Initiator efficiency of peroxides in high-pressure ethene polymerization

Becker, Philipp; Buback, Michael; Sandmann, Johannes

doi:10.1002/1521-3935(200210)203:14<2113::aid-macp2113>3.0.co;2-v

Cited by 19 publications

(27 citation statements)

References 6 publications

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“…: [8] DX r ¼ DX=c 0:5 I;dec (2) where c I,dec is the concentration of initiator decomposing in the CSTR under polymerization conditions. c I,dec is given by the difference between initiator feed concentration, c I,0 , and stationary initiator concentration, c I , in the CSTR.…”

Section: Resultsmentioning

confidence: 99%

“…[8][9][10][11] The scheme of the experimental set-up for polymerizations at pressures up to 3 000 bar and temperatures up to 300 8C is shown in Figure 1. After passing the catalyst tower and the drying unit, ethene is depressurized to about 10 bar prior to penetrating the mass-flow meter which monitors the ethene flux with an accuracy of AE1%, up to a maximum flow of 2 kg Á h À1 .…”

Section: Experimental Partmentioning

confidence: 97%

“…The mode of bond scission of the initiator molecule, e.g., whether single-bond scission or (more or less) concerted two-bond scission occurs, plays an essential role. The preceding study into peroxyester efficiency in ethene polymerization [8] revealed that f is not significantly dependent on temperature, but clearly varies with the mode of primary initiator bond scission. Within the present paper, the initiator efficiency in ethene high-pressure polymerization will be studied for a wide range of organic peroxyesters.…”

Section: Full Papermentioning

confidence: 99%

“…The determination of f is carried out via the quantity ''reduced peroxide-induced monomer conversion'', which has been introduced in ref. [8] (see also ''Results and Discussion'' below). Ethene polymerizations induced by peroxyesters have been chosen for the systematic study because of the following reasons: (i) These processes are of high technical relevance; (ii) propagation and termination rate coefficients of ethene, as required for modeling these polymerizations, are available from laser-assisted experiments; (iii) decomposition rate coefficients of a wide variety of peroxyesters have already been determined within wide pressure and temperature ranges in dilute solution of heptane [2,3] which should provide a molecular environment that is rather close to the one in ethene polymerization at low and moderate degrees of monomer conversion.…”

Section: Full Papermentioning

confidence: 99%

“…The miniplant device has already been detailed elsewhere [8][9][10] and thus will only very briefly be described in the ''Experimental Part''. In the preceding study, [8] the initiator efficiency in ethene polymerization of tert-butyl peroxide (DTBP), tert-butyl peroxy-2-ethylhexanoate (TBPEH), and tert-butyl peroxypivalate (TBPP) has already been measured. Within the present investigation, the efficiency of additional thirteen tert-alkyl peroxyesters R-C(CH 3 ) 2 -O-O-CO-R' (see Scheme 1 and Table 1) is studied.…”

Section: Full Papermentioning

confidence: 99%

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Initiator Efficiency of tert‐Alkyl Peroxyesters in High‐Pressure Ethene Polymerization

Buback

Fischer

Hinrichs

et al. 2007

Macro Chemistry & Physics

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High‐pressure ethene polymerizations using thirteen tert‐alkyl peroxyester initiators, RC(CH3)2OOCOR′ (with R = methyl, ethyl, neo‐pentyl, tert‐butyl and R′ = methyl, i‐propyl, propyl, butyl, tert‐butyl, 2‐heptyl) have been carried out in a CSTR. The initiator efficiency f has been determined for each peroxyester at 2 000 bar over a range of temperatures, partly up to 250 °C. The highest initiator efficiencies, up to about f = 0.9, are observed for tert‐butyl peroxyesters, in which the R' species is a primary radical, as e.g., with tert‐butyl peroxypentanoate and tert‐butyl peroxyacetate. The lowest efficiency value, of about f = 0.37, occurs with tert‐butyl peroxypivalate. The radicals from initiator decomposition, R′COO· and RC(CH3)2O., may undergo β‐scission reactions to produce R′ radicals by decarboxylation and R radicals by “deacetonization”, respectively. In‐cage termination reactions between oxygen‐centered and carbon‐centered radicals essentially control initiator efficiency.magnified image

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Partmentioning

confidence: 97%

Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

Section: Full Papermentioning

confidence: 99%

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Initiator Efficiency of tert‐Alkyl Peroxyesters in High‐Pressure Ethene Polymerization

Buback

Fischer

Hinrichs

et al. 2007

Macro Chemistry & Physics

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Kinetics of Polymerizations

Buback

Russell

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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First of all, the machinery for treating radical polymerization (RP) kinetics is presented. On the one hand, this involves kinetic descriptions that may be implemented without undue difficulty and that account for subtle but pivotal phenomena such as chain‐length‐dependent termination and penultimate‐unit effects in copolymerization. At the same time, this machinery also includes reliable, probing experimental methods for measuring rate coefficients. It is then shown how these tools have been used to develop mechanistic understanding of the fundamental RP reactions, which are initiation, propagation, termination, and chain transfer. In the case of propagation, there is a particular emphasis on entropic effects arising from hindered rotations, while with termination the composite model for chain‐length dependence is stressed, as is variation of overall termination rate coefficient with conversion. Finally, it is shown that chain transfer to polymer and β‐scission are recurring and important motifs in many RP systems. All in all, a pleasing picture of a scientifically maturing field is revealed as taking shape.

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