JP2009035674A - Rubber composition for base tread, and tire having base tread produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a base tread having a JIS-A hardness maintained at the optimum level and capable of improving rigidity, tensile strength, adhesiveness, abrasion resistance and driveability in balanced state and to provide a tire having a base tread produced by using the composition. <P>SOLUTION: The rubber composition for a base tread contains 2-5 pts.wt. of sulfur, 0.5-15 pts.wt. of a cashew oil modified phenolic resin and 0.5-10 pts.wt. of a partial condensate of hexamethylol pentamethyl ether based on 100 pts.wt. of rubber component and has a JIS-A hardness of 75-95 at 25°C after vulcanization. The invention further provides a tire having a base tread produced by using the composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for a base tread and a tire having a base tread using the same.

  Various means have been taken up in order to reduce the rolling resistance of the tire or improve the steering stability of the vehicle. As one of the means, it is known that the tire tread has a double structure (base tread and cap tread).

  In recent years, in addition to the remarkable enhancement of equipment and performance of automobiles, the road network has been expanded and developed, so it has become increasingly frequent at high speeds, especially at high speeds, which always improves stable handling stability and ride comfort. A tire having such a base tread is required, and sufficient rigidity and hardness are required for the base tread which has a great influence on the tire.

  In order to obtain such a base tread, a large amount of carbon black is added to the rubber composition for the base tread to improve the rigidity, but the rolling resistance is reduced, the steering stability and the ride comfort are sufficient. Tires that were compatible with each other could not be obtained. In addition, a large amount of sulfur is added to improve the rigidity and low heat buildup in a well-balanced manner, but the base tread was not sufficiently crack-resistant, so if the base tread is exposed after running, There was a problem that chipping of the tread and excessive wear occurred.

  Patent Document 1 discloses a pneumatic tire having a base tread blended with collagen particles. However, the driving stability, riding comfort, and reduction of rolling resistance when the car is traveling at high speeds are not fully satisfied.

  Thus, there is a need for a pneumatic tire that has a base tread with sufficient rigidity, hardness, and crack resistance, and that satisfies both driving stability, riding comfort, and reduced rolling resistance, especially during high-speed driving. Has been.

JP 2004-269684 A

  The present invention provides a rubber composition for a base tread capable of maintaining a proper JIS-A hardness and improving the rigidity, tensile strength, adhesiveness, abrasion resistance and steering stability in a balanced manner, and a base tread using the same. It aims at providing the tire which has.

  In the present invention, 2 to 5 parts by weight of sulfur, 0.5 to 15 parts by weight of cashew oil-modified phenol resin, and 0.5 to 5 parts of a partial condensate of hexamethylol pentamethyl ether are added to 100 parts by weight of the rubber component. The present invention relates to a rubber composition for a base tread containing 10 parts by weight and having a JIS-A hardness of 75 to 95 after vulcanization at 25 ° C.

  The present invention also relates to a tire having a base tread using the rubber composition for base tread.

  According to the present invention, the rubber component, sulfur, cashew oil-modified phenolic resin and hexamethylol pentamethyl ether partially condensate are contained in a specific amount, and by adjusting the JIS-A hardness appropriately, rigidity, tensile strength An object of the present invention is to provide a rubber composition for a base tread capable of improving the adhesion, wear resistance and steering stability in a well-balanced manner and a tire having a base tread using the same.

  The rubber composition for base treads of the present invention contains a rubber component, sulfur, cashew oil-modified phenol resin, and a partial condensate of hexamethylol pentamethyl ether.

  Examples of the rubber component include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), ethylene propylene diene rubber ( EPDM), styrene isoprene butadiene rubber (SIBR), and the like. Although not particularly limited, NR, IR, and BR are preferable because they are relatively inexpensive and have high reinforcing properties.

  Sulfur may be a common one used in the rubber industry such as powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.

  The compounding amount of sulfur is 2 parts by weight or more, preferably 2.5 parts by weight or more with respect to 100 parts by weight of the rubber component. When the amount of sulfur is less than 2 parts by weight, sufficient JIS-A hardness cannot be obtained, not only inferior in rigidity, wear resistance and steering stability, but also in the gradient of the rubber composition for breaker topping and sulfur concentration. In addition, since sulfur in the breaker topping is reduced, the adhesion between the breaker topping rubber composition and the breaker cord is deteriorated. Moreover, the compounding quantity of sulfur is 5 weight part or less with respect to 100 weight part of rubber components, Preferably it is 4 weight part or less. When the amount of sulfur exceeds 5 parts by weight, not only the tensile strength is lowered, but also it becomes too hard, so that the adhesion between the rubber composition for breaker topping and the breaker cord is deteriorated.

  The cashew oil-modified phenolic resin used in the present invention is obtained by modifying a phenolic resin obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, furfural or the like with an acid or alkali catalyst using cashew oil. Specifically, the formula (1):

（式中ｎは１〜９の整数である）
で示されるフェノール樹脂である。

(Where n is an integer from 1 to 9)
It is a phenol resin shown by.

  In the present invention, sufficiently high hardness can be obtained by modifying with cashew oil instead of tall oil or linseed oil.

  Note that resorcin resins and cresol resins have a problem that their hardness is not sufficiently high even if they are modified with cashew oil.

  The method for modifying the phenol resin with cashew oil is not particularly limited, and can be modified by a conventional method.

  The compounding amount of the cashew oil-modified phenol resin is 0.5 parts by weight or more, preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component. When the compounding amount of the cashew oil-modified phenol resin is less than 0.5 parts by weight, the hardness is not sufficiently increased. The compounding amount of the cashew oil-modified phenol resin is 15 parts by weight or less, preferably 14 parts by weight or less with respect to 100 parts by weight of the rubber component. When the compounding amount of the cashew oil-modified phenol resin exceeds 15 parts by weight, the JIS-A hardness becomes too high, the tensile strength is lowered, and the durability is lowered when used as a tire. Adhesiveness between the topping rubber composition and the breaker cord deteriorates.

  The partial condensate of hexamethylol melamine pentamethyl ether (HMMPME) used in the present invention is the formula (2):

で表されるものをいう。

The one represented by

  In formula (2), n is usually an integer of 1 to 3.

  The amount of the partial condensate of HMMPME is 0.5 parts by weight or more, preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component. If the blending amount of the partial condensate of HMMPME is less than 0.5 parts by weight, the hardness is not sufficiently increased. Moreover, the compounding quantity of the partial condensate of HMMPME is 10 weight part or less with respect to 100 weight part of rubber components, Preferably it is 9 weight part or less. When the amount of the partial condensate of HMMPME exceeds 10 parts by weight, the JIS-A hardness becomes too high, the tensile strength is lowered, and the durability is lowered when used as a tire. Adhesiveness between the topping rubber composition and the breaker cord deteriorates.

  In the present invention, as described above, not only contains a specific amount of the rubber component, sulfur, cashew oil-modified phenol resin and HMMPME partial condensate, but also maintains the durability by properly adjusting the JIS-A hardness. In addition, wear resistance and steering stability can be improved.

  The rubber composition for base tread of the present invention has a JIS-A hardness after vulcanization at 25 ° C. of 75 or more, preferably 76 or more. When the JIS-A hardness after vulcanization at 25 ° C. is less than 75, the rigidity is small, and the effect of improving wear resistance and steering stability is small. The JIS-A hardness after vulcanization at 25 ° C. is 95 or less, preferably 94 or less. When the JIS-A hardness after vulcanization at 25 ° C. exceeds 95, not only the tensile strength is lowered, but also when used as a tire, it tends to break down. Therefore, a rubber composition for breaker topping and a breaker cord The adhesiveness of deteriorates.

  The method for adjusting the JIS-A hardness of the rubber composition for a base tread of the present invention is not particularly limited, but the sulfur content, the cashew oil-modified phenol resin content, and the partial condensation of HMMPME. The method of adjusting the compounding quantity of a thing, the compounding quantity of carbon black, the compounding quantity of oil etc. is mention | raise | lifted. Specifically, a method of blending 40 parts by weight or more of carbon black, 2 parts by weight or more of sulfur, 0.5 parts by weight or more of cashew oil-modified phenolic resin, and 0.5 parts by weight or more of a partial condensate of HMMPME. can give.

  The rubber composition for base treads of the present invention preferably further contains carbon black.

  There is no restriction | limiting in particular as carbon black, SAF, ISAF, HAF, FEF etc. can be used.

  The compounding amount of carbon black is preferably 30 to 100 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of carbon black is within the above range, there is an advantage that durability is good. The blending amount of carbon black is further preferably 40 to 90 parts by weight.

  The rubber composition for a base tread according to the present invention includes, in addition to the rubber component, sulfur, cashew oil-modified phenol resin, partial condensate of HMMPME and carbon black, a compounding agent conventionally used in the rubber industry, for example, anti-aging Agents, waxes, aroma oils, stearic acid, zinc oxide, vulcanization accelerators and the like can be appropriately blended as necessary.

  The rubber composition for base tread of the present invention is produced by a general method. That is, the rubber component, sulfur, cashew oil-modified phenol resin, partial condensate of hexamethylol pentamethyl ether, and other compounding agents as needed are kneaded with a Banbury mixer, kneader, open roll, etc., and then vulcanized. By this, the rubber composition for base treads of this invention can be manufactured.

  The rubber composition for a base tread of the present invention is used as a base tread among tire members because of good steering stability.

  Using the rubber composition for a base tread of the present invention, a tire having a base tread can be produced by a usual method. That is, if necessary, the rubber composition for base treads of the present invention blended with the above-mentioned compounding agent is extruded into a base tread shape at an unvulcanized stage, and usually together with other tire members on a tire molding machine. The unvulcanized tire is formed by laminating by the above method. This unvulcanized tire is heated and pressurized in a vulcanizer to obtain the tire of the present invention.

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

老化防止剤：精工化学（株）製のオゾノン６Ｃ（Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン）
ワックス：大内新興化学工業（株）製のサンノックワックス
アロマオイル：出光興産（株）製のダイアナプロセスＡＨ４０
ステアリン酸：日本油脂（株）製のステアリン酸「桐」
酸化亜鉛：東邦亜鉛（株）製の銀嶺Ｒ
硫黄：鶴見化学工業（株）製の硫黄
加硫促進剤：大内新興化学工業（株）製のノクセラーＮＳ（Ｎ−ｔｅｒｔ−ブチル−２−ベンゾチアゾリルスルフェンアミド）
ヘキサメチロールペンタメチルエーテル（ＨＭＭＰＭＥ）の部分縮合物：住友化学（株）製のスミカノール５０７（メチレン基を有する物質約５０％とシリカおよびオイルの混合物）（式（２）中、ｎ：３）

ヘキサメチレンテトラミン（ＨＭＴ）：大内新興化学工業（株）製のノクセラーＨ Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Natural rubber (NR): RSS # 3
Carbon black: Diamond Black I (N220) manufactured by Mitsubishi Chemical Corporation
Cashew oil-modified phenolic resin: Sumitrite resin PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (in formula (1), n: 6)

Anti-aging agent: Ozonon 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Seiko Chemical Co., Ltd.
Wax: Sunnock wax aroma oil manufactured by Ouchi Shinsei Chemical Industry Co., Ltd .: Diana Process AH40 manufactured by Idemitsu Kosan Co., Ltd.
Stearic acid: Stearic acid “paulownia” manufactured by NOF Corporation
Zinc oxide: Silver candy R made by Toho Zinc Co., Ltd.
Sulfur: Sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Partial condensate of hexamethylol pentamethyl ether (HMMPME): Sumikanol 507 (mixture of about 50% of a substance having a methylene group and silica and oil) manufactured by Sumitomo Chemical Co. (in formula (2), n: 3)

Hexamethylenetetramine (HMT): Noxeller H manufactured by Ouchi Shinsei Chemical Co., Ltd.

Example 1 and Comparative Examples 1-5
In accordance with the formulation shown in Table 1, using a Banbury mixer, sulfur, a vulcanization accelerator, a partial condensate of HMMPME and various chemicals other than HMT are kneaded for 5 minutes at 150 ° C. to obtain a kneaded product. It was. Next, sulfur, a vulcanization accelerator, a partial condensate of HMMPME, and HMT are added to the obtained kneaded product, and kneaded for 5 minutes under a condition of 80 ° C. using a biaxial open roll. A composition was obtained. Furthermore, the obtained unvulcanized rubber composition was press vulcanized for 35 minutes under the conditions of 150 ° C. and 25 kgf to obtain vulcanized rubber compositions of Example 1 and Comparative Examples 1-5.

(JIS-A hardness)
According to JIS K 6253 “Method for testing hardness of vulcanized rubber and thermoplastic rubber”, JIS-A hardness of a rubber test piece after vulcanization at 25 ° C. was measured with a spring type A.

(Viscoelasticity test)
A 4 mm × 30 mm × 1.5 mm strip sample was prepared from the vulcanized rubber composition, and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., frequency 10 Hz, dynamic strain ± 2%, initial strain 10 The complex elastic modulus E * (MPa) at 70 ° C. was measured under the condition of%. The larger E *, the higher the rigidity and the better.

(Tensile test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, a tensile test was conducted using a No. 3 dumbbell-shaped test piece made of the vulcanized rubber composition, and the breaking strength of the test piece was measured. TB (MPa) was measured. It shows that it is excellent in tensile strength, so that TB is large, and the thing of 10 Mpa or less cannot be used as a tire.

(Adhesion test)
The unvulcanized rubber composition is molded into a base tread shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and press vulcanized for 35 minutes at 150 ° C. and 25 kgf. Thus, test tires (size: 195 / 65R15) of Example 1 and Comparative Examples 1 to 5 were manufactured.

A test piece of a predetermined size was cut out from the breaker portion (including the cord) of the manufactured tire, and subjected to wet heat deterioration treatment under conditions of a temperature of 80 ° C. and a humidity of 95% to prepare a test piece for a peel test. An adhesion test was performed using this test piece, and rubber coverage (%) and peel resistance (N / mm) were measured. Note that the rubber coverage indicates the ratio of the rubber on the peeled surface when the steel cord and the rubber are peeled (100%: the entire surface is covered). Further, the peel resistance was measured by Instron, the peel resistance index of the conventional example was set to 100, and the peel resistance of each formulation was indicated by an index by the following calculation formula. The larger the rubber coverage and the peel resistance index, the more difficult it is to peel off, indicating that the adhesive strength that was previously reduced by the generation of ammonia is maintained and is excellent, indicating that the rubber coverage is 70% or less and the peel resistance. Those with an index of 70 or less indicate that the tire cannot be used.
(Peeling resistance index) = (Peeling resistance of each formulation) ÷ (Peeling resistance of Comparative Example 1) × 100

(Abrasion resistance)
The manufactured test tire was mounted on a domestic FF vehicle and allowed to travel 8000 km, and the groove depth of the tread portion of the tire was measured. Further, from the measured groove depth, the travel distance required to reduce the groove depth of the tread part by 1 mm is calculated, and the abrasion resistance index of Comparative Example 1 is set to 100. The mileage of was displayed as an index. In addition, it shows that it is excellent in abrasion resistance, so that an abrasion-resistant index | exponent is large, and it shows that an effect is small at 110 or less.
(Abrasion resistance index) = (travel distance of each formulation) ÷ (travel distance of Comparative Example 1) × 100

(Maneuvering stability)
The manufactured test tire was mounted on a car and the vehicle was run, and steering stability was evaluated by a feeling test of steering wheel response, rigidity, and grip by a test driver. The evaluation was performed with a maximum score of 10 (higher is better), and the average value of the test driver scores was calculated. And the steering stability index of the comparative example 1 was set to 100, and the average value of the score of each compounding was displayed as an index by the following calculation formula. In addition, it shows that it is excellent in steering stability, so that a steering stability index | exponent is large.
(Maneuvering stability index) = (Average score of each formulation)
÷ (average score of Comparative Example 1) × 100

  The evaluation results are shown in Table 1.

Claims (2)

For 100 parts by weight of rubber component,
2 to 5 parts by weight of sulfur,
0.5 to 15 parts by weight of cashew oil-modified phenol resin, and 0.5 to 10 parts by weight of a partial condensate of hexamethylol pentamethyl ether,
A rubber composition for a base tread having a JIS-A hardness of 75 to 95 after vulcanization at 25 ° C. A tire having a base tread using the rubber composition for a base tread according to claim 1.