PROCESS FOR PREPARING A POLYESTER USING A 4-MEMBERED RING LACTONE

Abstract

The invention provides a process for preparing polyesters by reacting an H-functional starter substance with a lactone in the presence of a Brønsted-acidic catalyst which comprises initially charging the H-functional starter substance and the Brønsted-acidic catalyst to form a mixture i) and subsequently adding the lactone to the mixture i), wherein the process is carried out without adding an aromatic solvent and wherein the H-functional starter substance is an OH-functional starter substance and/or a COOH-functional starter substance and wherein the lactone is a 4-membered ring lactone. The invention further provides polyesters obtainable by the method of the invention.

Claims

1. A process for preparing a polyester by reaction of an H-functional starter substance with a lactone in the presence of a Brønsted-acidic catalyst, comprising: i) initially charging the H-functional starter substance and the Brønsted-acidic catalyst to form a mixture i); and ii) adding the lactone to the mixture i); wherein the process is performed without the addition of an aromatic solvent; wherein the H-functional starter substance comprises an OH-functional starter substance and/or a COOH-functional starter substance; and wherein the lactone comprises a 4-membered-ring lactone.

2. The process as claimed in claim 1, wherein the 4-membered-ring lactone comprises propiolactone, β-butyrolactone, diketene, preferably propiolactone, β-butyrolactone, or a mixture thereof.

3. The process as claimed in claim 1, wherein the lactone is continuously added to the mixture i) in step ii).

4. The process as claimed in claim 1, wherein the lactone is added stepwise to the mixture i) in step ii).

5. The process as claimed in claim 1, wherein the H-functional starter substance comprises ethylene glycol, diethylene glycol, dipropylene glycol, butane-1,3-diol, butane-1,4-diol, 1,1,1-trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose, xylitol, propane-1,2-diol, propane-1,3-diol, succinic acid, adipic acid, glutaric acid, pimelic acid, maleic acid, phthalic acid, terephthalic acid, lactic acid, citric acid, salicylic acid, or a mixture thereof.

6. The process as claimed in claim 1, wherein no solvent is used.

7. The process as claimed in claim 1, wherein the Brønsted-acidic catalyst has a pKa of less than or equal to 1.

8. The process as claimed in claim 1, wherein the Brønsted-acidic catalyst comprises an aliphatic fluorinated sulfonic acid, an aromatic fluorinated sulfonic acid, trifluoromethanesulfonic acid, perchloric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, fluorosulfonic acid, bis(trifluoromethane)sulfonimide, hexafluoroantimonic acid, pentacyanocyclopentadiene, picric acid, sulfuric acid, nitric acid, trifluoroacetic acid, methanesulfonic acid, paratoluenesulfonic acid, an aromatic sulfonic acid an aliphatic sulfonic acid, or a mixture thereof.

9. The process as claimed in claim 1, wherein the Brønsted-acidic catalyst is used in an amount of 0.001 mol % to 0.5 mol %, based on the amount of lactone.

10. The process as claimed in claim 1, wherein the molar ratio of the lactone to the H-functional starter substance is from 1:1 to 30:1.

11. A polyester obtained by the process of claim 1.

12. The polyester as claimed in claim 11, having a number-average molecular weight of 70 g/mol to 5000 g/mol as determined by means of gel permeation chromatography (GPC).

13. A process for preparing a polyurethane comprising reacting the polyester as claimed in claim 11 with a polyisocyanate.

14. The process as claimed in claim 13, wherein the polyisocyanate comprises butylene 1,4-diisocyanate, pentane 1,5-diisocyanate, hexamethylene 1,6-diisocyanate (HDI) or their dimers, trimers, pentamers, heptamers or nonamers or mixtures thereof, isophorone diisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate, isomeric bis(4,4′-isocyanatocyclohexyl)methanes or mixtures thereof having any desired isomer content, cyclohexylene 1,4-diisocyanate, phenylene 1,4-diisocyanate, tolylene 2,4- and/or 2,6-diisocyanate (TDI), naphthylene 1,5-diisocyanate, diphenylmethane 2,2′- and/or 2,4′- and/or 4,4′-diisocyanate (MDI) and/or higher homologs (polymeric MDI), 1,3- and/or 1,4-bis(2-isocyanatoprop-2-yl)benzene (TMXDI), 1,3-bis(isocyanatomethyl)benzene (XDI), alkyl 2,6-diisocyanatohexanoates (lysine diisocyanates) having C1 to C6 alkyl groups, or a mixture thereof.

Description

EXAMPLES

[0071] The present invention is elucidated in more detail by the figures and examples which follow, but without being limited thereto.

[0072] Starting Materials Used

[0073] Cyclic Lactones

[0074] β-Propiolactone (purity 98.5%, Ferak Berlin GmbH)

[0075] β-Butyrolactone (purity 98%, Sigma-Aldrich Chemie GmbH)

[0076] H-Functional Starter Substance

[0077] Ethylene glycol (EG, >99%, Oqema GmbH)

[0078] 1,1,1-Trimethylolpropane TMP, (purity >99.8%, Perstorp AB)

[0079] Glycerol (Gly, purity 99.5%, Brenntag AG)

[0080] Propane-1,2-diol (PD, purity >99.8%, Brenntag AG)

[0081] Adipic acid (AA, purity 99.5% (BioXtra), Sigma Aldrich Chemie GmbH)

[0082] Octane-1,8-diol (OD, purity 98%, Sigma Aldrich GmbH)

[0083] PEG 300 (PE, purity Carl Roth GmbH+Co. KG)

[0084] Catalysts

[0085] Trifluoromethanesulfonic acid (TfOH, purity 98%, Sigma-Aldrich Chemie GmbH)

[0086] Sulfuric acid (H2SO4, 95-97%, Sigma Aldrich Chemie GmbH)

[0087] Solvent

[0088] Toluene (Tol, >99.5%, Azelis Deutschland GmbH)

[0089] Description of the Methods:

[0090] Gel permeation chromatography (GPC): Measurements were performed on an Agilent 1200 Series (G1311A Bin Pump, G1313A ALS, G1362A RID), detection by RID; eluent: tetrahydrofuran (GPC grade), flow rate 1.0 ml/min at 40° C. column temperature; column combination: 2×PSS SDV precolumn 100 Å (5 μm), 2×PSS SDV 1000 Å (5 μm). Calibration was carried out using ReadyCal Kit Poly(styrene) low in the range Mp=266-66000 Da from “PSS Polymer Standards Service”. The measurement recording and evaluation software used was the “PSS WinGPC Unity” software package. The polydispersity index from weighted (Mw) and number-average (Mn) molecular weight from the gel permeation chromatography is defined as Mw/Mn.

[0091] .sup.1H NMR

1) The composition of the polymer was determined by .sup.1H NMR (Bruker DPX 400, 400 MHz; pulse program zg30, relaxation delay D1: 10 s, 64 scans). Each sample was dissolved in deuterated chloroform. The relevant resonances in the .sup.1H NMR (relative to TMS=0 ppm) and the assignment of the area integrals (A) are as follows: [0092] poly(hydroxybutyrate) (=polybutyrolactone) with a resonance between 1.30-1.08 ppm, area integral corresponds to 3 hydrogen atoms (CH.sub.3 group) [0093] unsaturated impurities (free crotonic acid, unsaturated end groups of the polymer) with a resonance between 1.87-1.81+1.67-1.55 ppm (sum total of both integrals), each area integral corresponds to 3 hydrogen atoms (CH.sub.3 group)

[0094] All areas stated are integrated to the sum of 1.00, where, after multiplication by 100, the molar proportion of the unsaturated impurities x.sub.unsaturated [%] results.

[0095] If beta-propiolactone was polymerized under the conditions stated in the table, the measurement accuracy of the NMR for determining integrals of the double bonds was too inaccurate. Evaluation was not performed here, but the value is in all cases <1%.

2) The conversion of the monomer was determined by .sup.1H NMR (Bruker DPX 400, 400 MHz; pulse program zg30, relaxation delay D1: 10 s, 64 scans). Each sample was dissolved in deuterated chloroform. The relevant resonances in the .sup.1H NMR (relative to TMS=0 ppm) and the assignment of the area integrals (A) are as follows: [0096] poly(hydroxybutyrate) (=polybutyrolactone) with resonances at 5.25 (1H), 2.61 (1H), 2.48 (1H) and 1.28 (3H). [0097] β-butyrolactone with resonances at 4.70 (1H), 3.57 (1H), 3.07 (1H) and 1.57 (3H). [0098] poly(hydroxypropionate) (=polypropiolactone) with resonances at 4.38 (2H) and 2.66 (2H) [0099] β-propiolactone with resonances at 4.28 (2H) and 3.54 (2H) The conversion is determined as an integral of a suitable polymer signal divided by the sum of a suitable polymer signal and monomer signal. All signals are referenced to 1H.

[0100] Infrared Spectroscopy

[0101] The percentage lactone conversion, based on the amount of lactone used, was determined by means of IR spectroscopy. For this purpose, the product carbonyl bands (polypropiolactone, polybutyrolactone: 1780-1660 cm.sup.−1) and the propiolactone reactant bands (e.g. reactant carbonyl bands 1800 cm.sup.−1-1830 cm.sup.−1) or butyrolactone reactant bands (1810 cm.sup.−1-1825 cm.sup.−1) were analyzed.

[0102] The percentage lactone conversion is then as follows:

X(lactone)[%]=F(polylactone)/[F(polylactone)+F(lactone)]*100  (III)

[0103] In formula (III), F (polylactone) is the area of the product carbonyl band at 1780-1660 cm.sup.−1 and F (lactone) is the area of the reactant bands at 1800-1830 cm.sup.−1 or 1810-1825 cm.sup.−1.

Examples 1.7.9, 10: Polyester Via Stepwise Lactone Addition without Addition of an Additional Solvent

[0104] A three-neck flask with a reflux condenser and precision glass stirrer was initially charged with 7.0 g (81.4 mmol, 0.29 eq.) of β-butyrolactone (BBL), trifluoromethanesulfonic acid (0.168 g, 1.12 mmol, 0.004 eq.) and ethylene glycol (17.3 g, 279 mmol, 1 eq.) (example 1, see table 1 for mass figures for examples 7, 9, 10). The clear solution was heated to 73° C. and the reaction process was monitored using ATR IR spectroscopy. After a conversion of the BBL of >70% was ascertained by means of IR spectroscopy (100 minutes), 7.0 g of BBL were added once again with no increase in temperature being observed. This procedure (addition of 6-7 g portions) was repeated until a total of 120.0 g (1.4 mol, 5 eq.) of BBL had been consumed. The highest temperature rise was from 70° C.-88° C., with the heat source not being removed. At the end of the reaction, the glass flask is cooled down and the polyol characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone, proportion of unsaturated compounds). In all cases, virtually complete conversions of the monomer could be achieved (≥99%). In addition, the molecular weight distributions were always monomodal and no signal of the free starter could be detected. As a result of the stepwise addition of the lactone, the steady-state amount of free lactone is considerably lower than in the batch process.

[0105] The mass figures for the remaining experimental examples can be gathered from table 1.

TABLE-US-00001 TABLE 1 m m m m Experiment (butyrolactone) (propiolactone) (starter) (TfOH) number [g] [g] [g] [g] 1 120  — 17.3 (EG) 0.168 7 10 — 1.77 (PD) 0.01  9 10 — 1.44 (EG) 0.028 (H.sub.2SO.sub.4) 10  — 10 1.72 (EG) 0.017

Example 2 (Comparative Example): Polyester Via Batch Preparation Process

[0106] A four-neck flask with a reflux condenser and precision glass stirrer was initially charged with 100 g (1.16 mol, 5 eq.) of β-butyrolactone (BBL), trifluoromethanesulfonic acid (0.14 g, 0.933 mmol, 0.004 eq.) and ethylene glycol (14.4 g, 232 mmol, 1 eq.) at 10-15° C. The clear solution was then heated to approx. 45-50° C., the temperature at which the reaction begins to commence, and the reaction progress was monitored with IR spectroscopy. After two hours, despite stirring with a precision glass stirrer, a sharp jump in temperature with a temperature difference of >60° C. was observed and the oil bath was therefore immediately removed. After cooling to room temperature, IR spectroscopy showed that the BBL had been completely consumed. The glass flask was cooled down and the polyol characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone, proportion of unsaturated compounds). The conversion was almost complete (≥99%). In addition, the molecular weight distributions were monomodal and no signal of the free starter could be detected. If this experiment is conducted on a small scale (10 g of BBL), the temperature jump only occurs from 55° C.

Example 3 (Comparative Example): Polyester Via Batch Preparation Process

[0107] Analogously to example 2, 0.0125 eq. of TfOH (=0.25 mol %), 10 g of BBL were used. As soon as the internal temperature of 45° C. had been exceeded, a sharp temperature rise with a temperature difference ΔT of >60° C. was observed and the heat source was removed immediately. The glass flask was cooled down and the polyol characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone, proportion of unsaturated compounds). The conversion was almost complete (≥99%). In addition, the molecular weight distributions were monomodal and no signal of the free starter could be detected. However, a significant proportion of unsaturated byproducts of 10% was detected by means of H NMR spectroscopy. In the original prior art, 1 mol % of TfOH was used as a minimum amount with a BBL amount of 200 μl. On a >10 g scale, this experiment would lead to a larger, uncontrollable temperature rise and was not carried out for safety reasons.

Example 4 (Comparative Example): Polyester Via Batch Preparation Process Using an Aromatic Solvent

[0108] A three-neck flask with a reflux condenser and magnetic stirrer was initially charged with 10 g (0.116 mol, 5 eq.) of β-butyrolactone (BBL) in toluene. Thereafter, trifluoromethanesulfonic acid (0.014 g, 0.0933 mmol, 0.004 eq.) and ethylene glycol (1.44 g, 23.2 mmol, 1 eq.) were added successively at 10-15° C. The clear solution was then heated to approx. 45-50° C. and the reaction progress was monitored with IR spectroscopy. After 100 minutes and heating to 62° C., despite stirring, a jump in temperature of >20° C. was observed and the heating of the oil bath was immediately switched off. After cooling to 64° C., the reaction was continued and monitored by means of IR spectroscopy. At the end of the reaction, the glass flask was cooled down and the polyol characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone, proportion of unsaturated compounds). The conversion was almost complete (≥99%). In addition, the molecular weight distributions were monomodal and no signal of the free starter could be detected. Again, a direct comparative example with at least 1 mol % of TfOH was dispensed with due to an uncontrollable temperature rise and the accompanying safety risks.

Example 5 (Comparative Example): Polyester Via Stepwise Lactone Addition Using an Aromatic Solvent

[0109] A three-neck flask with a reflux condenser and magnetic stirrer was initially charged with 1 g (0.0116 mol, 0.5 eq.) of β-butyrolactone (BBL), trifluoromethanesulfonic acid (0,014 g, 0.0933 mmol, 0.004 eq.), 10 ml of toluene and ethylene glycol (1.44 g, 23.2 mmol, 1 eq.) at 10-15° C. The clear solution was then heated to approx. 50-76° C. and the reaction progress was monitored with IR spectroscopy. After two hours, the conversion of the reaction according to IR spectroscopy was only approx. 14% (total amount of BBL planned: 10 g) and the batch was discarded, even though the portion-wise addition of the remaining 9 g of BBL remained to be done.

Examples 6, 8, 11-13: Polyester Via Continuous Lactone Addition

[0110] A 500 ml flange reactor is initially charged with 1. starter (amount: table 2) and 2. catalyst (amount: table 2) with the briefest possible contact with air. The reactor is closed, the stirrer is switched on (200-400 rpm) and purging is effected for 10-15 min with N.sub.2 (approx. 1 bubble/s). 10 g of lactone are added and the thermostat is then set to 60° C. The reaction is stirred for 60 min. A sample is then taken and IR measurement effected. If the conversion is <50%, the temperature is increased to 70° C. and the mixture is stirred for a further 60 min, A sample is then taken again and IR measurement effected. If the conversion is >50%, the reaction temperature is increased to 70° C. and a changeover to continuous metering is effected (flow rate of lactone of 0.5 g/min). The mixture is then stirred for a further 30 min and the conversion checked via IR. Stirring is continued until complete conversion has taken place (IR). At the end of the reaction, the flange reactor is cooled down and the polyol characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone). In all cases, virtually complete conversions of the monomer could be achieved (≥99%). In addition, the molecular weight distributions were always monomodal and no signal of the free starter could be detected.

TABLE-US-00002 TABLE 2 Overview of the amounts weighed in in experiments 6, 8, 11-13. m m m m Experiment (propiolactone) (butyrolactone) (starter) (TfOH) number [g] [g] [g] [g]  6 — 96.5  3.48 0.135  8 81.6 — 18.4 0.136 11 87.6 — 12.4 0.146 12 79.4 — 20.7 0.132 13 70.8 — 29.2 0.118

Examples 14-18 (Comparative Examples): Polyester Via Stepwise/Continuous Lactone Addition in the Presence of a DMC Catalyst

[0111] A 300 ml steel autoclave is initially charged with 1. starter, 2. catalyst (amount: table 3) and 3. solvent with the briefest possible contact with air. The reactor is purged with N.sub.2. At 130° C., the β-lactone is then continuously fed into the reactor over two hours. This was then followed by stirring for about two hours. Via IR analysis of the reaction solution, the reaction time and temperature of the following stirring time were optionally adapted in order to ensure complete conversion of the β-lactone. No exothermicity was observed during the time period of the continuous metering and the following stirring time. When using low molecular weight starter compounds (e.g. ethylene glycol), the starter is metered continuously into the reaction solution analogously to the monomer.

[0112] At the end of the reaction, the reactor is cooled down, volatile components are removed from the reaction solution and the polyol is characterized by GPC analysis (molecular weight distribution) and .sup.1H NMR (conversion of the β-lactone). In all cases, virtually complete conversions of the monomer could be achieved (≥95%), however unsaturated impurities were detected in the range of 2-7%. In addition, in all cases clear-cut setting of the molecular weight was not possible. The molecular weight distributions were always bimodal and, in addition to the polyester, in all cases free starter was additionally present in the product.

[0113] No solvent was used in experiment 18.

TABLE-US-00003 TABLE 3 Overview of the amounts weighed in in experiments 14-18. m m m m Experiment (toluene) (butyrolactone) (starter) (DMC) number [g] [g] [g] [g] 14 50 18.5 1.46 0.02 15 50 17.1 2.92 0.02 16 50 19.4 0.62 0.02 17 50 18.7 1.24 0.02 18 — 62.3 11.0   0.073

TABLE-US-00004 TABLE 4 Comparison of experiments 1 to 18. Addition H-funct. Lactone/ X(lactone) of starter x(cat) [mol %].sup.b) starter Mn [%] .sup.1H X.sub.unsaturated ΔT.sub.max Experiment lactone.sup.a) Lactone substance Catalyst [ppm].sup.c) [mol/mol] Solvent [g/mol] PDI NMR [%] [° C.]  1 sw BBL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 610 1.3 ≥99 0 18  2 (comp.) batch BBL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 690 1.2 ≥99 1 >60  3 (comp.) batch BBL EG TfOH 0.25.sup.b) 1200.sup.c) 5/1 — 500 1.7 ≥99 10 >60  4 (comp.) batch BBL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 toluene 660 1.1 ≥99 1 >20  5 (comp.) sw BBL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 toluene n.d. n.d. n.d. n.d. 0  6 cont. BBL EG TfOH 0.08.sup.b) 1200.sup.c) 20/1  — 2000 1.4 ≥99 0 0  7 sw BBL PD TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 780 1.2 ≥99 3 17  8 cont. BPL Gly TfOH 0.08.sup.b) 1200.sup.c) 5.6/1   — 820 1.4 ≥99 — 0  9 sw BBL EG H.sub.2SO.sub.4 0.08.sup.b) 2440.sup.c) 5/1 — 600 1.4 ≥99 3 6 10 sw BPL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 880 1.4 ≥99 — 10 11 cont. BPL EG TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 920 1.5 ≥99 — 0 12 cont. BPL EG TfOH 0.08.sup.b) 1200.sup.c) 3/1 — 560 1.3 ≥99 — 0 13 cont. BPL AA TfOH 0.08.sup.b) 1200.sup.c) 5/1 — 420 1.3 ≥99 — 0 14 cont. BBL OD DMC 1000.sup.c) 21.5/1   toluene 2500 + 6000 mm ≥95 7 0 (comp.) 15 cont. BBL OD DMC 1000.sup.c) 10/1  toluene 2000 + 4500 mm ≥95 3 0 (comp.) 16 cont. BBL EG DMC 1000.sup.c) 22.5/1   toluene 1300 + 2500 mm ≥95 3 0 (comp.) 17 cont. BBL EG DMC 1000.sup.c) 11/1  toluene 2200 + 4200 mm ≥95 2 0 (comp.) 18 cont. BBL PE DMC 1000.sup.c) 20/1  — 2000 + 4500 mm ≥95 4 0 (comp.) .sup.a)addition of lactone, batch, stepwise (sw), continuous (cont.), .sup.b)+c)catalyst amount [mol %].sup.b) or [ppm].sup.c) X.sub.unsaturated [%] .sup.d)proportion of unsaturated impurities n.d.: not determined, mm: multimodal