Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-10-03
2003-11-11
Egwim, Kelechi C. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S267000, C524S461000, C526S075000, C526S222000
Reexamination Certificate
active
06646055
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of a microgel. The term microgel includes microgels and star polymers.
Microgels are macromolecules which possess a very high molecular weight and yet a low viscosity similar to linear or branched polymers of relatively low molecular weight. Microgels are an intermediate structure between conventional linear or branched polymers such as polyethylene or polycarbonate and networks such as vulcanized natural rubber. The dimensions of microgels are comparable with high molecular weight linear polymers but their internal structure resembles a network.
The properties of microgels make them particularly useful in a wide range of applications such as in additives, in advanced material formulations for foams or fibers, in coating compositions, binders and redispersible latexes. Microgels can also be used to improve the ease of processing and to improve the structural strength and dimensional stability of the final products. A further potential use for microgels is as additives for high impact polymers. Microgels embedded in a matrix of conventional linear polymer can act to stabilize the whole structure by distributing mechanical tension. Microgels are also useful in biological systems and as pharmaceutical carriers.
Care is required in preparing microgels as the multiple double bonds present within these systems can readily undergo intermolecular reactions which can lead to intractable networks. PCT/AU98/00015 discloses a process for microgel preparation involving reacting an alkoxyamine with a crosslinking agent. Procedures such as those described by Okay and Funke in Macromolecules, 1990, 23, 2623-2628, require high purity solvent and reagents as well as an inert atmosphere and are complicated by undesirable side reactions. Despite the unique properties of microgels, the difficulties in preparing them have limited their potential and commercial use.
SUMMARY OF THE INVENTION
This invention concerns a new process for preparing microgel(s) employing a wide range of activatable prepolymers. The process of this invention produces a polymer composition of crosslinked component A and soluble components B and C from mono-olefinic and multi-olefinic monomers in the presence of catalyst and initiator. The process comprises:
I) introducing mono-olefinic monomer, catalyst, and initiator into a reactor in the absence of multi-olefinic monomer and producing an activatable prepolymer component B;
II) contacting the product of I) with multi-olefinic monomer to produce components A and C, optionally in the presence of additional initiator, also optionally in the presence of additional mono-olefinic monomer and initiator. The ratio of components A/(B+C) can be controlled by varying the mole ratio of (Component B)/(multi-olefinic monomer) from 0.05/1 up to 5/1, by decreasing said mole ratio to increase the ratio of A/(B+C), and increasing said mole ratio to decrease the ratio of A/(B+C).
Component B is the soluble species made in step I, A is the insoluble species made in Step II and C is the soluble species made in Step II.
The prepolymer, B, will be comprised of an activatable prepolymer. As will be understood by one skilled in the art having this disclosure as guidance, the activatable prepolymer is a polymer that under the conditions of the experiment can reversibly generate propagating radicals. The activatable prepolymer contains a group which is adapted to reversibly cleave from the prepolymer B under activating conditions to provide a reactive propagating radical and so promote living/controlled polymerization.
The term activatable prepolymer includes a polymer containing activated halogen (or pseudohalogen) groups, a polymer terminated with thiocarbonylthio groups (including dithiocarbamate, dithiocarbonate, trithiocarbonate, dithioester groups), a macromonomer (a polymer chain having at least one polymerizably-active functionality per polymer chain).
Methods for Preparing Component B(Step I)
Polymers containing halogen (or pseudohalogen) groups are activatable prepolymers in atom transfer radical polymerization (ATRP). Typical examples of transition metal catalysts for atom transfer radical polymerization include complexes such as CuX/2,2′-bipyridyl derivatives, CuX/Schiff base complexes, CuX/N-alkyl-2-pyridylmethanimine, CuX/tris[2-(dimethylamino)ethyl]amine, CuX/N,N,N′,N″,N″-pentamethyldiethylenetriamine, CuX/tris[(2-pyridyl) methyl]amine, Mn(CO)
6
, RuX
x
(PPh
3
)
3
, NiX{(O—O′—CH
2
NMe
2
)
2
C
6
H
3
}, RhX(PPh
3
)
3
, NiX
2
(PPh
3
)
2
and FeX
2
/P(n-Bu)
3
wherein X is halogen or pseudohalogen and preferably chlorine or bromine. An alumoxane Al(OR)
3
may be used as a cocatalyst. It is believed that the mechanism of ATRP is described in the following scheme:
Initially, the transition metal catalyst, M
t
n
, abstracts the halogen atom X from the initiator, an arene or alkane sulfonyl halide, R—X, to form the oxidized species, M
t
n+1
X, and the sulfur centered radical R•. In the subsequent step, the radical, R•, reacts with unsaturated monomer, M, with the formation of the intermediate radical species, R—M•. The reaction between M
t
n+1
X and R—M• results in the product, R—M—X, and regenerates the reduced transition metal species, M
t
n
, which further reacts with R—X and promotes a new redox cycle. When polymeric halides, R—M
n
—X, are reactive enough toward M
t
n
and monomer is in excess, a number of atom transfer radical events, i.e., a living/controlled radical polymerization occurs. Further, details of this mechanism are described in the reference: Macromolecules, 1995, 28, 7901. See also Macromolecules,1995, 28, 7970 and Macromolecules, 1996, 29, 3665 concerning living/controlled radical polymerization using a combination of an arenesulfonyl chloride or alkane sulfonyl chloride and a transition metal compound.
One part of the polymerization system in the process is an arenesulfonyl halide or an alkanesulfonyl halide of the Formula A
1
SO
2
X wherein A
1
is an aryl, substituted aryl group, an alkyl group or a substituted alkyl group, and X is chlorine, bromine or iodine. Included within the meaning of arenesulfonyl halide and alkanesulfonyl halide is any adduct, such as a 1:1 adduct, which is a reaction product of an arene- or alkyl-sulfonyl halide and any polymerizable vinyl monomer. In effect, such an adduct is one of the initial products in the polymerization process itself.
Another component of the polymerization process system is a compound containing a lower valent transition metal atom. By this is meant a compound containing at least one transition metal atom that is capable of existing in a higher valent state. Included within the definition of a compound containing a transition metal atom in a lower valent state is a compound or combination of compounds that under the polymerization process conditions can form in situ the desired compound containing a transition metal atom in a lower valent state. In some cases, this can include metal itself (or an alloy or a metal oxide thereof) which can dissolve and/or be solubilized to some extent in the process medium.
Suitable lower valent metals include Cu[I], Ru[I], Ni[II], Re[II], Pd[II], Cu[0], Ni[0], Fe[0], Pd[0], and Rh[II]. The transition metal compound should preferably be at least slightly soluble in the polymerization medium. Optionally, the transition metal compound which is added can be solublized by the addition of a complexing agent such as a 2,2′-bipyridine derivative, for example, 4,4′-di(5-nonyl)-2,2′-bipyridine. The complexing agent should also be chosen such that the transition metal has the appropriate redox potential. Other suitable complexes are listed above. The molar ratio of lower valent transition metal compound: arenesulfonyl halide or alkanesulfonyl halide is not critical, but it is preferred th
Berge Charles T.
Fryd Michael
Johnson Jeffrey W.
Moad Graeme
Rizzardo Ezio
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Egwim Kelechi C.
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