Europäisches Patentamt (19) European Patent Office Office européen des brevets (11) EP 0 990 652 A1 (12) EUROPEAN PATENT APPLICATION published in accordance with Art. 158(3) EPC (43) Date of publication: (51) Int. Cl.7: C07D 251/54, C09K 21/12, 05.04.2000 Bulletin 2000/14 C08K 5/51 (21) Application number: 98905654.4 (86) International application number: (22) Date of filing: 26.02.1998 PCT/JP98/00777 (87) International publication number: WO 98/39306 (11.09.1998 Gazette 1998/36) (84) Designated Contracting States: • SHINDO, Masuo, AT BE CH DE ES FR GB IT LI NL SE Nissan Chemical Industries Ltd Nei-gun, Toyama 939-2792 (JP) (30) Priority: 04.03.1997 JP 4921197 • IIJIMA, Motoko, Nissan Chemical Industries, Ltd (71) Applicant: Funabashi-shi, Chiba 274-8507 (JP) Nissan Chemical Industries, Ltd. Chiyoda-ku, Tokyo 101-0054 (JP) (74) Representative: Hartz, Nikolai F., Dr. et al (72) Inventors: Wächtershäuser & Hartz, • SUZUKI, Keitaro, Patentanwälte, Nissan Chemical Industries, Ltd Tal 29 Funabashi-shi, Chiba 274-8507 (JP) 80331 München (DE) (54) COMPOSITE SALT OF POLYPHOSPHORIC ACID WITH MELAMINE, MELAM, AND MELEM AND PROCESS FOR PRODUCING THE SAME (57) A melaminegmelamgmelem double salt of a polyphosphoric acid, which has a solubility of from 0.01 to 0.10 g/100 ml in water (25°C), a pH of from 4.0 to 7.0 as a 10 wt% aqueous slurry (25°C), and a melamine content of from 0.05 to 1.00 mol, a melam content of from 0.30 to 0.60 mol and a melem content of from 0.05 to 0.80 mol, per mol of the phosphorous atom; and A process for producing the above mentioned mela- minegmelamgmelem double salt of a polyphosphoric acid, which comprises the following steps (a) and (b): (a) a step of obtaining a reaction product by mixing melamine and phosphoric acid at a temperature of from 0 to 330°C in such a ratio that the melamine is from 2.0 to 4.0 mols per mol of the phosphoric acid (as calculated as orthophosphoric acid content), and (b) a step of baking the reaction product obtained in step (a) at a temperature of from 340 to 450°C for from 0.1 to 30 hours. EP 0 990 652 A1 Printed by Xerox (UK) Business Services 2.16.7/3.6 12EP 0 990 652 A1 Description for from 10 minutes to 5 hours, preferably from 1 to 4 hours. TECHNICAL FIELD [0007] A.C.S. Symposium Series No. 425 "Fire and Polymers", chapter 15, p. 211-238, American Chemical [0001] The present invention relates to a melamineg 5Society, Washington, D.C., 1990, discloses that melam melamgmelem double salt of a polyphosphoric acid ultraphosphate is formed by heating melamine phos- and a process for its production. The present invention phate [melamine/phosphorus atom = 1/1 (molar ratio)] further relates to a melaminegmelamgmelem double at a temperature of from 330 to 410°C. salt of a polyphosphoric acid having a small melamine [0008] Many proposals have been made up to present content and a high melem content, and a process for its 10 with respect to utilization of melamine phosphate as a production. flame retardant. For example, JP-A-53-49054 discloses a polyamide resin composition having the flame retar- BACKGROUND ART dancy improved by adding an inorganic filler and mela- mine phosphate to a polyamide. [0002] With respect to baked products of melamine 15 [0009] JP-A-61-126091 discloses that melamine con- and phosphoric acid, melamine orthophosphate, mela- densed phosphate is effective as a flame retardant for a mine pyrophosphate and melamine polyphosphate thermoplastic resin such as a polyester, a polyamide or have, for example, been known, and there have been a polyolefin, a thermosetting resin such as phenol or many reports on processes for their production. For urethane epoxy, or a cellulose material. example, JP-B-40-28594 discloses a process for pro- 20 [0010] The melamine polyphosphate or the melamine ducing baked melamine phosphate having part of mela- condensed phosphate as disclosed in the above-men- mine orthophosphate remained, which comprises tioned prior art can hardly be used effectively as a flame baking melamine orthophosphate at a temperature of retardant for a resin having a high molding temperature, from 180 to 250°C. However, it has been pointed out since desorption of melamine is substantial when that the melamine phosphate is a complex of melamine 25 heated at a temperature of at least 300°C. orthophosphate and melamine pyrophosphate, and has [0011] The present invention is to overcome the draw- no adequate water resistance. backs of the above-mentioned prior art and to present a [0003] U.S.P. 3,920,796 discloses a formation of mela- melaminegmelamgmelem double salt of a polyphos- mine pyrophosphate by baking melamine orthophos- phoric acid, which is useful for a wide range of applica- phate at a temperature of from 170 to 325°C. 30 tions as a flame retardant and which is produced from [0004] Further, U.S.P. 4,950,757 discloses a process melamine and phosphoric acid as starting materials, for producing melamine pyrophosphate by reacting and a process for its production. pyrophosphoric acid with melamine in an aqueous medium at a temperature of from 0 to 60°C. DISCLOSURE OF THE INVENTION [0005] JP-A-61-126091 discloses a process for pro- 35 ducing melamine condensed phosphate which com- [0012] The process for producing a melaminegmela- prises reacting condensed phosphoric acid and mgmelem double salt of a polyphosphoric acid, accord- melamine in a solid phase substantially in the absence ing to the present invention, will be described. of an aqueous medium under a temperature condition [0013] The process for producing a melaminegmela- of from naturally generated heat temperature to 170°C. 40 mgmelem double salt of a polyphosphoric acid which [0006] It is known to employ urea as a condensation has a solubility of from 0.01 to 0.10 g/100 ml in water agent in the production of a polyphosphate. For exam- (25°C), a pH of from 4.0 to 7.0 as a 10 wt% aqueous ple, JP-B-53-2170 discloses a process for producing a slurry (25°C), and a melamine content of from 0.05 to polyphosphoric acid amide (amide polyphosphate) con- 1.00 mol, a melam content of from 0.30 to 0.60 mol and taining amide-type nitrogen, which is obtainable by 45 a melem content of from 0.05 to 0.80 mol, per mol of the using ammonium orthophosphate, orthophosphoric phosphorous atom, comprises the following steps (a) acid, condensed phosphoric acid, phosphoric anhy- and (b): dride, urea phosphate, or a mixture thereof, as a phos- phoric acid source, and a cyanamide compound such (a) a step of obtaining a reaction product by mixing as melamine, dicyan cyanamide, guanidine or guanyl 50 melamine and phosphoric acid at a temperature of urea, as a nitrogen source, and subjecting a mixture from 0 to 330°C in such a ratio that the melamine is thereof to a heat condensation reaction in the presence from 2.0 to 4.0 mols per mol of the phosphoric acid of urea, urea phosphate or a mixture thereof, as a con- (as calculated as orthophosphoric acid content), densation agent. As the production conditions, it is dis- and closed to carry out the heat condensation in a ratio of 55 (b) a step of baking the reaction product obtained in urea/phosphoric acid (as H3PO4)/cyanamide com- step (a) at a temperature of from 340 to 450°C for pound = 0.8-1.5/1/0.05-1 (molar ratio) in an ammonia from 0.1 to 30 hours. gas atmosphere at a temperature of from 150 to 350°C 2 34EP 0 990 652 A1 [0014] Further, the process for producing a mela- ammonia desorbed therefrom. minegmelamgmelem double salt of a polyphosphoric [0020] The melem (Mp) is 2,5,8-triamino- acid having a low melamine content and a high melem 1,3,4,6,7,9,9b-heptaazaphenalene of the formula (4): content, according to the present invention, will be described. 5C6H6N10 (4). [0015] The process for producing a melaminegmela- mgmelem double salt of a polyphosphoric acid which This is a 1,3,5-triazine derivative having two molecules has a solubility of from 0.01 to 0.10 g/100 ml in water of melamine condensed to have two molecules of (25°C), a pH of from 4.0 to 7.0 as a 10 wt% aqueous ammonia desorbed therefrom. slurry (25°C), and a melamine content of from 0.05 to 10 0.40 mol, a melam content of from 0.30 to 0.60 mol and BRIEF DESCRIPTION OF THE DRAWINGS a melem content of from 0.30 to 0.80 mol, per mol of the phosphorous atom, comprises the following steps (a) [0021] and (b): 15 Figure 1 is a graph of the differential thermal analy- (a) a step of obtaining a reaction product by mixing sis of the melaminegmelamgmelem double salt of melamine and phosphoric acid at a temperature of a polyphosphoric acid obtained in Example 1. from 0 to 330°C in such a ratio that the melamine is Figure 2 is a powder X-ray diffraction pattern of the from 2.0 to 4.0 mols per mol of the phosphoric acid melaminegmelamgmelem double salt of a (as calculated as orthophosphoric acid content), 20 polyphosphoric acid obtained in Example 1. and (b) a step of baking the reaction product obtained in [0022] In Figure 1, symbol 1 indicates a curve showing step (a) at a temperature of from 340 to 450°C for the results of the differential thermal analysis (DTA), from 0.1 to 30 hours, while returning a sublimate of symbol 2 indicates a curve showing the results of the the melamine to the system, and discharging the 25 thermogravimetric analysis (TG), and symbol 3 indi- formed ammonia out of the system.