Hydrophilic siloxane latex emulsions

Details Hydrophilic siloxane latex emulsions Hydrophilic siloxane latex emulsions

1998-09-11

2001-03-27

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C528S052000, C526S279000, C524S837000, C524S845000, C524S765000, C524S731000, C424S070120, C424S401000, C424S059000, C424S064000

Reexamination Certificate

active

06207782

ABSTRACT:

BACKGROUND OF THE INVENTION
Acrylated polysiloxanes copolymerized with organic acrylates and emulsions thereof are known wherein the siloxane and acrylate have been applied to a substrate and are polymerized directly onto a surface. For example, U.S. Pat. No. 5,635,546 teaches a curable composition, having utility for threadlocking engageable members of a threaded mechanical fasteners. An emulsion of the reactive silicone acrylate and optional other polymerizable acrylate monomer is applied onto the engagement surface and polymerizing in situ to lock parts in place.
Another example, U.S. Pat. No. 5,171,638 teaches organopolysiloxane/acrylate ester copolymer emulsion compositions which offer release, antisoiling and water repellency for paints and textile. Similarly U.S. Pat. No. 5,612,433 describes monofunctional dimethysiloxane acrylates copolymerized with acrylate/methacrylate ester to produce water repellent films on fibers. Additional examples of the emulsified acrylate/methacrylate copolymers with hydrophobic organopolysiloxane, primarily intended for use in paints, is provided in U.S. Pat. No. 5,084,489.
SUMMARY OF THE INVENTION
Emulsions of polymers derived from hydrophilic acrylated siloxanes, offer such important properties like hydrophilicity and rewettability while maintaining other “silicone” characteristics, such as improved aesthetics and tactile properties. The use of these emulsions and copolymer formulations of these emulsions are also taught herein.
DETAILED DESCRIPTION OF THE INVENTION
The present invention describes radically polymerized acrylates/methacrylates of polyether modified polysiloxanes and their copolymers with organic acrylates, as well as emulsions including these polymers. The siloxanes have siloxane backbones with pendant polyether functionalities which polyethers are encapped with an acrylate or methacrylate functionality. The backbone may be linear, branched or cyclic. These acrylated siloxanes then are polymerized in a solvent to form an emulsion of the latex.
The acrylated siloxanes can be represented by Formula I
[R
3
SiO
1/2
]
m
[O
1/2
SiR
2
O
1/2
]
n
[SiO
3/2
R]
o
[SiO
4/2
]
p
wherein R is selected from the R
1
and P, wherein each R
1
can be the same or different and each is a monovalent hydrocarbon group; each P is R
3
[O(C
b
H
2b
O)
z
COCR
4
═CH
2
]
g
wherein, R
3
is a poly valent organic moiety, which may be hydroxy substituted alkylene, g is the valency of R
3
minus 1, R
4
is hydrogen or methyl; b=2 to 4, preferably 2 to 3; z=1 to 1000, preferably 3 to 30; and m+n+p+o=1 to 100, preferably 2 to 20, at least one R is P; n=1 to 100; when O is not zero n/o<10:1; when p is not zero n/p<10:1; and m=0 to 10.
Preferably the acrylated siloxane is of the formula (II)
QR
1
2
Si[OSiR
1
2
]
x
[O—SiR
1
P]
y
OSiR
1
2
Q
wherein x, and y can be 0 or an integer, preferably each x and y are from 0 to 100, most preferably 0 to 25; Q can be R
1
or P, with the proviso that the average acrylate functionality is >1 unsaturated groups per molecule. In the preferred embodiment y=0 and Q=P.
Preferably R is a C
1
-C
4
alkyl, an aryl or alkaryl. Specifically preferred R are methyl, ethyl, phenyl and ethyl phenyl. R may include heteroatom substituents preferably, which are nonreactive with acrylates.
P may be branched with several polyether branches originating from the alkyl bridge to the silicon atom. For example, P may be an alkoxylated trimethylol propane monoallyl ether which has been hydrosilated onto the siloxane backbone and esterified. Other polyvalent precursors for P, which may be hydrosilated, alkoxylated and esterified are glycerol monoallyl ether, pentaerythritol allyl ether and trisopropanol amine allyl ether. In a preferred embodiment, g=1 and R
3
is a linear C
2
-C
5
alkylene, most preferably C
2
-C
3
.
Not all polyethers in P need be the same as each other. Preferable P structures are ones with ethylene oxide (b=2) contents of greater than 80% by weight of the alkylene oxide (C
b
H
2b
O) content, most preferably all of the alkylene oxide chain is ethylene oxide.
Said acrylates of Formula I are derived from the polyether polysiloxane copolymers wherein the polyethers are attached to the siloxane backbone through a non-hydrolyzable Si—C bond. Moreover, the polyethers should be uncapped so that the hydroxyl group may be (trans)esterified with the acrylate. Said polyether polysiloxanes are commercially available.
The esterification is catalyzed with a Brönstead acid if the acid is the starting acrylate. If an ester is used an acid or base can be used to catalyze the transesterification.
The acrylated silicone copolymers are polymerized to form polymers (latexes), or if desired, copolymers of Formula I with other comonomers (e.g., other esters). Said polymerization may be conducted in various solvents, catalysts and temperatures as are known in the art for polymerizing acrylates. Said polymerization should not be conducted on a surface to form a film. Rather, polymerization in a solvent allows for production of a crosslinked latex gel which has broader utility than film forming. The emulsion should contain less than or equal to 90 wt %, preferably less than 50 wt %, of the polymer in solvent. Suitable solvents include polar solvents, e.g., water and alcohol, and non-polar solvents, such as many hydrocarbons or low molecular weight cyclic or linear polydimethylsiloxanes. Preferably polydimethylsiloxanes should have a viscosity of less than 100 cSt (25° C.).
Any organic acrylate or methacrylate can be employed in forming the copolymers with Formula I. Thus, for example, acrylic acid and methacrylic acid or their derivatives such as esters, nitrites and amides can be employed. The esters are preferred compounds. Specific examples of the acrylates that can be utilized are methyl acrylate, ethyl acrylate, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, vinyl acrylate, allyl acrylate, hydroxyethyl acrylate, perfluoroethyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate. A single acrylate or various combinations of acrylates can be employed in making the copolymers.
Copolymers of the acrylates/methacrylates of the polyether modified polysiloxanes, with the organic acrylates may consist of 1 to 99% by weight of the polysiloxanes, preferably 20-90% and most preferably 50-80% of the polysiloxane.
It is also an objective of the present invention to produce emulsions, comprising the polymerized acrylates/methacrylates polyether polysiloxanes copolymers and/or their copolymers with organic acrylates (i.e., latexes), which upon evaporation of water form films with good tactile properties and good integrity. These emulsions may in fact be dispersions of the latex.
One particular method to prepare emulsions is:
1. Dispersing an acrylate/methacrylate of polyether polysiloxane copolymers, as defined by Formula I, with or without a separate organic acrylate, using at 5-50% by weight of the siloxane emulsifiers selected from nonionic surfactants (such as alkylaryl-polyoxyethylene adducts and alkyl ethoxylates) or anionic surfactants (such as, carboxylates, sulfates, sulfonates, alkylaryl sulfonates and alkyl phosphates), to form a stable emulsion containing 10-50% of the dispersed siloxane phase, which can be further stabilized by addition of common thickeners, such as xanthan or guar gum, gellatin and cellulose derivatives.
2. Adding a free-radical catalyst, selected from the group of water soluble or oil soluble peroxides, such as hydrogen peroxide, ammonium persulfate, potassium persulfate, various organic peroxy catalysts, such as dialkyl peroxides, e.g., diisopropyl peroxide, dilauryl peroxide, di-t-butyl peroxide, dicumyl peroxide, alkyl hydrogen peroxides such as t-butyl hydrogen peroxide, t-amyl hydrogen peroxide, cumyl hydrogen peroxide, diacyl peroxides, for inst

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