Method for making poly(butylene oxide) polyols

Abstract

1,2-butylene oxide is homopolymerized or randomly copolymerized in the presence of a double metal cyanide catalyst such as a zinc hexacyanocobaltate catalyst complex. The polymers unexpectedly contain significant amounts of monofunctional impurities, which can be partially controlled through selection of polymerization conditions.

Claims

1. A semi-batch or continuous process for producing poly(1,2-butylene oxide) polymers, comprising polymerizing 1,2-butylene oxide or a mixture of at least 50% by weight 1,2-butylene oxide and up to 50% by weight of a copolymerizable alkylene oxide at a polymerization temperature of 110 to 140 C. in the presence of enough of a double metal cyanide catalyst to provide a cobalt concentration of 1 to 6 parts per million in the product and in the presence of a hydroxylic initiator compound having 2 to 6 hydroxyl groups, while maintaining a concentration of unreacted alkylene oxides at 2 to 6% by weight, to form a polymer or copolymer of 1,2-butylene oxide having at least one block of homopolymerized or randomly copolymerized 1,2-butylene oxide having a number average weight of at least 500 atomic mass units and which contains no more than 25 microequivalents per gram of monofunctional, unsaturated species.

2. A poly(1,2-butylene oxide) polymer made in accordance with claim 1.

3. The process of claim 1 wherein said least one block of homopolymerized or randomly copolymerized 1,2-butylene oxide has a number average weight of 800 to 2500 atomic mass units.

4. The process of claim 3 wherein 1,2-butylene oxide is homopolymerized to form at least one block of homopolymerized 1,2-butylene oxide.

5. The process of claim 4 wherein enough of the zinc hexacyanocobaltate catalyst complex is present to provide a cobalt concentration of 1 to 3 parts per million in the product.

6. The process of claim 5 wherein the polymerization temperature is 110 to 120 C.

Description

EXAMPLES 1-9

(1) Examples 1-9 are made using the following general procedure.

(2) 72.1 g of tripropylene glycol is combined with a zinc hexacyanocobaltate DMC catalyst and aluminum isopropoxide, and charged to a stirred 1 L Parr reactor. The amount of DMC catalyst is adjusted to give 20 to 50 ppm by weight DMC catalyst (about 2.4 to 6 ppm cobalt) in the product, as indicated in Table 1 below. The amount of aluminum isopropoxide is adjusted to provide 5 to 20 moles of aluminum/mole of zinc in the DMC catalyst, as indicated in Table 1 below. This mixture is dried for 90 minutes at 120 C.

(3) The reactor is heated to the polymerization temperature indicated in Table 1 below and maintained at that temperature during the polymerization process. The heated reactor is pressurized to 20 psig (138 kPa) with propylene oxide. When the reactor pressure drops to 10 psig (69 kPa), the catalyst is considered to have been activated, and additional propylene oxide is added until a total of 77.9 g of propylene oxide has been added. Then, 600 g of 1,2-butylene oxide is added to the reactor, maintaining the reactor pressure such that the concentration of dissolved 1,2-butylene oxide in the liquid phase is in the range of about 2 to 6% as indicated in Table 1. After all the 1,2-butylene oxide is added, the reactor contents are stirred until a constant internal pressure is achieved, which indicates complete polymerization of the 1,2-butylene oxide. The polyethers so produced are diols that have a target number average molecular weight of 2000. The polyethers contain the residue of the tripropylene glycol initiator (weight=190 amu), two internal poly(propylene oxide) blocks each having weights of about 105 amu, and terminal poly(1,2-butylene oxide) blocks each having weights of about 800 amu, as calculated from the masses of the starting materials.

(4) In each case, the product is cooled to room temperature. Unsaturation is measured in each case. A 50/50 by weight mixture of the product and a 0.025M solution of chromium acetylacetonate in acetone-d is placed in a 10 mm NMR tube, and the mixture is analyzed by C.sup.13 NMR at room temperature, using 4000 scans per data file, a 6 second pulse repetition delay, a spectral width of 25,200 Hz and a file size of 32 data points.

(5) Viscosity is measured at 38 C. on a Brookfield viscometer operating at 10 rpm.

(6) Results are as indicated in Table 1.

(7) TABLE-US-00001 TABLE 1 DMC Unreacted catalyst, Al/DMC monomer Unsat- Vis- Temp., as ppm mole concentration, uration, cosity, Ex. C. cobalt ratio ppm eq/gram cP 1 110 2.4 20 6 25 241 2 110 6 20 6 25 245 3 140 6 5 6 24 222 4 110 6 5 2 24 254 5 140 6 5 2 24 218 6 125 4.2 12.5 4 23 227 7 110 6 20 2 23 239 8 110 2.4 5 2 22 231 9 140 6 20 6 20 265

(8) The selection of a polymerization temperature of 110 to 140 C. together with a DMC concentration sufficient to provide 2.4 to 6 parts per million cobalt in the product leads to a low viscosity, 2000 molecular weight product having 25 microequivalents or less of unsaturated monofunctional species per gram of product.

EXAMPLES 10-14

(9) Examples 10-14 are made in the same general manner as Examples 1-9, except more 1,2-butylene oxide is fed into the reactor to produce a target product molecular weight of 4000. The polyethers contain the residue of the tripropylene glycol initiator (weight=190 amu), two internal poly(propylene oxide) blocks each having weights of about 105 amu, and terminal poly(1,2-butylene oxide) blocks each having weights of about 1800 amu, as calculated from the masses of the starting materials. Unsaturation and viscosity are measured as before, with results as indicated in Table 2.

(10) TABLE-US-00002 TABLE 2 Temp., DMC catalyst, Unsaturation, Ex. C. as ppm cobalt eq/gram Viscosity, cP 10 160 7.2 25 235 11 160 6 25 186 12 160 7.2 23.6 197 13 140 2.4 23.3 176 14 160 7.2 22 207

(11) Unsaturation levels of 25 microequivalents per gram are obtained in all cases even at polymerization temperatures in the range of 140 to 160 C. The lower polymerization temperature in conjunction with the lowest catalyst level provides the best balance of low unsaturation and low viscosity.

EXAMPLES 15-18

(12) Examples 15-18 are 8000 molecular weight diols made in two steps. The first step is the synthesis of a 2000 MW poly(butylene oxide) intermediate. The second step uses the 2000 MW intermediate as starter to prepare 8000 MW poly(butylene oxide) diols.

(13) A commercially available 425 molecular weight poly(propylene oxide) diol is acidified with 105 ppm of 70% H.sub.3PO.sub.4 and charged in a stainless steel reactor. The DMC catalyst (325 mg dry wt.) is dispersed in the diol starter and heated at 160 C. while applying vacuum to the reactor. 218 g of 1,2-butylene oxide are fed at 25 g/min to activate the catalyst. When the reactor pressure declines to less than 4.4 psia (30 kPa), 4945 g of butylene oxide are fed to the reactor with a feed rate of 16 g/min. When the oxide addition is complete, the reactor is maintained at 160 C. for one hour to allow free monomer to react.

(14) 1121 g of the resulting intermediate 2000 molecular weight poly(butylene oxide) diol are added to a reactor together with 364 mg of the DMC catalyst and 20 ppm of 70% H.sub.3PO.sub.4. The mixture is brought to a polymerization temperature as indicated in Table 3. 183 g of 1,2-butylene oxide are fed at 25 g/minute to activate the catalyst. When the pressure declines to less than 30 kPa, 4696 g of 1,2-butylene oxide are fed to the reactor. When the oxide addition is complete the reactor is maintained at the polymerization for one hour to allow free monomer to react. Unsaturation is measured as before, with results as indicated in Table 3.

(15) TABLE-US-00003 TABLE 3 Polymerization Catalyst concentration, Unsaturation, Example temperature, C. as ppm cobalt eq/gram 15 160 8.4 77 16 160 8.4 75 17 140 12 67 18 140 4.8 61

(16) In these examples, unsaturation levels as low as 61 microequivalents/gram are obtained even when making an 8000 molecular weight diol that has poly(1,2-butylene oxide) blocks having a weight of almost 4000 each. The lower polymerization temperature favors lower unsaturation, as does the lower amount of catalyst.