Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-07-06
2002-03-05
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...
C524S458000, C524S560000, C524S561000, C526S087000, C526S193000, C526S201000, C526S328500, C526S329700
Reexamination Certificate
active
06353065
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to emulsion polymerization and the resultant products, and especially to monomers polymerizable by the free radical mechanism.
SUMMARY OF THE INVENTION
The invention relates in particular to a process for the emulsion polymerization in the presence of a stable free radical of at least one monomer which can be polymerized by the radical route, which emulsion comprises a liquid aqueous phase and a liquid organic phase, the said aqueous phase comprising at least 50% by weight of water and the said liquid organic phase comprising more than 50% by weight of monomer(s) to be polymerized. The invention results, by a rapid controlled polymerization process, in a latex of polymer particles. The polymer obtained exhibits a low polydispersity (ratio of the weight-average molecular mass to the number-average molecular mass, Mw/Mn). A polymerization process is controlled if the number-average molecular mass increases linearly as a function of the degree of conversion of monomer to polymer. The greater the deviation from linearity, the poorer the control. A controlled polymerization system is also a living polymerization system and makes possible, for this reason, the preparation of block copolymers. The invention makes possible in particular the preparation of sequential polymers comprising blocks of the acrylate and/or methacrylate type.
The emulsion comprises an aqueous phase and an organic phase. The aqueous phase comprises at least 50% by weight of water. The liquid organic phase comprises, at each instant in the polymerization, more than 50% by weight of monomer still to be polymerized.
The emulsion also comprises an emulsifying agent and, preferably, a radical polymerization initiator.
The aqueous phase is the continuous phase of the emulsion, so that it is the organic phase which is dispersed in the form of droplets.
The emulsion comprises a stable free radical.
A stable free radical must not be confused with free radicals with a transitory lifetime (a few milliseconds), such as the free radicals resulting from the usual polymerization initiators, such as peroxides, hydroperoxides and initiators of azo type. Polymerization initiator free radicals tend to accelerate the polymerization. In contrast, stable free radicals generally tend to slow down the polymerization. It will generally be said that a free radical is stable within the meaning of the present invention if it is not a polymerization initiator and if, under the conditions of use of the present invention, the mean lifetime of the radical is at least 5 minutes. During this period of life, the molecules of the stable free radical continuously alternate the radical state and the state of a group bonded to a polymer chain via a covalent bond. Of course, it is preferable for the stable free radical to exhibit good stability throughout the duration of its use in the context of the present invention. A stable free radical can generally be isolated in the radical state at room temperature. A stable free radical is sufficiently stable for its free radical state to be able to be characterized by spectroscopic methods.
The stable free radical forms, during the polymerization, a reversible bond with the growing polymer chain. The stable free radical continuously alternates, at the end of the polymer chain, the state of a group bonded to the said chain via a covalent bond and the state of a stable free radical detached from the said chain in order to allow the insertion of a monomer unit, according to the following process:
−M−Y⇄−M
•
+Y
•
1)
−M
•
+M+Y
•
→−M−M−Y
2)
in which −M represents a monomer unit of the growing chain, M represents a monomer unit and Y
•
represents the stable free radical, for the case where the latter is monofunctional (F
SFR
=1, F
SFR
representing the functionality of the stable free radical, that is to say the number of sites on the same stable free radical molecule exhibiting the radical state). This process is repeated in order for the polymer chain to grow by insertion of monomer between the growing chain and the stable free radical.
It will be recalled that the notion of stable free radical is known to a person skilled in the art to denote a radical which is so persistent and unreactive with respect to the air and moisture in the surrounding air that the pure radical can be handled and stored at room temperature without more in the way of precautions than are the majority of commercial chemicals (see, in this respect, D. Griller and K. Ingold, Accounts of Chemical Research, 1976, 9, 13-19 or Organic Chemistry of Stable Free Radicals, A. Forrester et al., Academic Press, 1968).
The family of the stable free radicals includes in particular the compounds acting as radical polymerization inhibitors for the storage of monomers, stable nitroxyl radicals, that is to say comprising the ═N—O
•
group.
Use is to be made, as stable free radical, of, for example, the radicals represented by the following formulae:
in which n represents a non-zero integer and R
1
, R
2
, R
3
, R
4
, R′
1
and R′
2
, which can be identical or different, represent a hydrogen atom, a halogen atom, such as chlorine, bromine or iodine, a saturated or unsaturated, linear, branched or cyclic hydrocarbon-comprising group, such as an alkyl or phenyl radical, or a —COOR ester group or an —OR alkoxy group, or a —PO(OR)
2
phosphonate group, or a polymer chain which can, for example, be a poly(alkyl (meth)acrylate) chain, such as poly(methyl methacrylate), a polydiene chain, such as polybutadiene, or a polyolefin chain, such as polyethylene or polypropylene, but preferably being a polystyrene chain, and in which R
5
, R
6
, R
7
, R
8
, R
9
and R
10
, which can be identical or different, can be chosen from the same family of groups as that which has just been envisaged for R
1
, R
2
, R
3
, R
4
, R′
1
and R′
2
and furthermore can represent an —OH hydroxide group or an acid group, such as —COOH or —PO(OH)
2
or —SO
3
H.
In particular, the stable free radical can be 2,2,5,5-tetramethyl-1-pyrrolidinyloxy, sold under the trade name Proxyl, 2,2,6,6-tetramethyl-1-piperidinyloxy, generally sold under the name Tempo, 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, sold under the name 4-hydroxy-Tempo, or bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate, sold under the trade name CXA 5415 by the company Ciba Specialty Chemicals.
The stable free radical can also be chosen from the following list:
N-tert-butyl-1-phenyl-2-methylpropyl nitroxide,
N-tert-butyl-1-(2-naphthyl)-2-methylpropyl nitroxide,
N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide,
N-tert-butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide,
N-phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide,
N-phenyl-1-diethylphosphono-1-methylethyl nitroxide,
N-(1-phenyl-2-methylpropyl)-1-diethylphosphono-1-methylethyl nitroxide,
4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy,
2,4,6-tri(tert-butyl)phenoxy.
The stable free radical preferably comprises a linkage of formula:
in which the R
L
radical exhibits a molar mass of greater than 15. The R
L
radical can, for example, be chosen from the list of the radicals envisaged previously for R
1
, R
2
, R
3
, R
4
, R′
1
and R′
2
, as long as they exhibit a molar mass of greater than 15. The monovalent R
L
radical is said to be in the &bgr;-position with respect to the nitrogen atom of the nitroxide radical. The remaining valencies of the carbon atom and of the nitrogen atom in the formula (1) can be bonded to various radicals, such as a hydrogen atom or hydrocarbon-comprising radical, such as an alkyl, aryl or aralkyl radical, comprising from 1 to 10 carbon atoms. It is not excluded for the carbon atom and the nitrogen atom in the formula (1) to be connected to one another via a divalent radical, so as to form a ring. However, the remaining valencies of the carbon atom and of the nitrogen atom of the formula (1) are pre
Charleux Bernadette
Denie Sandrine
Lansalot Muriel
Pirri Rosangela
Vairon Jean-Pierre
Egwim Kelechi
Elf Atochem S.A.
Wu David W.
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