Process to make a wet-laid absorbent structure

• US 6,056,854 A
• Filed: 03/27/1998
• Issued: 05/02/2000
• Est. Priority Date: 03/27/1998
• Status: Expired due to Fees

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Corporation (BASF SE)
• Inventors: Woodrum, G. Thomas
• Primary Examiner(s): Fiorilla, Christopher A.
• Application Number:
  US09/049,427
• Time in Patent Office: 767 Days
• Field of Search: 162/141, 162/146, 162/164.1, 162/183
• US Class Current: 162/141
• CPC Class Codes: D21H 13/06 Cellulose esters
• CPC Class Codes: D21H 13/24 Polyesters
• CPC Class Codes: D21H 15/10 Composite fibres
• CPC Class Codes: D21H 21/22 Agents rendering paper porous, absorbent or bulky
• CPC Class Codes: D21H 23/14 by selecting point of addition or time of contact between components

Abstract

A process to form a nonwoven, wet-laid, superabsorbent, polymer particle-impregnated fibrous structure on a commercial scale wet-forming machine having a head box, a forming section and a drying section, including

adding SAP to water under and within 5 seconds of the SAP water contact,

providing agitation of at least 4000 Reynolds units thereby dispersing ungelled SAP particles throughout the fiber furnish,

delivering the furnish to a moving foraminous support, forming a wet laid web containing wetted SAP particles, draining of water from the moving wet web, and conveying the web to the dryer section,

wherein the maximum elapsed time from the point where SAP is mixed with water to the time the web passes into the dryer section is less than 45 seconds.

Claims

1. A process for the continuous production of a non-woven, SAP particle-impregnated fibrous structure on a wet-lay nonwoven apparatus, said apparatus comprising a head box, a moving foraminous support and a drying section, the process comprising:

adding SAP to a fiber furnish and within 5 seconds of the SAP-fiber furnish contact, providing agitation of at least 4000 Reynolds units thereby dispersing ungelled SAP particles in the fiber furnish,

delivering said furnish to said moving foraminous support,

forming a wet laid web containing wetted SAP particles,

draining water from the moving wet web, and

conveying the web to said drying section,

wherein the maximum elapsed time from the point where SAP contacts water to the time the web passes into the dryer section is less than or equal to 45 seconds.

2. The process of claim 1 wherein said superabsorbent is a crosslinked copolymer of 50 to 99.99% by weight ethylenically unsaturated carboxylic monomer and optional copolymerisable ethylenically unsaturated monomer.

3. The process according to claim 1 wherein said furnish as delivered to said foraminous support has a solids content of from 0.1 to 50 grams per liter.

4. The process according to claim 3, wherein said furnish as delivered to said foraminous support has a solids content, of from 0.1 to 20 grams per liter.

5. The process according to claim 4, wherein said furnish as delivered to said foraminous support has a solids content, of from 0.1 to about 5 grams per liter.

6. The process of claim 1 wherein said fibrous structure contains from 50% to 80% of said SAP and 20% to 50% of said fiber, and wherein said structure has a basis weight of from 100 to 500 gsm.

7. The process of claim 6 wherein said structure has a basis weight of from 100 to 400 gsm.

8. The process of claim 1 wherein said structure contains cellulose acetate fibers having a length of from 0.25 to 0.5 inches and wood pulp fibers having a length of from 0.25 to 0.75 inches.

9. The process of claim 1 wherein said fibers comprise, cellulose acetate, wood pulp fibers and bicomponent fibers.

10. The process of claim 1 wherein said SAP is surface crosslinked.

11. The process of claim 1 wherein said maximum elapsed time from the point where SAP contacts water to the time the web passes into the dryer section is less than or equal to 30 seconds ±

3 seconds.

12. The process of claim 1 wherein said maximum elapsed time from the point where SAP contacts water to the time the web passes into the dryer section is less than or equal to 25 seconds.

13. A process for the continuous production of a nonwoven, SAP particle-impregnated fibrous structure on a wet-lay nonwoven apparatus, said apparatus comprising a head box, a moving foraminous support and a drying section, the process comprising:

adding SAP to water and within 5 seconds of the SAP-water contact, combining the SAP and water with a fiber furnish and providing agitation of at least 4000 Reynolds units thereby dispersing ungelled SAP particles in the fiber furnish,

delivering said furnish to said moving foraminous support,

forming a wet laid web containing wetted SAP particles,

draining water from the moving wet web, and

conveying the web to said drying section,

wherein the maximum elapsed time from the point where SAP contacts water to the time the web passes into the dryer section is less than or equal to 45 seconds.