LU84248A1 - ZINC-RICH PAINTS CONTAINING PIGMENT MANGANOMANGANIC OXIDE SMOKE - Google Patents

Description

* * '’1 W I

* * ► · ELKEM METALS COMPANY for

Zinc-rich paints containing manganomanganese pigment oxide smoke.

The present invention relates generally to zinc-rich paints. More specifically, it relates to paints rich in zinc. containing manganomanganic oxide smoke pigmen taire which significantly improves the properties of CD.MdC.4F - 1 - T-125 * * r corrosion resistance of these paints.

Zinc-rich paints are formed from a binder with zinc dust added. The zinc concentration of the solvent-free binder is generally greater than 75% by weight when it constitutes the only pigment. These paints are prepared by mixing zinc dust with optional pigments, a resinous binder, solvent and other known constituents, such as dispersants, stabilizers, etc. The optional pigments must improve the resistance to. corrosion and impart a distinctive, attractive appearance to the paint, both alone and in conjunction with other pigments. In addition, the pigments must be stable so as to retain their color for a long time. Another important criterion is that the pigments must have a very fine particle size, generally less than about 10 μm, for example. The fineness of the particles improves the ability of the pigments to disperse easily in the paint during the preparation thereof and further ensures that the paint can be spread evenly in a thin layer on a surface without streaks or other imperfections and ensures thus uniform protection against corrosion. This last criterion is obviously of the utmost importance when the paint is to be applied by brush or roller in the usual manner.

The Applicant's patent of the same date entitled "Improved Color Pigment for Solvent-Based Paints" describes a solvent-based paint which contains an improved color pigment comprising manganomanganic oxide (M ^ O.) smoke or a material 'containing manganomanganic oxide smoke as the main constituent. The Applicant has discovered that the smoke of Mn3C> 4 used as a colored pigment confers CD.MdC.4F - 2 - T-125 tr a dark reddish brown coloration close but easily discernible from the brown coloration produced by the synthetic pigments of iron oxide, for example yellow, ocher or red pigments of iron oxide and that it has a very fine particle size of the order of approximately 10 / μm, which allows the pigment to be distributed uniformly in the paint .

The smoke of Μη3θ4 according to the invention is most advantageously prepared by passing a stream of oxygen through or over the surface of a molten ferro-manganese bath. Ordinary ferro-manganese produced in the blast furnace or electrometallurgical furnace, among others, at high temperatures of about 1200 ° C or more may contain up to 6% by weight or more of carbon. The carbon content is usually lowered, for example to about 1.5% by blowing oxygen or a mixture of oxygen and air through or against the surface of a molten ferro-manganese bath. This is carried out in a separate container which contains a bath of molten ferro-manganese freshly extracted from the electric oven and at a temperature of about 1000 ° C or more and preferably about 1300eC or more.

A process for lowering the carbon content of molten ferro-manganese is described in the patent of the United States of America of February 21, 1967. According to this preferred process for producing the manganomanganic oxide smoke of the invention, ferro -manganese is transferred from the electric oven where it is made in a treatment container such as a pocket or an oven at a temperature of about 1300eC or higher. Any slag is preferably removed and oxygen is then blown from above to the surface of the molten ferro-manganese bath using any suitable means, such as one or more CD.MdC.4F - 3 - T-125 conventional oxygen lances maintained at approximately 25 mm above the surface to project one or more streams of oxygen under a pressure of approximately 7.6 to 10.3 bar on the surface of the bath. The oxygen flow is approximately 1.82 to 2.27 kg per minute for a 227 kg molten bath in a pocket with a depth of approximately 760 mm and an internal diameter of approximately 500 mm . This technique can be performed on a larger scale, if desired. The resulting burned gas * contains very finely divided particles of spherical manganomanganic oxide smoke which are easily separated from the burnt gas using conventional collecting apparatus.

If desired, the manganomanganic oxide smoke of the invention can be obtained as a by-product of the specific process described in U.S. Patent No. 3,305,352 for lowering the carbon content of the bath of ferro-manganese. In this case, the ferro-manganese bath is at a temperature of around 1250 ° C and oxygen is blown from above at a rate sufficient to bring the bath to a temperature of 1700 ° C before the content carbon content of the molten bath has fallen below 1.5%. The oxygen blowing is continued until the bath temperature reaches approximately 1750 ° C. as described in this patent. Manganese oxide smoke is separated from the burnt gas in the usual way.

By smoke of ^ 304 and smoke of manganomanganic oxide, it is understood for the purposes of the invention the finely divided spherical smoke particles collected during the oxygen blowing of molten ferro-manganese as described above .

The invention therefore has the important aim of providing an improved colored pigment for use in CD.MdC.4F - 4 - T-125 Λ Y ’zinc-rich paints. A more specific object of the invention is to provide an improved zinc rich paint containing manganese oxide smoke which exhibits superior corrosion resistance properties.

These and other objects of the invention and the advantages thereof are achieved with the aid of an improved colored pigment for solvent-based paints which comprises manganese-manganese oxide smoke (Μη3θ4.) or a material containing manganomanganic oxide smoke, as the main constituent, in addition to zinc dust. By "zinc dust" is meant for the purposes of the invention very fine zinc particles with an average particle size of about 2 to 40 / µm. The smoke pigment of Mn3Ü4 - zinc can be used in painting with a resinous binder, a solvent and other constituents, such as pigment thinners, suspending agents, etc. Normally, the smoke pigment of Mn3 < D4 - zinc can form approximately 74 to 96% by weight of the complete paint, on a solvent-free basis. A preferred range is from about 80 to 92% by weight.

The present invention is based on the discovery that manganomanganic oxide smoke or a material containing mainly manganomanganic oxide smoke in the finely divided state gives as a color pigment in solvent-based zinc-rich paints metallic substrates, coatings having corrosion resistance properties superior to those of similar coatings formed only by means of the abovementioned smoke pigments of Mn3O4 or zinc. The degree of corrosion protection offered by the paint depends on the ratio of manganomanganic oxide smoke to zinc.

The smoke from Mn3C> 4 used as pigment CD.MdC.4P - 5 - colored T-125 gives a dark reddish-brown coloration close but easily discernible from the brown coloration produced by pigments, the usual synthetics of iron oxide , for example yellow, ocher or red pigments of iron oxide. The smoke from pigmentary pigments can, moreover, be produced in a certain variety of particle sizes approaching the fine particle size of the usual pigments for paints. This is a very important factor in the preparation of solvent-based paints for various reasons, for example the fineness of the particles improves the suspension properties and allows the pigment to distribute evenly throughout the paint. As a general rule, the smoke of pigmentary Mn3C> 4 should have a particle size such that for approximately 98% its particles have a size less than approximately 10 / μm.

As already indicated, the colored pigment used for the purposes of the invention is formed from manganomanganic oxide smoke or may be a material containing mainly manganomanganic oxide smoke, that is to say more than about 60% by weight. One such material is the aforementioned manganomanganese oxide smoke which is a by-product of the high temperature oxidation that manganese undergoes in electrometallurgical furnaces during the preparation of ferromanganese.

The following are some typical characteristics of the manganomanganic oxide smoke produced as specified above for carrying out the invention:

Chemical formula: Substance ^ 304. Normally 96 to 98% by weight of manganomanganic oxide, the remainder being a mixture which comprises calcium oxide, magnesium oxide, potassium oxide and CD.MdC.4F - 6 - T-125 silica, with less than about 1% by weight of free metallic manganese.

Chemical analysis (normal weight percentage): 65.27 Mn; 2.03 Fe; 0.029 Al? 0.28 Si; 0.17 C? 0.045 As; 0.46 Ca? 1.43 Mg; 0.072 K? 0.023 Cr; and 0.002 bp.

Apparent volumetric mass ; 721-1.442kg / m3.

Humidity; Normally 0.22% (1 hour at 107 ° C). Particle size: 98% below about 10 / µm (passes for 98% with a 0.044 mm mesh screen). pH; 9-13 (50% of Μη0θ4 in distilled H2O).

Form; Spherical.

Volumic mass; 4.6 to 4.75 g / cm3.

Thermal stability; no effect up to 600 ° C.

It is currently recommended in the field of coatings to use colored pigments of very fine particle size in order to improve the coloring efficiency (covering power), the suspension properties and the uniform distribution of the pigment in the paint. The Applicant has discovered that the smoke of Μη3θ4 used as a colored pigment according to the invention must have a particle size such that for approximately 98%, the particles have a size less than approximately 10 / μm. Normally, the smoke of Μη3θ4 collected from electrometallurgical furnaces according to the usual techniques mentioned above may contain approximately 1.0 to 2.0% of particles with a size greater than approximately 10 / μm. Therefore, it may be desirable and sometimes even necessary to remove these larger particles from the smoke of Μη3θ4 · This operation can be performed, for example, according to the usual techniques of classification or else according to impact techniques, by example * by ball milling. Manganese oxide smoke which has been classified or ground to a particle size such that for approximately 98% its particles CD.MdC.4F - 7 - T-125 have a size less than approximately 10 / μm can be dispersed easily in painting with the aid of an apparatus exerting a medium shear, for example a Cowles dissolver. The paints containing smoke of Μηβ de4 of this particle size range can generally be applied to the surface envisaged without any streaks or other imperfections appearing.

The solvent-based paint according to the invention can be prepared using almost any commercial grade zinc dust, for example zinc dust L-15 from the company Federated Metals. This zinc dust has an average particle size of about 5 µm.

Typical solvent-rich zinc-based paints which contain smoke of pigmented colored Mn3 <34 according to the invention have the following constitution:

Constituents Value Preferred normal value (% by weight) (% by weight) A. Softwood binder 4-25 8-20 B. Zinc dust 43-90 47-68 C. Smoke of Mn3O4 3-38 20-36 pigment D. Other pigments, in particular pigment thinners, fillers, etc. 0-35 1-15 E. Pigment suspending agent 0-5 0.5-3 F. Solvent * * * In an amount which gives the viscosity desired for the application.

The solvent-based paint containing a CD.MdC.4F - 8 - T-125 smoke of pigment colored Μ1Ί3Ο4 according to the invention can be prepared according to the usual techniques known to the specialist. For example, the paint can be prepared by mixing the resinous binder with the smoke of Μη3θ4, zinc dust, the other pigments and the agents for suspending the pigments, in addition to the solvent. A medium shear dispersion apparatus is suitable for this purpose, for example a Cowles dissolver. Such an apparatus consists of a vertical shaft carrying at its lower end a sawtooth agitator member. Under the effect of the rotation, the agitating member gives a high speed to the mixture of liquid and pigment and thus exerts a. shear. Another device, for example a ball mill, can be used with the same success, as is obvious to the specialist.

The binder used in the paint according to the invention may be any of the many known resins in common use for this purpose in the paint industry. As a general rule, the binder is chosen from one of four groups: (1) reactive binders, such as epoxy resins derived from bisphenol A and from epichlorohydrin which are hardened by polyamines, such as polyaminoamides, diethylenetriamine, triethylenetretramine or the tar or coal amines; (2) drying binders such as those resulting from the reaction of the diglycidyl ether of bisphenol A and fatty acids from vegetable oil; (3) binders soluble in organic medium which harden by evaporation of the solvent, such as the polyhydroxyl ether of Bisphenol A from Bisphenol A and epichlorohydrin (Phenoxy PKHH); and (4) binders in common use in moisture-curing systems, such as alkyl silicates prepared by hydrolysis or polymerization of CD.MdC.4F - 9 - T-125 tetraethyl alcohol alcohol and a glycol. Typical epoxy resins hardened by polyaminoamide which are suitable as binders are those sold under the name Epon 1001-CX75 (Shell Chemical Company) which is a condensation product of epichlorohydrin and Bisphenol A. This resin has an equivalent weight of epoxide of 450 to 550 g per gram equivalent of epoxide (ASTM D-1652) and is presented at 75% solids in a methylisobutylketone / xylene mixture in a 65/35 ratio. Suitable hardeners which can be used with this resin are sold under the trademark Versamid 415 (General Mills Company). These hardeners are reactive polyaminoamides based on polymerized vegetable fatty acids. They have an amine index of 230 to 246 mgKOH equivalent to the basic nitrogen content per gram of sample and a viscosity of approximately 31-38 poises (3.1-3.8 Pa.s) at 75 ° C . Esters of epoxy resin suitable as binders for drying systems by oxidation are those sold under the brand Epotuf 38-403 (Reichhold Company

Chemical). Polymerized ethyl silicate is a good example of a binder that is suitable for a moisture-cured system. Binders soluble in organic medium, which dry by evaporation of the solvent, are the polyhyroxylated ethers derived from Bisphenol A and from epichlorohydrin and sold under the name of "phenoxy resins" by the Union Carbide Corporation.

Other suitable organic soluble binders which can be used in paint are, for example, high molecular weight epoxy resins, alkyd resins, polyesters, chlorinated rubber and copolymers of vinyl chloride and vinyl chloride. vinyl acetate bearing or not functional hydroxyl or carboxyl radicals.

The mixture of manganomanganic oxide smoke CD.MdC.4F - 10 - T-125 * and pigmentary zinc dust can be used in the paint of the invention, either alone or with other conventional colored pigments, pigment diluents , fillers and corrosion inhibitors. For example, the pigment smoke of ^ 3 () 4 can be used with conventional TiO2i pigments as well as with different varieties of iron oxide pigments, for example red or yellow iron oxides. Different pigment diluents can also be used, such as talc, clays (hydrated aluminum silicate), diatomaceous earth and silica. Talc sold under the registered trademark Nytal 300 (RT Vanderbilt Company) is a good example of a pigment thinner suitable for painting. In addition, other corrosion inhibiting pigments such as zinc chromate, for example, can also be used in painting.

A pigment suspending agent can also be used. Typical suspending agents for paint are those sold under the trademark Bentone 27 (Company NL Industries), which is an organic derivative of hydrated aluminum silicate and magnesium, of Kelecine F (Company Spencer Kellog), which is a lecithin, and from Nuosperse (Company Tenneco Chemical Co.).

The solvent used in the paint of the invention may be any of the various solvents and solvent mixtures in common use for solvent-based paints. Suitable solvents and solvent mixtures which can be used are, for example, ketones, such as methyl isobutyl ketone, aromatic hydrocarbons and mixtures of ketones and aromatic hydrocarbons. Typical suitable aromatic solvents are xylene and toluene. Another commonly used aromatic solvent is CD.MdC.4F - 11 - T-125 that based on diethylbenzene sold under the name of SC-100 (Company Exxon). Other suitable solvents commercially available are those sold under the registered trademarks Cellosolve (monoethylene ethylene glycol ether) and Cellosolve acetate (monoethylene ethylene glycol ether acetate) from the Union Carbide Corporation. Cellosolve acetate is particularly recommended as a solvent for systems containing phenoxy resin, as described above. Likewise, when the binder soluble in organic medium is an alfcyde resin, the petroleum distillation mineral oil is of general use. Likewise, when the binder is a chlorinated rubber, toluene and xylene are good solvents. Other solvents suitable for these binders are in particular ketones and / or mixtures of ketones. Another solvent which can also be used in paint is a mixture of one third of xylene, one third of methyl isobutyl ketone and one third of Cellosolve.

The paints in accordance with the invention may also comprise other constituents of usual use in solvent-based paints which are known. For example, the properties of the applied layer can be improved using various additives. Commercial products suitable for this purpose are in particular that sold under the registered trademark Beetle 216-8 (American Cyanamid Company) which is a urea resin in 60% solution in butanol / xylene and the ethanol that it is recommendable to use with the Bentone 27 suspending agent. A viscosity regulating agent, such as diatomaceous earth, can also be added to the paint, for example that sold under the trademark Celite (Johns Manville Company ). Other constituents which can be used are the anti-bubble agents and CD.MdC.4F - 12 - T-125 water fixing agents, such as that sold under the registered trademark Syloid ZN-1 (Company WR Grâce) which is a gel of silica. Anti-skinning agents can also be used, for example that sold under the registered trademark Ex-Kin No. 2 (Société Tenneco Chemical Company).

The following examples further illustrate the invention.

EXAMPLE 1.-

A solvent-based paint is prepared by mixing together 120.0 g of Phenoxy PKHH (Union Carbide Corporation); 30 g of Phenolic BKR-2620 (Union Carbide Corporation); 1.1 g of suspending agent, namely MPA-60 (Company NL Industries); 1.1 g of suspending agent, namely Silanox 101 (Company Cabot Corporation), which is a silane pyrogenic silica and 170 g of zinc dust "Zinc Dust L-15" (Company Federated Metals). Phenoxy PKHH and Phenolic BKR-2620 are dissolved in Cellosolve acetate (Union Carbide Corporation) at 21% solids. The mixture is homogenized carefully in a Cowles dissolver for a sufficient time so that all the constituents are uniformly dispersed in the paint. The solids content of the paint is 84% on a weight basis and 48% on a volume basis. This painting is used as a witness for a series of experiments.

This paint is applied to a number of bare cold-rolled steel specimens of approximately 100 mm x 150 mm. The applied layer is baked at about 177 ° C for about 15 minutes. The thickness of the layer is measured, the average value of which turns out to be approximately 18 μm. The test pieces * are subjected to a salt spray corrosion test

in accordance with ASTM B-117-73 and the condition of the test pieces is assessed as indicated in the ASTM standards

CD.MdC.4F - 13 - T-125 (D714-56, D610-68).

EXAMPLE 2.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 1 / but by replacing the 179 g of zinc dust with 118 g of pigment Μη3θ4 smoke. The solids content of this paint turns out to be 78% on a weight basis and 48% on a volume basis. The paint is applied to cold-rolled steel test pieces by operating as in Example 1, the average thickness of the layer appearing to be 15 μm. The test pieces are subjected to the same salt spray corrosion test and evaluated according to the same ASTM standard.

EXAMPLE 3.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 2, but using a larger amount of pigmentary Mn3O4 smoke, in this case 147.5 g. This paint is found to have a solids content of 82% on a weight basis and 53% on a volume basis. The paint is applied to similar test pieces made of cold-rolled steel, operating as in Example 1, the thickness of the layer appearing to be 18 µm. The test pieces are subjected to the same corrosion test by salt spraying and evaluated according to the same ASTM standard.

EXAMPLE 4.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 3, but using a larger amount of pigment Μη3θ4 smoke, in this case 162.0 g. The paint is found to have a solids content of approximately 83% on a weight basis and 56% on CD.MdC. 4F - 14 - T-125 volume basis. The paint is applied to similar test pieces made of cold-rolled steel, operating as in Example 1, the average thickness of the layer appearing to be 20 µm. The test pieces were subjected to the same corrosion test by salt spraying and evaluated according to the same ASTM standard.

EXAMPLE 5.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 2, but using a larger amount of pigment Μη3θ4 smoke, in this case 177 g. The paint is found to have a solids content of 84% on a weight basis and 58% on a volume basis. The paint is applied to test pieces made of cold-rolled steel, operating as described in Example 1, the average thickness of the layer appearing to be 20 µm. The test pieces are subjected to the same corrosion test by salt spraying and evaluated according to the same ASTM standard.

EXAMPLE 6.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 1, but using a smaller amount of zinc dust, in this case 89.5 g in combination with 59 , 0 g of smoke from Μη3θ4 · The paint turns out to have a solids content of 82% on a weight basis and 48% on a volume basis. The volume ratio of Μηβθ4 smoke to zinc dust is approximately 1: 1. The paint is applied to test pieces made of cold-rolled steel, operating as described in Example 1, the thickness of the layer appearing to be 18 µm. The test pieces are subjected to the same corrosion test CD.MdC.4F - 15 - T-125 by spraying with salt and they are evaluated according to the same ASTM standard.

EXAMPLE 7.-

A solvent-based paint is prepared using the same constituents as those of the paint of Example 6, but using a smaller amount of smoke of Mn3C> 4, in this case 39 g, in combination with a larger amount, in this case 119 g, of zinc dust. The volume ratio of Μη3θ4 smoke to zinc dust in this case is about 1: 2. The paint is found to have a solids content of 83% on a weight basis and 48% on a volume basis. The paint is applied to test pieces made of cold-rolled steel, operating as in Example 1, the average thickness of the layer appearing to be 18 µm. The test pieces are subjected to the same corrosion test by salt spraying and evaluated according to the same ASTM standard.

The results of the salt spray corrosion tests of Examples 1-7 are collated in the table below.

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It appears from the results of the table that the paint of Example 2 containing 48% by volume of smoke of pigmented MnjC ^ exhibits a corrosion resistance approximately equal to that of the paint containing the same volume percentage of zinc dust up to '' about 260 hours of testing. It should however be remembered that paints containing zinc dust, as a corrosion-inhibiting pigment, are well known for their high performance under the conditions of the salt spray test and have therefore been chosen mainly as a witness. It should also be noted that increasing the amount of smoke of Mn3C> 4 beyond 118 g or 48% by volume does not improve the corrosion resistance offered by the paint, but on the contrary greatly reduces the ability of the pigment to prevent corrosion. Finally, it appears from the table that the results are surprisingly superior to those of the control paint when the smoke of Μη3θ4 is combined with the zinc dust and moreover that this improvement persists throughout the duration of the test, namely 360 hours. . The effectiveness of the anticorrosive power of the smoke of ^ 3 () 4 in a paint rich in zinc depends most often on the volume ratio of the smoke of

Mn3Û4 with zinc dust. The best results are obtained when this ratio is maintained at a value of approximately 1: 1 by volume.

The coatings based on phenoxy resin pigmented with manganomanganic oxide and zinc which the table relates to were examined by a scanning electron microscope for the comparison of surface conditions, in order to determine the mechanism of “protection exercised in these systems.

After exposure of 100 hours to the spraying of salt, the zinc particles of Example 1 are CD.MdC.4F - 19 - T-125 covered with crystalline corrosion products which tend to clog the pores of the coating and thus protect the substrate. On the other hand, the smoke of Mn3O4 from Example 2 appears to be eroded. Its corrosion products are however probably capable of forming a passivating deposit on the surface of the steel.

The protective effect of the combination of Μη3θ4 smoke and zinc dust appears to be due to the formation of one or more new compounds during exposure to the salt spray. The crystalline corrosion products formed are different from those produced by zinc or the smoke of Μη3θ4 during salt spraying. The formation of these new products probably decreases the rate of penetration of corrosion by salt due to a very tight stack. Hexagonal plates are clearly visible.

CD.MdC.4F - 20 - T-125

Claims (16)

1. Improved paint which mainly contains a resinous binder, a colored pigment and a solvent and which shows an improvement in the corrosion resistance properties, characterized in that it comprises finely divided zinc particles and a colored pigment formed from particles finely divided manganomanganic oxide smoke. 2. Painting according to claim 1, characterized in that the colored pigment of manganomanganic oxide is smoke of Μηβθ4 having the following properties: j. (a) a chemical composition such that the pigment does not contain less than 96% by weight of manganomanganic oxide, the remainder being a mixture comprising calcium oxide, magnesium oxide, potassium and silica, with less than 1% by weight of free metallic manganese, and (b) a particle size for 98% of less than about 10 / µm. 3. Painting, characterized in that it comprises approximately 4 to 25% by weight of a resinous binder; about 43 to 90% by weight of zinc dust? about 3 to 38% by weight of pigmentary Mn3O4 smoke; about 0 to 35% by weight of optional pigments, in particular of. pigment thinners and fillers; about 0 to 5% by weight of a pigment suspending agent and for the remainder a solvent in an amount necessary for a viscosity allowing the application. 4. Paint according to claim 3, characterized in that it contains approximately 8 to 20% by weight of a resinous binder. 5. A paint according to claim 3, characterized in that it contains 47 to 68% by weight CD.MdC.4F - 21 - T-125 ♦ 4 ”of zinc dust. 6. Paint according to claim 3, characterized in that it contains 20 to 36% by weight of Μη3θ4 · 7. Paint according to claim 3, characterized in that it contains approximately 1 to 15% by weight of optional pigments, in particular pigment diluents and fillers. 8. Paint according to claim 3, k characterized in that it contains approximately 0.5 to 3% by weight of a pigment suspending agent. 9. Painting according to claim 3, * characterized in that the binder is an epoxy resin derived from Bisphenol A and epichlorohydrin, which is m cured by means of a polyamine chosen from polyaminoamides, diethylenetriamine, triethylene- tetramine and the tar and coal amines. 10. Paint according to claim 3, characterized in that the binder is a drying resin resulting from the reaction of the diglycidyl ether of Bisphenol A with fatty acids from vegetable oils. 11. Painting according to claim 3, characterized in that the binder is a resin soluble in organic medium comprising a polyhydroxyl ether of Bisphenol A from Bisphenol A and epichlorohydrin. 12. Paint according to claim 3, characterized in that the resinous binder is an alkyl silicate prepared by hydrolysis or polymerization of tetraethyl silicate, an alcohol and a glycol. 13. Paint according to claim 3, Λ characterized in that the solvent is chosen from »ketones, aromatic solvents and mixtures of ketones and aromatic solvents. 14. Painting according to claim 3, CD.MdC.4F - 22 - T-125 β r characterized in that it contains an additive improving the properties of the layer which comprises a urea resin or ethanol. 15. Paint according to claim 3, characterized in that it also contains a viscosity regulating agent. 16. Paint according to claim 3, characterized in that it also contains an anti-bubble agent or a water-capturing agent. 4 Λ CD.MdC.4F - 23 - T-125