JP6616993B2 - Rubber composition for inner liner - Google Patents

Description

  The present invention relates to a rubber composition for an inner liner.

  An inner liner is provided on the inner side surface of the pneumatic tire as an air permeation suppression layer in order to keep the tire air pressure constant. The inner liner is required to further improve the durability performance.

  Patent Documents 1 to 3 disclose that a branched compound is added to the inner liner and the inner tube, but the purpose is to impart good hysteresis characteristics and sealing characteristics. There is no description about improvement of durability performance. Patent Document 4 describes a branched brominated butyl rubber, but it is not a mixture of a branched compound with brominated butyl rubber, and improves viscosity, relaxation behavior, green strength, and the like. This is intended and there is no description about improvement of durability performance.

Special table 2012-533670 gazette Special table 2012-52891 gazette Special table 2012-509370 gazette Special table 2010-53386

  An object of this invention is to provide the rubber composition for inner liners which can improve durability performance in view of the above point.

The rubber composition for an inner liner according to the present invention contains a brominated butyl rubber and a highly branched polymer having a carbonyl group in a branched chain, and the number of hydroxyl groups at the terminal of the highly branched polymer is 15 to 64. .

  The highly branched polymer may have a weight average molecular weight of 500 to 15000.

  The blending amount of the hyperbranched polymer can be 0.2 to 20 parts by mass with respect to 100 parts by mass of the brominated butyl rubber.

  According to this invention, durability performance can be improved by mix | blending the highly branched polymer which has a carbonyl group in a branched chain with brominated butyl rubber.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition for an inner liner according to this embodiment comprises a brominated butyl rubber and a highly branched polymer having a carbonyl group in a branched chain.

  The rubber component used in the rubber composition according to the present embodiment contains brominated butyl rubber from the viewpoint of interaction with the hyperbranched polymer. In this embodiment, brominated butyl rubber may be used in combination with other butyl rubber. The term “butyl rubber” as used herein is a concept including halogenated butyl rubber, butyl rubber (IIR), and a mixture thereof. Examples of the halogenated butyl rubber include brominated butyl rubber (BIIR) and chlorinated butyl rubber (CIIR).

  The rubber component is preferably a brominated butyl rubber alone or a blended rubber of brominated butyl rubber and other butyl rubber from the viewpoint of improving air permeability of the inner liner and interaction with the highly branched polymer. The proportion of brominated butyl rubber in the component is preferably 60% by mass or more, and more preferably 80% by mass or more.

  The rubber component preferably contains no rubber other than halogenated butyl rubber and butyl rubber from the viewpoint of air permeation resistance, but natural rubber (NR) and isoprene rubber are within the range not impairing the effects of the present invention. (IR), butadiene rubber (BR), diene rubber such as styrene butadiene rubber (SBR) may be included. For example, by adding natural rubber, tackiness can be imparted to the rubber composition to improve tire moldability, but the air permeation resistance is deteriorated. Therefore, the blending of these diene rubbers should be kept to a minimum, and the proportion of the rubber component is preferably 30% by mass or less, more preferably 10% by mass or less.

  The hyperbranched polymer is not particularly limited as long as it has a carbonyl group in the branched chain. For example, a hydroxy acid having two or more hydroxyl groups is bonded to the core having a hydroxyl group via an ester bond and / or Or it is preferable that it is the polymerized hyperbranched polymer. Although it does not specifically limit as a core which has a hydroxyl group, It is preferable that the number of hydroxyl groups is 2-6, for example, the compound represented by following (1) Formula is mentioned. Although it does not specifically limit as a hydroxy acid which has a 2 or more hydroxyl group, For example, 2, 2-bis (methylol) propanoic acid (bis-MPA) is mentioned. The number of hydroxyl groups at the ends of the highly branched polymer is not particularly limited, but is preferably 15 to 64. The hyperbranched polymer may be a hyperbranch type or a dendrimer type, but is preferably a hyperbranch type in which the branch structure is not uniform from the viewpoint of easy entanglement with brominated butyl rubber. Moreover, it is preferable that it is a hyperbranch type also from points, such as the ease of a synthesis | combination and the availability.

  Here, in this specification, the hyperbranch is a polymer having a dendritic branch but having a non-uniform branched structure, and means a non-spherical structure or an amorphous spherical structure. In contrast, a dendrimer is a polymer that is regularly and completely dendriticly branched from the core and has a spherical structure. In each case, the number of generations increases each time the branch is repeated from the center, and the structure has a sparse structure near the core and a dense structure near the branch end.

  By blending the above-mentioned hyperbranched polymer with brominated butyl rubber, the effect of improving the durability performance (breaking elongation and breaking strength) can be obtained. The reason is considered as follows. That is, the branched chain of the brominated butyl rubber and the highly branched polymer is entangled, and a physical bond interaction is exhibited between the bromine atom of the brominated butyl rubber and the oxygen atom of the carbonyl group contained in the highly branched polymer. Tangle between each other becomes stronger. A hyperbranched polymer has many branched chains, and the branched chain has a carbonyl group that reacts with a bromine atom, so that it can form a physical bond with two or more molecules of brominated butyl rubber. it can. Because one molecule of hyperbranched polymer interacts with a plurality of brominated butyl rubber molecules, the hyperbranched polymer exhibits an anchor effect on the interface between the molecular chains of brominated butyl rubber that had undergone initial fracture. The durability performance (breaking elongation and breaking strength) is considered to be improved.

  Although the weight average molecular weight of the said highly branched polymer is not specifically limited, It is preferable that it is 500-15000, More preferably, it is 1000-10000, It is further more preferable that it is 1500-8000. As the molecular weight increases, the number of branches increases and the branch ends have a dense structure, and it is presumed that the branched chains of the brominated butyl rubber and the highly branched polymer tend not to be entangled. When the molecular weight is 500 or more, it has a sufficient number of branches, and the carbonyl group of the bromine atom and the branched chain tends to show interaction at a plurality of locations, and when the molecular weight is 15000 or less, the branch end is Since it does not become too dense and entanglement between the brominated butyl rubber and the branched chain of the highly branched polymer tends to occur, it is considered that the effect of improving the durability performance (breaking elongation and breaking strength) is excellent.

  Here, the weight average molecular weight can obtain Mw in terms of polystyrene by measurement with gel permeation chromatography (GPC). Specifically, the measurement sample is 0.2 mg dissolved in 1 mL of THF. “LC-20DA” manufactured by Shimadzu Corporation was used, the sample was filtered, and passed through a column (“PL Gel 3 μm Guard × 2” manufactured by Polymer Laboratories) at a temperature of 40 ° C. and a flow rate of 0.7 mL / min. Detect with "RI Detector" manufactured by System.

  As the hyperbranched polymer, those having different branch structures may be used in combination, or those having different molecular weights may be used in combination.

  Examples of the hyperbranched polymer include “Hyperbranch bis-MPA polyester-16-hydroxyl, second generation”, “Hyperbranch bis-MPA polyester-32-hydroxyl, third generation” from Sigma-Aldrich Japan GK. , "Hyperbranch bis-MPA polyester-64-hydroxyl, 4th generation".

  The hyperbranched polymer under the above-mentioned trade name is considered to contain hyperbranched polymers each having a different branched structure. For example, “Hyperbranch bis-MPA polyester-16-hydroxyl, second generation” is described in the following (2 ) Formula, “Hyperbranch bis-MPA polyester-32-hydroxyl, third generation” is the following (3) formula, “Hyperbranch bis-MPA polyester-64-hydroxyl, fourth generation” is (4) ) Including a compound represented by the formula:

  The blending amount of the hyperbranched polymer is not particularly limited, but is preferably 0.2 to 20 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of brominated butyl rubber. More preferably, it is 10 mass parts. By being 0.2 parts by mass or more, the durability performance (breaking elongation and breaking strength) is excellent, and by being 20 parts by mass or less, the breaking elongation and breaking strength can be improved in a balanced manner.

  You may mix | blend a reinforcing filler with the rubber composition which concerns on this embodiment.

  As the reinforcing filler, it is preferable to use carbon black and / or silica. That is, the reinforcing filler may be carbon black alone, silica alone, or a combination of carbon black and silica. Preferably, carbon black or a combination of carbon black and silica is used. The compounding quantity of a reinforcing filler is not specifically limited, For example, it is preferable that it is 10-150 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 20-100 mass parts, More preferably, 30- 80 parts by mass.

  The carbon black is not particularly limited, and various known varieties can be used. As a compounding quantity of carbon black, the range of about 10-80 mass parts is preferable with respect to 100 mass parts of rubber components, More preferably, it is 10-70 mass parts.

  The silica is not particularly limited, but wet silica such as wet precipitation silica or wet gel silica is preferably used. When silica is blended, the blending amount is preferably 10 to 50 parts by weight, more preferably 15 to 50 parts by weight with respect to 100 parts by weight of the rubber component from the viewpoint of the balance of tan δ of rubber and reinforcement. Part.

  When silica is blended, a silane coupling agent such as sulfide silane or mercaptosilane is preferably used in combination, and the blending amount is preferably 2 to 20% by mass with respect to the silica blending amount.

  To the rubber composition according to the present embodiment, a hydrocarbon resin can be added as a tackifier for the purpose of improving the tackiness of the unvulcanized rubber and suppressing the opening of the joint portion at the time of tire molding. As the hydrocarbon resin, those having a softening point of 90 to 110 ° C are preferable. Here, the softening point is a value measured according to JIS K6220. Hydrocarbon resins are preferred in that they do not cause a decrease in air permeation resistance compared to softeners such as oil and plasticizers.

  As the hydrocarbon resin, it is preferable to use a petroleum resin obtained by polymerizing a C5 to C9 olefin obtained by thermal decomposition of naphtha in a mixed state, and more preferably a petroleum resin mainly composed of a C5 component. Such petroleum resin is excellent in compatibility with butyl rubber and excellent in the effect of improving adhesiveness.

  When the hydrocarbon resin is used, the blending amount is preferably 2 to 15 parts by mass with respect to 100 parts by mass of the rubber component.

  In the rubber composition according to the present embodiment, in addition to the above-described components, process oil, zinc white, stearic acid, softener, plasticizer, wax, anti-aging agent, vulcanization used in ordinary rubber industry Compounding chemicals such as an agent and a vulcanization accelerator can be appropriately blended within a normal range.

  It is preferable that the compounding quantity of zinc white is 1-5 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 2-4 mass parts.

  Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of the rubber component. It is preferable that it is 0.1-10 mass parts, More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. For example, in the first mixing stage (non-pro kneading process), the brominated butyl rubber is kneaded with the above hyperbranched polymer and other additives excluding the vulcanizing agent and vulcanization accelerator, and then kneaded. A rubber composition can be prepared by adding and kneading a vulcanizing agent and a vulcanization accelerator to the obtained mixture in the final mixing stage (pro-kneading process).

  The obtained rubber composition is extruded into a sheet shape with a roll or an extruder according to a conventional method, a green tire is produced by sticking the extruded sheet material inside the carcass ply, and the green tire is vulcanized and molded. Thus, a tubeless pneumatic tire having an inner liner made of a thin rubber layer on the tire inner surface is formed. In addition, although the thickness of an inner liner changes with tire sizes etc., it is 0.5-3.0 mm normally.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  In accordance with the composition (parts by mass) shown in Tables 1 and 2 below, using a Banbury mixer, components other than sulfur and vulcanization accelerator DM are added and mixed (discharge temperature = 160 ° C.), and then sulfur and vulcanization are accelerated. The agent DM was added and mixed (discharge temperature = 90 ° C.) to prepare a rubber composition. Details of each formulation in Tables 1 and 2 are as follows.

BIIR: “Bromobutyl 2222” manufactured by ExxonMobil
IIR: “Butyl 268” manufactured by ExxonMobil
Hyperbranched polymer 1: “Hyperbranch bis-MPA polyester-16-hydroxyl, second generation” manufactured by Sigma-Aldrich Japan G.K. (number of hydroxyl groups at branch ends = 16, weight average molecular weight = 1745.79)
Hyperbranched polymer 2: “Hyperbranch bis-MPA polyester-32-hydroxyl, third generation” manufactured by Sigma-Aldrich Japan G.K. (number of hydroxyl groups at the branch end = 32, weight average molecular weight = 3607.64)
Hyperbranched polymer 3: “Hyperbranch bis-MPA polyester-64-hydroxyl, 4th generation” manufactured by Sigma-Aldrich Japan G.K. (number of hydroxyl groups at the branch end = 64, weight average molecular weight = 73232.32)
・ Carbon black: GPF, “Seast V” manufactured by Tokai Carbon Co., Ltd.
・ Tackifier: “Escollet 1102” manufactured by ExxonMobil
・ Oil: “Process NC140” manufactured by JX Nippon Oil & Energy
・ Zinc flower: "Zinc flower 3" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S20” manufactured by Kao Corporation
・ Sulfur: “5% oil-treated powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator DM: “Noxeller DM-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  About the obtained rubber composition, breaking elongation and breaking strength were evaluated. The evaluation method is as follows.

・ Elongation at break: According to JIS K6251, a test piece vulcanized at 150 ° C. × 30 minutes was subjected to a tensile test (dumbbell shape No. 3) to measure the elongation at break. The index was displayed. The larger the value, the greater the elongation at break and the better the durability performance (reinforcing property).
-Breaking strength: According to JIS K6251, a test piece vulcanized at 150 ° C for 30 minutes was subjected to a tensile test (dumbbell shape No. 3) to measure the breaking strength, and the value of Comparative Example 1 was 100. The index was displayed. The larger the value, the greater the breaking strength and the better the durability performance (reinforcing property).

  The results are as shown in Tables 1 and 2. From the comparison between Comparative Examples 1 to 5 and Examples 1 to 3, the brominated butyl rubber was blended with a hyperbranched polymer having a carbonyl group in the branched chain. The elongation and breaking strength were improved, and the effect of improving the durability performance was recognized. In addition, from the results of Examples 4 to 7, the amount of the hyperbranched polymer is 0.2 parts by mass or more with respect to 100 parts by mass of brominated butyl rubber, thereby improving the elongation at break and the strength at break. It was recognized that when the durability performance was excellent and the content was 20 parts by mass or less, the elongation at break and the strength at break were improved in a well-balanced manner and the effect of improving the durability performance was obtained.

  The rubber composition for an inner liner of the present invention can be used as an inner liner in tubeless pneumatic tires such as passenger cars, light trucks, trucks and buses. Especially, it is used suitably for the tire for heavy loads whose use conditions are severe, and the durability performance can be improved.

Claims (3)

Contains a brominated butyl rubber and a highly branched polymer having a carbonyl group in the branched chain ,
The rubber composition for an inner liner , wherein the number of terminal hydroxyl groups of the hyperbranched polymer is 15 to 64 .   The rubber composition for an inner liner according to claim 1, wherein the hyperbranched polymer has a weight average molecular weight of 500 to 15000. The rubber composition for an inner liner according to claim 1 or 2 , wherein 0.2 to 20 parts by mass of the hyperbranched polymer is blended with respect to 100 parts by mass of the brominated butyl rubber.