CN-122008366-A - Preparation method of low-aldehyde-release and high-strength-synergistic multi-layer plywood

Abstract

The invention provides a preparation method of a multilayer plywood with low aldehyde release and high strength, and relates to the technical field of artificial board manufacturing. The method comprises the steps of carrying out water-based non-halogen flame retardant dipping treatment on a wood veneer, drying, carrying out activation modification on the surface of the veneer by utilizing normal-pressure low-temperature plasma, preparing a composite adhesive composed of styrene, vinyl acetate, maleic anhydride terpolymer, biomass raw materials and citric acid, spraying the adhesive on the veneer subjected to plasma treatment by an ultrasonic cyclone atomization system according to the sizing amount of 10-80 g/m 2 , assembling according to the odd-layer symmetry principle, carrying out cold pressing and sectional heating hot pressing curing, and finally carrying out conventional post-treatment operation. According to the method, the comprehensive improvement of the environment-friendly performance, the bonding strength and the flame retardant performance of the plywood is realized through the synergistic effect of the flame retardant pretreatment, the interface activation and the low-formaldehyde adhesive and the ultra-low sizing technology.

Inventors

• YANG CHAO
• YANG LIUYANG

Assignees

• 临沂金盈祥泉木业有限公司

Dates

Publication Date

20260512

Application Date

20260303

Claims (6)

1. 1. The preparation method of the multi-layer plywood with the low aldehyde release and high strength is characterized by comprising the following steps of: the veneer flame-retardant pretreatment, namely adopting a flame retardant solution to carry out flame-retardant treatment on the wood veneer, and drying the veneer after absorbing the flame retardant component to obtain a flame-retardant pretreated veneer; Plasma surface activation, namely performing plasma surface treatment on the surface of the flame-retardant pretreatment veneer to improve the activity and roughness of the veneer surface, so as to obtain an activated veneer; Preparing a low-formaldehyde composite adhesive, namely taking a urea-formaldehyde resin adhesive as a main body, and compositely mixing the urea-formaldehyde resin adhesive with aldehyde-free or low-formaldehyde components to obtain the composite adhesive with high bonding strength and low formaldehyde release; Applying the composite adhesive on the surface of the activated veneer, wherein the adhesive amount is lower than the conventional amount, and mutually and vertically stacking adjacent veneers in the grain direction to form a multi-layer veneer slab; and hot-press molding, namely hot-pressing the plate blank for a period of time at a preset temperature and pressure to solidify the composite adhesive, so as to obtain the finished product of the multi-layer plywood with low aldehyde release and high strength.
2. 2. The method for preparing the multi-layer plywood with the synergistic effect of low aldehyde release and high strength, which is characterized in that the veneer is subjected to flame retardant pretreatment by adopting a water-soluble flame retardant containing phosphorus and nitrogen to carry out dipping or spraying treatment, the concentration of the flame retardant solution is 10-20%, the dipping weight of the veneer is increased by 5-15%, and then the veneer is dried until the water content of the veneer is not higher than 8%.
3. 3. The method for preparing the multi-layer plywood with the synergistic effect of low aldehyde release and high strength according to claim 1, wherein the plasma surface treatment is preferably carried out by adopting atmospheric pressure low-temperature plasma, the treatment power is 1000-3000W, and the treatment time is 5-60 s.
4. 4. The preparation method of the low-formaldehyde release and high-strength synergistic multilayer plywood is characterized in that the composite adhesive is formed by compounding urea-formaldehyde resin adhesive and biomass adhesive, wherein the mass ratio of the urea-formaldehyde resin adhesive to the biomass adhesive is (70-90) (30-10).
5. 5. The method for preparing the multi-layer plywood with the synergistic effect of low aldehyde release and high strength according to claim 1, wherein the glue application amount of the composite adhesive is 10-80 g/m 2 of one side of each veneer.
6. 6. The method for preparing the multi-layer plywood with the low formaldehyde release and high strength synergy according to claim 1, wherein the hot pressing temperature in the hot pressing forming process is 120-150 ℃, the hot pressing pressure is 1.0-1.5 MPa, the total hot pressing time is 3-8 min, and the method can comprise cold pressing and prepressing the slab by 0.5-1.0 MPa before hot pressing to position and form the multi-layer plywood.

Description

Preparation method of low-aldehyde-release and high-strength-synergistic multi-layer plywood Technical Field The invention relates to the technical field of artificial board manufacturing, in particular to a preparation method of a low-aldehyde-release and high-strength-synergetic multi-layer plywood. Background The plywood is a board formed by laminating and gluing and hot-pressing a plurality of layers of wood veneers (veneer sheets), and is widely applied to the fields of furniture, buildings and the like. However, conventional plywood manufacturing generally uses Urea Formaldehyde (UF) or Phenol Formaldehyde (PF) adhesives synthesized from formaldehyde as a main raw material. After the urea-formaldehyde adhesive is cured, free formaldehyde can be slowly released, so that indoor environmental pollution and health hazard are caused, and strict requirements of public on the formaldehyde release amount of the artificial board are initiated. Reducing formaldehyde emissions from plywood has become a research hotspot and a technical problem in the field of wood products. In order to reduce formaldehyde emission of the plywood, various improvement measures are proposed in the prior art, such as adopting formaldehyde-free adhesives (such as soybean protein glue, MDI and the like) to replace urea-formaldehyde glue, avoiding formaldehyde emission from the source, reducing the glue application amount by plasma treatment on the surface of the veneer, thereby reducing the formaldehyde consumption in the adhesives, or coating a sealing facing on the surface of the plywood, and reducing formaldehyde escape. However, the improvement methods have the limitations that the formaldehyde-free adhesive has high cost or insufficient water resistance and strength performance, formaldehyde release can be reduced to a certain extent by simply reducing the sizing amount, but the bonding strength of the plate is reduced if other auxiliary means are not provided, formaldehyde can be blocked temporarily in surface sealing treatment, and the formaldehyde content in the plate is difficult to reduce fundamentally. In addition, the above-described methods mostly do not take into account the important need for improving the flame retardant properties of the board. For fire safety, the wooden boards often need to have flame retardant properties if applied to the fields of building decoration and the like. The traditional method is to impregnate the fire retardant or coat the fire retardant coating on the surface after the board is formed, thereby leading the board to reach the fire retardant grade. However, the flame retardant treatment may adversely affect the mechanical and bonding properties of the wood, for example, impregnation of water-soluble inorganic flame retardants (which often contain phosphorus, nitrogen, and boron components) may decrease the strength of the wood fibers, residual flame retardant salt crystals or high water content may cause the adhesive layer to adhere to be damaged, resulting in a decrease in bonding strength, and some organic flame retardant coatings, although having less effect on the mechanical properties of the wood, cannot penetrate into the interior of the adhesive layer, and increase process steps and costs. The preparation of the existing flame-retardant plywood often faces the contradiction that the flame-retardant effect and the mechanical strength are difficult to be compatible. In recent years, low temperature plasma surface modification techniques have been introduced in the field of wood gluing for activating veneer surfaces to enhance the bond strength. Researches show that the cold plasma treatment can improve the polarity and roughness of the wood surface under the condition of not damaging the inside of the wood, thereby remarkably improving the wetting penetration and bonding performance of the adhesive. For example, tests have shown that nitrogen plasma pretreatment of veneers can increase the strength of urea-formaldehyde glue veneers by up to about 88%. Therefore, the plasma treatment provides a new technical means for reducing the sizing amount and improving the gluing efficiency. The university of Nanjing forestry reports that the method of combining normal pressure plasma modification and glue atomization spraying is utilized, the glue application amount of the plywood is greatly reduced (reduced by 30-70%), and the product basically has no formaldehyde release. However, in the prior art, formaldehyde release is often reduced, bonding strength is improved, and flame retardance is given as independent improvement directions, and a synergistic scheme for organically combining flame retardant treatment, surface activation, adhesive modification and low-sizing technology is not yet available, so that flame retardance, safety (low aldehyde) and high-performance bonding of the plywood are realized at the same time. For this reason, it is necessary to provide a new technical path to compreh