Compositions – Leather or fur treating
Reexamination Certificate
1999-05-04
2001-09-25
Green, Anthony (Department: 1755)
Compositions
Leather or fur treating
C106S002000, C008S09410R, C008S094210, C427S389000, C428S473000, C525S199000, C525S200000
Reexamination Certificate
active
06294103
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to leather manufacture and the use of fluoroalkyl group containing amphiphilic copolymers therein. More in particular, the invention relates to fluoroalkyl group containing amphiphilic copolymers and their use in a waterproofness imparting composition for leather substrates. In another aspect, the invention relates to a method for imparting a high degree of waterproofness to leather substrates and to the resulting treated leather substrates.
BACKGROUND OF THE INVENTION
The treatment of hides and skins to form leather involves a number of interdependent chemical and mechanical operations. These operations may be divided into a sequence of “wet end” steps followed by a sequence of“dry” steps. A description of each of these operations is provided in Fundamentals of Leather Manufacturing, Prof Dr. Heidemann (Eduard Roether KG, 1993). The primary tanning operation involves the treatment of the hide to preserve it and form useful leather. Chrome tanning salts are well known and widely used for this purpose. Chrome-tanned hides or skins are known in the art as ‘wet blue leather’. In order to produce a uniform piece of leather with the required physical and aesthetic properties, a second tanning step, known as ‘retanning’, is employed. Retanning can be accomplished using a variety of naturally derived materials including extracts from vegetables or plants, and synthetic tanning agents known as “syntans”, or combinations thereof After or during retanning, the leather can be colored and fatliquored. The present invention relates to the wet end operations which take place after primary tanning, namely retanning and fatliquoring.
A number of publications have proposed various copolymers for treating leather during tanning and retanning, addressing the problem of making treated leather more water resistant or completely waterproof
EP-A-372 746 discloses a method and process for treating leather utilizing selected amphiphilic copolymers for improving the strength, temper and water resistance of the leather. The amphiphilic copolymers are formed from a predominant amount of at least one hydrophobic monomer and a minor amount of at least one copolymerizable hydrophilic monomer. The application states that the process may be particularly useful as a one step substitute for conventional retanning and fatliquoring treatment steps.
EP-A-682 044 discloses copolymers comprising ethylenically unsaturated dicarboxylic acid anhydrides, long chain olefins and fluorolefins. Leathers treated with these polymers are shown to yield good waterproofness results according to the Bally-Penetrometer test.
U.S. Pat. No. 5,124,181 discloses copolymers which contain (a) from 50 to 90% by weight of C
8
to C
40
alkyl methacrylates, vinyl esters of C
8
to C
40
carboxylic acids or mixtures thereof and (b) from 10 to 50% by weight of monoethylenically unsaturated C
3
to C
12
carboxylic acids, monoethylenically unsaturated dicarboxylic anhydrides, monoesters or monoamides of monoethylenically unsaturated C
4
to C12 dicarboxylic acids, amides of C
3
to C
12
monocarboxylic acids or mixtures thereof as copolymerized units and which have molecular weights of from 500 to 30,000. The copolymers are used in at least partially neutralized form in aqueous solution or dispersion for making leather and furs water repellent.
WO 94/01587 discloses water-dispersible and/or water-emulsifiable co-oligomers containing (a) fatty crotonates; (b) radically copolymerizable, hydrophilic, ethylenically unsaturated acids and/or their anhydrides; and possibly (c) minor amounts of other copolymerizable comonomers. These co-oligomers are used as amphiphilic agents for greasing leather and pelts.
Despite the various publications, employing different combinations of hydrophilic and hydrophobic monomers to obtain waterproofing properties of leather, there is still a need for further improvement particular under demanding conditions.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a method of treating leather comprising contacting a leather, in particular a tanned leather, with an amphiphilic copolymer, said amphiphilic copolymer comprising the following recurring units:
wherein:
R
f
represents a fluorinated alkyl group having at least 3 carbon atoms;
Q and Q′ each independently represent an organic linking group or other chemical linkage;
R
1
and R
2
each independently represent hydrogen or a C
1
-C
4
alkyl group; and
R
h
represents a hydrocarbon group having at least 8 carbon atoms and optionally containing I to 3 substituents;
and a recurring unit comprising at least one carboxylic acid group or salt thereof.
The present invention further provides amphiphilic copolymers as defined above and aqueous compositions comprising them.
Additionally, the present invention provides a use of an above defined amphiphilic copolymer in treating leather to provide waterproofness thereto.
Also the present invention provides leathers comprising an amphiphilic copolymer as defined above.
Finally, the present invention provides a method for making above defined amphiphilic copolymers.
The invention simplifies the manufacture of waterproof leather by providing in one step the desired properties normally obtained by separate, conventional wet end retanning and fatliquoring steps.
DETAILED DESCRIPTION OF THE INVENTION
A particularly preferred amphiphilic copolymer for use in connection with this invention is a copolymer wherein the recurring unit having at least one carboxylic acid group or salt thereof corresponds to the following formula (III):
wherein;
R
3
represents hydrogen or a C
1
to C
4
alkyl group;
Y represents an organic linking group or other chemical linkage and;
M represents a hydrogen or a cation.
A fluorinated alkyl group R
f
in the fluorochemical containing recurring unit according to formula (1), is preferably a fluorinated, stable, inert, preferably saturated, non-polar, monovalent alkyl group. It can be straight chain, branched chain, or cyclic or combinations thereof It can contain heteroatoms, bonded only to carbon atoms, such as oxygen, divalent or hexavalent sulfur, or nitrogen. R
f
is preferably a fully-fluorinated alkyl group, but hydrogen or chlorine atoms can be present as substituents but preferably not more than one atom of either is present for every two carbon atoms. The R
f
group has at least 3 carbon atoms, preferably 3 to 14 carbon atoms, and more preferably at least 6 carbon atoms. R
f
preferably contains about 40% to about 80% fluorine by weight, more preferably about 50% to about 78% fluorine by weight. The terminal portion of the R
f
radical is preferably a perfluorinated moiety, preferably containing at least 7 fluorine atoms, e.g., CF
3
CF
2
CF
2
-, (CF
3
)
2
CF-, F
5
CF
2
-. Preferred R
f
groups are fully or substantially fluorinated and are preferably those perfluorinated alkyls according to the formula C
n
F
2n+1
- where n is 3 to 14.
Linking groups Q, Q′ and Y in the above formulas (I) to (III) preferably contain from 1 to about 20 carbon atoms. They can optionally contain oxygen, nitrogen, or sulfur-containing groups or a combination thereof, and are preferably free of functional groups that substantially interfere with free-radical polymerization (e.g., polymerizable olefinic double bonds, thiols, easily abstracted hydrogen atoms such as cumyl hydrogens, and other such functionality known to those skilled in the art). Examples of suitable linking groups include straight chain, branched chain or cyclic alkylene, arylene, aralkylene, oxy, oxo, hydroxy, thio, sulfonyl, sulfoxy, amino, imino, sulfonamido, carboxyamido, carbonyloxy, urethanylene, ureylene, and combinations thereof such as sulfonamidoalkylene. Preferred linking groups for Q and Q′ include -(CH
2
CH
2
)
k
O- and -SO
2
N(R)CH
2
CH
2
- wherein k is 1 or 2 and R is a C
1
to C
4
-alkyl group. A preferred linking group Y is an aliphatic or aromatic linking group.
R
h
groups for use in connection with the present invention are hydrocarbon
3M Innovative Properties Company
Green Anthony
Jordan Robert H.
Maki Eloise J.
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