Process and apparatus for wetlaying nonwovens

Patent metadata

Field	Value
Publication number	US-11015292-B2
Application number	US-201616326823-A
Country	US
Kind code	B2
Filing date	Sep 1, 2016
Priority date	Sep 1, 2016
Publication date	May 25, 2021
Grant date	May 25, 2021

Abstract

A process and an apparatus for producing nonwoven materials are disclosed. The process comprises the following steps: a) providing a three-phase (gas-liquid-solid) suspension containing air, water, fibrous material and a surfactant, b) depositing the suspension onto a moving carrier sieve to produce a fibrous web on the carrier, c) removing aqueous residue of the suspension through the carrier sieve, d) conveying the aqueous residue through one or more phase separation tanks in an essentially horizontal direction while providing a depressurised headspace above the aqueous residue, e) recycling the aqueous residue conveyed in step d) to step a), f) preferably pre-integrating the fibrous web.

First claim

The invention claimed is:

1. A process of producing a nonwoven sheet material of natural and/or man-made fibres, comprising:
a) providing a three-phase (gas-liquid-solid) suspension containing water, natural and/or man-made fibres, a surfactant, and 20-50 vol. % of air,
b) depositing the suspension onto a moving carrier sieve to produce a fibrous web on the carrier,
c) removing aqueous residue of the suspension through the carrier sieve, and
e) recycling the aqueous residue to step a),
characterised in that the aqueous residue, before step e), is subjected to a step d) of phase separation, in which the aqueous residue is conveyed through one or more phase separation tanks in an essentially horizontal direction while providing a depressurised headspace above the aqueous residue, the phase-separation resulting in reducing the air content of the aqueous residue to below 20 vol. %,
wherein step d) includes spraying the aqueous residue with an amount of water.

2. The process according to claim 1 , wherein conveying the aqueous residue through the one or more separation tanks comprises breaking the foam.

3. The process according to claim 1 , wherein the aqueous residue is removed through the carrier by two or more suction boxes, the suction boxes being arranged consecutively along the direction of movement of the carrier, the residue collected in each suction box being conveyed to a distinct phase separation tank.

4. The process according to claim 1 , wherein, subsequently after step c), steps b) and c) are repeated as steps b′) and c′), respectively, such that the step b′) subsequent depositing of the suspension occurs onto the fibrous web deposited on the carrier at steps b) and c), and aqueous residue from step c′) is subjected to step d), wherein the aqueous residue from step c′) is conveyed through one or more phase separation tanks.

5. The process according to claim 4 , wherein the one or more phase separation tanks through which the aqueous residue from step c′) is conveyed are distinct from the one or more phase separation tanks through which aqueous residue from step c) is conveyed.

6. The process according to claim 1 , further comprising: f) the fibrous web produced in steps a) through c) is subsequently subjected to pre-integration by flushing with water, spent flushing water being removed through the carrier.

7. The process according to claim 6 , wherein removed flushing water is conveyed through a further phase separation tank and then fed to step a).

8. The process according to claim 6 , which further comprises, after step f):
g) optionally transferring the fibrous web from said moving carrier sieve, being a first moving carrier sieve, to a second moving carrier sieve, said second moving carrier sieve having a porosity which is smaller than the porosity of said first moving carrier sieve,
h) hydroentangling the fibrous web on said second moving carrier sieve,
i) drying the hydroentangled sheet and optionally imprinting, conditioning, dimensioning and/or packaging the dried sheet to produce a ready-for-use sheet material.

9. The process according to claim 1 , further comprising: f) the fibrous web produced in steps a) through c) is subsequently subjected to pre-integration by flushing with water, spent flushing water being removed through the carrier, and wherein spraying the aqueous residue with the amount of water includes spraying at least a portion of the spent flushing water through the headspace of the one or more phase separation tanks of step d) and the amount of water is collected in the aqueous residue.

10. The process according to claim 1 , which further comprises, after step b):
g) optionally transferring the fibrous web from said moving carrier sieve, being a first moving carrier sieve, to a second moving carrier sieve, said second moving carrier sieve having a porosity which is smaller than the porosity of said first moving carrier sieve,
h) hydroentangling the fibrous web on said second moving carrier sieve,
i) drying the hydroentangled sheet and optionally imprinting, conditioning, dimensioning and/or packaging the dried sheet to produce a ready-for-use sheet material.

11. The process according to claim 1 , wherein the suspension contains between 0.01 and 0.2 wt. % of surfactant.

12. The process according to claim 1 , wherein the surfactant is a non-ionic surfactant.

13. The process according to claim 1 , wherein the fibrous material in the suspension comprises short fibres of between 1 and 25 mm length, and includes at least 25 wt. % of cellulosic pulp having fibre lengths of between 1 and 5 mm.

14. The process according to claim 1 , wherein the three-phase suspension contains between 20 and 45 vol. % of air.

15. The process according to claim 1 , wherein the three-phase suspension is deposited in step b) at a rate of between 2100 and 6000 l/min per m width of produced fibrous web.

16. The process according to claim 1 , wherein prior to step b), a polymer web is deposited, which polymer web contains at least 50 wt. % of synthetic filaments, and the combined web resulting from the deposition of the pulp-containing suspension onto the polymer web contains between 15 and 45 wt. % of the synthetic filaments on dry matter basis of the combined web.

Assignees

• Essity Hygiene & Health Ab

Inventors

• Venema Arie
• Wijbenga Gaatze
• Ahoniemi Hannu
• Strandqvist Mikael

Classifications

• D21F11/002 Primary

  by using a foamed suspension · CPC title

• D04H1/732

  by fluid current, e.g. air-lay · CPC title

• D21H15/02

  characterised by configuration · CPC title

• D21F1/66 Primary

  Pulp catching, de-watering, or recovering; Re-use of pulp-water · CPC title

• D04H1/00

  Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres · CPC title