DE10324415A1 - Coating procedure for coating substrates with carbon based material, comprises carbonation of polymer film in oxygen free environment at temperature ranging from 200 to 2500 degrees Celsius - Google Patents

Abstract

Coating procedure comprises coating the outer surface of the substrate with a polymer film. The carbonation of the polymer film is performed in an oxygen free environment and at a temperature ranging from 200 to 2500 degrees Celsius. The polymer film includes additives which are selected from silicon oxides, alumina, zirconium oxides, titanium oxides. An independent claim is also included for a carbon coated substrate.

Description

The The present invention relates to a method for coating Substrates with carbon-based material by coating one Substrate with a polymer film on at least one of its outer surfaces and subsequent Carbonization of the polymer film in an atmosphere that is essentially free of oxygen, at temperatures in the range of 200 ° C to 2500 ° C.

Pyrolytic carbon has long been known as a high-strength, abrasion-resistant material with great property variability. Because of its structure and compositions, pyrolytic carbon is biocompatible, so that it has long been used as a material or coating material in medical technology, in particular for the manufacture of medical body implants of all kinds. Pyrolytic carbon with a turbostratic structure, possibly including silicon-alloyed carbon microcrystals, is used for example for coating Stents or also used for the production of artificial heart valves. For example, US Pat. No. 6,569,107 describes carbon-coated intraluminal stents in which the carbon material has been applied by chemical or physical vapor deposition methods (CVD or PVD). In the DE 3902856 describes pyrocarbon-containing moldings which are produced by coking carbon fiber objects, pyrocarbon infiltration and subsequent sealing of the surface with CVD carbon.

The deposition of pyrolytic carbon under PVD or CVD conditions requires the careful selection of suitable gaseous or vaporizable carbon precursors, which are deposited on a substrate at high temperatures, sometimes under plasma conditions, in an inert gas or high vacuum atmosphere. In addition, various high-vacuum sputtering processes for producing pyrolytic carbon of various structures are described in the prior art, see for example US 6,355,350 ,

all Common to these prior art methods is that Deposition of carbon substrates under extreme temperatures and / or Printing conditions with careful and complex process control takes place.

Further is due to different coefficients of thermal expansion of substrate material and the applied CVD carbon layer in the State of the art often only a slight adhesion of the layer on the Substrate achieved, flaking, cracks and general Deterioration in surface quality.

It there is therefore a need for easy to use and inexpensive Process for coating substrates with carbon-based material, which are able, for example, biocompatible superficial Coatings made of carbon material or carbon-coated Substrates for to provide microelectronic purposes.

The The object of the present invention is therefore to provide a method for Coating of substrates with carbon-based material for disposal to face that with inexpensive and diverse variable starting materials and easily controllable Processing conditions applies.

A Another object of the present invention is to use carbon-based Material coated substrates for use in medical technology, especially for medical implants of various types are available too represent their surface properties adapt specifically to the respective application to let.

A Another object of the present invention is to provide of a process for the production of carbon-coated substrates for microelectronic Purposes.

The solution of the invention The above-mentioned tasks consist in a method according to claim 1. Preferred embodiments of the inventive method result from the dependent Dependent claims.

in the It has been found within the scope of the present invention that carbon-coated Have products manufactured in a simple manner by first the present substrate is superficial is coated with a polymer film, which is then in an oxygen-free atmosphere is carbonized or pyrolyzed at high temperatures.

Under Carbonization or pyrolysis is within the scope of the present Invention the partial thermal decomposition or carbonization of carbon Understand starting compounds, usually polymer materials based on hydrocarbons, which have high proportions after carbonization leave amorphous carbon.

substrates

The substrates which can be used according to the invention can comprise all essentially temperature-resistant materials, that is to say materials which are among the carbonization or Pyrolysis conditions are stable and preferably dimensionally stable. Examples of substrates which can be used according to the invention are metals, alloys, ceramics, graphite, glass, stone, carbon fiber materials, carbon fiber composites, minerals, bone substance and bone imitations based on calcium carbonate and the like.

Also the use of ceramic green bodies as According to the invention, substrate is advantageously possible because this in parallel during the carbonization of the coating is sintered into the finished ceramic can.

For coated according to the invention Materials used in medical implants are all medical and dental field typically materials used, for example metals such as titanium, platinum, Palladium, gold, alloys such as Cobalt-chromium alloys, low porous graphite, Polymers, carbon fiber implants, ceramics such as calcium phosphate ceramics, Zeolites, aluminum oxides, apatite ceramics and the like, wherein this list not completely is.

The Substrates can almost any external shape if they are on at least one of their outer surfaces have a polymer film coated. Examples usable according to the invention Substrates are medical implants, such as prostheses and joint substitutes, bone implants, artificial hip joints and hip bone implants, intraluminally usable devices such as stents, for example Metal stents such as nitinol stents, polymer stents, surgical orthopedic aids like bone screws, nails, Plates and the like.

Further examples for usable according to the invention Substrates are components from the field of microelectronics and Micromechanics, construction materials such as metal ceramics in glass and stone as well as carbon fiber composites, Raschig rings, Sulzer packs and the same.

polymer films

To the inventive method the temperature resistant Substrates on at least one of their outer surfaces, in certain preferred applications, such as medical Devices usually with their entire outer surface coated with one or more polymer films.

The Polymer film can in one embodiment of the invention are in the form of a polymer film, for example is applied to the substrate by film shrinking or can also be glued on. Thermoplastic polymer films can also be heated on most substrates apply firmly.

suitable Films consist of homo- or copolymers of aliphatic or aromatic polyolefins such as polyethylene, polypropylene, polybutene, Polyisobutene, polypentene; Polybutadiene. Polyvinyls such as polyvinyl chloride or polyvinyl alcohol; Poly (meth) acrylic acid, polyacrylonitrile, polyamide, Polyester, polyurethane, polystyrene, polytetrafluoroethylene, mixtures and combinations of these homo- or copolymers and the like.

According to one another embodiment In the present invention, the polymer film can also be a coating of the substrate, which is selected from lacquers, laminates or covers.

suitable paint-based polymer films can, for example be made from a varnish that is made from a binder base Alkyd resin, chlorinated rubber, epoxy resin, acrylate resin, phenolic resin, Amine resin, oil based, Nitro base, polyester, polyurethane, tar, tar-like materials, Tar pitch, bitumen, starch, Cellulose, shellac, organic materials from renewable Has raw materials or combinations thereof.

In certain embodiments In the present invention, the polymer film with additives equipped be the carbonization behavior of the film and / or the macroscopic properties of the resulting from the process carbon-shaved substrate coating. Examples suitable additives are fillers, Pore formers, metals and metal powder, etc. Examples of inorganic Additive or filler are silicon oxides or aluminum oxides, aluminosilicates, zeolites, Zirconium oxides, titanium oxides, talc, graphite, carbon black, clay materials, phyllosilicates, Silicides, nitrides, metal powders, in particular of catalytically active transition metals such as copper, gold and silver, titanium, zircon, hafnium, vanadium, niobium, Tantalum, chrome, molybdenum, Tungsten, manganese, rhenium, iron, cobalt, nickel, ruthenium, rhodium, Palladium, osmium, iridium or platinum.

through Such additives in the polymer film can be, for example biological, mechanical and thermal properties of the films as well as the resulting carbon coatings vary and adjust. For example, through the installation of layered silicates the coefficient of thermal expansion of the carbon layer of a ceramic substrate, so that the applied carbon-based coating even with large temperature differences firmly adheres.

Polymer films have the advantage that they can be easily manufactured in almost any dimension or are commercially available. Polymer films are readily available, inexpensive and easy to apply to a wide variety of substrates. The polymer films used according to the invention can be structured in a suitable manner before pyrolysis or carbonization by folding, embossing, punching, printing, extruding, gathering, injection molding and the like, before or after they are applied to the substrate. In this way, certain structures of a regular or irregular type can be built into the carbon coating produced by the method according to the invention.

The usable according to the invention Polymer films from coatings in the form of lacquers or coatings can be made from the liquid, mushy or pasty Condition, for example by painting, painting, varnishing, dispersion or melt coating, extruding, casting, dipping or as Hot melts, from the solid state by means of powder coating, clamp spraying, Sintering or the like according to known methods on the Apply substrate. Also the lamination of suitably shaped Substrates with this Suitable polymer materials or films is one that can be used according to the invention Process for coating the substrate with a polymer film.

The polymer film applied to the substrate is optionally dried and subsequently pyrolytic decomposition under carbonization conditions subjected. Here, the polymer film coated on the substrate in an essentially oxygen-free atmosphere at elevated temperature carbonized. The temperature of the carbonization step is preferably in the range of 200 ° C up to 2500 ° C and is dependent on the specialist from the specific temperature-dependent properties of the used Polymer films and substrates selected.

preferred generally usable temperatures for the carbonation step of the method according to the invention are at 200 ° C up to about 1200 ° C. In some embodiments temperatures in the range of 250 ° C to 700 ° C are preferred. Generally the Temperature depending on the properties of the materials used chosen so that the polymer film with as much as possible low temperature expenditure essentially completely carbon-containing solid is transferred. The pyrolysis temperature can be selected or controlled appropriately the porosity, the strength and stiffness of the material and other properties be set specifically.

The the atmosphere is essential in the carbonization step of the method according to the invention free of oxygen. The use of inert gas atmospheres, for example, is preferred from nitrogen, noble gases such as argon, neon and any other inert gases not reacting with carbon or gas compounds as well as mixtures of inert gases. Nitrogen and / or are preferred Argon.

The Carbonization is common at normal pressure in the presence of inert gases such as those mentioned above carried out. If appropriate, however, higher inert gas pressures can also be used advantageously. In certain embodiments of the method according to the invention carbonation can also be carried out under vacuum or in a vacuum.

furnace process

The The pyrolysis step is preferably carried out in a continuous furnace process carried out. The possibly structured, coated or pretreated polymer films are fed to the furnace on one side and at the other end of the Exit the oven again. In preferred embodiments, the polymer film or the object formed from polymer films in the oven on a Perforated plate, a sieve or the like rest so that through the Polymer film during the pyrolysis and / or carbonization are applied under pressure can. this makes possible not just a simple fixation of the objects in the oven, but also one Suction and optimal flow the films or assemblies with inert gas during the pyrolysis and / or carbonization.

The The furnace can be divided into individual segments using appropriate inert gas locks in which one or more pyrolysis or carbonization steps, if necessary with different pyrolysis or carbonization conditions such as different Temperature levels, different inert gases or vacuum can be carried out can.

Further can in corresponding segments of the furnace, if necessary, also post-treatment steps such as Reactivate by reduction or oxidation or impregnation with metal salt solutions etc. carried out become.

alternative For this, the pyrolysis / carbonization can also take place in a closed Oven performed be, which is particularly preferred when pyrolysis and / or Carbonization should be carried out in a vacuum.

During the pyrolysis and / or carbonization in the process according to the invention, the weight of the polymer film usually drops by about 5% to 95%, preferably about 40% to 90%, in particular 50% to 70%, depending on the starting material used and pretreatment. In addition, shrinkage of the polymer film or of the structure or assembly produced from polymer films generally occurs during pyrolysis and / or carbonization in the process according to the invention. The shrinkage can be on the order of 0% to about 95%, preferably 10% to 30%.

in the method according to the invention can the electrical conductivity the coating depending the pyrolysis or carbonization temperature used and the type and amount of the additive or filler used can be set in wide ranges. This is especially for applications advantageous in microelectronics. So at temperatures in Range from 1000 to 2500 ° C due to the graphitization of the coating, a higher conductivity can be achieved than at lower temperatures. In addition, the electrical conductivity but also, for example, by adding graphite to the polymer film increase, which then pyrolyzes or carbonizes at lower temperatures can be. Coated substrates modified in this way are suitable for example for the manufacture of sensors.

The manufactured according to the invention carbon-based coating has, depending on the starting material, Quantity and type of filling materials, a carbon content of at least 1% by weight, preferably at least 25%, optionally also at least 60% and in particular preferably at least 75%. Coatings particularly preferred according to the invention have a carbon content of at least 50% by weight.

aftercare

In preferred embodiments of the method according to the invention can the physical and chemical properties of the resulting carbon-containing coating of the substrate after carbonization further modified by suitable post-treatment steps and the each desired Purpose to be adjusted.

By one- or two-sided coating of the polymer film with epoxy resins, Phenolic resin, tar, tar pitch, bitumen, rubber, polychloroprene or Poly (styrene-co-butadiene) -Latexmaterialien, Siloxanes, silicates, metal salts or metal salt solutions, for example transition metal salts, Carbon black, fullerenes, activated carbon powder, carbon molecular sieve, perovskite, Aluminum oxides, silicon oxides, silicon carbide, boron nitride, silicon nitride, Precious metal powders such as Pt, Pd, Au or Ag; and combinations thereof, or also through the targeted incorporation of such materials in the polymer film structure the properties of the after pyrolysis and / or carbonization resulting porous specifically influence and refine carbon-based coatings, or also multilayer coatings produce. For example, by installing layered silicates in the polymer film or coating the polymer film with layered silicates, Nanoparticles, inorganic nanocomposites, metals, metal oxides and the like, the coefficient of thermal expansion of the resulting Carbon coatings such as e.g. modified its mechanical properties become.

at the production according to the invention of coated substrates, consists of the installation of the above Additives in the polymer film the possibility of liability to improve the applied layer on the substrate and, for example, the thermal expansion coefficient of the outer layer that of the Adapt substrate, so that these coated substrates more resistant to breaks in and flaking of the coating. These coatings are thus more durable and long-term stable in concrete use than conventional ones Products of this kind.

The Application or installation of metals and metal salts, in particular also of precious metals and transition metals allows it, the chemical, biological and adsorptive properties of the resulting carbon-based coatings are desired in each case Adjust requirements so that the resulting coating for special Applications, for example, also with heterogeneous catalytic properties equipped can be.

In preferred embodiments of the method according to the invention are the physical and chemical properties of carbon-based Coating after pyrolysis or carbonization by suitable Post-treatment steps further modified and the desired one Adjusted for purpose.

suitable Aftertreatments are, for example, reducing or oxidative Post-treatment steps in which the coating with suitable Reducing agents and / or oxidizing agents such as hydrogen, carbon dioxide, Water vapor, oxygen, air, nitric acid and the like as well as possibly Mixtures of these are treated.

The post-treatment steps can optionally be carried out at elevated temperature, but below the pyrolysis temperature, for example from 40 ° C. to 1000 ° C., preferably 70 ° C. to 900 ° C., particularly preferably 100 ° C. to 850 ° C., particularly preferably 200 ° C. to 800 ° C. ° C and especially at about 700 ° C leads. In particularly preferred embodiments, the coating produced according to the invention is modified reductively or oxidatively, or with a combination of these post-treatment steps at room temperature.

By oxidative or reductive treatment, or the incorporation of additives, Fillers or Functional materials can be the surface properties of the manufactured according to the invention Effectively influence or change coatings. For example, by Incorporation of inorganic nanoparticles or nanocomposites such as layered silicates the surface properties of the Coating can be hydrophilized or hydrophobized.

Also can those produced according to the invention Coatings afterwards equipped with biocompatible surfaces by installing suitable additives and optionally used as bioreactors or drug carriers become. You can do this e.g. Drugs or enzymes are introduced into the material, the former possibly by suitable retardation and / or selective Permeation properties of the coatings released in a controlled manner can be.

Also can according to the inventive method the coating on the substrate is appropriately modified, e.g. by varying the pore sizes using suitable post-treatment step that the carbon-based Coating the growth of microorganisms or living cells favored or promotes. Appropriately coated substrates can then be used, for example, in bioreactors as a growth medium for Serve microorganisms. The porosity of the coating can advantageously be reduced adjust so that the supply of those located on the outer surface Cells or microorganisms with nutrients in or on the substrate or nutrient Drug depots guaranteed can be taking the nutrients from the substrate by permeation through the carbon-based Coating on the superficial Microorganism colonization.

The Carbonized coating can also be used in another optional process step, a so-called CVD process (Chemical Vapor deposition, chemical vapor deposition) around the surface or To further modify pore structure and its properties. For this the carbonized coating with suitable precursor gases treated at high temperatures. Such methods are in the state known for a long time.

Almost all known saturated and unsaturated hydrocarbons with sufficient volatility under CVD conditions are suitable as carbon-releasing precursors. Examples of these are methane, ethane, ethylene, acetylene, linear and branched alkanes, alkenes and alkynes with carbon numbers of C ₁ -C ₂₀ , aromatic hydrocarbons such as benzene, naphthalene etc., as well as mono- and polylalkyl, alkenyl and alkynyl-substituted aromatics such as toluene, xylene, cresol, styrene etc.

As the ceramic precursor BCl _3, NH _3, silanes such as tetraethoxysilane (TEOS), SiH _4, dichlorodimethylsilane (DDS), methyltrichlorosilane (MTS), Trichlorosilyldichloroboran (TDADB) Hexadichloromethylsilyloxid (HDMSO), AlCl _3, TiCl ₃ or mixtures thereof become.

This In CVD processes, precursors are mostly used in low concentrations from about 0.5 to 15 vol .-% in mixture with an inert gas, such as Nitrogen, argon or the like applied. Also the addition of Hydrogen to appropriate separation gas mixtures is possible. At temperatures between 500 and 2000 ° C, preferably 500 to 1500 ° C and particularly preferably 700 to 1300 ° C, the said compounds cleave hydrocarbon fragments or carbon or ceramic precursors, which are in the pore system pyrolyzed coating essentially evenly distributed precipitate, modify the pore structure there and so to one essentially homogeneous pore size and pore distribution in the sense lead to further optimization.

pyrolytic Carbon is usually a highly biocompatible material that is used in medical Applications such as the external coating of implants can be used. The biocompatibility of those coated according to the invention Substrates can also be built in by adding additives, fillers, Proteins or functional materials and / or medications in specifically influences the polymer films before carbonization, or changed as mentioned above. This allows rejection phenomena in body in manufactured according to the invention Reduce the implants or switch them off completely.

In particularly preferred embodiments, carbon-coated medical implants produced in accordance with the invention can be used by controlled adjustment of the porosity of the applied carbon layer for the controlled release of active substances from the substrate into the external environment. In this way, for example, medical implants can be used as a drug carrier with a depot effect, the carbon-based coating of the implant being used as a release-regulating membrane can. Drugs can also be applied to the biocompatible coatings. This is particularly useful where active substances cannot be applied directly in or on the substrate, as is the case with metals.

Further can those produced according to the invention Coatings in a further process step with drugs or drugs are loaded, or with markers, contrast agents to localize coated implants in the body, or also with therapeutic or diagnostic amounts of radioactive Spotlights. For the last one are the coatings of the invention based on carbon, because they are in contrast to Polymer layers of radioactive radiation not changed or to be attacked.

in the medical field prove to be coated according to the invention Implants as particularly long-term stable, because the carbon-based In addition to their high strength, coatings are also sufficiently elastic and are flexible so that they can accommodate the movements of the implant, in particular with highly stressed joints, can follow without the risk of that cracks form or the layer peels off.

Claims (12)

Process for coating substrates with carbon-based material, comprising the following steps: a) Coating a substrate with a polymer film on at least an outer surface of the substrate, b) Carbonization of the polymer film in an atmosphere that is essentially free of oxygen, at temperatures in the range of 200 ° C to 2500 ° C. A method according to claim 1, characterized in that the polymer film comprises additives selected from the group of fillers, Pore formers, metals, extenders, lubricants and pigments. A method according to claim 2, characterized in that the additives are selected are made of silicon oxides, aluminum oxides, aluminosilicates, zirconium oxides, Titanium oxides, talc, graphite, carbon black, zeolite, clay materials, Phyllosilicates, fullerenes, catalysts, metals and metal compounds and the same. Method according to one of the preceding claims, characterized characterized in that the polymer film comprises films selected from Homo- or copolymers of aliphatic or aromatic polyolefins such as polyethylene, polypropylene, polybutene, polyisobutene, polypentene; polybutadiene; Polyvinyls such as polyvinyl chloride or polyvinyl alcohol, Poly (meth) acrylic acid, Polyacrylonitrile, polyamide, polyester, polyurethane, polystyrene, polytetrafluoroethylene, as well as mixtures and combinations of these homo- or copolymers. A method according to claim 1 to 3, characterized in that the polymer film comprises a coating that is selected from paints, laminates or coatings. A method according to claim 5, characterized in that the polymer film is a paint film made from a paint with a binder base made of alkyd resin, chlorinated rubber, epoxy resin, Acrylic resin, phenolic resin, amine resin, oil-based, nitro-based, polyester, Polyurethane, tar, tar-like materials, tar pitch, bitumen, starch, cellulose, Shellac, organic materials from renewable raw materials or combinations thereof. Method according to one of the preceding claims, characterized characterized that the carbon-based material in the connection the carbonization of an oxidative and / or reducing aftertreatment, and possibly a CVD procedure for the deposition of carbon and / or Ceramic is subjected. Method according to one of the preceding claims, characterized characterized in that the substrate is selected from metals, alloys, Ceramics, zeolite, graphite, glass, stone, sand, carbon fiber composites, Bones or bone-like materials, bone substitutes, minerals, Precursors and ceramic green bodies, as well Combinations of these. Method according to one of the preceding claims, characterized characterized in that the substrate is selected from medical implants, stents, or catalyst supports. Method according to one of the preceding claims, characterized characterized in that the coated substrate with active ingredients or Microorganisms is loaded. A method according to claim 10, characterized in that the applied active ingredients are targeted in an application environment to be released. Carbon coated substrate, manufactured after the procedure according to a of the preceding claims.