DE10018583A1 - Use of water soluble cellulose ethers as anti-crate ring agents in electrophoretic coatings for the production of motor vehicle bodies and parts. - Google Patents

Abstract

The use of water soluble cellulose ethers as anti-crate ring agents in electrophoretic coatings is claimed.

Description

The present invention relates to the use of water-soluble cellulose ethers Anti-cratering agent in electro-dipping paints.

Electrodeposition, in particular cathodic electrodeposition, is a used worldwide for the purpose of priming and corrosion protection Method. It is used for painting all kinds of industrial components, such as small parts (screws or nuts) or containers (packaging, cans). In particular, it is used in the automotive industry for priming and Corrosion protection equipment applied to car bodies.

With electro-dipping paints (ETL), especially cathodically depositable electro-dipping paints (KTL), high quality paintwork can be produced. Kick frequently but in the burned-in paint surface defects, especially craters. At the color and / or effect used in automotive painting Multi-layer paints form these surface defects in the paint layers, that lie on the electric tach painting. But this is precisely in the field of Automobile painting is completely unacceptable, as this reduces the impression on the customer Quality of the expensive overall product "automobile" awakened.

In most cases, the cause of these surface defects is contamination, which were brought into the ETL baths. Examples of such contaminants are Deep-drawing greases, anti-corrosion greases, seam sealing materials or lubricating greases that are used in of an automobile factory are ubiquitous, so to speak. Even skin creams can be used Operators cause craters. When burning in the ETL, especially the KTL, it comes to the intolerance of contamination and ETL said surface defects.

From the European patent application EP 0 301 293 A1 anti-crater agents for KTL are known, which are homo- or copolymers of an alkyl vinyl ether of the general formula CH ₂ = CH-OR, in which R denotes an alkyl radical with 2 to 4 carbon atoms. These anti-cratering agents are highly effective. However, they have the disadvantage that they are comparatively incompatible with the ETL, which can lead to problems during the training or make the training relatively expensive.

ETL and ETL baths that contain water-soluble cellulose ethers are from the European patent application EP 0 640 700 A1 known. The water soluble Cellulose ethers above all improve the grip of the ETL and the edge protection on the coated metal parts. Evidence that the cellulose ether also as Anti-cratering agents do not appear from the European patent application.

The object of the present invention is on the one hand, a new use for To find cellulose ether and on the other hand to provide an anti-cratering agent that a offers a valuable alternative to the previously known.

Accordingly, the new use of water-soluble cellulose ethers as Anti-cratering agents found in electrocoat materials, hereinafter referred to as "the invention Use ".

Water-soluble cellulose ethers are common and known compounds in which the three hydroxyl groups per glucose unit with the same (simple cellulose ethers) or various (mixed cellulose ethers) with hydroxy and / or carboxyalkyl and / or aryl groups are partially or completely etherified. Checking theirs Properties take place according to DIN 55952: 1981-06.

According to the invention, the cellulose ethers are those with carboxyalkyl groups or Hydroxyalkyl groups are etherified, advantageous and are preferred according to the invention used. Examples of particularly suitable water-soluble cellulose ethers are Hydroxymethyl, carboxymethyl, hydroxyethyl, carboxyethyl, hydroxymethyl carboxymethyl, hydroxyethyl carboxyethyl, hydroxyethyl carboxymethyl and / or Hydroxymethyl-carboxyethyl cellulose, especially hydroxyethyl cellulose.

The water-soluble cellulose ethers preferably have substituents and / or Substitution patterns that make them resistant to microbial degradation. Examples suitable substituents and / or substitution patterns come from the American US 4,009,239 A1 and US 4,084,060 A1.  

The water-soluble cellulose ethers are supplied in a wide variety of viscosities. The viscosities vary greatly depending on the concentration of the solutions and / or the shear rate to which the solutions are exposed. Highly viscous cellulose ethers are non-Newtonian liquids with a high degree of pseudoplasticity. For example, a 2% solution of a highly viscous hydroxyethyl cellulose can have a viscosity of 100 mPas at a shear rate of 10,000 s ^-1 and viscosities of over 100,000 mPas at a shear rate of 0.1 s ^-1 . Low-viscosity types show Newtonian flow behavior and a low degree of pseudoplasticity.

According to the invention, the highly viscous types with non-Newtonian flow behavior preferred, as for example under the brand Cellosize® QP-100M, QP 5200H or QP-30000H are available from Union Carbide.

The water-soluble cellulose ethers preferably have a viscosity of 10,000 to 300,000, preferably 60,000 to 100,000, as a 2% solution in water at a temperature of 25 ° C. As a 1% solution in water, they have a viscosity of 500 to 12,000, preferably 1,000 to 10,000 MPas at 25 ° C and at a shear rate of 30 min ^-1 .

The water-soluble cellulose ethers to be used according to the invention are in the ETL or the ETL baths in an amount of, each based on that contained in the ETL Contain binder, 0.001 to 10 and preferably 0.05 to 2 wt .-%.

The use according to the invention is within the scope of all usual anodic (ATL) or cathodic (KTL) ETL baths advantageous.

The ETL baths are aqueous coating materials with a solids content of in particular 5 to 30% by weight.

The solid of the ETL consists of

• A) usual and known binders which are ionic or in ionic groups transferable functional groups (a1) and for chemical crosslinking  qualified functional groups (a2), whereby they are foreign and / or are self-networking, but especially third-party networking;
• B) if appropriate crosslinking agents, the complementary functional groups (b1) wear that with the functional groups (a2) chemical cross-linking reactions can enter, and then mandatory when the binders (A) are cross-linking;
• C) usual and known paint additives as well
• D) the water-soluble to be used according to the invention described above Cellulose ether.

Are the crosslinking agents (B) and / or their functional groups (b1) ready in the Binder (A) built in, one speaks of self-crosslinking.

The complementary functional groups (a2) of the binders (A) are preferably Thio, amino, hydroxyl, carbamate, allophanate, carboxy, and / or (Meth) acrylate groups, but especially hydroxyl groups, and as complementary functional groups (b1) preferably anhydride, carboxyl, epoxy, blocked Isocyanate, urethane, methylol, methylol ether, siloxane, amino, hydroxy and / or beta-hydroxyalkylamide groups, but especially blocked isocyanate groups in Consideration.

Examples of suitable ionic or convertible functional groups (a1) of the binders (A) are

• 1. functional groups by neutralizing agents and / or Quaternizing agents can be converted into cations, and / or cationic groups

or

• 1. functional groups which are converted into anions by neutralizing agents can, and / or anionic groups.

The binders (A) with functional groups (a11) are cathodically depositable Electrodeposition paints (KTL) are used, whereas the binders (A) are functional Groups (a12) are used in anodic electrocoating (ATL).

Examples of suitable functional groups (a11) to be used according to the invention which can be converted into cations by neutralizing agents and / or quaternizing agents can, are primary, secondary or tertiary amino groups, secondary sulfide groups or tertiary phosphine groups, especially tertiary amino groups or secondary Sulfide groups.

Examples of suitable cationic groups (a11) to be used according to the invention are primary, secondary, tertiary or quaternary ammonium groups, tertiary Sulfonium groups or quaternary phosphonium groups, preferably quaternary Ammonium groups or tertiary sulfonium groups, but especially quaternary ones Ammonium groups.

Examples of suitable functional groups (a12) to be used according to the invention which can be converted into anions by neutralizing agents are carboxylic acid, Sulphonic acid or phosphonic acid groups, especially carboxylic acid groups.

Examples of suitable anionic groups (a12) to be used according to the invention are Carboxylate, sulfonate or phosphonate groups, especially carboxylate groups.

The selection of groups (a11) or (a12) is to be made in such a way that no disturbing ones Reactions with the functional groups (a2) with the crosslinking agents (B) can react, are possible. The person skilled in the art can therefore make the selection easier Meet wisely based on his expertise.

Examples of suitable neutralizing agents for functional convertible into cations Groups (a11) are inorganic and organic acids such as sulfuric acid, hydrochloric acid, Phosphoric acid, formic acid, acetic acid, lactic acid, dimethylolpropionic acid or Citric acid, especially formic acid, acetic acid or lactic acid.  

Examples of suitable neutralizing agents for functional anions convertible into anions Groups (a12) are ammonia, ammonium salts, such as ammonium carbonate or ammonium bicarbonate, and amines, such as. B. trimethylamine, triethylamine, Tributylamine, dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine, Diethylethanolamine, methyldiethanolamine, triethanolamine and the like.

In general, the amount of neutralizing agent is chosen so that 1 to 100 Equivalents, preferably 50 to 90 equivalents of the functional Groups (a11) or (a12) of the binder (b1) are neutralized.

Examples of suitable binders (A) for ATL are from the patent specification DE-A-28 24 418 known. These are preferably polyester, epoxy resin esters, Poly (meth) acrylates, maleate oils or polybutadiene oils with a weight average Molecular weight of 300 to 10,000 daltons and an acid number of 35 to 300 mg KOH / g.

Examples of suitable KTL are from the patents EP 0 004 090 A1, EP 0 059 895 A 1, EP 0 012 463 A1, EP 0 082 291 A1, EP 0 234 395 A1, EP 0 227 975 A1, EP 0 178 531 A1, EP 333 327 A1, EP 0 310 971 A1, EP 0 456 270 A1, US 3,799,854 A1, US 3,948,299 A1, US 3,922,253 A1, US 4,031,050 A1, US 4,252,703 A1, US 4,332,711 A. 1, EP 0 261 385 A1, EP 0 245 786 A1, DE 27 01 002 A1, DE 31 03 642 A1, DE 31 O8 073 A1, DE 33 24 211 A1, EP 0 414 199 A1, EP 0 476 514 A1 or EP 0 640 700 A1 known. These are preferably primary, secondary, tertiary or quaternary amino or ammonium groups and / or tertiary sulfonium groups containing resins (A) with amine numbers preferably between 20 and 250 mg KOH / g and a weight average molecular weight of preferably 300 to 10,000 daltons. In particular, amino (meth) acrylate resins, amino epoxy resins, amino epoxy resins with terminal double bonds, aminoepoxy resins with primary and / or secondary Hydroxyl groups, aminopolyurethane resins, amino group-containing polybutadiene resins or modified epoxy resin-carbon dioxide-amine reaction products used.

According to the invention, KTL and the corresponding electro dip baths are preferred used.  

The ETL preferably contain crosslinking agents (B).

Examples of suitable crosslinking agents (B) are blocked organic polyisocyanates, in particular blocked so-called lacquer polyisocyanates, with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound, blocked isocyanate groups.

Polyisocyanates having 2 to 5 isocyanate groups per are preferred for their preparation Molecule and with viscosities from 100 to 10,000, preferably 100 to 5000 and in particular 100 to 2000 mPas (at 23 ° C) used. In addition, the Polyisocyanates modified in a conventional and known manner hydrophilic or hydrophobic his.

Examples of suitable polyisocyanates are, for example, in "Methods of Organic Chemistry ", Houben-Weyl, Volume 14/2, 4th edition, Georg Thieme Verlag, Stuttgart 1963, Pages 61 to 70, and by W. Siefken, Liebigs Annalen der Chemie, Volume 562, Pages 75 to 136. For example, those containing isocyanate groups are also suitable Polyurethane prepolymers obtained by reacting polyols with an excess of Polyisocyanates can be prepared and are preferably low viscosity.

Further examples of suitable polyisocyanates are isocyanurate, biuret, allophanate, Iminooxadiazindione, urethane, urea and / or uretdione groups Polyisocyanates. Polyisocyanates containing urethane groups are exemplified by Implementation of part of the isocyanate groups with polyols, such as. B. Trimethylolpropane and glycerin. Aliphatic or cycloaliphatic are preferred Polyisocyanates, especially hexamethylene diisocyanate, dimerized and trimerized Hexamethylene diisocyanate, isophorone diisocyanate, 2-isocyanatopropylcyclohexyl isocyanate, Dicyclohexylmethane-2,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate or 1,3- Bis (isocyanatomethyl) cyclohexane (BIC), diisocyanates derived from dimer fatty acids, as sold by the Henkel company under the trade name DDI 1410, 1,8-diisocyanato-4-isocyanatomethyl-octane, 1,7-diisocyanato-4-isocyanatomethyl-heptane or 1-isocyanato-2- (3-isocyanatopropyl) cyclohexane or mixtures thereof Polyisocyanates used.  

Examples of suitable blocking agents for producing the blocked polyisocyanates (B) are the blocking agents known from US Pat. No. 4,444,954, such as

• a) phenols such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, t- Butylphenol, hydroxybenzoic acid, esters of this acid or 2,5-di-tert-butyl-4- hydroxytoluene;
• b) lactams, such as ε-caprolactam, δ-valerolactam, γ-butyrolactam or β- Propiolactam;
• c) active methylenic compounds, such as diethyl malonate, dimethyl malonate, Ethyl or methyl acetoacetate or acetylacetone;
• d) alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monopropyl ether ethylene glycol monobutyl ether, Diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Propylene glycol monomethyl ether, methoxymethanol, glycolic acid, Glycolic acid esters, lactic acid, lactic acid esters, methylol urea, Methylolmelamine, diacetone alcohol, ethylene chlorohydrin, ethylene bromohydrin, 1,3- Dichloro-2-propanol, 1,4-cyclohexyldimethanol, trimethylolpropane or Acetocyanhydrin;
• e) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t- Dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol or Ethylthiophenol;
• f) acid amides such as acetoanilide, acetoanisidinamide, acrylamide, methacrylamide, Acetic acid amide, stearic acid amide or benzamide;
• g) imides such as succinimide, phthalimide or maleimide;  
• h) amines such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, Carbazole, aniline, naphthylamine, butylamine, dibutylamine or butylphenylamine;
• i) imidazoles such as imidazole or 2-ethylimidazole;
• j) ureas such as urea, thiourea, ethylene urea, ethylene thiourea or 1,3-diphenylurea;
• k) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;
• l) imines such as ethyleneimine;
• m) oximes such as acetone oxime, formal doxime, acetaldoxime, acetoxime, Methyl ethyl ketoxime, diisobutyl ketoxime, diacetyl monoxime, benzophenone oxime or chlorohexanone oximes;
• n) salts of sulfurous acid such as sodium bisulfite or potassium bisulfite;
• o) hydroxamic acid esters such as benzyl methacrylohydroxamate (BMH) or Allyl methacrylohydroxamate; or
• p) substituted pyrazoles, ketoximes, imidazoles or triazoles; such as
• q) mixtures of these blocking agents, in particular dimethylpyrazole and triazoles, Malonic ester and acetoacetic acid ester, dimethylpyrazole and succinimide or Ethylene glycol monopropyl ether and trimethylol propane.

Further examples of suitable crosslinking agents (B) are all known aliphatic ones and / or cycloaliphatic and / or aromatic polyepoxides, for example based Bisphenol-A or Bisphenol-F. Suitable polyepoxides are, for example, those in Trade under the names Epikote® from Shell, Denacol® from Nagase Chemicals Ltd., Japan, available polyepoxides, such as. B. Denacol EX-411 (Pentaerythritol polyglycidyl ether), Denacol EX-321 (trimethylolpropane polyglycidyl ether),  Denacol EX-512 (polyglycerol polyglycidyl ether) and Denacol EX-521 (Polyglycerol polyglycidyl ether).

Tris (alkoxycarbonylamino) triazines (TACT) of the general formula can also be used as crosslinking agents (B)

be used.

Examples of suitable tris (alkoxycarbonylamino) triazines (B) are described in the patents US 4,939,213 A1, US 5,084,541 A1 or EP 0 624 577 A1. In particular the tris (methoxy, tris (butoxy and / or tris (2- ethylhexoxycarbonylamino) triazine used.

The methyl-butyl mixed esters, the butyl-2-ethylhexyl mixed esters and the are advantageous Butyl ester. These have the advantage over the pure methyl ester of the better ones Solubility in polymer melts and also have less tendency to crystallize.

Further examples of suitable crosslinking agents (B) are amino resins, for example Melamine, guanamine, benzoguanamine or urea resins. Here also come usual and known aminoplast resins, the methylol and / or Methoxymethyl groups e.g. Defunk with carbamate or allophanate groups are nationalized. Crosslinking agents of this type are described in US Pat. No. 4,710,542 A1 and EP 0 245 700 B1 and in the article by B. Singh and co-workers "Carbamethylethylated Melamines, Novel Crosslinkers for the Coatings Industry" in  Advanced Organic Coatings Science and Technology Series, 1991, Volume 13, pages 193 to 207.

Further examples of suitable crosslinking agents (B) are beta-hydroxyalkylamides such as N, N, N ', N'-tetrakis (2-hydroxyethyl) adipamide or N, N, N', N'-tetrakis (2-hydroxypropyl) - adipamide.

Further examples of suitable crosslinking agents (B) are compounds with an average at least two groups capable of transesterification, for example reaction products of malonic acid diesters and polyisocyanates or of esters and partial esters more polyvalent Alcohols of malonic acid with monoisocyanates, as described in European patent EP 0 596 460 A1 to be discribed.

The amount of crosslinking agent (B) in the ETL can vary widely and depends in particular on the one hand according to the functionality of the crosslinking agent (B) and on the other others according to the number of crosslinking functional ones present in the binder (A) Groups (a2) as well as according to the cross-link density that you want to achieve. The expert can therefore the amount of crosslinking agent (B) due to its general Expertise, if necessary with the help of simple orientation experiments determine. The crosslinking agent (B) in the ETL is advantageously in an amount of 5 to 60% by weight, particularly preferably 10 to 50% by weight and in particular 15 to 45% by weight, each based on the solids content of the ETL. It is recommended here furthermore, the amounts of crosslinking agent (B) and binder (A) thus choose that the ratio of functional groups (b1) in the ETL Crosslinking agent (B) and functional groups (a2) in the binder (A) between 2: 1 to 1: 2, preferably 1.5: 1 to 1: 1.5, particularly preferably 1.2: 1 to 1: 1.2 and in particular 1.1: 1 to 1: 1.1.

The ETL can contain customary paint additives (C) in effective amounts. Examples of suitable additives (C) are

• - Organic and / or inorganic pigments, anti-corrosion pigments and / or Fillers such as calcium sulfate, barium sulfate, silicates such as talc or kaolin, Silicas, oxides such as aluminum hydroxide or magnesium hydroxide,  Nanoparticles, organic fillers such as textile fibers, cellulose fibers, Polyethylene fibers or wood flour, titanium dioxide, carbon black, iron oxide, zinc phosphate or Lead silicate; these additives can also be added to the pigment pastes ETL according to the invention are incorporated, the above as rubbing resins described binder (A) come into consideration;
• - radical scavenger;
• - organic corrosion inhibitors;
• - Crosslinking catalysts such as inorganic and organic salts and Complexes of tin, lead, antimony, bismuth, iron or manganese, preferably organic salts and complexes of bismuth and tin, in particular bismuth lactate, ethyl hexanoate or dimethylol propionate, Dibutyltin oxide or dibutyltin dilaurate;
• - slip additives;
• - polymerization inhibitors;
• - defoamer;
• - Emulsifiers, especially non-ionic emulsifiers such as alkoxylated alkanols and polyols, phenols and alkylphenols or anionic emulsifiers such as Alkali salts or ammonium salts of alkane carboxylic acids, alkane sulfonic acids, and Sulphonic acids of alkoxylated alkanols and polyols, phenols and Alkylphenols;
• Wetting agents such as siloxanes, fluorine-containing compounds, carboxylic acid semiesters, Phosphoric acid esters, polyacrylic acids and their copolymers or polyurethanes;
• - adhesion promoter;
• - leveling agent;  
• - film-forming aids such as cellulose derivatives;
• - flame retardants;
• - organic solvents;
• - Low molecular weight, oligomeric and high molecular weight reactive diluents, which on the thermal crosslinking can participate, especially polyols such as Tricyclodecanedimethanol, dendrimeric polyols, hyperbranched polyesters, polyols based on metathesis oligomers or branched alkanes with more than eight carbon atoms in the molecule; or
• - biocides;

Further examples of suitable paint additives are given in the textbook "Paint Additives" by Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998.

Finally, the invention teaches a method for painting electrically conductive Substrates in which (1) the electrically conductive substrate in an ETL bath according to the above is immersed, (2) the substrate as a cathode or anode, preferably as a cathode, (3) by direct current a film on the Substrate is deposited, (4) the painted substrate from the electrocoating bath is removed, (5) the deposited lacquer film is burned in, and (6) optionally, after step (5) a filler or a stone chip protection lacquer and a Solid-color top coat or alternatively a base coat and a clear coat applied and baked be, the basecoat and the clearcoat preferably after the wet-on-wet Process applied and baked. This results in the color and / or effect-giving multi-layer paintwork, especially in automotive OEM painting be used.

The resulting electrocoat finishes have an excellent grip, one excellent edge protection and, if at all, only a very small number of Surface defects such as craters. The liability of the electrocoat to the  Substrate and to the filler paint or stone chip protection primer is excellent.

Example and comparison test The use of hydroxyethyl cellulose as an edge protection agent

For the example and the comparative experiment were first

• The rubbing resin, as described in EP 0 640 700, page 6, lines 4 to 27,
• The pigment paste, as described in EP 0 640 700, page 7, lines 1 to 37,
• The binder, as in EP 0 640 700, page 7, line 39, to page 8, line 38, described
• The crosslinking agent, as described in EP 0 640 700, page 8, lines 40 to 51, and
• The emulsion as described in EP 0 640 700, page 9, lines 4 to 26,

manufactured.

For the example, a 2% solution of Cellosize® QP100M (Union Carbide) in Water.

For the example, 431 parts by weight of the emulsion, 1 part by weight of lactic acid, 123.5 parts by weight of the pigment paste, 402.5 parts by weight of deionized water and 20.9 Parts by weight of the solution of hydroxyethyl cellulose together at room temperature mixed and homogenized for one hour by stirring. After that the Mix with deionized water to a solids content of 22% by weight set. The resulting ETL bath was contaminated with 0.1 wt% ASTM oil. The oil was stirred in for one day.  

The example was repeated for the comparison experiment, except that none Hydroxyethyl cellulose solution was added.

The ETL baths of the example and the comparative test were kept under for 5 days Aging aged. Then the KTL were at 27 ° C and one for 2 min Voltage of 250 V is deposited on test sheets connected as cathodes. The resulting ETL layers were rinsed with deionized water and left for 20 min Baked at 175 ° C.

According to this, the electrodeposition coating of the example had no craters, whereas the electrodeposition coating of the comparative test had a statistical average of 52 craters / dm ² .

Claims (8)

1. Use of water-soluble cellulose ethers as anti-cratering agents in Electrocoating. 2. The use according to claim 1, characterized in that the water-soluble Cellusloseether is hydroxyethyl and / or carboxyethyl cellulose. 3. The use according to claim 2, characterized in that the water-soluble Cellulose ether is hydroxyethyl cellulose. 4. The use according to any one of claims 1 to 3, characterized in that the water-soluble cellulose ether in a 2% aqueous solution at 25 ° C Viscosity 10,000 to 300,000 mPas. 5. The use according to any one of claims 1 to 4, characterized in that the water-soluble cellulose ether in 1% aqueous solution at 25 ° C at a shear rate of 30 min ^{-1 has} a viscosity of 500 to 12,000 mPas. 6. The use according to any one of claims 1 to 5, characterized in that the water-soluble cellulose ether substituent and / or substitution pattern that make it resistant to microbial degradation. 7. The use according to any one of claims 1 to 6, characterized in that the water-soluble cellulose ether in the electrocoat or Electrocoating baths in an amount of 0.001 to 10 wt .-% based on the Baindmittel is included. 8. The use according to any one of claims 1 to 7, characterized in that the water-soluble cellulose ether in the electrocoat or Electrocoating baths in an amount of 0.05 to 2 wt .-% based on the  Binder is included.