Method for using ammonia gas to fumigate wood fibers to produce environment-friendly artificial boards

Abstract

The invention relates to a method for using ammonia gas to fumigate wood fibers to produce environment-friendly artificial boards, which belongs to the technical field of artificial board production. According to the technical scheme, the method includes: adding ammonia gas into dried wood fiber material in front of an entrance of a hot press, allowing the ammonia gas to disperse into a wood fiber layer, and feeding the wood fiber material with absorbed ammonia gas into the hot press, wherein free formaldehyde in the ammonia gas and the wood fiber material and formaldehyde released by splitting of resinoid hydroxymethyl and methylene ether link in hot pressing of the wood fiber material chemically react to generate urotropine, and accordingly the content of free formaldehyde in artificial products is reduced. Existing artificial board production equipment and facilities can be used to produce the artificial boards, only liquid ammonia storage, gaseous ammonia control and conveying equipment is added, operation is simple, operation cost is low, and common low-cost urea-formaldehyde resin can be used to produce high-grade environment-friendly artificial boards. By the method compared with the prior art, product cost is reduced by more than 5%, workshop work environment is improved, and evident economic benefit and environment protection effect are achieved.

Description

technical field [0001] The invention relates to a method for producing an environment-friendly wood-based panel by fumigation of wood fiber with ammonia gas, and belongs to the technical field of wood-based panel production. Background technique [0002] After curing, urea-formaldehyde resin has the advantages of non-toxic, colorless, aging resistance, long-term use without discoloration, low cost, etc., and is widely used in the production of wood-based panels; Improper use can easily lead to high residual free formaldehyde content in the urea-formaldehyde resin. At the same time, in the production process of the density board, formaldehyde is released due to the intervening resin methylol and methylene ether bonds of the adherend fiber. In actual production, The grade of wood-based panel products can generally reach E1 and E2 grades, and it is difficult to reach E0 grade. With the enhancement of people's environmental protection awareness and social progress, the requireme...

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Problems solved by technology

[0003] The main problem of the first method is: the cohesiveness of urea-formaldehyde resin decreases after the formaldehyde molar ratio decreases, resulting in a decrease in the strength of wood-based panel products; the second Adding a modifier to the first method has a certain effect, but the main problem is that the cost of the product increases significantly, and the formaldehyde released during the production of density boards cannot be treated, and the amount of formaldehyde released from wood-based board products is not significantly reduced; the third method is in sizing. Adding urea in the process has a certain effect. The main problem is that the formaldehyde released during the production of density boards is in the gaseous state. It is difficult to achieve uniform distribution of solid urea and cannot completely absorb the gaseous formaldehyde. The reduction of formaldehyde emission in wood-based panel products is not significant. The fourth method has a better effect on reducing the formaldehyde emission on the surface of wood-based panel products. The main problem is to add a vacuum treatment device. When the density of wood-based panels is high and thick, the free formaldehyde in the inner layer cannot be effectively treated. Thick wood-based panels are particularly prominent, the inner layer of each batch cannot be treated well, and intermittent operation, the balance and stability of product quality cannot be guaranteed, the amount of ammonia gas is large, the utilization rate is low, and the labor intensity is high. higher processing costs

Because the formaldehyde produced during the hot pressing process and part of the free formaldehyde in the wood fiber will diffuse into the air in the form of gas, the formaldehyde content in the air of the hot pressing workshop often exceeds the GBZ2.1-2007 regulations issued by the Ministry of Health of the People's Republic of China. The maximum allowable index of formaldehyde content in the air in the workplace is 0.5 mg / m3, and the actual value reaches 0.7-1.0 mg / m3. In the wood-based panel production equipment of the background technology, the formaldehyde content in the air of the hot-pressing workshop is generally high, and the production environment conditions are poor. question

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