The entire process involves fiber separation, slurry treatment, slab forming, hot pressing, and post-treatment. First, let’s talk about fiber separation, which is also known as pulping. It's the process of breaking down raw materials into individual fibers. There are primarily two approaches to this—mechanical and explosive methods. Within the mechanical category, we have thermal mechanical, chemical mechanical, and purely mechanical methods. For instance, the thermal mechanical method uses heat—either hot water or steam—to soften or partially dissolve the intercellular layers of fibers, making them easier to separate under pressure using machinery. Afterward, these fibers go through a disc refiner for further refinement. Dry fiberboard usually skips this step. This method results in fibers that are strong, well-draining, and retain their natural structure with minimal loss in length. Softwood pulp from this method can achieve yields up to 90-95%. However, finer grinding does shorten the fiber length, increases its surface area, and enhances its swelling properties, making it softer and more pliable.
The thermomechanical method is widely adopted in both domestic and international fiberboard industries due to its efficiency and cost-effectiveness. Meanwhile, the chemical mechanical method employs a small amount of chemicals like caustic soda or sodium sulfite to weaken lignin and hemicellulose before mechanical separation. On the other hand, the pure mechanical method directly crushes soaked raw materials into water, but this approach isn't commonly used. Lastly, the explosive method heats raw materials under high pressure (around 4 MPa) briefly to soften lignin and partially break down carbohydrates, followed by a sudden release of pressure to blast the material into fluffy fibers or fiber bundles. Next comes slurry treatment, where the fiber mixture undergoes various treatments depending on the intended use of the final product. These include water resistance, reinforcement, fire retardancy, and防è…处ç†. Hard and semi-hard fiberboards typically receive paraffin emulsion to enhance water resistance, whereas soft boards may use either rosin or a combination of rosin and paraffin-rosin emulsions. Waterproofing agents can be applied either in the slurry tank or a continuous glue box. Reinforcement often utilizes water-soluble adhesives like phenolic resins for harder boards. Fire-retardant treatments usually involve adding compounds like FeNH4PO4 or MgNH4PO4. Antiseptics such as pentachlorophenol or its copper salts are added for preservation. Once treated, the slurry is either dried for later use or sent directly to a forming machine for wet forming, creating slabs with predefined specifications and initial compaction.
For dry fiberboard production, hot pressing requires a moisture content between 6-8%, meaning the slurry must be dried beforehand. This can be achieved via two-stage pipe airflow drying. The first stage operates at temperatures around 250-350°C for 5-7 seconds, reducing moisture significantly, while the second stage lowers the temperature to 140-150°C until the moisture reaches the desired level. Drying equipment varies from straight tube, pulse, to casing types. Slab forming comes next, available in both wet and dry forms. Most softboards and some hardboards use the wet method, whereas medium-density boards and others opt for dry forming. Wet forming uses low-concentration slurries that gradually lose water to form slabs. Common techniques include box-frame molding, long-net molding, and rotary-net molding. Box-frame molding pumps a 1% concentrated slurry into a bottomless frame placed over a net, employing vacuum and pressure to remove excess water. Long-net molding resembles paper-making processes, where the slurry (1.2-2%) is poured onto a long net, naturally draining water by weight, vacuum, and rollers, leaving the slab with 65-70% moisture. Rotary-net molding similarly draws the slurry onto a circular net via vacuum, shaping and controlling the slab thickness. Waterborne epoxy emulsion is used for a new type of epoxy resin coating which is formed by mixing epoxy resin with water and stabilizing it with emulsifier. Compared with traditional solvent based epoxy coatings, waterborne epoxy emulsion has the advantages of environmental protection, non-toxic, tasteless, easy cleaning, easy construction, etc. At the same time, waterborne epoxy emulsion also has excellent film performance, with high hardness, abrasion resistance, chemical corrosion resistance and water resistance, and is widely used in the fields of architecture, automobile, electronics, furniture, etc. water based epoxy dispersion,non-ionic epoxy dispersion,epoxy for industrial coating,industrial paint use epoxy emulsion Shanghai Na Long Tech Co., Ltd , https://www.na-long.com