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
1999-01-20
2001-03-20
Mulcahy, Peter D. (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...
C525S332100, C525S383000, C525S385000, C525S342000, C152S450000
Reexamination Certificate
active
06204322
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rubber composition having a base of coupled and/or starred diene polymers comprising silica as reinforcing filler, which can be used for the manufacture of tires.
Since fuel economy and the necessity of protecting the environment have become a priority, it is desirable to produce polymers having good mechanical properties and a hysteresis which is as small as possible, in order to be able to use them in the form of rubbery compositions which can be employed for the manufacture of various semi-finished products entering into the constitution of tires, such as, for instance, under-layers, calendering or sidewall rubbers, or treads and to obtain tires having improved properties, in particular reduced resistance to rolling.
In order to achieve this, numerous solutions have been proposed which consist, in particular, or modifying, inter alia, the nature of the diene polymers and copolymers for polymerization by means of coupling or starring agents or functionalizing agents. All these solutions are concentrated essentially on the use of polymers modified with carbon black as reinforcing filler in order to obtain good interaction between the modified polymer and the carbon black, since the use of reinforcing white fillers, and in particular of silica, has proven unsuitable due to the low level of certain properties of such compositions, and therefore of certain properties of tires using these compositions. Furthermore, the use of silica raises difficulties in working due to silica/silica interactions which tend in raw state to cause an agglomeration of the silica particles before and even after mixing and thus to increase the consistency of the rubber compositions, and in any event to make the working more difficult than the working of carbon black. By way of illustrative examples of this prior art, we may cite U.S. Pat. No. 3,135,716, which describes the reaction of living diene polymers at the chain end with a polyfunctional organic coupling agent in order to obtain polymers having improved properties; U.S. Pat. No. 3,281,383 which, as coupling or grafting agents of living diene polymers, describes polyepoxides, polyisocyanates, polyimines, polyaldehydes, polyketones, polyanhydrides, polyesters and polyhalides, including polyhalogenated compositions of silicon; U.S. Pat. No. 3,244,664 which describes tetraalkoxysilanes as coupling and/or starring agent for diene polymers; French Patent 69 24444, which describes as starring agent compositions comprising either the —O—C(O)—O— group or the —O—C(O)—R—C(O)—O— group and which leads to diene polymers having improved working properties and properties in vulcanized state. U.S. Pat. No. 4,185,042 describes diene polymers coupled or starred by means of silicon compounds comprising an epoxide group, the coupling and/or starring agent being present in an amount of 0.05 to 4 moles per mole of living polymer or copolymer having the properties both of an elastomer and of a thermoplastic. There is no reference therein to filled mixtures and nothing permits the person skilled in the art to believe that such polymers could be of interest for compositions comprising silica as reinforcing filler.
The interest in using silica as reinforcing filler in elastomer compositions has existed for a long time, but the use of silica as reinforcing filler has remained very limited due to the drawbacks mentioned above, and this despite the attempts made to remedy the deficiency of the properties exhibited by such compositions. Thus, it has been proposed to use functionalized diene polymers instead of non-functionalized polymers. By way of example of such prior art, mention may be made of European Patent Application EP 0 299 074, which describes a silica-filled diene rubber having a base of a diene polymer functionalized by means of a silane having a non-hydrolyzable alkoxy radical. European Patent Application EP 0 447 066 describes a silica-filled composition containing a diene polymer functionalized by means of a halogenated silane compound. Despite the improvement in the properties obtained with use of such functionalized polymers, the silica compositions described in this prior art have not proved usable for forming the treads of tires, since the properties exhibited, although improved, nevertheless remain insufficient with respect to the level required. This interest in silica-reinforced compositions has recently been reawakened with the publication of European Patent Application EP 0 501 227 which discloses a sulfur-vulcanizable rubber composition obtained by thermomechanical working of a conjugated diene copolymer and an aromatic vinyl compound prepared by solution polymerization with 30 to 150 parts by weight to 100 parts by weight of elastomer of a special precipitated silica obtained by the process forming the object of European Patent Application EP 0 157 703.
SUMMARY OF THE INVENTION
The applicant has now surprisingly discovered that diene polymers coupled and/or starred with a coupling or starring agent which is an epoxidized alkoxysilane compound make it possible to decrease the hysteresis of an elastomeric composition having a base of said coupled and/or starred polymers comprising silica as reinforcing filler and furthermore to improve other properties.
The object of the present invention is a rubber composition having a base of coupled and/or starred polymers having improved hysteresis.
The invention also concerns semi-finished components which can be used in the manufacture of tires, in particular treads, as well as tires having reduced rolling resistance. The invention concerns a sulfur-vulcanizable rubber composition having a base of a diene polymer, characterized by the fact that it comprises silica as reinforcing filler and by the fact that the diene polymer is a coupled and/or starred polymer comprising 30% to 100% of chains coupled and/or starred with a coupling or starring agent having general formula I:
(Y)
m
—R
1
—Si(OR
2
)
3−n
—R
3
n
in which
Y represents the radical
R
1
represents an alkyl, cycloalkyl or aryl radical having 1 to 10 carbon atoms,
R
2
represents an alkyl, aryl, cycloalkyl, alkaryl or aralkyl radical having from 1 to 12 carbon atoms,
R
3
represents an alkyl, aryl or alkaryl radical having 1 to 12 carbon atoms,
R
4
represents a hydrocarbon radical having 1 to 6 carbon atoms and may comprise one or more oxygen atoms in the hydrocarbon chain,
n is a whole number selected from among the values 0 and 1,
m is a whole number selected from among the values 1 and 2,
p and q are whole numbers selected from among the values 0, 1, 2, 3 and 4, it being understood that the sum of p+q must represent a whole number between 2 and 5 inclusive.
Among the coupling and/or starring agents with general formula I, are preferably suitable 2-glycidoxyethyl-trimethoxysilane, 3-glycidoxypropyl-trimethoxysilane (GPTSI), 3-glycidoxypropyl-triethoxysilane, and 2-(3,4-epoxycyclo-hexyl)-ethyltrimethoxysilane (ECETSI).
By diene polymers there is understood any homopolymer obtained by polymerization of a conjugated diene monomer having from 4 to 12 carbon atoms or any copolymer obtained by copolymerization of one or more conjugated dienes with each other or with one or more aromatic vinyl compounds having from 8 to 20 carbon atoms. As conjugated dienes there are suitable, in particular, butadiene-1,3, 2-methyl-1,3-butadiene, the 2,3-di(C
1
to C
5
alkyl)-1,3-butadienes such as, for instance, 2,3-dimethyl-1,3-butadiene, 2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-3-isopropyl-1,3-butadiene, phenyl-1,3-butadiene, 1,3-pentadiene, 2,4-hexadiene, etc.
As aromatic vinyl compounds are suitable, in particular, styrene, ortho-, meta-, and para-methylstyrenes, the commercial “vinyl-toluene” mixture, para-tertiobutylstyrene, the methoxy-styrenes, the chloro-styrenes, vinyl mesitylene, divinyl benzene, vinyl naphthalene, etc.
The copolymers may contain between 99% and 20% by weight of diene units and 1% to 80% by weight of aromatic vinyl units. The polymers may have
Baker & Botts LLP
Compagnie Generale Des Establissements
Mulcahy Peter D.
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