Compositions – Leather or fur treating
Reexamination Certificate
2001-04-27
2002-10-29
Green, Anthony J. (Department: 1755)
Compositions
Leather or fur treating
C427S389000, C524S558000, C524S560000, C524S561000
Reexamination Certificate
active
06471885
ABSTRACT:
This invention relates to a leather coating composition. More particularly, this invention relates to an aqueous leather coating composition containing a multi-stage emulsion polymer having a lower Tg (glass transition temperature) polymer stage which contains a copolymerized carboxylic acid and which has been contacted with a divalent metal oxide, hydroxide, or carbonate and a higher Tg polymer stage which has been prepared in the presence of 1% to 15% by weight based on the weight of that stage of chain transfer agent. Also, the invention relates to a method for coating leather with the composition of this invention.
The present invention serves to provide a protective coating that is aesthetically pleasing. The dried coating may be subsequently embossed with a desired imprint in a heated press. The softness of the coated leather and an effective embossed imprint are desirable aesthetic properties of the coated leather.
U.S. Pat. No. 5,723,182 discloses an aqueous leather coating composition containing a multi-stage emulsion polymer which has been contacted with a transition metal oxide, hydroxide, or carbonate. Further improvements in the softness of the coated leather and the ability of the coating to be embossed effectively are desirable
The problem faced by the inventors is the provision of an aqueous leather coating composition which yields a dried coated leather that has improved softness and embossability relative to prior compositions, preferably with little or no increase in surface tack of the dried coating. Surprisingly, the inventors found that the use of 1-15% by weight based on the weight of the second stage polymer of a chain transfer agent such as a mercaptan during the formation of the second (harder) stage of a multi-stage emulsion polymer reduced the stiffness and improved the embossability of leather coated with an aqueous composition containing the multi-stage polymer.
According to a first aspect of the present invention there is provided an aqueous leather coating composition including a multi-stage aqueous emulsion polymer including (i) a predominantly acrylic first stage polymer including at least one copolymerized monoethylenically-unsaturated nonionic monomer and from 0.5% to 10% of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the first stage polymer, the first stage polymer being substantially free from copolymerized multiethylenically-unsaturated monomer; the first stage polymer having a Tg less than 10° C.; the first stage polymer having been contacted with a transition metal oxide, hydroxide, or carbonate at a pH of less than 9 in an amount greater than 0.1 equivalent of transition metal per equivalent of the copolymerized carboxylic acid monomer in the first stage polymer; and (ii) a second stage polymer including at least one copolymerized monoethylenically-unsaturated nonionic monomer and from 0% to 10% of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the second stage polymer, wherein the second stage polymer is formed in the presence of from 1% to 15% by weight based on the weight of the second stage polymer of chain transfer agent, provided that the second stage copolymerized carboxylic acid monomer is less than 25%, by weight, of the total copolymerized carboxylic acid monomer in the multi-stage emulsion polymer, the second stage polymer being substantially free from copolymerized multiethylenically-unsaturated monomer; the second stage polymer having a Tg greater than 20° C.; and the second stage polymer being from 1% to 50% of the weight of the first stage polymer, based on dry polymer weights, and.
According to a second aspect of the present invention there is provided a method for coating leather including
(a) forming an aqueous leather coating composition including a multi-stage aqueous emulsion polymer formed by a method including
(i) forming a predominantly acrylic first stage polymer including at least one copolymerized monoethylenically-unsaturated nonionic monomer and from 0.5% to 10% of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the first stage polymer, the first stage polymer being substantially free from copolymerized multiethylenically-unsaturated monomer; and the first stage polymer having a Tg less than 10° C.;
(ii) contacting the first stage polymer with a transition metal oxide, hydroxide, or carbonate at a pH of less than 9 in an amount greater than 0.1 equivalent of transition metal per equivalent of the copolymerized carboxylic acid monomer in the first stage polymer; and
(iii) forming a second stage polymer including at least one copolymerized monoethylenically-unsaturated nonionic monomer and from 0 to 10% of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the second stage polymer, wherein the second stage polymer is formed in the presence of from 1% to 15% by weight based on the weight of the second stage polymer of chain transfer agent, provided that the second stage copolymerized carboxylic acid monomer is less than 25%, by weight, of the total copolymerized carboxylic acid monomer in the multi-stage emulsion polymer, the second stage polymer being substantially free from copolymerized multiethylenically-unsaturated monomer; the second stage polymer having a Tg greater than 20° C.; the second stage polymer being from 1% to 50% of the weight of the first stage polymer, based on dry polymer weights,
(b) applying the coating composition to leather; and
(c) drying the coating composition.
This invention relates to a leather coating composition and a method for coating leather including a multi-stage polymer prepared by emulsion polymerization. The multi-stage emulsion polymer contains a predominantly acrylic first stage polymer comprising at least one copolymerized monoethylenically-unsaturated nonionic monomer and from 0.5% to 10% of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the first stage polymer, the first stage polymer being substantially free from copolymerized multiethylenically-unsaturated monomer. By “predominantly acrylic first stage polymer” is meant that greater than 50% of the copolymerized monomers forming the first stage polymer are acrylic, i.e., that they are selected from esters, nitrites, etc. of (meth)acrylic acid. By “nonionic monomer” herein is meant that the copolymerized monomer residue does not bear an ionic charge between pH=2-13. The first stage polymer contains at least one copolymerized monoethylenically-unsaturated nonionic monomer such as, for example, a (meth)acrylic ester monomer including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate; styrene or substituted styrenes; butadiene; vinyl acetate or other vinyl esters; vinyl monomers such as vinyl chloride, vinylidene chloride, N-vinyl pyrolidone; and (meth)acrylonitrile. The use of the term “(meth)” followed by another term such as (meth)acrylate or (meth)acrylonitrile, as used throughout the disclosure, refers to both acrylate and methacrylate or acrylonitrile and methacrylonitrile, respectively.
The first stage polymer also contains from 0.5% to 10%, preferably from 1% to 5%, of a copolymerized monoethylenically-unsaturated carboxylic acid monomer, based on the weight of the first stage polymer, such as, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride.
The first stage polymer used in this invention is substantially free from copolymerized multiethylenically-unsaturated monomers such as, for example, allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,2-ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and divinyl ben
Chiang Jin-chih
Chiou Shang-Jaw
Schindler Frederick James
Bakule Ronald D.
Green Anthony J.
Rohm and Haas Company
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