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...