Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-16
2003-02-25
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S571000, C524S565000, C524S566000, C524S574000, C524S575000, C524S575500
Reexamination Certificate
active
06525110
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polysiloxane-containing rubber composition having improved properties and a rubber compounding agent therefor.
2. Description of the Related Art
Rubber compositions comprising various rubbers and a filler such as silica are known in the art and are used, for example, as rubber compositions for tire treads having a low heat generation characteristic and superior in abrasion resistance etc. However, tire treads in which silica is formulated have a low rolling resistance and a good grip on wet roads, but there were the problems that the viscosity of the unvulcanized compound increases, the vulcanization is slowed, the kneading performance in the mixing falls, etc. and the productivity deteriorates. Various proposals have been made in the past to solve these problems, but unfortunately these are not practically satisfactory.
For example, it has been proposed to add diethylene glycol or a fatty acid (for example, see Gomu Kogyo Binran (or Rubber Industry Handbook), fourth version, pp. 517 to 518, published 1994), to add a metal salt of a carboxylic acid (for example, see Tire Technology International 1995, pp. 107 to 108), and to treat the silica in advance with silicone oil (for example, see Japanese Unexamined Patent Publication (Kokai) No. 6-248116). Further, the only way to deal with scorching during mixing and a fall in the kneading performance is to increase the number of times of mixture. Further, even when mixing carbon and silica, the practice is to either mix them separately or to increase the mixing time or frequency of mixture. None of these are unfortunately practically acceptable.
On the other hand, various metal oxides are used in many fields such as rubber, cosmetics, synthetic resins, coating compositions, adhesives, magnetic tapes. In most cases, since the metal oxides are added to organic materials, problems arise how the metal oxides are dispersed in the organic materials. For this purpose; various attempts have been made to solve these problems. For example, the treatment of the metal oxides with surface treatment agents has been proposed. JP-A-8-48910 discloses a method for treating a metal oxide with methyl hydrogen polysiloxane, in which the metal oxides are necessary for treating at a high temperature. JP-A-8-53630 discloses the treatment with an alkoxy silane, but this is not still sufficient.
On the other hand, rubber compositions comprising various rubbers and metal oxides such as silica, clay, talc are known and are used as, for example, rubber compositions for tire tread having excellent low heat build-up and abrasion resistance. However, when metal oxides are compounded, there are disadvantages, when compared in the case of carbon black, the modulus is decreased and the abrasion resistance is low. To solve these problems, the above-mentioned JP-A-6-248116 has been proposed. (i.e., silica is surface-treated under heating with, for example, a hydrophobic agent such as silicone oil comprising an organic silicon compound at, for example, 250° C. for 1 hour. However, this method has a disadvantage of a short scorching due to heating at a high temperature.
SUMMARY OF THE INVENTION
Accordingly, the objects of the present invention are to eliminate the above-mentioned disadvantageous of the prior art and to provide a filler-containing vulcanizing rubber composition which improves the processability of the unvulcanized rubber composition, without substantially impairing the properties of the filler-containing vulcanized rubber composition such as the low heat generation characteristic and the abrasion resistance.
Another object of the present invention is to provide a rubber compounding agent improving the vulcanized physical properties of a silica-containing vulcanizing rubber composition, in particular the modulus, abrasion resistance, and tan&dgr; balance etc. and a silica-containing vulcanizing rubber composition using the same.
A further object of the present invention is to provide a surface-treated metal oxide capable of increasing the reinforceability when compounding into rubber and of improving the modulus and the abrasion resistance of the rubber composition and a rubber composition containing the same.
A still further object of the present invention is to provide a silica-containing vulcanizing rubber composition for a tire tread which improves the processability of the unvulcanized rubber composition, without substantially impairing the properties of the silica-containing vulcanizing rubber composition, for example, the low heat generation characteristic and the abrasion resistance.
Other objects and advantages of the present invention will be apparent from the following description.
In accordance with the present invention, there is provided a rubber composition comprising a filler, said rubber composition containing a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having at least six alkoxy groups or at least two acyloxy groups directly bonded to the Si atom in the molecule thereof and having an average degree of polymerization of 3 to 10,000:
≡Si—OR
1
(I)
≡Si—OCOR
2
(II)
wherein, R
1
is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R
2
is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.
In accordance with the present invention, there is provided a rubber compounding agent comprising (A) a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000 and (B) a silane coupling agent in a ratio of (A)/(B)=95/5 to 5/95:
≡Si—OR
1
(I)
≡Si—OCOR
2
(II)
wherein, R
1
is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R
2
is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.
In accordance with the present invention, there is further provided a rubber composition comprising 100 parts by weight of a starting rubber, 5 to 100 parts by weight of silica, and an amount of the above-mentioned rubber compounding agent to give a content of the polysiloxane contained therein of 0.2 to 30% by weight in the total composition.
In accordance with the present invention, there is further provided a polysiloxane surface-treated metal oxide comprising 100 parts by weight of a metal oxide surface treated with 0.1-50 parts by weight of a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000:
≡Si—OR
1
(I)
≡Si—OCOR
2
(II)
wherein, R
1
is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 18 carbon atoms or an organic group containing an ether bond and R
2
is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms.
In accordance with the present invention, there is further provided a rubber composition comprising 100 parts by weight of a starting rubber and 5 to 100 parts by weight of the above-mentioned polysiloxane surface-treated metal oxide.
In accordance with the present invention, there is provided a rubber composition for a pneumatic tire tread comprising 100 parts by weight of a diene rubber, 2 to 80 parts by weight of carbon black, 5 to 80 parts by weight of silica, a silane coupling agent, and a polysiloxane having the following alkoxysilyl group (I) and/or acyloxysilyl group (II) and having an average degree of polymerization of 3 to 10,000:
≡Si—OR
1
(I)
≡Si—OCOR
2
(II)
wherein R
1
and R
2
are the same as defined above.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The term “filler” used herein means any conventional inorganic fillers (e.g., calcium carbonate, clay, talc, diatomaceous silica, mica, alumina, aluminum sulfate, barium sulfate, calcium sulfate, etc.) and so-called
Hashimura Yoshiaki
Ishikawa Kazunori
Kaido Hiroyuki
Kawazura Tetsuji
Yatsuyanagi Fumito
Moore Margaret G.
The Yokohama Rubber Co. Ltd.
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