Highly alternating ethylene styrene interpolymers

A process for preparing a highly alternating interpolymer consisting of from 20 to 70 weight % of ethylene and from 80 to 30 weight % of a C8-20 vinyl aromatic monomer wherein:

• (i) in the triad sequence of vinyl aromatic monomer and ethylene as determined by 13C NMR, the triads have the sequence vinyl aromatic monomer, ethylene, vinyl aromatic monomer and the ratio of the amount of triads having the sequence vinyl aromatic monomer, ethylene, vinyl aromatic monomer divided by the calculated amount of triads having the same sequence as determined by Bernoullian statistical modeling is from greater than 1.5 to 9.5;
• (ii) said polymer has ethylene vinyl aromatic monomer repeating units essentially in an atactic configuration;
• (iii) the maximum number of sequential vinyl aromatic monomer units in sequence does not exceed 2;
• and
• (iv) said polymer containing ethylene vinyl aromatic monomer repeating unit, having head to tail and tail to tail microstructure present
• comprising contacting a monomer mixture comprising from 70 to 30 weight % of a C8-12 vinyl aromatic monomer and from 30 to 70 weight % of ethylene with a catalyst comprising a phosphinimine compound of the formula:
• L′((R1)3P═N))—M—L2
• wherein each R1 is independently selected from the group consisting of C3-6 alkyl radicals, L′ is anionic ligand selected from the group consisting of a phosphinimine ligand of the formula —((R1)3P═N)—;
• wherein R1 is as defined above, a C1-6 siloxy ligand,
• an amide ligand, and M is selected from the group consisting of Ti, Zr and Hf, and each L is independently selected from the group consisting of a halogen atom, a hydrogen atom, a C1-10 alkyl radical, a C1-10 alkoxide radical, and a C6-10 aryl oxide radical, and at least one activator selected from the group consisting of:
• (i) a mixture comprising complex aluminum compound of the formula R22AlO(R2AlO)mAlR22 wherein each R2 is independently selected from the group consisting of C1-20 hydrocarbyl radicals and m is from 3 to 50, and a hindered phenol substituted in the 2, 4, and 6 position by a C2-6 alkyl radical to provide a molar ratio of Al:hindered phenol from 2:1 to 5:1;
• (ii) ionic activators selected from the group consisting of:
• (A) compounds of the formula [R3]+[B(R4)4]− wherein B is a boron atom, R3 is a cyclic C5-7 aromatic cation or a triphenyl methyl cation and each R4 is independently selected from the group consisting of phenyl radicals which are unsubstituted or substituted with from 3 to 5 substituents selected from the group consisting of 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—(R5)3;
• wherein each R5 is independently selected from the group consisting of a hydrogen atom and a C1-4 alkyl radical;
• and
• (B) compounds of the formula [(R8)tZH]+[B(R4)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 selected from the group consisting of 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 may form an anilinium radical and R4 is as defined above;
• and
• (C) compounds of the formula B(R4)3 wherein R4 is as defined above;
• and
• (iii) mixtures of (i) and (ii);
• in an inert hydrocarbyl medium at a temperature from 20° C. to 150° C. and a pressure from 15 psi to 600 psi.