JP2010111287A - Studless tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a studless tire that has excellent handling performance on ice and snow, while simultaneously having an excellent fracture strength and excellent durability (chunking resistance). <P>SOLUTION: The studless tire has a base tread formed using a rubber composition in which 1-10 pts.mass of a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid is blended with respect to 100 pts.mass of a rubber component. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a studless tire.

Conventionally, spike tires have been used for running on icy and snowy roads, and chains have been attached to the tires. However, environmental problems such as dust problems have occurred, and studless tires have been developed as alternatives to icy and snowy road running tires. Studless tires are used on snowy road surfaces where the unevenness of the road surface is large compared to general road surfaces, so the material and design aspects have been devised. Specifically, diene rubber with excellent low-temperature characteristics was blended Rubber compositions have been developed.

On the other hand, in order to satisfy various characteristics required for automobile tires, a tread of a tire is made to have a two-layer structure of a cap tread (surface layer) and a base tread (inner surface layer). Studless tires have also been proposed (Patent Document 1). With recent warming, there are increasing opportunities for running on paved roads even for studless tires, and there is a growing demand for improved durability (chunking resistance) in order to respond to driving opportunities on various road surfaces including paved roads. It is coming.

However, since the rubber hardness of cap treads tends to be set low while further improvement in performance on ice and snow is required, such cap tread alone can maintain durability on ice and snow while maintaining durability performance. It is difficult to raise. Further, for improving durability, generally, a method of increasing the blending amount of fillers such as carbon black and silica to increase the hardness and breaking strength is generally known. Even if the method is applied, there is a problem that flexibility at low temperature is lowered and handling on ice and snow is reduced in performance.

JP 2007-176417 A

An object of the present invention is to solve the above-mentioned problems and to provide a studless tire having good handling performance on ice and snow, and at the same time excellent in breaking strength and durability (chunking resistance).

The present invention provides a base tread produced using a rubber composition in which 1 to 10 parts by mass of a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid is blended with respect to 100 parts by mass of a rubber component. The present invention relates to a studless tire.

In the rubber composition, the rubber component preferably contains natural rubber and butadiene rubber.

According to the present invention, a studless tire having a base tread produced using a rubber composition containing a mixture of a predetermined amount of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. In addition to good handling performance on ice and snow, excellent breaking strength and durability (chunking resistance) can also be obtained.

The studless tire of the present invention has a base tread produced using a rubber composition containing a rubber component and a predetermined amount of a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. When natural rubber or butadiene rubber is sulfur vulcanized as a rubber component, vulcanization reversion (reversion) occurs, and the rubber deteriorates or the cross-linked state deteriorates, but reversion can be suppressed by using the mixture. . For this reason, the breaking strength can be improved, and the durability performance (chunking resistance performance) can be improved.

Also, unlike the method of increasing these performances by increasing the filling amount of carbon black or silica, the hardness at low temperature does not increase significantly even if the mixture is blended, so the handling performance on ice and snow is improved. It is possible to achieve both durability and handling performance on ice and snow without deteriorating.

The rubber component is not particularly limited. For example, natural rubber (NR), butadiene rubber (BR), epoxidized natural rubber (ENR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM) ), Chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), and the like. Among them, it is preferable to use NR and BR together in consideration of the environment and to prepare for a future decrease in the amount of oil supply, and because excellent fracture strength and durability can be obtained.

The rubber component includes at least one functional group selected from the group consisting of an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group (hereinafter referred to as a functional group). May be included. As the rubber having these functional groups, commercially available rubbers may be used, or they may be appropriately modified and used.

The NR is not particularly limited, and, for example, those commonly used in the studless tire industry such as SIR20, RSS # 3, and TSR20 can be used.

In the rubber composition, the content of NR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. If it is less than 10% by mass, the fracture strength, durability, and workability tend to decrease. The content of NR is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. When it exceeds 80 mass%, there is a tendency that performance on ice cannot be secured.

Examples of BR include butadiene rubber having a high cis content, butadiene rubber having a low cis content, and a linear type butadiene rubber having a reduced degree of molecular structure branching. A BR having a high cis content is preferably used. .

The cis content of the butadiene rubber is preferably 95% by mass or more. By blending such butadiene rubber, the effect of improving the breaking strength and durability is enhanced. The molecular weight distribution (Mw / Mn) of butadiene rubber is preferably 3.0 to 3.4. By using such butadiene rubber, the breaking strength and durability can be improved.

The content of BR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. If it is less than 10% by mass, it is difficult to lower the glass transition temperature and the handling performance on ice and snow tends to be lowered. The content of BR is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. If it exceeds 80% by mass, handling performance on ice and snow will be good, but breaking strength and durability tend to be reduced. In the present invention, if the ratio of butadiene rubber is made higher, it is possible to achieve both breaking strength and durability and handling performance on ice and snow.

In the rubber composition, when NR and BR are used in combination, it is preferable that the blending amount of these rubber components is 70% by mass or more in 100% by mass of the rubber component. By setting it as 70 mass% or more, favorable handling performance on ice and snow and durability can be achieved, and the effect of reversion resistance is also increased. The blending amount of these rubber components is more preferably 80% by mass or more, still more preferably 90% by mass or more, and most preferably 100% by mass.

The rubber composition contains a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. Reversion (reversion) is generally said to occur in NR, but the mixture is effective not only for NR but also for BR. That is, by blending a predetermined amount of the mixture, a reversion suppressing effect can be obtained regardless of the NR / BR ratio. In addition, since reversion can be suppressed, it is possible to prevent a decrease in mechanical strength such as modulus even when vulcanized at high temperature for a short time, and it is possible to improve productivity while maintaining durability. It is.

As for the aliphatic carboxylic acid zinc salt in the above mixture, as the aliphatic carboxylic acid, palm oil, palm kernel oil, camellia oil, olive oil, almond oil, canola oil, peanut oil, rice sugar oil, cocoa butter, palm oil , Aliphatic carboxylic acids derived from vegetable oils such as soybean oil, cottonseed oil, sesame oil, linseed oil, castor oil, rapeseed oil, aliphatic carboxylic acids derived from animal oils such as beef tallow, aliphatic carboxylic acids chemically synthesized from petroleum, etc. However, it is also possible to consider the environment, to prepare for a future reduction in the supply of oil, and to sufficiently suppress the vulcanization return, aliphatic carboxylic acids derived from vegetable oils are preferred, and palm oil, palm oil An aliphatic carboxylic acid derived from nuclear oil or palm oil is more preferable.

The aliphatic carboxylic acid preferably has 4 or more carbon atoms, more preferably 6 or more carbon atoms. If the aliphatic carboxylic acid has less than 4 carbon atoms, the dispersibility tends to deteriorate. The carbon number of the aliphatic carboxylic acid is preferably 16 or less, more preferably 14 or less, and still more preferably 12 or less. When the carbon number of the aliphatic carboxylic acid exceeds 16, there is a tendency that the vulcanization return cannot be sufficiently suppressed.

The aliphatic group in the aliphatic carboxylic acid may be a chain structure such as an alkyl group or a cyclic structure such as a cycloalkyl group.

Regarding the aromatic carboxylic acid zinc salt in the above mixture, examples of the aromatic carboxylic acid include benzoic acid, phthalic acid, mellitic acid, hemimellitic acid, trimellitic acid, diphenic acid, toluic acid, and naphthoic acid. Of these, benzoic acid, phthalic acid, or naphthoic acid is preferable because reversion can be sufficiently suppressed.

The content ratio of the zinc salt of aliphatic carboxylic acid and the zinc salt of aromatic carboxylic acid in the mixture (molar ratio, zinc salt of aliphatic carboxylic acid / zinc salt of aromatic carboxylic acid, hereinafter referred to as the content ratio) is 1/20 or more is preferable, 1/15 or more is more preferable, and 1/10 or more is still more preferable. If the content ratio is less than 1/20, it is not possible to consider the environment or prepare for a future reduction in the amount of oil supplied, and the dispersibility and stability of the mixture tend to deteriorate. The content ratio is preferably 20/1 or less, more preferably 15/1 or less, and still more preferably 10/1 or less. When the content ratio exceeds 20/1, there is a tendency that the vulcanization return cannot be sufficiently suppressed.

The zinc content in the mixture is preferably 3% by mass or more, and more preferably 5% by mass or more. If the zinc content in the mixture is less than 3% by mass, there is a tendency that the vulcanization return cannot be sufficiently suppressed. Moreover, 30 mass% or less is preferable and, as for the zinc content rate in a mixture, 25 mass% or less is more preferable. When the zinc content in the mixture exceeds 30% by mass, the workability tends to deteriorate.

Content of a mixture is 1 mass part or more with respect to 100 mass parts of rubber components, Preferably it is 2 mass parts or more, More preferably, it is 3 mass parts or more. If it is less than 1 part by mass, the effect is small, sufficient vulcanization resistance cannot be ensured, and it is difficult to obtain an effect of improving durability. The content of the mixture is 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 6 parts by mass or less. When the amount exceeds 10 parts by mass, the viscosity is unnecessarily lowered, the workability may be deteriorated, or the bloom may occur, and the improvement of the effect tends not to be observed.

The rubber composition may contain a fatty acid such as stearic acid, palmitic acid, myristic acid, lauric acid, caprylic acid, oleic acid, linoleic acid, etc. Among them, stearic acid is preferred because of its low cost.

The rubber composition includes, in addition to the rubber component, a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, a fatty acid, a compounding agent conventionally used in the rubber industry, such as carbon black, Fillers such as silica, silane coupling agents, oils or plasticizers, waxes, antioxidants, antiozonants, antioxidants, vulcanization accelerators, zinc oxides, peroxides, sulfur, sulfur-containing compounds, etc. These vulcanizing agents and vulcanization accelerators may be contained.

Examples of carbon black that can be used in the rubber composition include HAF, ISAF, and SAF, but are not particularly limited.

Carbon black having an average particle size of 25 nm or less and / or a DBP oil absorption of 100 ml / 100 g or more is preferable. By blending such carbon black, it is possible to provide the base tread with the necessary reinforcing properties as a studless tire, and to ensure block rigidity, uneven wear resistance, wear resistance, and durability. Further, if the viscosity is too low, the unvulcanized rubber composition becomes difficult to handle, and the molded products are excessively adhered to each other, so that the moldability is deteriorated or the workability is impaired. Can be used together with a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid to increase the viscosity of the unvulcanized rubber and improve processability.

If the average particle size of the carbon black exceeds 25 nm, the fracture strength tends to decrease or the wear resistance performance tends to deteriorate. The average particle size is more preferably 24 nm or less, still more preferably 23 nm or less. The average particle diameter is preferably 16 nm or more, more preferably 17 nm or more. If it is less than 16 nm, the rubber becomes hard at low temperatures, and there is a possibility that performance on ice and snow cannot be ensured.
In the present invention, the average particle diameter is a number average particle diameter and is measured by a transmission electron microscope.

If the DBP oil absorption of carbon black is less than 100 ml / 100 g, the breaking strength tends to decrease. The DBP oil absorption is more preferably 105 ml / 100 g or more, and still more preferably 115 ml / 100 g or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 40 m ² / g or more, more preferably 50 m ² / g or more. When it is less than 40 m ² / g, the reinforcing property is lowered and the durability tends to deteriorate. Also, _N 2 SA of carbon black is preferably 450 m ² / g or less, and more preferably not more than 400m ² / g. When it exceeds 450 m ² / g, the dispersibility of silica may be deteriorated.

The content of carbon black is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 35 parts by mass or more, and most preferably 40 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 15 parts by mass, the reinforcing property is insufficient, and it tends to be difficult to ensure the necessary block rigidity, steering stability, uneven wear resistance, wear resistance, and durability. The carbon black content is preferably 120 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 60 parts by mass or less. If it exceeds 120 parts by mass, the workability tends to deteriorate or the hardness tends to be too high.

The rubber composition may contain an oil or a plasticizer. Examples of oils and plasticizers that can be used include paraffinic process oil, aroma based process oil, and naphthenic process oil. Specific examples of the paraffinic process oil include PW-32, PW-90, PW-150, and PS-32 manufactured by Idemitsu Kosan Co., Ltd. Specific examples of the aroma-based process oil include AC-12, AC-460, AH-16, AH-24, and AH-58 manufactured by Idemitsu Kosan Co., Ltd.

The blending amount of the oil or plasticizer is preferably 5 parts by mass or more, more preferably 8 parts by mass or more, and still more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 parts by mass, the workability tends to deteriorate. On the other hand, the blending amount is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 20 parts by mass or less with respect to 100 parts by mass of the rubber component. When there are too many of these components, durability will fall and reversion resistance may also fall. In addition, handling performance on ice and snow may deteriorate.

Examples of the vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl-2- Examples include benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). Among these, it is preferable to use TBBS. In this case, as a retarding vulcanization accelerator, burning does not occur easily in the production process, it has excellent vulcanization characteristics, and the properties of rubber after vulcanization are excellent in low heat generation against deformation due to external force, and performance such as durability. Great effect on improvement.

The rubber composition is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

In the studless tire of the present invention, the rubber composition is used for a base tread of a tread having a two-layer structure of a cap tread and a base tread, for example.

The studless tire of the present invention is manufactured by a usual method using the rubber composition. That is, the rubber composition containing the above components is extruded in accordance with the shape of the base tread at an unvulcanized stage and molded together with other members by a normal method on a tire molding machine. Form a vulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a studless tire.

The studless tire of the present invention is suitably used for passenger cars, minivans, vans, light trucks and the like.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Natural rubber (NR): RSS # 3
Butadiene rubber (BR): BR150B manufactured by Ube Industries, Ltd. (cis 1,4 bond content 97%, ML _{1 + 4} (100 ° C.) 40, toluene solution viscosity 48 at 25 ° C., Mw / Mn 3.3)
Carbon Black: Dia Black I manufactured by Mitsubishi Chemical Corporation (ISAF carbon, average particle size 23 nm, DBP oil supply amount 114 ml / 100 g, N ₂ SA: 115 m ² / g)
Aroma oil: AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Mixture (mixture of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid): Activator 73A ((i) aliphatic carboxylic acid zinc salt: fatty acid derived from palm oil (carbon number: carbon number) 8-12) zinc salt, (ii) aromatic carboxylic acid zinc salt: zinc benzoate, content molar ratio: 1/1, zinc content: 17% by mass)
Stearic acid: Tungsten zinc oxide manufactured by Nippon Oil & Fats Co., Ltd .: Two types of zinc oxide manufactured by Mitsui Kinzoku Mining Co., Ltd. Anti-aging agent: NOCRACK 6C manufactured by Ouchi Shinsei Chemical Co.
Wax: Ozoace wax manufactured by Nippon Seiwa Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Industry Co., Ltd. TBBS: Noxeller NS (N-t-butyl- manufactured by Ouchi Shinsei Chemical Co., Ltd.) 2-Benzothiazyl sulfenamide)

Examples 1-7 and Comparative Examples 1-4
In accordance with the formulation shown in Table 1, using a Banbury mixer, the amount of chemical shown in Step 1 of Table 1 was added and kneaded at about 150 ° C. for 5 minutes. Thereafter, to the mixture obtained in Step 1, sulfur and a vulcanization accelerator in the blending amounts shown in Step 2 are added, and kneaded for 3 minutes at about 80 ° C. using an open roll. A vulcanized rubber composition was obtained.
The obtained unvulcanized rubber composition was molded into a base tread shape, bonded to another tire member, and vulcanized at 170 ° C. for 15 minutes to produce test studless tires of Examples and Comparative Examples. .

The following evaluation was performed using the obtained unvulcanized rubber composition and the studless tire for test (vulcanized rubber composition). Each test result is shown in Table 1.

(Reversion rate)
Using a curast meter, the vulcanization curve of the unvulcanized rubber composition at 170 ° C. was measured. The maximum torque increase value (MH-ML) is taken as 100, the torque increase value (M (15 minutes) -ML) 15 minutes after the start of vulcanization is shown as a relative value, and the value obtained by subtracting the relative value from 100 Version rate. The smaller the reversion rate, the better the reversion is suppressed and better.

(Tensile test)
An unvulcanized rubber composition was vulcanized at 170 ° C. for 12 minutes, and a test piece having a thickness of 2 mm was cut out from the rubber composition. No. 3 dumbbell according to JIS K6251 “Vulcanized rubber and thermoplastic rubber-Determination of tensile properties”. A tensile test was carried out using, and the breaking strength (TB) of each formulation was measured. The comparative example 1 was set to 100 and displayed as an index. The larger the numerical value (index), the better the strength.

(Chunking resistance)
Using test studless tires, the occurrence of chunking was measured when traveling a certain distance at a speed of 140 km / h on a dry circuit road surface, and the tire of Comparative Example 1 was evaluated with an index value of 100. The larger the index value, the better the anti-chunking performance. If this value is 95 or more, there is substantially no problem.

(Handling performance on ice and snow)
Using each test studless tire, actual vehicle performance was evaluated on ice and snow under the following conditions. As winter pneumatic tires, 195 / 65R15 size DS-2 pattern studless tires for passenger cars were manufactured, and these tires were mounted on domestic 2000cc FR cars. The test place was the Hokkaido Nayoro Test Course of Sumitomo Rubber Industries, Ltd., the temperature on ice was -1 to -6 ° C, and the temperature on snow was -2 to -10 ° C.
Handling performance (feeling evaluation): Starting, acceleration, and stopping were evaluated by feeling using the above vehicle. Feeling evaluation is based on Comparative Example 1 as 100, and the test driver judged that the performance was clearly improved was 120, and a good level that was never seen so far was 140. I did.

In Table 1, in Examples using a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, vulcanization reversion was suppressed, and the breaking strength and the chunking resistance were also good. Furthermore, while maintaining these performances, the handling performance on ice and snow was also good.

On the other hand, Comparative Example 1 in which the mixture was not blended and Comparative Example 2 in which the blending amount was small were inferior in vulcanization resistance, breaking strength, and chunking resistance. In Comparative Example 3 in which the amount of carbon black was increased without blending the mixture, and in Comparative Example 4 in which the amount of oil was further decreased without blending the mixture, the reversion resistance and handling performance on ice and snow were inferior. .

Claims (2)

A studless tire having a base tread produced using a rubber composition in which 1 to 10 parts by mass of a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid is blended with 100 parts by mass of the rubber component. The studless tire according to claim 1, wherein the rubber component contains natural rubber and butadiene rubber.