Binder for high wet-strength substrates

• US 7,056,847 B2
• Filed: 12/20/2002
• Issued: 06/06/2006
• Est. Priority Date: 01/18/2002
• Status: Expired due to Term

• Current Assignee: Celanese International Corporation (Celanese Corporation)
• Original Assignee: Celanese International Corporation (Celanese Corporation)
• Inventors: Walker, James L., Parsons, John C., Barcomb, Christopher, Mumick, Pavneet, Nass, David R.
• Primary Examiner(s): Morris, Terrel
• Assistant Examiner(s): Piziali, Andrew T.
• Application Number:
  US10/327,331
• Publication Number:
  US 20030176133A1
• Time in Patent Office: 1,264 Days
• Field of Search: 442/85, 442/152, 442/155, 442/164, 442/166, 442/180, 442/104
• US Class Current: 442/155
• CPC Class Codes: D04H 1/587 characterised by the bonding agents used
• CPC Class Codes: D04H 1/64 the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
• CPC Class Codes: Y10T 442/2213 Coating or impregnation is specified as weather proof, water vapor resistant, or moisture resistant
• CPC Class Codes: Y10T 442/2369 Coating or impregnation improves elasticity, bendability, resiliency, flexibility, or shape retention of the fabric
• CPC Class Codes: Y10T 442/2762 Coated or impregnated natural fiber fabric [e.g., cotton, wool, silk, linen, etc.]
• CPC Class Codes: Y10T 442/2787 Coating or impregnation contains a vinyl polymer or copolymer
• CPC Class Codes: Y10T 442/2861 Coated or impregnated synthetic organic fiber fabric
• CPC Class Codes: Y10T 442/60 Nonwoven fabric [i.e., nonwoven strand or fiber material]
• CPC Class Codes: Y10T 442/674 Nonwoven fabric with a preformed polymeric film or sheet

Abstract

The present invention is directed to a fibrous substrate made of chemically bonded fibers, where the fibers are bound with a polymeric binder in an amount which is sufficient to bind the fibers together to form a self-sustaining web, and where the binder is characterized as having a wet tensile strength of greater than 4500 grams per inch (g/in) when measured at a 20 percent add-on on Whatman #4 CHR chromatography paper which is drum dried for 90 seconds at 210 to 215° F. and cured for 2 minutes at 300 to 325° F. Preferably the level of free formaldehyde in the fibrous substrate is less than 15 ppm. The emulsion binders of the invention may be used to bind fibers together in a substrate; may be used to bind pigment, colors or other substances to a substrate; may be used as a backing material; or may be used to finish or surface-treat a substrate. Because of the high level of crosslinking, substrates bound, or treated with the emulsion polymer have excellent wet strength and good durability/weatherability and water/solvent resistance.

Claims

1. A fibrous substrate comprising fibers bonded with an emulsion polymer binder, said polymer comprising:

a) at least 50 percent by weight percent of vinyl acetate monomer units;

b) 0 to 40 percent by weight of ethylene monomer units;

c) 5 to 20 percent by weight of cross-linking monomer composition; and

d) 0 to 40 percent by weight of other co-monomers,

wherein said polymer binder provides a characteristic wet strength value of greater than 4,500 g/in.

2. The fibrous substrate of claim 1 wherein said substrate is a non-woven material.

3. The fibrous substrate of claim 2 wherein said non-woven material comprises a chemically-bonded dry-formed non-woven web.

4. The fibrous substrate of claim 1 wherein said fibers are natural fibers, synthetic fibers, or a mixture thereof.

5. The fibrous substrate of claim 1 wherein said cross-linking monomer comprises a blend of n-methylol acrylamide and acrylamide.

6. The fibrous substrate of claim 2 wherein said non-woven material is formed by an air-laid process.

7. The fibrous substrate of claim 1 wherein said substrate is a double recreped paper, fiberglass, an abrasive pad, a carpet or a floor covering, a wall covering, a fiberfill, or a paper.

8. The fibrous substrate of claim 1 comprising at least 7 percent by weight of cross-linking monomer composition.

9. The non-woven product of claim 1, comprising 7 to 12 percent by weight of cross-linking monomer composition.

10. The fibrous substrate of claim 1, wherein the cross-linking monomer composition comprises compounds with N-methylol(meth)acrylamide and/or N-alkoxy methyl(meth)acrylamide.

11. The fibrous substrate of claim 1, wherein the cross-linking monomer composition is selected from the group consisting of:

N-methylol acrylamide;

N-methylol methacrylamide;

a blend of N-methylol acrylamide and acrylamide;

N-methylol allyl carbamate, iso-butoxy methyl acrylamide, n-butoxy methyl acrylamide, and mixtures thereof.

12. The fibrous substrate of claim 1, wherein the cross-linking monomer composition comprises N-methylol acrylamide.

13. The fibrous substrate of claim 1, wherein the cross-linking monomer composition consists essentially of a blend of N-methylol acrylamide and acrylamide.

14. The fibrous substrate of claim 1, wherein the polymer comprises from 6 to 20 wt. percent cross-linking monomer composition.

15. The fibrous substrate of claim 1, wherein the polymer comprises about 7 wt. percent cross-linking monomer composition.

16. The fibrous substrate of claim 1, wherein the polymer comprises about 8 wt. percent cross-linking monomer composition.

17. The fibrous substrate of claim 1, wherein said polymer binder provides a characteristic wet strength value of greater than 4750 grams per inch (g/in).

18. The fibrous substrate of claim 1, wherein said polymer binder provides a characteristic wet strength value of greater than 5000 grams per inch (g/in).

19. The fibrous substrate of claim 1, wherein said fibrous substrate is characterized as having a free formaldehyde level of less than 15 ppm.

20. The fibrous substrate of claim 1, wherein the emulsion polymer is an ethylene-vinyl acetate copolymer.

21. A fibrous nonwoven web which includes a polymer binder that is derived from an aqueous emulsion, wherein said binder comprises an ethylene-vinyl acetate copolymer with from 6 to 20 wt. percent of cross-linking monomer composition,

wherein the aqueous emulsion exhibits a viscosity of less than 1350 cps when measured at a solids content of about 50 wt. percent, and

wherein said polymer binder provides a characteristic wet strength value of greater than 4,500 g/in.

22. The fibrous substrate of claim 21, wherein the aqueous emulsion exhibits a viscosity of less than 750 cps when measured at a solids content of about 50 weight percent.

23. The fibrous substrate of claim 21, wherein the aqueous emulsion exhibits a viscosity of less than 500 cps when measured at a solids content of about 50 weight percent.

24. The fibrous substrate of claim 21, wherein the aqueous emulsion exhibits a viscosity of less than 350 cps when measured at a solids content of about 50 weight percent.

25. The fibrous substrate of claim 21, wherein the polymer binder is emulsion polymerized at a reaction temperature in the range of from 25°

C. to 60°

C. for a controlled conversion rate with a redox initiator system that is slow-added during polymerization such that the rate of addition is adjusted to maintain conversion rate.

26. The fibrous substrate of claim 21, wherein the polymer binder is emulsion polymerized in the presence of a transition metal or salt thereof, and a chelating agent.