The use of polyacrylamide in the sugar industry, the residual monomer content of polyacrylamide is an important parameter to measure whether it is suitable for the food industry. Polyacrylamide polymers are non-toxic and have been widely used in tap water purification, food industry and sugar industry internationally. However, in industrial polyacrylamide, it is inevitable that trace amounts of unpolymerized acrylamide monomers remain. Therefore, the residual monomer content in polyacrylamide products must be strictly controlled. International regulations stipulate that the residual monomer content in polyacrylamide used in drinking water and food industry does not exceed 0.05%.
The anionic degree of polyacrylamide has a great impact on the use effect of the sugar industry, but its appropriate value depends on the type and nature of the material being processed, and there will be different optimal values in different situations.
According to our years of research and comparative tests and analysis of dozens of polyacrylamide samples, the anionic degree of polyacrylamide used in the sugar industry is 22 to 28% more suitable, and it has strong adaptability. It can be used for different materials (cane juice, syrup, brown sugar and raw sugar redissolution syrup) and different processes (sulfurous acid method, carbonation method and phosphorus float method). Most of the anionic degrees of polyacrylamide for sugar produced abroad are in this range.
If the ionic strength of the material being processed is high (containing more inorganic substances), the anionic degree of the polyacrylamide used should be higher, and vice versa. According to Clark's report, polyacrylamide with 20% anionic degree is commonly used in sugar mills in Australia, while higher values are commonly used in sugar mills in Florida, USA. Cress et al. found that after adding flocculant to cane juice and removing sediment, the amount of polyacrylamide remaining is related to the original anionic degree of polyacrylamide.
Some natural polymer organic compounds, such as polysaccharides containing more carboxyl groups and starches containing more phosphate groups, have flocculation properties. The introduction of active groups into macromolecules by chemical methods can improve this performance. For example, after etherification of a natural polysaccharide into active groups such as carboxyl groups and amide groups, the flocculation performance is better, and the sedimentation of cane juice can be accelerated. Graft copolymerization of natural polymer substances such as starch, cellulose, chitosan, etc. with acrylamide shows that the polymer has good flocculation properties or has some special properties. Some products developed in China have been tried in several sugar factories and have good results.
At present, the most widely used flocculants in sugar mills at home and abroad are synthetic polyacrylamide series products, which have developed rapidly and are widely used in various processes in the sugar industry.
Modern production of polyacrylamide has a variety of products with different anionic degrees. Users can choose the appropriate variety according to their needs and through actual tests. There is no need for hydrolysis, and it can be used after dissolution. However, due to customary reasons, some people still refer to the dissolution process of flocculants as hydrolysis. It should be noted that hydrolysis means adding water to decompose, which is a chemical reaction. The hydrolysis of polyacrylamide has ammonia gas release; while dissolution is only a physical effect, no chemical reaction. The two are essentially different and should not be confused.