BIS[3-ISOPROPENYL-ALPHA,ALPHA-DIMETHYLBENZYL]CARBODIIMIDE, PRODUCTION METHODS, AND USE OF SAID COMPOUND

Abstract

The present invention relates to novel processes for producing bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide, to the thus-produced bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide and to the use thereof as a hydrolysis inhibitor in polyurethane (PU)-based systems, preferably thermoplastic TPU, PU adhesives, PU casting resins, PU elastomers or PU foams.

Claims

1. A process for producing bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide, the process comprising cabodiimidizing 3-isopropenyl-,-dimethylbenzylisocyanate in the presence of 0.1-20 wt % of basic cesium salts at a temperature of 160 C. to 220 C.

2. The process as claimed in claim 1, wherein the basic cesium salts comprise cesium carbonate and/or cesium alkoxide, preferably cesium methoxide and/or cesium ethoxide.

3. The process as claimed in claim 1, further comprising filtering off the basic cesium salts following the carbodiimidization.

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

5. The process as claimed in claim 4, wherein the solvent comprises mono-, di-, tri- or polyalkyl-substituted benzenes and/or dibenzenes where alkyl=C.sub.1-C.sub.3.

6. The process as claimed in claim 5, wherein the alkyl-substituted benzenes are xylenes.

7. A bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide obtained by the process as claimed in claim 1.

8. A stabilizer comprising at least 90 wt % of the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide as claimed in claim 7, and not more than 1 ppm of heterocyclic phosphorus compounds.

9. A process for producing polyurethanes, the process comprising contacting polyols with diisocyanates in the presence of the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide as claimed in claim 7.

10. The process as claimed in claim 9, wherein the polyols, the diisocyanates, and the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide are mixed together to form a mixture, and the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide is present in the mixture in an amount of 0.1 to 2 wt %, preferably 0.5 to 1 wt %, based on the total mixture.

11. The process as claimed in claim 10, further comprising metering the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide into the mixture in liquid form, continuously or batchwise at a temperature of 20-50 C., particularly preferably 25-35 C.

12. (canceled)

13. The process according to claim 1, wherein the basic cesium salts are present at a concentration of 0.5 to 10 wt %, and the temperature is 180 C. to 210 C.

14. The process according to claim 1, wherein the process comprises: carbodiimidizing 3-isopropenyl-,-dimethylbenzylisocyanate in the presence of: 0.1-20 wt % of cesium carbonate and/or cesium alkoxide, and a solvent, at a temperature of 160 C. to 220 C. for a period of time sufficient for carbodiimidization of the 3-isopropenyl-,-dimethylbenzylisocyanate; and filtering off the cesium carbonate and/or cesium alkoxide following the carbodiimidization.

15. The process according to claim 14, wherein: the carbodiimidizing is in the presence of cesium methoxide and/or cesium ethoxide; the solvent is at least one xylene; the basic cesium salts are present at a concentration of 1 to 5 wt %; and the temperature is 190 C. to 200 C.

Description

EXEMPLARY EMBODIMENTS

Example 1

[0058] Inventive production of bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide based on the isocyanate 3-isopropenyl-,-dimethylbenzylisocyanate with cesium carbonate.

Examples 2-6

[0059] Production of bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide based on the isocyanate 3-isopropenyl-,-dimethylbenzylisocyanate with other catalysts as comparative examples.

General Production Procedure for Examples 1-5

[0060] 30 g of 3-isopropenyl-,-dimethylbenzylisocyanate were weighed into a 100 mL of three-necked flask fitted with an internal thermometer, reflux cooler and protective gas inlet and 0.6 g (2 wt %) of the respective catalyst as per table 1 were then added. An argon protective gas stream was passed over the vapor phase in the heating phase. The protective gas was turned off on commencement of CO.sub.2 evolution. The mixture was subjected to vigorous stirring for 3.5 h at 195 C. (example 1-5) and the reaction mixture was then filtered once it had cooled to about 100 C. The yield was determined by .sup.1H NMR spectroscopy (400 MHz, CDCl.sub.3).

[0061] Example 6 corresponds to example 1 from WO-A 2005/111136.

TABLE-US-00001 TABLE 1 Yields from the synthesis of the carbodiimide based on the isocyanate 3-isopropenyl-,-dimethylbenzylisocyanate (by NMR). T carbodiimide isocyanate byproduct example catalyst [ C.] [%] [%] [%] 1 (inv.) cesium 195 93 0 7 carbonate 2 (c) strontium 195 0 100 0 carbonate 3 (c) potassium 195 0 100 0 carbonate 4 (c) lithium 195 0 100 0 carbonate 5 (c) calcium 195 0 100 0 carbonate 6 (c) phospholene 180 37 not not oxide determined determined c = comparative example, inv. = inventive

[0062] As is apparent from table 1 the alkali metals of lithium and potassium and the alkaline earth metal carbonates of calcium and strontium have proven completely inutile in relation to use as catalyst for the carbodiimidization of 3-isopropenyl-,-dimethylbenzylisocyanate into bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide.

[0063] By contrast, cesium carbonate surprisingly exhibits a high catalyst activity for the carbodiimidization and results in yields of above 90% and is thus markedly better than the synthesis via phospholene oxide.

[0064] In addition the catalyst according to the invention may be removed simply by filtration while in the case of phospholene oxide as catalyst removal must be effected via a costly and inconvenient distillation under vacuum and the yield is therefore reduced further by this workup.

Hydrolysis Inhibition in TPU

[0065] To this end 1.0 wt %/1.5 wt % of the carbodiimide according to the invention (CDI inv) and of the commercially available carbodiimides:

CDI 1=a monomeric aromatic carbodiimide substituted with alkyl groups,
CDI 2=a polymeric aromatic carbodiimide,
were incorporated into the commercially available polyester-based thermoplastic polyurethane elastomer (TPU/Desmopan 2587A) by extrusion using a twin-screw extruder.

[0066] Injection molding processes are used to produce test specimens therefrom which were post-heated for 16 h at 80 C. Said specimens were then stored in water at 80 C. and the tensile strength measured at regular intervals.

[0067] Table 2 shows the percentage relative tensile strength starting at 100% at day 0.

TABLE-US-00002 TABLE 2 CDI CDI reference extruded CDI 1 CDI 2 (inv.) (inv.) material 1x 1.5% 1.5% 1.5% 1.0% day 0 100 100 100 100 100 100 day 5 82 85 83 94 100 n.d. day 8 63 62 n.d. n.d. 91 n.d. day 14 18 18 n.d. n.d. 86 n.d. day 19 7 7 79 90 83 n.d. day 26 0 0 76 88 82 n.d. day 39 72 88 82 n.d. day 45 63 82 76 91 day 53 57 88 73 n.d. day 57 42 86 76 n.d. day 63 21 64 76 n.d. day 67 0 13 73 n.d. day 80 n.d. 84 day 94 n.d. 80 day 98 68 n.d. day 105 71 n.d. day 112 66 n.d. day 118 n.d. 81 day 140 61 n.d. day 143 n.d. 73 day 171 n.d. 76 day 192 n.d. 62 day 196 .sup.55. *) n.d. day 213 n.d. 5 c = comparative example, inv. = inventive, n.d. = not determined, *) no test specimens remaining

[0068] The results in table 2 show that the bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide produced by the process according to the invention exhibits exceptional hydrolysis inhibition activity in thermoplastic PU (TPU) and is superior to the prior art carbodiimides.

Production and Color Stability of Ester-Based PU Hotmelts

Example 7

[0069] A hotmelt based on Dynacoll 7360, a linear copolyester having primary hydroxyl functions and an average molecular weight of 3500 g/mol which is obtainable from Evonik AG, was produced and additized as follows:

(A) 2 wt % of bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide produced by the process according to the invention,
(B) 2 wt % of bis[3-isopropenyl-,-dimethylbenzyl]carbodiimide produced by the process from WO-A 2005/111136.

[0070] All reported amounts are in wt %.

[0071] The hotmelt is produced as follows:

[0072] The copolyester Dynacoll7360 is initially evacuated for 30 minutes at 120 C. 11.67 wt % of diphenylmethanediisocyanate (MDI) based on the total formulation is then added and the mixture is reacted for 60 minutes at 120 C.

[0073] The additives were then incorporated into the hot melt and an exposure time to the additives of 1 hour was ensured.

[0074] The thus produced and additized hot melts were subjected to thermoageing at 130 C. for 48 hours in a cartridge. The hot-melt was filled into an aluminium cartridge (light- and moisture-tight) and aged in a circulating air oven for 48 hours at 130 C.

[0075] After the aging, the color and the foaming behavior of the samples was visually evaluated.

[0076] The results of the measurements are compiled in table 3:

TABLE-US-00003 TABLE 3 carbodiimide color foaming behavior example 7A (inv.) colorless to very no foam, very little, if any, slightly yellow bubble formation example 7B (c) reddish-yellow to foam formation/severe reddish-brown bubble formation c = comparative example; inv. = inventive

SUMMARY

[0077] These tests show that use of the carbodiimide according to the invention does not result in any notable disruptive side effects in terms of discoloration and foam formation. In comparison, carbodiimides produced by a synthesis catalyzed with phospholene oxide and still containing traces of organophosphorus compounds exhibit the reported disadvantages of discoloration and foam formation.