JP2017200960A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition having excellent ozone resistance.SOLUTION: A composition is formed by adding, to a rubber component, a hydrogenated polybutadiene with the content of 1,2-vinyl bonds of 50 mol% or more and a double bond hydrogenation rate of 20 mol% or more.SELECTED DRAWING: None

Description

  The present invention relates to a novel rubber composition.

A rubber composition for a bead apex containing a diene rubber and a hydrogenated liquid polybutadiene is known, and the hydrogenation rate of double bonds of the hydrogenated liquid polybutadiene is preferably 20 mol% or more, more preferably 30 mol% or more. More preferred is known. (See Patent Document 1)
A liquid in which the amount of 1,2-vinyl bonds before hydrogenation is 90% or more, the number average molecular weight is 3300, and the hydrogenation rate is 90% or more with respect to 100 parts by weight of the rubber component made of diene rubber. A rubber composition for tire bead filler to which 1 to 25 parts by weight of polybutadiene is added is known. (See Patent Document 2)
Further, (A) ethylene-α-olefin-nonconjugated diene copolymer rubber 10 to 70% by weight, (B) styrene-butadiene copolymer rubber or a mixture of styrene-butadiene copolymer rubber and polystyrene 15 to 70% by weight. And (C) 5 to 60% by weight of polybutadiene having a number average molecular weight of 700 to 4000 (provided that (A) + (B) + (C) = 100% by weight), and (B). (D) 10 to 30% by weight of reinforcing agent or filler and (D) per 100 parts by weight of the total amount of (A), (B) and (C) in which the content of styrene units is 50 to 95% by weight E) Rubber compositions containing 1 to 30 parts by weight of organic peroxide are known. (See Patent Document 3)
Further, olefinic block copolymers, liquid 1,2-polybutadiene as a crosslinking aid, and a composition containing an organic peroxide as a crosslinking agent are known. (See Patent Document 4)
On the other hand, the polymer component contains 10 to 40% by mass of syndiotactic-1,2-polybutadiene-containing polybutadiene rubber and 10 to 30% by mass of tin-modified polybutadiene rubber, and 10 parts by mass of silica with respect to 100 parts by mass of the polymer component. It is known that a rubber composition for a sidewall containing ˜40 parts by mass can improve cut resistance and ozone resistance and low fuel consumption of a vehicle. (See Patent Document 5)

JP 2010-174102 A JP 2014-15585 A Japanese Patent Laid-Open No. 10-45982 JP 59-47251 JP 2010-95554 A

However, although the composition described in Patent Document 1 has good processability, high strength, excellent steering stability, and good rolling resistance, it does not describe ozone resistance. Moreover, in the composition of patent document 2, workability and hardness are inferior to the non-added thing, and ozone resistance is not described. Patent Document 3 describes that a high-hardness vulcanized rubber composition having high altitude and excellent workability, heat resistance, ozone resistance, and compression set resistance can be obtained. The results of evaluating ozone resistance are not described. Patent Document 4 describes that a crosslinked olefin copolymer having a good balance of heat resistance, flexibility, strength, workability, and appearance can be obtained. Not listed. Patent Document 5 describes an ozone-resistant rubber composition, but it is silica and a silane coupling agent that contribute to ozone resistance, and polybutadiene used has a low hardness and low hardness. It is described that it contributes to heat generation, and it is not known that specific polybutadiene contributes to ozone resistance.
An object of this invention is to provide the rubber composition excellent in ozone resistance.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a rubber composition having improved ozone resistance can be obtained by adding polybutadiene having a specific structure. It came to be completed.

That is, the present invention
(1) A rubber composition containing a hydrogenated polybutadiene having an amount of 1,2-vinyl bonds of 50 mol% or more and a hydrogenation rate of double bonds of 20 mol% or more, and an organic peroxide,
(2) The rubber composition according to (1), containing 1 to 25 parts by mass of hydrogenated polybutadiene with respect to 100 parts by mass of the rubber component,
(3) The rubber composition according to (1) or (2), wherein the number average molecular weight of the hydrogenated polybutadiene is in the range of 1000 to 4000.
About.

  By using the composition of the present invention, a rubber composition having improved ozone resistance can be obtained.

The rubber component used in the rubber composition of the present invention is not particularly limited, and specific examples include natural rubber, diene polymer rubber, olefin polymer rubber, and the like.
Specific examples of the diene polymer rubber include isoprene rubber, butadiene rubber, 1,2-polybutadiene, styrene-butadiene rubber, chloroprene rubber, and nitrile rubber.
Specific examples of the olefin rubber include butyl rubber, chlorinated butyl rubber, brominated butyl rubber, and ethylene-propylene-diene rubber.
Among these, a homopolymer of a diene compound or a copolymer of a diene compound and an aromatic vinyl compound is preferable, and specific examples include isoprene rubber, butadiene rubber, and styrene butadiene rubber.
These rubbers can be used either alone or in a blend of two or more.

The rubber component is preferably cross-linked, and can be cross-linked by appropriately blending a cross-linking agent and a cross-linking accelerator usually used in the rubber industry.
Specific examples of the crosslinking agent include sulfur, phenol resin, metal oxide and the like. These can usually be used in an amount of about 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component.
In the rubber composition of the present invention, an organic peroxide is an essential component. Specifically, dicumyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, α, α′-di -T-butylperoxydi-p-diisopropylpyrbenzene, n-butyl-4,4-bis-t-butylperoxyvalerate, t-butylperoxybenzoate, t-butylperoxyisopropylcarbonate, 2 , 5-dimethyl-2,5-di (t-butylperoxy) hexane, etc., among which dicumyl peroxide is preferred.
Specific examples of the crosslinking accelerator include zinc oxide, stearic acid, 2,2-dithiobisbenzothiazole, 1,3-diphenylguanidine, tetramethylthiuram disulfide, zinc dimethylthiocarbamate, and mercaptobenzothiazyl disulfide. The These can use about 0.2-5 mass parts with respect to 100 mass parts of rubber components, for example.

  The polybutadiene before hydrogenation of the hydrogenated polybutadiene used in the present invention is a polymer that is liquid at normal temperature (23 ° C.) and is not included in the rubber component that is solid at normal temperature. The liquid polybutadiene has a number average molecular weight (Mn) of usually 1,000 to 100,000, and is clearly distinguished from the diene rubber of the rubber component, which has a number average molecular weight of usually 200,000 or more. The number average molecular weight of the liquid polybutadiene is preferably 1,000 to 50,000, more preferably 1,000 to 10,000, and still more preferably 1,000 to 4,000. The number average molecular weight is a value measured at 40 ° C. by GPC (gel permeation chromatography), solvent: THF (tetrahydrofuran).

The liquid polybutadiene has a 1,2-vinyl bond amount of 50 mol% or more, more preferably 70 mol% or more, and further preferably in the range of 80 to 95 mol%.
The 1,2-vinyl bond content is the content of 1,2-vinyl bond units relative to the content of butadiene units contained in the polymer, and is calculated by the integration ratio of the 1H NMR spectrum.

The hydrogenation rate of the hydrogenated polybutadiene used in the present invention (ratio of hydrogenated double bonds to double bonds of polybutadiene before hydrogenation) is preferably 20 mol% or more, more preferably 50 mol% or more, and further 90 More than mol% is preferable. The hydrogenation rate is calculated from the spectrum reduction rate of the unsaturated bond part in the 1H NMR spectrum. Hydrogenation can be performed by a known method using a catalyst such as palladium, and is not particularly limited.
The 1,2-vinyl bond unit is converted to an ethyl group by hydrogenation, but the 1,2-bond form itself having a side chain of a hydrocarbon group having 2 carbon atoms is retained. If the added and unhydrogenated 1,2-vinyl bond units are combined to form a 1,2-bond component, the hydrogenated polybutadiene contains 50 mol% or more of the 1,2-bond component, and an additional 70 mol. % Or more, and more preferably in the range of 80 to 95 mol%.
The number average molecular weight of the hydrogenated polybutadiene is in the range of a number obtained by adding the number of hydrogens according to the hydrogenation rate to the number average molecular weight of the polybutadiene before hydrogenation.

In addition to the above, the rubber composition of the present invention can be appropriately blended with compounding agents such as fillers, plasticizers, anti-aging agents, etc., which are usually used in the rubber industry, depending on the purpose and application. .
Specific examples of the filler include carbon black, silica, filler, calcium carbonate, mica, and flake graphite. More specifically, examples of carbon black include ISAF, HAF, FEF, GPF, and the like. The amount of the carbon black is not particularly limited, but is 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. It is preferably 50 to 90 parts by mass.
Plasticizers include paraffinic process oil, naphthenic process oil, petroleum process oil such as aromatic process oil, dibasic acid dialkyl such as diethyl phthalate, dioctyl phthalate and dibutyl adipate, liquid polybutene, liquid poly Low molecular weight liquid polymers such as isoprene are exemplified, and among them, liquid polybutene, liquid polyisoprene, and aromatic process oil are preferable because of compatibility with the rubber component.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, in the first mixing stage, the rubber component is added and mixed with the hydrogenated polybutadiene together with other additives excluding the vulcanizing agent and the vulcanization accelerator, and then the resulting mixture is mixed in the final mixing stage. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited to these Examples.

  Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than sulfur, vulcanization accelerator, and organic peroxide are added and mixed (heating temperature = 100). ° C), and then, sulfur, a vulcanization accelerator, and an organic peroxide were added and mixed to the obtained mixture in a final mixing stage, and kneaded with a roll machine (roll temperature = 50 ± 10 ° C) to obtain a rubber composition. Was prepared. The details of each component in Table 1 are as follows.

[Rubber component]
Synthetic rubber: SBR 1500 (manufactured by Zeon Corporation, Nipol (registered trademark) 1500)
[Liquid polybutadiene]
Liquid polybutadiene 1: “BI-3000” manufactured by Nippon Soda Co., Ltd. (unmodified hydrogenated liquid polybutadiene, Mn = 3,100, 1,2-vinyl bond amount (Vi) before hydrogenation = 90 mol%, hydrogen Addition rate = 99 mol% or more)
Liquid polybutadiene 2: “BI-3060” manufactured by Nippon Soda Co., Ltd. (unmodified hydrogenated liquid polybutadiene, Mn = 3,060, 1,2-vinyl bond content (Vi) = 72 mol%, hydrogenation rate = 59 Mol%)
Liquid polybutadiene 3: “BI-3030” manufactured by Nippon Soda Co., Ltd. (unmodified hydrogenated liquid polybutadiene, Mn = 3,030, 1,2-vinyl bond amount (Vi) = 82 mol%, hydrogenation rate = 27 Mol%)
Liquid polybutadiene 4: “B-3000” manufactured by Nippon Soda Co., Ltd. (unmodified liquid polybutadiene, Mn = 3,000, 1,2-vinyl bond amount = 90 mol%, hydrogenation rate = 0 mol%)
[Other ingredients]
Carbon black: “Seast 6” (ISAF) (registered trademark) manufactured by Tokai Carbon Co., Ltd.
・ Zinc: Hakusuitec Co., Ltd. Zinc oxide (2 types)
Anti-aging agent: “NOCRACK 6C (registered trademark)” manufactured by Ouchi Shinsei Chemical Co., Ltd .: “NOCRACK AW (registered trademark)” = 1: 2 (mass ratio)
・ Stearic acid: Nippon Seika Co., Ltd. ・ Sulfur: Hosoi Chemical Co., Ltd. Oil sulfur ・ Vulcanization accelerator: “Noxeller CM (registered trademark)” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Organic peroxide: “Park Mill D-40 (registered trademark)” manufactured by NOF Corporation

  Each rubber composition is subjected to a vulcanization test in an unvulcanized state, and at 170 ° C. for 8 minutes (in the case of a 2 mm-thick test piece) or 13 minutes (in the case of a large test piece) using an electric heating press. Various performances were evaluated using test pieces of a predetermined shape obtained by heat processing. Each evaluation method is as follows.

Ozone resistance test: according to JIS K 6259, using an ozone weather meter (OMS-HN, manufactured by Suga Test Instruments Co., Ltd.), a test piece having a thickness of 2 mm and a width of 10 mm (Dumbell-shaped No. 1, from sheet) Processing) was installed at a distance between grips of 40 mm, tensile strain 20%, ozone concentration: 50 ± 5 pphm (= 0.5 ± 0.05 ppm), temperature 40 ± 2 ° C., test time 96 hours (24, 48, The observation was made in the middle of 72 hours), and the presence and degree of cracking were visually measured based on the following indices.
Number of cracks A: Small number of cracks B: Many cracks C: Number of cracks
Crack size 1: Invisible to the naked eye but can be confirmed with a 10-fold magnifier 2: Observable with the naked eye 3: Deep crack and relatively large (less than 1 mm)
4: Deep and large crack (1 mm or more and less than 3 mm)
5: Those that are likely to cause cracks or cuts of 3 mm or more

The test results are summarized in Table 2.

  In Examples 1 to 3, a superior value was obtained in the ozone resistance test as compared to Comparative Example 1 in which hydrogen-free polybutadiene was added, and the performance was improved in ozone resistance by adding hydrogenated polybutadiene. It was observed.

Claims (3)

  A rubber composition comprising a rubber component, a hydrogenated polybutadiene having a 1,2-vinyl bond amount of 50 mol% or more and a hydrogenation rate of double bonds of 20 mol% or more, and an organic peroxide.   The rubber composition according to claim 1, comprising hydrogenated polybutadiene in an amount of 1 to 25 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 1 or 2, wherein the number average molecular weight of the hydrogenated polybutadiene is in the range of 1000 to 4000.