MXPA98001566A - Powder lacquer and its use for inner coating of env containers - Google Patents

Abstract

The present invention relates to a powder coating based on epoxy resins and phenolic hardeners, in particular for the internal coating of container container, and contains: 1) at least one epoxy resin with an epoxide equivalent weight of between 300 and 5500 and at least one hardener with more than one phenolic hydroxyl group per molecule, and an equivalent hydroxyl weight, relative to the phenolic OH groups, of between 100 and 500, the powder coating having a grain size distribution such that: a) at least 90% by mass of the powder coating particles have a particle size between 1 and 60æm, b) the maximum particle size of the powder coating particles at least 99% by mass of the particles is < - 1000m; c) the average particle size of the powder coating particles is between 5 and 20æm and d) the inclination of the grain distribution curve at the inflection point is > -100; and 2) a lubricant, preferably in an amount of < - 2% in pe

Description

POWDER LACQUER AND ITS USE FOR INTERNAL COATING OF PACKAGING CONTAINERS Object of the present invention are powder lacquers, in particular for internal coating of container containers, based on epoxy resins and phenolic hardeners, and a process for their manufacture. The present invention also relates to a method for the internal coating of container containers as well as to the use of powder coating materials. Packaging containers, such as, for example, canisters, two- or three-component beverage cans and the like, are provided with a coating on the interior, on the one hand to protect the contents from deterioration due to the constituents of the container. sheet metal that dissolves, and on the other hand, to avoid corrosion of sheet metal by aggressive contents. In practice, the container containers are coated in this way mainly by means of organically dissolved lacquers. However, this results in increased pollution of the environment by the solvents during the drying of the coating films. Therefore, more and more tests have been carried out to replace these lacquers with lacquers with little or no solvent. Thus, for example, thermoplastic powder lacquers are often already used to cover can seams. These products are produced from the corresponding thermoplastics by expensive cold crushing. EP-B-119164 discloses thermosetting powder coatings for covering welding seams of metal containers used to hold food or drinks. These thermoset powder coatings comprise, as a binder, a mixture of an aromatic epoxy resin having on average no more than 2 epoxide groups per molecule and an aromatic epoxy resin having on average more than 2 epoxy groups per molecule. The condensation product of diglycidyl ether of bisphenol A with bisphenol A, having an equivalent weight, based on phenolic hydroxyl groups, of 220 to 280 or an acidic polyester or a mixture thereof is used as hardener. These powder coatings are used only to cover the welding seams of the container containers. The document EP-B-119169 does not contain nor indications of use of these powder coatings for internal coating of container containers, nor indications of how these powder coatings should be modified for use as internal protective lacquers. In particular, EP-B-119 164 does not contain information on particle sizes and particle size distributions of powder coating materials. However, the use of these powder coatings of EP-B-119 164 with a customary particle size distribution for powder coatings leads to coatings having too high a porosity at low coating thicknesses of < 15 μm usual for internal coating finishes. Furthermore, DE-PS 23 12 409 discloses thermosetting solvent-containing and solvent-free coating agents for coating bodies for cars, machinery, installations and containers, comprising an epoxy resin having more than one group 1, 2-epoxide per molecule and a polyol having more than one phenolic OH group per molecule as well as other usual adjuvants and additives. For the manufacture of automotive top coatings, according to DE-PS 23 12 409, a powder coating having a particle size of not more than 0.044 mm is applied in a dry film thickness of 25 μm. Neither the size of the particles nor the size distribution of the powder coating particles is indicated for powder coatings which are suitable for the production of internal lacquers on container containers. Nor does DE-PS 23 12 409 contain any indication that the size of the particles and the particle size distribution should be specifically adjusted according to the intended use of the powder coatings. However, powder coatings having a maximum particle size of 44 μm and a conventional particle size distribution are not suitable for the manufacture of internal coatings for container containers in the conventional low coating thickness of <; 15 μm, since the resulting coatings have a too high porosity. In addition, powder lacquers for cans can be internally covered by US Pat. No. 3,962,486 which comprises an epoxy resin and a hardener. Catalytic hardeners, aromatic amines, epoxy-amine adducts and acid anhydrides are mentioned as typical hardeners in US Pat. No. 3,962,486 while phenolic hardeners are not mentioned. Coatings that meet the requirements normally imposed on internal coatings of food containers even with low coating thicknesses of less than 13 μm can be produced using the plasma spray coating process. To ensure that the application by means of the plasma spray process is possible, only powder coatings having a maximum particle size of < 100 μm and a sufficiently low melt viscosity. However, the particle size distribution of the powder coating materials used is not characterized in more detail in US Pat. No. 3,962,486. One drawback of the powder coatings described in 3,962,486 is the inadequate resistance of the resultant lacquers to sterilization due to the use of aminic hardeners. There is additionally the disadvantage that epoxy resins hardened with amines tend to become brittle and have very poor elasticities. The hardeners of acid anhydride have the drawback that they are very irritating, and therefore require special safety precautions during the formulation of the powder coating materials. Furthermore, US Pat. No. 4,183,974 discloses powder coatings for internal coating of cans, which on the other hand comprise an epoxy resin and an amine hardener. These powder coatings have average particle sizes between 1 and 100 μm, preferably between 1 and 10 μm. Although the resulting coatings already have the required low porosity at coatings thicknesses of < 13 μm, however it is necessary to improve the resistance of the resulting coatings for sterilization. There is additionally the drawback that the epoxy resins hardened with amines tend to become brittle and have very poor elasticities. Furthermore, German patent application P 40 38 681.3 discloses powders which are based on epoxy resins and which, after suitable adjustment of the particle size distribution of the powder coating, are suitable for both internal coating of container containers as to cover weld seams. These powder coatings contain, as hardeners, polyesters containing carboxyl groups. The use of hardeners is not described in this patent application. Finally, powder coatings based on epoxy resins and phenolic hardeners are known. Lacquers of this type are suitable for coating container containers. However, the properties are still not considered satisfactory, in particular with respect to flexibility, coating transparency and processing speed. The present invention is then based on the object of providing powder coatings that meet the requirements normally imposed on internal coatings for cans, even when applying low coating thicknesses of < 15 μm, when said powder lacquers are used for internal lining of container containers. In particular, these internal coatings should not be porous (determined with the help of the so-called rater enamel test), they should represent good adhesion to the substrate, they should have a high elasticity, and they should be stable under the usual pasteurization and sterilization conditions. . The powder coatings should be hardenable in this case during the usual short drying times for the coating of cans. This object is achieved, surprisingly, by a powder coating based on epoxy resins and phenolic hardeners, in particular, for internal coating of container containers, comprising 1. ) at least one epoxy resin having an epoxide equivalent weight of 300 to 5500 and at least one hardener having more than one phenolic hydroxyl group per molecule and one hydroxyl equivalent weight, based on the phenolic OH groups, of 100 to 500, wherein the powder coating has a particle size distribution so that a) at least 90 weight percent of the particles of the powder coating have a particle size between 1 to 60 μm. b) the maximum particle size of at least 99 weight percent of the powder coating particles is < 100 μm, c) the average particle size of the powder coating is between 5 to 20 μm and d) the gradient of the distribution curve of the particles at the inflection point is > 100. and 2) a lubricant, preferably in an amount of < 2% by weight. Furthermore, object of the invention are methods for the internal coating of container containers, in which powder coating materials are applied. Finally, object of the invention is also the use of powder coating materials for internal coating of container containers. It is surprising, and it was not foreseeable that the profile of the properties and hence the intended use of the powder coatings based on epoxy resins and phenolic hardeners and lubricants could be specifically controlled by establishing a specific particle size distribution. The powder coatings according to the invention can also be cured quickly, are easy to process and are easy to apply, have a good processing speed, good flexibility and transparency after coating. Additionally, the powder coatings according to the invention are characterized by the fact that the coatings having only very low coating thicknesses of < 15 μm have the properties required for internal lacquers by can manufacturers. In particular, these coatings have the required low porosity even with a low layer thickness of < 15 μm. Additionally, these lacquers are characterized by good adhesion, high flexibility and good resistance to pasteurization and sterilization. The individual components of the powder coating materials according to the invention will now be explained in more detail in the following. The epoxy resins used in the powder lacquers according to the invention are solid epoxy resins having an epoxy equivalent weight of 300 to 5500. The aromatic, aliphatic and / or cycloaliphatic epoxy resins are suitable. The aromatic epoxy resins based on bisphenol A and / or bisphenol F and / or epoxy resins of the Novolak type are preferably used. Epoxy resins based on bisphenol A or bisphenol F which are particularly preferably used have an epoxide equivalent weight of 500 to 2000. Novolak-type epoxy resins which are particularly preferably used have an epoxide equivalent weight of 500 to 1000. Epoxy resins based on bisphenol A or bisphenol F generally have a maximum functionality of 2, and Novolak type epoxy resins have a general functionality of at least 2. However, epoxy resins based on Bisphenol A or bisphenol F can also be carried to a functionality of more than 2 by branching, for example, by means of trimethylolpropane, glycerin, pentaerythritol or other branching reagents. Of course, other epoxy resins may also be employed, such as, for example, alkylene glycol diglycidyl ethers or branched side products thereof, epoxy resins based on bisphenol A or F which have become flexible with alkylene glycols or the like. Mixtures of several of the aforementioned epoxy resins are also suitable additionally. Suitable epoxy resins are, for example, the products obtained commercially under the following names: Epikote® 154, 1001, 1002, 1055, 1004, 1007, 1009 and 3003-4F-10 from Shell-Chemie, XZ 86 795 and DER® 664, 667, 669, 662, 642U and 672U from Dow, and Araldit®, GT 6064, GT 7072, GT 7203, GT 7004, GT 7304, GT 7097 and GT 7220 from Ciba Geigy. The epoxy resins approved by FDA are used here preferably. Suitable hardening components are all solid compounds having more than one phenolic OH group, preferably 1.8 to 4, particularly preferred <; 3, especially preferably from 1.8 to 2.2 phenolic OH groups per molecule, and an equivalent weight of hydroxyl, based on phenolic OH groups, of from 100 to 500, preferably from 200 to 300. The hardeners based on bisphenol A and / or bisphenol F are preferably used as hardeners. The condensation product of the diglycidyl ether of bisphenol A or bisphenol F, in particular the condensation product having an equivalent weight, based on phenolic hydroxyl groups, from 220 to 280, is particularly preferred as a hardener. These condensation products are usually prepared by the reaction of bisphenol generally in excess with a bisphenol diglycidyl ether in the presence of a suitable catalyst. The condensation product is preferably prepared by the reaction of diglycidyl ether with bisphenol in a weight ratio of 0.5 to 2. These hardeners based on said condensation products of bisphenol diglycidyl ether with a bisphenol generally have a maximum functionality. 2, being possible to establish higher functionalities using branching reagents. Additionally, the reaction products of bisphenols with Novolak-type epoxy resins are also suitable as hardeners. These hardeners are preferably obtained by the reaction of the epoxy resin with the bisphenol in a weight ratio of 0.5 to 2 in the presence of a suitable catalyst. For example, the phenolic hardeners described in DE-PS-23 12 409 are suitable in column 5, line 2 to column 6, line 55. These polyphenols correspond to the following general formulas: wherein A is a divalent hydrocarbon residue having from 1 to 6 C atoms or the residues or or II -C- -o-, -s-, -s-s-, -s-, or -s- II II O or X is a hydrogen or alkyl having 1 to 4 C atoms adopts a mean value of 1 to 9, preferably 2 to 7, and adopts a value of 0 or 1. In addition, the phenolic hardeners described in DE-OS-30 27 140 can also be used. Of course, hardeners modified with flexible branching agents and / or hardeners are also suitable. . Mixtures of several of the aforementioned hardeners can also be used. The hardeners approved by FDA are preferably used here. The epoxy resin component is normally used in the powder coatings according to the invention in an amount of 29 to 80% by weight, preferably 39 to 60% by weight, in each case based on the total weight of the paint in dust. The hardener component is normally used in the powder coatings according to the invention in an amount of 10 to 50% by weight, preferably 15 to 40% by weight, in each case based on the total weight of the powder coating. The powder lacquers according to the invention contain, as a further component, at least one hardening catalyst, usually in an amount of 0.01 to 5.0% by weight, preferably 0.05 to 2.0% by weight. weight, in each case based on the total weight of the powder coating. The catalyst is more advantageously imidazole, 2-methylimidazole, ethyltriphenylphosphonium chloride or another salt thereof, a quinoline derivative, as described, for example, in EP-B-10805, a primary, secondary, tertiary aminophenol, acetylacetonate. of aluminum or a salt of toluenesulfonic acid, or a mixture of several of the catalysts mentioned. Commercially available hardeners containing hydroxyl groups normally already comprise a hardening catalyst. Examples of such commercially available hardeners containing hydroxyl groups that are preferably used are the products commercially available under the following names: DEH® 81, DEH® 82 and DEH® 84 from Dow, Hardener XB 3082 from Ciba Geigy and Epikure® 169 and 171 of Shell-Chemie. The powder coating materials according to the invention can additionally comprise from 0 to 55% by weight, preferably from 15 to 25% by weight, of fillers. Preferably, filler substances approved by FDA are used.

Inorganic fillers, for example, titanium dioxide, are used in general, such as, for example, Kronos 2160 from Kronos Titan, Rutil R 902 from Du Pont and RC 566 from Sachtleben, barium sulfate and silicate-based filler, such as, for example, talc, kaolin, magnesium aluminum silicates, mica and the like. Titanium dioxide and quartz sand-type fillers are preferably used. The powder coatings according to the invention may additionally comprise, if appropriate, from 0.01 to 10% by weight, preferably from 0.1 to 2% by weight, based on the total weight of the powder coating of other auxiliaries and additives. Examples thereof are leveling agents, flow aids, deaeration agents, such as, for example, benzoin, pigments and the like. For use for the inner lining of container containers, the particle size distribution is adjusted so that at least 90 percent by weight of the powder coating particles have a particle size of between 1 and 60 μm, ie d 90 = 1 to 60 μm. Preferably, 90 percent by weight of the particles of the powder coating have a particle size between 1 and 40 μm (d 90 = 1 to 40 μm), and particularly, preferably between 5 and μi (d 90 = 5 to 25 μm). The maximum particle size of the powder coating for at least 99 percent by weight of the particles is <; 100 μm, preferably < 60 μm and particularly, preferably < 40 μm). The average size of the powder coating particles is between 5 to 20 μm, particularly, preferably between 5 to 12 μm. It is further essential with respect to the invention that, when powdered lacquers are used for the inner lining of container containers, the particle size distribution is adjusted such that the gradient S of the particle distribution curve in the turning point is > 100, preferably, > 150 and particularly, preferably > 200. To achieve coatings having particularly good properties, powder coatings in which the gradient S of the particle size distribution curve at the inflection point is > 300 are used especially preferably. The gradient S is defined here as the limit value for f (x2) - f (P that tends to zero from (f (x2) - f (x1)) / log ((x2 / x1)) at the inflection point of The distribution curve of the particles The distribution curve of the particles represents in this case the graph of the cumulative percentages by weight (f (x)) against the absolute particle diameter (x), the particle diameter being represented a logarithmic scale and the cumulative percentages by weight on a linear scale For use as an inner liner of container containers, powder lakes having only a very low proportion of very fine particles (particle size <) are therefore especially suitable. 5 μm) as well as at the same time only a very low proportion of coarse powder particles (particle size> 25 μm), that is, they have a particle size distribution as narrow as possible. e) The adjustment of the respective particle size distribution of the powder coating materials is carried out with suitable grinding equipment, optionally in combination with suitable selection and screening devices, for example, with fluidized bed counter-current mills ( AFG) of Alpine, Augsburg, in combination with extra fine Turboplex selectors from Alpine, Augsburg. Also essential with respect to the invention is the addition of lubricant. This lubricant is added, according to the invention, in amounts of less than 2% by weight. Additions of less than 1% by weight are preferred. The optimum tested range is 0.1 to 0.6% by weight. The lubricants use polypropylene waxes, modified polyethylene waxes, and acid amides. According to the invention, the propylene waxes are preferably used in micronized form. Waxes of this type can be obtained commercially, among others, under the designation Hoechst-Wachs pp. 230, Hoechst-achs C, Hoechst-Wachs C Mikropulver PM and Hoechst-Wachs R 31. Polyethylene waxes are, as a rule, waxes modified with polytetrafluoroethylene. These can be obtained commercially, among others, under the designations Hoechst-Wachs PED 121, 191, 136, 153, 261, 521, 522, and also Hostalup H 12 and Hostalup H 22. The acid amides that can be used in accordance with the invention include, above all, aric acid amide and oleic acid amide.

By adding the lubricants according to the invention unexpected surprising properties are achieved, especially when the powder coating materials are used for the inner coating of container containers. The lacquers obtained are, in particular, very flexible and resistant to superficial scratches. The corrosion protection properties are also improved. Finally, the material according to the invention, as a coating, exhibits excellent transparency. It is possible, additionally, to achieve a crosslinking between 10 seconds and several minutes at temperatures between 21 and 350 ° C. The production of the powder coating materials is carried out according to known methods (compare, for example, product information from BASF Lacke + Farben AG, "Pulverlacke", 1990) by homogenization and dispersion, for example, by means of an extruder. , mixer of screws and similar. It is essential with respect to the invention that, after their preparation, the powder coatings are adjusted by grinding and, if appropriate, by selection and screening to a particle size distribution suitable for the intended use.

According to the invention, the lubricant is preferably extruded and milled together with the powder coating material. By means of this method according to the invention, particularly good properties profiles can be obtained. After trituration, selection and application can be carried out, if desired, by means of crown or triboelectric charging installations. The result of a powder coating that has been prepared and applied in the manner described is a surprisingly high matte color, surface hardness, flexibility and adhesion improvement. The container containers that are coated with the powder coatings according to the invention can be manufactured from the most diverse materials, can have the most diverse sizes and configurations and can be produced according to various processes. However, in particular, the metal containers are coated with powder coatings according to the invention. These metal containers can be produced, first, by laminating the metal into sheets and then joining it by folding the edge back. The end pieces can then be fixed to the cylinder formed in this way. The powder lacquers according to the invention are used for internal coating of the housings of the can, which in general already have a base. The deep-drawn metal containers can also be additionally coated on the inner part with the powder coating materials according to the invention. However, powdered lacquers are, of course, also suitable for coating can lids and can bases. The container containers can be made of the most diverse materials, such as, for example, aluminum, black sheet, tin foil and various tin alloys and various iron alloys, which are provided, if appropriate, with a passivation layer. based on nickel, chromium and tin compounds. Containers of this type are commonly used as containers for food and beverages, for example, for beer, juices, carbonated beverages, soups, vegetables, meat dishes, fish and vegetable dishes, but also, for example, for animal feed. . The application is carried out according to known methods, such as are described, for example, in US Pat. No. 4,183,974. The electrostatic charge of the particles of the powder coating material is effected in this case by friction (triboelectricity). The application of the powder coating particles is carried out with the aid of special spray heads known to those skilled in the art. The powder coating materials according to the invention can also be applied, of course, according to the known electrostatic assistance method. For the inner lining of container containers, the powder coatings are normally applied in a layer thickness of <; 15 μm, preferably 10 to 14 μm. Even at these reduced layer thicknesses, the coatings meet the requirements normally imposed on films of this type. However, powder coatings can also be applied, of course, to higher coating thicknesses. The container container, the interior of which has been provided with the powder coating material according to the invention, is then subjected to a heat treatment for hardening the powder coating. This heat treatment can be carried out in several ways. In practice, the containers are often transported through a circulation oven for this purpose. The powder coatings in this case generally harden completely at an object temperature of between 230 and 350 ° C within a period of 5 to 30 seconds. In this case, the circulation oven can operate at a constant temperature, or it can have a temperature profile that is adjusted to the particular circumstances. The invention will now be described in more detail with the aid of working examples. All data on parts and percentages are in this case data by weight, unless otherwise expressly indicated. The powder coating is manufactured in each case by weighing all the constituents in cans, pre-mixing them in a pre-mixer, homogenizing the mixture from 60 ° to 80 ° C by means of an extruder, cooling it as quickly as possible and adjusting it to the Desired particle size distribution with crushing equipment.

Example 1 The following components were processed to obtain powder coating 1: 580 parts epoxidized novolak resin commercially available with an EEW of 500 (commercial product D.E.R® 642U from Dow), 270 parts of commercially available hardener containing OH groups, based on bisphenol A with a hydroxyl equivalent weight of 250 (commercial product D.E.H® 82 from Dow), parts of commercially available leveling agent based on an ionic acrylate, 143 parts of filler substance based on finely divided silicate of the quartz sand type and 2 parts auxiliary fluidizing agent based on pyrogenic silicic acid or aluminum oxide.

This powder mixture is extruded and milled together with erucic acid amide. In two experiments, an amount of 0.2% by weight and 0.5% by weight was added. Using grinding equipment, the particle size distribution was adjusted so that at least 90% by weight of the powder lacquer particles have a particle size between 1 and 25 μm. (d 90 = 1 to 25 μm). The maximum particle size of at least 99 percent by weight of the particles is < 100 μm, and the average particle size is 9 μm. The gradient S at the inflection point of the distribution curve of the particles is 250. 10 panels of white sheet were coated by means of corona charging with a) powder coating containing 0.2% erucic acid amide, b) powder lacquer containing 0.5% erucic acid amide, and the lacquer was cross-linked for 3 minutes in an oven at 220 ° C. From the panels, the club cans, that is, fish canning cans, were stamped and sterilized for one and a half hours at 128 ° C. The media tested were: - water, - 2% lactic acid solution, and - 3% acetic acid solution. The result shows that the powder lacquer without erucic acid amide fractures during stamping (fragile) and acquires a milky appearance. The can also shows corrosion. The powder coating with 0.2% lubricant is very flexible, it can be printed very well, but it shows a milky appearance with 2% lactic acid. With 0.5% lubricant, there are no objections of this nature. The results can be deduced from the following table.

Sterilization: h 128 ° C without + 0.2% + 0.5% lubricant amide amide acid erucic acid erucic erucic in H20 ++ ++ ++ 2% lactic acid + + ++ 5% lactic acid + ++ ++

Claims (14)

REIVI DICATIONS 1. Powdered lacquer based on epoxy resins and phenolic hardeners, in particular for internal coating of container containers, comprising

1. ) at least one epoxy resin having an epoxide equivalent weight of 300 to 5500 and at least one hardener having more than one phenolic hydroxyl group per molecule and one hydroxyl equivalent weight, based on the phenolic OH groups, of 100 to 500, wherein the powder coating has a particle size distribution so that a) at least 90 weight percent of the particles of the powder coating have a particle size between 1 to 60 μm, b) the maximum particle size of at least 99 weight percent of the powder coating particles is < 100 μm, c) the average particle size of the powder coating is between 5 and 20 μm and d) the gradient of the distribution curve of the particles at the inflection point is > 100 and 2) a lubricant, preferably in an amount of < 2% by weight.

2. Powdered lacquer according to claim 1, characterized in that it has a particle size distribution such that a) at least 90 percent by weight of the powder lacquer particles have a particle size between 1 and 40 μm, b) the maximum particle size of the powder coating is < 60 μm for at least 99 weight percent of the particles, c) the average particle size of the powder coating is between 5 and 12 μm and d) the gradient of the particle distribution curve at the inflection point is > 150.

3. Powdered lacquer according to claim 1, characterized in that it has a particle size distribution such that a) at least 90 percent by weight of the powder coating particles have a particle size of between 5 and 25 μm, b) the maximum particle size of the powder coating is < 40 μm for at least 99 weight percent of the particles, c) the average particle size of the powder coating is between 5 and 12 μm and d) the gradient of the distribution curve of particulates at the inflection point is > 200.

4. Powdered lacquer according to one of claims 1 to 3, characterized in that it comprises, as component A, epoxy resins based on bisphenol A and / or bisphenol F and / or epoxidized novolak resins. Powdered lacquer according to one of claims 1 to 4, characterized in that it comprises, as component A, epoxy resins based on bisphenol A and / or bisphenol F having an epoxide equivalent weight of 500 to 2000 and / or resins epoxy of novolak type having an epoxide equivalent weight of 500 to 1000. 6. Powdered lacquer according to one of claims 5, characterized in that it comprises, as component B, a hardener having a hydroxyl equivalent weight, based on the phenolic OH groups, from 200 to 300. 7. Powdered lacquer according to one of claims 1 to 6, characterized in that it comprises, as component B, a hardener having from 1.8 to 4, preferably < 3, phenolic hydroxyl groups per molecule. Powdered lacquer according to one of claims 1 to 7, characterized in that it comprises, as component B, a hardener based on bisphenol A and / or bisphenol F. 9. Powdered lacquer according to one of claims 1 to 8, characterized in that it contains A) from 29 to 80% by weight, based on the total weight of the powder coating, of epoxy resin component A and B) from 10 to 50% by weight, based on the total weight of the powder coating of the hardening component B. 10. Powder lacquer according to one of claims 1-9, characterized in that the proportion of the lubricant is < 1, preferably 0.1 - 0.6% by weight. Powdered lacquer according to one of claims 1-10, characterized in that acidic amides, polypropylene wax, modified polyethylene wax are used as lubricants. Process for the manufacture of a powder coating material based on epoxy resins and phenolic hardeners, in particular for the internal coating of container containers, characterized in that a powder coating material, comprising at least one epoxy resin having an epoxide equivalent weight of 300 to 5500 and at least one hardener having more than one phenolic hydroxyl group per molecule and an equivalent hydroxyl weight, based on the phenolic OH groups, of from 100 to 500, where the powder coating has a particle size distribution such that a) at least 90 percent by weight of the particles of the powder coating have a particle size of between 1 and 60 μm, b) the maximum particle size of the powder coating is < 100 μm for at least 99 weight percent of the particles, c) the average particle size of the powder coating is between 5 and 20 μm, and d) the gradient of the distribution curve of the particles at the inflection point is > 100 and lubricant, preferably in an amount of < 2% by weight, are extruded and ground. 13. Process for the internal coating of container containers, characterized in that a powder coating according to one of the claims 1 to 9 is applied in a layer thickness of < 15 μm. 14. Use of powder coating materials according to one of claims 1 to 9, for the internal coating of container containers. SUMMARY OF THE INVENTION The present invention relates to a powder coating based on epoxy resins and phenolic hardeners, in particular for the internal coating of container containers, and contains: 1) at least one epoxy resin with an equivalent weight of epoxy between 300 and 5500; and at least one hardener with more than one phenolic hydroxyl group per molecule, and an equivalent hydroxyl weight, relative to the phenolic OH groups, of between 100 and 500; the powder coating having a grain size distribution such that: a) at least 90% by mass of the powder coating particles have a particle size between 1 and 60 μm; b) the maximum particle size of the powder coating particles for at least 99% by mass of the particles is < 100 // m; c) the average particle size of the powder coating particles is between 5 and 20 μm; and d) the inclination of the grain distribution curve at the inflection point is > 100; and 2) a lubricant, preferably in an amount of < 2% by weight.