EngFnTring
Vinyl Plasticizers
Process - development
EFFECT ON PROCESSING POLYVINYL CHLORIDE IN BANBURY MIXERS I
H. S. BERGEN
AND
J. R. DARBY
MONSANTO C H E M I C A L C O . , ST. LOUIS, MO.
T h e rapid growth of plasticized vinyl compositions has necessitated the installation of additional equipment and the utilization of such equipment a t the highest efficiencies. The Banbury mixer is the main compounding unit for fluxing vinyl compounds. Plasticizers are added to vinyl resins not only for the desirable properties they impart but also for improving processability. This article discusses the effect of different plasticizers, fillers, and lubricants on vinyl compounding in the Banbury mixer. Plasticizers exert a considerable effect on the fusiou time of a vinyl compound. The plasticizers studied are broken down into five groups with respect to fusion ranges.
The type of plasticizer used also has an effect on the power required for Banbury operation. Increasing lubricant concentration increases fusion time; however, with certain plasticizers, higher concentrations of lubricant may be tolerated without resulting in incompatibility or excessive fusion times. The effect of filler concentration on fusion times varies with the concentration of the filler. Through the proper selection of a plasticizer formula, optimal fusion times and horsepower requirements can be developed. The data presented should be useful in wTorlting out optimal formulations which should result in increased plant efficiency.
P
RODUCTION of vinyl compounds has increased from operations. Often the power consumption must be reduced, yet slightly over 1,000,000 pounds in 1941 to approximately production maintained a t high rates. With the increase in calendering and extrusion rates, the compounding or fluxing operation 300,000,000 pounds in 1949. These compounds include either polyvinyl chloride or polyinyl chloride-polyvinyl acetate comust also be increased in capacity. This may be accomplished by installation of additional equipment, but also considerable polymers in combinat'ion with plast,icizers, fillers, pigments, and efficiency appears to be possible through optimal formulation of stabilizers. The film, sheeting, supported films, and extrusions vinyl compositions and proper operat'ion of the compounding accounted for the major portion of vinyl usage. Compounding techniques for such products general1)- iiivolve the use of heavy equipment. The latter met,hod of increasing production is genprocessing equipment including blendem: Banbury mixers, calenerally the most economical method. Plasticizers are added to vinyl resins not only for the purpose of ders, and extruders. With the accelerated rate of vinyl growth, imparting flexibility but also for improving the processability. the industrs.was confronted with the necessity of installing addiSince t h e plasticizer tional equipment and the n o r m a l l y constitutes one desirability of using such t'hird of the formulation, it equipment a t the highest efficiency. C o n s id e r a b 1e appeared reasonable that progress has been made in this constituent could exerthe direction of improving cise an appreciable influence on the rate of compoundthe efficiency of some procing, essing equipment ( 7 ) . This This paper discusses the is illustrated by calender results of a study of the rates increasing from an output of 20 to 30 yards per effectof plasticizers on vinyl compounding as determined minute up to a point where in the Banbury mixer. In 100 yards p'er minute have addition, the effect of fillers, been attained. stabilizers, and lubricants For compounding vinyl TT-as surveyed. formulations, it is common to premix resin, plasticizer, stabilizer, and other ingreAPPARATUS dients; flux into a homoThe compounding operageneous mass by means of a tion provides homogeneBanbury mixer; sheet on ously fused material to feed a %roll mill, and then feed the processing equipment. to the calender or chop for Since the fluxing operation is achieved in the Banbury, an extrusion compounder. this piece of equipment in In the use of this heavy the most important of the equipment it is necessary to compounding units. synchronize properly the A laboratory size B Banbury with air-operated Figure 1. Laboratory Size R Banbury Mixer production from the various 2404
October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
2405
Figure 2. Power Cycle during Banbury Study
floating weight, four-speed rotor, and pressure grease lubricator waa selected for this study. Figure 1 depicts the test setup. The design of the Banbury mixer embodies an enclosed mixing chamber, double cylindrical in form. Each cylindrical section haa a hollow mtor, pear-shaped in cross section. In revolving, each rotor surface converges acutely with the walls of the chamber. The two rotors revolve in opposite directions, producing a constant circulation of the stock. All parts of the batch are brought into contact with each other, producing a homogeneous mix. To conform with general trade practice on production size Banbury mixers, the air pressure was set a t a pressure of 20 pounds per square inch gage. This is equivalent to 32 pounds per square inch a t the base of the ram. Steam pressure was set a t 20 pounds per square inch gage. Other steam pressures were not investiated inasmuch as mechanical friction and the subsequent heat $eveloped when the compound is Banburicd are more significant factors than the temperature of the chamber walls and the rotor. Further, experience in the industry has indicated that regardless of the temperature selected for operation, compounding efficiencies of various plasticizers and resins will be of the same relative order. Four rotor meeds were available on the Banburv. These four speeds are i s follows: 80.8, 119 (standard speed); 158, and 242 revolutions per minute (r.p.m.). For this test work, speeds of 80.8 and 158r.p.m. were utilized. Power measurements were made on the drive motor with an Esterline-An us recording Wattmeter with a shunt producing a full scale reafing of 40 hp. Temperature was indicated and automatically recorded by a Leeds & Northrup Micromax recorder from a thermocouple located directly in the mixing chamber between the two rotors. The Wattmeter recorded the power requirements for shearing and compression a t i o n of the Banbury during seven revolutions and indicated the highest compression on the eighth revolution. Trade Name Santirizer 107 Santicizer 140 Santicizer 141 Santicizer 160 HB-40
MATERIALS USED
The twomost important ingredients in a vinyl formulation are the vinyl resin and the plasticizer. Throughout this study Ultron -300 resin (Monsanto Chemical Co., Springfield, Mass.) was utilized. This is a polyvinyl chloride resin of a high weight. The study Of the effect of different vinyl resins on proceasing may well be the subject of a further investigation. Industry recog-
P-4 Flex01 4 G 0
.
Plastolein 9250 Adipol 2EH ParaplexG-50
nizes that the various commercial vinyl resins differ somewhat in their ease of processing; however, ex rience has indicated that it is probable that the relative o r g r of mixing efficiencies of the classes of plasticizers studied will hold regardless of the vinyl resin used. The plasticizers used in this study, their chemical classification, and their source are listed in Table I. This group of plasticizers represents ten different chemical .types of plasticizers which include the most commonly used vinyl plasticizers. As a combination stabilizer and lubricant system, a mixture of 1 part fused lead stearate with 2 parts of Plumb-0-Si1 B (coprecipitated mixture of lead orthosilicate and silica gel) was used throughout; except in those instances noted wherein other stabilizer combinations or concentrations of lubricant (lead stearate) were investigated. For those formulations involving filler studies, Atomite filler (Thompson-Weinman and Co., Montclair, N. J.) was employed. Atomite is a calcium carbonate filler of the consolidated sugar calcite type. These basic raw materials of resin, olasticizer. and stabilizer. and, in some instances, filler were premixed a t various concentral tions of ingredients. FORMULATIONS AND TEST METHODS
Test batches were stirred, kneaded. and mixed a t room temperature. The general formulation was: Parts Ultron resin Plasticizer or plasticizer blend Stabilizer and lubricant Filler
100
40-60 0-3 0-100
TABLEI. PLASTICIZERS EVALUATED
Chemical Name Di-2-ethylhexyl phthalate Cresyl diphenyl phosphate
. . . ......
Butyl benzyl phthalate 40% hydrogenated terphenyl Tricresyl phos hate Methyl acety? ricinoleate Di-2-eth lhexyl ester of pol etxylene giyool Tetragydrofurfuryl oleate Di-2-ethylhexyl adipate
... . . . . . .
Chemical Classification Supplier Dialk 1 phthalate Monsanto Chemical Co. M i x e J a r y l phosphate Monsanto Chemical Co. Alkyl aryl hosphate Monsanto Chemical Co. Alkyl aryl pgthalate Monsanto Chemical Co. Partially saturated Monsanto Chemical Co. aromatic hydrocarbon Aryl phos hate Monsanto Chemical Co. Fatty acizester Baker Castor Oil Co. Dialkyl ester of polyCarbid? and Carbon ethylene glycol Chemicals Corp. F a t t y acid ester Emery Industries, Inc. Dialkyl adipate Ohio-Apex, Inc. Polyester type Rohm & Haas Co.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2406
Figure 3.
Temperature Cycle during Banbury Study
The formulations studied are indicated in Tables I1 and 111. The total size charge to the Banbury was 1530 grams (approximately 1200 cc.), except in the case of the filler study where the volume was maintained between 1065 and 1135 cc. (weight varied between 1520 to 1883 grams). These size charges utilized the recommended capacity of the mixing chamber. Prior to collecting test data, the Banbury was operated until standardized temperature conditions were obtained, The standard conditions set were to process each formulation for 10 minutes (except in the case of high speed operation where &minute cycles were utilized), dump the batch, and recharge with minimum delay a freshly premixed new formulation. These cycles were operated continuously and uninterruptedly subsequent to standardization. Power measurements were made directly on the motor which drove the Banbury rotors. This power was recorded by the recording wattmeter, and a typical plot is illustrated in Figure 2. KO-load horsepower is indicated by the straight line, A , which measures the power required to turn the rotors with the chamber empty. The first peak on the curve, B, represents a peak resulting from the air-operated ram pressing on the compound. The power curve proceeds to rise until a power peak results, C. After this peak, the power gradually lowers and substantially levels off, D, near the end of the time cycle. The power peak, C, was taken as a significant reproducible point on the curve, inasmuch as it represents the horsepower of maximum compression on the specimen. This condition arises when a compound is in the initial fluxing stage. The measurement of the time between lowering of the ram and the poxer
Vol. 43, No. 10
peak indicates the time required to achieve the initial stage of fluxing and, for the purpose of this discussion, is defined as fusion time. This is designated by the distance between B and C in Figure 2. Batch temperatures were automatically recorded and a typical temperature-time cycle is illustrated in Figure 3. When standard operating conditions were established, a batch was discharged, A , a t which time the temperature immediately dropped owing to heat losses t o the air, B. The compound was added and the air-operated ram nws lowered, pressing the compound into the mixing chamber, a t which time the temperature rapidly dropped to a minimum, C. From this minimum point the temperature of the compound rapidly builds up due t o the heat in the walls and rotor, as well as the mechanical frictional heat developed. After a period of time the rate of temperature'rise becomes very slow, D. From this temperature versus time chart, the time required to go from the minimum temperature, C, to the point where the temperature rise becomes very slow, D, is designated as the time to reach a uniform temperature. TEST DATA
From the temperature and power recordings, the data were derived as indicated in Tables 11and 111. In these tables fusion time, power peak, average horsepower after fusion, and horsepoxer a t end of cycle, no-load horsepower, temperature a t fusion, time to reach uniform temperature, and average uniform batch temperature are recorded for the various plasticizers and plasticizer blends studied. Data relative to fusion time, power peak, no-load horsepower, and time to reach uniform temperature were taken from the recorded power or temperature charts. The average horsepower from 1 second to 60 seconds after fusion was determined by averaging the horsepower every 15 seconds for 1minute after the power peak. The horsepower a t the end of the cycle is the horsepower required to shear the completely fluxed mass of compound just prior to discharge of the stock. No-load horsepower is the horsepower to turn the rotors when the mixing chamber is empty. The temperature a t fusion is the temperature as measured on the temperature chart which develops a t the exact time ae the iusion time, which is obtained from the power chart.
AND BANBURY TESTDATA TABLE 11. FORMULATIOSS
Formula
No. 1 2 3
4
Plasticizer Conon. (PHRIn
Fusion Time, See.
Power Peak,
HP.
Av. HP. from 1 t o 60 See. after Fusion
71
5.2 6.6 6.6 6.8 6.8 4.4 4.2 6.2 6.4 7.2 5.4 7.4 5.6 6.4 4.4 8.0 5.7 8.4 5.6 3.4 8.2 5.6 7.6 5.9 4.9 5.6 6.0 4.9 6.0 6.1
4.9 5.5 5.6 5.4 5.6 4.3 4.2 5.3 5.4 5.8 4.6 5.5 4.6 5.4 4.1 6.0 4.6 6.4 4.6 3.4 6.5 4.8 5.8 4.7 4.6 4.8 5.1 4.6 5.1 5.1
49 56 47 39 106 283 60 54 37.5 62 29 62 44 92 25 55
Time
Hp. a t E n d of Cycle 3.4 3.2 3.6 3.2 3.2 3.4 3.6 3.4 3.2 3.2 3.2 3.2 3.0 3.2 3.0 3.2 3.0 3.2 3.0 3.4 3.6 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2
No-
Load Hp. 1.6 1.6 1.6 1.6 1.6 1.6
Temp. a t Fusion,
6 1.6 7 1.6 8 1.6 9 1.6 10 1.6 11 1.6 12 1.6 13 1.6 14 1.6 15 1 .6 16 1.6 17 1 .6 18 18 1.6 56 19 1 . 6 274 20 1.6 32 21 1 . 6 67 22 1.6 24 23 1.6 50 24 1.6 71 25 1 .6 51 26 1.6 53 27 1 .6 78 28 1.6 47 29 1 . 6 45 30 a Concentrationin parts per hundred parts of resin. b Formulas 1 through 24 utilize a stabilizer-lubricant system of 1 part fused lead stearate plus 2 parts Plumb-0-Si1 B. c Formulas 25 through 27 stabilizer system composed of 1.5 P H R of Ferro 120 and 1.3 P H R of Ferro 221. d Formulas 28 through 30 stabllizer system composed of 1.5 PHR of Ferro 221 and 1.0 P H R of C and C A-5.
F.
245 240 240 240 235 260 280 240 225 230 245 220 230 240 2 50 210 233 220 250 260 230 250 235 245 230 230 240 245 220 230
to Reach Uniform Temp., Sec. 265 195 220 190 169 375 520 240 215 180 210 190 207 210 281 169 188 150 200 430 180 207 165 180 275 230 220 270 210 190
AI.. Uniform Temp., I 312 308 313 310 311 307 310 305 307 317 303 323 302 317 295 318 300 318 302 300 318 305 320 305 303 302 303 301 304 303
October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
2407
TABLE 111. ADDITIONALFORMULATIONS AND BANBURY TESTDATA Formula NO. F-1 F-2 F-3 F-4 F-5 F-6 F-7 F-8 F-9 F-10 F-1 1 F-12 F-13 F-14
Fusion Time, Sec. 58 57 65 55 85 65 66 44 42 43 42 51 44 54 56 72 47 63 28 51 61 42 45 69 43 40 67 60 47 40 103 50 37 55 51 49 37 33 32 39 35 30 20 20 14 22 58 46 44 39 60 74 63 55 40 46 31
Plasticizer Concn. ( P H R ) a
Power Peak, HP. 5.6 5.6 4.8 5.6 4.8 4.8 4.8 6.0 6.4 6.4 6.4 5.2 6.4 5.6 6.4 5.2 6.8 5.4 7.6 5.8 6.0 6.0 6.0 5.0 6.0 6.6 4.4 5.2 6.0 6.8 3.6 5.2 7.0 5.6 10.0 9.8 12.0 12.0 12.0 11.0 11.5 12.4 14.0 14.0 14.4 12.0
Av. Hp. from 1 t o 60 Sec. after Fusion 5.0 4.9 4.4 4.6 4.4 4.2 4.3 5.2 5.2 5.3 5.3 4.6 5.2 5.0 5.4 4.6 6.4 4.8 5.6 4.9 5.0 5.0 5.0 4.6 5.1 5.4 4.1 4.8 4.8 5.3 3.6 4.4 5.4 5.0 8.2 8.3
Time
to Reach Hp. a t E n d of Cycle 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 4.8 5.2 5.6 6.2 5.2 4.8 4.8 5.6 4.8 5.2 5.2 4.8 4.1 4.0 4.0 4.0 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2
NO-
Load HP. 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2.4 2 4 2.4 2.2 2.2 2.0 2.2 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6
Temp. a t Fusion,
F.
245 245 245 240 260 250 240 230 235 230 240 240 245 240 230 245 240 245 225 240 240 235 235 240 225 215 245 235 235 240 255 230 240 245 265 270 235 265 270 255 260 255 250 260 255 260 275 245 260 230 240 240 240 250 240 235 220 230
Uniform Temp., Sec. 230 230 29 5 240 325 295 295 195 210 195 200 250 195 235 225 255 195 270 190 265 220 210 220 235 210 195 265 255 230 195 600 295 170 240 135 135 125 120 110 115 115 105 85 85 80 85 125 115 110 105 300 325 345 300 240 240 240 225
Av. Uniform Temp., F. 315 315 317 314 318 316 315 310 310 311 311 314 310 315 304 311 310 313 320 311 311 310 309 311 310 310 313 311 310 310 305 307 309 310 335 337 332 335 335 338 338 352 349 349 355 345 333 320 320 325 313 311 31 1 31 I 314 310 311 31 1
F-12-A F-15 F-16 F-17 F-18 F-19 F-20 F-2 1 F-22 F-23 F-24 F-25 F-26 F-27 F-28 F-29A F-29B F-30.4 8.8 F-30B 8.8 F-31 8.8 F-32 9,2 F-33 8.6 F-34 9.7 F-35 9.8 F-36 9.4 F-37 9.9 F-38 8.6 F-39 8 6.8 F-40 8.8 6.8 F-41 8.8 7.0 F-42 10 7.5 F-43 4.8 4 3 F-44 4.8 4.3 F-45 5.4 4.7 F-46 4.9 5.6 F-47 6.0 5.0 F-48 5.2 4.4 F-49 6.6 5.2 F-50 7.2 31 5.7 0 Concentration in parts per hundred parts of resin. b Formulas F-1 through F-20 utiliae a stabilizer-lubricant system of 1 part fused lead stearate plus 2 parts Plumb-0-Bil B. C Formulas F-21 through F-28 lubricant study. d Formulas F-29A through F-42 standard stabilizer-lubricant system: formulas F-29A through F-42 are a t high rotor speed, all other formulations a t low rotor speed. 8 Formulas F-43 through F-50 filler study.
The average uniform temperature is the temperature when the batch is fluxed and after which the temperature increases only very slightly. Tables I1 and I11 include data obtained on various individual plasticizers and several plasticizer blends with the standard stabilizer system and other stabilizer systems as indicated. Table 111, formulas F-21 through F-28 list data obtained from a study of various concentrations of lubricant (lead stearate) with various plasticizers. T a o parts of Plumb-0-Si1 B were used throughout the study as stabilizer and the concentration of lubricant (lead stearate) in the various formulas was as follows:
RESULTS OF TESTS
Effect of Plasticizers on Banbury Mixing. Low ROTOR SPEED. In Figure 4 data are plotted illustrating the effect of various plasticizers and plasticizer concentration on fusion time 240
220 LOW ROTOR SPEED 80.0 R.P.M.
200 180
Parts
z
Formulas F-29A through F-42 list data on compounds which were processed at high rotor speed (158 r.p.m.) with various plasticizers. Formulas F-43 through F-50 are concerned with the effect of filler concentration on fusion characteristics of plasticized compounds.
20 PHR
0
4
Figure 4.
Effect of Various Plasticizers and Plasticizer Concentrations on Fusion Time
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
2408
Then lox rotor speed (80.8 r.p.ni.) was employed. Low fusion time was obtained with cresyl diphenyl phosphate (Santicizer 140), butyl benzyl phthalate (Santicizer 160), the alkyl aryl phosphate (Santicizer 141), and tricresyl phosphate. Greater lengths of time were required for dioctyl phthalate (Santicizer 107) and dioctyl adipate (Xdipol 2-EH). The polyester-type plastirizer (Paraplex G-50) required a much longer period of time than any of the simple ester-type plasticizers.
LOW ROTOR SPEED 80.8 R.P.M.
rl4050s TCP
405066 s-I41
4
Vol. 43, No. I0
and correlation to the plot line is good. \\'ith shorter fusion times, however, some variation in power peak is affected by the specific type of plasticizer. In Figure 7 (bot'tom) it is noted that ('rea;-1 diphenyl phosphate shoivs the fastest fusion with thc lowest power peak. Figure 8 illustrates the optimal plastic'izer concentration for obtaining fastest fusion time and lovest average horsepon-er consunipt,ion. Since a plasticizer concentratioii of approximntely 50 parts per 100 parts resin is commonly useful to the tratlc from the standpoint of imparting the desired physical propci'tic.s, it appears that the most suitable conditions are obtained with butyl benzyl phthalat,e, alkyl aryl phosphate, and cresyl dipliexi\-1phosphate. HIGHROTORSPEED. The use of high rotor speed (158 r.p,m.) reduces the fusion time with all plasticizers in relative proportion to the fusion times which existed at low rotor speed. Figure 9 illustrates the effect of various plasticizers and plasticizer concentrat,ion on fusion time a t high rotor speed. The plast'icizcrs xhich showed the shortest fusion time werc cresyl diphenyl phosphate, butyl benzyl phthalate, and the alkyl aryl phosphate. Lower plasticizer concentration of any one plasticizer yielded the lowest fusion time for that plasticizer.
OE 40
Figure 5 . Eflect of Various Plasticizers and Plasticizer Concentrations on Time to Reach Uniform Temperature
Except with the polyester-type plasticizer, a lover plasticizer concentration of any given plasticizer yielded a lower fusion time. In Figure 5 t,he effect of various plasticizers and plast'icizer concentration is plotted with reference to the time to reach a uniform temperature. In all cases, the plasticizers with the lowest fusion times as indicated in Figure 4 reached an average uniform temperature faster than those of long fusion times. The time to reach the uniform temperature is greater than the fusion timc, inasmuch as the time to reach a uniform temperature represents complete fusion of the batch, n-hereas the fusion time represents the initial fluxing time.
"
LOW ROTOR SPEED
a
3
a08 RPM.
2 L-~ _ ~ _ _ 0 IO 80 30 40 50 60 70 80 90 100 ID EO 130 140 150
FOSIOV TlislE I S E C O N D S I
L O W ROTOR SPEED)
3 7 Y
300 W
a I-
0:
L 250 4/0
20
30
40
50
60
70
80
90
100
FUSION TIME (SECONDS)
Figure 7.
" IW
E
/
LOW ROTOR SPEED (80.8 R.P.M.)
The relationship between fusion time and time to reach a uniform temperature is indicated in Figure 6. A straight line function is apparent for all plasticizers when utilized a t the same concentration. This is illustrated by the lines on Figure 6 for plasticizer concentrations of 40, 50, and 60 parts per 100 parts resin. The slope of the lines is approximately the same. The effect of various fusion times on power peak is indicated in Figure 7 (top). The lower the fusion time, the higher the power peak. For long fusion time plasticizers, the power peak is low
Fusion Time w. Power Peak
Figure 10 illustrates the relationship between fusion time and time to reach a uniform temperature at high rot,or speed. Straight line relationships are apparent for plasticizers of the same plasticizer concentration as indicated by the lines at 40, 50, and GO parts per 100 parts resin. A comparison is made in Figure 11 illustrat,ing the effect of high rotor speed and low rotor speed on the relationship existing between fusion time and time to reach a uniform temperature. In the case of the low rotor speed, a reduction in fusion time yields a greater saving in time to reach a uniform temperature than a corresponding reduction in fusion time when operating at, high rotor speed. High rotor speed operation produces greater average uniform batch temperature than operation a t low rotor speed. This effect along with the effect of fusion time on average uniform temperature is indicated in Figure 2 for several plasticizers. At high rotor speeds, lower average uniform temperature and faster fusion may be obtained with butyl benzyl phthalate, the alkyl
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1951
aryl phosphate, or cresyl diphenyl phosphate. At low rotor speeds, the average uniform temperature is approximately the same for different plasticizers a t the same concentration. The effect of Banbury rotor speed on power peak with relation t o various fusion times is indicated in Figure 13. High rotor speed requires more horsepower a t the power peak than a compound of corresponding fusion time requires a t low rotor speed. In all cases, as the fusion time decreases the power peak increases. The power peak increases less rapidly a t low rotor speed than a t high rotor speed. The average horsepower after fusion is higher with high rotor speed than with low rotor speed as illustrated in Figure 14. In
either case as the fusion time decreases the average horsepower after fusion increases. At either high or low rotor speed, cresyl diphenyl phosphate or butyl benzyl phthalate or the alkyl aryl phosphate produced a lower average horsepower for a given fusion time than tricresyl phosphate or dioctyl phthalate. Figure 15 indicates the optimal plasticizer concentration for fast fusion time and lowest average horsepower consumption after fusion with various plasticized compositions when operated a t high rotor speed. At the generally used plasticizer concentration of 50 parts per 100 parts resin, butyl benzyl phthalate and the alkyl aryl phosphate offer the most desirable properties. At only a slightly higher plasticizer concentration (54 parts per 100 parts resin) cresyl diphenyl phosphate offers a significantly lower aver-
LOW ROTOR SPEED 80.8 R.P.M.
v-
40 50 PLASTICIZER CONCENTRATION
30
1
HIGH ROTOR SPEED (158 WM.)
H I G H ROTOR SPEED
1 1
158 R . P . M
n
60
Figure 9. Effect of Various Plasticizers and Plasticizer Concentrations on Fusion Time
I
fOOP
141 / L \ 5 0 p ; q J
50 PHR PLASTICIZER
koJ 40 PHR
W
141 160
2 t
n
(PHR)
Figure 8. Optimum Plasticizer Concentration for Fastest Fusion Time and Lowest Average Horsepower Consumption rr
2409
/HIGH
/ 160
=,
SPEED (158 RRM.)
*141.DOP
80
/O
FUSION TIME (SECONDS)
Figure 10. Fusion Time us. Time to Reach Uniform Temperature
LL W
2 330
S 141
LL
a W I
S 160
_ _ - - - -- -
30
40
50 60 70 FUSION TIME (SECONDS)
80
Figure 11. Effect of Banbury Rotor Speed on Fusing Times
14
HIGH ROTOR SPEED (158 R P.M.)
L L '
20
9
13 12 II
10
9
Y a e 2
IO
20 30 40 50 60 70 80 90 100 ID I 20 I30 140 I50 160 170
FUSION TIME
(SECONDS)
Figure 12. Effect of Fusion Times and Banbury Rotor Speed on Average Uniform Temperature of Batch
7
3b
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 FUSION TIME (SECONDS)
Figure 13.
Effect of Banbury Rotor Speed on Power Peak
G CHEMISTRY
INDUSTRIAL AND ENGINPER1
Vol. 43, No. 10 I
s-141
L O N ROTOR SPEED (80.8 R.FIM.)
, i o 20 30 40 so
60 70
40 50 60 PLASTICIZER CONCENTRATION ( PWH)
eo eo
io0 110 120 FUSION TIME (SECONOS)
Figure 15. Optimum Plasticizer Concentration for Fastest Fusion Time and Lowest Average Horsepower Consump tion
Figure 14. Effect of Fusion Times and Banbnry Rotor Speed on ilverage Horsepower after Fusion
age horsepower and fusion time than either of the aforementioned materials. Effect of Fillers on Processing in Banbury Mixers. The effects of filler concentration on fusion times of various plasticizers are indicated in Figure 16. With either dioctyl phthalate or the alkyl aryl phosphate filler concentration in the region of 25 to 50 parts per 100 parts resin required longer fusion times than 10 parts. Filler concentration of 100 parts per 100 parts resin gave the lowest fusion time. Figure 17 illustrates the effect of filler concentration on time to reach a uniform batch temperature with various plasticizers. In the case of dioctyl phthalate, a longer time was required to reach a uniform temperature with 25 and 50 parts per 100 parts resin than with either 10 or 100. With the alkyl aryl phosphate, filler
concentrations up to 50 parts per 100 parts resin had no appreciable effect on varying the time to reach a uniform temperature. At 100 parts per 100 parts resin a shorter time 75-as required to reach a uniform temperature than with the other concentrations of filler. A straight line relationship between fusion time and time to reach a uniform temperature is apparent with the various concentrations of filler. This is illustrated in Figure 18. For both plasticizers tested, filler concentrations of 100 parts per 100 parts resin offered the lowest fusion time and the shortest time to reach a uniform temperature. w I-3
B W
5
L O W ROTOR S P E E D
50PHR P L A S T I C I Z E R CONSTANT VOLUME (IG~S~IU~CU?)
50 PHR PLASTICIZER LOW ROTOR SPEED CONSTANT VOLUME (1065435cu.')
360
pDOP.50 DOP.25
50p$2&/
100 FILLER PHR
'''!I
IOPt!R
Figure 16.
m
25PHR
50 PHR FILLER C O N C E N T R A T I O N
100 PHR
Effect of Fillers on Fusion Time of Various Plas ticizers
50
40 50 60 FUSION TIME (SECONDS)
70
80
t
50 PHR PLASTICIZER LOW ROTOR SPEED
100
a.
L
20
10 PHR FILLER
Figure 18. Relation between Fusion Time and Time to Reach Uniform Temperature with Various Concentrations of Filler
50 PHR PLASTICIZER LOW ROTOR SPEED CONSTANT VOLUME (1065-1 I35 CM! )
5
IO
141-100
80
3601
n
340 320
28 2
70 6o
50 40
W
30
z
3
240 w
220
!-
2oo
10PHR
25 PHR 50 PHR FILLER CONCENTRATION
Figure 17. Effect of Fillers on Time to Reach Uniform Temperature with Various Plasticizers
20
IO 0
PHR 0
0.5 1.0 LUBRICANT CONCENTRATION
2.0
3.0
Figure 19. Effect of Lubricant Concentration on Fusion Time
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1951
Effect of Lubricant Concentration on Banbury Mixing. As the lubricant (lead stearate) concentration was increased, the fusion time increased (Figure 19). At high lubricant concentrations of 2 to 3 parts, fusion time increased more rapidly with dioctyl phthalate than it did with the alkyl aryl phosphate. At a lubricant concentration of 3 parts per 100 parts resin, a fusion time of 103 seconds was obtained with dioctyl phthalate; however, 600 seconds were required for the batch temperature to build up to 305" F. and even after this condition of time and temperature, no fusion had occurred. I n the case of the alkyl aryl phosphate, however, no appreciable increase in fusion time occurred and the time to reach an average uniform temperature was 295 seconds with complete fusion occurring a t that time. These results indicate the higher compatibilizing action of the alkyl aryl phosphate plasticizer on poorly compatibIe ingredients. Effect of Plasticizer Blends on Banbury Mixing. Flexibilizing-type plasticizers when added to dioctyl phthalate or butyl benzyl phthalate increased the fusion time as illustrated in Figure 20. The butyl benzyl phthalate mixtures with these flexibilizingtype plasticizers fused faster than dioctyl phthalate mixtures. Plasticizer formulations typical of those used by the industry and their effects on fusion time are illustrated in Figure 21. In general, the fusion time of plasticizer blends is in proportion to the fusion times of the various plasticizers entering into the blend and is affected by the percentage concentration of each of these particular plasticizers. Typical trade formulations utilizing the alkyl aryl phosphate, butyl benzyl phthalate, or cresyl diphenyl phosphate are considerably faster in processing action than straight dioctyl phthalate.
241 1
of carefully considered plasticizer selection and operation procedures. To illustrate how greater production may be obtained through improved plasticizer formulation techniques, reference is made to formulations F-5 and F-14. If one assumes a plant Banbury can fuse 40 batches a day of formulation F-5 based on relative fusion times of F-5 versus F-14, it is indicated that 63 batches of F-14could be fused. This is calculated as follows: Fusion time of F-5 (85 sec.) X 40 batches = 63 batches F-14 Fusion time of F-14 (54 see.) 7C 6C
5c
;B
j
-B
%4c
YF
3c
fl
2c
IC
PLASTICIZER OR PLASTICIZER BLEND
Figure 20. Effect of Fatty Acid or Flexibilizing-Type Plasticizers Blended with Dioctyl Phthalate or Santicizer 160 on Fusion Time
REPRODUCIBILITY OF RESULTS
Since these plasticizers were studied not only over a range of plasticizer concentration, but also a t different rotor speeds and since the relative correlation was good in all cases, the trend of r e sults appears to be reliable and reproducible. While there was some slight variation in duplicate runs, this method of test served to substantiate the general trend of results. COiMPARISON OF LABORATORY BANBURY WITH PRODUCTION BANBURIES
The laboratory size B Banbury, except for its size and a few necessary simplifications, is practically the same as productiontype Banbury mixers ( 4 ) . The main differences between the laboratory B Banbury and the production size Banburies are with respect to rotor clearance t o the side wall and area exposed per pound of compound to the rotor blades. These differences often lead to a higher horsepower consumption per unit of compound for the small laboratory B Banbury than with large production units. The trade has established the following approximate relationship between data obtained in the laboratory B Banbury and that obtained in a production unit such as the 3A Banbury when the laboratory B Banbury is operated at a standard rotor speed of 119 r.p.m. Time cycle 3A Banbury
Time cycle laboratory B Banbury 0.6
These calculations assumed that tu11 Banbury time is used for compound fusion only. Actually, some time is lost for charging and discharging batches. I n these calculations, the lost time was taken as being negligible, which is not fully attained in practice, It is desirable to reduce power consumption without sacrificing Banbury production rates for economic reasons. In certain cases, it might be necessary to avoid exceeding peak power requirements on an over-all generating system or on the drive motor itself because of capacity limitations. If a Banbury is operating a t a high rotor speed, this may be accomplished by reducing to low rotor speed and adjusting the plasticizer formulation utiliz90 80
5 70 0 0
U
w60
L?. W
50
z
9
340 h.
30-
In a laboratory B Banbury 119 r.p.m. is equivalent in peripheral speed to 35 r.p.m. on a No. 3 Banbury; 22 r.p.m. on a No. 9 Banbury; and 20 r.p.m. on a No. 11Banbury. EXTRAPOLATION OF LABORATORY RESULTS TO TRADE PRACTICES
As a result of these laboratory studies, many possibilities are offered to increase plant efficiency either by producing more batches per day or producing greater quantities with lower power consumption and at lower batch temperatures through the means
2,
1 -0
8
Nc.12 P L A S T I C I Z E R OR P L A S T I C I Z E R FORMULATION NUMBER
Figure 21. Typical Trade Plasticizer Formulations and Their Effect on Fusion Time
ing fast fusion-type plasticizers so that the time cycle is not appreciably increased. For example, considering a composition similar to formulation F-29A at high rotor speed, the power peak required a t fusion time is 10 hp., the average horsepower is 8.2, and 135 seconds are required for the batch to reach a uniform temperature. If this same formulation is processed at a ION
2412
INDUSTRIAL AND ENGINEERING CHEMISTRY
rotor speed, the power peak would drop to approximately 5.2, the average horsepower to 4.9; but the time to reach a uniform temperature would increase t o 2G5 seconds. By utilizing a compound such as formulation 2, the fusion time is retained and the time to reach a uniform temperature, instead of being 265 seconds, is only 195 seconds. The power peak is 6.6 hp. with an average horsepower of 5.5, Thus, the power peak has been reduced from 10 to 6.6 hp., while maintaining substant,ially the original time cycle. Through considerations of fusion time or time to reach an average uniform temperature and horsepower consumption or power peak, optimal condit,ions exist if the plasticizer formulation is properly selected. When operating at a lo^ rotor speed and with fast processing formulations, proper selection of the fast fusion-type plasticizer will aid in reducing to some extent the power peak and the horsepower requirements (Figure 7, bottom). In t,he development of plasticizer formulations where it is necessary to add high concentrations of lubricant or flexibilizing plasticizers, it is advantageous to incorporate plasticizers oi IOK fusion time in order to maintain fast processing characteristics. Polyester plasticizers require the longest fusion time. In the development of formulations based on polyester-type plasticizers, it is useful to incorporate a fast fusion-t'ype plasticizer to reduce the time cycle of t,he plast'icizer blend. In most filled vinyl compositions, the concentration of filler ranges from 10 to 50 parts per 100 parts resin. As t'he filler concentration is increased within this range, a longer fusion time and time to reach a uniform temperat'ure are required (Figures 10 and 17). Fast fusion-type plasticizers will aid in counteracting these long time cycles. Heat stability of vinyl compounds is frequently a vital factor in production of these compounds, and it is desirable to utilize compositions which will process a t lower temperatures provided the time cycle is not increased. Thus, with fast fusion-type plasticizers, a lower rotor speed might be used with subsequent lovier average batch temperatures (Figure 12). EFFECT OF PL4STICIZER ON FUSION TIME
In Banbury operation, it v?-ouldappear that the tlvo factors primarily involved in affecting fusion are the solvent action of the plasticizer on the polymer and the rate of heat input into the mass. Internal friction imparted by the rotors is an important source of heat; but external heating is also a factor. Prior to testing, it was anticipated that the lower the plasticizer concentration, the longer would be the fusion time. It was also eypected that higher filler concentration would prolong fusion time. The reason for the more rapid fusion rates in the case where the plasticizer concentration was lowered or the filler increased to 100 parts is evidently attributable to the increase in friction of the stock. It is indicated, therefore, that the increased frictional effect offsets any decrease in solvent power. Based on considerations of thermodynamic theories of polyniersolvent interaction as treated by various authors (1,6) and considering the plasticizer as a solvent for the polymer, it might be expected that the fusion time would be related to the Huggins polymer-solvent interaction constant, ,u. Doty and Zable (8) have determined p values for plasticizers with polyvinyl chloiide at various elevated temperatures, There appears to be some correlation between p values and fusion time-that is, those plasticizers with p values greater than 0.4 yield long fusion times in a Banbury, whereas plasticizers of p values less than this are iastei in processing action. Several discrepancies are apparent, however, and it may be that these are influenced by the different irictional effects of various plasticized vinyl stocks in a Banbury. Doolittle ( 3 ) indicates that the temperature coefficient of solvent ability is influenced considerably by the shape of the solvent molecule. In this study, shape of the plasticizer molecule apparently exerts a pronounced effect. The more compact-shaped
Vol. 43, No. 10
plasticizers such as cresyl diphenyl phosphate, etc., exert a stronger fusion action and lower fusion time than extended molecules such as dioctyl phthalates, dioctyl adipates, or polyestertype plasticizers. Low melt viscosity or low viscosity of the plasticizers does not, exert a pronounced favorable effect on the fusion time in a Banbury mixer. It might be expected that a plasticizer of low viscosity which gives a low melt viscosity would favor rapid fusion. Correlation with this expectation was not achieved. The aryl phosphate, for example, has a higher viscosity than the dialkyl adipate or dialkyl phthalat'e, yet it processes faster. Electrical properties of a plasticizer or plast,icized vinyl stock do not show a good correlation with fusion time. It might be supposed that plasticizers possessing good electrical properties, being less polar compounds, would possess long fusion t'imes. There is no correlation to this theory, however. For example, both butyl benzyl phthalate and dioctgl phthalate possess good electrical properties (6) and are considerably different in their effect,on fusion time. CONCLUSIONS
Plasticizers exert a considerable effect on the fusion time of a vinyl compound when processed in a Banbury mixer. In general, the plasticizers studied may be broken down into five groups with respect to fusion ranges as follows: Group I. Plasticizers imparting very short fusion time@: cresyl diphenyl phosphate, butyl benzyl phthalate, and alkyl aryl phosphate. Group 11. Plasticizer imparting short fusion times : tricresyl phosphate. Group 111. Plasticizers imparting moderate fusion times: dioctyl phthalate, and partially hydrogenated aromatic hydrocarbon (HB-40). Group IV. Plasticizers imparting long fusion times: dioct,yl ester of polyethylene glycol, dioctyl adipate, and fatty acid esters (P-4, THFO). Group V. Plasticizer imparting very long fusion times: polyester type (Paraplex G-50). The type of plasticizer used also has an effect on the power peak and average horsepower required for Banbury operation. In general, the faster the fusion time the greater the horsepower requirement a t either high or low rotor speed. Through the proper balancing of plasticizer formulas, optimal fusion times and horsepower requirements can be developed. The data presented should be useful in working out these optimal formulat'ions for plant operations which should result in increased plant efficiency. ACKNOWLEDGMENT
The Farrel-Birmingham Co., Inc., is gratefully thanked for providing laboratory facilities and guidance in the operation oi the equipment. Particular acknowledgment is due Carl Brobeil and H. G. Breivster of this company for their generous assistance in performing this study and their aid in the translation of laboratory data to full-scale Banbury units. The authors arc a130 indebted to G. R. Buchanan, T. K. Smith, Jr., and P. Yesikmas of Monsanto Chemical Co. for their assistance in the test studies. LITERATURE CITED
(1) Boyer, R. F., J . A p p l i e d Phys., 20, 540 (1949). ( 2 ) Doolittle, A. K., IND. ENG.CHEM.,38, 535 (1946). (3) Doty, P., and Zable, H., J . Polymer Sci., 1, 90 (1946). (4) Farrel-Birmingham Co., Inc., Bull. 180 (1947). (5) Huggins, M. L., Ann. N . Y . A c a d . Sci., 43, 1 (1942). (6) Monsanto Chemical Co., "Monsanto Plasticizers," 1949.
(7) Oladko, A., Rubber Age, 65, 665 (September 1949).
RECEIVEDSeptember 14, 1950. Presented before the Division of P a i n t , Varnish, and Plastics Chemistry a t the 118th Meeting of the A M E R I C A N CHEMICAL SOCIETY, Chicago, Ill.
