Paper pulp molding production process Paper molding production process includes waste paper sorting, shredding, slurry preparation, pulp sizing, blending slurry (concentration), product molding, product cold extrusion, product drying and product finishing, etc. .
Waste paper is one of the main raw materials for the production of injection-molded products. It is necessary to carefully classify and eliminate various kinds of adulterants by using hydraulic attritors and sorters (waste newspapers, corrugated cardboard packaging, scraps, etc.). . Grinding waste paper can be realized either in an intermittent beater or in a continuous grinder or refiner. The sorted and purified waste paper is ground and smashed into a uniform pulp.
In the grinding process, several raw materials can be quantitatively added to the slurry according to the designed slurry ratio. Pulp sizing is used to improve the resistance to liquid penetration of injection molded parts. For paper-type packaging products, the sizing agent is generally a loose period, paraffin emulsion or rosin paraffin paste. Tests have shown that in order to obtain high-quality articles, rosin gum equivalent to 3% of pulp dry fiber must be added to non-bonded waste paper pulp, and 1.5% should be added to bonded waste paper pulp. - 2% rosin gum.
Mix the concentration in an open water bath heater with a stirrer. After adding soda ash or caustic soda and dissolving it, slowly add the rosin block of appropriate size and heat the solution to a temperature of 100-105Â°C. Stirring is continued for 3-4 hours until carbon dioxide no longer escapes. The glue should be uniform and free of clots. When checking with eyesight, a wooden spatula is used to pick up the glue and the glue flows down into a sheet.
After boiling, the gum should be oscillated in another intermediate container and slowly cooled, and then diluted with water to a suitable concentration. In the process of self-made pulp, the diluted glue is added to the pulp in the beater or agitating tank. In order to make the glue easy to adhere to the pulp fiber, an appropriate amount of aluminum sulfate solution having a concentration of 10% should be added. The degree of adherence of the rubber material to the pulp fibers is sufficient, depending on the pH of the medium. Generally, this value should be 4.5-5.0.
If necessary, give the pulp a certain single color, because there are various kinds of printing content on the waste paper, so that the injection-type parts do not have a single color. Unlike cardboard production, pulp sizing concentrations for the production of molded products should be relatively high, approximately 1-2%.
Molded products can be molded in three ways: vacuum molding, hydraulic molding, and compressed air molding. In practice, one of the above methods or as much as possible a combined method can be used to increase the production efficiency.
After filling the pulp with the model and the upper volume of the housing, the water will be discharged through the metal mesh wall of the model, and the fibers are attached to the surface of the mesh model. After molding is completed, the model is raised by means of a hydraulic cylinder, the product is taken out after compaction and transferred to the drying process. The compaction of the parts is achieved in special presses organized by upper and lower dies.
The structure of the press machine should ensure that the parts are not stretched in real time, otherwise it will cause the wall rupture. This equipment works on the principle that the parts are only compressed during the entire pressing process. In order to discharge the water from the place where it is pressed, it is necessary to have vacuum suction equipment.
Due to the different degree of extrusion, the moisture content of the parts is 50%-75%, and the moisture content should be reduced to 10%-12% through the drying process, and can be reduced to 3%-4% in some cases. Drying of the product is carried out in a drying oven that operates on a continuous or continuous basis. The product is placed on a shrink-proof model and fed into a drying oven. The product is dried with hot air. The temperature starts at 250-300Â°C (the product has a 50% reduction in moisture content within 7-10 seconds), and then the temperature drops to 100-105. Â°C. The continuous drying furnace has a conveying device. The pieces pass through different temperature zones in the furnace and are finally dried to a moisture content of about 10% to about 12%.
The production process of paper molding products has been accompanied by dehydration, from gravity dehydration, vacuum dehydration, press dehydration, to the final thermal dehydration, ie drying. Vacuum dehydration and press dewatering remove most of the water from the product. The remaining water must be dehydrated by heating and drying.
After drying, the use of extrusion on the hot post-forming machine is more compact, which is necessary for uniform thickness of the wall of the injection-type packaging product, smooth outer surface, and increased wall strength. Paper mouldings can be used after drying, but sometimes special treatments such as calendering, paint baking, or pattern printing on the surface are required.
Pulp molded products are used in the production of fast food products and packaging products are different in the process. Such as: disposable fast food requirements require water and oil, to meet the stiffness requirements, in line with health standards, the appearance of printing trademarks, smooth surface inside and outside clean. The general shape of the packaging products is relatively large and complex, and requires a bearing capacity, a buffer function, and a positioning function. Based on these special requirements, it is determined that the process characteristics of paper-type packaging products are: regardless of the complexity of the shape of the products, the wall thickness of the same product must be the same. Only in this way can the requirements of molding and shaping (or drying) of the products in the production process be met. .
The packaging of industrial products is sometimes not too high in size and shape accuracy, and requires certain strength and cushioning. Therefore, industrial packaging of pulp molded products seldom requires stereotypes. After the molding machine is down, it is dried and molded by the dryer. This kind of drying method changes the shape and size of the product due to the precipitation of moisture from the wet paper blank. Accumulating empirical data and grasping the change law in this regard can be used as the basis for future mold design.
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