EP4453054A1 - Polymeric carbodiimides, processes for the preparation and use thereof - Google Patents

Abstract

The invention relates to novel polycarbodiimides, which are simple and safe to prepare, have high average molar masses and bring about an excellent hydrolysis protection, and to processes for the preparation and use thereof.

Description

Polymeric carbodiimides, processes for their preparation and their use

Carbodiimides have proven themselves in many applications, e.g. as hydrolysis inhibitors for thermoplastics, polyols, polyurethanes, triglycerides and lubricating oils.

Strongly sterically hindered polycarbodiimides are preferably used for this. Highly steric aromatic polycarbodiimides with long Polymer chains (high molar masses) proven. However, these highly sterically hindered and long-chain polycarbodiimides, such as those based on triisopropylphenyl isocyanate, have the disadvantage that they can only be produced on an industrial scale with a considerable outlay in terms of apparatus and time. Polycarbodiimides that are based exclusively on diisocyanates have very high viscosities and can continue to polymerize uncontrollably even after the carbodiimidization step, which has various disadvantages, such as a very high cost of pastillation. Alternative manufacturing processes in solvents (crystallization) involve several process stages, are therefore expensive and lead to products in powder form, which is why the powder obtained in this way must then be additionally compacted to avoid dust in the end applications. Procedures for this include already described in EP176572 or EP2933285.

Although end-capped (capped) aromatic polycarbodiimides are less difficult to produce, they do not show the desired high level of stabilization in comparison and must be labeled because of toxic by-products.

There was therefore a need for new polycarbodiimides which do not have the stated disadvantages of the prior art, i.e. are simple and safe to produce, have high average molar masses, are as label-free as possible and provide excellent protection against hydrolysis. It was therefore the object of the present invention to provide corresponding polycarbodiimides and a process for their production.

Surprisingly, it has now been found that the above object is achieved by

Polycarbodiimides of formula (I) in which the radicals R can be the same or different and are selected from NCN-R ¹ , where the radicals R ¹ are Ci-C22-alkyl, unsubstituted or Ci-Ci2-alkyl-substituted C6-C12-cycloalkyl, unsubstituted or Ci-Ci2 -alkyl-substituted Ce-Cis-aryl or unsubstituted or Ci-Ci2-alkyl-substituted Ce-Cis-aralkyl and

R ¹ , R ² and R ³ are each identical or independently of one another and are methyl, ethyl, i-propyl or n-propyl, n-butyl or i-butyl or t-butyl and n is from 20 to 500, preferably from 30 to 100, particularly preferably 30 to 50, the average molar mass Mw being more than 10,000 and the proportion of polycarbodiimides having a molar mass of 30,000 g/mol or more being less than 20% by weight.

Since the chain length of the polycarbodiimides typically follows a distribution function, the above definition of the repeating units n should not be interpreted as meaning that the polycarbodiimides are free of compounds with a value of n that is less than or greater than the specified range. However, in view of the specified average molar mass and the proportion of polycarbodiimides with a molar mass of 30000 g/mol or more, the proportion of such compounds is typically in a negligibly small range.

In a preferred embodiment, R ¹ is Ci-Ci2-alkyl-substituted C6-Ci2-aryl, preferably Ci-C4-alkyl-substituted C6-Ci2-aryl, particularly preferably mono- to tri-Ci-C4-alkyl-substituted Ce-aryls, and very particularly preferably di- and/or triisopropylphenyl.

Preference is given to polycarbodiimides of the formula (I) where R ¹ , R ² and R ³ are i-propyl and R ¹ is diisopropylphenyl and/or triisopropylphenyl. The embodiment in which the radicals R ¹ in a molecule are the same is particularly preferred.

Preference is furthermore given to polycarbodiimides of the formula (I) which have average molar masses of 10000 g/mol to 20000 g/mol, preferably 12000 g/mol to 18000 g/mol, particularly preferably 14000 g/mol to 16000 g/mol. The mean molar masses (Mw) are determined by means of gel permeation chromatography (GPC), preferably using the method described in the exemplary embodiments. The proportion of polycarbodiimides with a molar mass of 30000 g/mol or more is preferably less than 15% by weight, particularly preferably less than 12% by weight. The proportion of carbodiimides with a molar mass (M) of 30000 g/mol is also determined by means of gel permeation chromatography (GPC).

The mass ratio of the radicals R to the radical of the compound of the formula (I) is preferably in the range from 1:100 to 1:20.

The carbodiimide content (NCN content, measured by titration with oxalic acid) of the carbodiimides according to the invention is usually 14-17% by weight, preferably 14-16% by weight, particularly preferably 14-15% by weight. To determine the NCN content, the NCN groups are reacted with excess oxalic acid and then the unreacted oxalic acid is back-titrated potentiometrically with sodium methoxide, taking into account the blank value of the system.

The polycarbodiimides according to the invention are ideal for stabilizing ester-based polymers, preferably polymers selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), copolyesters such as modified polyesters from cyclohexanediol and terephthalic acid (PCTA), thermoplastic polyester elastomers (TPE E), ethylene vinyl acetate (EVA), polylactic acid (PLA) and/or PLA derivatives, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA) and blends, such as preferably PA/PET or PHA/PLA Blends, polyurethane elastomers, preferably thermoplastic polyurethane elastomers (TPU), or rollable polyurethane, PU paints and coatings, preferably solvent-based dispersions.

The invention also relates to a method for stabilizing the above ester-based polymers by incorporating the polycarbodiimides according to the invention into the polymers. The aforementioned carbodiimides are preferably added to the ester-based polymers by means of solids metering units.

Solids metering units for the purposes of the invention are preferably: single-, twin- and multi-screw extruders, continuously operating co-kneaders (Buss type) and discontinuously operating kneaders, e.g. of the Banbury type.

The polycarbodiimides according to the invention can be obtained by a process for preparing polycarbodiimides of the formula (I) by carbodiimidization of aromatic diisocyanates of formula (II) and monoisocyanates of the formula R -NCO, where the radicals R, R ¹ , R ² , R ³ and R ¹ and n have the meanings given above, with elimination of carbon dioxide at temperatures of 80° C. to 200° C. in the presence of catalysts and optionally solvents, characterized in that the diisocyanates and monoisocyanates are used in a mass ratio of from 20:1 to 100:1, preferably from 25:1 to 50:1 and particularly preferably from 30:1 to 40:1.

According to the prior art, the polycarbodiimides of the formula (I) are synthesized by basic or heterocyclic catalysis. Usually, alkali metal or alkaline earth metal compounds, as well as heterocyclic compounds containing phosphorus, are used as catalysts. Corresponding catalysts are, for example, in Angew. Chem. 1962, 74, 801-806 and Angew. Chem. 1981, 93, 855-866.

1,3,5-Triisopropylphenyl diisocyanate (TRI DI), 2,6-diisopropylphenyl isocyanate (DI PI) or 2,4,6-triisopropylphenyl isocyanate (TRI PI) are particularly preferably used as isocyanates.

In one embodiment of the invention, strong bases or phosphorus compounds are preferred as catalysts for the carbodiimidization of the isocyanates to form carbodiimides of the formula (I). Preference is given to using phosphoiene oxides, phospholidines or phospholine oxides and the corresponding sulphides. Furthermore, tertiary amines, basic metal compounds, alkali metal, alkaline earth metal oxides or hydroxides, alcoholates or phenolates, carboxylic acid metal salts and non-basic organometallic compounds can be used as catalysts. As a catalyst are particularly alkyl phospholene oxides such. B. methylphospholene oxide preferred. The reaction (carbodiimidization) is preferably carried out in a temperature range from 140.degree. C. to 200.degree. C., particularly preferably from 160.degree. C. to 180.degree.

In a preferred embodiment of the invention, the isocyanates (diisocyanates and monoisocyanates) are first mixed together and then carbodiimidized as a mixture.

In a further embodiment, the diisocyanates of the formula (II) are first partially carbodiimidized in the presence of catalysts and, if appropriate, solvents, and then the monoisocyanates of the formula R'-NCO are added to the reaction mixture in order to complete the carbodiimidization.

In a preferred embodiment, after the carbodiimidization, the reaction mixture is stirred at elevated temperature, preferably at the reaction temperature under reduced pressure, and the residual isocyanate content is reduced to <0.1% by weight.

In a preferred variant of the invention, the final reaction mass is pastille systems z. B. the Fa. Sandvik Holding GmbH or a scale roller z. B. the company GMF Gouda made into lozenges or scales.

Another subject of the invention are compositions containing the polymeric carbodiimides according to the invention and ester-based polymers, preferably polymers selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), copolyesters such as modified polyesters from cyclohexanediol and terephthalic acid (PCTA), thermoplastic Polyester elastomers (TPE E), ethylene vinyl acetate (EVA), polylactic acid (PLA) and/or PLA derivatives, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxy alkanoate (PHA) and blends, such as preferably PA/PET - or PHA/PLA blends, polyurethane elastomers, preferably thermoplastic polyurethane elastomers (TPU), or rollable polyurethane, PU paints and coatings, preferably solvent-based dispersions. The weight ratio of polymeric carbodiimides to ester-based polymers is typically from 0.1:100 to 5:100, preferably from 0.5:100 to 4:100 and most preferably from 1:100 to 3:100.

The following examples serve to explain the invention without having a limiting effect. Examples:

Determination of the molar mass:

Apparatus Instrument Ultimate 3000

Detector RI ERC-7515A

Combination of 3 columns (PSS SDV 5p 100A, PSS SDV 5p 500A and PSS SDV 5p 10000A, material PL-Gel 10e4 A, length 300 mm, diameter 8 mm) PSS WlnGPC-Unichrom software

Volumetric bottle 25 mL

Pipetman 100 pL (± 0.0001 g)

Reagents standard samples

Polystyrene standards (polydispersity index less than 1.2)

Solvent 2,6-di-tert-butyl-1,4-methylphenol (BHT) tetrahydrofuran (THF) toluene

Parameter V (injection quantities) 100 pL Flow 1.0 mL / min

eluent THF

Pressure 36 bars

Temperature 40 °C carbodiimidization

Pure 1,3,5-triisopropylphenyl diisocyanate (TRIDI) for GDI 1 or a mixture of 1,3,5-triisopropylphenyl diisocyanate (TRIDI) and 2,6-diisopropylphenyl isocyanate (DI PI) in for GDI 2, 4, 5 and 6 or a mixture 1,3,5-Triisopropylphenyl diisocyanate (TRIDI) and cyclohexanol was carbodiimidized in the presence of about 0.1% methylphospholene oxide at 160° C. until an NCO content of <1% was reached.

The results are shown in Table 1 below. Were tested:

1) CDI 1: polycarbodiimide with an NCN content of about 14% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = NCO prepared from 1,3,5-triisopropylphenyl diisocyanate ( comparative example)

2) CDI 2: Polycarbodiimide with an NCN content of about 13.5% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = NCN-R ¹ with R ¹ = 2.6 -Diisopropylphenyl prepared from about 80% by weight of 1,3,5-triisopropylphenyl diisocyanate and 20% by weight of 2,6-diisopropylphenyl isocyanate (comparative example).

3) CDI 3: Polycarbodiimide with an NCN content of about 12.5% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = oxocyclohexyl prepared from about 80% by weight 1 , 3,5-triisopropylphenyl diisocyanate and 20% by weight cyclohexanol (comparative example).

4) CDI 4: Polycarbodiimide with an NCN content of about 14% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = NCN-R ¹ with R ^{1 =} 2,6-diisopropylphenyl prepared from about 92.5% by weight of 1,3,5-triisopropylphenyl diisocyanate and 7.5% by weight of 2,6-diisopropylphenyl isocyanate (comparative example).

5) CDI 5: polycarbodiimide with an NCN content of about 14.5% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = oxocyclohexyl prepared from about 97% by weight 1 , 3,5-triisopropylphenyl diisocyanate and 3% by weight cyclohexanol (comparative example).

6) CDI 6: Polycarbodiimide with an NCN content of about 14% by weight of the formula (I) with R ¹ , R ² , R ³ = isopropyl and R = NCN-R ¹ with R ^{1 =} 2,6-diisopropylphenyl prepared from about 97% by weight of 1,3,5-triisopropylphenyl diisocyanate and 3% by weight of 2,6-diisopropylphenyl isocyanate (according to the invention).

Table 1 :

Compare: Comparative example, Inventive: According to the invention As can be seen from Table 1, only the polycarbodiimide according to the invention can be easily and safely produced and packaged in comparison (no risk of complete polymerization in the reactor or in the lines to and in the processing area such as scale rollers or pelletizing belts) and simultaneously shows the desired molar mass (Mw > 10000 g/mol) and a reduced proportion of the toxic monomeric carbodiimide below the relevant limit of 0.1% by weight. Furthermore, the emission behavior is reduced with longer polymer chains and a low proportion of monomeric carbodiimide.

Hydrolysis protection in polyethylene terephthalate (PBT)

To evaluate the antihydrolysis effect in PBT, 2.5% by weight of each of the carbodiimides tested were dispersed in PET using a ZSK 25 laboratory twin-screw extruder from Werner & Pfleiderer before the measurement described below. The F3 standard test specimens used to measure tear strength were then produced from the granules obtained on an Arburg Allrounder 320 S 150-500 injection molding machine. For the hydrolysis test, these F3 standard test specimens were stored in water at a temperature of 120° C. and their tear strength was measured in MPa. Table 2 shows the relative tear strengths=(tear strength after x days of storage/tear strength after 0 days) x 100. The lower limit for relative tear strength is usually a value of 70-75%.

The results are listed in Table 2:

Dispersibility and compatibility in polyurethane-based formulations and in millable polyurethane

Table 3 shows the results of the compatibility tests in DMF/polyurethane dispersions and in millable polyurethane elastomer (llrepan® from LANXESS Deutschland GmbH) cf.=comparative example, req.=according to the invention

As can be seen from Table 3, the polycarbodiimide according to the invention--in comparison to the polycarbodiimide from the prior art--leads to stable and homogeneous polyurethane formulations due to better dispersibility and solubility. In addition, it can be seen that a low proportion of higher molecular weight polymer chains with more than 30000 g/mol in the polycarbodiimide according to the invention decisively improves the compatibility in many applications and formulations.

Claims

patent claims 1. Polycarbodiimides of formula (I) in which the radicals R can be the same or different and are selected from NCN-R ¹ , where the radicals R ¹ are Ci-C22-alkyl, unsubstituted or Ci-Ci2-alkyl-substituted C6-C12-cycloalkyl, unsubstituted or Ci-Ci2 -alkyl-substituted Ce-Cis-aryl or unsubstituted or Ci-Ci2-alkyl-substituted Ce-Cis-aralkyl and R ¹ , R ² and R ³ are each identical or independently of one another and are methyl, ethyl, i-propyl or n-propyl, n-butyl or i-butyl or t-butyl and n is from 20 to 500, preferably from 30 to 100, particularly preferably from 30 to 50, the average molar mass Mw being more than 10,000 and the proportion of polycarbodiimides with molar masses of 30,000 g/mol or more being less than 20% by weight. 2. Polycarbodiimides according to claim 1, wherein the average molar mass is from 10000 g/mol to 20000 g/mol, preferably from 12000 g/mol to 18000 g/mol, particularly preferably from 14000 g/mol to 16000 g/mol. 3. Polycarbodiimides according to one or more of claims 1 and 2, wherein the proportion of polycarbodiimides with a molar mass of 30,000 g/mol or more is less than 15% by weight, preferably less than 12% by weight. 4. Polycarbodiimides according to one or more of claims 1 to 3, wherein R ¹ is C1-Ci2-alkyl-substituted C6-Ci2-aryls, preferably for Ci-C4-alkyl-substituted C6-C12- aryls, particularly preferably for a up to tri-Ci-C4-alkyl-substituted Ce-aryls, and very particularly preferably di- and/or triisopropylphenyl, 5. Polycarbodiimides according to one or more of claims 1 to 4, wherein R ¹ , R ² and R ³ are i-propyl and R ¹ is diisopropylphenyl and / or triisopropylphenyl. 6. Polycarbodiimides according to one or more of claims 1 to 5, wherein the mass ratio of the radicals R to the radical of the compound of the formula (I) is in the range from 1:100 to 1:20. 7. Polycarbodiimides according to one or more of claims 1 to 6, wherein the carbodiimide content is 14-17% by weight, preferably 14-16% by weight, particularly preferably 14-15% by weight. 8. Process for preparing polycarbodiimides of formula (I) through implementation of Diisocyanates of formula (II) and monoisocyanates of the formula R-NCO, where the radicals R can be the same or different and are selected from NCN-R ¹ , where the radicals R ¹ are Ci-C22-alkyl, unsubstituted or Ci-Ci2-alkyl-substituted C6- Ci2-cycloalkyl, unsubstituted or Ci-Ci2-alkyl-substituted Ce-Cis-Aryl or unsubstituted or Ci-Ci2-alkyl-substituted Ce-Cis-Aralkyl mean and R ¹ , R ² and R ³ are each identical or independently of one another and are methyl, ethyl, i-propyl or n-propyl, n-butyl or i-butyl or t-butyl and n is from 20 to 500, preferably from 30 to 100, particularly preferably from 30 to 50, with elimination of carbon dioxide at temperatures from 80 ° C to 200 ° C in the presence of catalysts and optionally solvents, the mass ratio of diisocyanates to monoisocyanates from 20: 1 to 100: 1, preferably from is from 25:1 to 50:1 and most preferably from 30:1 to 40:1. Process according to Claim 8, in which the diisocyanates of the formula (II) are first mixed with the monoisocyanates of the formula R-NCO and then heated to the reaction temperature as a mixture and reacted. Process according to claim 8, wherein first the diisocyanates of formula (II) are partially carbodiimidized in the presence of catalysts and optionally solvents and then the monoisocyanates of formula RI-NCO are added to the reaction mixture to complete the carbodiimidization. Process according to one or more of Claims 8 to 10, in which, after the reaction, the mixture is stirred at elevated temperature, preferably at 160-180°C under reduced pressure, and the residual isocyanate content is reduced to <0.1% by weight. Process according to one or more of Claims 8 to 11, in which the polycarbodiimides obtained in the reaction are pastillated on a cooling belt or made up into flakes on a flaked roller. Process according to one or more of claims 8 to 12, wherein the reaction takes place at a temperature of 160°C to 180°C. Use of polycarbodiimides according to one or more of claims 1 to 7 for stabilizing ester-based polymers, preferably polymers selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly trimethylene terephthalate (PTT), copolyesters such as modified polyesters from cyclohexanediol and terephthalic acid ( PCTA), thermoplastic polyester elastomers (TPE E), ethylene vinyl acetate (EVA), polylactic acid (PLA) and/or PLA derivatives, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxy alkanoate (PHA) and blends such as preferably PA/PET or PHA/PLA blends, polyurethane elastomers, preferably thermoplastic polyurethane elastomers (TPU), or rollable polyurethane, PU lacquers and coatings, preferably solvent-based dispersions. Compositions containing: Ester-based polymers, preferably polymers selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), copolyesters such as modified polyesters from cyclohexanediol and terephthalic acid (PCTA), thermoplastic polyester elastomers (TPE E), Ethylene vinyl acetate (EVA), polylactic acid (PLA) and/or PLA derivatives, polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA) and blends, such as preferably PA/PET or PHA/PLA blends, Polyurethane elastomers, preferably thermoplastic polyurethane elastomers (TPU), or rollable polyurethane, PU lacquers and coatings, preferably solvent-based dispersions and polycarbodiimides according to one or more of claims 1 to 7.