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
2002-09-25
2004-06-08
Yoon, Tae H. (Department: 1714)
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...
C524S269000, C524S571000, C526S104000, C526S273000
Reexamination Certificate
active
06747085
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a conjugated diene polymer and a rubber composition obtained by compounding this polymer with silica, and more particularly to a conjugated diene polymer capable of providing a rubber composition having excellent properties such as wear resistance, mechanical properties, low heat build-up and the like by polymerizing a conjugated diene compound(s) with a novel rare earth element containing compound as a catalyst and then reacting the resulting polymer just after the polymerization with a compound having a particular functional group (a modifying agent) so as to interact with silica to improve a dispersibility of silica as well as a rubber composition obtained by compounding this polymer with silica.
2. Description of Related Art
As a polymerization catalyst for conjugated diene compounds, there have hitherto been proposed many catalysts, which play an important role in industry. Particularly, many polymerization catalysts giving a high content of cis-1,4-bond have been studied and developed for the purpose of providing conjugated diene polymers having excellent mechanical and thermal properties. For example, there is well-known a composite catalyst system containing a compound of a transition metal such as nickel, cobalt, titanium or the like as an essential component. Among them, some catalysts have industrially and widely been used as a polymerization catalyst of butadiene, isoprene or the like (see End. Ing. Chem., 48, 784(1956) and JP-B-37-8198).
On the other hand, in order to give a higher content of cis-1,4-bond and an excellent polymerization activity, there has been studied and developed a high stereospecific polymerization using a composite catalyst system comprising a rare earth metal compound and an organometal compound of an element of Group I-III.
In JP-B-47-14729 is disclosed a catalyst system comprising a rare earth metal compound such as cerium octanoate or the like and an alkyl aluminum hydride such as diisobutyl aluminum hydride or an aluminum hydride such as trialkyl aluminum, ethyl aluminum dichloride or the like. Especially, this publication discloses that a catalytic activity is increased by aging the catalyst system in the presence of butadiene.
And also, JP-B-62-1404, JP-B-63-64444 and JP-B-1-16244 propose a method wherein the catalytic activity is increased by enhancing a solubility of a compound of a rare earth element in a polymerization solvent. Further, JP-B-4-2601 discloses that a catalyst system comprising a rare earth metal compound, trialkyl aluminum or aluminum hydride and an organic halogen derivative indicates an activity higher than that of the conventional one in the polymerization of 1,3-butadiene.
However, the polymers obtained through the conventional catalyst system containing the rare earth metal compound becomes wider in the molecular weight distribution and do not sufficiently improve the wear resistance and rebound resilience.
Furthermore, JP-A-6-211916, JP-A-6-306113 and JP-A-8-73515 report that when a catalyst system using a neodymium compound and methyl aluminoxane indicates a high polymerization activity and provides a conjugated diene polymer having a narrow molecular weight distribution.
However, in order to provide polymers having the narrow molecular weight distribution while maintaining a sufficient catalytic activity in the above polymerization method, it is required to use a greater amount of aluminoxane as compared with the conventional catalyst using an organo-aluminum compound. Such an aluminoxane is expensive in the cost as compared with the usual organoaluminum compound and large in the cold flow and has problems in the storage stability and the like, so that there is a problem in practical use.
In order to solve these problems, JP-A-10-306113 and JP-A-10-35633 report that the conjugated diene polymer polymerized through a catalyst system using methyl aluminoxane is modified with a hetero three-membered ring compound, a halogenated metal compound, a metal carbonate or the like to suppress the cold flow.
Recently, resource-saving, environmental measure and the like are regarded as important and hence a demand for reducing fuel consumption of an automobile becomes more severer and also it is demanded to reduce the rolling resistance even in the tire for automobile in order to contribute the tire to the low fuel consumption. For the purpose of reducing the rolling resistance of the tire, a rubber material capable of providing a cured rubber having a low heat build-up is generally used as a rubber material for the tire.
However, when the aforementioned conjugated diene polymer is used to prepare a rubber composition with silica, the interaction between such a polymer (rubber) and silica is not sufficient and hence the dispersibility of silica into the resulting rubber composition is poor and also the properties of the resulting cured rubber such as wear resistance, mechanical properties, low heat build-up and the like do not arrive in a satisfactory level.
DESCRIPTION OF THE INVENTION
The inventors have made various studies and found that conjugated diene polymers having a high content of 1,4-cis bond, a low content of 1,2-vinyl bond and a narrow molecular weight distribution, and containing a specified functional group in their molecule are excellent in the interaction with silica and a vulcanizate of the resulting rubber composition has excellent properties such as wear resistance, mechanical properties, low heat build-up and the like, and as a result the invention has been accomplished.
A first aspect of the invention lies in a conjugated diene polymer having a content of cis-1,4-bond of not less than 85%, a content of 1,2-vinyl bond of not more than 2.0% and a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of not more than 5, and containing at least one functional group selected from epoxy group and hydroxyl group in its molecule.
In this case, it is favorable that the conjugated diene polymer is obtained by polymerizing a conjugated diene compound with a catalyst consisting essentially of the following components (a) to (c) and subsequently reacting with at least one compound selected from the group consisting of the following components (d) and (e):
Component (a): a compound containing a rare earth element belonging to atomic numbers 57-71 in Periodic Table, or a reaction product between such a compound and a Lewis base;
Component (b): an aluminoxane and/or an organoaluminum compound having a general formula of AlR
1
R
2
R
3
(wherein R
1
and R
2
are the same or different and are a hydrogen atom and a hydrocarbon group having a carbon number of 1-10, and R
3
is a hydrocarbon group having a carbon number of 1-10, provided that R
3
is the same or different from R
1
and R
2
);
Component (c): a halogen-containing compound;
Component (d): a hydroxyl group-containing vinyl compound;
Component (e): an epoxy compound.
The above halogen-containing compound (c) is preferable to be a reaction product between a metal halide and a Lewis base. It is favorable that the metal halide constituting the component (c) is a halide of a metal belonging to Group 1, 2 and/or 7 in Periodic Table, and the Lewis base is a phosphoric ester, a diketone compound, a carboxylic acid and/or an alcohol.
A second aspect of the invention lies in a rubber composition comprising 10-200 parts by weight of silica based on 100 parts by weight of rubber ingredient consisting of 10-100% by weight of the above conjugated diene polymer and 90-0% by weight of the other diene polymer or natural rubber.
The rubber composition is favorable to further contain 1-20 parts by weight of a silane coupling agent based on 100 parts by weight of the rubber ingredient.
DESCRIPTION OF PREFERRED EMBODIMENTS
The conjugated diene polymer according to the invention has a content of cis-1,4-bond of not less than 85%, preferably not less than 90%, a content of 1,2-vinyl bond of not more than 2.0%, preferably not more than 1.5% and a ratio of weight average
Hattori Iwakazu
Nonaka Katsutoshi
Sone Takuo
Yamazaki Daisuke
JSR Corporation
Yoon Tae H.
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