DE2356213C2 - Prepolymers terminated by ketimine groups and processes for their preparation - Google Patents

Description

In DE-PS 21 66 502 a process for the preparation of prepolymers containing enamine groups, can be prepared by reacting at least one secondary amine group and one aliphatic hydroxyl group bearing compounds in the first stage with aliphatic aldehydes or cycloaliphatic ketones and further reaction of the compounds thus obtained in the second stage with organic polyisocyanates described.

After reacting with epoxy compounds, these products give linear, i.e. H. thermoplastic end products with insufficient chemical resistance.

BE-PS 7 23 337 were products based on ketimines or ketimines and blocked isocyanates (Aryl carbamate) known. Compared to products based on this, the mixtures have been used the prepolymers terminated by ketimine groups and prepared according to the invention have the advantage an improved curing rate.

The invention relates to prepolymers terminated by ketimine groups, obtained by reacting a compound bearing at least one primary amine group and an aliphatic hydroxyl group in the first stage with aliphatic or cyclic ketones, the reaction being catalyzed, if appropriate, by acids, if appropriate with the supply of heat or cooling, with or without a solvent carried out and where the corresponding reaction water and the excess carbonyl compounds are removed, and further reaction of the compounds obtained in the first stage in the second stage with an isocyanate pre-adduct in an NCO / OH ratio equal to 1 with vigorous stirring and optionally with cooling at temperatures of 0 up to 30 ⁰ C.

Another object of the invention is a process for the preparation of ketimine terminated prepolymers of claim 1 by reaction > nn compounds bearing an aliphatic hydroxyl group and amino groups in the first stage with aliphatic or c> clic ketones, the reaction being catalyzed, if appropriate, by acids, if appropriate carried out with supply of heat or cooling with or without a solvent and removing the corresponding water of reaction and the excess carbonyl compounds, and further reaction of the compounds obtained in the first stage in the second stage with an isocyanate pre-adduct in an NCO / OH ratio equal to 1 with vigorous stirring and optionally with cooling at temperatures from 0 to 30 ^° C., which is characterized in that the compound used which carries aliphatic hydroxyl groups and amino groups contains at least one primary amino group and one aliphatic hydroxyl group.

Another form of process for producing the prepolymers terminated by ketimine groups is characterized in that the isocyanate pre-adducts are addition products of polypropylene glycols and excess diisocyanates used.

It was not previously known that ketimines which contain hydroxyl groups, while maintaining the ketimine structure add in the original form to isocyanates with the formation of urethane groups.

Rather, it is described in the literature that ketimines with isocyanates with the formation of cyclic addition products or products containing amide or urea groups react (K Harada, Makromol. Chem. 132, 295-304, 1970).

The ketimines used according to the invention are represented in such a way that the at least one primary Amino group and an aliphatic hydroxyl group-bearing compound with an excess of the aliphatic or cyclic ketones is added and the addition of the appropriate solvent (toluene, benzene) so heated under nitrogen on the water separator for a long time until the water separation has ended. In some cases the ketone itself can act as a tug.

Distillation of the ketimine is advantageous. The crude product can after removing the excess But ketones and the solvent can also be used directly.

Examples of aliphatic and cyclic ketones, which can be used with advantage for the preparation of the ketimines are cyclopentanone, trimethylcyclopentanone, cyclohexanone and trimethylcyclohexanone as well Methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone and diisopropyl ketone.

For the addition of the ketimines containing hydroxyl groups, pre-adducts from polypropylene glycols can be used and excess aliphatic diisocyanates are used.

The underlying polypropylene glycols are linear or branched products with an average molecular weight between 500 and 10,000.

It is advantageous to use aliphatic diisocyanates as this avoids chain lengthening will.

Such diisocyanates are, for. B. isophorone diisocyanate and trimethylhexamethylene diisocyanate. In the cases where chain extension is desired, hexamenthylene diisocyanate, 1-methyl-2,4-diisocyanatocyclohexane can also be used or 4,4'-diisocyanatodicyclohexylmethane can be used.

The diisocyanates are preferably added in a ratio of isocyanate to hydroxyl groups of 1.8 to 2.2. In general, it makes sense to mix the components with cooling at from 0 to 30 ^° C. and to add a catalyst, such as, for example, organic tin compounds or tertiary amines. The mixture is then heated to elevated temperatures of preferably 50 to 100 ° C. until the analytically determined isocyanate content corresponds to the calculated value.

The ketimines containing hydroxyl groups are added to the isocyanate pre-adduct in an NCO / OH ratio of 1. The admixture must take place with vigorous stirring and, if necessary, with cooling at temperatures of 0 to 30 ^° C. The egg is stirred until no more free ksocyanate can be detected by infrared spectroscopy.

The ketimine adducts according to the invention can be used as amine-releasing compounds, e.g. for moisture-curing Use polyurethane compounds.

For this purpose they are blocked with aromatic polyisocyanates in approximately stoichiometric Ratio gemisuit.

As masked polyisocyanates kor., .Nen this z. B. Adducts of trimethylolpropane and 2,4-toluene diisocyanate in a molar ratio of 1: 3, the free isocyanate groups can be blocked with phenol.

In addition, adducts of p-jypropylene glycols and 2,4-tolylene diisocyanate can be capped with nonylphenol Residual isocyanate groups are used.

example 1

la) In a 1 liter three-necked flask equipped with a water separator and stirrer, 91.5 g of ethanol, 225 g Submitted methyl isobutyl ketone and 100 ml of benzene. It is heated under reflux until the has deposited the calculated amount of water. Excess ketone and solvent are then stripped off and the residue is distilled in vacuo (bp 53 ° C / 0.5 mm).

Analysis:

calculated C 67% H 11.9% N 9.8%
found C 66.8% H 12.1% N 9.8%

In the infrared spectrum there is a strong ketimine band at 1655 enT ¹ .

Formula of the reaction product

CH ₅

HO-CH ₂ -CH ₂ -N = C CH,

\ /

CH ₂ -CH

CH,

Ib) A mixture of 5040 g of a trifunctional polypropylene glycol with an OH number of 35.6 and 711 g of isophorone diisocyanate 5.7 g of dibutyltin dilaurate are added and the mixture is kept at 75 ° C. for 3 hours under nitrogen touched. The reaction product has an isocyanate content of 2.2 percent by weight, corresponding to one Equivalent weight of 1914.

Ic) 100 g of the isocyanate pre-adduct prepared under Ib) are admixed with 74.83 g of the ketimine containing hydroxyl groups prepared under Ia) with cooling. Care is taken that the temperature does not rise above 30 ^° C. while stirring vigorously.

After 4 to 5 hours of stirring, free isocyanate can no longer be detected in the infrared spectrum. Against it the ketimine band has been preserved. The product has an equivalent weight of 2057.

Example 2

2a) A mixture of 105 g of 2- (2-aminoethoxy) ethanol and 150 g of cyclohexanone is mixed with 100 roles of benzene and heated for 4 hours on a water separator. 17.6 g of water separate out.
The excess ketone and the solvent are drawn off and the residue is distilled in vacuo (boiling point 103 ° C./0.2 mm).

Analysis:

calculated C 64.8% H 10.3% N 7.6%
found C 64.8% H 10.3% N 3.0%

The reaction product has the formula
HO-CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -N

2b) 1000 g of the isocyanate pre-adduct prepared under Ib) are added with cooling and vigorous stirring 96.6 g of the ketimine prepared under 2a) mixed

The temperature is kept ^{below 30 ° C. during the reaction.} After 5 hours of stirring, free isocyanate can no longer be detected in the infrared spectrum. The product has an equivalent weight of 2100.

Example 3

3a) 324 g of 2- (2-aminoethoxy) ethanol are mixed with 300.5 g of methyl isobutyl ketone and 300 ml of benzene. The mixture is heated under nitrogen on a water separator until the water separation has ended. The solvent is drawn off and the residue is distilled in vacuo.
The reaction product has the formula

CH ₃

HO-CH ₂ -CH ₂ -O-CH ₂ -CH ₂ -N = C CH ₃

CH ₂ -CH

CH ₃

3b) 1000 g of the isocyanate pre-adduct prepared under b) are mixed with 97.8 g of des with stirring and cooling under 3a) produced ketimines added.

After stirring for 4 hours, solid isocyanate can no longer be detected by infrared spectroscopy. That

Product has an equivalent weight of 2012.

Example 4

4a) 117 g of 1,6-hexanolamine are mixed with 150 g of cyclohexanone and 100 ml of benzene on a water separator t-Thitzt until no more water of reaction forms. The reaction is over after about 6 hours. The excess ketone and benzene are stripped off in vacuo and the residue is distilled in vacuo (Bp. 153 ° C / 0.8mm).

Analysis:

calculated C 73.0% H 11.7% N 7.1%
found C 73.5% H 11.7% N 6.8%

The infrared spectrum shows a strong C = N band at 1660 cm " ^1. The reaction product has the formula

HO— (CH ₂ ) ₆ -

4b) 1536 g of a branched polypropylene glycol with an OH number of 35.6 are mixed with 221 g of isophorone diisocyanate and 1.8 g of dibutyltin dilaurate were added.

The reaction mixture is heated to 75 ° C. and at this temperature for 2.5 hours with thorough stirring held. The reaction product has an isocyanate content of 2.39%.

4c) 1000 g of the isocyanate pre-adduct prepared under 4b) are mixed with 112.2 g of the one prepared under 4a) Ketimine containing hydroxyl groups stirred at room temperature. After the mixture has been mixed for approx.

'M has stood for 12 hours, free isocyanate can no longer be detected in the infrared spectrum.

Claims (4)

Patent claims: 1. Prepolymers terminated by ketimine groups, obtained by reacting a compound bearing at least one primary amine group and an aliphatic hydroxyl group in the first stage with aliphatic or cyclic ketones, the reaction being optionally catalyzed by acids, optionally carried out with the supply of heat or cooling with or without a solvent and the corresponding water of reaction and the excess carbonyl compounds being removed, and further reaction of the compounds obtained in the first stage in the second stage with an isocyanate pre-adduct in an NCO / OH ratio equal to 1 with vigorous stirring and optionally with cooling at temperatures from 0 to 30 ^° C. . 2. Prepolymers terminated by ketimine groups according to claim 1, obtained using a Isocyanate pre-adduct obtained by reacting polypropylene glycols and excess diisocyanates has been received 3. Process for the preparation of prepolymers of claim 1 terminated by ketimine groups by converting compounds containing an aliphatic hydroxyl group and amino groups into first stage with aliphatic or cyclic ketones, the reaction being carried out if necessary Acids catalyzed, optionally carried out with the supply of heat or cooling with or without a solvent and the corresponding water of reaction and the excess carbonyl compounds removed, and further reaction of the compounds obtained in the first stage in the second stage with a Isocyanate pre-adduct in an NCO / OH ratio equal to 1 with vigorous stirring and, if necessary, with cooling at temperatures from 0 to 30 ° C, characterized in that one is an aliphatic hydroxyl group and amino group-bearing compound uses those which have at least one primary amino group and contains an aliphatic hydroxyl group. 4. The method according to claim 3, characterized in that the isocyanate pre-adduct used is one obtained by reacting polypropylene glycols and excess diisocyanates is.