Process for producing nonwoven with improved surface properties
A hydroentangled nonwoven sheet material produced by a process including: 0) optionally providing a polymer web on a carrier; a) providing an aqueous suspension containing short fibers and a surfactant; b) depositing the aqueous suspension on the carrier; c) removing aqueous residue of the aqueous suspension deposited in step b) to form a fibrous web; b′) depositing aqueous suspension on a surface of the fibrous web formed in step c); c′) removing aqueous residue of the aqueous suspension deposited in step b′) to form a combined fibrous web; d) hydroentangling the combined fibrous web; and optionally e) drying the hydroentangled web, and/or f) further processing and finalizing the dried, hydroentangled web the web to produce the nonwoven end material. The hydroentangled non-woven sheet material obtainable by this process has a low degree of surface irregularity and contains low residues of surfactants.
1. A process of producing a hydroentangled nonwoven sheet material of at least one of natural or manmade fibres, comprising:
a) providing an aqueous suspension containing short fibres having lengths from 1 to 25 mm and a surfactant;
b) depositing the aqueous suspension on a carrier;
c) removing aqueous residue of the aqueous suspension deposited in step b) to form a fibrous web;
b′) depositing another aqueous suspension containing short fibres and surfactant on the surface of the fibrous web formed in step c) and at the side not facing the carrier, wherein the aqueous suspension and the another aqueous suspension include the same composition;
c′) removing aqueous residue of the aqueous suspension deposited in step b′) to form a combined fibrous web; and subsequently
d) hydroentangling the combined fibrous web.
2. The process according to claim 1 , wherein the short fibres comprise at least one of at least 25 wt. % of cellulosic pulp having fibre lengths of between 1 and 5 mm, or at least 3 wt. % of staple fibres having fibre lengths of between 5 and 25 mm.
3. The process according to claim 1 , wherein the another aqueous suspension is a portion of the aqueous suspension in step b).
4. The process according to claim 3 , wherein between 25 and 75 wt. % of the aqueous suspension, on dry solids basis, is applied in step b), between 15 and 60 wt. % of the aqueous suspension is applied in step b′), and between 0 and 40 wt. % of the aqueous suspension is applied in one or more optional further steps b″) following step c′).
5. The process according to claim 1 , wherein the dry solids content of the fibrous web after step c) and before step b′) is at least 15 wt. %.
6. The process according to claim 1 , wherein the aqueous suspension and the another aqueous suspension are each applied as a foam containing between 10 and 90 vol. % of air.
7. The process according to claim 1 , wherein the aqueous suspension contains between 0.01 and 0.1 wt. % of a non-ionic surfactant, and wherein the nonwoven sheet material contains less than 75 ppm of the surfactant.
8. The process according to claim 1 , wherein a polymer web is deposited prior to step b), after step c′), or a polymer web is deposited prior to step b) and after step c′).
9. The process according to claim 8 , wherein the polymer web contains at least 50 wt. % of synthetic filaments, and the combined web contains between 15 and 45 wt. % of the synthetic filaments on dry solids basis of the combined web.
10. The process according to claim 1 , wherein the nonwoven material as produced has front and back surfaces of different composition, in that hydroentanglement of step d) is performed only at one side.