MXPA00000814A - Powder coating crosslinking agents containing uretdione groups and free isocyanate - Google Patents

Abstract

The present invention relates to polyaddition compounds, which are solid below 40 C. and liquid above 125 C., are prepared by the reaction of an isocyanate component containing uretdione groups with a polyol containing ester and/or carbonate groups, other than hydroxypivalic acid neopentylglycol ester, and havea) an average isocyanate functionality of 2.0 to 8.0 and a content of free isocyanate groups (calculated as NCO;molecular weight=42) of 2.1 to 6.0 wt.%,b) a content of uretdione groups (calculated as C2N2O2;molecular weight=84) of 10 to 19 wt.%,c) a content of urethane groups (calculated as -NH-CO-O;molecular weight=59) of 10 to 17 wt.%andd) a content of ester groups -CO-O (calculated as -CO-O;molecular weight=44) and/or carbonate groups -O-CO-O (calculated as -CO-O;molecular weight=44) of 1 to 17 wt.%. The present invention also relates to a process for the preparation of these polyaddition compounds to two-component polyurethane powder coating compositions containing these polyaddition compounds as the crosslinking agent and isocyanate-reactive compounds as the binder.

Description

RETICUA TES OF POWDERED LACQUER, CONTAINING URETODIONA GROUPS AND FREE ISOCLANATOS GROUPS Field of the Invention The invention relates to novel polyaddition compounds containing uretdione groups, to a process for their production and to their use as starting components in the preparation of polyurethane plastics, in particular as crosslinking agent for hot crosslinkable powder coatings. .

Description of the Prior Art. As crosslinkers lacking blocking agents for highly weather-resistant polyurethane (PUR) powder coatings, polyaddition compounds containing uretdione groups are now increasingly used. The thermal retrodissociation of the uretdione structures in free isocyanate groups and their subsequent reaction with a hydroxy-functional binder is used as crosslinking principle in these compounds.

Although the powder coating crosslinkers have been known for a long time, they have not been Ref.: 32581 imposed so far in the market decisively. The reason for this lies, among other things, on the one hand in the comparatively low isocyanate content of the products commercially available so far and on the other hand in their low average functionalization which frequently reaches even less than 2.0. With regard to a sufficient crosslinking density, in lacquers and equivalent coatings with good stability properties, however, precisely crosslinking components with a high NCO content and as much functionalization as possible amounting to at least 2 are desired.

EP-A 45 994 discloses reaction products of a linear difunctional IPDI-uretdione and defect amounts of simple diols, which optionally have ether oxygen, as powder coating crosslinkers lacking blocking agents. These polyaddition products which can contain terminally up to 8% by weight of unblocked free isocyanate groups are in effect characterized by high isocyanate contents (sum of the free isocyanate groups present and in an internally blocked form of uretdione groups) and functionalization 2.0, but its production, especially on an industrial scale, is difficult.

Since the retrodissociation of the thermolabile urethodione structures in the presence of hydroxy-functional co-reactants already takes place markedly at 110 ° C, this temperature should not be exceeded as much as possible in the synthesis of polyaddition compounds containing uretdione groups. However, in this temperature range the products described in EP-A 45 994 have such high melt viscosities that limit their possibility of melt production due to the insufficient capacity to be stirred on an industrial scale. On an industrial scale, such uredodionic crosslinking agents can only be manufactured in solvents which are inert towards isocyanate groups. The coadjuvant solvent must then be separated in a further process step. A solvent-free manufacturing process described in EP-A 669 354 for such polyaddition compounds in which the reactants can be reacted in reaction screws or special extruders subjected to high cutting forces is on the contrary very expensive in terms of appliances.

The main drawback of the polyaddition products described in EP-A 45 994, however, lies in the relatively high content of unblocked free isocyanate groups, which already during the manufacture of powder coatings, usually by melt extrusion at approximately 100 ° C, react with the hydroxy-functional binder. These pre-crosslinked powder coatings in this way show in the baking process such unfavorable rheological behavior that they harden forming coatings with only moderate optical properties, especially with totally insufficient leveling.

The problem of undesired pre-crosslinking is in principle found for all powder coat hardeners having a high content of free isocyanate groups. For example, in the powder lacquer crosslinkers lacking blocking agents described in EPA 45 996 and EP-A 45 998 from IPDI-uretdione and simple diols, the free isocyanate groups in terminal position are therefore reacted less partially with monoamines or monoalcohols. In this way the disturbing pre-reaction in the extruder can be effectively avoided, however the chain interruption with a monofunctional compound clearly reduces the total isocyanate content, at the same time it reduces the average functionalization to a value less than 2. In addition to this the products of these two publications also present in the range of the retrodisocytization temperatures of the uretdione groups melt viscosities still so high that they can only be prepared safely and reproducibly in solution or according to the expensive process of EP-A 669 354 .

Patent EP-A 639 598 relates to the manufacture of urethodic powder lacquer crosslinkers using chain extenders containing ester or carbonate groups. The products that can be obtained according to this process already have, at temperatures only slightly above the melting point, melt viscosities so low that, for the first time, production without solvent was possible in simple agitated equipment. Also, the uretdionic crosslinking agents described in EP-A 720 994 in which dimerodiols are used for chain elongation have low melt viscosities, sufficient for solvent-free production. Due to the relatively high molecular weight of the chain extenders used, the products of both publications still have, compared to those of EP-A 45 996, reduced isocyanate contents.

According to the disclosure in EP-A 669 353, linear IPDI dimers with excess amounts of diols and / or polyesterdiols can be prepared by solvent-free reaction in intensive kneaders, special polyurethanes with terminal hydroxyl groups containing uretdione groups of a 2.0 average functionalization. The use of at least trifunctional polyols and / or branched polyester polyols makes possible, as indicated in EP-A 825 214 or in EP-A 780 417, even the production of uretdionic crosslinkers with terminal OHs with functionalization between 2 and 3 or > 3. However, the disadvantage of these polyaddition compounds is that the hydroxyl groups present in the crosslinker molecule under baking conditions also react with urethanization and thus clearly reduce the advantage of high functionalization. internally blocked NCO content arranged for crosslinking.

EP-A 760 380 discloses uretodionic crosslinking agents for powder coatings based on HDI dimers which optionally contain isocyanurate groups. These products have, due to the contained uretodione groups, very high NCO latent, but show, as usual for HDI polyisocyanates, such a low tendency to crystallization that even with an intense cooling only harden completely after hours or even of days. Manufacturing on an industrial scale is therefore not practicable.

The polyaddition products containing uretdione and isocyanurate groups of an IPDI dimer prepared by catalysis with tpalkylphosphine, diols and / or diacmas dissecundates as chain extenders and optionally monoalcohols or monoamines are the subject of EP-A 790 266. these products may have, in the case of high functionalization, relatively high amounts of isocyanate groups and consequently a high total isocyanate content. Due to the branched starting polusocyanate, which is formed as a function of the respective dimerization and processing conditions in addition to the respective strongly fluctuating amounts of trimepping, the manufacture is nevertheless achieved only after a laborious determination of the exact functionalization and also only in solution organic However, hitherto no uredodeionic powder coating crosslinker is known to meet all the requirements of the practice and to have particularly high total isocyanate group contents with the greatest possible crosslinking functionalization and at the same time to be easily accessible by a simple procedure.

It has therefore been the object of the present invention to provide powder lacquer crosslinkers containing uretdione groups which do not have the drawbacks described above in the prior art.

This objective has been achieved by providing the polyaddition compounds and the process for their production according to the invention described in more detail below. The polyaddition compounds according to the invention described in more detail below are based on the surprising observation that suitable compounds can be obtained as powder lacquer crosslinkers by reacting uredodionic polyisocyanates with defect molar amounts of polyols having ester groups and / or carbonate, in a solvent-free process, in simple device arrangements that provide, in combination with conventional commercial powder coating binders, despite a high content of free isocyanate groups, coatings characterized by outstanding leveling and gloss very high. This was surprising, since according to what is disclosed in EP-A 639 598 it was thought that such polyaddition compounds having ester and / or carbonate groups would only be suitable for use as crosslinkers of powder coatings up to an isocyanate group content. free of 2.0% by weight at the most, especially since it is also stated in EP-A 760 380 (page 7, lines 34 to 40) that products with such a high content of unblocked isocyanate groups lead, because to the inevitable pre-crosslinking in the extruder, to coatings with unsatisfactory optical properties.

Although EP-A 669 354 is indicated as starting compounds suitable for the solvent-free production of polyaddition compounds containing uretdione groups in intensive kneaders within a long series of simple diols, also, the neopentyl glycol ester of hydroxypivalic acid Nor could the person skilled in the art draw from this publication any information on the possibility of transforming uretodionic polyisocyanates with polyols containing ester and / or carbonate groups also into simple stirring apparatuses in molten uredodeionic crosslinkers of powder coatings containing very high isocyanate totals, which, despite a considerable proportion of free isocyanate groups, provided with conventional polyester polyols lacquer films of outstanding quality. Rather, it can be said that by exclusively using the neopentyglycol ester of hydroxypivalic acid as a chain extender with ester group content, the urethodic acid crosslinkers of powder coatings with free isocyanate groups produced, lead, unlike the products of the process according to invention, to coatings with remarkable surface alterations, especially a marked effect of orange peel.

BRIEF DESCRIPTION OF THE INVENTION The subject of the present invention are polyaddition compounds which occur in solid form, below 40 ° C, and in liquid form, above 125 ° C, produced by reaction of isocyanate components containing uretdione groups with polyols containing groups ester and / or carbonate, with the exception of the neopentyl glycol ester of hydroxypivalic acid, and having a) to an isocyanate functionalization of 2.0 to 8.0 a content of free isocyanate groups (calculated as NCO, molecular weight = 42) of 2.1 to 6.0 % in weigh, b) a content of uretdione groups (calculated as C2N202, molecular weight = 84) of 10 to 19% by weight, c) a content of urethane groups (calculated as -NH-CO-0, molecular weight = 59) of 10 to 17% by weight and d) a content of ester groups -CO-O (calculated as -CO-O, molecular weight = 44) and / or carbonate -O-CO-0 groups (calculated as -CO-O, molecular weight = 44) of 1 to 17% by weight, Another object of the invention is a process for the production of these polyaddition compounds, characterized in that they are reacted A) uretodionic polyisocyanates which are free of isocyanurate groups, and optionally B) up to 10% by weight, based on the total weight of components A) and B), of other isocyanates with C) polyhydroxyl compounds containing ester groups and / or carbonate of an average molecular weight of 134 to 2,000, preferably neopentylglycol hydroxypivalate, optionally 10 D) up to 70% by weight, based on the total weight of components C) and D), of other polyhydroxy compounds, which are free of ester and carbonate groups, and have a molecular weight of 62 up to 400, and E) up to 20% by weight, based on the total weight of compounds C), D), and E), of the compounds containing a reactive isocyanate group, optionally to an equivalent ratio of isocyanate groups to relative isocyanate groups of 1.2: 1 to 1.8: 1. The invention also relates to two component polyurethane powder coating compositions, which contain the polyaddition compound according to the invention as the crosslinking agent and a reactive isocyanate compound as the binder.

DETAILED DESCRIPTION OF THE INVENTION They are starting compounds A) for the process according to the invention, polyisocyanates lacking uretodiónicos isocyanurate groups as those obtainable in known manner by catalytic dimerization of a part of the isocyanate groups of diisocyanates and preferably, subsequent removal of excess diisocyanate that has not reacted, for example by thin film distillation. For the preparation of the starting compounds A), discretional diisocyanates with cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups, for example those of molecular weight in the range of 140 to 400, such as for example 1,4-diisocyanatobutane, are suitable. 1, 6-diisocyanatohexane (HDI), 2-methyl-1, 5-diisocyanatopentane, 1, 5-diisocyanato-2, 2-dimethylpentane, 2,2,4- or 2, 4-trimethyl-l, 6-diisocyanatohexane , 1, 10-diisocyanatodecane, 1,3- and 1,4-diisocyanatocyclohexane, 1, 3-diisocyanato-2 () -metilciclohexano, l-isocyanato-3, 3, 5-trimethyl-5-isocyanato-methylcyclohexane ( isophorone diisocyanate; IPDI), l-isocyanato-l-methyl-4 (3) -isocyanatomethylcyclohexane, 4,4'-diisocyanatodicyclohexylmethane, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2, 6-toluylene diisocyanate as well as discretional mixtures of these isomers, diphenylmethane-2, 4 '- and / or -4,' -diisocyanate and naphthylene-1, 5-diisocyanate as well as discretional mixtures of such diisocyanates.

As catalysts for the preparation of the starting compounds A) from the indicated diisocyanates are known compounds which catalyze the dimerization of isocyanate groups, for example tertiary organic phosphines, such as those described for example in US 4 614 785, column 4, lines 11 to 47, in DE-A 1 934 763 or in DE-A 3 900 053, tris (dialkylamino) -phosphines of the type indicated in EP-A 45 995, DE-A 3,227,779 or DE-a 3,437,635, substituted pyridines of the type indicated in DE-a 1081895, EP-a 317 744 or EP-a 854 141, imidazoles or substituted benzimidazoles of the type indicated in EP-A 417 603 or mixtures of such dimerization catalysts, such as those described for example in EP-A 780 377.

In the production known per se of the polyisocyanates having uretdione groups by catalytic dimerization of the diisocyanates indicated by way of example, they often occur., to a lesser extent, simultaneously to the dimerization reaction, a trimerization reaction with the formation of polyisocyanates having isocyanurate groups with functionalization greater than two. However, the starting compounds A) suitable for the process according to the invention are exclusively uredodion polyisocyanates lacking isocyanurate groups, where the concept "lacking isocyanurate groups" means, for the purposes of the present invention, that the proportion of isocyanurate groups is less than 5% by moles, preferably less than 2% by moles, based on the total amount of uretdione and isocyanurate structures, so that the average NCO functionalization of component A), referred to the free NCO groups, is less than 2.1 , preferably 2.0.

Preferred starting compounds A) for the process according to the invention are uredodion polyisocyanates lacking isocyanurate groups based on diisocyanates with aliphatic and / or cycloaliphatically bound isocyanate groups of the type mentioned above by way of example or mixtures of such polyisocyanates. The use of uredodion polyisocyanates lacking isocyanurate groups based on 1,6-diisocyanatohexane and / or l-isocyanato-3,5,5-trimethyl-5-isocyanatomethylcyclohexane is especially preferred.

If necessary, other diisocyanates B) can optionally be used in the process according to the invention. In this case, for example, the diisocyanates with aliphatic, cycloaliphatic, araliphatic and / or aromatically bound isocyanate groups indicated above are suitable for the preparation of the starting compounds A). These diisocyanates B) are used, if appropriate, in amounts of up to 10% by weight, preferably 5% by weight, based on the total weight of components A) and B). Preferred diisocyanates B), which optionally can be used in the process according to the invention, are represented by cycloaliphatically isocyanate-linked diisocyanates. The use of 1-isocyanate-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane and / or diisocyanatodicyclohexylmethane is especially preferred.

In the process according to the invention, polyhydroxylic compounds C) having ester and / or carbonate groups are used, with the exception of the neopentylglycol ester of hydroxypivalic acid, which have an average molecular weight, which can be calculated from the functionalization and the hydroxyl number. , from 134 to 2,000, preferably from 176 to 1,200, and an average OH functionalization from 2.0 to 4.0, preferably from 2.0 to 3.0. In this case, for example, these alcohols or mixtures of these alcohols are known per se, such as are obtained, for example, by reaction of polyvalent alcohols with defective amounts of polyvalent carboxylic acids, anhydrides of corresponding carboxylic acids, polycarboxylic acid esters. corresponding lower alcohols or lactones.

For the preparation of these alcohol alcohols suitable polyhydric alcohols are especially those with a molecular weight in the range of from 62 to 400, such as, for example, 1,2-ethanediol, 1,2- and 1,3-propanediol, the butanediols, pentanediols, hexanodiols, heptanediols and isomeric octane diols, 1,2- and 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4 '- (1-methylethylidene) -biscyclohexanol, 1,2,3-propanetriol, 1, 1 1-trimethylolethane, 1, 2, 6-hexanetriol, 1,1-trimethylolpropane, 2,2-bis (hydroxymethyl) -1,3-propanediol or 1, 3, 5-tris (2-hydroxyethyl) -isocyanurate.

The acids or acid derivatives used for the preparation of the alcohol alcohols can be aliphatic, cycloaliphatic, aromatic and / or heteroaromatic in nature and optionally substituted, for example with halogen atoms, or unsaturated. Examples of suitable acids are, for example, polyvalent carboxylic acids of the molecular weight range from 118 to 300 or their derivatives, such as, for example, succinic acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic acid, maleic acid, maleic anhydride, diamonds and trimers of fatty acids, the dimethyl ester of terephthalic acid and the bis-glycol ester of terephthalic acid.

Mixtures of the starting compounds indicated by way of example can also be used for the preparation of the alcohol alcohols. It is also possible to use mixtures of various alcohols of the type indicated in the process according to the invention.

In the process according to the invention, ester polyols, such as those which can be prepared in a known manner from lactones and simple polyvalent alcohols as starting molecules with ring opening, are preferably used as the starting component C).

Suitable lactones for the preparation of these ester polyols are, for example, β-propiolactone, β-butyrolactone, d-valerolactone, e-caprolactone, 3,5,5- and 3, 3, 5-trimethylcaprolactone or discrete mixtures of such lactones. . Suitable initiator molecules are, for example, polyvalent alcohols of molecular weight in the range of from 62 to 400 indicated above by way of example or discrete mixtures of these alcohols.

Polyhydroxyl compounds which have especially preferred ester groups C) for the process according to the invention are esters of molecular weight in the aforementioned range, especially those based on e-caprolactone.

Starting compounds C) for the process according to the invention are also represented by polyhydroxy compounds having carbonate groups.

In this case, it is carbonate alcohols of a type known per se, such as those obtainable, for example, by reaction of the polyvalent alcohols of molecular weight in the range of from 62 to 400, indicated above by way of example with diaryl carbonates, such as, for example, diphenylcarbonate. , phosgene or preferably cyclic carbonates, such as, for example, trimethylene carbonate or 2,2-dimethyl trimethylene carbonate (neopentyl glycol carbonate, NPC) or mixtures of such cyclic carbonates. Especially preferred carbonate alcohols are those which can be obtained from the aforesaid polyvalent alcohols, in particular divalent alcohols, such as initiator molecule and NPC with ring opening.

Polyhydroxy compounds having ester and carbonate groups are also suitable as starting materials C) for the process according to the invention. These ester carbonate alcohols can be prepared, for example, according to DE-A 17 70 245 by reaction of the polyvalent alcohols of molecular weight in the range of 62 to 400 indicated above by way of example with lactones of the type indicated above by way of example. example, especially with e-caprolactone, and subsequent reaction of the thus alcohols formed with diphenylcarbonate.

However, ester carbonate alcohols are preferably used, such as those obtainable by reacting the indicated polyhydric alcohols with mixtures of lactones and ring-opening cyclic carbonates.

The preparation of the above-described alcohol alcohols, carbonate alcohols and ester carbonate alcohols preferably used in the process according to the invention by ring-opening polymerization is generally carried out in the presence of catalysts such as, for example, Lewis or Brdnstedt acids, organic tin or titanium compounds. temperatures from 20 to 200 ° C, preferably from 50 to 160 ° C.

Mixtures of the alcohol alcohols, carbonate alcohols and ester carbonate alcohols indicated by way of example as starting material C) can optionally be used in the process according to the invention.

Optionally, polyhydroxy compounds without ester and / or carbonate groups D) having an average molecular weight of 62 to 400 can also be optionally used in the process according to the invention. In this case, it is, for example, the simple polyhydric alcohols described above in the preparation of the alcohol alcohols or of discrete mixtures of these alcohols. The alcohols without ester and / or carbonate groups D) are used, if appropriate, in amounts of up to 70% by weight, based on the total amount of starting compounds C) and D). Suitable mixtures of starting components C) and D) are also suitable for the process according to the invention if the polyhydric alcohols of the type indicated by way of example used as starting material are processed with defect amounts of acid or acid derivatives, diaryl carbonates or cyclic carbonates of the type indicated by way of example or phosgene only partially in polyhydroxy compounds having ester and / or carbonate groups.

In the process according to the invention, it is also optionally possible to use other monofunctional compounds E) which are reactive towards isocyanate groups. In this case, for example, simple aliphatic or cycloaliphatic monoalcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the pentanols, hexanols, octanols and non-isomers, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the methylcyclohexanal isomers and the hydroxymethylcyclohexane, ether alcohols, such as 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycol -monoethylether, diethylene glycol monobutyl ether, 3-methoxy-1-butanol and glycerin-1,3-diethylether or these alcohols, such as hydroxyethyl acetate, butyl glycolate, ethyl lactate, glycerin diacetate or those obtainable by reaction of the monoalcohols indicated with lactones.

These monofunctional compounds E) are optionally used in amounts of up to 20% by weight, preferably 15% by weight, based on the total weight of the starting compounds reactive with isocyanates C), D) and E).

Preferred starting compounds E) for the process according to the invention are simple aliphatic or cycloaliphatic monoalcohols of the type indicated.

In order to carry out the process according to the invention, the uretdionic polyisocyanates lacking isocyanurate groups A) are optionally reacted, optionally using other diisocyanates B) with polyhydroxy compounds having ester and / or carbonate groups C), optionally optionally using other polyhydroxy compounds without ester or carbonate groups D) and optionally other monofunctional compounds reactive towards isocyanates E) in the indicated ratio of isocyanate groups to groups reactive towards isocyanates from 1.2: 1 to 1.8: 1 , preferably from 1.25: 1 to 1.6: 1 at a reaction temperature of from 40 to 200 ° C, particularly preferably from 60 to 180 ° C, preferably until the theoretical calculated NCO content is reached.

In this respect, otherwise, the type and quantitative relationships of the starting components are chosen within the framework of the indications made so that the resultant psoiadiction compounds correspond to the data indicated under a) to d): (a) the polyaddition compounds preferably have an average functionalization of 2.0 to 6.0, more preferably 2.0 to 5.0 and a content of free isocyanate groups of preferably 2.2 to 5.0% by weight, particularly preferably 2.4 to 4.0% by weight (b) the content of uretdione groups preferably ranges from 12 to 18% by weight, particularly preferably from 14 to 17% by weight, (c) the content of urethane groups preferably from 11 to 17% by weight, particularly preferably from 12 to 16% by weight and (d) the content of carboxylic acid ester groups and / or carbonate groups of 2 to 12% by weight, particularly preferably 3 to 10% by weight, The solid polyaddition compounds being below 40 ° C and liquids above 125 ° C, especially having a melting point or melting range determined by differential thermoanalysis (TAD) which is within a temperature range of 40 ° C. at 110 ° C, particularly preferably within the temperature range of 50 to 100 ° C.

The polyaddition products having uretdione groups according to the invention are already characterized at temperatures slightly above their melting point or melting range by very low melt viscosities. They can be produced according to the process according to the invention very easily in the molten state at temperatures below the retrodissociation temperature of the uretdione groups. Although in the process according to the invention the isocyanate components are used in a molar excess relative to the polyol components, the products of the process according to the invention are generally formed with little monomer, ie with monomeric diisocyanate contents in general of less than 1% by weight, preferably less than 0.5% by weight, with particular preference of 0.3% by weight.

The reaction can also be carried out in special equipment, such as for example in intensive kneaders, at temperatures in the retrodisocylation range of the uretodiones, without a large increase in monomeric diisocyanates being observed if sufficiently short reaction times are maintained here. for example less than 5 minutes.

Of course, the reaction can also be carried out in a solvent inert against suitable isocyanate groups. Suitable solvents for this less preferred procedure are, for example, customary paint solvents known per se, such as, for example, ethyl acetate, butyl acetate, ethylene glycol monomethyl or ethyl ethyl acetate, 1-methoxy propyl 2- acetate, 2-butanone, 4-methyl-2-pentanone, cyclohexanone, toluene or mixtures thereof, but also solvents such as propylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol ethyl and butyl butyl acetate, N-methyl pyrrolidone and N-methyl caprolactam, or mixtures of such solvents.

These optionally used solvents, if appropriate, are separated once the reaction of the product of the process according to the invention has been carried out by suitable methods, for example by precipitation and filtration with simple suction, spray drying or melt extrusion on a screw of vaporization.

In order to accelerate the urethanization reaction, the usual known polyurethane chemistry catalysts can be used in the process according to the invention, for example tertiary amines such as triethylamine, pyridine, methylpyridine, benzyldimethylamine, N, N-endoethylene piperazine, N-methylpiperidine, pentamethyl ethylenetriamine, N, N-dimethylaminocyclohexane, N, Nf -dimethylpiperazine or metal salts such as iron (III) chloride, zinc chloride, zinc 2-ethyl-caproate, tin octoate (II), tin ethylcaproate (III) , tin palmitate (II), dibutyltin dilaurate (IV) and molybdenum glycolate.

These catalysts can optionally be used in amounts of 0.001 to 2.0% by weight, preferably 0.01 to 0.2% by weight, based on the total amount of the starting compounds used.

The polyaddition compounds according to the invention represent valuable starting materials for the manufacture of polyurethane plastics by the polyaddition process of isocyanates. They find application in particular as a crosslinking component in powder lacquers of PUR free of hot hardening blocking agents.

In this respect, suitable binders for the polyaddition compounds according to the invention are basically the binders known from the powder coating technology with groups reactive towards isocyanate groups, such as hydroxyl, carboxyl, amino, thiol, urethane or urea. Preferably, hydroxy-functional powder coat binders are used which are solids below 40 ° C and liquids above 130 ° C. The softening temperatures of these hydroxy-functional resins -determined by differential thermoanalysis, DTA- are preferably within the temperature range of 30 to 120 ° C, particularly preferably within the temperature range of 35 to 110 ° C.

Their hydroxyl numbers are between 20 and 200, preferably between 30 and 130 and their average molecular weight (calculated from functionalization and hydroxyl content) in general between 400 and 10,000, preferably between 1,000 and 5,000.

Such powder coating binders are, for example, polyesters, polyacrylates or polyurethanes containing hydroxyl groups such as those described in the aforementioned publications of the prior art, for example in EP-A 45 998 or in EP-A 254 152 , but also discretional mixtures of such resins.

For the production of a ready-to-use powder coating material, the polyaddition compounds according to the invention are mixed with suitable hydroxy-functional powder coat binders, optionally with other adjuvants and additives, such as, for example, catalysts, pigments, fillers or agents. of leveling, and are brought together for example in extruders or kneaders at temperatures above the melting range of the individual components, for example between 70 and 130 ° C, to form a homogeneous material.

The polyaddition compounds according to the invention and the hydroxy-functional binders are used here in quantitative ratios such that each hydroxyl group corresponds to 0.6 to 2.0, preferably 0.8 to 1.4, isocyanate groups, which are understood to be isocyanate groups in the polyaddition compounds according to the invention. to the invention the sum of the isocyanate groups present in dimeric form as uretdione groups and of the free isocyanate groups.

In the case of the catalysts to be used to accelerate the hardening, it is for example the usual compounds known in the chemistry of polyurethanes, such as those already described above in the process according to the invention for accelerating the reaction, or amidines, as for example, 1,5-diazabicyclo [4.3.0] non-5-ene (DBN), 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and 1,2-dimethyl-tetrahydropyrimidine, which, according to the teachings of EP-A 803 524, have proved to be particularly suitable catalysts for reducing the baking temperatures of uretho-dionic crosslinking agents in powder coating materials. These catalysts can optionally be added in amounts of 0.01 to 5.0% by weight, preferably 0.05 to 2.0% by weight, based on the total amount of organic binder, ie polyaddition compounds according to the invention in combination with the binders of the binder. hydroxy-functional powder coatings, but excluding the other adjuvants and additives used, if appropriate.

Under the conditions of powder coating production, the free isocyanate groups of the polyaddition compounds according to the invention react, as indicated by the analyzes by IR spectroscopy, practically in their entirety. The solid lacking free resulting isocyanate groups is milled and sieved out of grain fractions larger than the desired grain size, for example greater than 0.1 mm.

The ready-to-spray powder coating thus manufactured can be applied to the substrates to be coated by customary powder application methods, such as by electrostatic spraying or by fluidized-bed sintering. According to the invention, heat-resistant substrates, such as metals, wood or glass, can be coated.

The coating is hardened by heating at temperatures of 110 to 220 ° C, preferably 130 to 200 ° C, for example for a period of about 10 to 30 minutes. Hard and elastic coatings are obtained with good resistance to solvents and chemical products that are characterized by outstanding leveling and a very high gloss.

Examples In the following, all percentage data are referenced by weight, with the exception of Brightness Indexes Preparation of the starting compounds C) Diol C 1) having ester groups. 901 g of 1,4-butanediol and 1,712 g of e-caprolactone were mixed at room temperature under dry nitrogen, 0.3 g of tin octoate (II) were added. ) and then heated for 5 h at 160 ° C. After cooling to room temperature, a colorless liquid product was obtained with the following characteristic data: (23 ° C): 180 mPas OH number: 416 mg KOH / g free e-caprolactone: 0.1% medium molecular weight (cale, per ind. OH): 269 ester group content (cale.): 25.3% Diol C 2) having ester groups 761 g of 1,3-propanediol and 1,712 g of e-caprolactone were mixed at room temperature under dry nitrogen, 0.3 g of tin octoate (II) was added and then heated for 5 h 160 ° C. After cooling to room temperature a colorless liquid product was obtained with the following characteristic data: (23 ° C): 190 mPas OH number: 449 mg KOH / g free e-caprolactone: 0.3% average molecular weight (cale, per ind. OH): 249 ester group content (cale.): 26.7% Triol C 3) having ester groups A mixture of 1,341 g of 1,1-trimethylolpropane (TMP) and 1,712 g of methanol were mixed at room temperature under dry nitrogen. -caprolactone, 0.3 g of tin octoate (II) was added and then heated for 5 h at 160 ° C. After cooling to room temperature a colorless liquid product was obtained with the following characteristic data: (23 ° C): 2400 mPas OH index; 546 mg KOH / g free e-caprolactone: 0.2% average molecular weight (cale, per ind. OH): 308 ester group content (cale.): 21.6% Diol C 4) having carbonate groups. 901 g of 1,4-butanediol and 1,300 g of NPC were mixed at room temperature under dry nitrogen, 0.2 g of orthophosphoric acid was added and then heated for 8 h at 160 ° C. After cooling to room temperature, a virtually colorless liquid product was obtained with the following characteristic data: (23 ° C): 1,500 mPas OH number: 519 mg KOH / g Free NPC: 0.5% average molecular weight (cale, per ind. OH): 216 carbonate group content (cale.): 20.0% Example 1 1000 g (4.0 eq.) Of a polyisocyanate containing uretdione groups based on l-isocyanate-3, 3, 5-trimethyl-5-isocyanatomethyl-isohexane (IPDI) having a free isocyanate group content of 16.7% were mixed under dry nitrogen. an average functionalization of NCO of 2.0 and a content of uretdione groups (determined by hot titration) of 20.9% with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. Then a mixture of 215 g (1.6 eq.) Of the diol having C 1) ester groups and 72 g (1,6 eq.) Of 1,4-butanediol was added over the course of 20 min. And stirred at a temperature of reaction of 110 ° C maximum until the NCO content of the reaction mixture was reduced after approximately 20 min. at a value of 2.7%. The melt was poured to cool it on a sheet and a polyaddition compound according to the invention was obtained in the form of a pale yellow solid resin with the following characteristic data: NCO content (Jan./Kal.): 2.7 / 2.6% content of uretdione groups (cale.) 16.2% total NCO content (cale.) 18.8% NCO functionalization: 2.0 IPDl monomer: 0.19% melting range: 90-98 ° C ester group content (cale.): 4.2 % urethane group content (cale.): 14.7% Example 2 Dry magnesium 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 was mixed with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. Then a mixture of 150 g (1.2 eq.) Of the diol having C 2 ester groups) and 76 g (2.0 eq.) Of 1,3-propanediol was added over the course of 20 min. And stirred at a temperature of reaction of 110 ° C maximum until the NCO content of the reaction mixture was reduced after approximately 15 min. at a value of 2.9%. The molten mass was poured to cool it on a sheet and a polyaddition compound according to the invention was obtained in the form of a light yellow solid resin with the following characteristic data: NCO content (Jan./Ca.): 2.8 / 2.7% content of uretdione groups (cale.): 17.0% total NCO content (cale.): 19.7% NCO functionalization: 2.0 IPDI monomer: 0.21% melting range: 96-105 ° C ester group content (cale.) : 3.3% content of urethane groups (cale.): 15.4% Example 3 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 were mixed under dry nitrogen with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. Then a mixture of 269 g (2.0 eq.) Of the diol having C 1) ester groups and 54 g (1.2 eq.) Of 1,1-trimethylolpropane was added over the course of 20 minutes and stirred to a reaction temperature of 110 ° c maximum until the NCO content of the reaction mixture was reduced after about 20 mm to a value of 2.7%. The melt was poured to cool it on a sheet and a polyaddition compound according to the invention was obtained in the form of a light yellow solid resin with the following characteristic data: NCO content (Jan./Kal.): 2.7 / 2.5% content of uretdione groups (cale.): 15.8% total NCC content (cale.): 18.5% NCO functionalization: 4.0 IPDI monomer: 0.23% melting range: 100-110 ° C ester group content (cale.) : 5.1% content of urethane groups (cale.): 14.3% Example 4 Dry magnesium 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 was mixed with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. It was then added over the course of 20 min. A mixture of 215 g (1.6 eq.) Of the diol having ester groups C 1) and 164 g (1.6 eq.) Of the triol having ester groups C 3) and stirred at a reaction temperature of 110 ° C maximum until the NCO content of the reaction mixture was reduced after approximately 20 min. at a value of 2.6%. The molten mass was poured to cool it on a sheet and a polyaddition compound according to the invention was obtained in the form of a light yellow solid resin with the following characteristic data: NCO content (Jan./kg): 2.6 / 2.4% content of uretdione groups (cale.): 15.2% total NCO content (cale.): 17.6% NCO functionalization: 6.0% IPDI monomer: 0.32% melting range: 104-113% ester group content (cale.) 6.5% content of urethane groups (cale.): 13.7% Example 5 Dry magnesium was mixed with 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 with 0.1 g of dibutyltin dilaurate (DBTL) as a catalyst and heated to 80 ° C. It was then added over the course of 30 min. a mixture of 324 g (3.0 eq.) of the diol containing C 4 carbonate groups) and stirred at a reaction temperature of 110 ° C maximum until the NCO content of the reaction mixture was reduced after approximately 25 min. . at a value of 3.2%. The melt was poured to cool it on a sheet and a polyaddition compound according to the invention was obtained in the form of a light yellow solid resin with the following characteristic data: NCO content (Jan./kg): 3.2 / 3.2% content of uretdione groups (cale.): 15.8% total NCO content (cale.): 19.0% NCO functionalization: 2.0% IPDI monomer: 0.12% melting range: 89-97% ester group content (cale.) : 4.9% content of urethane groups (cale.) 13.4% Example 6 (Comparative) Dry magnesium 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 was mixed with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. They were then added over the course of 30 min. 144 g (3.2 eq.) Of 1,4-butanediol. Already during the addition of the diol, due to the rapidly increasing increase in the viscosity of the reaction mixture, the temperature of the heating bath had to be raised to 130 ° C to ensure agitability. After 15 min. the NCO content of the reaction mixture reached, as after 20 min., 3.8%. After 25 min. the temperature of the reaction mixture rose above 150 ° C due to the still increasing viscosity under the influence of the shearing forces that occur in the agitation, despite a constant external temperature of 130 ° C. The NCO content rose to 4.6% and was not reduced either by extending the duration of the reaction. The content of monomeric IPDI reached 1.4%.

Example 7 (Comparative) Dry magnesium 1000 g (4.0 eq.) Of the IPDI polyisocyanate containing uretdione groups of Example 1 was mixed with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as a catalyst and heated to 80 ° C. They were then added in portions over the course of 30 min. 326 g (3.2 eq.) Of neopentyl glycol ester of hydroxypivalic acid. Already towards the end of the addition of the diol, due to the strongly increasing increase in the viscosity of the reaction mixture, the temperature of the heating bath had to be raised to 120 ° C to guarantee the agitability. After 15 min. the NCO content of the reaction mixture reached 3.2%. After 20 min. The temperature of the reaction mixture rose to 147 ° C due to the still increasing viscosity under the influence of the shearing forces that occur in the agitation, despite a constant external temperature of 120 ° C. The NCO content was raised to 4.1% and was not reduced either by extending the duration of the reaction. The content of monomeric IPDI reached 1.1%.

Comparative Examples 6 and 7 indicate that in the reaction of the polyisocyanate containing uretdione groups with simple diols or with the neopentyl glycol ester of the hydroxypivalic acid in the molten state according to the procedure described in Example 1, dissociation of the uretdione groups occurs to a considerable extent . The intended NCO contents of 2.9% (Example 6) or 2.5% (Example 7) are not achieved and the monomeric diisocyanate contents clearly exceed 1%.

Example 8 (Comparative, analogously as in EP-A 45 994) At 80 ° C under dry nitrogen, 1,000 g (4.0 eq.) Of the polyisocyanate containing uretdione groups of Example 1 were placed in 1144 g of anhydrous toluene with 0.1 g of dibutyltin dilaurate (IV) (DBTL) as catalyst. They were then added over the course of 30 min. 144 g (3.2 eq.) Of 1,4-butanediol and stirred at a reaction temperature of 100 ° C until the NCO content was reduced to a value of 1.5%. From the light yellow solution obtained, the solvent was then completely removed by spray drying in a conventional commercial laboratory spray dryer Minispray Dryer 190 (Fa.Büchi). A pale yellow product was obtained with the following characteristic data: NCO content (Jan./Kal.): 2.7 / 2.6% content of uretdione groups (cale.): 18.3% total NCO content (cale.): 21.2 % NCO functionalization: 2.0 PDl monomer: 0.12% melting point: 111-120 ° C ester group content (cale.): content of urethane groups (cale.): 16.5% Example 9 (Application) 55.4 parts by weight of a polyester containing commercial hydroxyl groups (Crylcoat® 240, Fa UCB Chemicals) were thoroughly mixed with an OH number of 30 with 6.6 parts by weight of the polyaddition compound according to the invention of Example 1, corresponding to a ratio of total NCO to OH of 1: 1, 1.5 parts by weight of a commercial leveling agent (Modaflow® Powder III, Fa.Solutia), 1.0 parts by weight of tin (II) palmitate as a catalyst , 0.5 parts by weight of benzoin and 35.0 parts by weight of a white pigment (Kronos 2160, Kronos Titan) and then homogenized using a Buss coamator of type PLK 46 at 100 rpm and a shell temperature of 100 to 120 °. C in this part of the procedure. After cooling the solidified melt was ground and sieved using an ACM 2 sorting mill (Fa Hosokawa Mikropul) with a 90 μm sieve. The powder thus obtained which according to IR spectroscopy analysis no longer contained any free isocyanate group was sprayed with an ESB cup gun at a high voltage of 79 kv onto a degreased steel plate and hardened for 15 min. at 180 ° C.

For comparison, a powder coating was produced analogously from 56.1 parts by weight of the same polyester containing hydroxyl groups with 5.9 parts by weight of the polyaddition compound obtained according to Comparative Example 8, 1.5 parts by weight of a commercial leveling agent. (Modaflow® Powder III, Fa.Solutia), 1.0 parts by weight of tin (II) palmitate as a catalyst, 0.5 parts by weight of benzoin and 35.0 parts by weight of a white pigment (Kronos 2160, Kronos Titan), It was pulverized on a degreased steel plate and also hardened for 15 min. at 180 ° C. The equivalent ratio of total NCO to OH was likewise 1: 1.

Next, both coatings were analyzed for their technical lacquer properties. In addition to the brightness and milking indexes for the characterization of the surface structure, the orange peel effect was measured by means of a "wave sean plus" apparatus of the Fa. Byk-Gardner At layer thicknesses of approximately 60 μm the following properties were found: Powder lacquers with cores of Example 1 Example 8 polyaddition from (comparative) Impact (ASTM-D-2794-69) > 80 ip < 5 ip Brightness 60 ° / 20 ° (DIN 67530) 106/89 96/94 Haze (DIN 67350; ISO 2813) 55 90 Sweep wave: Long wave (nc / c) 35.4 / 33.1 57.3 / 55.9 Short wave (nc / c) 11 31.3 / 28.5 55.8 / 55.8 tension (nc / c) 11 10.3 / 10.7 6.7 / 7.0 1) nc / c: uncorrected or corrected values The comparison shows that by using the polyaddition compound according to the invention a completely crosslinked lacquer film is obtained, which with respect to the coating produced using the polyaddition compound known from the state of the art is characterized by a considerably higher elasticity, a higher brightness, lower lecosity and a clearly improved leveling. While the lacquer film obtained according to the invention is smoothly leveled, the comparison coating shows a strong orange peel structure and also has multiple pitting and vexing.

Example 10 to 13 (Application) They were prepared according to the process described in Example 9 starting from the polyester containing hydroxyl groups described in Example 9 and the polyaddition compounds 2, 3, 4 and 5 according to the invention powder lakes pigmented with white. The finished powder-form lacquers, which according to IR spectroscopy analysis are in all cases free of isocyanate groups without blocking, were respectively sprayed with an ESB cup gun at a high voltage of 70 kv onto degreased steel sheet and hardened for 15 minutes. min. at 160 ° C. The following table shows the compositions (parts by weight) of the powder coatings as well as the technical lacquer data of the coatings obtained with them (respective layer thickness of approximately 70 μm). 1. #} nc / c: uncorrected or corrected values It is noted that in relation to this date, the best method known to the applicant, to implement said invention is that which is clear from the manufacture of the objects to which it refers. Having described the invention as above, the content of the following is claimed as property.

Claims (8)

1. A polyaddition compound characterized in that it is solid below 40 ° C and liquid above 125 ° C, is prepared by reacting an isocyanate component containing uretdione groups with an ester containing polyol and / or carbonate groups, preferably ether Neopentyl glycol of hydroxypivalic acid, and has a) an isocyanate functionalization of 2.0 to 8.0, a content of free isocyanate groups (calculated as NCO, molecular weight = 42) of 2.1 to 6.0% by weight, b) a content of uretdione groups (calculated as C2N202, molecular weight = 84) of 10 to 19% by weight, c) a content of urethane groups (calculated as -NH-CO-O, molecular weight = 59) of 10 to 17% by weight and d) a content of ester groups -CO-O (calculated as -CO-O, molecular weight = 44) and / or carbonate -O-CO-0 groups (calculated as -CO-O, molecular weight = 44) of 1 to 17% by weight,

2. A process for the preparation of polyaddition compounds, which is solid below 40 ° C and liquid above 125 ° C and has a) to an isocyanate functionalization of 2.0 to 8.0 a content of free isocyanate groups (calculated as NCO, molecular weight = 42) of 2.1 to 6.0% by weight, b) a content of uretdione groups (calculated as C2N202, molecular weight = 84) of 10 to 19% by weight, c) a content of urethane groups (calculated as -NH-CO-O, molecular weight = 59) of 10 to 17% by weight and d) a content of ester groups -CO-O (calculated as -CO-O, molecular weight = 44) and / or carbonate -O-CO-0 groups (calculated as -CO-O, molecular weight = 44) of 1 to 17% by weight, which condition is characterized in that it comprises reacting A) uretodionic polyisocyanates which are free of isocyanurate groups, and optionally B) up to 10% by weight, based on the total weight of components A) and B), of other isocyanates with C) polyhydroxy compounds having ester and / or carbonate groups of an average molecular weight of 134 to preferably the neopentyl glycol ester of hydroxypivalic acid, optionally D) up to 70% by weight, based on the total weight of components C) and D), of other polyhydroxy compounds, which are free of ester and carbonate groups, and have a molecular weight of 62 to 400, and E) up to 20% by weight, based on the total weight of compounds C), D), and E), of the compounds containing a reactive isocyanate group, optionally at an equivalent ratio of isocyanate groups to isocyanate relative groups of 1.2 : 1 to 1.8: 1.

3. The process according to claim 2, characterized in that the uretdione polyisocyanate A) is prepared from a diisocyanate having isocyanate groups linked aliphatically and / or cycloaliphatically.

4. The process of claim 2, characterized in that the polyisocyanate A) is prepared from 1,6-diisocyanatohexane and / or 1-isocyanato-3,3,5-trimethyl-5-isocyanto-methylcyclohexane.

5. The process of claim 2, characterized in that the polyhydroxy compound C) is a polyester polyol prepared by the ring-opening polymerization of e-caprolactone.

6. The process of claim 3, characterized in that the polyhydroxy compound C) is a polyester polyester prepared by ring opening polymerization of e-caprolactone.

7. The process of claim 4, characterized in that the polyhydroxy compound C) is a polyester polyol, prepared by ring opening polymerization of e-caprolactone.

8. A two-component polyurethane powder coating composition, characterized in that it contains the polyaddition compound of claim 1, as the crosslinking agent and a reactive isocyanate compound as the binder. SUMMARY OF THE INVENTION A polyaddition compound characterized in that it is solid below 40 ° C and liquid above 125 ° C, is prepared by reacting an isocyanate component containing uretdione groups with an ester containing polyol and / or carbonate groups, preferably ether Neopentyl glycol of hydroxypivalic acid, and has a) to an isocyanate functionalization of 2.0 to 8.0 a content of free isocyanate groups (calculated as NCO, molecular weight = 42) of 2.1 to 6.0% by weight, b) a content of uretdione groups (calculated as C2N202, molecular weight = 84) of 10 to 19% by weight, c) a content of urethane groups (calculated as -NH-CO-O, molecular weight = 59) of 10 to 17% by weight and d) a content of ester groups -CO-O (calculated as -CO-O, molecular weight = 44) and / or carbonate -0-CO-0 groups (calculated as -CO-O, molecular weight = 44) of 1 to 17% by weight, The present invention also relates to a process for the preparation of these polyaddition compounds to two-component polyurethane powder coating compositions containing these polyaddition compounds such as the crosslinker and reactive isocyanate compounds as the binder.