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Surface sizing solutions consist of mainly modified starches and sometimes other hydrocolloids, such as gelatine, or surface sizing agents such as acrylic co-polymers. Surface sizing agents are amphiphilic molecules, having both hydrophilic (water-loving) and hydrophobic (water-repelling) ends. The sizing agent adheres to substrate fibers and ...
The alkenyl side-chain modifies the surface properties of the paper product. [2] The application is similar to that for alkyl ketene dimers. In the United States alkenylsuccinic anhydrides are the preferred paper sizing agents, whereas in Europe, alkyl ketene dimers (AKDs) predominate.
Desizing, irrespective of what the desizing agent is, involves impregnation of the fabric with the desizing agent, allowing the desizing agent to degrade or solubilise the size material, and finally to wash out the degradation products. The major desizing processes are: Enzymatic desizing of starches on cotton fabrics; Oxidative desizing; Acid ...
Sizing also improves the hydrophilic character, liquid spreading, and affinity for ink. 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]
In 1901, Edgar Wedekind published the synthesis of alkyl ketene dimers by the reaction of carboxylic acid chlorides with tertiary amines: [5] [6] RCH 2 COCl + R 3 N → RCH=C=O + R 3 NHCl The molecular weight determined by the early researchers indicated (CH 3) 2 CH=C=O) n where n > 1 for the dehydrohalogenation of isobutyryl chloride with triethylamine.
Last month, housing contract activity rose in all regions of the country except for the Northeast. The South saw the largest month-over-month increase, improving 5.2% from October and 8.5% from a ...
The size/starch solutions are applied to the paper web by means of various mechanical presses (size presses). Together with surface sizing agents the surface starches impart additional strength to the paper web and additionally provide water hold out or "size" for superior printing properties.
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