DE10057603A1 - Stable hardener for two-component coating material contains polyisocyanate with isocyanurate and-or biuret units and polyisocyanate with allophanate and-or urethane units, both derived from (cyclo)aliphatic di-isocyanate - Google Patents

Abstract

Mixtures containing (a) polyisocyanates (A) with isocyanurate and/or biuret units, derived from aliphatic or cycloaliphatic di-isocyanates (C) and (b) other polyisocyanates (B) with allophanate and/or urethane units, derived from (b1) di-isocyanates (C) as above and (b2) polyhydric aliphatic or cycloaliphatic alcohols (alcohols A'), with a mol ratio of (A):(B) = (200:1)-(5:1). Independent claims are also included for (i) a method for the production of these mixtures by reacting (C) with (A') in a mol ratio of (200:1)-(5:1), optionally in presence of catalysts for the formation of allophanates and urethanes, optionally deactivating the catalyst, optionally removing unreacted (C) and then mixing the resulting (B) with (A) in the above ratio; (ii) an alternative method in which (A) contains mainly isocyanurate units, involving the reaction of (C) with (A') as above, optionally in presence of catalysts for the formation of isocyanurates, allophanates and urethanes; (iii) an alternative method in which (A) contains mainly biuret unit, involving the reaction of (C), (A') and a biuretising agent (D) in mol ratios of (C):(A') = (200:1)-(5:1) and (C):(D) = (200:1)-(5:1), optionally in presence of catalysts for the formation of biurets, allophanates and urethanes; (iv) two-component coating materials containing a polyisocyanate mixture as above and an isocyanate-reactive component; (v) a method for coating objects by mixing the two components (see iv above) and coating the resulting mixture onto the substrate within 12 hours; (vi) coated objects obtained by this method.

Description

The present invention relates to mixtures containing

• a) polyisocyanates (polyisocyanates A) containing structure units selected from the group of isocyanurate and biuret, derived from aliphatic or cycloaliphatic diiso cyanates (diisocyanates C),
• b) polyisocyanates other than polyisocyanates A (poly isocyanates B) containing structural units selected from the group allophanate and urethane, derived from
• c) aliphatic or cycloaliphatic diisocyanates (Polyiso cyanate C) and
• d) polyhydric aliphatic or cycloaliphatic alcohols (Alcohols A),

the molar ratio of the polyisocyanates A to the polyiso cyanates B 200: 1 to 5: 1.

Crosslinking polyisocyanates and binder components with counter groups reactive over isocyanates are e.g. B. in the form of 2-component lac ken generally known (see. Kunststoff Handbuch, Volume 7, Polyure thane, 2nd edition, 1993, Carl Hanser Verlag Munich Vienna, p. 599 to 642; M. Bock, Polyurethanes for paints and coatings, Vin centz-Verlag, Hanover, 1999 and Journal for Practical Chemistry, 336 (1994) 185-200). This 2-component coating agent ent hold as a binder, for example, a polymeric polyol and as a crosslinker component (hardener) a compound with several free isocyanate groups.

The performance properties of paints, the polymeric binders of which are crosslinked with the isocyanates, are significantly improved compared to systems with low molecular weight binders. This applies in particular to usage properties such as

• - Insensitivity to mechanical stress like Tension, elongation, impact or abrasion,
• - Resistance to moisture (e.g. in the form of water steam) and diluted chemicals,  
• - Resistance to environmental influences such as temperature fluctuations and UV radiation,
• - high gloss of the coated surfaces,
• - high transparency.

It is expected that the hardener will not only cure the Lac ken the above-mentioned performance characteristics, but also the processing properties of the paints improve their mission or at least affect them as little as possible pregnant.

So that the paints easily using conventional methods, eg. B. by Spray on the surface to be coated, who applied can, the paints should have a limited viscosity. Contain paints based on 2-component coating agents therefore usually solvents. The high solvent content However, these paints cause problems because the processors of the Paints must take technically complex measures to ver avoid the solvents used when applying and drying the Paints are released, get into the atmosphere. There were therefore searched for hardeners that contain the viscosity of the binder Increase the component as little as possible or even better low. Of course, these hardeners are allowed to Room temperature have no significant volatility, such as this with commercially available monomeric isocyanates such as hexamethylene diisocyanate or isophorone diisocyanate is the case. Farther the hardeners are allowed to change their viscosities even after long storage do not increase, as this is a further addition of Solvents in the manufacture of the paint formulation itself would pull.

Furthermore, the 2-component coating compositions according to the Cure the application as quickly as possible so that the coated Items quickly processed or used after the order can be.

Products that have this property profile in at least one have peaceful scope, z. B. Allophanate units tra the polyisocyanates known from EP-A-303150. Polyisocyanates with isocyanurate units are e.g. B. from the EP-A-0017998 and US 4015155 known.  

These polyisocyanates are still in need of improvement, however the storage stability is particularly concerned with heat storage. at Prolonged storage will make the products more viscous, cloudy Flake or jell.

The object of the present invention was therefore a Polyisocyanate with the aforementioned property profile ready place, which can be stored for a long time without being in to significantly change properties.

Accordingly, the mixtures and processes defined at the outset for their manufacture, 2-component coating agents, the these contain blends as well as items related to them 2-component coating agents are coated, found.

The polyisocyanates A are known per se. They preferably contain 1, 2 or 3 structural units selected from the group of isocyanurate and biuret. Suitable polyisocyanates C, from which the polyisocyanates A are derived, are, in particular, those of the general formula (I) OCN-R ¹ -NCO, in which R ^{1 is} an alkylene or cycloalkylene unit having 4 to 20 carbon atoms, which is preferably distinguished by Abstraction of the NCO groups derived from hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).

The following polyisocyanates A are particularly preferred:

• 1. Isocyanurate group-containing polyisocyanates from aliphati or cycloaliphatic diisocyanates. Especially the corresponding isocyanato isocya are preferred nurates based on hexamethylene diisocyanate (HDI) or iso phosphoric diisocyanate (IPDI). With the present isocyanurates it is particularly simple tris-isocyanatoal kyl- or tris-isocyanatocycloalkyl isocyanurates, which cy are clical trimers of the diisocyanates, or mixtures with their higher, more than one isocyanurate ring (e.g. 2nd or 3 thereof) homologues. The Isocyanato Isocya nurates generally have an NCO content of 10 to 30 % By weight, in particular 15 to 25% by weight, and an average NCO Functionality from 2.6 to 4.5.

Isocyanurates of the general formula (IVa)

or the oligomeric forms derived therefrom, in which R4 has the same meaning as R ¹ in polyisocyanate A.

• A) Biuret groups containing polyisocyanates with aliphatic or cycloaliphatically bound isocyanate groups, the manufacturers lung z. B. in H. J. Laas et al., J. Prakt. Chem. 336 (1994) 185-200, or DE-A-8 09 663 (polyisocyanates AII). These are particularly those that differ from IPDI as well Derive bis (4-isocyanatocyclohexyl) methane (HMDI). Especially Tris (6-isocyanatohexyl) biuret or is particularly preferred its mixtures with its higher homologues. This biuret polyisocyanates containing groups generally have an NCO content of 10 to 30% by weight, in particular 18 up to 25% by weight and an average NCO functionality of 2.8 up to 4.5.

With the biuretizing agents, of which the biuret groups containing polyisocyanates A, it is water, Amine and a water generating substance. Suitable water genes Rational substances are, for example, monovalent tertiary alcohols Get like tert-butanol, iso-butanol or ion exchangers.

The polyisocyanates B are also known per se Links.

They are preferably derived from the same polyisocyanates C which are described above, particularly preferably from HMDI, HDI and IPDI.

With regard to alcohols A, all aliphatic or cycloaliphatic polyhydric alcohols can be used. These are preferably those of the general formula (II) HO-R ² -OH, in which R ^{2 is} an alkylene or cycloalkylene unit having 2 to 20 carbon atoms, which is optionally interrupted by oxygen atoms and in which 1 to 4 hydrogen atoms are substituted by C ₁ - to C ₁₂ -alkyl radicals. Branched diols such as propylene glycol, 1,2- and 1,3-butanediol, 2,2,4,4-tetra methyl-1,3-cyclobutanediol, 2-methyl-1,4-butanediol, 3-methyl are particularly preferred -1,3-butanediol, 1,2- and 1,3-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-2,4-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,2-, 1,3- and 1,4-hexanediol, 2-ethyl-1,3- hexanediol, 2,5-dimethyl-2,5-hexanediol, dipropylene glycol, tripropylene glycol, neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, particularly preferred are neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl -1,3-hexanediol, 2,4-diethyl-1,5-octanediol or mixtures thereof.

Preferred polyisocyanate B are those of the general formula (III)

in the
R ^{1 has} the same meaning as in the general formula I,
R ^{2 has} the same meaning as in the general formula II,
R ^{3 is} hydrogen or a radical -CO-NH-R ¹ -NCO, where R ^{1 has} the same meaning as in general formula I, with the proviso that at least one radical R ^{3 is} not hydrogen.

The molar ratio of the polyisocyanates A is preferably: the polyisocyanates B 100: 1 to 20: 1.

The mixtures according to the invention can also contain urethane and allophanate groups derived in small proportions, generally in amounts of 0.5 to 10% by weight, based on the polyisocyanates A, of monohydric primary or secondary C ₁ -C ₂₀ -alkyl alcohols Contain polyisocyanates. Suitable monohydric alcohols are, for example, aliphatic or cycloaliphatic alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol or 2-ethylhexanol.

The mixtures according to the invention can be prepared by various processes:
According to variant A, the procedure is such that polyisocyanate B is prepared by

• 1. Diisocyanates C and alcohols A in a molar mixture ver Ratio of 200: 1 to 5: 1, preferably 100: 1 to 20: 1, possibly in Presence of catalysts that prevent the formation of allophanates and accelerate urethanes,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted diisocyanate C is removed and
• 4. Polyisocyanate B then with a polyisocyanate A in the mixes specified in claim 1 proportions.

The implementation in step A1 can be carried out according to generally known methods which are carried out and differ, apart from that observing molar mixing ratio of the diisocyanates C to Al kohole A, not from the production of the well known, from monohydric alcohol-derived allophanates, such as those derived from the EP-A-303150 or EP-A-524501 are known. The same applies Step A2. Unreacted isocyanate is removed preferably under vacuum in a thin film evaporator (step A3). The mixing of the polyisocyanates A and B is not critical (Step A4).

Practically, however, the general procedure is to: carry out the reaction so that the polyisocyanates B and the polyisocyanates A are formed in one reaction step (Variants B and C).

Variant B primarily forms mixtures according to the invention in which the polyisocyanate A predominantly has isocyanurate units. To do this, proceed as follows:

• 1. Diisocyanates C and alcohols A in a molar mixture ver Ratio of 200: 1 to 5: 1, preferably 100: 1 to 20: 1 if necessary in the presence of catalysts that prevent the formation of Iso cyanurates, allophanates and urethanes accelerate to puts,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted isocyanate is removed.

Aside from the fact that polyhydric alcohols (alcohols A) are used, which the specified adjustment of the mol ratio of the starting materials alcohols A and polyisocyanates C. can be done here as it is in the EP-A-524501 is described, especially as regards catalysis Stop the reaction and remove the excess diiso cyanats.

In the case of variant C, mixtures of the invention in which the polyisocyanate A predominantly has biuret units are formed in particular. To do this, proceed as follows:

• 1. diisocyanates C, alcohols A and a biuretizing agent where at the molar mixing ratio of diisocyanates C to Al alcohols A 200: 1 to 5: 1, preferably 100: 1 to 20: 1 and the molar mixing ratio of diisocyanates C to that Biuretizing agent 200: 1 to 2: 1, preferably 100: 1 to 4: 1, possibly in the presence of catalysts, which Formation of biurets, allophanates and urethanes accelerate gene, implements,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted diisocyanate C is removed.

In step C1, the general procedure is to start with alcohol A and the total amount of polyisocyanate C. and the mixture at temperatures of 100 to 150 ° C warms and a few minutes later the biuretizing agent the catalyst that supports the formation of biurets, allophanates and Urethanes accelerated and possibly one in EP-A-809663 Add the written stabilizer and the mixture approx. 2 to 4 Hours at temperatures of 150 to 200 ° C. The steps C2 and C3 are then usually carried out as for variant A. and B. Otherwise applies to the manufacture of the Mix the same as in the preparation of polyisonates AII.

The mixtures according to the invention can be marketed in the form of preparations which, in addition to the mixtures according to the invention

• - Other iso different from polyisocyanates A and B. cyanate and
• - Other usually in two-component polyurethane paints included tools

contain.

The polyisocyanates according to the invention or the Mixtures according to the invention are particularly suitable as B-com component in the production of 2-component coating materials sen, which as a component A compound that with polyisocyanate reacting groups, preferably a hydroxy-functional Po lymer (A).

The hydroxy-functional polymers (A) are e.g. B. polymers with a hydroxyl group content of 0.1 to 20, preferably 0.5 to 10 wt .-%. The number average molecular weight M _{n of} the polymers is preferably 1000 to 100,000, particularly preferably 2000 to 10,000. The polymers are preferably those which comprise more than 50% by weight of C ₁ - to C ₂₀ - Alkyl (meth) acrylate, vinyl aromatics with up to 20 C atoms, vinyl esters of up to 20 C atoms containing carboxylic acids, vinyl halides, non-aromatic hydrocarbons with 4 to 8 C atoms and 1 or 2 double bonds, unsaturated nitriles and mixtures thereof consist. The polymers which consist of more than 60% by weight of C ₁ to C ₁₀ alkyl (meth) acrylates, styrene or mixtures thereof are particularly preferred.

In addition, the polymers (A) contain hydroxy-functional ones Monomers corresponding to the above hydroxyl group content and counter also other monomers, e.g. B. ethylenically unsaturated Acids, especially carboxylic acids, acid anhydrides or acid amide.

Other polymers (A) are e.g. B. polyesterols, as by Condensation of polycarboxylic acids, especially dicarboxylic acids, with polyols, especially diols, are available.

Also suitable as polymers (A) are polyetherols which by adding ethylene oxide, propylene oxide or butylene oxide H-active components are manufactured. Likewise, poly condensates from butanediol suitable.

The polymers (A) can of course also be compounds deal with primary or secondary amino groups.

May be mentioned for. B. so-called Jeffamine, d. H. with amino groups terminated polyetherols, or oxazolidines.

In addition to the A and B components listed above, in the 2-component coating agent further polyiso cyanates and compounds with polyisocyanates  capable groups, as is usually the case in two component coating compositions are present.

The molar ratio, formed from the sum, is preferably of the isocyanate groups in the B components compared to the sum of the groups of component (A) reactive with isocyanate groups, 0.6: 1 up to 1.4: 1, preferably 0.7: 1 to 1.3: 1, very particularly preferred 1: 1.

The coating compositions of the invention can still organic solvents, e.g. B. xylene, butyl acetate, methyl isobutyl contain ketone, methoxypropyl acetate, N-methylpyrrolidone. With Solvent is used for processing, i.e. H. to apply on Substrates, desired low viscosity of the coating material set.

The coating compositions can of course be further, in the Be Layering technology usual additives, e.g. B. pigments, fill contain substances, flow control agents etc.

You can also use catalysts for urethane formation, e.g. B. Dibutyltin dilaurate.

The production of the two-component polyurethane coating means can be done in a known manner. Usually the A- and the B component before the coating agents are applied mixed a substrate. Mixing is usually 0 up to 12 hours before the order. With solvent, the desired one Viscosity can be set.

The polyurethane coating compositions can in the usual way Spraying, pouring, rolling, brushing, knife coating etc. on substrates be applied across the board.

The coating compositions are particularly suitable for workpieces with surfaces made of metal, plastic, wood, wood materials, Ceramic or glass.

Experimental part 1. Preparation of the urethane and allophanate groups Polyisocyanurates from HDI and branched aliphatic diols

2500 g of hexamethylene diisocyanate (HDI) were under nitrogen submitted cover and heated to 80 ° C. At this temperature was the amount of alcohol shown in Table 1 or Alcohol mixture added. After the homogeneous interference of the  Alcohol or the alcohol mixture was 200 ppm by weight (referred on diisocyanate) of the catalyst N, N, N-trimethyl-N- (2-hydroxy propyl) ammonium 2-ethyl hexanoate added. After adding the kata A clear exotherm was found and the Temperature rose to 100-120 ° C. It was left at this temperature react and stopped the reaction given in Table 1 NEN content of the mixture by adding 250 ppm by weight (based on diisocyanate) di-2- (ethylhexyl) phosphate. The Reacti The mixture was then removed in order to remove the monomeric HDI Thin film evaporator at 165 ° C oil temperature and 2.5 mbar distill profiled. End product data is shown in Table 1.

Table 1

Modified polyisocyanurates

2. Production of the urethane and allophanate groups Polyisocyanurates from HDI and branched aliphatic mono alcohols, comparative tests

2500 g of hexamethylene diisocyanate (HDI) were under nitrogen submitted cover and heated to 80 ° C. At this temperature the amount of monoalcohol indicated in Table 2 was added ben. After homogeneous mixing of alcohol or  Alcohol mixture was 200 ppm by weight (based on diisocyanate) of the catalyst N, N, N-trimethyl-N- (2-hydroxypropyl) ammonium 2-ethyl hexanoate added. After adding the catalyst there was one clear exothermic and the temperature rose 100-120 ° C. It is allowed to react at this temperature and is stopped the reaction at the NCO content given in Table 2 Mixture by adding 250 ppm by weight (based on diisocyanate) Di-2- (ethylhexyl) phosphate. The reaction mixture was then to remove monomeric HDI in a thin film evaporator distilled at 165 ° C oil temperature and 2.5 mbar. End dates products are in table 2.

Table 2

Modified polyisocyanurates, comparative tests

3. Preparation of a urethane and allophanate group containing Polybiurets made from HDI and branched aliphatic diols

2500 g of HDI, 125 g of tert-butanol and 43.5 g of 2,2,4-trimethyl-1,3-pentanediol (2 mol% with respect to HDI) were placed under nitrogen blanket and heated to 130 ° C. At this temperature, a mixture of 15 g was tert within 2 min. Butanol, 2.5 g dist. Water and 2.2 g of urea added. There was a strong development of CO ₂ . After the evolution of gas had ended, the reaction mixture was stirred at 180 ° C. for 3 h. The reaction mixture was then distilled to remove the monomeric HDI in a thin film evaporator at 165 ° C oil temperature and 2.5 mbar. The modified polybiuret had a viscosity at 23 ° C of 19300 mPa.s and an NCO content of 20.6%.

4. Testing the storage stability of the polyiso according to the invention cyanate 4.1. Testing the storage stability at 23 ° C in ethyl acetate (water content 0.1%), closed container

The polyisocyanates according to the invention and the standard polyiso Basonat® HI 100 cyanate (comparison, BASF AG) were mixed with ethyl acetate diluted to a solids content of 30% and in sealed glass stored in a container. The samples were visually spaced daily Turbidity or flocculation checked.

Table 3

Storage stability at 23 ° C in ethyl acetate (water content 0.1%), closed container

3.2 Checking the storage stability in open containers in a standard climate (23 ° C, 50% relative humidity)

The polyisocyanates according to the invention, the comparison products and the standard polyisocyanate Basonat® HI 100 (comparison, BASF AG) were with solvent naphta / butyl acetate 1: 1 to a fixed content diluted by 70% and stored in open containers. Every day was the change in viscosity by determining the Flow time determined according to DIN EN ISO 2431 (4 mm discharge nozzle).

Table 3

Storage stability in open containers in a standard climate (23 ° C, 50% relative air humidity)

The polyisocyanates 1 to 7 according to the invention both showed opened containers in the presence of moist air as well Dilution with water-containing solvents is a comparison to the standard polyisocyanate and also compared to those with mono alcohol-modified products according to Table 2 clearly improved storage stability.

Testing the application properties of the inventor showed polyisocyanates according to the invention in polyurethane coating systems no differences compared to the standard.

Claims (13)

1. Containing mixtures

• a) polyisocyanates (polyisocyanates A) containing structural units selected from the group of isocyanurate and biuret, derived from aliphatic or cycloaliphatic diisocyanates (diisocyanates C),
• b) from the polyisocyanates A different polyisocyanates (polyisocyanates B) containing structural units, selected from the group of allophanate and urethane, derived from
  • 1. aliphatic or cycloaliphatic diisocyanates (diisocyanates C) and
  • 2. polyhydric aliphatic or cycloaliphatic alcohols (alcohols A),
• c) wherein the molar ratio of polyisocyanates A to polyisocyanates B is 200: 1 to 5: 1.

2. Mixtures according to claim 1, wherein it is in the Polyiso cyanates A are those with 1, 2 or 3 structure units selected from the group of isocyanurate and biuret, contain. 3. Mixtures according to claim 1 or 2, wherein the diisocyanate C is one of the general formula (I) OCN-R ¹ -NCO and R ^{1 is} an alkylene or cycloalkylene unit having 4 to 20 carbon atoms. 4. Mixtures according to claims 1 to 3, wherein it is Diisocyanate C is isophorone diisocyanate or hexamethylene is diisocyanate. 5. Mixtures according to claims 1 to 4, wherein the alcohol A is one of the general formula (II) HO-R ² -OH and R ^{2 is} an alkylene or cycloalkylene unit having 2 to 20 carbon atoms, optionally by oxygen atoms is interrupted and in which 1 to 4 hydrogen atoms are optionally substituted by C ₁ - to C ₁₂ -alkyl radicals. 6. Mixtures according to claims 3 to 5, wherein the polyiso cyanate B is one of the general formula (III),
in the
R ^{1 has} the same meaning as in the general formula I,
R ^{2 has} the same meaning as in the general formula II,
R ^{3 is} hydrogen or a radical -CO-NH-R ¹ -NCO, where R ^{1 has} the same meaning as in general formula I, with the proviso that at least one radical R ^{3 is} not hydrogen. 7. Preparations according to claims 1 to 6, containing
other isocyanates other than polyisocyanates A and B and
other auxiliaries usually contained in two-component polyurethane paints. 8. A process for the preparation of mixtures according to claims 1 to 7, wherein the polyisocyanate B is first prepared by

• 1. reacting diisocyanates C and alcohols A in a molar mixing ratio of 200: 1 to 5: 1, if appropriate in the presence of catalysts which accelerate the formation of allophanates and urethanes,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted diisocyanate C is removed
• 4. and the polyisocyanate B is then mixed with a polyiso cyanate A in the proportions specified in claim 1.

9. A process for the preparation of mixtures according to claims 1 to 7, in which the polyisocyanate A predominantly has isocyanurate units by:

• 1. reacting diisocyanates C and alcohols A in a molar mixing ratio of 200: 1 to 5: 1, if appropriate in the presence of catalysts which accelerate the formation of isocyanurates, allophanates and urethanes,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted diisocyanate C is removed.

10. A process for the preparation of mixtures according to claims 1 to 7, in which the polyisocyanate A predominantly has biuretein units, wherein

• 1. Diisocyanates C, alcohols A and a biuretizing agent, the molar mixing ratio of diisocyanates C to alcohols A being 200: 1 to 5: 1 and the molar mixing ratio of diisocyanates C to the biuretizing agent being 200: 1 to 2: 1, if necessary in the presence of catalysts which accelerate the formation of biurets, allophanates and urethanes,
• 2. if necessary, the catalysts are deactivated and
• 3. Any unreacted diisocyanate C is removed.

11. Two-component coating composition containing a ver bond bearing groups that react with polyisocyanate (A- Component), and a mixture according to claims 1 to 7 (B-component). 12. A method for coating objects, characterized in that one
produces a coating composition according to claim 11 by mixing components (A) and (B) and
apply the coating composition to an object within 12 hours after its production. 13. Coated articles produced according to claim 12.