JP5420882B2 - Insulation rubber composition and tire - Google Patents

Description

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

In an automobile tire, a member called an installation (inner ins) is disposed between an inner liner and a carcass. In the installation, natural rubber is used as a rubber component. However, when natural rubber is used and sulfur vulcanization is performed, it is called vulcanization reversion (reversion) in which the rubber deteriorates or the cross-linked state deteriorates. A phenomenon occurs.

On the other hand, in recent years, tires are often produced by vulcanization at a high temperature for a short time in order to increase the productivity of tires. In such a case, the above phenomenon becomes particularly remarkable. Furthermore, the modulus and hardness may decrease due to reversion, or tan δ may increase unnecessarily, resulting in a deterioration in fuel consumption.

Patent Document 1 contains a predetermined amount of a mixture of an aliphatic carboxylic acid and an aromatic carboxylic acid zinc salt, silica having a specific specific surface area, and a silane coupling agent, while suppressing reversion and rolling resistance and workability. A rubber composition that improves wear resistance and wet skid performance is disclosed. Patent Document 2 proposes a rubber composition containing carbon black and sulfur having predetermined characteristic values and improving the low heat build-up, rubber chip resistance and wear resistance in a well-balanced manner.

However, there is still room for improvement in terms of suppressing reversion and improving the rolling resistance and fracture strength in a well-balanced manner. In addition, no detailed examination has been made on application to installation.

JP 2007-321041 A JP 2007-131730 A

The present invention provides a rubber composition for installation that solves the above-mentioned problems, suppresses reversion, suppresses rolling resistance, and improves fracture strength, and a tire having an installation produced thereby. With the goal. It is another object of the present invention to produce the rubber composition and tire with higher production efficiency and provide them to consumers at a lower cost.

The present invention relates to a rubber composition for insulation containing a rubber component and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid.

The content of the mixture of the aliphatic carboxylic acid zinc salt and the aromatic carboxylic acid zinc salt is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

The present invention also relates to a tire having an insulation made using the rubber composition.

According to the present invention, since it is a rubber composition for insulation in which a rubber component is mixed with a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, reversion can be suppressed and rolling resistance can be suppressed. Reduction (low fuel consumption) and breaking strength can be achieved.

The rubber composition for insulation of the present invention includes a rubber component and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. By using the mixture, since reversion (reversion of vulcanization) is suppressed, deterioration of the rubber and the cross-linked state can be suppressed, and the breaking strength of the rubber can be improved. Moreover, when the said mixture is used, favorable low fuel consumption can also be obtained in a tire, maintaining the outstanding fracture strength. Furthermore, it is possible to obtain good processability in the unvulcanized rubber composition. Moreover, since reversion can be suppressed, vulcanization can be performed in a short time at a high temperature, which leads to an improvement in productivity.

The rubber component used in the rubber composition of the present invention is not particularly limited. For example, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), butyl rubber (IIR), Examples include chloroprene rubber (CR), ethylene-propylene-diene rubber (EPDM), and acrylonitrile-butadiene rubber (NBR). These may be used alone or in combination of two or more. Of these, NR and SBR are preferable from the viewpoint of processability and mechanical strength, and it is more preferable to use both components in combination.

In the rubber composition of the present invention, NR that can be used is not particularly limited. For example, SIR20, RSS # 3, TSR20, and the like that are common in the tire industry can be used.

When the rubber composition contains NR, the content of NR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and further preferably 50% by mass or more. If it is less than 30% by mass, it tends to be difficult to ensure fracture strength. The NR content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. When it exceeds 90 mass%, workability tends to deteriorate.

Examples of SBR that can be used in the rubber composition of the present invention include emulsion polymerization styrene butadiene rubber (E-SBR) and solution polymerization styrene butadiene rubber (S-SBR).

The styrene content of SBR is preferably 15% by mass or more, more preferably 20% by mass or more. If it is less than 15% by mass, the balance of fuel efficiency tends to deteriorate. The styrene content is preferably 45% by mass or less, more preferably 40% by mass or less. When it exceeds 45 mass%, there exists a tendency for fracture strength to fall.

When the rubber composition contains SBR, the content of SBR 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 workability tends to deteriorate. The content of SBR is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. If it exceeds 70% by mass, it tends to be difficult to ensure the fracture strength.

In the rubber composition for insulation, when NR and / or SBR are used, the total content of NR and SBR is preferably 70% by mass or more in 100% by mass of the rubber component. When the content is 70% by mass or more, excellent fracture strength is obtained, and the effect of reversion resistance is increased. The content 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.

As the aliphatic carboxylic acid in the zinc salt of 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, soybean oil, Examples include aliphatic carboxylic acids derived from vegetable oils such as cottonseed oil, sesame oil, linseed oil, castor oil and rapeseed oil, aliphatic carboxylic acids derived from animal oils such as beef tallow, and aliphatic carboxylic acids chemically synthesized from petroleum. It is also possible to prepare for future reductions in the supply of petroleum, and furthermore, since vulcanization reversion can be sufficiently suppressed, aliphatic carboxylic acids derived from vegetable oils are preferred, and palm oil, palm kernel oil or palm Oil-derived aliphatic carboxylic acids are more preferred.

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.

Examples of the aromatic carboxylic acid in the zinc salt of the aromatic carboxylic acid include benzoic acid, phthalic acid, melittic 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 decrease and the cost increases unnecessarily.

The content of the mixture is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and further preferably 3 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 1 part by mass, sufficient reversion resistance cannot be ensured, and the improvement effect of reducing rolling resistance and the like tends to be difficult to obtain. The content of the mixture is 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 5 parts by mass or less. If it exceeds 10 parts by mass, the viscosity may be unnecessarily lowered, resulting in poor processability or blooming.

The rubber composition of the present invention may be blended with fatty acids such as stearic acid, palmitic acid, myristic acid, lauric acid, caprylic acid, oleic acid, linoleic acid, and stearic acid because of its low cost. Is preferred.

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, Silica and other fillers, silane coupling agents, oil or plasticizers, antioxidants, ozone degradation inhibitors, anti-aging agents, vulcanizing agents such as zinc oxide, peroxides, sulfur, sulfur-containing compounds, vulcanization acceleration An agent, a vulcanization acceleration aid and the like may be contained.

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

Carbon black having an average particle size of 31 nm or less and / or a DBP oil absorption of 100 ml / 100 g or more is preferable. If the viscosity is too low, the unvulcanized rubber composition becomes difficult to handle, and the molded products are excessively adhered to each other, and the moldability is deteriorated or the workability is impaired. When used with a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, the viscosity of the unvulcanized rubber can be increased and the processability can be improved. Also, by blending such carbon black, block rigidity, uneven wear resistance, wear resistance, and breaking strength can be ensured.

If the average particle size of the carbon black exceeds 31 nm, the reinforcing property tends to deteriorate. The average particle diameter is more preferably 25 nm or less, still more preferably 23 nm or less. The average particle diameter is preferably 15 nm or more, more preferably 19 nm or more. If it is less than 15 nm, the workability deteriorates, the dispersion becomes worse, and the cost tends to increase.
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 tan δ of the rubber composition tends to be high, and good fuel economy tends not to be obtained. The DBP oil absorption is more preferably 110 ml / 100 g or more, and still more preferably 120 ml / 100 g or more. The DBP oil absorption is preferably 160 ml / 100 g or less, more preferably 150 ml / 100 g or less. When it exceeds 160 ml / 100 g, there is a tendency that good fracture characteristics cannot be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 100 m ² / g or more. When it is less than 50 m ² / g, the reinforcing property is lowered and the fracture strength tends to be deteriorated. Also, _N 2 SA of carbon black is preferably 200 meters ² / g or less, and more preferably not more than 150m ² / g. When it exceeds 200 m ² / g, the low heat build-up of the rubber composition after vulcanization is inferior, and the fuel efficiency tends to deteriorate.

The content of carbon black is 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and most preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. If the carbon black content is less than 10 parts by mass, the reinforcing property is insufficient, and it tends to be difficult to ensure necessary block rigidity, steering stability, uneven wear resistance, and breaking strength. The carbon black content is 100 parts by mass or less, preferably 80 parts by mass or less, and more preferably 60 parts by mass or less. When the content of carbon black exceeds 100 parts by mass, workability tends to deteriorate or the hardness tends to be too high.

The rubber composition of the present invention 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.

The rubber composition for insulation of the present invention is used for a member called an insulation provided between an inner liner and a carcass. Specifically, it is used in the installation section shown in FIGS. 1-2 of JP-A-2008-150523, FIG. 1 of JP-A-2007-269876, and FIGS. 1-2 of JP-A-2007-284537. The

The tire of the present invention is produced by a usual method using the rubber composition.
That is, the rubber composition for insulation containing the above components is extruded in accordance with the shape of the insulation at an unvulcanized stage, and is molded together with other tire members by a normal method on a tire molding machine. By doing so, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The tire having the insulation produced using the rubber composition for insulation of the present invention is suitably used for passenger cars, light trucks, vans, trucks and buses.

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
Styrene butadiene rubber (SBR): SBR1502 manufactured by JSR Corporation (styrene content: 23.5% by mass)
Carbon black: Diamond black N220 (N ₂ SA: 114 m ² / g, average particle size: 20 nm, DBP oil absorption: 114 ml / 100 g) manufactured by Mitsubishi Chemical Corporation
Stearic acid: Paulownia mixture of Nippon Oil & Fats Co., Ltd. (mixture of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid): Activator 73A ((i) zinc salt of aliphatic carboxylic acid: Zinc salt of fatty acid derived from palm oil (carbon number: 8 to 12), (ii) zinc salt of aromatic carboxylic acid: zinc benzoate, content molar ratio: 1/1, zinc content: 17% by mass)
Zinc Oxide: Toho Zinc Co., Ltd.
Sulfur: Sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS (Nt-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-2 and Comparative Examples 1-2
According to the mixing | blending content shown in Table 1, using a 1.7L Banbury mixer, materials other than sulfur and a vulcanization accelerator were knead | mixed for 5 minutes on 150 degreeC conditions, and the kneaded material was obtained. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes at 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was molded into an insulation shape, bonded to another tire member, and vulcanized under the vulcanization conditions shown in Table 1 to obtain a test tire (tire size: 11R22.5, Heavy load radial tire) was produced.

The following evaluation was performed using the obtained unvulcanized rubber composition and test tire (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)
Samples were cut out from the installations of the test tires produced in Examples 1-2 and Comparative Examples 1-2, and the breaking strength (tensile strength) and breaking elongation (elongation at break) were measured in accordance with JIS K6251-1993. Then, Examples 1 and 2 and Comparative Example 2 were indexed by the following formula with Comparative Example 1 as 100. The higher the index, the better.
(Index of tensile strength and elongation) = (Tensile strength and elongation of each formulation) / (Tensile strength and elongation of Comparative Example 1) × 100

(Rolling resistance)
Using a rolling resistance test, the test tire was mounted on a regular rim (22.5 × 8.25 15 ° deep rim), and the rolling resistance was measured at an internal pressure of 700 kPa, a speed of 80 km / h, and a load of 24.52 KN. The tire was taken as an index (rolling resistance index) when the tire of Comparative Example 1 was taken as 100. The larger the value, the smaller the rolling resistance and the better.

(Viscosity / workability)
In accordance with JIS K 6300-1 “Unvulcanized rubber—physical properties—Part 1: Determination of viscosity and scorch time using Mooney viscometer”, it was heated by preheating for 1 minute using a Mooney viscosity tester. Under the temperature condition of 130 ° C., the small rotor was rotated, and the Mooney viscosity (ML _{1 +} 4/130 ° C.) of the unvulcanized rubber composition after 4 minutes was measured. The numbers after the decimal point are rounded off. Processability was evaluated based on the Mooney viscosity, and those with 30 or more and less than 50 were evaluated as ○, and those with less than 30 or 50 or more were evaluated as ×.

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, reversion was suppressed and the fracture strength was good. Further, the rolling resistance (low fuel consumption) was good while maintaining the breaking strength. The processability of the unvulcanized rubber composition was also excellent. On the other hand, Comparative Examples 1 and 2 in which the mixture was not blended were inferior in reversion resistance, fracture strength, and rolling resistance.

Claims (4)

A rubber composition for insulation containing a rubber component, carbon black having a DBP oil absorption of 110 to 150 ml / 100 g, and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. The rubber composition for insulation according to claim 1, wherein the content of the mixture of the zinc salt of the aliphatic carboxylic acid and the zinc salt of the aromatic carboxylic acid is 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. . The rubber composition for insulation according to claim 1 or 2, comprising natural rubber and styrene butadiene rubber. A tire having an insulation made using the rubber composition according to any one of claims 1 to 3 .