U.S. patent number RE43,651 [Application Number 11/113,340] was granted by the patent office on 2012-09-11 for surface coatings.
This patent grant is currently assigned to N/A, The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ire. Invention is credited to Jas P. S. Badyal, Stuart A. Brewer, Stephen Richard Coulson, Colin R. Willis.
United States Patent |
RE43,651 |
Badyal , et al. |
September 11, 2012 |
Surface coatings
Abstract
A method of coating a surface with a polymer layer, which method
comprises exposing said surface to a plasma comprising a monomeric
unsaturated organic compound which comprises a chain of carbon
atoms, which are optionally substituted by halogen; provided that
where the compound is a perhalogenated alkene, it has a chain of at
least 5 carbon atoms; so as to form an oil or water repellent
coating on said substrate. Suitable compounds for use in the
methods are compounds of formula (I) where R.sup.1, R.sup.2 and
R.sup.3 are independently selected from hydrogen, alkyl, haloalkyl
or aryl optionally substituted by halo; provided that at least one
of R.sup.1, R.sup.2 or R.sup.3 is hydrogen, and R.sup.4 is a group
X--R.sup.5 where R.sup.5 is an alkyl or haloalkyl group and X is a
bond; a group of formula --C(O)O(CH.sub.2).sub.nY-- where n is an
integer of from 1 to 10 and Y is a bond or a sulphonamide group; or
a group --(O).sub.pR.sup.6(O).sub.q(CH.sub.2).sub.t-- where R.sup.6
is aryl optionally substituted by halo, p is 0 or 1, q is 0 or 1
and t is 0 or an integer of from 1 to 10, provided that where q is
1, t is other than 0. The method is particularly useful in the
production of oil- and/or water repellent fabrics.
Inventors: |
Badyal; Jas P. S. (Wolsingham,
GB), Coulson; Stephen Richard (Oxfordshire,
GB), Willis; Colin R. (Andover, GB),
Brewer; Stuart A. (Fyfield, GB) |
Assignee: |
The Secretary of State for Defence
in Her Britannic Majesty's Government of the United Kingdom of
Great Britain and Northern Ireland (Farnborough, Hampshire,
GB)
N/A (N/A)
|
Family
ID: |
10814111 |
Appl.
No.: |
11/113,340 |
Filed: |
June 11, 1998 |
PCT
Filed: |
June 11, 1998 |
PCT No.: |
PCT/GB98/01702 |
371(c)(1),(2),(4) Date: |
February 11, 2000 |
PCT
Pub. No.: |
WO98/58117 |
PCT
Pub. Date: |
December 23, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
09445800 |
Feb 11, 2000 |
6551950 |
Apr 22, 2003 |
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Foreign Application Priority Data
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Jun 14, 1997 [GB] |
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9712338 |
Sep 23, 1997 [GB] |
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9720078 |
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Current U.S.
Class: |
427/569; 427/488;
427/491; 427/487; 427/490; 427/575; 427/573; 427/572 |
Current CPC
Class: |
D06M
10/02 (20130101); D06M 14/18 (20130101); D06M
14/20 (20130101); D06M 10/025 (20130101); D06M
15/277 (20130101); D06M 2200/12 (20130101); D06M
2200/11 (20130101) |
Current International
Class: |
H05H
1/24 (20060101); H05H 1/00 (20060101); H05H
1/22 (20060101); H05H 1/30 (20060101); C08J
7/18 (20060101); C08F 2/46 (20060101); H05H
1/46 (20060101) |
Field of
Search: |
;427/487,488,490,491,492,508,513,569,572,573,575 ;442/43,59,63,79
;428/102 |
References Cited
[Referenced By]
U.S. Patent Documents
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0049884 |
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EP |
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EP |
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0403915 |
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EP |
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JP |
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May 1985 |
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SU |
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9713024 |
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WO |
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WO 97/13024 |
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WO |
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WO97/38801 |
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WO |
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WO 97/38801 |
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WO |
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9853117 |
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WO |
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WO 98/58117 |
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Dec 1998 |
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WO |
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WO 02/28548 |
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WO |
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02094906 |
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Nov 2002 |
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WO |
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03090939 |
|
Nov 2003 |
|
WO |
|
2004088710 |
|
Oct 2004 |
|
WO |
|
Other References
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|
Primary Examiner: Gambetta; Kelly M
Attorney, Agent or Firm: Russell; Dean W. Williams; Tiffany
L. Kilpatrick Townsend & Stockton LLP
Claims
What is claimed is:
.[.1. A method of coating a surface with a polymer layer, which
method comprises exposing said surface to a pulsed plasma
comprising a compound of formula (I) ##STR00002## where R.sup.1,
R.sup.2 and R.sup.3 are independently selected from hydrogen,
alkyl, haloalkyl or aryl optionally substituted by halo, provided
that at least one of R.sup.1, R.sup.2 and R.sup.3 is hydrogen, and
R.sup.4 is a group X--R.sup.5, where R.sup.5 is an alkyl or
haloalkyl group, and X is: a bond; or a group of formula
--C(O)O(CH.sub.2).sub.nY-- where n is an integer of from 1 to 10
and Y is a bond or a sulphonamide group; or a group
--(O).sub.pR.sup.6(O).sub.q(CH2).sub.t-- where R.sup.6 is aryl
optionally substituted by halo, p is 0 or 1, q is 0 or 1 and t is 0
or an integer of from 1 to 10, provided that where q is 1, t is
other than 0; so as to form an oil and/or water repellent coating
on said surface..].
.[.2. A method according to claim 1 wherein R.sup.5 is a haloalkyl
group..].
.[.3. A method according to claim 2 wherein R.sup.5 is a
perhaloalkyl group..].
.[.4. A method according to claim 3 wherein R.sup.5 is a
perfluoroalkyl group of formula C.sub.mF.sub.2m+1 where m is an
integer of 1 or more..].
.[.5. A method according to claim 4 wherein m is from 1-20..].
.[.6. A method according to claim 5 wherein m is from 6-12..].
.[.7. A method according to claim 1 wherein R.sup.1, R.sup.2 and
R.sup.3 are independently selected from hydrogen or a C.sub.1-6
alkyl or halo-C.sub.1-6alkyl group, provided that at least one of
R.sup.1, R.sup.2 and R.sup.3 is hydrogen..].
.[.8. A method according to claim 7 wherein R.sup.1, R.sup.2 and
R.sup.3 are all hydrogen..].
.[.9. A method according to claim 1 wherein X is a group of formula
--C(O)O(CH.sub.2).sub.nY-- and Y is a sulphonamide group of formula
--N(R.sup.6)SO.sub.2-- where R.sup.6 is hydrogen or alkyl..].
.[.10. A method according to claim 3 wherein the compound of
formula (I) comprises a compound of formula (II)
CH.sub.2.dbd.CH--R.sup.5 (II) where R.sup.5 is as defined in claim
1..].
.[.11. A method according to claim 1 wherein the compound of
formula (I) is an acrylate of formula (III)
CH.sub.2.dbd.CR.sup.7C(O)O(CH.sub.2).sub.nR.sup.5 (III) where n and
R.sup.5 are defined in claim 1 and R.sup.7 is hydrogen or C.sub.1-6
alkyl..].
.[.12. A method according to claim 1 wherein the surface is a
surface of a fabric, metal, glass, ceramics, paper or polymer
substrate..].
.[.13. A method according to claim 12 wherein the substrate is a
fabric..].
.[.14. A method according to claim 1 wherein the gas pressure of
the compound of formula (I) is from 0.01 to 10 mbar..].
.[.15. A method according to claim 1 wherein a glow discharge is
ignited by applying a high frequency voltage..].
.[.16. A method according to claim 15 wherein pulses are applied in
a sequence which yields low average power..].
.[.17. A method according to claim 16 wherein the average power
density is equivalent to less than 10 W in a volume of 470
cm.sup.3..].
.[.18. A method according to either of claim 16 wherein the average
power density is equivalent to less than 1 W in a volume of 470
cm.sup.3..].
.[.19. A method according to claim 15 wherein the sequence
comprises a duty cycle (the ratio of time for which the power is on
to the time for which the power is off) of between 1:500 and
1:1000. .].
.[.20. A hydrophobic and/or oleophobic substrate which comprises a
coating of a polymer which has been applied by the method according
to claim 1..].
.[.21. A hydrophobic and/or oleophobic substrate according to claim
20 wherein the polymer is a haloalkyl polymer..].
.[.22. A substrate according to claim 20 which is a fabric..].
.[.23. An item of clothing which comprises a fabric according to
claim 22..].
.[.24. A method of coating a surface with a polymer layer, which
method comprises exposing said surface to a plasma comprising a
monomeric unsaturated organic compound which comprises an
optionally substituted hydrocarbon group wherein any optional
substituents are halogen; provided that where the compound is a
straight chain perhalogenated alkene, it comprises at least 5
carbon atoms, wherein the plasma is pulsed so as to provide a low
average power, further wherein the average power density is
equivalent to less than 1 W in a volume of 470 cm.sup.3..].
.[.25. A hydrophobic and/or oleophobic substrate which comprises a
coating of a polymer which has been applied by the method according
to claim 24..].
.[.26. A substrate having a coating thereon, said coating being
deposited by pulsed plasma deposition and being derived from a
compound of formula (I) ##STR00003## where R.sup.1, R.sup.2 and
R.sup.3 are independently selected from hydrogen, alkyl, haloalkyl
or aryl optionally substituted by halo, provided that at least one
of R.sup.1, R.sup.2 and R.sup.3 is hydrogen, and R.sup.4 is a group
X--R.sup.5, where R.sup.5 is an alkyl or haloalkyl group, and X is:
a bond; or a group of formula --C(O)O(CH.sub.2).sub.nY-- where n is
an integer of from 1 to 10 and Y is a bond or a sulphonamide group;
or a group --(O).sub.pR.sup.6(O).sub.q(CH2).sub.t-- where R.sup.6
is aryl optionally substituted by halo, p is 0 or 1, q is 0 or 1
and t is 0 or an integer of from 1 to 10, provided that where q is
1, t is other than 0, the compound of formula (I) having been
treated such that the double bond reacts to form the coating but
otherwise, the structure of the monomer is substantially retained,
and wherein the coating is such that were it present on a planar
glass surface, it would have a surface energy of 5-6
mNm.sup.-1..].
.Iadd.27. A method of coating a surface with a polymer layer, which
method comprises exposing said surface to a pulsed plasma
comprising a compound of formula (I)
R.sup.1R.sup.2C.dbd.CR.sup.3R.sup.4 (I) where R.sup.1, R.sup.2 and
R.sup.3 are independently selected from hydrogen, alkyl, haloalkyl
or aryl optionally substituted by halo, provided that at least one
of R.sup.1, R.sup.2 and R.sup.3 is hydrogen, and R.sup.4 is a group
X--R.sup.5, where R.sup.5 is a perhaloalkyl group having from 6 to
20 carbon atoms and X is: a bond; or a group of formula
--C--(O)O(CH.sub.2).sub.nY-- where n is an integer of from 1 to 10
and Y is a bond or a sulphonamide group; or a group
--(O).sub.pR.sup.6(O).sub.q(CH.sub.2).sub.t-- where R.sup.6 is aryl
optionally substituted by halo, p is 0 or 1, q is 0 or 1 and t is 0
or an integer of from 1 to 10, provided that where q is 1, t is
other than 0; wherein a glow discharge is ignited by applying a
high frequency voltage and wherein pulses are applied in a sequence
which yields an average power density equivalent to less than 50 W
in a volume of 470 cm.sup.3 so as to form an oil and water
repellent coating on said surface..Iaddend.
.Iadd.28. A method according to claim 27, wherein R.sup.5 is a
perfluoroalkyl group of formula C.sub.mF.sub.2m+1 where m is an
integer from 6 to 12..Iaddend.
.Iadd.29. A method according to claim 27, wherein the coating is
such that were it present on a planar glass surface, it would have
a surface energy of 5-6 mJm.sup.-1..Iaddend.
.Iadd.30. A method according to claim 27, wherein the average power
density is equivalent to less than 1 W in a volume of 470
cm.sup.3..Iaddend.
.Iadd.31. A hydrophobic and oleophobic substrate which comprises a
polymer coated surface obtained by the method of claim
27..Iaddend.
.Iadd.32. A method of coating a surface with an oil and water
repellent polymer layer, which method comprises exposing said
surface to a pulsed plasma comprising a compound of formula (II)
CH.sub.2.dbd.CHR.sup.5 (II) where R.sup.5 is a C.sub.6-20
perhaloalkyl group of formula C.sub.mF.sub.2m+1 where m is an
integer from 6 to 20, in which a glow discharge is ignited by
applying a high frequency voltage, and in which the high frequency
voltage is applied as a pulsed field, in which pulses are applied
in a sequence which yields an average power density equivalent to
less than 50 W in a volume of 470 cm.sup.3 so as to form an oil and
water repellent coating on said surface..Iaddend.
.Iadd.33. A method according to claim 32, wherein the coating is
such that were it present on a planar glass surface, it would have
a surface energy of 5-6 mJm.sup.-1..Iaddend.
.Iadd.34. A method according to claim 32, wherein the average power
density is equivalent to less than 1 W in a volume of 470
cm.sup.3..Iaddend.
.Iadd.35. A method according to claim 32, in which the sequence is
such that the power is on for 20 .mu.s and off for from 10,000
.mu.s to 20,000 .mu.s..Iaddend.
.Iadd.36. A hydrophobic and oleophobic substrate which comprises a
polymer coated surface obtained by the method of claim
32..Iaddend.
.Iadd.37. A substrate according to claim 36, which is a
fabric..Iaddend.
.Iadd.38. A method according to claim 32, wherein R.sup.5 is a
perfluoroalkyl group of formula C.sub.mF.sub.2m+1 where m is an
integer from 6 to 12..Iaddend.
.Iadd.39. A method of coating a surface with an oil and water
repellent polymer layer, which method comprises exposing said
surface to a pulsed plasma comprising a compound of formula (III)
CH.sub.2.dbd.CR.sup.7C(O)O(CH.sub.2).sub.nR.sup.5 (III) where
R.sup.7 is hydrogen or C.sub.1-6 alkyl, n is an integer of from 1
to 10 and where R.sup.5 is a perfluoroalkyl group having from 6 to
20 carbon atoms, in which a glow discharge is ignited by applying a
high frequency voltage, and in which the high frequency voltage is
applied as a pulsed field, in which pulses are applied in a
sequence which yields an average power density equivalent to less
than 50 W in a volume of 470 cm.sup.3 so as to form an oil and
water repellent coating on said surface..Iaddend.
.Iadd.40. A method according to claim 39, wherein the coating is
such that were it present on a planar glass surface, it would have
a surface energy of 5-6 mJm.sup.-1..Iaddend.
.Iadd.41. A method according to claim 39, wherein R.sup.5 is a
perfluoroalkyl group of formula C.sub.mF.sub.2m+1 where m is an
integer from 6 to 12..Iaddend.
.Iadd.42. A method according to claim 39, wherein the average power
density is equivalent to less than 1 W in a volume of 470
cm.sup.3..Iaddend.
.Iadd.43. A method according to claim 39, in which the sequence is
such that power is on for 20 .mu.s and off for from 10,000 .mu.s to
20,000 .mu.s..Iaddend.
.Iadd.44. A hydrophobic and oleophobic substrate which comprises a
polymer coated surface obtained by the method of claim
39..Iaddend.
.Iadd.45. A substrate according to claim 44, which is a
fabric..Iaddend.
Description
.Iadd.Notice: More than one reissue application has been filed for
the reissue of U.S. Pat. No. 6,551,950. The reissue applications
are application Ser. Nos. 11/113,340 (the present application) and
12/332,750, which is a continuation reissue
application..Iaddend.
The present invention relates to the coating of surfaces, in
particular to the production of oil- and water-repellent surfaces,
as well as to coated articles obtained thereby.
Oil- and water-repellent treatments for a wide variety of surfaces
are in widespread use. For example, it may be desirable to impart
such properties to solid surfaces, such as metal, glass, ceramics,
paper, polymers etc. in order to improve preservation properties,
or to prevent or inhibit soiling.
A particular substrate which requires such coatings are fabrics, in
particular for outdoor clothing applications, sportswear,
leisurewear and in military applications. Their treatments
generally require the incorporation of a fluoropolymer into or more
particularly, fixed onto the surface of the clothing fabric. The
degree of oil and water repellency is a function of the number and
length of fluorocarbon groups or moieties that can be fitted into
the available space. The greater the concentration of such
moieties, the greater the repellency of the finish.
In addition however, the polymeric compounds must be able to form
durable bonds with the substrate. Oil- and water-repellent textile
treatments are generally based on fluoropolymers that are applied
to fabric in the form of an aqueous emulsion. The fabric remains
breathable and permeable to air since the treatment simply coats
the fibres with a very thin, liquid-repellent film. In order to
make these finishes durable, they are sometimes co-applied with
cross-linking resins that hind the fluoropolymer treatment to
fibres. Whilst good levels of durability towards laundering and
dry-cleaning can be achieved in this way, the cross-linking resins
can seriously damage cellulosic fibres and reduce the mechanical
strength of the material. Chemical methods for producing oil- and
water-repellent textiles are disclosed for example in WO 97/13024
and British patent No 1,102,903 or M. Lewin et al., `Handbood of
Fibre Science and Technology` Marcel and Dekker Inc., New York,
(1984) Vol 2, Part B Chapter 2.
Plasma deposition techniques have been quite widely used for the
deposition of polymeric coatings onto a range of surfaces. This
technique is recognised as being a clean, dry technique that
generates little waste compared to conventional wet chemical
methods. Using this method, plasmas are generated from small
organic molecules, which are subjected to an ionising electrical
field under low pressure conditions. When this is done in the
presence of a substrate, the ions, radicals and excited molecules
of the compound in the plasma polymerise in the gas phase and react
with a growing polymer film on the substrate. Conventional polymer
synthesis tends to produce structures containing repeat units which
bear a strong resemblance to the monomer species, whereas a polymer
network generated using a plasma can be extremely complex.
The success or otherwise of plasma polymerisation depends upon a
number of factors, including the nature of the organic compound.
Reactive oxygen containing compounds such as maleic anhydride, has
previously been subjected to plasma polymerisation (Chem. Mater.
Vol. 8, 1, 1996).
U.S. Pat. No. 5,328,576 describes the treatment of fabric or paper
surfaces to impart liquid repellent properties by subjecting the
surfaces to a pre-treatment with an oxygen plasma, followed by
plasma polymerisation of methane.
However, plasma polymerisation of the desirable oil and water
repellent fluorocarbons have proved more difficult to achieve. It
has been reported that cyclic fluorocarbons undergo plasma
polymerisation more readily than their acyclic counterparts (H.
Yasuda et al., J. Polym. Sci., Polym. Chem. Ed. 1977, 15, 2411).
The plasma polymerization of trifluoromethyl-substituted
perfluorocyclohexane mono- has been reported (A. M. Hynes et al.,
Macromolecules, 1996, 29, 18-21).
A process in which textiles are subjected to plasma discharge in
the presence of an inert gas and subsequently exposed to an
F-containing acrylic monomer is described in SU-1158-634. A similar
process for the deposition of a fluroalkyl acrylate resists on a
solid substrate is described in European Patent Application No.
0049884.
Japanese application no. 816773 describes the plasma polymerisation
of compounds including fluorosubstituted acrylates. In that
process, a mixture of the fluorosubstituted acrylate compounds and
an inert gas are subjected to a glow discharge.
The applicants have found an improved method of producing polymer
and particular halopolymer coatings which are water and/or oil
repellent on surfaces.
According to the present invention there is provided a method of
coating a surface with a polymer layer, which method comprises
exposing said surface to a plasma comprising a monomeric
unsaturated organic compound which comprises an optionally
substituted hydrocarbon group, wherein the optional substituents
are halogen; provided that where the compound is a straight chain
perhalogenated alkene, it includes at least 5 carbon atoms; so as
to form an oil or water repellent coating on said substrate.
Unsaturated organic compounds are those which contain at least one
double bond which is capable of reacting to form a polymeric
compound. The compounds used in the method of the invention
suitably include at least one optionally substituted hydrocarbon
chain. Suitable chains, which may be straight or branched, have
from 3 to 20 carbon atoms, more suitably from 6 to 12 carbon
atoms
Monomeric compounds used in the method may include the double bond
within a chain and so comprise alkenyl compounds. Alternatively,
the compounds may comprise an alkyl chain, optionally substituted
by halogen, as a substitutent which is attached to an unsaturated
moiety either directly or by way of an functional group, such as a
ester or sulphonamide group.
As used therein the term "halo" or "halogen" refers to fluorine,
chlorine, bromine and iodine. Particularly preferred halo groups
are fluoro. The term hydrocarbon includes to alkyl, alkenyl or aryl
groups. The term "aryl" refers to aromatic cyclic groups such as
phenyl or napthyl, in particular phenyl. The term "alkyl" refers to
straight or branched chains of carbon atoms, suitably of up to 20
carbon atoms in length. The term "alkenyl" refers to straight or
branched unsaturated chains suitably having from 2 to 20 carbon
atoms.
Monomeric compounds where the chains comprise unsubstituted alkyl
or alkenyl groups are suitable for producing coatings which are
water repellent. By substituting at least some of the hydrogen
atoms in these chains with at least some halogen atoms, oil
repellency may also be conferred by the coating.
Thus in a preferred aspect, the monomeric compounds include
haloalkyl moieties or comprise haloalkenyls. Therefore, preferably
the plasma used in the method of the invention will comprise a
monomeric unsaturated haloalkyl containing organic compound.
Suitable plasmas for use in the method of the invention include
non-equilibrium plasmas such as those generated by radiofrequencies
(Rf), microwaves or direct current (DC). They may operate at
atmospheric or sub-atmospheric pressures as are known in the
art.
The plasma may comprise the monomeric compound alone, in the
absence of other gases or in mixture with for example an inert gas.
Plasmas consisting of monomeric compound alone may be achieved as
illustrated hereinafter, by first evacuating the reactor vessel as
far as possible, and then purging the reactor vessel with the
organic compound for a period sufficient to ensure that the vessel
is substantially free of other gases.
Particularly suitable monomeric organic compounds are those of
formula (I)
##STR00001## where R.sup.1, R.sup.2 and R.sup.3 are independently
selected from hydrogen, alkyl, haloalkyl or aryl optionally
substituted by halo; and R.sup.4 is a group X--R.sup.5 where
R.sup.5 is an alkyl or haloalkyl group and X is a bond; a group of
formula --C(O)O(CH.sub.2).sub.nY-- where n is an integer of from 1
to 10 and Y is a bond or a sulphonamide group; or a group
--(O).sub.pR.sup.6(O).sub.q(CH.sub.2).sub.t-- where R.sup.6 is aryl
optionally substituted by halo, p is 0 or 1, q is 0 or 1 and t is 0
or an integer of from 1 to 10, provided that where q is 1, t is
other than 0.
Suitable haloalkyl groups for R.sup.1, R.sup.2, R.sup.3 and R.sup.5
are fluoroalkyl groups. The alkyl chains may be straight or
branched and may include cyclic moieties.
For R.sup.5, the alkyl chains suitably comprise 2 or more carbon
atoms, suitably from 2-20 carbon atoms and preferably from 6 to 12
carbon atoms.
For R.sup.1, R.sup.2 and R.sup.3, alkyl chains are generally
preferred to have from 1 to 6 carbon atoms.
Preferably R.sup.5 is a haloalkyl, and more preferably a
perhaloalkyl group, particularly a perfluoroalkyl group of formula
C.sub.mF.sub.2m+1 where m is an integer of 1 or more, suitably from
1-20, and preferably from 6-12 such as 8 or 10.
Suitable alkyl groups for R.sup.1, R.sup.2 and R.sup.3 have from 1
to 6 carbon atoms.
Preferably however, at least one of R.sup.1, R.sup.2 and R.sup.3 is
hydrogen and preferably R.sup.1, R.sup.2, R.sup.3 are all
hydrogen.
Where X is a group --C(O)O(CH.sub.2).sub.nY--, n is an integer
which provides a suitable spacer group. In particular, n is from 1
to 5, preferably about 2.
Suitable sulphonamide groups for Y include those of formula
--N(R.sup.7)SO.sub.2 where R.sup.7 is hydrogen or alkyl such as
C.sub.1-4alkyl, in particular methyl or ethyl.
In a preferred embodiment, the compound of formula (I) is a
compound of formula (II) CH.sub.2.dbd.CH--R.sup.5 (II) where
R.sup.5 is as defined above in relation to formula (I).
In compounds of formula (II), X in formula (I) is a bond.
In an alternative preferred embodiment, the compound of formula (I)
is an acrylate of formula (III)
CH.sub.2.dbd.CR.sup.7C(O)O(CH.sub.2).sub.nR.sup.5 where n and
R.sup.5 as defined above in relation to formula (I) and R.sup.7 is
hydrogen or C.sub.1-6 alkyl, such as methyl.
Using these compounds, coatings with water hydrophobicity values of
up to 10 and oleophobicity values of up to 8 have been achieved as
illustrated hereinafter.
Other compounds of formula (I) are styrene derivatives as are well
known in the polymer art.
All compounds of formula (I) are either known compounds or they can
be prepared from known compounds using conventional methods.
The surface coated in accordance with the invention may be of any
solid substrate, such as fabric, metal, glass, ceramics, paper or
polymers. In particular, the surface comprises a fabric substrate
such as a cellulosic fabric, to which oil- and/or water-repellency
is to be applied. Alternatatively, the fabric may be a synthetic
fabric such as an acrylic/nylon fabric.
The fabric may be untreated or it may have been subjected to
earlier treatments. For example, it has been found that treatment
in accordance with the invention can enhance the water repellency
and confer a good oil-repellent finish onto fabric which already
has a silicone finish which is water repellent only.
Precise conditions under which the plasma polymerization takes
place in an effective manner will vary depending upon factors such
as the nature of the polymer, the substrate etc. and will be
determined using routine methods and/or the techniques illustrated
hereinafter. In general however, polymerisation is suitably
effected using vapours of compounds of formula (I) at pressures of
from 0.01 to 10 mbar, suitably at about 0.2 mbar.
A glow discharge is then ignited by applying a high frequency
voltage, for example at 13.56 MHz.
The applied fields are suitably of average power of up to 50 W.
Suitable conditions include pulsed or continuous fields, but are
preferably pulsed fields. The pulses are applied in a sequence
which yields very low average powers, for example of less than 10 W
and preferably of less than 1 W. Examples of such sequences are
those in which the power is on for 20 .mu.s and off for from 10000
.mu.s to 20000 .mu.s.
The fields are suitably applied for a period sufficient to give the
desired coating. In general, this will be from 30 seconds to 20
minutes, preferably from 2 to 15 minutes, depending upon the nature
of the compound of formula (I) and the substrate etc.
Plasma polymerisation of compounds of formula (I), particularly at
low average powers has been found to result in the deposition of
highly fluorinated coatings which exhibit super-hydrophobicity. In
addition, a high level of structural retention of the compound of
formula (I) occurs in the coating layer, which may be attributed to
the direct polymerisation of the alkene monomer for instance a
fluoroalkene monomer via its highly susceptible double bond.
It has been noted, particularly in the case of the polymerisation
of compounds of formula (III) above, that low power pulsed plasma
polymerisation produces well-adhered coatings which exhibit
excellent water and oil repellency. The greater level of structural
retention in the case of pulsed plasma polymerisation can be
attributed to free radical polymerisation occurring during the duty
cycle off-time and less fragmentation during the on-time.
In a particularly preferred embodiment of the invention, a surface
is exposing a surface to a plasma comprising a compound of formula
(III) as defined above, wherein the plasma being created by a
pulsed voltage also as described above.
Suitably the compound of formula (I) includes a perfluoroalkylated
tail or moiety, the process of the invention may have oleophobic as
well as hydrophobic surface properties.
Thus the invention further provides a hydrophobic or oleophobic
substrate which comprises a substrate comprising a coating of a
alkyl polymer and particularly a haloalkyl polymer which has been
applied by the method described above. In particular, the
substrates are fabrics but they may be solid materials such as
biomedical devices.
The invention will now be particularly described by way of example
with reference to the accompanying diagrammatic drawings in
which:
FIG. 1 shows a diagram of the apparatus used to effect plasma
deposition;
FIG. 2 is a graph showing the characteristics of continuous wave
plasma polymerisation of 1H, 1H, 2H-pefluoro-1-dodecene;
FIG. 3 is a graph showing the characteristics of pulsed plasma
polymerisation of 1H, 1H, 2H-pefluoro-1-dodecene at 50 W P.sub.P,
T.sub.on=20 .mu.s and T.sub.off=10000 .mu.s for 5 minutes; and
FIG. 4 is a graph showing the characteristics of (a) continuous and
(b) pulsed plasma polymerisation of 1H, 1H, 2H,
2H-heptadecafluorodecyl acrylate.
EXAMPLE 1
Plasma Polymerisation of Alkene
1H, 1H, 2H-perfluoro-1-dodecene (C.sub.10F.sub.21CH.dbd.CH.sub.2)
(Fluorochem F06003, 97% purity) was placed into a monomer tube (I)
(FIG. 1) and further purified using freeze-thaw cycles. A series of
plasma polymerisation experiments were carried out in an
inductively coupled cylindrical plasma reactor vessel (2) of 5 cm
diameter, 470 cm.sup.3 volume, base pressure of 7.times.10.sup.-3
mbar, and with a leak rate of better than 2.times.10.sup.-3
cm.sup.3min.sup.-1. The reactor vessel (2) was connected by way of
a "viton" O-ring (3), a gas inlet (4) and a needle valve (5) to the
monomer tube (1).
A thermocouple pressure gauge (6) was connected by way of a Young's
tap (7) to the reactor vessel (2). A further Young's tap (8)
connected with an air supply and a third (9) lead to an E2M2 two
stage Edwards rotary pump (not shown) by way of a liquid nitrogen
cold trap (10). All connections were grease free.
An L-C matching unit (11) and a power meter (12) was used to couple
the output of a 13.56 Mhz R.F. generator (13), which was connected
to a power supply (14), to copper coils (15) surrounding the
reactor vessel (2). This arrangement ensured that the standing wave
ratio (SWR) of the transmitted power to partially ionised gas in
the reactor vessel (2) could be minimised. For pulsed plasma
deposition, a pulsed signal generator (16) was used to trigger the
R.F power supply, and a cathode ray oscilloscope (17) was used to
monitor the pulse width and amplitude. The average power <P>
delivered to the system during pulsing is given by the following
formula: <P>=P.sub.cw{T.sub.on/(T.sub.on+T.sub.off)} where
T.sub.on/(.sub.Ton+T.sub.off) is defined as the duty cycle and
P.sub.cw is the average continuous wave power.
In order to carry out polymerization/deposition reactions the
reactor vessel (2) was cleaned by soaking overnight in a chloros
bleach bath, then scrubbing with detergent and finally rinsing with
isopropyl alcohol followed by oven drying. The reactor vessel (2)
was then incorporated into the assembly as shown in FIG. 1 and
further cleaned with a 50 W air plasma for 30 minutes. Next the
reactor (2) vessel was vented to air and the substrate to be coated
(19), in this case a glass slide, was placed in the centre of the
chamber defined by the reactor vessel (2) on a glass plate (18).
The chamber was then evacuated back down to base pressure
(7.2.times.10.sup.-3 mbar).
Perfluoroalkene vapour was then introduced into the reaction
chamber at a constant pressure of .about.0.2 mbar and allowed to
purge the plasma reactor, followed by ignition of the glow
discharge. Typically 2-15 minutes deposition time was found to be
sufficient to give complete coverage of the substrate. After this,
the R.F generator was switched off and the perfluoroalkene vapour
allowed to continue to pass over the substrate for a further 5
minutes before evacuating the reactor back down to base pressure,
and finally venting up to atmospheric pressure.
The deposited plasma polymer coatings were characterised
immediately after deposition by X-ray photoelectron spectroscopy
(XPS). Complete plasma polymer coverage was confirmed by the
absence of any Si (2p) XPS signals showing through from the
underlying glass substrate.
A control experiment, where the fluoroalkene vapour was allowed to
pass over the substrate for 15 minutes and then pumped down to base
pressure was found to show the presence of a large Si (2p) XPS
signal from the substrate. Hence the coatings obtained during
plasma polymerisation are not just due to absorption of the
fluoroalkene monomer onto the substrate.
The experiments were carried out with average powers in the range
of from 0.3 to 50 W. The results of the XPS spectrum of a 0.3 W
continuous wave plasma polymer deposition onto a glass slide for 13
minutes is shown in FIG. 2.
It can be seen that in this instance, CF.sub.2 and CF.sub.3 groups
are the prominent environments in the C (1s) XPS envelope:
CF.sub.2 (291.2 eV) 61%
CF.sub.3 (293.3 ev) 12%
The remaining carbon environments comprised partially fluorinated
carbon centres and a small amount of hydrocarbon (C.sub.xH.sub.y).
The experimental and theoretically expected (taken from the
monomer) values are given in Table 1
TABLE-US-00001 TABLE 1 Experimental Theoretical F:C ratio 1.70 .+-.
0.3 1.75 % CF.sub.2 group 61% .+-. 2% 75% % CF.sub.3 group 12% .+-.
2% 8%
The difference between theoretical and experimental CF.sub.2 group
and CF.sub.3 group percentages can be attributed to a small amount
of fragmentation of the perfluoroalkene monomer.
FIG. 3 shows the C (1s) XPS spectrum for a 5 minute pulsed plasma
polymerisation experiment where:
P.sub.cw=50 W
T.sub.on=20 .mu.s
T.sub.off=1000 .mu.s <P>=0.1 W
The chemical composition of the deposited coating for pulsed plasma
deposition is given in Table 2 below.
TABLE-US-00002 TABLE 2 Experimental Theoretical F:C ratio 1.75 .+-.
0.7 1.75 % CF.sub.2 group 63% .+-. 2% 75% % CF.sub.3 group 10% .+-.
2% 8%
It can be seen that the CF.sub.2 region is better resolved and has
greater intensity which means less fragmentation of the
perfluoroalkyl tail compared to continuous wave plasma
polymerisation.
Surface energy measurements were carried out on slides produced in
this way using dynamic contact angle analysis. The results showed
that the surface energy was in the range of 5-6 mJm.sup.-1.
EXAMPLE 2
Oil and Water Repellency Test
The pulsed plasma deposition conditions described in Example 1
above were used to coat a piece of cotton (3.times.8 cm) which was
then tested for wettability using "3M Test Methods" (3M oil
repellency Test 1, 3M Test Methods Oct. 1, 1988). As a Water
repellency test, the 3M water repellency Test II, water/alcohol
drop test, 3M Test 1, 3M Test Methods, Oct. 1, 1988 was used. These
tests are designed to detect a fluorochemical finish on all types
of fabrics by measuring: (a) aqueous stain resistance using
mixtures of water and isopropyl alcohol. (b) the fabric's
resistance to wetting by a selected series of hydrocarbon liquids
of different surface tensions.
These tests are not intended to give an absolute measure of the
fabric's resistance to staining by watery or oily materials, since
other factors such as fabric construction, fibre type, dyes, other
finishing agents, etc., also influence stain resistance. These
tests can, however, be used to compare various finishes. The water
repellency tests comprises placing 3 drops of a standard test
liquid consisting of specified proportions of water and isopropyl
alcohol by volume onto the plasma polymerised surface. The surface
is considered to repel this liquid if after 10 seconds, 2 of the 3
drops do not wet the fabric. From this, the water repellency rating
is taken as being the test liquid with the greater proportion of
isopropyl alcohol which passes the test. In the case of the oil
repellency test, 3 drops of hydrocarbon liquid are placed on the
coated surface. If after 30 seconds no penetration or wetting of
the fabric at the liquid-fabric interface occurs around 2 of the 3
drops is evident, then the test is passed.
The oil repellency rating is taken to be the highest-numbered test
liquid which does not wet the fabric surface (where the increasing
number corresponds to decreasing hydrocarbon chain and surface
tension).
The ratings obtained for the pulsed plasma deposition of 1H, 1H, 2H
perfluoro-1-dodecene onto cellulose were:
Water 9 (10% water, 90% isopropyl alcohol)
Oil 5 (dodecane)
These values compare well with commercial treatments.
EXAMPLE 3
Plasma Polymerisation of Acrylates
The method of Example 1 described above was repeated using 1H, 1H,
2H, 2H-heptadecafluorodecyl acrylate (Fluorochem F04389E, 98%
purity) in place of the perfluoroalkene. As in Example 1, low
average powers were used for continuous wave and pulsed plasma
polymerisation experiments. For example, the XPS spectrum of a 1 W
continuous wave plasma polymer deposited onto a glass slide for 10
minutes is shown in FIG. 4(a). FIG. 4(b) shows the C(1s) XPS
spectrum for a 10 minutes pulsed plasma polymerisation experiment
where
P.sub.cs=40 W (average continuous wave power)
T.sub.on=20 .mu.s (pulsed time on)
T.sub.off =20000 .mu.s (pulsed time off)
<P>=0.04 W (average pulsed power)
Table 3 compares the theoretical (taken from the monomer,
CH.sub.2.dbd.CHCO.sub.2CH.sub.2CH.sub.2C.sub.8F.sub.17)
environments with what is actually found for polymer coatings.
TABLE-US-00003 TABLE 3 Theoretical Experimental Environment eV
percentages percentages CF.sub.3 293.2 7.7 7.8 CF.sub.3 291.2 53.8
47.0 O--C.dbd.O 289.0 7.7 13.0 CF 287.8 -- 0.7 C--CF.sub.n/C--O
286.6 15.4 13.4 C--C(O).dbd.O 285.7 7.7 3.9 C.sub.xC.sub.y 285.0
7.7 7.2
It can be seen that the CF.sub.2 group is the prominent environment
in the C(1s) XPS envelope at 291.2 eV. The remaining carbon
environments being CF.sub.3, partially fluorinated and oxygenated
carbon centres and a small amount of hydrocarbon (C.sub.xH.sub.y).
The chemical composition of the coatings deposited for continuous
wave and pulsed plasma conditions are given below in Table 4
(excluding satellite percentages) along with the theoretically
expected compositions).
TABLE-US-00004 TABLE 4 Theoretical CW Plasma Pulsed Plasma F:C
ratio 1.31 0.94 1.49 % CF.sub.2 group 53.8% 27.2% 47.0% % CF.sub.3
group 7.7% 3.8% 7.8%
It can be seen from FIG. 4(b) that the CF.sub.2 region is better
resolved and has greater intensity, which means less fragmentation
of the perfluoroalkyl tail occurs during pulsed plasma conditions
compared to continuous wave plasma polymerisation. In the case of
the continuous wave plasma experiments, the low percentages of
CF.sub.2 and CF.sub.3 groups occur.
Surface energy measurements as described in Example 1 shows a
surface energy of 6 mJm.sup.-1.
EXAMPLE 4
Oil and Water Repellency Test
Using the pulsed plasma deposition conditions of Example 3 except
that these were applied for 15 minutes, pieces of cotton (3-8 cm)
were coated with 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate.
Similar pieces of cotton were coated with the same compound using a
continuous wave at 1 W fo 15 minutes. These were then subjected to
oil and water repellency tests as described in Example 2 above.
Samples were then subjected to a benzotrifluoride Soxhlet
extraction for either 1 or 7 hours and the oil and water repellency
tests repeated. The results, expressed as described in Example
2,
TABLE-US-00005 Continuous wave Pulsed wave Time Oil- Water Oil
Water (hours) repellency repellency repellency repellency 0 7 4 8
10 1 -- 2 6 7 7 -- 2 5 7
Hence these coatings are highly hydrophobic and oleophobic and the
coatings have good durability.
EXAMPLE 5
Treatment of Silicone Coated Synthetic Fabric
A sample of a modifed acrylic/nylon fabric which already contained
a silicone coating to impart water repellency, was subjected to the
a pulsed acrylate plasma consisting of the compound
CH.sub.2.dbd.CHCOO(CH.sub.2).sub.2C.sub.8F.sub.17 and using the
conditions described in Example 3.
A sample of the same material was subjected to a two stage
deposition process in which the fabric was first exposed to a
continuous wave 30 W air plasma for 5 seconds followed by exposure
to the same acrylate vapour only. The products were then tested for
oil and water repellency as described in Example 2.
In addition, the durability of the coating was tested by then
subjecting the products to a 1 hour Soxhlet extraction with
trichloroethylene.
The results are as shown in Table 5
TABLE-US-00006 TABLE 5 Repellency Ratings Before After After
extraction Treatment Plasma Plasma with solvent Pulsed phase W2 O7,
O6 acrylate plasma W10 W8 Air plasma followed W2 O1, O1
(borderline) by exposure to W3 W2 acylate monomer
It appears therefore that the process of the invention can not only
enhance the water repellency of such as fabric, and also confer oil
repellency, the durability of the coating is higher than that
obtained using the known two step grafting polymerisation
process.
* * * * *