Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-04-26
2004-06-08
Zalukaeva, Tatyana (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S098000, C525S099000, C525S191000, C525S914000, C525S901000, C524S495000, C524S496000, C252S511000
Reexamination Certificate
active
06747095
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a certain crosslinked rubber particle and a rubber composition comprising as essential components such a crosslinked rubber particle and a non-crosslinked rubber component. A rubber composition of the invention exhibits an excellent processability, and also exhibits excellent handling performance and dimension stability, and the like especially when combined with a silica as a reinforcing agent. A vulcanized rubber obtained by vulcanizing a rubber composition of the invention can be used in various industrial field as a rubber product such as a belt, a hose, a roll, a tire, and the like.
2. Description of the Related Art
A starting rubber which has been employed frequently for a rubber product may for example be:
(A) a polymer whose repeating unit consists only of a conjugated diene unit such as a butadiene rubber, an isoprene rubber, a chloroprene rubber and a natural rubber;
(B) a polymer whose repeating units are a conjugated diene unit and an aromatic vinyl unit such as a styrene-butadiene copolymeric rubber, a styrene-isoprene copolymeric rubber and a styrene-isoprene-butadiene copolymeric rubber;
(C) a polymer whose repeating units are a conjugated diene unit and an &agr;,&bgr;-unsaturated nitrile unit such as an acrylonitrile-butadiene copolymeric rubber;
(D) a polymer in which an acrylate unit is essential as a repeating unit such as an acrylic rubber; and,
(E) a polymer whose repeating units are ethylene and an &agr;-olefin having 3 to 12 carbon atoms optionally with a non-conjugated polyene, such as an ethylene-propylene rubber.
Any of these starting rubbers, when combined with a silica as a reinforcing agent, can provide a colored rubber product except for a black colored product, and a favorable performance of a formulated rubber made therefrom is a heat generation kept at a low level. However, unlike to a carbon black, a silica may lead to a problematic reduction in the tensile strength and the wearing resistance of a vulcanized rubber, and the like. Additional problems associated with the incorporation of a silica include {circle around (1)} a reduction in the processability and the compound consistency upon kneading, {circle around (2)} an insufficient smoothness of the surface of a sheet made from a compound using a roll and an irregular sheet edge accompanied with a substantial shrinkage upon cooling, and the like.
Such problems may be due to an aggregation of a silica instead of a sufficient dispersion. A rubber composition in which a silica is not dispersed sufficiently poses a difficulty in obtaining a certain reinforcing effect of the incorporation of a reinforcing agent and undergoes a heat generation attributable to the interaction between poorly dispersed silica particles, resulting in a substantial reduction in the processability. Such poor dispersion of a silica occurs possibly because of the reasons that a silica has a high self-interacting effect when compared with a carbon black and tends to aggregate easily and that a starting rubber usually consists of carbon and hydrogen and has a lower polarity when compared with a silica which leads to a low affinity with the silica.
For the purpose of increasing the affinity of a silica with a hydrocarbon-based rubber, the use of a conjugated diene-based rubber to which a functional group having an affinity with the silica is introduced has been investigated. For example, a conjugated diene-based rubber to which a hydroxyl group is introduced (WO96/23027), a conjugated diene-based rubber to which an alkoxysilyl group is introduced (JP-A 9-208623) and a conjugated diene-based rubber to which an alkoxysilyl group and an amino group or a hydroxyl group are introduced (JP-A 9-208633) have been proposed. However, such conjugated diene-based rubber to which a functional group described above is introduced mostly exhibits problematically poor dispersion, excessive heat generation upon processing and poor processability, and the like since it undergoes an extensive aggregation with a silica when the silica is admixed.
On the other hand, a silane coupling agent is incorporated usually for the purpose of preventing an aggregation of a silica and achieving a uniform dispersion. This results in an improvement in the dispersibility of a silica to some extent and a substantial improvement in the processability of a rubber composition and the tensile strength and the wearing resistance of a vulcanized rubber and the like. Nevertheless, the smoothness of the surface and the edge of a sheet or the problematic shrinkage of a sheet upon cooling or the like has not adequately been improved. Furthermore, a sufficient improvement in the processability, the tensile strength or the wearing strength or the like requires the incorporation of a silane coupling agent in an amount as high as 8 to 15% by weight based on a silica, but such silane coupling agent is expensive and increases the cost for a rubber composition.
SUMMARY OF THE INVENTION
The present invention overcomes the problems experienced conventionally as described above, and is intended to provide a rubber composition having excellent processability and handling performance, which are experienced as a satisfactory processability upon kneading, a smooth sheet surface, a regular sheet edge and a less shrinkage upon cooling, and the like. Another objective of the invention is to provide a crosslinked rubber particle from which a rubber composition described above can be prepared. A vulcanized rubber obtained by vulcanizing a rubber composition described above has excellent tensile strength and wearing resistance, and the like.
We made an effort to solve the problems mentioned above and discovered that by incorporating a crosslinked rubber particle component having a certain composition into a rubber composition, it is possible to obtain a rubber composition which exhibits a satisfactory processability upon kneading and achieves a satisfactory smoothness of the sheet surface and the sheet edge and a less sheet shrinkage upon cooling even when using a silica as a reinforcing agent. It was also discovered that by using this rubber composition it is possible to obtain a vulcanized rubber exhibiting a less heat generation and having sufficient tensile strength and wearing resistance, and the like. In addition, even when a silane coupling agent is used only in a reduced amount or is not used, the processability and the tensile strength, and the like were revealed to be improved sufficiently to the levels at which no practical problems are experienced.
The present invention is based on the findings described above and can be described as follows.
A crosslinked rubber particle comprising as repeating units (a) 30 to 94.89% by weight of a conjugated diene unit, (b) 5 to 69.89% by weight of an aromatic vinyl unit, (c) (0.01 to 10% by weight of a monomer unit having at least two polymerizable unsaturated group and (d) 0.1 to 30% by weight of a monomer unit having one polymerizable unsaturated group and at least one functional group selected from an amino group, a hydroxyl group and an epoxy group and having a particle size of 10 to 500 nm and a toluene-insolubles of 80% by weight or more.
In the crosslinked rubber particle, the monomer forming said monomer unit (d) having one polymerizable unsaturated group and an amino group is at least one selected from dialkylaminoalkyl (meth) acrylates, N-dialkylaminoalkyl group-containing unsaturated amides, dialkylaminoalkyl (meth)acrylate and tertiary amino group-containing vinyl aromatic compound.
In the crosslinked rubber particle, the monomer forming said monomer unit (d) having one polymerizable unsaturated group and a hydroxyl group is at least one selected from hydroxyalkyl (meth) acrylates, mono (meth)acrylates of polyalkylene glycols (the number of alkylene glycol units is 2 to 23), hydroxyl group-containing unsaturated amides, hydroxyl group-containing vinyl aromatic compounds and (meth)allyl alcohol.
In the crosslinked rubber particle, the monomer for
Akema Hiroshi
Konno Tomohisa
Tadaki Toshihiro
Udagawa Yoshiyuki
JSR Corporation
Oblon, Spivak, McCelland, Maier & Neustadt, P.C.
Zalukaeva Tatyana
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