Analysis of factors affecting the quality of melamine impregnated paper decorative panels
Introduction: To produce high-quality products, it is necessary to choose excellent impregnated paper and substrates, and use reasonable processing techniques; In addition, it is necessary for operators and inspectors to work together to control the quality of the product, promptly identify and solve any problems that arise, in order to ensure product quality.
In order to expand the scope of use and improve the value of artificial boards, it is necessary to decorate their surfaces. The use of melamine impregnated paper to finish MDF and particle board has the advantages of less materials, low energy consumption, less processes, low cost and beautiful appearance. It not only improves the strength, stiffness and dimensional stability of the board, but also makes its surface wear resistant, heat resistant, water resistant and chemical pollution resistant.
The quality problems that often occur during the production process are analyzed as follows. 1、 Production process quality control 1. Production process Melamine impregnated paper faced medium density fiberboard (particle board) production process flow is as follows: base material preparation → board surface dedusting → forming → hot pressing → trimming → inspection → warehousing. 2. In the production of substrate quality control, the quality of medium density fiberboard substrate and impregnated paper should be regularly checked, and only after all technical indicators are qualified can they be put into production. (1) To ensure the quality of impregnated adhesive paper, high-quality decorative base paper must be used. No matter what type of paper is used, it should be inspected and qualified before use. Unqualified paper cannot enter the production line. During the impregnation process, the operation should be strictly carried out in accordance with the process requirements, with sampling and inspection every 39 minutes to ensure that the adhesive amount is 130% -150%, the volatile content is 6% -7%, and the pre solidification degree is ≤ 65%; After soaking and drying, the adhesive film paper should be immediately packaged with plastic film and sealed with adhesive strips. It should be stored in a warehouse with a temperature of 20 ℃ -25 ℃, humidity of 55% -65%, and air conditioning installed. Paper that cannot be used up at once should be immediately sealed and sent to the warehouse for storage to prevent moisture absorption, which can cause adhesive film paper to stick together and become unusable, 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 assembly process, it should be cleaned in a timely manner; Carefully inspect the substrate when feeding. (2) The base material requirements of veneered wood-based panels The commonly used MDF and chipboard should be purchased according to the different requirements of customers, but the particle board products must meet the requirements of GB/T489792 first-class products. ① The board surface should be flat and clean, without water or oil stains, and there should be no defects such as slipping or gnawing within the effective size; ② The thickness deviation of the board should not exceed 0.2mm, and the sanding should be uniform, without sand leakage defects; ③ The moisture content of the board should be controlled within the range of 6% -10%. As most particle board is purchased, the change of environment may cause the change of moisture content of the board. If the moisture content is too high, it may lead to phenomena such as blasting and layering during the veneer process; If the moisture content is low or the volatile content of the impregnated paper is low, it may cause delamination of the cardboard during hot pressing. Therefore, it is necessary to observe at any time during the production process and promptly remove unqualified substrates. (3) After the assembly of the substrate, it enters the assembly process. During the assembly process, it is necessary to ensure that the impregnation paper is fully covered on the surface of the substrate and that the centerline of the slab coincides with the centerline of the press to ensure accurate position of the slab after entering the press and avoid template contamination caused by slab displacement. 3. The three elements of hot pressing process quality control (hot pressing temperature, hot pressing pressure, and hot pressing time) are interdependent and interdependent, and need to be analyzed and adjusted uniformly when making process adjustments. The three factors have different effects on the veneer, and the hot pressing temperature mainly plays a catalytic role in the chemical reaction of the impregnating resin, that is, accelerating curing. According to the actual requirements and experience of production, a hot pressing plate temperature of 170 ℃~200 ℃, a unit pressure of 2.0-3.0 MPa on the plate surface, and a hot pressing time of 25-50 seconds are suitable for a pressure curve. The temperature and time can be adjusted appropriately based on the color and quality of the paper. Dark colored paper should be processed at low temperature and for a long time, with a general temperature of 170 ℃ -180 ℃ and a pressure holding time of more than 40 seconds; Light colored paper should use high-pressure and short-term processes. At the same time, the appearance quality of the decorative panel should be checked at any time to prevent paper scraps, insects, fingerprints, and other contamination of the panel surface. The appropriate hot pressing 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 can melt and solidify to form a closed and dense surface, allowing the small pores on the substrate surface to be filled. Usually, lower pressure should be used as much as possible without affecting product quality, which is beneficial for the service life of equipment, hydraulic oil, and the internal structure of the substrate; However, low pressure can affect the bonding strength and resin flow ability between the substrate and the impregnated paper. Therefore, in actual production, the unit pressure of the hot pressing plate should be adjusted appropriately for different substrates and the degree of novelty of the buffer pad. 4. Product quality control: Product quality control shall be carried out according to the superior product indicators in the CGBT15102-94 “Impregnated Adhesive Film Paper Facing Artificial Board” standard. 2、 Common quality defects and causes of medium density fiberboard (Chuanghua board) decorated with melamine impregnated paper: 1. Poor physical properties: 1. Low hot pressing temperature or short hot pressing time, incomplete tree curing, and easy adhesion of dust on the board surface during use, making it difficult to clean and form a dirty surface. 2 If the hot pressing temperature is too high, the template surface temperature is uneven or the substrate temperature is uneven, it is easy to form surface cracking (commonly known as cracking) The low resin content of the paper results in low surface detachment strength of the substrate Excessive unit pressure, uneven density of the board, asymmetric structure, and high hot pressing temperature cause panel warping. ⑤ When the moisture content of the board is too high, the substrate is abundant, and the board density is too low, the core layer generates significant vapor pressure during pressing, causing it to bubble or delaminate. 2. Uneven gloss on the board surface: ① The amount of adhesive soaked in the impregnated paper is uneven, the moisture content of the board is too high, and local bubbles appear on the board surface during pressing, resulting in uneven light selection on the board surface. ② The surface of the template is contaminated, the surface is dirty, or the buffer pad is damaged, and the temperature of the pad is uneven, resulting in poor demolding The moisture content of the board is too high, the hot pressing temperature is low, or the hot pressing time is short, which leads to water permeability on the board surface and uneven luster Low hot pressing pressure or long storage time of impregnated paper. The high degree of resin pre solidification results in poor resin fluidity during hot pressing, resulting in poor surface brightness There is dirt or fingerprints on the surface of the board during the assembly process, such as using paper. 3. Dry spots on the board surface (also known as dyed white spots or white spots) ① There is a pre curing layer on the surface of the substrate, which leads to low density of the board and high resin absorption, resulting in poor resin fluidity on the board surface. ② Local dents in the substrate. Insufficient pressure at the dents during hot pressing affects resin flow The hot pressing temperature is too high, the hot pressing pressure is too low, or there is dirt on the template surface. ④ The buffer pad is partially damaged or has been used for too long, resulting in excessive temperature in the local area of the pressure plate and uneven heating of the plate surface, resulting in dry spots. ⑤ The storage period of impregnated paper is too long, and the pre solidification degree is too high. The fluidity of trees and land is poor, or the resin impregnation amount is too large, resulting in steam bubbles and dry flowers on the board surface during pressing. 4. Board surface pattern (also known as water marks or watermarks): ① The moisture content of the substrate is too high, resulting in excessive water bubbles during pressing. ② Excessive volatile matter content in the impregnated paper or dampness of the impregnated paper Low hot pressing temperature or short hot pressing time. 5. Adhesive mold plate (i.e. poor demolding) ① Excessive resin impregnation or dirt on the surface of the template. ② The hot pressing temperature is low, the time is short, and the resin is not fully cured. ③ The local damage of the reinforcement pad results in uneven surface roughness of the template and low local temperature The high moisture content of the board affects resin curing and leads to poor demolding. In summary, to produce high-quality products, it is necessary to choose excellent impregnated paper and substrates, and adopt reasonable processing techniques; In addition, it is necessary for operators and inspectors to work together to control the quality of the product, promptly identify and solve any problems that arise, in order to ensure product quality.
