HK1086581B - Single-component polyurethane coating systems containing quadrivalent vanadium - Google Patents

Description

One-component polyurethane coating systems comprising tetravalent vanadium catalysts

The present invention relates to novel one-component polyurethane systems, to a process for their preparation, and to their use for the preparation of paints, inks and adhesives.

One-component (1K) baking systems based on polyurethanes are heat-curable materials which are stable on storage at room temperature and can be used for the preparation of paints, inks and adhesives. They generally consist of blocked polyisocyanates which are consumed during thermal curing by reaction with hydroxyl-containing polyesters, polyacrylates, other hydroxy-functional polymers and/or mixtures of different polymers. Another possible way of obtaining a baking enamel starting material which is storage-stable at room temperature is to partially block isocyanate groups in a polymer which contains blocked isocyanate groups and hydroxyl groups.

The main compounds used to block polyisocyanates and 1K baking systems are epsilon-caprolactam, methyl ethyl ketoxime (butanone oxime), secondary amines and triazole and pyrazole derivatives, as described in EP-A0576952, EP-A0566953, EP-A0159117, US-A4482721, WO 97/12924 or EP-A0744423. Blocking with malonic esters is also possible. However, when this blocking is carried out, the blocking agent is not returned to the original one after cleavage, but rather a transesterification reaction occurs in the malonic acid diethyl ester group.

Depending on the blocking agent used, temperatures of 100 ℃ and 160 ℃ are employed in the preparation of coatings from 1K PU stoving systems. However, selection of an appropriate capping agent for a particular system does not merely take into account the baking temperature. Other factors, such as the tendency of the system to yellow, odor and storage stability, also play an important role. In particular, recently, attention has been paid to the fact that the baking temperature of the coating systems must be reduced to a minimum, so that it is necessary in all cases to take account of the composition of the coating and the properties of the coating. It is therefore clear that there is a need for a new baking system which has optimum properties even at lower baking temperatures.

Numerous experiments have been carried out in the past in order to reduce the baking temperature of 1K systems by the use of catalysts. For example, EP-A0761705 has proposed that organobismuth compounds catalyze partially or fully blocked polyisocyanates. U.S. Pat. No. 3, 5859165 describes the reaction products of blocked poly (thio) isocyanates using manganese, cobalt, nickel, copper, zinc, germanium, antimony or bismuth and/or their oxides as catalysts. EP-A0726284 describes in general the catalytic action of metal salts and/or metal complexes on the reaction of blocked polyisocyanates with polyols, but the examples only describe dibutyltin dilaurate and dibutyltin acetate in particular.

In order to reduce the use of organic solvents and thus the emission of these solvents into the environment, and at the same time to improve the working conditions of coating lines by reducing the solvent emission, 1K coating systems comprising water as the main solvent component have been developed in recent years. A review of this technology is found in D.A. wicks and Z.W. wicks, Progress in organic coatings 2001, 41(1-3), 1-83. This technology is spreading. The presence of aqueous solvents and/or dispersion media places different demands on the use of catalysts than what are known as solvent-based systems. In the latter systems, it is therefore not necessary to ensure that the catalysts used are stable to water or to hydrolysis if they are used. Thus, the conventional catalysts used in solvent-based 1K systems cannot generally be used in so-called aqueous systems. Known representatives of such catalysts which are highly active (i.e., capable of significantly lowering the baking temperature) include bismuth 2-ethylhexanoate and organotin (IV) compounds such as dibutyltin Dilaurate (DBTL). In addition to these, a number of other compounds have been described, as described in Wicks et al, supra. It is also known that bismuth carboxylates are hydrolyzed in water.

To date, only a few catalysts have been disclosed as being useful for accelerating the cure of aqueous one-component systems. WO95/04093 outlines organotin-based systems. These catalysts are particularly useful in electrodeposition paint systems, the curing of which typically occurs at elevated temperatures of about 170 ℃ or above. The blocking agents and polyisocyanates used in each case are not specified in the examples. However, for ecological reasons, the use of organotin catalysts is not desirable. The activity of the above and other catalysts relative to other catalyst systems is also described in the following application.

WO 00/47642 on page 4 mentions very specific examples of catalysts for 1K aqueous applications, which describe organotin compounds and lead compounds, but from an ecological point of view they are not suitable for use in coatings.

WO 00/47642 also mentions catalysts for aqueous one-component systems based on bismuth oxide and a carbon chain length of C₁₁-C₃₆Of (2) a carboxylic acid. Although the catalyst in this system also undergoes hydrolysis, it is said that the catalyst can be reformed from the components at higher baking temperatures in excess of 165-180 ℃ and has high catalytic activity. However, the use of this catalyst system is limited to a very specific range of several resin and/or alcohol components.

The activity of the catalyst system is described only for several specific resins, in this case cationically hydrophilicized resins, i.e. resins obtained by reaction of biphenyl a-containing epoxy resins with amines. Depending on the amine used (primary, secondary, tertiary), quaternary ammonium groups may also be formed in the presence of excess epoxy resin and water and the acid used for neutralization. Thus, the resin is in principle an amine-containing resin, which is not suitable for forming automotive surfacers, since the surfacer should not be susceptible to yellowing and have long-term stability.

As an alternative to cationic hydrophilicization, aqueous 1K PU systems can be prepared by adding surfactants or emulsifiers. The above documents do not describe whether the catalyst systems described are used in such coating systems.

Aqueous 1K systems can also be prepared by hydrophilization with anionic hydrophilicizing agents (e.g. carboxylic acids) or nonionic hydrophilicizing agents (e.g. polyethers) incorporated into the resin, rather than as a separate component, as is the case with emulsifiers, etc. However, the abovementioned documents likewise do not describe whether the catalyst systems described are used in such coating systems.

Depending on the different possible ways of hydrophilizing 1K systems (cationic, emulsifier, anionic or nonionic hydrophilization), the catalyst system described in WO 00/47642 has no significant activity for use in systems other than cationically hydrophilized systems. For example, cationic hydrophilization can be achieved by stabilizing the ammonium salt of the ligand. The 1K systems which have not been cationically hydrophilicized lack this stabilizing effect.

Furthermore, the aforementioned documents only describe isocyanates blocked with alcohols. A typical blocking agent for blocking the only isocyanate described in this document, (polymeric) MDI (methylene-phenyl diisocyanate) is butoxyethoxyethanol (butyl carbitol). In addition, 2-ethoxyethanol and 2-methoxyethanol are mentioned. Elimination of this blocking agent (actually urethane cleavage) requires higher temperatures: the baking was carried out at 165-180 ℃ for 20 minutes.

For the application of the coating compositions to passenger cars, it is necessary to find a catalyst which enables the curing of the one-component systems at temperatures not exceeding 140 ℃ and preferably at lower temperatures.

Thus, there is currently no catalyst available for reducing the baking temperature to the desired level in aqueous systems based on a wide variety of blocking agents, blocked (poly) isocyanates and hydrophilization methods.

Therefore, the objective of the research was to find a catalyst suitable for general applications, which is effective at lower baking temperatures and in the presence of more blocking agents, resins and hydrophilizing agents. Ecological considerations are also taken into account.

This object is achieved by providing the catalysts of the invention based on certain vanadium compounds.

Polyisocyanates and one-component baking systems which are blocked catalytically with vanadium compounds have never been used to date. Particularly suitable catalysts are the high oxidation state compounds of vanadium. For example, vanadium compounds having an oxidation state of +5 (e.g.triethylvanadia as vanadate for the preparation of polyurethanes (see also DE-A1921952) or Saunders/Frisch: High Polymers, Vol.XVI (1962), p.169) have been used to catalyze the reaction of unblocked isocyanates with alcohols. However, DE-A1921952 also excludes the use of vanadium compounds in water-containing systems (due to the tendency of alkoxy vanadium oxides to hydrolyze), and describes only vanadium trialkoxides. Thus, accelerating the reaction of blocked isocyanates with polyols in the presence of vanadium compounds has not been mentioned in the prior art.

It has been found that by using the catalysts of the invention in 1K systems based on blocked isocyanates it is possible to reduce the baking temperature by around 20 ℃ depending on the blocking agent used. Therefore, the baking temperature can be reduced to about 130 ℃. However, the catalysts of the invention are also sufficiently active at lower temperatures, for example 120 ℃, as shown in the examples below.

The invention provides polyurethane-based one-component baking systems, characterized in that they comprise one or more organic and/or inorganic compounds of vanadium having a vanadium oxidation state of at least + 4.

These one-component systems are characterized in that they comprise:

(a) a blocked polyisocyanate;

(b) a polymer containing polyisocyanate reactive groups;

(c) one or more organic and/or inorganic compounds of vanadium having a vanadium oxidation state of at least + 4;

(d) water and/or an organic solvent or solvent mixture;

(e) other additives and adjuvants may be included if desired.

Wherein the amount of (a) + (b) is 20-89.9 parts by weight, the amount of (c) is 0.01-5 parts by weight, the amount of (d) is 10-70 parts by weight, the amount of (e) is 0-10 parts by weight, and the sum of the parts by weight of the components (a) - (e) is 100.

The invention also provides a process for the preparation of the one-component baking systems having the general components (a) to (e).

The invention also provides for the use of the one-component baking systems of the invention for the preparation of paints, inks and other baking systems, such as adhesives or elastomers, and for the coatings produced therefrom.

The 1K stoving systems of the invention comprise blocked polyisocyanates (a) as crosslinker component, obtainable in a customary manner by reacting any suitable organic polyisocyanates A) with any suitable blocking agents B), if necessary together with synthesis components C). Suitable polyisocyanates A) for preparing the blocked polyisocyanates (a) are any suitable organic polyisocyanates known from the usual polyurethane systems for crosslinking active hydrogen-containing compounds, i.e.aliphatic polyisocyanates (including cycloaliphatic polyisocyanates), aromatic polyisocyanates and heterocyclic polyisocyanates containing at least two isocyanate groups, and mixtures thereof. Typical examples of suitable polyisocyanates A) are aliphatic isocyanates, such as diisocyanates or triisocyanates, for example Butane Diisocyanate (BDI), pentane diisocyanate, Hexane Diisocyanate (HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN); or ring systems, e.g. 4, 4' -methylenebis (cyclohexyl isocyanate) (Desmodur)^®W, Bayer AG, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI) and omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Examples of aromatic polyisocyanates are 1, 5-naphthalene diisocyanate, diisocyanatodiphenylmethane (MDI) or crude MDI, diisocyanatomethylbenzene (TDI), in particular the 2, 4-and 2, 6-isomers, and technical-grade mixtures of the two isomers, and also 1, 3-bis (isocyanatomethyl) benzene (XDI). Likewise very suitable polyisocyanates are obtainable by reacting diisocyanates or triisocyanates with themselves via isocyanate groups, such as uretdione or carbodiimide compounds, or such as isocyanurate or iminooxadiazinedione (oxadiazinedione), which are obtained by reacting triisocyanate groups.

Other suitable polyisocyanates include oligomeric polyisocyanates containing biuret, allophanate and acylurea structural units, as well as any suitable mixtures of the polyisocyanates described. Mixtures of polyisocyanates containing the stated structural units and/or mixtures of modified polyisocyanates with isocyanate monomers may also be employed. The polyisocyanates thus modified can also be prepolymerized in proportion to other isocyanate-reactive groups. Proportionally modified polyisocyanates are more suitable. Also highly suitable are polyisocyanate prepolymers containing on average more than 1 isocyanate group per molecule. They are obtainable by preliminary reaction of a molar excess of one of the abovementioned diisocyanates, triisocyanates or polyisocyanates and modified polyisocyanates with an organic material containing at least two active hydrogen atoms per molecule, in the form of hydroxyl groups. Similarly, they may be proportioned to undergo a prepolymerization reaction, as described in the next section.

Other suitable polyisocyanates are low molecular weight polyisocyanates containing urethane groups, obtainable by reacting an excess of a diisocyanate, preferably IPDI or TDI, with simple polyols having a molecular weight in the range from 62 to 300, in particular trimethylolpropane or glycerol.

Suitable polyisocyanates A) also include the known prepolymers containing terminal isocyanate groups, obtainable in particular by reacting the abovementioned simple polyisocyanates, especially diisocyanates, with substoichiometric amounts of organic compounds having at least two isocyanate-reactive functional groups. In these known prepolymers, the ratio of isocyanate groups to NCO-active hydrogen atoms is from 1.05: 1 to 10: 1, preferably from 1.1: 1 to 3: 1, where the hydrogen atoms are preferably derived from hydroxyl groups. The nature and proportions of the starting materials used for preparing the NCO prepolymers are also preferably chosen such that the average NCO functionality in the NCO prepolymer is from 2 to 3 and the number-average molecular weight is from 500-.

Preferred polyisocyanates A) include uretdione, isocyanurate, iminooxadiazinedione, acylurea, carbamate, biuret or allophanate structures, preferably those based on 1, 6-hexanediisocyanate, 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane(IPDI), omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI) and 4, 4' -methylenebis (cyclohexyl isocyanate) (Desmodur^® W，Bayer AG，Leverkusen)。

Further polyisocyanates A) suitable for use in the present invention are polyurethane-, polyester-and/or polyacrylate-based polymers which contain free isocyanate groups. If appropriate also mixtures thereof, in which only part of the free isocyanate groups is reacted with blocking agents and the remainder is reacted with an excess of hydroxyl-containing polyesters, polyurethanes and/or polyacrylates and mixtures thereof, if appropriate, on heating to a suitable baking temperature to form polymers containing free hydroxyl groups, without further components, crosslinking of the isocyanate-reactive groups (self-crosslinking one-component baking systems).

All the polyisocyanates mentioned above can also be mixed with one another in any desired manner or with other crosslinkers, such as melamine resins, for the preparation of paints, inks and other formulations.

Suitable blocking agents B) include N-H or O-H functional compounds which are consumed by reaction with isocyanates and which, at suitable temperatures, can undergo crosslinking reactions with other N-H or O-H functional compounds. Examples of suitable blocking agents are dimethylpyrazole, diisopropylamine, tert-butylbenzylamine, butanone oxime, epsilon-caprolactam, ethoxyethanol, isopropoxyethanol and other alcohols such as carbitol. Secondary amines, such as dibutylamine, or other oximes, such as cyclohexanone oxime or acetone oxime, may also be used. For a review of suitable blocking agents in principle see Wick et al, Progress in organic Coatings 1975, 3, pp.73-79; 1981, 9, pp.3-28 and 1999, 36, pp.148-172. Preference is given to using 3, 5-dimethylpyrazole, diisopropylamine, tert-butylbenzylamine, butanone oxime and ethoxyethanol.

The ratio of isocyanate groups to blocking agent is generally 1: 1, but values between 0.5: 1 and 2: 1 may also be used. The ratio is preferably from 0.9: 1 to 1.1: 1, particularly preferably from 0.95: 1 to 1: 1.

The blocked polyisocyanates (a) can be prepared by customary methods. For example, the charging of the polyisocyanate(s) can be started and then the blocking agent metered in with stirring (for example, over a period of about 10 minutes). Stirring was continued until no free isocyanate could be detected anymore. One or more polyisocyanates may also be blocked with a mixture of two or more blocking agents, including suitable blocking agents outside the scope of the present invention. Blocked polyisocyanates can of course also be prepared in solvents. These solvents can be distilled off in a later preparation step and can also remain in the product.

Another preparation process of the blocked polyisocyanates (a) used in the present invention comprises hydrophilizing them by an ionic method, a nonionic method or both methods according to the usual procedures, and then adding water to dissolve or disperse them in water. Catalysts, cosolvents and other auxiliaries and additives may also be employed in the preparation of the polyisocyanates. The aqueous one-component baking systems can also be prepared by mixing unblocked or only partially blocked polyisocyanates with polyesters, polyacrylates, polyacrylate-modified and polyurethane-modified polyesters containing hydrophilic groups and then converting them into dispersions.

Other suitable synthesis components C include ionic or potentially ionic compounds C1), and/or compound C2 as non-ionic hydrophilicizing agents. Examples of ionic or potentially ionic compounds C1 are mono-and dihydroxycarboxylic acids, mono-and diaminocarboxylic acids, mono-and dihydroxysulfonic acids, mono-and diaminosulfonic acids and mono-and dihydroxyphosphonic acids and/or mono-and diaminophosphonic acids, and also their salts, such as dimethylolpropionic acid, hydroxytrimethylacetic acid, N- (2-aminoethyl) -beta-alanine, 2- (2-aminoethylamino) ethanesulfonic acid, ethylenediamine-propyl-or butylsulfonic acid, 1, 2-or 1, 3-propylenediamine-beta-ethanesulfonic acid, lysine, 3, 5-diaminobenzoic acid, the hydrophilicizing agents of example 1 of EP-A0916647 and their alkali metal and/or ammonium salts; adduct of sodium bisulfite and 2-butene-1, 4-diol, polyether sulfonate, 2-butanediol and NaHSO₃Propoxylated adducts of (A) as described, for example, in DE-A2446440, pp.5-9, formula I-III), and also transferrableUnits which are converted to cationic groups, such as N-methyldiethanolamine, are used as hydrophilic synthesis components.

Preferred ionic or potentially ionic compounds C1 are compounds comprising carboxyl or carboxylate groups and/or sulfonate groups and/or ammonium ions. Particularly preferred ionic compounds are those which contain carboxyl and/or sulfonate groups as ionic or potentially ionic groups, such as salts of N- (2-aminoethyl) -beta-alanine, salts of 2- (2-amino-ethylamino) ethanesulfonic acid, salts of hydrophilicizing agents and salts of dimethylolpropionic acid in example 1 of EP-A0916647.

In the synthesis of component C3, the compounds mentioned below for compound (b) may also be used.

The hydroxyl components contained in the components C1, C2, and C3 may contain double bonds, which may be from long chain aliphatic carboxylic acids or fatty alcohols, and the like. The functionalization with olefinic double bonds can be carried out, for example, by adding allyl groups or acrylic or methacrylic acid and esters thereof. With these substances, it is more possible to use desiccants (Co) in the presence of atmospheric oxygen in the subsequent oxidative crosslinking⁺³) Or further crosslinking by UV radiation.

After dispersion of the components (a) to (e) in water, by interaction between them and/or reaction with water, so-called PU dispersions are obtained which are essentially aqueous 1K PU coating systems. These PU dispersions may also comprise nonionically hydrophilicizing compounds C2, such as polyoxyalkylene ethers which contain at least one hydroxyl or amino group. These polyethers contain from 30% to 100% by weight of units derived from oxyethylene. Suitable polymers include polyethers having a linear structure and a functionality of 1 to 3, but also compounds of the general formula (VI),

wherein the content of the first and second substances,

R¹and R²Each is a divalent aliphatic, cycloaliphatic or aromatic radical having from 1 to 18 carbon atoms which may be interrupted byAn oxygen atom and/or a nitrogen atom are inserted,

R³is a polyester containing non-hydroxyl end groups or preferably a polyether. R³Particular preference is given to polyoxyethylene groups containing alkoxy end groups.

Non-ionic hydrophilic compounds used as further synthesis component C2 also include monovalent polyoxyalkylene polyether alcohols containing on average from 5 to 70, preferably from 7 to 55, oxyethylene units per molecule, which alcohols are obtainable by alkoxylation of suitable starter molecules by customary methods (for example Ullmanns encyclopedie der technischen Chemie, 4 th edition, volume 19, Verlag Chemie, Weinheim, pages 31 to 38). Examples of suitable starter molecules include saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, pentanol isomers, hexanol, octanol, nonanol, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, methylcyclohexanol or hydroxymethylcyclohexane isomers, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofuryl alcohol; diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether; unsaturated alcohols, such as allyl alcohol, 1-dimethylallyl alcohol or oleyl alcohol; aromatic alcohols, such as phenol, cresol or methoxyphenol isomers, arylaliphatic alcohols, such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol; secondary monoamines, such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis (2-ethylhexyl) amine, N-methyl-and N-ethylcyclohexylamine or dicyclohexylamine, heterocyclic secondary amines, such as morpholine, pyrrolidine, piperidine or 1H-pyrazole.

Preferred starter molecules are saturated monoalcohols and diethylene glycol monoalkyl ethers. Diethylene glycol monobutyl ether or methyl ether is particularly suitable as the starting molecule.

In particular, the alkylene oxides suitable for the alkoxylation reaction are ethylene oxide and propylene oxide, which can be used in any order or in mixtures for the alkoxylation reaction.

The polyoxyalkylene polyether alcohols may be pure polyethylene oxide polyethers or mixed polyoxyalkylene polyethers, in the latter case at least 30 mol%, preferably at least 40 mol%, of the alkylene oxide units being composed of ethylene oxide units. Preferred nonionic compounds are monofunctional mixed polyoxyalkylene polyethers containing at least 40 mol% ethylene oxide units and not more than 60 mol% propylene oxide units.

The PU dispersions of the invention can also be hydrophilicized with ionic and nonionic hydrophilicizing agents. Alternatively, cationic hydrophilizing agents may be used. If the former is the case, it is preferable to use an anionic and nonionic hydrophilizing agent in combination.

As noted above, the polyisocyanate is a self-crosslinking polymer or other crosslinker for any desired compound containing polyisocyanate reactive groups (b). Suitable compounds of said type (b) include the following (which may also be used in the form of mixtures):

polyhydroxy polyesters, polyhydroxy polyethers or hydroxyl-containing addition polymers, examples being the known polyhydroxy polyacrylates. The hydroxyl number of the compounds is generally from 20 to 200, preferably from 50 to 130, based on the product in 100% form.

Polyhydroxy polyacrylates are customary copolymers of styrene with simple esters of acrylic acid and/or methacrylic acid, with hydroxyalkyl esters, such as the 2-hydroxyethyl, 2-hydroxypropyl, 2-, 3-or 4-hydroxybutyl esters of these acids, being additionally used for the introduction of hydroxyl groups.

Suitable polyether polyols are suitable di-to tetravalent starter molecules, such as ethoxylation and/or propoxylation products of water, ethylene glycol, propylene glycol, trimethylolpropane, glycerol and/or pentaerythritol, etc., which are known per se in the field of polyurethane chemistry.

Examples of suitable polyester polyols are, in particular, polyols, such as alkyl polyols, which are reaction products of polyols of the type just exemplified with an excess of polycarboxylic acids and/or polycarboxylic anhydrides, in particular dicarboxylic acids and/or dicarboxylic anhydrides, which are known per se in polyurethane chemistry. Examples of suitable polycarboxylic acids and polycarboxylic anhydrides are adipic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, maleic acid, maleic anhydride, their Diels-Alder adducts with cyclopentadiene, fumaric acid or dimeric and/or trimeric fatty acids. In the preparation of the polyester polyols, it is of course possible to employ any desired mixtures of the exemplified polyols or any desired mixtures of the exemplified acids and anhydrides.

The polyester polyols are prepared by known methods, as described, for example, in Houben-Weyl, Methoden der organischen Chemie, volume XIV/2, G.Thieme-Verlag, 1963, pages 1 to 47. If desired, these polyhydroxyl compounds can be hydrophilically modified by customary methods, as described in EP-A0157291 or EP-A0427028.

Mixtures or other combinations of these polyols, polyacrylate-modified and/or polyurethane-modified polyesters may also be employed.

Polyol components (b) suitable for the one-component systems of the invention also include diols to hexaols which contain no ester groups and/or mixtures thereof. Typical examples are 1, 2-ethanediol, 1, 2-and 1, 3-propanediol, 1, 4-, 1, 2-or 2, 3-butanediol, 1, 6-hexanediol, 1, 4-dihydroxycyclohexane, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol and sorbitol. Of course, alcohols having ionic groups or groups that can be converted to ionic groups can also be employed. For example, 1, 4-or 1, 3-butanediol, 1, 6-hexanediol and/or trimethylolpropane are preferred.

In the preparation of the one-component baking systems according to the invention, it is also possible to use amino-group-containing compounds, such as ethanolamine and its derivatives, as component (b). Diamines such as hexamethylenediamine, ethylenediamine, isophoronediamine or hydrazine and/or their derivatives may also be used.

The ratio of groups which are reactive with the blocked isocyanates to blocked isocyanate groups can vary within a relatively wide range and is generally from 0.5: 1 to 2: 1. Preferably in a ratio of 1: 1 to 1.5: 1.

The one-component baking enamels according to the invention comprise organic and/or inorganic vanadium compounds as catalysts (c) for accelerating the crosslinking reaction.

Suitable vanadium compounds include all known vanadium compounds having an oxidation state greater than or equal to + 4. They may be soluble or partially soluble or insoluble in the one-component baking catalyst system. They may be organic or inorganic in nature; it is also possible to use mixtures of different vanadium compounds and mixtures of vanadium compounds with other catalysts, such as amines and/or tin compounds or bismuth compounds.

Examples of preferred vanadium compounds are ammonium, lithium, sodium and potassium vanadate, lithium, sodium and potassium orthovanadate, magnesium, calcium vanadate, vanadyl (IV) acetylacetonate (VO (C)₅H₇O₆)₂) Bis (tetramethylpimelic acid) oxovanadium (VO (TMHD)₂) And vanadic acid.

Vanadium compounds having oxidation states of +4 and +5 are preferred in the present invention. Thus, preference is given to derivatives of vanadic acid and/or orthovanadic acid. Vanadium compounds, in particular orthovanadates, are capable of undergoing condensation reactions with themselves, depending on the pH of the solution, without any change in the oxidation number of the vanadium. The use of these polyvanadium anions is described in the present invention. Furthermore, orthovanadates having different amounts of water of crystallization are obtained, which have no adverse effect on their activity as catalysts. Lithium vanadate Li is particularly preferred₃VO₄Sodium vanadate Na₃VO₄And potassium vanadate K₃VO₄Preferably lithium metavanadate LiVO₃Sodium metavanadate NaVO₃And potassium metavanadate KVO₃。

In addition to the above compounds, the substances in question may comprise complexes with alcohols, phenols, sugars, organic acids, (poly) ethers, etc. Lithium vanadate and sodium vanadate are particularly preferred.

The vanadium compounds are added in amounts of from 0.01 to 5% by weight, preferably from 0.1 to 2% by weight, particularly preferably from 0.2 to 1% by weight, based on the sum of components (a), (b) and (e). The vanadium compound may be added to the components or the finished coating during or after preparation from any of components (a), (b), (d) or (e) or mixtures thereof. The vanadium compound is preferably added to component (a) or (b) or to a mixture thereof during the preparation. In aqueous systems, the vanadium compounds according to the invention are added to the individual components, particularly preferably to the individual components, and then dispersed in water. The vanadium compounds of the present invention may be added as finely ground solids, as a suspension or solution in the desired liquid.

The one-component baking systems of the invention comprise the solvent (d) water and/or an organic solvent or mixtures thereof.

As organic solvents, all known solvents can be used. Solvents used in the paint industry, such as xylene, butyl acetate, ethyl acetate, butanediol acetate, methoxypropyl acetate, hydrocarbons, such as Solvesso100(Exxon Chemicals), N-methylpyrrolidone, are preferred.

In addition to the blocked polyisocyanates (a) and polyols (b), it is possible to add customary additives and further auxiliaries (e) (examples being pigments, fillers, levelling agents, defoamers, catalysts) to the formulations and, if desired, catalysts other than (c).

Paints, inks and other formulations can be prepared by conventional methods from the one-component baking systems of the invention. Regardless of the preparation method used, the one-component baking systems of the invention comprise the above-mentioned components (a) to (e) in amounts of from 20 to 89.9 parts by weight, (a) + (b) in amounts of from 0.01 to 5 parts by weight, (d) in amounts of from 10 to 75 parts by weight and (e) in amounts of from 0 to 10 parts by weight, with the proviso that the sum of the parts by weight of the components (a) to (e) is 100.

The one-component baking systems of the invention preferably comprise the individual components (a) to (e) mentioned above, provided that the sum of them is 100 parts by weight, the amount of (a) + (b) being from 30 to 69.9 parts by weight, the amount of (c) being from 0.01 to 2 parts by weight, the amount of (d) being from 30 to 70 parts by weight and the amount of (e) being from 0 to 8 parts by weight.

The one-component baking systems of the invention can be used for the preparation of baking enamels, for industrial coatings and OEM coating of passenger cars. These baking enamels can be primer, surfacer and topcoat. The baking enamel may contain pigments or may be a pure topcoat material. To this end, the coating compositions of the invention can be applied by knife coating, dipping, spraying (e.g.compressed air spraying or airless spraying) and electrostatic application, for example high-speed rotary bell coating. The dry film coating thickness may be, for example, 10-120 μm. The dry film may be cured by baking at a temperature in the range of 90-160 deg.C, preferably at 110-140 deg.C, and more preferably at 120-130 deg.C.

The invention also provides substrates coated with a coating which is obtainable from a formulation based on the one-component baking system of the invention.

The following examples serve to illustrate the invention.

Examples

In the following examples, all percentages are by weight.

Preparation of the self-crosslinking agent for examples 1-4

336.7g N-methyl-pyrrolidone was added to 789.8g (3.71 equivalents NCO) of an aliphatic polyisocyanate (HDI trimer, Desmodur)^®N3300, Bayer AG, D-Leverkusen). 374.9g (3.71 eq.) of diisopropylamine were added with stirring over 60 minutes at such a rate that the temperature would not exceed 70 ℃. Then stirred at 70 ℃ for 60 minutes; thereafter, no more isocyanate groups were detected by IR spectroscopy. 2311g (5.29 equivalents of hydroxyl) of a polyester polyacrylate (made from polyester polyol made from 1, 6-hexanediol, trimethylolpropane, peanut oil fatty acid, maleic anhydride and phthalic anhydride, with an OH number of 136, grafted with a mixture of butyl acrylate, methyl methacrylate and hydroxypropyl methacrylate) was added at 70 deg.C and the mixture was stirred for 20 minutes. Then, 115.5g (1.296 eq) of dimethylethanolamine was added, followed by stirring for 10 minutes.

To each 614g of the reaction mixture, fine powder of sodium orthovanadate in an amount shown in Table 6 was added at 70 ℃ and, thereafter, stirred for 30 minutes. Then, in each case, 581g of deionized water at 70 ℃ were added with vigorous stirring, after which the dispersion was cooled with stirring. The resulting dispersion had a solids content of 45% and also had other properties:

it is clear that the use of vanadium catalysts can bring about better chemical resistance. The pendulum hardness also increases. The decrease in the crosslinking temperature amounted to about 20 ℃.

Examples 1 to 4

PES/PAC/N3300 end-capped with DIPA	Without catalyst	0.75% sodium stannate	0.75% sodium orthovanadate	+ 0.75% sodium tellurite
					An (DIN cup 4)0 value after 4 weeks, 40 DEG C	52s	61s66	65s85s	62s67s
pH0 after 4 weeks at 40 deg.C	9.2	9.59.3	9.59.3	9.39.1
					Transparent coating: binder + Additol XW 395 (1.8%) + H2O
An (DIN cup 4)0 value after 11 days, 40 DEG C	32s27s	39s39s	38s42s	38s39s
					PendulumHardness of 30 ' 120 deg.C, 30 ' 130 deg.C, 30 ' 140 deg.C	24s29s67s	27s34s64s	83s92s126s	29s35s55s
Initial solubility 1 '30' 120 deg.C 30 '130 deg.C 30' 140 deg.C	444433441144	444433441144	114401240014	444433441144
					Clear coat test after 11 days of storage at 40 DEG C
The hardness of the mixture is measured by swinging at 30 ' 120 ℃, 30 ' 130 ℃, 30 ' 140 DEG C	29s32s63s	31s32s70s	69s88s134s	32s36s55s
					Initial solubility 1 '30' 120 deg.C 30 '130 deg.C 30' 140 deg.C	444433441144	444433441144	114411440014	444433441144

The comparative examples demonstrate that the solvent resistance and pendulum hardness of the coating system increase differently after catalytic curing by vanadate compounds.

Examples 5 to 11

Catalyst coating system: desmodur ® VPLS 2253+ PES/PAC-polyol	Without catalyst	0.4% sodium metavanadate (in dispersion)	0.4% sodium metavanadate (in melt)	0.4% vanadium sulfate oxide VOSO4	0.4% sodium orthovanadate (in melt)	0.4% lithium orthovanadate (in the melt)
							An (DIN cup 4)0 value	143s	235s	189s	200s	270s	285s
pH0 value	8.1	8.6	8.6	8.3	9.0	8.9
							Transparent coating: binder + Additol ® XW 395 (1.8%) + H2O
An (DIN cup 4)0 value after 7 days, 40 DEG C	36s20s	36s21s	36s21s	38s22s	38s27s	37s28s
							Hardness was measured immediately after 7 days of shaking, 30 '80 ℃ at 40 ℃, 30' 90 ℃, 30 '100 ℃, 30' 110 ℃, 30 '120 ℃ at 30' 130 DEG C	The adhesive tape is 8s/8s11s/11s39s/34s43s/55s	Sticking 14s/n.m.45s/45s76s/63s129s/132s153s/151s	Sticking 13s/n.m.46s/43s78s/77s136s/141s148s/148s	Sticking 6s/n.m.20s/27s36s/53s106s/105s144s/129s	Sticking 8s/n.m.36s/36s53s/87s127s/146s146s/150s	Sticking 10s/n.m.39s/57s78s/73s143s/139s160s/147s

1 ' immediately/-7 days after initial solubility, 40 ℃ 30 ' 80 ℃ 30 ' 90 ℃ 30 ' 100 ℃ 30 ' 110 ℃ 30 ' 120 ℃ 30 ' 130 DEG C

--5555/55555555/55554344/43444344/4244

-5555/-4444/43442244/32440044/00440014/0044

-5555/-4444/43442144/32440044/00440024/0044

-5555/-5555/44554355/43551144/11440044/0144

-5555/-4455/43552244/43550044/01440014/0044

-5555/-4445/44442244/31440044/01440014/0124

The blocked polyisocyanate used was hexamethylene diisocyanate trimer blocked with 3, 5-dimethylpyrazole (Desmodur ® VP LS2253, Bayer AG). The polyol used was a polyester polyacrylate made from 1, 6-hexanediol, trimethylolpropane, peanut oil fatty acid, maleic anhydride and phthalic anhydride, with an OH number of 136, grafted with butyl acrylate, methyl methacrylate and hydroxypropyl methacrylate, and from polyester polyol and acrylic acid.

Examples 12 to 14

Catalyst: the coating system comprises the following steps: desmodur ® VP LS 2253/Z4470/LS 2056(Ureth. mod. polyester-polyol)	Without catalyst	0.4% sodium metavanadate (in dispersion)	0.4% sodium metavanadate (in melt)
				pH0 value	7.9	8.0	8.0
Transparent coating: aditol ® XW 395 (1.8%) + H2O
				An (DIN cup 4)0 value after 7 days, 40 DEG C	35s20s	36s19s	34s17s
Hardness was measured immediately after 7 days of shaking, 30 '80 ℃ at 40 ℃, 30' 90 ℃, 30 '100 ℃, 30' 110 ℃, 30 '120 ℃ at 30' 130 DEG C	Sticking to 57s/62s64s/81s109s/106s130s/133s	29s/n.m.50s/n.m.88s/113s116s/134s151s/167s153s/165s	35s/n.m.60s/n.m.91s/113s133s/146s167s/174s164s/172s
				1 'immediately/-7 days after initial solubility, 40 deg.C 30' 80 deg.C 30 '90 deg.C 30' 100 deg.C 30 '110 deg.C 30' 120 deg.C30’130℃	--5555/55555555/55555555/55553455/5455	5555/-5555/-5555/55553455/34551244/12441244/1244	5555/-5555/-5555/55553355/34552244/22441244/1144

The blocked polyisocyanate used was hexamethylene diisocyanate trimer blocked with 3, 5-dimethylpyrazole (Desmodur ® VP LS2253, Bayer AG) and isophorone diisocyanate (IPDI Z4470, Bayer AG, Leverkusen) was mixed in proportions before reacting with PES-PUR polyol as described below. The polyol used in this case is the so-called PES-PUR polyol (Bayhydrol VP LS 2056, Bayer AG, Leverkusen, OH content 1.7% by weight) composed of neopentyl glycol, propylene glycol, trimethylolpropane, adipic acid, isophthalic acid, dimethylolpropionic acid, hexamethylene diisocyanate, N-methylpyrrolidone, dimethylethanolamine and water. The solids content was 47%.

In the case of examples 6-15, the baking temperature of the 1K aqueous system was found to be reduced by about 20 ℃ in the presence of the vanadium catalyst.

Claims (14)

1. Polyurethane-based one-component baking systems, characterized in that they comprise:

(a) a blocked polyisocyanate;

(b) a polymer containing polyisocyanate reactive groups;

(c) one or more organic and/or inorganic compounds of vanadium having a vanadium oxidation state of at least + 4;

(d) water and/or an organic solvent or solvent mixture;

(e) if desired, further additives and auxiliaries,

wherein the amount of (a) + (b) is 20-89.9 parts by weight, the amount of (c) is 0.01-5 parts by weight, the amount of (d) is 10-70 parts by weight, the amount of (e) is 0-10 parts by weight, and the sum of the parts by weight of the components (a) - (e) is 100.

2. The system of claim 1, wherein the vanadium compound is selected from vanadyl (IV) acetylacetonate VO (C)₅H₇O₅)₂Bis (tetramethylpimelic acid) vanadyl VO (TMHD)₂Compounds of derivatives of vanadic acid and/or derivatives of orthovanadic acid.

3. The system according to claim 2, wherein the derivative of vanadic acid is selected from the group consisting of ammonium, lithium, sodium, potassium, magnesium or calcium vanadate and the derivative of orthovanadic acid is selected from the group consisting of lithium, sodium or potassium orthovanadate.

4. The system according to claim 1, wherein the vanadium compound is selected from the group consisting of lithium vanadate Li₃VO₄Sodium vanadate Na₃VO₄Potassium vanadate K₃VO₄Lithium metavanadate LiVO₃Sodium metavanadate NaVO₃KVO, potassium metavanadate₃Lithium orthovanadate, sodium orthovanadate or potassium orthovanadate.

5. The system of claim 1, wherein the vanadium compound is lithium vanadate or sodium vanadate.

6. The system as claimed in any of claims 1 to 5, characterized in that aliphatic isocyanates are used as blocked polyisocyanates (a).

7. The system as claimed in any of claims 1 to 5, characterized in that aromatic isocyanates are used as blocked polyisocyanates (a).

8. The system according to any of claims 1 to 5, characterized in that blocked polyisocyanates (a) based on 1, 6-hexanediisocyanate, isophorone diisocyanate, 4' -diisocyanatodicyclohexylmethane, derivatives and/or mixtures thereof are used.

9. The system according to any of claims 1 to 5, wherein the polyisocyanate (a) is subjected to a hydrophilization treatment.

10. A process for the preparation of a system as claimed in any of claims 1 to 9, characterized in that component (c) is added to components (a) and/or (b) and then dispersed or dissolved in component (d).

11. A process for the preparation of a system as claimed in any of claims 1 to 9, characterized in that component (c) is added to component (d) and then components (a) and/or (b) are dispersed or dissolved therein.

12. A process for the preparation of a system as claimed in any of claims 1 to 9, characterized in that component (c) is added to one or more of components (a), (b), (d) and/or (e) and then dispersed again.

13. Use of a system according to any one of claims 1 to 9 for the preparation of paints, inks and adhesives.

14. A substrate coated with a coating made from the system of any one of claims 1-8.