High-pressure free-radical copolymerization of ethene-methacrylic acid and of ethene-acrylic acid, 1. (Meth)acrylic acid reactivity ratios

Abstract

SUMMARY: Free-radical copolymerizations of ethene (E)-methacrylic acid (MAA) and of E-acrylic acid (AA) have been carried out in a continuously operated device at 2 000 bar and at temperatures between 240 and 280 8 C. Even at low degrees of overall monomer conversion, below 1%, and at small (M)AA contents of the copolymerizing mixtures, below 0.5 mol-%, the resulting copolymer is not soluble in the reaction mixture at contents of acid units well above 6 mol-%. At such low (M)AA contents, the classical procedure of deriving both reactivity ratios, r E and r (M)AA , from fitting monomer and copolymer compositions to the differential copolymerization equation is not applicable. r E may be estimated by this procedure, but the composition range is too small to derive r (M)AA . Data for r (M)AA may, however, be deduced from relative amounts of (M)AA-centered triad sequences that are available from quantitative 13 C NMR spectroscopy of the copolymer. Because of assignment problems for the E-(M)AA copolymers, the 13 C NMR studies have been carried out on product samples after complete methyl-esterification to yield E-methyl(meth)acrylate copolymeric material. The resulting r MAA data are slightly above the r AA values. The numbers, e. g., for 240

Free‐Radical Polymerization: Homogeneous

“…The original interpretation of low-conversion rate data was based on a chemically controlled model utilizing a cross-termination factor [Eq. (54)]. …”

“…Reactivity ratios for alkyl methacrylates and acrylates (for example, methyl, butyl, dodecyl) exhibit a family type behavior, with the composition data of various systems fitted well by a single curve [52]. Values for ethylene copolymer systems at typical production conditions are summarized in Table 4.8: While r 1 (1 ¼ ethylene) values for alkyl methacrylates, alkyl acrylates, acrylic acid, and methacrylic acid could not be distinguished within experimental error [53], there were significant differences in the r 2 values [54].…”

“…With increasing temperature, the ratios tend to approach unity as demonstrated for styrene-butyl acrylate [55], butyl acrylate-methyl methacrylate [56], and ethylene copolymer systems [53,54]. The temperature dependence of the latter agrees well with activation energies reported for addition of monomers to small radicals [57].…”

Analysing the Chemical Composition Distribution of Ethylene‐Acrylate Copolymers: Comparison of HT‐HPLC, CRYSTAF and TREF

“…organometallic catalysts. The presence of microblocks in both samples can be explained by the copolymerisation parameters ( r 1 = 0.045 and r 2 = 5.3 for EMA) which favour the cross propagation reaction for the ethylene radical at the polymer chain end over the homo‐propagation reaction for the ending acrylate radical 28–30…”

High-Pressure Free-Radical Copolymerization of Ethene and Methyl methacrylate

“…In previous studies of our group, reactivity ratio data which are of key importance for the modeling of copolymerization behavior have been determined for the systems E/methyl acrylate (MA), [1] E/butyl acrylate (BA), [2] E/2-ethylhexyl acrylate (EHA), [3] E/butyl methacrylate (BMA), [4] E/acrylic acid (AA) [5,6] and E/methacrylic acid (MAA). [5,6] The ethene reactivity ratios, r E , are well below and the (meth)acrylate and (meth)acrylic acid reactivity ratios, r A , are well above unity.…”