WO1995028229A1

WO1995028229A1 - Method for applying a mass onto a substrate

Info

Publication number: WO1995028229A1
Application number: PCT/FI1994/000145
Authority: WO
Inventors: Pentti Valoranta
Original assignee: Pentti Valoranta
Priority date: 1994-04-18
Filing date: 1994-04-18
Publication date: 1995-10-26
Also published as: AU6431594A

Abstract

The present invention relates to a method for applying a mass onto a substrate with the aid of a spray comprising a mixer part (1) and a nozzle end (3). In the mixer part (1) dry, powder-like mass and water are mixed into a paste or sludge which is discharged through the nozzle end (3) onto the substrate with the aid of pressurized air. According to the invention, such dry, powder-like mass mixed with water contains mechanically ground alkali silicate and at least one non-hygroscopic component acting as the stabilizer of the alkali silicate. Now, the water added in the dry mass causes the alkali silicate to be dissolved prior to the discharge of the mass through the nozzle end. As taught by the invention, e.g. lime-based coating masses can be applied, in which the alkali silicate, such as waterglass or potassic waterglass, serves as a reinforcing component providing waterproofing and in which the stabilizer of the alkali silicate is e.g. quartz powder or aluminium silicate pearls, wherewith premature caking of the alkali silicate powder is prevented.

Description

Method for applying a mass onto a substrate

The present invention relates to a method for applying a mass onto a substrate using a spray, in the mixer part whereof dry, powder-like mass and water are supplied so that they are mixed into a paste or sludge conducted from the mixer part via the nozzle end of the spray onto a substrate.

Such spray coating apparatus are commercially available which comprise in the mixer part thereof a mixer screw rotating around the axis thereof in a cylindrical passage and where¬ through the mixer part has via a flexible hose been connected to the nozzle end. Said means are used by supplying dry, powder-like coating mass to the first end of the passage, wherefrom a screw pushes it towards the other end of the passage and the hose leading to the nozzle at the same time as the mass is being mixed with water fed to the passage from a supply pipe attached to the side thereof. In applying onto a substrate the sludge-like coating mass produced as the re- suit of mixing, pressurized air is used as an aid, this being fed via a separate pipe to the nozzle end.

With a view to the operability of the continuous-action spray-coating means, it is indispensable that the mixing of a dry, powder-like coating mass and water into homogeneous ap¬ plicable sludge takes place instantly. Therefore, it has not been possible to use the means for applying coating materials containing alkali silicates. Alkali silicates, such as water- glass Na₂0-nSi0₂ and potassic water-glass K₂0-nSi0₂, in which n=3-4, form in cements, mortars and paints a reinforcing in¬ gredient to provide waterproofing. Alkali silicates have been used for coating masses in the form of through-dry particles which are characterized by slow dissolution in water. There¬ fore, no alkali silicate particles have been included direct- ly as an ingredient of a dry, water-soluble coating mass, not to speak of that such coating mixture could be applied using said spray-coating apparatus known in the art; instead, the through-dry alkali silicate has in practice been dissolved separately in water, and the water solution thus obtained has been combined with the solid components of the coating on the site just before applying the coating. Said combining is out of question in said spray-coating apparatus intended to be connected to a water supply line for providing water into the mixing passage by means of the pressure prevailing in the water supply line.

The objective of the present invention is to produce a problem solution to enable the use of prior art spray coat¬ ing apparatus described above, provided with mixer screws or equivalent apparatus, also in applying masses containing al¬ kali silicate. The invention is characterized in that the dry, powder-like mass supplied to the mixer part of the means contains mechanically ground alkali silicate and at least one non-hygroscopic component acting as a stabilizer to the al¬ kali silicate, whereby the water added in the mass in the mixer part dissolves the alkali silicate prior the extrusion of the mass out of the nozzle end onto the substrate.

The problem-solution according to the present invention is made conceivable by the fact that an alkali silicate produced mechanically by grounding, such as ground water-glass or po- tassic water-glass, with particle size below 100 μm, prefer¬ ably 0.1 to 10 μ , is rapidly water-soluble. The dissolution is followed by instant gel-formation increasing the viscosity of the alkali silicate containing coating mass, and turning the mass first into porridge-like and then cement-like in a few minutes after water addition. Such rapid stiffening of the mass is a remarkable advantage, particularly on walls and other vertical surfaces, the mass applied whereon being soli- dified without starting to run.

An alkali silicate powder produced mechanically by grinding is not only fast-dissolving, but also highly hygroscopic. The powder absorbs moisture from the air, whereby it becomes caked and in the end turns into a hard, glassy mass, i.e. it returns into the state it had before being ground. Therefore, it is necessary that in a dry, powder-like mass used ac¬ cording to the invention, at least one stabilizer component is included, besides the alkali silicate, to prevent the mass from being caked. The function of the stabilizer is primarily to keep the alkali silicate particles sufficiently apart from one another, and the quality thereof is not as such critical. A stabilizer found to be appropriate is formed from hollow, water-indissoluble glass pearls made from alkali silicate, the particle size thereof being about 50 to 300 μm. A product like that is, for instance, Enlett 300 marketed by the Nor- diska Mineralprodukter AB, the maximum particle size thereof being 300 μm, the average particle size 75 μm, and which can absorb moisture 0.4 per cent by weight. Said product can be mixed in ground alkali silicate about 40 to 55 per cent by weight, preferably about 50 per cent by weight. As another appropriate stabilizer alternative, a finely powdered quartx powder may be mentioned, the particle size thereof being below 0.1 μm, preferably about 2 to 40 nm. Such product is, for instance, Aerosil 200 marketed by Degussa AG, being hy- drophilic and with an average particle size in the range of 7 to 40 nm. The stabilizing effect of the quartz particles is assumed to be based on the idea that they accumulate as a protective layer around larger alkali silicate particles, and it has been found that about 3 to 10 per cent by weight, ad¬ vantageously about 5 per cent by weight of quartz suffices for stabilization, calculated from the amount of alkali silicate.

In order to prevent the ground alkali silicate from caking, the stabilizer has to be added therein appropriately in the above weight ratios immediately after the grinding. In this manner the stabilized alkali silicate is therafter mixed with the rest of the solid components of the coating into a mass which can be produced in bags, emptied as such on the site into the supply end the mixer screw of the coating apparatus. For transforming the mass into sprayable paste or sludge, clean tap water conducted into the mixer part of the means is a sufficient measure.

The method according to the present invention is appropriate for applying coating masses containing particularly alkali silicate, such as water-glass or potassic water-glass, on various substrates. A substrate may consist of a stone, brick or concrete surface, or a gypsum, minerite or plastic board which can be positioned on a wall or floor either indoors or out of doors. Also providing an insulation material such as mineral wool with a coating layer is possible, whereby for supporting the coating e.g. glassfiber net can be used.

An alkali-silicate containing coating mass applied according to the invention can be cement-based mass or mortar, in which the base material can be limestone, sand or cement, or a mix¬ ture thereof. An appropriate proportion of alkali silicate in the mass is about 3 to 10 parts by weight per 100 parts by weight per said base material. For the portion by weight of the stabilizer included together with the alkali silicate will then be about 0.1 to 5 parts by weight depending on the stabilizer used. In addition to said components, the mass may contain e.g. iron oxide or equivalent colouring agent and other ingredients of coating masses known themselves in the art.

The invention is described below more in detail referring first to the accompanying drawing (Fig. 1) presenting a spray-coating means appropriate for mass application, and by presenting examples of the dry matter compositions of the coating mass.

The spray-coating means according to the drawing comprises a mixer part 1 standing supported by a stand 2, a nozzle end 3 and an elastic rubber hose 4 connecting the mixer part and the nozzle end. The mixer part 1 carries out the mixing of dry powder-like coating mass containing, according to the present invention, mechanically ground alkali silicate with water, the rubber hose 4 leads the mass sludge produced in the mixer part 1 to the nozzle end 3, and the nozzle end spreads the sludge with the aid of pressurized air onto a substrate to be coated.

The mixer part 1 comprises a fill-in container 5 open at the upper end, wherein the dry powder containing the solid in- gredients of the coating mass is vacated from a bag opened by breaking it by hitting it against an upwards curved toothed blade 6 arranged for said purpose in the upper end of the container. Below the container 5, a horizontal mixer screw 7 is placed, being rotated around the axis 8 by an electric motor 9 by means of a V-belt 10 and a groove wheel 11. The mixer screw 7 extends from the lower part of the container 5 into a passage 13 defined by a cylindrical mantle 12, from the latter end 14 whereof an opening leading to the hose 4 connecting the mixer part 1 and the nozzle end 3. On the op- posite sides of the passage mantle 12 water hoses 15 have been connected to supply tap water into the passage 13, said water being mixed with the dry powder-like solid matter into sludge pushed by the screw 7 via the hose 4 to the nozzle end 3.

For spreading the sludge by means of pressure, the nozzle end 3 is provided with a pressurized air line 16, which, for fa¬ cilitating the work, has according to the drawing been at¬ tached to the hose 4 supplying the sludge. The nozzle end 3 has moreover been provided with an on/off lever 17, a fine- adjustment screw 18 and a metal tip piece 19 provided with a nozzle aperture.

Example 1

Solid, glassy water-glass dried from an aqueous solution of sodium silicate is ground mechanically into a powder with particle size below 100 μm, prferably below 10 μm. In the powder thus obtained a product called Enlett 300 is added as a stabilizer so that the proportion of each component in the mixture is 50 per cent by weight.

For the basic material of the coating mass, 2 parts of lime stone powder Marmorcross F (Ernstrom), grain size 2.5 mm, 5 parts lime stone powder Marmorcross B (Ernstrom) , grain size 0.5 mm, 2 parts lime stone powder Myanit C (Ernstrom), grain size 0.1 mm, and 2.5 parts white cement are mixed.

The dry ingredients of the coating mass were mixed as follows:

100 parts by weight of the basic material, mixed as above, 5 parts by weight of stabilized alkali silicate, produced as above (waterglass + Enlett 300) 13 parts by weight of acrylic powder Mowilith DM 200 P, (Hoechst) , acting as a binding agent, 5 parts by weight of elastizing polymer powder Powder Polymer DP 2605 (Rohm and Haas) , acting as a binding agent 0.3 part by weight of defoaming agent, Dehydran 1922 (Henkel) 0.4 part by weight of antiabsorption agent Peramin A (marketed by Cemtu Oy) 0.2 part by weight of antirunning agent Combizell APR

200 (Aqualon GmbH) 0.5 part by weight of iron oxide pigment (marketed by Sverag AB)

All components of the coloured coating mass described above, with the exception of the pigment, are white. The weight of the mass is about 2 kg per dm³. The mass can be prepared as bulk goods in bags to be mixed on the site in the mixer part of the spray with water and applied via the nozzle end on a substrate to be coated. The powder composition described above can be varied in a number of part,s depending on the purpose of the coating. The amount of the pigment may vary in the range 0.5 to 4 parts by weight, and the type can be selected according to the colour desired. If the colour of the coating is of no significance, the lime stone can be replaced partly or totally with sand, and the white cement with ordinary cement. Stabilized alkali silicate can be used in 5 to 10 parts by weight so that when the basic material is coarser in grain size, the amount of the alkali silicate is greater. The stabilizer Enlett 300 can be replaced e.g. by a product called Aerosil 200, whereby the mixing ratio in a stabilized alkali silicate is e.g. 95 per cent by weight of alkali silicate and 5 per cent by weight of Aerosil 200.

Example 2

In mechanically ground waterglass powder, produced as in Example 1, finely powdered quartz powder Aerosil 200 (Degussa AG) was mixed with a weight ratio of 90 per cent by weight of waterglass and 10 per cent by weight of Aerosil 200.

The basic material of the coating mass was prepared by mixing 2 parts of lime stone powder Marmorcross F, 3 parts of lime stone powder Marmorcross B, 2.5 parts of glass pearls of aluminium silicate Enlett 1 (Nordiska Mineralprodukter AB) , 2.5 parts of a product called Perlite Microspheres (Noble Materials Inc.), and 1.8 parts white cement.

The powder-like coating mass was prepared by mixing

100 parts by weight of the basic material as above 3 parts by weight of stabilized alkali silicate (waterglass + Aerosil 200) as above 10 parts by weight of a product called Mowilith DM 200 P 3 parts by weight of a product called Powder Polymer DP 2605 0.3 parts by weight of a product called Dehydran 1922 0.3 parts by weight of a product called Peramin A

0.01 parts by weight of antirunning agent Culminal (Aqualon

GmbH) , and 0.4 parts by weight of iron oxide pigment.

A characteristic feature of the above coating mass is the lightness thereof, the mass weighing only about 1.2 kg per dm³. The mass is particularly appropriate for coating cei¬ lings and other interior surfaces. The composition may be varied, for instance, by increasing the proportion of coarser granules of the base material, whereby the amount of alkali silicate can respectively be increased. The amount of the stabilized alkali silicate may vary from 3 to 5 parts by weight and the amount of pigment e.g. 0.4 to 5 parts by weight per 100 parts of base material.

It is obvious to a person skilled in the art that various modifications of the invention are not confined to the de¬ tailed embodiment examples described above, and they may vary within the scope of the accompanying claims.

Claims

1. A method for applying mass onto a substrate using a spray, in the mixer part (1) whereof dry, powder-like mass and water are supplied so that they are mixed into a paste or sludge conducted from the mixer part via the nozzle end (3) of the spray onto the substrate, characterized in that the dry powder-like mass contains mechanically ground alkali silicate and at least one non-hygroscopic component acting as a stabilizer in the alkali silicate, whereby the water added in the mass in the mixing part (1) dissolves the alkali sili¬ cate before discharging the mass from the nozzle end (3) onto the substrate.

2. Method according to claim 1, characterized in that the dry mass contains mechanically ground waterglass or potassic waterglass with granular size below 100 μm, preferably below 0.1 to 10 μm.

3. Method according to claim l or 2, characterized in that for the stabilizer, hollow, water insoluble glass pearls of aluminium silicate, the granular size thereof being about 50 to 300 μm are used.

4. Method according to claim 1 or 2, characterized in that for the stabilizer, quartz powder with granular size below 0.1 μm, preferably about 2 to 40 μm, is used.

5. Method according to any one of the preceding claims, characterized in that it is used for applying coating mass.

6. Method according to claim 5, characterized in that by the method such lime coating is applied which contains 3 to 10 parts by weight of mechanically ground alkali silicate and 0.1 to 5 parts by weight of a stabilizer per 100 parts by weight of ground lime stone and/or cement.

7. Method according to claim 6, characterized in that the coating contains a colour pigment, such as iron oxide, in addition to the lime stone.

8. Method according to any one of the preceding claims, characterized in that the spray comprises in the mixer part (1) thereof a mixer screw (7) rotating around the axis (8) thereof in a cylindrical passage (12) , in the first end whereof dry, powder-like mass is supplied and in which the supply of water is carried out via the side of the cylin¬ drical passage.

9. Method according to claim 8, characterized in that the mass sludge or paste thus resulted is conducted through an elastic hose (4) at the latter end (14) of the screw (7) to the nozzle end (3) and is applied onto the substrate with the aid of the pressurized air carried to the nozzle end.