EP0000893A1 - Process for the preparation of polyisocyanates and their use - Google Patents

Abstract

S-triazine ring-containing polyisocyanates of the formula <IMAGE> in which X represents a residue such as that obtained by removing the more reactive isocyanate group from an organic diisocyanate of the formula OCN-X-NCO with isocyanate groups of different reactivity in the sense of the isocyanate addition reaction is obtained, and Y is a chlorine, bromine, C1-C8-alkyl, C1-C8-alkoxy, C6-C10-aryl, C6-C10-aroxy radical or a radical of the formula -NH-CO -NH-X-CNO is a process for their preparation by reacting s-triazine polyamines with diisocyanates which have isocyanate groups of different reactivity, and the use of the new compounds as buildable fillers in the production of polyurethane plastics.

Description

The present invention relates to the polyisocyanates according to claim 1, the process for their preparation according to claim 3 and their use according to claim 5.

It has been found that melamine and other s-triazine derivatives containing amino groups can be reacted with certain diisocyanates, which are described in more detail below, under certain reaction conditions, which are described in more detail below, to give new urea group-containing polyisocyanates without a chain extension reaction to give corresponding polyureas.

The polyisocyanates according to the invention which can be obtained by the process according to the invention correspond to the general formula of claim 1, where X and Y have the meaning given there. X is preferably a radical having isocyanate groups, as is the case by removing the in the sense of the isocyanate addition reaction, a more reactive isocyanate group can be obtained from an aromatic diisocyanate with isocyanate groups of different reactivity. X particularly preferably represents a 3-isocyanato-4-methylphenyl or a 4- (o-isocyanato-benzyl) phenyl radical. Y preferably represents a radical of the formula -NH-CO-NH-X, where X preferably has the last-mentioned preferred or in particular the last-mentioned particularly preferred meaning.

The compounds according to the invention are prepared by reacting amino-containing s-triazine derivatives of the formula mentioned in claim 3 with diisocyanates of the formula X-NCO, where X corresponds to the definition mentioned in claim 1 or preferably the last definitions made, and wherein Y 'is the in Claim 3 has the meaning given and preferably represents an H ₂ N group.

Diisocyanates X-NCO suitable for the process according to the invention are any organic diisocyanates which, in the sense of the isocyanate addition reaction, have isocyanate groups of different reactivity and are otherwise inert under the conditions of the process according to the invention.

Aromatic diisocyanates corresponding to this definition are preferably used in the process according to the invention.

The preferred aromatic diisocyanates include, in particular, those in the molecular weight range 174-400 which, in addition to a free, ie sterically unimpeded aromatically bound isocyanate group have a further aromatically bound isocyanate group which is sterically hindered by at least one substituent in the o-position. Such substituents, which can lead to steric hindrance of the isocyanate group, are in particular C ₁ -C _S -alkyl-, C ₆ -C ₁₀ -aryl-, C ₁ -C ₈ -alkoxy-, C ₁ -C ₈ -thioethers- , C ₁ -C ₈ alkoxycarbonyl, chlorine, bromine or cyano groups. Furthermore, there is a steric hindrance to the aromatically bound isocyanate groups when the basic structure of the diisocyanate is a system of several aromatic rings which may be linked via bridge members such as alkylene, ether, thioether, sulfoxide or sulfone groups and the (sterically hindered) isocyanate group in ortho position to the bridge link linking 2 aromatic rings is arranged.

wobei

• R' und R" für gleiche oder verschiedene Reste stehen und eine die sterische Hinderung der Isocyanatgruppe bewirkende Gruppe der oben beispielhaft genannten Art darstellen, wobei bei den Produkten der Formel (II) einer der Reste R' bzw. R" auch für Wasserstoff stehen kann, bzw. wobei in der Formel (II) auch beide R' und R" für Wasserstoff stehen können, falls die Isocyanatgruppe ortho-ständig zur Brücke R"' bzw. im Falle von n = 0 ortho-ständig zum linken aromatischen Ring angeordnet ist;
• R"' für eine die aromatischen Ringe verknüpfende Brücke der oben beispielhaft genannten Art und
• n für 0 oder 1 steht.

Suitable aromatic diisocyanates are therefore, for example, those of the formulas (I) and (II).

in which

• R 'and R "stand for the same or different radicals and represent a group which effects the steric hindrance of the isocyanate group of the type exemplified above, it being possible for one of the radicals R' or R" in the products of the formula (II) to also stand for hydrogen , or in the formula (II) both R 'and R "can also be hydrogen if the isocyanate group is arranged ortho to the bridge R"' or in the case of n = 0 to the left aromatic ring;
• R "'for a bridge linking the aromatic rings of the type exemplified above and
• n stands for 0 or 1.

It is also possible to use mixtures of aromatic diisocyanates in the process according to the invention in which aromatic diisocyanates with isocyanate groups of the same reactivity as, for example, 4,4'-diisocyanatodiphenyl-. methane or 2,6-diisocyanatotoluene are present if the proportion of such diisocyanates with isocyanate groups of the same reactivity does not exceed an upper limit of 50, preferably 40,% by weight, based on the total mixture.

The particularly preferred diisocyanates suitable for the process according to the invention include, for example, 2,4-diisocyanatotoluene, optionally in a mixture with up to 50% by weight, based on the total mixture of 2,6-diisocyanatotoluene, 2,4'-diisocyanatotoluene, optionally in a mixture with up to 50 wt .-% based on the total mixture of 4,4'-diisocyanatodiphenylmethane. Also suitable are, for example, 2,4'-Diisocyanatodiphenylpropan, 2,4'-Diisocyanatodiphenylsulfid, 2,4'-Diisocyanatodiphenyläther, 2,4'-Diisocyanatodiphenylsulfon, 2,4'- _D iisocyanatodiphenylsulfodioxid, 3-methyl-4,4'-diisocyanatodiphenylmethane , 3-ethyl-4,4'-diisocyanatodiphenylmethane, 3-isopropyl-4,4'-diisocyanatodiphenylmethane, 3,5-dimethyl-4,4'-diisocyanatodiphenylmethane, 3,5-diethyl-4,4'-diisocyanatodiphenylmethane or 3,5-diisopropyl-4,4'-diisocyanatodiphenylmethane, 3-carboxymethyl-4,4'-diisocyanatodiphenylmethane, 3-carboxyethyl-4,4'-diisocyanatodiphenylmethane

S-triazine derivatives which have amino groups and are suitable for the process according to the invention and correspond to the above are Melamine, 6-chloro-2,4-diamino-s-triazine, benzoguanamine, acetoguanamine or caprinoguanamine. !! elamin is particularly preferred.

When carrying out the process according to the invention, the reaction partners are used in such quantitative ratios that at least 2 isocyanate groups of the diisocyanate are present in the reaction mixture for each amino group of the s-triazine derivative, this quantity indication in the case of the use of the above-mentioned mixtures exclusively relating to the diisocyanate with NCO- Groups of different reactivity relates. In general, the s-triazine derivative is stirred in an excess of the initially introduced diisocyanate, and the solution or dispersion formed in the process is then heated to 60-180 ° C., preferably 100-160 ° C., optionally with the addition of known urethanization catalysts, such as zinc acetylacetonate, until the Isocyanate content of the reaction mixture shows the calculated waste. The process product according to the invention precipitates as a precipitate which is insoluble in the excess diisocyanate.

After the reaction mixture has cooled to room temperature, the process products according to the invention can be obtained in pure form by filtration and washing, for example with an inert solvent such as acetone, chloroform or petroleum ether. The way of working described represents the is by far the preferred procedure, since when using an NCO / NH ₂ equivalent ratio of ≥ 2: 1, for example in the presence of inert solvents, generally no process products according to the invention but rather highly crosslinked reaction products are obtained. (The use of non-polar diluents such as mineral spirits or aromatic hydrocarbons which do not dissolve the process products would be possible, however, is generally superfluous). In general, the excess of the diisocyanate component is chosen so that 5-8 NCO equivalents, based on all diisocyanates of the diisocyanate component, are present in the reaction mixture for each H2N equivalent of the s-triazine polyamine, preferably 3-10.

The new compounds according to the invention are sparingly to insoluble in practically all common organic solvents, with the exception, for example, of highly polar solvents such as dimethylformamide or dimethyl sulfoxide. The new compounds have a high melting point and decompose in the melt. They are suitable as an isocyanate component in powder coatings based on polyurethane and in particular as active fillers in the production of polyurethane plastics by the isocyanate polyaddition process known per se. In this preferred use of the compounds according to the invention, the compounds according to the invention are preferably dispersed in the isocyanate component used for the production of the polyurethane plastic. Such dispersions of the process products according to the invention in organic polyisocyanates are then processed in a manner known per se using polyhydroxy polyethers and / or polyhydroxy polyesters, if appropriate in combination with chain extenders known per se, to give polyurethane plastics, in particular polyurethane elastomers, which then, thanks to the use of the compounds according to the invention, are improved by improved heat Stability, improved tear propagation resistance, improved elongation at break and improved tensile strength.

If the use of the compounds according to the invention for the production of such improved polyurethane plastics is intended, it is often unnecessary to remove the excess diisocyanate used in the production of the process products according to the invention. Rather, the dispersion of the process products according to the invention in the starting diisocyanate used in excess in the reaction according to the invention can be used directly for the production of the polyurethane plastics. According to a preferred embodiment of the use according to the invention of the compounds according to the invention, the last-mentioned dispersions are reacted with the polyether polyols or polyester polyols known per se in polyurethane chemistry to form prepolymers containing NCO groups, in such proportions that the unmodified diisocyanate in the resulting NCO prepolymers originating isocyanate groups as well as the isocyanate groups of the compounds according to the invention are present. These NCO prepolymers are then reacted with chain extenders, for example a diamine of the type exemplified in Example 10, to give the high molecular weight polyurethane polyurea, the amount of chain extender either being chosen such that for all isocyanate groups of the prepolymer including the isocyanate groups of the dispersed compounds according to the invention First approximation, an isocyanate-reactive group of the chain extender is available or so that, in a first approximation Isocyanate-reactive groups of the chain extender are only available for the isocyanate groups of the prepolymer, which do not originate from the compounds according to the invention, a subsequent chemical incorporation of the initially dispersed compounds according to the invention being achieved by tempering the reaction products at 100-150 ° C. (cf. Example 10). Particularly in the first-mentioned case of using approximately equivalent amounts of the chain extender based on the total amount of the isocyanate groups present, it is advisable to use the known polyurethane catalysts such as, for example, dibutyltin dilaurate, tin dioctoate, diazobicyclooctane and / or dimethyltetrahydropyrimidine.

example 1

A mixture of 1000 g (5.75 mol) of tolylene isocyanate (2,4- and 2,6-isomers in a ratio of 80:20) and 72.5 g (0.575 mol) of melamine are stirred at 120 to 130 ° for 3 hours with vigorous stirring C. heated. After the reaction mixture has cooled, the reaction product is filtered off with suction and washed free of isocyanate with acetone. After drying in vacuo, 373 g of a colorless product which is extremely sparingly soluble in organic solvents are obtained. Yield, calculated on an addition product of melamine and tolylene diisocyanate in a molar ratio of 1: 3, 98%, mp = 350-380 (Z).

The triisocyanate reacts only slowly in the cold (RT) with aliphatic amines such as di-n-butylamine. The NCO value can therefore only be determined at RT after a longer reaction time:

If the titration is carried out at 50-70 ° C, on the other hand, an NCO value of 19.3% (calculated 19.5%) is found after only 3 to 5 minutes.

Example 2 (comparison)

A mixture of 63 g (0.5 mol) of melamine and 313 g (1.8 mol) of the tolylene diisocyanate of Example 1 in 1 liter of nitrobenzene is heated to 140 ° C. After 45 minutes, the reaction mixture can no longer be stirred. It is diluted with acetone and suction filtered. The dried precipitate has an NCO value of 2.5% (calculated 19.5%).

Example 3 (comparison)

31.5 g (0.25 mol) of melamine and 480 g (3 mol) of 1,3-phenylene diisocyanate are heated to 100-140 ° C. for 7 hours with vigorous stirring. The reaction mixture is then diluted with chloroform and suction filtered. The precipitate, dried in vacuo, has an NCO value of 10.9% (calculated 20.8%).

Example 4

31.5 g (0.25 mol) of melamine and 500 g (2 mol) of a diphenylmethane diisocyanate with approx. 40% 4,4'-isomers and 60% 2,4'-isomers are stirred at 100 ° C. for 4 hours with vigorous stirring heated. The reaction mixture is then diluted with chloroform / petroleum ether and suction filtered. The precipitate is dried in vacuo. Yield 200 g (91%). Fixed point 252-60 ° C (decomposition).

Example 5 (comparison)

A mixture of 12.6 g (0.1 mol) of melamine and 250 g (1 mol) of melted 4,4'-diphenylmethane diisocyanate is heated to 120 ° C. The reaction mixture is solid after 30 minutes.

Example 6

7.6 g (0.06 mol) of melamine and 252 g (1 mol) of 2,4'-diisocyanatodiphenyl ether are heated at 100 ° C. for 4 hours. The reaction mixture is then diluted with methylene chloride / petroleum ether and suction filtered. The precipitate is dried in vacuo. Yield 48 g (91%). Fixed point 265-68 ° C.

Example 7

0.567 kg (4.5 mol) of melamine are added to 7.1 kg (40.8 Mbl) of 2,4-tolylene diisocyanate at RT with stirring. The reaction mixture is heated to 125-130 ° C. After 2 hours, cool to 80-85 ⁰ C. The melamine triisocyanate is then prepolymerized in the form of a finely divided slurry containing excess 2,4-tolylene diisocyanate with 27.31 kg (13.7 mol) of a difunctional polypropylene glycol (OH number 56). After 4 to 5 hours at 80-85 ⁰ _C the prepolymer has an NCO value of 3.2-3.4%. If the NCO determination is carried out in the heat or in dimethyl sulfoxide solution, an NCO value of 4.4-4.6% is determined, since the NCO content of the melamine-diisocyanate adduct is then also included.

The solids content of the prepolymer is 8.4% and its viscosity is 4500 cP (25 ° C).

Example 8

14.4 g (0.11 mol) of melamine and 336 g (1.34 mol) of a diphenylmethane diisocyanate with about 40% of 4,4'-isomer and 60% of 2,4'-isomer are stirred for 4 hours with vigorous stirring 100 ⁰ C heated. Then 1000 g of a difunctional polyether diol (OH number 28) are added at 80 ° C. After 3 hours at 90 ° C, the prepolymer has an NCO value of 3.6%. Its solids content is 7.4%.

Example 9

27.5 g (0.24 mol) of ethylene glycol monobutyl ether in 100 ml of chlorobenzene are mixed with 50 g (0.08 mol) of the compound isolated in Example 1. The reaction mixture is heated to 130 ° C. It cannot be stirred after 90 minutes. If 0.5 g of dibutyltin dilaurate is added under otherwise identical conditions, the reaction mixture can no longer be stirred after 20 minutes, with the addition of 0.5 g of dime thyltetrahydropyrimidine after 14 minutes. The triisocyanate reacts under the usual conditions to form urethane.

Example 10

100 parts by weight of the modified NCO prepolymer prepared in Example 7 are degassed at 60 to 80 ° C in vacuo and then with 6 parts by weight of 3,5-diethyl-1-methyl-2,4-diaminobenzene within Stirred for 30 seconds. Half of the reaction mixture is then poured into a metal mold at 110 or 130 ° C. The casting time is approx. 2 minutes. The cast part can be removed from the mold after 4 to 5 minutes. After annealing at 110 ° C (24 hours) and at 130 ° C, the mechanical properties of the elastomer are determined:

From the increase in tensile strength, elongation at break and tear resistance with the same hardness, it can be seen that the filler is only incorporated into the PU matrix after the elastomer has been tempered at ≥ 130 ° C., which is clearly visible in the reinforcing effect.

Claims (5)

1) Polyisocyanates of the formula

in which X represents a radical as obtained by removing the more reactive isocyanate group from an organic diisocyanate with isocyanate groups of different reactivity in the sense of the isocyanate addition reaction, and Y is a chlorine, bromine, C ₁ -C ₈ alkyl, C ₁ -C ₈ alkoxy, C ₆ -C ₁₀ aryl, C ₆ -C ₁₀ hydroxy residue or a residue of the formula -NH-CO-NH-X is. 2) polyisocyanates of the formula according to claim 1, for which X represents a 3-isocyanato-4-methyl-toluyl or a 4- (o-isocyanatobenzyl) phenyl radical and Y stands for -NH-CO-NH-X. 3) Process for the preparation of polyisocyanates according to claim 1, characterized in that polyamines of the formula

with diisocyanates of the formula

in a molar NCO / NH ₂ ratio of at least 2: 1 to react, wherein X has the meaning given in claim 1 and Y 'for an -NH ₂ -, -Cl-, -Br-, C ₁ -C ₈ -alkyl-, C ₁ -C ₈ -alk-oxy-, C ₆ -C ₁₀ -aryl- or C ₆ -C ₁₀ -Aroxy group stands. 4) Process according to claim 3, characterized in that as the polyamine of the formula melamine and as the diisocyanate of the formula 2,4-diisocyanatotoluene, optionally in a mixture with 2,6-diisocyanatotoluene, and / or 2,4'-diisocyanatodiphenylmethane, optionally used in a mixture with 4,4'-di * isocyanatodiphenylmethane. 5) Use of the polyisocyanates according to claim 1 as buildable fillers in the production of polyurethane plastics,