November 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE
111.
2369
VAPOR PRESSURES O F SILICON COMPOUSDS
Temperature, _ C _ ~ ~___~___ 60 mm. 100 inm. 200 inm. 400 mni. 760 in1ii. 59.4 76.4 95.9 (116.8) 48.3 134 2 (178 6) (202.9) I55 2 120.1 115.2 135.2 157 6 (180.6) 101.7 87 5 108 I (130.4) 56.9 69.1 51.4 70.5 33.2 (6 5 ) (17 2 ) 274 8 (304.4) 246.8 222 2 205 9 37.8 20.4 56.0 (75.5) 9 1 58.4 41.5 77.9 30 4 (98.9) 117.7 99 2 (160 9) 138 8 86 8 (123.7) 81.3 63.1 51 . o 102.0 135.4 158.3 (182.3) 115 3 101.8 (250.3) 198,6 228.5 163.1 177.1 23.2 (10 9) 6.3 (-8.g) -18.7) (66.4) 29.3 47.3 13.5 (3.1) (201 . O ) 151.5 175.5 116 3 130 3 38.6 (57.3) ( - a 0) 5.3 20.9 14.6 (31.9) -25.8) ( - 1 6 . 2 ) (-1.8) 38.9 5.6 21.2 (57 6) (-4.7) 70.5 34.2 51.3 (90. B) 22.9 1160.5) 138.6 86.4 98.9 117.6 ~~
Compound .illyltrichlorosilane l3istrichlorosilylethane 1,2-Dichloroethyltrichlorosilane llietliyldichlorosilane l~imethyldichlorosilane Dio henyldic hlorosilane Etbyldichlorosilane Ethyltrichlorosilane Etliyltrietlioxysiiane
Formula 10 mm. 2~nim. CHz=CHCHzSiCla (16.1) (27.5) ClaSiCzHaSiCla 92,Y (77 7 ClCHzCHClSiCla (75.7) (21.0) (CZH5)zSiClz (33 7) ( -24,8) (-13.7) (CH3)zSlClz (158.4) ( 175.2) (CeHs zSiClz C2HadiHClz (-24.4) (-12 0) CZH~S~C~J (9.7) (-I.!) 63.4 (50.9) CzHaSi(OCzH5)a (28.1) (15.5) Ethylvinyldichlorosilane (CeH5) (CHz=CH SICIS -,-Chloropropyltrichlorosilane C H ~ C ~ C K ~ C H X S I ~ ~ ~(62.3) ’ (76 4) (123.0) Hexaethylcyclotrisiioxane (137.1) la (-47.1) (-36 9) LIethyldichlorosilane 1Iethyltriohlorosilane CHaSlCla (-16 5) (-27.3) (75.3) Phenyltrichlorosilane CoHsSiCls (89.8) Tctrachloroeilane Sic14 (-36.1) (-24.4) Triclilorosilane (-53,9) (-43.9) SiHCla Trimethylchlorosilane (-34.9) (CH43SiC1 ( - 21.2) CFII=CHSi Cla Vinyltric hlorosilane ( 10.7) (1.3) Vinyltriethoxysilane CHs=CHSi(OCzHs)a (49.4) (62 E) 0 Temperatiires in parentheses arc, abo\ e or below range of experiincntal value.
&$&El:
-
are within 1 1 . 0 mm., and a few deviations are as large as 8.8 niin. The ilntoine constants are given in Table 11, together with the normal boiling points derived from t,hese constants, and the boiling points of those compounds reported by others. The average deviation between our boiling points and those reported by S h l l (6) is 0.4” C., and for three of the compounds there is exact agreement. The boiling points a t pressures of 10, 20, 40, 60, 100, 200, 400, and 760 mm. of mercury are given in Table 111. All these boiling points were derived from the equations; those in parentheses are above or below the range of the experimental data.
Tiw author? wish to aclrnoirledgr the work of H. C. Givens
(:;,E?
(-1.4) 194 0 (0.8)
(22.3) 77 7 (42.1) 91.9 (152.9) ( - 25 . 5 ) (-4.6) 105.9
(-12.6)
(-32.9) (- 12,3) 14.5 77 2
and E. R. York in the purification of the samples used in these measurements. LITER4TURE CITED
(1) Booth, H. S., and Carnell, P. H., J . Am. Chem. Soc., 68, 2G50 (2)
(3) (4)
(5)
(6) (7) (8)
ACKNOU IXDGVlhUT
40 mm. (40. 1) 109.6
(1946). Booth, H. S., and Slartin, TV. F.. Ibid., 68, 2655 (1946). Booth, H. S., and Suttle, J. F.,Ihld.. 68, 2658 (1948). Osborne, K.S., and Myers, C . IS., J . Research Natl. Bur. Staizdards, 13 (1934) (Research Paper 891). Smith, A., and IUenzies, A. W.C., J . Am. Chem. Soc., 32, 1412 (1910). Stull, D. R., IND.ENG.CHEW,39, 517 (1947). Thomson, G. TV., Chem. Revs.. 38, 1 (1946). Thomson, G. W., “Physical Methods of Organic Cheniistry.” A. Weissberger, ed., 1-01. 1, Interscience, New York. 1949.
RECEIVED for review March 22, 19.54.
ACCEPTEDJuly 27, 1964.
Flow Properties of Vinyl Chloride Resin Plastisols E. T. SEVERS AND J. $1. AUSTIN Mellon Institute of Industrial Research, Pittsburgh 13, Pa.
0
XE of the best examples of the application of rheology to
industrial problems is found in the development of organic dispersions of vinyl chloride resins. Previous investigators (7-9, 15) have stressed the importance of flow properties in the formulation, manufacture, and application of these dispersions. Plastisols are fluid dispersions of vinyl chloride resin in plasticizer to which desired quantities of pigments, filler, and stabilizers have been added. Plastisols are converted to elastonleric compounds by heating to the point where the resin is solvated by the plasticizer and fused to a homogeneous product. The successful use of vinyl chloride resin plastisols demands a knowlrdge of the flow properties a t the rates of shear encountered during application. High speed roll and knife coating of cloth or paper and die coating of wire or tape subject plastisols to high rates of shear. Even processes such as slush molding and dip coating, ordinarily involving low ratcs of shear, may require pumping of plastisols a t relatively high rates of shear to replenish dip tanks and provide circulation. Mixing operations using roller mills or high energy input mixers will subject the plastisols to high shear stresses.
Flow properties have been measured by rotational viscometers and viscosity cups. Rotational viscometers, however, become quite elaborate when designed for high rates of shear, arid frictional heat buildup becomes serious. Viscosity cups, where the material flows through an orifice under its own head, are limited to measurements a t relatively low rates of shear. Furthermore, irregularly shaped or short orifices make difficult a fundainental analysis of flow data so obtained. An extrusion rheometer is Rssentially a pressurized viscosity cup with a cylindrical orifice. but it is capable of measuring viscosities a t high as well as low rates of shear. The instrument is rugged enough for production control, yet capable of yielding fundamental data. This instrument was used extensively in the present investigation to determine the effect of plasticizer composition and concentration and aging conditions on the flow properties of plastisols. One of the earliest extrusion rheometers put to practical use was the “grease gun” type which Barus ( 2 ) used for investigating marine pitches. Bingham (3) devised a gas-actuated capillary viscometer for measuring the viscosity of a variety of substances
2370
INDUSTRIAL AND ENGINEERING CHEMISTRY
Dillon and Johnson (4)used a piston type to evalua,te the flow Spencer and Dilproperties of unvulcanized rubber. Sason (j), lon (fi),and Severs ( I S ) have used gas-actuated rheometers for studying molten polymers. Slves, Boucher, and Pigford (1j have correlated dam a t rates of shear below 100 sec.-~lfrom an extrusion rheometer, a Brookfield viscometer, and a Irfacllichael viscometer on h-apalm solution, cellulose acetate solution, and lime slurry. These investigators estended the rate of shear measurements to as high R S 10,000 see.-' using an extrusion rheometer.
Vol. 46, No. 11
It was possible to determine flow curves on as many as eight plastisols per hour with six data points per plastisol. A commercial version of this rheometer is made by the CaYtor Laboratory Equipment Co., Carnegie, Pa. The obeerved data were pressure or hydraulic head, efflux weight, efflux time, and density. Rates of shear and shear stress were obtained by applying Poiseuille's law (6): Q =
rPR4 8Ln
01
I
RESERVOIR PRESSURE
3-WAY VALVE
'' '' -.
I
~
7i-B
--
2L
,RESERVOIR
=
an average rate of shear equal to rate of shear a t wall for Xewtonian liquid
= shear stress a t wall
This equation assumes Sewtonian flow; however, a plot of
PR./2L versus 4Q/rR3is a unique function for a non-Scutoniarr material. The rate of shear was calculated from the efflux weight and time as follows: 4 IV ___
PRESSURE su PPLY
'ORIFICE Figtire 1. Schematic Diagram of Extrusion Rheometer
The aforementioned extrusion rheometers were designed as research tools with little regard for the rapid manipulation required of a control instrument. The estrusion rheometer used in the present investigation was designed for ease of manipulation and cleaning. A schematic diagram of t8heinstrument is shown in Figure 1 and a photograph in Figure 2. ThP heart of the rheometer is the orifice. Several orifices constructed from drawn tubing were used. The length of each orifice was determined by a micrometer and the average diameter calculated by mercury volume. The dimensions of the orifices were as follows: seminal size, Inches 1i4 x 2 '/a x 4 1/4 x 8
Jllensions of Length
5.08 10.16 21).32
rR3pB
The rate of shear at the wall for a non-Newtonian material was obtained by using the relationship of Rabinowitsch (IO)
where c
=z
4Q d log TR -__ PR d log 2L
Orifices, Cm. Diameter 0.648 0.655 0.640
The orifice was fastened to the bottom of the fluid reservoir b y a hand-tightened cap. Another cap on reservoir top held the pressure supply in place. Gas pressure in the reservoir was measured by a calibrated gage: controlled by a pressure regulator and started and stopped b y a three-way valve that also vented the reservoir. Gas pressure was supplied by compressed air or nitrogen. An auxiliary gage measured the line pressure. Measurements of flov properties were made as follow: The orifice was closed with a at,opper and the reservoir filled with a plastisol. The height of the plastisol in the reservoir was measured. This was used to calculate the hydraulic pressure to correct the measured pressure where necessary. Khere measuremenk 11-ere desired a t low pre ures, the stopper was removed and approximately 25 mi. of pl tisol ivas collected in a k e d container during the timed interval. lleasurements at, other pressures were made by faskning the pressure cap on the reservoir and adjusting the pressure while stoppering the orifice. Again a sample was collected during a timed interval ani3 weighed. A series of measurements was made at, pressures up t o 80 pounds per square inch. Cleaning was accomplished eesily by removing the caps froin the reservoir and forcing out the remaining plastisol with a plunger. The orifices were clenried with xylene and pipe cleaners.
Figure 2.
Extrusion Rheometer
Plastiwl 18 beiug e-rtrudcdfrom reservoir thrnugki orifice under prr-kurc
November 1954
INDUSTRIAL AND ENGINEERING Flow Rate, em? per sec.
0.I
237 1
The Martinson Coater is a hand-operated knife coater used to prepare films on paper, foil, or cloth. A carriage moves on horizontal tracks under a fixed knife; the top of the carriage is a plane which supports the material to be coated. I n order to use the coater and obtain flow data, modifications were made as shown in Figure 4. A pulley was arranged for moving the carriage by a falling weight instead of by hand. The curved knife was inverted so that the flat top of the knife formed a plan? parallel to the carriage top. The tracks were smoothed with a polishing abrasive and lubricated with a polyethylene glycol lubricant (Ucon 50 HB 5100, Union Carbide and Carbon Corp.). Trials a i t h lighter oils were unsuccessful because of breakdown of the oil film on the tracks. The coater was calibrated and a plot made of velocity versus weight. Coatings were spread on aluminum foil by moving the carriage under the knife. The elapsed time for a fmed distance of carriage travel gave the velocity. Each weight was corrected by subtracting the weight required to move the carriage at the same velocity without coating. The clearance between the foil and knife was 0.025 am., the width of the knife was 1.19 om., and the length was 22.2 cm. The rate of shear and shear stress were calculated from the equation for two parallel planes:
1.0
I
CHEMISTRY
I(
0
F_ -
1’
ii
1 --)7
oc wherr - =
shear stress
’
an average rate of shear equal to rate of shear foi a
9
- =
Figure 3.
Effect of Orifice Length on Flow Data
Composition of plastisol, aged one day Vinyl chloride resin
LE (2-ethylhexy1)phthalate
Parts by Weight 100
60
Orifice Dimensions
3 A
L, cm.
D, cm.
5.08 10.16 20.32
0.645 0.655 0.640
L/D 7.9
15.5
31.7
The transit time or the average time for a particle to pass through the orifice is
h
Xewtonian liquid
The extrusion rheometer is used to evaluate the dilatancy of plastisols used in high speed coatings. Most of the comparisons are by empirical correlations since irregular-shaped knives and cylindrical rolls make difficult the analysis of the rate of shear. The maximum rate of shear may be estimated from the clearance and coating weight, and the performance in production may be compared with flow data obtained using the extrusion rheometer. COATING-,
,--KNIFE
L sD
__ .LQ
LTRACK
7rR3 Apparent viscosities were calculated as follows:
PR/2L 7=4&lrrR3
Thioxotropic materials will exhibit lower viscosities when passing through longer orifices since they are subjected to shear stress for a longer period ( I S ) . I n order to determine the effect of lengthto-diameter ratio ( L : D )the f l o ~properties of a vinyl chloride resin plastisol were measured with three orifices of approximately the same diameter but different lengths (Figure 3). Plots of pressure drop versus flow rates produced three parallel curves, but plots of shear stress a t the wall ( P R I 2 L )versus rate of shear 4QIrR3, produccd a single curve, indicating no thixotropy in this plastisol in the transit timer covered by the experiment. L:D 7.9 15.5 31.7
Transit Time, sec., at Rate of Shear of -___ 4 see. -* 160 sec. - 1 15.8 31.0 63.4
0.42 0.82 1.68
This indicates that the time for thixotropic breakdown is either shorter than 0.42 second or longer than 63.4 seconds.
4
WEIGHT
LA
Figure 4. Schematic Diagram of Modified Martinson coater
A direct comparison was obtained by comparing flon data from the rheometer with flow data from the modified Martinson coater. A viscous plastisol was used to increase the pulling weight, decrease the carriage velocity, and minimize the correction for track friction. The flow data obtained by the two methods are compaiecl in Figure 5. The flow curves are not too divergent when it is considered that they are compared in a region of high dilatancy where there is insufficient plasticizer to lubricate the flowing particles. Chattering, as evidenced by waves on the film parallel to the knife, did not occur until 22 see.-’. This was surprising
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
2372
skipped-\
Shear Stress
Vol. 46, No. 11
viscosity of the plastisol a t high shear st,ress. Slush molding or clip coating involves low shear stresses, and the viscosity under these conditions must be known. Storage time and conditions may affect the flow propel hence the choice of a plasticizer. A plastisol used with hours after preparation may be entirely satisfactory, but shipment of the same plastisol t o a distant point or st,orage a t elevatod temperatures may result in a radical change in viscosity. Thc resistance of a plastisol to changes in viscosity with timc ari.1 storage temperature (viscosity st,ahilitg) is largely dependcnt o n the plasticizer. The viscosity of thc plasticizer is an important factor and Polyell, Mullen, and associates ( 7 ) have s h o v n that with plssticizers of the same affinity for the resin, the viscosity of the plar;tisol is proportional t o the viscosity of the plasticizer if the conccritration is on a volume basis. s may be obtained n-ith the use of a balaricoil in the samc manner as Powell, QuBrles, an.1 associates (8)have used for organosols. Mixtures of plasticizer3 having strong and weak affinities may produce lower viscositiez and better stability than either of the components alone. S-iirious plasticizers were cornpared in plastisols in a weig!it ratio of GO parts of plitsticizer to 100 parts of vinyl chloride resin. The resin used, Bakelite vinyl resin QYKV, had the folloa-in@ properties: Vinvl chloride 75 Ifeating loss ( i s min. a t 1155 % Specific viscosity, 0.2 gram'100 ml. nitrobenzene at 20' C .
c.),
IO
I
Rate of Shear, sec-' Figure 5. Comparison of Flow Data Obtained with Extrusion Rheometer and 3Iartinson Coa ter Compositiou of plastisol Parts by Weight Vin,l chloride resin 100 Di ( 2 - e t h ~ l l i e \ ~ l ) ~ h t h a l a ~ e 55 Orifice, '12 X 2 inches Hun I
Run 2
9
-
w
V
Instrument Rheometer Coater
Shear Stress
PR/2L
F/ '4
Rate of Shear (du/dr)u z
'h
since dilatancy started at 5 s w - 1 , where slope of the flow curve esceeded unity. A t 40 see.-', the foil had bare spots or arcas where the coating had slripped. Sirice evidences of dilat,ancj- in the films did not occur until far beyond the occurrence of dilatancy in tmhcflow curve, it appears tha,t not, only t,he surface but a major portion of the film thickness must be in the dilatant region before dilatancy becomes apparent. The plasticizer is the liquid phase of a vinyl chloride resin plastisol and as such requires careful selection. A plasticizer ic h o ~ c nwith two objecti irs contribution to the propcrties of the fused plastisol film : its effect on the flow propertie. of tlie unfused plastisol. The film properties required are determined by the end uqe of the plastisol. Volat,ility, extractibility, efficiency a t the erature of use, electrical characteristics, and compatibility m e of the important properties affecting the performance of the plasticizer and plastisol films. There are considerable data on tlie performance o€ plastisols in vinyl chloride resin calendered Elms (11, 1.2); these can be used to estimate the performance of a plesticizer in a plastisol film. The present study has becn restricted t o the flow properties of plastisols in the unfused st,ate. The process used in applying the plastisol determines the flow properties required. It is important that these he determined 3t the proper shear rnte since the flov; is not Newtonian. High speed roller coating or knifr coating demands a knowledge of the
98.9 0.3,: 0 2!1ij
The plastisols were prepared by pony mixing tor 10 minuto,poor init hiah ratio, such of the resin by the plasticizer ip indicated. as s h o r n by dihesyl phthalatc, shows poor stability as n consc-quence of excessive solvency. Those ratios, which arc' very c!oic. to unity, characterize good stability rrhen initial cquilihriuni h . 4 heen established. The values of the stabilit? raztio or iiiticx arr lower for the measurements a t high shear stress than a t low shear. This i, helieved t o bc a result, of a weak structure formed lx:twec>ri reiin particles which contributes thixotropic and pscucloplactii~ flow characteristics t,o plastkols as the structure is destroyctl by stronger shearing forces. The effect of the chemical structure of the plasticizer on t,he viscosity of plastisols may be observed-that is, the effect of chain branching and aromatic character of the components, which are noted in the follon-ing data abstracted from the tahles:
November 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE I. VISCOSITYOF PLASTISOLS Apparent Viscosity a t Indioated Shear Stress (Plasticizer 60 Parts/100 Parts Resin), Poises Ratio, 0.159 Lb./sq. inch:;;;:3; 2.23 Lb./sq. inch 30 days: Initial 30 Days initial Initial 30 Days Initial Adipates Didecyl adipate Di(2-ethy1hexyl)adipate (Flexol plasticizer A-26) Diisobutyl adipate Diisooctyl adipate Mixed n-octyl-n-deoyl adipate (Hercoflex 290) Octyldecyl adipate (Adipol ODY) Azelates Di (2-ethylbutyl)azelate Di(2-ethylhexy1)azelate Diisooctyl arelate Benzoates Diethylene glycol dihenzoate (Flexol plasticizer 2GB) Citrates Acetyl tributyl citrate ricetyl triethyl citrate Octoates Z,Z’-(Z-ethylhexamido) diethyl di(2-ethylhesoate) (Flexol plasticizer 8N8) Polyethylene glycol di(2-ethylliesoate) (Flexol plasticizer 4GO) Oleates Tetrahydrofurfuryloleate Pelargonates Diethylene glycol dipelargonate Phosphates Diphenyl(2-ethylhexyI) phosphate Tricresyl phosphate Tri(2-ethylhexyl) phosphate (Flexol plasticizer TOF) Phthalates Butyl cyclohexyl phthalate Dibutyl phthalate Dibutyl cellosolve phthalate Dicapryl phthalate Di(:;eJhylhexyl) phthalate (Flexol plasticizer
bur!
Dideoyl ph thalate Dihexvl o h thalate (Flexol plasticizer D H P ) Dii sodctizl phthalate Di- n-octyl phthalate Diitlkyl phthalate (Staflex MP) Mi, . ..,xed isooctyl-n-octyl-n-decyl phthalate (Hercoflex 250) Mixed n-octyl-n-deoyl-phthalate (Herooflex 150) Hydrophthalates Di(2-ethylhexyl) tetrahydrophthalate (Flexol plasticizer 8HP) Di(2-ethylhexyl) hexahydrophthalate (Flex01 plasticizer CC-55) Ricinoleates Butyl acetyl polyricinoleate Methyl acetyl ricinoleate Methyl cellosolve acetyl ricinoleate Isobutyl acetyl ricinoleate Aebacates Dibutyl sebacate Dioctyl sebacate Miscellaneous Tetrabutyl thiodisuccinate (Flexol plasticizer TWS) Butyl polyacetoxy f a t t v acid ester (Estonox 206) Polyester (Flesol plastl’ciaer R2H) Polyester (Glypta12557) Polymeric (Plastolein 9720) ( D P 250) (Paiaplex G-60) (Paragleu G-62) Aromatic hydrocarbon (Sovaloid C ) (Stafles KA)
133
122
0.92
46 78 457 ru’oflow 72 67 58 67 55 58
0.93 1,15 1.05
56 109 129
95 158 100
1.70 1.45 0.78
5,800
5,500
0.95
305 3,315
336 5,250
1.10 1.59
377
452
1.20
129
136
1.05
56
67
1.20
84
92
1.10
630 1,780
1,64R 1,450
2 61 0.82
54
149
2 78
4,790 10,000 262 275
2.39 15.0 1.35 1.23
393 525 733
2,!;? 00.3
194 223
1.69
.
.
224 500 197 222 125 365
250 275
ai6
1.75 LO5 3.72 1.42 2.00 0.73
183 169
305 314
1.67 1.86
155
200
1.41
131
152
1.16
139 84 158 197
167 114 216 229
1.20 1.37 1.37 1.16
93 98
130 99
1.41 1.01
228 480
382 525
1.67 1.09
1 , 7 1 5 2,190 1,104 972 1,090 1,570 808 9 10 2,620 2,500 2,040 6,100 11,500 11,500
1.27 0.88 1.44 0,89 0.95 3.04 1.00
2373 chain of the alcohol residue Kith a continuous chain, as in di-n-octylphthalate, or saturating two double bonds in the phthalic acid residue, as in
di(2-ethylhexy1)tetrahydro-
phthalate, reduced the visc o s i t y of t h e p l a s t i s o l s . 178 101 1.07 312 2,265 7.30 , Eliminating the aromatic char325 257 0.79 acter of the phthalic acid 203 160 0.78 208 134 0.64 residue by saturating all three double bonds, as in di(2177 272 1.54 253 0.86 296 e t hy1 hexy1)hexahydrophthal280 0.75 375 ate, resulted in a further decrease in the viscosity of the 55,000 61,500 1.12 plastisols. Part of the decrease in viscosity of the plastisols 3,400 3,820 1.12 32,800 53,000 1.62 was due to a decrease in viscosity of the plasticizer. Di(22,385 2,422 1.02 ethylhexy1)phthalate was approximately twice a5 viscous as 683 704 1.03 d i ( 2 - e t h y 1hexy1)hexahydro255 217 0.85 phthalate of di-n-octyl phthalate, and this difference was 400 300 0.75 reflected in the viscosities of 1,805 3,400 1 88 the plastisols. However, the 13,700 15,400 1.13 latter two plasticizers, have ap139 253 1 82 proximately the same viscosity, did not produce plastisols hav0,510 15,600 2.40 1,230 4,100 3.33 ing the same viscosity since 687 1,510 2.20 other factors such as solvation 1,425 1,610 1.13 were operating. 1,245 1,800 1.45 3,280 3,140 0.96 The effect of increasing chain 1.91 910 1,740 length of the alcohol was ob1,410 1,780 1.26 667 875 1.31 served by noting the viscosity 1,540 1,470 0.96 increases shown in the tabula935 1,000 1.07 tion below 770 810 1.05 The viscosity of the plastisols decreased as the number of car1,305 1,425 1.09 bon atoms in the alcoholic por617 642 1.06 tion of the ester increased from four to eight. The contribu499 630 1.26 327 368 1.13 tion of the phthalate radical to 828 1,380 1.66 1,340 1,470 1.09 solvation of the resin was apparent in the 15-fold increase 188 206 1.10 in low shear viscosity of the 610 642 1.05 p l a s t is01 containing dibutyl phthalate as shown in Table I. 2,650 2,430 0.92 1,640 Mixtures of plasticizers may 1,750 1.07 be used in plastisols for a 8,550 7,150 0.84 5,200 5,700 1.10 number of reasons. Polymeric 35,000 27,500 1.30 4,680 5,000 plasticizers may be mixed with 1.07 17,700 15,900 0.90 monomeric plasticizers to com12,000 24,100 2.01 114,000 114,000 1.00 bine the low migration and low volatility of the former with the fluidity and plast i c i zi n g e f f i c i e n c y of t 11e latter. Plasticizer extenders having poor compatibility may be combined with plasticizers having good conipatibility to produce a compatible product. Other plasticizers may be mixed to obtain film properties, flow properties, and fusion characteristics intermediate between those imparted by the individual plasticizers. 770
685
0.89
~
Plasticize1 Di (2-ethylhexyl) phthalate Diisooctyl phthalate Di((2-ethylhexgl)tetrahydrophthalate Di-n-octyl phthalate Di(2-ethylhexyl) hexahydrophthalate
Viscosity, Poises, after 30 Days’ Aging Low shear High shear 393 1800 316 1780 220 2 60
1425 875
152
642
The first two esters listed were derivatives of branched-chain eight-carbon alcohols and an aromatic acid. Although the length and position of the branched chain were different, the viscosity effects of the esters were about the same. Replacing the branched
Plasticizer Dibutyl phthalate Di-n-hexyl phthalate Di-n-octyl phthalate
Viscosity after 30 Days’ Aging, Poises Low shear High s h e a r 10,000 4100 733 1740 250 875
I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y
2374
Flexol plasticizer D O P DCHP Flexol plasticizer CC-55 Halowax 4004 HB-40 Paraplex G-25 Paraplex G-60 Plastolein 5720 Flexol plasticizer R 2 H Eanticizer 141 TCP Flexol plasticize1 TbF
Flex01 DOP/FlexolRZH (90/10) Flexol DOP/Flexol R 2 H (80/20) rlexol DOP/Flexol R 2 H :70/30) Flexol DOP/IIB-40 (90110) Flexol DOP/HB-40 ( 8 0 / 2 0 ) Flexol DOP/HB-40 (70/30) Flexol DOP/Soraloid-C (90/10: Flexol DOP/Sovaloid-C (80/20! Flexol DOP/Sovaloid-C (70/30: rlexol D O P / T C P (90/10) Flexol D O P / T C P t 8 0 / 2 0 ) Flexol DOP/Halowax 4004 (90/10) 1 lexol DOP/Halowau 4004 (80/20) Flexol D O P / D C H P (90/10) Flexol D O P / D O H P (80/20) Flexol DOP/Halowax 4003 (90/10) Flexol DOP/Flexol TOF (70130) Flexol DOP/Santicizer 141 (70/30) Flexol DOP/Paraplex G-25 (90/10) Flexol DOP/Paraplex G-25 ( 8 0 1 2 0 ) Flexol DOP/Paraplex G-60 (70/30) Flexol DOP/Plastolein 9720 (70/30) Flexol DOP/Flexol CC-55(70/30) F l e d DOP/Flexol CC-:5(60/50) Flex01 DOP/Flexol CC-55(30/70) Plexol CC-551Flexol R2H (B0/10> Flexol CC-65/Flexol R 2 H (80/203 Flexol CC-BS/F'lexol R 2 H (70,'30) Flex01 CC-55/HB-40 (90/10) Flexol CC-55/HB-40 (80./201 Flexol CC-.j5/IiB-40 (70130) rlexol CC-55/Sovaloid-C (90/10) Flexol CC-55/Sovaloid-C (80/20) Flexol CC-56/Sovaloid-C (70/30) Flexol CC-55iTCP (90!1Oj Flexol CC-65/TCP (80/20> Flexol CC-56/Halowax 4004 (90/10) Flexol CC-55/Halorvax 4004 ( 8 0 / 2 0 ) Flexol CC-55/DCHP (90/10) Flexol CC-ZB/DCHP (80120) Flexol CC-55/Haloaas 41103 (90/10) Flexol CC-55/Flex?l,TOF (70/'30) Flerol CC45/Santicieer 111 (70/30) Flexol CC-jS/Paraplex G-25 (90/10) Flexol CC-55/Paraplex G-25 (80120) Flexol CC-55/Paraplex G-60 (70/30) Flesol CC-S5/Plastolein 9720 (70/30)
pounds per s uare inch shear x 2 inch stress using t i e orifice. The higlier plasticizer concenbration as uswl t o rcd u c e i n t e r a c t i o n bet,n.ecii swollen resin pwticlcs ~ r i t lto simulate concentrations used in ninny slush moldiiig. dipping,
Di :2-ethylhexyl)phthalate Dicyclohexylphthalate Di $2-ethylhexyl) hesahydrophthalate Clilorinawd paraffin broinatic hydrocarbon ( h l o n s a n t o ) Polyester Epoxy compound Polymeric Polyester L)i?lienyl(2-ethylhexyl)phosphate Tricresyl phosphate Tri(2-ethplhexyl) phosphate
Table ITT.
The severity of thc test was indicated by the large number of plastisols marked ' h o flow." This designation was applied t,o those plastisols which ~ ~ o u i t l uot flow from the quart container a t TO" F. under their on-n iveight. Gencrally, these had the consistency of fiini putty. However, those materials which, despite t,heir high apparent viscosity, could be transferred t o thc extrusion rheometer reservoir by vacuum irere examined. I n nearly all cases, thc viscosity dccreascd with increase in shear stress, iiidicatiiig plastic or pseudoplastic flow. Of the three phosphates teated, tri(2-ethylhexy1)phosphate was the only one that remained fluid. The other two phosphates having a r o m a t i c groups in their molecules 801vated the resin t o the point of gelation. The pht,halic esters of lower boilirig alcohols, such as butyl and hexyl, gelled the resin; Lvliereas those esters prepared I'rorn higher alcohols formed plastisols that were itill fluid after the heat aging. The same n-a,strue of the adipates. -1. more extensive series of tests TVRB conducted on plastisols prepared with di(2-ethylhexyl jhesa h y d r o p h t h a l a t e which had shown reasonably good aging stability in the previous tests. Plastisols were prepared at t'hree eoncentrations of plasticizer, Portions of each were heated 2 hours a t 180" F. and then aged 14 days at 70" P. The remaining portion was aged for the same length of time without any heating. Viscosity determinations were made on the heated and unheated plastisols a t '70" F. using the extrusion rheomcter.
hpparent Viscosity a t Indicated Shear Stress, Poises - . Ratio. Katio, 0.l:Q Lb /sa. inch 2 2 3_ Lh /sq. 30 days: _ _ inch _ ~30 days: . ~Initial Initial 30 DaysI Initial Initial 30 Days 1 61 315 440 1.40 2170 3500 1.03 550 786 1.43 $280 4400 1.25) 786 1 . 3 li 3850 4970 579 1.24 324 393 1.21 1710 2119 1.47 269 I .46 1453 2140 400 1 11 1 . 2 5 3500 315 386 3150 290 1 38 1.65 256; 478 4050 1.R1 393 688 1.75 3205 5925 734 1.80 4050 6400 1 , .58 407 275 440 1.00 2700 1 36 3076 1.41 297 1.37 2650 3750 407 21i0 1,36 385 478 2515 1,li 1.24 4.10 2315 1 li 355 2700 2300 393 579 1.47 1.38 3070 524 845 1.61 3203 1.46 4075 440 1 10 478 1.09 2370 2605 250 1.32 1325 183 I .37 1750 1675 239 324 1.48 1.35 2480 734 918 1.25 2750 3420 1.34 1375 1835 1.33 4810 5500 1.14 1855 393 458 1.16 2315 1.25 580 1.18 2658 478 1.15 3110 223 321 1.44 1850 1.30 2560 229 1.30 297 1900 2520 1.33 202 1765 1.38 275 1.36 2410 229 275 1.20 1480 1 06 1540 ,'i 53 393 1.11 1775 2050 1 05 .373 1.04 ,100 2575 2850 1.:0 204 1.22 970 1.24 167 1200 224 1.19 189 1165 1478 1.28 230 1.51 2490 379 1.48 3675 163 236 1.40 1720 2445 1.42 234 334 1.43 2030 1,65 3350 350 323 1.70 3350 5300 1 68 101 1.16 167 1275 1735 1 ,R l i 240 1.32 18Y 1695 2200 1.30 249 275 1.11 1350 1x25 1 13 366 458 1 25 3420 4160 1.22 225 22a 1.02 1875 2000 1.06 421 239 1.77 2230 2850 1 28 1 ,56 229 355 1495 1736 1.06 141 1.40 101 782 910 1.00 223 1.42 139 1150 1455 1 27 ,524 379 1.38 2775 3425 1.21 1.20 915 1100 4075 5925 1.27 !?E8 3!31 1.17 1610 1736 1.08 1.00 315 314 1760 1925 1.10 -~ -
Plasticizers and Ratio (60 Parts/100 Parts Resin Plastisols)
Vol. 46, No. 11
The flow properties of a series of plastisols prepared with mixed plasticizers are shorvn by Table 11. The phstisols were prepared and tested in the same inannor as t,he plastisols coiitaining single plasticizers. I n general, the flow properties of the mixtures were intermediate between those produced by the individual components. The mixtures with di(2-ethylhexy1)hexahydrophthalate mere more fluid than the corresponding mixtures with di(2-ethylhexyl) phthalate; hon-ever, increasing proportions of H B I O with the phthalate did not increase the plastisol viscosity at low shear as was the case with the hexahydrophthalate. The mixtures with the hesahydrophthalate were generally more stable with time than mixtures with the phthalate. Storage stability of a plastisol can be a consideration of prime importance. Drums of compounded material may stand in hot Bunlight or be subjected to extremes of heat in a dip tank. As a test of t,he solvation of resin by plasticizer at an elevated temperature, plastisols containing equal weights of resin and plasticizer were stored a t 150' F. for 16 hours, and viscosity of the gelled plastisol was measured at, ioo F. under 0.159 and 2.23
Apparent Viscosity at Indicated S ~ i c i i : Stress, Poises .. -
Concn. of
Dii2-ethylhexyl) hexahydrophthalate Parts/100 Parts Resin
70 80 90
~
O.l!h./
Initial I.OIb./ srL. inch
s q . inch
14 days' aging __ O.Ilb./ 10lh.l
sq. i n c h
sq inch
Plastisols not heat aged at 70' F 35 200 100 18 66 445 1%
22
230 62.7
27.:
Plastisols heated 2 hours et 180' F., aged at 70' 70 1,000 650 17 000 80 195 108 1'10 90 51 38 72
27.5
r 800 201 55
The unheated plastisols exhibited dilatancy at low plasticizer concentrations as indicated by the increase in viscoqitv with
INDUSTRIAL AND ENGINEERING CHEMISTRY
November 1954
TABLE 111. VISCOSITYOF PIASTISOLS (Aged
a t 150’ P.) Apparent Viscosity a t Indicated Shear Stress (Plasticizer 100 Parts/100 Parts Resin), Poises 0 159 Lb./sq.inch 2 . 2 3 Lb./sq. inch
l(i hours
5 5
Diisooctyl adipate Mixed n-octyl-n-decyl adipate (Hercoflex 290) Octyldecyl adipate :.\dip01 ODY) Aaelates Di(2-ethylbutyl) azelate Di(2-ethylhexyl) azelate Diisoocryl azelate Benzoates Diethylene glycol dibeneoate (Flexol plasticizer 2GB) Citrates Acetyl tributyl citrate Acetyl tricthyl citrate Octoates 2,2’-(2-ethylhexamido) diethyl di(2-ethylhexoate) (Flexol placticizer 8N8) Polyethylene glycol di(2-ethylhexoate) (Flesol plasticizer 400) Oleates Tetrahydrofurfuryl oleate Pelargonates Diethylene glycol dipelargonate
13 No flow 16 21 19
8.1
N o flow 8.1 7.9 7.8
353 26 25
110
No flow
No flow
No flow No flow
N o flow
1,370
550
4,2
9.1
x0 aor\.
21
16.5
17
11
48
25
No flow N o flow
575 Phthalates Butyl cyclohexyl phthalate Dibutyl phthalate Dibutyl Cellosolve phthalate Dicapryl phthalate Di(2-ethylhexyl) phthalate (Flexol plasticizer DOP) Didecyl phthalate Dihexyl phthalate (Flexol plasticizer D H P ) Diisoootyl phthalate Di-n-octyl phthalate Dialk 1 phthalate (Staflex MP) WIixeJ isoootyl-n-octyl-n-decyl phthalate (Hercoflex 250) Mixed n-octyl-n-deoyl phthalate (Hercoflex 250) Hydrophthalates Di(2-ethylhexyl) tetrahydrophthalate (Flexol plasticizer 8HP) Di(2-ethylhexyl) hexahydrophthalate (Fiesol plasticizer cc-55) Ricinoleates Butyl acetyl polyricinoleate Methyl acetyl ricinoleate Methyl Cellosolve acetyl ricinoleate Isobutyl acetyl ricinoleate Sebacates Dibutyl sebacate Dioctyl sebacate Miscellaneous Tetrabutyl thiodisuccinate (Flexol plasticizer TWS) Butyl polyacetoxy fatty acid ester (Estonox 206) Polyestei (Flexol plasticizer R2H) Polyester (Glyptal2557) Polymeric (Plastolein 5720) ( D P 260) f‘araplex G-GO) Paraplex G-62) romatic hydrocarbon (Sovaloid C) (Staflex Ii.4)
5.8
N o flow N o flow 1 ,971 153 550 100 I i o flow 780 010
6,850
solvation a t high temperature formed a gel structure unless separated by dilution. The extrusion rheometer is a useful instrument for measuring the viscosities of a variety of plastisol compositions. Correlation of flow data from this instrument with those determined from a modified coater indicate the usefulness of the flow data for predicting flow properties in actual applications. The viscosity and aging characteristics of a plastisol are dependent on structural composition of the plasticizer. Long alkyl chains reduce solvency while aromatic groups increase solvency for the resin. Mixed plasticizers produce flow properties and aging characteristics intermediate between the individual plasticizers. Concentration of the plasticizer has a more pronounced cffcct on the flow properties of highly solvated plastisols than on normal plastisols. The flow properties and aging characteristics of a plastisol are controlled by the choice of the plasticizer. Film properties are of equal importance in the selection of plasticizers. Plasticizers producing low viscosity and good aging characteristics often have low solvency for the resin and migrate from the fused cornpositron as a result of incompatibility. A judicious compromise must be made between optimum properties in the fused and unfused state. ACKNOWLEDGMENT
Bakelite Fellowship, Mellon Institute of Industrial Research, Pittsburgh, Pa.
No Ron
h’o flow 88
No flow No flow 2,190 94 171 64 No flow 550 265 134
UOMENCLATURE
A
=
area of parallel planes, sq. em. 4Q
d 1% c
=
yj3
._
PR d log 2L
D = orifice diameter, em. F = force, dynes h
=
Q
=
clearance between parallel planes, em.
I, = length of orifice, em. P = pressure drop, Ib. force per sq. inch or dynes per sq. em. volumetric flow rate, cc. per see.
1,030
123
810
100
52
38
6
222
81
Subscript. w
255 29
14 19
1,000 13
33.3 440 47 6.5
2,380
1,180
88 14,600 200 1,370 335 423 550
54 10, GOO 128 1,180 246 342
No flow 1,620
670
N o flow
1,400
shear stress; increases in plasticizer concentration reduced the dilatancy. Heating the plastisols removed the dilatancy at all concentrations tested. There was a marked decrease in viscosity with increase in plasticizer concentration in the case of the heated plastisols. Apparently the resin particles swollen by
= radius of cylindrical flow element, em.
R = radius of orifice, em. W = efflux weight, grams 7
51 8 626
2375
p
= apparent viscosity, poises = density, grams per cc. = efflux time, see. =
value a t wall LITERATURE CITED
(1) Alves, G. E., Boucher, D. F., Pigford, R. L., Chem. Eng. Progr.,
48,385 (1952). (2) Barus, C . , Am. J . Sei., 3rd Series, 45, 87 (1893). (3) Bingham, E. C., “Fluidity and Plasticity,” p. 319, McGraw-Hill, New York. 1922. (4) Dillon, J. H.; and Johnson, N., Physics, 4, 225 (1933). (6) Nason, H. K., J . A p p l . Phys., 16, 338 (1945). (6) Poiseville, J. L. M., Compt. rend., 15, 1167 (1842). (7) Powell, G. BI., Mullen, T. E., and associates, presented at 120th Meeting, ACS, Kew York, September 1951. (8) Powell, G. M., Quarles, R. W., and associates, Modern Plastics, 28, No. 10, 129 (June 1951). (9) Quarles,R. W., Can. CI~ern.Process I?ids., 81,33 (April 1946). (10) Rabinonitsch. B., 2. p h y s i k . Chem., A145, I (1929). (11) Reed, M. C., IND.Ewo. CHEM.,35,896 (1943). (12) Reed, M. C., and Connor, I,.,Ibid.,40, 1414 (1948). (13) Severs, E. T., Ph.D. dissertation, University of Delaware, May 8, 1950. (14) Spencer, R. S., and Dillon, R. E., J . Colloid Sci., 3, 163 (1948). (15) Todd, W. D., O ~ CDig. . Federation Paint & Varnish Production Cluba. No. 325,98 (1952). RE:CEWED for review April 21, 1954. ACCEPTEDJuly 14, 1954. Presented as part of the Industrial Rheology Symposium before the Division of Paint, Plastics, and Printing Ink Chemistry, 126th Meeting, ACS, Kansas City, Mo., March 1954.
