Binder for high wet-strength substrates

• US 20030176133A1
• Filed: 12/20/2002
• Published: 09/18/2003
• Est. Priority Date: 01/18/2002
• Status: Active Grant

• Current Assignee: Celanese International Corporation (Celanese Corporation)
• Original Assignee: Celanese International Corporation (Celanese Corporation)
• Inventors: Walker, James L., Mumick, Pavneet S., Parsons, John C., Barcomb, Christopher, Nass, David R.
• Granted Patent: US 7,056,847 B2
• Time in Patent Office: Days
• US Class Current: 442/394
• 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 chemically bonded fibers wherein said fibers are bonded by a polymeric binder wherein said binder is present in an amount which is sufficient to bind the fibers together to form a self-sustaining web, and wherein said binder is characterized as having an average cross-machine direction (CMD) wet tensile strength of greater than 4500 grams per inch (g/in) when measured at a 20 percent add-on using 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.

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 the level of free formaldehyde is less than 15 ppm.

5. The fibrous substrate of claim 4 wherein the level of free formaldehyde is less than 10 ppm.

6. The fibrous substrate of claim 1 wherein the binder is characterized as having a wet tensile strength of greater than 4750 g/in.

7. The fibrous substrate of claim 6 wherein the binder is characterized as having a wet tensile strength of greater than 5000 g/in.

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

9. A bonded substrate comprising

a) a substrate comprising fibers;

and

b) a polymeric binder comprising at least 6 percent by weight of cross-linking monomer units, wherein said bonded substrate is characterized as having less than 15 ppm of free formaldehyde, and wherein said binder is present in an amount which is sufficient to bind the fibers together to form a self-sustaining web.

10. The bonded substrate of claim 9 wherein said crosslinking monomer is n-methylol acrylamide.

11. The bonded substrate of claim 9 wherein said polymeric binder further comprises from 0.1 to 7 percent by weight of acrylamide, methacrylamide, or a mixture thereof.

12. The bonded substrate of claim 9 wherein said substrate comprises a non-woven product.

13. The bonded substrate of claim 9 wherein said non-woven product is formed by an air-laid process.

14. The bonded substrate of claim 9 wherein the level of free formaldehyde is less than 10 ppm.

15. The bonded substrate of claim 9 wherein said substrate is a double recreped paper, fiberglass, an abrasive pad, a carpet or a floor covering, a wall covering, or a paper.

16. The bonded substrate of claim 9 comprising at least 7 percent by weight of cross-linking monomer units.

17. A non-woven product comprising a non-woven web of fibers bonded together with an emulsion polymer binder comprising

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

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

c) 5 to 20 percent by weight of crosslinking monomer units;

d) 0.1 to 5 percent by weight of acrylamide, methacrylamide, or a mixture thereof.

e) 0 to 40 percent by weight of other co-monomers wherein said non-woven product has a free formaldehyde content after drying of less than 15 ppm.

18. The non-woven product of claim 17, comprising 7 to 12 percent by weight of crosslinking monomer.

19. The nonwoven product of claim 17, wherein said crosslinking monomer comprises n-methylol acrylamide.

20. The nonwoven product of claim 17, wherein said binder is characterized as having an average cross-machine direction wet tensile strength of greater than 4500 grams per inch (g/in) when measured at a 20 percent add-on using 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.