Laundry detergent, or washing powder, is a type of detergent (cleaning agent) that is added for cleaning laundry. While detergent is still sold in powdered form, liquid detergents have been taking major market shares in many countries since their introduction in the 1950s.
Laundry detergent pods have also been sold within the United States since 2012 when they were introduced by Procter & Gamble as Tide Pods. Earlier instances of laundry detergent pods include Salvo tablets sold in the 1960s and 1970s.
Video Laundry detergent
History
From ancient times, chemical additives were used to facilitate the mechanical washing of clothing with water. The Italians used a mix of sulfur and water with charcoal to clean cloth. Egyptians added ashes and silicates to soften water. Soaps were the first detergents. The detergent effects of certain synthetic surfactants were noted in Germany in 1917, in response to shortages of soap during World War I. 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 and 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, caused a fast growth of domestic use in the late 1940s.
Maps Laundry detergent
Components
Laundry detergents may contain builders (50% by weight, approximately), surfactants (15%), bleach (7%), enzymes (2 %), soil antiredeposition agents, foam regulators, corrosion inhibitors, optical brighteners, dye transfer inhibitors, fragrances, dyes, fillers and formulation aids.
Builders
Builders (also called chelating or sequestering agents) are water softeners. The calcium and magnesium ions present in hard water react with ionic surfactants in detergents to form undesirable soap scum. Builders remove the hard water ions 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). Since the 1930s, phosphates (sodium phosphates) and polyphosphates (sodium hexametaphosphate) were introduced, continuing with the introduction of phosphonates (HEDP, ATMP, EDTMP). These agents are now known to have serious environmental consequences leading to a drive towards more environmentally benign 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.
Surfactants
Surfactants act as detergents and provide most of the cleaning performance. They achieve this by emulsifying oily stains into the water and also by reducing the water's surface tension, which allows it to more effectively dissolve various stains. Normal soap is, by weight, relatively ineffective for laundry cleaning and it is highly sensitive to deactivation by hard water. Modern laundry detergents primarily use alkylbenzene sulfonates (LAS) which give better results and are also exceedingly inexpensive. The performance of LAS is often optimized by the addition of lower levels of various other surfactants, some of which may be significantly more expensive. An estimated 6 billion kilograms of detergents are produced annually for domestic markets.
Bleaches
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). Despite the name, modern bleaching agents 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 react with water to release hydrogen peroxide which performs the bleaching action. Bleach activators such as tetraacetylethylenediamine (TAED) are also increasingly used, these react with hydrogen peroxide to produce peracetic acid, which is an even more effective bleach, particuarly at lower temperatures (<60 °C).
Enzymes
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 (milk, cocoa, blood, egg yolk, grass), fats (chocolate, fats, oils), starch (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, ?-amylases for carbohydrates, and cellulases for cellulose.
Other ingredients
Many other ingredients are added depending on the specific application. 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 colouring other items. "Antiredeposition agents" are used to prevent fine soil particles from reattaching to the product being cleaned. Carboxymethyl cellulose is used for this purpose.
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 colourants. A variety of perfumes are also components of modern detergents, provided that they are compatible with the other components and do not affect the colour of the cleaned item. The perfumes are typically a mixture of many compounds, common classes include monoterpenoids (e.g. Citronellol, Geraniol, Linalool and Nerol) and aromatic aldehydes (e.g. Helional, Hexyl cinnamaldehyde, Lilial).
Environmental concerns
Phosphates in detergent became an environmental concern in the 1950s and the subject of bans in later years. Phosphates make laundry cleaner but can also cause harmful algal bloom as the wastewater goes back to the natural environment.
A recent 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)".
Early in the introduction of sulfonate-based detergents, concerns were voiced over the low rates of biodegradation of the branched alkylbenzenesulfonates. This problem was addressed by the introduction of linear alkylbenzenesulfonates.
A more profound problem arose from the heavy use of sodium triphosphate, which could comprise up to 50% by weight of detergents. The discharge of soluble phosphates into natural waters has led to problems with eutrophication, or the growth of living things, of lakes and streams, often where it is not desirable. The replacement of sodium triphosphate by zeolites offers some relief to this problem. With respect to the phosphate additives, between 1940 and 1970 "the amount of phosphates in city wastewater increased from 20,000 to 150,000 tons per year." With an increase in phosphates, especially in the absence of species feeding upon algae, algal blooms grow splendidly on the excess phosphorus and can produce toxins, killing fish, dolphins and plants. They can also indirectly cause oxygen depletion at greater depths, through microbial breakdown of dead algal cells. Most modern laundry detergents do not contain phosphates, but bring about water softening using zeolites.
See also
- List of cleaning products
References
External links
- Derbyshire, David (24 February 2008). "Don't bother with pre-wash (you're just wasting 6billion litres of water a year)". Mail Online. Retrieved 30 September 2010.
- About.com, Housewares/Appliances, What is HE Laundry Detergent & When are High-Efficiency Detergents Used by Mariette Mifflin
- Campbell tips for detergents chemistry, surfactants, and history related to laundry washing, destaining methods and soil.
Source of article : Wikipedia
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