The example also confirms this synergy and the importance of using an on-line inspection device with an on-line monitor. Technicians observed that the retention rate returned to normal, there will always be a periodic decrease, and further studies revealed that this decrease is directly related to the intermittent addition of fungicides. The dispersant used in the sterilization treatment is not conducive to the use of retention aids. The paper mill reduced the rate of change in the pulp retention rate to a normal level by replacing the faster sterilant feed switch system and changing the feed point. 4. Particle retention aid Particulate retention aids mainly include silica sol, bentonite and synthetic products. Paper mills use them together with starch and retention aids to improve slurry retention, water filtration, forming and paper machine operation. With the merger of some chemical companies, many of these technologies have been controlled by a single supplier. By concentrating on these technologies, the papermaking industry began to appear a particulate retention system that could improve both pulp retention and paper formation uniformity. This combination allows the slurry drainage to be improved while maintaining normal formation, and replaced with paper uniformity without losing slurry retention and drainage. These collaborative systems are still in their infancy, but their potential for development is huge for users. The problem it brings here is that its increased costs must be consistent with the benefits it generates. 5. Defoamer and additives at wet end Paper mills often use defoamers or deaerators to prevent foaming and deposits. However, they also have a positive effect on the addition of additives in the wet end. Auxiliaries use a clean, properly charged slurry fiber or fine fiber surface to be adsorbed and combined. If there is too much air in the slurry system, the surface of the slurry fiber or fine fiber will be covered with a lot of microbubbles. These bubbles make the auxiliary agent unable to make good contact with the fiber. European paper mills usually pay more attention to the control of defoaming and degassing measures in the pulp system than American paper mills. Therefore, under the appropriate defoamer and degassing agent addition monitoring measures, their chemical utilization efficiency and paper machine operation Relatively better. 6. Starch and internal sizing agent Adding sizing agent, such as alkenyl succinic anhydride (ASA), alkyl ketene dimer (AKD), when used alone, it is more difficult to stay on the fiber. Cationic starch can be used to increase the retention of sizing agent on the fiber. In some cases, manufacturers use starch as an emulsifier for sizing agents. Some sizing agent manufacturers use it as a sizing synergist. In addition, the synergistic effect of these two chemicals can improve paper strength while improving sizing efficiency. 7. Coagulant and internal sizing agent The coagulant and trapping agent can assist the retention of the sizing agent in two ways. The coagulant is added to the internal sizing agent to make it more conducive to adsorption on fibers and fine fibers. It can also remove garbage from the wet end, which provides a cleaner fiber or fine fiber surface for sizing agent adsorption. The technical difficulty lies in controlling the balance of system charge. Over-cationization of the system will cause desorption of other additives and sizing agents. 8. Internal sizing and surface pressing sizing The required sizing degree of paper can be achieved by grinding, internal sizing and surface sizing. Paper mills usually add sizing agent after the refining reaches the best level to meet the sizing requirements. The paper mill can add sizing agent at the wet end or sizing press section or both. Adding both the wet end and the sizing press at the same time can improve the sizing efficiency, reduce the cost and alleviate the phenomenon of charge deposit in the wet end. How to use this cooperative sizing method correctly depends on the paper machine structure and process parameters, but as long as you pay more attention, this method is still very feasible. 9. Alum in alkaline papermaking In the past few years, the use of alum in alkaline papermaking systems to improve papermaking performance is one of the most popular positive synergies. The alum retention chemistry theory shows that it cannot function effectively under alkaline pH conditions. However, in reality it does improve alkaline sizing efficiency and slurry retention. At the beginning of the conversion to alkaline papermaking systems, alum is often added to the ASA emulsion to stabilize its emulsion particles. When this type of ASA-alum emulsion is used in papermaking, the pulp retention rate and the cleanliness of the paper machine are significantly improved. Then people used alum alone, and similar advantages were obtained. Now paper mills have generally adopted alum as retention aid and sizing synergist. The problem is that at alkaline pH, excessive alum can easily form a precipitate and cannot be used normally. 10. Alum and rosin gum It has been agreed for many years that alum can form a rosin alum complex with rosin gum at an acidic pH to give the paper a good sizing degree. This is also a typical example of the active synergy of two different chemicals. No matter what kind of combination, attention should be paid to the proportion of additives, the way of addition and the place of addition, otherwise deposition may occur, resulting in a decrease in use efficiency. 11. Resin control Jing-talc powder Pulp mills generally use talc to control resin barriers and other stickies. It is often forgotten that it can also be used as a paper filler. Although the whiteness and opacity of talc is lower than that of ground calcium carbonate GCC and precipitated calcium carbonate PCC, it is still a good pulp filler. Therefore, talc powder can be used not only as a resin barrier control agent, but also as a filler. When the pulp plant talcum powder is used as the resin control agent and the dosage is 4.5 ~ 6.8kg / t, there is no side effect in the papermaking process. 12. Precipitated calcium carbonate (PCC) and ground calcium carbonate (GCC) The market competition for these two types of calcium carbonate has been going on for many years, but many examples show that they share a positive synergy. Each product has its own advantages and disadvantages, and the pros and cons can be weighed to meet the papermaking needs. Combined with the advantages of each technology to choose the right filler combination, the manufacturer will obtain the best cost performance, paper machine efficiency, physical performance and optical performance. 13. Titanium dioxide (TiO2) pigment blend Titanium dioxide, as a high-efficiency pigment, is often used in the wet end and in coatings to add excellent opacity and whiteness to the paper. Due to its high price, some alternatives have appeared in the market to share with titanium dioxide to obtain the required optical performance at a lower cost. Because of their lower dispersant requirements, these substitutes are generally easier to retain than titanium dioxide. Because the dispersant has a negative charge retention effect on the slurry, paper mills should pay attention to the amount of dispersant in these pigments. 14. Coloring agent and pink agent This title looks weird, but in fact, the interaction between colorants can have both positive and negative effects. Dyestuffs and brighteners can be mixed to meet the expected color, hue, color density, whiteness and opacity of paper. When the operator formulates the colorant reasonably, they can achieve the desired effect with less adverse effects. Only by exerting the synergistic effect between various colorants can the expected paper performance index be obtained, and it is impossible to do it with only one or two dyes. These dyes can also repel each other. The order of addition when they are shared is very important, and you should avoid changing the order at will. Some dyes are cationic, while some may be anionic. Be careful not to add dyes with opposite charges when they are added too close, otherwise they will interact before being adsorbed on the fiber. Even if they are all anionic, since they can form hydrogen bonds with each other to affect their adsorption, it is best to add them separately to promote their adsorption on the fiber. 15. Colorants and other additives The interaction between the dye and other wet end additives is also bidirectional. Dye fixing agents and coagulants are commonly used to fix anionic dyes, and their interaction is positive. Anionic dyes and pigments bring a large amount of negative charge to the wet part, which will adversely affect the use of cationic additives added to the wet part. Even if the anionic dye has been uniformly covered on the fiber surface, the increased negative charge will increase the additional burden of traditional cationic retention aids and coagulants. 16. Softener and defoamer Softeners are often used in the production of toilet paper and facial tissues to increase their softness, bulk and absorbency. Such additives are usually surfactants, which are prone to foaming. This requires an increase in the use of defoamers and deaerators. The advantage of using softener is that it can meet consumers' requirements for bulk, softness and absorbency. The disadvantage is that it increases the cost of defoaming chemicals. 17. Possible impact The examples listed above give possible synergies between papermaking auxiliaries, both positive and negative. There may be more examples. It is important that pulp mills and paper mills should take more effective measures for the use of functional additives, so that these additives (whether used alone or several types of shared) can better meet the performance of paper And cost requirements. Paper mills should pay close attention to the interaction of various additives and optimize their application processes to achieve the best cost performance.
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1. Coagulant and retention aid Coagulant (trapping agent) is usually used in broken head broken pulp and some other waste paper pulps to neutralize system charge or treat waste in the pulp. Such additives, when properly controlled and applied, will reduce the demand for short-range retention aids per ton of pulp. The reduction in the amount of polymer mass retention aids will significantly improve the evenness and tightness of the finished paper compared to the initial amount. However, when the coagulant makes the system charge excessive again, it will also have a negative effect, causing the retention aid to desorb on the slurry, reducing the efficiency of use.
In the factory, coagulant or low molecular weight retention aid is used to improve the water filtration in the forming area to achieve the best results. This situation is also applicable to the coagulation treatment of broken pulp and raw pulp.
2. Starch and retention aid Adding starch at the wet end can give paper strength. It is also a good source of positive charge, which is usually conducive to pulp retention and water filtration. In the production of high-end printing and writing paper, it is often seen that the addition of starch in the wet end can significantly reduce the amount of retention aid and filter aid, and at this time its main role is to help the retention of the internal sizing agent. With the development of starches with a high degree of cationic substitution, some manufacturers are working to use them to clean the system to facilitate the improvement of strength, retention and drainage. Similarly, starch can also cause over-cationization of the system, reducing the efficiency of the use of other additives.
3. The interaction between dispersants and retention aids will have adverse effects. During use, the dispersant is used to remove system rubbish or to assist in the diagnosis and killing of bacteria. Here the dispersion process will counteract the retention of the slurry. When manufacturers use dispersants, they will always observe a decrease in the use of retention aids.
Talking about the synergy of various functional additives in the papermaking process
Because these functional additives are rarely used alone, it is necessary to understand the synergy between them. The information provided below should provide some help for you to better use various additives. Before we start, let us review what are functional additives and synergies. The so-called functional additives refer to the use of these products to provide users with the required functions. From a different perspective, this applies to all additives. Synergy is a special term that indicates that when two or more additives are used together, the effect is different from the cumulative effect of using the additives alone. Generally speaking, synergistic effects are in terms of producing positive effects, but such synergistic effects can sometimes become negative.