Preparation of functionalized alkoxyamine initiator and its use

Details Preparation of functionalized alkoxyamine initiator and its use Preparation of functionalized alkoxyamine initiator and its use

2003-06-19

2004-02-03

Teskin, Fred (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S204000, C526S205000, C526S220000, C546S184000, C548S542000, C564S300000, C564S301000

Reexamination Certificate

active

06686424

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for the preparation of functionalized alkoxyamine initiators and to their use in radical polymerization.
SUMMARY OF THE INVENTION
A one-pot process for the preparation of functional alkoxyamines of the general formula (I),
is disclosed. The process entails (1) reacting an oxidizing agent with a sterically hindered secondary amine to produce an aqueous phase and a nitroxy radical (2) removing the aqueous phase and adding to the nitroxy radical one or more vinyl monomer(s) conforming to a formula and a system which produces free radicals. Also disclosed is a process of polymerizing monomers using the functional alkoxyamine.
BACKGROUND OF THE INVENTION
The use of the controlled radical polymerization (“CRP”) of vinyl monomers has increased rapidly because it allows the synthesis of a broad range of well-defined (co)polymers under uncomplicated experimental conditions. The polymerization may, for example, be carried out in aqueous media and under moderate polymerization temperatures and purification of the monomer prior to polymerization is not required. Additionally, the main molecular parameters of the polymer chain, for example its polydispersity, molecular weight, polymer architecture or the structure of the chain-ends may be easily controlled and adjusted. The CRP is also called “living” free radical polymerization. The aim of the precise control of free radical polymerization is achieved by reversible chain termination or blocking (“end-capping”) after each growth step. The equilibrium concentration of the polymerization-active (“living”) chain ends in this case is so low compared with the equilibrium concentration of the blocked (“dormant”) chain ends that irreversible termination and transfer reactions are greatly suppressed compared with the growth reaction. Since the end-capping proceeds reversibly, all the chain ends remain “living” if no termination reagent is present. This allows the control of the molecular weight, low polydispersity and controlled functionalization of the chain ends by termination reagents.
Of all the CRP systems presently under investigation, the nitroxyl-mediated polymerization (“NMP”) is one of the most attractive and efficient, because this technique provides advantages applicable to a broad range of monomers such as (meth)acrylates, acrylonitrile, styrenes, acrylamides, butadiene or isoprene and may be carried out in a metal-free, colorless and odorless manner.
Numerous publications have shown that alkoxyamines may be used to initiate and control the radical polymerization of vinyl monomers according to an NMP mechanism.
U.S. Pat. No. 4,581,429 discloses alkoxyamines which are formed by the reaction of linear or cyclic nitroxides, such as 2,2,6,6-tetra-methylpiperidin-1-oxyl (TEMPO) with organic carbon-based free radicals, and a process for the preparation of vinyl polymers using these compounds as initiators. The reactions typically have a low concentration of free radicals which, in the free radical polymerization of vinyl monomers, means that bimolecular termination reactions are less likely to occur than unimolecular growth reactions.
Other examples are described by Hawker et al. (
J. Am. Chem. Soc
. 1994, 116, 11185 and
J Am. Chem. Soc
. 1999, 121, 3904-3920) and in U.S. Pat. No. 5,322,912, U.S. Pat. No. 5,412,047, U.S. Pat. No. 5,449,724, U.S. Pat. No. 5,498,679, U.S. Pat. No. 6,258,911, DE-A 199 09 767 and EP-A 0 891 986.
The most commonly used method for the synthesis of alkoxyamines consists in coupling an alkyl radical to a nitroxyl radical. The alkyl radical R
0
may be generated by different methods, for example by decomposition of azo compounds (Hawker et al., Macromolecules 1996, 29, 5245-5254; Yozu Miura et al., Macromolecules 1998, 31, 6727-6729), by hydrogen removal from an appropriate substrate (Hawker et al., Macromolecules 1996, 29, 5245-5254; Yozu Miura et al., Macromolecules 1998, 31, 4659-4661) or by addition of a radical to an olefin (Hawker et al., J. Am. Chem. Soc. 1994, 116, 11185). The alkyl radical may also be generated from an halogenated compound R—X in the presence of a metallic catalyst following an atom transfer radical addition (“ATRA”) reaction (WO-A 00/49027; WO-A 00/61544).
EP-A 1 083 169 discloses a process for the preparation of functionalized alkoxy-amine initiators in which hydrogen peroxide is reacted with iron(II) sulfate in the presence of a nitroxyl radical and a vinyl monomer to form the alkoxyamine with a good yield in a one-pot process.
The major disadvantage of the methods described above is that the alkoxyamines have to be synthesised from costly nitroxyl radicals and generally must be purified before they may be used for polymerization.
The object of the present invention was to provide a new synthetic pathway for the synthesis of alkoxyamines in a one-pot process and to use these alkoxyamines as intermediates in a polymerization process which provides homo- and copolymers of narrow polydispersity with a specific molecular weight and which does not have the above-mentioned disadvantages of the prior art.
DETAILED DESCRIPTION OF THE INVENTION
Surprisingly, it has now been found that hydroxy-functional alkoxyamines may be produced from secondary amines in a one-pot process and used, without intermediate purification, in a controlled, free-radical polymerisation process.
The object of the present invention is a one-pot process for the preparation of functional alkoxyamines of the general formula (I)
wherein
R
1
, R
2
, R
3
are independently selected from the group consisting of: hydrogen, C
1
-C
20
alkyl, C
1
-C
20
cycloalkyl, C
6
-C
24
aryl, halogen, cyano, C
1
-C
20
alkylester C
1
-C
20
cycloalkylester, C
1
-C
20
alkylamide, C
1
-C
20
cycloalkylamide C
6
-C
24
-arylester and C
6
-C
24
-arylamide;
R
4
and R
5
are independently selected from the group consisting of: C
1
-C
18
alkyl, C
2
-C
18
alkenyl, C
2
-C
18
alkynyl, C
3
-C
12
cycloalkyl, C
3
-C
12
heterocycloalkyl, and C
6
-C
24
-aryl, all of which are optionally substituted by NO
2
, halogen, amino, hydroxy, cyano, carboxy, ketone, C
1
-C
4
alkoxy, C
1
-C
4
alkylthio, C
1
-C
4
alkylamino; or
R
4
and R
5
form, together with the nitrogen atom linking them, a C
3
-C
12
cycloalkyl radical, a (C
4
-C
12
alkanol)yl radical or a C
2
-C
13
-heterocycloalkyl radical containing oxygen, sulfur or nitrogen atoms; or
R
4
and R
5
together form a residue of a polycyclic ring system or a polycyclic heterocycloaliphatic ring system containing oxygen, sulfur or nitrogen atoms;
wherein the carbon atom of the R
4
and R
5
radicals directly adjacent to the alkoxyamine nitrogen atom is in each case substituted by 3 further organic substituents and
wherein optionally at least one of the radicals R
4
and R
5
contains a functional group Y which is capable of further reacting or crosslinking with the functional groups known from the coatings field;
comprising the reaction steps of
(1) reacting of an oxidizing agent (A) with a sterically hindered secondary amine of the general formula (II),
 wherein
R
4
and R
5
are independently selected from the group consisting of: C
1
-C
18
alkyl, C
2
-C
18
-alkenyl, C
2
-C
18
alkynyl, C
3
-C
12
cyclo-alkyl or C
3
-C
12
-heterocycloalkyl, C
6
-C
24
aryl, all of which are optionally substituted by NO
2
, halogen, amino, hydroxy, cyano, carboxy, ketone, C
1
-C
4
alkoxy, C
1
-C
4
alkylthio, C
1
-C
4
alkylamino; or
R
4
and R
5
form, together with the nitrogen atom linking them, a C
3
-C
12
cycloalkyl radical, a (C
4
-C
12
alkanol)yl radical or a C
2
-C
13
heterocycloalkyl radical containing oxygen, sulfur or nitrogen atoms; or
R
4
and R
5
together form a residue of a polycyclic ring system or a polycyclic heterocycloaliphatic ring system containing oxygen, sulfur or nitrogen atoms;
wherein the carbon atom of the R
4
and R
5
radicals directly adjacent to the alkoxyamine nitrogen atom is in each case substituted by 3 further organic substituents and
wherein optionally at least one of the radicals R
4
and R
5
contains a functional group Y which is capa

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