52 results about "Toluenediamine" patented technology

The invention provides a preparation method of a catalyst, the catalyst and a diethyltoluenediamine synthesis method based on the catalyst, and belongs to the technical field of chemical synthesis. After the surface of phosphoric acid modified zeolite is coated with aluminum oxide, a layer of quantum dot intercalation metal layered oxide is coated, the surface is modified by polydopamine, citric acid is coupled, cerium oxide and ruthenium oxide are loaded, and the catalyst is prepared. The prepared catalyst can well improve the conversion rate of toluenediamine, inhibit side reactions, improve the anti-coking capability, reduce the generation of carbon deposits, prevent the agglomeration of catalyst particles, prolong the service life, improve the mechanical strength and thermal stability, reduce the activation energy in the synthesis process of diethyltoluenediamine, make the reaction conditions milder, make the yield higher, and reduce the production cost. And the method can be repeatedly used and has a wide application prospect.

The invention provides a method for preparing toluene diisocynate through a phosgene method, and belongs to the technical field of toluene diisocynate preparation. According to the method, liquid phosgene is atomized into atomized phosgene through a high-pressure spraying device, the atomized phosgene is in countercurrent contact with a toluenediamine solution sprayed into a phosgenation reactor, the contact area of the atomized phosgene and the toluenediamine solution is increased, and the phosgenation reaction process is accelerated. In addition, due to the arrangement of the liquid homogenizer, the contact area between the atomized phosgene and the toluenediamine solution is increased, the reaction rate between the atomized phosgene and the toluenediamine solution is increased, and side reactions are reduced. Meanwhile, the phosgene participates in the phosgenation reaction in the form of mist droplets and is not dissolved in the solvent, so that the use of the solvent is greatly reduced, the concentration of the phosgene in the phosgenation reactor is improved, and side reactions are reduced. The liquid phosgene is subjected to high-pressure spraying treatment, so that the use of a solvent is saved, and subsequent solvent separation is facilitated. After the decomposition reaction is finished, hydrogen chloride gas and unreacted phosgene are separated in a freezing mode, phosgene recovery is achieved, and the recovery mode is simple.

The invention discloses a preparation method of dimethyl thio toluenediamine, which comprises the following steps: continuously introducing dimethyl disulfide into a reaction system containing diaminotoluene and a catalyst for reaction, and evaporating and condensing the dimethyl disulfide in the reaction process so as to bring out a byproduct methyl mercaptan, after the reaction is finished, purifying and decoloring by adopting a neutralization distillation method to obtain dimethyl thio toluenediamine; the neutralization distillation method comprises the following steps: adding dimethyl disulfide into a reaction solution after the reaction is finished for dilution, then filtering the reaction solution to obtain a filtrate, adding an alkali solution into the filtrate for neutralization, heating and stirring, and finally carrying out reduced pressure distillation. The preparation method disclosed by the invention has the advantages of small catalyst dosage, short reaction time, high product yield and economic and environment-friendly purification and decoloration modes.

The invention provides a production method of LC-grade diethyltoluenediamine, and belongs to the technical field of organic chemistry. The preparation method comprises the following steps: under the protection of inert gas, mixing toluenediamine and a catalyst, heating and stirring, introducing ethylene and composite gas at the same time, carrying out heat preservation and pressurization reaction, cooling, relieving pressure, discharging, and refining feed liquid to prepare LC-grade diethyltoluenediamine. The production method of the LC-grade diethyltoluenediamine is simple, few in side reaction, high in product yield, high in purity, easy to realize industrial application, wide in raw material source and mild in reaction condition, and the catalyst is easy to separate and can be repeatedly utilized for multiple times, so that the LC-grade diethyltoluenediamine has a wide application prospect.

The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses a composite coating with electromagnetic protection and explosion-proof functions as well as a preparation method and application of the composite coating. The coating comprises 40 to 60 parts of polycarbodiimide modified diphenylmethane diisocyanate, 40 to 60 parts of a semi-prepolymer which is synthesized from polycarbonate diol with the equivalent weight of 1000 and has the NCO content of 10 to 20 percent, 73 to 100 parts of a polyether amine curing agent, 15 to 20 parts of diethyl toluenediamine or dimethyl thio toluenediamine, 0.5 to 2 parts of calcium carbonate and 3 to 6 parts of magnetic powder. And the two components are quickly reacted and molded through a spraying process. According to the invention, the polyurea elastomer is used as a matrix, so that the coating is endowed with excellent impact resistance, explosion-proof characteristics, water impermeability, oil resistance, low temperature resistance and other environmental tolerance; meanwhile, an adjustable electromagnetic wave absorption function is realized by doping specific magnetic powder. The coating is simple in preparation process and excellent in comprehensive performance, and is particularly suitable for equipment surfaces with high requirements on stealth and survival protection, such as oil storage equipment.

The invention provides a refining process for producing toluene diisocynate, and belongs to the technical field of chemical processes. The method comprises the following steps: taking toluenediamine and phosgene as raw materials, carrying out phosgenation reaction in o-dichlorobenzene, carrying out primary separation to obtain a to-be-refined material, inputting the to-be-refined material into a refining tower, and extracting primary toluene diisocynate from a tower kettle of the refining tower; wherein the number of theoretical tower plates of the refining tower is 12-18, the number of feeding tower plates is 4-12, and the reflux ratio is 1-5, so that almost no ODCB exists in a tower kettle extract of the refining tower, the requirements of a subsequent production process are met, and the finishing and refining process is low in energy consumption and high in energy utilization rate; meanwhile, the preparation process disclosed by the invention can be used for refining 70 thousand tons of toluene diisocynate and 50 thousand tons of toluene diisocynate, and is suitable for industrial production.

The application discloses the technical field of organic synthesis and relates to a high-yield synthesis method of diethyltoluene diamine; the method comprises the following steps: firstly, a polyoxometalate-organic framework hybrid material is activated at medium temperature under nitrogen protection, and m-toluene diamine is pretreated by vacuum dehydration; then, the activated catalyst and the dehydrated m-toluene diamine are added into a reaction kettle, ethylene is introduced at high temperature after nitrogen replacement, and reaction is carried out; the reaction mixture is cooled and filtered, the filter cake is washed and dried, and then is activated and regenerated at medium temperature; the filtrate is subjected to rectification to collect main distillates to obtain the product. The catalyst is prepared by the following steps: reaction of phosphotungstic acid and aminopropyltrimethoxysilane, condensation with p-benzene dicarboxaldehyde, solvothermal crystallization with nickel nitrate, supercritical carbon dioxide treatment and calcination. The method has the advantages of high catalyst activity, reusability, mild reaction conditions and high yield of diethyltoluene diamine.

A first aspect of the invention relates to a mixture comprising 2,4- toluene diamine and 2,6-toluene diamine and comprising less than 10 weight-ppm of an amino methyl cyclohexenone compound of formula (I) based on the total weight of the mixture being 100 weight-%. In a second aspect, the invention is directed to a method for controlling a hydrogenation process for preparing toluene diamine (TDA) from dinitrotoluene (DNT), said TDA having a boiling temperature range BTRTDA with a lower boiling temperature limit value TTDA(L) and an upper boiling temperature limit value TTDA(U). A third aspect relates to a mixture comprising at least 2,4- toluene diamine and 2,6-toluene diamine obtained or obtainable from the method according to the second aspect. A fourth aspect of the invention is directed to a use of the mixture according to the first aspect of the invention or of the mixture of the third aspect of the invention for the preparation of toluene diisocyanate (TDI). In a fifth aspect, the invention relates to a process for preparing toluene diisocyanate (TDI) comprising: (I) Providing a mixture according to the first aspect of the invention or of the mixture of the third aspect of the invention; and (II) Phosgenation of the mixture provided in (I), thereby obtaining TDI.

The present invention relates to a process for preparing a rigid polyisocyanurate foam comprising the reaction of a composition (A) including a polyesterol, a foaming agent comprising formic acid, a catalytic system comprising at least one trimerization catalyst, and at least one polyisocyanate as component (B), wherein composition (A) further comprises at least one polyether alcohol prepared by the addition of alkylene oxides to toluenediamine. The present invention also relates to a rigid polyisocyanurate foam obtained or obtainable by the process of the present invention and to the use of said rigid polyisocyanurate foam as an insulating material.

The invention relates to a process for synthesizing toluene diisocynate by a low-energy-consumption non-phosgene method, which comprises the following steps: reacting toluenediamine with dimethyl carbonate to synthesize toluene dicarbamate, and then decomposing the toluene dicarbamate to prepare the toluene diisocynate. According to the process, heat of a reaction product for synthesizing methyl toluenediamine and dimethyl carbonate is utilized, and part of light components are evaporated out through flash evaporation operation; and then adding a solvent for the decomposition reaction of toluene dicarbamate into the flashed material, continuously evaporating components such as dimethyl carbonate and the like, and enabling toluene dicarbamate and the solvent to enter a decomposition refining reaction tower together for reaction and separation to obtain a product. Compared with the prior art, the method has the advantages that the process is simple, the energy consumption, the equipment and the operation cost are saved, the purity of the obtained product and byproduct is high, and the total production cost of the toluene diisocyanate is greatly reduced.

The present invention provides a method for producing LC-grade diethyltoluenediamine, belonging to the technical field of organic chemistry. Under inert gas protection, toluenediamine and a catalyst are mixed, heated and stirred, ethylene and a composite gas are introduced simultaneously, the mixture is kept warm and pressurized for reaction, the temperature is lowered, the pressure is released, the product is discharged, and the liquid is refined to produce LC-grade diethyltoluenediamine. The method for producing LC-grade diethyltoluenediamine is simple, exhibits few side reactions, produces a high product yield and purity, is readily industrially applicable, has a wide range of raw material sources, operates under mild reaction conditions, and the catalyst is easily separable and can be reused multiple times, thus having broad application prospects.

The invention provides diethyltoluenediamine epoxy resin, a preparation method thereof and modified epoxy resin, and belongs to the technical field of resin materials. The diethyltoluenediamine epoxy resin provided by the invention has a structure as shown in a formula I. The structure of the DETGA provided by the invention contains a rigid benzene ring structure and a flexible ethyl structure, so that the rigid strength and toughness of an epoxy system can be improved; meanwhile, DETGA has multiple epoxy groups and is similar to E-51 bisphenol A epoxy resin in structure, so that DETGA can be uniformly dispersed in a system; the epoxy value of the diethyltoluenediamine epoxy resin provided by the invention is greater than or equal to 0.80 eq / 100g, the viscosity is less than or equal to 4000 mPa.s, and the rigidity, toughness, high temperature resistance and processability of an E-51 epoxy resin cured product can be improved after the diethyltoluenediamine epoxy resin is doped into an E-51 epoxy resin system. # imgabs0 #

This invention relates to a method for recovering valuable substances from polyurethane foam, comprising: (A) providing a polyurethane foam based on an isocyanate component and a polyether polyol component; (B) chemically decomposing the polyurethane foam by reacting it with an organic chemical decomposition agent and water, wherein the organic chemical decomposition agent is selected from: (i) a primary or secondary chemically decomposable amine, (ii) a chemically decomposable amino alcohol having a primary or secondary amino group, (iii) a chemically decomposable alcohol, or (iv) a mixture of two or more of the said organic chemical decomposition agents; (C) distilling off the organic chemical decomposition agent and optionally toluene diamine or a portion thereof generated in (B), wherein solid components can be separated before and / or after distillation; (D) extracting the polyether polyol with an organic solvent, wherein an acid and water are added, and a polyol phase is obtained after separation of the acidic aqueous phase; and (E) post-treating the polyol phase to obtain at least one polyether polyol.

The invention relates to the field of reverse osmosis membranes, in particular to a preparation method of an organic-solvent-resistant reverse osmosis membrane, which comprises the following steps: preparing a base membrane; the base membrane is coated with an aqueous phase solution, the aqueous phase solution is prepared from the following raw materials in percentage by weight: 2 to 6 percent of quaternized modified 2.6-toluenediamine, 0.1 to 1 percent of 4-chloro-m-phenylenediamine, 2 to 4 percent of a pH regulator, 0.15 to 0.4 percent of a surfactant, 0.5 to 2.5 percent of an acid acceptor, 1 to 3 percent of modified zirconium-based organic framework filler and the balance of water, and drying is performed after coating; and coating an oil phase solution, and drying to obtain the organic solvent-resistant reverse osmosis membrane. The reverse osmosis membrane provided by the invention can still keep stable organic solvent resistance and separation performance in a strong-polarity organic solvent environment.

The present invention relates to a process for the preparation of toluene-2, 5-diamine or a salt thereof. The invention also relates to a method for preparing the toluene-2, 5-diamine sulfate. According to the method, carcinogenic and allergenic raw materials (such as o-toluidine) are not used, a brand-new synthesis route is adopted, and the method has the advantages that the used initial raw materials are easy to obtain, the reaction environment is safe, operation is easy, an intermediate is stable and easy to separate, and no use-prohibited components (such as o-toluidine) are used or generated.

The invention provides a catalyst and a synthesis method of diethyltoluenediamine based on the catalyst, and belongs to the technical field of chemical synthesis. After the surface of phosphoric acid modified zeolite is coated with aluminum oxide, a layer of quantum dot intercalation metal layered oxide is coated, the surface is modified by polydopamine, citric acid is coupled, cerium oxide and ruthenium oxide are loaded, and the catalyst is prepared. The prepared catalyst can well improve the conversion rate of toluenediamine, inhibit side reactions, improve the anti-coking capability, reduce the generation of carbon deposits, prevent the agglomeration of catalyst particles, prolong the service life, improve the mechanical strength and thermal stability, reduce the activation energy in the synthesis process of diethyltoluenediamine, make the reaction conditions milder, make the yield higher, and reduce the production cost. And the method can be repeatedly used and has a wide application prospect.

The application discloses a cold storage and heat preservation plastic foam and a preparation method thereof. The combined material formula comprises a boric acid polyether polyol and a high-hydroxyl-value o-toluidine polyether polyol. The boric acid polyether polyol has a characteristic of a triangular stable structure of boron atoms, and can improve the strength and dimensional stability of a plastic product and delay the attenuation of the strength and dimensional stability of the plastic product in application. The boric acid polyether polyol contains a part of insoluble B=O structure, which is easy to precipitate in the early stage of the reaction of the combined material with isocyanate, forms stable nucleation points, and through the synergistic effect of the high-hydroxyl-value o-toluidine polyether polyol, the cross-linking of product foam fibers is enhanced, the bubbles are inhibited and the bubbles are made more delicate, and the thermal conductivity of the product is reduced. The rapid cross-linking can reduce the volatilization of a foaming agent and reduce the surface bubbles at the end of product flow.

The presently claimed invention relates to an oxidative hair colouring composition comprising at least one oxidative coupler dye precursor selected from 6-hydroxybenzomorpholine (A), its addition salts, its solvates and / or solvates of its salts, at least one first oxidative primary dye precursor selected from N,N-bis(2-hydroxyethyl)-p-phenylenediamine (B), its addition salts, its solvates and / or solvates of its salts and, at least one second oxidative primary dye precursor selected from toluene-2,5-diamine (C), its addition salts, its solvates and / or solvates of its salts. Moreover, the presently claimed invention relates to a kit comprising a tint composition comprising components (A), (B), and (C), and a method of treating hair using the oxidative hair colouring composition.

The invention belongs to the technical field of product purification and organic synthesis, and particularly relates to an m-toluenediamine composition, a purification method of m-toluenediamine and application of m-toluenediamine. Through repeated research, the applicant finds that m-toluenediamine, 4-methyl-5-amino-1-cyclohexene-1-formaldehyde and 4-methyl-5-amino-2-cyclohexene-1-ketone can be subjected to a Schiff base reaction under the catalytic action to generate Schiff base tar, and then m-toluenediamine and 4-methyl-5-amino-2-cyclohexene-1-ketone are removed from m-toluenediamine in the form of heavy components; the contents are respectively reduced to below 50ppm; the purified m-toluenediamine is used for preparing crude TDI, the purity of the TDI product obtained through rectification and purification can reach 99.99 wt% or above, and the content of chlorine-containing impurities such as hydrolyzed chlorine is lower than 5 ppm. The polyurethane flexible foam prepared by adopting the TDI provided by the invention has the advantages that the foam hole structure is fine and smooth, the comfort level of a user is obviously improved, and the content of free monomers and volatile VOCs (Volatile Organic Compounds) is obviously reduced.

The invention relates to high-temperature-resistant premixed polyether polyol and a preparation method thereof, and belongs to the technical field of premixed polyether polyol. The high-temperature-resistant combined polyether is prepared from the following raw materials in parts by weight: 60-78 parts of a polyether polyol composition, 3-5 parts of a dispersing agent, 2-4 parts of a chain extender, 0.1-0.2 part of a catalyst, 1-1.5 parts of a composite antioxidant, 0.5-1 part of a high-temperature-resistant organic silicon surfactant, 10-15 parts of a cyclopentane foaming agent and 1-2 parts of an organic phosphonate stabilizer. Composite nanoparticles prepared by matching nano ZrO2, nano Al2O3 and nano SiO2 with a composite coupling agent in a specific proportion are matched with m-toluenediamine polyether and THEIC-based heterocyclic polyether, so that the high-temperature resistance of the polyether is improved, and by virtue of a synergistic system formed by the nanoparticles of the three components, m-toluenediamine polyether and THEIC-based heterocyclic polyether, the high-temperature resistance of the polyether is improved. The problems that traditional combined polyether is easy to decompose at high temperature, easy to retract and poor in stability are solved.

The invention relates to the field of membrane separation, in particular to a method for improving the molecular weight of dimethyl thio toluenediamine-based polyimide through partial crosslinking. According to the preparation method, pyromellitic chloride (BTC) is taken as a cross-linking agent, copolymerized polyamide acid formed by 4, 4 '-(hexafluoroisopropenyl) diphthalic anhydride (6FDA), dimethyl thio toluenediamine (DMTDA) and common diamine (MPD / PPDA) is taken as a cross-linking unit, and polyimide with a partial cross-linking structure is prepared through low-temperature solution polycondensation and chemical imidization processes. The molecular weight and branching degree of the polymer are effectively controlled by regulating the introduction amount (0-4%) of pyromellitic dichloride. The process is simple, reaction conditions are mild, raw materials are easy to obtain, and the obtained partially-crosslinked polyimide film has high molecular weight, good free volume and excellent gas permeation selectivity and is expected to be applied to the field of gas separation films on a large scale.

The invention belongs to the technical field of coatings and coating, and particularly relates to a polymer coating capable of rapidly hardening a protective coating on the surface of a composite rod at normal temperature, the polymer coating is composed of a component A and a component B. The component A comprises the following components in parts by mass: 40-60 parts of polyether polyol, 25-40 parts of diphenylmethane-4, 4 '-diketone, 1-3 parts of a catalyst and 1-3 parts of a catalyst. The invention discloses a water-soluble polyurethane resin, which is prepared from the following raw materials in parts by weight: 20-40 parts of 4, 4 '-diisocyanate, 25-40 parts of hexamethylene diisocyanate, 3-10 parts of dibutyl phthalate, 1-10 parts of a cetylpyridinium bromide surface modified chitosan modified zeolite compound and 2-5 parts of humic acid. The component B is prepared from the following components in parts by mass: 70 to 100 parts of polyether amine and 30 to 40 parts of diethyltoluenediamine. Wherein the mass ratio of the component A to the component B is (1: 1)-(1: 3). The polymer coating prepared by the invention can be quickly hardened at normal temperature, so that the construction time and the curing period are greatly shortened, and the construction efficiency is improved. The salt spray resistance of the coating is promoted through the combined action of the cetyl pyridinium bromide surface modified chitosan modified zeolite compound and humic acid.

The invention is directed to an improved process for producing at least one thioether-substituted, preferably thioalkylated, aromatic diamine X. Thioether-substituted aromatic diamines are aromatic diamines with at least one thioether group bound to the aromatic ring via the sulfur atom. They are of particular interest for use as curing agents. Preferred thioether-substituted aromatic diamines are monomethylthiotoluene diamine ("MMTDA") and dimethylthiotoluene diamine ("DMTDA"). In the process according to the invention, an aromatic diamine A is reacted with at least one organic disulfide B in the presence of at least one Lewis-acid catalyst D and at least one polyol E. A and E are obtained by depolymerization of at least one polyurethane PU. Preferably, the organic phase, comprising A, of the depolymerization raw product RP is employed in the reaction of the aromatic diamine with the organic disulfide B. The yield of mono- versus di-thioether substituted aromatic diamines may advantageously be controlled by drying the employed organic phase.

Disclosed are wash resistant compositions for altering the tone or color of the hair, the compositions comprising a hair coloring agent comprising an oxidation base chosen from toluene-2,5-diamine, acid salts thereof, or solvates thereof, and a coupler system comprising at least one coupler chosen from 1-napthol, 2-amino-4-hydroxyethylaminoanisole sulfate, and derivatives thereof, addition salts thereof, solvates thereof, or solvates of salts thereof; or mixtures thereof, as well as methods of using the compositions.

Provided is a paint composition including an isocyanate component, an amine component, and a refractory agent, the isocyanate component including an aliphatic polyisocyanate, the amine component including at least one polyamine (a) selected from the group consisting of a dimethylthiotoluenediamine, a diaminodiphenylmethane, and an aspartic ester amine.

This invention belongs to the field of polyether polyol preparation technology, specifically relating to an ultra-low thermal conductivity, high-performance flame-retardant polyether polyol for home appliances, its preparation method, and its application. The preparation method is as follows: (1) reacting hexamethylol melamine with methanol to obtain a partially etherified melamine resin containing water and mainly tetraetherified; (2) using the product of step (1) and o-toluenediamine as a mixing initiator, reacting with some epoxy alkane and then dehydrating; (3) heating and adding the remaining epoxy alkane for reaction; (4) adding low thermal conductivity microcapsules and stirring to disperse, the amount added being 2-5% of the total mass of the polyether system. This invention achieves ultra-low thermal conductivity through a dual technical path of "crosslinking structure optimization + microcapsule composite" while taking into account both high efficiency flame retardancy and excellent mechanical properties, meeting the requirements of new energy efficiency and safety standards for home appliances. This invention also provides its preparation method and its application in rigid polyurethane foam components for home appliances.

The invention relates to high-performance regenerated sponge and a preparation method thereof, and relates to the technical field of sponge processing. The high-performance regenerated sponge comprises the following raw materials in parts by mass: 100-120 parts of waste sponge, 25-35 parts of polyether, 20-24 parts of toluenediamine, 11-13 parts of an adhesive and 9-11 parts of a bacteriostatic agent, wherein the bacteriostatic agent comprises silicon dioxide; the method has the effect of improving the antibacterial performance of the regenerated sponge.

The invention discloses a waste gas condensation and recovery device for diethyl toluenediamine production, and particularly relates to the technical field of diethyl toluenediamine production, the waste gas condensation and recovery device comprises a condensation cavity, two gas pipes both extend into the condensation cavity, a cleaning mechanism is arranged in the condensation cavity, and the cleaning mechanism comprises a plurality of rotating cylinders arranged on a rotating shaft; the diameters of the multiple rotary drums are gradually increased in the flowing direction of waste gas, scraping plates and grinding wheels are arranged on the rotary drums, the scraping plates are arranged in front of the grinding wheels in the rotating direction of the rotary drums, and the rotary drums and the grinding wheels abut against the inner wall of the inner drum. According to the invention, by arranging the plurality of rotary drums of which the diameters are gradually changed along the flowing direction of the waste gas, the situation that the waste gas is depressurized and decelerated along with condensation is effectively avoided, and the waste gas can continuously flow in the condensation cavity in a state of impacting the condensation wall at high frequency, so that the condensation effect of the waste gas is effectively guaranteed; the DETDA gas in the waste gas can be fully condensed and recycled.

A first aspect of the invention relates to a purification process for obtaining vicinal toluenediamine. In a second aspect, the invention is directed to vicinal TDA (vTDA) obtained or obtainable from a process of the first aspect of the invention, comprising less than 100 weight-ppm of a toluidine compound of formula (I). A third aspect of the invention is related to vicinal TDA (vTDA) having a purity in the range of at least 99 weight- % and comprising less than 100 weight-ppm of a toluidine compound of formula (I).

The invention is directed to an improved process for producing at least one thioether-substituted, preferably thioalkylated, aromatic diamine X. Thioether-substituted aromatic diamines are aromatic diamines with at least one thioether group bound to the aromatic ring via the sulfur atom. They are of particular interest for use as curing agents. Preferred thioether-substituted aromatic diamines are monomethylthiotoluene diamine ("MMTDA") and dimethylthiotoluene diamine ("DMTDA"). In the process according to the invention, an aromatic diamine A is reacted with at least one organic disulfide B in the presence of at least one Lewis-acid catalyst D and at least one polyol E. A and E are obtained by depolymerization of at least one polyurethane PU. Preferably, the organic phase, comprising A, of the depolymerization raw product RP is employed in the reaction of the aromatic diamine with the organic disulfide B. The yield of mono- versus di-thioether substituted aromatic diamines may advantageously be controlled by drying the employed organic phase.