WO1991018909A1

WO1991018909A1 - Process for removing double metal cyanide complex catalyst residues from catalyst-residue containing polyols

Info

Publication number: WO1991018909A1
Application number: PCT/US1991/003240
Authority: WO
Inventors: Kiran B. Chandalia; John W. Reisch; Michael M. Martinez
Original assignee: Olin Corporation
Priority date: 1990-03-30
Filing date: 1991-05-10
Publication date: 1991-12-12
Also published as: CN1057644A; EP0532520A4; CN1032252C; EP0532520A1; AR246286A1; CN1120546A; JPH05508833A; MY106397A; AU7792991A

Abstract

A process for removing double metal cyanide complex catalyst residues from a catalyst-residue containing polyol characterized by: (a) treating a double metal cyanide complex catalyst-residue containing polyol with an alkali metal alkoxide or alkaline earth metal alkoxide in order to provide a treated polyol wherein said catalyst-residue is converted into insoluble ionic species, (b) contacting said treated polyol with ethylene oxide to produce an ethylene oxide-capped polyol wherein at least a portion of the secondary hydroxyl groups on said polyol are converted into primary hydroxyl groups, and (c) separating said insoluble ionic species from said ethylene oxide-capped polyol by filtration in order to provide a purified polyol that is essentially free of catalyst-residue. Also claimed is a process for preparing a purified polyol that is free of acid catalyst residues.

Description

PROCESS FOR REMOVING DOUBLE METALCYANIDECOMPLEXCATALYSTRESI¬ DUESFROMCATALYST-RESIDUECONTAINING POLYOLS

The use of double metal cyanide catalysts in the preparation of high molecular weight polyols is well-established in the art. For example, U.S. Patent 3,829,505, assigned to General Tire & Rubber Company, discloses the preparation of high molecular weight diols, triols etc., using these catalysts. The polyols prepared using these catalysts can be fabricated to have a higher molecular weight and a lower amount of end group unsaturation than can be prepared using commonly-used KOH catalysts. The '505 patent discloses that these high molecular weight polyol products are useful in the preparation of nonionic surface active agents, lubricants and coolants, textile sizes, packaging films, as well as in the preparation of solid or flexible polyurethanes by reaction with polyisocyanates.

In order to prepare polyols using double metal cyanide complex catalysts, it is necessary to employ propoxylated initiators as reactants since non-propoxylated initiators such as glycerine fail to react with propylene oxide in the presence of double metal cyanide complex ("DMC") catalysts. This lack of reaction is apparently due to the insolubility of the DMC catalyst in the initiator.

In view of this problem, propoxylated initiator precursors are conventionally prepared by the reaction of propylene oxide with the initiator (such as glycerine) in the presence of a potassium hydroxide ("KOH") catalyst. Unfortunately, the presence of even a small amount of KOH catalyst in the propoxylated precursor kills the catalytic activity of the DMC catalyst utilized in the subsequent polyol-forming reaction. Therefore, removal of the KOH catalyst from the propoxylated precursor must be effected prior to the use of this precursor in the DMC catalyzed production of polyols.

Removal of the KOH catalyst from the propoxylated precursor can be accomplished by any one of several methods described in the patent literature; however, the KOH catalyst removal step is expensive and time-consuming. Accordingly, a new method for providing the desired propoxylated precursors that does not utilize KOH catalyst, and does not require any catalyst separation step prior to the use of these precursors in the DMC catalyzed production of polyols, would be highly desired by the polyol manufacturing community.

Polyols prepared using double metal cyanide catalysts contain catalyst residues that interfere with the subsequent use of the polyol in a subsequent polyurethane-forming reaction. More specifically, the catalyst residues will cause undesirable side reactions to form unwanted by-products such as allophanates. Attempts have been made in the past to remove the catalyst residues from the polyol after production of the polyol. For example, U.S. Patent 4,355,188 teaches that removal of the double metal cyanide catalyst residues can be effected by adding to the polyol-residue mixture a strong base selected from potassium hydroxide, potassium metal, and sodium metal in order to convert the residues to ionic species, and adding ethylene oxide while the base is in contact with the polyol. The ionic species are then separated by filtration, for example by contact with an ionic exchange residue, in order to provide a purified polyol essentially free of the residues. Unfortunately, the use of the hydroxides causes water production in the polyol. The resulting polyol/water mixture poses a difficult and energy intensive separation problem. Also, the use and handling of sodium or potassium metal poses an unwanted fire and explosion hazard.

U.S. Patent 4,721,818 discloses a method for removal of double metal cyanide catalyst residues from a polyol which comprises adding an alkali metal hydride to the polyol-residue mixture to convert the double metal cyanide complex catalyst into an insoluble ionic metal species separable from the polyol. The insoluble species are then removed from the polyol by filtration. Unfortunately, the use of alkali metal hydrides presents an explosion and fire hazard, and therefore the use of these materials is undesirable.

In view of the increasing significance of high molecular weight polyols produced using double metal cyanide complex catalysts, new methods of separating the catalyst residues from these polyols would be highly desired by the polyurethanes manufacturing community, particularly a method that does not pose the above-mentioned explosion and fire hazards, and does not produce unwanted water and the accompanying separation problems associated therewith.

In one aspect, the present invention relates to a process for removing double metal cyanide complex catalyst residues from a catalyst-residue containing polyol which comprises: (a) treating a double metal cyanide complex catalyst-residue containing polyol with an alkali metal alkoxide or alkaline earth metal alkoxide in order to provide a treated polyol wherein said catalyst-residue is converted into insoluble ionic species, (b) contacting said treated polyol with ethylene oxide to produce an ethylene oxide-capped polyol wherein at least a portion of the secondary hydroxyl groups on said polyol are converted into primary hydroxyl groups, and

(c) separating said insoluble ionic species from said ethylene oxide-capped polyol by filtration in order to provide a purified polyol that is essentially free of catalyst-residue.

In another aspect, the present invention relates to a process for making a polyol which comprises the steps of:

(a) fabricating a propoxylated polyhydric initiator by reacting propylene oxide with a polyhydric initiator in the presence of an acid catalyst (preferably a Lewis acid or a protic acid), said reaction being conducted in the absence of a KOH catalyst, to produce a propoxylated polyhydric initiator containing acid catalyst residue(s) and free of KOH catalyst residue, and

(b) reacting said propoxylated polyhydric initiator containing acid catalyst residue(s) with an alkylene oxide in the presence of a double metal cyanide complex catalyst to produce a polyol.

In yet another aspect, the present invention relates to the above process, but wherein steps (a) and (b) are carried out simultaneously in a single step.

In still yet another aspect, the present invention relates to the polyol product produced by the above processes.

These and other aspects will become apparent from a reading of the following detailed description of the invention.

It has now been surprisingly found in accordance with the present invention that the ethylene oxide-capping of polyols treated with alkali metal alkoxide or alkaline earth metal alkoxides is advantageous in removing double metal cyanide complex catalyst residues from polyols containing these residues. Although not wishing to be bound by any particular theory, the present inventors speculate that the ("EO")-capping procedure provides two key advantages when utilized in the process of the present invention, namely (a) to convert at least a portion of the secondary hydroxyl groups on the polyol to primary hydroxyl groups, and (b) to assist the alkali metal alkoxide or alkaline earth metal alkoxide in the precipitation of the catalyst residues.

Another advantage associated with the present invention is that, while the prior art compounds utilized to facilitate this removal are either highly flammable or explosive (i.e., sodium metal, potassium metal and alkali metal hydrides) or produce water as an undesirable and difficult to remove by-product in the polyol (i.e., sodium or potassium hydroxide), the alkali metal alkoxides and alkaline earth metal alkoxides utilized in the present invention are not flammable or explosive, and produce an easy-to-remove alcohol as a by-product. The by-product alcohol is suitably removed from the polyol by a simple fractional distillation procedure, thus taking advantage of the low-boiling characteristic of the alcohols, particularly the lower alkoxides.

The alkali metal alkoxides and alkaline earth metal alkoxides useful in the process of the present invention generally have between one and 23, preferably between one and eight, more preferably between one and six, carbon atoms per molecule. Suitable alkali metal alkoxides include, for example, sodium methoxide, potassium methoxide, lithium methoxide, as well as the ethoxides, propoxides, butoxides, pentoxides, dodecyloxides, and the like. Suitable alkaline earth metal alkoxides include, for example, the calcium and magnesium salts of the above-mentioned alkoxides. It has also been surprisingly found in accordance with the present invention that the use of acid catalyst(s) in the production of propoxylated precursors for polyols makes it possible to produce polyols directly in a DMC-catalyzed reaction without purification of the propoxylated precursors. Thus, the acid catalysts provide the desired catalysis for producing propoxylated precursors without killing or otherwise adversely affecting the DMC catalyst. This surprising result will be of significant value to DMC-catalyzed polyol producers who heretofore have had to purify the propoxylated precursors prior to contacting the DMC catalyst in order to avoid the killing of the DMC catalyst by KOH catalyst or KOH catalyst residue(s).

The acid catalyst(s) useful in the process of the present invention are preferably Lewis acids, such as BF.Et-O (boron trifluoride etherate) , SbF₅ (antimony pentafluoride) , SbCl₅ (antimony pentachloride) , F₃CSO_H (trifluoromethane sulfonic acid), as well as protic acids such as HBF. (tetrafluoroboric acid), H2S0₄ (sulfuric acid), and combinations thereof, and the like. The acid catalyst is typically employed in an amount of up to a maximum of about one weight percent based upon the weight of the propoxylated precursor-forming reaction mixture, preferably between about 50 and about 1,500 ppm in the reaction mixture. Exceeding the one percent upper limit of acid catalyst may result in undesirable side reactions.

The polyols made in accordance with the process of and utilized in the present invention are typically prepared by* condensing a propylene oxide or a mixture of propylene oxide with an alkylene oxide, or a mixture of alkylene oxides using random or step-wise addition, with a polyhydric initiator or mixture of initiators, in the presence of a double metal cyanide catalyst. Illustrative alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, amylene oxide, aralkylene oxides such as styrene oxide, and combinations thereof, and the like. The most preferred alkylene oxide is propylene oxide or a mixture thereof with ethylene oxide using random or step-wise oxyalkylation. The polyhydric initiator used in preparing the polyol reactant includes the following and mixtures thereof: the aliphatic triols such as glycerol, propoxylated glycerol adducts, trimethylolpropane, triethylolpropane, trimethylolhexane, and diols such as ethylene glycol, 1,3-proρylene glycol, dipropylene glycol, butylene glycols, butane diols, pentane diols, and the like. In addition, monofunctional and higher functionality initiators are useful in the present invention, including, for example, butanol, sucrose, sorbitol, pentaerythritol, and the like. In addition to the above, other suitable polyhydric initiators are disclosed in U.S. Pat. Noε. 4,472,560 and 4,477,589 to Shell Chemical Company and U.S. Pat. Nos. 3,941,849 and 4,335,188 to General Tire & Rubber Company. Particularly preferred polyhydric initiators include glycerol, trimethylol propane, diethylene glycol, dipropylene glycol, and tripropylene glycol.

The alkylene oxide-polyhydric initiator condensation reaction is carried out in the presence of a double metal cyanide catalyst. Without wishing to be bound by any particular theory, it is speculated by the present inventor that unsaturated end groups result in monofunctional species that act as chain stoppers in elastomer formation. In polyol synthesis with KOH catalysis the unsaturation formed increases as a direct function of equivalent weight. Eventually conditions are established wherein further propylene oxide addition fails to increase the molecular weight. In other words the use of alkali catalysts to produce high molecular weight, hydroxy terminated polyoxypropylene ethers results in a substantial loss in hydroxy functionality. With double metal cyanide catalysis much less unsaturation is formed allowing higher equivalent weight polyols to be prepared. Typically, the polyol will have an equivalent in the range of between about 1,000 and 20,000, preferably between about 1,500 and about 5,000, although lower or higher equivalent weights may be produced as desired.

The double metal cyanide complex class catalysts suitable for use and their preparation are described in U.S. Pat. Nos. 4,472,560 and 4,477,589 to Shell Chemical Company and U.S. Pat. Nos. 3,941,849 and 4,335,188 to General Tire & Rubber Company.

One double metal cyanide complex catalyst found particularly suitable for use is a zinc hexacyanometal- late of formula:

Zn₃[M(CN)g]₂.xZnCl₂.yGLYME.zH₂0

wherein M may be Co(III), or Cr(III) or Fe(II) or Fe(III); x, y, and z may be fractional numbers, integers, or zero and vary depending on the exact method of preparation of the complex, preferably each independantly being between 0 and 15.

Any alkali metal alkoxide or alkaline earth metal alkoxide can be employed in the practice of the invention. Preferred alkoxides are sodium, potassium, lithium, magnesium and calcium salts, or combinations thereof. The total amount of alkoxide employed is that amount effective to convert the double metal cyanide complex catalyst residue into an insoluble ionic metal species. Broadly, molar ratios of hydroxyl groups on the polyol to alkali metal alkoxide or alkaline earth metal alkoxide of from 1:1 to 500:1 are contemplated. Although not required, in order to enhance the speed at which the insoluble ionic metal species forms it is desirable to heat the mixture. Heating at a temperature within the range of from about 40°C to about 100°C for up to five hours has been found advantageous.

After the double metal cyanide complex catalyst residue has been converted to the insoluble ionic metal species, it can be separated from the polyol by conventional methods such as filtration using, for example, diatomaceous earth, or passing through an acidic ion exchange resin as taught in U.S. Patent No. 4,355,188. In yet another embodiment of this invention, it has been found that the insoluble ionic metal species can be easily separated from the polyol by filtration if a minor amount of magnesium silicate, aluminum silicate, or mixtures thereof, is incorporated into the mixture prior to separation. The silicate can be used alone or in combination with conventional filter aids such as diatomaceous earth. In addition to facilitating separation, it has been discovered that treatment with silicate also converts polyol alkoxide groups to hydroxyl groups and absorbs the resulting alkali metal hydroxide.

Typically, the amount of silicate added will be from about 1 to about 5 parts by weight per each 100 parts by weight of the polyol containing catalyst residue mixture and the mixture will be heated for 1 to 12 hours at a temperature of from about 80°C to about 150^CC before filtration. It is preferred that the silicate can be finely divided and have a high surface area. As used herein, the term "molecular weight" is intended to designate number average molecular weight. EXAMPLE 1

Step (A) - Preparation of a High Molecular Weight Polvol With a Double Metal Cvanide Catalyst

A one liter autoclave was charged with lOOg of a propoxylated glycerine precursor (450 raw, 150 eq.wt., 0.667 eq.). Zinc hexacyanocobaltate glyme complex (Zn_(Co(CN-)₂ glyme) (0.64g) was added and the mixture was purged with nitrogen three times and then heated to 100C. Propylene oxide (30g, 0.517eq.) was added and after an initial induction period of 15 minutes a pressure drop was observed indicating that the catalyst was activated. An additional 600g (10.33 eq.) of propylene oxide was fed into the reactor over a period of 90 minutes. The pressure remained below 30 psi indicating that the PO was reacting rapidly. When the pressure fell below 10 psi, 550g of the product was removed from the reactor to allow space for additional oxide. To the 180g (0.164eq.) of product remaining in the reactor was added an additional 195g (3.36 eq.) of propylene oxide over a period of one hour. The product was post reacted for 30 minutes.

Step (B) - Catalyst Conversion with Potassium Methoxide

Potassium methoxide (1.9g, 0.027 eq.) was added to ionize the catalyst residue and the mixture was vacuum stripped at 100°C for one hour.

Step (C) - Ethoxylation

Ethylene oxide (60g, 1.36 eq.) was added over a period of one hour and then the mixture was post reacted at 100°C for 2 hours. Step (D) - Purification and Catalyst Removal

To the mixture was added 4.3g of water and 8.7g of sodium acid pyrophosphate (SAPP) and the mixture was heated at 110°C for 1 hour and then vacuum stripped for 1 hour. Magnesium silicate (8.7g) and celite (4.3g) were added and the mixture was stirred for 1 hour at 110°C. The mixture was vacuum stripped for 2 hours and then filtered. The product was analyzed and found to have an OH number of 22, with 11% EO and 74.1% primary hydroxyl groups. The product was analyzed for cobalt and zinc using both atomic absorption ad X-ray fluorescence. No cobalt or zinc were detected in the product at a detection limit of lppm.

EXAMPLE 2

Catalyst Ionization With Sodium Ethoxide

The procedure described in Example 1 was repeated except that sodium ethoxide was used instead of potassium methoxide. The product was analyzed and found to contain no cobalt or zinc at a detection limit of lppm.

COMPARATIVE EXAMPLE A

Preparation of a High Molecular Weight Polyol With Double Metal Cyanide Catalyst and Magnesium Silicate Treatment Without Alkali Metal Alkoxide Catalyst Conversion

A polyol was prepared with double metal cyanide catalyst as described in example la. Steps lb and lc, catalyst conversion with alkoxide and ethoxylation, were omitted and the polyol was treated with SAPP and magnesium silicate as described in example Id. The product was analyzed and found to contain 110 ppm cobalt and 280 ppm zinc.

EXAMPLE 3

Step (A) - Preparation of a Propoxylated Glycerine Precursor using an SbF,. Catalyst

Glycerine (lOOg, 1.09 mol., 3.26 eq.) was added to a flask equipped with a reflux condensor and blanketed with nitrogen. Antimony pentafluoride (0.10g, 0.00046 mol.) was added and the mixture was stirred and propylene oxide (400g, 6.89 eq.) was added through a dropping funnel over a period of one hour. The flask was cooled in an ice bath to maintain the temperature below 34°C. After the addition was complete the mixture was stirred for 0.5 hour and then an attempt was made to distill off unreacted propylene oxide. No propylene oxide distilled off indicating that it had all reacted. The theoretical molecular weight of the product was 460. A gel permation chromatograph was run of the sample and it showed a molecular weight of 439.

A number of propoxylated precursors were prepared with glycerine and dipropylene glycol using a similar procedure and a variety of acid catalysts and the data are presented in Tables 1 and 2. TABLE 1

Precursors Prepared From Glycerine

GMS OF GMS OF GMS PO EST. EST. MW T GLYCERINE REACTED HYDROXYL # EQ. WT. (BY GPC)

365 153. 6 365 153.6 439 365 153, 6 365 153.6 483 502 Ill, 7 365 153, 6 483 439 127 7 365 153 6 481 365 153 6 496 365 153 6 391

457 122.8 > I

Precursors From Dipropylene Glycol

GMS OF GMS OF GMS PO EST. EST. MW CATALYST CATALYST GLYCERINE REACTED HYDROXYL # EQ. WT. (BY GPC)

50 200 167 4 335 761 50 200 167 4 335 779 50 143 216 6 259 50 200 167 4 335 583 50 70 348 4 161

50 87.5 304 0 184 383

Step (B) - Use of a Precursor Prepared Using SbF5 to Prepare a Polvol Using DMC Catalysis

A propoxylated glycerine precursor (lOOg 0.748 eq.) that was prepared with SbF- catalyst was added to a 1 liter autoclave. Zinc hexacyanocobaltate catalyst Zn_(Co(CN)₆)₂ (0.64g) was added and the autoclave was flushed with nitrogen three times. The mixture was heated to 100°C. Propylene oxide (30g) was added and it reacted as evidenced by a drop in the pressure. Propylene oxide was fed into the reactor at a rate to maintain the pressure below 20 psi and 609g of PO was added within two hours. At this point 548g of the mixture was removed to allow space for more epoxide leaving 162.lg in the reactor. An additional 340g of propylene oxide was fed into the reactor over a period of 1.5 hours to produce a polyol with a molecular weight of 10,000, OH number 16.75.

In a similar manner precursors that were prepared with BF_/glycerine/PO and HBF./glycerine/PO and SbF_ς/glycerine/DPG were used to make 10,000 molecular weight polyols with zinc hexacyanocobaltate.

In all cases the reactivity of the DMC catalyst was not diminished by the presence of the acid in the precursor.

Direct Preparation of a Polvol with Glycerine/ SbF5/DMC catalvst/Propylene Oxide

Glycerine (33g, 0.358 mol., 1.07 eq.) was added to a reactor. Zinc hexacyanocobaltate (0.64g) and antimony pentafluoride 0.10g were added and the mixture was flushed with nitrogen. The mixture was maintained at 30°C and propylene oxide (133g, 2.29 eq.) was added slowly over a 1.5 hour period. The mixture was then heated to 100°C and no pressure formed indicating that all the propylene oxide had reacted. An additional 615g (10.6 eq.) of propylene oxide was fed into the reactor at a rate to maintain the pressure at 20 psi, which required approximately 2 hours. A portion of this mixture (625g) was removed from the reactor to allow room for additional epoxide leaving 148.6g in the reactor. An additional 516g of propylene oxide was fed into the reactor at a rate to maintain the propylene oxide pressure at 20 psi (approximately 2 hours) to produce a 10,000 molecular weight polyol, OH number 17.

Claims

WHAT IS CLAIMED IS:

1. A process for removing double metal cyanide complex catalyst residues from a catalyst-residue containing polyol characterized by:

(a) treating a double metal cyanide complex catalyst-residue containing polyol with an alkali metal alkoxide or alkaline earth metal alkoxide in order to provide a treated polyol wherein said catalyst-residue is converted into insoluble ionic species,

(b) contacting said treated polyol with ethylene oxide to produce an ethylene oxide-capped polyol wherein at least a portion of the secondary hydroxyl groups on said polyol are converted into primary hydroxyl groups, and

2. The process of claim 1 characterized in that said alkali metal alkoxide or alkaline earth metal alkoxide is employed in an amount sufficient to provide a molar ratio of hydroxyl groups on the polyol to alkali metal alkoxide or alkaline earth metal alkoxide of between 1:1 and 500:1.

3. The process of claim 1 characterized in that said alkali metal alkoxide or alkaline earth metal alkoxide contains between one and 23 carbon atoms per molecule on said alkoxide.

4. The process of claim 1 characterized in that said alkali metal alkoxide or alkaline earth metal alkoxide contains between one and eight carbon atoms per molecule.

5. The process of claim 1 characterized in that said alkali metal alkoxide or alkaline earth metal alkoxide is selected from the group consisting of the sodium, potassium, lithium, calcium, and magnesium salts of methoxide, ethoxide, propoxide, butoxide, pentoxide, hexaoxide, and combinations thereof.

6. The process of claim 1 characterized in that said filtration is effected by means of an ion exchange resin.

7. The process of claim 1 characterized in that a minor amount of magnesium silicate, aluminum silicate, or mixtures thereof, is incorporated into said catalyst residue-containing polyol prior to step (c) in order to facilitate the separation of step (c).

8. The process of claim 1 further characterized by the additional step of removing any by-product alcohol from said purified polyol by fractionally distilling said purified polyol.

9. The process of claim 1 characterized in that step (a) and step (b) are carried out either simultaneously or in sequential order.

10. A process for making a polyol characterized by the steps of:

(a) fabricating a propoxylated polyhydric initiator by reacting propylene oxide with a polyhydric initiator in the presence of an acid catalyst, said reaction being conducted in the absence of a KOH catalyst, to produce a propoxylated polyhydric initiator containing acid catalyst residue(s) and free of KOH catalyst residue, and (b) reacting said propoxylated polyhydric initiator containing acid catalyst residue(s) with an alkylene oxide in the presence of a double metal cyanide complex catalyst to produce a polyol.

11. The process of claim 10 characterized in that the acid catalyst is selected from the group consisting of Lewis acids and protic acids.

12. The process of claim 10 characterized in that the acid catalyst is selected from the group consisting of: boron trifluoride etherate, antimony pentafluoride, antimony pentachloride, trifluoromethane sulfonic acid, tetrafluoroboric acid, sulfuric acid, and combinations thereof.

13. The process of claim 10 characterized in that the acid catalyst is employed in a catalytically effective amount of up to about one weight percent based upon the weight of the propoxylated precursor-forming reaction mixture.

14. The process of claim 10 characterized in that the acid catalyst is employed in an amount of between about 50 and about 1,500 ppm in the reaction mixture.

15. The process of claim 10 characterized in that the polyhydric initiator is selected from the group consisting of glycerol, propoxylated glycerol adductε, trimethylolpropane, triethylolpropane, trimethylolhexane, ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, butylene glycols, butane diols, pentane diols, butanol, sucrose, sorbitol, pentaerythritol, and combinations thereof.

16. The process of claim 10, but characterized in that steps (a) and (b) are carried out simultaneously in a single step.

17. The polyol product characterized by being produced by the process of claim 10.

18. The polyol product characterized by being produced by the process of claim 16.