Manganese acetate and phosphoric acid effect on pet synthesis
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
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
Water solubility: soluble
Boiling Point:117.1°C at 760 mmHg
Flash Point: 40 °C
Appearance: light pint crystals
Synonyms: orthophosphoric acid;
Molecular Weight: 97.99
Water solubility: MISCIBLE
Appearance: clear liquid
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
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
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
Manganese phosphate may have magnetic properties and itmay settle at the bottom of reactor.
Excess of manganese acetate may create the followingproblems
2) Scaleor insolublematter formation
4) Low molecular weight
5) Broad MW distribution
6) It will reactwith phosphoric acid and forma manganese phosphate itmay not dissolvein EG
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
Title: Method for preventing scaleformation in a continuous ester-interchange reaction for production of
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
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.
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
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