Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-19
2004-07-20
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S262000, C524S492000, C524S571000, C524S572000, C152S196000, C152S209100
Reexamination Certificate
active
06765045
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to elastomer compositions comprising silica as reinforcing filler, said compositions having improved hysteretic properties in the vulcanized state.
Since economizing on fuel and protection of the environment have become priorities, it is desirable to produce mixtures having the lowest possible hysteresis, in order to be able to use them as semi-finished products which enter into the make-up of tire casings, semi-finished products such as undercoats, binding gums between rubbers of different types, or for calendering metallic or textile reinforcements, sidewall gums or treads, and to obtain tires with improved properties, said tires having a reduced resistance to rolling in particular.
To achieve this objective, numerous solutions have been proposed consisting, in particular, in modifying tile nature of the diene polymers and copolymers at the end of polymerization by means of coupling agents, starring agents or functionalizating agents. The great majority of these solutions are essentially concentrated on the use of polymers modified with carbon black as reinforcing filler, with a view to obtaining a good interaction between the modified polymer and the carbon black, since the use of white reinforcing agents, notably silica, has proved inappropriate owing to the low value of some of its properties, and, as a result, of certain properties of the tires using these compositions.
As an illustrative example from the prior art, mention may be made of U.S. Pat. No. 4,677,165, which describes the reaction of living diene polymers functionalized by means of a benzophenone derivative to obtain polymers having improved properties in compositions containing carbon black as reinforcing filler. EP-A-0,451,604 describes, as functionalizing agent, a compound having an amino function which permits an improved interaction between the modified polymers and carbon black. With the same objective, U.S. Pat. No. 4,647,625 describes the functionalization of elastomers by reaction of a living polymer with N-methylpyrrolidine. EP-A-0,590,491 and EP-A-0,593,049 describe polymers having a tertiary amino function at the end of the chain and also permitting better interaction with carbon black.
Certain solutions have also been proposed concerning the use of silica as reinforcing filler in the compositions designed to constitute treads of tires. Functionalized polymers comprising alkoxysilane functions at the end of the polymer chains, as described in EP-A-0,299,074 and EP-A-0,447,066, have been proposed For this purpose. It is only these functionalized polymers that have been described in the prior art as being effective in reducing the hysteresis and improving the resistance to abrasion, but the industrial manufacture of these polymers poses problems due to macrostructure development during the recovery stages such as stripping or drying. To attempt to solve these problems, the use of polymers functionalized with non-hydrolyzable alkoxysilane functions, as described in U.S. Pat. No. 5,066,721 have been proposed, but their effectiveness in a mixture with silica is reduced. The preparation of diene polymers having an amino function is known to persons skilled in the art, e.g. from U.S. Pat. No. 4,894,409, which describes the preparation of polymers functionalized with aromatic amines. The polymers having an amine function are not very effective when used with silica, as mentioned in EP-A-0,661,298.
This interest in silica-reinforced compositions was revived with the publication of EP-A-0,501,227 which discloses a rubber composition vulcanizable with sulfur, obtained by thermomechanical working of a copolymer of a conjugated diene and a vinylaromatic compound, prepared by solution polymerization, with 30 to 150 parts by weight per 100 parts by weight of elastomer of a particular precipitated silica, which represents an excellent compromise between several contradictory properties, and which for the first time permits the commercialization of tires possessing a silica-filled tread showing the excellent compromise that is required.
Mention may also be made of European Patent document EP-A-819,731, which discloses a silica-reinforced composition essentially comprising a diene elastomer consisting of a copolymer having amino functions and a silica/elastomer linking agent of the sulfurated silane type. Along its chain, this copolymer has amino groups originating from nonaliphatic or cycloaliphatic amines and an aminated vinylaromatic monomer.
It will be noted that the problem that is supposed to be solved in this last document does not relate to obtaining improved hysteretic properties.
SUMMARY OF THE INVENTION
The present invention relates to a new rubber composition containing silica or a mixture of silica and carbon black as reinforcing filler, said composition having satisfactory properties when used in the crude state and improved properties in the vulcanized state, particularly an excellent hysteresis and excellent reinforcement.
The invention also relates to treads of tires comprising at least one composition in accordance with the invention, as well as to treads obtained by vulcanization of these treads.
The invention also relates to casings of tires comprising at least one composition according to the invention, as well as to tire casings obtained by vulcanization of these casings, at least one composition of the invention being used, e.g., in the tread.
The rubber composition vulcanizable with sulfur, according to the invention, is characterized in that it comprises:
a) at least one polymer selected from the group consisting of diene polymers, olefin/monomeric diene copolymers and halogenated isoolefin/para-alkylstyrene copolymers;
b) silica as filler;
c) at least one agent promoting binding between silica and polymer, said agent having the formula
Z
1
—R
1
—S
n
—R
2
—Z
2
(I)
wherein
n is an integer between 2 and 8,
R
1
and R
2
, which may be the same or different, are each selected from among substituted or unsubstituted alkylene groups having 1 to 18 carbon atoms and substituted or unsubstituted arylene groups having 6 to 12 carbon atoms,
Z
1
and Z
2
, which may be the same or different, each represents a group
R
3
—Si—R4
R
5
where R
3
, R
4
and R
5
, which may be the same or different, are each selected from among alkyl groups having 1 to 4 carbon atoms, phenyl groups, alkoxy groups having 1 to 8 carbon atoms, and cycloalkoxy groups having 5 to 8 carbon atoms, with the proviso that at least one of R
3
, R
4
and R
5
is an alkoxy or cycloalkoxy; and
d) at least one guanidine substituted by at least two groups, which may be the same or different, and selected from among alkyl, aryl or aralkyl groups;
and wherein the rubber composition has at least one of the following characteristics:
It comprises at least one diene polymer which has at least one terminal amino group of an aliphatic or cycloaliphatic amine which is bonded thereto at the end of the chain, the polymer then being devoid of alkoxysilane and silanol group;
The composition comprises at least one free aliphatic or cycloaliphatic amine.
DETAILED DESCRIPTION OF THE INVENTION
In the description that follows, the term “polymer” covers both homopolymers and copolymers; the term “copolymer” referring to polymers obtained from two or more than two monomers, e.g. terpolymers.
Understood by a diene polymer is any homopolymer obtained by polymerization of a conjugated diene monomer having 4 to 12 carbon atoms, any copolymer obtained by copolymerization of one or more conjugated diene with each other or with one or more vinylaromatic compounds having 8 to 20 carbon atoms. As conjugated diene, mention may be made of e.g. 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C
1
-C
5
-alkyl)-1,3-butadiene such as, e.g., 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, an aryl-1,3-butadiene, 1,3-pentadiene, and 2,4-hexadiene.
Suitable vinylaromatic compounds are, in particular, styrene, ortho-, met
Daniel Marc
Labauze Gerard
Baker & Botts L.L.P.
Michelin & Recherche et Technique S.A.
Shosho Callie
LandOfFree
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