# US 8,772,439 B2 · Production of solutions of diacid/diamine salts > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,772,439 B2 - Document ID: US8772439B2 - Status: Granted - Kind: B2 - Application number: 12/451,851 - Filed: 2008-05-22 - Published: 2010-07-01 - Granted: 2014-07-08 - Earliest claimed: 2007-06-04 - Assignees: Rhodia Operations - Applicants: Jean-François Thierry - Inventors: Jean-François Thierry - Web page: https://patentgrep.com/patent/US8772439B2 ## CPC - C07C 209/68: from amines, by reactions not involving amino groups, e.g. reduction of unsaturated amines, aromatisation, or substitution of the carbon skeleton - C07C 51/412: {by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part} - C08G 69/28: Preparatory processes - B01J 2219/00006: Large-scale industrial plants - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS ## Abstract Solutions of a salt of a diamine and of a diacid, more particularly concentrated solutions of hexamethylene diammonium adipate salt (“nylon salt”), useful starting materials for the production of polyamides, more specifically of PA66, are prepared by mixing a diacid and a diamine, at a salt concentration by weight of from 50% to 80%, in a first stage, to provide aqueous solutions of diacid and diamine having a diacid/diamine molar ratio of greater than 1.1 and, in a second stage, adjusting the diacid/diamine molar ratio, by adding diamine, to a value of from 0.9 to 1.1, preferably from 0.99 to 1.01, and in fixing the salt concentration by weight by, optionally, adding water thereto. ## Claims ### Claim 1 A process for the production of an aqueous solution of salts of diamines and diacids, comprising: (a) producing an aqueous solution of diamine and diacid having a diacid/diamine molar ratio from 1.5 to 5 and a concentration of dissolved reactants comprising diamine and diacid in water from 40% to 75% by weight, in a first reaction zone containing either (i) at least 5% by volume of aqueous solution of diamine and diacid with a molar ratio ranging from 1.5 to 5, or (ii) water constituting at least 10% of the total amount of water to be introduced into said reaction zone, a stream comprising diacid, by feeding into said reaction zone a stream comprising diamine and, optionally, a stream of water, the flow rates of the feed stream comprising diacid and of the feed stream comprising diamine being controlled such that the temperature of the solution in said reaction zone is constantly below the boiling point at the operating pressure in said reaction zone and such that the diacid/diamine molar ratio is constantly greater than 1.1, the amount of acid introduced corresponding to at least 90% by weight of the total mass of the acid required to produce the desired amount of aqueous salt solution, the amount of water introduced constituting at least 75% by weight of the total mass of water required to produce the desired amount of the aqueous salt solution; (b) transferring the aqueous solution obtained in the first reaction zone into a second reaction zone equipped with a condenser; and (c) introducing into the second reaction zone a stream comprising diamine to provide a diacid/diamine molar ratio ranging from 0.9 to 1.1, the temperature of the solution being adjusted to at most 110° C. and, optionally, introducing amounts of additional water and/or diacid such as to provide the salt solution with the desired concentration and with the desired diacid/diamine ratio, thereby, obtaining an aqueous solution of salts of diamines and diacids at a salt concentration ranging from 50% to 80% by weight. ### Claim 2 (depends on 1) The process as defined by claim 1, wherein the concentration of dissolved reactants in the first reaction zone ranges from 45% to 65% by weight. ### Claim 3 (depends on 1) The process as defined by claim 1, wherein the diacid/diamine molar ratio in the second reaction zone ranges from 1.00 to 1.05. ### Claim 4 (depends on 1) The process as defined by claim 1, wherein the solution obtained in the second reaction zone is transferred into a third reaction zone, optionally maintained in the absence of oxygen, equipped with a condenser, into which are added a stream comprising diamine and/or a stream comprising diacid and, optionally, a stream of water such as to adjust the diacid/diamine ratio to 0.99 to 1.01 and to adjust the concentration by weight of salt. ### Claim 5 (depends on 4) The process as defined by claim 4, wherein at least the second and third reaction zones are maintained under an oxygen-free atmosphere. ### Claim 6 (depends on 4) The process as defined by claim 4, wherein at least the second and third reaction zones are under an oxygen-free atmosphere comprising nitrogen, a rare gas, steam or a mixture thereof. ### Claim 7 (depends on 1) The process as defined by claim 1, carried out in batch mode. ### Claim 8 (depends on 7) The process as defined by claim 7, wherein the aqueous solution forming the aqueous beginning solution constitutes at least 5% by volume of the desired amount of solution produced in said reaction zone at the end of the first stage. ### Claim 9 (depends on 8) The process as defined by claim 8, wherein the aqueous solution forming the aqueous beginning solution constitutes from 5% to 40% by weight of the desired amount of solution produced in said reaction zone at the end of the first stage. ### Claim 10 (depends on 1) The process as defined by claim 1, wherein the temperature in the second reaction zone is at most equal to the boiling point of the solution at the operating pressure, the condenser generating a reflux of condensed water. ### Claim 11 (depends on 4) The process as defined by claim 4, wherein the temperature in the third reaction zone is at most equal to the boiling point of the solution at the operating pressure, the condenser generating a reflux of condensed water. ### Claim 12 (depends on 1) The process as defined by claim 1, wherein the stream comprising diamine introduced into the first reaction zone comprises an aqueous solution of diamine. ### Claim 13 (depends on 12) The process as defined by claim 12, wherein the concentration of diamine in the said aqueous solution is at least 50% by weight. ### Claim 14 (depends on 1) The process as defined by claim 1, carried out in continuous mode. ### Claim 15 (depends on 14) The process as defined by claim 14, wherein the stream comprising diamine introduced into the first reaction zone at least partially comprises the concentrated salt solution produced thereby. ### Claim 16 (depends on 14) The process as defined by claim 14, wherein the second reaction zone comprises an external circulation loop including at least one static mixer. ### Claim 17 (depends on 16) The process as defined by claim 16, wherein an inlet of the stream comprising diamine into the second reaction zone is located upstream of the static mixer. ### Claim 18 (depends on 17) The process as defined by claim 17, wherein the inlet of the stream of salt solution originating from the first reaction zone is located upstream of the diamine feed. ### Claim 19 (depends on 16) The process as defined by claim 16, wherein means for measuring the pH of the solution is located downstream of the static mixer, and the diacid/diamine molar ratio is adjusted by introducing a stream of diamine and/or of diacid, downstream of a point at which the pH is measured and as a function of such measurement. ### Claim 20 (depends on 1) The process as defined by claim 1, wherein the diamine comprises hexamethylene diamine and the diacid comprises adipic acid.