JP2017031372A - Rubber composition and pneumatic tire - Google Patents

Abstract

[PROBLEMS] To suppress a decrease in hardness and a decrease in tearing performance while exhibiting an excellent effect of improving grip performance by blending a resin.
SOLUTION: To 100 parts by mass of diene rubber, 10 to 150 parts by mass of silica, 0.5 to 50 parts by mass of a resin having a softening point of 80 to 120 ° C., and 1 to 25 parts by mass of sucrose fatty acid ester. It is a rubber composition to contain. Moreover, it is a pneumatic tire provided with the tread rubber which consists of this rubber composition.
[Selection figure] None

Description

  The present invention relates to a rubber composition and a pneumatic tire using the same.

  Conventionally, for example, in order to improve grip performance on a dry road surface in a tread rubber of a pneumatic tire, it is known to add an adhesive resin. However, when an adhesive resin is blended, the rubber hardness is reduced. Therefore, Patent Document 1 discloses that a resorcin condensate is blended together with an adhesive resin having a softening point of 80 to 120 ° C. in order to improve grip performance while maintaining hardness.

  Further, as a method for improving the hardness, there is generally a weight reduction of oil, but there is a problem that the tearing performance is lowered. Therefore, it is required to suppress the decrease in hardness and the decrease in tearing performance while exhibiting the excellent effect of improving the grip performance by blending the resin.

  In Patent Document 2, in a tire rubber composition, a polyether containing a sucrose residue or a derivative thereof is blended in a molecule, and thereby processability, wear resistance, rolling resistance and wetness are mixed. It is disclosed that performance is improved. Patent Document 3 discloses that in a tire rubber composition, cyclodextrin or sucrose is blended with a silane coupling agent, thereby improving rolling resistance and wet performance. However, these documents do not disclose sucrose fatty acid esters, and do not suggest advantageous effects obtained by blending sucrose fatty acid esters with resins.

JP 2010-241919 A JP 2005-343963 A JP 2004-204176 A

  An object of the present invention is to provide a rubber composition capable of suppressing a decrease in hardness and a decrease in tearing performance while exhibiting an excellent effect of improving grip performance by blending a resin in view of the above points. And

  The rubber composition according to the present invention comprises 10 to 150 parts by mass of silica, 0.5 to 50 parts by mass of a resin having a softening point of 80 to 120 ° C., and 1 to 25 sucrose fatty acid esters with respect to 100 parts by mass of the diene rubber. Part by mass.

  A pneumatic tire according to a preferred embodiment of the present invention includes a tread rubber made of the rubber composition.

  According to the present invention, the effect of improving the grip performance can be obtained by blending the resin having the above softening point, and the hardness of the resin added can be increased by blending silica and sucrose fatty acid ester in addition to the resin. The tearing performance can be improved while suppressing the decrease.

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

  The rubber composition according to this embodiment contains (A) a diene rubber, (B) silica, (C) a resin, and (D) a sucrose fatty acid ester.

(A) Diene rubber The diene rubber as a rubber component is not particularly limited. Examples of usable diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene-isoprene rubber, butadiene-isoprene rubber, and styrene-butadiene-. Isoprene rubber, nitrile rubber (NBR) and the like can be mentioned, and these can be used alone or in admixture of two or more. More preferably, it is at least one selected from the group consisting of natural rubber, butadiene rubber, and styrene butadiene rubber.

  In one embodiment, the diene rubber preferably includes a styrene butadiene rubber, that is, the diene rubber may be a styrene butadiene rubber alone or a blend of styrene butadiene rubber and other diene rubbers. In the case of blending, it is preferable that 50 parts by mass or more of styrene butadiene rubber is contained in 100 parts by mass of the diene rubber. The other diene rubber is preferably butadiene rubber and / or natural rubber.

(B) Silica Silica is not particularly limited, but wet silica (hydrous silicic acid) is preferred. The compounding quantity of a silica is 10-150 mass parts with respect to 100 mass parts of diene rubbers, Preferably it is 20-120 mass parts, More preferably, it is 30-100 mass parts, 30-80 mass parts But you can.

(C) Resin A resin having a softening point of 80 to 120 ° C. is used. Since the resin having such a softening point has adhesiveness, the grip performance on a dry road surface can be improved by blending such an adhesive resin. When the softening point is less than 80 ° C., the properties are close to oil and it is difficult to exhibit grip performance. Moreover, when the softening point is 120 ° C. or lower, the grip performance is easily exhibited by softening in a high temperature range. The softening point is more preferably 85 to 110 ° C. Here, the softening point is a value measured by a ring and ball drop method in accordance with JIS K6220.

  Examples of such resins include petroleum resins, coumarone resins, terpene resins, phenol resins, rosin resins and the like, and these may be used alone or in combination of two or more.

  Examples of petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins. The aliphatic petroleum resin is a resin obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions corresponding to 4 to 5 carbon atoms (C5 fraction) (C5 petroleum resins). It may also be hydrogenated. An aromatic petroleum resin is a resin obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fraction) having 8 to 10 carbon atoms (C9 petroleum). It may also be referred to as a resin) and may be hydrogenated. The aliphatic / aromatic copolymer petroleum resin is a resin obtained by copolymerizing the C5 fraction and the C9 fraction (also referred to as C5 / C9 petroleum resin), and is hydrogenated. There may be.

  The coumarone-based resin is a resin having coumarone as a main component, and examples thereof include coumarone resin, coumarone-indene resin, and copolymer resin having coumarone, indene, and styrene as main components. Examples of the terpene resin include polyterpene and terpene-phenol resin. Examples of phenolic resins include phenol-formaldehyde resins, alkylphenol acetylene resins, alkylphenol acetylene resins, and oil-modified phenol formaldehyde resins. Examples of the rosin resin include a natural resin rosin and a rosin-modified resin obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification or the like.

  Among these, at least one petroleum resin selected from the group consisting of aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins, and / or coumarone resins are used. It is preferable.

  The compounding amount of the resin is 0.5 to 50 parts by mass, more preferably 3 to 30 parts by mass, and may be 5 to 20 parts by mass with respect to 100 parts by mass of the diene rubber. When the compounding amount of the resin is 50 parts by mass or less, a decrease in rubber hardness can be suppressed.

(D) Sucrose fatty acid ester Sucrose fatty acid ester is comprised with the fatty acid obtained from sucrose of a hydrophilic group, and edible fats and oils of a lipophilic group. By blending the sucrose fatty acid ester with silica, the tearing performance can be improved while compensating for the decrease in hardness caused by blending the above resin.

  Examples of fatty acids constituting sucrose fatty acids include saturated or unsaturated fatty acids having 8 to 24 carbon atoms, such as octanoic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid. , Palmitoleic acid, oleic acid, linoleic acid, linolenic acid, erucic acid and the like. These fatty acids may be used alone or in combination of two or more. Among these, C10-22 saturated fatty acids are preferable.

  Preferred examples of the sucrose fatty acid ester include sucrose lauric acid ester whose constituent fatty acid is mainly composed of lauric acid, sucrose myristate ester whose constituent fatty acid is mainly composed of myristic acid, and constituent fatty acid whose main component is palmitic acid. And sucrose stearate whose constituent fatty acid is mainly composed of stearic acid. Here, “having a certain fatty acid as a main component” means that 50 mass% or more, preferably 60 mass% or more of the constituent fatty acid is the fatty acid.

  The HLB value (hydrophilic / lipophilic balance) of the sucrose fatty acid ester is preferably 2 to 18, more preferably 4 to 16, 8 to 16, or 11 to 16. Here, the HLB value can be obtained experimentally by the atlas method proposed by Griffin et al.

  Specific examples of the sucrose fatty acid ester include S-1670 (HLB value: 16) and S-1570 (HLB value: 15), which are commercially available from Mitsubishi Chemical Foods Co., Ltd. under the trade name “Ryoto Sugar Ester”. ), S-1170 (HLB value: 11), S-970 (HLB value: 9), S-770 (HLB value: 7), S-570 (HLB value: 5), S-370 (HLB value: 3) ), Sucrose stearate such as S-270 (HLB value: 2), sucrose palmitate such as P-1670 (HLB value: 16), P-1570 (HLB value: 15), M-1695 ( Examples thereof include sucrose myristic acid esters such as HLB value: 16), and sucrose lauric acid esters such as L-1695 (HLB value: 16) and L-595 (HLB value: 5).

  The compounding quantity of sucrose fatty acid ester is 1-25 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 3-15 mass parts. When the blending amount of the sucrose fatty acid ester is 25 parts by mass or less, a decrease in rubber hardness can be suppressed.

(E) Other components In addition to the above components, the rubber composition according to this embodiment includes a silane coupling agent, carbon black, process oil, stearic acid, zinc white, anti-aging agent, wax, and vulcanizing agent. Various additives generally used in rubber compositions, such as vulcanization accelerators, can be blended.

  Examples of the silane coupling agent include sulfide silane and mercaptosilane, which can improve the dispersibility of silica. Although the compounding quantity of a silane coupling agent is not specifically limited, It is preferable that it is 2-20 mass% with respect to a silica compounding quantity.

  The carbon black is not particularly limited, and various furnace carbon blacks used as rubber reinforcing agents can be used. The compounding quantity of carbon black is not specifically limited, 80 mass parts or less may be sufficient with respect to 100 mass parts of diene rubbers, and 50 mass parts or less may be sufficient. In this embodiment, the reinforcing filler is preferably silica alone or a combination of silica and carbon black. When used in combination, the reinforcing filler is preferably composed mainly of silica, and the reinforcing filler It is preferable that 50 mass% or more of the agent is silica. Since carbon black is not essential, it may be blended in an amount of 3 to 10 parts by mass with respect to 100 parts by mass of the diene rubber for the purpose of coloring, for example.

  Examples of the vulcanizing agent include sulfur 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 diene rubber. It is preferable that it is 0.1-10 mass parts, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, at the first mixing stage, silica, resin and sucrose fatty acid ester are added to the diene rubber together with other additives excluding the vulcanizing agent and vulcanization accelerator, and then the resulting mixture is mixed. The rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing stage.

  The rubber composition thus obtained can be used for various rubber members for tires, vibration-proof rubbers, conveyor belts and the like. Preferably, it is used for tires, and can be applied to various parts of tires such as tires for passenger cars, heavy duty tires for trucks and buses, and tread parts and sidewall parts of pneumatic tires of sizes. That is, the rubber composition is formed into a predetermined shape by, for example, extrusion processing according to a conventional method, and is combined with other parts to produce an unvulcanized tire (green tire), and then heated at, for example, 140 to 180 ° C. By performing sulfur molding, a pneumatic tire can be manufactured. Preferably, it is used for the tread rubber constituting the ground contact surface of the tire. The tread rubber of a pneumatic tire includes a two-layer structure of a cap rubber and a base rubber, and a single-layer structure in which both are integrated, and is preferably used as a rubber constituting the ground contact surface. That is, if the tread rubber has a single layer structure, the tread rubber is preferably made of the rubber composition. If the tread rubber has a two-layer structure, the cap rubber is preferably made of the rubber composition.

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

  Using a Banbury mixer, according to the blending (parts by mass) shown in Table 1 below, first, in the first mixing stage, other blending agents excluding sulfur and vulcanization accelerator are added and kneaded (discharge) Then, in the final mixing stage, sulfur and a vulcanization accelerator were added and kneaded (discharge temperature = 90 ° C.) to prepare a rubber composition. The details of each component in Table 1 are as follows.

・ SBR: "HPR350" manufactured by JSR Corporation
-BR: “BR150B” manufactured by Ube Industries, Ltd.
-Sucrose stearic acid 1: "Ryoto Sugar Ester S-570" (HLB value: 5) manufactured by Mitsubishi Chemical Foods Corporation
-Sucrose stearic acid 2: "Ryoto sugar ester S-970" (HLB value: 9) manufactured by Mitsubishi Chemical Foods Corporation
-Sucrose stearic acid 3: "Ryoto sugar ester S-1570" (HLB value: 15) manufactured by Mitsubishi Chemical Foods Corporation
-Sucrose lauric acid: "Ryoto Sugar Ester L-595" (HLB value: 5) manufactured by Mitsubishi Chemical Foods Corporation
・ Sucrose: Tokyo Chemical Industry Co., Ltd. Sucrose “S0111”
Resin 1: Coumarone resin, “Coumaron G90” manufactured by Nikkiso Chemical Co., Ltd. (softening point: 90 ° C.)
Resin 2: C5 petroleum resin, “Escollet 1102” manufactured by ExxonMobil (softening point: 94-104 ° C.)
Resin 3: Coumarone resin, Kobe Oil Chemical Co., Ltd. “Process Resin 60” (softening point: 60 ° C.)
Resin 4: Maleic acid resin, Harima Chemical Co., Ltd. “Harimac 145P” (softening point: 139 ° C.)
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
Silane coupling agent: “Si69” manufactured by Evonik Degussa
Carbon black: “Dia Black N341” manufactured by Mitsubishi Chemical Corporation
-Oil: "Extract No. 4 S" manufactured by Showa Shell Sekiyu KK
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Wax: Nippon Seiki Co., Ltd. “OZOACE0355”
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

  About each rubber composition, the hardness, grip performance, and tear performance were measured using the test piece of the predetermined shape vulcanized at 160 degreeC for 30 minutes. Each measuring method is as follows.

  Hardness: Using a type A durometer based on JIS K6253, the hardness was measured at 23 ° C., and the value was shown as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness. It can be said that 103 or more has a sufficient improvement effect with respect to the comparative example 1.

  Grip performance: Using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd., tan δ was measured under the conditions of frequency 10 Hz, static strain 10%, dynamic strain ± 1%, temperature 100 ° C. Is shown as an index with 100 being 100. The larger the index, the larger the tan δ at 100 ° C., and thus the better the grip performance on the dry road surface. It can be said that it is sufficient improvement effect with respect to the comparative example 1 by 104 or more.

  ・ Tearing performance: A test piece punched in the crescent shape defined in JIS K6252 and cut into a 0.50 ± 0.08 mm in the center of the indentation was tested at a pulling speed of 500 mm / min with a Shimadzu Corporation tensile tester. Went. When Comparative Example 1 is 100, the larger the index, the better. It can be said that it is sufficient improvement effect with respect to the comparative example 1 by 106 or more.

  The results are as shown in Table 1. Compared to Comparative Example 1 in which the resin was blended, Examples 1 to 7 in which the sucrose fatty acid ester was blended together with the resin not only improved the hardness and grip performance, but also significantly improved the tear performance. . On the other hand, in Comparative Example 2 in which a resin and sucrose were blended, the improvement effect was insufficient with respect to any of hardness, grip performance and tear performance as compared with Comparative Example 1. Further, in Comparative Example 3 in which sucrose fatty acid ester was blended without blending resin, the improvement effect of hardness and tearing performance was seen with respect to Comparative Example 1, but the grip performance was significantly lowered. On the other hand, although the resin and the fatty acid ester were used in combination, in Comparative Examples 4 and 5 where the softening point of the resin was outside the specified range, the grip performance was inferior to that of Comparative Example 1. In Comparative Example 6 in which silica was not used as the filler, the grip performance was superior to that of Comparative Example 1, but the tear performance was inferior.

Claims (3)

  A rubber composition containing 10 to 150 parts by mass of silica, 0.5 to 50 parts by mass of a resin having a softening point of 80 to 120 ° C., and 1 to 25 parts by mass of a sucrose fatty acid ester with respect to 100 parts by mass of the diene rubber. object.   The rubber composition according to claim 1, wherein the sucrose fatty acid ester has an HLB value of 2 to 18.   A pneumatic tire provided with a tread rubber comprising the rubber composition according to claim 1.