The unique properties and shortcomings of pulp molding products

1. Process process Under normal circumstances, the production process of pulp molding products is shown in Figure 1. The production process can be changed according to the different requirements of customers for products, mainly including slurry preparation, molding, hot press setting, setting, molding and packaging and other auxiliary processes.

2. Raw material selection of pulp molded products The sources of pulp molded products are mainly divided into: Pulp, straw pulp and reed pulp, generally bleached commercial pulp (for fast-food boxes) or waste paper (for industrial packaging), will not produce secondary pollution in the production and use process, the product has the advantages of light weight, pressure resistance, earthquake resistance, good buffer performance, anti-static, strong air permeability and good recyclability. As a packaging product, it can replace polystyrene foam (EPS) for disposable fast food boxes, various electronic products, handicrafts, medical devices, mechanical equipment parts, poultry eggs, fruits, flowers, glass products, ceramic products and other fragile products.

Pulp molding products are generally divided into fast food boxes and industrial inner packaging, the production method is basically the same, but the raw materials used for the production of fast food boxes are bleached commercial pulp, quantitative and specification indicators are more strict, and sterilization, waterproof and oil-proof treatment, equipment and pipelines are mostly stainless steel and plastic materials, storage pool wall lined with tiles, The plant and operator health requirements are also higher.

3. Pulping Pulping is the first process in the production of pulp molded products. The pulping process includes: the pulp board is broken into fiber pulp with a hydraulic pulper, the broken fiber pulp is screened, sand removal and purification treatment, and then the fiber is properly spun by the pulper to improve the binding force between the fibers.

In the pulping process, strict control of the beating degree of various slurps is very important for the product molding and product quality of the following process. The beating degree is too high, when the product is vacuum adsorption molding, it will produce water filtration difficulties, and after drying by the drying channel, the product will produce a large shrinkage deformation (except for mold drying). If the beating is too low, the combination strength of the product is low, and the stiffness and compressive strength of the product will be greatly reduced, which will affect the performance of the product. Therefore, the corresponding beating degree should be determined according to the selected slurry, the proportion of the slurry, and the amount of beating required.

The equipment used in the pulping process of paper pulp molding products mainly includes hydraulic pulper, fiber desanding machine, cone desander, beater (or pulper) and pulp pool and other general equipment in the paper industry. For relatively simple and small scale production processes, only the use of hydraulic pulper and slurry tank can also meet its general production requirements.

4. Matching pulp is to add fillers, pigments, and functional additives such as waterproof and oil repellent to the purified and treated slurry, and to prepare the slurry suitable for the quality requirements of the product, and sometimes to control the pulp concentration. In order to ensure the continuous production process and the evenness of the product, it is necessary to control the liquid level height in the slurry storage tank and the slurry distribution tank, and to add fillers, water and ingredients regularly and quantitatively.

Pulp molding products according to the requirements of enterprises can choose to add waterproof, oil-proof and other functional additives. 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.