Catalytic polymerization process

Details Catalytic polymerization process Catalytic polymerization process

1998-08-19

2003-09-23

Zalukaeva, Tatyana (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S073000, C526S079000, C526S140000, C526S319000, C526S329100, C526S346000

Reexamination Certificate

active

06624261

ABSTRACT:

BACKGROUND OF THE INVENTION
Catalytic chain transfer is an effective way to control the molecular weight of polymers of methacrylates and styrenes. It is known that chain transfer catalysis (CTC) products contain a terminal vinylidene bond. This feature makes these products attractive as macromonomers for a variety of applications. However, CTC has not been known to be applicable for reduction of molecular weight in the polymerizations of other vinylic monomers such as acrylates.
Copolymerizations of methacrylate monomers with monosubstituted monomers in the presence of cobalt have been described in the art. However, the monosubstituted monomer is almost always present as a minor component. U.S. Pat. No. 4,680,354 describes molecular weight reduction using various Co(II) complexes in MMA-BA, MMA-EA and MMA-BA-St copolymerizations, wherein the abbreviations represent:
MMA=methyl methacrylate
BA=butyl acrylate
EA=ethyl acrylate
St=styrene.
U.S. Pat. No. 5,324,879 describes molecular weight reduction with Co(III) complexes in EA, St, and vinyl acetate (VAc) polymerizations, and MMA-EA copolymerization.
U.S. Pat. No. 4,680,352 describes molecular weight reduction and macromonomer (polymers or copolymers with unsaturated end-groups) synthesis in copolymerizations with acrylates and styrene with various Co(II) complexes. Various terpolymerizations are cited therein; however, no evidence of the nature or existence of terminal double bonds is given.
Gruel et al., Polymer Preprints, 1991, 32, p. 545, reports the use of Co(II) cobaloximes in low conversion St-MMA copolymerizations at low temperatures with end group analysis.
The references cited above cover the copolymerization of acrylates and styrene with methacrylate monomers, but do not disclose synthetic conditions for production of high purity macromonomers based on acrylates and styrene, nor branching of the resulting products. The conditions disclosed are unlikely to yield high purity macromonomers for systems composed predominantly of monosubstituted monomers. Disclosed temperatures of less than 80° C. are likely to provide substantial amounts of undesired graft copolymer at high conversion rates.
SUMMARY OF THE INVENTION
This invention concerns an improvement in a process for the free-radical polymerization of at least two unsaturated monomers to form a polymer whose molecular architecture comprises properties of molecular weight, branching, and vinyl-terminated end groups, the monomers having the formula
CH
2
═CXY
wherein
X is selected from the group consisting of H, CH
3
, and CH
2
OH;
Y is selected from the group consisting of OR, O
2
CR, halogen, CO
2
H, COR, CO
2
R, CN, CONH
2
, CONHR, CONR
2
and R′;
R is selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, substituted and unsubstituted aralkyl, substituted and unsubstituted alkaryl, and substituted and unsubstituted organosilyl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid and halogen; and the number of carbons in said alkyl groups is from 1 to 12; and
R′ is selected from the aromatic group consisting of substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, the substituents being the same or different and selected from the group consisting of carboxylic acid, carboxylic ester, epoxy, hydroxyl, alkoxy, primary amino, secondary amino, tertiary amino, isocyanato, sulfonic acid, substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted olefin and halogen;
by contacting said monomers with a cobalt-containing chain transfer agent and a free radical initiator at a temperature from about 80° to 170° C.;
the improvement which comprises controlling polymer architecture by introducing into the presence of the chain transfer agent at least one each of monomers A and B in the molar ratio of A:B, said molar ratio lying in the range of about 1,000:1 to 2:1, wherein for monomer A X is H and for monomer B X is methyl or hydroxymethyl; by one or more of the following steps:
I decreasing the ratio of A:B from about 1,000:1 toward 2:1;
II increasing the temperature from above 80° C. toward 170° C.;
III increasing the conversion of monomer to polymer toward 100% from less than about 50%;
IV decreasing the ratio of the chain transfer constant of A:B to below 1; and
V increasing the concentration of cobalt chain transfer agent;
whereby:
to effect lower molecular weight, employ at least one of steps I, II, IV and V;
to effect a higher degree of vinyl-terminated end groups, employ at least one of steps I, II, IV, and V; and
to effect increased branching, employ at least one of steps I, II, IV, and V with step III.
The nature of the derived products changes as a function of time. In the initial stages, linear macromonomers with one monomer-A in the terminal position can be obtained as essentially the only product. If the cobalt CTC catalyst levels are relatively low then CTC does not occur after every B-monomer insertion and the product mixture can include monomer-B units in the polymer chain as well as in the terminal position.
Cobalt chain transfer agent is employed in the form of cobalt complexes. Their concentrations are provided in the Examples in terms of ppm by weight of total reaction mass. Concentration will vary from 10 ppm to 1,500 ppm, preferably 10 to 1,000 ppm.
Later in the course of the reaction, when the concentration of the two above products is increased, then they can be reincorporated into a growing polymer chain. Thus, mono-branched product is obtained in the later stages of the reaction, usually around 90% conversion. At conversions above 95%, branches begin to appear on the branches, and the polymer becomes hyperbranched as conversions approach 100%.
Preferred monomers A are selected from the group consisting of acrylates, acrylonitrile and acrylamides;
and preferred monomers B are selected from the group:
a) substituted or unsubstituted &agr;-methylstyrenes;
b) substituted or unsubstituted alkyl methacrylates, where alkyl is C
1
-C
12
;
c) methacrylonitrile;
d) substituted or unsubstituted methacrylamide;
e) 2-chloropropene,
f) 2-fluoropropene,
g) 2-bromopropene,
h) methacrylic acid,
i) itaconic acid,
j) itaconic anhydride, and
k) substituted or unsubstituted styrenics.
If branched polymers are the desired product, it is possible to initiate the described process in the presence of preformed macromonomers. They can be of the type described in this patent. They can also be macromonomers based entirely upon methacrylates or the related species described previously in U.S. Pat. No. 4,680,354. Such a process would lead to products fitting the description above, but would allow for greater control over the polymer end-groups.
The branched polymers made by said process are polymers of this invention having the formula:
Y is as earlier defined;
n=1-20, m=1-5, p=1-20,and n+m+p≧3, and
Z is selected from the group CH
2
CHYCH
3
, CH
2
CMeYCH
3
, and, optionally,
m′=0-5, p′=0-20; n+m′+p′≧2;
and if m or m′>1, the m or m′ insertions respectively are not consecutive.
This invention also concerns a process comprising selecting A and B so the ratio of their chain transfer constants is less than 1, whereby functionality derived from Monomer B will be located on the vinyl-terminated end of the polymer.
This invention also concerns an improved process for the free-radical polymerization of at least two unsaturated monomers having the formula
CH
2
═CXY
wherein
X is selected from the group consisting of H, CH
3
, and CH
2
OH;
Y is selected from the group consisting of OR, O
2
CR, halogen, CO
2
H, CO
2
R, CN, CONH
2
, CONHR, CONR
2
, COR and R′;
R is selected from the group consisting of substitute

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