Preparation And Application Of Salt-tolerant Cross-linked Amphoteric Polyacrylamide

With the rapid development of papermaking industry,the proportion of white water circulation recycling in the papermaking system is increasing.And anionic trash and inorganic salt of the system accumulates extensively,which results in the effect of chemical agents reduce and even failure.In view of Two major problems in the wet end system,there are many methods to deal with problem of anionic trash,but the problem of inorganic salt has not been very good solution.In addition,the forest resources is shortage in our country,and the use of renewable fiber and non-wood fiber ratio is relatively high,which results in larger demand for paper strengthening agent.The current domestic market competition is intense,and few products can be adapted to the increasingly complex water system.Therefore,developing a salt resistance of dry strength agent product is urgent.The dry strength agent was synthesized by the technique of free radical copolymerization in water solution.We investigated the agent from three directions antipolyelectrolyte effect,hydrophobic monomers and crosslinking structure.The product was applied to the high conductivity high anionic trash system to enhancement strength properties of paper liner.The polyacrylamide of weak acid weak base,strong acid and strong alkali,and alkali weak acid were synthesized with different cationic and anionic monomer.The charge density of the polymer,the molar ratio of two kinds of cationic monomer,the total amount of ion monomer,the variety and dosage of crosslinking agent,the amount of chain transfer agent,reaction temperature and pH value were investigated on the polymerization process.The process conditions fitting for current production environment were as follows:cationic monomer were DMBC and DM,anionic monomer was IA,charge density of the polymer is 0.01 mmol/g,DMBC and DM mole ratio was 3.2:1,the total amount of ion monomer was 19.5%of the total dosage of monomer,crosslinking agent were NMA and AMA,the best dosage of NMA was 1.25%of the total monomers,the best dosage of AMA was 0.550‰ of the total monomers,the best dosage of SMAS was 0.85%of the total monomers,the best reaction temperature was 80? and the best pH value was 3-4.In order to explore the influence of inorganic salt on the polymer molecular structure,the apparent viscosity,particle size,absorbance and light transmittance of polyacrylamide solutions were investigated.The results show that the apparent viscosity and light transmittance of polymer solution was increasing along with the increase of the salt concentration,and the particle size and absorbance of polymer solution was decreasing along with the increase of the salt concentration,which implied the synthesized polyacrylamide had distinct antipolyelectrolyte effect.Effect of three kinds of dry strength agents were studied under different electrical conductivity.The results show the homemade dry strength agent was better than polyacrylamide with high positive charge and the agent from Japan,and the homemade dry strength was suitable for use under the environment of high conductivity.In addition,the salt resistance of polyacrylamide was studied with different types of inorganic salt.The results show that the homemade cross-linked amphoteric polyacrylamide had a certain resistance of Na+?Mg2+and Ca2+.According to the lab to optimize process conditions,the pilot production of product are implemented.The results showed that the pilot product performance and its enhancement effect was comparable to the laboratory sample,and it had excellent resistance to salt resistance.