Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
1999-12-07
2001-09-25
Shaver, Paul F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06294683
ABSTRACT:
BACKGROUND OF THE INVENTION
Rubber compositions often contain a filler, such as carbon black or silica, to attain desired physical properties. For instance, the rubber compositions used in tires normally contain one or more fillers. Carbon black has traditionally been used as a filler in manufacturing tires. However, there is a growing trend toward utilizing silica or a combination of silica and carbon black in tire rubbers to attain improved physical properties, such as wet traction characteristics.
A silica coupling agent is normally employed in rubber compounds that utilize silica as a filler in order to attain more optimal physical characteristics. Various sulfur containing organosilicon compounds are useful as reactive coupling agents. The use of such organosilicon compounds in silica containing rubbers improves physical properties by coupling the silica filler to the rubber. It should be noted that certain organosilicon compounds are also useful as adhesion primers for glass, metals and other substrates.
U.S. Pat. No. 3,842,111, U.S. Pat. No. 3,873,489 and U.S. Pat. No. 3,978,103 disclose the preparation of various sulfur containing organosilicon compounds. These organosilicon compounds are prepared by reacting (1) 2 moles of a compound of the formula:
Z-Alk-X
wherein X is a halogen selected from the group consisting of chlorine, bromine or iodine; wherein Z is
wherein R
1
is an alkyl group containing from 1 to 4 carbon atoms or a phenyl group and wherein R
2
is an alkoxy group containing from 1 to 8 carbon atoms or a cycloalkoxy group containing from 5 to 8 carbon atoms; wherein Alk is a divalent aliphatic hydrocarbon, an unsaturated hydrocarbon or a cyclic hydrocarbon containing 1 to 18 carbon atoms; with (2) 1 mole of a compound of the formula
M
2
S
n
wherein M is an ammonium group or a metal atom and n is a whole number from 2 to 6. Since the two starting materials are liquid, the reaction can take place in the absence of a solvent; however, the utilization of a volatile inert organic solvent is preferred and accordingly such an inert organic solvent is generally used. The reaction is carried out with the exclusion of water. The reason for the exclusion of water is to avoid the alkaline hydrolysis reaction of the silyl alkoxy groups which will ultimately lead to insoluble polymeric by-products and lower the overall yield of desired product. It is critical for the organic solvent to be inert and not to be soluble in water. Toluene, xylene, n-hexane and cyclohexane are representative examples of suitable inert organic solvents. At the end of the reaction between the two starting materials, the separated salt is removed by filtration. The filtrate is then freed from the solvent by distillation under vacuum. Unfortunately, this process is difficult to carry out on a commercial basis for a variety of reasons. For instance, most alcohols that are suitable for utilization as the solvent are difficult to obtain and maintain in a water-free (anhydrous) state. Additionally, most suitable alcohols, such as ethyl alcohol, have a low flash point which is highly undesirable in commercial applications.
U.S. Pat. No. 5,405,985 relates to a process for the production of organosilicon compounds of the formula
Z-Alk-S
n
-Alk-Z
in which Z is selected from the group consisting of
where R
1
is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;
R
2
is an alkoxy of 1 to 8 carbon atoms or a cycloalkoxy of 5 to 8 carbon atoms;
Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8; comprising reacting (A) a compound of the formula
Z-Alk-X
where X is Cl, Br or I; with (B) a compound of the formula
Me
2
S
n
where Me is an ammonium ion or an alkali metal ion; and wherein the reaction is conducted in the presence of a phase transfer catalyst and an aqueous phase.
U.S. Pat. No. 5,468,893 relates to a process for the production of organosilicon compounds of the formula
Z-Alk-S
n
-Alk-Z
in which Z is selected from the group consisting of
where R
1
is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;
R
2
is an alkoxy of 1 to 8 carbon atoms or a cycloalkoxy of 5 to 8 carbon atoms;
Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8; comprising reacting (A) a compound of the formula
Z-Alk-X
when X is Cl or Br; with (B) a compound of the formula
Me
2
S
n
where Me is ammonium or an alkali metal;
wherein the reaction is conducted in the presence of a phase transfer catalyst, an aqueous phase and a salt of the formula
XY
or
X
2
SO
4
where X is selected from the group consisting of Li, Na, K, Rb and Cs; and where Y is selected from the group consisting of F, Cl and Br.
U.S. Pat. No. 5,663,396 discloses a process for the production of organosilicon compounds of the formula
Z-Alk-S
n
-Alk-Z (I)
in which Z is selected from the group consisting of
where R
1
is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;
R
2
is an alkoxy of 1 to 8 carbon atoms or a cycloalkoxy of 5 to 8 carbon atoms;
Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8; comprising
(A) reacting sodium hydroxide with sulfur in the presence of a saturated NaCl aqueous solution to form a reaction mixture; and
(B) reacting said reaction mixture with a compound of the formula:
Z-Alk-X (II)
where X is Cl or Br in the presence of a phase transfer catalyst.
SUMMARY OF THE INVENTION
One embodiment of the present invention is based upon the discovery that sulfur containing organosilicon compounds that are suitable for use as silica coupling agents can be readily prepared in excellent yield by phase transfer catalysis in the presence of a filler, such as carbon black. The natural advantages of the phase transfer process with regard,to speed, purity and simplicity can be retained even in the presence of substantial levels of the filler. It has been further discovered that the presence of the filler allows for the elimination of the organic solvent. If the ratio of the final product to the filler is properly adjusted, a supported product that is heavily loaded can be obtained. In one embodiment of this invention, the filler takes the functional place of the solvent in the process of this invention.
Even though solvent is not required, the use of aqueous brine is still preferred for optimum yield. The final supported product is isolated as a dry free-flowing solid suitable for direct use in conventional rubber mixing equipment. This is advantageous since most customers of silica coupling agents prefer or require that the silane coupling agent be in solid form for simplified handling and use in conventional rubber mixing equipment. This new method greatly simplifies the two-step techniques described by the prior art and reduces processing complexity. Cost reduction is also achieved since the unit operation of blending on a carrier, such as carbon black, is eliminated.
This invention more specifically discloses a process for the production of sulfur containing organosilicon compounds of the formula Z-Alk-S
n
-Alk-Z wherein Z is selected from the group consisting of
wherein R
1
is an alkyl group containing from 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group; wherein R
2
is an alkoxy group containing from 1 to 8 carbon atoms or a cycloalkoxy group containing from 5 to 8 carbon atoms; wherein Alk is a divalent hydrocarbon of containing from 1 to 18 carbon atoms; and wherein n is an integer from 2 to 8; said process comprising reacting a compound of the formula Me
2
S
n
with a compound of the formula Z-Alk-X; wherein Me represents an alkali metal or an ammonium ion, wherein X represents a halogen selected from the group consisting of chlorine and bromine; wherein said reaction is carried out in the presence of a phase transfer catalyst; wherein said process is carried out in the presence of an aqueous phase containing a salt of the formula MX or M
2
SO
4
; wherein M represents a metal selected from the group consisting of lithium, sodium, potassium, rubidium and cesium; wherein X rep
Johnson Scott Edwards
Parker Dane Kenton
Shah Niranjan
Rockhill Alvin T.
Shaver Paul F.
The Goodyear Tire & Rubber Company
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