JP6242762B2 - Rubber composition for cord coating - Google Patents

Description

  The present invention relates to a rubber composition for covering a cord, and more particularly to a rubber composition used for coating a steel cord or an organic fiber cord in a belt, a carcass, a chacher or the like of a pneumatic tire.

  In pneumatic tires, especially radial tires, cords such as steel cords are frequently used as reinforcing materials for belt layers of passenger car tires, belts for large tires such as trucks and buses, carcass and chacher layers, etc. It is important to improve the reinforcing effect and maintain the durability over a long period of time, and the rubber composition covering the cord is required to have excellent adhesiveness with the cord. (For example, Patent Document 1).

  However, the rubber-cord composite in which the cord is coated with the rubber composition may be stored in an unvulcanized state, and in that case, there is a problem in that the adhesiveness between the rubber composition and the cord tends to decrease, The solution is demanded.

  The inventor of the present application has found that calixarene, which has been conventionally used for other purposes, is effective in solving the above problems. Calixarene is an oligomer in which several 2,6 positions of phenol are linked in a cyclic manner via a methylene group. Regarding the use of calixarene, for example, it is disclosed that it is added to a cyanoacrylate adhesive composition as a curing accelerating component (Patent Documents 2 and 3). However, these are different in the technical field from the present invention, and calixarene is added. There is also a difference in the function and effect, and no examples of using calixarene in the rubber composition for cord coating are found.

JP 2010-184992 A Special table 2010-513665 gazette Special table 2009-500517 gazette

  The present invention has been made in view of the above, and a cord in which the adhesiveness between the rubber composition and the cord is improved as compared with the conventional case when the cord is coated with the rubber composition and stored in an unvulcanized state. An object is to provide a rubber composition for coating.

Code rubber composition for coating of the present invention, in order to solve the above problems, 4-tert-butyl-calix [4] arene 15 parts by mass relative to the diene rubber 100 parts by weight, sulfenamide-based vulcanizing One or two or more vulcanization accelerators selected from a sulfur accelerator and a sulfenimide vulcanization accelerator are blended in an amount of 0.3 to 2.0 parts by mass .

  According to the rubber composition for covering a cord of the present invention, the adhesion between the rubber composition and the cord in the rubber-cord composite after being left unvulcanized by containing 4-tert-butylcalix [4] arene. The effect that is improved.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  The diene rubber usable in the present invention is not particularly limited, and examples thereof include various natural rubbers (NR), various polyisoprene rubbers (IR), various styrene butadiene rubbers (SBR), various polybutadiene rubbers (BR) and the like. Any of these may be used, or two or more of these may be used in combination. In addition, as these rubbers, modified diene rubbers into which amino groups, alkoxysilane groups, hydroxy groups, epoxy groups, carboxyl groups, cyano groups, halogens and the like have been introduced can be used as necessary. The diene rubber is preferably composed mainly of natural rubber and / or polyisoprene rubber in consideration of durability when the cord coated with the rubber composition of the present invention is used for a tire, and the total content of both Is preferably 50% by mass or more, and more preferably 80% by mass or more.

  4-tert-butylcalix [4] arene (Tetra-tert-butyl (tetrahydroxy) calix [4] arene, Japanese alias: tetra-tert-butyl (tetrahydroxy) calix [4] arene) used in the present invention is It is a compound having a structure represented by the following formula. This compound can be manufactured by a well-known method, and what is marketed can also be utilized.

  The content of 4-tert-butylcalix [4] arene in the composition of the present invention is 1 to 15 parts by mass with respect to 100 parts by mass of the diene rubber component in order to obtain the desired effect of improving adhesiveness. It is preferable that it is 2 to 12 parts by mass. Since 4-tert-butylcalix [4] arene has high polarity, it has a tendency to move to the interface between the rubber and the cord and inhibit the formation of the CuS layer, but when the content is 15 parts by mass or less, The negative effects are negligible.

  The rubber composition for cord coating of the present invention contains a predetermined amount of the 4-tert-butylcalix [4] arene, thereby allowing the rubber composition of the rubber-cord composite after unvulcanized storage to adhere to the cord. The mechanism by which sex is improved is not clear. However, it is considered that the decrease in adhesion between the rubber composition and the cord after being left unvulcanized is mainly caused by free amines generated from the vulcanization accelerator that is usually blended in the cord rubber composition. The blended 4-tert-butylcalix [4] arene is considered to adsorb this free amine to obtain the above effect.

  The rubber composition according to the present invention may contain a filler such as carbon black or silica as a reinforcing agent.

  The carbon black is not particularly limited, and for example, SAF, ISAF, HAF, FEF grade carbon black can be used, and two or more of them may be used in a blend. Although the compounding quantity of carbon black is not specifically limited, It is preferable that it is 20-100 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 40-80 mass parts.

  Examples of the silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), and surface-treated silica. When silica is blended, the blending amount is not particularly limited, but is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the diene rubber.

  The rubber composition according to the present invention usually contains sulfur as a vulcanizing agent. It is preferable that the compounding quantity of sulfur is 1-10 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 2-8 mass parts. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and oil-treated sulfur, and are not particularly limited.

  In the rubber composition of the present invention, various vulcanization accelerators can be used without any particular limitation. However, when a vulcanization accelerator that generates a free amine such as a sulfenamide vulcanization accelerator is used. The effect of the present invention is remarkably obtained.

  Specific examples of the sulfenamide-based vulcanization accelerator include N-cyclohexyl-2-benzothiazole sulfenamide (CZ, JIS abbreviation: CBS), N-tert-butyl-2-benzothiazole sulfenamide (NS , JIS abbreviation: BBS), N-oxydiethylene-2-benzothiazolesulfenamide (OBS), N, N-diisopropyl-2-benzothiazolesulfenamide (DPBS), N, N-dicyclohexyl-2-benzothiazole Sulfenamide (DZ, JIS abbreviation: DCBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N-ethyl-N-tert-butyl-2-benzothiazolylsulfenamide, N -Methyl-N-tert-butyl-2-benzothiazolylsulfate Amide, Nn-propyl-N-tert-butyl-2-benzothiazolylsulfenamide, N-isopropyl-N-tert-butyl-2-benzothiazolylsulfenamide, Nn-butyl-N- tert-butyl-2-benzothiazolylsulfenamide, N-isobutyl-N-tert-butyl-2-benzothiazolylsulfenamide, N-sec-butyl-N-tert-butyl-2-benzothiazolylsulfuramide Examples include phenamide, N, N-di (2-ethylhexyl) -2-benzothiazolylsulfenamide, N, N-di (2-methylhexyl) -2-benzothiazolylsulfenamide. These may be used alone or in combination of two or more.

  As other vulcanization accelerators, sulfenimide vulcanization accelerators such as Nt-butyl-2-benzothiazole sulfenimide (TBSI) can also be used.

  The content of the vulcanization accelerator is preferably 0.3 to 2.0 parts by mass with respect to 100 parts by mass of the rubber component. If the content exceeds 2.0 parts by mass, scorching may occur during rubber processing or storage, the vulcanization speed may be increased, and the reaction layer on the plating surface may become thick, which may adversely affect adhesion. Occurs.

  In the rubber composition according to the present invention, in addition to the above-described components, various compounding agents generally blended in the cord coating rubber composition can be arbitrarily blended. Examples of such a compounding agent include stearic acid, wax, oil, anti-aging agent, processing aid, and the like, and can be appropriately compounded within a range not violating the object of the present invention. The rubber composition of the present invention can be produced by kneading using a commonly used mixer such as a Banbury mixer or a kneader.

  The material of the cord to be coated with the rubber composition of the present invention is not particularly limited, and can be used for all types of cords such as various steel cords and organic cords. More specifically, the cord is currently generally used for steel cords. It can be suitably used for existing brass-plated steel cords. Examples of organic fiber cords include polyamides, polyesters, polyolefins such as polypropylene and polyethylene, polycarbonates, polyacrylates, styrene resins such as ABS resins, and thermoplastics such as vinyl chloride resins. It is done.

  Moreover, the cord used as a covering object includes a cord used as a reinforcing material such as a belt layer, a carcass layer, and a chacher layer of a pneumatic tire. In that case, according to a conventional method, a cord topping material is manufactured by a topping device such as a steel calender, and when this is cut, a rubber-coated (topping) cord is obtained. Using this as a tire reinforcing member, a pneumatic radial tire or the like can be produced by molding and vulcanizing according to a conventional method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. The blending ratio shown below is based on mass (“parts by mass”, “mass%”, etc.) unless otherwise specified.

[Examples and Comparative Examples]
According to the composition shown in Table 1 below (parts by mass unless otherwise indicated), first, components other than sulfur and vulcanization accelerator were mixed, and then sulfur and vulcanization accelerator were added and mixed to prepare a rubber composition. . The details of each formulation in Table 1 are as follows.

・ Carbon black: Toast Carbon Co., Ltd. Seest 300
・ Zinc flower: Zinc flower No. 3 manufactured by Mitsui Mining & Smelting Co., Ltd. ・ Stearic acid: N-50 manufactured by Nippon Oil & Fats Co., Ltd.
・ Anti-aging agent: Nouchi 6C manufactured by Ouchi Shinsei Chemical Co., Ltd.
Resorcin-alkylphenol-formalin resin: Sumikanol 620 manufactured by Sumitomo Chemical Co., Ltd.
-Hexamethoxymethylmelamine: Mitsui Cytec Co., Ltd. CYRETS 963L
Cobalt stearate: Corebond CS-9.5 manufactured by Taikou Precision Chemical Co., Ltd.
Insoluble sulfur: Shikoku Kasei Kogyo Co., Ltd. Mukuron OT-20
-N, N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS): Nouchisa DZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.
4-tert-butylcalix [4] arene: Tokyo Chemical Industry Co., Ltd. 4-tert-butylcalix [4] arene

  Each rubber composition was passed through a roll to produce a rubber sheet having a thickness of 1.0 mm. Steel cords with brass plating (structure: 3 x 0.20 mm + 6 x 0.35 mm) are arranged on this rubber sheet at 12/25 mm intervals, and the same rubber sheet is placed on top of this to place the steel cord layer 2 A laminated body sandwiched between two rubber sheets was prepared. Two laminates were stacked to prepare a rubber-steel cord unvulcanized composite sample in which two steel cord layers were present.

  The unvulcanized composite sample was left in a constant temperature and humidity chamber of 40 ° C. × 95% RH for 5 days and then vulcanized at 150 ° C. for 30 minutes. The vulcanized sample was subjected to a peel test between two layers of steel cords using an autograph (DCS500 manufactured by Shimadzu Corporation), and the rubber adhesion of the steel cords was visually confirmed to examine the rubber adhesion rate. . The result of Comparative Example 1 was taken as 100, and the larger the value, the better the adhesion after unvulcanized storage. The results are shown in Table 1.

  As can be seen from the results shown in Table 1, when the rubber composition of the example containing a specified amount of 4-tert-butylcalix [4] arene was used, the comparative example 1 of the blank was not specified. Compared with Comparative Examples 2 and 3, the adhesiveness after unvulcanized storage was good.

  The rubber composition for covering a cord of the present invention is useful as a rubber for covering a steel cord or an organic fiber cord which is a reinforcing material for a pneumatic tire. A rubber-cord composite using this rubber composition is used for a passenger car. It can be used for tire belt layers, belts of large tires for trucks and buses, carcass, chacher layers, and the like.

Claims (1)

One or two selected from 1 to 15 parts by mass of 4-tert-butylcalix [4] arene , sulfenamide vulcanization accelerator and sulfenimide vulcanization accelerator with respect to 100 parts by mass of diene rubber A rubber composition for covering a cord, characterized by blending 0.3 to 2.0 parts by mass of a vulcanization accelerator of at least one species .