PROCESS FOR PREPARING A POLYOXYALKYLENE CARBONATE POLYOL

Abstract

The invention relates to a process for preparing a polyoxyalkylene carbonate polyol by reacting a polyoxyalkylene polyol with a cyclic carbonate in the presence of an amine catalyst. The invention further relates to polyoxyalkylene carbonate polyols obtainable using the method according to the invention and to a process for preparing polyurethanes by reacting the polyoxyalkylene carbonate polyols according to the invention with polyisocyanates.

Claims

1. A process for preparing a polyoxyalkylenecarbonate polyol comprising reacting a polyoxyalkylene polyol with a cyclic carbonate in the presence of an amine catalyst.

2. The process as claimed in claim 1, wherein the number-average molar mass of the polyoxyalkylene polyol is ≥200 g/mol as determined by means of gel permeation chromatography (GPC) as disclosed in the experimental section.

3. The process as claimed in claim 1, wherein the molar ratio between cyclic carbonate and the hydroxyl end groups of the polyoxyalkylene polyol is from 1:1 to 20:1.

4. The process as claimed in claim 1, wherein the polyoxyalkylenecarbonate polyol is prepared in the absence of any alkylene oxide.

5. The process as claimed in claim 1, wherein the cyclic carbonate comprises 4-methyl-1,3-dioxolan-2-one, 1,3-dioxolan-2-one, 1,3-dioxan-2-one, 5,5-dimethyl-1,3-dioxan-2-one, or a mixture thereof.

6. The process as claimed in claim 1, wherein the amine catalyst comprises trimethylamine, triethylenediamine, tripropylamine, tributylamine, tripentylamine, trihexylamine, triphenylamine, dimethylethylamine, N,N-dimethylcyclohexylamine, tetramethylenediamine, 1-methyl-4-dimethylaminoethylpiperazine, triethylamine, tripropylamine, tributylamine, dimethylbutylamine, N,N-dimethylbenzylamine, N,N-dimethylcyclohexylamine, N,N′,N″-tris(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylformamide, N,N,N′,N′-tetramethylethylenediamine, N,N,N′,N′-tetramethylbutanediamine, tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane, bis(dimethylaminopropyl)urea, bis(dimethylaminoethyl) ether, N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethanolamine, diethanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, dimethylethanolamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,4-diazabicyclo[2.2.2]octane (DABCO), imidazole, 1-methylimidazole, 2-methylimidazole, 4(5)-methylimidazole, 2,4(5)-dimethylimidazole, 1-ethylimidazole, 2-ethylimidazole, 1-phenylimidazole, 2-phenylimidazole, 4(5)-phenylimidazole and N,N-dimethylaminopyridine, guanidine, 1,1,3,3-tetramethylguanidine, pyridine, 1-azanaphthalene (quinoline), N-methylpiperidine, N-methylmorpholine, N,N′-dimethylpiperazine, and N,N-dimethylaniline, or a mixture thereof.

7. The process as claimed in claim 1, wherein the polyoxyalkylene polyol has a proportion of secondary OH end groups of at least 75%, based on the sum total of primary and secondary OH end groups, as been determined by means of .sup.1H NMR spectroscopy as disclosed in the experimental section.

8. The process as claimed in claim 1, wherein the polyoxyalkylene polyol is a polyether polyol and/or polyethercarbonate polyol.

9. The process as claimed in claim 8, wherein the polyoxyalkylene polyol is a polyether polyol prepared by reaction of an H-functional starter substance with alkylene oxide in the presence of a double metal cyanide catalyst.

10. The process as claimed in claim 9, wherein the alkylene oxide is ethylene oxide and/or propylene oxide.

11. The process as claimed in claim 10, wherein the proportion by weight of propylene oxide is 80% by weight to 100% by weight based on the sum total of the masses of propylene oxide and of ethylene oxide metered in.

12. The process as claimed in claim 1, wherein the process is performed without addition of a solvent.

13. The process as claimed in claim 1, wherein the cyclic carbonate is added continuously or stepwise to the polyoxyalkylene polyol and is converted to the polyoxyalkylenecarbonate polyol.

14. A polyethercarbonate polyol obtained according to the process of claim 1, comprising a polyether block (A) and at least one polyethercarbonate block (B), wherein the proportion by weight of CO.sub.2 in the polyethercarbonate polyol is ≤4% by weight, as determined by means of .sup.1H NMR spectroscopy as disclosed in the experimental section, and wherein the polyethercarbonate polyol has a proportion of ≥65% primary OH end groups based on the sum total of primary and secondary OH end groups, as determined by means of .sup.1H NMR spectroscopy as disclosed in the experimental section.

15. A process for preparing a polyurethane by reacting the polyoxyalkylenecarbonate polyol as claimed in claim 14 with a polyisocyanate.

Description

EXAMPLES

[0088] The present invention is more particularly elucidated with reference to the figures and examples which follow but without being limited thereto.

Starting Materials Used

Cyclic Carbonates

[0089] 1,3-dioxolan-2-one (99+%, Acros Organics)

Catalysts

[0090] 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (98%, Aldrich Chemistry)
1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) (98%, Aldrich Chemistry)
DMC catalyst prepared in accordance with example 6 of WO 01/80994 A1
potassium orthovanadate (K.sub.3VO.sub.4) (99.9%, Alfa Aesar)

Polyoxyalkylene Polyol (Polyether Polyol)

[0091] Polyether polyol A was prepared using DMC catalysis as follows:

[0092] A 20 1 pressure reactor was initially charged under nitrogen with 1739.3 g of a poly(oxypropylene) triol having an OH number of 233 mg KOH/g and 0.367 g of DMC catalyst (prepared in accordance with example 6 of WO 01/80994 A1). The reactor was heated to 130° C., inertized by three times evacuating to 100 mbar (absolute) and repeated charging with nitrogen, and then stripping was performed for 30 min at 100 mbar and 130° C. with passage of nitrogen through the reactor. A mixture of 9256 g of propylene oxide and 1028 g of ethylene oxide was then metered in at 130° C. within three hours. After further reaction time at 130° C. until the pressure in the reactor was constant, volatile constituents were distilled off under reduced pressure at 90° C. for 30 min and then the reaction mixture was cooled to room temperature. The OH number of the product was 34.3 mg KOH/g, the viscosity 974 mPas, the number-average molecular weight M.sub.n6665 g/mol, the polydispersity 1.03, and the proportion of primary hydroxyl end groups 18%.

Description of the Methods:

Gel Permeation Chromatography (GPC):

[0093] The number-average molecular weight M.sub.n, the weight-average molecular weight M.sub.w and the polydispersity (M.sub.w/M.sub.n) of the products were determined by means of gel permeation chromatography (GPC). The procedure of DIN 55672-1 was followed: “Gel permeation chromatography, Part 1—Tetrahydrofuran as eluent” (SECurity GPC System from PSS Polymer Service, flow rate 1.0 ml/min; columns: 2×PSS SDV linear M, 8×300 mm, 5 μm; RID detector). Polystyrene samples of known molar mass were used for calibration.

.sup.1H and .sup.13C NMR Spectroscopy

[0094] Determination of the molar proportion of primary OH groups: by means of .sup.1H (Bruker AV III HD 600, 600 MHz, deuterochloroform) or .sup.13C NMR (Bruker AV III HD 600, 151 MHz, deuterochloroform):

[0095] To determine the content of primary OH groups, the polyol samples were first peracetylated.

[0096] This was done using the following peracetylation mixture:

9.4 g of acetic anhydride p.a.
1.6 g of acetic acid p.a.
100 ml of pyridine p.a.

[0097] For the peracetylation reaction, 10 g of polyol (polyoxyalkylene polyol or polyoxyalkylenecarbonate polyol) were weighed into a 300 ml flanged Erlenmeyer flask. The volume of peracetylation mixture was guided by the OH number of the polyol to be peracetylated, rounding the OH number of the polyol up to the next multiple of 10 (based in each case on 10 g of polyol); for every 10 mg KOH/g, 10 ml of peracetylation mixture are then added. For example, 50 ml of peracetylation mixture were correspondingly added to the sample of 10 g of a polyol having an OH number of 45.1 mg KOH/g.

[0098] After the addition of glass boiling chips, the flanged Erlenmeyer flask was provided with a riser tube (air cooler) and the sample was boiled under gentle reflux for 75 min. The sample mixture was then transferred into a 500 ml round-bottom flask, and volatile constituents (essentially pyridine, acetic acid and excess acetic anhydride) were distilled off at 80° C. and 10 mbar (absolute) over a period of 30 min. The distillation residue was then admixed three times with 100 ml each time of cyclohexane (toluene was used as an alternative in the cases in which the distillation residue did not dissolve in cyclohexane), and volatile constituents of the sample were removed at 100° C. and 10 mbar (absolute) for one hour.

[0099] For the determination of the molar proportions of primary and secondary OH end groups in the polyol, the sample thus prepared was dissolved in deuterated chloroform and analyzed using .sup.1H NMR (Bruker AV III HD 600, 600 MHz) or .sup.13C NMR (Bruker AV III HD 600, 151 MHz). The relevant resonances in the .sup.1H NMR (based on TMS=0 ppm) are as follows:

[0100] Methyl signal of a peracetylated secondary OH end group: 2.04 ppm

[0101] Methyl signal of a peracetylated primary OH end group: 2.08 ppm

[0102] The molar proportion of secondary and primary OH end groups is then found as follows:

Proportion of secondary OH end groups (CH—OH)=F(2.04)/(F(2.04)+F(2.08)).Math.100%   X)

Proportion of primary OH end groups (CH.sub.2—OH)=F(2.08)/(F(2.04)+F(2.08)).Math.100%   (XI)

[0103] In the formulae (X) and (XI), F represents the area of the resonances at 2.04 ppm and 2.08 ppm respectively.

[0104] The relevant resonances in the .sup.13C NMR (based on TMS=0 ppm) are as follows:

Methyl signal of a peracetylated secondary OH end group: 21.3 ppm
Methyl signal of a peracetylated primary OH end group: 20.9 ppm

[0105] The molar proportion of secondary and primary OH end groups is then found as follows:

Proportion of secondary OH end groups (CH—OH)=F(21.3)/(F(21.3)+F(20.9)).Math.100%   (XII)

Proportion of primary OH and groups (CH.sub.2—OH)=F(20.9)/(F(21.3)+F(20.9)).Math.100%   (XIII)

[0106] In the formulae (XII) and (XIII), F represents the area of the resonances at 21.3 ppm and 20.9 ppm respectively.

[0107] The relative composition of the polyoxyalkylenecarbonate polyols was determined by means of 1H NMR (Bruker AV III HD 600, 600 MHz, deuterochloroform). The relevant resonances in the 1H NMR spectrum (based on TMS=0 ppm) are as follows:

For remaining 1,3-dioxolan-2-one: signal at 4.53 ppm
For remaining 4-methyl-1,3-dioxolan-2-one: signal at 1.51-1.49 ppm
For linear propyl carbonate units incorporated in the polyoxyalkylenecarbonate polyol: resonances at 4.8-4.95 ppm
For linear ethylene carbonate units incorporated in the polyoxyalkylenecarbonate polyol: resonances at 4.2-4.35 ppm
For polypropylene oxide units incorporated in the polyoxyalkylenecarbonate polyol: resonances at 1.1 ppm
For polyethylene oxide units incorporated in the polyoxyalkylenecarbonate polyol: the remaining signal components in the range of 3.0-4.2 ppm

[0108] The proportions by weight (in % by weight) of the components in the reaction mixture are calculated by the formula (XIV) to (XIX) as follows:

Unconverted 1,3-dioxolan-2-one (cEC):

[00001]$\begin{array}{cc}{\mathrm{cEC}}_{\mathrm{wt}\%}=\frac{\left[F\left(4.53\right)\right]}{4}.Math.\frac{88}{N}.Math.100\%& \left(\mathrm{XIV}\right)\end{array}$

Unconverted 4-methyl-1,3-dioxolan-2-one (cPC):

[00002]$\begin{array}{cc}{\mathrm{cPC}}_{\mathrm{wt}\%}=\frac{\left[F\left(1.51-1.49\right)\right]}{3}.Math.\frac{102}{N}.Math.100\%& \left(\mathrm{XV}\right)\end{array}$

Polymer-bound linear propylene carbonate units (lPC):

[00003]$\begin{array}{cc}{\mathrm{lPC}}_{\mathrm{wt}\%}=\left[F\left(4.8-4.95\right)-\frac{\left[F\left(1.51-1.49\right)\right]}{3}\right].Math.\frac{102}{N}.Math.100\%& \left(\mathrm{XVI}\right)\end{array}$

Polymer-bound linear ethylene carbonate units (lEC):

[00004]$\begin{array}{cc}{\mathrm{lEC}}_{\mathrm{wt}\%}=\frac{\left[F\left(4.2-4.35\right)\right]}{4}.Math.\frac{88}{N}.Math.100\%& \left(\mathrm{XVII}\right)\end{array}$

Polymer-bound polypropylene oxide units (PPO):

[00005]$\begin{array}{cc}{\mathrm{PPO}}_{\mathrm{wt}\%}=\frac{\left[F\left(1.1\right)\right]}{3}.Math.\frac{58}{N}.Math.100\%& \left(\mathrm{XVIII}\right)\end{array}$

Polymer-bound polyethylene oxide units (PEO):

[00006]$\begin{array}{cc}{\mathrm{PEO}}_{\mathrm{wt}\%}=& \left(\mathrm{XIX}\right)\end{array}$$\frac{\left[F\left(3.-4.2\right)-F\left(1.1\right)-F\left(1.51-1.49\right)-2.Math.F\left(4.8-4.95\right)\right]}{4}.Math.\frac{44}{N}.Math.100\%$

where the value of D (“denominator” D) is calculated by formula (XX):

[00007]$\begin{array}{cc}D=\frac{\left[F\left(4.53\right)\right]}{4}.Math.88+\frac{F\left(1.51-1.49\right)}{3}.Math.102+\left[F\left(4.8-4.95\right)-\frac{\left[F\left(1.51-1.49\right)\right]}{3}\right].Math.102+\frac{\left[F\left(4.2-4.35\right)\right]}{4}.Math.88+\frac{\left[F\left(1.1\right)\right]}{3}.Math.58+\frac{\left[F\left(3.-4.2\right)-F\left(1.1\right)-F\left(1.51-1.49\right)-2.Math.F\left(4.8-4.95\right)\right]}{4}.Math.44& \left(\mathrm{XX}\right)\end{array}$

and the following abbreviations are used: [0109] F(4.53)=area of resonance at 4.53 ppm for 1,3-dioxolan-2-one (corresponding to four protons) [0110] F(1.51-1.49)=area of the resonance at 1.51-1.49 ppm for 4-methyl-1,3-dioxolan-2-one (corresponding to three protons) [0111] F(4.8-4.95)=area of the resonance at 4.8-4.95 ppm for linear propylene carbonate units in the polyoxyalkylenecarbonate polyols (corresponding to one proton) [0112] F(4.2-4.35)=area of the resonance at 4.2-4.35 ppm for linear ethylene carbonate units in the polyoxyalkylenecarbonate polyols (corresponding to four protons) [0113] F(1.1)=area of the resonance at 1.1 ppm for polypropylene oxide units in the polyoxyalkylenecarbonate polyol (corresponding to three protons) [0114] F(3.0-4.2)=area of the remaining signal components in the range of 3.0-4.2 ppm for polyethylene oxide units in the polyoxyalkylenecarbonate polyol (corresponding to four protons)

[0115] Taking account of the relative intensities, by the following formula (XXI), the proportion by weight (in % by weight) of CO.sub.2 in the polyoxyalkylene carbonate polyol (CO.sub.2 wt %) was calculated:

[00008]$\begin{array}{cc}{\mathrm{CO}}_{2_{\mathrm{wt}\%}}=\frac{\left[{\mathrm{lEC}}_{\mathrm{wt}\%}.Math.\frac{44}{88}+{\mathrm{lPC}}_{\mathrm{wt}\%}.Math.\frac{44}{102}\right]}{P}*100\%& \left(\mathrm{XXI}\right)\end{array}$

[0116] where the value for P.sub.wt % (“polymer” P) is calculated by formula (XXII) and reflects the polymer content (i.e. the proportion by weight of the polyoxyalkylenecarbonate polyols) (in % by weight) in the reaction mixture:

P.sub.wt %=lEC.sub.wt %+lPC.sub.wt %+PPO.sub.wt %+PEO.sub.wt %  (XXII)

[0117] In formula (XXI), the factor 44 results from the molar mass of ethylene oxide (molar mass 44 g/mol), the factor 88 from the sum total of the molar masses of CO.sub.2 (molar mass 44 g/mol) and of ethylene oxide, and the factor 102 from the sum total of the molar masses of CO.sub.2 and of propylene oxide (molar mass 58 g/mol).

OH Numbers

[0118] OH numbers were determined in accordance with the procedure of DIN 53240.

Viscosity

[0119] Viscosity was determined by rotary viscometer (Physica MCR 51, manufacturer: Anton Paar) by the method of DIN 53018.

Example 1

[0120] A 500 milliliter three-neck flask (equipped with reflux condenser, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 100° C. Subsequently, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan one/hydroxyl end groups of polyether polyol A: 7/1) was added, and the gas space in the flask was purged with nitrogen at 100° C. for 20 minutes. Thereafter, 0.65 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.5 mol % based on the 1,3-dioxolan-2-one used) was added and the mixture was heated up stepwise to 170° C. The resultant gas stream was observed by means of a bubble counter connected to the reflux condenser and discharged. The reaction mixture was stirred at 170° C. for 5 hours and then cooled to room temperature. The OH number of the product was 34 mg KOH/g, the viscosity 5470 mPas, and the proportion of primary hydroxyl end groups 71%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 2.44% was determined.

Example 2

[0121] A 500 milliliter three-neck flask (equipped with reflux condenser, dropping funnel, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 130° C., and the gas space in the flask was purged with nitrogen for 20 minutes. 0.65 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.5 mol % based on the amount of the 1,3-dioxolan-2-one used) was added, and then, by dropping funnel, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) was added (about 15 g/h). With commencement of the addition of the 1,3-dioxolan-2-one, the reaction mixture was heated to 170° C. and stirred at 170° C. for 5 hours. The resultant gas stream was observed by means of a bubble counter connected to the reflux condenser and discharged. Subsequently, the reaction mixture was cooled to room temperature. The OH number of the product was 31 mg KOH/g, the viscosity 4175 mPas, and the proportion of primary hydroxyl end groups 72%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 2.01% was determined.

Example 3

[0122] A 500 milliliter three-neck flask (equipped with reflux condenser, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 130° C. Subsequently, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) and 0.65 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.5 mol % based on the amount of the 1,3-dioxolan-2-one used) were added. The reaction mixture was heated up to 170° C. stepwise while passing nitrogen through, stirred at 170° C. for 5 hours while passing nitrogen through, and then cooled down to room temperature. The OH number of the product was 33 mg KOH/g, the viscosity 7550 mPas, and the proportion of primary hydroxyl end groups 73%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 2.38% was determined.

Example 4

[0123] A 500 milliliter three-neck flask (equipped with reflux condenser, dropping funnel, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 130° C. Subsequently, 0.65 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.5 mol % based on the amount of the 1,3-dioxolan-2-one used) was added, and, by dropping funnel, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) was added (about 15 g/h). With commencement of the addition of the 1,3-dioxolan-2-one, the reaction mixture was heated to 170° C. while passing nitrogen through and stirred at 170° C. for 5 hours while passing nitrogen through. Subsequently, the reaction mixture was cooled to room temperature. The OH number of the product was 29 mg KOH/g, the viscosity 6225 mPas, and the proportion of primary hydroxyl end groups 72%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 1.99% was determined.

Example 5

[0124] A 500 milliliter three-neck flask (equipped with reflux condenser and temperature sensor) was initially charged with 200 g of polyether polyol A and heated to 130° C. Subsequently, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) and 0.65 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (0.5 mol % based on the amount of the 1,3-dioxolan-2-one used) were added. The reaction mixture was heated up to 170° C. stepwise at 700 mbar, stirred at 170° C. and 700 mbar for 5 hours, and then cooled down to room temperature. The OH number of the product was 31 mg KOH/g, the viscosity 7450 mPas, and the proportion of primary hydroxyl end groups 73%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 2.50% was determined.

Example 6

[0125] A 500 milliliter three-neck flask (equipped with reflux condenser, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 130° C. Subsequently, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan one/hydroxyl end groups of polyether polyol A: 7/1) was added, and the gas space in the flask was purged with nitrogen at 130° C. for 20 minutes. Thereafter, 0.60 g of 1,5,7-triazabicyclo[4.4.0]dec ene (TBD) (0.5 mol % based on the 1,3-dioxolan-2-one used) was added and the mixture was heated up stepwise to 170° C. The resultant gas stream was observed by means of a bubble counter connected to the reflux condenser and discharged. The reaction mixture was stirred at 170° C. for 5 hours and then cooled to room temperature. The OH number of the product was 32 mg KOH/g, the viscosity 6975 mPas, and the proportion of primary hydroxyl end groups 73%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 2.30% was determined.

Example 7 (Comparative Example)

[0126] A 2 liter stainless steel reactor was initially charged with 200 g of the polyether polyol A and heated to 130° C. The reactor was inertized by three times evacuating to 100 mbar (absolute) and repeatedly charging with nitrogen. 75.0 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) was added, and the reaction mixture was stirred at 170° C. for 5 hours. The resultant gas stream was observed by means of a bubble counter connected to the reactor and discharged. Subsequently, the reaction mixture was cooled to room temperature. The OH number of the product was 31 mg KOH/g, the viscosity (at 50° C.) 236 mPas, and the proportion of primary hydroxyl end groups 12%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 0.36% was determined.

Example 8 (Comparative Example)

[0127] A 2 liter stainless steel reactor was initially charged with 200 g of the polyether polyol A and heated to 130° C. The reactor was inertized by three times evacuating to 100 mbar (absolute) and repeatedly charging with nitrogen. 75.0 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) was added, and the mixture was heated to 170° C. 130 g of propylene oxide was added, and the mixture was stirred at 170° C. for 5 hours. Subsequently, the reaction mixture was cooled to room temperature. The OH number of the product was 24 mg KOH/g, the viscosity 2510 mPas, and the proportion of primary hydroxyl end groups 17%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 0.51% was determined.

Example 9 (Comparative Example)

[0128] A 500 milliliter three-neck flask (equipped with reflux condenser, temperature sensor, nitrogen feed and gas exit/gas outlet with bubble counter) was initially charged with 200 g of polyether polyol A and heated to 120° C. Subsequently, 75.4 g of 1,3-dioxolan-2-one (molar ratio of 1,3-dioxolan-2-one/hydroxyl end groups of polyether polyol A: 7/1) was added, and the gas space in the flask was purged with nitrogen at 120° C. for 20 minutes. Thereafter, 0.99 g of potassium orthovanadate (K.sub.3VO.sub.4) (0.5 mol % based on the 1,3-dioxolan-2-one used) was added and the mixture was heated up stepwise to 170° C. The resultant gas stream was observed by means of a bubble counter connected to the reflux condenser and discharged. The reaction mixture was stirred at 170° C. for 5 hours and then cooled to room temperature. The OH number of the product was 40 mg KOH/g, the viscosity 12750 mPas, and the proportion of primary hydroxyl end groups 76%. By NMR spectroscopy, a proportion by weight of CO.sub.2 in the polyethercarbonate polyol of 4.26% was determined.

TABLE-US-00001 TABLE 1 Comparison of experiments 1 to 9. Carbonate/ OH CO.sub.2 in the Poly- hydroxyl Addition number Viscosity Primary polyethercarbonate Exper- oxyalkylene Carbon- Alkylene Cata- x(cat) end groups of [mg (25° C.) OH polyol iment polyol ate.sup.a) oxide .sup.b) lyst .sup.c) [mol %].sup.d) [mol/mol] carbonate .sup.e) KOH/g] [mPa*s] [%] [% by wt.] 1 Polyether EC — DBU 0.5 7 batch 34 5470 71 2.44 polyol A 2 Polyether EC — DBU 0.5 7 cont. 31 4175 72 2.01 polyol A 3 Polyether EC — DBU 0.5 7 batch 33 7550 73 2.38 polyol A 4 Polyether EC — DBU 0.5 7 cont. 29 6225 72 1.99 polyol A 5 Polyether EC — DBU 0.5 7 batch 31 7450 73 2.50 polyol A 6 Polyether EC — TBD 0.5 7 batch 32 6975 73 2.30 polyol A 7 (comp.) Polyether EC — DMC.sub.act — 7 batch 31 236 12 0.36 polyol A (50° C.) 8 (comp.) Polyether EC PO DMC.sub.act — 7 batch.sup.f) 24 2510 17 0.51 polyol A 9 (comp.) Polyether EC — K.sub.3VO.sub.4 0.5 7 batch 40 12750  76 4.26 polyol A .sup.a)1,3-dioxolan-2-one (ethylene carbonate, EC) .sup.b) propylene oxide (PO) .sup.c) 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD); DMC catalyst present from the preparation of polyether polyol A (DMC.sub.act), potassium orthovanadate (K.sub.3VO.sub.4) .sup.d)based on the amount of carbonate used .sup.e) carbonate addition: batchwise mode (batch); semi-batchwise mode with continuous carbonate addition (conti); .sup.f)carbonate addition in batchwise mode (batch) with continuous addition of the alkylene oxide (corresponding to teaching of WO2013/028437 A1)