METHOD FOR PRODUCING DOUBLE METAL CYANIDE CATALYSTS

Abstract

The present invention relates to a process for preparing a double metal cyanide catalyst (DMC) comprising the reaction of an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complex ligand and a complex-forming component, to form a dispersion, wherein the reaction is effected using a mixing nozzle and wherein the process temperature of the dispersion during the reaction is between 26° C. and 49° C. The subject matter of the invention further encompasses double metal cyanide catalysts (DMC) obtainable in accordance with the process according to the invention and also the use of the DMC catalysts for the preparation of polyoxyalkylene polyols.

Claims

1. A process for preparing a double metal cyanide catalyst (DMC) comprising i) reacting an aqueous solution of a cyanide-free metal salt, an aqueous solution of a metal cyanide salt, an organic complex ligand and a complex-forming component, in a first step to form a dispersion; wherein the reaction is effected using a mixing nozzle; and wherein the dispersion during the reaction is at a process temperature of between 26° C. and 49° C.

2. The process as claimed in claim 1, wherein said mixing nozzle comprises a jet disperser.

3. The process as claimed in claim 2, wherein said jet disperser has a pressure drop of 0.1 to 100 bar.

4. The process as claimed in claim 1, wherein said complex-forming component comprises a polyether.

5. The process as claimed in claim 4, wherein said polyether has a number-average molecular weight of ≥500 g/mol, with the number-average molecular weight being calculated from the OH number.

6. The process as claimed in claim 5, wherein said polyether comprises a polyether polyol.

7. The process as claimed in claim 6, wherein said polyether polyol comprises a poly(oxypropylene) polyol having a number-average molecular weight of ≥500 g/mol, with the number-average molecular weight being calculated from the OH number.

8. The process as claimed in claim 7, wherein said poly(oxypropylene) polyol comprises a poly(oxypropylene) diol and/or a poly(oxypropylene) triol having a number-average molecular weight of 700 g/mol to 4000 g/mol, with number-average molecular weight being calculated from the OH number.

9. The process as claimed in claim 1, wherein the process temperature in step i) 28° C. to 47° C.

10. The process as claimed in claim 1, additionally comprising (ii) separating the solid off from the dispersion obtained from (i) in a second step.

11. The process as claimed in claim 10, additionally comprising (iii) the separated solid from step (ii) with an aqueous solution of an organic complex ligand by means of a filtercake washing operation.

12. The process as claimed in claim 11, additionally comprising (iv) drying the solid obtained in (iii) in a fourth step.

13. The process as claimed in claim 11, wherein (ii) and/or (iii) are performed in a filter press.

14. The process as claimed in 12, wherein steps (ii), (iii) and/or (iv) are performed in a heatable filter press.

15. A double metal cyanide catalyst (DMC) obtainable by the process in accordance with claim 1.

16. A process for the preparation of polyoxyalkylene polyols comprising reacting a starter compound with an alkylene oxide in the presence of a double metal cyanide catalyst (DMC) as claimed in claim 1.

Description

EXAMPLES

[0109] OH numbers were determined according to the method of DIN 53240. Viscosities were determined by rotational viscometer (Physica MCR 51, Anton Paar) according to the method of DIN 53018.

[0110] Preparation of the DMC Catalysts:

Example 1 (Comparative)

[0111] The catalyst was prepared using an apparatus as per FIG. 4 from WO 01/39883 A1.

[0112] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated a solution of 258 g of zinc chloride in 937 g of distilled water and 135 g of tert-butanol at 25° C. (determined in the vessel D2 in FIG. 4 of WO 01/39883 A1). To this was metered a solution of 26 g of potassium hexacyanocobaltate in 332 g of distilled water. The pressure drop in the jet disperser was 2.9 bar. Subsequently, the dispersion formed was circulated at 25° C. and a pressure drop in the jet disperser of 2.9 bar for 60 min. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 (PPG-1000) was metered in and the dispersion was then circulated at 25° C. and a pressure drop in the jet disperser of 2.9 bar for 80 min.

[0113] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3, and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000. The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h.

Example 2

[0114] Example 2 was carried out analogously to example 1 (comparative) with the difference that the DMC dispersion was prepared at 30° C. instead of 25° C.

Example 3

[0115] Example 3 was carried out analogously to example 1 (comparative) with the difference that the DMC dispersion was prepared at 35° C. instead of 25° C.

Example 4

[0116] Example 4 was carried out analogously to example 1 (comparative) with the difference that the DMC dispersion was prepared at 40° C. instead of 25° C.

Example 5 (Comparative)

[0117] Example 5 (comparative) was carried out analogously to example 1 (comparative) with the difference that the DMC dispersion was prepared at 50° C. instead of 25° C.

Example 6 (Comparative)

[0118] Example 6 (comparative) was carried out analogously to example 1 (comparative) with the difference that the DMC dispersion was prepared at 70° C. instead of 25° C.

Example 7 (Comparative)

[0119] The catalyst was prepared using an apparatus as per FIG. 4 from WO 01/39883 A1.

[0120] In a loop reactor containing a jet disperser as per FIG. 2 from WO 01/39883 A1 having one bore (diameter 0.7 mm) was circulated a solution of 258 g of zinc chloride in 937 g of distilled water and 135 g of tert-butanol at 25° C. To this was metered a solution of 26 g of potassium hexacyanocobaltate in 332 g of distilled water. The pressure drop in the jet disperser was 5.0 bar. Subsequently, the dispersion formed was circulated at 25° C. and a pressure drop in the jet disperser of 5.0 bar for 60 min. Thereafter, a mixture of 5.7 g of tert-butanol, 159 g of distilled water and 27.6 g of polypropylene glycol 1000 was metered in and the dispersion was then circulated at 25° C. and a pressure drop in the jet disperser of 5.0 bar for 80 min.

[0121] 230 g of the dispersion obtained were filtered in a pressure suction filter with filter area 20 cm.sup.3, and then washed with a mixture of 82 g of tert-butanol, 42.3 g of distilled water and 1.7 g of polypropylene glycol 1000. The washed filtercake was squeezed mechanically between two strips of filter paper and finally dried at 60° C. under high vacuum at about 0.05 bar (absolute) for 2 h.

Example 8

[0122] Example 8 was carried out analogously to example 7 (comparative) with the difference that the DMC dispersion was prepared at 30° C. instead of 25° C.

Example 9

[0123] Example 9 was carried out analogously to example 7 (comparative) with the difference that the DMC dispersion was prepared at 35° C. instead of 25° C.

Example 10

[0124] Example 10 was carried out analogously to example 7 (comparative) with the difference that the DMC dispersion was prepared at 40° C. instead of 25° C.

Example 11 (Comparative)

[0125] Example 11 (comparative) was carried out analogously to example 7 (comparative) with the difference that the DMC dispersion was prepared at 50° C. instead of 25° C.

Example 12 (Comparative)

[0126] Example 12 (comparative) was carried out analogously to example 7 (comparative) with the difference that the DMC dispersion was prepared at 70° C. instead of 25° C.

Example 13 (Comparative)

[0127] Example 13 (comparative) was carried out analogously to example 3 with the difference that for the preparation of the DMC catalyst the complex-forming component polypropylene glycol 1000 was replaced with cholic acid sodium salt.

[0128] Catalyst Test (“8K Diol Stressed Test”):

[0129] The DMC catalysts were tested in the so-called “8K diol stressed test”. Here, a polypropylene glycol having a calculated OH number=14 mg KOH/g, that is to say molecular weight=8000 g/mol (“8K diol”) was prepared proceeding from a bifunctional polypropylene glycol starter having an OH number=147 mg KOH/g (“Arcol Polyol 725” from Covestro) with a short propylene oxide metering time (30 minutes). The decisive evaluation criterion for the catalyst quality/activity in this test is the viscosity of the polyol obtained, with a DMC catalyst of increased quality/activity leading to a lower 8K diol viscosity.

[0130] General Implementation:

[0131] A 1 liter stainless steel reactor was initially charged with 75 g of a bifunctional polypropylene glycol starter (OH number=147 mg KOH/g) and 30.7 mg of DMC catalyst. After changing 5 times between nitrogen and vacuum between 0.1 and 3.0 bar (absolute), the reactor contents were heated to 130° C. with stirring (800 rpm). The mixture was then stripped with nitrogen for 30 min at 130° C. and 100 mbar (absolute). 7.5 g of propylene oxide were then added at 130° C. and 100 mbar (absolute) to activate the catalyst. The catalyst activation manifested in an accelerated pressure drop in the reactor. After the catalyst had been activated, the remaining propylene oxide (685.7 g) was metered in within 30 min at 130° C. with stirring (800 rpm). After a post-reaction time of 30 min at 130° C., volatile constituents were distilled off under reduced pressure (<10 mbar) at 90° C. for 30 min. The product was then cooled down to room temperature and removed from the reactor.

[0132] The OH number and viscosity (25° C.) of the product obtained were measured. In the event of a deviation of the measured OH number from the calculated OH number (14 mg KOH/g), a “corrected viscosity” was determined from the measured viscosity using the following formula:

corrected viscosity (25° C.)=measured viscosity (25° C.)+659*(OHN−14)

[0133] The results of the catalyst tests in the “8K diol stressed test” are summarized in table 1.

TABLE-US-00001 TABLE 1 Pressure OH Viscosity Viscosity Catalyst DMC at the jet Temper- number 25° C./ 25° C./ test/ catalyst/ disp. ature [mg measured corrected Example Example [p] [° C.] KOH/g] [mPas] [mPas] 14  1 2.9 25 13.6 4595 4331 (comp.) (comp.) 15  2 2.9 30 13.8 4125 3993 16  3 2.9 35 13.8 4305 4173 17  4 2.9 40 13.8 4310 4178 18  5 2.9 50 13.8 4525 4393 (comp.) (comp.) 19  6 2.9 70 13.8 5305 5173 (comp.) (comp.) 20  7 5.0 25 13.9 4500 4434 (comp.) (comp.) 21  8 5.0 30 13.9 4190 4124 22  9 5.0 35 13.9 4120 4054 23 10 5.0 40 13.7 4495 4297 24 11 5.0 50 13.7 4610 4412 (comp.) (comp.) 25 12 5.0 70 13.7 5385 5187 (comp.) (comp.) 26 13 2.9 35 13.9 5895 5829 (comp.) (comp.)* *Cholic acid sodium salt instead of polypropylene glycol 1000 as the complex-forming component

[0134] The results show that, both with a pressure drop in the jet disperser of 2.9 bar and of 5.0 bar, the lowest viscosity values (corrected) in the “8K diol stressed test” are obtained when the temperature during the preparation of the DMC dispersion is 30-40° C.

[0135] In addition, it is apparent that a markedly higher viscosity (corrected) is obtained if the complex-forming component polypropylene glycol 1000 is replaced with cholic acid sodium salt in the preparation of the DMC catalyst.