Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-02-04
2001-01-30
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C524S544000
Reexamination Certificate
active
06180740
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a composition and process for preparing an aqueous emulsion composition of a fluorochemical copolymer for imparting oil and water repellency to textiles, the copolymer comprising perfluoroalkyl (meth)acrylates, vinylidene chloride and alkyl (meth)acrylates, wherein the resulting emulsion has improved stability under conditions of high alkalinity, a highly anionic environment, or high shear. (In all instances herein, the term “(meth)acrylate” is used to denote either acrylate or methacrylate).
BACKGROUND OF THE INVENTION
Fluoropolymer compositions are known having utility as textile treating agents. These fluoropolymers generally contain pendent 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 generally attached by various connecting groups to polymeric groups not containing fluorine which form the backbone polymer chains of the resulting copolymer. These backbone polymers may be (meth)acrylates, vinyl, vinylidene or other groups. They may act to extend the performance of the more expensive perfluoroalkyl groups, act as bonding agents to fix the copolymer to the fabric, or may serve other functions.
Generally, such copolymers are prepared in an aqueous emulsion stabilized with a cationic, nonionic or anionic surfactant. While it is not unusual for a nonionic surfactant to be used in combination with a cationic or anionic surfactant, a cationic and anionic surfactant are not combined as emulsion stabilizers because of their potential reactions with each other. However, some uses of combined cationic and anionic surfactants have been disclosed to obtain certain end-product characteristics in cosmetic, photographic and other non-textile applications.
While fluoropolymer-(meth)acrylate compositions disclosed in the prior art may be satisfactory under certain application conditions, their aqueous emulsions are not sufficiently stable under some harsh conditions. For example, under a highly anionic and/or high alkalinity environment, such as produced by the strong alkali remaining on a fabric after mercerization, the emulsion from prior art compositions will turn dark and precipitate within a few hours. In other applications, where the fluoropolymer emulsion is subjected to high shear conditions or high temperatures, the emulsion may also destabilize, resulting in precipitation of the polymer from the dispersion. Such failures can be extremely costly. Compositions and processes for preparing fabric treatment agents having improved stability under these conditions are of significant interest to the textile and apparel industries. The present invention provides such compositions and processes.
SUMMARY OF THE INVENTION
The present invention comprises a process for preparing an oil- and water-repellent aqueous emulsion composition comprising:
1) forming a mixture with water comprising:
(a) from about 50% to about 85% by weight on a water free basis of polymer chain units derived from a mixture of perfluoroalkylethyl acrylate monomers of the formula:
R
f
-Q-A—C(O)—C(R)═CH
2
wherein
R
f
is a straight or branched-chain perfluoroalkyl group containing from 2 to 20 carbon atoms,
R is H or CH
3
,
A is O, S, or N(R′),
Q is alkylene of 1 to 15 carbon atoms, hydroxyalkylene of 3 to 15 carbon atoms, —(C
n
H
2n
)(OC
q
H
2q
)m—, —SO
2
—NR′(C
n
H
2n
)—, or —CONR′(C
n
H
2n
)—,
R′ is H or alkyl of 1 to 4 carbon atoms, n is 1 to 15, q is 2 to 4, and m is 1 to 15;
(b) from about 1% to about 9.9% by weight on a water free basis of monomer chain units derived from vinylidene chloride; and,
(c) from about 10% to about 25% by weight on a water free basis of monomer chain units derived from an alkyl (meth)acrylate having an alkyl chain length of 2 to 18 carbons;
(d) from about 0.25% to about 5% by weight on a water free basis of cationic surfactant;
2) polymerizing said mixture, and
3) adding an anionic surfactant in an amount sufficient to yield an emulsion with a zeta potential of between +15 and +30 millivolts. Preferably the zeta potential is between +15 to +25 millivolts. More preferably the zeta potential is between +20 and +25 millivolts. Optionally, a nonionic surfactant is used with either surfactant.
In another embodiment of this invention, the above composition comprising (a), (b) and (c) is emulsified in water with from about 5% to about 15% by weight on a water free basis of anionic surfactant, the mixture is polymerized, and a cationic surfactant is added after polymerization to obtain an emulsion with the range of zeta potential between +15 and +30 millivolts. Optionally, a nonionic surfactant is used with either surfactant.
In still another embodiment, this invention comprises an oil- and water-repellent aqueous emulsion composition comprising by weight (water-free basis):
(a) from about 50% to about 85% polymer chain units derived from a mixture of perfluoroalkylethyl acrylate monomers of the formula:
R
f
-Q-A—C(O)—C(R)═CH
2
wherein
R
f
is a straight or branched-chain perfluoroalkyl group containing from 2 to 20 carbon atoms,
R is H or CH
3
,
A is O, S, or N(R′),
Q is alkylene of 1 to 15 carbon atoms, hydroxyalkylene of 3 to 15 carbon atoms, —(C
n
H
2n
)(OC
q
H
2q
)
m
—, —SO
2
—NR′(C
n
H
2n
)—, or —CONR′(C
n
H
2n
)—,
R′ is H or alkyl of 1 to 4 carbon atoms,
n is 1 to 15, q is 2 to 4, and m is 1 to 15;
(b) from about 1% to about 9.9% polymer chain units derived from vinylidene chloride;
(c) from about 10% to about 25% polymer chain units derived from an alkyl (meth)acrylate having an alkyl chain length of 2 to 18 carbons;
(d) a cationic surfactant and,
(e) an anionic surfactant,
said composition having the range of zeta potential of between +15 and +30 millivolts. Optionally a nonionic surfactant is used with either surfactant.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a process for preparation of an aqueous emulsion of a copolymer composition providing oil- and water-repellency to textiles and other substrates, said composition having stability under conditions of high alkalinity, high anionic concentration, and/or high shear conditions. By high alkalinity is typically meant a pH of between 8 and 12. By high anionic concentration is meant any anionic concentration that interferes with the application, which will vary with the particular application and fabric. By high shear conditions is meant the conditions arising from operations such as pumping or unusually vigorous agitation.
This invention depends in part on the discovery that, after using a cationic surfactant to create a polymer emulsion, emulsions with unusual stability to harsh conditions are made by then adding a small amount of an anionic surfactant to achieve a particular zeta potential. This latter step enables a precise control of the zeta potential, as well as the ability to make emulsions with controllable positive, negative and even zero zeta potentials not readily available by prior art methods. Similarly, it was discovered that an emulsion with a controllable zeta potential is created using an anionic surfactant to create a stable polymer emulsion, and then adding a measured amount of a cationic surfactant. Optionally, a nonionic surfactant is used in combination with either the cationic or anionic surfactant. Unexpectedly, emulsions prepared by this process have unusual stability under harsh conditions such as high alkalinity, a highly anionic environment or high shear.
While this method is used to create emulsions of unusual stability having either positive or negative zeta potentials by controlling the relative amounts of cationic and anionic surfactants, all such emulsions may not be suitable for all applications because a certain zeta potential may be needed for affinity to the substrate employed or for specific reaction conditions. The zeta potential needed for a particular application is generall
E. I. Du Pont de Nemours and Company
Rajguru U. K.
Seidleck James J.
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