Quality control in the production process of melamine impregnated paper faced MDF (particleboard)
- Production process The production process of melamine impregnated paper faced MDF (particleboard) is as follows: substrate preparation → dust removal on the board surface → preforming → hot pressing → trimming → inspection → warehousing.
- During the production of substrate quality control, the quality of MDF substrate and impregnated paper shall be checked frequently, and the production can only be started after all technical indicators are qualified.
(1) Paper quality and impregnation process To ensure the quality of impregnated paper, high-quality decorative base paper must be used. No matter what kind of paper is used, it can only be used after passing the inspection, and the unqualified paper can not enter the production line. During the impregnation process, the operation shall be carried out in strict accordance with the process requirements. Sampling inspection shall be carried out every 39min to ensure that the glue content is 130% – 150%, the volatile content is 6% – 7%, and the degree of pre solidification is ≤ 65%; The impregnated and dried adhesive film paper shall be immediately packaged with plastic film and sealed with adhesive tape. It shall be stored in the warehouse with air conditioner and temperature of 20 ℃ – 25 ℃ and humidity of 55% – 65%. The paper that cannot be used at one time shall be immediately sealed and sent to the warehouse for storage to prevent its moisture absorption from causing the adhesive film paper to stick up and cannot be used, resulting in unnecessary economic losses. In addition, avoid damage during the movement of impregnated paper; If the slab surface is found not clean in the process of assembling, clean it in time; Carefully check the base material when feeding.
(2) The substrate of veneered wood-based panels requires that the commonly used MDF and chipboard should be purchased according to the different requirements of customers, but the chipboard products must meet the requirements of GB/T489792 first-class products. ① The board surface shall be flat and clean, free of water and oil stains, and the effective size shall be free of defects such as edge slipping and head gnawing; ② The thickness deviation of the plate shall not exceed 0.2mm, and the sanding shall be uniform. No sand leakage is allowed; ③ The moisture content of plates shall be controlled within 6% – 10%. As most particleboards are purchased, changes in the environment may cause changes in the moisture content of the board. If the water content is too high, blasting, layering and other phenomena may occur in the veneer process; If the moisture content is low, or the volatile content of impregnated paper is low, cardboard delamination may occur during hot pressing. Therefore, it is necessary to observe at any time during the production process and remove unqualified base materials in time.
(3) After centering, the base material for assembling will enter the assembling process. During the assembling operation, ensure that the impregnated paper is completely covered on the surface of the base material, and ensure that the center line of the slab coincides with the center line of the press, so as to ensure that the position of the slab after entering the press is accurate, and avoid the pollution of the formwork due to the slab displacement. 3. Quality control of hot pressing process The three elements of 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 when adjusting the process. The three factors have different effects on the veneers. The hot pressing temperature mainly catalyzes the chemical reaction of the impregnated resin, that is, accelerating the curing. According to the actual requirements and experience of production, it is appropriate to pressurize the hot pressing plate at a temperature of 170 ℃~200 ℃, a unit pressure of 2.0-3.0MPa and a hot pressing time of 25-50s. The temperature and time can be adjusted appropriately according to the color and quality of the paper. The dark color paper should adopt a low temperature and long time process, with the general temperature of 170 ℃ – 180 ℃ and pressure holding for more than 40s; Light colored paper should adopt high pressure and short time process. At the same time, the appearance quality of the decorative panel shall be checked at any time to prevent paper scraps, insects, fingerprints, etc. from polluting the panel surface. The proper hot pressing pressure can ensure a good combination between the substrate and the impregnated paper. Under the proper temperature and pressure, the resin in the impregnated paper can be melted and solidified to form a closed and dense surface, so that the micro pores on the substrate surface can be filled. Generally, lower pressure should be used as far as possible without affecting the product quality, which is beneficial to the service life of equipment and hydraulic oil and the internal structure of the base material; However, too low pressure will affect the adhesive strength and resin flow ability of the substrate and impregnated paper. Therefore, in actual production, the unit pressure of hot pressing plate should be appropriately adjusted according to the new and old degree of different base materials and cushion pads.
- Product quality control The product quality control shall be carried out according to the superior product indicators in the standard CGBT15102-94 Impregnated Film Paper Decorated Wood based Panel.
