September 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
1115
speed of retraction test is more critical arid hencr hhould lw of significanccx, but value-; ai'Bilmes. L., ,I. ,Sei. Instruments. 22, 16 (1945). (lesrribcd in detail (11). The apparatus n a s provided with a 1oTv Royer. It. F.,and Spencer. R. S.,"Advaiirw in C'olloid Sri'eniprrature jacket (Figure 20). The jacket co eiive." 1-01,2 , p . 1. New York. Ititerscic~iic,e Pul)li$hri.. . Inr., qitudinal compartments, one containing a pan of 1946. Cotiant. 1;. H.. arid Li-ka. J. K., J . A p p l i r d I'hj/s., 15. 767 ~ h t test . piece. -1ir is circulated over the dry ice and througk thi, (,1!>441. sample compartment, bj- m w i s l i t a m a l l variahlcqxwl fan. Forinan. I).B.. I r u . Esu. (:HEM., 36, 73s i(1944). T h r tixnipprature is controlled 1)y manual adjuRtment, of t l i t , fail Gehnian, S.D.. Wnnrlfnrd, D. E., and Starnhaugh. I{, H . . f 0 ; d . . i p r d Suitable baffle$ to control t h r air f l o in ~ the samplt.corii33, 1032 (1941). Kemp. A. R . , Maliii. +'. R., and Winspear. (i. G.,Z h j d . , 35,4XR irartment ensure constariry (it' teniprraturc, along thc strc.1chid (19431. wiiplt' to about +=2'F. Leaderman. H.. "Elastic and Creep Propertie3 O i F i l ~ i i i e n t ~ ~ u s Figures 21 and 22 coniparr a p c w l of rvtraction rtwltsk for Butyl. Xnterials." p . 56. Washington. D . C., 'rhr Tcxtilt, Fniindatkvca, and GR-S tread stocks at room temprrature, 25" (',, and .tion. 1943. Liska, J. Vi., I s u . Exi.. ( ' H E M . , 36,40 ( 1 9 4 4 ~ . ieces w r r i~oolrd,stretched, and heltl foi. 1 Miillin>, L.. T i m i s . I n s t . RiihbFr I d . . 21, 217 (19451. . Tnslit~rtioiiof thtl curves s h o w a startling Stainhaugh. R . B.. Ilohiiw. AI.. arid Gehtrim, S.T),,./. . 4 p / ~ / i ~ d ~lrficiericvin t.lasticity for Butyl rulihrr at the lower tempt'raturr Phys., 15, 740 (1944). :+s c.iimpai,td t o Hwea and C;K-S, This n-ould n w e r t)r suapectecl Wonrl, I,. 1..xiid i i o t h . E'. L., l b i d . , 15, 710. 7 x 1 (l!l441; ere plotted in Figure 12. from iiindulus measurenimt r sucli Thew Butyl seems to he atrout o n a par with the other t l v o in thit ! i i . r ~ i . t ! ~ i i c * tof ~ its w l > t w r l i k ( t i.liauic,tw at I i i i v t i ~ i i i i ) i ~ ~ a t i iThta i~~~~.
:ttiII
I
-
Effect of Nitrogen-Containing Compounds on Drying of Paints 'l'he etfect of free anlilies o n t h e t t r j i n p of oleoresiiioiib p a i n t s w a s s t u d i e d , arid the d a t a i n d i c a t e t h a t t h e s e a m i n e s are e q u a l t o the complex coordinated r o b a l t aniirie* in a c c e l e r a t i n g the d r y i n g r a t e arid m a i n t a i n i n g the drying t i m e stability of t h e p a i n t s tested. It w a s f o u n d t h a t r e r t a i n h e t e r o c j clic, pol>cyrlic. p o l y a m i n e s c o n t a i n i n g tertiary n i t r o g e n atoms preatl? accelerate the d r j i n g rate of oleoresinous p a i n t s , H hereas a l i p h a t i c and other aromatic. a m i n e s either retard or ha>e l i t t l e effert on drjing r a t e . D a t a are presented w h i c h i n d i c a t e that there is little, if a n y , c o o r d i n a t i o n of t h e free a m i n e w i t h t h e cobalt m e t a l a t o m o f the n a p h t h e n a t e d r i e r a f t e r the t w o ha\e been mixed t o g e t h e r in the p a i u t .
T
HE study of the diying of pigriiented oil syuteni- ha\
twtsri
the subject of many research investigations. One phase of Such studies has involved the problem of so-called drier adsorption. I t has been frequrntlv observed that paints containing certain
pig!nr.iits exhihit 103s of tlryirig upo~iaging (1, 2 ) . Of particdar notice arc thosf, paints which contain carlion h1ac.k or t itanium iliosidc pigments. This arrion has h t ~ x n tit trit)iitd, i ~ ~ ~ r h a p ~ cwoneou.qly, to adsorption of the mcLtallir driw hy I h f b I~iynic~nt (1, 2, 6 ) . The llontrral Pain( and \.arnish Production ('luti madta an vxtrnsive study of the phenomenon of drier adsorption (31. The adsorption of simple and complex cobalt ion> on titanium clioxitle was studied hy Sicholiion (6). The lattcr o1)srrvc.r suggwttd (.$) that loss of drying may he due to changes in the polymrrization processes. This investigator also reported a study ( 5 ) in whieh coordinated cobalt amine oleates have bpen conipared wit ti simpk oleates of equal cobalt metal concentration as drying catalysts. According to this rrport ( 5 ) , "cobalt compounds when fully cyrdinated and oxidized t o the cobaltic state are extremrly stable to reduction. Thus, by preparing such a cobaltic compound and using this material as a drier in a paint, one n-ould expect practically no catalytic action by this material since t,he metal atom, heing fully coordinated, would be incapable of coordinating with
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1116
the unsaturated linkages of the oil, and because coordinated cobaltic cobalt is ver'y stable and resists reduction." The same study ( 5 ) using coordinated cobaltous and cobaltic o-phenanthroline oleate and the simple conipounds indicated ver,y little difference in the rate of oxygen absorption (gain in .i\-eight) of the unpigmented oil, when coniplesed or simple cobaltous oleate of equal metal concentration \vas used. Both materials greatly reduced the induction period, as compared \ v i t h coiiti~olscontaining no drier. However, when the oil was pignienttd \\-ithtitanium dioxide, the induction period of the paint was very gwatly retliicetl by the presence of coordinated drier, \Thereas the simple t1ric.r compound has little effect in comparison. This difference \vas: assnnicd to lie clur t o the fact that a metal atom surroundetl hy :I large neutral group or groups (a complexed drier) would havi, 1~ teiidtbiicy to bt, adsorbtd by pigment particle,bultous coinpount! in shortening the induction period. Since c o m dinat c d cohalt ic compounds are knon.n ior their re duc-tioit, and thi, cobtilt atonis prcsc'nt w r o full- roordiiiatc-(1,one woulci have expected this niateri:il to have little iffcct a? ii paint dricr. In view of thcsc rtwdts, stutlicl. \ v ( w carried out iti thih 1:itmutory to expand thr, wopcl of the aliovt~work and to dcterrnitics, tly practical drying tests, t i i c s effect of thi. siniplc and roniplezecl ~ ( I I I I pounds upon the drying rate arid drying tiiiic, stability of certiiiti oleoretinoni:paints. Preliminary experiment .: soon ititiiczt ct! that tht, additioii of free amine, t o the previously preparcd paint (lOiltaining simple cobalt oleate, as as effective in reducing the tlr.>-iiig rates as n-as the addition of the complexed coordinattd cobalt aniine oleates (at, equal cobalt and amine concentrations 11). nright). Therefore, the bulk of the ivork presented in this paper was carried on utilizing the free amines and simple cobalt oleatr in place of the coordinated compounds. Several hundred amines were tested; the results given in this paper represent but a feiv typical exaniplrs. TEST PROCEDURE
The films were considered to be lint-free if the block (\wight, 10 grams) fell off imniediately upon inversion of the panel. For the 500-gram lint-free point a 490-gram lead weight was placed on the 10-gram block. The drying tests were made on films applied 011 polished plate glass panels by means of a 0.004-inch Bird film applicator hladr. DRYING TIME DATA
COXII~LEX m.FREE. h i s E < . -1comparison of the dryiiig time3 of thc paints containing the compli-s (coordinated) or tho free (uncoortlin:tttd) aminrs indicates that the latter are approxiniately equal i n drying properties to the. complex compounds (Table I).
11 i- : ~ l - ~;tp1)tit:,11i i !li:tqL!Iw nizr. ol the complw ci!iiip~~uiid,aiiidicat t ~ t)y l t l i c a i i i i n i l x ~ i~i ~ coordiii:ttcd linkages (degree uf coot'tlinntion 1 , ha': little itifiueiicc, on Llie drying rate (TLthle I ) . , i i . i i ~ ~ . .~ \ A~I IiScK ~ A' I ~ R Y I S G ;\GEVT~. Short-chain secontlary nionouminea r*shihit faster drying rates than do the longwchain cc~nipoiind-, hu! both fail t o accelerate the drying of 1he paint (Taldi)11). Aliphatic primary tlianiiiies prolong the drying rate of the paint to a consideratilc extent, chain length having littlt, effect upon the drying properties of the compound (Tahle 11).
TABLE11. EFFECT O F CHAISLEXGTH ox DRYING
The coordinated compounds were prepared according to the method described by Sicholwn ( 5 ) . The following formula illustrates the t.ypc of paint employed in this work: Pounds
Gallons
r i t a n i u m dioxide" Vehiclek 10% Pb S a p h . Soln.
3.00 6.96 0.125
0.086 0 914 0 016
1 9 Co Oleate Drier S o l n
o
n OIB
104
Vol. 39, No. 9
t 0 . 6 L cPbuii v t . of oil (0.57 nt o f o i l
coon
~~~
number. 1 2
The complvs (coordinated) compounds \vi>re ad&d as 1.O"; c*olialtmetal solutions, and the free amines as jC; solutioni in a solvent mixture of 50% toluol and 50'", butanol (0.188 pound based on the above formula, giving 0.45q aniiric 011 the weight of thc oil). Simplc cobalt, oleate n-as employed ni!h tht. Cree aniiric~>. PRACTIC.II. DRYING TEST. A modified v-eighted felt method was developed to cieterniine the drying times of the paints. Two lint-free points were measured, at 10 arid at 500 gram3 per squarc inch applied pressure. The time of contact of the flannel-covcred block (1 inch Fquare) with the film ryas 5 minutes. This metliod proved to be accurate unclvr conditions of 5 0 5 relativi. humidity, 70" F., a constant artificial light source, and renen.al of the air jn the room approximately every 2 minuteP. The 500-gram lintErcLc, point for the paint in question proved t o be approximatcly q u a l to a Sn-ard hardness of 18-20?;, h t the 10-graIn lint-free point the films w r e dry to touch.
Drying Ti me,
A r r i i lie Control h r r y i i c nitrile Sucriiiic nitrile
.
Dryiiig
Time,
Hr.
Amine
Hr.
17 18 18
Ilipropylaniine Diamylaniine Et hylenedianiine Propylenediamine
22 105 105
li
Tcrtisry aliphiitic mono- and tliriitiogen-conFainingcompounds, juch as acrylic and suc,cinic nitrile, respectively, have little effc,ct on the drying rate of the paint. Hcre again, chain length ha? little influenre, and the number of nitrogen atoms present doc+ not affect the drying properties of the compound (Tahle 11). DRYISG PROPERTIES OF AROMATIC. ~ Y I N E S . The bulk of th(v work rrported in this paper was carried out with aromatic morioaniinw arid diamines. Observations of the drying propertiei: ot representative compounds are given in Table 111. Cyclic tertiary diamines, such as o-phenanthroline and a , CY 'dipyridyl,. accelerate the drying rate to a definite degree. Thi. acc~1cr:trion of drying is accomplished without altering othci paint and paint-film properties. Brittle films are not produccti film hardness being increased hy only a fcw peraccnt (Sward haulnrs* 1. Cyclic tertiary monoamines, in general, prolong the drying rati, to a cotisiderable extent. Pyridine,an exception, slightly accclcratcs the drying of thr paint. Pyridine, o-aminopyridine, aniline. and o-phenylenediamiiit: rcjv c d some interesting information regarding the nitrogen atom systeni which produces good drying. Pyridine (a monoaminit) has one tertiary amine grouping and accelerates the drying rate t o a slight drgree; o-aminopyridine (a diamine), containing one ter-
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
September 1947
tiary and one primary amine grouping, prolongs the drying coliCclerably. .I conipound such as aniline, containing a single pt,iniary aminc group, givcs slightly bc~ttcrdr?-ing than o-anii.i[ip>-ridine,whereas the presence of tivo priniai,y aniinil gloupiiip. :is in o-plicnylciicdiamiiie, is cxtrenic~lydctriniental t o the drying rate. The actiun of o-nminopyridinc is typical of cyclic diamint+ containing a t least onc primary amine group. Iit~placementof the primary aniinr group of o-aniinopyridino t)y ki Yiiiyi radical t o give o-vinylpyridine improves tIie drying propci'tiw of the conipound to a cotisiderahlr i,stc,nt but fails to aceelr~1,ate' the drying of the paint. :IR~\IATIC .IMIDES, X I T R I I X ~.&SI) , IWCYIS.ITES. c.onipat,ison of aniline and o-toluidine (Tables I11 and I\-, rcqectively) indicates that a methyl group attached to the benzene nuclc3us has little or no effect upon the drying properties of a n amine. A tertiary amine group (as in o-tolunitrile) does not givr any iniprovcnient in drying rate. Isocyanates vary in drying properties. o-Toll-1- and naphthylisocyanate do not alter the drying time of the paint to any great cstent, but the latter gives slightly faster drying than the control. Phenyl isocyanate prolongs the drying of the paint to sonic' extent. COSDESSED BENZENEAND "OR F I V E - ~ ~ E M B EHETERORED CYCLIC RISCS. Pyrrole accelerates the drying rate to a slight extent; it is similar to pyridine in this resppct. Benzimidazok definitely prolongs the drying, and henzotriazole is extremely drtrimental to the drying of the paint. Plinlary CO.fIPARISOS O F ALIPH.4TIC A S D A%ROM.4TIC .k\iISEG. diamines, whether straight chain or el-clic, produce poor drying properties. Primary and secondary monoamines, whether aliphatic or aromatic, retard the drying rate of the paint to a slight dcgree. Tertiary monoamines, whether aliphatic or aromatic, have little or no effect upon the drying rate. DRYIXG T n f E STABII,ITY.01dy a fen- of the amines are outstanding from this point of view. Thepe a m i n e are o-phenanthroline, a, ~i '-dipyridyl, and benzimidazole. -411 three are aromatic: hcterocyclic diamines; the first two h:ivc only tertiary amine groups, and the last has one acxcondarj- iind une tc,rtiary amine group. I n each case the carbon-nitrogen system is conjugated. I n o-phenanthroline and a , a'-dipyridyl the tertiary amino nitrogen atoms are separated by t w o carbon atoms. I n benzimidazole the secondary and tertiary amino nitrogen ittoms are separated by only one carbon atom which has an attached hydrogcn atom. These diffewnces may be Ic~spon.~ible for t h r poor initial drying r~xhihitedby benziniidazole.
1117
1;
30
,,
i 3 10 14
14
A\
DISCUSSIOY O F DATA '
Since the free amines give allnost esactly the sa!iie drying tiiiie as t lie complex coordinated amines. the> question arises as to tht,
possibility of the coordination of thts fr mine with the cobalt r the t\vo have bec~ll metal atom of the cobalt oleate drier, mixed together in the paint, The folloiving observations indicatti that cwordination of thr' t1,i.e iiiiiinc~t1oc.s not talw placc~in ;h p i t i t vc~hirl(~. Since thc prcwnce of it coordinatcx link i n a w n i p ) u n d grcat 11. iticwases ith dielecti~icconstaiit. the tIiclr~i.ti~icCCIII rc+inous solutions contiritiing cqiiivalcnt ;inioiirit.s o ~ilcxaniinci w're dctc~rniini.d: Vehicle SolutiL,u (1I 21
,:3 I
+ +
i-nriiish cobaltous oleate i-ariii-li c o b a l t o u - nleate u-iheiinnthroline \-arnisti T c o h a l t u u s u - p l i e i i n n t h ~ u l i ~ i e oleate
+
E. Iiiitinl
1)aj-a
E . :I
E , 2b Day-
2 '30
2.90
3 02
3 lJ1
3,lY
3 1'3
5 I15
5 03
5 111
The high dielectric constant of (3) is due to ihe coordinate linkages in the complex dricr; and although ( 2 ) s h o w a light increase in 3 days, it is not great enough to indicate that any a p . preciable coordination of the simple amine with the cobaltous oleate has taken place. (Drying times were determined within this 3-day time interval.)
17 20 1'3 Phenyl isucyanute S a p h t h y l isocyanate
1 tertiary 1 tertiary
C'onrrol I' y rr o 1e Retiziiriidazole Renzotrinzole
.. .... 1 secondary 1 secondary. 1 tertiary 1 -erondary. 2 t e r t i a r y
19
30 .15 36 :i6
18 20 16
35 36
17 15 36 84
,3 P
:io
34 40 96
I t is quite evident that the amine? which accelerate the drying timr to any great extent are heterocyclic, po containing tertiary nitrogen atoms. The m the ac.cvlcration of the drying time is ohtaincd is h i n g invrlsti-
rated. SURZMARY
F r c ~uncoordinated amines are equal to t h r b c*oniplc.\ ordinated amines from the standpoint of initial drying time and drying time stability. Thet,t, :rppears to be little, if any, coordination of thc, f r r ~aniine \vith t h r cobalt metal a t o m of the nap1ithen:itc. dric,r ni'tt,r t h r tn-o have been mixed together in t h r paint. Primary, secondary, and tertiary nionoaniinei, ~ v h r t h r raliphatic or aromatic, have little or no c ~ f f c ~ upnn rt t h r drying rate of oleoresinous paints. Certain heterocyclic, polycyclic polyaniinc~sI~ontainiilgtt3rtiar.y nitrogen atoiiis greatly accelerate the drying rate and niaintaiii the drying tinii. stability of certain oliwrwinous paints. The nicchanisni by w h i c h the accclera 11 of tht. drying time is obtainid, and the type of olcboresinoui- . li'm i n ivliicti i t takes placr,, are plobleni:, which are being investip:ttcd. A I I itifnirtxd absorption spectra 8rutly would hi, of ronsidi'i atilt, v:iluta to\varti thi, ,wlution of the, gr~nc.r:ilproblein. (10-
L I T E R l T U R E CITED
1-aini. ,II and Laccluer .Issoc.. ,ici. S c c t . C i x . 423 (1932j. Montreal Paint nnd Varnish Productioii Club, Ol,,fficial Digest Frderatimi Paint & T-nrnish P r o d i i c t i o ~ nClubs, h-o. 241, 56677 (1944). Sicholson. L). G.. I S U . !-zsc.. ( ' H E M . , 31, 1300 (1939). Ibid., 34, 1175 (19.42). ?;irholsori. D . (;., ./. S i n . ('hem. Soc.. 64, 2820 (19421 '
