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United States Patent (19) 11 Patent Number: 6,051,708 De Keijzer Et Al

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United States Patent (19) 11 Patent Number: 6,051,708 De Keijzer Et Al US006051708A United States Patent (19) 11 Patent Number: 6,051,708 de Keijzer et al. (45) Date of Patent: Apr. 18, 2000 54 PROCESS FOR THE PREPARATION OF FOREIGN PATENT DOCUMENTS CONDENSATION PRODUCTS OF 54-13553 2/1979 Japan. MELAMINE 54-13554 2/1979 Japan. 54-72258 6/1979 Japan. 75 Inventors: Augustinus E.H. de Keijzer, Sittard; 59-204653 11/1984 Japan. Bernardus J.H. Dijkstra, Heerlen, both of Netherlands OTHER PUBLICATIONS N.K. Gavrilova et al., Chemical Abstracts, “Synthesis of 73 Assignee: DSM N.V., Heerlen, Netherlands melam and its salts with inorganic acids”, vol. 87, No. 1, Jul. 4, 1977, Abstract No. 5918m. 21 Appl. No.: 09/034,349 V.A. Galperin et al., Chemical Abstracts, “Synthesis of 22 Filed: Mar. 4, 1998 melam from melamine,” vol. 7, No. 11, Nov. 1971, Abstract No. 59574. Related U.S. Application Data Translation from Zhumal Organicheskoi Khimi, vol. 7, No. 11, pp. 2431-2432, Nov., 1971. 62 Division of application No. 08/862,958, Jun. 2, 1997, Pat. Translation from Zhumal Organicheskoi Khimi, vol. 13, No. 5,985.960, which is a continuation of application No. No. 34, pp. 669-670, Mar, 1977. PCT/NL95/00402, Nov. 23, 1995. Primary Examiner Veronica P. Hoke 30 Foreign Application Priority Data Attorney, Agent, or Firm- Pillsbury Madison & Sutro LLP Dec. 1, 1994 BE Belgium ................................. 94O1088 57 ABSTRACT (51) Int. Cl. .............................................. C07D 251/54 A process for the preparation of a melamine condensation 52 U.S. Cl. .............................................................. 544/200 product comprising the Step of heating a starting material 58 Field of Search ............................ 524/100; 544/200; comprising melamine or a melamine Salt in the presence of: 252/606, 609 (i) at least one organic acid, (ii) at least one ammonia or 56) References Cited melamine Salt of the organic acid, or (iii) a mixture of (i) and (ii), under reaction conditions effective for the formation of U.S. PATENT DOCUMENTS the melamine condensation product. The melamine conden 2,475,709 7/1949 Mackay et al. ......................... 544/200 sation product with a residual condensation agent content of 2,819,265 1/1958 Healy et al. ............................ 544/203 less than 1 wt.% is useful in a moldable polymer compo 4,966.931 10/1990 Akitaya et al.. Sition possessing flame-retardant properties. 5,514,797 5/1996 Best et al. ............................... 544/203 5,677,450 10/1997 Suzuki et al. ........................... 544/200 12 Claims, No Drawings 6,051,708 1 2 PROCESS FOR THE PREPARATION OF milligram or gram Scale) in the presence of inorganic acids CONDENSATION PRODUCTS OF as condendation agents. Inorganic acids include HCl, HBr, MELAMINE Sulfuric acid, phosphoric acid, and mixtures thereof. The ammonia or melamine Salts of these acids can also be used. This is a divisional application from application Ser. No. 5 However, there are drawbacks to these alternative Small 08/862,958, filed Jun. 2, 1997 now U.S. Pat. No. 5,985,960, Scale Syntheses. These include, among others, a need for which was a continuation of PCT International Application high reaction temperature, low yields, a high degree of No. PCT/NL95/00402 filed Nov. 23, 1995 which designated melamine Sublimation, formation of by-products, and halo the U.S. gen residues in the end product. These drawbacks render these alternatives unsuitable for commercial Scale (e.g. BACKGROUND OF THE INVENTION kilogram- or tonnage Scale) production of a condensation 1. Field of the Invention product of melamine. The invention relates to a process for the preparation of a SUMMARY AND OBJECTS OF THE melamine condensation product, and more particularly, to INVENTION tho preparation of a melamine condensation product that is free of halogens and imparts flame-retardancy. 15 An object of the present invention is to provide a process for the preparation of a melamine condensation product that 2. Description of Related Art reduces or eliminates the need for the heretofore difficult Melamine forms melamine condensation products when practice of removing residues from the product. heated under certain reaction conditions. Ammonia is Another object of the present invention is to provide a evolved in the reaction. Similarly, melamine Salts form process capable of producing a melamine condensation condensation products when heated. Melamine condensa product on a large or commercial Scale. tion products include melam, melone, and melam, as well as A further object of the present invention is to provide an Salts thereof. Generally, melam (CHN) forms upon heat efficient proceSS for producing a melamine condensation ing melamine and/or melamine salts below 315 C. and is a product in the absence of halogens. by-product of melamine Synthesis. For purposes of the 25 Those and other objects are Satisfied by a proceSS for the present invention, a melamine condensation product encom preparation of at least one melamine condensation product passes a product that results from Self-condensation of comprising the Step of heating a Starting material comprising melamine or a melamine Salt with the evolution of ammonia. melamine or a melamine Salt in the presence of: (i) at least Hence, for example, a melamine condensation product is not one organic acid, (ii) at least one ammonia or melamine Salt the product from the condensation reaction between of the organic acid, or (iii) a mixture of (i) and (ii), under melamine and, for example, formaldehyde to yield amino reaction conditions effective for the formation of melamine CSS. condensation product. Specific processes relating to the preparation of melam A further object of the present invention is to provide a via condensation are described in, for example, V. A. moldable polymer composition which has flame-retardant proportion and thermal Stability. Galperin et al., Zhurnal Organicheskoi Khimi, Vol. 7, No. 35 11, pp. 2431-2432 (November 1971) and Gavrilova et al., These and other objects are Satisfied according to the Zhurnal Organicheskoi Khimi, Vol. 13, No. 3, pp. 669-670 present invention by a polymer composition comprising: 1) (March 1977). In laboratory scale experiments, melamine a melamine condensation product, and 2) moldable polymer, wherein the amount of the melamine condensation product was converted to a Salt of melam with use of a ZnCl2 and the amount of moldable polymer are Sufficient to pro condensation agent at a temperature between 290 C. and 40 vide flame retardancy and moldability to the polymer com 320 C. Specifically, 3.3 grams of melamine was mixed with position. 1.7 grams of anhydrous Zinc chloride and heated for 1 hour Advantages of the process of the present invention at a temperature of 290 C. in an open tube. The open tube include reducing or eliminating the need for the difficult Step is a So-called Stationary System. The product was washed of removing residual condensation agent. In addition, the with boiling methanol to remove residual zinc chloride. It 45 melamine condensation products obtained according to the was then washed with diluted hydrochloric acid to remove present invention impart the necessary levels of flame resis residual melamine. The Zinc Salt of melam thus obtained tance for many applications. contained 87.2 wt.% of melam and 11.8 wt.% of zinc. In It has further been found that melamine condensation an additional treatment to prepare melam from the melam products Such as melam with a residual condensation agent Zinc salt, the zinc salt of melam was boiled for 5-7 minutes 50 content of less than 1 wt.%, more in particular less than 0.5 in a 1% solution of sodium hydroxide. Next, the solution wt.%, are highly Suitable for use as flame-proofing agents was filtered off and cooled. The precipitate was washed with in polymer compositions. Melamine condensation products hot water and dried for 2 hours at a temperature of 170° C. possess high thermal Stability in comparison with other The yield of the product was 2.7 grams. flame-proofing agents Such as, for example, halogen com The percentages of Zinc and chlorine in the melam 55 pounds and melamine. Melam and higher melamine con product after this additional treatment were not reported in densation products Such as malem, melon and methone do this reference. In later work, however, the melam product of not extensively Sublime and decompose at temperatures this reaction was found to have a residual content of 3.5 wt. below 360° C. As a result, the polymer compositions accord ing to the present invention exhibit better thermal stability % of zinc and 1.6 wt. 76 of chloride. In other words, compared to compositions incorporating conventional flame Significant amounts of Zinc chloride remain in the melam, 60 proofing agents. A further advantage is that mold deposits even after attempts to remove it. tend not to form during injection molding of the melam The presence of Zinc and chloride impurities is a signifi filled polymer compositions. cant drawback. Both ions are difficult to wash out. Furthermore, Washing Zinc and chloride out of the product DETAILED DESCRIPTION OF THE can result in a high degree of hydrolysis of the melam. 65 INVENTION Alternatively, melamine can also be converted to a con The melamine condensation products of the present densation product like melam on a laboratory Scale (e.g. invention are the result of Self-condensation of a starting 6,051,708 3 4 material comprising melamine or melamine Salt resulting in The melamine condensation product Such as melam can the evolution of ammonia. Exemplary melamine condensa be mixed with polymers to yield flame-proof compositions. tion products include melam, melem, and melone. It has been found that melamine condensation products Such Preferably, the melamine condensation product comprises as melam, with a residual condensation agent content below mainly melam. 1 wt.%, more in particular below 0.5 wt.%, are highly Examples of melamine Salts include Salts prepared from Suitable for use as flame proofing agents in polymer com phosphoric acid, Sulfuric acid, nitric acid, fatty acids, and positions.
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