JP2002294008A - Ethylene/acrylic rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for ameliorating mold staining in vulcanizing an ethylene/acrylic rubber composition with easily regulating its vulcanization rate in an amine vulcanization system for the ethylene-acrylic rubber. SOLUTION: The objective ethylene/acrylic rubber composition is obtained by compounding 100 pts.wt. of an ethylene/(meth)acrylic ester copolymer rubber with 0.1-10 pt(s).wt. of a polyamine, 0.1-10 pt(s).wt. of an imidazole and 1-400 pt(s).wt. of an inorganic filler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement in the amine vulcanization system of ethylene acrylic rubber. More specifically, the present invention relates to a novel ethylene-acrylic rubber composition capable of adjusting the vulcanization time and improving mold contamination during vulcanization.

[0002]

2. Description of the Related Art Ethylene / acrylic rubber obtained by copolymerizing ethylene, (meth) acrylate, and, in some cases, a crosslinking site monomer is known as a rubber having good heat resistance, oil resistance and low-temperature properties. It is generally used in the form of a vulcanized rubber obtained by vulcanizing a raw rubber of ethylene / acrylic rubber with a polyamine or the like (for example, JP-A-50-49389).

In a vulcanization system using a polyamine, the vulcanization rate is slow only with the polyamine alone, so that a method of secondary vulcanization while using guanidine as a vulcanization accelerator has been generally employed. However, in a polyamine vulcanization system using guanidine as a vulcanization accelerator, the primary vulcanizate has a low modulus of elasticity and thus easily adheres to a mold, and tends to cause mold contamination, so that productivity cannot be increased. Was. Further, it is difficult to precisely adjust the vulcanization rate, and there is also a problem that it is difficult to achieve a good balance between the storage stability and the vulcanization rate.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to increase the modulus of primary vulcanizates in a polyamine vulcanization system, improve mold contamination, and improve the productivity of the vulcanization process. It is in. It is another object of the present invention to provide a polyamine vulcanization formulation that can easily adjust the vulcanization rate and can achieve a good balance between storage stability and vulcanization rate. It is still another object of the present invention to provide a polyamine vulcanization formulation that can reduce the amount of polyamine used as a vulcanizing agent.

[0005]

That is, according to the present invention, 0.1 to 10 parts by weight of polyamine and 0.1 to 10 parts by weight of imidazole per 100 parts by weight of ethylene / (meth) acrylate copolymer rubber. And inorganic fillers 1-4
An ethylene / acrylic rubber composition comprising 00 parts by weight is provided.

According to the present invention, there is also provided ethylene (meth)
0.1 to 10 parts by weight of polyamine and 0.1 to 1 parts of imidazole per 100 parts by weight of acrylate copolymer rubber
Vulcanization of the ethylene-acrylic rubber composition, wherein the ethylene-acrylic rubber composition comprising 0 parts by weight and 1 to 400 parts by weight of an inorganic filler is vulcanized in multiple stages under heating. A method is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION
(Meth) acrylate copolymer rubber (hereinafter sometimes referred to as ethylene-acrylic rubber) is ethylene,
It is a multi-component copolymer rubber comprising a (meth) acrylate and a crosslinking site monomer. Here, the description of (meth) acrylate means acrylate or methacrylate.

In consideration of rubber properties, such ethylene-acrylic rubber generally contains (meth) acrylic acid ester polymerization units in the range of about 25 to 70% by weight, preferably about 30 to 65% by weight. I do. As particularly suitable multi-component copolymer rubber, considering the vulcanization characteristics,
0.1 to 10% by weight of polymerized units of the crosslinking site monomer,
In particular, it is desirable to contain it in the range of 0.3 to 7% by weight.

In consideration of the processability and vulcanization properties of ethylene / acryl rubber, Mooney viscosity (ML
_{(1 + 4)} , 100 ° C.) is 5 to 100, preferably 10
It is preferable to use one of about 70.

(Meth) in ethylene acrylic rubber
Examples of the acrylate include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate. can do. Among these, it is preferable to use a copolymer rubber having methyl acrylate, ethyl acrylate or n-butyl acrylate as a copolymer component.

The cross-linking site monomer in the multi-component copolymer rubber includes acrylic acid, methacrylic acid, monomethyl maleate, monoethyl maleate, monoethyl maleate such as monoisopropyl maleate, glycidyl acrylate, and glycidyl methacrylate. Such unsaturated glycidyl monocarboxylates can be exemplified. Particularly preferred is the use of maleic monoesters such as monomethyl maleate and monoethyl maleate.

The polyamine which can be used as a vulcanizing agent in the present invention includes hexamethylene diamine, hexamethylene diamine carbamate, N, N'-dicinnamylidene-1,6-hexane diamine, diethylene triamine, triethylene tetramine, tetraethylene Aliphatic polyamines such as pentamine, 1,3-bis (aminomethyl) cyclohexane, 4,4'-methylenebiscyclohexylamine, 4,4'-methylenebiscyclohexylamine carbamate, p, p'-methylenedianiline Alicyclic polyamines such as partially hydrogenated products of
Examples thereof include aromatic polyamines such as p, p'-methylenedianiline, m-phenylenediamine, and metaxylenediamine, and polyamines derived from these polyamines, polyamidoamines, ketimines, and silamines. These polyamines may be used alone or in combination of two or more.

In the present invention, imidazoles are used as a vulcanization accelerator together with the polyamine vulcanizing agent. As the imidazoles, not only imidazole but also substituted imidazoles in which a hydrogen atom bonded to a carbon atom and / or a nitrogen atom of the imidazole ring is substituted with various hydrocarbon groups can be used. More specifically, imidazoles such as imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole,
Heptadecyl imidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-
Examples thereof include cyanoethyl-2-phenylimidazole. Such imidazoles can be used alone or in combination of two or more. Further, imidazoles and guanidines may be used in combination.

In the ethylene-acrylic rubber composition of the present invention, an inorganic filler is blended for the purpose of improving mechanical strength, increasing the amount, and for other purposes. Examples of the inorganic filler include silica, alumina, talc, clay, calcium carbonate, magnesium carbonate, calcium sulfate, barium sulfate, magnesium silicate, aluminum hydroxide, synthetic zeolite, carbon black, glass powder, titanium oxide, and hydrotalcite. Examples can be given. These can be used alone or in combination of two or more.

The amount of each of the above components in the ethylene / acryl rubber composition of the present invention is 0.1 to 10 parts by weight of polyamine per 100 parts by weight of ethylene / acryl rubber,
Preferably 0.5 to 5 parts by weight, 0.1% of imidazoles.
10 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and the proportion of the inorganic filler is 1 to 400 parts by weight, preferably 10 to 300 parts by weight.

By using an appropriate amount of polyamine,
Excellent vulcanized rubber properties based on cross-linking of ethylene / acryl rubber can be exhibited. If the amount of the polyamine used is too small, a sufficient degree of crosslinking cannot be obtained in the vulcanized rubber, so that satisfactory vulcanized rubber physical properties cannot be obtained.On the other hand, if the amount used is excessive, the crosslinking proceeds. At the same time, a sufficient elongation at break cannot be obtained, and the compression set deteriorates.

By using an appropriate amount of a polyamine as a vulcanization accelerator, it is possible to effectively promote the vulcanization of ethylene / acrylic rubber and obtain a vulcanized product having a high elastic modulus in the primary vulcanization. Mold contamination tendency is small,
Productivity can be increased. However, if the amount of use is excessive, the storage stability deteriorates. Therefore, it is necessary to avoid using more than necessary. Its usage is also
When other vulcanization accelerators to be described later are used in combination, it is necessary to adjust the use amount within the above range.

The compounding of the inorganic filler is useful for increasing the strength of the vulcanized rubber. If the compounding amount is too small, not only the strength becomes insufficient, but also the skin of the compound becomes rough and the processability deteriorates. It tends to be. On the other hand, if the amount is too large, sufficient elongation cannot be obtained, and the viscosity of the compound becomes too high to deteriorate processability.

In the ethylene-acrylic rubber composition of the present invention, various other additives can be blended if necessary. Examples of such additives include plasticizers,
Examples thereof include processing aids, antioxidants, other vulcanization accelerators, and coloring agents such as pigments and dyes. Such a plasticizer is compatible with ethylene / acryl rubber, and for example, a monomer-based plasticizer, a polyester-based plasticizer, an ether-ester-based plasticizer, and the like can be used. Examples of processing aids include polyethylene wax, higher fatty acids, higher fatty acid salts, higher aliphatic amines, higher fatty acid amides, higher alcohols, and phosphate esters.

As the anti-aging agent, phenol-based anti-aging agents, amine-based anti-aging agents, sulfur-based anti-aging agents, phosphorus-based anti-aging agents and the like can be used. Examples of other vulcanization accelerators include guanidines, tertiary amines, boron trifluoride compounds, and the like, and can be used in combination with imidazoles as long as vulcanization is not inhibited.

To mix ethylene acrylic rubber, polyamines, imidazoles, inorganic fillers and other optional additives, a Banbury mixer, kneader,
An ordinary rubber kneader such as an open roll may be used.

In order to vulcanize the ethylene-acrylic rubber composition of the present invention, the composition is molded into a predetermined shape and then, for example, at about 100 to 300 ° C., preferably 150 to 250 ° C.
The temperature may be maintained for about 10 minutes to about 10 hours. In general, it is desirable to perform primary vulcanization under mild conditions and then perform multi-stage vulcanization to complete vulcanization at a temperature equal to or higher than that.

In the ethylene-acrylic rubber composition of the present invention, a vulcanized product having a high elastic modulus can be obtained in such primary vulcanization, and it is difficult for the vulcanized product to adhere to a mold, so that productivity can be increased. Also, compared to the case where guanidine is used as a vulcanization accelerator, a vulcanized rubber having the same rubber properties can be obtained by using a smaller amount of a polyamine vulcanizing agent.

[0024]

The present invention will be described in more detail with reference to the following examples. In addition, the evaluation method of the raw material used in the Example and the comparative example and the obtained composition is as follows.

(1) Raw material AEM: random copolymer of ethylene / methyl acrylate / crosslinking site monomer (melt flow rate 12 g / 1
0 minutes, Mooney viscosity (ML _{1 + 4} , 100 ° C) 15)

Vulcanizing agent: MDA (p, p'-methylene dianiline) Vulcanization accelerator-1: 2MZ (2-methylimidazole, trade name: Curezol 2MZ, manufactured by the company) Vulcanization accelerator-2: DPG ( Diphenylguanidine, trade name: Suncellar D, manufactured by the company) Vulcanization accelerator-3: DOTG (diorthotrilguanidine, trade name: Suncellar DT, manufactured by the company) Vulcanization accelerator-4: OTBG (orthotrilbiguanidine, product) Name: Noxeller BG, manufactured by the company)

Inorganic filler: CB (carbon black, N
550CB, trade name SEAST SO, manufactured by Tokai Carbon Co., Ltd. Processing aid-1: stearic acid (manufactured by Kawaken Fine Chemical Co., Ltd.) Processing aid-2: octadecylamine (trade name: Armin 18D, manufactured by Lion Akzo) Processing aid Agent 3: Phosphate processing aid (trade name: Phosphanol RL210, manufactured by Toho Chemical Co.) Antioxidant: CD (4,4 ′-(α, α-dimethylbenzyl) diphenylamine, trade name: Nocrack CD, Ouchi Shinko Chemical Co., Ltd.)

(2) Evaluation method (a) Evaluation of vulcanization characteristics Raw materials other than the vulcanizing agent and vulcanization accelerator shown in Table 1 were kneaded with a Banbury mixer for 3 minutes, and then the vulcanizing agent and the vulcanization accelerator were added. The mixture was kneaded with a 6-inch mixing roll to prepare an ethylene-acrylic rubber composition.

Using an MDR2000 manufactured by ALFA TECHNOLOGIES, the vulcanization curve of the composition was determined under the conditions of a temperature of 180 ° C. and a time of 15 minutes. Maximum value of vulcanization torque (S'max)
And the minimum value (S'min), the time to reach S'min (tc0), the torque is 2%, 10%, 50% and 90%.
% Rising times tc2, tc10, tc50 and tc9
0 was measured respectively.

(B) Evaluation of physical properties of vulcanized rubber A vulcanized product obtained by subjecting the above-mentioned ethylene / acryl rubber composition to primary vulcanization at 180 ° C. for 10 minutes and then at 180 ° C.
Regarding the vulcanized product obtained by secondary vulcanization under the condition of 4 hours,
Based on JIS K6301 (vulcanized rubber physical test method), 100% modulus (M100), strength at break (T
B), elongation at break (EB) and hardness were measured.

[Example 1, Comparative Examples 1 to 3] Various physical properties of a composition obtained by using each of the raw materials shown in Table 1 (the numerical values of the raw materials in the table indicate parts by weight) were measured by the above evaluation methods. did. Table 2 shows the results.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from the comparison between Example 1 and Comparative Examples 1 to 3, the ethylene-acrylic rubber composition of the present invention has a high vulcanization rate, and has a primary vulcanized rubber property and a secondary vulcanized rubber physical property. It turns out that both are excellent.

[0035]

The ethylene-acrylic rubber composition of the present invention is excellent in the productivity of vulcanized rubber since the vulcanization time is short and there is little mold contamination. In addition, the amount of the polyamine vulcanizing agent used can be reduced as compared with the conventional guanidine compounding formulation, which is excellent in economy.

Claims (3)

[Claims] 1. A polyamine of 0.1 to 10 per 100 parts by weight of an ethylene / (meth) acrylate copolymer rubber.
An ethylene / acrylic rubber composition, which comprises 0.1 parts by weight of imidazoles and 1 to 400 parts by weight of an inorganic filler. 2. The ethylene / acrylic rubber composition according to claim 1, wherein the ethylene / (meth) acrylate copolymer rubber is a copolymer of ethylene, (meth) acrylate and a crosslinking site monomer. 3. A plasticizer, a processing aid, an antioxidant,
3. The ethylene / acryl rubber composition according to claim 1, wherein at least one additive selected from a vulcanization accelerator and a colorant is blended.