MXPA00007321A - Super-absorbing polymeric networks - Google Patents

Abstract

Super-absorbing polymeric networks of cross-linked polyaspartates are produced from cross-linked polysuccinimide. Super-absorbing polymeric networks are produced in a single reaction vessel by cross-linking polysuccinimide with at least one organic polyamine cross-linking agent in the presence of at least one nitrogenous base. The reaction is carried out in an aqueous reaction mixture to produce a polymeric network of cross-linked polyaspartate.

Description

SUPER-ABSORBENT POLYMERIC NETWORDS Field of the Invention The present invention relates to crosslinked polymers. More particularly, the invention relates to novel polymer networks capable of absorbing large amounts of water or aqueous solutions and to methods for preparing such super absorbent polymer networks. BACKGROUND OF THE INVENTION The term "water swellable polymer networks" as used herein, refers to highly crosslinked polymers that have a propensity to swell or gelatinize in the presence of water. Water-swellable polymer networks have found wide use in a variety of applications. See for example Odian, G, Principies of Polymerization, 3rd edition, published by Wiley Intercience, New York, 1991 and Glass, J.E., ed. "Polymers in Aqueous Media Performance Through Association", Advances in Chemistry Series 223, published by the American Chemical Society, Washington D.C. (1989). Water-swellable polymeric networks that are well known in the polymer art include, but are not limited to, carboxymethylcellulose, crosslinked polyacrylates, hydrolysis products of starch-acrylonitrile graft copolymers, polyvinyl alcohol resins, polyethylene oxide resins, polyvinylcaprolactam , crosslinked polyalkamates and polyacrylonitrile reams. Except for cross-linked polyaspartates, most of these polymeric materials are not readily biodegradable and thus contribute to the general chemical charge on the environment when released into tributary streams. The crosslinked polyaspartates are biodegradable but there are several synthetic problems associated with their manufacture that makes them somewhat expensive. Crosslinked polypeptides containing a relatively high percentage of anionic amino acids, such as aspartic acid or glutamic acid, which are said to be useful as absorbent materials, are described in U.S. Pat. 5,284,936 to Donachy et al. Although these materials have a better salt absorbency and are biodegradable, the relatively high cost of the initial amino acids makes these materials not economical. Similarly, the use of gamma radiation to produce cross-linked polyaspartate as described by M. Tomida et al., Polvmer, 38 (11): 2791-2795 (1997) is not practical due to the need for highly ionizing radiation and long time exposition. The North American patent no. No. 5,612,384 of Ross et al. Discloses the crosslinking of polysuccinimide with diamines in a polar aprotic solvent and subsequent hydrolysis of the succinimide units with alkali metal hydroxides to form crosslinked polyaspartates which are super absorbent polymer networks of excellent quality. However, the use of polar aprotic solvents and the removal of these solvent residues adds costs to this process. The North American patent no. 5,612,384 also discloses a method for crosslinking polysuccinides with diamines in aqueous suspension with the simultaneous hydrolysis of the remaining succinimide units by means of alkali metal hydroxides to produce super absorbent polymer networks based on polyaspartate. Although this particular method has the advantage that it uses water instead of solvents, it does not produce super absorbent polymer networks of the same high quality and degree of absorbency as the solvent-based method. Therefore, there is still a need for an improved, economical, water-based method for producing polyacrylate-based superabsorbent polymer networks by means of a chemical modification of polysuccinimide. The methods of this invention satisfy this need. Summary of the Invention The present invention provides an efficient method for producing biodegradable superabsorbent polymer networks by means of chemical modification of polysuccinimide. The term "polymer networks" used herein refers to random copolymers of cross-linked polyaspartate which can swell or gel in water or electrolyte solutions.The term "super absorbent polymer networks" and their grammatical variations used herein refer to polymer networks of cross-linked polyaspartates which can absorb at least 10 times more than 200 times their weight in water, and at least about 10 times to more than about 30 times its weight of an electrolytic solution such as synthetic urine. The super absorbent polymer networks can be produced by different embodiments of the present invention, each including the simultaneous crosslinking and the hydrolytic reaction of polysuccinimide in an aqueous medium containing at least one organic polyamine base having at least two primary amine groups. as a crosslinking agent and at least one nitrogen base. The crosslinking agent can be used in the form of a free base or as a salt of a mineral acid or an organic acid. The nitrogen base is preferably ammonia, an organic base, or an amino acid having an aqueous alkaline solution, an ionizable group with a pH of at least about 9. preferred method is to react polysuccinimide in water with a crosslinking agent of polyamine which is an organic base having at least two primary amine groups in an amount sufficient to form cross-linked polysuccinimide and in the presence of a nitrogen base which provides sufficient alkalinity to substantially simultaneously hydrolyze aspartate units the cross-linked polysuccinimide and in the presence of a nitrogen base which provides sufficient alkalinity to substantially hydrolyze simultaneously the aspartate units the crosslinked polysuccinimide and any monomeric succinimide unit remaining in the polymer. When the aqueous ammonia, a primary amine or a secondary amine are used as the nitrogen base, s form aspartamide or N-alkylaspartamide units in the super absorbent polymer network product. Preferably the total nitrogen functionality with respect to the succinimide functionality is maintained at a molar ratio of about 1: 1. Advantageously, the super absorbent polyimic network of this invention can be economically prepared in a single reaction vessel using aqueous reaction medium and then easily isolated for use. The superabsorbent polymer networks of the present invention are useful in a wide variety of applications in which liquid absorption, viscosity modification, chemical sequestration or dehydration and the like is required or desired. Exemplary applications include the use of polymer networks as super absorbents in diapers, incontinence products and sanitary napkins; as humectants in agricultural products, for the coating of seeds, and soil conditioning, as sludge coagulants in water treatment, as viscosity modifiers in the oil industry; as dehydrating agents, as chemical absorbers (for example to clean chemical spills) for the controlled release of chemical or pharmaceutical substances, for microencapsulation, as thickening agents, as fire retardants or fire control agents; as artificial snow for skiing, as a means for electrophoresis and chromatography (for example for gel permeate chromatography, capillary electrophoresis, etc.) in the manufacture of soft contact lenses, in surgical dressings, in the transportation of meat and fresh fish; in textiles, in the manufacture of pulp and paper, in filter media to dehydrate, and as wetting components in consumer products such as personal care products, cosmetics or the like. Detailed Description of the Invention The term "polyaspartate" and its grammatical variations as used herein, include polyaspartic acid, copolymers of aspartic acid with other monomers as well as polyaspartic acid salts or polyaspartic acid copolymers. Suitable polysuccinides for preparing superabsorbent polymer networks of the present invention can be synthesized by any of the many methods known in the art. There are numerous methods in the art for the polymerization of aspartic acid to polysuccinide. See, for example, Koskan et al., In US Pat. Nos. 5,057,597, 5,116,513, 5,219,952 and 5,221,733 and Batzel et al. American patent no. 5,508,434, Fox and Harada, Journal of the American Chemical Societv, 82, 3745-3751 (1959), describe the use of phosphoric acid to catalyze the polymerization of aspartic acid to produce high molecular weight polysuccinimides. Thus suitable polysuccinides may include, without limit, products of the thermal polymerization of aspartic acid, thermal polymerization of aspartic acid in the presence of phosphoric acid or polyphosphoric acid; thermal polymerization of monoethylenically unsaturated dicarboxylic acids (eg fumaric acid, maleic acid, itaconic acid, citraconic acid, aconitic acid, and the like) or their anhydrides with ammonia or amines, the thermal polymerization of maleic acid or fumaric acid; and copolymers of the aforementioned monomers with carboxylic acids, amines, alcohols, amino acids and other monomers containing carboxyl and the like. The term "polysuccinimide" as used herein defines a homopolymer having the structural formula (I), wherein n is greater than about 5, or a copolymer containing the structural units (I) with other co-monomers. m The super absorbent polymer networks of this invention are structurally consistent random copolymers of monomeric units of succinimide (structural formula S), alpha-aspartate (structural formula A), beta-aspartate (structural formula B) and cross-linking dimeric aspartamides (structural formula which has one of the following three structural formulas, L1, L2 and L3), For convenience these will be generally referred to as the structural formula (L). which has one of the following three structural formulas, L1, L2 and L3). For convenience these will generally be referred to as the structural formula (L).

Monomer Monomer of superoxide monomer (S) alpha a-span (A) beta-aspartate (B) In structural units A and B, M can be hydrogen, an alkali metal cation such as Na +, K + or Li +, ammonium, quaternary ammonium, or alkyl ammonium, dialkyl ammonium or trialkyl ammonium.

Onomer Monomer Crosslinker 11 Crosslinker 12 Crosslinker 13 In structural units L, L1, L2 and L3, R is a divalent organic linking group derived from the organic crosslinking agent. The organic crosslinking agent is preferably an organic base containing at least two primary amino groups capable of reacting with a monomeric succinimide unit to form its crosslinking. For convenience, reference to "L units" include any of the crosslinking monomeric structural units L without limitations. Optionally, the superabsorbent polymer networks of the present invention may contain alpha-aspartal ida (structural structure C) or beta-aspartamide structural units (structural formula D) Structure C of Structure D of alpha-aspartam to Beta-aspartamide wherein R2 and R2 are independently selected from the group consisting of H, Cx to C20 alkyl or substituted alkyl, aryl or substituted aryl, NH2, NHOH, hydroxyalkyl with from 1 to 20 carbon atoms, thioalkyl with 1 to 20 carbon atoms, sulfonyl or phosphonoalkyl and alkyl substituted with dialkylamino with 1 to 20 carbon atoms. The term "cross-linked polyaspartate" or "cross-linked polyaspartic acid" as used herein refers to polymer networks that are water-swellable random copolymers and swells in electrolyte solutions, consisting primarily of structural units A, B, and L and optionally C and D Preferably, the crosslinked polyaspartates do not contain S units or a relatively small amount thereof, for example less than about 20% S units. For convenience, the methods of this invention will be illustrated and discussed using polyamine crosslinking agents. The term "polyamine crosslinking agent" as used herein includes organic bases having at least two groups of primary amines available for reaction with the monomeric succinimide units of a polysuccinimide to form a crosslinking. The polyamine crosslinking agents can be used in the form of a free base or as salts of a mineral acid or an organic acid. Preferably the average molecular weight (MJ of the polysuccinimide is in the range of about 500 to greater than about 1,000,000, more preferably in the range of about 1,500 to about 500,000 and more preferably in the range of about 5,000 to 200,000. Polyamine crosslinker is preferably in the range of about 0.001 mole to about 0.5 mole per mole of succinimide.The amount of polyimine organic component can also be expressed as available moles of diamine per mole of monomeric units of succinimide x 100, called from here hereinafter referred to as "molar%." Based on this the amount of crosslinking agent may be in the range of about 0.1 to about 50 mole% The preferred amount of diamine available in a given case depends on the average molecular weight (MJ of the material starting material for polysuccinimides of M "in the range of approximately 500 to 4000, the preferred amount of diamine available in the crosslinking agent is from about 10 to about 30 mol%. For polysuccinimides of Mw in the range of about 4000 to 10000, the preferred amount of available diamine is in the range of about 1 to 20 mol%. For polysuccinimides with an M "greater than about 10,000, the preferred amount of available diamine is in the range of about 0.2 to about 15 mol%. The total functionality of amine nitrogen with respect to the succinimide functionality is preferably maintained at a molar ratio of about 1: 1. The crosslinking may occur between adjacent polymer chains or within the same polymer chain or both. Multiple crosslinks can also be incorporated into the polymer chains. The compounds useful as polyamine crosslinking agents in carrying out the methods of the present invention, include but are not limited to, aliphatic diamines such as ethylenediamine (EDA), 1,3-bis (aminoethyl) cylcohexane (1,3-BAC) and diamine. of hexamethylene (HMDA), arylaliphatic diamines, such as meta-xylylene diamine (MXDA), polyether diamines, such as polyoxyalkylene diamines and block copolymers terminated in polyoxyalkylene / polyalkylene glycols amines, sold in different ranges of approximate molecular weights of about 280 to 2000 under the trademark JEFFAMINE by Huntsman Chemical Company, diamino acids or diamines derived from amino acids such as lysine, methyl ether of lysine, cistamma, cysteine, cystine, dimethyl cystine ester, or the like. According to the supplier, the products of the JEFFAMINE * D series are polypropylene glycols finished in amine, which have an average of approximately 2 to 68 units of propylene oxide, the JEFFAMINE series of products "11 ED are polyethylene / polypropylene glycols finished in amine, which have a predominantly polyethylene oxide base Other useful polyether amines are triethylene glycol diamine (JEFFAMINE * EDR-148, or Huntsman XTJ-504) and tetraethylene glycol diamine (JEFFAMINEMREDR-192). Also useful are polyalkyleneimines terminated with amine, including for example triamines and pentamines, such as diethylenetriamine (DETA) and tetraethylenepentmaine (TEPA). Additionally, organic triamine, tetraamino and polyamino compounds can also be used as organic crosslinking agents to form new polymer networks of the present invention as long as the amino functional groups necessary for crosslinking are present. The use of these amino compounds can further lead to the incorporation of monomeric linking units such as the following structural formulas L4 and L5, wherein R2 is a trivalent or tetravalent organic radical linking group derived from the organic crosslinking agent.

Won the crosslinker trivatetiie L4 monomer reticulapte tetravelente L5 Examples of triamine, tetramine and polyamino compounds useful as organic crosslinking agents in the present invention include but are not limited to tris (2-aminoethyl) amine (TAEA), polyamine compounds sold under the trademark STARBURS ™ Dendrimers by Dendritech, Inc., the series of triamines based on propylene oxide sold in various ranges of approximate molecular weights from 440 to about 5000 under the trademark JEFFAMINEMR T by Huntsman Chemical Company, and polymers of polyamylamine. Useful nitrogen bases include ammonia, preferably aqueous ammonia, and organic bases, preferably primary and secondary amines. Suitable organic bases for carrying out the present invention, include without limitation alkylamines with from 1 to 20 carbon atoms, such as methyl amine, ethyl amine, propylamine, butyl amine, tertiary butyl amine, diethylamine, triethylamine, lauryl amine, stearyl amine , diisopropylethylamine, isopropylamine, dipropylamine, N-methyl-N-lauryl amine, piperidine, pyrrolidine, and the like; aryl amines with 1 to 20 carbon atoms such as aniline, naphthyl amine, aminophenols, aminonaphtols and the like; hydroxyalkylamines, such as 2-hydroxyethylamine, 3-hydroxypropylamine, 1-aminopropylene glycol, 2-aminopropylene glycol diethanolamine, triethanolamine and the like, sulfo or phosphonoalkylamines, such as taurine, 3-sulfopropylamine, 2-phosphonoethylamine, 3-phosphonoethylamine or the like; dialkylamino substituted amines, such as 3- (N.N-dimethyl) ropilamine, 2- (N, N-dimethyl) ethylamine and the like, and aromatic amines containing nitrogen ring such as pyridine, indole and the like.

Also useful are amines derived from amino acids which have, in aqueous alkaline solutions, a non-ionizable group with a pK value of about 8 or greater, such as natural amino acids, glycine, alanine, aspartic acid, glutamic acid, cystine, cysteine, leucine, serine, phosphoserine and the like, and the non-natural amino acids, beta-alanine, gamma-aminobutyric acid and the like. Preferably superabsorbent polymer networks of the present invention swell or gel in the presence of water at least about 10 to 200 times their dry weight, and in the presence of an electrolyte, such as synthetic urine, at least about 10 or more of 30 times its dry weight. Briefly described ones.

The polyaspartate superabsorbent polymer network of this invention can be produced using a single reaction vessel by crosslinking polysuccinimide with an organic crosslinking agent in the presence of a nitrogenous base in an aqueous reaction mixture. The nitrogenous base provides sufficient alkalinity to simultaneously hydrolyse any remaining monomeric succinimide unit and hydrolyze the crosslinked polysuccinimide to a polyaspartate-based superabsorbent polymer network that can be isolated from the reaction mixture and recovered in the form of a substantially solid gel or solid. dry. In one aspect of the preferred method, an aqueous solution of organic diamine crosslinking agent is mixed with a nitrogenous base, preferably a primary amine, a secondary amine, an aqueous amine, in molar quantities theoretically calculated to sufficiently or completely crosslink or hydrolyse all monomeric succinimide units of a polysuccinimide of a selected M ". Next, the aforementioned aqueous alkaline solution is mixed with dried polysuccinimide substantially to form a slurry. The polysuccinimide is then crosslinked by means of the diamine crosslinking agent and simultaneously hydrolyzed by means of the alkalinity of the aqueous nitrogenous base to a polymer network consisting of cross-linked polyasparate. The polymer network can then be isolated as a substantially dry solid or by filtration or centrifugation followed by decanting the liquid cream and then recovered as a substantially dry solid for use as a super absorbent polymer network. The drying can be carried out at room temperature or a reduced pressure and is generally carried out in a temperature range of about 30 to 80 ° C. A variation of the above procedure can be performed by suspending the polysuccinimide in water and then mixing the suspended polysuccinimide with an aqueous solution of diamine crosslinking agent and nitrogenous base to form a polymer network or alternatively, by mixing the crosslinking agent and the nitrogenous base sequentially in the aqueous polysuccinimide suspension. In another embodiment of the method, an aqueous solution of diamine cross-linking agent and nitrogenous base can be mixed with substantially dry polysuccinimide to form a polymeric network gel product. The polymeric network gel product can then be diluted with an excess of added water and the pH of the diluted reaction mixture adjusted to a pH of about 7 to 9 with sufficient base or inorganic acid as required. The polymer network can then be isolated by washing the gel product with water and filtering and then recovering by drying the filtered polymer network expends a substantially dry solid, such as in a pressurized air oven at a temperature of about 60 ° C. A variation of the isolating process can be performed by deflating the gel product from the polymer network by adding alcohol, such as methanol or the like to the above diluted reaction mixture and then isolating the polymer network by washing with water and filtering and then recovering the polymer network by drying the polymer network filtered to a substantially dry solid in a vacuum oven at a temperature of about 60 ° C. In another embodiment of the method, an aqueous solution of diamine crosslinking agent and nitrogenous base can be mixed with substantially dry polysuccinimide to form a polymeric network gel product. The polymeric gel gel product can be washed with water and filtered. The washed and filtered polymeric gel gel product can be suspended in water and sufficient acid selected from inorganic acid (preferably sulfuric acid or hydrochloric acid) or organic acid (preferably acetic or maleic acid) added to deflate the gel. The polymeric network gel product can then be filtered, re-suspended in water and sufficient aqueous base (preferably 50% w / w aqueous sodium hydroxide) to adjust the pH of the gelatinous mixture to at least about 9 and sufficient alcohol such as methanol or the like to deflate the gel further. The polymer network can then be isolated by filtering and recovering on drying to a substantially dry solid form in a pressurized or vacuum air oven. When primary, secondary or ammonia amines are used, the free base can also react with the polysucchimide to introduce aspartamide units C and D into the resulting superabsorbent polymer network. Surprisingly, the minimum absorbency of water and the absorbency of electrolytic solution of the super absorbent polymer networks produced by means of the methods of this invention was at least about 10 times its dry weight. The following examples illustrate the preparation of the embodiments of the polymeric superabsorbent networks of polysuccinimide polyaspartates by means of the different methods described. The examples and methods presented are illustrations of the preferred embodiments are not intended to be limitations. Water Absorbency Analysis Method The super-absorbent characteristics of the cross-linked polyaspartate polymer network of this invention were demonstrated by the following protocol using an aqueous solution of Blue Dextran (Blue Dextran). This method is known in the art as the Blue Dextran method. A description of the method can be found in U.S. Patent No. 5,284,936 from Donachy et al., The relevant portions of which are incorporated by reference. Blue Dextran is a water-soluble polymer of high molecular weight (approximately 2 million daltons) to which a blue dye is covalently linked. The method is based on the exclusion of Blue Dextran from the superabsorbent materials during the water absorption of a test solution. When a super absorbent polymer network is allowed to swell in an aqueous solution containing Blue Dextran, the large molecular size of the Blue Dextran molecules results in their being excluded from the pores of the swollen gel. The result of this exclusion is that the concentration of Blue Dextran in the liquid cream increases. Thus, the amount of water absorbed by the polymer network can be determined by means of the change in blue Dextran concentration above that of control, measured spectrophotometrically at 617 nanometers. Blue Dextran Method: Solutions to 0.002% (w / w)) of Blue Dextran are prepared by dissolving Blue Dextran either in water or in an electrolytic solution (synthetic urine). To determine the water absorbency, a substantially dry solid super absorbent polymeric network product of the invention was treated with solutions of Blue Dextran as follows. The super absorbent polymer network product (approximately 100 milligrams (mg)) were suspended in an aqueous solution of Dextran Blue (approximately 20 grams (g)) by stirring the mixture for about one hour. The swollen gel suspension was then centrifuged for about 5 minutes at a high speed and the centrifuged liquid cream was collected. The absorbance of the liquid cream at 617 nm was determined using an epectrophotometer. The absorbance of the Blue Dextran solution at 617_nm was also determined. The specific absorbance (that is, grams of water per turn of dry polymer) of the super absorbent polymer network is then calculated by means of the following equation. Specific Absorbency = (Blue Dextran mass / polymer mass) (1- Blue Dextran absorbance / cream absorbency) To determine electrolyte absorbency, the same procedure was followed, except that synthetic urine was used instead of water and the specific absorbance against that of Blue Dextran in synthetic urine. Synthetic urine was prepared by combining NaCl (10.09 g), CaCl22H20 (0.3015 g), MgCl2 (0.5938 g), an aqueous solution of the non-ionic surfactant, octoxinol-9, sold under the trademark TRITÓN® X-100 by Union Carbide Corporation, (2.5 g of a 1% by weight solution) and dilute the combination to 1 liter with deionized water. A similar recipe can be found in the US patent no. 5,284,936 to Donachy et al. The present invention is further illustrated by means of the following examples. Examples 1-15 Super-absorbent Polymeric Network Synthesis Method The following general procedures are used in the preparation of the polymeric superabsorbent network of Examples 1-15. Each method consists of a synthesis step, referred to herein as reaction method A, B, C or D and an isolation / recovery step, referred to herein for convenience as a Method of Processing by Isolated A, B, C, D, E, F and G as described below. Reaction Method A A solution of crosslinking agent, nitrogenous base and water was prepared. The solution was then added to dry polysuccinimide and the resulting reaction mixture was mixed with stirring until a gel reaction mixture was produced. Reaction Method B A solution of crosslinking agent, nitrogenous base and water was prepared. The solution was then added to a mixture prepared separately from water and dried polysuccinimide and the resulting reaction mixture was mixed until a gel reaction mixture was produced. Reaction method C A solution of crosslinking agent, nitrogenous base and water was prepared. The solution was then added to dry polysuccinimide and the resulting reaction mixture was mixed with stirring until a reaction mixture was produced. The gel reaction mixture was then diluted with water (about one liter) and its pH adjusted to a pH of about 11 by the addition of 50% w / w sodium hydroxide. Reaction Method D Nitrogen base and crosslinking agent were sequentially added to a mixture prepared separately from water and dry polysuccinimide and the resulting reaction mixture was mixed until a gel reaction mixture was produced. Processing method by isolate A The reaction mixture in crude gel obtained by means of the reaction method is dried to a substantially dry solid polymer network in a forced air oven at a temperature of about 60 ° C. Production method by isolate B The reaction mixture in crude gel obtained by the reaction method was washed with water and filtered. The washing and filtering steps were repeated several times to remove any water soluble substance that may be present. The isolated and washed polymer network is then dried to a substantially dry solid form in a forced air oven at a temperature of about 60 ° C. Processing method by isolated C The crude gel reaction mixture obtained by the reaction method was washed with water and filtered. The washing and filtering steps were repeated several times to remove any water soluble substance that may be present. The isolated and washed polymer network was then deflated by the addition of methanol. The polymer network was isolated by filtration and then dried to a substantially dry solid form in a forced air oven at a temperature of about 60 ° C. Method of processing by isolated D The procedure of the method of processing was followed by isolated C, except that the drying step was carried out under reduced pressure in a vacuum oven at a temperature of about 60 ° C. Processing Method by Isolated E The crude gel reaction mixture obtained by the reaction method was diluted with excess water to produce a free flowing mixture. The diluted gel reaction mixture is then centrifuged and the liquid cream is decanted. The sequential washing, centrifugation and decanting steps were repeated several times to remove any water-soluble substances that may be present. And the filtered and washed polymeric gel gel was deflated by the addition of methanol.

The polymer network was isolated by centrifugation, decanting the liquid cream and then dried to a substantially dry solid in a vacuum oven at a temperature of about 60 ° C. Production method per isolate F The crude gel reaction mixture obtained by the reaction method was washed with water and filtered. Sulfuric acid (18M, 98% w / w), hydrochloric acid (12M, 37% w / w) or maleic anhydride were added slowly, with stirring to deflate the gel. The deflated gel product was then filtered, suspended in water and enough aqueous sodium hydroxide at 50% w / w was added to adjust the pH of the resulting gelatinous suspension to approximately a pH of 9 and then deflated by means of the addition of methanol. The polymer network was then isolated by filtration and dried to a substantially dry solid in a vacuum oven at a temperature of about 60 ° C. Method of processing by isolate G The production method was followed by isolated F except that the drying step was carried out in a forced air oven at a temperature of approximately 60 ° C. Examples 1-15 illustrate the preparation of superabsorbent polymer networks by crosslinking polysuccinimide having an Mw in the range of about 5000 to 35,000 when practicing the reaction methods and methods of processing per isolate described above and in the combination indicated in Table 1 below, and the specificity of water absorbency (proportion of grams of water absorbed / grams of super absorbent polymer network) achieved by means of the Blue dextran method. * »29 Table 1 Synthesis of cross-linked polysuccinimide polyaspacinimide superabsorbent polymer networks (PSI) Reaction methods and water absorbency Ejera. Mw Water Method Method PSI Reaction Absorption Process (amu) (amounts per isolate AG / g reactive described below 1 35,000 DA 21 2 5,000 BA 15 3 35,000 BC 29 4 35,000 AF 16 10 5 35,000 AD 16 6 35,000 AD 17 7 35,000 AF 65 8 35,000 AF 76 9 35,000 AE 44 15 10 35, 000 AF 20 11 25,000 CB 72 12 25,000 CD 93 13 25,000 CC 141 14 25,000 CG 230 0 15 15,000 AG 50 'SI = polysuccinimide Mw = average molecular weight determined by means of size exclusion chromatography AMU atomic mass unit Amount of reagents used during the indicated reaction method Example 1: Triethylene glycol diamine (Huntsman XTJ-504, approximately 13.7 grams (g)) as the aqueous ammonium hydroxide crosslinking agent (15 M, approximately 49.5 milliliters (mi)) as the nitrogenous base, were added sequentially to a separately prepared mixture of approximately 200 ml of water and approximately 100 g of dry polysuccinimide. Example 2: The solution of crosslinking agent, nitrogenous base and water contained approximately 20.7 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, approximately 43.3 milliliters (mi) of 15 M aqueous ammonium hydroxide as the nitrogenous base, and approximately 50 ml of water. The solution was then added to a mixture prepared separately from about 50 ml of water and about 100 g of dry polysuccinimide. Example 3: The solution of crosslinking agent, nitrogenous base and water contained approximately 13.8 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, and about 103 ml of triethylamine (dissolved in 120 ml of water) as the nitrogenous base. The solution was then added to a separately prepared mixture of approximately 120 ml of water and approximately 100 g of dry polysuccinimide. Example 4: The solution of crosslinking agent, nitrogenous base and water contained approximately 13.7 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, approximately 45.3 g of ethanolamine as the nitrogenous base, and approximately 100 ml of water. The solution was then added to approximately 100 g of dry polysuccinimide. Example 5: the crosslinking agent solution, nitrogenous base and water contained approximately 6,878 G of triethylene glycol diamine (Huntsman XTJ-504) and about 10.4 g of cystamine diclohydrate as crosslinking agents, approximately 49.5 MI of 15m aqueous ammonium hydroxide as a nitrogenous base, and approximately 100 ml of water. The solution was then added to approximately 100 g of dry polysuccinimide. Example 6: The solution of crosslinking agent, nitrogenous base and water contained approximately 20.8 g of cystamine dihydrochloride as a crosslinking agent, approximately 68 ml of 15M aqueous ammonium hydroxide as the nitrogenous base and approximately 100 ml of water. The solution was then added to approximately 100 g of dry polysuccinimide.

Example 7: The solution of crosslinking agent, nitrogenous base and water contained approximately 6.87 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, approximately 49.5 ml of 15 M aqueous ammonium hydroxide as the nitrogenous base, and approximately 100 ml of water . The solution was then added to approximately 100 g of dry polysuccinimide. In the method of processing by isolate, maleic anhydride was used as a source of maleic acid in the acidification step. Example 8: The solution of crosslinking agent, nitrogenous base and water contained approximately 4.12 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, approximately 49.5 ml of ammonium hydroxide as the nitrogen base, and approximately 100 ml of water. The solution was then added to 100 g of dry polysuccinimide. In the method of processing by isolation, sulfuric acid was used in the acidification step. Example 9: The crosslinking agent solution, the nitrogenous base and water contained approximately 46.87 g of thienylene glycol diamine (Huntsman XTJ-504) as the crosslinking agent, approximately 45.3 g of ethanolamine as the nitrogenous base and approximately 100 ml of water. The solution was then added to approximately 100 g of dry polysuccinimide. Example 10: The solution of crosslinking agent, nitrogenous base and water contained approximately 6867 g of triethylene glycol diamine (Huntsman XTJ-504) as a crosslinking agent, approximately 39.2 ml of 18.94 M aqueous sodium hydroxide, approximately 55.6 g of glycine as the nitrogenous base, and approximately 100 ml of water. This solution was prepared by adding licina to the water and then adding sodium hydroxide to the resulting mixture. Then triethylene glycol diamine was added. The solution was then added to approximately 100 g of dry polysuccinimide. Sulfuric acid was used in the acidification stage in the production stage. Example 11: The solution of crosslinking agent, nitrogenous base and water contained approximately 51.4 g of cystamine dihydrochloride as a crosslinking agent, approximately 124 ml of 15M aqueous ammonium hydroxide as the nitrogenous base, and approximately 250 g of crushed ice. The solution was then added to approximately 250 g of dry polysuccimide. Example 12: The solution of crosslinking agent, nitrogenous base and water contained approximately 38.4 g of aqueous hexamethylene diamine 70% as a crosslinking agent, approximately 124 ml of 15M aqueous ammonium hydroxide as the nitrogenous base, and approximately 250 g of crushed ice. The solution was then added to approximately 250 g of dry polysuccinimide. Example 13: The solution of crosslinking agent, nitrogenous base and water contained approximately 38.4 g of aqueous hexamethylene diamine 70% as a crosslinking agent, approximately 124 ml of 15M aqueous ammonium hydroxide as a nitrogen base, approximately 38.7 ml of 12M hydrochloric acid, and approximately 250g of crushed ice. The hydrochloric acid was used to change the diamine in monohydrochloride salt or a dihydrochloride salt. The solution was formed by adding ammonium hydroxide to the ice and then adding diamine followed by hydrochloric acid. Then the resulting solution was added to approximately 250 g of polysuccinimide. Example 14: The solution of crosslinking agent, nitrogenous base and water contained approximately 38 g of aqueous 70% hexamethylene diamine as a crosslinking agent, approximately 124 ml of 15 M aqueous ammonium hydroxide as the nitrogenous base, approximately 38.7 ml of 12M hydrochloric acid and approximately 250 ml of water. The solution was formed by adding ammonium hydroxide to the water and then adding the diamine followed by hydrochloric acid. Then the resulting solution was added to about 3250 g of dry polysuccinimide. In the production method by isolation, sulfuric acid was used. Example 15: The solution of the crosslinking agent, nitrogenous base and water contained approximately 76.9 g of 70% aqueous hexamethylene diamine as a crosslinking agent, about 247 ml of 15M aqueous ammonium hydroxide as the nitrogen base, about 38.7 ml, of 12M hydrochloric acid, and about 500 g of crushed ice, the addition of the ingredients was the same as in example 13. In the Processing method by isolated, sulfuric acid was used. As shown in Table 1, the water absorbency of each of the super absorbent polymer networks prepared in Examples 1-15 determined by the Blue Dextran method was in the range of approximately 15 to 230 times the weight dry of the polymer network. EXAMPLE 16 The example illustrates a method for preparing a polyaspartate superabsorbent polymer network of this invention of crosslinked polysuccimide in an aqueous medium by means of a diamine crosslinking agent in the presence of a nitrogen base. Polysuccimide (928 mmol, approximately 100 g) was added in a resin flask. A solution of ammonium hydroxide was added to this flask with stirring. (742 mmol, approximately 49.5 ml) as a nitrogenated amine, triethylene glycol diamine (Hunstaman XTJ-504) 1 36 (46.4 mmol, approximately 6.87 g) as a cross-linked agent, and water (approximately 100 ml). The resulting cross-linked polymer network product was in the form of a wet gel. The gelatinous reaction mixture was then suspended in water (approximately 500 ml) to form a gelatinous suspension. Maleic anhydride (742 mmol, approximately 72.8 g) was added to the gelatinous suspension to reduce the pH of the suspension to a range of about 1 to 2 and deflate the gelatinous suspension.

The poiimeric network gel suspension was filtered and the polymeric gel gel isolate was resuspended in water (approximately 500 mi). The re-suspended gel product deflated by myself and filtered again. The filtered gel product was then suspended in aqueous methanol (50/50 v / v) and the pH of the resulting gelatinous suspension was adjusted to a pH of 10 by the addition of 18.94 M aqueous sodium hydroxide. The gelatinous suspension it was deflated by the addition of methanol to produce a substantially solid polymeric network product. The polymer network is then filtered and dried to a substantially solid form in a vacuum oven of about 60 ° C. The absorbency of water and electrolytes of the polymeric resin resulting from polyaspartate was determined by means of the Blue Dextran method. The absorbency was 65 times the dry weight of the polymeric network gel. The absorbance of electrolytic solution (synthetic urine) by means of the Blue Dextran method was approximately 12 times the dry weight of the gel of the polymer network. Example 17 This example illustrates another method for preparing a poly-superabsorbent polyaspartate network of this invention from a cross-linked polysuccinimide in an aqueous medium by means of a diamine cross-linking agent in the presence of a nitrogenous base. Polysuccinimide (Mw 15,000, 4.64 moles, approximately 500 g) was added to a rotary paddle mixer (KitchenAidmr). For this, a solution prepared separately from 15M aqueous ammonium hydroxide (3.71 moles, approximately 247 ml) was added as the nitrogen base, 70% aqueous hexamethylene diamine (464 mmol, approximately 76.9 g.) As a crosslinking agent, hydrochloric acid. aqueous 12M (464 mmol, approximately 38.7 ml) and molten melted ice (500 g). The mixture was stirred until a substantially dry and fluffy gelatinous reaction product formed. The above procedure was repeated four separate times and the resulting gels were combined. The combination of gei is suspended in enough water to produce a free-flowing suspension. Sufficiently concentrated sulfuric acid (18M, 98% w / w) was then added to reduce the pH of the suspension to a range of about 1 to 2, and deflate the polymeric network gel suspension. The deflated suspension was then filtered and the polymer net gel isolate was washed twice with water. The polymer gel network isolate is then suspended in approximately 12 liters of aqueous methanol (50/50 v / v). The pH of the resulting gelatinous suspension was adjusted to a pH of about 10 by the addition of 18.94M aqueous sodium hydroxide and then deflated by the addition of methanol. The polymer network was isolated by filtering and then dried in a forced air oven at about 60 ° C to a substantially dry solid. The absorbency of water and electrolytes of the polymeric resin resulting from polyaspartate was determined by means of the Blue Dextran method. The water absorbency was 50 times the dry weight of the polymer network gei. The absorbency of electrolytic solution (synthetic urine) was approximately 32 times the dry weight of the gel polymer network. EXAMPLE 18 This comparative example illustrates the preparation of the polyaspartate super absorbent polymer network using inorganic alkaline bases instead of nitrogen bases during the crosslinking of the polysuccinimide by means of the organic diamine crosslinking agent. The procedure of Example 17 was followed except that the nitrogen base was replaced by 18.94M aqueous sodium hydroxide (3.71 moles)., approximately 196 mi) and a single reaction procedure was carried out. A slightly gelatinous mixture was obtained. The resulting polymer network of polyaspartate had a water absorbency of about 9 times the dry weight of the polymeric network gel and an absorbency of electrolytic solution (synthetic urine) of about 1.1 times the dry weight of the polymeric network gel. A comparison of the absorbency of water and electrolytic solution (synthetic urine) of the superabsorbent polymeric network gel of example 17 with that of the product of comparative example 18 shows that the preparation of superabsorbent polymer network in the presence of nitrogen greatly improves the characteristics of water absorbency of the superabsorbent polymer networks derived from the crosslinking of polysuccinimide in an aqueous medium as compared to those of the product prepared in the presence of alkali metal hydroxide. Examples 1-17 illustrate that the superabsorbent polymer networks of the present invention have water absorbencies in the range of at least about 10 to more than 200 times the dry weight of the polymer network. Examples 16 and 17 also illustrate that the super absorbent polymer networks of the present invention have absorbencies of electrolytic solution (synthetic urine) minimum of at least approximately times the dry weight of the polymer network. This level of absorbency was achieved in a substantially aqueous medium and avoids the environmental costs and problems associated with the use of polar aprotic solvents such as DMF, DMSO and the like.

Claims (6)

1. NOVELTY OF THE INVENTION Having described the invention as above, the content of the following is claimed as property: CLAIMS 1.- A method for producing a cross-linked polyaspartate polymer network characterized in that it consists of the steps of: a) reacting polysuccinimide in a medium aqueous and in the presence of a nitrogenous base, with a cross-linking agent which is an organic base having at least two primary amino groups to form a cross-linked polysuccinimide product in a reaction mixture; the nitrogenous base is present in an amount sufficient to hydrolyze the crosslinked polysuccinide to a crosslinked polyamide cross-linked polymer network: b) isolate the polymeric network produced from the crosslinked polyaspartate of the reaction mixture; and c) recovering the polymer network isolated from cross-linked polyaspartate.
2. 2. The method according to claim 1, characterized in that the reaction mixture in step (a) is in a temperature range of about 30 ° C to about 80 ° C and is maintained in that temperature range until The polymerized network of cross-linked polyaspartate has been formed.
3. 3. The method according to claim 1, characterized in that the cross-linked polyaspartate polymer network is isolated in step (b) by means of filtering, and is recovered in step (c) by drying the filtered polymer network of cross-linked polyaspartate.
4. 4. The method according to claim 1 characterized in that the cross-linked polyaspartate polymer network is isolated in step (b) by means of washing with water and then removing the excess water.
5. 5. The method according to claim 1, characterized in that the cross-linked polyaspartate polymer network is isolated in step (b) by means of washing with a liquid that is a member of the group consisting of water, alcohol and their mixtures.
6. 6. The method according to claim 1, characterized in that the polyaspartate polymer network is in the form of a gel or a solid. 1 . - The method according to claim 1 characterized in that the polysuccinimide in step (c) has an average molecule weight in the range of about 500 to more than 100,000. 8. The method according to claim 1, characterized in that the functionality of nitrogen amine with respect to the succinimide functionality is a molar ratio of approximately 1: 1. 9. The method according to claim 1, characterized in that the crosslinking agent is in the form of a salt or an acid selected from the group consisting of a mineral acid and an organic acid. 10. The method according to claim 1, characterized in that the crosslinking agent is a polyamine selected from the group consisting of aliphatic diamine, arylaliphatic diamine, a polyether diamine, a diamine derived from an amino acid, a polyether polyamine and its derivatives. mixtures 11. The method according to claim 1, characterized in that the nitrogenous base is selected from the group consisting of ammonia, an amine or an amino acid having an ionizable amino group, which in the aqueous alkaline solution has a pH value of at least approximately 8 and their mixtures. 12. The method according to claim 1 further comprising the step of adjusting the pH of the product to a desired pH during the step of isolating (b). 13. A polyapartate superabsorbent polymer network obtained by means of the method of claim 1, characterized in that it is a random copolymer consisting mainly of aspartate units and aspartamide dimer units with less than about 20% succinimide units. 14. - A polyaspartate superabsorbent polymer network obtained by the method according to claim 1 which is a random copolymer consisting mainly of aspartate units and aspartamide units with less than about 20% succinimide units. 15. The polyapartate super-absorbent polymer network obtained by means of the method according to claim 14, characterized in that the aspartamide units are alpha aspartamide units having the structural formula: wherein R2 and R2 are independently selected from the group consisting of H, Cj to C20 alkyl or substituted alkyl, aryl or substituted aryl, NH2, NHOH, hydroxyalkyl with 1 to 20 carbon atoms, thioalkyl with 1 to 20 carbon atoms , sulfonoalkyl or phosphonoalkyl and alkyl substituted with dialkylamino with d 1 to 20 carbon atoms. poliaspartate obtained by means of the method according to claim 14, characterized in that the aspartamide units are beta aspartamide units having the structural formula: wherein R2 and R2 are independently selected from the group consisting of H, C1 to C20 alkyl or substituted alkyl, aryl or substituted aryl, NH2, NHOH, hydroxyalkyl with 1 to 20 carbon atoms, thioalkyl with 1 to 20 carbon atoms , sulfonoalkyl or phosphonoalkyl and alkyl substituted with dialkylamino with d 1 to 20 carbon atoms. 17. A polyaspartate superabsorbent polymer network obtained by means of the method according to claim 1 which consists of recycled polyaspartate random copolymer capable of absorbing water in an amount in the range of at least about 10 times to more than 200 times its dry weight. 18. A polyapartate super-absorbent polymer network obtained by means of the method according to claim 1 which consists of a random copolymer of cross-linked polyaspartate capable of absorbing an electrolytic solution in a minimum amount of at least 10 times its dry weight.