Note: Descriptions are shown in the official language in which they were submitted.
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HEAVY DUTY WASHING PROCESS
The present invention relates to detergent compositions
and their use in a washing process, more in particular,
an industrial heavy duty washiny process for laundering
greasy stains from a fabric.
It has always been difficult to obtain satisfactory
results when washlng heavily soiled articles such as
overalls 6tained with grease or motor oil. Good results
can be obtained using chlorinated hydrocarbons as
solvent in a dry-cleaning process, although there is a
tendency ~or the workwear to show some greying and to
have a harsh feel. However, the use of chlorinated
hydrocarbons is becoming more and more restricted for
environmental reasons.
Furthermore, it has been described in the British patent
speci~ication 1,518,576 to remove oily stains from
fabrics by means of a composition comprising a nonionic
and an organic solvent in a weight ratio in the range of
1 : 1 to 100 : 1. In this process the soiled fabric is
treated with an aqueous solution containing 0.01 to 2 %
by weight of said composition at a temperature above the
phase coalescence temperature. A draw-back of this
process is the large amount of organic waste containing
waste water.
It is an object of the present invention to provide
improvements on the wash process as described in the
British patent 1,518,676.
We have now ~ound that one or more of these objects can
be achi~ved by the process according to the present
invention, which is characterized in that the soiled
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~abric is treated with an aqueous detergent composition
comprising (a~ 0.5 to 5 % by weight of a nonionic
surfactant, (b) 1 to 10 % by weight of an apolar organic
solvent, whereby the ratio of (a) to (b) is from less
than 1 : 1 to 1 : 10, preferably from l~ss than 1 : 1 to
1 : 5.
Suitable nonionic sur~actants which may be used include
the reaction products of compoundra having a hydrophilic
group and a reactive hydrogen atom, for example
aliphatic alcohol6, acids, amides or alkyl phenols with
alkylene ox~de~, especially ethylene oxide either alon~
or in combination with propylene oxide and/or butylene
oxide. Specific nonionic detergent compounds are alkyl
(C6~C22) phenols-ethylene oxide condensates, the
condensation products of aliphatic (C8-Cl~) primary or
secondary linear or branched alcohols with ethylene
oxide, and products made by condensation of ethylene
oxide with the reaction products of propylene oxide and
ethylenedia~ine. So-called "capped" nonionics are also
suitabl~ Other suitable nonionic surfactants include
long chain tertiary amine oxides, long chain tertiary
phosphine oxides and dialkyl sulphoxides.
Pre~erably, the nonionic ~urfactant is an alkoxylated
~atty alcohol, wherein the alcohol is a primary or
secondary branched or linear alkanol having 10 to 16
carbon atoms. Ths alkoxy moiety consists of 3 to 10
: ethoxy groups, propoxy groups and/or ~utoxy groups. Th~
hydrophilic lipophilic balance (HL~) of the nonionic
surfactant, de~ined as one fifth of the weight
: percentage o~ alkylene oxide in the nonionic, is chosen
in the range of 10 to 14.
35 The apolar organic solvent may be an alkane, an
alkanol, a low-E0 nonionic, etc., or a mixture thereof.
Suitable alkanols contain 6 to 18 carbon atoms. ~ low-E0
nonionic is ~or ~he purpo~e of thls invention defined as
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a ~atty alcohol, alkoxylated with less than 3 ethoxy
groups. The apolar organic solvent is pre~erably an
aliphatic linear alkane or a mixture of alkanes having 8
to 16 carbon atoms, preferably 11 to 13 carbon atoms. An
attractive commercially available solvent is kerosine.
The detergent composition of the invention may comprise
other ingredients which are usual for washing proce ses
such as builders, alkaline agents to maintain a pH value
in the range of 8 to 13, pre~erably of 10 to 12.
Bleaching agents, etc. may also be present.
The builder may be any material capable of redu~ing the
level of free calcium ions in the wash liquor and will
prefarably at the same time provide other beneficial
properties such as the generation o~ an alkaline pH or
the euspension of soil removed from the fabric. The
builders may be inorganic such as tripolyphosphates or
zeolites, organic non-poly~eric such as nitrilotriacetic
acid, or organic polymeric such as copolymers o~ acrylic
acid and maleic acid. Thé builder is preferably present
in an amount of 0.25 to 2 % by weight of the
composition.
In the process for laundering fabrics according to the
present invention, the heavily soiled fabric is treated
with the above mentioned detergent composition. The
amount of detergent composition is relatively high, i.e.
in the order of 0.5 to 5 kg per kg soiled fabric.
Preferably, 1.5 to 2.5 kg per kg fabric is used. The
process of the invention can be carried out in any
suitable washing machine, such as a wash extractor or a
tunnel washer.
The washing process may be preceded by a pre-rinse to
re~ov~ loose dirt and soluble material. The actual wash
process may comprise more than one wash cycle. It is
preferably carried out at elevated temperatures. It was
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found to be particularly effective to first raise the
temperature to a~ove the so-called phase coalescence
temperature, which is usually around 55 C, and then
cycle around this temperature at least two times. After
a sufficiently long period to complete the washing
action of the detergent composition, usually in the
order of 10 minutes, the wash liquor is pumped off.
A~ter one or more rinse cycles, the wash load i6 removed
for further processing.
According to a further aspect of the present invention,
the used wash liquor containing su~pended soil and
emulgated grease and/or oil can be recycled instead of
being pumped to the sewage system. The water of the
pre-rinse and the first rinse cycle may be combined and
treated in the sam~ way.
Although it is particularly useful to apply the
recycling step to a wash process involving the aqueous
detergent compositions according to the invention, the
recycling step can al80 be used in combination with
similar aqueou~ detergent compositions having a
different nonionic to solvent ratio. For example, the
aqueous detergent compositiQn may comprise Sa) 0.5 - 5 %
by weight of a nonionic surfactant and (b) 1 10 % by
weight of an apolar organic solv~nt, whereby the ratio
of (a) to (b) is 1 : 1 to 100 : 1.
It was found to be advantageous to dump the hot wash
liquor ~rom the process into a storage tank from which
it is gradually pumped to a filtration unit comprising
one or more microfilters. In this unit the wash liquor
is continuously filtered under a pressure of
approximately 0.5 - 3 bar. The unit is preferably
operated in a cross-flow mode to avoid clogging of the
filter. The aqueous phase containing virtually all of
the water soluble components is separated from the
phase containing the organic solvent, the suspended
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solld and the emulgated oil and/or grease, and can be
recycled. The phase containing the oil and most of the
organic apolar solvent can now be distilled to recover
the organic solvent, or Xur her treated to reduce the
waste. Considerable savings in energy and chemicals can
thus be achieved. The process i5 also advantageous from
an environmental point of view because the amount of
waste to be disposed off can be greatly reduced.
It is preferred to use hydrophilic microfilters in the
present process. The aqueous phase passes through the
filter and can be continuou~ly recycled to the wash
process. The retantate contains increaslng amounts of
oil and at a sufficiently high concentration the
emulsion becomes unstable. Sometimes the emulsion will
even break and a layer of oil will separate. After a
certain amount of time, Por instance at the end of a
working day, the filtration process can be stopped and
the retentate can be removed for distillation, disposal
or further treatment. Preferably, the retentate has
first been concentrated to a water content of 50 to 70
by weight.
The microfilters to be used in the process of the
invention can be made of any suitable material, provided
that it is capable of withstanding elevated temperatures
sf up to lO0 C and highly alkaline wash liquors, having
pH values of up to 14. It should therPby also retain
its hydrophilic properties. Wa found that microfilters
having a pore size of 50 - lO00 nm, pre~erably
approximately lO0 nm and made of a mixture of
polyethersulphon and polyvinylpyrrolidon, are
exceptionally suitable. The microfilters are preferably
constructed of capillary tubes having an external
diameter of 1 to 10 mm. Such ~ilters are co~mercially
available, for instance from X-flow, Enschede, The
Netherlands.
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The invention will now be further illustrated by means
of the ~ollowing non-limiting axample.
EXAMPLE
The following heavy duty wash process was carried out.
400 kg overalls, heavily soiled ~ith motor oil and
greasy stains were placed in a Milnor wash extractor.
The load was pre-rinsed to remove any sand and other
loose dirt. The rinse water could be disposed off
directly to the sewage system, as it was not noticeably
polluted. Subsequently, the wash load was treated for 10
minutes at a temperature of 60 C with 1000 1 o~ an
aqueous detergent composition containing 3 % by weight
paraffin (ex Shell), 1.5 % by weight of a nonionic
mixture consisting of Dobanol 25-3 and 25-9 in a ratio
of 1 : 2.5 (ex Shell), 0.45 % by weight ~odium
tripolyphosphate, 1.4 % by weight sodium metasilicate
and 0.25 ~ by weight sodium hydroxide. The pH was
adjusted to 11.8. After this first main wash, the hot
wash liquor was pumped off to a thermally insulated
waste water storage tanX having a capacity of 5.5 m3.
The wash process was then repeated using the same amount
of detergent composition, whereby no paraffin was used
and the amount of nonionic was raised to 3 ~ by weight.
Again, the hot wash liquor was transferred to the waste
water storage tank. Thereafter, the was load as rinsed
using 3.2 m3 water. The rin~ing was repeated -twice,
whereby only the water ~rom the first rinse was pumped
to the waste water storage tank. The amount of chemicals
and solvant in the water of the second rinse was so low
that it could be dumped to the sewage ~ystem. After
drying, the wash load was inspected and it was found
that and excellent cleaning result had been obtained, as
substantially all greasy had been removed.
The combined waste water in the waste water storage tank
was continuously pumped to a thermally insulated
circulation tank having a capacity of approximately 5
m3. From this tank, the water was pumped under a
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pressure of 2 bar to a micro~iltration unit equipped
with hydrophilic microfilters made of a mixture of
polyethersulphon and polyvinylpyrrolidon, having a pore
size of 100 nm. The filters were obtained from X-flow,
Enschede, The Netherlands. The total ~urface area of the
unit was 50 m2 and it had a maximum capacity o~ about
5000 l/hour. The filtration unit was operated in a
cross-flow mode. The permeate contained water, nonionic
and salts and was substantially free ~rom organic
solvent. It was pumped to a permeate storage tank having
a capacity of about 5 m3 from which it could be used
again in ths wash process. It proved to be advantageous
to supplement the permeate with some of the detergent
composition after each cycle, to compensate for the
detergent components consumed in the wash cycle in
removing the soil. The retentate was then fed to a
distillation unit and the freshly distilled solvent was
also used again in the was process. Overnight the liquor
in the circulation tank was concentrated to a water
content of approximately 50 % by weight, whereby gel
formation was observed. This concentrate was finally
disposed off.
