CA2033530A1 - Aqueous coating composition, its preparation and use - Google Patents

Aqueous coating composition, its preparation and use

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Publication number
CA2033530A1
CA2033530A1 CA002033530A CA2033530A CA2033530A1 CA 2033530 A1 CA2033530 A1 CA 2033530A1 CA 002033530 A CA002033530 A CA 002033530A CA 2033530 A CA2033530 A CA 2033530A CA 2033530 A1 CA2033530 A1 CA 2033530A1
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CA
Canada
Prior art keywords
groups
coating composition
polyurethane resin
weight
compounds
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA002033530A
Other languages
French (fr)
Inventor
Michael Schwab
Uwe Kubillus
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hoechst AG
Original Assignee
Hoechst AG
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Filing date
Publication date
Application filed by Hoechst AG filed Critical Hoechst AG
Publication of CA2033530A1 publication Critical patent/CA2033530A1/en
Abandoned legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09DCOATING 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
    • C09D175/00Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04Polyurethanes
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00Polymeric products of isocyanates or isothiocyanates
    • C08G18/06Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08Processes
    • C08G18/0804Manufacture of polymers containing ionic or ionogenic groups
    • C08G18/0819Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00Polymeric products of isocyanates or isothiocyanates
    • C08G18/06Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08Processes
    • C08G18/10Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C08G18/12Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step using two or more compounds having active hydrogen in the first polymerisation step

Abstract

139.171 AQUEOUS COATING COMPOSITION, ITS PREPARATION AND USE
ABSTRACT OF THE DISCLOSURE
Aqueous coating compositions for preparing primers or primer surfacers containing at least one water-dispersible binder resin and crosslinking agents and optionally conventional addi-tives, wherein at least some of the water-dispersible binder resin is a polyurethane resin containing structural units derived from (A) polyisocyanates, (B) polyols having an average molecular weight ?n of at least 400, (C) optionally low-molecular weight polyols, (D) compounds having at least two groups which are reactive toward isocyanato groups and at least one group which is capable of anion formation, (E) polyols carrying no other groups which are reactive with iso-cyanato groups, these structural units (E) being in each case at the chain end of the polyurethane resin, (F) optionally compounds which are monofunctional or contain active hydrogen of varying reactivity and are different from (E), these struc-tural units (F) likewise being at the chain end of the polyurethane resin and, (G) optionally compounds which are different from (B), (C), (D), (E) and (F) and contain at least two groups which are reactive with NCO
groups.
The primer surfacers obtainable therefrom are distinguished, inter alia, by improved stone chip resistance at low temperatures and by good interlayer adhesion, while the corresponding primers show improved corrosion protection.

Description

5`TATE OF THE ART ~ ~ 3 3 ~ a3 0 Water-dilutable coating agents based on a~ueous polyur-ethane dispersions for the prepara-tion o~ surfacers are known from EP-OS No. 27~,3~. Polyether polyols haviny a functionality of at least 3 are used therein as longer-chain polyols for preparing the polyure-thane resin and the resulting dispersions are preferably used for improving the use properties of polyester/melamine resin mix-tures.

In contrast, German O~fenlegungsschrift No. 3,545r618 relates to water-dilutable coating agents based on aqueous polyurethane dispersions for producing the base coat of a multilayer topcoat.
To prepare the polyurethane resin, iOlliC prepolymers containing NCO groups are reacted with polyols containing at least three hydroxyl groups resulting in chain-lengthening and possibly chain branching. Mention of other areas of application than those for base coats is not made in this publication.

OBJECTS OF THE INVENTION

It is an object o~ the invention to provide aqueous coating compositions for primers and primer surfacers having good interlayer adhesion and improved stone chlp resistance and the process ~or their preparation~

It is another object o~ the invention to provide coated sub-strates, especially auto body par-ts, having improved corrosion protection and stone chip resistance.

These and other objects and advantages of the invention will become obvious from the following detailed description.

~ E~-IN-vr~-Nll~IoN 2 ~ 3 3 ~ ~ ~

'l'he novel aqueous coating composi-tions of the invention ~or preparing primers or prilner surfacers contain at least one wa-ter-clispersible ~lnder resin, and crosslinking agents and optionally conventional additives, wherein at least some of the water-dispersible binder resin is a polyure-thane resin containing struc-tural un:its derived from (~) polyisocyallates, (B) polyols haviny an average molecular weiyht Mn ~ at least ~00, (C) optionally low-molecular weiyht polyols, ~D) compounds havillg at least two yroups which are reactive toward isocyanato groups and a-t least one group which is capable of anion formation, (~) polyols carrying no o-ther groups which are reactive with iso-cyanato ~roups, these structural units (E) being in each case at the chain end of the polyurethane xesin, (F) optionally compounds which are monoEunctional or contain active h~drogen of varying reactivity and are dif~erent from (E), these s-truc-tural units (~) likewise being at the chain end o~
the polyurethane resin and, (G) optionally ccmpounds which are diEferen-t:Er~m (B), (C), (D), (E) and ~F) and conkain at least -two groups which are reacti.ve with NCO
group~

SurEacer or pr:imer surEacer la~ver is intended to mean the layer between the primer and topcoat, particularly in automotive bodies or parts tllereof, whicll serve Eor .ieveling out uneven places in the primer, whicll has the function of ensuring ~lawless appearance o~ the topcoat and Eor improving the stone chip resist-ance o~ the entire coating. By virtue of its plastic behavior, tl l~yer is intellded to prevent stone chip5 and the ~l~e;~ su~ch as are thrown agaillst the coating by other cars or even the car itself, from penetrating the coating. Moreover, the surfacer com-positions must produce relatively hard films to permit wet grinding of the coating without giving rise to glazing of the gri~ paper.

The polyurethane resin of the invention ha~ generally an average molecular weight Mn (calculated from the stoichiometry of the startiny material) o~ 1,600 to 50,000, preferably 1,600 to 10,000 and most preferably 2,000 to 6,000, an acid number of 10 to 80, pre~erably 25 to 60, and a hydroxyl number of 30 to 200, pre-ferably 50 to 100. It is water-dispersible at least in an alkaline medium and at low molecular weights frequently even water-soluble under these conditions. In general, the structure of the molecule chains of this polyurethane resin is pxedominantly linear, although in some cases a slight degree oE branching o~ preferably up to 30%, more preferably up to 10~, may be present. The gel content is generally less than 5~ by weight, preferably less than 1~ by weight. On statistical average, each polymer chain preferably con-tains at least two, preferably 4 to 6, groups having active hydro-gen such as amino and/or OH groups.

The polyisocyanates, pre~erably diisocyanates, (A) are com-pounds known in the area oE polyurekhanes or coatings such as aliphatic, cycloaliphatic or aromcltic diisocyanates. They pre-~erably have the Eormula Q(NCO)z, in which Q is a hydrocarbon of to ~0 carbon atoms, preerably ~ to 20 carbon atoms, and is more preEerably an aliphatic hydrocarbon of ~ to 12 carbon atoms, a cyclo-~liphatic hydrocarboll o~ 6 to 15 carbon atoms,an aromatic hydrocarbon of 6 to 15 carbon atoms, or an araliphatic hydrocarbon of 7 to 15 carbon atoms~ Examples o~ diisocyanates of this type to be used are preferably tetramethylene diisocyana-te, hexamethylene diisocyana-te, dodeca~ethylene diisocyana-te, 1~4-diisocyanatocyclohexane, 2 ~ ~ 3 ' ~1~
3~ ocyanat~m~t:hyl-3,5,5-tr.i~ ttly.Lcyclohexyl.

:isocyanate (isophorone diisocyanate), ~,~t-diisocyanato dicyclo-hexylmethane, 2,2-(4,4'-diisocyanatodicyclohexyl)-propane, 1,4-dii~
socyanatobenzene, 2,~- or 2,G ~iisocyana-totoluene or mixtures of these isomers, 4,~'- or 2,~'-diisocyanatodiphenylmethane, 2,2-(4,~'-diisocyanatodiphenyl)-propane, p-xylylene diisocyanate and a,a,a',a'-tetramethyl-m- or ~xylylene diis~cyanate and mixtures oE
these compounds.

Apart from these simple polyisocyanates, those containing hetero atoms in the group linking the isocyana~o yroups are also suitable. Examples of these are polyisocyanates having car-bodiimido groups, allophonato groups, isocyanurato groups, urekhane groups, acylated urea groups or biuret groups. As regards further suitable polyisocyanates, see for example, German Offenlegungs-schrift No. 2,928,552.

The polyisocyanate (~) content in the polyurethane resin is usually about 10 to 50~ by weight, preferably 25 to 35~ by weight, relative to the polyurethane resin.

The polyols o~ (B) preferably have an average molecular weight ~n oE 400 to 5,000, more preferably 800 to 2,000. Their hydroxyl number is genera].ly 30 to 2~0, pre~erably 50 to 200 and more pre-Eerably ~0 to 160, my o~ K0H/g.

~ xamples oP polyols o:E this type which are the compounds known Prom polyureth~ne chem:istry are polyather polyols, polyester polyol.¢, polycarbonate polyo:ls, polyesteramido polyols, polyamido polyols, epoxy resin polyols and their reaction products with COz, polyacrylate polyols and the like. Polyols of khis type which can also be used in a mixture are described, for example, in German Ol ...leyunysscil:riften No. 2,020,905; No. 2,314,51~ ~'a ~ ~ .
3,12~,7~4 and ~uropean Of~enlegunysschrift No. 120,466.

of these polyols, the polyether and polyester polyols are pre-ferred, preferably those having only terminal OFI groups and a functionality o less than 3, preferably 2.~ to 2 and most pre-ferably 2.

Examples of suitable polysther polyols are polyoxyethylene polyols, polyoxypropylene polyols, polyoxybutylene polyols and preEerably polytetrahydrofuran having terminal OH groups.

The polyester polyols which are particularly preEerred in khe invention are known polycondensation products of di- and, if appro-priate, poly(tri-, tetra)ols with di- and, if appropriate, poly (tri-, tetra)carboxylic acids, or hydroxycarboxylic acids or lactones. It is also possible to use the corresponding polycar-boxylic acid anhydrides or the corresponding polycarboxylic acid esters of lower alcohols, instead of the ~ree polycarbox~vlic acids, for preparing the polyesters. Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, further-more propanediol, 1,4-butanediol, 1,6-hexanediol, neopentylglycol or neopentylglycol hydroxypivalate, the three last-mentioned compounds bein~
preE~r:red~ Example~ o~ suitable polyols which optionally can also be used are krimethy:Lolpropalle, glycerol, erythrl~ol, pentaerythritol, krimekhylolbenzene or tris(hydroxyethyl.)isocyanurate.

Examples o~ suitable dicarboxylic acid~ are phthalia acid, isophthalic acid, kerephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexane-dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, "chlorendic acid'l, tet~ hlorophth~lic acicl, maleic acid, fumaric acid, itaconlc ac malonic acid, suberic acid, 2-methylsuccinic acid, 3,3-diethyl-glutaric acid and 2,2-dimethylsuccinic acid. Anhydrides of these acids are also useful insofar as they exist. Consequently, the anhydrides are also covered by the term "acid". It is also possible to use monocarboxylic acids such as benzoie acid and hexanecarboxylic acid, provided the average functionality of the polyol is higher than 2. Saturated aliphatie or aromatie aeids are preferred such as adipic acid or isophthalic aeid. A polycar-boxylic aeid which optionally may additiona:lly be used in relatively small amounts is trimellitie aeid.

Examples of hydroxycarboxylie acids which ean be used as reactants in the preparation of a polyestsr polyol having terminal hydroxyl include hydroxycaproic acid, hydroxybutyrie aeid, hydroxydecanoie acid, hydroxystearie acid and the like. Useful lactones ineluds eaprolaetone, butyrolaetone and the lika.

The amount of eomponent ~B~ in the polyurethane resin is usually between 15 and 80% by weight, preferably 40 to 60% by weight, relative to the polyurethane resin.

The low-moleeular-weight polyols (C) whieh optionally, may be used ~or synthesiziny the polyurethane resins usually have the e~Eect o~ stifEening the polymer ehain. In general, they hav~ a moleeular weight oE about 60 to ~00, preferably 60 to 200, and hydroxyl numbers oE, for example, 200 to 1,500. They ean eontain aliphatie, al:ieyclie or aromatie yroup~ and the amount thereof is generally 0 to 20, pre~erably 1 to ~0% by weight, relative to polyol eomponents (B) tu (D). ~xamples are the low-moleeular-weight polyols having up to about 20 carhon atoms per moleeule, for example ethylene glyeol, diethylene glyeol, 1,2-propanediol, 1-3-2~3~4~B
.~panecliol, ~ but~nediQl, l,3-butylene glycol cyclohexanediol, l,~-cyclohexanediDl~thallol, l,6-hexanediol, bisphenol A (2,2~bis(4 I-lydroxyphenyl)-prop~ne), hydrogenated bisphenol A (2,2-bis(4-hydroxycyclollexyl)-propane) and mix-tures thereof, and as triol trimethylolpropane.

Examples of compounds suitable ~or ~tru~-tural unit(D) are described in U.S. Patents No. 3,~12,054 and No. 3,640,924 and in German Offenlegungsschriften No. 2,624,442 and No. 2,744,544 incorporated herein by reference. In particular, khose polyols are suitable, pre~erably diols, which contain at least one carboxyl group, generally l to 3 carboxyl groups per molecule. Sulfo groups are also suitable as groups capable of anion formation. Examples of these are: dihydroxycarboxylic acids such as Nr ~-dialkylol alkanoic acids like ~, a-dimethylolalkanoic acids ~uch as 2,2-dimethylolacetic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, dihydroxy-succinic acid and polyhydroxy acids such as gluconic acid. Of these, 2,2-dimethylolpropionic acid is particularly pre~erred.
Examples of amino-containing compounds (D) are ~ diaminovaleric acid, 2,4-diaminotoluene-5-sul~onic acid and the like. Mixtures of the compounds (D) can also be used and the amount o~ component ~D) in the polyurethane resin is generally 2 to 20, preEerably 4 to 10%
by weiyht, relative to the polyurethane resin.
The polyurethane resins used in the invention also contain struc~ural uni~ ) which are predominantly, pre~erably to the extent o~ 70 to 90%, each present at the chain ends and terminate them ~chain termina-tors). Suitable polyols llere are those having at least three, pre~erably 3 or ~, hyroxyl yroups. Examples are ylycerol, hexanetriol, pentaerythritol and trimethylolpropane, the latter beiny preferred. 'rhe amount o~ ~E) is usually between 2 and 15, pre~erably 5 to 15% by weiyht, relative to the polyurethane 2~3~
1 .in. If desl.red, these ~tructur~l units(E) are present in the polyurethane resin in a mixture with structural units (F) .

The structural units(~'J are derived ~rom mono~unctional com-pounds whi.ch are reactive with NCO groups such as monoamines, particularly seco~dary monoamines or monoalcohols. Examples are methylamine, ethylamine, propylamine, butylamine, octylamine, laurylamine, stearylamine, isononyloxypropylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylaminopropyl-amine, diethyl(methyl~aminopropylamine, morpholine, piperidine, or suitably substituted derivatives thereof, amidoamines from primary diamines and monocarboxylic acids, monoketimines of primary dia~nes, primary/tertiary amines such as N,N-dimethylaminopropyl-amine and the like.

Preferably, suitable compounds for (F) are those containing active hydrogen of varying reactivity toward NCO groups such as compounds having, apart ~rom a primary amino group, also secondary amino groups, or, apart from an OH group, also COOH groups, or, apart from a primary or secondary amino group, also OH groups, the latter being preferred. Examples o~ these are: primary/secondary amines such as 3-amino-1-methylaminopropane, 3-amino-1-ethylamino-propane, 3-amino-1-cyclohexylaminopropane, 3-amino-1-methylamino-butane; monohydroxycarboxylic acids such as hydroxyacetic acid, lactic acid or malic acid, and al]canolamines such as N-aminoethyl-ethanolamine, ethanolamine, 3-aminopropanol, neoperltanolamine ancl particularly preEe.rably diethanolamine.

In this manner, functional groups are additionally incorpo-rated in the final polymer product which is thus made more reactive toward materials such as curing ayents. The amount oE (F) in the polyurethane resin is usually between 2 and 20, preferably 2~33~ ~
3 a~cl 10% by weight, rel~tive -to the polyurethane resin.

In addition -to the structuraL ~uts according to (E) and (F), -the polyuret~lane resi~ of the invention can op-tionally also contain structural units (G) which are derived from so-called chai.n-lellgthening agen-ts, although thi~ variation is less preferred.
Compounds which are suitable for this are the known compounds which are reactive toward NCO groups and are preferab:ly clifunc- .
tional compounds no-t .identical with (B~, (C), (D), (E) and (F) and in most cases having average molecular weights of up to 400.
Examples are water, hydrazine, poly(di)amines such as ethylene-cliamine, diaminopropane and hexamethylenediamine which can also ~arry substituents such as OH groups. Polyamines of this type are described, for example, in German Offenlegungsschri~t No.
3,644,371. The amount of (G) in the polyuretllane resin is usually between 1 and 10, preferably 2 and 5% by weight, relative to the polyurethane resin.

~ he polyurethane resin of the invention is preferably pre-pared in such a manner that first a polyurethane prepolymer is pre~
pared ~rom the polyisocyanates of (A), the polyols of (B) and optionally the low-molecular-weight polyols of (C) and the com-pounds o~ (D), which prepolymer contains on average at least 1.7, preferably 2 to 2.5, ~ree isocyanato groups per molecule, the pre-polymer is then reactecl with a stoichiometric excess of the com-pounds of (~ desired in a mixture with (F) and/or (G), in a non-aqueous system, and the completely reacted polyurethane resin is then preferably neutralized ancl transferrd into an aqueous system. If desired, the reaction with tG) can also take place after transfer into the aqueous system.

2~ ~3 ~ ~

The preparation oE the polyurethane prepolymer is carried out by known processes in whicl1 the polyisocyanate is used in excess, relative to polyols (B) to (V), resulting in a product having ~ree isocyanato groups. These isocyanato groups are terminal and/or pendant, pre~erably -terminal. A~vantageously, the amount o~ poly-isocyanate is such that the equivalent ratio of isocyanato groups to the overall number o~ O~l groups in polyols (B) to (D) is l.05 to l.4, preferably l.l to l.3.

The reaction for preparing the prepolymer is usually carried out at temperatures of 60 to s5c, preferably 6~ ~o 75C, depending on the reactivity of the isocyanate used, as a rule., in the absence of a catalyst, but preferably in t.he prasence of solvents inert to-ward isocyanate. In particular, those solvents are suitable for this which are water-compatihle such as the ethers, ketones and esters mentioned below and N-methylpyrrolidone. The amount o~ this solvent advantageously ~oes not exceed 20~ by weight, and is pre-ferably in the range of 5 to 15% by weight, in each case relative to the sum of polyurethane resin and solvent. Advantageously, the polyisocyanate is slowly added to the solution of the other com-ponellts .

The prepolymer or its solution is then reacted w:Lth the com-pound o~ (~), if desired in a mixture with (~) and/or ~G), the temperatur~ being advantageously in the range o~ 50 to 100C, pre-~erably between 60 and ~0C, un-til t~le NC0 content in the pre-polymer has virtually dropped to zero. For thi~ purpose, com-pound (E), i:e desired together with ~F) and/or (G)is used in excess.
The amount oE (El is advantageously such that the equivalent ratio of NCO groups of the prepolymer, which previously may already have been reacted with compounds according to (F) and/or (G), to reac-tive groups o~ (E~ is 1~1.1-to 1:5, preferably 1:1.5 -to 1:3. The amount 3~3~
of (F) and/or ~G) can be 0 t~ 90 %, preferably 0 to 20 ~, relative to (1:~.

A portion of the ~unneutralized) COOI-I groups, pre~erably 5 to 30% can, if desired, be reacted with difunctional compounds which are reac-tive w:ith COOH groups such as diepoxides.

For neutraliziny the result:ing product preferably containing COOH groups, in par-ticular tertiary amines are suitable. Examples are trialkylamines having 1 to 12, preferably l to 6 carbon atoms in each alkyl. Examples of these are trimethylamine, trie~hyl-amine, methyldiethylamine, tripropylamine. The alkyls can also carry, for example, hydroxyl groups as in the case of dialkyl-monoalkanolamines, alkyldialkanolamines and trialkanolamines. Anexample o~ these is dimethylethanolamine which preferably serves as neutralizing agent. Neutralizing agents which may also be used are inorganic bases such as ammonia or sodium hydroxide and potassiuim hydroxide.

In most cases, the neutralizing agent is used in a molar ratio o~ about 0.3:1 to 1.3:1, preferably about 0.5:1 to 1:1, relative to the COOH yroups of the prepolymer. The neutralization, which, as a rule, i5 carried out between room temperatures and 80C, pre-Eerably ~0 to ~0C can be carried out in any desired manner, Eorexample by adding the water-conta:Lning neutraliziny ayent to the polyurethane resin or vice versa. ~lowever, it :Ls also possible ~irst to add to the polyurethane resin the neutralizing agent and only then the water. In yeneral, this gives solids contents of 20 to 70%, preEerably 30 to 50%.

The polyurethane resin content in the aqueous coating composi-tion is generally 5 to 40, pre~erably 15 to 30% by weight, relative to the entire coating composition.

2 ~ ? 3 "~
~ part from the polyurethane r~sinr the aclueous coating CO~lpOSitiOIl can also contain, as binder, up to 60, preferably up-to 30% by weight, relative to the polyurethane resin, Oe other oligo-meric or polymeric materials such as crosslinkable, water-soluble or water-dispersible phenolic resins, polyester resins, epoxy resins or acrylic resins and the like as described in European Offenlegungsschrift No. 89,497.

Fur-thermore, excess polyol Oe t~) is usually present in the coating composition of the invention, in most cases in amounts of 1 to 10~, preferably 2 -to 5% by weight, relative to the polyurethane resin.

Suitable crosslinking agents are the curing agents customary for polyol resins as long as they are water-compatihle. Examples are water-compatible (water-soluble or water-dispersible~ amino resins, particularly commer~ially available etherifiad melamine/
formaldehyde condensation products such as hexamethoxymethyl-melamine, phenolic resinsor capped polyisocyanates as described in German Offenlegungsschrift No. 3,6~4,372. The amount of cross-linking agent is usually 10 to 35~ by weight, preferably 15 to 25%
by weight, relative to the sum of binder to be crosslinked ancl crosslinking agen-t.

~ he aqueous coa-ting compositions oE the invention, whose pH is in most cases in the range o~ about 6.0 to 10.0, pre~erably 6.8 to ~.5, aan additionally contain conventional paint additives such as piyments and Eillers, and paint additives, Por example anti-settl-ing agents, antieoams and/or wetting agents, flow-improving agents, raac-tlve thinners, plasticizers, catalysts, dissolution aids, thickeners and the like. At least part oE these additives do not have to be added to the coating composition until immediately ~3~
b~ ~re processint). Tlle s~lection alld dosage of these substances W}liCh can be added to -the individual components and/or the entire m.ixture are known ko one skilled in the art.

Examples o~ sui.table piyments are iron oxides, lead oxides, lead silicates, titanium dioxide, barium sulfate, zinc oxide, zinc sulfide, phthalocyanine complexes and the like, and suitable fillers are mica, kaolin, chalk, quartz powder, asbestos powder, slate powder, various silicas, silicates and -talc, including so-callecl micro-talc having a maximum particle size of 10 ~um (cf.
European Offenlegungsschrift No. 2~9,727). These pigments and/or fillers are usually used in amounts of 10 to 70, preferably 30 to 50% by weight,relative-to the overall solids content of ~he coating composition.

Suitable catalysts are the convenkion~l acid curing catalysts such as p-toluenesulfonic acid, dodecylhenzenesul~onic acicl and the like.

The dissolution aids, for example ethers such as dimethyl ~diethyl)glycol, dimethyl(diethyl)diglycol or tetrahydro~uran, ketones such as methyl ethyl ketone, acetone or cyclohexanone, esters such as butyl acetate, ethylglycol acetate or methylglycol acetate, methoxypropyl acetate, alcohols such as ethanol, propanol or butanol are used, i.~ ak all, only in very low amounts for reason~ oE environmental protection, usually not exceeding 10, pre-Perably 1 to 5~ by weight re].ative to water (a~ the main diluent).
The amount o~ water in the aqueous coating composition is in most cases 15 to 80~ by weiyht, prePerably 30 to 60% by wei~ht, relative to the entire coatiny composition.

2 ~ 3z~J~
~ he a~ueous coating compositions are prepared using conven-tional methods oE p~int production as can be seen from the standard recipe given below.

The aqueous coatiny composition which is infinitely dilutablP
with water and whose overall solids content (125C/2 hours) is generally 35 to 75, preferably 40 to 60~ by weight, is applied in a Xnown manner, for example by spraying using the compressed air process or by airless or electrostatic sprayiny processes. To cure the layers applied, temperatures o~ 120 to 200~C, preferably 150 to 170C, are generally applied. The curing time is generally 15 to 30 minutes, preferably 18 to 20 minutes.

The crosslinked coatings thus obtained are distinguishecl in particular by improved stone chip resistance at low temperatures (0C to -30C) and by good interlayer adhesion. Moreover, they have good elongation at break and excellent impact resistance. The resistance to atmospheric humidity and so~vents is also very good In the following examples, there are described several pre-ferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiments.

E~A~

~ mixkure was prepared ~rom 235 g of a polyester of molecular weiyllt 8~0 prepared from adipic acid, 1,6-hexanediol, neopentyl glycol and ~2.9 g of dimethylolpropionic acid and 75 g of N-mekhyl-pyrrolidone and the mixture was heated to 100C. The clear solu-tion was cooled to about 60C, and then 1~1.8 g of a mixture of 2/4~ and 2,6-toluylene diisocyanate were added dropwise at this 2033~?0 tel _rature ~t such a rate that the temperature did not exceed 65C
to 70c. S-tirr:ing ~t this temperature was then continued until the isocyanate value had reached 1.6% (=2 isocyanato groups per moleculQ). 29.5 g of trimethylolpropane were than ~dded, during which the system rernained readily stirrable. After neutralization with 22.4 CJ of dimethyle-thanolamine, the finished polyurethane resin was dispersed by addiny 590 g of deionized water to obtain a clear, approximately 40~ strength dispersion having a viscosity oE 1500 mPas.

235.6 g of a polyester with a molecular weightoE 1020 prepared from adipic acid, l,6-hexanediol and neopentyglycol were mixed with 56.0 g of polytetrahydrofuran (M = 1000), 42.9 g of dimethy-lolpropionic acid and 75 g of N-me-thylpyrrolidone and the mixture was reacted as described in Example 1 with toluylene diisocyanate (mixture of isomers). After reaction of the prepolymer with glycerol, the mixture was neutralized with 22.8 g of dimethyl-ethanolamine, and the resin was dispersed in 620 g of deionized water.

317.1 g of a polyester with a molecular weight of 1130 prepared ~rom aclipic acid, hexanediol, neopentyglycol and terephthalic acid were mlxed with 42.9 g o~ dimethylolpropionic acid and 90 g of N--methylpyrrolidone and the mixture was heated to 100C. After cooling to 65C, 1~3.7 g oE ~,4'~diisocyanatodicylcohexylmethane (Desmodur W) were added dropwise and the reaction batch was then maintainecl at 80C until the calculated isocyanate value of 1.33 (=2 isocyanato groups per molecule) had been reached. 80.4 g of 2 ~ 3 ~
t~ .ethylo~propane and then 22.8 y of dimethylethanolamine were added arlcl stirring of tile mixture was continued for 20 minutes.
The polyurethane resin was then d:isper~ed by adding 700 g of deionized water.

STANDAl~D RECIPE FOR SURFACER_ORMULATION
58.0 par-ts of the binder from Example 1 to 3 were dispersed with 4.0 parts of a commercially available melamine/ormaldehyde condensation product, 13.3 parts o~ titanium dioxide, 13.2 par-ts of barium sulfate (Blanc ~ix micro), 0.1 part of carbon black, 11.1 parts of deionized water and 0.3 parts of conventional paint addi-tives in a pearl mill for 20 minutes at ~000 rpm to form the sur-facer composition which was applied to a zinc-phosphat~d steel sheet coa-ted -to about 30 ~m with a cathodically deposited electro-primer with a compressed air gun. The curing o~ the surfacer wascarried out in a through-circulation oven at 80C for 10 minutes and then at 160C for 20 minutes toobtain a dry ~ilm thickness of 35 -~ 2 ~m. A commercially available alkyd/melamine automotive paint was applied on top o~ the surfacer coat and baked at 130C
for 30 minutes for dry film thickness of about 30+ 5 ~m. The test results are summarized in Table I below and the stabilities of the films (resistance to solvents and water) are those required in commercial practice.

~PPL~.~R~!CE OF '~E~TOPCOAT
Gloss and surEace oE the topcoat on various .surEacer materials were rated subjectively b~v a scale ~rom l = very yood to 5 = very poor.

STONE CHIP_RE~S~ CE
Tested by the stone chip testing apparatus o~ VD~ (from Erichsen, type 508). For this test, the test specimens were ~33~3~
bomb,~d~d in eacll case with 1 kg of steel shot (angular~ 4 5 mm) acc~lerated by compressed air ~2 bar). ~y comparison with control spec:imens, t:opcoa~ aclllesior~ (o = no chippi~g off Erom surfacer, 10 =
comple-te delamination) and penetratiolls down to the metal (o - no penetration, lO = a large number o~ penetrations) were rated.

T~BLE: 1 ~3xalllp1e 1 2 3 l~ppearallce Or t:ho I:opcoel 1;2 - 3 2 2 . .
Topcoat adllesion -~ 20C 1 - 2 1 2 - 3 . _ . ~ . . _ . _ . . .
Pene l:rations ~ 20~C 1 1 2 .. . . _ . . _ _ . _ _ .. _ Cros ~ha l:ch (accordlng t:o DIN 53151) ch 0 ch 0 ch 0 _ _ _ .. ..

Various modifications o~ the compositions and process of the invention may be made without departing from the spirit or scope thereof and it is to be understood that the invention is intended to be limited only as defined in the appended claims.

Claims (22)

1. An aqueous coating composition for preparing primers or primer surfacers containing at least one water-dispersible binder resin, and crosslinking agents and optionally conventional addi-tives, wherein at least some of the water-dispersible binder resin is a polyurethane resin containing structural units derived from (A) polyisocyanates, (B) polyols having an average molecular weight ?n of at least 400, (C) optionally low-molecular-weight polyols, (D) compounds having at least two groups which are reactive toward isocyanato groups and at least one group which is capable of anion formation, (E) polyols carrying no other groups which are reactive with iso-cyanato groups, these structural units (E) being in each case at the chain end of the polyurethane resin, (F) optionally compounds which are monofunctional or contain active hydrogen of varying reactivity and are different from (E), these structural units (F) likewise being at the chain end of the polyurethane resin and (G) optionally compounds which are different from (B), (C), (D), (E) and (F) and contain at least two groups which are reactive with NCO groups.
2. A coating composition of claim 1 wherein the amount of polyurethane resin in the aqueous surfacer composition is 5 to 40%
by weight, relative to the entire surfacer composition.
3. A coating composition of claim 1 wherein the aqueous sur-facer composition additionally contains at least one further binder in an amount of up to 60% by weight, relative to the polyurethane resin.
4. A coating composition of claim 2 wherein the aqueous sur-facer composition additionally contains at least one further binder in an amount of up to 60% by weight, relative to the polyurethane resin.
5. A coating composition of claim 1 which contains 10 to 35%
by weight, relative to the sum of the binder to be crosslinked and a crosslinking agent, of water-compatible amino resins as cross-linking agent.
6. A coating composition of claim 1 wherein the polyurethane resin has an average molecular weight ?n of 2,000 to 6,000.
7. A coating composition of claim 1 wherein the hydroxyl number of the polyurethane resin is 30 to 80.
8. A coating composition of claim 1 wherein the amount of structural unit(A) is 10 to 50% by weight, structural unit (B) is 15 to 80% by weight, structural unit (C) is 0 to 20% by weight, structural unit(D) is 2 to 20% by weight and structural unit(E) is 2 to 25% by weight , each relative to the polyurethane resin.
9. A coating composition of claim 1 wherein structural unit (B) is derived from polyether or polyester polyols having an average molecular weight ?n of 400 to 5,000.
10. A coating composition of claim 1 wherein the compounds of (D) are polyols containing at least one carboxyl group.
11. A coating composition of claim 10 wherein (D) is an .alpha.,.alpha.-dimethylolalkanoic acid.
12. A coating composition of claim 1 wherein the compounds of (E) are glycerol or trimethylolpropane.
13. A coating composition of claim 1 wherein the compounds of (F) are monoamines additionally containing at least one OH group.
14. A coating composition of claim 1 wherein the compounds of (G) are water, hydrazine or diamines which optionally contain OH
groups.
15. A process for the preparation of a coating composition of claim 1 comprising preparing a polyurethane prepolymer from the polyisocyanates of (A), the polyols of (B) and optionally the low-molecular-weight polyols of (c) and the compounds of (D) which pre-polymer contains on average at least 1.7, free isocyanato groups per molecule, reacting the prepolymer with an excess of the com-pounds of (E) optionally in a mixture with (F) and/or (G) in a non-aqueous system, and then optionally neutralizing the completely reacted polyurethane resin and then transferring it into an aqueous system, the further optionally binder resins, the crosslinking agent and the conventional additives added before, during, or after the preparation of the polyurethane resin.
16. The process of claim 15 wherein the prepolymer contains 2 to 2.5 free isocyanato groups per molecule.
17. The process of claim 15 wherein the compounds of (E) are used in such an amount that the equivalent ratio of NCO groups of the prepolymer which previously may already have been reacted with the compounds of (F) and/or (G), to reactive groups of (E) is 1:1.1 to 1:5.
18. The process of claim 15 wherein the amount of (F) and/or (G) is 0 to 90 %, relative to (E).
19. A primer or primer surfacer containing an effective amount of an aqueous coating composition of claim 1.
20. A substrate coated with a primer or primer surfacer of claim 19.
21. A coated substrate of claim 20 which substrate is an automotive body.
22
CA002033530A 1990-01-12 1991-01-03 Aqueous coating composition, its preparation and use Abandoned CA2033530A1 (en)

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DE4000748A DE4000748A1 (en) 1990-01-12 1990-01-12 AQUEOUS COATING, THEIR PRODUCTION AND USE

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US5710209A (en) * 1995-02-27 1998-01-20 Bayer Aktiengesellschaft Aqueous binders for coating compositions based on polyester polyurethanes
US6380342B2 (en) 1998-08-17 2002-04-30 Bayer Aktiengesellschaft Aqueous coating compositions, their preparation and use in stoving lacquers
US6423771B1 (en) 1999-12-23 2002-07-23 Solutia Austria Gmbh Aqueous coating composition
US6521700B1 (en) 1999-12-23 2003-02-18 Solutia Austria Gmbh Aqueous coating composition
US6583214B1 (en) 1999-04-01 2003-06-24 Basf Coatings Ag Aqueous coating material that is cured thermally and/or by actinic radiation, and its use
US6620511B1 (en) 1999-07-02 2003-09-16 Basf Coatings Ag Aqueous coating material, especially aqueous filler or protective base against stones
US6635723B1 (en) 1998-03-24 2003-10-21 Skw Bauchemie Gmbh Solvent-free polyurethane dispersion
US6713559B1 (en) 1999-08-27 2004-03-30 Basf Coatings Ag Sol-gel coating
US6797771B2 (en) 2000-02-02 2004-09-28 Basf Coatings Ag Aqueous composition that can be hardened physically, thermally or thermally and with actinic radiation and the derivatives and production thereof
US6824834B2 (en) 2001-11-19 2004-11-30 Solutia Austria Gmbh Coating composition
US6828381B1 (en) 1999-08-27 2004-12-07 Basf Coatings Ag Sol-gel coating
US6827983B2 (en) 2000-09-25 2004-12-07 Bayer Aktiengesellschaft Low temperature-drying waterborne coatings
US6872765B1 (en) 1999-03-06 2005-03-29 Basf Coatings Ag Sol-gel coating for single-layer or multi-layer varnishes
US7078102B2 (en) 2001-02-22 2006-07-18 Rohm And Haas Company Aqueous coating composition

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JP2005255860A (en) * 2004-03-12 2005-09-22 Kyowa Hakko Chemical Co Ltd Polyurethane and aqueous polyurethane resin
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US5710209A (en) * 1995-02-27 1998-01-20 Bayer Aktiengesellschaft Aqueous binders for coating compositions based on polyester polyurethanes
US6635723B1 (en) 1998-03-24 2003-10-21 Skw Bauchemie Gmbh Solvent-free polyurethane dispersion
US6380342B2 (en) 1998-08-17 2002-04-30 Bayer Aktiengesellschaft Aqueous coating compositions, their preparation and use in stoving lacquers
US6872765B1 (en) 1999-03-06 2005-03-29 Basf Coatings Ag Sol-gel coating for single-layer or multi-layer varnishes
US6583214B1 (en) 1999-04-01 2003-06-24 Basf Coatings Ag Aqueous coating material that is cured thermally and/or by actinic radiation, and its use
US6815494B2 (en) 1999-07-02 2004-11-09 Basf Coatings Ag Aqueous coating material, especially aqueous filler or protective base against stones
US6620511B1 (en) 1999-07-02 2003-09-16 Basf Coatings Ag Aqueous coating material, especially aqueous filler or protective base against stones
US6713559B1 (en) 1999-08-27 2004-03-30 Basf Coatings Ag Sol-gel coating
US6828381B1 (en) 1999-08-27 2004-12-07 Basf Coatings Ag Sol-gel coating
US6521700B1 (en) 1999-12-23 2003-02-18 Solutia Austria Gmbh Aqueous coating composition
US6423771B1 (en) 1999-12-23 2002-07-23 Solutia Austria Gmbh Aqueous coating composition
US6797771B2 (en) 2000-02-02 2004-09-28 Basf Coatings Ag Aqueous composition that can be hardened physically, thermally or thermally and with actinic radiation and the derivatives and production thereof
US6827983B2 (en) 2000-09-25 2004-12-07 Bayer Aktiengesellschaft Low temperature-drying waterborne coatings
US7078102B2 (en) 2001-02-22 2006-07-18 Rohm And Haas Company Aqueous coating composition
US6824834B2 (en) 2001-11-19 2004-11-30 Solutia Austria Gmbh Coating composition

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DK0436941T3 (en) 1994-05-16
ES2052154T3 (en) 1994-07-01
ZA91222B (en) 1991-10-30
DE4000748A1 (en) 1991-07-18
EP0436941A1 (en) 1991-07-17
DE59005358D1 (en) 1994-05-19
KR910014478A (en) 1991-08-31
ATE104325T1 (en) 1994-04-15
JPH0770514A (en) 1995-03-14
AR247905A1 (en) 1995-04-28
CN1053252A (en) 1991-07-24
EP0436941B1 (en) 1994-04-13

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