Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-12-11
2004-05-25
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S432000, C524S492000, C524S571000
Reexamination Certificate
active
06740704
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for producing a diene-based rubber/inorganic compound complex in which a silicic acid compound particle is dispersed uniformly in the diene-based rubber and which exerts a sufficient reinforcing effect, and a rubber composition containing this complex as an essential component. More particularly, the invention relates to a method for producing an improved diene-based rubber/inorganic compound complex for the purpose of generating a silica particle and the like in a diene-based rubber latex and dispersing the particle uniformly in the diene-based rubber, and a rubber composition containing the same. Now that the term “silicic acid compound” means a substance including silica or the like and it is hereinafter often expressed as “silicic acid compound including silica and the like”. A rubber composition of the invention can be converted into a vulcanized rubber which is excellent in terms of physical characteristics such as wearing resistance, and thus is useful especially as a tire rubber such as a tire tread as well as a rubber material for any of various rubber products such as belts, rubber rolls and hoses.
2. Description of the Related Art
In response to a recent demand for high gas mileage of automobile, rubber material such as a conjugated diene-based rubber capable of giving a rubber composition for a tire which has low rolling resistance, excellent destruction characteristics and wearing resistance, high wet skid resistance, a representative index of a driving stability, is desired.
Tire rolling resistance can be reduced by lowering hysteresis loss of vulcanized rubber. The hysteresis loss can be evaluated based on various physical properties. For example, compositions preferably have high impact resilience at 50 to 80° C., a low tans at 50 to 80° C. or low Goodrich heat release. Compositions including natural rubber, isoprene rubber, butadiene rubber and the like show low hysteresis loss, but these are also associated with the problem of low wet skid resistance.
In recent years, there have been proposed methods of using inorganic filler such as a silica and the like to serve as reinforcing agent, or combining inorganic filler with carbon black. Tire treads employing inorganic filler or both inorganic filler and carbon black have low rolling resistance and excellent driving stability, represented by, for example, the wet skid resistance. However, vulcanized rubber exhibit a problem of poor wearing resistance, tensile strength and the like as the vulcanized rubber. One cause is believed that the affinity of inorganic filler for the conjugated diene-based rubber is lower than that of carbon black, such that a sufficient reinforcing effect cannot be achieved.
In order to increase the affinity between the silica as an inorganic filler and the conjugated diene-based rubber, it has-been attempted to use conjugated diene-based rubbers introduced therein functional group with affinity for inorganic filler. For example, there have been proposed a conjugated diene-based rubber introduced a hydroxyl group therein (WO96/23027), a conjugated diene-based rubber introduced an alkoxysilyl group therein (Japanese Patent laid-open publication No. HEI-9-208623) and a conjugated diene-based rubber introduced an alkoxysilyl group and an amino and/or a hydroxyl group therein (Japanese Patent laid-open publication No. HEI-9-208633). However, most conjugated diene-based rubbers with such an introduced functional group exhibit strong interaction with an inorganic filler when the inorganic filler is combined therewith, and this creates such problems as impaired dispersion of the inorganic filler, greater heat release during processing, poor processability and the like.
On the other hand, Japanese Patent laid-open publication No. SHO-59-49247 or the like proposed a method for simplifying a process for kneading a mixture containing carbon black as a reinforcing agent or for improving the dispersibility in a rubber. That is, the method comprises a step for incorporating carbon black into an aqueous dispersion in which a rubber such as a latex has been dispersed, a step for dispersing the formulation and coagulating, and a step for forming a carbon black master batch. While an attempt was made to prepare a silica master batch by this method, a uniform master batch was difficult to be obtained due to a difficulty in aggregating the highly hydrophilic silica which leaded to an earlier aggregation and precipitation only of a rubber component.
SUMMARY OF THE INVENTION
The present invention solves the problems associated with prior arts described above and is intended to provide a method for producing a diene-based rubber/inorganic compound complex in which a silica and the like are dispersed uniformly in a diene-based rubber, by employing an aqueous dispersion in which a rubber such as a latex has been dispersed and an aqueous solution of a silicate or an aqueous dispersion containing a silicic acid compound such as a silica and also by employing a multivalent metal salt and a particular cationic substance and enabling a promotion of a co-coagulation of a rubber component and a silicic acid compound such as a silica as well as a sufficiently-reinforced rubber composition containing the same.
The present inventors studied in detail the method for producing a diene-based rubber/inorganic compound complex in which a silica and the like are dispersed uniformly in a diene-based rubber. A rubber composition containing the diene-based rubber/inorganic compound complex showed excellent processability, and a vulcanized rubber produced by using the complex showed low rolling resistance, excellent wearing resistance, excellent tensile strength or the like.
The present invention is based one the findings described above and can be described as follows.
1. A method for producing a diene-based rubber/inorganic compound complex containing a diene-based rubber and a silicic acid compound of the first aspect of the invention is comprising:
[1] a step for mixing a diene-based rubber latex (a) and an aqueous solution of a silicate (b) to form a mixture <p>,
[2] a step for mixing the mixture <p> and an aqueous solution of electrolytes <r> containing a cationic substance (c) which has an affinity to the diene-based rubber and also a multivalent metal salt (d) to co-coagulate a diene-based rubber and a silicic acid compound whereby forming an coagulated material, and,
[3] a step for drying the coagulated material.
2. The method for producing a diene-based rubber/inorganic compound complex according to 1 above wherein said cationic substance (c) is at least one selected from the group consisting of cationic polymers and cationic surfactants.
3. The method for producing a diene-based rubber/inorganic compound complex according to 1 above wherein said diene-based rubber contained in said diene-based rubber latex (a) is a rubber having hetero atom-containing polar group.
4. The method for producing a diene-based rubber/inorganic compound complex according to 1 above wherein an extending oil for a rubber is incorporated in said diene-based rubber latex (a).
5. A method for producing a diene-based rubber/inorganic compound complex containing a diene-based rubber and a silicic acid compound of the second aspect of the invention is comprising:
[1] a step for mixing a diene-based rubber latex (a), an aqueous solution of a silicate (b) and an aqueous solution of electrolytes <r> containing a cationic substance (c) which has an affinity to the diene-based rubber and also a multivalent metal salt (d) to co-coagulate a diene-based rubber and a silicic acid compound whereby forming an coagulated material, and,
[2] a step for drying the coagulated material.
6. A method for producing a diene-based rubber/inorganic compound complex containing a diene-based rubber and a silicic acid compound of the third aspect of the invention is comprising:
[1] a step for mixing a diene-b
Konno Tomohisa
Tadaki Toshihiro
Udagawa Yoshiyuki
Hu Henry S.
JSR Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wu David W.
LandOfFree
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