Abstract: The present invention accordingly provides a process for preparing light-colored polyphenylene-polymethylene polyisocyanates comprising the steps (a) providing an amount of chlorine, (b) separating the chlorine provided in the step (a) to obtain a first chlorine fraction having a content of free and bound bromine and iodine of <50 ppm and a second chlorine fraction having an increased content of free and bound bromine and iodine that depends on the original amount of bromine and iodine in the chlorine provided in step (a) and the separation split, (c) reacting carbon monoxide with at least a portion of the first chlorine fraction to form a first phosgene fraction, (d) reacting carbon monoxide with at least a part of the second chlorine fraction to form a second phosgene fraction, (e) reacting at least a portion of a first phosgene fraction with at least one amine of the diphenylmethane diamine series (MDA) to form the corresponding polyphenylene-polymethylene polyisocyanate (PMDI), and (f) reacting at leas

Abstract: The present invention relates to a process for the production of isocyanates, preferably diisocyanates and polyisocyanates of the diphenylmethane series (MDI), by reacting an amine with phosgene in the liquid phase or in the gas phase to form the corresponding isocyanates, subsequent removal of the solvent in at least two steps to obtain at least two solvent streams, individual treatment of the at least two solvent streams, and recirculation of at least a portion of the solvent streams.

Abstract: The present invention relates to a process for preparing light-colored polyphenylene-polymethylene-polyisocyanate (PMDI), comprising the steps (a) providing carbon monoxide and chlorine, (b) reacting carbon monoxide with chlorine to form phosgene, (c) reacting the phosgene from step (b) with at least one primary amine with the exception of mono- and polyphenylene-polymethylene polyamines with an excess of phosgene to form an at least one isocyanate containing reaction solution, and hydrogen chloride, (d) separating excess phosgene from the isocyanate-containing reaction solution obtained in step (c), (e) providing at least one polyphenylene-polymethylene polyamine, and (f) reacting at least a portion of the phosgene separated in step (d) with the at least one polyphenylene-polymethylene polyamine to form the light-colored polyphenylene-polymethylene polyisocyanate.

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 method of measuring entry of water and resulting corrosion in plants for producing isocyanates by reacting phosgene with one or more primary amines in a solvent. The invention further relates to an apparatus for producing such isocyanates, in the work-up section of which probes for monitoring corrosion are arranged in defined places.

Abstract: The present invention relates to a process for preparing light-coloured polyphenylene-polymethylene-polyisocyanate (PMDI), comprising the steps (a) providing carbon monoxide and chlorine, (b) reacting carbon monoxide with chlorine to form phosgene, (c) reacting the phosgene from step (b) with at least one primary amine with the exception of mono- and polyphenylene-polymethylene polyamines with an excess of phosgene to form an at least one isocyanate containing reaction solution, and hydrogen chloride, (d) separating excess phosgene from the isocyanate-containing reaction solution obtained in step (c), (e) providing at least one polyphenylene-polymethylene polyamine, and (f) reacting at least a portion of the phosgene separated in step (d) with the at least one polyphenylene-polymethylene polyamine to form the light-coloured polyphenylene-polymethylene polyisocyanate.

Abstract: The present invention accordingly provides a process for preparing light-coloured polyphenylene-polymethylene polyisocyanates comprising the steps (a) providing an amount of chlorine, (b) separating the chlorine provided in the step (a) to obtain a first chlorine fraction having a content of free and bound bromine and iodine of <50 ppm and a second chlorine fraction having an increased content of free and bound bromine and iodine that depends on the original amount of bromine and iodine in the chlorine provided in step (a) and the separation split, (c) reacting carbon monoxide with at least a portion of the first chlorine fraction to form a first phosgene fraction, (d) reacting carbon monoxide with at least a part of the second chlorine fraction to form a second phosgene fraction, (e) reacting at least a portion of a first phosgene fraction with at least one amine of the diphenylmethane diamine series (MDA) to form the corresponding polyphenylene-polymethylene polyisocyanate (PMDI), and (f) reacting at lea

Abstract: The invention relates to a method of measuring entry of water and resulting corrosion in plants for producing isocyanates by reacting phosgene with one or more primary amines in a solvent. The invention further relates to an apparatus for producing such isocyanates, in the work-up section of which probes for monitoring corrosion are arranged in defined places.

Abstract: The present invention relates to a process for the production of isocyanates, preferably diisocyanates and polyisocyanates of the diphenylmethane series (MDI), by reacting an amine with phosgene in the liquid phase or in the gas phase to form the corresponding isocyanates, subsequent removal of the solvent in at least two steps to obtain at least two solvent streams, individual treatment of the at least two solvent streams, and re-circulation of at least a portion of the solvent streams.

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 subject invention provides polyurethane foam and a method of purifying polyether polyols of non-volatile impurities for use in forming the polyurethane foam. The method includes the step of providing a crude polyether polyol having a non-volatile impurity present therein. The crude polyether polyol is contacted with an adsorbent selected from at least one of activated carbon, diatomaceous earth, charcoal, attapulgite, and clay to remove the impurity and filtered to form a purified polyether polyol. The filtering of the crude polyether polyol is carried out through a filter media that is used both in a pre-filtering step prior to adding the adsorbent and the filtering step to remove the adsorbent to reduce losses of the purified polyether polyol because of its high viscosity. The purified polyether polyol is then used to form a polyurethane foam having improved stability.

Abstract: The present invention provides a liquid methylene bis(phenylisocyanate) composition including a high concentration of methylene bis(phenylisocyanate) which has an improved storage stability. The invention further provides a method of making the liquid methylene bis(phenylisocyanate) compositions of the present invention.

Abstract: The present invention provides a liquid methylene bis(phenylisocyanate) composition including a high concentration of methylene bis(phenylisocyanate) which has an improved storage stability. The invention further provides a method of making the liquid methylene bis(phenylisocyanate) compositions of the present invention.