Production Of Absorbent Composites

Abstract

A process for producing an absorbent composite by contacting a solid supporting material with an emulsion comprising at least one polymeric material and at least one crosslinker and curing the mixture on the supporting material, the absorbent composites and also their use in sealing materials for road, tunnel and water engineering and also for excavations, high water protection and roof-sealing systems.

Description

EXAMPLES

Example 1

104.5 g of demineralized water were mixed with 562.5 g of acrylic acid (99.8%) pure and also 1246.0 g of 25% aqueous sodium hydroxide solution, 5.63 g of 1% aqueous methylene bisacrylamide, 1.25 g of 40% aqueous Trilon® C and 3.38 g of 1% aqueous Rongalit® C in a stirred vessel to form an aqueous phase. A second sealed stirred vessel (2 liter HWS equipped with anchor stirrer) was charged with 500 g of Shellsol® D 70 (100%) and 70 g of Emulan® GOE (100%) to form an organic phase, into which the aqueous phase was metered.

The combined aqueous and organic phases were then pre-emulsified in the second stirred vessel at 400 revolutions per minute for 60 minutes at 31° C. in a (15 liters/hour) stream of nitrogen and with bath immersion for temperature control. Thereafter, the speed of the stirrer was reduced to 200 revolutions per minute and 3.94 g of 10% aqueous sodium persulfate solution were added.

The polymerization kicked off immediately. When the internal temperature reached 35° C., the temperature-controlling bath was removed. The internal temperature reached a maximum of 66.2° C. After the temperature had decreased by 1° C., 28.13 g of 10% aqueous sodium persulfate solution was added followed 10 minutes later by 19.69 g of 1% aqueous Rongalit solution.

After the emulsion had cooled down, 12.5 g of Denacol EX 810 were added to it and the emulsion was mixed through at 200 revolutions per minute for a further 5 minutes. This gave an emulsion of mineral oil, water, carboxyl-rich acrylic acid copolymer and crosslinker.

Shellsol ® D 70  Mineral oil from Shell AG
Emulan ® GOE     Emulsifier from BASF Aktiengesellschaft, based on
                 oleyl glycerol ether ethoxylate
Trilon ® C       Complexing agent from BASF Aktiengesellschaft,
                 based on the trisodium salt of
                 hydroxyethylethylenediaminetriacetic acid in water
Rongalit ® C     Reducing agent from BASF Aktiengesellschaft,
                 based on the sodium salt of hydroxymethanesulfinic
                 acid
Denacol ® EX 810 Postcrosslinker from Nagase, based on
                 ethylene glycol diglycidyl ether

Example 2

A polyester needlefelt nonwoven fabric having a basis weight of 280 g/m² was saturated with the emulsion prepared in Example 1. A pad-mangle was used. The pad-mangle consisted of a trough filled with the emulsion and two stripping rolls having confining walls on the side. The fabric was led through the pad-mangle at a speed of 1 meter per minute. The emulsion-loaded fabric was dried at 170° C. for 5 minutes. The absorbent composite had a basis weight of 410 g/m², the weight increase (solids add-on) was 46%.

The absorbent composite was placed in water and an hour later the water uptake was determined by weighing back. The fabrics were further tested manually for hydrogel ooze and hence for leaching losses from the fabrics after particular times. A wetting test was carried out in addition. To this end, a droplet of water was applied to the surface of the absorbent composite and the time taken for the drop to disappear from the surface was measured. The results are summarized in Table 1.

Example 3

Example 2 was repeated using nonwoven polyester quilting having a basis weight of 80 g/m².

	TABLE 1
	Example 2	Example 3
	Solids add-on	46%	98%
	Wetting	10 seconds	about 1 second
	Hydrogel ooze	none	none
	Water uptake	1000 g/m2	600 g/m2

Claims

1. A process for producing an absorbent composite comprising contacting a solid supporting material with a mixture comprising at least one polymeric material and at least one crosslinker and curing the mixture on the supporting material, wherein the polymeric material comprises a carboxyl-rich polymer, not less than 50 mol % of the polymer being polymerized from unsaturated carboxylic acid monomers, the monomers of the carboxyl-rich polymer being wholly or partly neutralized with a base before or during the polymerization, and the mixture is an emulsion.

2. The process of claim 1 wherein the supporting material comprises fibers, tapes, or a mixture thereof.

3. The process of claim 1 wherein the supporting material comprises wovens, nonwovens, or a mixture thereof.

4. The process of claim 2 wherein the fibers are filaments, staple fibers, or a mixture thereof.

5. The process of claim 2 wherein the fibers are synthetic fibers.

6. The process of claim 1 wherein the emulsion comprises an organic solvent.

7. The process of claim 1 wherein the polymeric material comprises a carboxylic-rich polymer based on a copolymer of vinylically or allylically unsaturated carboxylic acids, or both, or their derivatives, or mixtures thereof.

8. The process of claim 1 wherein the polymeric material comprises a polymer based on a copolymer of acrylic acid, an ester or an amide of acrylic acid, methacrylic acid, and mixtures thereof.

9. The process of claim 8 wherein the polymeric material further comprises a granular superabsorbent polymer based on partially neutralized crosslinked polyacrylic acid.

10. The process of claim 1 utilizing a covalent crosslinking agent.

11. The process of claim 10 wherein the covalent crosslinking agent comprises a diepoxide.

12. The process of claim 1 wherein the curing is effected in a range from 100 to 200° C.

13. The process of claim 1 wherein the supporting material is coated, impregnated, padded, foamed, or sprayed with at least one polymeric material and subsequently cured.

14. An absorbent composite prepared by the process of claim 1 wherein the polymeric material is prepared by an emulsion polymerization.

15. A close-out comprising at least one absorbent composite of claim 1 and at least one sealing membrane comprising a plastic.

16. The close-out of claim 15 wherein the absorbent composite is disposed between two sealing membranes comprising a plastic.

17. (canceled)

18. (canceled)

19. A sealing material for a cable sheath comprising an absorbent composite of claim 14.

20. The sealing material of claim 19 to enhance water retention in agriculture and horticulture, to regulate humidity in rooms and containers, and for moisture regulation in sitting or lying furniture.

21. The process of claim 6 wherein the organic solvent comprises a mineral oil.