JP2010070641A - Rubber composition for chafer and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for chafer excellent in work efficiency of rim assembling, producing a tire having high rubber strength, and excellent in processability; and to provide a tire produced using the composition. <P>SOLUTION: The rubber composition comprises a diene type rubber and a hydrogenated liquid polybutadiene. Preferably, the rubber composition for chafer has a hydrogenated liquid polybutadiene content of 1-15 pts.mass based on 100 pts.mass of the diene type rubber, a number-average molecular weight of 600-20,000, and the hydrogen addition rate for the double bond of 20-60 mol%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a rubber composition for a chafer and a tire.

In recent years, there has been an increasing demand for low flat tires and run flat tires that can travel a certain distance even during puncture for the purpose of improving the performance of the tires. However, since these have the characteristics that the strength of the sidewall portion is high and the bending rigidity is high, the workability is inferior to that of the high flat tire when assembled to the tire wheel.

Furthermore, when performing rim assembly work with an automatic rim assembly machine, automatic assembly may not be possible due to the hardness of the sidewall portion. For example, damage such as tearing of the rubber directly in contact with the rim may occur, significantly reducing the safety of the tire and making it unusable.

As a means to improve such problems and improve fracture resistance, it is known to increase the amount of carbon black used as a reinforcing agent in the chafer part, or to reduce the particle size of carbon black. Both of these techniques deteriorate the processability during kneading of the rubber composition.

For example, although a rubber composition for a chafer in which carbon black is further blended with natural rubber and / or polyisoprene rubber and polybutadiene rubber is disclosed, there is room for further improvement in workability and workability of the rim assembly ( Patent Document 1).

JP 2001-226526 A

The present invention solves the above-mentioned problems, provides a tire having excellent workability of rim assembly, high rubber strength, and excellent processability, and is manufactured using the rubber composition for chafers and the composition. The object is to provide a tire.

The present invention relates to a rubber composition for chafers comprising a diene rubber and hydrogenated liquid polybutadiene.
The content of the hydrogenated liquid polybutadiene is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the diene rubber.
The content of the syndiotactic-1,2-polybutadiene is preferably 1 to 15% by mass in 100% by mass of the diene rubber.

The hydrogenated liquid polybutadiene preferably has a number average molecular weight of 600 to 20000 and a double bond hydrogenation rate of 20 to 60 mol%.
The present invention also relates to a tire having a chafer manufactured using the rubber composition.

According to the present invention, since the rubber composition for chafers in which hydrogenated liquid polybutadiene is blended with diene rubber is used, the rubber composition has good processability and at the same time uses the composition. In the conventional tire, excellent workability of the rim assembly and high rubber strength can be obtained.

The rubber composition for chafers of the present invention contains a diene rubber and hydrogenated liquid polybutadiene. Since the hydrogenated liquid polybutadiene is blended (total amount or partially substituted) instead of the process oil, the strength of the rubber of the tire can be increased without reducing the processability of the rubber composition. Therefore, it is possible to prevent damage to the portion that directly contacts the rim during the rim assembly operation.

Examples of the diene rubber include natural rubber (NR), various butadiene rubbers (BR), styrene-butadiene copolymer rubber (SBR), isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber ( CR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isoprene copolymer rubber, and isoprene-butadiene copolymer rubber. These may be used alone or in combination of two or more. NR and / or BR are preferable because an effect of improving rubber strength and fuel efficiency can be obtained.

It is preferable to contain 30% by mass or more of natural rubber in 100% by mass of the diene rubber. The blending amount of natural rubber is more preferably 35% by mass or more, and still more preferably 40% by mass or more. If it is less than 30% by mass, it tends to be difficult to ensure rubber strength. On the other hand, the upper limit of the blending amount is preferably mass%, more preferably 90 mass%, and still more preferably 80 mass%. When it exceeds 90% by mass, sufficient hardness cannot be obtained, and the durability of the bead tends to decrease.

It is preferable to contain 10% by mass or more of butadiene rubber in 100% by mass of the diene rubber. The blending amount of butadiene is more preferably 15% by mass or more, and further preferably 20% by mass or more. If it is less than 10% by mass, wear tends to deteriorate due to rubbing with the rim. On the other hand, the upper limit of the amount is preferably 70% by mass, more preferably 65% by mass, and still more preferably 60% by mass. When it exceeds 70 mass%, workability tends to deteriorate.

The rubber composition may contain syndiotactic-1,2-polybutadiene (hereinafter also referred to as “SPB”). By blending the material together with the hydrogenated liquid polybutadiene, the rubber strength is increased while maintaining the workability improving effect, and the workability of the rim assembly is also improved. As SPB, for example, butadiene rubber in which syndiotactic-1,2-polybutadiene is dispersed (hereinafter also referred to as “SPB-containing BR”) can be used.

In the SPB-containing BR, syndiotactic-1,2-polybutadiene is sufficiently finely dispersed in the BR serving as a matrix.

In the SPB-containing BR, the average primary particle size of SPB in BR is preferably 350 nm or less, more preferably 300 nm or less. If it exceeds 350 nm, sufficient hardness cannot be obtained in the chafer, and the durability of the bead tends to decrease. In addition, the said average primary particle diameter was measured as an average value of the absolute maximum length by the image analysis process of a transmission electron micrograph.

The content of SPB in the SPB-containing BR is preferably 8% by mass or more, more preferably 10% by mass or more. If it is less than 8 mass%, sufficient durability of the bead tends not to be obtained. The content is preferably 20% by mass or less, more preferably 16% by mass or less. When it exceeds 20 mass%, workability tends to deteriorate. In addition, the content rate of SPB in SPB containing BR is shown by the amount of boiling n-hexane insoluble matter.

The SPB in the SPB-containing BR is preferably a crystal in order to maintain high hardness in the operating temperature range.
Examples of the SPB-containing BR include Ube Industries, Ltd., VCR412, VCR617, and the like.

In the rubber composition, the amount of syndiotactic-1,2-polybutadiene in 100% by mass of the diene rubber is preferably 1% by mass or more, and more preferably 3% by mass or more. If it is less than 1% by mass, the effect of improving rubber strength tends to be small. Further, the content is preferably 15% by mass or less, and more preferably 12% by mass or less. When it exceeds 15% by mass, the rubber is not well organized in the rubber kneading step, and the processability tends to be deteriorated.

Hydrogenated liquid polybutadiene is a component used as a softening agent instead of process oil, and can be produced by hydrogenating liquid polybutadiene. Hydrogenation can be produced by a known hydrogenation method using a catalyst such as palladium.
In the present invention, hydrogenated liquid polybutadiene is not included in the diene rubber.

The number average molecular weight (Mn) of the hydrogenated liquid polybutadiene is preferably 600 or more, and more preferably 800 or more. Thereby, while improving workability, rubber strength can be improved. When the molecular weight is less than 600, the processability improvement effect is high, but the rubber strength improvement effect is small, and desirable physical properties tend not to be obtained. The number average molecular weight is preferably 20000 or less, and more preferably 18000 or less. When the molecular weight exceeds 20000, the effect as a rubber softener tends to be small.
In the present invention, the number average molecular weight is a value converted from standard polystyrene using a gel permeation chromatograph (GPC).

The hydrogenation rate of the double bond of the hydrogenated liquid polybutadiene is preferably 20 mol% or more, and more preferably 30 mol% or more. When the hydrogenation rate is less than 20 mol%, sulfur crosslinking occurs as a rubber component, and thus the effect as a softening agent tends to be difficult to obtain. The hydrogenation rate is preferably 60 mol% or less, and more preferably 55 mol% or less. When the hydrogenation rate exceeds 60 mol%, the rubber hardness tends to decrease. By setting the hydrogenation rate within the above range, better rubber strength can be obtained. Here, the hydrogenation rate can be calculated from the spectrum reduction rate of the unsaturated bond portion of the spectrum obtained by measuring proton NMR.

The compounding amount of the hydrogenated liquid polybutadiene is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and still more preferably 3 parts by mass or more with respect to 100 parts by mass of the diene rubber. When the blending amount is less than 1 part by mass, a sufficient softening effect tends to be hardly obtained. Moreover, 15 mass parts or less are preferable, as for a compounding quantity, 10 mass parts or less are more preferable, and 7 mass parts or less are still more preferable. If the blending amount exceeds 15 parts by mass, the workability decreases and the wear resistance tends to decrease. By setting the blending amount within the above range, both good processability and rubber strength can be achieved.

The rubber composition may contain an oil or a plasticizer together with the hydrogenated liquid polybutadiene. Thereby, while improving workability, the intensity | strength of rubber | gum can be raised.
As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used.

Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil (aromatic process oil). As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Of these, aromatic process oils, paraffinic process oils, and naphthenic process oils are preferably used from the viewpoint of excellent compatibility in the rubber composition and excellent processability.

When the said rubber composition contains oil, 2 mass parts or more are preferable with respect to 100 mass parts of diene rubbers, 3 mass parts or more are more preferable, and 5 mass parts or more are still more preferable. If the amount is less than 2 parts by mass, the workability improving effect and the strength improving effect tend not to be obtained. On the other hand, the blending amount is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, and still more preferably 15 parts by mass or less with respect to 100 parts by mass of the diene rubber. If it exceeds 20 parts by mass, wear due to rubbing with the rim tends to deteriorate.

You may mix | blend carbon black with the said rubber composition. Thereby, the fracture resistance of rubber can be improved. As carbon black, GPF, HAF, ISAF, SAF, etc. can be used, for example.

When carbon black is used, the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 30 m ² / g or more, and more preferably 40 m ² / g or more. When N ₂ SA is less than 30 m ² / g, the reinforcing property of rubber tends to be remarkably lowered. Also, _N 2 SA of carbon black is preferably 150 meters ² / g or less, more preferably 140 m ² / g. When N ₂ SA exceeds 150 m ² / g, the viscosity at the time of unvulcanization becomes very high, and the workability tends to deteriorate or the fuel consumption tends to deteriorate. The nitrogen adsorption specific surface area of carbon black is determined by the method A of JIS K6217, item 7.

The content of carbon black is preferably 30 parts by mass or more, more preferably 35 parts by mass or more, and still more preferably 40 parts by mass or more with respect to 100 parts by mass of the diene rubber. If it is less than 30 parts by mass, the reinforcing property is insufficient, and it tends to be difficult to ensure the required rigidity and wear resistance. The carbon black content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 70 parts by mass or less. If it exceeds 100 parts by mass, the workability tends to deteriorate or the hardness tends to be too high.

In addition to the diene rubber, syndiotactic-1,2-polybutadiene, hydrogenated liquid polybutadiene, oil, and carbon black, the rubber composition for chafer of the present invention, additives commonly used in the rubber industry, For example, zinc oxide, stearic acid, various anti-aging agents, vulcanizing agents such as wax and sulfur, vulcanization accelerators and the like can be appropriately blended.

As the vulcanization accelerator, commonly used ones can be used. For example, mercaptobenzothiazole, dibenzothiazyl disulfide, N-cyclohexylbenzothiazylsulfenamide, N-tert-butyl-2-benzothiazoli Examples include rusulfenamide and N, N-dicyclohexyl-2-benzothiazolylsulfenamide.

The rubber composition for a chafer of the present invention is produced by a general method. That is, it can be produced by kneading the above components and, if necessary, additives with a Banbury mixer, kneader, open roll or the like and then vulcanizing.

The rubber composition for a chafer of the present invention is applied to a chafer disposed on the side in contact with the rim, has excellent processability, and the rubber strength of the tire can be increased by using the composition. The workability of the rim assembly is improved.

The tire of the present invention is produced by a usual method using the chafer rubber composition. That is, the rubber composition for chafers blended with various additives as necessary is extruded to match the shape of the chafer at the unvulcanized stage, and molded by a normal method on a tire molding machine. Then, after bonding together with other tire members to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The tire to which the rubber composition is applied is not particularly limited, but can be suitably applied particularly to a low flat tire (flat ratio is 50% or less) and a run flat tire.

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

Production Example 1
After adding 300 g of THF and 10 g of 10% palladium carbon to 200 g of liquid polybutadiene (Ricton 130 (number average molecular weight 2500) manufactured by Sartomer), hydrogen was added so that the pressure became 5.0 kg / cm ² after nitrogen substitution. The reaction was carried out at 80 ° C. The hydrogenation rate was 52 mol% as calculated from the spectrum reduction rate of the unsaturated bond portion of 100-MHz proton NMR by preparing a 15% by mass solution using carbon tetrachloride as a solvent.

(material)
Natural rubber: RSS # 3 grade butadiene rubber: BR150B manufactured by Ube Industries, Ltd.
Syndiotactic-1,2-polybutadiene: VCR412 manufactured by Ube Industries, Ltd. (high cis BR with 98% cis 1,4 bond amount, 12% by mass of SPB having high crystallinity (average primary particle size of crystal 250 nm)) Added and dispersed alloy (SPB-containing BR), ML _{1 + 4} (100 ° C.) 45)
Carbon Black A: Show Black Cabot Show Black N550 (N ₂ SA: 42 m ² / g)
Carbon Black B: Show Black N220 manufactured by Showa Cabot (N ₂ SA: 113 m ² / g)
Hydrogenated liquid polybutadiene: Partial hydrogenation prototype of Ricon 130 manufactured by Sartomer Company, Inc .: manufactured in Production Example 1. Liquid polybutadiene: Ricon 130 manufactured by Sartomer Company, Inc. (number average molecular weight (Mn) = 2500)
Process oil: Diana process AH-24 (aromatic oil) manufactured by Idemitsu Kosan Co., Ltd.
Wax: Sunnock N (Ouchi Shinsei Chemical Co., Ltd.)
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Stearic acid “Kashiwa” manufactured by Nippon Oil & Fats Co., Ltd.
Zinc oxide: Zinc oxide sulfur manufactured by Mitsui Mining & Smelting Co., Ltd .: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Noxeller CZ manufactured by Ouchi Shinsei Co., Ltd.

Examples 1-6 and Comparative Examples 1-7
(Production method)
Among the blending contents shown in Table 1, various chemicals excluding sulfur and a vulcanization accelerator are kneaded with a Banbury mixer, and sulfur and a vulcanization accelerator are added to the obtained kneaded product, and an open roll is used. By kneading, an unvulcanized rubber composition was obtained.
The unvulcanized rubber composition was press vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

Further, the unvulcanized rubber composition is molded into a chafer shape and bonded together with other tire members on a tire molding machine to form an unvulcanized tire, and press vulcanized at 150 ° C. for 30 minutes. A repair tire was manufactured.

The following evaluation was performed using the obtained unvulcanized rubber composition, vulcanized rubber composition, and repair tire. Each test result is shown in Table 1.

(Rim assembly performance)
Rim assembly work was carried out on the produced repair tire using an automatic mounter. Three tests were carried out for each formulation and judged according to the following criteria.
×: Scratches occur in the chafer part in all three. Δ: Scratches occur in one or two.

(Rubber strength)
The prepared vulcanized rubber composition was subjected to a tensile test using a No. 3 dumbbell according to JIS K6251 and measured for breaking strength (TB) and elongation at break EB (%). The value of (TB × EB) / 2 was taken as rubber strength, and the measurement results were shown as an index with Comparative Example 1 taken as 100. The larger the value, the better the rubber strength.

(Rubber knead processability)
The Mooney viscosity of the unvulcanized rubber composition was measured at 130 ° C. according to JIS K6300. It was shown as an index with Comparative Example 1 as 100. The smaller the index, the lower the viscosity and the easier the processing.

In the examples, the rubber composition was excellent in rubber kneading workability, and at the same time, because it had high rubber strength, it was excellent in rim assembly workability. In Examples 3 to 6 using syndiotactic-1,2-polybutadiene, it was possible to increase the strength of the rubber while maintaining the rubber kneading processability. On the other hand, in the comparative example in which no hydrogenated liquid polybutadiene was blended, the rubber strength was low and the rim assembly workability was inferior.

Claims (5)

A rubber composition for chafers comprising a diene rubber and hydrogenated liquid polybutadiene. The rubber composition for chafers according to claim 1, wherein the content of the hydrogenated liquid polybutadiene is 1 to 15 parts by mass with respect to 100 parts by mass of the diene rubber. The rubber composition for chafers according to claim 1 or 2, wherein the content of syndiotactic-1,2-polybutadiene is 1 to 15% by mass in 100% by mass of the diene rubber. The rubber composition for chafer according to any one of claims 1 to 3, wherein the hydrogenated liquid polybutadiene has a number average molecular weight of 600 to 20000 and a hydrogenation rate of double bonds of 20 to 60 mol%. The tire which has a chafer produced using the rubber composition in any one of Claims 1-4.