formaldehyde - Sciencemadness Dot Org

12
FORMALDEHYDE
Tho t>*.:y:;.*:'k- acetate, OH^XHCOX&hvCHaCOOH, and the corresponding
hydrate. I'CHarXHCOXHsJis-HaO, which Scheibler, Trostler
and Seholz- obtained by the action of glacial acetic acid on monomethylolurea.
can V- readily interpreted a.- compounds of the structural type indicated
abf.rV^.
In the case *ti dimethylolurea. complex cross-linked resins may be formed
by a mechanism similar to that indicated in the case of monomethylohirea.
Cyclic s-trueture^ of the type whose formation is indicated below can also be
considered urlmaiv resin building blocks:
O—C /
K
X—CHJGH
XH HOCH,
CHjOH
H O
\ li
X—C—NH—CHaOH
H
X-
H2
-C O
/
i 0=C
\
> N—C—NH—CHsOH -r 2H,0
\ /
X—C
I H3
CH2OH
According to Hodgkins and Hovey 51 , the cross-linking, which is probably
responsible for the gelation and final set of urea-formaldehyde compositions,
is possible only with dimethylolurea or mixtures of di- and monomethylolurea,
and doe.-? not occur with methylolurea alone or its equivalent, viz.,
one-to-one molar ratios of urea and formaldehyde.
Some Investigators favor the theory that urea-formaldehyde resins are
formed by the polymerization of raethyleneureas, which are first formed by
the dehydration of mono- and dimethylolurea, as indicated below:
[
I
XH,
CHsO
XHCH-OH
I
XH-
XHCH-OH
I 2CHsO I
c=o —=-> c=o
I
XH2
NHCH*OH
-H-0
2HaO
X=CHS
•* c=o
X=CH2
I
I
X=OHa
"N=CH2"
i
c=o
!
N=CH2'
I
c=o
I
X=CH2
Thurston 43 has recently suggested that methyleneurea may polymerize to
form a triaxnide derivative of trimethylenetriamme;