Raw materials for chipboard

The raw materials for making particle board include wood or wood fiber materials, adhesives and additives. The former accounts for more than 90% of the dry weight of the board. Wood raw materials are mostly taken from felled timber in forest areas, small-diameter timber (the diameter is usually below 8 cm), harvesting residues and wood processing residues. Processed into flakes, strips, needles, granular wood chips, wood shavings, wood wire, sawdust, etc., called scrap. In addition, non-wood materials such as plant stalks and seed hulls can also be made into plates, and the name is often named after the materials used, such as hemp stalk (shaving board) board, bagasse (shaving board) board, etc. Adhesives mostly use urea-formaldehyde resin glue and phenolic resin glue. The former has a light fat color and a low curing temperature. It has a good bonding effect on various plant materials such as wheat straw and rice husks. The hot pressing temperature is 195-210 ° C. It is widely used in production, but has the disadvantage of releasing free formaldehyde to pollute the environment.

The shape of the shavings is the decisive factor for the quality of the particle board, so first of all, qualified shavings must be manufactured. The wood shavings remaining in the wood processing can be used as the core layer of the particle board after reprocessing. The surface shavings are mainly processed and made from high-level residues (timber truncation, board edge, etc.) in harvesting or processing. The length, thickness and width of shavings vary according to the production method and the core layer or surface layer. Processing equipment for preparing shavings includes chippers, re-crushers, sanders and fiber separators, and cutting methods include cutting, cutting and crushing. In order to obtain high-quality wood shavings, it needs to go through the process of primary crushing, grinding, crushing and sieving.

The processed wood shavings have an initial moisture content of approximately 40 to 60%, a core layer of 2 to 4% and a surface layer of 5 to 9%. Therefore, it is necessary to use a dryer to dry shavings with different initial water content to achieve a uniform final water content. The dried wood shavings are then mixed with liquid glue and additives. Generally, 8-12 grams of sizing is applied per square meter of surface area of wood shavings. After being sprayed from the nozzle, the rubber material becomes particles with a diameter of 8 to 35 microns, forming an extremely thin and uniform continuous rubber layer on the surface of the shavings. Then sizing the shavings into a slab, the thickness of which is generally 10 to 20 times the thickness of the finished product. It can be pre-pressed and hot-pressed. The pre-pressing pressure is 0.2 to 2 MPa, and it is carried out with a plate press or a roller press.