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
2001-10-05
2003-04-08
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...
C528S035000, C525S474000, C525S478000, C568S673000, C524S800000, C516S053000
Reexamination Certificate
active
06545085
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to silicone polymers, more specifically to polyether substituted silicone elastomers.
BACKGROUND OF THE INVENTION
The personal care industry thrives on being able to deliver multiple performance products based on a mixture of several components, each having performance characteristics important to the final formulation. One need in preparing these formulations is for materials that can both enhance performance as well as compatibilize and hold together in the formulation the various components of the formulation.
Recent technology has produced several crosslinked polydimethylsiloxane elastomers that are capable of absorbing cyclic and low molecular weight silicones useful in the personal care industry. The use of alpha-omega diallyl terminated polyethers as a chain extending component in making crosslinked siloxane elastomers has been shown (see, for example, U.S. Pat. Nos. 5,138,009; 5,412,004; 5,236,986). In one variation, these products suffer from the need to synthesize polyethers with an allyl functional group at both ends, and this is expensive because it requires a separate synthesis step to add the second allyl functional group. In addition, since the diallylpolyether is used as a chain extender, the amount that can be added to the composition is severely restricted by the need to form a polymer network. In a second variation, a polyether/hydrido substituted siloxane prepared in a separate, difficult and expensive reaction is used to introduce the polyether functionality. The present invention employs the use of a single vessel reaction to produce a uniquely structured elastomer and the polyether functionality is introduced using commercially available allyl started polyether compounds.
The synthesis of organically crosslinked siloxane elastomers that have been substituted with mono and diallyl terminated polyethers has been demonstrated (see, for example, U.S. Pat. Nos. 5,889,108; 5,811,487). These elastomers suffer from the requirement of having an alpha, omega-diolefin as the chain extender and a diffuse silylhydride crosslinker. This creates a different structure which may lose some of the desirable siloxane properties. Such organically crosslinked polymeric siloxanes appear to have significantly less absorbing efficiency relative to all siloxane based elastomers utilizing a higher functionality crosslinker.
A curable composition comprised of a branched, allylfunctional polyether, a branched, hydridosiloxy terminated polyether and a catalyst has also been disclosed (see, for example, U.S. Pat. No. 4,877,854). This composition requires difficult to make branched and allyl functional polyethers which determine the crosslink density, leaving no capability to control the amount of polyether content. The second component (siloxane) is equally difficult and expensive to make and ultimately limiting in the design flexibility to control performance. This system for making dental impressions forms a solid plastic unsuitable for making the small particle size required for personal care applications.
The structures defined in the above referenced patents are highly hydrophilic as a result of the total methyl substitution on silicone. Because of the hydrophilic nature, they are at best compatible with selected non-polar organic and siloxane based materials. This is a limiting feature as many formulated compositions useful in the personal care industry include water, polar organic materials such as low molecular weight alcohols, or a combination of both.
What is needed is a crosslinked siloxane elastomer which is efficient in absorbing low molecular weight silicones, has a pleasant feel and can be compatibilized or emulsified with water, polar organic materials, or a combination thereof.
SUMMARY OF THE INVENTION
In a first aspect, the present invention is directed to a cross-linked polyether substituted silicone elastomer, comprising the cross-linked hydrosilylation reaction product of:
(i) an alkenyl functional silicone compound;
(ii) a silylhydride functional siloxane; and
(iii) an allyl started, hydrogen, alkyl, aryl or acyl terminated polyether compound.
The silicone elastomer is hydrolytically stable, in that the polyether substituents are attached to the elastomer via Si—C bonds having good hydrolytic stability and can be easily and economically prepared in a single step. As used herein, the terminology “hydrolytically stable” means a tendency not to undergo changes in structure, such as, for example, cleavage of bonds, as a result of exposure to moisture.
Preferably, the silylhydride functional siloxane contain a sufficient number of Si—H groups to hydrosilylate the desired amount of allyl terminated polyether molecules with at least 1.5 SiH groups per molecule remaining for crosslinking with the alkenyl functional silicone compound.
Preferably, the alkenyl functional silicone compound contain at least 1.5 alkenyl units per molecule and has alkenyl substitutions on any or all of the M, D or T units. The number of available functional units on the SiH and alkenyl functional sites must be sufficient to form a gel on polymerization in a volatile siloxane.
This invention makes use of allyl started polyethers that may be commercially available and made without a second addition step. Since they are monofunctional, they can be flexibly introduced into the crosslinked siloxane elastomer while retaining the polymer network structure.
In a second aspect, the present invention is directed to a method for making a cross-linked polyether substituted silicone elastomer, comprising forming the hydrosilylation reaction product of:
(i) an alkenyl functional silicone compound;
(ii) a silylhydride functional siloxane; and
(iii) an allyl started, hydrogen, alkyl, aryl or acyl terminated polyether compound.
In a third aspect, the present invention is directed to a silicone composition, comprising a liquid medium, said liquid medium comprising an organic liquid, a silicone fluid or a mixture thereof; and a silicone elastomer of the present invention dispersed in the liquid medium. The elastomer of the present invention exhibits improved compatibility with organic liquids. As used herein, the “compatibility” of an elastomer with a liquid refers to the ability to form a stable dispersion of the elastomer in an organic liquid.
In a fourth aspect, the present invention is directed to an emulsion comprising an emulsion of a first liquid phase and a second liquid phase and a silicone elastomer of the present invention dispersed in the emulsion.
In a fifth aspect, the present invention is directed to a personal care composition comprising a silicone elastomer of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Silicone Elastomer
In preferred embodiment, the cross-linked alkyl substituted silicone elastomer of the present invention comprises the cross-linked hydrosilylation reaction product of, based on 100 parts by weight (“pbw”) of the combined alkenyl functional silicone compound, silylhydride functional silicone compound and allyl started, hydrogen, alkyl, aryl or acyl terminated polyether compound, from 10 pbw to 99.9 pbw, more preferably from 40 pbw to 99.5 pbw, even more preferably from 65 pbw to 95 pbw of the combined alkenyl functional silicone compound and silylhydride functional silicone compound and from greater than 0.1 pbw to 90 pbw, more preferably from 0.5 pbw to 60 pbw, even more preferably from 5 pbw to 35 pbw of the one or more an allyl started, hydrogen, alkyl, aryl or acyl terminated polyether compounds.
In a preferred embodiment, the polyether substituted silicone elastomer of the present invention forms a cross-linked three dimensional network that does not dissolve in, but is capable of being swollen by a suitable liquid medium, such as for example, a low molecular weight silicone or an organic liquid. The amount of crosslinking present in the cross-linked silicone elastomer network may be characterized with respect to the degree of swelling exhibited by the network in the liquid medium. In a preferred embodime
Chaiyawat Atchara
Firstenberg Donald E.
Kilgour John A.
Kuo An-Li
Dawson Robert
General Electric Company
Peng Kuo-Liang
Wheelock Kenneth S.
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