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Laundry detergent
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Laundry detergent is a type of detergent (cleaning agent) used for cleaning dirty laundry (clothes). Laundry detergent is manufactured in powder (washing powder) and liquid form.
While powdered and liquid detergents hold roughly equal share of the worldwide laundry detergent market in terms of value, powdered detergents are sold twice as much compared to liquids in terms of volume.[1]
History
[edit]
From ancient times, chemical additives were used to facilitate the mechanical washing of textile fibers with water. The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BC in ancient Babylon.[2]
German chemical companies developed an alkyl sulfate surfactant in 1917, in response to shortages of soap ingredients during the Allied Blockade of Germany during World War I.[1][3] In the 1930s, commercially viable routes to fatty alcohols were developed, and these new materials were converted to their sulfate esters, key ingredients in the commercially important German brand FEWA, produced by BASF, and Dreft, the U.S. brand produced by Procter & Gamble. Such detergents were mainly used in industry until after World War II. By then, new developments and the later conversion of aviation fuel plants to produce tetrapropylene, used in household detergents production, caused a fast growth of domestic use in the late 1940s.[3]
Soils
[edit]Washing laundry involves removing mixed soils from fiber surfaces. From a chemical viewpoint, soils can be grouped into:
- Water-soluble soils such as sugars, inorganic salts, urea, and perspiration.
- Solid particulate soils such as rust, metal oxides, soot (carbon black), carbonates, silicates, and humus.
- Hydrophobic soils such as animal fats, vegetable oils, sebum, mineral oil, and grease.
- Proteins such as blood, egg, milk, and keratin from skin. These require enzymes, heat or alkali to hydrolyze and denature them into smaller parts before they can be removed by the surfactants.
- Bleachable stains such as wine, coffee, tea, fruit juices, and vegetable stains. Bleaching is an oxidation reaction which turns the colored substance into a colorless one, which either stays on the fabric or may be easier to wash out.
Soils difficult to remove are pigments and dyes, fats, resins, tar, waxes, and denatured protein.[4]
Components
[edit]Laundry detergents may contain builders (50% by weight, approximately), surfactants (15%), bleach (7%), enzymes (2%), soil antideposition agents, foam regulators, corrosion inhibitors, optical brighteners, dye transfer inhibitors, fragrances, dyes, fillers and formulation aids.[4]
Builders
[edit]Builders (also called chelating or sequestering agents) are water softeners. Most domestic water supplies contain some dissolved minerals, especially in hard water areas. The metal cations present in these dissolved minerals, particularly calcium and magnesium ions, can react with surfactants to form soap scum which is much less effective for cleaning and can precipitate onto both fabric and washing machine components. Builders remove mineral ions responsible for hard water through precipitation, chelation, or ion exchange. In addition, they help remove soil by dispersion.
The earliest builders were sodium carbonate (washing soda) and sodium silicate (waterglass). In the 1930s phosphates (sodium phosphates) and polyphosphates (sodium hexametaphosphate) were introduced, continuing with the introduction of phosphonates (HEDP, ATMP, EDTMP). While these phosphorus-based agents are generally non-toxic they are now known to cause nutrient pollution, which can have serious environmental consequences. As such they have been banned in many countries, leading to the development of phosphorus-free agents, such as polycarboxylates (EDTA, NTA), citrates (trisodium citrate), silicates (sodium silicate), gluconic acid and polyacrylic acid; or ion exchange agents like zeolites.
Alkali builders may also enhance performance by changing the pH of the wash. Hydrophilic fibers like cotton will naturally have a negative surface charge in water, whereas synthetic fibers are comparatively neutral. The negative charge is further increased by the adsorption of anionic surfactants. With increasing pH, soil and fibers become more negatively charged, resulting in increased mutual repulsion. The optimum pH range for good detergency is 9–10.5.[5] Alkalis may also enhance wash performance via the saponification of fats.
Builder and surfactant work synergistically to achieve soil removal, and the washing effect of the builder may exceed that of the surfactant. With hydrophilic fibers like cotton, wool, polyamide and polyacrylonitrile, sodium triphosphate removes soil more effectively than a surfactant alone. It is expected that when washing hydrophobic fibers like polyesters and polyolefins, the effectiveness of the surfactant surpasses that of the builder, however this is not the case.[6]
Surfactants
[edit]
Surfactants are responsible for most of the cleaning performance in laundry detergent. They provide this by absorption and emulsification of soil into the water and also by reducing the water's surface tension to improve wetting.
Laundry detergents contain mostly anionic and non-ionic surfactants. Cationic surfactants are normally incompatible with anionic detergents and have poor cleaning efficiency; they are employed only for certain special effects, as fabric softeners, antistatic agents, and biocides. Zwitterionic surfactants are rarely employed in laundry detergents mainly for cost reasons. Most detergents use a combination of various surfactants to balance their performance.
Until the 1950s, soap was the predominant surfactant in laundry detergents. By the end of the 1950s so-called "synthetic detergents" (syndets) like branched alkylbenzene sulfonates had largely replaced soap in developed countries.[7][8] Due to their poor biodegradability these branched alkylbenzenesulfonates were replaced with linear alkylbenzenesulfonates (LAS) in the mid-1960s. Since the 1980s, alkyl sulfates such as SDS have found increasing application at the expense of LAS.
Since the 1970s, nonionic surfactants like alcohol ethoxylates have acquired a higher share in laundry detergents. In the 1990s, glucamides appeared as co-surfactants, and alkyl polyglycosides have been used in specialty detergents for fine fabrics.[4]
Bleaches
[edit]Despite the name, modern laundry bleaches do not include household bleach (sodium hypochlorite). Laundry bleaches are typically stable adducts of hydrogen peroxide, such as sodium perborate and sodium percarbonate; these are inactive as solids but will release hydrogen peroxide upon exposure to water. The main targets of bleaches are oxidisible organic stains, which are usually of vegetable origin (e.g. chlorophyll, anthocyanin dyes, tannins, humic acids, and carotenoid pigments). Hydrogen peroxide is insufficiently active as a bleach at temperature below 60 °C (140 °F), which traditionally made hot washes the norm. The development of bleach activators in the 1970s and 1980s allowed for cooler washing temperatures to be effective. These compounds, such as tetraacetylethylenediamine (TAED), react with hydrogen peroxide to produce peracetic acid, which is an even more effective bleach, particularly at lower temperatures.[4]
Enzymes
[edit]The use of enzymes for laundry was introduced in 1913 by Otto Rohm. The first preparation was a pancreatic extract obtained from slaughtered animals, which was unstable against alkali and bleach. Only in the latter part of the century with the availability of thermally robust bacterial enzymes did this technology become mainstream.
Enzymes are required to degrade stubborn stains composed of proteins (e.g., milk, cocoa, blood, egg yolk, grass), fats (e.g., chocolate, fats, oils), starch (e.g., flour and potato stains), and cellulose (damaged cotton fibrils, vegetable and fruit stains). Each type of stain requires a different type of enzyme: proteases (savinase) for proteins, lipases for greases, α-amylases for carbohydrates, and cellulases for cellulose.
Other ingredients
[edit]Many other ingredients are added depending on the expected circumstances of use. Such additives modify the foaming properties of the product by either stabilizing or counteracting foam. Other ingredients increase or decrease the viscosity of the solution, or solubilize other ingredients. Corrosion inhibitors counteract damage to washing equipment. Dye transfer inhibitors prevent dyes from one article from coloring other items, these are generally polar water-soluble polymers such as polyvinylpyrrolidone, to which the dyes preferentially bind. Antiredeposition agents such as carboxymethyl cellulose are used to prevent fine soil particles from reattaching to the product being cleaned.[4] Commercial or industrial laundries may make use of a laundry sour during the final rinse cycle to neutralise any remaining alkali surfactants and remove acid-sensitive stains.
A number of ingredients affect aesthetic properties of the item to be cleaned or the detergent itself before or during use. These agents include optical brighteners, fabric softeners, and colorants. A variety of perfumes are also components of modern detergents, provided that they are compatible with the other components and do not affect the color of the cleaned item. The perfumes are typically a mixture of many compounds, common classes include terpene alcohols (citronellol, geraniol, linalool, nerol) and their esters (linalyl acetate), aromatic aldehydes (helional, hexyl cinnamaldehyde, lilial) and synthetic musks (galaxolide).
Market
[edit]
Worldwide, while liquid and powdered detergents hold roughly equal market share in terms of value, powdered laundry detergent is more widely used. In 2018, sales of powdered detergent measured 14 million metric tons, double that of liquids. While liquid detergent is widely used in many Western countries, powdered detergent is popular in Africa, India, China, Latin America, and other emerging markets. Powders also hold significant market share in eastern Europe and in some western European countries due to their advantage over liquids in whitening clothes. According to Desmet Ballestra, designer and builder of chemical plants and detergent-making equipment, powdered detergents have a 30–35% market share in western Europe. According to Lubrizol, the powdered detergent market is growing by 2 percent annually.[1]
Environmental concerns
[edit]Phosphates in detergent became an environmental concern in the 1950s and the subject of bans in later years.[9] Phosphates make laundry cleaner but also cause eutrophication, particularly with poor wastewater treatment.[10]
A 2013 academic study of fragranced laundry products found "more than 25 VOCs emitted from dryer vents, with the highest concentrations of acetaldehyde, acetone, and ethanol. Seven of these VOCs are classified as hazardous air pollutants (HAPs) and two as carcinogenic HAPs (acetaldehyde and benzene)".[11]
The EEC Directive 73/404/EEC stipulates an average biodegradability of at least 90% for all types of surfactants used in detergents. The phosphate content of detergents is regulated in many countries, e.g., Austria, Germany, Italy, the Netherlands, Norway, Sweden, Switzerland, United States, Canada, and Japan.
See also
[edit]References
[edit]- ^ a b c McCoy, Michael (27 January 2019). "Almost extinct in the US, powdered laundry detergents thrive elsewhere in the world". Chemical & Engineering News. American Chemical Society. Archived from the original on 13 December 2019. Retrieved 13 December 2019.
- ^ Willcox, Michael (2000). "Soap". In Hilda Butler (ed.). Poucher's Perfumes, Cosmetics and Soaps (10th ed.). Dordrecht: Kluwer Academic Publishers. p. 453. ISBN 978-0-7514-0479-1. Archived from the original on 20 August 2016.
The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BCE in ancient Babylon.
- ^ a b Spriggs, John (July 1975), An economical of the development of substitutes with some illustrative examples and implications for the beef industry (PDF), Staff paper series, University of Minnesota, pp. 34–37, retrieved 9 May 2008
- ^ a b c d e Eduard Smulders; et al. (2007), "Laundry Detergents", Ullmann's Encyclopedia of Industrial Chemistry (7th ed.), Wiley, pp. 1–184, doi:10.1002/14356007.a08_315.pub2, ISBN 978-3527306732
- ^ Yangxin Yu; Jin Zhao; Andrew E. Bayly (2008), "Development of Surfactants and Builders in Detergent Formulations", Chinese Journal of Chemical Engineering, 16 (4): 517–527, doi:10.1016/S1004-9541(08)60115-9
- ^ Rubingh, D. (23 October 1990). Cationic Surfactants: Physical Chemistry. CRC Press. p. 475. ISBN 978-0-8247-8357-0.
- ^ SNELL, FOSTER DEE (January 1959). "Syndets and Soaps". Industrial & Engineering Chemistry. 51 (1): 42A – 46A. doi:10.1021/i650589a727.
- ^ Dee, Foster; Snell, Cornelia T. (August 1958). "50th ANNIVERSARY FEATURE—Fifty Years of Detergent Progress". Industrial & Engineering Chemistry. 50 (8): 48A – 51A. doi:10.1021/ie50584a005.
- ^ Knud-Hansen, Chris (February 1994). "HISTORICAL PERSPECTIVE OF THE PHOSPHATE DETERGENT CONFLICT". www.colorado.edu. CONFLICT RESEARCH CONSORTIUM. Archived from the original on 28 May 2010. Retrieved 21 March 2017.
- ^ Kogawa, Ana Carolina; Cernic, Beatriz Gamberini; do Couto, Leandro Giovanni Domingos; Salgado, Hérida Regina Nunes (February 2017). "Synthetic detergents: 100 years of history". Saudi Pharmaceutical Journal. 25 (6): 934–938. doi:10.1016/j.jsps.2017.02.006. PMC 5605839. PMID 28951681.
- ^ Anne C. Steinemann, "Chemical Emissions from Residential Dryer Vents During Use of Fragranced Laundry Products", Air Quality, Atmosphere and Health, March 2013, Vol. 6, Issue 1, pp. 151–156.
External links
[edit]Laundry detergent
View on GrokipediaHistory
Early Developments and Soap Precursors
The process of creating soap-like materials through saponification, involving the reaction of animal fats or vegetable oils with alkaline substances derived from wood or plant ashes, emerged in ancient civilizations as a practical response to the need for removing grease and dirt. In ancient Babylon, clay tablets dating to around 2800 BCE provide the earliest documented recipes for such substances, detailing the boiling of fats with ashes to yield a cleaning agent effective against organic soils.[8] Similar methods were employed by the Sumerians circa 2500 BCE, heating oils with wood ash to form rudimentary soaps, which facilitated better emulsification of fats in water compared to rinsing alone.[9] These early formulations relied on the natural lye (potassium carbonate) from ashes, enabling the hydrolysis of triglycerides into glycerol and fatty acid salts that could lower surface tension and lift soils.[10] Ancient Egyptians refined these techniques by around 1550 BCE, combining animal and vegetable fats with alkaline salts like trona (a natural sodium carbonate deposit) to produce both medicinal and cleansing pastes, as evidenced in medical papyri; this marked an empirical advancement in stability and solubility for laundry applications.[11] However, widespread use remained limited to elites due to labor-intensive production, with common laundry often relying on beating fabrics in rivers or urine-based ammoniacal solutions for protein stain breakdown.[12] In the Greco-Roman era, soap precursors spread via trade, but bathing declined post-Roman Empire, reducing systematic soap use in Europe amid scarce alkali sources and cultural shifts away from frequent washing.[13] By the 18th century in Europe, soap production shifted toward molded bars using tallow or olive oil saponified with potash or soda ash, enabling more consistent laundry cleaning; industrial scaling in Britain and France increased output, but high costs—exacerbated by England's 1712 soap tax of up to 3 pence per pound—restricted access to households with means.[14] Performance faltered in hard water regions, where calcium and magnesium ions precipitated fatty acids as insoluble scum, reducing lathering and efficacy by up to 50% in calcareous areas, prompting reliance on soft water sources or additives like vinegar for chelation.[15][16] The 19th century introduced sodium carbonate (washing soda) as a key precursor aid, synthesized via Nicolas Leblanc's 1791 process converting salt to soda ash at scale, which softened hard water by precipitating metals and boosted soap's alkalinity for alkaline hydrolysis of stains.[17][18] This compound, dosed at 1-2 ounces per gallon in boiling wash water, enhanced soil suspension without full saponification, addressing soap's limitations cost-effectively; by mid-century, it was integral to boiler-based laundering, reducing residue and enabling reuse of gray water in industrializing households.[19][20]Emergence of Synthetic Detergents
The development of synthetic detergents accelerated in the 1930s with the introduction of long-chain alkyl aryl sulfonates, pioneered by German chemists seeking alternatives to fat-based soaps amid resource constraints.[1] These branched alkylbenzene sulfonates (BAS) offered surfactant properties that emulsified oils and greases without the precipitation issues of soaps in hard water, marking a shift from natural to petroleum-derived feedstocks. World War II intensified adoption in the United States, where fats and oils essential for soap production were rationed and diverted to military needs like explosives and glycerin.[18] This scarcity prompted chemical firms to scale up synthetic production, with alkylbenzene sulfonates proving resilient to wartime disruptions in natural lipid supplies. Procter & Gamble launched Tide on January 21, 1946, as the first heavy-duty fully synthetic laundry detergent, relying on these sulfonates for robust cleaning action that suspended dirt particles and worked effectively across water hardness levels.[21][22] Tide's formulation emphasized first-principles surfactant design, enhancing stain removal through superior wetting and dispersion compared to soaps, which curdled in mineral-rich water. By the early 1950s, Tide held over 30% of the U.S. laundry market, driving broader synthetic penetration and reducing soap dominance as consumers prioritized performance amid postwar household demands.[21] Synthetic sales overtook soap by 1953, reflecting causal links between wartime innovation and market shifts toward constraint-resistant cleaning agents.[23]Mid-20th Century Innovations
The incorporation of phosphate builders, such as sodium tripolyphosphate, into synthetic laundry detergents during the 1950s markedly improved surfactant efficacy by sequestering hardness ions like calcium and magnesium, thereby preventing precipitation and enhancing soil removal in varied water conditions.[24] Phosphates had been utilized as builders since 1947, but their widespread adoption—reaching 30-50% of detergent formulations by 1959—coincided with the proliferation of automatic washing machines, which demanded consistent performance across diverse household water supplies.[25] This lab-engineered enhancement addressed empirical limitations of soap-based and early synthetic cleaners, driving market expansion as evidenced by Procter & Gamble's Tide achieving over 30% U.S. market share by the early 1950s through superior cleaning in machine washes.[21] In the 1960s, bacterial proteases like subtilisin, produced via microbial fermentation by companies such as Novo Industri, were added to detergents to catalyze the hydrolysis of proteinaceous stains including blood, milk, and grass.[26] These enzymes, stable under alkaline conditions typical of wash cycles, enabled targeted breakdown of organic soils at temperatures below 60°C, aligning with the energy-efficient cycles of increasingly common automatic washers.[27] Wash performance evaluations confirmed their efficacy, with enzyme-augmented formulas removing up to 20-30% more protein stains than non-enzymatic counterparts under controlled laundering tests, though initial formulations faced stability challenges resolved through genetic selection of robust strains.[28] By the 1970s, oxidative bleaches such as sodium perborate tetrahydrate were routinely formulated into detergents to provide controlled release of active oxygen for whitening and stain oxidation without damaging colored fabrics, a critical adaptation for the diverse loads processed in automatic machines.[29] This peroxygen compound decomposes in solution to hydrogen peroxide, offering milder action than chlorine bleaches and complementing phosphate-enzyme systems by tackling oxidized soils like tea and wine.[1] Its integration supported the causal shift toward higher-capacity, temperature-variable washers—U.S. household penetration exceeding 70% by decade's end—by ensuring broad-spectrum cleaning efficacy across synthetic and natural fibers prevalent in mid-century wardrobes.[30]Late 20th and 21st Century Advancements
In response to environmental concerns over eutrophication, phosphates were phased out of laundry detergents in many regions during the 1990s, with U.S. states implementing bans and the industry adopting a voluntary agreement to limit or eliminate them by the mid-1990s.[31][32] This shift prompted the widespread adoption of zeolite-based builders, such as zeolite A, which effectively softened water and supported surfactant performance, enabling formulations to achieve comparable cleaning results without phosphates.[33][34] Advancements in enzyme technology during the 2000s enabled effective cold-water washing, where specialized proteases, amylases, and lipases broke down proteins, starches, and fats at lower temperatures, reducing the need for hot water that accounts for up to 90% of a wash cycle's energy consumption according to life-cycle assessments.[35][36] Concentrated formulations also proliferated in the late 1990s and early 2000s, with products like Henkel's Dixan 2000 (1990) and U.S. ultra-concentrates (1991 onward) minimizing packaging and transport volumes while delivering equivalent efficacy through higher active ingredient densities.[24]Unit-dose formats emerged in the 2010s, exemplified by Procter & Gamble's Tide Pods launched in 2012, which encapsulated pre-measured surfactant, enzyme, and builder combinations in water-soluble films for precise dosing and reduced overuse.[37] More recent innovations include dissolvable laundry sheets, gaining traction since 2023 as lightweight, water-free alternatives that dissolve in washes, appealing to eco-conscious consumers seeking reduced plastic and shipping emissions.[38] The global laundry detergent market, driven by these efficiencies, is projected to reach $125.91 billion by 2033.[39]