Background of the invention

The invention concerns a product for the removal of layers of grime from glass, said grime layers comprising silicate-containing/silicon-containing compounds, for example from concrete elements, said product in its ap¬ plication form being fluid with a pH-value less than 7 and comprising at least two main components in aqueous solution, said main components comprising phosphoric acid and ammonium hydrogen-fluoride, and the use thereof. The invention also concerns a method for the removal of compounds containing silicate/silicon on glass surfaces.

The known technique

It is a commonly-known problem that glass surfaces are attacked by compounds containing silicate, stemming for example from concrete dust. Window panes in buildings constitute a special problem, in that concrete and similar building materials containing silicate/silicon are dissolved under the influence of the weather. The particles of dust arising from this situation become suspended in the rainwater which runs down the glass surfaces. The dissolved dust containing silicate/silicon remains hanging on the glass, which with time thus becomes matt and less transparent.

When magnified, the glass can be compared with a mountain landscape with valleys in which the dissolved building materials containing silicate/silicon are deposited. This reacts chemically with parts of the glass components, whereby the layer formed by the silicate/silicon con¬ nections in the dissolved building material adheres to

the glass not only mechanically but also in a purely chemical manner.

In order to remove this layer, it is common to carry out a grinding of the glass until this appears clear. By this the layer of silicate-containing/silicon-containing building materials is evidently removed, but besides a grinding of the glass itself takes place, said glass thus being worn out. Furthermore, the method is un- suitable for heavy attacks, for which reason these cases must be given up.

From DE-A-1025114 and from GB-A-878594 it is known to produce mixtures for the treatment of glass, where these mixtures comprise phosphoric acid and ammonium hydrogen- fluoride. However, the mixtures are composed in such a manner that, due to the high content of active hydrogen- fluoride, a strong etching of the glass occurs, and thus irreversible damage unless the glass/window panes are constantly supervised and the solution removed at a care¬ fully planned time. Moreover, the solutions can be used only for the polishing of glass and require a subsequent mechanical treatment. Consequently, the relevant solutions are not suitable for use commercially in con- nection with the removal of silicate compounds on the windows of buildings, and where it is necessary to allow these to remain for a time which is not constantly regulated and controlled and supervised, in that this will be practically impossible.

A solution is also known from DE-A-1496594, this comprising phosphoric acid and fluoric acid, and which is similarly unsuitable for the removal of deposits on the windows of buildings, in that the use of the fluid will require that this is constantly supervised in order to avoid irreversible damage, in that fluoric acid is a particularly active component and must not remain on the

glass material for too long a period of time.

Furthermore, all of the solutions disclosed are un¬ suitable for application on vertical surfaces, in that they are in an easily-running liquid form and can thus not remain hanging on the surfaces to which they are applied. Consequently, this requires that if the fluids are to be used for the cleaning of windows, these must first be dismounted and laid down in a horizontal plane, and as mentioned above they must also be constantly supervised so that the fluid does not remain sitting on the glass surfaces for too long a time.

Object of the invention

It is the object of the invention to provide a product which does not have the disadvantages of the known products and techniques, and where the silicate/silicon- containing building material is removed from the glass surfaces in a simple manner without giving rise to any irreversible and damaging effect on the glass itself, which thus appears as new after the treatment with the product, and whereby it is not necessary to supervise the applied product, in that the period of time for which it can be allowed to remain on the glass is not critical. Moreover, the product is suitable for application direct¬ ly on glass and window panes in buildings, in that the product is of such a consistency that it remains hanging on the vertical surfaces.

This object is achieved by composing the product so that the ammonium hydrogen-fluoride is an active component and constitutes 3-19 percent weight of the product, and that the phosphoric acid is a controlling and regulating component and constitutes 50-70 percent weight of the product, and that the product further comprises an auxiliary component, said auxiliary component being one

which increases the viscosity of the product and which constitutes 3-17, preferably 6-12 percent weight of the product.

The result of having a mixture comprising an active and a controlling part is as follows:

The controlling part, which thus consists of phosphoric acid in the stated amounts, causes the active part, which consists of ammonium hydrogen-fluoride in the stated amounts, to be chemically active in the area between the silicate/silicon-containing grime layer and the surface of the glass, so that the chemical binding in between the grime layer and the glass surface is broken, and as a consequence of the existence of the phosphoric acid the chemical reaction is limited to comprise the interface area without any attack taking place on the healthy parts of the glass surface, whereby it is avoided that the glass becomes matt. Since the product is also provided with a viscosity-increasing component in the stated amounts, it is also achieved that the fluid does not col¬ lect down at the bottom of the window pane, but is applied in an even layer on the whole surface of the glass and thus works actively on said whole surface.

By means of the ammonium hydrogen-fluoride, there is also achieved an effective decomposition of the silicate/- silicon-containing compounds between the layer of grime and the glass surface, and without any formation of fluoric acid which would attack and destroy the glass. This is a consequence of the existence of the phosphoric acid, which also controls the process's area of attack and extent.

By composing the product according to the invention as disclosed in claim 2, it is achieved that the moistening of the grime layer and the penetration of the solution ir

towards the surface of the glass and the interface of the grime layer is optimized, while at the same time the component possibly functions as a grime carrier.

By composing the product according to the invention as disclosed in claim 3, an optimum composition is achieved.

As disclosed in claim 4, by using the product for the removal of silicate/silicon-containing layers of grime from glass surfaces, there is achieved an effective, quick and inexpensive removal of a layer of grime which would otherwise normally require a mechanical and particularly time-consuming operation.

By using a method as disclosed in claim 5, there is achieved an effective operation and method for the removal of grime of a silicate/silicon-containing character.

When the method also comprises the characteristics disclosed in claims 6 and 7, an optimization of the method is achieved.

The invention will be explained in more detail in the following by way of embodiment examples.

The solution is formed by mixing phosphoric acid HgPO. together with ammonium hydrogen-fluoride in an aqueous solution which possibly also comprises a non-ionic tenside, for example SULFOSOFT, which also increases the viscosity. The product thus has a viscosity of 3.00

2 2 mmNNss//mm aatt 2200°° .. AAllll ooff tthhee ccoommppconents forming the solution have a pH which is less than 7,

The product is applied to the glass surface from which the silicate/silicon-containing components are to be removed by means of a soft brush. Before the application,

the surface is washed with an acid solution so that pos¬ sible basic substances are neutralized.

The solution must be allowed to remain on the surface for a suitable period of time, at least approx. 2-3 minutes, so that the chemical binding between the layer of grime and the surface of the glass can be broken. The solution may well be left on the surface for a longer period, up to several hours, without this giving rise to any damage to the glass. The expedient composition with phosphoric acid and ammonium hydrogen-fluoride, both of which are in liquid form, has the effect that there is no formation of fluoric acid which is known to react strongly in relation to glass and damage it. It is thus known that the use of fluoric acid alone for the removal of silicate/silicon connections will most certainly remove the layer of grime, but it will also attack the glass with the result that it becomes matt.

Since the product is thus self-working and can remain sitting for hours without any damage to the glass, it is thus possible in an effective manner to apply the solution to an almost unlimited number of glass panes in one working sequence, without this giving rise to any risk of irreversible damage.

The product is hereafter removed again and, if necessary, a new layer is applied to the glass surface, and finally the glass is washed in the normal way with soapy water or a similar basic product solution.

Example 1

The product is mixed in the following manner:

A 75% solution of phosphoric acid is poured into a container. The ammonium hydrogen-fluoride is then

dissolved in temperate water and mixed together with the phosphoric acid in the container. Finally, the non-ionic tenside, e.g. SULFOSOFT, is added and the whole mixture is stirred together.

The weight percentage of the individual components lies within the intervals disclosed earlier.

The glass which has been attacked by silicate/silicon- containing components is first washed in an acid solution. The product is then applied to a half-part of the glass, and the other half-part of the glass is washed with ordinary soapy water. After 5 minutes, the product is removed from the glass, and that half-part of the glass which has been treated now appears clear and one hundred percent transparent, while on the half-part which has been washed only with a soapy solution there is still a grey and unaffected film of silicate/silicon-containing components, the result being that this part of the glass is unclear and misty to see through.

Example 2

A product is produced as described in example 1, and the final mixture consists of:

65 percent weight phosphoric acid

7 percent weight ammonium hydrogen-fluoride

8 percent weight sulfosoft 20 percent weight water

Description of the test

In the investigation of the reaction of the glass to light, the following was used:

Light meter.

Hagner digital luxmeter EC1 No. 6699 "with certificate".

Light source.

Parabola, 10 cm in diameter with crypton 4.8 volt lamp, 0.75 amp., consumption during test 0.62 amp.

Power supply.

Adjustable D.C. power supply with built-in current limiter, with the effect that the light source can remain stationary.

Light-box with 12 mm inspection hole in the top. Internal dimensions: breadth 17.5 cm, depth 17.5 cm, height 105.0 cm. The object of the light-box is to prevent daylight influencing the luxmeter.

Mounting of light source and luxmeter.

The light source is mounted stationary, centrally in the top of the light-box. The luxmeter is mounted stationary in the bottom of the light-box with detector in the centre.

In the light-box, 1 meter from the top, there is milled a 6 mm groove which enables the insertion of a piece of glass which fills the whole of the inside of the light- box, and at the same time has contact between the detector itself and the glass.

Test glass. The glass comprises 3 pieces of 6 mm H.H.V, test no. 2-4 of 17.5 x 17.5 cm of the external, lowermost part of a double-glazed window, and which has been attacked by concrete silicates, and one piece of glass test no. 1 of 17.5 x 17.5 cm from the external, uppermost part of the same double-glazed window, which has not been attacked by concrete silicates because it has been protected by a minor projection. The window has been built and used in

concrete constructions since 1988.

Clinical observations:

Glass test Visual Lux Light Light no. 1 evaluation meter transmission transmission in relation in relation to empty to unattacked light-box glass Light-box empty 1710 100%

Unattacked Clear and 1580 92.4% 100% glass transpar¬ washed in ent. the normal way.

Glass test no. 2

Light-box empty 1710 100%

Attacked Greyish glass Unclear 1510 88.3% 95.6% washed in the normal way.

Same Clear as attacked test 1. 1580 92.4^ 100% glass to which the product has

been applied for 10 mins. and then washed in the normal way.

Glass test no. 3

Light-box empty 1710 100%

Attacked Greyish glass Unclear 1515 88.6% 95.9% washed in the normal way.

Same Clear as attacked test 1 1580 92.4% 100% glass to which the product has been applied for 3 hours and then washed in the normal way.

Glass test no. 4

Light-box

empty 1710 100%

Attacked Greyish glass Unclear 1540 90.0% 97.5% washed in the normal way.

Same Clear as attacked test 1 1580 92.4% 100% glass to which the product has been applied for

12 hours and then washed in the normal way.

By "washed in the normal way" is meant that the glass has been washed with a detergent and subsequently polished.

Conclusion:

From the tests it can be concluded that glass which has been treated with the product has its light transmission restored, and that it is of no significance whether the product has been applied to the glass for 5 minutes or 12 hours.