STORAGE-STABLE THERMOLATENT CATALYSTS FOR THE POLYMERIZATION OF ISOCYANATES

Abstract

The present invention relates to the use of metal salts of polymeric alcohols as storage-stable thermolatent catalysts for the manufacture of isocyanurate and polyisocyanate polymers.

Claims

1. Use of a metal salt of a polymeric alcohol as a catalyst for the polymerization of polyisocyanates.

2. The use according to claim 1, wherein the polymeric alcohol has a number average molecular weight between 400 g/mol and 22,000 g/mol.

3. The use according to claim 1, wherein the polymeric alcohol has a melting point between 25° C. and 160° C.

4. The use according to claim 1, wherein the polymeric alcohol is an alcohol selected from the group consisting of polyether alcohols, polyester alcohols and polycarbonate alcohols.

5. The use according to claim 1, wherein the metal ion has an oxidation state IV or less.

6. The use according to claim 1, wherein crosslinking of polyisocyanates results in at least one functional group selected from the group consisting of isocyanurate, uretdione, iminooxadiazinedione and oxadiazinetrione groups.

7. The use according to claim 1, wherein the polyisocyanates are selected from the group consisting of aliphatic, cycloaliphatic and aromatic polyisocyanates.

8. The use according to claim 1, wherein at least 50% of the isocyanate groups consumed during the polymerization of isocyanates form isocyanurate structures.

9. The use according to claim 1, wherein less than 30% of the total nitrogen content of the thermoset material is bound in urethane, thiourethane, urea, allophanate and thioallophanate groups.

10. A method for producing a thermoset polymer comprising the steps of a) providing a polymerizable composition comprising at least one polyisocyanate and at least one metal salt of a polymeric alcohol, wherein said reaction mixture is characterized by comprises a molar ratio of isocyanate groups to functional groups reactive with isocyanate in the composition is at least 2:1 b) storing said reaction mixture for at least 4 hours at a temperature between 4° C. and 50° C. without an increase of viscosity of more than 100%; and c) elevating the temperature to a temperature between 60° C. and 300° C. and maintaining said temperature until at least 80% of the free isocyanate groups originally present at the beginning of method step c) are consumed.

11. The method according to claim 10, wherein the polymeric alcohol is an alcohol selected from the group consisting of polyether alcohols, polyester alcohols, polycarbonate alcohols.

12. The method according to claim 10, wherein at least 50% of the isocyanate groups consumed during method step c) form isocyanurate groups.

13. A polymerizable composition comprising at least one metal salt of a polymeric alcohol and at least one polyisocyanate, wherein the molar ratio of isocyanate groups to functional groups reactive with isocyanate in the composition is at least 2:1.

Description

EXAMPLES

Materials and Methods

[0058] Poly(ethylene glycol)s (M.sub.n 0.4, 1, 4 and 10 kg/mol), magnesium di-tert-butoxide, aluminium tri-tert-butoxide, tin(IV) tert-butoxide and tert-butanol were purchased from Sigma-Aldrich. Potassium tert-butoxide was purchased from abcr GmbH. Poly(□-caprolactone) (M.sub.n 4 and 8 kg/mol) was kindly supplied by Perstorp Chemicals GmbH. Desmodur® N 3600, Desmodur® Z 4470 SN, Desmodur® IL BA, Desmodur® XP 2617 and Desmodur® VPLS 2397 were supplied by Covestro Deutschland AG. All chemicals were used as received.

[0059] Differential scanning calorimetry (DSC) measurements were performed under nitrogen on ca. 10 mg samples on a Perkin-Elmer Calorimeter DSC-7 in 3 heating runs from 20 to 200° C. with a heating rate of 20 K/min. and a cooling rate of 320 K/min. FTIR-spectra were recorded on a Bruker FTIR Spectrometer Tensor II with Platinum-ATR-unit with diamond crystal. Viscosities were measured on an Anton-Paar MCR51 Rheometer using a 50 mm cone-plate setup (CP-50) at 23° C. under a shear rate cycle increasing from 0.1 Hz to 1000 Hz and back. In the case of non-Newtonian behavior, the leveled-out viscosity at high shear rate (which at 100 Hz was reached for all cases), was selected.

1. Preparation of Tert-Butoxide (Base) Stock-Solutions in Tert-Butanol

[0060] 1a. Under dry conditions, weighed 2.21 g of anhydrous potassium tert-butoxide (19.7 mmol) into 50 mL Schlenck-flask and added 22.4 g dry tert-butanol. Under continuous stirring, the powder was dissolved (under slight yellowing of the solution). The final concentration of potassium tert-butoxide was then calculated as 2.21 g/(22.4 g+2.21 g)*100%)=8.98 wt %, corresponding to 0.80 mmol tert-butoxide g.sup.−1).

[0061] 1b. In analogy to Example 1a, except that 0.40 g of magnesium di-tert-butoxide was dissolved in 5.45 g tert-butanol (6.8 wt %; 0.80 mmol tert-butoxide g.sup.−1).

[0062] 1c. In analogy to Example 1a, except that 0.45 g of aluminium tri-tert-butoxide was dissolved in 6.37 g tert-butanol (6.6 wt %; 0.80 mmol tert-butoxide g.sup.−1).

[0063] 1d. In analogy to Example 1a, except that 0.70 g of tin(IV) tert-butoxide was added to 7.95 g tert-butanol (8.1 wt %; 0.79 mmol tert-butoxide g.sup.−1).

2. Deprotonation of Polymeric Alcohols

[0064] 2a. Under dry conditions, 2.0 g of poly(ethylene glycol) with a number average molecular weight (M.sub.n) of 4000 g mol.sup.−1 (corresponding to a total of 1 mmol of OH groups) as the polymeric alcohol and 7.0 g of tert-butanol were added to a 20 mL glass bottle and heated to 90° C. until a homogeneous solution was formed. Next, 1.0 g of potassium tert-butoxide solution from example 1a (corresponding to a total of 0.8 mmol of tert-butoxide) was added at 90° C. as the base, resulting in a homogeneous pale yellow solution. Next, the solution was allowed to cool to room temperature under continuous stirring, under the formation of an opaque thick suspension of fine white powder dispersed in yellow liquid.

[0065] 2b. In analogy to Example 2a, except that poly(ethylene glycol) with M.sub.n of 400 g mol.sup.−1 was used as the polymeric alcohol and the mixture remained a homogeneous liquid solution upon cooling to room temperature.

[0066] 2c. In analogy to Example 2a, except that poly(ethylene glycol) with M.sub.n of 1000 g mol.sup.−1 was used as the polymeric alcohol and the mixture remained a homogeneous liquid solution upon cooling to room temperature.

[0067] 2d. In analogy to Example 2a, except that poly(ethylene glycol) with M.sub.n of 10000 g mol.sup.−1 was used as the polymeric alcohol.

[0068] 2e. In analogy to Example 2a, except that poly(propylene glycol) with M.sub.n of 1000 g mol.sup.−1 was used as the polymeric alcohol and the mixture remained a homogeneous liquid solution upon cooling to room temperature.

[0069] 2f. In analogy to Example 2a, except that poly(propylene glycol) with M.sub.n of 2000 g mol.sup.−1 was used as the polymeric alcohol and the mixture remained a homogeneous liquid solution upon cooling to room temperature.

[0070] 2g. In analogy to Example 2a, except that poly(propylene glycol) with M.sub.n of 4000 g mol.sup.−1 was used as the polymeric alcohol and the mixture remained a homogeneous liquid solution upon cooling to room temperature.

[0071] 2h. In analogy to Example 2a, except that polytetrahydrofuran with M.sub.n of 650 g mol.sup.−1 was used as the polymeric alcohol.

[0072] 2i. In analogy to Example 2a, except that polytetrahydrofuran with M.sub.n of 1000 g mol.sup.−1 was used as the polymeric alcohol.

[0073] 2j. In analogy to Example 2a, except that polytetrahydrofuran with M.sub.n of 2000 g mol.sup.−1 was used as the polymeric alcohol.

[0074] 2k. In analogy to Example 2a, except that polycaprolactone with M.sub.n of 4000 g mol.sup.−1 was used as the polymeric alcohol.

[0075] 2l. In analogy to Example 2a, except that polycaprolactone with M.sub.n of 8000 g mol.sup.−1 was used as the polymeric alcohol.

[0076] 2m. In analogy to Example 2a, except that the magnesium tert-butoxide solution of example 1b was used as the base.

[0077] 2n. In analogy to Example 2a, except that the aluminium(III) tert-butoxide solution of example 1c was used as the base.

[0078] 2o. In analogy to Example 2a, except that the tin(IV) tert-butoxide solution of example 1d was used as the base.

3. Polymerization Reactions of Polyisocyanates Using Thermolatent Polymeric Alkoxide Catalyst Systems

[0079] 3a. 10.0 g of Desmodur® N3600 was weighed into a dried 20 mL glass bottle as the polyisocyanate, after which 0.35 g of the reaction mixture from example 2a was added as the polymeric alkoxide catalyst system. The mixture was then shaken vigorously by hand until a macroscopically homogeneous mixture was formed. No apparent heat formation or gelation was observed during mixing.

[0080] Next, 5 g of the reaction mixture was casted into an aluminium tin can lid, while another 5 g of the reaction mixture was transferred into a 20 mL glass bottle which was then sealed under a dry nitrogen atmosphere. The sample in the aluminium lid (denoted Sample A) was subsequently kept at 220° C. for 5 minutes while the sample in the glass bottle (denoted Sample B) was kept at room temperature for 24h. After these reaction times, Sample A was collected as a partially blistered solid transparent yellow film while Sample B remained liquid throughout the reaction time. Sample A was analyzed using Attenuated Total Reflection Fourier-Transformed Infrared Spectroscopy (ATR-FTIR). Sample B was analyzed visually by inverting the bottle and confirming a free flow of the mixture.

[0081] 3b. In analogy to example 3a, except that the reaction mixture of example 2b was used as the polymeric alkoxide catalyst system.

[0082] 3c. In analogy to example 3a, except that the reaction mixture of example 2c was used as the polymeric alkoxide catalyst system.

[0083] 3d. In analogy to example 3a, except that the reaction mixture of example 2d was used as the polymeric alkoxide catalyst system.

[0084] 3e. In analogy to example 3a, except that the reaction mixture of example 2e was used as the polymeric alkoxide catalyst system.

[0085] 3f. In analogy to example 3a, except that the reaction mixture of example 2f was used as the polymeric alkoxide catalyst system.

[0086] 3g. In analogy to example 3a, except that the reaction mixture of example 2g was used as the polymeric alkoxide catalyst system.

[0087] 3h. In analogy to example 3a, except that the reaction mixture of example 2h was used as the polymeric alkoxide catalyst system.

[0088] 3i. In analogy to example 3a, except that the reaction mixture of example 2i was used as the polymeric alkoxide catalyst system.

[0089] 3j. In analogy to example 3a, except that the reaction mixture of example 2j was used as the polymeric alkoxide catalyst system.

[0090] 3k. In analogy to example 3a, except that the reaction mixture of example 2k was used as the polymeric alkoxide catalyst system.

[0091] 3l. In analogy to example 3a, except that the reaction mixture of example 2l was used as the polymeric alkoxide catalyst system.

[0092] 3m. In analogy to example 3a, except that the reaction mixture of example 2m was used as the polymeric alkoxide catalyst system.

[0093] 3n. In analogy to example 3a, except that the reaction mixture of example 2n was used as the polymeric alkoxide catalyst system.

[0094] 3o. In analogy to example 3a, except that the reaction mixture of example 2o was used as the polymeric alkoxide catalyst system.

[0095] 3p. In analogy to example 3a, except that Desmodur® Z 4470 SN was used as the polyisocyanate.

[0096] 3q. In analogy to example 3a, except that Desmodur® IL BA was used as the polyisocyanate.

[0097] 3r. In analogy to example 3a, except that Desmodur® XP 2617 was used as the polyisocyanate.

[0098] 3s. In analogy to example 3a, except that Desmodur® VPLS 2397 was used as the polyisocyanate.

4. Quantification of the Reactivity of a Polyisocyanate Mixture Containing a Thermolatent Polymeric Alkoxide Catalyst System

[0099] In analogy to example 3a, a mixture was prepared using Desmodur® N 3600 as the polyisocyanate and the reaction mixture of example 2a as the thermolatent polymeric alkoxide catalyst system. The reactivity of the reaction mixture was then measured using Differential Scanning Calorimetry (DSC).

5. Quantification and Monitoring Over Time of the Viscosity of a Polyisocyanate Mixture Containing a Thermolatent Polymeric Alkoxide Catalyst System

[0100] In analogy to example 3a, a mixture was prepared using Desmodur® N 3600 as the polyisocyanate and the reaction mixture of example 2a as the thermolatent polymeric alkoxide catalyst system. The viscosities of the neat Desmodur® N 3600 and of the reaction mixture at the specified times after the addition of the polymeric alkoxide catalyst system were measured on an Anton-Paar MCR51 Rheometer using a 25 mm cone-plate setup. The results are collected in Table 1.

TABLE-US-00001 TABLE 1 Viscosities of Polyisocyanate mixtures. Mixture Viscosity at a shear rate of 100 Hz Desmodur ® N 3600 (neat) 1430 mPa .Math. s Reaction Mixture, day 0 1170 mPa .Math. s Reaction Mixture, day 7 1270 mPa .Math. s

5. Overview (Table) of Experimental Results

[0101]

TABLE-US-00002 TABLE 2 Overview of experimental results. time.sub.liquid shows the time the reaction mixture remained liquid at room temperature. T.sub.reaction and time.sub.reaction show the curing reaction temperature and time, respectively. Poly- Exp. isocyanate time.sub.liquid T.sub.reaction time.sub.reaction Reaction Nr. (Desmodur) Alkoxide Cation [days] [° C.] [min] product 3a N3600 PEG-4k K.sup.+ >7 220 5 Solid; w/slight yellowing 3b N3600 PEG-0.4k K.sup.+ >7 220 5 Solid 3c N3600 PEG-1k K.sup.+ <7 220 5 Solid 3d N3600 PEG-10k K.sup.+ >7 220 5 Solid 3e N3600 PPG-1k K.sup.+ >7 220 5 Solid 3f N3600 PPG-2k K.sup.+ >7 220 5 Solid 3g N3600 PPG-4k K.sup.+ >7 220 5 Solid 3h N3600 PTHF-0.65k K.sup.+ >7 220 5 Solid 3i N3600 PTHF-1k K.sup.+ >7 220 5 Solid 3j N3600 PTHF-2k K.sup.+ >7 220 5 Solid 3k N3600 PCL-4k K.sup.+ >7 220 5 Solid 3l N3600 PCL-8k K.sup.+ >7 nd nd nd 3m N3600 PEG-4k Mg.sup.2+ >7 nd nd nd 3n N3600 PEG-4k Al.sup.3+ >7 nd nd nd 3o N3600 PEG-4k Sn.sup.4+ >7 nd nd nd 3p Z 4470 SN PEG-4k K.sup.+ >7 nd nd nd 3q IL BA PEG-4k K.sup.+ >7 nd nd nd 3r XP 2617 PEG-4k K.sup.+ >7 nd nd nd 3s VPLS 2397 PEG-4k K.sup.+ >7 nd nd nd Ref. 1 N3600 MeO.sup.− K.sup.+ nd nd nd nd Ref. 2 N3600 tBuO.sup.− K.sup.+ nd nd nd nd nd: not determined