U.S. patent application number 10/408095 was filed with the patent office on 2004-01-15 for thermoplastic particles which comprise an antiviral or antimicrobial agent.
This patent application is currently assigned to Porex Corporation. Invention is credited to Yao, Li.
Application Number | 20040009227 10/408095 |
Document ID | / |
Family ID | 24068970 |
Filed Date | 2004-01-15 |
United States Patent
Application |
20040009227 |
Kind Code |
A1 |
Yao, Li |
January 15, 2004 |
Thermoplastic particles which comprise an antiviral or
antimicrobial agent
Abstract
This invention relates to novel porous materials that possess
antiviral and/or antimicrobial properties. The invention
encompasses a porous material having antiviral or antimicrobial
properties-which is comprised of a porous substrate and an
antiviral or antimicrobial agent. The invention also encompasses a
process for making porous materials that possess antiviral and/or
antimicrobial properties and the products of the process.
Inventors: |
Yao, Li; (Peachtree City,
GA) |
Correspondence
Address: |
PENNIE & EDMONDS LLP
1667 K STREET NW
SUITE 1000
WASHINGTON
DC
20006
|
Assignee: |
Porex Corporation
|
Family ID: |
24068970 |
Appl. No.: |
10/408095 |
Filed: |
April 8, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10408095 |
Apr 8, 2003 |
|
|
|
09519595 |
Mar 6, 2000 |
|
|
|
6551608 |
|
|
|
|
Current U.S.
Class: |
424/486 ;
424/618; 514/595; 514/634; 514/721 |
Current CPC
Class: |
A01N 25/10 20130101;
A01N 25/34 20130101; A01N 2300/00 20130101; A01N 31/16 20130101;
A61L 2/23 20130101; A01N 31/16 20130101; A01N 25/34 20130101; A61L
9/042 20130101; A01N 25/10 20130101; A01N 31/16 20130101 |
Class at
Publication: |
424/486 ;
424/618; 514/595; 514/634; 514/721 |
International
Class: |
A61K 033/38; A61K
009/14; A61K 031/17; A61K 031/075; A61K 031/155 |
Claims
What is claimed is:
1. A porous thermoplastic material which comprises a porous
thermoplastic substrate and an antiviral or antimicrobial
agent.
2. The porous thermoplastic material of claim I wherein the porous
thermoplastic substrate is a porous thermoplastic selected from the
group consisting of polyolefins, nylons, polycarbonates, poly(ether
sulfones), and mixtures thereof.
3. The porous thermoplastic material of claim 2 wherein the
thermoplastic is a polyolefin selected from the group consisting
of: ethylene vinyl acetate; ethylene methyl acrylate;
polyethylenes; polypropylenes; ethylene-propylene rubbers;
ethylene-propylenediene rubbers; poly(1-butene); polystyrene;
poly(2-butene); poly(1-pentene); poly(2-pentene);
poly(3-methyl-1-pentene); poly(4-methyl-1-pentene);
1,2-poly-1,3-butadiene; 1,4-poly-1,3-butadiene; polyisoprene;
polychloroprene; poly(vinyl acetate); poly(vinylidene chloride);
and mixtures and derivatives thereof.
4. The porous thermoplastic material of claim 3 wherein the
polyolefin is a polyethylene.
5. The porous thermoplastic material of claim 1 wherein the
antiviral or antimicrobial agent is selected from the group
consisting of: phenolic and chlorinated phenolic compounds;
resorcinol and its derivatives; bisphenolic compounds; benzoic
esters; halogenated carbanilides; polymeric antimicrobial agents;
thazolines; trichloromethylthioimides; natural antimicrobial
agents; metal salts; broad-spectrum antibiotics, and mixtures
thereof.
6. The porous thermoplastic material of claim 5 wherein the
antiviral or antimicrobial agent is selected from the group
consisting of: 2,4,4'-trichloro-2'-hydroxydiphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dich- lorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
7. The porous thermoplastic material of claim 1 which further
comprises a lubricant, colorant, or filler.
8. The porous thermoplastic material of claim 7 wherein the filler
is selected from the group consisting of: carbon black, cellulose
fiber powder, siliceous fillers, polyethylene fibers and filaments,
and mixtures thereof.
9. A porous thermoplastic material which comprises: a sintered
porous polyethylene substrate; and an antiviral or antimicrobial
agent selected from the group consisting of
2,4,4'-trichloro-2'-hydroxy-diphenyl ether,
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea,
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), silver ions, and salts and mixtures thereof.
10. A porous thermoplastic material which comprises: a sintered
porous polyethylene core; and a coating layer disposed over at
least part of the porous polyethylene core; wherein the coating
layer comprises an antiviral or antimicrobial agent.
11. The porous thermoplastic material of claim 10 wherein the
coating layer further comprises a thermoplastic or hydrogel
material.
12. The porous thermoplastic material of claim 11 wherein the
thermoplastic or hydrogel material is hydrophilic polyurethane.
13. A particle comprising an antiviral or antimicrobial agent
disposed within and/or on the surface of a thermoplastic core.
14. The particle of claim 13 which has a diameter of from about 5
.mu.m to about 1000 .mu.m.
15. The particle of claim 14 wherein the thermoplastic core is made
of a thermoplastic selected from the group consisting of
polyolefins, nylons, polycarbonates, poly(ether sulfones), and
mixtures thereof; and the antiviral or antimicrobial agent is
selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4- -dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
16. A process for making a porous thermoplastic material which
comprises sintering thermoplastic particles to form a porous
substrate and contacting the porous substrate with an antiviral or
antimicrobial agent.
17. The method of claim 16 wherein the thermoplastic particles are
particles of polyolefins, nylons, polycarbonates, poly(ether
sulfones), or mixtures thereof.
18. The method of claim 16 wherein the antiviral or antimicrobial
agent is selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphen- yl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
19. A product of the process of claim 16.
20. A process for making a porous thermoplastic material which
comprises sintering thermoplastic particles to form a porous
substrate, and contacting the porous substrate with a coating
mixture which comprises an antiviral or antimicrobial agent.
21. The method of claim 20 wherein the coating mixture further
comprises a thermoplastic or hydrogel material.
22. The method of claim 21 wherein the thermoplastic or hydrogel
material is hydrophilic polyurethane.
23. The method of claim 20 wherein the thermoplastic particles are
particles of polyolefins, nylons, polycarbonates, poly(ether
sulfones), or mixtures thereof.
24. The method of claim 20 wherein the antiviral or antimicrobial
agent is selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphen- yl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
25. A product of the process of claim 20.
26. A process for making a porous thermoplastic material which
comprises sintering thermoplastic particles which comprise an
antiviral or antimicrobial agent.
27. The method of claim 26 wherein the thermoplastic particles are
formed by underwater pelletizing a mixture comprised of a
thermoplastic and an antiviral or antimicrobial agent.
28. The method of claim 26 wherein the thermoplastic particles are
selected from the group consisting of particles of: polyolefins,
nylons, polycarbonates, poly(ether sulfones), and mixtures
thereof.
29. The method of claim 28 wherein the polyolefin is
polyethylene.
30. The method of claim 26 wherein the antiviral or antimicrobial
agent is selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphen- yl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
31. A product of the process of claim 26.
Description
1. FIELD OF THE INVENTION
[0001] This invention relates to porous plastic materials which
comprise antiviral and/or antimicrobial agents, and to methods of
making the same.
2. BACKGROUND OF THE INVENTION
[0002] Porous materials can be used as vents or filters in
innumerable medical, research, consumer and industrial applications
as. Unfortunately, the growth or accumulation of potentially
harmful viruses or microbes (e.g., bacteria, fungi and protozoa)
can occur in most porous materials. In many applications,
therefore, vents and filters must be changed frequently in order to
prevent the accumulation and/or growth of viruses or microbes.
[0003] Antiviral and antimicrobial agents, which prevent the growth
or accumulation of viruses or microbes, have for some time been
incorporated into solid and fibrous materials. For example: U.S.
Pat. No. 4,533,435 discloses the incorporation of an antimicrobial
additive into the binding agent of a heavy-duty, kraft-type paper;
U.S. Pat. No. 4,430,381 discloses the incorporation of a salt of a
monocarboxylate antimicrobial agent into an external binder system
which is applied to fabrics and papers; U.S. Pat. No. 4,736,467
discloses operating room garments having a layer of
baceriostatically-treated polyester/cotton fabric; U.S. Pat. No.
4,855,139 discloses a composition comprising a cellulosic textile
material that is chemically bonded to a fungicidally active
phenolic compound; U.S. Pat. No. 5,069,907 discloses a surgical
drape comprised of a synthetic polymeric film or fabric into which
an antimicrobial agent has been incorporated; U.S. Pat. No.
5,091,102 discloses a dry matrix for use in cleaning which
comprises an antimicrobial compound; U.S. Pat. No. 5,639,464
discloses a biocidal polymeric coating for heat exchanger coils;
U.S. Pat. No. 5,853,883 discloses fibers made from a
melt-extrudable thermoplastic composition comprising an
antimicrobial siloxane compound; U.S. Pat. No. 5,854,147 discloses
a non-woven web made from a melt-extrudable thermoplastic
composition which comprises an antimicrobial siloxane compound;
U.S. Pat. No. 5,894,042 discloses a conduit coating which comprises
a bacteriostatic, bacteriocidal, fungicidal, fungistatic or
mildew-suppressing material; U.S. Pat. No. 5,919,554 discloses a
fiber reinforced plastic comprising an antimicrobial composition;
and U.S. Pat. No. 5,968,538 discloses a method of coating antiviral
and antibacterial materials on a substrate material.
[0004] Although solid and fibrous materials comprising antiviral or
antimicrobial agents can be used in some applications, they are of
little use in applications that require a porous material that can
be molded into a particular shape, has a narrow distribution of
pore sizes, or has high mechanical strength. Consequently, there
exists a need for porous, non-fibrous materials that resist the
accumulation or growth of viruses and/or microbes.
3. SUMMARY OF THE INVENTION
[0005] This invention is directed to novel porous materials which
possess antiviral and/or antimicrobial properties. Particular
materials of the invention comprise a porous thermoplastic
substrate and an antiviral or antimicrobial agent. The invention is
further directed to methods of using the novel porous materials
disclosed herein, as well as to vents and filters made of, or
comprising, the novel porous materials disclosed herein.
[0006] Suitable thermoplastics that can be used to provide the
porous thermoplastic substrate include, but are not limited to,
polyolefins, nylons, polycarbonates, poly(ether sulfones), and
mixtures thereof. A preferred thermoplastic is a polyolefin.
Examples of suitable polyolefins include, but are not limited to:
ethylene vinyl acetate; ethylene methyl acrylate; polyethylenes;
polypropylenes; ethylene-propylene rubbers; ethylene-propylenediene
rubbers; poly(1-butene); polystyrene; poly(2-butene);
poly(1-pentene); poly(2-pentene); poly(3-methyl-1-pentene- );
poly(4-methyl-1-pentene); 1,2-poly-1,3-butadiene;
1,4-poly-1,3-butadiene; polyisoprene; polychloroprene; poly(vinyl
acetate); poly(vinylidene chloride); and mixtures and derivatives
thereof A preferred polyolefin is polyethylene. Examples of
suitable polyethylenes include, but are not limited to, low density
polyethylene, linear low density polyethylene, high density
polyethylene, ultra-high molecular weight polyethylene, and
derivatives thereof.
[0007] The porous thermoplastic materials of the invention can
further comprise materials such as, but not limited to, lubricants,
colorants, fillers, and mixtures thereof. Suitable fillers include,
but are not limited to: carbon black, cellulose fiber powder,
siliceous fillers, polyethylene fibers and filaments, and mixtures
thereof.
[0008] Suitable antiviral or antimicrobial agents include, but are
not limited to: phenolic and chlorinated phenolic compounds;
resorcinol and its derivatives; bisphenolic compounds; benzoic
esters; halogenated carbanilides; polymeric antimicrobial agents;
thazolines; trichloromethylthioimides; natural antimicrobial
agents; metal salts; broad-spectrum antibiotics, and mixtures
thereof. Preferred antiviral or antimicrobial agents include, but
are not limited to: 2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-(3,4-dichl- orophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
[0009] A first embodiment of the invention encompasses a porous
thermoplastic material which comprises a sintered porous
thermoplastic substrate having a surface at least part of which is
coated with an antiviral or antimicrobial agent.
[0010] Although the thermoplastic substrate can be made of any
thermoplastic, including those disclosed herein, it is preferably
made of polyethylene, more preferably ultra-high molecular weight
polyethylene. Preferred antiviral or antimicrobial agents include,
but are not limited to, 2,4,4'-trichloro-2'-hydroxy-diphenyl ether,
3-(4-chlorophenyl)-1-(3,4- -dichlorophenyl)urea,
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), silver ions, and salts and mixtures thereof.
[0011] A specific porous material of the invention thus comprises:
a sintered porous polyethylene substrate; an antiviral or
antimicrobial agent selected from the group consisting of
2,4,4'-trichloro-2'-hydroxy-d- iphenyl ether,
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea,
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), silver ions, and salts and mixtures thereof; and an
optional filler, wherein the sintered porous polyethylene substrate
has a surface at least part of which is coated with the antiviral
or antimicrobial agent.
[0012] Another specific porous material of the invention comprises
a sintered porous polyethylene core and a coating layer disposed
over at least part of the porous polyethylene core. Preferably, the
coating layer further comprises a thermoplastic or hydrogel
material. Suitable thermoplastic or hydrogel materials include, but
are not limited to, polyurethanes such as hydrophilic
polyurethane.
[0013] A second embodiment of the invention encompasses a porous
material which comprises a sintered porous thermoplastic substrate
and an antiviral or antimicrobial agent disposed throughout at
least part of the substrate.
[0014] Although the thermoplastic substrate can be made of any
thermoplastic, including those disclosed herein, it is it is
preferably polyethylene. Preferred antiviral or antimicrobial
agents include, but are not limited to,
2,4,4'-trichloro-2'-hydroxy-diphenyl ether,
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea,
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), silver ions, and salts and mixtures thereof.
[0015] A specific porous material of the invention thus comprises a
sintered porous polyethylene substrate and an antiviral or
antimicrobial agent disposed within at least part of the sintered
porous polyethylene substrate, wherein the antiviral or
antimicrobial agent is selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether,
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea,
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), silver ions, and salts and mixtures thereof. In an
even more specific material of the invention, the antiviral or
antimicrobial agent is disposed uniformly within at least about 75
percent, more preferably at least about 90 percent, and most
preferably at least about 95 percent of the porous polyethylene
substrate.
[0016] A third embodiment of the invention encompasses a particle
comprising an antiviral or antimicrobial agent disposed within
and/or on the surface of a thermoplastic core. A preferred particle
has a diameter of from about 5 .mu.M to about 1000 .mu.M, more
preferably from about 10 .mu.M to about 500 .mu.M, and most
preferably from about 20 .mu.M to about 300 .mu.M. Suitable
thermoplastics from which the core can be made include, but are not
limited to, polyolefins, nylons, polycarbonates, poly(ether
sulfones), and mixtures thereof. A preferred thermoplastic is a
polyolefin. A preferred polyolefin is polyethylene. Examples of
suitable polyethylenes are disclosed herein. Suitable antiviral or
antimicrobial agents are described herein. Preferred antiviral or
antimicrobial agents include, but are not limited to:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dic- hlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
[0017] A fourth embodiment of the invention encompasses a process
for making a porous thermoplastic material and the products of the
process. The process comprises contacting a sintered porous
substrate with an antiviral or antimicrobial agent. Preferably, the
porous substrate is made of polyethylene, more preferably
high-density polyethylene. Suitable antiviral or antimicrobial
agents are described herein. Preferred antiviral or antimicrobial
agents include, but are not limited to:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dic- hlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
[0018] A fifth embodiment of the invention encompasses a process
for making a particle and the products of that process. The process
comprises cooling a molten pre-particle, wherein the pre-particle
is comprised of a thermoplastic and an antiviral or antimicrobial
agent. Preferably, the molten pre-particle is formed by chopping a
molten extrudate. Preferably, the antiviral or antimicrobial agent
is selected from the group consisting of:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
[0019] A sixth embodiment of the invention encompasses another
process for making a porous thermoplastic material and the products
of the process. The process comprises contacting a sintered porous
substrate with a coating mixture which comprises an antiviral or
antimicrobial agent. Preferably, the coating mixture further
comprises a thermoplastic or hydrogel material. Suitable
thermoplastic or hydrogel materials include, but are not limited
to, polyurethanes such as hydrophilic polyurethane. Preferably, the
porous substrate is made of polyethylene, more preferably
high-density polyethylene. Suitable antiviral or antimicrobial
agents are described herein. Preferred antiviral or antimicrobial
agents include, but are not limited to:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
[0020] A seventh embodiment of the invention encompasses another
process for making a porous thermoplastic material and the products
of the process. The process comprises sintering particles which are
comprised of an antiviral or antimicrobial agent disposed about a
thermoplastic core. Preferred thermoplastics are disclosed herein.
A particularly preferred thermoplastic is polyethylene. Suitable
antiviral or antimicrobial agents are described herein. Preferred
antiviral or antimicrobial agents include, but are not limited to:
2,4,4'-trichloro-2'-hydroxy-diphenyl ether;
3-(4-chlorophenyl)-1-(3,4-dichlorophenyl)urea;
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride); silver ions; and salts and mixtures thereof.
3.1. Definitions
[0021] As used herein to describe a particle, the term
"substantially spherical" means that the particle is spherical or
that the length of its longest radius is no greater than about 2.0
times, more preferably no greater than about 1.5 times, even more
preferably no greater than about 1.2 times the length of its
shortest radius. When used to describe a mixture or collection of
particles, the term "substantially spherical" means that greater
than about 50%, more preferably greater than about 75%, even more
preferably greater than about 90%, and most preferably greater than
about 95% of the particles are substantially spherical.
[0022] As used herein, the term "substantial portion" means greater
than about 80%, more preferably greater than about 90%, and most
preferably greater than about 95%.
[0023] As used herein, the terms "degradation temperature" and
"decomposition temperature" mean the temperature at which a
particular chemical compound (e.g., an antiviral or antimicrobial
agent) decomposes or loses its ability to retard the growth or kill
a virus or microbe. As those skilled in the art will recognize, the
degradation temperature of a particular material will vary as a
function of, for example, pressure and exposure to oxidants,
reductants, or other reactive chemical moieties.
[0024] As used herein, the term "substantial degradation" means the
degradation of a substantial portion of the material described.
[0025] As used herein to describe a compound or moiety, the term
"derivative" means a compound or moiety wherein the degree of
saturation of at least one bond has been changed (e.g., a single
bond has been changed to a double or triple bond) or wherein at
least one hydrogen atom has been replaced with a different atom or
with a chemical moiety. Examples of different atoms and chemical
moieties include, but are not limited to, alkyl, aryl, halogen,
oxygen, nitrogen, sulfur, hydroxy, methoxy, alkyl, amine, amide,
ketone, and aldehyde.
4. DETAILED DESCRIPTION OF THE INVENTION
[0026] This invention is directed to novel porous materials which
resist the accumulation or growth of viruses and/or microbes. The
novel materials of the invention can be molded or formed into any
of a variety of shapes, and can thus be used to provide, for
example, filters or vents suitable for use in a variety of medical,
research, consumer and industrial applications. The mechanical
strength and uniform porosity of specific materials of the
invention further enable their use in applications for which
fibrous materials, such as papers and fabrics, are not suited.
[0027] The porous materials of the invention comprise a porous
substrate and at least one antiviral or antimicrobial agent,
examples of which are provided in Section 4.1.
4.1. Materials
[0028] Using methods such as those described herein, the porous
substrates of the materials of the invention are made from at least
one type of thermoplastic. Examples of suitable thermoplastics
include, but are not limited to, polyolefins, nylons,
polycarbonates, and poly(ether sulfones). Preferred thermoplastics
are polyolefins.
[0029] Examples of polyolefins suitable for use in the invention
include, but are not limited to: ethylene vinyl acetate (EVA);
ethylene methyl acrylate (EMA); polyethylenes such as, but not
limited to, low density polyethylene (LDPE), linear low density
polyethylene (LLDPE), high density polyethylene (HDPE), and
ultra-high molecular weight polyethylene (UHMWPE); polypropylenes;
ethylene-propylene rubbers; ethylene-propylene-diene rubbers;
poly(1-butene); polystyrene; poly(2-butene); poly(1-pentene);
poly(2-pentene); poly(3-methyl-1-pentene- );
poly(4-methyl-1-pentene); 1,2-poly-1,3-butadiene;
1,4-poly-1,3-butadiene; polyisoprene; polychloroprene; poly(vinyl
acetate); poly(vinylidene chloride); and mixtures and derivatives
thereof. Specific EVA materials include, but are not limited to,
those in the Microthene MU.RTM. and Microthene FE.RTM. series
manufactured by Equistar, Houston, Tex., such as Microthene MU
763-00 (9% vinyl acetate) and Microthene FE 532-00 (9% vinyl
acetate). Specific EMA materials include, but are not limited to,
those in the Optema TC.RTM. series manufactured by Exxon Chemical
Company, Baton Rouge, La., such as Optema TC-110 (21.5% methyl
acrylate). Specific polyethylene materials include, but are not
limited to, those in the Exact.RTM. series manufactured by Exxon
Chemical Company, such as Exact SLX-9090, Exact 3024, Exact, 3030,
Exact 3033, Exact 4011, Exact 4041, Exact SLP-9053, Exact SLP-9072,
and Exact SLP-9095. Specific examples of LDPE include, but are not
limited to, those in the 20 series manufactured by DuPont Chemical
Company, Wilmington, Del., such as 20 series 20, 20 series 20-6064,
20 series 2005, 20 series 2010, and 20 series 2020T. Specific
examples of LLDPE include, but are not limited to, those in the
Exact.RTM. series manufactured by Exxon Chemical Company, such as
Exact 3022 and Exact 4006. Specific examples of HDPE include, but
are not limited to, those in the Escorene HX.RTM. series
manufactured by Exxon Chemical Company, such as Escorene
HX-0358.
[0030] Ultra-high molecular weight polyethylenes suitable for use
in the invention include, but are not limited to, UHMWPE having a
molecular weight greater than about 1,000,000. Typically, UHMWPE
displays no measurable flow rate under normal test procedures. See,
U.S. Pat. No. 3,954,927. Ultra-high molecular weight polyethylene
also tends to have enhanced mechanical properties compared to other
polyethylenes, including, but not limited to, abrasion resistance,
impact resistance and toughness. Polyethylenes having weight
average molecular weights of 1,000,000 or higher, which are
included within the class designated as UHMWPE, typically an
intrinsic viscosity in the range of about 8 or more. Specific
examples of UHMWPE include, but are not limited to, Hostalen
GUR.RTM. sold by Ticona Inc., League City, Tex.
[0031] Polypropylenes suitable for use in the invention include,
but are not limited to: the Polyfort.RTM. series manufactured by A
Shulman Co., Akron, Ohio, such as FPP 2320E, 2321E, 2322E, 2345E,
PP2130, and PP2258; the Acctuf.RTM. series manufactured by BP Amoco
Corporation, Atlanta, Ga., such as Acctuf 3045, Amoco 6014, and
Amoco 6015; the Aristech.RTM. series manufactured by Aristech
Chemical Corp., Pittsburgh, Pa., such as D-007-2, LP-230-S, and
TI-4007-A; the Borealis.RTM. series manufactured by BASF
Thermoplastic Materials, Saint Paul, Minn., such as BA101E, BA110E,
BA122B, BA204E, BA202E, and BA124B; the Polypro.RTM. series
manufactured by Chisso America Inc., Schaumburg, Ill., such as
F1177 and F3020; the Noblen.RTM. series manufactured by Mitsubishi
Petrochemical Co. Ltd., Tokyo, Japan, such as MA8; the Astryn.RTM.
series manufactured by Montell USA Inc., Wilmington, Del., such as
68F4-4 and PD451; the Moplen.RTM. series manufactured by Montell
USA Inc., such as D 50S, D 60P, and D 78PJ; and the Pro-Fax.RTM.
series manufactured by Montell USA Inc., such as 6723, 6823, and
6824.
[0032] Sinterable thermoplastics in addition to those recited
herein can also be used in this invention. As those skilled in the
art are well aware, the ability of a thermoplastic to be sintered
can be determined from its melt flow index (MFI). Melt flow indices
of individual thermoplastics are known or can be readily determined
by methods well known to those skilled in the art. For example, the
extrusion plastometer made by Tinius Olsen Testing Machine Company,
Willow Grove, Pa., can be used. As discussed elsewhere herein, the
MFIs of thermoplastics suitable for use in this invention will
depend on the particular porous thermoplastic material and/or the
method used to prepare it. In general, however, the MFI of a
thermoplastic suitable for use in the materials and methods of the
invention is from about 0 to about 15, more preferably from about
0.2 to about 12, and most preferably from about 0.5 to about 10.
The temperatures at which individual thermoplastics sinter (i.e.,
their sintering temperatures) are also well known, or can be
readily determined by routine methods such as, but not limited to,
thermal mechanical analysis and dynamic mechanical thermal
analysis.
[0033] The novel materials of the invention next comprise at least
one antiviral or antimicrobial agent. Antiviral and antimicrobial
agents that can be used in the methods and materials of this
invention include agents that kill viruses or microbes as well as
agents that simply inhibit their growth or accumulation. For health
reasons, antiviral or antimicrobial agents that inhibit the growth
of microbes are preferably used for materials that are to be used
in, for example, consumer products.
[0034] Examples of antiviral and antimicrobial agents that can be
used in the materials and methods of the invention include, but are
not limited to, phenolic and chlorinated phenolic compounds,
resorcinol and its derivatives, bisphenolic compounds, benzoic
esters (parabens), halogenated carbonilides, polymeric
antimicrobial agents, thazolines, trichloromethylthioimides,
natural antimicrobial agents (also referred to as "natural
essential oils"), metal salts, and broad-spectrum antibiotics.
[0035] Specific phenolic and chlorinated phenolic antiviral and
antimicrobial agents that can be used in the invention include, but
are not limited to: phenol; 2-methyl phenol; 3-methyl phenol;
4-methyl phenol; 4-ethyl phenol; 2,4-dimethyl phenol; 2,5-dimethyl
phenol; 3,4-dimethyl phenol; 2,6-dimethyl phenol; 4-n-propyl
phenol; 4-n-butyl phenol; 4-n-amyl phenol; 4-tert-amyl phenol;
4-n-hexyl phenol; 4-n-heptyl phenol; mono- and poly-alkyl and
aromatic halophenols; p-chlorophenyl; methyl p-chlorophenol; ethyl
p-chlorophenol; n-propyl p-chlorophenol; n-butyl p-chlorophenol;
n-amyl p-chlorophenol; sec-amyl p-chlorophenol; n-hexyl
p-chlorophenol; cyclohexyl p-chlorophenol; n-heptyl p-chlorophenol;
n-octyl; p-chlorophenol; o-chlorophenol; methyl o-chlorophenol;
ethyl o-chlorophenol; n-propyl o-chlorophenol; n-butyl
o-chlorophenol; n-amyl o-chlorophenol; tert-amyl o-chlorophenol;
n-hexyl o-chlorophenol; n-heptyl o-chlorophenol; o-benzyl
p-chlorophenol; o-benxyl-m-methyl p-chlorophenol;
o-benzyl-m,m-dimethyl p-chlorophenol; o-phenylethyl p-chlorophenol;
o-phenylethyl-m-methyl p-chlorophenol; 3-methyl p-chlorophenol
3,5-dimethyl p-chlorophenol, 6-ethyl-3-methyl p-chlorophenol,
6-n-propyl-3-methyl p-chlorophenol; 6-iso-propyl-3-methyl
p-chlorophenol; 2-ethyl-3,5-dimethyl p-chlorophenol;
6-sec-butyl-3-methyl p-chlorophenol; 2-iso-propyl-3,5-dimethyl
p-chlorophenol; 6-diethylmethyl-3-methyl p-chlorophenol;
6-iso-propyl-2-ethyl-3-methyl p-chlorophenol;
2-sec-amyl-3,5-dimethyl p-chlorophenol;
2-diethylmethyl-3,5-dimethyl p-chlorophenol; 6-sec-octyl-3-methyl
p-chlorophenol; p-chloro-m-cresol p-bromophenol; methyl
p-bromophenol; ethyl p-bromophenol; n-propyl p-bromophenol; n-butyl
p-bromophenol; n-amyl p-bromophenol; sec-amyl p-bromophenol;
n-hexyl p-bromophenol; cyclohexyl p-bromophenol; o-bromophenol;
tert-amyl o-bromophenol; n-hexyl o-bromophenol;
n-propyl-m,m-dimethyl o-bromophenol; 2-phenyl phenol;
4-chloro-2-methyl phenol; 4-chloro-3-methyl phenol;
4-chloro-3,5-dimethyl phenol; 2,4-dichloro-3,5-dimethylphenol;
3,4,5,6-tetabromo-2-methylphenol- ; 5-methyl-2-pentylphenol;
4-isopropyl-3-methylphenol; para-chloro-metaxylenol (PCMX);
chlorothymol; phenoxyethanol; phenoxyisopropanol; and
5-chloro-2-hydroxydiphenylmethane.
[0036] Resorcinol and its derivatives can also be used as antiviral
or antimicrobial agents. Specific resorcinol derivatives include,
but are not limited to: methyl resorcinol; ethyl resorcinol;
n-propyl resorcinol; n-butyl resorcinol; n-amyl resorcinol; n-hexyl
resorcinol; n-heptyl resorcinol; n-octyl resorcinol; n-nonyl
resorcinol; phenyl resorcinol; benzyl resorcinol; phenylethyl
resorcinol; phenylpropyl resorcinol; p-chlorobenzyl resorcinol;
5-chloro-2,4-dihydroxydiphenyl methane;
4'-chloro-2,4-dihydroxydiphenyl methane;
5-bromo-2,4-dihydroxydiphenyl methane; and
4'-bromo-2,4-dihydroxydiphenyl methane.
[0037] Specific bisphenolic antiviral and antimicrobial agents that
can be used in the invention include, but are not limited to:
2,2'-methylene bis-(4-chlorophenol);
2,4,4'trichloro-2'-hydroxy-diphenyl ether, which is sold by Ciba
Geigy, Florham Park, N.J. under the tradename Triclosan.RTM.;
2,2'-methylene bis-(3,4,6-trichlorophenol); 2,2'-methylene
bis-(4-chloro-6-bromophenol); bis-(2-hydroxy-3,5-dichlorop- henyl)
sulphide; and bis-(2-hydroxy-5-chlorobenzyl)sulphide.
[0038] Specific benzoie esters (parabens) that can be used in the
invention include, but are not limited to: methylparaben;
propylparaben; butylparaben; ethylparaben; isopropylparaben;
isobutylparaben; benzylparaben; sodium methylparaben; and sodium
propylparaben.
[0039] Specific halogenated carbanilides that can be used in the
invention include, but are not limited to:
3,4,4'-trichlorocarbanilides, such as
3-(4-chlorophenyl)-1-(3,4-dichlorphenyl)urea sold under the
tradename Triclocarban.RTM. by Ciba-Geigy, Florham Park, N.J.;
3-trifluoromethyl-4,4'-dichlorocarbanilide; and
3,3',4-trichlorocarbanili- de.
[0040] Specific polymeric antiviral and antimicrobial agents that
can be used in the invention include, but are not limited to:
polyhexamethylene biguanide hydrochloride; and
poly(iminoimidocarbonyl iminoimidocarbonyl iminohexamethylene
hydrochloride), which is sold under the tradename Vantocil.RTM.
IB.
[0041] Specific thazolines that can be used in the invention
include, but are not limited to that sold under the tradename
Micro-Check.RTM.; and 2-n-octyl-4-isothiazolin-3-one, which is sold
under the tradename Vinyzene.RTM. IT-3000 DIDP.
[0042] Specific trichloromethylthioimides that can be used in the
invention include, but are not limited to:
N-(trichloromethylthio)phthali- mide, which is sold under the
tradename Fungitrol.RTM.; and
N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide, which is
sold under the tradename Vancide.RTM..
[0043] Specific natural antimicrobial agents that can be used in
the invention include, but are not limited to, oils of: anise;
lemon; orange; rosemary; wintergreen; thyme; lavender; cloves;
hops; tea tree; citronella; wheat; barley; lemongrass; cedar leaf;
cedarwood; cinnamon; fleagrass; geranium; sandalwood; violet;
cranberry; eucalyptus; vervain; peppermint; gum benzoin; basil;
fennel; fir; balsam; menthol; ocmea origanuin; hydastis;
carradensis; Berberidaceac daceae; Ratanhiae longa; and Curcuma
longa. Also included in this class of natural antimicrobial agents
are the key chemical components of the plant oils which have been
found to provide antimicrobial benefit. These chemicals include,
but are not limited to: anethol; catechole; camphene; thymol;
eugenol; eucalyptol; ferulic acid; farnesol; hinokitiol; tropolone;
limonene; menthol; methyl salicylate; carvacol; terpineol;
verbenone; berberine; ratanhiae extract; caryophellene oxide;
citronellic acid; curcumin; nerolidol; and geraniol.
[0044] Specific metal salts that can be used in the invention
include, but are not limited to, salts of metals in groups 3a-5a,
3b-7b, and 8 of the periodic table. Specific examples of metal
salts include, but are not limited to, salts of: aluminum;
zirconium; zinc; silver; gold; copper; lanthanum; tin; mercury;
bismuth; selenium; strontium; scandium; yttrium; cerium;
praseodymiun; neodymium; promethum; samarium; europium; gadolinium;
terbium; dysprosium; holmium; erbium; thalium; ytterbium; lutetium;
and mixtures thereof. A preferred metal-ion based antimicrobial
agent is sold under the tradename HealthShield.RTM., and is
manufactured by HealthShield Technology, Wakefield, Mass.
[0045] Specific broad-spectrum antimicrobial agents that can be
used in the invention include, but are not limited to, those that
are recited in other categories of antiviral or antimicrobial
agents herein.
[0046] Additional antiviral or antimicrobial agents that can be
used in the processes and materials of the invention include, but
are not limited to: pyrithiones, and in particular
pyrithione-including zinc complexes such as that sold under the
tradename Octopirox.RTM.; dimethyidimethylol hydantoin, which is
sold under the tradename Glydant.RTM.;
methylchloroisothiazolinone/methylisothiazolinone, which is sold
under the tradename Kathon CG.RTM.; sodium sulfite; sodium
bisulfite; imidazolidinyl urea, which is sold under the tradename
Germall 115.RTM.; diazolidinyl urea, which is sold under the
tradename Germall 11.RTM.; benzyl alcohol
v2-bromo-2-nitropropane-1,3-diol, which is sold under the tradename
Bronopol.RTM.; formalin or formaldehyde; iodopropenyl
butylcarbamate, which is sold under the tradename Polyphase
P100.RTM.; chloroacetamide; methanamine; methyldibromonitrile
glutaronitrile (1,2-dibromo-2,4-dicyanobutane), which is sold under
the tradename Tektamer.RTM.; glutaraldehyde;
5-bromo-5-nitro-1,3-dioxane, which is sold under the tradename
Bronidox.RTM.; phenethyl alcohol; o-phenylphenol/sodium
o-phenylphenol sodium hydroxymethylglycinate, which is sold under
the tradename Suttocide A.RTM.; polymethoxy bicyclic oxazolidine;
which is sold under the tradename Nuosept C.RTM.; dimethoxane;
thimersal; dichlorobenzyl alcohol; captan; chlorphenenesin;
dichlorophene; chlorbutanol; glyceryl laurate; halogenated diphenyl
ethers; 2,4,4'-trichloro-2'-hydroxy-diphenyl ether, which is sold
under the tradename Triclosan.RTM. and is available from
Ciba-Geigy, Florham Park, N.J.; and
2,2'-dihydroxy-5,5'-dibromo-diphenyl ether.
[0047] Additional antiviral and antimicrobial agents that can be
used in the materials and methods of the invention include those
disclosed by U.S. Pat. Nos. 3,141,321; 4,402,959; 4,430,381;
4,533,435; 4,625,026; 4,736,467; 4,855,139; 5,069,907; 5,091,102;
5,639,464; 5,853,883; 5,854,147; 5,894,042; and 5,919,554, all of
which are incorporated herein by reference.
[0048] Specific antiviral or antimicrobial agents that are
preferably used in the materials or methods of this invention
include, but are not limited to, those sold under the tradenames
Triclosan.RTM., Triclocarban.RTM., Vantocil.RTM. IB, and
HealthShield.RTM.. A particularly preferred antiviral or
antimicrobial agent is sold under the tradename Triclosan.RTM..
[0049] The porous virus- or microbe-resistant materials of the
invention can optionally comprise additional materials such as, but
not limited to, lubricants, colorants, and fillers. Examples of
fillers include, but are not limited to, carbon black, cellulose
fiber powder, siliceous fillers, polyethylene fibers and filaments,
and mixtures thereof. Specific polyethylene fibers and filaments
include, but are not limited to, those disclosed by U.S. Pat. Nos.
5,093,197 and 5,126,219, both of which are incorporated herein by
reference.
[0050] Using the materials described herein, the novel porous
thermoplastic media of the invention can be made using one of the
processes of the invention. In a first process of the invention, a
porous thermoplastic substrate is contacted with at least one
antiviral or antimicrobial agent. In a second process of the
invention, a porous thermoplastic substrate is contacted with a
coating mixture which comprises at least one antiviral or
antimicrobial agent. In a third process of the invention,
thermoplastic particles which comprise at least one antiviral or
antimicrobial agent are sintered together.
4.2. Coating- or Impregnation-Based Methods
[0051] In two processes of the invention, a porous thermoplastic
substrate is contacted with at least one antiviral or antimicrobial
agent. In a first process, an antiviral or antimicrobial agent
alone or in solution is contacted with the substrate, thereby
coating and/or impregnating at least part of the substrate with the
agent. In a second process, the porous substrate is contacted with
a coating mixture that comprises an antiviral or antimicrobial
agent and an additional material that will coat and/or impregnate
the porous substrate. In both methods, the porous substrate is
first prepared, preferably by sintering together thermoplastic
particles.
[0052] The thermoplastic particles used to provide a porous
substrate preferably have an average diameter of from about 5 .mu.M
to about 1000 .mu.M, more preferably from about 10 .mu.M to about
500 .mu.M, and most preferably from about 20 .mu.M to about 300
.mu.M. It is also preferred that the particles used to form the
porous substrate are all of about the same size. In other words, it
is preferred that the particles' size distribution be narrow (e.g.,
as determined using commercially available screens). It has been
found that particles of about the same size can be consistently
packed into molds. A narrow particle size distribution further
allows the production of a substrate with uniform porosity (i.e., a
substrate comprising pores that are evenly distributed throughout
it and/or are of about the same size). This is advantageous because
solutions and gases tend to flow more evenly through uniformly
porous filters and vents than through filters and vents which
contain regions of high and low permeability. Uniformly porous
substrates are also less likely to have structural weak spots than
substrates which comprise unevenly distributed pores of
substantially different sizes. In view of these benefits, if a
thermoplastic is commercially available in powder (i.e.,
particulate) form, it is preferably-screened prior to use to ensure
a desired average size and size distribution. However, most
thermoplastics are not commercially available in powder form, and
must therefore be converted into powder form by methods well known
to those skilled in the art such as, but not limited to, cryogenic
grinding and underwater pelletizing.
[0053] Cryogenic grinding can be used to prepare thermoplastic
particles of varying sizes. But because cryogenic grinding provides
little control over the sizes of the particles it produces, powders
formed using this technique may be screened to ensure that the
particles to be sintered are of a desired average size and size
distribution.
[0054] Underwater pelletizing can also be used to form
thermoplastic particles suitable for sintering. Although typically
limited to the production of particles having diameters of greater
than about 36 .mu.M, underwater pelletizing offers several
advantages. First, it provides accurate control over the average
size of the particles produced, in many cases thereby eliminating
the need for an additional screening step and reducing the amount
of wasted material. A second advantage of underwater pelletizing,
which is discussed further herein, is that it allows significant
control over the particles' shape.
[0055] Underwater pelletizing is described, for example, in U.S.
patent application Ser. No. 09/064,786, filed Apr. 23, 1998, and
U.S. provisional patent application No. 60/044,238, filed Apr. 24,
1999, both of which are incorporated herein by reference.
Thermoplastic particle formation using underwater pelletizing
typically requires an extruder or melt pump, an underwater
pelletizer, and a drier. The thermoplastic resin is fed into an
extruder or a melt pump and heated until semi-molten. The
semi-molten material is then forced through a die. As the material
emerges from the die, at least one rotating blade cuts it into
pieces herein referred to as "pre-particles." The rate of extrusion
and the speed of the rotating blade(s) determine the shape of the
particles formed from the pre-particles, while the diameter of the
die holes determine their average size. Water, or some other liquid
or gas capable of increasing the rate at which the pre-particles
cool, flows over the cutting blade(s) and through the cutting
chamber. This coagulates the cut material (i.e., the pre-particles)
into particles, which are then separated from the coolant (e.g.,
water), dried, and expelled into a holding container.
[0056] The average size of particles produced by underwater
pelletizing can be accurately controlled and can range from about
0.014" (35.6 .mu.M) to about 0.125" (318 .mu.M) in diameter,
depending upon the thermoplastic. Average particle size can be
adjusted simply by changing dies, with larger pore dies yielding
proportionally larger particles. The average shape of the particles
can be optimized by manipulating the extrusion rate and the
temperature of the water used in the process.
[0057] While the characteristics of a porous material can depend on
the average size and size distribution of the particles used to
make it, they can also be affected by the particles' average shape.
Consequently, in another embodiment of the invention, the
thermoplastic particles are substantially spherical. This shape
provides specific benefits. First, it facilitates the efficient
packing of the particles within a mold. Second, substantially
spherical particles, and in particular those with smooth edges,
tend to sinter evenly over a well defined temperature range to
provide a final product with desirable mechanical properties and
porosity.
[0058] In a specific embodiment of the invention, the thermoplastic
particles are substantially spherical and free of rough edges.
Consequently, if the thermoplastic particles used in this preferred
method are commercially available, they are thermal fined to ensure
smooth edges and screened to ensure a proper average size and size
distribution. Thermal fining, which is well known to those skilled
in the art, is a process wherein particles are rapidly mixed and
optionally heated such that their rough edges become smooth. Mixers
suitable for thermal fining include the W series high-intensity
mixers available from Littleford Day, Inc., Florence, Ky.
[0059] Thermoplastic particles made using cryogenic grinding are
likewise preferably thermal fined to ensure smooth edges and
screened to ensure a proper average size and size distribution.
Advantageously, however, if the particles are made using underwater
pelletizing, which allows precise control over particle size and
typically provides smooth, substantially spherical particles,
subsequent thermal fining and screening need not be performed.
[0060] Once thermoplastic particles of a desired average size
and/or shape have been obtained, they are optionally combined with
additional materials such as, but not limited to, lubricants,
colorants, and fillers such as those described above in Section
4.1. As those skilled in the art will recognize, the types and
amounts of optional materials incorporated into a porous substrate
will typically depend on the application for which the final
antiviral or antimicrobial material will be used.
[0061] After the thermoplastic particles and optional additional
materials have been blended, preferably to provide a uniform
mixture, the mixture is sintered. Depending on the desired size and
shape of the final product (e.g., a block, tube, cone, cylinder,
sheet, or membrane), this can be accomplished using a mold, a belt
line such as that disclosed by U.S. Pat. No. 3,405,206, which is
hereby incorporated by reference, or using other techniques known
to those skilled in the art. In a preferred embodiment of the
invention, the mixture is sintered in a mold. Suitable molds are
commercially available and are well known to those skilled in the
art. Specific examples of molds include, but are not limited to,
flat sheets with thickness ranging from about 1/8 inch to about 0.5
inch, round cylinders of varying heights and diameters, and small
conical parts molded to fit snugly into a pipette tip. Suitable
mold materials include, but are not limited to, metals and alloys
such as aluminum and stainless steel, high temperature
thermoplastics, and other materials both known in the art and
disclosed herein.
[0062] In a specific preferred embodiment of the invention, a
compression mold is used to provide the sintered material. In this
embodiment, the mold is heated to the sintering temperature,
allowed to equilibrate, and then subjected to pressure. This
pressure typically ranges from about 1 psi to about 10 psi,
depending on the composition of the mixture being sintered and the
desired porosity of the final product. In general, the greater the
pressure applied to the mold, the smaller the average pore size and
the greater the mechanical strength of the final product. The
duration of time during which the pressure is applied also varies
depending on the desired porosity of the final product, and is
typically from about 2 to about 10, more typically from about 4 to
about 6 minutes. In another embodiment of the invention, the
thermoplastic particles are sintered in a mold without the
application of pressure.
[0063] Once the porous substrate has been formed, the mold is
allowed to cool. If pressure has been applied to the mold, the
cooling can occur while it is still being applied or after it has
been removed. The substrate is then removed from the mold and
optionally processed. Examples of optional processing include, but
are not limited to, sterilizing, cutting, milling, polishing,
encapsulating, and coating. The substrate is then coated and/or
impregnated with at least one antiviral or antimicrobial agent, or
a mixture comprising at least one antiviral or antimicrobial agent,
as described below in Section 4.2.1 or 4.2.2.
4.2.1. Use of an Antiviral or Antimicrobial Agent Alone or in
Solution
[0064] In a first method of the invention, the porous thermoplastic
substrate is contacted with the antiviral or antimicrobial agent or
a mixture which comprises it. Any method of coating or impregnation
known to those skilled in the art can be used. For example, the
thermoplastic substrate can be dipped or immersed in a liquid
antiviral or antimicrobial agent, or in a solution comprising an
antiviral or antimicrobial agent, and then allowed to dry.
Alternatively, an antiviral or antimicrobial agent or a solution
comprising an antiviral or antimicrobial agent can be sprayed onto
the substrate.
[0065] The resulting porous thermoplastic coated or impregnated
material is then optionally further processed. Examples of further
processing include, but are not limited to, sterilizing, cutting,
milling, polishing, encapsulating, and coating.
[0066] 4.2.2. Coating or Impregnating with a Coating Mixture
[0067] In a second process of the invention, the porous substrate
is contacted with a coating mixture that comprises an antiviral or
antimicrobial agent and an additional material that will coat
and/or impregnate the porous substrate. Thus, one embodiment of the
invention provides a product with a porous thermoplastic core
surround at least in part by a coating layer which comprises an
antiviral or antimicrobial agent.
[0068] This second process of the invention provides several
advantages. First, it allows higher concentrations of antiviral or
antimicrobial agent to be located near or on the surface of the
final product. This can, for example, allow for a rapid release of
the agent into the surrounding environment. Second, this process
can used to minimize the difference between the surface energy of
the porous substrate and the layer of antiviral or antimicrobial
agent that covers at least part of it. Third, the process allows
certain porous substrates to be coated with antiviral or
antimicrobial agents that would otherwise not adhere to those
substrates.
[0069] Examples of additional materials that can be combined with
an antiviral or antimicrobial agent according to this process
include thermoplastics such as those disclosed herein and
hydrogels. Examples of hydrogels that can be used in this invention
include those disclosed in U.S. patent application Ser. No.
09/305,083, filed May 4, 1999, which is incorporated herein by
reference. Preferred additional materials are polyurethanes or
derivatives thereof, and hydrophilic polyurethane in
particular.
[0070] In a specific embodiment, the coating mixture is, or
comprises, a commercially available thermoplastic resin which
already comprises an antiviral or antimicrobial agent, such as
those described below in Section 4.3.
[0071] The porous substrate can be contacted with the antiviral or
antimicrobial mixture using any techniques known to those skilled
in the art, including those described in Section 4.2.1 above. After
the porous thermoplastic substrate has been contacted with the
antiviral or antimicrobial mixture such that the mixture coats
and/or impregnates at least part of the substrate, the resulting
material can be dried, cured or otherwise treated. For example,
chemical or radiation-induced crosslinking of the molecules within
the coating mixture can be used to form a hard, durable
coating.
[0072] The resulting porous thermoplastic coated or impregnated
material is then optionally further processed. Examples of further
processing include, but are not limited to, sterilizing, cutting,
milling, polishing, encapsulating, and coating.
4.3. Sintering-Based Impregnation and Coating Methods
[0073] In a third process of the invention, an antiviral or
antimicrobial agent is incorporated into the porous thermoplastic
substrate during, rather than after, the sintering process. This
process provides several advantages. First, it can be used to
locate antiviral or antimicrobial agents within the porous
material, and in particular at places or depths within the material
that may be inaccessible using dipping or coating methods. Second,
this process can be used to ensure that the distribution of
antiviral or antimicrobial agent(s) within the final material is
uniform; e.g., that the density of an antiviral or antimicrobial
agent is uniform throughout the material. A third advantage of this
process is that it can be used to trap large antiviral or
antimicrobial agents within pores that have small openings, as well
as large amounts of antiviral or antimicrobial agents. A final
advantage of this process is that it allows the use of commercially
available concentrates that already contain antiviral or
antimicrobial agents.
[0074] This process of the invention comprises the sintering of
thermoplastic particles which comprise at least one antiviral or
antimicrobial agent (referred to herein as "thermoplastic antiviral
or antimicrobial particles" or "PAA particles"), optionally with
thermoplastic particles which do not comprise antiviral or
antimicrobial agents and/or additional materials such as those
described above in Section 4.1.
[0075] In a first specific embodiment of this process, a
thermoplastic resin comprising at least one antiviral or
antimicrobial agent is cryogenically ground and optionally screened
and/or thermal fined to provide particles which can be sintered as
described above in Section 4.2. In a specific embodiment of this
process, each of the PAA particles is approximately the same size.
In another specific embodiment of this process, the PAA particles
are substantially spherical.
[0076] Thermoplastic resins which comprise antiviral or
antimicrobial agents (herein referred to as "PAA resins") such as
Microban.RTM. 4010-100 are commercially available from, for
example, Microban Products Company, Huntersville, N.C. Because
these resins typically contain large amounts of antiviral or
antimicrobial agents, it may be desirable to combine PAA particles
formed from them with other thermoplastic particles that do not
contain antiviral or antimicrobial agents in order to provide
porous materials with lower average concentrations of antiviral or
antimicrobial agent. In such cases, it is preferred that the
thermoplastic particles are of about the same size as the PAA
particles. In some cases, it may also be preferred that all of the
particles to be sintered are substantially spherical. As discussed
above in Section 4.2, this can help provide a final product having
uniform porosity and good mechanical characteristics.
[0077] If the PAA particles are combined with particles of other
thermoplastics and/or other materials such as lubricants, colorants
and fillers, it is preferred that the combination be mixed to
ensure that the components are evenly distributed. The resulting
mixture is then sintered to provide a porous material that resists
the accumulation or growth of viruses and/or microbes.
[0078] Suitable sintering conditions are known in the art and
include, for example, those described above in Section 4.2.
However, because some antiviral or antimicrobial agents may
decompose under particular sintering conditions, those skilled in
the art will recognize that the thermoplastic, the sintering
conditions, and/or the antiviral or antimicrobial agent will have
to be selected to provide a porous thermoplastic product of the
invention that is capable of resisting the growth or accumulation
of viruses or microbes to a desired degree. For example, a
thermoplastic with a low MFI or sintering temperature can be
selected such that the sintering temperature will not cause the
decomposition of a desired antiviral or antimicrobial agent.
Alternatively, a temperature-resistant antiviral or antimicrobial
agent (e.g., a metal-ion based agent such as HealthShield.RTM.) may
be selected if the preferred thermoplastic sinters only at high
temperatures.
[0079] In a second specific embodiment of this process, PAA
particles are formed by underwater pelletizing. Although typically
not necessary, the resulting PAA particles can optionally be
screened and/or thermal fined. Underwater pelletizing can be used
to provide PAA particles from commercially available PAA resins,
from mixtures comprising at least one thermoplastic and at least
one antiviral or antimicrobial agent, and from mixtures
thereof.
[0080] An advantage of sintering PAA particles formed by underwater
pelletizing is that the antiviral or antimicrobial agent(s) within
the particles thus formed are typically located near or on the
surfaces of the particles. Without being limited by theory, this is
believed to be due to a phenomenon known as "surface segregation,"
wherein antiviral or antimicrobial agents combined with molten
thermoplastic(s) move to the surface of the pellets during or after
their formation. Materials formed by sintering such PAA particles
will thus contain significant amounts of antiviral or antimicrobial
agents near or on the walls of the pores they contain, since these
pore walls are formed by the particles' surfaces. Consequently,
this method can be used to provide materials which comprise
antiviral or antimicrobial agents that are located where they will
most likely come into contact with viruses and/or microbes.
[0081] Because this process can be used to position antiviral or
antimicrobial agents within porous materials at locations where
they are most effective, it can be used to avoid the inefficient,
expensive, and potentially hazardous overuse of antiviral or
antimicrobial agents typical of prior methods of producing viral-
or microbe-resistant materials. For this reason, it may be
preferable to limit the concentration of antiviral or antimicrobial
agent in the final product by forming PAA particles from a
thermoplastic mixture made only in part from commercially available
PAA resin. Alternatively, PAA particles can be made solely by
combining the necessary amount of antiviral or antimicrobial
agent(s) with at least one conventional thermoplastic resin (i.e.,
a resin free of antiviral or antimicrobial agents).
[0082] As discussed above, if PAA particles are formed from a
mixture comprised of at least one thermoplastic and at least one
antiviral or antimicrobial agent, it is important to select the
thermoplastic(s) and antiviral or antimicrobial agent(s) to ensure
that at least a substantial portion of the antiviral or
antimicrobial agent(s) will not decompose during the underwater
pelletizing or sintering processes. This is easily done, however,
as the decomposition temperatures of individual antiviral or
antimicrobial agents are well known or can readily be determined by
conventional means. For example, an antiviral or antimicrobial
agent can be heated to a specific temperature (e.g., the
temperature at which the thermoplastic melts) and then allowed to
cool, after which its antiviral or antimicrobial activity can be
measured.
[0083] The flexibility of the processes of this invention allow the
production of porous materials using innumerable thermoplastics and
antiviral or antimicrobial agents. This and other novel and
unexpected advantages of the invention are further illustrated by
the following non-limiting examples.
5. EXAMPLES
5.1. Example 1
Antimicrobial Coated Porous Media Using Polyurethane as a
Carrier
[0084] A polyurethane solution was prepared by mixing
Pellethane.RTM., supplied by Dow Chemical, with isopropanol as a
solvent. The concentration of the polyurethane solution was
adjusted around 5 weight percent. After a transparent solution was
formed, Triclosan.RTM. was added into the solution to obtain a
concentration of 1 weight percent.
[0085] A porous polyethylene sheet having median pore size of 30
.mu.m (part number X-4711, available from Porex Corporation,
Fairburn, Ga.) was dipped into the prepared polyurethane solution
for more than 1 minute, after which the sheet was placed in a
conventional or vacuum oven to allow the solvent evaporated
completely. The dried product had a thin layer of polyurethane
without an obvious change of pore size and porosity.
5.2. Example 2
Antimicrobial Coated Porous Media Using Polyurethane Hydrogel as a
Carrier
[0086] A polyurethane hydrogel was synthesized according to Example
1 of U.S. patent application Ser. No. 09/375,383, filed Aug. 17,
1999, which is incorporated herein by reference. The polyurethane
solution was prepared by mixing the hydrogel with methanol as a
solvent. The concentration of the polyurethane solution was
adjusted around 0.5 weight percent. After a light yellowish
solution was formed, Triclosan.RTM. was added into the solution to
obtain a concentration of 1 weight percent.
[0087] A similar porous polyethylene sheet as described in Example
1 was submerged into the solution for more than 1 minute, then the
oven-dried. The dried part is coated with a thin layer of hydrogel,
which when exposed to water will swell to certain degree depending
on the hydrophilicity of the polyurethane hydrogel. Advantageously,
this swelling was not sufficient to seal the pores of the
polyethylene substrate.
5.3. Example 3
Antimicrobial Concentrates Incorporated Porous Media
[0088] Microban.RTM. 4010-100 concentrate in pellet form was
cryogenically ground in a WEDCO SE-12-L disk mill. The resulting
microban powder, which had a median particle size of about 100 mesh
(150 .mu.m), was mixed with an ultra high molecular weight
polyethylene (GUR 2122 from Ticona) via dry blending in a 2:8
weight ratio. Since the concentrates powder and GUR powder have the
similar particle size, the thorough mixing and uniform distribution
of the concentrates was expected. After the mixture was well
blended, it was placed into a 0.25 inch flat mold. The mold was
heated to 160.degree. C. using electricity-heated plate for 4
minutes. After heating, the mold is cooled and the sintered porous
sheet removed from it.
5.4. Example 4
Porous Media Made from Underwater Pelletized Powder
[0089] Micropellets were made from H8EFA1 poly(ethylene vinyl
acetate) (EVA; MFI=1.5) supplied by Equistar Chemicals, Houston,
Tex., using extruder equipped with a SLC-5 LPU underwater
pelletizer available from Gala Industries, Inc., Winfield, W.V.
Before extrusion, the EVA was premixed with Microban.RTM. 4010-100
concentrate in a weight ratio of 8:2. The extruder used has three
thermal zones set to 150.degree. C., 165.degree. C., and
180.degree. C. The underwater pelletizer was fit with a die with
0.020 inch holes drilled into it. The EVA was extruded through the
die and into the cutter of the underwater pelletizer, which was
rotating at 90-100 rpm to produce a powder of 50 mesh (300 micron)
diameter pellets.
[0090] The pellets were then dried and placed into a 0.25 inch flat
mold. The mold was heated to 140.degree. C. using
electricity-heated plate for 4 minutes. After heating, the mold was
cooled and the sintered porous sheet removed from it.
5.5. Example 5
Carbon Black Incorporated Porous Media
[0091] As described in Example 3, Microban.RTM. concentrates were
cryogenically ground to 200 mesh, then dried and mixed with carbon
black (Cabot Corporation, Special Black Division; average particle
size of about 30 .mu.m) and ultra high molecular weight
polyethylene (GUR 2122, available from Ticona Inc.) in a ratio of
5:10:85, respectively. After the three types of powder were
thoroughly mixed, the mixture was fed into a 0.25 inch flat mold.
The mold is heated to 140.degree. C. using electricity-heated plate
for 4 minutes. After heating, the mold was cooled and the sintered
porous sheet removed from it.
[0092] The embodiments of the invention described above are
intended to be merely exemplary, and those skilled in the art will
recognize, or will be able to ascertain using no more than routine
experimentation, numerous equivalents of the specific materials,
procedures, and devices described herein. All such equivalents are
considered to be within the scope of the invention and are
encompassed by the appended claims.
* * * * *