Patent Application
20250197361
The present invention relates to novel ammonium salts employable as catalysts, especially as catalysts for reactions with isocyanate-containing compounds. The present invention further relates to a process for their production and to the use thereof.
Reactions of isocyanate-containing compounds are of great interest for industrial chemistry. Especially the trimerization of isocyanates to isocyanurates and the conversion of isocyanates and hydroxy-containing compounds to urethane-containing compounds are of great industrial importance, since the corresponding products are used in many fields of application.
Polyisocyanurates are valuable input materials for the production of high-quality coatings with good mechanical properties and good resistance to light and weathering. Polyisocyanurates based on isophorone diisocyanate (IPDI) are also used as raw materials for PUR-based elastomer applications.
Polyisocyanurates are in principle obtained by catalytic trimerization of suitable isocyanates. Trimerizable isocyanates include for example aromatic, cycloaliphatic and aliphatic difunctional and higher-functional polyisocyanates. Contemplated catalysts include for example tertiary amines (DE 24 52 532 A1), complexes of basic alkali metal compounds and acyclic organic compounds (EP 0 056 159 A1), aminosilyl-containing compounds (U.S. Pat. No. 4,697,014) and quaternary ammonium salts (U.S. Pat. No. 4,503,226).
Catalysts particularly suitable for trimerization of isocyanates to isocyanurates further include quaternary hydroxyalkylammonium salts.
DE 26 31 733 A1 for example discloses the catalysis of trimerizations and urethane syntheses with quaternary hydroxyalkylammonium salts having a beta-hydroxyalkyl group.
DE 29 16 201 A1 also teaches that quaternary N-(hydroxyalkyl) ammonium salts can be used for trimerization of isocyanates to isocyanurates.
EP 1 454 933 A1 teaches that trimerization can employ quaternary beta-hydroxylated ammonium salts whose quaternary nitrogen atom bears three radicals X which together form a tricyclic ring. The tricyclic ring is formed via a further common nitrogen atom which may be hydroxyalkylated (and is then accordingly also in quaternary form).
Finally, DE 41 15 402 A1 discloses in the examples the production of N-(hydroxyalkyl) ammonium salts which may be used for trimerization of isocyanurates. It is always the case, inter alia, that one equivalent of N, N,N′-trimethyl-N′-(β-hydroxyethyl)-ethylenediamine is reacted with two equivalents of monocarboxylic acid before an excess of a monoepoxide is added, such that the resulting ammonium salt comprises two quaternary nitrogen atoms.
The ammonium salts disclosed in the prior art already solve many of the problems of the prior art, for example that the isocyanurates producible with them are storage-stable, low-colour and low-odour. However, the disadvantage is that the known catalysts are not yet sufficiently active.
The problem addressed by the present invention is accordingly that of providing catalysts which, similarly to the known ammonium salts, make it possible to produce storage-stable, low-colour and low-odour isocyanurates but which have the advantage of greater activity.
This problem is solved by the ammonium salt according to the invention having the following formula (I)
The radicals R may independently of one another be selected from the group consisting of —H, —CH3, —CH2CH3.
The ammonium salts according to the invention are ammonium salts producible by reaction of a ditertiary amine, where one of the tertiary amino groups is substituted with a hydroxyalkyl group, with an alkylene oxide and an acid HX. If the alkylene oxide and the acid are not present in a molar excess based on the total amount of the ditertiary amine, surprisingly only the amino group without the hydroxyalkyl group —(CR2)m—OH reacts with the alkylene oxide. Corresponding salts having an ammonium and a tertiary amino group in the cation are surprisingly more active than diammonium salts.
Preferred catalyst properties result when the ammonium salts are derived from acids HX selected from the group of carboxylic acids. It is further preferable when the carboxylic acids are selected from the group of aliphatic and heterocyclic carboxylic acids. It is yet more preferable when the carboxylic acid is an aliphatic carboxylic acid. It is yet more preferable when the carboxylic acid is an alkanoic acid or alkenoic acid. Particularly preferred carboxylic acids may be selected from the group of alkanoic acids having the formula RVCOOH where RV=CrH2r+1 where r=1-9. Corresponding ammonium salts have the formula (II):
In the formulae (I) and (II) the radicals R are independently of one another selected from the group consisting of —H, —CH3 and —CH2CH3. It is preferable when R is independently at each occurrence selected from the group consisting of —H and —CH3. It is more preferable when R is independently at each occurrence selected from the group consisting of —H and —CH3 with the proviso that each carbon atom bears at most one radical R that is a —CH3 radical. It is yet more preferable when all R=—H.
In formulae (I) and (II) the index n is a number selected from 1, 2, 3, 4 and 5. It is preferable when n is a number selected from 2, 3 and 4. It is it yet more preferable when n=2 or 3. It is very particularly preferable when n=2.
In formulae (I) and (II) the index m is a number selected from 2 and 3. It is yet more preferable when m=2.
The radicals R′, R″ and R″ may independently of one another be selected from the group consisting of —CH3 and —CH2CH3. It is preferable when each of the radicals R′, R″ and R′″=—CH3.
The radical RIV in formulae (I) and (II), which is derived from the alkylene oxide used to produce the ammonium salt, is selected from the group consisting of —H, —CH3 and —CH2CH3. Accordingly the radical RIV is derived from an alkylene oxide selected from ethylene oxide, propylene oxide and α-butylene oxide. It is preferable when the radical RIV is selected from the group consisting of —CH3 and —CH2CH3. Due to the combination of comparatively low toxicity and simple handling (above all due to the relatively high boiling point) of the α-butylene oxide necessary for the corresponding synthesis, it is very particularly preferable when RIV is —CH2CH3.
The present invention further relates to a process for producing the ammonium salts of formula (II) according to the invention in which a ditertiary amine, where one of the tertiary amino groups is substituted with a hydroxyalkyl group, is reacted with an alkylene oxide and an acid HX, preferably an alkanoic acid, in particular an alkanoic acid having the formula RVCOOH where RV=CrH2r+1 where r=1-9.
The alkylene oxide is preferably employed in a molar ratio of 0.9-1.1, more preferably 0.95-1.05, yet more preferably 0.98-1.02, and the acid in a molar ratio of 0.9-1.1, more preferably 0.95-1.05, yet more preferably 0.98-1.02, in each case based on the molar amount of the ditertiary amine.
The ditertiary amine preferably has the following formula (III)
The radical R is independently at each occurrence selected from the group consisting of —H, —CH3 and —CH2CH3. It is preferable when R is independently at each occurrence selected from the group consisting of —H and —CH3. It is more preferable when R is independently at each occurrence selected from the group consisting of —H and —CH3 with the proviso that each carbon atom bears at most one radical R that is a —CH3 radical. It is yet more preferable when all R=—H.
The index n is a number selected from 1, 2, 3, 4 and 5. It is preferable when n is a number selected from 2, 3 and 4. It is it yet more preferable when n=2 or 3. It is very particularly preferable when n=2.
The index m is a number selected from 2 and 3. It is yet more preferable when m=2.
The radicals R′, R″ and R″ may independently of one another be selected from the group consisting of —CH3 and —CH2CH3. It is preferable when each of the radicals R′, R″ and R′″=—CH3.
It is preferable to employ acids HX selected from the group of carboxylic acids. It is further preferable when the carboxylic acids are selected from the group of aliphatic and heterocyclic carboxylic acids. It is yet more preferable when the carboxylic acid is an aliphatic carboxylic acid. It is yet more preferable when the carboxylic acid is an alkanoic acid or alkenoic acid. Particularly preferred carboxylic acids may be selected from the group of alkanoic acids. Particularly preferred alkanoic acids may be selected from the group of alkanoic acids having the formula RVCOOH where RV=CrH2r+1 where r=1-9.
The alkylene oxide is yet more preferably selected from ethylene oxide, propylene oxide and α-butylene oxide. Corresponding products conform to formula (III). The alkylene oxide is yet more preferably selected from propylene oxide and α-butylene oxide. Due to the combination of comparatively low toxicity and simple handling (above all due to the relatively high boiling point), it is very particularly preferable when the alkylene oxide is α-butylene oxide.
The process according to the invention is preferably performed in such a way that the ditertiary amine is first mixed with the acid and subsequently the alkylene oxide is added.
The process according to the invention may in principle be carried out in the presence or absence of a solvent. However, it is preferably performed in the absence of a solvent. Preferred reaction temperatures are between RT and 120° C., more preferably between 40° C. and 80° C. The reaction may be checked for completeness by gas chromatography for example. As soon as alkylene oxide is no longer detectable the reaction is terminated.
The present invention further provides for the use of the ammonium salts according to the invention as catalysts. Also preferred is the use of the ammonium salts according to the invention as catalysts for trimerization of isocyanates to isocyanurates or for conversion of isocyanates and hydroxy-containing compounds to urethane-containing compounds. The ammonium salts according to the invention are very particularly suitable as catalysts for trimerization of isocyanates to isocyanurates.
146 parts of N,N,N′-trimethyl-N′-(hydroxyethyl)-ethylenediamine (1 mol of diamine) are mixed with 116 parts (1 mol) of hexanoic acid and then admixed portionwise with 72 parts (1 mol) of 1,2-butylene oxide at 40° C. under reflux and stirring. After complete addition the mixture is stirred at 40° C. for a further 96 h after which 1,2-butylene oxide is no longer detectable in the GC. According to NMR only the dimethylamine nitrogen reacted.
146 parts of N,N,N′-trimethyl-N′-(hydroxyethyl)-ethylenediamine (1 mol of diamine) are mixed with 232 parts (2 mol) of hexanoic acid and then admixed portionwise with 144 parts (2 mol) of 1,2-butylene oxide at 40° C. under reflux and stirring. After complete addition the mixture is stirred at 40° C. for a further 96 h after which 1,2-butylene oxide is no longer detectable in the GC.
1500 g of isophorone diisocyanate (IPDI) are heated to 70° C. and only then mixed with 3 g of catalyst before stirring. The duration of exothermicity, the maximum of the temperature curve and the final NCO number are determined.
The resulting partial trimerizates are not only stable and colourless but also low-odour. The catalyst according to the invention having one ammonium and one tertiary amino group in the cationic proportion is markedly more active than the catalyst of the comparative example with two ammonium groups in the cationic proportion.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23216564.7 | Dec 2023 | EP | regional |
