What affects the quality of melamine impregnated paper veneer？
In order to expand the use range of wood-based panels and improve the use value, it is necessary to decorate the surface. The use of melamine impregnated paper for veneer of medium density fiberboard and particleboard has the advantages of less material, low energy consumption, less process, low cost and beautiful appearance. The quality problems that often occur in the production process are now analyzed as follows.
Production process quality control
1. Production process
The production process of melamine-impregnated paper-faced MDF (particle board) is as follows: substrate preparation → board surface dust removal → blanking → hot pressing → trimming → inspection → storage.
2. Substrate quality control
During production, the quality of MDF base material and impregnated paper should be checked frequently, and the materials can be put into production only after all the technical indicators are qualified.
Paper Quality and Impregnation Process
In order to ensure the quality of the impregnated film paper, a high-quality decorative base paper must be tried. No matter what kind of paper, it can only be used after passing the inspection, and the unqualified cannot enter the production line. During the dipping process, the operation should be carried out in strict accordance with the technical requirements, and sampling and inspection should be carried out every 39 minutes to ensure that the amount of glue applied is 130%~150%, the content of volatile matter is 6%~7%, and the degree of recalcitrance is less than or equal to 65%. Technical requirements; dipping and dried adhesive film paper should be immediately packed with plastic film and sealed with adhesive tape. Store in a warehouse with a temperature of 25°C~25°C, a humidity of 55%~65%, and an air conditioner installed. Paper that cannot be used once should be sealed immediately and sent to the warehouse for storage to prevent it from absorbing moisture and causing adhesive film. They are glued together and cannot be used, causing unnecessary economic losses. In addition, damage should be avoided during the movement of the impregnated paper; if the board surface is found to be unclean during the process of forming the blank, it should be cleaned up in time; the substrate should be carefully checked when feeding.
Base material requirements for veneer wood-based panels
Commonly used medium density fiberboard and particleboard should be purchased according to different requirements of customers, but particleboard products must meet the requirements of GB/T4897-92 first-class products.
1) The board surface is flat and clean, no water or oil stains are allowed. There must be no slipping edge and gnawing head defects within the effective size;
2) The thickness deviation of the plate should not exceed ±0.2mm, and the sanding should be uniform, and no sand leakage defect is allowed;
3) The moisture content of the board should be controlled within the range of 6% to 10%. Since particleboards are purchased from outside, changes in the environment may cause changes in the moisture content of the boards. If the moisture content is low, or the volatile content of the impregnated paper is low, the paperboard may be delaminated during hot pressing. Therefore, it is necessary to observe at any time during the production process and promptly remove unqualified substrates.
Assemble the model
After the base material is centered, it enters the blank assembly process. During the blank assembly operation, it is necessary to ensure that all the impregnated paper covers the surface of the base material, and to ensure that the center line of the slab coincides with the center line of the press, so as to ensure the correct position of the slab after entering the press. , to avoid template contamination due to slab displacement.
Hot pressing process quality control
The three elements of the hot-pressing process (hot-pressing temperature, hot-pressing pressure, and hot-pressing time) are interdependent and mutually restrictive, and need to be analyzed and adjusted uniformly during process adjustment. The three factors have different effects on the veneer. The hot pressing temperature mainly catalyzes the chemical reaction of the impregnated resin, that is, accelerates the curing. According to the actual requirements and experience of production, the temperature of the hot pressing plate is 170°C~200°C, the unit pressure of the plate surface is 2.0~3.0MPa, the hot pressing time is 25~50s, and the hot pressing curve is a period of pressure. According to the color and quality of the paper, the temperature and time can be adjusted appropriately. Dark color paper is easy to use low temperature and long time process. The general temperature is 170°C~180°C, and the pressure is maintained for more than 40s; light color paper should use high pressure and short time process. . At the same time, the appearance quality of the decorative panel should be checked at any time to prevent paper scraps, insects, fingerprints, etc. from contaminating the panel surface. Appropriate hot pressing pressure can ensure a good bond between the substrate and the impregnated paper. Under the action of suitable temperature and pressure, the resin in the impregnated paper can be melted and solidified to form a closed and dense surface, so that the microscopic surface of the substrate can be formed. Pores are filled. Usually, on the premise of not affecting the quality of the product, the lower pressure should be used as much 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 will affect the bonding between the substrate and the impregnated paper. strength and resin flow. Therefore, in actual production, the unit pressure of the hot pressing plate should be adjusted appropriately for different substrates and the newness of the buffer pad.