Evaluation of Detergents for Textile Cleaniig WILLIAM P. UTERMOHLEN, J R . ~ ,AND MARY E. RYAN Institute of Textile Technology, Charlottesville, Vu. been directed toward estimaA review has been made of the methods employed to HE recent sharp rise in tion of the extent OC pigment measure the effects of washing procedures on soiled cotton the use of synthetic deremoval. Since the pioneer cloth. The method of estimating absolute soil removal tergents, due to their improvwork of Rhodes and Brainard values by linear proportionality to the surface reflectance ing level of performance and of the cloth, frequently employed in detergency work with (18), reflectance measure their relatively favorable ments with a photometer carbonaceous pigments, has been shown to be incorrect costs, has made the field of when applied to cloth soiled with a black iron oxide pighave been the most popular evaluation of detergents inmeans of estimating t,he soil ment, upon which both analyses and photometric meascreasingly important. This is content of unsoiled, soiled, urements can be made. Evidence is presented to show that particularly pertinent to the and washed pieces of cloth, the application of one of the Kubelka-Munk color equacase of textile materials, beand thus of det,ermining the tions to washed cloth to determine absolute soil content cause accurate and efficient amount of soil removal acis of only limited value where the soil is black iron oxide. means for the evaluation of complished by a washing Chemical measurement of amounts of analyzable pigment textile washing treatments process. This method has left on pieces of washed cloth may be used to obtain abhave always been difficult solute soil removal values in textile detergency work. been popular because the pigto attain. The principal apments found in many n:itural plication of such textile deand almost all synthetic soils tergency evaluations has been are carbonaceous and black, and thus are most practically estiin the washing of cotton fabrics, although many problems are mated by optical measurements. common to the washing of wool and the various synthetic mateRecent work in several laboratories has brought attention t o a rials as well. number of errors in the usual photometric procedures. One Textile detergency is concerned chiefly with two types of procgroup of errors appears in the methods used for reflectance mea& esses: the removal of soils such as wool grease, cotton waxes, urements. First, it is necessary to sort the test pieces before spinning oils, excess pigment from dyeing operations, etc., acwashing SO that all of the pieces in any one test have the same quired in nature or in finishing processes; and the removal of average initial reflectance because differences in initial reflectance soils acquivd in end-use, the province of commercial and domesare partially carried over after washing. Secondly, if the washtic laundering. These have many obvious differences, but, in ings are done in a Launder-Ometer (as is frequently the case), both cases, the objectives of cleaning are the same-first, to obmeasurements should be made on a sufficient number of test tain a satisfactory quality of cleaning, and secondly, t o achieve pieces, drawn from several test jars, to reduce the possible error this quality at a minimum total cost. Both of these factors must due to uneven mechanical action. Thirdly, i t is necessary to be considered carefully in making a choice of a particular determeasure the reflectivity values on a stack of test pieces thiok gent for a given application, and thus satisfactory means of enough to eliminate the effect of a n extraneous background. The evaluation are very important; improvements making these failure t o do this has been noticeable in some otherwise cardal methods more accurate, efficient, or simple are highly desirable. work by earlier workers. A general direct method of detergency testing involves preparaSupposing, however, that the reflectance measurements have tion of a soiled textile material, washing pieces of that material, been carefully made; the problem of translating reflectance data and estimation of the extent of soil removal. The common into estimates of soil content and soil removal still remains. In natural and artificial soils are either oils or a mixture of oily maa large number of investigations (3, 4,7-12, 18, 23, 24) the interial and pigments. In some cases, such as the scouring of raw crease in the per cent brightness (of washed over unwashed soiled wool, the object of the cleaning process is to remove a soil whose cloth) has been set numerically equal t o the per cent of soil re principal components are oily materials. No satisfactory means moval. Thus, a value of 0% soil may be assigned t o the reflectof evaluating removal of oily soil have been devised other than ance of the white unsoiled test fabric, 100% soil t o the reflectance weight measurements-e.g., the weight of scoured wool obtained of soiled cloth, and proportional per cent soil values t o the reflectfrom one pound of grease wool is measured, or the weight of the ances of washed soiled cloth swatches. This procedure will be nonvolatile matter from a solvent extraction of a weighed piece of termed the “linear method” in this paper. Other investigators cloth or skein of yarn is determined. This weight method is most (IS,20, 28, 24) have used such a linear comparison, but have satisfactory in the cases where the oily soil was present in a high stated that i t is not correct, recognizing t h a t the reflectivity of weight percentage. If the oil was present in only small amounts, soiled cloth does not bear a direct relation to the soil content. the weight losses from a cleaning process are small and may be Still others (1, 26) have given their data in terms of reflectance difficult to determine accurately. This is especially true if weight readings only, without attempting t o relate these values to the measurements are made on unwashed and washed pieces of cloth, actual soil content or t o the true extent of soil removal. rather than on the nonvolatile extracted matter, because differWork in this laboratory (21) has shown that reflectivity values ences in moisture content of the cloth can distort or obscure the of unwashed cloth soiled with carbon blacks or with a black iron weight losses due to oil removal. It has been generally found, oxide are related linearly to the logarithm of the quantity of soil however, that pigment soil is more difficult to remove from textile present. T h e problem is more difficult, for various reasons, in materials than is oily soil and is more easily seen and more objecthe case of washed soiled cloth. At the present time, there L tionable; therefore, most detergency evaluation procedures have still no accepted reflectance-measuring method of determining, ’Present addreas, Permutit Company, Birmingham, N. J.
T
% .
288 1
2882
INDUSTRIAL A N D ENGINEERING CHEMISTRY
even approximately, the true soil removal value of a washing treatment. I n recent years, two methods have been developed for measuring the extent of soil removal which do not depend on reflectance Vaughn and co-workers (23, 26) accomplished this by measuring the light absorption of the detergent solution before and after washing. Light absorption values were converted to milligrams of carbon removed per liter of detergent solution by reference to a calibration curve which had been constructed from light absorption values of suspensions prepared by adding various known amounts of carbon black t o distilled water (or t o detergent solution). T h e second method was developed by Utermohlen and Wallace (81) who used a black iron oxide pigment in place of carbon black for the soiling agent, and determined the pigment content of unwashed and washed samples of soiled cloth by analysis. The analytical method can measure either the per cent of removable soil or (more directly) the per cent of total soil which has been removed, while the light absorption method measures only the per cent of removable soil taken out. These total and total removable values are close to each other except for exhaustively washed cloth, in which the small remaining amount of irremovable soil becomes a large portion of the total remaining soil. Both the absorption and the analytical method are independent of the optical properties of the cloth itself. Despite the advances in knowledge made available by these last two methods, they are not so convenient to use or so generally accepted as are reflectivity measurements, and it would be desirable t o be able to use reflectance data to estimate the absolute, as well as the relative, extent of soil removal by detergent treatments. Bacon and Smith ( b ) have endeavored t o do this by applying an equation reported by Kubelka and Munk (16) and previously used by several workers in connection with color problems on paper (6, 17) and on textiles (15). The KubelkaMunk equation states that
where K = coefficient of reflectivity S = coefficient of light scattering R = observed fraction of monochromatic light vihich is reflected This equation can be applied to the calculation of the amount of a black pigment present on a fabric since the light reflected by such a system, as measured by a spectrophotometer, is the same a t all wave lengths in the visible spectrum, and the visible light reflected by a combination of white cloth and black pigment is, therefore] the equivalent of monochromatic light when using a photometer. Bacon and Smith showed that Equation 1 could be used t o predict the fractions of two lots of unwashed cotton batting, soiled separately to different reflectance values, required t o give mixtures of any desired intermediate reflectivity. The establishment of this fact was taken to indicate that K / S values were a linear function of the amount of black soil on an experimentally soiled bundle of fibers or fabric, and these values were used in the following equation to calculate the per cent black soil removed by a washing process:
K / S for soiled fabric - K / S for washed fabric K / S for soiled fabric - K / S for unsoiled fabric
soil-removal values obtained from use of Equation 2 and of the similar Equation 3 can be compared. P for soiled fabric - P for washed fabric loo = P for soiled fabric - P for unsoiled fabric per cent of black pigment remowd (3) P is the relative amount of the pigment present as determined by analysis. For example, if the pigment used was Mapico Black (black magnetic iron oxide), then the P values in Equation 3 would represent determinations of the iron content per unit weight of cloth. At the same time, comparisons can be made IIith the soil content values estimated by the linear method (similar t o Equation 3, with per cent reflectance values substituted for P values). The objective of this paper is to compare the measurement of removal of a black iron oxide soil, as indicated by the linear and the Bacon-Smith reflectance methods (both of which were developed from work with carbonaceous pigments), with the measurement of soil removal as given by the analytical method. EXPERIMENTAL METHODS AND PROCEDURES
General methods by which soiling mixtures were preparedcloth was soiled and stored, washing tests were made, and the extent of soil removal was measured-were essentially the same as described in an earlier work (21 ). Pigment (Germantown lampblack KO. 12 or hIapico Black) was stirred or ground with a mixture of Kujol mineral oil and Snowdrift shortening to make a soiling paste. A weighed quantity of the paste was dispersed in a measured volume of carbon tetrachloride to give a soiling mixture. Data on the particular soiling mixtures used are shown in the following table: Table I
Grams of Soiling Paste per 500 M I . CCI4 4.15
I1
5.5
I11
5.0
IV and V
5.5
Composition of Soiling Paste, Parts 2 3 . 2 Mapico Black 3 0 . 0 Snowdrift 4 3 . 0 Nuiol 2 0 . 0 Mapico, Black 4 5 . 0 Snowdrift 8 4 5 . 0 Nujol 1 0 . 0 Germantown lampblack Iio, 12 4 5 . 0 Snowdrift 45.0 Sujol 1 0 . 0 Mapioo Black 1 7 . 0 Snowdrift 17.0 Sujol
Because the soiling pastes used for Tables I, 11, IV, and V were separate preparations, the relative soiling power and ease of removal of the iron oxide pigment in these three lots could not be assumed to be identical. Mapico Black pigment was stated by its manufacturer to contain 98.8% black ferro-ferri oxide of iron, the residual 1.2% being moisture, water-soluble salts, etc. It does not contain any colorant other than the iron oxide. Pieces of bleached, kiered, and desized 80 X 80 nainsook cotton cloth were soiled by passing through such a mixture and through hand-driven wringer rolls. Soiled strips were air-dried in the laboratory, baked in an oven a t 70 C. for 30 minutes, and stored in an airtight container over anhydrous calcium chloride. Prior to the washing tests, the soiled strips were cut into 3-inch O
TABLEI. VALUES OF SOILREMOVAL FROM CLOTH SOILED LIQHTLY WITH MAPICO BLACKAND GIVEN SERIALWASHESWITH IVORY SNOWSOAP(0.25%)
loo=
per cent black pigment removed
Vol. 41, No. 12
(2)
Equation 2 was then applied to the calculation of the amounts of soil removed by various washing operations, but with no direct check on the validity of its application for this purpose and with no allowance being made for the varying mechanisms of action of d s e r e n t detergents. A method of checking the application of Equation 2 to detergency studies, which is obviously more direct than t h a t used by Bacon and Smith, is to use a black pigment for which analyses ILE well as photometric measurements can be made. Then the
History
of
Sample Soiled, not waahed 1 waeh 2 washes 3 washes 4 washes Original unsoiled
Reflectanoe,
K/S
%
Value
49.0 70.1 75.5 77.9 79.2
0.265 0.064 0.040
81.0
Iron Oxide Content Mg./2 G . Cloth
Calm. of Pigment Removal Using Using Kubelka- Analytilinear hhmk cal method, equation, Values,
%
0.027
3.5 0.62 0.29 0.24 0.20
(0.0) 65.9 82.8 90.3 94.4
0.022
0.00
(100.0)
0.031
%
%
$p:y
$02:)
92.5 96.3 98.0
91.5 93.2 94.2
(100.0)
(100.0)
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
TABLE 11. VALUESOF SOILREMOVAL FROM CLOTHSOILED WITH MAPICOBLACKAND GIVEN Two ~O-MINUTEWASHINGSWITH VARIOUS DETERGENTS (0.25%)
d.
History Reflectof ancle, Sample % Soiled, unwashed cloth 37.0 Washed Detergent A 40.0 45.0 Detergent B 47.5 Detergent C 49.5 Detergent D 51.5 Detergent E 52.0 Detergent F 53.0 Detergent G 53.0 Detergent H 55.0 Detergent I 59.0 Detergent J 60.5 Detergent K 81.0 Unsoiled cloth
Oxide Content K/S Value
?%! Cloth
0.536
6.8
0.450 0.336 0.290 0.258 0.228 0.222 0.208 0.208 0.184 0.138 0.129 0.022
5.2 4.5 3.4 3.1 3.1 3.0 2.6 2.3 2.2 1.4 1.0 0.0
Calm. of Piament Removd Using Using Kubelka- Analytilinear Munk cal method, equation, Values,
%
%
%
(0.0)
(0.0)
(0.0)
16.7 6.8 38.9 18.2 47.8 23.9 54.1 28.4 59.9 32.9 61.1 34.1 63.8 36.3 63.8 36.3 68.5 40.9 77.5 51.2 79.2 53.4 (100.0) (100.0)
23.5 33.8 50.0 54.4 54.4 55.9 61.8 66.2 67.6 79.4 85.3 (100.0)
TABLE 111. VALUESOF SOILREMOVAL FROM CLOTHSOILED WITH
GERMANTOWN LAMPBLACK AND GIVENONE 10-MINUTEWASHING WITH THE SAMEDETERGENTS (0.2570) USED IN TABLE I1 Calm. of Pinment
Soiled, unwashed cloth Detergent A Detergent B Detergent C Detergent D Detergent H Detergent E Detergent F Detergent G Detergent K Detergent I Detergent J Unsoiled cloth
30.0 35.5 43.0 46.5 47.5 49.5 51.0 52.5 52.5 55.0 57.0 60.0 81.0
0.817 0.586 0.378 0.308 0.290 0.258 0.235 0.215 0.215 0.184 0.162 0.133 0.022
(0.0) 29.1 55.2 64.0 66.3 70.3 73.2 75.7 75.7 79.6 82.4 86.0 100.0)
(0.0) 10.8 25.5 32.4 34.3 38.2 41.2 44.1 44.1 49.0 52.9 58.8 (100.0)
square pieces and these were sorted according to their reflectance values, In any one set of washing tests, the pieces in every jar had the same average reflectance. Washings were done in a n Atlas Launder-Ometer, Style B-1, for 10-minute periods of time, using a 42-r.p.m. machine speed, a temperature of 120" F., four pieces of soiled cloth, 200 ml. of.detergent dispersion, and forty 0.25-inch steel balls in each pint jar. Reflectance values were measured upon a stack of eight or more pieces of identical history, using a calibrated Photovolt Corporation Model 610 reflection meter. The iron oxide on the cloths soiled with Mapico Black was determined by ashing and colorimetric analysis (o-
TABLEIV. VALUESOF SOIL REMOVAL FROM CLOTHSOILED MAPICOBLACKAND WASHEDFOR VARIOUSLENGTHSOF TIMEWITH IVORY SNOW OR WITH DUPONOL ME (0.25%)
WITH '3
Detergent Ivory Snow
Calm. of Pigment Removal Iron Using Time Oxide Uaing Kubelka- Analytiof oal Content, linear Munk Wash- Reflectance, K / S Mg./2 G. method, equation, Values. ing, Value Cloth Min. % % % % 1
2.5 5 10 20"
43.2 51.1 55.1 59.1 65.1
0.373 0.234 0.183 0.142 0.094
4.5 3.0 2.2 1.5 0.70
26.6 41.9 49.7 57.5 69.1
57.2 74.2 80.4 85.4 91.2
58.7 72.5 79.8 86.2 93.7
..
29.5
0.842
10.9
(0.0)
(0.0)
(0.0)
Unsoiled cloth
..
81.0
0.022
0.0
(100.0)
(100.0)
(100.0)
Two IO-minute serial washes, using fresh detergent solution in the second
wash.
phenanthroline method), The intensity of the colored solution was compared with standards containing appropriate known amounts of magnetic iron oxide similarly treated. Each reflectance figure given in Tables I to V is the mean value of at least 32 readings, these being obtained by four readings (one toward each corner of a 3-inch square piece) on a t least eight swatchep. Pieces of this size when washed in pint jars in the Launder-Ometer often develop creases near or through the center of the piece, and these crease lines appear brighter than the main body of the test swatch. Readings near the corners were considered to represent the dominant effects of washing most accurately and were used throughout the work. The search unit of the reflectometer used scans an area 0.75 inch in diameter. The reflectometer readings were checked against a series of standard porcelain panels whose reflectivit?y values were certified by the National Bureau of Standards. The brightness of these standards and the corresponding readings (to the nearest 0.5% value) of the reflectometer, all relative to magnesium oxide, are given in the following table: National Bureau of Standards value for plate Reflectometer reading
18.6
19 0
39 4 5 9 . 1 6 7 . 4 7 8 . 7 40.0
5Q 0
67.5
78 5
Te&s for redeposition were made by including two pieces of white fabric in the same jar with four pieces of soiled fabric and washing in the usual wa using the detergents indicated in Tables I to I11 and V. The w g t e fabric employed was the same as used for preparing the soiled fabric and had a reflectivity of 81% ME. redeposition test pieces had a reflectivity of 80% or higher, even. after a washing period of 1 hour. It is obvious, therefore, that the tests, as performed, measured soil removal without the interference of a significant amount of rcdeposition. The values for iron oxide content in all of the tables in this paper were obtained by duplicate analyses, using four swatches in each analysis. The reflectance values and corresponding analytical determinations for iron were obtained from identical specimens. When more than eight swatches of a given treatment were available, eight, of the group were selected a t random for analysis. Standard deviation values were calculated for the varioua averaged reflectance values given in Tables I to V , and were found to range between 1.0 and 2.5 for almost all cases. The mean standard deviation was about 1 9 EXPERIMENTAL RESULTS AND DISCUSSION
Equations 2 and 3 were first applied to the data on the pieces of cotton fabric soiled to various initial reflectivities with Mapico Black pigment and then given four successive washes with a single detergent, Ivory Snow soap, in 0.25% concentration (21). Sample calculations are shown below for one such set of washed pieces. For soiled unwashed fabric, reflectivity equals 49%: (4) For unsoiled fabric, reflectivity equals 81%:
xK - (1 - 0.81)' o,81 = 0.022
(5)
When soiled pieces of this fabric were washed to a reflectivity of 70.1% ( K / S value = 0.064), then
calculated per cent pigment removed
(6) Values calculated from Equation 6 are shown in Table I under the heading "Using Kubelka-Munk Equation." The analytically measured values of per cent soil removal, calculated by use of Equation 3, are also shown in Table I.
R for washed fabric - R for soiled fabric R for unsoiled fabric - R for soiled fabric
Soiled, cloth unwashed
a
2883
loo=
per cent black soil removed
(7)
R equals the per cent reflectance. Equation 7 represents the linear method of calculating soil removal from reflectance valueb; values obtained by its application to these particular washed pieces are shown in Table I.
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
2884 'WI I
I
I
I 0
I
2.5
Figure 1.
I
I
I
I
5 WASHING TIME
IO MINUTES
-
Soil Removal
20
us. Washing Time
Iron oxide pigment soil removed from cotton cloth hy waahing in Ivory Snow
The values ralculated from the Kubelka-hIunk equation in Table I agreed well with the analytical values except for the most nearly cleaned samples. This represents the region in which the small amounts of nonsurface, irremovable soil become significant in the analytical determinations of the total amount of soil. The Kubelka-blunk equations are generally considered ( 2 ) not to hold very well for reflectance values near that of the original unsoiled fabric. The linear method values, on the other hand, agreed for the most-mashed samples, but were much too lo\$ in the case of the two least-washed samples. Similar results were obtained when reflectance and iron content values were compared an washed samples of another lot of soiled cloth, with reflectivity equal to 56.301,and iron oxide content of 2.2 ing. per 2 grains of d o t h for the soiled unwashed fabric. Similar comparisons were next made of the data obtained when pieces of cotton fabric soiled a i t h Mapico Black or uith Gcrmantown lampblack were washed with various detergents in 0.257, concentration. These comparisons are shown in Tables I1 and 111, the data in both tables being arranged in order of increasing effectiveness of the detergent. I n Table 11, the Kubelka-Munk values for per cent pigment removal paralleled the analytical values fairly well, considering &hat a number of detergents of different types were involved. The linear method values, on the other hand, were much too low throughout the entire series. In both Tables I1 and 111,the two sets of soil removal values calculated from reflectance measurements by the linear and by the Kubelka-hlunk methods were in serious disagreement a i t h each other, entirely apart from any Eack of agreement with the absolute analytical soil removal values. The apparent effectiveness of the detergents in removing lampblack pigment (Table 111) was much the same as for iron oxide (Table 11); detergents H and K Rere the only ones in Table I11 out of order with the relative arrangement in Table 11. Detergents A to D werc the poorest in both cases, and deteiyents I to IC the best. This similarity in washing effcctiveness, as judged by reflectance of washed pieces, has been taken to indicate that Mapico Black pigment and Germantown lanipblitck pigment have ett least some properties in common in then- removal characteristics. Their relative response to various detergents is certainly similar, aIthough a given concentrktion of a given detergent has always removed the iron oxide more readily than the lampblack.
Vol. 41, No. 12
Further experiments were then carried out, in which two causes of error noted above-a variety of detergents and a very high degree of cleaning (and hence a very high reflectance)-would be avoided. The first series of new experiments used either Ivor). Snow (soap) or Duponol ME (sodium alkyl sulfate) in 0.25% concentrat'ion as the detergent, with t'he variation in extent of soil removal being accomplished by varying the washing time from 1 to 20 minutes. Typical soil removal values obtained by the various methods are shown in Table IV, the washing8 being done on pieces of freshly soiled cloth of uniform initial reflectivit'y. For the Ivory Snow soap washings, the pigment removal values as calculated by the Kubelka-Munk method agreed very well with the analyt'ical values throughout; for the washings with Duponol ME, the Kubelka-Munk and analytical values agreed only for wash periods of a t least 5 minutes, the former values being higher throughout the series. In both cases, the linear calculated values were much too low for all periods of washing time. This is demonstrated graphically in Figures 1 and 2. A second set of experiments measured the extent of soil removal produced by 10-minute washings with varying concentrations of several detergents. The soil removal values obtained b)) use of the various estimating methods are shown for Ivory Snow, Duponol ME, Nacconol NR (an alkyl aryl sulfonate), and sodium oleate in Table V. The data in these tables indicate that both the concentrat'ion and the type of detergent are important in determining the extent of agreement between t,he Racon-Smith and t,he analytical values of soil removal.
.-ANALYSIS
0
1
0 I
I 2.5
Figure 2.
I 5 WASHING
FOR IRON
I
-
IO
TIME MINUTES Soil Removal us* Washing Time
20
Iron oxide pigment soil removed from cotton cloth by washing in Duponol M E
If washing was done for a sufficient length of time with an adequate concentration of detergent, the Kubelka-Munk values showed fair agreement with the analytical valucs for the synthetic detergents, and good agreement for the soaps. At shorter lengths of washing time or low concentrations of detergent, the two values generally were appreciably different, the value calculated from reflectancc data being the higher. In almost all the cases studied, the linear calculated values, on the other hand, were much too Ion. A graphical romparison of the data in Tablr V is shown in Figures 3 t o 6. In examining the data given in Tables I1 to V, it is possible to use some onc of thc dcitcrgents, or yome given concentration of dpteryent, or time of aashiny as a standard for comparison with the others in the table chosen. The relative detergency could then be expressed on a percentage basis, the figures so obtained being proportional to those in the present tables. By use of
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
70t
'
2885
B L
0-LINEAR 0-ANALYSIS FOR IRON
t
I
50 E
0-ANALYSIS FOR IRON
8'
1
,f'
0 ' 1 0 ,025 .05
I ,075
I .I25
I
.IO
I
I
.I5
J
I
,175 .20
DETERGENT CONCENTRATION- %
Figure 3.
Soil Removal
us.
Detergent Concentration
Iron oxide pigment soil removed from cotton cloth by washing in Ivory Snow
,075 .IO .I25 .I5 .I75 .20 DETERGENT CONCENTRATION- %
,025 .05
Figure 4.
Soil Removal
US.
25
Detergent Concentration
Iron oxide pigment soil removed from cotton cloth by washing in Duponol ME
either set of figures, a comparison of the differences between the values obtained by the three methods shows that the maximum TABLEV. VALUES OF SOIL REMOVALFROM CLOTHSOILED variations occur with the types of detergent, concentrations of WITH MAPICOBLACKAND WASHED FOR 10 MINUTESWITH detergent, or times of washing which had the Iowest soil-removal VARIOUS CONCENTRATIONS OF DETERGENTS characteristics. For example, a t detergent concentrations t h a t Calcn. of Pigment Removal are too low for effective washing, small variations in mechanical Iron Using agitation, extent of micelle formation, etc., which would normally Oxide Using Kubelka- AnalytiConcentration of ReflectContent linear Munk cal have little influence on the extent of soil removal, become inDetergent, ance, K / S Mg./2 G: method, equation, Values, creasingly important. consequently, a larger amount of variaValue Cloth % % % % % tion between the different methods might be expected a t this Ivory Snow level. Boiled, unwashed 0.536 cloth 37.0 6.0 (0.0) ;( :;I From these and similar experiments with the Mapico Black 17.3 40.1 6.0 0.447 0.025 42.6 30.0 0.317 46.0 4.2 0.05 20.5 pigment, several facts seemed t o be evident. First, when a b 58.6 50.0 51.0 3.0 0.075 0.235 31.8 solute values were sought, the much-used mode of expression 0.184 68.5 63.3 0.10 55.0 2.2 40.9 0.149 75.3 73.3 0.125 58.3 1.6 48.4 of soil removal as being linearly proportional to the increase in 77.0 80.0 0.15 0.131 60.3 1.2 53.0 0.124 1.3 80.2 78.3 0.175 reflectivity upon washing was far from correct. Secondly, the 61.1 64.8 0.131 77.0 80.0 0.20 1.2 60.3 53.0 application of the Kubelka-Munk equation, while a step in the 1.1 0.116 81.7 81.7 0.25 62.1 57.0 '100.0) (100.0) 0.022 0.0 (100.0) Unsoiled cloth 81.0 right direction and superior to the linear method, gave s a t i s Duponol ME factory soil removal values only for certain detergents above a Boiled, unwashed certain concentration level, and was less accurate when applied cloth 39.0 6.0 (::$) :); to nearly clean pieces of washed cloth. Thirdly, this lack of 5.7 39.9 0.025 43.2 22.9 25.0 4.5 0.05 10.0 general agreement between the results of optical and analytical 31.0 21.7 14.3 4.7 45.0 0.075 38.6 23.3 46.8 18.6 0.10 4.6 measurements indicated that the action of a given concentra46.6 37.6 23.3 0.125 18.1 4.6 tration of a given detergent upon the Mapico Black pigment 40.7 47.4 0.15 30.0 20.0 4.2 42.2 47.8 0.175 31.6 21.0 4.1 soil on cotton cloth could be somewhat different from the action 48.9 44.2 0.20 43.3 23.6 3.4 51.4 0.25 3.2 50.5 46.6 27.4 of another concentration, and much different from the actions Unsoiled 010th 81.0 (100.0) I:100.0) 0.0 (100.0) of other types of detergents, especially for short times of washing. Nacoonol NR A study of some of the data of Table V shows that comparisons Boiled, unwashed of reflectance values of washed samples of cloth soiled with cloth 33.5 (0.0) );:;( 18.8 0.025 36.9 Mapico Black could often lead to incorrect conclusions as to their n n.5 19.9 8.3 7.6 37.1 soil content values. The folIowing examples illustrate this point, 8.3 23.2 0.075 37.8 9.0 24.2 50.8 41.7 0.10 45.0 (All comparisons are of swatches soiled with the same lot of 56.3 39.6 0.125 46.9 28.2 56.6 45.9 0.15 47.0 28.4 Mapico Black-oil paste.)
y;)
(g
P
0
.25
(y:;)
0.176 0.20 0.25 Unsoiled 010th
28.2 31.4 32.8
46.9 48.4 49.1 81.0
56.3 60.3 62.1
60.0 51.0 52.1
(100.0)
100.0) (100.0)
(0.0)
(0.0) (0 IO) 46.0 16.1 51.6 35.7 64.2 49.1 79.6 68.8 85.2 82.0 88.2 86.7 (100.0) (100.0)
Sodium Oleate Boiled, unwashed cloth 0.025 0.05 0.075 0.10 0.16 0.20 Unsoiled cloth
27.3 37.1 38.9 43.8 52.4 67.0 59.9 81.0
11.2 9.4 7.2 5.7 3.6 2.0 1.5 0.0
18.2 21.6 30.7 46.4 55.3 60.7 (100.0)
Cloth washed 10 minutes in 0.05% Ivory Snow to a reflectance of 46.0% had a pi ment content value of 4.2,while cloth washed the same length oftime in 0.10 and 0.125% Nacconol N R t o this same reflectance value had an average pigment content value of 5.7. Incretlsing the Narconol NR concentration from 0.125 0.175% reduced the pigment soil content value from 5.8 to 4.7, but produced no change in reflectance value. Duponol Me in 0.05% concentration reduced the pigment soil content value of one batch of soiled cloth from 6.0 to 4.5, chanqing the reflectance value meanwhile from 39.0 to 43.2; but sodium oleate in 0.075% ooncentration, while changing the reflectanw
INDUSTRIAL AND ENGINEERING CHEMISTRY
2886
0
,025
Figure 5.
Vol. 41, No. 12
0 -KUBELKA-MUNK
.075 .IO 125 .I5 ,175 . 2 2.5 DETERGENT CONCENTRATION- % Soil Removal us. Detergent Concentration .05
Iron oxide p i g m e n t soil removed from c o t t o n c l o t h by washing i n Nacconol NR
value of a different batch of cloth from 27.3 to 43.8 (almost the same reflectance as obtained with the Duponol ME), reduced the pigment soil content value from 11.2 to only .5.7. These kxamples show that reflectance measurements often failed to represent true soil content values for the particular system under study. This result corroborated the observations made in earlier n ork (21). When differences between the Kubelka-Munk and the analytical values for a given piece of washed cloth appeared, they m-ere usually of the same t)-pe-Le., the soil-removal values as estimated by the Kubelka-Munk reflectance method of calculation were higher than when determined by chemical analysis. This means that, as a result of the action of certain detergency processes (especially those involving nonsoap synthetic detergents in low concentrations or for short washing times), the cloth surface appeared cleaner than the total soil content would indicate. At least two explanations for this behavior can be suggested. Flett ( 6 ) has stated that synthetic detergents of the type of PITacconolNR cause pigments such as lampblack to penetrate into the cotton fiber during washing. On the other hand, Schwartz (19) has suggested that the pigment may agglomerate on the surface of the cloth in the early stages of its exposure to many detergent dispersions and thus give a lowered color value. The obseivations recorded above nould be in accord with either of these explanations, as either penetration or agglomeration would lead t o higher surface reflectance values without changing the amount of pigment soil present. The data and conclusions presented above have been restricted to systems containing the black iron oxide pigment, Mapico Black, with the exception of the comparisons of the washing results shown in Tables I1 and 111. However, the authors believe t h a t their demonstration of the failure of reflectance measurements t o portray the true pigment-soil content values in these systems casts doubt upon the validity of using reflectance data t o calculate the true soil content in s y s t e m using other black pigment soils, such as carbon blacks. When reflectance values are determined on pieces of washed cloth, a composite effect, and not simply the amount of soil not removed by the Rashing process, is being measured. Soil removal into the washing solution, soil redeposition from the s'olution, pigment penetration of the fabric, and pigment agglomeration may all contribute to the total effect. The soil redisposition factor may be evaluated separately by means of so-called "whiteness retention" tests, in which clean pieces of fabric are exposed t o detergent suspensions of pigment soil, and the lowering of their surface reflectivity is noted. Reflectance values alone are of no aid, however, in evaluating the effects due to pigment penetration or agglomeration.
*-ANALYSIS OL 0
I .025
Figure 6.
I I I I I .05 ,075 . I O .I5 ,175 DETERGENT CONCENTRATION -%
Soil Removal
US.
FOR IRON
I
I
20
.25
Detergent Concentration
Iron oxide pigment soil removed from c o t t o n c l o t h by washing i n s o d i u m oleate
Despite the difficulties referred to above, the evaluation of a detergent process by reflectance measurements is still of great value in laboratory work, when relative rather than absolute soil removal values are sought, and when surface cleanliness is the principal criterion of soil removal. However, if a more nearly accurate determination of soil removal values is desired, the limitations of reflectance methods must be recognized. If analytical procedures could be developed for lampblacks and other carbon pigments, detergency evaluation with these frequently used latter materials could be put on an absolute basis, and accurate predictions of full-scale washing behavior from laboratory wash test data should be easier to make. Detergent manufacturers now use either reflectance determinations or a combination of the turbidity and whiteness retention methods for control tests to predict performance in full-scale laundering from laboratory results. A number of workers in this field have pointed out the desirability of comparing detergents in full-scale scouring or laundry trials in order to obtain reliable results. This is desirable, however, chiefly because of the differences between the methods of soiling and washing in the laboratory and in the commercial process, rather than because of differences in the evaluation of the effects the washing has produced. As in other fields of testing, laboratory evaluation is best used to screen out all but the superior materials, which are then subjected to full-scale use before the final selection is made. Light natural soils are frequently easier to remove than are heavy artificial soils, and full-scale tests may indicate that a certain detergent will remove these natural soils satisfactorily when it was not a preferred detergent on the basis of the laboratory cleaning of artificially soiled cloth. It would be desirable to reduce this difficulty by developing a satisfactory method for the use of natural soils in laboratory testing, and this is an active problem in current detergency research programs. SUMMARY
It has been shown t h a t the present methods of evaluation of detergent action on textiles using reflectance data give only relative soil removal values, when applied to washed cloth soiled with a black iron oxide pigment. The soil-removal values calculated by the linear method from reflectance data have been shown not to agree either with the values calculated by the use of t h e Kubelka-hlunk equation from reflectance data (when applied t o
December 1949
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INDUSTRIAL AND ENGINEERING CHEMISTRY
washed cloth soiled with either a carbon black or the iron oxide pigment), or with the absolute values obtained by analyses for iron (when applied t o washed cloth soiled with the latter pigment). Furthermore, the Kubelka-Munk soil-removal values agreed with the analysis values for only part of the detergent systems studied. Since the reflectance measurements often failed t o portray t h e true pigment soil content values in washed cloth soiled with a black iron oxide, it is proposed that the common practice of using such reflectance data t o portray the true pigment soil content in washed cloth soiled with other black pigment, such as carbon blacks, should be critically re-examined. The use of a method of detergency evaluation based on chemital analysis for the pigment soil appears t o be worth consideration as a means of evaluating the soil-removal action of detergents on textiles. Methods based on reflectance measurements may be preferable if surface appearance alone can be accepted as the criterion of the extent of cleaning. All types of laboratory detergency evaluation procedures, however, should be considered a s screening tests, to point the way for full-scale tests upon which the final selection of a detergent system should be based. ACKNOWLEDGMENT
The authors wish t o thank Miss E. Louise Wallace for performing the analyses for iron oxide cited above. LITERATURE CITED
(1) Bacon, 0. C., Am. Dyestuff Reptr., 34, 556-61 (Dec. 31, 1945). (2) Bacon, 0. C., and Smith, J . E., IND.ENG.CHEM.,40, 2361-70
(1948).
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Cobbs, W. W., Harris, J. C., and Eck, J. R., Oil & Soup, 17, No 1, 4-21 (1940). Dreger, E. E., Keim, G. I., Miles, G. D., Shedlovsky, L., and ROSR,J., IND.ENG.CHEM..,36, 610-17 (1944). Flett, L. H., Chem. Eng. NPWS,26, 1368-70 (May 10, 1948). Foote, Tech. Assoc. Papers, Ser. 22, 397 (1939). Harris, J. C., A.S.T.M. Bull., No. 125, 27-33 (December 1943). Ibdd., 140,76-83 (May 1946). Harris, J. C., Oil & Soap, 23, No. 4, 101-10 (1946). Harris, J. C., Rayon Textile Monthly, 26, No. 2, 83-6 (1945); NO. 3, 103-6. Harris, J. C., and Brown, C. L., Oil & Soup, 22, No. 1, 3-7 (1945) Harris, J. C . , Eck, J. R.,and Cobbs, W. W., Ibid., 19, No. 1, 3-13 (1942). Heron, G., Textile Mfr., 71, 253-5 (June 1945). Kubelka, P., and Munk, F., 2.tech. Physik, 12, 593 (1931). Laughlin, E. R.,Am. Dyestuff Reptr., 34, 280 (July 2, 1945). Lucy, F. A., Tertile W o r l d , 89, No. 9, 70-1 (1939). Nolan, P., Paper Trade J., 105, No. 14, 42-5 (1937) Rhodes, F. H., and Brainard, S.W., IND. ENG.CHEM.,21, 60-8 (1929). Schwartz,A . M., private communication. Snell, F. D., Food Inds., 13, No. 10, 48-50 (1941). Utermohlen, W. P., and Wallace, E. L., Teztdle Research J., 17, 670-81 (December 1947’1. Vaughn, T . H., and Smith, C. E., J . Am. Oil Chemists’ Soc., 25, NO. 2,44-51 (1948). Vaughn, T. H., and Vittone, A., IND.ENG.CHEM.,35, 1094-8 (1943). Vaughn, T. H., Vittone, A., and Bacon, L. R., Ibid., 33, 1011-19 (1941). Woodhead, J. A., Vitale, P. T., and Frantz, A. J., Oil & Soap, 21, NO. 11, 333-7 (1944). I
REWIVED August 30, 1948. Presented before the Division of Industrial and Engineering Chemistry a t the 114th Meeting of t h e RE ERIC AN CHEMICAL SOCIETY, Washington, D. C.
Endosperm Mucilages of Legumes OCCURRENCE AND COMPOSITION ERNEST ANDERSON University of Arizona, Tucson, Ariz.
il
I n a search for mucilages similar to carob mucilage, seeds from 163 species of legumes were studied from 1941 to 1943. Three fourths of these were found to contain mucilage yielding endosperms. By cutting across the mature seeds and observing the cut surface, the approximate amount, if any, of endosperm could be estimated. The mucilage was then dissolved in hot water, pressed through cloth, and the borax test made on it. The amount of endosperm in seeds of different species of legumes varied from zero to over 50% of the seed and the percentage of soluble niucilage in some cases amounted to over 4oyo of the seed. The endosperm mucilages of legumes are galactomannans. Although other naturally occurring mucilages were examined, none had the properties of carob mucilage. The relative amounts of ?nhydromannose and anhydrogalactose are not the same in mucilages from different species of legumes but vary from 81% anhydromannose to 16% anhydrogalactose in Sophora j a p o n i c a , to as low as 59% anhydromannose to 38% anhydrogalactose in guar. Since the physical properties of all these endosperm mucilages resemble closely those of carob mucilage, any one of them might be used in place of carob mucilage if it could be manufactured a t a suitable cost. Seeds of the legume guar yield over 4070 mucilage which can be milIed from the seed. Since this crop adds nitrogen to the soil and can be grown and harvested mechanically, guar seed appear
to be a promising industrial source of this mucilage. Tara seed occur i n Lima, Peru, as a by-product of exportation of tara pods for use in tanning. These, together with a number of other leguminous seeds from which endosperm mucilages can be milled form possible industrial sources of these mucilages. Beginning in 1943 the growth of guar in the southwestern United States was encouraged by General Mills, Inc., of Minneapolis, Minn. Soon afterward guar mucilage was placed on the market by this company.
P
R I O R t o World War I1 the mucilage from seed of the carob tree (Ceretonia silipua) was used extensively in the paper, textile, food, and some other industries under the name locust bean gum. Supplies of this seed come from countries around the Rlediterranean Sea and were greatly reduced early in the war. The carob tree is a legume. Seeds of some other legumes were also known t o be mucilaginous. I n searching for sourcm of similar mucilages, a study was made of the seed of legumes in general. LITERATURE
Von Wiesner (23) lists 10 genera of legumes containing species that have mucilaginous seed and summarizes work on these substances. Among early investigators of carob mucilage were Effront (6),Van Ekenstein (2$),and Marliere (16). Bourquelot
