Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-03-04
2002-11-12
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S255000, C526S304000, C526S307300, C526S307500, C526S307700, C526S320000, C526S323100, C526S323200, C526S329400, C526S329600, C526S330000, C526S333000
Reexamination Certificate
active
06479605
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an aqueous emulsion composition of a fluorochemical (meth)acrylate copolymer for imparting a highly-durable oil and water repellent finish to textiles, wherein the copolymer imparts little or no yellowing of the textiles upon curing. In all instances herein, the term “(meth)acrylate” is used to denote either acrylate or methacrylate, or mixtures thereof.
BACKGROUND OF THE INVENTION
Fluoropolymer compositions having utility as textile treating agents, generally contain pendant perfluoroalkyl groups of three or more carbon atoms, which provide oil- and water-repellency when the compositions are applied to fabric surfaces. The perfluoroalkyl groups are attached by various connecting groups to polymerizable groups not containing fluorine. The resulting monomer is then generally copolymerized with other monomers which confer additional favorable properties to the textile fabrics. The polymer chain backbone of the resulting copolymer may be (meth)acrylates, vinyl, vinylidene or other groups. They may act to extend the performance of the more expensive perfluoroalkyl groups, or act as bonding agent to fix the copolymer to the fabric, or may serve other functions. Generally, such copolymers are prepared by copolymerization of two or more monomers in an aqueous media stabilized with a surfactant.
These polymers are marketed as aqueous emulsions for easy application to the fabric. The fabric-treating composition may also include other additives in addition to those copolymerized with the fluoromonomer. In particular, various compounds such as blocked isocyanates are frequently added before or after polymerization to promote durability of a desired property such as repellency. In this usage, the blocking agent is removed from the isocyanate under the thermal conditions used when curing the treated fabric, allowing the isocyanate group to interact with the fabric and improve the desired durability.
Typically, the major monomers used for such copolymers include a perfluoroalkyl (meth)acrylate and a long-chain alkyl (meth)acrylate such as stearyl (meth)acrylate. Many such copolymers also contain vinyl or vinylidene chloride in order to improve the durability of the repellency treatment. Smaller amounts of various specialized monomers containing hydroxyl groups and/or alkylene oxide oligomers may be incorporated to impart improved cross-linking, latex stability and/or substantivity. Each ingredient may impart some potentially undesirable properties in addition to its desirable ones.
For example, U.S. Pat. No. 4,742,140 discloses a composition comprising by weight 40-75% of a specific perfluoroalkylethyl acrylate mixture, 10-35% vinylidene chloride and 10-25% alkyl (meth)acrylate having an alkyl chain length of 2-18 carbons. A preferred composition consists essentially of by weight 45-70% of the above perfluoroalkylethyl acrylate, 15-30% vinylidene chloride, 10-20% of the above alkyl (meth)acrylate, 0.1-2% N-methylol acrylamide, and optionally up to 5% chlorohydroxypropyl (meth)acrylate, and up to 5% poly(oxyethylene) (meth)acrylate. Improved repellency and durability are claimed over prior art compositions.
However, polymers containing such large amounts of vinylidene chloride may cause yellowing of the fabric upon curing, due to dehydrohalogenation of the vinylidene chloride. There is a need for compositions which impart a highly durable repellency to fabrics but which contain less than 10% by weight of vinylidene chloride. There is also a need for compositions having durable repellency properties but which require less fluorine to be present. The present invention provides such compositions.
SUMMARY OF THE INVENTION
The present invention comprises a copolymer composition, which imparts a highly durable, low yellowing repellent finish to fabrics and fabric blends comprising monomers copolymerized in the following percentages by weight:
(a) from about 40% to about 75% of a monomer of formula I:
R
f
—CH
2
CH
2
—OC(O)—C(R)═CH
2
I
(b) from about 15% to about 55% of a monomer of formula II:
R
2
—OC(O)—C(R)═CH
2
II
(c) from 1.5% to about 5% of a monomer of the formula III:
HO—CH
2
CH
2
—OC(O)—C(R)═CH
2
III
(d) from 1.5% to about 5% of a monomer of the formula IV:
H—(OCH
2
CH
2
)
m
—O—C(O)—C(R)═CH
2
IV
(e) from 1% to about 3% of a monomer of the formula V:
HO—CH
2
—NH—C(O)—C(R)═CH
2
V
wherein R
f
is a straight or branched-chain perfluoroalkyl group of from 2 to about 20 carbon atoms, each R is independently H or CH
3
; R
2
is an alkyl chain from 2 to about 18 carbon atoms; and m is 2 to about 10.
Optionally, the copolymer composition may also contain:
(f) from 0% up to about 9.8% of vinylidene chloride (formula VI) or vinyl acetate (formula VII), or a mixture thereof:
CH
2
═CCl
2
VI
CH 3—(O)COCH═CH2 VII
(g) from 0% to about 2% of a blocked isocyanate such as the monomer of the formula VIII:
(CH
3
)(CH
2
CH
3
)C═N—O—C(O)—NH—CH
2
—CH
2
—OC(O)C(R)═CH
2
VIII
wherein R is H or CH
3
.
The present invention further comprises a method of treating a fabric or fabric blend to impart oil and water repellency comprising application to the surface of the fabric or fabric blend of the composition as described above, and the fabric or fabric blend which has been so treated. The treated fabric or fabric blend has a fluorine content of from about 0.05% to about 0.5% by weight.
DETAILED DESCRIPTION OF THE INVENTION
Trademarks and tradenames are indicated herein by capitalization. This invention comprises improved fluorochemical copolymers useful for imparting repellent properties to fabrics or blends. By “fabrics” is meant natural or synthetic fabrics composed of fibers of cotton, rayon, silk, wool, polyester, polypropylene, polyolefins, nylon, and aramids such as “NOMEX” and “KEVLAR.” By “fabric blends” is meant fabric made of two or more types of fibers. Typically these blends are a combination of a natural fiber and a synthetic fiber, but also can include a blend of two natural fibers or of two synthetic fibers. Superior repellent properties, along with desirable properties of low yellowing and good durability are imparted to fabrics and fabric blends by the addition of these improved fluorochemical copolymers. They are applied to the fabric in the form of a dispersion in water or other solvent, either before, after, or during the application of other fabric treatment chemicals.
The copolymers of this invention are prepared by conventional emulsion polymerization techniques. The surfactant employed to stabilize the emulsion during its formation and during polymerization can be a cationic or non-ionic emulsifying agent or agents. The polymerization is conveniently initiated by azo initiators such as 2,2′-azobis(2-amidinopropane) dihydrochloride. These initiators are sold by E. I. du Pont de Nemours and Company, Wilmington, Del., commercially under the name of “VAZO”, and by Wako Pure Industries, Ltd., Richmond, Va., under the name “V-50.”
The emulsions produced are applied to textile surfaces by known methods to impart oil-, soil- and water-repellency. The copolymers are applied to the fabric or fabric blend either alone or in a mixture with other textile treatment agents or finishes. A distinguishing feature of the fluoropolymers of the present invention is their effectiveness at low application levels, low yellowing of the fabric upon curing, and high durability of the finish on the fabric.
The highly efficient copolymers discussed above are characterized in that they contain copolymerized comonomers in the following percentages by weight, relative to the total weight of the copolymers:
(a) from about 40% to about 75% of a monomer of formula I:
R
f
—CH
2
CH
2
—OC(O)—C(R)═CH
2
I
(b) from about 15% to about 55% of a monomer of formula II:
R
2
—OC(O)—C(R)═CH
2
II
(c) from 1.5% to about 5% of a monomer of the formula III:
HO—CH
2
CH
2
—OC(O)—C(R)═CH
2
III
(d) from 1.5% t
E. I. du Pont de Nemours and Company
Pezzuto Helen L.
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