JP2002037928A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition capable of providing a vulcanized product excellent in oil and weather resistances, mechanical characteristics and especially compression set properties. SOLUTION: This rubber composition comprises an acrylonitrile-butadiene copolymer rubber, an ethylene-propylene-diene copolymer rubber, sulfur and a sulfenamide-based vulcanization accelerator and/or a thiazole-based vulcanization accelerator and is obtained by specifying the viscosity ratio of both the rubbers and a product of the viscosity ratio of both the rubber and a volume fraction ratio of both the rubbers within a specific range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to oil resistance, weather resistance,
The present invention relates to a rubber composition having excellent mechanical properties and compression set.

[0002]

2. Description of the Related Art It is well known that two or more rubbers are mixed to obtain performance and characteristics that cannot be obtained with a single rubber. An acrylonitrile-butadiene copolymer rubber (NBR) having high polarity and excellent oil resistance but poor weather resistance and an ethylene-propylene-diene copolymer rubber (EPDM) having low polarity and poor oil resistance but excellent weather resistance are used. Attempts have been made to mix and balance the properties of both rubbers. However, since NBR and EPDM have significantly different polarities, the compatibility is poor, and the vulcanization rates are different. Therefore, due to the imbalance between the compatible (dispersed) state and the degree of vulcanization, the mechanical properties of the obtained composition There was a problem that the characteristics and the aging characteristics were reduced as compared with the case of using alone. There have been many proposals to improve this, including:
At present, there are few that can be satisfied, and in particular, there is no satisfactory with regard to compression set.

For example, a method of halogenating EPDM (Rubber Chem. Technal., 44, 1025 (1971)), a method of using a dialkyldithiocarbamate salt having a long-chain alkyl group or a tetraalkylthiuram disulfide as a vulcanization accelerator ( Rubber Chem. Technal., 44, 1065 (1971)), EP
After heating and mixing DM, sulfur and vulcanization accelerator in advance, NB
Method of mixing with R (Journal of the Rubber Association of Japan, 49,236,246 (197
6)), a method of compounding a styrene-based polymer and a polyalkenamer (JP-A-61-53341), and a method of compounding a styrene-butadiene copolymer rubber (SBR) (JP-A-6-63).
No. 2-172043) has been proposed.

[0004]

SUMMARY OF THE INVENTION The present invention improves the compatibility between acrylonitrile-butadiene copolymer rubber (NBR) and ethylene-propylene-diene copolymer rubber (EPDM), thereby bringing out the properties of both rubbers, and An object of the present invention is to provide a rubber composition that does not cause a decrease in mechanical properties, particularly compression set, of rubber during mixing.

[0005]

According to the present invention, a rubber composition defined by a specific viscosity ratio and a volume fraction ratio can obtain a finely dispersed state by mixing, and further comprises a suitable vulcanization accelerator. By rapidly vulcanizing and curing, a phase dispersion state can be obtained, resulting in excellent oil resistance, weather resistance,
Based on the idea that vulcanized rubber compositions having mechanical properties and compression set can be realized, NBR and EP
DM Mooney viscosity ratio η _a / η _e and Mooney viscosity ratio η _e
/ Η _a and the volume fraction ratio Φ _a / Φ _e are adjusted to a specific range, and sulfur vulcanization is performed using a specific vulcanization accelerator, so that both rubbers can be phased together without using a special compatibilizer. They have found that they can be solubilized and have no deterioration in rubber properties, and have reached the present invention.

Accordingly, the present invention relates to the method of_a(M
L_{1 + 4,}100 ° C.) is 65-85 and acrylonitrile
Acrylonitrile / butane having a content of 20 to 38% by mass
Tadiene copolymer rubber, Mooney viscosity η_e(ML_{1 + 4,}10
0 ° C) is 40 to 70 and the mass ratio of ethylene / propylene
Ethylene-propylene having a ratio of 40/60 to 80/20
-Contains diene copolymer rubber, sulfur and vulcanization accelerator
Acrylonitrile-butadiene
Copolymer rubber and ethylene-propylene-diene copolymer rubber
Mooney viscosity ratio η_a/ Η_eIs more than 1.0 and less than 4.0,
Knee viscosity ratio η _e/ Η_aAnd the volume fraction ratio Φ_a/ Φ_eIs the product of
Less than 1.5 and the vulcanization accelerator is a sulfenamide-based
It is a sulfur accelerator and / or a thiazole vulcanization accelerator
It is a rubber composition characterized by the above-mentioned.

The preferred rubber composition of the present invention is characterized in that the ethylene-propylene-diene copolymer rubber forms a matrix phase and the acrylonitrile-butadiene copolymer rubber forms a dispersed phase.

Further, the present invention preferably has a compression set (70).
(C, 22 hours) is 20% or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the rubber composition of the present invention, ethylene-propylene-diene copolymer rubber (EPDM) mainly forms a matrix phase, and acrylonitrile-butadiene copolymer rubber (NBR) forms a dispersed phase. .

The NBR of the present invention is a copolymer rubber of acrylonitrile and butadiene and has an acrylonitrile content of 20 to 38% by mass, preferably 20 to 35% by mass.
It is. When the amount is less than 20% by mass, even if the amount of NBR is within the range of the present invention, there is a problem that the improvement in oil resistance is very small and does not substantially improve. However, even when the Mooney viscosity and the volume fraction ratio are within the ranges of the present invention, there is a problem that the compatibility is poor and the mechanical properties are poor. When two or more NBRs are used in combination,
The average acrylonitrile content may be within the above range.

The present invention is a copolymer rubber of ethylene, propylene and a non-conjugated diene such as ethylidene norbornene, cyclopentadiene, 1,4-hexadiene and methylene norbornene. The mass ratio of ethylene / propylene is 40/60 to 80/20, preferably 45/55 to 75.
/ 25. The proportion of non-conjugated diene is 10 in terms of iodine value.
-30, preferably 15-25.

The Mooney viscosity η of NBR_a(ML_{1 + 4,}10
0 ° C.) is 65-85 and the Mooney viscosity η of EPDM
_e(ML_{1 + 4,}100 ° C) is 40-70. With NBR
EPDM Mooney viscosity (η_a, Η_e) Is out of the range
If there is, the viscosity ratio η_a/ Η_eAnd viscosity ratio η_e/ Η_aAnd body
Integral ratio Φ_a/ Φ_eProduct ((η_e/ Η _a) × (Φ_a/ Φ
_e)) Is difficult to satisfy. Where the viscosity ratio η
_a/ Η_eAnd the volume fraction ratio Φ_a/ Φ_eMeans NB when mixed
R and EPDM indicate the respective ratios, NBR, EPDM
Are reinforcing agents such as carbon black, fillers, soft
In the case of compositions containing a plasticizer, plasticizer, etc., the viscosity of each composition
Shows the ratio of volume and volume fraction.

As shown in the following formulas (1) and (2), NBR and EPDM are expressed by the Mooney viscosity ratio η _a /
η _e is more than 1.0 and less than 4.0, preferably more than 1.0 3.7
Below, the Mooney viscosity ratio η _e / η _a and the volume fraction ratio Φ _a /
It is prepared so that the product of Φ _e is less than 1.5, preferably 1.0 or less. _{1.0 <η a / η e <} 4.0 (1) preferably _{1.0 <η a / η e ≦} 3.7 (η e / η a) × (Φ a / Φ e) <1.5 (2) preferably (η _e / η _a ) × (Φ _a / Φ _e ) ≦
1.0

In the composition of the present invention, in order to obtain excellent weather resistance, it is preferable that EPDM forms a matrix phase and NBR forms a dispersed phase. The above formulas (1) and (2) indicate the viscosity for this purpose. Ratio and volume fraction ratio. That is, the above formula (1) shows a viscosity ratio (η _a / η _e ) at which NBR can be finely dispersed in EPDM. Under the mixing conditions, the viscosity of NBR is more appropriately than that of EPDM. It specifies that it is big. If the viscosity of NBR is extremely higher than the viscosity of EPDM, NBR cannot be dispersed to appropriate fineness.

Viscosity ratio (η _a / η _e ) that can take the above structure
Is 1.0, the NBR viscosity is EPD
If the viscosity is smaller than M, EPDM tends to be a dispersed phase, but the practical lower limit must satisfy the condition of the above formula (2) especially when the volume fraction ratio of NBR is large.
That is, the above equation (2) shows the volume fraction ratio (Φ _a / Φ _e ) that can disperse NBR into EPDM in appropriate fineness, and particularly, the viscosity ratio when the volume fraction ratio of NBR is large. Specifies the lower limit of (η _a / η _e ).

[0016] For example, (1) when _{Φ a / Φ e = 50/} 50, 1.0 <η a / η e <4.0 preferably _{1.0 ≦ η a / η e ≦} 3.7 (2 ) when _{Φ a / Φ e = 60/} 40, 1.0 <η a / η e <4.0 preferably _{1.5 ≦ η a / η e ≦} 3.7 (3) Φ a / Φ e = when _{70/30, 1.6 <η a / η} e <4.0 preferably when _{2.3 ≦ η a / η e ≦} 3.7 (4) Φ a / Φ e = 75/25, 2 _{.0 <η a / η e <} 4.0 preferably a _{3.0 ≦ η a / η e ≦} 3.7. If the relationship of the above equation (2) is not satisfied, NB
So-called phase inversion where R is a matrix phase and EPDM is a dispersed phase is likely to occur.

Even if NBR and EPDM are mixed with each other, one rubber or both rubbers are mixed in advance with a compounding component such as a reinforcing agent, a filler, a softening agent, or a plasticizer to form a rubber composition. And then both may be mixed. The composition containing NBR and EPDM of the present invention is vulcanized using sulfur as a vulcanizing agent. The amount of sulfur used is a normal amount. The vulcanizing agent such as sulfur may be added at the same time as the mixing of the two, but it is preferable to add the vulcanizing agent after the mixing of both, from the viewpoint of preventing scorch (burn).

The vulcanization accelerator used for vulcanization is a sulfenamide and / or a thiazole.
When these vulcanization accelerators are used, the mechanical properties of the rubber composition after vulcanization, particularly the compression set, are good.

Examples of the sulfenamides include N-cyclohexyl-2-benzothiazylsulfenamide, N,
N-dicyclohexyl-2-benzothiazylsulfenamide, N, N-diethyl-2-benzothiazylsulfenamide, N, N-diisopropyl-2-benzothiazylsulfenamide, Nt-butyl-2 -Benzothiazylsulfenamide, Nt-octyl-2-benzothiazylsulfenamide and the like are used. Preferred are N-cyclohexyl-2-benzothiazylsulfenamide and N, N-dicyclohexyl-2-benzothiazylsulfenamide.

Examples of thiazoles include 2-mercaptobenzothiazole, its sodium salt, its zinc salt, its cyclohexylamine salt, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N , N-Diethyldithiocarbamoylthiobenzothiazolyl sulfide, 2- (4'-morpholinodithio) benzothiazole, 1,3-bis (2-benzothiazolylmercaptomethyl) urea, 2-mercaptothiazoline, etc. are used. Preferred are 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and the zinc salt of 2-mercaptobenzothiazole.

The ratio when the sulfenamides and the thiazoles are used in combination is not limited. The vulcanization accelerator is NBR
And 0.05 to 5 based on 100 parts of the total mass of EPDM
Parts, preferably 0.1 to 4 parts.

The rubber composition of the present invention is blended with a general rubber compounding agent such as carbon black, a reinforcing agent, a filler, a plasticizer, a softening agent, a process oil, an antioxidant, a stabilizer, and the like. And the like. Then, it is molded, processed, and vulcanized by a conventional method.

The composition of the present invention comprises a hose, a packing,
It is suitably used as an industrial material for gaskets, oil seals, belts, boots and the like.

[0024]

EXAMPLES The following copolymer rubber, sulfur, vulcanization accelerator,
The other compounding agents were put in a Banbury mixer at the mass ratios shown in Table 1 and mixed at 40 ° C. for 4 minutes. After discharge, the mixture was heated at 150 ° C. for 40 minutes with a laboratory press molding machine and vulcanized. Physical properties of rubber composition before and after vulcanization (η _e /
η _a ), (η _e / η _a ) × (Φ _a / Φ _e ), tensile strength,
Tensile elongation, compression set, oil resistance) are shown in Table 1.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

NBR-1: "KRYNAC 34.80" Bayer
Η _a = 80, acrylonitrile content 33 mass% NBR-2: “PERBUNAN N3310” Bayer η _a = 76, acrylonitrile content 34 mass% NBR-3: “NIPOL 1042” Nippon Zeon Co., Ltd. η _a = 71, acrylonitrile content 33 mass% NBR-4: “NIPOL 1041” manufactured by Zeon Corporation η _a = 81, acrylonitrile content 41 mass%

EPDM-1: "Mitsui EPT 407
0 "manufactured by Mitsui Chemicals, Inc. η _e = 65, ethylene content 68% by mass, ENB-containing EPDM-2:“ Mitsui EPT 3091 ”manufactured by Mitsui Chemicals, Inc. η _e = 55, ethylene content 72% by mass, ENB Contained EPDM-3: "ESPRENER 505A" Sumitomo Chemical Co., Ltd.
Ltd. eta _e = 45, ethylene content 47 wt%, END containing EPDM-4: "ESPRENER 305" by Sumitomo Chemical Co., Ltd. eta _e = 57, ethylene content 66 wt%, DCPD content

Sulfur sulfenamides: N-cyclohexyl-2-benzothiazolylsulfenamide "Sancellar CM" manufactured by Ouchi Shinko Chemical Co., Ltd. Thiazoles: benzothiazyl disulfide "Suncellar DM" Ouchi Shinko Chemical Co., Ltd. Tetramethylthiuram disulfide “NOXELLER T
T "Ouchi Shinko Chemical Co., Ltd. EPDM / diene rubber blend co-vulcanization accelerator:" NOXELLER EP-60 "Ouchi Shinko Chemical Co., Ltd.

Carbon black: "HTC- # 10
0 "Dioctyl phthalate (DOP) manufactured by Shin Nikka Carbon Co., Ltd. Process oil manufactured by Chisso Petrochemical Co., Ltd .:" Fucor 1150N "Zinc flower stearic acid acetone-diphenylamine condensate (ADPAL) manufactured by Fujikosan Co., Ltd." Nocrack " RB ”Ouchi Shinko Chemical Co., Ltd.

The Mooney viscosity was measured at 100 ° C. according to JIS K6300. Moony Scoach is JI
It was measured at 125 ° C. according to SK6300. The tensile strength and the tensile elongation were measured according to JIS K6251. The compression set was measured by a test method specified in JIS K6262, after applying a compression rate of 25% and aged at 100 ° C. for 70 hours.

The ozone resistance is based on JIS K6259, and the elongation is 30% at an ozone concentration of 100 pphm at a temperature of 40 ° C.
Observe the state after aging treatment for 168 hours under the static conditions of
The case where there was no abnormality was evaluated as ○, and the case where there was an abnormal change such as crack or cut was evaluated as ×. The oil resistance was evaluated by a volume change rate (VC) after aging at 70 ° C. for 22 hours using JIS # 3 oil according to a test method specified in JIS K6258.

From the comparison between Examples 1 to 3 and Comparative Example 1, (η
_{When e} / η _a ) × (Φ _a / Φ _e ) exceeds 1.5, it is clear that the tensile strength, compression set and oil resistance of the composition are poor. From the comparison between Examples 4 to 6 and Comparative Example 2, (η _e /
When η _a ) × (Φ _a / Φ _e ) exceeds 1.5, it is clear that the tensile strength of the composition is poor. From the comparison between Examples 9 to 10 and Comparative Example 3, the acrylonitrile content was 38% by mass.
It is clear that the tensile strength of the composition is poor when the ratio exceeds. It is presumed that the cause is a poor compatibility state (poor dispersion state, phase inversion, etc.).

From the comparison between Examples 11 to 12 and Comparative Example 4,
It can be seen that scorch and ozone resistance are poor when the vulcanization accelerator is thiuram-based. Examples 11 to 12 and Comparative Example 5
It can be seen from the comparison that even if the conventional vulcanization accelerator is not blended with a sulfenamide vulcanization accelerator or a thiazole vulcanization accelerator, the compression set is poor. Accordingly, it can be seen that sulfenamide-based and thiazole-based vulcanization accelerators are effective for co-vulcanization of NBR and EPDM.

That is, the rubber composition defined by the viscosity ratio and the volume fraction ratio can obtain a finely dispersed state by mixing, and can be quickly vulcanized and cured with an appropriate vulcanization accelerator. It can be seen that a vulcanized rubber composition having excellent oil resistance, weather resistance, mechanical properties and compression set was realized as a result of maintaining and stabilizing the phase dispersion state.

[0038]

The rubber composition of the present invention is excellent in oil resistance, weather resistance, mechanical properties and compression set, and is suitably used as an industrial material.

Claims (3)

[Claims] 1. A Mooney viscosity η _a (ML _{1 + 4,} 100 ° C.) of 65 to 85 and an acrylonitrile content of 20 to 38.
Acrylonitrile-butadiene copolymer rubber having a Mooney viscosity η _e (ML _{1 + 4,} 100 ° C.) of _{40 to 7} % by mass
0, the mass ratio of ethylene / propylene is 40/60 to 8
A rubber composition containing an ethylene-propylene-diene copolymer rubber of 0/20, sulfur and a vulcanization accelerator, wherein a Mooney viscosity ratio η of an acrylonitrile-butadiene copolymer rubber and an ethylene-propylene-diene copolymer rubber is η. _a / η _e is more than 1.0 and less than 4.0, Mooney viscosity ratio η _e
/ Η _a and the volume fraction ratio Φ _a / Φ _e are less than 1.5, and the vulcanization accelerator is a sulfenamide vulcanization accelerator and / or a thiazole vulcanization accelerator. Rubber composition. 2. The rubber composition according to claim 1, wherein the ethylene-propylene-diene copolymer rubber forms a matrix phase and the acrylonitrile-butadiene copolymer rubber forms a dispersed phase. 3. A compression set (70 ° C., 22 hours) of 20%
The rubber composition according to claim 1 or 2, wherein: