KR20010015813A - Process for preparing polyether polyols and polyols prepared therewith - Google Patents

Abstract

Polyether polyols suitable for use in the production of rigid polyurethane foams are prepared by methods using imidazole catalysts. Imidazole catalysts can be used at higher temperatures to produce polyols without losing their reactivity at higher temperatures and thus reduce residence time and energy consumption in the polyol production process.

Description

Process for preparing polyether polyols and polyols prepared therewith

The present invention relates to a process for producing polyether polyols. The present invention relates in particular to a process for producing polyether polyols useful for the production of rigid polyurethane foams.

Polyether polyols are useful for making polyurethane products. It is known to use polyether polyols in the production of polyurethane products such as flexible foams, rigid foams, elastomers and sealants. Of these, rigid polyurethane foams are important products that have been used as insulation and structural agents.

Nodelman, US Pat. No. 4,332,936, describes a process for preparing polyether polyols which is described as being particularly suitable for the production of rigid polyurethane foams. It is described here that a polyhydric hydroxy initiator such as sucrose is mixed or dissolved with dimethylformamide and then the initiator is reacted in the presence of an alkylene oxide and an amine catalyst.

U.S. Patent Nos. 5,030,758 and 5,141,968 to Dietrich et al. Describe a process for preparing polyether polyols using amine catalysts. These references relate to aromatic amine disclosed polyols.

Preparation of polyols using methods that can be used at high temperatures would be desirable in the art for making polyether polyols useful for making rigid polyurethane foams. It would also be desirable in the art to prepare polyols using a method comprising using a highly reactive catalyst. In addition, it would be desirable in the art to prepare polyols using methods using catalysts having high reactivity at high temperatures. It is also preferred to prepare polyether polyols in post-treated polyether polyol diluents under imidazole catalysis conditions characterized by alkylene oxides which react with the initiator but not with the diluent.

In one aspect, the invention relates to a process for the preparation of polyether polyols comprising mixing an initiator with an alkylene oxide at high temperature alkoxylation conditions sufficient to produce a rigid polyether polyol in the presence of an imidazole catalyst, provided If aromatic amine initiators are used, the alkoxylation is carried out at temperatures above 125 ° C.

In another aspect, the invention is a polyether polyol prepared by a process comprising mixing an initiator with an alkylene oxide in the presence of an imidazole catalyst under high temperature alkoxylation conditions sufficient to produce a rigid polyether polyol, If aromatic amine initiators are used, the alkoxylation is carried out at temperatures above 125 ° C.

In one embodiment, the present invention relates to a process for preparing a rigid polyether polyol in the presence of an imidazole catalyst. For the purposes of the present invention, the imidazole catalyst is any compound of the formula:

Wherein X, Y, Z and Z 'are hydrogen, methyl, ethyl or phenyl groups which combine with the following compounds: imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, N-phenylimidazole, 2-phenylimidazole and 4-phenylimidazole. Mixtures of these compounds can be used and are also cited herein as imidazole catalysts.

In the process of the invention, polyols are prepared by mixing an initiator with an alkylene oxide in the presence of an imidazole catalyst. Initiators are useful starting materials for the preparation of polyols, which are characterized in that they comprise at least two active hydrogen containing groups. For the purposes of the present invention, an active hydrogen containing group is any group having hydrogen capable of reacting with an alkylene oxide in the presence of an imidazole catalyst. Preferably, the active hydrogen containing group is an amino or hydroxy group. Active hydrogen containing groups may be present on aliphatic or aromatic molecules. For example, an initiator useful in the process of the invention may be an aliphatic alcohol or amine having two or more active hydrogen containing groups. Alternatively, initiators useful in the process of the invention can be aromatic diamines or polyamines.

Initiators useful in the present invention include water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, unsubstituted or N-mono, N, N having from 1 to 4 carbon atoms in the alkyl moiety. And N, N'-dialkyl-substituted diamines, for example unsubstituted or mono- or dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3 And 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,3-, 2,4 And 2,6-tolylenediamine and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane. Other suitable initiator molecules useful in the present invention are alkanolamines such as ethanolamine, N-methyl- and N-methyl- and N-ethyl-ethanolamine, dialkanolamines such as diethanolamine, N-methyl And N-ethyl-diethanolamine, and trialkanolamines such as triethanolamine, and ammonia.

Preferably, the initiators used in the present invention are polyhydric alcohols, in particular dihydric and / or trihydric alcohols such as ethanediol, nonyl phenol, bisphenol-A, bisphenol-F, novolak phenolic resins, formaldehyde and Mannich base polyols, propylene glycols, dipropylene glycols, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylol derived from phenols or alkyl phenols reacted with diethanol or dipropanolamine (Mannich base) Propane, pentaerythritol, sorbitol, alpha methyl glucoside and sucrose. For the purposes of the present invention, water is a dihydric alcohol because the reaction product of water and alkoxide is a dihydric alcohol. More preferably, the initiators used in the present invention are glycerin, water, sucrose and mixtures thereof.

The initiator used in the present invention may also be the alkoxylation product of the initiator molecules listed above. For example, in a preferred embodiment, the initiator used in the present invention is propoxylated or ethoxylated ethylene glycol. Another example of a similar useful initiator is propoxylated or ethoxylated glycerin. Another example of a similar useful initiator is propoxylated or ethoxylated propylene glycol.

Mixtures of initiators may be used in the present invention and are also preferred. Examples of mixed initiators include mixtures such as: sucrose and water; Glycerin and sorbitol; Propylene glycol and sucrose; And ethylene glycol and sucrose. More preferably the initiator used in the present invention is a mixed initiator that is propoxylated. Most preferably the initiator used in the present invention is a propoxylated mixture of sucrose and glycerin.

In the process of the invention, polyols are prepared by mixing an initiator with an alkylene oxide in the presence of an imidazole catalyst. Alkylene oxides used in the present invention include any useful for the production of polyether polyols. The alkylene oxide preferably has 2 to 8 carbons. More preferably the alkylene oxide has 2 to 4 carbons. Most preferably the alkylene oxides are ethylene oxide, propylene oxide, butylene oxide and mixtures thereof.

The polyols produced by the process of the invention can be used in devices in which similar conventional polyols can be used, in particular in devices useful for the production of rigid polyurethane foams. Polyols useful in the production of rigid polyurethane foams generally have an OH functionality of from 2 to 8; OH of 200 to 2000; And a molecular weight of 62 to 2000. This range refers to the general reaction product by alkoxylation of an initiator such as water having a low OH functionality of 2 and sucrose having a high OH functionality of an initiator such as 8. The present invention also contemplates alkoxylation of mixtures of initiators as well as initiators with intermediate functionality.

Preferably the polyol of the present invention has an average functionality of 2 to 8, an OH of 200 to 800, and a molecular weight of 150 to 2,400. More preferably, the polyol of the present invention has an average functionality of 3 to 8, an OH of 200 to 600, and a molecular weight of 300 to 2,400. Most preferably the polyols of the present invention have an average functionality of 4 to 8, an OH of 300 to 600, and a molecular weight of 350 to 1,600.

In the process of the invention, the reaction of the initiator and the alkylene oxide is carried out in the presence of an imidazole catalyst. Preferably from 0.0001 parts to 0.01 parts of imidazole catalyst is used. Most preferably 0.001 parts of imidazole catalyst is used. The part of the catalyst is calculated by dividing the weight of the imidazole catalyst used by the total weight of the product and diluent present in the reactor.

The reaction of the initiator and the alkylene oxide is carried out under high temperature alkoxylation conditions sufficient to produce the polyether polyols by the process of the invention. The field of preparing conventional polyether polyols by conventional methods is well known to those skilled in the art of preparing polyols. The high temperature alkoxylation conditions of the present invention are substantially the same except that the temperature at which the alkoxylation is carried out is from 100 deg. C to the vicinity of the decomposition or discoloration point of the polyol (but not the decomposition point or discoloration point). Such conditions include pressures of 10 psig (69 kPa) to 100 psig (690 kPa) and temperatures of 100 to 150 ° C. More preferably the high temperature alkoxylation conditions are from 31 psig (206 kPa) to 80 psig (551 kPa). Even more preferably the temperature of the high temperature alkoxylation conditions is 120 to 150 ° C. Most preferably the temperature of the high temperature alkoxylation conditions is 130 to 145 ° C. When the process of the present invention is used to prepare polyols from formulations comprising aromatic amine initiators, the alkoxylation is carried out at temperatures above 125 ° C.

The advantage of the imidazole catalysts used in the process of the present invention is that when they are compared to other conventional amine catalysts such as triethylamine, trimethylamine and methyldiethylamine, the imidazole catalyst is at a high level at conventional alkoxylation temperatures. For most polyols and initiators, the reactivity of the imidazole catalyst increases with increasing temperature to the temperature at which it breaks down. For example, trialkylamine catalysts begin to lose catalyst activity as the alkoxylation temperature starts at about 110 ° C., but imidazole catalysts continue to increase catalyst activity until the reaction temperature reaches 150 ° C. or higher. . The ability for use in the process of the invention at elevated temperatures results in increased reaction rates and reduced residence time and energy consumption in the preparation of polyether polyols.

Another advantage of amine catalysts and in particular imidazole catalysts in general is that methods using such catalysts can be used to alkoxylate initiators without alkoxylating the diluents in polyol diluents. Suitable diluents are any polyether or polyester polyols in which two or more, preferably three alkylene oxides are added to each active hydrogen of the initiator. The amine catalyst activates the addition of one to three alkylene oxides per active hydrogen group of the initiator, so that when more than two alkylene oxides are added, the polyol does not further react with the alkylene oxide and the polyol is a diluent Can be used. This may be of particular advantage when alkoxylating solid initiators such as sucrose and sorbitol. It is particularly advantageous when one wants to produce a substantially homogeneous polyol made from a solid initiator, since a polyol substantially similar to the desired product polyol can be used as a solvent for the initiator.

Polyols are often prepared in both continuous and batch processes. In a batch process, the polyol fills the components of the formulation in one or more steps, but not all of the desired components need to be filled at once. For example, all initiators for polyols are placed in the reactor early in the reaction. This "batch" of raw material is then introduced into the steps of making the polyol to produce a single "batch" of polyol. In contrast, in a continuous process, the raw material is continuously fed into the production apparatus so that the polyol is present at different points in different stages of production. The imidazole catalyst of the present invention may be used in batch or continuous processes.

Polyols prepared by the process of the present invention are used in a similar manner to conventional polyols prepared using conventional methods. For example, the polyols of the present invention can be used as prepared or in admixture with additives. If desired, the polyols of the present invention may be mixed with other types of polyols.

The following examples are provided to illustrate the present invention. These examples are not intended to limit the scope of the present invention and should not be so interpreted. Unless otherwise stated, amounts are parts by weight or weight percent.

Example 1: A mixture of 300 g of glycerin and 0.5 g of 2-ethyl-4-methylimidazole is heated to 100 ° C. in a 1 L pressure vessel equipped with a stirrer. After the vessel has reached thermal equilibrium, 11.96 g of propylene oxide is injected into the vessel. Gas chromatography measures that the initial concentration of propylene oxide is 1.8%. After 195 minutes, the concentration of propylene oxide is 0.04%.

Example 2: A mixture of VORANOL 490 ^* 10.6 lb (4.8 kg) and VORANOL 370 ^** 7.1 lb (3.2 kg) is added to a 20 gal (75.7 L) pressure vessel. To this is added 0.1 lb (45.4 g) of 2-ethyl-4-methylimidazole and 16 lb (about 7.3 kg) of sucrose. The mixture is heated at 120 ° C. until it reaches thermal equilibrium and stirred under a pad of nitrogen. 43 lbs (about 19.5 kg) of propylene oxide are then added at a rate of 0.11 lbs (49.9 g) / minute and the mixture is maintained at 120 ° C. for 5 hours. The final product is analyzed for physical properties, has a viscosity of 78.7Cs at 210 ° F., has a hydroxyl content of 10.73% and Gardner Color 13. ^* VORANOL 490 is a trade name of The Dow Chemical Company. ^** VORANOL 370 is a trademark of The Dow Chemical Company.

Example 3 A series of experiments are carried out, where 1-methoxy-2-propanol is reacted with propylene oxide using trimethylamine and 2-ethyl-4-methylimidazole as catalysts. The reaction is carried out in a stirred stainless steel pressure vessel heated with a temperature of 1 L, electric coil heater. The vessel is loaded with about 300 g of 1-methoxy-2-propanol, closed and purged with nitrogen to remove oxygen. In experiments using trimethylamine as a catalyst, 300 ml of gas trimethylamine catalyst is added as a gas using 50 ml of syringe. In experiments using 2-ethyl-4-methylimidazole as a catalyst, 0.52 g of 2-ethyl-4-methylimidazole is introduced into a pressure vessel together with 1-methoxy-2-propanol. The vessel is then stirred, heated to the indicated reaction temperature, and about 6 g of propylene oxide is pressurized into another reaction vessel from another small pressure vessel using nitrogen gas. Samples are withdrawn into the liquid phase using the attached deep tube and analyzed by a) amine content, titration ^* and b) unreacted propylene oxide (PO), gas chromatography ^** . The amount of PO is determined by also including about 6 g of methyl tertiary butyl ether as an unreactive internal standard for gas chromography.

The reaction rate is calculated by plotting the unreacted PO concentration versus time. Plots of ln (natural log) of PO concentrations (as weight percent) provide linear rate constants for comparison of reaction rates when linear. In comparisons between experiments that may have different amine catalyst concentrations, the second order rate constant can be derived by dividing this slope by the base molarity. Table 1 below lists the rate data for this reaction. Reaction rates for propoxylation vary depending on the amine catalyst and the polyol reactant. Low equivalent alcohols or polyols react faster than materials already propoxylated. The rate of propoxylation decreases with reaction temperature for triethylamine and increases for imidazole.

Example 4: Approximately 150 weight equivalents of hydroxyl (specific range: 10.8 to 11.6% OH, viscosity 0.89 to 1.17 poise, 0.089 to 0.117 Ns /) of propoxylated polyol having a weight ratio of sucrose / glycerine of 60/40 M 2)) is added as a reaction solvent 468 g of this polyol are mixed with 419 g of sucrose and 1.82 g of N-methylimidazole This mixture is stirred in a 4 L pressure vessel, which is heated to 130 ° C. and 130 ° C. during the reaction It is maintained at ± 0.5 ° C. 1113 g of propylene oxide is added over 4 hours using a positive displacement pump The amount of residual propylene oxide is measured by monitoring the reactor pressure for the last 2 hours. Obtained by plotting the natural log versus time of pressure until the pressure is constant, the slope of this plot is subtracted from the linear primary plot with a slope of less than -0.0756 / min. Dividing this number by the catalyst concentration at the end of the reaction (measured at 1040 ppm or 0.0127 milliequivalents per gram) gives a second rate constant of 5.95 g / milliequivalents per minute The product is 12.16% OH and 210 It has a viscosity of 1.05 poise (0.105 Ns / m 2) at ° F (98.9 ° C).

Claims (10)

Mixing the initiator with an alkylene oxide in the presence of an imidazole catalyst under high temperature alkoxylation conditions sufficient to produce a polyether polyol, wherein when an aromatic amine initiator is used, the alkoxylation is performed at a temperature above 125 ° C. Method for producing a polyether polyol. The process of claim 1 wherein the polyether polyols are useful for the production of rigid polyurethane foams. The method of claim 2 wherein the initiator is a mixture of aliphatic alcohols. The method of claim 4 wherein the initiator is a mixture of glycerin and sucrose. The imidazole catalyst of claim 2, wherein the imidazole catalyst is imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimida Sol, N-phenylimidazole, 2-phenylimidazole, 4-phenylimidazole and mixtures thereof. The process of claim 5 wherein the imidazole catalyst is 2-ethyl-4-methylimidazole. The process of claim 2 wherein the alkylene oxide is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide and mixtures thereof. The method of claim 11, wherein the alkylene oxide is propylene oxide. The method of claim 2, wherein the high temperature alkoxylation conditions comprise a temperature of 120 ° C. to 150 ° C. 4. The method of claim 2 wherein the average functionality of the polyether polyol is between 4 and 8.