JP5545102B2 - Hydrophobic silica particle powder, production method thereof, and rubber composition using the hydrophobic silica particle powder - Google Patents

Description

  The present invention provides a hydrophobic silica particle powder having excellent hydrophobicity and fluidity, and having a small change in the BET specific surface area value of the inorganic particle powder before and after the treatment, a process for producing the same, and the hydrophobic silica particle powder. The present invention relates to a compounded rubber composition.

  In recent years, demands for lower fuel consumption of automobiles are increasing, and there is a strong demand to reduce rolling resistance of tires. Rolling resistance is related to the heat build-up of the rubber composition used for tire treads, etc., and reducing the hysteresis loss of the rubber composition, that is, keeping the loss factor (tan δ) low is low fuel consumption. It is known to be effective for conversion. In addition, in the tire tread rubber composition, in addition to low fuel consumption, in terms of safety, it is required to improve braking performance and handling stability on wet road surfaces, and to be excellent in wear resistance and fracture characteristics. Yes.

  Carbon, a reinforcing filler that has been generally used so far, for the purpose of obtaining various rubber compositions for tire treads that achieve both low fuel consumption, braking performance on wet roads, and handling stability. Silica is used instead of black.

  However, since silica by a wet method generally used in rubber compositions for tire treads has hydrophilicity, it has low affinity with hydrophobic rubber components, and mixing silica into rubber results in poor dispersion. Since it tends to occur, the processability, such as extrusion, is inferior, and sufficient reinforcing properties cannot be obtained, resulting in the disadvantage that the wear resistance and fracture characteristics of the rubber composition are lowered. In addition, since the particles tend to aggregate due to hydrogen bonding of the silanol group that is the surface functional group, it takes a long kneading time to disperse the silica in the rubber, which is a big problem in manufacturing the tire. ing.

  Furthermore, since silica by wet method has an acidic particle surface, the rubber composition is not sufficiently vulcanized to adsorb the basic vulcanization accelerator compounded in the rubber composition, and the elastic modulus is low. Since it does not rise, there is a drawback that the steering stability on the dry road surface is not sufficient.

  For the purpose of improving the above drawbacks, a method (Patent Document 1 to Patent Document 6) is known in which silica that has been previously hydrophobized with an alkoxysilane or a sulfur-containing silane coupling agent or the like is blended into a rubber composition. .

JP-A-6-248116 JP-A-9-12922 JP 2001-354805 A JP 2007-169559 A JP 2008-106205 A JP 2008-143725 A

  Patent Documents 1 to 4 described above describe a method in which silica particle powder surface-treated with an organosilicon compound or a sulfur-containing organosilicon compound is blended with a rubber composition, both of which are coated with higher fatty acids. The treatment is not taken into account, and as shown in the comparative examples described later, sufficient hydrophobicity and fluidity improvement effect cannot be obtained only by the treatment with the organosilicon compound, and therefore the dispersion in the rubber composition is insufficient. It will be a thing.

  In addition, in Patent Document 5 and Patent Document 6 described above, as a method of hydrophobizing silica particle powder, a method of wet or dry mixing a hydrophobizing agent such as a silane compound, a fatty acid, or a fatty acid metal salt is described. According to these methods, the change in the BET specific surface area value of the inorganic particle powder before and after the treatment is large, and the BET specific surface area value of the inorganic particle powder after the treatment is greatly reduced by the hydrophobic treatment. There is a problem that it becomes difficult to design particles having a large surface area (a large surface area).

  Then, this invention makes it a technical subject to provide the hydrophobic silica which has the outstanding hydrophobic property and fluidity | liquidity, and was excellent in the dispersibility in a rubber composition.

  The object can be achieved by the present invention as follows.

  That is, according to the present invention, the particle surface of the silica particle powder is coated with a sulfide silane and an amino-based silane coupling agent, and the coated surface is coated with a higher fatty acid. The average particle diameter is 0.01 to 0.3 μm. It is a hydrophobic silica particle powder characterized by comprising a silica particle powder (Invention 1).

Further, the present invention is the hydrophobic silica particle powder of the present invention 1 having a BET specific surface area value of 90 m ² / g or more (Invention 2).

  Further, the present invention is the hydrophobic silica particle powder of the present invention 1 or the present invention 2 having a powder pH value of 7.0 or more (Invention 3).

  Further, the present invention is the hydrophobic silica particle powder according to any one of the present invention 1 to the present invention 3, wherein the hydrophobicity due to methanol wettability is 60% or more (Invention 4).

  Further, the present invention is characterized in that the change rate of the BET specific surface area value of the silica particle powder before and after the coating treatment with sulfide silane, amino silane coupling agent and higher fatty acid is 56% or less. The hydrophobic silica particle powder according to any one of 1 to Invention 4 (Invention 5).

  Further, the present invention is the hydrophobic silica particle powder according to any one of the present invention 1 to the present invention 5, which has a fluidity index higher by 10 or more than the fluidity index of the silica particle powder before treatment. (Invention 6).

  In addition, the present invention adds a sulfide silane and an amino silane coupling agent to silica particle powder, and mixes and stirs to coat the particle surface of the silica particle powder with the sulfide silane and amino silane coupling agent. In the method for producing hydrophobic silica particle powder in which fatty acid is added, mixed and stirred to adhere higher fatty acid to the surface of the coating, all treatment steps are performed in a dry process, and the water content of the silica particle powder is added in advance. In addition to adjusting the amount of water necessary for hydrolysis of sulfide silane and amino silane coupling agent to 1 to 10 times the range, inorganic particle powder after adhesion of sulfide silane, amino silane coupling agent and higher fatty acid Heat treatment is performed in a temperature range of 120 to 210 ° C., according to any one of the present invention 1 to present invention 6. A method for producing hydrophobic silica particles (present invention 7).

  Further, the present invention is a rubber composition using the hydrophobic silica particle powder according to any one of the present invention 1 to the present invention 6 (Invention 8).

  The hydrophobic silica particle powder according to the present invention has excellent hydrophobicity and fluidity, and is excellent in dispersibility in the rubber composition. Therefore, the hydrophobic silica particle powder is used for various rubber compositions including tire tread rubber compositions. Suitable as a filler.

  The method for producing hydrophobic silica particle powder according to the present invention has a small change in the BET specific surface area value of the inorganic particle powder before and after the treatment, and also causes problems such as COD emission because all processes are performed in a dry process. Since it does not occur, it is suitable as a method for producing hydrophobic silica particle powder in consideration of the environment.

  The rubber composition according to the present invention is improved in workability by using the above-described hydrophobic inorganic particle powder according to the present invention as a reinforcing filler, and has rolling resistance characteristics and wetness without impairing wear resistance. It is suitable as a rubber composition that can improve the braking performance on the road surface.

  The configuration of the present invention will be described in more detail as follows.

  First, the hydrophobic silica particle powder according to the present invention will be described.

  The hydrophobic silica particle powder according to the present invention comprises a silica particle powder in which the particle surface of the silica particle powder is coated with a sulfide silane and an amino silane coupling agent, and the coated surface is coated with a higher fatty acid. .

  As the silica particle powder in the present invention, wet method silica such as precipitated silica (white carbon), silica gel, silica sol (colloidal silica), and dry method silica such as fumed silica can be used. Considering the reinforcing effect of the resulting rubber composition, silica by a wet method is preferable, and precipitated silica is more preferable.

  The particle shape of the silica particle powder may be any shape such as a spherical shape, a granular shape, an indefinite shape, a needle shape, and a plate shape. Considering the fluidity of the resulting hydrophobic silica particle powder and the dispersibility in the rubber composition, spherical particles or granular particles are preferred.

The silica particle powder in the present invention has an average particle diameter of 0.001 to 0.3 μm, a BET specific surface area value of 1.0 to 500 m ² / g, and a powder pH value of usually less than 7, and the degree of hydrophobicity due to methanol wettability. Is usually 0 to 40%.

  As the sulfide silane in the present invention, bis (3- (triethoxysilyl) propyl) disulfide, bis (3- (trimethoxysilyl) propyl) disulfide, bis (3- (methyldiethoxysilyl) propyl) disulfide, bis ( 3- (methyldimethoxysilyl) propyl) disulfide, bis (2- (triethoxysilyl) ethyl) disulfide, bis (2- (trimethoxysilyl) ethyl) disulfide, bis (2- (methyldiethoxysilyl) ethyl) disulfide , Bis (2- (methyldimethoxysilyl) ethyl) disulfide, and compounds in which the disulfides of these compounds are replaced with trisulfides and tetrasulfides.

  As the amino silane coupling agent in the present invention, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (2-aminoethyl) Examples include aminopropylmethyldimethoxysilane and 3-phenylaminopropyltrimethoxysilane.

  As the higher fatty acid in the present invention, a saturated or unsaturated fatty acid having 12 or more carbon atoms can be used. Specifically, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, n-octacosanoic acid, mellicic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, n-nonadecanoic acid N-heneicosanoic acid, tricosanoic acid, pentacosanoic acid, nonacosanoic acid, oleic acid, linoleic acid, isostearic acid and the like. These can be used alone or in combination of two or more. In view of handling properties, it is preferably a solid at room temperature. In view of the uniformity of the surface coating treatment, the melting point of the higher fatty acid is preferably 90 ° C. or lower, and more preferably 85 ° C. or lower. Furthermore, considering the fluidity and hydrophobicity improving effect of the obtained inorganic particle powder, it is preferable that the number of carbon atoms is larger.

  The average particle diameter of the hydrophobic silica particle powder according to the present invention is 0.01 to 0.3 μm, preferably 0.01 to 0.25 μm. When the average particle size is less than 0.01 μm, dispersion in the rubber composition becomes difficult due to an increase in intermolecular force due to the finer particles.

The BET specific surface area value of the hydrophobic silica particle powder according to the present invention is preferably 90 to 250 m ² / g, more preferably 95 to ²⁰⁰ m ² / g. When the BET specific surface area value is less than 90 m ² / g, it is difficult to obtain the reinforcing effect of the rubber composition. When the BET specific surface area exceeds 250 m ² / g, dispersion in the rubber composition becomes difficult due to an increase in intermolecular force due to finer particles.

  The change rate of the BET specific surface area value before and after the treatment of the hydrophobic silica particle powder according to the present invention is preferably 56% or less, more preferably 54% or less, and still more preferably 52%. .

  Further, the powder pH value of the hydrophobic silica particle powder according to the present invention is preferably 7.0 or more, more preferably 7.2 or more. Usually, the silica particle powder is in an acidic region having a powder pH value of less than 7.0, and the rubber composition is sufficiently vulcanized to adsorb the basic vulcanization accelerator compounded in the rubber composition. However, the silica particle powder according to the present invention can improve the above-mentioned drawbacks by changing the powder pH value from neutral to basic. is there.

  The hydrophobicity of the hydrophobic silica particle powder according to the present invention by methanol wettability (MW) is 60% or more, preferably 65% or more. When the degree of hydrophobicity by methanol wettability (MW) is less than 60%, the hydrophobicity of the silica particle powder is not sufficient, and when blended in a rubber composition, it is contained in rubber and other rubber compositions. Therefore, it is difficult to disperse uniformly.

  The fluidity of the hydrophobic silica particle powder according to the present invention is improved by 5 or more, preferably 10 or more, compared to the untreated silica particle powder.

  Next, a method for producing the hydrophobic silica particle powder according to the present invention will be described.

  The hydrophobic silica particle powder according to the present invention is obtained by adding a sulfide silane and an amino silane coupling agent to the silica particle powder, mixing and stirring the particle surface of the silica particle powder with a sulfide silane and an amino silane coupling agent. In the method for producing hydrophobic silica particle powder, in which a higher fatty acid is added, mixed and stirred to adhere the higher fatty acid to the surface of the coating, all treatment steps are performed in a dry process, and the silica particle powder is previously prepared. In addition to adjusting the amount of water in the range of 1 to 10 times the amount of water necessary for hydrolysis of the sulfide silane and amino silane coupling agent to be added, sulfide silane, amino silane coupling agent and higher fatty acid It can be obtained by heat-treating the adhered inorganic particle powder in a temperature range of 120 to 210 ° C.

  The water content of the silica particle powder is 1 to 10 times, preferably 1 to 8 times, more preferably 1 to 6 times the amount of water necessary for hydrolysis of the sulfide silane and amino silane coupling agent to be added. It is preferable to adjust to the range. Adjustment of the amount of water may be performed by heating or humidification according to a conventional method.

  The coating treatment with sulfide silane and amino silane coupling agent may be performed by adding and mixing sulfide silane and then adding and mixing amino silane coupling agent, or after adding and mixing amino silane coupling agent. You may add and mix. Further, sulfide silane and amino silane coupling agent may be added and mixed simultaneously. Considering the effect of higher fatty acid adhering to the surface of the silica particles, it is preferable to add and mix the sulfide silane and then add and mix the amino silane coupling agent.

The amount of coating with the sulfide silane and amino silane coupling agent was determined from the BET specific surface area value of the silica particle powder and the minimum coating area (m ² / g) of the sulfide silane and amino silane coupling agent. The amount is preferably 5 to 100%, more preferably 7 to 100% of the amount necessary for further covering the particle surface with the sulfide silane and amino silane coupling agent. By setting the coating amount with the sulfide silane and amino silane coupling agent in the above range, a coating layer of higher fatty acid can be effectively attached and formed on the particle surface of the silica particle powder.

  The coating amount of the higher fatty acid is preferably from 0.3 to 3.0 mol, more preferably from 0.003 mol to 1 mol of the organic functional group of the amino silane coupling agent coating the particle surface of the silica particle powder. 5-2.8 mol. When the coating amount of the higher fatty acid exceeds 3.0 mol with respect to 1 mol of the organic functional group of the amino silane coupling agent covering the particle surface of the silica particle powder, when dispersed in the rubber composition The higher fatty acids that could not be firmly attached to the surface of the silica particles by the amino silane coupling agent are liable to be detached, which is not preferable. In addition, when the coating amount of higher fatty acid is less than 0.3 mol with respect to 1 mol of the organic functional group of the amino silane coupling agent covering the particle surface of the silica particle powder, sufficient fluidity and hydrophobicity are obtained. It becomes difficult to obtain a hydrophobic silica particle powder having the same.

  The silica particle powder is coated with the sulfide silane and amino silane coupling agent, and the coating surface of the higher fatty acid is coated with the silica particle powder, sulfide silane and amino silane coupling agent. Mixing and stirring may be performed, or the silica particle powder may be mechanically mixed and stirred while spraying the sulfide silane and amino silane coupling agent components. Further, in order to uniformly coat the surface of the silica particles with the sulfide silane, the amino-based silane coupling agent and the higher fatty acid, it is preferable that the agglomeration of the silica particle powder is previously unraveled using a pulverizer.

  The silica particle powder is coated with a sulfide silane and an amino silane coupling agent on the particle surface, and the higher fatty acid is coated on the coating surface using an apparatus capable of applying a shearing force to the powder layer. In particular, a device capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneader, a ball-type kneader, a blade-type kneader, or a roll-type kneader can be used. Further, a wheel type kneader and a ball type kneader can be used more effectively.

  Examples of the wheel-type kneader include an edge runner (synonymous with “mix muller”, “simpson mill”, “sand mill”), multi-mal, stotz mill, wet pan mill, conner mill, ring muller, etc., preferably edge Runners, multi-mals, stocks mills, wet pan mills and ring mullers, more preferably edge runners. Examples of the ball-type kneader include a vibration mill, a rotary mill, a sand grinder, and preferably a vibration mill. Examples of the blade type kneader include a vertical granulator, a Henschel mixer, a planetary mixer, and a nauter mixer. Examples of the roll-type kneader include an extruder.

  The silica particle powder treated with the above-mentioned sulfide silane, amino-based silane coupling agent and higher fatty acid is subjected to a high-speed shear mill (specifically, a hybridizer, a nobilta, etc.) described in JP-A-2008-143725. When used for treatment, the treated particles are discolored and deteriorated, which is not preferable.

  The hydrophobic silica particle powder according to the present invention can be obtained by heat treatment at a temperature range of 120 to 210 ° C. for 30 minutes to 3 hours after mixing and stirring of the higher fatty acid. The heat treatment temperature is preferably 150 to 200 ° C., and the heat treatment time is preferably 1 to 3 hours. When the heat treatment temperature exceeds 210 ° C., the silica particle powder may be discolored or deteriorated, which is not preferable. When the temperature is lower than 120 ° C., it is difficult to effectively fix the sulfide silane, the amino-based silane coupling agent and the higher fatty acid on the particle surface of the silica particle powder. Note that the heat treatment may be performed according to a conventional method using a dryer or the like.

  Next, the rubber composition to which the hydrophobic silica particle powder according to the present invention is added will be described.

  The blending ratio of the hydrophobic silica particle powder in the rubber composition according to the present invention can be used in the range of 10 to 200 parts by weight with respect to 100 parts by weight of the rubber component, considering the handling properties of the rubber composition. For example, it is preferably 15 to 150 parts by weight, more preferably 20 to 100 parts by weight.

  As a constituent substrate in the rubber composition according to the present invention, a vulcanizing agent, a vulcanization accelerator, a coupling agent, a filling agent, which are usually used in the rubber composition, if necessary, together with a hydrophobic silica particle powder and a known rubber. Various additives such as an agent, a plasticizer, an anti-aging agent, and carbon black are blended.

  As rubber, natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), acrylonitrile butadiene Rubber (NBR), chloroprene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer Rubber, chlorosulfonated polyethylene, acrylic rubber, epichlorohydrin rubber, polysulfide rubber, silicone rubber, fluorine rubber, urethane rubber, and mixtures thereof can be used. As main components of rubber, natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber (X-IIR), It is preferable to include a diene rubber such as acrylonitrile butadiene rubber (NBR). Moreover, these can be used individually or in mixture of 2 or more types, respectively.

  The rubber composition according to the present invention is prepared by kneading the rubber and the hydrophobic silica together with various additives as necessary using a Banbury mixer, a mixing roll, an intensive mixer, an extruder, a kneader or the like by a conventional method. Can be obtained. Moreover, when using this rubber composition for a tire, according to a conventional method, it can be used for the rubber part (tread rubber, sidewall rubber, etc.) of various tires by carrying out vulcanization molding at 120-200 degreeC, for example.

  The rubber composition according to the present invention is applied to various rubber compositions such as tire members such as tread rubber and sidewall rubber, topping rubbers for belts and plies, beads fillers, tires such as rim strips, conveyor belts, and vibration-proof rubbers. Can be used.

  A typical embodiment of the present invention is as follows.

The average particle diameter of the silica particle powder and the hydrophobic silica particle powder was photographed using an electron microscope, the particle diameter of 350 particles shown therein was measured, and the average value was shown.

  The specific surface area value was indicated by a value measured by the BET method.

  The rate of change of the BET specific surface area value is a value calculated by measuring the specific surface area value of the particle powder before and after the treatment by the BET method according to the following formula 1.

<Equation 1>
Change rate of BET specific surface area value (%) = ((BET (B) −BET (A)) / BET (B)) × 100
BET (B): BET specific surface area value of silica particle powder before treatment with sulfide silane and amino silane coupling agent BET (A): BET specific surface area value of silica particle powder after treatment

  The water content (%) of the silica particle powder was indicated by a value measured by the Karl Fischer method.

  “Horiba Metal Carbon / Sulfur Analyzer EMIA-2200 Model” (manufactured by Horiba, Ltd.) is used for the coating amount of sulfide silane, amino silane coupling agent and higher fatty acid coated on the surface of silica particle powder. It was determined by measuring the amount of sulfur and the amount of carbon.

  The pH value of the powder was measured by weighing 5 g of a sample into a 300 ml Erlenmeyer flask, adding 100 ml of boiled pure water, heating and holding the boiled state for about 5 minutes, then plugging it and letting it cool to room temperature. After adding water corresponding to the above, stoppered again, shaken for 1 minute, allowed to stand for 5 minutes, and then measured the pH of the obtained supernatant according to JIS Z 8802-7. It was. For hydrophobic samples, add 5 to 10 mL of ethanol, wet the sample powder with ethanol, add 100 ml of boiled pure water, heat and hold the boiled state for about 5 minutes, then plug. The mixture was allowed to cool to room temperature, water corresponding to the weight loss was added, stoppered again, shaken for 1 minute, allowed to stand for 5 minutes, and then the pH of the obtained supernatant was measured according to JIS Z 8802-7. The obtained value was defined as the powder pH value.

  The degree of hydrophobicity of the silica particle powder and the hydrophobic silica particle powder was determined by the following procedure according to the methanol wettability method (MW method). A liquid for mixing methanol and water is prepared in advance so as to obtain a predetermined methanol concentration (in increments of 5 vol%). 50 ml of methanol solution of each concentration is put into a 100 ml beaker, and 0.2 g of sample powder is added. Next, it stirred with the magnetic stirrer and the methanol wettability value was calculated | required from the density | concentration of the methanol solution which the sample powder whole amount settled, and the methanol solution which did not settle.

  The flowability of silica particle powder and hydrophobic silica particle powder is determined by using powder tester (manufactured by Hosokawa Micron Co., Ltd.), each powder of repose angle (degree), compression degree (%), spatula angle (degree), and cohesion degree. Body characteristic values were measured, each index was calculated by replacing each measured value with a numerical value based on the same standard, and each index was expressed as a total liquidity index. The closer the fluidity index is to 100, the better the fluidity.

The dispersibility of the hydrophobic silica particle powder in the rubber composition was evaluated on a five-point scale by visually determining the number of undispersed aggregated particles on the surface of the rubber composition prepared by the method described later. 5 indicates the best dispersion state.
1: 50 or more per 1 cm ²
2: 10 or more and less than 50 per 1 cm ²
3: 5 or more and less than 10 per 1 cm ²
4: 1 or more and less than 5 per 1 cm ²
5: Undispersed material not recognized

The Mooney viscosity of the unvulcanized rubber composition is the Mooney viscosity ML _{1 + 4} (130 ° C.) of the rubber composition after 1 minute and 4 minutes of preheating at 100 ° C. according to JIS K 6300 using a Mooney viscometer. The value of the rubber composition of Comparative Example 1 was measured and expressed as an index. In addition, it shows that it is excellent in workability, so that the index of Mooney viscosity is small.

  The wear resistance of the rubber composition was determined by measuring the amount of wear loss in accordance with JIS K 6264 under the conditions of a load of 40 N, a temperature of 20 ° C., and a slip rate of 20% using a Lambone abrasion tester. The value of the composition was set to 100, and the amount of wear loss was shown as an index according to the following formula 1. In addition, it shows that abrasion resistance is so favorable that the index | exponent of a wear loss amount is large.

<Equation 1>
Lambourn abrasion index = (Abrasion loss amount of Comparative Example 1) / (Abrasion loss amount of each rubber composition) × 100

  The tensile strength of the rubber composition was measured according to JIS K 6301. It shows that fracture resistance is so favorable that tensile strength is large.

  The loss tangent (tan δ) of the rubber composition was measured using a viscoelasticity measuring device (Rheometrics) at a temperature of 60 ° C., a strain of 5%, and a frequency of 15 Hz. The loss tangent was shown as an index according to the following formula 2, where the value of the rubber composition was 100. Note that the smaller the loss tangent index, the less heat is generated and the lower the heat buildup.

<Equation 2>
Loss tangent index = (loss tangent of each rubber composition) / (loss tangent of Comparative Example 1) × 100

  Next, examples and comparative examples are shown.

Example 1-1 <Production of Hydrophobic Silica Particle Powder>
Silica particles 1 (particle shape: granular, average particle size: 15 nm, BET specific surface area value: 203.8 m ² / g, powder pH value: 6.1, fluidity: 57, degree of hydrophobicity (methanol wettability)) MW): 0%) A stirred and mixed granulator “Vertical Granulator VG-100 type” (product name, manufactured by POWREC Co., Ltd.) in which 8.0 kg is preheated to 90 ° C. is stirred and stirred for 20 minutes. The coagulation was loosened and the water content was adjusted to 4.0%.

Next, treatment agent A (type: bis (3- (triethoxysilyl) propyl) tetrasulfide, minimum coating area: 330 m ² / g, water amount required for hydrolysis of treatment agent A 1 g: 0.20 g / g) 640 g was added to the silica particle powder and mixed and stirred for 30 minutes. At this time, the treatment amount with the treatment agent A was 7.39% by weight.

Next, 120 g of treating agent C (type: 3-aminopropyltriethoxysilane, minimum covering area: 354 m ² / g, water amount required for hydrolysis of 1 g of treating agent A: 0.24 g / g) The mixture was added to the A-treated silica particle powder and mixed and stirred for 30 minutes. At this time, the treatment amount with the treatment agent C was 1.35% by weight, and the surface coverage of the silica particles 1 with the treatment agent A and the treatment agent C was 14.0%.

  Next, 400 g of a higher fatty acid A (type: stearic acid, melting point: 69.6 ° C.) is added to the silica particles 1 coated with the treatment agent A and the treatment agent C, mixed and stirred for 60 minutes, and then dried. Heat treatment was performed at 180 ° C. for 60 minutes using a machine to obtain hydrophobic silica particle powder of Example 1-1. The amount of treatment with the higher fatty acid at this time was 4.37% by weight, and the amount of the higher fatty acid covered with 1 mol of the organic functional group of the treatment agent C (amino silane coupling agent) was 2.59 mol.

The obtained hydrophobic silica particle powder has an average particle diameter of 15.7 nm, a BET specific surface area value of 108.2 m ² / g, a powder pH value of 7.4, a fluidity of 75, and a degree of hydrophobicity (methanol wettability). ) (MW) was 70%, and the change rate of the BET specific surface area value before and after the treatment was 46.9%.

<Example 2-1: Production of rubber composition>
Except for sulfur and a vulcanization accelerator, they were charged into a Banbury mixer according to a conventional method at the blending ratio shown below, and mixed and kneaded at 135 ° C for 5 minutes to obtain a kneaded product.

Styrene-butadiene copolymer 70.0 parts by weight Natural rubber 30.0 parts by weight Hydrophobic silica particle powder 40.0 parts by weight Zinc oxide 3.0 parts by weight Coupling agent 1.5 parts by weight (bis (3- (tri Ethoxysilyl) propyl) tetrasulfide)
Stearic acid 2.0 parts by weight Anti-aging agent 1.0 part by weight Wax 1.0 part by weight Sulfur 1.5 parts by weight Vulcanization accelerator 1.5 parts by weight

  Next, the kneaded product was transferred to a kneading roll machine, sulfur and a vulcanization accelerator were added, and mixed and kneaded at 50 ° C. for 5 minutes to obtain an unvulcanized rubber composition.

  The obtained rubber composition was press vulcanized at 160 ° C. for 20 minutes to produce test pieces (147 mm × 147 mm × 2 mm), and various tests were performed.

  The resulting rubber composition had a dispersibility of 5, a Mooney viscosity index of 94, an abrasion resistance index of 110, a tensile strength of 23.3 MPa, and a loss tangent index of 78.

  Hydrophobic silica particle powder was prepared according to Example 1-1. Various characteristics of each production condition and the obtained hydrophobic silica particle powder are shown.

Silica particles 1 and 2
As silica particle powder, silica particle powder having the characteristics shown in Table 1 was prepared.

Treatment agents A to D:
Treatment agent A and treatment agent B having various characteristics shown in Table 2 as sulfide silanes, and treatment agent C and treatment agent D as amino-based silane coupling agents were prepared.

Higher fatty acids A to C:
Higher fatty acids having various properties shown in Table 3 were prepared as higher fatty acids.

Examples 1-2 to 1-4, Comparative Examples 1-1 to 1-4
Example 1-1, except that the type of silica particle powder, the amount of moisture due to humidity control, the type and addition amount of the treatment agent, the type and addition amount of higher fatty acid, the heat treatment temperature and the treatment conditions for time were variously changed. In the same manner, hydrophobic silica particle powder was obtained.

  The production conditions at this time are shown in Table 4, and the properties of the obtained hydrophobic silica particle powder are shown in Table 5.

Examples 2-2 to 2-4, comparative examples 2-1 to 2-5
A rubber composition was obtained in the same manner as in Example 2-1, except that the type of filler was variously changed.

  Table 6 shows the production conditions at this time and various characteristics of the obtained rubber composition.

  The hydrophobic silica particle powder according to the present invention has excellent hydrophobicity and fluidity, and is excellent in dispersibility in the rubber composition. Therefore, the hydrophobic silica particle powder is used for various rubber compositions including tire tread rubber compositions. Suitable as a filler.

  The method for producing hydrophobic silica particle powder according to the present invention has a small change in the BET specific surface area value of the inorganic particle powder before and after the treatment, and also causes problems such as COD emission because all processes are performed in a dry process. Since it does not occur, it is suitable as a method for producing hydrophobic silica particle powder in consideration of the environment.

The rubber composition according to the present invention is improved in workability by using the above-described hydrophobic inorganic particle powder according to the present invention as a reinforcing filler, and has rolling resistance characteristics and wetness without impairing wear resistance. It is suitable as a rubber composition that can improve the braking performance on the road surface.

Claims (7)

The particle surface of the silica particle powder is coated with a sulfide silane and an amino silane coupling agent, and the coated surface is coated with one or more higher fatty acids selected from saturated or unsaturated fatty acids having 12 or more carbon atoms. a hydrophobic silica particles of silica particles having an average particle diameter 0.01~0.3μm who is a feature and this hydrophobicity with methanol wetting data capability of the hydrophobic silica particles is 60% or more Hydrophobic silica particle powder. The hydrophobic silica particle powder according to claim 1, wherein the BET specific surface area value is 90 m ² / g or more. The hydrophobic silica particle powder according to claim 1 or 2, wherein the powder has a pH value of 7.0 or more. Surufidoshiran, according to any one of claims 1 to 3 amino silane coupling agent and a higher fatty acid by coating treatment before and the rate of change in BET specific surface area value of the silica particles after the treatment is less than 56% Hydrophobic silica particle powder. The hydrophobic silica particle powder according to any one of claims 1 to 4 , which has a fluidity index higher by 10 or more than the fluidity index of the silica particle powder before treatment. Add sulfide silane and amino silane coupling agent to silica particle powder, mix and stir to coat the particle surface of silica particle powder with sulfide silane and amino silane coupling agent, then add higher fatty acid and mix In the method for producing hydrophobic silica particle powder that stirs and attaches higher fatty acid to the surface of the coating, the sulfide silane and amino-based silane in which all treatment steps are performed in a dry manner and the water content of the silica particle powder is added in advance. The water content is adjusted to a range of 1 to 10 times the amount of water necessary for the hydrolysis of the coupling agent, and the temperature of the inorganic particle powder after adhering to the sulfide silane, amino silane coupling agent and higher fatty acid is 120 to 210 ° C. hydrophobic silica particles according to any one of claims 1 to 5, characterized in that a heat treatment in the range Process for the preparation of powder. A rubber composition using the hydrophobic silica particle powder according to any one of claims 1 to 5 .