INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1955
National Research Council. The authors wish to express gratitude to M. G. DeFries. W. S. Wright, and A. L. Best for their efforts in obtaining the test results.
(8) &last, W. C., Smith, L. T., and Fisher, C . H., IND.ENG.CHEM., 37, 365 (1945). (9) Nuessle, A. C., and Kine, B. B., Ibid., 45, 1287 (1953). (IO) Owen, H. P., Rubber A g e , 66, 544 (1950). (11) Rehberg, C. E., and Fisher, C. H., IND.ENG.CHEM.,40, 1429 (1948). (12) Riddle, E. H., Chem. Eng. News, 31, 2854 (1953). (13) Schildknecht, C. E. "Vinyl and Related Polymers," p. 229, Wiley, New York, 1952 (14) Schmidt, E., IND.ENG.CHEM.,43, 679 (1951). (15) Sell, H. S., I n d i a Rubber W o r l d , 129,498 (1954). (16) Semegen, S. T., Rubber Age, 71, 57 (1952). (17) Wiley, R. H., and Brauer, G. M., J. P o l y m e r Sci., 3, 647 (1948).
LITERATURE CITED
(1) Crawford, J. W. C., J . Soc. Chem. I n d . , 68, 201 (1948). (2) Fram, P., Szlachtun, A. J., De Fries, M. G., and Leonard, F., IND.ENG.CHEM.,46, 1992 (1954). (3) LeBras, J., and Piccini, I., I b i d . , 43,381 (1951). (4) Leonard, F., Cort, I., and Blevins, T. E., I b i d . , 43,2500 (1951). (5) Mast, W. C . , and Fisher, C. H., Ibid., 40, 107 (1948). (6) I b i d . , 41,790 (1949). (7) Mast, W. c., Rehberg, C . E., and Fisher, c. H. (to U. S. GOVernment), U. S. Patent 2,449,612(Sept. 21, 1948).
1213
ACCEPTED January 15, 1955, RECEIVED for review September 22, 1964. Presented before the Division of Polymer Chemistry at the 126th Meeting of the AMERICAN CHEMICAL SOCIETY, New York. K. Y.,1964.
Alkyl Amates as Plasticizers of Elastomers J
ARTHUR WILLIAM CAMPBELL Research Department, Commercial Solvents Corp., Terre Haute, Ind.
T
HE development of various elastomeric substances during World War I1 was noteworthy in its primary objective, but
was accompanied by severe shortages in effective compounding ingredients. One of the weak spots was plasticizers, and this report covers the exploratory work done on one group of compounds in a n attempt t o relieve that shortage. The use of the esters of various acids, chiefly organic acids, as plasticizers of elastomers is not new. The use of imides, amides, and diamides was discussed by Campbell and Tryon (1). To combine the ester and amide groups in one molecule invoked a n old but little known type of compound, the amate ( 4 ) . Because two functional groups involving carboxyl are present in the amic acids, the starting point is a dibasic acid such as phthalic acid. By suitable treatments one carboxyl is esterified and the other converted to a n amide, resulting in a compound of the following structure. 0 0-4-0-R W-C-Y-Rz
e,
R,
The amates described in this paper have been prepared by various methods.
The product was distilled in vacuum through a six-bulb jacketed Snyder column; 78 grams were distilled u p to 80" C. a t 100 microns. T h e second fraction boiling between 80" C. at 100 microns arid 130" C. a t 50 microns weighed 166 grams and amounted to a yield of 60.5%. Analysis. C,,4H360aN. Molec- . ular weight, 266. Nitrogen calculated, 5.2601,; found, 5.53%. The compounds listed in Table I are new compositions of matter here characterized for the first time. TESTING PROCEDURE
Four elastomers were used in the evaluation of the various alkyl amates. Natural rubber (Hevea), a blend of four plantation crudes obtained from The B. F. Goodrich Co. Poly(viny1 chloride), Geon 101, Goodrich Chemical Co. Butadiene-acrylonitrile, Hycar OR-15, Goodrich Chemical Co. Butadiene-styrene, GRS, Rubber Reserve Code 1500 The formulation used in each case appears in the tabulation of the results. The mixing procedure followed the methods generally specified by the manufacturer for that particular elastomer. T h e press cures were made according to ASTM D 1541. T h e tensile test employed a Scott compensating head tensile machine and followed ASTM D 142-41, at a room temperature 2" F. The load, tensile, elongation, rebound, and of 82' hardness tests were all run at this temperature. The sheeted
PREPARATION OF AMATES *
n-Butyl N,N-Di-n-butyl Phthalamate. Phthalic anhydride (148 grams), butanol (74 grams), and benzene (50 ml.) were heated a t reflux until the anhydride had dissolved. Di-nbutylamine (129 grams) was added and this mixture was heated at reflux using a Dean and Stark separator to remove the water formed, When the theoretical amount of water had been eliminated, the product was distilled through a simple still. Low boilers were removed in aspirator vacuum. The main fraction distilled at 145" to 152" C. a t 75- to 80-micron pressure. Yield was 195 grams, 58.5%. Analysis. C Z O H ~ J O ~MolecN. ular weight 333. Nitrogen calculated, 4.20%; found, 4.443%. n-Butyl N, N-di-n-butyl Oxamate. Di-n-butyl oxalate (202 grams) and di-n-butylamine (129 grams) were charged into a 500-ml. flask under a 2 4 b u l b jacketed Snyder column. The pot heat was adjusted to provide a moderate reflux while the column was adjusted to remove 1-butanol. As the reaction started slowly, a n excess of 25y0 of the amine was added. After about 1 week of heating, the theoretical amount of alcohol had been removed.
I
SUBSTITUTED AMATES
. . . have both ester and amide functions . . . satisfactorily plasticize natural and synthetic rubber and PVC
Co m merci a I deve I o p ment depends on availability of low-cost
1
secondary amines
INDUSTRIAL AND ENGINEERING CHEMISTRY
1214
Table I.
Vol. 47, No. 6
Boiling Points and Analyses of Amates Molecular Weight
Ethyl N,N-di-n-butyl oxamate %-Butyl N,N-di-n-butyl oxamate n-Butyl N,N-di-n-butyl succinamate %-Butyl N-butyl adipamate n-Butyl N,A'-ditetrahydrofurfuryl adipamate Iso-octyl N,N-ditetrahydrofurfuryladipamate Iso-octyl N,N-di-n-butyl adipamate 2-Ethylhexyl N-2-ethylhexyl adipamate Ethyl X,N-di-n-butyl phthalamate n-Butyl N,N-di-n-butyl phthalamate n-Butvl N.N-diisobutvl nhthalamate
n-Butil N.N-di-n-butvl azelamate 2-EthGlhexyl N-2-ethylhexyl azelamate n-Butyl N,N-di-n-butyl sebacamate Benzyl N-2-ethylhexyl sebacamate %-Butyl bis(N,N-di-n-buty1)citramate
% Nitrogen Calcd. Found 6.12 6.48 5.45 5.50 4.91 4.74 5.45 5.17 4.84 4 57 3.29 3.34 3.68 3.79 3.79 4.08 4.59 4.85 4.46 4.20 4.20 4.09 5.05 5.22 3.62 4.12 3.60 3.54 3.60 3.47 2.68 2.79 3.87 3.94 3.18 3.41 3.79 3.10 3.26 3.47 5.31 5.96
Boiling Range, O C . 90-98 108-112 120-130 125-160 Not Not 180-19 6 220-228 140-150 145-152 165-175 140-150 180-190 165-185 165-185 195-220 177-200 200-225 175-190 223-225 Not
Pressure, Microns Hg
Table 11. Amates in Butadiene-Acrylonitrile Rubber I
Hvcar OR-15 Z h c oxide Stearic acid Dibenzothiazyl disulfide Sulfur FT carbon black (P-33) Di-2-ethylhexyl phthalate Butyl .V,N-di-n-butyl oxamate Iso-octyl N,S-di-n-butyl adipamate 2-Ethylhexyl iYJT-di-2-ethylhexyl phthal.amate Nonyl N,.V-di-n-butyl phthalamate +Butyl bis(N,.V-di-n-buty1)citramate Benzyl h7-2-ethylhexyl sebacamate 2-Ethylhexyl A'-2-ethylhexyl adipamate Press cure a t 310' F. 20 min. Load a t 300% Tensile Elongation 30 min. Load a t 300% Tensile Elongation 45 min. Load a t 300% Tensi1e Elongation Shore A hardness, 30 min. a t 310' F. Rebound, 30 min. a t 310" F. Mooney viscosity
L.
100 5 1 1.5 1.5 50
100 5 1 1.5 1.5 50 30
...
...
... ... , . .
... ... ... ...
...
... ...
3
30'
...
4
R u n No. 5
...
...
...
30
...
...
...
6
8
9
...
...
...
, . .
...
...
7
...
...
,..
, . .
... , . .
...
, . .
270 1650 785
290 760 603
420 950 595
450 1360 660
320 1060 655
350 850 533
400 2200 760
400 1650 700
, . .
320 1240 633
300
450 920 535
470 1200 520
350 1160 585
420 860 503
520 2070 690
500 1700 623
370 1060 560 31 40 38.5
320 800 587 42 40 Setup
470 1000 510 36 40 Setup
540 1120 500 22 45 31
450 1100 510 24 43 32 5
450 850 490 26 44 41
570 1890 600 38 34.5 35.5
590 1720 6 10 22.5 40 35.5
... ... ... I
.
.
, . .
, . .
...
... ... Setup
850
573
Table 111. Amates in Butadiene- Styrene Rubber 1
2
Run No. 3
4
0
5
..
...
...
GR-S rubber Zinc oxide
Stearic acid Di-2-ethylhexyl phthalate 2-Ethylhexyl N,N-di-Z-ethylhexyl phthalamate Benzyl N-2-ethylhexyl sebacamate 2-Ethylhexyl A'-2-ethylhexyl adipamate Press cure a t 275' F. 10 min. Load a t 500% Tensile Elongation 15 min. Load a t 500% Tensile Elongation 20 min. Load a t 500% Tensile Elongation Shore A hardness, 15 min. a t 275' F. Rebound, 20 min. a t 275 F. Mooney viscosity
.
.
I
... ...
...
...
... ..
510 1350 615
400 1130 670
360 1340 630
510 1000 560
650
550 1130 600
490 1340 600
690 1280 540
550 1160 513 56 56 31
750 1070 453 56 57 30.5
5
... ...
...
580 1100 560 740 1180 467
1180
.
I
.
850 1150 410 59 58 38
... 5
...
505
710 970 403 56 57.5 34
570 840 450 56 56.5 35.5
5
June 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
Table IV.
Rubber Zinc oxide Sulfur Dibenaothiazyl disulfide Stearic acid F T carbon black (P-33) Di-2-ethylhexyl phthalate %-Butyl N,N-di-n-butyl oxamate Octyl N N-di-n-butyl adipamate 2-Ethylhexyl N,.V-di-2-ethylhexyl phthalamate Nonyl N,N-di-n-butyl phthalamate n-Butyl bis (N,N-di-n-butyl) citramate Benzyl S-2-ethylhexyl sebacamate 2-Ethylhexyl iV-2-ethylhexyl adipamate Press cure a t 293’ F. 10 min. Load a t 500% Tensile Elongation 15 min. Load, a t 500% Tensile Elongation 20 min. Load a t 500% Tensile Elongation Shore A hardness, 15 min. a t 293’ F. Rebound, 20 min. a t 293’ F. Mooney viscosity
Amates in Natural Rubber
a
1
100 5 3 1.25 5 40
100 5 3 1.25 5 40
1215
3 100 5 3 1.25 5 40
4
100 5 3 1.25 5 40
Run No. 5 100 5
3 1.25 5 40
6 100
5 3 1.25 5 40
7 100 6 3 1.25 5 40
8 100 5 3 1.25 5 40
9 100 5
3 1.25
5
40
1490 3750 727
1450 3740 707
2250 3410 603
1500 3340 690
1330 3710 753
1600 3890 703
2150 3760 655
1510 3450 680
1550 3500 637
1910 3840 683
1760 3740 670
2340 2950 533
1820 3200 640
1630 3710 693
1940 3750 667
2200 3500 597
1720 3210 600
1750 3700 677
2170 3560 623
1970 3620 647
2450 2650 503
1910 2930 603
1800 3670 675
2050 3600 643
2210 3400 597
1770 3650 640
1800 3590 643
5s
55 76 18
52 74
55 74
18
18
55 77 18
52 73 34
52 74 28
55 75 30.5
54 76 19.5
Table V.
Amates in Poly(viny1 Chloride) Polymer
Ratioa Plas- Load a t ticiaer to 100 loo% Parts Resin Elong. Controls 54 Dibutyl phthalate 50 Di-2-ethylhexyl phthalate Amates 54 Ethyl r\r,T,N-di-n-butyloxamate 54 n-Butyl A‘ Y-di-n-butyl oxamate 54 n-Butyl N:IV-di-n-butyl succinamate 54 Iso-octyl N,N-diTn-butyladipamate Iso-octyl K,N-ditetrahydrofurfuryl adip54 amate 54 Iso-octyl S ,,V-dihexyl adipamate 54 n-Butyl A 7 N-di-n-butyl phthalamate %-Butyl AT~methyl-N-isopropylphthala54 mate 54 n-Butyl A’ S-di-see-butyl phthalamate 54 4-Oxaootyi .%‘,A’-di-n-butyl phthalamate 54 Nonyl S,.V-di-n-butyl phthalamate Hexamethylene bis(N,N-di-n-buty1)phthal54 amate 54 n-Butyl N,N-di-n-butyl azelamate 54 n-Butyl N,Ar-di-n-butyl sebacamate 54 n-Butyl bis(N,N-di-n-butyl)citramate 2-Ethvlhexvl N.N-di(2-ethslhexyl) phthal40 smite 2-Ethylbexyl N,N-di(2-ethylhexyl) uhthal50 amate 2-Ethylhexyl N,N-di(2-ethylhexyl) phthal60 amate 54 Benzyl AV-2-ethylhexylsebacamate 50 2-Ethylhexyl N-2-ethylhexyl adipamate a Basic formula Poly(viny1 chloride) polvmer, Geon 101 Stahi!iqer, Vanstay 16, 8. T. Vanderbilt Co. Plasticizer b Clash and Berg method. e Ultraviolet test descfibed in text. d 96 Hours in circulatlng air oven a t loo3 C.
77 19
Shore A Hardness
Tensile a t Break
Elong. a t Break
Torsionb Test, ’ C.
900 1500
2320 2450
260 217
- 26
78
800 580 940 1180
1790 1970 1850 2330
260 403 277 243
- 8 -21 - 36 - 50
1690 1700 1000
2500 2440 2750
183 185 235
- 20
1900 2100 1950 2040
2740 2820 2900 2790
250 243 247 257
- 13 - 12
Ultraviolet C Radiation
yoafter Heat96Lossd hr. a t 100’ C.
KO change No change
41.1 7.1
7s 79 75 79
No change No change Slight bleaching No change
17.3 19.4 23.0 18.0
79 78 80
No change No change Slight bleaching
10.2 5.1 2.1
77 81 78 78
Slight gloss Darkened Faded Slight bleaching
14.0 11.0 6.0 6.0
Compatible, sheet hard and useless when cold 167 - 40 68 1350 870 - 35 69 2090 290 880 1440 2650 240 - 24
No change Slight bleaching No change
3.5 4.1 14.3
T o o hard to test, even though compatible
99
Slight bleaching
3.4
1980
93
Slight bleaching
4.2
- 22 83 1570 2220 263 Compatible, but sweated excess!vely. Kot tested Compatible, but sweated excessively. Not tested
Slight bleaching
3.3
2590
170
-31
- 19
- 2 - 2
Too stiff
100 3 50 or as indicated by ratio.
stock and the cured sheets were stored under these same conditions. The plasticities were determined in the V. L. Smithers Laboratories, Akron, Ohio, using the Mooney Plastometer ( 3 ) . The rebound (test based on the Firestone ball rebound method and apparatus built from Firestone design) was determined by dropping a 0.5-inch steel ball on a block of rubber 3/4 X 2 inches and reporting the average rebound in percentage of the height dropped. The nitrogen analyses in Table I indicate that some samples contain some unreacted amine, or some diamide. The basic material would affect the rate of vulcanization, which should be reflected in the values of load, tensile, elongation, and Mooney viscosity. However, careful examination of these properties
indicates that only the Mooney viscosity value was affected to a marked extent. The two compounds showing setup in Table I1 were high in nitrogen by 0.05%, hardly enough to explain the setup. However, 30 parts of plasticizer were used, which would introduce 0.015 gram of amine, while 2-ethylhexyl S-2-ethglhexyl adipamate was 0.3’%high, introducing 0.09 gram of amine without “scorch.” The writer concludes that the amounts of amine present were not sufficient to cause the scorch observed and that the high nitrogen values were due to traces of the diamides. Evidently compounds 3 and 4, Table 11, do not plasticize even though compatible. I n Tables 11, 111, IV, and V di-2-ethylhexyl phthalate is used
1216
INDUSTRIAL AND ENGINEERING CHEMISTRY
as a representative commercial plasticizer. I n the cases where Mooney viscosity was determined, the amates were equal or superior to the ester, and as the ester used is one of the best currently employed, the amates are therefore superior t o it as plasticizers. I n Table V the torsion test of Clash and Berg (2) was adopted as the chief diagnostic piece of evidence, coupled with heat loss a t 100" C. Long-chain acids with long-chain alcohols and amines gave the best results. When used in'the poly(viny1 chloride) polymer, the plasticizers were compatible but in some cases did not soften the stock t o a satisfactory degree. Low heat loss and low torsion test in the Clash and Berg (2) apparatus were sought. n-Butyl N,N-di-nbutyl azelamate gives 3.5% and -40" C., respectively, t o hold first place. The corresponding sebacamate ranks second. The low temperature torsion test ranks the straight-chain dicarboxylic acids as the best, regardless of the substituent. Low heat loss seems best attained by use of large substituents on the ester and amide portions. Probably any compatible material of high molecular weight would be permanent. The ultraviolet exposure test was run for a week as follows: Strips, 1 X 5 inches, one half covered with aluminum foil, were mounted on a wooden disk. The disk, 30 inches in diameter and rotating a t 5l/2 r.p.m., carried the specimens past a Hanovia Type 16200 mercury arc lamp a t a distance of 6 inches. The exposure was about 2 seconds, thus subjecting the sample to some heat and ultraviolet light. It was thought that this alternating method might serve as a shock treatment and induce more rapid migration of the plasticizer to the surface. It seems to be effective, but no tests Were made using a static situation for comparison. Structure enters into the compatibility of the compound. For example, Campbell and Tryon ( 1 ) found that a long straight-
Vol. 47, No. 6
chain acid or a mono-substituted amide tended to increase the difficulty of incorporation or prevent it altogether in Hycar OR15. Benzyl N-2-ethylhexyl sebacamate, derived from sebacic acid, the esters of which are generally good plasticizers, does not function satisfactorily in natural rubber, Hycar OR-15, or Geon 101. It is fairly good in GR-S. These failures to plasticize adequately may be due to the benzyl group, but the author is inclined to place the blame on the mono-substituted amide, since the benzyl group does not appear t o a disadvantage in the esters where it has been used. Variation in structure appears again in iso-octyl N,N-di-nbutyl adipamate and 2-ethylhexyl N-2-ethylhexyl adipamate. I n Hycar OR-I5 the second compound is far superior; in natural rubber the first is much better, as it is in Geon 101. It is evident that the effect of structure varies with the polymer. Commercial development depends upon the availability of lowcoat secondary amines. ACKNOWLEDGMENT
The author is grateful to J. A. Riddick and his associates for the analytical data and to the V. L. Smithers Laboratories for the plasticity determinations. LITERATURE CITED (1) Campbell, A. W., and Tryon, P. F., IND.ENG.CHBM.,45, 125 (1953). (2) Clash, R. F., and Berg, R. M., Modern Plastics, July 1944, 35-40. (3) Mooney, Melvin, IND. ENG.CHEM.,ANAL.ED.,6, 147 (1934). (4) Patterson, A. M., Capell, L. T., and Magill, M. A,, C.A., 39, 5899 (1945). RECEIVED for review September 27, 1964. ACCEPTED February 1, 1955, Presented before the Division of Rubber Chemistry a t the 126th Meeting 'of the AMERICAN CHEMICAL SOCIETY, New Y o r k , N.Y., 1964.
Catalyst Activity in Crackingof Pure Hydrocarbons J
D. E. NICHOLSON Technical and Research Divisions, Humble Oil and R&ning Co., Baytown, Tex.
T
H E importance of catalyst activity for conversion of gas oils to gasoline, gas, and coke has been dealt with in many publications in recent years. Numerous tests have been developed to define relative activity of catalysts, and an excellent survey of the major physical tests has been made by Ries (8). These determinations include measuremente of surface area, pore volume, and pore radius from adsorption-desorption isotherms. I n the case of catalysts of substantially uniform chemical composition, it is possible to estimate the activity by following a property such as heat of wetting with methanol, which gives an indication of the extent of surface accessible to reactant molecules (6). The most widely used method of measuring catalyst activity involves cracking a standard gas oil in a flow-type system a t approximately 450" C., using 200 cc. of catalyst (1, 8 ) . Products from the cracking reactions are often characterized as dry gas, liquid of lower boiling point than the initial boiling point of the feed, and coke. Many variations on the general method have been reported (9). All of these procedures are essentially the same, except for modifications in reporting data, choice of experimental operating conditions, and the physical form in which the catalyst is admitted to the cracking unit. Thus, workers have employed granular, pilled, and fluidized catalyst (3, 5 ) .
The object of the present investigation was to study certain hydrocarbons of low molecular weight as potential starting materials in an activity test for rating cracking catalysts. The dealkylation of cumene has been recognized as suitable for screening catalysts ( 7 , IO, 21). So far as is known, no work has been reported on the use of light paraffins for measuring catalytic activity. A more rapid test than the gas oil method would be advantageous. By utilizing compounds such as isobutane (2methylpropane) or isopentane (2-methylbutane) it is possible to analyze the reaction products with a mass spectrometer rather than by distillation, effecting an appreciable saving in time. A further argument for using simple compounds is that differe n t batches of the standard gas oil prepared from time to time are not of identical composition. If a pure hydrocarbon would serve in the cracking test, the source of feed would not become unavailable in the future, the compound of interest being readily obtained in a state of high purity. Complete analysis of liquid products from the testing operation using gas oil is not possible because of the multitude of compounds present. More specifically, increased accuracy and precision are generally possible in an analysis of mixtures of a few components. The gas oil test for cracking catalyst activity as ordinarily performed does not detect conversion of molecules that are cracked b u t still boil at tempera-
-
