N,N-Dithioamines in Furnace Black Stocks M. C. Throdahl and M. W. Harman Moneanto Chemical Co., N i t r o , W . Va. ever, certain limiting factors preclude a reasonable solution by this approach. In considering this scorch problem chemically, a partial solution of it may be effected by use of well known sulfenamide type accelerators with elemental sulfur a8 the vulcanizing combination. However, still further progress has been made by replacing elemental sulfur with organic sulfur-containing compounds of the N,N'-dithioamine class. Bedford ( 8 ) in 1929 first described the vulcanization of rubber with N,N'-dithioamines or N,N'-polythioamines in the absence of elemental sulfur, but this work was limited to gum stocks. Blake ( 5 ) , Hand ( 7 ) , and Sibley (10) have recently reported vulcanizing data with thioamines in other type stocks. The present study extended the field of investigation to the preparation and testing of several new compounds of the N,N'-dithioamine class as replacements of elemental sulfur in furnace black stocks.
Recent adoption of high modulus and high abrasion furnace blacks for reinforcement of natural and synthetic rubber stocks has led to increased scorch problems during mixing and processing. A significant and practical means of reducing scorch of these furnace black stocks has been made by replacement of sulfur with certain N,N'-dithioamines. In general, many N, N'-dithioamines delay the scorch time over free sulfur two- to threefold at processing temperatures of 135' C. and yet give equally high modulus and tensile values at curing temperatures 8" to 10' C. higher. Evidence exists which indicates that the N,N'dithioamines do not just liberate sulfur at vulcanizing temperatures, for the total sulfur content of rubber stocks containing them is usually less than half that required to obtain equivalent cured physical properties when using free sulfur. The most effective N,N'-dithioamines also impart improved aging and flexing characteristics to rubber stocks containing furnace blacks.
Preparation of N,N'-Dithioamines The N,N'-dithioamines were prepared according to an improved procedure which gave higher yields than the methods given in the literature (%'-4, 6, 8, 9, 11). This improvement consists of an alternate-concurrent addition of the sulfur monochloride and caustic soda solution which tends to minimize the hydrolysis of sulfur monochloride and a t the same time effects complete conversion of the amine to disulfide according to the equation:
A
LTHOZ'GH the unique properties of elemental sulfur have made it a universally accepted vulcanizing agent for all types of rubber stocks, the chemical and patent literature contains many examples of the replacement of sulfur with other compounds to obtain improved properties of the final vulcanizates (1, 5, 7 , 10, 18-15). Recent adoption of high modulus (HMF) and high abrasion (HAF) furnace blacks as reinforcing agents for natural and synthetic rubbers together with the trend toward higher mixing temperatures have greatly increased the tendency of such stocks to scorch or prevulcanize. At first consideration this scorch problem would seem to be an engineering one. How-
Table I.
Solution A
Solvent (trichloroAmount, ethylene). ml. -grams 300 73 161.6 640 480 120.5 800 197.6
Amine Diethylamine Diisopropylamine Dioctylamine 8-ethylaminopropionitrile
2
)"+ S Z C ~+Z 2NaOH +
N-S-S-N
2NaCI
+ 2H20
In a three-necked round-bottomed flask of suitable size equipped with a sealed stirrer, thermometer, oppositely set gradu-
Preparation N , N'-Dithioamines
*
Solution CQ yield Solution Ba SaCla, Solvent, 25% NaOH, Product, scrams ml. Grams -grams 94.2 34 50 80 54 80 128 196.0 137.7 17 25 40 100 160 252.2C 67.5
Theoretioai Yield % ' 90.6 92.8 101.2 97.5
Physical Prouerties Solubility b Dark-redliquid 1 to 7 Redoil 1 to 7 Amberliquid 1, 2, 4 to 7 ; slight 3 (hot) Whitecrystals 2 t o 3 (hot), 4 , 6, 7 ; slight (m.p. 77' t o 1, 5 (hot) * " O r ( , , a U.,
160 80 160 40
279.5 139 314 89
75
120
253
75 50
120 80
274 205
97.7 97.2 100.0 94.7
Ambersirup Redoil Ambersirup Dark-red liquid
1 to 4, 6, 7 ; slight 5 [hot) 1 to7. 1 to 4, 6, 7 ; slight 5 (hot) 1 to 7
900 400 1000 315
213
850
50.6
amine Pyrrolidine Piperidine
232 183
R25 730
50.6 34
71.1 89 6
400d 400d
34 34
50 50
' 80 80
109
90
88.3 90.4
Redoil 1; slight2 to 7 Slight yellow nee- 1, 2, 3 (hot) 4 to 7 dles (m.p. 61° t o
Pipecoline Morpholine
99 2 87
400d 400d
34 34
50 50
80 80
118
91 84.5
Redoil- ' Whitecrystals (m.p. 124' t o 125' C . )
,9-cyclohexylaminopropionitrile N-cyclohexyltetrahydrofurfuryl-
67.5 34 67.5 17
100 50 100 25
226.6 112 258 78.5
8-iaopropylaminopropionitrile n-butylaminoacetonitrile ,4-n-butylaminopropionitrile N-n-butvltetrahsdrofurfuwlamine Cyclohexylaminoacetonitrile
Semicrystallized red sirup 9 9 . 8 Amber sirup 9 5 . 8 Aniber sirup
99.8
RdO
a
b c
-
OD 7
c>
1 to 4, 6, 7 ; slight 5 1 to 4 , 6, 7 ;
1 to 7
slight 5 (hot)
1, slight 2 to 7 2 (hot), 3 (hot), 4, 5 (hot), 6, 7; slight 1
Solutions D and E were identical with B and C b u t were added concurrently. 1 = ether. 2 = acetone; 3 alcohol. 4 = ethyl acetate. 5 = heptane. 6 = chloroform 7 = benzene: all preparations insoluble in water. 219 grams'white crystals, m.p. 77' to $9' C., and 33.2 g r a k yellow crystals, m.p. 65" to 70" C separated on concentrating in vacuo. Skellysolve C.
~~
42 1
Vof. 43, No. 2
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
422
SULFUR
c ~ H ~ ,
(cH,,&cH,
c ~ H ~ / ~ [CH$,CH*~-
c&, c4nS/’-
c&,, C~H,,“-
Figure 2. Vulcanization Characteristics of .?,.VII)ithioc?.anualkSlanlilles i n Natural Rirbber/IUI: Hliick
Figure 1. Vulcanization Characteristics of N,N’Dithioalkylamines in Natural Rubber/HAF Black Stock
Stork
-
Numbered bars = minutes of cure; shaded bar = 30096 moduluai total bar height = tensile strength
Numbered bare minutes of cure; shaded bar = 300% modulus; total bar height = tensile strength
100
75
06 I
50
$ E
25
E c
” SULFUR
0
- SULFUR
%+st,,
I
C M C H ~ ) ~
(Ck&CH\
CYC~,,+ c ~ c H ~ 1 2 / ~ cN(cn2i -
CI+.&H~)~,CwH2dN-
C&”, CN(C~);
CeHip CNCH;;”
Figure 3. Aging and Heat Generating Characteristics of N,N’-Dithiocyanoallrylaminesi n Natural Rubber/E€AF Black Stock
Figure 4. Vulcanization Charaoteristics of N,N’-Dithiocyanocycloallrylamines in Natural Rubber/HAF Black Stock
Shortest solid bar P 300% modulus; total bar height = tensile strength; shaded bar = temperature rise in Goodrich flexometor; stocks aged 12 hours at 121’ C., 80 lb./sq. inch, in air bomb
Numbered bars = minutes of cure; shaded 300% modulus; total bar height bar tensile strength
ated dropping funnels, and an ice-salt bath there was placed a solution ( A ) of 2 moles of an amine in an inert solvent. From one of the funnels, 0.5 mole of sulfur monochloride solution ( B ) was added dropwise, after which 1 mole of 25% caustic soda solution (C) was added from the other funnel to neutralize the amine-hydrochloride formed. This was followed by the concurrent addition of 0.5 mole of sulfur monochloride solution (D)
-
-
and I mole of 25% caustic soda solution ( E ) . The teniperature during the reaction was maintained a t 0” to 10”C. Following the first two additions, the mixture was stirred for 10 to 15 minutes, and after the last, for 30 to 60 minutes to permit completion of the reaction; then water was added to dissolve the sodium chloride formed. N,N’-dithioamnines, which precipitated from the reaction mixture as solids, wrre filtered off, washed with watcr until
Table 11. Analytical Data of N,iY’-Dithioamines Prepared for Testing as \’ulcanizing Agents Compound N , A”-dithioalkylamines N ,N‘-dithiobis(diethy1amine) N,N’-dithiobis \d/isopropylamine) A’,”-dithiobis dibutylamine) N,N’-dithiobis (dioctylamine) N, N’-dithiocyanoalkylamines hr A”-dithiobis(n-butyiaminoacetonitrile) N’N’-dithiobis(8-ethylaminopropionitrile) N:NJ-dithiobis(,9-isopropylaminopropionitrile) N,N’-dithiobis(8-n-butylaminopropionitrile) N , N’-dithiocyanocycloalkylamines N,N’-dithiobis(8-cyclohexylaminopropionitrile) N ,N’-dithiobis(cyoloheylarninoaoetonitri1e) N, N’-dithioheterocyclicamines N ,N’-dithiobis (pyrro!i$ine) N N’-dithiobis pipendpe)
N’N’-dithiobistpipecollqe) N’ N’-dithiobis morpholine)
Empirical Formula
Sulfur, %
Calcd.
Found
Nitrogen, % Calcd. Found
CsHzoNzSz CizHzaNzSz
30.77 24.24
31.6, 31.6 26.1, 2 5 . 9
13.46 10 60
13.45, 13.46 10.8, 10.9
CiaHsaNzSz CazHasNzSz
11.76
1 1 . 4 4 , 11.38
5.15
5.06, 5.02
CioHiaNaSz CilHzzNaSz CjdHzaN&
CizHzzNiSz
22.38 24.8 22.38 20.38
23.2, 23.7, 22.4, 20,3,
CisHaoNaSz CisHzsNiSg
17 48 18 93
17.5, 17.5 18.30,18.35
CsHisNiSi CioHzoiYzSz
31.38
33.2,
24.62 27.13
25.3, 25.5 26.73,26.58
14.95
15.6,
6.54
6.8,
6.5
17.02
17.6, 1 7 . 6
7.45
7.4,
7.6
......
...
...
CiaHz~NzSz
CsHiaNzOzSz
N:N’-dithiobialN-cy~~ohexyltetra~ydrofurfur~lamine) CzzH4oNzOzSz N ,N’-dithiobis(N-n-butyltetrahydrofurfurylamine) CisHtsNzOzSi N,N’-dithioarylalkylamines N , N’-dithiobis (phenylethylarnine) CuHmNzSi
...
23.3 24.0 22.5 20.3
33.0
15.5
19.58 21.7 19,58
19.5, 21.6, 19.4, 17,83 17.9,
19.6 21.8 19.4 17.9
15.30 16.57
15 .O. 16 ,5,
15 3 16.6
13.71
12.7,
13.0
10.76 11.85
9.66, 9.56 11.60,11.43
...
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
February 1951
.
% USED-
2.5
3.2
3.5
3.7
4. I
a
cSnll\
3
5
423
CH3(CH2)3\
~ ~ n , o m ~ c/ 4~V-. c n 2 yN-
3 v)
Figure 6.
Vulcanization CharacterieN,N'-Dithioheterocydic Amines in Natural Rubber/HAF Black Stock tics
-
Numbered bars = minutes of cure; shaded bar 300970 modulus; total bar height = tensile strength
of
Numbered bar = minutee of o w ; shaded bar soO% modulus; total bar height = tensile strength
free of chlorides, then dried a t 50" C.; those which remained in solution were isolated from the washed product layer by distilling off the solvent, first a t atmospheric pressure then in vacuo to a liquid temperature of 95" to 110" c./5 to 10 mm. The experimental data are given in Tables I and 11.
Compounding and Testing The base formula common to all exploratory tests with iiatural rubber was as follows: Smoked sheets HAF black (Philblack 0 ) Zincoxide ' Stearic acid Paraflux softener 6-Phenyl-l,Zdihydr0-2,2,4-trimethylquinoline N-cyclohexyi-2-benzothiazolesulfenamide Vulcanizing agent
. . I
Parts 100.0 50.0 5.0 2.0 3.0 1.5 0.8 As shown
Unless otherwise shown 2.5 parts of sulfur were used in the control stocks. Scorch tests were carried out a t specific temperatures in an NBS Model Mooney viscometer according to A.S.T.M. D 1077-491'. Stock master batches were mixed in a size 00 Banbury mixer under usual conditions and additions of vulcanizing agents were made on standard 6 X 12 inch laboratory rubber mills. Vulcanizing, preparation of test specimens, and testing were done in accordance with A.S.T.M. D 15-41 and D 412-49T. Stocks were aged in an air bomb operating a t 121" C. a t 80 pounds per square inch as described in A.S.T.M. D 45448. Heat generation, as measured by the Goodrich flexometer (A.S.T.M. D 623-41T Method A), was determined using 175 pounds per square inch stress, 0.175-inch stroke, and 30 cycles per second frequency. Flex cracking was measured in a DeMattia flexometer according to A.S.T.M. D 813-44T.
Results For convenience a comparison of the scorch characteristics of the entire aeries of N,N'-dithioamines is shown in Table 111. N,N'-Dithioalkylamines. I n addition to the three N ,N'dithioalkylamines prepared and described in Tables I and 11, N , N'-dithiobia(dibuty1amine) w a included in the group shown in Figure 1 and Table 111. All four compounds exhibited marked delay in scorch a t 135" C. Although equivalent quantities of each homolog were used (based on 1%sulfur content) the octyl homolog waa least scorchy of the group. Essentially no differences in scorch were observed among the ethyl, isopropyl, and butyl homologs. Modulus values decreased as the size of the
alkyl group increased, but tensile strength remEained relatively unchanged. N,N'-Dithiocyanoalkylamines. This group of four compounds shown, in Figure 2 and Table 111, exhibited marked delay in scorch. Based on equivalent amounts (1%) of total sulfur N,N'-dithiobis(n-butylaminopropionitrile) ia least scorchy of all and is followed by the &isopropylaminopropionitrile, 6-ethylaminopropionitrile, and n-hutylaminoacetonitrile analogs in that order. However, the cure data indicate that N$'-dithiobis(n-butylantinoacetonitrile) is a rather weak vulcanizing agent. T h e isopropylaminopropionitrile analog maintains a slight advantage over the other two in over-all properties of delayed scorch and cure. This compound was eventually selected for further study and is discussed later. Agings and heat build-up data with these same four compounds (Figure 3) indicate better aging than straight sulfur, but only the isopropylaminopropionitrile analog was better than sulfur in heat build-up. The weak vulcanizing activity of N,N'-dithiobis( n-butylaminoacetonitrile) is further demonstrated by the exceptionally high heat build-up. N,N'-Dithiocyanocycloalkylamines. Both analogs shown in Figure 4 and Table 111 were exceptional in delay of scorch but
Table 111. Mooney Scorch Data on N,N'-Dithioamines in Natural Rubber Base Stock Containing HAF Black N ,N'-Dithioamine
%
Used 3.2
Mooney Scorch Time, Min. a t 135O C.
8.8
16 14
8.7
19
5.0
15
N , N'-dithiocyanoalkylamines
N.N'-dithiobis (n-butvlrtminoacetonitrilel 4.3 A'-N'-dithiobis'B eth$lnminopropionitrile) 4.2 .V:N'-dit hiobisIs:isopropylaminopropionitrile) 4.5 .V.N'-dithiobis (n-butylaminopropionit rile) 4.9 A', .V'-dit hiocyanocycloalkylarnines S,A"-dithiobis(8-cyclohexyl~minopropionitrile) 5 . 7 5.5 S.N'-dithiobis(ayclohexylaminoaeetonitri1e) 3.2
Q
20
130 7
3.7
19
3.6
19 26
4.1
N , N'-dithioa lalkvlamines N,N'-dithi%is(phenylethylamine)a Physical properties were too poor to test.
17
22 24 30
0.4
18
6.7
19
4.8
>30
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
424
!
Vol. 43, No. 2
this class of N,N’-dithioamines does riot offer attractive possibilities for vulcanizing furnace black stocks.
t
0
Increased Scorch Temperatures.
f
gave low modulus stocks. AT,;\-’-ditliiobis(cyclohesylamiiioacetonitrile) was slower than ~V,il~’-dithiobis!p-cyclohex.laminopropionitrile). These .V,iV’-dithioamines were also employed a t concent’rationswhich gave 1% total sulfur in the stock. N,N’-Dithioheterocyclicamines. This series of compounds gave unusual results in that a wide spread of scorch characteristics was observed (Figure 5 and Table 111). The dithioamine from pyrrolidine was actually more scorchy than straight sulfur. Dithioamines from piperidine and its analog pipecolinc gave similar scorch and cure properties; grouped together the pipecoline derivative was slightly slower than the piperidine analog. On an equal sulfur content tmsis X,,\7’-dithiobis(n~orpholine) gave most delay in scorch of this series. However, all four analogs were practically equivalent in cure characteristics. Test results with two other N,X’-dithioheterocyclicamines of different structure are given in Figure 6 and Table 111. LV,Al”dithiobis(N-n-butyltetrahydrofurfurylamine) and N,N’-dithiobis(N-cyclohexyltetrahydrofurfurylamine) were equivalent, in scorch and cure characteristics but were not in the same class with X,N’-dithiobis( morpholine). N,”-Dithioalkylarylamines. When the known vulcanizing agent N,N’-dithiobis(ethylphenylamir1e) was employed under conditions suitable for other N,N’-dithioamines, vulcanization was effected, but the stocks were too weak to test. Apparently
Table Is’ shows a compari-
Table XV. &looneyScorch Characteristics of N,N’-Dithiohis(morpho1ine) and r~‘,~,S’-Dithiobis(~-isopropylaminopropionitrile) in Natural RubberHAF Black Stock (8ccelerator, N-cyolohexyl-2-benzothiazolesulfenamide) Test Mooney Used, Temp., Scorch vulcanizing -4gent Parts C. Time, Min. S IIIf II r (control)
.Y, .Y’-dithiobis(morpho1ine)
146
13 16
141
N,N’-dithiobis(P-isopropylrtminopropionitrile) 4 . 5
136 156 151 146
24
10 12
15 21 31
141
136
Effect of Concentration of N,N’-Dithioamine. ILIany te.its were made with the several N , N’-dithioamines at several Icvels of concentration. Experience showed that approximately 0.7 to 1.0% total sulfur content gave exceptional delay in scorch a\ well as best vulcanizing and aging characteristics. These general characteristics are demonstrated by the data in Figure 7 and Table V which are specific for N,N’-dithiobis(diisopropy1amine) but are also representative for all the N,Ar’-dithioamines
(121OC.)
”
0
.-a
4 u)
a
(D
k 3
1 3
v)
v) v)
w
W
e
k 2
$
LT
w
=! r n I z
=! v ) I z
w
w
I-
I-
-
O
% SULFUR (O-N%Sz
2.5
-
I
O
0.4 2.0
0.5
0.6
0.7
0.8
Qr. SULFUR-
1.85
1.70
1.55
1.40
(O-NtSo
VULCANIZING TEMP.-
144. C.
Figure 8. Scorch and Vulcanizing Characteristics of Natural Rubber/HAF Black Stocks with Variable Sulfur and N,N’-Dithiobis(morpho1ine) Content Numbered bar
2
W
minutes of cure; shaded bar = 300% modulus; total bar height = tensile strength
r
2.5
-
1
0.4
0.5
0.6
0.7
0.8
2.0 1.85 1.70 AGING TEMP.- 100°C.
1.55
1.40
Figure 9. Aging Characteristics of Natural Rubber/ HAF Black Stocks with Variable Sulfur and N,.V’Dithiobis(morpho1ine) Content Numbered bars = minutes of cure; shaded bar = 300Vo modulus; total bar height = tensile strength; stocks aged 48 hours in s i r oven
February 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
is
rli
1 h
9 d
.-s .-B 3
.C
t
3
E
Y
m E
8 6 U
L: ro
1 m
N
r?
B
d. d
h
425
tested and reported. As illustrated in Figure 7 the greater concentrations of N,N’-dithioamine were actually less scorchy than lower amounts. This phenomenon was observed in all the compounds tested. From an economic viewpoint the lowest quantity of vulcanizing agent which would give best over-all results was most desirable. Hence, this was the governing factor in the selection of concentrations of the N,N’-dithioamines tested. Effect of Partial Replacement of Elemental Sulfur. Further compounding studies revealed that partial replacement of elemental sulfur was feasible from the viewpoint of delayed scorch and was also economically attractive. The effect of replacing part of the sulfur in the natural rubberHAF black stock is shown in Figures 8 to 11. Using 2.5 parts of elemental sulfur as the control a group of five stocks, each containing an increasing amount of elemental sulfur, was prepared and tested. The total sulfur content of all stocks, except the control, was held to 1%. The delay in scorch was approximately twofold even with 0.8% elemental sulfur. All moduli were equivalent. Aging and flex-cracking of the stocks containing partial replacement of sulfur was considerably better than the control. Heat build-up was approximately the same for all stocks. Effect of Accelerator Variation with DhTerent Furnace Blacks. Sulfur, N , N’-dithiobis(morpho1ine). and AT,N’dithiobis(,9-isopropylsminopropionitrile),each with combinations of three different accelerators of the thiazole type, were compared in three types of furnace black stocks. These data are summarized in Tables VI, VII, and VIII. Both N , N’-dithioamines were effective in delaying scorch two- to threefold in all three combinations of accelerators and furnace blacks. This delayed action was particularly evident from the strewstrain data of the stocks accelerated with N-cyclohexyl-2-benzothiazole sulfenamide. Table VI shows the data obtained with an SRF black. The two N,N’-dithioamines were somewhat slower than straight sulfur in developing equivalent moduli but optimum cures were reached in no longer than BO minutes. N,N‘-dithiobis(morpho1ine) was more satisfactory in this respect than was N,N‘-dithiobis( P-isopropylaminopropionitrile). When using 2,2’-dithiobis( benzothiazole) and 2-mercaptobenzothiazole as accelerators both N,N’dithioamines gave higher moduli than were obtained with sulfur. The HAF and H M F black stocks shown in Tables VI1 and VI11 demonstrate even more effectively the two- to threefold delay in scorch obtained with the N,N’-dithioamines. I n these stocks the optimum cures are reached more quickly than with the SRF blacks. The 15-minute cures are indicative of the delay in scorch when stocks are vulcanized with the two N,N’-dithioamines. Stocks accelsulfenamide were erated with N-cyclohexyl-2-benzothiazole essentially equivalent in modulus and tensile strength with sulfur, but stocks in which 2,2’-dithiobis(benzothiazole) and 2-mercaptobenzothiazole were the accelerators showed that the two N,N’-dithioamines gave stiffer cures of higher modulus and tensile strength. N,N’-Dithiobis(morpho1ine) Used without Accelerator and Zinc Oxide. Additionally, N , N’-thioamines and N , N‘-polythioamines have been prepared and tested in t,his application of vulcanizing furnace black stocks, However, the N , N‘-thioamines are comparatively difficult to prepare; are not so attractive economically as the N,N’dithioamines; and are not quite so effective. The N,N’polythioamines, although not difficult to prepare, were found to be extremely scorchy. From the preceding data on the vulcanizing characteristics of the several
INDUSTRIAL AND ENGINEERING CHEMISTRY
426
Table VI.
Vol. 43, No. 2
Scorch and Vulcanizing Characteristics of N,N'-Dithiobis(morpho1ine) and
iV,N'-Dithiobis(P-isopropylaminopropionitrile)in Semireinforcing Furnace Black Stock Base formula Smoked sheets SRF black (Pelletex) Softener (Paraflux) Zinc oxide Stearic acid 6-Phenyl-l,2-dihydro-2.2,4-trimethylquinoline
Parts
100.0 50.0 3 .O 5.0 2.0 1.5
Ultimate Shore s40du1us, Tensile Cure at "A" Stren 144' C., Hard- . Lb./!q. th, % 135O C. Min. ness 300% 500% Inch N-Cyclohexyl-2-benzothiaaole Suifenamide Accelerator, 0.8 Mooney Scorch Used, Min. ai
Vulcanizing Agent Part A.
2.5
Sulfur
12
L;;(p
15 30 45
3,5
N,N'-dithiobis (morphoiiue)
N , +-'-dithiobis(@-iaopropyleminopro-
4
pion]trile)
G
27
>30
60 15 30 45 60 15
30 Part B.
N,N'-dithiobis (morpholine)
1475 1485 1535 1490
a
3125 3065 3070 3055
3253 3265 3200
238'5 1555 3375 1605 3295
3255 3405 3380
ioio
55 60 60 e
.
45
'48'5
160
55
1010 2565 60 60 1605 3305 2,2'-Dithiobis(benzothiazoie) Accelerator, 0.8 2.5 8 15 60 1000 2460 30 60 1025 2500 45 GO 1185 2555 GO GO 1155 2435 a 3.5 27 16 30 60 ii70 3335 46 GO 1770 . , . 60 GO 1830 . . . 45
Sulfur
66 65 60 GO
N,N'-dithiobis(B-isopropy laminopropionitrile)
Part C.
4.6
27
a
30 45
60
3.5
5
12
15 30 45
60
60
60
15
50
30 45 GO N,h"-dithiobis (~-isogropylal~linoPropionitrile)
4.6
17
1
