Catalyst modification to control polymer architecture

A method to increase the homogeneity of an ethylene copolymer comprising one or more comonomers chosen from propylene, 1-butene, 1-hexene, and 1-octene by reducing the amount of the component eluting at a temperature of greater than 90° C. in the temperature rising elution fraction analysis wherein the copolymer is produced using a solution polymerization process at pressures from 6,000 kPa to 22,000 kPa, comprising two or more reactors in series in which the first reactor is operated at temperatures from 120° C. to 180° C. and the second and subsequent optional reactors are operated at higher temperatures up to 220° C. in the presence of a catalyst system comprising:

• (I) transition metal catalyst of the formula:
• (L)n-M-(X)p
• wherein M is a transition metal, for example a transition metal chosen from Ti, Hf and Zr;
• L is a monoanionic ligand chosen from a cyclopentadienyl ligand, an indenyl ligand and a fluorenyl ligand which ligands are unsubstituted or up to fully substituted with one or more substituents chosen from chlorine atoms, fluorine atoms and C1-4 alkyl radicals which are optionally substituted with chlorine or fluorine atoms,
• and
• a phosphinimine ligand of the formula:
• wherein each R3 is independently chosen from a hydrogen atom;
• a halogen atom;
• C1-10 hydrocarbyl radicals which are optionally substituted by a halogen atom;
• a C1-8 alkoxy radical;
• a C6-10 aryl or aryloxy radical;
• and an amido radical which is optionally substituted by up to two C1-10 hydrocarbyl radicals;
• X is a monoanionic ligand chosen from C1-4 alkyl radicals and a chlorine atom;
• n is an integer from 1 to 3, and
• p is an integer from 1 to 3, provided that the sum of n+p equals the valence state of M, and
• further provided that two L ligands are optionally bridged by a silyl radical or a C1-4 alkyl radical;
• (II) a boron activator capable of ionizing the transition metal complex chosen from:
• (i) compounds of the formula [R5]+[B(R7)4]− wherein B is a boron atom, R5 is a cyclic C5-7 aromatic cation or a triphenylcarbenium cation and each R7 is independently chosen from phenyl radicals which are unsubstituted or substituted with from 3 to 5 substituents chosen from a fluorine atom, a C1-4 alkyl or alkoxy radical which is unsubstituted or substituted by a fluorine atom;
• and a silyl radical of the formula —Si—(R9)3;
• wherein each R9 is independently chosen from a hydrogen atom and a C1-4 alkyl radical;
• (ii) compounds of the formula [(R8)tZH]+[B(R7)4]− wherein B is a boron atom, H is a hydrogen atom, Z is a nitrogen atom or phosphorus atom, t is 2 or 3 and R8 is chosen from C1-8 alkyl radicals, a phenyl radical which is unsubstituted or substituted by up to three C1-4 alkyl radicals, or one R8 taken together with the nitrogen atom to optionally form an anilinium radical and R7 is as defined above;
• and
• (iii) compounds of the formula B(R7)3 wherein R7 is as defined above;
• (III) an aluminoxane of the formula (R4)2AlO(R4AlO)mAl(R4)2 wherein each R4 is independently chosen from C1-4 alkyl radicals, m is from 3 to 50:
• and adjusting one or more of:
• a) the ratio of components 2 and 3;
• or
• b) changing component 2.