Patent ID: 7481905

Claim:
An improved process for treatment of liquid packaging board with lactic acid or peroxide solutions, the process comprising manufacture of the board, in which a board pulp is subjected to a substantially non-delignifying treatment with a percarboxylic acid by adding to the pulp having a consistency of 0.1 to 40% and a pH of 3 to 11 percarboxylic acid in an amount of 0.5-5 kg/ton of dry pulp, indicated as a 100 percent percarboxylic acid, the addition substantially not effecting the pH of the pulp, whereafter, or simultaneously with the percarboxylic acid treatment, sizing of the pulp having the pH of 3 to 11 is carried out with a combination of a rosin size and a neutral size, which is followed by board forming from the pulp in a paper machine, wherein the percarboxylic acid comprises peracetic acid, prepropionic acid, or a mixture thereof, and the board pulp consists essentially of a pulp containing lignin, the pulp containing lignin being selected from a group consisting of groundwood mechanical pulp, refiner mechanical pulp, chemi-mechanical pulp, unbleached chemical pulp, and a mixture thereof, and subjecting the board to a lactic acid or peroxide solution, whereby the board has improved resistance to raw edge penetration (REP) of lactic acid or peroxide.