MXPA00005485A - Agent for coating transparent surfaces - Google Patents

Abstract

A composition for coating transparent surfaces containing a multilayer interference pigment comprising a transparent carrier material, with alternate layers consisting of a material of lower and a material of higher refractive index, the difference in refractive index being at least 0.1 is new. An Independent claim is included for a transparent surface coated with the composition.

Description

COMPOSITION FOR COATING TRANSPARENT SURFACES The present invention relates to a composition for coating transparent surfaces, as used, for example, for greenhouses, sheet constructions, ceiling light, skylights or roof covers, which possesses high transmission in the visible region of light solar and high reflection in the NIR region.

To avoid excessive temperatures in the enclosed space and to diffuse sunlight. In this incident, shading paints are currently used, consisting of one or more white pigments and a polymeric binder system. These shading paints are applied to the white surface in periods of intense solar irradiation, by sliding off, by roller or brush and removed again in the winter by washing.

EP-A-428 937 discloses a gray-white shading paint for greenhouses, consisting of a liquid binder and reflecting particles suspended therein. These particles are aluminum flakes or mica flakes (alumina and potassium silicates) coated with titanium dioxide.

REF. : 119726 white surfaces for temporary coatings in periods of intense solar irradiation, atomizing, brushing or rolling, and removed in the winter by washing with a jet of water.

In the market, shading paints are available under the designation "Nixol" from the Farball company, the Netherlands, and under the designation "Redusol Xtra" from the Mardenho company, Netherlands.

The shading paints diffuse the incident light and prevent burns on the plants. By absorption and reflection of the incident lumen, they also effect a reduction in temperature within the enclosed space. However, they have the disadvantage that by reducing the amount of transmitted light, they obscure the space and reduce the radiation intimately active (PAR) for the plant. The ratio of the transmutation of light to solar radiation is 1 or even less than 1.

EP 0 548 822 discloses a translucent IR reflecting structure consisting of a plastic base material and a coating layer adhered thereto. The coating layer contains from 20 to 40% by weight of a monolayer interference pigment. The disadvantages of ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ This structure is not only NIR radiation, but also a considerable proportion of the visible light is reflected and the transmitted light is green and the light reflected red.

The object of the present invention is therefore to provide a composition for the coating of transparent surfaces having high transmission in the region of visible light and high reflection in the NIR region, and for which the ratio of the transmuta t from light to solar transmittance is greater than 1.

This object is achieved according to the invention by a composition for coating transparent surfaces, comprising a multilayer interference pigment consisting of a transparent support material that is coated with alternating layers of low and high refractive index materials, the difference in the refractive indexes is at least 0.1, and b) at least one polymeric organic binder.

The composition of the invention additionally comprises components as are known from coating technology. These include thickeners, dispersion aids, humidifying agents, and plasticizers.

The multilayer interference pigment present in the composition of the invention has distinct advantages over the white pigments contained in the known shading paints, such as titanium dioxide, calcium carbonate, barium sulfate and magnesium oxide. The pigment has a much greater transmission in the region of visible light and in the region of photically active radiation (PAR) and results not only in the reflection of NIR radiation, but also in the diffusion of the incident light. The ratio of light transmission to solar radiation is greater than 1. Light transmission and solar radiation are defined more broadly in DIN EN 410.

Figure 1 shows the transmission and intensification of the composition of the invention compared to a commercially available shading paint (Nixol). A film of 100 μm thickness is applied to glass plates. The concentration of the pigment in the composition of the invention was 10%. The transmission of the composition of the invention in the PAR region is about 75%. The transmission curve in this case falls steeply towards the NIR region, since the intention is to reflect as much thermal radiation as possible. In contrast, the transmission of the known shading paint in the PAR region is only 25%. This means that, in the closed space of the plant, much less useful light is available and, therefore, growth is inhibited. Intensification curves show that, with virtually identical intensification in the NIR region, the composition of the invention possesses a transmission in the PAR region - which is greater than twice as high as the shading paint.

The multilayer interference pigment consists of a transparent, lamella-shaped support material. This support material may be natural or synthetic mica, other lamellar silicate, glass flakes, silica or alumina in the form of a lamella.

In general, 3 layers are applied to the support material. The first layer consists of material with a high refractive index, which could be Ti02, Zr02, Fe203, Fe204, Cr203, ZnO or a mixture of these oxides. The second layer consists of a material with a low refractive index, for example, Si02 or A1203. The third layer consists of a material with a high refractive index. A protective layer could also be applied, optionally, to this layer assembly. The preparation of the pigment, and its properties, are described in DE 196 18 569.

The multilayer interference pigment is present in the composition of the invention in concentrations of 1 to 30% by weight, preferably 3 to 15% by weight.

As the binders for the composition of the invention, use is made of polymers and copolymers which are known from the coating technology. Suitable binders include alkyd resins, vinyl resins, epoxy resins, polyurethanes, acrylates, chlorinated rubber, polycarbonates, polyesters, polyethylene glycol and copolymers thereof. The concentration of the binder in the shading paint is from 5 to 60% by weight, preferably from 10 to 30% by weight. The composition of the invention can be adapted to the respective substrate. To achieve better adhesion to glass, for example, 5% by weight of an acrylic polymer dispersion is used.

In addition to the two main components, the composition of the invention also includes additives as known from coating technology. These include thickeners, dispersion aids, humidifying agents and plasticizers, and also solvents, such as water, esters, ketones, alcohols or aromatics.

To increase the diffusion of light, additional additives can be added to the composition of the invention, such as calcium carbonate, magnesium carbonate, barium carbonate and zinc carbonate, magnesium oxide, barium sulfate or boron trioxide, in a concentration of 1 to 20% by weight.

The composition of the invention is applied to the white surfaces in a layer thickness of 20 to 200 μm, preferably 50 to 100 μm, by means of known techniques, such as spraying, by brush or roller or pouring. The white surfaces referred to are glass, a transparent material made of plastics, for example polymethyl methacrylate, polycarbonate, polystyrene or copolymer of ion-acrylatene, or polymer films, such as, for example, greenhouse films. As discussed above, the composition of the invention can be adapted to the respective substrate.

In a particular embodiment, the polymeric organic binder is in the form of an aqueous emulsion. It is consequently suitable for the temporary coating of transparent surfaces. In periods of intense solar irradiation, it can be applied by spraying, by brush or roller or spill and then in periods with low solar radiation can be removed again with the help of a water jet, with or without mechanical and / or chemical assistance.

The following example is intended to illustrate the invention without restricting it.

The empl o A composition of the invention consisting of Binder, 5% acrylic polymer dispersion (Neocryl®) Multilayer interference pigment (AC 870, 10% manufacturer Merck KGaA Plasticizer (PEG 3000 5% Dispersion aids (Rohagid SL-606 Humidi f i cant agent (BYK-34 1% Thickener (xanthan) 0.3% Water 75.7% It is applied to a glass plate by atomization in a layer with a thickness of 100 μm. The transmission and intensification of the applied layer are shown in Figure 1.

Comparative Example A commercially available shading paint, Nixol® from Farball, the Netherlands, is applied in a 100 μm thick layer to a glass plate. The transmission and intensification of the applied layer are shown in Figure 1.

Table Tr ansmi t ion of lu z / t ransmi t le solar in accordance with DIN EN 410.

E g em e e Comparative E xemployment Light transmission 63% 48% Solar transmission 49% 50% Solar factor 1.28% 0.95% The solar factor is the ratio of light transmittance to solar transmittance.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims (6)

1. The composition for coating transparent surfaces, characterized in that it comprises a multilayer interference pigment consisting of a transparent support material which is coated with alternating layers of a low refractive index material and a high refractive index material, the difference in the refractive indexes is at least 0.1, Y b) at least one polymeric organic binder.

2. The composition according to claim 1, characterized in that the multilayer interference pigment is present in a concentration of 1 to 30% by weight, based on the composition.

3. The composition according to claim 1 or 2, characterized in that the binder is an alkyd resin, vinyl resin, epoxy resin, polyurethane, acrylate, chlorinated rubber, polycarbonate, polyester, polyethylene glycol and a copolymer thereof. tíbtz- ^ S > ^

4. The composition according to at least one of claims 1 to 3, characterized in that the binder is present in a concentration of 5 to 60% by weight.

5. The composition according to at least one of claims 1 to 4, characterized in that the binder is in the form of an aqueous emulsion.

6. The transparent surfaces, characterized in that they are coated with a composition according to claims 1 to 5.