HK1069181B - Cyclic ketones as blocking agents - Google Patents

Description

Cyclic ketones as blocking agents

Technical Field

The present invention relates to novel blocked polyisocyanates, to a process for their preparation and to their use in polyurethane systems.

The blocking of polyisocyanates to temporarily protect their isocyanate groups has been a procedure known for a long time, and is described, for example, in Houben Weyl, methods of organic chemistry XIV/2, pp.61-70. Curable compositions containing blocked polyisocyanates are used, for example, in polyurethane paints, especially in one-component (1K) polyurethane systems.

One-component (1K) polyurethane systems are widely used in the industrial stoving varnish sector, for example for the large-scale production of automotive coatings and coil coatings, and are distinguished by very good varnish properties, such as resistance to chemical attack, scratch resistance and weathering. Such paint films are hardened by thermal activation (by a baking process) of the blocked polyisocyanate by means of a polyol, optionally in the presence of a suitable catalyst. A review of blocking agents which are suitable for use in principle is given, for example, in Wicks et al, organic coating Advances 1975, 3, pp.73-79, 1981, 9, pp.3-28 and 1999, 36, pp.148-172.

For use in the automotive coating field, the blocked polyisocyanates must be crosslinkable at a maximum baking temperature of 140 ℃ and must exhibit only very slight, preferably no, yellowing during baking. The baking temperature is controlled primarily by the reactivity of the blocked polyisocyanate.

Most stoving systems, for example melamine formaldehyde and urea-formaldehyde resins, are characterized by the release of volatile components during hardening, thus increasing the VOC (volatile organic compound) value.

Furthermore, a proportion of the blocking agent remains in the formed lacquer film and has a negative effect on its properties. Due to the residues of these blocking agents, the properties of one-component paint films, such as scratch and acid resistance, cannot be matched to those of so-called two-component (2C) polyurethane paint films (e.g. t.，E.Jürgens，《Farbe&Rock, cutt r. vincentz press, hannov 10/1995). In addition, the separation of the blocking agent from the paint film and its escape in gaseous form can lead to the formation of bubbles in the paint film. It may sometimes be necessary to subsequently incinerate the evolved endcapping agent.

Isocyanates blocked with diethyl malonate have recently been used mainly for particularly low baking temperatures in the range of 90 ℃ to 120 ℃ (for example, EP-a 10947531). Unlike blocking procedures using heterocyclic N compounds such as caprolactam or butanone oxime, this blocking agent does not split off completely in this case but causes a transesterification reaction on isocyanates blocked with diethyl malonate. Ethanol is separated off during the transesterification. The process is useful for lower baking temperatures because the second, adjacent ester functionality is an activated ester. The disadvantage of this process is that systems such as these are extremely sensitive to the action of acids due to the rapid cleavage of the active ester bonds. Thus, the application possibilities of such products are limited.

The object of the present invention is to provide a novel blocked polyisocyanate system which does not separate out the blocking agent during the reaction, i.e.does not evolve gas, and which can be crosslinked at low temperatures. It is also an object of the present invention that such blocked polyisocyanate systems should remain stable on storage at ambient temperatures and, in particular, in combination with suitable polyol components, be suitable for the production of one-component stoving lacquers.

Surprisingly, it has now been found that acidic CH-compound-blocked polyisocyanates having the basic structure of activated cyclic ketones, in particular cyclopentanone-2-carboxymethyl ester, are particularly suitable for obtaining coatings having a reduced tendency to yellowing and which do not generate gas.

The invention relates to organic polyisocyanates containing at least two isocyanate groups which are blocked by acidic CH-ring ketones of the general formula (I),

wherein

X is an electron-withdrawing group,

R¹and R²Independently of one another, represent the radicals hydrogen, C₁～C₂₀(cyclo) alkyl, C₆～C₂₄Aryl radical, C₁～C₂₀(cyclo) alkyl ester or amide, C₆～C₂₄Aryl esters or amides, or mixed aliphatic/aromatic groups containing 1 to 24 carbon atoms, which may also form part of a 4 to 8 membered ring,

n is an integer of 0 to 5,

and the content of blocked isocyanate groups (in terms of NCO) is 0.1 to 20 wt% based on the total amount.

The blocked isocyanate group (in terms of NCO) content is preferably 0.1 to 15.6% by weight. The blocked isocyanate group content (in terms of NCO) is particularly preferably from 0.1 to 14% by weight. Partial blocking of the polyisocyanate may optionally be carried out; the unblocked isocyanate groups are then available for further reaction. Typically, all isocyanate groups are blocked.

The electron withdrawing group X may comprise any substituent that results in the alpha-terminal hydrogen exhibiting acidic CH characteristics. The substituents may be ester groups, amide groups, sulfoxide groups, sulfone groups, nitro groups, phosphonate groups, nitrile groups, isonitrile groups, polyhaloalkyl groups, halogens such as fluorine, chlorine or carbonyl groups. Preference is given to nitrile and ester groups, particular preference to methyl carboxylate and ethyl carboxylate groups.

Compounds of the general formula (I), the rings of which optionally contain heteroatoms such as oxygen, sulfur or nitrogen atoms, are also suitable.

The size of the ring of the activated cyclic ketone of formula (I) is preferably 5(n ═ 1) or 6(n ═ 2).

Preferred compounds of the general formula (I) include cyclopentanone-2-carboxymethyl ester and-carboxyethyl ester, cyclopentanone-2-carboxynitrile, cyclohexanone-2-carboxymethyl ester and-carboxyethyl ester, or cyclopentanone-2-carbonylmethyl. Particular preference is given to cyclopentanone-2-carboxymethyl ester and-carboxyethyl ester and also to cyclohexanone-2-carboxymethyl ester and-carboxyethyl ester. Cyclopentanone systems can be conveniently prepared on an industrial scale by dieckmann condensation of dimethyl adipate or diethyl adipate. Cyclohexanone-2-carboxymethyl ester can be obtained by hydrogenation of methyl salicylate.

The polyisocyanate to be blocked may be any organic polyisocyanate suitable for use in the crosslinking reaction of active hydrogen-containing compounds, i.e., aliphatic polyisocyanates containing at least two isocyanate groups, including cycloaliphatic polyisocyanates, as well as aromatic and heterocyclic polyisocyanates, and mixtures thereof. Typical examples of polyisocyanates include aliphatic isocyanates such as di-or triisocyanates, for example Butane Diisocyanate (BDI), pentane diisocyanate, Hexane Diisocyanate (HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN), or cyclic systems such as 4, 4' -methylene-bis (cyclohexyl isocyanate) ((cyclohexyl isocyanate))W, Bayer, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethyl-cyclohexane (IPDI), or even omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Examples of aromatic polyisocyanates include 1, 5-naphthalene diisocyanate, diisocyanato-diphenylmethane (MDI) or crude MDI, diisocyanatomethylbenzene (TDI), in particular the 2, 4-and 2, 6-isomers thereof and technical mixtures of the two isomers, and even 1, 3-bis (isocyanatomethyl) benzene (XDI).

Polyisocyanates which are also very suitable are those polyisocyanates which are obtained by reacting di-or triisocyanates themselves via their isocyanate groups, for example uretdione or carbodiimide compounds, or for example isocyanurates or iminooxadiazinediones which are formed by reaction of three isocyanate groups. The polyisocyanates may also comprise monomeric di-and/or triisocyanates and/or oligomeric polyisocyanates containing biuret, allophanate and acylurea structural elements, monomeric di-or triisocyanates with a low monomer content or partially modified, or even mixtures of any of the above polyisocyanates.

Polyisocyanate prepolymers containing an average of more than 1 isocyanate group per molecule are also very suitable. These prepolymers are obtainable by preliminary reaction between a molar excess of one of the abovementioned polyisocyanates with organic materials containing at least two active hydrogens per molecule, for example in the form of hydroxyl groups.

Preferred polyisocyanates are those containing uretdione, isocyanurate, iminooxadiazinedione, acylurea, biuret or allophanate structures, for example those based on Butane Diisocyanate (BDI), pentane diisocyanate, Hexane Diisocyanate (HDI), 4-isocyanatomethyl-1, 8-octane diisocyanate (triisocyanatononane, TIN) or cyclic systems, for example 4, 4' -methylenebis (cyclohexyl isocyanate) ((cyclohexyl isocyanate))W, Bayer, Leverkusen), 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI), or even omega, omega' -diisocyanato-1, 3-dimethylcyclohexane (H)₆XDI). Examples of aromatic polyisocyanates include 1, 5-naphthalene diisocyanate, diisocyanato-diphenylmethane (MDI) or crude MDI, diisocyanatomethylbenzene (TDI), in particular the 2, 4-and 2, 6-isomers thereof and technical mixtures of the two isomers, and even 1, 3-bis (isocyanatomethyl) benzene (XDI).

Particularly preferred polyisocyanates are those based on Hexane Diisocyanate (HDI), on 4, 4' -methylene-bis (cyclohexyl isocyanate) or on 3, 5, 5-trimethyl-1-isocyanato-3-isocyanatomethylcyclohexane (IPDI).

The invention also relates to a process for producing blocked organic polyisocyanates according to the invention, which is characterized in that polyisocyanates are reacted with acidic CH cyclic ketones of the general formula (I) in the presence of catalysts, wherein 0.8 to 1.2mol of cyclic ketone of the general formula (I) are used per isocyanate group equivalent of the polyisocyanate to be blocked.

Wherein

X is an electron-withdrawing group,

R¹and R²Independently of one another, represent the radicals hydrogen, C₁～C₂₀(cyclo) alkyl, C₆～C₂₄Aryl radical, C₁～C₂₀(cyclo) alkyl ester or amide, C₆～C₂₄Aryl esters or amides, or mixed aliphatic/aromatic radicals having 1 to 24 carbon atoms, which may also form part of a 4 to 8-membered ring, and

n is an integer of 0 to 5,

1 equivalent of isocyanate groups the polyisocyanate to be blocked is preferably reacted with 1 equivalent of blocking agent.

Alkali metal and alkaline earth metal bases, for example, powdered sodium carbonate (soda ash), are suitable as catalysts. Depending on the cyclic ketone used, trisodium phosphate or Dabco (1, 4-diazabicyclo [2.2.2] octane) may also be used. Also suitable are carbonates of metals of subgroup II. Preferably, sodium or potassium carbonate is used. Alternatively, the reaction of the cyclic ketone with the isocyanate may be carried out in the presence of a zinc salt catalyst. The reaction using zinc 2-ethylhexanoate is particularly preferred. Mixtures of catalysts may also be used.

In the practice of the process of the invention, 0.05 to 10 wt.%, preferably 0.1 to 3 wt.%, of a catalyst is added to the polyisocyanate used. Most preferably, 0.2 to 1 wt% of catalyst is used.

The reaction can be carried out at room temperature or at elevated temperatures up to 140 ℃. The temperature is preferably in the range of 40-90 ℃, and particularly preferably 15-90 ℃.

The capping reaction can be carried out without a solvent or in the presence of a suitable solvent. Suitable solvents include the customary lacquer solvents, for example butyl acetate, methoxypropyl acetate or solvent naphtha as supplied by Exxon-Chemie (Esso (Germany) Inc., Hamburg) as solvent containing aromatic compounds, and also mixtures of the abovementioned solvents. The end-capping reaction is preferably carried out in the above-mentioned solvent, wherein the solid content should be adjusted to 10 to 90%.

In addition to the cyclic ketones of the formula (I) used according to the invention, any mixture of blocking agents can be used in the process according to the invention in order to achieve the desired lacquer properties in each case, the proportion of compounds of the formula (I) being at least 30% by weight, preferably 50% by weight and most preferably 100% by weight.

Finally, the invention relates to a process for producing 1-K PUR stoving lacquers, which is characterized in that the organic polyisocyanates according to the invention are used as crosslinking components for organic polyhydroxyl compounds.

The blocked polyisocyanates according to the invention are characterized in that they are cured at temperatures of 110 to 140 ℃, preferably 120 to 140 ℃ and baking times of 15 to 30min in the presence of suitable catalysts in combination with suitable organic polyhydroxyl compounds. The baking time depends inter alia on the amount of catalyst used. The baking is preferably carried out at a temperature of 120-140 ℃ for 30 min.

If the blocked polyisocyanates according to the invention are used for the production of coil coatings, these blocked polyisocyanates harden in a maximum baking time of 2 minutes, preferably 5 to 35 seconds. The furnace temperature is 300-400 ℃. The baking conditions depend of course on the material used and on the hardness of the metal sheet to be coated. The furnace temperature is typically a minimum of 180 ℃ and a maximum of 260 ℃ PMT. The preferred temperature range is 210 ℃ to 245 ℃ PMT. Particularly preferred is PMT at a temperature in the range of 216 ℃ to 241 ℃. Furthermore, the lacquer-technical properties of the stoving varnish, such as the solvent resistance, hardness and elasticity of MEK (methyl ethyl ketone) at a certain temperature, also depend on the amount of catalyst used. Baking at 232 deg.C for 38 seconds is preferred. Baking at 216 ℃ is also possible. Baking for 33 seconds when the substrate is aluminum. The optimum specific conditions can be determined by positional preliminary tests in the manner customary to the expert, and the temperature of the coil coating furnace is controlled by means of a thermal sensor (Sensitivland) during the application.

Suitable catalysts for crosslinking are, for example, DBTL (dibutyltin dilaurate), titanium 2-ethylhexanoate, titanium tetraisopropoxide and other customary titanium (IV) compounds, zirconium 2-ethylhexanoate and other customary zirconium (IV) compounds, aluminum triacetate, scandium trifluoromethanesulfonate, yttrium 2-ethylhexanoate, yttrium trifluoromethanesulfonate, lanthanum 2-ethylhexanoate, lanthanum trifluoromethanesulfonate, cobalt 2-ethylhexanoate, indium trifluoromethanesulfonate, gallium acetoacetate, nickel acetoacetate, lithium 2-ethylhexanoate, lithium trifluoromethanesulfonate, sodium 2-ethylhexanoate, sodium acetate, sodium trifluoromethanesulfonate, magnesium 2-ethylhexanoate, magnesium trifluoromethanesulfonate, calcium 2-ethylhexanoate, calcium trifluoromethanesulfonate, zinc 2-ethylhexanoate, Zinc dithiocarbamate, zinc acetoacetate, zinc tetramethylheptanedionate, zinc salicylate, zinc chloride and other common zinc (II) compounds, bismuth 2-ethylhexanoate and bismuth acetate. Preferred catalysts are zinc compounds and bismuth compounds, particularly preferably zinc 2-ethylhexanoate and bismuth 2-ethylhexanoate.

Suitable polyols for this purpose of use, as well as details concerning the production and use of stoving lacquers of this type, can be found, for example, in DE-A19738497 or EP-A0159117. The most preferred field of application of the products of the invention is their use as crosslinkers for automotive primer surfacers.

A high-grade, isolate-free coating or lacquer coating with reduced yellowing value is obtainable using the blocked polyisocyanates according to the invention.

In addition, the blocked polyisocyanates of the invention can be hardened with di-or polyamines. The reaction is preferably carried out at room temperature. It can be used for producing lacquer coatings or workpieces.

Coil coatings can be produced using polyester polyols, polycarbonates and polyacylated polyols. In principle, adhesives with a sufficiently high OH content can be used.

^*) Bayer products, Leverkusen, DE

As with the above components, the adhesives of the invention may also contain other stabilizersAdditives, such as HALS amines or solvents and OH-functional hydrazide compounds, which may be up to 5% by weight, based on the finished paint solids. Other additives also include, for example, CAB (cellulose acetate butyrate) and4F (flow agent (Verlaufmitel) and antifoam).

There may be added those of the general formula (II) already mentioned in EP-A0829500

An adduct of 2 moles of propylene carbonate with hydrazide hydrate of (b).

Examples

The polyisocyanate used was an HDI polyisocyanate having an isocyanurate structure, an NCO content of 21.8%, a viscosity of 3200mPa.s ((HDI-HDIN3300, bayer, Leverkusen).

Cyclopentanone-2-carboxymethyl ester and cyclohexanone-2-carboxymethyl ester used as blocking agents were ordered from the Fluka company and used without further purification.

Preparation of acidic alpha-cyclic ketone blocked polyisocyanates

Example 1

58.5g (0.3 eq) are dissolved in 81ml of butyl acetateThe N3300 solution was added slowly with vigorous stirring to a solution of cyclopentanone-2-carboxymethyl ester (42.7g, 0.3 eq) dissolved in 20ml of butyl acetate. 1.02g of 2-Zinc ethylhexanoate was added as catalyst. The batch was heated to 50 deg.C (about 8h) until the NCO value was determined to give a value of about 0.2%. Theoretical blocked NCO contentThe amount was 6.2%.

Example 2

42.6g (0.25 eq)A solution of N3300 in 71.4mL of butyl acetate was added slowly with vigorous stirring to a solution of cyclohexanone-2-carboxyethyl ester (42.6g, 0.25 eq.) in 20mL of butyl acetate. 0.9g of 2-Zinc ethylhexanoate was added as catalyst. The batch was heated to 80 ℃ until the NCO value had been determined to give a value of about 0.3% (after about 6 h). The theoretical blocked NCO content is 5.75%.

Preparation of the polyurethane paints according to the invention

The polyisocyanates listed in the table below are processed stoichiometrically with the polyols to give varnishes according to the formulations listed below, to which conventional additives are addedOL 17 (Bayer corporation, Leverkusen) (flow promoter), 0.1% solids, relative to the binder of the solid base) and(Monsanto, Solutia, USA; 0.01% solids, relative to the binder of the solid base).

Example 3

Paint formulation A

N3300 (bayer, Leverkusen), blocked with cyclopentanone-2-carboxymethyl ester (supplied as an approximately 50% solution in butyl acetate; blocked NCO content: 6.2%) (SN ═ solvent naphtha, MPA ═ methoxypropyl acetate, BA ═ butyl acetate):

blocked NCO/OH ratio: 1.0,

solid content: about 45 percent of the total weight of the composition,

catalyst content: 1.5% (solids, relative to the solid-based paint vehicle)

The system showed only very slight yellowing. This system can also be used successfully at an NCO/OH ratio of 1: 1.5.

Paint formulation B (comparison example)

Baking conditions: 30min, 140 deg.C

In the case of solvent-containing lacquers, the systems exhibit a pronounced yellowing even at relatively low baking temperatures. The Δ b values of the bulk systems are 3.2 at 140 to 160 ℃ and are therefore about 3 times higher than systems which show only slight yellowing (e.g. dimethylpyrazole) when applied to a primer containing a white solvent.

Determination of yellowing due to overbaking: after baking the lacquer at 140 ℃ for 30min, a first color determination is carried out by the so-called CIELAB method. The higher the positive b value determined in this way, the more yellow the varnish becomes. Subsequently, overbaking was carried out at 160 ℃ for 30 min. The increase in yellowing is then determined, i.e.the so-called Δ b value according to the CIELAB color system (DIN 6174, "colorimetric determination of body color separation according to the CIELAB formula" (version 01, 79). The value should be as close to 0 as possible for non-yellowing varnishes.

Examples of coil coating applications

Raw materials: blocked polyisocyanates

Preparation of acidic alpha-cyclic ketone blocked polyisocyanates

Blocked polyisocyanate A:

0.17g of 2-ethylhexylzinc (0.05% by weight) was added as a catalyst to 193.5g (1 eq)In a solution of N3300, the latter is dissolved in 14g of methoxypropyl acetate (8 parts) and 29.9g of xylene (17 parts), amounting to 70% of the solution. The following reaction takes place under nitrogen. After this mixture was stirred well, 156.2g (1 eq) of cyclopentanone-2-carboxyethyl ester (distilled) were carefully added dropwise. The reaction temperature must not exceed 40 ℃ during this time. After the dropwise addition of the ester, stirring was continued at 40 ℃ until an NCO value of zero was reached (after about 6 hours). The theoretical NCO content of the end-capping was 8.3%. The desired viscosity is then adjusted with 7% by solids of 2-butanone. Then adding 2.5% of solid770DF (8.7 g). The polyisocyanate formulated was an HDI polyisocyanate having an isocyanurate structure and an NCO content of 21.8% and a viscosity of 3000mPas (N3300, bayer, Leverkwsen).

Blocked polyisocyanate B:

3 equivalent (580.5g)N3300 and 1 eq (353g)Z4470 was dissolved in 415g of xylene under nitrogen (70% mixture after reaction). 1.45g (0.1 wt%) of zinc 2-ethylhexanoate was added as a catalyst to the mixture. After this mixture was mixed well, 4 equivalents (624.8g) of cyclopentanone-2-carboxyethyl ester were carefully added dropwise. The reaction temperature must not exceed 40 ℃ during this time. After the addition of the ester, stirring was continued at 40 ℃ until the NCO value was close to zero (about 12 hours). The blocked NCO content was thus 8.1%. After the reaction was completed, 101.7g of 2-butanol (7% as solid) and 29g (2% as solid) were further added770 DF. The polyisocyanate formulated was an HDI polyisocyanate having an isocyanurate structure and an NCO content of 21.8% and a viscosity of 3000mPs (c), (d), (N3300, Bayer Corp., Leverkusen) and a polyisocyanate having an isocyanurate structure prepared on the basis of IPDI (NCO content 11.9%, viscosity 2000mPs,z4470, bayer, Leverkwsen).

Blocked polyisocyanate C:

0.9 eq (174.2g)N3300 and 0.1 eq (29g)The W-trimer was dissolved in xylene under nitrogen (70% mixture after reaction). 0.351g (0.1 wt%) of zinc 2-ethylhexanoate was added as a catalyst to the mixture. After this mixture was stirred well, 1 equivalent (156.2g) of cyclopentanone-2-carboxyethyl ester was carefully added dropwise. The reaction temperature must not exceed 40 ℃ during this time. After the addition of the ester, stirring was continued at 40 ℃ until the NCO value was close to zero (about 12 hours). The blocked NCO content was 8.16%. After the reaction was complete, 7g (2% based on solids) of Tinuvin 770DF were added. The complex polyisocyanate was an HDI polyisocyanate having an isocyanurate structure and an NCO content of 21.8% and a viscosity of 3000mPas (N3300, Bayer corporation, Leverkusen) and one inMixture of polyisocyanates having an isocyanurate structure prepared on the basis of W (13.5%N3300, trimerDegree of conversion 20%, NCO content 14.5%, 65% solids (in xylene/methoxypropyl acetate)).

The blocking agent cyclopentanone-2-carboxyethyl ester used was purchased from Fluka.

Blocked polyisocyanates for comparison:

BL3175 (Bayer) a crosslinked baked urethane resin based on hexamethylene diisocyanate 75% soluble in solvent naphtha, having a viscosity of about 3300mPas, an NCO content (blocked) of about 11.1% and blocking agent butanone oxime.

BL3370 (Bayer), an aliphatic crosslinked baked urethane resin, about 70% soluble in 1-methoxypropyl acetate 2- (MPA), a viscosity of about 3500, 1200mPas, an NCO content (blocked) of about 8.9%, and a blocking agent of diisopropylamine.

The polyol used: see table below.

Preparation of the polyurethane paints according to the invention

The production of the paints according to the invention is described in the specification for the production of the blocked isocyanate component.

Coating varnish, white, polyol component for 1K-PUR coil coating1665

A ═ polyisocyanate a, B ═ polyisocyanate B, C ═ polyisocyanate C

Parameter(s)

Notes (4+5) CAB andthe 4F combination is used for degassing and flow.

Supplier (1) Kronos International INC, Leverkusen

(2) Deutsche Exxon，

(3) Brenntag，Mülheim/Ruhr

(4) BASF AG，Ludwigshafen

(5) Krahn Chemie，Hamburg

The raw materials used

1665 oil-free, saturated polyester based on isophthalic acid/adipic acid/NPG/propylene glycol, Bayer, Leverkusen, OH content: 1.7% at a supply of 65% dissolved in the solvent naphtha 100/isobutanol 31.5: 3.5.

CAB (cellulose acetate butyrate) supplier: krahn Chemie, hamburger; the manufacturer: eastman Kingsport USA; CAB531-1 (butyryl content about 53%, negligible hydroxyl content 1.7%)

4F manufacturer BASF corporation, Ludwigshafen, polymers (flow agents and defoamers) obtained on the basis of butyl acrylate

Esso/Exxon from 200S, solvent fragrance content 99%, evaporation coefficient (ether 1) to 1000

Determination of the white value

ASTM E313, white index

Whiteness (without DIN) according to the Berger method

Whiteness Ry +3(Rz-Rx)

DIN6167 yellow index was calculated according to the following formula:

standard colour number of X, Y + Z ═ DIN 5033

a red/green axis^*

b-blue/yellow axis^**

^*Positive valuesNegative value of redOf green colour

^**Positive valuesNegative value of yellowOf the blue

MEK stability assay

Description of the determination method (according to ECCA-T11 and DIN EN ISO 2812-1 and DINEN 12720):

the MEK rub test is a rapid test for the final hardening of the paint film. For this purpose, a cotton ball which has a constant pressure on the paint film and has been soaked with MEK is moved back and forth over the paint film.

Instrument/auxiliary tool: balance (Bizerba brand), 100g, 1Kg and 2Kg weights

The implementation is as follows:

a counter pressure of 1kg was applied to a coating thickness of 20 μm and a counter pressure of 2kg was applied to a coating thickness of 20 μm or more.

The metal sheet to be tested is fixed on the pan of the balance by means of film clips and an anti-slip film. The balance was calibrated with a 100g weight and taraaussleich taraauer. A cotton ball soaked with MEK was moved back and forth across the paint film with the selected test pressure until the paint film was destroyed.

And (3) analysis:

two-stroke numbers up to coating failure have been listed in the test report, with the largest two-stroke number being 100. After any 100 double strokes, the paint film is deformed (abgemistert) in view of the change (matt, softening) of the paint film.

Determination of T-bend test

The method is described according to ECCA T7 (ECCA: European coil coating Association):

the purpose is as follows:

the method describes determining the resistance of an organic coating to crack formation at a 180 ° degree of curvature.

The principle is as follows:

in this test, the sample is bent parallel to the direction of rolling by 180 ° in 1 to 2 seconds, during which the coating is on the outside. It must be bent to allow contact between the metal sheets to be made to ensure that a uniform degree of bending is achieved. The minimum bend radius at which crack-free bending of the sample occurs determines the resistance to 180 ° curvature. In this process, the adhesive tape was used to check the adhesion after each bending.

Appliance:

the apparatus that can be used to carry out the method has a screw-type vise and a set of protective clamps.

Preparation work:

the samples to be tested were stored in the laboratory at room temperature and air humidity for at least 24 hours. The test was performed under the same conditions.

If more detailed conditions are specified or in the arbitration case, the description of ISO 3270-1984, i.e. a temperature of 23. + -. 2 ℃ and a relative air humidity of 50. + -. 5%, should be noted.

The procedure is as follows:

a thin strip of metal about 2cm wide was cut in the rolling direction. Bending the metal thin strip in parallel with the rolling direction for 180 degrees within 1-2 seconds, wherein the coating is positioned on the outer side in the process. And then tightly pressed by a screw type vice.

The curved edge was inspected with a 20-fold magnifying glass. The adhesion phenomenon was then pressed three times, and one piece of the adhesive tape was torn off for inspection.

This deformation of 0T curvature (Abmuster), denoted by R for cracks and by H for adhesion, was evaluated with 0-5, 0 being the best value and 5 being the worst value.

The metal sheet is then bent back until the value 0 is reached when cracks form and adhesion phenomena occur.

The test ends at the latest at 3.0T.

Re-pull stability

The deformed T-bend metal strip is heated to 100 ℃ for 30 minutes and then deformed by pulling.

Preparation of the paint:

the test was carried out in a white coil-coating varnish according to the standard recipe (standard recipe RR 6830). This was done by first preparing a hard-milled material from an oil-free saturated polyester according to the following bead milling formulation:

9.8 parts (T1.) oil-free polyester1665, 65% supply style

7.8 parts of solvent200S

22.3 parts of white pigment Kronos 2330

The abrasive material was dispersed with 2mm silica beads.

Disperse within 1 hourOn a mixer (note: on a bead mill andthe same formulation can be used for dispersion on the mixer (shaker). By usingThe mixer has the advantage of dispersing multiple samples simultaneously and allows milling in a sealed container. The beads were then sieved and withdrawn. )

The ground material was separated from the glass beads by sieving.

The remaining paint components were added with stirring.

21.5 parts of oil-free polyester1665, 65% supply style

11.9 parts of blocked polyisocyanate^*)

0.7 part of DBTL inThe concentration in 200S is 10%

7.3 parts of cellulose acetate butyrate CAB531-1 inThe concentration in 200S/butyldiglycol (2:1) was 10%

1.5 parts of4F inThe concentration in 200S is 50%

X portion200S (10.3 parts in the case of BL3175 as blocked polyisocyanate).

^*) The amount of blocked PIC added depends on the equivalent weight of the PIC (in this caseBL3175 as control). Equivalent combinations of polyols and blocked polyisocyanates, i.e. when only fewer blocked NCO groups are available, the portion of blocked PICs that is dosed must be increased.

By usingThe 200S lacquer was adjusted to a processing viscosity of about 70sec DIN4/23 ℃.

The paint was applied to a chromic acid passivated aluminium plate (1mm thick) with a squeegee. Immediately after painting, the aluminum panels were baked in an Aalborg oven on a turntable.

Baking at 210 deg.C for 30 s at 350 deg.C for PMT

Baking at PMT216 deg.C and 350 deg.C for 33 s

PMT224 deg.C, baking at 350 deg.C for 35 s

PMT232 ℃ and baking at the furnace temperature of 350 ℃ for 38 seconds

The PMT is more than 254 ℃, and the baking is carried out for 50 seconds in a furnace temperature of 350 DEG C

The dry coating thickness is 20-22 μm.

In summary, some technical solutions provided by the present invention are as follows:

1. an organic polyisocyanate containing at least two isocyanate groups, the isocyanate groups of which are blocked by an acidic CH-cyclic ketone of the general formula (I),

wherein

X is an electron-withdrawing group,

wherein the electron withdrawing group X is selected from an ester, amide, sulfoxide, sulfone, nitro, phosphonate, nitrile, isonitrile, polyhaloalkyl group, fluoro, chloro or carbonyl group;

R¹and R²Independently of one another, represent the radicals hydrogen, C₁～C₂₀Alkyl radical, C₁～C₂₀Cycloalkyl radical, C₆～C₂₄Aryl radical, C₁～C₂₀Alkyl esters or amides, C₁～C₂₀Cycloalkyl esters or amides, C₆～C₂₄Aryl esters or amides, or mixed esters containing 1 to 24 carbon atomsAnd (b) aliphatic/aromatic groups which may also form part of a 4-to 8-membered ring,

n is an integer of 0 to 5,

and blocked isocyanate groups in an amount of 0.1 to 20 wt% based on the total amount of the organic polyisocyanate.

2. The organic polyisocyanates according to claim 1, wherein the acidic CH cyclic ketones of the general formula (I) include cyclopentanone-2-carboxymethyl ester and-carboxyethyl ester, cyclopentanone-2-carboxylic acid nitrile, cyclohexanone-2-carboxymethyl ester and-carboxyethyl ester or cyclopentanone-2-carbonylmethyl.

3. The organic polyisocyanates according to claim 1, wherein the acidic CH cyclic ketones of the general formula (I) include cyclopentanone-2-carboxymethyl ester and carboxyethyl ester, cyclohexanone-2-carboxymethyl ester and carboxyethyl ester.

4. A process for the production of the organic polyisocyanates according to claim 1, characterized in that polyisocyanates are reacted with acidic CH cyclic ketones of the general formula (I) as defined in claim 1 in the presence of catalysts, wherein 0.8 to 1.2mol of cyclic ketones of the general formula (I) as defined in claim 1 are used per isocyanate group equivalent of the polyisocyanate to be blocked.

5. The method according to claim 4, wherein the organic polyisocyanate has a uretdione, isocyanurate, iminooxadiazinedione, acylurea, biuret or allophanate structure.

6. The method according to claim 4, wherein the step of,

alkali metal-, alkaline earth metal-bases,

lewis acid

Used as a catalyst.

7. The method of claim 6, wherein the Lewis acid is a zinc salt.

8. A polyurethane baking varnish comprising the organic polyisocyanate of claim 1.

9. The polyurethane baking paint of technical scheme 8 is a single-component polyurethane-baking paint.

10. Use of the organic polyisocyanate of claim 1 for a filler.

11. Use of the organic polyisocyanate of claim 1 for coil coating.

12. A coating or polyurethane paint containing the blocked organic polyisocyanate of claim 1.

Claims (12)

1. An organic polyisocyanate containing at least two isocyanate groups, the isocyanate groups of which are blocked by an acidic CH-cyclic ketone of the general formula (I),

wherein

X is an electron-withdrawing group,

wherein the electron withdrawing group X is selected from an ester, amide, sulfoxide, sulfone, nitro, phosphonate, nitrile, isonitrile, polyhaloalkyl group, fluoro, chloro or carbonyl group;

R¹and R²Independently of one another, represent the radicals hydrogen, C₁～C₂₀Alkyl radical, C₁～C₂₀Cycloalkyl radical, C₆～C₂₄Aryl radical, C₁～C₂₀Alkyl esters or amides, C₁～C₂₀Cycloalkyl esters or amides, C₆～C₂₄Aryl esters or amides, or mixed aliphatic/aromatic radicals having 1 to 24 carbon atoms, which may also form part of a 4 to 8-membered ring,

n is an integer of 0 to 5,

and the content of blocked isocyanate groups in terms of NC0 accounts for 0.1-20 wt% of the total amount of the organic polyisocyanate.

2. The organic polyisocyanates according to claim 1, characterized in that the acidic CH cyclic ketones of the general formula (I) are cyclopentanone-2-carboxymethyl ester or-carboxyethyl ester, cyclopentanone-2-carboxylic acid nitrile, cyclohexanone-2-carboxymethyl ester or-carboxyethyl ester or cyclopentanone-2-carbonylmethyl.

3. The organic polyisocyanates according to claim 1, characterized in that the acidic CH cyclic ketones of the general formula (I) are cyclopentanone-2-carboxymethyl ester or-carboxyethyl ester, cyclohexanone-2-carboxymethyl ester or-carboxyethyl ester.

4. A process for the production of the organic polyisocyanates according to claim 1, characterized in that polyisocyanates are reacted with acidic CH cyclic ketones of the general formula (I) as defined in claim 1 in the presence of catalysts, wherein 0.8 to 1.2mol of cyclic ketone of the general formula (I) as defined in claim 1 are used per isocyanate group equivalent of the polyisocyanate to be blocked.

5. A process according to claim 4, characterised in that the organic polyisocyanate contains uretdione, isocyanurate, iminooxadiazinedione, acylurea, biuret or allophanate structures.

6. The method of claim 4, characterized in that,

alkali metal-or alkaline earth metal-bases, or

A Lewis acid, a basic metal oxide or a metal oxide,

used as a catalyst.

7. The method of claim 6, wherein the Lewis acid is a zinc salt.

8. Polyurethane stoving lacquers containing the organic polyisocyanates according to claim 1.

9. The polyurethane stoving varnish of claim 8, which is a one-component polyurethane-stoving varnish.

10. Use of the organic polyisocyanates according to claim 1 for fillers.

11. Use of the organic polyisocyanates according to claim 1 for coil coating.

12. A coating or polyurethane stoving varnish containing a blocked organic polyisocyanate according to claim 1.