Abstract: The present invention relates to a process for preparing di- and polyamines of the diphenylmethane series (MDA), a system for producing MDA and a process for operating a system for preparing MDA. The invention enables optimization of production standstills during operation of the MDA process with respect to time expenditure and optionally also with respect to energy and material consumption by means of a so-called recirculation mode for individual system components. During interruption of the process or interruption of the operation of individual system components, formaldehyde is not introduced into the reaction and the system components that are not affected by a revision, repair, or cleaning measure are operated in so-called recirculation mode.

Abstract: The present invention provides a process for preparing di- and polyamines from the diphenylmethane series by converting aniline and formaldehyde in the absence of an acid catalyst to give aminal and water, removing the aqueous phase and further processing the organic aminal phase to give the di- and polyamines of the diphenylmethane series, in which use of a coalescence aid in the phase separation of the process product obtained in aminal reaction reduces the proportion of water and hence also of water-soluble impurities in the organic phase containing the aminal. The di- and polyamines of the diphenylmethane series obtained by acid-catalyzed rearrangement and workup after further processing of the aminal phase are outstanding suitably for preparation of the corresponding isocyanates.

Abstract: The invention relates to a resin curing agent having the formula (I), wherein R1 to R4 are each individually selected from linear or branched C1 to C5 alkyl, a process for its manufacture, blends of the reaction products, and two-component curable resin systems.

Abstract: The invention relates to a process for preparing methylenediphenyldiamine (MDA), comprising the following steps a) to c): a) converting formaldehyde and aniline to aminal b) removing water from the aminal obtained in step a) to establish a water content of 0 to 5% by weight based on the aminal, and c) adding an acidic catalyst to the aminal having a water content of 0 to 5% by weight, which comprises using formaldehyde in step a) in the form of highly concentrated formaldehyde with a CH2O content of >50% by weight and preparing the formaldehyde by oxidative dehydrogenation from methanol.

Abstract: The invention relates to a process for preparing methylenediphenyldiamine (MDA) by reacting formaldehyde and aniline in the presence of an acidic catalyst, wherein the oxygen content in the process for preparing MDA is <10 000 ppm, based on all compounds present in the process. The invention further relates to the phosgenation of MDA to methylenediphenyl diisocyanate (MDI).

Abstract: Processes and apparatus for purifying brine are provided including (1) providing an aqueous brine solution comprising one or more inorganic salts and one or more organic compounds and (2) conducting at least one unit operation for removing organic compounds from the brine solution to obtain a purified brine solution.

Abstract: The invention relates to a process for recovering acids from product streams of organic syntheses, which comprises the steps a) neutralization of the acid with a base, b) removal of the base by means of adsorption, c) recovery of the acid.

Abstract: The invention relates to a process for preparing mixtures of diphenylmethanediamine and polyphenylenepolymethylenepolyamines, which comprises the steps a) reaction of aniline with formaldehyde in the presence of hydrochloric acid, b) neutralization of the reaction mixture formed in step a) c) separation of the organic phase from the aqueous phase, d) work-up of the organic phase, e) work-up of the aqueous phase, wherein step e) comprises at least the steps e1) extraction of the aqueous phase with an organic solvent, e2) stripping of the aqueous phase obtained in step e1), e3) absorption of the solution obtained from step e2).

Abstract: The invention provides a process for preparing diphenylmethanediamine, comprising the steps of: a) reacting aniline with formaldehyde in the presence of an acid, b) neutralizing the predominant part of the acid with ammonia and/or aqueous ammonia solution, c) separating the reaction mixture from step b) into an aqueous phase and an organic phase, d) neutralizing the other part of the acid, present in the organic phase, with aqueous alkali metal hydroxide solution, e) separating the reaction mixture from step d) into an aqueous phase and an organic phase, f) treating the aqueous phase obtained in step c) or optionally the combined aqueous phases from steps c) and e) with at least one oxide or hydroxide of an alkaline earth metal, g) removing the ammonia obtained in step f).

Abstract: The invention relates to a process for preparing methylenediphenyldiamine (MDA) by reacting formaldehyde and aniline in the presence of an acidic catalyst, wherein the oxygen content in the process for preparing MDA is <10 000 ppm, based on all compounds present in the process. The invention further relates to the phosgenation of MDA to methylenediphenyl diisocyanate (MDI).

Abstract: The invention relates to a process for preparing methylenediphenyldiamine (MDA), comprising the following steps a) to c): a) converting formaldehyde and aniline to aminal b) removing water from the aminal obtained in step a) to establish a water content of 0 to 5% by weight based on the aminal, and c) adding an acidic catalyst to the aminal having a water content of 0 to 5% by weight, which comprises using formaldehyde in step a) in the form of highly concentrated formaldehyde with a CH2O content of >50% by weight and preparing the formaldehyde by oxidative dehydrogenation from methanol.

Abstract: The invention relates to a process for preparing mixtures of diphenylmethanediamine and polyphenylenepolymethylenepolyamines, which comprises the steps a) reaction of aniline with formaldehyde in the presence of hydrochloric acid, b) neutralization of the reaction mixture formed in step a) c) separation of the organic phase from the aqueous phase, d) work-up of the organic phase, e) work-up of the aqueous phase, wherein step e) comprises at least the steps e1) extraction of the aqueous phase with an organic solvent, e2) stripping of the aqueous phase obtained in step e1), e3) absorption of the solution obtained from step e2).

Abstract: The present invention provides a method of preparing polymethylene-polyphenyl-polyamine (briefly referred to as polyamine, DAM), in which a high gravity rotating bed is used as the mixing reactor of formaldehyde and aniline hydrochloride, the mixing solution of aniline hydrochloride and circulation solution and the formaldehyde are fed into the high gravity rotating bed reactor proportionally to carry out mixing and condensation reaction under a condition of a very high gravity; the materials leaving the high gravity rotating bed reactor is introduced into a stirred vessel to proceed with the pre-condensation reaction and obtain a condensation solution; and the process steps of heating, molecular rearrangement, neutralization, water washing and purification, etc. are completed to obtain the refined DAM.

Abstract: The invention provides a process for preparing diphenylmethanediamine, comprising the steps of a) reacting aniline with formaldehyde in the presence of an acid, b) neutralizing the acid with ammonia, c) separating the reaction mixture from step b) into an aqueous phase and an organic phase, d) treating the aqueous phase obtained in step c) with an oxide or hydroxide of an alkaline earth metal, e) separating off the ammonia obtained in step d).

Abstract: The invention provides an improved process for preparing diamines and polyamines from the diphenylmethane series by reacting aniline and formaldehyde in the presence of an acid catalyst, the improvement involving the aniline containing less than about 3 wt. % of diamines and polyamines from the diphenylmethane series, based on the weight of the aniline.

Abstract: Process for preparing diamino diphenyl methane and poly-(diamino diphenyl methane) comprising reacting aniline with formaldehyde in the presence of hydrogen chloride added in the gaseous form wherein the aniline contains 0.1 to 7 wt %, preferably 2 to 5 wt % of a protic chemical, preferably water.

Abstract: Di- and polyamines of the diphenylmethane series are produced by a) converting nitrobenzene and methanol in the presence of a catalyst to aniline, formaldehyde and carbon monoxide, and then b) converting the aniline and formaldehyde produced in step a) in the presence of an acid catalyst to di- and polyamines of the diphenylmethane series, and c) converting the carbon monoxide produced in step a) with chlorine to phosgene.

Abstract: A process is described for preparing diaminodiarylmethanes comprising the steps a) reacting an aromatic amine with a methylene-donating agent in the presence of homogeneous acid catalysts, b) removing the homogeneous acid catalyst from the reaction product, c) working up and purifying the reaction product, which comprises removing the homogeneous acid catalyst from the reaction mixture by adsorption to a solid adsorbent.

Abstract: Di- and polyamines of the diphenylmethane series are prepared by a) mixing a first portion of aniline with an acid catalyst, b) mixing a second portion of aniline with formaldehyde, and c) mixing and reacting the mixtures prepared in each of steps a) and b). The diamines produced by this process may then be phosgenated to produce the corresponding di-/polyisocyanate.

Abstract: The invention relates to a method of producing polyisocyanates of the diphenylmethane series including the steps of a) reacting aniline and formaldehyde in the presence of HCl to provide a product mixture containing polyamines of the diphenylmethane series, HCl, aniline and water; b) removing excess aniline and water by distillation to provide a product mixture comprising polyamines of the diphenylmethane series, HCl, no more than 10 wt. % aniline based on the polyamines, and no more than 5 wt. % water based on the polyamines; and c) phosgenating the product mixture in (b).

Abstract: Described is a triarylmethane dye of the formula I where R1 and R2 are independently methyl, ethyl or hydroxyethyl, Q is substituted or unsubstituited phenyl or naphthyl and A? is the equivalent of an anion. It does not detach carcinogenic Michler's ketone.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: Polyisocyanates of the diphenylmethane series are produced by a) reacting aniline and formaldehyde in the presence of an acidic catalyst to produce a polyamine, b) neutralizing the reaction mixture from step a) with a base at a temperature of more than 110° C. or neutralizing the reaction mixture from step a) with a base and heating the neutralized mixture to a temperature of more than 110° C., and c) phosgenating the polyamine from step b) to convert it to the corresponding polyisocyanate.

Abstract: Disclosed herein is a process for preparing a reaction product containing methylene diphenylamine, comprising reacting aniline and formaldehyde in the presence of an acid catalyst wherein the acid level of the resulting reaction mixture is reduced during digestion of the reaction mixture.

Abstract: Polyisocyanates of the diphenyl methane series having reduced color values are obtained by a) reacting aniline and formaldehyde in the presence of an acid catalyst to form a polyamine, b) neutralizing the reaction mixture containing polyamine with a base, c) separating the neutralized mixture into the aqueous and the organic phases, d) adding a base to the organic phase and then e) phosgenating the resulting polyamine to produce the corresponding polyisocyanate.

Abstract: A method of reacting a solution comprising a mixture of chemical compounds which are in chemical equilibrium with one another with at least one further chemical compound (9) is provided. The method comprises the following steps: fractionation of the solution by means of a separation method to give at least two fractions (5, 6) which are enriched in different chemical compounds of the mixture; and reaction of a fraction (5) with the further chemical compound or compounds (9). The fractionation is advantageously carried out using a film evaporator (1). Unreacted fractions (6) can be recirculated via a residence time vessel (3) back to the fractionation step. The method is particularly suitable for reactions of an aqueous formaldehyde solution in which various components of the solution (formaldehyde, methylene glycol, polyoxymethylene glycols) react in different ways.

Abstract: A process for preparing methylenedianiline by reacting aniline with formaldehyde in the presence of acid catalysts comprising, in a semicontinuous process, introducing aniline with or without acid catalyst, feeding formaldehyde with or without acid catalyst through a mixing element into a circuit in which aniline with or without acid catalyst and with or without previously added formaldehyde is circulated and, after feeding in at least 50% of the total amount of formaldehyde to be fed in, heating the reaction mixture to a temperature above 75° C. In addition, the invention relates to a process for preparing polyisocyanates by phosgenation of amines obtainable in this manner and to the polyisocyanates obtainable by this process.

Abstract: In a process for preparing aromatic polyamine mixtures which contain compounds of the formula (I), H2N—A—CH2—B—NH2  (I) where A and B are 1,4-phenylene radicals each of which independently of one another can have 1 to 4 substituents selected from C1-20 alkyls and halogens, a compound of the formula (IV) H—A—NH—CH2—HN—B—H  (IV) and/or a compound of the formula (V) H—A—NH—CH2—B—NH2  (V) where A and B are substituted as above, are reacted at from 20° C. to 200° C.

Abstract: Disclosed herein is a process for preparing a reaction product containing methylene diphenylamine, comprising reacting aniline and formaldehyde in the presence of an acid catalyst wherein the acid level of the resulting reaction mixture is reduced during digestion of the reaction mixture.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and to the use thereof.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and the use thereof.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and their use.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and to their use.

Abstract: The invention relates to a process for the fractionation and purification of mixtures of aromatic polyamines and to the use thereof.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and the use thereof.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and to the use thereof.

Abstract: The invention relates to a process for the fractionation and purification of aromatic polyamine mixtures and the use thereof.

Abstract: The present invention encompasses an improved process for preparing polymethylene polyphenyl polyisocyanate comprising reacting phosgene with polymethylene polyphenyl polyamine, the improvement wherein the polymethylene polyphenyl polyamine is acidified prior to phosgenation.

Abstract: A method for producing polymethine dyes comprising the steps of:(a) reacting a 1,1-diaryl-2-metallo-ethene with an .omega., .omega.,-diaryl-polyalkene-aldehyde in an anhydrous solvent under an inert atmosphere; and(b) neutralizing the reaction mixture from step (a) with an acid, thereby producing a polymethine dye.

Abstract: The invention relates to an improved process for the production of polynuclear aromatic polyamines by condensation of aniline with formaldehyde in the presence of water and acidic catalysts and working up of the reaction mixture by extraction with a hydrophobic solvent, the acid catalyst accumulating in the aqueous phase of the extraction step being reused.

Abstract: A process for production of polyamines of the diphenylmethane series through a condensation reaction of aniline with formaldehyde in the presence of an acid catalyst, neutralization of the acid catalyst after reaction completion, and distillation of the resultant polyamine mixture is described. The key feature of the process is the abrupt increase in reaction temperature after the condensation reaction or after the first rearrangement step.

Abstract: Disclosed herein is a process for preparing a reaction product containing methylene diphenylamine comprising reacting aniline with an aldehyde, in the presence of a low level of an acid wherein the acid level is reduced before digesting reaction mixture at a high temperature which is sufficient to effect a rearrangement of the intermediates to produce a reaction product containing methylene diphenylamines and low levels of impurities.

Abstract: The present invention relates to blocked polyisocyanates based on the reaction product ofi) an organic polyisocyanate comprising a member selected from the group consisting of bis-(4-isocyanatocyclohexyl)-methane, NCO prepolymers prepared from bis-(4-isocyanatocyclohexyl)-methane, polyisocyanate adducts prepared from bis-(4-isocyanatocyclohexyl)-methane, isocyanurate group-containing polyisocyanates prepared from 1,6-hexamethylene diisocyanate and isocyanurate and allophanate group-containing polyisocyanates prepared from 1,6-hexamethylene diisocyanate withii) methylamyl ketoxime.

Abstract: The invention relates to an improved process for the production of polynuclear aromatic polyamines by condensation of aniline with formaldehyde in the presence of water and acidic catalysts and working up of the reaction mixture by extraction with a hydrophobic solvent, the acid catalyst accumulating in the aqueous phase of the extraction step being reused.

Abstract: Novel anilines of the 2,6-dialkyl-4-dialkylaminomethylaniline type are prepared by reacting a secondary amine and an aldehyde with a primary aniline reactant having a free para position and substituents in both ortho positions in the presence of an acid catalyst, the amounts of amine and acid employed being at least equimolar with respect to the amount of aldehyde, and the reaction being conducted by adding the primary aniline reactant to a preformed mixture of the secondary amine, aldehyde, and acid.

Abstract: A methylene-crosslinked polyarylamine is disclosed which contains a less amount of N-methylmethylenedianiline. A process for continuously preparing this kind of methylene-crosslinked polyarylamine is also revealed which comprises reacting aniline with formalin in the presence of hydrochloric acid under specific reaction conditions.

Abstract: 2,2'-Dichloro-6,6'-diethylmethylene-bis-aniline or mixtures thereof with compounds of the formula: ##STR1## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are straight-chained or branched alkyl radicals having 2 to 4 C atoms, or R.sub.1 and/or R.sub.3 are chlorine and the remaining R's have the above-mentioned significance, as chain-extension means or cross-linkage means for polyurethanes or epoxide resins. Process for the production of 2,2'-dichloro-6,6'-diethylmethylene-bis-aniline or such mixtures. 2-ethyl-6-chloroaniline is condensed with itself or an aniline having the formula: ##STR2## wherein R.sub.5 and R.sub.6 are the same or different and are straight-chained or branched having 2 to 4 C atoms, with the proviso that R.sub.5 can also be chlorine, in acidic medium with formaldehyde or compounds which form formaldehyde. The compounds in the mixture can be condensation products of two molecules of such aniline derivatives.

Abstract: New methylenebis(metachloro)anilines which are chain-lenghtening agents or cross-linking agents for polyurethanes.

Abstract: This invention relates to an improved process for the preparation of polynuclear aromatic polyamines in which the reaction product is prepared by condensing aniline with formaldehyde in the presence of water and acidic catalysts and is worked up by extraction with a hydrophobic solvent. The acid catalyst that accumulates in the aqueous phase during the extraction process is reused.

Abstract: An arylamine such as aniline is condensed with formaldehyde in the presence of aqueous hydrochloric acid to form a mass containing the hydrogen chloride salt of a polyarylpolyamine. The mass is contacted with additional aniline thereby forming an organic phase and an aqueous phase, the 4,4'-polyarylpolyamine overwhelmingly being liberated from its salt form in the aqueous phase and being transferred to the organic phase. High recoveries of the 4,4'-diamino polycondensate are achieved.