Chemicals Used In Drycleaning Operations
(The information in this newsletter has been gleaned from an EPA sponsored site http://www.drycleancoalition.org and enhanced with pictures obtained on the Web.)
Drycleaning is the washing of fabrics in non-aqueous solvents.
Spirits of turpentine is the first referenced drycleaning solvent – in 1690, but the first regular use of a non-aqueous solvent in garment cleaning was in 1716, when spirits of turpentine were used to remove grease and oil stains.
The drycleaning industry was established in Europe in the first half of the nineteenth century. The most widely used solvents in early drycleaning operations were petroleum based and included petroleum naphtha, benzene, kerosene, and white gasoline.
White gasoline was the predominant drycleaning solvent in the United States from the late nineteenth century until the early 1920s. White gasoline refers to clean-burning pure gasolines without additives such as tetraethyl lead. Due to the high volatility of these petroleum solvents, fires and explosions were major hazards associated with drycleaning operations.
In 1924, an Atlanta drycleaner named W. J. Stoddard worked with Lloyd E. Jackson of the Mellon Research Institute to develop specifications for a less volatile petroleum drycleaning solvent that became known as Stoddard solvent, or "White Spirit".
Drycleaners began using Stoddard solvent in 1928 and it was the predominant drycleaning solvent in the United States from the late 1920s until the late 1950s.
Stoddard solvent is a mixture of petroleum distillate fractions, which is composed of over 200 different compounds. Many people incorrectly refer to any petroleum drycleaning solvent as Stoddard solvent. More properly, Stoddard solvent is a mixture of C 5 – C 12 petroleum hydrocarbons (The "C" number indicates the number of carbon atoms in a molecule of the hydrocarbon family.).
Since the introduction of Stoddard solvent, the industry trend has been towards the development of higher flash point (less flammable) petroleum drycleaning solvents.
One of the problems associated with petroleum drycleaning solvents is biodegradation.
Bacteria introduced into the drycleaning system, through the clothing or in water introduced into the system, will feed on the petroleum solvent and degrade the petroleum compounds producing a “sour” odor. Once the solvent has degraded, it must be discarded.
To combat this problem, bactericides or biocides are added to the system, normally in detergents. The biocides used today are reportedly similar to those used in shampoos, laundry products and cosmetics.
The first chlorinated solvent utilized in drycleaning operations was carbon tetrachloride, which was used as a drycleaning solvent in the United States from the 1920s until the early 1950s.
Carbon tetrachloride was commonly blended with other solvents. Because of its high toxicity and tendency to corrode equipment, carbon tetrachloride is no longer used as a drycleaning solvent.
In 1930, trichloroethylene (TCE) was introduced as a drycleaning solvent in the United States. TCE causes bleeding of some acetate dyes and therefore, it is no longer used as a primary drycleaning solvent.
||Photo courtesy of Margaret Solomon Gunn, Quilts of Love Blog
In 1934, perchloroethylene (PCE) was introduced as a drycleaning solvent in the United States. The superior cleaning ability of PCE, coupled with petroleum shortages during World War II and municipal fire codes prohibiting the use of petroleum solvents resulted in increased use of PCE.
In 1948, PCE surpassed carbon tetrachloride use in drycleaning operations. By the early 1960s, PCE had become the predominant drycleaning solvent in the United States. It is estimated that over 80% of the commercial drycleaners in the United States use PCE today.
The National Institute for Occupational Safety and
Health (NIOSH) recommends that PCE be handled as a
potential carcinogen and that levels in workplace air
should be as low as possible.
(Source: EPA bulletin on PCE)
Prior to being drycleaned, heavily stained garments are usually pre-cleaned or “prespotted” using a wide variety of chemicals. Spot cleaning is also performed after the clothes are drycleaned and stains still remain on the clothing.
Spotting agents are used to remove oily- type stains, fats, waxes, grease, cosmetics, paints and plastics. The primary constituents include, or have included: PCE, TCE, TCA, carbon tetrachloride, methylene chloride, amyl acetate and petroleum solvents.
In general, from a contamination and regulatory standpoint, spotting agents include some of the most toxic chemicals used in drycleaning operations.
Bleaches are used in stain removal when other spotting techniques have failed to remove a stain. This process is known as “spot bleaching”. Bleaches are also used in conventional laundry operations, which are conducted at most drycleaning plants.
Sizing is a finish used to impart body to a fabric. It is applied to fabrics when they are manufactured and is depleted after several fabric cleanings.
Photo courtesy of Thai Craft Warehouse
Sizing used in drycleaning operations today is composed of hydrocarbon resins (polymers or polymer blends). Two forms of sizing are used in drycleaning operations: a solid form of sizing, the bead form, is commonly used in PCE drycleaning systems and a liquid form. Most of the liquid sizing used today has a petroleum naphtha carrier. It is not uncommon for liquid sizing to contain over 50% petroleum solvent by volume. Anti-static agents and optical brighteners are commonly added to sizing.
Historically, much of garment waterproofing was performed by drycleaners.
The waterproofing agent was usually a wax-base product and the predominant carrying agent utilized was PCE and petroleum solvent. Several methods have been used to apply the waterproofing agent, including immersion in the waterproofing agent in a dip tank; spraying the waterproofing agent on the garments in a tank; applying the waterproofing agent in the form of an aerosol spray and, in some cases, applying the waterproofing agent in an auxiliary tank in a drycleaning machine.
Stain retardants are generally applied by the garment manufacturer, but some drycleaners apply stain repellents to clothing. Historically, these products have been silicon based and the carrying agent has been 1,1,1-trichloroethane or petroleum naphtha.