AROMATIC CARBODIIMIDES, PROCESS FOR THE PREPARATION AND USE THEREOF

Abstract

The invention relates to novel carbodiimides, to processes for the production thereof and to the use thereof as a stabilizer in ester-based polyols, in polyethylene terephthalate (PET), in polybutylene terephthalate (PBT), in polytrimethylene terephthalate (PTT), in copolyesters, in thermoplastic polyester elastomers (TPE E), in ethylene vinyl acetate (EVA), in polylactic acid (PLA) and/or in PLA derivatives, in polybutylene adipate-terephthalates (PBAT), in polybutylene succinates (PBS), in polyhydroxyalkanoates (PHA), in blends, in triglycerides, in thermoplastic polyurethanes, in polyurethane elastomers, in PU adhesives, in PU casting resins, for PU coatings or in PU foams.

Claims

1. A carbodiimide of formula (I) ##STR00010## in which R may be identical or different and is selected from NCNR.sup.I and NHCOOR.sup.III, wherein R.sup.I represents C.sub.1-C.sub.22-alkyl, C.sub.6-C.sub.12-cycloalkyl, C.sub.6-C.sub.18-aryl or C.sub.6-C.sub.18-aralkyl, and R.sup.III represents an alkylated polyoxyalkylene radical, R.sup.1, R.sup.2 and R.sup.3 each independently of one another represent methyl, i-propyl or n-propyl, wherein on each benzene ring one of the radicals R.sup.1, R.sup.2 and R.sup.3 is methyl and n is from 0 to 500.

2. The carbodiimide according to claim 1, wherein R.sup.1, R.sup.2 and R.sup.3 each independently of one another represent methyl- or i-propyl-.

3. The carbodiimide according to claim 1, wherein carbodiimide content is 2-17% by weight.

4. The carbodiimide according to claim 1, wherein in formula (I) R represents NCNR.sup.I, and carbodiimide content is 10-17% by weight.

5. The carbodiimide according to claim 1, wherein in formula (I) R represents NHCOOR.sup.III, n is from 0 to 20, and carbodiimide content is from 4% to 13% by weight.

6. The carbodiimide according to claim 1, wherein in formula (I) R represents NHCOOR.sup.III and R.sup.III represents an alkylated polyoxyalkylene radical, n is from 0 to 20, and carbodiimide content is from 2-10% by weight.

7. The carbodiimide according to claim 6, wherein R.sup.III represents monoalkylated polyethylene glycol ethers having molar masses of 200-600 g/mol.

8. A process for producing carbodiimides according to claim 1, comprising the steps of: a) carbodiimidization of aromatic diisocyanates of formula (II) ##STR00011## to eliminate carbon dioxide at temperatures of 80? C. to 200? C. in the presence of catalysts and optionally solvent and b) functionalization of the free NCO groups of the carbodiimides obtained in step a) with alcohols of formula NOR.sup.III, wherein R.sup.1 to R.sup.3 and R.sup.III are as defined for the compounds of formula (I).

9. A process for producing carbodiimides according to claim 1, comprising the steps of: a) partial functionalization of the free NCO groups of aromatic diisocyanates of formula (II) ##STR00012## with alcohols of formula NOR and b) subsequent carbodiimidization of the partially functionalized aromatic diisocyanates of formula (II) obtained in step a) to eliminate carbon dioxide at temperatures of 80? C. to 200? C. in the presence of catalysts and optionally solvent, wherein R.sup.1 to R.sup.3 and R.sup.III are as defined for the compounds of formula (I).

10. A process for producing carbodiimides according to claim 1, comprising carbodiimidization of aromatic diisocyanates of formula (II) ##STR00013## to eliminate carbon dioxide at temperatures of 80? C. to 200? C. in the presence of catalysts and optionally solvent, wherein before, during or after the carbodiimidization of the diisocyanates, monoisocyanates of formula OCNR.sup.I are added and wherein R.sup.1 to R.sup.3 and R.sup.I are as defined for the compounds of formula (I).

11. The process according to claim 8, wherein the aromatic diisocyanates of formula (II) employed are compounds of formulae (III) ##STR00014## and/or (IV) ##STR00015##

12. The process according to claim 8, wherein R=NCNR.sup.I, wherein R.sup.I is as defined for the compounds of formula (I) and the melt of the carbodiimide obtained in the carbodiimidization is pelletized in unpurified form or after purification.

13. A method of inhibiting against hydrolytic decomposition in ester-based polymers, comprising incorporating a carbodiimide according to claim 1 into an ester-based polymer composition.

14. A method of protection against hydrolytic degradation in thermoplastic polyurethane (TPU) comprising incorporating a carbodiimide according to claim 1 into a thermoplastic polyurethane composition.

15. A composition containing at least one inventive carbodiimide according to claim 1 and at least one ester-based polymer.

16. The composition according to claim 15, wherein the ester-based polymer is thermoplastic polyurethane (TPU) or a blend of ester-based polymers.

17. The carbodiimide according to claim 1, wherein R.sup.I is triisopropylphenyl.

18. The carbodiimide according to claim 1, wherein n is from 1 to 100.

19. The carbodiimide according to claim 1, wherein n is from 1 to 50.

20. The carbodiimide according to claim 1, wherein n is from 0 to 20.

Description

WORKING EXAMPLES

[0058] Tests were carried out on: [0059] 1) CDI A: a solid carbodiimide having an NCN content of about 12% by weight based on about 80% by weight of diethyltolylene-2,4-diisocyanate and 20% by weight of diethyltolylene-2,6-diisocyanate end-functionalized with cyclohexanol (comparative example analogous to EP 2997010 B1). [0060] 2) CDI (B): a high-viscosity carbodiimide having an NCN content of about 14% by weight based on 80% by weight of diethyltolylene-2,4-diisocyanate and 20% by weight of diethyltolylene-2,6-diisocyanate end-functionalized with NCNR.sup.I, wherein R.sup.I=triisopropylphenyl and n>40 (comparative example). [0061] 3) CDI (C): a solid polymeric carbodiimide having an NCN content of about 14% by weight based on diisopropyltolylene diisocyanate (formulae III and IV in a weight ratio of about 1:4), end-functionalized with NCNR.sup.1, wherein R.sup.I=triisopropylphenyl and n>40 (inventive example). [0062] 4) CDI (D): a solid polymeric carbodiimide based on diisopropyltolylene diisocyanate, end-functionalized with ethylamine (comparative example analogous to CN 105778026). [0063] 5) CDI (E): a solid polymeric carbodiimide having an NCN content of about 6-7% by weight based on diisopropyltolylene diisocyanate (formulae III and IV in a weight ratio of about 1:4), end-functionalized with methyl polyethylene glycol (Mw about 550 g/mol), wherein n=4-5 (inventive example).

Ester-Based Polymers:

[0064] 6) Unstabilized thermoplastic polyurethane (TPU) obtainable from Covestro AG under the name Desmopan.

Production of Carbodiimide CDI (A)

[0065] A baked-out and nitrogen-filled 250 ml four-necked flask was initially charged with 150 g of diisocyanates and 37.5 g of cyclohexanol under a nitrogen stream. 50 mg of 1-methylphospholene oxide were added and the mixture was then heated slowly to 180? C. Carbodiimidization was then carried out at 180? C. until an NCO content of <1% by weight had been achieved.

Production of Carbodiimides CDI (B) and CDI (C):

[0066] A baked-out and nitrogen-filled 250 ml four-necked flask was initially charged with 150 g of diisocyanates and 37.5 g of triisopropylphenyl isocyanate under a nitrogen stream. 50 mg of 1-methylphospholene oxide were added and the mixture was then heated slowly to 180? C. Carbodiimidization was then carried out at 180? C. until an NCO content of <1% by weight had been achieved.

Production of Carbodiimide CDI (D)

[0067] A baked-out and nitrogen-filled 250 ml four-necked flask was initially charged with 150 g of diisocyanates and 7.0 g of ethylamine under a nitrogen stream. 50 mg of 1-methylphospholene oxide were added and the mixture was then heated slowly to 180? C. Carbodiimidization was then carried out at 180? C. until an NCO content of <0.1% by weight had been achieved.

Production of Carbodiimide CDI (E)

[0068] A baked-out and nitrogen-filled 250 ml four-necked flask was initially charged with 150 g of diisocyanates and 100 g of MPEG (methyl polyethylene glycol, Mw of about 550 g/mol). 50 mg of 1-methylphospholene oxide were added and the mixture was then heated slowly to 180? C. Carbodiimidization was then carried out at 180? C. until an NCO content of <0.1% by weight had been achieved.

Hydrolysis Inhibition in Thermoplastic Polyurethane (TPU)

[0069] To evaluate the hydrolysis inhibition in TPU, 1.5% by weight respectively of the carbodiimides investigated were dispersed into TPU using a ZSK 25 laboratory twin screw extruder from Werner & Pfleiderer prior to the measurement described below. The standard test specimens used for measuring breaking strength were then produced from the resulting pellets on an Arburg Allrounder 320 S 150-500 injection-moulding machine.

[0070] For the hydrolysis test, these standard test specimens were stored in water at a temperature of 80? C. and their breaking strength in MPa was measured.

[0071] The results are shown in table 1:

TABLE-US-00001 TABLE 1 Breaking Ex. 1 Ex. 2 Ex. 3 Ex. 4 strength (comp.) (comp.) (comp.) (inv.) (MPa) (TPU) (TPU, CDI A) (TPU/CDI D) (TPU/CDI E) 0 days 30 30 31 32 5 days 28 30 30 32 10 days 26 30 30 31 15 days 12 28 30 30 20 days 6 25 30 30 30 days 0 5 28 30 80 days 18 30 85 days 5 29 90 days 28 comp. = comparative example, inv. = inventive

[0072] The results from table 1 show that the inventive carbodiimides achieve markedly better hydrolysis inhibition relative to the prior art.

Solubility in Polyester Polyol

[0073] The stabilization of the ester-based TPU elastomers to hydrolysis is in principle carried out directly during production. To this end, the carbodiimide is normally added to the polyester polyol or polyester plasticizer before the reaction with isocyanates to afford the polyurethane is carried out. The solubility of the carbodiimide is therefore important. Table 2 shows the different carbodiimides in a standard polyester polyol based on adipic acid and ethanediol and having a Mw=2000 (Desmophen 2000 MM from Covestro AG) at 80? C.

TABLE-US-00002 TABLE 2 Ex. 5 (comp.) Ex. 6 (inv.) (CDI D) (CDI E) Solubility in insoluble soluble polyester polyol

Hydrolysis Inhibition in Polyethylene Terephthalate (PET)

[0074] To evaluate the hydrolysis inhibition in PET, 1.5% by weight respectively of the carbodiimides investigated were dispersed into PET using a ZSK 25 laboratory twin screw extruder from Werner & Pfleiderer prior to the measurement described below. The F3 standard test specimens for measurement of breaking strength were then produced from the resultant pellets in an Arburg Allrounder 320 S 150-500 injection-moulding machine.

[0075] For the hydrolysis test, these F3 standard test specimens were stored in water at a temperature of 90? C. and the breaking strength thereof was measured in MPa. Table 2 shows the relative breaking strengths=(breaking strength after x days of storage/breaking strength after 0 days)?100. The lower limit for relative breaking strength is usually 70-75%.

[0076] The results are shown in table 3:

TABLE-US-00003 TABLE 3 Relative breaking Ex. 7 (comp.) Ex. 8 (comp.) Ex. 9 (inv.) strength (%) (PET) (PET/CDI A) (PET/CDI C) 0 days 100 100 100 5 days 100 100 100 10 days 51 100 100 15 days 100 100 20 days 100 100 25 days 52 81 28 days 41 comp. = comparative example, inv. = inventive

Tests on Pelletizability and Meterability of the Solid Carbodiimides

[0077] For clarification of the processability, handling and meterability of the different solid carbodiimides, these were compared in terms of appearance, pelletizability and softening point. The softening points were determined using a Koffler bench.

[0078] The results are shown in table 4:

TABLE-US-00004 meterability Softening Appearance pelletiz- (T up to point Carbodiimide (at RT) ability 40? C.) (? C.) CDI (B), soft, tacky not possible <20 comp. composition CDI (D), hard, tacky not possible >120 comp. composition CDI (C), solid, brittle very good very good about 80 required comp. = comparative example, inv. = inventive

[0079] The results of table 4 show that the inventive carbodiimides based on diisopropyl, tolylene end-capped with a monoisocyanate show, compared to the polymeric carbodiimide based on diethyltolylene diisocyanate also end-capped with a monoisocyanate and compared to carbodiimide D, exceptional pelletizability and a high softening point, thus entailing advantages in the processing and metering of the solid in the stabilization of the ester-based polymers. The carbodiimide E according to the invention is liquid and may be added as such.