DE10243030A1 - Uretdione group containing compounds containing up to 10 mol.% isocyanurate structure, useful for polyurethanes, are prepared by dimerization of (cyclo)aliphatic isocyanates having exclusively secondary and/or tertiary isocyanate groups - Google Patents

Abstract

Uretdione group containing compounds (I) containing up to 10 mol.% isocyanurate structure (with respect to the sum of uretdione and isocyanurate groups) are prepared by dimerization of aliphatic and/or cycloaliphatic isocyanates (II) having exclusively secondary and/or tertiary isocyanate groups. An Independent claim is included for a process for the dimerization of isocyanates (II) in the presence of salt-type oligomerization catalysts that contain a 1,2,3- and/or 1,2,4-triazolate anion.

Description

The invention relates to new uretdione groups having compounds, a process for their preparation by Dimerization of aliphatic and / or cycloaliphatic isocyanates with exclusively secondary and / or tertiary bound isocyanate groups and the use of after this Process from diisocyanates with only secondary and / or tertiary bound isocyanate groups available Uretdione polyisocyanates as a starting component for polyurethane plastics, in particular as an isocyanate component for the production of uretdione powder coating crosslinkers.

The production of polyisocyanates with uretdione structure by catalytic dimerization and possibly simultaneous trimerization of monomeric aliphatic or cycloaliphatic diisocyanates is known. A comprehensive overview of the technically relevant dimerization process of the prior art and the catalysts or catalyst systems used can be found in J. Prakt. Chem. 336 (1994) 185-200.

Of the light-fast uretdione polyisocyanates, the linear dimerizates, ie those free of isocyanurate groups, in particular cycloaliphatic diisocyanates, are of great interest. They are preferred starting compounds for the production of blocking agent-free polyurethane (PUR) powder coating crosslinkers (e.g. EP-A 45 996 . EP-A 639 598 or EP-A 669 353 ).

While for linear catalytic dimerization of aliphatic and / or cycloaliphatic diisocyanates, which have at least one primarily bound isocyanate group, such as. B. 1,6-diisocyanatohexane (HDI) or 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate; IPDI), various processes exist (e.g. EP-A 45 995 . EP-A 317 744 . EP-A 735 027 and EP-A 896 973 ), some of which are also used on an industrial scale in the production of powder coating crosslinkers, are not known to date isocyanurate-free uretdione polyisocyanates made from aliphatic and / or cycloaliphatic diisocyanates with only secondary and / or tertiary-bound isocyanate groups. The usual dimerization catalysts show no or such a low activity with respect to such diisocyanates that even with the use of very high catalyst concentrations, the corresponding dimerizates cannot be produced or can only be produced in a negligibly low yield.

Although in some of the publications mentioned for the catalytic dimerization of isocyanates, e.g. B. in EP-A 178 520 . DE-A 34 20 114 . EP-A 317 744 or EP-A 896 973 , also disocyanates such as 2,4'- or 4,4'-diisocyanatodicyclohexylmethane, 1,3- or 1,4-diisocyanatocyclohexane, 1,3-diisoocyanatocyclobutane or 1,3-diisocyanato-2 (4) -methylcyclohexane as possible Starting compounds are mentioned, uretdione polyisocyanates from cycloaliphatic diisocyanates, which have no primarily bound isocyanate groups, have never been specifically described due to the lack of activity of the previously known dimerization catalysts.

Object of the present invention It was therefore a new process for the production of uretdione polyisocyanates from aliphatic and / or cycloaliphatic diisocyanates exclusively secondary and / or tertiary to provide bound isocyanate groups, the under Use of highly reactive and selective catalysts if possible supplies linear, preferably isocyanurate group-free products, as they are used as starting components for uretdione powder coating crosslinkers needed become.

Object of the present invention are aliphatic and / or cycloaliphatic by dimerization Isocyanates with only secondary and / or tertiary bound isocyanate groups available uretdione groups containing compounds with a molar proportion of isocyanurate structures, based on the sum of uretdione and isocyanurate groups, of maximum 10%.

Object of the present invention is also a process for the dimerization of compounds with only secondary and / or tertiary bound isocyanate groups in the presence of salt-like oligomerization catalysts, which contain 1,2,3- and / or 1,2,4-triazolate structures in the anion.

The invention also relates to the use of diisocyanates with only secondary and / or tertiary bound isocyanate groups available Uretdione polyisocyanates as starting components for polyurethane plastics, especially as isocyanate components for the production of uretdione powder coating crosslinkers.

Starting compounds for the process according to the invention are any aliphatic and / or cycloaliphatic mono- and diisocyanates with only secondary and / or tertiary-bonded isocyanate groups which can be obtained by any process, e.g. B. by phosgenation or by a phosgene-free route, for example by urethane cleavage. The term aliphatic or cycloaliphatic relates only to the type of carbon atoms carrying isocyanate groups, ie aromatic structures may also be present in the molecule. Suitable starting isocyanates are, for example, monoisocyanates, such as 2-isocyanatopropane, 2-isocyanato-2-methylpropane, isocyanatocyclohexane, 1-isocyanato-4-isopropenyl-1-methylcyclohexane, 4- (1-isocyanato-1-methylethyl) -1-methyl-1 -cyclohexene, 1,3-dimethyl-5-isocyanatoadamantane or 1- (1-isocyanato-1-methylethyl) -3-isopropenylbenzene (TMI), or diisocyanates such as 1,3- or 1,4-diisocyanatocyclohexane, 1,4 -Diisocyanato-3,3,5-trimethylcyclohexane, 1,3-diisocyanato-2-methylcyclohexane, 1,3-diisocyanato-4-methylcyclohexane, 1,8-diisocyanato-p-menthan, 4,4'-diisocyanato-1, 1'-bi (cyclohexyl), 4,4'-diisocyanato-3,3'-dimethyl-1,1'-bi (cyclohexyl), 4,4'-diisocyanato-2,2 ', 5,5'-tetramethyl -1,1'-bi (cyclohexyl), 4,4'-diisocyanatodicyclohexylmethane, 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane, 4,4'-diisocyanato-3,3 ', 5,5'-tetramethyldicyclohexylmethane , 1,3-diisocyanatoadamantane, 1,3-dimethyl-5,7-diisocyanatoadamantane, 1,3- and 1,4-bis (1-isocyanato-1-methylethyl) -benzene (TMXDI), bis (4- (1st -isocyanato-1-methyl- ethyl) phenyl) carbonate and any mixtures of such mono- and diisocyanates. Further also suitable starting isocyanates with exclusively secondary and / or tertiary-bound isocyanate groups can also be found, for example, in Justus Liebigs Annalen der Chemie Volume 562 (1949) pp. 75-136.

Preferred starting isocyanates for the process according to the invention are diisocyanates of the type mentioned. Particularly preferred starting compounds are 4,4'-diisocyanatodicyclohexylmethane, 1,3- or 1,4-diisocyanatocyclohexane or TMXDI. Most notably preferred starting isocyanate is 4,4'-diisocyanatodicyclohexylmethane.

enthalten, in welchen
R¹, R², R³ und R⁴ für gleiche oder verschiedenen Reste stehen und jeweils ein Wasserstoffatom, ein Halogenatom aus der Reihe Fluor, Chlor oder Brom oder eine Nitrogruppe, einen gesättigten oder ungesättigten aliphatischen oder cycloaliphatischen, einen gegebenenfalls substituierten aromatischen oder araliphatischen Rest, der bis zu 20 Kohlenstoffatome und gegebenenfalls bis zu 3 Heteroatome aus der Reihe Sauerstoff, Schwefel, Stickstoff enthalten und gegebenenfalls durch Halogenatome oder Nitrogruppen substituiert sein kann, bedeuten,
und wobei
R³ und R⁴ in Formel (II) auch gemeinsam mit den Kohlenstoffatomen des 1,2,3-Triazolatfünfringes anellierte Ringe mit 3 bis 6 Kohlenstoffatomen bilden können.Any salt-like compounds which contain 1,2,3- and / or 1,2,4-triazolate structures in the anion are used as oligomerization catalysts in the process according to the invention. These are compounds which have triazolate structures of the general formulas (I) and / or (II) in the anion

included in which
R ¹ , R ² , R ³ and R ^{4 represent} identical or different radicals and each represents a hydrogen atom, a halogen atom from the series fluorine, chlorine or bromine or a nitro group, a saturated or unsaturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic Radical which may contain up to 20 carbon atoms and optionally up to 3 heteroatoms from the series oxygen, sulfur, nitrogen and may optionally be substituted by halogen atoms or nitro groups,
and where
R ³ and R ⁴ in formula (II) can also form fused rings with 3 to 6 carbon atoms together with the carbon atoms of the 1,2,3-triazolate five-membered ring.

Preferred oligomerization catalysts are those which contain triazolate structures of the general formula (I) in which
R ¹ and R ^{2 represent} identical or different radicals and each represent a hydrogen atom, a halogen atom from the series fluorine, chlorine or bromine or a nitro group, a saturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical which has up to 12 carbon atoms and optionally contain up to 3 heteroatoms from the series oxygen, sulfur, nitrogen and can optionally be substituted by halogen atoms or nitro groups.

Also preferred as oligomerization catalysts are those which contain triazolate structures of the general formula (II) in the anion, in which
R ³ and R ⁴ stand for identical or different radicals and each represent a hydrogen atom, a halogen atom from the series fluorine, chlorine or bromine or a nitro group, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical which has up to 12 Contain carbon atoms and optionally up to 3 heteroatoms from the series oxygen, sulfur, nitrogen and may optionally be substituted by halogen atoms or nitro groups, and also form fused rings with 3 to 6 carbon atoms together with the carbon atoms of the 1,2,3-triazolate five-membered ring can.

Particularly preferred oligomerization catalysts for the inventive method are salts of 1,2,4-triazole, 1,2,3-triazole and / or 1,2,3-benzotriazole.

in welcher
E für Stickstoff oder Phosphor steht,
R⁵, R⁶, R⁷ und R⁸ für gleiche oder verschiedenen Reste stehen und jeweils ein Wasserstoffatom, einen gesättigten oder ungesättigten aliphatischen oder cycloaliphatischen, einen gegebenenfalls substituierten aromatischen oder araliphatischen Rest, der bis zu 24 Kohlenstoffatome und gegebenenfalls bis zu 3 Heteroatome aus der Reihe Sauerstoff, Schwefel, Stickstoff enthalten und gegebenenfalls durch Halogenatome oder Hydroxygruppen substituiert sein kann, bedeuten, und wobei
R⁸ auch für einen Rest der Formel (IV)

stehen kann, in welchem
X einen zweibindigen, gegebenenfalls substituierten aliphatischen, cycloaliphatischen, araliphatischen oder aromatischen Rest mit bis zu 12 Kohlenstoffatomen bedeutet und
R⁵, R⁶, R⁷ und E die oben angegebene Bedeutung haben.The catalysts to be used according to the invention can contain any cations as counterions to the catalytically active triazolate anions. Examples include alkali cations such as Li ⁺ , Na ⁺ and K ⁺ , alkaline earth cations such as Mg ²⁺ and Ca ²⁺ as well as ammonium or phosphonium cations, of the general formula (III),

in which
E represents nitrogen or phosphorus,
R ⁵ , R ⁶ , R ⁷ and R ^{8 represent} identical or different radicals and each represent a hydrogen atom, a saturated or unsaturated aliphatic or cycloaliphatic radical, an optionally substituted aromatic or araliphatic radical, which has up to 24 carbon atoms and optionally up to 3 heteroatoms the series contain oxygen, sulfur, nitrogen and may optionally be substituted by halogen atoms or hydroxyl groups, and where
R ⁸ also for a radical of the formula (IV)

can stand in which
X represents a divalent, optionally substituted aliphatic, cycloaliphatic, araliphatic or aromatic radical with up to 12 carbon atoms and
R ⁵ , R ⁶ , R ⁷ and E have the meaning given above.

Preferred cations are alkali ions or monovalent ammonium or phosphonium cations, of the general formula (III), in which
E represents nitrogen or phosphorus and
R ⁵ , R ⁶ , R ⁷ and R ^{8 represent} identical or different radicals and each represent a saturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic radical with up to 18 carbon atoms.

The process according to the invention salt-like compounds used as oligomerization catalysts are partly, e.g. in the form of their sodium salts, commercially available, otherwise according to common laboratory methods easily accessible.

These catalysts come in the process according to the invention generally in amounts of 0.01 to 3% by weight, preferably 0.1 up to 2% by weight, based on the amount of isocyanate used. The addition to the reaction mixture can be carried out in bulk; possibly can however, the catalysts are also in a suitable organic solvent solved be used. The degree of dilution of the catalyst solutions can be freely selected within a very wide range. Solutions are catalytically effective from a concentration of 0.01% by weight.

Suitable catalyst solvents are opposite, for example Solvents inert to isocyanate groups such as. Hexane, toluene, xylene, chlorobenzene, ethyl acetate, butyl acetate, Diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, ethylene glycol monomethyl or ethyl ether acetate, diethylene glycol ethyl and butyl ether acetate, Propylene glycol monomethyl ether acetate, 1-methoxypropyl-2-acetate, 3-methoxy-n-butyl acetate, Propylene glycol diacetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, Cyclohexanone, lactones such as β-propiolactone, γ-butyrolactone, ε-caprolactone and ε-methylcaprolactone, but also solvents such as N-methylpynolidone and N-methylcaprolactam, 1,2-propylene carbonate, Methylene chloride, dimethyl sulfoxide, triethyl phosphate or any Mixtures of such solvents.

If catalyst solvents are used at all in the process according to the invention, these are preferably those which carry groups which are reactive toward isocyanates and are incorporated in the reaction product. Examples of such solvents are monohydric or polyhydric simple alcohols, such as. B. methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, 2-ethyl-1-hexanol, ethylene glycol, propylene g lycol, the isomeric butanediols, 2-ethyl-1,3-hexanediol or glycerin; Ether alcohols such as e.g. B. 1-methoxy-2-propanol, 3-ethyl-3-hydroxymethyloxetane, tetrahydrofurfuryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl glycol, polyethylenethylene glycol, polyethyleneglycol glycol, Ester alcohols, such as. B. ethylene glycol monoacetate, propylene glycol monolaurate, glycerol mono- and diacetate, glycerol monobutyrate or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate; unsaturated alcohols such as B. allyl alcohol, 1,1-dimethyl-allyl alcohol or oleic alcohol; araliphatic alcohols such as e.g. B. benzyl alcohol; N-monosubstituted amides, such as. B. N-methylformamide, N-methylacetamide, cyanoacetamide or 2-pyrrolidinone or any mixture of such solvents.

If necessary, especially in the case the implementation of diisocyanates, the oligomerization reaction in the method according to the invention at the desired one Degree of conversion, for example if 10 to 60% of the originally in Have reacted from the starting mixture of the isocyanate groups present, canceled with the help of suitable catalyst poisons. Such catalyst poisons are, for example, inorganic acids such as hydrochloric acid, phosphorous Acid or Phosphoric acid, acid chlorides such as acetyl chloride, benzoyl chloride or isophthaloyl dichloride, sulfonic acids and sulfonic acid ester, like methanesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic, perfluorobutanesulphonic, dodecylbenzenesulfonic p-toluenesulphonate and ethyl p-toluenesulfonate, Mono- and dialkyl phosphates such as monotridecyl phosphate, dibutyl phosphate and dioctyl phosphate, but also silylated acids, such as trimethylsilyl methanesulfonate, trifluoromethanesulfonate, Phosphoric acid tris (trimethylsilyl ester) and phosphoric acid diethyl ester trimethylsilyl ester.

The amount needed to stop the reaction the catalyst poison depends on the molar amount the catalyst used; generally becomes an equivalent molar amount of the stopper, based on the one used at the beginning Oligomerization catalyst used. However, one may take into account while the catalyst losses occurring in the reaction can lead to Reaction stop even 20 to 80 mol% of the catalyst poison, based on the original molar amount of catalyst used, sufficient.

The catalyst poisons mentioned can both in bulk as well as in a suitable organic solvent solved be used. Suitable solvents are, for example, those already possible as catalyst solvents described solvents or their mixtures. The degree of dilution can can be freely selected within a very wide range, for example suitable solutions from a concentration of 10% by weight.

In addition to the organic solvents mentioned can in the method according to the invention also the abovementioned starting isocyanates with only secondary and / or tertiary bound isocyanate groups as solvents for the catalyst poisons serve if they are sufficiently inert to isocyanate groups, so that there are stable solutions have it made.

In the method according to the invention can optionally also additives customary in polyurethane chemistry as stabilizers can also be used. These are, for example, phenolic Antioxidants such as B. 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol and 3,5-di-tert-butyl-4-hydroxyanisole, or with alkyl and / or Aryl residues trisubstituted phosphite stabilizers, e.g. Triphenyl phosphite, tris (nonylphenyl) phosphite, Diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diisodecyl phenyl phosphite, diisooctyl octylphenyl phosphite, Phenylneopentyl glycol phosphite, 2,4,6-tri-tert-butylphenyl- (2-butyl-2-ethyl-1,3-propanediol) phosphite, Triisodecyl phosphite, trilauryl phosphite, tris (tridecyl) phosphite, Diisodecyl-pentaerythritol diphosphite, distearyl-pentaerythritol diphosphite, Bis (2,4-di-tert-butyl-phenyl) pentaerythritol diphosphite and tetraphenyl dipropylene glycol diphosphite or any mixtures such additives.

If these additives at all are used, they are the reaction mixture in an amount of up to 5% by weight, preferably up to 3% by weight, based on the amount added starting isocyanates added.

In a special embodiment of the method according to the invention serve liquid at room temperature Additives of the type mentioned, preferably the liquid phosphite stabilizers mentioned as a solvent for the used catalysts and / or catalyst poisons.

The method according to the invention is disregarded of optionally used catalyst and / or stopper solvents preferably carried out in bulk. But it can also if desired in the presence of further amounts of inert towards isocyanate groups solvents carried out become. For example, the catalyst solvents that are already possible above are suitable described non-reactive solvent or any mixtures of these solvents, which are optionally present in an amount of up to 80% by weight on the total amount of starting isocyanates and added solvent, can also be used.

To carry out the process according to the invention, the starting compounds mentioned are exclusively with isocyanate groups which are bonded only secondary and / or tertiary, optionally under an inert gas such as for example nitrogen, optionally in the presence of a suitable solvent and optionally a stabilizer of the type mentioned at a temperature of 0 to 100 ° C, preferably 20 to 60 ° C. Then an oligomerization catalyst or a solution of an oligomerization catalyst of the type mentioned above is added in the amount specified above and the reaction temperature, if appropriate by a suitable measure (heating or cooling) to a temperature of 20 to 100 ° C., preferably 25 to 80 ° C. set. The addition of the catalyst can in one or more portions but also continuously, for. B. with the aid of a suitable metering pump, over the entire reaction time. The reaction can optionally be terminated at a desired degree of oligomerization, for example when a degree of oligomerization of 10 to 60% is achieved, preferably 10 to 40%, by adding a catalyst poison of the type mentioned by way of example and, if appropriate, subsequently briefly heating the reaction mixture, for example to a temperature above 80.degree become. “Degree of oligomerization” is to be understood as the percentage of the isocyanate groups originally present in the starting mixture (these correspond to 100%), that during the reaction according to the invention (in particular by dimerization, in addition by trimerization and, if the described, for example alcoholic, catalyst solvents are used, by reaction with isocyanate groups, for example under urethanization). The degree of oligomerization mentioned is generally achieved after a reaction time of 30 minutes to 8 hours, preferably 1 to 6 hours.

Preferably the reaction mixture subsequently by thin film distillation when you press 0.001 to 20 mbar, preferably 0.01 to 5 mbar, if possible gentle conditions, for example at a temperature of 120 to 220 ° C, preferably from 140 to 190 ° C, of volatile Ingredients (excess monomer Starting isocyanates and any non-reactive ones used solvents and stabilizers).

In another, but less preferred embodiment of the method according to the invention the aforementioned volatile Components by extraction with suitable inert to isocyanate groups solvents for example aliphatic or cycloaliphatic hydrocarbons such as pentane, hexane, heptane, cyclopentane or cyclohexane from the oligomerization product separated.

This way you get in dependence on the type of chosen Starting isocyanates of bright or almost colorless uretdione groups containing products, the content of isocyanate groups depending of the degree of oligomerization up to 25.4% by weight, preferably up to 23.9% by weight, with exclusive Use of diisocyanates as starting compounds from 11.2 to 25.4% by weight, preferably from 12.8 to 23.9% by weight, and less than 5% by weight, preferably less than 2% by weight, particularly preferred contain less than 1 wt .-% of monomeric starting isocyanates. The molar proportion of isocyanurate structures in the process products according to the invention is based on the sum of uretdione and isocyanurate groups preferably at most 10%, particularly preferably at most 8% and very particularly preferably at most 5%.

The distillates that come alongside unreacted monomeric starting isocyanates optionally used solvent and stabilizers as well as if a catalyst poison is not used optionally containing active catalyst can be easily re-used Oligomerization can be used.

• 1. Das erfindungsgemäße Verfahren gestattet auf einfache Weise unter Verwendung sehr geringer Katalysatorkonzentrationen innerhalb sehr kurzer Reaktionszeiten erstmals die Dimerisierung sekundär und/oder tertiär gebundener Isocyanatgruppen.
• 2. Die nach diesem Verfahren aus Diisocyanaten mit ausschließlich sekundär und/oder tertiär gebundenen Isocyanatgruppen erhältlichen Uretdionpolyisocyanate bzw. deren Lösungen in monomeren Ausgangsdiisocyanaten stellen wertvolle Ausgangsmaterialien zur Herstellung von Polyurethankunststoffen nach dem Polyadditionsverfahren, bevorzugt zur Herstellung von Ein- oder Zweikomponenten-Polyurethanlacken, dar. Sie können dabei auch in mit aus der Polyurethanchemie an sich bekannten Blockierungsmitteln blockierter Form als Vernetzerkomponenten für Einkomponenten-Einbrennlacke eingesetzt werden. Geeignete Blockierungsmittel sind beispielsweise die aus der Polyurethanchemie als Blockierungsmittel für Isocyanatgruppen bekannten Oxime, wie z. B. Acetonoxim, Butanonoxim und Cyclohexanonoxim, Lactame, wie ε-Caprolactam, C-H-acide Verbindungen, wie Malonsäurediethylester und Acetessigester, N-Heterocyclen, wie 1,2,4-Triazol, Dimethyl-1,2,4-triazol, 3,5-Dimethylpyrazol und Imidazol sowie beliebige Gemische dieser Blockierungsmittel.

If necessary, in the process according to the invention after proportionate catalytic oligomerization and termination of the reaction at the desired degree of oligomerization by adding a catalyst poison, it is also possible to dispense with the removal of the excess, unreacted starting diisocyanate. In this case, the process products obtained are light-colored solutions of compounds containing uretdione groups in up to 70% by weight of monomeric starting isocyanate.

• 1. The process according to the invention allows for the first time the dimerization of secondary and / or tertiary-bound isocyanate groups in a simple manner using very low catalyst concentrations within very short reaction times.
• 2. The uretdione polyisocyanates obtainable by this process from diisocyanates with only secondary and / or tertiary bonded isocyanate groups or their solutions in monomeric starting diisocyanates represent valuable starting materials for the production of polyurethane plastics by the polyaddition process, preferably for the production of one- or two-component polyurethane paints. They can also be used as crosslinking components for one-component stoving enamels in the form of blocking agents known per se from polyurethane chemistry. Suitable blocking agents are, for example, the oximes known from polyurethane chemistry as blocking agents for isocyanate groups, such as, for. B. acetone oxime, butanone oxime and cyclohexanone oxime, lactams such as ε-caprolactam, CH-acidic compounds such as diethyl malonate and acetoacetic ester, N-heterocycles such as 1,2,4-triazole, dimethyl-1,2,4-triazole, 3, 5-dimethylpyrazole and imidazole and any mixtures of these blocking agents.

The according to the inventive method from diisocyanates with only secondary and / or Uretdione polyisocyanates obtainable with tertiary bound isocyanate groups are particularly suitable as starting components for the production of uretdione powder coating crosslinkers.

Examples

The following examples are for further explanation the invention. The term "degree of oligomerization" denotes the percentage of the isocyanate groups originally present in the starting mixture (these correspond to 100%) during the implementation according to the invention, for example by dimerization and trimerization becomes.

manufacturing of the catalysts

Catalyst 1: sodium 1,2,4-triazolate

200 ml of dry methanol and 48 ml of a 30% methanolic solution of natum methoxide, corresponding to 0.25 mol of sodium methoxide, were placed under dry nitrogen in a three-necked flask with mechanical stirrer, internal thermometer and reflux condenser. 17.4 g (0.25 mol) of 1,2,4-triazole were added in portions at room temperature. After the addition of the 1,2,4-triazole was complete, the reaction mixture was stirred at the reflux temperature for 4 hours. The solvent was then distilled off under reduced pressure and 200 ml of methylene chloride were added to the remaining oily residue at room temperature. The mixture was stirred at room temperature for 15 min and the product which had precipitated out as a solid was filtered off. 22.5 g of sodium 1,2,4-triazolate (yield: 98% of theory) were obtained in the form of a colorless powder. According to the ¹ H-NMR spectrum, the product was pure and free of 1,2,4-triazole.

Catalyst 2: sodium 1,2,3-triazolate

17.4 g (0.25 mol) of 1,2,3-triazole were reacted in 200 ml of methanol with an equivalent amount of methanolic sodium methanolate solution by the process described for catalyst 1. The reaction mixture was worked up as described above and 22.4 g of sodium 1,2,3-triazolate (yield: 98% of theory) were obtained in the form of an almost colorless powder. According to the ¹ H-NMR spectrum, the product was pure and free of starting material.

Catalyst 3: sodium benzotriazolate

29.8 g (0.25 mol) of benzotriazole were reacted according to the procedure described for catalyst 1 in 200 ml of methanol with an equivalent amount of methanolic sodium methanolate solution. The reaction mixture was worked up as described above and 34.2 g of sodium benzotriazolate (yield: 97% of theory) were obtained in the form of an almost colorless powder. According to the ¹ H-NMR spectrum, the product was pure and free of starting material.

Catalyst 4: tetrabutylphosphonium 1,2,4-triazolate

In a three-neck flask with mechanical stirrer, internal thermometer and reflux condenser, 18.0 g of a 30% strength methanolic sodium methoxide solution, corresponding to 0.1 mol of sodium methoxide, were placed at room temperature under dry nitrogen. A solution of 6.9 g (0.1 mol) of 1,2,4-triazole in 20 ml of methanol was added dropwise in the course of 20 minutes, the reaction mixture was stirred for an hour and then 41.3 g ( 0.1 mol) of a 71.4 wt .-% solution of tetrabutylphosphonium chloride in isopropanol (CYPHOS ^® 443P, Fa. Cytec Industries, Neuss) to. Immediately after the beginning of the phosphonium salt addition, the excretion of sodium chloride began. The reaction mixture was stirred for a further hour at room temperature, filtered and finally concentrated on a rotary evaporator at a bath temperature of 40 ° C. and a pressure of approx. 1 mbar to an amount of approx. 50 ml. The residue was filtered again and 42.5 g of a clear, almost colorless solution of tetrabutylphosphonium-1,2,4-triazolate were obtained in a mixture of methanoisopropanol. The content of active catalyst after acidimetric titration with 0.1 N HCl against phenolphthalein was 73.0% by weight, the gas-chromatographically (GC) determined ratio of methanol to isopropanol was 25.4: 74.6% (area% ).

Catalyst 5: methyl trioctylammonium 1,2,4-triazolate

According to the process described for catalyst 4, 6.9 g (0.1 mol) of 1,2,4-triazole were dissolved in 20 g of methanol first with 18.0 g (0.1 mol) of 30% methanolic sodium methoxide solution and subsequently 80.6 g of a 50% solution of methyltrioctylammonium chloride (Aliquat ^® 336, Cognis Germany GmbH & Co. KG, Diisseldorf) in methanol, corresponding to 0.1 mol methyltrioctylammonium implemented. After filtration, removal of the solvent on a rotary evaporator and renewed filtration, 40.3 g of methyltrioctylammonium-1,2,4-triazolate were obtained as a clear, light yellow liquid. The content of active catalyst after acidimetric titration with 0.1 N HCl was 92.3% by weight.

Catalyst 6: trihexyltetradecylphosphonium 1,2,4-triazolate

In a three-necked flask with mechanical stirrer, internal thermometer and reflux condenser, 180 g of a 30% methanolic sodium methanolate solution, corresponding to 1.0 mol of sodium methoxide, were placed at room temperature under dry nitrogen. A solution of 69 g (1.0 mol) of 1,2,4-triazole in 200 ml of methanol was added dropwise within 45 min and the reaction mixture was stirred for 12 hours. Was then added dropwise over 1 hour a solution of 518 g (1.0 mol) trihexyltetradecylphosphonium chloride (CYPHOS ^® 3653, Fa. Cytec Industries, Neuss, Germany) dissolved in 60 g of methanol. Immediately after the beginning of the phosphonium salt addition, the excretion of sodium chloride began. The reaction mixture was stirred overnight at room temperature, the precipitated sodium chloride was filtered off and the solvent was then distilled off in a commercially available thin-film evaporator at a temperature of 50 ° C. and a pressure of about 0.3 mbar. The residue was filtered again and 510 g (yield: 92.6% of theory) of trihexyltetradecylphosphonium-1,2,4-triazolate were obtained as a clear, almost colorless liquid with a viscosity of 570 mPas (23 ° C.) and one Refractive index n _D ²⁰ of 1.4821. The residual methanol content was 0.1% by weight.

example 1

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were at 30 ° C under dry nitrogen and stirring with a solution of 2 g (0.022 mol) of sodium 1,2,4-triazolate (catalyst 1) in 25 ml Dimethyl sulfoxide (DMSO) was added, whereupon the temperature of the reaction mixture rose to 39 ° C. due to the heat of reaction liberated. After a reaction time of 60 minutes, during which the exotherm subsided, the NCO content of the reaction mixture had dropped to 26.3% by weight, corresponding to a degree of oligomerization of 15.6%. The catalyst was now deactivated by adding 4.6 g (0.022 mol) of dibutyl phosphate. The resulting turbidity was filtered off and the clear, colorless reaction mixture was freed from volatile constituents (excess diisocyanate and catalyst solvent) using a thin-layer evaporator at a temperature of 155 ° C. and a pressure of 0.2 mbar. A colorless uretdione polyisocyanate with a free NCO group content of 14.1% by weight, a monomeric 4,4'-diisocyanatodicyclohexylmethane content of 0.4% by weight and a viscosity (according to DIN 53 018) of more than 200,000 mPas (23 ° C) and a color number (APHA), determined on a 10% strength by weight solution in methylene chloride, of 12. According to ¹³ C-NMR spectroscopy, the molar ratio of uretdione to isocyanurate structures was 98. 4: 1.6.

Example 2

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were at 30 ° C under dry nitrogen and stirring with a solution of 2 g (0.022 mol) of sodium 1,2,3-triazolate (catalyst 2) in 25 ml Dimethyl sulfoxide (DMSO) was added, whereupon the temperature of the reaction mixture rose to 39 ° C. due to the heat of reaction liberated. After a reaction time of 60 minutes, during which the exotherm subsided, the NCO content of the reaction mixture had dropped to a value of 26.7% by weight, corresponding to a degree of oligomerization of 14.3%. The catalyst was then deactivated by adding 4.6 g (0.022 mol) of dibutyl phosphate and the reaction mixture was worked up as described in Example 1. A highly viscous colorless uretdione polyisocyanate with a free NCO group content of 14.1% by weight, a monomeric 4,4'-diisocyanatodicyclohexylmethane content of 0.5% by weight and a color number (APHA) was determined a 10% by weight solution in methylene chloride, of 14. The molar ratio of uretdione to isocyanurate structures was 99.1: 0.9 according to ¹³ C-NMR spectroscopy.

Example 3

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylethane were at 30 ° C under dry nitrogen and stirring with a solution of 3.0 g (0.021 mol) of sodium benzotriazolate (catalyst 3) in 40 ml of dimethyl sulfoxide (DMSO) added, whereupon the temperature of the reaction mixture rose to 37 ° C. due to the heat of reaction released. After a reaction time of 60 minutes during which the exotherm subsided, the NCO content of the reaction mixture was 26.5% by weight, corresponding to one Degree of oligomerization of 13.6%, decreased. The catalyst was then deactivated by adding 4.4 g (0.021 mol) of dibutyl phosphate and the reaction mixture was worked up as described in Example 1. A highly viscous colorless uretdione polyisocyanate with a free NCO group content of 14.0% by weight, a monomeric 4,4'-diisocyanatodicyclohexylmethane content of 0.5% by weight and a color number (APHA) was determined of a 10% by weight solution in methylene chloride, of 21. The molar ratio of uretdione to isocyanurate structures was 96.4: 3.6 according to ¹³ C-NMR spectroscopy.

Example 4

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were at 30 ° C under dry nitrogen and stirring with a solution of 2.3 g (5.1 mmol) of catalyst 4 (tetrabutylphosphonium-1,2,4- triazolate in methanol / isopropanol) ver, whereupon the temperature of the reaction mixture rose to 42 ° C. due to the heat of reaction released. After the exothermic reaction had subsided, a further 2.3 g (5.1 mmol) of catalyst solution were post-catalyzed after 40 minutes. After a total reaction time of 1 hour 25 minutes, the NCO content in the reaction mixture was 26.5% by weight, corresponding to a degree of oligomerization of 13.6%. The catalyst was then deactivated by adding 2.15 g (10.2 mmol) of dibutyl phosphate and the reaction mixture was freed from excess diisocyanate by thin-layer distillation as described in Example 1. A highly viscous pale yellow uretdione polyisocyanate was obtained with a free NCO group content of 14.2% by weight, a monomeric 4,4'-diisocyanatodicyclohexylhexane content of 0.4% by weight and a color number (APHA) a 10% by weight solution in methylene chloride, of 17. The molar ratio of uretdione to isocyanurate structures was 97.2: 2.8 according to ¹³ C-NMR spectroscopy.

Example 5

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were degassed for 1 hour in vacuo (2 mbar), then aerated with dry nitrogen and heated to 30 ° C. While stirring, 8 g (0.02 mol) of catalyst 5 (methyltrioctylammonium-1,2,4-triazolate) were added, the reaction mixture heating to 43 ° C. due to the heat of reaction released. After a reaction time of 70 minutes, during which the exotherm subsided, the NCO content in the reaction mixture was 26.6% by weight, corresponding to a degree of oligomerization of 16.2%. The catalyst was then deactivated by adding 4.2 g (0.2 mol) of dibutyl phosphate and the resulting clear, colorless mixture was freed from excess diisocyanate by thin-layer distillation as described in Example 1. A highly viscous, almost colorless uretdione polyisocyanate with a free NCO group content of 14.0% by weight, a monomeric 4,4'-diisocyanatodicyclohexylmethane content of 0.3% by weight and a color number (APHA) was determined on a 10% by weight solution in methylene chloride, of 10. The molar ratio of uretdione to isocyanurate structures was 99.3: 0.7 according to ¹³ C-NMR spectroscopy.

Example 6

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were degassed for 1 hour in vacuo (2 mbar), then aerated with dry nitrogen and heated to 30 ° C. Subsequently, 12 g (0.022 mol) of catalyst 6 (trihexyltetradecylphosphonium-1,2,4-triazolate) were added continuously over a reaction time of 3 hours with the aid of an infusion laboratory pump (KDS 100, KD Scientific, Boston). After a subsequent stirring time of 30 minutes, the NCO content in the reaction mixture was 26.2% by weight, corresponding to a degree of oligomerization of 17.1%. The catalyst was then deactivated by adding 4.6 g (0.022 mol) of dibutyl phosphate and the resulting clear, colorless mixture was freed from excess diisocyanate by thin-layer distillation as described in Example 1. A highly viscous, almost colorless uretdione polyisocyanate with a free NCO group content of 14.2% by weight, a monomeric 4,4'-D-isocyanatodicyclohexylmethane content of 0.5% by weight and a color number (APHA) was determined on a 10% by weight solution in methylene chloride, of 11. According to ¹³ C-NMR spectroscopy, the product only contained uretdione groups. No isocyanurate structures were detectable.

Comparative Example 1 (according to EP-A 317 744 )

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylethane were at room temperature with dry nitrogen and stirring with 20 g (2% by weight) of 4-dimethylaminopyridine (DMAP) were added as a catalyst. After 5 days, the almost colorless reaction mixture remained unchanged NCO content of 31.4% by weight. Neither was found in the IR spectrum Reference to uretdione groups.

Comparative Example 2 (according to EP-A 317 744 )

1000 g of 4,4'-diisocyanatodicyclohexylethane were as described in Comparative Example 1 with 20 g (2 wt .-%) DMAP offset and then for 5 days to 50 ° C heated. The pale yellow reaction mixture showed an unchanged NCO content of 31.4% by weight. There was no evidence in the IR spectrum Uretdione.

Comparative Example 3 (according to EP-A 317 744 )

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were mixed with 100 g (10% by weight) of 4-dimethylaminopyridine (DMAP) as a catalyst at room temperature under dry nitrogen. After 5 days, a very weak band at 1760 cm ^{-1 could} be seen in the IR spectrum, which can be interpreted as an indication of the presence of small amounts of uretdione groups. The NCO content of the light yellow reaction mixture had dropped from 29.0 to 28.6% by weight, which corresponds to a degree of oligomerization of 1.4%.

Comparative Example 4 (according to EP-A 317 744 )

1000 g (3.82 mol) of 4,4'-diisocyanatodicyclohexylmethane were at room temperature with dry nitrogen and stirring with 50 g (5 wt .-%) hexamethylphosphoric triamide as a catalyst added. After 5 days the almost colorless reaction mixture showed unchanged an NCO content of 31.3% by weight. There was no evidence in the IR spectrum Uretdione.

The comparative examples show that the known catalysts for highly selective dimerization of isocyanates in contrast to the catalysts of the process according to the invention towards secondary bound Isocyanate groups no or one even in high concentrations very little, completely insufficient for the technical production of uretdione polyisocyanates activity exhibit.

Examples 7 and 8

According to that described in Example 6 500 g of 4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane (Example 7) and TMXDI (Example 8) at 30 ° C oligomerized in the presence of catalyst 6. The reaction mixtures were each with equimolar Amount of dibutyl phosphate stopped and then by thin film distillation worked up. The following table shows the used ones Amounts of catalyst and stoppers (each in% by weight based on the amount of starting isocyanate used), reaction times and Characteristics of the resins obtained after thin film distillation.

Example 9

100 g of cyclohexyl isocyanate were mixed with 1% by weight of catalyst 6 at room temperature under dry nitrogen. After 24 hours at room temperature, the NCO content had dropped from an initial 33.6% by weight to 29.9% by weight, corresponding to an oligomerization rate of 10.1%. According to the IR spectrum, only uretdione structures (band at 1760.7 cm ^-1 ) had formed; isocyanurate structures were not detectable.

Example 10

100 g of tert-butyl isocyanate were at room temperature under dry nitrogen with 1 wt .-% catalyst 6 added. After 24 h at room temperature, the NCO content had dropped from an initial 42.0% by weight to 35.7% by weight, corresponding to a degree of oligomerization of 15.0%. According to the IR spectrum, only uretdione structures (band at 1763.5 cm ^–1 ) had formed; isocyanurate structures were not detectable.

Claims (11)

Compounds containing uretdione groups a molar proportion of isocyanurate structures, based on the sum of uretdione and isocyanurate groups, of a maximum of 10%, obtainable from Dimerization of aliphatic and / or cycloaliphatic isocyanates with exclusively secondary and / or tertiary bound isocyanate groups. Compounds according to claim 1, by dimerization aliphatic and / or cycloaliphatic Diisocyanates with only secondary and / or tertiary bound isocyanate groups available are. Compounds according to claim 2, which are obtainable by dimerization of 4,4'-diisocyanatodicyclohexylmethane. Process for the dimerization of compounds with exclusively secondary and / or tertiary-bound isocyanate groups in the presence of salt-like oligomerization catalysts which contain 1,2,3- and / or contain 1,2,4-triazolate structures. A method according to claim 4, characterized in that salt-like compounds are used as oligomerization catalysts, the triazolate structures of the general formulas (I) and / or (II) in the anion

contain, in which R ¹ , R ² , R ³ and R ⁴ stand for identical or different radicals and each have a hydrogen atom, a halogen atom from the series fluorine, chlorine or bromine or a nitro group, a saturated or unsaturated aliphatic or cycloaliphatic, one optionally Substituted aromatic or araliphatic radical which contain up to 20 carbon atoms and optionally up to 3 heteroatoms from the series oxygen, sulfur, nitrogen and can optionally be substituted by halogen atoms or nitro groups, where R ³ and R ⁴ together with the carbon atoms of the 1,2,3-triazolate five-membered rings can form fused rings with 3 to 6 carbon atoms. Process according to Claim 5, in which salt-like compounds are used as oligomerization catalysts which contain triazolate structures of the general formula (I) in the anion, in which R ¹ and R ² stand for identical or different radicals and each have a hydrogen atom, a halogen atom from the fluorine series , Chlorine or bromine or a nitro group, a saturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic radical which contain up to 12 carbon atoms and optionally up to 3 heteroatoms from the series oxygen, sulfur, nitrogen and are optionally substituted by halogen atoms or nitro groups can mean. A process according to claim 5, in which the oligomerization catalysts used are salt-like compounds which contain triazolate structures of the general formula (II) in the anion, in which R ³ and R ⁴ stand for identical or different radicals and each have a hydrogen atom, a halogen atom from the fluorine series , Chlorine or bromine or a nitro group, a saturated or unsaturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic radical which contains up to 12 carbon atoms and optionally up to 3 heteroatoms from the series consisting of oxygen, sulfur, nitrogen and optionally by halogen atoms or nitro groups may be substituted, mean, or together with the carbon atoms of the 1,2,3-triazolate five-membered ring form fused rings having 3 to 6 carbon atoms. Method according to claim 5, in which salts of 1,2,4-triazole as oligomerization catalysts, 1,2,3-triazole and / or 1,2,3-benzotriazole can be used. A method according to claim 4, characterized in that one uses oligomerization catalysts, the alkali ions or monovalent ammonium or phosphonium cations of the general formula (III)

contain in which E represents nitrogen or phosphorus and R ⁵ , R ⁶ , R ⁷ and R ^{8 represent} identical or different radicals and each represent a saturated aliphatic or cycloaliphatic, an optionally substituted aromatic or araliphatic radical having up to 18 carbon atoms. Use of the compounds containing uretdione groups according to claim 1 as starting components in the production of polyurethane plastics. Use of the polyisocyanates containing uretdione groups according to claim 1 as starting components in the production of uretdione powder coating crosslinkers.