PHOTOLUMINESCENT CEMENTITIOUS COMPOSITIONS BASED ON HYDRAULIC BINDERS PARTICULARLY SUITABLE FOR USE IN SAFETY SIGNS

Abstract

The present invention relates to a photoluminescent cementitious composition suitable for use in safety signs in accordance with DIN 67510-1 standard, characterized by including a hydraulic binder, an aggregate and/or a filler and at least a photoluminescent pigment selected from strontium aluminates or silicates doped with rare earths selected from europium and dysprosium. The invention also relates to the use of a photoluminescent pigment in the manufacturing of concrete articles with aesthetic quality given by persistent photoluminescent properties.

Claims

1. Photoluminescent cementitious composition suitable for use in safety signs in accordance with DIN 67510-1 standard, characterized by including a hydraulic binder, an aggregate and at least a photoluminescent pigment selected from strontium aluminates and silicates doped with rare earths selected from europium and/or dysprosium.

2. Composition as claimed in claim 1 characterized in that said pigment has formula SrAl.sub.2O.sub.4:Eu.sup.+2, Dy.sup.+2; or Sr.sub.2SiO.sub.4:Eu.sup.+2, Dy.sup.+2.

3. Composition as claimed in claim 1 characterized in that said photoluminescent pigment is a doped strontium aluminate.

4. Composition as claimed in claim 1 characterized in that said photoluminescent pigment is a doped strontium silicate.

5. Composition as claimed in claim 1 characterized in that said photoluminescent pigment comprises doped strontium aluminates and silicates together.

6. Composition as claimed in claim 1 characterized in that said photoluminescent pigment includes europium or dysprosium together as doping substance.

7. Composition as claimed in claim 1 characterized in that said photoluminescent pigment includes europium and dysprosium together as doping substance.

8. Composition as claimed in claim 1 characterized in that said photoluminescent pigment comprises the following oxides: SrO, Al.sub.2O.sub.3, Dy.sub.2O.sub.3, Eu.sub.2O.sub.3.

9. Composition as claimed in claim 1 characterized in that said pigment is in the form of a solid with particle size ranging between 0.1 μm and 10 mm

10. Composition as claimed in claim 9 characterized in that said pigment has particle size in the range X.sub.50(μm)=10-500.

11. Composition as claimed in claim 10 characterized in that said pigment has particle size in the range X.sub.50(μm)=20-300.

12. Composition as claimed in claim 10 characterized in that said pigment has particle size in the range X.sub.50(μm)=30-150.

13. Composition as claimed in claim 1 characterized in that it comprises: a) a hydraulic binder; b) at least a rheology modifying agent; c) a calcareous, siliceous or silico-calcareous aggregate; d) one or more of said photoluminescent pigments.

14. Composition as claimed in claim 13 characterized in that said hydraulic binder is a cement.

15. Composition as claimed in claim 13 characterized in that said rheology modifying agent is a cellulosic ether or a chemically modified starch, having Brookfield viscosity ranging between 200 and 120000 mPa.Math.s.

16. Composition as claimed in claim 13 characterized in that said c) aggregate consists, at least in part, of one or more fillers in accordance with UNI EN 13139 standard.

17. Method for providing safety signs in accordance with DIN 67510-1 standard, characterized in that a photoluminescent pigment is selected from strontium aluminates and silicates doped with rare earths selected from europium and/or dysprosium, and it is formulated in a composition comprising a hydraulic binder and an aggregate, and/or a filler.

18. Method as claimed in claim 17 characterized in that said pigment is formulated in a composition as claimed in claims from 1.

19. Method as claimed in claim 17 characterized in that said composition is mixed with water in order to obtain a fluid and homogeneous mortar, suitable to be applied as a photoluminescent coating layer in the form of paint, or render or plaster on a suitable substrate for safety signs in accordance with DIN 67510-1 standard.

20. Method as claimed in claim 17 characterized in that said composition is mixed with water according to a water/hydraulic binder weight ratio ranging from 0.2 to 3.

21. Method as claimed in claim 19 characterized in that the thickness of said coating layer is in the range between 0.2 e 20 mm.

22. Manufactured article for safety signs in accordance with DIN 67510-1 standard characterized in that it includes a suitable substrate, such as a traffic separation element, a panel, a plate, a road surface, pavement, floor structure, wall structure, front and roof of a building, architectural or urban design element, said substrate being coated at least in part by a paint, or render or plaster layer consisting of a composition as claimed in claim 1.

23. Method for manufacturing articles having aesthetic quality given by persistent photoluminescent properties, characterized in that a photoluminescent pigment is selected from strontium aluminates and silicates doped with rare earths selected from europium and/or dysprosium, and it is formulated in a composition including a hydraulic binder and an aggregate, and/or a filler.

24. Method for manufacturing high-tech mortars for restoration and repair applications, and for producing non-structural elements such as architectural facades and manufactured articles having design of a decorative nature, characterized in that a photoluminescent pigment is selected from strontium aluminates and silicates doped with rare earths selected from europium and/or dysprosium, and it is formulated in a composition comprising a hydraulic binder and an aggregate, and/or a filler.

Description

DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 in the accompanying drawing shows a spectrum obtained by scanning electron microscopy (SEM) performed on a photoluminescent pigment according to the invention. The ordinates show the count rate expressed in cps, counts per second; the abscissas the voltage expressed in keV.

[0043] The profile of the components measured, including SrO, Al.sub.2O.sub.3, Dy.sub.2O.sub.3, Eu.sub.2O.sub.3, is summarized at the top of the spectrum.

EXAMPLES

[0044] In order to better understand the features and the advantages of the invention, non-limiting embodiment examples are described hereinafter.

Example 1

[0045] The following cementitious composition suitable as a render, was prepared according to the invention:

TABLE-US-00002 Component % by weight Rocca Bianca 42.5 R cement 14.57 Calcareous aggregates, component c) 78.96 Fiore hydrated lime 1.63 FL1210 (Elotex) 1 vinyl or acrylic polymer, tackifying agent Aqualon ST 2000 (Ashland) 0.1 chemically modified starch, 300-800 MPA.s, rheology modifier MHG-6B (Arcacolour) 3.74 photoluminescent pigment strontium aluminate (Sr.sub.2AlO.sub.4:Eu.sup.+2, Dy.sup.+2) Water, % by weight on the pre-mix 20

[0046] All the components in the form of powder were mixed in an intensive Eirich type mixer for 5 minutes in order to achieve good homogenization; water was then added and mixing was continued for another 3 minutes. The resulting cementitious mortar was applied as a coating layer in the form of finishing render, using a spatula, on a plasterboard panel sized 50×50 cm. The applied render thickness is equal to 2 mm.

[0047] Luminance measurements, expressed in mcd/m.sup.2 at the times (minutes) in accordance with DIN 67150, were carried out on the coated panel as described above after 7 days from preparation, and reported along with the decay time in the following table:

TABLE-US-00003 Luminance values minutes 10 ± 0.1 60 ± 0.3 1150 mcd/m.sup.2 20.1 4.2 0.3

Example 2

[0048] The following cementitious composition suitable as a paint, was prepared according to the invention:

TABLE-US-00004 Component % by weight Rocca Bianca 42.5 R cement 27.79 Calcareous filler, component c) 59.13 Fiore hydrated lime (Unicalce) 1.46 FL1210 (Elotex) 1 vinyl or acrylic polymer tackifying agent C4051 (Culminal) 0.21 Methylcellulose, 65000-85000 mPa.s, rheology modifier AGITAN P845 (Munzing) 0.1 polyglycol, air removing agent MHG-2C (Arcacolour) 10.31 photoluminescent pigment strontium aluminate (Sr.sub.2AlO.sub.4:Eu.sup.+2, Dy.sup.+2) Water, % by weight on the pre-mix 65

[0049] All the components in the powder phase were mixed in an intensive Eirich type mixer for 5 minutes in order to achieve good homogenization; water was then added and mixing was continued for other 3 minutes. The resulting cementitious mortar was applied as a coating layer in the form of paint using a brush on a concrete slab sized 40×40 cm. Luminance measurements, expressed in mcd/m.sup.2 at the times (minutes) in accordance with DIN 67150, were carried out on the coated panel as described above after 7 days from preparation, and reported along with the decay time in the following table:

TABLE-US-00005 Luminance values minutes 10 ± 0.1 60 ± 0.3 630 mcd/m.sup.2 20.3 3.7 0.3

Comparative Example 3

[0050] By following a similar process, the following reference cementitious composition was prepared, corresponding to the composition of example 2 except for a different photoluminescent pigment not belonging to the invention, i.e. zinc sulfide doped with copper, ZnS:Cu.

TABLE-US-00006 Component % by weight Rocca Bianca 42.5 R cement 27.79 Calcareous filler 59.13 Fiore hydrated lime 1.46 FL1210 (Elotex) 1 C4051 (Culminal) 0.21 Methylcellulose, 65000-85000 mPa.s, rheology modifier AGITAN P845 (Munzing) 0.1 Lumilux N-FG (Honeywell) 10.31 photoluminescent pigment zinc sulfide doped with copper, ZnS:Cu Water, % by weight on the pre-mix 65

[0051] All the components in the powder phase were mixed in an intensive Eirich type mixer for 5 minutes in order to achieve good homogenization; water was then added and mixing was continued for another 3 minutes. The resulting cementitious mortar was applied as a coating layer in the form of paint using a roller on a concrete slab sized 40×40 cm, having the function of a luminous sign. Luminance measurements, expressed in mcd/m.sup.2 at the times (minutes) in accordance with DIN 67150, were carried out on the slab painted as described above after 7 days from preparation, and reported along with the decay time in the following table:

TABLE-US-00007 Luminance values minutes 10 ± 0.1 60 ± 0.3 mcd/m.sup.2 1 0

[0052] The following conclusions are drawn from the above examples.

[0053] Bearing in mind that in order to meet DIN 67510-1 standard, after 10 minutes the luminance value must be at least 20 mcd/m.sup.2, after 60 minutes not less than 2.8 mcd/m.sup.2 and the decay time at luminance 0.3 mcd/m.sup.2 must be greater than 340 minutes, it is seen that the compositions of examples 1 and 2 according to the invention meet these requirements while this is not the case for example 3, which at 10 minutes already shows a luminance close to decay, which is reached at the measurement after 60 minutes. On the other hand, it is seen that in particular the composition of example 1 according to the invention allows reaching a decay time of more than 19 hours.

[0054] Furthermore, the compositions of the invention were found to be provided with optimum rheology within the usage scope object of the invention.

[0055] The invention therefore achieves the object of providing a photoluminescent cementitious composition according to the reference standard, and together provided with optimum rheology, easily applicable at the fluid state on the desired substrate according to the need in the form of paint or render or plaster, using a limited number of components.

[0056] Compliance with DIN 67510-1 standard allows applications for photoluminescent safety signs alternative to non-cement signs, often more expensive.

[0057] As an alternative use, a photoluminescent cementitious composition according to the present invention also allows the manufacturing of articles with aesthetic or ornamental quality given by the persistent photoluminescent properties thus obtained.