Investigation of the stability of the modified urea

Investigation of the stability of the modified urea

POLIMERY 200't,49, nr
S.
i
49
A. KURTA, S, V FEDORCHENKO, M. V CHABER
Precarpathian University, Deparhent of Chemistry
Pushkina Strect, 4/62, 77-300 Kalush, Ukraine
Investigation of the stability of the modified urea-formaldehyde resin
(UD lvas
Summary
- Commercial KFMT-I5 type urea-formaldehyde resin
modificd with an addition of 4 wt. % of various alcohols (methanol. ethanol,
isopropanol, butanol). Chan8es ofpH,relative viscosity, hot $lation time and
fuec formaldehyde contentduring storage (up to 4 months)were investigated.
Chemical intelPr€tation of the results obtained has been proposed. lt was
found that isopropanol is the most advantageous modifier
- from the point
of vicw of UF uscful propcrties (especially emission of formaldehyde).
Key words: urea-formaldehyde resins, modification, aliphatic aicohols, storage stability.
Urea-fomaldehydc (UF) resins modificd with monohydric and polyhydric alcohols have been well kno\a'n
for a long time, but influencc of modificrs added ai the
slagc of polycondensation (l -8'7J on UF resins propeF
ti€s has not bccn sufficicntly fuvcsti8at€d Il_3t'
]t is especially important for thc stabilizatiolr of UF
resins properties durjng long timestora8e, forexample l
to 4 months. The problem ,as interesting for us, and
additionaily our custońcrs claimcd that they wantcd to
gct UF resins with stable properties and technical characteristiG. At th€ same tim€ thc modificr content in UF
resin should not be hi8h (up to 10 91t, because Breater
amounts of thc moclificls make UF resins very expcn-
amounts 4 wt. "/.) or dioctyl phthalatc (DOP as a plasti
cizer). To this precondensatc, after thc stage of acid condensation at pH = 4.3_4.6, the modifier has been add€d
and the resin was heated to
hours.
Aftcr the introduction of alcohols to the prccondensate, thc following reactions (1) and (2) took part be
tween an ur€a and methylol derivatives of urea at th€
stage of ihc acid polycondensation:
HNCH,OIt
co
+ c.H,..
HNCH,OH
At the CsC ,,Lukor" \r'r'orks the ureałormaldchyde
resins arc produced by continuous gas phase method
accodinS to which urea solution interacts with formal-
,ou:l'Śo
l
IINCH,OII
'
co
I
+ IJ,o
tNCHrOC,llr,,
I
)
llNcll:OH
HN-CH"-Nlt
.O
, rO
r()
; '
IJN CI trOC
HNC
,OH
IINCH,OH
"H.,,.,
dehyde rich gases dcrived from the process ofmethanol
oxiclaiion. Thc technological linc of a condensation step
consists of the cascade of the reactors.
nonłnodificd
EXPERlMENTĄL
A laboratory installation enablcd to repeate the work
of thc cascadc of reaciors with high accuracy was constructcd for thc modificd resins with stable properties
Production' Addińonally, th€ installation rvas €quiPPed
rĄ'ith a thcrmostat with an autornatjc le8ulatol of tem
perature and pl'l metcr.
For our tests lve used crude UF r€situ (precondensates) that wcrc formcd aft€r thc alkahre sta8e of urea
condcnsaiio with gas fonnaldchyde at the molar ratio
of 1:1.8 and the modifier was introduced at thisstagc [4].
This Product has b€en chos€n for our investigations'
Crudc UF rcsins modification was made by monohy
dric alcohols (methanol, ethanol, isopropa nol, butanol at
60-90''c during 1-2
:
ItN_ CHr_ N_ C
Cn
CO
r-1,r,
Ul'lcsjns
r_
NH
CO
(2)
llo
ItNCHrOC,Hrn,r HNCl.l:OH HNCrl:OtI
The first rcaction (1) took place in the weak acid me-
dium (pH = 5--{), while the reaction (2)
3.H.5
[5].
As
-
at pH
a result of the above processes thc
=
modi
fied UF resins werc obtained. This product was then stabilized with additional urea (to the molar ratio urea:for"
maldehyde equal 'l:1.2) coolcd and analyzed. Modified
UF resins were kcpt du ng 4 months. Sampling and
product analysis wcre donc cach month an.l viscosity,
hot gelation time and ftec formaldch)'de conient wcrc
POLIMERY 2004,49, nr
50
determined according io [6J. Modified products properties were compared with non-modified KFMT-1s resin,
in which the final ratio of wea and formaldehyde was
the same: 1:1.2 i7l.
RESULTS
pH ofmodified UF resins and
non-modified KFMT-I5 one undergoes the obvious
changes in the cou$e of storage iime. At ihe be$nnin&
fol th€ first month of stola8e, PH of aLnost all resins
decreases. ]t is the most obvious for the KFMT-1s resin
dnd UF reslns modińed bV ethanol' The decrcase is Prac_
tically the sańe for ihe UF resins, modified by the isopropanol orplasiified by dioctyl phthalate DOP Dur
ing the lorger stomge, pH of the resins increase. After 4
months the highest pH value (exceedlng the initial one)
shows ihe non-modified resin while the lowest (lolver
than initial pH)
the resinmodified with buianol.
As it is shov/n in Fig.
0r211
170
150
Slo
getimc. nront|s
fig. 1. UF resitl pH dependence on stonge titne: 1
no,1
nodit'iŁd UF rcsh KFMT-1'; the fesins madit'ied wilh: 2
-
ethanol,3 1t- b talnl,4-l
DoP (plasticŁer)
ethnnol, S
5
130
$
l
2
rro
90
1,
-
1
70
0t234
Slorage
tinc, monLhs
Fig.3. UF tesin hot &elatin tijne (HGT) dcpendence
age tine; fot sVmbols see FiS. 1
o
stot-
An inoease in hot gelation time (HGn of
at1 resins
month of stora8e (Fi8. 3) is connected ł.ith the
intermoleĆulaT reaciion takir€ P]ace in the structure of
the resins and a further reaction of UF resins derivaiives,
that leads to the considerable inĆreasc h intermolecular
bonds in a resin.llcT order ofihe products ofmodification is fo11ov/ing: ethanol > methanol > butanol > iso
propanol so there is no dependence on hydrocarbon
chain length. li seems ethanol shows better reaciivity
towards methylol troups than methanol white tu case of
isoproPanol the sieric hindrances decrease the reaĆiivity'
Lo rer reactivity of a modifier prolonts gelation time.
After 4 months storage HGT values of majoriiy of the
modified products are lower. Only the restu modified
with isopropanol is an exception.
Our supposition is also confirmed by the changes of
free formaldehyde content du ng storage time shown in
during
1
Fig. 4.
-isapropanol,6
0,6
4
2
I
2
l
6
i
l
0'4
I
5
Ę o,z
5
01234
stola8c tiDc. monthŚ
Slorulctnnc, morrhs
Fig.
2 .
UF rcsir rclatbe pkcasitV
time; fot symbols see FiS.
As
ftl,
)
deperulence on storage
Fir' 4. DependeĄce rl ftee t'olnnldehyde (Fol cantcttt
rcsin ak stofą4e tifiq|or sy|1tbols see Fis' 1
i1 lJF
1
rell the viscosity of all UF resins sliShrly de
creased during the first month of stora8e (Fig. 2), but
durin8 th€ next months of stola8e the viscosity, as well
a" pH-vrlue increascd. Sigr'/icani irrcrpdse in v scosir)
after the whole siorage was observed in case of nonmodified resin or the resins modified with ethanol or
DISCUSSION
It is clear from the results prescntcd that the certajn
part of meihylol derivative of urea undergoes transformation in the UF resins solutions. Later process in ihe
UF resins seems to undergo a pscudo-stabilizatjon pe
riod. This assumption can be confirmed by the stability
of viscosity that in fact did not change at this siage dur-
inB frsr 45 diys ot uF r6ins *orasc poiod (Fi8 2).
cgbtion iimc .bilizś, bÓ, hlt only bclweel ] łnd 2
ńodh
alrohol lntod
valuc and
^pParendy,
ris.osity Du!ng thc se.ond month rhe
chaĘes of free formaldchyd€.onhnt in thc UF PsilB
nodified by al.oho]s c iŃcEśtińg. Fomaldchyd€ Ón
tent dKrcascs d! I3 this Śb!ag. pc od fmm 0.3
045'l' lo 0.05 a]5'r,' Ircan bc cxp]ained by thc ńd
tl'atpH d.aeas* atthc fnst *a8c oI sbnse (up b30
diyo wlr aĆaie5 rh.
.onditn n5 lol .thcrili'alor.ble .dions Th rnnor
hk! Plł.c it PH = 77 3'r, but.i| oc.ur at PlJ =
Dlijng stoIłgc the Irce fÓmaldchyd. nads with al
.ohÓlŚ and jś.on.cnłatiÓn iń UF
sidclably l]ut ihe łbśrn.!of ęcc tonnaldohyde in thc
aM pirh.l d{omPÓsition of thc lowu nole.ular dc.
.vativ.s Fre fornrJldchyd..onĆ.Ńatjo. Gc. Fig .t)
ina.ases lÓrashon timqbutthcpl.viousvi]uesarenÓt
N tornaldchvdcon
jday
lnLJFrcsilBsonsca!.o|]yo'r j 3l';.óńlr'm
ńon Fodlficd r.sitr thc frcc folmJldĆllydc .ontcnl
90'
is the EŚuIt of thc
!'ork donc
'cs.ai.h
rr
obbnr thc mw srad.s
Pcsiblo
so,
givs i óanĆe
thcirslu.qualiii.s, ih!.lÓg'
lo rg8uble
jv
solidif iotion and iherhal Śabil
It was lound urat thc nodrficd resins keeD rhcn
physi.G.hcmi.al i nd i.cs n the pemjlhd llńlb;wmA
ńonihs
on the base of ińc re.eived r*UlE thc l,si mod GB
of UF resińs on th. da8. of Polycondcnsiiion aPP.a!.d
lobe k.PrcpJnoland bubnoLis wclliŚ d n.hlphthr_
lil. a pLiłkżel Thł E whv lhey .ould b! rcom
nendcd for lh. synthesis of mÓdified UF rcsiN' whi.h
alc usld in rh. pmdudiÓn ol vamishcs and painb, as
]
4
wcll as in rhc paper, woÓdwork
Th. $ond{h]P.nd Mvd.hbc'
ind
Plitśrc.r
vcd on th.
LowłoxiĆ becaus€ oI ih. lowcr f.ec fom;Hóydc oF
tcni wh is a very ińPo ant r6ult of th. wolk Thc
.onsune6 in rhe branch oi idhcsi
slłntl]' looking 1or th. soluiio| oI dre Prcbl; of lre
fońaldchvd. cnissioB lo the eńv
Th!opt ńJlsoluhonoj thsPfub cm i]]L mpńvclh.
c.oloA- ltlJhon o
h.e
'mnmci
I
it b..ame
ation h.s been nadc
thc*aEc of slnthesisoIlow ńolc.ularrethył' and
n'ethylenc dcrnnuv.s .I !(i during ihe pro.e$ or UF
This lcr obrain thc uF rcsim
3rad.5 nodili.d hy thc noholG ola mÓdliclbuj]d iI
inlo t]trtr nruJu|! ! thout thc lhi |ss n fh! procś
Thesr rc'ns sholv sońc sPccjlic proPc i* The d.reasld ontcnt of r6idlal ncc fomatdehvd.sivcs thc
poŚibiliN to r.du.r lhe to\iciiy
ft vcd Un thctr bi5e Mudłtr
'on
'.l.Ę'.fo'".lń.t
d ors.nicsolvcnb. '^rr
2.
val€
c'
3' FńnhoBl H
ł' ldoloIUł
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