METHOD OF PREPARING A SIZING BOOST ADDITIVE

A method of preparing a sizing boost additive， comprising the steps of I) combining a lignin oil and an aqueous solution of gelatinized cationic polysaccharide， and optionally water， to obtain a lignin/polysaccharide blend， wherein the lignin oil is obtained by base catalyzed depolymerization of lignin; and the gelatinized cationic polysaccharide is prepared by cooking dry cationic polysaccharide in water until completely gelatinized; and wherein the lignin oil and the cationic polysaccharide are included in the lignin/polysaccharide blend so that a weight ratio of lignin oil:polysaccharide in the blend is 1:0.5-2， preferably 1:0.9-1.1， where the weight of the polysaccharide is the weight of dry polysaccharide added in preparation of the aqueous solution ofgelatinized cationic polysaccharide; and the combined weight of lignin and polysaccharide is 1-10 wt-% based on the total weight of the resulting blend; followed by II) mixing the lignin/polysaccharide blendat a temperature of 40 -100°C， preferably 90-95°C， until the blend has changed color from grey-white to brown; a sizing boost additive thus obtained; a method of producing hydrophobic paper， comprising the step of adding the sizing boostadditive and a hydrophobization agent to a lignocellulosic pulp suspension at the wet end of a paper manufacturing process; and a hydrophobic paper thus obtained. A method of preparing a sizing boost additive， comprising the steps of I) combining a lignin oil and an aqueous solution of gelatinized cationic polysaccharide， and optionally water， to obtain a lignin/polysaccharide blend， wherein the lignin oil is obtained by base catalyzed depolymerization of lignin; and the gelatinized cationic polysaccharide is prepared by cooking dry cationic polysaccharide in water until completely gelatinized; and wherein the lignin oil and the cationic polysaccharide are included in the lignin/polysaccharide blend so that a weight ratio of lignin oil:polysaccharide in the blend is 1:0.5-2， preferably 1:0.9-1.1， where the weight of the polysaccharide is the weight of dry polysaccharide added in preparation of the aqueous solution ofgelatinized cationic polysaccharide; and the combined weight of lignin and polysaccharide is 1-10 wt-% based on the total weight of the resulting blend; followed by II) mixing the lignin/polysaccharide blendat a temperature of 40 -100°C， preferably 90-95°C， until the blend has changed color from grey-white to brown; a sizing boost additive thus obtained; a method of producing hydrophobic paper， comprising the step of adding the sizing boostadditive and a hydrophobization agent to a lignocellulosic pulp suspension at the wet end of a paper manufacturing process; and a hydrophobic paper thus obtained.