Branched polyolefin synthesis

Details Branched polyolefin synthesis Branched polyolefin synthesis

2000-01-14

2003-02-11

Wu, David W. (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S173000, C526S348200, C526S318000, C526S291000, C526S297000, C526S082000

Reexamination Certificate

active

06518383

ABSTRACT:

BACKGROUND OF THE INVENTION
Macromolecular engineering using commodity monomers is becoming a major trend in polymer technology to satisfy the demand for new properties, improved cost effectiveness, ecology and quality. Functional polymers with low molecular weight, low polydispersity, compact, branched structures and terminally-located reactive groups are expected to exhibit superior performance/cost characteristics, by virtue of lower inherent viscosity and higher reactivity vs. conventional linear statistical copolymers.
The terminally-functional branched polymers appear to be ultimate reactive substrates for networks, because the branch points can substitute for a significant portion of expensive reactive groups and provide better distribution of the reactive groups. Polymers having large numbers of short branches below critical molecular weight are unlikely to form any entanglements and should exhibit low inherent viscosity and good flow even in concentrated solutions.
Conventional techniques for synthesizing well-defined branched polymers require expensive multistep processes involving isolation of reactive intermediate macromonomers. The macromonomers have polymerizable end groups, which are usually introduced using functional initiator, terminating or chain transfer agent. Well-defined branched polymers are prepared by the macromonomer homopolymerization or copolymerization with suitable low molecular weight comonomer selected based on known reactivity ratios. These methods have been reviewed and only single-branch polymers from single incorporation of the macromonomers are reported; multiple reincorporation of the growing macromonomers was never attempted, e.g., R. Milkovich, et al., U.S. Pat. No. 3,786,116; P. Remp, et al., Advan. Polymer Sci., 58, 1 (1984); J. C. Salamone, ed., Polymeric Materials Encyclopedia, Vol.3 and 4 (1996).
Several linear macromonomers were prepared by end-capping of living anionic polyolefins with unsaturated terminating agents providing polymerizable olefin end-groups, e.g., R. Asami et al., Macromolecules, 16, 628 (1983). Certain macromonomers have been incorporated into simple graft polymers by homo- or copolymerization with branched structure not well-characterized and reincorporation of the macromonomers into more complex structures was not considered.
Dendrimers or hyperbranched polymers are conventionally prepared using expensive, special multifunctional monomers or expensive multistep methods requiring repetitive isolation of the reactive intermediates. Nothing in the prior art discloses synthetic conditions for production of macromonomers or polymers containing branches upon branches.
SUMMARY OF THE INVENTION
This invention relates to a general process for the synthesis of polyolefins containing branches upon branches and having polymerizable olefin end groups by a convenient one-pot polymerization of selected vinyl monomers with chain polymerization initiators and a method to provide olefin end groups by chain termination agents. The polymerization is carried out in such a manner that chain termination occurs gradually and each chain termination event terminates that particular polymer chain with polymerizable olefinic functionality. Subsequent reincorporation of the linear polymer chains produced early in the reaction leads to branching of subsequently-formed macromolecules which are terminated with polymerizable olefinic functionality. Subsequent reincorporation of the branched macromolecules leads to subsequently-formed polymer molecules containing branches upon branches which are terminated with polymerizable olefinic functionality. Spontaneous repetition of the process leads to highly branched or hyperbranched dendritic products still retaining polymerizable olefinic termini.
This invention concerns an improved process for the anionic polymerization of at least one vinylic monomer to form a branched polymer comprising contacting, in the presence of an anionic initiator:
(i) one or more anionically polymerizable vinylic monomers having the formula CH
2
═CYZ, and
(ii) an anionic polymerization chain terminating agent of formula CH
2
═CZ—Q—X,
wherein:
Q is selected from the group consisting of a covalent bond, —R′—, —C(O)—, and —R′C(O)—;
Y is selected from the group consisting of R, CO
2
R, CN, and NR
2
;
X is selected from the group consisting of halogen, and RSO
3
;
Z is selected from the group consisting H, R, and CN;
R is selected from the group consisting of unsubstituted and substituted alkyl, vinyl, aryl, aralkyl, alkaryl and organosilanyl groups and R′ is selected from the group consisting of substituted or unsubstituted alkylene, arylene, aralkylene, alkarylene and organosilanylene groups; the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, hydroxyl, alkoxy and amino;
where acidic protons, if any, can be protected from example by organosilanyl, tertiary alkyl or benzyl;
wherein the improvement comprises obtaining higher yields of branched polymer, the polymer having dense branch upon branch architecture and polymerizable vinylic chain termini, employing steps I, III, VI and at least one of II, IV and V:
I. reacting (i) with an anionic initiator in a first step:
II. decreasing the ratio of (i) to anionic initiator toward 1;
III. adding (ii) optionally with some (i) in a second step;
IV. selecting the rate of the (ii) addition, dependent on the (ii) reactivity;
V. increasing the ratio of (ii) to anionic initiator toward 1; and
VI. increasing the conversion of (i), (ii) and olefinic end groups from 70 to 100%.
Based on the disclosure and Examples presented herein, one skilled in the art can select the optimum steps I-VII with minimum experimentation. One skilled in the art will also be able to select the appropriate anionic initiator and chain transfer agent for the monomer(s) being polymerized, by reference to the well-known conditions for anionic polymerization. Optionally, the process includes the step, VII, of converting anionic-growing end groups into non-polymerizable end groups. It is preferred to operate process step V at a ratio of about 0.7 to 1, most preferably from 0.8 to 1. In step IV, the rate of addition will vary in the same direction as reactivity of (ii) so that addition will be relatively slow for less reactive component (ii) and will increase commensurate with increased reactivity of component (ii).
This invention further concerns the product of the above reaction which is composed primarily of a polymer having a branch-upon-branch structure and a polymerizable olefinic end group, having the structure:
B′=Z, B;
n=1-100, m=0-50, p=0-100, n+m+p≧2;
if m>1, then the m insertions are consecutive or not consecutive;
A=anionic initiator moiety selected from the group consisting of R; and
Q, Y, Z are as earlier defined.
Branch-upon-branch polymers (BUBP) are superior over straight branch polymers (SBP) in terms of more compact structure, reflected in lower inherent viscosity and better flow properties in melts and solutions for any given molecular weight of polymers. Therefore, BUBPs require less solvents and lower temperature than SBPs for processing.
BUBPs with terminal end groups are superior over SBP substrates by having much larger network fragments, which can be preformed and incorporated into new topology networks. BUBPs allow formation of new types of hybrid networks by combining different BUBPs with a good control on molecular level.
BUBPs allow incorporation of larger numbers of branch points per macromolecule, which are equivalent to curing sites. This improves economy and conversion of reactive coatings by reducing the number of expensive curing sites.
In general, BUBPs offer at least a 10 percent improvement over SBPs of the same molecular weight in such characteristics as lower viscosity, reduced need for solvent, fewer curing sites in reactive substrates for networks and higher conversion of curing sites in final coatings, all of which provide

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