Rubber composition

Abstract

To provide a rubber composition that features an excellent balance of wet grip, rolling resistance, and wear resistance, combined with excellent processability.SOLUTION: A rubber composition comprises 100 pts.mass of a rubber component in combination with 10-40 pts.mass of a cycloolefin copolymer with a softening point of 60-130°C, a bromine number of 10-60, and a number average molecular weight of 800-5,000.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention provides a novel rubber composition having excellent performance for use in tires. [Background technology]

[0002] In recent years, with the advancement of high performance and high functionality of automobiles, the demand for tire performance is increasing. For example, tires with improved wet grip, rolling resistance, and abrasion resistance, which are in a contradictory relationship, are required. In addition, electric vehicles and plug-in hybrid vehicles equipped with a driving battery are subject to increased loads on tires as the vehicle weight increases, and tires with improved durability are required. To improve rolling resistance, a technique of compounding silica into rubber and a technique of using terminal-modified rubber in which a functional group that has high affinity with silica or can be chemically bonded to the terminal is introduced to increase the dispersibility of silica are used.

[0003] In tire compounding, tackifier resins such as petroleum resins with a molecular weight of 10,000 or less (see, for example, Patent Document 1) and terpene resins (see, for example, Patent Document 2) are used in rubber to improve mechanical properties and impart good adhesion to unvulcanized rubber compositions. These tackifier resins are generally produced by cationic polymerization or thermal polymerization of monomers.

[0004] On the other hand, cycloolefin polymers are used mainly in optical components as a substitute for glass due to their excellent optical properties and low moisture absorption, and are also used in medical containers and semiconductor containers due to their moldability and light weight.

[0005] It is known that a low molecular weight cycloolefin polymer having a number average molecular weight (Mn) of 10,000 to 50,000 and a molecular weight distribution dispersity (Mw / Mn) of 2.0 to 10.0 can be produced by melting a cycloolefin polymer (number average molecular weight of 30,000 or more) and pyrolyzing it at 330 to 380°C (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5309529 [Patent Document 2] Patent No. 5076365 [Patent Document 3] Patent No. 6083597 Summary of the Invention [Problem to be solved by the invention]

[0007] The low molecular weight cycloolefin polymer described in Patent Document 3 has poor affinity with rubber, and therefore does not exhibit the mechanical properties and adhesive performance required for a tackifier resin. [Means for solving the problem]

[0008] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems and have found that a rubber composition containing a cycloolefin copolymer within a specific molecular weight range exhibits excellent rubber properties, thereby completing the present invention.

[0009] That is, the respective aspects of the present invention are as follows [1] to [4]. [1] A rubber composition comprising, per 100 parts by mass of a rubber component, 5 to 40 parts by mass of a cycloolefin copolymer having a softening point of 60 to 130°C, a bromine number of 10 to 60, and a number average molecular weight of 800 to 5,000. [2] The rubber composition according to [1], wherein the rubber component contains 10% by mass or more of styrene-butadiene rubber. [3] The rubber composition according to [1] or [2], further comprising 5 to 200 parts by mass of silica per 100 parts by mass of the rubber component. [4] A tire comprising a vulcanizate of the rubber composition according to any one of [1] to [3]. Effect of the Invention

[0010] INDUSTRIAL APPLICABILITY The present invention can provide a rubber composition having an excellent balance between wet grip properties, rolling resistance and abrasion resistance, and further having excellent processability, and a tire using the same, which is extremely useful industrially. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below based on preferred embodiments thereof.

[0012] The rubber composition according to one embodiment of the present invention contains a rubber component, and a cycloolefin copolymer having a softening point of 60 to 130° C., a bromine number of 10 to 60, and a number average molecular weight of 800 to 5,000.

[0013] The rubber component may be any rubber that belongs to the category called rubber, for example, a diene rubber having a carbon-carbon double bond, more specifically, natural rubber (sometimes written as NR), polyisoprene rubber (sometimes written as IR), polybutadiene rubber (sometimes written as BR), styrene-butadiene copolymer rubber (sometimes written as SBR), styrene-isoprene copolymer rubber, etc. may be mentioned. These may be used alone or in combination. There is no particular limitation on the method for producing the rubber, and it may be an anionic polymer or an emulsion polymer. There is no particular limitation on the molecular weight or microstructure, and it may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group, etc., or may be epoxidized. Among these, it is preferable to use at least one of natural rubber, polybutadiene rubber, and polyisoprene rubber in combination with styrene-butadiene copolymer rubber, since this makes it possible to provide a rubber composition that can achieve high levels of both wet grip performance and rolling resistance when made into a rubber composition, and it is preferable for the styrene-butadiene copolymer rubber to contain 10 mass % or more.

[0014] The softening point of the cycloolefin copolymer is preferably 60 to 130° C., more preferably 80 to 120° C., in accordance with JIS K-2207, since this provides excellent compatibility with the rubber component and processability.

[0015] The cycloolefin copolymer may contain a carbon-carbon double bond. As an index of this, the bromine number measured according to JIS K-2605 (1996) is 10 to 60 (g-Br2 / 100g). If the bromine number is 60 or less, the cycloolefin copolymer has excellent heat resistance and is less likely to develop coloration due to thermal decomposition.

[0016] The number average molecular weight of the cycloolefin copolymer is 800 to 5000, and preferably 800 to 3000. When the number average molecular weight is within this range, compatibility with rubber is good.

[0017] The cycloolefin copolymer is preferably a copolymer containing a cycloalkene having a norbornene skeleton and a non-cyclic monoolefin as constituent monomers.

[0018] Examples of the cycloalkene having a norbornene skeleton include monocycloalkenes having 7 to 25 carbon atoms and a norbornene skeleton {norbornene (bicyclo[2.2.1]-2-heptene), tricyclo[4.3.0.1 2,5 ]-3-decene, 8-ethyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, tricyclo[4.3.0.1 2,5 ]-3-decene, tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, pentacyclo[6.5.1.1 3,6 .0 2,7 .0 9,13 ]-4-Pentadecene, Pentacyclo[7.4.0.1 2,5 .1 9,12 .0 8,13 ]-3-Pentadecene, Pentacyclo[8.4.0.1 2,5 .1 9,12 .0 8,13 ]-3-Hexadecene, Pentacyclo[6.6.1.1 3,6 .0 2,7 .0 9,14]-4-Hexadecene, Hexacyclo[6.6.1.1 3,6 .1 10,13 .0 2,7 .0 9,14 ]-4-Heptadecene, Hexacyclo[6.6.1.1 3,6 .1 10,13 .0 2,7 .0 9,14 ]-4-Heptadecene, Heptacyclo[8.7.0.1 2,9 .1 4,7 .1 11,17 .0 3,8 .0 12,16 ]-5-Eicosene, heptacyclo[8.7.0.1 3,6 .1 10,17 .1 12,15 .0 2,7 .0 11,16 ]-4-Eicosene, heptacyclo[8.7.0.1 3,6 .1 10,17 .1 12,15 .0 2,7 .0 11,16 ]-4-Eicosene, heptacyclo[8.8.0.1 2,9 .1 4,7 .1 11,18 .0 3,8 .0 12,17 ]-5-Henneicosene, Octacyclo[8.8.0.1 2,9 .1 4,7 .1 11,18 .1 13,16 .0 3,8 .0 12,17 ]-5-docosene, and nonacyclo[10.9.1.1 4,7 .1 13,20 .1 15,18 .0 2,10 .0 3,8 .0 12,21 .0 14,19 ]-5-pentacosene.

[0019] Among the above cycloalkenes having a norbornene skeleton, preferred are tricyclo[4.3.0.1 2,5 ]-3-decene, 8-ethyl-tetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene, tetracyclo[4.4.0.1 2,5.1 7,10 ]-3-dodecene, and norbornene (bicyclo[2.2.1]-2-heptene).

[0020] The acyclic monoolefin is preferably acyclic monoolefin having 2 to 10 carbon atoms.

[0021] Among the acyclic monoolefins having 2 to 10 carbon atoms, those having 4 or more carbon atoms are acyclic monoolefins having a double bond at the terminal. Examples of these acyclic monoolefins include ethylene, propylene, and α-olefins having 4 to 8 carbon atoms (1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, etc.). Among these, ethylene and propylene are preferred.

[0022] The molar ratio of the cycloalkene having a norbornene skeleton to the non-cyclic monoolefin constituting the cycloolefin copolymer [cycloalkene / olefin] varies depending on the target resin, but is preferably 2 / 98 to 50 / 50, more preferably 5 / 95 to 40 / 60, and particularly preferably 10 / 90 to 30 / 70.

[0023] The cycloolefin copolymer can be produced by melting a cycloolefin polymer containing a cycloalkene having a norbornene skeleton and a non-cyclic monoolefin as constituent monomers, and pyrolyzing the melted polymer at 300 to 450°C.

[0024] A preferred method for adjusting the cycloolefin copolymer to have the above number average molecular weight is to reduce the molecular weight by subjecting the cycloolefin polymer to a thermal decomposition reaction to partially cleavage of the main chain.

[0025] The cycloolefin polymer can be any cycloolefin polymer having a number average molecular weight of 10,000 to 200,000, which is composed of the cycloalkene having a norbornene skeleton and the acyclic monoolefin, and is not limited thereto. Commercially available products (e.g., Zeonex series and Zeonor series manufactured by Zeon Corporation, Apel series manufactured by Mitsui Chemicals, Inc., and TOPAS series manufactured by Polyplastics Co., Ltd.) may also be used.

[0026] The pyrolysis is preferably carried out in an atmosphere of a gas that is not reactive with the cycloolefin polymer (hereinafter referred to as an inert gas) at 300 to 450°C for 0.5 to 10 hours. Specific examples of the inert gas include argon, nitrogen, carbon dioxide, and water vapor, and nitrogen is preferred. The inert gas is preferably passed through the reaction vessel at a flow rate of 0.1 to 100 L / min during heating.

[0027] The heating temperature is preferably 300 to 450° C., more preferably 320 to 450° C. When the reaction temperature is within this range, the coloring of the cycloolefin copolymer is reduced and the generation of odor is suppressed, which is preferable. Hereinafter, the fact that the coloring is reduced and the generation of odor is suppressed is referred to as "good color tone and odor."

[0028] The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 7 hours. When the reaction time is within this range, the color and odor of the unsaturated bond-containing cycloolefin copolymer become good, and homogeneous thermal decomposition can be achieved, which is preferable.

[0029] The pressure for pyrolysis is between normal pressure (atmospheric pressure) and 200 kg / cm 2 is preferable, and more preferably from normal pressure to 150 kg / cm 2 Within this range, the color tone and odor of the unsaturated bond-containing cycloolefin copolymer will be good.

[0030] The thermal decomposition method may be either a batch method or a continuous method.

[0031] When using a batch method, the process can be carried out by passing an inert gas through a reaction vessel made of stainless steel or the like equipped with a stirrer, placing the raw material cycloolefin polymer in the reaction vessel, and heating the reaction vessel at a predetermined temperature for a predetermined period of time while stirring.

[0032] When a continuous process is used, an inert gas is passed through a continuous reaction vessel such as a tubular reactor or an extruder, the raw material cycloolefin polymer is placed in the reaction vessel, and the raw material is heated and melted while adjusting the amount of the raw material introduced so that the raw material remains in the reaction vessel at a predetermined temperature for a predetermined time, thereby carrying out thermal decomposition.

[0033] The thermal decomposition may be carried out by adding a phenol-based antioxidant. Examples of the phenol-based antioxidant include hindered phenol compounds such as 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2,4-methylphenol, 2,6-di-tert-butylphenol, and 2-tert-butyl-4-ethylphenol.

[0034] In the thermal decomposition, a catalyst can be used to promote the decomposition reaction. Examples of the catalyst to be added include radical generating catalysts [peroxides such as benzoyl peroxide, di-tert-butyl peroxide, and dicumyl peroxide; azonitriles such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 4,4'-azobis(4-cyanovaleric acid)] and cracking catalysts (silica-alumina, silica-magnesia, activated clay, etc.).

[0035] The rubber composition contains 5 to 40 parts by mass, preferably 8 to 30 parts by mass, of a cycloolefin copolymer relative to 100 parts by mass of the rubber component. If the cycloolefin copolymer is less than 5 parts by mass, the resulting composition is inferior in wet grip property and abrasion resistance. On the other hand, if the cycloolefin copolymer is more than 40 parts by mass, the resulting composition is inferior in rolling resistance.

[0036] In addition, the rubber composition preferably contains 5 to 200 parts by mass of silica per 100 parts by mass of the rubber component, particularly preferably 10 to 150 parts by mass, and more preferably 20 to 120 parts by mass, in order to improve rolling resistance. The silica in this case is not particularly limited, and those used in commercially available rubber compositions can be used, among which wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), colloidal silica, etc. can be used, and wet silica is particularly preferred. In particular, a rubber composition containing a cycloolefin copolymer can reduce viscosity, so that even if it contains 70 parts by mass or more of silica at a high content, it is a rubber composition that can provide a tire that is excellent in processability and balance between wet grip properties, rolling resistance, and abrasion resistance.

[0037] When silica is used, it is preferable to use a silane coupling agent in combination. By using a silane coupling agent in combination, the bond between the rubber component and silica is strengthened via the silane coupling agent, and the balance of wet grip performance, rolling resistance, and abrasion resistance can be highly improved. Examples of the silane coupling agent include sulfide-based, mercapto-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, and chloro-based silane coupling agents. These silane coupling agents can be used alone or in combination.

[0038] In the rubber composition, in addition to the silica, for example, carbon black can be used in combination as a reinforcing filler, and the carbon black may have a grade such as FEF, SRF, HAF, ISAF, SAF, etc. The content of the carbon black is preferably 10 to 60 parts by mass per 100 parts by mass of the diene rubber, since it provides excellent rolling resistance.

[0039] The rubber composition may further contain additives that are usually compounded in resin compositions or rubber compositions. For example, compounding agents such as crosslinking agents including sulfur, vulcanization accelerators, vulcanization accelerator assistants, stearic acid, zinc oxide, plasticizers, oils, and antioxidants may be added. Commercially available products can be suitably used as these compounding agents.

[0040] The rubber composition may contain additives that are usually blended into resin compositions and rubber compositions, such as a phenol-based antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant, a lactone-based antioxidant, an ultraviolet absorber, a pigment, calcium carbonate, glass beads, etc., as long as the blend does not deviate from the object of the present invention.

[0041] Furthermore, the rubber composition includes its form and shape, and may be a crosslinked product (vulcanized product) that contains a crosslinking agent, a vulcanization accelerator, a vulcanization acceleration assistant, and the like and has been crosslinked (vulcanized).

[0042] The rubber composition can be prepared by blending diene rubber, cycloolefin copolymer, and various compounding agents appropriately selected as necessary, and mixing them using a mixing method such as a Banbury mixer, a pressure kneader, an open roll, etc. The unvulcanized rubber composition obtained can be crosslinked using, for example, a calendar, a roll, an extruder, a press, etc., to produce a vulcanized product.

[0043] According to the present invention, it is possible to provide a vulcanizate of a rubber composition which is excellent in wet grip property, abrasion resistance and further in processability, and which can be applied to various rubber applications such as rolls, mats, tubes, grips, handles and the like. Among these, it is possible to provide an excellent tire constituent material, in particular a tread, a tire having the same, and further a studless tire and an all-season tire. EXAMPLES

[0044] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The analytical and test methods used in the examples and comparative examples are as follows.

[0045] The analytical methods for cycloolefin copolymers are shown below.

[0046] ~Measurement of weight average molecular weight (Mw) and number average molecular weight (Mw)~ Polystyrene was used as the standard substance and measurements were performed by gel permeation chromatography in accordance with JIS K-0124 (2011).

[0047] ~Bromine number~ The measurement was performed according to a method conforming to JIS K-2605 (1996).

[0048] ~Softening point~ The measurement was performed according to JIS K-2207 (1996) (Ball and Ring Method).

[0049] The methods for measuring the properties of the vulcanized rubber composition (wet grip property, rolling resistance, abrasion resistance) are shown below.

[0050] ~Wet grip~ Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ was measured at a temperature of 0° C., a strain of 5%, and a frequency of 15 Hz, and the value at 0° C. was evaluated as wet grip performance.

[0051] When tan δ at 0° C. was 0.27 or more, the wet grip performance was determined to be good.

[0052] ~Rolling resistance~ Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ was measured at a temperature of 60° C., a strain of 5%, and a frequency of 15 Hz, and the value at 60° C. was evaluated as the rolling resistance.

[0053] When tan δ at 60° C. was 0.14 or less, the rolling resistance was determined to be good.

[0054] ~Abrasion resistance~ Vulcanized rubber test pieces were prepared, and the amount of wear was measured at 23° C. using a Lambourn abrasion tester in accordance with JIS K-6264.

[0055] Wear at 23℃ is 24mm 3 / min or less, the abrasion resistance was determined to be good.

[0056] Manufacturing Example 1 A small quartz pyrolysis device was used as the pyrolysis device. 10 g of cycloolefin polymer (ZEONEX690R, Mn 15,000, manufactured by Zeon Corporation) was charged into the pyrolysis device, and after replacing the inside of the system with nitrogen, it was heated and melted at an internal temperature of 350°C. After 60 minutes, it was cooled to room temperature, and the reaction system was returned to normal pressure. The residue in the pyrolysis device was dissolved in hot xylene, and then dropped into methanol for reprecipitation and purification, to obtain cycloolefin copolymer A. The evaluation results are shown in Table 1.

[0057] Manufacturing Examples 2 to 4 Cycloolefin copolymers B to D were obtained in the same manner as in Production Example 1, except that the pyrolysis conditions (temperature, time) and the type of cycloolefin polymer were as shown in Table 1. The evaluation results are shown in Table 1. TOPAS6013M-07 (Mn 50,000) is a cycloolefin polymer manufactured by Polyplastics Co., Ltd.

[0058] [Table 1]

[0059] Example 1 In a Banbury mixer (volume 1.7 liters), 55 parts by mass of a solution polymerized terminal-modified styrene-butadiene copolymer rubber (modified S-SBR) (manufactured by ENEOS Material Co., Ltd., (trade name) HPR-340: styrene content 10% by mass) and 45 parts by mass of polyisoprene rubber (IR) (manufactured by ENEOS Material Co., Ltd., (trade name) IR2200) were mixed and masticated for 30 seconds, and then 2 parts by mass of stearic acid (manufactured by New Japan Chemical Co., Ltd.), 70 parts by mass of silica (manufactured by Tosoh Silica, (trade name) Nipsil AQ), 5.6 parts by mass of a silane coupling agent (manufactured by Shin-Etsu Silicone, (trade name) KBE46), and 20 parts by mass of the cycloolefin copolymer A obtained in Production Example 1 were added to 100 parts by mass of the diene rubber component, and the total kneading time was 5 minutes, after which the mixture was taken out. The ram pressure and rotation speed were adjusted so that the compound temperature at the time of taking out was 140°C to 150°C. The obtained compound was cooled to room temperature, and then 1 part by mass of an antioxidant (manufactured by Ouchi Shinko, product name: 810NA), 3 parts by mass of zinc oxide (manufactured by Inoue Lime Industry), 1.2 parts by mass of a vulcanization accelerator (1) (manufactured by Ouchi Shinko, product name: Noccela CZ), 1.5 parts by mass of a vulcanization accelerator (2) (manufactured by Ouchi Shinko, product name: Noccela D), and 1.5 parts by mass of sulfur (manufactured by Tsurumi Chemical Industry) as a vulcanizing agent were added and kneaded for about 1 minute (the temperature at the time of removal was 110°C or less), and then sheeted using an 8-inch roll to obtain an unvulcanized rubber composition.

[0060] The rubber composition was then vulcanized using a steam heating press at a temperature of 150°C for 30 minutes to obtain a vulcanized rubber composition. The properties of the vulcanized rubber composition obtained (wet grip, rolling resistance, abrasion resistance) were measured. The results are shown in Table 2.

[0061] [Table 2]

[0062] Examples 2 to 3 Unvulcanized and vulcanized rubber compositions were prepared and evaluated in the same manner as in Example 1, except that cycloolefin copolymers B and C were used instead of cycloolefin copolymer A. The results are shown in Table 2.

[0063] Examples 4 to 5 Unvulcanized rubber compositions and vulcanized rubber compositions were prepared and evaluated in the same manner as in Example 1, except that cycloolefin copolymer B was used in the amount shown in Table 2 instead of 20 parts by mass of cycloolefin copolymer A. The results are shown in Table 2.

[0064] The rubber compositions obtained in Examples 1 to 5 were excellent in balance between wet grip properties, rolling resistance and abrasion resistance.

[0065] Comparative Example 1 An unvulcanized rubber composition and a vulcanized rubber composition were obtained in the same manner as in Example 1, except that cycloolefin copolymer A was not used. The evaluation results are shown in Table 2.

[0066] Comparative Example 2 An unvulcanized rubber composition and a vulcanized rubber composition were prepared and evaluated in the same manner as in Example 1, except that cycloolefin copolymer D was used instead of cycloolefin copolymer A. The results are shown in Table 2.

[0067] Comparative Examples 3 to 4 Unvulcanized rubber compositions and vulcanized rubber compositions were prepared and evaluated in the same manner as in Example 1, except that cycloolefin copolymer A was used in the amount shown in Table 2. The results are shown in Table 2. [Industrial Applicability]

[0068] According to the present invention, by blending a cycloolefin copolymer in a specific molecular weight range, it is possible to provide a rubber composition which is excellent in balance between wet grip properties, rolling resistance and abrasion resistance and further has excellent processability. The rubber composition can be used as a tire tread rubber to provide a tire or an all-season tire, and the industrial value of the rubber composition is extremely high.

Claims

1. The rubber composition contains 5 to 40 parts by mass of a cycloolefin copolymer having a softening point of 60 to 130° C., a bromine number of 10 to 60, and a number average molecular weight of 800 to 5,000, per 100 parts by mass of a rubber component.

2. The rubber composition according to claim 1 , wherein the rubber component contains 10% by mass or more of styrene-butadiene rubber.

3. The rubber composition according to claim 1, further comprising 5 to 200 parts by mass of silica per 100 parts by mass of the rubber component.

4. A tire comprising a vulcanizate of the rubber composition according to any one of claims 1 to 3.

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