DD236743A1 - METHOD FOR PRODUCING ONE COMPONENT POLYURETHANE SYSTEMS - Google Patents

Abstract

The invention relates to the production of isocyanate group-containing one-component systems, which can be further processed into polyurethanes, mainly with pore structure, and intermediates in the manufacture of fabric coatings, Impraegnierungen, technical composite materials u. Like. Represent. The aim of the invention is to provide isocyanate group-containing one-component systems of one or more polyhydroxyl compounds, diisocyanates and strong tertiaer-amine catalysts with a storage stability of at least 24 hours by an economic method available. According to the invention, di- and / or polyisocyanates are mixed with a mixture of polyhydroxyl compounds containing between 0.1 and 2% by weight of the tertiary amine catalyst, the ratio of the sum of all hydroxyl groups to the sum of all isocyanate groups being between 1: 2.1 and 1 : 21 and the mixture of polyhydroxyl compounds from those of the functionality 1.5 to 6 and the average molecular weight 62 to 10,000 is characterized.

Description

Field of application of the invention

The invention relates to a process for the preparation of isocyanate group-containing one-component systems which can be further processed to give polyurethanes or polyurethane polyureas having a predominantly pore structure and are valuable intermediates in the production of fabric coatings, impregnations, technical composite materials, etc.

Characteristic of the known technical solutions

The preparation of prepolymers from isocyanates and a molar deficiency of polyhydroxy compounds is known. For this purpose, polyether alcohols and polyester alcohols, aliphatic and aromatic isocyanates can be used. These prepolymers with terminal, free isocyanate groups are storage stable for several months in the absence of moisture, elevated temperature and / or basic impurities and can be further processed after storage to give polyurethanes or polyurethane polyureas having the same properties as the freshly prepared products. Such isocyanate prepolymers are z. In DE-PS 1,008,484 and DE-OS 2,232,525, in US-PS 3,725,357, in GB-PS 1,520,846.

With the addition of tertiary amines, which are necessary to accelerate the formation of urethane or urea from the isocyanate groups in the case of application, is usually very schneiI a cyclotrimerization under IsocyanurateIdung. so z. B. in GB-PS 908,337 a process for the preparation of polyurethane isocyanurates, which are obtained by cocatalysts of the resulting Ca rbamatgruppen and a tertiary Am in. Similar methods are described in DE-PS 1,013,869 and DE-OS 1,904,575. In the latter, triethylenediamine (diazabicyclooctane) is used as the tertiary amine, and polyether alcohols are used as the polyhydroxy compounds. German Offenlegungsschrift No. 1,495,937 teaches to prepare stable prepolymers of polyalkylene ether glycols and diisocyanates in several stages by first preparing a prepolymer of polyalkylene ether polyol with 1.1 to 2.1 mols of an organic diisocyanate; this is then reacted with further polyalkylene ether polyol and the resulting intermediate with sufficient polyisocyanate, so that a still free isocyanate groups containing prepolymer is formed. This is immediately before processing with catalyst, water u.a. Additives mixed and processed into foams. According to this invention critical importance of a certain viscosity is attributed, which is necessary for the structure of the cell structure.

GB Patent 980,021 teaches the preparation of prepolymers from polyether alcohols, diisocyanates in the case of catalysis by tertiary amines, in particular diazabicyclooctane; these products should be storage-stable in the closed container for three days. These prepolymers are also prepared in several stages at temperatures up to 5O ⁰ C, wherein the stages are necessary in that a reaction of the isocyanate with itself under isocyanurate formation is prevented by several successive additions. In addition, the amine concentration is very low at 0.05% by weight. A variant of this method with linear polypropylene glycols, diisocyanates and weaker tertiary amines, eg. N-methylmorpholine and triethylamine, which are known to catalyze very little trimerization, are described in British Pat. No. 898,272.

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In order to prevent trimerization of the isocyanate groups in prepolymers catalyzed with tertiary amines, a process is described according to DE-OS 2,232,525, according to which a prepolymer is prepared from propylene glycol, diisocyanates and phenethylenimine, which is then stabilized with methyl p-tosylate.

This effect can be achieved according to JP-PS 73-25756 in that are used in place of the purified crude isocyanates with about 10 to 65 wt .-% impurities. If, in this way, e.g. from the crude tolylene diisocyanate, a tertiary amine as a catalyst and a polyether or polyester polyol, a prepolymer is prepared, the acidic impurities of Rohisocyanats act as stabilizers as in the case of DE-OS 2,232,525. Good storage stability, which is not specified, is achieved by this method, although up to 10% by weight of strong tertiary amine catalysts are used.

How necessary such a stabilization of the prepolymers is clear from the teaching of DE-PS 1,013,869 or GBPS 908,337. At temperatures of 80 to 100 ⁰ C, a mixture of 100Tl. Isocyanate, 1 part. Alcohol and 1Tl. Pentamethyldiethylenetriamine within a short time, ie here, the forming carbamates and the tertiary amines act as cocatalysts in the trimerization of the isocyanates.

The disadvantage here is that in catalyzed prepolymers containing isocyanate groups to ensure a sufficiently long service life for the technology stabilization is necessary, but the substances used for stabilization negatively affect the processing conditions and properties of the final products.

Object of the invention

The object of the invention is therefore, according to an economical method, to provide isocyanate group-containing one-component systems comprising one or more polyhydroxy compounds, diisocyanates and strong tertiary amine catalysts having a storage stability of at least 24 hours, these prepolymers being sufficiently strongly catalysed to react at comparatively low temperatures cure with water vapor or moisture within a short time to form even, thin layers with pore structure or when using fibers to bond.

Explanation of the essence of the invention

According to the invention, the object is achieved in that di- and / or polyisocyanates at a temperature of 10 to 60 ⁰ C with polyhydroxy compounds whose functionality is between 1.5 and 6 and their molecular weight between 62 and 10000, are reacted, the polyol mixture a contains such high concentration of tertiary amine, that this concentration of the tertiary amine in the prepolymer between 0.1 and 2Gew .-% and wherein the ratio of the sum of all hydroxyl groups to the sum of all isocyanate groups between 1: 2.1 and 1:21.

Surprisingly, in contrast to the teaching of DE-PS 1,013,869 it was found that in the reaction of isocyanates with hydroxyl compounds in the presence of a concentration of strong tertiary amine catalysts for the intended application according to the invention without additional energy supply, the reaction proceeds with such a high reaction rate without a trimerization reaction takes place, but that the prepolymer has reached its final value of the isocyanate groups after only 15 to 20 minutes reaction time, ie the reaction is complete. The urethane formation is controlled by suitable addition rate of the mixture of the polyhydroxy compounds so that the temperature does not exceed 60 ⁰ C. The addition of the Poiyetheralkohol catalyst mixture can be carried out in three forms, namely

1. the polyether alcohols are mixed together before the reaction and the catalyst dissolved therein and then the mixture is added to the isocyanate;

2. the catalyst is dissolved in one of the Pölyetheralkohole, added this mixture to isocyanate and then added the other Pölyetheralkohole successively or as a mixture;

3. a polyether alcohol is reacted with the isocyanate to an isocyanate group-containing precursor and then a polyether alcohol-catalyst mixture is reacted with this precursor to the reaction.

It has proved to be particularly advantageous and represents a preferred embodiment of the method according to the invention to use several polyhydroxy compounds of different molecular weight and functionality, wherein the catalysts are preferably the polyhydroxy compounds of the functionality 2 premixed or dissolved in them. By the concentration of amine in the mixture of polyhydroxy compounds and the dosage on the rate of addition of the polyhydroxyl compound-catalyst mixture can be adjusted without external energy supply such a temperature increase that a maximum space-time yield achieved, but no trimerization of the isocyanate groups is effected. The fact that the prepolymers do not have any isocyanurate structures during the reaction and within a period of at least 24 hours after preparation has the result that the favorable, low viscosity of the prepolymers is retained and, in addition, the block structure of the polyurethanes and / or polyurethanes to be produced therefrom. polyureas is not disturbed. The use of the catalysts and the ability to carry out the reaction at temperatures up to 6O ⁰ C, in turn means that at a batch size up to 20 kg no later than 20 minutes after addition of the mixture of polyhydroxy compounds and catalyst, the reaction is complete and the previously calculated value of the isocyanate concentration is determined.

One of the further embodiments of the method according to the invention comprises reacting the isocyanate component with a part or the total amount of a polyhydroxyl compound, preferably the one with the highest functionality, and only then adding a mixture of further polyhydroxy compounds with the dissolved catalyst. This gives a component A and a component B from the mixture of polyhydroxy compounds and the catalyst or from a long-term storage-stable prepolymer containing isocyanate groups. The catalyst-containing, inventive prepolymer is then prepared in a known manner by mixing the two components A and B in a previously calculated mixing ratio without energy or cooling at temperatures between 10 and 60 ⁰ C. The catalyst-containing prepolymer produced in this way is stable in storage for at least 24 hours.

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As a mixture of polyhydroxyl compounds, preference is given to:

a) 20 to 95 eq.% of a polyether triol of average molecular weight 400 to 10,000;

b) 1 to 50 equivalent% of a polyether alcohol of average functionality 2.05 to 2.75 and of average molecular weight 750 to 7500;

c) 0.5 to 20 equivalent% of a polyether diol of average molecular weight 300 to 3000;

d) 0.5 to 30 equivalent% of a diol of molecular weight 62 to 400.

Preference is given to polyether alcohols which are prepared from one or more starter molecules of the functionality 2 and / or 3 and ethylene oxide and / or propylene oxide. However, it is also possible to use polytetramethylene glycols, polycaprolactone polyols, polyester alcohols or functionalized polycarbonates or polybutadienes and so-called polymer polyols.

All aromatic di- and / or triisocyanates and their crude technical products can be used in isocyanates. However, preferred are 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyl diisocyanate, p-phenylene diisocyanate or mixtures thereof.

Suitable catalysts are, for. B. triethylenediamine, Ν, Ν, Ν ', Ν'-tetramethylbutanediamine, Ν, Ν, Ν', Ν'-tetramethyl-hexanediamine * 1,6, Ν, Ν'-dimethylpiperazine, N-methylmorpholine, tetramethylguanidine, etc. Preference is given to triethylenediamine.

From the catalyzed prepolymers of several polyhydroxyl compounds having isocyanate groups prepared by the process according to the invention, polyurethane-polyureas having excellent properties can be prepared by hardening with water-as water, water vapor or air moisture.

Such applications where e.g. rapid curing is desired, are foams prepared by reaction with water, stabilizers and other additives in a conventional manner, or thin foam layers obtained by curing in a moisture-containing atmosphere at elevated temperature and composites of substrates and the polyurethane Polyureas, which may have a pore structure. By suitable selection of the ratio of the polyhydroxyl compounds and the ratio of hydroxyl groups to isocyanate groups, the properties of the products can be varied within wide limits, for. For example, the hardness and elasticity can be matched to the substrate used.

Such applications are described in the DD-WP Appl. No. (Rev. No. 81/24) and DD-WP Note. No. (Rev. No. 82/02) and in the DD-WP-Anm. B32B / 231.213. / 8 described.

embodiments example 1

To 5.8 equivalents (505 g) of tolylene diisocyanate (isomer mixture with 80% 2,4-isomer and 20% 2,6 isomer) is added in a 4 l three-necked flask with stirrer, thermometer at room temperature with stirring within 20 minutes, a mixture of 1 equivalent ( 1760g) of polyether polyol (from glycerine, propylene oxide and ethylene oxide, molecular weight 4400), 0.3 equivalent of (90g) polyethylene glycol 600 and 0.4 equivalent (40g) of dipropylene glycol containing 33% dissolved triethylenediamine. During the addition the temperature rises to 60 ° C; the reaction is completed about 20 minutes after the addition of the polyether alcohol mixture, wherein heating or cooling are not necessary. The catalyzed prepolymer thus prepared has a Isocyanatäquivalentvon 600g / mole NCO and a viscosity (20 ⁰ C) of 3100mPas. It is stable in storage for 24 hours.

Example 2

Analogously to Example 1, a mixture of 35.2 kg (20 equivalents) of polyether polyol (as in Example 1), 1.8 kg (6. 1) in a 60 l stainless steel stirred tank to 10.1 kg (116 equivalents) of toluene diisocyanate (isomer mixture) at room temperature Equivalents) of polyethylene glycol 600 and 0.8 kg of a 33% solution of triethylenediamine in dipropylene glycol (8 equivalents) over 45 minutes. The temperature rises to 33 ° C; After stirring 10 minutes, the catalyzed prepolymer to a Isocyanatäquivalentvon 592 g / mole NCO and a viscosity (20 ⁰ C) of 2850 mPas. It is stable in storage for more than 24 hours.

Example 3

There are produced for the preparation of the prepolymer according to the invention two precursors, which are referred to as component A and B:

Component A: At room temperature, 435.6 g (0.33 equivalents) of a polyether polyol (from glycerol, propylene oxide and ethylene oxide, molecular weight 3000) with 53 g (0.53 equivalents) of a 33% solution; of triethylenediamine in dipropylene glycol. The mixture has a viscosity (20 ⁰ C) of 850mPas and is unlimited location-'ähig in sealed containers.

Component B: In a 21 three-necked flask to 356,7g (4.1 equivalents) tolylene diisocyanate (mixture of isomers) at 60 ⁰ C within 15 minutes 1126,4g (0.64 equivalents) of a polyether alcohol (from glycerin, propylene oxide and ethylene oxide, Mol mass 4000). The mixture is then stirred at 80 ° C for two hours. This product has an isocyanate equivalent of 430 g / mol NCO and a viscosity (20 ^° C.) of 1250 mPas. It is stable in storage in sealed containers for more than nine months.

Preparation of the prepolymer according to the invention:

Before the final processing, the components are mixed together in the ratio A: B = 1: 3 at room temperature. The prepolymer produced thereby has an isocyanate equivalent of 760 g / mol of NCO and a viscosity (2O ⁰ C) of

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Example 4

The reaction is carried out in a 601 stainless steel stirred tank analogously to Example 3: Component A: 22.6 kg of polyether alcohol (12.8 equivalents)

1,6kgTriethylendiaminlösung in dipropylene glycol (16,7Äquivalente) Viscosity (20 ⁰ C): 760 mPas stored indefinitely in sealed containers.

Component B: To 10.7 kg (123 equivalents) of tolylene diisocyanate (mixture of isomers) are added at 60 ⁰ C within 15 minutes 21.1 kg (12 equivalents) of polyether alcohol as in Example 3 and stirred at 8O ⁰ C for two hours. The product has an isocyanate equivalent of 29OgZMoI NCO and a viscosity (2O ⁰ C) of 1020 mPas; it is storage stable in sealed containers for more than nine months. Preparation of the prepolymer according to the invention:

To prepare the catalyzed prepolymer, the two components are mixed together in the ratio A: B = 4: 5. Due to the liberated heat of reaction, the temperature rises to 50 ⁰ C. The key figures of the prepolymer are:

Isocyanate equivalent: 720 g / mol NCO Viscosity (20 ^° C.): 4300 mPas

Shelf life: 24 hours

Claims (7)

Invention claim: 1. A process for the preparation of isocyanate group-containing one-component polyurethane systems having a storage stability of at least 24 hours of polyhydroxy compounds, di- and / or polyisocyanates and strong tertiary amine catalysts at temperatures of 10 to 60 ⁰ C within 5 minutes to 3 hours, characterized in that the diisocyanates and / or polyisocyanates are reacted with a mixture of polyhydroxy compounds which contain between 0.1 and 2% by weight of the tertiary amine catalyst dissolved by control over the rate of addition so that the temperature achieved by the heat of reaction 60 ⁰ C and thereby does not use trimerization of isocyanate groups, wherein the ratio of the sum of all hydroxyl groups to the sum of all isocyanate groups between 1: 2.1 and 1:21 and the mixture of polyhydroxy compounds from those of the functionality 1.5 to 6 and the average molecular weight 62 to 10,000 is characterized. 2. The method according to item 1, characterized in that the tertiary amine catalysts are dissolved in a polyhydroxyl compound, this solution is mixed into further polyhydroxy compounds and the mixture is reacted at room temperature with temperature increase up to 60 ⁰ C with the di- and / or polyisocyanate , 3. The method according to item 1, characterized in that prepared from one or more polyhydroxy compounds in a known manner with a diisocyanate, a precursor with isocyanate groups and this is reacted with a mixture of at least one polyhydroxyl compound and a tertiary amine catalyst at temperatures up to 60 ⁰ C. , 4. The method according to item 1, 2 or 3, characterized in that the tertiary amine catalyst dissolved in a diol of molecular weight 62 to 10,000, as this solution is added to further polyhydroxy compounds and this mixture at 10 to 60 ⁰ C with a di- and / or polyisocyanate or mixture is reacted. 5. The method according to item 1,2,3 or 4, characterized in that the tertiary amine catalyst is dissolved in a polyether alcohol or mixture of functionality 2 to 3 and an average molecular weight of 300 to 6000 and then this mixture with the di- and / or polyisocyanates is reacted. 6. The method according to item 1 to 5, characterized in that the preparation of the isocyanate prepolymer is carried out without additional heating or cooling only by controlling the rate of addition of the polyether alcohol catalyst solution at temperatures of 10 to 60 ⁰ C. 7. The method according to item 1 to 6, characterized in that a solution of a tertiary amine catalyst in one or more polyhydroxy compounds to di- and / or polyisocyanates at 10 to 6O ⁰ C is added and this mixture is reacted with one or more other polyhydroxy compounds.