Because the resin contains a large number of imine groups and tertiary amine groups, and contains lone pairs of electrons, it can show cationicity only in strong acidic media, and it mainly exists in the form of free amines under weak acidic conditions, and the concentration of amine cations is very low. . This structure and performance determine that the resin has greater solubility only in strong acid media. Therefore, the modification is mainly to improve its water solubility, introduce more polar groups or quaternary money groups, so that it can show cationic properties in a wide range of values, and achieve the purpose of combining with fibers. [1]
Wet Strength Agent for Papermaking
Melamine formaldehyde resin (MF) is a wet strength agent and water repellent widely used in China's paper industry. It can be directly added to the pulp and the paper can obtain good wet strength after thermal drying. Paraformaldehyde is used instead of formaldehyde solution, and small molecular alcohol is used as the etherifying agent. A small amount of alcohol amine controls the molecular weight. A three-step synthesis method has prepared a modified MF wet strength agent with high solid content and improved stability. Research shows , A high-solid content etherified modified MF with a stability of more than 6 months was prepared with methanol etherified paraformaldehyde and melamine. Its effect on paper moisturizing strength (paper wet strength retention rate 24%) is slightly lower than MF is commonly used, but its stability has obvious advantages.