INDUSTRIAL AND ENGINEERING CHEMISTRY
396
(1) B e a v e r , E. AI., IND. Ex:. CH ( 2 ) RurIlett, R. E,, et (LL, (to Gel 2,628,178 (Feb. 10, 1953).
(6) H a r d y , A. C., “ H a n d b o o k of Coloriiiii,ti y , ”1). 30, (’anihridgr. T h e Teclinology Press. 1936. ( 7 ) I-Iarris, R . 11. (to :hnerirall (’yanaiilid (‘o..). L-. i;.h t 527 (:ipril 19, 1949). (8; H u n t e r , Iherelat,ionship is generall5niatics in the oils. At the left,, the temperat,ure rise is shown for similar with increase in aromaticity. but the scatter of the results the vulcanizat,es cured 15 minutes beyond the time of preferred of a few of the samples appears t o be wider. cure. There seems to be general correlation n-ith the aromatic Ultimate elongat'ions at t, shown in Figure 3 are plotted a,gainst content. When the values were obt,ained a t 10% set, which repthe per cent aromatics. With the mill-mixed tread-type coinresent overcures in most cases, the hysteresis increased with thc pounds, modulus increased relatively uniformly with the aroaromaticity. I n both methods the values in the circles for tho maticity, but the elongation dat>a gave no pattern. With the vulcanizate with WS-2432 are high-in other words, temperatuvc Banbury-mixed stock in the sanir recipe, modulus data had no rise properties are poor. The hysteresis for the vulcanizates with pattern, but the elongation incrcased regularly, except for the the oils high in nit'rogen bases (ITS-2131, Dutres 20, and Califlux CARCASS TYPE REGIPE
TREAD TYPE RECIPE
TREAD TYPE RECIPE
MILL MIXED
-
g,, E
TREAD T Y P E RECIPE t
TREAD T Y P E RECIPE
a/
BANBURY MIXED
MILL MIXED
/
310
yR::iN MILL MIXED
/.
'0. z
CARCASS T Y P E RECIPE
,I
/'
w
0,
/
a
40
60
80
'~ROMATICS"
4
100
1
20
*
40
-
I
60
I
1
80
, 100
-
20
40
60
80
%-AROMATICS"
"AROMATICS"
Figure 4. 'l'eiisile Strength at I , us. P e r Cent 4rotnatios
100
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 1954
TREAD TYPE RECIPE
TREAD TYPE RECIPE
MILL MIXED AT OPT1 MUM CURE
I
399 y:
CARCASS RECIPE MILL M I X E D AT SY. SET
CARCASS RECIPE
M I L L MIXED AT 10% SET
MILL MIXED AT OPTIMUM CURE
0
0
1
LL'
J 2 W
4
ell
45
ClRC/ROSIN
O
0
5s.
a
0
0
COp0-p---
3-52 50.
a
0
3
5
X
'4
0
45.
a
0 w
40.
$ t
RESIN 731
1,
2b
40
$0
%'kROM ATICS"
Figure 5.
ab
160
v. ' ~ R O M A T I C S "
Hysteresis Temperature Rise ws. Per Cent Aromatics
I . . 0
20 '/e
Figure 6.
I
.
40
.
.
GO
.
1
EO
'hROMATlCS"
1
.
100
I . . . . . . . . .
0
20
40
60
60
100
%"AROMATICS"
Hysteresis Temperature Rise vs. Per Cent Aromatics
no differences could be noticed in this series of experiments in the condition of the polymer as discharged, or in the wattmeter charts as noted from the shape of the curves. By this last statement, it is meant that the power consumption in all cases started off high and decreased regularly without a break. In Figure 9, it is shown that, a t the end of 5 and 10 minutes of mastication of 1500 grams of masterbatch in the laboratory Banbury, the power consumption decreased with the aromaticity of the oil in the masterbatch. At 900- and 1000-gram loadings, there was no correlation. Compounds of the masterbatches with black and fatty acid required less power for mixing in a fully loaded Banbury as the aromaticity of the oil increased. According to the data presented, many of the properties of masterbatches made with a series of oils with considerable differences in their paraffinicity, or aromaticity, can be correlated
GP shown in the squares), are good a t the optimum cure, and are on the lower side of the trend shown for 10% set. The rather low but good hysteresis values for the vulcanizate containing Resin 731 are of interest. Hysteresis temperature rise shown in Figure 6 of the mill-mixed stocks of the various masterbatches compounded in the carcass recipe are plotted against the per cent aromatics a t the optimum cure and a t 5% set. Both curves indicate, in general, greater temperature rise with increase in aromaticity, The rebound measured a t 77" F. for both the tread- and carcass-tvue reciDes was about the same regardless of aromaticity, a few oils being high or low. At 212' F., the rebound seemed to increase with aromaticity. TABLE V. MILLPROCESSING AND EXTRUSION INDICES OF MILLMIXEDSTOCKS The Shore A hardness of both Mill Mill the tread- and carcass-type Time, Minutes, to ShrinkProcGarvey c o m p o u n d s increased with Viscosity, ML-4 , Roughessing Die Oil in M.B. down Band '8' ness Indexa Index (3) aromaticity. Tread-type recipe Flex life shown in Figure 7 is Neoton 60 1 69 62 0.1 15 3.5 16 plotted against the aromaticity WS-2426 67 1 14 16 59 0.1 3.8 WS-2427 of the oils. The trend appears 64 3.5 58 11 16 71 1 0.1 Circosol-2XH 66 73 1 15 16 65 3 . 2 0.1 to indicate better flex life with WS-2479 56 71 0.1 2 10 16 62 4.1 WS-2428 60 74 2 4.0 0.1 15 16 65 d e c r e a s e d aromaticity. The Roxtone 180 2 6b 78 70 4.1 0.1 13 16 WS-2430 flex life value of NUSO-125 2 64 74 65 4.2 0.1 30 16 Sundex-53 1 70 75 16 68 3 . 1 0 . 1 18 fell outside of the trend, but it NUSO-125 2 16 65 76 0.1 22 67 4.1 WS-2432 63 2 76 16 67 4 . 1 0 . 1 15 is very good. WS-2431 16 63 2 83 73 4.4 0.1 15 A c c o r d i n g to the plotted 52 Csliflux GP 61 2 69 11 0.1 16 4.1 Dutrex 20 66 1 79 0.1 16 70 3.6 15 data of Figure 8, the Gehman Resin 731 105 98 3.6 22 2 90 0.1 15 Circ.-2XH/Resin 731 82 70 2 73 7 0.1 15.5 3.7 freeze points of the cured stocks Carcass-Type Recipe increased with increase in the Necton 60 57 1 50 45 0.1 12 ,.. per cent aromatics in the oils. WS-2426 57 0.1 1 ... 45 41 12 The mill processing characWS-2427 0.1 ... 1 50 12 45 58 46 50 0.1 ... 66 1 10.5 Circosol-2XH teristics and Garvey die ex49 ... 2 11 WS-2479 1 .o 44 56 60 WS-2428 51 0.1 1 ... 46 12.5 trusion indices (§') of the stocks 50 1 ... 13 63 Roxtone 180 0.1 45 WS-2430 50 1 ... 12 0.1 45 64 mixed in both the tread- and 2 9.5 Sundex-53 52 . . . 0.1 47 70 carcass-type recipes are shown ... 10.5 NUSO-125 1 52 47 65 0.1 1 . . . 10.5 WS-2432 63 0.1 51 47 in Table V. There seems to ... 11.5 68 1.o 5 WS-2431 51 70 ... 9.5 Califlux GP 44 0.1 1 40 52 be no correlation; the results Dutrex 20 2 ... 10 66 0.1 53 47 7.5 2 ... Resin 731 78 66 98 0.1 are mostly within experimentaJ 0.1 1 ... 9 Circ.-PXH/Resin 731 56 70 52 error. At 1000- and 1500a Carbon black stiffening. gram loadings of the masterb The lower the index, the better the prooessability. batches in a size B Banbury, " I
%
INDUSTRIAL AND ENGINEERING CHEMISTRY
400
MILL MIXED
MILL M I X E D
@
12' 11'
10-
0
9.
0
0
0
81
% X W
LL
5-
$
4-
5
3-
c!
o
0 0
0
2I-
x
o.
a b * ' " s " ' ' a 40 so 'JIROMATICS"
20
01. "AR OM AT Ics *
Figure 7.
4~
Flex Life X
80
tor
2;s. Per Cent Aromatics
Cured for t p plus 15 miuuteq
with this diffelence in the oils. Tensile strength, modulus, optimum cure, hysteresis, freeze point, hardness, and possibly hot rebound, increased with a decrease in the paraffinic content of the oil used in the masterbatch. Flex life became poorer. S o correlation in processing could be found as measured by the mill processing index, or roughnrss and shrinkagp of the Banburymixed, milled stocks, or by the Garvey die extrusion index with type of oil. However, a t full Banbury loadlng, the power required t o mix the raw masterbatches or compounds decreased with increased aromaticity of the oils.
Vol. 46, No. 2
The dilute solution viscosity and gel contents were determinccl by the modified Baker ( 5 ) method. The corrected dilute solution viscosity on a polymer basis was obtained by dividing thc observed dilute solut'ion viscosit,y by 100 minus the acetone extract of the masterbatch. The ARIL4 and ADSV were obtained by subtracting the observed values from the highest valucs obtained for the masterbatches. RXSCLTS AND DISCUSSION. The liooney viscosities ( M I A ) or ihc varioue masterbatches wcre first determined within 24 hours after they were dry, and the dilute solution viscosity mcasurcirient,s were made about 30 days later. Both sots of tests were later repeated and the values, in some cases, were found to h a w changed markedly. I n Figure 10, the changes in ML-4 values with time of storago a t room temperature start.ing from May I, 1952, are shown. Thc differences in the original viscosities of the batches are believed t80 be due to variation in the heat-softening of the polymers during drying. The acetone extracts, rrhich are indicative of the oil cont'ent, were ail within the range of 35.5 f 1.8Y0and repeated checks were within these limits. A very few samples, after heat aging a t 300" F. for 2 hours, were found to have lost up to 1.6% oil. A\t8the end of about 220 days' storage, t'he mast'erbat'ches containing W;8-2479 and 55:s-2432 were found to be softer in some spots than others. Acetone-extraction determinations of the softer port,ions were within experimental error of those obtained Il2CI
1040 IOE0
I MASTICATION 0
RIOLECULlR STRUCTURE
Samplcs of the dried masterbatches, after baling, PROCEDURE. were subsequently stored at room temperature and portions were heat-aged in a forced-draft oven a t 140'. 200". and 300' F. and 5.HINUTE MASTICATION
'la2
0
10
Figure 9.
20
30
40
vo
50 63 ' AROMATI CIT 7 ' '
70
10
90
Power Consumption us. Aromaticity 1500-gram loading
' 0
' 0
'\" N
ap N N t
L
20
.
30
.
40
.
50
rn .r N
60
70
80
90
100
% "AROMATICS"
Figure 8.
Freeze Point .ironlatics
DS.
Per Cent
originally. The changes in Mooney viscosity with time of storage can be considered in t,wo ways: the final viscosity of each masterbatch a t the end of 160 days, and thc changc in MIA viscosit,y from that, of the highest, value (70 ML-4). Variations in t,hcse values are caused by t'he effect' of the oil on the polymer during t,hc drying or storage of the mast,erbat,ch. Thew two viscosity relat,ionships have been plotted against the per c o n l :iromatics in the oil and are shown in Figure 11. The chitngc: from 70 ML-4 became greater Kith the increase in the aromat>io cont,ent of the oil used in the masterbatch, especially with the oils containing over 15yonitrogen hases. The changes in dilut,e solut,ion viscoeit,y of tht: polymer in t h e various masterbatches with time of storage (Figure 12) JVCI'C coinparable in trend t,o the lIooney viscosity changes. T h c changr:s in dilute solut,ion viscosity from the valuc of thc original mastcrlxiteh are plotted in Figure 13 (dotted line) against t h perccntagc. of a.romaticP in the oil. Vsing t,he samc approilxh as presentc.tl ii,bove: similiii. mlationships as were shown for Mooricy viscosi1,ics iirc sho\ni For the dilutc solutioii visc:oeit,y valuc~sby t>hcbroiicxir ant1 hi11 1inc.s. Thc rclalionships of t,lic cii:ingcs in lloonoy : ~ t i t l clilutc solut ioii viucoait'ics arc: cliffclciit.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1954
It has been postulated that if the change in Mooney viscosity as compared to the change of dilute solution viscosity is different for two polymers similarly treated, then the lubricating qualities have been affected differently in the two polymers. A change in dilute solution viscosity of a polymer indicates a change in the weight-average molecular weight. But a change in weightaverage molecular weight does not tell how the molecular weight distribution has been affected. For instance, consider a polymer in which all molecules have a molecular weight represented by a dilute solution viscosity of 4. If the chains are broken into two parts to give an average dilute solution viscosity of 2, the resultant molecular fractions, merely for the purpose of illustration, could be represented by dilute solution viscosity values of 3 and 1, or bv 2 and 2 . The Moonev viscosity of a polymer having a 3 and 1 dilute solution viscosity distribution would not be expected to be the same as that of a polymer having a 2 and 2 distribution. The polymer having the 3 and 1dilute solution viscosity distribution would be expected to be lower in &looney viscosity than the polymer having a 2 and 2 distribution. If this is true, then the ratio of change in Mooney viscosity ( AML-4) to the change in dilute solution viscosity ( ADSV) should express a relative molecular weight distribution pattern, and any change in such quotients of treated stocks made from comparable original material should represent differences in distributions in the treated stocks.
The samples of masterbatches, after storage of about 3 weeks, were aged a t various temperatures in a forced air oven. Figures 16 and 17 show the dilute solution viscosity values of the contained polymer plotted against the time of heating a t 140' and 200' F. These results indicate the differences in the effects of the various oils on the rate of chain scission caused by heating in air. In a few cases condensation has become predominant. Shown in Figure 18 are results of similar aging tests a t 300' F. Again, differences caused by the oils are shown. The results reported here a t 300" F. do not show the condensation in the short test times that were shown with Dutrex 20, Circosol-2XH, Califlux GP, and Sundex-53 in previous work (9). The oil loadings here were 45 parts, whereas 30 parts were used in the earlier work, and the viscosity of the base polymer was higher in this series than in the first. A4rough correlation of the chain scission and condensation oC the polymer with the aromaticity of the oil in the masterbatch is
-
70
FINAL M L - 4 OF MASTERBATCH AT END OF 180 DAY?'STORAGE - A
80-
'
A
k,
* To substantiate the foregoing hypothesis, molecular weight distributions were determined by the alcohol-benzene technique for the purified base polymer and several of the masterbatches after storage. These results are shown in Figure 14. It has been assumed, where there is no gel involved, and where the values are large enough t o be significant, that a change in the ratio of AML-4 to ADSV means a change in the ratio of high to low molecular weight. From the data presented in Figure 14, the average dilute solution viscosity representing the weightaverage molecular weight in the half of the material in the high range as well as that in the other half in the low range can be estimated. This weight-average molecular weight ratio plotted against the AML-4/ADSV ratio for the same polymers is shown in Figure 15, and the correlation indicates that the previous concept of the manner of chain cleavage is correct. The point on the lower right of the line has not been considered as valid by the authors. The power curve for the 10-minute Banbury treatment of this masterbatch is abnormally low, correlating the low hlooney viscosity. Slippage is apparent in both the Banbury and hlooney machine. Additional data from another program also substantiate the general line as shown.
40 1
A
.'\.
50-
CHANGE IN YL-4 FROM 70 hr ENDOFIBO ~ ~ ~ s ' s r o r t m - o
; 5 40-
8 s
30-
eo
t 0
lot
' ;O
'
40
'
80 '
eb
'
IO0
70 "AROYATIOB"
Figure 11. Change i n Mooney Viscosity o f Masterhatches after 160 Days' Stnrage VR. Per Cent Aromatics in Oil
3'00[
WS-2426
2.50 CIRGOSOL- 2 X H
70
CIRCOSOL'PXH
60
40 30
DUTREX 20
DUTREX-PO
gw
20
t
WS-2426 ws-2479 WS-2427
2.00
WS-2426 WS- 2420 WS-2427 ws- 2 4 7 9 431
50
to L .40
80
120
160
200
0
40
80
120
160
200
240
3.00
A
' 0
1.10
240
NEGTON 60
5 70
WS-2430
2 60
ROXTONE I 8 0
0
5
ROXTONE 180 NUSO 126
50
SUNDEX-53
40 30
NUSO 12s SUNOEX 5 3
2 00
CALIFLUX GP
I50
20
CALIFLUX GP
ob
40
io
1o;
I60
ebo
e&
TIME OF STORAQE, DAY8
Figure 10. Change i n Mooney Viscosity of Masterbatches with Time of Storage
40
80 I20 160 ZOO TIME OF STORABE, DAYS
E40
Figure 12. Change in Dilute Solution Viscosity of Masterbatches with Time of Storage
INDUSTRIAL AND ENGINEERING CHEMISTRY
402
shown in Figure 19. The values were calculated to an oil-free basis, using the corrected dilute solution viscosity of the base, polymer as thc original. The time of heating for the (winparison in each case was chosen a t the earliest time where a break occurredin the curve of dilute solutionviscosity us. time of heating at, each kmperature. In IT'S-2179, t,he point shown in a circle, the
d A
E N D OF 160 DAYS STORAGE
A
k
- A
CHANGE I N DSV FROM
2 6 5 AT E N D OF 160 STORAGE - e
/!!DAYS
0.50
-
No. 2
(data not shown), were not alike l)ut were generally similar tlJ those obtained vitli dilute solution viscosity. Tn Figure 19 wa,s shown the effect of chain scission a t the e:trliest time of heating where t,he first' break occurred in the curve8 of dilute solution viscosity us. h i o of heating for the masterbatches heated at 140°, ZOO", and 300" F. Similar data for Mooney viscosity changes are shown plotted in Figure 21 versu? the aromat'icit'y of the oils. The two upper curves in Figure 21 show reasonably good correlation of Mooney breakdown with increasing aroniat,icit,y. At 300' F'. , Mooney viscosity decreawti with aromaticity, as did the tiilut~c~ solution viscosity values prrviously shown. The revci~salin slope of the curves indicates that, a t the higher temperature, the rat'e of change in Mooney viscosit,y increases with increase in paraffinic content rather than with increase in aromaticity, as was observed a t the lower temperatures. At a temperature estimated to be between 250" arid 300" F., the amount of breakdown in the presence of the
FINAL DSV OF MASTERBATCH AT
d
O-hb..,
Vol. 46,
J
3.00 e.90
b
2.80
L.?O 2.60
material that is causing chain scission was relatively active at, 140' and 200" F., but inactive at. 300" F. Since no gel was formed after heating a t 300" F. for 2 hours, it is indicated that little or no condensation occurred. On the other hand, the material contained in WS-2430, shown in a square, that promotes chain scission was inactive at 140°, and was relatively inactive a t 200" and 300" F. However, after heating for 2 hours at 300" F., chain scission c,ontinued and again there was no evidence of condensation. Results obtained with these oils tend t'o indicate that the materials in each that' promot? chain scission vary in degree of activity with temperature. The rate of breakdown, a8 measured '077 change in Mooney viscosity with time of heating the masterbat,ches (Figure ZO), is shown to be dissimilar for the various oils. Thjs relationship is generally similar to t,hat found for the change in dilute solution viscopity. The rates of change of Mooney viscosity of the masterbatches made with the various oils, when heated at 200" and 300" F.
2.50
0
IO
20
30
40
50
Y L * 4 / A D8V
Figure 15, A&IL-4/ADSV vs. .llolecular. Weight Distri hi1t io t i Ratio
various oils should be similar. ;It temperatures above 1,hk estimated point,, the presence of paraffinic oils caused fa down of the polymer than do the aromatic oils. These statementa probably apply only t o the -&part loading used, since similar plots made from previous work (9) n-ith 30 parts each 01 the four oils not from the Esso Standard Oil Co. show a greater slope at 140' than a t 200' and 300" F., with the slope a t 300' F. inclined upward with increase in aromaticity, rather t,han d o r n ward a8 was found with 45-part loading. This is evidence, though very meager, that as the oil loading is increased in the masterbatch, the effect'of differences among the oils on the Mooney viscosity breakdoim of the BASE POLYMER masterbatch becomes less. The changes in the measured dilute solution viscosity of the various mast,erbatches from 2.65 (the highest dilute solution viscosity of the O 0 2 4 s e masterbatches) that occurred when 1000 and 1500 grams of each sample were Banbury treated WS-2427 CIRCOSOL 115-2479 WS-2428 for 5 minutes are plotted against the aromaticity 30 of the contained oil and shown in Figure 22. The AML-4, the change from 70 ML-4 (the highest viscosity of the oil-masterbatches), foi. the same conditions is d o t t e d against the aromaWS-9451 CALIFLUX-QP DUTREX-LO ticity of the contained oil, and shown in Figure 23. SUNOEX 53 The tensile strength values a t time of preferred cure for the various masterbatches have been Fhown t o increase generally with the aroma10 0 ticity. The tensile strength values of the e e e Banbury-mixed stocks when plotted against the DSV RAN% ADSV from the Banbury breakdown treatment8 are shown in Figure 24. Figure 14. Molecular Weight Distributions of Stored Samples
::m -
"Fi,z-mnh ~
*
-
February 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
The increase in tensile strength with the apparent increased breakdown of the polymer means that at, least another factor other than the average molecular weight must be involved. To show with the type of polymer involved in this case that as the dilute solution viscosity decreased the tensile strength decreased significantly, 1000 grams of the unmasterbatched polymer were mixed in the laboratory Banbury for 5 minutes, alone, and with 0.5, 1. and 3% of its weight of RPA 3 (xylyl mercaptan, obtained from E. I. du Pont de Nemours & (30.1. These treated stocks were then mill-mixed according to the tread-type recipe The tensile strength values of the vulcanizates drweased from about 4300 to 3800 pounds per square inch, as the polymer was broken down from 150 to 59 ML-4 and from 3.65 to 1.95 DSV
the various conditions of treatment, the polymer has been affected by the presence of the particular oil in the masterbatch The comparison of the ratio of Mooney viscosity to dilute solution viscosity changes of the various ramples when stored foi. 3 weeks and for 160 days plotted against the percentage of aromzbtics is shown a t the upper left of Figure 25, for those values where the changes have been large enough to be of significance. The effect of temperature, a t the times indicated, on the relationship of this ratio with aromaticity of the oil is shown in the upper right of this same figure. At the end of 48 hour4 at 140' F. and 6 hours a t 200" F., the effect of the increase in aromaticity is reasonably uniform. The ratio does not vary as uniformly with aromaticity when samples are heated a t 300" F. for 0.5 hour. The trends
NECTON 60 BASE POLYMER WS-2426
2n
BASE POLYMER WS-2430
P
ROXTONE 180 CIRCOSOL-2XH SUNDEX- 5 3 NUSO-I25
WS-2427 WS-2428
E
ws-2431
w a
0
i
WS-2432
I
DUTREX 2 0
I
403
HOURS
HOURS 30 PTS. CIRCOSOL-2XH I S PTS. RESIN 731 BASE POLYMER
Figure 16. Breakdown of Polymer Masterhatched with 45 Parts of Various I'lasticizetw Heated a t 140' E'.
P
HOURS
In an attempt to find some relationship betwren dispersion and tensile values and to explain why the cured stocks of masterbatches having the greatest tendency to breakdom had the highest tensile values, samples of the masterbatches ma& with Necton 60, WS-2431, and Dutrex 20 were mill-mixed with all ingredients except the curatives and remilled twice after 24-hour resting periods. The curatives mere then added and the compounds were cured. The tensile strength of the stocks containing Necton 60-the paraffinic oil-decreased IO%, while those with the two aromatic oils, WS-2431 and Dutrex 20, increased about 80 pounds per square inch each. This indicated that the dispersion caused by remilling did not afford greater increase in tensile strength for the stocks containing a paraffinic oil. Without a direct measure of dispersion, it was not possible to correlate procedures which improve dispersion4 with better tensile results Figures 10. 12, 16, 17, 18, anti 20 through 23 show changes in Mooney or diLute solution viscosity that occurred under various heat-aging conditions or Banbury treatment of the raw polymer. From these, the AML-4/ADST' relationships can be calculated. URing this ratio as evidence of differenrcs in the point in the polymer chain where scission takes place, it is possible to postulate from the heat treating and Banbury breakdoyn data howl-,with
shown by these curves indicate that the point of cleavage along the chain varied with the aromaticity of the oils. Heat treating in an oven a t these temperatures is not the same as factory processing, but these relationships do show that temperature, and possibly time, as well as exposure to oxygen or air during processing, probably alter the molecular weight distribution of a given high Mooney GR-S, depending upon the oil used in masterbatching. The ratio of AML-4 to ADSV for the masterbatches broken down in the Banbury at two loadings, plotted against the percentage of aromatics in the oil, is shown a t the bottom of Figure 25. This relationship indicates that in Banbury treatment the presence of the more aromatic oils causes the chain t o break near the middle. The ratio of the measured viscosities during Banbury treatment of the polymer alone should be indicative of what is happening during the Banbury mixing of the polymer alone followed by addition of the black and fatty acid. The ratios of the viscosity differences of the 1000- and 1500-gram loadings are plotted against the tensile values a t time of preferred cure (Figure 26) for stocks mixed in the Banbury by a tread-type recipe. As 1039 grams of masterbatch were mixed for 1 minute before the first
404
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 2
addition of blnck in the Banbury compounding, the 5-niinui Banbury breakdolyn of 1000 grams more nearly gives the contlitions used when the stock is mixed, so that, correlations shown in Figure 26 would be expected to be better for the data using 1000 grams than for those using 1500 grams. These data seem to intiicate, if Flory's theory (2) and the theory of Kauzmann and E y i n g ( 4 )apply here, that' a s the chain was broken towards the end, the tensile values decreased. This then, explttins n h y tho higher aromatic oils act'ually gave higher tensile values. Figure 4 indicates an increase in tensile strengt,h with increaw in aromaticity. But Figures 22 and 23 indicated a decrease of th(s actual dilute solution viscosity, and Rlooney viscosity with an increase in aromatic content after Banbury treatment. Nowever, actual breakdown and mixing of compounding ingredients are not as simple a procedure as just breaking down the polymer alone. 11' the compounding in a Banbury were under conditions such that, the Mooney viscosity level of the masterbatches containing the more aromatic oils was higher than that of the less aromatic oils, then the tensile strength relationships noted would be explained. Assuming that the compounded Mooney viscosity of the mixed stocks is in relatively the 8ame relationship as that of the polymer alone, the results shown in Figure 27 indicate that, in these cases, the masterbatches containing the more aromatic oils have riot only been broken down more nearly at the middle of the chain but, also have been reduced less in Mooney viscosity when being compounded in a Banbury. It is possible that the less aromatic oils tend to keep the polymer from forming the polymer-black gel as rapidly as the more aromatic oils and that this is the reason for tlie lower compounded viscosity wit'h the less aromatic oils. Molecular weight distribution dat,a pertaining to the breakdown of oil-masterbatched polymers during storage suggest the probability that with the more aromatic oils scission of the polymer molecules occurs nearer the center of the chain, arid t'hat tho point of scission appears to line up with the aromaticity of' tho oil. Banbury conditions also appear t>oinfluence the point' of nttack in a regular manner. The molecular weight distribution of the polymer in the final compounded stock thus bec8omc.s impoi,tunt, if Flory's theory ( 2 ) that small chains contribute to pooi' properties of vulcanizates applies. The better tensile propert iw of the st,ocks made with the polyniers containing oils of higher aromaticity can then be explained by the smaller riumher of loose ttr1ds. (1
FACTORS Ih-FLUENCISG POLYMER BREAKDOWN
A medium process oil and conRESVLTS. ~ N D DISCUSSIOK. centrated nitrogen bases, having the analyses shown in Table VI, were lilended in varying proportions to give the calculated contents of nit,rogen bases shown in Table VII. These oils were
TABLE VI. ASALYSESOB OILS Medium Process OilQ
Coned. XBasesa
Dutrev 20
595 46.7 12.2 27.5 0.14
13,040 106 4.0 43.8
...
Solid 326 3.6 45.5 3.1 0.53
Si1 2.5
0 2
1.0
84 2
Si1 21.0
0.1 4.4 43 7 50.9
0.5 17.3
84.2 7 2
17. I 26.4
64.2 16 0
7 0 1.4
45.9
5.8
54.0 43.5 2.5
14.0 81.0 5.0
1.8
5.1 83.7
Circosol2XH Tis?,, S.V.S. .At 1000 E'. A t 2100 F. Gravity, .&PI a t 60" F. Bromine S o .
s.qo
s, %"
Rosrler analyses, % (6') Asplialtenes
- __
\.. h a s e r I I
S bases, insol. n-pen-
n
tarie-HC1, % 1st acidaffins 2nd acidaffins Paraffins Silica gel analyses, 3'% Sonaromatics Aromatics Polar compounds a
2010 83
... ...
0.07 0 01 Xi1
Furnished by F. S. Rostler, Golden Bear Oil Co.
43.1 56.1
0.7!4 0.90
11 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1954
405
BASE POLYMER
HOURS 4.0
>
HOURS
I.
3.5
v)
Figure 18. Breakdown of Polymer Masterbatched with 45 Parts of Various Plasticizers
n 0
3.0
Heated at 300' I?.
0
w K K
g
2.5
0.25
0.6
a75
2
I
HOURS
latex-masterbatched with a gel-free GR-S-1500 type latex (containing 1,50y0 phenyl-2-naphthylamine) prepared a t 41' F. from a 75/25 butadiene-styrene charge to 62.6% conversion and 150 ML-4. The masterbatches containing 45 parts of oil per 100 parts of rubber were dried a t 140" F. to a maximum moisture content of 0..5% in a forced-air dryer, and then samples were aged a t 140°, 200°, and 300' F. in a forced-draft oven for various times. Dilute solution viscosity and Mooney viscosity values were plotted against time of heating a t each of the three test temperatures, and from these curves the values shown in Figure 28 were obtained. It is evident that a t a loading of 45 parts of oil, the increase in polymer breakdown a t 140' and 200' F. became marked a t about the 15% nitrogen base level. At 300' F., the amount of polymer breakdown as measured by dilute solution viscosity and Mooney viscosity decreased as the level of nitrogen bases increased to 20%, but then increased. These data confirm the results reported above, and indicate that nitrogen bases above 15% in the oils used for masterbatching bring about large changes in both dilute solution viscosity and Mooney viscosity a t the lower temperatures.
TABLE VII.
I
6 HOURS AT 2 0 s
--
0
20
KO
40
IW
80
0
20
AROMATICS
40
KO
80
100
AROMATICS
1/2 HOUR AT 300eF:
CHANGE IN DSV BETWEEN 0.5 AND 2 HOURS AT 300.F:
2/1 CIRC./RESIN 731 0 0
CALCULATED ANALYSESOF BLENDS
Med. proc. oil, % N bases, % Rostler fraction Asphaltenes, % N bases, % N bases insol. pentane1st acidLffins, 7 2nd acidaffins, Para5ns, % Silica gel method Nonaromatics, % Aromatics % ' Polar combounds, %
%'
48 HOURS AT 140.F.
I
95 5
85 15
80 20
75 25
Nil 6.7 0.5 16.9 61.1 15.3
Nil 14.7 0.4 15.8 55.7 13.8
Nil 18.8 0.4 15.4 52.7 13.1
Nil 22.9 0.4 14.8 49.9 12.4
13.4 79 0 7.6
12.2 75.2 12.6
11.6 73.2 15.2
10.9 71.3 17.8
20
% AROMATICS
Figure 19.
40
60
80
100
AROMATICS
Change in Dilute Solution Viscosity of HeatAged Polymers us. Per Cent Aromatics
INDUSTRIAL AND ENGINEERING CHEMISTRY
406
Vol. 46, No. 2
1
100
, ,
IO
0''
6
12
24
48
72
0
HOURS.
6
I2
24
40
72
HOURS
70
NECTON 60 WS - 2 4 9 8 WS-2431
Figtire 20. Mooney Breakdown 'L'irnr of' Heating at 140" F.
L'S.
DUTREX 9 0
The Mooney viscosities (Table V I I I j of the various mnuterbatch samples, measured shortly after drying and then 111 days later, indicated that little or no change occurred during storage of the masterbatches, but the corrected dilute solution viscosity results for t.he samples containing the higher qwntities of nitrogen bases indicated chain scission. The results reported in the first part of this paper obtained on samples prepared from the same latex as was used in preparing these shown in Table VIII, had indicated that the masterbatches with oils of low paraffin content containing over la7c nitrogen bases were unstable during stforage. The dat.a in Table VI11 show the same trend to a lesser degree. IN VISCOSITIESWITH STOR.IGC TABLE VIII. CHAXGE
N bases in blend, % Original ML-4 3IL-4 a t end of 111 days Original corrected DSV CorrectedDSVatendof l l l d a y s
0 65 65 4.08 3.94
5 61 65
4.05 4.12
15 66 65 4.05 3.97
20 60 61
3.81 3.48
25 53
50 3.39 2.82
Two antioxidants, phenyl-2-naphthalalnine and an alkvl aryl phosphite (Polygard, obtained from Naugatuck Chemical Co.). mere incorporated in latices of cold rubber (about BO AIL-4 viecosity) and in latices of high Mooney viscosity (about 115 hIL-4) cold rubber. Portions of the high viscosity latices were coagulated alone and as oil-polymer masterbatches using 30 parts of Dutrex 20 or Circosol-2XH per 100 parts of polymer. The dilute solution viscosity results obtained after oven-aging these polymers are shown in Figure 29. With the BO VL-4 polymer, shown in the upper three curve#, Polygard protected the
polymer better from change in molecular weight than did phenyl2-naphthylamine. With the base polymers of high Moone), viscosity, essentially the same conclusions can be drawn. JVhen conditions of treatment were severe (300" F.), the samples of base polymer containing Polygard showed a tendency to condense and form gel sooner than those with phenyl-2-naphthylamine. The u6e of twice the specification amount of eit,her antioxidant seemed to cause chain scission to take place more rapidly, and condensation to begin earlier and to proceed a t 8, more rapid rate. The presence of Circosol-2XH when masterbatched with the high molecular weight polymer did not seem to chmge the relative effects of the antioxidant, but merely to increase the rate 0 1 chain scission, and to shorten the time before condensation hecame predominant compared to the results obtained with the antioxidants in lower Mooney viscosity polymer. With t'he oilfree polymer of high Mooney viscosity, the same relative effect' was obtained by doubling the amount of antioxidant. From this same point of view, Dutrex 20 accentuated these effects more than did Circosol-2XH. These comparisons suggest the possibility that the two oils contained materials that behaved similarly to these antioxidants with respect to their effect on the molecula~rchain of the polymer. The Mooney viscosity changes of the same materials, except) for the high Mooney viscosity base polymers, are shown in Figure 30. For the stock of the 50 R4L-4 polymer, the general relationships of the results shown in Figures 29 and 30 were somewhat similar. I n the ca8e of the masterbatch containing Circosol-2XH and heated a t 300' F., the relationships after 0.75 hour were different in slope in the two figures. This same difference in t8he slopes of the curves was found at 200' and 300' F. with the maeterbatches containing Dutrex 20 a t both antioxidant levels.
INDUSTRIAL AND ENGINEERING CHEMISTRY
February 1954
407
HEATED 48 HOURS AT 140°F.
0
Ld
I
0
0
0
/'
0 0
0
0
N
OD
0
m * i
N
P
N
3r
m
Q
N
s
t
b
0
$
i
%
I 20
40
60
Ye
80
100
AROMATICS HEATED I/e HOUR AT300.F:
s 'I Figure21.
Change in Mooney
\'inc-osity m . Pel- Cent Aromatics
P
I I
I
20
I
I
I
40
I
60
I
80
100
% AROMATICS
From the data used in preparing Figures 29 and 30, the AML4/ADSV ratio has been calculated for varying conditions, as noted in Table IX. It is evident from the change of values of the AML-4/ADSV ratio obtained under any one set of conditions with time of heating that there may be optimum processing conditions, which may vary with each antioxidant, oil, and possibly polymer, for producing the minimum amount of undesirable breakdown associated with formation of short chains in the final product. 9 number of oil-free polymers were heat-treated for varying lengths of time in a forced-draft oven a t 200' F. The polymers with a content of 1.25 or 1.50% phenyl-2-naphthylamine were all made from pilot plant latices shock-coagulated with salt and acid. These heat-aging results are shown in Figure 31. It appears that the length of the induction period prior to chain scission was reduced as the Mooney viscosity of the polymer increased. Samples 8 and 9 were from the same latex, and this latex had been stored in covered drums without agitation. Sample 9 was coagulated 200 days later than sample 8. Samples 7 and 2 were from the same latex. No. 7 waa coagulated when freshly made, but No. 2 was stored and continuously agitated for 120
days before being coagulated. Since the breakdown curves of 8 and 9 were comparable and were also similar to the curve for the unstored No. 7 latex, storage in drums had not changed the breakdown characteristics of the polymer. However, storage
TABLE Ix. EFFECTO F ANTIOXIDANT,OIL, ON AML-4/ADSV Oil Used h-onea
a
T ~ , of~ ~ .~i~~ Heating, Heated, O F. Hours 300
GR-S made to 50 ML-4 a t 41' F.
1/4 1/2
AND
HEST-AQING
Polygard, % PBNA, % 1.25 2.50 1.28 2.50 Ratio AMIA-4/ADSV BO 58
.. , .
40 73
..
..
INDUSTRIAL AND ENGINEERING CHEMISTRY
408 1.2-
7
1008-ORAffl LOADING
1.1.
1.00.9.
I
Vol. 46, No. 2 1000-BRAM LOADING
1500-GRAM LOADING CALIFLUX
3200 31001 3000
> 0.9
e ~ 3 ,
DUTREX
z","
e479
SUHDEX
10
0.7
0.6 '
-
0.5
0.4.
0.30.20.I .
w
i
1900-GRAM LOADING
34001
3100
2479
'OXTOHE
30001 CIRCOSOL
0
20
40
60
80
20
1000
40
9 . "AROMATICS"
%
60
2 BOO
27001
100
80
'ZROMATICS'
2600
Figure 22. Change in Dilute Solution Fiscosity during S-hlinute Ranburg Treatment 2;s. Per Cent Aromatics in Oil
2500
2427
2426
*
2432
0
O't
0'4
0'6
1'0
0'8
1'2
d DSV (5-MINUTES IN BANBURY)
1000-GRAM LOADING
Figire 24.
1500-GRAM LOADING
Tensile Strength at t ,
TS.
ADS\-
Ranliurv-mixed, tread-type
40
P 90. 4
A
eo.
A
WITH TIME OF STORAGE
WITH TIME OF HEATING
70 I00 LIAS STORAGE-0
4
-
0
'
% "AROMATlC.3"
20
'
4b 96
io
'
so
'
IO0
4 8 HOURS AT 1 4 0 . F - 0
%ROUATICS"
Change in & I I A diiring .i-;\Iinute Ranhury Treatment 7:s. Per Cent Aromatics in Oil
Figlire 23.
40
60
Masterbat,ches were made with a high viscositj- GR-S-1500 type latex containing 1.57i phenyl-2-naphthylamine using 45 parts of Dutrex 20 and Circosol-2XH. The base polymer with 1.5% phenyl-2-naphthylamine was coagulated with 0, 0.5, 1.0, and 1.5 parts of xylyl mercaptan (RPA 3) per hundred parts of rubber. These samples \?ere dried at 140' F. in a forced-air dryer and mere then heat-aged at 140" and 200" F. in air and in nitrogen. The breakdown curves are shown in Figure 32. The data show that the polymer8 containing RPA 3, except for that, n-ith 1.0 part, as well as the inasterbatch with Dutrex 20, were broken don-n to varying degrees on drying. I n the presence of air there were a markedly higher rate of breakdown and an absence of condensation; as compared with the much lower rate of breakdown followed by condensation found in the presence of nitrogen. The com-
40
80
Bo
100
5-MINUTE BANBURY MIXING
f Yith mixing in the presence of air had apparently producer1 a polymer that lyas less suscepti'rde t o breakdown.
100
60
1000-GRAM LOADING
m
1
15000RAM LOADING
*
40
30
to
I " " " " 40
00
00
vo "AROYATICS
Figure 25.
100, 'I
20
40
60
80
vo "AROMATICS"
100
Relationship of Per Cent Aromatics to AML-4/ADSV for Various Conditions
zt " 8.
Y?
2m
::
2
om oo
vI
m w m
c m m u 1 .
roe mat
traviolet light produced 100 to 300 p.p.m. of active oxygen, and air-blowing the oils also showed the presence of measurable q u a n t i t i e s (30 p.p.m.) of active oxygen. Therefore, samples of GR-S-
e a
4
ap 2
1
z
65
:" 1 0
m
5. 5s *.
2 W 0
= 30-
P
0 W
z
g
w
-
.)
45'
a
/
(D
m z0
1 : i
to about the same extent when diied in either air or nitrogen. With added cumene hydroperoxide, the air-dried eample broke down during the drying more than did the one dried in nitrogen Heataging of the samples in air a t 200' F. caused both samples to break down rapidly. Cumene hydroperoxide did not influence the
00
0
0
x
3
8
W
X
Y
rN- r nC
* N
8a 3
e N
U
z
m
i
:
D
go20
$ 4
ONCOI
2
N
x
@?
3
EO
40
60
W
A B E D A T Z0O.E
W K
P 2
I
0
%
0
2.40
AOED AT I40.F.
Y
x (nZN
CHANGE IN DSV TO MINIMUM VALUE
In
fj 1 8 0 I-
m 2
--
IO0
0
iao
om
AOED AT 3W'C:
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
410
Vol. 46,No. 2 N
a a (1
5 L
rr: 0
n
0 0
0 c
t
0
lo r)
c t
n
P
d
x
0
k4 a@
n
-
a! I
I
x
Y
-I 0
In
0 0
E 0 LL' 0
0 0
R1
v)
I-
0
2
l-
a
I
rL
I
z
4
m a W !-
Q)
4
I
D
February 1954
41 1
0
m
G
LL 0
0
2
c 4
h 01
m
e
01 e
W
(D
L
0
b
0
412
INDUSTRIAL AND ENGINEERING CHEMlSTRY
Vol. 46, No. 2
DRIED IN AIR A? 140eF:AND AQED I N AIR A? '2OO.F:
--..
2.50
--
BASE POCVUER CIRCOSOL-ZXH- 30PARTS w i r n 0.01MRT CIRWSOL-PXH-30 P I R T 8
cw
DUTREX 20-30 PARTS
c 0 w
DRIED IN NITROGEN AT 140.F. AND AQED I N NITROGEN
e
AT e0O.F: 3.10
II . . 01 3
2.90 I91
I32
Z.70
ex,
8
6
24
I2 HOURS
i'
IRGOEOL-DXH OEOL-DXH 0.01PART
2.30
'UO PART8 WITH
cw
2.10
Figure 31. Breakdown at 200" F. of Various Oil-Free Polymers
I .30
CIRCOSOL-eXn' XI PUTS DUTREX 20-30 PARTS W WITH IT
1.70
"-- 0
T R f X IO-SOPARTS
I=.?
chain scission reaction. I n samples dried in nitrogen, cumene hydroperoxide had no effect on the breakdown of the Dutrex 20 inasterbatch during heat-aging in nitrogen, as both samples were broken down to about t'he same degree. I n nitrogen, however, the condensation reaction n m definite. With Circosol-2x13, the breakdown in the presence of nitrogen was greater than in the presence of air. Cumene hydroperoxide in the Circosol-2XH mast'erbatrh inhibited breakdown during heat-aging in air and enhanced the breakdown during heat-aging in nitrogen. The retardation effect of the air on the breakdown of the base polymer is shown by the comparison of the curves in the two atmospheres. This supports the postulation made earlier (Figure 31) that mixing of the latex in air can alter the tendency of t'he coagulated base polymer to break down on heat-aging. Also under the conditions mliere peroxide was added to Circosol2XH and the masterbatch heat-aged in a,ir, molecular oxygen has been shown to retard or inhihit the effect,s of oxidation. It is also
3.5
HOURS
Figure 33. Heat-kging in Air and Nitrogen of Oil Masterbatches with and without Added Peroxides
evident that the t,xo oils contain materials which vary in their inhibitive effects on breakdown of polymer or vhich differ in their promotion of condensation. Sapht,henicacids, furnished by the Esso Standard Oil Go., were added to Kecton 60, an oil of IOT aromatic content, in amounts of 0 to 2.25 parts per 100 part,s of GR-S-1500 polymer with which 45 parts of the blend was masterbatched. The base polymer contained 1.5% of phenyl-2-naphthylamine. Heat-softening data showed that the acid in combination n-it,h the Necton 60 did not materially change the breakdown characteristics of the polymer.
DRIED IN AIR AND AGED IN AIR
DRIED IN AIR AND AGED I N AIR
P4
5
AT 200°t?
0 A S E WLYMER
LITERATURE CITED (1) Eby, L. T., Anal. Chem., 25, 1057 (1953). ( 2 ) Flory, P. J., private communication to Reconstruction Finance Corg., Office of Synthetic R u b b e r . (3) G a r v e y , B. S.,Jr., Whitlock, AI. H., a n d Freese, J. A., IND.EKG.C m s f . , 34,1309 (1942). (4) K a u z m a n n , W..and E y r i n g , H., ,J. Am. Chevi. Soc.. 62, 3113 (1940). ( 5 ) 3IulIir1, J. W., and Baker, W. O., grivatc coinniuiiication t,o Oficc of Ituhticr ltcserve. (6) Ilostlcr, E'. s., and StPrnberg, 11. h D . \
I I PART RPA
0.6PIIRY RPA CIRCOSOL-PXH4 6 PARTS
I
w.,
en
DUTREX eo46 PARTS
...
17
>
CIRC080L-OXH-48 PARTS
ENG.CHEJI., 41,598 (1949). (7) Rostlei, F. S., and White, It. 31., 22iibber 4 g e , 70, 735 (1952). (8) Schade, J. W., India Rubber W o r l d , 123, 311 (1950). (9) T a f t , TJ7. K., D u k e , J., Snyder, A. D.. Feldon, M., a n d Laundrie, R . W., Is],. E K G . CHEhI., 45, 1043 (1953). (10) W a t s o n , W. F.. Pram. Inst. RzibbeT I d , 29, 32 (1953). RECEXYXD f o r reyiew ;\lay 11, 1953. AccfiPi~i~n Ortoher 7 , 1933. Presented before the Division of Rubber Chemistry.
.4lIERICAX
CtltXIICAL
SOCIEYT,
ROStOn,
LIass., 1Iay 27, 1993. Work poiformed as part of tho rc,wnri,h project s.pon;orcd by the Reconstriict,ion l'inanrr Coip., ORcc of Synthetic Rubher, in conncction wich t h c govcrnmeiit synthetic rubher progritin.
