WO2013079263A1

WO2013079263A1 - Glass sheet with non-slip properties

Info

Publication number: WO2013079263A1
Application number: PCT/EP2012/070956
Authority: WO
Inventors: Pierre Boulanger; Christine Deneil; Fabian Mariage
Original assignee: Agc Glass Europe
Priority date: 2011-11-29
Filing date: 2012-10-23
Publication date: 2013-06-06
Also published as: BE1020330A3

Abstract

The invention relates to a glass sheet, which has non-slip properties that are stable over time, is hardly sensitive to wear and for which the optical properties of the glass sheet it is composed o fare practically retained,and which does not require the use of noxious and/or corrosive products, in particular hydrofluoric acid. In particular, the invention relates to a glass sheet with non-slip properties comprising particles, which are partially incorporated into the bulk of the glass and which comprise at least one inorganic compound, wherein the size of the particles is not smaller than 5 micrometers and is not larger than 200 micrometers, and the density of said particles per unit area ranges between 100 and 10000 particles per mm².

Description

GLASS SHEET WITH NON-SLIP PROPERTIES

1. Field of the Invention

The present invention relates to a glass sheet with non-slip properties.

Because of its non-slip properties, the glass sheet according to the invention has a particular advantage for use as floor covering or covering for steps in external or internal applications. It can also be used for articles of furniture, on which objects must not slide: e.g. for tables, shelving or shop displays.

2. Solutions of the Prior Art

It is known to use glass in the construction of floors and steps, but this use has generally been curbed because of the smooth nature of glass, which causes it to be slippery, particularly when damp.

To remedy this problem, it has been proposed, for example, to glue zones of rough material to the surface of the glass, in particular strips arranged transversely to the direction people walk over them. However, these glued zones are not resistant to wear over a long period. They become unstuck and thus pose additional risk.

Another solution known from application WO 2008/046877 Al consists of using glass sheets that are acid-textured over their entire surface for applications for floors or steps. Such acid-textured glass sheets are more resistant over time and are hardly sensitive to wear. Unfortunately, the production of these acid-textured glass sheets requires the use of hydrofluoric acid HF, which is known to be a noxious and corrosive substance and must therefore be handled with caution. Moreover, the acid-texturing has a substantial impact on the optical properties of the initial glass sheet. In particular, such an acid-textured glass sheet is translucent: it diffuses light. It has also been proposed in application EP 805126 Al to increase the roughness of certain zones of the glass by depositing a glass frit. Adherence of the glass frit to the glass is achieved by a thermal treatment (sintering). Such a treatment is complicated and costly. Moreover, the sintering of frit particles rounds their angles to such an extent that the resulting roughness on the surface of the glass is not very severe. Finally, the roughness is provided by means of a layer of material foreign to the glass itself and covering it. This results in an impairment to the final aesthetics of the glass product and a reduction in its wear-resistance.

3. Objectives of the Invention The objective of the invention, in particular, is to overcome these disadvantages of the prior art. In particular, an objective of the invention is to provide a glass sheet, which has highly satisfactory non-slip properties that are stable over time, is hardly sensitive to wear and for which the optical properties of the glass sheet it is composed of are practically retained. Another objective of the invention in at least one of its embodiments is to provide a glass sheet with highly satisfactory non-slip properties that does not require the use of noxious and/or corrosive products, in particular hydrofluoric acid.

Finally, a further objective of the invention in one of its embodiments is to provide a glass sheet with highly satisfactory non-slip properties that can be produced quickly and economically, in particular by means of a process in a single step allowing easy control of the non-slip properties.

4. Disclosure of the Invention

In accordance with a particular embodiment, the invention relates to a glass sheet with non-slip properties comprising particles that are partially incorporated into the bulk of the glass and that comprise at least one inorganic compound. According to the invention, the size of the particles is not smaller than 5 micrometers and is not larger than 200 micrometers. Moreover, still according to the invention, the density of the particles per unit area is in the range of between 100 and 10000 particles per mm². Thus, the invention rests on a completely novel and inventive approach since it enables the aforementioned disadvantages of the prior art to be overcome and the set technical problem to be solved. The inventors have in fact proved that because of the particles of a specific size, which are partially incorporated into the bulk of the glass, comprise at least one inorganic compound and are present in a specific density, it has been possible to obtain a glass sheet, which has highly satisfactory non-slip properties that are stable over time and which is hardly sensitive to wear, and wherein the optical properties of the glass sheet it is composed of are practically retained.

Other characteristics and advantages of the invention will become clearer upon reading the following description that explains in particular preferred embodiments of the invention by way of illustrative and non-restrictive examples.

The sheet according to the invention is formed from glass that can belong to various categories. Thus, the glass can be a soda-lime-silica type of glass, a boron glass, a lead glass, a glass containing one or more additives distributed homogeneously in its bulk such as, for example, at least one inorganic colouring agent, an oxidising compound, a viscosity-regulating agent and/or a fusion- promoting agent. The glass of the invention is preferably a soda-lime-silica glass. The glass of the invention can be a float glass, a drawn glass or a "cast" type glass (laminated between rollers). It can be clear, extra-clear or solidly coloured. The expression "soda-lime-silica glass" is used in its broad sense here and relates to any glass that contains the following base components (expressed in percentages of the total weight of glass): SiO₂ 60 to 75%

Na₂O 10 to 20%

CaO 0 to 16%

K₂O 0 to 10%

MgO 0 to 10%

Al₂O₃ 0 to 5%

BaO 0 to 2%

BaO + CaO + MgO 10 to 20%

K₂O + Na₂O 10 to 20% It also relates to any glass containing the above base components that can additionally contain one or more additives.

According to an embodiment of the invention, the glass sheet is a sheet of float glass. The glass sheet is preferably a sheet of soda-lime-silica type float glass.

The glass sheet can have a thickness ranging from 1.8 to 16.2 mm. In order to obtain an adequate mechanical strength in the case of use for a floor or steps, the glass sheet is preferably thick (e.g. has a thickness greater than 6 mm).

In general, it is also preferred that the glass sheet has not been covered by any layer before the treatment of the present invention, at least on the face intended to be rendered non-slip. According to the invention the glass sheet comprises particles that are partially incorporated into the bulk of the glass. Particle partially incorporated into the bulk of the glass is understood to mean a particle, which is located both in the bulk of the glass and outside the bulk of the glass, i.e. each particle has a portion of its volume in the glass and the other potion of its volume in the external medium. In other words, the particle is not completely enclosed by the glass. According to the invention the particles comprises at least one inorganic compound. Inorganic compounds include, for example, minerals (such as oxides, hydroxides), metal salts (such as silicates), coordination compounds, molecular compounds of non- metallic elements such as silicon, phosphorus ...

The inorganic compound according to the invention preferably has a Mohs' hardness higher than or at least equal to that of the glass used for the sheet of the invention. For example, in the case of a soda-lime-silica glass (hardness—5.5 on the Mohs' scale), suitable compounds (sometimes depending on their crystalline form) are:

• single oxides of aluminium, silicon, iron(III) , titanium and zirconium;

• the mixed oxides Be(AlO₂)₂, MgAl₂O₄ and Y₂Al₃O₁₄;

• silicate-type oxides such as ZrSiO₄ and LiAlSi₂O₆; and

• carbides of boron, silicon and tungsten.

According to a preferred embodiment, the inorganic compound is selected from single oxides, mixed oxides, nitrides, oxynitrides, carbides and combinations of at least two of the abovementioned compounds.

Good results with respect to non-slip properties have been obtained with single oxides of aluminium, silicon, iron(III), titanium and zirconium.

According to an embodiment of the invention the particles are at least partially crystallised, i.e. each of the particles comprises at least a proportion of 5% of their weight formed by crystals. The particles can comprise multiple crystalline forms of the same inorganic compound. In a variant, the particles can only comprise one crystalline form of the same inorganic compound. Each of the particles preferably comprises at least a proportion of 50% of its weight formed by crystals. It is particularly preferred if the particles are completely crystallised. According to another embodiment of the invention, the shape of the particles is quasi-spherical. Quasi-spherical denotes a three-dimensional shape, the volume of which comes close to that of a sphere that would have a diameter equal to the largest dimension of an object having this quasi-spherical shape. The particles preferably have a volume equal to at least 60% of that of the sphere with a diameter equal to the largest dimension of the particles. It is more preferred if the particles have a volume equal to at least 70% of that of the sphere with a diameter equal to the largest dimension of the particles.

According to the invention the size of the particles is not smaller than 5 micrometers and preferably not smaller than 10 micrometers. Moreover, the size of the particles is not larger than 200 micrometers and preferably not larger than 100 micrometers. It is absolutely preferred if the size of the particles is not smaller than 10 micrometers and not larger than 100 micrometers.

According to the invention the glass sheet has a density of the particles per unit area in the range of between 100 and 10000 particles per mm². The density of said particles per unit area is preferably in the range of between 500 and 5000 particles per mm². Such density values allow improved non-sip properties to be obtained. The density of the particles per unit area can be measured by using images obtained by optical profilometry.

In addition to particles partially incorporated into the bulk of the glass, the glass sheet according to the invention can comprise particles that are completely incorporated into the bulk of the glass and that are found at a short distance below the surface of the glass. These particles that are completely incorporated into the bulk of the glass do not have any role in the non-slip properties of the glass sheet according to the invention. In addition to particles partially incorporated into the bulk of the glass and possibly particles that are completely incorporated into the bulk of the glass, the glass sheet according to the invention can also comprise particles that adhere to the surface of the glass, but are not enclosed in its bulk. The glass sheet according to the invention has lasting non-slip properties that persist (or are even better) on contact with wet floor surfaces. In particular, the glass sheet according to the invention has highly satisfactory non-slip properties evaluated by measurement of the coefficient of dynamic friction (μ_¼) in dry conditions (dry path) or in wet conditions (wet path) obtained in accordance with the standard ISO 8295 : 1995. The higher the value of the coefficient of dynamic friction is, the better the resistance of the glass sheet to slipping. Advantageously, the glass sheet with non-slip properties according to the invention has a coefficient of dynamic friction (μ_¼) higher than or equal to 0.4. The glass sheet with non-slip properties according to the invention preferably has a coefficient of dynamic friction (μ_¼) higher than or equal to 0.5.

Advantageously, when tested in accordance with standard DIN 51130:2004-6 ("ramp test"), the glass sheet with non-slip properties according to the invention has an R value ranging from R9 to Rll.

The glass sheet with non-slip properties according to the invention has optical properties that have been practically retained in relation to the glass sheet it is composed of (i.e. before treatment). The optical properties according to the invention relate principally to haze, clarity and gloss.

Standard ASTM O 1003-61 defines haze as the percentage of transmitted light which when passing through the analysed specimen deviates from the incident beam at an angle of more than 2.5° (also referred to as large-angle diffusion). Clarity (or low-angle diffusion) defines the percentage of transmitted light which when passing through the analysed specimen deviates from the incident beam at an angle of less than 2.5°. Gloss can be defined as the specular reflection of the glass at 60° and is determined in accordance with standard ASTM C 584.

The glass sheet with non-slip properties according to the invention can be thermally or chemically toughened or simply annealed or also semi-toughened. To meet safety standards, the glass sheet with non-slip properties according to the invention is preferably laminated, i.e. it is laminated to another glass sheet by means of a thermoplastic film and the face bearing the particles forms an outside face of the laminated assembly, wherein the particles are then positioned on the passable side during assembly.

The glass sheet with non-slip properties according to the invention can be produced in various dimensions. As an example, a square glass sheet of 50 x 50 cm, 80 x 80 cm or 1 m x 1 m, 8 mm thick laminated to another sheet of clear glass 8 mm thick by means of an interlayer polyvinyl butyral film can be used for a floor tile. Also as an example, steps of a staircase can be 30 cm wide and 90 cm long, for example, and can be made from two glass sheets 10 mm thick assembly by means of polyvinyl butyral.

For the cited applications a single face of the glass sheet preferably has partially enclosed particles. The glass sheet according to the invention can be obtained by any process capable of generating and partially enclosing particles in the bulk of the glass of said sheet.

For example, the glass sheet according to the invention can be obtained by a process which comprises (a) the production of particles, (b) the deposition of the particles onto the surface of said sheet, and (c) the supply of energy to the particles and/or to said surface such that the particles are diffused/ partially incorporated into the glass.

The formation and deposition of particles on the surface of the glass sheet can be conducted simultaneously in one step by known methods such as · chemical vapour deposition (CVD): a modified chemical vapour deposition process (MCVD) can be used in the present invention. This modified method differs from the classic method in that the precursor reacts in the gaseous phase rather than on the surface of the glass.

• wet deposition such as sol-gel deposition, for example, or

• flame spraying starting with a liquid, gaseous or solid precursor. In flame spraying, which is cited as an example and is disclosed in particular in patent application FI954370, the particles are generated by atomising a solution of at least one chemical precursor in an aerosol transported into a flame where combustion occurs to form solid particles. These particles can then be deposited directly onto the surface located close to the edge of the flame.

In a variant, the formation and deposition of particles on the surface of the glass sheets can be performed consecutively in two steps. In this case, the particles are generated firstly in solid form or in the form of a suspension in a liquid using the vapour method, the wet method (sol-gel, precipitation, hydrothermal synthesis ...) or using the dry method (mechanical grinding, mechanical-chemical synthesis ...). An example of a method that enables particles to firstly be generated in solid form is the method known as combustion chemical vapour condensation (or CCVC). This method consists of converting a precursor solution in vapour phase in a flame that undergoes a combustion reaction to form particles that are then collected. Alternatively the suitable particles can simply be purchased.

In the two precited cases the particles previously obtained can be transferred to the surface of the glass sheet using different known methods and the energy necessary for the diffusion/partial incorporation of the particles into the bulk of the glass can be supplied, for example, by heating the glass sheet to an appropriate temperature. According to the invention, the energy necessary for the diffusion/partial incorporation of the particles into the bulk of the glass can be supplied at the time of deposition of the particles or after deposition. The following examples illustrate the invention without intending to restrict its coverage in any way.

Example 1 (comparative)

A sheet of clear glass 4 mm thick, 30 cm wide and 90 cm long was washed with an aqueous detergent and carefully rinsed with water, then dried.

The glass sheet was then treated by acid etching in a known manner, but for a longer time period than the conventional time (according to the example of application WO 2008/046877): an acid solution composed of 170 ml of 40% HF, 100 g of Na₂CO₃, 170 ml of glacial acetic acid and 660 ml of water at 25°C was poured over the entire surface of the glass sheet and left in situ for 25 minutes (instead of 8 minutes conventionally). The solution was then eliminated by rinsing with water, then the glass sheet was cleaned with an aqueous detergent solution.

Example 2 (according to the invention)

A sheet of clear glass identical to that used for the treatment in Example 1 was cleaned with an aqueous detergent and carefully rinsed with water, then dried.

Hydrogen and oxygen were then fed into a linear burner in order to generate a flame at the outlet of said burner. The burner used had a width of 20 cm. The washed glass sheet was heated firstly in a furnace to a temperature of 600°C and at this temperature was then passed under the burner located at a distance of 100 mm above the glass sheet at a speed of about 7 m/min. The solution fed into the flame by means of the nozzles contained non-ahydrate aluminium nitrate, Al(NO₃)₃.9H₂O, dissolved in methanol (aluminium/methanol dilution ratio by weight = 1/120, solution flux = 203 ml/min). Particles of aluminium oxide were thus generated in the flame and directed towards the surface of the glass sheet. The glass sheet was then cooled in ambient air. The surface of the glass sheet treated as described above was analysed by optical microscopy, scanning electron microscopy and by means of an optical profilometer (Cotec - Altisurf 500 profilometer equipped with a 300 μπ optical sensor; scanning speed = 500 μΓη/sec; surface area analysed = 9 mm²).

The analyses performed demonstrated that the aluminium was incorporated in the form of aluminium oxide particles partially incorporated into the bulk of the glass. The particles are quasi-spherical in shape and have a size varying from 12 to 40 micrometers. They are present on the surface of the glass in a density in the order of 800 particles/mm².

Optical and Non-Slip Properties

The haze, clarity and gloss of the glass sheet obtained in Example 1 (comparative), of the glass sheet obtained in Example 2 (according to the invention) and of the initial clear glass were determined.

The haze was determined in accordance with standard ASTM O 1003- 61. The gloss was determined by means of a Glossmeter Micro-tri-gloss device according to standard ASTM C584: a ray of light is directed onto the surface to be analysed and the intensity of the specular reflection is evaluated by a receiver placed in optical alignment with the source. The device is calibrated using standard specimens supplied by the manufacturer.

Table 1 illustrates the results obtained for the optical properties of the glass sheet according to Example 2 (according to the invention) compared to those obtained for the glass sheet according to Example 1 (comparative) and the initial clear glass sheet (before treatment according to Example 1 or 2). Table 1

a measurement of the acid-textured side b measurement of the side having the particles These results show that the glass sheet according to the invention retains optical properties very close to those of the initial clear glass sheet, whereas the acid-textured glass sheet has optical properties very far therefrom. In other words, the glass sheet according to the invention can be qualified as "transparent", whereas the acid-textured glass sheet is "translucent" (which is typical with this type of acid treatment).

The coefficients of dynamic friction (μ_¼) for the glass sheet of Example 1 , the sheet of Example 2 and the initial clear glass sheet (before treatment according to Example 1 or 2) were obtained using a Ray-Ran friction tester device according to standard ISO 8295 : 1995 in dry conditions (dry path) or wet conditions (wet path). Table 2

a measurement of the acid-textured side b measurement of the side having the particles According to the Tortus test scale, the evaluation of the non-slip properties is as shown in the following table:

0 < μ_¼ < 0.19 Dangerously slippery

Product of class 1

0.20 < μ_¼ < 0.39 Excessively slippery

0.40 < μ_¼ < 0.74 Satisfactory friction

Product of class 2

0.75 < μ_¼ Excellent friction

Claims

1. Glass sheet with non-slip properties comprising particles, which are partially incorporated into the bulk of the glass and which comprise at least one inorganic compound, characterised in that the size of the particles is not smaller than 5 micrometers and is not larger than 200 micrometers, and in that the density of said particles per unit area ranges between 100 and 10000 particles per mm².

2. Glass sheet according to claim 1 , characterised in that the density of said particles per unit area ranges between 500 and 5000 particles per mm².

3. Glass sheet according to claim 1 or 2, characterised in that the size of the particles is not smaller than 10 micrometers and is not larger than 100 micrometers.

4. Glass sheet according to one of the preceding claims, characterised in that the particles are at least partially crystallised.

5. Glass sheet according to the preceding claim, characterised in that the particles are completely crystallised.

6. Glass sheet according to one of the preceding claims, characterised in that the particles are formed from an inorganic compound.

7. Glass sheet according to one of the preceding claims, characterised in that the inorganic compound is selected from single oxides, mixed oxides, nitrides, oxynitrides, carbides and combinations of at least two of the abovementioned compounds.

8. Glass sheet according to the preceding claim, characterised in that the inorganic compound is selected from single oxides of aluminium, silicon, iron, titanium and zirconium.

9. Glass sheet according to one of the preceding claims, characterised in that the particles are quasi-spherical in shape.

10. Glass sheet according to one of the preceding claims, characterised in that it is a sheet of soda-lime-silica float glass.