Process for preparing liquid compositions of etherified melamine formaldehyde resins

Patent metadata

Field	Value
Publication number	US-11739235-B2
Application number	US-201716472041-A
Country	US
Kind code	B2
Filing date	Dec 20, 2017
Priority date	Dec 21, 2016
Publication date	Aug 29, 2023
Grant date	Aug 29, 2023

Abstract

The present invention relates to a process for preparing liquid compositions of etherified melamine formaldehyde resins, namely melamine formaldehyde resins etherified with a primary C 1 -C 6 -alkanol, which have low formaldehyde contents. The invention also relates to such liquid compositions of etherified melamine formaldehyde resins having a content of free formaldehyde of less than 0.3% by weight. The liquid compositions of etherified melamine formaldehyde resins are useful as crosslinking agents in coating compositions.

First claim

We claim:

1. A process for preparing a liquid composition of an etherified melamine formaldehyde resin, the process comprising:
i. reacting melamine, formaldehyde and a primary C 1 -C 6 -alkanol at least temporarily under acidic conditions in the presence of an excess of the primary C 1 -C 6 -alkanol, which means that a molar amount of the primary C 1 -C 6 -alkanol employed in i. exceeds a molar amount of formaldehyde employed in i., to obtain a mixture of the etherified melamine formaldehyde resin, water, unreacted formaldehyde and unreacted primary C 1 -C 6 -alkanol;
ii. distilling off at least 50% of the unreacted primary C 1 -C 6 -alkanol, unreacted formaldehyde and water comprised in the reaction mixture obtained in i., to obtain a concentrated composition of the etherified melamine formaldehyde resin;
iii. diluting the concentrated composition of the etherified melamine formaldehyde resin by addition of at least one solvent; the at least one solvent being selected from the group consisting of water, a primary C 1 -C 6 -alkanol, a solvent B, and mixtures thereof, where the solvent B is selected from the group consisting of a C 1 -C 2 -alkoxy-C 2 -C 4 -alkanol, a secondary C 3 -C 6 -alkanol, a tertiary C 4 -C 6 -alkanol, an aliphatic monoketone having 3 to 8 carbon atoms, a cyclic monoketone having 5 to 8 carbon atoms, a C 1 -C 6 -alkyl ester of a C 1 -C 4 -alkanoic acid, a C 1 -C 2 -alkoxy-C 2 -C 4 -alkyl ester of a C 1 -C 4 -alkanoic acid and an aromatic hydrocarbon;
wherein in iii. both of the following measures a) and b) are taken, where measure a) is performed first and then measure b) is taken:
a) adding water or a mixture of water and at least one organic solvent, which is selected from the group consisting of water-miscible organic solvents B as defined herein and the primary C 1 -C 6 -alkanol and mixtures thereof, to the concentrated composition of the etherified melamine formaldehyde resin obtained in ii. and removing at least a major portion of the added water by evaporation under reduced pressure;
b) subsequently adding at least one solvent thereby diluting the concentrated composition of the etherified melamine formaldehyde resin in iii., where the at least one solvent comprises at least 50% by weight, based on a total weight of solvent used, of at least one organic solvent B.

2. The process of claim 1 , wherein the amount of water, which is added to the concentrated composition of the etherified melamine formaldehyde resin, is from 0.5 to 15% by weight of the concentrated composition of the etherified melamine formaldehyde resin.

3. The process of claim 1 , wherein at least 80% of the water, which has been added to the concentrated composition of the etherified melamine formaldehyde resin, is removed by evaporation.

4. The process of claim 1 , wherein the at least one solvent used for diluting the concentrated composition of the etherified melamine formaldehyde resin is an organic solvent comprising at least 50% by weight, based on a total weight of solvent used for dilution, of at least one organic solvent selected from the group consisting of an aliphatic monoketone having 3 to 8 carbon atoms, a cyclic monoketone having 5 to 8 carbon atoms, a C 1 -C 6 -alkyl ester of a C 1 -C 4 -alkanoic acid, a C 1 -C 2 -alkoxy-C 2 -C 4 -alkyl ester of a C 1 -C 4 -alkanoic acid and a methyl substituted benzene.

5. The process of claim 4 , wherein the at least one solvent used for diluting the concentrated composition of the etherified melamine formaldehyde resin comprises at least 50% by weight, based on the total weight of solvent used for dilution, of at least one organic solvent selected from the group consisting of a C 2 -C 6 -alkyl ester of acetic acid, a methyl substituted benzene and a C 1 -C 2 -alkoxy-C 2 -C 4 -alkyl ester of acetic acid.

6. The process of claim 1 , where in i) formaldehyde is used in an amount of from 2.5 to 12 mol per 1 mol of melamine.

7. The process of claim 1 , where in i) the C 1 -C 6 -alkanol is used in an amount of from 5.0 to 50 mol per 1 mol of melamine.

8. The process of claim 1 , where i) is performed at a pH in a range of from pH 2.0 to pH 6.0.

9. The process of claim 1 , where i) is performed by heating a mixture of melamine, formaldehyde and the excess of the primary C 1 -C 6 -alkanol under acidic conditions.

10. The process of claim 1 , where i) comprises
i.1) heating a mixture of melamine, formaldehyde and a primary C 1 -C 6 -alkanol under acidic conditions, to obtain a first reaction mixture;
i.2) distilling off at least a major portion of volatiles comprised by the first reaction mixture, to obtain a concentrated reaction mixture;
i.3) adding primary C 1 -C 6 -alkanol to the concentrated reaction mixture and heating the thus obtained mixture under acidic conditions, to obtain a mixture of the etherified melamine formaldehyde resin, water and primary C 1 -C 6 -alkanol.

11. The process of claim 1 , where in ii. the unreacted primary C 1 -C 6 -alkanol, unreacted formaldehyde and water are distilled off until a solid content of the concentrated composition is at least 80% by weight.

12. The process of claim 1 , where in iii. the concentrated composition is diluted until a solid content of the liquid composition of the etherified melamine formaldehyde resin is in a range of from 50 to 98% by weight.

Assignees

• Basf Se

Inventors

• Weinkoetz Stephan
• Weilacher Dieter
• Scherr Guenter
• Steinbeck Jens
• Fuchs Evelyn
• Strohmeier Ralf
• Flojhar Daniel

Classifications

• C09D161/34 Primary

  Condensation polymers of aldehydes or ketones with monomers covered by at least two of the groups C09D161/04, C09D161/18 and C09D161/20 · CPC title

• C08G14/02

  of aldehydes · CPC title

• C09D7/20

  Diluents or solvents · CPC title

• C08G12/32 Primary

  Melamines · CPC title

• C08G12/427 Primary

  Melamine · CPC title