Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C263/00—Preparation of derivatives of isocyanic acid
  • C07C263/10—Preparation of derivatives of isocyanic acid by reaction of amines with carbonyl halides, e.g. with phosgene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G18/00—Polymeric products of isocyanates or isothiocyanates
  • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
  • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
  • C08G18/72—Polyisocyanates or polyisothiocyanates
  • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
  • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
  • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
  • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups

Definitions

• the invention relates to light isocyanates, a process for the preparation of light isocyanates and their use in urethane compounds, in particular in polyurethanes, for example in polyurethane foams.
• Isocyanates and isocyanate mixtures are prepared by known processes by phosgenation of the corresponding amines.
• di- or polyfunctional aromatic isocyanates of the diphenylmethane diisocyanate series (MDI) are used for polyurethane foams. Due to the manufacturing process, after the phosgenation and the subsequent work-up (removal of the solvent; removal of monomeric MDI), dark-colored products are often obtained, which in turn produce yellowish-colored polyurethane foams or other, likewise discolored PUR materials. This is undesirable because such coloring affects the overall visual impression and allows slight inhomogeneities to emerge, e.g. B. as streaks in the foam obtained. Bright isocyanates or isocyanates that contain a reduced amount of coloring components are therefore preferred as raw materials.
• EP-A 0 546 398 describes a process for the production of polymer MDI, in which the polymethylene polyphenylene polyamine used as starting material is acidified before phosgenation.
• EP-A 0 446 781 relates to a process for the preparation of polymer MDA (monomeric and oligomeric polymethylene polyphenylene polyamines) which are first treated with hydrogen and then subjected to phosgenation, a lighter MDI being obtained.
• polymer MDA monomeric and oligomeric polymethylene polyphenylene polyamines
• US Pat. No. 5,364,958 relates to a process for the preparation of polyisocyanates in which, after phosgenation, the phosgene is completely at low temperature. dig is removed and then the isocyanate is treated with HCl gas in the heat.
• DE 19817691.0 describes a process for the production of MDI / PMDI mixtures with a reduced content of chlorinated by-products and a reduced iodine color number by adhering to defined parameters in the phosgenation reaction.
• This method has the disadvantage that a variation of the parameters in the phosgenation becomes more difficult and the quality of the phosgenation becomes very susceptible. Due to the lack of flexibility of the parameters in the phosgenation, a practical implementation of the phosgenation is also very difficult and requires a high level of technical effort.
• EP-A 0 581 100 relates to a process for the preparation of polyisocyanates, in which, after phosgenation, a chemical reducing agent is added before the solvent is separated off, bright products also being obtained according to this publication.
• a chemical reducing agent is added before the solvent is separated off, bright products also being obtained according to this publication.
• water is added to the crude product obtained after the phosgenation for lightening the color.
• EP-A 538 500, EP-A 0 445 602 and EP-A 0 467 125 describe the addition of carboxylic acids, alkanols or polyether polyols after the phosgenation.
• EP-A 0 133 538 describes the purification of isocyanates by extraction, whereby fractions of a light MDI are obtained.
• EP-A 0 561 225 relates to a process for the preparation of isocyanates or isocyanate mixtures which, according to this document, have no coloring components, the isocyanates being hydrogenated at a pressure of 1 to 150 bar and a temperature of 100 after the phosgenation of the corresponding amines be subjected to up to 180 ° C. According to the examples described there, isocyanate end products are hydrogenated as such or in the form of their solutions in suitable solvents.
• the object of the present invention is accordingly to provide a new process for the preparation of isocyanates which have no or only small amounts of coloring components.
• Another object of the invention is to provide a process for the preparation of isocyanates which, without the treatment steps mentioned above, leads to pale isocyanates which are suitable for the production of polyurethanes or their precursors which have little or no coloration.
• the object of the invention was surprisingly achieved by using phosgene which has less than 50 ppm of bromine or bromine-containing compounds or iodine or iodine-containing compounds in the preparation of the isocyanates.
• the present invention accordingly relates to a process for the preparation of isocyanates by reacting an amine or a mixture of two or more amines with phosgene, characterized in that the phosgene used contains less than 50 ppm of bromine or iodine or their mixture in molecular or contains bound form.
• bromine or iodine in molecular form is understood to mean those molecules which only consist of bromine or iodine atoms.
• Bromine or iodine in bound form means molecules which in addition to bromine or iodine each contain other atoms different from the atoms mentioned.
• the phosgene used in the context of the present invention thus contains less than 50 ppm of bromine or bromine compounds or iodine or iodine compounds; or bromine and iodine; or bromine and iodine and bromine compounds; or iodine compounds and bromine and iodine; or bromine compounds and iodine compounds; or bromine and iodine and bromine compounds and iodine compounds.
• the process according to the invention leads to isocyanates which, if desired, can already be used for the production of urethane compounds, such as polyurethanes or their precursors, which have no or only slight coloration, without the additional treatments indicated above.
• the result according to the invention was particularly surprising insofar as it was not previously known that extremely small traces of molecular or bound bromine or iodine or the above-mentioned mixtures in the phosgene used to prepare isocyanates are sufficient to influence the product color in an undesirable manner.
• the phosgene used for the production of isocyanates generally has a certain content of molecular or bound bromine or iodine or the above-mentioned mixtures.
• the content of bromine or iodine or such mixtures in the phosgene results from the chlorine used for the phosgene production, which usually has a certain proportion of bromine or iodine or a mixture thereof.
• the chlorine content of bromine or iodine or their mixture in turn generally results from the corresponding content of the salt used for the production of chlorine.
• the phosgene to be used in the context of the present invention with a low bromine or iodine content or the abovementioned mixtures can be prepared in various ways known to the person skilled in the art.
• One possibility of guaranteeing a low content of bromine or iodine or the above-mentioned mixtures in the phosgene is, for example, the use of starting compounds in phosgene production which already have a correspondingly low content of bromine or iodine or a mixture thereof.
• the use of chlorine with a correspondingly low bromine or iodine content or a mixture thereof is appropriate.
• any chlorine can be used in the context of the present invention which fulfills the above specification, ie has less than about 50 ppm bromine or iodine or the mixtures mentioned above, for example 25 ppm or less.
• chlorine can be used which was produced by the electrolysis process or oxidation of HCl, for example by the Deacon process.
• No. 3,660,261 describes the production of chlorine with a particularly low bromine content by oxidative treatment of the salt used for the electrolysis.
• bromine or iodine or their mixture of chlorine by distillation, selective condensation of the bromine or iodine in the chlorine stream or by reactions with substances selectively react with bromine or iodine or a mixture thereof, as described, for example, in JP 0075319.
• appropriately suitable starting materials for chlorine synthesis can also be used which themselves contain essentially no bromine or iodine or a mixture thereof, e.g. B. essentially bromine and iodine free salt or bromine and iodine free HCl.
• Suitable processes are described, for example, in DE-OS 18 00 844, DE-AS 12 55 643 or in DE-AI 197 26 530.
• the degree of depletion of bromine or iodine or their mixture achieved depends in the manner customary for absorption and distillation processes on system pressure, the amounts of electricity, the concentrations and the internals used; the design of the column based on the desired degree of bromine depletion is therefore a purely routine task.
• Another way to obtain phosgene with a low content of molecular or bound bromine or iodine or their mixture is the separation of molecular and bound bromine and iodine from the phosgene itself.
• all common separation processes can be used here, for example distillation, adsorption and the like.
• it is ultimately only the observance of the abovementioned upper limit for the concentration of molecular or bound bromine or iodine or the abovementioned mixtures that is decisive.
• phosgene which has a bromine or iodine content or the abovementioned mixtures of less than 40 ppm, 35 ppm, 30 ppm or 25 ppm or less, in particular of 10 ppm or less.
• the isocyanate preparation taking place in the context of the process according to the invention is carried out in a manner known to the person skilled in the art by reacting an amine or a mixture of two or more amines with phosgene in a stoichiometric amount.
• all processes can be used in which a primary amine or a mixture of two or more primary amines is reacted with phosgene to form one or more isocyanate groups.
• the process according to the invention i.e. the reaction of the amine or the mixture of two or more amines with the phosgene, is carried out in a solvent or a mixture of two or more solvents.
• solvents suitable for the production of isocyanates can be used as solvents. These are preferably inert aromatic, aliphatic or alicyclic hydrocarbons or their halogenated derivatives.
• solvents are aromatic compounds such as mono- or dichlorobenzene, for example o-dichlorobenzene, toluene, xylenes, naphthalene derivatives such as tetralin or decalin, alkanes with about 5 to about 12 carbon atoms such as hexane, heptane, octane, nonane or decane, Cycloalkanes such as cyclohexane, inert esters and inert ethers such as ethyl or butyl acetate, tetrahydrofuran, dioxane or diphenyl ether.
• all primary amines which can react in a suitable manner with phosgene to form isocyanates are suitable as amines.
• all linear or branched, saturated or unsaturated aliphatic or cycloaliphatic or aromatic primary mono- or polyamines are suitable, provided that these can be reacted with phosgene to give isocyanates.
• Suitable amines are 1,3-propylene diamine, 1,4-butylene diamine, 1,5-pentamethylene diamine, 1,6-hexamethylene diamine and the corresponding higher homologues of this series, isophorone diamine (IPDA), cyclohexyl diamine, cyclohexylamine, aniline, phenylene diamine , p-toluidine, 1,5-naphthylenediamine, 2,4- or 2,6-toluenediamine or a mixture thereof, 4,4'-, 2,4'- or 2,2'-diphenylmethane diamine or a mixture thereof and higher molecular weight isomers, oligomeric or polymeric derivatives of the above amines and polyamines.
• IPDA isophorone diamine
• cyclohexyl diamine cyclohexylamine
• aniline phenylene diamine
• p-toluidine 1,5-naphthylenediamine
• the abovementioned compounds are present in the form of the corresponding isocyanates, for example as 1,6-hexamethylene diisocyanate, isophorone diisocyanate, cyclohexyl isocyanate, cyclohexyl diisocyanate, phenyl isocyanate, phenylene diisocyanate, 4-toluyl isocyanate, 1,5-naphthylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate or their corresponding mixtures, 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures of two or more thereof, as well as higher molecular weight oligomeric or poly- mere derivatives of the above-mentioned isocyanates or as mixtures of two or more of the above-mentioned isocyanates or isocyanate mixtures.
• isocyanates for example as 1,6-hexamethylene diisocyanate,
• the isomers, primary diphenylmethane diamines (MDA) or their oligomeric or polymeric derivatives are used as amines, i.e. the amines of the diphenylmethane diamine series.
• Diphenylmethane diamine, its oligomers or polymers are obtained, for example, by the condensation of aniline with formaldehyde.
• Such oligo- or polyamines or mixtures thereof are also used in the context of a preferred embodiment of the invention.
• bromine- and iodine-poor or even bromine and iodine-free phosgene to be used in the context of the present invention and within the scope of the abovementioned restrictions with one of the amines mentioned above or a mixture of two or more such amines can be carried out continuously or batchwise in one or more Levels. If a one-stage reaction is carried out, this reaction is preferably carried out at about 60 to 200 ° C., for example at about 130 to 180 ° C.
• the implementation can also be carried out in two stages, for example.
• a first step the reaction of the phosgene with the amine or the mixture of two or more amines is carried out at a temperature between about 0 and about 130 ° C. for example, about 20 to about 110 ° C or about 40 to about 70 ° C, wherein a period of about 1 min to about 2 hours is allowed for the reaction between amine and phosgene.
• the temperature is then raised to about 60 to about 190 ° C., in particular about 70 to 170 ° C., for example over a period of about 1 minute to about 5 hours, for example within about 1 minute to about 3 hours. elevated.
• the reaction is carried out in two stages.
• increased pressure can be applied during the reaction, for example up to about 100 bar or less, for example about 1 bar to about 50 bar or about 2 bar to about 25 bar or about 3 bar to about 12 bar.
• the implementation can also take place without pressure.
• the work is therefore carried out at ambient pressure, generally about 1 bar. In a further preferred embodiment, it is also possible to work at a pressure which is reduced in relation to the ambient pressure.
• Excess phosgene is preferably removed after the reaction at a temperature of about 50 to 180 ° C.
• the remaining traces of the solvent are preferably removed under reduced pressure, for example the pressure should be about 500 mbar or less, preferably less than 100 mbar.
• the various components are separated in the series of boiling points, and mixtures of the various components can also be separated in a single process step.
• Another object of the invention are bright isocyanates, as can be produced by the process according to the invention.
• the invention further relates to the use of isocyanates which can be prepared by the process according to the invention or prepared by such a process for the production of urethane compounds, in particular polyurethanes.
• the isocyanates according to the invention are used in the production of polyurethane foams, such as are commercially available, for example, as rigid foams, semi-rigid, integral and flexible foams.
• the bromine content in the phosgene was calculated from the bromine content of the chlorine used for the phosgene synthesis.
• the bromine content in the chlorine was determined by means of X-ray fluorescence analysis.
• the isocyanate characteristics of the products produced as examples 1 to 3 were determined.
• the iodine color number usually specified for MDI was specifically determined.
• the samples (1: 5 diluted in monochlorobenzene) were measured with a photometer (company Dr. Lange, Berlin) in the IFZ program mode.
• NCO content (determined according to ASTM D 5155) iodine color number
• the results show a good color brightening of raw MDI when using low-bromine chlorine.

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• 1999
  • 1999-06-23 DE DE19928741A patent/DE19928741A1/de not_active Withdrawn
• 2000
  • 2000-06-16 PT PT00943828T patent/PT1187808E/pt unknown
  • 2000-06-16 AT AT00943828T patent/ATE247635T1/de not_active IP Right Cessation
  • 2000-06-16 KR KR1020017016494A patent/KR100686302B1/ko not_active Expired - Lifetime
  • 2000-06-16 DE DE50003380T patent/DE50003380D1/de not_active Expired - Lifetime
  • 2000-06-16 HU HU0201848A patent/HU222987B1/hu not_active IP Right Cessation
  • 2000-06-16 JP JP2001506982A patent/JP4722352B2/ja not_active Expired - Fee Related
  • 2000-06-16 EP EP00943828A patent/EP1187808B1/de not_active Expired - Lifetime
  • 2000-06-16 US US10/018,636 patent/US6900348B1/en not_active Expired - Lifetime
  • 2000-06-16 WO PCT/EP2000/005610 patent/WO2001000569A1/de not_active Ceased
  • 2000-06-16 ES ES00943828T patent/ES2206268T3/es not_active Expired - Lifetime
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