JP2001098032A - Acrylic rubber and its composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic rubber excellent in oil resistance, and also excellent in balance between cold resistance and heat resistance, and a composition thereof. %, 0 to 10% by weight of a crosslinkable monomer unit and 99.9 to 80% of ethyl acrylate and butyl acrylate monomer units
% Of ethyl acrylate in the total of ethyl acrylate and butyl acrylate is 60 to 100% by weight.
Acrylic rubber in weight%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic rubber excellent in oil resistance, heat resistance and cold resistance and a composition thereof.

[0002]

2. Description of the Related Art In recent years, as industries have become larger and faster,
The rubber parts used for these are required to maintain higher and higher durability. In particular, larger sizes and higher speeds increase the operating temperature of machines and equipment, so rubber parts are required to have high heat resistance, and at the same time, oil resistance is improved for rubber parts that come into contact with lubricating oil. Is required. In addition, demands for cold resistance of rubber parts have been increasing due to use in harsh environments such as cold regions due to widespread industrial activities.

On the other hand, in the engine room of automobiles, thermal conditions have become more severe due to measures against exhaust gas, high output of the engine, and the like. Instead, acrylic rubber having excellent heat resistance and oil resistance has been used.
However, it has been known that the severer thermal conditions in the engine and the engine room create an environment in which the engine oil itself deteriorates, and the deteriorated engine oil further attacks the rubber hose to deteriorate the rubber material. Therefore, lubricating oil hose materials used in engine rooms are expected to have higher oil resistance, cold resistance and heat resistance than ever, and even acrylic rubber that has come to be used as a heat and oil resistant material. There is a demand for improved performance. Furthermore,
As the lubricating oil has a lower viscosity due to the higher performance of the automotive lubricating oil, further improvement in oil resistance has been required.

Japanese Patent Publication No. Sho 59-14498 discloses an ethylene (A) -vinyl acetate (B) -acrylate (C) copolymer in which (C) is 6 to 90% by weight and (A) /
It is described that a rubber composition comprising a copolymer having a weight ratio of (B) of 1 or less and a vulcanizing agent is excellent in oil resistance, heat resistance and weather resistance. Also, JP-A-63-3123
No. 38 discloses a copolymer of ethylene having a content of ethylene component of 3 to 10% by weight and another copolymer component, wherein the other copolymer component is vinyl acetate 0 to 10% by weight, acrylic Copolymers comprising more than 20% to 45% by weight of ethyl acrylate and 45 to less than 45% by weight of n-butyl acrylate and compositions thereof are described. In these compositions, some improvement in oil resistance is recognized, and in the latter, some improvement effect of cold resistance is also recognized.However, due to the harsh use conditions as described above, oil resistance, cold resistance and heat resistance are improved. Further improvement was required in the balance of sex.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides an acrylic rubber excellent in oil resistance and excellent in balance between cold resistance and heat resistance, and a composition thereof.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that ethylene monomer units, crosslinkable monomer units and specific acrylate ester monomer units It has been found that a copolymer consisting of the following provides a rubber having a very excellent balance of cold resistance, oil resistance and heat resistance at a specific composition ratio, and completed the present invention. That is, the present invention comprises 0.1 to 10% by weight of an ethylene monomer unit, 0 to 10% by weight of a crosslinking monomer unit, and 99.9 to 80% by weight of an ethyl acrylate and butyl acrylate monomer unit. It is an acrylic rubber in which the proportion of ethyl acrylate in the total of ethyl acrylate and butyl acrylate is 60 to 100% by weight.

Hereinafter, the present invention will be described in detail. The acrylic rubber of the present invention contains 0.1 to 10% by weight of an ethylene monomer unit, 0 to 10% by weight of a crosslinking monomer unit, and 99.9 to 8% of ethyl acrylate and butyl acrylate monomer units.
0% by weight, and the ratio of ethyl acrylate to the total of ethyl acrylate and butyl acrylate is 60 to 10%.
It is an acrylic rubber of 0% by weight. The ethylene monomer unit is particularly preferably 0.1 to 2.9% by weight,
If the ethylene monomer unit is too large, oil resistance tends to be insufficient. The proportion of ethyl acrylate in the total of ethyl acrylate and butyl acrylate is 75 to 10
0% by weight is preferable, and when the proportion of ethyl acrylate is small, oil resistance tends to be insufficient.

The crosslinkable monomer used in the acrylic rubber of the present invention includes one containing an epoxy group, one containing an active chlorine group, a carboxylic acid group, and one containing both an epoxy group and a carboxylic acid group. .

Specific examples of the crosslinking site monomer used in the present invention include those having an active chlorine group such as 2-chloroethyl vinyl ether, 2-chloroethyl acrylate, vinyl benzyl chloride, vinyl chloroacetate, and allyl chloroacetate. In addition, acrylic acid, methacrylic acid, crotonic acid, 2-pentenoic acid, maleic acid, fumaric acid, itaconic acid, those containing a carboxylic acid group such as maleic acid monoalkyl ester,
Glycidyl acrylate, glycidyl methacrylate,
Those containing an epoxy group such as allyl glycidyl ether and methallyl glycidyl ether are exemplified. The acrylic rubber in the present invention desirably contains these crosslinkable monomer units in an amount of 0 to 10% by weight, preferably 0.1 to 5% by weight, particularly preferably 0.5 to 3% by weight.

The acrylic rubber of the present invention may be obtained by copolymerizing another monomer copolymerizable with the above-mentioned monomer within a range not to impair the object of the present invention. Other copolymerizable monomers include methyl acrylate, n-propyl acrylate, isobutyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-methylpentyl acrylate, n-octyl acrylate, 2-ethylhexyl Acrylate, n-decyl acrylate, n-dodecyl acrylate, n-octadecyl acrylate, cyanomethyl acrylate, 1-cyanoethyl acrylate, 2-cyanoethyl acrylate, 1-cyanopropyl acrylate, 2-cyanopropyl acrylate, 3-cyanopropyl acrylate, 4 -Cyanobutyl acrylate, 6
Alkyl acrylates such as -cyanohexyl acrylate, 2-ethyl-6-cyanohexyl acrylate, and 8-cyanooctyl acrylate.

Also, 2-methoxyethyl acrylate,
2-ethoxyethyl acrylate, 2- (n-propoxy) ethyl acrylate, 2- (n-butoxy) ethyl acrylate, 3-methoxypropyl acrylate,
And alkoxyalkyl acrylates such as -ethoxypropyl acrylate, 2- (n-propoxy) propyl acrylate and 2- (n-butoxy) propyl acrylate.

Further, 1,1-dihydroperfluoroethyl (meth) acrylate, 1,1-dihydroperfluoropropyl (meth) acrylate, 1,1,5-trihydroperfluorohexyl (meth) acrylate,
1,2,2-tetrahydroperfluoropropyl (meth) acrylate, 1,1,7-trihydroperfluoroheptyl (meth) acrylate, 1,1-dihydroperfluorooctyl (meth) acrylate, 1,1-dihydroperfluorodecyl (meth) A) Fluorine-containing acrylates such as acrylate, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxyl-containing acrylates such as hydroxyethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dibutyl Tertiary amino group-containing acrylates such as aminoethyl (meth) acrylate, methacrylates such as methyl methacrylate and octyl methacrylate, and alkyl vinyls such as methyl vinyl ketone Ketones, vinyl and allyl ethers such as vinyl ethyl ether and allyl methyl ether, vinyl aromatic compounds such as styrene, α-methyl styrene, chlorostyrene and vinyl toluene, vinyl nitriles such as acrylonitrile and methacrylonitrile, ethylene, propylene, chloride Examples include ethylenically unsaturated compounds such as vinyl, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl acetate, vinyl propionate, and alkyl fumarate.

The acrylic rubber of the present invention can be obtained by copolymerizing the above monomers by a known method such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization.

The acrylic rubber of the present invention is used after vulcanization using a vulcanization system usually used for acrylic rubber. The vulcanization system applied is a vulcanization system containing an imidazole compound. Particularly, a vulcanization system obtained by adding trimethylthiourea to this is more preferably used.

As the imidazole compounds, 1-methylimidazole, 1,2-dimethylimidazole, 1-methylimidazole,
Methyl-2-ethylimidazole, 1-benzyl-2-
Ethyl imidazole, 1-benzyl-2-ethyl-5
Methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-phenylimidazole.
Trimellitate, 1-aminoethylimidazole, 1
-Aminoethyl-2-methylimidazole, 1-aminoethyl-2-ethylimidazole, 1-cyanoethyl-
2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4
-Methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-methylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 1-cyanoethyl-
2-ethyl-4-methylimidazole trimellitate,
1-cyanoethyl-2-undecyl-imidazole trimellitate, 2,4-diamino-6- [2′-methylimidazolyl- (1) ′] ethyl-s-triazine / isocyanuric acid adduct, 1-cyanoethyl-2 -Phenyl-4,5-di- (cyanoethoxymethyl) imidazole, N- (2-methylimidazolyl-1-ethyl) urea, N, N'-bis- (2-methylimidazolyl-1-)
Ethyl) urea, 1- (cyanoethylaminoethyl) -2
-Methylimidazole, N, N '-[2-methylimidazolyl- (1) -ethyl] -aziboyldiamide, N,
N '-[2-methylimidazolyl- (1) -ethyl]-
Dodecandioyl diamide, N, N '-[2-methylimidazolyl- (1) -ethyl] -eicosandioildiamide, 2,4-diamino-6- [2'-methylimidazolyl- (1)']-ethyl -S-triazine, 2,4
-Diamino-6- [2'-undecylimidazolyl-
(1) ']-ethyl-s-triazine, 1-dodecyl-
2-methyl-3-benzylimidazolium chloride,
1,3-dibenzyl-2-methylimidazolium chloride and the like.

The amount of the imidazole compound is preferably from 0.2 to 100 parts by weight of the acrylic rubber.
It is 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight. If it is less than 0.2 parts by weight, the physical properties of the vulcanized product are not sufficient. May be damaged.

The addition amount of trimethylthiourea is preferably 0.1 to 5.0 parts by weight, more preferably 0.3 to 4.0 parts by weight, based on 100 parts by weight of the acrylic rubber. If the amount is less than 0.1 part by weight, the vulcanization rate and the compression set are not sufficiently improved. If the amount exceeds 5.0 parts by weight, there is a possibility that a problem may occur in molding.

In the present invention, for the purpose of adjusting the vulcanization rate, a curing agent for an epoxy resin, for example, a pyrolytic ammonium salt, an organic acid, an acid anhydride, an amine, sulfur, a sulfur compound and the like are further used in the present invention. The effect can be added as long as the effect is not reduced.

Further, the acrylic rubber composition of the present invention comprises:
When put to practical use, molding and vulcanization can be performed by adding a filler, a plasticizer, a stabilizer, a lubricant, a reinforcing material and the like according to the purpose. The carbon black used as a filler in the vulcanizate of the present invention preferably has an average particle diameter of less than 20 to 30 nm and a DBP oil absorption of 115 ml / 100 g or more. Specific examples thereof include Tokai Carbon Co., Ltd., Seast 7H, Seast # 6, Seast 5H, Seast KH,
Asahi # 80 manufactured by Asahi Carbon Co., Ltd., and the like. The average particle size of carbon black refers to a value represented by a length average particle size measured by an electron microscope. The DBP oil absorption is based on JIS
It refers to a value measured according to the A method (mechanical method) of K6221. If the average particle size or DBP oil absorption of the carbon black is out of the above range, the balance between the extrudability, the surface smoothness and the tensile strength tends to be lost. These carbon blacks can be used alone or as a mixture of two or more kinds due to required rubber properties. These carbon blacks are added in a total amount of 30 commonly used for 100 parts by weight of the acrylic rubber.
-100 parts by weight are preferred.

As the machine for kneading, molding and vulcanizing the acrylic rubber, the acrylic rubber composition and the vulcanizate thereof of the present invention, those usually used in the rubber industry can be used.

The acrylic rubber, acrylic rubber composition and vulcanized product thereof of the present invention are suitably used particularly as sealing parts such as rubber hoses, gaskets, packings and the like. The rubber hose is specifically used for hoses used in various piping systems of automobiles, construction machines, hydraulic equipment, and the like. In particular, the rubber rubber obtained from the acrylic rubber of the present invention, an acrylic rubber composition and a vulcanized product thereof have excellent rubber properties such as extrudability and tensile strength, as well as oil resistance, cold resistance and Because of its excellent heat resistance, it is very suitably used especially as a rubber hose for automobiles, which has recently become severe in its use environment.

The rubber hose may be composed of a single hose made of acrylic rubber or, depending on the use of the rubber hose, a synthetic rubber other than acrylic rubber, for example, fluorine rubber, fluorine-modified acrylic rubber, hydrin rubber, C
Application to a composite hose in which SM, CR, NBR, ethylene / propylene rubber, or the like is applied to the inner layer, the intermediate layer, or the outer layer is also possible. Further, depending on the characteristics required of the rubber hose, it is also possible to provide a reinforcing thread or a wire in the middle of the hose or on the outermost layer of the rubber hose, as is generally done.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Examples 1 to 3 In a pressure-resistant reaction vessel having an inner volume of 40 liters, 11 kg of a mixture of ethyl acrylate and n-butyl acrylate was saponified in such a ratio that the composition ratio of the copolymer shown in Table 1 could be obtained. 17 kg of a 4% by weight aqueous solution of polyvinyl alcohol,
22 g of sodium acetate, glycidyl methacrylate 12
Then, 0 g was charged and mixed well with a stirrer in advance to prepare a uniform suspension. After replacing the air in the upper part of the tank with nitrogen, ethylene was injected into the upper part of the tank and the pressure was adjusted to 5 to 40 kg / cm ² . After continuing stirring and maintaining the inside of the tank at 55 ° C.,
Separately, an aqueous solution of t-butyl hydroperoxide was injected from an injection port to start polymerization. The temperature in the tank during the reaction is 55 ° C
And the reaction was completed in 6 hours. An aqueous sodium borate solution was added to the resulting polymerization solution to solidify the polymer, and the polymer was dehydrated and dried to obtain a raw rubber.

Example 4 A method similar to that of Example 1 was adopted except that the ethylene pressure was increased to 50 k.
g / cm ² to obtain a raw rubber of a copolymer.

Example 5 A method similar to that of Example 1 was adopted except that the ethylene pressure was set to 80 k.
g / cm ² to obtain a raw rubber of a copolymer.

COMPARATIVE EXAMPLE 1 The same method as in Example 1 was used, except that 11 kg of a mixed solution of ethyl acrylate and n-butyl acrylate was adjusted so that the composition ratio was 51% by weight: 49% by weight. Polymer raw rubber was obtained.

Comparative Examples 2 to 4 The same method as in Example 1 was used, except that ethylene was not introduced to obtain a raw rubber as a copolymer.

Preparation of vulcanized products (Examples 1 to 5, Comparative Examples 1 to 5)
4) The raw rubbers obtained in the above Examples and Comparative Examples were kneaded with an 8-inch open roll according to the composition shown in Table 2, and separated into sheets having a thickness of 2.4 mm.
Press vulcanization was performed at 70 ° C. for 10 minutes. This vulcanized product was further subjected to a heat treatment at 170 ° C. for 4 hours in a gear oven and subjected to a physical property test.

Analytical Test Method After the raw rubber of the copolymer was tightly passed through a roll, it was dissolved in toluene, the nuclear magnetic resonance spectrum was collected, and each component of the copolymer was quantified to determine the composition. Nuclear magnetic resonance spectra were collected using JNMα-500 manufactured by JEOL.

Method for Testing Physical Properties Tensile strength and elongation were measured according to JIS K6251. The hardness was measured according to JIS K6253.
The compression set is 150 according to JIS K6262.
The strain at 70 ° C. after 70 hours was measured. Oil resistance (ΔV) is J
In accordance with IS K6258, 15 for IRM-903 oil
The volume change ΔV (%) after immersion at 0 ° C. for 70 hours was determined. The cold resistance was determined based on the impact embrittlement temperature Tb according to JIS K6261. Heat resistance AR (EB) is JIS
According to K6257, the elongation retention AR (EB) (%) in a tensile test after exposure at 175 ° C. for 70 hours was determined. Table 1 shows the measurement results of the vulcanizates for each example and comparative example.

[0031]

[Table 1]

[0032]

[Table 2]

Comparing the data of Example 1 and Comparative Example 2 in which the level of oil resistance is the same as 14% in volume change ΔV,
Example 1 of the present invention is extremely excellent in cold resistance Tb. Also, when comparing Example 2 with Comparative Example 3 in which the level of oil resistance ΔV is equal to 19%, the cold resistance of Example 2 of the present invention is similarly high. Excellent in nature. Also, when comparing Example 3 with Comparative Example 4 in which the level of oil resistance ΔV is equal to 21%, Example 3 of the present invention is similarly obtained.
Has excellent cold resistance. Example 4 is superior to Comparative Example 3 in both oil resistance and cold resistance, and all of Examples 1, 2, 3, and 4 of the present invention have good heat resistance levels. On the other hand, when the level of cold resistance is Tb-
Comparing Example 5 equal to 25 ° C. with Comparative Example 5, Example 5 of the present invention is far superior in oil resistance. Example 5 of the present invention also has an excellent level of heat resistance. Also,
Comparative Example 1 has good cold resistance, but has a large oil resistance level of 41% at ΔV as compared with the examples of the present invention, and lacks oil resistance.

[0034]

As shown by the comparison between the examples and the comparative examples, the vulcanizates comprising the acrylic rubbers and the compositions thereof of the present invention have excellent rubber properties and oil resistance, as well as excellent cold resistance and heat resistance. Excellent balance.

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Claims (5)

[Claims] 1. An ethylene monomer unit of 0.1 to 10% by weight, a crosslinkable monomer unit of 0 to 10% by weight, and ethyl acrylate and butyl acrylate monomer units of 99.9 to 80%.
% Of ethyl acrylate in the total of ethyl acrylate and butyl acrylate is 60 to 100% by weight.
Acrylic rubber characterized by weight%. 2. An acrylic rubber composition comprising the acrylic rubber according to claim 1 and a crosslinking agent. 3. A vulcanizate obtained by vulcanizing the acrylic rubber composition according to claim 2. 4. A rubber hose comprising the vulcanized product of claim 3. 5. A seal component comprising the vulcanizate of claim 3.