Polyacrylamide is a linear polymer compound. It is the general term for linear water-soluble molecular chemicals formed by homopolymerization of acrylamide or copolymerized with other monomers. It is also a widely used variety in water-soluble polymer compounds. one. Since the structural unit contains an amide group, it is easy to form hydrogen bonds, which makes it have good water solubility. It is easy to obtain multiple modifications with chain or network structure through grafting or crosslinking. It is an important type of flocculant, thickener, mud treatment agent, soil conditioner, water and soil moisturizer, seed coating agent, surface active agent, and paper enhancer, which is widely used in petroleum exploration, water treatment, textile, papermaking, Mineral processing, medicine, agriculture and other industries are known as "Auxiliary for All Industries".
Polyacrylamide (PAM) has a wide range of uses in the paper industry. Due to the negative charge of PAM, it can be used as a pulp dispersant. The relative molecular weight of PAM is low, which can effectively improve the uniformity of paper; the average relative molecular weight PAM of 500,000 to 1 million can be used as an enhancer; PAM of medium relative molecular mass (2 million to 4 million) is usually used as a retention and drainage aid in the wet end of a paper machine; and high relative molecular mass (> 7 million) ) PAM is mostly used as a flocculant in the treatment of papermaking wastewater and a suspending agent for long-fiber pulp paper.
When using waste paper to make paper, in order to maintain good paper tensile strength and other properties and meet the needs of modern rotary printing, cationic polyacrylamide (abbreviated as CPAM) paper enhancer can be used. Its molecular length provides good adsorption performance and The position of bonding with the chlorine bond strengthens the bonding between fibers and has multiple functions such as enhancement, retention, and drainage, especially to increase the tear index, which can effectively increase the emphasis of paper; used as a dispersant to improve The evenness of the page, Polyacrylamide for papermaking.
1. The role of retention and drainage
The paper industry is developing rapidly, and the speed of the paper machine is constantly increasing, which makes the retention and filtration technology of the wet end of the paper machine more and more important. PAM significantly improves the retention rate of fines and fillers in the papermaking process through bridging and flocculation, and accelerates the filterability of the paper material in the paper machine wire. In the particle flocculation system, CPAM is added to form large flocs, which are dispersed into small flocs under the action of shearing force, and then cationic micro-colloidal silica is added, which can react with small flocs to form dense and more easily dehydrated fines Flocculation system, in order to achieve a higher retention rate, good uniformity and drainage performance, improve the formation of the paper and product quality.
There are two ways to strengthen paper: internal paper enhancer and sizing press surface paper enhancer. There are two types of internal paper enhancers: dry paper enhancers and wet paper enhancers. After Hoffman molecular rearrangement, a carbamoyl-containing water-soluble cationic polyacrylamide is made, which not only has good retention and drainage, but also improves the tear index of paper. It can be used as a dry strengthening agent to effectively improve The strength of the paper. Its mechanism of action is mainly that the amide group of cationic polyacrylamide and the hydroxyl group of the fiber form a hydrogen bond between the fibers, which enhances the bonding force between the fibers, thereby achieving the purpose of increasing the strength of the paper. Cationic glyoxal acid polyacrylamide can be used as a wet strength agent to give the paper a certain wet strength to resist water damage.
3. Dispersion, flocculation and others
The main dispersant used is cationic polyacrylamide with low relative molecular weight, which can effectively improve the uniformity of the paper. Amphoteric PAM is a good flocculant in the paper industry. Its unique amide group that can form hydrogen bonds with multi-material systems can adsorb particles dispersed in water together to form clusters of flocs to promote particles Settlement and filtration.
The cationic PAM made by adding acrylamide solution to modifier, sodium hypochlorite and alkali is mainly used as paper strengthening agent. Use PAM type reinforcing agent to make heat and water resistant paper. For example, use 0.5 part of fatty acid sizing agent, 0.2 part of PAM type paper enhancer, 1.0 part of aluminum sulfate and 0.7 part of epoxy enhancer, and then add it to chemical pulp to make paper. After the paper is immersed in 200C water for 1 hour, the tear strength is still up to 183g, good printing performance, Polyacrylamide manufacturer.
The copolymer of acrylamide, acrylic acid and glycol acrylate grafted with ionic tapioca starch was added to the Canadian standard beating 560ml pulp, and then Al2(SO4)3 was added to produce a paper with a basis weight of 74.2g/m2. The fracture length is 8950m, the strength of the intermediate layer is 148g, and the tear factor is 135. When the vehicle speed is 800m/min, the online concentration is 0.6%, and the ash content of the finished paper is 20%, the use of PAM retention aid can achieve 80% of the first trip retention rate and 50% of the first trip retention rate of ash. In the particle flocculation system, first add CPAM to form large flocs, which are dispersed into small flocs under the action of shearing force, and then add negative particulate colloidal silicon, which can react with the small flocs and combine to become denser and easier to dehydrate The small flocculation system can achieve higher retention, good uniformity and filtration performance.