Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/62—Metallic pigments or fillers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/62—Metallic pigments or fillers
  • C09C1/64—Aluminium
  • C09C1/644—Aluminium treated with organic compounds, e.g. polymers
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/62—Metallic pigments or fillers
  • C09C1/64—Aluminium
  • C09C1/648—Aluminium treated with inorganic and organic, e.g. polymeric, compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK  ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
  • C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
  • C09C1/66—Copper alloys, e.g. bronze
• • 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
  • C09D5/36—Pearl essence, e.g. coatings containing platelet-like pigments for pearl lustre
• • 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
  • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
  • C09D5/4488—Cathodic paints
  • C09D5/4492—Cathodic paints containing special additives, e.g. grinding agents

Definitions

• the invention relates to pigments based on metal effect pigment platelets which can be deposited in the course of cathodic electrocoating.
• the invention further relates to a process for producing these electrocoat material pigments and to the use thereof in a cathodic electrocoat material or in cathodic electrocoating.
• the invention finally also relates to a cathodic electrocoat material.
• Electrocoating is a process for applying particular water-soluble coating materials, so-called electrocoat materials, to electrically conductive substrates, for example a workpiece. Between a workpiece immersed into a coating bath and a counterelectrode, an electrical direct current field is applied.
• AEC anodic electrocoating
• CEC cathodic electrocoating
• the coating material binder contains functional groups of particular polarity, which are present in salt form due to neutralization and as a result colloidally dissolved in water.
• hydroxide ions form in CEC or H + ions in AEC.
• These ions react with the binder salt, causing the functionalized binders to lose their salt form (“salting out”), become insoluble and coagulate at the surface of the workpiece.
• the coagulated binder particles lose water owing to electroosmosis procedures, which causes further compaction.
• the workpiece is withdrawn from the immersion bath, freed of noncoagulated coating material particles in a multistage rinsing process and fired at temperatures of 150-190° C. (Brock, Groteklaes, Mischke, “Lehrbuch der Lacktechnologie” [Textbook of coating technology] 2 nd edition, Vincentz Verlag 1998, p. 288 ff.).
• Electrocoating has several economic and ecological advantages over conventional coating methods such as wet coating or powder coating.
• a primary factor which should be mentioned here is the comparatively exactly adjustable layer thickness.
• electrocoating also homogeneously coats difficult-to-access parts of the workpiece. This results from the following fact: first, the deposition of the binder takes place at points of high field strength, such as corners and edges. However, the film which forms has a high electrical resistance. The field lines therefore shift to other regions of the workpiece and are concentrated toward the end of the coating operation entirely on the most inaccessible points, for example regions or points in the interior of the workpiece (inner coating).
• the coating of particularly difficult-to-access points of a workpiece can be improved once more by the provision of auxiliary electrodes.
• Electrocoating it is therefore possible to coat workpieces of any shape, provided that they are electrically conductive. EC is additionally associated advantageously with properties such as minimal solvent emissions, optimal material yield and noncombustibility. Droplet- and run-free paintwork is obtained. Electrocoating is performed in an automated manner and is as a result a very inexpensive coating method, especially since it can be performed at comparatively low current densities of a few mA/cm 2 .
• electrocoating at present finds use in numerous systems.
• the most common are basecoats, for example in automotive OEM finishing, and single-layer topcoats.
• Electrocoats are found, for example, on radiators, control cabinets, office furniture, in construction, in iron and household products, in storage technology or in rack construction, in climate control and lighting technology, and in apparatus construction and mechanical engineering.
• anodic electrocoating AEC
• cathodic electrocoating CEC
• AEC anodic electrocoating
• CEC cathodic electrocoating
• CEC finds use especially in chassis coating. This process firstly achieves corrosion protection, and secondly protects the coating from stonechipping. CEC can be used as a corrosion protection coating for all metallic substrates; mention should be made here, for example, of supports or racks for outside use. Owing to the substantial absence of organic solvent, environmental compatibility completes the advantages of cathodic electrocoating as a highly efficient and attractive coating method.
• Electrocoat materials in use to date have especially been waterborne coating materials which usually comprise self-crosslinking or extraneously crosslinking synthetic resins as binders, which can be dispersed through protonation with acid in water. Protonation of the functional groups present in the synthetic resins forms ammonium, phosphonium or sulfonium groups.
• the synthetic resins are, for example, polymerization, polyaddition or polycondensation products containing primary or tertiary amino groups, such as amino epoxy resins, amino poly(meth)acrylate resins or amino polyurethane resins.
• the electrocoat materials may contain conventional color pigments, which are generally organic and inorganic color pigments. However, the range of color shades which is actually used commercially is very limited. The use of effect pigments in electrocoat material is commercially unknown to date.
• the CEC bath contains binder, pigment paste, water-miscible organic solvent and water.
• the essential constituent of binder and pigment paste is frequently epoxy resin. Binder and pigment paste make up the majority of the about 20% solids content of the coating material.
• the electrocoat material further consists to an extent of about 80% by weight of water. There is additionally a small portion of organic solvents (1-2%), acids (0.4%) and additives.
• the epoxy resin is converted to a water-dispersible form by adding a neutralizing agent.
• An organic acid is used for this purpose (principally acetic acid). Often only a portion of the functional groups is reacted with neutralizing agent. The molar ratio of acid to functional group is referred to as the degree of neutralization. A degree of neutralization of about 30% is sufficient to achieve the desired water dispersibility.
• An organic acid is also used to establish the slightly acidic pH in the CEC bath.
• EP 0 477 433 A1 discloses metal effect pigments coated with synthetic resins, a very thin siloxane layer being applied as an adhesion promoter between metal effect pigment surface and the synthetic resin layer. This document does not make any reference to electrocoating.
• EP 0 393 579 B1 discloses a metal pigment-containing waterborne coating material which is said to be applicable to a substrate by means of electrocoating.
• EP 0 393 579 B1 does not disclose any metal effect pigments suitable for cathodic electrocoating.
• the metal effect pigments must be corrosion-stable to the aqueous electrocoat material medium and be depositable reproducibly even after more than 60 days of bath time. Electrocoatings thus produced should have a metallic effect whose optical quality preferably corresponds to at least that of powder coatings.
• the object is achieved by providing electrocoat material pigments which are metal effect pigment platelets coated with at least one coating material, said coating material comprising
• the object is additionally achieved by providing a process for producing electrocoat material pigments as claimed in one of claims 1 to 12 , wherein the process comprises the following steps:
• the object underlying the invention is also achieved by the use of electrocoat material pigments as claimed in one of claims 1 to 12 in a cathodic electrocoat material or in cathodic electrocoating.
• the invention further relates to a cathodic electrocoat material comprising electrocoat material pigments as claimed in one of claims 1 to 12 .
• the metal effect pigments may consist of metals or alloys which are selected from the group consisting of aluminum, copper, zinc, tin, brass, iron, titanium, chromium, nickel, steel, silver and alloys and mixtures thereof. Preference is given here to aluminum pigments and brass pigments, particular preference being given to aluminum pigments.
• the metal effect pigments are always platelet-shaped in nature. This is understood to mean pigments in which the longitudinal dimension is at least ten times, preferably at least twenty times and more preferably at least fifty times the mean thickness. In the context of the invention, when metal effect pigments are mentioned, what is meant is always metal effect pigment platelets.
• the metal effect pigments used in the inventive electrocoat material possess mean longitudinal dimensions which are determined as sphere equivalents by means of laser granulometry (Cilas 1064, from Cilas) and are reported as the d 50 value of the corresponding cumulative undersize distribution. These d 50 values are 2 to 100 ⁇ m, preferably 4 to 35 ⁇ m and more preferably 5 to 25 ⁇ m.
• the mean thickness of the inventive metal effect pigments is preferably 40 to 5000 nm, more preferably 65 to 800 nm and most preferably 250 to 500 nm.
• Electrocoat materials are always waterborne systems. For this reason, metal effect pigments present in an electrocoat material have to be stabilized for use in aqueous systems. For example, they are provided with a protective layer in order to prevent the corrosive influence of water on the metal effect pigment. In addition, they must have suitable surface charges in order to possess sufficient electrophoretic mobility in the electrical field.
• metal effect pigments are coated with a coating material, said coating material having one or more functional groups for adhesion or attachment to the pigment surface and at least one protonatable or positively charged amino-functional group.
• adheresion is understood to mean noncovalent interactions, for example hydrophobic interactions, hydrogen bonds, ionic interactions, van der Waals forces, etc., which lead to immobilization of the coating material on the pigment surface.
• attachment is understood to mean covalent bonds which lead to covalent immobilization of the coating material on the pigment surface.
• metal effect pigments in cathodic electrocoating have outstanding electrophoretic mobility when the metal effect pigments are provided with a coating material which contains an amino-functional group.
• the protonatable or positively charged amino-functional group after introduction of the coated metal effect pigments into the electrocoat medium, preferably projects into the electrocoat medium.
• the protonatable or positively charged amino-functional group is preferably arranged spaced apart from the metal effect pigment surface by a spacer.
• the spacer is a preferably organic structural element which is unreactive under electrocoating conditions and binds the adhering or attaching group on the metal effect pigment surface and the protonatable or positively charged amino-functional group to one another.
• the unreactive organic structural element may, for example, be a linear or branched alkyl chain having 1 to 20 carbon atoms, preferably having 2 to 10 carbon atoms, more preferably having 3 to 5 carbon atoms.
• this linear or branched alkyl chain may contain heteroatoms or heteroatom groups such as O, S or NH.
• the protonatable or positively charged amino-functional group is a terminal, substituted or unsubstituted amino group, i.e. an amino group arranged terminally on the spacer, which is spaced apart to the maximum degree from the group which provides attachment or adhesion to the metal effect pigment surface.
• the amino-functional group is preferably a protonatable amino group or a positively charged amino group.
• the positively charged amino-functional group is preferably a quaternary ammonium compound.
• Such quaternary ammonium compounds are preferably obtained by alkylating amine compounds.
• the charge state can be controlled by lowering the pH, by adding acid to protonate the amino-functional group(s).
• the amino-functional group is an —NH 2 group arranged on the spacer.
• the amino-functional group is an —NR 1 R 2 group arranged on the spacer
• R 1 and R 2 may be the same or different from one another and may each independently be hydrogen, alkyl having 1 to 20 carbon atoms, preferably having 2 to 10 carbon atoms, more preferably having 3 to 5 carbon atoms, or R 1 and R 2 may be joined to one another and, together with the nitrogen atom, form a heterocycle which preferably contains 4 or 5 carbon atoms.
• the amino-functional group is an —NR 1 R 2 R 3 group arranged on the spacer
• R 1 , R 2 and R 3 may be the same or different from one another and may each independently be hydrogen, alkyl having 1 to 20 carbon atoms, preferably having 2 to 10 carbon atoms, more preferably having 3 to 5 carbon atoms.
• the metal effect pigments are provided with an inorganic and/or organic coating, optionally in the form of an inorganic/organic mixed layer, coated with synthetic resin or surface oxidized so as to inhibit corrosion (ALOXAL® product series from Eckart GmbH & Co.) or colored metal effect pigments (for example ALUCOLOR® product series from Eckart GmbH & Co.) and treated with at least one coating material which contains binder functionalities suitable for electrocoat materials.
• an inorganic and/or organic coating optionally in the form of an inorganic/organic mixed layer, coated with synthetic resin or surface oxidized so as to inhibit corrosion (ALOXAL® product series from Eckart GmbH & Co.) or colored metal effect pigments (for example ALUCOLOR® product series from Eckart GmbH & Co.) and treated with at least one coating material which contains binder functionalities suitable for electrocoat materials.
• the metal effect pigments coated with synthetic resins contain a coating of polymers. These polymers are polymerized onto the metal effect pigments proceeding from monomers.
• the synthetic resins include polyacrylates, polymethacrylates, polyesters and/or polyurethanes.
• the coated metal effect pigment is coated with at least one polymethacrylate and/or polyacrylate.
• metal effect pigments which have been produced according to the teaching of EP 0 477 433 A1, which is hereby incorporated by reference.
• Such pigments preferably contain, between the metal effect pigment and the synthetic resin coating, an organofunctional silane which serves as an adhesion promoter.
• organofunctional silane which serves as an adhesion promoter.
• coatings composed of preferably multiply crosslinked polyacrylates and/or polymethacrylates. Such coatings already constitute a certain though not completely reliable corrosion-inhibiting protection against the aqueous medium of electrocoat materials.
• Similar pigments are described in DE 36 30 356 C2, an ethylenically unsaturated carboxylic acid and/or phosphoric mono- or diester as an adhesion promoter being arranged here between the metal effect pigment and the synthetic resin coating.
• crosslinkers which can be used with preference in the present invention are: tetraethylene glycol diacrylate (TEGDA), triethylene glycol diacrylate (TIEGDA), polyethylene glycol-400 diacrylate (PEG400DA), 2,2′-bis(4-acryloyloxyethoxyphenyl)propane, ethylene glycol dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DEGDMA), triethylene glycol dimethacrylate (TRGDMA), tetraethylene glycol dimethacrylate (TEGDMA), butyldiglycol methacrylate (BDGMA), trimethylolpropane trimethacrylate (TMPTMA), 1,3-butanediol dimethacrylate (1,3-BDDMA), 1,4-butanediol dimethacrylate (1,4-BDDMA), 1,6-hexanediol dimethacrylate (1,6-HDMA), 1,6-hexanediol dime
• the thickness of the corrosion-inhibiting coating is preferably 2 to 50 nm, more preferably 4 to 30 nm and especially preferably 5 to 20 nm.
• the proportion of organic coating or synthetic resin coating, based in each case on the weight of the uncoated metal effect pigment depends in the individual case on the size of the metal effect pigments and is preferably 1 to 25% by weight, more preferably 2 to 15% by weight and especially preferably 2.5 to 10% by weight.
• the coating material is applied to the metal effect pigments after the application of the organic coating or of the synthetic resin layer and/or of another corrosion-inhibiting layer, for example of an inorganic coating such as a metal oxide-containing layer or metal oxide layer.
• the corrosion-inhibiting coating may, for example, comprise essentially metal oxide, especially silicon dioxide, or consist thereof.
• a metal oxide layer can be applied using different processes known to those skilled in the art.
• a silicon dioxide layer can be applied by means of sol-gel methods with hydrolysis of tetraalkoxysilanes, where the alkoxy group may be methoxy, ethoxy, propoxy or butoxy.
• the corrosion-inhibiting coating may also be a surface oxide layer.
• a surface oxide layer For example, it is possible to provide aluminum effect pigments with an impervious surface oxide layer which is corrosion-inhibiting with respect to aqueous media.
• the oxide layer may additionally comprise color pigments.
• the color pigments can be introduced during the application of the metal oxide layer, especially silicon dioxide layer, or during the surface oxidation of the surface of the metal oxide layer.
• the corrosion-inhibiting coating for example synthetic resin layer, may completely surround the pigments, but it may also be present in not entirely continuous form or have cracks.
• Use of the coating material with protonatable or positively charged amino-functional group and with functional groups for adhesion and/or attachment to the pigment surface in the present invention covers possible corrosion sites which can be caused by such cracks or by an incomplete corrosion-inhibiting coating on the metal effect pigment.
• the coating material used in the present invention is capable, especially when it attaches to the metallic pigment surface, of penetrating into such gaps or cracks in the corrosion-inhibiting coating, preferably synthetic resin coating, thus bringing about the required corrosion stability.
• the coating material used in the present invention also has corrosion-inhibiting properties in the case of metal effect pigments
• this coating material is used primarily in order to make the metal effect pigments cathodically depositable.
• the coating material with protonatable or positively charged amino-functional group makes the metal effect pigments electrophoretically mobile in the electrocoating bath, i.e. they migrate in the direction of the object to be coated which is connected as the cathode.
• Metal effect pigments which are coated only with synthetic resin or other corrosion-inhibiting coatings and have not been treated with the coating material with amino-functional group used in the present invention can be cathodically deposited only insufficiently, or cannot be cathodically deposited effectively, in cathodic electrocoating.
• Metal effect pigments are not usable per se in electrocoat materials. Even if they are corrosion-stable to the aqueous medium of the electrocoat material as a result of a suitable protective layer, for example a metal oxide or a synthetic resin, they are either not or are no longer deposited after a few hours to days after an initial deposition, which is referred to as inadequate bath stability.
• a suitable protective layer for example a metal oxide or a synthetic resin
• the inventive metal effect pigments can be deposited reliably and over long periods in cathodic electrocoating, and the electrocoat material has a bath stability of more than 60 days.
• the inventive metal effect pigments present in the cathodic electrocoat material are therefore deposited reliably on the workpiece even after 60 days, preferably after 90 days.
• they have sufficient corrosion stability, such that no significant gassing (in the case of aluminum or iron pigments) or release of metal ions (in the case of brass pigments) occurs within this time in the electrocoat material.
• the coating material in this case must have one or more amino-functional groups. These are at least partly protonated in the electrocoat material. These protonated amino groups are thought to impart sufficient positive surface charges to the inventive electrocoat material pigment to be well-dispersed in the predominantly aqueous medium of the electrocoat material. Moreover, the inventive metal effect pigments are thought to be positively charged at their surface such that migration in the electrical field applied toward the cathode is enabled within the Nernst diffusion layer. It is thought that the surface of the inventive metal effect pigments is matched chemically in this way to the binders of the cathodic electrocoat material. This enables the effect that the metal effect pigments can firstly migrate electrophoretically in the electrical field and secondly take part in the deposition mechanism of the electrocoat materials at the cathode.
• the coating materials contain functional groups which bring about or can bring about adhesion and/or attachment to the surface of the metal effect pigment or the stabilizing coating thereof.
• the pigment surface may directly be the metal effect pigment surface.
• the pigment surface may, however, also be the metal effect pigment surface coated with an inorganic or organic coating, preferably with synthetic resin. In this way, the coating materials can be anchored to the metal effect pigments reliably and to a sufficient degree.
• These functional groups for adhesion or attachment to the coated or uncoated metal effect pigment surface are, for example, phosphonic ester, phosphoric ester, carboxylate, metallic ester, alkoxysilyl, silanol, sulfonate, hydroxyl, polyol groups, and mixtures thereof. Particular preference is given to the alkoxysilyl and/or silanol groups of suitable organofunctional silanes.
• Such functionalized coating materials contribute to the corrosion stability of the metal effect pigments in the aqueous electrocoat material.
• gassing i.e. evolution of hydrogen, can surprisingly be suppressed effectively.
• the coating material must necessarily have at least one protonatable or positively charged amino-functional group and at least one functional group for adhesion or attachment to the pigment surface.
• the coating material must necessarily have at least one protonatable or positively charged amino-functional group and at least one functional group for adhesion or attachment to the pigment surface.
• aliphatic amines which lack the at least one functional group for adhesion or attachment to the pigment surface are unsuitable for providing metal effect pigments which are effectively cathodically depositable in a cathodic electrocoat material system.
• coating materials preference is given to using, as coating materials, amines which can be protonated to ammonium salts.
• Particularly preferred coating materials comprise amino-functional silanes of the formula
• R 1 is an organofunctional group which contains at least one amino-functional group
• R 2 is a further organofunctional group which does not contain an amino-functional group
• R′ is independently H or an alkyl group having 1 to 6 carbon atoms, preferably having 1 to 3 carbon atoms, and where a and b are integers, with the proviso that a may be 1 to 3 and b may be 0 to 3, where a and b in total are not more than 3.
• R′ is preferably ethyl or methyl.
• R 2 is preferably substituted or unsubstituted alkyl having preferably 1 to 6 carbon atoms, for example methyl or ethyl.
• R 2 may be substituted by functional groups, for example acrylate, methacrylate, vinyl, isocyanato, hydroxyl, carboxyl, thiol, cyano, epoxy or ureido groups.
• the at least one protonatable or positively charged amino-functional group which contains R 1 is preferably a primary, secondary, tertiary amine or an ammonium group.
• the amino-functional group is preferably as defined above.
• silanes are commercially available. For example, these are many representatives of the products which are produced by Degussa, Rheinfelden, Germany and are sold under the trade name Dynasylan®, or the Silquest® silanes produced by OSi Specialties, or the GENOSIL® silanes produced by Wacker, Burghausen, Germany.
• N-benzyl-N-aminoethyl-3-aminopropyltrimethoxysilane (Dynasylan 1161), N-vinylbenzyl-N-(2-aminoethyl)-3-aminopropylpolysiloxane (Dynasylan 1172), N-vinylbenzyl-N-(aminoethyl)-3-aminopropylpolysiloxane (Dynasylan 1175), aminopropyltrimethoxysilane (Dynasylan AMMO; Silquest A-1110), aminopropyltriethoxysilane (Dynasylan AMEO) or N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (Dynasylan DAMO, Silquest A-1120) or N-(2-aminoethyl)-3-aminopropyltrimeth
• the coating materials with protonatable or positively charged amino-functional group are preferably used in amounts of 1 to 100% by weight based on the weight of the uncoated metal effect pigment. Below 1% by weight, the effect may be too minor, such that the metal effect pigments can no longer be deposited reliably, especially after more than 60 days of bath time. Above 100% by weight, an unnecessarily large amount of coating material with amino-functional group is used. In addition, excess coating material with an amino-functional group can adversely affect the properties of the electrocoat material.
• the coating material(s) with an amino-functional group are preferably used in amounts of 5 to 70% by weight and especially preferably of 7 to 50% by weight, more preferably of 10 to 30% by weight, based in each case on the weight of the metal effect pigment uncoated with coating material. These figures are based in each case on the coating material itself and not on any solvent which is possibly present and in which the coating material with an amino-functional group is supplied in its commercially available administration form.
• the coating material may, but need not, completely surround the metal effect pigments.
• a process for providing the inventive metal effect pigments comprises the coverage of the metal effect pigment with the coating material with an amino-functional group. It comprises the following steps:
• the coverage can take place in many different ways.
• the metal effect pigment can be initially charged, for example, in a mixer or kneader in the form of a paste, for example in an organic solvent or in a mixture of organic solvent and water. Subsequently, the coating material with a protonatable or positively charged amino-functional group is added and allowed to act on the metal effect pigment preferably for at least 5 min.
• the coating material is preferably added in the form of a solution or dispersion. This may be an aqueous solution or a predominantly organic solution.
• the metal effect pigment can first be dispersed in a solvent.
• the coating material is then added thereto with stirring.
• the solvent in which the coating material is dissolved should preferably be miscible with that in which the metal effect pigment is dispersed. If required, higher temperatures up to the boiling point of the solvent or of the solvent mixture can be established, but room temperature is usually sufficient to apply the coating material effectively to the metal effect pigment.
• the pigment is freed from the solvent and either dried to give the powder and/or optionally converted to a paste in another solvent.
• Useful solvents include water, alcohols, for example ethanol, isopropanol, n-butanol, or glycols, for example butylglycol.
• the solvent should be miscible with water.
• the inventive pigment is traded as a paste or powder.
• the pastes have a nonvolatile component of 30 to 70% by weight based on the weight of the overall paste.
• the paste preferably has a nonvolatile component of 40 to 60% by weight and more preferably of 45 to 55% by weight.
• the paste form is a preferably dust-free and homogeneous preparation form of the inventive electrocoat material pigments.
• the inventive electrocoat material pigments may also be present in dust-free and homogeneous form as pellets, sausages, tablets, briquettes or granules.
• the aforementioned preparation forms can be produced in the manner known to those skilled in the art by pelletization, extrusion, tabletting, briquetting or granulation. In these compacted preparation forms, the solvent has substantially been removed.
• the residual solvent content is typically within a range of less than 15% by weight, preferably less than 10% by weight, more preferably between 0.5 and 5% by weight, based in each case on the weight of the pigment preparation.
• the coating material with a protonatable or positively charged amino-functional group may, before the coating of the metal effect pigment, be present in a neutralized or partly neutralized form. However, it can also be neutralized after the coating operation. The neutralization/partial neutralization can also not be effected until the pH adjustment of the electrocoat material.
• Customary acids are suitable for neutralization of the basic functionalities. Examples thereof are: formic acid, acetic acid, hydrochloric acid, sulfuric acid or nitric acid, or mixtures of these acids.
• a sufficient amount of acid should be used that at least 25%, preferably 40%, of the basic groups of the metal effect pigment covered with the coating material are present in neutral form.
• basic groups also include functional groups which may originate from the metal effect pigment itself.
• steps (a) and (b) of the process according to the invention are also possible to combine steps (a) and (b) of the process according to the invention to one step, by applying the coating material as a solution or dispersion to metal effect pigments moving in a gas stream.
• inventive electrocoat material pigments can be produced by a process with the following steps:
• the pigments can be neutralized and converted to paste as described above.
• the inventive electrocoat material pigments are used in cathodic electrocoat materials or in cathodic electrocoating.
• the invention further provides a cathodic electrocoat material comprising the inventive electrocoat material pigments, a binder and water.
• the binders are, for example, polymerization, polyaddition or polycondensation products containing primary or tertiary amino groups, for example amino epoxy resins, amino poly(meth)acrylate resins or amino polyurethane resins.
• further customary additions such as fillers, additives, organic and/or inorganic color pigments, etc. may be present in the electrocoat material.
• the amino groups of the binders and preferably the amino groups of the coating material of the inventive electrocoat material pigments are at least partly protonated. This has the effect that the binders and the inventive electrocoat material pigments move toward the cathode in the applied electrical field and take part in the deposition mechanism of the cathodic electrocoating.
• the coatings obtained in this way have an attractive metal effect which has been unknown to date in cathodic electrocoat material and are exceptionally abrasion-stable.
• inventive electrocoat material pigments can optionally also be neutralized as early as after the coating with coating material.
• Dynasylan 1161 N-benzyl-N-aminoethyl-3-aminopropyltrimethoxysilane from Degussa, Germany
• Dynasylan 1172 N-vinylbenzyl-N-(2-aminoethyl)-3-aminopropylpolysiloxane from Degussa, Germany
• the paste is dried cautiously in a vacuum drying cabinet at approx. 60° C. to give the powder.
• Dynasylan 1175 N-vinylbenzyl-N-(aminoethyl)-3-aminopropylpolysiloxane from Degussa, Germany
• VEK 40871-02 CEC binder 800 by weight epoxy resin from Cytech, Austria
• wetting agent from FreiLacke, Bönlingen, Germany
• 465 g of VEK 40871-0-03 CEC binder 34.5% by weight epoxy resin from Cytech, Austria
• 662 g of water 662 g
• the dip-coating materials produced according to this formulation for cathodic dip-coating feature a viscosity of 9 ⁇ 1 seconds, measured at a temperature of 20° C. in a DIN 4 flowcup.
• the electrocoat materials possess a solids content of 13 to 17% by weight based on the weight of the overall electrocoat material.
• the proportion of the aluminum pigments is approx. 1% by weight.
• the measured pH of the electrocoating baths at 25° C. is a pH of about 5.5 to 6.5.
• the electrochemical deposition operation is effected in an electrically conductive vessel, a so-called tank, which consists of an electrically conductive material and is connected as the anode in the circuit.
• the workpiece to be coated in the inventive example a metal sheet of dimensions 7.5 cm ⁇ 15.5 cm is connected as the cathode and immersed into the electrocoating bath for 2 ⁇ 3 of its length.
• the electrocoat material is moved with a mean flow rate of approx. 0.1 m/s. Subsequently, a voltage of 100 V is applied over a period of 120 seconds. The temperature of the electrocoating bath is 30° C. The workpiece thus coated is subsequently rinsed off thoroughly with distilled water in order to remove residues of uncoagulated resin. The workpiece is then left to vent for a period of 10 minutes. Subsequently, the electrocoat material is crosslinked and fired at 170° C. for 20 minutes. The coating layer thickness thus achieved is 30 ⁇ 2 ⁇ m.
• the cathodic electrocoat materials produced with the pigments from inventive examples 1 to 4 have an exceptionally high storage and deposition stability in relation to the aluminum effect pigments present therein. This is evident from Table 1.
• the coating materials were stored at room temperature and, within a time interval of 7 days, metal sheets as described above were electrocoated. These tests were stopped after 60 days.
• inventive examples 1 to 4 were stored at 40° C. for 30 days. Subsequently, they were incorporated into an electrocoating material as described above, and metal sheets were electrocoated. With regard to the optical properties of these applications, no difference from applications with freshly produced samples were found.
• the electrocoat material comprising pigments of comparative example 1 was likewise gassing-stable, but had virtually no deposition stability.
• the aluminum effect pigments not provided with a coating of comparative example 2 are neither gassing-stable in the electrocoat material nor do they possess sufficient deposition stability.
• the powder coating material thus produced is applied by means of the customary corona discharge technique (GEMA electrostatic spray gun PG 1-B) to a customary test sheet (“Q panel”).
• GEMA electrostatic spray gun PG 1-B customary corona discharge technique
• the application conditions of the powder coating technique applied here corresponds to the following: powder hose connection: 2 bar; purge air connection: 1.3 bar; voltage: 60 kV; material flow regulator: approx. 500; gun-sheet distance: approx. 30 cm.
• the firing time is 10 minutes at a temperature of 200° C.
• the dry layer thickness to be achieved in this process is 50-75 ⁇ m.
• inventive examples 1 to 4 were compared with the substrates of comparative examples 3 and 4 coated by powder coating technology.
• inventive examples 1 to 4 and comparative examples 3 and 4 aluminum effect pigments of similar particle size and coloristic properties were used.
• inventive examples 1 to 4 exhibit excellent covering capacity, which corresponds in terms of goodness and quality to the powder coating material of comparative examples 3 and 4.
• inventive examples 1 to 4 have no significant differences with regard to brightness and metallic effect from the conventional powder coating material application in comparative examples 3 and 4.
• DIN 53230 For the assessment of the optical properties, reference is made to DIN 53230.
• DIN 53 230 lays down a homogeneous assessment system. This describes how test results which cannot be reported by means of directly obtained measurements should be assessed.
• a metal effect pigment treated without coating material virtually cannot be deposited in the cathodic electrocoat material or in the electrocoating, even though the metal effect pigment has a synthetic resin shell.
• the coating material with protonatable or positively charged amino-functional group has to be applied directly to the metal effect pigment and cannot be added later to the electrocoat material. It is further suspected that the coating material with its functional groups for adhesion or attachment forms a physisorptive and/or chemisorptive adhesion or attachment to the pigment surface, which then appears to play a crucial key role in the deposition performance of the pigment.

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• 2006
  • 2006-10-31 DE DE102006051893A patent/DE102006051893A1/de not_active Withdrawn
• 2007
  • 2007-10-27 EP EP07819394A patent/EP2087047B1/de not_active Not-in-force
  • 2007-10-27 CN CNA2007800479211A patent/CN101568605A/zh active Pending
  • 2007-10-27 DE DE502007006562T patent/DE502007006562D1/de active Active
  • 2007-10-27 US US12/447,997 patent/US20100163420A1/en not_active Abandoned
  • 2007-10-27 WO PCT/EP2007/009351 patent/WO2008052720A2/de active Application Filing
  • 2007-10-27 JP JP2009533746A patent/JP2010508378A/ja active Pending
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