Process for preparing polysuccinimide polymers

Abstract: Polysuccinimide polymers comprising from about 5 to 100 percent by weight of methylenesuccinimide moieties, and from 0 to about 95 percent by weight of one or more amino acid moieties are provided. Also provided is a process for preparing polysuccinimide polymers by forming a polymerization mixture of poly(alkylene glycol), ammonia, one or more monoethylenically unsaturated poly(carboxylic acid) and, optionally, one or more other monoethylenically unsaturated compound; heating the mixture to an elevated temperature; and maintaining the mixture at the elevated temperature to form polysuccinimide polymers.

Description: The present invention is concerned with a process for preparing polysuccinimide polymers, including polymethylenesuccinimide, polysuccinimide and copolymers thereof and their use in certain compositions. Several methods are known for obtaining polysuccinimide which, when hydrolyzed to form the corresponding poly(amino acid), is useful as an absorbent, hard-surface cleaner, water-treatment additive for boiler waters and cooling towers and as a detergent additive acting as a builder, anti-filming agent, dispersant, sequestering agent and encrustation inhibitor. However, all of the previously known methods for preparing polysuccinimide suffer from the drawbacks of excessively long process times, expensive starting materials, or require the handling of solid materials which poses many difficulties in a manufacturing environment. United States Patent 5,057,597 to Koskan discloses a solid-phase process for preparing polysuccinimide by fluidizing an amino acid with agitation in a nitrogen atmosphere at a temperature of at least 180°C for three to six hours. The resultant polysuccinimide is then hydrolyzed to form a poly(amino acid). United States Patent 4,839,461 to Boehmke, et al. discloses a process for preparing poly(aspartic acid) by combining maleic acid or maleic anhydride and an ammonia solution in a molar ratio of 1:1-1.5. The mixture is then heated to 120°-150°C. and the resulting solution of ammonium salt and maleic acid is evaporated, leaving a crystal mash. The crystal mash is then melted, during which time the waters of condensation and crystallization distill off. A porous mass of poly(aspartic acid) results. The entire process requires six to eight hours to complete. Japanese Patent 52-0088773 B assigned to Ajinomoto, discloses a solvent-based process for preparing poly(aspartic acid). The process described therein utilizes a hydrohalic acid salt of aspartic acid anhydride in one or more organic solvents. The solvents disclosed are organic acids such as propionic acid, butyric acid, and valeric acid; alcohols such as tert-butyl alcohol and tert-amyl alcohol, esters such as ethyl acetate and butyl acetate; ketones such as methyl isobutyl ketone and cyclohexanol; ethers such as tetrahydrofuran and dioxane; halogenated hydrocarbons such as ethylene dichloride and dichlorobenzene; hydrocarbons such as toluene, xylene and decalin; and amides such as dimethylformamide. These solvents may impart additional hazards, expense, odor, toxicity and removal steps to obtain the final product. The prior art methods for the synthesis of polysuccinimides and poly(amino acids) are time consuming, complex and/or use large volumes of volatile organic solvents or inert gases. The present invention enables a solvent process to be provided for producing polysuccinimide polymers. The present invention also enables a method to be provided for preparing poly(aspartic acid) which does not utilize aspartic acid as a starting material. The present invention further enables a solvent process to be provided for producing polysuccinimide polymers which may not require a product separation step. According to the present invention there is provided a process for preparing polysuccinimide polymers, which comprises: a) forming a polymerization mixture comprising poly(alkylene glycol) of molecular weight of from 300 to 30,000, ammonia, one or more monoethylenically unsaturated poly(carboxylic acid) and, optionally, one or more other monoethylenically unsaturated compound; b) heating the mixture to an elevated temperature; and c) maintaining the mixture at the elevated temperature to form polysuccinimide polymers. The present invention also provides the use, as an absorbent, hard-surface cleaner, water treatment additive for boiler waters and cooling towers, or detergent additive, of a composition comprising polysuccinimide polymer and poly(alkylene glycol). As used herein in connection with the present invention: "polysuccinimide polymers" refers to polymeric materials which contain succinimide moieties, including methylenesuccinimide moieties, in the polymer chain and may contain other moieties; "polysuccinimide" refers to polymeric materials which contain only such moieties; "methylenesuccinimide moieties" refers to methylenesuccinimide radicals at the terminus of a polymer chain (i.e. connected to the polymer chain by one covalent bond) and methylenesuccinimide radicals in the interior of a polymer chain (i.e. connected to the polymer chain by more than one covalent bond); "amino acid moieties"refers to amino acid radicals, including the anydrous form of amino acid radicals, at the terminus of a polymer chain and amino acid radicals in the interior of a polymer chain. The polysuccinimide polymers to be prepared and used according to the present invention include polymethylenesuccinimide of from 5 to 100 percent by weight of methylenesuccinimide moieties. Methylenesuccinimide moieties which are radicals in the interior of a polymer chain (i.e. connected to the polymer chain by more than one covalent bond) have the structural formula: Upon hydrolysis, the ring structure of the methylenesuccinimide moieties may open to yield either the α- or β- substituted methyleneaspartic acid moieties. Methylenesuccinimide moieties can be incorporated into the polysuccinimide polymers by incorporating into the polymerizing mixture itaconic acid, itaconic anhydride, or the amic acid thereof. The amic acid of itaconic anhydride may be formed in situ in the process of the present invention in the presence of ammonia or other amine. In one preferred embodiment, the polysuccinimide polymer is 100 percent by weight methylenesuccinimide moieties. The polysuccinimide polymers may also include from 0 to 95 percent by weight of one or more amino acid moiety. Preferred amino acid moieties are radicals, including anhydrous radicals, of alanine, glycine, lysine, asparagine, aspartic acid and glutamic acid. More preferably, the one or more amino acid moiety is a radical of aspartic acid. Preferably, the one or more amino acid moietys comprises from 5 to 80 percent by weight, and most preferably from 5 to 50 percent by weight, of the polysuccinimide polymers. The process of the present invention for preparing polysuccinimide polymers, including polymethylenesuccinimide, includes forming a polymerization mixture of one or more monoethylenically unsaturated poly(carboxylic acid). Suitable monoethylenically unsaturated poly(carboxylic acids) include maleic acid, mesaconic acid, fumaric acid, methylenemalonic acid, itaconic acid, citraconic acid, aconitic acid, alkylmaleic acids, alkenylsuccinic acids, monoethylenically unsaturated oligomers of poly(acrylic acid) and poly(methacrylic acid), butene-1,3,4-tricarboxylic acid, and anhydrides, partial esters, complete esters, partial ammonium salts, complete ammonium salts, and partial alkali metal salts, for example anhydrides, of any of the aforementioned acids. In one embodiment of the present invention the one or more monoethylenically unsaturated poly(carboxylic acid) is selected from maleic acid, maleic anhydride, mesaconic acid, fumaric acid, methylenemalonic acid, itaconic acid, itaconic anhydride, citraconic acid, aconitic acid, alkylmaleic acids, alkenylsuccinates, monoethylenically unsaturated oligomers of poly(acrylic acid), monoethylenically unsaturated oligomers of poly(methacrylic acid), butene-1,3,4-tricarboxylic acid, monomethyl maleate, dimethyl maleate, monomethyl itaconate, dimethyl itaconate, monoammonium maleate, diammonium maleate, monosodium maleate and monopotassium maleate. Other suitable monoethylenically unaturated poly(carboxylic acids) include the partial and complete esters of the monoethylenically unsaturated poly(carboxylic acids) such as monomethyl maleate, dimethyl maleate, monomethyl itaconate and dimethyl itaconate. Salts of the monoethylenically unsaturated poly(carboxylic acids) can also be used such as the partial or complete ammonium salts or the partial alkali metal salts. Suitable partial and complete ammonium salts include monoammonium maleate and diammonium maleate. Partial alkali metal salts of the monoethylenically unsaturated poly(carboxylic acids) include monosodium maleate and monopotassium maleate. The preferred monoethylenically unsaturated poly(carboxylic acids) are itaconic anhydride, itaconic acid, maleic anhydride, maleic acid, and the monoammonium salts thereof. The most preferred monoethylenically unsaturated poly(carboxylic acids) are itaconic acid, itaconic anhydride, and the monoammonium salts thereof. The poly(alkylene glycols) useful in the process of the present invention are those which are fluid at the reaction temperature. Suitable poly(alkylene glycols) include poly(tetramethylene glycol), poly(ethylene glycol), and poly(propylene glycol). The poly(alkylene glycol) can also be terminated at one or both ends by carboxylic acids, alkyl groups of from 1 to 30 carbon atoms, or amines, or alkylamines in which the alkyl group contains from 1 to 10 carbon atoms, or any combination thereof. Therefore, in one embodiment of the present invention the poly(alkylene glycol) is selected from: poly(tetramethylene glycol); poly(ethylene glycol); poly(propylene glycol); poly(tetramethylene glycol), poly(ethylene glycol), poly(propylene glycol) which are terminated at one or both ends by carboxylic acids, alkyl groups of from 1 to 30 carbon atoms, amines, alkylamines in which the alkyl group contains from 1 to 10 carbon atoms; and combinations thereof. Preferably the poly(alkylene glycol) is selected from poly(ethylene glycol), methyl-terminated poly(ethylene glycol), and poly(propylene glycol). Preferably the poly(alkylene glycol) is poly(ethylene glycol), methyl-terminated poly(ethylene glycol), or poly(propylene glycol). Most preferably, the poly(alkylene glycol) is poly(ethylene glycol). The molecular weight of the poly(alkylene glycol) is 300 to 30,000, preferably from 300 to 20,000, and most preferably from 1,000 to 15,000. The one or more other monoethylenically unsaturated compound which can be incorporated into the polymerization mixture includes monoethylenically unsaturated monocarboxylic acids containing from three to six carbon atoms and the ammonium salts thereof, such as acrylic acid, methacrylic acid, crotonic acid and the ammonium salts thereof. The one or more other monoethylenically unsaturated compound which can be incorporated into the polymerization mixture can also be monoethylenically unsaturated carboxyl-free compounds including C 1 -C 4 alkyl esters of acrylic or methacrylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and isobutyl methacrylate; hydroxyalkyl esters of acrylic or methacrylic acids such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. The one or more other monoethylenically unsaturated compound which can be incorporated into the polymerization mixture can also be selected from acrylamide and methacrylamide. Thus, in one embodiment of the present invention the one or more other monoethylenically unsaturated compound is selected from monoethylenically unsaturated monocarboxylic acids containing from three to six carbon atoms and the ammonium salts thereof, C 1 -C 4 alkyl esters of acrylic acid, C 1 -C 4 alkyl esters of methacrylic acids, hydroxyalkyl esters of acrylic acid, hydroxyalkyl esters of methacrylic acid, acrylamide and methacrylamide. For example, the one or more other monoethylenically unsaturated compound may be selected from: acrylic acid, methacrylic acid, crotonic acid, and the ammonium salts thereof; methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and isobutyl methacrylate; hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and hydroxypropyl methacrylate; acrylamide; and methacrylamide. Preferably, the one or more other monoethylenically unsaturated compound is selected from acrylic acid, methacrylic acid, and the ammonium salts thereof. The ammonia may be introduced into the polymerization mixture as a gas or as a solution. When the ammonia is introduced into the polymerization mixture as a solution, it is preferred that the solution be as concentrated as possible. The ammonia can be dissolved in water to form an aqueous solution of ammonium hydroxide, or it can be dissolved in alcohols such as methanol, ethanol or propanol, or any other suitable organic solvent. It is also possible, and desirable, to add the ammonia to the polymerization mixture by dissolving it in the poly(alkylene glycol). The one or more monoethylenically unsaturated poly(carboxylic acid) are preferably added to the polymerization mixture at a level of from 10 to 98 percent by weight relative to the poly(alkylene glycol), more preferably from 20 to 90, and most preferably from 30 to 85, percent by weight relative to the poly(alkylene glycol). The poly(alkylene glycol) is preferably added to the polymerization mixture at a level of from 2 to 90 percent by weight relative to the monoethylenically unsaturated poly(carboxylic acid), more preferably from 20 to 90, and most preferably from 30 to 85, percent by weight relative to the monoethylenically unsaturated poly(carboxylic acid). The one or more other monoethylenically unsaturated compound is preferably added to the polymerization mixture at a level of from 0 to 95 percent by weight relative to the one or more monoethylenically unsaturated poly(carboxylic acids), more preferably from 5 to 80, and most preferably from 5 to 50, percent by weight relative to the one or more monoethylenically unsaturated poly(carboxylic acids). Ammonia is preferably added to the polymerization mixture at a level sufficient to provide a molar ratio of ammonia to carboxylic acid of from 0.5-10:1, more preferably from 1.0-5.0:1, and most preferably from 0.9-2.5:1. The atmosphere of the polymerization is preferably substantially free of oxygen, including the oxygen present in air. An atmosphere substantially free of oxygen is preferred since, at the temperatures needed for the polycondensation reaction to occur, the poly(alkylene glycols) will oxidize, discolor or degrade. Suitable means for achieving an atmosphere substantially free of oxygen is by blanketing, sweeping or bubbling the reactor with an inert gas, preferably nitrogen, or conducting the polymerization at reduced pressure. The elevated temperature for the process of the present invention must be high enough to provide polycondensation. The preferred temperature will vary with the operating conditions. For example, the preferred temperature may increase as the ratio of monoethylenically unsaturated poly(carboxylic acids) to poly(alkylene glycol) increases, or as the pressure at which the polycondensation is conducted increases. However, the preferred temperature may decrease, for example, in the presence of azeotropic solvents. In general, the preferred elevated temperature is from 120 to 250°C. The polysuccinimide polymers are formed by a condensation reaction. It is therefore desirable to remove the by-products, such as water or alcohol, which are liberated in order to drive the reaction toward completion. Suitable means of removing water includes addition of one or more azeotropic solvents to the polymerization mixture such as toluene, xylene, or tetralin, and removing the azeotropic distillate from the polymerization mixture. Another means of removing the water is by adding to the polymerization mixture one or more drying agent such as aluminosilicates. Another means of removing the water is by bubbling an inert gas through the polymerization mixture, or sweeping an inert gas over the surface of the polymerization mixture. Another means of removing the water is by conducting the polymerization under reduced pressure. The polymerization can be conducted as a batch or continuous process. Suitable reactors include batch tank reactors, continuous stirred tank reactors, plug-flow reactors, pipe reactors and scraped-wall reactors. The temperature of the reaction must be sufficient to effect the condensation reaction. This temperature will vary according to whether an azeotropic solvent is employed and the pressure at which the polymerization is conducted which can be subatmospheric, atmospheric or supraatmospheric. The products which result from the process of the present invention are solutions, suspensions or dispersions of polysuccinimide polymers in poly(alkylene glycol). Poly(alkylene glycols) are useful in many of the applications for the polysuccinimides such as, for example, in detergent formulations. Thus, there is no need for a separation step to isolate the polysuccinimide polymers from the poly(alkylene glycol) when the product is used in a detergent application. If desired, the polysuccinimide polymers can be hydrolyzed by any conventional means to form the corresponding poly(amino acids) such as poly(aspartic acid) or poly(methyleneaspartic acid). A preferred means of hydrolysis is by contacting the product with an aqueous alkaline solution such as sodium hydroxide. The mixtures of polysuccinimides and poly(amino acids) with poly(alkylene glycol) prepared according to the present invention may, for example, be used as absorbents, hard-surface cleaners, water-treatment additives for boiler waters and cooling towers, and detergent additives. The following Examples are presented to illustrate certain embodiments of the present invention. EXAMPLE 1 Preparation of Polysuccinimide To a 500 milliliter three-neck round bottom flask equipped with a mechanical stirrer and condenser was added 42.0 grams of maleic anhydride (0.428 moles) and 98.0 grams of polyethylene glycol having a molecular weight of 3350 (0.029 moles). The flask was immersed in an oil bath. The contents of the flask were stirred and the temperature was raised to 75-80°C. After thirty minutes at this temperature, 25.14 grams of 29 percent by weight aqueous solution of ammonium hydroxide (0.428 moles) was added dropwise. The ammonium hydroxide was added slowly to avoid loss of ammonia by evolution of gas. After the addition of the ammonium hydroxide was complete, the flask was fitted with a Dean Stark condensing trap and a nitrogen sweep was begun. The contents of the flask were heated to a reaction temperature of 200°C over 1 hour and maintained at that temperature for 1.5 hours then cooled to room temperature. EXAMPLE 2 The same procedure was followed as in Example 1 except that 50.31 grams (0.858 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 170°C over 50 minutes and maintained at that temperature for 4 hours. EXAMPLE 3 The same procedure was followed as in Example 1 except that 29.4 grams (0.30 moles) of maleic anhydride, 29.8 grams (0.009 moles) of polyethylene glycol, and 34.3 grams (0.601 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 150°C over 30 minutes and maintained at that temperature for 3 hours. EXAMPLE 4 The same procedure was followed as in Example 1 except that 98.0 grams (1.00 moles) of maleic anhydride, 42.0 grams (0.013 moles) of polyethylene glycol, and 117.45 grams (2.00 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 160°C over 1 hour and maintained at that temperature for 1.5 hours. EXAMPLE 5 The same procedure was followed as in Example 1 except that 29.9 grams (0.302 moles) of maleic anhydride, 29.9 grams (0.006 moles) of polyethylene glycol methyl ether having molecular weight of 5,000, and 35.5 grams (0.622 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 170°C over 1 hour and maintained at that temperature for 3 hours. EXAMPLE 6 The same procedure was followed as in Example 1 except that 23.4 grams (0.200 moles) of maleic acid, 23.5 grams (0.007 moles) of polyethylene glycol, and 23.2 grams (0.406 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 200°C over 50 minutes and maintained at that temperature for 3 hours. EXAMPLE 7 To a 100 milliliter three-neck round bottom flask equipped with a magnetic stirrer, Dewar condenser, and an inlet and outlet for nitrogen was added 5.0 grams of maleic anhydride (50 millimoles) and 5.0 grams of polyethylene glycol having a molecular weight of 3350. The flask was purged with nitrogen and immersed in an oil bath maintained at 70°C. The contents of the flask were stirred and the mixture became clear and homogeneous. The Dewar condensor was filled with dry ice and acetone. 1.2 liters (50 millimoles) of ammonia gas were bubbled into the contents of the flask over 3.75 minutes. After the addition of the ammonia was complete, a nitrogen sweep was begun. The contents of the flask were heated to a reaction temperature of 150-160°C, maintained at that temperature for 3 hours then cooled to room temperature. EXAMPLE 8 Preparation of Polymethylenesuccinimide The same procedure was followed as in Example 1 except that 25.9 grams (0.197 moles) of itaconic acid, 25.9 grams (0.008 moles) of polyethylene glycol, and 11.3 grams (0.198 moles) of ammonium hydroxide solution were used; and the contents of the flask were heated to a reaction temperature of 200°C over 1 hour and maintained at that temperature for 3 hours.

Claims: A process for preparing polysuccinimide polymers, which comprises: a) forming a polymerization mixture comprising poly(alkylene glycol) of molecular weight of from 300 to 30,000, ammonia, one or more monoethylenically unsaturated poly(carboxylic acid) and, optionally, one or more other monoethylenically unsaturated compound; b) heating the mixture to an elevated temperature; and c) maintaining the mixture at the elevated temperature to form polysuccinimide polymers. A process as claimed in claim 1, wherein the poly(alkylene glycol) is selected from: poly(tetramethylene glycol); poly(ethylene glycol); poly(propylene glycol); poly(tetramethylene glycol), poly(ethylene glycol), and poly(propylene glycol) which are terminated at one or both ends by carboxylic acids, alkyl groups of from 1 to 30 carbon atoms, amines, alkylamines in which the alkyl group contains from 1 to 10 carbon atoms; and combinations thereof. A process as claimed in claim 1, wherein the poly(alkylene glycol) is selected from poly(ethylene glycol), methyl-terminated poly(ethylene glycol), and poly(propylene glycol). A process as claimed in any of claims 1 to 3, wherein the one or more monoethylenically unsaturated poly(carboxylic acid) is selected from maleic acid, mesaconic acid, fumaric acid, itaconic acid, methylenemalonic acid, citraconic acid, aconitic acid, alkylmaleic acids, alkenylsuccinic acids, monoethylenically unsaturated oligomers of poly(acrylic acid), monoethylenically unsaturated oligomers of poly(methacrylic acid), butene-1,3,4-tricarboxylic acid, and anhydrides, partial esters, complete esters, partial ammonium salts, complete ammonium salts, and partial alkali metal salts thereof. A process as claimed in any of claims 1 to 3, wherein the one or more monoethylenically unsaturated poly(carboxylic acid) is selected from maleic anhydride, itaconic anhydride, alkenylsuccinates, monomethyl maleate, dimethyl maleate, monomethyl itaconate, dimethyl itaconate, monoammonium maleate, diammonium maleate, monosodium maleate, and monopotassium maleate. A process as claimed in any of claims 1 to 3, wherein the one or more monoethylenically unsaturated poly(carboxylic acid) is selected from maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, and the monoammonium salts thereof. A process as claimed in any of claims 1 to 6, wherein the one or more other monoethylenically unsaturated compound is selected from monoethylenically unsaturated monocarboxylic acids containing from three to six carbon atoms and the ammonium salts thereof, C 1 -C 4 alkyl esters of acrylic acid, C 1 -C 4 alkyl esters of methacrylic acids, hydroxyalkyl esters of acrylic acid, hydroxyalkyl esters of methacrylic acid, acrylamide, and methacrylamide. A process as claimed in any of claims 1 to 7, wherein the mixture is maintained at the elevated temperature in an atmosphere substantially free of oxygen. A process as claimed in any of claims 1 to 9, which further comprises hydrolysing the polysuccinimide polymers to form the corresponding poly(amino acids). Use, as an absorbent, hard-surface cleaner, water treatment additive for boiler waters and cooling towers, or detergent additive, of a composition comprising polysuccinimide polymer and poly(alkylene glycol).

Inventors: PAIK YI HYON, SIMON ETHAN SCOTT, SWIFT GRAHAM, PAIK, YI HYON, SIMON, ETHAN SCOTT, SWIFT, GRAHAM
Applicants: ROHM & HAAS, ROHM AND HAAS COMPANY
Application year: 1993
Main classification: C08G69
IPC codes: C08G69, C08G65, C08G63