PROCESS FOR MAKING POLYETHERS WITH REDUCED AMOUNTS OF UNSATURATED MONOLS

Abstract

Unsaturated polyether monols are removed from polyether polyols by reaction with a functionalized thiol compound or a polythiol compound. This process replaces the terminal unsaturation with a functional group, or else couples two or more of the monols to form a polyol. The functionality of the polyether polyol product is increased by the removal of the monols.

Claims

1. A process for making a polyether, comprising a) polymerizing one or more alkylene oxides at a temperature of 80 to 200 C. in the presence of at least one polyhydric initiator compound and an alkylene oxide polymerization catalyst to produce a polyether mixture containing polyether polyol molecules and unsaturated polyether monols having a hydroxyl group at an end of a polyether chain; and b) reacting the polyether mixture with a thiol compound having (1) at least one thiol group and at least one other functional group that is less reactive with propenyl and allylic unsaturation than the thiol group(s) or (2) at least 2 thiol groups, to convert at least a portion of the unsaturated polyether monols to (i) polyethers having a terminal hydroxyl group at one end of the polyether chain and at least one functional group corresponding to the functional group of the thiol compound at the other end of the polyether chain, (ii) coupled polyethers linked by a residue, after removal of thiol hydrogens, of the thiol compound.

2. The process of claim 1, wherein the polyether mixture produced in step a) contains at least 0.05 meq of unsaturated polyether monols per gram of the polyether mixture.

3. The process of claim 2, wherein the one or more alkylene oxides is 1,2-propylene oxide by itself or a mixture of 90 to 99.5 weight-% by weight 1,2-propylene oxide and correspondingly 0.5 to 10 weight-% ethylene oxide.

4. The process of any preceding claim claim 2, wherein the polyether mixture produced in step a) has a number average molecular weight of at least 500, at least 1000, at least 1500.

5. The process of claim 2, wherein the thiol compound has only one thiol group, and in step b) at least a portion of the unsaturated polyether monols are converted to polyethers having a terminal hydroxyl group at one end of the polyether chain and at least one functional group corresponding to the functional group of the thiol compound at the other end of the polyether chain.

6. The process of claim 6 wherein the thiol compound is a thiol-substituted alcohol.

7. The process of claim 2, wherein the thiol compound has two or more thiol groups and in step b) c at least a portion of the unsaturated polyether monols are converted to coupled polyethers linked by a residue, after removal of thiol hydrogens, of the thiol compound.

8. The process of claim 2, wherein in step b) the amount of unsaturated polyether monols is reduced by at least 75%, compared to the amount of unsaturated polyether monols in the polyether mixture produced in step a).

9. A process for converting an unsaturated polyether monol to a polyether polyol, wherein the unsaturated polyether monol has a polyether chain terminated at one end with a hydroxyl group and at the other end with an allylic or propenyl group, comprising reacting the unsaturated polyether monol with a thioalcohol compound having at least one thiol group and at least one alcohol group such that the thiol group of the thioalcohol compound reacts with the allylic or propenyl group to form a bond between the thiol sulfur atom and one of the carbon atoms of the allylic or propenyl group.

10. The process of claim 9, wherein the unsaturated polyether mixture is a polymer of 1,2-propylene oxide by itself or a mixture of 90 to 99.5 weight-% by weight 1,2-propylene oxide and correspondingly 0.5 to 10 weight-% ethylene oxide.

11. The process of claim 10, wherein the thiolalcohol compound is selected from 2-mercaptoethanol, 2-mercaptoisopropanol, 2-mercapto-n-propanol, 3-mercapto-n-propanol, 4-mercapto-n-butanol, 6-mercapto-n-hexanol, 1-thioglycerol (3-mercapto-2,3-dihydroxypropane), 1-mercapto-3,4-dimethylol-n-butane, or a mixture of any two or more thereof.

Description

EXAMPLES 1-5 AND COMPARATIVE SAMPLES A AND B

[0052] An allyl alcohol-initiated, 200 molecular weight poly(ethylene oxide) (Polyether A) is used as a model compound. On C.sup.13 NMR, this material (Comparative Sample A) exhibits resonances corresponding to the allylic carbons, at about 116 and 135 ppm relative to tetramethylsilane.

[0053] To produce Example 1, Polyether A is combined with an approximately equal number of equivalents of 1-thioglycerol and about 5% by weight, based on the weight of 1-thioglycerol, of tert-amyl peroxy-2-ethylhexanoate (Trigonox 121 from Akzo Nobel Industrial Chemicals). The mixture is heated under nitrogen to 90 C. for 2 hours, and then allowed to cool to room temperature. C.sup.13 NMR indicates the complete disappearance of allylic carbons, indicating that all of the starting material had been converted to a triol, in which two of the three hydroxyl groups have been supplied by the 1-thioglycerol.

[0054] Example 2 is made in the same general manner, substituting 2-mercaptoethanol for the 1-thioglycerol. C.sup.13 NMR again indicates complete disappearance of the allylic carbons. The product is a diol.

[0055] To produce Example 3, Polyether A is combined with an approximately equal number of equivalents of 1-thioglycerol. 2,2-dimethoxy-2-phenylacetophenone is added as a photo-triggered radical initiator, in about 5-6 wt.-%, based on the weight of 1-thioglycerol. The mixture is stirred at room temperature for 2 hours under a UV light intensity of 6W (Philips TL 6W08). Complete disappearance of the allylic carbons is seen on C.sup.13 NMR indicating the formation of a triol.

[0056] Example 4 is made in the same general manner as Example 1, except the catalyst is Trigonox 121 (about 5%, based on the thiol compound), and the reaction conditions are 65 C. for 5 hours. Complete disappearance of the allylic carbons is seen on C.sup.13 NMR indicating the formation of a triol.

[0057] A quantity of Comparative Sample A is heated at 150 C. in the presence of a palladium/carbon catalyst to isomerize a portion of the allyl groups to propenyl groups (Comparative Sample B). C.sup.13 NMR indicates the presence of allylic carbon resonances at about 116 and 136 ppm, and in addition the presence of propenyl hydrogen resonances at about 10 and 146 ppm.

[0058] Example 5 is made by reacting approximately stoichiometric amounts of Comparative Sample B and 2-mercaptoethanol in the presence of Trigonox 121 for 3 days at 90 C. Complete loss of the allylic carbon signals is seen on C.sup.13 NMR, indicating the formation of a triol.

EXAMPLES 5 AND 6 AND COMPARATIVE SAMPLES C AND D

[0059] Comparative Sample C is an approximately 6000 molecular weight glycerine-initiated polypropylene oxide) end-capped with ethylene oxide. Comparative Sample C has 0.025 meq/g of propenyl unsaturation and 0.048 meq/g of allylic unsaturation, for a total unsaturated polyether monol content of 0.073 meq/g. Its hydroxyl number is 27.4.

[0060] A quantity of Comparative Sample C is treated with 2-mercaptoethanol in the same general manner as described in Example 2. C.sup.13 NMR of the treated product (Example 5) shows a complete disappearance of allylic carbon resonances. The hydroxyl number of Example 5 increases to 31.8 meq/g. Example 5 is a mixture of a polyether triol with about 0.07 meq/g of polyether diols corresponding to the reaction product of the mercaptoethanol and unsaturated polyether monols in Comparative Sample C.

[0061] Comparative Sample D is an approximately 6000 molecular weight glycerine-initiated polypropylene oxide) end-capped with ethylene oxide. Comparative Sample C has 0.002 meq/g of propenyl unsaturation and 0.153 meq/g of allylic unsaturation, for a total unsaturated polyether monol content of 0.155 meq/g. Its hydroxyl number is 32.4. Example 6 is made from Comparative Sample D, in the same general manner as described for Example 5. The C.sup.13 NMR of Example 6 shows complete disappearance of the allylic carbon resonances. The hydroxyl number of Example 6 is increased to 38.3. Example 6 is a mixture of a polyether triol with about 0.13 meq/g of polyether diols corresponding to the reaction product of the mercaptoethanol and unsaturated polyether monols in Comparative Sample D.

[0062] Comparative Samples C and D and Examples 5 and 6 each are evaluated in a model polyurethane foam system. Tack-free time is measured in each case by applying a spatula to the surface of the reaction mixture periodically is it rises and cures, until such time as the reaction mixture no longer sticks to the spatula (the tack-free time). The tack-free time for the foam made with Comparative Sample C is 48 seconds. That for Example 5 is 45 seconds, which is consistent with a higher average hydroxyl functionality due to the conversion of monols to diols via the treatment with mercaptoethanol. The tack-free time of the foam made with Comparative Sample D is 47 seconds, and that of Example 6 is only 45 seconds, again consistent with the removal of monols from the material.