MXPA00010781A - Acid-treated double metal cyanide complex catalysts - Google Patents

Abstract

The amount of high molecular weight impurity present in a polyether polyol produced by alkoxylation of an active hydrogen-containing initiator and a substantially noncrystalline highly active double metal cyanide complex catalyst may be advantageously lowered by treating the catalyst prior to use in polymerization with a protic acid. Suitable protic acids include phosphoric acid and acetic acid. The higher purity polyether polyols thereby produced are particularly useful in thepreparation of slab and molded polyurethane foams, which tend to collapse or become excessively tight when elevated levels of high molecular tail are present in the polyether polyol.

Description

COMPLEX CATALYSTS OF METALLIC CYANIDE DOUBLE TREATED WITH ACID FIELD OF THE INVENTION This invention pertains to a method for improving the performance of a highly active, non-crystalline, double metal cyanide complex catalyst characterized by the presence of zinc-idroxyl groups. More particularly, the invention relates to the contacting of such a catalyst with a protic acid, whereby the acid-treated catalyst thus obtained is capable of producing polyether polyols having reduced levels of high molecular weight glue. Such polyether polyols have increased processing latitude in the preparation of molded polyurethane foam and for plates.

BACKGROUND OF THE INVENTION The polyurethane polyols are prepared by reacting a di- or polyisocyanate with a polyfunctional isocyanate-reactive compound, in particular polyether polyols with group Ref: 124356 functional hydroxyl. There are numerous classes recognized in the art of polyurethane polymers, for example cast elastomers, polyurethane RIMs, microcellular elastomers, and molded and patterned polyurethane foam. Each of these polyurethane varieties presents unique problems in formulation and processing. Two of the highest volume categories of polyurethane polymers are molded polyurethane foam and plate. In the plate foam, the reactive ingredients are supplied on a mobile conveyor and allowed to rise freely. The resulting foam board, often 2 to 2.6 m (6 to 8 feet) wide and high, can be sliced into thinner sections for use as seat cushions, carpet underlay and other applications. The molded foam can be used for contoured foam parts, for example, seat cushions for automobiles. In the past, polyoxypropylene polyether polyols useful for molded foam and plate applications have been prepared by base catalyzed propoxylation of suitable water initiators such as propylene glycol, glycerin, sorbitol, etc., producing the diols, triols, and respective polyoxypropylene hexoles. As is now well documented, a rearrangement of propylene oxide to allyl alcohol occurs during base catalyzed propoxylation. The monofunctional, unsaturated allyl alcohol possesses a hydroxyl group capable of reacting with propylene oxide, and its continuous generation and propoxylation produces an increasing amount of unsaturated polyoxypropylene monools having a broad molecular weight distribution. As a result, the effective functionality of the produced polyether polyols is significantly diminished from the "normal" or "theoretical" functionality. In addition, the generation of monol places a relatively low practical limit on the molecular weight obtainable. For example, a molecular weight diol of 4000 Da (Daltons) (weight equivalent to 2000 Da) catalyzed by base, may have a measured unsaturation of 0.05 meq / g, and thus contain 30 mol% of polyoxypropylene monol species unsaturated The resulting effective functionality will be only 1.7 instead of the "nominal" functionality of 2 expected for a polyoxypropylene diol. Since this problem becomes even more severe, as the molecular weight is increased, the preparation of the polyoxypropylene polyols having equivalent weights greater than about 2200-2300 Da is impractical using conventional base catalysts. Double metal cyanide complex ("DMC") catalysts such as zinc hexacyanocobaltate complexes were found to be catalysts for propoxylation approximately 30 years ago. However, its high cost, coupled with the modest activity and the difficulty in removing significant amounts of catalyst residues from the polyether product, prevented its commercialization. The level of unsaturation of the polyoxypropylene polyols produced by these catalysts was found, although it was low. The relatively modest polymerization activity of these conventional double metal cyanide complex catalysts has been recognized as a problem by workers in the field. A method for improving the polyether polyol yields obtained from such catalysts is proposed in U.S. Patent No. 4,472,560. This publication proposes a process for the polymerization of epoxide using as a catalyst a double metal cyanide compound, wherein said process is carried out in the presence of one or more acids that do not contain metal, of which a 0.1 N solution in water at 25 ° C it has a pH not exceeding 3. The acid is introduced as a solution in a suitable solvent with stirring in a suspension of a metal double-hydroxide metal cyanide complex. After evaporation of the volatile compounds, the solid obtained in this way is used or stored for use as a polymerization catalyst without any filtration or centrifugation. Example 1 of the patent illustrates the preparation of a solid catalyst containing about 1 HCl per mole of Zn3 [Co (CN) 6] 2. Example 16 shows that the yield of polyether polyol is improved by about 90% when 2 HCl is present per mole of Zn3 [Co (CN) 6] 2ZnCl2. No mention is made of the effect of the acid on the other characteristics of the polyether polyol, such as the amount of high molecular weight glue. Recently, as indicated by U.S. Patent Nos. 5,470,813, 5,482,908, 5,545,601, and 5,712,216, the researchers at ARCO Chemical Company have produced substantially non-crystalline or amorphous DMC complex catalysts, with exceptional activity, which have been also found capable of producing polyether polyols having unsaturation levels in the range of 0.002 to 0.007 meq / g (levels previously obtainable only through the use of certain solvents such as tetrahydrofuran). The polyoxypropylene polyols prepared in this way were found to react in a quantitatively different manner from the polyols with "low" unsaturation prior, in certain applications, mainly cast elastomers and microcellular foams. However, the substitution of such polyols for their catalyzed analogs based on molded and plated foam formulations is not direct. In molded foams, for example, the stiffness of the foam is increased to such a degree that the necessary crushing of the foams after molding is difficult, if not impossible. In molded foams and in plate foams, collapse of the foam often occurs, making such foams unable to occur. These effects occur even when the high effective functionality of such polyols is purposely decreased by the addition of lower functionality polyols to achieve effective functionality similar to that of base catalyzed polyols. The polyoxypropylene polyols catalyzed with DMC have exceptionally narrow molecular weight distribution, as can be seen from the gel permeation chromatograms of the polyol samples. The molecular weight distribution is often much narrower than the base-catalyzed analog polyols, particularly in the larger equivalent weight range, for example. Polydispersions of less than 1.5 are generally obtained, and polydispersions in the range of 1.05 to 1.15 are common. In view of the low levels of unsaturation and low polydispersity, it was surprising that the DMC-catalyzed polyols did not prove to be "excess error" replacements for polyols catalyzed based on polyurethane foam applications. Because propoxylation with modern DMC catalysts is highly efficient, it could be very desirable to make possible the production of polyoxypropylene polyols catalyzed with DMC, which can be used in applications of polyurethane foam in plates and molding, without causing excessive stiffness of the foam or foam collapse. Surprisingly, when one or more molar equivalents of an acid such as hydrochloric acid are combined with a highly active, substantially non-crystalline, double metal cyanide complex catalyst of the type described in U.S. Patent Nos. 5,470,813, 5,482,908, 5,545,601 and 5,712,216, the complete deactivation of the catalyst is observed. This result was unexpected in view of the teaching of U.S. Patent No. 4,472,560 such that the acids will function as promoters for conventional double metal cyanide complex catalysts.

BRIEF DESCRIPTION OF THE INVENTION It has now been discovered that polyether polyols containing polymerized propylene oxide and which mimic the behavior of the base-catalyzed analogs in plated and molded polyurethane foams can be obtained using a double metal cyanide complex catalyst, substantially no crystalline, highly active, if the catalyst is first treated with a protic acid. The excess acid is separated from the acid-treated catalyst before its use in the epoxide polymerization.

DETAILED DESCRIPTION OF THE INVENTION Intensive research into the chemical and physical characteristics of polyoxypropylene polyols has led to the discovery that despite the narrow molecular weight distribution and low polydispersity of the polyols catalyzed by double active cyanide complex catalysts, highly active , substantially non-crystalline, the small fractions of high molecular weight are largely responsible for the excessive stiffness of the foam (stabilization) and the collapse of the foam. A comparison of the gel permeation chromatograms of the base-catalyzed and catalyzed polyols by DMC shows significant differences. For example, a base-catalyzed polyol shows a significant "leader" portion of low molecular weight oligomers and polyoxypropylene monools before the main molecular weight peak. Beyond the peak, the weight percentage of the highest molecular weight species falls rapidly. A similar chromatogram of a DMC-catalyzed polyol reveals a strongly weighted peak with very little "low molecular weight" "leader" portion, but with a higher molecular weight portion ("high molecular weight" tail) showing the presence of species measurable at very high molecular weights. Due to the low concentration of these species, generally 2 to 3 percent by weight of the total, polydispersity is low. However, intensive research has revealed that the higher molecular weight species, despite their low concentrations, are largely responsible for the abnormal behavior of the polyols catalyzed by DMC in molded polyurethane foam and plaque applications. It is presumed that these high molecular weight species exert a surfactant-like effect which alters the solubility and thus the phase separation of the growing polyurethane polymers during the isocyanate-polyol reaction. By fractionation and other techniques, it has been determined that the high molecular weight tail can be divided into two molecular weight fractions based on the different effects in which these fractions influence. The first fraction, referred to herein as the "intermediate molecular weight tail", consists of polymer molecules having molecular weights in the range of about 20,000 Da to 400,000 Da, and greatly alters the stiffness of the foam, in molded foam and in foam in high elasticity plate (HR). An even higher molecular weight fraction (hereinafter, "ultra-high molecular weight glue"), dramatically influences the collapse of foam, molded foam and plate foam of conventional and high-elastic varieties (HR). Thus, a completely effective method to avoid production of the high molecular weight tail during propoxylation using complex DMC catalysts has not been known in the art. The use of processes such as the continuous addition of initiator in the batch and continuous polyol preparation, as described in WO 97/29146 and in U.S. Patent No. 5,689,012, have proven to be partially effective in the decrease in the amount of high molecular weight glue in some cases. However, the remaining portion is still higher than that which is optimal if the polyether polyol is to be used for the preparation of polyurethane foam. Commercially acceptable methods for the removal or destruction of high molecular weight glue have not yet been developed. The destruction of high molecular weight species by peroxide-induced cleavage is somewhat effective, but also breaks the desired molecular weight species. Fractionation with supercritical C02 is effective with some polyols, but not with others, and is too expensive to be commercially acceptable. It has been observed that double active, substantially non-crystalline, highly active cyanide complex catalysts containing higher levels of free (unbonded) zinc-hydroxyl groups ("Zn-OH") tend to be the catalysts that produce polyether polyols which have higher amounts of high molecular weight tail impurity. Without wishing to be bound by any theory, it is thought that the zinc-hydroxyl groups are somehow involved in the formation of such impurities. It has unexpectedly been found that the problem of reducing the high molecular weight tail in a polyether polyol obtained by using a double active, highly active, substantially amorphous metal cyanide complex catalyst, characterized by the presence of zinc-hydroxyl groups, can be easily solved by contacting the catalyst with a protic acid for a time and at a temperature effective to react the catalyst with at least a portion of the protic acid. In this context, the term "react" includes the chemical interactions that lead to the formation of covalent or ionic bonds between the protic acid and the catalyst, such that the protic acid that is reacted becomes bound in some way or otherwise with the catalyst, and is not easily removed by solvent washing, evaporation or other means of this type. At least a portion, and preferably essentially all, of any excess protic acid (unreacted) are separated from the acid-treated catalyst before use in an epoxide polymerization reaction. By properly adjusting the proportion of protic acid to the catalyst and careful selection of the acid treatment conditions, the time required to activate the catalyst and the rate at which the catalyst polymerizes an epoxide can also be significantly improved. to the catalyst that has not been contacted with acid. The choice of protic acid is not believed to be critical, although as mentioned above, the use of hydrogen halides such as hydrochloric acid at high concentrations should be avoided. Protic acids include the class of chemical substances, both organic and inorganic, that when placed in water are able to donate hydrogen ions (H +) to water molecules to form hydronium ions (H30 +). Strong and weak protic acids can be used in the present invention. Illustrative examples of suitable protic acids include, but are not limited to, phosphorous oxyacids (eg, phosphorous acid, hypophosphorous acid, phosphoric acid), sulfur oxyacids (eg, sulfuric acid, sulfonic acids), carboxylic acids (e.g. , acetic acid, halogenated acetic acids), nitrogen oxyacids (eg, nitric acid) and the like. Phosphorous acid, sulfuric acid, and acetic acid are particularly preferred protic acids. * The optimum amount of the protic acid used in relation to the amount of catalyst to be treated, will vary depending, among other factors, on the acidity (for example, the strength of the acid or pKa) of the protic acid and the conditions of treatment (acid concentration, temperature, contact time, etc.). At a minimum, the proportion of protic acid to the catalyst must be sufficiently high to reduce the amount of high molecular weight glue that the catalyst produces when a polyether polyol is used to catalyze the formation. However, care must be taken to avoid using such a large amount of protic acid so that the activity of the catalyst is adversely affected. It will normally be advantageous to select the acid treatment conditions such that the polymerization activity of the untreated catalyst (as measured by the amount of propylene oxide reacted per minute per 250 ppm of catalyst at 105 ° C) is not reduced by more than 20% (more preferably, no more than 10%). Routine experimentation wherein the acid: catalyst ratio is systematically varied to a given group of reaction conditions will allow rapid determination of the preferred range of proportions. Generally speaking, when protic acid is a relatively strong acid such as hydrochloric acid, the amount of acid used must be low in relation to the amount of catalyst to be treated. Conversely, relatively high concentrations of weak protic acid such as acetic acid are typically favorable. Without wishing to be bound by any theory, it is believed that the improvements in catalyst performance, made by the application of the recent invention, are at least in part due to the reaction of the protic acid with the zinc-hydroxyl groups initially present in the catalyst. That is, it has been observed that when the catalyst is treated with a protic acid such as acetic acid, the infrared absorption bands assigned to the free (non-associated) Zn-OH are largely eliminated and replaced with absorption bands attributed to the zinc acetate groups. The double metal cyanide catalysts treated with the protic acid are substantially amorphous (for example non-crystalline) and are comprised of a double metal cyanide, an organic complexing agent, and a metal salt. The catalyst has very high polymerization activity; for example, it is capable of polymerizing the propylene oxide at a rate greater than 3 g (more preferably, 5 g) of propylene oxide per minute per 250 ppm of catalyst (based on the combined weight of the initiator and propylene oxide) at 105 ° C. The complex double metal cyanide catalysts that meet these requirements and the methods for their preparation are described in detail in U.S. Patent Nos. 5,470,813, 5,482,908, 5,545,601 and 5,712,216, each of which is incorporated by reference herein. , In its whole. The metal cyanide. double more preferably is the zinc hexacyanocobaltate, while the metal salt (used in excess in the reaction to form the double metal cyanide) is preferably selected from the group consisting of zinc halides (zinc chloride being especially preferred), sulfate of zinc and zinc nitrate. The organic complexing agent is desirably selected from the group consisting of alcohols, ethers and mixtures thereof, with water-soluble aliphatic alcohols such as tert-butyl alcohol which is particularly preferred. The double metal cyanide complex catalyst is desirably modified with a polyether, as described in U.S. Patent Nos. 5,482,908, and 5, 545, 601. The catalyst is contacted with the protic acid for a time and a effective temperature to react the catalyst with at least a portion of the protic acid. The degree of reaction can be easily verified by standard analytical techniques. For example, where the protic acid is phosphoric acid or sulfuric acid, the elemental composition of the treated catalyst can be measured to determine the amount of residual phosphorus or sulfur in the catalyst after removal of any unreacted protic acid. When a carboxylic acid such as acetic acid is used, the relative concentration of the zinc carboxylate groups as compared to free zinc-hydroxyl groups can be evaluated by infrared spectroscopy. Generally speaking, the catalyst treatment method of this invention can be more conveniently practiced by suspending the catalyst (which is normally in a powder or particulate form) in a suitable liquid medium having the protic acid dissolved in the catalyst. East. The suspension is heated to a suitable temperature for the desired period of time, preferably while stirring or otherwise mixing. In an alternative embodiment, the catalyst is deployed in a fixed bed with the liquid medium containing the protic acid which is passed through the catalyst bed under conditions effective to achieve the desired level of catalyst reaction with the protic acid. Since many of the protic acids usable in the present invention are water soluble, it will normally be advantageous if the liquid medium is aqueous in nature. While water alone may be used, one or more organic solvents miscible in water, such as a lower aliphatic alcohol or tetrahydrofuran may also be present. The acid treatment process of this invention can thus be conveniently incorporated into the catalyst preparation processes described in U.S. Patent Nos. 5,470,813, 5,482,908, 5,545,601 and 5,712,216. The highly amorphous, highly active double metal cyanide complex catalysts shown by these patents are commonly synthesized by the combination of an aqueous solution of a metal cyanide salt such as potassium hexacyanocobaltate with an aqueous solution of an excess of a metal salt such as zinc chloride. The double metal cyanide then precipitates from a solution to form an aqueous suspension. An organic complexing agent such as a water-soluble aliphatic alcohol (for example, tert-butyl alcohol) may be present in one or both of the initial aqueous solutions or added to the aqueous suspension. The resulting aqueous suspension can be conveniently treated with protic acid according to the present invention prior to the isolation of the catalyst in anhydrous form which is described in the aforementioned patents. Alternatively, of course, a soluble, anhydrous metal cyanide complex catalyst prepared by the prior art methods or a wet filter cake of such a catalyst can be resuspended in a liquid medium and treated with acid if desired. As previously mentioned, the type of acid selected for use will affect the reaction conditions necessary to modify the catalytic performance to the desired degree. Generally speaking, the use of a weak acid such as acetic acid will require higher concentrations of acid in the liquid medium, higher reaction temperatures, and / or longer reaction times than would be the case for a strong protic acid such such as sulfuric acid or hydrochloric acid. Suitable acid concentrations can thus typically be in the range of 0.01 to 10 N; suitable reaction temperatures may be in the range of 0 ° C to 200 ° C, and suitable reaction times may be in the range of 1 minute to 1 day.

After contact with the protic acid, the treated catalyst is separated from the unreacted protic acid (excess) by any suitable means such as filtration, centrifugation or decantation. Preferably, all or substantially all of the unreacted protic acid is removed. To achieve this, it will often be desirable to wash the unreacted protic acid, from the catalyst, using water, a water-miscible organic solvent such as an alcohol, or a mixture of water and a water-soluble organic solvent, or an organic solvent in the which protic acid is soluble. The washing solvent can, for example, be passed through a filter cake of the catalyst, or the catalyst can be resuspended in the washing solvent and then separated again by filtration or other means of this type. After washing, the acid treated catalyst may be dried if desired to reduce the amount of residual wash solvent or other volatile materials. Typically, the drying step is carried out at relatively moderate conditions (e.g., room temperature at 100 ° C). A vacuum can be applied to accelerate the drying speed. In an alternative embodiment of the invention, the double metal cyanide complex catalyst is exposed to the protic acid in the vapor phase. For example, a gaseous stream containing the protic acid can be passed through a filter press cake of the catalyst at a suitable temperature until the desired degree of catalyst reaction is achieved. This process can be conveniently used where the protic acid selected for use in the catalyst treatment is relatively volatile (eg, acetic acid or other light carboxylic acid). Unreacted residual protic acid is separated from the acid treated catalyst before using the catalyst in the epoxide polymerization. The concentration of the acid-treated catalyst when used in an epoxide polymerization process is generally selected such that sufficient catalyst is present to polymerize the epoxide at a desired rate within a desired period of time. It is desirable to minimize the amount of catalyst used, for economic reasons and to avoid having to remove the catalyst from the polyether polyol produced. The activities of the catalysts obtained by the practice of this invention are extremely high; catalyst concentrations in the range of 5 to 50 parts per million, based on the combined weight of initiator containing active hydrogen and epoxide, are thus typically sufficient. The catalysts obtained by the practice of this invention are particularly useful for polymerizing propylene oxide alone, since the homopolymerization of propylene oxide is particularly apt to form undesirably high levels of the high molecular weight glue. However, the process can also be employed to polymerize other epoxides such as ethylene oxide, 1-butene oxide and the like, either alone or in combination with other epoxides. For example, copolymers of ethylene oxide and propylene oxide can be produced. The initiator containing active hydrogen can be any of the substances known in the art to be capable of performing the epoxy alkoxylation using a double metal cyanide complex catalyst and is selected based on the desired functionality and the molecular weight of the polyol product of polyether. Typically, the initiator (which may also be referred to as a "starter") will be oligomeric in character and will have a number average molecular weight in the range of 100 to 1000 and a functionality (number of active hydrogens per molecule) of 2 to 8. Alcohols (for example, organic compounds containing one or more hydroxyl groups) are particularly preferred for use as initiators. The polymerization can be conducted using any of the alkoxylation processes known in the art of double metal cyanide complex catalysts. For example, a conventional batch process can be used where the catalyst and the initiator are introduced into a batch reactor. The reactor is then heated to the desired temperature (for example, 70 to 150 ° C) and an initial portion of epoxide introduced. Once the catalyst has been started, as indicated by a drop in pressure and consumption of the initial epoxide charge, the remainder of the epoxide is added in increments with good mixing of the rector's content and reacted until it is reached the desired molecular weight of the polyether polyol product. The initiators, monomers, and polymerization conditions described in U.S. Patent No. 3,829,505 (incorporated herein by reference in its entirety) can be readily adapted for use in the present process. Alternatively, a conventional continuous process can be employed whereby a pre-activated initiator / catalyst mixture is fed continuously into a continuous reactor such as a continuously stirred tank reactor (CSTR) or tubular reactor. An epoxide feed is introduced into the reactor and the product is continuously removed. The process of this invention can also be easily adapted for use in the continuous addition of processes with starters (initiators), either batch or continuous, such as those described in detail in U.S. Application No. Series 08 / 597,781, filed on February 7, 1996, now U.S. Patent No. 5,777,177 and U.S. Patent No. 5,689,012, which are hereby incorporated in their entirety. The polyether polyols produced by the operation of the process of the invention preferably have functionalities, molecular weights and hydroxyl numbers suitable for use in molded and plate-like foams. The normal functionalities are in the range generally from 2 to 8. In general, the average functionality of the polyether polyol blends are in the range of about 2.5 to 4.0. The equivalent weights of polyether polyol are generally in a somewhat less range of 1000 Da to about 5000 Da. The unsaturation is preferably 0.015 meq / g or less, and more preferably in the range of 0.002 to about 0.008 meq / g. The hydroxyl numbers are preferably in the range of 10 to about 80. The mixtures can, of course, contain polyols of lower and higher functionality, equivalent weight, and hydroxyl number. The performance of the polyether polyols can be evaluated by testing these polyether polyols in the "Stiffness Foam Test" (TFT) and "Super Critical Foam Test" (SCFT). The polyether polyols that pass these tests have been found to work well in commercial applications of plated and molded foam, without excessive rigidity, and without collapse of the foam. The SCFT consists of the preparation of a polyurethane foam using a formulation that is specifically designed to amplify the differences in the behavior of polyether polyol. In SCFT, a foam prepared from a given polyether polyol is reported as "seated" if the surface of the foam appears convex after blowing and is reported as collapsed if the surface of the foam is concave after blowing. The amount of collapse can be reported in a relatively quantitative way by calculating the percentage change in a cross-sectional area taken through the foam. The foam formulation is as follows: polyether polyol, 100 parts; water, 6.5 parts; methylene chloride, 15 parts; Niax® A-l amine type catalyst, 0.10 parts; tin catalyst T-9, 0.34 parts; silicone surfactant L-550, 0.5 parts. The foam is reacted with a mixture of 2,4- and 2,6-toluene diisocyanate 80/20 at an index of 110. The foam can be conveniently emptied into a standard 0.028 m 3 (1 cubic foot) cake-type box. , or a standard 3,755 liter (1 gallon) ice cream container. In this formulation, polyether polyols conventionally prepared, for example base catalyzed, having high secondary hydroxyl content cause the foam to settle or settle approximately 10-20%, in general 15% ± 3%, whereas polyether polyols prepared from. of DMC catalysts which contain unacceptably high levels of high molecular weight glue cause the foam to collapse by about 35-70%. While SCFT is used to evaluate differences in foam stability, the Stiffness Foam Test (TFT) amplifies the differences in reactivity, as reflected by the porosity of the foam. In the stiffness foam test, the resin component consists of 100 parts of polyether polyol, 3.2 parts of water (Reactive blowing agent), 0.165 parts of amine catalyst C-183, 0.275 parts of tin catalyst T-9, and 0.7 parts of silicone surfactant L-620. The resin component is reacted with toluene diisocyanate 80/20 at an index of 105. The stiffness of the foam is evaluated by measuring the air flow in the conventional manner. Rigid foams have reduced air flow. The analytical procedure useful for measuring the amount of high molecular weight glue in a given polyether polyol, catalyzed with DMC, is a conventional technique of high performance liquid chromatography (HPLC), which can be easily developed by a person of experience in the technique. The molecular weight of the high molecular weight fraction can be estimated by comparing its elution time in the GPC column with that of an appropriate molecular weight polystyrene standard. As is well known, high molecular weight fractions elute from a GPC column more rapidly than the lower molecular weight fractions, and to help maintain a stable baseline, it is appropriate, after elution of the fraction from high molecular weight, divert the rest of the HPLC eluate to the waste, instead of allowing to pass through the detector, overloading the latter. Although many suitable detectors may be used, a convenient detector is an evaporative light scattering detector (ELSD) such as those commercially available. In the preferred analysis method, a Jordi Gel DVB 103 Angstrom column, of 10 x 250 mm, with a particle size of 5 microns, is employed with a mobile phase consisting of tetrahydrofuran. The detector used is a Varex Model IIA evaporative light scattering detector. The polystyrene reserve solutions are made from polystyrenes of different molecular weights by appropriate dilution with tetrahydrofuran, to form standards containing 2, 5 and 10 mg / l of polystyrene. Samples are prepared by weighing 0.1 gram of polyether polyol in a 28.3 gram (1 oz) bottle, and adding tetrahydrofuran to the sample to bring the total sample weight and tetrahydrofuran to 10.0 grams. The samples of the calibration solutions of 2, 5 and 10 mg / l of polystyrene are sequentially injected into the GPC column. The duplicates of each polyether polyol sample solution are then injected, followed by a reinjection of the various polystyrene standards. The peak areas for the polystyrene standards are electronically integrated, and the electronically integrated peaks for the two groups of each candidate polyol are electronically integrated and averaged. The calculation of the high molecular weight tail in ppm is then performed by standard data manipulation techniques. Having generally described this invention, further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.

EXAMPLES Example 1 This example demonstrates the treatment of a double metal cyanide complex catalyst with acetic acid according to the invention. A 62.5% solution of zinc chloride in 120 grams of water was diluted using a mixture of 230 ml of deionized water and 50 ml of terbutyl alcohol. Separately, 7.5 grams of potassium hexacyanocobaltate was dissolved in a mixture of 100 ml of deionized water and 20 ml of tert-butyl alcohol. The potassium hexacyanocobaltate solution was added to the zinc chloride solution in 35 minutes, while homogenizing at 20% of the maximum intensity. After the addition was completed, homogenization was continued at 40% of the maximum intensity for 10 minutes. The homogenizer was then stopped and a solution of 8 grams of a propylene glycol diol of molecular weight of 1000 in a mixture of 50 ml of deionized water and 2 ml of tetrahydrofuran was added to the mixture. After shaking slowly for 3 minutes, the mixture was filtered under pressure at 2.81 kg / cm2 (40 psig) through a 20 micron nylon membrane. The filter press cake of the catalyst was resuspended in a mixture of 130 ml of tert-butyl alcohol, 55 ml of deionized water and 3 grams of acetic acid at 40% of the maximum homogenization intensity for 10 minutes. The homogenizer was then stopped and 2 grams of propylene glycol diol in 2 grams of tetrahydrofuran were added. After stirring slowly for 3 minutes, the suspension was refiltered as previously described. The filter press cake of the catalyst was resuspended in 185 ml of terbutyl alcohol at 40% of the maximum homogenization intensity for 10 minutes. The homogenizer was then stopped and 1 gram of polypropylene glycol diol in 2 grams of tetrahydrofuran was added. After stirring slowly for 3 minutes, the suspension was refiltered as previously described. The catalyst filter cake obtained in this way was dried at 60 ° C under vacuum (762 mmHg) until a constant weight was obtained.

EXAMPLE 2 This example illustrates an alternative process for treating a complex catalyst of double metal cyanide with acetic acid, according to the present invention. A 62.5% aqueous solution (302.6 grams) of zinc chloride was diluted with 580 ml of deionized water and 126 ml of tert-butyl alcohol. Separately, a solution of 18.9 grams of potassium hexacyanocobaltate in 252 grams of deionized water and 50 ml of tert-butyl alcohol was prepared. The potassium hexacyanocobaltate solution was added to the zinc chloride solution in 2 hours at 50 ° C under agitation of 900 rpm. After the addition was complete, stirring was continued for another hour at 900 rpm. Stirring was decreased to 400 rpm and a solution of 15 grams of polypropylene glycol diol with molecular weight of 1000 in 120 ml of deionized water and 10 ml of tetrahydrofuran was added. After stirring for 3 minutes, the mixture was filtered under pressure at 2.81 kg / cm2 (40 psig) through a 20 micron nylon membrane. The filter press cake of the catalyst was resuspended in a mixture of 328 ml of tert-butyl alcohol and 134 ml of deionized water at 50 ° C for one hour (agitation of 900 rpm). The stirring speed was decreased to 400 rpm and 5.1 grams of polypropylene glycol diol dissolved in 5.1 grams of tetrahydrofuran were added. After stirring for 3 minutes, the mixture was filtered under pressure as previously described. The catalyst filter cake was resuspended in 185 ml of tert-butyl alcohol and stirred for 1 hour at 50 ° C (900 rpm stirring). After reducing the stirring speed to 400 rpm, a solution of 2.5 grams of polypropylene glycol diol in 5 grams of tetrahydrofuran was added. After stirring 3 minutes, 70 grams of acetic acid was added and the mixture was stirred for 2 hours before filtering under pressure as previously described. The filter press cake of the catalyst was dried at 60 ° C under vacuum (762 mmHg) until a constant weight was obtained.

Examples 3A-3C These examples demonstrate the treatment of the zinc hexacyanocobaltate complex catalyst with a variety of protic acids. A 62.5% aqueous solution (302.6 grams) of zinc chloride was diluted with 580 ml of deionized water and 126 ml of tert-butyl alcohol. Separately, a solution of 18.9 grams of potassium hexacyanocobaltate in 252 ml of deionized water and 50 ml of tert-butyl alcohol was prepared, then added to the zinc chloride solution in 2 hours at 50 ° C (900 rpm). After the addition was complete, stirring was continued at 900 rpm for one hour before the stirring speed was decreased to 400 rpm and a solution of 15 grams of a polypropylene glycol diol of 1000 molecular weight in 120 ml of water was added. deionized and 10 ml of tetrahydrofuran. After stirring for 3 minutes, the mixture was filtered under pressure at 2.81 kg / cm2 (40 psig) through a 20 micron nylon membrane. The filter press cake of the catalyst was resuspended in a mixture of 328 ml of tert-butyl alcohol and 134 ml of deionized water at 50 ° C for 1 hour (900 rpm stirring). The suspension was then divided into three equal portions (A, B, C). Each portion was combined with aqueous acid as follows: Portion Acid A 0.33 g acetic acid + 8 g water B 0.54 g 37% HCl + 8 g Water C 0.36 g hydrophosphorous acid + 8 g water Each portion was then homogenized at 40% of the maximum intensity for 10 minutes, then combined with 1.7 grams of polypropylene glycol diol dissolved in 2 grams of tetrahydrofuran. After stirring slowly for 3 minutes, each portion was filtered under pressure as previously described and then resuspended in 156 ml of terbutyl alcohol at 50 ° C for 10 minutes while mixing with a homogenizer. The homogenization was stopped and 0 to 83 grams of the polypropylene glycol diol dissolved in 2 grams of tetrahydrofuran was added to each portion. After stirring slowly for 3 minutes, the catalyst was again collected by pressure filtration and then dried at 60 ° C under vacuum (762 mmHg) until a constant weight was obtained.

EXAMPLE 4 This example demonstrates the effect of the treatment of the highly amorphous, highly active double metal cyanide complex catalysts characterized by the presence of zinc-hydroxyl groups with varying concentrations of acetic acid. The catalysts used were comprised of zinc hexacyanocobaltate, zinc chloride, tert-butyl alcohol (organic complexing agent), and a polyether polyol, and had been prepared according to the general procedures described in U.S. Pat. 5,482,908. The acid treatment was carried out by stirring the wet filter press cake in aqueous solutions of tert-butyl alcohol of acetic acid (concentrations of 1, 5 and 15%) following the methods described in Example 1 above.

The catalytic performances of the acid treated catalysts were compared to that of a control catalyst which had not been treated with acid in the preparation of polypropylene glycol triol of number average molecular weight of 3200 containing 12% by weight of ethylene oxide. The polymerizations were carried out in a Buchi reactor of 1 liter at 130 ° C using a feed time of 2 hours after the start of the epoxide addition and a catalyst concentration of 30 ppm based on the final weight of the triol of polypropylene glycol. The results obtained are shown in the following table.

Table 1 1 Comparative (control ND = Not Detected When the concentration of acetic acid during the acid treatment was only 1 or 5%, the small reduction in the amount of high molecular weight glue was observed in comparison to the control catalyst (compare Example 4B with Example 4A). This was consistent with the infrared spectroscopic analysis of the acid-treated catalysts, which showed no change in the acute absorption bands at 3609 cirT1 (assigned to the stretching vibration of free or unbound Zn-OH) and 642 cm " 1 (assigned to the Zn-OH bending vibration) A weak absorption band was visible at 1620 cm-1 which is assigned to the stretch vibration of the carboxylate (zinc acetate) in the catalyst that had been treated with 15% acetic acid for 2 hours, however, the IR absorption bands at 3609 cm "1 and 642 cm" 1 were no longer present and the band at 1620 cm "1 was more intense (indicating that a higher degree of conversion of the zinc-hydroxyl groups to the zinc acetate groups). The polypropylene glycol triol prepared using the catalyst treated with 15% acetic acid (Example 4C) contained undetectable levels of impurities having molecular weights greater than 400,000 and passed the Supercritical Foam Test.

Example 5 Portions of a highly active, substantially non-crystalline double active metal cyanide complex catalyst, comprised of zinc hexacyanocobaltate, tert-butyl alcohol, zinc chloride and polyether polyol and prepared according to the process described in U.S. Patent No. 5,482,908 , were treated either with phosphoric acid or sulfuric acid. The residual phosphorus in the catalyst treated with phosphoric acid was only 0.4% by weight by elemental analysis. The catalytic performance of each catalyst was compared to that of a control (without acid treatment) in the preparation of a polypropylene glycol triol of number average molecular weight of 3000, using 40 ppm of catalyst (based on the final weight of the triol). polypropylene glycol) at 105 ° C. The control catalyst required approximately 100 minutes until the rapid polymerization of the propylene oxide was initiated. In contrast, the start (activation) times for the acid treated catalysts under comparable conditions were only about 30 to 40 minutes. In addition, the proportion of the polypropylene glycol triols made from acid-treated catalysts having a molecular weight greater than 100,000 was reduced by about 35% compared to the triol prepared using the control catalyst (untreated).

Example 6 The effects of the treatment of a highly active, substantially non-crystalline double metal cyanide catalyst of the type used in Examples 4 and 5 with varying amounts of phosphoric acid were examined. To prepare the catalyst 6B, for example, a solution of 0.83 grams of 85% phosphoric acid dissolved in a mixture of 80 grams of tert-butyl alcohol and 20 grams of distilled water was used at room temperature to treat the catalyst. The zinc hexacyanocobaltate complex catalyst (6 grams) was added slowly and the resulting mixture was stirred at room temperature for 2 hours. The catalyst was collected by filtration and dried for 4 hours at 50 ° C. 6-C and 6-D catalysts were prepared in a similar manner using higher concentrations of phosphoric acid. The catalysts were evaluated in the preparation of a polypropylene glycol triol of molecular weight from 3000 to 120 ° C (30 ppm catalyst). The results obtained are summarized in the following table.

Table II * Comparative example (control) 1 By analysis in catalyst 2 Catalyst deactivated by polymerization 3 The foam settled approximately 37% and a division in the foam was observed.

Examples 7-9 Polypropylene glycol triols of number average molecular weight of about 3200 and containing 12% by weight of ethylene oxide (the remainder being propylene oxide) were prepared using a polymerization temperature of 130 ° C and a time of 2 hour epoxide feed, to compare the operation of the acid treated Catalysts 3B and 3C (see Example 3) with that of a double analogue metal cyanide catalyst which had not been treated with acid. The results obtained are shown in the following table.

TABLE III Comparative ND = Not detected Both acid-treated catalysts gave products containing lower levels of molecular glue impurities (particularly those with impurities having a molecular weight greater than 400,000) than those produced by the control catalyst used in Example 7. At the same time, no Adverse effects of the acid treatment were observed on the other characteristics of the product such as hydroxyl number, polydispersity or viscosity.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (21)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A method for modifying a double metal cyanide complex catalyst comprising zinc hydroxyl groups, characterized in that the method comprises reacting said catalyst with a Bronsted acid; and separating at least a portion of any excess acid from the catalyst.

2. A method for increasing the yield of a complex catalyst of double metal cyanide, highly active, substantially non-crystalline, according to claim 1, characterized in that the catalyst is contacted with a protic acid for a time and a temperature effective to make reacting the catalyst with at least a portion of the protic acid.

3. A method according to claim 1 or 2, characterized in that the protic acid comprises a substituted or unsubstituted carboxylic acid.

4. A method according to claim 3, characterized in that the protic acid comprises acetic acid or a halogenated derivative thereof.

5. A method according to any of the preceding claims, characterized in that the protic acid comprises an inorganic acid.

6. A method according to claim 5, characterized in that the inorganic acid is selected from the group consisting of sulfur oxyacids and phosphorus oxyacids.

7. A method according to claims 3 to 6, characterized in that the protic acid is selected from the group consisting of acetic acid, sulfuric acid, phosphoric acid and mixtures thereof.

8. A method according to any of the preceding claims, characterized in that the reaction is carried out using a suspension of the catalyst in a liquid medium in which the protic acid is soluble.

9. The method according to claim 8, characterized in that the protic acid is present at a concentration of 0.01 N to 10 N in the liquid medium.

10. A method according to any preceding claim, characterized in that the step of separating the unreacted protic acid from the catalyst is achieved by filtering the suspension to obtain a filter press cake comprising the catalyst.

11. A method according to claim 10, characterized in that it comprises the additional step of washing the press filter cake with one or more solvents in which the unreacted protic acid is soluble.

12. A method according to any preceding claim, characterized in that essentially any excess of protic acid is separated from the catalyst.

13. A method according to any preceding claim, characterized in that the catalyst is comprised of a double metal cyanide, an organic complexing agent and a metal salt.

14 A method according to any preceding claim, characterized in that the double metal cyanide complex is zinc hexacyanocobaltate.

A method according to claim 13 or 14, characterized in that the organic complexing agent comprises a water-soluble aliphatic alcohol.

16. A method according to claim 15, characterized in that the complexing agent of the water-soluble alcohol is terbutyl alcohol.

17. A method according to any of the preceding claims, characterized in that the catalyst further comprises a polyether polyol.

18. A method according to any of the preceding claims, characterized in that at least one equivalent of protic acid is used per equivalent of zinc-hydroxyl groups.

19. A method according to any of claims 13 to 18, characterized in that the metal salt comprises a zinc halide.

20. An epoxide polymerization process, characterized in that it comprises reacting an epoxide and an initiator containing active hydrogen, in the presence of a complex catalyst of double metal cyanide, highly active, substantially non-crystalline, prepared according to the method of conformity - with any of the preceding claims, for a time and at a temperature effective to form a polyether polyol.

21. An epoxide polymerization process according to claim 20, characterized in that the epoxide comprises propylene oxide and the initiator comprises an alcohol.