Vinyl acetate/ethylene and ethylene/vinyl chloride blends as binders for nonwoven products
This invention is directed to an improvement in binders particularly suited for use in preparing nonwoven products and to the nonwoven products. The improved binders comprise a blend of emulsion polymerized ethylene-vinyl chloride (EVCl) polymer and an emulsion polymerized self crosslinkable vinyl acetate-ethylene-N-methylolacrylamide (VAE-NMA) polymer. The blends of the EVCl polymer emulsion and the VAE-NMA polymer emulsion can be applied to cellulose and cellulose/synthetic nonwoven substrates and cured in the absence of an acid catalyst to provide a self-sustaining web having excellent wet strength performance. The blends of EVCl and VAE-NMA polymers do not require an acid catalyst to facilitate cure.
1. A nonwoven product comprising a nonwoven web of fibers to which is applied a non acid catalyzed binder to form a binder impregnated web, the non acid catalyzed binder comprised of an emulsion blend of a first polymer comprised of emulsion polymerized units of vinyl acetate, ethylene, and N-methylolacrylamide, and a second polymer comprised of emulsion polymerized units of vinyl chloride, ethylene and N-methylolacrylamide or acrylamide or both N-methylolacrylamide and acrylamide, wherein the binder impregnated web is dried sufficiently to bind the fibers together and form a self-sustaining web.
2. The nonwoven product of claim 1 wherein the first polymer comprises 50 to 94 wt % vinyl acetate, 5 to 40 wt % ethylene, and 0.5 to 10 wt % N-methylolacrylamide, based on the total weight of the polymer, and the second polymer comprises 55 to 95 wt % vinyl chloride, 5 to 35 wt % ethylene, and 0.1 to 10 wt % of N-methylolacrylamide or acrylamide or both N-methylolacrylamide and acrylamide, based on the total weight of polymer.
3. The nonwoven product of claim 2 wherein the second polymer comprises 60 to 90 wt % vinyl chloride, 10 to 30 wt % ethylene, and 0.5 to 5 wt % of N-methylolacrylamide or acrylamide or both N-methylolacrylamide and acrylamide, based on the total weight of polymer.
4. The nonwoven product of claim 2 wherein the second polymer comprises 70 to 85 wt % vinyl chloride, 13 to 26 wt % ethylene, and 2 to 4 wt % of N-methylolacrylamide or acrylamide or both N-methylolacrylamide and acrylamide, based on the total weight of polymer.
5. The nonwoven product of claim 3 wherein the first polymer comprises 64 to 79 wt % vinyl acetate, 20 to 30 wt % ethylene, and 1 to 6 wt % N-methylolacrylamide, based on the total weight of the polymer.
6. The nonwoven product of claim 4 wherein the first polymer comprises 64 to 79 wt % vinyl acetate, 20 to 30 wt % ethylene, and 1 to 6 wt % N-methylolacrylamide, based on the total weight of the polymer.
7. The nonwoven product of claim 2 wherein the blend, based on 100 parts by dry weight of total polymer, comprises 5 to 70 parts of the second polymer, less than 10 parts of a third polymer, and the remaining parts consisting of the first polymer.
8. The nonwoven product of claim 2 wherein the blend is comprised of 50 to 80 weight parts of the first polymer and 20 to 50 weight parts of the second polymer, per 100 weight parts of the blend.
9. The nonwoven product of claim 2 wherein the binder is applied to the nonwoven web in an amount of 3% to 50% by weight add-on, on a dry basis.
10. The nonwoven product of claim 2 wherein the binder is applied at about 10% to 30% by weight add-on, on a dry basis.
11. The nonwoven product of claim 2 wherein the blend consists essentially of the first polymer and the second polymer.
12. The nonwoven product of claim 11 wherein the blend excludes N-methylolacrylamide reactive polymers.
13. The nonwoven product of claim 2 wherein the nonwoven web of fibers comprises cellulose or synthetic polymeric fibers or combinations of both cellulose and synthetic polymeric fibers.
14. The nonwoven product of claim 2 wherein the nonwoven web of fibers comprises natural polymeric fibers.