Veneer wood-based panel is a new type of wood-based panel product after processing and decoration on the surface of wood-based panel with impregnated paper, veneer, thermoplastic coating material, coating or texture Photocopying Technology (including 3D printing technology).
Facing wood-based panel has the characteristics of wear-resistant surface, high temperature resistance, easy care, acid and alkali corrosion resistance, stain resistance and texture diversity, and has been widely used in furniture (mainly cabinets, wardrobe, etc.), floor, door, decorative wallboard, table and other fields.
According to incomplete statistics, China's wood-based panel output in 2018 is about 300 million m3, but only 30% of the wood-based panels are directly used in the form of plain boards, and 70% of the wood-based panels are used after surface processing. In many wood-based panel facing products, the proportion of impregnated paper facing wood-based panel is more than 60%, paint facing wood-based panel is 30%, PVC thermoplastic material facing and other facing wood-based panel is about 10%.
The overall qualification rate of veneer wood-based panel products in China is not high, and the main problems of quality defects are attributed to the veneer materials and veneer technology.
In the field of dip adhesive paper, the performance of dip adhesive is very important, which determines the performance of dip adhesive paper and the film technology. Therefore, it is of great significance to study the dip adhesive for dip adhesive paper.
At present, the commonly used adhesives for impregnation include melamine formaldehyde (MF), urea formaldehyde (UF) and phenol formaldehyde (PF).
MF resin
MF resin has the advantages of simple synthesis process, fast curing, strong adhesion, light color, scratch resistance and high temperature resistance, and occupies the main share of adhesives for impregnated paper. The special structure of melamine not only brings the superior performance of the resin, but also leads to the disadvantages of poor stability, short storage period and poor fluidity of the resin, and then brings the defects to the impregnated paper, such as the brittleness of the impregnated paper, easy cracking and difficult storage. Therefore, pure MF resin is rarely used for impregnation directly and must be modified. The common modification methods include the introduction of low molecular substances to reduce the formation of intermolecular hydrogen bonds.
Commonly used modifiers are dibutyl phthalate, polyvinyl acetate, urea, glycol monobutyl ether, Polyols (diethylene glycol, polyvinyl alcohol, glycerin, etc.), caprolactam, sucrose and sorbitol sugar solutions, isocyanurate and hyperbranched polymers, etc. The addition of these modifiers can not only reduce the synthesis cost of MF resin, but also play a role in toughening the resin, and improve the surface properties of veneer. Compared with other coating materials, the biggest advantage of impregnated paper is wear resistance. The excellent wear resistance can be partly attributed to the characteristics of MF impregnated resin, but more to the addition of wear-resistant materials. Aluminum oxide is the most common wear-resistant agent. Other materials such as nano materials can also improve the wear resistance. Diallyl phthalate (DAP) is also known as diallyl phthalate, 1,2-diallyl phthalate. DAP monomer is a kind of light yellow or colorless oil liquid. Sodium phthalate is produced by the reaction of phthalic anhydride and liquid base. It reacts with chloropropene at 40-60 ℃ under atmospheric pressure to obtain crude product. Then, the product is obtained by filtration, neutralization, water washing and distillation. DAP resin is characterized by excellent electrical insulation and stability, which can be used as crosslinking agent, toughening agent and reinforcing agent.
Wang Wenli, Zhou Xiaojian, etc. of Southwest Forestry University added DAP as modifier in the preparation process of MF resin, in order to improve some properties of MF resin for impregnated paper.
One
Materials and methods
1.1 test materials
1.2 test method
1.2.1 synthesis of melamine formaldehyde resin
1.2.2 base paper impregnation process
1.2.3 coating process of veneer
1.3 performance characterization
1.3.1 differential scanning calorimetry (DSC) analysis
1.3.2 FT-IR analysis
1.3.3 analysis of physical and mechanical properties
Two
Results and analysis
2.1 the basic properties of MF resin modified by DAP are colorless and transparent liquid. Due to the small amount of DAP added, the solid content of MF resin is basically not affected (Table 2). The occasional difference is not the result of adding DAP, but the result of the different amount of water vapor volatilization in the resin synthesis process, which is consistent with the conclusion reached by the research group in the early stage of using polyamide? Amine modified melamine urea formaldehyde resin (MUF). It can also be seen from table 2 that the viscosity of MF resin gradually increases with the increase of DAP addition, but within the controllable range, it will not have adverse effect on the impregnation effect. Therefore, it is predicted that DAP is not involved in the synthesis of MF resin, but only as a physical and catalytic modifier.
The infrared spectrum of MF resin before and after DAP modification is shown in Figure 3. Referring to the analysis method of literature, 3200-3500cm-1 can be determined as N-H stretching vibration peak, 1600cm-1 as C = O vibration absorption peak, 1553cm-1 as N-C = n bending and ring deformation vibration absorption peak in triazine ring, 1000-1400cm-1 as - CH2OH strong absorption peak, C = O stretching vibration and N-H swinging vibration peak in hydroxymethyl Dynamic absorption peak, C-O-C symmetric expansion vibration, CH3O antisymmetric expansion and - CH2 bending vibration; 900cm-1 is the C-H deformation vibration absorption peak formed between C in triazine ring and H outside the adjacent ring; 600cm-1 is the C-H deformation vibration in amide. It is found that the infrared spectrum of MF resin has no obvious change before and after modification, which shows that the addition of DAP has no obvious effect on the chemical structure of MF resin, and DAP only improves some physical properties. Therefore, the 13C NMR structure of MF resin modified by DAP was not analyzed.
The DSC map of MF resin before and after DAP modification is shown in Figure 4. It can be seen from Figure 4 that each curve has two exothermic peaks. From left to right, the first exothermic peak belongs to the exothermic peak of water molecules or small molecules in resin system, and the second exothermic peak is the exothermic peak of curing reaction. The exothermic peak of the curing reaction of the modified resin moved to the right, indicating that the curing temperature of the modified resin increased to some extent. Therefore, the amount of DAP must be controlled in a reasonable range, otherwise the increase of curing temperature will directly lead to the increase of energy consumption in the production of impregnated products. The increase of curing temperature is attributed to the presence of benzene ring, double bond and ester group in DAP. According to the results of DSC, the temperature of hot press lamination was set to 180 ℃.
2.2 see Fig. 5 for the tensile strength test and stress-strain curve of dip film paper after DAP modified MF resin with different proportion of mechanical properties. As can be seen from Fig. 5b, the addition of DAP can significantly increase the tensile strength of impregnated paper. When all diethylene glycol was replaced by DAP, the tensile strength of the paper increased from 33.00mpa to 5.33mpa, with an increase of 178%; however, with the increase of DAP, the toughness of the paper decreased gradually, showing that the deformation corresponding to the maximum tensile strength decreased gradually. When the amount of DAP is 20%, the toughness and tensile strength of the paper are improved, among which the tensile strength is increased from 3.00mpa to 4.00mpa, with an increase of 133%. The main reason for the obvious improvement of the mechanical properties of MF resin impregnated paper is the existence of DAP benzene ring structure in the modified resin, which affects the intermolecular force in the resin, so that the tensile strength is enhanced, and it is precisely because of the existence of the benzene ring structure in DAP that the toughness of the resin becomes poor.
2.3 veneer performance the surface wear resistance of particleboard before and after MF resin modification is shown in Table 3. It can be seen from table 3 that after DAP is added, the surface abrasion value of the decorative panel is significantly reduced. When DAP is added at 40% and 60%, the abrasion value is the lowest, only 61.4 and 62.3mg / (100r). After 350r test, the surface is free of exposed bottom, which shows that the wear resistance of the decorative panel is enhanced after DAP is added, and it can meet the requirements of the national standard without adding any wear-resistant agent.
The peel resistance and cold and hot cycle resistance of the veneer were tested. It was found that the effect of DAP before and after adding and the proportion of DAP on the peel resistance and cold and hot cycle resistance of the impregnated paper on the veneer surface was not obvious. According to the test results of cold and heat resistance cycle, a slight crack can be seen on the surface after observation with an 8-power magnifying glass, which is a first-order crack, but there is no bubble phenomenon, which is consistent with the conclusion of previous research. The difference is that after DAP modification, there is no obvious change in the test results of cold and hot cycle resistance of the decorative panel before and after the test, while the performance of MF resin modified by polyamide amine (pammams) in the previous research has obvious improvement effect in cold and hot cycle resistance, water vapor resistance and surface pollution and corrosion resistance. In this study, there was no significant change in water vapor resistance and surface corrosion resistance of dip coated paper before and after adding DAP, indicating that the addition of DAP had no significant effect on these properties. Conclusion
X
In this study, different mass ratio DAP was used to replace diethylene glycol to modify MF resin. The properties of MF resin before and after modification, the tensile strength of impregnated paper and the surface properties of adhesive paper veneer were characterized. The following conclusions were obtained: 1) the appearance characteristics, solid content and chemical structure of MF resin before and after DAP modification had no obvious change, but the addition of DAP increased the viscosity of MF resin The curing temperature of MF resin was increased. 2) The addition of DAP increased the tensile strength of MF resin impregnated paper. When diethylene glycol was replaced by DAP, the tensile strength of MF resin impregnated paper increased from 3.00mpa to 5.33mpa, up to 178%, but the addition of DAP decreased the toughness of the resin. When the amount of DAP is 20%, the toughness and tensile strength of MF resin are improved, and the tensile strength is increased by 133%. 3) The addition of DAP did not affect the cold and hot cycle resistance, water vapor resistance, peel resistance and surface corrosion resistance of the veneer, but significantly improved the surface wear resistance of the veneer. When the addition of DAP was 40% and 60%, the surface wear value of the veneer was the lowest, only 61.4 and 62.3 mg / (100r), and there was no bottom phenomenon after 350r.
This paper is published in Journal of forestry engineering, No. 2, 2020.
Citation format: Wang Wenli, Peng JINDA △, Zhao Ziyuan, et al. Modification of melamine formaldehyde resin for decorative panel [J]. Journal of forestry engineering, 2020,5 (2): 42-47
WANG W L,PENG J D,ZHAO Z Y,et al.Modification of melamine-formaldehyde resin for decoration board[J].Journal of Forestry Engineering,2020,5(2):42-47.
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