Synthetic Resins from Coal-Tar Hydrocarbons W.H. CARMODY, W. SHEEHAN, AND H. KELLY The Neville Company, Pittsburgh, Pa.
catalyst. The various steps in OUMARONE-indene Resins have been produced by a new this development leading from resins have been comheat polymerization process, using as laboratory scale of 5 cc. to commercially produced from raw materials those unsaturated aromatic mercial scale of 8000 gallons are crude coal-tar solvents in the bodies previously considered as by-proddescribed in the present article. United S t a t e s a n d f o r e i g n ucts of troublesome nature, low value, countries for nearly three decRaw Material ades. Methods of production and limited use. Dicyclopentadiene, inhave been subjected to continual As is well known, the cardene, and coumarone are the raw mateimprovement; such efforts have bonization of coal in the highrials for this new process: their polymers been directed mainly to improvtemperature process results in are now produced in quantity at low cost ing physical characteristics such a quantity of light oil in the for the floor tile and varnish industry. as color, melting point, and range 100-200" C. The comsolubility. These newer methOther specialized uses have been deposition and volume of this ods have been concerned princicut are influenced by the source veloped to utilize their valuable properpally with the reactive materials of the coal, by the nature of ties. They are chemically inert bodies, coumarone and indene, and use the coal, and to a greater extent and are unaffected by practically all insulfuric acid as the c a t a 1 y s t. by the carbonization schedule. dustrial brines, acids, and alkalies. Other reactive compounds, cycloFractionation of material yields pentadiene and dicyclopentat h e u s u a 1 coumarone-indene diene, have been mentioned in recent patents as being a detricrudes. The present type of material is somewhat different mental factor in the production of light colored resins. Traces in relative composition from the usual naphthas, and its of each of these materials cause color changes entirely out of distillation range is shown in curve A, Figure 1. The main proportion to the amounts present. Such a condition is constituents and their boiling ranges are indicated. Not emphasized when these materials become relatively abundant all of them are useful in the present process; the xylene and and form the greater proportion of certain crude solvent styrene cuts are removed for other use. A relatively small naphthas resulting from the distillation of light oils. quantity of cyclopentadiene results from depolymerization The presence of styrene and dicyclopentadiene to the extent of the dicyclopentadiene and is also eliminated during fracof more than 50 per cent makes such naphthas entirely usetionation. The narrow-range light oil used in quantity is less for resin production. Such rich crudes of high potential shown in curve B, Figure 1. It is composed principally of value were available in quantity, and this fact led to a study dicyclopentadiene, with indene and coumarone as minor of methods which might be commercially applicable. constituents. The total unsaturated bodies a t times amount Prior to this development, these oils were sold as crude to 85 per cent by weight. The general characteristics are solvent naphtha. Prolonged standing of the materials conas follows: taining dicyclopentadiene and related compounds resulted in Boiling range, C. 164-198 Naphthalene, % u p to 2 spontaneous resin formation. Examination of this resin Specific gravitv 0.97-0.99 Molecular.weigh t 120-130 Dicyclopentadiene, yo 60-65 Aniline point, C . 26- 27 and an appreciation of its valuable properties encouraged Pale amber Indene, % 15-20 Color studies which eventually led to methods of accelerated Coumarone, % 5-10 production. Many catalysts and methods of polymerization were examined. For one reason or another these were Such a charging stock is very sensitive to change and, when considered as economically unsatisfactory and were elimiheated even slightly, begins to polymerize, oxidize, and nated. Polymerization by heat proved to be attractive from darken. Circumstances surrounding its storage determine an operating viewpoint; it is subject to exact control, introto some extent which of these reactions occurs. duces no corrosive or hazardous conditions, and results in a resin with desirable characteristics. A commercial method Early Experimental W o r k for producing these new resins has been developed which is A study of the coefficient of expansion was the single lead of aid to the paint, varnish, tile, molding, and adhesive inby which the process eventually was developed. I n carrying dustry because of low cost and large volume. This development originated from laboratory experiments carried out in out expansion experiments, samples of material were sealed glass ampules, which originally were intended to provide in glass tubes, and the length of t h e liquid column in each tube data concerning the coefficient of expansion of various was observed a t 20" C. Generally the tubes were heated to aromatic hydrocarbons. Careful examination of irregularielevated temperatures separated by approximately 20" ties in the coefficient for crudes containing dicyclopentadiene intervals. The expansion was proportional t o the temperaindicated the possibility of utilizing heat as a convenient ture to approximately 200" C.; at 215" C. the coefficient
C
O
245
INDUSTRIAL AND ENGINEERING CHEMISTRY
246
decreased in value. Kear 235" C. the expansion ceased to increase, and at higher temperatures a diminution in volume indicated that polymerization was an important disturbing factor. The possibility of using such a characteristic to follow quantitatively the course of reaction immediately suggested itself, and refinements ended in a method for evaluating such factors as time, temperature, yield, effect of concentration, rate of polymerization, and type of resin.
VOL. 30, NO. 3
heated to 200-205° C. in an oil bath, and volatile material was removed under a vacuum of 10-15 mm. This step removed no polymeric heavy oils and yielded true polymer weight. The resin at this time was composed of approximately 5 per cent dimers; the greater part of the balance consisted of tetramers and octamers of the original components. The polymers were dissolved in the test tubes to form a 2 per cent solution in c. P. benzene for molecular weight determination; color of the resins was determined by comparison with standard values established by the Xeville Company for evaluating commercial resins. When the technic was carefully carried out, reliable information was obtained from 3-5 cc. of original material. The speed of carrying through such a procedure enabled the effects of any temperature or time feriod t o be investigated with a minimum of laboratory work. n separate prior experiments it was found that pressures at times reached a value of 200 pounds per square inch. Hence a double number of tubes were used in each experiment because of the frequent loss of an ampule. Four representative experiments are summarized to show the general type of information. Table I gives a comparison of the manner in which results are influenced over periods of time a t definite polymerizing temperatures. Table I1 indicates that all molecular weights are essentially the same, regardless of time or temperature. The type of resin formed is almost the same from beginning to end of the reaction. No appreciable change in molecular weight occurs during any single experiment.
Heat Stability of Polymers Prior literature (4) states that indene or cyclopentadiene It is recognized that the experimental technic here described is of low accuracy, but the general deductions were found correct when applied to large-scale operation. The following table indicates the type of data upon which the entire development was based: Obser- - Temp. vation of Oil Obsvd. ExpanNo. Beth Length sion OC. Mm. % 159 20 0.0 1.9 162 40 3.8 65 165 6.2 100 169 9.5 174 135 12.6 165 179
Obser- Temp. vation of 011 Obsvd. ExpanNo. Bath Length sion O C . Mm. % 200 16.3 7 185 14.5 182 215 8 14.5 9 182 235 12.6 215 10 179 8.2 11 172 215 -3.3 20 12 154
polymers undergo considerable depolymerization a t elevated temperatures. Polymers with molecular weights of 1500 to 2200 undergo serious change when subjected t o temperatures as low as 180" C. for 15 days or longer. The same article shows that an indene polymer with a molecular weight of 600 undergoes little change when heated to 214' C. for 15 days. This information was of interest but not par-
It is apparent that, when the temperature is greater than 200' C., active polymerization occurs; the rate of polymerization rapidly increases so that above this temperature a reduction in the percentage of expansion occurs. This apparent decrease is accompanied by an increase in specific gravity which, in turn, is directly caused by the formation of polymers of specific gravity greater than unity. The simplicity involved in preparing samples for examination and the directness of the results obtained permitted a complete polymerization study to be made in a short time. Polymerizing ampules were constructed from 5-mm. Pyrex glass tubing. Several dozen of these tubes were filled to a depth of approximately 200 mm. with the crude solvent naphtha, whose composition is indicated in curve B , Figure 1. The ends were sealed, and the tubes were allowed to drain in a vertical position at 20" c.
Polymerization of the contents of a series of tubes was carried out by immersion in an oil bath maintained at a predetermined tem erature. The entire group was simultaneously immersed in t f e bath and withdrawn separately at regular intervals. The composition of each tube represented the results of reaction and all influencing factors in operation during the interval while at reaction temperature. After removal from the bath each ampule was cooled by plunging into oil and finally adjusted for measurement in a vertical position at the initial temperature. Comparison of the initial length with final length showed a decrease in volume. This was assumed to be directly indicative of the extent of polymerization. The analytical work began by opening the tubes at both ends and draining the polymerizate into weighed test tubes. They were
HOURS
FIGURE 2. COMPARATIVE YIELDSAND CONTRACTIONS AT VARIOUS TEMPERATURES
MARCH,r1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
247
I
TABLE I. EFFDCTOF TIME IN OIL BATHON POLYMERYIELD AT VARIOUS TEMPERATURES Time in Oil Bath Hours 0.25 0.5 0.75 1 1.5 2 3 4 5 6 7 8 9 10 11 13 15 17
18
0.25 0.5 0.75 1 1.5 2 2.5 3.0 4 5 6 8 10 12 14 20 24 30 38 43 48 0.25 0.5 0.75 1 1.5 2
2.5 3 4 6 8 10 12 16 20 24 26 30 36 0.25 0.5 0.75 1 1.25 1.5 2
2.5 3
3.5 4.25 4.5 6.5 8.5 7.5 10.5 a
Initial Final Length Length Mm. Mm. Experiment 198.0 193.5 229.0 223.0 231.5 225.0 205.5 198.5 203.5 196.5 224.0 215,O 220.5 211.0 220.5 210.0 223.0 234.5 204.0 215.0 211.0 224.0 208 0 196.0 220.5 207,5 210.0 197.5 206.0 192.0 214.0 199.0 212.5 198.0 210.5 196.0 222.0 207.0 Experiment 196.0 191.5 203.0 197.0 213.0 207.0 190.5 197.0 201.0 210.0 205.0 196.0 210.5 201.0 204.5 195.0 199.0 188.5 217.0 204.5 211.0 197.5 221.0 205.5 228.0 211.0 195.0 180.0 206.5 190.5 200.0 183.0 209.0 191.5 201.0 182.5 208.0 188.5 205.0 188.5 206.0 186.0 ExDeriment 219.5 215.0 220.5 213.5 224.5 216.0 197.0 187.5 205.0 193.5 205.0 192.0 210.0 197.0 187.0 174.5 194.5 209.5 212.0 195.0 189.5 207.0 201.0 220.5 215.5 196.0 206.0 227.0 201.0 181.5 202.5 181.5 219.5 197.0 229.0 206.0 237.0 213.5 ExDeriment 222.0 214.5 207.0 197.0 190.0 178.5 205.5 193.5 208.0 194.5 199.0 185.0 215.0 198.5 231.0 212.5 199.5 183.5 200.5 183.0 207.0 188.5 206.0 187.5 214.6 195.0 200.5 181.5 200.5 181.5 201.0 181.6 I
Contraction Mm.
207, 21.5' 4.5 6.0 6.5 7.0 7.0 9.0 9.5 10.5 11.5 11.0 12.5 12.0 13.0 12.5 14.0 15.0 14.5 14.5 15.0 202. 225O 4.5 5.5 6.0 6.5 8.5 9.0 9.5 9.5 10.5 12.5 13.5 15.5 17.0 15.0 16.0 17.5 17.5 18.5 19.5 19.3 20.0 203. 245O 4.5 7.0 8.5 9.5 11.5 13.0 13.0 12.5 15.0 17.0 17.5 19.5 19.5 21.0 19.5 21.0 22.5 23.0 23.5 206. 265' 7.5 10.0 11.5 12.0 14.0 14.0 16.5 18.5 16.0 17.5 18.5 18.5 19.5 19.0 19.0 19.5 ~I
~~~
% C.0 2.27 2.62 2.82 3.41 3.44 4.02 4.32 4.75 4.92 5.12 5.57 5.76 5.90 5.95 6.80 7.00 6.83 6.88 6.76 C.b 2.29 2.71 2.82 3.30 4.04 4.38 4.42 4.53 5.27 5.77 6.39 7.01 7.45 7.69 7.75 8.73 8.36 9.20 9.38 9.51 9.72
Polymer Mol. Yield Weight
C.d 3.38
4.82 6.04 5.84 6.72
7.04 7.67 8.00 8.02 8.73 8.94 8.99 9.08 9.49 9.48 9.70
c.
Time in Oil Bath Hours
% 10.4
396
2 i :4
33s
..
t .
...
...
35:4
327
34'0
4is
43:7
336
46:s
335
.. ..
245
...
6 9
...
49:5
330
52:6
387
0.5 1.5 3.5
12 16 22 26 30
... 22s
1 3
5
..
..
... ...
23:7
343
..
..
.
I
.
,..
39'3
344
..
493
..
4s:4
434
5h:8
445
63:O
456
6517
505 480 560
65:9 .
I
...
...
...
...
29:9
4oi
4318
404
50: 8
43s
5i:7
..
478
64:6 67.8
508 520
69:5 71.3 70.5
520 490
..
..
..
...
...
... ...
...
...
...
32.9
332
48:s
4ii
..
54:o
... bii
63:2
53 1
66:4
475
69:2 69.0 70.2
463 514 461
.. ..
8
12 16 20 30 38 43 48
...
C.0 -.
2.05 3.18 3.78 4.83 5.61 6.34 6.18 6.69 7.15 8.01. 8.45 8.83 9.05 9.26 9.70 10.35 10.25 10.01 10.00
TABLBIJ. ASSEMBLEDMOLECULAR WEIGHTS Polymerizing Temp.
215
0.25 1 3 5
li
15 18
Resin Used Grams 0.680 0.660 0.928 0.899 0,706 0.710 0.808 0.657
Benzene Used Grams 27,858 27.260 38.771 37,823 30.944 30.107 34,657 28.019
Solution 2.44 2.42 2.39 2.38 2.29 2.36 2.33 2.34
pression Degree 0.397 0.311 0.240 0.237 0.265 0.270 0.268 0.241
0.555 0.593 0,653 0.962 1.012 0.956 0.908 1.096 1.062 1.108
23.065 25.086 29.442 40.910 42.325 40.447 39.310 45,748 44.996 47.963
2.40 2.37 2.22 2.34 2.38 2.37 2.31 2.31 2.36 2.31
0.313 0.310 0.272 0.259 0.262 0.247 0.235 0.250 0.240 0.249
407 404 433 478 482 508 520 490 520 490
0.370 0.661 0.669 0.799 0.810 1.110 0.995 0.813 1.048 0.913 1.121
16.023 29.131 29.604 35.232 34.930 46.592 43.694 35.647 45.437 39.396 47.762
2.31 2.27 2.26 2.27 2.32 2.38 2.28 2.28 2.31 2.32 2.34
0.357 0.350 0.243 0.277 0.276 0.288 0.265 0.239 0.255 0.219 0.244
343 344 493 434 445 438 456 505 480 560 508
0.184 0.390 0.687 0.670 0.838 0.808 0.823 0.939
2.78 2.54 2.39 2.38 2.41 2.38 34.400 ., 2.39 37.930 2.47
0.372 0.398 0.388 0.302 0.380 0.377 0.383 0.338
396 338 327 418 336 335 330 387
%
I
Obsvd. Mol. Wi. 3 32 413 527 531 475 463 46 1 514
is paramount. The obvious limiting factors are the temperatures a t which depolymerization sets in and the ability to control the reaction and remove the heat as rapidly as liberated; the characteristics of the resin at equilibrium result from the ability to control such factors. Color, melting point, solubility, and molecular magnitude can all be controlled within certain limits. I n the determination of this critical point, ample margin was allowed by selecting for examination a resin with a slightly higher molecular weight than those resins produced in the process. Such a step apparently shows a lower critical temperature than is actually necessary. These resins were produced on a small scale by the use of a metallic halide catalyst and then purified to yield polymers for study. Samples of the resins were heated in small tubes
... ...
... ...
Color ranged from 3 to 3l/2 on the Neville Company's resin color standThe average molecular weight for this series was 358. C Color, 31/2-5. d Color, 4-5.
ard scale.
b Color, 3'/2-4.
ticularly satisfying, since higher temperatures and much shorter times were involved. It is recognized that the lower polymers are more stable than the higher ones. From a n economic point of view the recognition of a definite critical point and its location expressed in terms of temperature is important. Heat polymerization of the materials dealt with here is shown to be accelerated with continued rise in temperature. Acceleration of the reaction to obtain its maximum rate and maximum yield in the shortest time
De-
1
*
INDUSTRIAL AND ENGINEERING CHEMISTRY
248
a t constant controlled temperatures, and a t predetermined time intervals a tube of resin was withdrawn for examination. A comparison of molecular weight before and after heating indicated the presence or absence of depolymerization. Slight evaporation of dimeric polymer and the possibility of continued slow heat polymerization was evidenced by a slight rise in molecular weights as anticipated. This occurred only below cracking temperature. At this point these two factors are rapidly overcome, and a definite drop in molecular size is actually found. Such conflicting factors make it necessary to consider the trend rather than numerical values in the experimental data. Table I11 indicates the molecular weights found a t the end of definite exposure times to the depolymerizing temperatures shown. The molecular weight of the resin used was 775; increase in all cases was found where the exposure was less than 8 hours a t 260' C. Longer periods revealed greater disruption of the molecule. This temperature is evidently an approximate "critical value" below which commercial polymerization may be carried out. Also the constancy of molecular weights of the polymers formed throughout the reaction indicates that the above critical value is applicable throughout the polymerization period, and that there is no drifting downwards as molecular weight builds up. This might have been expected from published literature but was by no means certain until confirmed in the present work.
VOL. 30. NO. 3
COUMARONE
I
GH2
WEIGHTSAFTER EXPOSURE TO VARIOUS TABLE111. MOLECULAR DEPOLYMERIZATION TEMPERATURES Depolymerising Heating Temp. Time O c. Hours 220 1 3 5 8 21
Mol.
Resin
Benzene
Solution
Weight
Gram
Grams
%
0.205 0 221 0.215 0.193 0.221
19.42 21.64 21.59 19.09 21.67
1.05 1.02 0.99 1.01 1.02
794 820 862 907 933
240
1 3 5 8 21
0,210 0 223 0.200 0 197 0 214
20.91 21.75 19.92 18.75 21.17
1.00 1.02 1.00 1.05 1.01
780 806 815 816 976
250
1 3 5 8 15 21
0,234 0,247 0 213 0 229 0.219 0 218
23.35 24.87 21.59 21.37 22.98 21.91
1.00 0.99 0.99 1.08 0.96 1 .00
832 814 846 859 863 895
260
1 3 5 8 16 21
0 207 0.197 0 213 0 208 0.213 0 224
19.83 19.92 20.87 20.41 21.57 22.42
1.04 0.99 1.07 1.06 0.99 1.00
725 740 714 705 688 697
Structure of Polymers Obtained Various structures have been postulated for polymers of cyclopentadiene, indene, and coumarone (1-6). Recent discoveries in the polymerization of such compound leads one to question the validity of the structures. They appear to have been offered as possibilities rather than probabilities. Unsaturation characterizes the polymers, but its exact location has not been definitely stated. Present work, and other work now in progress, confirms an open-chain structure rather than ring or other interconnecting structures. It is definitely known but not yet published that cyclopentadiene and indene polymerize to give structures similar to those illustrated in the flow sheet which follows. Polymers are built up by the stepwise and end-to-end molecular addition, and not by the formation of dense ring structures. Hitherto unexplained properties of such polymers are readily understood in the light of the new structures offered; previous structures could not explain the observed facts and could not serve as a basis for new predicted reactions,
OGTAMER
TETRAMER
MARCH, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
gresses and can easily be calculated from the specific gravity of the material. Similar fundamental data were used for the design and erection of a commercial unit with a cycle of 30-36 hours. Figure 3 is a simplified diagram of the heat polymerizer. The vessel, P , of 10,000-gallon capacity, is charged and drained through line M-N by pump K . The charge is circulated a t approximately 400 gallons per minute by pump C through the furnace and coils a t A and B. The heating coils are directfired by gas and consist of approximately 500 linear feet of 2-inch steel tubing. Expansion joints E and F provide flexibility between the various rigid units of the polymerizer system. Temperature is automatically recorded a t three points in the system by the unit D. The reaction is initiated by heating the contents to polymerizing temperature when the exothermic reaction becomes self-sustaining and liberates a large quantity of heat, which is removed from the system by coils J through which water is circulated at the necessary rate. Views of the gas furnace during construction are shown in Figure 4; Figure 5 presents the complete unit. I n Figure 6A are plotted the data obtained from the poljmerization of 8000 gallons of crude solvent naphtha. The increase in specific gravity with heating is shown. The yield rapidly increases above 200" C.; in the particular case presented the reaction was complete within 4 to 5 hours after it started. It is clearly brought out that the violence of the reaction might become extreme when a moderating or cooling influence is not present. In the specific example, polymerizer P was charged and the system closed ; circulation and heating were started, and a t 150" C. the pressure exceeded 75 pounds per square inch. This pressure originated from expansion of air in the system and from a diminishing volume of free space due to oil expansion. The system was vented down to normal pressure. Continuation beyond this point with the system closed completed the reaction in which the maximum pressure approached 125 pounds per square inch. I n some of the earlier runs the specific point termed "control point" (235" C.), at which heating was to be eliminated, was overstepped, and the reaction went out of bounds and reached
249
to completion a n d maximum yield developed. The attainment of constant specific gravity marked the end of the reaction. The thick viscous polymerized mass was cooled slightly, and withdrawn from the system to storage and then to batch stills where the unreacted material and lower polymers were removed by combined steam and vacuum distillation. Figure 6B illustrates an ideal run in which perfect control was obtained with a maximum temperature of 260" C.; the recognition of the c o n t r o l point a t 235-240" C. made this possible. Reaction progressed until constant s p e c i f i c gravity and maximum yield w e r e o b tained. Figure 7 reveals an interesting relation; as the percentage of unsatur a t e s increases from 38 to 83 per cent, the recovery r a p i d l y becomes more f a v o r a b l e . The efficiency a t higher concentration is such that a t l e a s t 85 p e r cent of hard, salFIGURE 5. COMPLETE HEATPOLYMERIZER able, good quality
INDUSTRIAL AND ENGINEERING CHEMISTRY
250
VOL. 30, NO. 3
It is ideally suited for electrical work since its breakdown is in excess of 1400 volts per mil of thickness. It is odorless, tasteless, and nontoxic and can be 3 so used for such products as can linings, chewing 40 gum composition, i m 30 pregnation of paper, etc. It is stable to discolora20 tion w h e n h e a t e d t o temperatures not in ex/O cess of 225' C. Its mode of production i s s u c h 30 40 50 60 70 EO that it has been stabiUNSA TUR ATES lized toward decomposiFIGURE7. EFFECTOF UNtion at temperatures beSATURATES ON EFFICIENCY AND l o w t h i s v a l u e . It RECOVERY flashes above its melting point and depolymerizes rapidly above 850" C. It is soluble in a multitude of various types as shown in the following table:
8
Acetone Amyl acetate Amyl stearate Benzene Butyl acetate Butyl Cellosolve Butyl oxalate Butyl stearate Carbon disulfide Carbon tetrachloride Chlorinated naphthalene Chlorobenzene Chloroform Cyclohexanone
hWUR.5
FIQURE 6. DATAFROM POLYMERIZATION OF CRUDESOLVENT NAPHTHA
resin is obtained. From an economic point of view this is one reason why the original crude solvent naphtha was fractionated to obtain a rich narrow-boiling cut. Besides removing inert diluent, more efficient operation and recovery are obtained. Table IV shows the formation of resinous material a t different temperatures as a function of length of reaction period. The relative hourly rates of production have been approximated and play an important part in the over-all operative time of the unit. For comparison, a t 215", 225O, 245", and 260" C. a 50 per cent yield of resin is obtained in 3, 1.5, 1, and 0.25 hours of reaction time, respectively.
Diacetone alcohol Diamyl phthalate Dibutyl phthalate Dioxane Ethers Ethyl acetate Ethyl Cellosolve Ethyl lactate Gasoline Hexalin Hexyl acetate Hi-flash naphtha Isobutyl acetate Isopropyl acetate
Mineral spirits Petroleum thinners Pine oils Propyl acetate Pyridine Rosin oil Solvent naphthas Solvesso solvents Terpineol Toluene Tricresyl phosphate Triphenyl phosphate Turpentine Xylene
NONSOLVENTS FOR DICYCLOPENTADIENE RESINS Aqueous brines Diethylene glycol Ethanol
Ethanolamines Ethylene glycol Glycerol
Methyl Cellosolve Methanol
Solution of the resin in all its solvents gives low-viscosity liquids a t concentrations up to 7 pounds of resin per gallon of solvent. This 50 per cent solution is extremely valuable for blending, impregnating, waterproofing, etc. Its low
Properties and Uses of Heat Polymer Resins This new type of heat polymer resin, consisting mainly of cyclopentadiene polymers, is being adapted to various industrial uses because of its unusual properties. Because it is entirely hydrocarbon in nature, it shows remarkable resistance to alkali, acid, and brine solutions. It is nonsaponifiable and is of extreme value where its use brings about exposure to strong soap solutions, corrosive fumes, acid vapors, etc. Coating preparatioas containing it resist weathering on outdoor exposure; and because it is unaffected by most chemicah, it protects other materials used with it. It has an unusually low iodine number and resists oxidation, and its mode of manufacture does not introduce any acidic properties or inorganic ash. It is indifferent to basic pigment and does not bring about the so-called livering of such materials.
TABLE IV. EFFECT OF REACTION TIMEON RESINFORMATION -215' Time Hours 0.25 0.50 0.76 1 1.5 3 3.5 4.5 5 6
7
8
9 11 12 15 16 18 26 36 48
Totd resin
C.Hourly increase
---225'
Total resin
C
.
Hourly increase
8,320
...
33,280
...
... ...
iS:iio
14,400
18;960
18;960
31;440
12;480
3f.920
1,830
28,300
... ...
...
... 4,600 ... ...
...
... ...
34;960
1;330
37,440
1,000 ... 540
39,000 42',000
... ...
...
...
...
.... .. ... . ,.
...
38,720 43,200 44.640 47,360 5Y.840 64;800
Tot.al resin
Pounds
7
... ...
... ... ... ... ...
720 ... ... ...
160
...
-260'
7 7 2 4 5 " '2.Hourly increase
C.--
Total resin
Hourly increase
26,300
105,300
7
23,920
...
47,800
...
37,440
22;i40
35,040
1i, iio
40,640
2;s00
43,760 50,560
7 70 4:60
53',iio
46,960
...
2,100
1;ioo ... ...
50:640
1;ioo
54',240
...
...
55,600 56,400
...
...
...
... ...
...
500 136 80
...
55,360
...
700
INDUSTRIAL AND ENGINEERING CHEMISTRY
MARCH, 1938
molecular weight renders it rapidly soluble a t normal temperature with mechanical agitation. More rapid solution can be obtained by fusing the resin and then cutting back with the desired high-boiling solvent. This practice is useful in special cases. Heavy bodied solutions have been successfully used as aluminum paint vehicle, gloss oil, gum lacquer, leather dressing, and surface protective finishes. Most raw and refined vegetable oils are compatible with this new type of resin; blown oils do not always give satisfactory results. This heat polymer resin forms an excellent varnish material in bodied drying oils. Such varnish films possess quick through-drying and high luster, and have good grinding properties with asbestine, silica, or kaolin. It is compatible with such pigments as carbon black, chrome green, lithopone, titanium, and zinc oxides. It is recommended principally for inside use or where it is not exposed to direct sunlight. It does not react with other varnish components and is without effect upon driers.
25 1
The floor tile industry consumes large quantities of this new resin every year; where pale colors are not desired, it is without equal in the low-price resin field. Its properties render it most suitable for such use. The same resin of lower melting point has found widespread use in the adhesive and rubber industry. Printing inks have been made from it. Continued development of these hew cyclopentadiene and indene heat polymers is in progress and gives promise ,of extending the use of this resin into new and more diversified fields.
Literature Cited Alder and Stein, Ann., 485, 2 2 3 4 6 (1931). Kraemer and Spilker, Ber., 23, 3296 (1890). Staudinger and Bruson, Ann., 447,9 7 (1926). Whitby and Kata, Can. J . Research, 4, 344-60 (1931). (5) Whitby and Kata, J. Am. Chem. Soc., 50, 1160 (1928)
(1) (2) (3) (4)
RECEIVED August 27, 1937.
Recent Developments in
Tantalum and Columbium
T
HE various steps involved in producing tantalum and columbium powders from the minerals tantalite and columbite, and the methods by which these powders are converted into finished ingots, were described in a previous paper.' Since that time, work has been under way in the laboratory to improve and refine the various steps in the process. Engineering research work has resulted in new applications of the metals, primarily in the chemical industries, These efforts have resulted in a more uniform product and an increased volume of production. Occurrence High-grade ores of tantalum and columbium are scarce. Although tantalite and columbite occur in numerous localities, their concentration is usually too small to make mining operations profitable. Heretofore, most of the tantalite used in the production of tantalum has come from western Australia. Recently mining operations have been undertaken in the Black Hills near Tinton, S. Dak. A good ore is being obtained from this source, but its concentration in the matrix material is rather low. Two and one-half tons of rock must be mined, milled, concentrated, and processed to produce one pound of tantalum.
Metallurgy Tantalum and columbium are produced by the methods of powder metallurgy. At no point in the process are the metals actually melted. Workable ingots are made by the heat treatment of bars, produced by compression of the metals while in powder form. The results obtained by this type of metallurgy depend in large measure upon the chemical and physical characteristics of the initial powder. Tantalum and columbium powders have been subjected to a searching investigation in reference 1
IND.ENQ.CHEM.,27, 1166 (1935).
CLARENCE W. BALKE Fansteel Metallurgical Corporation, North Chicago, 111.
to the effects of small residual impurities such as carbon, iron, silica, alumina, and residual fluoride salts. Carbon is removed by means of a calculated amount of a suitable oxide admixed with the original powder. The carbon content of the finished metal should be below 0.01 per cent. Iron cannot be completely eliminated, but its presence in the order of 0.01 per cent is not detrimental. Materials such as silica, alumina, and residual salt are almost completely eliminated by the high temperature obtained during the heat treatment of the bars. The elimination of such impurities is further aided by the fact that this heat treatment is conducted in a vacuum, and some tantalum itself is volatilized during this operation. Hydrogen may be considered an impurity in the initial powder, and its presence is due to the chemical treatments used in the final purification of the powder. This hydrogen may vary between a few volumes to over 100 volumes. The presence of this gas affects the pressability of the powder and makes it necessary to modify the heat-treating schedules. The removal of this gas is one of the major objects to be accomplished in the heat treatment of tantalum and columbium. The furnace and pumping equipment have been greatly improved, with the result that the h a 1 gas pressure a t the completion of the heat treatment of a tantalum or columbium bar is of the order of one micron. Oxygen in any form is a detrimental impurity in these metals. Its presence produces abnormally high hardness:, increases the difficulty of annealing, and reduces the stretch of the material. A strip of pure tantalum sheet 0.010 inch in thickness will have an elongation of as much as 50 per cent. This is materially reduced by the presence of small amounts of impurities.
