A kind of nano-cellulose modified low molar ratio urea-formaldehyde resin adhesive and preparation method thereof

Abstract

The invention discloses a nanometer cellulose modified low-toxic urea formaldehyde resin adhesive and a preparation method thereof. According to the invention, formaldehyde and urea with a low molar ratio are adopted as raw materials; N,N'-dimethylpyridine is used as a catalyst; a weak acid-strong acid-strong acid-weak acid-neutral twice polycondensation process is employed; oxidized nanofiber isadded in the process of synthesis to form a softness-hardness alternated structure with the nanofiber as hard segments and urea formaldehyde resin as soft segments; thus, 1) the crystallinity of resinis improved, and the crystalline region is uniformly dispersed; 2) the branching degree of resin molecules is improved, and the molecular weight of the resin is increased under same viscosity; and 3)toughness and impact resistance of the resin are improved; bonding strength is improved; and the formaldehyde release amount of a bonding product is reduced. The invention has the following advantages: a weak acid-strong acid-strong acid-weak acid-neutral synthetic process is adopted; the oxidized nanofiber is modified; the N,N'-dimethylpyridine is used as the catalyst; a basic flow approximatesto a common process; the process is simple; operation is convenient; and transformation of conventional equipment is not needed.

Description

technical field [0001] The invention relates to an adhesive, in particular to a low-toxic urea-formaldehyde resin adhesive used for preparing wood-based panels and a preparation method thereof, belonging to the field of adhesives. Background technique [0002] my country is short of precious wood resources, but there are abundant artificial forest resources. The wood-based panels prepared by using artificial forest fast-growing wood and agricultural and forestry processing residues through adhesives are the main raw materials for furniture floors and interior decoration in the living environment. In 2015, The total output of wood-based panels in my country is 310 million cubic meters, accounting for about 50% of the world's total output. Based on the average production of 9 cubic meters of wood-based panels per ton of adhesive, the consumption of wood adhesives in my country in 2015 was about 40 million tons (solid content 50%), of which urea-formaldehyde resin and its modifi...

AI Technical Summary

Problems solved by technology

For example: 1) Although the use of a low molar ratio modified urea-formaldehyde resin adhesive can effectively reduce the formaldehyde emission of wood-based panel products, the bonding strength of the product decreases sharply, which cannot meet the requirements of use; and it can lead to prolonged curing time and reduced production efficiency; 2 ) Adding formaldehyde scavenger to the urea-formaldehyde resin adhesive for wood-based panels can effectively reduce the release of free formaldehyde from wood-based panels, but it often reduces the bonding strength of wood-based panels at the same time; at the same time, the price of general formaldehyde scavenger is often much higher than that of urea-formaldehyde resin. Adhesive, its addition increases product cost and reduces product competitiveness; 3) Post-treatment of wood-based panels, such as using ammonia vacuum method to prepare environmentally friendly wood-based panels, using formaldehyde absorbing agent to treat wood-based panels, not only makes artificial The board manufacturing process is complicated, and the production cost is significantly increased. In addition, the formaldehyde release will rebound to a certain extent in the long run; 4) The use of other environmentally friendly adhesives, such as isocyanate adhesives, leads to a substantial increase in the production cost of wood-based panels and difficult production processes. It is difficult for enterprises and users to accept it if it is enlarged; the glue strength of wood-based panels prepared by ordinary protein adhesives is low, the water resistance is poor, it is easy to mold, the sizing performance is poor, and the wood-based panels are easy to open.

In summary, although the above measures can effectively reduce the release of free formaldehyde from wood-based panels, they cannot completely solve the problem of formaldehyde release, or cannot be popularized due to reasons such as high production costs.

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