I published several articles on the pulp molding process in the “China Packaging News†and “Paper Mold Researchâ€. After receiving articles on talc and application of retention aids, I received requests from many manufacturers to ask for them. Introduce it further. Some key technical issues concerning the use of modified starch as a retention aid and filter aid are described below.
Starch and its derivatives are important chemical additives in papermaking fine chemicals. Starch has the advantages of rich resources, low price, stable supply, easy use, chemical modification and biodegradation. As the modified starch can improve the physical strength and surface properties of paper and board, improve the dehydration and retention of fibers and fillers on the net, reduce the waste pollution of paper mills and reduce the cost of papermaking, it has been widely and extensively applied in the paper industry. The pulping principle and product forming principle of pulp moulding products are very similar to the papermaking process. Therefore, the use of modified starch in the production of pulp moulding products can also achieve such a purpose: firstly, to improve the papermaking process and improve the internality of paper moulding products. Performance (such as mechanical properties, retention, filtration aids, etc.); second is to improve the surface quality of paper molded products (such as smoothness, whiteness, gloss, etc.).
1. Types and Properties of Modified Starch The basic types of modified starch used in pulp molding pulping are cationic starch, anionic starch, amphoteric starch, and multiple starch. The most commonly used varieties are quaternary ammonium salt cationic starch and amphoteric starch or multiple starch.
Cationic starch properties 1. Cationic starch has a positive charge on its nitrogen atom. This performance characteristic makes it have good application value in many fields.
2. Cationic starch pastes have the ability to swell in cold water (even when the degree of substitution is very low). Quaternary ammonium salt cationic starches are more prominent in this regard.
3. The gelatinization temperature of cationic starch decreases as the degree of substitution increases, and the paste maintains better fluidity and transparency at low temperatures. The paste has weak retrogradation and is not prone to delamination.
4. There are conditions for further processing to produce new starch, and there are also conditions for sharing with other synthetic polymers.
Because the pulp fiber has a negative charge, the papermaking industry uses cationic starch as an additive in the slurry and uses the principle of positive and negative charge attraction to increase the fiber retention (reduce pulp consumption) and increase the wet strength and dry strength of paper products.
Properties of multiple starches Polyester starches (including amphoteric starches) refer to starches in the same starch that have both cations and two or more reactive groups such as anions or nonionics. It is a kind of pulp additive with both anionic and cationic properties. It has wider pH range and better use effect than cationic starch. It can obviously improve the charge properties in the pulp and improve the slurry retention rate. The water permeability of the pulp makes the strength and bending resistance of the paper products greatly improved.
The application of modified starch is common in the papermaking industry, but there are not many companies that use cationic starch and multiple starch as retention aids and reinforcing agents for China's pulp molded products industry. , promotion process. In the process of use, the most important thing is to master the correct use method according to the specific conditions of each manufacturer. For example, when cationic starch is used as a wet-end additive, the amount of its addition and the location of addition are different because of different purposes (mainly enhancement or mainly improvement of retention). Incorrect use, there will be the use of modified starch can not achieve the desired effect.
Second, how to choose cationic starch Starch cationic high-low three kinds of substitution, its nitrogen content was 0.3% (degree of substitution DS = 0.035), 0.2% (DS = 0.023) and 0 .1% (DS=0.012). The degree of substitution refers to the number of hydroxyl groups on each glucose unit that are etherified. When used as a retention aid, a cationic starch with a middle degree of substitution is generally used; when a good coagulation property is required, a starch with a high degree of substitution is used. In addition, with silicic acid or colloidal, so the consumption of oil repellent and water repellent also increased accordingly. If the retention aid is first added, flocculation of the fine fibers will occur, the surface area will be reduced, and the consumption of the oil-repellent agent and the water repellent agent will be accordingly reduced, so that the purpose of reducing the amount of the oil-repellent agent and the water repellent agent can be achieved.
Fifth, the use of modified starch economic benefits Modified starch in pulp molding applications, can obtain significant economic and social benefits, mainly in the following areas: reduce the loss of fiber and fines, reducing the oil The amount of agent and water repellent agent, the concentration of the white pool is reduced; the pulp filter water performance is improved, the pulp is easier to form, and the yield is improved. For paper-based China's paper mold industry, the effect will be more prominent, if the paper mold industry manufacturers can generally attach importance to the application of this technology, will play a very good role in reducing production costs and improving product quality. .
Six, gelatinization of modified starch paste starch paste method is:
1. Add a certain volume of soft water or clean cold water with a lower volume of hardness to the gelatinization tank, and start the stirrer (agitating rotation speed is 60-100 rpm), and slowly add starch. Generally, the gelatinization concentration is 5%, and then direct steam heating, but the steam pressure can not be opened too high to prevent the high-temperature steam degradation of the starch. If you can use steam heating between the better. While continuing to stir, heat up to 90-95°C to make it a gelatinization liquid and hold it at this temperature for about 20 minutes. This step is critical. Also note that the gelatinization is not completely starch, because the starch particles are not fully dispersed, will affect the use of the effect. However, the holding time should not be too long and the temperature should not be too high, so as to prevent degradation of starch under high temperature for a long time.
2. Gelatinized starch paste should be diluted in time (concentration of 1-2%), the diluted starch paste is best used in time, if you need to store for some time, you need to heat at about 65 °C, otherwise Starch paste is prone to ageing and delamination occurs, affecting the effect of use.
3. The gelatinized starch paste should not be continuously agitated. In particular, high-speed stirring is prevented so that the molecular chain of the paste liquid is not sheared and destroyed.
4. The gelatinized diluted starch paste can be added to the slurry pool but must be added first before the oil and water repellents.
The use methods described above, manufacturers with steam conditions may wish to try it, but before the test must have the technicians first test. Before going into production applications, detailed operating procedures should be worked out according to the experimental conditions and operators should be trained. This is very important for achieving good results.
Starch and its derivatives are important chemical additives in papermaking fine chemicals. Starch has the advantages of rich resources, low price, stable supply, easy use, chemical modification and biodegradation. As the modified starch can improve the physical strength and surface properties of paper and board, improve the dehydration and retention of fibers and fillers on the net, reduce the waste pollution of paper mills and reduce the cost of papermaking, it has been widely and extensively applied in the paper industry. The pulping principle and product forming principle of pulp moulding products are very similar to the papermaking process. Therefore, the use of modified starch in the production of pulp moulding products can also achieve such a purpose: firstly, to improve the papermaking process and improve the internality of paper moulding products. Performance (such as mechanical properties, retention, filtration aids, etc.); second is to improve the surface quality of paper molded products (such as smoothness, whiteness, gloss, etc.).
1. Types and Properties of Modified Starch The basic types of modified starch used in pulp molding pulping are cationic starch, anionic starch, amphoteric starch, and multiple starch. The most commonly used varieties are quaternary ammonium salt cationic starch and amphoteric starch or multiple starch.
Cationic starch properties 1. Cationic starch has a positive charge on its nitrogen atom. This performance characteristic makes it have good application value in many fields.
2. Cationic starch pastes have the ability to swell in cold water (even when the degree of substitution is very low). Quaternary ammonium salt cationic starches are more prominent in this regard.
3. The gelatinization temperature of cationic starch decreases as the degree of substitution increases, and the paste maintains better fluidity and transparency at low temperatures. The paste has weak retrogradation and is not prone to delamination.
4. There are conditions for further processing to produce new starch, and there are also conditions for sharing with other synthetic polymers.
Because the pulp fiber has a negative charge, the papermaking industry uses cationic starch as an additive in the slurry and uses the principle of positive and negative charge attraction to increase the fiber retention (reduce pulp consumption) and increase the wet strength and dry strength of paper products.
Properties of multiple starches Polyester starches (including amphoteric starches) refer to starches in the same starch that have both cations and two or more reactive groups such as anions or nonionics. It is a kind of pulp additive with both anionic and cationic properties. It has wider pH range and better use effect than cationic starch. It can obviously improve the charge properties in the pulp and improve the slurry retention rate. The water permeability of the pulp makes the strength and bending resistance of the paper products greatly improved.
The application of modified starch is common in the papermaking industry, but there are not many companies that use cationic starch and multiple starch as retention aids and reinforcing agents for China's pulp molded products industry. , promotion process. In the process of use, the most important thing is to master the correct use method according to the specific conditions of each manufacturer. For example, when cationic starch is used as a wet-end additive, the amount of its addition and the location of addition are different because of different purposes (mainly enhancement or mainly improvement of retention). Incorrect use, there will be the use of modified starch can not achieve the desired effect.
Second, how to choose cationic starch Starch cationic high-low three kinds of substitution, its nitrogen content was 0.3% (degree of substitution DS = 0.035), 0.2% (DS = 0.023) and 0 .1% (DS=0.012). The degree of substitution refers to the number of hydroxyl groups on each glucose unit that are etherified. When used as a retention aid, a cationic starch with a middle degree of substitution is generally used; when a good coagulation property is required, a starch with a high degree of substitution is used. In addition, with silicic acid or colloidal, so the consumption of oil repellent and water repellent also increased accordingly. If the retention aid is first added, flocculation of the fine fibers will occur, the surface area will be reduced, and the consumption of the oil-repellent agent and the water repellent agent will be accordingly reduced, so that the purpose of reducing the amount of the oil-repellent agent and the water repellent agent can be achieved.
Fifth, the use of modified starch economic benefits Modified starch in pulp molding applications, can obtain significant economic and social benefits, mainly in the following areas: reduce the loss of fiber and fines, reducing the oil The amount of agent and water repellent agent, the concentration of the white pool is reduced; the pulp filter water performance is improved, the pulp is easier to form, and the yield is improved. For paper-based China's paper mold industry, the effect will be more prominent, if the paper mold industry manufacturers can generally attach importance to the application of this technology, will play a very good role in reducing production costs and improving product quality. .
Six, gelatinization of modified starch paste starch paste method is:
1. Add a certain volume of soft water or clean cold water with a lower volume of hardness to the gelatinization tank, and start the stirrer (agitating rotation speed is 60-100 rpm), and slowly add starch. Generally, the gelatinization concentration is 5%, and then direct steam heating, but the steam pressure can not be opened too high to prevent the high-temperature steam degradation of the starch. If you can use steam heating between the better. While continuing to stir, heat up to 90-95°C to make it a gelatinization liquid and hold it at this temperature for about 20 minutes. This step is critical. Also note that the gelatinization is not completely starch, because the starch particles are not fully dispersed, will affect the use of the effect. However, the holding time should not be too long and the temperature should not be too high, so as to prevent degradation of starch under high temperature for a long time.
2. Gelatinized starch paste should be diluted in time (concentration of 1-2%), the diluted starch paste is best used in time, if you need to store for some time, you need to heat at about 65 °C, otherwise Starch paste is prone to ageing and delamination occurs, affecting the effect of use.
3. The gelatinized starch paste should not be continuously agitated. In particular, high-speed stirring is prevented so that the molecular chain of the paste liquid is not sheared and destroyed.
4. The gelatinized diluted starch paste can be added to the slurry pool but must be added first before the oil and water repellents.
The use methods described above, manufacturers with steam conditions may wish to try it, but before the test must have the technicians first test. Before going into production applications, detailed operating procedures should be worked out according to the experimental conditions and operators should be trained. This is very important for achieving good results.
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