EP2872671A1

EP2872671A1 - Method of processing porous article and porous article

Info

Publication number: EP2872671A1
Application number: EP13807445.5A
Authority: EP
Inventors: Petteri Kinnunen; Jari Ruuttu
Original assignee: COLIGRO Oy
Current assignee: COLIGRO Oy
Priority date: 2012-06-21
Filing date: 2013-06-20
Publication date: 2015-05-20
Also published as: WO2013190185A1; FI124932B; FI20125694A

Abstract

A method and a porous article. The article comprises a first surface and a second surface. The method comprises: hydrophobizing the first and the second surfaces and at least some of the pores, and arranging hydrophilic material or precursors thereof only on the first surface of the article.

Description

METHOD OF PROCESSING POROUS ARTICLE AND POROUS ARTICLE

BACKGROUND

The invention relates to a method of processing a porous article.

The invention further relates to a porous article.

Many stones and construction materials have porosity which is the main reason for their degradability and aspect deterioration. The reason for this is that water as well as polluting and corrosive species can diffuse or adsorb inside the stone, thus potentially reducing its mechanical and chemical resistances. BRIEF DESCRIPTION

Viewed from a first aspect, there can be provided a method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces and at least some of the pores, and arranging hydrophilic material or precursors thereof only on the first surface of the article. Thereby an article which does not take up water may be achieved.

Viewed from a further aspect, there can be provided a porous article comprising a first surface and a second surface, wherein the article comprises non-conformal coatings on said first and second surfaces so that the first surface comprises a hydrophilic material layer, and the second surface comprises a hydrophobized layer. Thereby an advantageous construction material may be achieved.

The method and the porous article are characterised by what is stated in the characterising parts of the independent claims. Some other embodiments are characterised by what is stated in the other claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit sub-tasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments.

In a preferred structure the method comprises of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces and at least some of the pores, and arranging hydrophilic material or precursors thereof only on the first surface of the article.

In one embodiment the hydrophobizing is executed by using hydrophobizing dispersion comprising silicone, silicone precursors and/or silicone monomers.

In one embodiment the hydrophobizing is executed by using dispersion comprising hydrophobized silica (S1O2), preferably as nanoparticles.

In one embodiment the hydrophobizing is executed by using dispersion comprising organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids.

In one embodiment the hydrophilic material comprises photoactive material, such as ΤΊΟ2, Ag-, S-, N- or P-doped ΤΊΟ2, MgTa2O6, ZnS, ZnO, SnO2 or precursors thereof.

In one embodiment the hydrophilic material or precursors thereof is arranged on the first surface of the article in a process step prior to the hydrophobizing of the article.

In one embodiment the hydrophilic material or precursors thereof is arranged on the first surface of the article in a process step after the hydrophobizing of the article.

In one embodiment the hydrophilic material or precursors thereof is arranged on the first surface after installation of the article.

In one embodiment the article consists of a three dimensional body, wherein the first surface forms the frontal face of the article, the second surface comprises a back surface and an edge surface, the back surface being situated opposite to the front face and the edge surface being situated between the front face and the back surface.

In one embodiment the method comprises processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces by dispersion comprising S1O2, and arranging hydrophilic material comprising ΤΊΟ2 or precursors thereof only on the first surface of the article.

In one embodiment the method comprises processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first surface by dispersion comprising silicone, silicone precursors and/or silicone monomers, hydrophobizing the second surface by dispersion comprising S1O2, and arranging hydrophilic material comprising ΤΊΟ2 or precursors thereof only on the first surface of the article.

In one embodiment the method comprises processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces by dispersion comprising silicone, silicone precursors and/or silicone monomers, and arranging hydrophilic material comprising ΤΊΟ2 or precursors thereof only on the first surface of the article.

In one embodiment the method comprises processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces by dispersion comprising organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids, and arranging hydrophilic material comprising ΤΊΟ2 or precursors thereof only on the first surface of the article.

In another preferred structure, a porous article comprises a first surface and a second surface, wherein the article comprises non-conformal coatings on said first and second surfaces so that the first surface comprises a hydrophilic material layer, and the second surface comprises a hydrophobized layer.

In one embodiment the article is a brickstone, a tile, or a cladding element of a building.

In one embodiment the article has a shape of a slab, the frontal face of which being said first surface, and the second surface comprising a back surface and an edge surface, the back surface being situated opposite to the front face and the edge surface being situated between the front face and the back surface.

In one embodiment all surfaces of the article comprise the hydrophobized layer, and the hydrophilic material arranged on the hydrophobized layer.

In one embodiment the hydrophobized layer comprises hydrophobizing material in pores of the article. In one embodiment the thickness of the hydrophobized layer is about 0.5%, 1 %, 5%, 10%, or 25% of the total thickness of the article.

In one embodiment the thickness of the hydrophilic material layer is in range of 80 to 150 nm . BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which

Figure 1 is a schematic side view of a part of a porous article, Figure 2 is a schematic side view of a part of another porous article, Figure 3 is a schematic side view of a part of a third porous article,

Figure 4 is a schematic side view of a part of a fourth porous article, Figures 5a - 5c are schematic views of further porous articles, Figure 6 is a schematic view of a first method of processing porous article,

Figure 7 is a schematic view of a second method of processing porous article,

Figure 8 is a schematic view of a third method of processing porous article, and

Figure 9 is a schematic view of a fifth porous article.

For the sake of clarity, the figures show the embodiments in a simplified manner. Like reference numbers identify like elements.

DETAILED DESCRIPTION

Figure 1 is a schematic side view of a part of a porous article. The porous article 1 comprises a first surface 3 and a second surface 4, 4'.

The article has a three dimensional body having shape of a slab manufactured from a material 2. The first surface 3 may form the frontal face 5 of the article 1 , whereas the second surface 4, 4' comprises a back surface 4 and an edge surface 4'. The back surface 4 may be situated opposite to the frontal face 5. The edge surface 4' is situated between the frontal face 5 and the back surface 6.

The frontal face 5 will be arranged to form a part of fagade or frontal side of a building, outer surface of a roof covering, upper surface of a flooring tile etc. The material 2 may be, for instance, natural stone, concrete, and/or burnt clay. The natural stone may be, for instance, marble, sand stone, granite, gneiss, limestone, sandstone, thermal stone, etc.. The article 1 may be a brickstone, a tile, or a cladding element of a building. The thickness of the article may be, for instance, in range of 10 to 120 mm.

The article 1 comprises non-conformal layers on its surfaces so that the first surface 3 comprises a hydrophilic material layer and the second surface 4, 4' comprises a hydrophobic layer. The term "non-conformal layers" means here that the article 1 comprises differently processed surfaces. The term "layer" means here either added material penetrated into pores of the material 2 or material layer on the surface of the material 1 , or combination thereof. It is to be noted here that material layers on the surface of the material are shown separated from the material 1 and adjacent layer(s) for clarity reasons.

All the surfaces, i.e. the first surface 3 and the second surface 4, 4' of the article 1 may comprise a hydrophobized layer 9. This layer 9 may comprise e.g. silicone.

The first surface 3 which consists of the frontal face 5 of the article 1 comprises further a hydrophilic material layer 8. This comprises hydrophilic material, e.g. titanium dioxide (T1O2) or precursors thereof. The second surface 4, 4' does not comprise said hydrophilic material layer 8.

Instead of T1O2 or mixed therewith some other oxides, such as N or

P-doped T1O2, MgTa2O6, or SnO2, may be used as hydrophilic material . Said oxides are photoactive or photocatalytic material. They have an ability to be exited by light radiations to create very reactive radical species at their surface upon recombination of excitons with atmospheric water and oxygen. In the case where an organic contamination deposits and lays at the vicinity of the photoactive material, a progressive decomposition of the contaminant into inertial CO2 and H₂O will take place.

The term "precursor" covers here any starting compound in solid, liquid or gas form that can be converted to the desired oxide, carbonate, or phosphate directly or by post-treatments. The term "precursor" covers also materials that originally are not in the form of oxides, carbonates or phosphates, but which can be converted to such compounds by thermal or chemical treatments. Also preformed particles of the desired oxide, carbonate, or phosphate are count as precursors.

According to another embodiment the hydrophobized layer 9 comprises organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids.

Examples of organic phosphates and phosphonates include, but are not limited to, fluorocarbons, hydrocarbons, mixtures of fluorocarbons and hydrocarbons, phospholipids, polymers containing phosphate or phosphonate groups, polymerizable smaller molecules including a phosphate and/or phosphonate group in at least one of the starting materials, chemical post- modifications of organic molecules introduced into or onto the article 1 where at least one of the molecules contains at least one phosphorous in its structure to form phosphate and/or phosphonate groups.

However, depending on the chemical nature of the material 2, other hydrophobization agents may be used as well.

The hydrophilic material layer 8 arranged only on the first surface 3 of the article 1 may then comprise T1O2 or precursors thereof.

The hydrophilic material layer 8 may be arranged on top of the hydrophobized layer 9, or alternatively, at least part of the hydrophilic material layer 8 may be mixed with the hydrophobized layer 9.

The thickness of the hydrophobized layer 9 may be, for instance, about 0.5%, 1 %, 5%, 10%, or 25% of the total thickness of the article 1 .

Nanoscale and/or microscale particles may be used in the hydrophilic material layer 8. The thickness of the hydrophilic material layer 8 may be in range of 80 to 150 nm, for example.

The layer 8, 9 may cover continuously and complete the whole surface it has been arranged to, or it may comprise holes, gaps or openings here and there so that the underlying surface penetrates through said layer 8, 9.

The second surface 4, 4' of the article 1 may have higher degree of roughness than the first surface 3. The roughness of the second surface 4, 4' may be a result of diamond cutting or frame saw. This kind of surface may be advantageous when pursuing a highly hydrophobic surface in the porous article 1 . The first surface may be e.g. grinded or polished.

Figure 2 is a schematic side view of a part of another porous article. This article 1 comprises not only the layers shown in Figure 1 but further a hydrophobic material layer 10. The hydrophobic material layer 10 has been arranged on the second surface 4, 4' only and it may comprise nanoscale and/or microscale particles comprising e.g. S1O2.

A hydrophilic material layer has been arranged only on the first surface 3 of the article 1 .

The thickness of the hydrophobic material layer 10 may be in range in range of 80 to 150 nm .

Figure 3 is a schematic side view of a part of a third porous article. The article 1 comprises a hydrophobized layer 9, a hydrophilic material layer 8, and hydrophobic material layer 10, 10' according to the description above.

The article 1 comprises, in addition, a hydrophobic material layer 10" on the first surface 3. The hydrophobic material layer 10, 10', 10" may thus be extended to all surfaces of the article 1 . The hydrophobic material layer 10, 10', 10" may comprise e.g. S1O2.

The hydrophobic material layer 10, 10', 10" may have equal thickness and physical structure on all the surfaces it has been arranged to. The physical structure means here e.g. porosity or presence of holes, gaps or openings in the layer. Alternatively, he hydrophobic material layer 10, 10', 10" may have first thickness and/or structure on the back surface 6 and second, different thickness and/or structure on the edge surface 7.

Figure 4 is a schematic side view of a part of a fourth porous article. This article 1 comprises a hydrophobized layer 9 that extends on the first surface 3 and on a part of the second surface, i.e. on surface not comprising hydrophilic material layer 8. The hydrophobized layer 9 may comprise e.g. silicone.

Rest of the second surface 4, 4' comprises a hydrophobic material layer 10, 10' that may comprise e.g. S1O2. The hydrophobic material layer 10, 10' may overlap with the hydrophobized layer 9.

A hydrophilic material layer 8 comprising e.g. T1O2 has been arranged on the first surface 3 of the article 1 only.

Figures 5a - 5c are schematic views of further porous articles. The shape and profile of the article 1 may vary. The article 1 may have profiled edge surface 7 as shown in Figure 5a. This may facilitate e.g. fixing the articles to each other.

The article 1 may have projections and/or recesses that modify its architectural image as shown in Figure 5b. The article 1 may be a corner brick or stone as shown in Figure 5c.

It is to be noted here that according to an embodiment the first surface 3 consists of frontal face 5 of the article 1 only. According to another embodiment the first surface 3 comprises frontal face 5 and at least part of the edge surface 7.

Figure 6 is a schematic view of a first method of processing porous article. The method may comprise four main steps A to D.

In step A the article 1 may be pretreated for removing pre-adsorbed water and, if desired, crystal water from the material 2 before further surface treatment. Thereby the chemical attachment of the coatings and/or impregnation materials to the material 2 can potentially be increased.

The pre-treatment may be based on a heat treatment, vacuum treatment, chemical treatment, physical treatment or combination thereof.

At least some surfaces of the article may also be activated in the pre-treatment. Down to the activation the surfaces are more attractive to the hydrophobic material or precursors thereof and/or the hydrophobizing dispersion.

The pre-treatment may comprise e.g. treatment by hydrogen peroxide, gas flame, laser, infra-red radiation, ultraviolet radiation, plasma etc.

It is to be noted that the step A is optional, not essential step of the method.

In step B the first and the second surfaces and at least some of the pores of the article 1 are hydrophobized arranging hydrophobic material or precursors thereof.

The hydrophobizing step may be executed by using suitable hydrophobizing dispersion. This dispersion may comprise e.g. silicone, silicone precursors and/or silicone monomers, hydrophobized silica (S1O2), preferably as nanoparticles, or organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids, or combination thereof. Silica may be hydrophobized by e.g. arranging a hydrophobic layer on the surface of silica particle.

The hydrophobizing dispersion may comprise continuous medium that is solvent, such as water, ethanol, propanol, methanol, acetone, butanol, water, 1 -methoxy-2-propanol, ethylene glycol, THF (tetrahydrofuran), DMSO (dimethyl sulfoxide), cyclohexane etc. or mixtures thereof. The hydrophobizing step may be implemented by several ways. According to an embodiment the hydrophobizing dispersion is let to adsorb into the material 2 establishing surfaces of the article 1 .

According to another embodiment the hydrophobizing dispersion is sprayed onto the article 1 which may have been heated to elevated temperature. The continuous medium will, at least partially, evaporate. The surface of the article 1 will cool down as the continuous medium evaporates.

According to still another embodiment the hydrophobizing dispersion is applied to the article 1 by capillary condensation from a gas phase. The gas phase may be overpressurized.

According to still another embodiment the hydrophobizing dispersion is brushed on the article 1 .

According to still another embodiment the hydrophobizing dispersion is printed using e.g. an inkjet printer or piezoelectric printer.

It is also possible to combine two or more above-mentioned methods in the hydrophobizing step.

In step C hydrophilic material or precursors thereof are arranged on the first surface 3 of the article. The hydrophilic material may be e.g . photoactive material that comprises T1O2, Ag-, S-, N- or P-doped T1O2, MgTa2O6, ZnS, ZnO, SnO2 or precursors thereof.

The particles of the hydrophilic material may comprise nanosize or microsize particles or mixture thereof.

The hydrophilic material or precursors thereof may be deposited onto the article 1 by e.g. wet-methods, like spraying, dip-coating, or by other wet-chemical methods, or by a sol-gel process or deposited in pre-formed particulate form.

In step D the article 1 is post processed. For example, a thermal treatment may be applied in order to increase the stability of the layer structure arranged in the article 1 .

Post processing equipment may execute e.g. plasma treatment, thermal treatment, UV-treatment, IR-treatment, VIS-treatment, ozone treatment, laser treatment, or any combination of these. The post processing may be applied to transform the precursors, if any, of the layer materials into the desired form and to further reinforce cohesion of the impregnated and/or deposited materials by increasing the density of strong chemical bonds to the material 2 and/or within the impregnated and deposited substances etc. It is to be noted that the step D is optional, not essential step of the method.

Figure 7 is a schematic view of a second method of processing porous article. This method differs from the method shown in Figure 6 in that the hydrophilic material or precursors thereof is arranged on the first surface 3 of the article prior to the hydrophobizing of the article 1 .

The hydrophilic material or precursors thereof may be e.g. T1O2. The hydrophobizing dispersion is applied on the T1O2 layer. The hydrophobizing dispersion penetrates through the T1O2 layer and absorbs in the material 2. A portion of the hydrophobizing dispersion may remain in and/or on the T1O2 layer.

The hydrophilic material or precursors thereof may be applied in a process line prior to the attachment of the article 1 in its place in building, pavement etc. The hydrophobizing dispersion may also be applied to the article in the process line prior to said attachment or, alternatively, to the article that has already attached in its place.

There may be a period of time, e.g. 24 hours, between step C and step B. During said period of time the hydrophobic material or precursors thereof may make bonds to the material 2 of the article. During the period of time the article 1 may be kept in relatively low temperature between 5 to 30° C, or in elevated temperature between 30 to 200° C, e.g. in 90° C.

Figure 8 is a schematic view of a third method of processing porous article. This method differs from the methods shown in Figures 6 and 7 in that the hydrophilic material or precursors thereof is arranged in two steps B1 and B2 on the article 2.

First hydrophilizing step B1 may include absorbing hydrophobizing dispersion that forms the hydrophobized layer 9 shown in Figures 1 - 4 in the material 2 of the article.

Then second hydrophilizing step B2 may include arranging hydrophobic material layer 10 shown in Figures 2 - 4 on the article.

Steps B, B1 and C are preferably carried out as a factory production prior to delivering the article in the installation site. Step B2 may be carried out after installation of the article but, of course, also as a factory production.

It is to be noted here that steps B, B1 , B2 and C may comprise one or more sub-steps, such as thermal treatment steps etc. According to an embodiment the hydrophilic material or precursors thereof is arranged on the first surface 3 after installation said article in building, pavement etc.

Figure 9 is a schematic view of a fifth porous article. The porous article 1 consists of a three dimensional body. A first surface 3 of the article forms the frontal face 5 of the article 1 . A second surface 4 forms the back surface 6 of the article 1 . The back surface 6 is situated opposite to the frontal face 5. The article 1 further comprises an edge surface 7 between the frontal face 5 and the back surface 6. The edge surface 7 comprises a contact layer 12 that promotes adhesion of a sealant member 1 1 to the article 1 .

The sealant member 1 1 may be selected from any known sealants that are used for sealing gaps or joints of two or more building or construction elements. The material of the sealant member 1 1 may comprise silicone, polyurethane, acrylics etc.

It is shown in Figure 9 an embodiment where the sealant member

1 1 is arranged between two articles 1 made of identical materials and layers. According to another embodiment, the sealant member 1 1 is arranged between construction elements which are not identical, e.g. they may be manufactured form different materials. One of said construction elements may be manufactured of metal and another of glass, for instance.

According to an embodiment, the contact layer 12 may comprise epoxy resin.

According to a further embodiment, the contact layer comprises a silicon surfactant, such as Byk 375 by BYK Additives & Instruments.

According to a still further embodiment the contact layer comprises isocyanate. This is especially favourable embodiment when the sealant member 1 1 comprises polyurethane.

Materials and compounds of the contact layer 12 may be applied to the edge surface 7 by spraying, dipping, brushing or any other known method.

The contact layer 12 may be applied to the edge surface 7 prior to the steps of hydrophobizing the first and the second surfaces 3, 4, and arranging hydrophilic material or precursors thereof on the first surface 3. Alternatively, the contact layer 12 may be applied to the edge surface 7 after the step of hydrophobizing the first and the second surfaces 3, 4, but prior to the step where hydrophilic material or precursors thereof are arranged on the first surface 3. According to a third alternative method, the contact layer 12 is applied to the edge surface 7 in a method step following the steps of hydrophobizing the first and the second surfaces 3, 4, and arranging hydrophilic material or precursors thereof on the first surface 3.

The contact layer 12 may be included in all porous articles 1 described in this description, especially in those porous articles 1 shown in Figures 1 to 5c.

To summarize, the article 1 is, for example, a stone product which does not take up water due to the hydrophobized layer 9 and/or hydrophobized material layer 10, 10', 10". Said hydrophobized layer(s) 9, 10, 10', 10" arranged on the first surface 3 of the article 1 is/are protected against ultraviolet radiation by hydrophilic material layer 8. The hydrophilic material layer 8 may also introduce a self-cleaning function to the article 1 .

The drawings and the related description is for the purpose of illustrating the idea of the invention only. The invention may vary in detail within the scope of the claims.

Reference symbols

1 article

2 material

3 first surface

4, 4' second surface

5 frontal face

6 back surface

7 edge surface

8 hydrophilic material layer

9 hydrophobized layer

10, 10', 10" hydrophobic material layer

1 1 sealant member

12 contact layer

A pretreatment step

B, B1 , B2 hydrophobizing step

C hydrophilizing step

D post processing step

Claims

1 . A method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises:

hydrophobizing the first and the second surfaces and at least some of the pores, and

arranging hydrophilic material or precursors thereof only on the first surface of the article.

2. A method as claimed in claim 1 , wherein the material of the article is natural stone, concrete, and/or burnt clay.

3. A method as claimed in claim 1 or 2, wherein the hydrophobizing is executed by using hydrophobizing dispersion comprising silicone, silicone precursors and/or silicone monomers.

4. A method as claimed in any of the preceding claims, wherein the hydrophobizing is executed by using dispersion comprising hydrophobized silica (S1O2), preferably as nanoparticles.

5. A method as claimed in any of the preceding claims, wherein the hydrophobizing is executed by using dispersion comprising organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids.

6. A method as claimed in any one of the preceding claims, wherein the hydrophilic material comprises photoactive material, such as ΤΊΟ2, Ag-, S-, N- or P-doped ΤΊΟ2, MgTa2O6, ZnS, ZnO, SnO2 or precursors thereof.

7. A method as claimed in any one of the preceding claims, wherein the hydrophilic material or precursors thereof is arranged on the first surface of the article in a process step prior to the hydrophobizing of the article.

8. A method as claimed in any one of claims 1 to 6, wherein the hydrophilic material or precursors thereof is arranged on the first surface of the article in a process step after the hydrophobizing of the article.

9. A method as claimed in any one of the preceding claims, wherein the hydrophilic material or precursors thereof is arranged on the first surface after installation of the article.

10. A method as claimed in any one of the preceding claims, wherein the article consists of a three dimensional body, wherein

the first surface forms the frontal face of the article,

the second surface comprises

a back surface and an edge surface,

the back surface being situated opposite to the front face and the edge surface being situated between the front face and the back surface.

1 1 . A method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises:

hydrophobizing the first and the second surfaces by dispersion comprising S1O2, and

arranging hydrophilic material comprising ΤΊΟ2 or precursors thereof only on the first surface of the article.

12. A method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises:

hydrophobizing the first surface by dispersion comprising silicone, hydrophobizing the second surface by dispersion comprising S1O2, and

13. A method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises: hydrophobizing the first and the second surfaces by dispersion comprising silicone, and

14. A method of processing a porous article, said article comprising a first surface and a second surface, wherein the method comprises:

hydrophobizing the first and the second surfaces by dispersion comprising organic material having one or more functional group(s) selected from phosphate, phosphonate, phosphinic acid, betadiketonate, thiol, silane, siloxane, and carboxylic acid or any salts of the corresponding acids, and

15. A method as claimed in any one of claims 1 to 9, wherein the article consists of a three dimensional body, wherein

the first surface forms the frontal face of the article,

the second surface forms the back surface of the article, the back surface being situated opposite to the front face, wherein the article further comprise an edge surface,

the edge surface being situated between the frontal face and the back surface.

16. A method as claimed in claim 15, comprising

arranging a contact layer on the edge surface for promoting adhesion of a sealant member to the article.

17. A method as claimed in claim 16, wherein the contact layer comprises epoxy resin.

18. A method as claimed in claim 16, wherein the contact layer comprises a silicon surfactant.

19. A method as claimed in claim 16, wherein the contact layer comprises isocyanate.

20. A porous article comprising a first surface and a second surface, wherein the article comprises non-conformal coatings on said first and second surfaces so that

the first surface comprises a hydrophilic material layer, and the second surface comprises a hydrophobized layer.

21 . A porous article as claimed in claim 20, wherein the material of the article is natural stone, concrete, and/or burnt clay.

22. A porous article as claimed in claim 21 , wherein the article is a brickstone, a tile, or a cladding element of a building.

23. A porous article as claimed in any one of claims 20 to 22, wherein the article has a shape of a slab, the frontal face of which being said first surface, and

the second surface comprising a back surface and an edge surface, the back surface being situated opposite to the front face and the edge surface being situated between the front face and the back surface.

24. An article as claimed in any one of claims 20 to 22, wherein the article consists of a three dimensional body, wherein

the first surface forms the frontal face of the article,

the edge surface being situated between the frontal face and the back surface.

25. An article as claimed in claim 24, comprising a contact layer on the edge surface for promoting adhesion of a sealant member to the article.

26. An article as claimed in claim 25, wherein the contact layer comprises epoxy resin.

27. An article as claimed in claim 25, wherein the contact layer comprises a silicon surfactant.

28. An article as claimed in claim 25, wherein the contact layer comprises isocyanate.

29. A porous article as claimed in any one of claims 20 to 28, wherein all of its surfaces comprise the hydrophobized layer, and the hydrophilic material arranged on the hydrophobized layer.

30. A porous article as claimed in any one of claims 20 to 29, wherein the hydrophobized layer comprises hydrophobizing material in pores of the article.

31 . A porous article as claimed in any one of claims 20 to 30, wherein the thickness of the hydrophobized layer is about 0.5%, 1 %, 5%, 10%, or 25% of the total thickness of the article.

32. A porous article as claimed in any one of claims 20 to 30, wherein the thickness of the hydrophilic material layer is in range of 80 to 150 nm.