JP2003192834A - Vulcanizable rubber composition and vulcanizate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitrile group-containing copolymer rubber vulcanizate having excellent dynamic characteristics and small compression set. <P>SOLUTION: This vulcanizable rubber composition comprises 100 pts.wt. of a rubber component composed of 5-50 pts.wt. of a nitrile group-containing copolymer rubber (A) having 10-60 wt.% content of an α,β-ethylenically unsaturated nitrile monomer unit and 180-430 iodine value and 50-95 pts.wt. of a nitrile group-containing copolymer rubber (B) having 10-60 wt.% content of the α,β- ethylenically unsaturated nitrile monomer unit and 40-100 iodine value and sulfur and/or 4,4'-dithiodimorpholine in an amount of 0.1-1.5 pts.wt. based on 100 pts.wt. of the rubber component and expressed in terms of the amount of sulfur. The vulcanizable rubber composition is vulcanized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a vulcanizate having excellent dynamic characteristics and heat resistance and a small compression set, and a rubber composition as a material thereof.

[0002]

2. Description of the Related Art It is generally known that a nitrile group-containing copolymer rubber such as an acrylonitrile-butadiene copolymer rubber has excellent oil resistance. Further, a hydrogenated acrylonitrile-butadiene copolymer rubber obtained by hydrogenating an acrylonitrile-butadiene copolymer rubber is known for the purpose of improving heat resistance, chemical resistance, weather resistance, tensile strength and the like. However, the hydrogenated acrylonitrile-butadiene copolymer rubber has a problem that the compression set becomes larger than that of the acrylonitrile-butadiene copolymer rubber.

Therefore, it has been proposed to blend an acrylonitrile-butadiene copolymer rubber and a hydrogenated acrylonitrile-butadiene copolymer rubber and vulcanize it with sulfur (Japanese Patent Laid-Open No. 63-142046). However, since a hydrogenated acrylonitrile-butadiene copolymer rubber having an iodine value of 30 or less is used, the vulcanization rate is greatly different because the unsaturated bond amounts of the two types of rubber are greatly different, and the co-addition is not performed. Sulfurization is difficult, and in order to solve this, sulfur is used in a large amount of 2 to 10 parts by weight per 100 parts by weight of the rubber component for vulcanization. However, the vulcanizate thus obtained has a large amount of sulfur, and therefore has a problem that the hardness tends to increase due to heat aging, the elongation tends to decrease, and the compression set increases.

On the other hand, a vulcanized rubber obtained by vulcanizing these two kinds of blended rubber with an organic peroxide instead of sulfur has been proposed (JP-A-9-67471). However, this vulcanized rubber has a problem that it has a bad odor.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vulcanized product which is excellent in dynamic characteristics and heat resistance and which is vulcanized with sulfur having a small compression set and a rubber composition which is a material thereof. .

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention have found that if two nitrile group-containing copolymer rubbers having an iodine value in a specific range are used in combination, a small amount of sulfur can be obtained. However, it was found that strong co-vulcanization occurs between the two, and the present invention has been completed based on this finding.

Thus, according to the present invention, the nitrile group-containing copolymer rubber (A) 5 to 50 having an α, β-ethylenically unsaturated nitrile monomer unit content of 10 to 60% by weight and an iodine value of 180 to 430. 50 parts by weight and α, β-ethylenically unsaturated nitrile monomer unit content 10 to 60% by weight, iodine value 40 to 100 nitrile group-containing copolymer rubber (B) 50
Vulcanizability containing 100 parts by weight of a rubber component consisting of ˜95 parts by weight and 0.1 to 1.5 parts by weight of sulfur and / or 4,4′-dithiodimorpholine in terms of the amount of sulfur. A rubber composition and a vulcanized product obtained by vulcanizing the vulcanizable rubber composition are provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A vulcanizable rubber composition of the present invention is a rubber comprising 5 to 50% by weight of a nitrile group-containing copolymer rubber (A) and 50 to 95% by weight of a nitrile group-containing copolymer rubber (B). 100 parts by weight of the component, and 0.1 to 1.5 parts by weight of sulfur and / or 4,4'- in terms of the amount of sulfur.
It contains dithiodimorpholine.

The nitrile group-containing copolymer rubber (A), which accounts for 5 to 50 parts by weight in 100 parts by weight of the rubber component contained in the vulcanizable rubber composition of the present invention, is an α, β-ethylenically unsaturated nitrile type rubber. A rubber obtained by copolymerizing a monomer with another monomer, having an α, β-ethylenically unsaturated nitrile monomer unit content of 10 to 60% by weight and an iodine value of 180 to 430. .

Examples of the α, β-ethylenically unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and the like.
Acrylonitrile is preferred. The content of the α, β-ethylenically unsaturated nitrile monomer in the nitrile group-containing copolymer rubber (A) is 10 to 60% by weight, preferably 12 to 55.
%, More preferably 15 to 50% by weight. α,
If the β-ethylenically unsaturated nitrile monomer content is too low, the oil resistance of the vulcanizate is poor, and conversely if it is too high, the cold resistance is poor.

In the nitrile group-containing copolymer rubber (A), the monomer to be copolymerized with the α, β-ethylenically unsaturated nitrile monomer is a conjugated diene monomer or a non-conjugated diene monomer. Examples thereof include a body and α-olefin. Examples of the conjugated diene-based monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene, and 1,3-butadiene and isoprene are preferable. Particularly preferred is 1,3-butadiene. The non-conjugated diene-based monomer preferably has 5 to 12 carbon atoms, and examples thereof include 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, and dicyclopentadiene. The α-olefin preferably has 2 to 12 carbon atoms and is exemplified by ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and the like. Furthermore, aromatic vinyl monomers, fluorine-containing vinyl monomers, α, β-ethylenically unsaturated monocarboxylic acids, α, β
-Ethylenically unsaturated polycarboxylic acid or anhydride thereof,
A copolymerizable antiaging agent or the like may be copolymerized.

The aromatic vinyl-based monomer is, for example,
Examples thereof include styrene, α-methylstyrene, vinylpyridine and the like. Examples of the fluorine-containing vinyl-based monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene, tetrafluoroethylene and the like. Examples of the α, β-ethylenically unsaturated monocarboxylic acid include acrylic acid and methacrylic acid. Examples of the α, β-ethylenically unsaturated polycarboxylic acid include itaconic acid, fumaric acid, maleic acid and the like. α, β-
Examples of the ethylenically unsaturated polycarboxylic acid anhydride include itaconic anhydride, maleic anhydride and the like. Examples of the copolymerizable antiaging agent include N- (4
-Anilinophenyl) acrylamide, N- (4-anilinophenyl) methacrylamide, N- (4-anilinophenyl) cinnamamide, N- (4-anilinophenyl) crotonamide, N-phenyl-4- (3 -Vinylbenzyloxy) aniline, N-phenyl-4- (4-
Vinylbenzyloxy) aniline and the like.

The iodine value of the nitrile group-containing copolymer rubber (A) is 180 to 430, preferably 200 to 400, more preferably 230 to 380. If the iodine value is too small, the rubber elasticity of the vulcanizate will be poor, and if the iodine value is too high, the oil resistance and heat resistance of the vulcanizate will be poor. The iodine value is a value indicating the amount of unsaturated bonds in the main chain, and is mainly determined by the content of the conjugated diene monomer unit. If the iodine value is too small, the rubber elasticity of the vulcanizate will be poor, and if the iodine value is too large, the oil resistance and heat resistance of the vulcanizate will be poor. If necessary, the nitrile group-containing copolymer rubber (A) may be hydrogenated to saturate the unsaturated bond and the iodine value may be adjusted by a known method.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the nitrile group-containing copolymer rubber (A) is preferably 20 to 3
00, more preferably 30 to 250, particularly preferably 4
It is 0 to 200. If the Mooney viscosity is too low, the mechanical properties of the vulcanizate may be inferior, and if too high, the processability may be inferior.

The nitrile group-containing copolymer rubber (B) which accounts for 95 to 50 parts by weight in 100 parts by weight of the rubber component contained in the vulcanizable rubber composition of the present invention is the nitrile group-containing copolymer rubber (A). Similarly, it is a rubber obtained by copolymerizing an α, β-ethylenically unsaturated nitrile monomer with another monomer, and has an α, β-ethylenically unsaturated nitrile monomer unit content of 10 to 10. It is 60% by weight. The nitrile group-containing copolymer rubber (B) has an iodine value of 40 to 100.

Α, β of the nitrile group-containing copolymer rubber (B)
-Ethylene unsaturated nitrile monomer content is 10-6
It is 0% by weight, preferably 12 to 55% by weight, more preferably 15 to 50% by weight. If the content of the α, β-ethylenically unsaturated nitrile monomer is too small, the vulcanizate has poor oil resistance, and if it is too large, the vulcanizate has poor cold resistance.

The iodine value of the nitrile group-containing copolymer rubber (B) is 40 to 100, preferably 45 to 90, more preferably 50 to 80. If the iodine value is too small, the compression set of the vulcanized product will be large, and co-vulcanization with the nitrile group-containing copolymer rubber (A) will be difficult. On the contrary, if the iodine value is too large, the heat resistance is poor. Since there are many conjugated diene monomer units, there are many unsaturated bonds in the main chain, and nitrile group-containing copolymer rubber having a large iodine value is hydrogenated by a known method to reduce the unsaturated bonds in the main chain. The iodine value may be adjusted to a small value before use.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the nitrile group-containing copolymer rubber (B) is preferably 10 to 3
00, more preferably 20 to 250, particularly preferably 3
It is 0 to 200. If the Mooney viscosity is too low, the mechanical properties of the vulcanizate may be inferior, and if too high, the processability may be inferior.

100 parts by weight of the rubber component contained in the vulcanizable rubber composition of the present invention is 5 to 50 parts by weight, preferably 10 to 45 parts by weight of the nitrile group-containing copolymer rubber (A). 20 to 40 parts by weight and 95 to 50 parts by weight of the nitrile group-containing copolymer rubber (B), preferably 9
0 to 55 parts by weight, more preferably 80 to 60 parts by weight. The rubber component may contain a rubber other than the nitrile group-containing copolymer rubbers (A) and (B), but in 100 parts by weight of the rubber component, preferably 30 parts by weight or less, more preferably 20 parts by weight or less. And particularly preferably 1
It is 0 parts by weight or less.

The vulcanizable rubber composition of the present invention contains sulfur and / or 4,4'-dithiodimorpholine as a vulcanizing agent. The content thereof is 0.1 to 1.5 parts by weight, preferably 0.2 to 1 part by weight, more preferably 0.3 to 0.8 part by weight in terms of the amount of sulfur with respect to 100 parts by weight of the rubber component. Contains. If the amount of the vulcanizing agent is too small, sufficient vulcanization is not performed, the strength of the vulcanized product becomes insufficient, and if the amount of the vulcanizing agent is too large, not only the elongation deteriorates, but also the elongation when the heat is applied. Drastically reduced.

When sulfur and / or 4,4'-dithiodimorpholine is used as a vulcanizing agent, a vulcanization accelerator is usually used together. Examples of the vulcanization accelerator include zinc white, sulfenamide-based vulcanization accelerator, guanidine-based vulcanization accelerator, thiazole-based vulcanization accelerator, thiuram-based vulcanization accelerator, and dithioate-based vulcanization accelerator. Can be mentioned. The amount of the vulcanization accelerator used is not particularly limited and may be determined according to the application of the vulcanized product, the required performance, the type of the vulcanization accelerator, and the like.

The vulcanizable rubber composition of the present invention contains a compounding agent used for general rubber, such as carbon black,
Reinforcing agents such as silica and short fibers; fillers such as calcium carbonate, clay, talc and calcium silicate; α, β-
An ethylenically unsaturated carboxylic acid metal salt; a plasticizer; a pigment; an antioxidant; a tackifier; a processing aid; a scorch inhibitor;

The method for preparing the vulcanizable rubber composition of the present invention is not particularly limited, and may be prepared by a general method for preparing a vulcanizable rubber composition, using an internal mixer or an open roll. After blending the vulcanizing agent, kneading may be performed so as to maintain the vulcanization starting temperature or lower.

The vulcanized product of the present invention is obtained by vulcanizing the above vulcanizable rubber composition. The method of vulcanizing the rubber composition,
The vulcanizable rubber composition may be heated. Generally, it is molded and then heated, or simultaneously with molding.

The temperature during vulcanization is preferably 100 to 20.
The temperature is 0 ° C, more preferably 130 to 195 ° C, and particularly preferably 140 to 190 ° C. If the temperature is too low, the vulcanization time may be long and the vulcanization density may be low. If the temperature is too high, molding may be defective. The vulcanization time varies depending on the vulcanization method, vulcanization temperature, shape, etc., but is preferably 1 minute to 4 hours from the viewpoint of vulcanization density and production efficiency.

The heating method for vulcanization may be appropriately selected from the methods used for vulcanizing rubber such as press heating, steam heating, oven heating and hot air heating.

Depending on the shape and size of the vulcanized product, the inside may not be vulcanized even if the surface is vulcanized. In such a case, after the vulcanization as described above, the secondary vulcanization that is maintained at a high temperature may be performed.

[0028]

EFFECTS OF THE INVENTION The vulcanized product of the present invention has excellent dynamic characteristics and heat resistance, has a small compression set, and has a hose, tube,
It is used for seals, gaskets, boots, rolls, belts, diaphragms, etc., but is particularly suitable for rolls, belts, boots, diaphragms, etc. used in a dynamic state.

[0029]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. Parts and% are, unless otherwise specified,
It is based on weight. The evaluation method is as follows.

Heat Resistance Evaluation The prepared vulcanizable rubber composition was vulcanized at 160 ° C. for 20 minutes under a pressing pressure of 10 MPa to obtain a sheet having a thickness of 2 mm. This sheet was punched out to prepare a test piece. Using these test pieces, Japanese Industrial Standard JIS K625
The tensile strength and elongation of the vulcanizate were measured according to 1.
According to IS K6253, the hardness of the vulcanizate was measured using a durometer hardness tester type A type. Thereafter, the test piece was held at 120 ° C., and after 168 hours and 336 hours, the tensile strength, elongation and hardness of the vulcanized product were measured, and the amount of change in those measured values before the holding was examined. The larger the change, the poorer the heat resistance.

Evaluation of Dynamic Characteristics A cylindrical test piece having a diameter of 17.8 ± 0.1 mm and a height of 25 ± 0.15 mm was vulcanized at 160 ° C. for 20 minutes and then A
It evaluated by the flexometer test prescribed | regulated by STM D623-78. The test was carried out using a Goodrich flexometer at a test temperature of 100 ° C., an initial load of 25 pounds (11.34 kg) and a dynamic displacement of 4.45 mm.
After performing dynamic displacement for 5 minutes, HBU (heat generation amount: the difference between the measured temperature of the test piece and the ambient temperature of 100 ° C. was taken as the heat generation temperature) and PS (permanent strain) were measured. HB
The smaller U and PS, the better the dynamic characteristics.

Constant Elongation Fatigue Test The prepared vulcanizable rubber composition was vulcanized at 160 ° C. for 20 minutes under a press pressure of 10 MPa, and then vulcanized in a gear type oven for 1 minute.
Secondary vulcanization was performed at 50 ° C. for 2 hours to obtain a sheet having a thickness of 2 mm. This sheet was punched out using a No. 3 type dumbbell to prepare a test piece. Using these test pieces, the both ends were fixed with grippers so that the distance between them was 75 mm, and the test pieces were stretched at 0 to 100% at 3 min / min.
The test piece was repeatedly reciprocated 00 times at 23 ° C., and the number of times the test piece was broken was measured.

Using a mold having a compression set diameter of 29 mm and a thickness of 12.5 mm, the vulcanizable rubber composition was heated at 160 ° C. for 25 minutes at a pressing pressure of 10 MP.
It was vulcanized with a to obtain a test piece. The compression set is JI
Using these test pieces according to SK 6262, 2
After holding at 5% compression condition at 120 ° C for 70 hours,
After holding for 68 hours, measurement was performed.

Example 1 Nitrile group-containing copolymer rubber A-1 (Nipol DN1)
042AL, manufactured by Zeon Corporation, acrylonitrile-butadiene copolymer rubber, acrylonitrile unit content 33.
5%, iodine value 313, Mooney viscosity ML _{1 + 4} , (1
(00 ° C) 46) 40 parts, nitrile group-containing copolymer rubber B
(Zetpol 2030L, manufactured by Zeon Corporation, hydrogenated acrylonitrile-butadiene copolymer rubber, acrylonitrile unit content 36.2%, iodine value about 56, Mooney viscosity ML _{1 + 4} , (100 ° C.) 57.5) 60 parts, Carbon black (N762, Asahi # 50, Asahi Carbon Co., Ltd.)
65 parts, stearic acid 1 part, zinc oxide 5 parts, tri- (2
-Ethylhexyl) trimellitate (plasticizer) 8 parts,
2,2,4-trimethyl-1,2-dihydroquinoline polymer (antiaging agent, Nocrac 224, manufactured by Ouchi Shinko Co., Ltd.) 1.5 parts, N-isopropyl-N ''-phenyl-
1.5 parts of p-phenylenediamine (antiaging agent), 1 part of wax (Santite S, manufactured by Seiko Scientific Co., Ltd.), sulfur (32
0.8 parts of vulcanization accelerator (tetramethylthiuram disulfide 1.5 parts and N-cyclohexyl-2-benzothiazyl sulfenamide 1.5 parts)
Three parts were roll kneaded at 50 ° C. to prepare a vulcanizable rubber composition. This vulcanizable rubber composition was vulcanized, each test piece was manufactured, and heat resistance evaluation, dynamic characteristic evaluation, and compression set were measured. The results are shown in Table 1.

Example 2 The amount of the nitrile group-containing copolymer rubber A-1 was changed from 40 parts to 20 parts.
The amount of the nitrile group-containing copolymer rubber B is 60 parts to 8 parts.
The same process as in Example 1 was carried out except that the amount was changed to 0 part. The results are shown in Table 1.

Example 3 Instead of the nitrile group-containing copolymer rubber A-1, a nitrile group-containing copolymer rubber A-2 (Nipol DN1201L,
Nippon Zeon Co., acrylonitrile-butadiene-isoprene copolymer rubber, acrylonitrile unit content 35
%, Iodine value about 280, Mooney viscosity ML _{1 + 4} , (10
(0 ° C.) 46) was used and treated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 The same process as in Example 1 was carried out except that the amount of sulfur was changed to 1.3 parts. The results are shown in Table 1.

Example 5 Example 1 was repeated except that 3 parts of 4,4'-dithiodimorpholine (sulfur equivalent amount 0.91 part) was used instead of 0.8 part of sulfur.
The same process was carried out. The results are shown in Table 1.

Comparative Example 1 The same treatment as in Example 1 was carried out except that the nitrile group-containing copolymer rubber A-1 was not used and the amount of the nitrile group-containing copolymer rubber B was changed from 60 parts to 100 parts. The results are shown in Table 1.

Comparative Example 2 The amount of the nitrile group-containing copolymer rubber A-1 was changed from 40 parts to 10 parts.
The treatment was carried out in the same manner as in Example 1 except that the content was changed to 0 part and the nitrile group-containing copolymer rubber B was not used. The results are shown in Table 1.

Comparative Example 3 The amount of the nitrile group-containing copolymer rubber A-1 was changed from 40 parts to 70 parts.
The amount of the nitrile group-containing copolymer rubber B is 60 parts to 3 parts.
The same process as in Example 1 was carried out except that the amount was changed to 0 part. The results are shown in Table 1.

Comparative Example 4 Instead of the nitrile group-containing copolymer rubber B, a nitrile group-containing copolymer rubber b (Zetpol 2020, manufactured by Nippon Zeon Co., Ltd., hydrogenated acrylonitrile-butadiene copolymer rubber,
Acrylonitrile unit content 36.2%, iodine value about 2
_No. 8, Mooney viscosity ML _{1 + 4} , (100 ° C.) 78) was used and treated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 5 The same treatment as in Example 1 was carried out except that the amount of sulfur was changed from 0.8 part to 2.5 parts. The results are shown in Table 1.

[0044]

[Table 1]

Vulcanized product of a rubber composition containing no nitrile group-containing copolymer rubber (A) having a large iodine value (Comparative Example 1)
Has a large compression set and a small number of fractures in a constant elongation fatigue test. The vulcanized product (Comparative Example 2) of the rubber composition not containing the nitrile group-containing copolymer rubber (B) having a small iodine value has a small number of breaks in the constant elongation fatigue test. A vulcanizate (Comparative Example 3) of a rubber composition containing a large amount of a nitrile group-containing copolymer rubber (A) having a large iodine value and a small amount of a nitrile group containing copolymer rubber (B) having a small iodine value was tested by a constant elongation fatigue test. The number of fractures is small. The vulcanized product (Comparative Example 4) of the rubber composition using the nitrile group-containing copolymer rubber (b) having an excessively small iodine value has an excessively large compression set. The vulcanized product (Comparative Example 5) of a rubber composition having too much sulfur has a small elongation even in normal physical properties, but when heat is applied, the rate of elongation decrease is large and the heat resistance is poor. It is also inferior to PS.

On the other hand, the vulcanizates (Examples 1 to 5) of the rubber composition of the present invention had a small compression set, excellent heat resistance, small HBU and PS, and a fracture in a low elongation fatigue test. The number of times is large and it is difficult to break.

Claims (2)

[Claims] 1. An α, β-ethylenically unsaturated nitrile monomer unit content of 10 to 60% by weight and an iodine value of 180 to 43.
0 to 50 parts by weight of nitrile group-containing copolymer rubber (A), 10 to 60% by weight of α, β-ethylenically unsaturated nitrile monomer unit content, and iodine value of 40 to 100 nitrile group-containing copolymer rubber (B) 100 parts by weight of the rubber component consisting of 50 to 95 parts by weight, and 0.1% by weight of the amount of sulfur.
A vulcanizable rubber composition containing ˜1.5 parts by weight of sulfur and / or 4,4′-dithiodimorpholine. 2. A vulcanized product obtained by vulcanizing the vulcanizable rubber composition according to claim 1.