Reinforced Waterproof Technology for Pulp Molding Industrial Packaging Products

In the process of "white pollution", pulp molded products used for industrial packaging have developed rapidly. According to statistics in 1997, paper products used in industrial packaging in China accounted for only about 1% of the total amount of packaging products, while Western developed countries accounted for about 15% of the total. In the past two years, China has made considerable progress in the packaging of industrial products with paper and wood, and liner packaging with paper and plastics. The main types of paper packaging products are honeycomb paperboard tray series and honeycomb paperboard packaging box series which are based on recycled kraft paper and are manufactured using modern electromechanical equipment. They are used to replace wooden pallets and wooden packing boxes; scraps of cardboard and scrap are used. Newspapers and Other materials are used as raw materials, and paper mold lining products produced by pulp molding machines are used instead of foamed plastic products. However, these paper-based packaging products, especially the paper-mold lined packaging products, are weaker than the plastic foam packaging products, and their strength is poor. In shipping and humid environments, paper-molded products tend to absorb moisture and reduce their strength. Therefore, it is necessary to solve the problem of the reinforcement and waterproofing of paper packaging products.
There are four major factors that affect the strength of paper-based packaging products:
1 the strength of the fiber itself;
2 The strength of bonding between fibers and fibers;
3 fiber-bound surface area;
5 The distribution of bonds.
For the above four factors, the solutions are:
First, in the pulping process, medium and thick long fibers are used for viscous beating. Medium-strength pulping refers to a beating method carried out in medium-strength pulping equipment with a beating concentration of 4-6%. The long-fiber viscous beating method requires that the fibers be cut as much as possible so that the fibers retain a certain length. , And a high degree of defibrillation, with a good swelling and hydration of a beating method. The advantages of this beating method are:
1 less fiber cut, more distortion and good finished product strength;
2 When the strength of paper products is the same, pulping degree and water retention value are low, and the dewatering performance is better;
3 Beating time is shortened, energy consumption is reduced, equipment performance is improved, and product cost is reduced. The medium-strength pulping can save 20-30kw hîž„t dry pulp because of the reduction of concentration and dilution.
2. Dissolve after pulping. At present, most manufacturers only have the pulping process without pulping and deliming processes, which makes the finished fiber lack the conditions for increasing the strength portion. Although the time required for the paper material to pass through the disintegration machine is only a few seconds, the pulverization of the pulverized pulp by the hydraulic pulper is cut off, disentangled, and finely fibrillated by the disintegrator, which can not only make the paper product cloth uniform but also increase the finished product. strength.
Third, add enhancer to increase the strength of the product; add waterproof agent to increase the product's waterproof and moisture resistance.
There are two methods for enhancing the chemical additives of paper products, one is an internal reinforcing agent and the other is a surface reinforcing agent. Intensifiers for internal use are divided into dry enhancers and wet enhancers.
Reinforcing agents used to increase packaging products for pulp molded industrial products generally use dry reinforcing agents. Dry reinforcing agents are fine chemicals that are used to increase the bonding between fibers to increase 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, they can form hydrogen bonds with the hydroxyl groups of cellulose, which can meet the requirements for the enhancement of paper products.
Commonly used dry enhancer species are: cationic starch, anionic starch, amphoteric starch, multiple starch and ionic polyacrylamide.
Cationic starches and multiple starches (including amphoteric starches) are good retention aids for filter aids and are good dry enhancers. Its strengthening principle is mainly through the electrostatic attraction between the cationic groups in the starch and the negative charges on the surface of the fiber, which attaches to the surface of the fiber and adsorbs to the fiber through a hydrogen-bonded bridge, so that the deuterated fibers form an adhesive between the fibers. The overall, so as to achieve the purpose of improving the strength of paper products.
The use of starch as a reinforcing agent, the amount is generally 1 ~ 2% of the dry pulp material, the starch can not be directly added to the pulp pool without gelatinization, the starch must be gelatinized, processed into a starch paste (no gelatinization conditions can be Purchased dextrin) before use. The method of gelatinization is:
1 In the gelatinization tank, first add a certain volume of soft water or clean cold water with low hardness, turn on the stirrer (60-100 rpm), and slowly add starch to fully disperse the starch. Generally, the gelatinization concentration is 5%, and then the direct steam heating, but the steam pressure can not be opened too high, to prevent high-temperature steam degradation of starch. If you can use steam heating between the better. With continued stirring, the temperature was raised to 90-95°C to make it a gelatinized liquid, and it was kept at this temperature for about 20 minutes. This step is very important, and we must also pay attention to the starch that is not fully gelatinized, because the starch particles are not fully dispersed and influence the use 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 After gelatinization, the starch paste should be diluted in time (concentration of 1-2%). The diluted starch paste is best used in time. If it needs to be stored for a period of time, it must be kept at a temperature of about 65°C. , otherwise the starch paste is prone to ageing and stratification may affect the effect of use.
(3) The gelatinized starch paste should not be continuously agitated, especially high-speed stirring, so as to prevent the molecular chain of the paste from being sheared and destroyed.
5 Gelatinized and diluted paste can be added to the slurry pool.
Fourth, in order to increase the strength of paper packaging industry packaging products and waterproof moisture problem, after adding the starch paste, add a cardboard water-resistant reinforcing agent, the amount of starch added to the dry weight of 5% (directly added to the starch paste evenly ). The honeycomb paperboard substrate and the pulp molded product processed through this processing process have the advantages of water resistance, moisture resistance, smoothness, firmness, pressure resistance, impact resistance and the like.