The cloud point behavior of ethene-acrylic acid ester and ethene-methacrylic acid copolymers in ethene and partly in ethene-comonomer mixts. has been measured in an extended pressure and temp. range up to 300 MPa and 260 °C, resp. Copolymer synthesis is carried out in a continuously operated stirred tank reactor (CSTR) which ensures prodn. of chem. homogeneous copolymer material. Part of the phase behavior studies are performed under flow-through conditions in a second CSTR which is penetrated by the mixt. from the polymn. reactor. Alternatively, the copolymer is isolated after synthesis and, after prepn. of a polymer-monomer mixt., the phase behavior is mapped out in a discontinuously operated high-pressure cell. The influence of copolymer compn. on the cloud point behavior in mixts. with ethene (E) has been systematically studied for E + Me acrylate (MA), E + Bu acrylate (BA), E + ethylhexyl acrylate (EHA), E + acrylic acid (AA), and E + methacrylic acid (MAA) copolymers. For E + MA and E + BA copolymers also the variation of cloud point pressure (CPP) with the comonomer content of the monomer mixt. has been investigated and nos. for the specific change in CPP have been deduced. The CPPs of the E + BA + poly(E-co-BA) system are primarily detd. by entropic effects. At lower temp., interactions of polar segments with the solvent come into play. They are even more important with the E + MA + poly(E-co-MA) system. At high copolymer MA contents, the phase behavior of E + MA + poly(E-co-MA) is addnl. affected by intra-segmental interactions of the Me ester groups. With the E + poly(E-co-MAA) systems, strong intra-segmental interactions via hydrogen bonds are operative which largely reduce copolymer soly. in ethene. The variation of CPP with both copolymer compn. and with the compn. of the monomer mixt. has been detd. within extended regions. The data allow to est. homogeneous reaction conditions for ethene copolymns. in wide pressure, temp., and compn. regions.
The data obtained at systematic variation of the type and amt. of polar comonomer within both monomer mixt. and copolymer should be perfectly suited for modeling purposes.