half-life temperature of 200 ° C. or lower, particularly preferably an organic peroxide crosslinking agent having a 1-minute half-life temperature of 170 to 190 ° C. Specifically, dicumyl peroxide (1 minute half-life temperature: 175 ° C.), dimethyldi (t-butylperoxy) hexane (1 minute half-life temperature: 180 ° C.), bis (t-butylperoxyisopropyl) benzene (1 minute half-life temperature: 175 ° C.). Preferably, dicumyl peroxide is used. These organic peroxide crosslinking agents may be used alone or in combination of two or more.

  The compounding ratio of the organic peroxide crosslinking agent is, for example, 0.05 to 20 parts by weight, preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of EPDM.

  The rubber composition contains a foaming agent for foaming EPDM. Examples of the foaming agent include organic foaming agents and inorganic foaming agents.

  Examples of the organic foaming agent include azo foaming agents such as azodicarboxylic amide (ADCA), barium azodicarboxylate, azobisisobutyronitrile (AIBN), azocyclohexylnitrile, and azodiaminobenzene, such as N N-nitroso-based blowing agents such as N, N'-dinitrosopentamethylenetetramine (DTP), N, N'-dimethyl-N, N'-dinitrosoterephthalamide, trinitrosotrimethyltriamine, for example, 4,4'- Oxybis (benzenesulfonylhydrazide) (OBSH), paratoluenesulfonyl hydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 2,4-toluenedisulfonylhydrazide, p, p-bis (benzenesulfonylhydrazide) ether, benzene- 1,3-disulfo Hydrazide-based blowing agents such as nylhydrazide and allylbis (sulfonylhydrazide), for example, p-toluylenesulfonyl semicarbazide, semicarbazide-based blowing agents such as 4,4′-oxybis (benzenesulfonyl semicarbazide), such as trichloromonofluoromethane, dichloro Examples include fluorinated alkane-based blowing agents such as monofluoromethane, triazole-based blowing agents such as 5-morpholyl-1,2,3,4-thiatriazole, and other known organic foaming agents. Examples of the organic foaming agent include thermally expandable fine particles in which a heat-expandable substance is enclosed in a microcapsule. Examples of such thermally expandable particles include microspheres (trade name, Matsumoto). And commercial products such as those manufactured by Yushi Corporation.

  Examples of the inorganic foaming agent include hydrogen carbonates such as sodium hydrogen carbonate and ammonium hydrogen carbonate, for example, carbonates such as sodium carbonate and ammonium carbonate, for example, nitrites such as sodium nitrite and ammonium nitrite, for example hydrogen. Examples thereof include borohydride salts such as sodium borohydride, for example, azides, and other known inorganic foaming agents. Preferably, an azo foaming agent is used. These foaming agents may be used alone or in combination of two or more.

  The blending ratio of the foaming agent is, for example, 0.1 to 50 parts by weight, preferably 1 to 30 parts by weight with respect to 100 parts by weight of EPDM.

  Further, the rubber composition appropriately contains a crosslinking aid and a foaming aid as necessary. Examples of the crosslinking aid include thiazoles (eg, dibenzothiazyl disulfide, 2-mercaptobenzothiazole, etc.), thioureas (eg, diethylthiourea, trimethylthiourea, dibutylthiourea, etc.), dithiocarbamic acids (eg, dimethyldithiocarbamic acid). Sodium, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, etc.), guanidines (eg diphenylguanidine, di-o-tolylguanidine etc.), sulfenamides (eg benzothiazyl-2-diethylsulfene) Amide, N-cyclohexyl-2-benzothiazylsulfenamide), thiurams (eg, tetramethylthiuram monosulfide, tetramethylthiu) Mudisulfide, etc.), xanthates (eg, sodium isopropylxanthate, zinc isopropylxanthate), aldehyde ammonia (eg, acetaldehyde ammonia, hexamethylenetetramine, etc.), aldehyde amines (eg, n-butyraldehyde aniline, butyl) Aldehyde monobutylamine, etc.). Preferably, thiazoles and thioureas are mentioned.

  These crosslinking aids may be used alone or in combination of two or more. Preferably, thiazoles and thioureas are used in combination. By blending these, a good foam shape and flexibility of the obtained EPDM foam can be secured.

  The blending ratio of the crosslinking aid is, for example, 0.01 to 20 parts by weight, preferably 0.02 to 10 parts by weight, and more preferably 0.06 to 4 parts by weight with respect to 100 parts by weight of EPDM. Specifically, when thiazoles are used, the mixing ratio of the thiazoles is, for example, 0.01 to 5 parts by weight, preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of EPDM. . Moreover, when using thiourea, the mixture ratio of the thiourea is 0.01-5 weight part with respect to 100 weight part of EPDM, Preferably, it is 0.1-1 weight part.

  In the case where thiazoles and thioureas are used in combination, the weight ratio of thioureas to thiazoles (thioureas / thiazoles) is, for example, 0.1 to 10, preferably 0.2 to 0.9. is there.

  Examples of foaming aids include urea foaming aids, salicylic acid foaming aids, and benzoic acid foaming aids. Preferably, a urea foaming aid is used. These foaming aids may be used alone or in combination of two or more.

  The blending ratio of the foaming aid is, for example, 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of EPDM.

  Further, the rubber composition can appropriately contain a polymer other than EPDM, a processing aid, a pigment, a filler, a softening agent and the like as necessary.

  Examples of polymers other than EPDM include rubber polymers and non-rubber polymers. Examples of the rubber-based polymer include rubber-based copolymers containing, for example, a cyclic or non-cyclic polyene having a non-conjugated double bond (for example, α-olefin-dicyclopentadiene such as butene-1 or ethylidene norbornene). , Ethylene-propylene rubber, silicone rubber, fluorine rubber, acrylic rubber, polyurethane rubber, polyamide rubber, natural rubber, polyisobutylene rubber, polyisoprene rubber, chloroprene rubber, butyl rubber, nitrile butyl rubber, styrene-butadiene rubber, styrene-butadiene -Styrene rubber, styrene-isoprene-styrene rubber, styrene-ethylene-butadiene rubber, styrene-ethylene-butylene-styrene rubber, styrene-isoprene-propylene-styrene rubber, chlorosulfonated polyethylene rubber Etc., and the like.

  Non-rubber polymers include, for example, polyethylene, polypropylene, acrylic polymers (for example, poly (meth) acrylic acid alkyl ester, etc.), polyvinyl chloride, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyester, Examples include chlorinated polyethylene, urethane polymer, styrene polymer, silicone polymer, and epoxy resin. Preferably, a non-rubber polymer is used, more preferably polyethylene. These polymers other than EPDM may be used alone or in combination of two or more.

  The blending ratio of the polymer other than EPDM is, for example, 100 parts by weight or less, preferably 50 parts by weight or less, usually 1 part by weight or more with respect to 100 parts by weight of EPDM.

  Examples of the processing aid include stearic acid and its esters, zinc oxide and the like. These processing aids may be used alone or in combination of two or more. The blending ratio of the processing aid is, for example, 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight with respect to 100 parts by weight of EPDM.

  Examples of the pigment include carbon black. These pigments may be used alone or in combination of two or more. The blending ratio of the pigment is, for example, 1 to 50 parts by weight, preferably 2 to 30 parts by weight with respect to 100 parts by weight of EPDM.

  Examples of the filler include calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silicic acid and salts thereof, clay, talc, mica powder, bentonite, silica, alumina, aluminum silicate, acetylene black, Examples include inorganic fillers such as aluminum powder, organic fillers such as cork, and other known fillers. These fillers may be used alone or in combination of two or more. The blending ratio of the filler is, for example, 10 to 300 parts by weight, preferably 50 to 200 parts by weight, and more preferably 100 to 200 parts by weight with respect to 100 parts by weight of EPDM.

  Examples of the softener include petroleum oils (for example, paraffinic process oil (such as paraffin oil), naphthenic process oil, drying oils and animal and vegetable oils (such as linseed oil), aroma-based process oil, etc.) , Asphalts, low molecular weight polymers, organic acid esters (eg, phthalate esters (eg, di-2-ethylhexyl phthalate (DOP), dibutyl phthalate (DBP)), phosphate esters, higher fatty acid esters, alkyls Sulfonic acid esters, etc.) and thickeners. Preferably, petroleum-based oils, more preferably paraffin-based process oils are used. These softeners may be used alone or in combination of two or more. The blending ratio of the softening agent is, for example, 10 to 60 parts by weight, preferably 20 to 50 parts by weight with respect to 100 parts by weight of EPDM.

  Furthermore, the rubber composition can be used, for example, in a range that does not affect the excellent effect of the obtained EPDM foam, depending on its purpose and use, for example, a flame retardant, plasticizer, anti-aging agent, antioxidant, colorant, Known additives such as fungicides can be appropriately contained.

  And a rubber composition mixes each above-mentioned component suitably, and prepares it as an admixture by kneading | mixing using a kneader, a mixer, or a mixing roll. In this kneading, heating can be appropriately performed. In addition, kneading is performed by, for example, first kneading components other than the additive component to be added in a small amount, such as a crosslinking agent, a foaming agent, a crosslinking aid, and a foaming aid, and then adding the additive component to the kneaded product. It can also be kneaded.

  And the EPDM foam can be obtained by foaming the prepared rubber composition. The foaming of the rubber composition is not particularly limited, and a known method is used. For example, the mixture may be molded into a sheet or the like using a calender molding machine or an extrusion molding machine and foamed. it can. Moreover, it can also be molded into a complicated shape such as irregularities and foamed using, for example, injection molding or press molding.

  Further, the heating temperature for foaming is appropriately selected depending on, for example, the crosslinking start temperature of the blended crosslinking agent, the foaming temperature of the blended foaming agent, and the like, for example, 450 ° C. or less, preferably 100 It is -350 degreeC, More preferably, it is 120-250 degreeC.

  This foaming causes the admixture to crosslink while foaming to form an EPDM foam.

The foaming ratio (density ratio before and after foaming) of the EPDM foam thus obtained is, for example, 10 times or more, preferably 15 times or more, and usually 30 times or less. The density of the EPDM foam is, for example, 0.04 to 0.20 g / cm ³ , preferably 0.04 to 0.15 g / cm ³ . Further, 25% compressive load value of the EPDM foam, in view of flexibility, for example, 0.05~5.0N / cm ^2, preferably from 0.05~3.0N / cm ^2.

  In this EPDM foam, a quinoid crosslinking agent and an organic peroxide crosslinking agent are used in combination as crosslinking agents. Therefore, corrosivity can be reduced compared with the case where sulfur is used as a crosslinking agent. Moreover, the combined use of the quinoid crosslinking agent and the organic peroxide crosslinking agent can sufficiently ensure crosslinking on the surface of the EPDM foam, and can reduce the occurrence of stickiness on the surface. And the EPDM foam of this invention can ensure the high foaming and the softness | flexibility equivalent to the case where it bridge | crosslinks with sulfur.

  Therefore, the EPDM foam of the present invention aims at dustproofing, heat insulation, soundproofing, vibration proofing, buffering, watertightness and airtightness, for example, dustproofing material, heat insulating material, soundproofing material, vibration proofing material, buffering material, filler For example, in industrial products that require sealing, such as automobiles, electrical products, housing products, etc., for example, automobile exterior sealing materials, electrical product sealing materials, housing sealing materials, etc. It can be used suitably as a sealing material for sealing.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the examples and comparative examples.
1) Preparation of Examples and Comparative Examples In the formulation shown in Table 1, first, EPDM, other polymer, processing aid, pigment, filler, softener, N, N′-dibutylthiourea was blended, A primary mixture was prepared by kneading with a 3 L pressure kneader.

  Separately, a cross-linking agent, a cross-linking aid (excluding N, N'-dibutylthiourea), a foaming agent and a foaming aid are blended, blended into the primary blend, and kneaded with a 10 inch mixing roll. A secondary blend (rubber composition) was prepared.

  Thereafter, this rubber composition was extruded into a sheet having a thickness of about 10 mm using a single screw extruder (45 mmφ), and then the sheet was cut into a width of 100 mm and a length of 100 mm to produce a sheet.

The cut sheet is preheated at 100 ° C. for 10 minutes in a hot air circulating oven, then heated to 160 ° C. over 15 minutes, heated at 160 ° C. for 15 minutes, and foamed to form an EPDM foam. Obtained.
2) Evaluation The following items were evaluated for the EPDM foams of each Example and each Comparative Example. The results are shown in Table 1.
(Silver corrosive)
0.5 g of the EPDM foam of each Example and each Comparative Example was placed in a 100 mL sealed bottle, and polished and washed silver (plate-like) was attached to the inside of the lid of the sealed bottle. This was put into a constant temperature bath at 85 ° C. for 7 days, and the presence or absence of silver corrosion was confirmed. The case where corrosion was not confirmed was evaluated as “none”, and the case where corrosion was confirmed was evaluated as “present”.
(Surface tack)
The surface of the EPDM foam of each example and each comparative example was touched with a finger to confirm whether the surface was sticky. Those that did not feel sticky were rated as “none”, and those that did feel sticky were rated as “yes”.
(Foam shape)
The appearance of the EPDM foams of each Example and each Comparative Example was visually observed. “XX” indicates that the crosslinking is clearly insufficient, “×” indicates that cracking occurs, “△” indicates that surface shrinkage occurs, and neither crack nor surface shrinkage occurs. Those whose appearance was confirmed were evaluated with “◯”.
(25% compression load value)
The upper and lower skin layers of the EPDM foams of each example and each comparative example were removed to prepare a test piece having a thickness of 10 mm. Then, based on the compressive load test of JISK6767, it calculated | required by reading the compressive load of 10 second after compressing by the compression rate of 10 mm / min using the compression tester.
(density)
The upper and lower skin layers of the EPDM foams of each example and each comparative example were removed to prepare a test piece having a thickness of 10 mm. Thereafter, the weight was measured, and the weight per unit volume was calculated.

Details in Table 1 are shown below.
EPDM A: Esprene 505A (diene content 9.5% by weight), Sumitomo Chemical EPDM B: EPT4045 (diene content 8.0%), Mitsui Chemicals EPDM C: Esprene 501A (diene content 4% by weight) ), P-quinone dioxime manufactured by Sumitomo Chemical Co., Ltd .: p, p′-dibenzoylquinone dioxime manufactured by Ouchi Shinsei Chemical Co., Ltd .: Parkmill D-40 manufactured by Ouchi Shinsei Chemical Co., Ltd .: 40% by weight of dicumyl peroxide Powder, Nippon Oil & Fats Co., Ltd. dibenzothiazyl disulfide: Ouchi Shinsei Chemical Co., Ltd. N, N'-dibutylthiourea: Ouchi Shinsei Chemical Co., Ltd. sulfur formulation: 1.2 parts by weight of sulfur, Noxeller PZ (dimethyldithiocarbamine) Zinc oxide, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.0 part by weight, Noxeller EZ (zinc diethyldithiocarbamate, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 0 parts by weight, 1.2 parts by weight of Noxeller M (2-mercaptobenzothiazole, manufactured by Ouchi Shinsei Chemical Co., Ltd.) and azodicarboxylic acid amide are blended and blended with the above-mentioned primary blend to obtain 10 inches. A secondary mixture (rubber composition) was prepared by kneading with a mixing roll. Thereafter, in the same manner as described above, a sheet was prepared and foamed to obtain a sulfur vulcanized EPDM foam (Comparative Example 3).

Claims (5)

Ethylene-propylene-diene rubber, Ri Na and a quinoid crosslinking agent and a rubber composition containing an organic peroxide crosslinking agent is foamed,
The quinoid crosslinking agent contains p-quinone dioxime and p, p′-dibenzoylquinone dioxime,
p-quinone dioxime is contained in an amount of 0.05 to 2 parts by weight based on 100 parts by weight of ethylene / propylene / diene rubber;
An ethylene / propylene / diene rubber foam characterized by containing 0.05 to 10 parts by weight of p, p'-dibenzoylquinonedioxime with respect to 100 parts by weight of ethylene / propylene / diene rubber. body.   The ethylene-propylene-diene rubber foam according to claim 1, wherein the content of dienes in the ethylene-propylene-diene rubber is 3 to 20% by weight. 3. The foamed ethylene / propylene / diene rubber according to claim 1, wherein the organic peroxide-based crosslinking agent contains an organic peroxide-based crosslinking agent having a one-minute half-life temperature exceeding 160 ° C. body. The organic peroxide crosslinking agent, characterized in that 0.05 to 20 contain parts of the ethylene-propylene-diene rubber 100 parts by weight ethylene as claimed in any one of claims 1 to 3 Propylene diene rubber foam. The ethylene / propylene / diene rubber foam according to any one of claims 1 to 4 , wherein the rubber composition further contains thiazoles and thioureas as a crosslinking aid.