Various fluoropolymers have been proposed for imparting oil and water repellency to leather. Commonly, these fluoropolymers are amphiphilic; i.e., they are made from at least one monomer which is hydrophobic and at least one monomer which is hydrophilic. The present invention identifies and remedies disadvantages associated with the ability of amphiphilic fluoropolymers to impart oil and water repellency to leather. Contrary to conventional thinking, it has now been discovered that the incorporation of hydrophilic groups in a fluoropolymer undesirably reduces its ability to impart water resistance to leather. Correspondingly, it has also been discovered that a fluoropolymer incorporating fewer or no hydrophilic groups imparts superior oil and water repellency to leather when compared to fluoropolymers incorporating more hydrophilic groups. Therefore, this invention provides fluoropolymers which incorporate reduced levels of hydrophilic groups.
1. A fluoropolymer comprising at least 20 weight percent of hydrophobic fluorinated acrylic units, at least 35 weight percent of hydrophobic vinylic units, and optionally other monomeric units, provided that no more than 10 weight percent of any hydrophobic monomeric units other than said hydrophobic fluorinated acrylic units and said hydrophobic vinylic units are present and no more than 5 weight percent of any hydrophilic monomeric units are present, said fluoropolymer imparting repellency to leather contacted therewith, and represented by the following:
wherein x is a non-zero positive integer denoting the number of hydrophobic fluorinated acrylic units; y is a non-zero positive integer denoting the number of hydrophobic vinylic units; the sum of x and y is at least 21 and the ratio of x:y is from 2:8 to 6:4; each R f independently represents a perfluorinated alkyl group, optionally interrupted by oxygen, having 2 to 6 carbon atoms; each R 1 is independently chosen from a C 1 -C 20 hydrocarbylene; each R 8 is independently chosen from a C 1 -C 20 hydrocarbyl or hydrogen; each R 2 is independently chosen from hydrogen, fluorine, or a C 1 -C 4 alkyl; each m is independently 1; each R h independently represents a linear or branched hydrocarbon group having at least 4 carbon atoms; each Z is divalent and independently selected from the group consisting of —OC(O)—, —HNC(O) —, and —C 6 H 4 —; and each R 3 is independently chosen from hydrogen or a C 1 -C 4 alkyl group.
2. The fluoropolymer of claim 1 wherein R 1 is a linear C 1 -C 5 hydrocarbylene; R 8 is chosen from linear C 1 -C 5 hydrocarbyl or hydrogen; and R 2 and R 3 is chosen from hydrogen or methyl.
3. The fluoropolymer of claim 1 wherein Z is —OC(O)—.
4. The fluoropolymer of claim 1 having a molecular weight of at least 10,000 grams/mole.
5. The fluoropolymer of claim 1 in an organic solvent, an aqueous dispersion, or an aqueous emulsion.
6. A method for imparting water and/or oil repellency to leather, the method comprising contacting a leather substrate with the fluoropolymer of claim 1 .
7. The method of claim 6 wherein the contacting is by core or surface treatment.