Advantages and weaknesses of pulp molding products

At present, the water proofing agents used in paper pulp molding products are mainly rosin, iron sulfate and cationic starch, which are attached to the surface of paper fiber ions and strengthen the adhesion between ions.

5. Molded pulp molding products mainly use vacuum adsorption forming method, forming is to prepare the fiber slurry on the mold with metal mesh by vacuum adsorption forming (product shape), and remove a lot of water. According to the mold sizing method can be divided into grouting type and suction type two categories, grouting molding machine is the earliest used for the production of pulp molding tableware, and suction molding machine is the future development direction of pulp molding packaging container molding equipment.

The working procedure is: punch down to the slurry pool → vacuum suction → punch up → punch up → die closure pressurization and dewatering → die transfer billet moving up and blowing → mold release.

The forming principle is: the slurry is filled in the slurry pool, and the net die is fixed on the concave die. Through the flow of the slurry in the slurry tank and the movement of the die in the slurry tank, the slurry is stirred to make the slurry uniform. When the die is moved down to the liquid level of the slurry tank, the slurry is deposited on the mesh mold through vacuum suction, and then it is moved out of the slurry tank and closed with the punch, and the billet with higher dryness is obtained by pressurization and dehydration.

The thickness of the molded product can be controlled by controlling the suction time during the molding process. Since the strength of the vacuum adsorption in each direction is the same, the thickness of the resulting pulp molded product should theoretically be uniform.

However, during the suction process, due to the flow rate of the slurry and gravity, there may be uneven thickness of the molded product.

6. Shaping refers to the process of heating, pressurizing and dewatering the wet paper blank directly after forming it. The wet paper blank is dried and set in the mold by shaping. The product processed by the mold has smooth and beautiful surface, accurate size, solid and good rigidity. Pulp molding disposable fast food utensils are made of this mold.

In the process of industrial packaging, some small, precise, large number of small items are packaged in a multi-layer stacked way, and the packaging products used for positioning between each layer need to be shaped if the pulp molding products are used to manufacture. The general industrial packaging products are single-sided work without shaping, wet paper billet directly into the dryer to dry.

7. Due to the filtration resistance of the fiber layer, the dryness of the wet pulp molded by vacuum adsorption can usually only reach 20% to 30%, and the wet blank can only meet the requirements after heating and drying, and the final dryness of the general pulp molded products should reach more than 90%.

Because the wet paper blank will have different degrees of deformation after drying or drying, it must be rounded when the appearance, shape and precision of the product are high. The water content of paper molding products before finishing is 20% ~ 30%, but it is difficult to accurately control the water content of paper molding products in production applications. If the water content is too high, the molding process will consume high energy and take a long time, and if the water content is too low, the molding will become very difficult.

In the process of molding, the general hot pressing temperature is controlled between 150 and 180 ° C, which can be moderately adjusted according to the size of the product, but the hot pressing temperature can not be less than 135 ° C.

8. Auxiliary process Auxiliary processes mainly include integral trimming, sterilization, product packaging, inspection, etc. Shaping and trimming is to correct the shape of the dried products, calender, remove the net marks left by the mold mesh molding, so that the internal and external surfaces are smooth and smooth, and can be pressed on some words and patterns according to different customers and use requirements, while cutting the burrs on the edge of the product, pressing the indentation that is easy to fold and open the lid.

Sterilization is one of the processes that distinguish food packaging containers (such as egg cartons) from ordinary pulp molding products. At present, there are three main methods for the sterilization of finished products: First, the tunnel type ozone sterilization machine is used to carry out final sterilization of finished products; The second is to sterilize the finished product with ultraviolet light; The third is the use of high temperature drying channel sterilization.

After the dried or finished products are inspected for quality, they are collected, stacked, counted, and packaged in the required quantity, thus completing the entire production process of pulp molded products. The production of pulp molding products, after forming and drying, has more raw edges, irregular appearance and beautiful appearance, and sometimes it is necessary to cut edges to ensure that the product appearance is neat and beautiful.