DE19729262A1 - Polyisocyanates containing urea and uretdione groups with high functionality - Google Patents

Abstract

Polyisocyanates (I) containing urea and uretdione groups, have a functionality > 2 and free, partly or totally blocked isocyanate (NCO groups are new. (I) are obtained by reacting (A) uretdiones of formula (II) with (B) (cyclo)aliphatic polyamines (III) containing > 2 amino groups. (III) contain groups derived from diamines of formula R<1>-HN-A-NH-R<2> (IV) and groups containing isocyanurate and/or biuret groups derived from polyisocyanates of formula OCN-(B)-Xn-NCO (VA) and are obtained from 1-10, preferably 1-8 mol (IV)/NCO group in (V); in which R = a group of formula (VI), -(CH2)6- and/or -CH2-CH(CH3)-(CH2)3-; A = optionally alkyl-substituted 2-16C (cyclo)aliphatic hydrocarbyl; R<1>, R<2> = 1-14C (cyclo)alkylene, which may be branched, -HC(COOR<3>)-CH2-COOR<3> and/or -CH2-CH2-COOR<3>; R<3> = optionally alkyl-substituted 1-14C hydrocarbyl; B = as R or -CH2-CH(CH3)-CH2-C(CH3)2-CH2-CH2-, -CH2-C(CH3)2-CH2-CH(CH3)-CH2-CH2- or a group of formula (VIIA) or (VIIB); Xn = an isocyanurate group (VIIIA) or biuret group (VIIIB) of the formulae; n = 1-4. (I) (a) contains <= 5 free NCO groups; (b) has a total NCO content (free and latent and/or blocked) of 3-20, preferably 4.5-16 wt.%/ (c) has a molecular weight of 1400-15000, preferably 2000-10000; and (d) has a varying melting range of 70-200 deg C. The (V) group may also contain a group of formula OCN-(B)-NCO (VB); in which case the (VA):(VB) weight ratio = (100-20):(0-80). Also claimed are (i) a method of producing (I); and (ii) polyurethane (PUR) powder lacquers containing (I).

Description

The invention relates to polyisocyanates containing urea and uretdione groups with free, partially or totally blocked isocyanate groups and a functionality greater than 2, a process for their preparation and the use for the production of Polyurethane (PUR) paint systems, especially of PU powder paints and the after coatings produced.

Polyisocyanates containing urea and uretdione groups have only been known for a short time and described in DE-OSS 195 46 750, 196 37 377, 196 30 844 and 196 37 375. The products described there have a maximum functionality of 2. she are reaction products from uretdione of isophorone diisocyanate and primary / second där as well as secondary diamines or water, the free isocyanate groups can be partially or totally irreversible or reversibly blocked. Be used them in the PU powder coating sector for the production of coatings with glossy to matt surfaces.

As can be seen from EP-A 254 152 (page 2, column 1, line 63 to the end of the sentence), this is Fact of bifunctionality (or even less) for practice - manufacture of High quality paint systems - a big disadvantage. It was the first time recently succeeded in polyisocyanates containing uretdione groups with a functionality greater than 2 - as described in DE-OSS 195 05 566, 195 47 878 and 196 33 218.4 - to manufacture and to use advantageously in PU powder coatings. However, these contain no urea groups.

The production of polyisocyanates containing urea and uretdione groups with a Functionality larger than 2 could not be realized so far because of the high reactivity stands in the way of the amino groups. In DE-OS 195 46 750 this is considered described advantageously, but the manufacturing temperatures (see e.g. Claim 12) "... and the temperature does not rise above 40 ° C" the  Problems of the reaction between free isocyanate groups and amino groups, if it is isocyanato uretdione.

The object of the present invention was to contain urea and uretdione groups To provide polyisocyanates with a functionality greater than 2 that are for the production of PUR powder coatings and the coatings produced afterwards with a glossy to matt surface.

The present invention thus relates to polyisocyanates containing urea and uretdione groups with a functionality greater than 2 and free, partially or totally blocked isocyanate groups, obtainable by reacting

• A) Uretdiones of the formula I:
  means
  With
• B) (cyclo) aliphatic polyamines which contain more than two amino groups, these containing residues of diamines of the formula II
  R ¹ -HN-A-NH-R ² (II),
  where A represents a (cyclo) aliphatic hydrocarbon radical with 2-16 C atoms, which may be alkyl-substituted,
  R ¹ and R ^{2 are} a (cyclo) alkylene radical, which can be branched, with 1-14 C atoms and / or a radical of the formulas
  R ^{3 are} identical or different hydrocarbon radicals with 1-14 C atoms, which can be alkyl-substituted

and isocyanurate and / or biuret group-containing residues of polyisocyanates of the formula III:

i) OCN- (B) - [X] _n -NCO (III)

where B

n is 1-4, and 1 to 10 mol, preferably 1 to 8 mol, of the diamines II are used per NCO group of the formula III, the polyisocyanates containing urea and uretdione groups having the following properties:

• a) a content of free NCO groups of ≦ 5
• b) a total NCO content (free and latent and / or blocked) of 3 to 20,  preferably from 4.5 to 16% by weight,
• c) a molecular weight between 1400 and 15000, preferably between 2,000 and 10,000 as well
• d) a varying melting range from 70 to 200 ° C.

The radicals of the formula III can additionally be radicals of the formula

ii) OCN- (B) -NCO

included, the weight ratio i): ii) equal to (100-20): (0-80) is.

The free isocyanate groups of the uretdiones of component A are with the secondary amino groups of component B reacted so that the NH / NCO Ratio is equal to 1: 1.8 to 3, preferably 1: 2 to 2.5 and, if necessary, the free Isocyanate content of the polyisocyanates according to the invention through irreversible and / or reversible blocking 50 is set to be <5, preferably <3, in particular Is <2% by weight. The total NCO content (free and latent and / or blocked) is at 3 to 20% by weight, preferably at 4.5 to 16% by weight. The molecular weights are between 1,400 and 15,000, preferably between 2,000 and 10,000. The Melting range varies within a wide range from 70 to 200 ° C.

Another object of the present invention is a method for manufacturing the polyisocyanates containing urea and uretdione groups according to the invention free, partially or totally irreversibly and / or reversibly blocked isocyanate groups.

The uretdiones (component A) used according to the invention are made from Obtain diisocyanates by known methods; in principle, all are known Diisocyanates can be used.

However, preferred uretdiones are derived from the diisocyanates selected from the Group hexamethylene diisocyanate, 2-methylpentamethylene diisocyanate, 2.2.4 (2.4.4) - Trimethylhexamethylene diisocyanate or isophorone diisocyanate (IPDI), the  aliphatic diisocyanate uretdiones only used in a mixture with IPDI uretdione can be.

The uretdione of isophorone diisocyanate is particularly preferably used. Here it is the IPDI uretdione, as it is in DE-OSS 30 30 513 and 37 39 549 is described with a free NCO content of 16.8-18.5%, d. that is, more or less high levels of polyurethane of the IPDI are present in the reaction product have to. The monomer content is <1%. The total NCO content of the IPDI Uretdions after heating to 180-200 ° C (0.5 h) is 37.4-37.8%.

With the secondary polyamines (component B) to be used according to the invention A functionality greater than 2 is known compounds that are in the DE-OSS 195 46 750, 196 30 844, 196 37 375, 196 37 377 and 44 39 421 in detail are described.

The secondary diamines (formula II) are with isocyanurate and / or Polyisocyanates of the formula III containing biuret groups are reacted so that the Weight ratio of i): ii) is equal to (100-20): (0-80) and per NCO group 1 to 10 mol, preferably 1 to 8 mol, of diamine II are used, with the addition of 100 to 190 ° C heated diamine II, the polyisocyanate III with vigorous stirring and Nitrogen cover is added in portions. After finished Polyisocyanate addition, the reaction mixture is further heated for about 10 minutes; then it is cooled to room temperature.

The polyamines to be used according to the invention with more than two Polyisocyanates of the formula III suitable for amino groups are isocyanurate and / or Polyisocyanates containing biuret groups. The production of this isocyanato Isocyanurate is described in DE-OSS 23 25 826, 26 44 684, 28 21 109, 29 16 201, 29 16 301.

As a rule, for the reaction of the diamines with the isocyanato isocyanurates the monomer-exempt isocyanato  Isocyanurates (III i) used. In some cases it has proven to be useful the partially trimerized diisocyanate mixture (III i + ii) without prior separation of the to use unreacted diisocyanate.

The polyisocyanates containing biuret groups which are suitable according to the invention are described in DE-OS 23 08 015 described. They are manufactured by implementing Water with excess diisocyanate, but not after biuret formation reacted diisocyanate is separated by thin film distillation. That applies here the same as for the polyisocyanates containing isocyanurate groups. Usually the monomer-free biuret group-containing polyisocyanate (III i) is used; in some cases, however, diisocyanate separation can be dispensed with.

Mixtures of isocyanurate and / or biuret groups have also been found containing aliphatic diisocyanates with isocyanurate groups (Cyclo) aliphatic or cycloaliphatic diisocyanates have been found to be advantageous.

A variant for the production of component B is that the primary diamines of the formula IV

H ₂ NA-NH ₂ (IV),

where A is a (cyclo) aliphatic hydrocarbon radical with 2-16 C atoms, which is optionally alkyl-substituted, are reacted with isocyanurate and / or biuret groups-containing polyisocyanates of the formula III in the 1st stage, and then this is brought to room temperature cooled reaction mixture with maleic or fumaric acid ester and / or acrylic acid ester reacted so that an NH ₂ equivalent can be reacted with 1 mol maleic or fumaric acid ester and / or acrylic acid ester in a known manner.

As a reversible blocking agent for the free NCO groups of the invention Connections come ketoximes, such as B. acetone oxime, methyl ethyl ketoxime, Acetophenone oxime and cyclohexanone oxime, lactams such as caprolactam (CL) as well  Triazoles, e.g. B. 1.2.4-triazole.

The irreversible blocking agents for the free NCO groups include all Zerewittinow active hydrogen-bearing monofunctional compounds such as Alcohols, e.g. B. methanol, ethanol, propanol, butanol, 2-ethylhexanol (EHL), or secondary amines such as dibutylamine (DBA), di-2-ethylhexylamine, methylcyclo hexylamine.

Another object of the present invention is a method for manufacturing the polyisocyanates containing urea and uretdione groups according to the invention free, partially or totally blocked isocyanate groups and a functionality greater than 2 by reacting polyisocyanaturetdione (s) with secondary polyamines more than two amino groups and possibly reversible and / or irreversible Blocking agents.

The compounds according to the invention are prepared in such a way that the polyisocyanate Uretdione (A) or uretdione mixtures presented in the solvent and component B - if necessary also dissolved in the solvent - is added at room temperature so that the Reaction temperature does not rise above 40 ° C. According to the invention, the reversible and / or irreversible, partial or total blocking of the free NCO Groups are carried out.

If caprolactam or alcohol is used as a blocking agent, it has proven to be Proven useful, catalysts, e.g. B. organic tin compounds such as Dibutyltin dilaurate (DBTL), Sn-II octoate or tin maleate in a concentration of Add 0.01 to 0.5 wt .-% and the reaction temperature to 70 to 80 ° C. increase.

The course of the reaction is followed by titrimetric NCO determination.

Suitable solvents can be selected from the group of aromatic hydrocarbons, esters or ketones such as toluene, ethyl or butyl acetate, acetone, methyl ethyl ketone,  Methyl isobutyl ketone and any mixtures of these solvents. Preferred The solvent is acetone.

In a preferred embodiment for the partially or totally blocked Compounds according to the invention are in the 1st stage the calculated amount Blocking agent reacted with the free NCO groups of the uretdione, and in A second document is implemented with the secondary polyamines with more as two amino groups.

After the reaction, the solvent is in suitable units such as Evaporation screws, film trudder or spray dryer removed.

Another object of the present invention is the use of polyisocyanates containing urea and uretdione groups according to the invention with a Functionality greater than 2 with free, partially or totally blocked isocyanate groups for the production of polyurethane coating systems, especially in combination with polymers containing hydroxyl groups and / or those customary in PUR chemistry Additives for the production of transparent and pigmented PUR Powder coatings.

To produce PUR powder coatings with reduced gloss, it can be advantageous the compound according to the invention in a grain size <100 μm, preferably <50 µm, especially <30 µm.

Compounds that can be used as reaction partners for PU powder coatings are wear such functional groups that deal with isocyanate groups during the Implement hardening process depending on temperature and time, e.g. B. Hydroxyl, carboxyl, mercapto, amino, urethane, (thio) urea groups. As Polymers can be polymers, polycondensates and polyaddition compounds be used.

In principle, any polymer can be used that contains more than two OH  Contains groups and melts at at least 70 ° C. These are polyether polyols, Polyester amide polyols, polyurethane polyols, hydroxylated acrylate resins, etc., whose OH Groups for crosslinking with those containing uretdione groups according to the invention Polyisocyanates are determined. Are particularly preferred among the numerous Possibilities for hydroxyl-bearing polymers in the context of the invention Polyester polyols. The hydroxyl-containing ones used with particular preference Polyesters have an OH functionality of greater than 2 and an OH number of 20 to 200 mg KOH / g, preferably 30 to 150 mg KOH / g, a viscosity at 160 ° C of < 60,000 mPa.s, preferably <40,000 mPa.s, and a melting point of <70 to <120 ° C, preferably 75 to 100 ° C.

Such polyesters can be condensed in a manner known per se Inert gas atmosphere at temperatures from 100 to 260 ° C, preferably 130 to 220 ° C, can be obtained in the melt or in an azeotropic mode of operation, as described in Methods of Organic Chemistry (Houben-Weyl), Vol. 14/2, pp. 1-5, 21-23, 40 - 44, Georg Thieme Verlag, Stuttgart, 1963 or from C. R. Martens, Alkyd Resins 51-59, Reinhold Plastics Apl. Series; Reinhold Publishing Comp., New York, and in the DE-OSS 19 57 483, 25 42 191, 30 04 876 and 31 43 060 is described.

The mixing ratio of the hydroxyl-containing polymers and the Polyisocyanates according to the invention are generally chosen so that an OH Group 0.5 to 1.2, preferably 0.8 to 1.1, very preferably 1.0 NCO group comes.

In order to increase the gelling speed of the thermosetting powder coatings, one can Add catalysts. Organotin compounds are used as catalysts such as dibutyltin dilaurate (DBTL), Sn-II octoate, dibutyltin maleate, etc. The amount of added catalyst is 0.1 to 5 parts by weight. to 100 parts by weight of Polyester bearing hydroxyl groups.

The isocyanate component is used for the production of PUR powder coatings suitable hydroxyl-containing polymers and optionally catalysts and Pigments and common auxiliaries such as fillers and leveling agents, e.g. B.  Silicone oil, acrylic resins, mixed and homogenized in the melt. This can be done in suitable units, such as. B. heatable kneaders, but preferably by Extrude, take place, with upper temperature limits of 130 to 140 ° C not should be exceeded.

The extruded mass is after cooling to room temperature and after suitable Grind the powder into ready-to-spray powder. Applying the spray ready Powder on suitable substrates can be prepared using known methods such as electrostatic powder spraying, sintering, electrostatic sintering, respectively. After powder application, the coated workpieces become Curing heated to a temperature of 180 to 220 ° C for 30 to 10 min.

The subject matter of the invention is explained in more detail below with the aid of examples. The abbreviations used are in the appropriate places in the description explained.

Experimental part A Connections not according to the invention I. Secondary diamines 1. Preparation of the N, N'-disubstituted diamines in two stages General manufacturing instructions

In the first stage, the aldehyde or the ketone is stirred vigorously added dropwise to the diamine (molar ratio 2: 1) so that the temperature of the Reaction mixture does not rise above 40 ° C. After aldehyde or Ketone addition is stirred at 40 ° C for 1 h. Then the aqueous Phase separated from the organic. To separate the residual water the organic phase is heated at 60 ° C and 10 mbar until no water  more passes. In the second stage, the Schiff base is hydrogenated on a co-contact at 25 ° C and 300 at. Then the crude product distilled.

Table 1

2. Reaction products from 1 mol diamine and 2 mol maleic acid ester General manufacturing instructions

1 mol of diamine is added to 2 mol of maleic or fumaric acid ester at 50-60 ° C added dropwise that the temperature of the reaction mixture does not rise above 70.degree.  

After the addition of diamine is complete, the reaction is completed Heat for a further 2 hours at 60 ° C. For further implementation with the Polyisocyanate is a further treatment (distillation) of the Reaction mixture not required.  

3. Reaction products from 1 mol of diamine and 2 mol of acrylic acid ester General manufacturing instructions

1 mol of diamine is added dropwise to 2 mol of acrylic acid ester at 60-70 ° C. in such a way that the temperature of the reaction mixture does not rise above 80 ° C. After Completion of the diamine addition will complete the reaction continue heating at 70 ° C for approx. 2 h. For further implementation with the Polyisocyanate is a further treatment (distillation) of the Reaction mixture not required.

Table 3

4. Reaction products from 1 mol of diamine and 1 mol of maleic acid ester and 1 mol Acrylic acid ester General manufacturing instructions

1 mol of acrylic acid ester is added dropwise to 1 mol of diamine at 60-70 ° C. in such a way that  the temperature of the reaction mixture does not rise above 80 ° C. After The addition of acrylic acid ester is continued at 70 ° C. until until the amine content has reached the calculated value. Then 1 mol Maleic or fumaric acid ester added dropwise at 50-60 ° C so that the temperature the reaction mixture does not exceed 70 ° C. After finishing painting The acid is added to complete the reaction for about 2 hours at 70 ° C continues to heat. Another is for further reaction with the polyisocyanate Treatment (distillation) of the reaction mixture is not necessary.

Table 4

5. Reaction product from 1 mol primary / secondary diamine and 1 mol maleic or fumaric acid ester or 1 mol acrylic acid ester

The following commercially available products were used as primary / secondary diamines:

General manufacturing instructions

1 mol IPD-M or Laromin® C 252 are mixed with 1 mol male or Fumaric acid ester or 1 mol acrylic acid ester as described under A.II. or A.III. described, implemented. For further reaction with the polyisocyanate no further treatment (distillation) of the reaction mixture required.  

Table 5

II. Polyisocyanates

Polyisocyanate 1:
Commercial isocyanuratoisocyanate based on isophorone diisocyanate with an NCO content of 17.3 + 0.3% by weight.

Polyisocyanate 2:
Commercial isocyanurato isocyanate based on hexamethylene diisocyanate with an NCO content of 21.8 ± 0.3% by weight.

Polyisocyanate 3:
Commercial biuret based on hexa methylene diisocyanate with an NCO content of 21.8 ± 0.3 wt .-%.

III. Reaction products from the AI and the secondary diamines Polyisocyanates AII (component B) General manufacturing instructions

The polyisocyanate becomes the dis- secondary diamine heated to 100-150 ° C with vigorous stirring and nitrogen blanketing in portions within added about 0.5 h. After the addition of polyisocyanate is completed, Cooled to room temperature.  

a) Reaction products from AI1 and A.II.

Table 6

b) reaction products from AI2 and A.II.

Table 7

c) reaction products from AI3 and A.II.

Table 8

d) reaction products from AI4 and A.II.

Table 9

e) reaction products from AI5 and A.II.

Table 10

IV. Reaction products from primary diamines and polyisocyanates A. II. General manufacturing instructions

The polyisocyanate is added to the diamine heated to 150-180 ° C intensive stirring and nitrogen blanket added in portions so that the temperature of the reaction mixture does not rise above 190 ° C. After The addition of polyisocyanate is completed in about 10 minutes. continues to heat. The reaction is then ended.  

Table 11

V. Reaction products from A. IV. And maleic or fumaric acid esters and / or Acrylic acid ester (component B) General manufacturing instructions

The secondary amines with a functionality greater than 2 are prepared analogously to the preparation of the compounds described under AI2, AI3 or AI4, with 1 mol of maleic or fumaric or acrylic acid esters or 0.5 mol of maleic or fumaric acid esters and Acrylic acid ester 1 amine equivalent of amines A.IV. comes to reaction.

B. Preparation of the Compounds According to the Invention (Components A and B) General manufacturing instructions

The polyamine according to Tables 6 to 10 and 12 is metered into the acetone solution of the IPDI uretdione at room temperature with vigorous stirring so that the temperature of the reaction solution does not exceed 40.degree. After the polyamine addition has ended, the reaction is practically complete; the acetone is removed. If the free NCO groups of the IPDI uretdione / polyamine addition product are blocked with secondary monoamines, the procedure is such that, after the IPDI uretdione / polyamine reaction, the blocking agent is added in portions at about 40 ° C. and for about 1 h 60 ° C is further heated. The acetone is then removed. If the free NCO groups of the IPDI uretdione / polyamine addition product are to be blocked with alcohols (HO-R ⁴ ), the following procedure has proven to be advantageous:

• a) Implementation of the IPDI uretdione with the alcohol in substance at approx. 70 ° C (0.5 h),
• b) subsequent cooling and solution in acetone,
• c) implementation of this acetone solution with the polyamines.

The reversible blocking agents can also be used in the manner mentioned the free NCO groups are implemented, the reaction time between Is 1 and 5 hours.

For faster implementation between the blocking agent and the free NCO groups are advantageously used from 0.01 to 0.3% by weight of DBTL.

The IPDI uretdione (UD) used had the following characteristics:
NCO content (free) 16.8-18.5% by weight
NCO content (total) 37.4-37.8% by weight.

The urea and according to the invention listed in the following tables polyisocyanates containing uretdione groups with a functionality greater than 2 were synthesized according to the general instructions.

The polyisocyanates according to the invention according to Tables 6 to 10 (A.III.a. bis A.III.e.) and Table 12 (A.V.) are shown in Table 13.  

Table 13

Table 13: Continuation

Table 13: Continuation

C. Polyol component General manufacturing instructions

The starting components - terephthalic acid (TS), dimethyl terephthalate (DMT), hexanediol 1.6 (HD), neopentyl glycol (NPG), 1.4-dimethylol cyclohexane (DMC) and trimethylol propane (TMP) - are placed in a reactor and heated with the help of an oil bath. After most of the substances have melted, 0.5% by weight of di-n-butyltin oxide is added as a catalyst at a temperature of 160 ° C. The first elimination of methanol occurs at a temperature of approx. 170 ° C. The temperature is raised to 220 to 230 ° C. within 6 to 8 hours and the reaction is completed within a further 12 to 15 hours. The polyester is cooled to 200 ° C. and largely devoid of volatile components by applying a vacuum (1.33 mbar) within 30-45 minutes. The bottom product is stirred throughout the reaction time and a weak stream of N _{2 is} passed through the reaction mixture.

Table 14 shows polyester compositions and polyester of the market with the corresponding physical and chemical characteristics.

D. Polyurethane powder coatings General manufacturing instructions

The crushed products - polyisocyanates containing uretdione groups (Crosslinker), polyester, leveling agent - possibly catalyst masterbatch if necessary with the white pigment, if necessary with filler, intimately in a pan mill mixed and then homogenized in the extruder up to a maximum of 130 ° C. After cooling, the extrudate is broken up and opened with a pin mill a grain size <100 microns ground. The powder thus produced is with a electrostatic powder spraying system at 60 kV for degreased, possibly pretreated iron sheets applied and in a convection oven Temperatures baked between 180 and 200 ° C.

Leveling agent masterbatch

There are 10 wt .-% of the leveling agent - a commercial copolymer of Butyl acrylate and 2-ethylhexyl acrylate - in the corresponding polyester in the The melt is homogenized and crushed after solidification.

Catalyst masterbatch

There are 5 wt .-% of the catalyst - DBTL - in the corresponding Polyester homogenized in the melt and crushed after solidification.

The abbreviations in the following table mean:
SD = layer thickness in µm
ET = Erichsen cupping in mm (DIN 53 156)
GS = cross cut test (DIN 53 151)
GG 60 ° ∡ = measurement of gloss according to Gardner (ASTM-D 5233)

Claims (21)

1. Polyisocyanates containing urea and uretdione groups with a functionality greater than 2 and free, partially or totally blocked isocyanate groups, obtainable by reacting

• A) Uretdiones of the formula I:
  means
  With
• B) (cyclo) aliphatic polyamines which contain more than two amino groups, these containing residues of diamines of the formula II
  R ¹ -HN-A-NH-R ² (11),
  where A represents a (cyclo) aliphatic hydrocarbon radical with 2-16 C atoms, which may be alkyl-substituted,
  R ¹ and R ^{2 are} a (cyclo) alkylene radical, which can be branched, with 1-14 C atoms and / or a radical of the formulas
  R ^{3 are} identical or different hydrocarbon radicals with 1-14 C atoms, which can be alkyl-substituted
  and isocyanurate and / or biuret group-containing residues of polyisocyanates of the formula III:
  • i) OCN- (B) - [X] _n -NCO (III),
    where B
    n is 1-4, and 1 to 10 mol, preferably 1 to 8 mol, of the diamines II are used per NCO group of the formula III, the polyisocyanates containing urea and uretdione groups having the following properties:
    • a) a content of free NCO groups of ≦ 5,
    • b) a total NCO content (free and latent and / or blocked) of 3 to 20, preferably of 4.5 to 16% by weight,
    • c) a molecular weight between 1400 and 15000, preferably between 2,000 and 10,000 and
    • d) a varying melting range from 70 to 200 ° C.
      The radicals of the formula III can additionally be radicals of the formula
      ii) OCN- (B) -NCO
      included, the weight ratio i): ii) being equal to (100-20): (0-80).

2. polyisocyanates containing urea and uretdione groups according to claim 1, characterized in that the polyisocyanates according to formula III additionally linear radicals of the formula
ii) OCN- (B) -NCO
contain. 3. urea and uretdione polyisocyanates according to claims 1 and 2, characterized, that the uretdiones from isophorone diisocyanate and / or hexamethylene diisocyanate and / or 2-methyl-pentamethylene diisocyanate. 4. urea and uretdione polyisocyanates according to claims 1 to 3, characterized, that component B residues of the reaction products of secondary diamines, prepared by condensation and subsequent hydrogenation Carbonyl compounds with primary diamines selected from ethylenediamine, 1.2- Diaminopropane, 2-methylpentamethylene diamine, hexamethylene diamine, 2.2.4 (2.4.4) - Trimethylhexamethylene diamine, isophorone diamine, 1,2- and 1,4-diaminocyclohexane, Contains 4-bis (aminomethyl) cyclohexane and polyisocyanates of the formula III. 5. urea and uretdione polyisocyanates according to claims 1 to 3, characterized, that component B residues from reaction products of maleic and / or Fumaric and / or acrylic acid esters and diamines according to claim 3, or selected from 1,3-diamonopropane, 1,4-diaminobutane, 1,5-diaminopentane, 2.4- and / or 4,4'-diaminocyclohexylmethane, 1.11-diaminoundecane, 1.12- Contains diaminododecane and polyisocyanates of the formula III.   6. polyisocyanates containing urea and uretdione groups according to claims 1 to 3, characterized, that component B residues from reaction products of maleic and / or Fumaric and / or acrylic acid esters and primary / secondary diamines and Contains polyisocyanates of the formula III. 7. polyisocyanates containing urea and uretdione groups according to claims 1 to 3, characterized, that component B residues from reaction products of primary diamines with Polyisocyanates of the formula III and subsequent reaction with maleic and / or contains fumaric and / or acrylic acid esters. 8. urea and uretdione polyisocyanates according to claims 1 to 7, characterized, that as diisocyanates hexamethylene diisocyanate, 2-methylpentane diisocyanate, 2.2.4 (2.4.4) trimethylhexamethylene diisocyanate, isophorone diisocyanate and 4.4'- Diisocyanatdicyclohexylmethane can be used. 9. urea and uretdione polyisocyanates according to claims 1 to 8th, characterized, that they are partially or totally with methanol, ethanol, butanol, 2-ethylhexanol, Dibutylamine, di-2-ethylhexylamine, methylcyclohexylamine irreversible and / or with Acetone oxime, methyl ethyl ketoxime, acetophenone oxime, cyclohexanone oxime, Caprolactam and 1,2,4-triazole are reversibly blocked.   10. Process for the preparation of urea and uretdione groups Polyisocyanates with free, partially or totally blocked isocyanate groups and one Functionality greater than 2 according to claims 1 to 9, characterized, that the reaction in the solvent, preferably in acetone, preferably in Room temperature up to 40 ° C takes place. 11. The method according to claim 10, characterized, that the solvent by means of evaporation screws, film trudder or spray dryer Will get removed. 12. The method according to claims 10 to 11, characterized, that catalysts such as organic tin compounds to accelerate the reaction, e.g. B. dibutyltin dilaurate, in amounts of 0.01 to 0.5 wt .-%, preferably 0.05 up to 0.15% by weight. 13. Use of the polyisocyanates containing urea and uretdione groups with a Functionality greater than 2 in combination with hydroxyl groups Polymers for the production of PUR coating systems, especially PUR Powder coatings and coatings produced afterwards. 14. PUR powder coatings, characterized, that they contain urea and uretdione polyisocyanates with a Functionality greater than 2 according to claims 1 to 9 in combination with contain hydroxyl group-containing polymers and other additives.   15. PUR powder coatings according to claim 14, characterized, that an OH / NCO ratio of 1: 0.5-1.2, preferably 1: 0.8-1.1, in particular of 1: 1 is based. 16. PUR powder coatings according to claims 14 and 15, characterized, that the PU powder coatings are added catalysts in one Concentration of 0.01 to 0.5 wt .-%, including those already included Amount of catalyst from the polyisocyanates containing urea and uretdione groups. 17. PUR powder coatings according to claims 14 to 16, characterized, that added organic tin compounds as a catalyst to the PU powder coatings become. 18. PUR powder coatings according to claims 14 to 17, characterized, that 0.05 to 0, 15 wt .-% catalysts used in the PUR powder coatings become. 19. PUR powder coatings according to claims 14 to 18, characterized, that as hydroxyl-containing polymers polyester with a functionality greater as 2, an OH number of 20 to 200 mg KOH / g, a viscosity at 160 ° C. <60,000 mPa.s and a melting range of <70 to ≦ 120 ° C become.   20. PUR powder coatings according to claims 14 to 19, characterized, that the hydroxyl-containing polymers polyester with a functionality greater than 2, an OH number of 30 to 150 mg KOH / g, a viscosity at 160 ° C. <40,000 mPa.s and a melting range of 75 to ≦ 100 ° C can be used. 21. PUR powder coatings according to claims 14 to 20, characterized, that they contain urea and uretdione polyisocyanates in grain sizes Contain <100 microns, preferably <50 microns, especially <30 microns.