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Retention agents (retention aids) are used in the papermaking industry. These are added in the wet end of the paper machine to improve retention fine particles and fillers during the formation of paper. Retention aids can also be used to improve the retention of other papermaking chemicals, including sizing and cationic starches. The improved ...
A Retention agent is added to bind fillers to the paper. Fillers, such as calcium carbonate, usually have a weak surface charge. The retention agent is a polymer with high cationic, positively charged groups. An additional feature of a retention agent is to accelerate the dewatering in the wire section of the paper machine.
These are dependent on physical contact between the fibres and can be broken by wetting of the fibres. The residual strength of a wetted paper can be less than 10% of the original strength. [1] Various techniques, such as refining of the pulp and wet pressing on the paper machine can be used to reduce the strength loss of the paper upon wetting ...
Starch is the most common sizing agent. Cationic starch and hydrophilic agents are also applied, including alkenyl succinic anhydride (ASA) and alkyl ketene dimers (AKD). [5] Cationic starch increases strength because it binds to the anionic paper fibers. [6] The amount added is usually between ten and thirty pounds per ton.
the retention or fixation of the ASA emulsion droplets on the wet paper pulp; bursting the emulsion droplets via spreading on the surface and penetration into the pulp; the formation of a hydrophobic paper surface with contact angles >100° by covalent linkage of the ASA molecules with the hydroxyl groups of the cellulose
the retention of the AKD particles on the wet paper mass on the paper screen; the spreading of the AKD particles on the surface and the penetration in the paper mass; the chemical reaction of the hydroxyl groups of the cellulose (esterification) with the alkylated ketene dimers to form beta-ketocarboxylic esters.
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A mixture of acrylic acid, water, cross-linking agents and UV initiator chemicals are blended and placed either on a moving belt or in large tubs. The liquid mixture then goes into a "reactor" which is a long chamber with a series of strong UV lights. The UV radiation drives the polymerization and cross-linking reactions.