Carbodiimide manufacturing method

Abstract

The present invention relates to a novel process for the preparation of carbodiimides, comprising the steps of: a) carbodiimidization of an isocyanate in the presence of a catalyst; b) separation of the catalyst and / or monomeric isocyanate from the carbodiimide by distillation or extraction to obtain an unpurified (crude) carbodiimide comprising the monomeric isocyanate; and c) addition of one or more alcohols and partial or complete reaction of the alcohols with the monomeric isocyanates of the unpurified (crude) carbodiimide.

Description

[Technical Field]

[0001] The present invention relates to a novel process for preparing carbodiimides having reduced residual isocyanate monomer content. [Background technology]

[0002] Carbodiimides have proven useful as hydrolysis inhibitors in many applications, such as thermoplastics, polyols, polyurethanes, triglycerides, and lubricating oils.

[0003] Prior art carbodiimide synthesis typically proceeds from isocyanates, which are carbodiimidized in the presence of basic or heterocyclic catalysts with the elimination of CO. This allows the conversion of mono- or polyfunctional isocyanates into monomeric or polymeric carbodiimides.

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

[0005] The removal of the isocyanate used as a raw material from the product after carbodiimidization is very complicated, especially when preparing polymeric carbodiimides. The goal of reducing the residual isocyanate monomer content to substantially less than 0.1% by weight without impairing the product quality (especially the color number) is usually achieved only by repeated crystallization operations, which entails a significant loss of yield. Alternatively, as described in Patent Document 1, carbodiimides containing isocyanate and urethane groups and having a low residual isocyanate monomer content can be prepared by repeatedly distilling off the monomers in a short-path evaporator, however, this is time-consuming and costly. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent No. 1451239 [Non-patent literature]

[0007] [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]

[0008] The object of the present invention was therefore to provide an improved process for preparing carbodiimides with reduced isocyanate content, which to a great extent avoids the above-mentioned disadvantages of the prior art and achieves economically feasible high yields and high product quality. [Means for solving the problem]

[0009] Surprisingly, the aforementioned object is achieved by the invention of a compound of formula (I): R III -(-N=C=NR I -) n -N=C=NR II (I) (In the formula, n is a number from 1 to 500, preferably from 2 to 50, very particularly preferably from 4 to 20, R I is C1~C 24 Alkylene and / or C5-C 12 Cycloalkylene, C1-C 12 -Alkyl-substituted or C1-C 24 -oxyalkyl-substituted cycloalkylene, C1-C 12 -Alkyl-substituted arylene, C1-C 24 -oxyalkyl-substituted arylene, C7-C 18-Alkylaryl-substituted arylene, and optionally C1-C8 alkylene bridged through a C1-C8 alkylene group and having a total of 8 to 30 carbon atoms; 12 - optionally alkyl-substituted arylene, and arylene, and R II , R III are the same or, independently of each other, C1 to C 24 -Alkyl- and / or C5-C 24 -cyclo- or C1-C 12 -Alkyl-substituted or C1-C 24 -oxyalkyl-substituted cycloalkyl, C1-C 12 -Alkyl-substituted or C1-C 24 -oxyalkyl-substituted aryl, C7-C 18 - alkylaryl-substituted aryl, and optionally C1-C8 alkylene bridged through a C1-C8 alkylene group and having a total of 8 to 30 carbon atoms; 12 -alkyl-optionally substituted aryl, and aryl) 1. A process for preparing a carbodiimide of formula (I), comprising the steps of: a) carbodiimidization of an isocyanate in the presence of a catalyst to obtain a reaction mixture comprising a carbodiimide and a monomeric isocyanate; b) at least partial separation of the catalyst and / or the monomeric isocyanate from a reaction mixture comprising the carbodiimide and the monomeric isocyanate by distillation or extraction to obtain an unpurified (crude) carbodiimide comprising the monomeric isocyanate; c) adding one or more alcohols to the crude carbodiimide containing the monomeric isocyanate and allowing the alcohol to react partially or completely with the monomeric isocyanate of the crude carbodiimide; It has been discovered that this can be achieved by a preparation process comprising:

[0010] wherein the isocyanate used in step a) has the formula OCN-R I -NCO, OCN-R II , and OCN-RIII It is a monomer compound of the formula: DETAILED DESCRIPTION OF THE INVENTION

[0011] In an alternative embodiment, in step a), the compound of formula OCN-R is already in oligomerized or polymerized form. I —NCO compounds (i.e., compounds of the formula OCN-R I -(-N=C=NR I -) (n-1) -NCO) has the formula OCN-R II and OCN-R III is carbodiimidized with the compound

[0012] In a further alternative embodiment, in step a), a compound of formula OCN-R I The compounds of -NCO are used in the already oligomerized or polymerized form and in the already end-capped form. In these cases, i.e., compounds of formula R III -(-N=C=NR I -) n The compound -NCO has the formula OCN-R II or a compound of formula R II -(-N=C=NR I -) n The compound -NCO has the formula OCN-R III It is carbodiimidized with the compound

[0013] C1-C2 optionally bridged via alkylene groups and having a total of 8 to 30 carbon atoms 12 -Alkyl-substituted C6-C 10 Arylene has the general structure -alkylene-arylene-alkylene-, where the alkylene can be straight or branched, and the arylene group has up to four C1-C 12 It may have alkyl substituents, provided that the total number of carbon atoms does not exceed 30.

[0014] wherein the arylene group is bridged via an alkylene group and does not have an alkyl group on the arylene group, and in each case the two alkylene groups have 1 to 6 carbon atoms. 10 Arylene is preferred.

[0015] In a preferred embodiment, R I is C1~C 12 -Alkyl-substituted C6-C 12 Arylene, preferably C1-C4-alkyl-substituted C6-C 12 Arylene, particularly preferably mono- to tri-C1-C4-alkyl-substituted C6 arylene, and very particularly preferably di- and / or triisopropylphenylene.

[0016] In a preferred embodiment, R II and R III are independent of each other, C1 to C 12 -Alkyl-substituted C6-C 12 Aryl, preferably C1-C4-alkyl-substituted C6-C 12 Aryl, particularly preferably mono- to tri-C1-C4-alkyl-substituted C6 aryl, and very particularly preferably di- and / or triisopropylphenyl.

[0017] In a further preferred embodiment, R I is C1~C 12 -Alkyl-substituted C6-C 12 arylene, and R II and R III are independent of each other, C1 to C 12 -Alkyl-substituted C6-C 12 It is aryl.

[0018] In a further preferred embodiment, R I C1-C4-alkyl-substituted C6-C 12 arylene, and R II and R III are, independently of each other, C1-C4-alkyl-substituted C6-C 12 It is aryl.

[0019] In a further preferred embodiment, R I is mono- to tri-C1-C4-alkyl-substituted C6 arylene, and R II and R III are, independently of each other, mono- to tri-C1-C4-alkyl-substituted C6 aryl.

[0020] In a further preferred embodiment, R I is di- and / or triisopropylphenylene, and R II and R III are, independently of one another, di- and / or triisopropylphenyl.

[0021] In a preferred embodiment, the carbodiimide has the following formula (II): [ka] (In the formula, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are the same or independently H, C1 to C 20 Alkyl, C3-C 20 Cycloalkyl, C6-C 15 Aryl and / or C7-C 15 is aralkyl, R 7 =C1~C 18 Alkylene, C5-C 18 Cycloalkylene, C1-C 20 -Alkyl-substituted arylene and / or C7-C 18 Aralkylene, preferably C1-C8-alkyl-substituted arylene and / or C7-C 18 aralkylene, and n is a number in the range of 1 to 500. Corresponds to.

[0022] Preferably, n is a number in the range of 1-50, preferably 3-20.

[0023] In the above-described embodiments of the invention, mixtures of compounds of formula (I) and / or (II) having different values ​​for n may also occur, in which case fractions for n may also occur when determining the average value.

[0024] The carbodiimidization of isocyanates in the presence of a catalyst in step a) of the process according to the invention is typically carried out in a condensation reaction with elimination of CO, as described, for example, in Angew. Chem. 93, pp. 855-866 (1981) or DE-A-11 30 594 or Tetrahedron Letters 48 (2007), pp. 6002-6004.

[0025] The carbodiimidization can be carried out in the substance or in a solvent. Alternatively, the carbodiimidization can be initiated in the substance first, and a solvent can be added during the reaction. Suitable solvents can be easily determined by those skilled in the art. Examples of such solvents include petroleum ether, benzene, and / or alkylbenzenes.

[0026] The isocyanate used is particularly preferably 1,3,5-triisopropylphenyl diisocyanate (TRIDI), 2,6-diisopropylphenyl isocyanate (DIPI), or 2,4,6-triisopropylphenyl isocyanate (TRIPI).

[0027] In one embodiment of the present invention, the preferred catalyst for the carbodiimidization of isocyanates to carbodiimides of formula (I) in step a) is a strong base or a phosphorus compound. It is preferred to use phospholene oxide, phospholidine, or phospholine oxide and the corresponding sulfide. Further catalysts that can be used are tertiary amines, basic metal compounds, oxides, hydroxides, alkoxides, or phenoxides of alkali metals and alkaline earth metals, metal carboxylates, and non-basic organometallic compounds. As the catalyst, alkylphospholene oxides, such as methylphospholene oxide, are particularly preferred.

[0028] This reaction (carbodiimidization) is preferably carried out at a temperature in the range of 140°C to 200°C, particularly preferably 160°C to 180°C.

[0029] In a further embodiment of the invention, the reaction product from step a) is filtered between step a) and step b).

[0030] The at least partial separation of the catalyst and / or monomeric isocyanate in step b) aims to achieve the removal of most of these substances. Considering process efficiency, it is acceptable here if the monomeric isocyanate is not completely separated. This separation can be carried out by distillation or extraction, with distillation being preferred. Any solvents that can be used in the carbodiimidization can also be separated simply by distillation. The distillation in step b) is preferably carried out at temperatures of 140°C to 200°C, particularly preferably 160°C to 180°C. The distillation is generally carried out under reduced pressure at a pressure of 0.1 to 50 mbar, preferably 1 to 30 mbar, particularly preferably 10 to 20 mbar. In a preferred embodiment, the distillation is carried out batchwise in a stirred reactor.

[0031] Preferably, the addition and / or reaction of the alcohol in step c) is carried out at a temperature of 140° C. to 200° C., particularly preferably 160° C. to 180° C. Particularly preferably, both the addition and the reaction of the alcohol in step c) are carried out at a temperature in the range of 140° C. to 200° C., most preferably 160° C. to 180° C.

[0032] Typically, in step c) 0.1% to 5% by weight, preferably 0.2% to 2% by weight, particularly preferably 0.3% to 0.5% by weight of alcohol is added, based on the amount of carbodiimide present.

[0033] Preferably, the alcohol used is an aliphatic and / or aromatic alcohol, preferably a linear, branched, and / or cyclic aliphatic C-C 18 Alcohols, particularly preferably n-octanol, isooctanol, dodecanol, 2-ethylhexanol, oleyl alcohol, stearyl alcohol, and / or cyclohexanol.

[0034] Step c) may optionally be followed by a distillation to remove any excess alcohol present.

[0035] The carbodiimides obtained by the process according to the invention typically have a monomeric isocyanate content of less than 1000 ppm, preferably less than 750 ppm, particularly preferably less than 500 ppm, more preferably less than 300 ppm, and most preferably less than 100 ppm.

[0036] The following examples are intended to illustrate the invention without, however, having a limiting effect. [Example]

[0037] <Determination of Residual Isocyanate Monomer Content> The residual isocyanate monomer content was determined by HPLC after reaction with a reagent solution (1-pyridyl-2-piperazine in 100 ml of THF). The eluent used was a mixture of ammonium acetate solution and methanol. Calibration was performed beforehand with various concentrations of monomeric isocyanate.

[0038] <Examples of Carbodiimides>: Carbodiimides of formula (II) (wherein R 7 = triisopropylphenylene, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 = isopropyl and n = approximately 18).

[0039] <Example 1: Carbodiimidization> A mixture of 1,3,5-triisopropylphenyl diisocyanate (TRIDI) and 2,4,6-triisopropylphenyl isocyanate (TRIPI) was carbodiimidized in the presence of approximately 0.2% methylphospholene oxide at 160° C. until an NCO content of less than 1% was achieved. The reaction product was distilled for 2 hours at 160° C. and 10 mbar.

[0040] Example 2: Batch distillation The carbodiimide from Example 1 was distilled in a stainless steel tank for 5 hours with a short distillation bridge, the temperature in the distillation tank was in the range of 160°C to 180°C, and the final pressure was about 10 mbar.

[0041] Example 3: Distillation by thin film / short path evaporator The carbodiimide from Example 1 was distilled at approximately 180° C. and 1 mbar using a thin film / short path evaporator combination.

[0042] Example 4: Recrystallization The carbodiimide from Example 1 was dissolved in toluene in a stainless steel tank at 60° C. and then recrystallized from acetone at 10-20° C. After filtration, the ground carbodiimide was dried in an oven under a reduced pressure of 10 mbar for several hours.

[0043] Example 5: Reaction with alcohol To the carbodiimide from Example 1 was added 0.5% 2-ethylhexanol in a stainless steel tank and the mixture was stirred at 160° C. for approximately 30 minutes.

[0044] Example 6: Reaction with alcohol To the carbodiimide from Example 1 was added 2.0% 2-ethylhexanol in a stainless steel tank and the mixture was stirred at 160° C. for approximately 30 minutes.

[0045] The residual content of monomeric isocyanate was determined by HPLC. The color was measured by CIE L * a * b * The b value was evaluated according to the method ISO 11664-4.

[0046] The results are listed in Table 1 below.

[0047] [Table 1]

[0048] As can be seen from Table 1, the residual isocyanate monomer content cannot be achieved by simple batch distillation, even after very long distillation times. Furthermore, this leads to a significant deterioration in the color of the product. The desired quality characteristics are first achieved by recrystallization or by a thin film / short path evaporator combination; however, these methods are complicated and involve yield losses. A simple reaction with a small amount of alcohol (here, 2-ethylhexanol) produces the desired result while avoiding the drawbacks of known processes.

Claims

1. The following formula (I): R ＩＩＩ -(-N=C=N-R Ｉ -) ｎ -N=C=N-R ＩＩ (I) (In the formula, n is a number from 1 to 500, R Ｉ are, independently of each other, C １ ~C ２４ Alkylene, C ５ ~C １２ Cycloalkylene, C １ ~C １２ -alkyl-substituted or C １ ~C ２４ -oxyalkyl-substituted cycloalkylene, C １ ~C １２ -alkyl-substituted arylene, C １ ~C ２４ -oxyalkyl-substituted arylene, C ７ ~C １８ -alkylaryl-substituted arylene, C １ ~C ８ bridged via alkylene groups and having a total of 8 to 30 carbon atoms, optionally C １ ~C １２ - is selected from the group consisting of optionally alkyl-substituted arylene, and arylene; R ＩＩ , R ＩＩＩ are identical or, independently of one another, C １ ~C ２４ -Alkyl, C ５ ~C ２４ -cycloalkyl, C １ ~C １２ -alkyl-substituted or C １ ~C ２４ -oxyalkyl-substituted cycloalkyl, C １ ~C １２ -alkyl-substituted or C １ ~C ２４ -oxyalkyl-substituted aryl, C ７ ~C １８ -alkylaryl-substituted aryl, C １ ~C ８ bridged via alkylene groups and having a total of 8 to 30 carbon atoms, optionally C １ ~C １２ -alkyl-optionally substituted aryl, and aryl. A method for producing a carbodiimide of the formula a) carbodiimidization of an isocyanate in the presence of a catalyst to obtain a reaction mixture comprising a carbodiimide and a monomeric isocyanate; b) at least partial separation of the catalyst and / or monomeric isocyanate from the reaction mixture comprising carbodiimide and monomeric isocyanate by distillation or extraction to obtain a crude carbodiimide comprising monomeric isocyanate; c) adding 0.1% to 5% by weight, based on the amount of carbodiimide present therein, of one or more alcohols to the crude carbodiimide containing monomeric isocyanates, and allowing the alcohols to react partially or completely with the monomeric isocyanates contained in the crude carbodiimide; A manufacturing method comprising:

2. 2. The method of claim 1, wherein the addition and / or reaction of the alcohol in step c) is carried out at a temperature in the range of 140 to 200°C.

3. 3. The method according to claim 1 or 2, wherein the alcohol used is an aliphatic and / or aromatic alcohol.

4. The method of any one of claims 1 to 3, wherein the reaction product from step a) is filtered between step a) and step b).

5. 5. The method according to any one of claims 1 to 4, wherein the adding and / or reacting in step c) is carried out with stirring.

6. The carbodiimide has the following formula (II): 【Chemistry 1】 (In the formula, R １ , R ２ , R ３ , R ４ , R ５ , and R ６ are the same or, independently of one another, H, C １ ~C ２０ Alkyl, C ３ ~C ２０ Cycloalkyl, C ６ ~C １５ Aryl, and C ７ ~C １５ aralkyl; R ７ are, independently of each other, C １ ~C １８ Alkylene, C ５ ~C １８ Cycloalkylene, C １ ~C ２０ -alkyl-substituted arylene, and C ７ ~C １８ aralkylene, and n is a number ranging from 1 to 500. The method according to any one of claims 1 to 5, wherein

7. 7. The method of claim 6, wherein n is a number in the range of 1 to 50.

8. The process according to any one of claims 1 to 7, wherein the distillation in step b) is carried out at a temperature of from 140°C to 200°C.

9. 9. The process according to any one of claims 1 to 8, wherein the distillation in step b) is carried out at a pressure of 0.1 to 50 mbar.

10. 10. The method of any one of claims 1 to 9, wherein the catalyst in step a) is selected from the group consisting of phospholene oxides, phospholidines, phospholine oxides and sulfides thereof, tertiary amines, basic metal compounds, alkali metal oxides, alkali metal hydroxides, alkaline earth metal oxides, alkaline earth metal hydroxides, alkoxides, phenoxides, metal carboxylates, and non-basic organometallic compounds.

11. The method according to any one of claims 1 to 10, wherein the carbodiimidization is carried out in the presence of a solvent.

12. 12. The method according to any one of claims 1 to 11, wherein the isocyanate used is a combination of a diisocyanate which is 1,3,5-triisopropylphenyl diisocyanate (TRIDI) and a monoisocyanate selected from the group consisting of 2,6-diisopropylphenyl isocyanate (DIPI) and 2,4,6-triisopropylphenyl isocyanate (TRIPI).

13. 13. The method of any one of claims 1 to 12, wherein following step c) excess alcohol is removed by distillation.

14. 14. The process according to any one of claims 1 to 13, wherein after step c) or after the optional distillation subsequently to step c), a carbodiimide is obtained having a monomeric isocyanate content of less than 1000 ppm.

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