UREA-FORMALDEHYDE RESIN PRODUCTION PROCESS (OPTIONS) Russian patent published in 2005 - IPC

FIELD: polymer production.

SUBSTANCE: invention relates to technology of production of urea-formaldehyde resins with reduced toxicity used for manufacturing wood chipboards, plywood, carpenter's building ware, gluing furniture parts, for glues, varnishes, and paints. Process is accomplished by condensation of urea with urea-formaldehyde concentrate on heating in aqueous media in several steps with variable medium acidity. Starting and final urea-to-formaldehyde molar ratios are 1:(1.95-2.0) and 1:(1.05-1.2), respectively. Condensation is carried out in presence of catalyst: mother liquor of urotropin containing at least 45 wt % hexamethylenetetramine and 0.5-14 wt % formate ion and, optionally, in presence of modifier: molasses or industrial-grade lignosulfonates. Process conditions: 90-100°C and reaction time 30-60 min at pH varying from 9.0-7.0 to 5.8-5.0. After-condensation is conducted by adding urea for 30-90 min at 65-90°C followed by stabilizing product with sodium tetraborate, adjusting pH to 7.5-8.5, and cooling product to 20-30°C.According to second embodiment, process is accomplished by condensation carried out first in alkali medium (pH 8,5-6.0) for 20-40 min followed by cooling mixture to 80-85°C, and performing acid condensation at pH 5.3-5.8 in presence of acid catalyst (ammonium chloride, sulfuric acid, formic acid, acetic acid). According to third embodiment, process is accomplished by condensation in presence of at least one modifier chosen from triethanolamine, polyvinyl alcohol, and caprolactam added in two portions at starting and final urea-to-formaldehyde molar ratio 1:2.2 and 1:(1.14-1.4), respectively. In this case, condensation is conducted first in alkali medium (pH 7.3-6.0) at 85-95°C and then in acid medium (pH 4.0-5.0) in presence of acid catalyst (sulfuric acid, acetic acid). Second portion of urea is added at 55-60°C. Resulting urea-formaldehyde resins are nontoxic, have low contents of methanol (0.03-0.07%) and free formaldehyde (0.045-0.12%), high solid residue, and easily mix with water.

EFFECT: optimized process parameters and improved consumer's properties of resins.

12 cl, 3 tbl, 12 ex