JP5415741B2 - Rubber composition for breaker topping or band topping and pneumatic tire - Google Patents

Description

The present invention relates to a rubber composition for breaker topping or band topping and a pneumatic tire.

In recent automobile society, tires are required to have wear resistance and low rolling resistance (LRR) performance, and various measures have been taken. On the other hand, if the wear resistance performance of the tire is improved, the period of use in the market becomes longer, so there is a concern about durability performance due to internal damage of the tire. A typical example of internal damage is breaker edge damage (BEL: BRAKER EDGELOOSENS), and various causes of BEL are known. One of them is the fracture characteristics of breaker topping rubber and band topping rubber. There is a thing by the fall of.

As a technique for improving the fracture characteristics of breaker topping rubber and band topping rubber, it has been conventionally known to increase the amount of filler such as carbon black. However, in this method, the heat generation performance of the rubber is deteriorated and the rolling resistance performance is disadvantageous. Therefore, it is necessary to improve the fracture characteristics of the rubber without deteriorating the rolling resistance performance.

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 improving the fracture characteristics of rubber without deteriorating the heat generation performance (rolling resistance performance). Further, application to breakers and bands has not been studied in detail.
JP 2007-321041 A JP 2007-131730 A

The present invention solves the above-described problems and provides a rubber composition for breaker topping or band topping which improves the rolling resistance performance and rubber fracture characteristics in a well-balanced manner, and a pneumatic tire having a breaker and / or a band produced using the same The purpose is to provide.

The present invention contains a rubber component and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid, and the natural rubber content in 100% by mass of the rubber component is 40% by mass or more. The present invention relates to a rubber composition for topping or band topping.

The present invention also relates to a pneumatic tire having a breaker and / or a band produced using the rubber composition.

According to the present invention, a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid is further added to a rubber composition for break topping or band topping containing a predetermined amount of natural rubber as a rubber component. Therefore, both rolling resistance performance and rubber fracture characteristics can be achieved in a well-balanced manner.

The rubber composition for break topping or band topping of the present invention contains a predetermined amount of natural rubber (NR) as a rubber component, and contains a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid. When a rubber composition containing NR is sulfur vulcanized, a phenomenon called vulcanization reversion (reversion) occurs in which the rubber deteriorates or the cross-linked state deteriorates, but by further blending the mixture, vulcanization reversion can be achieved. Since it can suppress, the fracture | rupture characteristic of the outstanding rubber | gum can be acquired in a tire. Moreover, since deterioration of the heat generation performance is also suppressed, good rolling resistance performance can be obtained at the same time.

In addition, since reversion can be suppressed, it is possible to prevent a decrease in mechanical strength such as modulus and an increase in tan δ even if vulcanization is performed at a high temperature for a short time, while maintaining fracture characteristics and rolling resistance performance. It is also possible to improve the performance. Furthermore, in the unvulcanized rubber composition containing the mixture, good processability can be obtained.

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.

Examples of other rubber components that can be used together with NR in the rubber composition of the present invention include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), butyl rubber (IIR), and halogenated butyl rubber (X -IIR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), 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. Especially, in the rubber | gum composition for band toppings, it is preferable to use NR and SBR together from the reason that a favorable fracture characteristic is acquired.

In the rubber composition of the present invention, the content of NR in 100% by mass of the rubber component is 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more. If it is less than 40% by mass, the mechanical strength tends to decrease and the fracture strength tends to deteriorate.

Examples of SBR 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 of the present invention contains SBR together with NR, the content of SBR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. It is. If it is less than 10% by mass, the reversion resistance is lowered, and the fracture strength and steering stability tend to deteriorate. The content of SBR is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less. If it exceeds 50% by mass, the thermal stability at high heat tends to deteriorate.

When the rubber composition contains NR and optionally SBR, the total content thereof in 100% by mass of the rubber component is preferably 70% by mass or more. When the content is 70% by mass or more, excellent fracture strength is obtained, and the effect of reversion resistance is increased. The total 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 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 possible to consider the environment, to prepare for a future reduction in the supply of petroleum, and to sufficiently suppress reversion, vegetable oil-derived aliphatic carboxylic acids 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 decrease and the cost increases unnecessarily.

The content of the mixture is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, particularly preferably 1.4 parts by mass with respect to 100 parts by mass of the rubber component. That's it. If the amount is less than 0.2 parts by mass, sufficient vulcanization resistance cannot be ensured, and an improvement effect such as durability performance tends not to be obtained. The content of the mixture is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. If it exceeds 10 parts by mass, the processability may be deteriorated due to blooming, unnecessarily lowering the viscosity or increasing the adhesiveness. Moreover, the improvement of the effect commensurate with the added amount is reduced, and the cost is increased.

The rubber composition includes, in addition to the rubber component, a mixture of an aliphatic carboxylic acid zinc salt and an aromatic carboxylic acid zinc salt, compounding agents conventionally used in the rubber industry, such as carbon black, silica, etc. Fillers, silane coupling agents, oils or plasticizers, waxes, antioxidants, antiozonants, antioxidants, 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 50 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. Further, by blending such carbon black, necessary reinforcing properties can be imparted, and block rigidity, uneven wear resistance, and breaking strength can be secured.

If the average particle size of the carbon black exceeds 50 nm, the reinforcing property tends to deteriorate. 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 30 m ² / g or more, more preferably 50 m ² / g or more. When it is less than 30 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 preferably 25 parts by mass or more, more preferably 35 parts by mass or more, still more preferably 45 parts by mass or more, and most preferably 55 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 25 parts by mass, the reinforcing property is insufficient, and it tends to be difficult to ensure the required block rigidity, steering stability, uneven wear resistance, and fracture strength. The carbon black content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, and still more preferably 80 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 the case of the rubber composition for breaker topping, it is preferable to contain cobalt organic acid. Since the organic acid cobalt plays a role of cross-linking the cord and the rubber, the adhesion between the cord and the rubber can be improved by containing the organic acid cobalt. Specific examples of the organic acid cobalt include, for example, cobalt stearate, cobalt naphthenate, cobalt neodecanoate, and cobalt boron decanoate.

When it contains organic acid cobalt, 0.05 mass part or more is preferable in conversion of cobalt with respect to 100 mass parts of rubber components, and, as for content of organic acid cobalt, 0.1 mass part or more is more preferable. If it is less than 0.05 parts by weight, the (wet heat) adhesion between the steel cord plating layer and the rubber tends to be insufficient. Moreover, 3 mass parts or less are preferable, and, as for content of the said organic acid cobalt, 2 mass parts or less are more preferable. If it exceeds 3 parts by weight, thermal degradation tends to occur during processing, during vulcanization and during use.

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 a breaker topping and the rubber composition for a band topping according to the present invention are used for a breaker disposed inside the tread and radially outside the carcass, and a band disposed radially outside the breaker, respectively. Is done. Specifically, it is used for a breaker and a band shown in FIG. 3 of JP-A-2003-94918, FIG. 1 of JP-A-2004-67027, and FIGS. 1-4 of JP-A-4-356205.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, the rubber composition for breaker topping and band topping containing the above components is extruded in accordance with the shape of the breaker and / or the band at an unvulcanized stage, and put on the tire molding machine together with other tire members. Then, an unvulcanized tire is formed by molding by a usual method. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

A pneumatic tire having a breaker and / or a band produced using the rubber composition for a breaker topping or a band topping of the present invention is suitably used for a tire for a passenger car, a light truck tire, and a truck bus tire.

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 (styrene content: 23.5% by mass) manufactured by JSR
Carbon black: N550 manufactured by Showa Gabot (N ₂ SA: 42 m ² / g, average particle size: 48 nm, DBP oil absorption: 113 ml / g)
Reversion inhibitor (mixture of zinc salt of aliphatic carboxylic acid and zinc salt of aromatic carboxylic acid): Activator 73A ((i) zinc salt of aliphatic carboxylic acid: fatty acid derived from palm oil ( (Zinc number of carbon: 8-12), (ii) aromatic carboxylic acid zinc salt: zinc benzoate, content molar ratio: 1/1, zinc content: 17% by mass)
Cobalt naphthenate: Cobalt naphthenate aging inhibitor manufactured by Nikka Sansho Co., Ltd .: NOCRACK 6C (N- (1,3-dimethylbutyl) -N'-phenyl-p manufactured by Ouchi Shinsei Chemical Co., Ltd.) -Phenylenediamine zinc oxide: Zinc Hana No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS (N-t manufactured by Ouchi Shinsei Chemical Co., Ltd.) -Butyl-2-benzothiazyl sulfenamide)

Examples 1-8 and Comparative Examples 1-4
According to the blending contents shown in Tables 1 and 2 (Table 1: Rubber composition for breaker topping, Table 2: Rubber composition for band topping), using a Banbury mixer, among the blended materials, other than sulfur and vulcanization accelerator The material was kneaded for 5 minutes at 150 ° C. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was vulcanized at 150 ° C. for 30 minutes to obtain a vulcanized rubber composition.

The following evaluation was performed using the obtained unvulcanized rubber composition and vulcanized rubber composition. Each test result is shown to Tables 1-2.

(Processability)
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.

(Viscoelasticity test)
A strip-shaped sample of 4 mm width × 30 mm length × 1.5 mm thickness was prepared from the vulcanized rubber composition, using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., temperature 70 ° C., frequency 10 Hz, dynamic strain ± The complex elastic modulus (E ^* ) and loss tangent (tan δ) of each formulation were measured under the condition of 2%. In addition, it shows that rigidity is high and it is favorable, so that E ^* is large, and exothermic property is low, and it shows that it is excellent.

(Tensile test)
For the vulcanized rubber composition, using a No. 3 dumbbell according to JIS K6251, the sample is punched out so that the tensile direction is parallel to the tire circumferential direction, and a tensile test is performed to measure the breaking strength and breaking elongation. did.

In the examples in which the anti-reversion agent was blended, good breaking strength and breaking elongation were obtained without deteriorating the heat generation performance, and both the heat generation performance and the fracture characteristics could be satisfactorily achieved. Moreover, rigidity and workability were also good. Specifically, when 3 parts by mass of the anti-reversion agent is added, the tensile properties are improved, but if the amount of sulfur remains the same, E ^* increases, which may affect the steering stability performance ( Examples 1 and 5). Therefore, by reducing the amount of sulfur, the hardness E ^* does not increase, the tensile properties are improved, and the workability can be expected to be improved (Examples 2 to 4 and 6 to 8).

On the other hand, in Comparative Examples 1 and 3 in which no anti-reversion agent was blended, the breaking strength and breaking elongation (particularly breaking elongation) were inferior, and it was impossible to achieve both heat generation performance and breaking characteristics. Moreover, the performance was inferior also in Comparative Examples 2 and 4 in which the NR amount was 30% by mass.

Claims (3)

Containing a rubber component , a carbon black having a DBP oil absorption of 100 to 160 ml / 100 g, and a mixture of a zinc salt of an aliphatic carboxylic acid and a zinc salt of an aromatic carboxylic acid,
A rubber composition for breaker topping or band topping, wherein the natural rubber content in 100% by mass of the rubber component is 40% by mass or more. The rubber composition for breaker topping or band topping according to claim 1, wherein the rubber component includes natural rubber and / or styrene butadiene rubber. A pneumatic tire having a breaker and / or band manufactured with claim 1 or 2 rubber composition.