Polymerization of silicone in a surfactant medium

Details Polymerization of silicone in a surfactant medium Polymerization of silicone in a surfactant medium

2001-09-24

2003-02-25

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S837000, C516S055000, C526S060000, C528S012000, C528S020000, C528S033000, C528S034000

Reexamination Certificate

active

06525130

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to the polymerization of silicone fluids. More particularly, the present invention relates to the copolymerization of silicone fluids and functional silanes in a surfactant medium using a basic catalyst. The functional silanes are generally substituted methoxy- or ethoxy-silanes.
BACKGROUND OF THE INVENTION
Polymerized silicones have many useful applications. They may be employed as fabric softeners, lubricants, release agents/coatings for adhesives, and waterproofing applications, to name a few. According to the targeted application, the silicone polymerization may be functionalized with particular silanes that provide the silicone polymerization with properties beneficial to that chosen application. Particularly, silicone fluids and silanes are copolymerized to provide a compound useful for a given application. To aid in handling and use, such copolymerizations are typically provided as an emulsion.
Typical reactions for the copolymerization of silicone fluids and silanes employ either cyclic silicone fluids or hydroxy-terminated silicone fluids together with functional silanes in an esterification reaction. These reactions are carried out in an alcohol medium with platinum or other similar metal catalyst. Isopropylanol or methanol is usually added at the beginning of the reaction to function as a diluent to reduce viscosity and aid in the polymerization process. After the polymerization is complete and the fluid has been produced, the alcohol is stripped and the catalyst is filtered out for reuse.
This process produces strong corrosive acids that are damaging to the equipment and the environment. Additionally, the platinum and/or Group VIII metal-based catalysts typically employed are expensive, and the need for stripping solvents, alcohols, viscosity modifiers, and other undesired diluents further increase the production costs. Such silicone fluid production is indicated in U.S. Pat. Nos. 5,352,751, 5,391,674, 5,852,110, and 5,837,784.
To produce a silicone emulsion after the silicone fluid has been produced, the fluid must be emulsified in a separate step using a surfactant package for emulsification. The emulsification process can be carried out through either mechanical or chemical methods. These types of emulsion systems and procedures have been taught in U.S. Pat. Nos. 6,013,682, 5,817,714, and 5,304,621. Notably, in the prior art, polymerization of the silicone fluid occurs in a medium separate from that required to emulsify the final product, and, between the polymerization and emulsification steps, solvents, alcohols, viscosity modifiers, and other undesired diluents must be stripped from the polymerization product before emulsification is begun. Thus, there exist a need in the art for a process for polymerizing and emulsifying a silicone in a surfactant medium, which process does not require stripping the surfactants, alcohols, viscosity modifiers or other undesired diluents, thereby decreasing the necessary process steps.
SUMMARY OF INVENTION
The process of this invention is also an esterification, but proceeds by polymerizing a silicone fluid and functional silane in a surfactant medium that allows for emulsification of the copolymerized final product for commercial use. Because polymerization and emulsification occur in the same medium, this reaction does not require stripping solvents, alcohols, viscosity modifiers, or other undesired diluents. Additionally, the present process does not employ heavy metal catalysts, such as platinum and other, expensive Group VIII metals. The same functional silanes and hydroxy-terminated silicone fluids employed in polymerizations of the prior art may be employed in the present invention; however, the present process yields a pre-emulsified silicone fluid that is cleaner and free of heavy metal catalyst. This process can be carried out in a single vessel instead of multiple vessels, and produces a final product that meets or exceeds commercial standards for silicone fluids. The final silicone fluid emulsion performs equal to or better than currently available commercial silicone fluid products. Additionally, these advantages are accomplished with reduced potential for adverse environmental impact.
In general, the present invention provides a process for producing a polymerized silicone fluid comprising the steps of charging to a reaction vessel a hydroxy-terminated silicone fluid, an ethoxy-or methoxy-terminated functional silane, a basic catalyst, and a surfactant package having a cloud point of between 2 to 20° C. below the reaction temperature needed to react the functional silane with the hydroxy-terminated silicone fluid; heating the contents of the reaction vessel to a temperature that is about 2 to about 20° C. above the cloud point of the surfactant package to copolymerize the silicone fluid and functional silane; terminating the copolymerization reaction; and diluting the product with water to form an emulsion.
Thus, in the process of this invention, the silicone fluid and functional silanes are polymerized in a surfactant package that allows for the subsequent emulsification of the polymerized silicone fluid upon the addition of water, without the need for stripping solvents, alcohols, viscosity modifiers, or other diluents.
PREFERRED EMBODIMENT FOR CARRYING OUT THE INVENTION
As mentioned, the present invention provides an emulsified silicone fluid by copolymerizing, within a surfactant medium, a silicone fluid and functional silanes. The polymerization is effected by a basic catalyst that is neutralized after copolymerization of the silicone fluid and functional silanes. Once the polymerization reaction is terminated and the catalyst is neutralized, the polymerization product is diluted with water and agitated to form an emulsion. The process disclosed herein is desirable over processes of the prior art in that the copolymerization of the silicone fluid and the emulsification of the polymerization product occur in the same medium (a surfactant medium) such that the production of the emulsified product does not require stripping steps.
The selection of suitable hydroxy-terminated silicone fluids for use in this invention is limited to those fluids capable of mixing with the other components during polymerization. This ability to mix will typically be affected by the hydroxy-terminated silicone fluid's viscosity, which generally relates to the molecular weight of the silicone fluid. Preferably, the viscosity of the hydroxy-terminated silicone fluid ranges from about 80 to about 2500 centistoke (cs). Such viscosities are typical for silicone softeners or lubricants found in the market.
The higher the viscosity of the silicone fluid, the shorter the reaction time necessary to achieve the desired viscosity in the final product. Additionally, the A-B repeating block structure and the degree of functionality of the copolymer product will differ based upon the molecular weight of the hydroxy-terminated silicone fluid. The A-B block structure will affect both product performance and the type and amount of surfactants chosen for polymerization and eventual emulsification. Each of these factors should be considered, and the proper starting reagents should be chosen at the start of the polymerization in order to achieve the desired end product.
Due to the high viscosity of some hydroxy-terminated silicone fluids, it is necessary to select surfactants and silanes that allow for proper agitation during polymerization. For instance, high viscosity hydroxy-terminated silicone fluids require the presence of tridecyl alcohol surfactants to aid in viscosity control during polymerization. The presence of low molecular weight silanes may also help in the initial mixing of the components before polymerization starts. Also, the use of hydroxy-terminated silicone fluids of differing viscosities will achieve different end use properties in the polymerized silicone fluid. For example, in textile applications, a 100 cs hydroxy-terminated silicone fluid will produce a product that

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