PROCESS FOR THE PREPARATION OF POLYETHERCARBONATE POLYOLS

Abstract

A process for the preparation of polyethercarbonate polyols comprises the reaction of a reaction mixture comprising one or more H-functional starter compounds, one or more alkylene oxides, carbon dioxide and a double metal cyanide (DMC) catalyst. The reaction is conducted in a reactor under stirring with a specific power input into the reaction mixture, expressed as Watts per liter (W/L), of ≧0.07 to ≦5.00.

Claims

1. A process for the preparation of polyethercarbonate polyols comprising the reaction of a reaction mixture comprising one or more H-functional starter compounds, one or more alkylene oxides, carbon dioxide and a double metal cyanide (DMC) catalyst, wherein: the reaction is conducted in a reactor under stirring with a specific power input into the reaction mixture, expressed as Watts per liter (W/L), of ≧0.07 to ≦5.00; wherein the specific power input (P/V) is calculated by: a) for the turbulent flow range the specific power input is calculated with:
P/V=Ne*n.sup.3*d.sup.5*density/V; wherein Ne=Newton number of the reactor; n=agitator speed; d=agitator diameter; density of the reaction mixture, and V=filling volume (which is the volume of the reaction mixture at the end of the reaction); and b) for the laminar flow range the specific power input is calculated with:
P/V=C*n.sup.2*d.sup.3*viscosity/V; wherein C=Re*Ne and Re=Reynolds number of the agitator used for mixing the reaction mixture, and Ne is the Newton number of the reactor.

2. A process for the preparation of polyethercarbonate polyols comprising the reaction of a reaction mixture comprising one or more H-functional starter compounds, one or more alkylene oxides, carbon dioxide and a double metal cyanide (DMC) catalyst, wherein: (α) the DMC catalyst, a suspending agent which comprises no H-functional groups and/or one or more H-functional starter compounds are initially introduced into the reactor; (γ) one or more alkylene oxides, carbon dioxide and optionally one or more H-functional starter compounds are copolymerized in the reactor; and (β) optionally, the reaction is conducted under an atmosphere of inert gas, inert gas/carbon dioxide mixture or under a carbon dioxide atmosphere, a fraction (based on the total amount of alkylene oxides used in steps (β) and (γ)) of one or more alkylene oxides is added into the reactor in one or more portions to the mixture from step (a) at temperatures of 50 to 200° C., wherein: the copolymerisation (step (γ)) is conducted in a reactor under stirring with a specific power input into the reaction mixture, expressed as Watts per liter (W/L), of ≧0.07 to ≦5.00 wherein the specific power input (P/V) is calculated by: a) for the turbulent flow range the specific power input is calculated with:
P/V=Ne*n.sup.3*d.sup.5*density/V; wherein Ne=Newton number of the reactor; n=agitator speed; d=agitator diameter; density is the density of the reaction mixture at the end of the reaction, and V=filling volume (which is the volume of the reaction mixture at the end of the reaction); and b) for the laminar flow range the specific power input is calculated with:
P/V=C*n.sup.2*d.sup.3*viscosity/V; wherein C=Re*Ne and Re=Reynolds number of the agitator used for mixing the reaction mixture, and Ne is the Newton number of the reactor.

3. The process according to claim 2, wherein step (α) comprises: (α1) placing the H-functional starter compound or a mixture of at least two H-functional starter compounds in the reactor; and (α2) passing an inert gas, an inert gas/carbon dioxide mixture or carbon dioxide into the resulting mixture of DMC catalyst and one or more H-functional starter compounds at a temperature of 50 to 200° C. and at the same time establishing a reduced pressure (absolute) of 1000 Pa (10 mbar) to 80000 Pa (800 mbar) in the reactor by removal of the inert gas or carbon dioxide.

4. The process according to claim 2, wherein step (α) comprises: (α1) placing the H-functional starter compound or a mixture of at least two H-functional starter compounds in the reactor under an inert gas atmosphere, under an atmosphere of inert gas/carbon dioxide mixture or under a pure carbon dioxide atmosphere; and (α2) passing an inert gas, an inert gas/carbon dioxide mixture or carbon dioxide into the resulting mixture of DMC catalyst and one or more H-functional starter compounds at a temperature of 80 to 160° C., and at the same time establishing a reduced pressure (absolute) of 4000 Pa (40 mbar) to 20000 Pa (200 mbar), in the reactor by removal of the inert gas or carbon dioxide; the double metal cyanide catalyst being added before or after the H-functional starter substance or the mixture of at least two H-functional starter substances.

5. The process according to claim 1, wherein the stirring is conducted at a constant speed.

6. The process according to claim 1, wherein the specific power input is determined after the volume of the reaction mixture has obtained a constant value.

7. The process according to claim 1, wherein the stirring is conducted using any kind and/or combination of radial or axial flow agitator.

8. The process according to claim 1, wherein the reaction is carried out in: an agitated tank reactor which optionally comprises an external loop with pump that recirculates material back into the reactor; a tubular reactor which optionally comprises an external loop with pump that recirculates material back into the reactor; or a loop reactor; the reactors furthermore optionally comprising an external heat exchanger.

9. The process according to claim 1, wherein the one or more H-functional starter compounds and one or more alkylene oxides are metered continuously in the presence of carbon dioxide into the reactor.

10. The process according to claim 1, wherein the DMC catalyst is metered continuously into the reactor, the resulting reaction mixture comprising polyethercarbonate polyols is removed continuously from the reactor and one or more H-functional starter compounds are metered continuously into the reactor.

11. The process according to claim 1, wherein the H-functional starter compounds are selected from the group comprising: monohydric alcohols, polyhydric alcohols, polybasic amines, polyhydric thiols, amino alcohols, thio alcohols, hydroxy esters, polyether polyols, polyester polyols, polyesterether polyols, polycarbonate polyols, polyethercarbonate polyols, polyethyleneimines, polyetheramines, polytetrahydrofurans, polytetrahydrofuranamines, polyetherthiols, polyacrylate polyols, castor oil, ricinoleic acid mono- or diglyceride, fatty acid monoglycerides, chemically modified fatty acid monoglycerides, chemically modified fatty acid diglycerides, chemically modified fatty acid triglycerides, fatty acid C.sub.1-C.sub.24-alkyl esters containing an average of at least 2 OH groups per molecule, and combinations of any thereof.

12. The process according to claim 1, wherein the DMC catalyst contains zinc hexacyanocobaltate(III), zinc hexacyanoiridate(III), zinc hexacyanoferrate(III) and/or cobalt(II) hexacyanocobaltate(III).

13. The process according to claim 1, further comprising: obtaining a polyethercarbonate polyol with a polydispersity index M.sub.w/M.sub.n, determined using gel permeation chromatography against polystyrene standards, of ≦1.22 and/or with a CO.sub.2 content, expressed as carbonate groups in the polyol, of ≧15 weight-% to ≦25 weight-%, based on the total weight of the polyol.

14. The process according to claim 1, wherein the concentration of free alkylene oxides during the reaction is >0 to ≦10 weight-%, based on the total weight of the reaction mixture.

15. The process according to claim 1, wherein the specific power input into the reaction mixture, expressed as Watts per liter (W/L), is ≧0.25 to ≦5.0.

Description

EXAMPLES

[0163] The present invention will be described further with reference to the following examples without wishing to be limited by them.

[0164] H-Functional Starter Compound (Starter) Used:

[0165] PET-1: bifunctional poly(oxypropylene) polyol with an OH number of 240 mg KOH/g.

[0166] Catalyst Used:

[0167] The DMC catalyst was prepared according to example 6 of WO 01/80994 A1.

[0168] Reactor Used:

[0169] The 970 ml pressurized reactor used in the examples had a height (internal) of 13.7 cm and an internal diameter of 9.5 cm. The reactor was fitted with an electric heating jacket (1000 watt maximum heating capacity). The counter cooling consisted of a serpentine-shaped dip tube of external diameter ¼ inch which projected into the reactor to within 27 mm of the bottom and through which cooling water at approx. 10° C. was passed. The water stream was switched on and off by means of a solenoid valve. The reactor was also fitted with an inlet tube of diameter ¼ inch and a temperature probe of diameter ½ inch, both of which projected into the reactor to within 17 mm of the bottom.

[0170] During the activation [step (β)] the electric heating jacket was on average at approx. 20% of its maximum heating capacity. Due to regulation, the heating capacity varied by ±5% of the maximum value. The onset of an increased evolution of heat in the reactor caused by the rapid conversion of propylene oxide during the activation of the catalyst [step (β)] was observed in a reduction of the heating capacity of the heating jacket, the switching-on of the counter cooling and, if appropriate, a temperature rise in the reactor. The onset of an evolution of heat in the reactor caused by the continuous conversion of propylene oxide during the reaction [step (γ)] led to a lowering of the capacity of the heating jacket to approx. 8% of the maximum value. Due to regulation, the heating capacity varied by ±5% of the maximum value.

[0171] The hollow shaft agitator used in the examples was one in which the gas was introduced into the reaction mixture through a hollow shaft of the agitator. The agitating body attached to the hollow shaft had four arms of diameter 50 mm and height 18 mm. Three gas outlets of diameter 3 mm were attached to each end of the arm. As the agitator rotated, a pressure reduction was created such that the gas above the reaction mixture (CO.sub.2 and optionally alkylene oxide) was aspirated and passed through the hollow shaft of the agitator into the reaction mixture.

[0172] Power Input:

[0173] The measurement of the power input (P) was not possible as the power losses at the gasket due to friction is higher than the actually applied power input in the reaction mixture for the used laboratory set-up. This is typical for the small laboratory scale. Therefore the specific power input P/V[Watts/liter] (short [W/L]) was calculated as follows for the reactor mentioned above. The calculation does not take into account any dispersed gas bubbles within the liquid reaction mixture. The amount of gas bubbles are difficult to predict or determine during an experiment. The specific power input calculation is based on a calibration curve determined without gasket with model liquid without gas input in the appropriate viscosity range.

[0174] For the turbulent flow range the specific power input is calculated in general with:

P/V=Ne*n.sup.3*n.sup.3*d.sup.5*density/V

[0175] (Ne=Newton number; n=agitator speed; d=agitator diameter (50 mm); density=950 kg/m.sup.3, V=filling volume (which is the volume of the reaction mixture at the end of the reaction)

[0176] The Newton number is a constant value in the turbulent flow range. It depends on the geometry of agitator and the internals of the stirred tank reactor such as baffles or cooling pipes. Values can be found for example in the chapter “Stirring” by M. Zlokarnik as part of Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag Weinheim.

[0177] The flow range is characterized by the calculated Reynolds number (Re) Re=n*d.sup.2*density/viscosity. In general the turbulent flow range is characterized by high Re numbers, the laminar flow range is characterized by low Re numbers. A transitional flow range exists between both flow ranges. The numerical values for Re for separation of the flow ranges depend on the exact geometry of agitator and the internals of the stirred tank reactor such as baffles ro cooling pipes. Values can be found for example in the chapter “Stirring” by M. Zlokarnik as part of Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH Verlag Weinheim.

[0178] In the above described laboratory set-up for the following examples the agitation resulted in the laminar and transitional flow range.

[0179] For the laminar flow range the specific power input is calculated with:

P/V=C*n.sup.2*d.sup.3*viscosity/V

[0180] In the laminar flow range the Newton number multiplied by the Reynolds number is a constant value (C).

[0181] (C=Re*Ne; Re=Reynolds number; C=0.36983*Re+1246.63301 measured during gasket free reactor set-up with model fluid with the help of torque measuring device on a rotating shaft; viscosity=0.1 Pa.Math.s, V=610 ml−filling volume of the reactor at the end of the batch)

[0182] The following table gives the calculation results for the specific power input of the above-mentioned reactor used in the reaction examples which are outlined further below.

TABLE-US-00001 N P/V Ne Re C [min.sup.−1] [W/liter] [—] [—] [—] 50 0.02 63.36 19.79 1253.95 100 0.07 31.86 39.58 1261.27 200 0.29 16.12 79.17 1275.91 262 0.50 12.39 103.71 1284.99 448 1.50 7.40 177.33 1312.22 628 3.00 5.38 248.58 1338.57 803 5.00 4.29 317.85 1364.19

[0183] Analysis of the Polyethercarbonate Polyols:

[0184] In addition to the cyclic propylene carbonate, the copolymerization produced a polyethercarbonate polyol containing on the one hand polycarbonate units:

##STR00002##

and on the other hand polyether units:

##STR00003##

[0185] The reaction mixture was characterized by .sup.1H-NMR spectroscopy and gel permeation chromatography:

[0186] The ratio of the amount of cyclic propylene carbonate to polyethercarbonate polyol (selectivity), the molar ratio of carbonate groups to ether groups in the polyethercarbonate polyol (ratio e/f) and the proportion of converted propylene oxide (C in mol %) were determined by .sup.1H-NMR spectroscopy. Each sample was dissolved in deuterated chloroform and measured on a Bruker spectrometer (AV400, 400 MHz). The relevant resonances in the .sup.1H-NMR spectrum (relative to TMS=0 ppm), which were used for integration are as follows: [0187] I1: 1.11-1.17: methyl group of polyether units; resonance area corresponds to three H atoms [0188] I2: 1.25-1.32: methyl group of polycarbonate units; resonance area corresponds to three H atoms [0189] I3: 1.45-1.49: methyl group of cyclic carbonate; resonance area corresponds to three H atoms [0190] I4: 2.95-2.99: CH group of free, unreacted propylene oxide; resonance area corresponds to one H atom

[0191] The molar ratio of the amount of cyclic propylene carbonate to carbonate units in the polyethercarbonate polyol (selectivity, g/e), the CO.sub.2-content (in weight-%) and the molar ratio of carbonate groups to ether groups in the polyethercarbonate polyol (ratio e/f) were calculated by taking the relative intensities into consideration, the values being calculated as follows:

[0192] Selectivity (g/e): molar ratio of the amount of cyclic propylene carbonate to carbonate units in the polyethercarbonate polyol

g/e=I3/I2

[0193] Selectivity (e/f): molar ratio of carbonate groups to ether groups in the polymer

e/f=I2/I1

[0194] CO.sub.2-content (weight-%): the amount of CO.sub.2 incorporated in the polyethercarbonate polyol

CO.sub.2 content (weight %)=[(I2.Math.44)/((I1.Math.58)+(I2.Math.102))].Math.100

[0195] The molar proportion of unreacted PO (UR.sub.PO) in the crude product:

UR.sub.PO=[(I4)/((I1/3)+(I2/3)+(I3/3)+(I4))].Math.100%

[0196] The number-average and weight-average molecular weights, M.sub.n and M.sub.w, of the polymers formed were determined by gel permeation chromatography (GPC) using the procedure according to DIN 55672-1: “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 molecular weight were used for calibration.

[0197] The OH number (hydroxyl number) was determined according to DIN 53240-2, except that N-methylpyrrolidone was used instead of THF/dichloromethane as solvent. Titration was carried out with 0.5 molar ethanolic KOH solution (end point detection by potentiometry). The test substance used was castor oil of certified OH number. The recorded unit “mg KOHg.sup.−1” refers to mg[KOH]/g[polyethercarbonate polyol].

[0198] The viscosity was determined on an Anton Paar Physica MCR 501 rheometer equipped with a D-CP/PP 7 (25 mm Cone-Plate) measuring system. The shear rate was increased from 0.01 to 1000 l/s in 60 increments, whereby a constant shear rate was applied for 10 seconds each. The viscosity was calculated as the average of the 60 measurements. The data measured were processed using Rheoplus version 3.40 software.

Example 1

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring speed of 803 rpm

[0199] [Step (α)]

[0200] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (803 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0201] [Step (β)]

[0202] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (803 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (803 rpm) each time.

[0203] [Step (γ)]

[0204] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 803 rpm at 100° C.

[0205] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0206] The stirring speed of 803 rpm corresponds to a specific power input of 5.0 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0207] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00002 Selectivity g/e 0.18 e/f 0.39 CO.sub.2 content weight % 17.7 Molecular weight (g/mol) M.sub.n 3793 M.sub.w 4552 Polydispersity index 1.20 OH number (mg KOH .Math. g.sup.−1) 63.3

[0208] Example 1 was repeated two times with respect to batch to batch consistency. The following table gives an overview of the results of the series of repeated experiments:

TABLE-US-00003 Specific OH no. power input Stirring CO.sub.2 content M.sub.n (mg Example 1 (W/L) (rpm) g/e e/f [weight %] (g/mol) PDI KOH .Math. g.sup.−1) Batch 1 5.0 803 0.18 0.39 17.7 3793 1.20 63.3 Batch 2 5.0 803 0.17 0.42 18.4 3792 1.17 62.7

Example 2

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 628 rpm

[0209] [Step (α)]

[0210] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (628 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0211] [Step (β)]

[0212] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (628 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (628 rpm) each time.

[0213] [Step (γ)]

[0214] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stored for 2 h setting a stirring speed of 628 rpm at 100° C.

[0215] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0216] The stirring speed of 628 rpm corresponds to a specific power input of 3.0 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0217] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00004 Selectivity g/e 0.19 e/f 0.40 CO.sub.2 content weight % 17.2 Molecular weight (g/mol) M.sub.n 3297 M.sub.w 3956 Polydispersity index 1.20 OH number (mg KOH .Math. g.sup.−1) 63.6

Example 3

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 448 rpm

[0218] [Step (α)]

[0219] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (448 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0220] [Step (β)]

[0221] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (448 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (448 rpm) each time.

[0222] [Step (γ)]

[0223] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 448 rpm at 100° C.

[0224] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0225] The stirring speed of 448 rpm corresponds to a specific power input of 1.5 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0226] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00005 Selectivity g/e 0.18 e/f 0.40 CO.sub.2 content weight % 17.8 Molecular weight (g/mol) M.sub.n 3295 M.sub.w 3921 Polydispersity index 1.19 OH number (mg KOH .Math. g.sup.−1) 63.1

Example 4

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 262 rpm

[0227] [Step (α)]

[0228] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (262 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0229] [Step (β)]

[0230] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (262 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (262 rpm) each time.

[0231] [Step (γ)]

[0232] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 262 rpm at 100° C.

[0233] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0234] The stirring speed of 262 rpm corresponds to a specific power input of 0.50 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0235] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00006 Selectivity g/e 0.17 e/f 0.38 CO.sub.2 content weight % 17.4 Molecular weight (g/mol) M.sub.n 3243 M.sub.w 3924 Polydispersity index 1.21 OH number (mg KOH .Math. g.sup.−1) 63.0

Example 5

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 200 rpm

[0236] [Step (α)]

[0237] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (200 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0238] [Step (β)]

[0239] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (200 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (200 rpm) each time.

[0240] [Step (γ)]

[0241] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 200 rpm at 100° C.

[0242] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0243] The stirring speed of 200 rpm corresponds to a specific power input of 0.29 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0244] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00007 Selectivity g/e 0.18 e/f 0.38 CO.sub.2 content weight % 17.2 Molecular weight (g/mol) M.sub.n 3189 M.sub.w 3826 Polydispersity index 1.20 OH number (mg KOH .Math. g.sup.−1) 63.6

Example 6

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 100 rpm

[0245] [Step (α)]

[0246] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (100 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0247] [Step (β)]

[0248] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (100 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (100 rpm) each time.

[0249] [Step (γ)]

[0250] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 100 rpm at 100° C.

[0251] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0252] The stirring speed of 100 rpm corresponds to a specific power input of 0.07 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0253] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00008 Selectivity g/e 0.17 e/f 0.37 CO.sub.2 content weight % 17.1 Molecular weight (g/mol) M.sub.n 3113 M.sub.w 3797 Polydispersity index 1.22 OH number (mg KOH .Math. g.sup.−1) 63.3

Comparative example 7

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Strongly Dried DMC Catalyst Setting a Stirring Speed of 50 rpm

[0254] [Step (α)]

[0255] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 130° C. and the mixture was agitated for 30 min (50 rpm) at 130° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0256] [Step (β)]

[0257] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (50 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (50 rpm) each time.

[0258] [Step (γ)]

[0259] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 50 rpm at 100° C.

[0260] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0261] The stirring speed of 50 rpm corresponds to a specific power input of 0.02 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0262] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00009 Selectivity g/e 0.27 e/f 0.38 CO.sub.2 content weight % 17.2 Molecular weight (g/mol) M.sub.n 3043 M.sub.w 4412 Polydispersity index 1.45 OH number (mg KOH .Math. g.sup.−1) 69.1

[0263] Comparison

[0264] The following table gives an overview of the results of examples 1 to 7:

TABLE-US-00010 Specific OH no. power input Stirring CO.sub.2 content M.sub.n (mg Example (W/L) (rpm) g/e e/f [weight %] (g/mol) PDI KOH .Math. g.sup.−1) 1 5.0 803 0.18 0.39 17.7 3793 1.20 63.3 2 3.0 628 0.19 0.40 17.2 3297 1.20 63.6 3 1.5 448 0.18 0.40 17.8 3295 1.19 63.1 4 0.5 262 0.17 0.38 17.4 3243 1.21 63.0 5 0.29 200 0.18 0.38 17.2 3189 1.20 63.6 6 0.07 100 0.17 0.37 17.1 3113 1.22 63.3 7 (Comp.) 0.02 50 0.27 0.38 17.2 3043 1.45 69.1 Comp.: Comparative Example

[0265] The ratio g/e is a measure of the selectivity of cyclic carbonate formation to the carbonate units in linear polyethercarbonate polyols: the smaller the value of this ratio, the lower the proportion of cyclic carbonate formed during the reaction. A comparison of examples 1-6 with comparative example 7 shows that the polyethercarbonate polyol was obtained in high selectivity, when the reaction was performed with a specific power input in the range from 0.07 to 5.0 W/L. Similarly, a comparison of example 1-6 with comparative example 7 shows that the polyethercarbonate polyol was obtained with a narrow polydispersity index when the reaction (copolymerization) was performed with a specific power input in the range from 0.07 to 5.0 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

Example 8

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 803 rpm

[0266] [Step (α)]

[0267] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (803 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0268] [Step (β)]

[0269] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (803 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (803 rpm) each time.

[0270] [Step (γ)]

[0271] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 803 rpm at 100° C.

[0272] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0273] The stirring speed of 803 rpm corresponds to a specific power input of 5.0 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0274] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00011 Selectivity g/e 0.12 e/f 0.40 CO.sub.2 content weight % 18.0 Molecular weight (g/mol) M.sub.n 3276 M.sub.w 4226 Polydispersity index 1.29 OH number (mg KOH .Math. g.sup.−1) 59.9

Example 9

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 628 rpm

[0275] [Step (α)]

[0276] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (628 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0277] [Step (β)]

[0278] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (628 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (628 rpm) each time.

[0279] [Step (γ)]

[0280] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 628 rpm at 100° C.

[0281] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0282] The storing speed of 628 rpm corresponds to a specific power input of 3.0 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0283] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00012 Selectivity g/e 0.12 e/f 0.44 CO.sub.2 content weight % 18.7 Molecular weight (g/mol) M.sub.n 3705 M.sub.w 4631 Polydispersity index 1.25 OH number (mg KOH .Math. g.sup.−1) 58.9

Example 10

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 448 rpm

[0284] [Step (α)]

[0285] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (448 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0286] [Step (β)]

[0287] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (448 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (448 rpm) each time.

[0288] [Step (γ)]

[0289] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 448 rpm at 100° C.

[0290] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0291] The stirring speed of 448 rpm corresponds to a specific power input of 1.5 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0292] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00013 Selectivity g/e 0.08 e/f 0.44 CO.sub.2 content weight % 18.9 Molecular weight (g/mol) M.sub.n 3470 M.sub.w 4580 Polydispersity index 1.32 OH number (mg KOH .Math. g.sup.−1) 56.9

Example 11

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 262 rpm

[0293] [Step (α)]

[0294] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (262 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0295] [Step (β)]

[0296] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (262 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (262 rpm) each time.

[0297] [Step (γ)]

[0298] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 262 rpm at 100° C.

[0299] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0300] The storing speed of 262 rpm corresponds to a specific power input of 0.5 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0301] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00014 Selectivity g/e 0.12 e/f 0.39 CO.sub.2 content weight % 17.7 Molecular weight (g/mol) M.sub.n 4518 M.sub.w 6415 Polydispersity index 1.42 OH number (mg KOH .Math. g.sup.−1) 60.1

Example 12

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 200 rpm

[0302] [Step (α)]

[0303] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (200 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0304] [Step (β)]

[0305] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (200 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (200 rpm) each time.

[0306] [Step (γ)]

[0307] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 200 rpm at 100° C.

[0308] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0309] The stirring speed of 200 rpm corresponds to a specific power input of 0.29 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0310] The conversion of the propylene oxide was shown to be complete by .sup.1H-NMR spectroscopic analysis of the reaction mixture.

TABLE-US-00015 Selectivity g/e 0.10 e/f 0.41 CO.sub.2 content weight % 18.0 Molecular weight (g/mol) M.sub.n 4114 M.sub.w 6047 Polydispersity index 1.47 OH number (mg KOH .Math. g.sup.−1) 58.6

Example 13

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 100 rpm

[0311] [Step (α)]

[0312] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (100 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0313] [Step (β)]

[0314] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (100 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (100 rpm) each time.

[0315] [Step (γ)]

[0316] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 100 rpm at 100° C.

[0317] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0318] The stirring speed of 100 rpm corresponds to a specific power input of 0.07 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0319] The molar proportion of unreacted PO (UR.sub.PO) in the crude product was 4.81 mol %.

TABLE-US-00016 Selectivity g/e 0.14 e/f 0.23 CO.sub.2 content weight % 12.4 Molecular weight (g/mol) M.sub.n 3075 M.sub.w 4643 Polydispersity index 1.51 OH number (mg KOH .Math. g.sup.−1) 68.7

Comparative Example 14

Copolymerization of Propylene Oxide and CO.SUB.2 .with a Weakly Dried DMC Catalyst Setting a Stirring Speed of 50 rpm

[0320] [Step (α)]

[0321] A mixture of DMC catalyst (116 mg) and PET-1 (135 g) was placed in a 970 ml pressure reactor equipped with a hollow shaft agitator. The reactor was closed and the pressure inside was reduced to 5 mbar for five minutes. The reactor pressure was then regulated to 50 mbar by passing a gentle stream of Ar and simultaneously removing the gas with a pump. The reactor was heated to 100° C. and the mixture was agitated for 30 min (50 rpm) at 100° C. under reduced pressure (50 mbar) and a gentle stream of Ar.

[0322] [Step (β)]

[0323] A pressure of 50 bar of CO.sub.2 was applied, causing the reactor temperature to fall slightly. The temperature was readjusted to 130° C. and the reactor pressure was kept at 50 bar during the subsequent steps by feeding CO.sub.2. Subsequently, a 1.sup.st portion of propylene oxide (13 g) was added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (50 rpm). A further two portions (13 g each) of propylene oxide were added into the reactor with an HPLC pump (6.5 mL/min) and the reaction mixture was stirred for 20 min (50 rpm) each time.

[0324] [Step (γ)]

[0325] After cooling to 100° C., a further 301 g of propylene oxide were added with an HPLC pump (6.5 mL/min), while the CO.sub.2 pressure was maintained at 50 bar throughout the reaction by feeding CO.sub.2. The mixture was stirred for 2 h setting a stirring speed of 50 rpm at 100° C.

[0326] The reaction was ended by subsequently cooling the reactor with ice-cold water, the excess pressure was removed and the resulting product was analysed.

[0327] The stirring speed of 50 rpm corresponds to a specific power input of 0.02 W/L after the volume of the reaction mixture has obtained a constant value of 610 ml.

[0328] The molar proportion of unreacted PO (UR.sub.PO) in the crude product was 2.87 mol %.

TABLE-US-00017 Selectivity g/e 0.54 e/f 0.07 CO.sub.2 content weight % 5.0 Molecular weight (g/mol) M.sub.n 2136 M.sub.w 3887 Polydispersity index 1.82 OH number (mg KOH .Math. g.sup.−1) 109.6

[0329] Comparison

[0330] The following table gives an overview of the results of examples 8 to 14:

TABLE-US-00018 Specific OH No. power input Stirring rate CO.sub.2 content M.sub.n (mg Example (W/L) (rpm) g/e e/f (weight %) (g/mol) PDI KOH .Math. g.sup.−1)  8 5.0 803 0.12 0.40 18.0 3276 1.29 59.9  9 3.0 628 0.12 0.44 18.7 3705 1.25 58.9 10 1.5 448 0.08 0.44 18.9 3470 1.32 56.9 11 0.5 262 0.12 0.39 17.7 4518 1.42 60.1 12 0.29 200 0.10 0.41 18.0 4114 1.47 58.6 13 0.07 100 0.14 0.23 12.4 3075 1.51 68.7 14 (Comp.) 0.02 50 0.54 0.07 5.0 2136 1.82 109.6 Comp.: Comparative Example

[0331] The ratio g/e is a measure of the selectivity of cyclic carbonate formation to the carbonate units in linear polyethercarbonate polyols: the smaller the value of this ratio, the lower the proportion of cyclic carbonate formed during the reaction. A comparison of examples 8-13 with comparative example 14 shows that the polyethercarbonate polyol was obtained in high selectivity, when the reaction was performed with a specific power input in the range from 0.07 to 5.0 W/L. Similarly, a comparison of examples 8-13 with comparative example 14 shows that the polyethercarbonate polyol was obtained with a narrow polydispersity index, when the reaction (copolymerization) was performed with a specific power input in the range from 0.07 to 5.0 W/L after the volume of the reaction mixture has obtained a constant value.

[0332] Comparison of examples 8 to 12 with examples 1 to 5 shows that a weakly dried DMC catalyst provides a higher selectivity to the polyethercarbonate polyol (lower value of ratio g/e) and a higher CO.sub.2 content in the polyethercarbonate polyol (higher value of ratio e/f).

[0333] Another comparison between the results of examples 12, 13 and 14 is shown in the molecular weight distributions of FIG. 1. Examples 12 (200 rpm) and 13 (100 rpm) exhibit essentially the same distribution with a polydispersity index of ca. 1.5, whereas the curve corresponding to comparative example 14 (50 rpm) documents a polydispersity index of ca. 1.8. Furthermore a so-called high molecular weight tail (HMWT) is present in the sample according to the comparative example. This HMWT is consisting of high molecular weight polyethercarbonate portions present in the sample. These high molecular portions are undesired because they impair the final product properties (e.g. by increasing product viscosity) and are suspected to unfavourably affect processing of the polyethercarbonate polyols to polyurethane materials(e.g. polyurethane flexible foams).