JP2003246877A - Rubber foam and automotive sealing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber foam which is lightweight and, simultaneously, excels in compression set, surface skin, and shape retention by foaming/ crosslinking a rubber composition which contains a specific ethylene-α-olefin- nonconjugated diene copolymer rubber as the rubber component, maintains excellent processability, and enables a high expansion ratio (a low density), and an automotive sealing material using the rubber foam. <P>SOLUTION: The rubber foam has a density of 0.30-0.50 g/cm<SP>3</SP>, and is obtained by foaming/crosslinking a rubber composition containing an ethylene-α- olefin-nonconjugated diene copolymer rubber which meets the conditions such that (A) the amount of cyclohexane insolubles is 5 wt.% to 30 wt.%; (B) the weight ratio of the ethylene to the α-olefin is 73/27 to 40/60; (C) the content of the nonconjugated diene as the iodine value is 18-36; and (D) the Mooney viscosity [ML<SB>1+4</SB>(121°C) in the JIS-K-6300-Mooney viscosity test] is 50-120. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber foam and a sealing material for automobiles. More specifically, the present invention contains a specific ethylene-α-olefin-non-conjugated diene copolymer rubber as a rubber component,
A lightweight rubber that is obtained by foaming and crosslinking a rubber composition that maintains excellent processability and has a high expansion ratio (low density), and that has excellent compression set, surface texture and shape retention. The present invention relates to a foam and a sealing material for automobiles using the rubber foam.

[0002]

2. Description of the Related Art Ethylene-.alpha.-olefin-non-conjugated diene copolymer rubber is characterized by excellent weather resistance, heat resistance and ozone resistance and is widely used for automobile parts. As an application of the automobile parts, there is an application in which a copolymer rubber is foamed and crosslinked to form a rubber foam, which is used as an automobile sealant (weather strip). The rubber foam used for the application is required to have a high sealing property over a long period of time, and thus is required to have excellent compression set, and from the viewpoint of cost reduction and weight reduction, it has a high expansion ratio. It is required that foaming is possible. Further, in terms of designability, good surface texture and shape retention are also required.

In recent years, such demands have become more sophisticated. However, from the viewpoint of maintaining excellent workability, being capable of foaming under a high expansion ratio, and being excellent in compression set, surface texture and shape retention,
It was hard to say that conventional rubber is sufficient.

[0004]

Under such circumstances, the problem to be solved by the present invention is that it contains a specific ethylene-α-olefin-non-conjugated diene copolymer rubber as a rubber component and has excellent processability. Maintains high expansion ratio (low density)
A rubber foam which is obtained by foaming and cross-linking a rubber composition which is capable of being obtained and which is excellent in compression set, surface skin and shape retention, and a sealing material for automobiles using the rubber foam. There is a point to do.

[0005]

That is, the first invention of the present invention is a rubber containing an ethylene-α-olefin-non-conjugated diene copolymer rubber that satisfies the following conditions (A) to (D). The present invention relates to a rubber foam having a density of 0.30 to 0.50 g / cm ³ obtained by foaming / crosslinking the composition. (A): 5 to 30% by weight of cyclohexane insolubles (B): Ethylene / α-olefin weight ratio of 73/2
7-40 / 60 (C): content of non-conjugated diene is 18-36 (D): Mooney viscosity (JIS-K-6300-ML _{1 + 4} (121 ° C) in Mooney viscosity test) is 50 ~ 1
20 A second aspect of the present invention relates to an automobile sealing material using the rubber foam according to the first aspect of the present invention.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION As the ethylene-α-olefin-non-conjugated diene copolymer rubber of the present invention, those satisfying the following (A) to (D) are used.

(A): Cyclohexane insoluble content is 5% by weight
-30% by weight, preferably 5-15% by weight. If the cyclohexane insoluble content is too small, the expansion ratio becomes small, resulting in a rubber foam having a high density, or the shape retention of the rubber foam after foaming / crosslinking becomes poor. on the other hand,
If the cyclohexane insoluble content is too large, the kneading processability and the skin of the rubber foam will deteriorate.

(B): The ethylene / α-olefin weight ratio is 73/27 to 40/60, preferably 67 /
33-45 / 55. If the ethylene ratio is too high, the compression set of the rubber foam at low temperatures becomes extremely poor, and the recoverability of the rubber foam is extremely poor, making it unsuitable as a sealing material. On the other hand, if the ethylene ratio is too small, the reinforcing agent such as carbon black and inorganic filler is insufficiently dispersed, which causes deterioration of the surface texture of the rubber foam.

(C): The content of non-conjugated diene is 18 to 36 in iodine value, preferably 20 to 29. If the iodine value is too small, the crosslink density decreases and the compression set deteriorates. On the other hand, even if the iodine value is excessively large, the effect of improving the compression set does not increase.

(D): Mooney viscosity (JIS-K-63
00-ML _{1 + 4} (121 in Mooney viscosity test
C)) is 50-120, preferably 60-95. If the Mooney viscosity is too low, the foaming agent decomposed gas during foaming is poorly retained, resulting in a rubber foam with a high density.
The skin of the foam may become bad. In addition, shape retention is also deteriorated. On the other hand, if the Mooney viscosity is too high, kneading processability and extrusion processability deteriorate.

The cyclohexane insoluble matter is measured by the following method. [Procedure 1] Copolymer rubber was cut into about 1 mm square and about 0.
5 g is weighed (precisely weighed to 0.1 mg), and the weight is defined as Ag. [Procedure 2] The copolymer rubber weighed in Procedure 1 and cyclohexane (2,6-Di-tert-bu which is an antioxidant)
250 ml of tyl-4-methylphenol (containing 0.1% by weight) is placed in a 500 ml Erlenmeyer flask with a stopper. [Procedure 3] The Erlenmeyer flask of Procedure 2 is left at 25 ° C for 24 hours. [Procedure 4] The Erlenmeyer flask of Procedure 3 is attached to a shaker, and shaken (120 rpm) at room temperature for 1 hour. [Procedure 5] Weigh a wire mesh of 120 mesh (weigh accurately to 0.1 mg). Let the weight be Bg. [Procedure 6] The liquid in the Erlenmeyer flask, which has been shaken in Procedure 4, is filtered using the wire mesh of Procedure 5. [Procedure 7] The residue remaining in the Erlenmeyer flask in procedure 6 is washed into the wire net with about 40 ml of new cyclohexane. [Procedure 8] The wire net of Procedure 7 is dried in an atmosphere of 60 to 90 ° C for 3 hours. [Procedure 9] The wire net of Procedure 8 is left in a desiccator for about 30 minutes and cooled to room temperature. [Procedure 10] The wire net of Step 9 is weighed (weigh accurately up to 0.1 mg). Let its weight be Cg. [Procedure 11] Cyclohexane insoluble matter is calculated by the following formula. Cyclohexane insoluble matter (%) = ((C−B) / A) × 1
00

The α-olefin of the ethylene-α-olefin-non-conjugated diene copolymer rubber used in the present invention is, for example, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-olefin. 1-pentene, 1-
Examples thereof include octene and 1-decene, and one kind thereof may be used alone, or two or more kinds thereof may be used in combination. Among them, propylene and 1-butene are preferable.

The diene in the non-conjugated diene of the ethylene-α-olefin-non-conjugated diene copolymer rubber used in the present invention is a term that includes a polyene other than a diene, in addition to the diene. 4-hexadiene,
Chain non-conjugated dienes such as 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene; cyclohexadiene, dicyclo Cyclic non-conjugated dienes such as pentadiene, methyltetraindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene, 6-chloromethyl-5-isopropenyl-2-norbornene; 2,3-diisopropylidene-5 Trienes such as norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene; or 5-vinyl -2-norbornene, 5- (2-propenyl) -2-norbornene,
5- (3-butenyl) -2-norbornene, 5- (4-
Pentenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 5- (5-heptenyl) -2
-Norbornene, 5- (7-octenyl) -2-norbornene, 5-methylene-2-norbornene, 6,10-
Dimethyl-1,5,9-undecatriene, 5,9-dimethyl-1,4,8-decatriene, 4-ethylidene-
8-methyl-1,7-nonadiene, 13-ethyl-9-
Methyl-1,9,12-pentadecatriene, 5,9,
13-trimethyl-1,4,8,12-tetradecadiene, 8,14,16-trimethyl-1,7,14-hexadecatriene, 4-ethylidene-12-methyl-1,
11-Pentadecadiene may be mentioned, and one kind thereof may be used alone, or two or more kinds thereof may be used in combination. In addition, 5-ethylidene-2-norbornene and / or dicyclopentadiene are preferable.

The method for producing the ethylene-α-olefin-non-conjugated diene copolymer rubber used in the present invention is not particularly limited, and various catalysts such as titanium-based catalyst, vanadium-based catalyst or metallocene-based catalyst are used. Can be manufactured.

The ethylene-α-olefin-non-conjugated diene copolymer rubber used in the present invention further includes a foaming agent, a plasticizer, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a filler, and polyethylene. Various compounding agents such as resin such as polypropylene and polypropylene are appropriately added and blended.

As the foaming agent used in the present invention, sodium bicarbonate, sodium carbonate, ammonium bicarbonate,
Ammonium carbonate, ammonium nitrite, N, N'-dimethyl N, N'-dinitron-terephthalamide, N,
N'-dinitron-pentamethylene-tetramine, azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene, barium-azodicarboxylate, benzene-sulfonyl-hydrazide, toluene-sulfonyl-hydrazide, toluene- Sulfonyl-hydrazide derivative, P-toluene-sulfonyl-semicarbazide, 4,4'-oxybis (benzenesulfonyl-hydrazide), diphenylsulfone-3,3'-disulfonyl-hydrazide, calcium azide, 4,4'-diphenyl- Examples thereof include disulfonyl azide-bala-toluene-malphonyl azide, P-toluenesulfonylacetone hydrazone, hydrazodicarbonamide, etc., which may be used alone or in combination of two or more. May be. Further, it is preferable to use a powder having a median diameter of 10 μm or less as the foaming agent in order to increase the expansion ratio of the rubber foam.

The blowing agent is preferably added in an amount of 0.5 to 20 parts by weight with respect to 100 parts by weight of the ethylene-α-olefin-nonconjugated diene copolymer rubber. If the amount of the foaming agent is too small, the expansion ratio of the rubber foam may be small, while if the amount of the foaming agent is too large, the surface texture of the rubber foam may be deteriorated.

If desired, a foaming auxiliary agent may be used in combination with the foaming agent. As the foaming aid, urea compounds and zinc white, inorganic salts such as tribasic lead sulfate, and
Examples thereof include metal soaps such as zinc stearate and lead stearate, and salicylic acid.

Examples of the plasticizer used in the present invention include castor oil such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, vaseline, coal tar pitch, linseed oil, sub, beeswax, ricinoleic acid. , Palmitic acid, barium stearate, calcium stearate, zinc laurate, atactic polypropylene, coumarone indene resin and the like. Among them, process oil is particularly preferably used. These plasticizers are ethylene-α-olefin-
10 to 150 parts by weight, preferably 30 to 150 parts by weight, relative to 100 parts by weight of the non-conjugated diene copolymer rubber,
More preferably, it is used in an amount of 50 to 150 parts by weight.

As the vulcanizing agent used in the present invention, sulfur, sulfur chloride, sulfur dichloride, 4,4'-dithiodimorpholine, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide,
Selenium dimethyldithiocarbamate, dicumyl peroxide, 2,5-dimethyl-2,5-di (tertiary butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl −
2,5- (tert-butylperoxy) hexyne-3, di-tert-butyl peroxide, di-tert-butyloxy-3,3
Examples thereof include 5-trimethylcyclohexane and tert-butyl hydroperoxide. Sulfur, dicumyl peroxide, di-tert-butyl peroxide and di-tert-butyl peroxide-3,3,5-trimethylcyclohexane are particularly preferable.

Sulfur is usually added in an amount of 0.1% based on 100 parts by weight of the ethylene-α-olefin-non-conjugated diene copolymer rubber.
It is used in a proportion of 1 to 10 parts by weight, preferably 0.5 to 5 parts by weight. The organic peroxide is usually used in a proportion of 0.1 to 15 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-non-conjugated diene copolymer rubber. .

When sulfur or a sulfur-based compound is used as a vulcanizing agent, a vulcanization accelerator and a vulcanization aid are used in combination, if necessary. As the vulcanization accelerator, N-cyclohexyl-2-benzothiazole-sulfenamide, N-
Oxydiethylene-2-benzothiazole-sulfonamide, N, N-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole, 2- (2,4-dinitrophenyl) mercaptobenzothiazole, 2- (2,6- Diethyl-4-morpholinothio) benzothiazole, dibenzothiazyl-disulfide, diphenylguanidine, triphenylguanidine, diorthotolylguanidine, orthotolyl-by-
Guanide, diphenylguanidine-phthalate, acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde ammonia, 2-mercaptoimidazoline, thiocarbanilide, diethylthiourea, dibutylthiourea, trimethylthiourea, diorthotri Ruthiourea, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutyl thiuram disulfide, dipentamethylene thiuram tetrasulfide, zinc dimethyldithiocarbamate, zinc diethylthiocarbamate , The-
Examples thereof include zinc n-butyldithiocarbamate, zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, selenium dimethyldithiocarbamate, tellurium diethyldithiocarbamate, zinc dibutylxanthogenate, and ethylenethiourea. These vulcanization accelerators are used in a proportion of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, based on 100 parts by weight of the ethylene-α-olefin-nonconjugated diene copolymer rubber.

Examples of the vulcanization aid include metal oxides such as magnesium oxide and zinc oxide, and the use of zinc oxide is preferred. Usually, these vulcanization aids are used in an amount of 3 to 20 parts by weight based on 100 parts by weight of the ethylene-α-olefin-nonconjugated diene copolymer rubber.

When crosslinking with a peroxide, sulfur, a quinone dioxime such as P-quinone dioxime,
A cross-linking aid such as polyethylene glycol dimethacrylate, diallyl phthalate, triallyl cyanurate, or divinylbenzene may be used.

The filler used in the present invention is SR
F, GPF, FEF, HAF, ISAF, SAF, F
Inorganic fillers such as carbon black commonly used in rubbers such as T and MT, finely divided silicic acid, calcium carbonate, talc, and clay are preferably used. The content of the filler per 100 parts by weight of the ethylene-α-olefin-non-conjugated diene copolymer rubber is preferably 30 to 300 parts by weight, more preferably 70 to 200 parts by weight.

The rubber foam of the present invention has the above-mentioned condition (A).
To (D) are obtained by foaming and crosslinking a rubber composition containing an ethylene-α-olefin-non-conjugated diene copolymer rubber, and preferably satisfy the conditions (A) to (D). In addition to the ethylene-α-olefin-non-conjugated diene copolymer rubber, foam a rubber composition containing the above-mentioned foaming agent, plasticizer, vulcanizing agent, vulcanization accelerator, vulcanization aid, and filler. It is obtained by crosslinking. The amount ratio of each component is as described above.

[0027] and wherein the resulting rubber foam, density of ^{0.30g / cm 3 ~0.50g / cm 3} , preferably ^{0.34g / cm 3 ~0.42g / cm 3} .
If the density of the rubber foam is too low, the compression set of the rubber foam deteriorates. On the other hand, if the density of the rubber foam is too high, the requirements for weight reduction and cost reduction cannot be satisfied.

A specific method for obtaining a foam by foaming / crosslinking is as follows. Condition (A)
To ethylene-α-olefin-non-conjugated diene copolymer rubber satisfying (D), a foaming agent, a plasticizer, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, and a filler, if necessary. Depending on the type, such as zinc oxide, stearic acid, polyethylene glycol, flame retardant, calcium oxide, foaming aid, anti-aging agent, adhesive substances such as polybutene and rosin, resins such as polyethylene and polypropylene, using Banbury or kneader and roll. And kneaded to obtain a rubber composition. Next, a foam is obtained by foaming and crosslinking the rubber composition by heat or the like. As the device in this case, an oven, a continuous hot air crosslinking device, a microwave heating device, a fluidized bed of glass beads,
A molten salt tank, a hot mold, etc. can be used.

The rubber foam of the present invention can be optimally applied as a sealing material for automobiles.

[0030]

EXAMPLES Next, the present invention will be explained by examples. Examples 1 to 7 and Comparative Examples 1 to 3 using a Banbury mixer (internal volume 1.5 liters),
Of the compounding ingredients shown in Table 3, after kneading except for calcium oxide, a foaming agent, sulfur, and a crosslinking (vulcanization) accelerator, a calcium oxide, a foaming agent, shown in Table 3 with an 8-inch open roll,
Iou, a compound was prepared by adding a crosslinking (vulcanization) accelerator. Next, a tube-shaped die (inner diameter 10 mm, wall thickness 1.0 mm) was attached to a 45 mm extruder, and the compound was extruded under the conditions of a die temperature of 80 ° C. and a cylinder temperature of 60 ° C. to form a tube. In the evaluation of the extruded skin shown in Tables 1 and 2, the smoothness of the appearance of the tube at this time was visually judged, and the one having high smoothness was regarded as good. This molded product was introduced into a hot air vulcanization tank at 230 ° C. and heated for 4 minutes to obtain a tubular rubber foam. The smoothness of the tube appearance of the rubber foam after foaming / crosslinking was visually determined, and the one with high smoothness was evaluated as having good surface skin. In addition, the degree of collapse of the tube at this time was visually determined, and those having less collapse were evaluated as having good shape retention. The density of the rubber foam was determined as a test piece by cutting it to a length of 50 mm, its volume was obtained from the weight in air and buoyancy when immersed in water, and was obtained from the weight / volume value. For the compression set, a tubular rubber foam was cut into a test piece having a length of 20 mm.
A sponge compression set measuring die was compressed by 50% with respect to the outer diameter of the tube and heat-treated in a gear oven at 70 ° C. for 96 hours to perform a physical test method for expanded rubber (SRIS-01.
01).

In each of Examples 1 to 7 satisfying the requirements of the present invention, the density of the rubber foam was low, and the surface texture, shape retention and compression set were good. On the other hand, in Comparative Examples 1 and 2 in which the cyclohexane insoluble content is lower than the specified range of the present invention, the surface texture of the rubber foam is good, but the shape retention is poor and the density tends to be large, which is unsatisfactory. And the Mooney viscosity (J
IS-K-6300-ML in Mooney viscosity test
_In Comparative Example 3 in which _{1 + 4} (121 ° C.) is lower than the specified range of the present invention, the extruded skin of the unvulcanized product is good, but the surface skin after foaming / crosslinking is poor and the density tends to be large. However, it is unsatisfactory because the compression set is poor.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

(Explanation of Tables) * 1: Non-conjugated diene is 5-ethylidene-2-norbornene * 2: Mooney viscosity (JIS-K-6300-ML 1 _{+ 4} (121 ° C) in Mooney viscosity test) * 3: Carbon Black: "Asahi 50H" manufactured by Asahi Carbon Co., Ltd.
G "* 4: Process oil:" PS430 "manufactured by Idemitsu Kosan Co., Ltd. * 5: Foaming agent Y: 4,4 'oxybisbenzenesulfonyl hydrazide powder foaming agent Z: Median diameter of 4 µm 4,4 'Oxybisbenzenesulfonyl hydrazide powder * 6: Crosslinking (vulcanization) accelerator: M, BZ, TE, PZ, Varnock R (manufactured by Ouchi Shinko Chemical Co., Ltd.) mixture Evaluation of Tables 1 and 2 In the column, "○" represents "good",
“Δ” represents “somewhat good”, and “x” represents “evil”.

[0036]

As described above, according to the present invention, a specific ethylene-α-olefin-non-conjugated diene copolymer rubber is contained as a rubber component, excellent processability is maintained, and a high expansion ratio (low density) is maintained. To provide a rubber foam which is lightweight and is excellent in compression set, surface texture and shape retention by foaming / crosslinking a rubber composition capable of being used, and an automobile sealing material using the rubber foam. I was able to.

Claims (7)

[Claims] 1. A density obtained by foaming and crosslinking a rubber composition containing an ethylene-α-olefin-non-conjugated diene copolymer rubber satisfying the following conditions (A) to (D) is 0.30. ~ 0.50 g / cm ³ rubber foam. (A): 5 to 30% by weight of cyclohexane insolubles (B): Ethylene / α-olefin weight ratio of 73/2
7-40 / 60 (C): content of non-conjugated diene is 18-36 (D): Mooney viscosity (JIS-K-6300-ML _{1 + 4} (121 ° C) in Mooney viscosity test) is 50 ~ 1
20 2. The cyclohexane insoluble content is 5% by weight to 15%.
% By weight and Mooney viscosity (JIS-K-630
0-ML _{1 + 4} (121 ° C) in Mooney viscosity test)
Is 60 to 95, The rubber foam according to claim 1. 3. The rubber foam according to claim 1, having a density of 0.34 to 0.42 g / cm ³ . 4. The rubber foam according to claim 1, wherein the α-olefin of the ethylene-α-olefin-non-conjugated diene copolymer rubber is propylene. 5. The ethylene-α-olefin-nonconjugated diene copolymer rubber has a non-conjugated diene of 5-ethylidene-2-
Norbornene or dicyclopentadiene.
The rubber foam described. 6. The rubber foam according to claim 1, which is obtained by using a powder having a median diameter of 10 μm or less as a foaming agent. 7. A sealing material for automobiles, which uses the rubber foam according to any one of claims 1 to 6.