WO2012069414A1 - Polyurethane resin with high carbonate group content - Google Patents

Polyurethane resin with high carbonate group content Download PDF

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Publication number
WO2012069414A1
WO2012069414A1 PCT/EP2011/070559 EP2011070559W WO2012069414A1 WO 2012069414 A1 WO2012069414 A1 WO 2012069414A1 EP 2011070559 W EP2011070559 W EP 2011070559W WO 2012069414 A1 WO2012069414 A1 WO 2012069414A1
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Prior art keywords
weight
groups
water
dispersable
component
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PCT/EP2011/070559
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French (fr)
Inventor
Marc Claudius Schrinner
Uwe Klippert
Heinz-Dietmar Gewiß
Martin Melchiors
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Bayer Materialscience Ag
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Publication of WO2012069414A1 publication Critical patent/WO2012069414A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/65—Low-molecular-weight compounds having active hydrogen with high-molecular-weight compounds having active hydrogen
    • C08G18/66—Compounds of groups C08G18/42, C08G18/48, or C08G18/52
    • C08G18/6633—Compounds of group C08G18/42
    • C08G18/6659—Compounds of group C08G18/42 with compounds of group C08G18/34
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/0804—Manufacture of polymers containing ionic or ionogenic groups
    • C08G18/0819—Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups
    • C08G18/0823—Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups containing carboxylate salt groups or groups forming them
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/0804—Manufacture of polymers containing ionic or ionogenic groups
    • C08G18/0819—Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups
    • C08G18/0828—Manufacture of polymers containing ionic or ionogenic groups containing anionic or anionogenic groups containing sulfonate groups or groups forming them
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C08G18/44—Polycarbonates
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/721—Two or more polyisocyanates not provided for in one single group C08G18/73 - C08G18/80
    • C08G18/722—Combination of two or more aliphatic and/or cycloaliphatic polyisocyanates

Definitions

  • the present invention relates to a water-dispersable polyurethane resin.
  • the invention also relates to a process for preparing the water-dispersable polyurethanes, an aqueous coating system comprising the water-dispersible polyurethane resin according to the invention, the use of the water-dispersable resin for coating, varnishing and/or sealing a substrate, the use of the water-dispersable resin for producing a soft-feel effect coating material and a substrate coated with a crossiinked coating system comprising the water-dispersable polyurethane resin.
  • Soft-feel effect in the context of the present invention refers to a particular touch sensation (haptic quality) of the coated surface.
  • This hap tic quality can be expressed by terms such as velvety, soft, rubber-like or warm, whereas, say, the surface of the coated car body or else a plastic sheet (e.g. polycarbonate sheet) or plexiglass, uncoated or coated with a conventional clearcoat or topcoat material, feels smooth and cold.
  • EP-A 0 529 094 describes, for example, a solvent-based surface coating with soft-feel effect, the haptic quality there being achieved through the combination of a urethane resin with elastic particles or with a porous inorganic material.
  • EP-A 0 669 352 describes special aqueous polyester-polyurethane dispersions which, in combination with crosslinker resins and. where appropriate, with linear, hydroxyl-free polyurethane dispersions, can be cured to give coatings havin a good soft-feel effect, good mechanical properties, and a generally satisfactory solvent resistance.
  • the resistance particularly the resistance to suntan lotion, are still in need of improvement.
  • EP-A 0 926 172 describes aqueous two-component (2K) polyurethanc coatin materials in which the resistance to suntan lotion (which penetrates the film, causing delamination and/or other damage) can be improved by using special ester-modified polyisoeyanates.
  • the binders used in that case are mixtures of carboxylate- and/or sulfonate-hydrophilicized. polyester polyol dispersions with physically drying, carboxylate- and/or sulfonate- hydrophil icized polyurethanc dispersions.
  • EP-A 0 578 940 describes water dispersible polyurethanc polyols on the basis of polyester and polycarbonate polyols or segmented polyester carbonate polyols containing 2 to 100% of acid groups neutralized with bases, corresponding to an acid number of 6 to 45 mg KOH/g, with a hydroxy! number of 20 to 250 mg KOH/g, a molecular weight M w of 2000 to 150000, a urethane group content of 2 to 16 weight- % and a carbonate group content of 1 to 25 weight-%.
  • EP-A 1 418 192 is concerned with water-d i spersable polyurethanc resins with a carbonate group content of 5.8 to 20.0 weight-% and which is present in a solvent, the solvent being inert towards isocyanate groups.
  • Aqueous polyurethanc dispersions with isolated urea groups are the subject of the patent application WO 00/50482.
  • the present invention therefore has the object of providing water-dispersable polyurethaiies with a considerable carbonate group content which experience less of a change in viscosity over a prolonged period of time while at the same time not compromising other coating-reiated features.
  • this object is achieved by a water-dispcrsable polyurethane resin obtained by react ing Al) at least one polycarbonate polyol with a number average molecular weight of from 400 to 6000 g/mol,
  • A2) optionally, a polyester polyol which is different from component (Al) with a number-average molecular weight M n of from 400 to 6000 g/mol,
  • A3) optionally, a low molecular weight compound containing two or more hydroxy and/or amino groups having a molecular weight of from 60 to 400 g/mol,
  • At least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions
  • the resultant polyurethane dispersion contains from 1 ,5 % to 25,0 % by weight, more preferably from 3,0 to 18,0 % by weight, of incoiporated carbonate groups - ( ) ( ( ⁇ ) )( ) -. It has been found that the dispersions according to the inv ention experience a predictable and very slow change in viscosity over the course of sev eral hours. 1 n preferred embodiments the viscosity has been virtually constant ov er six hours. At the same time, the suntan lotion resistance of coatings achieved with the dispersions did not deteriorate.
  • Component (Al) suitably comprises hydroxy l-containing polycarbonates whose molecular weight Mn is 400 to 6000 g/mol, in some cases from 600 to 3000 g/mol, and which are obtainable, for example, by reacting carbonic acid derivatives, e.g. diphenyl carbonate, dimethyl carbonate or phosgene, with polyols, and in some cases diols.
  • carbonic acid derivatives e.g. diphenyl carbonate, dimethyl carbonate or phosgene
  • suitable such diols include ethylene glycol. 1.2- and 1 ,3 -propanediol, 1 ,3- and 1 .4- butanediol.
  • the diol component contains preferably from 40 to 100% by weight of hexanediol, preferably 1 ,6-hexanediol and/or hexanediol derivatives, preferably those which in addition to terminal OH groups contain ether groups or ester groups, examples being products obtained by reacting 1 mol of hexanediol with at least 1 mol. in some cases 1 to 2 mol, of eapro!aetonc or by etheri tying hexanediol with itsel to give dihexylene or trihexylene glycoi. Additionally the polyether- polycarbonate diols described in DE-A 37 17 060 can be employed.
  • the hydroxy I polycarbonates (Al) are preferably linear. They may, however, be slightly branched where appropriate through the incorporation of polyfunctional components, especially low molecular weight polyols.
  • Compounds suitable for this purpose include for example glycerol, trimethylolpropane, hexane- 1 ,2.6-triol, butane- 1 .2,4-triol, trimcthylolcthane, pentaerythritol. quinitol, mannitol, and sorbitol, methylglyeoside or 1 ,3,4.6-dianhydrohexitols.
  • Polyester polyols which can be used as component (A2) have a molecular weight M n of from 400 to 6000 g/mol, in some cases from 600 to 3000 g/mol. Their hydroxy! number is generally from 22 to 400, in some cases from 50 to 200 and in other cases from 80 to 160 mg KOH/g. The OH functionality is in the range from 1 .5 to 6, in some cases from 1.8 to 3, and in other cases from 1.9 to 2.5.
  • Highly suitable compounds arc the conventional polycondcnsatcs of diol and also, where appropriate, polyols (triols, tetraols) and dicarboxyl ic and also, where appropriate, polycarboxylic (tricarboxylic, tetracarboxylic) acids or h y d r o x y c a r b o x y 1 i c acids or lactones.
  • free polycarboxyl ic acids it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols to prepare the polyesters.
  • diols examples include ethylene glycol, butylcne glycol, diethylene glycol, tri ethylene glycol, polyalkylene glycols such as polyethylene glycol, and also propanediol or butane- 1 ,4-diol, preference being given to hexane- l ,6-diol, neopentylglyeol or neopentylglycol hydroxypivalate.
  • polyols such as trimethylolpropanc. glycerol. erythritol, pentaerytliritol. trin ethylolbenzene or tri shy droxy ethyl isocyanurate, for example, as well.
  • dicarboxylic acids examples include phthalie acid, isophthalic acid, terephthalie acid, tetrahydrophthalie acid, hexahydroplithalic acid, cycloliexane dicarboxylic acid, adipic acid, azeleic acid, sebacic acid, glutaric acid, tetraehlorophthalie acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methyl succinic acid, 3,3- diethylglutaric acid, 2.2-dimethyl succinic acid.
  • the possible anhydrides of these acids are likewise suitable. I n the content of the present invention the anhydrides are always embraced by "acid".
  • monocarboxylic acids such as benzoic acid and hexanecarboxylic acid, provided that the average functionality of the polyol is greater than 2.
  • Saturated aliphatic or aromatic acids are preferred, such as adipic acid or isophthalic acid.
  • polycarboxylic acid is also possible to use relatively small amounts of polycarboxylic acid as well, such as trimcllitic acid.
  • Hydroxycarboxyl ic acids which can be used as reaction participants in the preparation of a polyester polyol having terminal hydroxy! groups are for example hydroxycaproic acid. hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones are, for example, caprolactone or butyrolactone.
  • Compounds of component (A2) may also include, at least proportionally, primary or secondary amino groups as isoeyanate-rcaetivc groups.
  • the low molecular weight polyols (A3) are used in general for the purpose of stiffening and/or branching the polymer chain.
  • the molecular weight is preferably in the range from 60 to 400 g/mol, more preferably in the range from 62 to 200 g/mol. They can contain aliphatic, cycloaliphatic or aromatic groups.
  • Suitable polyols (A3) arc compounds having up to about 20 carbons per molecule, such as ethylene glycol, diethylene glycol, tri ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 .4-butanediol, 1 ,3-butylene glycol, cyclohexanediol, 1 ,4-eyciohexanedimethanol, 1 ,6-hexanediol, hydro-quinone dihydroxyethyl ether, bisphenol A [2,2-bis(4-hydroxyphenyl)propane], hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane) and also mixtures thereof, and also trimcthylolpropane.
  • ethylene glycol diethylene glycol, tri ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1
  • Ester diols as well such as ⁇ - hydroxybutyl-e-hydroxy-caproic esters, co-hydroxyhexyl-y-hydroxybutyric esters, adipic acid ⁇ -hydroxyethyl esters or terephthaiic acid bis(P-hydroxyethyl) ester, for example, can be used.
  • Diamines or polyamines and also hydrazides can likewise be used as (A3), examples being ethyienediamine, 1 ,2- and 1 ,3-diaminopropane, 1 ,4-diaminobutane, 1 ,6-diaminohexane, isophoronediamine, the isomer mixture of 2,2,4- and 2,4,4-trimethyl- hexamethylenediamine, 2-methylpentamethylene-diamine, diethylenetriamine, 1 ,3- and 1 ,4-xylyienediamine, ⁇ , a .
  • Component (A3) preferably contains at least 2% by weight, based on components (Al) to (A6), of at least one compound which has a functionality of three or more in respect of reaction with NCO groups.
  • the polyurethane resin may where appropriate also include units (A4) which are each located at the chain ends, and cap them.
  • These units are derived on the one hand from monofunctional, isocyanate-reactive compounds, such as monoamines, especially mono- secondary amines, or monoalcohols. Mention may be made here by way of example of methylamine, ethyiamine, propylamine, butylamine, octylamine.
  • component (A4) are compounds containing active hydrogen atoms which differ in reactivity towards isocyanate groups, such as compounds which in addition to a primary amino group also contain secondary amino groups or in addition to an OH group also contain COOH groups or in addition to an amino group (primary or secondary) also contain OH groups. Preference is given to compounds (A4) which in addition to an amino group (primary or secondary) also contain OH groups. Examples of such are primary/secondary amines, such as 3-amino- 1 -metliylaminopropane, 3-amino-i- ethylaminopropane, 3-amino- 1 -cyclohcxylaminopropanc. 3-amino- !
  • Ionic or potentially ionic compounds suitable as component (A5) include for example mono- and d i h y d r o x y c a r b o x y l i c acids, mono- and diaminocarboxylic acids, mono- and dihydroxysulfonic acids, mono- and diaminosulfonic acids and salts thereof such as dihydroxycarboxylic acids, hydroxypivalic acid, -( 2-am i noet hy I )-
  • Preferred ionic or potential ionic compounds (A5) are those which possess carboxyl and/or carboxylate groups.
  • Particularly preferred ionic compounds (A5) are d i hydroxy carboxy I i c acids, especially ⁇ , ⁇ -dimethyioiaikanoic acids, such as 2,2-dimethylolacetie acid, 2,2-dimethylolpropionic acid, 2.2-dimethyloibutyrie acid, 2.2-dimethyl-olpentanoic acid or dihydroxysuceinie acid.
  • components (Al) to (A5) may also contain compounds hav ing a nonionically hydrophii icizing activity, examples being polyoxyalkylcne ethers having at least one hydroxy! or amino group.
  • These polyethers include a fraction of from 30% by weight to 1 00% by weight of units derived from ethylene oxide. They suitably include polyethers of linear construction with a functionality of between 1 and 3, but also compounds of the general formula (I)
  • R 1 and R 2 independently of one another are each a divalent aliphatic, eycloaliphatic or aromatic radical having 1 to 18 carbon atoms, which can be interrupted by oxygen and/or nitrogen atoms, and R 3 is a non-hydroxy-terminated polyester or, preferably, polyether, in particular an alkoxy- tcrminated polyethylene oxide radical.
  • component (A6) comprises hcxamcthylenc diisocyanatc (HDI ) and di i socy anatodicy c I oh exy I met h ane (H12-MDI) and/or isophorone diisocyanatc (IPDI). It is preferred that no other polyisocyanates, apart from higher oligomers of I PDI, HDI and Hi2-MDI and technically unavoidable impurities, are present in (A6).
  • HDI hcxamcthylenc diisocyanatc
  • IPDI isophorone diisocyanatc
  • the polyisocyanatc component A6) comprises > 75 weight-% to ⁇ 85 weight-% of hexamcthyicne diisocyanatc and > 15 weight- % to ⁇ 25 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisocyanatc, the total weight percentages amounting to ⁇ 100 weight-%.
  • Preferred ranges for HDI and I PDI are 78 weight-% to ⁇ 82 weight-% and for H n-MDl are > 12 weight-% to ⁇ 22 weight-%.
  • the average molecular weight (M n ) (of the resin) is from 1000 to 30,000 g/mol
  • the acid number is from 10 to 80 mg KOH/g determined according to DI 53402
  • the OH content is from 0.5 to 5% by weight.
  • the M n is from 1 500 to 10 000 g/mol
  • the acid number from 10 to 80 or from 15 to 40 mg KOH/g determined according to DIN 53402
  • the polyurethane has been synthesized from
  • Al from 25 to 80% by weight of at least one polycarbonate polyol having a molecular weight (Mn) of from 400 to 6000 g/mol and which has a carbonate group content of at least 10% by weight, A2) from 0 to 60% by weight of at least one polyester polyol which is different from component (Al) and has a number-average molecular weight M n of from 400 to 6000 g/moi,
  • A3 from 0 to 20% by weight of at least one low molecular weight compound which contains two or more hydroxyl and/or amino groups and has a molecular weight of from 60 to 400 g/mol,
  • a 5 from 2 to 10% by weight of at least one compound containing at least two isocyanate-react ive groups and at least one group capable of forming anions
  • A6) a polyisocyanate component comprising > 5 weight-% to ⁇ 95 weight-% of hexamethylene diisocyanate and > 5 weight-% to ⁇ 95 weight-% of diisoeyanatodieyciohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to ⁇ 100 weight-%.
  • component (Al) is linear hydroxyl polycarbonates (Al).
  • the polyurethane resin is free from sulfonic acid groups.
  • Another aspect of the present invention is a process for preparing the watcr-dispcrsabic polyurethanes according the present invention, comprising preparing an OH- and/or H- functional polyurethane from components (Al), (A5) and (A6) and optionally components
  • the water-dispersable polyurethane resins of the invention can be prepared, for example, by first preparing an i s o c y a n a t e - f u n c t i o n a I prepolymer from component (A6) and components (Al) and (A5) and, if desired, (A2), (A3) or (A4) and, in a second reaction step, by reaction with one or more of the compounds (A3), (A4) or if desired, (A2) in a suiiable solvent medium, e.g. acetone or methy!ethy!ketone, obtaining an OH- and H- functional polyurethane, as described for example in HP- A 0 355 682, p. 4, lines 39 - 45.
  • a suiiable solvent medium e.g. acetone or methy!ethy!ketone
  • the urethanization reaction in the preparation of the prepolymer is normal ly conducted at temperatures from 0° to 140 °C, depending on the reactivity of the isocyanate used.
  • suitable catalysts such as are known for the acceleration of the C ' O-OH react ion to the person skilled in the art.
  • suitable catalysts such as are known for the acceleration of the C ' O-OH react ion to the person skilled in the art.
  • tertiary amines such as triethylaminc.
  • organotin compounds such as dibutyltin oxide, dibutyltin dilauratc or tin bis(2-ethylhexanoate), for example, or other organometallic compounds.
  • the water-dilutable polyurethane resin can be prepared using all of the prior art methods, such as the prepolymer mixing method, acetone method or melt dispersing method, for example.
  • the urethanization reaction is conducted in the presence of solvents which are inactive towards isocyanate groups.
  • solvents which are inactive towards isocyanate groups are those solvents which arc compatible with water, such as ethers, ketones and esters, and also N-methylpyrrolidone, for example.
  • the amount of this solvent appropriately does not exceed 30% by weight and is in some cases in the range from 10 to 25% by weight, based in each case on the sum of polyurethane resin and solvent.
  • the polyisocyanate (A6) can be added swiftly to the solution of the other components.
  • the acid groups incorporated in the polyurethane resin by component (A5) can at least proportionally be neutralized.
  • Particularly suitable for the neutralization arc tertiary amines, examples being trialkylamines hav ing 1 to 12, in some cases 1 to 6, carbon atoms in each alkyl radical. Examples thereof are trimethylamine, triethylaminc, methyldiethylamine, tripropylamine and diisopropylethylamine.
  • the alkyl radicals may, for example, also carry hydroxy! groups, as in the case of the dialkylmonoalkanol-. alkyldialkanol- and trialkanolamines. An example of such is dimethylethanolamine, which serves preferably as neutral izing agent.
  • neutralizing agent it is also possible where appropriate to use inorganic bases, such as ammonia or sodium or potassium hydroxide.
  • the neutralizing agent is used in a molar ratio to the acid groups of the prepolymer of from 0.3: 1 to 1.3: 1, in some cases from 0.4: 1 to 1 : 1.
  • the free COOH groups of the polyureihane resin of the invention can be neutralized before, during or after the urethanization reaction.
  • the neutralizing step is preferably conducted following the urethanization reaction, generally of between room temperature
  • Neutralization may also take place simultaneously with dispersing, with the dispersing water already containing the neutralizing agent.
  • water-dispersable polyureihane resin in a non-neutralized form and to carry out the neutralization not until during the preparation of the aqueous coating composit ion: for example, when incorporating the water-dispersable polyuretliane resin of the invention into the OH-frce polyuretliane dispersion(s).
  • the polyuretliane resin of the invention for the purpose of hydrophilicization, to add, in addition to the acid groups, and proportionally, monomer units containing alkyiene oxide, in incorporated form, or else external emulsifiers.
  • the external emulsifiers w ich can be used in this context arc anionic and/ or non-ionic in nature.
  • anionic emulsifiers those having carboxylatc groups, sulfate, sulfonate, phosphate or phosphonate groups can be used.
  • Preferred emulsifiers have sulfate, sulfonate, phosphate or phosphonate groups.
  • Suitable non-ionogenic external emulsifiers which can be employed generally in combination with the abovementioned anionic emulsifiers. include reaction products of al iphatic, araliphatic, cycloaliphatic or aromatic carboxylic acids, alcohols, phenol derivatives and/or amines with epoxides, such as ethylene oxide, for example.
  • the reaction products w ith ethylene oxide arc oligocthers or polyethers having degrees of polymerization of between 2 and 100, in some cases between 5 and 50.
  • the external emulsifiers can be added in amounts of from 0.
  • the aqueous coating systems are preferably prepared such that the water-dispersable polyurethane resin of the invention is incorporated under shearing into an aqueous binder component.
  • the cross! inker component which in some cases comprises a polyisocyanate having free NCO groups, is incorporated into the aqueous stock v arnish thus obtained.
  • the customary coatings auxiliaries and additiv es can be incorporated into the finished aqueous coating material either together with the crossl inker component, with the binder components, or subsequently.
  • the present invention is further directed towards an aqueous coating system comprising a) at least one water-dispersiblc polyurethane resin according to the present invention, b) optionally one or more aqueous binder components comprising at least one hydroxyl- free polyurethane dispersion, c) optionally, auxiliaries and additives and d) at least one crosslinker component.
  • aqueous coating system comprising a) at least one water-dispersiblc polyurethane resin according to the present invention, b) optionally one or more aqueous binder components comprising at least one hydroxyl- free polyurethane dispersion, c) optionally, auxiliaries and additives and d) at least one crosslinker component.
  • "Hydroxyl-free" means, for the purposes of the present invention, that the polyurethane carries no hydroxy! groups, with the exception of the terminal groups of the polymer chains.
  • the concentration o the terminal groups is low, corresponding to an OH content of ⁇ 0.5% by weight; customarily of ⁇ 0.2% by weight.
  • hydroxyl-free polyurethane dispersions are used which in addition to non-ionic, hydrophilic groups in the form of polyethylene oxide units also contain anionic groups, preferably earboxylate and/or sulfonate groups, more preferably sulfonate groups, and especially their alkal i metal salts, as hydrophilic groups.
  • the resulting amount of n on ionic hydrophilic groups in the form of polyethylene oxide units is between 0.1 ands 10% by weight, in some cases between 1 to 7% by weight, based on resin solids, and the amount of ionic groups is from 2 to 20, in some cases from 2.5 to 1 5 mmol/100 g resin solids.
  • suitable components b) also include any desired hydroxy- functional, aqueous or water-dilutable, ionomeric binders from the classes of the polyester, poiyuretliane, pol yu rea-po I y uret h ane and polyacrylate resins and/or any desired combinations of the aforementioned types such as polyurethane-polyacrylate or polyestcr- polyacrylate graft polymers, for example.
  • one particularly preferred embodiment poiyuretliane resins are used in a dispersion that is free of cosolvents, i.e. a cosolvcnt content of from 0.0 to 0.3 % by weight.
  • Cosolvents within the scope of the present invention are polar organic solvents.
  • Cosolvents are preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm 3 ) 0 - 5 and a p n value > 7.
  • Cosolvents arc particularly preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm 3 ) 0 5 and a pKe value > 8.
  • Cosolvents are most particularly preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm 3 ) 0 5 and a pKe value > 9.
  • the Hansen parameters are disclosed inter alia in "Polymer Handbooks", Eds. Brandrup, J; Immergut, E.H.; Grulke, E.A., 4th Edition, John Wiley, New York, 1999, VI I/pages 675-71 1.
  • Preferred cosolvents within the scope of the present invention arc polar organic solvents selected from the group consisting of acetone, methyl ethyl ketone, butyl diglycol. dimethyl sulfoxide, N-ethylpyrrolidone. -methylpyrrolidone, dimethylformamide, dimethylacetamide and dipropylene glycol dimethyl ether.
  • the cosolvents are on the one hand solvents which have already been used in the synthesis of the poiyuretliane polymer and on the other hand solvents which have been added to the polyurethane dispersion subsequently in order to establish the desired properties.
  • polyurethane dispersions are used with a content of NMP from 0.0 to 0.5 wt.%, particularly preferably from 0.0 to 0.3 wt.%, most particularly preferably from 0.0 to 0.1 wt.%, by weight.
  • the polymer mixture according to the invention is free of NMP.
  • free of NMP means that the content of NMP in the polymer mixture is less than or equal to the detection limit (i.e. ⁇ 0. 1 ppm) when measured by gas chromatography.
  • aqueous coating systems comprising the polyurethane resins of the invention can where appropriate also contain other binders or dispersions, based for example on polyesters, polyurethancs, polyethers, polyepoxides or polyaerylates, and, where appropriate, pigments and other auxiliaries and additives t at are known in the coatings industry.
  • binders or dispersions based for example on polyesters, polyurethancs, polyethers, polyepoxides or polyaerylates, and, where appropriate, pigments and other auxiliaries and additives t at are known in the coatings industry.
  • crossl inkers it is possible, depending on the reactivity or. where appropriate, blocking of the crossl inkers, to prepare both one-component (IK) and two- component (2K) coating materials.
  • IK coating materials for the purposes of the present invention are coating materials in which binder component and crosslinker component can be stored together without any crosslinking reaction takin place to a marked extent or to an extent which is detrimental to the subsequent application.
  • the crosslinking reaction takes place only on application, after the crosslinker has been activated. This activation can be effectuated, for example, by raising the temperature.
  • 2K coating materials for the potposes of the present invention are coating materials in which binder component and crosslinker component have to be stored in separate vessels owing to their high reactivity. The two components are not mixed until shortly prior to application, w hen they react generally without additional activation. 1 n order to accelerate the crosslinking reaction, however, it is also possible to use catalysts or to employ higher temperatures.
  • Suitable crossl inkers are polyisocyanate crossl inkers, amide- and a mine- formaldehyde resins, phenolic resins, aldehyde resins and ketone resins, such as phenol formaldehyde resins, resoles, furan resins, urea resins, carbarn ic ester resins, triazine resins, melamine resins, benzoguanamine resins, cyanamide resins, anil ine resins, as described in "Lackharze " , D. Stoye, W. Freitag, Carl Hanser Verla Miinehen, 1996.
  • Preferred crossl inkers are polyisocyanates.
  • Polyisocyanates can be used with free and/or blocked isocyanate groups. Suitable such crosslinker resins include blocked polyisocyanates based for example on isophorone di isocyanate, hexamethylene di isocyanate, 1 ,4-diisoeyanatoeyelo-he.xane, bis(4- isocyanaiocyclohexane)methane or 1,3-diisocyanatobenzene or based on paint polyisocyanates such as polyisocyanates which contain biuret or isocyanurate groups and are derived from 1 ,6-di isoeyanatohexane, isophorone diisocyanate or bis(4-iso- cyanatocyclohexane)methane or paint polyisocyanates which contain urethane groups and are based on 2,4- and/or 2,6-diisocyanato-toluene or isophorone diisocyanate on the one hand
  • Suitable blocking agents for the staled polyisocyanates are, for example, monohydrie alcohols such as methanol, ethanol, butanol, hexanol, eyclohexanol, benzyl alcohol, oximes such as acetoxime, methyl ethyl ketoxime, cycloliexanone oxime, lactams such as ⁇ -caprolactam. phenols, amines such as diisopropylamine or dibutylamine, dimethylpyrazole or triazolc. and also dimethyl malonatc, diethyl malonatc or dibutyl malonatc.
  • polyisocyanates with free isoeyanate groups based on aliphatic, eyeioaliphatic, araliphatic and/or aromatic isocyanates, more preferably on aliphatic or eyeioaliphatic isocyanates. Since in this way it is possible to achieve a particularly high lev el of resistance in t e coating film.
  • the advantages of the binder dispersions of the invention are most clearly manifested in combination with these crosslinkers.
  • These polyisocyanates generally hav e at 23 °C a viscosity of from 10 to 3500 m Pas measured according to DIN 53019 at a shear rate of 40 s "1 .
  • the polyisocyanates can be employed as a blend of small amounts o inert solvents, in order to lower the viscosity to a level within the stated range.
  • Triisocyanatononane as well can be used alone or in mixtures as a crosslinker component.
  • the water-dispersable polyurethane resin and the hydroxy 1-frec polyurethane dispersion described herein arc generally of sufficient hydrophilicity, so that the dispersibiiity of the crosslinker resins, where the substances in question are not water-soluble or water- dispersible in any case, is ensured.
  • Water-soluble or gap dispersible polyisocyanates are obtainable, for example, by modification with carboxylate, sulfonate and/or polyethylene oxide groups and/or polyethylene ox i de/po I yp ropy I en e oxide groups.
  • Hydrophilicization of polyisocyanates for example, is possible by reaction with substoichiometric amounts of monohydric hydrophilic polyether alcohols. The preparation o hydrophilicized polyisocyanates of this kind is described for example in EP-A
  • 3 line 5 are suitable, as are polyisocyanates hydrophilicized with ionic groups (sulfonate groups, phosphonate groups), as described, for example, in DE-A 10 024 624 (p. 3 lines 13 - 33).
  • ionic groups sulfonate groups, phosphonate groups
  • a further possibility is that of hydrophil icization through the addition of commercially customary emulsifiers.
  • auxiliaries and additives which, as already described earlier on above, can be added both to the aqueous coating system before, during or after its preparation and to the binder or crosslinker components present in the said system, the following come into consideration for example: defoamcrs, thickeners, pigments, dispersing auxiliaries, dulling agents, catalysts, anti-skinning agents, anti-settling agents or emulsifiers and also adjuvants which are able to intensify the desired soft-feel effect.
  • the crosslinker component is hydrophobic or hydrophil icized polyisocyanates containing free isocyanate groups based on aliphatic, cycloaliphatic. araliphatic and/or aromatic isocyanates.
  • the crosslinker component is hydrophobic or hydrophilicized polyisocyanates containing free isocyanate groups based on aliphatic or cycloaliphatic isocyanates.
  • the invention also relates to a process for preparing aqueous coating systems according the invention, further comprising incorporating the watcr-dispcrsable polyurethanc resin into an aqueous phase optionally comprising at least one hydroxyl-free aqueous polyurethane dispersion and, if desired, auxiliaries and additives and subsequently at least one crosslinker component and also, where appropriate, further auxiliaries and additives are dispersed into this aqueous stock varnish.
  • Th e aqueous coating systems thus obtained, comprising the polyurethane resin of the invention are suitable for all fields of use in which aqueous paint and coating systems with high requirements in terms of the surface quality resistance of the films are used.
  • another aspect of the invention is the use of the water-dispersable resin of the present invention for coating, varnishing and/or sealing a substrate, wherein the substrate is selected from mineral construction material surfaces, wood, wood materials, metallic surfaces, asphaltic coverings, bituminous coverings, and plastics surfaces.
  • the invention also encompasses the use of the water- dispersable resin of the present invention for producing a soft- feel effect coating material.
  • plastic or wood is coated, where curing takes place normally at temperatures between room temperature (23 °C) and 130 °C.
  • the two-component technology with non-blocked polyisocyanate crosslinkers allows the use o comparatively low curing temperatures.
  • aqueous coating systems comprising the water-dispersable polyurethanes of the invention are normally used in one-coat coating materials or in the clearcoat or topcoat
  • the invention furthermore also relates to a substrate coated with a cross! inked coating system comprising the water-dispersable polyurethane resins according to the present invention.
  • the coating can be produced by any of the various spraying methods, such as air pressure spraying, airless spraying or electrostatic spraying methods, for example, using one- component or. where appropriate, two-component spraying equipment.
  • the coating materials and coating systems comprising the polyurethane resins of the invention can. however, also be applied by other processes, for example by brushing, rollin or knife coating.
  • Desmophen C XP 2613 polycarbonate polyol. OH number 56 mg KOH/g, molecular weight Mn 2000 g mol ( Bayer MateriaiScience AG, Leverkusen, DE)
  • Desmodur W diisocyanatodicyclohexylmethane (H12-MDI)
  • Tanafoam DNE 01 defoamer; Blend of fatty acid esters and higher-rated hydrocarbons with
  • BYK 348 po I yet her modified siloxane surfactant, BYK, DE
  • Aquacer 1 10 RC 1 174 wax additive, BYK, DE
  • Siilitin Z 86 clay filler, Hoffmann M ineral. DE
  • Acematt 3300 modified pyrogenic silica, Evonik, DE
  • XP 2655 Hydrophiiic aliphatic polyisoeyanate based on HDI
  • Viscosity measurements were conducted in a cone and plate viscometer in accordance with DIN 53019 at a shear rate of 40 s -1 .
  • the acid number was determined according to DIN 53402 ( mg KOH/g sample, titration with 0.1 mol/1 NaOH solution).
  • the solids content was determined according to DIN EN 1 SO 325 1 (thick-layer method: lid, 1 g sample, 1 h 125 C, convection oven).
  • the OH number was determined according to DIN 53240 ( mg KOH/g sample, acetyiat ion, hydrolysis, titration with 0.1 mol/1 NaOH).
  • the pH w as measured according to international standard ISO 976.
  • the molecular weight (M n , M w ) is determined by means of gel permeation
  • the components of group I were weighted into a reaction vessel and heated to 1 0 °C within 2 hours. 15-16 liters of nitrogen gas w ere blown over the mixture. The mixture was kept at a temperature of 130 °C for 1 hour and subsequently cooled to 90 °C. The components of group 11 were mixed and the mixture was rapidly added to the heated components I. The temperature was raised to 130 °C, kept at this temperature for 2 hours and then lowered to 100 °C.
  • Component III was then added over a course o 30 minutes at a temperature of the reaction mixture of 90 °C.
  • Component I V was added over a course of 30 minutes at a temperature of 70 °C. This temperature was kept for 2 hours and the lowered to 45 °C. The viscosity was set to a desired level by further adding water.
  • FIG. 1 shows the results of rheology experiments. 1 n these experiments, dispersions were sheared with 1000 rpm and the flow times out of a DIN 6 cup were determined.
  • the data points of graph 1 arc associated with a dispersion according to the invention and prepared as described above (batch 1).
  • the data points of graph 2 are from the comparative example (batch 4).
  • Aqueous coating systems according to the invention were prepared from the following components. Amounts are given in weight parts in the table below, unless otherwise stated.
  • FIG. 1 Flow time in Din 6 cup: under constant sheer stress in dependence of time t.

Abstract

A water-dispersable polyurethane resin is obtained by reacting: at least one polycarbonate polyol; optionally, a polyester polyol which is different from the polycarbonate polyol; optionally, a low molecular weight compound containing two or more hydroxy and/or amino groups; optionally, a compound which is monofunctional in terms of reaction with NCO groups or which contains active hydrogen atoms differing in reactivity, these units being located in each case at the chain end of a polymer containing urethane groups; at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions; and a polyisocyanate component comprising ≥ 5 weight- % to ≤ 95 weight-% of hexamethylene diisocyanate and ≥ 5 weight- % to ≤ 95 weight- % of diisocyanatodicyclohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to ≤100 weight-%. The resultant polyurethane resin contains from 1.5% to 25.0% by weight of incorporated carbonate groups -O(C=O)O-.

Description

Polyurethane resin with high carbonate group content
The present invention relates to a water-dispersable polyurethane resin. The invention also relates to a process for preparing the water-dispersable polyurethanes, an aqueous coating system comprising the water-dispersible polyurethane resin according to the invention, the use of the water-dispersable resin for coating, varnishing and/or sealing a substrate, the use of the water-dispersable resin for producing a soft-feel effect coating material and a substrate coated with a crossiinked coating system comprising the water-dispersable polyurethane resin.
"Soft-feel effect" in the context of the present invention refers to a particular touch sensation (haptic quality) of the coated surface. This hap tic quality can be expressed by terms such as velvety, soft, rubber-like or warm, whereas, say, the surface of the coated car body or else a plastic sheet (e.g. polycarbonate sheet) or plexiglass, uncoated or coated with a conventional clearcoat or topcoat material, feels smooth and cold. EP-A 0 529 094 describes, for example, a solvent-based surface coating with soft-feel effect, the haptic quality there being achieved through the combination of a urethane resin with elastic particles or with a porous inorganic material.
Modern aqueous coating compositions are capable of substituting for binders in organic solution in many applications. However, for certain applications with specific profiles of requirements, such as the coating of substrates, and more particularly plastics substrates, with soft-feel effect coating materials, for example, there has to date been a lack of aqueous binders which meet all of the requirements imposed, particularly those concerning the resistance properties of the films. Thus, for example, EP-A 0 358 979 describes aqueous two-component reactive polyurethane systems based on secondary dispersions of vinyl polymer and on polyisocyanate crossiinkers, which already have a good level of properties, particularly as far as resistance to solvents and other chemicals is concerned. Nevertheless the target haptic quality of soft feel cannot be achieved with these coating compositions.
EP-A 0 669 352 describes special aqueous polyester-polyurethane dispersions which, in combination with crosslinker resins and. where appropriate, with linear, hydroxyl-free polyurethane dispersions, can be cured to give coatings havin a good soft-feel effect, good mechanical properties, and a generally satisfactory solvent resistance. For certain appii cat ions, however, the resistance, particularly the resistance to suntan lotion, are still in need of improvement.
EP-A 0 926 172 describes aqueous two-component (2K) polyurethanc coatin materials in which the resistance to suntan lotion (which penetrates the film, causing delamination and/or other damage) can be improved by using special ester-modified polyisoeyanates. The binders used in that case are mixtures of carboxylate- and/or sulfonate-hydrophilicized. polyester polyol dispersions with physically drying, carboxylate- and/or sulfonate- hydrophil icized polyurethanc dispersions.
EP-A 0 578 940 describes water dispersible polyurethanc polyols on the basis of polyester and polycarbonate polyols or segmented polyester carbonate polyols containing 2 to 100% of acid groups neutralized with bases, corresponding to an acid number of 6 to 45 mg KOH/g, with a hydroxy! number of 20 to 250 mg KOH/g, a molecular weight Mw of 2000 to 150000, a urethane group content of 2 to 16 weight- % and a carbonate group content of 1 to 25 weight-%. Also described are a method for the production of water- dispersable binder combinations from 30 to 90 weight-% of such polyols and 2 to 70 weight-% of a cross-linker resin and the use of such polyols as binder component in coatings or seal ing materials.
EP-A 1 418 192 is concerned with water-d i spersable polyurethanc resins with a carbonate group content of 5.8 to 20.0 weight-% and which is present in a solvent, the solvent being inert towards isocyanate groups.
Aqueous polyurethanc dispersions with isolated urea groups are the subject of the patent application WO 00/50482.
Whereas considerable improvements have already been made in the field of the above- mentioned polyurethanc dispersions, there is always room for improvement particularly with respect to the flow characteristics. This is important for the end users wishing to apply coatings based on such dispersions because a change in rhco logical parameters will necessitate different application parameters.
The present invention therefore has the object of providing water-dispersable polyurethaiies with a considerable carbonate group content which experience less of a change in viscosity over a prolonged period of time while at the same time not compromising other coating-reiated features.
According to the present invention this object is achieved by a water-dispcrsable polyurethane resin obtained by react ing Al) at least one polycarbonate polyol with a number average molecular weight of from 400 to 6000 g/mol,
A2) optionally, a polyester polyol which is different from component (Al) with a number-average molecular weight Mn of from 400 to 6000 g/mol,
A3) optionally, a low molecular weight compound containing two or more hydroxy and/or amino groups having a molecular weight of from 60 to 400 g/mol,
A4) optionally, a compound which is monofunctional in terms of reaction with NC'O groups or w ich contains active hydrogen atoms di fering in reactivity, these units being located in each case at the chain end of a polymer containing urethane groups,
A5) at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions, and
A6) a polyisocyanate component comprising > 5 weight- % to < 95 weight-% of hexamethylene diisoeyanate and > 5 weight-% to < 95 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisoeyanate, the total weight percentages amounting to < 100 weight-%, the resultant polyurethane resin containing from 1.5 % to 25.0 % by weight of incorporated carbonate groups -0(C=0)0-.
Preferably the resultant polyurethane dispersion contains from 1 ,5 % to 25,0 % by weight, more preferably from 3,0 to 18,0 % by weight, of incoiporated carbonate groups - ()( (· ))()-. It has been found that the dispersions according to the inv ention experience a predictable and very slow change in viscosity over the course of sev eral hours. 1 n preferred embodiments the viscosity has been virtually constant ov er six hours. At the same time, the suntan lotion resistance of coatings achieved with the dispersions did not deteriorate. Component (Al) suitably comprises hydroxy l-containing polycarbonates whose molecular weight Mn is 400 to 6000 g/mol, in some cases from 600 to 3000 g/mol, and which are obtainable, for example, by reacting carbonic acid derivatives, e.g. diphenyl carbonate, dimethyl carbonate or phosgene, with polyols, and in some cases diols. Examples of suitable such diols include ethylene glycol. 1.2- and 1 ,3 -propanediol, 1 ,3- and 1 .4- butanediol. 1,6-hexanediol, 1 .8-octancdiol, neopcntyl glycol, 1.4-bishydroxymethyl- cyclohexane, 2-methyl- l ,3-propanediol, 2,2.4-trimethylpentane- 1 ,3-diol, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A, and also laetone-modified diols. The diol component contains preferably from 40 to 100% by weight of hexanediol, preferably 1 ,6-hexanediol and/or hexanediol derivatives, preferably those which in addition to terminal OH groups contain ether groups or ester groups, examples being products obtained by reacting 1 mol of hexanediol with at least 1 mol. in some cases 1 to 2 mol, of eapro!aetonc or by etheri tying hexanediol with itsel to give dihexylene or trihexylene glycoi. Additionally the polyether- polycarbonate diols described in DE-A 37 17 060 can be employed.
The hydroxy I polycarbonates (Al) are preferably linear. They may, however, be slightly branched where appropriate through the incorporation of polyfunctional components, especially low molecular weight polyols. Compounds suitable for this purpose include for example glycerol, trimethylolpropane, hexane- 1 ,2.6-triol, butane- 1 .2,4-triol, trimcthylolcthane, pentaerythritol. quinitol, mannitol, and sorbitol, methylglyeoside or 1 ,3,4.6-dianhydrohexitols.
Polyester polyols which can be used as component (A2) have a molecular weight Mn of from 400 to 6000 g/mol, in some cases from 600 to 3000 g/mol. Their hydroxy! number is generally from 22 to 400, in some cases from 50 to 200 and in other cases from 80 to 160 mg KOH/g. The OH functionality is in the range from 1 .5 to 6, in some cases from 1.8 to 3, and in other cases from 1.9 to 2.5.
Highly suitable compounds arc the conventional polycondcnsatcs of diol and also, where appropriate, polyols (triols, tetraols) and dicarboxyl ic and also, where appropriate, polycarboxylic (tricarboxylic, tetracarboxylic) acids or h y d r o x y c a r b o x y 1 i c acids or lactones. Instead of the free polycarboxyl ic acids it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols to prepare the polyesters. Examples of suitable diols arc ethylene glycol, butylcne glycol, diethylene glycol, tri ethylene glycol, polyalkylene glycols such as polyethylene glycol, and also propanediol or butane- 1 ,4-diol, preference being given to hexane- l ,6-diol, neopentylglyeol or neopentylglycol hydroxypivalate. I desired it is also possible to use polyols such as trimethylolpropanc. glycerol. erythritol, pentaerytliritol. trin ethylolbenzene or tri shy droxy ethyl isocyanurate, for example, as well.
Examples of suitable dicarboxylic acids are phthalie acid, isophthalic acid, terephthalie acid, tetrahydrophthalie acid, hexahydroplithalic acid, cycloliexane dicarboxylic acid, adipic acid, azeleic acid, sebacic acid, glutaric acid, tetraehlorophthalie acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methyl succinic acid, 3,3- diethylglutaric acid, 2.2-dimethyl succinic acid. The possible anhydrides of these acids are likewise suitable. I n the content of the present invention the anhydrides are always embraced by "acid".
It is also possible to use monocarboxylic acids, such as benzoic acid and hexanecarboxylic acid, provided that the average functionality of the polyol is greater than 2. Saturated aliphatic or aromatic acids are preferred, such as adipic acid or isophthalic acid. If desired it is also possible to use relatively small amounts of polycarboxylic acid as well, such as trimcllitic acid.
Hydroxycarboxyl ic acids which can be used as reaction participants in the preparation of a polyester polyol having terminal hydroxy! groups are for example hydroxycaproic acid. hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones are, for example, caprolactone or butyrolactone.
Compounds of component (A2) may also include, at least proportionally, primary or secondary amino groups as isoeyanate-rcaetivc groups.
The low molecular weight polyols (A3) are used in general for the purpose of stiffening and/or branching the polymer chain. The molecular weight is preferably in the range from 60 to 400 g/mol, more preferably in the range from 62 to 200 g/mol. They can contain aliphatic, cycloaliphatic or aromatic groups. Suitable polyols (A3) arc compounds having up to about 20 carbons per molecule, such as ethylene glycol, diethylene glycol, tri ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 .4-butanediol, 1 ,3-butylene glycol, cyclohexanediol, 1 ,4-eyciohexanedimethanol, 1 ,6-hexanediol, hydro-quinone dihydroxyethyl ether, bisphenol A [2,2-bis(4-hydroxyphenyl)propane], hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane) and also mixtures thereof, and also trimcthylolpropane. glycerol or pentaerythritol. Ester diols as well, such as δ- hydroxybutyl-e-hydroxy-caproic esters, co-hydroxyhexyl-y-hydroxybutyric esters, adipic acid β-hydroxyethyl esters or terephthaiic acid bis(P-hydroxyethyl) ester, for example, can be used.
Diamines or polyamines and also hydrazides can likewise be used as (A3), examples being ethyienediamine, 1 ,2- and 1 ,3-diaminopropane, 1 ,4-diaminobutane, 1 ,6-diaminohexane, isophoronediamine, the isomer mixture of 2,2,4- and 2,4,4-trimethyl- hexamethylenediamine, 2-methylpentamethylene-diamine, diethylenetriamine, 1 ,3- and 1 ,4-xylyienediamine, α , a . a' a ' - t e t ra m e t h y I - 1 .3 - and - 1 ,4-xylylenediamine and 4,4- diaminodicyclohexyimethane, dimethyl-ethylenediamine, hydrazine or adipic dihydrazide. Component (A3) preferably contains at least 2% by weight, based on components (Al) to (A6), of at least one compound which has a functionality of three or more in respect of reaction with NCO groups. The polyurethane resin may where appropriate also include units (A4) which are each located at the chain ends, and cap them. These units are derived on the one hand from monofunctional, isocyanate-reactive compounds, such as monoamines, especially mono- secondary amines, or monoalcohols. Mention may be made here by way of example of methylamine, ethyiamine, propylamine, butylamine, octylamine. iauryiamine, stearylamine, isononyloxypropylamine, dimethylamine, diethylamine, dipropyiamine, dibutylamine, N-methyiaminopropyiamine, diethyl(methyi)aminopropylamine, morpholine, piperidine or the substituted derivatives thereof, amido amines from diprimary amines and monocarboxyiic acids, monoketimines of diprimary amines, primary/tertiary amines, such as Ν,Ν-dimethylaminopropylamine, for example . Likewise suitable as component (A4) are compounds containing active hydrogen atoms which differ in reactivity towards isocyanate groups, such as compounds which in addition to a primary amino group also contain secondary amino groups or in addition to an OH group also contain COOH groups or in addition to an amino group (primary or secondary) also contain OH groups. Preference is given to compounds (A4) which in addition to an amino group (primary or secondary) also contain OH groups. Examples of such are primary/secondary amines, such as 3-amino- 1 -metliylaminopropane, 3-amino-i- ethylaminopropane, 3-amino- 1 -cyclohcxylaminopropanc. 3-amino- ! -methylaminobutanc; mono-hydroxy-carboxylic acids, such as hydroxyacetic acid, lactic acid or malic acid, and also alkano!amines such as N-aminoethylethanolamine, ethanolamine, 3-amino-propanol, neopentanolamine, and, with particular preference, diethanolamine. In this way it is possible additionally to introduce functional groups into the polymer end product. Ionic or potentially ionic compounds suitable as component (A5) include for example mono- and d i h y d r o x y c a r b o x y l i c acids, mono- and diaminocarboxylic acids, mono- and dihydroxysulfonic acids, mono- and diaminosulfonic acids and salts thereof such as dihydroxycarboxylic acids, hydroxypivalic acid, -( 2-am i noet hy I )-|5-a I an i ne, 2-(2- aminoethylamino)ethanesulfonic acid, et h y I e n e- d i a m i n e- p rop y 1 - or butylsulfonie acid, 1 ,2- or 1 .3-propylcnediaminc-|5-cthylsulfonie acid. lysine, 3,5-diaminobenzoic acid, the hydrophiiicizing agent according to Example 1 from EP-A 0 916 647 and its alkali metal salts and/or ammonium salts; the adduct of sodium bisulfite with but-2-cne- l ,4-diol polyethersulfonate or the propoxylated adduct of 2-butenediol and aHSO* (e.g. in DE-A 2 446 440, page 5-9, formula 1-111 ). Preferred ionic or potential ionic compounds (A5) are those which possess carboxyl and/or carboxylate groups. Particularly preferred ionic compounds (A5) are d i hydroxy carboxy I i c acids, especially α,α-dimethyioiaikanoic acids, such as 2,2-dimethylolacetie acid, 2,2-dimethylolpropionic acid, 2.2-dimethyloibutyrie acid, 2.2-dimethyl-olpentanoic acid or dihydroxysuceinie acid.
The components (Al) to (A5) may also contain C=C double bonds, which come, for example, from long-chain aliphatic carboxyl ic acids or fatty alcohols. Functionalization with olefini c double bonds is also possible, for example, by the incorporation of allylic groups or of acryl ic acid or mcthaerylic acid and also their respective esters.
Furthermore, components (Al) to (A5) may also contain compounds hav ing a nonionically hydrophii icizing activity, examples being polyoxyalkylcne ethers having at least one hydroxy! or amino group. These polyethers include a fraction of from 30% by weight to 1 00% by weight of units derived from ethylene oxide. They suitably include polyethers of linear construction with a functionality of between 1 and 3, but also compounds of the general formula (I)
Figure imgf000008_0001
in which
R1 and R2 independently of one another are each a divalent aliphatic, eycloaliphatic or aromatic radical having 1 to 18 carbon atoms, which can be interrupted by oxygen and/or nitrogen atoms, and R3 is a non-hydroxy-terminated polyester or, preferably, polyether, in particular an alkoxy- tcrminated polyethylene oxide radical.
According to the invention, component (A6) comprises hcxamcthylenc diisocyanatc (HDI ) and di i socy anatodicy c I oh exy I met h ane (H12-MDI) and/or isophorone diisocyanatc (IPDI). It is preferred that no other polyisocyanates, apart from higher oligomers of I PDI, HDI and Hi2-MDI and technically unavoidable impurities, are present in (A6).
The present inv ention is now described in connection with preferred embodiments. Unless the context is clearly to the contrary, the embodiments may be combined freely with each other.
In an embodiment of the present invention, the polyisocyanatc component A6) comprises > 75 weight-% to < 85 weight-% of hexamcthyicne diisocyanatc and > 15 weight- % to < 25 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisocyanatc, the total weight percentages amounting to < 100 weight-%. Preferred ranges for HDI and I PDI are 78 weight-% to < 82 weight-% and for H n-MDl are > 12 weight-% to < 22 weight-%.
I n another embodiment of the present inv ention, the average molecular weight (Mn) (of the resin) is from 1000 to 30,000 g/mol, the acid number is from 10 to 80 mg KOH/g determined according to DI 53402 and the OH content is from 0.5 to 5% by weight. Preferably the Mn is from 1 500 to 10 000 g/mol, the acid number from 10 to 80 or from 15 to 40 mg KOH/g determined according to DIN 53402 and the OH content of from 0.5 to 5% by weight, preferably from 1.0 to 3.5% by weight.
1 n another embodiment of the present invention, the polyurethane has been synthesized from
Al) from 25 to 80% by weight of at least one polycarbonate polyol having a molecular weight (Mn) of from 400 to 6000 g/mol and which has a carbonate group content of at least 10% by weight, A2) from 0 to 60% by weight of at least one polyester polyol which is different from component (Al) and has a number-average molecular weight Mn of from 400 to 6000 g/moi,
A3) from 0 to 20% by weight of at least one low molecular weight compound which contains two or more hydroxyl and/or amino groups and has a molecular weight of from 60 to 400 g/mol,
A4) from 0 to 10% by weight of at least one compound which is monofunctionai in terms of reaction with NCO groups or contains active hydrogen atoms differing in reactivity, these units being located in each case at the chain end of a polymer containing urethane groups.
A 5 ) from 2 to 10% by weight of at least one compound containing at least two isocyanate-react ive groups and at least one group capable of forming anions, and
A6) a polyisocyanate component comprising > 5 weight-% to < 95 weight-% of hexamethylene diisocyanate and > 5 weight-% to < 95 weight-% of diisoeyanatodieyciohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to < 100 weight-%.
I n another embodiment of t e present invention, component (Al) is linear hydroxyl polycarbonates (Al).
In another embodiment of the present invention, the polyurethane resin is free from sulfonic acid groups.
Another aspect of the present invention is a process for preparing the watcr-dispcrsabic polyurethanes according the present invention, comprising preparing an OH- and/or H- functional polyurethane from components (Al), (A5) and (A6) and optionally components
(A2) to (A4). The water-dispersable polyurethane resins of the invention can be prepared, for example, by first preparing an i s o c y a n a t e - f u n c t i o n a I prepolymer from component (A6) and components (Al) and (A5) and, if desired, (A2), (A3) or (A4) and, in a second reaction step, by reaction with one or more of the compounds (A3), (A4) or if desired, (A2) in a suiiable solvent medium, e.g. acetone or methy!ethy!ketone, obtaining an OH- and H- functional polyurethane, as described for example in HP- A 0 355 682, p. 4, lines 39 - 45.
The urethanization reaction in the preparation of the prepolymer is normal ly conducted at temperatures from 0° to 140 °C, depending on the reactivity of the isocyanate used. In order to accelerate the urethanization reaction it is possible to use suitable catalysts, such as are known for the acceleration of the C'O-OH react ion to the person skilled in the art. Examples are tertiary amines such as triethylaminc. for example, organotin compounds such as dibutyltin oxide, dibutyltin dilauratc or tin bis(2-ethylhexanoate), for example, or other organometallic compounds.
The water-dilutable polyurethane resin can be prepared using all of the prior art methods, such as the prepolymer mixing method, acetone method or melt dispersing method, for example.
In one embodiment the urethanization reaction is conducted in the presence of solvents which are inactive towards isocyanate groups. Particularly suitable for this purpose are those solvents which arc compatible with water, such as ethers, ketones and esters, and also N-methylpyrrolidone, for example. The amount of this solvent appropriately does not exceed 30% by weight and is in some cases in the range from 10 to 25% by weight, based in each case on the sum of polyurethane resin and solvent. The polyisocyanate (A6) can be added swiftly to the solution of the other components.
The acid groups incorporated in the polyurethane resin by component (A5) can at least proportionally be neutralized. Particularly suitable for the neutralization arc tertiary amines, examples being trialkylamines hav ing 1 to 12, in some cases 1 to 6, carbon atoms in each alkyl radical. Examples thereof are trimethylamine, triethylaminc, methyldiethylamine, tripropylamine and diisopropylethylamine. The alkyl radicals may, for example, also carry hydroxy! groups, as in the case of the dialkylmonoalkanol-. alkyldialkanol- and trialkanolamines. An example of such is dimethylethanolamine, which serves preferably as neutral izing agent. As neutralizing agent it is also possible where appropriate to use inorganic bases, such as ammonia or sodium or potassium hydroxide. The neutralizing agent is used in a molar ratio to the acid groups of the prepolymer of from 0.3: 1 to 1.3: 1, in some cases from 0.4: 1 to 1 : 1. The free COOH groups of the polyureihane resin of the invention can be neutralized before, during or after the urethanization reaction. The neutralizing step is preferably conducted following the urethanization reaction, generally of between room temperature
(23 °C) and 80 °C, in some cases between 40 to 80 °C. Neutralization may also take place simultaneously with dispersing, with the dispersing water already containing the neutralizing agent.
It is also possible to provide the water-dispersable polyureihane resin in a non-neutralized form and to carry out the neutralization not until during the preparation of the aqueous coating composit ion: for example, when incorporating the water-dispersable polyuretliane resin of the invention into the OH-frce polyuretliane dispersion(s).
If desired it is possible during the preparation of the polyuretliane resin of the invention, for the purpose of hydrophilicization, to add, in addition to the acid groups, and proportionally, monomer units containing alkyiene oxide, in incorporated form, or else external emulsifiers. The external emulsifiers w ich can be used in this context arc anionic and/ or non-ionic in nature. Of the anionic emulsifiers, those having carboxylatc groups, sulfate, sulfonate, phosphate or phosphonate groups can be used. Preferred emulsifiers have sulfate, sulfonate, phosphate or phosphonate groups. Suitable non-ionogenic external emulsifiers, which can be employed generally in combination with the abovementioned anionic emulsifiers. include reaction products of al iphatic, araliphatic, cycloaliphatic or aromatic carboxylic acids, alcohols, phenol derivatives and/or amines with epoxides, such as ethylene oxide, for example. Examples thereof are reaction products of ethylene oxide with carboxylic acids of castor oil, abiatic acid, with relatively long-chain alcohols such as oleyl alcohol, lauryl alcohol, stearyi alcohol, with phenol derivatives such as substituted benzyl-, phenyl-phenols, nonylphenols, for example, and with relatively long-chain amines such as dodecylamine and stearylamine, for example. The reaction products w ith ethylene oxide arc oligocthers or polyethers having degrees of polymerization of between 2 and 100, in some cases between 5 and 50. The external emulsifiers can be added in amounts of from 0. 1 to 10% by weight, based on the non- volatile fraction of the water-dispersable polyuretliane resin, to the water-dispersable polyuretliane resin or to another component of the aqueous coating system. In some cases, however, only acid groups are used, in a purely internal hydrophilicization. I n one embodiment of the present invention the aqueous coating systems are preferably prepared such that the water-dispersable polyurethane resin of the invention is incorporated under shearing into an aqueous binder component. Then, in a second step under shearing, the cross! inker component, which in some cases comprises a polyisocyanate having free NCO groups, is incorporated into the aqueous stock v arnish thus obtained. The customary coatings auxiliaries and additiv es can be incorporated into the finished aqueous coating material either together with the crossl inker component, with the binder components, or subsequently.
The present invention is further directed towards an aqueous coating system comprising a) at least one water-dispersiblc polyurethane resin according to the present invention, b) optionally one or more aqueous binder components comprising at least one hydroxyl- free polyurethane dispersion, c) optionally, auxiliaries and additives and d) at least one crosslinker component. "Hydroxyl-free" means, for the purposes of the present invention, that the polyurethane carries no hydroxy! groups, with the exception of the terminal groups of the polymer chains. Because of the comparatively high molecular weight (compared to the water- dispersable polyurethane resin of the invention) the concentration o the terminal groups is low, corresponding to an OH content of < 0.5% by weight; customarily of < 0.2% by weight.
In one preferred embodiment of the aqueous coating systems, comprising the polyurethanes of the invention, hydroxyl-free polyurethane dispersions are used which in addition to non-ionic, hydrophilic groups in the form of polyethylene oxide units also contain anionic groups, preferably earboxylate and/or sulfonate groups, more preferably sulfonate groups, and especially their alkal i metal salts, as hydrophilic groups. In the selection of the base materials it should be ensured that the resulting amount of n on ionic hydrophilic groups in the form of polyethylene oxide units is between 0.1 ands 10% by weight, in some cases between 1 to 7% by weight, based on resin solids, and the amount of ionic groups is from 2 to 20, in some cases from 2.5 to 1 5 mmol/100 g resin solids. I n another embodiment, suitable components b) also include any desired hydroxy- functional, aqueous or water-dilutable, ionomeric binders from the classes of the polyester, poiyuretliane, pol yu rea-po I y uret h ane and polyacrylate resins and/or any desired combinations of the aforementioned types such as polyurethane-polyacrylate or polyestcr- polyacrylate graft polymers, for example.
1 n one particularly preferred embodiment poiyuretliane resins are used in a dispersion that is free of cosolvents, i.e. a cosolvcnt content of from 0.0 to 0.3 % by weight.
Cosolvents within the scope of the present invention are polar organic solvents. Cosolvents are preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm3)0-5 and a p n value > 7. Cosolvents arc particularly preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm3)0 5 and a pKe value > 8. Cosolvents are most particularly preferably organic solvents having a Hansen parameter in the range from 7.2 to 16.0 (cal/cm3)0 5 and a pKe value > 9. The Hansen parameters are disclosed inter alia in "Polymer Handbooks", Eds. Brandrup, J; Immergut, E.H.; Grulke, E.A., 4th Edition, John Wiley, New York, 1999, VI I/pages 675-71 1.
Preferred cosolvents within the scope of the present invention arc polar organic solvents selected from the group consisting of acetone, methyl ethyl ketone, butyl diglycol. dimethyl sulfoxide, N-ethylpyrrolidone. -methylpyrrolidone, dimethylformamide, dimethylacetamide and dipropylene glycol dimethyl ether.
The cosolvents are on the one hand solvents which have already been used in the synthesis of the poiyuretliane polymer and on the other hand solvents which have been added to the polyurethane dispersion subsequently in order to establish the desired properties.
1 n one particularly preferred embodiment polyurethane dispersions are used with a content of NMP from 0.0 to 0.5 wt.%, particularly preferably from 0.0 to 0.3 wt.%, most particularly preferably from 0.0 to 0.1 wt.%, by weight. Yet more preferably, the polymer mixture according to the invention is free of NMP. Within the scope of the present invention, free of NMP means that the content of NMP in the polymer mixture is less than or equal to the detection limit (i.e. < 0. 1 ppm) when measured by gas chromatography.
The aqueous coating systems comprising the polyurethane resins of the invention can where appropriate also contain other binders or dispersions, based for example on polyesters, polyurethancs, polyethers, polyepoxides or polyaerylates, and, where appropriate, pigments and other auxiliaries and additives t at are known in the coatings industry. Through combination with crossl inkers it is possible, depending on the reactivity or. where appropriate, blocking of the crossl inkers, to prepare both one-component (IK) and two- component (2K) coating materials. IK coating materials for the purposes of the present invention are coating materials in which binder component and crosslinker component can be stored together without any crosslinking reaction takin place to a marked extent or to an extent which is detrimental to the subsequent application. The crosslinking reaction takes place only on application, after the crosslinker has been activated. This activation can be effectuated, for example, by raising the temperature. 2K coating materials for the puiposes of the present invention are coating materials in which binder component and crosslinker component have to be stored in separate vessels owing to their high reactivity. The two components are not mixed until shortly prior to application, w hen they react generally without additional activation. 1 n order to accelerate the crosslinking reaction, however, it is also possible to use catalysts or to employ higher temperatures.
Examples of suitable crossl inkers are polyisocyanate crossl inkers, amide- and a mine- formaldehyde resins, phenolic resins, aldehyde resins and ketone resins, such as phenol formaldehyde resins, resoles, furan resins, urea resins, carbarn ic ester resins, triazine resins, melamine resins, benzoguanamine resins, cyanamide resins, anil ine resins, as described in "Lackharze", D. Stoye, W. Freitag, Carl Hanser Verla Miinehen, 1996. Preferred crossl inkers are polyisocyanates.
Polyisocyanates can be used with free and/or blocked isocyanate groups. Suitable such crosslinker resins include blocked polyisocyanates based for example on isophorone di isocyanate, hexamethylene di isocyanate, 1 ,4-diisoeyanatoeyelo-he.xane, bis(4- isocyanaiocyclohexane)methane or 1,3-diisocyanatobenzene or based on paint polyisocyanates such as polyisocyanates which contain biuret or isocyanurate groups and are derived from 1 ,6-di isoeyanatohexane, isophorone diisocyanate or bis(4-iso- cyanatocyclohexane)methane or paint polyisocyanates which contain urethane groups and are based on 2,4- and/or 2,6-diisocyanato-toluene or isophorone diisocyanate on the one hand and low molecular weight polyliydroxyl compounds such as trimethylolpropane, the isomeric propanediols or butanediols or any desired mixtures o such polyliydroxyl compounds on the other.
Suitable blocking agents for the staled polyisocyanates are, for example, monohydrie alcohols such as methanol, ethanol, butanol, hexanol, eyclohexanol, benzyl alcohol, oximes such as acetoxime, methyl ethyl ketoxime, cycloliexanone oxime, lactams such as ε-caprolactam. phenols, amines such as diisopropylamine or dibutylamine, dimethylpyrazole or triazolc. and also dimethyl malonatc, diethyl malonatc or dibutyl malonatc. Preference is given to the use of low-viscosity, hydrophobic or hydrophilicized polyisocyanates with free isoeyanate groups based on aliphatic, eyeioaliphatic, araliphatic and/or aromatic isocyanates, more preferably on aliphatic or eyeioaliphatic isocyanates. since in this way it is possible to achieve a particularly high lev el of resistance in t e coating film. The advantages of the binder dispersions of the invention are most clearly manifested in combination with these crosslinkers. These polyisocyanates generally hav e at 23 °C a viscosity of from 10 to 3500 m Pas measured according to DIN 53019 at a shear rate of 40 s"1. I f necessary the polyisocyanates can be employed as a blend of small amounts o inert solvents, in order to lower the viscosity to a level within the stated range. Triisocyanatononane as well can be used alone or in mixtures as a crosslinker component. The water-dispersable polyurethane resin and the hydroxy 1-frec polyurethane dispersion described herein arc generally of sufficient hydrophilicity, so that the dispersibiiity of the crosslinker resins, where the substances in question are not water-soluble or water- dispersible in any case, is ensured. Water-soluble or gap dispersible polyisocyanates are obtainable, for example, by modification with carboxylate, sulfonate and/or polyethylene oxide groups and/or polyethylene ox i de/po I yp ropy I en e oxide groups. Hydrophilicization of polyisocyanates, for example, is possible by reaction with substoichiometric amounts of monohydric hydrophilic polyether alcohols. The preparation o hydrophilicized polyisocyanates of this kind is described for example in EP-A
0 540 985 (p. 3, line 55 - p. 4 line 5). Also highly suitable are the polyisocyanates containing allophanate groups described in EP-A-0 959 087 (p. 3 lines 39 - 51), which can be prepared by reacting low-monomer-content polyisocyanates with polyethylene oxide polyether alcohols under ailophanatization conditions. The water-dispersible polyisocyanate mixtures based on triisocyanatononane, as well, which are described in DE-A 100 078 21 (p. 2 line 66 - p. 3 line 5 ) are suitable, as are polyisocyanates hydrophilicized with ionic groups (sulfonate groups, phosphonate groups), as described, for example, in DE-A 10 024 624 (p. 3 lines 13 - 33). A further possibility is that of hydrophil icization through the addition of commercially customary emulsifiers.
In principle it is of course also possible to use mixtures of different crosslinker resins.
As customary coatings auxiliaries and additives, which, as already described earlier on above, can be added both to the aqueous coating system before, during or after its preparation and to the binder or crosslinker components present in the said system, the following come into consideration for example: defoamcrs, thickeners, pigments, dispersing auxiliaries, dulling agents, catalysts, anti-skinning agents, anti-settling agents or emulsifiers and also adjuvants which are able to intensify the desired soft-feel effect. In an embodiment of the system, the crosslinker component is hydrophobic or hydrophil icized polyisocyanates containing free isocyanate groups based on aliphatic, cycloaliphatic. araliphatic and/or aromatic isocyanates.
1 n another embodiment of the system, the crosslinker component is hydrophobic or hydrophilicized polyisocyanates containing free isocyanate groups based on aliphatic or cycloaliphatic isocyanates.
The invention also relates to a process for preparing aqueous coating systems according the invention, further comprising incorporating the watcr-dispcrsable polyurethanc resin into an aqueous phase optionally comprising at least one hydroxyl-free aqueous polyurethane dispersion and, if desired, auxiliaries and additives and subsequently at least one crosslinker component and also, where appropriate, further auxiliaries and additives are dispersed into this aqueous stock varnish. Th e aqueous coating systems thus obtained, comprising the polyurethane resin of the invention, are suitable for all fields of use in which aqueous paint and coating systems with high requirements in terms of the surface quality resistance of the films are used. Therefore, another aspect of the invention is the use of the water-dispersable resin of the present invention for coating, varnishing and/or sealing a substrate, wherein the substrate is selected from mineral construction material surfaces, wood, wood materials, metallic surfaces, asphaltic coverings, bituminous coverings, and plastics surfaces.
With preference, however, they are suitable for producing soft-feel effect coating materials which ensure good solvent resistance and, in particular, good resistance to suntan lotion (in the suntan lotion test). Hence, the invention also encompasses the use of the water- dispersable resin of the present invention for producing a soft- feel effect coating material.
In an embodiment of this use plastic or wood is coated, where curing takes place normally at temperatures between room temperature (23 °C) and 130 °C. The two-component technology with non-blocked polyisocyanate crosslinkers allows the use o comparatively low curing temperatures.
The aqueous coating systems comprising the water-dispersable polyurethanes of the invention are normally used in one-coat coating materials or in the clearcoat or topcoat
(topmost coat) of multi-coat systems.
The invention furthermore also relates to a substrate coated with a cross! inked coating system comprising the water-dispersable polyurethane resins according to the present invention.
The coating can be produced by any of the various spraying methods, such as air pressure spraying, airless spraying or electrostatic spraying methods, for example, using one- component or. where appropriate, two-component spraying equipment. The coating materials and coating systems comprising the polyurethane resins of the invention can. however, also be applied by other processes, for example by brushing, rollin or knife coating.
The present invention will be further described with reference to the following example and figure without restricting it. Glossary: polyester based on adipic acid, phthalic anhydride and 1 ,6-hexane-diol
Desmophen C XP 2613: polycarbonate polyol. OH number 56 mg KOH/g, molecular weight Mn 2000 g mol ( Bayer MateriaiScience AG, Leverkusen, DE)
Desmorapid SO: Sn( l I )-octoate
Desmodur W: diisocyanatodicyclohexylmethane (H12-MDI)
Desmodur H: hexamethylene diisocyanate (HDI)
Tanafoam DNE 01 : defoamer; Blend of fatty acid esters and higher-rated hydrocarbons with
carbon acid salts, Tanatex, DE
BYK 348: po I yet her modified siloxane surfactant, BYK, DE
Aquacer 1 10 RC 1 174: wax additive, BYK, DE
Tego Wet K 1.245 : polyether siloxane copolymer, Evonik, DE
Siilitin Z 86: clay filler, Hoffmann M ineral. DE
Acematt 3300: modified pyrogenic silica, Evonik, DE
N 3600: HDI trimer
XP 2655: Hydrophiiic aliphatic polyisoeyanate based on HDI
MPA: methyl propyl acetate ( 1 -methoxy-2-propanol acetate)
All figures in % relate to weight, unless noted otherwise. Viscosity measurements were conducted in a cone and plate viscometer in accordance with DIN 53019 at a shear rate of 40 s-1. The acid number was determined according to DIN 53402 ( mg KOH/g sample, titration with 0.1 mol/1 NaOH solution). The solids content was determined according to DIN EN 1 SO 325 1 (thick-layer method: lid, 1 g sample, 1 h 125 C, convection oven). The OH number was determined according to DIN 53240 ( mg KOH/g sample, acetyiat ion, hydrolysis, titration with 0.1 mol/1 NaOH). The pH w as measured according to international standard ISO 976.
The molecular weight (Mn, Mw) is determined by means of gel permeation
chromatography (GPC). The samples were characterized in tetrahydrofuran eluent in accordance with DIN 55672- 1 . Mn ( UV )=numbcr average molar weight (GPC, UV detection), result in g/mol M* ( U V )=mass av erage molar weight (GPC. UV detection), result in g/mol Mean particle sizes were determined by laser correlation spectroscopy.
Polyurethane dispersions according to the invention
Dispersions were as follows:
Batch 1 :
Figure imgf000020_0001
Batch 2:
Figure imgf000020_0002
Batch 3:
Figure imgf000020_0003
Figure imgf000021_0001
The components of group I were weighted into a reaction vessel and heated to 1 0 °C within 2 hours. 15-16 liters of nitrogen gas w ere blown over the mixture. The mixture was kept at a temperature of 130 °C for 1 hour and subsequently cooled to 90 °C. The components of group 11 were mixed and the mixture was rapidly added to the heated components I. The temperature was raised to 130 °C, kept at this temperature for 2 hours and then lowered to 100 °C.
Component III was then added over a course o 30 minutes at a temperature of the reaction mixture of 90 °C.
Component I V was added over a course of 30 minutes at a temperature of 70 °C. This temperature was kept for 2 hours and the lowered to 45 °C. The viscosity was set to a desired level by further adding water.
Prior to filtration the mixture was cooled to 30 °C. Then a filtration was performed. The following table lists the results obtained:
Figure imgf000022_0001
FIG. 1 shows the results of rheology experiments. 1 n these experiments, dispersions were sheared with 1000 rpm and the flow times out of a DIN 6 cup were determined. The data points of graph 1 arc associated with a dispersion according to the invention and prepared as described above (batch 1). The data points of graph 2 are from the comparative example (batch 4).
Polyurethane dispersions as of comparative example:
Batch 4:
Figure imgf000022_0002
Figure imgf000023_0002
From FIG. 1 it can clearly be seen that in a dispersion according to the invention virtually no change in flow time and hence in viscosity is experienced over the course of several hours. This is not the case for the comparative example.
Aqueous coating systems according to the invention
Aqueous coating systems according to the invention were prepared from the following components. Amounts are given in weight parts in the table below, unless otherwise stated.
Figure imgf000023_0001
I n order to test the substrates, the coating systems were applied to a substrate at room temperature (23 °C) and about 55% relative humidity. Drying was performed for 10 minutes at room temperature, 30 minutes at 80 °C and 16 hours at 60 °C. The results were to produce reproducible coating films for different application times. FIG. 1 Flow time in Din 6 cup: under constant sheer stress in dependence of time t.
1 : sample as of invention (Batch 1): constant flow time; 2: comparative sample (Batch 4): changing during flow time

Claims

Claims
1. A water-dispersable polyurethaiie resin obtained by reacting
A 1 ) at least one polycarbonate polyol with a number average molecular weight of from 400 to 6000 g/mol,
A2) optionally, a polyester polyol which is different from component (Al) with a number-av erage molecular weight Mn of from 400 to 6000 g/mol,
A3) optionally, a low molecular weight compound containing two or more hydroxy and/or amino groups having a molecular weight of from 60 to 400 g/mol,
A4) optionally, a compound which is monofunctional in terms of reaction with
'O groups or which contains active hydrogen atoms differing in reactivity, these units being located in each case at the chain end of a polymer containing urethane groups,
A5) at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions, and
A6) a polyisocyanate component comprising > 5 weight- % to < 5 weight-% of hexamethylene diisocyanate and > 5 weight-% to < 95 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to < 100 weight-%, the resultant polyurethaiie resin containing from 1.5 % to 25.0 % by weight of incorporated carbonate groups -0( ( -())()-.
2. The water-dispersable polyurethaiie resin according to Claim 1 , wherein the polyisocyanate component A6) comprises > 75 weight-% to < 85 weight-% of hexamethylene diisocyanate and > 1 5 weight-% to < 25 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to < 100 weight-%.
3. The water-dispersable polyurethane resin according to Claim 1 , wherein the average molecular weight (Mn) is from 1000 to 30,000 g/mol, the acid number is from 10 to 80 mg KOH/g and the OH content is from 0.5 to 5% by weight.
4. The water-dispersable polyurethane resin according to Claim 1, wherein the polyurethane has been synthesized from
Al) from 25 to 80% by weight of at least one polycarbonate polyol havin a molecular weight (Mn) of from 400 to 6000 g/mol and which has a carbonate group content of at least 10% by weight,
A2) from 0 to 60% by weight of at least one polyester polyol which is different from component (Al) and has a number-average molecular weight Mn of from 400 to 6000 g/mol,
A3) from 0 to 20% by weight of at least one low molecular weight compound which contains two or more hydroxy! and/or amino groups and has a molecular weight of from 60 to 400 g/mol,
A4) from 0 to 10% by weight of at least one compound which is monofunctional in terms of reaction with NCO groups or contains active hydrogen atoms differing in reactivity, these units being located in each case at the chain end of a polymer containing urethane groups,
A5) from 2 to 10% by weight of at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming anions, and
A6) a polyisocyanate component comprising > 5 weight-% to < 95 weight-% of hexamethylene diisocyanate and > 5 weight-% to < 95 weight-% of diisocyanatodicyclohexylmethane and/or isophorone diisocyanate, the total weight percentages amounting to < 100 weight-%.
5. The water-dispersable polyurethane resin according to Claim 1, wherein component (Al) is linear hydroxy 1 polycarbonates (Al).
6. The water-dispersable polyurethane resin according to Claim 1 , wherein the resultant polyurethane resin containing from 1.5 % to 20.0 % by weight of incorporated carbonate groups -O(C=O)O-.
7. A process for preparing the water-dispersable polyurethanes according to Claim 1 , comprising preparing an OH- and/or NH-functional polyurethane from components (Al), (A5) and (A6) and optionally components (A2) to (A4).
8. An aqueous coating system comprising a) at least one watcr-dispcrsible polyurethane resin accordi ng to Claim 1 , b) optionally one or more aqueous binder components comprising at least one hydroxyl-free polyurethane dispersion, c) optionally, auxiliaries and additives and d) at least one crossl inker component.
9. The aqueous coating system according to Claim 8, wherein the crossl inker component is hydrophobic or hydrophilicized polyisocyanates containing free isocyanate groups based on aliphatic, eyeloaliphatie, araliphatic and/or aromatic isocyanatcs.
10. The aqueous coating system according to Claim 9, wherein the crossl inker component is hydrophobic or hydrophilicized polyisocyanates containing free isocyanate groups based on aliphatic or eyeloaliphatie isocyanatcs.
1 1. The process for preparing aqueous coating systems accordin to Claim 8, further comprising incorporatin the water-dispersable polyurethane resin into an aqueous phase optionally comprising at least one hydroxyl-free aqueous polyurethane dispersion and, if desired, auxiliaries and additives and subsequently at least one crosslinker component and also, where appropriate, further auxiliaries and additives are dispersed into this aqueous stock varnish.
12. Use of t e water-dispersable resin of Claim 1 for coating, varnishing and/or sealing a substrate, wherein the substrate is selected from mineral construction material surfaces, wood, wood materials, metallic surfaces, asphaltic coverings, bituminous coverings, and plastics surfaces.
13. Use of the water-dispersable resin of Claim 1 for producing a soft-feel effect coating material.
14. The use of Claim 13, wherein plastic or wood is coated.
. A substrate coated with a crosslinked coating system comprising the water-dispersable polyurethane resins according to Claim 1.
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WO2015120941A1 (en) * 2014-02-13 2015-08-20 Basf Coatings Gmbh Two-component coating compositions and coatings that are made therefrom and exhibit high resistance to erosion
DE102015014864A1 (en) 2015-11-17 2017-05-18 Gt Elektrotechnische Produkte Gmbh Process for the preparation of cellular, elastic polycarbonate urethane materials and the polycarbonate urethane materials

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