Low temperature curing of nonwoven products bonded with N-methylolacrylamide-containing copolymers

Claim 2

In a method for preparlng a nonwoven product bonded with an N-methylolacrylamide-containing copolymer resin which comprises applying the aqueous resin emulsion containing an acidic curing agent to a nonwoven web of fibers and drying and curing the nonwoven web at elevated temperatures to drive off water and to effect cross-linking of the N-methylolacrylamide-containing resin, the improvement which comprises (a) adding to a vinyl acetate/ethylene/N-methylolacrylamide or a vinyl chloride/ethylene/N-methylolacrylamide copolymer emulsion a curingly effective amount of an acidic curing agent having a pK a ranging from about 1 to 2 and applying to a nonwoven web, (b) heating the treated nonwoven web for a time and at a temperature sufficient to volatilize a substantial amount of the water but insufficient to effect substantial crosslinking of the resin and (c) maintaining the copolymer on the dried nonwoven web at a temperature which is less than the temperature of step (b) and for a time sufficient to develop essentially full cure.

Claim 3

The method of claim 1 in which the N-methylolacrylamide-containing copolymer is a vinyl acetate/ethylene/N-methylolacrylamide copolymer.

Claim 4

The method of claim 1 in which the acidic curing agent is oxalic acid, maleic acid, or sodium bisulfate.

Claim 5

The method of claim 2 in which the acidic curing agent is oxalic acid, maleic acid, or sodium bisulfate.

Claim 6

The method of claim 1 in which the curing agent is maleic acid.

Claim 7

The method of claim 2 in which the curing agent is maleic acid.

Claim 8

The method of claim 1 in which the curing temperature of step (c) ranges from ambient to 200° F.

Claim 9

The method of claim 2 in which the curing temperature of step (c) ranges from ambient to 200° F.

Claim 10

The method of claim 1 in which the copolymer emulsion treated nonwoven web is dried in step (b) to a moisture content of about 8 to 20%.

Claim 11

The method of claim 2 in which the copolymer emulsion treated nonwoven web is dried in step (b) to a moisture content of about 8 to 20%.

Claim 12

In a method for preparing a nonwoven product bonded with an N-methylolacrylamide-containing copolymer resin selected from the group consisting of a vinyl acetate/ethylene/N-methylolacrylamide copolymer and a vinyl chloride/ethylene/N-methylolacrylamide copolymer which comprises applying the aqueous resin emulsion containing an acidic curing agent to a nonwoven web of fibers and drying and curing the nonwoven web at elevated temperatures to drive off water and to effect cross-linking of the N-methylolacrylamide-containing resin, the improvement which comprises (a) adding to the copolymer emulsion a curingly effective amount of an acidic curing agent having a pK a ranging from about 1 to 2 and applying to a nonwoven web, (b) heating the treated nonwoven web for a time and at a temperature sufficient to dry the web to a moisture content of about 8 to 20% but insufficient to effect substantial crosslinking of the resin, and (c) maintaining the copolymer on the dried nonwoven web at a temperature ranging from ambient to 200° F. which temperature is less than the temperature of step (b) and for a time sufficient to develop essentially full cure.

Claim 13

In a method for preparing a nonwoven product bonded with an N-methylolacrylamide-containing copolymer resin selected from the group consisting of a vinyl acetate/ethylene/N-methylolacrylamide copolymer and a vinyl chloride/ethylene/N-methylolacrylamide copolymer which comprises applying the aqueous resin emulsion containing an acidic curing agent to a nonwoven web of fibers and drying and curing the nonwoven web at elevated temperatures to drive off water and to effect cross-linking of the N-methylolacrylamide-containing resin, the improvement which comprises (a) adding to the copolymer emulsion a curingly effective amount of an acidic curing agent having a pK a ranging from about 1 to 2 and applying to a nonwoven web, (b) heating the treated nonwoven web for a time and at a temperature sufficient to dry the web to a moisture content of about 8 to 20% but insufficient to effect substantial crosslinking of the resin, and (c) maintaining the copolymer on the dried nonwoven web at a temperature ranging from ambient to 200° F. which temperature is less than the temperature of step (b) and for a time sufficient to develop essentially full cure.

Claim 14

The method of claim 11 in which the N-methylolacrylamide-containing copolymer is a vinyl acetate/ethylene/N-methylolacrylamide copolymer.

Claim 15

The method of claim 11 in which the acidic curing agent is oxalic acid, maleic acid, or sodium bisulfate.

Claim 16

The method of claim 12 in which the acidic curing agent is oxalic acid, maleic acid, or sodium bisulfate.

Claim 17

The method of claim 11 in which the curing agent is maleic acid.

Claim 18

The method of claim 12 in which the curing agent is maleic acid.

Claim 19

The method of claim 11 in which step (b) is performed at 150° to 200° F.

Claim 20

The method of claim 12 in which step (b) is performed at 150° to 200° F.

Claim 21

The method of claim 11 in which step (b) is performed at about 300+ F.

Claim 22

The method of claim 12 in which step (b) is performed at about 300° F.