China Wood Oil in Lacquer-I' W. E. F l e d and D. C . Booth with Walter H. Beisler ~ ~ K E X S I T 017 Y
FLORIDA, GAIX'BSVILLIE. PLA.
HIS investigation , ~ a 6started ill i,rdcr iodeterulille whether China wood oil could be used to advantage in lacsuer formulas, and to study what prowties the oil would impart to the lacquer films. The lkerature shows few references to the use of China wood oil in lacquers. Wilson* disposes of the matter as follows:
T
The oil *erns to have some field in pyroxylin lafquen = a softener, but little is known of its application in this connection. The raw oil has a tendency to give with pyroxylin opaque films of very low tensile strength or durability, but a properly processed oil might prove of value.
The following quotation is taken with permission from a personal communication from Doctor Wilson: The raw oil is practically useless in any type of formula. The treated oil-that is, oil that has been properly bodied in the presence of s m a i ~ amourrts of rosin, ester gum, or similmsnhstancecan he incorporated in lacquers to a certain limited extent, but it does not impart plasticity to the lacquer. 1 do not think its place in lacquer is that of a plasticizer, hut it may eventually of resin and impart a trifle Serve to repkce a certain additional waterproofness and adhesion.
Kolkea predicts quite general useof lacquerscontainingdrying oils, and describes some experiments in which he mixed raw tung oil with 20 and 30 per cent solutions of '/zseeond nitrocellulose in butyl acetabe. He gives no account of the nature or durability of the films from such mixtures. Raw Materials The cotton used in this study was R. S. I/i-second nitrocellulose nlanufactured by the Hercules Powder Company. It vas dried at lO0'C. before use.
Specific gi*?itY (15.5' C.) Refractive mder (25' C.) Acid No.
0.9416 1.517
3.7
Saponification No. Iodine No. (Henus)
nrowneheat test
191.2 168.0
11.0
minutea
This oil had beon in storage for 12 to 18 nlonths, I+, pale amber in color and perfectly clear. The solvents were plrchased from the u, s, Solvents corporaCompany and the tion. The dduents were e. P. grade. The solvents were tested for acidity by means of copper strips and found to contain no freeacid. Prelimlnary Experiments l'lie present investigation began with attempts to prepare a satisfactory lacquer hy adding raw imported tung oil to solutious of '/flecond nitrocellulose in butyl acetate and butanol. The films obtained were opaque and of low tensile strength. Further studies of lacquers containing raw tung oil are contemplated in the future. Bodied China wood oil prepwed by heating the raw ported oil with 6 per cent by weight of gYeero1 at 200" C . for 1 hour after which superheated steam was passed through the mixture at 150' C . for 45 minutes. The function of the steam wa8 to remove any uncombined glycerol. The bodied oil was perfectly clear, but red in color. A lacquer of the following composit~on wBs
*-
% by wetab< Cotton (dry) I3rter gam Bodied tung oil Ethanol R"tCn*l
12.24 8.70
4.02
4.00
3.36
% by mri8hI Butyl acetate Amyl acetate Diacetone alcohol
Tolueoe
40.98
8.18
8.52 11.94
The film from this lacquer blushed had$. After drying, the film was yellow and erhibit,ed a frosted appearance.
Left: Lacquer 36 on cypress (coptdns tung oil and 60 per cent of plnrtlazer) Right: Lacaver 48 on cgpre~s(free trtun% oil, contains 60 per cent of plaStlCrzerJ
PIaure 2
It was soft and lacked toughness. Although this particular formula was far from satisfactory, it is believed that careful adjustment of the proportions of the various ingredients might lead to a good lacquer. A further investigation of I Received March 1, 1928. This PSP" is b a e d upom P thesin pcerurted this problem is now in progress. by W. E. Flood tothefacultyof the Univernityof Floridain partial fulfilment Tung Oil-Ester G u m Resins of the requiremultr for the degree of master of sdence. "Pyroiylin Ennmels and Lacquers." p. 65, D. Vnn Nostrand e.. The uext step was to introduce the China wood oi1,in the 1926. form of oil-ester gum mixtures, which were made by heating 1 Fvrban-CiB., 84, 2710 11927). 88. 861 (192s)
Except where otherwise noted the China wood oil was pressed in this country from Florida nuts. Its constants were a8 follows:
f
INDUSTEIAL A N D ENQINEEEING CISEMISTRY
610
Lift: Lacquer %a ,IT/ cypress (cont=;nr tung oil and 10 per cent 01 plasticizer) Right: Lncquci 12 on cyprcss (free iron, tung oil, cont;lins SO pcr ceut o i
Val. 20, No. 6
Lelt: Isequri 84 on oak (contains tung oil and 30 per eerie plsrtid~er) Right: Lacsucr 44 On oak (free from tung 011. c~mtacna30 per cent of
plaStiCiZeC)
plaStiCiZei)
Figure 3
Figure 4
(I) The formula of the lacquer to be prepared was written showina the weights . of each in-
gredien?
(2) T h e d r y nitrocellulose was dissolved in the mixture of
solvents. (3) The resin was dissolved
Lett: lacquer A on ~ i n e Right: lacquer B O Dpine Figure 5
raw tonp oil, glycerol (6 per cent of the weight of the oil), and ester gum. Crude ester gum was prepared by heating pale rosin with 10 per cent by weight of glycer C. for 20 minutes. After the ester gum ?I.& ~ ~ ~ 0 0 1 mixed with tung oil and glycerol in a round-hott A short reflux condenser was fitted'to the flask to a1 to escape and to avoid loss of glyercol vapor. was stirred mechanically. The flask was heat bath at 275" C . for 2 hours, after which sup was passed through the charge for 45 minutes The resins obtained in this way were clear, tr in color, and fairly hard at room temperature. 30 per cent China wood oil The acid numbers of these cohol-benzene method,&var color of t.hese resins may be kept low hy using relatively large quantities (500 grams or more) and avoiding orerheating and unnecessary exposure to the air during the heating. It is probable that similar resins may be prepared in one heating operation from rosin, glycerol, and raw tung oiL6 Preparation of Lacquers Keyed6 general formula for an automobile lacquer wm used as a guide in attacking tho problem of lacquer formulation. The following procedure was found to be very convenient after some experience with lacquer preparation had been gained:
____ 4
3
tly cracked on ends
Many cross-grain cracks Same Very few cracks Few cross-grain cracks Few cross-grain cracks Many cross-grain cracks Few cross-erain cracks Many cro%i-graincracks Few cross-grain cracks e7ycross-grain cracks
U.h.
U.L.
U.h.
O.K. O.K. Slightly cracked on ends
O.K. O.K. Many fine cracks CYPRESS PANELS Many cracks Same Very few cracks Very few cracks Few cracks Many cracks Few cracks Few cracks Few cracks Badly cracked O.K. Many cracks O.K. Badly cracked
Few short cracks Very few fine cracks Badly cracked, peeling
Same Same Badly cracked Bad!y cracked Badly cracked Badly cracked Badly cracked Badlv cracked Badlg cracked Badly cracked Very few cracks Many fine cracks Many long cracks Same
Same Same Badly cracked Badly cracked Few long cracks Badly cracked Many cracks, peeling Peeling badly Slight peeling Same O.K. Same O.K. Same
Badly cracked Same Badly cracked, peeling Badly cracked, peeling Badly cracked Same Badly cracked, peeling Badlv cracked. Deeled Badly cracked; peeling Badly cracked, peeling Several long cross-grain cracks Badly cracked, peeling Several long cross-grain cracks Badly cracked and peeled
Slightly cracked on ends Badly cracked Slightly cracked on ends Slightly cracked on ends O.K. O.K. Slightly cracked on ends Slightly cracked on ends Slightly cracked on ends O.K. O.K. O.K. O.K. Slightly cracked on ends B 0 TO indicates t h a t lacquer contains tung oil. b DP indicates t h a t lacquer contains dibutyl phthalate.
T h e percentages are based on the weight of dry cotton in the lacquer
F., while films from lacquer 31 were perfectly clear after drying when the relative humidity was 74 per cent at 85’ F. The film from lacquer 31 was very hard, but tough and adherent, which seemed to indicate that the tung oil was acting as a plasticizer. After 5 days’ exposure in the laboratory the film lost most of its plasticity, and it could be removed from the glass in large flasks when cut with a knife. Lacquers 32 to 36, inclusive, were then prepared. They were identical with lacquer 31, except that 10, 20, 30, 40, and 60 per cent, respectively, of dibutyl phthalate (based on the weight of dry cotton) was added. The films from these lacquers retained their plasticity in the laboratory. The film from lacquer 34 (30 per cent of dibutyl phthalate) appeared to be the best. It was somewhat tougher than the others. Test tubes coated with the commercial lacquers and with lacquers 31 to 36, inclusive, were immersed in boiling water, then in 50 per cent ethanol, and finally in 0.1 N hydrochloric acid. 411 the films withstood these tests satisfactorily. Exposure Tests
In order to determine the effects on durability produced by the tung oil, lacquers 41 to 46, inclusive, were prepared. These lacquers were identical with lacquers 31 to 36 except that no tung oil was used. Ester gum alone was used as the resin. The ester gum had an acid number of 5.6 as determined by the alcohol-benzene method. For example, lacquer 41 had the following composition: Cotton (dry) Ester gum Ethanol Ethyl acetate
% by weight 19.21 5.78 8.24 6.77
% b y weight Amyl acetate Diacetone alcohol Benzene Toluene
Badly cracked Same Same Same Same Same Same Same Same
30.00 3.00 13.50 13.50
For outside exposure tests panels of oak, cypress, and pine 45 X 15 X 2.5 cm. were secured. The oak panels were filled with white lead in linseed oil toned with ochre and burnt umber. No filler or priming coat was used on the cypress or pine. Lacquers 31 to 36 and 41 to 46, inclusive, and the two commercial lacquers were applied in two coats on these panels, using a brush. The backs and edges of the panels were sealed with a spar varnish. I n order to overcome inconsistencies that might arise on account of differences in the character or seasoning of the
individual panels, two lacquers that differed only by the presence or absence of tung oil were placed side by side on the same panel. The panels were exposed November 17, 1927, at Gainesville, Fla., facing south a t an angle of 45 degrees from the vertical. The accompanying table shows the results of the exposure test. All the films on the pine panels, except those from lacquers 36 and 46, were badly cracked after 3 days’ exposure. This failure was obviously due to warping and cracking of the wood. I n many cases large areas of the films became detached from the wood, as is well illustrated by the lighter portions of the films shown in Figure 5. At the end of the exposure test, January 28, 1928, the film from lacquer 36 (60 per cent of dibutyl phthalate) was still in perfect condition, which demonstrated that this lacquer was more durable on wellseasoned pine than on cypress or oak. It was very plainly evident during the exposure test that the samples containing tung oil were more durable than the corresponding samples without the oil. The films containing tung oil showed much less cracking and peeling, which indicates that the oil renders the film more elastic and adherent. Photographs of representative areas of several of the panels were taken on January 5, 1928, with a copying lens attachment on the camera in order to show the extent and nature of the deterioration. The effects of tung oil and plasticizer on the durability of the films are clearly apparent. Conclusions
1-Tung oil, when heated in presence of ester gum, can be incorporated satisfactorily in a lacquer. 2-Tung oil increases the durability of the lacquer films markedly, and appears to make the films more adherent. 3-Increasing amounts of dibutyl phthalate, up to the maximum used (60 per cent of the weight of the dry cotton), resulted in increase in durability. Acknowledgment
The authors wish to express their sincere appreciation of the cobperation given them by several industrial organizations.
