December, 1931
INDUSTRIAL A N D ENGINEEIZING CHEMISTRY
Since the closed process makes possible the use of a much thicker film of material, this permits the very cunsiderablc reduction in size of the apparatus. The actual effective refrigerative surface required per pound of product produced by the merged process as compared to that required by the roll and picker box type of apparatus is as 10:lMl. So here again, on the question of space, the merged process has the advant.age, being many times more compact. The relative control ability of the two processes may be answered by the statement that full automatic controls are available and have already been applied to the merged process,
1357
whereas the exposed roll and picker box apparatus has not heen supplied with such control, if any has been worked out during its 25 years of use. The question remains as to the extent of the profitable application of this process. Results of preliminarytestsandstudies show that the application of this method of heat treatment and heat transfer, with its confined layer, its effective agitation, and its continuous motion in a controlled direction and under controlled conditions, indicates, and in fact insures, very worthwhile results in the ancient but indispensable art of heat transfer as applied in the process industries.
Scorch Retarders and Scorch-Retarding Materials' H. R. Thies GOODYBAR
'nne A N D
RVSBBR
co..AKRON. o m
The effect of several softeners upon retardation of It was used in the masterCLASS of m a t e r i a l s , scorch is shown. This effect is also obtained by using batch m e t h o d . Scorch-reknown as scorch reLarders, h a s heen small amounts of some organic materials which might tarding materials were added be classified as scorch retarders. The effect of some of t o t h i s c o m p o u n d in t h e availa& for Some time and these materials upon the temperature coefficient of amounts of 0.25, 0.50, 0.75, has heen the subject of inscorch is found to be ofdifferent value at different temand 1.0 part per 100 parts vestigation in various lahoraof rubber; with softeners or perature increments below t h a t of t h e curing temperatories for a c o n s i d e r a b l y ture. and it seems that t h e temperature coefficient of activators, 1.0, 2.0, 3.0, and longer time. The ideal ma4.0 parts were used. terial of this typeisone which scorching decreases as t h e temperature is raised. In selecting a definite decan he added to a rubber compound and render it decidedly less scorchy at milling and cal- gree of scorch for all comparisons, solubility and swelling endering temperatures, yet not interfere with the curing rate of tests were made as shown in Figure 1. Here are shown the compound at its curing temperature. Such a material the turbid suspensions of rubber compound in gasoline, and, slrould have no effectupon color, should not be detrimental to in corresponding order, the same treated-rubber pellets which the aging properties of rubher compounds, and should he prac- have been soaked in gasoline for 2 hours. It is evident tically odorless when used in rubber; and its activity should be that the rubber sample which has been heated for a length such that it is necessary to use only a small amount of the of time sufficient to give a 105-mm. height of obscuring column (when immersed in gasoline 16 minutes and shaken 1 retarder. Practical experience has taught that certain softeners are of minute) just begins to swell after 2 hours; this indicates benefit when scorching trouhle is encountered in the factory, setup, whereas the smooth dissolving as in the case of pellets hut the usual conception is that such ingredients soften the heated for a shorter time does not. The time necessary to oompound; the fact that these materials possess a definite reach this definite degree of scorch is taken as the so-called inscorch-retarding effect has not been so widely taught. The use Time hented (niin.) Soaked in xasoline of a scorch retarder seems to he a comparatively new practice, 5 10 15 20 30 2 hours (1, 8, 6), but, ae will be shown later, the industry has been using compounds which function as such for years. The effect that these materials have seems to indicate that the temperature coefficient at some temperature under that of the practical cure is altered by the scorch-retarding componnd. If the same degree of cure is to be maintained in the same time in the presence of a scorch-retarding material as in its absence, and if a t lower temperatures the material does hold off premature vulcanization, this change in temperature coefficient should he observable. I n order to ascertain whether or not this condition is true, and in order to demonstrate the hehavior of these retarding materials at various temperatures, the work reported herein was undertaken. Method of Determining Scorch The solubility method of determining scorch (6) was employed upon a compound of simple constituents. Thc com35 40 45 10SCIear 6 IO 15 20 2.5 Hdiilit of column irnm.1 Time heated (min.) pound consisted of the following ingredients:
A
Pa,,*
Flame I S o l U b l U t r and Swelllne Testa 00 Rubber
100
10 10 3
1
_____
."_
1*A
t Rccdved September IO. 1931. Prepented before the Division of Rubber ChemirtrV at the 82nd Meeting of the American Chemical Society. BuUdo. N. Y.,August 31 to September 4, 1931.
dex number, and i t is felt that it represents a sharp duplicable end point. Particular stress is laid upon the fact that all oomparisons in this work are made using this degree of scorch. I n selecting a temperature range for study of scorching, four ternP'?ratures Were chosen and were Obtained by boiling the following liquids in the special container:
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1358
O
Ethylene dichloride Water Butyl alcohol Ce'losolve
c.
82 99.5 113.5 130
F. 180 210 236 266 O
The first of these temperatures might be considered as close
to good milling temperature, the second could be considered as fair milling temperature, while the third would be called a high milling temperature. The fourth temperature tried is slightly above the temperature of cure. Materials Used
Pine tar (8, mineral oil, and rosin oil were used as softeners. The mineral oil was a heavy viscous oil (specific gravity 1.06), known under the trade name of Para Flux. The rosin oil was a synthetic oil containing 50 per cent rosin and 50 per cent light petroleum oil. Stearic acid was tried as an activator and softener combined. The retarding materials tried were: benzoic acid, o-chloro-
Vol. 23, No. 12
benzoic acid, glyceryl phthalate, furoic (pyromucic) acid, rosin, and zinc resinate. Results
The results obtained have been plotted in the charts. Tensile strength and 700 per cent modulus values are shown to give an indication of the physical properties of the stock; the index-number curves are plotted from values obtained a t the various temperatures. I n Table I1 a tabulation of these numbers is given after corrections, which are discussed later, have been applied. Chart 1 shows the effect of various amounts of pine tar. These data show that pine tar has a very definite retarding effect upon scorching a t 82", 99", and 113.5' C., with little effect a t 130" C. Therefore, this material is a scorch retarder of long-standing usage. The index-number curves show graphically the great effect that a difference of 31 O C.in milling temperature, for example, would have upon scorchability of these stocks. At 82" C. there is a difference of 256 minutes in scorching time between the control stock and that containing
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December, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
4.0 parts of pine tar; a t 113.5' C. the difference is only 20 minutes. It is also pointed out that the actual time necessary to scorch the control a t 113.5' C. is 17 minutes, while a t 82' C., 222 minutes are required, These values for the stock containing 4.0 parts of pine tar are 37 minutes at 113.5' C. and 478 minutes a t 82' C.
It is possible from the index-number curves to find the effect of any normal differences in milling or calendering temperatures. For factory scorching indications, it might be well to take a more advanced state of scorch for index-number comparisons. This, of course, could be accomplished by a more severe treatment of the pellet in gasoline. I n Chart 2 the effect of stearic acid is shown. It isevident that this material activates Captax and a t the same time decreases its scorchability. Three parts of the acid are about as useful for this purpose as are 4.0 parts and represent a gain in time of scorch of 144 minutes a t 82' C. and of only 8 minutes a t 113.5' C. I n Chart 3 the effect of a mineral oil, comparable to pine tar in its softening effect, is shown. Its effect on tensile values is the same as that of pine tar, but it softens the modulus to a lesser degree. However, it is also evident that its scorchretarding effect is not as great, 4.0 parts giving a gain in time of 147 minutes at 82' C. against 256 minutes obtained with 4 parts of pine tar. The effect of a synthetic rosin oil is shown in Chart 4. The behavior of a typical scorch-retarding material is shown in Chart 5. Furoic acid (sometimes known as pyromucic acid) is used. From the tensile and modulus properties it is seen that all stocks containing the acid give curves which cross those of the control somewhere in the range of best hand-tear cure, i. e., between 20 and 30 minutes; this indicates that a t these points the physical properties of the control are exactly duplicated, and that an increase in scorchiness is obtained, as indicated by the index-number curves. The effect of this material on temperature coefficient of scorch will be discussed later. The results obtained using WW rosin are shown in Chart 6. Its effect upon scorching is of such magnitude that it was classified as a scorch-retarding material and used as such in small amounts. Its effectiveness is quite good with this type of acceleration, but it does not follow that i t will function with an accelerator of another type. Several cases have been observed where a scorch-retarding material works with mercapto-
1359
benzothiazole, for example, and is without effect when used with tetramethylthiuram disulfide. Chart 7 gives the behavior found when zinc resinate was used as a retarding material. It is evident that this material is practically as effective in its action as rosin. I n Chart 8 the behavior of benzoic acid is shown. This material has desirable properties as a retarder. All modulus curves cross those of the control within the best-cure range, as do all tensile curves, with the exception of that of the stock containing 1.O part. Critical-point curves show decided retarding in scorchiness a t all temperatures except 130' C. It is also evident that 0.75 part of the acid is almost as effective as 1.0 part. These stocks set up over 200 minutes slower a t 82 degrees than does the control stock. Chart 9 shows that o-chlorobenzoic acid is an effective retarder and can be used in smaller amounts than can benzoic acid, 0.25 part of the former being about equal in retarding action to 0.50 of the latter. Both of the materials tend to act as activators, in so far as modulus values are concerned, giving higher values a t the longer cures than the control. If tensile values are considered, it can be seen that benzoic acid tends to give higher values than does the control; with o-chlorobenzoic acid the tensile values are not quite so high. The effect of a material which possesses a violent retarding effect is shown in Chart 10. Glyceryl phthalate retards scorching very effectively, but it also interferes with cure to such an extent that it would certainly be necessary to use less than 0.25 part on the rubber; in such small amounts it is not as desirable in retarding properties as are some of the other materials discussed. Temperature Coefficient of Scorching Inasmuch as the index-number values represent the time at which a certain definite and sharp degree of vulcanization exists, it was thought that a calculation of the temperature
coefficient of scorch, carried to this particular degree, would be of value and should show a change in temperature coefficient a t various temperature increments under 127" C. I n making such calculations, the index-number values as observed were corrected for temperature lag so that they represented actual cure equivalents for their respective temperatures. Using a temperature coefficient of 1.50 per 10' F. (5.6' C.), which serves in normal curing practices, the correction values were found as follows:
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I N D U S T R I A L A N D ENGINEERING CHEMISTRY
The actual time-temperature curves were plotted from data obtained by thermocouple measurement, having the thermocouple junction placed in the center of the pellet. From these curves temperature values were taken a t small time intervals, and these values were plotted as rates by using the Goodyear l / T values for the corresponding temperatures. The curves thus obtained were chemical-work or rate-of-vulcanization curves, and the area under them represented the equivalent cure. The difference between the equivalent cure and the total time of cure is given as the correction to be applied a t the various temperatures. TEMP.
INDEX No.
130 113.5 99.5 82
Minutes 5 or over 10 or over 10 or over 10 or over
c.
SUBTRACT Minutes 4 4 4 3
An interesting observation was that, if the rate of temperature rise of the pellets, when subjected to the foregoing temperatures was plotted, the curves for these temperatures were almost identical, and all pellets were up to the bath temperature in 10 minutes. The same statement as to shape applies to the cooling curves when the tubes containing the pellets were removed from the boiler and cooled in water at room temperature. The time for cooling to room temperature was 8.5 minutes. The previous correction factors also include this value. Table I gives the temperature coefficients found, using furoic acid as an example and obtaining the rate of change by dividing the corrected index number a t 130" C. into that a t 113.5" C. for temperature change of 113.5' to 130" C. Then the 113.5' C. values were divided into 99.5' C. values and 99.5' C. values into those found at 82"C. Table I-Temperature Temperature change, O C. Increment, C. Theoretical (Coefficient 1.5O Control (no retarder) Control 4- 0.25 furoic acid ' 0 . 5 furoic acid 0.75 furoic a d d 1.00 furoic acid Average for furoic acid
Coefficient of Scorching (Rated per loo C.) 113.5-130 82-99.5 99.5-113.5 14.0 16.5 17.5 2.04 2.04 2.04 per 10' F.) 3.07 2.07 2.02 2.74 1.82 3.40 2.46 1.62 3.22 2.23 1.92 3.35 2.16 1.82 3.04 2.45 1.82 3.32
The data in Table I show that, if one considers these coefficients as rate-of-change values, the control (mercaptobenzothiazole stock) shows a greater rate from 82" to 99.5" C. than it does at the other two temperature increments, but a t these increments of temperature the values are almost the same. They are close to those reported by Park (4) for the temperature coefficient of vulcanization, and are not far removed from the theoretical values. The addition of furoic acid increases the values of the temperature rate of change at the two lower temperature increments, while i t is decreased at the higher increment as compared to the control stock. This statement is in line with the data obtained upon the curing characteristics of the stock and seems to be the manner in which a scorch retarder functions. Table I1 gives the corrected index numbers for all experiments cited and also shows the ratio between these values at various temperatures. These ratios are reduced to a 10" C. rating in Table 111. The values in Table IV offer some interesting comparisons. The three control stocks were of the same formulas but contained different lots of rubber (previously tested and found to cure a t the same rate), yet they show different behavior in so far as scorching is concerned. This variation is not unusual and requires that in this work a control be examined along with each group of experimental compounds. Attention is called to the fact that for the simple mercaptobenzothiazole control stock the average coefficient a t 82-99.5' C. is decidedly greater than for the other two differences in temperature studied.
Table 11-Corrected A
".
C.) Minufes
Control 1 1 . 0 stearic acid 2 . 0 stearic acid 3,O stearic acid 4.0 stearic a d d 1 . 0 pine tar 2 . 0 pine t a r 3.0 pine tar 4 . 0 pine tar 1 . 0 mineral oil 2 . 0 mineral oil 3.0 mineral oil 4 . 0 mineral oil 1 . 0 rosin oil 2 . 0 rosin oil 3 . 0 rosin oil 4 . 0 rosin oil Control 2 +0.25 rosin 0.50 rosin 0.75 rosin 1.00 rosin 0.25 zinc resinate 0 , 5 0 zinc resinate 0 , 7 5 zinc resinate 1.00 zinc resinate 0.25 furoic acid 0.50 furoic acid 0 , 7 5 furoic acid 1.00 furoic acid Control 3 +0.25 benzoic acid 0.50 benzoic acid 0.75 benzoic a d d 1.00 benzoic a d d 0.25 o-chlorobenzoic a d d 0.50 o-chlorobenzoic a d d 0.75 o-chlorobenzoic acid 1.00 o-chlorobenzoic a d d 0.25 glyceryl phthalate 0.50 glyceryl phthalate 0.75 glyceryl phthalate 1.OO glyceryl phthalate 1
+
VOl. 23, No. 12 Index N u m b e r s B C D (AT (AT, 99.5 113.5' 130 A/B C.) B/C C.). C/D C.) , MinMinMin-
219 4.86 255 5 . 0 290 4.68 361 3.87 363 4.22 340 5.16 423 4.97 444 4.36 475 3.80 263 5 . 2 6 263 4.75 360 6.22 366 6.10 260 4.73 327 4.24 451 5.07 456 4.08 156 5 . 3 8 217 6 . 7 8 268 6.70 298 7.46 317 5.76 238 6.42 254 6 . 2 0 299 6.50 327 6.06 273 5.94 310 5.64 347 5.88 357 5.32 227 4.48 324 5.00 458 4 . 9 4 529 4.48 529 4.20 399 5.24 455 5.24 523 4.50 569 4.00 424 ''4.90 499 4.16 631 4.16 666 3.74
AT^
Utes ..~
UlCS
45 51 62 82 86 66 85 102 125 50 55 58 60 55 77
3.46 4.6 3.27 3.9 4.1 3.9 3 9 4.9 3.8 3.85 3 05 2.75 2.86 3.23 3.08
112 89 29 32 40 49 55 37 41 46 64 46 55 59 67 50 64 92 117 125 76
4.0 3.30 2.9 3.56 3.63 4.07 4.23 3 36 3.73 4.14 4.16 3.83 3.44 3.10 3.19 3.85 3.55 3.53 3.77 4.03 3.62
117 87 142 86 120 152 178
3.66 3.48 3.95 3.45 3.53 4.11 3.49
13 11 19 21 21 17 22 21 33 13 18 21 21 17 25 27 28 10 9 11 12 13 11 11 11 13 12 16 19 21 13 18 26 31 35 21 25 32 36 25 34 37 51
...__
VlLF
3.25 4 2.75 4 3.8 5 3.5 6 3.5 6 4.24 4 3.67 6 3.5 6 4.12 8 3.25 4 4.5 4 4.2 5 4.2 5 3.4 5 4.34 6 4.5 6 4.0 7 3.33 3 3.0 7 3.67 3 4.00 3 3.25 4 3.67 7 3.67 3 3.67 3 3.25 4 3.00 4 2.67 6 3.17 6 3.0 7 3.25 4 3.60 5 4.34 6 4.43 7 4.38 8 3.50 6 3.58 7 4.57 7 4.00 9 4.17 6 4.25 8 3.70 10 4.22 12
T a b l e 111-Temperature CoeBBcient of Scorching (Rated per 10' C.) 113.5-130 82-99.5 99.5-113.5 Temperature change, C. 14.0 16.5 17.5 Range, C. 2.47 1.97 Control 1 2.76 3.28 1.68 + I , 0 stearic a d d 2.86 2.33 2.30 2.0 stearic acid 2.67 2.78 2.12 3.0 stearic acid 2.21 2.12 2.93 2.41 4.0 stearic acid 2.85 2.05 2.54 Average 2.79 2.56 2.95 1 . 0 pine tar 2.79 2.22 2.83 2.0 pine tar 3.50 2.12 2.49 3.0 pine t a r 2.71 2.50 2.17 4.0 pine t a r 2.10 2.95 2.62 Averaee 2.74 1.97 3.0 1 . 0 mineral oil 2.18 2.72 2.71 2.0 mineral oil 1.96 2.54 3.55 3 . 0 mineral oil 2.04 2.54 3.48 4.0 mineral oil 2.44 2.48 3.19 Average 2.31 2.06 2.70 1.0 rosin oil 2.20 2.63 2.43 2.0 rosin oil 2.72 2.36 2.90 3 . 0 rosin oil 2.42 2.86 2.33 4.0 rosin oil 2.43 2.46 2.69 Average 2.07 2.02 3.07 Control 2 2.54 1.82 3.87 +0.25 rosin 2.23 2.58 3.83 0 . 5 rosin 2.44 2.90 4.26 0 . 7 5 rosin 1.96 3.53 3.28 1.00 rosin 2.16 2.86 3.81 Average 2.22 2.40 3.66 0.25 zinc resinate 2.22 2.66 3.54 0.50 zinc resinate 2.22 2.96 3.71 0 , 7 5 zinc resinate 1.98 2.97 3.47 1.00 zinc resinate 2.75 2.11 3.81 Average 2.74 1.82 3.40 0.25 furoic acid 2.46 1.62 3.22 0.50 furoic acid 1.92 2.23 3.35 0.75 furoic acid 1.82 2.16 3.04 1.00 furoic acid 1.82 2.45 3.32 Average 1.97 2.75 2.56 Control 3 2.18 2.53 2.86 +0.25 benzoic acid 2.52 2.63 2.83 0.50 benzoic acid 2.70 2.68 2.56 0.75 benzoic acid 2.65 2.87 2.40 1.00 benzoic acid 2.54 2.66 2.66 Average 2.12 2.58 2.99 0 . 2 5 o-chlorobenroic acid 2.17 2.48 2.99 0 50 o-chlorobenzoic acid 2.73 2.61 2.57 0.75 o-chlorobenzoic acid 2.42 2.82 2.28 1.00 o-chlorobenzoic a d d 2.36 2.62 2.71 Average 2.52 2.46 2.80 0 . 2 5 glyceryl phthalate 2.57 2.52 2.38 0.50 glyceryl phthalate 2.24 2.95 2.38 0 . 7 5 glyceryl phthalate 2.55 2.48 2.14 1.00 glyceryl phthalate 2.47 2.60 2.42 Average
I N D U S T R l A L A N D ENGINEERING CHEMISTRY
December, 1931
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The agreement of values found for a single group of stocks, containing different amounts of the same scorch-retarding material, is not good and may demonstrate the fact that the compounds are dissimilar. However, if these values are averaged, there is a definite trend which shows that the temperature coefficient of scorching decreases in value as the temperatures are raised, and most of the materials tend to give greater rate of decrease than does the control stock. Table IV CONTROL
99.5'
Min. 219 156 227
Min. 45 29
c.
1 2 3
NUMBERS 113.5' 130'
TEMPERATURE COEFFICIENT
CORRECTED I N D E X
82'
c.
50
C. Min.
13 10 13
C.
Min. 4 3 4
OF
SCORCHING
829 9 . 5 - 113.599.5' C. 113.5' C. 130° C.
2.70 3.07 2.56 Average 2 . 7 0
1361
2.47 2.07 2.75 2.43
1.97 2.02 1.97 1.99
It should also follow that the increment of temperature which gives the greatest difference between the control stock and that of a stock containing scorch-retarding material is the
temperature range in which the retarding material functions most efficiently. This, however, does not necessarily mean that this is the range in which the retarder is most useful for practical purposes. Conclusions
Softeners, such as pine tar, rosin oil, and mineral oil, are useful when scorching trouble is encountered, owing to their scorch-retarding properties as well as to the fact that they soften the rubber batch. Stearic acid functions as a scorch-retarding material as well as an activating material when used with Captax. A decided gain in scorching time is demonstrated by use of scorch-retarding material without alteration to a great extent of the physical properties of the compound used. There is a definite change in the temperature coefficient of scorching encountered between 82" and 130" C., this coefficient being greater when rated per 10" C. for the temperature change between 82" and 99.5" C. than it is either between 99.5" and 113.5"C., or between 113.5' and 130" C.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
1362
There is a tendency on the part of the stocks containing some retarders to give a greater percentage decrease in temperature coefficient of scorching over the range studied than does the control stock. With other retarding materials this does not hold. A scorch-retarding material is best measured by its effect upon index numbers of a control stock rather than by its effect upon the temperature coefficient of scorching. Acknowledgment
The author wishes to thank A. J. Crawford for work done on measurement of rate of temperature rise and fall and calcula-
Vol. 23, No. 12
tion of theoretical temperature coefficients of scorching. Thanks are also due L. B. Sebrell and R. P. Dinsmore for permission to publish this paper. Literature Cited (1) Cadwell, S. M., U. S. Patents 1,778,707-709, incl. (Oct. 4. 1930). (2) DeFrance. M. J.. and Krantz. W. J.. I N D . ENG CHBM.28, 524 (1931). (3) Morse H . B , U. S. Patents 1,734 633-640, incl. (Nov. S, 1929) (4) Park, C. R.. Paper presented before 82nd Meeting of American Chemical Society Buffalo N. Y.. Aug. 3 1 to Sept 4 1931 (5) Somerville. A. A., U. S. Patent 1.791.876 (Peb. 10, 1930). (6) Thies, H. R.. INO. ENG.CIIBM., 40, 1223 (1928).
Compatibility Relationships of Aroclors in Nitrocellulose Lacquers' Russell L. Jenkins and Robert N. Foster SWANNRESEARCH, INC..ANNISTON. ALA.
I
This paper deals with certain physical properties of preciable h a r d e n i n g upon the chlorinated diphenyl products, known commersented preliminary data heating to moderately high cially as aroclors. The aroclors are described, and a obtained on the aroclors temperatures. discussion is presented of their stability to light, to or polychlorodiphenyls, esIf the series of aroclors of hydrolytic influences, and to heat. Data are given pecially as rega.rds their comprogressively increasing visshowing the relative permanency or vaporization rates patibility with nitrocellulose cosity is considered, the folof the aroclors and the more common plasticizers and and with systems containing lowing p r o p e r t i e s increase softeners. A table is given of the physical properties nitrocellulose and resins or when ascending the series: of the aroclors used in this investigation. density, r e s i s t a n c e to displasticizers. The main part of the paper deals with the compaticoloration by sunlight, softenThe nitrocellulose-lacquer bility relationships of the aroclors with common ining point, tendency to crysfield lends itself more readily gredients of lacquers. The relative effectiveness of tallize, flash and fire-points, to scientific approach t h a n different plasticizers in increasing the limiting comand lack of odor. the other protective-coating patible ratios of aroclor to nitrocellulose is shown On the other hand, in defields, because p r a c t i c a l l y graphically. Trilinear diagrams are given for a numscending the series from the its e n t i r e development has ber of three-component systems containing 1/2-second more viscous aroclors to the occurred within recent times. nitrocellulose, an Aroclor, and certain typical resins. less viscous ones, the following It is less t r a m m e l e d with propertiesincrease: volatility, tradition and the art of comDoundina. and it has already been systematically invee- ccmpatitility with nitrocellulose, and solubility in solvents. I nthe lacquer field the choice of suitable aroclors for investitigated It is fortunate that this is-the case when new materials like the aroclors appear on the market because it is gation depends on a balance of some of the above-named possible to study the properties of the new substances with, properties. The maximum compatibility with nitrocellulose respect to the lacquer field and to determine with some is desired; the volatility must be low enough to give perdegree of certainty the best methods for the formulation of manency to the aroclor in the lacquer film; good solubility in lacquer solvents is necessary, and presumably the resistance to lacquers from the new substances. It is already well known that the aroclors are chlorinated discoloration or change by ultra-violet light should be as high diphenyl products, varying from water-white mobile oils as possible. I n certain cases a low density may be desirable through viscous oils and soft waxes to pale amber brittle for economic reasons. Taking these and other factors into account, aroclors 1254 resins and opaque crystalline solids. The aroclors are nondrying. They are not polymerized or condensed products in and 1262 have been chosen as the most suitable for investigathe ordinary sense of this term, nor do they show any ap- tion. Where less permanence is not objectionable, aroclor 1242 is of interest because of its greater compatibility with Presented before the Division of Paint 1 Received August IS, 1931. nitrocellulose. Aroclor 1819 is regarded as too volatile for and Varnish Chemistry at the S2nd Meeting of the American Chemical lacquer work except in special cases. Society, Buffalo, N. Y.,August 3 1 to September 4, 1931.
N THIS paper are pre-
5).
Table I-Physical Color (Lovibond yellow: 1 inch depth of liquid) pergram Maximum acidity (mg. NaOH per gram of aroclor) Viscosity, seconds Saybolt at 100' C. Distilling range (cor.) (cor.), C. Pour point (A. S. T. M.), pour M . ) , 0' C. Freezing point, e C. Specific gravity at 2eo/25O C. g Coefficient of expansion, cc./cc./" C. Coef >d, e C. Flash poi point, Cleveland open-cup method, Fire point n&-v Fire C. Refractive' index (n D at 27' C.) Refr 0 At 99' C. (210' F.). b At 90"/90° C. --'-I
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Data on Aroclors Used in This Investigation
-
1819 0.2 0.005 30 278-295
.....
14 1.15 0,00079 138 177 1,6125
1242 0.3 0.004 34a 320-360 Minus 16 or lower
Non-crystalline at 0
1.38 0.00073 Above 165 (indistinct) Above 300 1,6248
AROCLOR
1262
1254
0.5 0.01 46 366-399
0.9 0.02 96 388-431
Not higher than 10 Non-crystalline at 0
Ndd-Gystalline at
N o~... ne .
.... None
0.00072 1.55
None
1.6391
1.63b
None
1.6493
o
