Oil Types in the Program for OilExtended Rubber W. K. TAFT, MILTON FELDON, JUNE DUKE, R. W. LAUNDRIE, AND D. C. PREllI Government Laboratories, University of Akron, Akron, Ohio
#
T
HE standardization of oils for use in masterbatching with high Mooney viscosity GR-S made a t 41" F. is essential, as oil-masterbatched polymer is increasing in commercial importance. The Office of Synthetic Rubber, Reconstruction Finance Corp., had set up three classifications of oils-highly aromatic, aromatic, and naphthenic-within which oils are interchangeable (8). Rostler and White (IO) had also suggested three groups, but called them extenders, processing aids, and lubricants. The Office of Synthetic Rubber classification is based primarily on content of saturated hydrocarbons, the percentage of which increases from Type I to Type 111. Rostler's classification is based on viscosity of the oils and a somewhat different balance of components. The two groupings are shown in Table I. The first and last groups of both classifications are essentially similar, differing mainly in name, but the two types in t h e middle category are different. The aromatic oil of the Office of Synthetic Rubber is for all practical purposes a blend of the highly aromatic and naphthenic oils, whereas the processing aid of Rostler is low in nitrogen bases and does not permit a high concentration of saturates or paraffins. Rostler and Sternberg have shown (9) that nitrogen bases affect the cure and staining properties, and the authors ( I S ) have pointed out that the nitrogen bases afiect the stability and breakdown of the polymer in the masterbatches. Rostler's work was done by adding the oils to various rubbers on a mill. T o see whether these results were confirmed with latex-masterbatched polymers, two series of masterbatches were made. One series was made up t o compare t h e relatively concentrated components as defined by Rostler and furnished by the Golden Bear Oil Co. The other series consisted of masterbatches containing commercial oils selected to approximate four classifications, three of which were essentially similar to both the OSR and Rostler classifications, and the fourth was similar to the extender classification of Rostler, but lower in nitrogen bases. The viscosities of the oils within each of t h e four classifications were varied.
Table I.
Classification of Oils
OSR Classification Product Type Highly aromatic Aromatic Xaphthenic SUS viscosity a t 210' F. 300 max. 100 max. 100 max. Sa. R r . at 60"/60° F. 0.965-1.050 0.965-0.995 0.935-0.965 Asphltenes, % 0 . 1 max. 0 1 max. 0 1 max. N bases, % 10-25 12 max. 3 max. Unsaturates, Group I, % 12-28 8-21 3-10 Unsaturates, Group 11, % 40-63 48-65 34-45 Saturates, 70 5-15 15-32 48-56
Viscosity, cp. at 25' C. Sa. er. at 6Oo/6O0 F. LspEaltenes, % N bases % 1st acidkffins, % 2nd acidaffins, 70 Paraffins (liquid), % ' AnnSH
Rostler Specifications Processing Extender aid Lubricant 20,000-40,000 200-1000 1000-10,000 1.00-1.02 0.96-1.00 0.91-0.97 0.0 0.0 0.0 15-25 5 max. 3 max. $ .:;: Balance Balance 5-15 10-20 40-60 >0.025 > O , 025 >0.025
COMPONENTS OF OILS
Twenty-five parts of the concentrates as defined by the Rostler classification were latex masterbatched with 100 parts of polymer, and the dried materials were tested. PROCEDURE
The latex for the experimental masterbatches was prepared in 500-gallon reactors a t 41 a F., using a 75/25 butadiene-styrene charge ratio and a conventional iron-pyrophosphate recipe with rosin soap as the emulsifier. The reactions were stopped a t 60 f 3% conversion with 0.14 part per 100 parts of monomers of a mixture of sodium dimethyl dithiocarbamate and sodium polysulfide; t h e polymers were stabilized with 1.5% of phenyl-2naphthylamine, added on the basis of the total solids in the latex. Samples of the stabilized latices were coagulated in the absence of oil.
Table 11. Analyses of Petroleum Products Sp. gr. at 60°/600 F. SUS viscosity at 210' Vaporization loss b , % Bromine N 0 . C Nitrogend, %
Ashe, %
F.
Nitrogen Basesa 1.05 326 0.21 45.9 3.1 0.74
1st and 2nd Acidaffinsa 1.03 112 0.31 37.2 0.29 0.03
Med. Process Oil 0.98 47 0.89 27.5 0.14 0.02
2nd Acidaffinsa 1.00 72 1.50 11.9 0.02 0.01
Paraffinsa 0.89 40 1.59 1.2
0.01 0.01
Ciroosol-2XH 0.94 83 0.1 7.2 0.09 0.01
Rostler Analysisf Asphaltenes, % Nitrogen bases, % Group I h , % Group 11, % 1st acidaffins, % 2nd acidaffins, % Paraffins, %
0.2 84.2 84.2
0.2 9.8
7.2 7.0 1.4
29.6 54.7 5.7
...
... ...
...
2.5 0.5 2.0 17.3 64.2
16.0
...
0.5
... ...
6.6 80.3 12.6
...
0.78
...
14.0 85.3
Elution Method i Nonaromatics, % 1.8 5.6 14.0 12.3 90.6 Aromatics, % 42.1 87.3 81.0 88.0 9.0 Polar compounds, 70 56.1 7.1 5.0 2.7 0.4 a ExDerimental concentrates furnished bv " F. S. Rostler: other oils are commercial Droducts. b Afbr heating for 3 hours at 163" C. Total of N bases and 1st acidaffins. (3). h Precipitable by HC1 gas. d Determined by Kjeldahl method. 6 Determined at 550' C . to constant weight. (6). 2 Obtained on another sample. f (9).
1077
...
1.0 0.1 0.9 4.4 43.7 50.9
55.43 44.63
...
INDUSTRIAL AND ENGINEERING CHEMISTRY
1078
The oil-latex masterbatches were prepared, using the oils and oil fractions shown in Table 11. The usual techniques were employed, except that trisodium phosphate dodecahydrate (1.5 parts, on an anhydrous basis, per 100 parts of oil) was used to neutralize the charge particles of the nitrogen bases concentrate, since without the added electrolyte, the oil and latex emulsion did not mix. With the mixed unsaturates or acidaffins concentrate (material reactive with concentrated sulfuric acid), it was necessary to use 4.0 parts of potassium rosin soap per 100 parts of oil to obtain a stable oil-latex mixture. All polymer samples were dried a t 140' F. in forced-draft, tray-type ovens.
Table 111.
Vol. 47, No. 5
behave alike and have little effect, if any, on cure rate. On the basis of combined sulfur, t h e sulfur demands increased with the oils in the following order: paraffins, second acidaffins (unsaturates, Group 11),first acidaffins, and nitrogen bases, thus substantiating with the masterbatched oils the results found by Rostler (9) in dry compounding. Compounds containing the paraffins had the best low temperature flexibility and freeze point, those with the second acidaffins were next, compounds having t h e f i s t acidaffins were next, and those containing the nitrogen bases had the highest values for these properties, as shown in Table VI.
Raw Masterbatches before and after Banbury Treatment
Banbury Treatment, 1000 Grams" 5 Minutes 10 Minutes Raw Polymer Power DSVO Gelc, Acetone Visc. DSVC Gelc, used, Visc. DSVG GelC, Visc. b % ext., % ML-4 e0rr.d % w.-hr. ML-4 c0rr.d % ML-4 Det. C0rr.d 25.6 2.35 3.16 55 2.63 628 40 2.39 72 26.6 50 2.29 3.12 2.64 30 2.04 599 72 601 26.3 50 3.19 2.72 2.38 27 2.07 70 27.8 48 3.17 2.74 607 2.29 27 2.11 68 617 26.1 50 3.34 3.11 39 2.47 2.67 62 26.1 54 2.75 614 69 2.42 3.27 43 2.56 a Rotor speeds, 120 r.p.m. for front and 132 r.p.m. for back. b Mooney viscosity (reading a t end of 4 minutes), determined with large rotor a t 212' F. c Gel and dilute solution viscosity (DSV) determined by method of Baker and Mullen ( 4 ) . d Calculated to polymer basis, aietone extracts assumed same as those of originals. ~
RESULTS AND DISCUSSION
Results of Banbury treatment of the masterbatches are shoum in Table 111. One thousand grams of the raw masterbatches were mixed for 5 and 10 minutes in a size B Banbury. The changes t h a t occurred in Mooney viscosity and molecular weight, as measured by the dilute solution viscosity, are shown in Figure 1. It is evident that the paraffin fraction is relatively inert and tends to minimize the polymer breakdown. The nitrogen bases are most reactive at the start of mixing, but on further mixing the breakdown curves flatten out. The effect of the acidaffins is characterized by a polymer breakdown that is not as rapid a t the start as in the presence of nitrogen bases but continues toward a lower dilute solution viscosity level. These data suggest that by proper control of composition of oils the effects of one constituent can be modified or overcome by another constituent. These masterbatches were mill-mixed and compounded according to the rather fast curing recipes using a high oil-absorptive black shown in Table IV. Plots of the 300% modulus against time of cure (Figure 2 ) indicate t h a t t h e gradual stabilizing of the modulus caused by t h e nitrogen bases still holds when the accelerator level is lowered, as shown by the curves marked nitrogen-bases 0.75 and 0.25 part Altax, thus indicating t h e beneficial effect of nitrogen bases on cure level. The other constituents behave similarly to each other and probably lack this tendency. ~~
1148 1082 1107 1089 1121 1134
MOONEY VISCOSITY VERSUS TIME I N BANBURY ( 1000 GRAM LOADING)
-
70
e
65
I
60
I
55
c g
45
-I
50
40 5
35
30
2s --
,CORRECTED D S V VERSUS TIME IN BANBURY
Compounding Recipes
Ineredient Masterbatch HAF black (Philbleck 0) Zinc oxide Sulfur Benzothianyl disulfide (Altax) Stearic acid Mill-mixed stocks cured for 25, 50, and 100 minutes a t 292' F. a Used for all masterbatches except X-628. Used for X-628.
PARAFFINS CIRCOSOL- 2XH N BASES 2nd. ACIDAFFINS
The various measurements showing the effect of the fractions of oil on the cure rate are shown in Table V. The cure index and free and combined sulfur data substantiate the very rapid cure rate for the masterbatch containing nitrogen bases. The cure index values indicate that the other three concentrates
vv.-h;.
I n Table VI1 are shown data for volume increase of a high Mooney viscosity base polymer when submerged in various types of oil. A rough correlation of compatibility has been shown (16) t o exist with swelling index, as determined by submerging for 7 days at 140' F. vulcanisates of raw polymer compounded according to a gum stock recipe and measured by the ASTM procedure ( 1 ) . It can be seen from t h e data in Table VII, using compounds of a base polymer having a Mooney viscosity of 126 ML-4, t h a t the paraffins were absorbed to a volume increase of
~
Table IV.
Power used
2.00
'
0
OIL 5
IO
TIME I N BANBURY, MINUTES
Figure 1. Effect of Banbury treatment
May 1955
"'i
INDUSTRIAL AND ENGINEERING CHEMISTRY
130'%, the second acidaffin samples t o a volume increase of about 21070; the control, Circosol-2XH, which is a mixture of acidaffins and paraffins, was absorbed to a volume increase of 149%. The nitrogen bases were absorbed to a volume increase of only loo%, probably because of their high viscosity (low mobility). The medium process oil was absorbed to a volume increase of 295%, which again is probably influenced by the low viscosity. It is evident that, besides the specific chemical nature of the oil fraction, the viscosity of the oil has entered into the quantitative results. I n general, however, the order of increasing absorption is paraffins, second acidaffins, first acidaffins, and possibly the nitrogen bases, a t the same viscosity levels.
1079
LAROE ROTOR AT 2l2.F.
84 83 82 81
80
79 78
77 78
75 27001
N BASES
74 73
1st 8 2nd. ACIDAFFINS
72
0. PROCESS OIL (0)
71
2nd. ACIDAFFINS
70
CIRCOSOL-PXH (e)
69 68
2nd. ACIDAFFINS
\b PARAFFINS
87 66 0
"
1
"
2
"
"
3
4
TIME MINUTES
Figure 3. Effect of time on Rlooney viscosity reading Reading at 4 minutes is the ML-4 value I300
-
Another indication of the degree of compatibility can be obtained from Mooney viscosity curves. Fenson (6) states that the greater trend toward constancy in Mooney viscosity during time of mastication in the viscometer indicates greater ease of orientation of the polymer chains. As the masterbatches under discussion were all made from similar base polymer, the lesser slopes of the curves for the second acidaffins and paraffins as shown in Figure 3 may represent easier orientation and therefore less compatibility of the polymer chains in the presence of these oils than with the other oils. T h e other masterbatches with the more compatible oils exhibited greater change in Mooney viscosities with time (greater slope). These results, combined with the oil absorption results previously discussed, confirm in masterbatches the lubrication by the more saturated compounds reported by Rostler for dry mixing.
coNcLusIoNs
Under conditions of low Banbury loading, nitrogen bases caused the most rapid initial breakdown of the polymer when mixed in a Banbury, with subsequent reduction in the rate of breakdown. The paraffins caused the least initial breakdown and may act as stabilizers or buffers for the other fractions. The acidaffins caused continual breakdown. Nitrogen bases accelerated the cure rate and the modulus was unaffected by extended curing time. The other constituents were about alike with respect to their effect on cure, except that the paraffins gave somewhat faster curing stocks than the acidaffins a t the same sulfur level. The sulfur demand correlated with the unsaturation. The effect on freeze point varied in the orderparaffins, second acidaffins, first acidaffins, and nitrogen bases, the latter being the poorest. Compatibility with polymer became greater as the unsaturation increased, as shown by oil absorption and ease of orientation of the polymer chain.
COMMERCIAL OILS T o check on the additivity of properties of the fractions, commercial oil samples were obtained from various sources and oil fields to agree roughly with the three classes of oils suggested by Rostler and the Office of Synthetic Rubber. In addition. another grpup similar to the Table V. Curing Characteristics highly aromatic oils of the OSR classification but contain300% Modulus, Lb./Sq. Inch (at Sulfur6 25-Mid. % Cure).h - T At opt. Index5, Cure Type of Oil Min. 25 min. 50 min. 100 min. Free Combined cure0 Max. ing less total nitrogen bases N bases 18 2390 2490 2500 0.02 1.95 3630 3680 was obtained on the assump... 1650d 19504 199Od ... ... 3570d 3830d tion of the authors (13) that a 1st and 2nd acidaffins 27.5 1300 1680 2020 0.60 1.35 3360 3430 Med. proc. oil 28.5 1430 1840 2260 0.56 1.39 3400 3580 maximum of 15% nitrogen 2nd acidaffins 29.5 1330 1740 2200 0.66 1.28 3360 3470 bases might be desirable. Oils 1590 1910 2290 0.62 1.26 3290 3400 Paraffins 26 Ciroosol-2XH 27 1620 1990 2360 0.58 1.35 3480 3620 of differing viscosity within ... ... 3330 3390 X-628" 30.5 1530 2200 2650 Base polymer ... ... ... ... 0.74 1.19 ... ... each type were used, Latex scorch point, where scorch masterbatches were made to a According t o (18)using equation, cure index = 6 (cure point - scorch point) point is, 1ast.time of minimum reading and cure point is time a t which viscosity has increased 30 units above miniContain 37.5 parte Of Oil per 100 mum viscosity. parts of rubber and the masterb Total sulfur b y Parr bomb method. Free sulfur as described by Oldham and coworkers (7). C As described by Schade (11). batches were tested. d Altax reduced from 2.5 to 0.75 part. e Altax level 2.0 and stearic acid 0.75 oart. The source and analysis of the oils are shown in Tables
+
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
1080 '
VI11 and IX and are identified as numbers rather than trade names. Type I is similar to the OSR highly aromatic oil or Rostler's extender, with the exception of viscosity of some of the oils. Type I1 oils are of the same type, but the content of nitrogen bases is below 15%. The Type 111 oils include in oils 12, 13, and 14 essentially the aromatic oils according to the OSR classification, while oil 15 is a processing aid as defined by Rostler and is within the OSR classification for an aromatic oil. 'Type I V oils are in the group of naphthenic oils or lubricants. PROCEDURE
A gel-free GR-S-1500 type latex was prepared a t 41' F. from 75/25 butadiene-styrene charge to 61.2% conversion and a Mooney viscosity of about 140 for the contained polymer. The polymerizations were shortstopped with 0.15 part of a sodium dimethyl dithiocarbamate-sodium polysulfide mixture per 100 of combined monomers. The latex was divided into two parts; one part was kept unstirred in a covered tank and the other was aerated for 7 2 hours by blowing with air a t room temperature. The various oils were emulsified with 2% potassium oleate based on the oil, and coprecipitated with the latex and 1.25% phenyl-2naphthylamine (PBNA) based on the latex solids. Polygard (furnished by the Naugatuck Chemical Co.) was used in place of phenyl-2-naphthylamine with the aerated latex to make masterbatches containing oils of the lowest aromatic content, for staining tests. The Type 111 oils were compared with one Type IV oil for staining and discoloration by mill mixing with GR-S-1502. Coprecipitation using 37.5 parts of oil per 100 of polymer was affected by brine and sulfuric acid and drying was done for a minimum time at 140' F. in forced-air tray-type ovens. Except for the staining and discoloration tests, the stocks were compounded according to two types of recipes. One requi'red a high black loading using a highly absorptive HAF black and the other required a lower loading of a less absorptive E P C black. These two recipes were used to show the results that might be expected from a tread-type recipe (high black loading), by which the effects of differences in oil composition may be minimized and in a lower loading where the effects should be accentuated. About 400 grams of masterbatch were used for mixing on a 6 X 12 inch mill and 900 grams for mixing in a size B Banbury. Compounding Recipes Masterbatch Philblack 0 NBS standard EPC Zinc oxide Sulfur Stearic acid Altax Total
Parts 137.5 88.75
...
5.00 2.70 0.75 1.50 216.20
-
Parts 137.5
4'0.00 5.00 2.70 0.75 1.50
Masterbatch
rately. The effect of the aeration process on the physical properties of vulcanizates was investigated to determine whether or not aeration is effective with all four types of oils. The oils were chosen on the basis of the proportions of the various fractions in each oil, so as to attempt to define the effect of each constituent in the presence of the others. Because the effect of the nitrogen bases is due to the presence of polar groups, the molecular weight of this fraction must be taken into account. I n compliance with this requirement, nitrogen base content has been calculated to an equivalent basis b y dividing the percentage of nitrogen bases by average molecular weight. Average molecular weights used for this calculation were taken from a table b y Rostler and White (IO) showing viscosity os. average molecular weight. Although this calculation assumes that the nitrogen bases in the sample have the same molecular weight as the total mixture, which is probably not exactly true, it is accurate enough for the purpose of establishing equivalents, especially as any error is apt to be of the same order for all the samples. Reasonably narrow viscosity ranges for specification purposes would limit the molecular weight factor. As oils of too high a viscosity are difficult to pump, emulsify, and possibly to'disperse evenly on coagulation, a medium viscosity appears desirable from this point of view. Rostler's specifications (Table I ) seem to take this consideration into account. The stress-strain results for the vulcanizates of both aerated and nonaerated masterbatches mixed in the H A F black recipe, and for the aerated latex masterbatches mixed in the E P C black recipe; are shown in Table X, as well as the curing characteristics. The t, values of the E P C black stocks are the most reproducible, with the cure index being less significant in this set. I n the H A F recipes, the cures are all so fast that differences caused by the oils become small as measured both by t , and cure index. However, it is evident from the 1, figures of the E P C stocks, that of the stocks containing the oils of Type I, Nos. 1, 2, and 5 are a t one extreme of curing range and No. 6 is a t the other. Stocks with oils 4 and 7 are slower curing than those with No. 6. Oil 6 is different when compared with the other oils of this group, in that it is of lower molecular weight, highest in Group I nitrogen bases, and low in paraffins. Oils 1 and 2 are not only high in molecular weight but low in amount of Group I nitrogen bases and paraffins. Oil 5 is different, in that its paraffin content is the highest. From these data, i t appears that the Group I nitrogen bases, and not the Group I1 bases, are the active ones in affecting cure, and that the paraffin, depending on the amount, may serve as a stabilizer. The results obtained from Banbury mixing (not shown) were essentially similar to the mill-mixing results. The slower cure times shown by vulcanizates of the Type I1
187.45
The staining and discoloration tests were made with stocks mixed in the following recipes: Type of Polymer Ingredients Polymer Titanium oxide Zinc oxide Sulfur Altax Total
Vol. 47, No. 5
Table VI.
Tz
Type of Oil
GR-S-1502
All the mixed stocks were vulcanized at 292' F
Effect of Processing Oil on Low Temperature Properties
24 26 32 32 41 31
N bases 1st and 2nd acidaffins Med. proc. oil 2nd acidaffins Paraffins Circosol-2XH a
-'C. Tim 42 44 51 49 58 50
F.P. 42 46 52 50 59 52
(2).
Table VII.
Volume Increase of High Mooney Polymer in Various Oils
RESULTS AND DISCUSSION
Masterbatches of all but the high-paraffin naphthenic oils were made from the same latex, which was divided into two parts, one of which was aerated, as previous results (IS, 14) had indicated that aeration of the latex increased the stability of the molecular structure on heating and storage. The storage results obtained with these series of masterbatches are reported sepa-
Gehman Valuesa, T6 Ti0 33 35 35 38 43 46 43 40 50 52 42 45
Type of Oil
Tu' bases
2nd acidaffins Paraffins Circosol-2XH G. B. med. proc.
Visc., SUS a t 140' F. 15,000
Volume Increase % Composition, Yo in 7 Days N bases 1st acid. 2nd acid. Paraf. a t 140' E'. 84.2 7.2 7.0 1.4 100
65 140
2.5
17.
May 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY Table VIII.
,
Oil No. Viscosity a t 25' C., cp. SUS 210' F. Sp. &-. a t 60°/600 F. Bromine No. b Rostler analyses Asphaltenes, % N bases, yo Total Group I , precipitable by HC1 gasd 1st acidaffins, % 2nd acidaffins, % Paraffins. 92 n2,of paraffins Av. molecular weighte
1 a
676 0.9971 15.0
AnDSH
Wax, % Volatile matter (3 hours at 325' Viscosity index Oil field Source of oil
Esso chromatographic method Nonaromatics, yo Aromatics, % Polar compounds, 70 a
Analytical Data of Type I Oils
(Highly aromatic, over 15y0 N bases) 2 3 4 a 52,400 47,300 166 441 336 1.0172 1,0121 1.0275 20.4 20.8 30.4
0
0
0
1 5.7(35) 0 1.0(2) 16.6 62.9 4.8 1.4885 450 0.033 0.15 0.13
15.9(35) 2.9(6) 18.9 60.8 4.4 1.4891 450 0.033 0.03 0.08
mT. Texas
W. Texas Shell
26.2(58) 15,0(32) 18.8 45.1 9.9 1,4931 450 0.037 0 0.09 -723.3 W. Coast G. Bear
Phillips
10.5 81.8 7.7
1081
7.2 85.8 7.0
~
0
0
2 1 .3(57) 13.9(37) 19.3 49.4
10.0
1.4921 375 0.041
0
0.18 -478.0 W. Coast G. Bear
11.1 77.2 11.7
5 4,300 130 0,9881 18.5
10.8 76.9 12.3
16.0(38) 6 . N15) 14.7 52.7 16.6 1.4815 425 0.028 0.43 0.13 -79.9 Mid-Contment S. Ind. 19.3 72.0 8.7
6 37,150 106 1.0373 43.8
'
7 14,420 97 1.0201 32.9
0
0
22.3(64) 17.1(49) 18.4 53.4 5.9 1.4913 350 0.042
0.01
0.3 -606.9 W. Coast Shell
16.1(46) 11.6(33) 18.4 54.2 11.3 1.4914 350 0.042 0 0.2 -448.2 W. G.Coast Bear
5.1 83.7 11.2
12.6 73.2 14.2
Too heavy to measure.
* Figures (9). in parentheses are per cent N bases divided by average molecular weight (as explained in text) times loa. C
d e
Group I1 is difference between total nitrogen bases and Group Calculated from table given by Rostler and White (IO).
I.
oils are in line with the reduced concentration of nitrogen bases. The curves of 3ooyOmodulus us. time of cure are shown in Figures 4 and 5 for the aerated stocks containing several oils of Types I and I1 with one of Type IV, mixed according to the HAF and EPC recipes. The curves for the stocks with three Type I oils ( 5 , 6, and 7 ) have all flattened out, with the curves for the stocks containing oils 6 and 7 becoming flat at a n earlier point in the plot. The curves for the vulcanizates containing the Type I1
6
600-
u)
56
3 0'
500-
400-
0
s
0 0
-
2300
k
*
-
2400
700-t
300-
m
200
,i 2 2 0 0 -
g 2100-
g 2000 -
100
\
ca'
2 8 s zt
b 5:
-
1900-
I
I50
1800-
TIME OF CURE, MINUTES
-
1700-
I600
Figure 5.
Effect of time of cure on modulus for stocks mill-mixed in EPC recipe
15001400;
Two parts of masterbatch 6 were mixed with 1 part of masterbatch 18 to obtain a n oil composition in the masterbatch blend that had the same proportion of total and Group I nitrogen bases as that contained in the oil used in masterbatch 7 . The paraffin content of the oil contained in this blend was 20.6%, as compared with 11.370in oil 7. The tp value obtained for vulcanizates mixed according to the EPC recipe was 58 minutes for the blend, compared with 56 for that of the stock with oil 7 , indicating t h a t the effect of the paraffin content in controlling the cure rate was slight in this case, but in the right direction. Another experiment was performed by mixing 1 part of the masterbatch containing oil 6 with 3 parts of the masterbatch containing oil 18 to obtain in the masterbatch blend an oil composition equal in total nitrogen bases to oil 14. However, this blend contained oils with paraffin content of 39% as compared to 21.6% in oil 14, and with 4.5% nitrogen bases, Group I, compared with 1.9% in oil 14. The cure time for this batch was 69 minutes as compared to 75 minutes obtained with stock containing oil 14, thus showing that the Group I nitrogen bases are the effective component. This cure time is exactly the arithmetic mean of the cure times of the individual proportions of the two masterbatches. Thus, from the standpoint of cure, the aromatic oil of the OSR
:risf_
II O 0
1000
8OO0 900
25
50
78
100
I25
150
TIME OF CURE, MINUTES
Figure 4. Effect of time of cure on modulus for stocks mill-mixed in HAF recipe
oils (8,9, and 11)are not so flat as that of 5 (5,8,9, and 11contain about the same Group I nitrogen base equivalents), but approach it. The curve representing the stock with Type IV (18) oil containing a very small quantity of nitrogen bases is continuing its marked upward trend beyond the point indicat,ing further curing. Thus, from the standpoint of flat cure curves, Type I oils with over 15YGnitrogen bases, of which 10% would be Group I, are somewhat preferable to Type I1 oils which contain from 10 to 15% total nitrogen bases and about 3.5% Group I nitrogen bases.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1082
E/ m
- I
Y
w 0
Vol. 47, No. 5
class could be obtained by blending the highly aromatic and naphthenic oils, or their masterbatches. The stress-strain and curing characteristics of stocks containing the naphthenic oils, Nos. 12, 13, and 14, are not significantly different from those of the stock with the processing aid, No. 15. The previous discussion indicated that the Group I nitrogen bases were the component that affected the curing characteristics of the compounds. This group is the most reactive of the nitrogen bases from the standpoint of cure because it contains the nitrogen as part of an end group, whereas Group I1 probably includes the nitrogen mostly as part of a ring structure or in some other shielded configuration. To see whether the data support this reasoning, the cure time, t,, has been plotted against the total and Group I nitrogen bases on an equivalent basis as shown in Figure 6, and the correlation factor calculated for the data of the stocks compounded according to the two types of recipes. No correlation is found for the data obtained with the Group I1 nitrogen bases, but the correlation factor for the data obtained with Group I is better than that with the total nitrogen bases data, The correlation factor calculated on the equivalent basis is somewhat better than when determined on the percentage basis, so that the assumption for calculating the equivalence appears justified in establishing the true trend. The Banbury mixing data (not shown) are in agreement with the cure data reported on the mill-mixed vulcanizates. Considering that the Group I nitrogen bases are the active curatives and that Group I1 nitrogen bases are polar compounds containing oxygen and sulfur as well as the nitrogen in a shielded configuration, it can be understood why the total nitrogen bases are not the controlling factor on cure, but rather only those of Group I. The masterbatches were heat-softened in a forced-air oven at 140°, 200°, and 300' F. Plots of the corrected dilute solution viscosity (acetone extract of heated samples showed no oil loss) obtained the same as previously noted, for the various master-
42
-2 Y
L
0 NONAERATED
AERATED
40% b
A
360
@
34
0
8
-
32-
o
?00 ; @
30-
1
--
-
b
0 0
' m
'
-
75
70 65 60
- 5s-
Y
-502
A
g 3 5 . o
- 603
a
3
33-
fiK
3l-
0 0 0
.
0
..
I
31
@,'
"0 GROUP
;
" .02 .d3 .de P N BASES. EXPRESSED
I;,
55
O
50 .;5 .d6 67 AS EOUIVALENTS
Figure 6. Relation between preferred cure time and nitrogen bases (equivalents) for mill-mixed stocks
May 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
1083
aerated latex broke down more in dilute solution viscosity a t 900-gram loadings than the Aerated Latex Mill-iMixed-HAF Black - Nonaerated Latex Mill-Mixed-HAF Black Tensile 300% Tensile 300% stocks from nonaerated latex, Cure stren thb, modulus), Cure stren thb, modubut differences in Mooney visindex, 1b.fsq. lusb, lb./ Elong.b, lb./sq. Elong. 6 , M,L-4 tp:, ML-4 lb,yBq. tp,", index, inch sq.inch % min. m1n.c inch yo visc. inch min. min. Oil No. visc. cosities were generally within TYPEI experimental error; a t 16001170 A70 1300 650 58 33 3060 35 33 3200 gram loadings, the stocks from 1240 050 33 3130 1280 690 55 34 30 3180 aerated latex decreased less in 1330 610 3140 29 600 61 33 3220 1500 31 30 1350 630 3230 610 57 30 3200 1420 31 dilute solution viscosity and 1270 620 33 3050 620 57 33 3150 1330 37 1510 570 30 3230 560 58 1700 formed less gel on further mas31 30 3370 1500 590 30 3170 29 3200 570 58 1560 30 tication than the stocks from 33 3220 1440 610 58 32.7 33 3140 1340 620 Av. 60 32.6 nonaerated latex; the changes TYPEI1 in Mooney viscosity caused by 1220 640 29 3020 1270 620 62 37 30 3000 8 59 37 aeration were small. There 1260 630 36 3110 1340 670 56 33 33 3040 9 52 39 1240 630 .. ... ... ... 66 36 30 3060 10 .. were exceptions at both load1220 650 60 37 36 3030 30 2990 1240 640 37 11 57 ings. Thus when mixing in 1220 640 32 3040 1280 640 61 36.8 32 3030 Av. 54 36.5 the Banbury is under oxidaTYPE I11 tive conditions a t relatively 36 2920 1170 640 55 37 37 3100 1220 650 1258 41 low temperature, aeration of 660 57 39 36 2920 1230 640 33 3070 1230 13 61 39 33 2990 1220 630 67 34 31 3310 1370 620 60 14 40 the latex causes more break.. .. .. ... 32 3000 1240 620 ....... 15 60 37 down in dilute solution vis34 2990 . 1220 640 60 36.7 35 3110 1270 640 39.3 Av. 60 cosity but does not reduce the TYPEI V work accomplished by the 620 .. ... .. ... ... ... 32 3100 1250 16 62 37 Banbury treatment as meas... ... 1150 630 .. ... .. ... 30 3010 17 58 36 610 .. ... .. ... ... 30 2990 1220 36 ured by reduction in Moonpy 18 58 36.3 31 3030 1210 620 Av. 59 viscosity. A t capacity Banbury loadings where masticaAerated Latex iMill-Mixed-EPC Black tion, not oxidation, is predomiTensile strengthb, 300% modulusb, t p a , min. Cure index min.0 lb./sq. in. lb./sq. in. Elong.b, % Oil No. nant and the stock temperaTYPEI tures are high, aeration of the 70 57 2650 310 790 latex reduced the breakdown 800 68 60 2820 290 in dilute solution viscosity, ... ... .. .. 2740 360 55 770 61 and also decreased the amount 2700 340 73 790 73 2740 54 750 390 51 of gel formed. 2830 56 420 740 66 The change in Mooney and 2750 AV. 63.2 59.2 350 770 dilute solution viscosities durTYPEI1 ing the period of maximum 2700 380 8 68 65 790 breakdown, as determined from 2640 300 9 71 63 780 ... ... 10 .. .. ... the heat aging curves, is shown 820 2700 370 11 70 71 in Table XII. At 140' F., 2680 350 Av. 70 66 800 the average amount of breakTYPE I11 down decreased with increas12 66 2700 370 68 810 ing saturation of the oil-that 400 2690 13 69 71 810 2780 480 72 75 800 14 is, the polymers containing 2750 380 15 70 71 800 Type I oil broke down the 2730 Av. 71.3 69.3 410 810 most, and those containing TYPBI V Type I V oil broke down the 71 60 2750 360 820 16 least. The variations in poly72 2840 320 820 76 17 75 76 2800 340 820 18 mer breakdown of master2800 Av. 74 69.3 340 820 batches made with oils within a According to method described by Schade (11). each oil type were, however, b Values a t t p . relatively large, and were reAccording t o procedure of Shearer, Juve, and Musch ( I t ) , using equation, cure index = 6 (cure point - scorch point) f scorch point, where scorch point,is lagt time of minimum reading and cure point is time a t which viscosity lated to the balance of equivahas increased 30 units above minimum viscosity. lent nitrogen bases and paraffins. As the temperature of heating increased, differences between the polymer breakdown of the various masterbatches batches made from both the aerated and nonaerated latex with time of heating are shown in Figures 7 to 12, and for the Mooney became smaller, so that a t 300" F. all masterbatches were about alike in their breakdown characteristics. viscosity against time in Figures 13 to 18. It has been shown (IS)that polymer breakdown increased at Comparison of the curves for the masterbatches made from 140" F. with increase in the aromaticity of the oils, the aromatic the aerated and nonaerated latex shows that the breakdown is generally slower for the masterbatches prepared from the aerated content being defined as the sum of the nitrogen bases and first latex. Thus, aeration of the latex increases the heat stability and second acidaffins. The active hydrogen in the hydrocarbons of the masterbatch, and by inference, the storage stability. (16),as well as the nitrogen bases (IS), has been demonstrated t o This is more apparent with the reactive oils and less with the influence breakdown. The total nitrogen bases are the most saturated oils; however, aeration of latex is definitely indicated. active constituent in influencing polymer breakdown a t 140' F. Banbury treatment data, given in Table XI, for the aerated and the first acidaffins are a somewhat less active constituent. and nonaerated stocks showed that generally the stocks from Examination of the lowering of the dilute solution viscosity Table X.
Stress-Strain Values a t 77" F.
.
.
I
INDUSTRIAL AND ENGINEERING CHEMISTRY
1084
I
TYPE
3BL 3.2
O!LS
Vol. 47, No. 5
3.4 3.2
0
POLY MER
3.0
3.0 28
(m
2.6
6
28 2.6
4
e
2.4
2A 2.2
-L
2
3.0
0 Q
2.6
E
8 I-
8
2.4 2.2
38
3.2 3.0 28
2.6
e 2.4
-.-
34
TYPE P OILS
,3.4
BASE POLYMER
2.6
8 e
2.0
TYPE 1 ' 1 OILS
3.4 L 32
TYPE
t
m
22
OILS
15
3.4
BASE POLYMER
3.2
32
-
31) 2.6
2.6
3.0
28 19
2.6
13
TYPE
e4 2.2 2.0
OILS
1.8
0 8 I2
0 6
I2
24
48 72 HOURS AQED AT I 4 O 0 F :
48 72 HOURS AQED AT 140.F:
Figure 8 . Relation between dilute solution viscosity breakdown and time of heating at 140' F.
Figure 7. Relation between dilute solution viscosity and time of heating a t 140" F.
TYPE 0 OILS
TYPE I OILS
3.41
24
TYPE m OILS
24
01
3
6
12
'
24
HOURS ABEDAT eOO.1
Figure 9.
Dilute solution viscosity breakdown with time of heating a t 200' F. Aerated latex
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1955
Table XI.
Oil No.
1
2 3 4 5 6 7
Av. 8 9 11
Av. 12 13 14 15
Av. 16 17 18 Av.
Original ML-4 D S V a
ML-4
Banburv Breakdown Results (1500-gram loading) 5-Minute Treatment AML-4 DSVa ADSV AERATED LATEX
ML-4
10-Minute Treatment AML-4 Gel, % b DSV
3.18 3.16 3.11 3.22 3.33 3.16 3.24 3.20
47 48 46 46 44 45 41 45.3
13 15 13 14 16 13 19 14.7
Type I 3.02 2.96 2.84 2.94 2.99 2.80 2.90 2.92
0.16 0.20 0.27 0.28 0.34 0.36 0.34 0.28
49 51 49 49
59 52 57 56
3.22 3.09 3.09
45 39 39 41
14 13 18 15
Type I1 3.11 2.66 3.06 2.94
0.11 0.43 0.03 0.19
46 41 45 44
12 12
58 61 60 60
3.09 3.23 3.33 3.39 3.26
15 14 14 15 14.5
Type 111 2.94 3.14 3.05 3.14 3.07
0.15 0 09 0.28 0.25
50.7
43 47 46 45 45.2
0.19
45 48 52 50 48.7
13 13 8 10 11
51 44 46 47
Type I V 11 3.28 14 3.00 12 3.08 12.3 3.12
0 0.28 0.17 0.15
55 46 46 49
7 12 12 10.3
60 63 59 60 60 58 60
60
62 58 58 59.3
3.13
3 28 3.28 3.25 3.27
50
45 42 47.9
11 12 10 11 10 13 18 12.1
13 11
24 6 15 12 16 3 1 11
2.34 2.90 2.50 2 74 2.23 2.88 2.75 2.62
1 3 0 1
3.18 2.79 3.22 3.06
6 0 7 13 6.5
2.65 2.93 2.77 2.56 2.73
9 6 7 7.3
2.78 2.68 2.56 2.67
NONAERATED LATEX 1 2 3 4 5 6
7
Av. 8 9 10 11
Av. 12 13 14 15 Av.
58 55 61 57 57 .5 8 58 57.7
3.24 3.12 3.25 3.11 3.16 3.08 3.02 3.14
48 44 46 45 40 42 40 43.6
10 11 15 12 17 16 18 14.1
Type 1 2.91 2.84 2.93 2.94 2 91 2 90 2 80 2.86
0.33 0.28 0.32 0.17 0.25 0 18 0 22 0.25
47 49 49 47 49 46 47 47.7
11 6 12 10 8 12 11 10
10 26 12 24 6 15 6 14
2.62 2.47 2.77 2.34 2.79 2.47 2.69 2.59
E 66
47 45 45 46 45.5
15 11 21 14 15.5
Type I1 2.97 2.78 2.96 2.96 2.90
0.24 0.30 0.38 0.16 0.28
48
60 61
3.21 3.08 3.34 3.12 3.19
48 46 50 48
14 8 20 10 13
3 4 7 15 9
2.91 2.72 2.54 2.29 2.61
55 57 67
3.12 3.02 3.34
45 43 48
10 14 19
Type I11 2.87 2.72 3.06
0.25 0.30 0.28
48 49 51
7 8 16
12
...
19
2.48 2.68 2.34
59.7
3.16
45.3
14.4
2.88
0.28
49.3
10.4
13
2.50
...
...
...
...
...
...
...
7
...
...
900-Gram Loading, 5-Minute Treatment -. Aerated LatexC Konaerated Latex Type I 1 2 3 4 5 6 7 Av.
ML-4 52 52 53 51 53 45 50 50.9
AML-4 8 11 6 9 7 13 10 9.1
DSV 2.59 2.94 2.60 3.00 3.05 2.75 2.96 2.84
ADSV 0.59 0.22 0.51 0.22 0.28 0.41 0.28 0.36 0.28 0.49
ML-4 51 46 49 49 48 46 44 47.6
AML-4 7 9 12 8 9 12 14 10.1
DSV 2.91 2 94 2 87 2.93 2.93 2.96 2.75 2.90
ADSV 0.31 0.18 0.38 0.18 0.23 0.12 0.27 0.24
50 48 54 46 49.5
12 8 12 14 11.5
3.02 2.59 3.19 2.60 2.85
0.19 0.49 0.15 0.52 0.34
46 44 56
9 13 11
2.87 2.81 3.19
0.25 0.21 0.15
48.7
11
2.96
0.20
... ...
... ... ...
Type 11
50 47 39 47 45.7
9 5 10 10 8.5
2.94 2.60 2.66 2.84 2.76
0.25 0.36
12 13 14 15 Av.
46 50 51
12 11 9 8 10
2.82 2.60 3.02 3.19 2.91
0.27 0.63 0.31 0.20 0.35
16 17 18 Av.
52 50 50 50.7
10
3.09 3.03 3.05 3.06
0.19 0.25 0.20 0.21
8 9 10 11
Av.
0.43
1085 of the polymer vs. time of heating a t 140"F. indicates clearly that the polymer breakdown increases with an increase in equivalents of the total nitrogen bases; the increase in paraffins content retards this breakdown. When the masterbatches are broken down in the Banbury a t 900-gram loadings, the same general conclusions seem to hold, but not as clearly. From the standpoint of heat aging a t 140" F., the masterbatches made with Type I1 oils on an average broke down less than those made with Type I oils, a l t h o u g h t h e r e w e r e masterbatches with oils of each type that overlapped, showing the necessity for taking into account in specifications the oil viscosity and narrow limits of the ratio of total nitrogen bases to paraffin content. Masterbatches of oils 12, 13, and 14 (Type I11 classification of the aromatic type according to the OSR n o m e n c l a t u r e ) broke down more an heating and when mixed in the Banbury at 900-gram loadings than did the masterbatch with oil 15, which is the processing aid suggested by Rostler. The main difference in these classifications is in the amount of nitrogen bases, oil 15 containing less than 3% nitrogen bases. No consistent significant differences in the masterbatches could be detected in mill processing, Banbury processing, or extrusion properties. Masterbatches were made from latex containing 1.25% of Polygard ( a nonstaining antioxidant) and 37.5 parts of the oils shown in Table X I I I . GR-S-1502, containing WingStay S (obtained from the Goodyear Tire and Rubber Co.), which is interchangeable with Polygard as a nonstaining antioxidant, was used as c o n t r o l . T h e f o u r masterbatches were compounded according to a titanium dioxide recipe and vulcanized speci-
Type I11
52
49.7
...
...
...
...
Type I V 8
8 8.7
... ... ...
...
... ... ...
I
.
.
' Samples gel-free. Corrected values given for all DSV. b Corrected values given for all gels reported herein. Duplicates of two separate Banbury treatments. All checks were excellent.
1086
INDUSTRIAL AND ENGINEERING CHEMISTRY
c
3.4 3 .
2
h
c
I OIL*
TYPE
n
TYPk
Vol. 47, No. 5
OILS
.
IMER
IA 1.2 ' 01
6 (9)
'
3
'
I
6
24
12
3.4
01 TYPE
I-
3
12
6
24
OILS
POLYMER
1.21
'
01
'
3
'
6
12 24 HOURS AGED AT e0O'F.
Figure 10. Dilute solution viscosity breakdown with time of heating a t 200' F. Nonaerated latex
3.2
8
TYPE
I OILS
1
TYPE H OILS
TYPE
m
1
TYPE 13L OILS
OILS
3.2
2.0 1.8 1.6 1.4
-
0
BASE POLYMER
I
0.25
0.50
0.75
I
2 0 0.26 HOURS AQED A T 800.8
0.60'
0.75
I
Figure 11. Dilute solution viscosity breakdown with time of heating a t 300' F. Aerated latex
P
1087
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1955
TYPE I OILS TYPE II OILS
c
TYPE
m
OILS
Figure 12. Dilute solution viscosity breakdown with time of heating at 300" F. Nonaerated latex
mene were prepared for staining and discoloration tests. The unlacquered portions of the specimens were exposed for 24 hours under a standard sun lamp. Color readings of the exposed and unexposed portions of each specimen were made n-ith Model 610 Photovolt reflection meter (green triatimulus filter). Higher readings indicate a lighter color. TYPE I OILS 70t 60
5 7 1
so
z4
40
f
The oils darkened the unlacquered samples. I n resistance to discoloration, the vulcanbate with oil 18 was definitely superior to those with oils 15 and 17, which were within experimental error on the amount of discoloration observed. For actual color of the exposed portions the vulcanizate with oil 15 was best and that with oil 17 poorest, but the exposed portion of all of the specimens was of the same level of color. With the lacquered samples, oils 15 and 18 stained the lacquer'ed coating to about the same extent, with 18 staining slightly less; oil 17 was definitely the most staining of the oils. For the actual color of the exposed portions, the coatings of
4 701
5 ci, 30L 70
TYPE I OILS
TYPE II OILS
I
1-
I
1
TYPE
m
* 70L
OILS
TYPE IC OILS
I
-I.-
15
60
14
50 40
13
I2
260
g 50
g 40
u
>
30 20 TYPE
IU
OILS
701 60 50 70
14
40
60
13
30
50 40
0 6 I2
,IL
I
24
48
72
HOURS AOED AT 140.E
48 H O U R S AOED AT 140.F:
72
Figure 13. Mooney viscosity breakdown with time of heating a t 140" F.
Figure 14. Mooney viscosity breakdown with time of heating at 140" F.
Aerated latex
Nonaerated latex
1088
INDUSTRIAL AND ENGINEERING CHEMISTRY Table XII.
Oil No.
1 2 3 4 5 6 7
Av.
8 9 11 A\,.
Changes i n Viscosities during Drying and Breakdown Period
Original Corrected ML-4" DSVb
Heat Aged 3 Hr. a t ZOOo F. 48 Hr. a t 140' F. AML-4C ADSVC AML-46 ADSVC AERATED LATEX
0.25 Hr. at 300' F. AML-4C ADSVC
59 58 59 58 60 58 62 59.1
3.17 3.05 3.11 3.25 3.33 3.19 3.27 3.17
20 24 22 21 12 26 13 19.7
Type 1 0.64 0.69 0.80 0.60 0.21 0.69 0.37 0.57
40 43 40 40 28 38 35 37.7
1.32 1.40 1.29 1.18 0.72 1.12 1.08 1.16
42 44 43 46 44 47 43 44.1
0.92 1.10 1.04 1,17
57 52 56
3.22 3.24 3.09 3.18
14 23 19 19
Type I1 0.35 0.64 0.59 0.53
36 36 42 38
1.12 1.01 1.24 1.12
47 45 47 46.3
1.20 1.02 1.18 1.13
55
1.18 1.01 0.97 1.06
Vol. 47, No. 5 fication shown in Table XV offers the necessary limits for the required oils from the standpoint of quality of the masterbatch and limitation of the number of types required to those now in use. This classification is suggested, not from the standpoint of ease of manufacture of the oil, but from that of the quality and stability of the masterbatches in use.
SUMMMARY
Aeration of the latex increased the heat stability of 44 1.43 46 1.07 21 3.07 5ld 12 the masterbatched polymers a t 0.96 37 1.06 47 17 3.16 58 13 140" F., especially those with 31 0.84 43 0.97 11 3.36 59 14 31 0.80 49 1.08 10 60 3.42 15 the unsaturated oils, but did 35.7 1.03 46.2 1.02 14.7 59 3.25 Av. not affect their physical propType I V erties. Aeration of the latex 1.10 0.12 18 0.36 43 6 60 3.29 16 reduced the lowering of the 1.01 0.12 26 0.74 39 8 63 3.26 17 dilute solution viscosity when 0.81 0.14 21 0.58 32 7 60 3.28 18 the masterbatched polymer was 0.13 22.3 0.56 0.97 38 01 7 sv. 3 28 mixed under full loading conditions in the Banbury, and also reduced the gel forma1.36 0.72 43 49 0.96 22 1 57 3.27 tion, but had little effect on 1.44 1.15 0.78 46 48 27 56 3.13 2 46 1.44 1.16 31 0.97 47 60 3.19 3 the lowering of the Mooney 1.37 1.19 48 0.84 30 47 3.13 56 4 1 .09 1.04 40 45 0.46 18 3.22 5 55 viscosity. Aeration increased 1.19 46 45 1.46 0.89 32 58 3.13 6 the lowering of dilute solu1.31 1.12 45 47 0.74 25 51 3.07 7 tion viscosity when small (90026.4 0.77 44.9 1.35 1.12 46.9 A\.. 56.1 3.16 gram) loadings of masterType I1 batch were used, but had 13 0.35 36 0 . 9 6 44 0 . 9 2 3 . 2 4 8 1.00 24 0.68 45 1.42 44 3.10 9 little effect on the lowering of 14 0 . 4 5 37 1 . 1 0 46 1.00 3.30 62 10 the Mooney viscosity. 0.91 1.32 46 30 0.84 47 3.17 57 11 The Group I nitrogen bases 20 0.58 41 1.20 0.96 45 3.20 58 Av. are the controlling factor in Type I11 the oils that affect cure rate 32 0.83 52 1.34 1.08 45 53 3.12 12 30 0.83 44 1.30 1.16 46 3.07 52 13 and level of cure. Oils of 7 0.18 32 0.76 1.00 44 3.25 65 14 the aromatic or extender type ... , . . ... ... ,.. ... ... 15 1.08 containing less than 15% ni23 0.61 43 1.13 45 A\,. 57 3.14 trogen bases minimized the Samples extruded through l/s-inch round opening. Previous tests had indicated no change caused by extrusion. (Discrepancy is shown between these results and those in Table VI.) effect of heating a t 140" F., b All samples corrected on basis that 37.5 parts of oil p.h.r. were in masterbatch. Acetone extractions indicated this assumption as correct as analysis. with some sacrifice of the stac Change from g5 1ML-4 and 3.32, highest Mooney viscosity and average DSV of raw stocks. bilization of the modulus on d Not included in averages. extended curing. The amount of polymer breakdown a t 140" and 200" F. correlates with the amount of total nitrogen bases plus the first the specimens containing oils 15 and 18 were about alike, the acidaffins in the oil of the masterbatch, and there is some evidence coating of the specimens with oil 17 being definitely the most that the nitrogen bases are the most reactive of the two. Parstained. The original masterbatches were all darker than the affins retard breakdown, so that specifications should define the oil-free control. limits of the ratio of nitrogen bases to paraffins in highly aromatic I n order to compare the staining and discoloration of Type I11 oils. oils with the nonstaining Type IV oil, 15 parts of each of the oils Differences between the aromatic type oil of the Office of were mixed with GR-S-1502, and these vulcanizates were made Synthetic Rubber and the processing aid suggested by Rostler from compounds prepared according to the titanium dioxide recipe. The vulcanizates were tested as above, except that the lacquer formula was different (Table XIV). It is evident from these tests that the three oils (12, 13, and 14) containing 6.8 to 8.9% nitrogen bases are the darkest in color, Table XIII. Test Data o n Discoloration and Staining whereas No. 15, containing 2,5y0 nitrogen bases, is definitely Unlacquered ~ i ~ Lacquered lighter and most like No. 18 containing 1.8% nitrogen bases. Oil No. Type Orig. Exposed colored Orig. Exposed Stained All the oils have produced somewhat darker stocks than the con15 I11 68.0 33.8 34.2 78.3 39.0 39.3 17 IV 67.0 30.8 36.2 76.8 32.0 44.8 trol containing no oil. 18 IV 60.8 32.0 28.8 77.5 40.3 37.2 , , 72.0 49.6 22.4 82.6 72.4 10.2 GR-9-1502 According to present knowledge, based not only on pilot plant and laboratory results but also on production polymers, the classiType I11 0.45 0.52 0.33 0.12 0.35
i;
I . .
,
1089
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1955
::h? 60
TYPE
I OILS
50
TYPE
I OILS
TYPE
P.OILS
TYPE
m
40
30
eo
-6
10 TYPE
P
I
OILS
a
a
60 50
0
40
g
30
> eo IO TYPE
m
OILS
OILS
'10 60
50 40
30
eo IO TYPE Z OILS
0
'01
le
6
3
e4
HOURS AOED AT e0O.F:
Figure 16. Mooney viscosity breakdown with time of heating at 200" F. Nonaerated latex
HOURS AGED AT 2OO.F.
Figure 15. Mooney viscosity breakdown with time of heating a t 200" F. Aerated latex
Table XIV. Oil No. 12 13 14 15 18 GR-S-1502
Test Data on Discoloration and Staining
Type I11 I11 I11 I11 IV
...
Table X V .
Unlacquered =isOrig. Exposed colored 58.6 33.8 24.8 57.1 32.5 24.6 60.3 31.5 28.8 70.6 49.8 20.8 70.6 52.0 18.6 72.0 58.1 13.9
I (High!y Aromatic) 80-170 0 99-1.02
11 (Aromatic) 45-60 0 96-1.0
40
-
Suggested Classification of Oils
Type SUS viscosity a t 210° F. Sp. g r . a t 60°/600 F. Rostler analyses Asohaltenes. 5% .. bases Total 5% Groub I % 1st acidaffini, % 2nd acidaffins, %} Paraffins, % Wax, 7% Volatile matter max. (3 hours a t 325' F.), %
TYPE SL OILS
Lacquered Orig. Exposed Stained 66.9 52.6 14.3 67.0 53.5 13.5 67.6 54.4 13.2 75.6 61.0 14.6 74.8 66.4 8.4 76.5 72.1 4.4
TYPE
III
OILS
111 (Naphthenic) 65-110 0 91-0 97
0.1 max.
None
h-one
14 i. 2 8 * 2 Balance 10-15 None
5 max.
3 max.
Baiinoe 50 min. 10-20 None
Balance 40-60 Sone
1.0
1.0
1.0
...
TYPE
OILS
'
are that the latter, owing to the lower content of nitrogen bases, produces less polymer breakdown and is less discoloring. General substantiation of the OSR and Rostler methods of classification has been obtained-that is, in general, the methods divide the oils into groups, each of which represents a type of oil, and the oils within each group behave alike as far as cure rate, polymer breakdown during aging a t 140" F., and polymer break-
Rk=F--eo
IO
'7
OCI
o.hs o.;o
16
0;s
I
e
HOURS AQED AT 3OO.I
Figure 17. Mooney viscosity breakdown with time of heating at 300' F. Aerated latex
1090
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 5
acidaffins, second acidaffins, and paraffins, on polymers containing them, is specific when tested in the form of concentrates. When tested in form of a blend, as available in commercial oils, their effects are additive.
TYPE I OILS 50 40
30 20
ACKNOWLEDGMENT
IO 70
t I
50n
The authors are indebted to the Golden Bear Oil Co., Gulf Oil Co., Phillips Petroleum Co., Shell Oil Co., Standard Oil Co. of Indiana, and Sun Oil Co. for preparing and supplying the samples of oil tested in this investigation.
TYPEII OILS
40
LITERATURE CITED
s
t
(1) Am. Soc. Testing Materials, D 47146T, Method B. (2) Am. SOC.Testing Materials, D 1053-52 T.
'u)
0
L
-
TYPE JII OILS
HOURS AQED AT 5 0 0 . 1
Figure 18. Mooney viscosity breakdown with t i m e of h e a t i n g at 300' F. Nonaerated latex
down in the Banbury are concerned. There does, however, seem to be a factor not yet covered by the specifications. The influence of the fractions defined as nitrogen bases, first
(3) Am. SOC.Testing Materials, D 1158-511'. (4) Baker, W. O., and Mullen, J. W., private communication to Office of Synthetic Rubber. (5) Eby, L. T., Anal. Chem., 25, 1057 (1953). (6) Fenson, D. S., Fifth Canadian High Polymer Forum, London, Ontario, Canada, November 1953. (7) Oldham, E. W., Baker, L. M., and Craytor, M. W., IND.ENO. CHEM.,ANAL.ED.,8,41 (1936). (8) Reconstruction Finance Corp., Office of Synthetic Rubber, Specifications for Government Synthetic Rubber, revised ed., Oct. 1, 1952. (9) Rostler, F. S., and Sternberg, H. W., IND.ENG.CHEM.,41, 598-608 (1949). (10) Rostler, F. S., and White, R. M., Ibid., 46, 610-20 (1954). (11) Schade, J. W.,lndia Rubber World, 123,311 (December 1950). (12) Shearer, R., Juve, A. E., and Musch, J. H., Ihid., 117,216 (1947). (13) Taft, W. K., Duke, J., Laundrie, R. W., Snyder, A. D., Prem, D. C., and Mooney, H., IND. ENG.CHEM.,46,396-412 (1954). (14) Taft, W. K., Duke, J., Snyder, A. D., and Laundrie, It. W., Rubber Age, 75, No. 1, 61-4 (1954). (15) Taft, W. K., Laundrie, R. W., Harrison, T. B., and Duke, J., Ihid., 75, NO. 2, 223-6 (1954). (16) Taft, W. K., Snyder, A. D., and Duke, J., Ihid., 75, No. 6, 830-40 (1954). R E C E I V ~for D review .4pril21, 1954. ACCEPTED October 26, 1954. Presented before the Division of Rubber Chemistry, AMERICAX CHEMICAL SOCIETY,Louisville, Ky., April 1954. Work performed as a part of the research project sponsored by the Reconstruction Finance Gorp., Office of Synthetic Rubber, in connection with the government synthetic rubber program.
Bisalkylation Theory of Neoprene Vulcanization PETER ICOVACIC Jackson Laboratory, E. I . du Pont de Nemours & Co., Znc., Wilmington, Del.
MONG the organic compounds that are recommended ( 6 ) for use with magnesia and zinc oxide as vulcanizing agents for neoprene are ethylenethiourea (2-imidazolidinethione), p , p'diaminodiphenylmethane and t,he di-o-tolylguanidine salt of dicatechol borate. I n the absence,of sulfur, these agents in combination with zinc oxide do not vulcanize natural rubber. This points up a marked difference in the way these elastomers vulcanize. Although a major structural difference is the chlorine atom in neoprene in place of the side methyl group in natural rubber, the small amount of tertiary allylic chlorine formed by 1,2polymerization (8) is the important functional difference. The labile chlorine amounts to about 1.5% of the total chlorine in a
general-purpose neoprene made a t 40" C., such as Neoprene Type W used in this work. I n neoprene latex this active chlorine is gradually liberated, and the polymer becomes cross-linked ( 2 ) . This paper demonstrateB the importance of the labile chlorine in the vulcanization of dry neoprene, accounts for the difference in the vulcanization of neoprene and natural rubber, and suggests a bisalkylation theory of neoprene vulcanization. R E S U L T S AND DISCUSSION
Untreated Neoprene. A small number (about 1.5 mole %) of the monomer units in neoprene are incorporated in the chain by 1,2- addition during polymerization (2, 2, 8, 12).
