Note: Descriptions are shown in the official language in which they were submitted.
1339~1~
LOW ADHESION COMPOSITIONS OF PERFLUOROPOLYETHERS
Field of the Invention
This invention relates to articles, such as
pressure-sensitive adhesive tapes, having a substrate with
a coating layer, or liner, of a low adhesion composition of
perfluoropolyethers and to a process for preparing such
coated or lined articles.
Pressure-sensitive tapes are widely used articles
of manufacture. One type of pressure-sensitive adhesive
tape is that which is wound directly upon itself in roll
form. Such tape has a substrate which has a
pressure-sensitive adhesive on one face and generally has a
low adhesion backsize, or release, coating on the other
face to facilitate unwinding of the tape without
delamination of the adhesive. Another type of
pressure-sensitive adhesive tape is a composite-type tape
as sold for use. This composite-type tape has a base, such
as film, paper, or the like which has a pressure-sensitive
adhesive on one face and a disposable protective web having
a substrate with a low-adhesion release layer on one face,
the low-adhesion release layer contacting and protecting
the pressure-sensitive adhesive. Any such low-adhesion
coating must both adhere strongly to its underlying
substrate and be sufficiently cohesive so as to not
contaminate the adhesive, i.e., not to interfere unduly
with its adhesiveness.
Pressure-sensitive adhesive tapes having porous
backings such as breathable medical tapes have a particular
need for highly effective low adhesion backsize coatings
when wound upon themselves into roll form. Unless the
low-adhesion backsize coating is sufficiently effective,
the pressure-sensitive adhesive may gradually migrate into
the pores of the backing creating a mechanical bond such
that the adhesive layer splits upon unwinding. For some
-2- 1339~1~
such tapes, use of a nonporous, disposable, low-adhesion
web is required where sufficiently effective low-adhesion
backsize coatings are not available.
Certain pressure-sensitive adhesives such as
poly(dimethylsiloxane) are extremely aggressively tacky.
Pressure-sensitive adhesive tapes utilizing such adhesives
also have a need for highly effective low-adhesion backsize
coatings, especially after prolonged storage. Unless the
low adhesion backsize coating is sufficiently effective,
such adhesives can carry away such coating material, and
thus be contaminated by appreciable amounts of the
low-adhesion material.
Various substrates require low-adhesion backsize
coatings for a variety of purposes, e.g., nonstick coatings
for cookware, ice-releasing coatings for aircraft, and
lubricative coatings for magnetic recording media. Such
low-adhesion coatings are sometimes called "release
coatings", a term which also encompasses release agents for
molds, which may be effective only by failing cohesively.
Lubricants usually function as release coatings by cohesive
failure. To distinguish release coatings which are
designed to fail cohesively from those which are designed
to resist cohesive failure, the latter are sometimes called
"liners" and more specifically, "low energy liners" because
low energy is important to their effectiveness.
U.S. Patent No. 3,536,749 (Groves) discloses
fluorocarbon-acrylate products which are useful as
low-adhesion backsize coatings for many pressure-sensitive
adhesive tapes. These fluorocarbon-acrylate products are
adducts of fluorocarbon amides having at least one hydrogen
atom bonded to the amide nitrogen atom with an ester of
acrylic acid and are in the form of monomeric solids when
used as low-adhesion backsize coatings.
A perfluoropolyether low surface energy liner
useful as a low-adhesion backsize coating for
pressure-sensitive adhesive tape is disclosed in U.S.
Patent No. 4,472,480 (Olson). The liner comprises an
3 13~'g~1~
insoluble polymer of polymerized, film-forming monomer
having a polymerizable functionality greater than one,
preferably within the range of 1.5 to 2.0 in order to
provide covalent bonding at both ends of most of the
segments, and a perfluoropolyether segment which is a
plurality of perfluoroalkylene oxide repeating units. A
composite low surface energy liner of perfluoropolyether is
disclosed in U.S. Patent No. 4,567,073 (Larson et al).
This composite liner has an inner layer of insoluble
polymer made from polymerizable film-forming monomer having
a polymerization functionality greater than one and an
outer layer of insoluble polymer made from a polymerizable
film-forming monomer copolymerizable with the monomer of
the inner layer and having a perfluoropolyether segment
which is a plurality of polyalkylene oxide repeating units
and which preferably has a functionality within the range
of 1.5 to 2.0 in order to provide covalent bonding at both
ends of most of the segments.
Perfluoropolyether polymers are known to function
effectively for the lubrication of plastics and metallized
magnetic recording media. For example, U.S. Patent No.
4,404,247 (Dominguez/Burguette et al.) discloses magnetic
recording medium protected by an ultra-thin, composite low
surface energy covering provided by an inner layer of
insoluble polymer and an outer layer of insoluble polymer
which are made by in situ polymerization. The inner layer
is made from two monomers, a film-forming aromatic or
heterocyclic polymerizable monomer having a plurality of
ethylenically unsaturated polymerizable groups and a vinyl
aromatic comonomer, and the outer layer is made from
polymerizable perfluoropolyether monomer having
ethylenically unsaturated polymerizable groups.
U.S. Patent No. 4,268,556 (Pedrotty) discloses
rigid magnetic recording disks lubricated with a thin
coating of a fluorinated telechelic polyether polymer
having a backbone of -CaF2aO- units, where a is an integer
of 1 to 4, terminated by at least one polar group, such
_4_ 133961~
that ~2/MW of the polymer is at least l9x10-4
Debye2-moles/g. Useful polar groups include -CONHCH2CH2OH,
-COOCH3~ -CoNHcH2c6H5~ and -COCF3
U.S. Patent No. 4,239,828 (Knope et al.)
5 discloses a flexible magnetic recording disk contained in
an envelope having a wiping fabric impregnated with a
highly fluorinated alkyl polyether having a viscosity index
of 10-130 such that the polyether transfers to the disk as
it rotates within the envelope to lubricate the interface
between the rotating disk and a magnetic recording head.
Although the perfluoropolyether lubricants are
generally better than alternative lubricants with regard to
improved lubricity and reduced coefficients of friction on
both plastics and metals, e.g. metallized recording media,
greater lubricity and reduction in the coefficients of
friction is desired.
U.S. Patent No. 3,250,807 ~Fritz et al.~
discloses dicarboxylic acids of fluorocarbon ethers and
fluorides, esters, amides and salts thereof. The
fluorocarbon ethers have perfluoropolyether backbone
segments and are obtained by the reaction of diacid
difluorides with hexafluoropropylene epoxide.
U.S. Patent No. 3,810,874 (Mitsch et al.)
discloses polyfunctional poly(perfluoroalkylene oxides),
their preparation and their use in the preparation of
polymers such as polyurethanes, polysiloxanes, polyesters,
polycyanurates, polytriazines, polyamides, polyimides, and
others.
U.S. Patent No. 4,080,319 (Caporiccio et al.)
discloses elastomeric copolyimides which have biscycloimide
units linked to perfluoropolyether blocks and which are
prepared by reacting fluorinated polyether diamines with
tetracarboxylic acids in the form of anhydrides or esters
of the acids.
U.S. Patent No. 4,321,404 (Williams et al.)
discloses radiation curable compositions for abherent
coatings which comprise a polyfluorinated acrylate
1339614
compound, a polyethylenically unsaturated crosslinking
agent and a film-forming organic polymer. Among the
preferred polyfluorinated acrylate compounds are
poly(fluorooxyalkylene)urethane acrylates and methacrylates
5 which contain perfluoropolyether segments in the backbone.
U.S. Patent No. 4,647,413 (Savu) discloses
perfluoropolyether oligomers and polymers which can be
prepared by the condensation or addition reaction of a
perfluoroaliphatic diacyl fluoride with hexafluoropropylene
epoxide to produce an acid fluoride-terminated adduct or
oligomer product which is then subjected to ultraviolet
light-induced cleavage/coupling reaction or
photopolymerization to yield an acid fluoride-terminated
coupled or block polymer. This photopolymer product can be
further reacted to yield derivatives.
Perhaps even more pertinent is U.S. Patent No.
4,681,925 (Strepparola et al.) which discloses fluorinated
polymers prepared from acrylic esters and/or acrylamides, in
which the cross-linking degree of the final product is
controlled by using, as a starting product, a mixture of
mono- and di-acryl monomers, the monomers being
characterized in that they include in their structure a
perfluoropolyoxyalkylene chain. These polymers are
described as being elastomeric and very flexible at low
temperatures and possessing excellent resistance to thermal
degradation, excellent oil- and water-repellent properties,
high resistance to the action of mineral oils and vegetable
oils, high resistance to oxidizing agents and excellent
surface physical properties which result in extremely low
values of the critical surface tension and of the
wettability of films prepared therefrom, and are
particularly suitable for imparting a high resistance to
soiling and to water absorption to fabrics.
Monofunctional perfluoropolyether monomers, such
as those disclosed in U.S. Patents No. 3,810,874, 4,080,319
and 4,321,404 provide polymers which are generally less
effective in many applications as low adhesion coatings and
-6- 1339~1~
liners than difunctional perfluoropolyether monomers. The
difunctional perfluorpolyether monomers, such as those
described in U.S. Patents No. 3,250,807, 3,810,874,
4,321,404, 4,472,480, 4,567,073 and 4,647,413 provide
5 polymers having good low energy properties for low adhesion
coatings and liners, but are often difficult and expensive
to prepare.
There has been a long-felt need for a low adhesion
coating having the excellent release properties generally
provided by the difunctional perfluoropolyether monomers and
the cost effectiveness of the monofunctional perfluoro-
polyether monomers.
The present invention provides a substrate having
a release coating thereon, the coating comprising a
copolymer prepared from a mixture of at least 10 weight
percent of at least one monofunctional perfluoropolyether
monomer having a number average molecular weight of about
1500 to 2500, which monomer comprises a plurality of
perfluoroalkylene oxide, -CaF2~O-, repeating units, where
subscript a in each unit is independently an integer from 1
to 4 and at least one difunctional perfluoropolyether
monomer having a number average molecular weight of about
1500 to 2500, which monomer comprises a plurality of
perfluoroalkylene oxide, -CaF2aO-, repeating units, where
subscript a in each unit is independently an integer from 1
to 4. The monofunctional perfluoropolyether monomer and the
difunctional perfluoropolyether monomer are present in
amounts such that the coating provides a release peel value
less than that provided by a polymer coating of the
monofunctional perfluoropolyether monomer and substantially
similar to or less than that of a polymer coating of the
difunctional perfluoropolyether monomer at the same
thickness. The term "substantially similar to" as used in
regard to the release peel values of the coating prepared
from the mixture of monomers and the coating prepared from
the difunctional monomers is intended to include those
coatings prepared from mixtures which provide release peel
_7_ 1339614
values up to about 35% greater than that provided by
coatings prepared from the difunctional monomer.
Preferably, the release peel values of the coating prepared
from the mixture of monomers is at least equal to that
5 prepared from the difunctional monomer.
Preferably, the monofunctional perfluoropolyether
monomer comprises about 10 to 75 weight percent, more
preferably 25 to 75 weight percent, and the difunctional
perfluoropolyether monomer comprises about 25 to 90 weight
percent, more preferably 25 to 75 weight percent, of the
mixture. Preferably the thickness of the coating is in the
range of about 5 to 500 nm, more preferably in the range of
10 to 100 nm.
The term "difunctional" as used herein includes
monomers having a functionality of 1.5 to 2.0 or greater.
The cured copolymers provide improved properties as
components of coatings, layers and liners.
Surprisingly, it has been found that less
expensive copolymers prepared from mixtures of the
monofunctional perfluoropolyether monomer and the
difunctional perfluoropolyether perform at least as well as
polymers prepared from the difunctional perfluoropolyether
and, in many cases, perform better than polymers prepared
from the difunctional perfluoropolyether monomer when
evaluated for release properties.
The present invention further provides a
pressure-sensitive adhesive tape comprising a flexible web
having a pressure-sensitive adhesive layer adherently bonded
to at least one side thereof, and a liner comprising a
copolymer prepared from a mixture of at least 10 weight
percent of at least one monofunctional perfluoroether
monomer having a number average molecular weight in the
range of about 1500 to 2500, which monomer comprises a
plurality of perfluoroalkylene oxide, -CaF2aO- repeating
units where subscript a in each unit is independently an
integer from l to 4, and at least one difunctional
perfluoropolyether monomer having a number average molecular
8 1339614
weight in the range of about 1,500 to 2,500, which monomer
comprises a plurality of perfluoroalkylene oxide, -CaF2aO-
repeating units where subscript a in each unit is independently
an integer from 1 to 4, the monofunctional perfluoropolyether
monomer and the difunctional perfluoropolyether monomer being
present in amounts such that the liner provides a release peel
value less than that provided by a polymer coating of the mono-
functional perfluoropolyether monomer and substantially similar
to or less than that of a polymer coating of the difunctional
perfluoropolyether monomer at the same thickness.
Preferably, the monofunctional perfluoropolyether
monomer comprises about 10 to 75 weight percent, more preferably
25 to 75 weight percent, and the difunctional perfluoropolyether
monomer comprises about 25 to 90 weight percent, more preferably
25 to 75 weight percent, of the mixture. Preferably the thickness
of the coating is in the range of about 5 to 500 nm, more
preferably in the range of 10 to 100 nm.
The present invention also provides a method of making
a substrate with a liner, comprising the steps of (a) providing
a dilute solution of polymerizable monomers comprising a mixture
of at least 10 weight percent of at least one monofunctional
perfluoropolyether monomer having a number average molecular
weight in the range of about 1,500 to 2,500, which monomer
comprises a plurality of perfluoroalkylene oxide, -CaF2aO-
repeating units where subscript a in each unit is independently
an integer from 1 to 4, and at least one difunctional perfluoro-
polyether monomer having a number average molecular weight in the
-8a- 1~ ~3 ~1 ~
range of about 1,500 to 2,500 which monomer comprises a plurality
of perfluoroalkylene oxide, -CaF2aO- repeating units where
subscript a in each unit is independently an integer from 1 to 4,
(b) coating said solution onto the substrate, (c) drying the
coating, and
9 133961~
(d) in-situ polymerizing the monomers to provide
an insoluble, cohesive polymer network which
is adhered to the substrate,
the monofunctional perfluoropolyether monomer and the
S difunctional perfluoropolyether monomer being present in
amounts such that the coating provides a release peel value
less than that provided by a polymer coating of the
monofunctional perfluoropolyether monomer and substantially
similar to or less than that of a polymer coating of the
difunctional perfluoropolyether monomer at the same
thickness.
Preferably, the monofunctional perfluoropalyether
monomer comprises about 10 to 75 weight percent, more
preferably 25 to 75 weight percent, and the difunctional
perfluoropolyether monomer comprises about 25 to 90 weight
percent, more preferably 25 to 75 weight percent, of the
mixture. Preferably the thickness of the coating is in the
range of about 5 to 500 nm, more preferably in the range of
10 to 100 nm.
The new copolymers when provided coated on or
layered with various substrates have greatly improved
properties for release coating applications and are less
expensive than coatings or layers prepared from only
difunctional monomers due to the use of the less expensive
monofunctional comonomer.
One class of monofunctional perfluoropolyether
monomers which can be used for making the copolymers of the
present invention are those represented by Formula I:
3 O Q( C~F2aO ) ~cCA ~ F2a +1
wherein Q comprises a polymerizable, preferably addition
polymerizable, group attached to a chain of randomly
distributed perfluoroalkylene oxide, -CaF2aO-, repeating
unit segments, in each of which a is independently an
integer of 1 to 4, k is the number of such repeating units
in the perfluoroalklylene oxide segments and has a value
from 5 to 30 such that the segment preferably has a number
1~39~1~
--10--
average molecular weight in the range of about 1500 to 2500
and a' is an integer of 1 to 4. Typically the
perfluoroalkylene oxide units will be -CF2O-, -C2F4O-
and/or -C3 F60- .
One subclass of perfluoropolyether monomers is
that which includes the monofunctional ethylenically-
unsaturated perfluoropolyether monomers wherein Q of the
above Formula I is selected from
R O~
a) H2C=C-C-O-CH2-
R O H O
b) H2c=c-c-o-(cH2)2N-c-ocH
and the like wherein R is hydrogen or methyl, the
preparation of which is disclosed in U.S. Patent No.
4,321,404 (Williams et al.). These monomers are prepared
from perfluoropolyether acids through esters thereof by
reduction to 1,1-dihydroalcohols and reaction with
compounds which provide useful polymerizable groups such as
those listed for Q above as a) and b).
Another subclass of monomers may be prepared by
reduction of the amide group of perfluoropolyether acid
amides and reaction of the resulting 1,1-dihydroperfluoro-
polyether amines the preparation of which is described in
U.S. Patent No. 4,080,319 (Caporiccio et al.) to provide Q
groups such as
R O
l 11
c) H C=C-C-NHCH - and
R o H O
1 11 1 11
d) H2C=C-C-O-(CH2) 2 -N - C - NHCH2 -
wherein R is hydrogen or methyl.
1~39~1~
--11--
A further subclass of monomers is that which
includes monofunctional monomers prepared as described by
U.S. Patent No. 3,810,874 (Mitsch et al.), wherein Q of the
above Formula I can be represented by XbYZ~, where X is a
polyvalent, preferably divalent, linking organic radical
such as -CONR-, -CO2-, -COS-, -CO-,
-C=N-f'N-C=N, -C-N-C3C-O, -C=N-N=C-O, -C=N-N=C-S,
~ 1 ~ I 1 1 1
-C=N-N=~C-NR , -C=N-C=C-NR , -C=N-O-C=N
b is zero or one, c is an integer of 1-3, Rl is hydrogen,
lower alkyl (e.g., CH3, -CH2CF3, -C6Hl3), aryl of less than
13 carbon atoms (e.g., -C6H5, -C6H4CH3, CloH7) o c
radical, Y is a polyvalent linking organic radical free of
olefinic unsaturation such as alkylene (eg., -CH2-,
-C2H4-), oxa-alkylene (e.g., -CH2OCH2-), cycloalkylene
(e.g. -C6Hlo~)r thia-alkylene (e.g., -CH2SCH2-), arylene
(e.g. -C6H4-, -C6H4OC6H4-), and the like, or combinations
thereof, such as aralkylene and alkarylene, Z is a
polymerizable functional group such as -OH,
-SH, -SR2, -N(R2)2, -CO2H, -SiR dJ3 d' -CN, -NCO, -C=C,
-C -~C-, -C02R , -OS02CF3, -OCOCl, -OCN, -N(R )CN,
o
-(O)COC(O), -I, -CHO, -CH(OCH3)2, -S02Cl,
-C(OCH3)=NH, -C(NH2)=NH, and the like, wherein R is
hydrogen, aryl, or lower alkyl, J is halogen, -oR2, -OCOR2,
or -CH=CH2; and d is 0 or an integer of 1 to 3. Z may also
be oCR3 R4R o r
-N-CH=N-CH=CH,
wherein R3 is hydrogen, lower alkyl or lower fluoroalkyl,
R4 is hydrogen or lower alkyl and Rf is lower fluoroalkyl.
Z is preferably
-12- 1339~14
ol o
-CH2OCH2CH=CH2, -CNHCH2CH=CH2 or -COCH2CH-CH2.
Other suitable Q groups include polymerizable
o
isocyanate (-NCO), epoxy (-C-CH-R5 wherein each R5 is
R5
independently lower alkyl) or hydrolyzable silane (e.g,
SiR6R37p wherein each R6 is independently a lower alkyl and
p is an integer of 1 to 3) groups.
A presently preferred subclass of monofunctional
comonomers is that wherein the perfluoropolyether chain is
of the formula
C3F70(C3F6O)tCF(CF3)- II
wherein t is 4 to about 14 to provide monomers having a
number average molecular weight from about 1500 to 2500. In
these monomers the perfluoroalkyl chain generally contains
-CF(CF3)CF2O- units, with optional -CF2CF2CF2O- units.
Monomers of this subclass which are currently most readily
available and are most preferred are those of about 1500 to
2500 average molecular weight, i.e., those monomers wherein
t is about 8 to 16.
Suitable difunctional perfluoropolyether
monomers for making the copolymers of the invention include
monomers represented by Formula III:
Q' (CaF2ao)~c~F2a~Q III
wherein a, a' and k are as defined hereinabove for Formula
I, and Q' is a polymerizable, preferably addition
polymerizable, group.
Although truly difunctional monomers are
preferred, monomers having average functionalities greater
than one, and usually within the range of 1.5 to 2.0, will
generally operate as equivalents to the difunctional
monomers when mixed with monofunctional monomers to form
I339~1~
-13-
the copolymeric mixtures of this invention. It will be
apparent that for most purposes mixtures prepared from
primarily monofunctional and difunctional monomers will
allow more simple and direct correlations of properties
with functionality and for that reason they are preferred.
A class of perfluoropolyether monomers of
Formula III is,that which includes the difunctional
ethylenically-unsaturated monomers wherein Q' of the above
Formula III is selected from
R O
11
H2 C-C-C-O-CH2 -
R O H O
1 11 1 ll
H2C C C-O(CH2)2 N-C OCH2
H2C=CHCH2NHC-
H2 C=CHCH2 O-
and the like wherein R is hydrogen or methyl the
preparation of which monomers is disclosed in U.S. Patents
No. 3,810,874 (Mitsch et al.), No. 3,544,537 (srace), No.
3,553,179 (Bartlett), No. 3,864,318 (Caporiccio et al.),
and No. 4,321,404 (Williams et al.).
Another class of difunctional intermediates
is that which includes monomers represented by Formula IV:
O CF CF CF CF O IV
Il 1 3 1 3 1 3 1 3 11
FC--CF(OCF2CF)nO(CF2)mO(CFCF20)n,CF CF
wherein the ratio m/n is 0.2/1 to 5/1, and m is 3 to 45 and
35 n + n' is 2 to 15. The preparation of these difunctional
monomers is described in u.S. Patent No. 3,250,807 (Fritz
-14- 133961~
et al).
Another class of difunctional monomers which
could be useful themselves or as intermediates for
preparing useful monomers is that which includes monomers
represented by Formula V:
A - CF(OCF2lCF)xOCF2(R'f)yCF2O(lCFCF2O)zlCF A V
CF3 CF3 CF3 CF3
-- w
wherein each A is independently a functional, i.e.,
polymerizably reactive, moiety, such as COF or a derivative
thereof, such as one containing a polymerizable group, w is
a number greater than 1, e.g. 2 to 10, and preferably 2 to
4, x and z are independently zero or a number up to about
10, with the proviso that the sum of x + z is equal to at
least 1 and can be as high as about lS, y is zero or 1, and
R'f is a fluoroaliphatic group, e.g. perfluoroalkylene,
which can contain one or a plurality of, e.g. 2 to 4 hetero
atoms, such as catenary oxygen or nitrogen atoms, e.g.
oxybis(perfluoroalkylene), said fluoroaliphatic groups
having, for example, 1 to 21 carbon atoms, preferably 1 to
4 catenary carbon atoms, particularly where R'f is
perfluoroalkylene. The preparation of these difunctional
monomers is disclosed in U.S. Patent No. 4,647,413.
A further subclass of ethylenically-unsaturated
perfluoropolyether monomers is that which includes monomers
represented by Formula VI:
Q~-cF2o(cF2cF2o)r(cF2o)5cF2 Q VI
wherein Q~, is as defined above and r and s designate the
number of randomly distributed perfluoroethyleneoxy and
perfluoromethyleneoxy backbone repeating units,
133961~
respectively, r and s having independently values, for
example, from 1 to 200 and the ratio r/s is 0.2/1 to 5/1.
Examples of polymerizable perfluoropolyether
monomers of Formula III which would be expected to be
useful for making the low-energy copolymers of the
invention are those having the following formulas wherein
the perfluoroalkylene oxide units are randomly distributed,
the given numbers of which are average values.
The polymerizable perfluoropolyethers of Formula
I are similar to those set forth hereinbelow except that
the functional group is present on only one terminal
portion of the formula, the other terminal portion being
-Ca F2a l1 where a is an integer from 1 to 4.
Perfluoropolyether Monomer
O O Q O
Il ll 11 11
H2C=CH-CO-CH2CH2NHC-CFO(CF2CIFO)3(CF2)3(0~CFCF2)30lCF-CNH-CH2CH2-OC-CH=CH2
CF3 CF3 CF3 CF3
O O
ll 11
H C=cH-co-cH2cF2o(cF2cF2o)8(cF2o)l4cF2cH2-oc CH 2
III
O O
Il 11
H C=c-co-cH2cF2o(cF2cF2o)l6(cF2o)28cF2cH2-oc-cl C 2
CH3 CH3
IV
H C=cHcH2ocH2cF2o(cF2cF2o)l6(cF2o)z8cF2cH2ocH2cH 2
0 0 0 0
I l 11 ll ll
H C=C-CO~CH ~ NHCO-CH2CF20(CF2CF20)8(CF20)l4CF2CH2-OCNH(c 2)2 1 2
CH3 CH3
-16- 133961~
VI
H2C=CH-CNH(CH2 ) 30CNH~0 0
NHCO(CH2 ) 20C-CF20(C3F60) 4 (CF2~) 3CF2
H3C 0 0
ol IO ~ NHCO(CH2)3NHC-CH=CH2
-C~(CH2)20CNH
VII
o
H2C=CHCH2-OCNH f ~I<CH3
~ CH3 1~~ ~11
H3C CH2-NHco(cH2)2NHc-cF2o(cF2cF2o)8(cF2o)l4cF2
H3C 0
H3C ~ NHCO-cH2cH=cH2
O O
2 0
-CNH(CH2)20CNH-cH2 CH3
VIII
O O O O
U 11 11 11
H C=cHco(cH2)2NHc-cF2o(cF2cF2o)8(cF2o)l4cF2-cNH(cH2)2 2
IX
O O O O
Il 11 ll 11
H2c=cH-cNH-c(cH3)2cNH-cH2cFzo(cF2cF2o)8(cF2o)l4cF2cH2-NHc-c(cH3)2NHc-cH=cH2
X
O O
H C=CHCH2NHC-CF20(CFzCF2~)8(CF2~)l4CF2CNH CH2C 2
H C CHcH2ocH2-cF2o(cF2cF2o)8(cF2o)l4cF2-cF2ocH2c 2
\0/ ' \0/
-17- 13~9614
XII
~ ~o-cH2-cF2o(cF2cF2o)8(cF2o)l4cF2-cH2-o~ --
OH OH
XIII
O O
Il 11
"_~" CH2-OC~,_~,OH HO~ ~CO-CHz~
~ CH3 H3C ~ oc-cF2o(cF2cF2o)l6(cF2o)28cF2-co CH3 H3C
XIV
O O
(H CCH O) Si(CH )3NHC-CF2O(CF2CF2O)l6(CFZO)28cF2-cNH( 2)3 2 3 3
XV
H3C CH3
O IO ~C' O
20 (H3cco)2lsi(cH2)2NHcNH-cH2 ~ NHCO CH2cF2o(cF2cF2o)l6(cF2o)28cF2cF2
CH3 CH3
H3C CH3
~ X O O
Il I ll 11
-OCNH _ ~ CH2NHCNH(CH2)2sli(OccH3)2
CH3 CH3
XVI
H,C ~ NHCCFzO(CF2CF2O)~(CFz0)14CFzCNH ~ CH3
OCN NCO
The copolymers of the invention are prepared from
mixtures of monomers of Formula I and Formula III, These
35 copolymers provide surprisingly good release properties at
lower cost than polymers prepared from monomers of Formula
III. It has been found that copolymeric mixtures having
from 25 to 50 weight percent of monomers of Formula I
-18- 1 3 3 g 6 1 4
provide the best release properties in certain presently
preferred mixtures.
It is known that small amounts of impurities can
be found in the mono- and difunctional monomers used to
make the polymers of the invention. These impurities are
primarily nonfunctional, i.e., non-polymerizable, materials
or monomers with functionality different than that
primarily planned. It is preferred that the nonfunctional
impurities be kept at a level less than 10%, and more
preferably as low as practical, to allow good quality
control. Monofunctional monomers can be purchased with
less than 1% nonfunctional impurities. Difunctional
monomers with about 5% nonfunctional impurities are
available.
When the perfluoropolyether monomers have
polymerizable functional groups having ethylenic
unsaturation such as acryloyl, acrylamide, and vinyl ether,
polymerization can be effected by exposing the coated
substrate to ultraviolet radiation, preferably in an inert
20 atmosphere. Generally, the use of photoinitiators to
enhance the rate of polymerization is not necessary when
the perfluoropolyether monomer coating layer is thin, e.g.,
less than about 100 nm on a substrate such as polyester
film or other photoactive substrate. The rate of
25 polymerization of thicker coatings can be enhanced by
adding about 0.01 to 5 percent, preferably about 0.25 to 1
percent by weight photoinitiator, such as benzoin ethers,
to the monomer mixture. When the perfluoropolyether
monomer has hydrolyzable silane, epoxy, or isocyanate
30 polymerizable groups, thermal polymerization can be
employed by exposing the coated substrate to thermal
radiation. When the polymerizable groups are epoxy,
ultraviolet radiation may be employed in air in the
presence of an aromatic onium salt polymerization catalyst,
35 such as diphenyliodonium hexafluoroantimonate or
triphenylsulfonium hexafluoroantimonate, incorporated into
the coating solution.
~339~14
--19--
In any event, ~he polymer ~aking up ~he layer
tends to be insoluble, i.e., crosslinked, as manifested by
its insolubility in FreonTM 113 (1,1,2-trichloro-2,2,1-
trifluoroethane) at 20~ C.
The thickness of the low energy layer of
copolymer is conveniently controlled by the proportion of
solvent in the solution from which the perfluoropolyether
monomer is coated. Coating techniques-useful for in-line
processing include brushing, wire or knife coating,
spraying, curtain coating and gravure coating. While the
thickness of the low energy layer is preferably less than
500 nm because of the high cost of perfluoropolyether
monomer, much greater thicknesses are useful. The coating
can be as thin as 5 or 10 nm. The particular thickness
15 used will also depend on the particular application or
utility of the liner.
The perfluoropolyether segments in the polymer
form a cohesive network which apparently becomes bonded to
the contiguous substrate at a large number of points, and
20 even though the bonds may be individually quite weak,
together they adequately adhere the network to the
substrate.
Suitable substrates to which the coating can be
applied, include, for example, paper, glass, steel,
25 aluminum, polymers such as polyethylene, polyester,
polyvinyl chloride, polypropylene, non-woven fabrics and
the like. The present invention provides a low surface
energy liner which is effective as a low-adhesion coating
for use with the most aggressive pressure-sensitive
30 adhesives without unduly diminishing the adhesiveness of
said adhesives. For those applications in which the
release coated article is to be a pressure-sensitive tape
or sheet, it is desirable that the substrate be flexible.
A preferred substrate is polyester film. The low surface
35 energy liners of the invention are also useful in a variety
of other applications such as nonstick coatings for cooking
utensils, ice-releasing coatings for aircraft, and
1339614
-20-
lubricative coatings for m~gnetic recording media. If the
low surface energy liner does not adhere well to the
substrate, it may be desirable to first apply a primer or
an adhesion-promoting coating, as is well-known in the art.
In making a low surface energy layer of the
invention, one or more other types of monomers
copolymerizable with the perfluoropolyether monomer may be
dissolved into the solution. The layer is most effective if
the amount of the perfluoropolyether monomer is such that
at least 75 weight percent is provided by perfluoro-
polyether segments. When the perfluoropolyether monomer
has polymerizable groups which are ethylenically
unsaturated, useful copolymerizable monomers include
acrylic and methacrylic esters, amides, urethanes, and
15 vinyl ethers-
When Q of Formula I or Q' of Formula III is a
1,2-epoxy group, useful copolymerizable monomers include
1,2-epoxy-substituted esters, ethers, siloxanes, and
nitriles such as listed in columns 3 and 4 of U.S. Patent
20 No. 4,219,377-
When Q of Formula I or Q' of Formula III is a
hydrolyzable silane group, useful copolymerizable monomers
include silanes which may be linear or cyclic and may have
alkoxy, halo, cyano, aceto, methacryloxy, lower alkenyl, or
25 phenyl substituents.
When Q of Formula I or Q' of Formula III is an
isocyanato group, useful copolymerizable monomers include
isocyanates, polyols, and polyamines.
The present invention includes articles
30 containing coatings and liners of the copolymers of the
invention. Optionally these articles include a substrate
having a composite liner provided by an inner layer of
insoluble polymer made from polymerizable film-forming
monomer having a polymerizable functionality greater than 1
35 such as is disclosed in U.S. Patent No. 4,567,073 (Larson
et al.), and an outer layer of insoluble copolymer of the
present invention made from a polymerizable film-forming
133961~
-21-
monomer copoly~erizable with the m~n~er of said inner
layer and having perfluoropolyether segments. Preferably
the monomers are addition polymerizable and the monomers
are in-situ polymerized. Apparently the contiguous
monomers of the two layers copolymerize, thus bonding the
perfluoro- polyether segments to the substrate through the
inner layer.
By polymerizing both layers in their contiguous
relationship, the perfluoropolyether segments have
significantly greater adherence to the substrate than they
would have had if the perfluoropolyether monomers had been
applied directly to the substrate and then polymerized in
situ. By virtue of that greater adhesion, the low surface
energy liner not only better resists transfer when used as
a low-adhesion coating for a pressure-sensitive adhesive,
but becomes highly resistant to removal when subjected to
abrasion or wear. Even though the total thickness of the
composite may be ultra-thin, i.e., 10 to 100 nm, the
- adhered perfluoropolyether provides a barrier or liner
20 which prevents the most aggressive pressure-sensitive
adhesives from becoming appreciably bonded to the
underlying substrate, and continues to provide effective
lubrication even after prolonged storage.
The composite low surface energy layer of liner
25 Of the invention may be applied to a substrate by the steps
of
(a) coating onto the substrate a first dilute
solution of said inner layer monomer to provide
an inner coating of monomer,
(b) coating over the coating of step (a) a second
dilute solution of said perfluoropolyether
monomers thus providing an outer coating,
(c) drying the twice coated substrate, and
(d) polymerizing said monomers, thus bonding the
perfluoropolyether segments to the substrate
through the inner layer.
-22- 1339614
The polymerization is carried out as previously
described.
The thickness of the low energy layer is
conveniently controlled by the proportion of solvent in the
two dilute solutions. Coating techniques described
hereinabove are useful. Curtain coating permits essentially
simultaneous application of both solutions. If the coating
technique used for applying the second solution involves
mechanical contact of the inner layer coating, e.g.,
gravure coating, the inner layer coating preferably is
first dried or partially polymerized to develop some
abrasion resistance before applying the second solution,
and the solvent of the second solution should not be a
solvent for the material deposited from the first solution.
The thickness of the inner layer may range from
about 10 nm to about 0.2 mm. Toward the higher end of that
range, the composite low surface energy liner may have
better resistance to abrasion, but for some uses it is
preferred that the low surface energy liners be as thin as
20 possible, e.g., when used as protective lubricating
coatings for magnetic recording media, it being desirable
to minimize the spacing between the heads and the
magnetizable material of the recording media. Generally
the outer layer should be thin, e.g., less than 500 nm,
25 preferably less than 100 nm, because the polyfluoro-
polyether monomer is expensive, and it may be as thin as 5
or 10 nm. on the other hand, the outer layer can be
thicker than 500 nm for some uses.
Suitable monomers for use in making the inner
30 layer of the composite, low surface energy liners of the
invention are one or more of any film-forming polymerizable
monomers containing at least two polymerizable groups,
preferably groups having ethylenic unsaturation, at least
one of which is copolymerizable with that of the monomers
35 used to make the outer layer. Examples of such inner layer
monomers are the acrylate and methacrylate esters of
alkanepolyols such as 1,6-hexamethylene diacrylate,
-23- 1339614
pentaerythritol triacrylate, pentaerythritol tetraacrylate,
trimethylolpropane triacrylate and dipentaerythritol
pentaacrylate; 1,3,5-tris(2-methacryloyloxyethyl)-s-
triazine; polyester polyol acrylates and methacrylates such
O Q O O
as (H2C=CH-CO-CH2)3-CCH2-OCCH2CH2-CO-CH2C(CH2-OCCH=CH2) 3;
other polyester acrylates and methacrylates whose
- preparation is disclosed in U.S. Patent No. 4,050,936
(Takedo et al.), the heterocyclic polyol acrylates and
methacrylates such as
o
O OH C OH O
Il I / \ 1 11
(H2C=CH-CO-CH2)3CCH2-OCH2CHCH2-N N-CH2-CHCH20CH2C(CH2-OC-CH=CH2)3,
O=C-C-CH3
CH3
1,3-bis[3-(2-acryloyloxyethoxy)-2-hydroxypropyl]-5,5-
dimethyl-2,4-imidazolidinedione, whose preparation is
described in U.S. Patent No. 4,306,954 (Wendling et al.),
20 glycidyl methacrylate, isocyanatoethyl methacrylate, and
3-methacryloxypropyltrimethoxysilane; tris(2-methoxy-
ethoxy)vinylsilane; 3,4-epoxycyclohexylmethyl-3,4-
epoxycyclohexanecarboxylate; and diallyl phthalate.
The following specific, but non-limiting examples
25 will serve to illustrate the invention. In these examples,
all parts and percentage are by weight unless otherwise
indicated. In these examples, the following tests are
used.
30 Release Peel Test, Type A: A poly(dimethylsiloxane) [DC
355 from Dow Corning, available as a 18.5% solution in
FreonTM 113] is coated onto the film having the monomer
treated surface using a knife coater and allowed to dry for
2 hours to provide an aggressive pressure-sensitive
35 adhesive layer having a thickness of 0.038 mm. To the
adhesive surface is laminated 0.038 mm poly(ethylene
terephthalate) film. After aging the sample at 70~C (dry
133961~
-24-
heat) f~r 24 hours, the sample is al]owed to cnol to 22~C.
The release peel force required to remove the silicone
pressure-sensitive adhesive from the monomer treated film
is measured by peeling off the poly(ethylene terephthalate)
film at an angle of 180~ and at a peel rate of 2.3 m/min.
Release Peel Test, Type B: A pressure-sensitive adhesive
tape having a 0.025 mm thick poly(dimethylsiloxane~
pressure-sensitive adhesive (Dow Corning DC 284) layer on a
0.038 mm thick biaxially-oriented poly(ethylene
terephthalate) film having no backsize coating is pressed
against the film having the monomer treated surface using a
smooth plastic bar. The sample is aged for 15 days at 70~C
and the release peel force is measured by peeling off the
poly(ethylene terephthalate) film at an angle at 180~ and
at a rate of 2.3 m/min.
Readhesion Peel Test: The pressure-sensitive adhesive tape
removed in the Release Peel Test is applied to a clean
20 glass plate and the peel force for its removal measured at
a peel rate of 2.3 m/min. and at a peel angle of 180~.
Examples 1-8 and Comparative Examples 1-4
Coating solutions containing a monofunctional
25 perfluoropolyether monomer, CF3(C3F6O)3 4CF2CH2OCOC 2'
designated MFM, and/or a difunctional perfluoropolyether
monomer, CH2=cHcOOcH2cF20(c2F4o)8(cF2o)l4cF2cH2o 2
designated DFM1, in the ratios set forth in Table 1, as
0.50 weight percent monomer in 1,1,2-trichloro-2,2,1-tri-
30 fluoroethane, were coated onto a 2.9 mil (0.074 mm)
poly(ethylene terephthalate) film using a No. 3 wire wound
rod. The solvent was evaporated to provide a calculated
dry thickness of 35 nm in Examples 1-4 and Comparative
Examples 1-2 and a calculated dry thickness of 70 nm in
35 Examples 5-8 and Comparative Examples 3-4. This coated
film was then passed once at 1830 cm/min through an
ultraviolet processor Model QC 1202AN31R, available from
1339614
-25-
PPG Ind~stries, irradiating with tw~ medium pressllre
mercury lamps at 80 watts per centimeter in a nitrogen
atmosphere to form a liner on the polyethylene
terephthalate film.
The release peel force and readhesion peel force
were determined using Release Peel Test, Type B, and the
Readhesion Peel Test. The results are set forth in Tables
1 and 2. The readhesion peel force for the
poly(dimethylsiloxane) pressure-sensitive adhesive tape
which had not previously been subjected to the Release Peel
Test was about 2600 g/cm.
Table 1
(Coating Thickness: 35 nm)
Release Readhesion
Peel Force Peel Force
ExampleMFM/DFM1 ratio (g/cm) (g/cm)
Comp 1 0/100 135 2130
1 25/75 46 1570
2 50/50 36 1850
3 75/25 46 2350
4 90/10 56 2490
Comp 2 100/0 860 2200
Table 2
(Coating Thickness: 70 nm)
Release Readhesion
Peel Force Peel Force
30 ExampleMFM/DFM1 ratio (g/cm) (g/cm)
Comp 3 0/100 30 1350
25/75 25 1570
6 50/50 23 1780
7 75/25 33 2420
8 90/10 41 2130
Comp 4 100/0 145 2200
-26- 1339~14
As can be seen from the data in Table 1, the
monomer mixture containing both the monofunctional and
difunctional perfluoropolyether monomers provided liners
which exhibited significantly improved release peel force
5 with good readhesion peel force at a thickness of 35 nm
when compared to liners prepared from either the
monofunctional or difunctional perfluoropolyether monomer
alone. As can be seen from the data ln Table 2, the liners
of Examples 5-8 exhibited good readhesion peel force and
release peel force significantly better than Comparative
Example 4 prepared from only the monofunctional
perfluoropolyether monomer and substantially similar to or
better than Comparative Example 3 prepared from only the
more expensive difunctional perfluoropolyether.
Examples 9-11 and Comparative Examples 5 and 6
Coating solutions containing the monofunctional
perfluoropolyether monomer, CF3(C3F6O)3~qCF2CH2 2
used in Examples 1-8 and designated MFM, and/or a
20 difunctional perfluoropolyether monomer,
O - O
Il 11
CH2=CHCOCH2 SF(OCF2CF)pO(CF2)40( lCFCF20)qClF CH20CCH=CH2
_CF3 CF3 CF3 3~ 2.4
designated DFM2 wherein p+q is 2. 5 and the number average
molecular weight is 2200, at the ratios set forth in Table
3, as 50 weight percent monomer in 1,1,2-trichloro-2,2,1-
trifluoroethane were coated onto a 2.9 mil (O. 034 mm)
30 polyethylene terephthalate film using a No. 3 wire wound
rod. The solvent was evaporated to provide a calculated
dry thickness of 35 nm. The coated films were then passed
once at 1830 cm/min through an ultraviolet processor Model
QC 1202AN31R, available from PPG Industries, irradiating
35 with two medium pressure mercury lamps at 80 watts per
centimeter while under a nitrogen atmosphere to form liners
- on the film.
- - -
-27- 13~9614
The release peel force and readhesion peel force
were determined using Release Peel Test, Type A, and the
Readhesion Peel Test.
The readhesion peel force for the
poly(dimethylsiloxane) pressure-sensitive adhesive tape
which had not previously been subjected to the Release Peel
Test was about 4800 g/cm.
Table 3
Release Readhesion
Peel Force Peel Force
ExampleMFM/DFM2 ratio (g/cm~ (g/cm)
Comp 5 0/100 4760 2490
Comp 6 10/90 3490 1780
15 Comp 725/75 1780 2630
9 50/50 500 4200
75/25 240 3910
Comp 8 100/0 1560 3060
As can be seen from the data in Table 3, the
liners of Examples 9 and 10 exhibit significantly improved release p
eel force and readhesion peel force over the liners
of Comparative Examples 5-8.
The various modifications and alterations of this
25 invention will be apparent to those skilled in the art
without departing from the scope and spirit of this
invention and this invention should not be restricted to
that set forth herein for illustrative purposes.
