Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2003-03-21
2004-11-30
Cheung, William K. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S348000, C524S878000
Reexamination Certificate
active
06825299
ABSTRACT:
The present invention relates to a process for controlled radical polymerization in aqueous dispersion in the presence of selected nitroxyl radicals having a defined partition equilibrium between water and monomer as measured by their log p, wherein p is the partition coefficient of the nitroxyl radical in octanol and water.
Polymerization processes using water as a continuous dispersing phase wherein initially the monomers and after polymerization the polymers are dispersed are widely used for manufacturing polymers (aqueous dispersion polymerization). Mostly, water and a water-insoluble monomer, an emulgator and/or a protective colloid and a suitable initiator system are mixed by generally known methods building a monomer swollen micellar system or stabilized monomer droplets.
Of particular interest are emulsion polymerizations, wherein usually water soluble initiator systems are used.
The monomers are essentially insoluble in the aqueous phase and form finely distributed droplets therein. The addition of dispersing agents such as for example sodium dodecyl-sulfate is in many cases necessary to achieve such stable droplets and micelles. Examples of dispersing agents are for example given in “Ullmann Enzyklopädie der technischen Chemie, Bd.10, 4. Auflage, Verlag Chemie, Weinheim (1975), page 449”.
Several variations are known in the state of the art, for example emulgator free emulsion polymerization, mini emulsion polymerization and micro emulsion polymerization. These variations are characterized by changes of kind and amount of the emulgator and initiator systems leading to different polymer products especially with regard to molecular weight, polymer particle size and their distributions.
Polymers or copolymers prepared by free radical polymerization processes inherently have broad molecular weight distributions or polydispersities which are generally higher than about four. One reason for this is that most of the free radical initiators have half lives that are relatively long, ranging from several minutes to many hours, and thus the polymeric chains are not all initiated at the same time and the initiators provide growing chains of various lengths at any time during the polymerization process. Another reason is that the propagating chains in a free radical process can react with each other in processes known as combination and disproportionation, both of which are irreversibly chain-terminating reaction processes. In doing so, chains of varying lengths are terminated at different times during the reaction process, resulting in resins consisting of polymeric chains which vary widely in length from very small to very large and which thus have broad polydispersities. If a free radical polymerization process is to be used for producing narrow molecular weight distributions, then all polymer chains must be initiated at about the same time and termination of the growing polymer-chains by combination or disproportionation processes must be avoided.
A method to reduce polydispersity and to avoid the disadvantages of conventional radical polymerization has already been described by Solomon et al., U.S. Pat. No. 4,581,429, issued Apr. 8, 1986, wherein a free radical polymerization process is disclosed which controls the growth of polymer chains to produce short chain or oligomeric homopolymers and copolymers, including block and graft copolymers. The process employs an initiator having the formula (in part) R′R″N—O—X, where X is a free radical species capable of polymerizing unsaturated monomers. The reactions typically have low conversion rates. Specifically mentioned radical R′R″N—O. groups are derived from 1,1,3,3 tetraethylisoindoline, 1,1,3,3 tetrapropylisoindoline, 2,2,6,6 tetramethylpiperidine, 2,2,5,5 tetramethylpyrrolidine or di-t-butylamine.
In WO 99/00426 emulsion polymerization of ethylenically unsaturated monomers in the presence of nitroxyl radicals has been described in greater detail, pointing out that the monomer droplets have a size of less or equal 500 nm.
Recently in EP 970973 emulsion polymerization in the presence of a stable free radical has been described, pointing out that the water solubility of the stable free radical is at least 0.1 g/l at 25° C. Additionally, in WO 99/11674 the requirement of the molale solubility of the nitroxyl radicals in the aqueous medium is described as being at least 10
−6
mol/kg and most preferred at least 10
−1
mol/kg at 25° C. and 1 bar.
In the instant invention it has been found, that the most important property of the nitroxyl radicals is not the good solubility in water but the partition equilibrium between water and monomer as reflected by the log p value of the nitroxyl. The right balance between solubility in water and solubility in the monomer droplets influences strongly the efficiency in terms of polydispersity, rate of polymerization and yield.
The partition coefficient log p (octanol/water) is a widely used parameter for example in rating the environmental impact of chemical compounds. Its calculation is described by W. M. Meylan, P. H. Howard in J. Pharmaceutical Sciences 84, (1995), 83-92.
One subject of the instant invention is a process for preparing an oligomer, a cooligomer, a polymer or a copolymer (block or random) by free radical polymerization in aqueous dispersion of at least one ethylenically unsaturated monomer or oligomer, which comprises forming an aqueous dispersion, having the monomer in the disperse phase and (co)polymerizing the monomer or monomers/oligomers at elevated temperature in the presence of
a) at least one stable free nitroxyl radical which has a log p (octanol/water) of between −0.5 and 7.5 and which is selected from the group consisting of a compound of formula (A), (B), (C), (D), (E), (F), (G), (H) or (I)
wherein
R is hydrogen, C
1
-C
18
alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic-acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an &agr;,&bgr;-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms;
R
101
is C
1
-C
12
alkyl, C
5
-C
7
cycloalkyl, C
7
-C
8
aralkyl, C
2
-C
18
alkanoyl, C
3
-C
5
alkenoyl or benzoyl;
R
102
is C
1
-C
18
alkyl, C
5
-C
7
cycloalkyl, C
2
-C
8
alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula —CH
2
CH(OH)—Z or of the formula —CO—Z or —CONH—Z wherein Z is hydrogen, methyl or phenyl;
G
6
is hydrogen and G
5
is hydrogen or C
1
-C
4
alkyl, and
G
1
and G
3
are methyl and G
2
and G
4
are ethyl or propyl or G
1
and G
2
are methyl and G
3
and G
4
are ethyl or propyl;
R
1
, R
2
, R
3
and R
4
independently of each other are C
1
-C
18
alkyl, C
3
-C
18
alkenyl, C
3
-C
18
alkinyl, C
1
-C
18
alkyl, C
3
-C
18
alkenyl, C
3
-C
18
alkinyl which are substituted by OH, halogen or a group —O—C(O)—R
5
, C
2
-C
18
alkyl which is interrupted by at least one O atom and/or NR
5
group, C
3
-C
12
cycloalkyl or C
6
-C
10
aryl or R
1
and R
2
and/or R
3
and R
4
together with the linking carbon atom form a C
3
-C
12
cycloalkyl radical;
R
5
, R
6
and R
7
independently are hydrogen, C
1
-C
18
alkyl or C
6
-C
10
aryl;
R
8
is hydrogen, OH, C
1
-C
18
alkyl, C
3
-C
18
alkenyl, C
3
-C
18
alkinyl;
C
1
-C
18
alkyl, C
3
-C
18
alkenyl, C
3
-C
18
alkinyl which are substituted by one or more OH, halogen or a group —O—C(O)—R
5
, C
2
-C
18
alkyl which is interrupted by at least one O atom and/or NR
5
group, C
3
-C
12
cycloalkyl or C
6
-C
10
aryl, C
7
-C
9
phenylalkyl, C
5
-C
10
heteroaryl, —C(O)—C
1
-C
18
alkyl, —O—C
1
-C
18
alkyl or —COOC
1
-C
18
alkyl; and
R
9
, R
10
, R
11
and R
12
are independently hydrogen, phenyl or C
1
-C
18
alkyl; and
b) a free radical initiator.
The alkyl radicals in the various substituents may be linear or branched. Examples of alkyl containing 1 to 18 carbon atoms are methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, isobut
Cheung William K.
Ciba Specialty Chemicals Corporation
Stevenson Tyler A.
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