Antifouling/anticorrosive composite marine structure

A composite marine structure comprises a marine substrate having adhered to at least a portion of its surface a layer of a water-permeable composite article comprising a non-woven fibrous web having entrapped therein active particulate to provide said marine substrate with protection against at least one of fouling and corrosion. Underwater surfaces such as ship hulls, buoys, docks, intake pipes, etc., can be protected against marine growth and corrosion by adhering thereto the composite sheet article of the invention.

FIELD OF THE INVENTION 
This invention relates to articles which are antifouling/anticorrosive 
composite structures comprising a marine substrate having adhered to at 
least a portion of one surface a water-permeable composite article 
comprising a non-woven, fibrous web with active particulate entrapped 
therein. In another aspect, a method of preventing corrosion or the 
accumulation of marine growth, or both, is disclosed. Submerged marine 
subtrates to which the articles are attached are provided with fouling 
protection, corrosion protection, or both. 
BACKGROUND OF THE INVENTION 
Objects which are submerged in water, such as ship hulls and anchored 
structures, are prime targets for undesired marine growth accumulation 
because many marine organisms require permanent attachment to a solid 
object. Such accumulation and eventual encrusting can promote corrosion 
and interfere with the normal workings of submerged structures. To prevent 
such fouling, antifouling paints containing various biotoxins have been 
used to coat submerged structures. Biotoxin-loaded paints prevent fouling 
by interfering with the ability of marine organisms to attach to submerged 
structures, either by weakening or killing the organism. 
Typical antifouling paints contain one or more marine biotoxins contained 
in a resin. To achieve a lethal concentration of biotoxin at the 
water-substrate interface, such paints rely on diffusion of biotoxin 
through the resin to the paint surface. Because the rate of diffusion of 
biotoxin from the surface into the water is much faster than the rate of 
diffusion of biotoxin from the bulk resin to the surface, the surface 
concentration of biotoxin drops below the lethal limit long before all of 
the biotoxin in the paint is depleted. Both material and time (i.e., that 
necessary to repaint the substrate) are wasted through this inefficient 
method. 
Recent advances in this area include erodible, or "self-polishing", paints. 
With such paints, a fresh surface of paint, and thus of biotoxin, is 
continuously exposed through the slow dissolution or disintegration of the 
outer layer of paint into the surrounding water. Significant amounts of 
water-eroded polymer are left to pollute the water body in question, 
however. 
Alternative antifouling materials have been developed. For instance, marine 
organisms can be removed (e.g., by high pressure sprays) from surfaces 
treated with release coatings, such as silicones and fluorinated epoxy 
polymers, more easily than from non-treated surfaces. A similar approach 
is to bond a sheet containing such a coating to the marine surface through 
an intermediate barrier layer. A copper-nickel alloy plate with a primer 
layer and an adhesive is described in U.S. Pat. No. 4,814,227. Another 
alternative, described in U.S. Pat. No. 4,865,909, is a hydrophobic 
polymeric membrane, containing numerous pores, which is adhered to the 
surface to be protected by a biotoxin-containing paint. Here, the paint is 
still the antifouling agent, but the membrane prevents random leaching of 
the active agent into the surrounding water. The preferred polymeric 
substance for this method is polytetrafluoroethylene (PTFE). 
Particle-loaded, non-woven, fibrous articles wherein the non-woven fibrous 
web can be compressed, fused, melt-extruded, air-laid, spunbonded, 
mechanically pressed, or derived from from phase separation processes have 
been disclosed as useful in separation science. Sheet products of 
non-woven webs having dispersed therein sorbent particulate have been 
disclosed to be useful as, for example, respirators, protective garments, 
fluid-retaining articles, wipes for oil and/or water, and chromatographic 
and separation articles. Coated, inorganic oxide particles have also been 
enmeshed in such webs. Such webs with enmeshed particles which are 
covalently reactive with ligands (including biologically-active materials) 
have also been recently developed. 
Numerous examples of PTFE filled with or entrapping particulate material 
are known in many fields. Many applications for PTFE filled with 
electroconductive materials are known. These include circuit boards, oil 
leak sensors, electrical insulators, semipermeable membranes, and various 
types of electrodes. Other such combinations have been used as gasket or 
sealing materials and wet friction materials. Still others have been used 
to produce high-strength PTFE films and sheets with applications as 
structural elements and electronic components. Where the particulate has 
catalytic properties, this type of combination provides a form which can 
be conveniently handled. U.S. Pat. No. 4,153,661 discloses various 
particulate, including cupric oxide, distributed in a matrix of entangled 
PTFE fibrils as being useful in, among other things, electronic insulators 
and semipermeable membranes. 
Numerous combinations of PTFE and metals in which the metal is not 
entrapped within a PTFE matrix are also known. These include PTFE 
membranes completely or partially coated with metal and metal matrices 
with a network of fibrillated PTFE in the pores thereof. PTFE powder with 
metal filler has been used (in paste form) as a battery electrode and as a 
self-lubricating layer coated on bronze bearings. PTFE films coated onto 
metal films and plates are also known. 
Methods of preparing fibrillated PTFE webs have been described in, for 
example, U.S. Pat. Nos. 4,153,661, 4,460,642, and 5,071,610. 
SUMMARY OF INVENTION 
Briefly, the present invention provides a composite marine structure 
comprising a marine substrate having adhered to at least one portion of 
its surface a layer of a water-permeable composite article comprising: 
(a) a non-woven, fibrous web and 
(b) active particulate entrapped in said web, 
wherein said composite article provides at least one of fouling protection 
to said marine structure and corrosion protection to said marine 
substrate. 
In another aspect, the present invention provides at least one of the 
above-described composite articles for use with a marine substrate wherein 
the article further comprises on at least one surface thereof a liner 
strippably adhered thereto. 
In yet another aspect, the present invention provides at least one 
composite article useful with a marine substrate wherein the article 
comprises 
(a) a non-woven web, 
(b) particulate entrapped in said web, which particulate is active toward 
at least one of fouling and corrosion, and 
(c) a dual-sided tape attached to at least a portion of one surface of said 
web, 
wherein said dual-sided tape can be either a transfer tape or a 
double-coated tape (i.e., a tape construction with an adhesive on each 
side of a substrate, which adhesives can be the same or different). 
In a further aspect, the present invention provides a method of interfering 
with at least one of (1) accumulation of marine organism growth on, and 
(2) corrosion of underwater surfaces, comprising the steps of: 
(a) allowing fresh or sea water to come into contact with a composite sheet 
article which is in intimate contact with a marine substrate, said 
composite sheet article comprising a porous, non-woven, fibrous web with 
active particles entrapped therein, and 
(b) allowing the active particles of the composite marine substrate to 
interfere with the life cycle of the marine organisms, passivate the 
marine substrate, or both. 
In this application, the following definitions will apply: 
"fibers" means fibrils, microfibers, and macrofibers; 
"fouling" means the attaching and subsequent encrusting of marine life 
forms on underwater surfaces; 
"antifouling" means capable of reducing or preventing accumulation and 
growth of undesired marine life forms on underwater surfaces; 
"web" means an open-structured, entangled mass of fibers; 
"entrapped" means encaged within, adhesively attached to, or encased within 
the material defining the porous structure; 
"macrofibers" means thermoplastic fibers having an average diameter in the 
general range of 50 .mu.m to 1000 .mu.m. (As used in this application, the 
term "macrofibers" encompasses textile size fibers as well as what are 
generally known as macrofibers.); 
"microfibers" means thermoplastic fibers having an average diameter of more 
than zero to 50 .mu.m, preferably of more than zero to 25 .mu.m; and 
"active" means having chemical or biological activity. 
The present invention teaches a conformable, water-permeable composite 
sheet article attached to a marine substrate. All or nearly all portions 
of this article which are immersed in a permeating fluid such as water are 
completely accessible to that permeating fluid. This composite sheet 
article is comprised of a non-woven, fibrous matrix in which is entrapped, 
preferably homogeneously, at least one of an antifouling agent and an 
anticorrosive agent. It may be desirable to provide a water-resistant 
adhesive on a surface of the sheet article or on an outer surface of the 
marine substrate to ensure good adherence of the sheet article to the 
marine substrate when submerged in fresh or sea water. Because the entire 
thickness of the submerged portion of the sheet article is accessible to 
water, all reactive particles are available as antifoulant and/or 
anticorrosive agents to protect that portion of the marine substrate which 
is submerged. This obviates the need for frequent reapplications of 
traditional antifoulant and/or anticorrosive coatings due to their loss of 
efficacy upon depletion of reactants from their surface layers. 
The possibility of incorporating in the composite sheet article a plurality 
of antifouling and anticorrosive particulate is also envisioned within the 
scope of the present invention. In certain embodiments, it may be 
advantageous for the composite substrate to comprise strata of different 
particulate. For example, when the marine substrate is metallic, the 
particulate layer of the composite sheet article closest to the marine 
substrate can comprise anticorrosive particulate whereas other layers can 
comprise antifouling particulate. If the substrate is wooden, the 
particulate layer closest to the substrate can comprise a wood 
preservative such as pentachlorophenol or creosote. Other strata of the 
composite sheet article can contain various other particulate including 
pigments. Use of a single, multipurpose composite marine structure 
eliminates the need for application of numerous coats of separate, 
distinct protectants to a marine substrate and provides the opportunity to 
customize antifouling agents for particular uses and areas. 
The present invention provides marine substrates with fouling protection, 
corrosion protection, or both, while potential pollutants which provide 
little or no fouling protection, such as resins and water-erodible 
polymers, are eliminated.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 shows composite marine structure 10 having marine substrate 12 and 
one embodiment of water-permeable composite article 14 which is attached 
to the marine substrate by means of adhesive layer 24. Composite article 
14 has a web of polymeric fibers 16 which entrap and hold a variety of 
particulate 18, 20, and 22. Particulate are arranged in strata such that 
particulate having anticorrosive properties 18 is closest to marine 
substrate 12. Different types of antifouling particulate 20 and 22 are in 
the layers closest to the article-liquid interface. Adhesive 24 can be 
pre-applied to composite article 14 or can be applied to substrate 12 
before article 14 is to be applied thereto. 
FIG. 2 shows a second embodiment of water-permeable composite article 14 
including layer of double-coated tape 26. Anticorrosive particulate 18 and 
antifouling particulate 22 are essentially uniformily distributed 
throughout and entrapped in a single layer of article 14. Particulate 18 
and 22 are held in article 14 by means of polymeric fibers 16. 
Anticorrosive particulate 28, which can be the same as or different from 
anticorrosive particulate 18, is included in the adhesive of the tape 26. 
FIG. 3 shows a third embodiment of water-permeable composite article 14' 
including layer of double-coated tape 26 to which has been strippably 
adhered release liner 30. Release liner 30 comprises release coating 32 
and backing 34. Tape 26 preferentially releases from coating 32. 
Antifouling particulate 18 is homogeneously spread throughout and 
entrapped in a single layer of article 14' by means of polymeric fibers 
16. 
FIG. 4 shows a fourth embodiment of composite article 14" including release 
liner 30 and water-soluble release coating 36. Release liner 30 comprises 
double-coated tape 26 and backing 34. Tape 26 preferentially releases from 
coating 36 and adheres to backing 34. Coating 36 harmlessly dissolves once 
article 14" is submerged, thus rendering article 14" water permeable. 
Antifouling particulate 18 is homogeneously spread throughout and 
entrapped in a single layer of article 14" by means of polymeric fibers 
16. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Preparation of the composite marine structure of the present invention 
requires providing a water-permeable composite sheet article comprising a 
non-woven, fibrous polymeric matrix having active particulate entrapped 
therein and adhering the same to at least a portion of a marine substrate. 
Substrates amenable to use in the present invention include, but are not 
limited to, wood, plastic, plastic composite (e.g., fiberglass), and metal 
objects which are or can be submerged in salt or fresh water. Examples 
include buoys; piers and the pilings thereof; ship, boat, and submarine 
hulls, rudders, and propellers; anchors; water intake pipes and conduits; 
and lock gates. 
I. Making the Sheet Article 
A. PTFE Webs 
In one embodiment of the article of the present invention, an aqueous PTFE 
dispersion is used to produce a fibrillated web. This milky-white 
dispersion contains about 30% to 70% (by weight) of minute PTFE particles 
suspended in water. A major portion of these PTFE particles range in size 
from 0.05 .mu.m to about 0.5 .mu.m. Commercially available aqueous PTFE 
dispersions may contain other ingredients such as surfactants and 
stabilizers which promote continued suspension. Examples of such 
commercially available dispersions include Teflon.TM. 30, Teflon.TM. 30B, 
and Teflon.TM. 42 (DuPont de Nemours Chemical Corp.; Wilmington, Del.). 
Teflon.TM. 30 and Teflon.TM. 30B contain about 59% to 61% (by weight) PTFE 
solids and about 5.5% to 6.5% (by weight, based on the weight of PTFE 
resin) of a non-ionic wetting agent, typically octylphenyl polyoxyethylene 
or nonylphenyl polyoxyethylene. Teflon.TM. 42 contains about 32% to 35% 
(by weight) PTFE solids and no wetting agent (but does contain a surface 
layer of organic solvent to prevent evaporation). 
The composite sheet article comprising fibrillated PTFE preferably is 
prepared as described in any of U.S. Pat. Nos. 4,153,661, 4,460,642, and 
5,071,610, the processes of which are incorporated herein by reference, by 
blending the desired reactive particulate into the aqueous PTFE emulsion 
in the presence of sufficient lubricant to exceed the absorptive capacity 
of the solids yet maintain a putty-like consistency. This putty-like mass 
is then subjected to intensive mixing at a temperature preferably between 
40.degree. and 100.degree. C. to cause initial fibrillation of the PTFE 
particles. The resulting putty-like mass is then repeatedly and biaxially 
calendered, with a progressive narrowing of the gap between the rollers 
(while at least maintaining the water content), until the shear causes the 
PTFE to fibrillate and enmesh the particulate and a layer of desired 
thickness is obtained. Removal of any residual surfactant or wetting agent 
by organic solvent extraction or by washing with water after formation of 
the sheet article is generally desirable. The resultant sheet is then 
dried. Such sheets preferably have thicknesses in the range of 0.1 mm to 
0.5 mm. Sheet articles with a thickness in the general range of 0.05 mm to 
10 mm can be useful. 
If a sheet article with multiple particulate layers is desired, the 
component layers themselves are placed parallel to each other and 
calendered until they form a composite where the PTFE fibrils of the 
separate layers are entwined at the interface of adjacent sheets. 
Multilayer articles preferably have thicknesses in the range of 0.1 mm to 
10 mm. 
The void size and volume within such a web can be controlled by regulating 
the lubricant level during fabrication as described in U.S. Pat. No. 
5,071,610. Because both the size and the volume of the voids can vary 
directly with the amount of lubricant present during the fibrillation 
process, webs capable of entrapping particles of various sizes are 
possible. For instance, increasing the amount of lubricant to the point 
where it exceeds the lubricant sorptive capacity of the particulate by at 
least 3% (by weight) and up to 200% (by weight) can provide mean void 
sizes in the range of 0.3 .mu.m to 5.0 .mu.m with at least 90% of the 
voids having a size of less than 3.6 .mu.m. This process can be used to 
create a web with one or more kinds of reactive particulate enmeshed 
therein. The PTFE which forms the web within which particulate is to be 
trapped can be obtained in resin emulsion form wherein the PTFE and 
lubricant are already pre-mixed (e.g., Teflon.TM. 30 or 30B, DuPont de 
Nemours; Wilmington, Del.). To this emulsion can be added additional 
lubricant in the form of water, water-based solvents such as a 
water-alcohol solution, or easily-removable organic solvents such as 
ketones, esters, and ethers, to obtain the aforementioned desired 
proportion of lubricant and particulate. 
B. Non-PTFE Webs 
In other embodiments of the article of the present invention, the fibrous 
web can comprise non-woven, polymeric macro- or microfibers preferably 
selected from the group of polymers consisting of polyamide, polyolefin, 
polyester, polyurethane, polyvinylhalide, or a combination thereof. (If a 
combination of polymers is used, a bicomponent fiber is obtained.) If 
polyvinylhalide is used, it preferably comprises fluorine of at most 75% 
(by weight) and more preferably of at most 65% (by weight). Addition of a 
surfactant to such webs may be desirable to increase the wettability of 
the component fibers. 
1. Macrofibers 
The web can comprise thermoplastic, melt-extruded, large-diameter fibers 
which have been mechanically-calendered, air-laid, or spunbonded. These 
fibers have average diameters in the general range of 50 .mu.m to 1000 
.mu.m. 
Such non-woven webs with large-diameter fibers can be prepared by a 
spunbond process which is well known in the art. (See, e.g., U.S. Pat. 
Nos. 3,338,992, 3,509,009, and 3,528,129, the fiber preparation processes 
of which are incorporated herein by reference.) As described in these 
references, a post-fiber spinning web-consolidation step (i.e., 
calendering) is required to produce a self-supporting web. Spunbonded webs 
are commercially available from, for example, AMOCO, Inc. (Napierville, 
Ill.). 
Non-woven webs made from large-diameter staple fibers can also be formed on 
carding or air-laid machines (such as a Rando-Webber.TM., Model 12BS made 
by Curlator Corp., East Rochester, N.Y.), as is well known in the art. 
See, e.g., U.S. Pat. Nos. 4,437,271, 4,893,439, 5,030,496, and 5,082,720, 
the processes of which are incorporated herein by reference. 
A binder is normally used to produce self-supporting webs prepared by the 
air-laying and carding processes and is optional where the spunbond 
process is used. Such binders can take the form of resin systems which are 
applied after web formation or of binder fibers which are incorporated 
into the web during the air laying process. Examples of such resin systems 
include phenolic resins and polyurethanes. Examples of common binder 
fibers include adhesive-only type fibers such as Kodel.TM. 43UD (Eastman 
Chemical Products; Kingsport, Tenn.) and bicomponent fibers, which are 
available in either side-by-side form (e.g., Chisso.TM. ES Fibers, Chisso 
Corp., Osaka, Japan) or sheath-core form (e.g., Melty.TM. Fiber Type 4080, 
Unitika Ltd., Osaka, Japan). Application of heat and/or radiation to the 
web "cures" either type of binder system and consolidates the web. 
Generally speaking, non-woven webs comprising macrofibers have relatively 
large voids. Therefore, such webs have low capture efficiency of 
small-diameter particulate which is introduced into the web. Nevertheless, 
particulate can be incorporated into the non-woven webs by at least four 
means. First, where relatively large particulate is to be used, it can be 
added directly to the web, which is then calendered to actually enmesh the 
particulate in the web (much like the PTFE webs described previously). 
Second, particulate can be incorporated into the primary binder system 
(discussed above) which is applied to the non-woven web. Curing of this 
binder adhesively attaches the particulate to the web. Third, a secondary 
binder system can be introduced into the web. Once the particulate is 
added to the web, the secondary binder is cured (independent of the 
primary system) to adhesively incorporate the particulate into the web. 
Fourth, where a binder fiber has been introduced into the web during the 
air laying or carding process, such a fiber can be heated above its 
softening temperature. This adhesively captures particulate which is 
introduced into the web. Of these methods involving non-PTFE macrofibers, 
those using a binder system are generally the most effective in capturing 
particulate. Adhesive levels which will promote point contact adhesion are 
preferred. 
Once the particulate has been added, the particle-loaded webs are typically 
further consolidated by, for example, a calendering process. This further 
enmeshes the particulate within the web structure. 
Webs comprising larger diameter fibers (i.e., fibers which average 
diameters between 50 .mu.m and 1000 .mu.m) have relatively high flow rates 
because they have a relatively large mean void size. 
2. Microfibers 
When the fibrous web comprises non-woven microfibers, those microfibers 
provide thermoplastic, melt-blown polymeric materials having active 
particulate dispersed therein. Preferred polymeric materials include such 
polyolefins as polypropylene and polyethylene, preferably further 
comprising a surfactant, as described in, for example, U.S. Pat. No. 
4,933,229, the process of which is incorporated herein by reference. 
Alternatively, surfactant can be applied to a blown microfibrous (BMF) web 
subsequent to web formation. Particulate can be incorporated into BMF webs 
as described in U.S. Pat. No. 3,971,373, the process of which is 
incorporated herein by reference. 
Microfibrous webs of the present invention have average fiber diameters up 
to 50 .mu.m, preferably from 2 .mu.m to 25 .mu.m, and most preferably from 
3 .mu.m to 10 .mu.m. Because the void sizes in such webs range from 0.1 
.mu.m to 10 .mu.m, preferably from 0.5 .mu.m to 5 .mu.m, flow through 
these webs is not as great as is flow through the macrofibrous webs 
described above. 
3. Microfibrillar 
The web can also comprise a microfibrillar structure generated by the phase 
separation of a polymer/diluent solution. Preferred polymeric materials 
include such thermoplastic polyolefins as polypropylene and polyethylene. 
A preferred diluent is mineral oil. 
Use of these materials to form such a microfibrillar material is described 
in, for example, U.S. Pat. No. 4,539,256. That reference discloses a 
microporous sheet material characterized by a multiplicity of spaced, 
randomly dispersed, equiaxed, non-uniformily shaped particles of the 
thermoplastic polymer. 
Sheet materials are prepared by (1) melt blending a crystallizable 
thermoplastic polymer with a compound which is miscible with the 
thermoplastic polymer at the polymer's melting temperature but which phase 
separates upon cooling at or below the polymer's crystallization 
temperature; (2) forming the melt blend into a shaped article; and (3) 
causing the thermoplastic polymer and the miscible compound to phase 
separate by cooling the shaped article to a temperature at which the 
polymer crystallizes. 
Particulate can be incorporated into these microfibrillar webs during the 
initial melt blending step according to the procedure described in U.S. 
Pat. No. 5,130,342, wherein the crystallizable thermoplastic polymer is 
melt blended with a dispersion of the desired particulate in the 
above-described diluent. Preferably, the diluent is removed from the phase 
separated web after cooling by extraction with a solvent which is miscible 
with the diluent but which is not miscible with the thermoplastic polymer 
or the particulate. This extraction results in a microporous, 
particle-loaded, thermoplastic polymer web which is practically 
diluent-free, wherein the particulate is non-agglomerated. 
Microfibrillar webs of the present invention have average fibril diameters 
of more than zero up to 3 .mu.m, preferably from 0.01 .mu.m to 2 .mu.m, 
and most preferably from 0.1 .mu.m to 1 .mu.m. The void sizes in these 
webs range from 0.01 .mu.m to 4 .mu.m, preferably from 0.1 .mu.m to 2 
.mu.m, and their void volumes range from 50% to 90%, preferably from 60% 
to 80%. If increased void size and porosity is desired, stretching in the 
plane of the web can be performed. Because of the relatively small void 
sizes and volumes, the flow rates of these webs are somewhat less than the 
microfibrous webs previously described. 
Because the preferred thermoplastic polymeric materials which define these 
webs are usually hydrophobic and because the void sizes of these webs are 
of a size where capillary forces dominate the penetration of a liquid into 
the voids, the surfaces of the microfibrillar structure are preferably 
treated so as to make them hydrophilic. An example of such a treatment is 
the coating of the microfibrils with a surfactant as described in U.S. 
Pat. No. 4,501,793. Although surfactants can be extracted by water and 
many other solvents, the voids of the web will remain filled with water 
once initial wetting of the web (in the marine environment) occurs. 
Therefore, the temporary nature of the described surfactant treatment is 
not a detriment. 
II. Particulate 
Active particulate useful in the present invention includes any antifouling 
and anticorrosive materials which can be immobilized in a non-woven, 
fibrous matrix. Particles of all shapes can be used in such a matrix. 
Average diameters of particles useful when the matrix comprises PTFE 
fibrils are within the range of 0.1 .mu.m to 100 .mu.m, more preferably 
within the range of 0.1 .mu.m to 50 .mu.m, and most preferably within the 
range of 1 .mu.m to 10 .mu.m. When the matrix of the sheet article 
comprises non-woven fibers of a polymer other than PTFE, the average 
diameters of the particles are within the range of approximately 0.1 .mu.m 
to 600 .mu.m, preferably within the range of 5 .mu.m to 200 .mu.m. It has 
been found that, where the web comprises macrofibers, larger particles are 
better retained. Such particulate can be incorporated directly into the 
membrane. 
Where fouling protection is desired, particulate which is toxic to marine 
organisms will be entrapped in the web. Particularly effective biotoxins 
include those species of copper in solid form which are capable of 
producing aqueous copper ions, such as oxides of copper and copper 
particles. Where the aqueous environment in which the article is to be 
used is at least slightly acidic, a particularly useful species of copper 
is copper iodide. Not only are copper ions released as biotoxin, but 
iodine (another biotoxin) is also formed. Other useful metals and metal 
salts which have antifouling properties can also be so incorporated. 
Representative examples include organotin compounds and zinc salts. 
Anticorrosive agents in forms which can be incorporated into the sheet 
article can be used to produce an anticorrosion layer. Representative 
examples include encapsulated sodium nitrite, certain amines, and 
combinations of a metal whose oxidation potential is greater than that of 
iron and a salt of that metal comprising said metal and an appropriate 
anion (such as zinc/zinc chromate). 
Some forms of particulate can be incorporated as encapsulated reactant. For 
instance, antibiotics such as oxytetracycline can be encapsulated in 
polyurea. These capsules are either semipermeable or manufactured in such 
a way so as to have a time release effect. Antibiotics may also be 
incorporated into a polymeric binder matrix. This matrix system preferably 
produces a time release effect, also. Active particulate can also be bound 
to inert particles (i.e., coatings on solid supports). For example, 
enzymes which interfere with the ability of marine organisms to attach to 
marine substrates (e.g., by weakening or killing the organisms) can be 
covalently bonded to polyazlactone supports such as beads. Another form of 
incorporation is the entrapping of viable cells which produce enzymes with 
antifouling properties, such as Aspergillus niger and Bacillus subtilis, 
in the sheet article. This method of incorporation provides fouling 
protection of potentially unlimited duration. 
Particulate is generally distributed uniformly in the web, but matrices 
which include combinations of particulate can be prepared. Alternatively, 
layers containing different particulate can be calendered into a single 
matrix with distinct strata of particulate. Such multilayer composites 
show minimal boundary mixing (between the various particulate) and retain 
good uniformity throughout each layer. Whether in a heterogeneous or 
homogenous form, this type of article can assure protection against 
fouling from diverse forms of marine life, protection against corrosion, 
or both. 
Pigment and adjuvant particles with average diameters in the same ranges as 
listed previously with respect to active particulate can be included. 
Representative examples of useful pigments include carbon, copper 
phthalocyanine, taconite, zinc oxide, titanium dioxide, and ferric oxide. 
Such pigment particles can be included as part of an otherwise reactive 
layer or as a separate layer which is then calendered with reactive layers 
to form a multilayer composite. Other adjuvants which can be incorporated 
in the composite marine structure of the invention include silica, 
diffusion modifiers, bioactivity intensifiers, and ultraviolet radiation 
blockers. When present, such non-active particulate can comprise from more 
than 0% to 95% (by weight), preferably from more than 0% to 50% (by 
weight), and most preferably from more than 0% to 15% (by weight) of the 
sheet article. 
The sheet article of the present invention preferably comprises active 
particulate in an amount of at least 10% (by weight), more preferably 
comprises active particulate in an amount of at least 50% (by weight), and 
most preferably comprises active particulate in an amount of at least 80% 
(by weight). The sheet article can comprise particulate in an amount up to 
97% (by weight), (although particulate amounts in the range of 90-95% (by 
weight) tend to produce more stable webs). High active particulate loading 
is desirable to extend the useful life of the substrate. The particulate 
material can be of regular (flat, spherical, cubic, etc.) or irregular 
shape. The enmeshing fibrils or the fibrous web retain the enmeshed 
particulate, by entrapment or adhesion, within the matrix, and the 
enmeshed particles resist sloughing. 
Once a sheet article with the desired properties is obtained, a 
water-resistant adhesive layer can be attached so that the article will 
adhere to the marine substrate to be protected. If the composite article 
of the marine structure comprises an anticorrosive stratum, the 
anticorrosive stratum is preferably adhered directly to the marine 
substrate so that the anticorrosive particulate will be as close as 
possible to the surface to be protected. Additionally, anticorrosive 
particulate can be dispersed in the adhesive layer itself so that maximum 
contact will be obtained. If pigment has been included has been included 
as a separate stratum of particulate, that stratum (which is also 
water-permeable) will necessarily be on the side opposite of the adhered 
surface. 
In another aspect, the present invention provides a composite article 
comprising the water-permeable article of the above-described composite 
marine structure with a dual-sided tape attached to at least a portion of 
a surface thereof. This composite article can then be attached directly to 
the marine substrate to be protected. 
In another aspect, the present invention provides a composite article 
comprising a non-woven web with active particulate enmeshed therein having 
a liner attached to at least one surface of the web. The liner can be 
attached to either side, or both sides, of the article. Where an adhesive 
has been attached to one side of the web, a differential release liner can 
be attached to the adhesive. This release liner can preferentially be 
peeled away from the adhesive, leaving the adhesive attached to the sheet 
article which can then be adhered to at least a portion of the marine 
substrate to be protected. Alternatively, a liner could be attached to 
that surface of the article which is not intended to be attached (either 
mechanically or by means of a water-soluble adhesive) to the marine 
substrate in order to provide said surface with protection from damage 
during handling or storage. In use, such a liner and attaching adhesive, 
if any is present, is removed from the sheet article. 
In another aspect, the present invention provides a method of interfering 
with or inhibiting at least one of (1) accumulation of marine growth, and 
(2) corrosion of a marine substrate, the method comprising the step of 
allowing fresh or sea water to come into contact with a composite sheet 
article which is attached to a marine substrate, the composite sheet 
article comprising a porous, non-woven, fibrous web with active 
particulate enmeshed therein, the active particulate providing at least 
one of fouling or corrosion protection to the marine substrate. 
The composite sheet article of the present invention can provide both 
fouling and corrosion protection to marine substrates of many shapes and 
sizes. The composite sheet article also can eliminate the need for a 
separate paint coating on the substrate since pigment particles of various 
hues can be incorporated in the sheet article. 
Objects and advantages of this invention are further illustrated by the 
following examples, but the particular materials and amounts thereof, as 
well as other conditions and details, recited in these examples should not 
be construed to unduly limit this invention. 
EXAMPLES 
Example 1 
This example describes the preparation of a copper particulate-loaded PTFE 
web using a commercial antifoulant paint pigment. The copper particles 
used were those included in VC17M.TM. boat bottom paint kits 
(International Paint, Inc.; Union, N.J.), which have a composition of 
84.8% (by weight) copper and 15.2% (by weight) inert materials. 
A 40.0 g portion of these copper particles was mixed with 11.76 g of 
Teflon.TM. 30B emulsion (60% solids) using a plastic beaker and a spatula. 
Two grams of ethanol were added to aid the wetting process, and a 
putty-like mixture was obtained after about 10 minutes of mixing with a 
spatula. 
The gap of a rubber mill in its calendering mode was adjusted to 0.190 cm 
(75 mil). The roller temperature was set at 43.3.degree. C. (110.degree. 
F.). The putty-like mass was subjected to 15 initial passes that included 
three layer foldings and cross rotations between each pass. 
The thick membrane produced by the 0.190 cm (75 mil) gap was subsequently 
made thinner by reducing the gap by 30% increments until the thickness of 
the web was about 0.01 cm (4.2 mils). 
Example 2 
This example describes a copper particulate-loaded, fibrillated PTFE web 
which was laminated with transfer tape to provide an article which was 
then adhered to a substrate to prevent biofouling. 
A mixture of 56 g of copper powder (Fisher Chemicals; Fair Lawn, N.J.), 
water (10 ml), and 10 ml Teflon.TM. 30B emulsion (with 60% solids by 
weight) was worked on a rubber mill in its shearing mode, as described 
previously, to produce a microporous, leather-like web which was 15.2 cm 
wide, 91.4 cm long, and 0.1 mm thick (6 in..times.3 ft..times.0.1 mm). Due 
to outstanding conformability and good physical integrity, this web could 
be intimately conformed to all irregular surfaces without tearing. The web 
was soaked in water for 2 days to remove the soap present in the 
Teflon.TM. 30B emulsion. The web was dried and laminated on one side with 
Scotch.RTM. Adhesive Transfer Tape (3M; St. Paul, Minn.). 
The low-stick backing of the transfer tape on this article was removed, and 
the article was attached to flat surfaces, such as stainless steel, glass 
or fiberglass composite plates. 
The plates were immersed in fresh water environments, such as indoor fish 
tanks and outdoor ponds, and exposed to air and light over a period of 
several years. During this time, the treated surface remained clear of 
algae, whereas all other surfaces became covered with algae. The fish 
swimming in such environments showed no ill effects. 
Example 3 
A mixture of 10 g of copper oxide powder (Fisher Chemicals), with particle 
diameters in the range of 1 .mu.m to 10 .mu.m, and 1 ml of a Teflon.TM. 
30B emulsion (with 60% solids) was milled on a rubber mill as described in 
Example 1 to produce a leather-like, microporous web. The film was washed, 
dried, and then laminated on one side with transfer tape. After removal of 
the low-adhesive paper backing, this construction was laminated to flat 
surfaces (stainless steel or glass plates). The laminate was immersed in 
fresh water environments (fish tanks, outside ponds) intermittently for 6 
months over a period of 5 years. No evidence of algae growth was noted on 
the Cu.sub.2 O-PTFE surface, but unprotected comparative surfaces were 
covered with algae growth. 
Example 4 
To demonstrate that all enmeshed Cu.sub.2 O particles were accessible to 
liquid and subject to slow leaching, two 1 cm.times.4 cm fibrillated PTFE 
sheets enmeshing Cu.sub.2 O (90% by weight) were immersed in dilute 
aqueous NH.sub.4 OH for about one week. During that time, all Cu.sub.2 O 
dissolved from the sheet, leaving a white framework of enmeshing PTFE 
fibers completely free of all the previously enmeshed particles. This 
shows that all reactive particles are accessible to fluids. In paints, 
only those particles at the surface are accessible. Other trials using 
fluid containing indicator dye and PTFE composite membranes comprising 
chromatographic alumina showed that fluids flow through the membranes 
without channeling. 
Example 5 
To demonstrate that non-metallic particulate can be enmeshed in a polymeric 
web, the following components were mixed: 
1.4 g polyurea capsules (3M Encapsulation Technology Center; St. Paul, 
Minn.) containing 3% oxytetracycline (Sigma Chemical Co.; St. Louis, Mo.) 
1.9 g polyazlactone beads* containing alcalase (Novo Laboratories; Danbury, 
Conn.) 
1.5 g polyazlactone beads* containing protease (Novo Labs) 
2.4 g polyazlactone beads* containing .beta.-amylase (Novo Labs) 
2.0 g water 
3.0 g Teflon.TM. 30B aqueous emulsion (60% solids) 
FNT *As described in U.S. Pat. No. 4,737,560 (beads having a diameter of 
approximately 10 .mu.m) 
Additional water (3.0 g) was added to this mixture in order to form a 
dough. This putty-like mass was processed according to the procedure of 
Example 1 with 11 initial passes in a two-roll mill with a gap of 0.25 cm 
(100 mil). This produced a membrane with a thickness of 1.75 mm. 
Additional passes compressed the web to a final thickness of 0.5 mm. 
Example 6 
To demonstrate that a commercially-available metallic paint pigment can be 
incorporated into a fibrillated PTFE web, the following were mixed: 
30.0 g MD 4760.TM. copper shade pigment (M. D. Both Inc.; Ashland Mass.) 
9.0 g Teflon.TM. 30B aqueous emulsion (60% solids) 
2.5 g water 
Although the resulting putty-like mass was quite liquid, it was processed 
according to the procedure of Example 1 with numerous passes through a 
two-roll mill into a 0.025 cm (10 mil) web. 
The webs described in Examples 7 and 8 were prepared to show the 
feasibility of incorporating low-cost fillers into a web. 
Example 7 
A membrane with the following components was prepared as follows: 
200.0 g MD 4760.TM. copper shade pigment 
200.0 g Davisil.TM. TLC-grade silica (Davison Chemical; Baltimore, Md.) 
117.6 g DuPont Teflon.TM. 30B emulsion (60% solids by wt.) 
560.0 g 50:50 isopropanol/water mixture 
Using the procedure of Example 1, this putty-like mass was calendered down 
to a finishing gap of 0.46 mm (18 mil). 
Example 8 
A membrane with the following components was prepared as follows: 
200 g VC17M.TM. copper particles (as described in Example 1) 
200 g Davisil.TM. TLC-grade silica 
117.6 g Teflon.TM. 30B emulsion (60% solids by wt.) 
419 g 50:50 isopropanol/water mixture 
Using the procedure of Example 1, this putty-like mass formed a web after 
eight initial passes. The web was thinned to a finishing gap of 0.03 cm 
(12 mil). 
Example 9 
A membrane with the following components was prepared as follows: 
200 g Purple Copp.TM. 97N cuprous oxide, 99.5% 325 mesh particles (American 
Chemet; Deerfield, Ill.) 
37 g Teflon.TM. 30B emulsion (60% solids by wt.) 
Using the procedure of Example 1, the membrane which formed from the 
putty-like mass was calendered to a thickness of 0.25 mm (10 mil). 
The webs described in Examples 5-9 were backed with Scotch.RTM. Hi 
Strength.TM. adhesive (3M; St. Paul, Minn.) and attached to 22.9 
cm.times.12.7 cm (5 in..times.9 in.) gel-coated fiberglass test panels. No 
fouling occurred on the copper-filled membranes after six months static 
immersion off the coast of Miami, Fla. Some fouling occurred on the web 
filled with the enzyme and antibiotic particles. No enzyme or antibiotic 
activity was detected in the web after the six months of immersion. 
Example 10 
A membrane with the following components was prepared as follows: 
1200 g Purple Copp.TM. 97N cuprous oxide, 99.5% 325 mesh particles 
222 g Teflon.TM. 30B emulsion (60% solids by wt.) 
After calendering according to the procedure of Example 1, the membrane 
thickness was 0.25-0.30 mm (10-12 mil). After being immersed in the ocean 
for fifteen months, this membrane showed slight biofouling, which was 
easily removed by brushing. The copper color was readily restored by hand 
polishing with a SCOTCHBRITE.TM. scour pad (3M; St. Paul, Minn.). 
A membrane covering a section of a racing yacht rudder remained adhered 
during seven and one half months of operation. 
Example 11 
The samples described herein show the feasibility of a microfibrillar 
polymer matrix. These samples can be characterized as 
Sample 1 Unfilled polyethylene web 
Samples 2-3 Copper oxide in an expanded polyethylene web 
Samples 4-5 Copper oxide in a surfactant-treated expanded polyethylene web 
Sample 1 was prepared according to Example 1 of World Patent No. 92/07899. 
Samples 2-5 were prepared according to Example 7 of U.S. Pat. No. 
4,957,943, except that copper oxide particles with an average diameter of 
0.5 .mu.m (Charles B. Edwards & Co.; Minneapolis, Minn.) were dispersed in 
a mineral oil diluent at a loading adjusted to give a net copper content 
(relative to the weight of polyethylene) of 16.2% (by weight) in the 
finished membrane. Samples 4 and 5 were coated with Tween 21.TM. (ICI 
Americas Co.; Wilmington, Mass.), a nonionic surfactant, according to the 
procedure described in Example 2 of U.S. Pat. No. 4,501,793. The samples 
were adhered to fiberglass test panels. The panels were immersed in sea 
water for six months. Sample 1 displayed no antifouling activity. Although 
samples 2-3 contained biotoxin, they displayed no antifouling activity, 
likely because the webs were hydrophilic. Samples 4 and 5 showed a 
dramatic increase in activity (i.e., fouling protection), although a few 
barnacles and some algae had attached. 
Example 12 
This example shows the feasibility of webs comprising non-PTFE polymeric 
fibers. 
On several layers of RFX.TM. spunbond polypropylene web (AMOCO, Inc.; 
Hazelhurst, Ga.) was poured a generous amount of Purple Copp.TM. 97N 
(American Chemet) cuprous oxide, 99.5% 325 mesh particles. These layers 
were shaken until visual inspection showed that a large portion of the 
copper particles had become entrapped in the voids of the web. Ten of 
these layers were calendered into a loose web, and five other layers were 
calendered into another. These loose webs and a ten-layer comparative 
sample containing no copper were then pressed between the heated 
(approximately 400.degree. F.) stainless steel plates of a Sentinel Press 
808 (Packaging Industries Group; Hyannis, Mass.) for a few seconds until 
unitary webs were formed. The ten-layer web was 74% (by weight) copper, 
and the five-layer web was 76% (by weight) copper. 
A 50 cubic centimeter Gurley.TM. Densometer Model 4110 (W. & L.E. Gurley 
Company; Troy, N.Y.) was used to test how tightly the webs were pressed 
together. The results of those tests were as follows: 
Comparative web: 27.2 sec 
10-layer web: 11.9 sec 
5-layer web: 0.1 sec 
Thus, although this process produces unitary copper-containing nonwoven 
webs (i.e., not subject to easy delamination), the resultant webs are 
sufficiently porous to allow for free fluid flow. 
Various modifications and alterations which do not depart from the scope 
and spirit of this invention will become apparent to those skilled in the 
art. This invention is not to be unduly limited to the illustrative 
embodiments set forth herein.