MXPA01005683A - Malonic acid ester/triazole mixed blocked hdi trimer/formaldehyde stabilization - Google Patents

Abstract

The invention relates to blocked polyisocynate cross-linking agents, the production and use thereof in 1K baking enamels, especially in OEM clear varnishes (original equipment material, primary enamel).

Description

TRIMERIZED OF 1, 6-DIISIOCIANATOHEXANO COBLOCKED WITH MALONIC ESTER / TRIAZOLE / STABILIZATION WITH FORMALDEHYDE DESCRIPTION OF THE INVENTION The present invention relates to blocked polyisocyanate crosslinkers, their manufacture and their use in kiln drying lacquers of 1C, especially in OEM transparent lacquers (Originalequipmentmaterial, original lacquered). As is known, blocked polyisocyanates are used as builder additives in 1C kiln drying lacquers in automotive lacquering. With blocked polyisocyanates, relatively high demands on the technical properties of improved lacquers can be met. Other properties, such as, for example, a low baking temperature of up to 140 ° C maximum or low heat-browning in the annealing, can not be achieved on the contrary with all available raw materials. The most significant technical lacquer polyisocyanates are based on 1,6-diisocyanatohexane (HDI). As blocking agents for polyisocyanates available on an industrial scale, if unblocking temperatures of 140 ° C are considered at most, the malonic ester and the 1,2,4-triazole are offered. The combination of HDI-based polyisocyanates with malonic ester or 1,2,4-triazole or, as discussed in the Comparative Example below, with a mixture of malonic ester / 1,2,4-triazole, does not lead to a crosslinking agent of lacquers Ref: 129633 Usable stable to storage and liquid, since these products crystallize. The crystallization tendency of the HDI polyisocyanates blocked with malonic ester is known from EP-A 600 314 and that of the polyisocyanates blocked with triazole by EP-A 654 490 and 741 157. The purpose of the invention consists in modifying HDI-based polyisocyanates coblocked with malonic ester and 1, 2, 4-triazole in such a way that liquid crosslinking agents, which do not crystallize in solvents, result for kiln drying lacquers of 1C. This objective has been solved with the blocked polyisocyanates described below. The subject of the invention are aliphatic and / or cycloaliphatic polyisocyanates, whose isocyanate groups are present in blocked form (transformed) in A) 5-95, preferably 70 to 30% in equivalents with an ester with CH acids, B) 5-95, preferably 70 to 30% equivalents with 1,2,4 triazole and C) 0-10% equivalents with other blocking agents other than A) and B), characterized in that they contain 0.05-1.0 mol of formaldehyde in Embodied form, referred to 100% of NCO group equivalents blocked. Another subject of the invention is a process for the production of the non-crystallized polyisocyanates blocked according to the invention from a) 100% equivalents of aliphatic and / or cycloaliphatic polyisocyanate components, b) 5-95, preferably 70 to 30 % equivalents of a blocking agent of the group of the esters with CH acids, c) 5-95, preferably 70 to 30% equivalents of 1,2,4-triazole d) 0 to 10% equivalents of an agent of blocking other than b) and c) and e) 0.05-1.0 mol of formaldehyde, characterized in that the formaldehyde is added with catalytic amounts of a base after the total transformation of the NCO groups present and is reacted. The polyisocyanates which do not crystallize blocked according to the invention can preferably have a content of stabilizers against thermoblacking at a level of 0.1-5.0% by weight of hydrazides with the structural unit of formula (I) and 0.1-5.0% by weight of "HALS amines" with the structural unit of formula (II) Such stabilizers are known, for example, from EP-A 829 500. Finally, the invention also relates to the use of the blocked polyisocyanates according to the invention as crosslinking agents for organic polyhydroxy compounds in polyurethane kiln drying lacquers, example for automotive clearcoats. The formaldehyde content is essential according to the invention for the claimed polyisocyanate crosslinkers.

The formaldehyde surprisingly has two modes of action: on the one hand it prevents the crystallization of the blocked polyisocyanates, especially when the polyisocyanate component is based on HDI. On the other hand, it increases the resistance of the blocked polyisocyanates to the thermo yellowing. 100% of blocked polyisocyanate equivalents are preferably 0.1 to 0.4 mol of paraformaldehyde and are reacted by means of a catalyst, such as, for example, sodium methylate. This represents approx. 0.8 to 5.0% by weight of formaldehyde, based on blocked polyisocyanate. A formaldehyde content of 2.0 to 3.0% by weight, based on blocked polyisocyanate, is very particularly preferred. The process according to the invention is carried out in the following way: The polyisocyanate component is, if appropriate together with low solvent, for example l-methoxy-2-propyl acetate (MPA), at approx. 50 ° C, the ester is added with acidic CH, eg malonic ester, as a mixture with ca. 2% of a 30% Na methylate solution and reacted at 70-90 ° C until the calculated NCO content. After this, the calculated amount of 1,2,4-triazole, dissolved in more MPA, is added and reacted at approx. 90 ° C until some NCO group is no longer detectable. The reaction mixture is cooled to ca. 45 ° C and the clear paraformaldehyde solution, approximately 3%, based on paraformaldehyde, is added in a solution of 30% Na methylate as base and isobutanol and subsequently stirred at 45 ° C for 1 hour. The formaldehyde is incorporated in this way, its free content being found within the limits of analytical detection. It is added to this approx. 0.5%, based on the reaction mixture, of dibutyl phosphate and thus a pH of 7.5-7.0 is adjusted. In addition to this transparent solution, according to the special embodiment according to the invention, further stabilizers can be added to the thermal blacking.

The polyisocyanates from which the blocked polyisocyanates according to the invention are obtained are polyisocyanates of known lakes with isocyanate groups linked aliphatically and / or cycloaliphatically and / or aromatically and having an isocyanate content of 7 to 30, preferably 12 to 25% by weight . Preferably used polyisocyanates of lacquers known per se having biuret, isocyanurate, urethane, allophanate and / or uretdione groups based on 1,6-diisocyanatohexane (HDI), l-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (IPDI) and / or bis- (4-isocyanatocyclohexyl) -methane (H12MDI or Desmodur W® / Bayer AG). In addition, polyisocyanates can be used as polyisocyanates of asymmetrically trimerized lacquers which also have isocyanurate groups also of iminooxadiazinedione groups based on 1,6-diisocyanatohexane, such as those described, for example, in EP-A 798 299. They can also be used polyisocyanates based on other isocyanates, such as diisocyanatobutane-1, 4, 2,4- or 2,6-diisocyanato-1-methyl-cyclohexane, 2,5- and / or 2,6-bis-isocyanato-norbornane , 3- and / or 4-isocyanatomethyl-1-methylcyclohexane, 1,4-bis- (2-isocyanato-prop-2-yl) -benzene, 1,3-diisocyanatomethylbenzene, 1,3- or 1,4-bis -isocyanatomethyl-cyclohexane. Polyisocyanate polyisocyanates having isocyanurate groups based on 1,6-diisocyanatohexane are, however, very particularly preferred as the polyisocyanate component. As the blocking component, on the one hand, esters with acidic CH are considered, for example diethyl malonate or ethyl acetoacetate and / or their methyl, isopropyl, isobutyl or tert-butyl derivatives. Diethyl malonate is preferred. On the other hand, 1, 2, 4-triazole is used in this coblocking. The latter is obtained industrially from 1 mole of hydrazine hydrate and at least 2 mole of formamide. The esters with CH acids and the triazole can be used in respective amounts of 5-9% equivalents, preferably respectively 20-80% equivalents. As additional blocking agents, they can be used in amounts of up to 50% equivalents, preferably up to 20% equivalents: oximes, such as butanone oxime, secondary amines, eg diisopropylamine, heterocycles with acid NH, such as p. eg imidazole or 3,5-dimethylpyrazole or lactams, eg e-caprolactam.

The stabilizers known from EP-A 0 829 500 can be used as further stabilization components. In this context, the hydrazide which can be incorporated is easily accessible by the addition of hydrazine hydrate and 2 mol of polypropylene carbonate of formula (I). (the) (molecular weight 236) and the unsubstituted HALS amine at the N Tinuvin 770 DF® atom (Fa.Novrtis). Of the abovementioned stabilizer, preferably from 3 to 6% by weight and from the aforesaid preferably from 0.5 to 1.5% by weight, based on blocked polyisocyanate, are used in this respect. Solvents which can be used are inert solvents against known NCO groups of polyurethane chemistry, for example l-methoxy-2-propyl acetate, Solventnaphta 100 or butyl acetate. If the NCO groups are blocked, then alcohols, for example isobutanol, are also preferably used to enable transesterification with the alcohol moieties of the blocking agent. The advantages of the polyisocyanate crosslinker according to the invention, in particular good storage stability, ie no crystallisation, low heat yellowing and good technical properties of lacquer, are illustrated with the help of the following examples. TC Examples < atnplp i (according to the invention) This co-blocked polyisocyanate is stabilized with 3.0% formaldehyde, based on the solid matter of the blocked polyisocyanate. The ratio of the blocking agent is malonic ester: triazole = 40: 60% equivalents, based on 100% equivalents of NCO groups. Formulation 200.0 g (1 equiv.) Of a lacquer polyisocyanate containing isocyanurate based on 1,6-diisocyanatohexane (HDI) with an NCO content of approx. 21% 64.0 g (0.4 mol) of diethyl malonate 41.4 g (0.6 mol) of 1,2,4-triazole 9.0 g (0.3 mol) of paraformaldehyde 65.2 g of methoxypropyl acetate 65.2 g of isobutanol 434.8 g (1.0 equiv.) Of blocked NCO groups Solid matter content: 70% NCO content blocked: 9.6% Viscosity at 23 ° C: approx. 6.000 Pa.s Aspect: transparent, almost colorless NCO equivalent: 435 g Embodiment The polyisocyanate and methoxypropyl acetate were placed and heated to ca. 50 ° C. To this stirred solution was added the malonic ester mixture and 1.2 g of Na methylate solution (30% in methanol) and stirred for ca. 2 hours at 70 ° C, until the NCO content was less than 7.6% calculated. Then the colorless triazole flakes were added, the interior temperature was increased to 90 ° C and stirred for approx. 3 h more until it was no longer detectable NCO group. It cooled to approx. 45 ° C and the solution of paraformaldehyde, isobutanol and 0.3 g of Na methylate solution (30%) was added and then stirred for 1 h at 40-45 ° C. Finally, 2.1 g of dibutyl phosphate was added and a solution of a clear, almost colorless blocked polyisocyanate crosslinker was obtained, stable for storage for 6 months. • p.jotnplf > (Comparative Example) This example is qualitatively and quantitatively equivalent to that of Example 1, except that the modification of the blocked polyisocyanate with formaldehyde is omitted. It turned out a product that began to crystallize after a week of storage at room temperature. Therefore, this blocked polyisocyanate can not be used in storage stable 1C lacquer formulations. Example 3 (according to the invention) This co-blocked polyisocyanate was stabilized with 2.7%, based on the solid material of the blocked polyisocyanate. In addition, two other stabilizers (see EP-A 829 500 A2) are also added to the mixture in the solution of the blocked polyisocyanate, namely 2.0% of an already exposed hydrazide and 1.0% of a HALS amine. . Formulation 300.0 g (1.5 equiv.) Of a lacquer polyisocyanate containing isocyanurate based on 1,6-diisocyanatohexane (HDI) with an NCO content of approx. twenty-one%, a viscosity at 23 ° C of approx. 3,000 mPa.s and a functionality of approx. 3.5 120.0 g (0.75 mol) of diethyl malonate 51.7 g (0.75 mol) of 1,2,4-triazole 13.5 g (0.45 mol) of paraformaldehyde 4.9 g (1% / MS) of Tinuvin® 770 DF (Novartis AG) 9.8 g (2% / MS) of the hydrazine adduct explained in the assay of 1 mole of hydrazine hydrate and 2 mole of propylene carbonate with a molecular weight of 236 107.8 g of methoxypropyl acetate 107.8 g of isobutanol 715.5 g (1.5 equiv.) Of blocked NCO groups Solid matter content: 70% NCO content blocked: 8.8% Viscosity (23 ° C): approx. 5,000 mPa.s Appearance: transparent, Hazen 60 NCO Equivalent (blocked): 477 g Embodiment Polyisocyanate and methoxypropyl acetate were arranged. At approx. 50 ° C and with stirring the mixture of diethyl malonate was incorporated with ca. 2%, ie 2.4 g, of Na methylate solution (30% in methanol) in portions. The temperature was raised to 70 ° C and stirred for approx. 1 ^ h, until the NCO content was less than 5.95% calculated. The colorless 1,2,4-triazole flakes were then added, the temperature was increased to 90 ° C and stirred for ca. 3 h more until it was no longer detectable any NCO group (IR spectrum). It cooled to approx. 45 ° C and the solution of a partial amount of isobutanol, paraformaldehyde and 0.5 g of Na methylate solution (30% -) was added. It was then stirred for approx. 1 h at 45 ° C. After this, Tinuvin 770 DF, the described hydrazine adduct and the remaining amount of isobutanol were added. Finally, 3.5 g of dibutyl phosphate were added while stirring and a clear, storage-stable, almost colorless polyisocyanate crosslinking agent (Hazen 60) with an NCO equivalent (blocked) of 447 g was obtained. t ?. c-m i (application example) The crosslinker according to Example 3 was mixed with the following components forming a clear lacquer. This clear lacquer was applied to test sheets coated with a commercially available white basecoat, for example from Spies & Hecker / Cologne, with a wet layer thickness of approx. 120 to 150 μm and, as illustrated in the following Table, was baked and tested. Formulation 37.2 g of Desmophen® A VP LS 2009/1, 70% in BA (Bayer AG), equivalent of OH 565 g 31.4 g of crosslinker according to Example 3, NCO: OH = 1: 1 0.5 g of dibutyltin dilaurate, 100% 11.2 g of methoxypropyl acetate / Solventnaphta® 100 (1/1) Results of the technical test of lacquer Spray solid matter with discharge time of 23 s% approx. fifty% Baking conditions 30 '140 ° C Pendular damping (oscillations) 1 * 143 (s) 20 Resistance to solvents (note *) 2) (X / MPA / EA / AC) 1 min 1234 5 min 2244 Resistance to chemicals (° C) 3) (oven method with gradient) Tree resin 36 Brake fluid 36 Pancreatin, 50% 36 NaOH, 1% 36 H2SO4, 1% 41 FAM; 10 min (note *) 2 Thermo yellowing4) Transparent lacquer based on LM Yellowing starting (b) 0.1 Yellowing annealing at 30 '160 ° C (? B) 1, 9 Clear lacquer based on H2O Starting yellowing (b) -1,2 Yellowing annealing at 30 * 160 ° C (? b) 1, 2 Scratch resistance (laboratory wash tunnel) 5 Starting brightness 20 ° 90.8 Loss of brightness after 10 wash cycles 23.2 *) 0 - good; 5 - bad As can be seen, the system according to the invention together exhibits good lacquer properties X) DIN ISO 1522 21 Bayer test method; evaluation according to DIN 53230 3) According to the Daimler-Benz test method 4) DIN 6174 (CIELAB) 51 According to the DFO test method Deutsche Forschungesellschaft für Oberflachenbehandlung (German research society for surface treatment) e.V. Dusseldorf It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (4)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. Aliphatic and / or cycloaliphatic polyisocyanates, whose isocyanate groups are present in blocked form (transformed) in A) 5-95% equivalents with an ester with CH acids, B) 5-95% equivalents with 1,2,4 triazole and C) 0-10% equivalents with other blocking agents other than A) and B), characterized in that they contain 0.05-1.0 mol of formaldehyde in incorporated form, based on 100% equivalents of blocked NCO groups.

2. Process for the production of non-crystallized polyisocyanates blocked according to the invention from a) 100% equivalents of aliphatic and / or cycloaliphatic polyisocyanate components, b) 5-95% equivalents of a blocking agent of the ester group with CH acids, c) 5-95% equivalents of 1, 2, 4-triazole d) 0 to 10% equivalents of a blocking agent other than b) and e) 0.05-1.0 mol formaldehyde, characterized in that the formaldehyde is added with catalytic amounts of a base after the total transformation of the NCO groups present and it is reacted.

3. Blocked polyisocyanates according to claim 1, characterized in that they have a content of stabilizers against thermo yellowing at a level of 0.1-5.0% by weight of hydrazides with the structural unit of formula (I) O -C-NH-NH- (I), and 0.1-5.0% by weight of "HALS amines" with the structural unit of formula (II)

4. Use of the blocked polyisocyanates according to claim 1 as crosslinking agents for organic polyhydroxy compounds in drying lacquers of polyurethane, for example for automotive clearcoats. TRIMERIZADD OF 1, 6-DIISIOCIANAT0HEXAN0 COBLOCKED WITH MALONIC ESTER / TRIAZOL / STABILIZATION WITH FORMALDEHYDE SUMMARY OF THE INVENTION The present invention relates to blocked polyisocyanate crosslinkers, to their manufacture and to their use in 1C oven-dried lacquers, especially in OEM transparent lacquers (Originalequipmentmaterial, original lacquering).