Method for making aqueous emulsions of functionalized...

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...

Reexamination Certificate

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C525S477000, C525S902000, C424S070120

Reexamination Certificate

active

06214927

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is directed to a method of making stable aqueous emulsions of organopolysiloxane particles having a volume average particle diameter (Dv) of at least about 300 nanometers (nm) which have been functionalized with a chemically combined polar group such as a mercaptoorgano, epoxyorgano, or carboxy group.
There is shown by Craig in U.S. Pat. Nos. 5,726,270, 5,856,402, and 5,900,460, semi-continuous methods for making acid catalyzed aqueous dispersions of organopolysiloxane particles from cyclic poly(diorganosiloxane)s. The aqueous dispersions of organopolysiloxane particles have been found to be useful in coating applications including personal care. For example, in the formulation of a silicone composition useful in hair shampoos, experience has shown that desirable results can be achieved with the use of an aqueous dispersion of organopolysiloxane particles having a volume average particle diameter in the range between about 300 nanometers and about 1 micron. It has been found that improvements in hair styling can be obtained with a silicone-containing shampoo, because the silicone can impart a “smoothing out” effect. It is speculated that shampoos containing silicones in the form of aqueous dispersions of organopolysiloxane particles having a volume average particle diameter (Dv) of at least about 300 nanometers, can more readily coat the surface of the hair shaft to achieve a smoother surface.
It also has been suggested that additional enhancements can be obtained in coating and personal care applications based on the use of aqueous dispersions of organopolysiloxane particles by modifying the dispersed particles with a polar functional group, such as a mercaptoorgano, epoxyorgano, or carboxy radical. However, previous efforts to synthesize aqueous emulsions of functionalized organopolysiloxane particles having a volume average particle diameter of at least about 300 nanometers in a semi-continuous manner have been unsuccessful. Attempts to incorporate an organosilicon polar functionalizing source material, for example an alkoxy silane having a polar functional group attached to silicon by a carbon-silicon bond, into an aqueous organopolysiloxane equilibration mixture of cyclic poly(diorganosiloxane) using a conventional acid catalyst typically results in organopolysiloxane particles with volume average particle diameter less than 300 nanometers. It is speculated that the limitation in particle size growth in such a polar group-substituted alkoxysilane-containing mixture is due to a difference in reactivity between the cyclic poly(diorganosiloxane) and alkoxysilane in an acid catalyzed environment. A satisfactory method is therefor needed to make stable aqueous emulsions of functionalized organopolysiloxane particles having a volume average particle diameter of at least about 300 nanometers using an acid catalyzed process.
BRIEF SUMMARY OF THE INVENTION
In one embodiment, the present invention is a method for making a substantially stable aqueous emulsion having a total solids content in a range between about 5% and about 60% by weight of functionalized organopolysiloxane particles, comprising effecting reaction at a temperature in a range between about 25° C. and about 110° C., and in the presence of an effective amount of an acid catalyst surfactant, between (A) an aqueous emulsion of organopolysiloxane particles consisting essentially of chemically combined diorganosiloxy units and having a volume average particle diameter of at least about 300 nanometers, and (B) an organosilicon polar functionalizing source material, wherein there is utilized in the resulting reaction mixture by weight in a range between about 0.1 and about 20 parts of (B) per 100 parts of (A).
In another embodiment, the present invention is a method for making a substantially stable aqueous emulsion having a solids content in a range between about 5% and about 60% by weight of functionalized organopolysiloxane particles having a volume average particle diameter of at least about 300 nanometers, comprising the steps of:
(1) equilibrating a cyclic poly(diorganosiloxane) in a semi-continuous manner in the presence of an effective amount of an acid catalyst surfactant to form an aqueous emulsion of organopolysiloxane particles having a volume average particle diameter of at least about 300 nanometers, and
(2) effecting reaction between the organopolysiloxane particles in the aqueous emulsion of (1), and an organosilicon polar functionalizing source material in a range between about 0.1 part and about 20 parts by weight per 100 parts of such organopolysiloxane particles.
DETAILED DESCRIPTION OF THE INVENTION
As used hereinafter, the term “organosilicon polar functionalizing source material” means a polar group-substituted alkoxy silane, cyclic poly(diorganosiloxane), or poly(diorganosiloxane) fluid, said fluid having a viscosity which can include a range between about 10 centipoise and about 10
5
centipoise at 25° C., depending upon the particular chemically combined functional group, such as a mercaptoorgano, epoxyorgano, or carboxy group, or a mixture thereof. The term “substantially stable aqueous emulsion” means an emulsion in which the dispersed particles do not appreciably agglomerate during the typical shelf-life of the emulsion. “Semi-continuous” in one of its embodiments refers to a process for functionalizing organopolysiloxane particles which employs organopolysiloxane particle seeds prepared in a separate step. In other embodiments, “semi-continuous” refers to a reaction which does not need to be stopped in order to add more reactants.
The present invention is based on the discovery that an average particle size of organopolysiloxane particles can be substantially maintained during functionalization of such particles by reducing or avoiding direct contact between the organosilicon polar functionalizing source material and the organopolysiloxane precursor, for example an appropriate cyclic poly(diorganosiloxane). “Substantially maintained” refers to a volume average particle size of organopolysiloxane particles which changes less than about 50%, preferably less than about 20%, and most preferably less than about 10%. Accordingly, useful results have been achieved by effecting direct contact under suitable equilibration conditions and in the presence of an acid catalyst surfactant, between the organosilicon polar functionalizing source material and an aqueous emulsion of organopolysiloxane particles, or “seeds” having a volume average particle diameter of at least about 300 nanometers.
In one embodiment, a substantially stable aqueous emulsion of functionalized organopolysiloxane particles with the desired size range is produced by a two-staged, acid-catalyzed semi-continuous/semi-continuous or semi-continuous/batch process whereby the particle size is substantially maintained from the first stage and functionalization occurs in a second stage through equilibration of a polar group-substituted alkoxy silane, cyclic poly(diorganosiloxane), or poly(diorganosiloxane) fluid into the particles. Often, a semi-continuous process is utilized in the first stage wherein, for example, a cyclic poly(diorganosiloxane), acid catalyst surfactant, and water are added to a preheated reactor, either as separate feeds or in various combinations with each other, or as a pre-emulsified mixture containing water and optionally additional surfactant over some specified time period. The reaction mixture may be heated for a period of time after addition of precursor to ensure formation of organopolysiloxane particles in the desired size range. Upon completion of the first stage, the reaction mixture may be cooled to any desired temperature, for example to about room temperature, or maintained at reaction temperature. The organosilicon polar functionalizing source material may be added, either semi-continuously or batchwise, at which point the reactor may be heated to a desired reaction temperature or simply maintained at a desired reaction temperature for a period of time to

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