Patent ID: 8568564

Claim:
A method of improving a strength property of a sheet-formed fibrous material formed from an aqueous slurry of cellulose fiber, comprising a) providing a coating formulation consisting of: a polysaccharide containing at least two carboxylic groups, selected from the group consisting of carboxymethyl cellulose (CMC); polyuronic acid; oxidatively degraded polyuronic acid; sodium carboxymethyl starch; oxidized starch; carboxmethyl hemicellulose; carboxymethyl lignocellulose; and mixtures thereof; or stoichometric and non-stoichiometric sodium and potassium salts thereof; a low molecular weight organic mono-, di- or poly-carboxylic acid, selected from the group consisting of acetic acid, mandelic acid, citric acid, tartaric acid, aspartic acid, glutamic acid, formic acid, propionic acid, butanoic acid, pentanoic acid, oxalic acid, maleic acid, succinic acid, and glutaric acid; or a mixture of said organic mono-, di- or poly-carboxylic acids; and an aqueous carrier; b) dispensing the coating formulation on at least one face of said sheet-formed fibrous material by spraying, brushing or gravure coating; and c) keeping the coated face of the sheet-formed fibrous material with the coating formulation dispensed thereon at a temperature of 70° C. to 100° C. for a time sufficient to obtain an improved strength property.