Grafting of polymers with fluorocarbon compounds

Details Grafting of polymers with fluorocarbon compounds Grafting of polymers with fluorocarbon compounds

1999-07-13

2001-02-20

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...

C525S288000, C525S200000, C526S242000, C526S243000, C526S247000

Reexamination Certificate

active

06191231

ABSTRACT:

FIELD OF THE INVENTION
Fluorine containing olefins can be grafted onto polymers containing carbon-hydrogen bonds in the presence of a source of free radicals. The resulting grafted polymers have unique structures, and may be used as catalysts.
TECHNICAL BACKGROUND
Organic polymers containing fluorine substitution have traditionally been made by (co)polymerizing one or more fluorine containing monomers, optionally with unfluorinated monomers. It is well known that polymers containing large amounts of fluorine often have desirable properties, such as improved heat and/or chemical resistance. However, polymers containing only relatively small amounts of fluorine also often have desirable properties (compared to unfluorinated polymers), such as altered surface properties or being useful as catalysts. Therefore versatile, cost effective methods of making polymers with relatively low fluorine contents are desired.
SUMMARY OF THE INVENTION
This invention concerns a process for producing a partially fluorinated polymer, comprising, contacting in the liquid phase a first polymer with contains hydrogen bound to carbon with a compound of the formula H
2
C═CHCR
1
R
2
R
6
Y, and a source of free radicals, wherein:
R
1
and R
2
are each independently fluorine or perfluoroalkyl containing 1 to 20 carbon atoms;
R
6
is fluorinated alkylene containing 1 to 20 carbon atoms and optionally containing one or more ether groups or alkylene containing 1 to 20 carbon atoms and optionally containing one or more ether groups; and
Y is hydrogen or a functional group;
and provided that said contacting is carried out at a temperature at which said source of free radicals generates free radicals.
This invention also concerns a polymer, comprising, branches having the formula —CH
2
-CH
2
CRiR
2
R
6
Y, wherein:
R
1
and R
2
are each independently fluorine or perfluoroalkyl containing 1 to 20 carbon atoms;
R
6
is fluorinated alkylene containing 1 to 20 carbon atoms and optionally containing one or more ether groups or alkylene containing 1 to 20 carbon atoms and optionally containing one or more ether groups; and
Y is hydrogen or a functional group;
and provided that a main chain of said polymer contains hydrogen bound to carbon.
DETAILS OF THE INVENTION
Herein certain terms arc used, and they are defined below:
By “fluorinated alkylene” is meant an alkylene group containing one or more fluorine atoms.
By a “functional group” is meant any univalent group, as defined in R. T. Morrison, et al., Organic Chemistry, 6
th
Ed., Prentice hall, Englewood Cliffs, N.J., 1992, p. 167-168, and is an atom or group of atoms that defines the structure of a particular family of organic compounds and, at the same time, determines (at least partially) their properties. Any functional group present should not interfere with any contemplated reaction such as the grafting described above, nor should it result in any compound in which it is present being unusably unstable.
By “grafting herein” is meant attachment of a branch to a preexisting polymer. Herein a branch will usually be monomeric, i.e., contain only one of the grafting molecules.
By a “source of free radicals” is meant any compound or other means of generating free radicals such as ionizing radiation. If the free radicals are generated thermally, then the grafting reaction takes place at temperatures at which the source of free radicals reacts to form free radicals.
By “containing one or more ether groups” means containing one or more ether oxygen atoms between alkylene segments.
By hydrocarbyl is meant a univalent group containing on carbon and hydrogen. By substituted hydrocarbyl is meant a hydrocarbyl group containing one or more functional groups.
The grafting process described herein takes place in the liquid phase. This means that all of the ingredients are in the liquid phase at the time of the grafting reaction. However this does not mean that all of the ingredients must be in the same liquid phase, nor does it mean that any additional liquids must be present (such as a “solvent”) during the process. The polymer itself and, or the fluorinated compound to be grafted may be liquids and liquify the other component. If a chemical free radical source is used, it too may be a liquid or dissolve in one of the other components, but it will often be present in relatively small quantities, and so unable to dissolve the other components.
Useful groups Y include —SO
2
F, —CO
2
R
3
, P(O)(OR
3
)
2
, —SO
8
M, and —S(O)
2
NHS(O)
2
R
4
, wherein each R
3
is independently hydrocarbyl or substituted hydrocarbyl containing 1 to 20 carbon atoms, and R
4
is perfluoroalkyl containing 1 to 20 carbon atoms. In a preferred compound or polymer, Y is halogen, more preferably fluorine; sulfonyl fluoride: sulfonic acid; or hydrogen.
In preferred compounds and polymers R
6
contains 1 to 50 carbon atoms. Preferred groups R
6
are perfluoroalkylene or ether substituted pertluoroalkylene, and especially preferably —(CF
2
)
d
— wherein d is 2 to 20 and —CF
2
OCF
2
CF
2
—.
Sources of free radicals are well known in the art. see for instance J. Brandrup. et al., Ed.. Polymer Handbook, 3rd Ed., John Wiley & Sons, New York, 1989, p. II-I to II-65 and H. Mark, et al., Ed., Encyclopedia of Polymer Science and Engineering, vol. 13, John Wiley & Sons, New York, 1988, p. 754-789 both of which are hereby included by reference. These “sources” may be chemical compounds such as peroxides or other means of generating free radicals, such as ionizing radiation. Most commonly chemical compounds which are sources of free radicals will be used. These compounds may form free radicals by any method, for instance by decomposing thermally to form free radicals, or by the reaction of a redox couple to form free radicals. Thermal decomposition of a free radical source is a preferred method of forming free radicals. Useful sources of free radicals include compounds such as t-butyl peroxide and benzoyl peroxide. If a compound is used as a free radical source, relatively small amounts are usually used, about 0.1 to about 25 mole percent, preferably about 1 to 10 mole percent, of the grafting molecule present being typical.
The amount of grafting molecule, H
2
C═CHCR
1
R
2
R
6
Y, grafted onto the polymer will vary according to the amount of H
2
C═CHCR
1
R
2
R
6
Y relative to the polymer, the amount of free radical source present, and the efficiency of the grafting process. It is preferred that about 1 g to about 5000 g, more preferably about 500 g to about 2000 g, of grafting molecule per kg of ungrafted (starting) polymer actually be grafted onto the polymer. In another preferred process and its resulting polymer, the grafted polymer has more hydrogen atoms than fluorine atoms, more preferably the ratio of hydrogen atoms to fluorine atoms is about 3 or more, especially preferably about 5 to about 150.
The polymers which may be grafted in the process described herein, i.e., are suitable, are those which do not suffer so much decomposition, typically lowering of molecular weight, in the presence of free radicals as to render the final product unusable. It is well known in the art, see for instance H. Mark. et al., Ed., Encyclopedia of Polymer Science and Engineering, vol. 13, John Wiley & Sons, New York, 1988, p. 667-682, that some polymers are relatively stable in the presence of free radicals, while others may undergo chain scission and lowering of molecular weight relatively easily. For example linear polyethylene is thought of as relatively stable, while most polypropylenes are thought to be relatively unstable.
Nevertheless, even “relatively unstable” polymers may be grafted under some circumstances. For instance, when it is desired to graft only a small amount of H
2
C═CHCR
1
R
2
R
6
Y onto the polymer, only small amounts of free radical source may be needed, and the resulting loss of molecular weight (if any) in the polymer being grafted may be acceptable in the application contemplated.
Exposure to free radicals may also crosslink some polymers, depending on the conditions. A situation suc

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