DE1954093A1 - Process for the preparation of polymeric organic isocyanates - Google Patents

Description

»954093

MOBAY CHEMICAL COMPANY Penn Lincoln Parkway West. Pittsburgh, Pennsylvania 152O5

Leverkusen, the

27 OCT. 1969

Process for the preparation of polymeric organic isocyanates

The present invention relates to an improved process for the preparation of organic isocyanurates of increased stability.

The trimerization of organic isocyanates, especially aromatic ones Polyisocyanates in the presence of aliphatic isocyanates using aliphatic, araliphatic or mixed aliphatic-araliphatic phosphines are known. The method allows the production of free isocyanate groups containing isocyanurates, in particular those isocyanurates which simultaneously contain free aromatic and aliphatic NCO groups exhibit. These isocyanate trimers are particularly suitable for the production of relatively stable adhesives, paints, elastomers and foams. To manufacture the Is trimerization products with reproducible properties

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however, it is necessary to finish the polymerization reaction accurately and quickly at a predetermined point. In order to achieve such a sharp stopping of the trimerization reaction at the desired degree of polymerization *, the reaction mixture compounds were added so far that cancel the effectiveness of the catalyst. Anhydrous hydrogen chloride, benzoyl chloride, acetyl chloride, dimethyl sulfate, methyl p-toluene sulfonate, mixtures of the two last-mentioned compounds and other compounds have been proposed as such catalyst poisons. T) Ie ae catalyst poisons, however, have the disadvantage that their addition to the reaction mixture does not immediately and completely terminates the action of the catalyst, so that in general after-heating is necessary for complete inactivation of the catalyst, whereby a strictly controlled termination of the polymerization reaction is impossible is. In addition , isocyanurates which have been produced using the cited catalyst poisons have the undesirable property of aging on storage, which is particularly noticeable in an undesirable increase in viscosity and discoloration of the products.

As has now been found, surprisingly, it is possible to avoid the disadvantages mentioned if elemental sulfur is added to the reaction mixture as a catalyst poison.

The present invention thus relates to a method for the production of polymeric isocyanates by polymerizing an organic isocyanate or polyisocyanate in Presence of a phosphine as a catalyst and termination of the polymerization reaction by subsequent addition of a Catalyst poison, characterized in that the catalyst poison used is sulfur.

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To terminate the polymerization reaction are in general. mean one to three moles of sulfur are required per mole of catalyst used.

Any aliphatic, cycloaliphatic, arali phatic or aromatic isocyanates are suitable as starting materials for the process according to the invention. Suitable isocyanates are in particular those of the general formula

R (NCO) _x

in which ß an optionally indifferenten.Substituenten

^b ° araiiphatic

containing aliphatic, cycloaliphatic ^ or aromatic hydrocarbon and χ stands for an integer from 1 to 4, in particular 1 to 3, t. Examples of suitable aromatic isocyanates are 2,4- and 2,6-diisocyanatotoluene and mixtures thereof, 4,4'-Diisoeyanatodiphenylnethan, phenylene, 4-tert-butyl-m-phenylene diiso cyanate, 1-methoxyphenylene-2,4-diisocyanate, diphenyl-4,4-diisocyanate, 1,5-diisocyanatonaphthalene, 1,4 -Diisocyanatonaphthalene, 4-, 4'-, 4 "-Tri4socyanato-triphenylmethane, Tris- (p-isocyanatophenyl) -thiophosphate and similar compounds called.

Examples of aliphatic, cycloaliphatic or araliphatic I-olyisocyanates are ethylene diisocyanate, 1 _f 4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,5-diisocyanato-2,2-dimethylpentane, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, cyclohexylene 1,3-diisocyanate, 1 _t 3 _f 5 -Iri ~ isocyanatocyclohexane, etc. called.

Any monoisocyanates may be the inventive method also used as Ausgangsmaterjalien be i *. Examples of this are phenyl isocyanate, benzyl isocyanate, p-To-Ki: .i _r 1 -Naphthyl isocyanai, p-methox3 ^r plienylj socy ^ Ka ⁴ - "

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o-chlorophenyl isocyanate, p-chlorophenyl isocyanate, methyl isocyanate, Propyl isocyanate, hexyl isocyanate and similar compounds.

Polyisocyanates to be used with preference as starting material are 2,4-diisocyanatotoluene, its mixtures with 2,6-diisocyanatοtoluene, Hexamethyl diisocyanate and mixtures of an aromatic isocyanate with an aliphatic, cycloaliphatic or araliphatic isocyanate, the ratio of aliphatically to aromatically bound NCO groups as follows it is chosen that in the starting mixture per aromatic NCO group at least 0.25 aliphatic NCO groups, preferably there are more than 1 aliphatic NGO groups, in particular up to 10 aliphatic NCO groups. .

Any desired phosphines can be used as catalyst in the process according to the invention, such as, for example, aliphatic, araliphatic or mixed aliphatic-aromatic phosphines. Trialkylphosphine such as trimethylphosphine, triethylphosphine, tri-n-propylphosphine and tri-iso- are suitable, for example. propylphosphine, ethyldibutylphosphine, tri-n-butylphosphine, tri-isobutylphosphine, tri-tert.-butylphosphine, tribenzylphosphine, dimethylbenzylphosphine, dimethylphenylphosphine, etc. Phosphines yes aen 2 JL-alkylphosphine form a ring such as p-acyclopentyl are also suitable. The amount of catalyst can vary within wide limits. In general, 0.001 to 10.0 percent by weight, preferably 0.001 to 1.0 percent by weight, in particular 0.01 to 0.1 percent by weight, based on the reaction mixture, of catalysts are added.

The process according to the invention can be in the presence or absence be carried out by solvents. When using solvents, a slightly higher content is preferred used on catalyst. Suitable inert organic solution

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Medium are e.g. dioxane, esters such as methyl acetate, ethyl acetate, Butyl acetate, methyl glycol acetate, etc., ketones such as acetone, Methyl ethyl ketone, cyclohexanone, etc., aromatic, aliphatic ^ or also chlorinated hydrocarbons with the exception of carbon tetrachloride.

The trimerization reaction can take place at reduced reaction temperatures. Generally, the reaction at -20 ° to +100 ⁰ O is preferably carried out at 20 to 60 ⁰ C. . Unusually high temperatures should be avoided in order to counteract the formation of garbodiimides and discoloration of the reaction mixture. The reaction can be carried out at any pressure, but is preferably carried out at atmospheric pressure.

Unreacted monomeric starting material can be used after completion the reaction can be removed by any separation operations such as distillation or extraction.

The compounds prepared by the process of the invention can have one or more isocyanurate ceramics in the molecule. They are particularly suitable for Manufacture of adhesives, lacquers, elastomers and foams as well as hardeners for polyester lacquers. The isocyanurates preferably in 50 to 70% solutions. Suitable solvents for this are esters, ketones, hydrocarbons, etc.

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Examples.

(1 Δ) 1300 parts by weight of an 80/20 isomer mixture of 2,4- and 2,6-diisocyanatοtoluene together with 2600 parts by weight of hexamethylene diisocyanate are heated ^{to 60 ° C. in a suitable reaction vessel;} then 0.78 parts by weight of tri-n-butylphosphine are added. The Tempemtur of the reaction mixture is maintained at 6Q ⁰ C by slight cooling. After about 4.5 hours the reaction mixture has an NCO content of about 36%. At this time, the reaction is p-toluenesulfonate methyl-by the addition of 1.56 parts by weight of a mixture of dimethyl sulfate and brought and brief heating at 100 ⁰ C to a standstill. During this post-heating, the reaction only slows down, which is noticeable in a further drop in the NCO content. The unreacted monomer mixture is finally removed by De st Hat ion at a pressure of 1 mm Hg and a temperature of 175 to 180 ^° C. in a thin-film evaporator. 2065 parts by weight of a brittle yellowish resin with an NCO content of 19.8 % are obtained.

(1 B) In a suitable reaction vessel are 1300 parts by weight of an 80/20 isomer mixture of 2,4- and 2,6-diisocyanatotoluene with 2600 GewichtsidLlen HexamethyJaidiisocyanat to 6O ⁰ C is heated; then 0.78 parts by weight of tri-n-butylphosphine are added. The temperature of the reaction mixture is kept at 60 ^° C. by cooling slightly. After about 4.5 hours the reaction mixture has an NCO content of about 36 #. At this point the reaction is stopped by adding 0.2 parts by weight of sulfur. Reheating is not necessary here, as the sulfur causes the reaction to stop immediately. Am further drop in the NCO content after the sulfur

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e-entry cannot be determined. The unreacted Monomerengeoisch is finally entferat by distillation at a pressure of 1 mm Hg and a temperature of 175 to 180 ^0C. 2221 parts by weight of a brittle yellowish resin with an NCO content of 2QOj6 are obtained.

The resins obtained according to IA and 1B each become Solutions made in Itnylacetat. The aging stability the solution is determined by measuring the increase in viscosity determined by time.

solution from aging Aging after 21 months viscosity
cP bed 25 ⁰ C to
took colour No. # Viscosity
NCO eP at 25 ⁰ C temperature 2550
1170 373 %
283 Ji Gardner
number 1A
1B 11.36 684
11.75 415. 20 ⁰ C
20 ⁰ C 5
3.

A 60 # solution in ethyl acetate of a resin prepared according to 1 A but using 3.12 parts by weight of a mixture of dimethyl sulfate and methyl p-toluenesulfonate shows a viscosity 8 increase from 574 cF to 2260 ^{after storage for 21 months at 25 ° C} cP. The color of the solution corresponds to the Gardner color number 5. The 293% increase in viscosity shows that even an increased addition of the known catalyst poison does not lead to satisfactory results. From this it follows that the heaktiona abort by

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Addition of sulfur to aging-stable and less colored ones Products.

Example_3

336 g of hexamethylene diisocyanate are mixed with 1.2 g of tri-n-butylphosphine and the mixture is ^{stirred at 50 to 60 °} C. for about eight hours. The NCO content is then dropped from 49.5 to 35 to # 36i ". The reaction is stopped by addition of 0.2 g of sulfur and distilling the low-viscosity reaction product twice through a thin film evaporator (vacuum 0.3 Torr, Umlauftemperatar desHkLzmediums 160 to 170 ⁰ C). 161 g of distillate and 170 g of polymer with an NCO content of 21.1% and a free hexamethylene diisocyanate content of less than 1 % are obtained. The viscous yellowish Hissigkelt shows absorption in the IR spectrum at 2.75 - 3.4 - 4.4 - 5.68 - 5.9 - 6.85 7.45 - 9.2 - 11.6 - 12.75 and 13.05 Ai * The band at 4.6 u, which is characteristic of the carbodiimides, is completely absent. Molecular weight 500 to 510.

3 g of tri-n-butylphosphine are added to a solution of 500 g of 2,4-tolylene diisocyanate in 500 g of butyl acetate with thorough stirring. The temperature rises to 50 to 60 ⁰ C. The mixture is stirred at this temperature for 30 to 40 hours and reaches a NC0-Gehal1; from 9.0 to 9.5 5 ^. The reaction is ended by adding 0.5 g of sulfur at 50 to 60 ^{° C.} Any small amounts of unreacted sulfur by filtration of the ReaktionGgemisches example via a ¹ ^ pressure filter to be removed after cooling.

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Claims (7)

Claims: '■ Statute of limitations for the production of polymeric isocyanates by polymerizing an organic isocyanate or polyisocyanate in the presence of a phosphine as a catalyst and Termination of the polymerization reaction by subsequent addition of a catalyst poison, characterized in that sulfur is used as the catalyst poison. 2. The method according to claim 1, characterized in that an aromatic isocyanate or polyisocyanate is used as the organic isocyanate or polyisocyanate. 3. The method according to claim 1, characterized in that that the organic isocyanate or polyisocyanate is an aliphatic Isocyanate or polyisocyanate is used. 4. The method according to claim 1, characterized in that that the organic isocyanate or polyisocyanate is a mixture of aromatic and aliphatic isocyanates or polyisocyanates is used. 5. The method according to claim 1 and 2, characterized in that the organic isocyanate or polyisocyanate used is 2,4-biisocyanatotoluene or a mixture of 2,4-diisocyanatotoluene with 2,6-diisocyanatotoluene. 6. The method according to claim 1 and 3, characterized in that that as an organic isocyanate or polyisocyanate hexamethylene diisocyanate is used. Mon 1092 - 9 - 009825/1933 7. The method according to claim 1 and 4t, characterized in that the organic isocyanate or polyisocyanate
2,4-diisocyanatotoluene or a mixture of 2,4-diisocyanatotoluene with 2,6-diisocyanatotoluene in a mixture with hexamethylene diisocyanate is used. Mon 1092-10 - 009825/1933