# US 2014/0155599 A1 · Process for the preparation of condensation products of melamine

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- Number: US 2014/0155599 A1
- Document ID: US20140155599A1
- Status: Published application
- Kind: A1
- Application number: 14/007,075
- Filed: 2012-03-27
- Published: 2014-06-05
- Earliest claimed: 2011-03-28
- Assignees: Dsm IP Assets B.V.
- Inventors: Christiaan Johannes Cornelis Stoelwinder; Gerard Jan Kwant
- Web page: https://patentgrep.com/patent/US20140155599A1

## CPC

- C07D 251/54: Three nitrogen atoms
- C07D 251/70: Other substituted melamines
- C07D 403/12: linked by a chain containing hetero atoms as chain links
- C07D: HETEROCYCLIC COMPOUNDS (macromolecular compounds C08)

## Abstract

The invention relates to a process for the purification of a melamine condensation product, comprising the steps of a) making a diluted slurry of a reaction product mixture comprising the melamine condensation product in a solution of a base in water with a pH of at least 9, b) keeping the diluted slurry for a period of at least 1 hour, c) concentrating the diluted slurry, thereby obtaining a concentrated slurry and an eluent, and d) washing the concentrated slurry by diluting the concentrated slurry with aqueous liquid and repeating step c, wherein the washing is performed by counterflow washing wherein eluents of downstream concentration steps are used to wash the slurry in upstream concentration steps.

## Claims

### Claim 1

Process for the purification of a melamine condensation product obtained by a process comprising the step of heating a starting material comprising melamine or a melamine salt in the presence of:
(i) at least one organic or inorganic acid, or
(ii) at least one ammonia or melamine salt of the acid, or
(iii) a combination of (i) and (ii),
under reaction conditions effective for the formation of a melamine condensation product, resulting in a reaction product mixture comprising melamine condensation product and the organic or inorganic acid and/or salts or other residues thereof wherein the purification process comprises the steps of
a) making a diluted slurry of the reaction product mixture in a solution of a base in water with a pH of at least 9,
b) keeping the diluted slurry for a period of at least 1 hour,
c) concentrating the diluted slurry, thereby obtaining a concentrated slurry and an eluent, and
d) washing the concentrated slurry by diluting the concentrated slurry with aqueous liquid and repeating step c,
wherein the washing is performed by counterflow washing wherein eluents of downstream concentration steps are used to wash the slurry in upstream concentration steps.

### Claim 2 (depends on 1)

Process according to claim 1, wherein the washing of the concentrated slurry is carried out in N washing steps, N being a positive integer, wherein in step n1=x, x being an integer (selected) from 1 up to and including N−1, the mixture is washed with water used in step n2=x+1 and wherein in step n3=N the condensation product is washed with a fresh aqueous liquid, preferably water.

### Claim 3 (depends on 2)

Process according to claim 2, wherein N is an integer in the range of 2-10.

### Claim 4 (depends on 1)

Process according to claim 1, wherein less than 50 liters of aqueous solution per kg of purified condensation product is used.

### Claim 5 (depends on 1)

Process according to claim 1, wherein the filtration is done by dead end filtration combined with counterflow washing.

### Claim 6 (depends on 1)

Process according to claim 1, wherein the amount of base is at least in a stoichiometric amount with the acid in the reaction product mixture.

### Claim 7 (depends on 1)

Process according to claim 1, wherein as the base sodium hydroxide is used.

### Claim 8 (depends on 1)

Process according to claim 1, wherein the step b) of keeping the diluted slurry is carried of at a temperature of 20-70° C.

### Claim 9 (depends on 1)

Process according to claim 1, wherein the step b) of keeping the diluted slurry is carried out for a period of at most 14 hours.

### Claim 10 (depends on 1)

Process according to claim 1, wherein the step b) of keeping the diluted slurry is carried out in a stirred vessel.