JPH11279365A - Crosslinkable acrylic rubber composition and crosslinked rubber molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition which can give a crosslinked rubber reduced in the deterioration in tensile strength after thermal aging by compounding a carboxyl-containing acrylic rubber with a hydrazido-containing compound. SOLUTION: The carboxyl-containing acrylic rubber used is usually one obtained by polymerizing 10-99.9 wt.% alkyl acrylate, 0-50 wt.% alkoxyalkyl acrylate, and 0.1-40 wt.% carboxyl-containing monomer and having a Mooney viscosity (ML1+4 , 100 deg.C) of, usually, about 10-150, and a carboxyl content of, desirably, 0.0005-0.06 mol per 100 g of the acrylic rubber. The hydrazido- containing compound is a compound having at least two hydrazido groups and is used in an amount of 0.0005-0.1 mol, (in terms of the hydrazido functional groups), per 100 of the carboxyl-containing acrylic rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinkable acrylic rubber composition, and more particularly to a carboxyl group-containing acrylic rubber compounded with a specific crosslinking agent, which is subjected to a heat history (after heat load). The present invention relates to a crosslinkable acrylic rubber composition suitable for producing a crosslinked acrylic rubber molded article in which the deterioration in physical properties is improved.

[0002]

2. Description of the Related Art Acrylic rubber has properties such as oil resistance, cold resistance and heat resistance, and is therefore a crosslinked rubber in various fields such as gasket materials for automobile engines, various oil-resistant seal materials, and hose materials for oil transfer. Widely used in the manufacture of molded articles. As an acrylic rubber, an acrylic rubber containing a cross-linking point such as an active chlorine group, an epoxy group, or a carboxyl group is known, but a cross-linked acrylic that requires scorch resistance, compression set resistance, heat resistance, and the like is required. In the production of rubber molded articles, it is common to use a carboxyl group-containing acrylic rubber, which has particularly excellent performance.

As cross-linking agents for carboxyl group-containing acrylic rubber, polyepoxys and polyamines have been known. Among these, the crosslinked carboxyl group-containing acrylic rubber using a polyvalent amine as a crosslinking agent is characterized by a small rate of change in compression set and elongation after heat load compared to before heat load. However, the carboxyl group-containing acrylic rubber cross-linked with polyamines has a disadvantage that the rate of change in tensile strength after heat load is large, and the rate of change in tensile strength after heat load is required to be small. Not suitable for use. On the other hand, carboxyl group-containing acrylic rubbers cross-linked with other cross-linking agents such as polyepoxys have a very large elongation change rate after heat aging,
In addition, since it has poor compression set resistance, it was unsuitable as a raw material rubber for molded articles used at high temperatures.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a crosslinked carboxyl group-containing acrylic rubber using a conventional crosslinking agent, which is a disadvantage after heat aging. An object of the present invention is to provide a crosslinkable acrylic rubber composition having an improved decrease in tensile strength. The inventor has
As a result of intensive studies to achieve this object, the compound obtained by adding a hydrazide group-containing compound to a carboxyl group-containing acrylic rubber as a cross-linking agent can significantly reduce the tensile strength of the resulting cross-linked acrylic rubber after heat aging. And completed the present invention based on the findings.

[0005]

According to the present invention,
Provided are a crosslinkable acrylic rubber composition comprising a carboxyl group-containing acrylic rubber and a hydrazide group-containing compound, and an acrylic rubber molded product obtained by crosslinking the composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to embodiments. The carboxyl group-containing acrylic rubber used in the present invention is a polymer obtained by polymerizing an alkyl acrylate as an essential monomer and has a carboxyl group. The thing which hydrolyzed the ter group to the carboxyl group can also be used. Hereinafter, a carboxyl group-containing acrylic rubber obtained by copolymerizing a carboxyl group-containing monomer will be described.

As the alkyl acrylate used in the present invention, any of those conventionally used in acrylic rubbers can be used and is not particularly limited. For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-acrylate
Butyl ester, n-amyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, (2-ethylhexyl) acrylate, n-nonyl acrylate, n acrylate And alkyl acrylates having an alkyl group having about 1 to 10 carbon atoms, such as -decyl ester. Among them, preferred are ethyl acrylate and n-butyl acrylate. These acrylic acid alkyl esters can be used alone or in combination of two or more.

In the present invention, preferably, an alkoxyalkyl acrylate is copolymerized. As the alkoxyalkyl acrylate, any of those conventionally used in known acrylic rubbers can be used and is not particularly limited. For example, alkylene groups having about 1 to 5 carbon atoms such as methoxymethyl acrylate, ethoxymethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, and the like; Acrylic acid alkoxyalkyl esters having about 1 to 5 alkoxy groups are exemplified. Among them, acrylic acid 2-methoxyethyl ester and acrylic acid 2-ethoxyethyl ester are preferred. These acrylic acid alkoxyalkyl esters can be used alone or in combination of two or more.

The carboxyl group-containing monomer used in the present invention is not particularly limited as long as it is a monomer having a carboxyl group copolymerizable with an alkyl acrylate and an alkoxyalkyl acrylate. For example,
Unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid; fumaric acid, maleic acid,
Unsaturated polycarboxylic acids such as itaconic acid and their partial esters (monoalkyl esters having about 1 to 10 carbon atoms in the alkyl group, alkylene chains having about 1 to 5 carbon atoms and about 1 to 5 carbon atoms) Monoalkoxyalkyl ester having an alkoxy group). Above all, monoesters of unsaturated dicarboxylic acids are preferred, for example, fumaric acid and maleic acid (these are called butenedioic acids) monomethyl, monoethyl, monon
-Propyl, mono-n-butyl, mono-n-amyl, mono-n
Esters such as -hexyl, mono-n-pentyl, mono-n-octyl, mono (2-ethylhexyl), monomethoxymethyl, and mono (2-methoxyethyl).
Among them, monoalkyl maleate such as monoethyl maleate, monobutyl maleate and mono (2-ethylhexyl) maleate is particularly preferable. These carboxyl group-containing monomers can be used alone or in combination of two or more.

Examples of the monomers which can be copolymerized with the above-mentioned monomers used in the present invention include, for example, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; α-olefins of ethylene and propylene; Aromatic vinyl compounds such as styrene and α-methylstyrene; vinyl monomers such as vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether; hydroxyalkyl acrylate, alkoxyalkyl methacrylate, cyclohexyl acrylate Other derivatives of acrylic acid and methacrylic acid such as esters, benzyl acrylate, furfuryl acrylate and acrylamide; conjugated dienes such as isoprene, butadiene, chloroprene and piperylene; dicyclopentane Non-conjugated dienes such as diene, norbornene, ethylidene norbornene, hexadiene, norbornadiene; and polyfunctional compounds such as divinylbenzene, ethylene glycol diacrylate, propylene glycol diacrylate, ethylene glycol dimethacrylate, and propylene glycol dimethacrylate. These copolymerizable monomers can be used alone or in combination of two or more.

The carboxyl group-containing acrylic rubber used in the present invention can be obtained by radical polymerization of the above-mentioned monomers in the same manner as ordinary polymerization of acrylic rubber. In the present invention, the polymerization form such as emulsion polymerization, solution polymerization, suspension polymerization, batch system, polymerization system such as continuous system, polymerization conditions such as polymerization temperature, recovery method and the like are not particularly limited, and any polymerization method It may be.

The proportion of each monomer in the monomer mixture used in the present invention is appropriately determined according to the characteristics required for a molded article using a carboxyl group-containing acrylic rubber. The alkyl ester is 10 to 99.9% by weight, preferably 50 to 97.8% by weight, more preferably 70 to 94.5% by weight, and the alkoxyalkyl acrylate is 0 to 50% by weight, preferably 2 to 9% by weight. 30
%, More preferably 5 to 20% by weight, and the carboxyl group-containing monomer is 0.1 to 40% by weight, preferably 0.2 to 20% by weight, more preferably 0.5 to 10% by weight. is there. If necessary, other monomers copolymerized with these monomers are used in a range of 0 to 30% by weight in the monomer mixture.

The thus obtained carboxyl group-containing acrylic rubber used in the present invention has a Mooney viscosity (ML)
_{1 + 4} , 100 ° C.) is usually about 10 to 150. Further, since the amount of the carboxyl group-containing monomer charged in the polymerization and the amount of bonding in the polymer vary considerably depending on the type of the monomer, the preferred content of the bonding carboxyl group in the acrylic rubber is the acrylic rubber. It is 0.0005 to 0.06 mol, preferably 0.001 to 0.03 mol, more preferably 0.003 to 0.015 mol in terms of the amount of carboxyl functional group (ephr) per 100 g. 0.0005
If the amount is less than the mole, it is difficult to sufficiently crosslink, and the strength of the crosslinked rubber decreases. On the other hand, if it exceeds 0.06 mol, the elongation decreases, and the strength and heat resistance become insufficient, which is not preferable.

In the present invention, the crosslinking agent to be added to the carboxyl group-containing acrylic rubber is a hydrazide group (-CONHNH).
₂ ) a compound having at least two such compounds, for example, a reaction of an organic polycarboxylic acid such as an aliphatic polycarboxylic acid such as adipic acid or sebacic acid, or an aromatic polycarboxylic acid such as terephthalic acid or isophthalic acid with hydrazine or the like. Can be obtained by For example, isophthalic dihydrazide, terephthalic dihydrazide, phthalic dihydrazide, 2,6-naphthalenedicarboxylic dihydrazide, naphthalic dihydrazide, oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, glutaric dihydrazide, adipic dihydrazide Suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, brassyl acid dihydrazide, dodecane diacid dihydrazide, acetone dicarboxylic acid dihydrazide, fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, trimellitic acid dihydrazide, trimellitic acid 3,5-hydrazide Benzotricarboxylic dihydrazide, aconitic dihydrazide, pyromellitic dihydrazide and the like can be mentioned. These can be used alone or in combination of two or more.

The preferred amount of the hydrazide group-containing compound as a cross-linking agent is as follows.
0.0005 to 0.1 in terms of the amount of hydrazide functional group per 0 g
Mole, more preferably 0.001 to 0.06 mole, more preferably 0.003 to 0.03 mole. If the amount of the crosslinking agent is too small, the acrylic rubber will be insufficiently crosslinked, making it difficult to obtain practical strength. Conversely, if it is too large, the elongation tends to decrease, and the strength and the heat stability tend to be unsatisfactory.

In the present invention, a crosslinking accelerator can be used together with a crosslinking agent, if necessary. Examples of the crosslinking accelerator include alkali metal salts of organic or inorganic acids such as sodium stearate, potassium stearate, potassium oleate, sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide, or alkali metal hydroxide. Substances: tetramethylammonium bromide, benzyltriphenylphosphonium chloride, trimethyloctadecylammonium bromide,
4th such as tetramethylphosphonium iodide
Quaternary ammonium salts and phosphonium salts; tertiary amines such as triethylenediamine, imidazole, pyridine and quinoline; and guanidines such as diphenylguanidine, di-o-tolylguanidine and tetramethylguanidine. These can be used alone or in combination of two or more. The amount of the crosslinking accelerator to be used is generally 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, more preferably 0.4 to 5 parts by weight, per 100 parts by weight of the carboxyl group-containing acrylic rubber.

The crosslinkable rubber composition of the present invention comprises a carboxyl group-containing acrylic rubber and a crosslinking agent and, if necessary, other known compounding agents, for example, reinforcing agents such as carbon black and silica, and fillers such as calcium carbonate and talc. And a phenol-based or amine-based stabilizer, a plasticizer, a lubricant, or the like, and mixing and kneading using a commonly used mixer such as a roll, a Banbury, or an internal mixer.

The crosslinkable rubber composition thus obtained is, for example, formed into a tube by an extruder in the case of a hose and vulcanized by steam vulcanization (crosslinking) or the like, and in the case of a sealing material or the like. Compression molding, transfer molding,
Alternatively, a crosslinked molded product is manufactured by vulcanizing and molding into various shapes using a mold by injection molding or the like. In the present invention, the molding method and the vulcanization (crosslinking) method can use those methods that are usually carried out in the production of each molded article, and are not particularly limited. Examples of the molded article obtained by crosslinking the crosslinkable rubber composition of the present invention include, for example, an automobile fuel hose and an automobile ATF.
Examples include hoses, air duct hoses, gaskets for automobile engines, bearing seals, and the like, but are not limited to these examples.

[0019]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following, parts and percentages are by weight unless otherwise specified.

Example 1, Comparative Example 1 37.3 parts of ethyl acrylate, n-butyl acrylate 4
A monomer mixture consisting of 1.9 parts, 14.0 parts of 2-methoxyethyl acrylate and 6.8 parts of mono-n-butyl maleate was copolymerized by emulsion polymerization to give a bound carboxyl group of 7.4.10. ^-3 ephr, Mooney viscosity (M
(L _{1 + 4} , 100 ° C.) to give a carboxyl group-containing acrylic rubber having 40 (acrylic rubber A).

In accordance with the formulation shown in Table 1, the acrylic rubber A and each of the ingredients except the crosslinking agent and the crosslinking accelerator were mixed in a 09-liter Banbury, and the resulting mixture was mixed with the crosslinking agent and the crosslinking accelerator for 6 inches. The mixture was mixed and kneaded with a roll to prepare a crosslinkable rubber composition. Each crosslinkable rubber composition was press-vulcanized (primary vulcanization: 160 ° C. × 30 minutes) to obtain a 2 mm-thick cross-linked sheet, which was secondarily vulcanized with heated air (170 ° C.).
× 4 hours). Using this crosslinked sheet and a test piece for measuring compression set prepared under the above conditions, the tensile strength elongation and the 100% tensile stress under normal conditions were measured according to JIS K6251 and the hardness was measured according to JIS K6253.
The heat aging property was measured according to JIS K6257, and indicated by a rate of change before heat load. The compression set was measured according to JIS K6262. Table 1 shows the results.

[0022]

[Table 1] (Note) (1) Seat 116 manufactured by Tokai Carbon Co., Ltd. (2) Grec G-8205 manufactured by Dainippon Ink and Chemicals, Inc. (3) Diak No. 3 manufactured by DuPont

From the results shown in Table 1, the cross-linking agent of Comparative Example 1 is the most effective of the conventional cross-linking agents for carboxyl group-containing acrylic rubbers in that the cross-linked acrylic rubber has excellent properties even after heat load. However, it can be seen that, compared with this crosslinking agent, the crosslinking agent used in the present invention imparts more excellent properties to the crosslinked acrylic rubber even after heat load.

[0024]

According to the present invention described above, by crosslinking a carboxyl group-containing acrylic rubber with a compound having a hydrazide group as a crosslinking agent, excellent heat aging resistance, particularly excellent retention of tensile strength after heat resistance is obtained. A crosslinked rubber is provided. By using the crosslinkable rubber composition of the present invention, it is possible to produce molded articles such as gaskets for automobile engines and bearing seals.

A preferred embodiment of the present invention is as follows. (1) The amount of the hydrazide group-containing compound according to claim 1 or 2 is 100 g of a carboxyl group-containing acrylic rubber.
The amount of the hydrazide functional group per unit is preferably 0.0005 to 0.1 mol, more preferably 0.001 to 0.06 mol, and even more preferably 0.003 to 0.03 mol. (2) The carboxyl group-containing acrylic rubber according to (1),
The amount of carboxyl functional groups per gram (ephr) is 0.0
005 to 0.06 mol, preferably 0.001 to 0.0
It is 3 moles, more preferably 0.003 to 0.015 mole. (3) In (1) or (2), the carboxyl group-containing acrylic rubber has an acrylic acid alkyl ester of 10 to 10.
99.9% by weight, preferably 50-97.8% by weight, more preferably 70-94.5% by weight, and the alkoxyalkyl acrylate is 0-50% by weight, preferably 2-30% by weight, It is preferably 5 to 20% by weight, and the carboxyl group-containing monomer is 0.1 to 40% by weight, preferably 0.2 to 20% by weight, more preferably 0.5 to 10% by weight. (4) The amount of the hydrazide group-containing compound to be used is 0.0005 to 0.1 mol, more preferably 0.1 to 0.5 mol, per 100 g of the carboxyl group-containing acrylic rubber.
001 to 0.06 mol, more preferably 0.003 to
0.03 mol.

Claims (2)

[Claims] 1. A crosslinkable acrylic rubber composition comprising a carboxyl group-containing acrylic rubber and a hydrazide group-containing compound. 2. A crosslinked rubber molded article obtained by crosslinking the crosslinkable acrylic rubber composition according to claim 1.