EP0000963A1 - Isocyanurates containing blocked isocyanate groups, and process for their preparation - Google Patents

Abstract

The subject matter is blocked isocyanate and isocyanurate group-containing mixtures of at least 10% by weight of an isocyanurate containing dimethylketoxime, before blocking at least 2 isocyanate groups and optionally an amount of 100% by weight of a monomeric polyisocyanate blocked with dimethylketoxime and a content of unblocked NCO Groups of> 0.5% by weight. The monomeric polyisocyanate should preferably be identical to that used to prepare the isocyanurate. A particularly suitable monomeric polyisocyanate is 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate. The isocyanurate can also be a mixture of the trimerization product and higher addition products of the monomeric polyisocyanate. The invention also relates to a process for the preparation of compounds containing blocked isocyanate and isocyanurate groups from aliphatic and / or cycloaliphatic polyisocyanates and monofunctional acidic hydrogen-containing blocking agents, the polyisocyanates being converted in a known manner into an isocyanurate-isocyanate mixture containing at least 2 free isocyanate groups and then reacted with dimethyl ketoxime at 50-120 ° C in such amounts that there is one equivalent of dimethyl ketoxime for every NCO group equivalent. The monomeric polyisocyanate can also be removed from the isocyanurate / isocyanate mixture before blocking.

Description

The present invention relates to a process for the preparation of new compounds with an adjusted isocyanurate group content, and to the compounds obtainable by this process.

The production of masked isocyanates, also called isocyanate releasers, is known and is described in Houben-Weyl, Methods of Organic Chemistry XIV / 2 pp. 61-70. Tertiary alcohols, phenols, acetoacetic esters, malonic esters, acetylacetone, phthalimide, imidazole, hydrogen chloride, hydrogen cyanide and ε-caprolactam are known as blocking agents.

These blocked isocyanates have the property of reacting like isocyanates at elevated temperature. The more acidic the H atom of the masking group is, the easier it is to split off. Such blocked isocyanates are described in DT-OS 21 66 423. Terminally blocked isocyanates are also the in addition, uretdione groups have been described in DT-OS 25 02 934.

Surprisingly, there is no information in the literature about isocyanurate groups and terminally blocked isocyanate groups-containing aliphatic polyisocyanates. Blocked aromatic isocyanurates for the production of heat-resistant, abrasion-resistant urethane stoving enamels, especially for electrical wire insulation, are listed in a JA-AS 73.30453, registered on 12/24/69. In contrast, the production of aliphatic polyisocyanates containing blocked isocyanurate groups has hitherto been unknown.

The invention relates to a process for the preparation of blocked isocyanate group and isocyanurate group-containing compounds from aliphatic and / or cycloaliphatic polyisocyanates and monofunctional acidic hydrogen-containing blocking agents, which is characterized in that first the aliphatic and / or cycloaliphatic polyisocyanates transferred in a known manner into a mixture comprising at least 2 free isocyanate group-containing isocyanurate and then reacting this intermediate with dimethyl ketoxime as a monofunctional, acidic hydrogen-containing blocking agent at 50-120 ° C., the dimethyl ketoxime being used in amounts such that a NCO group equivalent comes one equivalent of dimethyl ketoxime. One variant is that the intermediate product obtained is first freed of the monomeric polyisocyanate and then the practically monomer-free polyisocyanate is then blocked in the manner described.

The invention further relates to blocked isocyanate group and isocyanurate group-containing compounds consisting of at least 10% by weight of an isocyanurate containing dimethyl ketoxime and at least 2 isocyanate groups before blocking and optionally an amount of a monomeric polyisocyanate blocked with dimethylketoxime and 100% by weight, and an unblocked NCO group content of <0.5% by weight.

The monomeric polyisocyanate is expediently identical to that which was used to prepare the isocyanurate. Because of the good optical properties, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate is particularly preferred because of the good optical properties and the addition products derived therefrom as isocyanurates. The isocyanurate can also be a mixture of the trimeric and higher addition product of the monomeric polyisocyanate. The isocyanurate group content in the compounds produced according to the invention is 2-8% by weight.

Polyisocyanates, in particular diisocyanates, such as aliphatic, cycloaliphatic and / or araliphatic, ie aryl-substituted aliphatic diisocyanates, as described, for example, in the article by W. Siefken in Justus Liebigs Annalen der Chemie 562, pages 75, are suitable for the preparation of the isocyanurate isocyanates, ie for trimerization - 136, are described, such as 1,2-ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexaethylene diisocyanate, 2,2,4- or 2,4,4-trimethyl-1, 6-hexamethylene diisocyanate (TMDI), 1,12-Dodscan diisocyanate, ω, ω'-diisocyanatodipropyl ether, cyclobutane-1,3-diisocyanate, cyclohexane-1,3 and 1,4-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, which is also known as Isophorone diisocyanate and is abbreviated IPDI, hexahydro-1,3- or -1,4-phenylene-di-isocyanate, 2,4- and 2,6-hexahydrotoluenediisocyanate, perhydro-2,4'- and / or -4.4 '-diphenylmethane diisocyanate, ω, ω'-diisocyanato-1,4-diethylbenzene and any mixtures of these iso meren. Further suitable isocyanates are described in the article mentioned in the annals on page 122 f. described.

As a rule, particularly preferred are the technically easily accessible aliphatic or cycloaliphatic diisocyanates, such as 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate, 2,4- and 3,6-hexahydrotoluenediisocyanate, perhydro-2,4'-and / or -4,4'-diphenylmethane diisocyanate and 1,6-hexamethylene diisocyanate and their isomeric mixtures.

In the trimerization of the polyisocyanates, aliphatic and / or cycloaliphatic monoisocyanates comparable to the above polyisocyanates can also be used to a limited extent, provided that the isocyanurate isocyanate formed contains on average at least 2 free isocyanate groups.

These starting materials for the process according to the invention are then subjected to trimerization in a known manner, as described for example in GB-PS 1 391 066 and DT-OS 23 25 826. The trimerization of the aliphatic or cycloaliphatic isocyanates described is a catalytic reaction. Metal compounds from the group consisting of salts and bases and homeopolar metal compounds such as metal naphthenates, sodium benzoate in DMF, alkaline earth metal acetates, formates and carbonates, metal alkoxides, AlCl ₃ and Fe acetylacetonate can be used as catalysts. The proposed catalyst system composed of N, N'-3ndoethylene piperazine and propylene oxide is particularly suitable for the trimerization of aliphatic isocyanates. The trimerization can be carried out in bulk or in inert organic solvents. To carry out the trimerization process, it is essential to terminate the reaction at a certain isocyanate content of the mixture, preferably when 30-50% of the NCO groups have reacted with trimerization. The unreacted isocyanate is then separated from the isocyanurate formed by thin-layer distillation.

In the process according to the invention, the isocyanurate isocyanates thus accessible can be used either as the exclusive isocyanate component or as a mixture with isocyanurate-free poly Isocyanates are used. The addition of isocyanurate group-free polyisocyanates allows the properties of the process products, in particular their melting point, to be varied in a desired manner in a simple manner.

It is particularly advantageous to use the abovementioned triisocyanate mixture, which is prepared in situ and is accessible by partial trimerization of a suitable diisocyanate, as the isocyanurate component in the process according to the invention.

The isocyanurate group-containing polyisocyanates, preferably triisocyanates, or mixtures thereof with isocyanurate group-free polyisocyanates, preferably diisocyanates, are the precursors to the process products according to the invention, which are referred to above as intermediates.

In a further step of the method according to the invention, this intermediate stage is now described below without further modification in the present invention _e isocyanurate and transferred terminally blocked isocyanate groups product of the process.

Dimethyl ketoxime has proven to be particularly suitable since it easily undergoes an addition reaction with the compounds containing isocyanate groups at temperatures above 50 ° C., preferably between 80-120 ° C. The addition products thus obtained in a mixture with non-volatile polyols containing primary hydroxyl groups react at temperatures between 100 and 200 ° C. with the release of dimethylketoxime with the non-volatile polyols with urethane formation.

To carry out the blocking reaction, the isocyanate component is generally initially introduced and the blocking agent is added. The reaction can be in substance or in counter suitable (inert) solvents had to be carried out. The blocking reaction is generally carried out at 80-120 ° C. The dimethyl ketoxime is used in such amounts that there is one equivalent of blocking agent per NCO group equivalent. The customary isocyanate polyaddition reaction accelerating catalysts, such as tin (II) octoate, can also be used. The catalysts are generally used in an amount between 0.001 and 1% by weight, based on the amount of compounds having hydrogen atoms which are reactive toward isocyanates.

The process products according to the invention are generally compounds of the molecular weight range 300-3000, preferably 400-2000. The process products have melting points or ranges from 30-200 ° C., preferably 60-170 ° C. The preferred polyisocyanates containing isocyanurate groups according to the invention are moreover terminated by a content of isocyanurate groups (calculated as (CO-N-) ₃ ) of 2% by weight to 14% by weight, preferably 3-10% by weight and a content of terminal Isocyanate groups present in blocked form (calculated as NCO) of 2-18, preferably 10-17,% by weight are characterized.

The compounds of the invention described above are particularly suitable because of their low melting points and at the same time higher molecular weights than cocatalysts for the anionic polymerization of E-caprolactam.

The process products are also suitable as hardeners for higher functional thermoplastic compounds containing Zerewitinoff active hydrogen atoms. In combination with such compounds having Zerewitinoff-active hydrogen atoms, the process products form above 120 ° C. Systems that can be hardened to high-quality plastics, preferably at 160 - 200 ° C. The most important field of application for such systems is their use as binders for (PUR) powder coatings. The process products according to the invention are also well suited for the production of storage-stable one-component stoving enamels (especially for coil coating).

The invention is illustrated by the following examples:

• a. Herstellung des Triisocyanurats:
  • 100 Gew.-T. Isophorondiisocyanat (IPDI) wurden mit 0,5 Gew.-T. des Katalysatorsystems aus 1,4-Diazobicyclooctan-[2,2,2] (auch Dabco® genannt) und Propylenoxid 3 h bei 120°C erhitzt. Während dieser Zeit fiel der NCO-Gehalt von 37,8 % (entsprechend 100 % IPDI) auf 28,4 % (50 % IPDI-Umsatz). Zur Desaktivierung des Katalysators wurde das Reaktionsgemisch auf 40 °C abgekühlt und bei dieser Temperatur 1/2 h mit Stickstoff gestrippt. Dabei veränderte sich der NCO-Gehalt des Reaktionsgemisches noch geringfügig auf 28,2 %.
• b. Blockierung des Triisocyanurats:
  • Zu 100 Gew.-T. dieses Isocyanato-isocyanurat-Gemisches wurden bei 100 °C 49 Gew.-T. Dimethylketoxim portionsweise so zugegeben, daß die Reaktionstemperatur nicht über 120 °C anstieg. Zur Vervollständigung der Reaktion wurde das Reaktionsgemisch noch 2 Stunden bei 120 °C gehalten.
    

Example 1:

• a. Production of the triisocyanurate:
  • 100 parts by weight Isophorone diisocyanate (IPDI) was mixed with 0.5 part by weight. the catalyst system of 1,4-diazobicyclooctane [2,2,2] (also called Dabco®) and propylene oxide heated at 120 ° C for 3 h. During this time, the NCO content fell from 37.8% (corresponding to 100% IPDI) to 28.4% (50% IPDI turnover). To deactivate the catalyst, the reaction mixture was cooled to 40 ° C. and stripped with nitrogen at this temperature for 1/2 h. The NCO content of the reaction mixture changed slightly to 28.2%.
• b. Blocking the triisocyanurate:
  • To 100 parts by weight this isocyanato-isocyanurate mixture was 49 parts by weight at 100 ° C. Dimethylketoxime added in portions so that the reaction temperature did not rise above 120 ° C. To complete the reaction, the reaction mixture was kept at 120 ° C. for a further 2 hours.
    

Fig. 1 shows the IR spectrum of the reaction product.

• a. Herstellung des Triisocyanurats:
  • 100 Gew.-T. IPDI wurden mit 0,75 Gew.-T. eines Katalysatorsystems entsprechend Beispiel 1a 2 h bei 120 °C erhitzt. In dieser Zeit fiel der NCO-Gehalt von 37,8 % auf 29,4 %. Zur Desaktivierung des Katalysators wurde bei 120 °C und 30 Torr 15 Minuten evakuiert. Während dieser Zeit verändertesich der NCO-Gehalt des Reaktionsgemisches auf 27 %.
• b. Blockierung des Triisocyanurats:
  • Zu 100 Gew.-T. dieses Isocyanatoisocyanurat-Gemisches wurden bei 110 °C 46,9 Gew.-T. Dimethylketoxim portionsweise so zugegeben, daß die Reaktionstemperatur nicht über 120 °C anstieg. Zur Vervollständigung der Reaktion wird das Reaktionsgemisch noch 2 Stunden bei 120 °C gehalten.
    

Example 2:

• a. Production of the triisocyanurate:
  • 100 parts by weight IPDI were 0.75 parts by weight. a catalyst system according to Example 1a heated at 120 ° C for 2 h. During this time, the NCO content fell from 37.8% to 29.4%. To deactivate the catalyst, evacuation was carried out at 120 ° C. and 30 torr for 15 minutes. During this time the NCO content of the reaction mixture changed to 27%.
• b. Blocking the triisocyanurate:
  • To 100 parts by weight this isocyanato-isocyanurate mixture was 46.9 parts by weight at 110 ° C. Dimethylketoxime added in portions so that the reaction temperature did not rise above 120 ° C. To complete the reaction, the reaction mixture is kept at 120 ° C. for a further 2 hours.
    

Fig. 2 shows the IR spectrum of the reaction product.

• a. Herstellung des Triisocyanurats:
  • 100 Gew.-T. IPDI wurden mit 0,5 Gew.-T. des in Beispiel 1a beschriebenen Katalysators 4,5 h bei 120 °C erhitzt. Das Fortschreiten der Trimerisierung wurde mit Hilfe des Brechungsindex, Viskosität oder NCO-Gehalt verfolgt. Bei einem NCO-Gehalt von 25,8 % wurde eine halbe Stunde bei 20 Torr evakuiert. Nach Abkühlen hatte das Reaktionsgemisch einen NCO-Gehalt von 25 %.
• b. Blockierung des Triisocyanurates:
  • Zu 100 Gew.-T. dieses Isocyanatoisocyanurat-Gemisches wurden bei 120 °C 43,4 Gew.-T. Dimethylketoxim langsam unter gutem Rühren zudosiert. Nach erfolgter Dimethylketoxinzugabe wurde das Reaktionsgemisch noch eine Stunde auf 130 °C erhitzt.
    

Example 3:

• a. Production of the triisocyanurate:
  • 100 parts by weight IPDI were with 0.5 parts by weight. of the catalyst described in Example 1a heated at 120 ° C for 4.5 h. The progress of the trimerization was followed using the refractive index, viscosity or NCO content. With an NCO content of 25.8%, evacuation was carried out at 20 torr for half an hour. After cooling, the reaction mixture had an NCO content of 25%.
• b. Blocking the triisocyanurate:
  • To 100 parts by weight This isocyanato-isocyanurate mixture was 43.4 parts by weight at 120 ° C. Dimethylketoxim slowly metered in with good stirring. After the addition of dimethyl ketoxin, the reaction mixture was heated at 130 ° C. for a further hour.
    

Fig. 3 shows the IR spectrum of the reaction product.

• a. Herstellung des Triisocyanurats:
  • Nach dem in 1a - 3a beschriebenen Verfahren wurde aus IPDI ein Isocyanatoisocyanurat-Gemisch (mit deaaktiviertem Kat.) hergestellt, dessen NCO-Gehalt 20,9 % betrug.
• b. Blockierung des Triisocyanurats:
  • Zu 100 Gew.-T. dieses Gemisches (NCO: 20,9 %) wurden bei 140 °C unter intensiver Rührung 36,3 Gew.-T. Dimethylketoxim so zugegeben, daß durch die Reaktionswärme das Gemisch bei 140 °C gehalten wurde. Nach erfolgter Dimethylketoximzugabe wurde zur Vervollständigung der Umsetzung noch 1 h bei 140 °C erhitzt.
    

Example 4:

• a. Production of the triisocyanurate:
  • An isocyanato-isocyanurate mixture (with deactivated cat.), The NCO content of which was 20.9%, was prepared from IPDI by the process described in FIGS. 1a-3a.
• b. Blocking the triisocyanurate:
  • To 100 parts by weight this mixture (NCO: 20.9%) was 36.3 parts by weight at 140 ° C with vigorous stirring. Dimethylketoxime added so that the mixture was kept at 140 ° C by the heat of reaction. After the addition of dimethyl ketoxime, the reaction was heated at 140 ° C. for a further 1 h.
    

Fig. 4 shows the IR spectrum of the reaction product.

Claims (6)

1 _L process for the preparation of blocked compounds containing isocyanate groups and isocyanurate groups from aliphatic and / or cycloaliphatic polyisocyanates and monofunctional, acidic hydrogen-containing blocking agents, characterized in that firstly the aliphatic and / or cycloaliphatic polyisocyanates are used in a known manner a mixture of at least 2 free isocyanurate-containing isocyanurate is transferred and this intermediate is then reacted with dimethyl ketoxime as a monofunctional, acidic hydrogen-containing blocking agent at 50-120 ° C., the dimethyl ketoxime being used in amounts such that an NCO group Equivalent one equivalent of dimethyl ketoxime is coming. 2. The method according to claim 1, characterized in that the intermediate product obtained is freed of the monomeric polyisocyanate and the then practically monomer-free polyisocyanate is then blocked in the manner described. 3. Blocked mixture containing isocyanate groups and isocyanurate groups at least 10% by weight of an isocyanurate containing dimethyl ketoxime, before blocking at least 2 isocyanate groups and optionally an amount of a monomeric polyisocyanate blocked with dimethylketoxime and a content of unblocked NCO groups of 100% by weight
<0.5% by weight. 4. Blocked isocyanate groups - and isocyanurate groups - containing mixture according to claim 3, characterized in that the monomeric polyisocyanate is identical to that which was used for the preparation of the isocyanurate. 5. Blocked isocyanate groups - and isocyanurate groups - containing mixture according to claim 4, characterized in that the monomeric polyisocyanate is 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate. 6. Blocked isocyanate groups - and isocyanurate groups - containing mixture according to claims 4-6, characterized in that the isocyanurate blocked with dimethyl ketoxime is a mixture of the trimerization product and higher addition products of the monomeric polyisocyanates. dr.kn-nei

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