Requirements and production process of raw materials for impregnated laminated veneer plywood and blockboard
1.1 Substrate Requirements
Plywood and blockboard substrates should meet the requirements of GB/T 9846-2015 General Plywood and GB/T 5849-2006 Blockboard respectively. The following aspects should be noted:
1) The thickness of the base material should be uniform and the surface of the board should be smooth and smooth, otherwise sanding treatment should be carried out.
2) The appearance quality of both sides of the base material should meet the requirements of GB/T 9846-2015 grade I products, and the bonding strength should meet the requirements of class II plywood.
3) The moisture content of the base material is an important index. The low moisture content of the base material results in the decrease of the bonding strength of the surface of impregnated adhesive paper veneer plywood and blockboard, and the defects of surface dry flower, etc. The moisture content of the base material is too high, and the defects of bubbling, stratification and wet flower are easy to occur during hot pressing, so the moisture content should be controlled at 6%-16%.
4) The surface of the base material should be the whole veneer as far as possible. If splicing is used, the seam should be tight. Otherwise, the seam defects will be reflected on the surface of impregnated plywood and blockboard.
Requirements for 1.2 Sheet
The sheet covers between the base material and the impregnated film paper, which plays a role in covering the defects to a certain extent. Generally including veneers, decorative veneers (commonly known as science and technology wood). Thin plate requirements: 1) uniform thickness; 2) basically no defects on the surface, color is basically the same; 3) seamless whole; 4) moisture content to meet 6% – 16%.
Requirements for 1.3 Impregnated Film Paper
Generally speaking, considering the operation and use of impregnated film paper, most manufacturers usually use the second impregnation method, that is, the first impregnation of urea-formaldehyde resin on decorative paper, after drying, and then spraying melamine resin on the surface.
The physical and chemical properties such as volatile content, pre-curing degree and formaldehyde emission of impregnated paper directly affect the quality of eco-board products. The volatile content of impregnated film paper is low, and it is easy to produce dry flowers; the impregnated amount is insufficient, it is easy to produce surface pore and poor wear resistance; the volatile content of impregnated film paper is high, and it is easy to produce uneven surface luster; the fluidity of impregnated film paper adhesive is poor, the sealing ability of the adhesive is poor, and it is easy to cause poor surface pollution resistance and surface water vapor resistance. Poor performance.
2. Production process of impregnated laminated paper veneer plywood and blockboard
2.1 Production process of direct veneer
Impregnated laminated paper+sheet+blockboard/plywood base material, i.e. one-time lamination method, the production process is shown in Figure 1.
2.2 Production process of overlay veneer
The impregnated film paper is first hot pressed with the sheet, and then pressed onto both sides of the substrate, i.e. the “secondary coating method”. The production process is shown in Fig. 2.
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