Processin Oil-Extended and
Carbon Black GR-S Masterbatches HARRY L. ERICSOS Continental Carbon Co., 1400 West 10th Ace., Amarillo, Tex.
L. D. CARVER Witco Chemical Co., 260 Madison Ace., New York 16, N. Y .
URIKG the past few years considerable work has been presented on the technical aspects of low temperature GR-S and black GR-S masterbatch (4, 7 , 9, 10, 11). With the more recent development of the oil-extended GR-S polymers by the General Tire and Rubber Go. Research Division ( 9 ) , renewed interest has arisen in the processing of these polymers with high abrasion furnace (HAF) black to produce tread compounds giving improved wear and cut growth resistance. Most of the papers to date have dealt mainly with the raw polymer studies, the carbon gel complex, and some tire test results (1, 5-6, 8). The effects of compounding and processing variables, particularly on the oil-extended polymers, have been investigated but little data have been published. This report is concerned with the results obtained from a laboratory investigation of the effects of compounding and processing variables on H A F black-low temperature GR-S masterbatch and two oil-extended low temperature polymers, GR-S X-628 and GR-S X-629. JThile it is generally known t h a t laboratory and factory processing cannot be directly compared it is possible to change conditions, using a Size B laboratory Banbury mixer, t o produce variables to shorv how a compound is affected by temperature changes, Banbury rotor speeds, etc. The results of a study of this type, as shown by ultimate physical properties, abrasion resistance, flex cracking, and processability can be of considerable help to the rubber compounder in predetermining results when setting up factory-mixed stocks and procedures. STANDARD OPERATING CONDITIONS
T o simulate factory processing temperatures the Size B Banbury mixing cycles and other conditions used for this study were set to give discharge temperatures in the range of 275" F. to as high as 390' F. The base formulations shown in Table I were used and the following 8-minute mixing cycle was used as a control or standard with 120" F. circulating cooling water through the jacket and rotors, 115 r.p.m. rotor speed.
onds before sheeting off of the 6 X 12 inch mill during the sulfuring operations using a 4 X 6 inch template placed against the front roll. The 4 X 6 inch shrinkage samples were carefully placed on a flat, freely dusted silicone paper surface to allow the samples t o shrink without sticking t o the surface, After mixing, the batches were allowed t o rest overnight before curing. Mooney viscosity determinations at 212" F. were run 4 t o 6 hours after mixing, and Mooney scorch tests a t 250" F. the folIowing day. Stress-strain data ( 1 2 ) vere obtained using standard 6 X 6 inch tensile sheets cured a t 307" F. The results using these standard conditions are shown in Table 11. Generally, the optimum cure appears to be a t 60 minutes, and this cure is shown in the remainder of this paper. To verify the data given in this paper, all of the compounds have been run in triplicate over a period of 4 months. I n each of the compounds shown 0.8 part antioxidant per 100 parts rubber hydrocarbon was used, disregarding the amount of oil plasticizer present, because it was found in previous work that up to 1.5 parts antioxidant there was no advantage gained. The cost of higher amounts of antioxidant is substantial and the physical characteristics after aging in circulating hot air for 7 2 hours a t 212' F. were about the same whether 0.8 part or 1.5 parts were used. The processing of hot GR-S and cold GR-S and the effects of varied operating conditions has been n~ell covered by other investigators ( 1 , 2, IO). This study was therefore centered on GR-S black masterbatch X-688, containing 100 parts low temperature polymerized (LTP) GR-S and 50 parts H A F black, and the two oil-extended polymers, GR-S X-628 and X-629, with 100 parts L T P GR-S, 25 parts processing oil, and the X-629 with 50 parts HAF black. E F F E C T S OF VARIABLES
EXTRUSIOK SMOOTHSESS.GR-S X-628 and X-629 containing 62.5 parts H A F black (compounds 4 and 5) extrude with a slightly
Mixing Cycle
Add polymer, stearic acid, accelerator Add zinc oxide, antioxidant Add H A F black (Continex H A F ) Add H A F black (Continex H A F ) Add HAF black (Continex H S F ) Add processing oil Discharge and total time
At Time, Minutes 0 1
2 3'/a
5 6'/2 8
TABLE I. BASE
GR-S X-539 (122O polymer) GR-S X-478 (41° polymer) GR-S X-688 GR-S X-628 GR-S X-629 Processing oil NBSa stearic acid h'BSQ zinc oxide Antioxidant Santocure Continex HAF NBSQ sulfur
Immediately after discharge from the Banbury the batches were banded on a laboratory 6 X 12 inch open roll mill; t h e Total sulfur was added and mixed for a total of 4 minutes using a 0.045a National Bureau inch roll nip. A constant batch size of 1250 t o 1300 grams wzp used throughout. Mill shrinkage samples were taken 30 sec792
of Standards
FORxfCLATIOR'S
1 100
.. .. ..
10.0
..
Compound No. 2 3 4
..
..
..
150
100
.. la.o
, .
.. ii.o
..
128
..
L O
8
.. ..
176
5.0
2.0 2.0 2.0 2.0 3.0 3.0 3.0 3.0 0.8 0.8 0.8 0.8 1.1 1.1 1.1 1.1 .. 50.0 50.0 62.5 12.5 1.8 1.8 1.8 1.8 1.8 166.7 172.7 172.7 201.2 201.2 3.0 0.8 1.1
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLE 11. RESULTB USING STANDARD OPERATINQCONDITIONS Compound No. Polymer Max temp., a F. Mill shrinkage, % Power, kw. Cure at 307' F., Min. 30 60 75 90
1 x-539 341 28 12
3235 3265 3260 3220
30 60 75 90
1720 1685 1670 1630
30 60 75 90
475 490 475 465
30 60 75 90
60 61 61 61
90
50
2 X-478 319 34 11
3 X-688 321 24 15
4 X-628 325 40 11
5 X-629 352 37 14
Tensile Strength, Lb./Sq. In. 3695 3375 3210 3770 3395 3250 3885 3585 3190 3875 3480 3110
2745 3000 2980 2960
300%. Lb./Sq. In. 1150 1125 1425 1405 1430 1425 1420 1390
1160 1445 1510 1435
Modulus a t 1125 1295 1360 1355
Ultimate Elongation, % 685 665 585 600 575 510 600 570 5 10 590 560 500
515 485 475 460
Hardness (Instant. Shore A)
Figure 1. Effect of Banbury Discharge Temperatures on 300% Modulus and Abrasion Loss
59 61 61 61
58 60 60 60
58 59 60 60
58 58 59 60
52
54
Rebound (Lupke), % 50
55
rough surface, while GR-S X-688 containing 50 parts H A F black Heat Build-Up, (St. Joe, 25-Min. Run), O F . (compound 3 ) extrudes with a very glossy and smooth surface. 90 261 244 220 212 209 The addition of HAF black t o a total of 75 parts t o the oil-extenAbrasion Loss (Goodyear-Huber), cc./20 min. ded GR-S X-628 and X-629 polymers does not give smooth 90 extrusions equal to GR-S X-688. 4.1 3.2 3.0 1.7 1.6 When 12.5 parts H A F black and 5 parts hard hydrocarbon are Flex Crack Growth (DeMattia), kc. to I/: Inch added to compound 3 (Table 111) an exceptionally smooth and 90 21 102 182 49 52 glossy extruding stock is produced with good physical charachlooney Viscosity (ML4-212O F.) teristics and a decided improvement in flex crack resistance. .. 54 56 50 68 74 CIRCULATINGCOOLINQWATER TEMPERATURE. The oilextended polymers, GR-S X-628 and GR-S X-629, with 62.5 Mooney Scorch (MS-250' F.), Min. parts total H A F black were next studied using varied circulating .. 20 50 60$ 37 37 cooling water temperatures covering a range from 80' to 180' F. A11 other Banbury mixing conditions remained the same as those given above. The results are shown in Table IV and V. Varied TABLE 111. GR-S X-688 BLACKMASTERBATCH Banbury circulating cooling water had no effect on the maximum Compound No. 3 6 power requirements for either polymer. Increasing the temperaX-688 X-688 ture of the circulating cooling water when mixing the oil-extended 50.0 62.5 GR-S X-628 polymer gives higher discharge temperatures, which 14.0 19.0 323 344 in turn increases modulus, Shore A hardness, Mooney viscosity, 25 19 15 15 Mooney scorch time, and mill shrinkage. Resistance to abrasion 3685 3090 is slightly improved but flex cracking is notably poorer. When 1325 1540 610 510 mixing the HAF oil masterbatched GR-S X-629 polymer the 59 61 55 48 increase in temperature of the circulating cooling water has little 62 56 or no effect on the modulus and abrasion resistance. Other 218 276 2 . 9 2 .6 Abrasion 10s; cc./20 min. characteristics are about the same as for GR-S X-628. A 170 500+ Flex crack grbwtb, ka. t o 1/n inch 47 60 F.) Mooney visoosit (ML 4 212O comparison of these two polymers as affected by the varied Mooney scorch &S-250° F.), min. 60+ 60+ circulating cooling water temperatures is shown in Figure 1. BANBURYROTOR SPEEDS. TABLE Iv. EFFECTO F VARYING CIRCULATING COOLING WATER TEMPERATURES Varying Banbury rotor speeds GR-S X-629 GR-S X-628 Po 1 y m e r were the next considerations 140 160 180 120 180 80 100 140 160 120 80 100 Circulating cooling water, E'. 357 364 368 342 346 327 335 348 354 in the processing of GR-S X330 308 328 Max. temp., a F. 38 38 40 37 40 38 34 35 38 35 35 35 Mill shrinkage, % 628 and GR-S X-629. Speeds 14 14 14 11 14 14 14 11 11 11 11 11 Power kw. 3210 3270 3235 3220 3265 3225 3160 3010 3045 3015 2925 2950 Tensilb strength, lb./sq. in. of 77, 115, and 155 r.p.m. were Modulus at 300%, lb./sq. in. 1390 1495 1465 1505 1510 1525 1300 1330 1310 1345 1305 1330 485 485 485 500 485 485 525 475 485 485 studied. The results are given 500 485 Elongation % 58 58 58 57 57 57 62 62 61 60 59 59 Hardness &hore A in Table V. It appears that 54 54 54 54 52 54 53 52 52 52 51 52 Rebound' Lupke) % 214 220 218 212 215 220 218 223 220 216 233 225 Heat b u d u p (St: Joe)! F. increased rotor speeds do not 1.4 1.5 1.6 1.4 1.5 1.6 1.5 1.5 1.4 1.5 1.7 1.6 Abrasion loss cc./20 min. materially affect the physical Flex crack grbwth, kc. to '/n 34 29 48 56 56 38 52 40 50 43 61 52 inch p r o p e r t i e s . However, disMooney viscosity (ML-478 80 80 75 75 76 75 70 74 69 65 68 212' F.) charge temperatures increase Moqney scorch (MS-250' F.), 39 38 37 37 37 38 36 38 39 37 with the increased rotor speeds; 32 35 min. maximum power requirements '
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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are greater; Mooney viscosities are lower; and the stocks scorch more readily. Resistance to flex cracking is greatest a t the 115 r.p.m. rotor speed and appears to become poorer a t the lower and higher speeds.
Vol. 45, No. 4
KO significant differences were noted among these processing oils with respect to processing and physical characteristics except for Dutrex 20 and Witcoil No. 170, which give somewhat faster extrusion rates (Table VIII). Processing Oil Evaluation
so+
Parts by wt. 100.0 30.0 62.5 0.8 2.0 3.0 1.1 1.8 201.2
LTP GR-S (128 Mooney) Processing oil Continex HAF Antioxidant KBS stearic acid NBZ zinc oxide Santocure XBS sulfur Total
-
The processing oils studied were: Cauliflux GP, Circosol 2XH, Dutrex 20, Shell SPX 97, Sundex 53, and Witcoil S o . 170. CONCLUSIONS
-
/200
I
i
6
I
8
1
/O
8
12
i
14
I
/6
From the results of this laboratory study it has been shown that Jyhere a great deal of consideration has been given to the formation of carbon gel there are also numerous factors in com-
BHHRURY M/X/h'G CYCLE , M/NUT€S
Figure 2.
Effect of Banbury Mixing Cycle on Mooney Viscosity and 300y' Modulus
LEXGTHOF BANBURY MIXIKGCYCLES. The effect of varying the length of Banbury mixing cycles was investigated covering a range of 6 to 16 minutes. Batch discharge temperatures increase with increased mixing time, whereas modulus, ?*looney viscosity, and mill shrinkage decrease (Figures 2 and 3). Up to the 12-minute mixing cycle the flex crack resistance decidedly improves, while additional mixing, very similar to the 155 r.p.m. rotor speeds, appears to make flex cracking more prevalent (Figure 3). Other properties remain fairly constant, including tensiles, elongations, hardness, and abrasion loss (Table VI). REJ~ILLIXG AND EXTRUDISG. The effect of remilling and extrusion of GR-S X-628 and GR-S X-629 was studied using the regular %minute mixing cycle with remilling times the following day on a 6 X 12 inch, 120' F. laboratory mill for 0 to 10 minutes. The stocks were then extruded through a No. Royle extruder with a Garvey die at 200' F., sheeted off the 6 X 12 inch mill, and then tested in the same manner as for the previous studies. Tensiles, elongations, Shore A hardness, abrasion losses, and Mooney scorch time remain practically constant (Table VII). Modulus decreased with increased remilling in much the same manner as for increased mixing cycles except that the modulus level is approximately 300 pounds per square inch lower due to the additional breakdown caused by the extrusion operation (Figure 4). Similarly, Mooney viscosities and mill shrinkages decrease with increased milling and extrusion. Flex crack growth tests varied so widely in the individual stocks that they could not be interpreted correctly. PROCESSING OILS. Where the oil-extended high Mooney viscosity polymers contain relatively high amounts of processing oil, attention was next centered on a study of some of the processing oils applicable to extending these polymers. To 100 parts of high Mooney LTP GR-S polymer (mean raw Rlooney 128 ML-4) 25 parts processing oil were added on an open mill. This is equivalent to GR-S X-628 containing 100 parts polymer and 25 parts processing oil. The stocks were then mixed as previously described.
+5-t
200
t
6
I
I
8
/O
I
/2
I
/4
16
BRN8URY M/X/NG CYCLE, hlNUTES Figure 3. Effect of Banbury Mixing Cycle on Mill Shrinkage and Flex Crack Growth
TABLE V.
EFFECT OF VARYII~G BAXBURY ROTORSPEED
Polymer Rotor speed, r.p.m. F. Max temp Power kw. Millshrink&e, % T e n d strength, lb./sq. in. Modulus at 30076,Ib./sq. in. Elongation % Hardness (Shore A) Rebound Lupke) % Heat buii6-up (St: Joe), F. Abrasion loss, cc./20 min. inch Flex crack growth kc. to Mooney v i J o o s i t y . ' ~ ~ - 4 - 2 1 2F. 0 Mooney scorch, MS-260' F.
GR,-S X-629 115 155 344 387 38 41 14 20 10 2865 2935 2936 1485 1475 1545 465 450 465 59 60 59 54 55 53 220 224 219 77 292 37
1.8
50 84 37
1 6 59
75 35
1 8
36 75 27
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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pounding and processing which affect the quality and perforP mer GR-S X-628 GR-S X-629 mance of -HAF black-LTP - n l v ----Mixing cycle time, min. 6 8 10 12 14 16 6 8 10 12 14 16 GR-S tread stocks. 040 345 347 352 Max temp. F. 326 335 341 340 344 347 315 3'Smoother and glossier tread Mill ahrinkbee 41 7 40 38.5 39 6 37.5 3 6 . 5 39.6 37' . 5 3 8 . 5 3 8 . 5 36.5 85.0 _. ------D1, 4, ," ~.6 stocks can be extruded using gowe:! kw. A!,i,l i l , U vo.?; oo,?; o~r?t? Y2e0w2" 2 ;:12' -,?I? Qn&? '2l,f;4 30204 298014 307514 I ensile srrengm ~ u . / s q . iu. Modu1;s a t 300%, lb./sq. in. 1595 1545 1535 1460 1480 1440 1630 1410 1265 1265 1240 1265 HAF black masterbatch-LTP 490 490 500 500 485 510 485 500 490 500 510 500 Elongation, Yo 59 57 58 57 58 GR-S than when using the oil60 59 59 59 59 Hardness (Shore A) $7 58 53 54 52 52 52 52 51 Rebound (Lupke) % 54 54 55 55 55 extended GR-S polymers. In222 21 1 ___ _._ 217 210 221 219 215 27 2 _. 220 222 224 225 Heat build-up (St: Joe)' F. 2 .O 1.8 1.9 1.9 1.8 Abrasion loss, cc.!ZO min. , , 1.9 1.6 1.4 1.6 1.7 1.5 1.6 creased Banbury circulating Flex crack growth, k C . t O '/z 33 59 98 116 87 73 57 63 80 172 148 84 cooling water temperatures give inrh Mooney viscosity (MI-4- 78.0 75.0 74.0 72.0 73.0 69.0 6 6 . 5 65.0 60.0 57.0 65.5 54.0 higher stock discharge tempera212O F.) Moqneyscorch (MS-250' F.), tures and faster scorching and 34 34 37 35 36 38 38 39 38 36 36 38 min. harder processing stocks with decidedly lower resistance t o TABLEVII. EFFECT OF REMILLING AND EXTRUSION flex cracking. Abrasion losses D^,...,.^" CR-R Y A"-9R GR-S X-629 were not noticeably affected by "'y"'"' Banbury cooling water tem0 2 4 6 8 1 0 0 Remilling time, min. ,'? A, h i o w 339 339 341 . 340 339 340 337 Max. temp., F. 3 340 7 . 5 36.5 342 3 340 6 . 5 peratures over the range of 38.5 38.5 35.4 42.7 37.5 3 6 . 5 38.5 37.5 Mill nhrinkaen. % 42.7 .-... , Power, kw. 11 o -11o ~ oonn 11 ? , i11 14 2950 14 3025 14 3010 14 discharge temperatures studied _ - _ _r~ I L I - _ .1':onen n ~ 11 1 a9i n11 n~ 9 a14 7 ~ 9 a14 ~ n andn 1 8 1 , Y l l t : Lic'allga,,, ,lJ.,sq. (308' to 268' F.) Excessive Modulus a t 300%, lb./sq. in. 1285 1245 2140 1190 1115 1130 1180 1155 1080 1095 1015 1020 500 510 510 540 525 510 500 515 515 550 535 Elongation, % 515 Banbury rotor speeds give Horrlnnsm \I_.__I S h n r n --, AI -57. 5 - 7. 57 .. 58 .57 58 58 59 58 58 58 59 Rebound Lupke) % 53 53 53 53 53 53 54 54 53 54 54 53 harder processing and faster Heat buil6-up (St: .Joe), F. 219 222 226 216 220 224 229 228 230 224 231 230 Abrasion loss, cc./20 min. 2.0 1.9 2.1 2.1 1.9 1.9 1.8 1.7 1.9 1.9 1.7 1.8 scorching stocks with lower reMooney sistance t o flex cracking. 212' F.) viscosity (ML-4- 65.0 63.0 6 2 . 5 6 2 . 0 61.0 60.0 62.0 60.0 60.0 59.5 59.0 57.6 Flex crack resistance of oilMoo~neyscorch(MS-2500F~)~ min. 27 28 28 27 29 27 28 31 29 30 31 29 extended GR-S tread stocks reach a maximum with a definite Banbury mixing cycle TABLE VIII. PROCESSING OIL EVALUATION after which additional mixing causes reduced flex crack reCaul- CirDuSun- Witsistance. Remilling and extrusion of oil-extended GR-8 tread iflux cos01 trex Shell dex coil Processing oil GP ~ X H 20 S P X ~ 53 ~ ~0.170 stocks reduces modulus, viscosity, and mill shrinkage. Other Max. temp., F. 331 330 332 331 335 330 properties are not seriously affected except for flex cracking, Mill shrinkage, % $!, ?: f: which becomes quite variable within individual stocks. No 291; 2 9 G 3 145 2965 2915 2965 significant differences were noted among the six processing oils 1590 1625 1,505 1600 1580 1615 475 490 included in this study. 490 485 465 475 MIXINGCYCLE TABLE VI. EFFECTOF VARYINGLENGTHOF BANBURY
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