March 1949
64 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE XI.
COMPOUNDS OBTAINED BY FRACTIONATION OF ScIssIoN PRODUCTS From Ethyl Oleate Oxidized in Bomb Vol., ml. Wt., g. Wt. %
Compound Ethyl caproate Ethyl heptylate Ethvl csurvlate
;e
26 33 49 63 12 7 74 91 30 26 20 93
23 29 43 55 10 6
73 89 26 25 19
80
4 4 7
8
2 1 11 13 4 4 3 12
From Ethyl Oleate Oxidized in Acetic Acid Vol., ml. W t , , 6. Wt. 7 0
21
28
43 48
;
64 62
18 13 A
From MEUFA Oxidized in Acetic Acid Val., ml. Wt., g. Wt. % 17 15 8
5 6 9 11 1 2 16
19
25
38 43 4 6 63 61 16 13 6 40
11 17 17 3 6 27 24
15
4 3 1 10
LITERATURE CITED
8
8 17
s
5 15
5
8
8
1 3 14 12 4 4 8
8
H. S., IND.ENG.CHEM.,
(18)
(1) Anderson, R. H., and Wheeler, D. H., Oil & Soap, 22, 137 (1945). (2) Atherton, D., and Hilditch, T. P., J . Chem. Soc., 1944, 105. (3) Barnicoat, C. R., Ihid., 1927, 2928. (4) Bolam, T. R., and Sim, W. S., J. SOC.Chem. I n d . , 60, 50T (1941). (5) Braun, J. von, and Danziger, E., Ber., 45, 1975 (1912). (6) Braun, J. von, and Sobecki, W., Ibid., 44, 1471 (1911). (7) Canzoneri, F., and Bianchini, G., Ann. chim. applicata, 1 , 24 (1914). (8) Ciamician, G., and Silber, P., Ber., 47, 640 (1914). (9) Conant, J. B., and Quayle, 0. R., “Organic Syntheses,” Coll. Vol. I, p. 211, New York, John Wiley & Sons, 1941. (10) Deatheridge, F. E., and Mattill, H. A., IND.ENG.CHEM.,31, 1425 (1939).
10 15 15 3 5 27 24 7
(11) Ellis, G. W., Biochem. J . , 30, 753 (1936). (12) Ellis, G. W., J . SOC.Chem. I n d . , 45, 198T (1926). (13) Farmer, E. H., et al., Trans. F a r a d a y SOC., 38, 340, 348, 356 (1942); 42, 228 (1946); J. Chem. Soc., 1943, 119, 122. (14) Franke, W., and Jerchel, D., Ann., 533, 4 6 (1937). (15) Gunstone, F. D., and Hilditch. T . l’.. J . Chem. soc., i 9 4 5 , 836. (16) Hamilton, L. A., and Olcott,
(19) (20) (21)
29, 217 (1937). (17) Krafft, F., and Noerdlinger, H., Ber., 22, 818 (1889). Lapworth, A., and Mottram, E. N., J . Chem. Soc., 127, 1628 (1925). Le Seuer, H. R., I b i d . , 79, 1313 (1901). Robertson, P. W., J. Chem. Soc., 115, 1220 (1919). Robinson, G. M., and Robinson, R., Ihid., 127, 175 (1925). Salway, A. H., and Williams, P. N., I b i d . , 121, 1343 (1922). Scala, A., Staz, sper. agrar. ital., 30, 613 (1897).
Schaeffer, B. B., Roe, E. T., Dixon, J. A , , and Ault, W. C., J . Am. Chem. Soc., 66, 1924 (1944).
Shonle, H. A., and Row, P. Q., I h i d . , 43, 363 (1921). Skellon, J. H., J.Soc. Chem. I n d . , 50, 3821‘ (1931). Swern, D., Knight, H. B., Scanlan, J. T., and Ault, W. C., J. Am. Chem. Soc., 67, 1132 (1945). RECEIVED Sovember 5, 1947.
Vulcanization of Neoprene with Antimony Trisulfide J
M. F. TORRENCE Rubber Laboratory, E. I . du Pont de Nemours & Company, Inc., Wilmington, Del. Antimony trisulfide increases the modulus, hardness, and resilience, and decreases the permanent set and heat build-up of neoprene compounds. The magnitude of the effect is directly proportional to the concentration of antimony trisulfide and is obtained with less loss of processing safety than when Permalux is used. The effects of antimony trisulfide are less noticeable on the hardness and stress at low elongations than they are on the stress at elongations near hrealr. Antimony trisulfide is effective in the absence of other activating materials such as magnesium oxide and zinc oxide. Certain other sulfides display the same activating effects as antimony trisulfide.
E O P R E N E is generally cured with a combination of magnesium oxide and zinc oxide, a s proposed by Bridgwater and Krismann ( 1 ) in 1932. Many of the properties attributed t o proper vulcanization, such as maximum tensile, near-maximum modulus, and near-maximum hardness, can be obtained with these oxides alone in a normal curing time of 30 t o 40 minutes at 287” F. However, t o obtain low permanent set and high resilience, other activating materials are frequently added. Torrence and Fraser ( 4 )showed t h a t various amines, phenols, and quinones are effective. T h e most commonly used material is the di-otolylguanidine salt of dicatechol borate ( 2 ) , sold under the trade name Permalux. Antimony trisulfide is in many respects a more effective activator than Permalux. I t s influence on the properties of the
vulcanizate is different from t h a t of Permalux and from t h a t which would be expected from merely increasing the rate of cure. Antimony trisulfide affects the modulus at low elongatioiie much less than a t high elongations, and the hardness of stacks coritaining i t is lower than would be expected for stocks with so low a permanent set and so high a resilience. Varying amounts of antimony trisulfide and Permalux were tested by adding them t o a stock having the following conventional composition: ,
Neoprene GRM-10 Sodium acetate Stearic acid Extra light calcined magnesia EPC carbon black Light process oil Zinc oxide
100.0 parts 1 .o
1 .o
4.0 31 . O 3.0 5.0
One batch of the base stock was mixed on a 30-inch mill. Antimony trisulfide, in the ratios of 0.125, 0.26, and 0.5 part, and Permalux, in the ratios of 0.5 and 1.0 part, on 100 parts by weight of neoprene were added on a 12-inch mill t o portions of this batch. T h e stocks were then cured and tested according t o standard A.S.T.M. procedure. T h e heat build-up was obtained with a Goodrich flexometer ( 3 ) on pellets 0.75 inch in inch, the diameter and 1 inch in height; the stroke was load 150 pounds per square inch, and the speed 1800 cycles per minute. The compression set was run according t o A.S.T.M. Method A, D 395-40T-i.e., 400-pound load for 22 hours at 70 O C. (158” F.). T h e resilience was determined on the Yerzley oscillograph in accordance with A.S.T.M. Specification D 945-48T.
INDUSTRIAL AND ENGINEERING CHEMISTRY
642
Vol. 41, No. 3 __
__
80-
--- SP EbR2 Ms 3A L U X
____
w
Sb2S3
2
PER MALUX
sd
w
I '
0'
I
x'
.I25
PARTS
PER 100 PARTS
PARTS
..-
NEOPRENE
Figure 2.
PERMALUX IQO Sb2S3 .50
.51 .25
76-------1______
~
100 PARTS N E O P R E N E
PER
Effect of Activator on Resilience
Figure 1. Effect of Activator on Strcss and Hardness of Compounds Cured 30 Minutes at 281" F.
-__ - ~ ~ ~ _ _ _
I
ASLM. M E T H O D A 4 O O x LOAD 2Znrs. a t 70T.
GOODRICH F L E X O M E T E R STROKE 3/16'' LOAD 150X PER SO.IN. FREQUENCY le00 cpm
.
"*f
i
---_-
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90' oi 28I.F.
J
PERMALUX
.25
,125
PARTS PER 100 PARTS NEOPRENE
I 50L---L--
.le5 PARTS
Figure 3.
PERMALU): SbpSs 1.5 .0
PER
.5 1 .2 5 100 PARTS NEOPRENE
PERMALUX S b 2 SJ
I.Od
Figure 4. Effect of activator on Comprcssion Set
.50
Effect of Activator on Heat Build-up i n Flexometer
--I
GOODRICH FLEXOMETER STROKE 3/16" LOAD 150" PER SQ.IN FREQUENCY II S O ccpm pm SO 00
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VOL OF EPC PER
Figure 6. 20'
I
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20
IO
TIME
- MIN.
30
I
15 eo 100 V O L . 0 F NEOPRENE
25
Effect of Antimony Trisulfide on Heat Buildup of Stocks Containing EPC Black
I 40
Figure 5. Effect of Activatoi on Mooney Scorch a t 250' F. PHYSICAL PROPERTIES
Figure 1 shows the effect of various amounts of antimony trisdfide and Permalux on the hardness and the modulus a t 200 and 500% elongation when the stocks were cured 30 minutes a t 281 F. On Figures 1 to 4 the scale for Permalux concentration is twice t h a t for antimony trisulfide, and therefore 0.25 part of antimony trisulfide is represented by the same point as 0.5 part of Permalux. Comparison of any amount of antimony trisulfide with twice the amount of Permalux shows t h a t the hardness is increased less, the modulus a t 200% t o about the same extent, and $he modulus at 500% is increased more. I n other words, anti-
mony trisulfide has less effect on t'he hardness and the stress af, low elongations than i t does on the stress a t high elongations. Table 1: lists a portion of the physical test data for three of the compounds t o show the effect on a range of cures broader than that, represented in Figure 1. With all t'hree cures the Permalux increases the hardness and the modulus a t 200% elongation mor(. than does antimony trisulfide, although at 400% elongation antimony trisulfidc shows the grcater effect. These data a,lso indicate t h a t neither Permalux nor antimony trisulfide has a significant effect on age resistance. Figure 2 shows the effect of the same variations in the concentration of antimony trisulfide and Permalux on the resilience of stocks cured 45 and 90 minutes a t 281 F. These data indicate t h a t less than 0.125 part of antimony t,risuIfide is necessary 1.0 give as high resilience in 45 minutes as is obtained in 90 minutes
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1949
BND ANTIMONYTRISULFIDE ON PHYSICAL TABLE I. EFFECTOF PERMALUX PROPERTIES OF A CONVENTIONAL NEOPRENE COXPOUND, CURED ** 2810
Compound No. Antimony trisulfide Permalux Stress a t 200% elongation, lb./sq.30in.min. Cured 60 min. 120 min. Stress at 400% elongation, Ib./sq. in. Cured 30 min. 60 min. 120 min. Tensile strength a t break, lb./sq. in. Cured 30 min. 60 min. 120 min.
809C-3 None None
809C-5 0.25part None
_A__
orig.
~
i
~02b a orig.
620
930 710 900 1110 1250 900 1000 1220 . . . 1110 1675 2300 2250 2600 2800 2450 2850 . . .
809'2-7 None 0.5 part-
-----
~Opba orin. Airs ozb 790 1200 1100 1180 1380 990 1280 1320 1320 , . . 1180 1330 ~
i
,
...
...
2000 2725 2550 3000 3025
...
643
antimony trisulfide increases the scorching tendency markedly, but the test indicates t h a t this stock is much more processable than a corresponding stock containing 0.5 part of Permalux. Compounded stocks containing antimony trisulfide have been stored at m ~ m a Summer l temperatures for several months with no loss in processing qualities. EFFECT O F BLACK CONCENTRATION
2000 2700 2500 2950 2 i 2 i 2875
There are undoubtedly many ways t o take advantage of the properties imparted b y antimony trisulfide. A typical one is the possibility of in3250 3325 2650 3225 3350 3350 creasing black concentration to improve tear and 3425 3250 3050 3325 3150 3000 3225 3025 302s 3225 3300 . . . 3075 3100 . . . 3350 3050 ... abrasion resist,ance without increasing heat build-up or decreasing resilience beyond the limits Xlongation st break, % 710 56.5 .i 505 465 ,375 . . 630 485 4i; Cured 30 min. 575 480 i 0 480 420 4g5 415 imposed b y service requirements. 60 min. 120 min. 490 455 . . . 410 380 . . . 445 395 ... Figure 6 shows the effect of varying the concenHardness (Shore A) tration of black in the base recipe used for the pre62 69 . , , 64 71 . . 65 71 , Cured 30 min. 65 69 74 66 70 74 69 73 74 ceding illustrations, in one case with no activator 60 min. 120 min. 66 70 . . . 67 72 . . . 70 73 . .. and in the other case with 0.5 part of antimony a Aged 2 days in looo C. (212' F.) air oven. trisulfide. The heat build-up obtained on samples b Aged 28 days in 70° C. (158' F.) oxygen bomb. cured 45 and 90 minutes a t 281' F. is plotted against the volume loading of E P C carbon black. TRISULFIDII ON VULCANIZATION OF TABLE 11. EFFECTOF ANTIMONY For the short cure (45 minutes) the test speciNEOPRENE WITHOUT METALLIC OXIDES mens containing no activator and less than 15 1227N- 1227N- 1227N- 1227N- 1227Nvolumes of E P C black were too soft to Lest. T h e Compound No. 1227N 995 996 997 998 999 Neoprene GRM-10 100.0 100.0 100.0 100.0 100.0 100.0 heat build-up with a n y concentration of black is Antimony trisulfide 0 0.25 0.5 1.0 2.0 4.0 less on the 45-minute cure when antimony trisulModulus a t 400T0 elongation, lb./sq. in. fide is present than on the 90-minute cure when Cured 45 min., 227' F. .. ... ... ... 125 150 45 .min., 281' F. 75 125 150 250 350 5 0 it is absent. This is in agreement with the d a t a 60 rnin., 281' F. 125 150 250 350 425 of Figure 3, and indicates t h a t where the pro120 min., 281° F. .100 .. 150 200 275 350 450 duction requirements limit the cure to the equivTensile strength a t break, lb./sq. in. Cured 45 min., 227' F. ... ... 1702 2 % alent of 45 minutes at 281" F. and at t h e same 45 min., 281° F. 1275 1650 1500 2325 1250 1150 time low heat build-up is required, an activator 60 rnin., 281" F. 1450 1725 1% 1275 1300 1050 is almost essential, regardless of the volume load120 rnin., 281' F. . .. 1950 950 850 850 900 ing of black. Elongation at break, % Cured 45 rnin., 227' F. ... .. 1110 1140 While not a recommended procedure, antimony 45 min., 281' F. io55 860 '7QO 860 675 630 trisulfide produces fair vulcanizates with neoprene 60 rnin 281° F. 915 820 760 680 650 620 120 min:: 281' F. ... 820 640 600 565 540 without metallic oxides or other curing or acHardness (Shore A) celerating agents. The data shown in Table I1 Cured 45 rnin., 227' F. .. .. 34 34 45 min., 281' F. io 36 is 36 39 39 were obtained b y incorporating the indicated 60 rnin., 281' F. 32 37 37 39 39 39 amounts of antimony trisulfide with no other 120 min., 281' F. .. 37 39 39 40 42 compounding ingredients into Neoprene GRM-10 on a 10-inch mill, and curing and testing the stocks in accordance with standard A.S.T.M. specificawithout it. They also show t h a t antimony trisulfide is more eftions. These data show that the maximum modulus, irrespective fective in increasing the resilience than twice its concentration of of length of cure, is increased as the amount of antimony trisulfide Permalux. The increase in resilience is apparently directly is increased, and t h e time required t o reach i t and the maximum proportional t o the increased concentration of activator. tensile are decreased. For instance, the time required t o reach As would be expected, the same general conclusions relative t o the ma9imum tensile strength decreased from 120 minutes at t h e effect on resilience are applicable t o the effect on heat build281" F. t o 45 minutes at 2270 F, when the amount of antimony up. For example, 0.5 part of antimony trisulfide produces trisulfide was increased from 0.25 to 2.0 parts. lower heat build-up in a sample cured 45 minutes than' can be obThe data presented here were obtained with one type of antitained without it in a sample cured 90 minutes (Figure 3). mony trisulfide. However, the various polymorphous forms as Compression set is often considered as a reliable measure of well as the pentasulfide are equally effective. Furthermore, t h e state of cure. The data plotted in Figure 4 show t h a t the some other sulfides have a similar effect-for example, those of compression set obtained with a given cure is decreased as the arsenic, bismuth, phosphorus, sodium, and potassium. Still concentration of the activator is increased, and t h a t again antiothers have no effect or in some cases retard the rate of cure. mony trisulfide is more effective than twice the same amount of Permalux. As would be expected from a material t h a t increases LITERATURE CITED the rate Of the effects Of the antimony are more IND. ENQ.CHEM.,25, (1) Bridgwater, E. R.,and Xrismann, E, H,, pronounced when the cures are short. 280 (1932). These effects of antimony trisulfide are obtained with much less ( 2 ) Catton, N. L., Fraser, D. F., and Forman, D. B., Du Pont Co., Rubber Chem. Div., R e p t . 40-2,15 (1940). increase in scorching tendencies than when Permalux is used. (3) Lessip, E.T., IND. ENG.CHEM.,ANAL.ED.,9, 582 (1937). Figure shows that the addition Of part Of antimony tri(4) Terrence, M. F.,and Fraser, D. F., IN=. ENG,CHBM,,31, 939 sulfide does not increase the Mooney scorch of the stock, and the (1939). addition Of 0.25 part Of antimony produces Only a RECEIVED April 28, 1948. Presented before the Division of Rubber Chemdetectable change in f3corchiness. T h e addition of 0.5 Part of istry a t the 113th Meeting of the AMERICAN CHEMICAL SOCIETY, Chicago, Ill.
...
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..
...
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I
.
.
.
I
