Method for preparing adhesive for grade-E0 medium density fiberboards

Abstract

The invention provides an adhesive for grade-E0 medium density fiberboards. The raw materials of the adhesive include formaldehyde, polyvinyl alcohol, urea and tripolycyanamide. The production process of the adhesive comprises: firstly, adding all formaldehyde into a reaction kettle, regulating the pH value of formaldehyde solution to 7.5 to 8.5 by using sodium hydroxide solution, adding the 40 to 50 percent of polyvinyl alcohol and urea and adding 80 to 90 percent of tripolycyanamide and adding the 10 to 20 percent of urea; secondly, adjusting the pH value to 5 to 6 by using formic acid, reacting for 20 to 30 minutes till a cloud point, regulating the pH value to 705 to 8.5 with caustic soda solution, and adding the 10 to 20 percent of tripolycyanamide and 20 to 30 percent of urea; and finally, adding 10 to 20 percent of urea, regulating the pH value of the adhesive to 6.6 to 7.5, and discharging. The adhesive has the advantages that: the free formaldehyde content is very low, and the manufactured medium density board is of grade E0; the curing time is proper, the storage stability is high, and the normal-temperature storage period is about 1 month; and the manufactured medium density board has high internal combining strength and high waterproof and dampproof performance.

Description

Technical field [0001] The invention relates to the production technology category of adhesives, in particular to a preparation method of adhesives for E0 grade medium density fiberboards. Background technique [0002] At present, my country's medium density fiberboard production has exceeded 70 million m3, but its products are mainly all kinds of wood-based panels for ordinary indoor use. Adhesives used in board making basically use urea-formaldehyde resin, which is the main problem that causes the variety of wood-based board products in my country to be small, the product quality is not high, and the product's formaldehyde emission is high. With the development of medium density fiberboard production and the expansion of application fields, higher requirements are put forward for the water resistance and durability of wood-based panels. And along with the enhancement of world environmental protection awareness, people are more and more stringent to the content of the orga...

AI Technical Summary

Problems solved by technology

In recent years, the variety of wood-based panels in our country has been increasing, such as moisture-proof medium-density fiberboard and quasi-water-resistant wood-based panels. No matter whether ordinary urea-formaldehyde glue or phenolic glue is used, it cannot meet product performance and environmental protection requirements. Some domestic colleges and universities have also carried out Some studies on melamine-modified urea-formaldehyde resin, but none of them have achieved industrialization and practical application