Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
• • 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
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
  • B05D7/16—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies using synthetic lacquers or varnishes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G8/00—Condensation polymers of aldehydes or ketones with phenols only
  • C08G8/28—Chemically modified polycondensates
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
  • C09D5/08—Anti-corrosive paints
  • C09D5/12—Wash primers
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
  • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
  • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
  • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
  • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
  • C23C22/361—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing titanium, zirconium or hafnium compounds
• • 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
  • B05D2202/00—Metallic substrate

Definitions

• This invention relates to a new functionalized phenol-aldehyde resin and to the use of this or related resins for the anti-corrosion treatment of metal surfaces.
• the metal surfaces may be bare, i.e. non-pre-treated, metal surfaces or metal surfaces which already have a corrosion-inhibiting conversion layer.
• a particular feature of the invention in this regard is that no toxic chromium has to be used.
• Structural elements fitted together from metal sheets can be assembled from metal sheets which do not yet have a permanent corrosion-inhibiting coating.
• a permanent corrosion-inhibiting coating consisting of a conversion layer and a paint layer can be produced after the metal parts have been assembled.
• a known example of this is the process sequence of phosphating and painting which is normally applied, for example, in car manufacture.
• the actual phosphating is only one step in a treatment chain which, besides cleaning and rinsing steps, generally comprises activation before phosphating, the actual phosphating and often a post-passivation after phosphating. These treatment steps are followed by several painting steps.
• the pre-treatment before painting requires several treatment steps which, in turn, necessitate a correspondingly extensive and hence expensive pre-treatment plant.
• waste containing heavy metals accumulates in the phosphating step and has to be expensively disposed of.
• a “conversion layer” is understood to be a layer on a metal surface which is formed by “conversion treatment” under the effect of a “conversion solution” and which contains elements both from the metal surface and from the conversion solution. Typical examples are phosphate layers or chromating layers.
• conversion treatment for example using conversion solutions based on complex fluorides of boron, silicon, titanium or zirconium. These complex fluorides are mostly used together with organic polymers. Examples of such conversion treatments can be found in DE-A-101 31 723 and in the literature cited therein. However, none of these alternative processes has so far been able to replace phosphating as a pre-treatment before painting in car manufacture.
• EP-B-8 942 discloses treatment solutions containing
• WO 92/07973 teaches a chromium-free treatment process for aluminium which uses 0.01 to about 18% by weight of H 2 ZrF 6 and 0.01 to about 10% by weight of a 3-(N—C 1-4 -alkyl-N-2-hydroxyethylaminomethyl)-4-hydroxystyrene polymer as essential components in an acidic aqueous solution.
• Optional components are 0.05 to 10% by weight of dispersed SiO 2 , 0.06 to 0.6% by weight of a solubilizer for the polymer and surfactant.
• WO 97/31135 discloses a solution for the post-rinsing of conversion-treated metal surfaces which contains compounds, for example hexafluoro complexes, of Ti, Zr or Hf and a phenolic resin.
• the phenolic resin may contain differently substituted phenols.
• the molecular weight of the resin is in the range from 100 to 1,000.
• U.S. Pat. No. 6,419,731 discloses a solution for the conversion treatment of aluminium which contains a zirconium compound, fluoride ions and a water-soluble resin.
• the water-soluble resin may be inter alia a phenolic resin.
• U.S. Pat. No. 5,246,507 also relates to a composition for treating metal surfaces which contains metal compounds that may be selected, for example, from compounds of Ti, Zr and Hf and an organic polymer.
• the polymer may be, for example, a condensation product of formaldehyde with phenol and a phenolic carboxylic acid.
• U.S. Pat. No. 5,846,917 describes phenolic imidazolines which can be obtained by a condensation reaction of hydrocarbyl polyaminophenols with carbonyl compounds. They are used primarily as antioxidants, but are also expected to show corrosion-inhibiting and passivating activity. These polymers differ structurally from phenolic resins in that they do not contain any alkylene-bridged phenol units.
• Japanese patent application with the publication number 59-157110 discloses phenolic resins which contain an imidazole ring. These resins are used as a component of heat-resistant adhesives for, for example, copper-containing laminates, circuit boards or the like.
• Derwent Abstract AN (acquisition number) 1999-018521 contains a summary of Japanese document JP 10287859, according to which phenolic adhesives of the resol resin type additionally containing imidazole are produced. The adhesives are used for the production of plywood or veneer.
• Phenol-aldehyde condensation products more particularly phenol-formaldehyde condensation products, have long been known under the names of phenolic resins, phenolics, novolaks, resols, B-stage resins or C-stage resins. Information on their production and properties can be found, for example, in Römpps Chemie Lexikon under the keywords mentioned.
• the problem addressed by the present invention was to provide new, functionalized polymers of the phenolic resin type which can be used, more particularly in the form of an aqueous solution or emulsion, for the surface treatment of bare metal surfaces or metal surfaces already carrying a conversion layer.
• the treatment of the metal surfaces with the polymers improves corrosion prevention and/or the adhesion of a subsequently applied paint or an adhesive to the metal surface.
• Another aspect of the invention provides a process for the production of the functionalized phenol-aldehyde resin described herein, characterized in that aqueous aldehyde solution is added to an aqueous solution containing the phenolic component, aromatic hydroxycarboxylic acid and imidazole, followed by mixing for 10 minutes to 10 hours at a temperature between 40° C. and the boiling point.
• Another aspect of the invention provides a process for the production of the functionalized phenol-aldehyde resin of the invention wherein:
• an aqueous solution of a phenol-aldehyde resin containing incorporated aromatic hydroxycarboxylic acids is prepared and
• the aforementioned processes are characterized in that the concentration of the organic compounds in the aqueous reaction solution is selected so that an aqueous solution of the functionalized phenol-aldehyde resin of the invention with a solids content of 10 to 50% by weight is obtained.
• a process for the corrosion-inhibiting treatment of bare or conversion-coated metal surfaces characterized in that the metal surfaces are contacted with an aqueous treatment solution containing one or more phenol-aldehyde resins, characterized in that at least one phenol-aldehyde resin contains incorporated imidazole and is preferably the functionalized phenol-aldehyde resin as described herein.
• the aqueous treatment solution contains at least 5, preferably at least 20 and up to 2,000, preferably up to 200 mg/l phenol-aldehyde resin which contains incorporated imidazole. It is also desirable that the aqueous treatment solution has a pH of at least 1.5, preferably at least 1.8 to at most 6, preferably to at most 4.5.
• aqueous treatment solution additionally contains fluoride ions and/or one or more compounds of elements of the fourth main or transition metal group of the periodic system, preferably compounds of Si, Ti and/or Zr.
• the cleaned, assembled structural component is contacted with a chromium-free aqueous treatment solution which produces a passivation layer that is not a zinc phosphate layer on those areas of the metal surface formed in step a) that are not covered by the coating based on organic polymers, the aqueous treatment solution containing one or more phenol-aldehyde resin(s), at least one phenol-aldehyde resin containing incorporated aromatic hydroxycarboxylic acids and/or incorporated imidazole and preferably being a functionalized phenol-formaldehyde resin as described herein,
• step c) if desired, the structural component treated in step c) is rinsed one or more times with water, although this is not essential, and
• the invention provides an aqueous treatment solution for treating bare or conversion-coated metal surfaces which contains one or more of the functionalized phenol-aldehyde resins according to the invention.
• a metal sheet, a metal part or an article containing metal parts is provided characterized in that at least one surface of the metal sheet or the metal parts has been treated by the compositions and/or processes of the invention.
• a first aspect of the invention relates to a functionalized phenol-aldehyde resin which comprises a phenol-aldehyde condensation product, having a phenol component with no carboxyl group, and an aromatic hydroxycarboxylic acid and imidazole as constituents.
• a “phenol-aldehyde resin” is understood in particular to be a phenol-formaldehyde resin.
• aldehydes such as furfural for example, may be used instead of, or in admixture with, the formaldehyde as aldehyde components.
• the phenolic component may be, above all, phenol itself. In a preferred embodiment, at least 50% and preferably at least 90% of the phenolic component is phenol.
• aromatic hydroxy compounds such as, for example, alkyl- or aryl-substituted phenols, for example cresols, polyhydric phenols, for example pyrocatechol, resorcinol or hydroquinone, trihydric phenols (pyrogallol, phloroglucinol, hydroxyhydroquinone) or anellated phenols, such as, for example, ⁇ - and ⁇ -naphthol, or alkyl-bridged diphenols, such as bisphenol A for example, may be used as the phenolic component.
• polyhydric phenols for example pyrocatechol, resorcinol or hydroquinone
• trihydric phenols pyrogallol, phloroglucinol, hydroxyhydroquinone
• anellated phenols such as, for example, ⁇ - and ⁇ -naphthol
• alkyl-bridged diphenols such as bisphenol A for example
• the aromatic hydroxycarboxylic acid by definition has an aromatic ring system to which at least one hydroxy group and at least one carboxylic acid group are attached.
• the simplest examples of this are the position isomers of hydroxybenzoic acid, such as salicylic acid and m- or p-hydroxybenzoic acid.
• the aromatic ring system may carry further substituents such as, for example, alkyl groups, nitro groups, amino groups or even further hydroxy or carboxylic acid groups.
• the aromatic hydroxycarboxylic acid may even have a condensed aromatic ring system and may be, for example, one of the position isomers of hydroxynaphthoic acid.
• One example of an aromatic hydroxycarboxylic acid containing more than one carboxyl group is hydroxyphthalic acid.
• aromatic hydroxycarboxylic acid is preferably selected from hydroxybenzoic acids, more particularly from salicylic acid and p-hydroxybenzoic acid.
• imidazole is preferably meant the parent compound itself.
• the parent compound may carry substituents, more particularly at the C atoms. These substituents may represent another aromatic ring system, as in the case of benzimidazole for example.
• the molar ratio of phenolic component to aromatic hydroxycarboxylic acid and the molar ratio of phenolic component to imidazole are preferably selected independently of one another so that the proportion of phenolic component in the functionalized phenol-aldehyde resin is at least as large as, but preferably larger than, the proportion of aromatic hydroxycarboxylic acid or the proportion of imidazole.
• the molar ratio of phenolic component to aromatic hydroxycarboxylic acid and the molar ratio of phenolic component to imidazole are selected independently of one another so that each is in the range from 1:1 to 100:1.
• the two molar ratios may of course be substantially the same or different.
• the molar ratios are preferably selected so that a molar ratio of aromatic hydroxycarboxylic acid to imidazole in the range from 100:1 to 1:100 and more particularly in the range from 10:1 to 1:10 is obtained.
• a molar ratio of 1:1 to 10:1 is especially preferred.
• composition of the functionalized phenol-aldehyde resin is preferably such that at least 50% and preferably at least 90% consists of the phenolic component, aromatic hydroxycarboxylic acid and imidazole and the bridging alkylene groups emanating from the aldehyde component (methylene groups where formaldehyde is used).
• the other constituents of the polymer may represent, for example, aromatic aminocarboxylic acids such as, in particular, aminobenzoic acids instead of the aromatic hydroxycarboxylic acid or other aromatic or aliphatic heterocycles instead of the imidazole.
• At least 50%, preferably at least 90% and more particularly at least 100% of the phenolic component consists of the parent compound phenol
• at least 50%, preferably at least 90% and more particularly 100% of the aromatic hydroxycarboxylic acid consists of a hydroxybenzoic acid (more particularly salicylic acid)
• at least 50%, preferably at least 90% and more particularly 100% of the imidazole component consists of the parent compound, imidazole, itself.
• a functionalized phenol-aldehyde resin which consists entirely of phenol, hydroxybenzoic acid (more particularly salicylic acid), imidazole and the bridging alkylene groups (more particularly methylene groups) is particularly preferred.
• the average molecular weight of the functionalized phenol-aldehyde resin which can be determined, for example, by gel permeation chromatography with polyethylene glycol as standard, is preferably at least 500, more particularly at least 1,000 and preferably at most 50,000 and more particularly at most 10,000.
• the general process for the production of phenol-aldehyde resins by condensation of a phenol with an aldehyde in aqueous solution is generally known and is described in chemical textbooks and encyclopedias.
• the above-described functionalized phenol-aldehyde resins with their at least 3 aromatic components can be produced, for example, by adding aqueous aldehyde solution to an aqueous solution containing the phenolic component, aromatic hydroxycarboxylic acid and imidazole and mixing for 10 minutes to 10 hours at a temperature of 40° C. to the boiling point.
• this solution may be boiled under reflux which, in itself, can produce an adequate mixing effect. Otherwise, mixing can be achieved by stirring or shaking.
• This production process represents another aspect of the present invention.
• the mixing of the solution both in the first step a) and in the second step b) can be achieved by refluxing, stirring or shaking.
• the concentration of the organic compounds in the aqueous reaction solution is preferably selected so that an aqueous solution of the functionalized phenol-aldehyde resin with a resin solids content of 10 to 50% by weight is obtained at the end of the reaction.
• this solution need not be further purified. Rather, it can be directly marketed as such and used for the production of the treatment solution described in the following by dilution with water or for supplementing this treatment solution with active ingredient.
• Another aspect of the present invention relates to the use of the functionalized phenol-aldehyde resin described above or of a mixture of two or more such resins for the corrosion-inhibiting treatment of bare metal surfaces or metal surfaces already carrying a conversion layer.
• the metal surfaces are preferably selected from surfaces of steel, galvanized or alloy-galvanized steel, aluminized steel, zinc, aluminium, magnesium or alloys of which at least 50 atom-% consists of zinc, aluminium or magnesium.
• the conversion layer on the metal surfaces may be, for example, an anodizing layer, a phosphating layer such as can be produced by a layer-forming or non-layer-forming phosphating process or a coating based on fluorocomplexes of, for example, B, Si, Ti, Zr, Hf, as described, for example, in the literature cited at the beginning.
• a phosphating layer such as can be produced by a layer-forming or non-layer-forming phosphating process or a coating based on fluorocomplexes of, for example, B, Si, Ti, Zr, Hf, as described, for example, in the literature cited at the beginning.
• the present invention also relates to a process for the corrosion-inhibiting treatment of bare metal surfaces or metal surfaces already provided with a conversion layer, in which the metal surfaces are contacted with an aqueous treatment solution containing one or more phenol-aldehyde resins, at least one phenol-aldehyde resin containing incorporated imidazole and preferably being a functionalized phenol-aldehyde resin as described herein.
• the metal surfaces may be completely bare or completely coated with a conversion layer. However, they may also be metal surfaces of complex structural parts such as, for example, car bodies which consist partly of bare and partly of conversion-coated metal parts. A corrosion-inhibiting layer is then produced on the bare metal parts by the process according to the invention and the corrosion-inhibiting effect of the conversion-treated metal surfaces is improved.
• the metal surfaces may already partly carry an organic coating which is locally damaged, for example at cut edges, ground areas or spot welds, so that the metal surface is again bare at such places. Such conditions prevail, for example, when complex structural parts, such as car bodies or domestic appliances, are at least partly assembled from precoated sheets.
• the minimum requirement in this regard is that at least one phenol-aldehyde resin is present which at least contains incorporated imidazole, but not necessarily the aromatic hydroxycarboxylic acid, too.
• the above-described preferred embodiments in regard to components and molar ratios apply accordingly to such phenol-aldehyde resins with incorporated imidazole, but without incorporated aromatic hydroxycarboxylic acid.
• the metal surfaces are preferably contacted with an aqueous treatment solution which contains at least one of the above-described functionalized phenol-aldehyde resins that comprises the three components: a phenol-aldehyde resin which contains a phenol component with no carboxyl group, aromatic hydroxycarboxylic acid and imidazole as constituents. Most preferably a functionalized phenol-aldehyde resin as described herein.
• the aqueous treatment solution preferably contains at least 5 mg/l and, more particularly, at least 20 mg/l, but preferably at most 2,000 and, more particularly, at most 200 mg/l of phenol-aldehyde resin containing incorporated imidazole and preferably a functionalized phenol-aldehyde resin according to the invention.
• the corrosion-inhibiting effect diminishes increasingly. Even higher contents can adversely affect corrosion prevention or at least are uneconomical.
• the aqueous treatment solution preferably has a pH of at least 1.5, more particularly of at least 1.8 to at most 6.0 and, more particularly, to at most 4.5.
• a pH of at least 1.5 more particularly of at least 1.8 to at most 6.0 and, more particularly, to at most 4.5.
• the metal is increasingly too seriously attacked by the pickling effect.
• layer formation increasingly deteriorates as, hence, does the corrosion-inhibiting effect.
• the temperature of the treatment solution is preferably in the range from 20 to 60° C. and more particularly in the range from 25 to 40° C.
• the preferred contact time of the metal surface with the treatment solution is preferably in the range from 5 to 240 seconds and, more particularly, in the range from 30 to 200 seconds.
• the metal surface may be contacted with the treatment solution in the usual way, for example by immersion in the treatment solution, by spraying with the treatment solution or by combinations thereof or even by roller application of the treatment solution.
• the conversion layer on the one hand can have been produced immediately before the after treatment according to the invention and, accordingly, may still be wet.
• a rinse with water may be carried out between formation of the conversion layer and the after treatment according to the invention. However, it may also be omitted.
• a relatively long period of time may also elapse between formation of the conversion layer and the after treatment according to the invention. This is the case, for example, when structural parts, such as car bodies or domestic appliances for example, are assembled from prephosphated steel and then after treated by the treatment process according to the invention.
• a cleaning step may be inserted between the conversion treatment and the after treatment according to the invention.
• the aqueous treatment solution preferably contains one or more compounds of elements of the 4 th main or transition metal group of the periodic system, more particularly Si, Ti and/or Zr.
• the Ti, Zr and/or Si ions mentioned may be completely used in the form of hexafluoro complexes such as, for example, the hexafluoro acids or their salts soluble in water in the concentration range mentioned, such as the sodium salts for example. In this case, the atomic ratio is 1:6.
• complex compounds where less than six fluoride ions are attached to the central elements Ti, Zr or Si may also be used. These may be spontaneously formed in the treatment solution if both hexafluoro complexes of at least one of the central elements Ti, Zr or Si and at least one other compound of one of these central elements are added to the treatment solution.
• Suitable other compounds are, for example, nitrates, carbonates, hydroxides and/or oxides of the same central element or of another of the three central elements mentioned.
• the treatment solution may contain hexafluorozirconate ions and (preferably colloidal) silica (SiO 2 ) or reaction products thereof. Unreacted silica may be suspended in the treatment solution.
• a treatment solution such as this may also be obtained by using hydrofluoric acid or (optionally acidic) salts thereof together with compounds of Ti, Zr and/or Si which are capable of forming fluoro complexes therewith. Examples are the already mentioned nitrates, carbonates, hydroxides and/or oxides.
• a preferred embodiment is characterized in that, in all, such a quantity of Ti, Zr and/or Si as the central metal and such a quantity of fluoride are used that the atomic ratio of central metal to fluoride is 1 : 2 or lower, more particularly 1:3 or lower.
• the atomic ratio may even be lower than 1:6 if the treatment solution contains more fluoride, for example in the form of hydrofluoric acid or salts thereof, than is stoichiometrically necessary for forming the hexafluoro complexes of the central metals Ti, Zr and/or Si.
• the aqueous solution may additionally contain 0.001 to 2 g/l and preferably 0.005 to 0.5 g/l ions of one or more of the metals Mn, Ce, Li, V, W, Mo, Mg, Zn, Co and Ni.
• the metals Mn, Ce, Li, V, W, Mo, Mg, Zn, Co and Ni are preferably 0.005 to 0.5 g/l ions of one or more of the metals Mn, Ce, Li, V, W, Mo, Mg, Zn, Co and Ni.
• the treatment solutions in practice will additionally contain metal ions that have been dissolved out from the metal surface. Apart from the zinc already mentioned, these metal ions may be, in particular, iron and aluminium.
• Their concentrations may also be in the range from 0.001 to 2 g/l and more particularly in the range from 0.005 to 0.5 g/l.
• aluminium ions in the form of soluble aluminium compounds to the treatment solution from the outset in the concentration range mentioned.
• zinc ions for example as nitrate salt
• the aqueous solution may additionally contain 0.001 to 1.5 g/l and preferably 0.1 to 1 g/l phosphoric acid, phosphorous acid, phosphonic acid and/or anions and/or esters thereof. Esters should be selected so that they are soluble or dispersible in water. These additions also improve the corrosion-inhibiting effect and paint adhesion. However, in line with the basic concept of the present invention, it is important to ensure that no combination of additions that would lead to the formation of a crystalline zinc-containing phosphate layer is selected, because this would lead to a conventional zinc phosphate layer which is known in the prior art and which only creates an adequate corrosion-inhibiting effect if the usual steps of activation and post-passivation are additionally carried out.
• the present invention seeks precisely to avoid this more complicated sequence of process steps. This is achieved, for example, if the treatment solution does not simultaneously contain zinc and/or manganese in concentrations of more than 0.3 g/l and phosphoric acid or phosphate ions in concentrations of more than 3 g/l.
• the aqueous solution additionally contains one or more of the components which are known in the phosphating field as so-called phosphating accelerators.
• phosphating accelerators the principal function of such accelerators is to prevent the formation of bubbles of elemental hydrogen on the metal surface.
• This effect is also known as depolarization.
• the effect of depolarization in the process according to the invention, as in conventional phosphating, is that the conversion layer is formed more quickly and more uniformly.
• the aqueous solution contains one or more phosphating accelerators selected from
• the process according to the invention is generally incorporated in a treatment chain which usually begins with the cleaning of the parts to be treated.
• These parts may be bare metal parts which are coated by the treatment process according to the invention with a surface layer which improves corrosion prevention and the adhesion of a subsequently applied organic coating.
• the treatment with the treatment solution according to the invention may be the only treatment step which produces such a surface layer.
• the process according to the invention may also be used to improve corrosion prevention and paint adhesion on metal surfaces which are already coated with a conversion layer. This layer can have been applied by the manufacturer of the sheet material, so that a relatively long period of time can elapse between the first conversion treatment and the application of the treatment process according to the invention.
• the conversion layer may also be formed in an after treatment step immediately before application of the process according to the invention.
• Rinsing with water is generally carried out one or more times between the individual treatment steps and also after application of the process according to the invention.
• Deionized water is preferably used for the final rinse after application of the process according to the invention.
• the metal surfaces treated by the process according to the invention are then generally coated with another layer based on organic polymers.
• This other layer may be, for example, a single- or multi-layer paint.
• this paint may be a typical automotive paint of which the layer next to the metal is normally a cathodic dipping paint.
• the paint may also be applied as a powder which is regarded as adequate, for example, for domestic appliances, metal furniture and the like.
• the surface layer produced on the metal surfaces by the treatment process according to the invention may also serve as a primer for bonding.
• the treated metal surface is coated with an adhesive.
• Metal parts may be bonded to one another, to glass or to plastic parts or even to rubber.
• the process may be used as a pre-treatment for rubber-to-metal bonding.
• Corresponding materials are known, for example, under the names of Granocoat®, Durasteel®, Bonazinc® and Durazinc®. They carry a thin organic coating over a conversion layer, for example a chromating or phosphating layer.
• the organic coating consists of polymer systems such as, for example, epoxy or polyurethane resins, polyamides and polyacrylates.
• Solid additives, such as silicas, zinc dust and carbon black improve corrosion protection and, by virtue of their electrical conductivity, enable the metal parts coated with layers about 0.3 to about 10 ⁇ m and preferably up to about 5 ⁇ m thick to be electrically welded and electrolytically painted.
• the substrate materials are generally coated in a two-stage process, in which the inorganic conversion layer is first produced and the organic polymer film is then applied in a second treatment stage. More information on this process can be found in DE-A-100 22 075 and the literature cited therein.
• metal sheets provided with a coating based on organic polymers by coil coating are already partly in use in the manufacture of vehicle bodies, domestic appliances and items of furniture.
• corrosion prevention and paint adhesion have to meet the strictest requirements because vehicles are exposed to the most serious corrosive stresses.
• no vehicle bodies are made exclusively from organically precoated metal sheets. Instead, this material is made up into the vehicle bodies together with non-precoated sheets. Accordingly, the assembled bodies at present still go through the usual pre-treatment process before painting, i.e. they are subjected to the expensive process of phosphating.
• the phosphating process could be replaced by a less expensive pre-treatment process if the vehicle bodies were to be made exclusively from organically precoated metal substrate.
• organically precoated metal substrates where electrolytically galvanized or hot dip galvanized steel is used as the metal substrate are frequently used in vehicle manufacture.
• organically coated metal substrates such as these, the areas mentioned where the organic layer is damaged are particularly difficult to handle because they differ from the usual metal surfaces in regard to their electrochemical potentials and their chemical reactivity.
• parts both of the steel substrate (i.e. iron) and of the zinc coating generally remain bare.
• a high local area ratio of steel (iron) to zinc, for example a ratio of >9:1, can be present. This is the case in particular with cut edges which represent a cross-section through the coated steel substrate.
• Another aspect of the present invention relates to a process for the production of a structural component containing painted metal parts, in which
• the treatment solution used in step c) comprises 20-200 mg/l of the functionalized phenol-aldehyde resin; and the treatment solution contains one or more compounds of elements of the fourth main or transition metal group of the periodic system, most preferably Si, Ti and/or Zr. Most preferably, the aqueous treatment solution additionally contains fluoride ions.
• step c) is preferably the only treatment step after step a) which produces a passivation layer on those areas of the metal surface formed in step a) that are not covered by the coating based on organic polymers.
• This special process may be used in particular when all the metal parts of the structural component subjected to steps b) to e) consist solely of the sheets of galvanized steel with a coating based on organic polymers.
• all the metal parts of the structural component may consist of organically precoated metal, more particularly galvanized steel.
• the structural component may contain plastic components, as is the case, for example, in car manufacture. Accordingly, to produce a vehicle body for example, the metal parts of organically precoated material may be assembled together with plastic parts.
• galvanized steel encompasses hot-dip-galvanized steels and electrolytically galvanized steels. It also encompasses alloy-galvanized steels where the coating may consist, for example, of a zinc/nickel alloy or a zinc/aluminium alloy. The steels may be tempered after galvanizing, so that an iron/zinc alloy is formed at the interface between steel and zinc.
• the assembly of the sheets to form the structural component in step a) may be carried out by any of the usual known methods, for example by bonding, flanging, riveting, edging and/or welding, more particularly by electrowelding.
• joining by welding has the effect—attributable to the resulting damage to the coating based on organic polymers—that other areas not covered by the coating based on organic polymers are formed on the structural component. These other areas are also passivated in step c), as are bare metal areas formed by abrasion.
• This embodiment of the process according to the invention is particularly suitable for the production of structural components using organically precoated sheets with a 1 to 10 ⁇ m thick coating based on organic polymers which contains electrically conductive particles in addition to the organic polymers.
• the structural components can be joined together by electrowelding.
• coatings can be found in DE-A-197 48 764, DE-A-199 51 113, DE-A-100 22 075 and in the literature cited therein.
• metal coils with such coatings are commercially available under various names.
• the passivation layer produced in step c) is not intended to be a conventional zinc phosphate layer because a shortened and hence more economical treatment chain than zinc phosphating is intended to be used in accordance with the present invention.
• a zinc phosphate layer is not formed if the treatment solution does not simultaneously contain at least 0.3 g/l zinc ions and at least 3 g/l phosphate ions (as phosphoric acid or any pyrolysis stage thereof).
• step c) the assembled structural component can be contacted with the acid aqueous treatment solution in various ways, for example by immersion in the treatment solution or by spraying with the treatment solution.
• This step may be followed by rinsing with water although this is not imperative.
• the process may be used as a rinse process or as a no-rinse process.
• the treatment in step c) is preferably not a post-passivation of a conversion layer formed primarily in a preceding step, but is the only treatment step after assembly of the parts which produces a passivation layer on the bare metal areas.
• This sequence of process steps may be used in particular in the manufacture of vehicle bodies, domestic appliances, items of furniture or parts thereof.
• an aqueous treatment solution for treating bare or conversion-coated metal surfaces which contains at least one functionalized phenol-aldehyde resin according to the invention, as characterized in detail herein, or a mixture of two or more such resins.
• the treatment solution used in step c) comprises 20-200 mg/l of the functionalized phenol-aldehyde resin; and the treatment solution contains one or more compounds of elements of the fourth main or transition metal group of the periodic system, most preferably Si, Ti and/or Zr.
• the aqueous treatment solution additionally contains fluoride ions.
• the present invention also relates to a metal sheet, a metal part or an article containing metal parts, characterized in that at least one surface of the metal sheet or the metal parts has been treated by the process according to the invention.
• the metal parts may have a coating based on organic polymers, i.e. for example a paint or adhesive, on the treated surfaces.
• Ridoline® and Ridosol® are alkaline cleaners from Henkel KGAA.
• the quantitative ratios of the resin components are molar ratios.
• Phenol-Salicylic Acid-Formaldehyde Resin (Phenol/Salicylic Acid 3:1)
• a solution of 20 g phenol, 9.78 g salicylic acid and 37.8 g 30% sodium hydroxide is prepared at 80° C. After the phenol has completely dissolved, 23.3 g of a 36.5% formaldehyde solution are added over a period of 30 minutes from a dropping funnel. The solution is then heated to 95° C. and stirred for 6 h.
• a solution of 10 g phenol, 14.68 g salicylic acid and 28.3 g 30% sodium hydroxide is prepared at 80° C. After the phenol has completely dissolved, 17.5 g of a 36.5% formaldehyde solution are added over a period of 30 minutes from a dropping funnel. The solution is then heated to 95° C. and stirred for 6 h.
• a solution consisting of 44.5 g phenol-salicylic acid-formaldehyde resin (phenol/salicylic acid 3:1, see 1.a.) and 3.62 g imidazole is prepared at 80° C. After the educts have completely dissolved, 3.8 g of a 36.5% formaldehyde solution in 10 g water are added over a period of 15 minutes from a dropping funnel. The solution is then heated to 95° C. and stirred for 6 h.
• a solution consisting of 39.5 g phenol-salicylic acid-formaldehyde resin (phenol/salicylic acid 1:1, see 1.b.) and 1.81 g imidazole is prepared at 80° C. after the educts have completely dissolved, 1.89 g of a 36.5% formaldehyde solution in 10 g water are added over a period of 15 minutes from a dropping funnel. the solution is then heated to 95° C. and stirred for 6 h.
• a solution consisting of 39.5 g phenol-salicylic acid-formaldehyde resin (phenol/salicylic acid 1:1, see 1.b.) and 1.21 g imidazole is prepared at 80° C. after the educts have completely dissolved, 1.26 g of a 36.5% formaldehyde solution in 10 g water are added over a period of 15 minutes from a dropping funnel. the solution is then heated to 95° C. and stirred for 6 h.
• a solution consisting of 39.5 g phenol-salicylic acid-formaldehyde resin (phenol/salicylic acid 1:1, see 1.b.) and 0.9 g imidazole is prepared at 80° C. after the educts have completely dissolved, 0.95 g of a 36.5% formaldehyde solution in 10 g water are added over a period of 15 minutes from a dropping funnel. the solution is then heated to 95° C. and stirred for 6 h.
• a solution consisting of 10.2 g phenol-formaldehyde resin (see 2.a.) and 1.25 g imidazole is prepared at 80° C. after the educts have completely dissolved, 1.31 g of a 36.5% formaldehyde solution in 25 g water are added over a period of 15 minutes from a dropping funnel. the solution is then heated to 95° C. and stirred for 6 h.
• Pre-treatment was carried out by one of applicants' standard methods.
• the paint used was Polyester PES 5807/RAL 5009 GL (TIGC-free, from IGP); ca. 60-80 ⁇ m (as above). Relative corrosion protection >1.
• Pre-treatment was carried out by one of applicants' standard methods.
• the paint used was Polyester PES 5807/RAL 5009 GL (TIGC-free, from IGP); ca. 60-80 ⁇ m (as above). Relative corrosion ⁇ 1.
• Example 6 and Comparative Examples 4a and 4b Addition of Powder coating polymer mg/l (DIN 50021 SS, Test solids 21 d) U/2 in mm Comp. Ex. 4a 0 2.6 Ex. 6a 40 1.3 Ex. 6b 100 1.1 Ex. 6c 500 1.9 Ex. 6d 1000 2.1 Comp. Ex. 4b 37 mg/l 3.0 (see below) Sokalan ® HP56

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• 2003
  • 2003-12-11 DE DE10358309A patent/DE10358309A1/de not_active Withdrawn
• 2004
  • 2004-10-30 EP EP04820579A patent/EP1692201A1/de not_active Withdrawn
  • 2004-10-30 JP JP2006543385A patent/JP4890261B2/ja not_active Expired - Fee Related
  • 2004-10-30 WO PCT/EP2004/012324 patent/WO2005061570A1/de active Application Filing
• 2006
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