Process for producing aqueous polyurethane formulations

Abstract

A process for producing aqueous polyurethane preparations comprises the steps of: A) providing a solution in at least one solvent of at least one polymeric polyurethane bearing ionizable groups, B) using at least one neutralizing agent to partially neutralize the at least one polymeric polyurethane bearing ionizable groups, C) dispersing the at least one polymeric polyurethane bearing ionizable groups in water, D) optionally removing the at least one solvent, E) optionally diluting the mixture after solvent removal with further water, F) admixing neutralizing agent after solvent removal.

Claims

1. A process for producing an aqueous polyurethane preparation, which comprises B) partially neutralizing with at least one neutralizing agent an at least one polymeric polyurethane bearing ionizable groups present in a solution comprising at least one solvent, such that from 1 to 60 mol % of the ionizable groups present in the polymeric polyurethane are neutralized, C) dispersing the partially neutralized at least one polymeric polyurethane bearing ionizable groups in water, D) optionally removing the at least one solvent, E) optionally diluting the dispersion after solvent removal, whether or not carried out, with further water, F) admixing further neutralizing agent after solvent removal, whether or not carried out, to the dispersion to neutralize additional ionizable groups.

2. The process according to claim 1 wherein said C) to F) are carried out in the stated order.

3. The process according to claim 1 wherein the at least one ionizable group is a carboxyl group or is a sulfonic acid group.

4. The process according to claim 1 wherein the polymeric polyurethane comprises at least one polyol bearing carboxyl groups.

5. The process according to claim 1 wherein the at least one neutralizing agent is an organic base.

6. The process according to claim 1 wherein the at least one neutralizing agent is an amine.

7. The process according to claim 1 wherein the at least one neutralizing agent is triethylamine.

8. The process according to claim 1 wherein the solvent comprises acetone.

9. A method for manufacturing leather comprising applying a polyurethane dispersion obtained according to claim 1 to the leather.

10. The method according to claim 9 wherein the dispersion is applied in adhesion primer amounts.

Description

EXAMPLES

Measurements

(1) NCO contents were determined volumetrically to DIN-EN ISO 11909.

(2) Solids contents were determined to DIN-EN ISO 3251.

(3) Particle sizes were determined by dynamic light scattering in a Malvern Zetasizer APS.

(4) Reported viscosities were determined by rotary viscometry to DIN 53019 at 23 C. at 500/s using a rotary viscometer from Anton Paar Germany GmbH, Ostfildern, DE.

(5) Abbreviations

(6) DBTL dibutyltin dilaurate

(7) DMPA dimethyloipropionic acid

(8) Lupranol 1000 polypropylene oxide of molecular weight 2000 g/mol

(9) TDI tolylene diisocyanate, 20% 2,6-isomer, 80% 2,4-isomer

(10) TEA triethylamine

Comparative Example 1

(11) A mixture of 87.1 g (0.50 mol) of TDI, 400 g (0.20 mol) of Lupranol 1000, 40.2 g (0.30 mol) of DMPA and 0.2 g of DBTL was reacted at 95 C. for 5.5 hours. This was followed by cooling to 30 C. and determination of the NCO group content, which was found to be 0.26 wt %, based on the reaction mixture. The reaction mixture was then diluted with 400 g of acetone and admixed with 29.1 g (0.29 mol, corresponds to 96 mol %, based on DMPA) of TEA and also with 1750 g of water by stirring.

(12) To distill the acetone-containing dispersion, the temperature was raised to 50 C. and the pressure gradually reduced to 100 mbar.

(13) The distillation could not be carried out because of severe foaming, requiring the addition of 5 drops of Silicone Antifoam defoamer from Aldrich. Thereafter, the distillation could be carried out within 1.5 hours.

(14) This gave 2380 g of a finely divided PUD having a solids content of 23.4 wt %.

Example 2

(15) A mixture of 87.1 g (0.50 mol) of TDI, 400 g (0.20 mol) of Lupranol 1000, 40.2 g (0.30 mol) of DMPA and 0.2 g of DBTL was reacted at 95 C. for 5.5 hours. This was followed by cooling to 30 C. and determination of the NCO group content, which was found to be 0.26 wt %, based on the reaction mixture. The reaction mixture was then diluted with 400 g of acetone and admixed with 12.1 g (0.12 mol, corresponds to 40 mol %, based on DMPA) of TEA and also with 1250 g of water by stirring.

(16) To distill the acetone-containing dispersion, the temperature was raised to 50 C. and the pressure gradually reduced to 100 mbar.

(17) This gave 1730 g of a finely divided PUD having a solids content of 31.2 wt %.

(18) Only minimal foaming occurred during the distillation, the distillation could be carried out within 1.5 hours. There was no need to use defoamers.

(19) The distilled dispersion was admixed with 17.7 g (0.17 mol, corresponds to 56.6 mol %, based on DMPA). The TEA overall content was accordingly 29.8 g (0.29 mol, corresponds to 96 mol % based on DMPA).

(20) This gave 2440 g of a finely divided PUD having a solids content of 22.8 wt %.

(21) TABLE-US-00001 Comparative example 1 Example 2 solids content after addition of TEA (wt %) 23.4 particle size after addition of TEA (nm) 17.3 viscosity after addition of TEA (mPas at 500/s, 56 25 C.) solids content after first addition of TEA 31.2 (wt %) particle size after first addition of TEA (nm) 110 viscosity after first addition of TEA (mPas at 11 500/s, 23 C.) solids content after second addition of TEA 22.8 (wt %) particle size after second addition of TEA (nm) 13.5 viscosity after second addition of TEA 43 (mPas at 500/s, 23 C.)

(22) The example shows that, by virtue of the process according to the present invention, only 73% of the mass has to be transported and stored following the first neutralization than is obtained according to the comparative example. The second neutralization gives a product which is fully and entirely equivalent to that obtained according to the prior art.

(23) The reactor has an improved space yield in processes according to the present invention, and the use of defoamer can be eschewed.