Bleaching and dyeing; fluid treatment and chemical modification – Cleaning or laundering
Reexamination Certificate
2000-02-18
2002-06-04
Gupta, Yogendra N. (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Cleaning or laundering
C008S141000, C134S010000, C134S042000, C210S650000, C210S257200
Reexamination Certificate
active
06398820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for washing laundry, more particularly work clothing, in which the laundry is washed with a product combination of an alkali component and a surfactant component in a standard washing machine for institutional laundries and the wastewater is treated in a membrane filtration unit, and to a product combination containing an alkali component and a surfactant component for use in institutional laundries.
2. Discussion of Related Art
Work clothing and other linen from hotels and guesthouses, hospitals, the food industry, for example abattoirs, meat markets, etc. and textiles and work clothing from the automotive sector are mainly washed in institutional laundries. The soils occurring in work clothing and in the institutional sector often lead to particularly heavy pollution of the wastewater. Accordingly, efforts are made to treat the wastewater from institutional laundries before it is discharged into the public effluent system by removing the pollutants.
The pollutants and impurities can be removed, for example, by passing the wastewater through membrane filtration units after the washing process. The already known membrane filtration units have proved to be very effective systems in the treatment of wastewater. However, it has been found that the membranes clog up very quickly in the treatment of wastewater from institutional laundries. Studies have shown that this is due to the surfactants and polymers present in the detergents.
Although the clogged-up membranes can be cleaned with special auxiliaries, complete cleaning generally cannot be achieved by this cleaning process so that the membranes cannot be restored to their original capacity and their useful lives are thus shortened.
DESCRIPTION OF THE INVENTION
International patent application WO 92/05235, for example,
DESCRIPTION OF THE INVENTION describes a liquid nonionic surfactant combination with improved low-temperature stability containing
a) 20 to 50% by weight of an alcohol ethoxylate derived from primary linear C
12-15
alcohols containing on average 2 to 7 ethylene oxide groups (EO),
b) 20 to 50% by weight of an alkoxylate derived from primary C
12-15
alcohols containing on average 3 to 7 ethylene oxide groups (EO) and 2 to 8 propylene oxide groups (PO),
c) 5 to 50% by weight of an alcohol ethoxylate derived from mixtures of primary linear and 2-methyl-branched C
12-15
alcohols (oxo alcohols) containing on average 2 to 8 ethylene oxide groups.
However, the problem of membrane clogging could not be completely solved.
The problem addressed by the present invention was to provide a process for washing laundry, more particularly work clothing, in a standard washing machine for institutional laundries and subsequent treatment of the wastewater in membrane units, in which the laundry would be washed with a product combination of surfactant and alkali components which would have substantially the same cleaning performance as the detergents known from the prior art but which, in the treatment of the wastewater in membrane filtration units, would not have any adverse impact on the actual wastewater treatment process, i.e in particular would not lead to clogging of the membranes and hence to a reduction in the throughflow rate. In addition, the throughflow rate in the wastewater treatment process would actually be increased in relation to the throughflow of clean water.
The present invention relates to a process for washing laundry, more particularly work clothing, in which the laundry is washed in a standard washing machine for institutional laundries with a product combination of at least two components,
(A) a washing alkali component containing
(A1) anionic surfactant and water-soluble silicate and/or
(A2) alkali metal hydroxide and
(A3) complexing agent and
(B) a surfactant component containing preferably nonionic surfactant, and the wastewater is treated in a membrane filtration unit.
The present invention also relates to a product combination of at least two components,
(A) a washing alkali component containing
(A1) anionic surfactant and water-soluble silicate and/or
(A2) alkali metal hydroxide and
(A3) complexing agent and
(B) a surfactant component containing preferably nonionic surfactant, for use in institutional laundries.
It has surprisingly been found that not only is the throughflow rate through the membranes not impaired, it can actually be increased through the use of the product combination according to the invention, in other words the product combination appears to have a cleaning effect on the membranes.
In addition, this positive outcome is not dependent on the membrane material so that standard membranes based on polypropylene, ceramics and carbon may be used with considerable advantage.
The process according to the invention may be carried out in standard washing machines for institutional laundries. No special measures have to be taken in the washing process.
The washing alkali component (A) used in accordance with the invention may be present both in solid form and in liquid form. If component (A) is present in solid form, it preferably contains anionic surfactant and water-soluble silicate (A1) and a complexing agent (A3). If the washing alkali component is added in liquid form, it preferably contains alkali metal hydroxide (A2), more particularly in the form of an aqueous solution, and a complexing agent (A3).
The anionic surfactant used may be any of the anionic surfactants typically used in detergents such as, for example, C
8-18
alkyl sulfates, C
8-18
alkyl ether sulfates, C
8-18
alkane sulfonates, C
8-18
&agr;-olefin sulfonates, sulfonated C
8-18
fatty acids, C
8-18
alkyl benzene sulfonates, sulfosuccinic acid mono- and di-C
1-12
-alkyl esters, C
8-18
alkyl polyglycol ether carboxylates, C
8-18
-N-acyl taurides, C
8-18
-N-sarcosinates, C
8-18
alkyl isethionates and mixtures thereof.
The anionic surfactants are present in a quantity of preferably 1 to 10% by weight and more preferably 2 to 6% by weight, based on the washing alkali component A.
The water-soluble silicates used may be any of the silicates used in detergents. The silicates not only act as a washing alkali, i.e. increase the pH value, they also have builder properties. Suitable water-soluble silicates are both crystalline and amorphous silicate. Crystalline layer-form sodium silicates corresponding to the general formula NaMSi
x
O
2x+1
.yH
2
O, where M is sodium or hydrogen, x is a number of 1.9 to 4 and y is a number of 0 to 20, preferred values for x being 2, 3 or 4, are particularly suitable. Crystalline layer silicates such as these are described, for example, in European patent application EP-A-0 164 514. Preferred crystalline layer silicates corresponding to the above formula are those in which M is sodium and x assumes the value 2 or 3. Both &bgr;- and &dgr;-sodium disilicates Na
2
Si
2
O
5
.yH
2
O are particularly preferred.
Amorphous sodium silicates with a modulus (Na
2
O:SiO
2
ratio) of 1:2 to 1:3.3, preferably 1:2 to 1:2.8 and more preferably 1:2 to 1:2.6 are also suitable. Amorphous sodium silicates which dissolve with delay and exhibit multiple wash cycle properties are particularly preferred. The delay in dissolution in relation to conventional amorphous sodium silicates can have been obtained in various ways, for example by surface treatment, compounding, compacting or by overdrying. In the context of the invention, the term “amorphous” is also understood to encompass “X-ray amorphous”. In other words, the silicates do not produce any of the sharp X-ray reflexes typical of crystalline substances in X-ray diffraction experiments, but at best one or more maxima of the scattered X-radiation which have a width of several degrees of the diffraction angle. However, particularly good builder properties may even be achieved where the silicate particles produce crooked or even sharp diffraction maxima in electron diffraction experiments. This may be interpreted to mean that the products have microcrystalline regions betwe
Merz Thomas
Schnepf Christine
Shamayeli Khalil
Gupta Yogendra N.
Henkel-Ecolab GmbH & Co. OHG
Mruk Brian P.
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