Fiberboard basic process content
It is fiber separation → slurry treatment → slab forming → hot pressing → post-treatment. 1 fiber separation. Also known as pulping, it is the process of separating pulping materials into fibers. The fiber separation method can be divided into two major categories: mechanical method and blasting method, wherein the mechanical method is divided into thermal mechanical method, chemical mechanical method and pure mechanical method. The thermal mechanical method first treats the raw materials with hot water or saturated steam to soften or partially dissolve the intercellular layers of the fibers, and separate them into fibers by mechanical force under normal pressure or high pressure, and then finely grind through a disc refiner ( Dry fiberboard pulping is generally not refined. The fiber pulp produced by this method has complete fiber shape, strong interlacing, good water drainage and high yield. The yield of softwood pulp can reach 90-95%. The power consumption is small; the length of the fiber is shortened after the fine grinding, the specific surface area is increased, the outer layer and the end portion are deuterated, the water swelling property is improved, the softness, the plasticity is increased, and the interlacing property is good. Therefore, the thermomechanical method is the main pulping method used in the domestic and foreign fiberboard industries. The chemical mechanical method uses a small amount of chemicals, such as caustic soda, sodium sulfite, etc. to pretreat the raw materials, so that the lignin and hemicellulose are damaged or dissolved to some extent, and then separated into fibers by mechanical force. The pure mechanical method is to directly pulverize the fiber raw material into water after being soaked in water, and according to the shape of the raw material, it is divided into a log refining method and a wood chip refining method, and the method is rarely applied. The blasting method is to heat the raw material in a high-pressure vessel with a pressure of 4 MPa for a short time (about 30 seconds) to soften the lignin, partially hydrolyze the carbohydrate, and then raise the vapor pressure to 7-8 MPa, keeping 4 to 5 seconds, then quickly start the valve, the fiber raw material is blasted into floc fiber or fiber bundle. 2 slurry treatment. That is, according to the use of the product, waterproofing, reinforcement, fire resistance and anti-corrosion treatment are separately carried out to improve the performance of the finished product. Hard and semi-hard fiberboard pulps should be treated with paraffin emulsion to improve water resistance, while soft board pulp can be used with both rosin and paraffin-rosin emulsions. The application of the water repellent can be carried out in a slurry tank or a continuous glue box. The reinforcing agent used for the reinforcement treatment is soluble in water, can be adsorbed by the fiber, and can be adapted to the hot pressing or drying process of the fiberboard, and the hard fiber board is mostly made of phenolic resin glue. Refractory treatment to apply refractory agents such as FeNH4PO4 and MgNH4PO4 is more common. The addition of pentachlorophenol or pentachlorophenol copper salt to the slurry serves as an antiseptic. The treated slurry is dried or dried for drying; or after being adjusted to a concentration, it is directly introduced into a molding machine for wet forming to form a wet slab having a certain specification and having a preliminary compactness. Dry production of fiberboard requires a fiber moisture content of 6 to 8% at hot pressing, and a slurry moisture content of 40 to 60% after sizing, so it is necessary to dry before molding. The fiber drying can be carried out by two kinds of pipe airflow drying methods: the first drying method temperature is 250-350 ° C, the time is 5-7 seconds; the second-stage drying method first temperature is 160-180 ° C, and the water content is reduced to 20%. The second stage temperature is 140-150 ° C, the water content is reduced to 6-8%, and the total time of the two-stage drying is about 12 seconds. The drying equipment has three types: straight tube type, pulse type and casing type. 3 Slab forming has two types of wet forming and dry forming. The soft board and most of the hard board are formed by wet method; the medium density board and some hard boards are dry formed. The low-concentration slurry for wet forming is gradually dehydrated to form a slab. The basic methods include box-frame molding, long-net molding, and round mesh molding. The box frame molding is to pump the slurry with a concentration of about 1% from the slurry pump into a bottomless box frame placed on the pad net, vacuum dewatering at the bottom of the box, and pressure dehydration at the top of the box frame. This method is mainly used for production. Soft fiberboard. The equipment used for long net forming is similar to the long net paper machine in the paper industry. The 1.2~2.0% concentration slurry is copied from the net front box to the long net, and the wet slab is formed by self-weight dehydration, vacuum dehydration, and roller press dehydration, and the water content is 65-70%. Rotary net forming is also transplanted from the paper industry. In the production of fiberboard, vacuum single-web type is used. The slurry concentration is 0.75~1.5%. It is adsorbed on the circular net by vacuum working slurry and dehydrated by roller. And control the thickness of the slab.
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