Fiberboard production technology
raw material
The basic unit constituting the fiberboard is a separate wood fiber or fiber bundle. The raw materials for fiber production mainly come from forest harvesting residues, such as branches, tips, small diameter materials, etc.; and wood processing residues, such as edge, shavings, sawdust and so on. In addition, wastes from chemical processing of forest products (such as silicone and hydrolyzed residues) and other plant stems can be used to make fibers. The fiber content of the softwood is high, and the fiber length is 30 to 50% longer than that of the broadleaf. If hardwood is used, it must be treated first: it can be mixed with needles and hardwoods, or chemically treated with wood chips. Hot water and steam can also be used. Before the fiber separation, the raw material was cut into pieces of 20 to 30 mm, 3 to 5 mm thick, and 15 to 25 mm in width by a chipper. The wood chips are too large, and it is difficult to soften or soften unevenness during the pre-heat treatment and refining process, and the fiber separation degree is small; when the wood chips are too short, the proportion of the fibers to be cut is large, and the interlacing performance is poor, resulting in a decrease in the strength of the fiberboard. The cut wood chips are sent to the silo after screening, re-crushing, washing, etc., in preparation for fiber separation.
Production Process
There are three types of wet, dry and semi-dry methods. The wet production process uses water as a carrier for fiber transportation. The mechanism is to make a certain strength by using the fibers intertwined to produce friction, the binding force between the fibers on the surface of the fibers, and the binding force generated by the fibers. Fiberboard. The dry production process uses air as the fiber transport carrier. The fiber is prepared by a single separation method. Generally, the resin is not subjected to fine grinding, and the adhesive is applied. The fiber is dried before the slab is formed, and is usually not heat treated after hot pressing into a plate. Same as wet method. The semi-dry process is also formed by air flow, the fiber is maintained at a high water content without drying, and the rubber is not used or used, so the semi-dry method overcomes the main disadvantages of the dry and wet processes and maintains some of its advantages.
Basic process content
It is fiber separation → slurry treatment → slab forming → hot pressing → post-treatment (see picture).
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.
Click Vinyl Floor,Wood Flooring ,Vinyl Wood Flooring ,Luxury Vinyl Flooring
Plastic Floor Co., Ltd. , http://www.nbfloorings.com