Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-12-22
2002-02-26
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S084000, C524S085000, C525S331900, C525S333100, C525S354000
Reexamination Certificate
active
06350797
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to use of certain sulfur-containing silanes in sulfur-vulcanizable, silica-reinforced tire rubber compositions to provide a coupling agent with a high ratio of sulfur to silicon. In its more preferred aspects, the use of certain cyclic sulfur silanes in tire rubber compositions of this type produces tires exhibiting reduced rolling resistance and maintained or improved wet traction, modulus and abrasion resistance.
Rubber compositions for tire treads have traditionally employed carbon black as a principal reinforcing filler. However, due to recent increased demands for fuel efficiency and performance, the use of silica instead of carbon black has become more prevalent as a principal filler. In some cases, the use of silica in tire treads has been found to give lower rolling resistance without sacrificing abrasion resistance, modulus, or wet traction. However, in order for silica to be an effective reinforcing filler, an effective coupling agent is required. In this regard, see U.S. Pat. Nos. 3,451,458; 3,664,403; 3,768,537; 3,884,285; 3,938,574; 4,482,663; 4,519,430; 4,590,052; 5,066,721; 5,089,554; and 5,753,732 and British Patent No. 1,424,503. The coupling agents most often used in practice are polysulfide silanes of a type such as Silquest® A-1289 silane, which is a bis-3-(triethoxysilylpropyl)tetrasulfide silane, or Silquest® A-1589 silane, which is a bis-3-(triethoxysilylpropyl)disulfide silane. As has been established by a great deal of testing, not all coupling agents are effective in achieving the sometimes competing objectives of the present invention.
There is a need for the development of sulfur-vulcanizable, silica-reinforced tire rubber compositions that can employ silanes other than a limited group commercially available and known to give improvements in rolling resistance without having a detrimental impact on other properties. Norbornanylsulfursilanes, or trithiane silanes, are known for use in some applications as coupling agents, although not in tire rubber compositions for treads where their properties are unknown. See, for example, U.S. Pat. No. 4,100,172 to Mui, J. Y. P. and Kanner B., assigned to Union Carbide Corporation, New York, 1978. The previously published syntheses of trithiane silanes are disadvantageous and the advantages of the use of trithiane silane compounds and compositions as coupling agents in sulfur-vulcanizable, silica-reinforced tire rubber compositions has not been known. On the prior art process, see Shields, T. C. and Kurtz, A. N., Journal of the American Chemical Society, 1969, 91, 5415, and Bartlett, P. D. and Ghosh, T., Journal of Organic Chemistry, 1987, 52, 4937.
There remains a need for a process that enables the production of tires and parts such as treads for tires exhibiting reduced rolling resistance and road noise and maintained or improved wet traction, modulus and abrasion resistance, and this is provided by the invention through the use of sulfur silane coupling agent compounds and compositions in sulfur-vulcanizable, silica-reinforced tire rubber compositions.
BRIEF DESCRIPTION OF THE INVENTION
It is an object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions.
It is another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit reduced rolling resistance.
It is another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit improved modulus.
It is another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit improved wet traction.
It is another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit reduced road noise.
It is another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit improved abrasion resistance.
It is still another object of the invention to provide an improved process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions and tires and tire parts, vulcanized and unvulcanized, made from these compositions, where tires made from the vulcanized rubber exhibit reduced rolling resistance and road noise and maintained or improved modulus, wet traction and abrasion resistance.
These and other objects are achieved by the present invention, which provides a process for preparing sulfur-vulcanizable, silica-reinforced tire rubber compositions comprising:
preparing a blend of sulfur-vulcanizable rubber, silica reinforcing filler and a coupling agent comprising a sulfur-containing norbornanyl silicon compound of the structure
[S
y
—R]
n
—SiX
4−n
wherein each X is chosen from monovalent hydrocarbon groups or hydrolyzable groups, including, but not limited to, alkoxy, halide or an oxygen which oxygen in turn is bonded to another silicon atom to form a siloxane; y is 1 to 5, when y is 1 the compound is an episulfide, and when y is 2 to 5 the sulfur atoms form a polysulfide wherein each sulfur atom is bonded to another sulfur atom and the terminal valences of the polysulfide are bonded to vicinal carbon atoms; n is 1, 2 or 3; R is a polyvalent polycycloaliphatic hydrocarbon radical.
Tires and tire parts, vulcanized and unvulcanized, made employing the above rubber compounds are also new.
Many of the preferred aspects of the invention are described below.
DETAILED DESCRIPTION OF THE INVENTION
The following description will illustrate the use of preferred norbornanyl silicon compositions as coupling agents for sulfur-vulcanizable, silica-reinforced tire rubber compositions. Also described will be vulcanized and unvulcanized tire parts and tires employing these compositions. The invention is however, not limited to the specific compositions illustrated. Vulcanized tires made of these compositions and the preforms for preparing them are novel and exhibit improvement in one or more aspects of reduced rolling resistance, reduced road noise, improved modulus, improved wet traction and improved abrasion resistance.
This sulfur containing norbornanyl silicon compounds (cyclic sulfur silanes) used according to the invention are characterized by the following structure (Formula I):
[S
y
—R]
n
—SiX
4
−n (Formula I)
wherein each X is chosen from monovalent hydrocarbon groups or hydrolyzable groups, such as alkoxy, halide or an oxygen, which oxygen in turn is bonded to another silicon atom to form a siloxane; y is 1 to 5, when y is 1 the compound is an episulfide, and when y is 2 to 5 the sulfur atoms form a polysulfide wherein each sulfur atom is bonded to another sulfur atom and the terminal valences of the polysulfide are bonded to vicinal carbon atoms; n is 1, 2 or 3; R is a polyvalent polycycloaliphatic hydrocarbon radical including but not limited to the following:
In the above structures, the valencies to the left would be connected to the sulfur so as to form a ring and the valency to the right would be connected to the silicon atom.
Each X may be the same or different. Among the hydrocarbon
Crompton Corporation
Dilworth Michael P.
Egwim Kelechi
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