JP2000001547A - Preparation of carbon-silica wet masterbatch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a masterbatch having improved kinetic physical properties by adding a rubber latex to an aqueous dispersion of a silica of which surface is subjected to hydrophobic treatment and a carbon black and thereafter conducting a salting-out. SOLUTION: Any carbon black is optionally used if only the carbon black is one used as a reinforcing filler for a rubber. As a silica, either one of a fine silicic acid powder mainly composed of SiO2 (a silicic anhydride or a hydrous silicic acid) or an artificial silicate (a hydrous calcium silicate) can be used. Usually, the carbon black and the silica are used in a ratio of about 2-150 wt.% and about 1-100 wt.%, respectively, based on the rubber content in a rubber latex. The hydrophobic treatment of the silica surface is generally carried out by using a silane coupling agent. A wet masterbatch is usually prepared by dispersing a filler with a surfactant in water to form a slurry of the filler, adding thereto an aqueous latex of a rubber and mixing, and thereafter introducing an acid or an electrolyte aqueous solution to conduct a salting- out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a carbon-silica wet masterbatch. More particularly, the present invention relates to a method for producing a carbon-silica wet masterbatch having improved mechanical properties.

[0002]

2. Description of the Related Art Conventionally, a rubber-based wet (wet) master batch is mainly composed of carbon black alone. When silica is mixed with the master batch, a separate kneading step needs to be performed. As a result, the advantages of a wet masterbatch that does not require kneading of the agent are impaired.

[0003] The reason for this is that carbon black having a hydrophobic surface and silica having a hydrophilic surface have different surface characteristics. Therefore, in order to prepare a slurry of these two types of fillers, 2 is required. Different types of surfactants had to be used. Since the filler slurries prepared in this way have different properties such as the stability of the surfactant used, uniform precipitation cannot be performed in the subsequent salting out, and the In fact, it is inevitable that poor dispersion of the agent and, consequently, deterioration of the mechanical properties of the vulcanized rubber using such a master batch cannot be avoided.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a carbon-silica wet masterbatch having improved mechanical properties.

[0005] The object of the present invention is to provide a carbon-silica system by adding a rubber latex to an aqueous dispersion of silica and carbon black whose surface has been hydrophobized and then salting out. This is achieved by manufacturing a wet masterbatch.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As carbon black, any carbon black can be used as long as it is used as a reinforcing filler for rubber. As the silica, any of finely divided silicic acid (silicic anhydride, hydrous silicic acid) and artificial silicate (hydrous calcium silicate) containing SiO2 as a main component can be used. These are generally about 2 to 150% by weight, preferably about 5 to 100% by weight, and silica are about 1 to 100% by weight, preferably about 1 to 100% by weight, based on the rubber component amount in the rubber latex. It is used in a ratio of about 2 to 60% by weight.

In general, a wet master batch is prepared by dispersing a filler in water together with a surfactant to form a filler slurry, adding an aqueous latex of rubber thereto and mixing, and then adding an acid or electrolyte aqueous solution. It is carried out by charging and salting out.

In the present invention, a surfactant such as sodium stearate and potassium stearate is preferably used in an amount of about 1 to 30% by weight, preferably about 2 to 20% by weight. Because only one kind of such a surfactant is used (here, one kind means one kind in terms of surface activity, and only one kind of the above-listed surfactants is used. This does not mean that the surface hydrophobicity of the carbon black is matched.

The surface hydrophobization treatment of silica is generally performed using a silane coupling agent. Examples of the silane coupling agent include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- ( (N-vinylbenzylaminoethyl) -γ-aminopropylmethyldimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane,
Ethyl triethoxy silane, vinyl triacetoxy silane, γ-chloropropyl trimethoxy silane, hexamethyldisilazane, γ-anilinopropyl trimethoxy silane, vinyl trimethoxy silane, etc. are used. It is desirable to be selected and used in the relationship of.

The surface treatment of silica with a silane coupling agent can be performed by any method such as an aqueous solution method, an organic solvent method, and a spray method. The silica subjected to the hydrophobic surface treatment in this manner is, together with carbon black, in an aqueous solution in which the surfactant is dissolved, stirred and dispersed using a homogenizer or the like, and then an aqueous latex of rubber is added thereto. After sufficiently stirring, the mixture is prepared into a wet master batch by salting out.

As the aqueous latex of rubber, an aqueous latex such as acrylic rubber, fluoro rubber, nitrile rubber or the like is used, and the filler contains about 10 to 160% by weight in total with respect to the amount of the rubber component in the rubber latex. , Preferably about 20-
A masterbatch added at a rate of 120% by weight is formed.

[0012]

According to the method of the present invention, a wet master batch using two kinds of fillers, carbon black and silica, can be easily produced by using only one kind of surfactant. In the masterbatch, no dispersion failure is observed between the two types of fillers. By using such a wet masterbatch, a vulcanized rubber having excellent mechanical properties can be obtained.

[0013]

Next, the present invention will be described with reference to examples.

EXAMPLE A sodium hydroxide aqueous solution having a pH of 9 was charged into a 2 L eggplant-shaped flask, 50 g of silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) was added thereto, and the mixture was stirred and dispersed, and 10 g of ethyltriethoxysilane was added. The mixture was stirred at 70 ° C for 4 hours. After completion of the reaction, filtration, washing with methanol and drying under reduced pressure were performed to obtain surface-treated silica.

After adding 20 g of sodium stearate to 2 L of water and stirring at 50 ° C. to completely dissolve, 60 g of FEF carbon black and 40 g of the above-mentioned surface-treated silica were added, and the mixture was stirred and dispersed with a homogenizer for 30 minutes. Thereto was added 1.5 L of an acrylic rubber latex (ethyl acrylate-vinyl acetate copolymer rubber, solid content concentration: 20% by weight), and after sufficient stirring, 200 ml of a 10% by weight aqueous solution of CaCl2 was added for salting out. After filtering, washing with water and drying under reduced pressure, carbon-
A silica wet masterbatch (a filler amount of 33% by weight in total with respect to the acrylic rubber) was obtained.

To 160 parts by weight of the obtained carbon-silica wet master batch, 5 parts by weight of potassium stearate,
Roll kneading by adding 20 parts by weight of sodium stearate and 0.5 parts by weight of sulfur, 180 ° C, press vulcanization for 8 minutes and 175 ° C, oven vulcanization for 4 hours (secondary vulcanization),
Test pieces were prepared.

Comparative Example In the examples, no silica surface treatment was performed, and 5 g of dodecylethylenediamine was used in addition to 20 g of sodium stearate in preparing a wet master batch.

With respect to the test pieces obtained in the above Examples and Comparative Examples, the physical properties in a normal state were measured according to JIS K-6301, and the results shown in the following table were obtained. Table Measurement item Example Comparative example Tensile strength (MPa) 16.7 12.6 Elongation (%) 205 180 100% modulus (MPa) 5.1 3.2

Claims (3)

[Claims] 1. A method for producing a carbon-silica wet masterbatch, comprising adding a rubber latex to an aqueous dispersion of silica and carbon black whose surfaces have been hydrophobized and then salting out. 2. The method according to claim 1, wherein a silane coupling agent is used for the hydrophobic treatment of the silica surface. 3. A carbon-silica wet masterbatch produced by the method according to claim 1, which is blended with an acrylic rubber.