A triply labeled particulate soil for detergency studies

A kaolinite type of clay made radioactive by neutron irradiation (Spinks Bandy Black), described in an earlier report, has undergone extensive testing to determine its suitability as a particulate component of an artificial radioactive soil. The other components of the soil are labeled with¹⁴C and tritium. The incorporation of the radioactive clay into an established soil required the development of a reproducible padding procedure and the development of suitable analytical methods for the clay, as well as modification of the existing method for¹⁴C and tritium in the presence of the radioactive clay. A problem arose when it was noticed that, after the padding step, the specific activity of the clay adhering to the fabric was higher than the starting clay. This was traced to the fact that Spinks Bandy Black is not only a mixture of varying particle sizes, but of changing chemical composition with varying particle size. Thus, one could not readily convert radioactivity to weight. The problem has been resolved by resorting to chemical analysis for SiO₂ and Al₂O₃ of a few representative swatches from each padding run to give the weight of clay per swatch and thus the specific activity. Chemical and radiochemical analyses of the swatches after laundering have demonstrated that further disproportionation of the clay is minor. A large Terg-O-tometer washing study was made under a variety of conditions to determine the precision of the method for all three labeled components of the soil. It was found from sets of four replicates that the precision for clay detergency is ±2.5%; for the polar fatty soil detergency (¹⁴C) is ±2.3%; and for the nonpolar fatty soil detergency (tritium) is ±3.5%. Redeposition of the clay in the presence of a built detergent is usually less than 1%.     

Further studies of detergency correlation

The significance of the relationships of the linearity constants of a previously reported detergency-micellar solubilization function (1) to surfactant HLB (hydrophile-lipophile balance), boundary tensions, and soil dipole moment was extended, first, by demonstrating their existence in systems of four homologous surfactants with one soil or four classes of soil with one surfactant, and second, by showing in every case that they are probably physical rather than random because they contain fewer constants than the number of points (four) used in their derivation. A study of a series of surfactant-soil systems consisting of a family of polyoxyethylated nonyl phenols and a family of saturated fatty acid soils (12–18 carbon) revealed linearity of the R-log (M/CMC) and surfactant HLB-log (M/CMC) functions for values of R (ethylene oxide mole ratio) between 15–50 and 10–100, respectively (M=surfactant concentration giving ca 100% removal of 16 and 18 carbon fatty acids, and CMC=critical micelle concentration). The validity of the semi-logarithmic functions was confirmed by the fact that they indicated linearity between R and surfactant HLB as previously reported (2). Abnormally high nonyl phenol adduct concentrations (2.7–3.8%) were required to give good fatty acid removal. It was suggested that the initial decrease in detergency with increase of fatty acid soil HLB from 6.5–9.8, followed by increasing detergency as the soil HLB continued to increase to 11.25, was due to differences in the relative magnitudes of the soilsubstrate adhesive forces and micellar solubilization existing in the soil HLB range. Sodium dodecyl benzene sulphonate was a good detergent of the saturated fatty acids, soil removal being independent of soil HLB for the 12–18 carbon acids. The fatty acid soaps were poor detergents of these soils. A “net ethylene oxide solubilizing power” method of computing HLB was proposed, based on known polar group hydrophobe-solubilizing values.     

Worldwide studies of mixed active laundry detergency

A cooperative study involving laboratories in the United States, Europe and Japan was conducted to investigate the detergency performance of mixed active detergents. Each location tested mixtures commonly manufactured in their region using wash conditions typical of their area. The utility of the data in selecting optimum cost/performance formulations is discussed. Under typical wash conditions found in the United States and Japan, a mixed-active formulation is not required. In most cases, optimum detergency is obtained by a linear alkylbenzene sulfonate (LAS) based formulation. In Europe, a mixed active detergent is required. Although LAS provides optimum performance, some soap (or soap plus nonionic |NI|) must be added to control foam.     

Cold water detergency studies using radiolabeled soils

The effects of single and multiple washing and of resoiling-rewashing of cotton and synthetic fabrics have been studied in Tergotometer tests at various levels of temperature, detergent concentration and water hardness. The soiling mixture consisted of a seven component sebum tagged with tritium and carbon-14; in some tests gammaray emitting Kaolinite clay was also used. Linear primary alcohol ethoxylate (LAEO) and linear alkylbenzene sulfonate (LAS) were used for surfactant type comparisons. In single wash tests in both hot and cold water, LAEO was generally more effective than LAS in removing sebum. This was particularly noticeable at low product concentration where insufficient sodium tripolyphosphate was present to sequester the water hardness. A 1/1 blend of the two surfactants approached LAEO in performance. The nonpolar sebum fraction was more readily removed from Dacron or nylon in cold water; otherwise, detergency was generally better at high temperatures. In rewash tests, using labeled lube oil, cholesterol and clay, a progressive increase in soil removal was found during five wash cycles. The nonpolar lube oil component was the most difficult to remove from permanent press Dacron-cotton (PP), but was more readily removed from cotton. The more polar cholesterol and especially the clay were more easily removed from PP. LAEO gave better detergency both hot and cold than LAS, especially in hard water. On cotton swatches resoiled with sebum after each wash the residual sebum content was still increasing after five cycles. With PP in soft water, a steady state was reached after three to five cycles. Soil buildup was greater as hardness increased and as wash temperature and active matter concentration decreased, and was generally greater on cotton than on PP. LAEO allowed appreciably less soil buildup than did LAS especially at low concentration in hard water, indicating a reduced requirement for sodium tripolyphosphate. Presented before the AOCS Meeting, New Orleans, April 1970.     

A method to improve reproducibility in detergency tests

Conclusions 1. A method for detergency tests has been described which, it is felt, yields a higher degree of reproducibility than the soiled fabric-Launderometer Method commonly employed. In terms of Standard Deviation, the reproducibility of a determination was found to be about ±0.7 when results were expressed as units of black removed, and under the conditions described in this paper. 2. This method makes it possible to determine with reasonable assurance differences between detergents which are greater than 6% (Detersive Efficiency). 3. The simplicity of apparatus required for the test should make it available for use in other laboratories. There is also the possibility that any type of standard soiled fabric could be used in the test, inasmuch as the manner of using the soiled fabric more than the manner of preparing it, largely determines the reproducibility of the method. (This point is at present under investigation.) 4. The method, it is thought, might be adapted to measure relative efficiencies of various types of washing machines, as well as for evaluating detergents.     

Dimensional analysis applied to detergency

Six fundamental soil and surfactant variables of the detergency process have been combined by dimensional analysis into a complete and valid set of three dimensionless products which represent the mechanism by a diagram comprising a family of curves of two of the products at fixed values of the third. Five soils and six surfactants have been combined into eighteen soil-surfactant systems to validate the dimensional analysis. The dependent parameter of soil removal, normally viewed as dimensionless, was assigned the dimensions of mass times length following more subtle considerations of the mechanism. This means of representing the detergency process is a considerable improvement over the previously established transcendental relationships of selected groups of soil-surfactant systems (2).     

Statistical approach to detergency. III. Effect of artificially soiled test cloth

The relative effectiveness of several proprietary detergents is measured in cleaning “standard” soil cloths. Quantities of soil removal are related to detergent type, and to polarity or hydrophilicity of the soil and cleaning media. Various calculation methods and statistical treatments of detergency data are discussed.     

Behavior of surfactant mixtures in model oily-soil detergency studies

A study of roll-up in a model oily-soil detergent system has shown that the addition of a second surfactant in a minor amount to an effective detergent can either enhance or inhibit roll-up. Which effect takes place depends on the relative surface activity of the components, the levels used, and, for ionic surfactants, the electrolyte content. Addition of anionic surfactants can reduce the performance of an effective nonionic under low ionic strength/low hardness conditions. However, in high ionic strength/high hardness solutions, where the anionic is effective, the situation is reversed and addition of the nonionic component can, in some cases, reduce the rate of roll-up. Roll-up behavior appears to be controlled by the oil/ water interfacial tension. When the interfacial tension increases above a critical value, roll-up is inhibited. A theory that has been used to predict surface tensions of mixtures is also useful in estimating oil/water interfacial tensions. The theory provides an understanding of why the interfacial tension can rise when mixed micelles are formed.     

The development of a particulate radioactive soil for detergency studies

A sample of kaolinite clay has been tagged by neutron irradiation. After an extended cooling period (18 months) to allow the short lived nuclides to decay, the clay is still sufficiently radioactive to use it in detergency studies. Extraction tests show that about 25% of the radioactivity is labile, i.e., removed by sodium tripolyphosphate but that the remainder is strongly fixed in the clay matrix, resisting extraction by built detergents. The clay has a number of nuclides emitting both beta and gamma radiation. Analytical methods for both types of radiation have been developed for use with fabrics and wash waters. The clay has been combined with the doubly labeled fatty soil (³H and¹⁴C) to make a triply labeled particulate soil. Tergotometer runs with three test fabrics show good precision for all three labeled components of the soil. Redeposition measurements were also made and showed that a considerable fraction of the residual clay on a washed swatch may in fact be due to redeposition rather than retention. Some problems remain in the application of this synthetic soil: the padding step must be modified so that the clay is more tenaciously bound to the fabric; a more automatic method of padding is required to handle large numbers of samples; the specific activity of the clay should be increased so that liquid scintillation analysis for all three tagged components can be made on a single sample of wash water. Presented at the AACC-AOCS Joint Meeting, 1968, Washington, D.C.     

The determination of doubly labeled artificial soil in detergency studies

A liquid scintillation method for the determination of carbon-14 and tritium labeled soil on white fabric has been developed. The method involves the use of an external standard to determine the counting efficiency for each isotope. The requirement that these determinations be made on swatches of fabric complicates the analysis because of their variable antiquenching effect. The method has been appied to cotton, Dacron, nylon, and Dacron/cotton. A computer program has been written which accepts the raw counting data and performs all necessary calculations, printing out the data in a convenient form. The great convenience of the method has encouraged its application to large scale screening studies without sacrificing the precision, accuracy, or selectivity normally associated with small model systems.     

A kinetic study of fabric detergency

The kinetics of soil removal were investigated under domestic laundry conditions by incorporating small swatches of four artificially soiled test fabrics into a standard load of clean cotton goods. This prevented soil redeposition from affecting the soil removal rate. Two runs were analyzed, one with an anionic and the other with a nonionic detergent. Assessment of the amount of soil remaining on the fabric was made by reflectivity measurements interpreted according to the Kubelka-Munk equation. First-order kinetics were found to prevail for periods ranging from the first 6 min of the wash cycle to the entire 20 min, depending upon test fabric and detergent. For these lengths of time, the rate of soil removal was directly proportional to the amount of soil remaining on the fabric. The 8 first-order rate constants had rather similar values, varying at most by a factor of 2.3. The average value, 0.109 min⁻¹, corresponds to a 6.4-min wash period for removing one-half of the soil and to a 21-min period for removing 90% of the soil from the soiled fabric. The magnitude of the response of the four artificially soiled test fabrics to the two detergents is compared and discussed in terms of the soiling materials. The nonionic detergent was more effective in cleaning a fabric soiled mainly with kaolin and wool fat, while the anionic detergent was more effective with a fabric containing large amounts of liquid oily soil plus carbon black and oleophilic bentonite.     

Kinetic studies of detergency. I. Analysis of cleaning curves

The kinetics of removal of thin films of pure radioactive tristearin from a stainless-steel surface by .03M NaOH was studied in a circulation system. The data obtained are consistent with the presence of two species of tristearin, each species being removed simultaneously by a first-order process and behaving independently of the other. The principal evidence for the existence of the two species is the excellent agreement of the experimental data with the mathematical techniques of kinetics over a wide range of experimental conditions. Rate constants for the removal of each species and the relative proportions of the two species are given for different experimental conditions. It is shown that the difference between the two species must be based on some physical factor, and possible explanations are discussed. The presence of two species gives a satisfactory explanation for hitherto unexplained results of other workers.     

Statistical approach to detergency evaluation. Correlation of performance data with gas chromatographic patterns of alkylbenzenes

The precision of a standardized detergency test based on the use of a Tergotometer and U.S. Test Cloth was found at a concentration of 0.4 and 0.5%. At these concentrations, the standard deviation was 0.56% soil removal units, and precision at a 95% confidence limit was±1.12% soil removal units. The detergency of some built spray-dried detergents was examined by this method and found to differ significantly, though chemical compositions were identical. Gas chromatographic analysis of the alkylbenzenes obtained by desulfonation of the alkylbenzene sulfonates indicated small structural variations which correlated with the observed variations in the detergency. Paper II in a series entitled Detergency Evaluations, presented at the meeting of the American Oil Chemists' Society, St. Louis, Missouri, May 1–3, 1961.     

A one-pot approach to dendritic star polymers via double click reactions

A class of well-defined dendritic star polymers with poly (ε-caprolactone) (PCLs) on the periphery has been prepared via one-pot double click reactions (Cu-catalyzed azide/alkyne click chemistry, i.e., CuAAC and Diels–Alder [4+2] cycloaddition reactions). The predecessors for Diels–Alder reaction, maleimide end-functionalized PCLs were produced by ring-opening polymerization (ROP). Obtained dendritic star polymers were characterized by ¹H NMR, size exclusion chromatography (SEC), UV/vis, and fluorescence spectroscopy.     

A motor oil soil for detergency testing

Bright Stock/Pale Oil (BS/PO) soil represents a typical motor oil soil, but it is more constant in composition than clean or dirty commercial motor oil. It does not require the addition of any dye, as is the case with mineral oil or cooking oil, and when applied to cloth, it produces very uniform soilings. The statistical reproducibility of detergency tests run with BS/PO is better than mineral oil and about as good as sebum.     

Application of statistical analysis to mixed soil detergency

In previous studies, statistical method using distribution of detergent power and that of resistance of soil against washing was applied to analyze detergency of oily soil and solid particle soil. In this paper, this method was applied to an analysis of detergency of mixed soil. Artificially soiled cloth prepared by aqueous dispersion method was used as a mixed soil sample. Four-time consecutive washing tests were conducted under the same washing condition in Terg-O-Tometer using two kinds of detergent solution and distilled water. Change of removal efficiencies due to repetitive washing was used to determine the two distributions. Result shows that detergent power can be expressed as cumulative distribution function. In washing simulation using the cumulative distribution functions, the predicted removal efficiencies corresponded with experimental values. Moreover, the effect of soil aging on distribution of soil resistance against washing was found to move the distribution curve toward high resistance. These results show that the method using two statistical distributions can be applied to the detergency of mixed soil.