DD151159A2 - PROCESS FOR THE PREPARATION OF POLYISOCYANATES WITH BIURET STRUCTURE - Google Patents

Abstract

The invention relates to an additional, particularly rational embodiment of the process for the preparation of polyisocyanates having a biuret structure and an isocyanate functionality groeszer 2 according to PS 140 744. Such polyisocyanates have lower toxicity towards monomeric di- / triisocyanates and are valuable intermediates for the synthesis of polyurethanes, which i.a. find use as light-resistant polymers in the form of paints and coatings or as foam products with increased flame resistance. Gemaesz the aim of the invention to make the process principle according to PS 140 744 more economical, the reaction of the reactants - monomeric di- and / or triisocyanates and conventional biuretizing - in the ratio of 1: 1 to 10: 1 at temperatures in the preferred range of 80 and 100 degrees C in the presence of the catalytically highly effective organotin compounds of the general formula (R & ind 3! Sn) & ind 2! O with R = C &ngr; H & ind2n + 1! and n> / 4 erfindzesz at catalyst concentrations down to 0.003 mol .-%, based on the isocyanate compound. Analogously to PS 140 744, this catalyst-sparing procedure gives, without by-products, clear and light, liquid to resinous, biavailable polyisocyanates with biuret structure whose NCO concentration can be exactly determined beforehand by the ratio of monomeric isocyanate used to biuretizing agent.

Description

2 1 09 4 9 -4-

Title of the invention

Process for the preparation of biuret polyisocyanates

Field of application of the invention

The invention relates to an additional, in particular more rational embodiment of the process for the preparation of polyisocyanates having a biuret structure and an isocyanate functionality greater than 2 according to Pste-nt / HO 1-1 Hr »

Polyisocyanates of this type are preferred starting materials for the synthesis of polyurethanes due to their low toxic action against monomeric di- and triisocyanates. They can both for the production of light-stable polymers, eg. B. of paints and coatings, as well as for the production of foam products with increased flame resistance are used *

Characteristics of the known technical solutions article according to f ^ tit _4H0 ^ * ¹ * _{is a} process for the preparation of polyisocyanates with a biuret structure and an isocyanate functionality greater than 2 by heat treatment of di- and / or triisocyanates with conventional biuretizing in the presence of organotin compounds and optionally a solvent , According to the invention, the reactants at a ratio of the isocyanate component to the biuretizing agent of 1: 1 to 10: 1, preferably 1: 1 bi9 8: 1, at temperatures in the range between 50 C.

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and 120 ⁰ C, preferably in the range between 80 ° and 100 ⁰ C, in the presence of an organotin compound of the general formula (R ₃ Sn) ₂ O, wherein R represents an alkyl substituent C _n H ₂ ^ with η & 4 substituted by halogen can be implemented.

In the proposed method is disadvantageous that the catalyst concentration of organotin compound with 0.03 to 7 mol%, based on the amount of isocyanate compound used, is relatively high.

Object of the invention

It is the object of the invention to make the process principle advantageous per se for the preparation of polyisocyanates with biuret structure according to TovHut ^ * to ^ W technically and economically more favorable by reducing the catalyst concentration.

Explanation of the essence of the invention

The object is achieved by the present invention, the catalyzed reaction of the reaction mixture of di- and / or triisocyanates and Biuretisierungsmitssln at a concentration of the organotin compound having the general formula (R ₃ Sn) ₂ O down to 0.003 mol%, based on the amount of isocyanate Verblndung , is carried out.

All conventional di- or triisocyanates, such as tolylene diisocyanate, hexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate and triphenylmethane triisocyanate, are also suitable for carrying out this more economical, catalyst-saving and also technically simpler procedure according to the invention. The biuretizing agents are again preferably water and / or disubstituted urea isocyanates synthesized from diisocyanates. Equally successful, the proposed method may optionally also in organic solvents such as aromatic hydrocarbons, eg. As dichlorobenzene, practiced.

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The addition of the inventively low catalyst concentration of the defined organotin compounds, wherein the bis (tributyltin) oxide is a preferred representative of these species, for the biuret synthesis advantageously takes place directly to the isocyanate starting component before adding the biuretizing, especially water, but can also by adding in the isocyanate-water, the isocyanate-water-urea or the isocyanate-urea mixture, the latter may be either starting or intermediate stage of the inventive solution, optionally in the presence of the organic solvent. Technically easier and time-saving, however, the proposed teaching can be realized by the immediate addition of the organotin catalyst to Isocyanatausgangskomponente.

The excellent specific efficiency with high hydrolysis · Stability of the proposed catalysts allows their use in extremely low concentration not only in anhydrous, but also equally successful in aqueous systems, the reaction rate is in each case precisely controlled. The substituted or produced as an intermediate substituted urea is quantitatively converted to biuret even in the presence of extremely low catalyst concentration in a short time, so that there is no formation of insoluble polyureas in the present case nor the undesirable, high viscosity increasing trimerization to isocyanurates in detectable Extent appears. Accordingly, the use of solvents to prevent the precipitation of insoluble by-products from the reaction mixture is not required, and further, the obtained biuret polyisocyanates have a relatively low viscosity.

With regard to the introduction of the biuretizing in the isocyanate catalyst system, an extremely continuous approach is recommended, since thus a precipitate formation is avoided in the reaction medium in particular when using aromatic compounds.

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With the proposed solution according to the invention, the predicted concentration of the forming polyisocyanate with biuret structure, which is essentially obtained when using diisocyanate as triisocyanate and when using triisocyanate as tetraisocyanate, is achieved analogously to the method according to -§74 It is of crucial advantage that the inventive reaction of the starting materials by the presence of highly effective organotin catalysts even at extremely low concentration even at temperatures below 100 ⁰ C in comparatively short time compared to uncatalyzed systems can be completed. The gentle conditions thus also prevent the unwanted, the economy of the process burdensome side reactions - the formation of monomeric mono- and diisocyanates using appropriate biuretizing - and provide clear and bright, no colored products.

The isocyanate may be metered in to the extent in the reaction mixture, Dae desired for further processing NCO concentration of the biuret according contained in the reaction product. Since the catalysts are present in the resulting biuret polyisocyanate by the in dissolved form, the catalytic activity can also be used for polyurethane formation from these biurethaitigen polyisocyanates.

The erfindungsgesäß economical and technically easier to produce flößigen to resinous polyisocyanates with biuret structure, with respect to the process parameters and

'füjL.l' 4 ^! Property characteristics of the target products according to ' G / 2tA & M have no limiting factors, have also been shown to be storable for months and can be in a known manner by the isocyanate polyaddition with conventional polyhydroxyl compounds, such as polyether or polyester polyols, optionally with the addition of further known excipients, such as pigments, propellants, fillers, plasticizers, cell regulators and other catalysts, to form polyurethanes in the form of paints, coatings, adhesives or foams.

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embodiments

example 1

Trial A:

Under nitrogen atmosphere at 80 ⁰ C to 174 parts by weight.

2,4-tolylene diisocyanate and 0.08 parts by weight. Bis (tributyltin) oxide for 3 hours 3.6 wt. Tie. Water registered.

The reaction mixture is then heated for a further hour at 95 ^° C.

Trial B:

For comparison, however, experiment A is used without catalyst addition.

In both experiments, the control of the turnover is carried out by the isocyanate determination by the usual titration method and also by IR spectroscopy in 1,2-dichloroethane on the biuret carbonyl band at 1717 cm.sup.1 During test A after a reaction time of 4 hours in total (addition of biuretizing agent for 3 hours) + 1 hour post-reaction) at an NCO content of approximately 35 % (calculated 34.85 % NCO) has already been completed, only an NCO content of 38.3 % is achieved after 10 hours according to Experiment B. The biuret formation is in this Only about 70 % .

Example 2 to 5

In a nitrogen atmosphere, 174 wt. ToIuylendiisocyanat (mixture of 80 wt.% 2.4- and 20 wt.% 2,6-isomers) with different amounts of bis (tributyltin) oxide and mixed with different amounts of water. The amounts of water and catalyst, reaction conditions and the percent NCO-amount in the reaction product are summarized in the following table.

Time d. reaction

Weight parts. Tem-water time after

At- Water Catal. Perat. zuqabe water train. % NCO (g) ( ⁰ C) (h) (h) calc.

2 2.7 0.07 75-83 ^& 3.5 1.5 38.3 38.1

3 3.6 0.08 70 8 4.5 (72 ⁰ C) 34.85 34.25

4 3.6 0.08 75-80 4 1.25 (80 ^° C) 34.85 34.1

5 4.5 0.12 77-83 4.5 1.5 31.4 32.4

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Example 6 and 7

Under a nitrogen atmosphere, 168 parts by weight of TIn. Hexamethylene diisocyanate with 0.08 and 0.16 wt. Tin. Bis (tributyltin) oxide in 15.5 or 2.5 hours 3.6 parts by weight. Given water. The other working conditions (temperature and reaction time) and the NCO Kennvverte the reaction products are summarized in tabular form.

Weight "-Tle. Tempe reaction time

In the case of catalytic converter, the temperature is lower than that of the water. % NCO (g) ( ⁰ C) (h) calc.

6 0.08 80-82 1 36.1 35.4

7 0.16 90 - 93 0.5 36.1 35.8

Claims (1)

₇ 10949 invention claim Process for the preparation of polyisocyanates having a biuret structure and an isocyanate functionality greater than 2 by reacting di- and / or triisocyanates with customary biuretizing agents in a ratio of 1: 1 to 10: 1, preferably 1: 1 to 8: 1, at temperatures in the range between 50 and 120 C, preferably in the range between 80 and 100 C, in the presence of an organotin compound of the general formula (R ₃ Sn) ₂ O, wherein R represents an alkyl substituent CH - with η ά 4, which may be substituted by halogen, and optionally one Lösunasmittel according to characterized in that the Implementation of the reactants in the presence of a catalyst concentration of the organotin compound down to 0.003 mol%, based on isocyanate Ver.bindung used takes place.