Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2518/00—Other type of polymers
  • B05D2518/10—Silicon-containing polymers
  • B05D2518/12—Ceramic precursors (polysiloxanes, polysilazanes)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0209—Multistage baking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0254—After-treatment

Definitions

• the invention relates to a coating for a substrate, with a coating or base layer, and to a method for applying such a coating to a substrate.
• Substrate coatings based on fluoropolymers are known in the prior art, for example the coating of cooking appliances.
• Polytetrafluoroethylene (PTFE) is an extremely frequently used fluoropolymer which, however, in the liquid state, depending on the molecular weight above 300-340 ° C, has such a high melt viscosity that it can be processed either only by compressed sintering or at very high temperature.
• PTFE polytetrafluoroethylene
• the usual stoving temperature is therefore above 420 ° C.
• this results in the processing temperature being above the decomposition temperature of the polymer, releasing aggressive acid which attacks metals and carbons.
• PEEK polyetheretherketone
• PTFE polyetheretherketone
• halogens for example hydrofluoric acid
• a coating made of PEEK alone has neither a good non-stick effect nor is it suitable as a sealing material only if the pressure is very high.
• fluoropolymers are limited in their use temperature.
• the softening temperature of many fluoropolymers is in the range of about 250 ° C. Such a temperature range comes in use of, for example, frying pans quite.
• the high baking temperature of over 420 ° C for many substrates to be coated is simply too high, for example, for many aluminum castings and aluminum alloys, even more so for plastic parts, for example, fiber composite plastics such as those with "carbon" fibers
• a coating for a substrate which dispenses with the use of fluoropolymers would therefore be advantageous.
• silicone elastomers and silicone resins which are used as non-stick and as sealing materials are known from the prior art. These have the disadvantage that they are not very resistant to wear, build only low adhesion to the substrate and are therefore unsuitable for increased requirements.
• the temperature-resistant silicone resins are very brittle, which on the one hand causes poor wear properties on the other hand also causes great sensitivity to surface damage.
• the scratch resistance is insufficient.
• non-stick coatings known on the basis of so-called ceramic coatings with titanatic or zirconatic binding systems. Although these are very temperature-resistant and hard, but also very brittle and scratch-sensitive. In addition, the resistance to media, especially hot water and alkalis, is very bad.
• non-stick coating consisting of a make coat and a make coat in which the make coat contains a fluoropolymer and a binder resin, for example a polyimide resin, and the overcoat contains a multimodal blend of non-melting fluoropolymer.
• the DE 10 2006 061 940 A1 describes a coating for an article having a topcoat as the sole or topmost layer, the topcoat comprising a binder and filler.
• the binder comprises, as a main quantitative component, a high performance thermoplastic polymer, while the filler comprises, as a main quantitative component, a metal oxide powder.
• the DE 10 2005 037 338 A1 discloses a non-stick coating on a substrate having at least one primer layer on the substrate, wherein the at least one primer layer has inclusions in a grain size in the range of 0.5 to 50 microns, and at least one cover layer on the at least one primer layer, wherein the cover layer at least one component On silicone and / or silicate-based.
• the coatings known from the prior art often have the disadvantages that they wear very quickly, show poor adhesion to the substrate and have a fairly high brittleness. Additional disadvantages are lack of scratch resistance and poor corrosion protection.
• the invention has for its object to provide a versatile coating for a substrate, which overcomes the disadvantages of the prior art.
• the coating should allow good adhesion to a substrate, show improved wear behavior and less brittleness.
• a coating is to be provided which completely dispenses with fluoropolymers, in particular polytetrafluoroethylene (PTFE, Teflon), and nevertheless forms a thermally and mechanically extremely resistant, scratch-resistant coating which adheres well to the substrate.
• PTFE polytetrafluoroethylene
• a coating for a substrate with a coating layer or base layer on the substrate, wherein the coating or base layer comprises a binding matrix selected from the group consisting of silicone resin, titanate, zirconate, silanes and mixtures thereof wherein the binder matrix contains from 0.5 to 20% by weight, based on the weight of the base layer, of a thermoplastic, preferably less than 15% or 10%.
• the present invention relates to a layer structure of a substrate and a coating or base layer. Between the substrate and the base layer, a bonding agent can be arranged.
• the binder matrix degrades its organic content upon annealing to a temperature above the softening or liquidus temperature of the thermoplastic, leaving only a ceramic residue.
• the softening temperature of PEEK is about 320 ° C. and the liquidus temperature is 340 ° C., while for PPS the corresponding temperatures are each about 60 ° C. lower.
• silicone resin as the binding matrix, only a ceramic residue, namely SiO 2 , is thus retained after sufficiently long tempering.
• titanate or zirconate compounds with organic radicals These decay under hydrolysis under temperature also into ceramic components.
• a particularly preferred embodiment of a coating according to the invention is the use of a mixture of silicone resin and a titanate, for example isobutyl titanate, as a binding matrix.
• Suitable silicone resins are, for example, methyl silicone resin and / or phenyl silicone resin.
• substrates for example, metallic substrates, in particular aluminum (cast), (stainless) steel, steel enamel, copper, brass, bronze, nickel, chromium and magnesium, ceramic substrates and plastics and fiber materials, for example glass fibers and carbon fibers, may be mentioned.
• metallic substrates in particular aluminum (cast), (stainless) steel, steel enamel, copper, brass, bronze, nickel, chromium and magnesium, ceramic substrates and plastics and fiber materials, for example glass fibers and carbon fibers, may be mentioned.
• the coating according to the invention is most preferably characterized by a cover layer on the base layer which contains a binder matrix with a smaller proportion of a thermoplastic than the base layer.
• the base layer contains 30 to 99% by weight of silicone resin (dry weight), more preferably more than 50% by weight of silicone resin, and especially free of polytetrafluoroethylene.
• the proportion of the silicone resin refers to the proportion in the starting product with which the coating is produced. After tempering at more than 240 ° C, the silicone resin decomposes into Si0 2 .
• the topcoat may contain 35 to 100 weight percent silicone resin (dry weight).
• thermoplastic material in the base layer and / or in the cover layer is selected from the group consisting of liquid crystalline polymer (LCP), polyaryletherketone, polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketone ketone (PEKK), polyphenylene sulfide ( PPS), polyethersulfone (PES), polyphenylene ether sulfone (PPSU) and mixtures thereof.
• LCP liquid crystalline polymer
• PEK polyetherketone
• PEEK polyetheretherketone
• PEKK polyphenylene sulfide
• PPS polyethersulfone
• PPSU polyphenylene ether sulfone
• the temperature resistance of the thermoplastics used is preferably above 200 ° C., more preferably above 250 ° C.
• the invention preferably provides that the proportion of thermoplastic in the top layer is less than or equal to 2% by weight or less than or equal to 1% by weight.
• the cover layer may be free of thermoplastic material.
• the cover layer is free of polytetrafluoroethylene. In fact, experiments with (added) fluoroplastics have yielded negative results.
• the cover layer contains a thermoplastic other than the base layer.
• the base layer and / or top layer may contain a filling of mineral, metallic and / or ceramic particles whose particle size may be in the range of 10 to 200 nm, in particular 30 to 70 nm. The proportion of particles can be from 0.1 to 10% by weight, based on the base layer or covering layer.
• metallic fillers and their oxides are suitable, in particular aluminum, aluminum oxide, copper or copper chromium.
• Preferred fillers are SiO 2 , Al 2 O 3 and aluminum semolina.
• the top layer should be less filled than the base layer.
• particles in the nanometer range in addition to these nanoparticles, particles with a particle size in the micrometer range, for example between 10 to 50 microns, are included. However, these particles in the micrometer range should be contained in a smaller proportion than the nanoparticles. This applies in particular to the cover layer, which preferably contains no such (macroscopic) fillers.
• both the base layer and the top layer may contain titanatic or zirconic binders, amounting to 0.05-5% by weight.
• titanate or zirconate can be provided merely as additives to the silicone resin, for example in an amount of 3% by weight.
• An exemplary coating composition could be as follows: 85% by weight of isobutyl titanate, 5% by weight of aluminum grits, 5% by weight of PEEK and 5% by weight of inorganic pigment, where a stoving temperature at 360 ° C. or higher.
• the invention provides that the proportion of thermoplastic within the base layer decreases in the direction away from the substrate. Furthermore, it is preferably provided that the proportion of thermoplastic material decreases within the cover layer in the direction of a free surface of the cover layer, wherein in particular the cover layer on the free surface is free of thermoplastic material.
• the invention further provides a method for applying a coating to a substrate, wherein a coating layer or base layer containing a binder matrix selected from the group consisting of silicone resin, titanate, zirconate, silanes and mixtures thereof is applied to the substrate which binder matrix contains from 0.5 to 20% by weight, based on the weight of the base layer, of a thermoplastic, preferably less than 15% or 10%.
• a coating layer or base layer containing a binder matrix selected from the group consisting of silicone resin, titanate, zirconate, silanes and mixtures thereof is applied to the substrate which binder matrix contains from 0.5 to 20% by weight, based on the weight of the base layer, of a thermoplastic, preferably less than 15% or 10%.
• an adhesion promoter can be applied to the substrate.
• a cover layer is applied to the base layer, which contains a binding matrix with a smaller proportion of a thermoplastic than the base layer.
• the base layer and / or the cover layer can be applied in liquid form or in powder form.
• the coating can thus be applied to a substrate wet or by means of powder, for example electrostatically, and in combinations thereof.
• the coating is also suitable for dip coatings, especially for drum coatings.
• a base layer can be applied wet as a powder and a cover layer or vice versa.
• the binder matrix of the base layer is crosslinked at a temperature which is below a softening or liquefaction temperature of the thermoplastic, or at a temperature which is at or above a softening or liquefaction temperature of the thermoplastic.
• the invention also provides a powder, a granule, a dispersion or a solution for producing a base layer for a coating according to the invention comprising a binder matrix which is selected from the group consisting of silicone resin, titanate, zirconate, Silanes and mixtures thereof, wherein the binder matrix contains a proportion of 0.5 to 20 wt .-% of a thermoplastic, preferably less than 15% or 10%.
• the invention is based on the surprising finding that a combination of binding matrix with a high-temperature thermoplastic already shows a noticeable increase in the wear behavior even with only a small proportion of thermoplastic. In addition, the adhesion to a substrate is considerably improved and the otherwise occurring brittleness considerably reduced. Already an addition of, for example, 1 wt .-% of the thermoplastic material shows a sudden improvement of the properties mentioned.
• An advantageous embodiment of the present invention is achieved by coating a base layer of silicone resin containing about 4% by weight of PEEK on a substrate, and coating a cover layer of silicone resin on the base layer, the cover layer containing no thermoplastic.
• cover layer is particularly advantageous when non-stick properties are in the foreground. If this is not the case, such a cover layer is not absolutely necessary.
• a coating according to the invention is illustrated by means of a 1000h salt spray test of coated ferritic steel.
• a coating was applied to ferritic steel, which had the following composition: 63% by weight of silicone resin, 7% by weight of PEEK, 3% by weight of titanate, 7% by weight of aluminum grits, 5% by weight of pigment and 15 Wt .-% fillers.
• a cover layer was applied containing 100 wt .-% silicone resin.
• the baking temperatures of the base and top layers were 200 ° C / 320 ° C for the first and second annealing step.
• test was then carried out at room temperature by spraying a five percent NaCl solution in water in accordance with the standard with cross-hatch.
• the coating of the invention showed at a layer thickness of only 20 microns no infiltration of the cross-hatch and no detachment.
• the coating according to the invention thus performs better in the corrosion protection behavior than coatings of the individual components, for example a 100% PEEK coating or a 100% polymethylsiloxane coating. Both comparative coatings showed detachment at cross-hatch and undercrossings with red rust.
• the coating according to the invention improves the wear behavior and the adhesion to a substrate and reduces the brittleness of the coating.
• the non-stick properties of the "free" surface of the coating according to the invention can be particularly preferably improved by providing a two-layer structure for the coating according to the invention.
• a base layer is first applied to a substrate, such as a metal surface of a cooking appliance, which contains, for example, a silicone resin in a proportion of 0.5 to 10 wt .-%, preferably 1 to 4 wt .-%, of a thermoplastic material , On this base layer, a cover layer is then applied, which contains, for example, a silicone resin with a smaller proportion of a thermoplastic material than the base layer, for example below 1 wt .-%.
• the non-stick properties of the cover layer can be further increased by containing mineral and / or ceramic particles, for example in a proportion of 0.1 to 10 wt .-%, based on the cover layer.
• the size of the particles may be in the range of, for example, 10 to 200 nm, for example between 30 and 70 nm.
• thermoplastic component already exists within the base layer, wherein the thermoplastic fraction in the vicinity of the substrate is relatively high and relatively low in the vicinity of the transition to the cover layer. It is further favorable if in the cover layer little or no thermoplastic is included, or if in the cover layer a corresponding gradient as in the base layer is present and the proportion of thermoplastic decreases in the direction of a free surface of the cover layer and on the surface only slightly or preferably no thermoplastic is contained.
• the base layer and / or the cover layer can be applied either in flowable form or in powder form.
• the silicone resin can be crosslinked at a temperature which is below a softening or liquefaction temperature of the thermoplastic, it is advantageous if the crosslinking temperature is at or above a softening or liquefaction temperature of the thermoplastic, so that the favorable wear and adhesion properties of the Base layer can be further increased.
• Advantageous properties arise in a production process even at a processing temperature of only 150 ° - 230 ° C, in which the binder matrix system crosslinked, but the thermoplastic material is not soft or liquid, but is above its glass transition temperature.
• first annealing step leads to crosslinking of the silicone resin portion, while the second annealing step serves for attachment to the thermoplastic portion.
• the first annealing step is thus intended to serve that when silicone resin is used in the binding matrix, it can crosslink to such an extent that it withstands a required higher temperature without undesired decomposition.
• the first heat treatment stage is preferably at 150 to 230 ° C. and, if appropriate, this first heat treatment stage can be replaced in some systems by crosslinking at room temperature, which then, however, requires a significantly longer time.
• the organic portion of the binding matrix disintegrates, at least partially, but not necessarily completely. Without the previous precrosslinking, however, an amorphous layer without strong bonding is obtained in many cases.
• the coating according to the invention can be used extremely advantageously as a non-stick coating, for example for coating cooking appliances.
• the coating according to the invention consisting merely of a base layer of binder matrix with a proportion of thermoplastic material can advantageously be used as a low-wear primer for sealing coatings.
• a base layer may be composed of silicone resin, mineral and / or metallic fillers or metal oxides, thermoplastic and other additives, such as titanate or zirconate (Lewis acid).
• a cover layer based on a silicone resin may be provided.
• Such a primer is much more resistant than conventional, known from the prior art silane coupling agent.
• Advantages arise in particular with regard to the chemical resistance of the bond as well as the additional wear and corrosion protection. The resistance to mechanical tearing due to overloading is enormously reduced.
• Particularly advantageous is the repeated covering of the base layer described above by a few micrometers thick silicone resin layer for the wear behavior.
• at least the uppermost silicone resin layer can not be crosslinked, so that a post-curing results after the gasket installation.
• Another very advantageous application of the coating according to the invention results from the coating or impregnation of fibrous materials, ie fiber fabrics or even random fiber distributions.
• the use in the coating or impregnation of carbon fibers is advantageous because here the bond to the fiber is very good. In comparison to conventional carbon materials with bonding resins based on epoxides or phenolic resins, this results in a superior temperature resistance of up to 500 ° C in the short term.
• a base coat is applied containing 4 to 10% (all unless otherwise stated, by weight) polyetheretherketone (PEEK) or polyetherketone (PEK), 0-25% fillers and the remainder methyl silicone resin.
• a topcoat containing less fillers and about 0-4% polyphenylene sulfide (PPS) is applied to this basecoat. This coating is cured after drying at about 200 ° C for about 20-60 minutes and then post-annealed at about 300 ° C-360 ° C for about 5-30 minutes.
• a construction comprising a base layer and a soft, set resin, polymer or elastomer layer arranged thereon is advantageous.
• Exemplary polymer or elastomer layers can be, for example, layers based on fluoroelastomers, PTFE or PEEK.
• the cover layer becomes softer, for example, by a lower addition of a crosslinker, less strong filling, etc.
• Another possibility for the control lies in the addition of crosslinking inhibitors, for example silicone oil.
• a high-performance polymer layer underneath the base layer which serves as a lower layer.
• This underlayer would need to be baked before applying the base coat, advantageously above the liquefaction temperature of the high performance polymer.
• PEEK a temperature of more than 340 ° C., preferably more than 360 ° C., would be advantageous, when using PPS a temperature of more than 285 ° C., preferably more than 300 ° C.

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• 2009
  • 2009-11-10 DE DE200910052398 patent/DE102009052398B4/de not_active Expired - Fee Related
• 2010
  • 2010-11-10 EP EP20100014486 patent/EP2319631B1/fr active Active

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