Polymeric binders having specific peel and cure properties and useful in making creped webs
This invention is directed to alkylphenol ethoxylate (APE)-free polymer binders formed by aqueous free radical emulsion polymerization and having specific peel and cure properties. The APE-free polymeric binders have a peel value, when adhered to a heated metal surface, of 35% to 200% of the peel value shown by a standard APE-based polymer binder control and exhibit a cure profile such that at least 55% cure is achieved within 30 seconds at a temperature required for cure, and a wet tensile strength at 30-seconds of cure of at least 1000 g/5 cm. Wet tensile strength is used as a measure of cure. Binders having the peel and cure properties described herein can be considered for use in crepe processes, especially DRC processes.
1. In a crepe process that comprises applying a polymer binder to a nonwoven web, drying, and creping the nonwoven web on a creping drum, the improvement which comprises using an alkylphenol ethoxylate free aqueous polymer emulsion binder formed by aqueous free radical emulsion polymerization of one or more ethylenically unsaturated monomers and one or more crosslinking monomers, said binder having a peel value of 35% to 200% of a standard alkylphenol ethoxylate-based vinyl acetate-ethylene polymer emulsion control, a cure profile in which 55% cure is achieved within 30 seconds of being exposed to a temperature required for cure, and a wet tensile strength at 30 seconds of cure of at least 1000 g/5 cm.
2. The crepe process of claim 1 wherein the one or more crosslinking monomers are selected from the group consisting of an N-alkylol acrylamide, an N-alkylol methacrylamide, i-butoxy methylacrylamide, acrylamidoglycolic acid, acrylamidobutyraldehyde, and a dialkyl acetal of acrylamidobutyraldehyde, wherein alkyl is 1 to 4 carbons.
3. The crepe process of claim 2 wherein the peel value is 50 to 125% of the polymer emulsion control.
4. The crepe process of claim 2 wherein the wet tensile strength at 30 seconds of cure is at least 1500 g/5 cm.
5. The crepe process of claim 1 , wherein the process is a double recrepe process comprising applying said polymer binder to one side of said nonwoven web, drying, and creping the nonwoven web on said creping drum, followed by applying said polymer binder to the opposite side of the nonwoven web and again drying and creping the nonwoven web on a creping drum.
6. The double recrepe process of claim 5 having a viscosity of 5 to 80 cps at about 30% solids.
7. The crepe process of claim 1 wherein the binder is a copolymer of ethylene, vinyl acetate and one or more crosslinking monomers selected from the group consisting of an N-alkylol acrylamide, an N-alkylol methacrylamide, i-butoxy methylacrylamide, acrylamidoglycolic acid, acrylamidobutyraldehyde, and a dialkyl acetal of acrylamidobutyraldehyde, wherein alkyl is 1 to 4 carbons.
8. The crepe process of claim 7 wherein the one or more crosslinking monomers is N-methylol acrylamide.
9. A creped nonwoven web prepared by the process of claim 1 .
10. A double recreped nonwoven web prepared by the process of claim 5 .