1.1 Paper quality and impregnation process
To ensure the quality of impregnated adhesive film paper, high-quality decorative base paper must be used. No matter what kind of paper is used, it should be used after passing the incoming/temporary inspection. Unqualified paper must not be left on the production line. During the impregnation process, the operation shall be carried out in strict accordance with the process requirements, and sampling inspection shall be conducted every half an hour to ensure that the glue application amount is within 130% - 150%, the volatile content is 6% - 7%, and the pre solidification degree is ≤ 65%; The impregnated and dried adhesive film paper should be immediately packaged with plastic film and sealed with adhesive tape; Store in an air-conditioned warehouse with a temperature of 20-25 ℃ and a humidity of 55-65%. The storage time should not exceed three doors; When using, the principle of using and opening should be followed. Paper that cannot be used up at a time should be immediately sealed and sent to the warehouse for storage, to prevent moisture absorption causing adhesive film paper to stick together and become unusable, causing unnecessary losses.
1.2 Base material quality
The base materials for veneered wood-based panels are commonly medium density fiberboard and particle board. For particle board, it should be purchased according to different customer requirements, but particle board products must meet the requirements of GB/T4897-92 first-class products.
Quality requirements for substrate:
(1) The board surface shall be flat and clean, free from water and oil stains, and there shall be no sliding edges, gnawing heads, etc. within the effective size;
(2) The thickness deviation of the plate should not exceed ± 0.2mm, and the sanding should be uniform, without sand leakage;
(3) The moisture content of the plate should be controlled within the range of 6% - 10%. Due to the fact that particleboards are mostly purchased externally, changes in the environment can lead to
Change in moisture content of the starting plate. If the water content is too high, it may lead to phenomena such as blasting and layering during the veneering process; If the moisture content is low, or the volatile content of impregnated paper is low, it may cause the surface to not be well wetted during hot pressing, resulting in cardboard delamination. Therefore, during the production process, it is necessary to observe at any time and timely remove unqualified base materials.
1.3 Hot pressing process
The three elements of the hot pressing process are interdependent and mutually constraining, and unified analysis and adjustment are required during process adjustment. The three factors have different effects on the laminate, and the hot pressing temperature mainly plays a catalytic role in the chemical reaction of the impregnated resin, i.e., accelerating curing. According to the actual requirements of production and the author's experience, the temperature of the hot pressing plate is more suitable at 145~165 ℃. High temperature is conducive to demolding after pressing, and can shorten the hot pressing period and increase production. However, too high temperature prevents the resin from uniformly flowing and solidifying, resulting in small pores on the board surface. According to the national quality inspection data of impregnated adhesive film paper faced wood-based panels in 1998, a considerable number of enterprises have shortened the hot-pressing time by increasing the hot-pressing temperature in order to achieve the goal of increasing production. As a result, the panel surface is prone to rebound and is not smooth. It seems to have increased production, but in fact it is at the expense of product quality, which also has an impact on regular product manufacturers.
Appropriate pressure can ensure a good bonding between the substrate and the impregnated paper. Under the action of appropriate temperature and pressure, the resin in the impregnated paper melts and cures, forming a closed and dense surface. It can also fill uneven and micro pores on the substrate surface. Generally, the pressure is generally 2.0 to 3. OMPa. On the premise of not affecting the product quality, it should be as low as possible, which is beneficial to the service life of the equipment, hydraulic oil, and the internal structure of the substrate; However, too low pressure affects the adhesive strength and resin flow ability of the substrate and the impregnated paper. Therefore, in actual production, the unit pressure should be appropriately adjusted for different substrates and buffer pads, depending on their newness and obsolescence.
The length of hot pressing time depends on the curing speed and hot pressing temperature of the impregnating resin, and is generally suitable in the range of 40 to 50 seconds. Prolonged time can cause excessive resin curing, loss of elasticity, and easy to cause cracks or internal stress in the product, resulting in cracks and warpage during subsequent processing; If the time is too short and the resin is not cured sufficiently, it is easy to produce plate adhesion, and affect the physical and chemical properties of the product surface, affecting the durability of the product. The time required for different materials is different, so the curing degree of each new product's board surface should be tested, and then the hot pressing parameters should be adjusted based on the test results.
In addition, during operation, the movement of the impregnated paper needs to be careful to avoid damage; It is not allowed to wear dirty gloves for operation; If the slab surface is found to be unclean during the assembly process, it should be cleaned in a timely manner; When feeding the base material, it is necessary to carefully inspect it. If defects such as large shavings, missing corners, damage, and sand marks are found on the board surface, they should be promptly removed and rejected for use; The pressure roller of the paving machine, the large suction cups for discharging, the small suction cups for stacking and grading, and each conveying roller should be cleaned regularly to prevent the plate surface from having suction cup marks and dust that may cause product degradation.