Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2001-08-22
2002-12-10
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S021000, C528S042000
Reexamination Certificate
active
06492479
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for producing fluorosilicone polymers, such as oils and gums.
BACKGROUND OF THE INVENTION
Fluorosilicone oil is used in a variety of applications such as silicone greases, hydraulic fluids, anti-foam compositions and paper-release compositions. High molecular weight, high viscosity fluorosilicone polymers are known as gums. Fluorosilicone oils are of lower molecular weight and viscosity.
Previously, fluorosilicone oil was produced by a cumbersome and expensive process which resulted in a low yield of product and a significant amount of waste. U.S. Pat. No. 4,267,298 to Bluestein discloses a process for producing triorganosilyl end-stopped diorganopolysiloxane fluids by polymerizing fluoro-substituted cyclic trisiloxane with itself, by reacting it with other cyclo-trisiloxanes in the presence of potassium hydroxide and water, or by reacting it with silanol end-stopped siloxane. The resulting disilanol stopped fluorosilicone oil is then treated with a large excess of trimethylchlorosilane to provide trimethylsiloxy termination. The excess chlorosilane and hydrochloric acid byproduct from chain stopping are removed by adding excess methanol to the reaction and then stripping the methanol, HCl and trimethoxysilane fry the product.
The Bluestein process produces a significant amount of waste acidic methanol and only about 85% oil and 15% volatiles. The process is also inconsistent, and it is difficult to achieve a product with a desired target viscosity. As a result, separate batches of fluorosilicone fluid are typically blended to achieve the final viscosity desired.
U.S. Pat. No. 3,607,899 to Brown discloses a method for producing fluorosilicone oil in which fluorosilicone trimer is reacted with hexamethyldisiloxane in the presence of an acid-activated clay. This process is also cumbersome in that a first reaction occurs at a temperature of 75-90° C., followed by a subsequent reaction at 120-140° C. The reaction is cooled and the acid-activated clay must be removed by filtration. For products exceeding about 1,000 cps, the removal of the acid-activated clay is difficult. Such products first must be dissolved in a solvent. The solution must then be filtered to remove the clay, and the solvent removed by stripping. The yield of product after a long strip of high temperature is described as between 68-82%. The process also generates unusable fluorosilicone volatile waste, adding to the expense and difficulty of the process.
U.S. Pat. No. 4,317,899 to Bluestein et al. discloses a process for producing a fluorosilicone polymer by polymerizing a cyclic polysiloxane with a polymerization catalyst and a low molecular weight silanol terminated diorganopolysiloxane polymer. The process results in very high molecular weight polymers. The patent does not disclose rearrangement of the polymer to disproportionate the fluoropolymer of a given molecular weight with hexaorganodisiloxane to form a final polymer of intermediate molecular weight.
There is a need in the art to produce fluorosilicone polymers such as oils and gums in high yield in an efficient manner, in which the process yields a large amount of product and a limited amount of waste.
SUMMARY OF THE INVENTION
The present invention comprises a process for making fluorosilicone polymers such as oils and gums by reacting a triorganosilanol with a fluorosilicone trimer in the presence of an alkali silanolate, thereby forming a triorganosilyl and silanol end-stopped diorganopolysiloxane; condensing the silanol end-stopped diorganopolysiloxane by removing water from the reaction and/or silylating the diorganopolysiloxane, thereby forming a fluorosilicone of reduced silanol content; and stripping the volatiles from the triorganosilyl end-stopped diorganopolysiloxane polymer.
DETAILED DESCRIPTION OF THE INVENTION
The invention compises reacting a triorganosilanol and a fluorosilicone trimer (hereinafter, “D(F)3”) in the presence of an alkali silanolate to yield a species a triorganosily end-stopped diorganopolysiloxane fluid in yields of greater than 95%. The polymer may be condensed, thereby increasing the viscosity of the polymer and reducing the silanol content. Volatiles are removed by stripping.
In an embodiment of the invention triorganosilanol is reacted with D(F)3 in the presence of an alkali silanolate to catalyze polymerization of the D(F)3 and triorganosilanol. The reactants are subjected to condensation wherein water of condensation is removed to drive the polymerization reaction forward. The reaction is stopped by neutralizing the alkali silanolate. Thereafter, volatiles may be removed by stripping.
In another embodiment of the invention, triorganosilanol is reacted with D(F)3 in the presence of an alkali silanolate, thereby forming a triorganosilyl and silanol end-stopped diorganopolysiloxane. The reaction is stopped by neutralizing the alkali silanolate. The polymer is subjected to condensation to form a fluorosilicone oil of increased viscosity and reduced silanol content. A silylating agent may be added to further reduce the silanol content. The volatiles may then be removed by stripping.
Condensation reactions are well known in the art and can be conducted by any method without particular limitation. For instance, the reactants may be contacted in the presence of a condensation catalyst while the water of condensation is removed by vacuum distillation or by a nitrogen purge. Removing the water of condensation drives the polymerization reaction forward, increasing the viscosity and reducing the silanol content of the product.
Stripping of volatiles is well known in the art and may be accomplished by any method. After the silanolate catalyst has been neutralized, the product is heated to a temperature of no more than about 250° C. and the volatiles are removed by vacuum or by employing a nitrogen purge. Stripping reduces the volatiles content of the final product.
The fluorosilicone trimer used in the present invention has the general formula (I):
wherein R
1
is a monovalent hydrocarbon of 1-8 carbon atoms, and R
2
is a perfluoroalkylethyleneyl radical of 3-8 carbon atoms. Of the trifluorosilicone trimers useful in the present invention, 1,3,5-tris(3,3,3-trifluoropropyl)-1,3,5-trimethylcyclotrisiloxane is preferred. D(F)3 is added in amounts suitable for obtaining the particular amount of polymer in the target size range and viscosity. Polymers of the present invention may range in viscosity from about 50-100,000,000 centipoises (cps). Target polymer sizes are influenced by the amount of chain-stopping triorganosilanol added to the D(F)3.
The triorganosilanols which may be used in the process of the invention have the general formula (R
3
)
3
SiOH, wherein R
3
is a monovalent hydrocarbon radical of 1-8 carbon atoms. Examples of triorganosilanols which are useful in the present invention include, but are not limited to trimethylthsilanol, dimethylvinylsilanol, triethylsilanol, tripropylsilanol, tributylsilanol, tripentylsilanol and triphenylsilanol, and the like. Of the triorganosilanols that are useful in the present invention, trimethylsilanol and dimethylvinylsilanol are preferred.
The triorganosilanols are added in amounts selected based on the target viscosity of the final product. A wide range of viscosities may be achieved by varying the amount of the triorganosilanol employed in the reaction and whether the product is condensed and/or treated with a silylating agent. The overall range that may be achieved using the process of the invention may be from about 50 to about 100,000,000 cps. Viscosities in the is range of 300-10,000,000 are more easily achieved. The viscosities achieved are a function of the amount of triorganosilanol added. Triorganosilanol in an amount of about 1.0 wt % yields fluorosilicone oil with a viscosity of about 18,000-19,500 cps. Triorganosilanol in an amount of about 2.0 wt % yields fluorosilicone oil with a viscosity of about 9,000-10,000 cps. Triorganosilanol in an amount of about 3.0 wt % yields fluorosilicone oil with a viscosity
Gosh Nancy E.
Razzano John S.
General Electric Company
Moore Margaret G.
Wheelock Kenneth S.
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