SEMI-BATCH ALKYLENE OXIDE POLYMERIZATION PROCESS

Abstract

Polyether polyols are prepared by polymerizing one or more alkylene oxides in the presence of a Lewis acid polymerization catalyst. The reaction is performed by forming a starting reaction mixture containing a starter and catalyst. The alkylene oxide and more catalyst are then added simultaneously. continuously and separately under reaction conditions that include a temperature of at least 75 C.

Claims

1. An alkylene oxide polymerization process comprising the steps of a) forming a starting reaction mixture comprising 1) a starter having at least one functional group capable of being oxyalkylated and 2) at least one Lewis acid alkylene oxide polymerization catalyst, the mixture being at a temperature of at least 75 C.; b) while maintaining a temperature of at least 75 C., continuously and simultaneously adding to the starting reaction mixture, in separate streams, 3) at least one alkylene oxide and 4) additional Lewis acid alkylene oxide polymerization catalyst, combining the separate streams with the starting reaction mixture and polymerizing the alkylene oxide to produce a polyether corresponding to a reaction of the at least one alkylene oxide with the starter, wherein step b) is performed without removal of the polyether product; and optionally c) discontinuing simultaneously adding the alkylene oxide and additional Lewis acid alkylene oxide polymerization catalyst streams; d) after step c), optionally heating the reaction mixture to at least 75 C. to continue polymerizing alkylene oxide that remains in the reaction mixture at the conclusion of step b) and e) recovering a polyether product.

2. The alkylene oxide polymerization process of claim 1, wherein the at least one Lewis acid alkylene oxide polymerization catalyst includes at least one compound represented by the structure:
M(R.sup.1).sub.1(R.sup.3).sub.1(R.sup.8).sub.1(R.sup.4).sub.0 or 1 wherein M is boron, aluminum, indium, bismuth or erbium, R.sup.1 is a fluoroalkyl-substituted phenyl group, R.sup.2 and R.sup.3 each are a fluoroalkyl-substituted phenyl group, a fluoro-substituted phenyl group, a chloro-substituted phenyl group, or a fluoro- and chloro-substituted phenyl group, and R.sup.4 is a functional group or functional polymer group.

3. The alkylene oxide polymerization process of claim 2, wherein R.sup.1, R.sup.2 and R.sup.3 are not all the same.

4. The alkylene oxide polymerization process of claim 2, wherein R.sup.1, R.sup.2 and R.sup.3 are all the same.

5. The alkylene oxide polymerization process of claim 1 wherein the reaction mixture formed in step a) is formed by combining the starter with 50 to 2000 parts by weight of the at least one Lewis acid alkylene oxide polymerization catalyst per million parts by weight of the starter.

6. The alkylene oxide polymerization process of claim 1 wherein the reaction mixture formed in step a) is formed by combining the starter with 100 to 1000 parts by weight of the at least one Lewis acid alkylene oxide polymerization catalyst per million parts of the combined weight of the starter and all alkylene oxide added to the reaction mixture during the alkylene oxide polymerization process.

7. The alkylene oxide polymerization process of claim 1 wherein during step b) the at least one alkylene oxide is added at a rate R.sub.ao g/minute and the at least one Lewis acid alkylene oxide polymerization catalyst is added at a rate of 0.0001 to 0.001 R.sub.ao.

8. The alkylene oxide polymerization process of claim 1 wherein the amount of the at least one Lewis acid alkylene oxide polymerization catalyst added to the reaction mixture in steps a) and b) is 50 to 1000 parts by weight per million parts by weight of the combined weight of the starter and the at least one alkylene oxide.

9. The alkylene oxide polymerization process of claim 1 wherein steps b) and c) are repeated.

10. The alkylene oxide polymerization process of claim 1 wherein step b) is performed in two or more stages, wherein a first alkylene oxide is added in a first stage of step b), and a different alkylene oxide is added in a subsequent stage of step b).

Description

EXAMPLES 1-3 AND COMPARATIVE SAMPLES A AND B

[0052] In the following examples, the catalyst in all cases is a tetrahydrofuran adduct of bis (3,5-bis(trifluoromethyl)phenyl)(2,4,6-trifluorophenyl)borane. This catalyst corresponds to Catalyst 6 of WO 2019/055727 and is suitably prepared in the manner described with regard to Catalyst 6 of WO 2019/055727. The catalyst solution contains 10 weight percent of this catalyst in 90 weight percent of a 425 M.sub.n poly(propylene oxide) diol.

[0053] The thermal stability of this catalyst is evaluated as follows: Poly (propylene glycol) (425 g/mol) is sparged with dry nitrogen for 18 hours at 110 C. In an oxygen-free wet box, degassed water (50 L) is added to 10 mL of the poly (propylene glycol) in a 20 mL glass vial. 664 L of resulting wet poly (propylene glycol) is combined with 35 mg of the catalyst in a 8 mL glass vial and stirred vigorously for 15 minutes. The solution is transferred to a 5 mm NMR tube that contains a sealed glass capillary which holds a 10 vol % solution of C.sub.6F.sub.6 in toluene-d.sub.8. The NMR tube is capped, sealed with electrical tape heated to 60 C. and maintained at that temperature. .sup.19F NMR spectra are collected on Varian 400-MR and Bruker Avance 500 NMR spectrometers, using standard pulse sequences, with ns=32, d1=5 s. Spectra are collected every 15 minutes for 15 hours. Integrations are normalized to the C.sub.6F.sub.6 internal standard. The decomposition is calculated from the integrals of the signals corresponding to the ortho-fluorine atoms of the bis (3,5-bis(trifluoromethyl)phenyl)(2,4,6-trifluorophenyl)borane tetrahydrofuran complex. The amount of catalyst decomposition after 15 hours at 60 C. is about 2.9% by weight.

[0054] When this test is repeated at 90 C., 14.5% of the catalyst decomposes after only 4 hours and 39.6% decomposes after 15 hours. When again repeated at 120 C., 96.8% of the catalyst decomposes after 4 hours, with complete decomposition being seen after 15 hours.

Comparative Sample A

[0055] 270.48 g of a 700 M.sub.n poly (propylene oxide) triol starter is charged to a 1.88 L stainless steel reactor along with 3.62 g of the catalyst solution. This corresponds to an initial catalyst concentration of 1338 ppm with respect to the product, which is taken as the combined weight of starter and added alkylene oxide. The reactor temperature is brought to 120 C. At that temperatures, 1,2-propylene oxide is then added to the reactor at a constant feed rate of 1.66 g (2 mL) per minute. The concentration of unreacted 1,2-propylene oxide (URO) is continuously monitored. The URO reaches 10% by weight of the reaction mixture after 75 minutes of 1,2-propylene oxide addition. This URO value indicates that essentially none of the added 1,2-propylene oxide has polymerized onto the starter, presumably because the catalyst has deactivated under these temperature conditions. The 1,2-propylene oxide feed is discontinued at this point while maintaining the reaction temperature at 120 C. The URO does not decline, further indicating the catalyst has become deactivated.

Comparative Sample B

[0056] 269.54 g of the starter described in Comparative Sample A is charged to the same reactor. No initial charge of catalyst is made. The reactor contents are brought to 120 C. 1,2-propylene oxide is fed to the reactor at a constant rate of 1.66 g/min (2 mL/min), while maintaining the reactor temperature at 120 C. Starting at the same time, the catalyst solution is fed to the reactor as a separate stream at the rate of 0.018 g/min. The feed ratios are such as to provide and maintain a catalyst loading of approximately 1084 parts per million based on the amount of added 1,2-propylene oxide. The total amount of added catalyst after 21 minutes is approximately 124 parts per million based on the combined weight of starter and added 1,2-propylene oxide. After 21 minutes the URO reaches 10 weight-%, indicating that essentially none of the 1,2-propylene oxide has polymerized.

[0057] This experiment demonstrates that continuous feeding of the catalyst alone is insufficient in a semi-batch process at 120 C.

Example 1

[0058] 260.54 g of the starter and 1.57 g of the catalyst solution are charged to the same reactor as described in the Comparative Samples. These amounts correspond to about 602 parts per million catalyst based on starter weight, on an active basis. The reaction mixture is brought to 120 C. While maintaining that temperature, 1,2-propylene oxide is fed into the reactor at the rate of 1.66 g/minute (2 mL/minute). Beginning at the same time, the catalyst solution is fed into the reactor as a separate stream, at the rate of 0.01 g/minute (0.001 g/minute active catalyst). This addition rate maintains the cumulative amount of added catalyst at about 602 parts per million at all times during the addition of the feed streams. The 1,2-propylene oxide and catalyst streams are continued for about 202 minutes, during which time 335.94 g of 1,2-propylene oxide (R.sub.ao=1.663 g/min) and 2.04 g of catalyst solution (0.204 g active catalyst, addition rate=0.0006 R.sub.ao) are fed into the reactor. URO remains at or below 2% during the entire time the 1,2-propylene oxide and catalyst feeds are continued, indicating that the 1,2-propylene oxide is polymerizing at approximately the rate at which it is fed into the reactor.

[0059] Upon completion of the feeds, the reactor is kept at 120 C. to allow for complete digestion of the remaining unreacted oxide, and the product is recovered by devolatilizing it and removing it from the reactor. The total amount of added catalyst is about 603 ppm with respect to the weight of the final product mass. The product has a number average molecular weight of approximately 1600 g/mol, which represents the target molecular weight for this polymerization.

[0060] As this experiment demonstrates, the addition of an additional charge of catalyst coupled with a continuous addition of fresh catalyst simultaneously and separately from the 1,2-propylene oxide addition achieves rapid and complete polymerization even at the 120 C. operating temperature.

Example 2

[0061] 265.60 g of the starter and 1.60 g of the catalyst solution are charged to the reactor. This corresponds to an initial catalyst concentration of about 600 ppm. The reaction mixture is brought to 120 C. While maintaining that temperature, 1,2-propylene oxide is fed into the reactor at the rate of 1.66 g/minute (2 mL/minute). Beginning at the same time, the catalyst solution is fed into the reactor as a separate stream, at the rate of 0.01 g/minute (0.001 g/minute active catalyst, addition rate=0.0006 R.sub.ao). This addition rate maintains the cumulative amount of added catalyst at about 602 parts per million at all times during the addition of the feed streams. Both feeds are continued for 96.5 minutes, as which point 160.19 grams of 1,2-propylene oxide and 0.097 g of catalyst have been fed to the reactor. The URO does not exceed 2% during the entire feed period.

[0062] The 1,2-propylene oxide and catalyst feeds are stopped for 10 minutes while retaining the reactor temperature at 120 C., then continued at their previous respective rates for 107 addition minutes. URO is below 1% during this second feed period.

[0063] Upon completion of the feeds, the reactor is kept at 120 C. to allow for complete digestion of the remaining unreacted oxide, and the product is recovered by devolatilizing it and removing it from the reactor. The cumulative amount of added catalyst amounts to about 602 parts per million based on the weight of starter plus added 1,2-propylene oxide. The product has a number average molecular weight of approximately 1600 g/mol, which represents the target molecular weight for this polymerization.

[0064] Again, the addition of an additional charge of catalyst coupled with a continuous addition of fresh catalyst simultaneously and separately from the 1,2-propylene oxide addition achieves rapid and complete polymerization at the 120 C. operating temperature.

Example 3

[0065] 260.54 g of the starter and 1.63 g of the catalyst solution are charged to the same reactor. These amounts correspond to about 602 parts per million catalyst based on initiator weight. The reaction mixture is brought to 120 C. While maintaining that temperature, a 2:1 by weight mixture of 1,2-propylene oxide and butylene oxide is fed into the reactor at the rate of about 1.64 g/minute (2 mL/minute). Beginning at the same time, the catalyst solution is fed into the reactor as a separate stream, at the rate of 0.01 g/minute (0.001 g/minute). This addition rate maintains the cumulative amount of added catalyst at about 600 parts per million at all times during the addition of the feed streams. The alkylene oxide and catalyst streams are continued for about 209 minutes, during which time 343.2 g of the alkylene oxide mixture and 2.09 g of catalyst solution are fed into the reactor. The catalyst addition rate is 0.0006 R.sub.ao on an active basis. URO remains at or below 2% during the entire time the alkylene oxide and catalyst feeds are continued, indicating that the 1,2-propylene oxide and butylene oxide are polymerizing at approximately the rate at which they is fed into the reactor.

[0066] Upon completion of the feeds, the reactor is kept at 120 C. to allow for complete digestion of the remaining unreacted oxides, and the product is recovered by devolatilizing it and removing it from the reactor. The total amount of added catalyst is about 600 ppm with respect to the weight of the final product mass. The product has a number average molecular weight of approximately 1600 g/mol, which represents the target molecular weight for this polymerization.

[0067] As this experiment demonstrates, similar results are obtained when polymerizing a mixture of 1,2-propylene oxide and butylene oxide. The low URO values seen during the course of the reaction show that the catalyst effectively catalyzes the butylene oxide polymerization as well as 1,2-propylene oxide polymerization, evidencing that the process of the invention will be effective in homopolymerizing butylene oxide.