I. Basic production process of pulp molding products
The base materials and additives of pulp molding products are the same as those of paper, and the technology is very close, except that the pulp molding products are formed on the mesh mold.
When the pulp passes through the web mold, the fiber is intercepted by the web mold, the water is filtered out, and the pulp fiber is formed according to the shape of the web mold. The pulp fiber is formed by the combination of hydrogen bonds between the fibers to form a wet paper billet. After drying or heat setting, the wet paper becomes pulp molded products. This is the basic process of pulp molding.
II. Characteristics of pulp mold
Pulp molding is the use of mold in the pulp state of paper products, so mold is the key to pulp molding technology.
The paper pulp molding is used to produce disposable fast tableware. As long as the box, bowl and plate are used, the shape of the product is relatively simple and has certain universality. When pulp molding is used in industrial inner packaging and other aspects, the products are relatively large, the shape is very disorderly, and each type is "seat to seat", there is no universality, so the mold planning and production should always be accompanied.
Pulp molded products are different from rubber and plastic products in the mold cavity. The pulp used in the forming of pulp molded products is an aqueous solution containing only about 10% fiber. It is necessary to ensure that most of the water flow off, so the pulp molded products forming mold is necessary to be mesh mold.
The forming of pulp molded products is a continuous process of draining a large amount of water out of the pulp. The paper products form a certain thickness on the mesh mold, so the product forming is necessary to form on the surface of a single convex or concave mesh mold. The forming process of pulp molded products is also a filtering process, with the thickness added, the filtering function decreases, and the thickness composition speed is lower As a result, the wall thickness of the products is synchronous. No matter how messy the shape of the products, the thickness of the walls is the same everywhere. After the pulp molding product is formed, it is a wet paper blank with moisture content of 70-75%, because the power to make the pulp face the mesh mold filtration is the vacuum degree, and the maximum strength does not exceed one atmosphere.
The wet paper blank of initial forming is adsorbed on the mesh die, and the wet strength is very low. It is necessary to place the wet paper blank in the cavity after die closing by another corresponding convex or concave die, and transfer it by air pressure. The paper pulp molding products are formed on a single convex or concave die, and then transferred in the cavity after die closing. Because of the particularity of pulp molding, it increases the difficulty of product planning and die planning.
III. key to structural planning
In addition to the strength and durability of paper products, pulp molding products can also be made into various disordered shapes according to the functional requirements. When it is used as disposable tableware, its shape is relatively simple and its strength requirement is not high. When it is used as industrial inner packaging, its shape is very disorderly. It is necessary to satisfy the three requirements of industrial inner packaging: first, positioning requirements. It is necessary for packaging products to ensure that the packed items have a fixed position in the packaging box. It is required that the shape of the packaging products and the packed items are synchronous, the contact is appropriate and the scale is accurate. Second, buffer requirements. All products shall have certain tolerance and flexibility, and the appearance shall be soft. In case of contact and conflict with the packed goods, the surface luster of the packed goods shall not be damaged, and the impact of bumping and vibration of the packed goods during transfer shall be eliminated. Third, bearing. The products are required to have certain strength and rigidity to support the package and accept external pressure. In order to satisfy the functional requirements of products, in addition to the selection of appropriate raw materials, additives and production processes, more importantly, structural planning.
(1) functional structure:
The forming process characteristics of pulp molded products decide that the same product can only have one thickness. In order to get used to the functional requirements, the cavity and vertical bar can be used when adjusting the strength and buffering, the cavity can add the elasticity and flexibility of the whole product, and the vertical bar can add the strength and rigidity of the product. In a relatively large plane with high bearing capacity requirements, it can be planned to be corrugated or honeycomb.
(2) technological structure: because of pulp molding
In the initial stage of product forming, it is a wet paper blank. In the production process, water should be separated gradually, and the shape, orientation and scale of the product will change greatly. In the same plane and direction of the product, the total shortening amount of the product is different. At this time, the product will warp or change the deformation. In order to adjust the deformation, only the structural shape is adopted for balance. The structural shape used to adjust the shortening deformation is called the technological structure of the product.
Pulp molding technology is the new born of the old paper industry, and pulp molding mold is the soul of this new born.
The article comes from: Zhongshan paper pulp molding http://www.jmyfbz.com/