Organic compounds -- part of the class 532-570 series – Organic compounds
Reexamination Certificate
1999-12-22
2001-04-03
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
C549S004000
Reexamination Certificate
active
06211345
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to preparation of certain cyclic sulfur silanes in a simple, solventless manner. In its more preferred aspects, it provides silanes that can be used without further purification for applications such as coupling agents in rubber for making tires exhibiting reduced rolling resistance.
Rubber compositions for tire treads have traditionally employed carbon black as a principal reinforcing filler. Recently, as demands for fuel efficiency and performance have increased, the use of silica instead of carbon black as a principal filler has become more prevalent. 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, a 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-289 silane, which is a bis-3-(triethoxysilylpropyl)tetrasulfide silane, or Silquest® A-1589 silane, which is a bis-3-(triethoxysilylpropyl)disulfide silane.
There is a need for other types of silanes that can 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. T he previously published syntheses of cyclic sulfur silanes are disadvantageous, because they involve the use of ammonia gas as a base, and large quantities of solvent. Shields, T. C. and Kurtz, A. N., Journal of the American Chemical Society, 1969, 91, 5415, and Bartlett, Paul D. and Ghosh, Tirthankar, Journal of Organic Chemistry, 1987, 52, 4937. Its manufacturing process is therefore impractical and uneconomical due to the problems associated with the handling of a dangerous gas and the cost associated with the recovery or disposal of the solvent.
There remains a need for a process that can simply and efficiently prepare certain cyclic sulfur silanes without the use of solvents, reduces the need to handle dangerous materials, provides increased pot yields and ideally eliminates the need for further purification.
BRIEF DESCRIPTION OF THE INVENTION
It is an object of the invention to provide an improved process for the synthesis of episulfide, dithiane, trithiane, tetrathiane and pentathiane silanes (collectively, “Cyclic Sulfur Silanes”).
It is another object of the invention to provide an improved process for the synthesis of Cyclic Sulfur Silanes which reduces the need to handle dangerous materials.
It is another object of the invention to provide an improved process for the synthesis of Cyclic Sulfur Silanes which eliminates the need for solvents.
It is another object of the invention to provide an improved process for the synthesis of Cyclic Sulfur Silanes which increases pot yields.
It is another object of the invention to provide an improved process for the synthesis of Cyclic Sulfur Silanes which produces a reaction mixture that can be used without further purification.
It is still another object of the invention to provide a process by which one can simply and efficiently prepare Cyclic Sulfur Silanes without the use of solvents, the need to handle dangerous materials is decreased, increased pot yields arc provided and ideally the need for further purification is eliminated.
These and other objects are achieved by the present invention, which provides a process for preparing sulfur containing norbornanyl silicon compounds characterized by 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, the process comprising:
reacting sulfur with an unsaturated silicon compound of the formula
[R
3
]
n
—SiX
4−n
where R
3
is a polycycloaliphatic group containing at least one reactive strained double bond and X is as defined for Formula I above,
the sulfur and silicon compound being reacted in the presence of an acid catalyst.
The unpurified products prepared in the above manner are unique in composition and properties.
Many of the preferred aspects of the invention are described below.
DETAILED DESCRIPTION OF THE INVENTION
The following description will illustrate the preparation of preferred norbornanyl silicon compounds, suitable for use as coupling agents for low rolling resistance tire applications. The invention is, however, not limited to the specific compounds illustrated or this particular use.
This invention relates to the improved synthesis of sulfur containing norbornanyl silicon compounds 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, 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 including but not limited to
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 groups for X are alkyl groups, preferably lower alkyls including from one to four carbons. Among the hydrolyzable X groups are halides, such as chlorine, siloxies, such as trimethoxysiloxy or methyltriethoxysiloxy, the lower alkoxy groups, preferably those containing from one to four carbons. Mixed alkoxy groups (e.g., one being methoxy and another being ethoxy are a potential embodiment. In one embodiment, the silane may be a dimer of the Cyclic Sulfur Silane, such that the siloxy group is another alkoxy silane containing the sulfur group, e.g., 1,3-bis[(ethyl)-2-(3,4,5-trithiatricyclo[5.2.1.0
2.6
]decyl)]tetraethoxy disiloxane. The most preferred X groups are ethoxy and methoxy.
Y is preferably 1, 3 or 5, more preferably 1 or 3.
The group R can be derived from a variety of polycycloaliphatic compounds containing at least one reactive, strained double bond, such as those represented by Formulas II, III and IV, as follows:
Where m=1 or 2, n=0 to 8, R
1
is selected from the group of H, C
1
-C
12
alkyl, or C
2
-C
12
alkenyl and R
2
is a C
2
-C
4
alkene.
Non-limiting examples of the above compounds of Formulas II, III and IV are preferably selected from the group g-k:
The sulfur-substituted polycycloaliphatic compounds of this invention, as characterized by Formula I, can be produced by the reaction of sulfur from any suitable source with an aliphatically unsaturated precursor of the silicon compound according to Formula Va in the presence of an acid catalyst. Among the suitable sources of sulfur are any of those that are capable of providing sulfur for the reaction under conditions effective to produce the desired products, e.
Hwang Lesley
Weller Keith J.
Ma Shirley S.
Shaver Paul F.
Witco Corporation
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