JPH08231768A - Vulcanizable nitrile-based rubber composition - Google Patents

Abstract

PURPOSE: To provide a rubber composition capable of obtaining a vulcanized product excellent in wear resistance and oil resistance. CONSTITUTION: This vulcanizable nitrile-based rubber composition comprises 100 pts. wt. unsaturated nitrile-butadiene-isoprene three dimensional polymeric rubber containing 35-55wt.% amount of the bound unsaturated nitrile, 65-45wt.% amount of the total bound diene consisting of 30-60wt.% bound butadiene-1,3 and 70-40wt.% bound isoprene, 5-100 pts.wt. reinforcing filler and a vulcanizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an unsaturated nitrile-butadiene-isoprene terpolymer rubber (hereinafter referred to as "NBI").
R)) and a reinforcing filler. The vulcanizate obtained from the rubber composition of the present invention has, in addition to the properties such as good oil resistance and heat resistance generally possessed by nitrile-conjugated diene copolymer rubber, in particular, significantly improved abrasion resistance. And therefore,
It is useful as a material requiring particularly high wear resistance such as a printing roll blanket.

[0002]

Copolymer rubber (NBR) of acrylonitrile and butadiene is generally known as a rubber material having good oil resistance, and various rubber rolls, sealing materials,
Widely used for belts, hoses and gaskets. Further, various improvements have been made to the NBR depending on the application. For example, as a rubber having the characteristics of NBR and acrylonitrile-butadiene copolymer rubber (NIR), JP-A-50-104291 discloses a bound acrylonitrile amount of 15 to 45% by weight and a bound butadiene-1,3. An acrylonitrile-butadiene-isoprene terpolymer rubber having a total amount of styrene and bound isoprene of 85 to 55% by weight has been proposed, and a vulcanized product of the terpolymer rubber has a good oil resistance. Others have been reported to have good and balanced tensile strength, tensile strength after heat aging, cold resistance, compression set and impact resilience.

However, rubber rolls, belts, and seal members, which are required to have oil resistance, are used under severe conditions as the speed of machines increases. Since the rubber member used under such a severe condition is significantly worn, there is a problem that the functions of the member cannot be sufficiently fulfilled or the life thereof is short because of rapid change in size and shape. Conventional NBR does not sufficiently meet such requirements.
JP-A-62-240338 reports that the heat resistance of NBR is remarkably improved by combining NBR with both a silica-based inorganic compounding agent and a vinyl-type silane coupling agent. However, the wear resistance of this rubber composition is not significantly improved.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to provide a vulcanizate having significantly improved abrasion resistance while maintaining good oil resistance and other properties of NBR. It is intended to provide a vulcanizable nitrile rubber composition produced.

[0005]

As a result of earnest studies, the present inventors have found that the abrasion resistance of a vulcanizate obtained from a rubber composition in which a reinforcing filler is blended with NBIR having a specific composition is The inventors have found that the vulcanizate obtained from a rubber composition in which a reinforcing filler is blended with NBR is dramatically improved in wear resistance, and have completed the present invention.

Thus, according to the present invention, the amount of bound unsaturated nitrile is 35 to 55% by weight, and the total amount of bound dienes composed of bound butadiene-1,3 and bound isoprene is 65 to 4.
Unsaturated nitrile-butadiene-isoprene ternary copolymer of 5% by weight, the amount of bound butadiene-1,3 in the total amount of bound dienes is 30 to 60% by weight, and the amount of bound isoprene is 70 to 40% by weight. A vulcanizable nitrile rubber composition comprising 100 parts by weight of a united rubber, 5 to 100 parts by weight of a reinforcing filler, and a vulcanizing agent is provided.

The unsaturated nitrile-butadiene-isoprene terpolymer used in the present invention must contain unsaturated nitrile, butadiene-1,3 and isoprene in the above-mentioned predetermined proportions. As the unsaturated nitrile, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile or the like is used, and acrylonitrile is preferable.

The amount of bound unsaturated nitrile must be 35 to 55% by weight, and the total amount of bound dienes must be 65 to 45% by weight. If the amount of bound acrylonitrile is too small and the total amount of bound dienes becomes too large, the wear resistance is reduced. When the amount of bound acrylonitrile is too large and the total amount of bound dienes is too small, moldability, compression set resistance and cold resistance are deteriorated.

Bound butadiene in total bound dienes
The amount of 1,3 is 30 to 60% by weight, and the amount of bound isoprene is 70.
Must be -40% by weight. Bonded butadiene-
If the amount of 1,3 is too small and the amount of bound isoprene is too large, abrasion resistance and cold resistance are deteriorated, heat generation becomes poor, and impact resilience is further deteriorated. Conversely, bound butadiene-1,
If the amount of 3 is too large and the amount of bound isoprene is too small, the wear resistance and the heat aging resistance decrease. The unsaturated nitrile-butadiene-isoprene terpolymer used in the present invention is
Other copolymerizable monomers may be copolymerized as long as the effects of the invention are not impaired.

Other copolymerizable monomers include vinyl-based monomers such as styrene, α-methylstyrene and vinylpyridine; non-conjugated diene-based monomers such as vinylnorbornene, dicyclopentadiene and 1,4-hexadiene. Monomers; unsaturated carboxylic acids such as (meth) acrylic acid, itaconic acid, maleic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate,
Alkyl esters of unsaturated carboxylic acids such as butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, and lauryl (meth) acrylate; acrylic acid, ethoxyethyl, methoxyethoxyethyl acrylate, etc. Unsaturated carboxylic acid alkoxyalkyl ester; cyanoethyl (meth) acrylate,
(Meth) acrylic acid cyano-substituted alkyl ester such as cyanopropyl (meth) acrylate and cyanohexyl (meth) acrylate; (meth) acrylamide and N-
N-substituted (meth) acrylamides such as methylol (meth) acrylamide, N, N'-dimethylol (meth) acrylamide, N-ethoxymethyl (meth) acrylamide; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate , Epoxy (meth) acrylate, urethane (meth) acrylate and the like. These can usually be used in the range of 10% by weight or less based on the total monomers.

The unsaturated nitrile-butadiene-isoprene terpolymer has a Mooney viscosity of preferably 15-.
150, more preferably 30 to 100. If the Mooney viscosity is less than 15, only a molded product with low strength can be obtained,
Further, there is a problem in that a large amount of flash is generated in the injection molding. When the Mooney viscosity exceeds 150, the viscosity increases and injection molding and other molding become difficult.

The unsaturated nitrile-butadiene-isoprene copolymer used in the present invention contains unsaturated nitrile, butadiene-1,3 and isoprene in the presence of a radical polymerization initiator, if necessary with a molecular weight modifier. It is prepared by copolymerization. The radical polymerization initiator used is
Although not particularly limited, it is usually an organic peroxide,
Redox polymerization initiators, azo compounds, persulfates and the like are used. The amount of these polymerization initiators used is usually 0.005 to 3 parts by weight per 100 parts by weight of the total amount of the monomers. The polymerization temperature is preferably in the range of 0 to 100 ° C.

As the molecular weight modifier, 2,2 ', 4,
6,6'-pentamethylheptane-4-thiol, 2,
Alkylthiols such as 4,4-trimethylpentane-2-thiol, dodecane-12-thiol, 2,2,6,6-tetramethylheptane-4-methanethiol and 2,4,6-trimethylnonane-4-thiol Compounds;
Xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, and diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide Hydrocarbons such as pentaphenylethane; and acrolein, methacrolein, allyl alcohol, 2-ethylhexyl thioglycolate,
Terpinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer (preferably 50% by weight or more of 2-4-diphenyl-4-methyl-1-pentene), 2,5-dihydrofuran, 3 , 6-
Examples thereof include dihydro-2H-pin, phthalane, 1,2-butadiene, 1,4-hexadiene and the like.
The amount of the molecular weight modifier used is usually 0.05 to 3 parts by weight based on 100 parts by weight of the total amount of the monomers.

The radical polymerization method is not particularly limited, and bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like can be appropriately selected as necessary. Of these, emulsion polymerization is preferred. In the case of production by emulsion polymerization, polymerization is carried out by a usual emulsion polymerization method, and when a predetermined conversion rate is reached, hydroxylamine, sodium carbamate, etc. are added to terminate the polymerization. Then, the residual monomer is removed by heating, steam distillation or the like. Furthermore, a coagulant such as an inorganic coagulant, a polymer coagulant, or a heat-sensitive coagulant used in ordinary emulsion polymerization is added to the obtained polymer latex to coagulate and recover the copolymer.

In the present invention, as the reinforcing filler to be blended with the unsaturated nitrile-butadiene-isoprene terpolymer rubber (NBIR), those exhibiting a reinforcing effect when blended with NBIR are preferably used. Specific examples of such a reinforcing filler include carbon black; particle size 1
Silica such as silicic acid, silicate, anhydrous silicate, hydrous silicic acid and synthetic silicate in the form of ultra-fine bulky white powder of 0 to 15 microns; activated calcium carbonate, special calcium carbonate, heavy calcium carbonate, etc. Calcium carbonate; basic magnesium carbonate; ultrafine magnesium silicate; hard clay; talc; diatomaceous earth; alumina and the like. Of these, silica is preferred.

The amount of the reinforcing filler compounded is generally 5 to 100 parts by weight, preferably 20 to 80 parts by weight, based on 100 parts by weight of the unsaturated nitrile-butadiene-isoprene terpolymer rubber. It is a department. If the blending amount of the reinforcing filler is too small, the wear resistance and strength are low, and conversely, if the blending amount of the reinforcing filler is too large, moldability and elongation at break decrease.

As the vulcanizing agent to be added to the nitrile vulcanizable rubber composition of the present invention, those generally known as vulcanizing agents for unsaturated nitrile-conjugated diene copolymer rubbers can be used. The vulcanizing agent used is a sulfur-based vulcanizing agent,
Examples include organic peroxide vulcanizing agents and combined vulcanizing agents. The amount of the vulcanizing agent used is not particularly limited, but is usually 0.10 to 10 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the copolymer rubber.

As the sulfur-based vulcanizing agent, powdered sulfur, sulfur flower, precipitated sulfur, colloidal sulfur, surface-treated sulfur, sulfur such as insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N,
Sulfur compounds such as N'-dithio-bis (hexahydro-2H-azepinone-2), phosphorus-containing polysulfide, and polymeric polysulfide; and further, tetramethylthiuram disulfide, selenium dimethyldithiocarbamate, 2- (4 '
-Morpholinodithio) benzothiazole and the like can be mentioned. Furthermore, in addition to these sulfur-based vulcanizing agents,
Vulcanization accelerators such as zinc white and stearic acid; guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiourea-based,
Other vulcanization accelerators such as the xanthate type can be used.

Examples of the organic peroxide type vulcanizing agent include, for example,
t-butyl hydroperoxide, cumene hydroperoxide, di-t-butyl peroxide, t-butyl cumyl peroxide, 2,5-dimethyl-t-butylperoxyhexane, 2,5-dimethyl-t-butylperoxyhexyne, 1 , 3-bis (t-butylperoxyisopropyl) benzene, p-chlorobenzoyl peroxide, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, t-butylbenzoate and the like. Further, a polyfunctional compound such as trimethylolpropane trimethacrylate, divinylbenzene, ethylene dimethacrylate, triallyl isocyanurate can be used in combination with the organic peroxide vulcanizing agent.

Further, metal soap / sulfur type, triazine / dithiocarbamate type, polycarboxylic acid / onium salt type, polyamine type (hexamethylenediamine, triethylenetetramine, hexamethylenediaminecarbamate, ethylenediaminecarbamate, triethylenediamine, etc.), A vulcanizing agent such as ammonium benzoate may also be used if necessary.

The vulcanizable rubber composition of the present invention may contain a silane coupling agent together with the reinforcing filler. Among the silane coupling agents, a silane coupling agent having a vinyl group is preferable because it contributes to the improvement of heat resistance. Examples of the vinyl group-containing silane coupling agent include vinyltrichlorosilane, vinyltriacetoxysilane, vinyltriethoxysilane, vinyl-tris (β-methoxyethoxy) silane, N′-vinylbenzyl-N-trimethoxysilylpropylethylenediamine. Examples include salt. The compounding amount of the silane coupling agent is preferably in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the nitrile copolymer rubber.

The rubber composition of the present invention, if necessary,
Other usual compounding agents used in the rubber field, for example, process oil (plasticizer), antioxidant, antiozonant, non-reinforcing filler and the like can be added.
In addition, the rubber composition of the present invention may optionally contain acrylic rubber, fluororubber, styrene-butadiene copolymer rubber, ethylene-propylene-diene terpolymer rubber (E
Other rubbers such as PDM), natural rubber, polyisoprene rubber can be used in combination with the unsaturated nitrile-butadiene-isoprene terpolymer rubber.

The method for producing the rubber composition of the present invention is not particularly limited, but usually, the raw material rubber and silica are kneaded with a vulcanization system and other compounding ingredients by an ordinary mixer such as a roll or a Banbury mixer. The rubber composition is produced by mixing.

EXAMPLES The present invention will be described in more detail with reference to the following examples. In addition, parts and% in the examples and comparative examples are based on weight unless otherwise specified.

The properties of the rubber composition vulcanizate were measured as follows. (1) Vulcanized physical property evaluation test According to Japanese Industrial Standard JIS K6301, an unvulcanized rubber composition prepared according to the formulation of Table 1 was vulcanized at 160 ° C. for 20 minutes to obtain a sheet having a thickness of 2 mm. Was punched out using a No. 3 type dumbbell to prepare a test piece, and the tensile strength (unit: kgf / cm ² ) and the elongation (unit:%) were measured. The hardness was measured using a JIS spring type A hardness tester.

(2) Oil resistance Regarding the oil resistance, according to JIS K6301, the lubricating oil No. Three
(Kinematic viscosity 31.9 to 34.1, aniline point 69.5 ± 1
(° C, flash point 162.7 ° C), the rubber test piece was immersed at 120 ° C for 70 hours, and the volume change rate (unit:%) was measured. (3) Abrasion resistance (Akron abrasion test) A ring-shaped test piece according to JIS K6264 was vulcanized and molded, and attached to an Akron tester (Kamishima Seisakusho) at a tilt angle of 15 °, and a familiar operation of 500 times with a load of 27N. After the completion, the test weight is measured, and the abrasion test operation is performed 1000 times.
Then, the weight of the test piece is re-measured to obtain the wear loss volume. This operation is performed on three sets of test pieces, and the average value is taken as the wear loss volume of the sample. The abrasion resistance index was determined as follows. Abrasion resistance index = (S / T) × 100 (%) S: Abrasion loss volume of acrylonitrile-butadiene copolymer with 35% bound nitrile amount T: Abrasion loss volume of sample Abrasion resistance increases as abrasion resistance index increases. Is good.

The bound nitrile amount of the copolymer was measured according to JIS K6384 by the Kjeldahl method to measure the nitrogen content in the copolymer, and the bound nitrile amount was calculated (unit:%). Regarding the copolymerization ratio of butadiene-1,3 and isoprene in the copolymer, Mayo-Lewis
Copolymerization reactivity ratios of acrylonitrile and butadiene-1,3 and acrylonitrile and isoprene, which were experimentally obtained by the intersection method using the differential equation of
"Journal of Polymer Science" by Young
(Vol. 54, 1961, p. 411), using the copolymerization reactivity ratio of butadiene-1,3 and isoprene, the relationship between the reaction rate depending on the charged monomer composition and the composition of the produced copolymer was calculated. It was The Mooney viscosity ML of the copolymer was measured at 100 ° C. according to JIS K6383 using 40 grams of the copolymer.

Examples 1 to 7 and Comparative Examples 1 to 5 Copolymerization of acrylonitrile, butadiene-1,3 and isoprene was carried out with various monomer compositions. The following components were added to 100 parts by weight of the total amount of monomers, and a polymerization reaction was carried out at 5 ° C in an autoclave. Parts by weight of water 230 Sodium dodecylbenzenesulfonate 2.0 trisodium dibutyl sodium naphthalene sulfonate 1.5 phosphate 0.2 tertiary-dodecyl mercaptan 0.35 FeSO ₄ · 7H ₂ O 0.006 ethylenediaminetetraacetic acid trisodium salt 0.020 Sodium formaldehyde sulfoxylate 0.08 Paramenthane hydroperoxide 0.06

When the polymerization rate reaches 89%, the monomer 100 is added.
Polymerization was terminated by adding 0.2 part by weight of hydroxylamine sulfate per part by weight. Then, the mixture is heated under reduced pressure to remove residual monomers, 2.5 parts by weight of alkylated allyl phosphite antioxidant is added to 100 parts by weight of the obtained rubber, and latex is coagulated with an aqueous solution of calcium chloride. The obtained crumbs were washed with water and then dried under reduced pressure at 50 ° C.

The bound nitrile amount (%) in the acrylonitol-butadiene-isoprene terpolymer obtained as described above and the bound butadiene amount (%) and the bound isoprene amount (%) in the total bound diene amount, Also, the Mooney viscosity of the copolymer is shown in Table 1. Next, the acrylonitrile-butadiene-isoprene terpolymer was kneaded with a reinforcing filler (silica) and other additives shown in Table 1 by a Banbury mixer according to the compounding recipe shown in Table 1 to obtain a vulcanizable rubber composition. Then, the product was press-vulcanized at 160 ° C. for 20 minutes, and the physical properties of the obtained vulcanized product were evaluated. The results are shown in Table 1.

[0030]

[Table 1]

Note * 1: Reinforcing filler component (silica) (1) Nipsyl VN-3 (manufactured by Nippon Silica, wet process silica) (2) Aerosil 200 (manufactured by Degussa, dry process silica) Other components (1) ) Valcup 40KE (peroxide, Hercule
(2) Naugard 445 (antiaging agent, Uniroya
Chem. (3) Noxera-TT (Tetramethylthiuram disulfide, Ouchi Shinko Co., Ltd.) (4) Noxera-CZ (N-cyclohexyl-2-benzothiazylsulfenamide, Ouchi Shinko Co., Ltd.)

As shown in Table 1, the vulcanized molded product obtained from the rubber composition of the present invention is excellent in both oil resistance and abrasion resistance. When the amount of bound nitrile in the copolymer is small (Comparative Example 1), the abrasion resistance is extremely low. Further, instead of the above terpolymer (NBIR), acrylonitrile-butadiene copolymer (NBR) (Comparative Examples 4 and 5) and acrylonitrile-butadiene-isoprene terpolymer (NBIR) having a high butadiene content (NBIR) ( Comparative example 3)
In that case, the abrasion resistance is remarkably low. in this way,
Addition of a reinforcing filler (silica) to NBR or NBIR having a high butadiene content does not significantly improve the wear resistance of the vulcanizate, but the specific composition of acrylonitrile-butadiene-isoprene used in the present invention It is considered surprising that in the original copolymer (NBIR), the wear resistance is remarkably improved by the addition of the reinforcing filler.

Examples 8-11 and Comparative Examples 6 and 7 Acrylonitrile-butadiene-isoprene terpolymer same as used in Examples 1, 3 and 5 and acrylonitrile same as used in Comparative Examples 4 and 5. Using the butadiene copolymer, vulcanization molding was performed in the same manner as in Examples 1 to 7 and Comparative Examples 1 to 5 according to the formulation shown in Table 2, and the physical properties of the vulcanized product were evaluated. Table 2 shows the results.

[0034]

[Table 2]

Note: Carbon black (FEF manufactured by Asahi Kasei)
# 60) As seen in Table 2, even when carbon black is blended as a reinforcing filler, NBR (Comparative Example 6) has low abrasion resistance, but NBIR having a specific composition used in the present invention.
(Examples 8 to 10) The wear resistance is remarkably improved. As shown in Tables 1 and 2, the vulcanizates having excellent wear resistance and oil resistance were obtained by using the sulfur vulcanizing agent as the vulcanizing agent (Examples 1 to 6, 8 to 10) and It can be obtained in any case where a peroxide is used (Examples 7 and 11).

[0036]

The butadiene / isoprene copolymerization ratio is 30.
/ 70 to 60/40 Vulcanized product obtained from the vulcanizable rubber composition of the present invention obtained by blending a reinforcing filler with an unsaturated nitrile-butadiene-isoprene terpolymer (NBIR) Has excellent wear resistance and oil resistance. Considering that the abrasion resistance is low when the reinforcing filler is blended with the unsaturated nitrile-butadiene copolymer (NBR) or the NBIR having a high butadiene content, the NBIR having the above specific composition and the reinforcing filler are used. It is considered surprising that a vulcanized product excellent in both abrasion resistance and oil resistance can be obtained by the combination of The vulcanizable nitrile-based rubber composition of the present invention is useful as various rubber rolls, belts, hoses, and sealing materials that are required to have wear resistance and oil resistance, particularly as a printing roll blanket that requires high wear resistance. is there.

The vulcanizable nitrile rubber composition of the present invention, that is, the amount of bound unsaturated nitrile is 35 to 55% by weight, and the total amount of bound diene composed of bound butadiene-1,3 and bound isoprene is 65 to 45. % By weight, and the amount of bound butadiene-1,3 in the total amount of bound dienes is 30 to 60.
%, An unsaturated nitrile-butadiene-isoprene terpolymer rubber having a bound isoprene content of 70 to 40% by weight, 100 parts by weight of an inorganic filler, and 5 to 100 parts by weight of a vulcanizing agent. The preferred embodiments of the vulcanizable nitrile rubber composition are summarized as follows.

(1) The Mooney viscosity of the terpolymer rubber is 15 to 150, more preferably 30 to 100. (2) The reinforcing filler is silica. (3) The content of the reinforcing filler is 10% by weight of the terpolymer rubber 10.
It is 20 to 80 parts by weight with respect to 0 parts by weight. (4) As the vulcanizing agent, a sulfur-based vulcanizing agent and / or an organic peroxide-based vulcanizing agent is blended in an amount of 0.10 to 10 parts by weight with respect to 100 parts by weight of the terpolymer rubber. (5) Furthermore, 0.5 to 10 parts by weight of a silane coupling agent having a vinyl group is blended.

Claims (1)

[Claims] 1. The amount of bound unsaturated nitrile is 35 to 55% by weight, the total amount of bound diene composed of bound butadiene-1,3 and bound isoprene is 65 to 45% by weight, and the total amount of bound diene is Bonded butadiene-1,3 amount is 30
To 60% by weight, 100 to 100 parts by weight of an unsaturated nitrile-butadiene-isoprene terpolymer rubber having a bound isoprene content of 70 to 40% by weight, a reinforcing filler of 5 to 100 parts by weight, and a vulcanizing agent. A vulcanizable nitrile rubber composition characterized by: