Abstract: Melamine impregnated adhesive film veneer artificial board, also known as melamine board, is made by soaking different textures and colors of raw paper in melamine resin, drying it, and laying it on the surface of particleboard, density board, or multi-layer board. After hot pressing, it forms a decorative board. Melamine decorative base paper can be imported or domestically produced, with significant differences in price and quality. This article explores the decorative process of melamine impregnated adhesive film paper, hoping to promote the improvement of melamine board processing level.
Melamine board has high utilization value and is widely used in furniture manufacturing, interior decoration, and various building decoration projects. Melamine board has a highly simulated texture and perfect decorative surface, which can achieve good decorative effects through the selection of different colors. Decorative base paper is the main raw material for melamine board, which can be imported or domestically produced. Imported paper is more than three times more expensive than domestically produced paper. Although it has a higher decorative effect, it directly affects the price of finished board products and reduces market competitiveness. This article explores the melamine impregnation finishing process, hoping to solve the production problems of domestic paper and improve the economic benefits of melamine boards.
Ⅰ. The problems of domestic decorative base paper
The quality indicators of domestically produced decorative base paper are relatively poor, with low pH value, low wet strength, low inorganic content, and uneven fiber distribution. Therefore, it exhibits unstable performance in use. In addition, domestic decorative paper performs poorly in terms of high temperature resistance and water resistance, which is an important issue in the quality of domestic decorative paper.
Ⅱ.Solution to defects
（1）Solving the problem of insufficient wet strength of domestic paper through the use of organic solvents
The amino resin used in impregnating paper is water-soluble. When producing amino resin, it contains a lot of water inside. In the later use process, a large amount of water needs to be added for debugging to ensure the viscosity of the amino resin and achieve good impregnation effect. When the base paper is impregnated, the moisture in the resin will be absorbed by the paper, while domestically produced decorative paper has lower wet strength and is prone to fracture under the tension of the impregnation machine. This situation cannot simply rely on reducing the amount of water added to the resin, as it will cause excessive viscosity and fail to meet the requirements of the impregnation process; Reducing the reaction time to reduce the degree of reaction will also affect the various performance indicators of impregnated paper. To solve this problem, organic solvents can be added to replace some water, which solves the problem of wet strength of domestic paper. The selection of organic solvents should be based on the principle that the strength of the original paper should not be greatly affected after absorption, it should not evaporate at room temperature, and it should be able to evaporate quickly during the drying process. At the same time, it should be safe and not flammable or explosive; Less pollution to the environment, avoiding overly irritating odors during processing and causing difficulties in production.
（2） Adjusting the impregnation drying equipment to solve the problem of impregnation engineering losses
By replacing some water with organic solvents, the shortcomings of domestic paper in wet strength can be compensated for, reducing most of the losses during impregnation. However, after the implementation of this method, there will still be some losses, and experiments have shown that the loss rate accounts for about 15%. To further reduce the 15% loss, it can be achieved by changing the operating parameters and process conditions of the impregnation drying equipment. The method is to reduce the height of the breathing section on the impregnation machine to about 65% of the original, and reduce the breaking by reducing the tension and self gravity of this section of paper; The water in the impregnation resin has been replaced with an organic solvent, and the volatility of the organic solvent is stronger than that of water. Therefore, at the same temperature, the volatility index has changed, which can reduce the temperature of the drying section to 110-140 degrees Celsius.
（3） Solve the problem of sticking plates
After the impregnation paper is laid on the board for hot pressing, it cannot automatically detach from the lining plate of the press. On the one hand, it will affect the speed of hot pressing, and on the other hand, it will also cause damage to the surface, resulting in defects in appearance quality, and even serious damage to the lining plate. This situation may occur due to the lining itself, but the problem of impregnated paper also exists. We conducted research on the adhesive board generated by impregnated paper. The reasons for the occurrence of sticking to the board are as follows:
1.UF resin penetration
Due to the poor uniformity and permeability of the original paper, after adopting measures such as replacing water with organic solvents and adjusting the drying temperature, there are still some papers that cannot be fully dried after impregnating with UF resin. When impregnating with MF resin, UF resin penetrates into the surface of the paper, causing sticking to the board;
2.Insufficient drying
Due to its relatively low pH value and instability, in order to avoid excessive curing of the resin in the impregnated paper, the degree of drying is usually reduced. Insufficient drying can lead to resin penetration and cause sticking of the board.
3.Ink contamination
Domestic paper ink has poor water resistance, and during the impregnation of the original paper, some ink may dissolve in the resin, causing contamination and resulting in sticking to the board. To solve the problem of domestic paper adhesive boards, we need to start from the following aspects: on the one hand, we need to control the impregnation amount and drying degree of UF resin, adjust the amount of curing agent and drying conditions for each roll of paper with different pH values, and adjust the ratio of release agent and addition.
There are many types of release agents, with significant differences in their scope of use and effectiveness. When selecting, it is necessary to focus on the compatibility between the release agent and amino resin, which must have a certain degree of compatibility, not complete compatibility, and also have both internal and external release effects. The release agent does not decompose at a temperature of 180-200 degrees Celsius, which is the temperature during pressing, and still maintains its own efficacy. In actual production, oleic acid based film removers and composite film removers are usually selected. The quality of oleic acid production in our country is not high, and the use effect of the produced oleic acid release agent is often not ideal. The effect of the composite release agent anti stick plate is better than that of the oleic acid release agent.
（4） Solve the problem of poor decorative effect after pressing and pasting
The inorganic content of domestically produced base paper in our country is low, and the fiber distribution is uneven. After pressing, there is often a problem of bottom penetration. This is mainly due to the low covering ability, resulting in unsatisfactory decorative effects. The usual practice is to add titanium dioxide to the impregnating resin, which is also widely used abroad and has significant effects. However, this method also has some shortcomings. Titanium dioxide needs to be prepared into an emulsion, which requires a high quality of titanium dioxide. During the mixing process of titanium dioxide and impregnating agent, continuous stirring is required to keep the titanium dioxide from precipitating, in order to achieve better usage effects. Another method is to adjust the amount of impregnation, which can avoid the fading of ink at high temperatures and contamination of the press pad, and the effect is relatively ideal.
Ⅲ. Development of melamine impregnated adhesive film paper veneer technology
In recent years, China has developed rapidly in the process of melamine impregnated paper veneer, and has also produced many high-end products, especially in the surface texture processing, achieving a comprehensive effect of visual and tactile perception. I believe that through the efforts of China’s board decoration industry, the gap with international advanced technology can be narrowed.
Melamine board has a relatively large usage and a wide range of applications in China. However, in terms of the production quality of raw paper, domestic paper has more problems than imported paper, but it has a significant price advantage. In the process of producing melamine board, production enterprises can only effectively avoid the problems existing in domestic paper by continuously researching and improving production processes and technologies, thereby reducing board production costs and enhancing market competitiveness.
