Method of forming a fibrous product

1. A method of forming a molded fibrous product having a density of 5 to 100 kg/m3 and an air content of 90 to 99.5% by volume, said product containing fibers, which are bonded together essentially by hydrogen bonds and an inner part of the product is essentially free from thermoplastic bonding agents and thermoplastic fibers, said method comprising the steps of:

foaming an aqueous suspension comprising natural fibers to provide a first fibrous foam,

feeding the first fibrous foam into a mold,

mechanically withdrawing a part of the water contained in the first fibrous foam to produce a solidified, moist fibrous composition, and

evaporating water from the solidified, moist fibrous composition to produce a dry fibrous product,

wherein

water is removed from the fibrous foam by suction,

the mold comprises an internal surface for receiving the fibrous foam and an opposite external surface, at least one side of the internal surface being made of permeable material adapted to retain fibrous material and to allow passage of water from the internal surface to the external surface, and

the mold further comprising on the internal surface a protruding three-dimensional male part, covered on the internal surface with a permeable material, said male part corresponding to a cavity in the dry fibrous product, wherein the male part is covered on the internal surface with a permeable material

the natural fibers have an average length of greater than 0.1 mm.

2. The method according to claim 1 , further comprising foaming the aqueous suspension to a fibrous foam having an air content of more than 30% by volume of the foam.

3. The method according to claim 1 , wherein the fibrous foam is provided by a method selected from:

intensive mixing of the aqueous suspension of the fibers;

reducing of pressure;

dispersing of air into the aqueous suspension of the fibers by injection; or

a combination of any of the afore-mentioned methods.

4. The method according to claim 3 wherein reducing of pressure is achieved by increasing temperature of the aqueous suspension of the fibers.

5. The method according to claim 1 , wherein the consistency of the aqueous suspension is 0.1-10% based on the weight of the suspension.

6. The method according to claim 1 , wherein the moist fibrous foam has a water content of up to 70% by volume of the suspension.

7. The method according to claim 1 , wherein the dry fibrous product has a water content of 12% by weight or less.

8. The method according to claim 1 , wherein a surfactant is incorporated into the aqueous suspension to enhance foam formation.

9. The method according to claim 1 , further comprising forming a homogenous multi-phase mixture by foaming of the aqueous suspension of natural fibers.

10. The method according to claim 1 , wherein the mold comprises two internal surfaces which face each other and which allow for removal of water in opposite directions.

11. The method according to claim 1 , wherein the suction is applied to the fibrous foam from the external surface of the mold.

12. The method according to claim 1 , wherein the suction subjects the fibrous foam to a pressure.

13. The method according to claim 1 , wherein evaporation is effected by means selected from the group of microwaves, infrared waves, air impingement, air drying, and convective drying and combinations thereof.

14. The method according to claim 1 , wherein a second fibrous foam of fibers is fed into the mold on top of the first fibrous foam so as to cover at least a portion of the first fibrous foam fed into the mold.

15. The method according to claim 14 , further comprising feeding into the mold further fibrous foams on top of preceding fibrous foams to form a multilayered dry fibrous product.

16. The method according to claim 14 , further comprising removing water and drying of the second or further fibrous foam(s).

17. The method according to claim 14 , comprising:

withdrawing by suction a part of the water contained in the first foam before feeding the second fibrous foam, or

feeding the first and the second and further foams consecutively into the mold before applying suction in order to withdraw water from the foams.

18. The method according to claim 14 , wherein the fibers of the second or further fibrous foam(s) are different from those of the first or of the preceding fibrous foam(s).

19. The method according to claim 1 , wherein the fibers of the first fibrous foam are selected from the group of thermomechanical pulp fibers, chemithermomechanical pulp fibers, kraft pulp fibers, sulphite pulp fibers, soda pulp fibers, dissolving pulp fibers, fluff pulp fibers, NBSK pulp fibers, SBSK pulp fibers, recycled pulp fibers, deinked pulp fibers, organosolv pulp fibers, bleached pulp fibers and mixtures thereof.

20. The method according to claim 1 , further comprising producing a three-dimensional object having a smallest dimension of at least 5 mm.

21. The method according to claim 20 , further comprising producing a package or package material.

22. The method according to claim 1 , further comprising foaming the aqueous suspension to a fibrous foam having an air content between 50 and 90% by volume of the foam.

23. The method according to claim 1 , wherein the product is essentially free from thermoplastic bonding agents or thermoplastic fibers, and the natural fibers are bonded together only by hydrogen bonds.

24. The method according to claim 1 , wherein the fibers are uncut fibers.

25. The method according to claim 1 , wherein all fibers of the fibrous product have an average length of greater than 0.1 mm.

26. The method according to claim 1 , wherein the fibers of the fibrous product have an average length of greater than 1 mm.

27. The method according to claim 1 , wherein the fibers of the fibrous product have an average length in the range of 2 mm to 100 mm.