JP2007182463A - Rubber composition for sidewall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for sidewall, which satisfies both an excellent whitening prevention effect and electrical conductivity while keeping a high content ratio of resources except petroleum. <P>SOLUTION: The rubber composition for sidewall comprises natural rubber, a rubber component containing one or more rubbers selected from the group consisting of natural rubber, epoxidized natural rubber and butadiene rubber, a white filler and conductive carbon black. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition for a sidewall.

  Pneumatic tires have a tendency to generate cracks when subjected to strain during traveling. Particularly, in the side walls of radial tires and the like, this strain is particularly large, and therefore it is necessary to prevent the occurrence of cracks.

  In order to prevent the growth of cracks due to strain, polybutadiene rubber (BR) has been blended together with the rubber composition for sidewalls.

  In order to further improve the effect of preventing the occurrence of cracks, Patent Document 1 discloses a rubber composition for sidewalls that further contains carbon black with respect to a diene synthetic rubber such as BR.

  Thus, in order to suppress the occurrence of side wall cracks, it was necessary to rely heavily on petroleum-derived materials such as synthetic rubber and carbon black.

  However, in recent years, environmental issues have become more important, carbon dioxide emissions regulations have been tightened, and the existing amount of petroleum is limited, so there are limits to the use of raw materials derived from petroleum resources. There is a need for the development of sidewalls that replace some or all of the raw materials derived from petroleum resources with raw materials derived from non-oil resources.

  As for the reinforcing filler contained in the rubber composition for sidewalls, carbon black derived from petroleum resources is replaced with white filler derived from non-petroleum resources, but the white filler is added to the rubber composition. When a large amount of is added, the harmful effect of whitening due to exposure to sunlight occurs.

  Therefore, it is necessary to blend carbon black derived from petroleum resources to some extent, and the content ratio of non-petroleum resources in the rubber composition for sidewalls is still high.

JP 2003-113270 A

  An object of the present invention is to provide a rubber composition for a sidewall which has a large content ratio of non-petroleum resources and exhibits a good whitening prevention effect.

  The present invention relates to a rubber composition for a sidewall containing a rubber component containing at least one rubber selected from the group consisting of natural rubber, epoxidized natural rubber and butadiene rubber, a white filler, and conductive carbon black. .

  The white filler is preferably silica, and the conductive carbon black is preferably acetylene black.

  According to the present invention, the rubber composition for a sidewall containing a specific rubber component, a white filler and conductive carbon black has a high content of non-petroleum resources, and has a good whitening prevention effect and conductivity. It can be compatible.

  The rubber composition for a side wall of the present invention includes a rubber component, a white filler, and conductive carbon black.

  The rubber component includes one or more rubbers selected from the group consisting of natural rubber (NR), epoxidized natural rubber (ENR), and butadiene rubber (BR).

  As NR, those commonly used in the rubber industry such as RSS # 3 and TSR20 may be used.

  The content of NR in the rubber component is preferably 30% by weight or more, and more preferably 40% by weight or more. If the content of NR is less than 30% by weight, the strength of the rubber tends to be inferior, and more is preferable from the environmental viewpoint. The NR content is preferably 70% by weight or less, and more preferably 60% by weight or less. When the NR content exceeds 70% by weight, the crack growth resistance tends to deteriorate.

  As ENR, commercially available ENR may be used, or NR may be epoxidized.

  The method for epoxidizing NR is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method. Examples of the peracid method include a method of reacting NR with an organic peracid such as peracetic acid or performic acid.

  ENR has a large interaction with silica, and an interaction such as intermolecular force or hydrogen bond is exerted between an epoxy group and a silanol group on the silica surface or a surface functional group of carbon black.

  The epoxidation rate of ENR is preferably 5% or more. When the epoxidation rate is less than 5 mol%, the effect of suppressing crack growth resistance tends to decrease due to the compatibility of ENR with NR. Further, the ENR epoxidation rate is preferably 60 mol% or less, and more preferably 50 mol% or less. When the epoxidation rate exceeds 60 mol%, the rubber strength tends to be insufficient.

  The content of ENR in the rubber component is preferably 20 to 40% by weight. When the content of ENR is less than 20% by weight, the effect of suppressing crack growth resistance due to compatibilization with NR does not appear, and the content ratio of non-petroleum resources tends not to increase. On the other hand, if the content of ENR exceeds 40% by weight, the heat deterioration resistance of the rubber tends to be unsustainable.

  As the butadiene rubber (BR), those commonly used in the rubber industry such as cis-1,4-polybutadiene and trans-1,4-polybutadiene can be used.

  The BR content in the rubber component is preferably 20 to 40% by weight. If the BR content is less than 20% by weight, there is a tendency that the inherent inhibitory effect of bending crack growth cannot be exhibited. On the other hand, when the BR content exceeds 40% by weight, the content ratio of non-petroleum resources decreases, which is not preferable from an environmental point of view, and the trauma resistance tends to deteriorate.

  As the rubber component, in addition to NR, ENR and BR, styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, butyl rubber (IIR) within the range not impairing the effects of the present invention. ), Halogenated butyl rubber (X-IIR), and a synthetic rubber such as a halogenated copolymer of isobutylene and p-methylstyrene.

  Examples of the white filler include silica, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide. Among these, silica, calcium carbonate, and titanium oxide are preferable as the white filler from the viewpoint of maintaining the reinforcing property of the rubber, and silica and / or calcium carbonate is more preferable.

When silica is used as the white filler, the BET specific surface area of silica is preferably 155 to 195 m ² / g. When the BET specific surface area is less than 155 m ² / g, there is a tendency that a sufficient rubber reinforcing effect cannot be obtained. On the other hand, if the BET specific surface area exceeds 195 m ² / g, the kneading process increases, and the productivity tends to decrease.

  The content of the white filler is preferably 30 parts by weight or more and more preferably 40 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of the white filler is less than 30 parts by weight, a sufficient reinforcing effect cannot be obtained, and the ratio of resources other than petroleum tends to decrease. Further, the content of the white filler is preferably 55 parts by weight or less, more preferably 50 parts by weight or less with respect to 100 parts by weight of the rubber component. When the content of the white filler exceeds 55 parts by weight, the kneading process is increased, and the productivity tends to be lowered.

  In the present invention, it is preferable to use a silane coupling agent in combination with a white filler. There is no restriction | limiting in particular as a silane coupling agent, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3 -Trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-tri Ethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilyl) Spotted L) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis Those commonly used in the rubber industry such as (2-trimethoxysilylethyl) disulfide and bis (4-trimethoxysilylbutyl) disulfide can be used.

  The content of the silane coupling agent is preferably 3 to 8 parts by weight with respect to 100 parts by weight of the white filler. When the content of the silane coupling agent is less than 3 parts by weight, there is a tendency that a sufficient reinforcing effect cannot be obtained. On the other hand, when the content of the silane coupling agent exceeds 8 parts by weight, a large amount of unreacted silane coupling agent remains, which tends to cause an adverse effect that the silane coupling agent adheres to the kneading / extrusion equipment.

  Conductive carbon black is different in structure in colloidal characteristics from general furnace black. That is, in the present invention, the conductive carbon black means a high structure.

  Specific examples of the conductive carbon black include those showing excellent conductivity such as acetylene black.

  Acetylene, which is a raw material for acetylene black, is not produced by cracking natural gas, synthetic petroleum waste gas, coke oven gas, or petroleum-based oil in terms of using non-oil resources. What was manufactured from the carbide obtained is preferable.

The nitrogen adsorption specific surface area (N ₂ SA) of the conductive carbon black is preferably 60 m ² / g or more, and more preferably 65 m ² / g or more. When N ₂ SA of the conductive carbon black is less than 60 m ² / g, good conductivity tends not to be obtained. Also, N ₂ SA of the conductive carbon black is preferably 80 m ² / g or less, 70m ² / g or less is more preferable. When N ₂ SA of the conductive carbon black exceeds 80 m ² / g, there is a tendency that sufficient dispersion cannot be obtained and good performance cannot be exhibited.

Conductive dibutyl phthalate oil absorption of carbon black (DBP oil absorption) is preferably from 150 cm ^3/100 g or more, 170cm ^3/100 g or more is more preferable. The DBP oil absorption is less than 150 cm ^3/100 g, tends not sufficient conductivity can be obtained. Further, DBP oil absorption of the conductive carbon black is preferably not more than 230 cm ^3/100 g, more preferably at most 220 cm ^3/100 g. When the DBP oil absorption exceeds 230 cm ^3/100 g, similar to the N ₂ SA, there is a tendency that the dispersion is not obtained sufficient carbon black.

  In the present invention, general carbon black such as furnace black can be contained as long as it is 10 parts by weight or less, preferably 5 parts by weight or less based on 100 parts by weight of the rubber component. If the content exceeds 10 parts by weight, the content ratio of non-petroleum resources is low, which is not preferable from an environmental point of view. Further, the whitening prevention effect is small, and the rolling resistance reduction effect tends to be difficult to obtain. .

  In addition to the rubber component, the white filler, and the conductive carbon black, the side wall rubber composition of the present invention includes a compounding agent usually used in a side wall rubber composition, such as oil, fatty acid, wax, An antioxidant, a crosslinking agent such as sulfur, a crosslinking aid, a vulcanization accelerator, and the like can be appropriately blended.

  The rubber composition for a sidewall of the present invention is used for producing a tire and can be made into a tire by a usual method. That is, if necessary, the rubber composition for a sidewall of the present invention blended with the additive is extruded in accordance with the shape of the sidewall of the tire at an unvulcanized stage, and is usually used on a tire molding machine. An unvulcanized tire is formed by molding by the method. The unvulcanized tire is heated and pressurized in a vulcanizer to produce a tire.

  The present invention will be described in detail based on examples, but the present invention is not limited to these examples.

  Various chemicals used in the examples are described below.

(Raw materials made from non-oil resources)
NR: TSR20
Epoxidized natural rubber (ENR): ENR50 (epoxidation rate: 50 mol%) manufactured by Kumpulan Guthrie Berhad (Malaysia)
Acetylene black: Acetylene black (N ₂ SA: 68 m ² / g, DBP oil absorption: 175 ml / 100 g) manufactured by Denki Kagaku Kogyo Co., Ltd.
Silica: Silica: Degussa VN3 (BET specific surface area: 175 m ² / g)
Calcium carbonate: White glazed CC manufactured by Shiraishi Kogyo Co., Ltd.
Silane coupling agent: Si69 made by Degussa
Stearic acid: Paulownia zinc flower manufactured by Nippon Oil & Fats Co., Ltd .: Zinc oxide type 2 powder sulfur manufactured by Mitsui Mining & Smelting Co., Ltd. (containing 5 parts by weight of oil with respect to 100 parts by weight of pure sulfur): Tsurumi Chemical Industry 5% oil-treated powder sulfur manufactured by KK

(Raw materials consisting of petroleum resources)
BR: BR150B manufactured by Ube Industries, Ltd.
Furnace Black: Seast 50 manufactured by Tokai Carbon Co., Ltd. (average particle size: 43 nm, N ₂ SA: 42 m ² / g, DBP oil absorption: 115 ml / 100 g, iodine adsorption: 44 cm ² / g)
Oil: X140 made by Japan Energy
Wax: Wax: Ozoace 0355 manufactured by Nippon Seiwa Co., Ltd.
Anti-aging agent: Anti-aging agent: Antigen 6c manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator BBS: Noxeller NS manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-3
<Production of test tire>
Chemicals other than sulfur and a vulcanization accelerator were blended according to the blending recipe shown in Table 1, and kneaded at 160 ° C. for 3 minutes with a Banbury mixer. Thereafter, sulfur and a vulcanization accelerator were added to the obtained kneaded material according to the formulation shown in Table 1, and kneaded with a biaxial open roll at 100 ° C. for 5 minutes to obtain an unvulcanized rubber composition. . The obtained unvulcanized rubber composition was molded into a sidewall shape, bonded to another tire member, and press vulcanized at 170 ° C. for 15 minutes to obtain a test tire (tire size: 215 / 45R17). Manufactured and used in the following tests.

<Non-oil resource ratio>
The non-petroleum resource ratio (% by weight) of each formulation of Examples and Comparative Examples is shown.

<Rubber strength (Hs) evaluation>
The hardness (Hs) of the test piece cut out from the sidewall of the test tire was measured using a JIS-A hardness meter.

(Actual running test)
The following tests were carried out using test tires run on a drum for 30,000 km under conditions of an internal pressure of 270 kPa, a load of 6.03 kPa and a speed of 80 km / h.

<Electrical conductivity evaluation>
A sidewall portion of a test tire actually run was placed on an iron plate under conditions of an internal pressure of 270 kPa and a load of 6 kN, and a specific resistance value (volume resistivity) between the rim portion and the iron plate was measured at an applied voltage of 1000V.

The obtained fixed resistance value was evaluated in three stages as follows.
A: 10 ⁴ to 10 ⁶ (Ω · cm)
○: 10 ⁶ to 10 ⁷ (Ω · cm)
×: 10 ⁷ to 10 ⁸ (Ω · cm)

<Whitening evaluation>
The test tires actually run were left outdoors for 60 days so as not to be exposed to rainwater. Thereafter, the appearance was visually observed and evaluated in three stages.
◎: No white change ○: Partial white change ×: White discoloration

  The results of the above tests are shown in Table 1.

Claims (2)

A rubber component comprising at least one rubber selected from the group consisting of natural rubber, epoxidized natural rubber and butadiene rubber;
A rubber composition for a sidewall containing a white filler and conductive carbon black. The rubber composition for a sidewall according to claim 1, wherein the white filler is silica and the conductive carbon black is acetylene black.