A method for manufacturing paper is disclosed. A pulp slurry is produced, a paper sheet is formed from the slurry, an aldehyde functionalized polymer or polymers in combination with at least one additional strength additive is added to the slurry before and/or after sheet formation, and a water soluble acid is added on the paper sheet.

The invention relates to an aqueous coating composition, comprising: a) an aqueous polymer dispersion with said polymer containing monomeric units of at least one dicarboxylic acid monomer, bearing two carboxylic acid functional groups and said polymer remaining insoluble in water after neutralization and remaining in the form of dispersed polymeric particles having a mean particle size varying from 10 to 1000 nm, b) a crosslinker selected from aminoacids bearing at least two amino functional groups capable of reacting with said carboxylic functional groups. It also relates to its use in the treatment of flexible fibrous substrates, a method for and the coated or treated fibrous substrate.

The invention relates to a fibrous mat facer for preparing a gypsum board, to a gypsum board comprising said mat facer and to a system comprising said gypsum board. The fibrous mat comprises at least one ply of a non-woven fabric, and a binder composition, wherein the binder composition represents from 10 to 40 wt % of the total weight of the mat. The binder composition comprises a copolymer comprising a co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid, said copolymer being present in an amount from 25 to 100 wt % of the binder composition weight.

The invention relates to a fibrous mat facer for preparing a gypsum board, to a gypsum board comprising said mat facer and to a system comprising said gypsum board. The fibrous mat comprises at least one ply of a non-woven fabric, and a binder composition, wherein the binder composition represents from 10 to 40 wt % of the total weight of the mat. The binder composition comprises a copolymer comprising a co-monomer unit of a vinyl ester of an alpha branched aliphatic monocarboxylic acid, said copolymer being present in an amount from 25 to 100 wt % of the binder composition weight.

The disclosure relates to methods and compositions for enhancing the performance of a sizing agent in a papermaking process using a sizing agent enhancer. The sizing agent can be emulsified with an emulsifier and the sizing enhancer can be a polymer comprising at least one primary or secondary amine containing monomer. The method can comprise emulsifying the sizing agent with the emulsifier; and thereafter adding the emulsified sizing agent and the sizing enhancer, separately from or contemporaneously with the emulsified sizing agent, to a fiber furnish of a papermaking process. The combination of the emulsified sizing agent and the sizing enhancer improves the sizing of product paper over the use of the sizing agent without the sizing enhancer. In at least some embodiments, the emulsified sizing agent is ASA emulsified with a polymer comprising at least one primary or secondary amine containing monomer and the sizing enhancer comprises a diallylamine-acrylamide copolymer.

Disclosed is a method for thickening or dehydrating sludge, which includes at least: a) a step of adding flocculants to the sludge to be treated; b) a step of flocculation by agitation of the sludge with the flocculants thus added in order to form a mixture of flocks and an aqueous solution; c) a step of mechanical separation of the flocks and the aqueous solution formed during the preceding step; d) a step of recovering the aqueous solution and the flocks that make up a treated sludge; wherein: the added flocculants are made up of at least one cationic starch (S) and at least one cationic polyacrylamide (P); the cationic starch or starches (S) including a fixed weight percentage of nitrogen of at least 2%; and the weight ratio (R) w.sub.s/(w.sub.s+w.sub.p), expressed as solids, is included between 0.6 and 0.99.

Disclosed is a method for thickening or dehydrating sludge, which includes at least: a) a step of adding flocculants to the sludge to be treated; b) a step of flocculation by agitation of the sludge with the flocculants thus added in order to form a mixture of flocks and an aqueous solution; c) a step of mechanical separation of the flocks and the aqueous solution formed during the preceding step; d) a step of recovering the aqueous solution and the flocks that make up a treated sludge; wherein: the added flocculants are made up of at least one cationic starch (S) and at least one cationic polyacrylamide (P); the cationic starch or starches (S) including a fixed weight percentage of nitrogen of at least 2%; and the weight ratio (R) w.sub.s/(w.sub.s+w.sub.p), expressed as solids, is included between 0.6 and 0.99.

Provided is a method of making paper and paperboard. In particular graft copolymers of vinyl monomers and functionalized vinylamine-containing base polymers by Michael addition are added to a paper furnish. The composition can be used alone or in combination with other additives for use in paper making and to improve paper making processes such as paper dry and wet strength properties.

Provided is a method of making paper and paperboard. In particular graft copolymers of vinyl monomers and functionalized vinylamine-containing base polymers by Michael addition are added to a paper furnish. The composition can be used alone or in combination with other additives for use in paper making and to improve paper making processes such as paper dry and wet strength properties.

The present invention relates to methods for preparing an aqueous acrylamide solution having a low acrylic acid concentration. In addition, the present invention relates to methods for reducing the acrylic acid concentration of an aqueous acrylamide solution. The methods involve a bioconversion of acrylonitrile to acrylamide in the presence of a biocatalyst, wherein during the bioconversion the content of acrylonitrile is maintained at 0.3 w/w % or more referred to the total weight of the composition in the reactor. Also provided is an aqueous acrylamide solution which is obtained by the methods of the present invention. Furthermore, the present invention is related to an acrylamide homopolymer or copolymer obtained by polymerizing the acrylamide of the aqueous solution.