METHOD FOR MODIFYING AT LEAST PENTAMETHYLENE DIISOCYANATE BY MEANS OF SPIROCYCLIC AMMONIUM SALTS AS CATALYST

Abstract

The invention relates to a method for modifying isocyanates, in which at least pentamethylene diisocyanate is oligomerized in the presence of at least one catalyst, the catalyst comprising at least one spirocyclic ammonium salt having a cation of formula I as catalyst for the isocyanate modification,

##STR00001##

the N-position substituents X and Y representing the same or different, substituted or unsubstituted C.sub.2-C.sub.20 alkylene chains optionally interrupted by heteroatoms (0, N, S) and by aromatic rings. The invention further relates to the modified isocyanates obtainable or obtained by means of the method and to the use of such a catalyst to oligomerize at least pentamethylene diisocyanate.

Claims

1: A method for modifying isocyanates, in which method at least pentamethylene diisocyanate is oligomerized in the presence of at least one catalyst, wherein the catalyst comprises at least one spirocyclic ammonium salt having a cation of the formula I as catalysts for the isocyanate modification, ##STR00007## where the nitrogen substituents X and Y are identical or different, substituted or unsubstituted C.sub.2-C.sub.20-alkylene chains optionally interrupted by heteroatoms (O, N, S) and aromatic rings.

2: The method as claimed in claim 1, characterized in that X and/or Y are each independently optionally substituted C.sub.4-C.sub.6-alkylene chains and are especially of linear structure.

3: The method as claimed in claim 1, characterized in that the anion of the spirocyclic ammonium salt is selected from hydroxide, alkanoate, carboxylate, heterocycles having at least one negatively charged nitrogen atom in the ring, especially azolate, imidazolate, triazolate or tetrazolate, fluoride, hydrogendifluoride and mixtures of these.

4: The method as claimed in claim 1, characterized in that the oligomerization is conducted in the presence of a solvent and/or additive.

5: The method as claimed in claim 1, characterized in that, in addition to pentamethylene diisocyanate, at least one monomeric organic isocyanate is also used selected from aliphatic diisocyanates, especially from hexamethylene diisocyanate (HDI), 2-methylpentane 1,5-diisocyanate, 2,4,4-trimethylhexane 1,6-diisocyanate, 2,2,4-trimethylhexane 1,6-diisocyanate, 4-isocyanatomethyloctane 1,8-diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate (IMCI), isophorone diisocyanate (IPDI), 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), 1,3- and 1,4-bis(isocyanatomethyl)cyclohexane (H6XDI) and mixtures of these.

6: The method as claimed in claim 1, characterized in that only pentamethylene diisocyanate is used as isocyanate for the oligomerization.

7: The method as claimed in claim 1, characterized in that the catalyst of the formula I is used in an amount of 0.001 to 5 mol %, based on the sum total of the molar amounts of the PDI used and of the aforementioned isocyanates to be optionally concomitantly used, and of the catalyst, preferably 0.002 to 2 mol % of catalyst.

8: The method as claimed in claim 1, characterized in that the method is conducted in the temperature range from 0 C. to +250 C., preferably 20 to 180 C., particularly preferably 40 to 150 C.

9: The method as claimed in claim 1, characterized in that the oligomerization is stopped after 5 to 50%, preferably 5 to 40%, particularly preferably 30 to 40%, of the total amount of isocyanate groups of the PDI used and of the isocyanates to be optionally concomitantly used have reacted.

10: The method as claimed in claim 9, characterized in that the oligomerization is stopped by deactivating the catalyst, especially by addition of an acid or an acid derivative such as benzoyl chloride, an acidic ester of phosphorus- or sulfur-containing acids, these acids themselves, adsorptive binding of the catalyst and subsequent removal by filtration or combinations thereof.

11: The method as claimed in claim 9, characterized in that unreacted monomeric organic isocyanate is separated from the reaction mixture.

12: A modified isocyanate preparable or prepared according to a method as claimed in claim 1.

13: The use of a spirocyclic ammonium salt having a cation of the formula I, ##STR00008## where the nitrogen substituents X and Y are identical or different, substituted or unsubstituted C.sub.2-C.sub.20-alkylene chains optionally interrupted by heteroatoms (O, N, S) and aromatic rings, as catalysts for the oligomerization of at least pentamethylene diisocyanate.

14: The use as claimed in claim 13, characterized in that only pentamethylene diisocyanate is used as isocyanate for the oligomerization.

Description

EXAMPLES

[0052] All percentages and ppm data, unless noted otherwise, are based on weight.

[0053] All reactions were carried out under a nitrogen atmosphere.

[0054] The NCO contents were determined by titrimetry according to DIN EN ISO 11909:2007-05.

[0055] The HC/AC contents were determined in accordance with ISO 15028:2014.

[0056] The dynamic viscosities were determined at 23 C. using the viscometer Physica MCR 51 from Anton Parr in accordance with DIN EN ISO 3219:1994-10. By measurements at different shear rates, it was ensured that the flow behaviour of the polyisocyanate mixtures described according to the invention and also that of the comparative products corresponds to that of ideal Newtonian fluids. The indication of the shear rate can therefore be omitted.

[0057] The residual monomer contents were determined by gas chromatography using an internal standard in accordance with DIN EN ISO 10283:2007-11.

[0058] Mol % figures were determined by NMR spectroscopy and always relate, unless specified otherwise, to the sum total of the NCO conversion products. The measurements were effected on the Bruker DRX 700 instrument on ca. 1% (.sup.1H NMR) or ca. 50% (.sup.13C NMR) samples in dry C.sub.6D.sub.6 at a measurement frequency of 700 MHz (.sup.1H NMR) or 176 MHz (.sup.13C NMR). The C.sub.6D.sub.5H present in the solvent was used as reference signal for the ppm scale: .sup.1H NMR chemical shift 7.15 ppm, .sup.13C NMR chemical shift 128.02 ppm. Data for the chemical shift of the compounds in question were taken from the literature (cf. D. Wendisch, H. Reiff and D. Dieterich, Die Angewandte Makromolekulare Chemie 141, 1986, 173-183 and literature cited therein and EP-A 896 009).

[0059] The diisocyanates used are products of Covestro Deutschland AG, D-51365 Leverkusen; all other commercially available chemicals were sourced from Aldrich, D-82018 Taufkirchen.

[0060] The preparation of a catalyst to be used according to the invention is described in Example 1.

[0061] 6-Chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride was obtained according to WO 2012/041789, Example 3.2 on page 83, line 20 to page 84, line 5. As a deviation from the method described therein, 6-chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride was obtained after repeated rectification under reduced pressure at ca. 99% (GC, area percent, not normalized) purity as a pale yellowish liquid (bp 66 C. at 0.3 mbar, identity proved by .sup.1H- and .sup.13C-NMR).

Example 1 Catalyst Preparation: 5-azoniaspiro[4.5]decanium Hydrogendifluoride

[0062] To a mixture pre-heated to 100 C. of 13.1 g (0.15 mol) of piperidine and 20 g (0.18 mol) of 50% aqueous potassium hydroxide solution were added dropwise 20 g (0.16 mol) of 1,4-dichlorobutane such that the internal temperature did not exceed 110 C. After addition was complete, the mixture was stirred for a further four hours at 100 C. and then cooled to room temperature.

[0063] To the resulting reaction mixture were added at room temperature with stirring 360 g of a ca. 5% methanolic potassium fluoride solution. The mixture was stirred for a further 8 hours at room temperature, filtered, largely freed of methanol under reduced pressure, taken up in ca. 200 g of 2-ethylhexanol, filtered again, 3 g of anhydrous hydrofluoric acid were added and the mixture was stirred for a further 2 hours at room temperature. The mixture was then heated to reflux under reduced pressure with batchwise distillate removal as long as gas chromatographically pure 2-ethylhexanol distilled off. The catalyst solution thus obtained (ca. 125 g, ca. 20% of 5-azoniaspiro[4.5]decanium hydrogendifluoride) was used in the following experiments.

Example 2 (Comparative Examples)

[0064] 1055 g of HDI were initially charged, and freed from dissolved gases by stirring for one hour under vacuum (<1 mbar), in a jacketed vessel with flat-ground joints which was maintained at a temperature of 60 C. by means of an external circulation and which was fitted with a stirrer, a reflux condenser connected to an inert gas unit (nitrogen/vacuum) and thermometer. After venting with nitrogen, the amount of catalyst specified in Table 1 was metered in in portions in such a way that the exothermicity of the reaction did not exceed 2-3 C. After the NCO content had fallen to

[0065] a) ca. 45+/0.5%

[0066] b) ca. 30+/1%

[0067] the catalyst was deactivated by adding to the catalyst an equimolar amount of dodecylbenzenesulfonic acid, 70% in 2-PrOH, stirring at reaction temperature for a further 30 min and then the mixture was worked-up.

[0068] The work-up was carried out by vacuum distillation in a thin-film evaporator of the flash evaporator (FE) type with a preevaporator (PE) connected upstream (distillation data: pressure: 0.1+/0.05 mbar, PE temperature: 120 C., ME temp.: 140 C.), with separation of unreacted monomer as distillate and the low-monomer polyisocyanate resin as bottom product (starting run). The polyisocyanate resin was separated, filtered and the distillate was collected in a second flange stirring apparatus of identical construction to the first, and made up to the starting amount (1055 g) with freshly degassed HDI. Thereafter, the mixture was treated again with catalyst and the procedure as described at the outset was followed. This procedure was repeated several times (experiments a1, a2, a3 . . . or b1, b2, b3 . . . etc.). The results can be found in Table 1.

TABLE-US-00001 TABLE 1 Resin Viscosity Color Example Catalyst amount [mPas/ number fr. HDI Iminooxadiazinediones no. sol. [g] [g] NCO [%] 23 C.] (APHA) [%] [mol-%].sup.1) 2a-1 0.72 169 23.7 688 66 0.11 54 2a-2 0.76 195 23.6 795 51 0.08 51 2a-3 0.70 178 23.7 652 40 0.07 55 2a-4 0.55 182 23.6 741 42 0.08 53 2a-5 0.54 177 23.9 710 45 0.05 54 2a-6 0.55 175 23.7 724 35 0.05 54 2b-1 1.35 633 19.4 13 200 60 0.08 32 2b-2 1.23 620 19.5 12 900 32 0.04 35 2b-3 1.31 640 19.3 13 400 47 0.05 34 2b-4 1.28 645 19.3 13 200 50 0.06 35 2b-5 1.30 642 19.3 13 250 44 0.06 33 2b-6 1.15 633 19.5 12 950 46 0.04 32 .sup.1)Iminooxadiazinedione group content relatively in total trimers (iminooxadiazinediones and isocyanurates, determined by NMR)

[0069] The resins obtained were, without exception, light-colored clear viscous liquids with no perceptible amine odor. The products produced with high conversion (Example Series 2b) have without exception a significantly lower content of iminooxadiazinedione groups than the products produced with lower conversion of Example Series 2a.

Example 3 (Inventive)

[0070] In an apparatus as described in Example 2, 1000 g of PDI were initially charged, of which the content of 6-chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride had been adjusted to 190 ppm by addition of the pure substance specified at the start, and treated analogously to the procedure described therein, with the difference that a molar amount of deactivator was metered in equivalent to the amount of catalyst used after the NCO content had fallen to [0071] a) ca. 50+/0.5% [0072] b) ca. 35+/1%.

[0073] The work-up and continuous recycling was carried out in a manner analogous to that described in Example 2 using the PDI quality described above. The results can be found in Table 2.

TABLE-US-00002 TABLE 2 Resin Viscosity Color Example Catalyst amount [mPas/ number fr. PDI Iminooxadiazinediones no. sol. [g] [g] NCO [%] 23 C.] (APHA) [%] [mol-%].sup.1) 3a-1 1.20 110 25.8 922 54 0.16 49 3a-2 0.95 115 25.7 890 35 0.11 51 3a-3 0.88 117 25.7 900 32 0.09 52 3a-4 0.85 120 25.6 910 30 0.07 53 3a-5 0.90 110 25.9 900 25 0.06 55 3a-6 0.85 115 25.7 890 28 0.07 55 3b-1 3.02 540 22.0 6900 52 0.04 47 3b-2 2.95 550 21.9 7140 42 0.03 48 3b-3 3.10 550 22.1 6950 39 0.05 48 3b-4 3.21 535 21.9 6830 40 0.04 45 36-5 3.15 560 22.0 6720 45 0.03 49 3b-6 3.10 525 22.2 7130 38 0.03 48 .sup.1)Iminooxadiazinedione group content relatively in total trimers (iminooxadiazinediones and isocyanurates, determined by NMR)

[0074] The resins obtained were, without exception, light-colored clear viscous liquids with no perceptible amine odor. The products produced with high conversion (Example Series 3b) have a virtually constant content of iminooxadiazinedione groups compared to the products produced with lower conversion of Example Series 3a.

Example 4 (Inventive)

[0075] This was conducted analogously to Example Series 3b with the difference that the reaction in experiments 4-1 to 4-4 was conducted at 80-85 C. and the latter two experiments at 100-105 C. and 1000 g of PDI was used, of which the content of 6-chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride had been adjusted to 540 ppm by addition of the pure substance specified at the start. The results can be found in Table 3.

TABLE-US-00003 TABLE 3 Resin Viscosity Color Example Catalyst amount [mPas/ number fr. PDI Iminooxadiazinediones no. sol. [g] [g] NCO [%] 23 C.] (APHA) [%] [mol-%].sup.1) 4-1 2.75 500 21.8 5200 75 0.12 38 4-2 1.65 550 21.3 5900 45 0.14 30 4-3 1.63 540 22.0 6200 48 0.13 29 4-4 1.63 550 21.7 7500 58 0.05 31 4-5 1.96 500 21.0 8000 72 0.06 16 4-6 2.00 550 21.4 6560 62 0.05 15 .sup.1)Iminooxadiazinedione group content relatively in total trimers (iminooxadiazinediones and isocyanurates, determined by NMR)

[0076] The resins obtained were, without exception, light-colored clear viscous liquids with no perceptible amine odor. The resins produced at higher reaction temperature (Examples 4-5 and 4-6), at only marginally worse color number, have an, as expected, lower content of iminooxadiazinedione groups than the products produced at lower reaction temperature (4-1 to 4-4).

Example 5 (Inventive)

[0077] This was conducted analogously to Example Series 4 with the difference that the reactions were conducted at 70-73 C., the catalyst was used as a ca. 1% solution in 2-ethylhexanol, 1000 g of PDI was used, of which the HC/AC content was below the limit of detection (<5 ppm) and in which no 6-chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride was detectable by gas chromatography and toluenesulfonic acid monohydrate, 50% dissolved in iPrOH, was used as deactivator.

[0078] The results can be found in Table 4.

TABLE-US-00004 TABLE 4 Resin Viscosity Color Example Catalyst amount [mPas/ number fr. PDI Iminooxadiazinediones no. sol. [g] [g] NCO [%] 23 C.] (APHA) [%] [mol-%].sup.1) 5-1 4.78 540 22.5 9340 55 0.07 20 5-2 4.86 530 21.7 9000 20 0.08 14 5-3 4.86 520 22.3 9630 54 0.05 19 5-4 4.39 550 21.7 9800 39 0.05 16 5-5 4.76 520 22.3 9400 44 0.14 16 5-6 4.80 520 22.0 9480 38 0.11 14 .sup.1)Iminooxadiazinedione group content relatively in total trimers (iminooxadiazinediones and isocyanurates, determined by NMR)

[0079] The resins obtained were, without exception, light-colored clear viscous liquids with no perceptible amine odor.

Example 6 (Inventive)

[0080] In an apparatus as described in Example 2, a mixture of 200 g of PDI, of which the content of 6-chloro-3,4-dihydropyridine-1(2H)-carbonyl chloride had been adjusted to 190 ppm by addition of the pure substance specified at the start, and 800 g of HDI were initially charged and treated analogously to the procedure described in Example 2, with the difference that a molar amount of deactivator was metered in equivalent to the amount of catalyst used after the NCO content had fallen to [0081] a) ca. 47.0+/0.5% [0082] b) ca. 33.0+/1%.

[0083] The work-up and continuous recycling was carried out in a manner analogous to that described in Example 2 using the PDI/HDI mixture described above.

[0084] The results can be found in Table 5.

TABLE-US-00005 TABLE 5 Example Catalyst sol. Resin Viscosity fr. PDI fr. HDI Iminooxadiazinediones no. [g] amount [g] NCO [%] [mPas/23 C.] [%] [%] [mol-%].sup.1) 6a-1 1.18 160 23.8 1100 0.03 0.04 43 6a-2 1.29 180 23.8 850 0.05 0.10 52 6a-3 1.49 180 23.7 770 0.09 0.10 52 6b-1 1.92 590 20.3 7700 0.05 0.06 50 6b-2 1.92 620 19.4 11 800 0.05 0.13 48 6b-3 2.01 610 20.2 11 200 0.09 0.04 47 .sup.1)Iminooxadiazinedione group content relatively in total trimers (iminooxadiazinediones and isocyanurates, determined by NMR)

[0085] The products produced in Example Series 6b with high conversion are light-colored, clear viscous liquids with APHA color numbers of 40 and without perceptible amine odor and also have a high content of iminooxadiazinedione groups compared to the products of Example Series 6a produced with lower conversion, which is not the case with the exclusive use of HDI (Comparative Examples 2b).

[0086] Measurement of the Storage Stability

[0087] All products of Examples 3 to 6 produced by the method according to the invention were stored at 50 C. in sealed aluminum containers and were tested with respect to their color development at regular intervals over a period of 6 months. In no case could a significant increase of the Hazen color number be observed and sometimes even a significant lightening of up to 30 APHA occurred.