A kind of highly branched polyvinyl alcohol-acrylamide graft copolymer and its preparation method and application

Abstract

The invention relates to a preparation method of a highly branched polyvinyl alcohol-acrylamide graft copolymer. After dissolving the polyvinyl alcohol in water, blowing nitrogen gas, lowering the temperature, adding a catalyst, reacting for 10-30 minutes, and then adding a monomer mixture solution dropwise , control the dropping time for 30-90 minutes, during which the reaction temperature is controlled between 65°C-95°C, after dropping, control the temperature between 85°C-95°C for 20-30 minutes, add catalyst, and continue at 80°C React at ‑95°C for 15-25 minutes, add catalyst, take samples during the reaction to measure the viscosity, after the viscosity reaches 1500-15000 mPa.s at 25°C, add a terminator to stop the reaction, adjust the solid content, and the product is ready. The graft copolymer of the present invention has high molecular weight, many branched chains, low viscosity, less gel, good retention, and strong anti-interference ability of impurities. As a dry strength agent for papermaking, it can also Satisfactory enhancement effect is achieved.

Description

technical field [0001] The invention relates to the fields of polymer synthesis and dry strength agents, in particular to a highly branched polyvinyl alcohol-acrylamide graft copolymer, its preparation method and its application as a dry strength agent. Background technique [0002] In view of the current situation that my country's papermaking raw materials mainly use waste paper pulp, coupled with being forced by the national policy of energy saving, emission reduction and environmental protection, papermaking enterprises have to vigorously promote clean production, resulting in closed circulation of white water, serious accumulation of garbage and impurities in the system, high temperature and high conductivity. Under the system, the amount of additives is large, the retention rate is low, and the paper strength is poor. In order to improve retention and improve paper quality, paper mills use dry strength agents in large quantities. [0003] Dry strength agents are an imp...

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Problems solved by technology

[0007] Chinese patent publication CN 103333352A discloses a preparation method of a cross-linked graft modified polyvinyl alcohol surface enhancer, which is to mix polyvinyl alcohol with water to obtain a polyvinyl alcohol aqueous solution; heat the aqueous solution, and add a ketone-containing carbonyl Vinyl monomers, cationic monomers, vinyl monomers containing long side chain groups, self-crosslinking monomers and other types of vinyl monomers, then add the initiator aqueous solution dropwise, and adjust the pH with alkali after polymerization value, add hydrazine or its derivatives and stir evenly to obtain a cross-linked grafted modified polyvinyl alcohol surface enhancer; the strengthener and fiber bonding points obtained in this patent are less, and the retention rate is low, so it is not suitable for adding in pulp

The above patents all use the method of adding a cross-linking agent to prepare a branched or cross-linked dry strength agent. There is a common problem: the polymerization is difficult to control after adding a cross-linking agent, and the degree of branching is generally not high, because cross-linking Adding too much linking agent will easily cross-link the molecular chain of the gel, and the water solubility will become poor; while adding less cross-linking agent will have less branched chains, which will not achieve the purpose of high branched chains, and the reinforcing effect will be poor.

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