Adding sizing agents when papermaking and paperboard are used to impart water resistance to products. Currently applied change chemicals mainly include rosin/alum sizing system, alkaline modification of AKD, ASA, and polymerization sizing agent for surface sizing in certain applications. The following discusses the superiority and limitations of different sizing systems and the interrelationships with coating operations and coated paper properties.
Advantages and Limitations of Several Sizing Systems 1:1 Rosin Sizing In the rosin sizing system, rosin is added to the slurry with alum or other precipitants such as polymerized aluminum and sodium aluminate. The complex hydrophobic compound, aluminum rosinate, is deposited on the surface of the paper fibers. In the formation and drying of the sheet, aluminum rosinate diffuses to the surface of the fibers, producing a relatively uniform water resistant layer in the paper and paperboard. The best sizing effect can be obtained when the pH of the rosin sizing is 6-7. At this time, clay can be added and calcium carbonate can not be added. The degree of sizing is mainly controlled by adjusting the amount of rosin added, the pH of the wet part or the acidity. The main problems of rosin sizing are the decrease of the strength of the paper sheet, the poor resistance to aging, and the great corrosion of the equipment. With rosin internal sizing, only low-to-medium sizing leather can be obtained, and it is difficult to obtain a high degree of sizing.
1.2 Alkyl ketene dimer (AKD) Alkaline sizing AKD is a cellulose reactive sizing agent prepared from depolymerized hard fatty acids. It can be used as an internal sizing agent as well as a surface sizing agent. AKD reacts with cellulose fibers to form keto ester derivatives and is positioned on the fibers. The hydrophobic end faces the surface of the fiber and forms a hydrophobic layer. The reaction between AKD and cellulose continues for a certain period of time. Therefore, as the storage time increases, the sheet rubber coating rises. The AKD has the best sizing effect at PH 7-9. It can be filled with calcium carbonate. The paper produced by the AKD is stronger than the rosin sizing paper and has good anti-aging properties. High-sizing paper sheets have a certain resistance to acid and alkali. The problem with AKD sizing is that it is difficult to control the final degree of sizing due to the slow reaction of AKD and cellulose, and a slime may be formed in the wet end, and wear of the mesh and felt increases when CaCO is added.
1.3 The ASA alkaline sizing reaction of ASA and cellulose is similar to that of AKD, but the reaction speed is fast, reaching at least 8% of the final sizing when the sheet leaves the machine. The reactivity of ASA is also detrimental. For example, matured ASAs are greatly reduced in storage time due to rapid hydrolysis. Therefore, the emulsification of ASA is performed on site before use. ASA can sizing over a wide range of pH, but the best sizing is at pH 6-8. Can add CaCO. Frequently, a small amount of alum is added to the system at the time of ASA modification. The purpose is to increase the sizing efficiency and reduce the squeeze roll problem caused by ASA hydrolysate. When applying ASA sizing, care should be taken to increase the ASA's one-pass retention rate to reduce the circulation of ASA in white water and reduce the deposition problems caused by hydrolysis. The stability of the wet end is the key to the effective use of ASA. The disadvantage is that the degree of sizing is difficult to control when the amount of ASA is large.
2. Effect of sizing on coating The quality of the sizing of the coating base paper directly affects the covering ability of the coating, and thus directly affects the coating process. When the unsized paper is in contact with the coating, rapid water absorption of the fibers can lead to dehydration of the coating and poor coating coverage. The effect of the sized paper on the transfer of the coating to the capillary tube is less than the effect of the forming of the base paper and the proportion of the paste. At low sizing, fluctuations in sizing can affect the operation of the coater and the characteristics of paper formation.
2.1 Effect of sizing on the coating operation Dewatering of the coating on the coating head poses a serious threat to the operation of the coating machine, such as fluctuations in the coating amount, severe abrasion of the squeegee, scratches, etc., especially when the coating is solid. More serious when the content is high. Changes in the degree of sizing of the coating base paper can affect the hiding of the coating. In this case, the formulation of the coating needs to be adjusted, such as adding an adhesive and a water retaining agent, but it will increase the cost of the coating. Changes in the degree of sizing cause fluctuations in the moisture entering the coater's paper sheet, which affects the size press. When the vehicle speed is low, the impact of the sizing degree has little effect on the pulling of the paper when the speed of the paper machine is over 1000 m/min. At present, many paper mills do not apply glue to the coated base paper.
2.2 Effect of sizing on the quality of coated paper In general, increasing the hiding power of the coating can improve the opacity and printing performance of the coated paper. Different sizing degrees of the base paper lead to different amounts of migration of the adhesive, resulting in adhesives in the coating. The fluctuation of the content will affect the gloss of the coated paper and the ink absorption performance. When the base paper sizing is low, the paper sheet absorbs more paint, which reduces the thickness, smoothness and gloss of the paper surface coating.
2.3 One of the measures to reduce the sizing problem is to carefully select the formulation of the coating to accommodate the large changes in sizing. Carefully select the sizing system for the base paper to make it easier to control. The advantages and disadvantages of different sizing systems should be considered based on the operation of the entire system and the type of base paper.
Advantages and Limitations of Several Sizing Systems 1:1 Rosin Sizing In the rosin sizing system, rosin is added to the slurry with alum or other precipitants such as polymerized aluminum and sodium aluminate. The complex hydrophobic compound, aluminum rosinate, is deposited on the surface of the paper fibers. In the formation and drying of the sheet, aluminum rosinate diffuses to the surface of the fibers, producing a relatively uniform water resistant layer in the paper and paperboard. The best sizing effect can be obtained when the pH of the rosin sizing is 6-7. At this time, clay can be added and calcium carbonate can not be added. The degree of sizing is mainly controlled by adjusting the amount of rosin added, the pH of the wet part or the acidity. The main problems of rosin sizing are the decrease of the strength of the paper sheet, the poor resistance to aging, and the great corrosion of the equipment. With rosin internal sizing, only low-to-medium sizing leather can be obtained, and it is difficult to obtain a high degree of sizing.
1.2 Alkyl ketene dimer (AKD) Alkaline sizing AKD is a cellulose reactive sizing agent prepared from depolymerized hard fatty acids. It can be used as an internal sizing agent as well as a surface sizing agent. AKD reacts with cellulose fibers to form keto ester derivatives and is positioned on the fibers. The hydrophobic end faces the surface of the fiber and forms a hydrophobic layer. The reaction between AKD and cellulose continues for a certain period of time. Therefore, as the storage time increases, the sheet rubber coating rises. The AKD has the best sizing effect at PH 7-9. It can be filled with calcium carbonate. The paper produced by the AKD is stronger than the rosin sizing paper and has good anti-aging properties. High-sizing paper sheets have a certain resistance to acid and alkali. The problem with AKD sizing is that it is difficult to control the final degree of sizing due to the slow reaction of AKD and cellulose, and a slime may be formed in the wet end, and wear of the mesh and felt increases when CaCO is added.
1.3 The ASA alkaline sizing reaction of ASA and cellulose is similar to that of AKD, but the reaction speed is fast, reaching at least 8% of the final sizing when the sheet leaves the machine. The reactivity of ASA is also detrimental. For example, matured ASAs are greatly reduced in storage time due to rapid hydrolysis. Therefore, the emulsification of ASA is performed on site before use. ASA can sizing over a wide range of pH, but the best sizing is at pH 6-8. Can add CaCO. Frequently, a small amount of alum is added to the system at the time of ASA modification. The purpose is to increase the sizing efficiency and reduce the squeeze roll problem caused by ASA hydrolysate. When applying ASA sizing, care should be taken to increase the ASA's one-pass retention rate to reduce the circulation of ASA in white water and reduce the deposition problems caused by hydrolysis. The stability of the wet end is the key to the effective use of ASA. The disadvantage is that the degree of sizing is difficult to control when the amount of ASA is large.
2. Effect of sizing on coating The quality of the sizing of the coating base paper directly affects the covering ability of the coating, and thus directly affects the coating process. When the unsized paper is in contact with the coating, rapid water absorption of the fibers can lead to dehydration of the coating and poor coating coverage. The effect of the sized paper on the transfer of the coating to the capillary tube is less than the effect of the forming of the base paper and the proportion of the paste. At low sizing, fluctuations in sizing can affect the operation of the coater and the characteristics of paper formation.
2.1 Effect of sizing on the coating operation Dewatering of the coating on the coating head poses a serious threat to the operation of the coating machine, such as fluctuations in the coating amount, severe abrasion of the squeegee, scratches, etc., especially when the coating is solid. More serious when the content is high. Changes in the degree of sizing of the coating base paper can affect the hiding of the coating. In this case, the formulation of the coating needs to be adjusted, such as adding an adhesive and a water retaining agent, but it will increase the cost of the coating. Changes in the degree of sizing cause fluctuations in the moisture entering the coater's paper sheet, which affects the size press. When the vehicle speed is low, the impact of the sizing degree has little effect on the pulling of the paper when the speed of the paper machine is over 1000 m/min. At present, many paper mills do not apply glue to the coated base paper.
2.2 Effect of sizing on the quality of coated paper In general, increasing the hiding power of the coating can improve the opacity and printing performance of the coated paper. Different sizing degrees of the base paper lead to different amounts of migration of the adhesive, resulting in adhesives in the coating. The fluctuation of the content will affect the gloss of the coated paper and the ink absorption performance. When the base paper sizing is low, the paper sheet absorbs more paint, which reduces the thickness, smoothness and gloss of the paper surface coating.
2.3 One of the measures to reduce the sizing problem is to carefully select the formulation of the coating to accommodate the large changes in sizing. Carefully select the sizing system for the base paper to make it easier to control. The advantages and disadvantages of different sizing systems should be considered based on the operation of the entire system and the type of base paper.
For the working population, sedentary is a common normal, all kinds of lumbar disease, cervical spondylosis "into" people's body, bring a lot of trouble to people. Sitting for more than 2 hours without standing up and changing sitting posture is considered as sedentary.
Stand up desk is of great help to healthy office, and modern people's demand for health is also growing. Fully stand in the perspective of users to think about the problem, and the lifting desk with freely adjustable height can bring users a new experience of healthy office.
stand up desk can adjust the height of the desk according to its own needs, so that it can work in the most comfortable state.
Stand Up Desk,Motorized Standing Desk,Stand Up Computer Desk,Ergonomic Stand Up Desk,Adjustable Desk
Suzhou Uplift Intelligent Technology Co., Ltd , https://www.upliftecdesk.com