DE102006061940A1 - Coating, especially for articles with a metal or ceramic surface, comprises a thermoplastic polymer binder with a high stoving temperature and a metal oxide filler - Google Patents

Abstract

Coating comprises at least 60 wt.% of a thermoplastic polymer binder with a stoving temperature of at least 300[deg] C and 0.5-30 wt.% of a metal oxide filler. Independent claims are also included for: (1) article with a metal or ceramic surface on which a coating as above is deposited; (2) producing an article with an adherent, dense, smooth surface by applying a coating as above in powder form and stoving the coating at at least 300[deg] C.

Description

The Invention relates to a an article provided on the basis of a plastic material, around a surface to get with certain characteristics. Common plastic coatings mostly serve the protection of the object or give the coated surface special properties that the coated article without this Can not deliver coating. Known coatings serve for example, the electrical or chemical insulation and in particular the corrosion protection, as far as it is metallic coated objects is. The coating may continue to wear the article counteract by giving the surface additional hardness or elasticity, represents an abrasion protection and optionally a non-stick effect implied.

It Coatings with so-called high-performance polymers are known, which produce particularly hard and resistant coatings to let. By definition, such high-performance polymers are characterized in particular their high continuous temperature capacity of 260 ° Celsius and more.

at Plastic-containing coatings is the problem, a smooth and crater-free surface especially if the coating is not direct on the surface polymerizing the object to be coated, or the coating is not in liquid Form can be applied directly, as stated in the above High performance polymers is the case.

task The present invention is therefore, efficient and in particular to provide electrically insulating coatings, the can be smoothly applied with improved flow behavior.

These The object is achieved by a A coating according to claim 1 solved. Advantageous embodiments of the coating, a coated Article, a process for coating and advantageous uses the coating and coated objects are further claims remove.

It a coating is given which has a new topcoat (= uppermost Layer). The cover layer comprises a binder and a Filler, in the top layer in a proportion of 0.5 to 30 weight percent is included. The binder itself has as a quantitative main component at least a high performance thermoplastic polymer characterized by a Burning temperature of at least 300 degrees Celsius and a high Durable temperature rating of 260 ° Celsius and more. It is in the top layer in an amount of at least 60% by weight contain. The filler in turn comprises as the main quantitative component a metal oxide powder.

Surprised shows that the flow properties of the thermoplastic High-performance polymer through the metal oxide powder of the cover layer are significantly improved. With the added metal oxide powder are already significant improvements from a percentage of one percent by weight achieved the flow properties of the cover layer. It appears, that the miscibility of the components and thereby also the homogeneity by the addition of the metal oxides is improved. In addition, an improved Seizability observed, especially when baking the coating. Due to this improved flow behavior becomes a coating which is smooth, nonporous and dense. Accordingly, too improved all the properties of the coating associated with it stand. A coating according to the invention is therefore regarding Corrosion protection, friction behavior, abrasion and wear resistance improved.

The improved tightness of the coating according to the invention is already achieved with relatively low layer thickness. Smooth and non-porous layers can for example, from about 5 to 10 microns to be obtained.

The dense and non-porous layer has an increased abrasion resistance, which is the Coating further advantageous applications open. It is inert with regard to chemicals, can and is safe to come into contact with food Physiologically harmless and therefore for medical applications suitable. With the coating can therefore temporarily or permanently in direct contact with living tissue or body fluids standing objects like medical devices, surgical tools or orthopedic and other implants be provided. Further applications emerge from the already for thermoplastic High performance polymers known applications, especially for loaded and resilient Surfaces. The coatings can also be produced electrically insulating.

The inert behavior of the surface is also interesting for applications in the electrical and semiconductor industry. Thus, coatings according to the invention can be provided in clean rooms and, in particular, for those surfaces which are in direct contact with semiconductor materials. In this case, no contamination of the semiconductor material takes place and no abrasion is generated which causes problems in the manufacture of semiconductor components could.

The inert surfaces inventive coatings are also for chemical applications advantageous, so that appropriate coatings also for Vessels, devices and lines suitable for contact with chemicals.

Of Further, a variety of metal oxides also usually used for coloring pigments, so that an appropriate selection the metal oxides also a colored design of the coating possible is. For example, with the help of titanium oxide as a filler at the same time a white one Coating be generated. Colorful pigments or colorful Oxides are also known by the metals iron, copper and chromium, which are used a series of different colors and shades can be obtained simultaneously improve the leveling properties of the coating. Others too Metal oxides are for coloring the coating suitable.

The remaining ingredients inventive coatings or for the coating used cover layers are selected so that at least they do not worsen the mentioned properties. Suitable further constituents are essentially further fillers and additives. In this case, such further constituents are excluded, the a coloration or can cause abrasion and thus contamination.

Fewer suitable for a coating according to the invention is soot. Also less suitable are metallic fillers in the topcoat. Without major disadvantages can but still contain, for example, 1% by weight of metal powder, without thereby z. B. the electrical insulation effect and the inert behavior of the coating is lost. As a component further excluded are substances or particles that are thermal are unstable and the coating by firing at 300 degrees Celsius and more can not survive. Even materials that fleeting are or fleeting Compounds and in particular release gases are usually for the topcoat not suitable.

Advantageous is the binder, so the organic or plastic part of the Coating exclusively from the high-performance thermoplastics. Ingredients other than the High performance thermoplastics and the metal oxides are in the topcoat contained in a proportion of a maximum of ten percent by weight. Such Ingredients are essentially additives that have further coating properties improve. The adhesive properties of the cover layer can be increased by adding of fluorine-containing and in particular perfluorinated polymers improved become.

at Addition of z. For example, five Weight percent polytetrafluoroethylene PTFE shows surprising that with it the surface the coating can be further improved in their properties can.

When other additives can Molybdenum sulfide and Graphite can be used.

All Constituents of the coating are selected so that they are sufficiently temperature-stable, to survive the burn-in to produce the coating.

The Main component of the cover layer is selected from appropriately high performance thermoplastics. These can selected be made of liquid crystalline Polymers (LCP) polyaryletherketones, polyetherketone (PEK), polyetheretherketone (PEEK), Polyphenylene sulfide (PPS), polyethersulfone (PES) polyphenylene ether sulfone (PPSU) and mixtures of the polymers mentioned. Also fluorinated thermoplastics By definition, PTFE, PFA and FEP fall into the category of high-performance polymers. You can especially in larger proportions For example, up to 30% by weight can be used if the requirements in hardness and mechanical strength of the coating are not too high. It is advantageous if the proportion of fluorinated in the binder Thermoplastics is lower than that of non-fluorinated high-performance polymers.

Advantageous it is when the topcoat of the coating next to the filler exclusively high performance polymers selected from polyaryletherketones, polyetherketone (PEK), polyetheretherketone (PEEK) and polyphenylene sulfide (PPS) or mixtures thereof.

Further coatings are advantageous in addition to the above four Materials or mixtures thereof as a minor proportion of fluorinated thermoplastics contain the above selection. Particularly preferred are mixtures from PEEK with PTF PFA, FEP or with mixtures of these fluorinated ones Thermoplastics.

As well advantageous are coatings containing as filler exclusively metal oxide powder include. Suitable coatings can therefore exclusively consist of said high performance polymers and one or more metal oxide powders.

The advantageous properties of the coating, which already have a low layer thickness, make it possible to use coatings for all of the proposed applications in which the layer thickness of the cover layer is at most 150 μm. Advantageous layer thicknesses are for example between 5 and 100 microns for the Covering layer and in particular between 10 and 30 microns.

Become as a filler for the Topcoat exclusively Metal oxides and other components used that neither electrical Conductivity still Semiconductor properties, so a coating of the invention also be used as an electrically insulating coating. With the cover layer according to the invention For example, an electrical breakdown strength of 10 kV already achieved with a layer thickness of about 100 microns become.

electrical insulating metal oxides and thus electrically good insulating coatings support also the electrostatic application in a powder coating process, because it better maintains the charge of the powder particles can be what makes the coating easier.

It but it is also possible to use semiconducting metal oxides, if the coating is not electrical must be set insulating. Such oxides may, for. From Sn, Zn and Al be derived.

advantageous Coatings in the topcoat account for a proportion of the high performance thermoplastic polymer from 80 to 95 percent by weight.

Next the metal oxide powders can in the top layer still ceramic nanoparticles, fibers or platelet-shaped particles be included. Also suitable are glass fibers, carbon fibers and Diamond as well as natural Minerals, for example, barium sulfate or in particular the platelet-like modification present mica. Also suitable are silicates, quartz, silica, Glass, ceramic particles or zeolite.

For a smooth surface the coating, it is advantageous if the fillers and other solid Constituents have a maximum particle diameter in the range of Have layer thickness of the cover layer. It is better, though the quantitatively predominant Proportion of particles has diameters that are significantly lower as the layer thickness, for example by a factor of two smaller. In general, it is advantageous that the filler particles are so finely divided as possible use.

Independent of the layer thickness of the cover layer, it is advantageous if at least 90 percent by weight of the fillers and other solid components particle diameters of maximum 10 μm too exhibit.

With The coating according to the invention can be coated with articles are having a metallic or ceramic surface. The Coating can be exclusive consist of the topcoat, which has excellent adhesion to has metallic and ceramic surfaces and therefore the Strength and strength of the coating improved.

Is possible it also, between the base body to be coated and the cover layer, an intermediate layer to arrange the transition from the main body improved to the topcoat or the entire coating additional Lends properties. The requirements for such an intermediate layer consist in that they are connected to the main body and the components of the Cover layer is compatible, forming both good adhesion and in particular the application process for the cover layer, in particular survives the burn-in at a temperature of more than 300 degrees Celsius.

For such Intermediate layers are in particular the thermoplastic mentioned High performance polymers are suitable as main components. Such intermediate layers can besides having an optionally higher proportion of fillers, the choice for the fillers in the intermediate layer is not subject to the limitations of the fillers of the topcoat. So can in the intermediate layer thoroughly electrically conductive filler particles and in particular contain metal particles, thus increasing the adhesion to metallic surfaces can be improved. The intermediate layer can also be set to be electrically conductive, since an electrical isolation accomplished only by the cover layer can be. about The intermediate layer can also reduce the hardness of the overall coating can be adjusted, wherein the intermediate layer, for example, set harder is called the topcoat.

With the coating provided basic body can arbitrary surface geometries exhibit. Preferred are easily coated surfaces, the either flat or have a continuous surface contour. adversely are undercuts and indentations in which two surfaces of the the body cut at an acute angle. Uncritical, however, are basic bodies, the edges have, independently whether they are sharp or dull.

Also suitable are basic body, which are designed as wire. Such wires can be completely provided with the coating according to the invention and, in particular, coated with the coating in an electrically insulating and corrosion-resistant manner. It is possible, for example, to apply the coating on wires with diameters of 0.1 to 1.0 millimeters tight and smooth. On wires Coatings with layer thicknesses of 10 to 200 μm can be produced. These layer thicknesses are sufficient for the production of electrical insulation, so that such coated wires can also be used as electrical conductors and connecting wires and require no further sheathing.

Of the Coating process can be made so that not only the wire itself but also associated electrical components and especially the transition From the wire to the component coated dense and electrically insulating is.

To the Generation of coatings according to the invention can the coating components and in particular the components of the Cover layer applied in a first step as a powder layer and then burned in a second step. The powder layer comprises a homogeneous and finely divided mixture of all components of the cover layer.

The Powder layer can be applied by methods known per se, in particular electrostatic and wet methods suitable are. In wet form can the finely divided homogeneous powder as a dispersion in preferably aqueous or water-containing solvent sprayed, spin coated or applied by dipping. In such Dispersion method it is possible the stability the applied powder layer by burnable, viscous or to improve low polymer components as binders exclusively for the powder layer, which completely decompose upon baking of the powder layer or volatilize and completely off can escape the resulting coating. Also bonding the powder can be used for application.

But even without such additional layer-forming additions the layer thickness of coatings according to the invention can be arbitrary be increased by the total coating in the form of several successively applied sub-layers is generated. It is it is possible several layers of powder on top of each other apply, or to apply a first part layer as a powder layer and burn in before the next Partial layer is applied as a powder layer. Furthermore, it is about a multi-layered Application possible, different partial layers or partial layers with different To combine compositions, wherein lower sub-layers of the composition of the invention the cover layer may have deviating compositions.

Well However, coatings whose partial layers are all suitable are also suitable the for the topcoat listed restrictions to obey.

Advantageous It may be several sublayers that together form a coating or even give the topcoat, so in their compositions to vary that regarding a component or property over the total layer thickness a gradient results. Such a gradient can, for example, a increasing or decreasing hardness, be a corresponding density or elasticity.

in the The following will describe the invention and the method of manufacture a coating based on embodiments and the associated figures explained in more detail. The Figures are purely schematic and not to scale, allowing the figures neither absolute nor relative dimensions can be inferred are.

1 shows a basic body with two-layer coating on the basis of a schematic cross section,

2 shows different process stages in the production of the coating,

3 shows a process variant in the production of a multilayer coating.

1 shows a two-layer embodiment of the coating BS according to the invention. On the surface of a basic body GK a first partial layer TS1 and above a second partial layer TS2 are arranged, for example a base layer and a cover layer. The material of the base body GK is arbitrary, but preferably made of glass, ceramic or metal, or has at least a corresponding surface of these materials. The thickness h _{TS2 of} the cover layer TS2 is, for example, twenty to 30 μm. The thickness h _{TS1 of} the underlayer TS1 is at least 5 μm. Preferably, however, the layer thickness of the underlayer is adapted to the achievement of a specific property associated with it or a property profile and, if appropriate, correspondingly reinforced.

The surface the coating BS, consisting here of the first sub-layer TS1 and the above arranged second sub-layer TS2, the latter alone or together with the first sub-layer can form the cover layer, is smooth and non-porous. The fine structure of the sublayers is homogeneous.

The layer thicknesses of the partial layers TS1 and TS2 are selected according to the desired Ge velvet thickness of the coating BS adjusted. With a high overall thickness, a higher number of partial layers can be produced one above the other. This makes it possible to produce each sub-layer in a respect to the manufacturing process optimal and independent of the subsequent total thickness layer thickness.

2 shows different process steps when coating a body GK schematic cross-sections through the same. Generally, the surface of the base body intended for the coating is at least cleaned, but preferably also pretreated (see arrows in FIG 2a ). The pretreatment may involve mechanical or chemical roughening, for example sandblasting or treatment with acids or alkalis. The pretreated surface can be used to create additional bonding sites for better adhesion of the layers applied thereto.

On this pretreated and optionally roughened surface is now a coatable Mixture applied, which are converted into the desired coating can. Starting point for any coatable Mixture is a fine powder of one or more thermoplastics, metal oxides and the other additives provided for each layer are. The powders are fine, homogeneous and with a particle size distribution, the possible narrowly elected becomes. The average size of the particulate used Thermoplastics, for example, the D50 value, is according to the desired Layer thickness of the layer to be produced selected. It is true that the D50 value the particle size maximum twice the layer thickness of the finished layer to be produced (Cover layer) may correspond. That is, with a powder mixture with a D50 of, for example, 20 μm, partial layers with layer thicknesses can be used produced from 10 microns become.

To the Producing fine powder mixtures of thermoplastic particles is, for example, cryogenic grinding of the particles and a corresponding grain size sorting suitable. Bonding can also be used.

Also the for the respective layer provided fillers are possible finely ground and sorted by grain size added to the thermoplastic powder and the whole mixed homogeneously. The fillers can also compounded and then ground again and in particular be cryogenically ground to increase the homogeneity of the powder mixture. Possibly This process can be repeated several times. For fillers and other non-thermoplastic components already applies mentioned stricter restriction regarding the allowed particle diameter and particle size distributions.

A coatable Mixture may consist of the powder alone, which, if necessary Additionally is dried. For Another coating method becomes the homogeneous powder a dispersion prepared by adding solvent, preferably aqueous Base, optionally in admixture with miscible solvents in particular alcohols and optionally dispersion aids can be done.

The Applying the coatable mixture can then be correspondingly by powder coating or by dispersion coating or by thermal spraying. For the powder coating is sprayed or sprinkled the powder mixture on a substrate, which either as described the basic body GK with the metallic or ceramic surface is, or in another (not further described below and also not shown) variant already with a coating (Intermediate or lower layer) provided basic body. The adhesion of the particles the surface of the basic body can be electrostatically supported Be prepared by mixing the powder mixture before or during the coating process electrically charged and the substrate is grounded accordingly.

Is possible it too, the surface of the basic body to heat up so far that the thermoplastic components of the Soften and stick powder when hitting the surface, so that at least one pre-consolidation occurs.

The Dispersion can also be sprayed on. Is possible it too, the main body into a dispersion, or to print the dispersion, stamp, roll or coat. Depending on the condition of the main body can also be suitable for a spin-on process.

For coating thermally sensitive base body GK or corresponding parts of the same thermal spraying can be used. In this process, the thermoplastic particles of the coatable powder mixture are melted and sprayed or sprayed finely distributed on the colder and optionally cooled surface. In all variants, an optionally preconsolidated first powder layer PS1 is obtained, as in 2 B shown.

In the next step, the first powder layer PS1 is transferred into the finished compacted first part-layer by placing the assembly in an oven and bringing it to a temperature, which is above the melting point of the highest melting thermoplastic contained in the powder mixture. Preferably, a temperature program is run in the oven to ensure the best possible compression and thus a homogeneous and stable structure of the layer.

Is possible it also to use a tunnel kiln, which is different Having temperature zones. The temperature program can then be driven be moved by the arrangement through the tunnel kiln and in the individual temperature regions for the temperature program corresponding predetermined time lingers.

2c With the first partial layer TS1 produced in this way, provided that it meets the requirements for the cover layer, the main body is already provided with a finished coating according to the invention, but as described with reference to FIGS 2d and 2e shown, can be reinforced with other sub-layers.

For reinforcement or thickening, a second powder layer PS2 can be applied and baked onto the first partial layer TS1 and then solidified to the second partial layer TS2 (see FIG 2e ). The first sub-layer may be an intermediate layer or only a first sub-layer of the cover layer.

3 shows a variant of the process for several optionally different sub-layers, in which the compaction of all applied powder layers takes place together in a final step. 3a shows a main body GK, which is provided with two superposed powder layers PS1 and PS2 for a first and second partial layer TS1, TS2. At least the powder layer PS1 for the lower layer can be precompressed, which facilitates the application of the powder layer PS2 for the second partial layer TS2 covering layer. 3b shows the arrangement of the common compression according to said baking.

For desired coatings with more than two layers, the procedure is adjusted accordingly.

The Invention has been explained only with reference to a few embodiments but not limited to these. Coatable or coated main body can in particular of the illustrated flat bodies have different arbitrary shaped surfaces and on one Subarea, on different faces or on their entire surface be provided with the coating. The coated basic body can be made out consist of uniform material or of different materials be composed. Preferably, those with the coating provided surfaces however, made of metal, glass or ceramic.

The Although coatings already have low layer thicknesses desired Properties on, can of course also in larger layer thickness are generated as specified.

Claims (28)

Coating for an object, With a cover layer as a single or top layer, wherein the cover layer a binder and filler includes, - at the binder as a quantitative main component at least one high performance thermoplastic polymer having a stoving temperature of at least 300 ° C includes - at the filler as a quantitative main component comprises a metal oxide powder - in the proportion of high-performance polymer in the top layer at least 60 wt.% Is - at the filler content in the top layer 0.5 to 30 wt.% Is. The coating of claim 1, wherein the high performance polymers selected are made of polyetheretherketone PEEK, polyetherketone PEK, polyphenylene sulfide PPS and mixtures of the polymers mentioned. Coating according to claim 1 or 2, in which Binder exclusively High performance polymers are included. A coating according to any one of claims 1 to 3, wherein the filler exclusively consists of metal oxide powder. A coating according to any one of claims 1 to 4, wherein in the Covering next to the high-performance polymer and the metal oxide more Additives, pigments, additives or fillers in a total amount by Max. 10% by weight are included. Coating according to one of claims 1 to 5, having a layer thickness the top layer of a maximum of 150 microns. Coating according to one of claims 1 to 6, having a layer thickness from 5 to 100 μm and in particular from 10 to 30 μm. Coating according to one of claims 1 to 7, in which the metal oxides selected From the oxides, at least one of the metals of Al, Fe, Cu, Cr and Ti. Coating according to one of claims 1 to 8, in which the metal oxides are selected from electrically insulating metal oxides, in which no other electrically conductive constituents are present in the cover layer. Coating according to one of claims 1 to 9, in which the proportion of high-performance polymer in the topcoat 80 to 95 wt.% Is. Coating according to one of claims 1 to 10, at which the fillers and other solid constituents have a maximum particle diameter have in the range of the layer thickness of the cover layer, at the vast majority Proportion of fillers and other solid constituents by more than a factor of 2 have smaller particle diameter, and in the independent of the layer thickness of the cover layer at least 90 wt.% Of the fillers and other solid constituents have a maximum particle diameter of 10 μm exhibit. Coating according to one of claims 1 to 11, in which in the cover layer to improve the surface properties fluorinated high performance polymers selected from polytetrafluoroethylene PTFE, PFA, FEP or mixtures thereof in a proportion of not more than 30% by weight are included. The coating of claim 12, wherein the binder is adjacent the fluorinated high-performance polymers consist only of PEEK. Object with a basic body with metallic or ceramic surface, on which a coating according to any one of claims 1 to 12 is applied. An article according to claim 14, wherein the coating only from the directly adhering to the metallic or ceramic surface Cover layer exists. An article according to claim 14, wherein between the body and the cover layer is provided with an intermediate layer which, relative to the application method at a baking temperature of at least 300 ° C is compatible with the topcoat and as a main component, a high-performance thermoplastic polymer includes. An article according to any one of claims 13 to 15, further comprising Wire formed body, which is completely covered with the coating. The article of claim 16, wherein the wire / body has a Diameter of 0.1 to 1.0 mm and the coating a layer thickness from 10 to 150 μm having. Method for producing an article with firmly adhering, dense and smooth surface, where a basic body with a coating is provided, for the covering layer of a powder layer applied and baked at a temperature of at least 300 ° C. becomes - in which the powder layer is a homogeneous finely divided mixture of all components the top layer represents, - wherein the cover layer a Binder and a filler includes, - in which the major component of the binder is a high performance thermoplastic polymer with a stoving temperature of at least 300 ° C and in a proportion of at least 60% by weight is contained in the cover layer, - in which the filler as a quantitative main component comprises a metal oxide powder - in which the filler content in the outer layer is 1 to 30 wt.%. The method of claim 19, wherein the powder layer is applied dry in an electrostatic process. The method of claim 19, wherein the powder layer as a dispersion in an aqueous or at least water-comprising solvent in a spray, spin-on or dipping method is applied. A method according to any one of claims 19 to 21, wherein the Coating in the form of several sub-layers is applied, wherein for every Partial layer applied a powder layer and then baked will be before the next one Partial layer is applied and baked in the same way above. The method of claim 22, wherein for the individual Sublayers different compositions are chosen each one for yourself for the the top layer claimed features met. Use of the coating according to one of claims 1 to 13 or an article according to any one of claims 14 to 18 in medical technology. Use of the coating according to one of claims 1 to 13 or an article according to any one of claims 14 to 18 in medical technology for objects, those in temporary or permanent contact with a living organism or parts thereof stand. Use of the coating according to any one of claims 1 to 13 or an article according to one of claims 14 to 18 in the electrical or electronic industry for electrically insulating surfaces. Use of the coating according to one of claims 1 to 13 or an article according to any one of claims 14 to 18 in clean room technology in the manufacture and processing of semiconductors and semiconductor devices for abrasion resistant and non-contaminating surfaces. Use of the coating according to one of claims 1 to 13 or an article according to any one of claims 14 to 18 in food technology for surfaces that in contact with food.