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
1998-10-15
2001-01-09
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S195000, C525S196000, C525S213000, C525S232000, C525S235000, C525S236000, C525S237000
Reexamination Certificate
active
06172160
ABSTRACT:
TECHNICAL FIELD
The present invention relates to diene polymer compositions which exhibit excellent heat build-up resistance, and also have excellent tensile strength, abrasion resistance and processability when silica is compounded as a reinforcing agent thereinto, and a production process thereof. The present invention also relates to rubber compositions having excellent heat build-up resistance, tensile strength, abrasion properties and processability.
BACKGROUND ART
As much importance has been attached to saving in resources and countermeasures to environment in recent years, requirements to reduce fuel consumption of automobiles have been increasingly severe. Automobile tires have also been required to lower their rolling resistance so as to contribute to reduction in the fuel consumption. In order to lower the rolling resistance of tires, it is generally effective to use a rubber material capable of providing vulcanized rubber having low heat build-up as a rubber material for the tires.
In general, rubber compositions in which carbon black is compounded into a diene rubber such as natural rubber (NR), polybutadiene (BR), polyisoprene (IR) or styrene-butadiene copolymer rubber (SBR) are widely used as rubber materials for tires. However, the rubber compositions obtained by compounding carbon black into the diene rubber have insufficient heat build-up resistance.
It has heretofore been proposed to use, as a rubber material for tires, a rubber composition with silica compounded in place of carbon black as a reinforcing agent into a diene rubber so as to reduce heat build-up. However, the silica-compounded rubber composition has involved a problem that its abrasion resistance and tensile strength are insufficient compared with the carbon black-compounded rubber composition. A cause for this problem is considered to be attributed to the fact that the affinity of the silica for the diene rubber is lower than that of the carbon black, so that a reinforcing effect cannot be sufficiently developed.
In order to enhance the affinity of the silica for the diene rubber, it has heretofore been investigated to use a diene rubber with a substituent group having high affinity for silica introduced therein. For example, a diene rubber with a tertiary amino group introduced therein has been proposed for a diene rubber according to an emulsion polymerization process (Japanese Patent Application Laid-Open No. 101344/1989). Besides, a diene rubber with a substituent group such as an alkylsilyl group (Japanese Patent Application Laid-Open No. 188501/1989), a halogenated silyl group (Japanese Patent Application Laid-Open No. 230286/1993) or a substituted amino group (Japanese Patent Application Laid-Open No. 22940/1989) introduced therein has been proposed for a diene rubber according to an anionic polymerization process.
However, many of the diene rubbers with these substituent groups introduced therein have demerits that their processability is poor upon blending with silica, and their properties such as heat build-up resistance, tensile strength and abrasion resistance are not sufficiently improved.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a diene polymer composition which is excellent in heat build-up resistance, which is taken as an index to rolling resistance, and exhibits excellent tensile strength, abrasion resistance and processability, and a production process thereof.
Another object of the present invention is to provide a rubber composition which comprises a diene rubber containing the diene polymer composition having such excellent properties as described above, and a reinforcing agent, and has excellent heat build-up resistance, tensile strength, abrasion resistance and processability.
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described problems involved in the prior art. As a result, it has been found that when a diene polymer composition containing (1) a branched diene polymer component having at least three branched diene polymer chains through a polyfunctional coupling agent and (2) a linear diene polymer component having a quaternary ammonium group is used as a rubber component compounded with silica, a rubber composition excellent in all the properties of heat build-up resistance, tensile strength, abrasion resistance and processability can be provided. The diene polymer composition can be easily obtained by allowing an active metal-bonded diene polymer obtained by using an active organometallic compound as an initiator to react with a polyfunctional coupling agent and a modifying agent capable of introducing a tertiary amino group, and then allowing an alkylating agent to react with a formed product to convert the tertiary amino group into a quaternary ammonium group. The present invention has been led to completion on the basis of these findings.
According to the present invention, there is thus provided a diene polymer composition composed of a branched diene polymer component (A) having at least three branched diene polymer chains through a polyfunctional coupling agent and a linear diene polymer component (B) having a quaternary ammonium group, and having a weight average molecular weight (Mw) within a range of from 100,000 to 2,000,000.
According to the present invention, there is also provided a process for producing a diene polymer composition having a weight average molecular weight (Mw) within a range of from 100,000 to 2,000,000, the process comprising (1) allowing an active diene polymer with an active metal bonded to its molecular chain to react with a coupling agent which is trifunctional or polyfunctional to a degree higher than three and a modifying agent capable of introducing a tertiary amino group into the polymer chain by reacting with the active metal to form a branched diene polymer component (A) having at least three branched diene polymer chains through the coupling agent and a linear diene polymer component with the tertiary ammonium group introduced therein, and then (2) allowing an alkylating agent to react with the linear diene polymer component to convert the tertiary amino group into a quaternary ammonium group, thereby forming a linear diene polymer component (B) having the quaternary ammonium group.
According to the present invention, there is further provided a rubber composition comprising a rubber component containing a diene polymer composition which is composed of a branched diene polymer component (A) having at least three branched diene polymer chains through a polyfunctional coupling agent and a linear diene polymer component (B) having a quaternary ammonium group, and has a weight average molecular weight (Mw) within a range of from 100,000 to 2,000,000, and a reinforcing agent.
BEST MODE FOR CARRYING OUT THE INVENTION
Diene Polymer Composition:
The feature of the diene polymer composition according to the present invention resides in that it is composed of a branched diene polymer component (A) having at least three branched diene polymer chains through a polyfunctional coupling agent and a linear diene polymer component (B) having a quaternary ammonium group.
No particular limitation is imposed on the branched diene polymer component so far as it has a structure that at least three branched diene polymer chains are contained through a polyfunctional coupling agent. For example, a polymer component represented by the following formula (1):
(P
1
)
m
Y
1
(1)
wherein P
1
is a diene polymer chain, m is an integer of 3 or greater, and Y
1
is a residue of a polyfunctional coupling agent, is used.
P
1
in the formula (1) denotes a diene polymer chain (a), and specific examples thereof include polymer chains of a conjugated diene, and copolymer chains of a conjugated diene and another monomer which is copolymerizable with the conjugated diene.
Examples of the conjugated diene include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene and 1,3-pentadiene. Of these, 1,3-butadiene and 2-meth
Nakamura Masao
Takagishi Yukio
Armstrong, Westerman, Hattori, McCleland & Naughton
Nippon Zeon Co. Ltd.
Nutter Nathan M.
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