JP2007327004A - Acrylic elastomer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acrylic elastomer composition to be crosslinked with an organic peroxide by which, even when the composition is steam-vulcanized to be molded into a hose, a yellow bloom or the like is not generated, which does not cause an appearance failure. <P>SOLUTION: This acrylic elastomer composition comprises an acrylic elastomer produced by copolymerizing 5 to 80 wt.% of alkoxyalkyl acrylate, a maleimide co-crosslinker having at least two phenyl groups and an organic peroxide. Preferred examples of the maleimide co-crosslinker having at least two phenyl groups include 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, bisphenol A diphenylether bismaleimide and 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acrylic elastomer composition. More specifically, the present invention relates to an acrylic elastomer composition that does not generate colored bloom in a vulcanized molded product to which steam vulcanization is applied.

It is known that an acrylic elastomer copolymerized with an alkoxyalkyl (meth) acrylate can be crosslinked by hot pressing, steam, or the like by adding a bismaleimide compound and an organic peroxide thereto. That is, the acrylic elastomer which is a copolymer having an ether group called an alkoxyalkyl group enables peroxide crosslinking by a reaction with respect to the ether group of the bismaleimide compound.
JP-A-10-231386

  Peroxide crosslinking is a vulcanization system commonly used in (hydrogenated) NBR and the like, so if peroxide crosslinking is possible for acrylic elastomers, (hydrogenated) NBR and acrylic elastomers Since lamination molding becomes possible, it can be said that this is a vulcanization method that has been attracting attention recently.

  In Patent Document 1, in the case of a peroxide-crosslinkable acrylic elastomer copolymerized with an alkoxyalkyl (meth) acrylate, steam vulcanization is performed using N, N'-m-phenylenedimaleimide as a co-crosslinking agent. Thus, it is said that a vulcanized product such as a hose excellent in vulcanizability, vulcanized physical properties, heat aging resistance and the like can be obtained. However, in steam vulcanization, which is mainly used as the primary vulcanization of extrusion molding and large rolls such as hoses, yellow bloom due to N, N'-m-phenylene dimaleimide occurs during vulcanization, There is a problem of poor appearance.

  An object of the present invention is an acrylic elastomer composition that is crosslinked by an organic peroxide, and does not generate yellow bloom or the like even when steam vulcanized to form a hose or the like, resulting in poor appearance. It is to provide something that does not occur.

  The object of the present invention is achieved by an acrylic elastomer composition containing an acrylic elastomer copolymerized with 5 to 80% by weight of alkoxyalkyl acrylate, a maleimide co-crosslinking agent having at least two phenyl groups, and an organic peroxide. Is done.

  The acrylic elastomer composition according to the present invention does not generate yellow bloom or the like due to the maleimide co-crosslinking agent, even in steam vulcanization mainly used as primary vulcanization of extrusion and large rolls such as hoses, Provided is a vulcanizate that does not cause poor appearance due to this. For this reason, it can utilize effectively as vulcanization molding materials, such as various hoses which implement steam vulcanization, various sealing materials, a diaphragm, and various rolls.

  As the acrylic elastomer, 5 to 80% by weight, preferably 10 to 70% by weight of alkoxyalkyl group having 2 to 6 carbon atoms, such as methoxymethyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate , 2-butoxyethyl acrylate, 3-ethoxypropyl acrylate, etc., and preferably an acrylic elastomer copolymerized with 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate. If the copolymerization ratio of the alkoxyalkyl acrylate is less than this, the balance between cold resistance and oil resistance will be poor, and the crosslink density will be low. More specifically, the crosslink density becomes very high, the elongation decreases and the function as a rubber is lost.

  These alkoxyalkyl acrylates are 80 to 5% by weight, preferably 70 to 10% by weight of alkyl (meth) acrylate, such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, n-hexyl acrylate, An acrylate having an alkyl group having 1 to 8 carbon atoms such as 2-ethylhexyl acrylate and n-octyl acrylate or a corresponding methacrylate, preferably ethyl acrylate, n-butyl acrylate, or both are copolymerized Acrylate is preferably used in terms of a balance between oil resistance and cold resistance. In general, when the chain length of the alkyl group is long, it is advantageous in terms of cold resistance, but it is disadvantageous in terms of oil resistance, and when the chain length is short, the opposite is the case.

  In the acrylic elastomer copolymer, other copolymerizable ethylenically unsaturated monomers such as styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene, (meth) acrylonitrile, acrylic acid at a ratio of about 30% by weight or less. Amides, vinyl acetate, cyclohexyl acrylate, benzyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, ethylene, propylene, piperylene, isoprene, pentadiene, butadiene, and the like can be copolymerized.

  Further, about 10% by weight of (meth) acrylate having an ether bond in the side chain, such as phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, etc. Copolymerization can be carried out at the following ratio.

  If necessary, for the purpose of improving kneading processability, extrusion processability, etc., a polyfunctional unsaturated monomer or oligomer, such as ethylene glycol di (meth) acrylate, of about 5% by weight or less in the acrylic elastomer copolymer. , Propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di ( Alkylene glycol di (meth) acrylates such as (meth) acrylate, tetraethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, bisphenol A / ethylene oxide adduct diacrylate, di Methylol tricyclodecane diacri Rate, glycerin methacrylate acrylate, 3-acryloyloxyglycerin monomethacrylate and the like can be copolymerized.

  The copolymerization reaction of each monomer component is performed by various polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization and the like, and the copolymerization reaction is performed until the polymerization conversion rate reaches 90% or more. The charged weight ratio of the components is almost the copolymerized weight ratio.

ビスフェノールA・ジフェニルエーテルビスマレイミドまたは3,3′-ジメチル-5,5′-ジエチル-4,4′-ジフェニルメタンビスマレイミドが用いられ、これらの例にみられるようにフェニル基は低級アルキル基等で置換されていてもよい。これらのマレイミド共架橋剤は、アクリルエラストマー 100重量部当り0.2〜15重量部、好ましくは1〜10重量部の割合で用いられる。これ以上の割合で共架橋剤が用いられると、加硫物の強度、伸び等の一般物性が損なわれるようになり、一方これ以下の割合では、加硫物の一般物性が不十分なものとなる。 Examples of maleimide co-crosslinking agents having at least two phenyl groups include 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide,

Bisphenol A / diphenyl ether bismaleimide or 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide is used. As seen in these examples, the phenyl group is substituted with a lower alkyl group, etc. May be. These maleimide co-crosslinking agents are used in a proportion of 0.2 to 15 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of the acrylic elastomer. When the co-crosslinking agent is used in a proportion higher than this, the general physical properties such as strength and elongation of the vulcanized product will be impaired, while in the proportion lower than this, the general physical properties of the vulcanized product are insufficient. Become.

  An ethylene-acrylate copolymer rubber may be used in combination with an acrylic elastomer copolymerized with an alkoxyalkyl acrylate, and in such a case, the above-mentioned ratio of the co-crosslinking agent is used per 100 parts by weight of the total amount. The ethylene-acrylate copolymer rubber is used in a proportion of not more than 50% by weight, preferably not more than 30% by weight, in the total amount with the acrylic elastomer copolymerized with alkoxyalkyl acrylate.

  The ethylene-acrylate copolymer rubber is a copolymer rubber obtained by copolymerizing 20 to 75% by weight, preferably 30 to 65% by weight of ethylene, and the balance of the above-mentioned alkyl acrylate, preferably methyl acrylate or ethyl acrylate. Yes, there can be further copolymerized with an alkoxyalkyl acrylate as described above. In this copolymer rubber, 30% by weight or less, preferably 0.5 to 15% by weight, and more preferably 3 to 5% by weight of a crosslinking site monomer can be copolymerized.

  Examples of organic peroxides include di-tert-butyl peroxide, dicumyl peroxide, di-tert-butyl cumyl peroxide, 1,1-di (tert-butyl peroxy) -3,3,5-trimethylcyclohexane. 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 1,3-di (tert (3-butylperoxydiisopropyl) benzene, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, tert-butylperoxybenzoate, tert-butylperoxyisopropyl carbonate, n-butyl-4,4-di (Tertiary butyl peroxy) valerate or the like is used in a proportion of 0.2 to 10 parts by weight, preferably 0.75 to 2 parts by weight, per 100 parts by weight of the acrylic elastomer.

  The composition was prepared by kneading each component except the organic peroxide crosslinking agent and the co-crosslinking agent with a kneading machine such as a Banbury mixer or kneader, adding the crosslinking agent and the co-crosslinking agent, and kneading with an open roll. The resulting composition is subjected to primary vulcanization at about 150 to 230 ° C. for about 1 to 40 minutes, and the primary vulcanization is preferably performed by extrusion steam vulcanization, but a molding method such as hot pressing may be applied. If necessary, secondary vulcanization is performed at about 150 to 200 ° C. for about 0.5 to 20 hours.

  Next, the present invention will be described with reference to examples.

Example 1
Acrylic elastomer A Note) 100 parts by weight Stearic acid 1 〃
4,4'-bis (α, α-dimethylbenzyl) diphenylamine 2
2,2'-methylenebis (4-ethyl-6-tert-butylphenol) 0.75 〃
FEF carbon black (N550) 55 〃
1,3-di (tert-butylperoxyisopropyl) benzene 0.5 〃
4,4'-diphenylmethane bismaleimide 6

Note) Ternary copolymer obtained by continuing emulsion polymerization reaction until 30% by weight of ethyl acrylate, 35% by weight of n-butyl acrylate and 35% by weight of 2-methoxyethyl acrylate reach 90% polymerization conversion. Rubber

  Each of the above components (excluding the crosslinking agent and co-crosslinking agent) is kneaded using a Banbury mixer, the crosslinking agent and the co-crosslinking agent are added to the kneaded product using an open roll, and the resulting composition is formed into a hose shape. After extrusion molding, steam vulcanization (primary vulcanization) was performed at 160 ° C. for 30 minutes in a vulcanizing can, and then oven vulcanization (secondary vulcanization) was performed at 175 ° C. for 4 hours.

  The obtained secondary vulcanization hose was measured for vulcanized physical properties (based on JIS K-6253, JIS K-6251), and the appearance of the steam vulcanized hose was visually confirmed (presence of yellow bloom). It was.

Example 2
In Example 1, the same amount of polyphenylenemethane maleimide was used in place of 4,4′-diphenylmethane bismaleimide.

Example 3
In Example 1, the same amount of bisphenol A · diphenyl ether bismaleimide was used in place of 4,4′-diphenylmethane bismaleimide.

Example 4
In Example 1, the same amount of 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane bismaleimide was used in place of 4,4′-diphenylmethane bismaleimide.

Example 5
In Example 1, 25 parts by weight of 100 parts by weight of the acrylic elastomer was substituted with ethylene-acrylate copolymer rubber (DuPont product Vamac DP).

Example 6
In Example 1, acrylic elastomer B obtained by copolymerizing 2-methoxyethyl acrylate in acrylic elastomer A by replacing 2-ethoxyethyl acrylate in the same proportion was used in the same amount instead of acrylic elastomer A.

Comparative Example In Example 1, the same amount of N, N'-m-phenylene dimaleimide was used in place of 4,4'-diphenylmethane bismaleimide.

The results obtained in the above examples and comparative examples are shown in the following table.
table
Example comparison
Measurement / evaluation items 1 2 3 4 5 6 cases
[Vulcanized physical properties]
Hardness (Duro A) 55 58 53 47 56 55 51
Tensile strength (MPa) 9.0 8.7 8.0 6.8 9.8 8.8 9.8
Elongation at break (%) 230 210 250 360 260 230 250
[Steam vulcanizate appearance]
Yellow Bloom No No No No No No Yes Yes

Claims (8)

  An acrylic elastomer composition comprising an acrylic elastomer copolymerized with 5 to 80% by weight of an alkoxyalkyl acrylate, a maleimide co-crosslinking agent having at least two phenyl groups, and an organic peroxide.   Maleimide co-crosslinkers with at least two phenyl groups are 4,4'-diphenylmethane bismaleimide, polyphenylmethane maleimide, bisphenol A diphenyl ether bismaleimide or 3,3'-dimethyl-5,5'-diethyl-4 The acrylic elastomer composition according to claim 1, which is 4,4'-diphenylmethane bismaleimide.   The acrylic elastomer composition according to claim 1 or 2, wherein 0.2 to 15 parts by weight of a maleimide co-crosslinking agent is used per 100 parts by weight of the acrylic elastomer.   The acrylic elastomer composition according to claim 1, wherein an ethylene-acrylate copolymer rubber is used together with an acrylic elastomer copolymerized with an alkoxyalkyl acrylate.   The acrylic elastomer composition according to claim 4, wherein the ethylene-acrylate copolymer rubber is used in a proportion of not more than 50% by weight in the total amount with the acrylate copolymerized with alkoxyalkyl acrylate.   6. The acrylic elastomer composition according to claim 1, wherein steam vulcanization is applied as primary vulcanization.   A hose formed by applying steam vulcanization to the acrylic elastomer composition described in Example 6 as primary vulcanization and vulcanization molding. A roll or seal material in which steam vulcanization is applied to the acrylic elastomer composition described in Example 6 as primary vulcanization and vulcanized.