JP6099429B2 - Side rubber composition for tire and tire - Google Patents

Description

  The present invention relates to a rubber composition or the like for a sidewall portion on a tire side surface.

  Conventionally, an amine-based anti-aging agent and a crack improving agent such as wax have been blended in a rubber composition of a sidewall, particularly among pneumatic tires. However, amine anti-aging agents have the characteristic of turning brown when blooming on the sidewall surface, and the wax is white when blooming on the surface, and in either case, the side appearance is impaired. there were. In the first place, the anti-aging agent is gradually consumed to exhibit its effect, the effect is lowered, and stability with time is lacking.

  In order to solve such problems, Patent Document 1 discloses a two-layer structure in which a low unsaturated rubber and a high unsaturated rubber, an amine anti-aging agent, a wax and the like are partially blended at a reduced content ratio. Having a sidewall portion has been studied. However, as long as amine-based antioxidants and waxes are used, even if they are used in a reduced amount only for the inner layer side rubber composition, those components are immediately put on the outside due to the high diffusion rate. However, the problem of discoloration due to bloom and loss of appearance was unavoidable.

JP 59-14502

  A composition for a side rubber having both scratch resistance and ozone resistance, which does not depend on an anti-aging agent, which does not affect the appearance and can maintain the effect for a long period of time, and a tire using the composition.

The present invention resides in the following (1) to (3).
(1) When the total amount of the rubber component is 100 parts by mass, a low unsaturated rubber selected from the group consisting of at least 8-70 parts by mass of butyl rubber and ethylene propylene rubber, and 10-80 parts by mass of styrene A rubber composition comprising a butadiene copolymer.
(2) Carbon black is contained in 15 to 60 parts by mass with respect to 100 parts by mass of the rubber component, and 1 to 50 parts by mass of silica, alumina, clay, calcium carbonate, magnesium carbonate, titanium oxide, and barium sulfate as inorganic fillers. It is characterized by being.
(3) A tire characterized in that a coating film is formed on the outside of the rubber composition as described in (1) or (2) above.

  ADVANTAGE OF THE INVENTION According to this invention, even if it does not use an anti-aging agent, ozone resistance and abrasion resistance are highly compatible, and there is no influence on external appearance, and a composition for side rubber and a tire using the same are provided. . Therefore, bloom does not occur, appearance is not damaged, structural measures are not required, design is not restricted, and fuel consumption is not deteriorated due to increase in weight of the tire itself Is provided. Further, since a complicated two-layer structure is not required, productivity is also improved.

Hereinafter, embodiments of the present invention will be described in detail.
When the total amount of the rubber component is 100 parts by mass, the low unsaturation rubber selected from the group consisting of at least 8 to 70 parts by mass of butyl rubber and ethylene propylene rubber and 10 to 80 parts by mass of styrene-butadiene copolymer A rubber composition characterized by containing a coalescence, and a tire using the rubber composition, which does not contain an anti-aging agent or is not partly blended, but has excellent ozone resistance The rubber composition for tires also has excellent scratch resistance. In the present invention, the low-unsaturated rubber means a rubber having a proportion of a unit derived from a diene monomer in a monomer unit constituting the non-low-unsaturated rubber being 5 mol% or less. Here, examples of the diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, and the like. On the other hand, examples of non-diene (non-diene) monomers constituting the saturated rubber include ethylene, propylene, and isobutene.

  In the present invention, since the ozone resistance is improved without using an anti-aging agent, it is difficult to cause a reaction with ozone. From a butyl rubber and an ethylene propylene rubber excellent in ozone resistance with a low degree of unsaturation. The low-unsaturated rubber selected from the group consisting of 8 to 70 parts by mass when the total amount of rubber components is 100 parts by mass.

  The content of the low-unsaturation rubber selected from the group consisting of butyl rubber and ethylene propylene rubber is preferably 10 to 60 parts by mass, and more preferably 15 to 40 parts by mass. If the content of the low unsaturated rubber selected from the group consisting of this butyl rubber and ethylene propylene rubber is less than 8 parts by mass, sufficient improvement in ozone resistance cannot be expected, while on the other hand it exceeds 70 parts by mass. In addition, the strength of the rubber itself and the adhesive strength with the surrounding rubber are significantly reduced, which is not preferable in terms of durability.

  In the low unsaturated rubber selected from the group consisting of butyl rubber and ethylene propylene rubber, the copolymer composition ratio of ethylene, propylene, and diene component is 1.5 to 20% by mass (hereinafter,% by mass) of diene component. It is preferable that ethylene accounts for 30 to 70%. If the diene component is less than 1.5%, crosslinking by vulcanization cannot be sufficiently performed, and if it exceeds 20%, the degree of unsaturation becomes too large and ozone resistance is lowered, which is not preferable.

  Examples of the diene component of the low-unsaturated rubber selected from the group consisting of butyl rubber and ethylene propylene rubber include ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene, and the like. Among them, those having ethylidene norbornene as the third component are preferable because they have excellent ozone resistance and a good balance in vulcanization.

  The content of the styrene-butadiene copolymer is preferably 10 to 80 parts by mass, and more preferably 20 to 70 parts by mass. When the content ratio of the styrene-butadiene copolymer is less than 10 parts by mass, the scratch resistance is not sufficiently improved, and when it exceeds 80 parts by mass, the degree of unsaturation becomes too large and the ozone resistance is lowered.

  The rubber composition of the present invention may contain other rubber components in addition to the low-unsaturated rubber and styrene-butadiene copolymer selected from the group consisting of the above-mentioned essential butyl rubber and ethylene propylene rubber, A rubber selected from natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and the like can be appropriately blended.

  The rubber composition of the present invention is usually added to a rubber component including a low unsaturation rubber and a styrene-butadiene copolymer selected from the group consisting of the above-mentioned essential butyl rubber and ethylene propylene rubber. Carbon black, inorganic fillers, softeners, vulcanizing agents, vulcanization aids, vulcanization accelerators, and the like, which are blended in the rubber composition, can be blended in appropriate amounts that are usually blended.

  Carbon black is preferably blended in an amount of 15 to 60 parts by mass with respect to 100 parts by mass of the total amount of the rubber component, and in addition, 1 to 50 parts by mass of other inorganic fillers are preferably blended.

  Examples of inorganic fillers include silica, alumina, clay, talc, aluminum hydroxide, magnesium hydroxide, magnesium oxide, calcium carbonate, magnesium carbonate, titanium oxide, barium sulfate, and at least one selected from these. Can be blended. In particular, when 1 to 20 parts by mass of silica is blended, the scratch resistance is improved, which is preferable. Not only the scratch resistance but also a low exothermic property can be appropriately blended.

  The rubber composition of the present invention can be produced by kneading each of the above components with, for example, a Banbury mixer, a kneader, etc., and the sidewalls of tires for passenger cars, trucks, buses, heavy machinery, motorcycles, etc. It can be suitably used as a part.

  The rubber composition of the present invention does not contain a stain-proofing anti-aging agent, and the appearance is not impaired by coloring with bloom, so it is not subject to design restrictions, so it improves aesthetics by painting. It is also possible to form a functional coating film.

  Examples of the functional coating film include a conductive coating as disclosed in JP-A No. 11-240313, and an antifouling coating film as disclosed in International Publication No. 2002/074451.

  In particular, in the antifouling coating film disclosed in International Publication No. 2002/074451, in the coating film formation, a process with a high risk of ozone generation, such as ultraviolet irradiation or plasma discharge, and ozone It is disclosed that it is performed in an atmosphere. Even under such conditions, the rubber composition of the present invention is applicable to deterioration due to ozone and weather resistance.

  Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these.

  Various rubber compositions having the blending contents shown in Table 1 below, Examples 1 to 3 and Comparative Examples 1 to 3 were kneaded and prepared in a Banbury. About the sample which vulcanized these at 145 degreeC for 30 minutes, the measurement test was done as follows about ozone resistance, abrasion resistance, and discoloration property.

NR: natural rubber SBR: styrene-butadiene copolymer styrene butadiene rubber (JSR 1500 made by JSR)
EPDM: ethylene-propylene-diene copolymer rubber (EP25 manufactured by JSR)
IIR: Butyl rubber (trade name: Bromobutyl 2255, manufactured by Exxon)
1) Tokai Carbon Seast 300
2) Tosoh Silica Nip Seal AQ
3) Vulcanizing aid (manufactured by Nippon Nippon Chemical Co., Ltd. 50S)
4) Vulcanization accelerator (Haxitec Zinc Oxide)
5) Anti-aging agent: N- (1,3-dimethylbutyl) -N′-p-phenylenediamine, manufactured by Ouchi Shinsei Chemical Co., Ltd., Knock Rack 6C
6) Vulcanization accelerator: cyclohexylbenzothiazylsulfenamide, manufactured by Ouchi Shinsei Chemical Co., Ltd., CZ
7) Hosoi Chemical, ordinary sulfur

[Cut resistance]
A tire in which each formulation was applied to the sidewall portion was run for 20,000 km, and the degree of occurrence of the sidewall cut after running was visually evaluated as a numerical value when Example 1 was set to 100 (the higher the value, the better).
[Ozone resistance]
The degree of appearance after leaving the test piece in an ozone weather meter under the conditions of ozone concentration 30 ppm, 40 ° C., 48 hours was evaluated by a numerical value with the case of Example 1 being 100 (the higher the value, the better).
[Discoloration]
Tires with each formulation applied to the side wall were visually evaluated for discoloration before and after being left in the field exposed to direct sunlight for 6 months. The evaluation score was given in five stages.

Example 1 is superior to Comparative Example 1 in both scratch resistance and ozone resistance. In Example 2 in which silica is further added to Example 1, the scratch resistance is further improved.
In Comparative Example 2 in which an anti-aging agent is added to Comparative Example 1, the ozone resistance is improved, but it does not reach that of Examples 1 to 3, and the scratch resistance is not improved.
Further, in Comparative Example 3 in which a small amount of low-unsaturation rubber selected from the group consisting of styrene-butadiene copolymer, butyl rubber, and ethylene propylene rubber was blended, scratch resistance and ozone resistance were compared with Comparative Example 1. Although improvement is seen in both, it does not reach to Examples 1-3, and the improvement of ozone resistance also does not reach Comparative Example 2 using an anti-aging agent. It can be seen that a small amount of low-unsaturation rubber selected from the group consisting of styrene-butadiene copolymer, butyl rubber and ethylene propylene rubber is not effective.
Furthermore, as a matter of course, in Comparative Example 2 using an anti-aging agent, discoloration was observed, and even in Comparative Examples 1 and 3 that were not used, ozone resistance was deteriorated. In contrast to the discoloration, Examples 1 to 3 which do not use an anti-aging agent and also have ozone resistance hardly show discoloration.

  The rubber composition of the present invention is not subject to design restrictions and can be suitably used for tire members, particularly sidewall portions.

Claims (4)

Can to have the total amount of the rubber component is 100 parts by mass, 8-70 parts by weight of diene monomer derived units in the proportion below 5 mol% of butyl-based rubber and 10 to 80 parts by weight of styrene - butadiene copolymer A rubber composition containing each of them and containing no anti-aging agent .   Carbon black is 30 to 50 parts by mass with respect to 100 parts by mass of the total amount of rubber components, and at least one component selected from silica, alumina, clay, calcium carbonate, magnesium carbonate, titanium oxide, and barium sulfate as an inorganic filler is 1 to 1. 50 parts by mass is contained, The rubber composition according to claim 1 characterized by things. The rubber composition according to claim 1 or 2, comprising 8 to 70 parts by mass of an ethylene-propylene rubber containing 1.5 to 20% by mass of the diene component with respect to 100 parts by mass of the total amount of the rubber component. The tire according to any one of claims 1 to 3 , wherein a coating film is formed on the outer side of the rubber composition.