Decades ago, soaps, alkaline salts and bleach were mainly used to treat linen by most laundries. However, in time the compositions have evolved to suit various linen treatment requirements. Laundry expert Vijay Rodda elaborates…
The detergent sector in the laundry care industry has grown from `57 billion in 2003 to `130 billion in 2011, registering a growth of compounded 11% during the period. It is estimated that the industry could reach levels of `241 billion by 2017. Let us understand the evolution and composition of chemicals used for linen care.
Soaps
Soap basically is a Sodium (or Potassium) salt of higher fatty acids. It has a very good cleansing power due to its property of emulsifying oily soil as well as bombarding particulate soil with heavy radicals of higher fatty anions. It peptizes and disperses solid soil by forming micells and also holds the dispersed soil in suspension due to micelle formation.
However, it has its drawbacks too. The heavy soil soap can split causing acid soap and this can settle on fabrics/linen/garments & the wash goods can become grey. With hardness of more than 60ppm, soap can form lime soap, which also can settle on fabric to make it grey. It is necessary to know the titre of soap and washing done at a particular range of temperature, compatible with titre only. If the wash temperature is higher or lower than required, it may be insoluble and can disturb quality. Moreover, pure soap has pH = 10.0.
To protect soap, alkaline salts are added. These salts need to have pH>10.5. The water must have TDS upto 250-300 ppm and hardness up to 60-70 ppm and not more. The alkali added to protect soap can turn linen/wash goods grey, if added in excess and acid soap could be formed if alkalis are added lesser than required.
Detergents
In order to do away with such delicate balance of pH, TDS, hardness and temperature, laundry industry preferred built detergents over time.
Detergents have:
- Synthetic surfactants made from LABSA/AOS/LS/ LES/ or LA Ethoxylate or a mixture thereof
- Alkaline builders
- Water softening chemicals
- Iron & heavy metallic ion chelators
- Electrolytes as performance enhancers
- Constituents helping detachment of soil, by bombarding its tiny particles
- Suspenders of soil
- Bleaches
Detergents are better than soap with respect to stability and to get quality, one must add required quantity of detergents or in other words, detergents are to be added as required for garments, linen, fabrics vis-a-vis soil, construction, composition, dyes used, embellishment, stitching threads, padding and water quality. There are ways to find the right quantity out.
Following factors/chemicals are required for detergent formulation:
a. Builders: These give alkalinity/ MO alkalinity & pH. One needs to adjust these 3 factors vis-a-vis TDS/pH/hardness/Langlier Index and also soil / dye / fabric weave / construction / temperature, to have quality.
b. Electrolytes: To increase soil detachment from washgoods.
c. Surfactants: Emulsification and aiding dispersion
d. Suspenders: To suspend dispersed and peptized soil, so as not to allow settling on wash goods
e. Chelating agents: Will chelate hardness causing chemicals and react with heavy metal cations to render them ineffective
f. Heavy radicals & other constituents for bombarding soil & converting it into smaller particles, to have stable suspension and dispersion
g. Optional: Oxidising bleaches – Either incorporated or separate.
h. Optional: Sours & anti-bleaches
Anti-bacterial or anti-microbial chemicals
Treatment with chemicals to get rid of spores (extremely difficult), bacteria and fungi especially for healthcare industry one needs to
take extensive trials to observe efficacy of all chemicals.
Chemicals for Dry-Cleaning
a. Dry-cleaning detergents:
Detergents and ones with antibacterial chemicals have been designed to help remove soil more effectively and removal of perspiration/foul odour from garments/carpets especially in dry-cleaning. Various chemicals, including detergents for washing/ dry-cleaning have been tried with success.
b. Dry-cleaning solvents:
Launderers used soap-nuts (Rithaa or Arithaa or Shikakai), wherein surface tension is reduced and wet cleaning was facilitated. Even with soap nuts being neutral, shrinkage/ colour fading persisted. So also, all soil, especially solid soil adsorbed on to the garment was not removed. thus, in the past, laundry technicians resorted to dry-cleaning solvents.
i. Stoddard’s Solvent:
Stoddard’s solvent was used to dry-clean as the washmen found shrinkage and colour fading associated with wet wash. It was highly fire-prone, as it was mixture of C7 to C12 aliphatic & aromatic hydrocarbons.
ii. Hydrocarbon viz. Mineral Turpentine Oil (MTO):
This was introduced later. It was a mixture of many hydrocarbons and due to the presence of higher molecules (C25 to C30 or more) in minute quantities, obnoxious odour developed. It was also fire-prone though not as much as Stoddard’s solvent, hence all precautions for fire protection had to be taken. It was found to remove oil stains, oily soil and even solid soil to a certain extent. The chemical bled some dyes.
iii.Trichloroethylene (TCE) – Chlorinated Hydrocarbon:
The chemical was found to be better in oily soil removal, however, was bleeding many more dyes than MTO and wetwash. It was also corrosive on metals of machines. It was also explosive under certain conditions.
iv. Perchloroethylene (PCE):
The chemical was one step ahead of TCE. It was completely chlorinated and hence not fire prone. Though it bled less dyes than TCE, it still bled more dyes than MTO and wet cleaning. It dissolved some plastic, hence buttons and zips, as also plastic embellishments were constantly under threat.
v. Hydrocarbon (HC):
To remove the problem of plastic dissolution, colour bleeding, hydrocarbon solvents have been introduced. These are mixtures of hydrocarbons that have very similar molecular weight, less colour bleeding, and least plastic dissolution. However, cleaning properties are very less compared to PCE. There is chance of embellishment and studded stones breaking off, as in TCE and PCE.
vi. Green Earth Solvent:
Made from silicon through catenation. Cleaning properties are lesser than PCE, however, slightly more than HC. It bleeds some of the dyes. It is very costly and needs a specially designed machine that is also very costly.
vii. CO2 Liquid:
This also proved very good on garments. However, it has not taken off due to operations under very high pressure to liquify CO2.
c. Spotting solvents/detergents
d. Anti-bacterial chemicals to be compatible with dry solvents.
Both soap & paraphernalia, and detergent, as stated above, are in powder form. Hence, addition or dosing depends upon manual interference. With it, there can be errors and deterioration of quality and longevity of wash goods.
Liquid Detergents
With the turn of the century or mid of the last decade, liquid system of detergents was introduced. The system has advantages over powder detergents in terms of solubility, time of dosage adjusted and executed with precision and addition of chemicals precise and exact. Hence, the high-end laundries are switching over to liquid system.
Additions and precautions are necessary for liquid system of detergents to succeed:
a. Machinery must be compatible with liquid dosing so that both systems that is machine programmer and liquid dosing system can be adjusted together for exact chemical addition at correct time.
b. Pumps and tubes must be maintained
c. Containers for liquid chemicals must be checked for levels.
d. Alarms for low level/no or less pumping.
Ozone Wash
Ozone has been studied for wet cleaning with good results. However, it needs to be constantly monitored, concentrations in atmosphere due to some minute leakage checked and all parts of machines to be compatible with it.
Trials with ozone have been successful with very good results in hospitality laundry. Ozone wash should and will be extremely useful for healthcare industry, for disinfecting, even sterilizing linen and uniforms, and also linen even from OT.
Ozone, once successfully tried there, could eliminate HAI. Extensive trials need to be taken in Health-care Laundry, though!