BE1020601A3 - HYDROPHORIZING METHODS AND PRODUCTS FOR PHOTOCATALYTIC APPLICATIONS TO REMOVE SALTS AND OTHER RESIDUAL PRODUCTS. - Google Patents

Description

Hydrophobic Methods and Products for Photo Catalytic Applications to Incinerate Salts and Other Restor Products.

Domain of the invention:

The invention relates to the various methods and products that can be used to more easily remove salts and residual products from photocatalytic substrates.

In photocatalytic reactions, organic components (NOx, SOx, VOCs) are converted into salts and into CO2. -

To obtain good photocatalytic reactions, there are a number of parameters that should be taken into account, namely: the light intensity (UV or visible light), the relative humidity, the type of surface, the adhesion of the photocatalyst and the contact of the photocatalyst with the pollutant for degradation.

The problem with surface salts obtained after photocatalytic oxidation reactions is that they can block contact with the pollutants. This can lead to a reduction of the degradation reactions or even to a complete stop of the degradation.

This problem mainly occurs with horizontal cement applications. For this type of cement applications (pavers, concrete roads, ...) we can use hydrophobic additives such as silicones and stearates that make the entire cement mass water-repellent.

To improve the water-repellent properties of the cement mass, it is also possible to add products that reduce the capillaries of the cement mass and ensure that the porosity of the cement application is reduced. For this, one can use, among other things, acrylic-based polymers, polycatboxylate ethers or sterines. By combining these two types of products, a better hydrophobicity of the surface is obtained, which facilitates the removal of the salts and other residual products.

For vertical surfaces, cement or other types of surfaces such as natural stones, we can apply an extra coating on top of the photocatalytic surface that reduces the surface tension of the substrate. A polytetrafluoroethylene or PTFE coating (with C6 or C8 chains) is the most suitable for this. These coatings remove the salts and also ensure that photocatalytic reactions work better in environments with a higher relative humidity.

B. Current scientific state of affairs:

Photocatalytic compositions that include nanoparticles of photocatalytic materials, such as titanium dioxide, are well known in current science. After irradiation with UV or visible light, these materials become photocatalytically active, resulting in a non-selective oxidation process. These oxidations are responsible for the breakdown of a large number of organic components and biological species that are located near the nanoparticules. Especially after irradiation with UV light, oxygen-containing radicals are created (O and OH ’) on the surface of the photocatalytic particle. These then react with organic components that are converted into salts and into CO2. Examples of organic / biological species that are degraded by photocatalysis include bacteria, viruses, fungi and other types of proteins and toxic components (particulate matter due to the self-cleaning effect). Due to their unique physical and chemical properties, photocatalytic elements can be used for various applications (in cement, in coatings, on metals, on glass, ...).

To obtain good photocatalytic reactions, there are a number of parameters that have to be taken into account, namely: the light intensity (UV or visible light), the relative humidity, the type of surface and the adhesion and the contact with the pollutant for degradation.

This new invention was made to ensure that the photocatalytic surfaces continue to function over time and thus to counteract the inhibiting effect of salts on photocatalic reactions.

There are two significant patents for cement applications: WO 2004/074202 A1 from Ital-Cementi SPA talks about an invention with Tio2 in cement applications (concrete paving stone / clinker, other cement compositions and a dry concrete / cement mix) with a maximum of 50% , but ideally 4.9% Tio2 added in proportion to the cement mass. One photocatalytic cement composition must consist of a hydraulic binder (cement), a photocatalyst (titanium dioxide), water, aggregates (granules and sand) and optionally a water reducing additive.

EP 0 786 283 B1 of Mitsubishi Materials Corporation talks about an invention with Tio2 in cement applications (concrete paving stone / clinkers) where between 5% and 50% Tio2 is added in proportion to the cement mass of the top layer of a clinker. A photocatalytic cement composition according to this octooi must consist of a hydraulic binder (cement), a photocatalyst (titanium dioxide), water, aggregates (granulates, sand or silica glass) and absorbent materials such as zeolite or clay to make the substrate less smooth.

Neither of the patents speaks of the necessity and importance of bulk sealants or an additional coating that facilitates the removal of salts. If the salts can be removed in an optimal way from the anatase Tio2, then the anatase Tio2 can still come into contact with the pollutants in the air.

C. Summary of the Invention ...... The inventor has discovered that the photocatalytic activity can be maintained by making use of hydrophobizing additives or an additional hydrophobic coating. The removal of salts (nitrates, etc.) and other residual products is of paramount importance to guarantee a long service life for a photocatalytic substrate.

The horizontal photocatalytic surfaces on the current commercial market are mostly cement applications (pavers, concrete streets, ...). These horizontal photocatalytic surfaces can best be treated in the mass with waterproofing agents (stearates / soaps or silicones) distributed throughout the mass during the production process.

In order to improve the water-repellent properties of the cement mass, products can also be added which reduce the capillaries of the cement mass and ensure that the porosity of the cement application is reduced.

The second method is to treat vertical surfaces with an aftercare PTFE or polytetrafluoroethylene coating. A PTFE coating, with C6 or C8 chains, ensures that the substrate gets an extra low surface tension, so that the salts do not adhere to the surface. These PTFE coatings also ensure that the photocatalytic surfaces continue to work better in environments with a high relative humidity (higher than 50%). These PFTE coatings can also be applied on top of other photocatalytic coatings.

Extensive description of the Invention

To make it easier to clean porous surfaces from salts (nitrates) and other contamination, the inventor has found two methods to treat the surfaces.

The first method for cement applications consists of adding a water-repellent additive. Between & .2% and 4% wt, water-repellent additives must be added to the cement mass to make the capillaries of the substrate watertight. The best method for this is between 0.2% and 3.0% wt, liquid calcium stearates (50% wt active material: stearates), ideally between 0.2% and 1.5% wt on the. cement mass. It is also possible to add between 0.2% and 1.8% wt of solid calcium stearates (100% wt of active material: stearates), ideally between 0.2% and 1% wt on the cement mass.

It is also possible to use silicones, such as Glenium (20% active material), to add between 0.3% and 2.2% wt on the cement mass.

Stearates in particular have a very good effect because they bind completely around the cement and have a specific micel structure. A micel is a microscopically small structure that consists of, among other things, molecules of surfactants in water. The stearate micelle molecules consist of hydrophilic heads on the surface and hydrophobic tails that distribute in the cement mass. The stearates ensure that the water can properly drag and remove dirt from the surface, but the water cannot penetrate the cement mass.

The stearates or silicones already provide a very good water-repellent effect, but to improve the hydrophobic properties, it is also possible to add products to the cement mass that make the capillaries smaller and reduce the porosity of the cement mass. .......... ~ 7

To achieve this improved hydrophobic effect, it is possible to use, for example, polymers based on acrylic, polycarbate, ethers or stearins. Between 0.2% and 4.0% of this type of product must be added to the cement mass.

Of the acrylic-based polymers, such as the EOC 4600/2, one can add between 0.2% and 4.0% wt, to the cement base, ideally between 0.2% and 2% wt.

For liquid stéarines, such as Soft HB (50% wt active material), cut between 0.3% and 3.0% wt, ideally between 0.3% and 1.4% wt on the cement mass. It is also possible to add between 0.2% and 2.0% wt solid sterines (100% wt active material), ideally between 0.2% and 1.0% wt always on the cement mass.

Stearates and stéarines can be mixed together in advance in the cement mass in an aqueous solution. The aqueous solution requires an acidity in excess of 10. Calcium hydroxide is the most appropriate for raising the pH of this aqueous solution.

With the combined use of stearates and stearjnes in the cement mass, there is an ideal posture, yor gm mix or jet. For 100 items of active material, you need at least 55 parts of stearates. The ideal ratio in the cement mass is 75 parts stearates and 25 parts stéarines.

Thus, in the mercury mass, two types of products can be added. The water-repellent products, stearates and silicones, which are essential to remove residual products, salts or fouling, and the products that reduce capillaries to improve hydrophobicity, but are optional.

If a photocatalytic cement application is treated with these hydrophobic products, then these products must be especially | in the photocatalytic part of the cement application. The entire cement mass can be treated with these products, but especially the treatment of the photocatalytic part is of paramount importance: ...... ........-

These methods of mass treatment can be used for horizontal and vertical cement / concrete surfaces.

The two method is especially applicable for vertical surfaces. A photocatalytic substrate that has already been treated in the mass with anatase T102 alone or that has already been treated with a photocatalytic coating can be further treated with a PTFE or polytetrafluoroethylene coating (with C6 or C8 chains) to reduce the surface tension of the surface to lower.

For treatment with an extra coating; PTFE coatings are especially recommended because the (CF2) n complexes with C6 or C8 chains are not degraded by photocatalytic reactions. Other coatings that also have a water vapor permeability between 70% and 100%, such as silicone, are degraded by photocatalytic reactions.

A PTFE coating consists of between 2% and 15% wt, from active materials (C6 or C8 molecules), ideally between 3% and 8% wt active materials. The other elements, between 85 to 98% wt, are solvents (water, desaromatized hydrocarbons, alcohol or a combination of solvents such as: water / alcohol).

The advantage of an additional PTFE coating is that the photo catalytic reactions continue to work better in environments with a higher relative humidity. JIZ standard testing for NOx degradation, JIS TR Z 0018, is done with a relative humidity of 50%. General science has already proven that the degradation results go down by a third if the relative humidity rises to 70%.

With an additional PTFE coating, the efficiency of a photocatalytic surface only drops between 5 and 15% when the relative humidity rises from 50% to ..... 70%. : / "................". ................ .......:. ·.

A PTFE coating is therefore also important to achieve better results in the degradation of Volatile Organic Component Nets (toluene, benzene, ...) in environments with a higher relative humidity. : -. .......

With 1 liter of a PTFE coating you can go between 0.5 m2 and 12 m2, ideally between 0.5 m2 and 6 m2, depending on the solvent used and the porosity of the surface ......

An additional PTFE coating can also be applied to horizontal photocatalytic surfaces, but due to the friction on the surfaces (footsteps, trolleys, ...) ...... these coatings have a limited service life.-Once the coating is removed by friction the nitrate problem manifests very quickly. Between! one month and a year after the removal of the PTFE layer, the photocatalytic reaction is dramatically reduced. "........... ....... - ^ -. Examples Example 1

With the experiments that follow below, we show the results of this new invention and the importance of water repellants in the mass. The photocatalytic effect was measured according to the parameters of the JIS TR Z 0018 "Photocatalytic materials - Air purification test procedure" test.

The standard test has a duration of 2 hours. To prove the removal of the nitrates, we have extended the duration and have the samples work in an urban outdoor environment for specific periods in order to obtain a saturation reed nitrates.

For the following example, we have tested a concrete paving stone / clinker with a size of 10 cm x 19 cm according to the parameters of the JIS TR Z 0018 "Photocatalytic materials-Air purification test procedure. In the coating we have 3% on the total cerrient amount anatase TioVmët added a size of 15 hm, the Tio2 is Kronos VLP The coating was also treated with a spray of Eoxolit Stone P, a photocatalytic spray in which 8 g of anatase Kronos VLP Tio2 is incorporated in the coating, we have 1.2% wt solid calcium stearate 100% active substance) added to the amount of cehient to make the surface hydrophoobic.

The EP 9238 test of steel 7713/2, conducted at the Belgian Road Research Center, shows, among other things, the impact of water-repellents.

Phase 1: After the selection of steel 7713/2 on November 11, we measured NOx reductions. For this phase the light intensity was 5W / m2:

Degradation results (initial and final values are presented): UV light: 1000 ppm -0.679 ppm

The duration of this test was 60 minutes

Phase 2: After running steel 7713/2 for 15 days in an urban environment, we have tested the lifetime of the Eoxolit Stone P Spray treatment against capillary pressure through water infiltrations. We tested steel 7713/2 3 times 60 minutes or NOx degradation according to the JIZ Standard. To perform each 60 minute test, the sample was immersed in water for 120 minutes and then completely dried. For this phase the light intensity was 5W / m2:

Degradation results (initial and final values are presented):

First 60 minutes: UV light: 1000 pprri -0.722 ppm Second 60 minutes: IIV light: 1000 ppm -0.579 ppm Third 60 minutes: UV light: 1000 ppm -0.696 ppm

Phase 3: In this phase we have resistance resistance against friction testing of steel 7713/2. We did this by repeating the following procedure five times: first the steel was sanded 50 times with a metal brush. In the second part, the steel was fully immersed in water for 120 minutes. It was then tested for NOx degradation for 360 minutes according to the JIZ standard. For this phase the light intensity was 10W / m2:

Degradation results (initial and final values are presented):

First 360 min: UV light: 1ÖÖÖ ppm -0.401 ppm Second 360 min: UV light: 1000 ppm -0.413 ppm Third 360 min: UV light: 1000 ppm -0.430 ppm Fourth 360 min: UV light: 1000 ppm -0.457 ppm Fifth 360 min: UV light: 1000 ppm -0.539 ppm

Phase 4: After leaving steel 7713/2 in open city air for 45 days in winter, we conducted a short test of 20 minutes to measure efficiency without cleaning the surface

Degradation results (initial and final values are presented): UV light: 1000 ppm - 830 ppm

Phase 5: For the last test of 60 minutes for NOx degradation, according to the JIZ standard, we let steel 7713/2 work for 90 days in the open city air. We then sanded the surface 50 times with a metal brush and immersed in water for 120 minutes. The relative humidity for this test was 60%, in contrast to the previous tests, the relative humidity was 50%. The light intensity was 10 W / m2.

Degradation results (initial and final values are presented): UV light: 1000 ppm -0.761 ppm Example 2:

The following experiments below show the importance of PIRE coatings in environments with higher relative humidity. The photocatalytic effect was measured according to the parameters of the JIS TR Z 0018 "Photocatly materials -Air purification test pre-procedure" test. The tests always last 30 minutes and the light intensity is 10 W / m2. The samples have a large van; 19x9 cm. We used two samples for this comparative test. The first sample was treated with. only a photocatalytic coating, the second sample was treated with the same photocatalytic coating and on top of that the extra PTFE coating:

Sample 1: The first sample was treated with an Eoxolit Stone P, The second sample was treated with Eoxolit Stone P and then Pelicoat Pro Stone FC. Eoxolit Stone P is a photocatalytic coating that treats the surface with anatase Tio2 from Kronós (VLP). The Pelicoat Pro Stone is a PTFE coating with 4% wt active material (C8 PTFE from Dupont).

Degradation results (initial and final values are presented):

Test: OCW 6452 (steel without PTFE): 50% relative humidity: 995 ppm -0.282 ppm 70% relative humidity: 995 ppm -0.387 ppm

Degradation results (initial and final values are presented):

Test: OCW 6455 (steel with PTFE): 50% relative humidity: 1008 ppm -0.276 ppm 70% relative humidity: 995 ppm -0.366 ppm

Claims (8)

1. This invention relates, inter alia, to the methods and products for making photocatalytic substrates (cement / concrete substrates, natural stones and bricks) hydrophobic for easier removal of salts (nitrates), pollution and other residual products. 2. For Horizontal and Vertical cement applications, between 0.2% wt and 4% wt on the cement amount, water-repellent additives can be added to make the capillaries of the substrate watertight. These additives are of paramount importance. Stearates or silicones, solid or liquid, can be used as a water-repellent additive in the cement mass. ·; ·· ::: Of solid calcium stearates with 100% active material, one should ideally add between 0.2% wt and 1.8% wt on the cement mass. For liquid calcium stearates with 50% active material, one should ideally add between 0.2% wt and 3.0% wt on the cement mass. Silicone can also be added as a water-repellent additive. For silicone with 20% active material, one should ideally add between 0.2% wt and 2.2% wt on the cement mass. 3. In order to obtain a better hydrophobic effect, it is also possible to add products in the cement mass that make the capacities smaller and reduce the porosity of the cement mass. Among other things, acrylic-based polymers, polycarboxylate ethers or sterines can be used for this. Between 0.2% and 4.0% of this type of product must be added to the cement mass. 4. Before addition to the cement mass, stearates and stéarines can be mixed together in advance in an aqueous solution. The aqueous solution requires an acidity in excess of 10. Calcium hydroxide is the most appropriate for raising the pH of this aqueous solution. 5. With the combined use of stearates and stéarines in the cement mass, there is an ideal mixture, pre-mixed or not. For 100 parts of active material, you need at least 55 parts of stearates. The ideal ratio in the cement mass is 75 parts stearates and 25 parts stéarines. 6. In order to better remove nitrates from vertical and horizontal photocatalytic substrates (concrete substrates, natural stones, bricks, ...), an additional PTFE or Polytetrafluoroethylene coating can also be applied ....... 7. To limit the impact of relative humidity in photocatalytic reactions, an additional PTFE or Polytetrafluoroethylene coating can be applied. 8. A 1L coating is ideally between 2% and 18% wt PTFE molecules and between 85% and 98% wt solvents. The PTFE molecules can consist of C6 and C8 chains and the solvents can consist of water, desaromatized hydrocarbons, alcohol or a combination of solvents (such as: water / alcohol). With 1L you can treat between 0.5m2 and 12m2, ideally between lm2 and 6rn2.