Method for preparing glufosinate-ammonium or isomer or salt thereof

Abstract

The present invention relates to a method for preparing glufosinate ammonium, the method comprising treating a first solution comprising glufosinate ammonium and an inorganic salt by means of a membrane; and precipitating the glufosinate ammonium from the second solution.

Description

Technical Field

[0001] The present invention relates to a method for preparing glufosinate ammonium, and in particular, the method relates to preparing glufosinate ammonium that is substantially free of inorganic salts. Background Art

[0002] Glufosinate ammonium is used to control a variety of annual and perennial broadleaf weeds and grasses in orchards, vineyards, rubber and oil palm plantations, ornamental trees and shrubs, non-crop land, and pre-emergence vegetable crops. It is also used as a desiccant in crops such as potatoes and sunflowers. It can also control annual and perennial weeds and grasses in genetically modified glufosinate-tolerant crops such as rapeseed, corn, soybeans, and sugar beets. Glufosinate ammonium acts as a glutamine synthetase inhibitor and causes ammonia accumulation, which in turn inhibits photosynthesis. Glufosinate ammonium is one of the most widely used non-selective contact herbicides. Translocation occurs only within leaves, primarily from the base to the tip.

[0003] A well-known method for preparing glufosinate-ammonium, as disclosed in US Pat. No. 4,264,532, involves the Strecker synthesis of α-aminonitriles from the corresponding aldehydes using ammonium chloride / ammonia and sodium cyanide, or alternatively, a mixture of ammonia and hydrocyanic acid. The α-aminonitriles are further hydrolyzed with acid or base to obtain glufosinate-ammonium (Scheme 1).

[0004]

[0005] Solution 1

[0006] It has been noted that during this process, a large amount of inorganic salts are produced along with glufosinate ammonium, which are difficult to separate by conventional methods due to the high solubility of both salts in water. Large amounts of solvents and water are required for purification, which makes the process cumbersome, dangerous and expensive.

[0007] US6359162 discloses that glufosinate-ammonium can be separated from inorganic salts by recrystallization from methanol. However, this simple recrystallization method cannot effectively separate the inorganic salts, thereby producing a low-quality product.

[0008] CN102268037A discloses a method for purifying glufosinate ammonium from a reaction mixture, wherein the method comprises esterifying glufosinate hydrochloride with methanol to obtain the corresponding methyl ester, separating the inorganic matter by filtration, hydrolyzing it back to glufosinate hydrochloride, and then converting it into glufosinate ammonium by treating it with aqueous ammonia (Scheme 2).

[0009]

[0010] Option 2

[0011] However, the process is lengthy, involves multiple filtration, acidification, and crystallization steps, and produces large amounts of effluent.

[0012] Therefore, there is a need to develop robust purification methods to obtain high-quality glufosinate ammonium, thereby avoiding multiple purification steps.

[0013] Purpose of the Invention

[0014] The object of the present invention is to provide an industrially feasible, environmentally friendly method for preparing glufosinate-ammonium or its isomers or salts without inorganic salts.

[0015] Another object of the present invention is to provide a process for the preparation of glufosinate ammonium which avoids multiple purification steps.

[0016] Another object of the present invention is to provide a method for preparing glufosinate-ammonium containing less than 3 wt % of inorganic salts.

[0017] Another object of the present invention is to provide a method for preparing L-glufosinate-ammonium containing less than 3 wt % of inorganic salts. Summary of the Invention

[0018] In one aspect of the present invention, a method for preparing glufosinate-ammonium or an isomer or salt thereof is provided.

[0019] In one aspect of the present invention, there is provided a method for preparing glufosinate ammonium having less than 3 wt% of inorganic salts, the method comprising precipitating glufosinate ammonium by treating a solution comprising glufosinate ammonium with ammonia, the solution comprising glufosinate ammonium being prepared by passing a first solution comprising glufosinate ammonium and an inorganic salt through a membrane.

[0020] In one embodiment, passing a first solution comprising glufosinate and an inorganic salt through a membrane produces a solution comprising glufosinate ammonium that can be treated with ammonia; and a permeate.

[0021] In one aspect, a method for preparing glufosinate ammonium having less than 3 wt% inorganic salts is provided, the method comprising precipitating glufosinate ammonium by treating a solution comprising glufosinate ammonium with ammonia, the solution comprising glufosinate ammonium being prepared by passing a first solution comprising glufosinate ammonium and an inorganic salt through a membrane.

[0022] In another aspect of the present invention, there is provided a method for preparing glufosinate-ammonium, the method comprising:

[0023] a) treating a first solution comprising glufosinate and an inorganic salt through a membrane to obtain a second solution and a permeate; and

[0024] b) precipitating glufosinate ammonium from the second solution by treatment with ammonia; wherein the glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0025] In another aspect of the present invention, there is provided a method for preparing L-glufosinate-ammonium, the method comprising:

[0026] a) treating a first solution comprising L-glufosinate and an inorganic salt through a membrane to obtain a second solution and a permeate; and

[0027] b) precipitating L-glufosinate ammonium from the second solution by a treatment comprising ammonia; wherein the L-glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0028] In another aspect of the present invention, there is provided a method for preparing glufosinate-ammonium, the method comprising the following steps:

[0029] a) preparing a first solution comprising glufosinate-ammonium and an inorganic salt having a total dissolved solute content of less than 15%;

[0030] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0031] c) precipitating glufosinate-ammonium from the second solution by treatment with ammonia;

[0032] The glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0033] In another aspect of the present invention, there is provided a method for preparing L-glufosinate-ammonium, the method comprising the following steps:

[0034] a) preparing a first solution comprising L-glufosinate and an inorganic salt having a total dissolved solute content of less than 15%

[0035] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0036] c) precipitating L-glufosinate-ammonium from the second solution by treating with gaseous ammonia and methanol;

[0037] The L-glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0038] In another aspect, the present disclosure provides a herbicide composition comprising glufosinate ammonium or L-glufosinate ammonium having less than 3 wt% of inorganic salts and at least one agrochemically acceptable excipient. DETAILED DESCRIPTION

[0039] Those skilled in the art will appreciate that the invention described herein is subject to variations and modifications other than those specifically described. It is to be understood that the invention described herein includes all such variations and modifications. The present invention also includes all such steps, features, compositions and methods referred to or indicated in this specification, whether singly or collectively, and any and all combinations of any two or more of said steps or features.

[0040] definition :

[0041] For convenience, before further describing the present invention, some terms and embodiments adopted in the specification are described herein. These definitions should be read in light of the remainder of this disclosure and understood as those skilled in the art. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art would normally understand. The definitions of terms used throughout the specification are as follows, unless otherwise limited in specific circumstances.

[0042] The terms used herein are defined below.

[0043] The term "purity" refers to the purity determined by HPLC ("high pressure liquid chromatography").

[0044] As used herein, the terms "substantially pure," "pure," or "high purity" mean that the material is at least 95% pure.

[0045] As used herein, the term "about" or "approximately" includes the stated value and means within an acceptable deviation range of a particular value as determined by one of ordinary skill in the art, taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±10 or ±5 of the stated value. Unless otherwise indicated herein, the enumeration of numerical ranges is intended only to serve as a shorthand method for individually referring to each individual value falling within the range, and each individual value is included in the specification as if it were individually enumerated herein. The endpoints of all ranges are included in the range and are independently combinable. It should be understood that where a parameter range is provided, all integers and tenths thereof within the range are also provided. For example, "0.1%-80%" includes 0.1%, 0.2%, 0.3%, etc. up to 80%.

[0046] As used herein, the terms "comprising," "including," "having," "containing," "involving," etc. should be understood as open-ended, meaning including but not limited to.

[0047] The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain benefits under certain circumstances. In one embodiment, the aspects and embodiments described herein should also be interpreted as replacing the clause "comprising" with "consisting of" or "consisting essentially of" or "consisting essentially of."

[0048] As used herein, the term "glufosinate" should be taken to mean racemic glufosinate, L-glufosinate, D-glufosinate, or a mixture of L-glufosinate and D-glufosinate in which the ratio of the L-isomer to the D-isomer is in the range of 1:99 to 99:1.

[0049] As used herein, the term "ammonium glufosinate" should be taken to mean the ammonium salt of racemic glufosinate, L-glufosinate, D-glufosinate, or a mixture of L- and D-glufosinate wherein the ratio of L-isomer to D-isomer is in the range of 1:99 to 99:1.

[0050] As used herein, the term "glufosinate hydrochloride" should be taken to mean the hydrochloride salt of racemic glufosinate, L-glufosinate, D-glufosinate, or a mixture of L-glufosinate and D-glufosinate, wherein the ratio of the L-isomer to the D-isomer is in the range of 1:99 to 99:1.

[0051] As used herein, the term "L-glufosinate" is the L-isomer of glufosinate, and the meaning includes glufosinate or a salt thereof having an isomer purity greater than 90%.

[0052] As used herein, the term "nanofiltration" should be taken to mean synthetic membranes providing a nominal molecular weight cut-off in the range of 100 unit Da to 200 unit Da.

[0053] As used herein, the term "feed" means and should be used interchangeably throughout this disclosure as the first solution comprising glufosinate and an inorganic salt that enters the nanofiltration membrane.

[0054] As used herein, the term "permeate" should be taken to mean the fluid that passes through the membrane and has a high content of inorganic salts.

[0055] As used herein, the term "concentrate" means and should be used interchangeably throughout this disclosure as a second solution containing glufosinate-ammonium that is substantially free of inorganic salts.

[0056] The term "glufosinate ammonium substantially free of inorganic salts or L-glufosinate ammonium substantially free of inorganic salts" means glufosinate ammonium or L-glufosinate ammonium as defined above containing less than 3%, preferably less than 2% of inorganic salts.

[0057] The term "total dissolved solutes" is a measure of the dissolved combined content of all inorganic and organic matter present in a liquid in molecular, ionized or particulate suspended form. The terms "total dissolved solutes" and (TDS) shall be used interchangeably throughout this disclosure.

[0058] The present inventors have developed a process for preparing glufosinate-ammonium, wherein the process includes efficient separation of inorganic salts during the process, thereby avoiding subsequent purification processes such as esterification. The advantageous process results in a higher purity product, reduces solvent usage and effluent production, and is cost-effective.

[0059] Below will be described according to exemplary embodiments of the present invention.As such embodiments are disclosed, various modifications, adaptations or variations of such exemplary embodiments may become apparent to those skilled in the art. It should be understood that all such modifications, adaptations or variations that rely on the teachings of the present invention are considered to be within the scope of the present invention.

[0060] Therefore, in one aspect of the present invention, there is provided a method for preparing glufosinate ammonium having less than 3 wt% of inorganic salts, the method comprising precipitating glufosinate ammonium by treating a solution comprising glufosinate ammonium with ammonia, the solution comprising glufosinate ammonium being prepared by passing a first solution comprising glufosinate ammonium and an inorganic salt through a membrane.

[0061] In one embodiment, passing a first solution comprising glufosinate and an inorganic salt through a membrane produces a solution comprising glufosinate ammonium that can be treated with ammonia; and a permeate.

[0062] In one aspect, a method for preparing glufosinate ammonium having less than 3 wt% inorganic salts is provided, the method comprising precipitating glufosinate ammonium by treating a solution comprising glufosinate ammonium with ammonia, the solution comprising glufosinate ammonium being prepared by passing a first solution comprising glufosinate ammonium and an inorganic salt through a membrane.

[0063] In another aspect of the present invention, there is provided a method for preparing glufosinate-ammonium, the method comprising:

[0064] a) treating a first solution comprising glufosinate and an inorganic salt through a membrane to obtain a second solution and a permeate; and

[0065] b) precipitating glufosinate ammonium from the second solution by a treatment comprising ammonia; wherein the glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0066] In one embodiment, in step a), the glufosinate used is racemic glufosinate or L-glufosinate.

[0067] In one embodiment, the first solution comprising glufosinate and the inorganic salt is obtained from a hydrolyzed reaction mass comprising glufosinate hydrochloride and the inorganic salt.

[0068] The hydrolyzed reaction mass comprising glufosinate hydrochloride and an inorganic salt is a base hydrolyzed reaction mass or an acid hydrolyzed reaction mass.

[0069] In one embodiment, the hydrolyzed reaction mass comprising glufosinate hydrochloride and an inorganic salt is subjected to

[0070] i) adjusting the total dissolved solute concentration to less than 15%; and

[0071] ii) Adjust the pH to within the range of 6 to 8

[0072] to obtain a first solution comprising glufosinate-ammonium and an inorganic salt.

[0073] In one embodiment, in step i), the total dissolved solute concentration is adjusted by dilution with water.

[0074] In another embodiment, step i) and step ii) are performed in any order.

[0075] In another embodiment, a method for preparing a first solution comprising glufosinate-ammonium and an inorganic salt is provided, the method comprising the following steps:

[0076] i) adjusting the total dissolved solute concentration of the hydrolyzed reaction mass comprising glufosinate hydrochloride and the inorganic salt to less than 15%; and

[0077] ii) adjusting the pH of the solution within the range of 6 to 8 to obtain a first solution comprising glufosinate-ammonium and an inorganic salt.

[0078] In another embodiment, a preparation of a first solution comprising glufosinate-ammonium and an inorganic salt is provided, the preparation comprising the following steps:

[0079] a) adjusting the pH of the hydrolyzed reaction mass comprising glufosinate hydrochloride and an inorganic salt to be in the range of 6 to 8; and

[0080] b) adjusting the total dissolved solute concentration to less than 15% to obtain a first solution comprising glufosinate-ammonium and an inorganic salt.

[0081] In one embodiment, in step i), the total dissolved solute concentration is adjusted by diluting the hydrolyzed reaction mass with water, and in step ii), the pH is adjusted using a base.

[0082] In another embodiment, the steps of adjusting the total dissolved solute concentration to less than 15% and pH adjustment are performed in any order.

[0083] In another embodiment, the total dissolved solute concentration is adjusted to less than 15% by dilution with water.

[0084] In another embodiment, the reaction mass comprising glufosinate hydrochloride and the hydrolysis of an inorganic salt is prepared by reaction of 3-[ethoxy(methyl)phosphoryl]propanal with sodium cyanide and ammonium chloride, followed by hydrolysis.

[0085] The reaction can be schematically represented as Scheme 3.

[0086]

[0087] Option 3

[0088] In another embodiment, the reaction mass comprising L-phosphinothricin hydrochloride and the hydrolysis of an inorganic salt is obtained by acid hydrolysis of ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butanoate. The reaction can be schematically represented as Scheme 4

[0089]

[0090] Option 4

[0091] In another embodiment, ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butanoate used to prepare the hydrolysis reaction mass can be prepared by methods known in the art.

[0092] One method for preparing ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butanoate is carried out by reacting ethyl (2S)-4-chloro-2-[(ethoxycarbonyl)amino]-butyrate and diethyl methylphosphinate, as shown in Scheme 5.

[0093]

[0094] Option 5

[0095] In another embodiment, the total dissolved solute concentration of the hydrolyzed reaction mass is adjusted to less than 15% by dilution with water.

[0096] In another embodiment, the total dissolved solute concentration of the hydrolyzed reaction mass is adjusted to less than 10% by dilution with water.

[0097] In one embodiment, the adjustment of pH is performed by treatment with a base.

[0098] In one embodiment, the base used is selected from, but not limited to, ammonia, ammonium hydroxide, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, and alkali metal or alkaline earth metal alkoxides.

[0099] In one embodiment, the base used is selected from, but not limited to, ammonia, ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium ethoxide, sodium methoxide, and the like.

[0100] In one embodiment, the base used is ammonia.

[0101] In one embodiment, the base used is aqueous ammonia.

[0102] In one embodiment, the base used is gaseous ammonia.

[0103] In one embodiment, an inorganic salt is formed in the process, such as sodium chloride, potassium chloride, ammonium chloride, lithium chloride, and the like.

[0104] In one embodiment, the inorganic salt formed is ammonium chloride.

[0105] In one embodiment, the inorganic salt formed is sodium chloride.

[0106] In another embodiment, the first solution may further comprise glufosinate-ammonium.

[0107] In one embodiment, the first solution comprises from about 1% to about 7% by weight glufosinate.

[0108] In one embodiment, the first solution comprises from about 2% to about 12% by weight of the inorganic salt.

[0109] In one embodiment, the first solution is processed through a membrane.

[0110] In one embodiment, the membrane used in step a) is a nanofiltration membrane.

[0111] In one embodiment, the nanofiltration membrane is made of a polymeric material.

[0112] In one embodiment, the membrane used in the method of the present invention may be formed from any polymeric material that provides a separation layer capable of fractionating glufosinate content or separating the desired glufosinate from inorganic salts.

[0113] In one embodiment, the polymer material used is selected from the group including but not limited to polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polysulfone, polyethersulfone, polyacrylonitrile, polyamide, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone (PEEK), polybenzimidazole, polyester, vinyl polymer or mixtures thereof.

[0114] The membranes used can be prepared by any technique known in the art, including sintering, stretching, track etching, template leaching, interfacial polymerization, or phase inversion.

[0115] In one embodiment, the polymeric material used is polyamide.

[0116] In one embodiment, the membrane has a molecular weight cut-off in the range of about 100 unit Da to about 200 unit Da.

[0117] In one embodiment, the nanofiltration membrane has a molecular weight in the range of about 100 unit Da to about 200 unit Da.

[0118] In one embodiment, fractionation of the inorganic salts can be achieved by contacting the first solution with a membrane that retains the glufosinate (i.e., as a concentrate) and allows the inorganic salts (i.e., as a permeate) to permeate. The contents permeate through the membrane due to transmembrane pressure.

[0119] In one embodiment, the first solution is processed through the membrane at a transmembrane pressure in the range of about 3 (g) bar to about 50 (g) bar.

[0120] In one embodiment, the second solution comprises less than 6 wt% inorganic salt, based on the total weight of the second solution.

[0121] In one embodiment, the obtained second solution may be processed again through a nanofiltration membrane to obtain a solution containing a desired weight percentage of inorganic salts.

[0122] In another embodiment, the obtained second solution can be processed through a nanofiltration membrane multiple times to obtain a solution containing a desired weight percentage of inorganic salts.

[0123] In one embodiment, in step b) prior to the treatment with ammonia, the second solution is distilled to remove water and obtain a reaction mass.

[0124] In one embodiment, about 50% to 95% by weight of the water is removed from the second solution to obtain the reaction mass.

[0125] In one embodiment, the reaction mass is treated with an alcohol at reflux temperature followed by treatment with ammonia.

[0126] In one embodiment, the alcohol used is selected from, but not limited to, C1-C5 alcohols.

[0127] In one embodiment, the alcohol used is selected from, but not limited to, C1-C5 alcohols, such as methanol, ethanol, n-propanol, isopropanol, and the like.

[0128] In one embodiment, the alcohol used is methanol.

[0129] In one embodiment, the volume ratio of alcohol to reaction mass is in the range of 0.2:1 to 1:1.

[0130] In another embodiment, the treatment with ammonia is carried out at a temperature in the range of 30°C to 50°C.

[0131] In another embodiment, the treatment is performed with gaseous ammonia.

[0132] In one embodiment, the glufosinate ammonium prepared according to the present invention has a purity of about or greater than 95% as measured by HPLC.

[0133] In one embodiment, glufosinate ammonium prepared according to the present invention contains less than 3 wt% inorganic salts, preferably less than 2 wt% inorganic salts.

[0134] In one embodiment, the glufosinate ammonium obtained in step b) is racemic glufosinate ammonium.

[0135] In one embodiment, the glufosinate ammonium obtained in step b) is L-glufosinate ammonium.

[0136] According to another aspect of the present invention, there is provided a method for preparing glufosinate-ammonium, the method comprising the following steps:

[0137] a) preparing a first solution comprising glufosinate-ammonium and an inorganic salt having a total dissolved solute content of less than 15%;

[0138] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0139] c) precipitating glufosinate ammonium from the second solution by a treatment comprising ammonia; wherein the glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0140] In another embodiment, the total dissolved solute concentration of the first solution in step a) is adjusted to less than 15% by dilution with water.

[0141] In another embodiment, the pH of the solution is adjusted to be in the range of 6 to 8 after adjusting the total dissolved solute concentration of the first solution.

[0142] The pH of the first solution is adjusted by treating it with an alkali.

[0143] In one embodiment, the base used is selected from, but not limited to, ammonia, ammonium hydroxide, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, and alkali metal or alkaline earth metal alkoxides.

[0144] The base used is selected from, but not limited to, ammonia, ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium ethoxide, sodium methoxide, and the like.

[0145] In one embodiment, the base used is aqueous ammonia.

[0146] In one embodiment, the base used is gaseous ammonia.

[0147] In another embodiment, the glufosinate ammonium obtained in step iii) is racemic glufosinate ammonium or L-glufosinate ammonium.

[0148] In another embodiment, the glufosinate ammonium obtained in step iii) is racemic glufosinate ammonium.

[0149] In one embodiment, the racemic glufosinate ammonium is obtained substantially free of inorganic salts.

[0150] The obtained racemic glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0151] In one embodiment, the racemic glufosinate ammonium obtained contains less than 2% by weight of inorganic salts.

[0152] In one embodiment, racemic glufosinate ammonium is obtained having a purity greater than 95%.

[0153] In another embodiment, the glufosinate ammonium obtained in step iii) is L-glufosinate ammonium.

[0154] In one embodiment, the obtained L-glufosinate ammonium is substantially free of inorganic salts.

[0155] The obtained L-glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0156] In one embodiment, the obtained L-glufosinate ammonium contains less than 2 wt% of inorganic salts, preferably less than 1 wt% of inorganic salts, more preferably less than 0.5 wt% of inorganic salts.

[0157] In one embodiment, the L-glufosinate ammonium produced according to the methods of the present invention has a purity greater than 95%.

[0158] According to another aspect of the present invention, there is provided a method for preparing glufosinate-ammonium, the method comprising the following steps:

[0159] a) preparing a first solution comprising glufosinate-ammonium and an inorganic salt having a total dissolved solute content of less than 15%;

[0160] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0161] c) precipitating glufosinate ammonium from the second solution by treatment with gaseous ammonia and methanol

[0162] The glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0163] In another embodiment, the glufosinate ammonium obtained in step iii) is racemic glufosinate ammonium.

[0164] According to another aspect of the present invention, there is provided a method for preparing L-glufosinate-ammonium, the method comprising the following steps:

[0165] a) preparing a first solution comprising L-glufosinate and an inorganic salt having a total dissolved solute content of less than 15%;

[0166] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0167] c) precipitating L-glufosinate ammonium from the second solution by treatment with gaseous ammonia and methanol

[0168] The L-glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0169] In one embodiment, there is provided a method for preparing L-glufosinate ammonium, the method comprising the following steps:

[0170] a) preparing a first solution comprising L-glufosinate and an inorganic salt having a total dissolved solute content of less than 10%;

[0171] b) treating the first solution through a membrane to obtain a second solution and a permeate; and

[0172] c) precipitating L-glufosinate ammonium from the second solution by treating with gaseous ammonia and methanol

[0173] The L-glufosinate ammonium contains less than 3% by weight of inorganic salts.

[0174] In one aspect of the present invention, there is provided a method for preparing a glufosinate-ammonium salt, the method comprising:

[0175] a) treating a first solution comprising glufosinate and an inorganic salt through a membrane to obtain a second solution and a permeate; and

[0176] b) preparing a glufosinate salt from the second solution by treating with a base; wherein the glufosinate salt contains less than 3% by weight of inorganic salts.

[0177] In one embodiment, the first solution may further comprise a glufosinate salt, such as ammonium glufosinate, sodium glufosinate, potassium glufosinate, and the like.

[0178] In one embodiment, the first solution comprises an inorganic salt, such as sodium chloride, potassium chloride, ammonium chloride, lithium chloride, and the like.

[0179] In one embodiment, the base used is selected from, but not limited to, ammonia, ammonium hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, sodium ethoxide, sodium methoxide, and the like.

[0180] In one embodiment, the glufosinate salt prepared is L-glufosinate salt.

[0181] In one embodiment, the present invention provides high purity glufosinate ammonium or L-glufosinate ammonium.

[0182] In one embodiment, the present invention provides a purification method for preparing high-purity glufosinate ammonium or L-glufosinate ammonium.

[0183] In one embodiment, the purification method of the present invention comprises

[0184] a) passing a first solution comprising glufosinate and an inorganic salt through a nanofiltration membrane to obtain a second solution and a permeate; and

[0185] b) preparing a glufosinate salt from the second solution by treating the second solution with a base; wherein the glufosinate salt contains less than 3% by weight of an inorganic salt.

[0186] In one embodiment, the first solution comprises a high content of inorganic salts, preferably greater than 3% by weight.

[0187] In one embodiment, the process for preparing glufosinate-ammonium salts according to the present invention reduces the high content of inorganic salts to less than 3% by weight.

[0188] In another aspect of the present invention, there is provided glufosinate ammonium having less than 3 wt% inorganic salts.

[0189] In another aspect of the present invention, there is provided L-glufosinate ammonium having less than 3 wt% of inorganic salts.

[0190] In one embodiment, the present invention provides a herbicide composition comprising glufosinate ammonium or L-glufosinate ammonium having less than 3% by weight of inorganic salts and at least one agrochemically acceptable excipient.

[0191] The agrochemically acceptable excipient may be any one or combination of an adjuvant, a cosolvent, a surfactant, a colorant, a dispersant, an emulsifier, a thickener, an antifreeze agent, a biocide, an antifoaming agent, a stabilizer, a wetting agent, or a mixture thereof.

[0192] Exemplary surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants.

[0193] Examples of nonionic surfactants include polyarylphenol polyethoxy ethers, polyalkylphenol polyethoxy ethers, polyethylene glycol ether derivatives of saturated fatty acids, polyethylene glycol ether derivatives of unsaturated fatty acids, polyethylene glycol ether derivatives of aliphatic alcohols, polyethylene glycol ether derivatives of alicyclic alcohols, fatty acid esters of polyoxyethylene sorbitan, alkoxylated vegetable oils, alkoxylated acetylenic glycols, polyalkoxylated alkylphenols, fatty acid alkoxylates, sorbitan alkoxylates, sorbitol esters, C8-C 22 Alkyl or alkenyl polyglycosides, polyalkoxystyryl aryl ethers, alkylamine oxides, block copolymer ethers, polyalkoxylated fatty acid glycerides, polyalkylene glycol ethers, linear aliphatic or aromatic polyesters, silicones, polyarylphenols, sorbitan ester alkoxylates, polyalkylene oxide block copolymers, acrylic acid copolymers and mono- and diesters of ethylene glycol and mixtures thereof.

[0194] Examples of anionic surfactants include alcohol sulfates, alcohol ether sulfates, alkyl aryl ether sulfates, alkyl aryl sulfonates such as alkylbenzenesulfonates and alkylnaphthalenesulfonates and their salts, alkylsulfonates, monophosphates or diphosphates of polyalkoxylated alkyl alcohols or alkylphenols, C 12 -C 15 Alkanol or polyalkoxylated C 12 -C 15 Mono- or disulfosuccinates of alkanols, alcohol ether carboxylates, phenol ether carboxylates, polyacid esters of ethoxylated polyoxyalkylene glycols composed of butylene oxide or tetrahydrofuran residues, sulfoalkylamides and salts thereof, such as sodium salt of N-methyl-N-oleoyl taurate, polyoxyalkylene alkylphenol carboxylates, polyoxyalkylene alcohol carboxylates alkyl polyglycoside / alkenyl succinic anhydride condensation products, alkyl ester sulfates, naphthalenesulfonates, naphthalene formaldehyde condensates, alkylsulfonamides, sulfonated aliphatic polyesters, sulfates and sulfonates of styrylphenyl alkoxylates and the corresponding sodium, potassium, calcium, magnesium, zinc, ammonium, alkylammonium, diethanolammonium or triethanolammonium salts thereof, lignin sulfonates, such as sodium, potassium, magnesium, calcium or ammonium salts, polyarylphenol polyalkoxy ether sulfates and polyarylphenol polyalkoxy ether phosphates, and sulfated and phosphated alkylphenol ethoxylates.

[0195] Cationic surfactants include but are not limited to C8-C 18 Fatty acids and C8-C 18 Alkanolamides of fatty amine polyalkoxylates, C 10 -C 18Alkyl dimethyl benzyl ammonium chloride, coconut oil alkyl dimethyl aminoacetic acid, and C8-C 18 Phosphate esters of fatty amine polyalkoxylates.

[0196] Emulsifiers that can be advantageously used herein can be readily determined by those skilled in the art and include various nonionic, anionic, cationic, and amphoteric emulsifiers, or blends of two or more emulsifiers. Examples of nonionic emulsifiers that can be used to prepare emulsifiable concentrates include, for example, polyalkylene glycol ethers and condensation products of alkylphenols and arylphenols, aliphatic alcohols, aliphatic amines, or fatty acids with ethylene oxide, propylene oxide (such as ethoxylated alkylphenols), and carboxylic acid esters solubilized with polyols or polyoxyalkylenes. Cationic emulsifiers include quaternary ammonium compounds and fatty amine salts. Anionic emulsifiers include oil-soluble salts (e.g., calcium) of alkylarylsulfonic acids, oil-soluble salts, or salts of sulfated and phosphated polyethylene glycol ethers.

[0197] In one embodiment, colorants may include, but are not limited to, iron oxide, titanium oxide, and Prussian blue, as well as organic dyes such as alizarin dyes, azo dyes, and metal phthalocyanine dyes, and salts of trace elements such as iron, manganese, boron, copper, cobalt, molybdenum, and zinc.

[0198] Exemplary thickeners and binders include, but are not limited to, molasses, granulated sugar, alginates, karaya gum, guar gum, tragacanth gum, polysaccharide gums, mucilages, xanthan gum, or combinations thereof. In another embodiment, the binder can be selected from silicates such as magnesium aluminum silicate, polyvinyl acetate, polyvinyl acetate copolymers, polyvinyl alcohol, polyvinyl alcohol copolymers, cellulose, including ethylcellulose and methylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, hydroxymethylpropylcellulose, polyvinylpyrrolidone, dextrin, maltodextrin, polysaccharides, fats, oils, proteins, gum arabic, shellac, vinylidene chloride, vinylidene chloride copolymers, calcium lignin sulfonate, acrylic acid copolymers, starch, polyethylene acrylate, zein, gelatin, carboxymethylcellulose, chitosan, polyethylene oxide, acrylamide polymers and copolymers, polyhydroxyethyl acrylate, methacrylamide monomer, alginates, ethylcellulose, polychloroprene and syrups or mixtures thereof; polymers and copolymers of vinyl acetate, methylcellulose, vinylidene chloride, acrylic acid, cellulose, polyvinylpyrrolidone and polysaccharides; polymers and copolymers of vinylidene chloride and vinyl acetate-ethylene copolymers; combinations of polyvinyl alcohol and sucrose; plasticizers such as glycerol, propylene glycol and polyethylene glycol.

[0199] In another embodiment, exemplary antifreeze agents include, but are not limited to, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-pentanediol, 3-methyl-1,5-pentanediol, 2,3-dimethyl-2,3-butanediol, trimethylolpropane, mannitol, sorbitol, glycerol, pentaerythritol, 1,4-cyclohexanedimethanol, xylenol, bisphenols such as bisphenol A, etc. In addition, ether alcohols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene oxide or polypropylene oxide glycols having a molecular weight of up to about 4000, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, butoxyethanol, butanediol monobutyl ether, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, heptaglycerol, and octaglycerol.

[0200] According to one embodiment, exemplary biocides include, but are not limited to, benzothiazole, 1,2-benzisothiazolin-3-one, sodium dichloro-s-triazinetrione, sodium benzoate, potassium sorbate, 1,2-phenyl-isothiazolin-3-one, and m-chloroxylenol butyl paraben.

[0201] According to one embodiment, defoaming agents include, but are not limited to, polydimethoxysiloxanes, polydimethylsiloxanes, alkyl polyacrylates, castor oil, fatty acids, fatty acid esters, fatty acid sulfates, fatty alcohols, fatty alcohol esters, fatty alcohol sulfates, olive oil, mono- and diglycerides, paraffin oil, paraffin, polypropylene glycol, silicone oil, vegetable fats, vegetable fat sulfates, vegetable oils, vegetable oil sulfates, vegetable waxes, vegetable wax sulfates, and agents based on silicon or magnesium stearate.

[0202] Exemplary additives for formulation include, for example, solid carriers such as kaolinite, sericite, diatomaceous earth, slaked lime, calcium carbonate, talc, white carbon, kaolin, bentonite, clay, sodium carbonate, sodium bicarbonate, saltpeter, zeolite or starch; solvents such as water, toluene, xylene, solvent naphtha, dioxane, dimethyl sulfoxide, N,N-dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone or alcohol; anionic surfactants such as salts of fatty acids, benzoates, polycarboxylates, salts of alkyl sulfates, alkyl sulfates, alkylaryl sulfates, alkyl diglycol ether sulfates, salts of alcohol sulfates, alkyl sulfonates, alkylarylsulfonates, arylsulfonates, ligninsulfonates, alkyl diphenyl oxide disulfonates, polystyrenesulfonates, salts of alkyl phosphates, alkylarylphosphates, styrylarylphosphates, salts of polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, polyoxyethylene alkylaryl salts of ether sulfates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylaryl phosphates, polyoxyethylene aryl ether phosphates, naphthalenesulfonic acid condensed with formaldehyde or salts of alkylnaphthalenesulfonic acid condensed with formaldehyde; nonionic surfactants such as sorbitan fatty acid esters, glycerol fatty acid esters, fatty acid polyglycerol esters, fatty acid alcohol polyethylene glycol ethers, acetylene glycol, acetylene alcohol, oxyalkylene block polymers, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene Alkenyl styryl aryl ether, polyoxyethylene glycol alkyl ether, polyethylene glycol, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerol fatty acid ester, polyoxyethylene hydrogenated castor oil or polyoxypropylene fatty acid ester;And vegetable oil or mineral oil such as olive oil, kapok oil, castor oil, palm oil, camellia oil, coconut oil, sesame oil, corn oil, rice bran oil, peanut oil, cottonseed oil, soybean oil, rapeseed oil, linseed oil, tung oil or liquid paraffin.As long as the purpose of the present invention is met, these additives can be appropriately selected to be used alone or as a mixture combination of two or more of them.In addition, additives other than the above-mentioned additives can be appropriately selected for use in those additives known in the art.For example, various additives commonly used can be adopted, such as fillers, thickeners, anti-settling agents, antifreeze agents, dispersion stabilizers, safeners, mildew inhibitors, foaming agents, disintegrants and binding agents.

[0203] The agrochemical formulation may also contain one or more antioxidants. Preferably, the agrochemical formulation contains an antioxidant. Exemplary antioxidants are, for example, amino acids (e.g., glycine, histidine, tyrosine, tryptophan) and their derivatives, imidazoles and imidazole derivatives (e.g., urocanic acid), peptides (e.g., D,L-carnosine, D-carnosine, L-carnosine and their derivatives (e.g., anserine)), carotenoids, carotenes (e.g., α-carotene, β-carotene, lycopene) and their derivatives, lipoic acid and its derivatives (e.g., dihydrolipoic acid), aurothioglucose, propylthiouracil and its further thio compounds (e.g., thioglycerol, thiosorbitol, thioglycolic acid, thioredoxin, glutathione, cysteine, cystine, cystamine and their glycosyl groups, N-acetyl, methyl, ethyl, propyl, amyl, butyl, lauryl, palmitoyl, oleyl, γ-linoleyl, cholesteryl, and glyceryl esters) and salts, dilauryl thiodipropionate, distearyl thiodipropionate, thiodipropionic acid and its derivatives (esters, ethers, peptides, lipids, nucleotides, nucleosides, and salts), and sulfoximine compounds (e.g., buthionine sulfoximine, homocysteine ​​sulfoximine, buthionine sulfone, pentathionine sulfoximine, hexathionine sulfoximine, heptathionine sulfoximine) at very low tolerated doses, as well as metal chelators (e.g., α-hydroxy fatty acids, ethylenediaminetetraacetic acid (EDTA), ethylene glycol-bis(β-aminoether)-N,N,N',N'-tetraacetic acid (EGTA), phytic acid, lactoferrin), α-hydroxy acids (e.g., citric acid, lactic acid, malic acid), humic acid, bile acids, bile extracts, gallic acid esters (e.g., propyl gallate, octyl gallate, and dodecyl gallate), flavonoids, catechins, bilirubin, biliverdin and its derivatives, unsaturated fatty acids and their derivatives (e.g., gamma-linolenic acid, linoleic acid, arachidonic acid, oleic acid), folic acid and its derivatives, hydroquinone and its derivatives (e.g., arbutin), ubiquinone and ubiquinol and their derivatives, vitamin C and its derivatives (e.g., ascorbyl palmitate, stearate, palmitic acid diester, acetate, magnesium ascorbyl phosphate, sodium and magnesium ascorbate, disodium ascorbyl phosphate and disodium ascorbyl sulfate, potassium ascorbyl tocopheryl phosphate, chitosan ascorbate), erythorbic acid and its derivatives benzoin resin, rutin, rutin and its derivatives, disodium rutin disulfate, cinnamic acid and its derivatives (e.g., ferulic acid, ethyl ferulate, caffeic acid), kojic acid, chitosan glycolate and salicylate, butylated hydroxytoluene, butylated hydroxyanisole, nordihydroguaiaretic acid, nordihydroguaiaretic acid, trihydroxybutyrophenone, uric acid and its derivatives, mannose and its derivatives, selenium and selenium derivatives (e.g., selenomethionine), stilbene and stilbene derivatives (e.g., stilbene oxide, trans-stilbene oxide). According to the present invention, mixtures or plant extracts containing suitable derivatives (salts, esters, sugars, nucleotides, nucleosides, peptides and lipids) of these antioxidants and these specified active ingredients (e.g., tea tree oil, rosemary extract and rosmarinic acid) can be used. In general, mixtures of the above antioxidants are possible.

[0204] According to one embodiment, examples of solvents include, but are not limited to, water, aromatic solvents (e.g., xylene), paraffins (e.g., mineral oil fractions such as kerosene or diesel), coal tar and oils of plant or animal origin, aliphatic, cyclic and aromatic hydrocarbons, such as toluene, xylene, paraffin, tetralin, alkylated naphthalenes or their derivatives, alcohols (e.g., methanol, butanol, amyl alcohol, benzyl alcohol, cyclohexanol), ketones (e.g., cyclohexanone, gamma-butyrolactone), pyrrolidones (NMP, NEP, NOP), acetates (ethylene glycol diacetate), glycols, fatty acid dimethylamides, fatty acids and fatty acid esters, isophorone and dimethyl sulfoxide. In principle, solvent mixtures can also be used.

[0205] According to one embodiment, examples of carriers include, but are not limited to, mineral earths such as silica gel, silicates, talc, kaolin, magnesian clay, attapulgite, limestone, lime, chalk, red basalt, loess, clay, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate, magnesium oxide, ground synthetic materials, fertilizers such as ammonium sulfate, ammonium phosphate, ammonium nitrate, urea and products of plant origin such as grain flour, bark flour, wood flour and nut shell flour, cellulose powder, polyvinyl pyrrolidone and other solid carriers.

[0206] Exemplary preservatives include, for example, 1,2-benzisothiazolin-3-one and / or 2-methyl-2H-isothiazol-3-one or sodium benzoate or benzoic acid.

[0207] The herbicidal combinations and compositions of the present disclosure may be in any conventional agriculturally useful form, for example, in the form of a ready-to-use formulation, or in the form of a tank mix.

[0208] Advantages of the present invention

[0209] 1. The present invention provides high-purity glufosinate ammonium that is substantially free of inorganic salts

[0210] 2. The present invention further provides a method for preparing high-purity glufosinate-ammonium that is substantially free of inorganic salts

[0211] 3. The method provides separation of glufosinate ammonium from inorganic salts, thereby avoiding multiple purification steps

[0212] 4. The method is an industrially feasible and environmentally friendly method for separating glufosinate ammonium from inorganic salts

[0213] Example :

[0214] The present invention is explained in more detail by the following examples. However, it should be understood that the scope of the present invention is not limited by these examples in any way. It should be understood by those skilled in the art that the present invention includes the following examples and can also be modified and changed within the technical scope of the present invention.

[0215] Analytical method details :

[0216] HPLC method: The samples were analyzed on a high performance liquid chromatograph with UV detection using an Inertsil – pH 3 (250 × 4.6 mm id, 5 μm) column.

[0217] Example 1: Method for preparing racemic glufosinate ammonium

[0218] 107 kg of a hydrolyzed reaction mass containing glufosinate hydrochloride and inorganic salts, obtained by reacting 3-[ethoxy(methyl)phosphoryl]propanal with potassium cyanide and ammonium chloride, followed by hydrolysis, according to Example 3 of US Pat. No. 4,264,532, was diluted with 350 kg of water and then neutralized with aqueous ammonia to yield a first solution having a total dissolved solute content of less than 9%. The first solution was passed through a nanofiltration membrane, namely a Biotech Element D Series Thin Film Membrane (TFM*) nanofiltration membrane. The solution was filtered through the membrane at 20°C-50°C while maintaining a transmembrane pressure of approximately 14 to 38 bar to yield 111 kg of a second solution and 250 kg of permeate. The second solution was then vacuum distilled to remove 80%-90% of the water, yielding a reaction mass. 38.9 kg of methanol was added to the reaction mass, and the mixture was refluxed at 75°C-80°C for 1 hour. The reaction mixture was then cooled to 40°C-45°C, and ammonia gas was purged into the mixture until the pH reached 9-10. The mixture was then cooled to 5-10°C to obtain a precipitate of glufosinate ammonium. The product was then filtered, washed with methanol and dried to obtain 10.7 kg of glufosinate ammonium with a wt / wt purity of >96% (inorganic salt content = <2% 0).

[0219] Example 2: Method for preparing L-glufosinate ammonium

[0220] Step 1: Preparation of ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butanoate

[0221] 550 g (1 molar equivalent) of ethyl (2S)-4-chloro-2-[(ethoxycarbonyl)amino]-butyrate and 490 g (1.5 molar equivalents) of diethyl methylphosphinate were charged to a reaction flask at 25-30°C. The mixture was heated at 140°C for 20 hours while continuously flushing the system with nitrogen. After the reaction was complete, the excess diethyl methylphosphinate was distilled off under vacuum to yield crude ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butyrate.

[0222] Step 2: Preparation of hydrolyzed material

[0223] To 618 g of crude ethyl (2S)-2-[(ethoxycarbonyl)amino]-4-(ethoxymethylphosphinyl)butanoate was added 2579 g of concentrated HCl (30% concentration), and the mixture was refluxed for 16 hours. The resulting mixture was distilled to obtain 1612 g of a hydrolyzed reaction mass.

[0224] Step 3: Preparation of L-glufosinate ammonium

[0225] To the hydrolyzed material obtained in step 2, 1000 g of water was added, and the pH was adjusted to 7.1 by purging with ammonia gas. The mixture was then diluted with 5300 g of water to produce a first solution with a total dissolved solute content of less than 8%. The first solution was passed through a nanofiltration membrane (for this experiment, a Biotech Element D Series Thin Film Membrane (TFM*) nanofiltration membrane was used). The solution was filtered through the membrane at a temperature of 20°C to 50°C, maintaining a transmembrane pressure of approximately 10 to 20 bar, to produce 3830 g of a second solution and 3549 g of permeate. The second solution was then vacuum distilled to remove 80%-90% of the water, yielding a reaction mass. 996 g of methanol was added to the reaction mass, and the mixture was refluxed for 2 hours. The mixture was then cooled to 30°C to 40°C, and ammonia gas was purged into the mixture until the pH reached 8-10. The temperature was then raised to 60°C to 70°C for 2 hours, followed by cooling to 5°C to 10°C to produce a precipitate of L-glufosinate-ammonium. The product was then filtered, washed with methanol and dried to obtain 300 g of L-glufosinate ammonium with a wt / wt purity of 96.4% (inorganic salt content = 0.3%) and a chiral ratio of 98:02 (L:D).

Claims

1. A method for preparing glufosinate ammonium having less than 3 wt% of inorganic salts, the method comprising precipitating glufosinate ammonium by treating a solution comprising glufosinate ammonium with ammonia, the solution comprising glufosinate ammonium being prepared by passing a first solution comprising glufosinate ammonium and an inorganic salt through a membrane.

2. The method for preparing glufosinate-ammonium according to claim 1, comprising: a) treating a first solution comprising glufosinate and an inorganic salt through a membrane to obtain a second solution and a permeate; and b) precipitating glufosinate-ammonium from the second solution by treatment with ammonia; The glufosinate ammonium contains less than 3% by weight of inorganic salts.

3. The method according to claim 2, wherein in step a), the glufosinate used is racemic glufosinate or L-glufosinate.

4. The method according to claim 2, wherein the first solution comprising glufosinate-ammonium and an inorganic salt is obtained from a hydrolyzed reaction mass comprising glufosinate-ammonium hydrochloride and an inorganic salt.

5. The method according to claim 4, wherein the hydrolyzed reaction mass is subjected to i) adjusting the total dissolved solute concentration to less than 15%, and ii) Adjust the pH value to within the range of 6 to 8 To obtain the first solution containing glufosinate-ammonium and inorganic salt.

6. The process according to claim 5, wherein in step i), the total dissolved solute concentration is adjusted by diluting the hydrolyzed reaction mass with water, and in step ii), the pH value is adjusted using a base. The method according to claim 5 , wherein the step i) and the step ii) are performed in any order.

8. The process according to claim 6, wherein the base is selected from ammonia, ammonium hydroxide, alkali metal or alkaline earth metal hydroxides, alkali metal or alkaline earth metal carbonates, alkali metal or alkaline earth metal alkoxides.

9. The method of claim 4, wherein the first solution comprises from about 1 wt% to about 7 wt% glufosinate and from about 2 wt% to about 12 wt% of an inorganic salt.

10. The method according to claim 1, wherein the membrane used in step a) is a nanofiltration membrane made of a polymer material selected from the group consisting of polyamide, polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile, polyimide, polyamideimide, polyetherimide, cellulose acetate, polyaniline, polypyrrole, polyetheretherketone, polybenzimidazole, polyester, vinyl polymer or a mixture thereof.

11. The method of claim 9, wherein the nanofiltration membrane has a molecular weight in the range of about 100 unit Da to about 200 unit Da.

12. The method of claim 1, wherein the first solution is processed through the membrane at a transmembrane pressure in the range of about 3 (g) bar to about 50 (g) bar.

13. The process of claim 1, wherein the glufosinate ammonium is obtained having a purity greater than about 95% as measured by HPLC.

14. A method for preparing glufosinate-ammonium, comprising the following steps: a) preparing a first solution comprising glufosinate-ammonium and an inorganic salt having a total dissolved solute content of less than 15%; b) treating the first solution through a membrane to obtain a second solution and a permeate; and c) precipitating glufosinate ammonium from the second solution by treatment with ammonia, comprising; wherein the glufosinate ammonium contains less than 3% by weight of inorganic salts.

15. A method for preparing L-glufosinate-ammonium, the method comprising the following steps: a) preparing a first solution comprising L-glufosinate and an inorganic salt having a total dissolved solute content of less than 15%; b) treating the first solution through a membrane to obtain a second solution and a permeate; as well as c) precipitating glufosinate ammonium from the second solution by a treatment comprising ammonia; wherein the glufosinate ammonium contains less than 3% by weight of inorganic salts.

16. Glufosinate ammonium having less than 3% by weight of inorganic salts.

17. L-glufosinate ammonium having less than 3% by weight of inorganic salts.

18. A herbicide composition comprising glufosinate ammonium or L-glufosinate ammonium having less than 3% by weight of inorganic salts and at least one agrochemically acceptable excipient.

Images