JP2006241346A - Cement for tire tread splice - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve tack property, adhesiveness, and workability of a cement for a tire tread splice. <P>SOLUTION: This cement for a tire tread splice comprises 70-100 parts by weight styrene/butadiene rubber, 0-30 parts by weight natural rubber, and 3-15 parts by weight liquid styrene/butadiene copolymer resin, and the liquid styrene/butadiene copolymer resin has a number average molecular weight of 2,000-9,000, and a vinyl quantity of 20-80%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tire tread splice cement. More specifically, the present invention contains little or substantially no volatile organic compounds harmful to the environment such as toluene, and is good regardless of the type and temperature of the rubber component constituting the tread. The present invention relates to a tire tread splice cement that exhibits excellent tack and provides excellent molding workability.

  Conventionally, in the manufacture of tires, the tread portion is formed by extruding an unvulcanized rubber composition from an extruder to obtain a strip-shaped material, then cutting the strip-shaped material into a certain length, and then on the molding drum. It has been practiced to wrap in a ring and join both ends together and vulcanize molding. As this joining method, rubber cement has been applied to the splice surfaces of both ends and then bonded together. . Many of the conventional cements for splicing tire treads use volatile organic solvents such as rubber volatile oil and toluene in order to achieve high tackiness. Especially when the splice part of a fuel-efficient tread is joined using such cement in winter when the temperature is low, the fuel-efficient tread itself generally reduces the amount of plasticizer to improve fuel efficiency. Therefore, such a cement is required to have a higher tackiness and have a sufficient pot life, i.e., the cement itself over time. Even if the solvent contained in the solvent is volatilized, it is required to maintain a sufficiently high tackiness. Conventionally, in the case of a fuel-efficient tread, there has been a problem that failure due to poor adhesion generally called an open splice occurs due to insufficient tack. In order to improve the tackiness of splicing cement, some volatile organic compounds such as rubber volatile oil and toluene are used as solvents, but they are harmful volatile organic due to occupational safety and health and environmental problems. There is a need to reduce the amount of compound used as much as possible. In particular, volatile organic compounds such as toluene that have been used as rubber solvents due to their high solvency are required to reduce their usage as much as possible due to various regulations regarding their discharge to the environment. In order to improve tackiness, there is a method of blending tackifiers such as Choledin (trademark) (manufactured by BASF) which is a condensate of tert-butylphenol and acetylene, but tackiness is not sufficiently improved . As a cement for joining tire tread splice parts, for example, a solventless cement containing a liquid elastomer (Patent Document 1), an adhesive composition containing liquid rubber, a curing agent and an inorganic filler as main components (Patent Document) 2) and a rubber cement having a tack value of at least 400 g / cm (Patent Document 3) has been proposed, but it is still less harmful to the environment and depends on the type and temperature of the rubber component constituting the tread. Therefore, there is a need for a tire tread splice cement having high tackiness, stable tackiness over time and adhesiveness, and excellent molding workability.

JP 2000-191840 A JP-A-56-90868 Japanese Patent Laid-Open No. 4-119830

  The present invention has high tackiness and stable tackiness and adhesiveness over time without depending on the type and temperature of the rubber component constituting the tread, has excellent molding workability, and is harmful to the environment. It aims at providing the cement for tire tread splices which has the outstanding characteristic that there is little.

  In the present invention, in a cement for a tread splice mainly composed of a styrene-butadiene copolymer rubber (SBR) and a natural rubber (NR) if present, a liquid styrene-butadiene copolymer is used as a part of the solvent for the rubber component. When a polymer resin is used, it has a high tackiness and a long time with respect to an unvulcanized tire tread due to the high dissolving power of the liquid styrene-butadiene copolymer resin with respect to the main component styrene-butadiene copolymer rubber. It has been found that it has stable tackiness and adhesiveness, is excellent in molding workability, and can reduce the use of volatile organic compounds harmful to the environment such as toluene. The high tackiness provided by the tread splice cement of the present invention and the stable tackiness and adhesiveness over time are the types of rubber components constituting the tread and the splice parts using the tread splice cement of the present invention. It does not depend on the temperature when bonding.

  According to the present invention, a tire tread splice comprising 70 to 100 parts by weight of styrene-butadiene rubber, 0 to 30 parts by weight of natural rubber, and 3 to 15 parts by weight of liquid styrene-butadiene copolymer resin. Cement for use is provided.

  The tire tread cement of the present invention includes a liquid styrene-butadiene copolymer resin that exhibits a dissolving power with respect to the main component styrene-butadiene copolymer rubber, and thus depends on the type and temperature of the rubber component constituting the tread. In the past, it has high tackiness and stable tackiness and adhesiveness over time, has excellent molding workability, and can reduce the use of organic substances harmful to the environment such as toluene. It offers excellent benefits.

  The styrene-butadiene copolymer rubber used as a main agent in the tire tread splice cement of the present invention preferably has a bound styrene content of 25 to 35% by weight. The styrene-butadiene copolymer rubber preferably has a vinyl content (1,2-bond amount) of 15 to 25%. The bonding mode of the polymer main chain of the styrene-butadiene copolymer rubber may be random or block. In addition to the styrene-butadiene copolymer rubber, natural rubber may be blended as a main agent. When blending natural rubber, the total amount of styrene-butadiene copolymer rubber and natural rubber is 100 parts by weight, and styrene-butadiene copolymer rubber is blended in an amount of 70 parts by weight or more, and natural rubber is 30 parts by weight. It mixes with the quantity below the part. If the blending amount of the natural rubber exceeds 30 parts by weight, the compatibility with the styrene-butadiene copolymer rubber is lost, which is not preferable.

  In the tire tread splice cement of the present invention, the liquid styrene-butadiene copolymer resin blended in the main agent has a number average molecular weight of 2000 to 9000, preferably 4500 to 8600, and 20 to 80%, preferably 30 to 70. % Vinyl content. This liquid styrene-butadiene copolymer resin provides high solvency for the styrene-butadiene copolymer rubber blended as a main agent, high tackiness, and stable tackiness and adhesiveness over time. This makes it possible to reduce volatile organic compounds such as toluene that have been conventionally used. The amount of the liquid styrene-butadiene copolymer resin is 3 to 15 parts by weight per 100 parts by weight of the total amount of styrene-butadiene copolymer rubber and natural rubber. When the blending amount of the liquid styrene-butadiene copolymer resin is less than 3 parts by weight per 100 parts by weight of the total amount of the styrene-butadiene copolymer rubber and the natural rubber, significant tackiness cannot be achieved. If it exceeds 15 parts by weight, the ratio of the liquid styrene-butadiene copolymer resin to the main agent is too high, and the adhesive strength is lowered.

  The cement for tire tread splice according to the present invention includes a chain or cyclic aliphatic saturated hydrocarbon having 5 to 9 carbon atoms as a solvent for the rubber component, a petroleum fraction having a boiling point range of 80 ° C to 160 ° C, and an aroma. A solvent selected from petroleum fractions having a group hydrocarbon content of less than 1% by weight, alcohols having a boiling point in the range of 80 ° C. to 160 ° C., and mixtures thereof can be included. Examples of the linear or cyclic aliphatic saturated hydrocarbon having 5 to 9 carbon atoms include, for example, cyclohexane and hexane. As an example of a petroleum fraction having a boiling point range of 80 ° C. to 160 ° C. and an aromatic hydrocarbon content of less than 1% by weight, volatile rubber oil (or “industrial gasoline 2”) in JIS K2201 And petroleum fractions having an aromatic hydrocarbon content of less than 1% by weight. The volatile rubber oil specified in JIS K2201 has a distillation property such that the initial distillation temperature is 80 ° C. or higher, the 50% distillation temperature is 120 ° C. or lower, and the end point is 160 ° C. or lower. Rubber volatile oil is generally an aggregate of aliphatic hydrocarbons (paraffinic hydrocarbons), alicyclic hydrocarbons (naphthene hydrocarbons), and aromatic hydrocarbons, such as benzene, toluene, Known to contain a large amount of harmful volatile aromatic organic compounds such as xylene, or to reduce the content of these harmful volatile aromatic organic compounds while maintaining the ability to dissolve in rubber. In the present invention, by using the liquid styrene-butadiene copolymer resin as described above, the content of harmful volatile aromatic organic compounds such as toluene and xylene conventionally used is less than 1% by weight. Or a rubber volatile oil substantially free of such aromatic organic compounds can be used. When using a rubber volatile oil having a harmful volatile aromatic organic compound content of less than 1% by weight as a solvent, such as toluene and xylene, the safety and working environment are greatly improved. , Legal systems that require management of chemical substances that have a large impact on the environment (for example, chemicals that are subject to notification when the substances subject to management are contained in raw materials or materials by 1% by weight or more. Under the substance discharge and transfer notification system (PRTR), complicated work associated with management and notification is reduced. Examples of alcohols having a boiling point in the range of 80 ° C. to 160 ° C. that can be used in the present invention include alcohols having a boiling point in the range of 80 ° C. to 160 ° C., for example, propyl alcohol (boiling point 97 .4 ° C), n-butyl alcohol (boiling point 117.7 ° C), pentyl alcohol (boiling point 137 ° C (740 mmHg)), hexyl alcohol (boiling point 155 ° C), isopropyl alcohol (boiling point 82.4 ° C), isobutyl alcohol (boiling point) 107 ° C), sec-butyl alcohol (boiling point 99.5 ° C), tert-butyl alcohol (boiling point 82.41 ° C), isopentyl alcohol (boiling point 132.0 ° C), 2-methyl-1-butanol (boiling point 128- 129 ° C), tert-pentyl alcohol (boiling point 102 ° C), cyclopentanol (boiling point 140.85 ° C) Allyl alcohol (boiling point 96.9 ° C.), crotyl alcohol ((E) isomer: boiling point 121.5 ° C., (Z) isomer: boiling point 123.6 ° C.), 3-buten-2-ol (boiling point 96-97 ° C.) ) And the like.

  In the present invention, by blending the liquid styrene-butadiene copolymer resin as described above, due to the high dissolving power of the liquid styrene-butadiene copolymer resin with respect to the styrene-butadiene copolymer rubber, the styrene-butadiene copolymer is used. High tackiness and adhesiveness can be obtained without using harmful volatile aromatic organic compounds such as toluene and xylene, which have been conventionally used as solvents for polymer rubber, etc., or by reducing their amounts considerably. Thus, a tire tread splice cement excellent in molding workability is provided.

  In addition to the above chain or cyclic aliphatic saturated hydrocarbon as a solvent, isopropyl alcohol should be included to adjust the volatility of the final tire tread splice cement to ensure the desired working time. Can do.

  The amount of the solvent consisting of a linear or cyclic aliphatic saturated hydrocarbon and isopropyl alcohol, if present, is preferably based on 100 parts by weight of the total amount of styrene-butadiene copolymer rubber and natural rubber. 550 to 650 parts by weight.

The cement for tire tread splice of the present invention is preferably applied to one of the tread splice surfaces at a rate of 10 to 75 g / m ² , and then the other splice surface is bonded to this to press pressure during vulcanization. Adhere closely. The cement of the present invention can be applied to the splice surface by any appropriate application method such as brushing or roller coating. According to the cement of the present invention, in addition to obtaining high tackiness and stable tackiness and adhesiveness over time as described above, there is little change in tack over time when applied to the splice surface. As a result, the workability of attaching the tread splice portion is improved.

  Various additives such as carbon black, tackifiers, zinc oxide, sulfur, vulcanization accelerators, and the like can be added to the tire tread splice cement of the present invention as long as the object of the present invention is not impaired. .

  The present invention will be described in more detail with reference to the following examples and comparative examples, but it goes without saying that the technical scope of the present invention is not limited by these examples.

Preparation of tire tread splice cement First, in the composition shown in (I) of Table 1 below, the components other than the vulcanization accelerator and sulfur were kneaded for 3 minutes in a 1.5 liter hermetic mixer, and 130 ± 5 When it reached ℃, it was discharged to obtain a master batch. The masterbatch was kneaded with a vulcanization accelerator and sulfur with an open roll, and then made into a sheet having a thickness of 1 mm. Next, after cutting the obtained sheet, it was immersed in a solvent containing the component shown in (II) of Table 1 for 12 hours, and then mixed for about 4 hours with a stirrer for each example and comparative example. A tire tread splice cement was obtained. The performance of the cements of the obtained examples and comparative examples was determined by the following test methods.

Test Methods The performances of the cements obtained in the following examples and comparative examples were determined by the following test methods.
(1) Solubility After immersing the plate glass in the cement of each example or comparative example and pulling it up, the surface of the plate glass is visually observed to see if there is a lump of the main agent (rubber component). It was evaluated that the solubility was good, and when a lump was present, the solubility was evaluated as insufficient.

(2) Volatility 30 mg of the cements of the examples and comparative examples were hung on a filter paper placed on a precision balance in an environment with an air temperature of 25 ° C. and a relative humidity of 50%. The time until the solvent was volatilized and the mass of the filter paper became constant was measured. When the solvent was volatilized within 30 seconds and the mass of the filter paper reached a certain amount, it was evaluated that the volatility was good, and when it took 30 seconds or more, it was evaluated that the volatility was insufficient.

(3) Tack For two types of rubbers with the composition shown in Table 2 below, a rubber sheet is attached to the attachment position of the measuring machine, and is pressed onto the rubber coated with the cement of each example and comparative example, and peeled off vertically. The force was measured. The measurement was performed using a PICMA II type tack tester manufactured by Toyo Seiki Seisakusho Co., Ltd., with a pressure bonding speed of 500 mm / min, a pressure bonding load of 4.9 N, a pressure bonding time of 0.5 seconds, and a peeling speed of 1250 mm / min. The measured value was expressed in units of 1 / 1000N.

(4) Adhesive properties SBR-based tread rubber sheets having the composition shown in Table 2 below, to which the cements of Examples and Comparative Examples were applied, were bonded together, vulcanized at 160 ° C. for 20 minutes, and cut into strips having a width of 25 mm. Thereafter, as shown in Table 2 below, each test piece was left at 5 ° C. or 25 ° C. for 4 hours or 12 hours and then subjected to a peel test at 5 ° C. or 25 ° C. The peeling speed was 50 mm / min. The test results were evaluated as “insufficient” when the interface peeling occurred, “medium” when both the interface peeling and rubber material destruction occurred, and “good” when the rubber material destruction occurred.

Examples 1-2 and Comparative Examples 1-4
The results of the above test are shown in Table 3 below.

  Each Example and Comparative Example showed good results in tests on solubility and volatility, but as can be seen from Table 3 below, in the tack and adhesion tests, the examples of the present invention were In addition to maintaining a high tack value that is desirable as a tire tread splice cement than the comparative example, it has good adhesion and good workability.

  From Table 3 above, cement containing only styrene-butadiene copolymer rubber or cement containing styrene-butadiene copolymer rubber and natural rubber as the main ingredients, with the addition of liquid styrene-butadiene copolymer resin While maintaining good solubility, volatility and adhesiveness comparable to when toluene is used as a solvent, it has high tackiness regardless of the type and temperature of the rubber component constituting the tread, and high It can be seen that it provides molding workability.

Claims (4)

  A tire tread splice cement comprising 70 to 100 parts by weight of styrene-butadiene rubber, 0 to 30 parts by weight of natural rubber, and 3 to 15 parts by weight of liquid styrene-butadiene copolymer resin.   The cement for tire tread splice according to claim 1, wherein the liquid styrene-butadiene copolymer resin has a number average molecular weight of 2000 to 9000 and a vinyl content of 20 to 80%.   The tire tread splice cement is a chain or cyclic aliphatic saturated hydrocarbon having 5 to 9 carbon atoms, a petroleum fraction having a boiling point range of 80 ° C to 160 ° C, and an aromatic hydrocarbon content of 1 The cement for tire tread splice according to claim 1 or 2, comprising a petroleum fraction less than wt%, an alcohol having a boiling point in the range of 80 to 160 ° C, and a solvent selected from a mixture thereof.   The tire tread splice cement according to claim 3, wherein the solvent contains isopropyl alcohol.