Method for preventing marks caused by drying and a vehicle washing system

Abstract

A method for cleaning vehicles by means of which the formation of marks caused by drying is prevented. The method comprises a rinsing step using water. In the method, the anions forming poorly soluble salts with alkaline earth metals dissolved in water are removed from the water, while cations causing the water hardness are retained. Furthermore, a vehicle washing system includes: at least one application device for applying rinsing fluid to a vehicle to be cleaned; and an ion-exchange device for removing anions from the rinsing fluid prior to the application to the vehicle.

Claims

1. A method for cleaning of vehicles, said method comprising: removing from water, which has a water hardness, anions forming poorly soluble salts with alkaline earth metals dissolved in the water, while retaining in the water cations causing the water hardness, the anions forming poorly soluble salts with alkaline earth metals dissolved in the water being exchanged with anions that form readily soluble salts with alkaline earth ions; and after the removing from the water of the anions while retaining the cations, spraying a vehicle being cleaned with the water.

2. The method according to claim 1, wherein in the removing from the water of the anions while retaining the cations, the anions forming poorly soluble salts with alkaline earth metals dissolved in the water are exchanged with chloride ions.

3. The method according to claim 1, wherein the removing from the water of the anions while retaining the cations comprises using a strongly basic anion exchanger to remove the anions forming poorly soluble salts with alkaline earth metals dissolved in the water.

4. The method according to claim 3, further comprising preloading the strongly basic anion exchanger with the anions that form readily soluble salts with alkaline earth ions.

5. The method according to claim 4, further comprising preloading the strongly basic anion exchanger with chloride ions.

6. The method according to claim 1, wherein in the removing from the water of the anions while retaining the cations, the anions forming poorly soluble salts with alkaline earth metals dissolved in the water are at least 30% removed.

7. The method according to claim 3, further comprising regenerating the strongly basic anion exchanger with a solution containing sodium chloride.

8. The method according to claim 1, wherein the anions forming poorly soluble salts with alkaline earth metals dissolved in the water are chosen among carbonate, hydrogen carbonate, and sulfate.

9. The method according to claim 1, wherein the water from which the anions are removed is fresh water.

10. A vehicle washing system comprising: at least one application device to apply a rinsing fluid to a vehicle being cleaned; and an ion exchange device coupled to the at least one application device to remove anions from the rinsing fluid before the rinsing fluid is applied to the vehicle, the ion exchange device removing anions forming poorly soluble salts with alkaline earth metals dissolved in the rinsing fluid from the rinsing fluid while retaining in the rinsing fluid cations that cause water hardness of the rinsing fluid, the anions forming poorly soluble salts with alkaline earth metals dissolved in the rinsing fluid being exchanged with anions that form readily soluble salts with alkaline earth ions.

11. The vehicle washing system according to claim 10, wherein the that form readily soluble salts with alkaline earth ions comprise chloride ions.

12. The vehicle washing system according to claim 10, wherein the rinsing fluid comprises fresh water.

13. The vehicle washing system according to claim 10, wherein the rinsing fluid comprises a chemical drying aid.

14. The vehicle washing system according to claim 10, wherein the application device includes a spray device to spray the rinsing fluid onto the vehicle.

15. The vehicle washing system according to claim 10, further comprising an additional application device to apply a treatment fluid to the vehicle.

16. The vehicle washing system according to claim 15, wherein the treatment fluid applied to the vehicle comprises service water treated by water treatment from already consumed treatment fluid and/or rinsing fluid.

17. The method according to claim 1, wherein in the removing from the water of the anions while retaining the cations, the anions forming poorly soluble salts with alkaline earth metals dissolved in the water are exchanged with anions that form readily soluble and hygroscopic salts with alkaline earth ions.

18. The method according to claim 1, wherein in the removing from the water of the anions while retaining the cations, the anions forming poorly soluble salts with alkaline earth metals dissolved in the water are exchanged with anions other than OH.

19. The method according to claim 1, further comprising: before spraying the vehicle with the water, spraying the vehicle with a treatment fluid.

20. The vehicle washing system according to claim 10, wherein the rinsing fluid comprises water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described below by means of detailed embodiment examples with reference to the accompanying drawings. The drawings show:

(2) FIG. 1 a photographic depiction of lime spots;

(3) FIG. 2 a photographic depiction of calcium chloride spots;

(4) FIG. 3 a schematic depiction of a portal washing system in which the method according to the invention is used;

(5) FIGS. 4A and 4B a schematic depiction of a drying process over time with a) treated rinsing fluid (FIG. 4A) and b) untreated rinsing fluid (FIG. 4B);

(6) FIGS. 5A and 5B mass-time diagrams for a drying process with a) treated rinsing fluid (FIG. 5A) and b) untreated rinsing fluid (FIG. 5B).

DETAILED DESCRIPTION OF THE INVENTION

(7) The water used for rinsing in a vehicle cleaning method is generally so-called fresh water. Fresh water is generally of the quality of drinking water, but this is not necessary. Any qualitative equivalent surface water, for example, clear river water, rain water, etc., can also be used for the present purpose, as long as it can be prepared according to the invention. The objective of water treatment according to the invention is the reduction of poorly soluble ions in conjunction with cations of group IIA, especially magnesium and calcium. It has been shown that, when these anions are eliminated by at least 30%, preferably 50%, more preferably 60%, especially 70%, still more preferably 80%, ideally 90% and more, the result of rinsing after drying is particularly satisfactory, i.e., visible drying spots are no longer observed. The achieved extent depends on the corresponding water hardness and the capacity of an ion exchange device.

(8) Depending on the location, drinking water can have different compositions. For example, calcium values in the range of about 70 to about 90 mg/L, magnesium values in the range of about 16 to about 25 mg/L, hydrogen carbonate values in the range of about 224 to about 380 mg/L, carbon dioxide values from about 6 to about 32 mg/L, and carbonate values from about 0.4 to about 0.7 mg/L are stated for Munich drinking water. These values can vary sharply, depending on the location in Germany.

(9) The method according to the invention is generally applicable to all types of surfaces that must be cleaned and on whose surface spots of residual salts produced by water hardness are conspicuous. In this respect, the invention is particularly suited for dark, high-gloss painted sheet metal, as in vehicles. The method is especially suitable for vehicles that can pass through ordinary car washes or portal washing systems. This is especially true for cars of any size, sport cars, SUVs, vans, transport vehicles, mobile homes or campers.

(10) The removal of anions can occur in different ways. There are, e.g., chemical methods or sorption methods, especially adsorption methods. Methods with basic anion exchangers, preferably strongly basic anion exchangers (SBA), are preferred. Anion exchanger types used for full desalinization in mixed beds can also be used here.

(11) The following steps occur during removal of undesired anions A.sup., if a strongly basic anion exchanger in chloride form is used.

(12) Activation Step:
Resin-N.sup.+(CH.sub.3).sub.3OH+NaCl.fwdarw.resin-N.sup.+(CH.sub.3).sub.3Cl.sup.+Na.sup.+OH.sup.

(13) Exchange Step:
Resin-N.sup.+(CH.sub.3).sub.3Cl.sup.+A.sup..fwdarw.resin-N.sup.+(CH.sub.3).sub.3A.sup.+Cl.sup.

(14) Regeneration Step:
Resin-N.sup.+(CH.sub.3).sub.3A.sup.+Na.sup.+Cl.sup..fwdarw.resin-N.sup.+(CH.sub.3).sub.3Cl.sup.+Na.sup.+A.sup.

(15) Carbon dioxide is predominantly dissolved in water as HCO.sub.3.sup. (A.sup.=HCO.sub.3.sup.). Calcium hydrogen carbonate is soluble in water, but upon drying converts into the poorly soluble carbonate, which then forms the insoluble lime spot. Anions forming poorly soluble salts are also SO.sub.4.sup.2 anions.

(16) Any basic, especially strongly basic, anion exchanger resins are generally suitable as anion exchanger. The matrix of the resin can be arbitrary, an acryl or polystyrene base being preferred. Modification generally occurs via aliphatic quaternary side groups. The resin generally consists of spherical beads of the transparent gel type. The total capacity is usually 0.9 to 1.4 equivalent per L, for example, 1.3 equivalent per L (28.4 kg/ft.sup.3) for the chloride form.

(17) The method according to the invention can be used in any vehicle cleaning and/or washing systems. For example, FIG. 3 schematically depicts a known portal washing system 1 in a front view (left) and a corresponding side view (right).

(18) The portal washing system 1 then has a washing portal 2 movable in the longitudinal direction with a first spray device 3 arranged thereon for application of cleaning liquid for cleaning of the vehicle.

(19) For this purpose, the already-consumed washing liquid is collected in a sludge tank 4 beneath the washing zone and then re-treated with water treatment 5 as service water. The service water is then re-mixed with the cleaning agents, such as foam, shampoo, etc., and again supplied to the first spray device 3.

(20) The washing portal 2 also has a second spray device 6 arranged thereon for application of water treated according to the invention for rinsing of the vehicle. For this purpose, fresh water is treated in an ion exchange device 7 according to the invention.

(21) The vehicle is thus cleaned in one step within the overall process with treated service water, and the vehicle is rinsed clean of residual dirt in a subsequent step, in which the fresh water treated according to the invention is advantageously used in the last step. A chemical drying aid (CDA) can be applied with the fresh water treated according to the invention or preferably before. Such aids include, for example, organic and/or organosilicon amino/hydroxy-alkoxy compounds and/or alkoxy alcohols. It is then dried in a subsequent step with a blower (not shown).

(22) It should be mentioned that a known CDA application with osmosis water in comparison with the method according to the invention described here is connected with a noticeable performance loss that does not occur in the water treated according to the invention.

(23) A number of advantages are gained with respect to the method according to the invention relative to the known methods. It should initially be emphasized that an ion exchange device of the usual type, as is already often used in washing systems, can be employed, with the modification that an anion exchanger is now used instead of the cation exchanger. The invention can therefore be used in existing systems without significant modification.

(24) The favorable effect of the invention is presumably due to the fact that, instead of leaving behind insoluble chalky lime or gypsum spots on the vehicle surface, the calcium or magnesium salts, depending on the extent of removal, are now present at most as water-soluble and hygroscopic deposits, for example, CaCl.sub.2 or MgCl.sub.2 on the surface of the vehicle. Such deposits also attract water so that the film of possible spots is no longer visible. FIG. 2 clearly shows the transparent appearance of the spots caused by the hygroscopic behavior of calcium and magnesium chlorides. Some of the insoluble salts can also become moist and therefore kept invisible by water. The spots can also completely subsequently disappear, for example, during rain. Lime or gypsum spots, on the other hand, remain and are visible in the dry state (cf. FIG. 1), which clearly shows deposited spots having a conspicuous white appearance.

(25) This is again shown by means of the schematic depiction of a drying process over time in FIG. 4 and by mass-time diagrams in FIG. 5 with treated rinsing fluid (FIGS. 4a, 5a) and untreated rinsing fluid (FIGS. 4b, 5b).

(26) FIG. 4a shows a drying process according to the invention from left to right with time. Residual water of the rinsing fluid with the water treated according to the invention, depicted by the drops 9, then remains on the vehicle surface 8 being cleaned after rinsing and usually even after intense blower drying. The water contained in drops 9 then evaporates, in which case, complete drying does not occur owing to the properties of the water treated according to the invention, but a residual drop 10 with residual moisture as described above remains. This is also apparent in FIG. 5a, where a certain fraction of moisture is retained.

(27) In contrast thereto, it is apparent in FIG. 4b that the drops 11 of the rinsing fluid with untreated water remaining there after the rinsing process dry up completely with time and a distinctly recognizable drying spot 12 with sharply delimited edges therefore remains, as also shown in FIG. 1. It can also be deduced from FIG. 5b that the drop 11 completely dries up and only the readily visible drying spot 12 therefore remains on the vehicle surface 8.

(28) Another advantage is that regeneration is only performed for the anion exchanger, i.e., regeneration chemicals are saved. In addition, regeneration of the anion exchanger with the physiologically and environmentally largely non-problematical sodium chloride is advantageous. No hazardous substances are present. Surfactants or other chemicals that burden the environment can also be dispensed with.

(29) Relative to methods with an osmosis membrane desalinization, the method has the advantage that failure of the ion exchanger (for example, by failed regeneration) causes no damage to the system. An osmosis membrane is permanently damaged during failure of softening by blocking with lime, gypsum, etc. Such an event has no significant effect in the method according to the invention because functional capability can be rapidly restored by regeneration of the ion exchange device. The method according to the invention preferably includes neither a (reverse) osmosis step nor removal of salts by distillation.

(30) The affinity of different ions to the ion exchange resin varies so that the quality of ion exchange depends on the number and type of ions dissolved in the water and is therefore location-dependent. In order to achieve the desired exchange efficiency even in the presence of many ions with low affinity, it might be necessary to over-dimension the exchanger. In this case, it should not be operated to its nominal capacity because the ions of lower affinity, for example, HCO.sub.3.sup. ions, which are to be removed as thoroughly as possible, then already break through.

(31) The degree of removal of carbonate or sulfate ions can therefore be simply regulated by the ion exchange capacity and length of the ion exchange device. Monitoring of consumption of the ion exchange device can occur via the volumetric flow rate, with knowledge of the actual water hardness. An empirical scale that correlates degree of hardness with the parameters of the employed ion exchanger can be used in order to determine the safe time for regeneration of the ion exchange device.

(32) The effect of the method according to the invention can also be advantageously checked by a test. The actual rinsing water is then dripped onto high gloss-painted sheet metal and allowed to dry in an air stream. If the ion exchanger is functional, white or bright spots are not apparent to the naked eye at a distance of 1 m. Otherwise the ion exchanger is used up and must be regenerated. The pH value or another chemical or physical parameter can also optionally be checked.

(33) Ordinary line pressure can be used in setting up the method. The increased pressure necessarily required in an osmosis device in front of the osmosis membrane is not necessary. The ion exchange device and the spray device can, in principle, be exposed to the same pressure.

(34) The volumetric flow rate of the ion exchange device is sufficient for all common applications. Intermediate storage of the treated rinsing fluid is not necessary. The volumetric flow rate is set so that the prescribed cleaning objective is achieved.

(35) The rinsing step according to the invention can be integrated in an existing cleaning method for vehicles without a significant change of the essential parameters. Advantageous variants of cleaning methods can also be designed. For example, a chemical drying aid can be added to the rinsing water treated according to the invention. In usual methods, especially those using osmosis membranes, a separate step would be required for this purpose.

LIST OF REFERENCE NUMBERS

(36) 1 Portal washing system

(37) 2 Washing portal

(38) 3 First spray device (service water)

(39) 4 Sludge tank

(40) 5 Water treatment

(41) 6 Second spray device (fresh water)

(42) 7 Ion exchange device

(43) 8 Vehicle surface

(44) 9 Drops of rinsing fluid treated according to the invention

(45) 10 Residual drops of treated rinsing fluid

(46) 11 Drops of untreated rinsing fluid

(47) 12 Drying spots