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
  • 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
  • B05D3/10—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 other chemical means
  • B05D3/102—Pretreatment of metallic substrates
• • 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

Definitions

• the present invention relates to a method for modifying cleaned or chemically pretreated metal surfaces with aqueous solutions of organic polymers and the use of the modified metal surfaces for painting, in particular for cathodic electrocoating.
• the phosphating of iron and iron alloys is a commonly used method to increase the corrosion resistance of the metal and to improve the adhesion to a paint.
• Electrodeposition coating is generally carried out on a phosphated surface. Improved paint adhesion, particularly with regard to electrocoating paints, is often achieved by modifying the phosphating baths (cf. e.g. DE-A 22 32 067, Japanese patent application No. 58 144 477 (Chemical Abstracts 99/216843) and DE-A 34 08 577).
• the paint adhesion and in particular the corrosion resistance on the conversion layers used do not always meet the requirements.
• this object can be achieved particularly advantageously by coating the cleaned or chemically pretreated metal surface with a thin layer of a polymer containing amino groups.
• the present invention relates to a method for modifying cleaned or chemically pretreated metal surfaces with aqueous solutions of organic polymers, which is characterized in that the cleaned or chemically pretreated metal surfaces are treated with an aqueous solution of organic polymers containing amino groups.
• Treatment with aqueous solution of the organic polymer containing amino groups can be carried out by pouring, spraying or dipping.
• the metal surfaces are, in particular, those of iron, iron alloys, zinc, aluminum, copper, cobalt, nickel or manganese, whereby preferably chemically pretreated metal surfaces, in particular metal surfaces with phosphate conversion layers, optionally rinsed with water or chromate solution, can also be used.
• Organic polymers containing amino groups for the process according to the invention are preferably hydrolysis products of polymers which have units of the general formula (I) contain or consist of, wherein R1 and R2 are the same or different and are H or alkyl having 1 to 6 carbon atoms.
• the present invention also relates to the use of the modified metal surfaces produced by the process according to the invention for painting, in particular for cathodic electrocoating.
• the metal surfaces modified by the process according to the invention are distinguished by significantly improved corrosion protection, which is particularly evident after an electro-dip coating, in particular a cathodic electro-dip coating.
• Suitable metal surfaces to be modified for the process according to the invention are those made of iron, iron alloys, steel, zinc, aluminum, copper, cobalt, nickel and manganese, which are either cleaned (degreased) or chemically pretreated, e.g. can be phosphated and / or chromated.
• the organic polymer containing amino groups is generally applied from an aqueous solution, for example by pouring, spraying, dipping and then drying the metal surfaces modified in this way.
• Suitable organic polymers containing amino groups are preferably amino group-containing hydrolysis products of polymers which have structural units of the general formula (I) contain or consist of, wherein R1 and R2 are the same or different and are hydrogen or alkyl having 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, amyl, n -Hexyl, isohexyl or cyclohexyl can stand.
• R1 and R2 are the same or different and are hydrogen or alkyl having 1 to 6 carbon atoms, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, amyl, n -Hexyl, isohexyl or cyclohexyl can stand.
• hydrolysis products examples include hydrolysis products of homo- and copolymers of N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide and N- Vinyl-N-methylpropionamide, N-vinylformamide being preferred as being very easily hydrolyzable.
• Suitable comonomers are monoethylenically unsaturated carboxylic acids with 3 to 8 carbon atoms and the water-soluble salts of these monomers.
• This group of comonomers includes, for example, acrylic acid, methacrylic acid, dimethylacrylic acid, ethacrylic acid, maleic acid, citraconic acid, methylene malonic acid, allylacetic acid, vinyl acetic acid, crotonic acid, fumaric acid, mesaconic acid and itaconic acid. From this group of monomers, preference is given to acrylic acid, methacrylic acid, maleic acid or else mixtures of the carboxylic acids mentioned, in particular mixtures of acrylic acid and maleic acid or mixtures of acrylic acid and methacrylic acid.
• the comonomers can be used either in the form of the free carboxylic acids or in partially or completely neutralized form in the copolymerization.
• alkali metal for example alkali metal, alkaline earth metal bases, ammonia or amines, e.g. Sodium hydroxide solution, potassium hydroxide solution, soda, potash, sodium hydrogen carbonate, magnesium oxide, calcium hydroxide, calcium oxide, ammonia, triethylamine, ethanolamine, diethanolamine, triethanolamine, morpholine, diethylene triamine or tetraethylene pentamine.
• alkali metal alkaline earth metal bases
• ammonia or amines e.g. Sodium hydroxide solution, potassium hydroxide solution, soda, potash, sodium hydrogen carbonate, magnesium oxide, calcium hydroxide, calcium oxide, ammonia, triethylamine, ethanolamine, diethanolamine, triethanolamine, morpholine, diethylene triamine or tetraethylene pentamine.
• Suitable comonomers are, for example, the esters, amides and nitriles of the above-mentioned carboxylic acids, for example methyl acrylate, ethyl acrylate, n- and isopropyl acrylate, n- and isobutyl acrylate, hexyl acrylate, methyl methacrylate, methyl methacrylate, methyl acrylate, hydroxylethyl, hydroxyethyl, hydroxyl , Hydroxyisobutylacrylat, hydroxyethyl methacrylate, hydroxypropyl methacrylate, Hydroxyisobutylmethacrylat, monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylamide, methacrylamide, N-dimethylacrylamide, N-tert-butylacrylamide, acryl
• acrylamidoglycolic acid vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, acrylic acid (3-sulfopropyl) ester, methacrylic acid (3-sulfopropyl) ester and acrylamidomethylpropanesulfonic acid as well as monomers containing phosphonic acid groups, such as vinyl phosphate, allyomophosphate phosphate and acrylamide phosphate phosphate.
• the copolymers should contain at least 20% by weight, preferably at least 50% by weight, of copolymerized N-vinylamides.
• the copolymers can be prepared by known processes, e.g. solution, precipitation, suspension or emulsion polymerization using compounds which form free radicals under the polymerization conditions.
• the polymerization temperatures are usually in the range from 30 to 200, preferably 40 to 110 ° C.
• Suitable initiators are, for example, azo and peroxy compounds and the customary redox initiator systems, such as combinations of hydrogen peroxide and reducing compounds, e.g. Sodium sulfite, sodium bisulfite, sodium formaldehyde sulfoxylate and hydrazine. These systems can optionally also contain small amounts of a heavy metal salt.
• the homo- and copolymers to be used according to the invention generally have K values of 7 to 300, preferably 10 to 250.
• the K values can be in aqueous solution at 25 ° C., at concentrations which, depending on the K value, between 0.1% and 5% are measured.
• the above-described homopolymers or copolymers of the general formula (I) are modified by the action of acids or bases in such a way that, as a result of this treatment, the formyl group is split off from the polymerized N-vinylformamide to form amine or ammonium groups.
• the solvolysis temperatures are usually in the range from 20 to 100 ° C., preferably 70 to 90 ° C.
• Suitable acids are, for example, carboxylic acids such as formic acid, acetic acid or propionic acid, a sulfonic acid such as benzenesulfonic acid or toluenesulfonic acid or an inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid or hydrobromic acid.
• Suitable bases are sodium hydroxide solution or potassium hydroxide solution as well as ammonia, amines and alkaline earth metal bases such as calcium hydroxide.
• the usual methods such as ion exchangers, electrodialysis or ultrafiltration are used to desalinate the polymers.
• the process according to the invention is particularly suitable for the treatment of iron, iron alloys and chemically pretreated substrates, such as phosphated metal surfaces which may have been rinsed with water or chromate solution. However, it is also suitable for the surface modification of zinc, aluminum, copper, cobalt, nickel and manganese.
• the aqueous polymer solution is advantageously applied by dipping, pouring or spraying.
• Polymer solutions with solids contents between 0.01 and 5, preferably between 0.1 and 1% by weight in the temperature range between 20 and 80 ° C. can be used for the process according to the invention.
• the metal or chemically pretreated metal surfaces modified with the method according to the invention are in principle suitable for all purposes for which chemically pretreated metal surfaces are suitable.
• the polymer layers bring about an unusually strong improvement in the resistance of the paint film to rust penetration under corrosive stress. This advantage is particularly evident in cathodic electrocoating, which is why the method is used particularly advantageously for this type of painting.
• the method according to the invention finds practical application e.g. for modification of phosphated car bodies.
• Test sheets measuring 190 ⁇ 105 ⁇ 0.75 mm were immersed in aqueous polyvinylamine solutions (K value 30) for 1 minute each.
• the concentrations of the polymer solutions were 0.01; 0.1; 1 and 2 %.
• the bath temperature was 23 ° and 50 ° C, see. Table. After drying in air, the sheets were immersed in deionized water for a further 5 seconds and dried again in air.
• the pretreated test panels were coated with an electrocoat.
• An immersion bath solution as specified in DE-A-42 08 056 as a comparative example, was used as the electrodeposition paint.
• the lacquer was deposited on the test sheets connected as cathode in the usual way at room temperature and baked at 175 ° C. for 25 minutes. With deposition voltages of 320 to 380 V, layer thicknesses of 23 ⁇ m were achieved.
• the rusting on the scratch was determined as a measure of the adhesion of the paints.
• a 0.1 mm wide longitudinal cut was carved into the coating on the steel sheets, and a 0.1 mm wide cross cut was cut into the sheets with a phosphate conversion layer, which reached down to the sheet metal substrate.
• the painted steel sheets were then tested for 15 days in the salt spray test (40 ° C., 5% NaCl solution: DIN 50 021) for corrosion resistance.
• the painted steel sheets with a phosphate conversion layer were tested in the salt water soak test.
• the test sheet was immersed in a 5% NaCl solution heated to 55 ° C. for 10 days.
• the table shows the maximum and average amount of rusting (in millimeters) at the interface on both sides.
• the reference samples were electrocoated analogously using the methods described above and then subjected to corrosion tests with the only difference that no adhesion-promoting layer was applied.
• Degreased body steel sheet e.g. St 1405
• aqueous polyvinylamine solutions of various concentrations, aftertreated and electrocoated.
• the overall appearance of the paint surface also shows a significant improvement over the prior art as a result of the method according to the invention. While the paint surfaces of the reference samples show strong blistering, the paint surface on the metal surface modified with aqueous polyvinylamine solution is perfect.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Chemical Treatment Of Metals (AREA)
• Paints Or Removers (AREA)
• Chemically Coating (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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• 1994
  • 1994-03-18 DE DE4409306A patent/DE4409306A1/de not_active Withdrawn
• 1995
  • 1995-03-10 EP EP95103462A patent/EP0672467B1/fr not_active Expired - Lifetime
  • 1995-03-10 DE DE59504710T patent/DE59504710D1/de not_active Expired - Lifetime
  • 1995-03-10 AT AT95103462T patent/ATE175365T1/de not_active IP Right Cessation
  • 1995-03-15 US US08/404,713 patent/US5494535A/en not_active Expired - Fee Related
  • 1995-03-16 JP JP7057058A patent/JPH0847666A/ja not_active Withdrawn

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