Patent application EP19180266A (EP), filed 2019-06-14
Publication number: EP3750872A1
Title: INCREASE OF GUANIDINE CARBONATE YIELD BY REDUCTION OF MOTHER LIQUOR DISPOSAL AND QUALITY IMPROVEMENT DUE TO INCREASE OF TEMPERATURE SPREAD
Abstract: The present invention refers to a method for increasing the guanidine carbonate yield and purity from an aqueous solution containing melamine and guanidine carbonate in a guanidine carbonate treatment process, wherein the guanidine carbonate treatment process comprises at least one melamine precipitation stage and at least one guanidine carbonate precipitation stage; wherein the temperature in the guanidine carbonate precipitation stage is at least 6°C, preferably at least 8°C, more preferably at least 10°C higher than in the melamine precipitation stage.
IPC codes: C07C 277/    06            A I
C07C 279/    02            A I
C07D 251/    60            A I
C07D 251/    62            A I
Claims: number: 1
text: Method for increasing the guanidine carbonate yield and purity from an aqueous solution containing melamine and guanidine carbonate in a guanidine carbonate treatment process (20),
wherein the guanidine carbonate treatment process (20) comprises at least one melamine precipitation stage (22) and at least one guanidine carbonate precipitation stage (26);
wherein the temperature in the guanidine carbonate precipitation stage (26) is at least 6°C, preferably at least 8°C, more preferably at least 10°C higher than in the melamine precipitation stage (22).
number: 2
text: Method according to claim 1, characterized in that the temperature difference between the at least one melamine precipitation stage (22) and the at least one guanidine carbonate precipitation stage (26) is in a range between 6 and 20°C, preferably between 8 and 15°C, more preferably between 10 and 12°C.
number: 3
text: Method according to one of the preceding claims, characterized in that the temperature in the melamine precipitation stage (22) is between 14°C and 30°C, preferably between 17 and 27°C.
number: 4
text: Method according to one of the preceding claims, characterized in that the temperature in the guanidine carbonate precipitation stage (26) is between 20°C and 50°C, preferably between 23°C and 40°C, more preferably between 26 and 35°C.
number: 5
text: Method according to one of the preceding claims, characterized in that the aqueous solution containing melamine and guanidine carbonate comprises melamine mother liquor (MML) obtained in a melamine process (10) and guanidine carbonate mother liquor (GCML) obtained in the guanidine carbonate treatment process (20).
number: 6
text: Method according to claim 5, characterized in that at least 60%, preferably at least 80%, more preferably to 100% of the guanidine carbonate mother liquor (GCML) are recycled within the guanidine carbonate treatment process (20).
number: 7
text: Method according to claim 6, characterized in that none of the guanidine carbonate mother liquor (GCML) is disposed from the guanidine carbonate treatment process (20).
number: 8
text: Method according to claim 6, characterized in that the guanidine carbonate mother liquor (GCML) is recycled with a recycling rate of 100% within the guanidine carbonate treatment process (20) for a predetermined time period followed by a recycling rate of at least 60% for a time period which is less than the time period for the recycling rate of 100%.
number: 9
text: Method according to one of the preceding claims, characterized in that guanidine carbonate mother liquor (GCML) is obtained in the guanidine carbonate treatment process (20) comprising the steps of:
number: 10
text: Method according to claim 9, characterized in that 15-30 wt%, preferably 20-25wt%, based on the total amount of the mother liquor?, gaseous or liquid ammonia are added to the mother liquor for precipitation of guanidine carbonate.
number: 11
text: Method according to one of claims 5 to 10, characterized in that the guanidine carbonate mother liquor (GCML) comprises urea, melamine, ammonia and guanidine carbonate, preferably said liquor comprises 30 - 150 g/l, preferably 70 - 100 g/l urea, 2 - 8 g/l, preferably 3 - 5 g/l melamine, 100 - 350 g/l, preferably 180 - 270 g/l, more preferably 200 - 250 g/l ammonia and 10 - 60 g/l, preferably 20 - 40 g/l guanidine carbonate.
number: 12
text: Method according to one of the preceding claims, characterized in that the guanidine carbonate treatment process (20) is combined with a melamine process (10) such that the melamine mother liquor (MML) obtained in the melamine process, in particular a low pressure melamine process (10), is channeled into the guanidine carbonate treatment process (20).
number: 13
text: Method according to one of claims 5 to 12, characterized in that the melamine mother liquor (MML) is obtained in a melamine low pressure process comprising the steps:
number: 14
text: Method according to one of claims 5 to 12, characterized in that the melamine mother liquor (MML) comprises urea, melamine, ammonia and guanidine carbonate, in particular said liquor comprises 10 - 150 g/l, preferably 30 - 70 g/l urea, 2 - 10 g/l, preferably 4 - 6 g/l melamine, 50 - 300 g/l, preferably 100 - 200 g/l, more preferably 140 - 150 g/l ammonia and 5 - 60 g/l, preferably 15 - 35 g/l guanidine carbonate.
number: 15
text: Guanidine carbonate, preferably obtainable in a method according to one of the preceding claims, characterized by a purity higher than 99.7 %, preferably higher than 99.8%, in particular preferably higher than 99.85%.
Office action: search_report, dated 2020-12-16
Rejection reasons: novelty_epc_54
inventive_step_epc_56
Prior art cited: ref_id: DE938843C
ref_type: patent
severity: background
ref_id: US2221478A
ref_type: patent
severity: background
ref_id: DE1593472A1
ref_type: patent
severity: background
ref_id: AT317918B
ref_type: patent
severity: background
ref_id: AT336035B
ref_type: patent
severity: background
ref_id: US3952057A
ref_type: patent
severity: background
ref_id: AT317918B
ref_type: patent
severity: background
ref_id: US3984471A
ref_type: patent
severity: background
ref_id: AT317918B
ref_type: patent
severity: novelty_destroying
ref_id: US3952057
ref_type: patent
severity: novelty_destroying
ref_id: US3984471
ref_type: patent
severity: novelty_destroying
Final disposition: pending (2020-12-16)