1344
INDUSTRIAL AND ENGINEERING CHEMISTRY
The disadvantage of the method is t,he requirement of a small hole. The rate of effusion is consequently low and the weighing must be delicate or the experiment must continue for a long time. I n this work, vapor pressure is an adjunct, rather than a primary measurement and some precision can be sacrificed for a gain in speed. This was achieved by making the diameter of the hole 1 t o 5 mm. (in a bulb 10 mm. in diameter) instead of the usual 0.5 mm. or less. The rate of effusion was thereby accelerated from 4 to 100 times. With these larger diameters of hole, Equation 10 no longer holds. Inside the bulb, the pressure is below the saturated vapor pressure, and t'he observed rate is lon-er than expected. Correction factors to the ideal formula were derived as follows: The rate of escape, gram per hour per square centimeter of hole, was determined, using dibutyl phthalate a t 61.9" C., for glass bulbs having an approximately constant diameter of 10 mm. but TTaryiiig size of hole. The rate was not independent of the size of t,he hole, as expected from Equation 10, but fell with increasing size. .\ plot of rate versus area of hole appears in Figure 13. Sewn different bulbs xere used. Some nearly alike in diameter, v i t h one repeat reading as indicated on Figure 13. From the discussion a b o w it is evident that the proper rate for use in the
Vol. 46, No. 6
ideal Equation 11 is the rate for zero area. The rate for any other area must be corrected according to the line of Figure 13. Correction factors based on Figure 13 are shown in Figure 14. The formula for vapor pressure then became:
p = 0.00-4TB
m
.f
%' 17
where the factor, f,for a particular area of hole is given in Figure 14. With the area of hole used by others (diameter 0.05 em., area 0.002 sq. cm.), the correction factor is very close to 1.00. The bulb was suspended in the high vacuum system 10-4 mm. of mercury from a calibrated steel spring having an extensibility of 100 mm. per gram. The contraction of t>hespring as vapor escaped was observed with a traveling telescope, and plotted in the manner similar to the one used in preparing Figure 15, in which a reasonably precise effusion rate was established af t,er only 3 hours. I n Figure 15, the diameter of the hole was 0.271 em., f was 0.92, M was 435, m was 0.230, and the vapor picmure was calculat,ed to be 0.00122 mm. of mercury. RECEITED for review J u 1 ~ 10, - 1353.
ACCEPTEDJ a n u a r y 28, 1954.
(Plasticizers in Vinyl ChEori
REMOVAL BY OIL, S
s
WAT
3%. C. REED. H. E'. MLERSRI, AK'D E. F. SCNULZ Bakelite Co., a Dizision of enion Carbide and Carbon Corp., .\'ea ECAUSE of the practical importance of plasticizer lose from flexible vinyl film and sheeting, many tests have been used for the measurement of extraction by oil and soapy n-ater. Because the amount of loss depends on time of exposure and sheet thickness, these tests have been rather empirical. S e w tests, described in this paper, have been developed nhich measure the resistance of these sheetinge to extraction. The rcsulte are expressed in terms of a constant which is independent' of time of extraction and sheet thickness. Vinyl upholstery eheet,ing sometimes stiffens in service because of plasticizer loss. This stiffening is sometimes caused by !\-ashiiig ivith soapy water or other fluids, but plasticizer may also be removed by rubbing action of dry clothing. A rubbing test has been devised for predicting susceptibility of sheeting t o loss against dry media. Losses by this test are similar to those obtained by extraction in oil or soapy tvater. Results are obtained rapidly and TTith good precision. Plasticizer rub-off, and extraction by oil and soapy water, are diffusion phenomena dependent on plasticizer species and conccntration. Extract,ion and rub-off constants are given in Table 111 for 16 plasticizers in three concentrations each, and suggestions are given for the use of these data in the forniulatioii of sheetings for specific uses. OIL EXTRACTIQV
Khen a sheet of plasticized vinyl chloride polymel or copolymer resin is immersed in mineral oil, some of the plasticizer from the surfdce of the sheet dissolves in the oil and is carried away. T h e resultant impoverishment of the surface causes plasticizer to migrate from the interior of the sheet to the surface, and in turn be extracted by the oil. A concentration gradient is thus extablished and the reaction proceeds according to the usual diffusion pattern, the rate of loss decreasing with time.
170rk l i , ,V.I .
I n the ideal case no oil diffuses into t'hc sheet, the oil has a viscosity much lees than that of the sheet, and both media have a high tolerance for plasticizer. Under such conditions the amount of plasticizer loss from the sheet varies linearly with the square root of time. These conditions usually applj- when the extractant is mineral oil comparable t,o the medicinal grade of liquid petrolatum. A met,hod of evaluating oil-extraction properties of vinyl sheets and film has been devised. The met'hod consists of inimersing a disk of any convenient, thickness, 3 inches in diameter, in mineral oil a t 50" C. for 4 hours and determining the weight loss. The specimens are not conditioned before initial weighing and are wiped with tissue before weighing after immersion. The per cent weight lose is calculated, and if the loss in 4 hours is over lo%, the test is repeated using a 1-hour immersion. If the loss in 4 hours is less than 374, the test is repeated using 24-hour immersion. T h e mineral oil used in this xork had a specific gravity of 0.845 t o 0.865 a t 26 "jl5.5' C. and a viscosity of 25 t'o 35 centipoises a t 25" C. Flat-bottomed glass dishes such as Petri or crystallieing dishes were used. Pieces of coarse stainless steel wire cloth were used to separate the specimens from the bott'om of the dish and from each other by a distance of a t least 0.05 inch to provide adequate contact TTith the oil. Specimens were run in triplicate, three specinlens of the same material being used in one dish. The oil-extraction constant, IC, characteristic of the sheeting composition, wari calculated as follow:
where Wl is the original weight of the specimen in grams, TV2 is the weight of the specimen after immersion, a is the area (both
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1954
TABLE I. EFFECTo r EXTRACTION TIMEON WEIGHTLoss
OF
COUP~CA-D A
TABLE 11. EFFECTOF SPECIMEN THICKNESS OS WEIGHTLoss OF COMPOUND A
(0.004 inch, 50° C., mineral oil) Extraction Time, Hours Loss, % K ,G. M-2t-'" 2.23 2 5.0 2.27 7.2 4 2.31 9.7 7 14.6 1.88 24 15.0 1.75 29 1.47 18 16.2
(24 hours, 50' C., mineral oil)
w-1
0
1
2
fl
3 (TZTIME
4
5
Plasticizer Designation A-26
CC-55
6
7
P a r t s b y Weight 100 0 2 3 48 1 150 4
-
_-Soap 3.3 4 6 7.1 4.8 1.1 1.9 3.3 2.9
0.9 2.0 4.8 3.6
1.2 2.0 4.9 3.6
TOF
40 50 70 59
3.0 4.7 7.7 6.0
2.5 4.3 5.8 4.8
40 50 70 64
0.9 1.8 5.1 4.2
1.2 2.4 5.5 4.6
2GB
40 50 70 63
1.3 2.3 6.0 4.9
...
... ... ...
1.4 2.5 6.4 5.2
3G0
40 50 70 59
4.4 5.2 8.7 7.0
4.2 5., 9.3 7.8
-1.8 5.4 9.5 7.5
4G0
40 50 70 62
2.7 4.8 8.8 7.3
3.0 4.5
8.7 7.2
3.1 4.5 8.3 6.7
40 50 70 64
0.5
1.2 3.5 2.8
0.8 1.4 3.7 3.1
0.7 1.3 3 6 3.0
40 50 70 67
1.5 3.3 7.1 6.5
, . .
... ...
1.4 3.0 6.4 5.8
40 50 70 53
...
...
...
...
, . .
A
40 50 70 60
4.4 6.8 10.0 8.6
KP-504
40 50 70 71
0.40 0.69 3.0 3.1
E
50 70 69
2.0 4.2 4.1
40 50 70 59
0.84 1.7 4.9 3.3
40 50 70 68
0.54 1.3 3.3 3.1
8N8
c
Compound A Vinyl chloride-acetate copolymer, VYNW-5 Liquid stabilizer a n d lubricant Di-2-ethylhexyl phthalate
(Formulation B, 0 004 inch, 50D C ) K ,G. M - 2 Hr.-': Concn. PHRa Oil Rub-off 40 3.9 4.0 5.4 50 6.2 11 . o 70 11.6 51 6.3 6.8 40 1.3 1.5 50 2.6 2.8 70 6.3 6.3 64 5.2 5.3 40 50 70 61
0.004 inch, 50° C., mineral oil
The limitation that the loss falls between 3 and 10% is necessary in both equations. Very small losses may be unreliable for predicting failure in service, because some compounds contain only a minor amount of a relatively fugitive plasticizer, stabilizer, or lubricant. Thus, the initial rate of loss may be high but not sustained t o the failure point. Above 10% weight loss the specimen becomes sufficiently hardened so that the amount of plasticizer lost is no longer linear with the square root of time. It is permissible to use extraction times greater than 24 hours where necessary, but the range of 3 % in 24 hours to 10% i n 1 hour is sufficient to include most materials. For the initial part of this work a 0.004-inch calendered film was prepared from Compound A.
Hi t-'"
1.66 1.94 1.94 1.95 1.96
DOP
IN HOURS)
Figure 1. Effect of Extraction Time on Weight Loss of Compound A
Jf-2
Loss COSSTANT
TWS
0
K, G
1L2.3 7.3 4.7 3,5 3.1
TABLE 111. EFFECTOF PLASTICIZER AYD COXCENTRATIOS ON
(2)
~
Loss, %
Thickness, R I h 4.1 8.4 13.0 17.2 20.3
sides and edges) of the specimen in square meters, and 1 is the time of immersion in hours. The per cent loss of a sheet of any thickness for any period of immersion may be calculated by rearranging Equation 1 in the following form: 100 Ka V'z Per cent weight loss = __
1345
D
160
S/Y-C-DOP, 1
to 2
...
0.8 1.o 2.2 1.7 *
2.8 4.0 6.1 5.0 1.1 2.3 4,9
4.2
. , ,
6.9 7.5 9.5 8.0
4.7 6.9 10.1 8.5
2.6 3.0 3.5 3.2
, . .
0.74 1.7 3.7 3.8 I . .
...
... ...
... ... ... ... ... ... .
I
.
0.43 0.86 2.9 3.0 2.5 5.0 4.9 0.89 1.9 4.9 3.4 0.51 0.98 2.0 1.9
Parts plasticizer per 100 parts resin, by weight.
This compound has a specific gravity of 1.24. Specimens in the form of 3-inch disks were immersed in mineral oil a t 50" C. for varying periods of time. Weight loss was calculated as per cent and in terms of K , as defined in Equation 1. Results, shown in Figure 1 and in Table I, confirm linearity with the square root of time up to approximately 10% loss.
Similar specimens of Compound A, but in a range of thickness, were extracted for 24 hours a t 50" C. in mineral oil, with the results shown in Table 11. The low value of K for the 4.1-mil
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
1346
specimens reflects the reduction in extraction rate after the loss becomes excessive. Plasticizer extraction increases with increasing plasticizer concentration. This is in part clue to the decreased rigidity of the compound Jvhich perrnit,s more rapid migration of plasticizer to the surface. Higher plasticizer concent,ration nl:o rexilts in a more readily available supply of plasticizer to support the loss at the surface.
Vo!. 46, No. 6
Light petroleum fractions such as hexane, octane, gasoline, and kerosine, as well as manj- other solvents including methanol, ethyl acetate, and benzene, are knovin to s\wll plasticized vinyl resins. TS'hen appreciable swelling occurs, the rigidity of t,he plastic is reduced. This permits more rapid extraction of plasticizer than by extractants like mineral oil, which penetrate the compound only aliglitly. For this reason Equation 1 cannot b(! applied to solvents which act'ivcly penetrate the plastic conipound. Zquation 1 ~vouldalso be limited to iisc wit,h extract:mts which are good solvents for the plasticizer. ltion. ii in ivhioh the Schulz (9)ha? proposed :i ~ m t ~ i . - c x t i ~ a c t i omethod q x c i n i c n is sinrounded by coarse activated carbon and thc voids betn-cen the c a r l ~ o ngraiiia are filled ni:h water. This method
3fPC
4pOC
5yC
33
32
31
6yC 30
!OOO 7
Effect of Temperature on Loss Constant of Compound A
Figure 2.
0.004 Inch, mineral oil and rub-off. K V S . 1000/T in O K .
Plotted as log
Coinparison of diff erent plasticizer? at the smie concoiitratioii r e g a r d h a of plasticizing eRriency is misleading because the compounder adjust's plasticizer concentration to ivhat,ever level best achieves the desired con~binationof properties. He i. interested in the properties conferred by each plasticizer at it.; opt'imum concentrst'ion and not a t the same arbitrary concentration for all plasticizers. Pia&cizer cfficiency mey 11e cxprc.?wd as the parts of plasticizer necessary to produce a Qpecifiedresult such as a Duromet,er h a r d ~ i e sof~ ~70, an elongation of 757, at 1000 pounds p ~ square r inch of tensile loading, or any one of numerous criteria. I n Table I11 the valueP for oil extraction, ill term;: of K , are sholvn for a number of plaFticizerr a t concentrations of 40, 50, and 70 parts per 100 parts of resin. The last concentration s1ion.n under cnch plasticizer is that concentration required to yield an elongation of 75% a t 1000 po11n~lsper square inch of original c r o ~ esection aod a rate of loading of 15,000 pounds per square inch per minute at 23" C., a? descrihpd by Reed and Harding (8). Oil extractions listed in Table I11 vere made a t 50' i 1 ' C. using the mineral oil previously described, and data iyere calculated on extractions between 3 and lOy0 of the original specimen n-eight. All plasticizers were used in three concentratione in Formulation B. 17ormulation R Parts by K e i g h t Vinyl chloride-acetate rcsin I T S W - 5 Basic lead silicate S o . 201 Calcium stearate Plasticizer
100.0 3.0 1.0 40, 50, or 70
Raising the temperature increased the oil-extraction constant, as shown in Figure 2 and Table 117. Data v-ere obtained on Compound A in the form of 0.004-inch calendered film. Because of the low loss rates at temperatures below 50" C., some of the extractions were carried beyond 24 hours.
Figure 3.
Modified Ice Cream Freezer Used as Specimen Holder
June 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
reduces the distance which a plasticizer molecule must travel before being captured. Thus the loss of plasticizer is accelerated. Even greater acceleration is accomplished when soap is dissolved in the water. Di-2-ethylhexyl phthalate, which is very sparingly soluble in mater and has a very low water-extraction rate, is extracted by soap vat'er a t high enough rates to render the plasticized film unsuitable for applications requiring frequent laundering. The mechanism of plasticizer extraction is as follows: The plasticizer molecule escapes from the film surface and diffuses through the soap solution. Before it has progressed far it is captured by soap molecules which form a protective layer around the plasticizer molecule, prcvent'ing re-entry into t'he film. Other molecules may then escape and are in turn captured by soap, and the extraction process continues without hindrance from the increasing concentration of plasticizer in the soap solution. The greater the soap concentration the smaller the distance which a plasticizer molecule must traverse before it is put out of action. At some soap concentrations, in the order of 575, redeposition of plasticizer becomes negligible and the diffusion of plasticizer within the vinyl compound, rather than removal from the sheet surface, determines the rate of loss. Using 5% soap, extraction is comparable in rate to oil extraction or to rub-off as described in a later section of this paper. At low soap concentrations the progress of the plasticizer through water controls the rate of loss. Thus, extraction rate is dependent on solution turlsulence or on scrubbing action-that is, on the mechanical action of the laundering equipment. This introduces numerous empirical test restrictions and the behavior of plasticized film under practical laundry conditions cannot be readily predicted from static extractions in dilute soap solutions. These considerations led to the development of a soap-extraction test employing higher than normal soap concentrat'ion. According to this method specimens were immersed in aqueous 5% Ivory soap beads a t 50" C. and extraction was expressed as K value, loss in grams per square meter divided by the square root of time in hours. As in the case of oil extraction, the specimen was extracted for 4 hours. Folloxing extraction, the specimen i m s wiped off and dried for 2 hours a t 50" C. If t,he loss was less than 3.0y0,another determination was made using 24-hour immersion time. If 4 hours of extraction caused more than 10.0% l o s ~another , specimen was ext,racted for 1 hour. Flat dishes with coarse screens for separators were used as in the oil-extraction method. The close agreement, among oil extraction, soap extraction, and rub-off is illustrated by the respect,ive K values of 2.2, 1.9. and 2.5 for Compound A. Some plasticizers appear to be hydrophylic, enabling water t o enter the vinyl compound and accelerate extraction. Other plasticizers show low soap-extract,ion values, indicating a low affinity for soap or an ext,remely low water solubility. Such anomalies in plasticizer behavior made hazardous the prediction of resistance t o laundering from oil extraction or rub-off. For these reasons actual measurements of exbraction by concentrated soap solution are recommended $There prediction of laundry resistance is necessary. Table I11 shows the soap extraction K values of a number of common plasticizers in several concentrations in Bakelite vinyl resin VYKTV-5 ( a copolymer of 96% vinyl chloride and 4% vinyl acetate). RUB-OFF
Some instances of failure of plastic sheeting used in upholstery applications have indicated that plasticizer can be removed by rubbing with solid media, and that contact with oils, gasoline, soapy water, or other liquids was not requisite to plasticizer loss. Geenty ( 8 ) has shown t h a t when plasticized vinyl films are packed in a fine absorbent powder and held a t a pressure of 10 pounds per square inch, a considerable quantity of plasticizer
1347
is removed. Tumbling of specimens in dry powders u-as tried, but results were erratic, in part because the poviders clung to the specimens. A test was then developed in which film specimens were mounted on a stationary shaft in the rotating can of a 4quart electric ice cream freezer. The can was filled with a mixture of equal parts by weight of Silene EF (a calcium silicate supplied by Pittsburgh Plate Glass Co. and having an average particle diameter of 0.03 micron) and Hyflo Super-Cel (a diatomaceous earth supplied by Johns-hlanville Corp. ). The wooden tub of the freezer was filled with water and thermostatically controlled.
Figure 4. Detail of Specimen Holder
This combination of powders was found to be satisfactory for most films. The Silene EF provided a large absorptive area, but clung to some films if used alone. The Hyflo Super-Cel provided ready release of the powder and uniform rubbing action. Figure 3 shows the modified ice cream freezer used in these tests and Figure 4 shows the mounting of one pair of specimens. Specimens were 2.00 x 1.25 inches with an area of 1.25 X 1.25 inches exposed to the rubbing action of the powder. Specimens, in triplicate, were weighed and mounted as indicated. The assembly holding the specimens was t>heninserted in the can with the preheated powder and set in rotation for 4 hours, after which the specimens were removed and reweighed. Weight loss in per cent was determined, the actual loss being multiplied by 1.6 to correct for the unexposed part of the specimens. Rub-off loss ronstant was calculated according to the following equation:
(3) where the quantities have the same significance as in the case of oil extraction. Initial tests were made a t 50" C. for 4 hours and were rerun a t 1 hour or 24 hours if necessary to obtain loss values between 3.0 and 10.0%. The dependence of rub-off on temperature is shown in Table I V and Figure 2. Data were obtained on 0.004-inch film of Compound A a t 30",40", SO", and 60" C. and a t times of 0.25 t o 7.0 hours. Values of K were essentially independent of time, except a t 30" C. where losses were too low t o obtain good precision. These data were obtained early in the project and are probably 10 t o 15% low, because inadequate shielding of the specimens near the clamps caused some reduction in the efficiency of rub-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1348
TABLE 5'. EFFECT OF SPECI~ICN THICKNESS LND R r BBIYG T I X E O N LOSS O F COl\IPoL%W -4AT 50" c. 0.004 Inch ~ ~ H o u r s ' 0.25 1.61 2.32 0.3 2.24 2.28 1.0 3.23 2.33 2.0 4.13 2 . 2 5 4.0 6.39 2.23 7.0 8.00 2.17 Av. 2.24 ~
i
Weight Loss a t Thickness of 0.008 0.012 0.016 0 020 Inch , Inch Inc!i Incli % K % K % K % K % K 0 . 7 8 2 . 2 0 0.20 3 . 0 3 0 . 4 9 2 . 8 2 0 4 1 3 . 1 6 1 . 1 6 2 . 3 6 0 . ( 8 2 . 4 0 0 . 6 5 2 . 6'; 0 3, 2 8 8 1 . 7 5 2 . 5 3 1 . 2 2 2 . 6 3 0 . 9 3 2 . 6 8 0 79 2 85 2 . 4 2 2 . 5 3 1 . 5 6 2 . 4 4 1 . 3 7 2 . 8 6 1 0 4 2 71 3 . 7 9 2 . 7 3 2 . 3 5 2 , 5 4 1 . 8 0 2 . 6 0 1 30 2 . 8 2 4 42 2 . 1 2 2 96 2 , 1 1 2 . 4 5 2 . 6 6 2 . 0 2 7 7 1 2 47 2.55 2.71 2 86
-al K 2.72 2.51 2.60 2 56 2 58 2 18 2,57
bing. Figure 2, hoiT-ever, clearly indicates the trend t o increasing rub-off with increasing temperature. The effect of specimen thickness and rubbing time is shown, for Compound A, in Table 5'. The value of K is seen to be essentially independent of thickness or rubbing time: even though, in this case, losses ranged from 0.29 to 11.6%. These data, plotted as per cent loss against the reciprocal of thickness, are shovr-n in Figure 5 . The similarity of plasticizer removal by rub-off to that accomplished by oil extraction or by zoapy water extraction is apparent. Rubbing with dry powders appears to be a better measure of diffusion than the other t,wo procedures, because the rubbing test, avoids complications caused by inadequate emulsifying action, or by liquid penetrating the specimen and causing soft,ening or reduced compatibility.
Vol. 46, No. 6
compound of equal hardness; if the point lies below the line, it is superior. I n place of Durometer hardness, any other appropriate measui e of compound property such as elongation a t 1000 pounds per square inch tensile loading or brittle temperature may be used and rub-off susceptibility may be judged without reference t o plasticizer efficiency. I n one instance a least squares line wab drawn through a plot of K against elongation a t 1000 pounds per square inch of tension loading for a heteiogeneous group of films varying both in plasticizer species and concentration. Those below the line vere considered superior to the average of the group. Consistent results Piere obtained with vinyl-coated cloth samples, two specimens of which \\ere stapled back to back and rubbed for an appropriate time. After rubbing, the staples were removed, the poTyder was bloryn off, the sample weighed, and the K value calculated. Correlation with service performance was indicated, although the service data were too meager for certain confirniation.
4
h
0.
60
70 DUROMETER
80
90
HMDNESS
Figure 6. Relation of Rub-Off Constant to Durometer Hardness Formulation B, 0.004 inch, 50' C.
I n the rub-off test some o€ the resin is removed by the abrasive action of the ponder. The very small losses obtained s i t h the more permanent plasticizers and the linearity IT ith square root of time for all types o€ sheeting shoiv that the abrasion effect is not significant. With fugitive plasticizers, niarked stiffening as well as lateral and longitudinal shrinking occurs.
RECIPROCAL OF
Figure 5 .
THICKNESS
IN
CORRELATION OF RIETIIODS
INCHES
Relation of Weight Loss t o Thickness a t \\'arious Rub-Off Exposure Times Compound .i. S O 3 C.
Increasing plasticizer concentration causes a greater rate of plasticizer removal, as is evident from Table 111. I n applying rub-off data to practical formulation problems the efficiency of the plasticizer in reducing the hardness, flexural modulus, or other rigidity properties must be taken into account. T o establish a base line for the selection of the best plasticizer blend for upholstery sheeting, for example, rub-off K value map be plotted against Durometer hardness as in Figure 6. I n this instance a series of batches based on Formulation B was prepared using different concentrations of Flexol plasticizer DOP (di-2ethylhexyl phthalate). Durometer hardness (Type A) a t 23" C. and rub-off K values a t 50" C . were determined (Table VI). Using the plot of Figure 6 as a reference, data obtained on any new compound may be spotted on this graph. If the point lies above the line, it is more susceptible to rub-off than the reference
Removal of plasticizer from vinyl sheeting by the above three methods is controlled primarily by diffusion of plasticizer through the compound. Good agreement in loss data among these methods would be expected and is in most cases realized. Mineral oil introduces some complications, chief of which appears to be absorption of oil b y the sheet,. The absorption may reduce the calculated weight loss or niay accelerate loss by rendering the plasticizer less compatible Kith the resin.
TABLEVI.
RELATION OF RUB-OFF TO DUROMETER EIIRDXESS
(Different concentrations of Flexol plasticizer DOP in TYXW-5 resin Formu!ation B, 60' (2.1 Loss Conatant, h', G. DOP, PHR" Durometer Hardness J - 2 FIr,-''2
40 50
70 a
87 77 61
P a r t s plasticizer per 1 0 0 parts resin.
1.2
E::
June 1954
INDUSTRIAL AND ENGINEERING CHEMISTRY
Soap extraction is sometimc,s complicated by water absorption by the specimen or by poor emulsification, as previously discussed. For these reasons rub-off data are believed t o reflect more accuratelv the diffusion moperties of plasticizers. As shown by Quackenbos, the diffusion constant of a plasticizer may be calculated from the exposcd area of the specimen, the initial plasticizer concentration, the weight loss, and the time of exposure. For most formulation problems, however, the K value determined on the compound a t hand provides a more direct indication of service behavior. A knowledge of plasticizer concentration is not necessary for the calculation of K value.
- -
1349
assisted in obtaining the data shown herein and in preparing this paper. The exploratory work of R. H. Lindh on the rub-off test and the suggestions of H. M. Quackenbos on interpretation of data have been especially helpful. REFERENCES
Barrer, R. M., “Diffusion in and through Solids,” 1st ed., pp. 216 ff , New York, NIacmillan Co., 1941. Geenty, 3. R., India Rubber W o r l d , 126, 646-9 (August 1952). Haward, R. N., Analyst, 68, 303-5 (1943). Hopke, E. R., and Sears, G. W., J . Chem. Phys., 19, 134551 (1951).
PRECISION OF TESTS
A statistical analysis of replicated test data by several operators, over an extended period of time and involving several oompounds, has been made to permit a valid estimation of th6 test reproducibility. Data of 27 oil-extraction, 60 rub-off, and 60 soapy water-extraction tests were analyzed. On the basis of theqe measurements over-all test precisions of 3 ~ 1 5 ,&16, and *37% were obtained for the proposed oil-extraction, rub-off, and soapy water-extraction tests, respectively, a t the 95% certainty level.
Liebhafsky, H. il., Marshall, 4 . L., and Verhoek, F. H., IND. ENG.CHEM., 34, 704-8 (1942). Parks, G. S., and hloore, G. E., J . Chem. Phgs., 17, 1151-3 (1949).
Perry, J. W., “Chemical Engineers’ Handbook,” 3rd ed., pp. 538, 545, Xew York, McGraw-Hill Book Co., 1950. Reed, AI. C.,and Harding, J., ISD. ENC.CHmr., 41, 675-84 (1949).
Schulz, E. F., A S T M BUZZ.,183, 75-8 iJuly 1952). Small, P. -4., J . SOC.Chem. Ind.,66, 17-19 (1947). Small, P. A,, Small, K. W., and Cowley, P., Trans.Faradau SOC.,44, 810-16 (1948).
Verhoek, F. H., and Marshall, 8. I,., J . Am. Cliein. SOC.,61,
ACKNOWLEDGMENT
2737-42 (1939).
The authors wish to express their appreciation to the others of the Development Department of -Bakelite co., who have
R E C E I V E D for
review June 30,1953
. ~ C C E P T E D Deceiiibei
5 , 1953.
Relation of Molecular Structure to Detergency of Some Alkylbenzene Sulfonates F. N. BAUMGARTNER ESSO
Laboratories, Standard Oil Development C o . , Linden, N. J .
T
H E chemistry of surface active agents has had widespread development during the past decade. The present investigation is concerned with the effect of molecular structure on the surface active properties of alkyl-benzene sulfonates. For this purpose a series of eleven sodium dodecylbenzene sulfonate isomers and homologs was used. These compounds are represented by the generic formula
RIikeska, Smith, and Lieber (6). A modification of the sulfonation procedure of Leiserson, Bost, and Le Baron (3) was used to prepare the sodium sulfonates. The entire sequence of preparations is Lidicated as follows:
0 ;!
+ Ar H AlC13 --+R
RCCl
p
.4r
R-CH-R’ 0
‘USO&a where R is an alkyl group and R ’ is hydrogen or an alkyl group. The detersive ability, surface tension, and wetting power were determined. Measurements were made in aqueous media on the sulfonates both in the pure form and in the presence of sodium sulfate.
OH
I
The secondary alkylbenzenes were prepared most conveniently by the procedure of Gilman and Meals ( I ) . The n-alkylbenzenes were prepared using the modified Clemmenson reduction of
HI
--
kr
PREPARATION OF SODIUM SULFONATES
R-CH-R’
i
.4r
P
+ R-CH-R’
R-C-R’ I
(3)
Ar
SO3 NaOH R-CH-R’
SO2
I
.Ir-SO,n‘a
(4)
