Low formaldehyde release volume urea formaldehyde resin preparation method

Abstract

This invention relates to a preparation method for urea-formaldehyde resin with low emission of formaldehyde, belonging to a wood processing industrial field. The present method or lower molar ratio causes other negative effects; or formaldehyde-containing wastewater discharge, environmental pollution, long cycle and high cost of equipment; or high cost of additives introduced. The invention uses the process of adding formaldehyde (F) once and urea (U) for four times, which includes: (1) adding formaldehyde solution into ammonium chloride solution with pH of 1.5-2.5 and heating to 60-70DEG C; (2) keeping the formaldehyde / urea molar ratio at 0 .9-1.25 / 1.0; (3) adding the first batch of urea 36.4% -36.8%, heating to 90-95DEG C and maintaining for 55-65 minutes, and adjusting pH to 8.5-10.0 with sodium hydroxide, (4) adding the second batch of urea 13.4% -18.4% and maintaining for 40 minutes; (5) adding the third batch of urea 5.0% -14.1%, adjusting pH to 3.0-5.5 with ammonium chloride and reacting for 5-10 minutes, and adjusting pH to 8 .5-10.0 with sodium hydroxide; and (6) adding the fourth batch of urea 30.1% -45.0% and reacting for 30 minutes, and cooling to room temperature to obtain the final product. The invention makes the free formaldehyde content lower than the national standard: free formaldehyde content less than 0.1%, no discharge of formaldehyde-containing wastewater, environmental friendliness, and reduced cost.

Description

technical field [0001] Preparation of urea-formaldehyde resin with low formaldehyde emission, the product is suitable for wood processing industry glue. Background technique [0002] With the increase of people's production activities, the demand for wood is also increasing, resulting in a large number of trees being felled, resulting in a sharp decline in global forest coverage, leading to serious soil erosion in many areas, especially in developing countries, and a sharp deterioration of the ecological environment. Therefore, in order to protect forests and protect the environment, people are increasingly using wood-based panels instead of natural wood panels, such as three-plywood, five-plywood, particleboard, fiberboard, etc., which also saves resources and reduces the cost of wood panels. At present, the glue used for wood-based panels is mainly urea-formaldehyde resin adhesive. The adhesive has the advantages of low cost, readily available raw materials, convenient us...

AI Technical Summary

Problems solved by technology

If the molar ratio is too low, it will cause other negative effects

②Vacuum dehydration to extract free formaldehyde is also a commonly used method, but aldehyde-containing wastewater is discharged, which pollutes the environment, and at the same time the production cycle is prolonged and the equipment cost is high; ③In recent years, people have begun to add various formaldehyde to the reaction system Catcher and resin modifier, which is a better way to reduce free formaldehyde and modify resin

However, the introduction of such additives makes the cost of the resin rise too high, which affects its popularization and application, and needs further research.