ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 12, pp. 2022!2024. + Pleiades Publishing, Inc., 2006.
Original Russian Text + V.Z. Maslosh, N.P. Golovnenko, O.V. Maslosh, N.F. Tyupalo, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79,
No. 12, pp. 2046!2048.
AND POLYMERIC MATERIALS
A Zero-Discharge Procedure for Production
of Urea!Formaldehyde Resins
V. Z. Maslosh, N. P. Golovnenko, O. V. Maslosh, and N. F. Tyupalo
Severodonetsk Technological Institute, Dal’ East-Ukrainian National University, Ministry of Education
and Science of Ukraine, Severodonetsk, Lugansk oblast, Ukraine
Received August 2, 2006; in final form, May 2006
Abstract-A zero-discharge procedure was suggested for preparing urea3formaldehyde resins by poly-
condensation of urea, formaldehyde, and dimethylolurea at variable pH, with urea added continuously or
in a single portion.
Urea3formaldehyde resins (UFRs), used as a binder
in production of woodchip boards, wood fiberboards,
and plywood are large-volume commercial products;
the features of their preparation are fairly well under-
stood . The raw materials for their production, urea
(U) and formaldehyde (F), are cheap and commercial-
ly available in large quantities. A specific feature of
the production of all the commercial UFR brands is
the use of 37% Formalin, which gives rise to large
amounts of waste, so-called tar for water. Their amount
in various UFR brands is 3003 400 kg per ton, with
the free F content ranging from 2.5 to 8.0 wt %. Vari-
ous methods for their treatment or reprocessing have
been described in the literature , but these processes
require additional expenditure and equipment.
Our goal was to develop a zero-discharge proce-
dure for UFR production. Published solutions to this
problem involve using, instead of F, difficultly avail-
able and relatively expensive paraform or U precon-
densate (solution in U methylol derivatives in F) .
We examined the possibility of preparing UFR by
joint polycondensation of U, F, and dimethylolurea
Dimethylolurea was prepared by condensation of U
with F according to . Urea3formaldehyde resins
were synthesized as follows. A 500-ml glass flask was
charged with 45 ml of water and 162 g (2 mol) of
37% F; pH 8.038.5 was adjusted by adding a NaOH
solution, and 120 g (2 mol) of DMU was added
(step I). After DMU dissolved completely, the mixture
was heated to 60370oC and kept at this temperature
for 1 h; then 120 g (2.0 mol) of U was added (con-
tinuously over a period of 131.5 h in one series of
experiments and in a single portion in another series).
Then the mixture was heated to 94398oC and kept at
this temperature for 1 h. The mixture was acidified to
pH 4.03 4.5 by adding ammonium chloride and stirred
for 0.5 h, after which a NaOH solution was added to
pH 8.539.5, and the mixture was kept until the refrac-
tive index n reached a value of 1.452031.4560.
In industry, UFR is produced by polycondensation
of F with U (molar ratio 1.33 : 1) at 94398oC and
variable pH. In the first step of the polycondensation,
the concentration of F is relatively high, 23.8 wt %
(Fig. 1, curve 1), and its reaction with U yields meth-
ylol derivatives of U; in the process, the methylol
groups (MGs) are accumulated and the F concentra-
Fig. 1. Content c of (1, 2) formaldehyde and (1<, 2<) methyl-
ol groups vs. time J of polycondensation of F with U.
UFR: (1) commercial and (2) synthesized.