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
2001-02-22
2002-08-13
Lipman, Bernard (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...
C525S328200, C525S328700, C525S328800, C525S329900, C525S390000, C525S333600, C525S375000, C525S377000, C526S082000
Reexamination Certificate
active
06433100
ABSTRACT:
The present invention relates to a process for the preparation of polymers containing N→O terminal groups and to compositions comprising polymers obtained by this process.
The present invention relates to the preparation of polymers characterized by a low polydispersity range, preferably a polydispersity range which is lower than 3, and an enhanced monomer to polymer conversion efficiency. In particular, this invention relates to a stable, free radical initiated polymerization process by the ATRP (Atom Transfer Radical Polymerization) method which produces homopolymers, random copolymers, block copolymers, multiblock copolymers, graft copolymers and the like having a low polydispersity range and predetermined molecular weights.
Polymers or copolymers prepared by a conventional free radical polymerization reaction inherently have broad molecular weight distributions and a polydispersity range which is generally greater than three. This is explained by the fact that the half-life of most free radical initiators is relatively long, ranging from several minutes to hours. Polymeric chain reactions are initiated at different points of time which enables the initiators to generate growing chains of various lengths at any time period during the polymerization process. Moreover, the propagating chains may react with each other in free radical side reactions known as combination and disproportionation. Both are irreversible chain terminating reaction steps. The formation of chains of varying lengths is terminated at different points of time during the reaction, resulting in polymers of very different chain lengths, i.e. from very small to extremely long, and broad polydispersity ranges. Whenever a homogeneous molecular weight distribution is desirable in a free radical polymerization process, the growth of the polymer chains is to be initiated simultaneously to avoid termination at different points of time.
Therefore, any conventional free radical polymerization process is characterized by significant drawbacks, such as difficulties in predicting or controlling the molecular weight distribution of the polymer obtained and the polydispersity range. Furthermore, free radical polymerization processes are difficult to control. Most polymerization reactions are strongly exothermic, rendering it almost impossible to efficiently remove heat from the highly viscous polymer reaction mixture. The problems of conventional free radical polymerization reactions of the types mentioned above may also result in an undesirable formation of gel-type polymers of broad molecular weight distribution. They are difficult to handle in subsequent working-up steps, such as separation, purification, filtering and drying.
There is an urgent need for suitable agents which are useful for overcoming these drawbacks and which provide an efficient control of free radical initiated polymerizations. This will result in the preparation of polymers of defined chemical, and physical properties, such as viscosity, hardness, gel content, clarity, high gloss, durability and the like.
Therefore, the efficient control of reaction parameters in free radical polymerization processes is highly desirable. Among the different proposed methods some may be defined by the term “living” polymerization. This method aims at a defined chain growth by the efficient reduction of chain terminating side reactions. Such a polymerization would provide for molecular weight control and narrow molecular weight distribution (MWD).
U.S. Pat. No. 4,581,429 discloses a free radical polymerization process which controls the controlled or “living” growth of polymer chains to produce oligomeric homopolymers and copolymers, including block and graft copolymers. A process embodiment is the use of initiators of the partial formula R′R″N—O—X. In the polymerization process the free radical species R′R″N—O. and .X are generated. .X is a free radical group, e.g. a tert.-butyl or cyanoisopropyl radical, capable of polymerizing monomer units containing ethylene groups. The monomer units A are substituted by the initiator fragments R′R″N—O. and .X and polymerize to structures of the type: R′R″N—O—A
n
—X. Specific R′R″N—O—X initiators mentioned are derived from cyclic structures, such as 2,2,6,6-tetramethylpiperidine, or open chain molecules, such as di-tert.-butylamine.
WO 96/30421 discloses a controlled or “living” polymerization process of ethylenically unsaturated polymers such as styrene or (meth)acrylates by employing the ATRP method. According to this method initiators are employed which generate a radical atom such as .Cl, in the presence of a redox system of transition metals of different oxidation states, e.g. Cu(I) and Cu(II), providing “living” or controlled radical polymerization.
A general drawback of this prior art method is seen in the fact that the polymer chains prepared by ATRP contain halogen as terminal fragment which has been transferred from the polymerization initiator. The content of halogen is generally undesirable in polymers. Halogen, especially chlorine and bromine, is subject to the removal as hydrogen halide depending on temperature, especially above 150° C. The double bond thus formed is subject to a reaction with atmospheric oxygen which decreases the antioxidative resistance of the polymer. Moreover, hydrogen halide liberated from the polymer reacts with other functional groups present in the polymer, such as ester groups present in acrylates. Depending on the type of the polymer, chlorine is also removed in the form of a radical which might initiate undesirable chain reactions in the polymer structure.
The removal of halogen from the polymer structure, especially the terminal position of the polymer chain, is the problem to which the present invention particularly relates. It is desirable to have the halogen replaced with suitable substituents.
M. Sawamoto and M. Kamigaito,
J. Macromol. Sci.
(
J.M.S.
)—
Pure Appl. Chem.
A 34(10, pp. 1803-1814 (1997) disclose ATRP of methyl acrylate with the initiator dichloroacetophenone and a catalyst system consisting of RuCl
2
(PPh
3
)
3
and the co-catalyst Al(O-iPr)
3
. They report that the polymerization reaction is terminated with the addition of large amounts of TEMPO (=2,2,6,6-TEtraMethylPiperidyl-1-Oxide) or galvinoxyl. No products are reported to have been isolated and no properties have been disclosed.
It has surprisingly been found that terminal halogen in polymerisates, especially prepared by ATRP, is effectively replaced by the free radical species R′R″N—O., which may have an open chain or cyclic structure.
The present invention relates to a process for the preparation of a polymer of the formula
wherein:
In represents a polymerization initiator fragment of a polymerization initiator capable of initiating polymerization of monomers or oligopolymers containing ethylene groups;
p represents a numeral greater than zero and defines the number of initiator fragments;
A represents an oligopolymer or polymer fragment consisting of repeating units of polymerizable monomers or oligopolymers containing ethylene groups;
x represents a numeral greater than one and defines the number of repeating units in A;
B represents a monomer, oligopolymer or polymer fragment copolymerized with A;
y represents zero or a numeral greater than zero and defines the number of monomer, oligopolymer or polymer repeating units in B;
q represents a numeral greater than zero;
one of R
1
and R
2
represents C
1
-C
7
-alkyl and the other represents C0-C
4
-alkyl or C
1
-C
4
-alkyl substituted by C
1
-C
4
-alkoxycarbonyl or C
1
-C
4
-alkoxy; or
R
1
and R
2
together with the adjacent carbon atom both represent C
3
-C
7
-cycloalkyl;
R
3
and R
4
are as defined as R
1
and R
2
;
R
a
represents C
1
-C
4
-alkyl, cyano, C
1
-C
4
-alkoxycarbonyl, C
1
-C
4
-alkanoyloxy, C
1
-C
4
-alkanoyloxy-C
1
-C
4
-alkyl, carbamoyl, mono- or di-C
1
-C
4
-alkylcarbamoyl, mono- or di-2-hydroxyethylcarbamoyl, amidino, 2-imidazolyl, 1-hydroxy-2-hydroxymet
Kramer Andreas
Mühlebach Andreas
Rime François
Ciba Specialty Chemicals Corporation
Mansfield Kevin T.
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