Compositions: coating or plastic – Materials or ingredients – Pigment – filler – or aggregate compositions – e.g. – stone,...
Reexamination Certificate
1999-11-24
2003-11-25
Mulcahy, Peter D. (Department: 1713)
Compositions: coating or plastic
Materials or ingredients
Pigment, filler, or aggregate compositions, e.g., stone,...
C423S449200, C524S261000
Reexamination Certificate
active
06652641
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a modified carbon black for rubber reinforcement (hereinafter sometimes simply referred to as “modified carbon black”). More specifically, the present invention relates to a process for producing a composite of carbon black and silica by using an organoalkoxysilane compound to produce a modified carbon black. The modified carbon black for rubber reinforcement thus obtained can be used in rubber compositions for tires and also for various types of rubber products such as rubber compositions for belt conveyors and industrial rolls, to provide rubber physical properties such as the decrease in tan &dgr; at a high temperature atmosphere (60° C.-100° C.), low heat generation due to the deformation and low loss of the driving energy. Especially, when the rubber composition containing the modified carbon black is used as a rubber composition for a tire tread, etc., tan &dgr; at around 60° C. corresponding to the rolling resistance of the tire can be decreased, without decreasing tan &dgr; at around 0° C. corresponding to braking performance of the tire, and therefore, tires having superior braking performance and low combustion cost can be produced. In addition, the modified carbon black of the present invention can be produced, without any major changes in the conventional carbon black production facilities, and therefore, can be produced at a low cost.
2. Description of the Related Art
Reinforcing fillers such as carbon black and silica have long been used for reinforcing rubber as is well known in the art. Since, among these fillers, silica, as compared with carbon black, has properties of providing a low tan &dgr; at high temperatures (i.e., around 60° C.) and a high tan &dgr; at low temperatures (i.e., around 0° C.), when used for rubber compositions for tire treads for example, a tire having a low rolling resistance and a high gripping power can be advantageously produced. However, silica is inferior to carbon black in the poor abrasion resistance and the low electrical conductivity, and therefore, if used for tires, there is the problem that the tire will pick up a charge when driven on and will cause various problems such as noise and, in some cases, even misoperation in electronic equipments such as radios.
Covering the surface of a pigment, etc. with silica etc. to improve the dispersion and to increase weather resistance has been proposed in, for example, Japanese Examined Patent Publication (Kokoku) No. 50-14254, Japanese Examined Patent Publication (Kokoku) No. 7-30269 and Japanese Unexamined Patent Publication (Kokai) No. 8-277347. For example, Japanese Examined Patent Publication (Kokoku) NO. 7-30269 discloses a method of treating the surface of carbon black used for a powder paint comprising the steps of dispersing carbon black in water, adjusting the pH to 6 or more, and, while maintaining the temperature of 70° C. or more, precipitating amorphous silica on the surface of the particles of carbon black using sodium silicate. Further, Japanese Unexamined Patent Publication (Kokai) No. 8-277347 discloses the adhesion of silica to the surface of carbon black used for rubber reinforcement. However, there are still needs for modified carbon black for rubber reinforcement capable of improving the balance of tan &dgr; (0° C.) and tan &dgr; (60° C.) when compounded into rubber.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a process for simply and cheaply producing a modified carbon black for reinforcement of rubber having a superior balance of tan &dgr; (0° C.) and tan &dgr; (60° C.), without losing the other characteristics.
In accordance with the present invention, there is provided a process for producing a modified carbon black for rubber reinforcement comprising:
adding, to carbon black, water-dispersed silica and an organosilane compound having the formula (I):
R
1
n
—Si—(OR
2
)
4-n
(I)
wherein R
1
represents a hydrocarbon group having 1 to 10 carbon atoms, R
2
represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, n is 1 or 2, and R
1
and R
2
may be the same or different, and
mixing and dispersing the mixture.
In accordance with the present invention, there is also provided a rubber composition comprising a crosslinkable rubber and the modified carbon black, compounded therein, produced by the above-mentioned process.
BEST MODE FOR CARRYING OUT THE INVENTION
As the carbon black for rubber reinforcement used as the starting material for production of a modified carbon black for rubber reinforcement in the present invention, it is possible to use any carbon black which is generally used in the past for tires and other rubber compositions. Preferable carbon blacks are the SRF to SAF grades. It is possible to use the same differently or blend two or more types depending on the application of the rubber composition.
A general method for producing a modified carbon black for rubber reinforcement according to the present invention will be explained below. First, as the water-dispersed silica, it is possible to use those produced by mixing and reacting a metal silicate salt and an acid. The form of the water-dispersed silica (e.g., it may be either a sol or a gel) and the concentration of the silica in the water-dispersed silica are not particularly limited, but a sol type silica in which the silica particles exist independently is preferred. A silica concentration of 50,000 ppm or less, which is stable for a sol, is suitable. Further, as the water-dispersed silica, it is also possible to use a commercially available water-dispersed silica. As a commercially available water-dispersed slurry, those having a diameter of the silica particles contained of from 1 to 100 nm are preferred, more preferably those having a diameter of 5 to 80 nm, and having a sodium ion of 1.0% by weight or less, in terms of Na
2
O are preferred. This type water-dispersed silica is composed of primary particles or aggregates containing plural primary particles dispersed in water. Usually, the electrolyte content is extremely small, and therefore, it is stabilized in a basic state containing a high concentration of silica. Thus, the water-dispersed silica may be particularly suitably used when the silica content is intended to be increased in modified carbon. In the present invention, when producing a modified carbon black, the water-dispersed silica can be added, without particularly adjusting the pH thereof, but it is also possible, for example to add an acid to adjust the neutral conditions to prevent the gelation of the silica or to prevent the corrosion of the granulator. Thereafter, the silica is mixed with the carbon black, whereby the composite of the carbon black is formed.
According to the present invention, in the production of the carbon black for rubber reinforcement, the organosilane compound having the formula (I), in addition to the water-dispersed silica, is added. In the formula (I), the group R
1
represents a hydrocarbon group having 1 to 10 carbon atoms, that is, a saturated or unsaturated aliphatic hydrocarbon group (i.e., typically alkane, alkene or alkyne group) having 1 to 10, preferably 1 to 6, carbon atoms, a alicyclic hydrocarbon group (i.e., typically cycloalkyl group) having 3 to 10, preferably 3 to 8, carbon atoms, or an aromatic hydrocarbon group (i.e., typically phenyl group) having 6 to 10, preferably 6 to 8, carbon atoms, and R
2
represents a hydrogen atom or a hydrocarbon group similar to R
1
.
In the production of the modified carbon black for the rubber reinforcement according to the present invention, the total amount of the water-dispersed silica and the organosilane compound is preferably 0.1% to 50% by weight, more preferably 0.5% to 25% by weight, in terms of SiO
2
, based upon the total weight of the modified carbon black. Further, the amount of the organosilane compound is preferably 80% by weight or less, more preferably 1% to 50% by weight, in terms of SiO
2
, based
Arent Fox Kintner & Plotkin & Kahn, PLLC
Mulcahy Peter D.
The Yokohama Rubber Co. Ltd.
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