Measuring detergency of oily soils in the vicinity of phase inversion temperatures of commercial nonionic surfactants using an oil-soluble dye

We have used a simple technique to measure the detergency of model oily soil from 63∶35 blended polyester/cotton fabrics using solutions of commercial linear lauryl alcohol ethoxylates in the vicinity of their phase inversion temperatures (PIT). The method involves incorporation of an oil-soluble dye in the oily soil, and measurement of reflectance at an appropriate wavelength directly on the fabric before and after wash. This technique was validated for our systems, and it provides an additional visual cue for the efficiency of soil removal. Hexadecane, which represents the linear hydrocarbon part of sebum (typical soil encountered in detergency) and has been widely studied in the literature, was used as the model oily soil. Maximal detergency occurs as a function of washing temperature at approximately 35, 62, and 80°C for ethoxylates with four, five, and six moles of ethylene oxide (C₁₂EO₄, C₁₂EO₅, and C₁₂EO₆), respectively. The oil/water interfacial tension, measured using the spinning drop method, exhibits corresponding minima and complements the detergency results. Addition of sodium carbonate, a salting-out electrolyte, decreases the optimal detergency temperature (ODT) of C₁₂EO₅, shifting its behavior toward C₁₂FO₄ whereas addition of anionic surfactant increases the ODT of C₁₂FO₅, mimicking the behavior of a higher ethoxylate.     

Phase behavior and detergency study of lauryl alcohol ethoxylates with high ethylene oxide content

Nonionic surfactants such as fatty alcohol ethoxylates have been extensively used in many detergent applications, because of their high calcium ion tolerance, low critical micelle concentrations, and mildness. Although ethoxylates containing high ethylene oxide (EO) content (EO>10 moles) score higher than their low-FO counterparts on many of these desired properties, they have not been studied adequately in the context of detergency, primarily because their cloud points (CP) are higher than normal wash temperatures, typically >100°C, and thus cannot be measured. However, once the CP are manipulated appropriately using salting-out electrolytes, these surfactants can offer certain distinct advantages in terms of their molecular and phase structure. We have studied the phase structure and clouding behavior of tetradecyl ethylene-oxide mono dodecyl alcohol (C₁₂EO₁₄), a broad-range ethoxylate, as a function of the concentrations of various electrolytes. We found that, beyond a certain critical concentration, the CP decreases monotonically with increasing salt concentration. For sodium salts of various anions, the CP depression is inversely proportional to the lyotropic number of the anion. Similarly, for chloride salts of various cations, CP depression is inversely proporitional to the lyotropic number of the cation However, the effect of changing anion is stronger than that of changing cation. A micrograph of a water penetration scan at room temperature indicates the presence of isotropic L₁; hexagonal, isotropic L₂; and solid phases with increasing surfactant concentration. As is the case with low-FO nonionics, a maximum in detergency of model oily soils was found to correlate well with the minimum in oil/water interfacial tension when plotted vs. temperature. Ross Miles foam height increases with increasing concentration of salt.     

Optimization of nonionic/anionic surfactant blends for enhanced oily soil removal

Previously reported results for alcohol ethoxylate surfactants have shown that optimum removal of both nonpolar and sebum- like liquid soils from polyester/cotton fabric occurs at the phase inversion temperature (PIT) of the surfactant- water- soil system. A similar correlation between phase inversion and optimum detergency has been identified for detergent systems containing mixtures of nonionic and anionic surfactants such as alcohol ethoxylates and alcohol ethoxysulfates. Experimental techniques other than direct detergency studies are described which allow determination of the optimum nonionic/ anionic surfactant ratio for removal of a particular soil at a specified temperature. In addition, implications of these results for development of temperature- insensitive detergent formulations containing alcohol ethoxylates are discussed.     

脂肪醇乙氧基化物的环氧乙烷加合数对非离子/阴离子表面活性剂混合体系洗涤力的影响

研究了在非离子表面活性剂／阴离子表面活性剂／电解质的混合体系中,直链脂肪醇乙氧基化的ＥＯ数对体系洗涤力的影响效果,并用相转移化温度（ＰＴＴ）和油／水界面张力（ＩＦＴ）的观点对实验结果进行了解释,研究表明,随着体系中非离子与阴离子表面活性剂相对含量的增大,为达到最大洗涤力,非离子表面活性剂的ＥＯ数也需随之增大;随着体系中电解质含量的增大,最佳ＥＯ数也需随之增大,但前者的影响效果远高于后者。     

Nonionic surfactants containing propylene oxide

Physical and surface active properties of ethoxylates are altered by the inclusion of propylene oxide (PO) groups. The location of PO within the ethoxylate (EO) chain can be as important a factor as the relative amounts of PO and EO. The optimum position of the PO was shown to be a single discrete block of PO located in approximately the middle of the ethoxylate chain. The influence of PO on surfactant properties was assessed for several alcohol ethoxylates and nonyl-phenol ethoxylates. Pour points and gelling tendencies were lowered at the expense of detergency, foaming and wetting power. Presented at the AOCS meeting in Philadelphia, PA in May 1985.     

Formulating Nonionic Detergents via the Integrated Free Energy Model

This work explores the optimum detergency conditions of alkyl ethoxylate (C_XEO_Y) surfactants with the integrated free energy model (IFEM). IFEM is a molecular thermodynamic model that calculates the free energy of formation of oil-swollen spherical micelles, with a core solubilization radius Ro, using surfactants from empty (oil-free) micelles and oil molecules from a continuous oil phase. The described geometry allows for rapid calculations, using a personal laptop (3.4 GHz processor), where each solubilization energy profile (free energy vs. Ro curve) can be solved in 5 min or less. While previous work showed quantitative agreement between IFEM predictions and experimental solubilization of alkanes in C_XEO_Y micelles, this work explores the possibility of using IFEM as a tool in surfactant selection. Experimental work has shown that detergency improved when operating near the phase inversion temperature (PIT) of the surfactant-hexadecane system. The IFEM simulations in this work show, for the first time, that IFEM can be used to predict the PIT of surfactant-oil systems, and that the surfactants selected via this method are consistent with the selection guided by experimental observations.     

High-temperature stability of alcohol ethoxylates

The oxidative stability of alcohol ethoxylates during storage and handling is studied. Realistic conditions are modelled by heating in quiescent air. More rigorous, extensively aerated conditions are modelled by thermogravimetry with mass spectrometric detection and differential scanning calorimetry with vapor-phase sampling. In quiescent air, C_12–15 alcohol with an average of 7 moles ethylene oxide (EO) is discolored at 204°C, with some increase in aldehydes, but there is no change in the EO distribution of the sample. Under extensively aerated conditions, increased oxidation occurs above 150°C, with a loss of one EO unit on average, and increases in CO and CO₂ occur in the vapor phase above the sample. High-temperature oxidation under extensive aeration is not affected by an antioxidant or by raising the pH of the sample from 6.4 to 7.5.     

Laundry Detergency of Solid Nonparticulate Soil or Waxy Solids: Part II. Effect of the Surfactant Type

In this work, methyl palmitate with a melting point around 30°C was used as a model of waxy soil. Its detergency was evaluated with a hydrophilic surface (cotton) or a hydrophobic surface (polyester) using different surfactants: alcohol ethoxylate (EO9), sodium dodecyl sulfate (SDS), methyl ester sulfonate (MES), methyl ester ethoxylate (MEE), and two extended surfactants (C_12,14-10PO-2EO-SO₄Na and C_12,14-16PO-2EO-SO₄Na). The detergency efficiency at a 0.2 wt.% surfactant and 5 wt.% NaCl gradually increased while redeposition gradually decreased with increasing washing temperature in most studied surfactant solutions; this was observed both above and below the melting point of methyl palmitate on both studied fabrics. If the methyl palmitate was heated above the melting point when deposited on the fabric, it was better able to penetrate into the fabric matrix as compared to deposition below the melting point, resulting in poorer detergency for heated deposition, particularly for washing temperatures lower than the melting point. Among the surfactants studied, the nonionic surfactant (EO9) showed the highest detergency efficiency (73–94%) at any washing temperature especially on the polyester fabric. For washing temperatures below the melting point, detergency performance correlated well with the contact angle of surfactant solution on the solid methyl palmitate surface for all studied surfactants when salinity was varied. In this work, conditions resulting in the highest detergency below the melting point corresponded to the highest detergency above the melting point, suggesting this as a systematic approach to formulating below the melting point of the soil. Charge of particles or fabric was not observed to be important to the detergency mechanism, but steric factors resulting from surfactant adsorption were observed to be important mechanistic factors in waxy solid detergency.     

Foam enhancement by short-chain hydrophobe alcohol ethoxylates in light-duty liquids

This study examined linear alcohol ethoxylates as foam-enhancing agents in light-duty liquids. The ethoxylates were formulated as supplementary surfactants to an anionic main surfactant system. The relationship between ethoxylate structure and performance was elucidated, comparisons were made between ethoxylates and other recognized foam-enhancing agents, and a representative light-duty liquid formula was optimized. Performance evaluation focused on manual plate washing capacity but also included agitation foam volume, surface activity, cloud and clear temperatures, viscosity and grease cutting. Shortchain alcohol ethoxylates with a high degree of ethoxylation (such as C₈ with 70% or 7 moles of ethylene oxide) gave optimum performance that was comparable to or better than acknowledged foam-enhancing agents. The substitution of an alcohol ethoxylate for a fatty acid ethanolamide in the test formulation resulted in substantially lower formulation viscosity.     

Selecting the optimal linear alcohol ethoxylate for enhanced oily soil removal

Use of nonionic surfactants in detergent products has become increasingly popular because of their tolerance to hardness ions and their effect on lowering the critical micelle concentration of anionics. Their performance as detergents, however, is very sensitive to changes in temperature and electrolyte concentration, which need to be carefully controlled in order to ensure that phase inversion conditions prevail. For a fixed temperature in an application, the only variables available for optimizing the performance of a system containing nonionics are: the type of nonionic, and the concentrations of electrolytes and anionics. Based on the mutual interactions of these ingredients in mixed systems, we have devised some guidelines for selection of the optimal ethylene oxide (FO) chain length in lauryl alcohol ethoxylate type of nonionics for a range of electrolytes and anionic surfactant concentrations. For any given concentration of electrolytes (sodium carbonate and sodium tripolyphosphate), anionic (sodium linear alkyl benzene sulfonate) and nonionic, the detergency of synthetic sebum from blended polyester/cotton fabrics shows a maximum as a function of average FO moles in the nonionic. Oil/water interfacial tension shows an expected reverse trend. The optimal EO moles (for maximal detergency) show a monotonically increasing trend when plotted as a function of the ratio of nonionic to anionic concentration for a fixed level of electrolyte. The optimal EO moles also increase with increasing level of electrolytes in the system. However, the effect of nonionic/anionic ratio is much stronger than the effect of electrolytes on the optimal EO moles.     

Comparison of high-temperature gas chromatography and CO2 supercritical fluid chromatography for the analysis of alcohol ethoxylates

This work compares capillary supercritical fluid chromatography (SFC) and capillary high-temperature gas chromatography (HTGC) for the quantitative characterization of nonionic alcohol ethoxylate surfactants. Supercritical fluid chromatographic separations of the alcohol ethoxylates were obtained with a density-programmed carbon dioxide mobile phase and a fused silica capillary column. High-temperature gas chromatographic separations were obtained with a high-temperature polyimide-coated fused silica capillary column. In addition, a procedure was developed for the quantitation of the capillary chromatographic data using flame ionization molar response factors based on the effective carbon theory. The alcohol and ethoxylate distributions, mean molecular weights and average moles of the ethylene oxide are rapidly calculated from the chromatographic data. Advantages and limitations of SFC and HTGC procedures are illustrated and discussed. Based on this work, the following conclusions can be drawn: i) For routine quality control analyses of known alcohol ethoxylates, SFC and HTGC appear to be equally applicable. ii) SFC has the advantage of time because derivatization is not required, although derivatization does improve resolution. iii) HTGC has the advantage of resolving C₁₂ through C₁₈ alcohol ethoxylate oligomers, avoiding ambiguous identification of components. iv)SFC and HTGC both have disadvantages. SFC has a resolution limitation and HTGC discriminates against high molecular-weight components. Presented in part at the 83rd Annual Meeting in Chicago, IL, May 1991.     

The effect of “peaking” the ethylene oxide distribution on the performance of alcohol ethoxylates and ether sulfates

In comparison to conventional ethoxylates, a “peaked” ethoxylate has less unethoxylated alcohol, is more soluble, and has a higher concentration of the more desired homologs. A “peaked” ethoxylate therefore has a lower odor, is easier to formulate into liquids, and can perform better in terms of detergency and wetting performance. Since “peaked” ethoxylates have less unethoxylated alcohol, less alcohol sulfate is formed during sulfation. Decreasing the content of alcohol sulfate increases the capacity to salt-thicken and can potentially improve skin mildness.     

Polarity of broad and narrow distributed ethoxylates of fatty alcohols

The polarity of broad- and narrow-range alcohol ethoxylates was studied by inverse gas chromatography. The narrow-range alcohol ethoxylates (NRD) exhibit higher polarity at 70°C than the broadly distributed products (BRD). The difference in polarity between BRD and NRD products decreases, however, with increasing temperature and diminishes at 110°C, which can be predicted from structural increments. The rise of the average number of oxyethylene units increases polarity of the examined products. The changes of ethoxylate polarity are well described by examined parameters with the exception of ΔG^m _s(CH₂).     

Cold Water Detergency of Triacylglycerol Semisolid Soils: The Effect of Salinity,Alcohol Type,and Surfactant Systems

Cold water detergency of triacylglycerol semisolid soils is much more challenging than liquid vegetable oils due to poorer interaction between surfactants and semisolid soil. This research seeks to improve the removal efficiency of semisolid soils below their melting points using surfactant-based formulations containing different alcohol additives. To this end, cold water detergency of solid coconut oil and solid palm kernel oil was investigated in various surfactant/alcohol systems, including single anionic extended surfactants, single nonionic alcohol ethoxylate surfactants, and a mixture of anionic surfactants. A series of alcohols (2-butanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol) were added to the surfactant formulations to investigate cold water detergency improvement. While cold water detergency using surfactants alone was poor, it was considerably improved when optimum salinity (S*) and 1-heptanol, 1-octanol, or 1-nonanol were introduced to the studied surfactant formulations. The maximum detergency of solid coconut oil exceeded 90% removal in the 0.1 w/v% C_14-15-8PO-SO₄Na/0.2 w/v% 1-octanol/4 w/v% NaCl system (a final optimized surfactant system) at a washing temperature of 10°C versus 22.9 ± 2.2% in the surfactant alone (not at optimum salinity and no additive). Further analysis showed that improved cold water detergency using surfactant/intermediate-chain alcohols/NaCl could be correlated with high wettability (low contact angle) as well as favorable surfactant system-soil interaction as observed by lower interfacial tension values. In contrast, the improved cold water detergency was observed to be independent of dispersion stability. This work thus demonstrates that surfactant system design, including additives, can improve cold water detergency of semisolid soils and should be further explored in future research.     

Effect of alkyl carbon chain length and ethylene oxide content on the performance of linear alcohol ethoxylates

A grid of 30 surfactants varying from C₈ to C₁₈ in carbon chain length and from 40 to 80% in ethylene oxide (EO) content were examined to determine the effect of molecular structure on the physical properties (density, melting point, solution viscosity) and performance properties (surface activity, detergency, hard-surface cleaning, foaming, wetting) of linear alcohol ethoxylates. Results show that while physical propeties are influenced primarily by EO content, both carbon chain length and EO content are important to performance. Optimum carbon chain length is also shown to depend strongly on surfactant concentration. Presented at the AOCS meeting in New Orleans in May 1987.     

Ethylene oxide oligomer distribution in nonionic surfactants via high performance liquid chromatography (HPLC)

A high performance liquid chromatography (HPLC) method using adsorption columns combined with linear gradient elution has been developed for the determination of ethylene oxide (EO) distribution in nonionic surfactants. The quantitative ethoxylate adduct distribution in single-carbon-number and mixed-carbon-number primary alcohol-based samples can be obtained. The HPLC method is also applicable for determining the molar EO distributions in diverse ethylene oxide adduct compounds such as alkylphenol ethoxylates, branched alcohol ethoxylates and secondary alcohol ethoxylates. Nonionic surfactant samples containing adducts up to 25 mol have been successfully separated and the individual adducts quantitated.     

The effect of polar soil components on the phase inversion temperature and optimum detergency conditions

Previously reported results have shown that optimum removal of a hydrocarbon soil from polyester/cotton fabric occurs above the cloud point at the phase inversion temperature (PIT) of nonionic surfactant/water/soil systems. Through comparison of phase behavior measurements to radiotracer detergency studies using model sebum soils, i.e., cetane/oleyl alcohol and cetane/oleic acid blends, the relevance of the PIT for removal of nonpolar/polar soil mixtures has also been demonstrated. For these soils, the PIT is typically below the cloud point, and the highest level of soil removal is found between the PIT and cloud point rather than only at the PIT. This relatively temperature-insensitive soil removal is attributed to the preferential solubilization of polar soil components which continually changes the composition of the residual soil during the washing cycle. These findings explain the long-observed results that 4- to 5-EO alcohol ethoxylates are preferred for the removal of nonpolar soils while 6- to 9-EO ethoxylates are the more effective surfactants for sebum soils.     

脂肪酸甲酯乙氧基化物的物化性能研究

对不同烷链和不同EO加合数的脂肪酸甲酯乙氧基化物的物化性能进行了测试,并对FMEE在洗衣粉中替代AEO9进行了初步研究。结果表明,与脂肪醇乙氧基化物相比,FMEE泡沫低,水溶速度快,对油脂增溶能力强,用棕榈油甲酯乙氧基化物替代AEO9在洗衣粉中应用可改善去污性能并降低成本。     

Studies on viscosity build‐up properties of sodium alcohol ether sulphates

Narrow and broad range distributed ethoxylates of linear C₁₂–C₁₄ alcohols were synthesised using a calcium‐based unconventional catalyst and NaOH, respectively. Their composition was determined by gas chromatography. Sulphates were synthesised in the traditional way by reaction of ethoxylates with sulphur trioxide in a film reactor and neutralised with sodium hydroxide. Products were characterized by the ethoxylate homologue distributions and acid value of the intermediate sulphuric acid derivatives. Viscosity build‐up properties of the narrow and broad range distributed ethoxylates‐based sodium alcohol ether sulphates were studied. Effects of ethoxylate homologue distribution were compared with those of average ethoxylation grade and sulphation degree. It was shown that the acid number of the obtained sulphates, ethoxylate homologue distribution, average polyaddition degree and sodium chloride content influenced remarkably the thickening ability of ethoxylates. Furthermore, it was found that the limited content of the longer ethoxylate chains in narrow range distributed alcohol ethoxylates is responsible for enhanced viscosity build‐up properties of their sodium sulphate derivatives. The following empirical relationship was obtained: log η = (2.99 ± 1.25) + (3.78 ± 0.86) × 10⁻²V − (1.48± 0.15)N_av − (2.69 ± 0.7) × 10⁻²A_N + (0303 ± 0.058) × C_surf + (0.832 ± 0.041) × C_NaCl where η is the viscosity in cP, V is the distribution coefficient, N_av is the average oxyethylation degree, A_N is the acid number of alcohol ether sulphuric acid and C_surf and C_NaCl are concentrations (wt%) of the studied surfactants and sodium chloride, respectively. © 1999 Society of Chemical Industry     

The energetics of surfactant adsorption at the air-water interface

The standard free energy, enthalpy, and entropy changes (ΔG, ΔH, and ΔS, respectively) for the adsorption at the air-water interface of a commercial ethylene oxide (EO) adduct of straight chain nonylphenol from monomer solution at the critical micelle concentration (CMC) have been calculated from surface tension-concentration data at 21C–45C using the Gibbs equation, the standard free energy change equation ΔG=−RT (In interfacial monomer concentration/CMC), and the Gibbs-Helmholtz equation which gave ΔH directly from the slope of the (ΔG/T) vs (1/T) function. The CMC and surface tension at the CMC (γCMC) decreased, and −ΔG and molecular area increased slightly, with increasing temperature. The ΔH and ΔS values were positive, and appear explainable by the postulations applied to micellization. At ambient temperature (28C) an increase in the (EO) mol ratio of straight chain nonylphenol and C₁₃ secondary alcohol ethoxylates resulted in increases of CMC, γCMC, and molecular area, and slight decreases in −ΔG. A comparison of the 9 (EO) mol ratio adducts of C₁₃ straight chain primary and secondary alcohols showed that the CMC and molecular area of the secondary alcohol ethoxylate were larger, and the γCMC and −ΔG smaller, than the corresponding values of the primary alcohol ethoxylate.