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Manganese acetate and phosphoric acid effect on pet synthesis

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Manganese acetate and phosphoric acid effect on Polyester Synthesis

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Manganese acetate and phosphoric acid effect on pet synthesis

  1. 1. Effect of Manganese acetate and phosphoric acid/ phosphoric acid ester (TMP) in PET Synthesis. Introduction of additives Generally manganese acetate areused preferably becauseof their superior catalytic activity,itincreasethe esterification reaction rate. Major function of phosphoric acid or trimethyl phosphateis heat stabilizer.Itwill reducethe polymer degradation and formation of –COOH end group in polycondensation stage. Phosphoric acid or their esters (TMP) must be added at the end of esterification reaction.There are two reasons to add at the end of esterification 1. Phosphoric acid stabilizers are inactivein presenceof higher –COOH end groups 2. Transesterification catalyst(Mn) will be deactivated if you use phosphoric acid atearly stage But there are considerablebenefits by the individual addition of manganese acetate and phosphoric acid at deferent stages. What is the effect if I can use both manganese acetate and phosphoric acid or their esters at a time? There is a disadvantageby addingboth manganese acetate and phosphoric acid or their ester in the beginningof the esterification stage. Manganese acetate may react with phosphoric acid and forma manganese phosphate. It i s very difficultto dissolvein ethylene glycol and incorporation in polymer matrix. Manganese Acetate: Phosphoric Acid Trimethyl phosphate  CAS: 638-38-0  Molecular Formula:C4H6MnO4  Molecular Structure: Chemical Properties  Molecular Weight:173.026  Density:1.589  Water solubility: soluble  Boiling Point:117.1°C at 760 mmHg  MeltingPoint: 180°C  Flash Point: 40 °C  Solubility: soluble  Appearance: light pint crystals CAS :7664-38-2 Molecular Formula:H3PO4 Synonyms: orthophosphoric acid; Molecular Structure: Chemical Properties Molecular Weight: 97.99 Density: 1.685 Water solubility: MISCIBLE Boiling Point:158℃ MeltingPoint:21℃ CAS: 512-56-1 Molecular Formula:C3H9O4P Molecular Structure: Chemical Properties Molecular Weight:140.07 Density:1.197 Boiling Point:197℃ MeltingPoint:-46℃ Flash Point:107℃ Refractive index:1.395-1.397 Solubility: good Appearance: clear liquid
  2. 2. 3Mn(CH3COO)2 + 2H3PO4 ---------------------- Mn3O8P2 Manganese acetate Phosphoric Acid Manganese phosphate The use of manganese compounds suffers from the defect that foreign materials areformed in the reaction system. These foreign materials adhereto the equipment, such as a reaction vessel or piping,to form scales which in turn prevent the normal operation of the equipment The scaleis believed to be insolublemanganeseterephthalate itis formedbythe reactionof manganese acetate catalystwithterephthalicacid Manganese has a very high reactivity in both the ester interchangereaction and the polycondensation reac tion. However, it is generally preferred to sequester manganese at the end of the ester interchangeprocess, otherwise manganese produces a polymer with bad color,the polymer has a broader molecular weight distribution, which is undesirable,and when manganese is activeas a catalystin thepolycondensation stage,many by-products such as oxides,etc., arecreated, which discolor theresultantpolymer. The excess of manganese acetate will enhancethe beta-elimination (itis a major thermal degradation reaction of PET) So it will givehigher –COOH end groups and difficultto get high IV in SSP it must be kept in mind that manganese yields bad color,undesirableby-products,and broad molecular weight distribution for the polymer formed Source: http://144.206.159.178/ft/862/10095/194702.pdf Manganese phosphate may have magnetic properties and itmay settle at the bottom of reactor. Source: http://www.chem.tamu.edu/rgroup/dunbar/Publications/2003-172.pdf Conclusion: Excess of manganese acetate may create the followingproblems 1) Discoloration 2) Scaleor insolublematter formation 3) Degradation 4) Low molecular weight 5) Broad MW distribution 6) It will reactwith phosphoric acid and forma manganese phosphate itmay not dissolvein EG
  3. 3. References: 1) US20090043022 Relevant Text: Further, the present invention is intended for lightshielding,and thus stability of the polymer upon exposure to sunlight,in particular UVlight,is of primary importance.As such,UV stability iscertainly necessary and thereby it is importantto add a UV stabilizer.As a resultof various tests, the present inventors have found that manganese phosphate is mosteffective. However, manganese phosphateis insolublein ethylene glycol,thereby making it difficultto be incorporated into the polymer. Therefore, the present inventors have found that it is most proper to synthesize manganese phosphate in a reaction system by separately introducing manganese acetate and phosphoric acid to the reactor, instead of directly introducing manganese phosphate into a reactor. The content of manganese acetate utilized for synthesis of manganese phosphateis preferably in the range of 0.1 to 500 ppm, and more preferably 0.2 to 200 ppm, based on manganese atoms in the polymer. If the content of manganese acetate is below0.1 ppm, it is difficultto obtain the desired UV stability.If the content of manganese acetate exceeds 500 ppm, problems associated with dispersibility arise,thereby leadingto increased pack pressureupon spinning.In addition,the content of phosphoric acid ispreferably in the range of 0.1 to 500 ppm, and more preferably 0.2 to 200 ppm based on the phosphorus atom content relative to the polymer. Although phosphorus based materials may be added in any amount, so long as the reaction between the phosphorus material and the manganese saltis notinhibited,concentrations greater than 500 ppm may lead to decreased catalytic activity, thereby it makingdifficultto prepare the desired flame retardantpolyester. 2) Magnetic Property Studies of Manganese-Phosphate Complexes Phosphoric acid forms two distinctcoordination compounds with manganese salts in aqueous media ,a two- dimensional layered structure,[Mn(HPO4)â(H2O)3], 1, under ambient conditions,and a three-dimensional synthetic mineral,[Mn5(í-OH2)2(HPO4)2(PO4)2(H2O)2],2, under hydrothermal procedures, at120 °C. In compound 1, the oxygen atom of the doubly deprotonated phosphoric acid interconnects themetal centers to form a layered structure. The neutral hydrophiliclayersof 1 are separated by 5.5 Å and may potentially intercalate hydrophilic organic guest molecules.The metal centers in 2 are octahedral and bridged by PO43-, HPO4 2-, and OH2 groups to form a complex three-dimensional network. XPS analysison 1 and 2 confirms that manganese exists in the +2 oxidation state.Compound 2 is a poor ion exchanger, but some improvement is observed on partial dehydration. The magnetic properties of both 1 and 2 were studied in detail to examine the amplitudeof the magnetic interactions through phosphate ligand bridges. While1 reveals dominantantiferromagnetic interactions between the spin carriers,a complete investigation of the magnetic properties of 2 revealed its true nature to be a glassy magnet. 3) US4057534A Title: Method for preventing scaleformation in a continuous ester-interchange reaction for production of polyesters In order to perform the ester-interchange reaction smoothly, various metal compounds are used as a catalyst,and manganese compounds such as manganese acetate are used preferably because of their superior catalytic activity. The use of such manganese compounds, however, suffers from the defect that foreign materials areformed in the reaction system. These foreign materials adhereto the equipment, such as a reaction vessel or piping,to form scales which in turn prevent the normal operation of the equipment. Hence, the equipment must be disassembled
  4. 4. and cleaned. Since this requires a complicated procedure, the working efficiency of the equipment is reduced. Furthermore, the adhesion of the scales gives riseto an increasein heattransmission resistance,and makes it difficultto maintain the reaction system at a predetermined temperature. These defects are very serious especially in a continuous ester-interchange reaction,and are required to be removed. 4) US4154921 The scaleis believed to be insolublemanganeseterephthalate, presumably formed by reaction of manganese acetate catalystgenerated as a resultof a sidereaction during the ester exchange reaction of dimethyl terephthalate with excess ethylene glycol.Preferably an alkali metal saltof an organic acid,such as sodiumacetate or lithiumacetate is also used to give a synergistic effectin combination with the hindered acid. Primarily insolublemanganeseterephthalate, presumably formed by the reaction of manganese acetate catalyst with terephthalic acid EP425215A2 Manganese is the preferred catalystfor ester interchange reactions, but the amount of manganese employed must be strictly controlled. The presence of too littlemanganese duringthe ester interchange reaction results in very longreaction times, whilethe presence of too much manganese results in unwanted sideproducts duringthe polycondensation reaction (thus loweringthe yield of monomer), and unacceptabledegradation of the polymer resultingin poor color (thus lowering the quality). The exact range of manganese which proves to be the most desirablemustgenerally be determined through trial and error becausemany factors affect the reactivity of the manganese. For example, reaction temperature, reaction pressure, the degree of mixing duringreaction,the purity of the rawmaterials,the presence of other additives,etc., all affectthe effectiveness of manganese. In prior artprocesses,manganese was employed to obtain suitableester interchange reaction times, but the manganese had to be sequestered after ester interchange or duringpolycondensation by a polyvalent phosphorous compound to aid in reducingthe discoloration and unwanted sideproducts. Generally,prior art processes employed about 50 ppm to 150 ppm manganese based on the expected yield of the polymer, as the ester interchangecatalyst.Usingmore than about150 ppm manganese resulted in polymer degradation even if phosphorous was employed in excess to seguester the manganese. It is believed that this occurred because the phosphorous was incapableof complexingwith the manganese to the degree necessary to prevent discoloration

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