CONTINUOUS DILUTION OF POLYISOCYANATES

Abstract

The invention relates to a process for producing a polyisocyanate composition comprising addition of at least one isocyanate-inert solvent to at least one polyisocyanate, characterized in that the addition of the solvent is carried out in one or more stages and at least one of these stages is performed as a continuous dilution. The invention further relates to the polyisocyanate compositions obtainable by the process, to the use of the polyisocyanate compositions, to a two-component system containing the polyisocyanate composition and to composite systems produced with the two-component system.

Claims

1. A process for producing a polyisocyanate composition comprising addition of at least one isocyanate-inert solvent to at least one polyisocyanate, wherein the addition of the solvent is carried out in one or more stages and at least one of these stages is performed as a continuous dilution.

2. The process as claimed in claim 1, wherein the polyisocyanate is based on at least one aliphatic, cycloaliphatic, araliphatic or aromatic diisocyanate.

3. The process as claimed in claim 1, wherein the polyisocyanate is based on tolylene diisocyanate.

4. The process as claimed in claim 1, wherein the addition of the solvent is carried out in at least two stages, wherein the first stage is performed as a continuous dilution.

5. The process as claimed in claim 1, wherein a solids content of 30% to 90% by weight is established in the first stage.

6. The process as claimed in claim 4, wherein a solids content of 10% to 80% by weight is established in the second stage, wherein the solids content established in the first stage is reduced by at least 15% by weight in the second stage.

7. The process as claimed in claim 3, wherein the polyisocyanate is produced from tolylene diisocyanate by (i) reaction of tolylene diisocyanate to form a polyisocyanate and (ii) removal of the unconverted tolylene diisocyanate down to a residual content of monomeric tolylene diisocyanate of 0.5% by weight, based on the total weight of the polyisocyanate composed of tolylene diisocyanate.

8. The process as claimed in claim 7, wherein the removal of the unconverted tolylene diisocyanate in step (ii) is carried out by means of at least one thermal separation process.

9. The process as claimed in claim 8, wherein the at least one thermal separation process is performed at a heating medium temperature of 140 C. to 235 C.

10. The process as claimed in claim 7, characterized wherein the polyisocyanate composed of tolylene diisocyanate is an isocyanate-containing polyisocyanurate composed of tolylene diisocyanate, wherein the reaction of tolylene diisocyanate in step (i) to form isocyanurate groups is carried out in the presence of at least one catalyst and terminated at a content of isocyanate groups of 30% to 46% by weight by addition of at least one catalyst poison.

11. The process as claimed in claim 7, wherein steps (i) and (ii) are performed in the presence of 0% to <1% by weight of distillation aids that are inert under distillation conditions, liquid and have a boiling point at least 50 C. higher than that of tolylene diisocyanate and/or 0% to <1% by weight based on the total weight of the compounds employed in step (i) and (ii) of compounds comprising one or more hydroxyl groups.

12. The process as claimed in claim 7, wherein addition of the at least one isocyanate-inert solvent to the at least one polyisocyanate is followed in a further step by addition of at least one polyisocyanate composition composed of tolylene diisocyanate which is at least one polyisocyanurate composition composed of tolylene diisocyanate and/or at least one polyurethane composition composed of tolylene diisocyanate, and optionally by addition of one or more assistant and additive substances.

13. A polyisocyanate composition produced by the process of claim 1, wherein the polyisocyanate is based on one selected from the group consisting of 1,5-diisocyanatopentane (PDI), 2-methyl-1,5-diisocyanatopentane, 1,5-diisocyanato-2,2-dimethylpentane, 1,10-diisocyanatodecane, 2,4- and 2,6-diisocyanato-1-methylcyclohexane, 2,4-diisocyanatodicyclohexylmethane, 1-isocyanato-1-methyl-4(3)isocyanatomethylcyclohexane, bis(isocyanatomethyl)norbornane, 1,3- and 1,4-bis(isocyanatomethyl)benzene (XDI), 1,3- and 1,4-bis(2-isocyanato-prop-2-yl)benzene (TMXDI), tolylene diisocyanate (TDI), 2,4- and 4,4-diisocyanatodiphenylmethane (MDI), 1,5-diisocyanatonaphthalene, 1,3- and 1,4-phenylene diisocyanate, and any mixtures of these diisocyanates.

14. In a process for preventing cloudiness in a polyisocyanate composition, the improvement comprising inclusion of process according to claim 1.

15. In a process for production of an adhesive coating material, the improvement comprising including the polyisocyanate composition as claimed in claim 13 as a crosslinking agent.

16. A two-component system comprising an isocyanate component A) containing at least one polyisocyanate composition as claimed in claim 13 and an isocyanate-reactive component B) containing at least one isocyanate-reactive compound.

17. A composite produced by curing the two-component system as claimed in claim 16 applied to at least one substrate.

Description

EXAMPLES

[0070] All reported percentages are based on weight unless otherwise stated.

[0071] The NCO contents were determined by titrimetry according to DIN EN ISO 11909:2007-05.

[0072] The residual monomer contents were measured according to DIN EN ISO 10283:2007-11 by gas chromatography with an internal standard.

[0073] Cloudiness was determined according to DIN EN ISO 7027-1:2016.

Example 1 (Noninventive)

[0074] 1500 g of a tolylene diisocyanate isomer mixture composed of about 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate are initially charged in a 2 L flask at 80 C. 0.52 g of a Mannich base (bisphenol/formaldehyde/dimethylamine 25% in butyl acetate/xylene 19:56) is then added over 2 hours with stirring while maintaining a temperature of 78-82 C. Once an NCO content of 40.4% is achieved 1 g of dibutyl phosphate is added to terminate the reaction. The excess diisocyanate is then continuously removed from the thus obtained crude product by distillation at temperatures of 180 C. and a pressure of 0.05 mbar. The obtained hot resin (370 g) is conveyed directly to 863 g of boiling ethyl acetate in a stirred flask fitted with a reflux cooler using a pump which corresponds to a one-stage, discontinuous dilution from 100% solids content to 30% solids content. This affords a solution having the following properties:

[0075] NCO: 7.1%

[0076] Monomer content: 0.08%

[0077] Cloudiness: 21 NTU

Example 2 (Inventive)

[0078] 1500 g of a tolylene diisocyanate isomer mixture composed of about 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate are initially charged in a 2 L flask at 80 C. 0.52 g of a Mannich base (bisphenol/formaldehyde/dimethylamine 25% in butyl acetate/xylene 19:56) is then added over 2 hours with stirring while maintaining a temperature of 78-82 C. Once an NCO content of 40.4% is achieved 1 g of dibutyl phosphate is added to terminate the reaction. The excess diisocyanate is then continuously removed from the thus obtained crude product by distillation at temperatures of 180 C. and a pressure of 0.05 mbar. The hot resin discharged from the distillation is conveyed directly at 105 g/h into a stirred 500 ml 4-necked flask fitted with a reflux cooler using a pump. 245 g/h of ethyl acetate are simultaneously added from a dropping funnel and the continuously diluted product is continuously transferred at 350 g/h into a cooled receiver flask via a submerged riser tube using a pump. The contents of the 4-necked flask remain constant at about 400 g and have a temperature of about 80 C. This affords a solution having a solids content of 30% and the following properties:

[0079] NCO: 7.0%

[0080] Monomer content: 0.03%

[0081] Cloudiness: 12 NTU

Example 3 (Inventive)

[0082] 1500 g of a tolylene diisocyanate isomer mixture composed of about 80% 2,4-tolylene diisocyanate and 20% 2,6-tolylene diisocyanate are initially charged in a 2 L flask at 80 C. 0.52 g of a Mannich base (bisphenol/formaldehyde/dimethylamine 25% in butyl acetate/xylene 19:56) is then added over 2 hours with stirring while maintaining a temperature of 78-82 C. Once an NCO content of 40.4% is achieved 1 g of dibutyl phosphate is added to terminate the reaction. The excess diisocyanate is then continuously removed from the thus obtained crude product by distillation at temperatures of 180 C. and a pressure of 0.05 mbar. The hot resin discharged from the distillation is conveyed directly at 105 g/h into a stirred 500 ml 4-necked flask fitted with a reflux cooler using a pump. 57 g/h of ethyl acetate are simultaneously added from a dropping funnel and the continuously diluted product is continuously transferred at 162 g/h into a cooled receiver flask via a submerged riser tube using a pump. The contents of the 4-necked flask remain constant at about 400 g and have a temperature of about 80 C.

[0083] The contents of the receiver flask are subsequently diluted to 30% solids content with ethyl acetate in a discontinuous step. This affords a solution having the following properties:

[0084] NCO: 7.0%

[0085] Monomer content: 0.05%

[0086] Cloudiness: 2 NTU