Mat and gypsum boards suitable for wet or humid areas

1. A fibrous mat for a gypsum board comprising at least one ply of a non-woven fabric and a binder composition impregnated therein, wherein:

said binder composition represents from 10 to 40 wt % of the total weight of the mat;

said binder composition comprises a copolymer comprising a co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid and an acrylic co-monomer, wherein the co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid is present in an amount of 40 to 70 wt % of the copolymer and the acrylic co-monomer is present in an amount of 34 to 60 wt % of the copolymer; and

said copolymer being present in an amount from 50 to 100 wt % of the binder composition weight;

wherein the fibrous mat is a facer of the gypsum board.

2. The fibrous mat according to claim 1 , wherein said copolymer of the binder composition is a copolymer obtained from the co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid and the acrylic co-monomer which is an acrylate monomer.

3. The fibrous mat according to claim 1 , wherein said alpha branched aliphatic monocarboxylic acid comprises a chain length from 5 to 20 carbon atoms.

4. The fibrous mat according to claim 1 , wherein:

said binder composition represents from 20 to 30 wt % of the total weight of the fibrous mat; and

said copolymer of the binder composition is present in the binder composition in an amount from 50 to 60 wt % of the binder composition weight; and

said copolymer comprises the co-monomer unit of a vinyl ester of alpha branched aliphatic monocarboxylic acid having a chain length from 7 to 15 carbon atoms in an amount ranging from 40 to 50 wt % of said copolymer weight.

5. The fibrous mat according to claim 1 , wherein the binder composition is free or substantially free of fluorocarbons and/or formaldehydes.

6. The fibrous mat according to claim 1 , wherein:

said binder composition represents from 20 to 30 wt % of the total weight of the fibrous mat; and

wherein the binder composition comprises a mixture of a copolymer comprising said co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid in an amount from 40 to 60 wt % of the binder composition weight, and of an acrylic self-cross-linkable copolymer in an amount from 60 to 40 wt % of the binder composition weight.

7. The fibrous mat according to claim 1 , wherein the binder composition further comprises one or more additives selected from the group consisting of mineral filler particles, water resistant agents, water repellent agents, biocides, fire resistant agents, and pigments.

8. The fibrous mat according to claim 1 , wherein the binder composition further comprises additives and is free or substantially free of a mineral filler.

9. The fibrous mat according to claim 1 , wherein said non-woven fabric comprises fibres selected from the group consisting of:

mineral fibres selected from the group consisting of glass fibres and basalt fibres;

synthetic polymeric fibres selected from the group consisting of polyamide fibres, polyaramide fibres, polyethylene fibres, polypropylene fibres, polyester fibres; and

organic fibres which are cellulose based fibres selected from the group consisting of flax, wood pulp, cotton fibres, sisal, abaca, viscose, rayon, and lyocell;

wherein said cellulose based fibres represent more than 25 wt % of the weight of the non-woven fabric.

10. The fibrous mat according to claim 9 , wherein said non-woven fabric is free or substantially free of polyester fibres.

11. The fibrous mat according to claim 9 , wherein said non-woven fabric comprises fibres selected from the mineral fibres and the organic fibres, and wherein the amount of organic fibres varies from 40 to 100 wt % of the total weight of the fibres.

12. The fibrous mat according to claim 9 , wherein said cellulose based fibres comprise fibres of soft wood origin and fibres of hard wood origin, and wherein said fibres of soft wood origin represent from 25 to 85 wt % of the total weight of the cellulose based fibres.

13. The fibrous mat according to claim 9 , the fibres of said non-woven fabric consisting of the glass fibres and the cellulosic based fibres.

14. The fibrous mat according to claim 9 , wherein said mineral fibres have an average diameter of from 2 to 11 μm.

15. The fibrous mat according to claim 1 , wherein said non-woven fabric comprises a mixture of cellulose based fibres and glass fibres:

said glass fibres comprise glass fibers having an average diameter from 10 to 15 μm; and

said cellulose based fibres being present in the mixture in an amount from 40 to 85 wt % of the total weight of the fibres.

16. The fibrous mat according to claim 1 , wherein said fibrous mat has two sides, an inner side that is intended to contact a gypsum core, and an outer side that is intended to face away from the gypsum core, wherein an embossing pattern is formed at least on one side of the fibrous mat.

17. The fibrous mat according to claim 16 , said fibrous mat comprising a surface roughness Sa in at least one of said two sides, said surface roughness Sa being less than 60 μm.

18. The fibrous mat according to claim 16 , wherein the inner side and the outer side each comprise a surface roughness, and wherein the inner side comprises a surface roughness in a range of 10 to 40 μm and the outer side comprises surface roughness is less than 12 μm.

19. The fibrous mat according to claim 1 , wherein said mat comprises two plies of a non-woven fabric, one of said two plies being an inner ply intended to contact a gypsum core, and an outer ply intended to face away from said gypsum core; wherein the composition of the inner ply is different from the composition of the outer ply.

20. The fibrous mat according to claim 19 , wherein the inner ply comprises a mixture of organic fibres and mineral fibres and said fibres are present in the mixture in a ratio from 50 to 60% of organic fibres to 40 to 50% of mineral fibres; and/or the outer ply comprises more than 90% of organic fibres.

21. The fibrous mat according to claim 1 , wherein the total basis weight of the fibrous mat is from 80 to 160 g/m 2 .

22. The fibrous mat according to claim 19 , wherein based on the final weight of the fibrous mat, the inner ply represents from about 30 to about 120 g/m 2 , the outer ply represents from about 10 to about 70 g/m 2 , and the binder composition represents from about 20 to about 60 g/m 2 .

23. A process to produce a fibrous mat comprising impregnating at least one ply of a non-woven fabric with an aqueous dispersion or solution of the binder composition according to claim 1 .

24. The process according to claim 23 , comprising:

forming said non-woven fabric on at least one screen from a suspension of fibres;

drying said non-woven fabric, thereby obtaining a dried web; and

impregnating said web with said binder via a wet-laid process.

25. A gypsum board comprising a gypsum core with at least one side covered by the fibrous mat according to claim 1 ; wherein the gypsum board further comprises a water resistant agent, fire resistant agent, a mineral filler, a biocide and/or a pigment in said gypsum core and/or in said non-woven fabric of said fibrous mat.

26. The gypsum board according to claim 25 , wherein the gypsum core comprises:

at least a water-resistant additive, in an amount sufficient such that the core absorbs less than about 10% water when tested in accordance with ASTM method C-473 and/or in accordance with EN 520 method section 5.9.2,

at least a fire-resistant additive in an amount sufficient such that the board achieves an ASTM E-119 and/or C36-95 fire rating of at least about one hour, and/or

set hydratable calcium sulphate, obtained from a hydratable calcium sulphate having a particle size distribution such that, after splitting in water:

d10 is from 1 to 2 μm; and

d50 is from 5 to 35 μm; and/or

d90 is from 35 to 85 μm.

27. The gypsum board according to claim 25 , said gypsum board having a Cobb 2 hours value less than 100 g/m 2 and a ratio Flexural strength/basis weight of the mat of at least 5.5 in ambient conditions (23° C.; 50% RH) when calculated in MD with breaking load of 660N for a 12.5 mm board and a mat weight of 120 g/m 2 , and of at least 5 in humid conditions(30° C. 90% RH).

28. A process for producing a gypsum board according to claim 26 , comprising the step of laminating a gypsum core with said fibrous mat; and further comprising a step of producing said fibrous mat by a wet-laid process.

29. A system for an interior or exterior of a building comprising the gypsum board according to claim 26 .

30. The system according to claim 29 , further comprising:

an insulating material having an inner surface and an outer surface, the inner surface of which is adhered to the surface of the non-woven fabric of said gypsum board by an adhesive material and an exterior finishing material overlying the outer surface of said insulating material, optionally including a reinforcing member sandwiched between said insulating material and said finishing material; or

an underlying structural support element which is covered with an overlying finishing material; or

a metal or wood framework, or studs for supporting said gypsum board.

31. The fibrous mat according to claim 1 , wherein the fibrous mat is capable of obtaining a Class A+ certification (<10 μg/m 3 formaldehyde-Indoor Air Quality).

32. The fibrous mat according to claim 1 , wherein the binder composition is present in an amount of from about 20 to about 60 g/m 2 .

33. The fibrous mat according to claim 1 , wherein the fibrous mat comprises a Cobb 2 hours value of less than 40 g/m 2 .