Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-12-02
2001-06-19
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C524S588000, C516S053000, C528S018000, C528S037000
Reexamination Certificate
active
06248855
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to a method of making an oil-in-water (O/W) emulsion wherein the oil component of the emulsion is a polymer containing a silicon atom. More particularly, the method involves polymerization of an OH endblocked polydimethylsiloxane (PDMS) monomer with an amine functional trialkoxysilane monomer in the presence of a metal catalyst, an interruption of the polymerization reaction by the addition of an acid anhydride, and an emulsification of the resulting copolymer following interruption of the polymerization reaction.
BACKGROUND OF THE INVENTION
Commercial emulsions containing an amine functional polydimethylsiloxane fluid are limited in their market appeal as they are known to contain only relatively low viscosity amine functional polydimethylsiloxane fluids.
In addition, these commercial emulsions may often contain in excess of about one percent of a volatile cyclic species of polydimethylsiloxane such as octamethylcyclotetrasiloxane, in addition to the low viscosity amine functional polydimethylsiloxane fluid, and this content of volatile species is unacceptable according to recent safety and environmental regulations and guidelines.
While higher viscosity polysiloxane polymers with a content of volatile cyclic species less than 0.5 percent have been obtained by reacting certain polysiloxanes with a crosslinking agent in the presence of a catalyst, such chain extensions have been obtained using an OH endblocked PDMS and a dialkoxysilane. This procedure is very slow and often takes weeks in order to reach completion. When such processes have been attempted to be modified in order to speed up the reaction, the use of a trialkoxysilane instead of a dialkoxysilane has led to the production of crosslinked elastomeric materials which are undesirable in many applications.
Where the prior art does refer to an emulsion containing an amine functional polydimethylsiloxane, the patents are either silent as regards the particular viscosity or molecular weight of the amine functional polydimethylsiloxane fluid contained in the emulsion, or where the viscosity or molecular weight of the amine functional polydimethylsiloxane fluid is mentioned, it is significantly below the levels now required in the personal care arena industry-wise. In patents where a higher viscosity or a higher molecular weight of the amine functional polydimethylsiloxane fluid is mentioned, however, the patents are generally silent as to how the emulsion is prepared. One example is U.S. Pat. 5,326,483 (Jul. 5, 1994).
In any event, although the prior art known to applicants is replete with patents relating to various types of cured systems containing high viscosity and high molecular weight polysiloxanes, it is not believed to be generally know to employ a trialkoxysilane in order to polymerize an OH endblocked PDMS in bulk, and to produce by such a procedure, a high molecular weight linear non-crosslinked silicone polymer in emulsion form. This is the essence of the contribution of the present invention.
Moreover, it is not believed to be generally know to conduct a polymerization, and then to interrupt the process of polymerization by addition of an anhydride and emulsification, particularly in this silicone cure system, which is known to be unstable and subject to reversion, i.e., depolymerization or post polymerization. However, by the addition of a low level of a carboxylic anhydride directly into the silicone polymer prior to its emulsification, applicants herein have discovered an efficient means avoid this type of reversion.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to manufacture a silicone polymer utilizing a silicone cure system in which a trialkoxysilane is employed, and to interrupt the polymerization when a desired viscosity has been achieved by a step of acidification and phase inversion emulsification. While this process can be used to make emulsions containing a silicone polymer having a viscosity in the range of from about 1,000 mm
2
/sec to 1,000,000 mm
2
/sec, it is most preferred that the silicone polymer in the emulsion have a viscosity generally in the range of about 30,000 mm
2
/sec to about 500,000 mm
2
/sec.
Thus, according to the present invention, a linear silicone polymer can be obtained provided there is employed a low amount of trialkoxysilane, and provided the step of interrupting polymerization is carried out when the polymer is still linear. In essence, therefore, the step of anhydride addition and emulsification is used in order to stop the polymerization. Reversion of the polymer is avoided by inclusion of an acid anhydride to the polymer prior to emulsification.
Among some of the benefits obtained according to the present invention are that there can be provided a useful silicone emulsion containing a much higher molecular weight linear amine functional polysiloxane polymer which possesses improved hair conditioning than can be presently obtained with state of the art manufacturing techniques.
In addition, the use of a trialkoxysilane significantly speeds up the polymerization kinetics when compared to techniques employing a dialkoxysilane, and quite unexpectedly, this does not leads to a crosslinked material when the trialkoxysilane is used in low amounts, and polymerization is stopped by anhydride addition and emulsification. While the trialkoxysilane can be used in an amount as high as about 5 percent by weight, it is preferred to use it at a level which is generally less than about 3 percent by weight.
These and other objects, features, and benefits of the present invention will become apparent from a consideration of the following detailed description thereof.
DETAILED DESCRIPTION OF THE INVENTION
The method according to the present invention is carried out in essentially two steps. The first step involves polymerization of an OH endblocked polydimethylsiloxane monomer with an amine functional trialkoxysilane monomer, in the presence of a metal catalyst. In the second step, the condensation reaction occurring in the first step is interrupted by addition of an anhydride, and its emulsification by the addition of a surfactant(s) and water.
The polydimethylsiloxane monomer used in the above reaction in the first step of the process generally comprises a substantially linear polymer of the structure:
In this structure, each R independently represents a hydrocarbon group having up to 20 carbon atoms, such as an alkyl group, representative of which are methyl, ethyl, propyl, or butyl. R can also be an aryl group such as phenyl. R′ represents OH. n is a positive integer greater than one. Preferably n is an integer that results in a polysiloxane with a viscosity between about 1 and about 1×10
6
mm
2
/sec at 25° C.
If desired, the polysiloxane can have a small amount of branching, e.g., less than 2 mole % of the siloxane units, without affecting the invention, i.e., the polymers are substantially linear. Preferably, all of the R groups are methyl groups.
The organosilicon material which reacts with the OH endblocked PDMS in the condensation reaction is an aminotrialkoxysilane. This material can be represented by the formula Q—Si—(OR″)
3
where R″ is an alkyl group containing 1-6 carbon atoms; Q denotes an amine functional substituent of the formula —R′″Z wherein R′″ is a divalent alkylene radical of 3 to 6 carbon atoms; and Z is a monovalent radical selected from the group consisting of —NR
2
″″, and —N″″(CH
2
)
m
NR
2
″″, where R″″ denotes hydrogen or an alkyl group of 1 to 4 carbons, and m is a positive integer having a value of from 2 to 6.
Suitable R″ groups are represented by and may be independently selected from among methyl, ethyl, propyl, isopropyl, butyl, and isobutyl.
The alkylene radicals represented by R′″ may include trimethylene, tetramethylene, pentamethylene, —CH
2
CHCH
3
CH
2
—, and —CH
2
CH
2
CHCH
3
CH
2
—. Silanes where R′″ is a trimethylene or an alkyl su
Dalle Frederic
Marteaux Leon
Cesare James L. De
Dawson Robert
Dow Corning S.A.
Zimmer Marc S.
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