Method for the Synthesis of Polymer Carbodiimides with Added Cesium Salts, Polymer Carbodiimides, and Use Thereof

Abstract

The present invention relates to processes for producing polymeric carbodiimides by addition of cesium salts and to polymeric carbodiimides produced by this process and to the use thereof as a hydrolysis inhibitor, especially in polyurethane (PU)-based systems, preferably thermoplastic TPU, PU adhesives, PU casting resins, PU elastomers or PU foams.

Claims

1. A process for producing polymeric carbodiimides of formula (I)
R.sup.tR.sup.2(NCNR.sup.2).sub.mR.sup.1(I), in which: m represents an integer from 2 to 500, R.sup.2=C.sub.1-C.sub.18-alkylene, C.sub.5-C.sub.18-cycloalkylene, arylene, C.sub.7-C.sub.18 alkylarylene and/or C.sub.7-C.sub.18-aralkylene, and R.sup.1=NCO, NCNR.sup.2, NHCONHR.sup.4, NHCONHR.sup.2, NHCONR.sup.4R.sup.5 or NHCOOR.sup.6, wherein in R.sup.1: independently of one another, R.sup.4 and R.sup.5 are identical or different and represent a C.sub.1-C.sub.6-alkyl, C.sub.6-C.sub.10-cycloalkyl or C.sub.7-C.sub.18-aralkyl radical, and R.sup.6 has one of the definitions of R.sup.1 or represents a polyester or a polyamide radical or (CH.sub.2).sub.hO[(CH.sub.2).sub.kO].sub.gR.sup.7, where: h=1-3, k=1-3, g=0-12; and R.sup.7=H or C.sub.1-C.sub.4-alkyl, the process comprising carbodiimidizing isocyanate-containing compounds of formula (II)
OCNR.sup.2R.sup.1(II), optionally in the presence of isocyanate-containing compounds of formula (III)
OCNR.sup.2(III), wherein R.sup.1 and R.sup.2 are as defined above, in the presence of at least one basic cesium salt, and at a temperature of 120 C. to 220 C.

2. The process as claimed in claim 1, wherein the basic cesium salt is cesium carbonate and/or cesium alkoxide.

3. The process as claimed in claim 1, wherein the isocyanate-containing compounds comprise: any of (IIa), (IIb), (IIc) or (IId) alone, or (IIa) and (IIb) together, wherein these compounds correspond to the following formulae ##STR00004##

4. The process according to claim 1, wherein the basic cesium salt is employed in a concentration of 0.1 to 20 wt %, based on the overall mixture.

5. The process according to claim 1, further comprising, following the carbodiimidization, filtering off and/or removing the basic cesium salts by extraction using a solvent, preferably water and/or alcohol.

6. The process as claimed in claim 1, further comprising conducting the carbodiimidization in the presence of a solvent.

7. The process according to claim 6, wherein the solvent comprises at least one C.sub.7-C.sub.22-alkylbenzene.

8. A Stabilizer comprising at least 90% of the polymeric carbodiimides according to claim 1 and less than 1 ppm of organic phosphorus compounds.

9. A process for producing polyurethanes, the process comprising one of: reacting polyester polyols with isocyanates in the presence of the polymeric carbodiimides produced according to claim 1, or reacting polyester polyols with isocyanates, and following the reaction, adding the polymeric carbodiimides produced according to claim 1.

10. The process according to claim 9, wherein the polymeric carbodimide is employed in an amount of 0.1 to 2 wt %, preferably 0.5 to 1.5 wt %, particularly preferably 1.0 to 1.5 wt %, based on the overall mixture.

11. The process according to claim 9, wherein the polymeric carbodiimide is employed in an amount of 1.0 to 1.5 wt %, based on the overall mixture.

12. Use of the polymeric carbodiimides as claimed in claim 8 for hydrolysis protection, preferably in polyurethanes.

13. The process as claimed in claim 1, wherein: m represents an integer from 3 to 20; R.sup.2=C.sub.7-C.sub.18 alkylarylene and/or C.sub.7-C.sub.18-aralkylene; and the temperature is 160 C. to 200 C.

14. The process as claimed in claim 13, wherein: m represents an integer from 4 to 10; the isocyanate-containing compounds comprise: any of (IIa), (IIb), (IIc) or (IId) alone, or (IIa) and (IIb) together, wherein these compounds correspond to the following formulae ##STR00005## the basic cesium salt is employed in a concentration of 0.1 to 20 wt %, based on the overall mixture.

15. The process as claimed in claim 14, wherein: the basic cesium salt is cesium methoxide, and the basic cesium salt is employed in a concentration of 2 to 4 wt %, based on the overall mixture; and the isocyanate-containing compounds of formula (II) are converted in the presence of the isocyanate-containing compounds of formula (III) at a temperature of 180 C. to 200 C.

Description

EXEMPLARY EMBODIMENTS

Example 1

[0058] Production of a polymeric carbodiimide by reaction of the compound of formula (IIc) with cesium carbonate (inventive).

Example 2

[0059] Production of a polymeric carbodiimide by reaction of the compound of formula (IIc) with potassium methoxide (comparative).

Example 3

[0060] Production of a polymeric carbodiimide by reaction of the compound of formula (IIc) with potassium carbonate (comparative).

Example 4

[0061] Production of a polymeric carbodiimide by reaction of the compound of formula (IIc) with sodium carbonate (comparative).

Example 5

[0062] Production of a polymeric carbodiimide by reaction of the compound of formula (IIc) phospholene oxide (comparative).

General Production Procedure for Examples 1-5

[0063] 30 g of the isocyanate-containing compound of formula (IIc) were weighed into a 100 mL three-necked flask equipped with an internal thermometer, a reflux cooler and a protective gas inlet and subsequently for examples 1 to 4 0.9 g (3 wt %) and for example 5 0.03 g (0.1 wt %) of the respective catalyst according to table 1 were added. During the heating phase a light argon stream was passed over the vapor phase. The protective gas was turned off on commencement of CO.sub.2 evolution. The mixture was allowed to stir vigorously for 3 h at 190 C. (example 1 and 5) or 12 h at 190 C. (example 2) or 6 h at 190 C. (examples 3 and 4) and the reaction mixture, once cooled to about 100 C., was subsequently filtered.

TABLE-US-00001 TABLE 1 Carbodiimide synthesis yields T Duration Example Catalyst [ C.] [h] Carbodiimide Isocyanate Byproducts 1 cesium 190 3 >98% <1.0% <1.0% carbonate 2 k-methoxide 190 12 <60% >30% >5.0% 3 potassium 190 6 <1% 99% n.d. carbonate 4 sodium 190 6 0% 100% carbonate 5 phospholene 190 3 >95% <1.0% >1.0% oxide

[0064] Surprisingly, the cesium carbonate shows a high catalyst activity for the carbodiimidization and resulted in yields of over 98% after only 3 hours of reaction time and is accordingly markedly better than the synthesis via K methoxide or K or Na carbonate.

[0065] In addition the inventive catalyst may be removed simply by filtration whereas in the case of catalysis by a phosphorus-containing catalyst (methylphospholene oxide) a costly and complex distillation under vacuum must be performed to effect removal.

Production of Ester-Based PU Hotmelts and Characterization Thereof

Example 6

[0066] A hotmelt based on linear copolyester having primary hydroxyl functions and an average molecular weight of 3500 g/mol (Dynacoll 7360) was produced and additized as per the following table:

[0067] Carbodiimides employed were: [0068] (A) 2 wt % of polymeric carbodiimide of formula (I) where m=4-5 and R.sup.1=NHCOOR.sup.6, wherein R.sup.6 is a polyethylene glycol radical, produced by catalysis with cesium carbonate (inventive, as per example 1 but end-functionalized with polyethylene glycol), [0069] and

##STR00002##

[0070] Characterization: no organic phosphorus compound detectable (<1 ppm phosphorus) [0071] (B) 2 wt % of polymeric carbodiimide of formula (I) where m=4-5 and R.sup.1=NHCOOR.sup.6, wherein R.sup.6 is a polyethylene glycol article, produced by catalysis with methylphospholene oxide (comparative, see also process from WO-A 2005/111136), and

##STR00003## [0072] Characterization: residues of phosphorus detectable.

[0073] All reported quantities are in wt % based on the overall mixture.

[0074] The hotmelt was produced as follows:

[0075] The linear copolyester having primary hydroxyl functions was initially evacuated for 30 minutes at 120 C. This was followed by addition of 11.67 wt % of diphenylmethane diisocyanate (MDI) based on the overall formulation and the mixture was reacted for 60 minutes at 120 C. to afford the polyurethane adhesive.

[0076] The respective carbodiimides reported in table 2 additives were then incorporated into the hotmelt and an exposure time to the additives of 1 hour was ensured.

[0077] The thus produced and additized hotmelts were subjected to thermoageing at 130 C. for 48 hours in a cartridge. The hotmelt was filled into an aluminium cartridge (light- and moisture-tight) and aged in a circulating air oven for 48 hours at 130 C.

[0078] The samples was visually evaluated after ageing.

[0079] The results of the measurements are compiled in table 2:

TABLE-US-00002 TABLE 2 Carbodiimide Characterization Example 6A (inv.) No foam formation, very little bubble formation, if any, Example 6B (C) Foam/severe bubble formation (C) = comparative example; (inv.) = inventive

SUMMARY

[0080] These tests show that use of the phosphorus-free carbodiimide according to the invention does not result in any appreciable disruptive side effects in terms of foaming. On the contrary, carbodiimides catalyzed with phospholene oxide and still containing traces of organophosphorus compounds exhibit the reported disadvantages of foam formation.