JP2006225600A - Pneumatic tire using rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire using a rubber composition highly manifesting low exothermicity together with workability in a supersized tire by suppressing outbreak of chipping. <P>SOLUTION: The pneumatic tire comprises the rubber composition comprising: a rubber component (A) composed of a rubber master batch obtained by mixing a rubber latex with a slurry solution which is a dispersion of carbon black in water, and then coagulating; and silica (B) which is heat-treated with silicone oil of ≥ pts.wt. based on the 100 pts.wt., of the rubber component (A). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire using a rubber composition.

  Conventionally, silica that has been heat-treated with silicon oil is often used as a reinforcing filler for rubber in order to obtain workability (see, for example, Patent Document 1).

In addition, it is known to use a masterbatch as a method for producing rubber having excellent processability. This is because the rubber latex is mixed with a slurry in which carbon black or the like is mixed in advance at a certain ratio and the filler is finely dispersed in water by a mechanical force, and then a coagulant such as an acid, inorganic salt, or amine is added. In addition, the solidified product is obtained by collecting and drying (see, for example, Patent Document 2).
JP 2004-123926 A JP 2004-99625 A

  By the way, in recent years, in the market, it is required to suppress the occurrence of chipping which is partially generated on a pneumatic tire and to achieve both high exothermicity and workability particularly in a super-large tire. .

  The above-described master batch is excellent in terms of greatly improving carbon dispersion and reducing heat generation. However, while greatly improving the carbon dispersion, it was difficult to make a blend that satisfies the performance required by the market, such as a high degree of compatibility between low heat generation and workability associated with further ultra-large tire requirements. .

  Therefore, in view of the above problems, the present invention provides a pneumatic tire using a rubber composition that can suppress the occurrence of chipping and can achieve both high exothermic property and workability in a particularly large tire. The purpose is to provide.

  The present inventors have found that the above object can be achieved by using a masterbatch production method and containing silica heat-treated with silicon oil in a rubber composition used in a pneumatic tire. As a result, the present invention has been completed.

  A feature of the present invention is that a rubber component (A) comprising a rubber master batch obtained by mixing a rubber latex and a slurry solution in which carbon black is dispersed in water and coagulating, and 100 parts by weight of the rubber component (A) On the other hand, the gist of the present invention is a pneumatic tire using a rubber composition characterized by containing silica (B) heat-treated with 5 parts by weight or more of silicon oil.

  According to the pneumatic tire according to the feature of the present invention, it is possible to suppress the occurrence of chipping and to achieve both high exothermic property and workability at a high level, particularly in an ultra-large tire. In addition, it is preferable that a silica (B) contains 5 weight part or more with respect to 100 weight part of rubber components (A). Further, the silica (B) is more preferably contained in an amount of 5 to 90 parts by weight, more preferably 5 to 50 parts by weight, relative to 100 parts by weight of the rubber component (A). If the content of silica (B) is less than 5 parts by weight with respect to 100 parts by weight of the rubber component (A), the exothermic property and chipping improvement effect are insufficient. On the other hand, when the content of silica (B) is more than 90 parts by weight with respect to 100 parts by weight of the rubber component (A), it is difficult to ensure workability. .

Further possible, the rubber composition according to the aspect of the present invention, silica (B) a nitrogen adsorption specific surface area _(N 2 SA) is preferably a 130~300m ² / g, a 180~270m ² / g Is more preferable. When the nitrogen adsorption specific surface area (N ₂ SA) of silica (B) is smaller than 130 m ² / g, chipping improvement and abrasion resistance on a rough road due to improvement of hysteresis loss are not sufficient. On the other hand, if the nitrogen adsorption specific surface area (N ₂ SA) of silica (B) exceeds 300 m ² / g, it may cause a dispersion failure and may cause a significant decrease in heat generation, wear resistance, and improved workability. is there.

  The rubber composition according to the feature of the present invention is a step of mixing a rubber latex and a slurry solution in which carbon black is dispersed in water. (I) The particle size distribution of the filler in the water-dispersed slurry solution is: The volume average particle diameter (mv) is 25 μm or less, the 90 volume% particle diameter (D90) is 30 μm or less, and (ii) the 24M4DBP oil absorption amount of the filler recovered by drying from the aqueous dispersion slurry solution is dispersed in water. It is preferable to hold 93% or more of the previous 24M4DBP oil absorption. If the particle size is too large, the filler dispersion in the rubber may be deteriorated, and the reinforcement and wear resistance may be deteriorated.

  The rubber masterbatch is preferably mixed by adding a surfactant to the rubber latex or slurry solution.

  In the step of drying the rubber master batch after coagulation, it is preferable to perform drying while applying mechanical shearing force. By applying a mechanical shearing force, the dispersibility of the filler is further improved. Although this drying can be performed using a general kneader, it is preferable to perform drying using a continuous kneader from the viewpoint of industrial productivity. Furthermore, it is preferable to use a double-screw kneading extruder such as rotating in the same direction or rotating in the different direction.

In the rubber composition according to the feature of the present invention, the carbon black contained in the rubber master batch has a nitrogen adsorption specific surface area (N ₂ SA) of 50 to 200 m ² / g, or a dibutyl phthalate oil absorption (DBP) of 60. It is preferable that it is -130 ml / 100g. When the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is smaller than 50 m ² / g, the exothermic property is excellent, but the destructive properties such as wear resistance are remarkably lowered, while when it exceeds 200 m ² / g, Workability is significantly reduced. The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is more preferably 50 to 160 m ² / g.

  In addition, when the dibutyl phthalate oil absorption (DBP) is less than 60 ml / 100 g, it is difficult to obtain wear resistance, and when it exceeds 130 ml / 100 g, the fatigue resistance is lowered and the wear resistance is reduced due to chipping. May decrease. Here, it is preferable that 20-100 weight part of carbon black contained in a rubber masterbatch is contained with respect to 100 weight part of rubber components (A). Moreover, it is preferable that carbon black contains 30-60 weight part with respect to 100 weight part of rubber components (A). When the content of carbon black is more than 20 parts by weight with respect to 100 parts by weight of the rubber component (A), it is preferable because the heat generation is excellent. Further, if the content of carbon black is less than 100 parts by weight with respect to 100 parts by weight of the rubber component (A), it is preferable because the heat generation and wear resistance are excellent and dispersion can be improved.

  In the rubber composition according to the feature of the present invention, the rubber master batch is preferably a natural rubber master batch. Natural rubber is a rubber with excellent mechanical properties, low heat build-up, and abrasion resistance, and is also attracting attention as an environmentally friendly material.

  The rubber composition according to the feature of the present invention is preferably a heavy duty pneumatic tire. Moreover, it can use especially suitably for an off-road tire.

  According to the present invention, it is possible to provide a pneumatic tire using a rubber composition that can suppress the occurrence of chipping and can achieve both high exothermic property and workability at a high level, particularly in an ultra-large tire.

  Next, the present invention will be described in detail.

(Rubber composition)
The rubber composition of the present invention comprises a rubber component (A) comprising a rubber masterbatch obtained by mixing a rubber latex and a slurry solution in which carbon black is dispersed in water and coagulating the rubber component (A) 100. The silica (B) heat-treated with 5 parts by weight or more of silicon oil is contained with respect to parts by weight.

  In the rubber composition, the rubber component (A) and silica (B) are kneaded with a dry mill.

  Hereinafter, the rubber component (A), silica (B), and carbon black will be described in detail.

(Rubber component (A))
As the rubber component (A), natural rubber is mainly used among natural rubber and diene rubber. Examples of the diene rubber include isoprene rubber (IR), styrene-butadiene rubber (SBR), polybutadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). May be used alone or in combination of two or more.

  The method for producing the master batch of the rubber component (A) will be described in detail later.

(Silica (B))
In the rubber composition used for the tire of the present invention, silica (B) heat-treated with silicon oil can be blended. This silica (B) is kneaded by a dry mill. The silica (B) preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 130 to 300 m ² / g, and more preferably 180 to 270 m ² / g. When the nitrogen adsorption specific surface area (N ₂ SA) of this silica (B) is smaller than 130 m ² / g, the chipping improvement on the rough road due to the improvement of the hysteresis roll and the wear resistance are not sufficient. On the other hand, if the nitrogen adsorption specific surface area (N ₂ SA) of the silica (B) exceeds 300 m ² / g, it may cause a dispersion failure, which may cause a significant decrease in heat generation, wear resistance, and factory workability. is there.

The nitrogen adsorption specific surface area of the silica _(B) (N 2 SA) is a one hour drying at 300 ° C., was measured according to ASTM D4820-93 value.

  Examples of the silica (B) include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among these, wet silica is particularly preferable.

  Further, the silica (B) of the present invention is preferably contained in an amount of 5 parts by weight or more based on 100 parts by weight of the rubber component (A). Silica (B) is preferably contained in an amount of 5 to 90 parts by weight, more preferably 5 to 50 parts by weight, relative to 100 parts by weight of rubber component (A). If the content of silica (B) is less than 5 parts by weight with respect to 100 parts by weight of the rubber component (A), the exothermic property and the effect of improving chipping are insufficient. On the other hand, when the content of silica (B) is more than 90 parts by weight with respect to 100 parts by weight of the rubber component (A), it is difficult to ensure workability. .

  Silica (B) heat-treated with silicon oil can reduce surface energy, weaken aggregation between silica particles, and improve fluidity. Examples of silicone oils used for these purposes include dimethyl silicone oil, methyl hydrogen silicone oil, alkoxy group-containing methyl silicone oil, and the like. Thereafter, a heat baking process is performed as necessary.

  In the rubber composition used in the tire of the present invention, when silica (B) heat-treated with silicon oil is blended, the bond between silica (B) and rubber component (A) is strengthened, and low heat build-up is achieved. In order to maintain and improve the wear resistance, it is preferable to further add a silane coupling agent.

  Examples of the silane coupling agent used for this purpose include bis (3-triethoxysilylpropyl) polysulfide, bis (2-triethoxysilylethyl) polysulfide, bis (3-trimethoxysilylpropyl) polysulfide, and bis ( 2-trimethoxysilylethyl) polysulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3 Nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, 3-tripropyl Toxisilylpropyl-N, N-dimethylthiocarbamoyl polysulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl polysulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl polysulfide, 3-trimethoxysilyl Propylbenzothiazole polysulfide, 3-triethoxysilylpropylbenzothiazole polysulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) polysulfide, 3-mercapto Propyldimethoxymethylsilane, 3-nitropropyldimethoxymethylsilane, 3-chloropropyldimethoxymethylsilane, dimethyl Methyl silyl propyl -N, N-dimethylthiocarbamoyl polysulfide, etc. dimethoxymethylsilylpropyl benzothiazole polysulfides and the like.

  These may be used alone or in combination of two or more. Among these, bis (3-triethoxysilylpropyl) polysulfide, 3-trimethoxysilylpropylbenzothiazole polysulfide and the like are preferable.

  As a compounding quantity of the said silane coupling agent, 5-20 weight% is preferable with respect to the compounding quantity of the silica (B) heat-processed with silicon oil, and 5-15 weight% is more preferable.

(Carbon black)
The carbon black contained in the rubber masterbatch of the present invention preferably has a nitrogen adsorption specific surface area (N ₂ SA) of 50 to 200 m ² / g or a dibutyl phthalate oil absorption (DBP) of 60 to 130 ml / 100 g. . When the nitrogen adsorption specific surface area (N ₂ SA) of carbon black is less than 50 m ² / g, the heat generation is excellent, but the fracture characteristics such as wear resistance are remarkably lowered, and when it exceeds 200 m ² / g, the workability is improved. It drops significantly. The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is more preferably 50 to 160.

  Also, if the dibutyl phthalate oil absorption (DBP) is less than 60 ml / 100 g, it is difficult to obtain wear resistance, and if it exceeds 130 ml / 100 g, the fatigue resistance is lowered, and the wear resistance is lowered due to the occurrence of chipping, etc. There is a risk.

  The carbon black contained in the rubber masterbatch of the present invention is preferably contained in an amount of 20 to 100 parts by weight with respect to 100 parts by weight of the rubber component (A). The carbon black is more preferably contained in 30 to 60 parts by weight with respect to 100 parts by weight of the rubber component (A). When the carbon black content is more than 20 parts by weight with respect to 100 parts by weight of the rubber component (A), it is preferable because the heat generation is excellent. On the other hand, when the content of carbon black is less than 100 parts by weight with respect to 100 parts by weight of the rubber component (A), it is preferable because the heat generation and wear resistance are excellent and dispersion can be improved.

In addition, the nitrogen adsorption specific surface area (N ₂ SA) of carbon black contained in the rubber masterbatch is a value measured according to ASTM D3037-88, and DBP is based on JIS K6221-1982 (A method). Measured value.

  There is no restriction | limiting in particular as said carbon black, Arbitrary things can be suitably selected and used from what is conventionally used as a reinforcing filler of rubber | gum. As an example, HAF, ISAF and SAF which are excellent in wear resistance are preferable.

  In addition, the rubber component (A) used in the rubber composition used in the tire of the present invention has a remarkable effect of improving processability in a system of natural rubber alone or a blend rubber of natural rubber and synthetic rubber. When the rubber component (A) contains natural rubber, it is possible to reduce the amount of natural rubber polymer gel without reducing the molecular weight of the natural rubber molecule, and to increase the slip between the rubber molecules. While improving workability | operativity, the physical property fall of an unvulcanized or vulcanized rubber is suppressed, Furthermore, dispersion | distribution of a silica filler can be improved significantly.

  In any case, excellent rubber processability can be obtained without adversely affecting the physical properties of the vulcanized rubber composition.

(Other ingredients)
If necessary, other rubber compounding agents such as sulfur, vulcanization accelerators, process oils, anti-aging agents and the like can be appropriately compounded with the rubber composition used in the tire of the present invention.

(Manufacturing method of master batch)
The rubber component (A) of the rubber composition of the present invention comprises a rubber master batch. Although the manufacturing method of the natural rubber masterbatch which uses natural rubber latex is demonstrated below, this invention is applicable not only to a natural rubber masterbatch but to the masterbatch using synthetic rubbers, such as a diene type synthetic rubber.

  In the step of mixing the modified latex and the slurry solution, it is necessary to manufacture a slurry solution in which carbon black is dispersed in water in advance, and a known method can be used as a method for manufacturing the slurry solution. Yes, it is not particularly limited. For example, the slurry solution can be prepared by putting a predetermined amount of filler and water in a homomixer and stirring for a certain period of time.

  In the method for producing a natural rubber masterbatch according to the present invention, when producing a slurry solution of the filler, the particle size distribution of the filler in the water-dispersed slurry solution and the 24M4DBP oil absorption of the filler are limited to those in a specific range. The That is, the method for producing a natural rubber masterbatch according to the present invention includes the step of mixing natural rubber latex and a slurry solution in which carbon black is dispersed in water. (I) Particle size distribution of filler in the water-dispersed slurry solution The volume average particle diameter (mv) is 25 μm or less, the 90 volume% particle diameter (D90) is 30 μm or less, and (ii) the 24M4DBP oil absorption amount of the filler recovered by drying from the water-dispersed slurry solution is It is necessary to hold 93% or more of the 24M4DBP oil absorption before dispersion. Here, the 24M4DBP oil absorption is a value measured according to ISO 6894.

  More preferably, the volume average particle diameter (mv) is 20 μm or less, and the 90 volume% particle diameter (D90) is 25 μm or less. If the particle size is too large, the filler dispersion in the rubber may be deteriorated, and the reinforcement and wear resistance may be deteriorated.

  On the other hand, if an excessive shearing force is applied to the slurry in order to reduce the particle size, the structure of the filler is destroyed and the reinforcing property is lowered. It is necessary that the 24M4 DBP oil absorption amount of the filler recovered by drying from the aqueous dispersion slurry solution is 93% or more of the 24MDBP oil absorption amount of the filler material before being charged into the slurry. More preferably, it is 96% or more.

  A rotor / stator type high shear mixer, high-pressure homogenizer, ultrasonic homogenizer, colloid mill, or the like is used for the production of the aqueous dispersion slurry solution of the filler.

For example, the slurry solution can be prepared by putting a predetermined amount of filler and water in a colloid mill and stirring at high speed for a certain time.

  In the method for producing a natural rubber masterbatch of the present invention, the carbon black used is not particularly limited, and any one of those conventionally used as a reinforcing filler for rubber can be appropriately selected and used. it can. As an example, various grades of carbon black such as SAF, HAF, ISAF, FEF and GPF can be used alone or in combination, but HAF, ISAF and SAF which are excellent in wear resistance are more preferable.

The carbon black contained in the rubber masterbatch has a nitrogen adsorption specific surface area (N ₂ SA) of 50 to 200 m ² / g or a dibutyl phthalate oil absorption (DBP) of 60 to 130 ml / 100 g, and the rubber component (A It is preferable to contain 20 to 100 parts by weight of the carbon black with respect to 100 parts by weight. Carbon black is more preferably contained in an amount of 30 to 60 parts by weight.

Moreover, although it does not specifically limit as silica used by this invention, Wet silica, dry silica, and colloidal silica are preferable. Further, the silica contained in the rubber master batch or a nitrogen adsorption specific surface area of silica is added after (N ₂ SA) of is preferably 130~300m ² / g. Further, the content of silica (B) heat-treated with silicon oil added later using a dry mill is preferably 5 parts by weight or more per 100 parts by weight of the rubber component (A).

  The slurry concentration of the filler containing carbon black is preferably 0.5% by weight to 60% by weight and more preferably 1% by weight to 30% by weight with respect to the slurry.

  The filler is preferably added in an amount of 5 to 100 parts by weight, more preferably in the range of 10 to 70 parts by weight, with respect to 100 parts by weight of the rubber component (A) of the natural rubber masterbatch. If the amount of the filler is less than 5 parts by weight, sufficient reinforcement may not be obtained, and if it exceeds 100 parts by weight, the workability may be deteriorated.

  Next, as a mixing method of the slurry solution and the natural rubber latex that has undergone the amide bond decomposition step, for example, the slurry solution is placed in a homomixer and the latex is dropped while stirring, or the latex is stirred. However, there is a method of dropping the slurry solution. Also, a method of mixing a slurry flow having a constant flow rate and a latex flow under conditions of vigorous hydraulic stirring can be used.

  As a method for coagulating the masterbatch, it is carried out using a coagulant such as formic acid or sulfuric acid, or a salt such as sodium chloride as usual. In the present invention, coagulation may be performed by adding natural rubber latex and slurry without adding a coagulant.

  In addition, various additives such as surfactants, vulcanizing materials, anti-aging materials, coloring materials, and dispersing agents can be added to the carbon black as desired.

  Drying is usually performed as the final step of master batch production. In the present invention, a normal dryer such as a vacuum dryer, an air dryer, a drum dryer, or a band dryer can be used. In order to further improve the dispersibility of the filler, a mechanical shear force is applied. It is preferable to perform drying. Thereby, rubber excellent in processability, reinforcement, and low fuel consumption can be obtained. Although this drying can be performed using a general kneader, it is preferable to use a continuous kneader from the viewpoint of industrial productivity. Furthermore, it is more preferable to use a twin-screw kneading extruder that rotates in the same direction or in different directions.

  In the step of drying while applying the shearing force, the moisture in the masterbatch before the drying step is preferably 10% or more. When this moisture is less than 10%, the improvement width of the filler dispersion in the drying process may be reduced.

(Pneumatic tire)
The rubber composition of the present invention described above is suitably used for tire tread rubber and tread base rubber. In addition, a pneumatic tire is manufactured by a normal method using the rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention containing various chemicals as described above is extruded into, for example, a tread member at an unvulcanized stage and pasted on a tire molding machine by a usual method. A green tire is formed by attaching. The green tire is heated and pressed in a vulcanizer to obtain a tire.

  The rubber composition of the present invention can be suitably used in various fields, but can be suitably used for large tires and heavy duty pneumatic tires.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

A rubber composition having the composition shown in Table 1 and Table 2 was prepared, and a test tire (size: 3700R57) was made using each rubber composition as a tread.

* 1. Anti-aging material 6C: N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine * 2. Wax: Seiko Chemical Co., Ltd., trademark “WMO2”
* 3. Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide * 4. Coupling material: Trademark “Si69” manufactured by Degussa
In Comparative Examples 2 to 4 and Examples 1 to 5, rubber compositions were prepared using a master batch, and the master batch used here was manufactured by the following manufacturing method.

A. Preparation of latex (1) Latex 1
Natural rubber field latex (rubber content 24.2%) was diluted with deionized water to give a rubber content of 20%.

(2) Latex 2
By adding 0.5% of anionic surfactant (Decaur N made by Kao) and 0.1% of alkaline protease (Alkalase 2.5L type DX made by Novozymes) to Latex 1, and stirring at 40 ° C. for 8 hours, The amide bond in natural rubber was broken.

B. Stirring method for water-dispersed slurry of filler (1) Stirring method 1
A colloid mill with a rotor diameter of 50 mm was charged with 1425 g of deionized water and 75 g of carbon black (N110), and stirred for 10 minutes at a rotor-stator gap of 1 mm and a rotational speed of 1500 rpm.

(2) Stirring method 2
In the same manner as in the stirring method 1, stirring was performed for 10 minutes at a rotor-stator gap of 0.3 mm and a rotational speed of 5000 rpm.

(3) Stirring method 3
To the stirring method 1, 0.05% of an anionic surfactant (Kao Demol N) was further added, and the mixture was circulated three times using a pressure homogenizer at a pressure of 500 kPa.

(4) Stirring method 4
It was made to circulate 5 times on the conditions of the pressure of 1000 kPa similarly to the stirring method 3.

Table 3 shows the particle size distribution (mv, D90) of the filler in the water-dispersed slurry obtained above, the 24M4DBP oil absorption (hereinafter referred to as 24M4DBP) and the retention rate of the dried and collected filler. In addition, 24M4DBP of the filler before adding the slurry is described in the note in Table 3.

(Note) 24M4DBP of the filler before the slurry is charged
Carbon black; N110 (24M4DBP: 98)
Carbon black; N220 (24M4DBP: 100)
Carbon black; N330 (24M4DBP: 88)
Aluminum hydroxide; Heidilite H-43M, Showa Denko KK (24M4DBP: 52)
Moreover, various measurements in each slurry were performed as follows.

(I) Measurement of particle size distribution of filler in slurry solution (volume average particle diameter (mv), 90 volume% particle diameter (D90))
A laser diffraction particle size distribution meter (MICROTRAC FRA type) was used, and measurement was performed using an aqueous solvent (refractive index: 1.33). A particle refractive index of 1.57 was used for all measurements. Further, in order to prevent re-aggregation of the filler, measurement was performed immediately after dispersion.

(II) 24M4DBP oil absorption of the filler was measured according to ISO 6894.

C. In the coagulation step homomixer, the latex and slurry prepared as described above were added to 100 parts by weight of rubber so that each filler shown in Table 2 was 50 parts by weight. Added until pH 4.5. The solidified master batch was collected, washed with water, and dehydrated until the water content was about 40%.

D. Drying process Using a band dryer method that uses a band dryer to dry at a temperature of 120 ° C., or using a Kobe Steel twin-screw kneading extruder (co-rotating screw diameter 30 mm, L / D = 35, 3 vent holes) This was carried out by any one of the twin-screw kneading extruder methods for drying at a temperature of 120 ° C. and a rotation speed of 100 rpm.

The amount of filler in the master batch obtained as described above was about 50 parts by weight with respect to 100 parts by weight of natural rubber.

E. Preparation of rubber composition 3 parts by weight of zinc oxide, 1.2 parts by weight of sulfur with respect to the filler-containing rubber obtained by the masterbatch or dry kneading (100 parts by weight of natural rubber and 50 parts by weight of filler), 2 parts by weight of stearic acid, 1 part by weight of Nt-butyl-2-benzothiazolylsulfenamide (NS) and 1 part by weight of N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine (6C) In addition, when the filler was silica, 4 parts by weight of a silane coupling material (Si69 “trademark” manufactured by Degussa) was blended and kneaded with a plast mill to obtain a rubber composition.

  The test was conducted on the following items.

(1) Low exothermic property A drum test under constant speed and step load conditions was performed, and the temperature in a constant depth city inside the tire tread was measured. The larger the index value, the greater the effect of reducing heat generation.

(2) Chipping property The chipping property was expressed as an index with the comparative example 1 being 100, by determining the area ratio of the tread rubber surface 30 cm × 30 cm with no missing rubber in the tire after running for 2000 hours. The larger the index value, the better the chipping property.

(3) Viscosity of kneaded rubber Using an RPA manufactured by Monsanto, it was measured at 130 degrees, and Comparative Example 1 was set as 100 and indicated as an index. The larger the index value, the higher the viscosity.

<Result>
From the results shown in Tables 1 and 2, the rubber compositions of Examples 1 to 5 suppress the occurrence of chipping and achieve both high exothermicity and workability at a high level as compared with the rubber compositions of Comparative Examples 1 to 4. I found out that For this reason, by mixing a rubber latex and a slurry solution in which carbon black is dispersed in water and using a rubber component (A) consisting of a rubber master batch obtained by pseudo-solidification, the occurrence of chipping is suppressed, It was found that low exothermicity and workability are highly compatible.

Further, it has been found that the inclusion of silica (B) heat-treated with silicon oil in the rubber component (A) further suppresses the occurrence of chipping and achieves both low exothermic properties and workability at a higher level. .

Claims (11)

A rubber component (A) comprising a rubber master batch obtained by mixing and coagulating a rubber latex and a slurry solution in which carbon black is dispersed in water;
A pneumatic tire using a rubber composition, comprising 100 parts by weight of the rubber component (A) and silica (B) heat-treated with 5 parts by weight or more of silicon oil. _{2. The} pneumatic tire using the rubber composition according to claim 1, wherein the silica (B) has a nitrogen adsorption specific surface area (N ₂ SA) of 130 to 300 m ² / g.   In the step of mixing the rubber latex and the slurry solution in which the carbon black is dispersed in water, (i) the particle size distribution of the filler in the water-dispersed slurry solution has a volume average particle diameter (mv) of 25 μm or less. , 90 volume% particle size (D90) is 30 μm or less, and (ii) 24M4DBP oil absorption of the filler recovered by drying from the water-dispersed slurry solution retains 93% or more of 24M4DBP oil absorption before being dispersed in water A pneumatic tire using the rubber composition according to claim 1 or 2.   The pneumatic tire using the rubber composition according to any one of claims 1 to 3, wherein the rubber master batch is mixed by adding a surfactant to the rubber latex or the slurry solution. .   5. The pneumatic tire using the rubber composition according to claim 1, wherein drying is performed while applying mechanical shearing force in the step of drying the rubber masterbatch after coagulation. .   The pneumatic tire using the rubber composition according to claim 5, wherein drying is performed using a continuous kneader.   The pneumatic tire using the rubber composition according to claim 6, wherein the continuous kneader is a double-screw kneading extruder. The nitrogen adsorption specific surface area (N ₂ SA) of carbon black contained in the rubber masterbatch is 50 to 200 m ² / g, or the dibutyl phthalate oil absorption (DBP) is 60 to 130 ml / 100 g. The pneumatic tire using the rubber composition of any one of claim | item 1 -7.   The pneumatic tire using the rubber composition according to any one of claims 1 to 8, wherein the rubber masterbatch is a natural rubber masterbatch.   A pneumatic tire using the rubber composition according to any one of claims 1 to 9, wherein the pneumatic tire is a heavy duty pneumatic tire. A pneumatic tire using the rubber composition according to claim 10, which is an off-road tire.