CA2431829A1 - Aqueous and/or water-dilutable polyisocyanates blocked with secondary benzyl amines - Google Patents

Abstract

The invention relates to aqueous and/or water-dilutable blocked polyisocyanates, their preparation and use in optionally self-crosslinking one-component systems.

Description

Le A 35 720-US PB/klu/NT
BLOCKED POLYISOCYANATES
CROSS REFERENCE TO RELATED APPLICATION
The present patent application claims the right of priority under 35 TJ.S.C. ~

(a)-(d) of German Patent Applications No. 10226927.0, 10226931.9, 10226926.2, 10226925.4 and 10226924.6, all filed June 17, 2002.
BACKGROUND OF THE INVENTION
Field of the Invention The invention relates to aqueous and/or water-dilutable blocked polyisocyanates, to their preparation and use in optionally self crosslinking one-component systems.
Description of the Related Art The use of blocking agents for the temporary protection of isocyanate groups has been known for a long time. Blocked polyisocyanates are used for preparing heat-curable 1K PU baking systems which are stable on storage at room temperature.
The blocked polyisocyanates therein are mixed, for example, with hydroxyl-containing polyesters, polyacrylates, other polymers, and further constituents of paints and inks such as pigments, cosolvents or additives. Another way to obtain baking varnishes which are stable on storage at room temperature is to block some of the isocyanate groups of polymers containing both blocked isocyanates and hydroxyl groups.
The major compounds used for blocking polyisocyanates are s-caprolactam, methyl ethyl ketoxime, malonates, secondary amines, and triazole and pyrazole derivatives, as described, for example, in EP-A 0 576 952, EP-A 0 566 953, EP-A 0 159 117, US-A 4 482 721, WO 97/12924 or EP-A 0 744 42?..

Le A 35 720-US - 2 Secondary amine blocking agents are described in EP-A 0 096 210. Although the claims of that patent extend to aralkyl-substituted amines as blocking agents, their use is not disclosed in the examples. The use of such amines in aqueous systems is not known from EP-A 0 096 210.
Industrially, the most frequently used blocking agents for isocyanate~s are s-caprolactam and butanone oxime. Whereas baking temperatures of around 160°C are generally employed in the case of s-caprolactam, blocked 1K
baking varnishes for which butanone oxime has been used as the blocking agent can be baked even at temperatures 10-20°C lower. Admittedly, in some coating systems, the desired level of properties is no longer attained at these baking temperatures.
However, even these temperatures are occasionally regarded as being too high, so that there is a need for baking systems which crosslink completely even at lower temperatures.
SUMMARY OF THE INVENTION
It is an object of the present invention, therefore, to find blocked polyisocyanates which exhibit a lower crosslinking or baking temperature than polyisocyanates blocked with butanone oxime.
This object has been achieved with the blocked polyisacyanates of the invention and self crosslinking one-component baking systems comprising thE;m.
The present invention provides aqueous and/or water-dilutable blocked polyisocyanates and self crosslinking 1K (one-components baking systems based on polyurethane of the formula (I~

Le A 35 720-US - 3 -~3~
X
B-CO -NH A H°-CO ' (~), JZ
in which A denotes the radical of a polyisocyanate, B denotes the radical of a cationic, anionic and/or nonionic hydrophilicizing agent, Rl, R2 and R3 may be identical or different and denote hydrogen, Cl-C4-alkyl or C6-Clo-cycloalkyl, preference being given to hydrogen, R4 denotes C1-CQ-alkyl, C6-Cro-cycloalkyl or C1-C14-aralkyl, preferably methyl, ethyl, isopropyl and tert-butyl, with particular preference tert-butyl, x stands for the number I, 2, 3, 4 or 5 and y denotes a number from 1 to 8, preferably from 2 to 6, with particular preference from 2.5 to 4.0 and z denotes a number from 0.1 to 4, preferably from 0.2 to 2;
the eduivalents ratio of y to z being from 20:1 to 1:1, preferably front 10:3 to 3:1, with particular preference from 8:1 to 4:1.

LeA35720-US -4-The invention also provides a process for preparing the blocked polyisocyanates of the general formula (I), characterized in that polyisocyanates are reacted with secondary amines of the formula (II) R, tRa)x HN'~~ ~ (II), ~a R2 in which RI, R2, R3 and R4 and x have the meanings specified for formula (I).
Particular preference is given to asymmetric substituted secondary amines, i.e.
secondary amines having two different substituents.
The invention further provides for the use of the blocked polyisocyanates of the invention for preparing paints, inks and other baking systems such as adhesives or elastomers.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages such as those for amounts of materials, times and temperatures of reaction, ratios of amounts, values for molecular weight, and others in the following portion of the specification may be read as ifprefaced by the word "about" even though the term "about" may not expressly appear with the value, amount or range.
Examples that may be mentioned of secondary amines according to the invention include the following: N-methyl-, N-ethyl-, N-(iso)propyl-, N-n-butyl-, N-isobutyl-, N-tent-butylbenzyl or 1,I-dimethylbenzylamine, N-alkyl-N-1,1-dimethylmethylphenylamine, adducts of benzylamine with compounds having activated double bonds such as malonates, N,N-dimethylaminopropylbenzylamine Le A 35 720-US - 5 -and other optionally substituted benzylamines containing tertiary amino groups, and/or dibenzylamine. Naturally it is also possible to use mixtures of these amines with one another and/or with other blocking agent.
Suitable polyisocyanates for the purposes of the invention include a1;1 conventional hydrophilicized, aliphatic, cycloaliphatic and aromatic polyisocyanates having an isocyanate content of from 0.5 to 50%, preferably from 3 to 30%, with particular preference from 5 to 25% by weight such as tetramethylene diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate, hexamethylene diisocyanate (HDI), 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), methylenebis(4-isocyanatocyclohexane), tetrarr~ethylxylylene diisocyanate (TMXDI), triisocyanatononane.
Also suitable in principle are aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane 2,4'- and/or 4,4'-diisocyanate ( MDI), triphenylmethane 4,4'-diisocyanate, naphthylene I,5-diisocyanate.
Preferred suitability is possessed by polyisocyanates containing heteroatoms in the radical containing the isocyanate groups. Examples thereof are poly:isocyanates containing carbodiimide groups, allophanate groups, isocyanurate groups, urethane groups and biuret groups.
Suitable with particular preference for the invention are the known polyisocyanates used principally in the production of paints, examples being modification products of the abovementioned simple polyisocyanates, in particular of hexamethylene diisocyanate or of isophorone diisocyar~ate, that contain biuret, isocyanurate or uretdione groups.
Also suitable are low molecular weight polyisocyanates containing urethane groups, as may be obtained by reacting IPDI or TDI employed in excess with simple polyhydric alcohols of the molecular weight range 62-300, in particular with trimethylolpropane or glycerol.

Le A 35 720-US - 6 -Suitable polyisocyanates are, furthermore, the known prepolyrners containing terminal isocyanate groups, as are obtainable in particular by reacting the abovementioned simple polyisocyanates, especially diisocyanates, ~rith substoichiometric amounts of organic compounds containing at least two isocyanate-reactive functional groups. In these known prepolymers the ratio of isocyanate groups to NCO-reactive hydrogen atoms is from 1.05:1 to 10:1, preferably from 1.1:l to 3:1, the hydrogen atoms coming preferably from hydroxyl groups. The nature and proportions of the starting materials used in the preparation of NCO prepolymers are preferably chosen, moreover, so that the NCO prepolymers preferably have an average NCO functionality of from 2 to 3 and a number-average molar mass of 500-10 000, preferably 800-4000.
Further suitable polyisocyanates for the purposes of the invention are those polyurethane-, polyester- and/or polyacrylate-based polymers containing free isocyanate groups, and optionally mixtures of such polymers, in which only some of the free isocyanate groups are reacted with the blocking agents of the invention while the remainder are reacted with an excess of hydroxyl-containing polyesters, polyurethanes andJor polyacrylates and also, where appropriate, mixtures thereof so as to give a polymer which contains free hydroxyl groups and which, on heating to suitable baking temperatures without addition of further isocyanate-reactive groups, undergoes crosslinking (self crosslinking one-component baking systems).
Naturally, all the polyisocyanates mentioned may also be used as mixtures with one another or else with other crosslinkers such as with melamine resins for preparing paints, inks and other formulations.
The blocked polyisocyanates of the invention may be prepared by methods which are known per se. For example, one or more polyisocyanates may be introduced initially and the blocking agent may be metered in with stirring (over about minutes, for example). Stirring is continued until free isocyanate is no longer detectable. It is also possible to block one or more polyisocyanates with a mixture Le A 35 720-US - 7 -of two or more blocking agents. Also possible, of course, is preparation in optionally water-miscible solvents, which where appropriate are removed again after preparation. It is, however, also possible to prepare the polyisocyanates of the invention in water-immiscible solvents and then to disperse these mixtures in water or to dilute them with water-miscible solvents such as acetone or N-methyl-pyrrolidone to give water-miscible solutions. In the preparation of the palyisocyanates of the invention it is also possible to use catalysts, cosolvents and other auxiliaries and additives.
An essential constituent of the preparation of the blocked polyisocyanates of the invention is their hydrophilicization, which results in the polyisocyanates thus prepared remaining in solution following the addition of water or else forming fine, sedimentation-stable dispersions.
As hydrophilicizing agents it is possible in this case to use all cationic, anionic andlor nonionic compounds suitable for this purpose, such as mono- and/or dihydroxycarboxylic acids or monofunctional alkyl ethoxylates. Naturally, mixtures of different hydrophilicizing agents can also be used.
The hydrophilicizing agents can be incorporated into the polyisocyanates of the invention by processes which are known per se. Thus, for example, first some of the isocyanate groups can be reacted with the blocking agents of the invention and then the remainder can be reacted with the hydrophilicizing agent. It is, however, also possible to reverse this procedure or else to proceed in such a way that the blocking of the isocyanate groups takes place in two steps, namely before and after the hydrophilicization.
Naturally, the hydrophilicizing agents can also be added at another point in time during the preparation of the polyisocyanates of the invention, such as during the preparation of the prepolymers, for example. As hydrophilicizing agents it is also possible, furthermore, to use hydrophilicized polyethers, polyesters and/or polyacrylates, such as are used, for example, in the preparation of self crosslinking one-component baking varnishes.

Le A 35 720-US - 8 -Where mono- or dihydroxycarboxylic acids are used for hydrophilicization, this is followed by full or partial neutralization of the carboxyl groups.
Neutralization can be carried out with any desired amines, such as triethyl-, dimethylcyclohexyl-, methyldiisopropyl- or dimethylethanolamine. Ammonia is also suitable.
The blocked polyisocyanates of the invention are used in the form of hydrophilicized aqueous and/or water-dilutable blocked polyisocyanates as crosslinkers preferably in a composition of:
a) 100 equivalent% of polyisocyanate b) 40-90, preferably 60-85, equivalent% of secondary benzylamine c) 10-40, preferably 10-30, with particular preference 10-25, equivalent% of a hydrophilicizing agent and optionally d) 0-40, preferably 5-25, equivalent% of a preferably difunctional hydroxyl-and/or amino-containing compound with an average molar weight of from 62 to 3000, preferably from 62 to 100, the proportions of the reactants being chosen such that the equivalents ratio of NCO groups of component a) to isocyanate-reactive groups of components b), c) and d) is from 1:0.8 to 1:1.2, and also, where appropriate, adjuvants and auxiliaries.
Suitable difunctional chain extender components c) include, for example, diamines, diols and also hydroxyamines in the molecular weight range from 32 to 300. Examples are hydrazine, ethylenediamine, isophoronediamine, the bisketimine of isophoronediamine and methyl isobutyl ketone, 1,4-dlihydroxy-butane, 1,6-hexanediol, ethanolamine, N-methylethanolamine, hydroxyethyle-Le A 35 720-US - 9 -thylenediamine, the adduct of 2 mot of propylene carbonate and 1 mot of hydrazine of the formula (III) in question.

The aqueous and/or water-dilutable blocked polyisocyanates are either in the form of solutions in preferably water-miscible solvents such as N-methyllayrrolidone with a concentration of 40-95%, preferably 60-85% by weight or else in the form of fine dispersions having a solids content of 25-70%, preferably 35-50% by weight.
The polyisocyanates of the invention are, as described above, either self crosslinking polymers or else crosslinkers for polyol components. S~xitable polyol components, which may also be used as mixtures, include:
polyhydroxypolyesters, polyhydroxypolyethers or hydroxyl-containing polymers, for example the polyhydroxypolyacrylates known per se. The compounds generally have a hydroxyl number of from 20 to 200, preferably from 50 to 130, based on products in 100% form.
The polyhydroxylpolyacrylates are conventional copolymers of styrene with simple esters of acrylic acid andlor methacrylic acid, hydroxyl grout>s being introduced by the use of hydroxyalkyl esters, such as, for example, the 2-hydroxy-ethyl, 2-hydroxypropyl, 2-, 3- or 4-hydroxybutyl esters of these acids.
Suitable polyetherpolyols are the ethoxylation and/or propoxylation products, known per se from polyurethane chemistry, of suitable starter molecules with a functionality of 2 to 4, such as water, ethylene glycol, propanediol, trimethylol-propane, glycerol and/or pentaerythritol, for example.

Le A 35 720-US - 10 -Examples of suitable polyesterpolyols are, in particular, the reaction.
products, known per se in polyurethane chemistry, of polyhydric alcohols, for example alkanepolyols of the type just exemplified, with excess amounts of polycarboxylic acids or polycarboxylic anhydrides, especially dicarboxylic acids or dicarboxylic anhydrides. Examples of suitable polycarboxylic acids and polycarb~oxylic anhydrides are adipic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, malefic acid, malefic anhydride, the Diels-Alder adducts thereof with cyclopentadiene, fumaric acid or dimeric or trimeric fatty acids. In the preparation of the polyesterpol.yols it is of course possible to use mixtures of the polyhydric alcohols exemplified or mixtures of the acids and acid anhydrides exemplified.
The polyesterpolyols are prepared by known methods, as described, for example, in Houben-Weyl, Methoden der organischen Chemie, volume XIV/:?, G. Thieme-Verlag, 1963, pages 1 to 47. The hydrophilic modification of these holyhydroxyl compounds, which may be necessary, takes place in accordance with methods known per se, as disclosed, for example, in EP-A-0 157 291 or EP-A-0 427 028.
It is of course also possible to use mixtures or else reaction products based on polyesters, polyethers and polyacrylates, also modified where appropriate by polyurethanes of the known kind.
The blocked polyisocyanates of the invention are used for preparing; baking varnishes, for the coating of substrates, preferably comprising metals, minerals, wood, plastics, for industrial coating and in automotive OEM finishing, for example. For these purposes the coating compositions of the invention may be applied by knifecoating, dipping, spray application such as compressed-air spraying or airless spraying, and also by electrostatic application, for example high-speed rotational bell application. The dry film thickness can be;, for example, 10-120 Vim. The dried film is cured by baking in the temperature range of 90-160°C, preferably 110-140°C, with particular preference 120-130°C.

Le A 35 720-US - I I -The paints, inks and other formulations are prepared from the polyisocyanates of the invention by methods which are known per se.
Besides the polyisocyanates and polyols, customary additives and oi;her auxiliaries (e.g. pigments, fillers, levelling agents, defoamers, catalysts) may be added to the farmulations in amounts which are easy for the person skilled in the art to determine.
EXAMPLES
Particle sizes were determined by Larver correlation spectroscopy (I~,SC) Example 1: (Preparation of a water-dilutable polyisocyanate crosslinker) 58.80 g (0.297 eq) of a commercial isocyanurate-containing paint polyisocyanate based on 1,6-diisocyanatohexane (HDI), having an NCO content of 21.4% by 15 weight, a viscosity at 23°C of about 3000 mPas and a functionality of about 3.5, 7.08 g (0.06 mol) of hydroxypivalic acid and 56.57 g of N-methylpyrrolidone were mixed with stirring and heated to 70°C over 30 minutes. The mixture was stirred at this temperature for 2 hours and then the temperature was o:°aised to 80°C.
After a further 2 hours an NCO content of 7.60% was reached, the reaction 20 mixture was cooled to 55°C and then 36.24 g (0.222 mol) of benzyl--tert-butylamine were added over the course of I S minutes, the temperatL~re rising to 60°C.
Stirring was continued at 60°C for 10 minutes and the completeness of the 25 reaction was determined by IR spectrum. Subsequently, at 60°C, 5.35 g (0.06 mol) of dimethylethanolamine were added and stirring was continued for I O minutes.
This gave a clear solution of the blocked polyisocyanate having a solids content of 66.6% and a blocked NCO group content of 5.69%.
30 Example 2: (Preparation of an aqueous dispersion of the invention) Le A 35 720-US - 12 -58.80 g (0.297 eq) of a commercial isocyanurate-containing paint polyisocyanate based on 1,6-diisocyanatohexane (HDI), having an NCO content of 21.4% % by weight, a viscosity at 23°C of about 3000 mPas and a functionality of about 3.5 were admixed with stirring at room temperature with 31.09 g (0.189 mol) of benzyl-tert-butylamine over the course of 20 minutes. During this time the temperature rose to 43°C, the NCO content of the reaction mixture reaching 5.04% (theoretically 5.07%). The reaction mixture was heated to 70°C
with stirring and then, over a total period of 30 minutes, the following were added in succession: 1.61 g (0.0135 mol) of I,6-hexanediol and 6.42 g (0.054 mol) of hydroxypivalic acid, the latter in solution in 10.36 g of N-methylpyrrolidone.
Stirring was continued at 70°C for 2 hours, the NCO content reaching 0.5%. Then, at 70°C, 5.34 g (0.0594 mol) of dirnethylethanolamine were added and stirring was continued for 15 minutes. Thereafter, 143.84 g of hot (70°C) deionized water were added and dispersion was carried out at 70°C for 1 hour. This 1?roduced a stable white dispersion have the following properties:
Solids content: 40%
pH: 9.22 Viscosity (23°C): 200 mPas Average particle size (LCS): 20I nm Example 3: (Preparation of a dispersion of the invention) 343.20 g (1.76 eq) of a commercial isocyanurate-containing paint polyisocyanate based on 1,6-diisocyanatohexane (HDI), having an NCO content of 21.4% by weight, a viscosity at 23°C of about 3000 mPas and a functionality of about 3.5, were heated to 70°C with stirring and 9.45 g (0.08 g mol) of I,6-hey;anediol were added over the course of 10 minutes. Following the addition of a solution of 37.76 g (0.32 eq) of hydroxypivalic acid in 60.93 g of 1\~-methylpyrrolidone (over the course of 10 minutes) the mixture was stirred at 70°C for 4 hours.
The NCO
content of the reaction mixture was then 11.02%. Subsequently, at 70°C, 193.30 g (1.184 mol) of N-benzyl-tent-butylamine were added over the course of 60 Le A 35 720-US - 13 -minutes followed by stirring for 20 minutes. At that point 1VC0 could no longer be found by IR spectroscopy. Over the course of 10 minutes, at 70°C, 31.38 g (0.352 mol) of dimethylethanolamine were added, the mixture was stirred for minutes and then, with stirring, 861.7 g of hot (70°C) deionized water were 5 added followed by stirring at 70°C for 1 hour. Cooling with stirring to morn temperature gave a dispersion having the following properties:

Le A 35 720-US - 14 -Solids content: 40%

pH: 9.41 blocked NCO: 3.23%

Viscosity: 300 mPas Particle size (LCS):19 nm Example 3a:
The procedure described in Example 3 was repeated but v~Tith dropwise addition of hydroxypivalic acid over the course of 3 hours and with the use as polyisocyanate of a 70% strength solution of the trimer of isophorone diisocyanate in methoxypropyl acetate/xylene (Desmodur~ Z 4400 M/X, Bayer AG). The dispersion obtained had the following properties:
Solids content: 35%

pH: 9.28 Viscosity (23C): 60 mPas Particle size (LCS): 85 nm Example 3b:
The procedure of Example 3 was repeated but using as polyisocyanate a mixture of IPDI trimer and 4-isocyanatomethyl-1,8-octane diisocyanate (Desmodur° Z
4460 TIN, Bayer AG). The dispersion obtained had the following properties:
Solids content: 40%
pH: 9.5 Viscosity (23°C): 45 mPas Particle size (LCS): 255 nm Le A 35 720-US - I5 -Example 4:
78.00 g (0.4 eq) of a commercial isocyanurate-containing paint polyisocyanate based on 1,6-diisocyanatohexane (HDI), having an NCO content of 2I.4% % by weight, a viscosity at 23°C of 3000 mPas and a functionality of about 3.5, were introduced with stirring at 70°C and a solution of 4.72 g (0.04 mol) of hydroxypivalic acid and 1.34 g (0.01 moI) of dimethylolpropionic a<;id in 11.17 g of N-methylpyrrolidone was added over the course of 5 minutes. Fo:tlowing the addition of 4.00 g (0.008 mot) of Pluriol 500 (methyl oligoethylene glycol, MW
500) and 1.18 g (0.02 mol) of 1,6 hexanediol, the mixture was stirred at 70°C for 90 minutes. The NCO content was then 13.01 % (theoretically 13.05%). At 70°C, 50.94 g (0.312 mol) of N-benzyl-text-butylamine were added over tine course of minutes followed by stirring at 70°C for 15 minutes. At that point no NCO groups could be detected by IR spectroscopy. At 70°C, 4.46 g (0.05 mol) of°dimethyle-thanolamine were added followed by stirring for 10 minutes and them by the addition of 205.79 g of hot water at 50°C. Stirring was continued at 50°C for 1 hour. The resulting bluish dispersion had the following properties:
Solids content: 40%

pH: 9.7 Viscosity (23C): 2000 mPas Particle size (LCS): 37 nm Example 5: (Preparation of a dispersion) The procedure of Example 3 was repeated but using, instead of N-benzyl-tert-butylamine, a mixture of diisopropylamine and N-benzyl-tent-butylamine in a molar ratio of 2:1. The dispersion obtained had the following propexties:
Solids content: 40%
pH: 9.3 Le A 35 720-US - 16 -Viscosity (23°C): 330 mPas Particle size (LCS): 24 nm Example 6: (Preparation of a dispersion of the invention) The procedure of Example 4 was repeated but using, instead of N-benzyl-tert-butylamine, in mixture of diisopropylarnine and N-benzyl-tart-butylamine in a molar ratio of 2:1. The dispersion obtained had the following properties:
Solids content: 40%
pH: 9.75 Viscosity (23°C): 850 rnPas Average particle size (LCS): 23 nrn Example 7 (Comparative Example I) The procedure described in Example 2 was repeated but using butanone oxime instead of N-benzyl-tart-butylamine. The dispersion obtained had the following properties:
Solids content: 38%
pH: 8.5 Viscosity (23°C): 4000 mPas Particle size (LCS): 42 nm Example 8: (Preparation of a self crosslinking one-component baking system) A mixture of 337.5 g (3.035 eq) of isophorone diisocyanate, 18.02 g (0.2 moI) of 1,4-butanediol, 13.42 g (0.01 mol) of trimethylolpropane, 22.5 g (0.045 mol) of methanol ethoxylate of average molar weight 500 and 205.80 g (0.4'9 eq) of a polyester made from adipic acid and hexanediol with an average molar weight of 840 was admixed at 85°C with 53.66 g (0.4 mol) of dimethylpropionic acid in Le A 35 720-US - 17 -solution in 106.80 g of N-methylpyrrolidone, with stirring, and the reaction mixture was stirred at this temperature for 4 hours. The NC~ content was then 4.78% (theoretically 4.80%). ~ver the course of 20 minutes 18.02 g (0.61 eq) of butanone oxime were added. Then 318.18 g (I eq) of a polyester formed from adipic acid, isophthalic acid, trimethylolpropane, neopentyl glycol and propylene glycol were added and the reaction mixture was stirred at 85°C for 10 hours. After that it was no longer possible to detect NC~ groups by IR spectroscopy.
Thereafter 35.57 g (0.4 mol) of dimethylethanolamine were added and stirring was continued for 10 minutes. Following the addition of 1525.5 g of hot (70°C) I O deionized water, dispersion was carried out at 70°C for 1 hour.
The white dispersion obtained had the following properties:
Solids content: 40%
pH: 8.I5 I5 Viscosity (23°C): 4000 mPas Particle size (LCS): 47 nm Example 9: (Comparative Example II) 20 The procedure described in Example 8 was repeated but using butanone oxime instead of the blocking agent of the invention. The dispersion obtairded had the following properties:
Solids content: 40%
pH: 8.6 25 Viscosity (23°C): 3800 mPas Particle size (LCS): 51 nm Examples (Use Examples) 30 The examples below show the advantages of the blocked polyisocyanates of the invention over the state of the art.

Le A 35 720-US - 18 -Clearcoat materials were prepared with the following composition. ~Che clearcoat materials were used to produce films, which were dried at room temperature for minutes and then baked at 130°C for 30 minutes. The films obtained were assessed for performance. The results are compiled in Table 1.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that piurpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

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Claims (10)

1. Aqueous and/or water-dilutable blocked polyisocyanates of the formula (I) in which A denotes the radical of a polyisocyanate, B denotes the radical of a cationic, anionic and/or nonionic hydrophilicizing agent, R1, R2 and R3 may be identical or different and denote hydrogen, C1-C4-alkyl or C6-C10-cycloalkyl, R4 denotes C1-C4-alkyl, C6-C10-cycloalkyl or C1-C14-aralkyl, and x stands for the number 1, 2, 3, 4 or 5 and y denotes a number from 1 to 8, and z denotes a number from 0.1 to 4, the equivalents ratio of y to z being from 20:1 to 1:1.

2. Blocked polyisocyanates according to Claim 1, wherein N-benzyl-tert-butylamine is used as secondary amine.

3. Process for preparing the blocked polyisocyanates according to Claim 1, wherein polyisocyanates are reacted with secondary amines of the general formula (II) in which R1, R2, R3 and R4 and x have the definition specified in Claim 1 for formula (I).

4. Method for preparing one of a paint, an ink, an adhesive and an elastomer, comprising adding a blocked polyisocyanate according to Claim 1 to a formulation.

5. Method according to Claim 4, wherein the one of a paint, an ink, an adhesive and an elastomer is a baking system.

6. Method according to Claim 4, wherein the one of a paint, an ink, an adhesive and an elastomer is a self-crosslinking system.

7. Method according to Claim 4, wherein the one of a paint, an ink, an adhesive and an elastomer is a baking system for the coating of substances comprising wood, metals, minerals and plastics.

8. Hydrophilicized, aqueous and/or water-dilutable composition comprising blocked polyisocyanates according to Claim 1, the composition comprising:
a) 100 equivalent% of polyisocyanate b) 40-90 equivalent% of secondary benzylamine c) 10-40 equivalent% of a hydrophilicizing agent, the proportions of the reactants being chosen such that the equivalents ratio of NCO groups of component a) to isocyanate-reactive groups of components b) and c) is from 1:0.8 to 1:1.2.

9. Hydrophilicized, aqueous and/or water-dilutable composition comprising blocked polyisocyanates according to Claim 1, the composition comprising:
a) 100 equivalent% of polyisocyanate b) 60-85 equivalent% of secondary benzylamine c) 10-25 equivalent% of a hydrophilicizing agent and d) 0-40 equivalent% of a hydroxyl- and/or amino-containing compound with an average molar weight of from 62 to 3000, the proportions of the reactants being chosen such that the equivalents ratio of NCO groups of component a) to isocyanate-reactive groups of components b), c) and d) is from 1:0.8 to 1:1.2.

10. The composition of Claim 9, wherein the hydroxyl- and/or amino-containing compound is difunctional, present in an amount from 5-25 equivalent%, and has a molar weight from 62 to 1500, the composition also comprising adjuvants and auxiliaries.