LAUNDRY DETERGENTS FORMULATION

LAUNDRY DETERGENTS: Powders/ Bars or Cakes/ Liquids

General purpose detergents are suitable for all washable fabrics. Powders are especially effective in lifting out clay and ground-in dirt. Liquids work best on oily soils and for pretreating soils and stains. Light duty detergents are used for hand or machine washing lightly soiled items and delicate fabrics. Cake or detergent bars are used.

LAUNDRY DETERGENT FORMULATION

In addition to the surfactant modern detergent formulations contain a number of other substances to improve the detergency, to bleach, to lessen redeposition of dirt, to brighten, or simply to reduce the cost of the formulation. A substance added to a surfactant to increase its detergency is called a builder. The commonly used ingredients are as follows-

1.      SURFACTANTS

Linear alkylbenzene sulphonic acid (LABSA), Linear alkene benzene sulphonate (LABS), Sodium laureth sulphate, or sodium lauryl ether sulphate (SLES), Sodium lauryl sulphate (SLS), Alpha olefin sulphonate (AOS), Methyl ester sulphonates (MES), Alkyl polyglyucosides (APG), Lauryl alcohol ethoxylates (LAE). Detergent surfactants are made from a variety of petrochemicals (derived from petroleum) and/or oleo chemicals (derived from fats and oils). 

Role: Multiple roles including- Cleaning (soil removal), Foaming, Wetting agent, Antiredeposition agent, Dispersing agent.

Mechanism: 
A) Surfactant converts greasy and oily dirt into micelle that become dispersed in water. Solubilisation of oil, achieved by micellar action When the detergent dissolves in water, detergent molecules group themselves around an oil droplet (a). The water-repelling part of the molecules (light area) projects into the droplet, while the water-soluble part (dark area) remains in the water (b). The oil is held in suspension by the emulsifying action of the detergent and is carried away with the dirty water (c).
B) Surfactants decreases the surface tension of water, making it better wetting agent .
C)Removal of particulate soil from the fabric, achieved by electrostatic repulsion. Surfactant keep the greasy micelle in suspension and prevents them redepositing until they can be washed away.
D) Suspension of soiling matter in the wash liquor.

 

2.     BUILDERS

Soda ash or Sodium carbonate, Sodium tripolyphosphates, Sodium silicate, Zeolite (special form of clay - hydrated sodium aluminium silicate), Sodium Citrate.

Role: Water softeners, added to inactivate hard water minerals. This is done either by

·         Sequestration or chelation (holding hardness minerals in solution),

·         Precipitation (forming an insoluble substance), or

·         Ion exchange (trading electrically charged particles).

Complex phosphates and sodium citrate are common sequestering builders. Sodium carbonate and sodium silicate are precipitating builders. Sodium aluminosilicate (zeolite) is an ion exchange builder. Since detergents are more effective in soft water, these products increase cleaning power. Builders can also supply and maintain alkalinity, which assists cleaning, especially of acid soils; help keep removed soil from redepositing during washing; and emulsify oily and greasy soils.

Alkalis: Ex. Sodium carbonate, Sodium silicate and Sodium hydroxide. The potassium analogue (potassium carbonate, potassium silicate and potassium hydroxide) is used for the liquid detergents due to their higher solubility.
Role:
1. Neutralization of acidic soils
2. Saponification of fatty soil
3. Enhancement of soil removal, for example, with anionics
4. Improving soil suspension and preventing re-deposition
5. Optimising bleach conditions
6. Optimising enzyme conditions

3.     FILLERS

Sodium chloride, Sodium sulphate, China clay, Dolomite, Calcite and Water

Role: To lower the cost of formulation and maintain the physical properties like to make detergents fluid or to turn fluidized detergents into powders. They're used to change the consistency of the detergent, to make it more pourable, more soluble and to help it disperse evenly.

Sodium sulfate is added to make the detergent powder flow freely. Without it, the detergent would stick together and become one big block.

4.     ENZYMES

Amylase, Protease, Cellulase, Proteinase and Savinase

Role: To break down soils to simpler forms for removal by detergent.

·         Proteases: break down protein stains (such as blood, dairy products, eggs, meat, mud, and grass), into small units called “peptides”),

·         Amylases: break down carbohydrate (such as starch, potato, pasta and rice) into smaller molecules called “oligosaccharides” or “monosaccharides”.

·         Lipases (break down fats (or “lipids”) such as butter and oil)

Mechanism: Enzymes break down large molecules such as proteins, carbohydrates and fats into smaller segments. These smaller segments are either water-soluble, or are of size and polarity compatible with surfactants meaning that they can be suspended in solution. Whatever the type of stain, after its enzymatic breakdown, surfactants suspend the resulting fragments in solution.   Most enzymes are destroyed by high temperatures, i.e. above 60 °C. They are usually most effective at warm water temperatures (e.g. 40 °C), however some enzymes are best for use in cold water.

Colour and fabric care: Some enzymes act to smooth cotton fabrics by cleaving fibres that protrude from the surface. A smoother cotton surface means that soils are less readily taken up by fibres, and are more easily liberated.

Enzymes can also help remove fuzz and pills, and can assist colour protection of fabrics.

5.     ANTIREDEPOSITION AGENTS

Sodium carboxymethyl cellulose, Polyethylene glycol (PEG), Polyvinyl alcohol, Polyvinyl pyrrolidone.

Role: To prevent soils from resettling after removal during washing.

Mechanism: Anti-redeposition agents increase the negative charge on the fabric surface, so that the surface repels Mechanism: soil particles because these are also negatively charged.

6.     BLEACHING AGENTS

Sodium perborate, Hydrogen Peroxide, Chlorine

Role: Bleaches (chlorine and oxygen) whiten and brighten fabrics and help remove stubborn stains.

Mechanism: Active oxygen bleaches work by oxidation of the stain. This means that the active component of the bleach accepts electrons from the stain, resulting in either:

·         Cleavage of chemical bonds in the stain and its breakdown, following which fragments can be suspended in solution by surfactant action.

·         A change in the oxidation state of the stain, rendering it colourless

Liquid chlorine bleach (usually in a sodium hypochlorite solution) can also disinfect and deodorize fabrics. Oxygen (color-safe) bleach is gentler and works safely on almost all washable fabrics. The active ingredient in oxygen bleach is hydrogen peroxide.

7.     OPTICAL BRIGHTENERS (Fluorescent Whitening Agent)

CBSX (Disodium distearyl biphenyl sulphonate), Tinolux, Tinopal, coumarins, and stilbenes etc.

Role: To create a whitening effect. Optical brighteners enhance the light reflected from the fabric surface and can make fabrics appear whiter and brighter, helping to keep them looking newer for longer.

Mechanism: Bluings/ Optical Brighteners contain a blue dye or pigment taken up by fabrics in the wash or rinse. Bluing absorbs the yellow part of the light spectrum, counteracting the natural yellowing of many fabrics.

Different colours exist because light can have many different wavelengths, depending on the nature of the substance that the light is being emitted or reflected from. The colour that is observed comes from a combination of all the wavelengths of light that reach the eye. Humans can only see a small fraction of all the wavelengths of light that exist, known as the visible spectrum; white is a combination of all the wavelengths in the visible spectrum. Just beyond the visible spectrum lies the ultraviolet region.

Optical brighteners attach to fabrics, absorb invisible ultraviolet light and convert it to visible blue-violet light. The blue light that is emitted interacts with the yellow light emitted by the fabric, giving an overall appearance of whiteness.

8.     Fabric softeners

Cationic surfactants such as long-chain amines and long-chain quaternary ammonium compounds.

Role: Fabric softeners, added to the final rinse or dryer, make fabrics softer and fluffier; decrease static cling, wrinkling and drying time; impart a pleasing fragrance and make ironing easier.

Mechanism: Softness, smoothness and reduced crinkling: Fabric softeners are cationic surfactants, meaning that their polar head-groups bear a positive charge. These are attracted to the negatively charged fabric surface and associate with the fibres. With the positively charged headgroup associated with the fabric, the fatty tail protrudes from the surface and imparts a feeling of softness or smoothness to the fabric. The layer of molecules on the surface may also endow the fabric with some water-proofing properties.

Reduced static: Electrical charge, or static, builds up on fabrics as the fibres rub together, especially in the clothes drier. When fabric softeners coat the fibres (as described above), they provide a lubricating coat that enables fibres to rub together without the same static build up. The coat of fabric softener molecules also conducts electricity, and so allows discharge of any static that has built up.

9.     HYDROTROPES

Short-chain aromatic sulfonates such as xylenesulfonate, cumenesulfonate, some glycol ether sulphates, and urea.

Role: Hydrotropes, or solubilisers, assist in maintaining the pouring characteristics of liquid detergents by preventing gel formation or separation into layers in the bottle.

Mechanism: Hydrotropes are similar to surfactants in that they have two domains: a polar (hydrophilic) domain and a non-polar (hydrophobic) domain. Despite these similarities they are typically smaller and less linear than surfactant molecules. They interrupt the formation of surfactant micelles in the bottle that can lead to high viscosity gel structures and insoluble phases. In this way, inclusion of hydrotropes in liquid detergent formulations help maintain a uniform composition throughout the liquid detergent and also maintain the pouring properties required for ease of use.

10.PRESERVATIVES

EDTA

Role: All organic detergent ingredients, such as the surfactants and enzymes, are biodegradable. This means that they can be broken down by bacteria in the environment. Preservatives prevent this spoilage by killing bacteria.

11.FRAGRANCES

Role: Pleasant smell. They can also enhance the mood and help create pleasant associations with ‘doing the laundry’.

12.PROCESSING AIDS

Role: To maintain the physical characteristics of laundry detergents during processing, storage and consumer use.

·         DESICCANTS:

Sodium sulphate

Role: Desiccants are able to bind multiple molecules of water, forming “hydrates”. This effectively locks up any moisture that enters the detergent, maintaining a dry, free-flowing powdered detergent. Sodium sulphate is a common example.

·         SOLVENTS:

Ethanol and propanol

Role: Solvents help dissolve the detergent ingredients in liquid laundry detergents. Some solvents that are miscible (can mix) with water are able to dissolve ingredients that water alone does not dissolve. This maintains a uniform composition throughout the liquid detergent. Alcohols are one example of solvents that have an additional effect of lowering the freezing point of liquid laundry detergents. This prevents disruption to the physical properties of the detergent that would be caused by crystal formation during cold storage. Examples are ethanol and propanol.

13.FOAM REGULATORS

Lauryl alcohol ethoxylates, soaps, siloxanes and paraffins

Role: Foam regulators either prevent the formation of foam by disrupting the surfactants at the air-water interface of the forming bubble, or cause foam bubbles to collapse by forming hydrophobic bridges across multiple bubbles.

Foam regulators inhibit the formation of suds during the washing cycle. Particularly in front-loading washing machines, mechanical energy comes from the wash items colliding with the sides of the rotating tub. High amounts of a foam cushion the collision impact and decrease the effectiveness of the wash.

 TYPICAL COMPOSITION DIFFERENT TYPES A DETERGENT POWDERS AND DETERGENTS BARS.

POWDER