Method for hydrophobing a cellulose substrate

1. A method for hydrophobing of a cellulose substrate that comprises a first side and a second side, which faces away from the first side, the method comprising the steps of:

drying the cellulose substrate to a dry content above 80%

adding a vaporized fatty acid halide, to the first side of the cellulose substrate, and, at the same time perform,

vacuum sucking at the second side of the cellulose substrate, such that, the vaporized fatty acid penetrates the cellulose substrate in a predetermined direction through the cellulose substrate.

2. The method according to claim 1 , wherein the dry content of the cellulose substrate is above 90%.

3. The method according to claim 1 , wherein the fatty acid is palmitoyl chloride, C16.

4. The method according to claim 1 , wherein the cellulose substrate is a paper- or paperboard web.

5. The method according to claim 4 , wherein the web is a multilayer web.

6. The method according to claim 1 , wherein the method further comprising a step of heating the substrate, before adding the vaporized fatty acid.

7. The method according to claim 6 , wherein the heating step is performed by IR heating.

8. The method according to claim 1 , wherein the vacuum sucking is performed by a vacuum box.

9. The method according to claim 1 , wherein the vacuum sucking is performed by a rotating vacuum cylinder.

10. The method according to claim 1 , wherein the dying step dries the cellulose substrate to a dry content above 85%.