Chemicals Used In Drycleaning Operations
This info-letter is the second entry of our series on drycleaning operations, their impact on the environment and ensuing hurdles they pose in real estate transactions.
The previous entry can be viewed here
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 (petroleum
naphtha), 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 petroleum drycleaning
solvents which have very low aromatics content (generally less than
4%).
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.
In
1934, perchloroethylene 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.
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.
Dry-side
spotting agents are used to remove oily- type stains, fats, waxes,
grease, cosmetics, paints and plastics. The primary constituents of
dry-side agents include, or have included: PCE, TCE, TCA, carbon
tetrachloride, methylene chloride, amyl acetate and petroleum solvents.
In
general, from a contamination and regulatory standpoint, dry-side
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.
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.
(The information in this newsletter has been gleaned from an EPA sponsored site http://www.drycleancoalition.org and enhanced with pictures obtained from the Web.)
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