Process for the continuous production of polyether polyols

Abstract

This invention relates to a process for the continuous production of polyether polyols, polyether polyols produced by the inventive continuous process and their use in polyurethane applications.

Claims

1. A process for continuous production of polyether alcohols, the process comprising: (a) continuously adding at least one aromatic amine (AA) at one dosing point D1 to an arrangement R1 comprising at least one plug-flow reactor (PFR) and/or a cascade of at least two continuously stirred tank reactors (CSTRs), and reacting with at least one alkylene oxide 1 (AO1) which is continuously dosed into the arrangement R1 at one or more dosing points D2 to generate an intermediate (I); and subsequently (b) continuously transferring the intermediate (I) into another arrangement R2 comprising at least one further reactor, and reacting with at least one alkylene oxide 2 (AO2) in the presence of at least one amine compound (AC), wherein at least one of the at least one amine compounds AC is selected from the group consisting of imidazoles, wherein the transferring (b) is initiated when the amount of free aromatic amine (AA) in the adding (a), as determined by gas chromatography, is less than 2% by weight, in relation to the total amount of the intermediate.

2. The process according to claim 1, wherein the arrangement R1 in the adding (a) consists of a cascade of two continuously stirred tank reactors (CSTRs).

Description

(1) Some drawings are added to show certain preferred embodiments of the present invention. In these drawings, AO denotes alkylene oxide, AA means aromatic amine, I denotes intermediate product I, and M stands for a motor (stirrer motor).

(2) FIG. 1 illustrates certain embodiments of the present invention wherein at least two continuously stirred tank reactors (CSTRs), but no plug-flow reactors (PFRs) are used for step (a) of the process according to claim 1.

(3) FIG. 2 illustrates certain embodiments of the present invention wherein at least one PFR, but no CSTRs are used for step (a) of the process according to claim 1.

(4) FIG. 3 illustrates certain embodiments of the present invention wherein a combination of PFRs and CSTRs are used for step (a) of the process according to claim 1.

(5) The following examples illustrate some aspects of the present invention. They are not intended to limit the scope of the claims in any way.

(6) In the following examples, the residual TDA content was measured as follows.

(7) The content of TDA was determined by gas chromatography. An Agilent 7890 gas chromatograph equipped with a split/splitless injector and a flame ionization detector (FID) was used. The GC conditions are described below: Column: DB17, 30 m0.25 mm ID0.25 m film thickness Carrier gas: helium Flow: constant, 1.9 ml/min Split flow: 73 ml/min Injection volume: 1 l Inlet temperature: 250 C. Detector temperature: 300 C. Oven program: initial temperature: 75 C. (4 min hold) first ramp: 150 C. (2 min hold, rate: 10/min) second ramp: 250 C. (30 min hold, rate: 10/min)

(8) A nine point external standard calibration was made for each TDA isomer (2,3-TDA,3,4-TDA,2,4-TDA and 2,6-TDA).

(9) For each measurement 600 mg of standard solution or of sample were dissolved in 2 ml methanol.

(10) The concentration of standard solutions was in the range of 5-1000 ppm per TDA isomer.

(11) The amount of free PO in the reactor is determined by measuring the density of the reactive mixture with a Coriolis mass flow meter, calibrated with an unreactive solution; in addition, the concentration is measured by NIR (near infrared) measurements, calibrated with an unreactive solution.

1) COMPARATIVE EXAMPLE

(12) Vicinal Toluenediamine (vTDA) was continuously pumped to a continuously stirred tank reactor (CSTR) at 140 C. with a residence time of 1.5 h. 2.7 mol Propylene Oxide (PO) per mol vTDA were added continuously to the reactor. Free PO in the CSTR was 4.9 wt %. The autocatalytic intermediate had a residual vTDA content of 6.5 wt %. The intermediate was pumped to a CSTR at 140 C. with a residence time of 6 h and a plug flow reactor (PFR) with a residence time of 2 h. Imidazole in watery solution as a catalyst and further 3.6 mol PO per mol vTDA were added to the CSTR. Free PO in the CSTR was 5.2 wt %. The final polyol had an OH value of 423 mgKOH/g and a residual vTDA content of 0.17 wt %.

2) COMPARATIVE EXAMPLE

(13) vTDA was continuously pumped to a CSTR at 150 C. with a residence time of 2.6 h. 2.7 mol PO per mol vTDA were added continuously to the reactor. Free PO in the CSTR was 3.5 wt %. The autocatalytic intermediate had a residual vTDA content of 6.8 wt %. The intermediate was pumped to a CSTR at 140 C. with a residence time of 6 h and a PFR with a residence time of 2 h. Imidazole in watery solution as a catalyst and further 3.6 mol PO per mol vTDA were added to the CSTR. Free PO in the CSTR was 4.5 wt %. The final polyol had an OH value of 427 mgKOH/g and a residual vTDA content of 0.23 wt %.

3) INVENTIVE EXAMPLE

(14) vTDA is continuously pumped to a plug flow reactor at 110 C. with a residence time of 1.3 h. 2.35 mol PO per mol vTDA are added continuously at 7 dosing points in such a way that free PO in the reactor never exceeds 15 wt %. Free PO at the exit of the PFR is not detectable. The autocatalytic intermediate has a free vTDA content of 1.5 wt %. The intermediate is pumped to a cascade of 2 CSTR at 130 C. with a residence time of 4 h and 2 h and a PFR with a residence time of 4 h. Imidazole in watery solution as a catalyst and further 3.6 mol PO per mol vTDA are added to the first CSTR. Free PO in the first CSTR is 10 wt % and in the second CSTR 6 wt %. The final polyol has an OH value of 416 mgKOH/g and a residual vTDA content of 0.08 wt %. It is thus below the limit of 1000 ppm.

4) INVENTIVE EXAMPLE

(15) vTDA is continuously pumped to a plug flow reactor at 130 C. with a residence time of 0.9 h. 2.55 mol PO per mol vTDA are added continuously at 5 dosing points in such a way that free PO in the reactor never exceeds 18 wt %. Free PO at the exit of the PFR is not detectable. The autocatalytic intermediate has a free vTDA content of 0.6 wt %. The intermediate is pumped to a cascade of 2 CSTR at 130 C. with a residence time of 4 h and 2 h and a PFR with a residence time of 4 h. Imidazole in watery solution as a catalyst and further 4 mol PO per mol vTDA are added to the first CSTR. Free PO in the first CSTR is 10 wt % and in the second CSTR 6 wt %. The final polyol has an OH value of 389 mgKOH/g and a residual vTDA content of 0.03 wt %. It is thus below the limit of 1000 ppm.

5) INVENTIVE EXAMPLE

(16) vTDA is continuously pumped to a plug flow reactor at 150 C. with a residence time of 1 h. 2.4 mol PO per mol vTDA are added continuously at 5 dosing points in such a way that free PO in the reactor never exceeds 15 wt %. Free PO at the exit of the PFR is not detectable. The autocatalytic intermediate has a free vTDA content of 1 wt %. The intermediate was pumped to a cascade of 2 CSTR at 130 C. with a residence time of 4 h and 2 h and a PFR with a residence time of 4 h. Imidazole in watery solution as a catalyst and further 3.9 mol PO per mol vTDA were added to the first CSTR. Free PO in the first CSTR was 9.5 wt % and in the second CSTR 5.5 wt %. The final polyol had an OH value of 410 mgKOH/g and a residual vTDA content of 0.04 wt %. It was thus below the limit of 1000 ppm.

6) INVENTIVE EXAMPLE

(17) vTDA is continuously pumped to a cascade of 3 CSTR at 140 C. with a residence time of 0.25 h each and a PFR with 0.3 h residence time. 2.7 mol PO per mol vTDA are added equally split between the three CSTR. Free PO in the reactor never exceeds 3 wt %. Free PO at the exit of the PFR is not detectable. The autocatalytic intermediate has a free vTDA content of 1 wt %. The intermediate is pumped to a cascade of 2 CSTR at 130 C. with a residence time of 4 h and 2 h and a PFR with a residence time of 4 h. Imidazole in watery solution as a catalyst and further 3.9 mol PO per mol vTDA are added to the first CSTR. Free PO in the first CSTR is 10 wt % and in the second CSTR 6 wt %. The final polyol has an OH value of 382 mgKOH/g and a residual vTDA content of 0.03 wt %. It is thus below the limit of 1000 ppm.

7) INVENTIVE EXAMPLE

(18) vTDA is continuously pumped to a cascade of 3 CSTR at 140 C. with a residence time of 0.25 h each and a PFR with 0.3 h residence time. 2.2 mol PO and 0.5 mol Ethylene Oxide (EO) per mol vTDA are added equally split between the three CSTR. Free Alkylene Oxide (AO) in the reactor never exceeds 2.5 wt %. Free AO at the exit of the PFR is not detectable. The autocatalytic intermediate has a free vTDA content of 0.9 wt %. The intermediate is pumped to a cascade of 2 CSTR at 130 C. with a residence time of 4 h and 2 h and a PFR with a residence time of 4 h. Imidazole in watery solution as a catalyst and further 3.3 mol PO per mol vTDA are added to the first CSTR. Free PO in the first CSTR is 8 wt % and in the second CSTR 4 wt %. The final polyol has an OH value of 427 mgKOH/g and a residual vTDA content of 0.04 wt %. It is thus below the limit of 1000 ppm.