Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
IN SITU FLUOROPOLYMER POLYMERIZATION
INTO POROUS SUBSTRATES
FIELD OF THE INVENTION
5 This invention relates to the polymerization of fluoropolymers into porous
substrates. The fluoropolymer/substrate network that results is present on the
surface of the substrate and is also deposited into the substrate at
appreciable
depths. Depending upon the proportion of fluoropolymer relative to substrate,
the
fluoropolymer may provide a protective coating for the substrate and/or the
substrate may improve the physical properties of the fluoropolymer.
TECHNICAL BACKGROUND OF THE INVENTION
Porous materials have a host of uses. Common uses for leather and porous
polyurethane are to produce clothing and furniture. Common uses for wood
include use as a building material and for the production of furniture.
Polyimide
15 compositions are known to have unique performance characteristics, which
make
them suitable for uses in the form of bushings, seals, electrical insulators,
compressor vanes, brake linings, and others as described in U.S. Patent
No. 5,789,523. Para-oriented aromatic polyamides {para-aramids) are used to
make fiber substrates that are useful for wear resistant applications.
20 All of the porous materials described may degrade and decay over time by
staining, wetting, warping, tearing or wearing. It is desirable to treat
porous
materials to improve resistance to wear, tear, creep, decay, and degradation
by
wetting, staining and warping, and to improve durability while maintaining the
appearance of the materials.
25 For many years, textiles have been chemically treated to improve water
and oil repellency. Different applications are commercially available to
protect
different kinds of substrates from oil and water staining. For example,
Scotchgard~ brand protector for fabrics sold by the 3M Company, and Teflon~
Fabric Protector sold by E. I. du Pont de Nemours and Company, are available
to
30 consumers for use with textiles and fabrics. The use of granular fluoro-
compounds is also discussed in Japanese Patent 05318413. The invention
involves a method whereby a raw wood material is impregnated with fluorinated
microparticles having a diameter of 5 microns and a compound which changes to
insoluble cured resin.
35 There are several references which have used fluoro-compounds in wood
to enhance the properties of wood. For example, U.S. Patent No. 3,962,171
discusses a protective coating composition. The composition is used for
painted
and unpainted metal, plastic and wood surfaces. The method comprises preparing
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a mixture of a solution of 20 parts of granular polytetrafluoroethylene in
Freon~.
The composition is sprayed onto an acrylic painted surface, dried and wiped to
form a transparent coating.
The use of granular fluoro-compounds is also discussed in Japanese Patent
5 05318413. The invention involves a method whereby a raw wood material is
impregnated with fluorinated microparticles having a diameter of 5 microns and
a
compound which changes to insoluble cured resin. The compound is cured to fix
the microparticles with the resin. The uses and advantages listed in the
abstract
include use as building materials, woody appearance, contamination resistance,
and moisture and water resistance. The invention does not teach polymerization
of a fluoro-compound into the wood as the present invention does.
Other references include the treatment of microporous materials with
fluoroacryiate to achieve permanent water and oil repellency. For example,
U.S.
Patent No. 5,156,780 teaches a method for treating microporous substrates to
15 achieve water and oil repellency while maintaining porosity. In the '780
method,
the substrates are impregnated with a solution of monomer in a carrier
solvent.
The carrier solvent is first substantially removed from the substrate for the
express
purpose of leaving the monomer as a thin conformal coating on all internal and
external substrate surfaces. In this manner, the monomer is converted to
polymer
and the polymer does not block the pores or restrict flow in subsequent use as
a
filtration membrane.
If enough fluoromonomer is polymerized into a porous structure, a point is
reached at which there is more fluoropolymer than substrate and the
composition
can be considered a filled fluoropolymer. Fluoropolymers such as PTFE are
25 commonly filled with substances such as glass fibers, graphite, asbestos,
and
powdered metals (Kirk-Othmer Encyclopedia of Chemical Technology, Fourth
Edition, Volume 11, John Wiley and Sons, New York, pages 626 and 630). The
filler is generally added for the purpose of improving some property of the
fluoropolymer, such as creep or hardness.
30 Most often, filled fluoropolymers are made by physically mixing the
fluoropolymer with the filler or by coagulating an aqueous fluoropolymer
emulsion on the filler, but such methods have their problems. Adhesion of
fluoropolymer to filler can be quite poor, particularly if the fluoropolymer
does
not wet the filler and penetrate its pores and finer surface features.
Fluoropolymer
35 melts can be very stiff, making mixing/dispersion poor and nonuniform.
Mechanical mixing can degrade some fillers, for example by breaking fine
fibers.
It is desirable to polymerize fluoromonomer onto the surface and into the
pores of
2
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a substrate to achieve intimate fluoropolymer/substrate interpenetration and
dispersion with minimal mechanical stress.
It is desirable to treat porous substrates, such as wood, wood by-products,
aramids, polyimides, porous polyurethane, and leather compositions, such that
the
porous substrate is more resistant to degradation, especially by staining,
warping
and wetting.
SUMMARY OF THE INVENTION
Disclosed in this invention is a process for preparing a
fluoropolymer/substrate composition, comprising:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an
initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous
fluoromonomer under polymerization temperature and
pressure conditions wherein the fluoromonomer polymerizes
into said substrate;
wherein said polymerized gaseous fluoromonomer partially or completely fills
and blocks the pores in the substrate;
or in the case of liquid fluoromonomer
20 (a) preparing a solution comprising initiator and liquid
fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization
temperature and pressure conditions wherein the
25 fluoromonomer polymerizes into said substrate, optionally in
the presence of gaseous fluoromonomer;
wherein said polymerized liquid fluoromonomer partially or completely fills
and
blocks the pores in the substrate.
Also disclosed is a composition of matter made by a process for preparing
30 a fluoropolymer/substrate composition wherein said process, comprises:
in the case of gaseous fluoromonomer
(a) contacting a porous substrate with a solution comprising an
initiator dissolved in a suitable solvent;
(b) exposing said substrate and said initiator to gaseous
35 fluoromonomer under polymerization temperature and
pressure conditions wherein the fluoromonomer polymerizes
into said substrate;
3
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wherein said polymerized gaseous fluoromonomer partially or completely fills
and blocks the pores in the substrate;
or in the case of liquid fluoromonomer
(a) preparing a solution comprising initiator and liquid
fluoromonomer;
(b) contacting a porous substrate with said solution; and
(c) polymerizing the liquid fluoromonomer under polymerization
temperature and pressure conditions wherein the
fluoromonomer polymerizes into said substrate, optionally in
the presence of gaseous fluoromonomer;
wherein said polymerized liquid fluoromonomer partially or completely fills
and
blocks the pores in the substrate.
A further disclosure of the present invention is a composition of matter,
comprising: a porous substrate wherein said substrate is an open pore
structure
15 having a surface and interconnecting pores throughout the substrate; and
polymerized fluoropolymer, wherein said fluoropolymer is present within and on
the surface of said substrate, and wherein the amount of fluoropolymer present
in
said composition is, in the case of a non-wood substrate, from about 0.1
percent to
about 300 percent of the weight of said non-wood substrate, and in the case of
a
wood substrate, from about 0.1 to about 150 percent of the weight of said wood
substrate.
Also disclosed is the use of these compositions as filler materials for other
polymers.
BRIEF DESCRIPTION OF THE DRAWINGS
25 Figure 1 is a depiction of a block of redwood as described in Example 2 in
the present invention.
Figure 2 is a depiction of the cross sectioning and electron microscopy
scanning of a block of redwood as described in Example 2 in the present
invention.
30 Figure 3 is a depiction of a block of oak as described in Example 3 in the
present invention.
Figures 4 is a depiction of the cross sectioning and electron microscopy
scanning of a block of oak as described in Example 3 in the present invention.
DETAILED DESCRIPTION OF THE INVENTION
35 The present invention discloses a fluoropolymer/substrate composition.
The presence of fluoropolymer in the composition provides a protective
material
for the substrate and may also add aesthetic qualities to the substrate. A
further
4
CA 02341682 2001-02-22
wo oonas2s rcrius99nso~~
advantage of the fluoropolymer/substrate composition is that the physical
properties of the fluoropolymer are improved.
The present invention also discloses a method for in-situ fluoropolymer
polymerization into porous substrates. The method produces a
5 fluoropolymer/substrate composition wherein the presence of fluoropolymer
adds
aesthetic quality to some substrates, enhances some of the porous substrates,
or
functions as a protective material for other porous substrates. The method
used
leaves the initiator and the initiator carrier solvent in the substrate during
polymerization and uses undiluted monomer or, in its preferred embodiment,
10 gaseous monomer, to penetrate and block all pores to the greatest depth
possible.
The object of the present invention is to provide a method for treating the
substrate such that the presence of the fluoropolymer/substrate composition
decreases or eliminates penetration of agents that cause degradation so as to
increase the substrate's resistance to wetting by oil and water, reduce
warping and
15 staining by oil, water, and other common materials, and to improve
durability.
The fluoropolymer/substrate composition improves resistance to wear, tear,
creep
and decay.
The disclosed fluoropolymer/substrate compositions that result have
properties that give them a variety of utilities. For example, when the
preferred
20 fluoromonomer, TFE, is used in the process for waod substrates, a PTFE/wood
composition results and the wood is protected by the presence of the PTFE.
PTFE
polymerized into the wood increases the wood's resistance to wetting by oil
and
water, reduces staining by oil and water, decreases warpage and improves
durability. These properties make the composition attractive for building
25 materials. The method disclosed herein for preparing intimately
interpenetrated
fluoropolymer/substrate compositions improves the functional lifetime and/or
the
appearance of the substrates.
Coating the surface and blocking the pores of a substrate with
fluoropolymer prevents or slows degradation by wetting and penetration of the
30 substrate by agents such as water, acids, bases, foodstuffs, and cosmetics,
thereby
preventing staining, warping, and unwanted chemical or physical property
changes in the substrate. As a case in point, the Ultrasuede~/PTFE composition
of Example 15 below wets less readily than untreated Ultrasuede~. Coating the
surface and blocking the pores of a substrate with fluoropolymer can also slow
35 mechanical degradation by such means as abrasion, creep, or tearing. As a
case in
point, the polyimide/PTFE composition of Example 8A abraded 8X more slowly
than untreated polyimide.
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Going further, once the volume of polymerized fluoropolyrner exceeds
that of the substrate or once the fluoropolymer/substrate network has been
blended into pure fluoropolymer, the substrate can then be considered as
dispersed
in the fluoropolymer for the purpose of modifying fluoropolymer properties.
5 These compositions are commonly referred to as "filled fluoropolymers". For
example, intimately interpenetrated porous polyimide or aramid particulates
can
be added to poly(tetrafluoroethylene) to potentially decrease PTFE creep. In a
process disclosed in the present invention, the fluoromonomer is polymerized
both on the surfaces and into the pores of a substrate to achieve intimate
10 fluoropolymer/substrate interpenetration and dispersion. By using this
method,
the filled fluoropolymer is prepared with minimal mechanical stress. This
process
reduces degradation, and thereby, offers a solution to the problem of
degradation
that occurs with mechanical mixing.
By "porous substrate" is meant any solid material penetrated throughout
15 with interconnecting pores of a size such as to allow absorption of liquid
initiator
solution and monomer. The porous substrates can take any form including
microscopic particulates, microscopic fibers, coarse particulates, pulp,
fibrids,
chunks, blocks, uncompressed, partially or fully compressed parts, sheets,
films,
membranes, and coatings. Porous substrates are not meant to include materials
20 such as cloth where the only mechanism of fluoropolymer entrainment is
gross
entrapment between separate fibers rather than subsurface penetration into a
substrate's pores. This process works with any porous substrate that does not
inhibit fluoromonomer polymerization. Substrates not inhibiting polymerization
include wood (including wood by-products such as paper), p-aramid fibers,
25 molded polyimide parts, porous polyurethane and leather. By "wood" we mean
raw lumber as well as more processed forms of wood and its by-products
including wood veneer, wood chips, sawdust, paper, and cardboard. Whether a
substrate will inhibit polymerization must be determined empirically substrate
by
substrate and may vary for the same substrate, depending upon prior finishing
and
30 treatment.
The inventive process involves in situ polymerization of fluoromonomer
into substrates. Polymerization temperatures range from about 0°C to
about
300°C, for non-wood substrates, preferably from about 0°C to
about 100°C for all
disclosed substrates, most preferably from about 5°C to about
30°C for all
35 disclosed substrates. For those substrates that retain their rigid pore
structures at
high temperatures and do not thermally decompose, polymerizations can be run
at
temperatures up to about 300°C.
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Polymerization pressures may vary. For gaseous monomers, pressures are
generally from about 7 psia to about 500 psia. In the case of liquid monomers,
such as 4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole (PDD) or perfluoro
(2-methylene-4-methyl-1,3-dioxolane) (PMD), the reaction is generally carried
5 out under atmospheric pressure unless copolymers with TFE or other gaseous
monomers are desired. In the absence of a pure gaseous monomer phase, oxygen
should be excluded and an inert atmosphere, such as nitrogen, provided.
The process of the present invention uses fluoromonomer in either the
gaseous or liquid state. Gaseous monomers include tetrafluoroethylene (TFE),
trifluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, hexafluoro-
isobutylene and perfluoro methyl vinyl ether. Liquid monomers include PDD,
PMD and perfluoro propyl vinyl ether. These monomers may be
homopolymerized or copolymerized to make compositions known to those skilled
in the art. Examples include tetrafluoroethylene homopolymer,
tetrafluoroethylene/4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole
copolymer,
and tetrafluoroethylene/perfluoro (2-methylene-4-methyl-1,3-dioxolane)
copolymer.
In the case of liquid fluoromonomer, such as PDD and PMD, the carrier
solvent can be the monomer or the monomer containing a small amount of
initiator solution (for example, hexafluoropropylene oxide dimer peroxide (DP)
1
CF3CF2CF20CF(CF3)(C=O)00(C=O)CF(CF3)OCF2CF2CF3
1, DP
in a Freon~ solvent).
25 For an active monomer such as TFE, polymerization often deposits about
0.1 to 10 wt. % PTFE in the substrate at atmospheric pressure. Higher TFE
pressures yield higher weight gains. When higher pressures are used, standard
barricading must be employed to protect against TFE deflagration and runaway
polymerization.
30 The process invention disclosed herein works for most organic initiators
commonly used for fluoroolefin polymerizations, including, but not limited to,
diacylperoxides, peroxides, azos and peroxydicarbonates. The preferred
initiator
is DP. DP has a half life of about 4 hours at 20°C which means that DP
lasts long
enough for a polymerization run to be set up at room temperature without
35 excessive initiator loss and yet DP still reacts fast enough at room
temperature for
polymerizations to run to completion fairly quickly. Preferred run times are
from
about 4 to about 24 hours.
In the preferred embodiment of this invention, the initiator is first
synthesized in any solvent that is compatible with fluoroolefin polymerization
and
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the initiator solution then absorbed into the substrate. Suitable solvents
comprise
chlorofluorocarbons such as Freon~ 113 (CFC12CF2C1), hydrofluorocarbons, such
as Vertrel~ XF (HFC-43-lOmee; 2,3-dihydroperfluoropentane) specialty fluid,
perfluorocarbons, such as perfluorohexane, perfluoroethers, such as
Fluorinert~ FC-75 sold by 3M Company, perfluoroamines, such as
Fluorinert~ FC 40, and perfluorodialkylsulfides, such as
CF3CF2CF2CF2SCF2CF2CF2CF2CF3. The preferred solvents for DP are
Vertrel~ XF and Freon~ E1(CF3CF2CF20CFHCF~).
In this invention, the preferred initiator solution comprises a solution of
DP in Vertrel~ XF (CF3CFHCFHCF2CF3). It is further preferred that the
fluoromonomer is tetrafluoroethylene. TFE polymerizes to form PTFE.
In the preferred embodiment of the process where the substrate is wood,
the wood is soaked in a solution of free radical initiator. The preferred
initiator
when wood is used as a substrate is DP. The wood is then removed from the
15 initiator solution and the free liquid is allowed to drain away. By "free
liquid" is
meant solution that is not absorbed by the substrate during soaking. The
initiator-
soaked wood is then placed in an apparatus suitable for polymerization. The
apparatus is filled with gas phase fluoromonomer, and the polymerization
allowed
to run. The polymerization apparatus can be a simple plastic bag for
atmospheric
pressure polymerization or an autoclave for polymerization at pressures up to
several hundred psi.
When a preferred substrate is used, the porous aramid or polyimide is
immersed for about 1 minute in a 0.1 to 0.2 M solution of DP in
CF3CFHCFHCF2CF3 solvent. The excess solvent is filtered off or is drained
from the aramid or polyimide, and the still damp polymer placed in a container
with 1 atmosphere pressure of tetrafluoroethylene gas until the substrate has
gained preferably 5 to 20% of its weight by polymerization of the tetrafluoro-
ethylene to poly(tetrafluoroethylene).
The preferred aramids are polyp-phenylene terephthalamide) (hereinafter
30 "PPD-T") fibers and poly(m-phenylene isophthalamide)(hereinafter "MPD-r~ in
the form of fiber, particles, pulp or fibrids, that are dried or never-dried.
Examples of preferred aramids are polyp-phenylene terephthalamide) fibers sold
by the DuPont Company under the tradename "Kevla~", and poly(m-phenylene
isophthalamide) sold by the DuPont Company under the tradename "Nomex~".
35 A "never-dried aramid" means an aramid coagulated from a solution by
contact with a non-solvent (usually an aqueous bath of some sort, such as
water or
an aqueous solution). When contacted with the non-solvent, the polymer
coagulates and most of the solvent is removed from the aramid. The aramid has
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an open sponge-like structure, which usually contains about 150-200% by weight
of the aramid of non-solvent (again, usually water). It is this open sponge-
like
structure, which has imbibed the non-solvent, which is referred to herein as
"never-dried aramid".
5 By PPD-T is meant the homopolymer resulting from mole-for-mole
polymerization of p-phenylenediamine and terephthaloyl chloride and, also,
copolymers resulting from incorporation of small amounts of other aromatic
diamine with the p-phenylene diamine and of small amounts of other aromatic
diacid chloride with the terephthaloyl chloride. Examples of other acceptable
10 aromatic diamines include m-phenylene diamine, 4,4'-diphenyldiamine,
3,3'-diphenyldiamine, 3,4'-diphenyldiamine, 4,4'-oxydiphenyldiamine,
3,3'-oxydiphenyldiamine, 3,4'-oxydiphenyldiamine, 4,4'-
sulfonyldiphenyldiamine,
3,3'-sulfonyldiphenyldiamine, 3,4'-sulfonyldiphenyldiamine, and the like.
Examples of other acceptable aromatic diacid chlorides include 2,6-naphthalene-
15 dicarboxylic acid chloride, isophthaloyl chloride, 4,4'-oxydibenzoyl
chloride,
3,3'-oxydibenzoyl chloride, 3,4'-oxydibenzoyl chloride, 4,4'-sulfonyldibenzoyl
chloride, 3,3'-sulfonyldibenzoyl chloride, 3,4'-sulfonyldibenzoyl chloride,
4,4'-dibenzoyl chloride, 3,3'-dibenzoyl chloride, 3,4'-dibenzoyl chloride, and
the
like. As a general rule, other aromatic diamines and other aromatic diacid
20 chlorides can be used in amounts up to as much as about 10 mole percent of
the
p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher,
provided only the other diamines and diacid chlorides have no reactive groups
which interfere with the polymerization reaction.
By MPD-I is meant the homopolymer resulting from mole-for-mole
25 polymerization of m-phenylenediamine and isophthaloyl chloride and, also,
copolymers resulting from incorporation of small amounts of other aromatic
diamine with the m-phenylene diamine and of small amounts of other aromatic
diacid chloride with the isophthaloyl chloride. Examples of other acceptable
aromatic diamines include p-phenylene diamine, 4,4'-diphenyldiamine,
30 3,3'-diphenyldiamine, 3,4'-diphenyldiamine, 4,4'-oxydiphenyldiamine,
3,3'-oxydiphenyldiamine, 3,4'-oxydiphenyldiamine, 4,4'-
sulfonyldiphenyldiamine,
3,3'-sulfonyldiphenyldiamine, 3,4'-sulfonyldiphenyldiamine, and the like.
Examples of other acceptable aromatic diacid chlorides include 2,6-naphthalene-
dicarboxylic acid chloride, terephthaloyl chloride, 4,4'-oxydibenzoyl
chloride,
35 3,3'-oxydibenzoyl chloride, 3,4'-oxydibenzoyl chloride, 4,4'-
sulfonyldibenzoyl
chloride, 3,3'-sulfonyldibenzoyl chloride, 3,4'-sulfonyldibenzoyl chloride,
4,4'-dibenzoyl chloride, 3,3'-dibenzoyl chloride, 3,4'-dibenzoyl chloride, and
the
like. As a general rule, other aromatic diamines and other aromatic diacid
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chlorides can be used in amounts up to as much as about 10 mole percent of the
m-phenylene diamine or the isophthaloyl chloride, or perhaps slightly higher,
provided only the other diamines and diacid chlorides have no reactive groups
which interfere with the polymerization reaction.
5 Substrates specifically exemplified for the present invention include wood,
molded polyimide parts, porous polyimide powder (or polyimide particulate),
porous para-aramids such as poly(para-phenylene terephthalamide) [PPD-T] in
the forms of powder, pulp and/or fiber, and porous meta-aramids, such as
poly(m-phenylene isophthalamide) [MPD-I] in the forms of powder, fibers or
fibrids, porous polyurethane, and leather (pigskin and cowskin).
The present invention also provides a fluoropolymer/substrate composition
wherein the substrates are open structures with interconnecting pores
throughout
their bulk and the level of fluoropolymer in the fluoropolymer/substrate
composition is about 0.1% to about 300%, for non-wood substrates, and about
0.1
15 to about 150% for wood substrates, of the weight of the substrate.
Substrates
usefixl in this invention include wood, paper, leather, porous polyurethane,
and
aramids and polyimides that have been precipitated as porous particulates or
porous fibers and then left wet, dried, or molded only so far as to preserve
enough
porosity for subsequent penetration by fluoromonomer and initiator. Preferred
ZO substrates are porous aramid, polyimide particulates and polyimide parts.
EXAMPLES
EXAMPLE I
POLYMERIZATION OF PTFE) INTO DIFFERENT WOODS
DECREASED WATER ABSORPTION, INCREASED DURABILITY
25 A. Polymerization of TFE into wood
A saw was used to cut samples of cedar, cherry, oak, pine, poplar,
redwood, and walnut into cubes which measured roughly 0.75 inches on a side.
Using glass jars, three cubes of each wood were soaked for 1 hour in ~50 ml of
0.185 M hexafluoropropylene oxide dimer peroxide (1 DP) at -15°C
CF3CF2CF20CF(CF3)(C=O)00(C=O)CF(CF3)OCF2CF2CF3
1, DP
in Freon~ E1 (CF3CF2CF20CFHCF3). Each group of three cubes was air dried
for about 30 seconds and then transferred to a 400 ml autoclave. In all cases
the
autoclave was chilled, evacuated, and filled with tetrafluoroethylene (TFE)
gas.
Fifty grams of TFE gas were charged in the case of cedar, cherry, pine,
poplar,
and redwood, but only 25 g were charged in the case of oak and walnut. The
wood cubes were recovered, dried for 16 hours under pump vacuum, scraped with
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a spatula to remove loose polymer from the surface, and put under pump vacuum
again until, after several days, a constant weight was achieved. Averaged over
the
three cubes of each wood type, weight gains from TFE polymerized into the wood
as PTFE ranged from 14 to 95% as shown in Chart 1 below, wherein the woods
5 are listed in order of decreasing sample weight and density. Most often, the
less
dense the starting wood, the greater the weight of PTFE deposited into the
wood.
TABLE
1
PTFE Weight
Gains
for Different
Woods,
Averaged
over
3 Cubes
Grams Average Average Average Weight
Wood TFE Cube Wt. Cube Wt. Wt. Gain Gain As
T a Loaded Before After PTFE A
to Percent
Autoclave
Oak 25 g* 5.25 g 6.01 g 0.76 g 14.5%
Walnut 25 g* 4.53 g 5.45 g 0.92 g 20.3%
Cherry 50 g 4.34 g 5.63 g 1.29 g 29.7%
Poplar 50 g 4.08 g 5.65 g 1.56 g 38.2%
Pine 50 g 4.02 g 5.73 g 1.71 g 42.5%
Cedar 50 g 2.81 g 4.23 g 1.42 g S0.5%
Redwood 50 g ~ 2.09 g ~ 4.08 1.99 g ~ 95.2%
g
*Strong exotherm and charring of the wood observed with 50 g TFE
B. Effect of PTFE on Water Absorption
10 For each wood type, cedar, cherry, oak, pine, poplar, redwood, and walnut,
three cubes 0.75" on a side were assembled:
Cube #1: A cube from part A above containing poiymerized PTFE
Cube #2: A cube from part A above containing polymerized PTFE,
the surface of which has been lightly sanded to remove
15 most visible traces of PTFE. In the discussion that follows
these lightly sanded cubes are referred to as "PTFE/wood
blocks".
Cube #3: A cube untreated except that it has been put under pump
vacuum overnight to mimic the final devolatilization step of
20 part A above. In the discussion that follows the blocks that
were not chemically treated are referred to as the "control"
blocks.
For each wood type, all three cubes were simultaneously immersed in
distilled water in the same glass jar. In every case the control block showed
an
25 immediate darkening when immersed in water whereas the PTFE/woad blocks
retained much of their natural color and appearance. The cubes were then
11
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periodically withdrawn, patted damp dry, weighed to determine the amount of
water absorbed, and reimmersed in the water. A comparison of water absorption
data of the control and PTFElwood blocks after 600 cumulative hours of
immersion in water is shown in Chart 2.
-.
TABLE
2
Affect
of
PTFE
on
Water
Abso
tion
After
600
Hours
of
Immersion
ML H20 (ML PTFE
StartingAbsorbed/MLML PTFE/ ML H20/ +
Wood Wood of Wood ML of ML of WoodML H20/
Densi Control Wood PTFE/Wood)ML Wood
PTFE/wood PTFE/wood
Oak 0.76 0.60 ml 0.048 0.52 ml 0.57 ml
g/ml ml
Walnut 0.66 0.58 ml 0.058 0.38 ml 0.44 ml
g/ml ml
Cherry 0.63 0.64 ml 0.081 0.42 ml 0.50 ml
g/ml ml
Poplar 0.59 0.71 ml 0.098 0.35 ml 0.45 ml
glml ml
Pine 0.58 0.63 ml 0.11 ml 0.32 ml 0.43 ml
g/ml
Cedar 0.41 0.51 ml 0.089 0.42 ml 0.51 ml
g/ml ml
Redwood0.30 0.52 ml 0.13 ml 0.20 ml 0.33 ml
g/ml
All starting cubes measured about 1.90 cm on a side for a net volume of
about 6.9 ml each. Densities were calculated, as shown in column 2, from the
average weights in Chart 1. The weight of the water absorbed over the course
of
10 600 hours of immersion divided by the volume of the wood sample (6.9 ml),
gave
the volume of water absorbed per milliliter of wood in the control blocks, as
shown in column 3. There was little correlation between wood density and the
volume of water absorbed. For example, although redwood was calculated to
have less than half the density of oak, redwood absorbed slightly less water.
15 Using the weight gains from Chart 1 and an assumption of about 2.3 g/ml for
the
PTFE, the volume of PTFE deposited per ml of wood in the PTFE/wood cubes
was calculated, as shown in column 4. The weight of water absorbed by the
PTFE/wood blocks over 600 hours of immersion was divided by 6.9 to calculate
the volume of water absorbed per ml of wood in the PTFE/wood blocks
20 (column 5). Wood samples that contained PTFE absorbed 13 to 62% less water
(column 5) than the same wood cubes without PTFE (column 3). With the
exception of cedar, the combined volume of PTFE and of water in the PTFE/wood
blocks (column 6) was less than the volume of water absorbed by the control
blocks (column 3). That is, in all cases but cedar, the PTFE did more than
just fill
25 void space that would otherwise be filled by water.
12
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WO 00/24528 PCT/US99/25077
C. Effect of Repetitive Polymerization.
Three cubes of poplar 0.75" on a side and with an average weight of
3.7942 grams were soaked for 15 minutes at -15°C in 0.16 M DP in Freon~
E1
which had been previously filtered through a 0.45 p, filter. The soaked
blocks, the
5 average weight of which increased to 5.6650 grams in the soaking process,
were
briefly air dried and charged to a stainless steel autoclave. The autoclave
was
chilled, evacuated and further charged with 50 g of TFE. The autoclave was
heated for 4 hours at 40°C. The cubes were recovered, lightly sanded to
remove
loose surface polymer, and dried at room temperature overnight with pump
10 vacuum. The average cube weight was brought to 5.4960 g, which was a 45%
weight increase compared to the starting weight.
The cubes were soaked a second time for 15 minutes in -15°C 0.16 M
DP
solution. The average weight of the cubes was 5.7628 g. The cubes were
reloaded into the 400 ml autoclave with 25 g of TFE. The autoclave was heated
15 for 4 hours at 40°C. The cubes were recovered, lightly sanded, and
dried under
pump vacuum overnight. The average weight was brought to 6.383 g.
The cubes were soaked a third time in DP, reacted with 25 g TFE in a 400
ml autoclave tube, recovered, lightly sanded, and dried for 3 days at room
temperature under pump vacuum. The average weight was brought to 6.4953 g,
20 which was a 71.2% weight gain compared to the start.
One of the cubes was immersed in water along with an untreated poplar
control cube. Once again weight gain was followed as a function of cumulative
immersion time. Chart 3 compares the 600-hour water absorption results for the
poplar cubes prepared in part C of this Example to the poplar cubes of part B
of
25 this Example. While the poplar cube exposed to three polymerization cycles
contained almost twice as much PTFE as the cube exposed to a single
polymerization cycle, no difference was detected in the amount of water
absorbed
after 600 hours.
TABLE
3
Affect
of PTFE
on Water
Absorption
After
600 Hours
of Immersion
ML H20 (ML PTFE
+
Starting Absorbed/ ML PTFE/ ML H20/ ML H20)/
Wood ML of WoodML of ML of ML Wood
Wood Wood
Wood Densi Control PTFE/wood)PTFE/woodPTFE/wood
Poplar, 0.59 g/ml0.71 ml 0.098 0.28 ml 0.38 ml
IX ml
Poplar, 0.55 g/ml0.83 ml 0.17 ml 0.28 ml 0.45 ml
3X
13
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WO 00/24528 PCT/US99/25077
D. Resistance to Prolonged Water Exuosure
The soaking experiments described in part B of this Example were
continued for 8 to 9 months at room temperature. After the wood cubes were
removed from the water, the surfaces were wiped damp dry with a tissue. The
5 PTFE containing wood samples were uniformly less darkened and less "wet"
looking as recorded in the Chart 4 below.
TABLE
4
Effect
of Prolonged
Water
Exposure
Appearance of Appearance of Appearance of
Wood Water Untreated Wood PTFE/Wood
Oak Yellow with Dark brown to Tan, more like
black solids black starting
~ i? wood
Walnut Orange with Black Brown with occasional
black solids
~ i? black s ots
Cherry Yellow with Dark brown Tan with occasional
black solids dark
~ i? s ots
Poplar Pale yellow Medium brown Blonde, more like
with black starting
solids fun i? ~'~d
Pine Colorless Light brown Blonde, more like
starting
wood
Cedar Yellow with Dark brown Tan, much like
black solids starting
~ i? wood
Redwood Yellow with Dark brown ~ Tan, much like
white solids starting
wood
EXAMPLE 2
10 EVIDENCE FOR PTFE PENETRATION INCHES DEEP INTO REDWOOD
The experiments below establish that TFE polymerizes in wood at least
inches below the wood surface and that, while deposition along the grain may
be
mildly favored, penetration occurs in other directions as well. Gaseous
monomer,
such as TFE, penetrates wood particularly easily.
15 A. Evidence for Deen Penetration
Two redwood blocks were cut so as to detect anisotropy in the penetration
and polymerization of TFE. The first block measuring 10.8 cm X 2.6 cm X
1.8 cm was cut so that the grain of the wood ran in the 10.8 cm direction. It
is
referred to hereinafter as the "lengthwise" block. A second block measuring
20 11.0 cm X 2.7 cm X 1.8 cm was cut so that the grain of the wood ran in the
2.7 cm direction. It is referred to as the "crossgrain" block. It is supposed
that if
TFE can penetrate wood substrates only along the direction of the grain of the
wood, then TFE must travel 5.4 cm to get to the center of the lengthwise block
but
14
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WO 00/24528 PCT/US99/25077
only 1.35 cm to get to the center of the crossgrain block. The two blocks
could
thus differ greatly in PTFE weight gain and how any PTFE is distributed
spatially.
Each block was weighed and then soaked for 1 hour at -15°C in 0.16
M DP in
Freon~ E 1. The blocks were briefly air dried and then transferred to separate
5 400 ml stainless steel autoclaves. Each tube was charged with SO g of TFE
and
heated for four hours at 40°C. The blocks were recovered, lightly
sanded to
remove loose PTFE from the surface, dried for at least 4 days under pump
vacuum, and reweighed. The lengthwise block increased in weight from 17.9 g to
30.3 g for a 69% weight gain. The crossgrain block increased in weight from
10 16.0 g to 28.7 g for a 79% weight gain. The volume of PTFE picked up per ml
of
wood was 0.103 ml of PTFE for the crossgrain sample and 0.108 ml for the
lengthwise sample. These results are likely the same within experimental error
and are not much different from the 0.13 ml of PTFE per ml of wood reported
above for the much smaller redwood cubes in Example 1. This experiment
15 provided the first indication that grain direction did not dominate
deposition, that
PTFE deposition is not limited primarily to the wood surface, and that sample
size
did not dramatically affect results up to dimensions of several inches.
Untreated wood contains no fluorine while PTFE is 76% by weight
fluorine. Thus, the concentration of PTFE in a treated wood sample is
20 proportional to the wood's fluorine content. As illustrated in Figure l,
the
crossgrain sample (block 10 of Figure 1 ) was sawed in half creating two new
blocks (blocks 12 and 13 of Figure 1), each measuring roughly 5.5 cm X 2.7 cm
X
1.8 cm. The cut wood sample exposed the interior of the original block as two
new faces. One of the two new block faces was scanned across its full width
with
25 the beam of an electron microscope set to a 50 micron spot size (scans #2 -
#7).
The electron microscope was operated in energy dispersive mode so as to give
an
output signal proportional to the fluorine content of the wood. In this way
microscopic variations in relative fluorine concentration (y axis) could be
plotted
across the full width of the wood block (x axis).
30 Scan #3 was in the direction of the wood grain (the 2.7 cm dimension)
while scan #6 was perpendicular to the grain (the 1.8 cm direction). The scans
showed choppy alternation between areas of high and low fluorine concentration
which was attributed to random areas of cellulose, void and PTFE that were
crossed by the beam during the scan. While high fluorine concentrations were
35 observed throughout the bulk of the wood, fluorine concentrations were
noticeably higher toward the surface of the wood in scans #3 and #6.
A similar analysis was then done on the lengthwise block. As shown in
Figure 2, the block (block 20 of Figure 2) was first cut in half to create two
new
CA 02341682 2001-02-22
WO OO/Z4528 PCT/US99/25077
faces (blocks 21 and 22 of Figure 2). One of the new faces was scanned with
the
beam of an electron microscope in energy dispersive mode to measure relative
fluorine concentration as shown by the direction of the arrows in Figure 2.
Three
scans were performed in the 1.8 cm direction (scans #9, # 10, and # 11 )and
three
5 scans were performed in the 2.6 cm direction (scans #12, #13, and #14). All
six
scans performed were perpendicular to the wood grain. High and low fluorine
concentrations alternated irregularly across the full width of all six scans.
There
was no discernable preference for fluorine at the swface. One of the two 5.4
cm
X 2.6 cm X 1.8 cm blocks created by the first cut was cut into half again. Two
additional blocks were created (blocks 23 and 24 of Figure 2) that measwed
~5.4 cm X 2.6 cm X 0.9 cm. The fresh cut face of one of the blocks was scanned
three times along the grain of the wood, traveling each time the 5.4 cm
distance
from what had been the center of the original block to an outside end (scans
#CE 15, #CE 16, and #CE 17). The fluorine concentrations increased 10 to
15 20 times from the center to the outer face of the block. Fluorine
concentrations
measured much lower at the center of the block for scan #CE16, than when
scanned end on as in scans #9 through #14 of Figure 2. Combustion analysis was
used to resolve the inconsistency.
Three small wood chips were cut from the end of the block where electron
20 microscopy had shown high concentrations and three small wood chips from
the
end of the block (i.e., the deep interior of the original block before the
block was
cut in the first instance) where electron microscopy had shown 10 to 20 times
lower concentrations in Figwe 2 scans #CE15, #CE16, and #CE17, and one small
wood chip was cut from the middle of the face. The weight percents of fluorine
25 found by combustion analysis for all seven wood chips are provided in
Figure 2.
The fluorine content varied from an average of 30 wt % in the deep interior of
the
block to an average of 44 wt % at the outer end of the block. Electron
microscopy
had shown the correct trend but in an exaggerated fashion. The exaggeration is
attributed to the effects of wood morphology and angle of viewing on PTFE
30 content. This example provides a basis for concluding that there is a mild
preference for TFE polymerization along the direction of the wood grain and
that
penetration occws easily to depths of at least 5.4 cm.
B. Morphology of PTFE Deposits within the Wood
As shown in Figure 2, the redwood "lengthwise block" was cut into three
35 pieces. A piece measuring ~5.4 cm X 2.6 cm X 0.9 cm and weighing about 4.5
g
was digested chemically by heating it to reflux with 10 ml of concentrated
sulfuric
acid. Additional sulfuric acid was added to reduce the wood to an oily black
residue. The carbon responsible for the black color was then burned away by
the
16
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/25077
gradual addition of concentrated nitric acid. The residue was diluted with
water,
filtered, and dried. A white fibrous PTFE deposit was recovered. The residue
accounted for 35.6% of starting sample weight, which was similar to the
fluorine
levels measured by combustion analysis. At 100X to 20,OOOX magnification,
5 electron microscopy detected rod shaped structures 20p.-60p across and of
indefinite length. At 20,OOOX magnifications, the rods showed a spongy fine
structure. Such spongy morphology is often seen when TFE is polymerized in the
gas phase. Perhaps the void spaces in wood function as microscopic gas phase
polymerization reactors for TFE. In this invention, the polymerization appears
to
10 have filled the pores in the wood substrates with spongy PTFE deposits
rather
than having deposited the PTFE as a conformal coating on the walls of
the.pores.
EXAMPLE 3
EVIDENCE FOR PTFE PENETRATION INCHES DEEP INTO OAK
Two oak blocks were cut so as to detect anisotropy in the penetration and
15 polymerization of TFE. The first block which measured 12.1 cm X 2.5 cm X
I .9 cm, was cut so that the grain of the wood ran in the 12.1 cm direction.
It will
be referred to hereafter as the "lengthwise" block in this Example (block 40
of
Figure 4). A second block which measured 2.1 cm X 2.5 cm X 1.9 cm was cut so
that the grain of the wood ran in the 2.5 cm direction. It will be referred to
20 hereafter as the "crossgrain" block in this Example (block 30 of Figure 3).
To the
extent that the TFE gas can penetrate the wood only along the direction of the
grain, the TFE must travel 6.05 cm to get to the center of the lengthwise
block but
only 1.25 cm to get to the center of the crossgrain block. The two blocks
could
thus differ greatly in PTFE weight gain and how any PTFE is distributed
spatially.
25 Each block was weighed and then soaked for 1 hour at -15°C in 0.16 M
DP in Freon~ E1. The blocks were briefly air dried and then transferred to
separate 400 ml stainless steel autoclaves. Each tube was charged with 25 g of
TFE and heated for four hours at 40°C. The blocks were recovered,
lightly
sanded to remove loose PTFE from the surface, dried for at least 4 days under
30 pump vacuum, and reweighed. The lengthwise block increased in weight from
44.36 to 47.98 g for an 8.1% weight gain. The crossgrain block increased in
weight from 42.54 g to 49.81 g, or a 17.1 % weight gain. The crossgrain sample
picked up 0.05 ml of PTFE/ml of oak and the lengthwise sample picked up
0.03 ml of PTFE/m1 of oak. This compares to 0.048 ml of PTFE per ml of oak in
35 the case of the 0.75" oak cubes of Example 1. The ~2X greater deposition of
PTFE in the crossgrain block suggested a mild preference for penetration in
the
direction along the wood's conductive tissues by which food and nutrients
travel.
I7
CA 02341682 2001-02-22
WO 00/24528 PCTIUS99125077
Cross section experiments were done next. The crossgrain sample was cut
in half to create two new blocks (blocks 31 and 32 of Figure 3). Each block
measured roughly 6.05 cm X 2.5 cm X 1.9 cm. A 50 ~ spot size was used to scan
one of the new faces by electron microscopy. The scans were performed in
5 energy dispersive mode to measure relative fluorine concentrations in the
direction of the arrows as shown in Figure 3.
Scans #19, #20, and #21 shown in Figure 3 were in the direction of the
wood grain (the 2.5 cm dimension) while scans #22, #23 and #24 were
perpendicular to the grain (the 1.9 cm direction). All six scans showed choppy
10 alternation between areas of high and low fluorine concentration which was
attributed to the random crossing of areas of cellulose, void, and PTFE by the
electron microscope beam. High PTFE concentrations occurred throughout the
wood and were not clustered near the surface.
A similar analysis was then done on the lengthwise block. The block was
15 first cut in half to create two new faces (blocks 41 and 42 of Figure 4).
One of the
new faces was scanned by electron microscope in energy dispersive mode
measuring relative fluorine concentration in the direction of the arrows in
Figure 4
below.
Three scans were performed in the 2.5 cm direction as indicated by the
20 arrows #26, #27, #28 of Figure 4 and three scans were performed in the 1.9
cm
direction, indicated by the arrows #29, #30, and #31 of Figure 4. All six
scans
were performed perpendicular to the wood grain. High and low fluorine
concentrations alternated irregularly across the full width of all six scans.
There
was no discernable preference for fluorine at the surface. One of the two 6.05
cm
25 X 2.5 cm X 1.9 cm blocks that was created by the first cut was cut in half
again to
create two more blocks (blocks 43 and 44 of Figure 4). The blocks measured
6.05 cm X 2.5 cm X 0.95 cm each. The fresh cut face of one was scanned three
times along the grain of the wood, traveling each time the 6.05 cm distance
from
what had been the center of the original block to an outside end, as indicated
in
30 arrows #CE32, #CE33, and #CE34 of Figure 4. While the scans indicated by
arrows #CE32, #CE33, and #CE34 showed very little fluorine towards the center
of the block, high fluorine concentrations were detected at the center of the
block
in scans #26 to #31 of Figure 4. As in the redwood block of Example 2, the
same
dependence of fluorine concentration upon scan direction was seen and
elemental
35 analysis was used to support the higher fluorine concentrations. It was
concluded
that there was a mild preference for TFE polymerization along the direction of
the
wood grain and that penetration easily occurred to depths of at least 6 cm.
18
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/25077
EXAMPLE 4
PROTECTION OF WOOD
A. High Pressure Process
A 3.8 cm X 8.6 cm rectangle was cut from each of the six types of wood in
5 a package of Band-it~ Real Wood Variety Veneer (Cloverdale Company, Inc., P.
O. Box 400, Cloverdale, VA 24077). While the exact identities of the woods
were unknown, their visual appearance suggested common woods such as walnut,
pine, maple, and redwood. All six rectangles were notched so as to enable
later
identification and weighed and then soaked for one hour at -15°C in
0.175 M DP
10 in Freon~ E1. The strips were briefly air dried and loaded into a pre-
chilled
400 ml autoclave along with SO g tetrafluoroethylene gas. As the autoclave was
warmed towards 40°C, pressure peaked at 261 psi at 20.7°C and
then decreased to
74 psi at 38.5°C at the end of the run, about four hours later. All six
strips became
heavily coated with PTFE. Loose PTFE was removed from the surface and
15 residual volatiles were removed. The surface of the wood still appeared
white.
Weight gains of 38%, 66%, 70%, 89%, 97%, and 145% were observed for the six
different types of wood samples. The samples that showed weight gains of 38%,
66%, 97%, and 145% were sanded to return the wood to a reasonably natural
surface appearance. Those samples were then spotted with Lea & Perrins~
20 Worcestershire Sauce, Pathmark~ Yellow Mustard, and Pathmark~ Tomato
Ketchup. After 5 to 10 minutes, the wood samples were wiped clean with a
tissue
and any residual moisture was allowed to air dry. No stains were readily
apparent
to the eye. The original starting woods that were not treated with TFE were
stained by Worcestershire Sauce, Mustard, and Ketchup under the same
25 conditions. The samples were compared to the starting woods. The wood/PTFE
compositions prepared in this example were more resistant to staining, more
easily cleaned, and more durable.
B. Low Pressure Process
A 30 mm X 40 mm rectangle was cut from each of the six types of wood
30 in a package of Band-it~ Real Wood Variety Veneer (Cloverdale Company,
Inc.,
P. O. Box 400, Cloverdale, VA 24077). While the exact identities of the woods
were unknown, their visual appearance suggested common woods such as walnut,
pine, maple, and redwood. All six rectangles were notched so as to enable
later
identification and weighed. The strips were soaked for one hour at -
15°C in
35 0.165 M DP in CF3CFHCFHCF2CF3, briefly air dried, loaded into a 20.3 cm X
25.4 cm zip lock polyethylene bag (Brandywine Bag Co., part number 301630)
equipped with a polypropylene gas inlet valve, and the bag was clamped shut.
The bag was taped to a rectangular wire frame attached in turn to an ordinary
19
CA 02341682 2001-02-22
wo oonas2s PcrnJS99nso~~
laboratory stirrer motor. The bag was evacuated/purged three with N2 and two
times with TFE and then inflated loosely with TFE gas. For the next ~18 hours
the bag and its contents were slowly tumbled using the stirrer motor mounted
in a
horizontal position. The wood strips were unchanged in visual appearance. The
5 strips were devolatilized for 72 hours under pump vacuum and reweighed. The
strips had a weight gains of 0.9 wt % to 7 wt % as shown in Chart 5, column 2.
Drops of water were placed on the wood and advancing contact angles measured
about 10 minutes later. Advancing contact angles were uniformly high,
120° to
127° (Chart 5, column 3), indicative of PTFE at the surface. The
behavior of the
10 untreated control samples containing no polymerized PTFE was markedly
different. While reasonably high contact angles of 90 to 122° were
observed for
the untreated control wood samples initially (Chart 5, column 5), these
contact
angles could be observed only briefly because the water droplets started to
spread
out over the surface after only about 15 seconds to 2 minutes (Chart 5, column
6).
15 The PTFE treated and the control samples were next submerged in water at
room
temperature and then air dried to observe what effect the PTFE treatment had
on
warpage.
Before any exposure to water, PTFE, or other chemicals, the Band-it~
Real Wood Variety Veneer starts off with a slight curvature, the decorative
wood
20 surface being on the convex side. Under immersion conditions, both the PTFE
and control samples wet through with water. PTFE treated samples remained
reasonably flat after 375 minutes of water immersion. After air drying
overnight,
five out of six of the untreated control samples noticeably curled back on
themselves creating semicircular or even tubular shapes (Chart 5, column 7)
while
25 the PTFE treated samples varied from slight curling to flattening {Chart 5,
column 4). Three of the untreated control samples also showed mild water
staining while none of the PTFE treated samples showed any visible water
marks.
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/25077
TABLE
Water
Contact
Angles
and
Warpage
for
Low
Pressure
Polymerization
Samples
Wood with Polymerized Untreated
PTFE Wood
Controls
Immerse Immerse
PTFE in H20 Initial Time in H20
Weight Contact Then Contact for Then Dry
Angle Dry
Wood Gain with H Overni An le WettinOverni ht
O ht
#1 0.9% 120 Slight 110 ~2 No Effect
min on
Flattening Shape, Slight
Stain
#2 2% 123 Curled 1 IO -2 Nearly
to min
Semicircle Tubular,
Slight
Stain
#3 3% 127 Flattened122 ~2 Slight Curling
min
#4 4% 127 Slight 115 ~2 Slight Curling,
min
Curling Slight Stain
#5 5% 122 Slight 105 ~ I Nearly Tubular
S
sec
Flattenin
#6 7% 122 Flattened90 -.15 Slight Curling
sec
In a final test, a drop of Squibb mineral oil 1 to 3 mm in diameter was
placed on all the control and PTFE treated samples. The mineral oil
immediately
wetted and spread out over the surface of the control samples leaving a large
oily
5 mark. In contrast the mineral oil beaded up on the PTFE treated samples.
After
waiting 10 to 15 minutes, the oil droplet was wiped off the PTFE treated
samples
leaving an oily mark visible only where the oil droplet had contacted the
wood.
Both the control and PTFE treated samples were then repeatedly rinsed with
Freon~ 113 (CF2C1CC12F) and air dried. All the untreated samples still showed
a
10 faint patch of darker wood 20 mm to 40 mm in maximum dimension where the
oil
had been. Of the PTFE treated woods, only wood #6 showed a faintly darker
patch 8 mm in diameter where the oil had been.
TFE polymerized into the wood makes the wood harder to wet by oil and
water, less subject to staining by oil and water, and less subject to warpage
when
15 wetted and then dried.
EXAMPLE 5
LIOUID PHASE PERFLUOROMONOMER
A. In Wood Under Inert Atmosphere
A jar was chilled to about -1 S°C and 25 ml of PMD and 2 ml of
0.16 M
20 DP in CF3CF2CFHCFHCF3 solvent were added. A cube of redwood ~1.9 cm on
a side weighing 2.46 g was immersed in the solution contained in the jar for
about
1 hour at -15°C. The redwood cube was removed, allowed to drain and
then
21
CA 02341682 2001-02-22
WO 00/24528 PCTlUS99/25077
transferred to a 20.32 cm X 25.4 cm zip lock polyethylene bag (Brandywine Bag
Co., part number 301630) equipped with a polypropylene gas inlet valve. The
bag
was clamped shut, inflated and evacuated 3 times with nitrogen, and allowed to
sit
over the weekend. The cube was removed and a few pieces of white polymer
5 rubbed off its surface with a spatula. After devolatilizing for 9 days under
pump
vacuum at room temperature, the cube weighed 4.45 g for a 81% weight gain.
One side of the cube was lightly sanded revealing an attractive brown surface
slightly darker in appearance. A drop of water placed on the surface remained
there for about two hours until it evaporated. A drop of water placed on an
untreated redwood cube wet the surface within a minute and took about
30 minutes to soak into the cube, having spread out into a visibly large wet
area
on the cube.
B. In Wood Under TFE Atmosphere
A cube of redwood, ~1.9 cm on a side and weighing 2.27 g was immersed
in the PMD/DP solution left over from part A of this Example for 1 hour at -
15°C.
The redwood cube was removed, allowed to drain and then transferred to a
20.32 cm X 25.4 cm zip lock polyethylene bag (Brandywine Bag Co., part
number 301630) equipped with a polypropylene gas inlet valve. The bag was
clamped shut, inflated and evacuated three times with nitrogen, inflated and
20 evacuated three times with TFE, loosely inflated with TFE, and allowed to
sit
over a three days. The cube was removed along with 2.9 g of PTFE. Most of the
PTFE removed was loose but some of it was scraped off of the redwood cube.
After devolatilizing for 9 days under pump vacuum at room temperature, the
cube
weighed 4.51 g for a 99 percent weight gain. One side of the cube was light
25 sanded revealing an attractive silvery brown surface darker in appearance
than at
the start. A drop of water placed on the surface remained on the surface of
the
cube for about two hours until it evaporated. A drop of water placed on an
untreated redwood cube wet the surface of the cube within a minute and took
about 30 minutes to soak into the cube, having spread out into a visibly large
wet
30 area on the cube.
EXAMPLE 6
PENETRATION AND DEPOSITION OF FLUOROPOLYMER
Lumber is most often cut with the wood grain running lengthwise. For
monomer and initiator to thoroughly penetrate a long board, much of this
35 penetration must either occur perpendicular to the wood grain or else
monomer
and initiator must be able to enter at the ends and travel rapidly down the
wood
grain. The experiments below show that significant penetration and PTFE
deposition occurs perpendicular to the wood grain.
22
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/250TI
A. PTFE Deposition Perpendicular to Wood Grain
A block of pine measuring 14.5 cm X 2.6 cm X 1.9 cm and with the grain
running lengthwise was cut roughly in half creating two new blocks: Block A
measuring ~7.0 X 2.6 X 1.9 cm and weighing 16.1 g and Block B measuring ~7.4
5 X 2.6 X 1.9 cm and weighing 17.2 g. Using Epoxy-Patch~ cement (Hysol
Engineering Adhesives, The Dexter Corporation, Seabrook, NH) 2.6 X 1.9 cm
patches of aluminum foil (Reynolds Wrap~, Reynolds Metal Company,
Richmond, Virginia) were glued to the far ends of Block A. After 3 days of
drying, Block A (plus foil) weighed 16.5 g. The purpose of the aluminum foil
10 was to block entry and travel by initiator and monomer in the direction of
the
wood grain to test for ease of perpendicular penetration. Blocks A and B were
immersed for 1 hour at -15°C in 0.16 M DP in CF3CF2CF20CFHCF3 solvent.
The blocks were removed, briefly drained, chilled on dry ice, and loaded into
a
chilled (less than -20°C) 400 ml autoclave. The autoclave was evacuated
and
15 loaded with 50 g of TFE. After four hours at 40°C, the wood blocks
were
recovered, trace loose PTFE wiped off the surface with a tissue, and the
blocks
were dried under pump vacuum for 3 days. Block A weighed 23.9 g for a 46%
weight gain and Block B weighed 25.0 g for a 45% weight gain. Thus, PTFE
deposition was not particularly dependent upon the direction of the wood
grain; or
20 upon which wood surfaces (end grain or non-end grain) were exposed to
initiator
and TFE.
EXAMPLE 7
TFE POLYMERIZATION INTO AS-MOLDED POLYIMIDE PARTS
A. Preparation of molded polyimide test bars with variable porosity
25 Polyimide resin powder used in the following Examples 1, 2 and 3 was
prepared from pyromellitic dianhydride and 4,4'-oxydianiline, according to the
procedures of U.S. Patent No. 3,179,614 or U.S. Patent No. 4,622,384.
Polyimide
powder samples weighing 2.1 to 2.5 g were cold pressed at room temperature
into
tensile bars. These tensile bars were dogbone shaped, measuring 90 mm long by
30 5 mm to 10 mm wide. In order to vary the porosity of the tensile bars, six
different compressive forces were used, 10,000 psi, 20,000 psi, 30,000 psi,
40,000 psi, 50,000 psi, and 100,000 psi, the resulting bars being called the
lOK,
20K, 30K, 40K, SOK, and I00K bars respectively. After pressing, the bars had
thicknesses typically running from 2.7 to 3.3 mm. When the bars were dried
35 overnight in a 75°C oven, they lost 1 to 3% of their weight. Pore
volumes for
dried polyimide powder starting material and dried tensile bars measured by
nitrogen porosimetry are shown in the Table 6 below.
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TABLE 6
Sample Pore Volume for Pores 17 to 3000
Starting Powder 0.18 cc/g
10 K Bar 0.09 cc/g
20 K Bar 0.050 cc/g
30 K Bar 0.01 cc/g
40 K Bar 0.002 cc/g
50 K Bar nil
100 K Bar nil
B. Atmospheric Pressure TFE Polymerization Tensile Tests
One each of a l OK, a SOK, and a 100K bar were soaked at -15°C in
initiator solution, a 0.14 M DP 1 solution in Vertrel~ XF solvent
(CF3CFHCFHCFZCF3). After 3 hours, the bars were pulled from the initiator
solution, excess initiator solution allowed to drain, and then loaded into a 6
X 9"
ziplock polyethylene bag equipped with a gas inlet valve. The bag was
evacuated
and filled 3X with N2 and then 3X with tetrafluoroethylene (TFE). The bag was
inflated with TFE and allowed to stand ~20 hours overnight at room
temperature.
The next morning the three test bars were recovered and loose white PTFE
powder was wiped off the surface. After 4 days of devolatilization under pump
vacuum, the bars were reweighed with the weight changes shown in the table
below. The bars were further compressed to 100,000 psi at room temperature.
These bars were then finished by heating to 405°C for three hours.
Tensile tests
on these bars are also shown in the table below versus control polyimide bars
containing no PTFE. Fluorine analyses on the broken remains of the bars are
shown in Table 7 below.
TABLE
7
Nominal PTFE % ElongationWeight % Fluorine
S le Wei ht Gain PSI at at Break by
Break Combustion Anal
sis
Control 11,500 10.9 -
lOK 6.5 wt % Broke - 2.0% F
when
co ressed
SOK -0.5 wt % 11,400 9.1 0.71% F
100K -0.6 wt % 11,000 11.3 0.17% F
The apparent weight losses for the SOK and 100K bars needs comment. The
starting polyimide powder and bars showed 1 to 3% weight loss when dried
overnight at 75°C. The polyimide bars used here for TFE polymerizations
were
24
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not dried before the TFE polymerization step but were devolatilized
afterwards.
The apparent weight change over the course of the experiment thus is the net
result of volatiles loss and PTFE weight gain. Apparently volatiles loss is
greater
than PTFE weight gains for bars compressed at 50,000 and 100,000 psi.
C. Hi~~h Pressure TFE Polymerization.
One each of a l OK, a SOK, and a 100K bar were soaked at -15°C in
initiator solution, a 0.15 M DP 1 solution in Vertrel~ XF solvent
(CF3CFHCFHCF2CF3). After 30 minutes, the three bars were pulled from the
initiator solution allowing excess initiator to drain away and then stored on
dry ice
10 until they could be loaded into a 400 ml autoclave prechilled to -
20°C. The
autoclave was evacuated and filled with 10 g of TFE. Polymerization was
allowed to run overnight at room temperature, TFE pressure in the autoclave
reaching a maximum of 111 psi at 16.3°C. The next morning, the test
bars were
recovered from a large volume of white PTFE fluff, using a tissue to wipe
loose
15 white PTFE off the surface. After 12 days of devolatilization under pump
vacuum, the bars were analyzed for fluorine content by combustion analysis
with
the results shown in Table 8 below.
TABLE 8
Bar Fluorine by Combustion Analysis
lOK 13.97 wt%F
SOK 0.93 wt % F
1 OOK 0.51 wt % F
20 The fluorine contents are higher than observed when the TFE polymerization
was
run at atmospheric pressure in section B immediately above.
D. Atmospheric Pressure Polymerization
Groups of four to eight 20K, 30K, and 40K bars were soaked at -
15°C in
20 to 30 ml of initiator solution, 0.16 M DP 1 in Vertrel~ XF solvent
25 {CF3CFHCFHCF2CF3). After 60 minutes, the bars were pulled from the
initiator
solution allowing excess initiator to drain away and then loaded into a 6 X 9"
ziplock polyethylene bag equipped with a gas inlet valve. The bag was
evacuated
and filled 3X with N2 and then 3X with tetrafluoroethylene (TFE). The bag was
inflated with TFE and allowed to stand overnight at room temperature. The next
30 morning the test bars were recovered, loose white PTFE powder wiped off the
surface, and dried in a 75°C vacuum oven. Three bars from each set were
further
compressed at 100,000 psi at room temperature and then sintered by raising
temperature at 1.5°C/min to 405°C and holding at 405°C
for 3 hours. Tensile
tests were performed and the broken fragments analyzed for fluorine content as
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shown in the table below. The data results in Table 9 below show that
polymerization of TFE into an as-molded polyimide bar does not have a major
effect on ultimate tensile properties.
T ABLE 9
PSI at ElongationWeight Percent
Test Break at Break Fluorine by
Bar Combustion Anal
sis
From Center of From End of
Bar Bar
20K 10,980 14.5% 0.79 0.59
20K 10,930 9.5%
20K 10,676 8.5%
30K 10,974 9:8% 0.49 0.14
30K 10,209 6.3%
30K 11,335 7.8%
40K 11,241 8.5% 0.66 0.56
40K 11,699 8.9%
40K 11,312 8.1%
EXAMPLE 8
POROUS POLYIMIDE POWDER. ATMOSPHERIC
PRESSURE TFE POLYMERIZATION
A. Polyimide/PTFE Anal z~inQ for 6.34% Fluorine
10 A 500-ml round-bottomed flask loaded with 15.59 g of polyimide powder
and ~SS ml of Vertrel~ XF was chilled overnight in a -15°C
refrigerator. The
next morning 5 ml of 0.16 M DP in Vertrel~ XF was added and then excess
solvent was rapidly pulled off first using a rotary evaporator (~20 min) and
then a
vacuum pump (~13 min) so as to keep the reaction mixture cold by evaporative
cooling. The polyimide powder, now impregnated with DP, was loaded into a
6 X 9" Ziplock~ polyethylene bag equipped with a gas inlet valve. The bag was
inflated and then evacuated 3X with N2 and 3X with tetrafluoroethylene (TFE).
The bag was inflated a final time with TFE and polymerization allowed to run
until about half the TFE had been reacted as judged by visible deflation of
the
20 bag. This took about 72 minutes. The surface of the polyimide powder
remained
yellow indicating that the bulk of the PTFE polymerization was occurring
within
the pores of the particles rather than on the surface. The recovered polyimide
powder weighed 19.33 g upon removal from the bag, 16.48 g after 147 minutes in
a 75°C vacuum oven, and 16.38 g after continuing another ~70 hours in
the 75°C
25 vacuum oven. Weight gain was 0.79 g or 5.1 % relative to the weight of the
starting polyimide powder. Combustion analysis on the product found 6.34 wt
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fluorine. Finding 6.34 wt % fluorine versus a 5.1 wt % gain overall is, as
observed with the test bars above, consistent with starting with a raw
polyimide
powder that had not been devolatilized.
Samples of this powder were compressed at 100,000 psi at room
temperature into three tensile bars measuring 90 mm long by 5 mm to 10 mm
wide (dogbone-shaped). These bars were then finished by heating to
405°C for
three hours. In tensile tests these bars broke on average at 6,675 psi with
4.7%
elongation. Combustion analysis on the broken pieces found 4.99 wt % fluorine.
The polyimide/PTFE composite made in this experiment was tested for
resistance to wear using the method described in U.S. Patent No. 5,789,523,
column 4, line 51. The powder was compressed at 100,000 psi into a disk 1" in
diameter by about 0.25" thick. This disk was then heated to 405°C for
three hours. After cooling to room temperature, the parts were machined to
final
dimensions for test specimens. The 0.25" (6.35 mm wide) contact surface of the
wear/friction disk was machined to such a curvature that it conformed to the
outer
circumference of the 1.375" (34.9 mm) diameter X 0.375" (9.5 mm) wide metal
mating ring. The disks were oven dried and maintained dry over desiccant until
tested. Wear tests were performed using a Falex No. 1 Ring and Block Wear and
Friction Tester. The equipment is described in AS'TM Test method D2714. After
weighing, the dry polyimide/PTFE disk was mounted against the rotating metal
ring and loaded against it with the selected test pressure. Rotational
velocity of
the ring was set at the desired speed. No lubricant was used between the
mating
surfaces. The rings were SAE 4620 steei, Rc 58-63, 6-12 RMS. A new ring was
used for each test. Test time was usually 24 hours, except when friction and
wear
were high, in which case the test was terminated early. At the end of the test
time,
the block was disconnected, weighed, and the wear calculated using the
following
calculation:
Weight Lost (grams)
Wear volume (cc/hr) = Material density(grams/cc) X Test duration (hours)
In this test the wear volume of the polyimide/PTFE sample was at least 8X less
than for a polyimide sample free of PTFE.
B. Polyimide/PTFE Analyzing for I4.I5% Fluorine
A 500-ml round-bottomed flask loaded with 15.82 g of polyimide powder
and ~55 ml of Vertrel~ XF was chilled for 1 hour in a -15°C
refrigerator. About
5 ml of 0.16 M DP in Vertrel~ XF was added and then excess solvent was
rapidly pulled off first using a rotary evaporator (10-1 S min) and then a
vacuum
pump (~S min) so as to keep the reaction mixture cold by evaporative cooling.
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The polyimide powder, now impregnated with DP was loaded into a 6 X 9"
ziplock polyethylene bag equipped with a gas inlet valve. The bag was purged
of
air by inflating and evacuating the bag 3X with N2 and 3X with tetrafluoro-
ethylene (TFE). Polymerization was started by inflating the bag with TFE and
5 allowing polymerization to deflate the bag over about a 2 hour period. The
still
yellow polyimide powder was dried overnight in an 88°C vacuum oven.
Combustion analysis on the product found 14.15 wt % fluorine.
Samples of this powder were compressed at 100,000 psi at room
temperature into three tensile bars measuring 90 mm long by 5 mm to 10 mm
wide (dogbone-shaped). These bars were then heated from to 405°C for
three hours. In tensile tests these bass broke on average at 1,369 psi with
0.5%
elongation. Combustion analysis on the broken pieces found 13.89 wt %
fluorine.
C. Pol~nmide/PTFE AnalvzinQ for 19.93% Fluorine
A 500-ml round-bottomed flask loaded with 15.51 g of polyimide powder
and ~55 ml of Vertrel~ XF was chilled for 1 hour in a -15°C
refrigerator. About
S ml of-0.16 M DP in Vertrel~ XF was added and then excess solvent was
rapidly pulled off first using a rotary evaporator (~l 5 min) and then a
vacuum
pump (~4 min) so as to keep the reaction mixture cold by evaporative cooling.
The polyimide powder, now impregnated with DP, was loaded into a 6 X 9"
ziplock polyethylene bag equipped with a gas inlet valve. The bag was purged
of
air by inflating and evacuating the bag 3X with N2 and 3X with
tetrafluoroethylene (TFE). Polymerization was started by repeatedly inflating
the
bag with TFE and allowing polymerization to deflate the bag twice, the
defilations
taking 40 minutes and overnight respectively. The still yellow polyimide
powder
was dried for ~4 days in a 75°C vacuum oven. Combustion analysis on the
product found 19.93 wt % fluorine.
Samples of this powder were compressed at 100,000 psi at room
temperature into three tensile bars measuring 90 mm long by 5 mm to 10 mm
wide (dogbone-shaped). These bars were then heated to 405°C for three
hours.
In tensile tests these bars broke on average at 1,385 psi with 0.6%
elongation.
Combustion analysis on the broken pieces found 18.76 wt % fluorine.
D. Polyimide/PTFE Analyzing for 23.99% Fluorine
A 500-ml round-bottomed flask loaded with 15.66 g of polyimide powder
and ~55 ml of Vertrel~ XF was chilled overnight in a -1 S°C
refrigerator. The
35 next morning 5 ml of 0.16 M DP in Vertrel~ XF was added and then excess
solvent was rapidly pulled off first using a rotary evaporator (~18 min) and
then a
vacuum pump (~9 min) so as to keep the reaction mixture cold by evaporative
cooling. The polyimide powder, now impregnated with DP, was loaded into a
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6 X 9" ziplock polyethylene bag equipped with a gas inlet valve. The bag was
purged of air by repeatedly inflating and evacuating the bag 3X with N2 and 3X
with tetrafluoroethylene (TFE). Polymerization was started by repeatedly
inflating the bag with TFE and allowing polymerization to deflate the bag
three
5 times, the defilations taking 55, 50, and 130 minutes respectively. The
still
yellow polyimide powder was dried overnight (~17 hrs) in a 75°C vacuum
oven.
Combustion analysis on the product found 23.99 wt % fluorine.
Samples of this powder were compressed at 100,000 psi at room
temperature into three tensile bars measuring 90 mm long by S mm to 10 mm
10 wide (dogbone-shaped). These bars were then heated to 405°C for
three hours.
In tensile tests these bars broke on average at 1,688 psi with 0.9%
elongation.
Combustion analysis on the broken pieces found 24.26 wt % fluorine.
E. Polvimide/PTFE AnalyzingLfor 27.77% Fluorine
A 500-ml round-bottomed flask loaded with 16.01 g of polyimide powder
15 and ~55 ml of Vertrel~ XF was chilled for 1 hour in a -15°C
refrigerator. About
5 ml of 0.16 M DP in Vertrel~ XF was added and then excess solvent pulled off
first using a rotary evaporator (~12 min) and then a vacuum pump (~7 min) so
as
to keep the reaction mixture cold by evaporative cooling. The polyimide
powder,
now impregnated with DP, was loaded into a 6 X 9" ziplock polyethylene bag
20 equipped with a gas inlet valve. The bag was purged of air by inflating and
evacuating the bag 3X with N2 and 3X with tetrafluoroethylene (TFE).
Polymerization was started by repeatedly inflating the bag with TFE and
allowing
polymerization to deflate the bag four times, the defilations taking 21, 23,
23, and
42 minutes respectively. The still yellow polyimide powder was dried overnight
25 (~19 hrs) in a 75°C vacuum oven. Combustion analysis on the product
found
27.77 wt % fluorine.
Samples of this powder were compressed at 100,000 psi at room
temperature into three tensile bars measuring 90 mm long by S mm to 10 mm
wide (dogbone-shaped). These bars were then heated to 405°C for three
hours.
30 In tensile tests these bars broke on average at 1442 psi with 0.6%
elongation.
Combustion analysis on the broken pieces found 26.32 wt % fluorine.
F. Polyimide/PTFE AnalyzinQ for 37. 94% Fluorine
A round-bottomed flask chilled to ~0°C was loaded with 16.6 g of
polyimide powder, 40 ml of Vertrel~ XF, and 10 ml of 0.16 M DP in Vertrel~
35 XF. Excess solvent was rapidly pulled off first using a rotary evaporator
and then
a pump so as to keep the reaction mixture cold by evaporative cooling. The
polyimide powder, now impregnated with DP, was loaded into a 6 X 9" ziplock
polyethylene bag equipped with a gas inlet valve. The bag was purged of air by
29
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inflating and evacuating the bag 3X with N2 and 3X with tetrafluoroethylene
(TFE). Polymerization was started by repeatedly inflating the bag with TFE and
allowing polymerization to deflate the bag over an afternoon and then
overnight.
The next morning the polyimide powder was recovered. After three days of
devolatilization under pump vacuum, combustion analysis on the product found
37.94 wt % fluorine.
Samples of this powder were compressed at 100,000 psi at room
temperature into f ve tensile bars measuring 90 mm long by 5 mm to 10 mm wide
(dogbone-shaped). These bars were then heated to 405°C for three hours.
In
10 tensile tests these bars broke on average at 733 psi with 0.4% elongation.
Combustion analysis on the broken pieces found 31.85 wt % fluorine.
G. Summary of Results on Polyimide Powder with PTFE Polymerized into its
Pores
Table 10 below summarizes the results for parts A through F above.
TABLE 10
Weight % Fluorine
by
Combustion Anal
sis
After
Starting Bar PSI at BreakElon ation at
Pol 'mide/PTFE Pressed Break
and
Heated
6.34% 4.99% 6,675 psi 4.7%
14.15% 13.89% 1,369 psi 0.5%
19.93% 18.76% 1,385 psi 0.6%
23.99% 24.26% 1,688 psi 0.9%
27.77% 26.32% 1,442 psi 0.6%
37.94% 31.85% 733 psi 0.4%
EXAMPLE 9
POROUS POLYIM>DE. ATMOSPHERIC PRESSURE
TFE POLYMERIZATION; C02 AS CARRIER FOR INITIATOR
20 A 400-ml stainless steel autoclave was loaded first with 15.05 g of
polyimide powder and then with a 100-g layer of dry ice on top. Five ml of
0.16 M DP in Vertrel~ XF was poured over the dry ice. The autoclave was
sealed and its contents shaken without any provision for additional cooling.
As
soon as the contents of the autoclave reached 0°C, the C02 was vented.
The
25 polyimide powder was recovered and chilled on dry ice until it could be
transferred to a 6 X 9" ziplock polyethylene bag equipped with a gas inlet
valve.
The bag was inflated and evacuated 3X with N2 and 3X with tetrafluoroethylene
(TFE). The bag was inflated a final time with TFE. Polymerization was allowed
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to run 132 minutes until about a quarter of the TFE had been reacted as judged
from deflation of the hag. Drying for 21 hours in a 75°C vacuum oven
gave
13.69 g of polyimide powder that analyzed for 2.49 wt % fluorine by combustion
analysis.
EXAMPLE 10
POROUS POLYP-PHENYLENE TEREPHTHALAMIDE) POWDER.
ATMOSPHERIC PRESSURE TFE POLYMERIZATION
Porous polyp-phenylene terephthalamide) particulates were prepared by
adding polyp-phenylene terephthalamide) precipitate as made in N-methyl-
10 pyrrolidinone/CaCl2 to water, filtering, rinsing with water, and sucking
dry on the
filter. A 25.6 g sample of these polyp-phenylene terephthalamide) particulates
was soaked in 30 ml of 0.18 M HFPO dimer peroxide in Vertrel~ XF at -
15°C.
After 15 minutes, the polyp-phenylene terephthalamide) was separated by
vacuum filtration, stopping filtration as soon as the liquid flow seemed near
an
15 end. The polyp-phenylene terephthalamide), still damp with initiator
solution,
was transferred to a 6 X 9" ziplock polyethylene bag equipped with a gas inlet
valve. The bag was evacuated and filled 3X with N2 and 3X with TFE. The bag
was inflated a final time with TFE and the polymerization allowed to run at
room
temperature. Over the next several hours the bag was reinflated four times
with
20 TFE. Before reinflation, the contents of the bag were shaken and/or
squeezed
lightly with finger pressure to break up nascent lumps. The polymerization was
allowed to continue overnight at room temperature. The next morning the
contents of the bag were poured out, avoiding as much as possible entrainment
of
white PTFE deposits attached to the walls of the bag. After two days under
pump
25 vacuum, the product consisting largely of yellow granules plus a few white
PTFE
flakes from the wall of the bag, weighed 32.9 g for a weight gain of 28%.
Taking
just the yellow granules, combustion analysis found 15.70 wt % fluorine.
EXAMPLE 11
POROUS POLYP-PHENYLENE TEREPHTHALAMIDEI POWDER,
30 ATMOSPHERIC PRESSURE TFE POLYMERIZATION
A. Lower PTFE Loading
Porous polyp-phenylene terephthalamide) particulates were prepared by
adding polyp-phenylene terephthalamide) precipitate as made in N-methyl-
pyrrolidinone/CaCl2 to water, filtering, rinsing with water, and sucking dry
on the
35 filter. These particulates were then dried overnight in a 150°C
vacuum oven. A
36 mL sample of ~O.I7 M HFPO dimer in Vertrel~ XF at -15°C was added to
360 ml of room temperature Vertrel~ XF with swirling for ~l minute. This
initiator solution was then added immediately to 218.1 g of dried
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polyp-phenylene terephthalamide) in a large crystallizing dish. In order to
ensure
thorough mixing, the contents of the crystallizing dish were worked for 1
minute
with a spatula. The resulting polyp-phenylene terephthalamide) slurry was
filtered using a Buchner funnel, the vaccuum being applied for ~1 minute so as
to
5 leave the polyp-phenylene terephthalamide) still damp with initiator
solution
(weight 295 g). The polyp-phenylene terephthalamide) was transferred to a
8 X I O" ziplock polyethylene bag equipped with a gas inlet valve. The bag was
evacuated and filled 3X with N2 and 3X with TFE. The bag was inflated a final
time with TFE to a height of ~3.5 inches and the polymerization allowed to run
at
10 room temperature. As TFE polymerization proceeded the bag periodically
deflated to a near vacuum and was then reinflated with TFE gas first 10 and
again
18 minutes into the run. Throughout the run, the bag was noticeably warm to
the
touch. After the last deflation, 28 minutes into the run, the contents of the
bag
were transferred back to a large crystallizing dish. Residual volatiles were
15 removed by first putting under pump vacuum overnight and then in a
150°C
vacuum oven overnight. The product consisting largely of yellow granules,
weighed 227.8 g for a weight gain of 4.4% and combustion analysis found
4.16 wt % fluorine or 5 wt % PTFE in reasonable agreement with the measured
weight gain. It should be noted that when running with an oven dried
20 polyp-phenylene terephthalamide) sample and at much larger scale than in
Example 4 above, no free PTFE particulates on the walls of the bag or mixed in
with the polyp-phenylene terephthalamide) were apparent to the eye.
B. Intermediate PTFE Loading
Porous polyp-phenylene terephthalarnide) particulates were prepared by
2S adding polyp-phenylene terephthalamide) precipitate as made in N-methyl-
pyrrolidinone/CaCl2 to water, filtering, rinsing with water, and sucking dry
on the
filter. These particulates were then dried overnight in a 150°C vacuum
oven. A
36 mL sample of -~-0.17 M HFPO dimer in Vertrel~ XF at -15°C was added
to
360 ml of room temperature Vertrel~ XF with swirling. This initiator solution
30 was then added immediately to 218 g of dried polyp-phenylene
terephthalamide)
in a large crystallizing dish. In order to ensure thorough mixing the contents
of
the crystallizing dish were worked for I minute with a spatula. The resulting
polyp-phenylene terephthalamide) slurry was filtered using a Buchner funnel,
the
vacuum being applied for only 50 seconds so as to leave the polyp-phenylene
35 terephthalamide) still damp with initiator solution. The polyp-phenylene
terephthalamide) was transferred to an 8 X 10" ziplock polyethylene bag
equipped
with a gas inlet valve. The bag was evacuated and filled 3X with N2 and 3X
with
TFE. The bag was inflated a final time with TFE and the polymerization allowed
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to run at room temperature. As TFE polymerization proceeded the bag
periodically deflated to a near vacuum and was then reinflated ~2 to 3" tall
with
TFE gas 8, 14, 25, 37, 46, 62, and 80 minutes into the run. During much of the
run, the bag was noticeably warm to the touch. After the last deflation,
5 98 minutes into the run, the contents of the bag were transferred back to a
large
crystallizing dish. Residual volatiles were removed by first putting under
pump
vacuum overnight and then in a 150°C vacuum oven overnight. The product
consisting largely of yellow granules, weighed 244 g for a weight gain of 12%
and combustion analysis found 8.40 wt % fluorine or 11 wt % PTFE in reasonable
10 agreement with the measured weight gain.
C. Higher PTFE Loading
Porous polyp-phenylene terephthalamide) particulates were prepared by
adding polyp-phenylene terephthalamide) precipitate as made in N-methyl-
pyrrolidinone/CaCl2 to water, filtering, rinsing with water, and sucking dry
on the
15 filter. These particulates were then dried overnight in a 150°C
vacuum oven. A
36 mL sample of 0.17 M HFPO dimer in Vertrel~ XF at -15°C was added to
360 ml of room temperature Vertrel~ XF with swirling. This initiator solution
was then added immediately to 217 g of dried polyp-phenylene terephthalamide)
in a large crystallizing dish. In order to ensure thorough mixing the contents
of
20 the crystallizing dish were worked for 1 minute with a spoon. The resulting
polyp-phenylene terephthalamide) slurry was filtered using a Buchner funnel,
the
vacuum being applied for only 50 seconds so as to leave the polyp-phenylene
terephthalamide) still damp with initiator solution. The polyp-phenylene
terephthalamide) was transferred to a 8 X 10" ziplock polyethylene bag
equipped
25 with a gas inlet valve. The bag was evacuated and filled 3X with N2 and 3X
with
TFE. The bag was inflated a final time with TFE and the polymerization allowed
to run at room temperature. As TFE polymerization proceeded the bag
periodically deflated to a near vacuum and was then reinflated ~2 to 4" tall
with
TFE gas 9, 18, 27, 40, 50, 57, 67, 81, 97, 110, 133, 161, 199, and 250 minutes
into
30 the run. During much of the run, the bag was noticeably warm to the touch.
After
the last deflation, 303 minutes into the run, the contents of the bag were
transferred back to a large crystallizing dish. Residual volatiles were
removed by
first putting under pump vacuum overnight and then in a 150°C vacuum
oven for
73 hours. The product consisting largely of yellow granules, weighed 261 g for
a
35 weight gain of 20% and combustion analysis found 12.33 wt % fluorine or
16 wt % PTFE in rough agreement with the measured weight gain.
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EXAMPLE 12
POLYMERIZATION OF PTFE IN POROUS POLYP-PHENYLENE
TEREPHTHALAMIDE) FIBERS
Never dried polyp-phenylene terephthalamide) fibers, containing 30% to
5 70% by weight water, was first made ready for TFE polymerization by
replacing
the water in its pores with a solvent suitable for fluoroolefin
polymerization.
Thirty-five grams of never dried polyp-phenylene terephthalamide) fibers were
mixed in a jar with 50 ml of trifluoroacetic acid. After standing overnight,
the
contents of the jar were washed into a chromatography column using additional
10 trifluoroacetic acid. Excess trifluoroacetic acid was drained off. Fifty ml
of fresh
trifluoroacetic acid were added to the top of the column and excess fluid
again
drained off, leaving the liquid level in the column about 3 cm above the
polyp-phenylene terephthalamide) layer. Over the following days, the
polyp-phenylene terephthalamide) in the chromatography column was washed in
15 turn with 50 ml trifluoroacetic acid, 50 ml of Freon~ El
(CF3CF2CF20CFHCF3),
50 ml Freon~ E1, SO ml Freon~ El, and 50 ml of chilled 0.03 M DP in
Freon~ E1. The cold DP solution was drained through the polyp-phenylene
terephthalamide) as rapidly as possible while low pressure nitrogen was
applied to
the top of the column towards the end for the purpose of expelling most
20 unabsorbed fluid. In this operation the nitrogen flow was stopped before
drying
out of the polyp-phenylene terephthalamide) particulates occurred. The
polyp-phenylene terephthalamide) having DP initiator in its pores was chilled
on
dry ice and transferred to a 400 ml autoclave pre-chilled to less than -
20°C. The
autoclave was evacuated and 25 g of TFE was added, raising pressure to ~78 psi
25 at -43°C. After shaking overnight at room temperature, pressure in
the autoclave
had decreased to 7 psi. Upon recovery and drying under pump vacuum, the
polyp-phenylene terephthalamide) weighed 38.3 g. The appearance of the
composition after recovery was a mix of free flowing particulates and
agglomerated particulates, and was cream colored. The polyp-phenylene
30 terephthalamide) was yellow in color prior to TFE polymerization.
Examination
by optical microscopy under cross polarizers showed bright, irregularly-shaped
polyp-phenylene terephthalamide) particles with dark PTFE deposits filling
most
of the pores. Little PTFE was visible at the surface of the polyp-phenylene
terephthalamide) particles. Most often, the dark PTFE areas were 50 microns to
35 200 microns in diameter. Combustion analysis of one of the agglomerated
chunks
showed 57.1 % fluorine by weight.
34
CA 02341682 2001-02-22
WO 00/24528 PCTNS99/25077
EXAMPLE 13
POROUS POLY(M-PHENYLENE ISOPHTHALAMIDEI POWDER,
ATMOSPHERIC PRESSURE TFE POLYMERIZATION
A. Intermediate PTFE Loading
5 Porous poly(m-phenylene isophthalamide) [MPD-I] particulates were
prepared by precipitating MPD-I solution (in dimethylacetamide/CaCl2) in
water,
washing with water and drying in vacuum at 100°C. A 4.83 g sample of
these
poly{m-phenylene isophthalamide) particulates was soaked at -15°C in 40
ml of
CF2CICC12F containing 1.0 ml 0.16 M HFPO dimer peroxide in Vertrel~ XF.
10 After 15 minutes, the poly(m-phenylene isophthalamide) was separated by
vacuum filtration, stopping filtration as soon as the liquid flow seemed near
an
end. The poly(m-phenylene isophthalamide), still damp with initiator solution,
was transfer ed to a 6 X 9" ziplock polyethylene bag equipped with a gas inlet
valve. The bag was evacuated and filled 3X with N2 and 3X with TFE. The bag
15 was inflated a final time with TFE and the polymerization allowed to run at
room
temperature. Most of the TFE reacted over the next 2.5 hours as seen in the
near
total deflation of the bag. The contents of the bag were poured out. After
~64 hours under pump vacuum, the product weighed 7.50 g (153% of starting
weight) and consisted largely of white lumps not much different in visual
20 appearance than at the start. Combustion analysis found 12.8 wt % fluorine.
B. Higher PTFE Loading
Porous poly(m-phenylene isophthalamide) [MPD-I] particulates were
prepared by precipitating MPD-I solution (in dimethylacetamide/CaCl2) in
water,
washing with water and drying in vacuum at 100°C... A 6.5 g sample of
these
25 poly(m-phenylene isophthalamide) particulates was soaked at -1 S°C
in 50 ml of
0.18 M HFPO dimer peroxide in Vertrel~ XF. After 15 minutes, the
poly(m-phenylene isophthalamide) was separated by vacuum filtration, stopping
filtration as soon as the liquid flow seemed near an end. The poly(m-phenylene
isophthalamide), still damp with initiator solution, was transferred to a 6 X
9"
30 ziplock polyethylene bag equipped with a gas inlet valve. The bag was
evacuated
and filled 3X with N2 and 3X with TFE. The bag was inflated a final time with
TFE and the polymerization allowed to run at room temperature. Over the next
3 hours the bag deflated and was refilled with TFE five times. The contents of
the
bag were poured out. After four days under pump vacuum, the product weighed
35 20.5 g (315 % of starting weight) and consisted largely of white lumps not
much
different in visual appearance than at the start. Combustion analysis found
48.7 wt % fluorine.
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/25077
EXAMPLE 14
POROUS POLY(M-PHENYLENE ISOPHTHALAMIDE) FIBRIDS,
ATMOSPHERIC PRESSURE TFE POLYMERIZATION
A. Intermediate PTFE Loading
Porous [poly(m-phenylene isophthalamide)] fibrids were prepared by
precipitating MPD-I solution (in dimethylacetamide/CaCl2) in water under
shear,
washing with water and drying in vacuum at 100°C. A 6.52 g sample of
these
poly(m-phenylene isophthalamide) fibrids was soaked at -IS°C in 40 ml
of
CF2CICCI2F containing 1.0 ml 0.16 M HFPO dimer peroxide in Vertrel~ XF.
After 15 minutes, the poly(m-phenylene isophthalamide) was separated by
vacuum filtration, stopping filtration as soon as the liquid flow seemed near
an
end. The poly(m-phenylene isophthalamide), still damp with initiator solution,
was transferred to a 6 X 9" ziplock polyethylene bag equipped with a gas inlet
valve. The bag was evacuated and filled 3X with N2 and 3X with TFE. The bag
was inflated a final time with TFE and the polymerization allowed to run at
room
temperature. Most of the TFE reacted over the next 1.5 hours as seen in the
near
total deflation of the bag. The contents of the bag were poured out. After a
weekend under pump vacuum, the product weighed 9.84 g ( 151 % of starting
weight) and consisted largely of flat white clumps of fibrids not much
different in
visual appearance than at the start. Combustion analysis found 40.5 wt
fluorine.
B. Higher PTFE Loading
Porous poly(m-phenylene isophthalamide) [MPD-I] particulates were
prepared by precipitating MPD-I solution (in dimethylacetamide/CaCl2) in
water,
washing with water and drying in vacuum at 100°C:. A 6.5 g sample of
these
poly(m-phenylene isophthalamide) particulates was soaked at -15°C in 50
ml of
0.18 M HFPO dimer peroxide in Vertrel~ XF. After 15 minutes, the
poly(m-phenylene isophthalamide) was separated by vacuum filtration, stopping
filtration as soon as the liquid flow seemed near an end. The poly(m-phenylene
isophthalamide), still damp with initiator solution, was transferred to a 6 X
9"
ziplock polyethylene bag equipped with a gas inlet valve. The bag was
evacuated
and filled 3X with N2 and 3X with TFE. The bag was inflated a final time with
TFE and the polymerization allowed to run at room temperature. Over the next
3 hours the bag deflated and was refilled with TFE five times. The contents of
the
bag were poured out. ARer four days under pump vacuum, the product weighed
18.1 g (278% of starting weight) and consisted largely of flat white clumps of
particulates not much different in visual appearance than at the start.
Combustion
analysis found 55.3 wt % fluorine.
36
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WO 00/24528 PCT/US99/25077
EXAMPLE 15
ULTRASUEDE~, ATMOSPHERIC PRESSURE TFE POLYMERIZATION
A rectangular sample of blue Ultrasuede~ (a leather mimic believed to be
a foamed polyurethane) weighing 2.I g and measuring 7.6 cm X 8.2 cm X
5 0.09 cm thick, was immersed in a 0.16 M solution of DP in Vertrel~ XF
maintained at -15°C. After 15 minutes, the Uitrasuede~ was removed from
the
initiator solution and excess fluid allowed to drain for five or 10 seconds.
The
Ultrasuede~ still wet with absorbed initiator was transferred to a 6 X 9"
ziplock
polyethylene bag provided with a gas inlet valve. The bag was sealed,
evacuated
10 and inflated 3X with N2 and 3X with TFE. The bag was inflated a fourth time
with TFE. Using an exterior clamp, all but a corner of the Ultrasuede~ sample
was held away from contact with the walls of the bag. The Ultrasuede~ was
recovered 23 hours later and devolatilized for 3 days under pump vacuum. While
unchanged in appearance, the Ultrasuede~ weighed 2.4 g, ~14% more than at the
15 start. Combustion analysis found 6.00 wt % fluorine. A drop of distilled
water
placed on either side of the Ultrasuede~ sample treated here took ~46 minutes
to
show initial wetting and never soaked into the Ultrasuede~ prior to
evaporation.
For comparison purposes, an untreated Ultrasuede~ sample was found to
completely absorb a drop of water within about one minute on one side and to
not
20 be wetted at all by water on the reverse side (combustion analysis found
0.14 wt % F on the starting Ultrasuede~ suggesting a fluorinated finish at the
start).
EXAMPLE 16
PIGSKIN AND COWSKIN
25 A 5-cm square of commercial beige pigskin purchased at retail (chrome
tanned split, one side suede, reverse side rough) weighing 1.69 g and
measuring
-r0.15 cm thick was immersed in a 0.16 M solution of DP in Vertrel~ XF
maintained at -1 S°C. A 5 cm square of commercial black cowhide
purchased at
retail (chrome tanned split, suede both sides) weighing 2.09 g and measuring
30 0.12 cm thick was immersed in a 0.16 M solution of DP in Vertrel~ XF
maintained at -15°C. After 60 minutes, the two leather samples were
removed
from the initiator solution and excess fluid allowed to drain for five or 10
seconds.
The leather samples still wet with absorbed initiator were transferred to a 6
X 9"
ziplock polyethylene bag provided with a gas inlet valve. The bag was sealed,
35 evacuated and inflated 3X with N2 and 3X with TFE. The bag was inflated a
fourth time and the bag and its contents tumbled overnight at room
temperature.
After recovery, the leather samples were devolatilized to constant weight
under
pump vacuum. The pigskin, slightly darkened in appearance, now weighed 1.86 g
37
CA 02341682 2001-02-22
WO 00/24528 PCT/US99/25077
for a 10% weight gain and analyzed for 9.56 wt % F by combustion analysis.
While unchanged in appearance, the cowskin weighed 2.25 g for a 5% weight
gain and analyzed for 9.15 wt % F by combustion analysis. It should be noted
that the starting pigskin and cowhide samples analyzed for 1.77 and 0.39 wt %
F
5 before the treatment described here.
38
