IL107878A - Paint compositions possessing high reflectivity in the thermal infra-red spectral region comprising pigments containing at least one calcined metal oxide - Google Patents

Description

.TITO!) 107,878/2 "PAINT COMPOSITIONS POSSESSING HIGH REFLECTIVITY IN THE THERMAL INFRA-RED SPECTRAL REGION COMPRISING PIGMENTS , CONTAINING AT LEAST ONE CALCINED METAL OXIDE. πτ η -ΊΠΓΙΠ mnm nnua πιτππ unj. ••"ruon" .n^ina^s tr^pnn OITN-NIDI^N *?OJ ·,-Ι¾>Ϊ?9ΟΠ ηπκ m j? mmnn nxiann mnsV o'VOan THE APPLICANT: : ΠωίΡ,ΜΓΐ STATE OF ISRAEL, ,*tnUP niMH Ministry of Defense, (*"N91) ΠΙΤΠ* ·>ΌΧΤΜ mivs* niunn Armament Development Authority, .31021 Π3"·Π ,2250 .7.Π P.O.Box 2250, Haifa 31021.

THE INVENTOR: tlWSnnn Shulamit WASSERMANN ΙΤΠΟΙ mnVlU) in, Hatishbi st. in "•αωππ mm H A I F A Π ΕΙ ^ Π The present invention relates to improved paint compositions. More particularly, the invention relates to improved paint compositions having high reflectivity in the thermal infra-red spectral region.

BACKGROUND OF THE INVENTIO Paints are defined as liquids, or pastes consisting of a suspension of a pigment in oil or water. Generally, they comprise more colouring constituents in a liquid-forming binder, which are designed to provide, after their application and drying, a hard thin covering of the surface coloured by the pigment, which impart protective, functional or decorative properties to a substrate.

The main components present in a paint are: pigment, binder, extender or filler and a solvent system.

Pigments, consist of particulate solids dispersed in the paint, their main purpose being to provide optical properties, such as colour and in some cases also opacity, durability, corrosion protection or mechanical strength. There are known many inorganic pigments, such as: metal oxides, metal chromates, metal sulfides,metal molybdates, carbon black and ferrocyanides and also various organic pigments .

Binders, are generally polymeric resins which provide film forming properties.

Extenders, have the property to modify properties such as gloss, flow, permeability, and also in protecting the paint from weathering of the paint.

The solvent system, comprises volatile liquids added to the paint in order to dissolve the binder and to control the viscosity of the liquid paint.

In our previous Patent Application Number 105,167, there were described low glossy compositions for high reflectance film in the thermal infra-red region. The compositions comprise as extender, a polyolefin selected from polyethylene, polypropylene, copolymer of ethylene-propylene and mixtures thereof. It was found that these specific extenders, in contrast to the known extenders such as calcium carbonate, talc, silica, reduce substantially the gloss of the paint while maintaining higher reflectivity in the infra-red, thus being most useful as paints for camouflage purposes. - 2a - 107,878/2 In . the Israeli Patent number 56485, it is described a paint composition for the spectrally selective coating of metal surfaces, comprising a pigment and a binder, said pigment comprising at least one metal oxide in a powder form having a good transparency for heat radiation. The binder after conditioning as described in the specification is holding the pigment in place on a metal surface, such that a layer of the paint composition, after having been applied to the metal surface and conditioned, gives such metal surface at least a medium selectivity.

It is an object of the present invention to provide paint compositions which possesses a high reflectivity in the thermal infra-red region. It is another object of the present invention to provide paint compositions which possess excellent weathering and light fastness characteristics wherein all the components are compatible.

BRIEF DESCRIPTION OF THE INVENTION.

Paint compositions comprising pigments, binders, extenders and a solvent system, and optionally auxiliary additives, having a high reflectivity in the thermal infrared spectral region, being characterized by the fact that the pigments used comprise at least one metal oxide which was calcined at a temperature of above 600°C. The preferred metals are selected from: cobalt, aluminium, iron, chromium, zinc, titanium, manganese, antimonium, nickel, copper and magnesium or any mixture thereof. It was surprisingly found that only when said calcination is carried out at above said temperature, there is a substantially high reflectivity of the paint composition containing said pigment in the thermal infra-red spectral region. It seems that the calcination of the metal oxide at a temperature of above 600°C, gives a solid solution which is transparent in the thermal infra-red region and thus will contribute to a paint film possessing a high reflection in that region. - 4 - DETAILED DESCRIPTION OF THE INVENTION.

According to the present invention, it was found that by carrying out the calcination of the metal oxide at a temperature below 600°C, the paints obtained with the respective pigment are not transparent in the thermal infra-red region, and therefore can not be incorporated in the infra-red reflective paint films.

The colour of the pigment is not critical and actually various materials may be used to produce the desired colour, such as: red, green, yellow, brown, black,etc. It was found that the calcined oxides, used according to the present invention, are compatible with the known binders being non-migratory, non-bleeding and possessing excellent weathering and light fastness characteristics. In order to obtain the desired colour, a mixture of two or more oxides may be used. The amount of the pigment may be selected in a broad range, depending on the particular use of the paint. Generally, this amount will be in the range of between 15% to 50% by weight of the composition and most preferably between 25% to 40% by weight.

The extenders to be used, may be selected from the known extenders of the polyolefin type, such as polyethylene or modified polyethylene, polypropylene or modified polypro- pylene or any mixture thereof. The amount of the extender is not so critical and may be selected in a broad range of between 1% to 10% by weight of the paint composition. The organic solvent to be used may be selected from any organic solvent generally used in the art of paints, such as aliphatic and aromatic hydrocarbons, ketones, ethers; typical examples are: xylene, toluene or derivatives thereof .

As will be shown in the experimental part and the attached Figures, when the paint compositions contain a metal oxide pigment, according to the present invention, the reflectivity of the paint was substantially higher than those containing the metal oxides as available on the market. The paints containing the pigments according to the present invention, may be used for many purposes such as for agricultural appl cations, in greenhouses, on solar collectors, for camouflage purposes, in fabrics, or plastic sheets.

The invention will be hereafter illustrated by a number of Examples, wherein Examples 1, 3 and 5 as well as Figures A, C and E do not represent the present invention and are given only for comparison purposes. - 6 - In the Examples, the percentages are given by weight, unless otherwise stated.

EXAMPLE 1. (for comparison purpose).

An amount of 40 g of a medium length soya oil alkyd (as binder) was mixed with 40 g of a commercial yellow-brown iron oxide (as pigment) , 4 g of polyethylene (as extender), 10 g of xylene (as solvent) and 3 g of known additives as used in a paint composition.

The yellow paint obtained had an average reflectivity of 0.08 (in the region of 3-5 urn).

Figure A, illustrates the correlation between the percent of reflectance and wavelength (in microns) .

EXAMPLE 2.

The same paint composition as in Example 1 was prepared with the difference that the pigment used consisted of 40 grams of a mixture of titanium oxide, antimonium oxide and chromium oxide, calcined at a temperature of about 1000° Celsius.

The yellow paint obtained had an average reflectivity of 0.18 (in the region of 3-5 urn).

Figure B, illustrates the correlation betwen the percent of reflectance and wavelength (in microns). - 7 - EXAMPLE 3 (for comparison purposes).

The same paint composition as in Example 1 was prepared with the difference that the pigment used consisted of 30 grams of a commercial yellow lead chromate oxide.

The yellow paint obtained had an average reflectivity of 0.09 (in the region of 3-5 pi).

Figure C, illustrates the correlation between the percent of reflectance and wavelength (in microns).

EXAMPLE 4.

Te same paint composition as in Example 1 was prepared with the difference that the pigment used consisted of 40 grams of a mixture of cobalt oxide and chromium oxide calcined at a temperature of about 1100°C.

The green paint obtained had an average reflectivity of 0.14 (in the range of 3-5 um).

Figure D, illustrates the correlation between the percent of reflectance and wavelength (in microns).

EXAMPLE 5. (for comparison purposes).

The paint composition was prepared from: 3 g of carbon black; 60 g of the alkyd as used in Example 1; 4 g of - 8 - polyethylene (as extender) and 20 g of xylene (as the solvent) .

The black paint obtained had an average reflectivity of 0.08 (in the region of 3-5 urn).

Figure E, illustrates the correlation between the percent of reflectance and wavelength (in microns).

EXAMPLE 6.

The same paint composition as In Example 1 was prepared with the difference that the pigment used consisted of 40 grams of a mixture of titanium oxide, antimonium oxide and nickel oxide, which were calcined at a temperature of about 950° Celsius.

The yellow paint obtained had an average reflectivity of 0.16 (in the region of 3-5 urn).

Figure F, illustrates the correlation between the percent of reflectance and wavelength (in microns).

Claims (7)

9 - 107, §78/3 C L A I M S :-

1. Paint compositions comprising: pigments, binders, extenders and a organic solvent system, and optionally auxiliary additives, having a high reflectivity in the thermal infra-red spectral region, being characterized by the fact that the pigments used comprise at least one metal oxide which was calcined at a temperature of above 600°C.

2. The paint composition according to Claim 1, wherein said metal is selected from cobalt, aluminium, iron, chromium, zinc, titanium, manganese, antimonium, nickel, copper, and magnesium or any mixture thereof.

3. The paint composition according to Claims 1 and 2, wherein the paint composition contains more than one calcined metal oxide.

4. The paint composition according to Claims 1 to 3, wherein the amount of pigment is between 15% to 50% by weight of the paint composition.

5. The paint composition according to Claims 1 to 4, wherein the extender used is of the polyolefin type. - 10 - 107 ,878/2

6. The paint composition according to Claim 5, wherein said polyolefin is selected from polyethylene, modified polyethylene, polypropylene , modified polypropylene or any mixture thereof.

7. Paint composition comprising: pigment, binder, extender and a solvent system, substantially as described in the specification and claimed in any one of the Claims 1 to 6. For the Applicant, Simon Lavie Patent Attorney