Swelling of Oil-Varnish Films in Water The increasing number of resins, oils, and varnishes has created a need for an exact method of determining their characteristics. The method already published for determining the swelling of drying oil films in water (2) was therefore applied to oil varnishes. The results indicate the superiority of phenol resins and the influence of relatively small amounts of tung oil (20-30 per cent) on the water absorption of varnish films. The theory of the action of different driers during film formation (as described in the paper on drying oil films) was confirmed, and additional data are given.
T
HE method previously described by Rinse and Wiebols (2) Is now applied to films of oil varnishes, The films of 30 p thickness were made on tin slides, dried for 14 days, and then immersed in a water bath a t 30' C. through
J. RINSE,'W.H.G. WIEBOLS, AND H. V. TAKES Laboratory Pieter Schoen & Zoon N. V., Zaandam, Holland
nishes described here. However, in general, high water absorption and large loss of material during swelling are accompanied by high permeability. Therefore, in addition to furnishing interesting facts on the drying problem, the data on absorption already give indications of the practical value of the materials tested.
I . Linseed Oil Varnishes Varnishes were made up of one part of phenol-ester gum resin, three parts of oil, and varying amounts of drier (i. e., 0.1 per cent cobalt, 0.4 per cent lead, or 0.1 per cent manganese). The linseed oil was used in the raw state and also bodied to 20 and 65 poises a t 20" C. The first varnish was made a t 60" C., the other two at 200" C. The data in Table I and Figure 1 demonstrate that the swelling of the raw linseed oil varnishes is greater a t first than for the bodied-oil varnishes; but after 2 weeks the raw-oil varnishes pass a maximum, and, probably because of the greater loss of material, the swelling diminishes somewhat. The lead films show the greatest water absorption in all three cases; the most viscous oil is the least absorbent, regardless of drier used. The loss of material for the bodied-oil varnish films is smallest with lead.
which a continuous stream of potable water was directed. The slides were weighed after different intervals, and the in11. Bodied Linseed-Tung and Linseed-Oiticica crease in weight is expressed in percentage of the film weight Oil Varnishes before immersion. The separately prepared bodied oils with viscosities of 20, One minor change in the method was necessary because of a 150, and 700 poises, respectively, a t 20" C. were mixed (one corrosion phenomenon a t the contact points with the carrier part of linseed oil to two parts of tung or oiticica oil) and for the slides. This difficulty was met by treating the free heated to 200" C. One part of phenol-ester gum resin was sides of the slide with a short-oil varnish consisting of tung dissolved in three parts of oil mixture, and the solutions were oil and pure phenolic resin, which was stoved a t 180' C. This stoGing varnish showed no change during the immersion and accordingly did not affect the results with the varnishes under OF LINSEEDOIL VARNISHES TABLEI. WATERABSORPTION test. ---Raw Oil-Bodied Oil, 20 Poiaes- -Bodied Oil, 65 PoisesThe varnishes to be tested were made as % Absorption described below, and metal-naphthenate soluafter : Co Pb Mn Go Pb Mn Co Pb Mn tions (driers) were added. Mixed solutions 31 45 24 26 21 80 78 15 18 1 day 42 22 38 49 111 84 28 101 26 2 days as well as single driers were used, in quanti144 66 80 36 68 46 113 39 127 4 days 113 109 104 180 60 68 123 63 138 ties corresponding to 0.1 per cent lead, 0.026 7 days 181 157 161 128 137 196 102 113 102 14 days per cent manganese, and 0.0026 per cent cobalt, 173 182 217 174 120 130 132 140 119 21 days based on the nonvolatile content of the varLoss of material nish. I n series V only half the amount of after swelling, 16.0 16.2 16.3 12.6 6.9 13.7 11.8 6.0 12.6 % cobalt was used. All varnishes were thinned with mineral spirits. This investigation deals not with the moisOF TUNG-LINSEED AND OITICICATABLE11. WATERABSORPTION ture transmission of the swollen film; this LINSEEDOILVARNISHES property, together with the water-absorption, --Tung-Linseed--Oiticica-Linseed-is very important in determining the pracyo Absorption after: Co Pb M n Co-Pb-Mn Co Pb M n Go-Pb-Mn 4.3 1.5 6.5 4.3 2.8 2.3 0 . 8 3.0 tical value of a paint or varnish film. 1 day 4.5 7.0 2.5 9.0 7.0 3 days 2.0 0.3 2.5 The permeability may be measured by the 11.5 14.0 4.8 17.5 4.8 3.5 1.0 3.8 7 days 24.0 10.3 29.6 20.5 7.5 5.5 5.5 1.0 14 days method of Edwards ( I ) , and it would be worth 9.5 30.0 27.5 9.5 37.5 5.0 0.0 5 . 5 21 days while to make this measurement on the varPresent address, Chemisch en Verf-technisch Laboratorium en Adviesbureau, Haarlem, Holland. 1
Loss of material after swelling, %
1043
7.8
5.3
7.8
7.4
10.1
4.0
9.5
9.1
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thinned with mineral spirits and naphthenate driers (0.1 per cent cobalt, 0.1 per cent manganese, or 0.4 per cent lead, calculated on the total oil and resin content of the varnish). As shown in Table 11, the oiticica oil films behave like the tung oil films but absorb more water. In contrast to the behavior of the linseed oil varnishes of Table I, the lead fdms swell less than the cobalt or manganese films. The loss of material of the oiticica oil films is the same as for the tung oil films. [In the previous paper (2) a greater difference was shown for the bodied oils alone.] The lead films show less gloss after swelling than the films containing other driers.
111. Dehydrated Castor Oil Varnishes Varnishes consisting of three parts of dehydrated castor oil (34 poises, acid number 9.3) and one part of phenol-ester gum were heated to 200" C. and thinned with mineral spirits; driers were added as in series 11. As shown in Table 111,the lead films which dry most slowly, absorb least water, and loss of material is smallest. The cobalt films absorb most water and lose more material, which demonstrates a stronger oxidation action.2 The cobalt films after the test were dull and strongly attacked by water.
TABLE111. WATERABSORPTION OF DEHYDRATED CASTOROIL VARNISHFILMS yo Absorption after:
Co
Pb
Mn
8.9
13.4
Co-Pb-Mn
1 day 2 days 4 days
9 days 14 days 21 days
Loss of material after swelling, 70
IV.
14.4
12.0
7
14
DAYS.
Linseed-Tung Oil Varnishes
Long-oil varnishes, consisting of 25 per cent resin, 45 per cent bodied linseed oil (20 poises), and 30 per cent bodied tung oil (180 poises) were made. The resin was dissolved in the oil mixture a t 2OOoC., and thevarnish was thinned with mineral spirits and mixed naphthenate driers. Three resins were used-phenol-ester gum (P. E. G.), ester gum (E. G.), and coumarone melting a t 55" C. (C. R.). short-oil varnishes consisted of 50 per cent resin, 30 per cent bodied linseed oil (20 poises), and 20 per cent bodied tung oil (180 poises). As shown in Table IV, the coumarone resin varnishes take up considerably more water than the other types; the phenolester gum resin is most water resistant. The loss of material is greater for the long-oil varnishes than for the short-oil range. Coumarone varnishes show the largest losses in both short- and long-oil types. OF LONG-AND SHORT-OIL TABLEIV. WATERABSORPTION VARNISHES
% Absorption after: 1 day 3 days 7 days 14 days 21 days
Loss of material after awelling, %
-Lon
-Oil Varnish-
P . E . 8 . E.G. C.R. 4 11 14 15 13
5 14 20 20 24
9 21 33
9
10
12.5
46 58
--Short-Oil Varnish-P.E.G. E.Q. C.R. 4 4 10 9 7 21 14 14 31 17 57 17 l5 22 70 1
1.5
6
2 After this investigation was completed, a new sample of dehydrated castor oil (synourin oil) was received. Its viscosity is the same but its acid value is lower than that of the first sample. The water absorption of the second oil is lower than that of the first oil, and the varnishes made from the new oil will probably have better water resistance than those from the first, although not equal to that of tung oil varnishes.
W.
Effect of Resins on Linseed-Tung Oil Varnishes
Eight resins of commercially well-known brands were tested: a. Limed rosin
Ester gum (acid value 5 ) Phenol-ester g u m L (10 per cent phenol) d. Phenol-ester g u m H (30 per cent phenol) e. Phenol resin A (oil-reactive) f. Phenol resin B (oil-nonreactive) g. Coumarone resin (melting point, 55" C.) h. Phenol resin C (oil-nonreactive) 6.
c.
A mixture of four parts linseed oil and one part tung oil was bodied a t 300" C. until a viscosity of 20 poises (20" C.) was reached. The resin was dissolved in this oil mixture at 250' C. (phenol resin A a t 200" C.) until reaction was complete. The solutions were thinned with mineral spirits and mixed naphthenate driers. LONG-OIL VARNISHES. Three parts of oil mixture and one part of resin gave the results shown in Table V and Figure 2. Important differences are found between varnishes made with phenol-free resins, which show a strong water absorption, and those made with phenol resins, which show less than 50 per cent absorption. The oil-reactive phenolic resin (e) reaches only 11 per cent as a maximum. This favorable behavior is confirmed by the low loss of material of the phenolic resin films and by the retention of gloss of the test panels after redrying; the phenol-free resin films are dull and heavily attacked by water. SHORT-OILVARNISHBS. One part of oil mixture and one part of resin, combined with drier and thinner as above, gave the results shown in Figure 3 and Table V. Here also the
SEPTEMBER, 1938
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thinning with mineral spirits and naphthenate driers. Results are given in Table VI. Resins With the exception of limed rosin, all var% Absorption after: a b c d e f g h nishes take up less than 10 per cent water. Long-Oil Varnish Films Phenol resin varnishes f and h absorb the 27 9 10 2 11 9 126 29 1 day 15 44 15 13 6 64 14 166 2 days least water, and their gloss remains the best. 64 22 8 23 19 95 17 175 3 days 11 31 118 35 28 31 176 Ester gum and coumarone resin varnishes (b 198 7 days 184 38 9 39 38 31 188 221 14 days and g) are considerably better than those var42 38 211 0 44 33 220 178 21 days nishes in which part of the oil is linseed. The Lossof materialafterswelling, % 29.1 14.5 1 4 . 1 1 2 . 5 4 . 6 6.4 15.3 7 . 4 results for the long-oil varnishes of series V, IV, Short-Oil Varnish Films and VI (tung oil content, 15,30,and 75 per cent, 99 5 2 3 2 3 7 4 1 day 117 8 2 3 3 4 1 0 5 respectively) show that the ester gum varnishes 2 days 145 11 3 4 4 5 14 6 3 days are much more sensitive to a variation in linseed 300 31 9 9 8 13 35 12 7 days 316 70 13 12 12 16 57 21 14 days oil content than the phenol-ester gum varnishes. 344 98 19 19 17 26 96 31 22 days The amount of water absorbed by ester gum Loss of material afterswelling, % 29.5 5.6 2.9 2.5 3.5 2.5 6.5 2.6 is 220, 24, and 8 per cent, and for the phenol resin, 33, 13, and 10 per cent,. respectively. These data seem to show that an increase in tung oil content from 15 to 30 per cent has much more effect high water resistance of phenol resins is outstanding. The on the film than a n increase from 30 to 75 per cent. limed rosin varnish gives the worst results (absorption 344 per cent, and loss of material nearly 30 per cent). A limed rosin varnish is accordingly unsuitable for marine purposes. TABLE VI. EFFECTOF RESINON WATERABSORPTIONOF Although the absorption of the varnish made with phenol TUNG; OIL FILMS resin C (h) is slightly higher than that of the other phenol resin Resin varnishes, the gloss of the film after the test remains exceed% Absorption after: abed f u h ingly high, as shown by Figure 4. The high resistance of 13 2 .. .. 3 0 1 day i 3 1 .. slides e and h and the low resistance of a, b, and g are apparent. 2 days OF VARNISH FILMS TABLE V. EFFECTOF RESINON WATERABSORPTION
-
VI.
3 days 7 days 14 days 21 days
Tung Oil Varnishes
Varnishes were prepared by dissolving one part of resin in three parts of bodied tung oil (180 poises) a t 220’ C . , and
Loss of material after swelling. %
ig 3 2 7 5 4 1 7 49 8
2 3 4 5
15.8 5.3
3.6
3 5 9 10
4.3
FIGURE 3. WATER ABSORPTION O F VARNISH FILMS OF BODIEO LINSEED-TUNO OIL [4:1] WITH DIFFERENT RESINS OIL! R E S I N . 1 : l .
r
OF”-
yoLOSS IN WEIGHT OF
DRIED FILMS
C,
E, 6-
0-
A
7
14
DAYS
-
0 1 1 -2
6.0
3 4 7
i 1 3 3
6.3
5.4
10
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FiOUnE 4.
SLIDES
OF
SHOBT-OIL VARNIsElEs WITH SWELLING TEST
Conclusions 1. The water ahsorption of oil varnishes IS determined to a considerable degree by the nature of the resin. Phenolic resins are much more water resistant than other resins; the pure oil-reactive phenol resin (e) is most resistant of all. 2. Other factors which determine the swelling are: a. The amount of tung oil in the film. This oil exerts a distinct infiuenceeven in small percentages and is able to neutralize the swelling tendency of larger quantities of linseed oil. b. The proportion of oil to resin. This relation is less important with an oil mixture of higher tung oil CODtent. Long-oil varnishes with high linseed oil content absorb more water than s h o r t 4 varnishes (limed rosin and oil-reactive phenol resin excluded). e. The nature of the drier in the varnish. 3. The greatest loss of material of the films (leaching out) after the swelling test is shown by long-oil and by limed rosin varnishes. Pure phenolic resin varnishes show smallest losses in both long- and short41 varnishes. 4. The drier has a considerable influence and here again (just 8s with the drying oil films, 8) lead has a different action on linseed oil than on tung oil varnish. Leaddried lmseed oil varnishes take up more water (after 3-week immersion) than cobalt- or manganesedried films; tung oil and oiticica oil varnishes show a smaller absorption with lead drier. In both types of varnishes the loss of material of films containing lead is smallest. This difference may be explained by the nature of the film formation, which takes place through combined action of oxidation and polymerisation. Cobalt catalyzes oxidation,
RBsilrS c l TO
h
VOI,. 30, h0. 9
AFTER THE
and lead influences polymerization most. Linseed oil varnishes dry more by oxidat.ion; tung oil, oiticica oil, and dehydrated castor oil varnishes are affected more by polymerization. Oxidized films are leached out by water to a higher degree than polymerized films, and insufficiently dried films (lead-linseed oil) show a higher water absorption but smaller material loss than cobalt- or manganese-dried linseed oil films. Tung oil dries sufficientlywith only lead as the drier and these films show a low water absorption as well as a small material loss. These conclusions were first presented in the previous paper (8) and are here confirmed for varnisb films. That manganese belongs to the group of driers that catalyze oxidation reactions is definitely proved. A conclusion of more practical importance is that in tung oil varnishes the application of cobalt or manganese drier must be as small as possible. 5. Dehydrated castor oil varnishes behave like tung oil and oiticica oil varnishes, but are much less water resistant.
Acknowledgment This investigatioii was carried out with the aid of the Cu’ederlandsche Chemische Vereeniging and with a grant from the Hoogewerff Fund, for which the authors expres their gratitude. They are also indebted to the directors of Pieter Sehoen & Zoon, paint, color, and varnish manufacturers, for their permission to publish the results of these experiments.
Literature Cited (1) Edwerds, IND. ENO.Cam&, 18. 519 (1936). (2) Rime and Wiebols, Ib% 29. 1140 (19371. R ~ c m v e oMarch 11, 1938
