Process for producing aromatic polymeric carbodiimides

Abstract

The present invention relates to a process for producing aromatic polymeric carbodiimides, to the aromatic polymeric carbodiimides obtainable thereby, and to their use as hydrolysis inhibitors.

Description

[Technical Field]

[0001] The present invention relates to processes for producing aromatic polymeric carbodiimides, aromatic polymeric carbodiimides produced by those processes, and their use as hydrolysis inhibitors in polyurethane (PU)-containing compositions, preferably thermoplastic TPUs, PU adhesives, PU casting resins, PU elastomers or PU foams. [Background technology]

[0002] Carbodiimides have been found to be useful as hydrolysis inhibitors for many applications, such as thermoplastics, ester-based polyols, polyurethanes, triglycerides, and lubricating oils.

[0003] Prior art carbodiimide synthesis methods start with isocyanates, which are carbodiimidized under the action of basic or heterocyclic catalysts with CO elimination. This allows the conversion of mono- or polyfunctional isocyanates into monomeric or polymeric carbodiimides. In the context of the present invention, the term "polymer" should be interpreted broadly, i.e., very short polymers, such as oligomers, are also included within this definition.

[0004] Typically used catalysts are compounds of alkali metals or alkaline earth metals, such as alkali metal alkoxides, and phosphorus-containing heterocyclic compounds, as described, for example, in (Non-Patent Document 1) and (Non-Patent Document 2).

[0005] In the prior art, the preparation of sterically hindered polymeric carbodiimides proceeds very well using phosphorus-containing catalysts, such as phospholenes. However, as described in U.S. Pat. No. 5,623,999, these phosphorus-containing catalysts cannot be completely removed without using costly and complicated processes involving several distillation steps. Because carbodiimides are favored in the production of polyurethanes, the presence of trace amounts of phosphorus catalysts causes significant problems and must be avoided.

[0006] Processes from the prior art, such as those described in US Pat. No. 5,629,399, use phosphorus-free catalysts. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] European Patent No. 2897996B1 [Patent Document 2] European Patent No. 3307709B1 [Non-patent literature]

[0008] [Non-Patent Document 1] Angew.Chem.,1962,74,801~806 [Non-patent document 2] Angew.Chem.,1981,93,855~866 Summary of the Invention [Problem to be solved by the invention]

[0009] However, both the above-mentioned multi-stage distillation and the use of phosphorus-free catalysts have the drawback of producing dark or discolored carbodiimides. In many polyurethane applications, for example, in clear, colorless, or light-colored components, color plays a central role. [Means for solving the problem]

[0010] In the context of the present invention, the term "aromatic carbodiimide" is understood to mean a carbodiimide in which the carbodiimide functional group is directly bonded to an aromatic group. The term "polymeric carbodiimide" generally means a carbodiimide having at least two repeating units, and furthermore, the term is understood to include oligomeric carbodiimides.

[0011] It is therefore an object of the present invention to provide a polymeric aromatic carbodiimide that can be produced inexpensively, is substantially free of organophosphorus compounds, and has a CIE L chromatographically consistent color according to ISO 11664-4. * a * b * The object of the present invention is to provide an improved process which gives polymeric aromatic carbodiimides which have a low color number, measured as a b value by the 2000 JIS method, of less than 50, preferably less than 35, particularly preferably less than 25, and most preferably less than 15 (so that they can be used in the production and / or stabilization of PU systems with high colorfastness).

[0012] Surprisingly, it has now been found that the aforementioned object is achieved by reacting (carbodiimidizing) aromatic diisocyanates in the presence of at least one phosphorus-containing catalyst at very low concentrations at temperatures between 120° C. and 220° C., preferably between 160° C. and 200° C., and very particularly preferably between 180° C. and 200° C. Accordingly, the present invention provides a process for producing polymeric aromatic carbodiimides of formula (I) by carbodiimidizing aromatic diisocyanates in the presence of at least one phosphorus-containing catalyst at temperatures between 120° C. and 220° C., preferably between 160° C. and 200° C., at a concentration of 15 to 40 ppm by weight, preferably between 20 and 30 ppm by weight, based on the aromatic diisocyanate: R 4 -R 8 -(-N=C=NR 8 -) m -R 4 (I) [In the formula, m represents an integer of 2 to 500, preferably 3 to 20, and very particularly preferably 4 to 10; R 8 is C1~C 12 -Alkyl-substituted arylene, C7-C 18 -alkylaryl-substituted arylene, or C1-C 12 represents an alkyl-substituted, alkylene-bridged arylene, wherein each depicted arylene is substituted with at least two of the aforementioned alkyl and / or alkylaryl groups, with the proviso that R 8 contains a total of 9 to 30 carbon atoms, and R 4 -NCO, -NCNR 5 , -NHCONHR 5 , -NHCONR 5 R 6 , or -NHCOOR 7 (where R 5 and R 6 are the same or different, C1 to C 12 -Alkyl, C6-C 12 -Cycloalkyl, C7-C 18 - represents an aralkyl or aryl group, and R 7 is C1~C 22 -Alkyl, C6-C 12 -Cycloalkyl, C6-C 18 -aryl or C7-C 18 -Aralkyl group, unsaturated C2-C 22 -represents an alkyl group or an alkoxypolyoxyalkylene group)]

[0013] base R 8 In the group R, the alkyl substituents typically have a total of 3 to 24 carbon atoms. 8 wherein the alkyl substituents preferably have a total of 4 to 24 carbon atoms, with the proviso that R 8 has a total of 10 to 30 carbon atoms. 8wherein the alkyl substituents most preferably have a total of 6 to 18 carbon atoms, with the proviso that R 8 has a total of 12 to 30 carbon atoms. DETAILED DESCRIPTION OF THE INVENTION

[0014] In a preferred embodiment of the present invention, R 8 C1-C substituted with at least two of the above alkyl groups 12 -alkyl-substituted arylene, provided that R 8 has a total of 10 to 24 carbon atoms.

[0015] In a further preferred embodiment of the present invention, R 8 represents diisopropylphenylene and / or triisopropylphenylene. A particularly preferred embodiment of the present invention is a compound of formula (II): [ka] [In the formula, R 4 is defined above, and n=1 to 20, preferably n=1 to 15.

[0016] The aromatic diisocyanates that can be used in the carbodiimide conversion are R 8 corresponds to formula (III) as defined above: OCN-R 8 -NCO (III)

[0017] In the context of the present invention, the phosphorus-containing catalyst is a phospholene or a phospholidine. The phospholene employed is preferably a phospholene oxide, particularly preferably an alkylphospholene oxide, such as methylphospholene oxide, and the phospholidine employed is preferably a phospholidine oxide.

[0018] For example, 1,3-dimethyl-2-phenyl-1,3,2-diazaphospholidine 2-oxide (CAS No. 6226-05-7) may be employed as the phospholidine.

[0019] The carbodiimidization catalyst employed is preferably selected from one or more phospholene oxides, more preferably from one or more methylphospholene oxides.

[0020] The carbodiimidization catalyst used is represented by the general formula (1): [ka] (In the formula, R 1 and R 2 are each independently H or an aliphatic C1-C 15 -Hydrocarbon group, alicyclic C5-C 15 -Hydrocarbon group, aryl-C6-C 15 -Hydrocarbon group, aralkyl-C6-C 15 -Hydrocarbon group or alkaryl-C6-C 15 -representing a hydrocarbon group) or a double bond isomer thereof is particularly preferred.

[0021] R 1 is preferably H or an aliphatic C1-C 10 -hydrocarbon group or aryl-C6-C 15 a hydrocarbon group, particularly preferably a methyl, ethyl or propyl group, or a phenyl or benzyl group, and most preferably a methyl or phenyl group.

[0022] R 2 is preferably H or an aliphatic C1-C 10 - a hydrocarbon group, particularly preferably H or a methyl, ethyl or propyl group, most preferably H or a methyl group.

[0023] Particularly preferred phospholene oxides are the following: 3-methyl-1-phenyl-2-phospholene 1-oxide, 1-phenyl-2-phospholene 1-oxide, 1-methyl-2-phospholene 1-oxide, 1,3-dimethyl-2-phospholene 1-oxide, 1-ethyl-3-methyl-2-phospholene 1-oxide, and their double bond isomers 3-methyl-1-phenyl-3-phospholene 1-oxide, 1-phenyl-3-phospholene 1-oxide, 1-methyl-3-phospholene 1-oxide, 1,3-dimethyl-3-phospholene 1-oxide, 1-ethyl-3-methyl-3-phospholene 1-oxide.

[0024] The most preferably employed carbodiimidization catalyst is 1-methyl-2-phospholene 1-oxide (MPO) and / or its double bond isomer, 1-methyl-3-phospholene 1-oxide.

[0025] In further embodiments, additional inorganic or organic compounds, such as co-activators, synergists and / or solvents, may be added to the phosphorus-containing catalyst.

[0026] In a further embodiment, the phosphorus-containing catalyst may be admixed with additional phosphorus-containing compounds that have little, if any, effect on carbodiimidization and do not exhibit any additional adverse effects on the application of the PU, possible examples of which include phosphates, polyphosphates, and monomeric or polymeric phosphoric acid esters.

[0027] In further embodiments, additional phase transfer catalysts or compounds may be employed, with ionic liquids or ethers being preferred for this purpose.

[0028] Particularly preferred aromatic diisocyanates employed independently or in combination with other aromatic diisocyanates are compounds of formula (IV) or (V). [ka]

[0029] The compound of formula (IV) is triisopropylphenyl diisocyanate.

[0030] In a preferred embodiment of the process according to the invention, the phosphorus-containing catalyst is separated after carbodiimidization by simple distillation and / or optionally by extraction or recrystallization using a solvent.

[0031] The carbodiimidization can be carried out either in substance or in a solvent. The solvents preferably used are C7 to C 22 The solvent may be alkylbenzene, paraffin oil, polyethylene glycol dimethyl ether, a ketone, or a lactone.

[0032] The carbodiimidization is preferably stopped once the reaction mixture has the desired NCO group content, which corresponds to an average degree of condensation of m=2 to 500, preferably 3 to 20, very particularly preferably 4 to 10.

[0033] In a preferred variant of the preparation of the aromatic polymeric carbodiimide according to the invention, the excess isocyanate monomer and the phosphorus-containing catalyst are then removed by distillation at a temperature of 150 to 200°C, preferably 160 to 180°C.

[0034] In a further embodiment of the present invention, the free terminal isocyanate groups of the carbodiimide are then reacted with aliphatic and / or aromatic amines, alcohols, and / or alkoxypolyoxyalkylene alcohols, preferably in a slight excess of -NH, -NH2, and / or -OH groups, optionally in the presence of a catalyst known to those skilled in the art, preferably a tert-amine or an organotin compound, particularly preferably DBTL (dibutyltin dilaurate) or DOTL (dioctyltin dilaurate). The molar ratio of amine, alcohol, and / or alkoxypolyoxyalkylene alcohol to the polymeric carbodiimide of formula (I), based on the N=C=O groups present, is preferably (1.005-1.05):1, particularly preferably (1.01-1.03):1.

[0035] In a further embodiment of the present invention, in order to terminate the carbodiimidization reaction, the temperature of the reaction mixture is lowered to 50 to 120°C, preferably 60 to 100°C, particularly preferably 80 to 90°C, and optionally, preferably C7 to C 22 After adding a solvent selected from the group of alkylbenzenes, particularly preferably toluene, the free terminal isocyanate groups of the carbodiimide are reacted with aliphatic and / or aromatic amines, alcohols, and / or alkoxypolyoxyalkylene alcohols, preferably in a slight excess of -NH, -NH2, and / or -OH groups, optionally in the presence of a PU catalyst known to those skilled in the art, preferably tert-amines or organotin compounds, particularly preferably DBTL (dibutyltin dilaurate) or DOTL (dioctyltin dilaurate). The molar ratio of amines, alcohols, and / or alkoxypolyoxyalkylene alcohols to the polymeric carbodiimide of formula (I) is preferably (1.005-1.05):1, particularly preferably (1.01-1.03):1, based on the N=C=O groups present.

[0036] In a further embodiment of the present invention, primary or secondary amines or alcohols and / or alkoxypolyoxyalkylene alcohols are used to prepare isocyanate-containing compounds of formula (I), where R 4 The preparation of the polymeric carbodiimide of formula (I) according to the present invention is carried out by terminally functionalizing only a portion, preferably less than 50%, preferably less than 40%, of the free NCO groups in the carbodiimide (=-NCO).

[0037] The carbodiimides of the present invention are preferably purified after their preparation. The crude reaction product can be purified by distillation and / or solvent extraction. Suitable solvents for purification include those in the range of C7 to C8. 22 Alkylbenzenes, paraffin oils, alcohols, ketones or esters. These are commercially available solvents.

[0038] The present invention further provides a method for measuring the CIE L * a * b * Also provided are polymeric carbodiimides of formula (I) which have a color number, measured as a b value by the method, of less than 50, preferably less than 35, particularly preferably less than 25, and most preferably less than 15, and a content of the phosphorus-containing catalyst of the present invention of at most 10 ppm, preferably at most 5 ppm, and particularly preferably at most 1 ppm, which are obtainable by the process of the present invention.

[0039] The present invention further provides a hydrolysis stabilizer for polyurethanes, which comprises at least 90% of an aromatic polymeric carbodiimide of formula (I), which comprises the phosphorus-containing catalyst according to the invention in a proportion of at most 10 ppm, preferably at most 5 ppm, particularly preferably at most 1 ppm.

[0040] These stabilizers in particular enable exceptionally good hydrolysis protection.

[0041] The present invention further provides a process for producing polyurethanes (PU), preferably thermoplastic polyurethanes, wherein the reaction of a polyol, preferably a polyester polyol, with an isocyanate is carried out in the presence of a polymeric carbodiimide according to the present invention and / or after the reaction, a polymeric carbodiimide according to the present invention is added to the polyurethane.

[0042] In a further preferred embodiment of the present invention, the process is carried out in the presence of a PU catalyst and auxiliary and / or additional substances.

[0043] The preparation of the polyurethane is preferably carried out as described in WO 2005 / 111136 A1.

[0044] Polyurethanes are formed almost quantitatively by the polyaddition reaction of polyisocyanates with polyhydric alcohols, polyols, preferably polyester polyols. The bond is formed by the reaction of the isocyanate group (-N=C=O) of one molecule with the hydroxyl group (-OH) of another molecule to form a urethane group (-NH-CO-O-).

[0045] The reaction profile between diisocyanates and polyols depends on the molar ratio of these components. Intermediates with the desired average molecular weight and desired end groups can be easily obtained. These intermediates are then reacted (chain extended) with diols or diamines in the next step to form the desired polyurethane or polyurethane-polyurea hybrid. These intermediates are commonly called prepolymers.

[0046] Suitable polyols for preparing the prepolymer are polyalkylene glycol ethers, polyether esters, or polyesters with terminal hydroxyl groups (polyester polyols).

[0047] Polyols in the context of the present invention are preferably compounds with a molecular weight (units: g / mol) of up to 2000, preferably in the range from 500 to 2000, particularly preferably in the range from 500 to 1000.

[0048] In the context of the present invention, the term "polyol" includes both diols and triols, as well as compounds with more than three hydroxyl groups per molecule. It is particularly preferred to use triols.

[0049] Preferred polyols are polyester polyols and / or polyether ester polyols.

[0050] Advantageously, the polyol has an OH number of up to 200, preferably between 20 and 150, particularly preferably between 50 and 115.

[0051] Particularly suitable are polyester polyols, which are reaction products of various polyols with aromatic or aliphatic dicarboxylic acids and / or polymers of lactones.

[0052] In this case, preference is given to aromatic dicarboxylic acids that can be used to form suitable polyester polyols, with particular preference given here to terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, and substituted dicarboxylic acids having a benzene ring.

[0053] Preferred aliphatic dicarboxylic acids are those that can be used to form suitable polyester polyols, with sebacic acid, adipic acid, and glutaric acid being particularly preferred.

[0054] Preferred polymers of lactones are those that can be used to form suitable polyester polyols, most preferably polycaprolactones.

[0055] Both dicarboxylic acid and lactone polymers are commercially available materials.

[0056] Particular preference is further given to polyols which can be used to form suitable polyester polyols, very particular preference being given to ethylene glycol, butanediol, neopentyl glycol, hexanediol, propylene glycol, dipropylene glycol, diethylene glycol and cyclohexanedimethanol.

[0057] In a further preferred embodiment of the invention, the polyol is a polyetherester polyol.

[0058] Preferred for this purpose are reaction products of the various polyols mentioned above with aromatic or aliphatic dicarboxylic acids, and / or polymers of lactones (eg, polycaprolactone).

[0059] Polyols that can be employed include commercially available compounds such as those sold under the trade names Baycoll® or Desmophen®, products of Bayer MaterialScience AG.

[0060] Preferred diisocyanates are aromatic and aliphatic diisocyanates. Particular preference is given to toluene 2,4-diisocyanate, toluene 2,6-diisocyanate, phenylene diisocyanate, 4,4-diphenylmethane diisocyanate, methylenebis(4-phenylisocyanate), naphthalene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and / or hexaethylene 1,6-diisocyanate, very particularly preferably toluene 2,4-diisocyanate and toluene 2,6-diisocyanate.

[0061] Diisocyanates which can be employed include commercially available compounds such as those sold under the trade name Desmodur®, products of Bayer MaterialScience AG.

[0062] In a further embodiment of the invention, the composition further comprises at least one diamine and / or diol.

[0063] Preferred diamines employed for chain extension are the following: 2-methylpropyl 3,5-diamino-4-chlorobenzoate, bis(4,4'-amino-3-chlorophenyl)methane, 3,5-dimethylthio-2,4-tolylenediamine, 3,5-dimethylthio-2,4-tolylenediamine, 3,5-diethyl-2,4-tolylenediamine, 3,5-diethyl-2,6-tolylenediamine, 4,4'-methylenebis(3-chloro-2,6-diethylaniline), and 1,3-propanediol bis(4-aminobenzoate).

[0064] Preferred diols are: butanediol, neopentyl glycol, hexanediol, propylene glycol, dipropylene glycol, diethylene glycol, and / or cyclohexanedimethanol.

[0065] The diamines or diols employed for chain extension in the context of the present invention are commodity chemicals available from Lanxess Deutschland GmbH under the trade name Addolink®.

[0066] The catalyst employed is preferably dibutyltin dilaurate or triethylenediamine in dipropylene glycol.

[0067] Possible catalysts include commercially available compounds such as those sold under the trade name Addocat®, products of Rheinchemie Rheinau GmbH.

[0068] The aromatic polymeric carbodiimide of formula (I) in the present invention is preferably employed in an amount of 0.1% to 2% by weight, particularly preferably 0.5% to 1.5% by weight, most preferably 1.0% to 1.5% by weight, based on the total mixture.

[0069] The polyurethane (PU)-based systems produced by this process are characterized by excellent hydrolytic stability.

[0070] The present invention therefore further provides the use of the aromatic polymeric carbodiimides according to the invention as hydrolysis stabilizers in polyurethane-containing compositions, preferably thermoplastic TPUs, PU adhesives, PU casting resins, PU elastomers or PU foams, as well as in products obtainable therefrom. [Example]

[0071] The following examples are intended to illustrate the invention but do not have any limiting effect.

[0072] General manufacturing procedures, examples 1-9: 200 g of monomeric diisocyanate was weighed into a 500 ml three-neck flask equipped with an internal thermometer, a reflux condenser, and an inert gas inlet, followed by the addition of each catalyst from Examples 1 to 9 in the ratios specified below (CDI1-9, based on the weight of the diisocyanate). During the heating stage, a small stream of argon was passed through the gas phase. Once CO evolution began, the inert gas was discontinued. Carbodiimidization was continued at 180 °C with stirring until the NCO content reached approximately 12 wt%. After the remaining monomeric diisocyanate and liquid catalyst were distilled off under vacuum at 180 °C, the temperature was reduced to approximately 120 °C, and the remaining free NCO groups of the polymeric carbodiimide were end-functionalized (end-capped) with methyl polyether alcohol (MPEG). Any solid catalysts (Cs carbonate) present were removed by filtration.

[0073] Example 1: Preparation of an aliphatic polymeric carbodiimide by reaction of 1,3-bis(2-isocyanato-2-propyl)benzol (TMXDI) with 0.2 wt% of 1-methyl-1-oxo-3-phospholene (MPO) (Comparative Example).

[0074] Example 2: Preparation of aromatic polymeric carbodiimides by reaction of compounds of formula (IV) with 0.5 wt % potassium methoxide (Comparative Example).

[0075] Example 3: Preparation of an aliphatic polymeric carbodiimide by reaction of the compound TMXDI with 0.5% by weight of potassium methoxide (Comparative Example).

[0076] Example 4: Preparation of aromatic polymeric carbodiimides by reaction of the compound of formula (IV) with 3 wt % Cs carbonate (Comparative Example).

[0077] Example 5: Preparation of an aliphatic polymeric carbodiimide by reaction of the compound TMXDI with 3 wt. % Cs carbonate (Comparative Example).

[0078] Example 6: Preparation of aromatic polymeric carbodiimides by reaction of a compound of formula (IV) with 0.2% by weight (MPO) based on diisocyanate (Comparative Example).

[0079] Example 7: Preparation of aromatic polymeric carbodiimides by reaction of a compound of formula (IV) with 20 ppm (0.002 wt %) MPO based on diisocyanate (inventive example).

[0080] Example 8: Preparation of aromatic polymeric carbodiimides by reaction of a compound of formula (IV) with 30 ppm (0.003 wt %) MPO based on diisocyanate (inventive example).

[0081] Example 9: Preparation of an aromatic polymeric carbodiimide by reaction of a compound of formula (IV) with 50 ppm (0.005 wt %) MPO based on diisocyanate (Comparative Example).

[0082] Color measurement Color measurements are based on the CIE L standard as described in ISO 11664-4. * a * b * Conducted in accordance with the law. * was evaluated.

[0083] PU responsiveness testing for devastating side effects Residual catalytic phosphorus compounds significantly interfere with the production of polyurethanes and adversely affect their quality.

[0084] First, 1 part polycarbodiimide and 9 parts 4,4'-methylenedi(phenylisocyanate) (MDI) were charged into a 250 ml four-neck flask. This was followed by inerting with nitrogen. The mixture was then heated to 80°C and stirred. The mixture was then checked for foaming / gas evolution. After 24 hours, a final sample was used to assess viscosity buildup.

[0085] The properties of the polymeric carbodiimides obtained in Examples 1 to 9 are shown in Table 1.

[0086] [Table 1]

[0087] The results show that the process of the present invention makes it possible to obtain polymeric aromatic carbodiimides with extremely low color numbers. The use of basic catalysts results in dark-colored carbodiimides.

[0088] Furthermore, the use of aromatic polymeric carbodiimides in the present invention results in no destructive side effects in PU reactivity testing, in stark contrast to the reaction products obtained in (Comparative) 6 using large amounts of phosphorus-containing catalyst, which are not suitable for use in most PU applications without additional distillation.

[0089] Experiments on the conversion of aromatic and aliphatic diisocyanates. For this purpose, the reduction in isocyanate content after 24 hours at 180°C was demonstrated using 0.002 wt. % (Examples 10, 11, and 13) or 0.001 wt. % (Example 12) of 1-methyl-1-oxophospholene (MPO amount based on diisocyanate). These studies showed that aliphatic diisocyanates could not be carbodiimidized in the presence of 0.002 wt. % of a phosphorus-containing catalyst, and aromatic diisocyanates could not be carbodiimidized in the presence of 0.001 wt. % of a catalyst. Therefore, the process of the present invention is only suitable for producing aromatic polymeric carbodiimides using specific catalyst amounts. Even under the reaction conditions described in EP 2897996 B1 (pressure 300 mbar, nitrogen flow rate 10 L / h), conversion of isocyanates to carbodiimides was not possible (Example 11).

[0090] Measurement of NCO content The NCO content was determined by potentiometric titration, which is based on the reaction of isocyanates (aliphatic or aromatic) with primary or secondary amines to produce the corresponding urea derivatives, followed by back-titration of an excess of the amine solution with hydrochloric acid.

[0091] For this purpose, the initially charged sample is mixed with an excess of the reactant solution (0.1 N solution of dibutylamine in toluene). Finally, the amount of reagent not consumed in this procedure is determined by back-titration with another suitable titrant solution (0.1 N isopropanolic hydrochloric acid solution).

[0092] The measurement results are shown in Table 2.

[0093] [Table 2]

Claims

1. Formula (I) R ４ -R ８ -(-N=C=N-R ８ -) ｍ -R ４ (I) [In the formula, m represents an integer of 2 to 500; R ８ is C １ ~C １２ -alkyl-substituted arylene, C ７ ~C １８ -alkylaryl-substituted arylene, or C １ ~C １２ represents an alkyl-substituted, alkylene-bridged arylene, where every arylene described is substituted with at least two of the aforementioned alkyl and / or alkylaryl groups, with the proviso that R ８ contains a total of 9 to 30 carbon atoms, and R ４ is -NCO, -NCNR ５ , -NHCONHR ５ , -NHCONR ５ R ６ , or -NHCOOR ７ (where R ５ and R ６ are the same or different, and C １ ~C １２ -Alkyl, C ６ ~C １２ -cycloalkyl, C ７ ~C １８ - represents an aralkyl or aryl group, and R ７ is C １ ~C ２２ -Alkyl, C ６ ~C １２ -cycloalkyl, C ６ ~C １８ -aryl, or C ７ ~C １８ -aralkyl group, unsaturated C ２ ~C ２２ -alkyl or alkoxypolyoxyalkylene groups), A process by carbodiimidizing an aromatic diisocyanate at a temperature of from 120°C to 220°C in the presence of at least one phosphorus-containing catalyst at a concentration of from 15 to 40 ppm by weight based on the content of the aromatic diisocyanate, wherein said phosphorus-containing catalyst is selected from phospholenes and phospholidines.

2. group R ８ wherein the alkyl substituents have a total of 3 to 24 carbon atoms, with the proviso that R ８ The process of claim 1, wherein has a total of 10 to 30 carbon atoms.

3. R ８ But there are at least two C １ ~C １２ -C substituted with alkyl groups １ ~C １２ -alkyl-substituted arylene, provided that R ８ The process of claim 1 or 2, wherein:

4. R ８ 3. The process of claim 1 or 2, wherein represents diisopropylphenylene and / or triisopropylphenylene.

5. The polymeric aromatic carbodiimide is represented by the formula (II) 【Chemistry 1】 (In the formula, R ４ is as defined above and n=1 to 20.

6. 2. The process of claim 1, wherein the phosphorus-containing catalyst is selected from phospholenes and phospholidines.

7. 3. The process of claim 1 or 2, wherein the phosphorus-containing catalyst is selected from phospholene oxides and phospholidine oxides.

8. The phosphorus-containing catalyst is represented by the general formula (1) 【Chemistry 2】 (In the formula, R １ and R ２ are each independently H or aliphatic C １ ~C １５ -hydrocarbon group, alicyclic C ５ ~C １５ -hydrocarbon group, aryl-C ６ ~C １５ -hydrocarbon group, aralkyl-C7-C １５ -hydrocarbon group or alkaryl-C7 to C １５ -represents a hydrocarbon group) or a double bond isomer thereof.

9. R in formula (1) １ is H or aliphatic C １ ~C １０ -hydrocarbon group, or aryl-C ６ ~C １５ represents a hydrocarbon group, and R in formula (1) ２ is H or aliphatic C １ ~C １０ The process of claim 8, wherein - represents a hydrocarbon group.

10. R in formula (1) １ represents a methyl group, an ethyl group, or a propyl group, or a phenyl group or a benzyl group, and R ２ 9. The process of claim 8, wherein represents H or a methyl, ethyl, or propyl group.

11. R in formula (1) １ represents a methyl group or a phenyl group, and R in formula (1) ２ 9. The process of claim 8, wherein represents H or a methyl group.

12. 3. The process according to claim 1 or 2, wherein the phosphorus-containing catalyst employed is 1-methyl-2-phospholene 1-oxide and / or its double bond isomer 1-methyl-3-phospholene 1-oxide.

13. The polymeric aromatic carbodiimide of formula (I) according to CIE L 14444 as defined in ISO 11664-4. ＊ a ＊ b ＊ 3. The process according to claim 1, wherein the color number is less than 50, measured as the b value by the .beta.-method, and the content of phosphorus-containing catalyst selected from phospholenes and phospholidines is at most 10 ppm.

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