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
2001-12-20
2004-04-06
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S245000, C525S329500, C526S319000, C526S329700, C526S171000, C526S318440, C526S144000
Reexamination Certificate
active
06716918
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for producing a methacrylate-based polymer by a living radical polymerization method, and a methacrylate-based polymer produced by the process.
Conventionally, the following three types of living radical polymerization methods have been studied.
(1) First, a propagating radical is produced from a radical polymerization initiator or a covalent bond chemical species. Then, a pseudo-termination reaction in which the propagating radical and a complementary radical are reacted with each other while incorporating monomers thereinto for producing the covalent bond chemical species, and a reaction in which the complementary radical is dissociated from the covalent bond chemical species to form the propagating radical again, are reversibly caused, so that the polymerization proceeds.
(2) First, a low-valence metal chemical species oxidatively abstracts an atom from a covalent bond chemical species, thereby producing a propagating radical and a high-valence metal chemical species. Then, a pseudo-termination reaction in which the propagating radical and the high-valence metal chemical species are reacted with each other while incorporating monomers thereinto for producing a low-valence metal chemical species, and a reaction in which a high-valence metal chemical species is dissociated from the low-valence metal chemical species to form the propagating radical again, are reversibly caused, so that the polymerization proceeds.
(3) First, a propagating radical is produced from a radical polymerization initiator. Then, a pseudo-termination reaction in which the propagating radical and a chain transfer agent are reacted with each other while incorporating monomers thereinto for producing a chain transfer radical, a reaction in which the chain transfer radical and the chain transfer chemical species are reacted with each other to transfer the radical, and a pseudo-termination reaction in which the chain transfer radical and the monomer are reacted with each other to produce the chain transfer radical again, are simultaneously caused, so that the polymerization proceeds.
Among these methods, the method (2) which is classified into atom transfer radical polymerization method, is expressed by the following reaction formula:
In the above reaction formula, P represents a polymer chain; (M) represents a transition metal; X represents a halogen atom; Y and L are ligands capable of coordinating to (M); n and n+1 are valences of (M); and (1) and (2) represent a low-valence metal complex and a high-valence metal complex, respectively, constituting a redox conjugated system.
First, the low-valence metal complex (1) radically abstracts the halogen atom X from the halogen-containing polymerization initiator P-X, thereby producing the high-valence metal complex (2) and a carbon-centered radical P. (the reaction rate of the reaction between the low-valence metal complex (1) and the halogen-containing polymerization initiator P-X is expressed by K
act
). As shown in the above reaction formula, the carbon-centered radical P. is then reacted with a monomer to form a similar intermediate radical species P. (the reaction rate of the reaction between the carbon-centered radical P. and the monomer is expressed by K
propagation
). The reaction between the high-valence metal complex (2) and the radical P produces the product P-X and simultaneously regenerate the low-valence metal complex (1) (the reaction rate of the reaction between the high-valence metal complex (2) and the radical P. is expressed by K
deact
). Then, the low-valence metal complex (1) and the product P-X are further reacted with each other, so that the polymerization reaction further proceeds. In order to control the above polymerization reaction, it is most important to reduce the concentration of the propagating radical species P. to a low level.
Specifically, the following atom transfer radical polymerization methods have been reported:
(1) Polymerization of styrene conducted in the presence of CuCl and a bipyridyl complex using &agr;-chloroethylbenzene as a polymerization initiator (J. Wang and K. Matyjaszewski,
J. Am. Che. Soc
., 117, 5614 (1995)).
(2) Polymerization of methyl methacrylate conducted in the presence of RuCl
2
(PPh
3
)
3
and an organoaluminum compound using CCl
4
as a polymerization initiator (M. Kato, M. Kamigaito, M. Sawamoto and T. Higashimura, “Macromolecules”, 28, 1821 (1995)).
Thereafter, with further development of ligands, metal species, polymerization initiators, etc., the atom transfer radical polymerization method has been widely applied to various monomers including acrylate monomers.
However, the equilibrium condition shown in the above reaction formula cannot be sometimes established. The non-equilibrium reaction is frequently observed when applied especially to polymerization of methacrylate. The reason therefore is considered to be that the concentration of the propagating radical becomes considerably high because of any electronic or steric effect by substituents of the ester group.
In U.S. Pat. No. 5,807,937, it is described that the radical concentration can be reduced by adding the high-valence metal complex (2) (e.g., CuCl
2
) in an amount of preferably 0.2 to 10 mol % to the low-valence metal complex (1) (e.g., CuCl). However, in some cases, this method is still insufficient to maintain the equilibrium condition as shown in the above reaction formula. Even if the high-valence metal complex (2) is added in a higher amount, since the complex (2) has a poor solubility, the polymerization reaction itself still proceeds considerably slowly because of the too low concentration of the high-valence metal complex (2) contributing to the above equilibrium reaction.
Also, when it is intended to apply the atom transfer radical polymerization method to the production of block copolymers, the block polymerization sometimes fails to smoothly proceed depending upon kinds of monomers used. It is considered that the poor block polymerization is caused by the difference between easiness of abstracting the halogen atom from the end of the polymerization initiator and easiness of abstracting halogen bonded to the end of the successively added monomer, i.e., K
act
in the above reaction formula. In particular, in the case where the first block chain is constituted from acrylate-based monomers, since the rate for abstracting halogen from the end of the acrylate is too slow, it becomes difficult to conduct the subsequent formation (i.e., block polymerization) of the second block chain composed of methacrylate-based monomers.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a living radical polymerization method applicable to the polymerization of a methacrylate monomer, and a process for producing a methacrylate-based polymer by the living radical polymerization method. Also, the present invention provides a process for producing a copolymer comprising a first block chain composed of an acrylate-based monomer and a second block chain composed of a methacrylate-based monomer by an atom transfer polymerization method, and the like.
To accomplish the aims, in a first aspect of the present invention, there is provided a process for producing a methacrylate-based polymer, comprising:
polymerizing (d1) a radical-polymerizable monomer containing at least one methacrylate-based monomer in the presence of (c1) a redox catalyst comprising a metal complex containing at least one transition metal as a central metal selected from the group consisting of elements of Groups 7 to 11 of the Periodic Table, said redox catalyst containing a low-valence metal (M)
n
wherein n represents an atomic valence of the metal, and a high-valence metal (M)
n+1
both constituting the redox catalyst system, and having a molar ratio of (M)
n
to (M)
n+1
of 90/10 to 0.1/99.9, upon initiation of the polymerization, using (a1) at least one polymerization solvent selected from the group consisting of water, ethers, amides, nitriles and alcohols, and (b1
Fukuda Takeshi
Nishizawa Osamu
Saito Takahiro
Asinovsky Olga
Mitsubishi Chemical Corporation
Nixon & Vanderhye P.C.
Seidleck James J.
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