Trimerization catalyst

Abstract

The invention relates to a trimerization catalyst. The subject matter of the invention is ammonium salts of formula (I) wherein R =-H,-CH3,-CH2CH3; n = 1, 2, 3, 4 or 5; m is equal to 2 or 3; r ', R' ', R' ''=-CH3,-CH2CH3, RIV =-H,-CH3,-CH2CH3 and X = monovalent counterion # imgabs0 #

Description

Field of the Invention

[0001] The present invention relates to novel ammonium salts which can be used as catalysts, in particular for reactions with compounds containing isocyanate groups. The present invention further relates to a process for their preparation and to their use. Background of the Invention

[0002] The reactions of compounds containing isocyanate groups are of great significance for industrial chemistry. In particular, the trimerization of isocyanates to isocyanurates and the reaction of isocyanates with compounds containing hydroxyl groups to give compounds containing urethane groups are of great industrial significance, since the corresponding products are used in many fields of application.

[0003] Polyisocyanurates are valuable starting materials for the preparation of high-quality coatings having good mechanical properties and good light and weather resistance. Polyisocyanurates based on isophorone diisocyanate (IPDI) are also used as starting materials for PUR-based elastomer applications.

[0004] 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. Catalysts which may be considered 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), carbosilane-containing compounds (US 4,697,014) and quaternary ammonium salts (US 4,503,226).

[0005] Particularly suitable for the trimerization of isocyanates to isocyanurates further include quaternary hydroxyalkylammonium salts.

[0006] For example, DE 26 31 733 A1 discloses the use of quaternary hydroxyalkylammonium salts having β-hydroxyalkyl groups for the trimerization and urethane synthesis.

[0007] DE 29 16 201 A1 also teaches that quaternary N-(hydroxyalkyl)ammonium salts can be used for the trimerization of isocyanates to isocyanurates.

[0008] EP 1 454 933 A1 teaches that the trimerization can be carried out using quaternary β-hydroxylated ammonium salts, the quaternary nitrogen atom of which bears three groups X which together form a tricyclic ring. The tricyclic ring is formed by another common nitrogen atom which can be hydroxyalkylated (and is then also in the quaternary nitrogen form accordingly).

[0009] Finally, DE 41 15 402 A1 discloses in an embodiment the preparation of N-(hydroxyalkyl)ammonium salts which can be used for isocyanurate trimerization. In particular, in each case one equivalent of N,N,N'-trimethyl-N'-(β-hydroxyethyl)-ethylenediamine is always reacted with two equivalents of a monocarboxylic acid, and then an excess of a monocyclic epoxide is added such that the resulting ammonium salt contains two quaternary nitrogen atoms.

[0010] Although the ammonium salts disclosed in the prior art have solved many problems of the prior art, for example, isocyanurates which can be made therefrom are storage-stable, have a low color, and have a low odor. However, the disadvantage is that the known catalysts are still insufficient in activity. SUMMARY OF THE INVENTION

[0011] Accordingly, it is an object of the present invention to provide a catalyst which, similar to the known ammonium salts, enables the preparation of isocyanurates which are storage-stable, have a low color, and have a low odor, but which also has the advantage of higher activity.

[0012] This object is achieved by an ammonium salt according to the invention having the following formula (I)

[0013]

[0014] wherein

[0015] R = -H, -CH3, -CH2CH3

[0016] n = 1, 2, 3, 4, 5,

[0017] m = 2, 3,

[0018] R', R'', R''' = -CH3, -CH2CH3

[0019] R IV = H, -CH3, -CH2CH3

[0020] and X = a monovalent counterion.

[0021] Herein, the groups R can be independently selected from -H, -CH3, -CH2CH3.

[0022] The ammonium salts according to the invention are ammonium salts which can be prepared by reacting a diamine in which one of the tertiary amino groups is substituted by 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 diamine, it is surprising that only the amino groups without the hydroxyalkyl group -(CR2) m -OH react with the alkylene oxide. The corresponding salts having ammonium and tertiary amino groups in the cation are surprisingly more active than the diammonium salts.

[0023] Preferred catalyst performance is obtained when the ammonium salt is derived from an acid HX selected from carboxylic acids. More preferably, the carboxylic acid is selected from aliphatic and heterocyclic carboxylic acids. Even more preferably, the carboxylic acid is an aliphatic carboxylic acid. Even more preferably, the carboxylic acid is an alkanoic or alkenoic acid. Particularly preferred carboxylic acids may be selected from alkanoic acids having the formula R V COOH, where R V =C r H 2r+1 , where r = 1 - 9. The corresponding ammonium salt has the formula (II):

[0024]

[0025] In formulas (I) and (II), the groups R are independently selected from -H, -CH3, and -CH2CH3. Preferably, the Rs are independently selected from -H and -CH3. Even more preferably, the Rs are independently selected from -H and -CH3, provided that each carbon atom bears at most one group R which is a -CH3 group. Even more preferably, all R = -H.

[0026] In formulas (I) and (II), the exponent n is a number selected from 1, 2, 3, 4, and 5. Preferably, n is a number selected from 2, 3, and 4. Even more preferably, n = 2 or 3. Very particularly preferably, n = 2.

[0027] In formulas (I) and (II), the exponent m is a number selected from 2 and 3. Even more preferably, m = 2.

[0028] The groups R', R'', and R''' may be independently selected from -CH3 and -CH2CH3. Preferably, each R', R'', and R''' = -CH3.

[0029] The group R in formulas (I) and (II) derived from the alkylene oxide used to prepare the ammonium salt IV is selected from -H, -CH3, and -CH2CH3. Thus, the group R IV is derived from an alkylene oxide selected from ethylene oxide, propylene oxide, and α-butylene oxide. Preferably, the group R IV is selected from -CH3 and -CH2CH3. Due to the combination of relatively low toxicity and simple handling (especially due to the relatively high boiling point) of α-butylene oxide required for the corresponding synthesis, very particularly preferably R IV is -CH2CH3.

[0030] The subject of the present invention is also a method for preparing the ammonium salt of formula (II) according to the present invention, wherein a di-secondary amine in which one of the tertiary amino groups is substituted by a hydroxyalkyl group is reacted with an alkylene oxide and an acid HX, preferably an alkanoic acid, particularly an alkanoic acid having the formula R V COOH, where R V=C r H 2r+1 , where r = 1 - 9.

[0031] Preferably, the alkylene oxide is used in a molar ratio of 0.9 - 1.1, more preferably 0.95 - 1.05, still more preferably 0.98 - 1.02, and the acid is used in a molar ratio of 0.9 - 1.1, more preferably 0.95–1.05, still more preferably 0.98 - 1.02, in each case based on the molar amount of the diamine.

[0032] The diamine preferably has the following formula (III)

[0033]

[0034] where

[0035] R = -H, -CH3, -CH2CH3

[0036] n = 1, 2, 3, 4, 5,

[0037] m = 2, 3, and

[0038] R', R”, R”' = -CH3, -CH2CH3.

[0039] The groups R are independently selected from -H, -CH3, and -CH2CH3. Preferably, the Rs are independently selected from -H and -CH3. Still more preferably, the Rs are independently selected from -H and -CH3, provided that each carbon atom bears at most one group R which is a -CH3 group. Still more preferably, all R = -H.

[0040] The index n is a number selected from 1, 2, 3, 4, and 5. Preferably, n is a number selected from 2, 3, and 4. Still more preferably, n = 2 or 3. Very particularly preferably, n = 2.

[0041] The index m is a number selected from 2 and 3. Still more preferably, m = 2.

[0042] The groups R', R” and R”' can be independently selected from -CH3 and -CH2CH3. Preferably, each R', R” and R”' = -CH3.

[0043] Preferably, an acid HX selected from carboxylic acids is used. Still more preferably, the carboxylic acid is selected from aliphatic and heterocyclic carboxylic acids. More preferably, the carboxylic acid is an aliphatic carboxylic acid. More preferably, the carboxylic acid is an alkanoic acid or an alkenoic acid. Particularly preferred carboxylic acids can be selected from alkanoic acids. Particularly preferred alkanoic acids can be selected from alkanoic acids having the formula R V COOH, where R V =C r H 2r+1, where r = 1 - 9.

[0044] Even more preferably, the alkylene oxide is selected from ethylene oxide, propylene oxide and α - epoxybutane. The corresponding product conforms to formula (III). The alkylene oxide is more preferably selected from propylene oxide and α - epoxybutane. Due to the combination of relatively low toxicity and simple operation (especially due to the relatively high boiling point), it is very particularly preferred that the alkylene oxide is α - epoxybutane.

[0045] The process according to the invention is preferably carried out in such a way that the di-secondary amine is first mixed with the acid and then the alkylene oxide is added.

[0046] The process according to the invention can in principle be carried out in the presence or absence of a solvent. However, it is preferably carried out in the absence of a solvent. The preferred reaction temperature is from room temperature to 120 °C, more preferably from 40 °C to 80 °C. For example, the completeness of the reaction can be checked by gas chromatography. Once the alkylene oxide is no longer detectable, the reaction is terminated.

[0047] The subject of the invention is also the use of the ammonium salts according to the invention as catalysts. Preferably, the ammonium salts according to the invention are used as catalysts for the trimerization of isocyanates to isocyanurates or for the reaction of isocyanates with hydroxy - containing compounds to produce compounds containing urethane groups. The ammonium salts according to the invention are very particularly suitable as catalysts for the trimerization of isocyanates to isocyanurates. Detailed Description

[0048] Examples

[0049] Example A of the invention:

[0050] 146 parts of N,N,N'-trimethyl - N'-(2 - hydroxyethyl) - ethylenediamine (1 mole of diamine) were mixed with 116 parts (1 mole) of hexanoic acid, and then 72 parts (1 mole) of 1,2 - epoxybutane were added portionwise at 40 °C under reflux and stirring. After complete addition, stirring was continued at 40 °C for 96 hours, after which 1,2 - epoxybutane was no longer detectable in the GC. According to NMR, only the dimethylamine nitrogen reacted.

[0051] Example B not according to the invention (according to DE4115102)

[0052] 146 parts of N,N,N'-trimethyl - N'-(2 - hydroxyethyl) - ethylenediamine (1 mole of diamine) were mixed with 232 parts (2 moles) of hexanoic acid, and then 144 parts (2 moles) of 1,2 - epoxybutane were added portionwise at 40 °C under reflux and stirring. After complete addition, stirring was continued at 40 °C for 96 hours, after which 1,2 - epoxybutane was no longer detectable in the GC.

[0053] Trimerization

[0054] General procedure:

[0055] Heat 1500 g of isophorone diisocyanate (IPDI) to 70 °C, then add 3 g of catalyst and stir. Measure the exothermic duration, the maximum of the temperature curve and the final NCO value here.

[0056]

[0057] The resulting partial trimer is not only stable, colorless, but also has a low odor. The activity of the catalyst according to the invention having an ammonium and a tertiary amino group in the cationic part is significantly higher than that of the catalyst of the comparative example having two ammonium groups in the cationic part.

Claims

1. Ammonium salt of formula (I) in R=-H、-CH3、-CH2CH3 n＝1、2、3、4、5 m＝2、3， R', R", R"'=-CH3, -CH2CH3 R IV =-H、-CH3、-CH2CH3 and X = monovalent counter ion.

2. The ammonium salt according to claim 1, characterized in that It has the formula (II) Where R V =C r H 2r+1 And r=1–9.

3. The ammonium salt according to any one of the preceding claims, characterized in that R=-H.

4. The ammonium salt according to any one of the preceding claims, characterized in that n=2 or 3.

5. The ammonium salt according to any one of the preceding claims, characterized in that m＝2。 6. The ammonium salt according to any one of the preceding claims, characterized in that R'=R"=R"'=-CH3.

7. The ammonium salt according to any one of the preceding claims, characterized in that R IV =-CH2CH3。 8. A process for preparing an ammonium salt according to any one of the preceding claims, characterized in that A ditertiary amine in which one of the tertiary amino groups is substituted by a hydroxyalkyl group is reacted with an alkylene oxide and an acid HX.

9. The method according to claim 8, characterized in that The alkylene oxides are used in a molar ratio of 0.9 to 1.1, the acids in a molar ratio of 0.9 to 1.1, based in each case on the molar amount of the ditertiary amine.

10. The method according to any one of claims 8 or 9, characterized in that The ditertiary amine has the formula in R=-H、-CH3、-CH2CH3 n＝1、2、3、4、5， m = 2, 3, and R', R", R"'=-CH3, -CH2CH3.

11. The method according to claim 10, characterized in that The acid HX is an alkanoic acid selected from V COOH alkanoic acid, where R V =C r H 2r+1 , where r = 1-9.

12. The method according to claim 11, characterized in that The alkylene oxide is selected from ethylene oxide, propylene oxide and α-butylene oxide.

13. Use of the ammonium salt according to any one of claims 1 to 7 as a catalyst, in particular for the trimerization of isocyanates to isocyanurates or for the reaction of isocyanates with hydroxyl-containing compounds to give compounds containing urethane groups.

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