Enhanced Waterproofing Technology for Pulp Molded Industrial Packaging Products

In the process of controlling "white pollution", the pulp molded products used for industrial packaging have developed rapidly. In recent years, China has made great progress in replacing wood with paper in the outer packaging of industrial products and replacing plastic with paper in the inner packaging. The types of paper packaging products mainly include honeycomb cardboard pallet series and honeycomb cardboard packing box series produced by recycled kraft paper as the base material and modern mechanical and electrical equipment, which are used to replace wooden pallet and wooden packing box. Paper mold lining products produced by pulp molding machines instead of foamed plastic products are made of leftover materials and waste newspapers. However, these paper packaging products, especially the paper mold lining packaging products, compared with plastic foam packaging products, the weakness is poor strength, in the sea and humid environment, the paper molded products are easy to absorb moisture, the strength is reduced, so it is necessary to solve the paper packaging products to strengthen and waterproof and moisture-proof problems.

There are four main factors that affect the strength of paper mold packaging products:

1. Strength of fiber itself;

2. bonding strength between fibers;

3. fiber bonding surface area;

4. Distribution of binding bonds.

For the above four factors, the solution is:

In the pulping process, the 1. uses a medium-thick long fiber viscous pulping method. Medium concentration pulping refers to a pulping method carried out in medium concentration pulping equipment under the condition of pulping concentration of 4-6%. The long fiber viscous pulping method requires to avoid cutting the fibers as much as possible, to keep the fibers at a certain length, and to carry out high filament brooming, which has good swelling and hydration. The advantages of this pulping method are:

① Less fiber cut, more distortion and deformation, good strength of the finished product;

At the same time, the pulp beating degree and water retention value are low, and the dewatering performance is good;

The beating time is shortened, the energy consumption is reduced, the equipment performance is improved, and the product cost is reduced.

Medium consistency pulping can save 20-30kwh/t absolute dry pulp by reducing the range of concentration and dilution.

Dispelling is carried out after the 2. is crushed. At present, most manufacturers only beating process and no pulping process, which makes the finished fiber lack of increased strength part of the conditions. Although the time for the paper material to pass through the dredging machine is only a few seconds, the pulp crushed by the hydraulic pulper is cut off, divided into filaments and fine fiber by the dredging machine, which can not only make the paper products uniform, but also increase the strength of the finished product.

Reinforcing agents are added 3. to increase the strength of the product; waterproof agents are added to increase the waterproof and moisture-proof properties of the product.

There are two methods for chemical additives to enhance paper products, one is internal reinforcement and the other is surface reinforcement. Internal enhancers are divided into dry enhancers and wet enhancers.

The reinforcing agent used to increase the packaging products of pulp molding industry generally uses dry reinforcing agent. Dry strengthening agents are fine chemicals used to promote bonding between fibers to increase the physical strength of the paper product without affecting its wet strength. This kind of chemical has a certain molecular weight of the active group, because of its own colloidal molecules binding strength can form hydrogen bonding with the hydroxyl of cellulose, can achieve the requirements of paper products to enhance.

The commonly used dry enhancers are: cationic starch, anionic starch, amphoteric starch, polyfunctional starch and ionic polyacrylamide.

Cationic starches and polystarches (including amphoteric starches) are both good retention and drainage aids and good dry enhancers. Its reinforcement principle is mainly through the starch in the cationic groups and the electrostatic attraction between the negative charge on the fiber surface and attached to the fiber surface and with the fiber through the hydrogen bond bridge adsorption, so that the formation of a network of fibers between the whole glue, so as to achieve the purpose of improving the strength of paper products.

The application of starch as a reinforcing agent, the amount of dry pulp material is generally 1 to 2%, without gelatinization treatment.

The starch cannot be directly added to the slurry pool. Starch must be gelatinized and processed into starch paste (no

Can buy dextrin with gelatinization conditions) before it can be used. gelatinization method is:

Add a certain volume of soft water or clean cold water with low hardness into the gelatinization tank, start the mixer (stirring speed is 60-100 rpm), and then slowly add starch to fully disperse the starch. Generally, the gelatinization concentration is 5%, and then the steam is directly heated, but the steam pressure cannot be opened too high to prevent the high temperature steam from degrading the starch. If you can use indirect steam heating better. With continued stirring, the temperature was raised to 90-95 ° C. to form a gelatinization solution, and the temperature was maintained for about 20 minutes. This step is very critical, should also pay attention to the starch paste is not completely, because the starch granules are not fully dispersed meeting affect the use effect. However, the holding 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.

The starch paste liquid after gelatinization should be diluted in time (the concentration is 1 ~ 2%). The diluted starch paste liquid is best used up 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 liquid is easy to age and stratification will affect the use effect.

③ Do not continue to stir the starch paste after gelatinization treatment, especially to prevent high-speed stirring, in order to prevent the molecular chain of the paste from being shear damaged. The paste liquid after gelatinization and dilution can be added in the slurry tank.

4. In order to increase the strength and waterproof and moisture-proof problems of paper mold industrial packaging products, a cardboard water resistance enhancer is added after starch paste liquid is added, and the addition amount is 5% of the dry weight of starch (it is also possible to directly add starch paste and stir 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 and impact resistance.