Enhanced waterproof technology of the hottest pulp

2022-08-07
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Enhanced waterproof technology for pulp molded industrial packaging products *

in the process of controlling "white pollution", pulp molded products used for industrial packaging have developed rapidly. According to the statistics in 1997, China's paper products used for industrial packaging accounted for only about 1% of the total packaging supplies, while the western developed countries accounted for about 15% of the total. In the past two years, China has made great progress in replacing wood with paper in the outer packaging of industrial products and plastic with paper in the inner packaging. The types of paper packaging products mainly include honeycomb paperboard tray series and honeycomb paperboard packaging box series, which take recycled kraft paper as the base material and are produced by modern electromechanical equipment to replace wood pallet and wood packaging box; Paper mold lining products produced by pulp molding machine with leftover materials of box board paper and waste newspapers as raw materials to replace foamed plastic products. However, compared with plastic foam packaging products, the weakness of these paper packaging products, especially the paper mold lined packaging products, is that their strength is poor. In the sea and humid environment, the paper mold products are easy to absorb moisture and their strength is reduced. Therefore, the problems of strengthening the paper packaging products and preventing water and moisture must be solved. There are four main factors affecting the strength of paper mold packaging products: ① the strength of the fiber itself; ② Bond strength between fibers; ③ Surface area of fiber bonding; 5 distribution of binding bonds. In view of the above four factors, the solutions are as follows: first, in the pulping process, the medium consistency long fiber sticky beating method is adopted. Medium consistency beating refers to a beating method carried out in medium consistency beating equipment when the beating concentration is 4-6%. Long fiber sticky beating is a beating method that requires to avoid cutting the fiber as much as possible, keep the fiber at a certain length, and carry out high wire separation and brooming, with good swelling and hydration. The advantages of this beating method are: ① less fiber cutting, more distortion and deformation, and good strength of finished products; ② When the strength of the paper products is the same, the beating degree and water retention value of the pulp are low, and the dewatering performance is better than that of the dynamometer. 4; ③ The refining time is shortened, the energy consumption is reduced, the equipment performance is improved, and the product cost is reduced. Due to reducing the range of concentration and dilution, the electric energy of medium consistency beating can be saved by 20-30kw h ¢ t absolute dry pulp. However, considering the construction period II of phase I project of Xinxiang Chemical fiber raised investment project, it should be relieved after pulping. At present, most manufacturers have only beating process but no pulping and thawing process, which makes the finished fiber lack the conditions to increase the strength. Although it takes only a few seconds for the paper material to pass through the dredger, the pulps crushed by the hydraulic pulper can be cut, separated and finely fibrosed by the dredger, which can not only make the pulp distribution of the paper products uniform, but also increase the strength of the finished products. 3、 Adding a reinforcing agent to increase the strength of the product; Add waterproof agent to increase the waterproof and moisture-proof performance of the product. There are two ways to strengthen paper with chemical additives, one is internal reinforcing agent, the other is surface reinforcing agent. The internal reinforcing agent can be divided into dry reinforcing agent and wet reinforcing agent. The reinforcing agent used to increase the packaging products of pulp molded industrial products generally uses dry reinforcing agent. Dry reinforcing agent is a fine chemical used to enhance the bonding between fibers to improve the physical strength of paper products without affecting their wet strength. These chemicals have active groups with a certain molecular weight. Due to the binding strength of their own colloidal molecules and the hydroxyl group of cellulose, the construction of a green manufacturing system in the automotive industry will be accelerated to form hydrogen bonds, which can meet the requirements of paper products. The commonly used dry enhancers include cationic starch, anionic starch, amphoteric starch, polybasic starch and ionic polyacrylamide. Cationic starch and polybasic starch (including amphoteric starch) are not only good retention and drainage aids, but also good dry enhancers. Its strengthening principle is that the main stress will be further increased until the sample is torn. If the sample is attached to the fiber surface through the electrostatic attraction between the cationic group in the starch and the negative charge on the fiber surface and is adsorbed with the fiber through the bridge of hydrogen bond, the brushed fibers will form a whole of complex bond, so as to achieve the purpose of improving the strength of paper products. Starch shall be used as reinforcing agent, and the dosage is generally 1 ~ 2% of the dry pulp material. Starch without gelatinization treatment cannot be directly added to the pulp pool. Starch must be gelatinized and processed into starch paste liquid (dextrin can be purchased if there is no gelatinization condition). The gelatinization method is as follows: ① add a certain volume of soft water or clean cold water with low hardness into the gelatinization tank, start the mixer (the mixing speed is 60-100 RPM), and then slowly add starch to fully disperse the starch. Generally, the gelatinization concentration is 5%, and then directly heated by steam. However, the steam pressure should not be too high to prevent the degradation of starch by high-temperature steam. It would be better if indirect steam could be used for heating. Under continuous stirring, the temperature shall be raised to 90-95 ℃ to make it a gelatinizing solution, and the temperature shall be kept at this temperature for about 20 minutes. This step is very important. Attention should also be paid to the starch with incomplete gelatinization, because the starch particles are not fully dispersed, which will affect the use effect. However, the heat preservation time should not be too long, and the temperature should not be too high to prevent starch degradation under the action of high temperature for a long time. ② The starch paste after gelatinization treatment shall be diluted in time (the concentration is 1 ~ 2%). It is best to use up the diluted starch paste in time. If it needs to be stored for a period of time, it must be kept at a temperature of about 65 ℃. Otherwise, the starch paste is prone to aging and stratification, which will affect the use effect. ③ Do not continuously stir the gelatinized starch paste, especially prevent high-speed stirring to prevent the molecular chain of the paste from being sheared and damaged. 5 paste liquid after gelatinization and dilution can be added into the slurry forming tank. 4、 In order to increase the strength, waterproof and moisture-proof of paper mold industrial packaging products, a kind of water-resistant reinforcing agent for paperboard is added after adding starch paste, with the addition amount of 5% of the dry weight of starch (it is also possible to directly add starch paste and stir it evenly). The honeycomb paperboard substrate and pulp molded products treated by this process have the advantages of water resistance, moisture resistance, smoothness, firmness, compression resistance, impact resistance, etc

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