JP2010070039A - Rubber composition for clinch apex, and tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a tire having excellent wear resistance and rolling resistance, and to provide a rubber composition for a clinch apex having excellent workability and the tire made by using the same. <P>SOLUTION: With regard to the rubber composition for the clinch apex including diene rubber and hydrogenation liquid polybutadiene, the content of the hydrogenation liquid polybutadiene is 1-15 pts.mass per 100 pts.mass of the diene rubber, the content of syndiotactic-1, 2-polybutadiene is 1-15 mass% in 100 mass% of the diene rubber, and in the hydrogenation liquid polybutadiene, it is preferable that the number-average molecular weight is 600-20,000 and the hydrogenation rate of double bonds is 20-60 mol%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

Tires are used by being assembled on rims, and rubber that rubs against the rims may wear during driving, braking, and cornering. If the rubber of the part that rubs against the rim wears, the frictional force between the rim and the tire decreases, and the tire and rim may shift in the rotational direction during braking, which may deteriorate the static balance of the tire. . In addition, there is a possibility that air will not be retained between the rim and wear in the rim, and in the worst case, there is a risk of causing a burst.

For this reason, dilute polymers such as NR, BR, and SBR are usually used as rubber having excellent wear resistance, and carbon black is blended as a reinforcing agent in the clinch apex of a tire.

In order to further improve the wear resistance, it is conceivable to increase the amount of carbon black or to reduce the particle size of the carbon black to enhance the reinforcing property. This is not an effective technique because it deteriorates the workability of the tire and the rolling resistance of the tire.

For example, a rubber composition for clinch apex in which carbon black is blended with diene rubber has been disclosed, but it is improved in terms of ensuring all of good processability, rolling resistance, and wear resistance. (See Patent Document 1).

JP 2008-156446 A

The present invention solves the above-mentioned problems, provides a tire having excellent wear resistance and rolling resistance, and has excellent processability, and a rubber composition for a clinch apex, and a tire manufactured using the composition The purpose is to provide.

The present invention relates to a rubber composition for clinch apex 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 clinch apex produced using the rubber composition.

According to the present invention, since a rubber composition for clinch apex in which hydrogenated liquid polybutadiene is blended with diene rubber is used, the rubber composition has good processability and at the same time, In the used tire, excellent wear resistance and rolling resistance can be obtained.

The rubber composition for clinch apex of the present invention contains a diene rubber and hydrogenated liquid polybutadiene. Since hydrogenated liquid polybutadiene is blended (total amount or partially substituted) instead of process oil, good processability and rolling resistance can be maintained, and at the same time, excellent rubber strength and wear resistance can be obtained. .

Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), chloroprene rubber ( CR), ethylene propylene diene rubber (EPDM), halides of copolymers of isomonoolefin and paraalkylstyrene, and the like. 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 wear resistance is obtained.

It is preferable to contain 10% by mass or more of natural rubber in 100% by mass of the diene rubber. The blending amount of natural rubber is more preferably 15% by mass or more, and further preferably 20% by mass or more. If it is less than 10% by mass, it tends to be difficult to ensure rubber strength. On the other hand, the upper limit of the amount is preferably 60% by mass, more preferably 50% by mass, and still more preferably 40% by mass. When it exceeds 60% by mass, sufficient hardness cannot be obtained, and the durability of the bead tends to decrease.

It is preferable to contain 40% by mass or more of butadiene rubber in 100% by mass of the diene rubber. The blending amount of butadiene is more preferably 50% by mass or more, and still more preferably 60% by mass or more. If it is less than 40% by mass, the wear resistance tends to deteriorate. On the other hand, the upper limit of the amount is preferably 90% by mass, more preferably 85% by mass, and still more preferably 80% by mass.
If it exceeds 90% by mass, there is a problem in terms of workability.

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 and the wear resistance is improved while maintaining the effect of improving processability. 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. When it exceeds 350 nm, sufficient hardness cannot be obtained in the clinch apex, 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% by mass, sufficient durability 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 25 parts by mass or less, more preferably 20 parts by mass or less, and still more preferably 18 parts by mass or less with respect to 100 parts by mass of the diene rubber. When it exceeds 25 parts by mass, the wear resistance 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 the carbon black is preferably at most 160 m ² / g, more preferably at most 150m ² / g. When N ₂ SA exceeds 160 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 40 parts by mass or more, more preferably 45 parts by mass or more, and still more preferably 50 parts by mass or more with respect to 100 parts by mass of the diene rubber. If it is less than 40 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 120 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 90 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.

In addition to the diene rubber, syndiotactic-1,2-polybutadiene, hydrogenated liquid polybutadiene, oil, and carbon black, the rubber composition for clinch apex of the present invention includes additives usually used in the rubber industry. For example, zinc oxide, stearic acid, various anti-aging agents, waxes, vulcanizing agents such as 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 clinch apex 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 clinch apex of the present invention is applied to a clinch apex that is a rubber part disposed on the inner end of the sidewall, and is excellent in processability, by using the composition, The rubber strength of the tire is increased, and good wear resistance and rolling resistance can be obtained at the same time.

The tire of the present invention is produced by a usual method using the rubber composition for clinch apex. In other words, the rubber composition for clinch apex blended with various additives as necessary is extruded in accordance with the shape of the clinch apex at the unvulcanized stage, and is processed on a tire molding machine by a normal method. After forming and bonding together with other tire members to form an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

Further, the tire to which the rubber composition is applied is not particularly limited, but can be suitably applied particularly to a passenger vehicle 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 N220 (N ₂ SA: 113 m ² / g)
Carbon Black B: Show Black N110 made by Showa Cabot (N ₂ SA: 126 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: JOMO process X140 (Aroma oil) manufactured by Japan Energy Co., Ltd.
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Stearic acid “Kashiwa” manufactured by Nippon Oil & Fats Co., Ltd.
Zinc oxide: Zinc Hua 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS

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 produce a vulcanized rubber composition.

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

(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.

(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.

(Abrasion resistance)
About the produced vulcanized rubber composition, the amount of wear was measured using a Lambone-type wear tester under the conditions of room temperature, a load of 2.0 kgf, and a slip rate of 35%. The reciprocal of the amount of wear was displayed as an index with Comparative Example 1 as 100. Higher values indicate higher wear resistance.

(Rolling resistance)
Using the viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the vulcanized rubber composition thus prepared was measured for tan δ of each formulation under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ of Comparative Example 1 was set to 100, and the index was expressed by the following calculation formula. The larger the index, the better the rolling resistance.
(Rolling resistance index) = (tan δ of Comparative Example 1) ÷ (tan δ of each formulation) × 100

In the examples, the rubber composition was excellent in rubber kneadability, and at the same time had excellent rubber strength, wear resistance, and rolling resistance. 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 which did not mix | blend hydrogenated liquid polybutadiene, it was not able to have all these performances.

Claims (5)

A rubber composition for clinch apex comprising a diene rubber and hydrogenated liquid polybutadiene. The rubber composition for clinch apex 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 clinch apex according to claim 1 or 2, wherein the content of the syndiotactic-1,2-polybutadiene is 1 to 15% by mass in 100% by mass of the diene rubber. The rubber composition for clinch apex 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%. A tire having a clinch apex produced using the rubber composition according to claim 1.