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The Polyacrylamide is one of the earliest and the widest used additives in pape rmaking industry, it is even called as “the pape rmaking additive”.
The polyacrylamide as the additive in the pap ermaking industry mainly has the following applications:
1. The polyacrylamide working as the retention agent can achieve the below effects:
It can improve the retention rate of the fine fiber and the filler, which is reflected in the increase of the ash content and the increase of the quantitative.
It can decrease the concentration of the white water under the net, accelerate the sedimentation velocity of the white water, improve the performance efficiency of the white water recovery device.
It can improve the paper closed drainage performance. From the movement of the waterline in the net, it increases the dehydration speed, thereby, it improves the working speed and the dry degree of the paper leaving the net, which saves the steam.
With more adding of the anionic polyacrylamide, there is only a little influence to the paper strength, but the paper evenness gradually gets worse.
2. The polyacrylamide can be used as the reinforcing agent. As the water soluble high polymer, in recent year, the polyacrylamide is paid more attention in the papermaking industry as the reinforcing agent, it can work as both the dry strengthening agent but also the wet strengthening agent. As the dry strengthening agent, it is suitable to be sued in food packaging paper, the bleached paperboard, the toilet paper, the tissue paper and the surface cardboard etc. As the wet strengthening agent, it could be used as for the marine drawings, the banknote paper, the photographic base paper, the poster paper and the high grade wrapping paper etc.
3. The polyacrylamide can be used as the dispersing agent. The dispersing agent is a common additive in the paper making industry to reduce the fiber flocculation which can improve the paper formation, thereby, it is also known as the “resistance” or the “suspension” of the flocculant. In both the handmade paper and the mechanical copy paper, the fiber dispersant is required to be used, in order to make the good evenness of the paper product. The production practice shows that the molecular weight of the anionic polyacrylamide (APAM) which is used as the dispersant should not be less than 700 x 104, and should not be affected by the heat and the high shear force, furthermore, it could be recovered and be used repeatedly, that is beneficial to both improve the strength of the fiber and reduce the production cost.
The main usage of the fiber dispersant is to reduce the flocculating of the fiber and to improve the formation of the paper material, which make the final paper product soften and make the wrinkling even. Its specific roles are: 1. It can increase the viscosity of the water solution, this can make the paper sheet material have good suspension performance without excessive settlement, so that the fiber can disperse completely, the uniformity of the paper product is improved; 2. It has a certain adhesion, it can be adsorbed on the surface of the fiber and form a water film layer which is smooth but not sticky, this film layer is similar to the lubricant and can prevent the fiber from flocculating; 3. it has a certain requirement of the pyrolysis, the good quality fiber dispersant can gradually decomposed along with the increasing of the temperature, the viscosity is also decreased accordingly, thereby, the fiber dispersant rarely has the residues in the dried paper sheet, that will not affect the original performance of the fiber and the performance of the paper product by using this kind of fiber dispersant.
4. The polyacrylamide could be used as the flocculant. It could be sued as the flocculant in the waste water treatment segment in the paper making industry, which to help to accelerate the sedimentation process and the sludge dewatering process.