U.S. patent application number 11/710290 was filed with the patent office on 2008-01-31 for removable antimicrobial coating compositions and methods of use.
Invention is credited to Christian Hoffmann, Lynn Leger, Christian Peter Lenges, Helen S.M. Lu, Shaun F. Malone, Barry Stieglitz, Judith Johanna VanGorp.
Application Number | 20080026026 11/710290 |
Document ID | / |
Family ID | 38326198 |
Filed Date | 2008-01-31 |
United States Patent
Application |
20080026026 |
Kind Code |
A1 |
Lu; Helen S.M. ; et
al. |
January 31, 2008 |
Removable antimicrobial coating compositions and methods of use
Abstract
This invention relates to a method for controlling
microorganisms comprising coating a surface with a removable,
antimicrobial film-forming composition.
Inventors: |
Lu; Helen S.M.;
(Wallingford, PA) ; Hoffmann; Christian; (Newark,
DE) ; Lenges; Christian Peter; (Wilmington, DE)
; Stieglitz; Barry; (Wynnewood, PA) ; Leger;
Lynn; (Mississauga, CA) ; VanGorp; Judith
Johanna; (Wilmington, DE) ; Malone; Shaun F.;
(Ajax, CA) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
38326198 |
Appl. No.: |
11/710290 |
Filed: |
February 23, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60776081 |
Feb 23, 2006 |
|
|
|
60831983 |
Jul 19, 2006 |
|
|
|
Current U.S.
Class: |
424/405 ;
422/28 |
Current CPC
Class: |
C09D 5/1625 20130101;
A23V 2002/00 20130101; C09D 5/14 20130101; A61L 2/232 20130101;
C09D 5/008 20130101; A23L 3/3526 20130101; C09D 5/1668 20130101;
A61K 9/7015 20130101; A01N 33/12 20130101 |
Class at
Publication: |
424/405 ;
422/028 |
International
Class: |
A01N 25/00 20060101
A01N025/00; A01P 1/00 20060101 A01P001/00; A61L 2/00 20060101
A61L002/00 |
Claims
1. A method of providing control of microorganisms at a locus
comprising a) providing a removable liquid coating composition
comprising: i) a film-forming water soluble or water-dispersible
agent; ii) at least one antimicrobial agent; and iii) an inert
solvent; b) applying said composition to the locus whereby a
coating is formed; and c) removing said coating with an aqueous
solution at a temperature of about 15.degree. C. to about
100.degree. C.
2. The method of claim 1, wherein the surface tension of the liquid
coating composition is below 40 mN/m.
3. The method of claim 1, wherein the composition is applied to the
locus by spraying or aerosolizing.
4. The method according to claim 1, wherein said film-forming agent
is one or more polyvinyl alcohols and copolymers thereof, polyvinyl
pyrrolidones, polyacrylic acid, acrylate copolymers, ionic
hydrocarbon polymers, and polyurethanes or combinations
thereof.
5. The method according to claim 4, wherein said polymer is
polyvinyl alcohol and copolymers thereof.
6. The method of claim 1, wherein said locus is the surface of one
or more: tanks, conveyors, floors, drains, coolers, freezers,
refrigerators, equipment surfaces, walls, valves, belts, pipes,
joints, crevasses, a building surface, kitchen surface, an
inanimate surface found in a food processing facility, veterinary
or animal care facility, animal care equipment, or animal husbandry
or hatchery facility, the surface of a hospital or surgery center
wall, bed, equipment, textile worn in a hospital or other
healthcare setting, including scrubs, shoes, and other hospital
surfaces.
7. The method of claim 6, wherein said surface comprises one or
more metals selected from the group consisting of aluminum, steel,
stainless steel, chrome, titanium, iron, alloys and mixtures
thereof.
8. The method of claim 6, wherein said surface comprises one or
more plastic material selected from the group consisting of
polyolefins, including polyethylene, polypropylene, polystyrene
polymethacrylate, polymethylmethacrylate, acrylonitrile, butadiene,
ABS, acrylonitrile butadiene; polyesters, including polyethylene
terephthalate; and polyamides, including nylon; and combinations
thereof.
9. The method of claim 6, wherein said surface is brick, tile,
ceramic, porcelain, wood, vinyl, linoleum, carpet, paper, leather,
combinations thereof, and the like.
10. The method of claim 1 wherein said locus is an inanimate
surface comprised of metals, minerals, polymers, plastics, fibrous
substrates or non-wovens, or mixtures thereof, or coated or painted
surfaces.
11. The method claim 1, wherein said aqueous solution consists
essentially of water; water and an acid; or water and a base; or
water and a detergent.
12. The method of claim 5, wherein said polyvinyl alcohol has an
average degree of hydrolysis from 70-96 mole-percent.
13. The method of claim 5, wherein said polyvinyl alcohol has an
average degree of hydrolysis from 85-90 mole-percent.
14. The method according to claim 4, wherein said film-forming
agent has molecular weight ranging from about 4,000-186,000.
15. The method of claim 1, wherein said inert solvent is water.
16. The method of claim 1, wherein said liquid coating composition
further comprises, one or more plasticizer, surfactant,
cross-linking agent, colorant, solubilizing agent, rheology
modifier, antioxidant, pH adjuster, wetting agent, antifoaming
agent, extender, lubricant, processing aid, color fastness agent
and film performance enhancer or one or more enzymes.
17. The method of claim 6, wherein said locus is a food processing
equipment surface.
18. The method of claim 17, wherein said food processing surface is
the surface of one or more of tanks, conveyors, floors, drains,
coolers, freezers, equipment surfaces, walls, valves, belts, pipes,
joints, crevasses, or combinations thereof.
19. The method of claim 1, wherein said locus is a food surface,
including one or more of beef, poultry, pork, vegetables, fruits
and seafood.
20. The method of claim 1, wherein said coating is a barrier to
microbial contamination.
21. The method of claim 1, wherein said at least one antimicrobial
agent is one more antibacterial, fungicide, fungistat, moldicide,
mildewcide, antiseptic, disinfectant, sanitizer, germicide,
algicide, or antifouling agent.
22. The method of claim 1, wherein said antimicrobial agent is one
or more quaternary ammonium compound or mixtures thereof.
23. The method of claim 1, wherein said removal is performed by
spraying or washing said locus.
24. The method of claim 1, wherein the coating provides a reduction
of microorganisms of at least 3-log when applied to a contaminated
surface.
25. The method of claim 24, wherein the coating provides a
reduction of microorganisms of at least 5-log when applied to a
contaminated surface.
26. The method of claim 1, wherein the coating prevents growth of
at least one type of microorganism at said locus.
27. The method of claim 1, wherein the control of microorganisms at
said locus comprises a reduction of microorganisms harbored in a
biofilm.
28. The method of claim 1, wherein said coating is substantially
continuous and homogenous.
29. The method of claim 28, wherein said coating has a thickness of
about 0.3 to about 300 microns.
30. The method of claim 29, wherein said coating has a thickness of
about 0.5 to about 100 microns.
31. A removable food-processing shut-down spray composition
comprising: i) a film-forming water soluble or water-dispersible
agent; ii) at least one or more antimicrobial agent; iii) an inert
solvent; and iv) optionally, one or more plasticizer, surfactant,
cross-linking agent, colorant, solubilizing agent, rheology
modifier, antioxidant, pH adjuster, wetting agent, antifoaming
agent, extender, lubricant, processing aid, colorfastness agent,
film performance enhancer or enzymes; wherein said composition is
durable and removable when subjected to an aqueous solution
treatment above 15.degree. C.
32. The composition of claim 31, wherein said composition comprises
a surfactant that provides a surface tension of about 20 to about
50 mN/m.
33. The composition of claim 32, wherein said surfactant is an
organo-silicone.
34. The composition of claim 32, wherein said surfactant is at a
concentration of about 0.01 wt % to about 1.0 wt % of the
composition.
35. The composition of claim 31, wherein said composition comprises
a rheology control agent that provides shear thinning properties to
the composition.
36. The composition of claim 31, wherein said composition provides
a reduction of microorganisms of at least 3-log when applied to a
contaminated food processing surface.
37. The composition of claim 31, wherein said composition is a
disinfectant, sanitizer, preservative, or physical barrier to
contamination when applied to a contaminated surface and wherein
said composition is capable of residual antimicrobial efficacy when
applied to a contaminated surface that is subject to subsequent
contamination.
38. The composition of claim 31, wherein said film-forming agent is
one or more polyvinyl alcohols and copolymers thereof, including
polyvinyl pyrrolidones, polyacrylic acid, acrylate copolymers,
ionic hydrocarbon polymers, and polyurethanes or combinations
thereof.
39. The method of claim 31, wherein said at least one antimicrobial
agent is an antibacterial, fungicide, fungistat, moldicide,
mildewcide, antiseptic, disinfectant, sanitizer, germicide,
algicide, or antifouling agent.
Description
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/776,081, filed Feb. 23, 2006 and U.S.
Provisional Application No. 60/831,983 filed Jul. 19, 2006, both of
which are incorporated by reference herein for all purposes as if
fully set forth.
FIELD OF THE INVENTION
[0002] This invention relates to a method for controlling
microorganisms comprising coating a surface with a removable,
antimicrobial film-forming composition, durable and readily
removable antimicrobial compositions, and methods of applying said
compositions.
BACKGROUND
[0003] The present invention relates to a method for providing
control of microorganisms at a locus by contacting said locus with
a removable coating composition comprising at least one
antimicrobial agent.
[0004] An area of particular concern for controlling microorganism
contamination relates to food processing. Microbial contamination
of food represents one of the major United States and worldwide
public health problems. The actual incidence of microbial
food-borne illness is unknown, but the CDC estimates it to be
between 7 to 81 million illnesses per year, with over 325,000
hospitalizations, and 5,000 deaths in the U.S. annually. The costs
of human illness in the U.S. due to food-borne pathogens are in the
billion of dollars annually. In addition to the toll of illness and
death, contaminated food represents a huge economic loss for many
food-processing plants.
[0005] Current stringent sanitation procedures in food processing
plants are effective in reducing the incidence of microbial
contamination of food, but have not prevented the occurrence of
serious outbreaks resulting in death and disability. These
procedures are costly in terms of materials and in terms of time
and effort put into practicing the procedures effectively. In
addition, problems caused by microbial contamination of foods tend
to be expensive; particularly if these result in consumer
recalls.
[0006] Poor sanitation of food contact surfaces, equipment, and
processing environments has been a contributing factor in
food-borne disease outbreaks, especially those involving Listeria
monocytogenes and Salmonella enterocolitis. Improperly cleaned
surfaces promote soil buildup, and, in the presence of water,
contribute to the development of bacterial biofilms, which may
contain pathogenic microorganisms. Cross contamination occurs when
food passes over contaminated surfaces or via exposure to aerosols
or condensate that originate from contaminated surfaces (R. A. N.
Chmielewski and J. F. Frank "Biofilm Formation and Control in Food
Processing Facilities" in Comprehensive Reviews in Food Science and
Food Safety, 2003, 2, 22-32; Boulange-Petermann, Laurence.
Biofouling, 1996, 10, 275-300). Factors, such as the type of food
contact surface and topography, play a significant role in the
inability to decontaminate a surface. Abraded surfaces accumulate
soil and are more difficult to clean than smooth surfaces. Surface
defects further complicate the removal of soil and microbes,
resulting in microbial growth even after attempts at
decontamination and, potentially, biofilm formation due to said
growth. (Boulange-Petermann, supra; D. A. Timperley, R. H. Thorpe,
and J. T. Holah "Implications of Engineering Design in Food
Industry Hygiene" in Biofilms--Science and Technology, 35-41, L. F.
Melo et al. (eds.), Kluwear Academic Publishers, 1992, Netherlands;
J. T. Holah, R. H. Thorpe, J. Applied Bacteriology, 1990, 69,
599-608).
[0007] Moreover, microbes within a biofilm are more resistant to
disinfectants, which may assist the survival of Listeria and other
food-borne pathogens in the food processing environment (J. F.
Frank, R. A. Koffi, J. Food Protection, 1990, 53, 550-554; E. P.
Krysinski, L. J. Brown, and T. J. Marchisello, J. Food Protection,
1992, 55, 246-251). Hence, proper control methods for biofilms are
necessary for a safe food processing operation.
[0008] Microbial contamination is of particular concern when the
food processing equipment is either shut-down or temporarily not in
operation or use. This is in fact an opportune time for biofilm
formation, especially on parts of equipment that are hard to reach
with disinfectants, as described above. Currently, practices to
avoid contamination during such shutdown periods involves
multi-step approaches for disinfection prior to restart-up of
processing, including disinfecting, coating, and removing any
potentially harmful disinfectant with other solutions that often
include other harsh means or components. These approaches are
costly and may be of questionable efficacy. Thus, there is a need
for a method to better address protection against microbial
contamination during such shutdown periods. Moreover, in addition
to the food industry, there are several other industries that could
benefit from a disinfectant composition capable of forming a
durable, yet easily removable, antimicrobial coating that provides
the appropriate protection. The appropriate protection is achieved
by certain characteristics of the coating, such as good spreading
and surface tension control.
[0009] Good spreading of the liquid antimicrobial formulation onto
the surface after application is beneficial in achieving a
homogeneous and continuous film, especially when spraying or
aerosolizing is used as the application method. Good spreading
properties can enhance the antimicrobial properties of an
antimicrobial formulation by achieving complete surface coverage
without leaving uncovered gaps in the created antimicrobial film or
coating. These gaps allow for growth of microorganisms.
Antimicrobial properties can further be enhanced by the reduced
surface tension by allowing the liquid antimicrobial formulation to
flow into surface imperfections known to harbor microorganisms.
[0010] U.S. Pat. No. 5,585,407 provides water-based coating
compositions that can be applied to a substrate to inhibit growth
of microbes for extended periods of time. The coating comprises an
acrylate emulsion polymer and an organoalkoxysilane and can be
removed under alkaline conditions.
[0011] U.S. Pat. No. 5,017,369 provides a prophylactic treatment of
mastitis in a cow between milkings comprising coating the cow teats
with an aqueous composition comprising an antimicrobial agent. The
composition comprises at least 2 wt % partially hydrolyzed
polyvinyl alcohol, from about 0 wt % to about 10 wt % of an
opacifier, about 0.1 wt % to about 10 wt % of an antimicrobial
agent, and at least 65 wt % water. A water wash is used to remove
the film from the cow teat prior to milking.
[0012] Thus, a need exists for a disinfectant composition capable
of forming a durable yet easily removable film or coating on
surfaces, such as hard surfaces formed of ceramics, glass, formica,
plastics, metals and the like, which film can entrain germicidal
substances such as a quaternary ammonium compound or a phenolic
compound. A further need exists for a disinfectant film or coating
providing extended protection against microbial contamination.
Additionally a need exists for easily removable long-lasting,
homogeneous and continuous films or coatings that can be applied on
a variety of surfaces. None of the above methods and coatings
applied in said methods provide for a durable and yet readily
removable coating composition for coating surfaces described
herein. Thus, the problem to be solved is the lack of a method for
controlling microorganisms at a particular locus with a coating
composition, comprising at least one antimicrobial agent, wherein
said coating is durable, provides residual antimicrobial efficacy
and is readily removable.
SUMMARY
[0013] The present invention addresses the problems identified
above with the following methods and compositions.
[0014] An aspect of this invention is directed to a method of
providing control of microorganisms at a locus comprising [0015] a)
providing a removable liquid coating composition comprising: [0016]
i) a film-forming water soluble or water-dispersible agent; [0017]
ii) at least one antimicrobial agent; and [0018] iii) an inert
solvent; [0019] b) applying said composition to the locus whereby a
coating is formed; and [0020] c) removing said coating with an
aqueous solution at a temperature of about 15.degree. C. to about
100.degree. C.
[0021] In another aspect, the surface tension of the liquid coating
composition described herein is below 40 mN/m.
[0022] In another aspect, the film-forming agent in the above
method is one or more polyvinyl alcohols and copolymers thereof,
including polyvinyl pyrrolidones, polyacrylic acid, acrylate
copolymers, ionic hydrocarbon polymers, and polyurethanes or
combinations thereof.
[0023] In another aspect, the coating formed by the methods herein
provides a reduction of microorganisms of at least 3-log when
applied to a contaminated surface.
[0024] In another aspect, the coating provides a reduction of
microorganisms of at least 5-log when applied to a contaminated
surface.
[0025] In another aspect, the coating prevents growth of at least
one type of microorganism at a locus.
[0026] In another aspect the control of microorganisms at a locus
comprises a reduction of microorganisms harbored in a biofilm.
[0027] In another aspect, the coating formed by the method above is
substantially continuous and homogenous.
[0028] In another aspect, the coating formed by the method above
has a thickness of about 0.3 to about 300 microns, preferably, it
has a thickness of about 0.5 to about 100 microns.
[0029] Another aspect of the invention, is a removable
food-processing shut-down spray composition comprising: [0030] i) a
film-forming water soluble or water-dispersible agent; [0031] ii)
at least one or more antimicrobial agent; [0032] iii) an inert
solvent; and [0033] iv) optionally, one or more plasticizer,
surfactant, cross-linking agent, colorant, solubilizing agent,
rheology modifier, antioxidant, pH adjuster, wetting agent,
antifoaming agent, extender, lubricant, processing aid, color
fastness agent, film performance enhancer or enzymes [0034] wherein
said composition is durable and removable when subjected to an
aqueous solution treatment above 15.degree. C.
[0035] In another aspect, the compositions described herein
comprise a surfactant that provides a surface tension of about 20
to about 50 mN/m. In another aspect, the surfactant is an
organo-silicone. In yet another aspect, the surfactant is at a
concentration of about 0.01 wt % to about 1.0 wt % of the
composition.
[0036] In another aspect, the composition comprises a rheology
control agent that provides shear thinning properties to the
composition.
[0037] In another aspect, the composition provides a reduction of
microorganisms of at least 3-log when applied to a contaminated
food processing surface. In another aspect, the composition is a
disinfectant, sanitizer, preservative, or physical barrier to
contamination when applied to a contaminated surface and wherein
said composition is capable of residual antimicrobial efficacy when
applied to a contaminated surface that is subject to subsequent
contamination.
[0038] In another aspect of the invention the locus is the surface
of one or more: tanks, conveyors, floors, drains, coolers,
freezers, refrigerators, equipment surfaces, walls, valves, belts,
pipes, joints, crevasses, a building surface, kitchen surface, an
inanimate surface found in a food processing facility, veterinary
or animal care facility, animal care equipment, or animal husbandry
or hatchery facility, the surface of a hospital or surgery center
wall, bed, equipment, textile worn in a hospital or other
healthcare setting, including scrubs, shoes, and other hospital
surfaces.
[0039] In another aspect of the invention the locus is composed of
one or more metals selected from the group consisting of aluminum,
steel, stainless steel, chrome, titanium, iron, alloys and mixtures
thereof.
[0040] In another aspect of the invention the locus is the surface
comprises one or more plastic material selected from the group
consisting of polyolefins, including polyethylene, polypropylene,
polystyrene, polymethacrylate, polymethylmethacrylate, polymers of
acrylonitrile, butadiene, ABS, acrylonitrile butadiene; polyesters,
including polyethylene terephthalate; and polyamides, including
nylon; and combinations thereof.
[0041] In another aspect of the invention the locus is made of
brick, tile, ceramic, porcelain, wood, vinyl, linoleum, carpet,
paper, leather, combinations thereof, and the like.
[0042] In another aspect of the invention the locus is an inanimate
surface comprised of metals, minerals, polymers, plastics, fibrous
substrates or non-wovens, or mixtures thereof, or coated or painted
surfaces.
BRIEF DESCRIPTION OF FIGURES
[0043] The invention can be more fully understood from the
following Detailed Description and the accompanying Figures.
[0044] FIG. 1 shows mechanisms by which the coating composition
provides protection. Arrows indicate migration of biocidal active
component into microbially-contaminated regions above and below the
antimicrobial coating. The coating composition also provides a
physical barrier to soil and other solid contaminants.
[0045] FIG. 2 shows cross-sections of an antimicrobial coating.
Shown are x-z-cross-sections through the polymer film formed from
Formulation #2 (top), and y-z-cross-sections of the same film
(bottom). The film was visualized by confocal laser-scanning
microscopy after addition of traces of a fluorescent dye (rhodamine
123) to the film-forming composition.
[0046] FIG. 3 shows the release of a quaternary ammonium compound
(QAC) over time from films sprayed from three liquid compositions
of the invention on stainless steel coupons, then dried and
submerged into water.
DETAILED DESCRIPTION
[0047] When an amount, concentration, or other value or parameter
is given either as a range, preferred range, or a list of upper
preferable values and lower preferable values, this is to be
Understood as specifically disclosing all ranges formed from any
pair of any upper range limit or preferred value and any lower
range limit or preferred value, regardless of whether ranges are
separately disclosed. Where a range of numerical values is recited
herein, unless otherwise stated, the range is intended to include
the endpoints thereof, and all integers and fractions within the
range. It is not intended that the scope of the invention be
limited to the specific values recited when defining a range.
[0048] There has been a longstanding need for antimicrobial agents
having improved antimicrobial efficacy and improved speed of
action. The specific requirements for such agents vary according to
the intended application (e.g., sanitizer, disinfectant, sterilant,
aseptic packaging treatment, etc.) and the applicable public health
requirements. For example, as set out in Germicidal and Detergent
Sanitizing Action of Disinfectants, Official Methods of Analysis of
the Association of Official Analytical Chemists, paragraph 960.09
and applicable sections, 15th Edition, 1990 (EPA Guideline 91-2), a
sanitizer should provide a 99.999% reduction (5-log order
reduction) within 30 seconds at room temperature, 25.+-0.2.degree.
C, against several test organisms. The term "antimicrobial" as used
herein includes agents capable of killing microorganisms, blocking
or preventing microbial contamination (such as a forming a
barrier), or suppressing or preventing growth of microorganisms,
trapping microorganisms for killing, or preventing biofilm
formation. The term "sanitizer" as used herein means an agent which
reduces the number of microbial contaminants to safe levels as
judged by public health requirements. According to an official
sanitizer test, a sanitizer is a chemical that kills 99.999% of the
specific test microorganisms in 30 seconds under the conditions of
the test (EPA policy DIS/TSS-4: "Efficacy data
requirements--Sanitizing rises for previously cleaned food-contact
surfaces", United States Environmental Protection Agency, Jan. 30,
1979).
[0049] The term "disinfectant" as used herein means an agent which
provides antimicrobial activity. According to an official
disinfectant test, a disinfectant is a chemical that kills 99.9% of
the specific test microorganisms in 10 minutes under the conditions
of the test. (Germicidal and Detergent Sanitizing Action of
Disinfectants, Official Methods of Analysis of the Association of
Official Analytical Chemists, paragraph 960.09 and applicable
sections, 15th Edition, 1990 (EPA Guideline 91-2)). The term "ppm"
as used herein means micrograms per gram.
[0050] The present invention relates to a method and composition
for controlling microorganisms. Said method comprises coating a
surface with a removable, antimicrobial film-forming composition.
Specifically, the invention relates to a method of providing
control of microorganisms at a locus comprising [0051] a) providing
a removable liquid coating composition comprising: [0052] i) a
film-forming water soluble or water-dispersible agent; [0053] ii)
at least one antimicrobial agent; and [0054] iii) an inert solvent;
[0055] b) applying said composition to the locus whereby a coating
is formed; and [0056] c) removing said coating with an aqueous
solution at a temperature of about 15.degree. C. to about
100.degree. C.
[0057] The coating can be removed with an aqueous solution at a
temperature of about 15.degree. C. to about 100.degree. C., or more
preferably at a temperature of about 30.degree. C. to about
80.degree. C.
[0058] A locus of the invention comprises part or all of a target
surface suitable to be coated. Target surfaces include all surfaces
that can potentially be contaminated with microorganisms, including
surfaces typically difficult to apply a film or coating to (such as
hard-to-reach surfaces). Examples of target surfaces include
equipment surfaces found in the food or beverage industry (such as
tanks, conveyors, floors, drains, coolers, freezers, refrigerators,
equipment surfaces, walls, valves, belts, pipes, drains, joints,
crevasses, combinations thereof, and the like); building surfaces,
including buildings under construction, new home construction, and
surfaces in or on seasonal properties like vacation home surfaces
(such as walls, wood frames, floors, windows), kitchens (sinks,
drains, counter-tops, refrigerators, cutting boards), bathrooms
(showers, toilets, drains, pipes, bath-tubs), (especially for mold
removal), decks, wood, siding and other home exteriors, asphalt
shingle roofing, patio or stone areas (especially for algae
treatment); boats and boating equipment surfaces; garbage
disposals, garbage cans and dumpsters or other trash removal
equipment and surfaces; non-food-industry related pipes and drains;
surfaces in hospital, surgery or out-patient centers or veterinary
surfaces (such as walls, floors, beds, equipment, clothing worn in
hospital/veterinary or other healthcare settings, including scrubs,
shoes, and other hospital or veterinary surfaces) first-responder
or other emergency services equipment and clothing; lumber-mill
equipment, surfaces and wood products; restaurant surfaces;
supermarket, grocery, retail and convenience store equipment and
surfaces; deli equipment and surfaces and food preparation
surfaces; brewery and bakery surfaces; bathroom surfaces such as
sinks, showers, counters, and toilets; clothes and shoes; toys;
school and gymnasium equipment, walls, floors, windows and other
surfaces; kitchen surfaces such as sinks, counters, appliances;
wooden or composite decks, pool, hot tub and spa surfaces; carpet;
paper; leather; animal carcasses, fur and hides; surfaces of barns,
or stables for livestock, such as poultry, cattle, dairy cows,
goats, horses and pigs; and hatcheries for poultry or for shrimp.
Additional surfaces also include food products, such as beef,
poultry, pork, vegetables, fruits, seafood, combinations thereof,
and the like.
[0059] Additional loci suitable for use in the present invention
comprise fibrous substrates and include fibers, yarns, fabrics,
textiles, nonwovens, carpets, leather, or paper. The fibrous
substrates are made with natural fibers such as wool, cotton, jute,
sisal, sea grass, paper, coir and cellulose, or mixtures thereof;
or are made with synthetic fibers such as polyamides, polyesters,
polyolefins, polyaramids, acrylics and blends thereof; or blends of
at least one natural fiber and at least one synthetic fiber. By
"fabrics" is meant natural or synthetic fabrics, or blends thereof,
composed of fibers such as cotton, rayon, silk, wool, polyester,
polypropylene, polyolefins, nylon, and aramids such as "NOMEX.RTM."
and "KEVLAR.RTM.." By "fabric blends" is meant fabric made of two
or more types of fibers. Typically these blends are a combination
of at least one natural fiber and at least one synthetic fiber, but
also can be a blend of two or more natural fibers or of two or more
synthetic fibers. Nonwoven substrates include, for example,
spunlaced nonwovens, such as SONTARA available from E. I. du Pont
de Nemours and Company (Wilmington, Del., USA), and laminated
nonwovens, such as spunbonded-meltblown-spunbonded nonwovens.
[0060] Examples of surface materials are metals (e.g., steel,
stainless steel, chrome, titanium, iron, copper, brass, aluminum,
and alloys thereof), minerals (e.g., concrete), polymers and
plastics (e.g., polyolefins, such as polyethylene, polypropylene,
polystyrene, poly(meth)acrylate, polyacrylonitrile, polybutadiene,
poly(acrylonitrile, butadiene, styrene), poly(acrylonitrile,
butadiene), acrylonitrile butadiene; polyesters such as
polyethylene terephthalate; and polyamides such as nylon).
Additional surfaces include brick, tile, ceramic, porcelain, wood,
vinyl, and linoleum.
[0061] Equipment or surfaces protected with a temporary coating can
be in use or not in use while protected. The target surface can be
hydrophobic or hydrophilic. The antimicrobial, removable coating
composition useful for the invention can be used as a replacement
for standard sanitation products (such as diluted quaternary
ammonium compound solutions, peracid foams, and the like), and can
be used for daily sanitation as protective coatings for equipment
in use or not-in use as well as for longer term protection (weeks
or months).
[0062] Use of the antimicrobial, removable coating composition
provides several advantages. The coating composition provides
antimicrobial efficacy in a number of ways, including, but not
limited to killing (both loose microorganisms and biofilms),
reducing the growth of, or preventing the growth of microorganisms,
by preventing the formation of biofilms, and by trapping
microorganisms in, beneath or attached to the coating.
[0063] Application of the coating composition also reduces water
usage because a concentrate of antimicrobial agent is directly
applied in a thin film, and the antimicrobial agent can be
maintained in higher concentrations and for longer periods of time
at the substrate. In addition, labor can be reduced because the
antimicrobial coating is applied once and removed in a later
process step. The coating composition can be modified by
formulating the composition with flow modifiers to coat
hard-to-reach surfaces. This enables application of the
antimicrobial agent to surfaces on or in equipment otherwise not
accessible by application of conventional antimicrobial solutions
with traditional shear-viscosity profiles. Horizontal and vertical
surfaces can be covered with a thin layer of protective coating
without waste of antimicrobial agent. By formulating compositions
with appropriate flow modification and degree of cross-linking,
coating compositions with various coating properties can be
prepared that will vary in the degree of surface finish and
protection as well as ease of removal.
[0064] In one embodiment of the invention, the antimicrobial,
removable coating composition useful for the invention is applied
to equipment, for example, in the food, dairy, or beverage
industries, during shutdown periods of the equipment. When the
equipment is started up, the coating is removed by a method
described herein. In another embodiment, the antimicrobial,
removable coating composition is used for sanitation of surfaces,
such as surfaces of equipment of the food or beverage industry, for
daily or weekly sanitation purposes. In yet another embodiment,
fruit surfaces can be coated with the removable coating composition
to prevent microbial spread and cross-contamination in food
processing facilities. In still another embodiment, hospital walls,
beds, and other hospital surfaces can be coated with the
antimicrobial, removable coating composition useful for the
invention. In another embodiment drains are coated with the
removable coating composition. In another embodiment, building
surfaces, such as in new home construction, walls or other surfaces
are coated for prevention of mold contamination or mold
removal.
[0065] The coating composition offers several mechanisms of
protection towards contamination of microbial or non-microbial
origin, such as soiling.
[0066] First, as the fluid composition is applied, planktonic or
loosely adhering cells on the surface are killed (or growth is
reduced or prevented) by the antimicrobial agent in the coating
formulation.
[0067] Second, cells harbored by biofilms on the surface will be
killed (or growth will be reduced or prevented) by diffusion of the
antimicrobial(s) from the fluid coating into the hydrated biofilm.
As the antimicrobial coating dries, the antimicrobial agent is
likely to remain active because of the high water content retained
at the interface between biofilm and antimicrobial coating. Due to
the film being semi-permeable, the antimicrobial agent is mobile
within the film contributing to a more effective barrier and longer
lasting activity. The antimicrobial film thus formed constitutes a
reservoir of antimicrobial agent providing much longer contact time
than conventional sanitary rinse solutions that typically drip off
within seconds or minutes.
[0068] Third, planktonic cells reaching the antimicrobial coating
from outside, after application of the antimicrobial coating, will
be killed (or growth will be reduced or prevented) by the
antimicrobial agent. Again, the antimicrobial coating will act as a
reservoir of antimicrobial agent maintaining its microbiocidal
properties until it is exhausted from the coating. This mechanism
will also prevent biofilms from growing on the antimicrobial
coating until the antimicrobial agent has been exhausted from the
coating. The term "biofilm" refers to a collection of
microorganisms (either one species, or multiple species) surrounded
by a matrix of extracellular polymers (i.e., exopolymers or
glycocalyx). These extracellular polymers are typically
polysaccharides, but they can contain other biopolymers as well,
and they can be attached to either an inert or living surface.
Typical biofilm microorganisms are Gram positive and/or Gram
negative bacteria, acting as pathogens, indicator organisms, and/or
spoilage organisms.
[0069] Fourth, the coating constitutes a physical barrier for
microorganisms, soil, fat and other matter. These solid
contaminants will remain on the surface of the coating and will
wash off at the time of removal of the coating.
[0070] A fifth protection mechanism occurs in situations in which
the coating traps microorganisms so that they cannot reach or
permeate a target surface and contaminate it. FIG. 1 illustrates
various protection mechanisms described above. The protection
mechanisms can operate individually, or simultaneously in any
combination, depending on environmental conditions.
[0071] The long lasting activity while the coating is present on
the locus is especially beneficial in a variety of applications.
This residual benefit is far superior to antimicrobial agents such
as a rinse solution that drips off quickly, or an agent that is
subject to removal by touching or minor abrasion of the surface
after application. The variation of film flexibility, viscosity,
strength, and adhesion of the coating of the present invention
permits it to be tailored to specific applications, thus making
sustained antimicrobial protection available in numerous situations
where such sustained activity (residual benefit) was not previously
available.
Components of the Composition
[0072] The following provides a detailed description of the
components of the film or coating described herein.
Film-Forming Water Soluble or Water Dispersible Agent:
[0073] The film-forming water soluble or water dispersible agent
can be at least one of any agent, as described below, that is
durable and removable. The film or coating is removable, for
instance, when subjected to an aqueous solution treatment above
15.degree. C., preferably above 30.degree. C. Examples include, but
are not limited to, polyvinyl alcohols, polyvinyl alcohol
copolymers, polyvinyl pyrrolidones, polyacrylic acid, acrylate
copolymers, ionic hydrocarbon polymers, and polyurethanes, or
combinations thereof.
Polyvinyl Alcohol and Copolymers Thereof
[0074] Polyvinyl alcohol, sometimes referred to as poly(vinyl
alcohol), is made from polyvinyl acetate by hydrolysis. The
physical properties of polyvinyl alcohol are controlled by the
molecular weight and the degree of hydrolysis. The most commonly
available grades of polyvinyl alcohol, ranked by degree of
hydrolysis, are an 87-89% grade (containing 11-13 mole % residual
vinylacetate units), a 96% hydrolysis grade (containing 4 mole %
residual vinyl acetate units), and the "fully hydrolyzed" and
"superhydrolyzed" grades, which are about 98% and greater-than-99%
hydrolyzed, respectively. Lower degrees of hydrolysis (e.g. 74% and
79%) are also commercially available. Some preferred degrees of
hydrolysis are greater than 85 mole %, or greater than 92 mole %.
The polyvinyl alcohol component of the present invention can also
be a copolymer of vinyl alcohol, such as one obtained by
hydrolyzing a copolymer of vinyl acetate with small amounts (up to
about 15 mole %) of other monomers. Suitable co-monomers are e.g.
esters of acrylic acid, methacrylic acid, maleic or fumaric acids,
itaconic acid, etc. Also, copolymerization of vinyl acetate with
hydrocarbons e.g. alpha.-olefins such as ethylene, propylene or
octadecene, etc., with higher vinyl esters such as vinyl butyrate,
2-ethyl hexoate, stearate, trimethyl acetate, or homologues thereof
("W-10" type of vinyl esters sold by Shell Chem. Co.), etc. gives
copolymers that can be hydrolyzed to suitable polyvinyl alcohol
copolymers. Other suitable comonomers are N-substituted
acrylamides, vinyl fluoride, allyl acetate, allyl alcohol, etc.
Also the free unsaturated acids such as acrylic acid, methacrylic
acid, monomethyl maleate, etc. can act as comonomers.
[0075] Because of the variety of grades either known in the
literature or commercially available, one skilled in the art can
formulate a polyvinyl alcohol solution having an average degree of
hydrolysis ranging from 74 to more than 99% simply by blending the
known or commercial grades in any desired ratios. Accordingly, the
term. "partially hydrolyzed grade polyvinyl alcohol", as used in
this description should be understood to include both a single
grade and a mixture of grades, and the term "average degree of
hydrolysis" should be understood to refer to the degree of
hydrolysis arrived at by averaging (with appropriate weighting on
the basis of proportions) the partially hydrolyzed grades in the
mixture, if a mixture is used, or the average degree of hydrolysis
of a single grade, if a single grade is used (an "88% grade", for
example, may be the average of a spectrum ranging from 87 to 89%
within the same grade).
[0076] Variation of film flexibility, water sensitivity, ease of
solvation, viscosity, film strength and adhesion of the polyvinyl
alcohol film can be varied by adjusting molecular weight and degree
of hydrolysis. In one embodiment, the polyvinyl alcohol for use in
the process of this invention has a degree of hydrolysis from about
85% to greater than 99%. In another embodiment, the polyvinyl
alcohol has a degree of hydrolysis from about 92% to greater than
99%. In one embodiment, the polyvinyl alcohol has a number-averaged
molecular weight (Mn) that falls in the range of between about
4,000 to about 200,000, or about 4,000 to about 186,000, or 30,000
to about 186,000. In another embodiment, the polyvinyl alcohol has
a molecular weight that falls in the range of between about 70,000
and 130,000. In another embodiment, the polyvinyl alcohol of
various molecular weights can be blended to give the desired
properties. In one embodiment, the polyvinyl alcohol is used at
about 2% to about 30% by weight of the weight of the solution. In a
more specific embodiment, the polyvinyl alcohol is used at about 2%
to about 15% by weight of the weight of the solution. In an even
more specific embodiment, the polyvinyl alcohol is used at about 3%
to about 6% by weight of the weight of the solution.
Polyvinylpyrrolidone (PVP)
[0077] The film-forming composition of the present invention can
contain PVP at a concentration of about 0.25 to about 50% by
weight. Suitable grades of PVP are available from International
Specialty Products (Wayne, N.J., USA). Such grades include: K-15,
having a molecular weight range of about 6,000 to about 15,000;
K-30, having a molecular weight range of about 40,000 to about
80,000; K-60, having a molecular weight range of about 240,000 to
about 450,000; K-90, having a molecular weight range of about
900,000 to about 1,500,000; and K-120, having a molecular weight
range of about 2,000,000 to about 3,000,000. Mixtures of PVP's can
be employed, as can combinations of PVP and other film-forming
compounds.
[0078] The amount and molecular weight distribution of the PVP used
will influence the viscosity, coverage, and cost of the final
product. The viscosity should preferably be between about 20 to
about 1000 centipoise, and more preferably between about 20 to 100
centipoise. Typically, lower molecular weight PVP will give a less
viscous product than a higher molecular weight PVP at the same
concentration. For a given concentration of PVP, as the molecular
weight range increases, the viscosity will also increase. The
present invention can employ PVP having any of a number of
molecular weight ranges. For example, film-forming compositions can
utilize the PVP grades K-15, K-30, K-60, K-90, or K-120 described
above. It is preferred, however, to use PVP with a molecular weight
distribution between about 15,000 and about 3,000,000. PVP having
this molecular weight distribution typically gives a film-forming
composition with a viscosity, which can be easily adjusted and
washes off a surface easily with no visible signs of interaction
with a painted surface. In a preferred embodiment, PVP with a
molecular weight distribution between about 15,000 and about
3,000,000 is present at a concentration of between about 0.25% and
about 40% by weight. In another preferred embodiment, PVP with a
molecular weight distribution between about 60,000 and about
1,200,000 is present at a concentration of between about 2% and
about 30% by weight.
Polyacrylate
[0079] The film-forming compositions of the invention can also
include an acrylate emulsion polymer. Preferred acrylate polymers
are those composed of one or more copolymers of ethylenically
unsaturated comonomers. The monomers useful in the compositions of
the invention comprise one or more ethylenically unsaturated polar
or non-polar, non-ionizing monomers and at least one ethylenically
unsaturated carboxylic acid. The monomers can include more than one
ethylenically unsaturated sites and the suitable carboxylic acids
preferably include one or more carboxyl groups. Suitable
ethylenically unsaturated acids include acrylic, methacrylic,
butenoic, maleic, fumaric, itaconic, and cinnamic acids as well as
dimer acids such as acrylic and methacrylic dimer acids and
combinations of the foregoing. Ethylenically unsaturated polar or
non-polar, non-ionizing monomers include ethylenically unsaturated
esters, ethylenically unsaturated nitriles, ethylenically
unsaturated alcohols, aryl vinyl compounds and arylalkyl vinyl
compounds. Based on commercial availability, the acrylate polymers
are preferably copolymers of acrylic acid esters and methacrylic
acid esters, such as C1 to C6 alkyl acrylates or methacrylates, in
combination with acrylic or methacrylic acid, cyanoacrylates and
methacrylates (e.g., acrylonitrile) and other known acrylic, vinyl
and diene monomers. The acrylate polymer component can optionally
contain one or more metal salt complexing agents effective as
cross-linking agents. When present such complexing agents bond with
the pendant carboxyl groups on the acrylate polymers to form a
cross-linked polymer, which is more water resistant than a
comparable acrylate polymer which is not cross-linked. Suitable
metal salt complexing agents include those containing zinc such as
zinc ammonium carbonate, for example. Other useful complexing
agents include known salts of various metals including zirconium,
calcium, magnesium and the transition metals, for example.
Exemplary complexing agents include polyvalent metal complexes such
as ammonium zinc carbonate, ammonium calcium ethylenediamine
carbonate, ammonium zinc acetate, ammonium zinc acrylate, ammonium
zinc maleate, ammonium zinc amino acetate and ammonium calcium
aniline and combinations of the foregoing.
[0080] Commercially available carboxylated acrylate polymer
emulsions can be used either alone or in combination with one
another in the film-forming compositions of the invention. Suitable
commercial emulsions include those with a metal complexing agent as
described above as well as those without added metal complexing
agents. Suitable metal free emulsions include commercially
available materials such as those available under the trade names
of "Rhoplex" NT 2624 (Rohm and Haas Company, Philadelphia, Pa.);
"Esi-Cryl" 20/20 (Emulsion Systems, Valley Stream, N.Y., USA); and
"Syntran" 1905 (Interpolymer of Canton, Mass., USA). Commercial
emulsions which include a zinc complexing agent suitable for
inclusion in the compositions of the invention include those
available under the trade designations "Duraplus" I and "Rhoplex"
B-825 (both from Rohm and Haas), "Conlex" V (Morton International,
Chicago, Ill., USA) and "Esi-Cryl" 2000 (Emulsion Systems Ltd.,
Valley Stream, N.Y., USA). Other metal containing and metal free
acrylate emulsions can be used, as known by those skilled in the
art.
[0081] The acrylate polymer component is preferably prepared as an
emulsion and is present in the film-forming composition of the
invention at a concentration ranging from about 0.25 to 30 wt %,
and more preferably from about 2 to 20 wt % based on total weight
of the composition.
Ionic Hydrocarbon Copolymers
[0082] Ionic hydrocarbon copolymers useful for the present
invention include a polymer of an .alpha.-olefin having the general
formula RCH.dbd.CH.sub.2 where R is a radical selected from the
class consisting of hydrogen and alkyl radicals having from 1 to 8
carbon atoms, the olefin content of said polymer being at least 50
mol % based on the polymer, and an .alpha.,.beta.-ethylenically
unsaturated carboxylic acid having 1 or 2 carboxylic groups, the
acid monomer content of said polymer being from 0.2 to 25 mol %
based on the polymer. This type of polymer is described in U.S.
Pat. No. 3,264,272, specifically incorporated herein by
reference.
Polyurethane Dispersion
[0083] A polyurethane dispersion or solution refers to an aqueous
dispersion or solution of a polymer containing urethane groups. A
cross-linked polyurethane dispersoid refers to an aqueous
dispersion of a polymer containing urethane groups and
cross-linking, as those terms are understood by persons of ordinary
skill in the art. Depending on the degree of cross-linking, the
polyurethane may be an aqueous solution (no cross-linking or low
cross-linking) or an aqueous dispersion.
[0084] Cross-linked polyurethane dispersions are described in the
U.S. Patent Application 2005/0215663, herein incorporated
specifically by reference. These polymers can incorporate
hydrophilic functionality to the extent required to maintain stable
dispersion of the polymer in an aqueous solution. These polymers
can also incorporate ionic and nonionic functionality to the extent
required to maintain a stable dispersion of the polymer in water.
Alternatively, these polymers can be prepared by emulsification of
hydrophobic polyurethanes in water with the aid of suitable
external emulsifiers, surfactants and the like, and/or utilizing
strong shear forces to form an oil-in-water dispersion.
[0085] In general, the stability of the cross-linked polyurethane
in the aqueous vehicle is achieved by incorporating anionic,
cationic and/or non-ionic components in the polyurethane polymer,
which facilitates stabilizing the cross-linked polyurethane in
aqueous systems. The amount of cross linking is chosen to give the
desired water resistance. External emulsifiers can also be added to
stabilize the polyurethane. Combinations of incorporated anionic,
cationic and/or non-ionic components, and/or external emulsifiers
can also be used.
Antimicrobial Agent:
[0086] The antimicrobial agent useful for the invention can be
either an inorganic or organic agent, or a mixture thereof. The
invention is not to be limited to the selection of any particular
antimicrobial agent, and any known water-soluble or
water-dispersible antimicrobial may be included in the compositions
of the invention such as antimicrobials, mildewcides, antiseptics,
disinfectants, sanitizers, germicides, algicides, antifouling
agents, preservatives, and combinations of the foregoing and the
like provided that the antimicrobial agent is chemically compatible
with other components in the composition. Suitable classes of
antimicrobial agents are described below.
[0087] The term "inorganic antimicrobial agent" used herein is a
general term for inorganic compounds which contain a metal or metal
ions, such as silver, zinc, copper and the like which have
antimicrobial properties. The term "organic antimicrobial agent"
used herein is the general term for natural extracts, low molecular
weight organic compounds and high molecular weight compounds all of
which have antimicrobial properties and which generally contain
nitrogen, sulfur, phosphorus or like elements. Examples of useful
natural antimicrobial agents are chitin, chitosan, antimicrobial
peptides such as nisin, lysozymes, wasabi extracts, mustard
extracts, hinokitiol, tea extracts and the like. High molecular
weight compounds having anti-microbial properties include those
having an ammonium salt group, phosphonium salt group, sulfonium
salt group or like onium salts, a phenylamide group, diguanide
group attached to a straight or branched polymer chain, for example
phosphonium salt-containing vinyl polymers, as are known in the art
(E.-R. Kenawy and Y. A.-G. Mahmoud "Biologically active polymers,
6: Synthesis and antimicrobial activity of some linear copolymers
with quaternary ammonium and phosphonium groups" in Macromolecular
Bioscience (2003), 3(2), 107-116).
[0088] Examples of useful low molecular weight antimicrobial agents
include chlorhexidine, chlorhexidine gluconate, glutaral, halazone,
hexachlorophene, nitrofurazone, nitromersol, thimerosol,
C1-C5-parabens, hypochlorite salts, clofucarban, clorophen,
phenolics, mafenide acetate, aminacrine hydrochloride, quaternary
ammonium salts, chlorine and bromine release compounds (e.g. alkali
and alkaline earth hypochlorites and hypobromites, isocyanurates,
chlorinated derivatives of hydantoin, sulfamide, amine, etc.),
peroxide and peroxyacid compounds (e.g. peracetic acid, peroctanoic
acid), protonated short chain carboxylic acids, oxychlorosene,
metabromsalan, merbromin, dibromsalan, glyceryl laurate, sodium
and/or zinc pyrithione, trisodium phosphates,
(dodecyl)(diethylenediamine)glycine and/or
(dodecyl)(aminopropyl)glycine and the like. Useful quaternary
ammonium salts include the N--C10-C24-alkyl-N-benzyl-quaternary
ammonium salts which comprise water solubilizing anions such as
halide, e.g., chloride, bromide and iodide; sulfate, methosulfate
and the like and the heterocyclic imides such as the imidazolinium
salts. Useful phenolic germicides include phenol, m-cresol,
o-cresol, p-cresol, o-phenyl-phenol, 4-chloro-m-cresol,
chloroxylenol, 6-n-amyl-m-cresol, resorcinol, resorcinol
monoacetate, p-tert-butylphenol and o-benzyl-p-chlorophenol. Useful
antimicrobial agents known to be effective in preventing the
visible growth of mildew colonies, include, for example,
3-iodo-2-propynl butylcarbamate, 2-(4-thiazolyl)benzimidazole,
diiodomethyl-p-tolylsulfone, tetrachloroisophthalonitrile, the zinc
complex of 2-pyridinethiol-1-oxide (inciuding salts thereof) as
well as combinations of the foregoing.
[0089] The coating composition comprising the antimicrobial agent
offers protection against diverse microorganisms. The term
"microorganism" is meant to include any organism comprised of the
phylogenetic domains of bacteria and archaea, as well as
unicellular (e.g. yeasts) and filamentous (e.g. molds) fungi,
unicellular and filamentous algae, unicellular and multicellular
parasites, viruses, virinos and viroids.
[0090] In one embodiment, the coating composition protects against
Gram positive or Gram negative bacteria. Gram positive bacteria
which are inhibited or killed by the coating include, but are not
limited to, Mycobacterium tuberculosis, M. bovis, M. typhimurium,
M. bovis strain BCG, BCG substrains, M. avium, M. intracellulare,
M. africanum, M. kansasii, M. marinum, M. ulcerans, M. avium
subspecies paratuberculosis, Staphylococcus aureus, S. epidermidis,
S. equi, Streptococcus pyogenes, S. agalactiae, Listeria
monocytogenes, L. ivanovii, Bacillus anthracis, B. subtilis,
Nocardia asteroides, and other Nocardia species, Streptococcus
viridans group, Peptococcus species, Peptostreptococcus species,
Actinomyces israelii and other Actinomyces species,
Propionibacterium acnes, and Enterococcus species. Gram negative
bacteria which are inhibited or killed by the coating include, but
are not limited to, Clostridium tetani, C. perfringens, C.
botulinum, other Clostridium species, Pseudomonas aeruginosa, other
Pseudomonas species, Campylobacter species, Vibrio cholerae,
Ehrlichia species, Actinobacillus pleuropneumoniae, Pasteurella
haemolytica, P. multocida, other Pasteurella species, Legionella
pneumophila, other Legionella species, Salmonella typhi, other
Salmonella species, Shigella species Brucella abortus, other
Brucella species, Chlamydia trachomatis, C. psittaci, Coxiella
bumetti, Escherichia coli, Neiserria meningitidis, N. gonorrhea,
Haemophilus influenzae, H. ducreyi, other Haemophilus species,
Yersinia pestis, Y. enterolitica, other Yersinia species,
Escherichia coli, E. hirae and other Escherichia species, as well
as other Enterobacteriacae, Brucella abortus and other Brucella
species, Burkholderia cepacia, B. pseudomallei, Francisella
tularensis, Bacteroides fragilis, Fusobacterium nucleatum,
Provetella species, Cowdria ruminantium, Klebsiella species, and
Proteus species. In another embodiment, the coating provides
protection against fungi, including but are not limited to,
Alternaria alternata, Aspergillus niger, Aureobasidium pullulans,
Cladosporium cladosporioides, Drechslera australiensis, Gliomastix
cerealis, Monilia grisea, Penicillium commune, Phoma fimeti,
Pithomyces chartarum, and Scolecobasidium humicola.
Enzymes:
[0091] Enzymes useful for the present invention include those that
have beneficial effects such as cleaning, destaining, and biofilm
degradation. These enzymes include one or a mixture of:
deacetylase, amidase, cellulase, esterase, glycosidase, xylanase,
amylase, transaminase, laminarinase, beta-galactosidase,
beta-mannosidase, pullulanase, phosphatase, protease, lipase, and
perioxidase.
Surfactants:
[0092] The compositions useful for the present invention can also
contain one or more surfactants. While not being bound by theory,
it is believed that a surfactant will aid wetting of the surface to
be covered and will aid even coverage by the film. The surfactant
is also believed to aid foaming by the film when removed, thereby
aiding removal of the film and washing of the protected surface.
Suitable surfactants have a preferred hydrophilic-lipophilic
balance (HLB) of from about 9 to about 17. Suitable surfactants
include, but are not limited to: amphoteric surfactants, such as
Amphoteric N from Tomah Products; silicone surfactants, such as BYK
348 available from BYK Chemie (BYK-Chemie GmbH, Wesel, Germany);
fluorinated surfactants such as Zonyl.RTM. FS300 from DuPont
(DuPont, Wilmington, Del., USA); and nonylphenoxypolyethoxyethanol
based surfactants, such as Triton N-101 available from Dow
(Midland, Mich., USA). Other suitable surfactants include
ethoxylated decynediols such as Surfynol 465 available from Air
Products & Chemicals (Allentown, Pa., USA); alkylaryl
polyethers such as Triton CF-10 available from Dow; octylphenoxy
polyethoxy ethanols such as Triton X-100 available from Dow;
ethoxylated alcohols such as Neodol 23-5 or Neodol 91-8 available
from Shell (The Hague, the Netherlands); Tergitol 15-S-7 available
from Dow, Steol-4N, a 28% sodium laureth sulfate from Stepan
Company (Northfield, Ill., USA), sorbitan derivatives such as Tween
20 or Tween 60 from Uniqema (New Castle, Del., USA), and quaternary
ammonium compounds, such as benzalkonium chloride.
[0093] Other suitable surfactants include organo-silicone
surfactants such as Silwet.RTM.L-77 from Setre Chemical Company
(Mephis, Tenn., USA), DowCorning.RTM. Q2-5211 from DowCorning
Silicones (Midland, Mich., USA), or Silsurf.RTM. A008 by Siltech
Corporation (Toronto, ON, Canada).
[0094] The preferred range for use of the surfactant is from about
0.001 to about 1 wt % of the formulation, and more preferably from
about 0.01 to about 0.2 wt %.
Solvents:
[0095] Inert solvents useful for the invention include water.
Additional solvents include mono alcohols monofunctional and
polyfunctional alcohols, preferably containing from about 1 to
about 6 carbon atoms and from 1 to about 6 hydroxy groups. Examples
include ethanol, isopropanol, n-propanol, 1,2-propanediol,
1,2-butanediol, 2-methyl-2,4-pentanediol, mannitol and glucose.
Also useful are the higher glycols, polyglycols, polyoxides, glycol
ethers and propylene glycol ethers. Additional solvents include the
free acids and alkali metal salts of sulfonated alkylaryls such as
toluene, xylene, cumene and phenol or phenol ether or diphenyl
ether sulfonates; alkyl and dialkyl naphthalene sulfonates and
alkoxylated derivatives.
Additional Components:
[0096] Additional components that can be added to the coating
composition include colorants, rheology modifiers, cross-linking
agents, plasticizers, surfactants, solubilizing agents,
antioxidants, pH adjusters, wetting agents, antifoaming agents,
extenders, lubricants, processing aids, color fastness agents, and
additional performance-enhancing agents. Wetting agents lower the
surface tension of the formulation to allow it to wet the surfaces,
spread on the surfaces and potentially penetrate into, under, and
around soils, solid matter, microorganisms, biofilms, surface
contaminations, fat and surface crevices.
Colorants:
[0097] Colorants useful for the present invention include dyes and
pigments such as food grade pigments.
[0098] Dyes useful for the invention include both water soluble and
water insoluble dyes. Water soluble dyes can be formulated easily
in the aqueous systems of the invention. Water insoluble dyes can
be included in an oil phase that can be dispersed or suspended in
the antimicrobial coating compositions useful for the invention.
Useful dyes for the purpose of this invention are typically organic
compounds that absorb visible light resulting in the appearance of
a detectable color. Fluorescent dyes can also be used, for example,
for purposes of visualizing a film by ultraviolet light.
[0099] For the food processing industry, including restaurant
surfaces, and for fruit, in one embodiment of the invention common
FD&C approved dyes can be used since these materials are
typically approved for use as direct additives for food stuffs. The
dyes typically useful in this invention are colorants approved for
use in foods, drugs, cosmetics and medical devices.
[0100] Colorants currently in use and their status follow.
Colorants permitted in foods that are (1) subject to certification:
FD&C Blue No. 1, FD&C Blue No. 2, FD&C Green No. 3,
FD&C Red No. 3, FD&C Red No. 40, FD&C Yellow No. 5,
FD&C Yellow No. 6, Citrus Red No. 2, and Orange (B) (2) exempt
from certification: annatto extract, theta-apo-8'-carotenal,
canthaxanthin, caramel, theta-carotene, carrot oil, cochineal
extract (carmine), corn endosperm oil, dehydrated beets (beet
powder), dried algae meal, ferrous gluconate, fruit juice, grape
color extract, grape skin extract, paprika, paprika oleoresin,
riboflavin, saffron, synthetic iron oxide, tagetes meal and
extract, titanium dioxide, toasted partially defatted cooked
cottonseed flour, turmeric, termeric oleoresin, ultramarine blue,
and vegetable juice. Colorants permitted in drugs (including
colorants permitted in foods) that are (1) subject to
certification: FD&C Red No. 4, D&C Blue No. 4, D&C Blue
No. 9, D&C Green No. 5, D&C Green No. 6, D&C Green No.
8, D&C Orange No. 4, D&C Orange No. 5, D&C Orange No.
10, D&C Orange No. 11, D&C Red No. 6, D&C Red No. 7,
D&C Red No. 17, D&C Red No. 21, D&C Red No. 22, D&C
Red No. 27, D&C Red No. 28, D&C Red No. 30, D&C Red No.
31, D&C Red No. 33, D&C Red No. 34, D&C Red No. 36,
D&C Red No. 39, D&C Violet No. 2, D&C Yellow No. 7,
D&C Yellow No. 8, D&C Yellow No. 10, D&C Yellow No. 11,
and Ext. D&C Yellow No. 7. Additionally cantaxanthin, beta
carotene, chlorophyllin, and other colors are known.
[0101] For a more detailed listing and/or discussion on approved
colors, see D. M. Marmion, Handbook of U.S. Colorants, Foods,
Drugs, Cosmetics and Medical Devices, John Wiley & Sons Inc.,
New York (1991) and U.S. Code of Federal Regulations, Title 21,
parts 70-82.
Rheology Modifiers:
[0102] The composition useful for the invention can also contain
one or more rheology modifiers, or rheology agents, employed to
enhance viscosity, or thicken and cause the aqueous treatment or
coating composition to cling to the surface. Clinging enables the
composition to remain in contact with transient and resident
microorganisms for longer periods of time, promoting
microbiological efficacy and resisting waste because of excessive
dripping. The rheology modifier can be a film former or act
cooperatively with a film-forming agent to form a barrier that
provides additional protection. Water soluble or water dispersible
rheology modifiers that are useful can be classified as inorganic
or organic. The organic thickeners can further be divided into
natural and synthetic polymers with the latter still further
subdivided into synthetic natural-based and synthetic
petroleum-based.
[0103] Inorganic thickeners are generally compounds such as
colloidal magnesium aluminum silicate (VEEGUM.RTM.), colloidal
clays (Bentonites), or silicas (CAB-O-SIL.RTM.) which have been
fumed or precipitated to create particles with large surface to
size ratios. Natural hydrogel thickeners of use are primarily
vegetable derived exudates. For example, tragacanth, karaya, and
acacia gums; and extractives such as carrageenan, locust bean gum,
guar gum and pectin; or, pure culture fermentation products such as
xanthan gum are all potentially useful in the invention.
Chemically, all of these materials are salts of complex anionic
polysaccharides. Synthetic natural-based thickeners having
application are cellulosic derivatives wherein the free hydroxyl
groups on the linear anhydro-glucose polymers have been etherified
or esterified to give a family of substances which dissolve in
water and give viscous solutions. This group of materials includes
the alkyl and hydroxylalkylcelluloses, specifically
methylcellulose, hydroxyethylmethylcellulose,
hydroxypropylmethylcellulose, hydroxybutylmethylcellulose,
hydroxyethylcellulose, ethylhydroxyethylcellulose,
hydroxypropylcellulose, and carboxymethylcellulose. Another
preferred group of thickeners include polyacrylates such as the
proprietary Acusol thickeners, (e.g. Acusol 823, Rohm and Haas,
Philadelphia, Pa., USA), and Carbopol thickeners, such as Carbopol
934 or Carbopol Aqua-30 Polymer (B F Goodrich, Cleveland, Ohio,
USA). A polyacrylate thickener can be used at concentrations of up
to about 3 wt % of the film former weight. Mixtures of thickening
agents can also be employed where the total amount can be up to
about 3 wt % depending on the thickeners used and the desired
viscosity of the final product.
[0104] Other potential thickeners for this application include
dextrin, cornstarch and hydrous magnesium silicates, such as sodium
magnesium silicate sold under the trade name Laponite XLG (Southern
Clay Products, Inc., Gonzales, Tex., USA).
Cross-Linking Agents:
[0105] The present invention may optionally include cross-linking
agents. Advantages of using cross-linking agents with the
film-forming composition include influencing the mechanical film
properties, such as tackiness and mechanical strength, as well as
solubility of the coating. In the present invention, cross-linked
films yielded much more mechanically robust films. Furthermore,
cross-linking decreases tackiness and prevents soil and
microorganisms from physically adhering to the polymer film, which
may be desirable for certain applications. In the present
invention, cross-linking had a beneficial impact on release of the
antimicrobial agent from the film. The degree of cross-linking is
adjusted so to achieve the desired combination of properties.
[0106] Cross-linking agents suitable for use with polyvinyl alcohol
and copolymers thereof include, but are not limited to: aldehydes
(e.g. formaldehyde, glyoxal, glutaraldehyde), boric acid, sodium
tetraborate, metal ions (e.g. ions of Zn, Fe, Al, Ni, V, Co, Cu,
Zr, Ti, Mn), organometallic compounds (e.g. organic titanates such
as DuPont Tyzor.RTM., organic Cr(III) complexes such as DuPont
Quilon.RTM.), siloxanes (e.g., tetraethoxysilane,
polydimethylsiloxane), isocyanates (e.g. of the blocked,
water-soluble or dispersed type), epoxides (e.g. diglycidyl ether),
dicarboxylic acid (e.g., oxalic, maleic, fumaric, phthalic), urea
based cross-linkers (e.g. Sunrez 700). Bi- and trivalent metal
cations (e.g. Fe(II), Fe(III), Al(III)) are preferred because they
provide the formation of a coordinative linkage between the PVOH
polymer chains upon film drying. This allows the cross-linker to be
added to the film-forming liquid in a `one-pot` mixture. Care must
be taken to choose an adequate concentration in order to
efficiently cross-link the polymer without precipitating other
ingredients such as particulate rheology control agents.
[0107] In most cases the cross-linking agent will be mixed with
other ingredients using standard mixing techniques. The
cross-linking reaction can optionally be carried out in the
presence of a catalyst, as is well known to those skilled in the
art. In the case of the aldehydes, isocyanates, siloxanes,
diglycidyl ether, and dicarboxylic acid, heat and an acid catalyst
or metal catalyst can be used additionally.
[0108] The cross-linking agent concentration in the formulation can
be zero to an upper limit which is either determined by the
stability limit of the formulation where precipitation starts to
occur, or the inability of the resulting film to be removed
efficiently. The preferred cross-linking agent concentration can
depend strongly on the type of cross-linking agent used and is
typically below 25 wt % of the polymer content, more preferably
below 10 wt % of the polymer content.
Plasticizers:
[0109] It is important for flexibility and integrity of the
protective film that the resultant film be plasticized.
Plastization of the film has been accomplished for the purposes of
this invention by the incorporation of a suitable plasticizing
agent such as polyethylene glycol or glycerol. Other plasticizers
suitable for the invention include, but are not limited, to
solvents, polyols, polyethylene glycols of and average molecular
weight between 200 and 800 g/mole and sorbitol. PEG is preferred
over glycerol since glycerol is easily metabolized by
microorganisms potentially resulting in microbial growth.
[0110] Inclusion of a plastisizer generally also allows the film to
retain a slightly tacky surface feel. As the plastisizer level
increases, the resulting film will also exhibit an increasing
degree of tackiness. Such tackiness can be desirable at low levels
in order to capture airborne particles and soil or other materials.
If plastisizer levels are too high, however, the coating becomes
too tacky and will show low resistance to accidental mechanical
removal, by wiping, for example. The preferred plasticizer amount
is from about 1.0 wt % to about 20 wt % of the weight of the film
former, and more preferably from about 5 wt % to about 8 wt %.
Additional Performance-Enhancing Agents:
[0111] In addition to the foregoing components, the composition of
the present invention can also comprise one or more performance
enhancing additives, "performance enhancers". These include flash
rust inhibitors, which include any of a number of organic or
inorganic materials used in a water-based system to prevent rust
from forming on contact with the material and bare metal. One
example is sodium benzoate.
[0112] Another optional performance enhancing additive is one or
more of an array of defoamers recommended for water-based systems,
to prevent unwanted foaming of the product during application. Too
much foam can disrupt the required continuous film formation of the
product and result in product failure. It can also be advantageous
to add a foam control product, to aid in mixing and processing the
masking composition, such as Drewplus L475 from Ashland Chemical,
Inc. Drew Industrial Division (Covington, Ky., USA).
[0113] Additional optional performance enhancing additives are
antioxidants to increase the shelf life of the coating formulation.
One example is butylated hydroxytoluene. Additional additives
include fragrances.
[0114] Foaming agents can additionally be added to create gas
bubbles in the applied coating. Gas bubbles can function as an
opacifying agent to facilitate the application and/or to allow for
longer contact time with a surface e.g. by preventing dripping from
an inclined surface and/or to reduce the amount of coating
formulation needed to treat a certain surface area or volume.
[0115] Application indicators may also be added. Some of these are
described above, but include pigments, dyes, fluorescent dyes or
gas bubbles generated during application.
[0116] Small amounts (typically less than 1 percent by weight) of
these additional materials can be added with an appropriate
adjustment of the water or other components. It is to be understood
that mixtures of any one or more of the foregoing optional
components can also be employed.
[0117] For loci comprised of fibrous substrates, an optional
performance-enhancing ingredient is an agent that provides a
surface effect. Such surface effects include no iron, easy to iron,
shrinkage control, wrinkle free, permanent press, moisture control,
softness, strength, anti-slip, antistatic, anti-snag, anti-pill,
stain repellency, stain release, soil repellency, soil release,
water repellency, oil repellency, odor control, antimicrobial, or
sun protection,
Applying the Antimicrobial Coating Composition:
[0118] The film or coating can be applied to the target surface or
locus by any means, including pouring. The film or coating is
applied to achieve a continuous and/or homogenous layer on a target
surface. Coating systems routinely used for paints and coatings,
such as, but not limited to, brushes, rollers, paint pads, mats,
sponges, combs, hand-operated pump dispensers, compressed air
operated spray guns, airless spray guns, electric or electrostatic
atomizers, backpack spray application equipment, clothes, papers,
feathers, styluses, knives, and other applicator tools can be used
for coating. If dipping is used as a method to apply the coating,
no special equipment is required. For fibrous substrates, such as
textiles and carpets, the coating can be applied by exhaustion,
foam, flex-nip, nip, pad, kiss-roll, beck, skein, winch, liquid
injection, overflow flood, roll, brush, roller, spray, dipping,
immersion, and the like. The coating can also be applied by use of
the conventional beck dyeing procedure, continuous dyeing procedure
or thread-line application.
[0119] The coating system may also be one more components, and may
include a catalyst.
[0120] In one embodiment of the invention, electrostatic sprayers
can be used to coat the surface. Electrostatic sprayers impart
energy to the aqueous coating composition via a high electrical
potential. This energy serves to atomize and charge the aqueous
coating composition, creating a spray of fine, charged particles.
Electrostatic sprayers are readily available from suppliers such as
Tae In Tech Co, South Korea and Spectrum, Houston, Tex., USA.
Generally, the coating is allowed to set or dry for about greater
than 5 minutes in order to form the film. However, the coating may
be antimicrobially effective in a shorter time-frame, such as after
30 seconds. The coating may be removed before it is dried or
anytime thereafter depending on the desired use. The drying time
will be partially dependent on a number of factors, including
environmental conditions such as humidity and temperature. The
drying time will also depend on the thickness of the applied
coating.
[0121] In another embodiment of the invention, an airless spray
guns can be used to coat the target surface. Airless spray guns use
high fluid pressures and special nozzles, rather than compressed
air, to convey and atomize the liquid. The liquid is supplied to an
airless gun by a fluid pump at pressures typically ranging from 500
to 6500 psi. When the paint exits the fluid nozzle at this
pressure, it expands slightly and atomizes into tiny droplets
without the impingement of atomizing air. The high velocity of the
exiting paint propels the droplets toward the target surface. The
fluid nozzle on an airless gun differs substantially from the fluid
nozzle on an air atomized gun. Selection of the proper nozzle
determines how much paint is delivered and the fan pattern of
application. The size of the airless nozzle orifice determines the
quantity of paint to be sprayed. Airless fluid delivery is high,
ranging from 700-2000 mL/min. Recommended gun distance is 12 inches
from the target, and depending upon the nozzle type, a fan pattern
of 5 to 17 inches is possible. Thus, nozzles can be selected for
each application based on the size and shape of the target surface
and the thickness of the coating to be applied. Airless guns create
little air turbulence that can repel the liquid from "hard to reach
areas", such as would be found in food processing equipment,
hatcheries etc. The high flow rate makes airless advantageous in
cleaning and disinfecting situations, where the antimicrobial
coating is to be applied over a large surface area and multiple
surfaces.
[0122] The thickness of the applied and dried film will depend on a
variety of factors. These factors include the concentration of the
film forming agent, the concentration of rheology control additives
and/or other additives, as well as the application temperature and
humidity. Film thickness and film uniformity also depend, at least
in part, on parameters of the application equipment, such as fluid
delivery, spray orifice diameter, air pressure or piston pump
pressure in the case of airless application, and the distance of
the spray applicator to the target surface. Therefore, the liquid
formulation may be adjusted to yield the desired film thickness.
The atomization of the coating solution is chosen such that a thin
film is applied homogeneously to the target area.
[0123] Generally, the coating is allowed to set or dry for about 5
to about 60 minutes in order to form the film. The present
composition, when applied onto a surface, will form a film or a
coating by evaporation of the inert solvent. The solvent
evaporation could occur by allowing the coating to dry in place, or
alternatively by blowing dry with heated or unheated air. However,
the coating may be effective as an antimicrobial agent in a shorter
time-frame, such as after 30 seconds. The coating may be removed
before it is dried or anytime thereafter depending on the desired
use. The drying time will be partially dependent on a number of
factors, including environmental conditions such as humidity and
temperature. The drying time will also depend on the thickness of
the applied coating. The coating is preferably used at a thickness
of about 0.3 to about 300 microns. In a more specific embodiment,
the coating is used at a thickness of about 0.5 to about 100
microns. In an even more specific embodiment, the coating is used
at a thickness of about 1.0 to about 30 microns.
Film or Coating Thickness:
[0124] The thickness of the film or coating applied onto the target
surface influences the time needed for removal and the amount of
biocide per unit area applied to the surface. Thicker films
increase the time interval until the film has to be re-applied to
maintain the desired antimicrobial properties. Thinner films will
be easier and faster to remove by rinsing. It is thus important to
apply the formulation in a fashion that results in a film thickness
that allows both easy removal of the coating and long-lasting
antimicrobial properties. As described above, the film or coating
has a thickness of about 0.3 to about 300 microns. In a more
specific embodiment, the film or coating has a thickness of about
0.5 to about 100 microns. In an even more specific embodiment, the
film or coating has a thickness of about 1.0 to about 30
microns.
Film Removal:
[0125] This invention is directed to films that can be removed at a
time determined appropriate by the user. The time of removal can be
determined by either (i) the desired minimum contact time to allow
for the desired antimicrobial activity, typically expressed as
amount of killed or inactivated microorganisms out of a starting
population or (ii) the need or desire to take the coating off the
surface before starting a subsequent operation or process step.
Although the coating can be removed at any time, such as after
drying, the film thickness, concentration of antimicrobial agent,
and specific use determines the appropriate time for removal. For
instance the user may wish to put treated equipment back into
normal operation after a period of operational shutdown. Fruit, for
example, will require washing prior to eating. Upon exhaustion of
the biocide in the film, the film could be removed and a fresh
coating layer could be applied. For example, drains can be treated
periodically such as daily, weekly or biweekly. Antimicrobial
activity can be measured as early as after 30 seconds, hours, days,
weeks, months, even years after application of the film. Therefore,
timing of removing the coating is a function of the application for
which the coating is employed.
[0126] Film removal can be achieved by dissolution or dispersion of
the resulting coating. This can be achieved by the application an
aqueous solution onto the coating. In one embodiment, the
temperature of the solution is in the range of about 15 degrees
Centigrade to about 100 degrees Centigrade. In another embodiment,
the temperature of the solution is from about 30 to about 80
degrees Centigrade. The application of the solution, or water, can
be achieved by a simple rinse or spray onto the surface. Coating
removal can also be achieved by use of a pressure washer,
facilitating removal by additional mechanical forces. Coating
removal can also be achieved by washing with water together with a
cloth or sponge. Further, mild additives can utilized or mixed with
the aqueous solution to help solubilize or disperse the
film-forming or water-dispersible agents, including commonly used
acids or bases, chelators or detergents. Alternatively, the film
can be degraded, such as in a drain, by repeated washing of water
and/or other components down the drain. The film can also be
removed by peeling it off a surface, being abraded or brushed from
the surface, or other mechanical mechanisms of removal.
[0127] Besides the intentional removal by an operator, removal also
includes the removal by an automated or robotic system and the
non-intentional removal by a liquid continuously or periodically
contacting the coating over time, e.g. in a pipe or drain, or by
continuous or periodical application of mechanical forces, such as
wear.
Other Terms:
[0128] For clarity, terms used herein are to be understood as
described herein or as such term would be understood by one of
ordinary skill in the art of the invention. Additional, explanation
of certain term used herein, are provided below:
Aqueous Solution:
[0129] An aqueous solution used for coating removal is any solution
containing 60 to 100 wt-% water, the remaining components being
dissolved components. Dissolved components can include but are not
limited to solvents such as alcohols, solubilizing agents,
surfactants, salts, chelators, acids and bases.
Durable:
[0130] Durable in this context relates to the dried coating matter
remaining on the surface until its removal is purposely initiated
or allowed to occur. Use conditions are the environmental
conditions prevalent during the period the coating remains on the
target surface for the application areas of this invention and can
include inadvertent contact with water of a temperature below 40
degrees Centigrade.
Continuous:
[0131] Continuous, or substantially continuous, in this context
refers to a coating that covers the target surface without
uncovered areas, coating defects, such as craters and holes.
Homogeneous:
[0132] Homogeneous, or substantially homogenous, in this context
refers to a coating with only negligible thickness variations
across the coating surface. Coatings that are not homogeneous or
not substantially homogenous will not provide even antimicrobial
and removal properties across the whole surface the coating is
applied to.
Residual Antimicrobial Efficacy:
[0133] The term `residual antimicrobial efficacy` (or
self-sanitizing properties) describes the property of coatings
formed as described herein which remain active even after repeated
challenges with microbes. According to this invention, at least a
3-log unit reduction is achieved after each inoculation over at
least 2 inoculation cycles of at least 10.sup.6 cells per square
inch. The test method used to determine residual antimicrobial
efficacy is described in Example 16.
Contact Time for the Antimicrobial Coating:
[0134] Depending on the specific requirements for the antimicrobial
formulations, the contact time would vary, as set out in Germicidal
and Detergent Sanitizing Action of Disinfectants, Official Methods
of Analysis of the Association of Official Analytical Chemists,
paragraph 960.09 and applicable sections, 15th Edition, 1990 (EPA
Guideline 91-2). If the intended application of the present
invention is use as a sanitizer, then the composition should
provide a 99.999% reduction (5-log order reduction) within 30
seconds at room temperature (25+/-2.degree. C.) against several
test organisms. On the other hand, if the intention is to use the
invention as a disinfectant, then the composition should provide a
99.9% reduction (3-log order reduction) within 10 minutes. If the
intended application is to be applied as a residual antimicrobial
activity, then the present invention would be allowed to have
greater than 10 minute contact time with microorganisms.
Physical Barrier:
[0135] A physical barrier is defined as the film formed from the
present film forming composition. The resulting film seals the
treated surface from contamination from the surrounding, such as
soil, fat, dust, microorganisms etc. These contaminants will remain
on the surface of the coating and will wash off at the time of
removal of the coating.
[0136] All of the methods and compositions disclosed and claimed
herein can be made and executed without undue experimentation in
light of the present disclosure. While the methods and compositions
of the present disclosure have been described in terms of various
aspects of the invention and preferred embodiments, it will be
apparent to those of skill in the art that variations can be
applied to the compositions and methods and in the steps or in the
sequence of steps of the method described herein without departing
from the concept, spirit, and scope of the invention. More
specifically, it will be apparent that certain agents, which are
chemically related, can be substituted for the agents described
herein while the same or similar results would be achieved. All
such similar substitutes and modifications apparent to those
skilled in the art are deemed to be within the spirit, scope, and
concept of the invention as defined by the appended claims.
EXAMPLES
[0137] The present invention is further defined in the following
Examples. It should be understood that these Examples, while
indicating certain preferred embodiments of the invention, are
given by way of illustration only. From the above discussion and
these Examples, one skilled in the art can ascertain the essential
characteristics of this invention, and without departing from the
spirit and scope thereof, can make various changes and
modifications of the invention to adapt it to various uses and
conditions.
Abbreviations and other Terms:
[0138] In the following examples, "degrees Centigrade" is
abbreviated ".degree. C.".
ATCC--American Type Culture Collection
BHI--brain heart infusion
BHT--butylated hydroxytoluene
CFU--colony forming unit
Conc.--concentration
cP--centipoise
DI--deionized
L--liter
LB--Luria Bertani broth
M--mole/liter
MW--molecular weight in grams/mole
NA--not applicable
ND--not determined
PBS--phosphate buffered saline solution (buffer)-10.times. stock
solution contains (g/800 mL): NaCl (80); KCl (2.0);
NaH.sub.2PO.sub.4 (14.4); KH.sub.2PO.sub.4 (2.4) at pH 6.8
PEG--polyethylene glycol
PVOH--polyvinyl alcohol
QAC--quaternary ammonium compound
RAC--removable antimicrobial coating
RPM--revolutions per minute
SS316-stainless steel, type 316 (ASTM standard)
UHMWPE--ultra-high molecular-weight polyethylene
wt %--weight percent
ZOD--zone of diffusion
[0139] All chemicals were obtained from Sigma-Aldrich (St. Louis,
Mo., USA) unless stated otherwise. Laponite.RTM. was obtained from
Rockwood Additives Ltd. (Widnes, UK). Pseudomonas F-Agar was
obtained from Fisher Scientific (Pittsburgh, Pa., USA); yeast
extract, Brain Heart Infusion (BHI), Tryptic Soy Agar, Tryptic Soy
Broth, and Oxford Medium Base were from Difco products (Becton
Dickenson, Franklin Lakes, N.J., USA); dextrose and magnesium
sulfate heptahydrate were from JT Baker (Phillipsburg, N.J., USA);
Elvanol.RTM. (71-30 and 52-22), polyurethane (RCP 31374),
Zonyl.RTM. surfactants and titanium dioxide were from DuPont
(Wilmington, Del., USA). Kollicoat.RTM.-IR was obtained from BASF
(Ludwigshafen, Germany). Silwet.RTM.L-77 was obtained from GE
Silicones (Wilton, Conn., USA). BYK.RTM. 425 was obtained from BYK
Chemie (BYK-Chemie GmbH, Wesel, Germany). DowCorning.RTM. Q2-5211
and Antifoam C were obtained from DowCorning.RTM. Silicones
(Midland, Mich., USA). Silsurf.RTM. A012 was obtained from Siltech
Corp. (Toronto, ON, Canada). Sil-co-sil.RTM. was obtained from U.S.
Silica.RTM. Company (Berkeley Springs, W. Va., USA). Ticaxan,
Carrageenan, and Guar 8/22 were supplied by TIC Gums (Belcamps,
Md., USA). Alcogum.RTM. L1228, L15, L520 and L251 rheology
additives were obtained from Alco Chemical.RTM. (Chattanooga,
Tenn., USA) and were neutralized as specified by the supplier upon
formulation after addition to antimicrobial compositions.
Viskalex.RTM. HV100 and HV30 were obtained from Ciba.RTM. (Basel,
Switzerland).
General Methods:
[0140] Test Methods for Antimicrobial Efficacy in Solutions:
[0141] Biocidal or antimicrobial efficacy in solutions can be
determined by assays generally known in the art and as described in
the following Examples.
[0142] Test Method for Antimicrobial and Antifungal Efficacy of
Coatings by Zone-of-Diffusion Test:
[0143] To evaluate the antimicrobial and antifungal efficacy of
antimicrobial coatings a zone-of diffusion (ZOD) test was employed
as described below.
[0144] Stainless steel coupons (1 inch.times.3 inch) were dipped
into RAC formulations and allowed to dry completely overnight. An
overnight culture of Staphylococcus aureus ATCC 6358 was prepared
by taking with a sterile inoculating loop a single colony from a
refrigerated stock plate and inoculating into 25 mL of tryptic soy
broth in a 250 mL sterile Erlenmeyer flask. The culture was
incubated overnight at 30.degree. C. while shaking at 150 RPM.
Fungal spores (Aspergillus niger and Penicillium expansium) were
prepared by growing stock plates (malt extract agar) for 2 weeks at
25.degree. C., and harvesting spores by flooding plates with 15 mL
of filter-sterilized saline solution (0.85% NaCl plus 0.05% Triton
X-100). Plates were then scraped with a sterile plastic cell
scraper, the liquid was pipetted off, vortexed and filtered through
3-4 layers of sterile cheesecloth. Spore suspension CFU was
determined by plating serial dilutions onto malt extract agar
plates. Coated coupons were placed on the surface of LB agar plates
(center of plate) for 60 minutes, allowing soluble components of
the coating to diffuse into the agar. A soft agar (0.7 wt-% agar in
PBS buffer or water) was prepared, aliquoted into 5 mL portions in
sterile plastic centrifuge tubes and held at 50.degree. C. in a
water bath until use. After 60 minutes, the coupons were removed by
lifting straight up with sterile forceps, taking care not to slide
the coupons across surface of agar. Any coating pieces that are
left on the surface of the agar were also removed with sterile
forceps. Each soft agar tube is inoculated with 100 .mu.L of a 1:10
dilution of the overnight bacterial culture prepared above. The
soft agar was inoculated with approximately 10.sup.3 spores/mL when
fungal spores were used in the test. The agar was mixed gently by
rocking tube and then agar was poured onto surface of LB agar
plates which held coated coupons. Plates were swirled to completely
cover surface with soft agar. The soft agar solidified almost
immediately. Bacterial inoculated plates were incubated overnight
at 35.degree. C. and fungal inoculated plates were incubated at
25.degree. C. for 2 days. All plates were photographed to record
the zone of inhibition provided by the antimicrobial that diffused
from the antimicrobial coating into the agar. The area of this zone
of diffusion (ZOD) was analyzed by image analysis software (ImageJ,
version 1.36b, National Institute of Health, USA) and normalized by
the area of the coupons used. All agar diffusion studies had
control coupons coated with a formulation lacking the antimicrobial
agent.
[0145] Determination of rheological properties: The rheological
properties of liquid antimicrobial formulations was assessed using
a rheometer, running ascending and descending flow curves. The
rheometer used was a Brookfield HADV-III+ (Brookfield Engineering,
Middleboro, Mass., USA) with a couette geometry, small sample
adapter, spindle SC4-21 and sample chamber 13RP. The temperature
was kept at 25.degree. C. with a thermostat bath. Samples were
loaded by pouring or scooping into the Brookfield sample holder.
The program contained a pre-shear time of 5 min. at a pre-shear
shear rate of 250 1/s, followed by a rest time of 10 min. Viscosity
measurement were taken at: 0.1, 0.5, 5, 50, 100, 200, 100, 50, 5,
0.5, 0.1 RPM. The viscosity measurement interval was 2 min.
Example 1
[0146] Polyvinyl alcohol (PVOH) (DuPont Elvanol.RTM., grade 71-30,
MW approximately 94,000, degree of hydrolysis 99.0-99.8%; DuPont,
Wilmington, Del., USA) was used as the film forming agent. PVOH
stock solutions were prepared by mixing Elvanol.RTM. grade 71-30
powder into deionized water of 90.degree. C. to yield a 3 to 8 wt %
solution. The mixture was stirred using a magnetic bar stirrer for
approximately 20 minutes until the polyvinyl alcohol was completely
dissolved. The mixture was allowed to cool to room temperature.
[0147] Blend base solutions were prepared by mixing the polyvinyl
alcohol stock solutions with varying amounts of benzalkonium
chloride (QAC) as active biocide, poly(ethylene glycol) (PEG) of
MW.about.300 grams/mole as film plasticizer, polyoxyethylene
sorbitan laurate surfactants as wetting agent(s), and butylated
hydroxytoluene (BHT) as antioxidant. The QAC used was a mixture of
mostly C12 and C14 analogues of alkylbenzyldimethyl-ammonium
chloride (Sigma-Aldrich) but also contained small amounts of lower
and higher analogues.
[0148] The blend base solution was then mixed with additional
additives to yield the final spray formulation. These additives
included cross-linkers such as ferric and ferrous chloride,
rheology control modifiers such as synthetic layered silicate
(Laponite.RTM.), and colorants and opacifying agents, such as food
colorants and titanium dioxide. Liquid film-forming mixtures were
prepared as outlined in Table 1. The mixtures are referenced in the
subsequent examples by formulation number. TABLE-US-00001 TABLE 1
Examples of film-forming antimicrobial compositions prepared using
PVOH (Elvanol .RTM. grade 71-30) Formulation number #2 #10 #14a #16
#17 #18 #19 Deionized 95.9% 96.1% 95.0% 95.2% 90.9% 95.1% 96.6%
water Elvanol .RTM. 71-30 4.0% 2.9% 2.9% 1.4% 2.73% 3.0% 3.0%
PEG-300 -- -- 0.29% 0.51% 1.00% 0.21% 0.21% Tween .RTM. 20 -- --
1.08% -- 1.22% 0.02% 0.02% Tween .RTM. 60 -- -- -- 0.5% 2.2% -- --
FeCl.sub.3*6H.sub.2O -- 0.057% -- -- 0.090% -- FeCl.sub.2*4H.sub.2O
-- -- -- 0.48% 0.95% -- -- Benzalkonium 0.100% 0.096% 0.079% 0.047%
0.091% 0.100% 0.100% chloride Laponite .RTM. -- -- 0.560% 1.40% --
1.40% -- clay Kollicoat .RTM. IR -- 0.961% -- 0.466% 0.91% -- --
BHT -- -- -- -- -- 0.050% 0.050% Colorant trace -- trace trace
trace 0.060% -- Total 100% 100% 100% 100% 100% 100% 100%
Formulation number #20 #21 #22 #23 #24 #25 #26 Deionized 96.5%
96.1% 96.4% 96.3% 95.9% 94.4% 94.5% water Elvanol .RTM. 71-30 3.0%
3.0% 3.0% 3.0% 3.0% 4.0% 4.0% PEG-300 0.21% 0.21% 0.21% 0.21% 0.21%
0.28% 0.28% Tween .RTM. 20 0.02% 0.02% 0.02% 0.02% 0.02% 0.02%
0.28% Tween .RTM. 60 -- -- -- -- -- -- -- FeCl.sub.3*6H.sub.2O --
-- -- -- -- -- -- FeCl.sub.2*4H.sub.2O 0.10% 0.50% -- 0.10% 0.50%
0.12% 0.12% Benzalkonium 0.100% 0.100% 0.300% 0.300% 0.300% 0.150%
-- chloride Laponite .RTM. -- -- -- -- -- 1.00% 1.00% clay
Kollicoat .RTM. IR -- -- -- -- -- -- -- BHT 0.050% 0.050% 0.050%
0.050% 0.050% 0.050% 0.050% Colorant -- -- trace trace trace -- --
Total 100% 100% 100% 100% 100% 100% 100%
Example 2
[0149] This example demonstrated that coatings are substantially
continuous and homogeneous.
[0150] Films were prepared from the liquid mixtures outlined in
Example 1. This was done by either spraying the liquids onto
coupons (22 mm.times.60 mm) or by dipping coupons into the
solutions. To spray the liquids they were filled into standard
pump-action spray bottles and sprayed onto coupons. In most cases
stainless steel was used as the coupon material. When spraying was
used coupons were oriented vertically to model vertical food
equipment surfaces to be treated with an antimicrobial formulation.
For both dipping and spraying, coupons were then allowed to dry in
vertical orientation at room temperature for at least 2 hours,
typically overnight. The thickness of some films was measured using
confocal laser-scanning microscopy after adding trace amounts of a
fluorescent dye (rhodamine 123) to the film forming composition. A
Zeiss LM 510 confocal microscope with Zeiss LSM-5 image analysis
software (Carl Zeiss MicroImaging, Thornwood, N.Y., USA) was
used.
[0151] Formulations with 4.0 wt-% PVOH were found to have a
thickness of approx. 20 micrometers. Lower PVOH concentrations
yielded thinner films. FIG. 2 shows cross sections of Formulation
#2 through the depth of the film coating in two perpendicular
planes. The high degree of uniformity in film thickness and absence
of structural film defects (such as holes, cracks, craters, air
inclusions etc.) can clearly be observed. High film uniformity is
of high importance for protection functionality. Structural film
defects or significant thickness variations could result in some
areas remaining inefficiently protected from microbial
contamination.
[0152] Different film textures were prepared depending on the
formulations. Spraying of formulation #14a resulted in a rubbery
and soft film after drying. In contrast, spraying of formulation
#16 resulted in a very rigid and hard film after drying. Said
textures can be utilized in accordance with operator need.
[0153] Dripping of the film-forming liquid from vertical surfaces
after spraying could be prevented by addition of 0.5-1.5 wt % of
colloidal synthetic layered silicate (Laponite.RTM. RD) as a
thixotropic rheology control modifier.
Example 3
[0154] This example demonstrates that the coating solubility
depends on cross linking agent concentration.
[0155] The formulation can be adjusted to allow easy removal of the
film over a wide range of water temperatures. Film formulations can
be developed to allow the film to be soluble in either cold or hot
water temperatures. For example, films formed from Formulation #2
and #10 could easily be wiped off mechanically using a swab and
could readily be dissolved after either a rinse of 20.degree. C. or
98.degree. C. water. Films formed from Formulation #14a could
easily be wiped off mechanically and dissolved easily in 98.degree.
C. water but did not readily dissolve in 20.degree. C. water. To
achieve cold water stability a cross-linker had to be added to the
mixture. Both Fe(II)-chloride and Fe(III)-chloride were suitable
cross-linkers at concentrations between 0.1 and 1 wt % of the
liquid formulation.
Example 4
[0156] Two plastic cover slips (type Thermanox.RTM. #174942, 22
mm.times.60 mm; Nalge Nunc International, Rochester, N.Y., USA)
were dipped into a 4 wt % PVOH solution containing 1.0 g/L of
benzalkonium chloride biocide. An additional two cover slips were
dipped into a 4 wt % PVOH solution without benzalkonium chloride as
control. The cover slips were placed into 50 mL centrifuge tubes
and allowed to air-dry over night.
[0157] A culture of Listeria welshimeri (ATCC 35897) was prepared
by growing a single cell colony in 25 mL BHI (37 g/L) in a 125 mL
capacity shaker flask and incubated overnight at 30 C while shaking
at 150 RPM. The cell concentration of this overnight culture was
approximately 1.times.09 cells per mL. The culture was diluted
100-fold with modified Welshimer's medium (see Table 2 for medium
composition) to provide a cell concentration of approximately
1.times.10.sup.7 cells/mL. The coupons were placed in 50 mL
centrifuge tubes and the cell suspension (10 mL) added to the
tubes. Due to the high cell concentration the cell suspension was
completely opaque in the 50 mL tube. Tubes were loosely covered
with caps and incubated at 22.degree. C. while shaking at 150
RPM.
[0158] After 24 hours, the liquid with the biocide QAC-containing
coupon turned completely transparent to the human eye indicating
considerable cell lysis. In contrast, the liquid with the coupon
lacking QAC was still completely opaque indicating lack of any
significant cell lysis. TABLE-US-00002 TABLE 2 Formulation of
Modified Welshimer growth medium used amount per Ingredient liter
Supplier KH.sub.2PO.sub.4 6.56 g J T Baker, Philipsburg, NJ, USA
Na.sub.2HPO.sub.4*7H.sub.2O 30.96 g Acros, Morris Plains, NJ, USA
MgSO.sub.4*7H.sub.2O 0.41 g J T Baker, Philipsburg, NJ, USA Ferric
0.088 g Sigma-Aldrich, St. Louis, MO, USA citrate Glucose 10 g J T
Baker, Philipsburg, NJ, USA L-Leucine 0.1 g Sigma-Aldrich, St.
Louis, MO, USA L-Isoleucine 0.1 g Sigma-Aldrich, St. Louis, MO, USA
L-Valine 0.1 g Sigma-Aldrich, St. Louis, MO, USA L-Methionine 0.1 g
Sigma-Aldrich, St. Louis, MO, USA L-Arginine 0.1 g Sigma-Aldrich,
St. Louis, MO, USA L-Cysteine 0.1 g fresh Sigma-Aldrich, St. Louis,
MO, USA L-Glutamine 0.6 g fresh Sigma-Aldrich, St. Louis, MO, USA
Riboflavin 0.5 mg Eastman, Rochester, NY, USA Thiamine 1.0 mg
Sigma-Aldrich, St. Louis, MO, USA Biotin 0.5 mg Sigma-Aldrich, St.
Louis, MO, USA Thioctic 0.005 mg Sigma-Aldrich, St. Louis, MO, USA
acid
Example 5
[0159] One stainless steel coupon (format 22 mm.times.60 mm.times.1
mm) was coated with Formulation #22 by dipping and allowed to
air-dry. A second coupon remained uncoated as control. The two
coupons were placed into 50 mL centrifuge tubes.
[0160] A culture of L. welshimeri (strain DUP-1074) was prepared by
growing a single cell colony in 25 mL of BHI as outlined above. The
cell concentration of this overnight culture was approx.
1.times.10.sup.9 cells per mL. The culture was diluted
.times.10,000 with modified Welshimer's medium to provide a cell
concentration of approximately 1.times.10.sup.5 cells/mL. This cell
suspension (25 mL) was added to each coupon in 50 mL centrifuge
tubes and the tubes were horizontally placed into an
incubator-shaker and shaken at 25.degree. C. while shaking at 150
RPM.
[0161] Samples (500 .mu.L) were withdrawn from each tube after 10
and 240 minutes. Serial dilutions were made of each sample and 100
.mu.L of each dilution was plated onto standard LB agar plates
(Teknova, Inc., Hollister, Calif., USA) and incubated at 33.degree.
C. The number of CFU was counted after 24 hours. No significant
decrease in cells (versus control) was observed in the sample taken
after 10 minutes. However, the viable cell concentration reduced
from 4.7.times.10.sup.4 cells/mL to only 30 cells/mL after 240
minutes representing a significant 3.2 log reduction in the cell
viability.
Example 6
[0162] Experiments were conducted to observe if surfaces sprayed
with antimicrobial film coatings can delay the onset of biofilm
formation. Coupons of stainless steel (SS316, 22 mm.times.60
mm.times.1 mm) were either sprayed with formulations #14a, #16 and
#17 in vertical position or left untreated. The treated coupons
were allowed to air-dry overnight in vertical position.
[0163] A culture of Pseudomonas fluorescens (ATCC 700830, Manassas,
Va., USA) was prepared from a single colony grown overnight in 25
mL of standard M9 medium (see Table 3) at 30.degree. C. while
shaking at 150 RPM. The overnight culture was then diluted 100-fold
with a solution of diluted LB medium (1.0 part LB diluted with 9
parts deionized water and filter sterilized). The diluted culture
in the LB medium (10 mL) was added to each centrifuge tube. Tubes
were loosely covered with caps and incubated while shaking at 150
RPM at 30.degree. C. on. The medium was replaced each day by 10 mL
fresh diluted LB medium.
[0164] Table 4 outlines biofilm control properties of selected
antimicrobial PVOH films challenged with P. fluorescens
(.about.1.times.10.sup.6 cells/mL) and daily change of medium. The
growth of biofilms was delayed with all formulations. With
Formulation #14a no biofilm was observed after 2 days.
TABLE-US-00003 TABLE 3 M9 growth medium used Ingredient amount per
(sterile solutions) liter Supplier 20% Glucose 2.5 mL J T Baker,
Philipsburg, NJ, USA 10% Bacto .TM. 0.2 mL Difco, Sparks, yeast
extract MD, USA 1.0 M MgSO.sub.4*7H.sub.2O 2 mL J T Baker,
Philipsburg, NJ, USA 1.0 M CaCl.sub.2 0.1 mL Sigma-Aldrich, St.
Louis, MO, USA
[0165] TABLE-US-00004 TABLE 4 Biofilm control properties of
selected antimicrobial PVOH films challenged with P. fluorescens
ATCC 700830 Film formulation Result Untreated control Visible
biofilm at interface after 24 hours. Formulation #14a No visual
biofilm after 48 hours. Formulation #16 No visual biofilm after 24
hours. Slight biofilm starting at interface after 48 hours.
Formulation #17 No visual biofilm after 24 hours. Slight biofilm
starting at interface after 48 hours.
Example 7
[0166] The release of QAC from sprayed PVOH films was demonstrated
by release experiments. Films were sprayed on stainless steel
coupons, air-dried, submerged into deionized water and samples were
taken over time to determine the released QAC. The concentration of
the released QAC was determined by an HPLC method adapted from the
literature (R. C. Meyer, J. Pharm. Sci. 1980, 69, 1148-1150).
[0167] FIG. 3 shows the weight fraction of QAC released from the
films sprayed with Formulations #19, #20 and #21 over time. These
three formulations differed only in the amount of the cross-linker
added to the formulation. The film thickness for the sprayed films
was approximately 7.0 .mu.m as determined by a micrometer gage. The
total QAC available in the film was calculated from the
concentration in the liquid formulation and the film volume. The
semi-logarithmical graph shows the released fraction of QAC over
time up to 7 days. A very fast initial release of QAC can be
observed for all three film types. The addition of iron salt to the
formulation increases the amount of QAC released from the film.
Adjusting the amount of cross-linker in the liquid formulation
provides a means of controlling the release profile over time,
allowing a controlled and sustained release of the antimicrobial
agent.
Example 8
[0168] An aqueous solution (25 wt %) of benzalkonium chloride (QAC)
was added to a 10 wt % aqueous solution of polyvinyl pyrrolidone
(PVP K-120 in water; International Specialty Products, Wayne, N.J.,
USA) solution. The final concentration of PVP was 5 wt % and the
final concentration of benzalkonium chloride was 1 wt %. This PVP
film-forming solution was used to treat coupons for prevention of
biofilm formation.
[0169] An overnight culture of L. welshimeri was grown from a
single colony in 25 mL TSB/YE medium (Tryptic Soy Broth plus 0.6 wt
% yeast extract) in a shaker flask (30.degree. C. with shaking at
150 RPM) to a density of 1.times.10.sup.9 cells per mL. Sterile
centrifuge tubes were uncapped in a biohood and each PVC coupon
that had been thoroughly sprayed with 70 wt % ethanol was placed in
a centrifuge tube. The caps were left off of the tubes to allow the
coupons to air dry. For biofilm formation experiments, an overnight
culture of L. welshimeri was diluted 1:100 in the modified
Welshimer's medium (for example: for 20 tubes/coupons, 2 mL of
overnight culture plus 200 mL of modified Welshimer's medium was
required). A portion of this solution (10 mL) was added to each
centrifuge tube. The tubes were covered loosely with caps and
incubated at 22.degree. C. on a shaker while shaking at 150 RPM.
The medium was replaced every other day with fresh modified
Welshimer's medium.
[0170] For the experiments summarized in Table 5, the L. welshimeri
was grown on PVC (polyvinyl chloride) coupons (22 mm.times.60 mm;
Lid for Flexible Plate PVC coupons, Becton Dickenson) for a
specified time (see Table 5) to form a biofilm. When the biofilm
was formed, the coupon was treated with the PVP film-forming
solution by coating 100 .mu.L of the PVP film-forming solution onto
each side of the coupon. The PVP film was allowed to remain on the
coupon for a specified treatment time. At the end of the treatment
time, each coupon was gently rinsed with sterile PBS to remove
loosely adhering cells, and cell viability of the biofilm was
determined as described below. Each treatment was carried out in
duplicates.
[0171] To determine cell viability, the biofilm was removed from
the coupons by scraping the coupons with a sterile object (for
example, plastic, metal or wood). Both sides of the coupon were
scraped and the film was re-suspended in 10 mL of PBS buffer. The
suspension was mixed by vortexing to homogenize the cell
suspension. Serial dilutions (1:10 in PBS buffer) of the cell
suspensions were prepared, and 100 .mu.L aliquots were spread onto
Petri plates containing either the LB or the Modified Oxford Agar.
The plates were incubated at 30-37.degree. C. overnight, and
colonies were counted the following day. TABLE-US-00005 TABLE 5
Bactericidal activity of coupons treated with PVP and QAC against
Listeria welshimeri Biofilm Treatment time log reduction Sample age
(hr) (hr) (CFU/mL) PVP/QAC 16 3 7.7 PVP/QAC 16 16 7.7 PVP/QAC 48 3
7.5 PVP/QAC 48 16 7.5 PVP/no QAC 16 3 0.7 PVP/no QAC 16 16 2.2
PVP/no QAC 48 3 2.1 PVP/no QAC 48 17 1.5
Example 9
[0172] A film-forming solution of PVP K-120 and benzalkonium
chloride was prepared such that the final concentration of PVP was
5 wt % and the final concentration of benzalkonium chloride was
0.01 wt %. This solution was used to treat biofilm coupons as
described in Example 8.
[0173] The L. welshimeri biofilm was grown on PVC coupons as
described in Example 8 for 2 days after which the biofilm coupon
was treated with the PVP film-forming solution as described in
Example 8. The PVP film-forming solution was allowed to remain in
contact with the biofilm for three hours. At the end of the
treatment time, the cell viability of the biofilm was determined as
described in Example 8. Each treatment was carried out in
duplicate. The PVP film with 0.01 wt % benzalkonium chloride
yielded a 7.7 log reduction in CFU/mL.
Example 10
[0174] Polyvinyl alcohol (PVOH) (MW 100,000, >99% hydrolyzed,
Sigma Aldrich) was dissolved in water. Sodium dichloroisocyanurate
was added to this PVOH solution to achieve a final film-forming
composition of 0.1 wt % sodium dichloroisocyanurate, 5 wt % PVOH,
and the balance to 100% of DI water. This composition was used to
coat a PVC coupon which was covered by a 2 day old Listeria
welshimeri biofilm (prepared as described in Example 8). Cell
viability was determined as described in Example 8 after three
hours of contact time. The PVOH coating with sodium
dichloroisocyanurate yielded a 7.3 log reduction in CFU per mL.
Example 11
[0175] Polyurethane dispersion was synthesized as described in
US2005/0215663 paragraphs 212 through 217 (see also paragraphs 154
through 187 for abbreviations). The preparation yielded a 30 wt %
aqueous dispersion of polyurethane.
[0176] The polyurethane dispersion was diluted to 10 wt % with
ethanol. A polyurethane film-forming composition was prepared by
adding aqueous benzalkonium chloride solution to the diluted
polyurethane dispersion. The final film-forming composition was 5
wt % polyurethane, 0.5 wt % benzalkonium chloride, 25 wt % ethanol
and the balance to 100 wt % of Dl water. The coating was applied to
the surface of PVC coupons as described in Example 8, and the
coupons were air dried and placed in sterile centrifuge tubes.
[0177] An culture of Pseudomonas aeruginosa (ATCC 27853) was grown
overnight from a single colony in 25 mL of M9 Medium in a shaker
flask (30.degree. C. while shaking at 150 RPM) to a density of
1.times.10.sup.9 cells per mL. The culture was then diluted 1:100
in 0.1.times.LB medium (for example: for 20 tubes/coupons, 2 mL of
overnight culture plus 200 mL of one-tenth strength LB medium was
required). A portion of this solution (10 mL) was added to each
centrifuge tube to partially immerse the coupon. The tubes were
covered loosely with caps and incubated at 30.degree. C. for 24
hours while shaking at 150 RPM.
[0178] At the end of the treatment time, each coupon was gently
rinsed with sterile PBS to remove loosely adhering cells, and cell
viability of the biofilm was determined. Each treatment was carried
out in duplicates.
[0179] Cell viability was determined as described in Example 8,
except that Pseudomonas F Agar was used in the Petri plates. An 8
log reduction in CFU/mL was observed in this treatment; in
addition, no visible biofilm formation was observed on treated
coupons while the uncoated coupon which had a visible biofilm
formation.
Example 12
[0180] Two pipes (PVC-1120, J-M Manufacturing, Livingston, N.J.,
USA) were cut open lengthwise to yield to half pipes. The pipes
were taped together again from the outside using standard
Scotch.RTM. duct tape (3M, St. Paul, Minn., USA). Pipe geometry is
given in Table 6. The pipes were coated with formulation #91 using
a Wagner spray system (Wagner Power Painter, Model 0500179, Wagner
Spray Tech Corp., Plymouth, Minn., USA) by aligning the spray
nozzle of the system coaxially to one end of the horizontally
oriented pipes and spraying for 10 seconds.
[0181] Formulation #91 had the following composition: Elvanol.RTM.
grade 71-30 (5.0 wt %); benzalkonium chloride (0.63 wt %); Silwet
L-77.RTM. (0.15 wt %); BYK.RTM.-425 (0.1 wt %); erythrosine B (0.05
wt %) and the balance to 100 wt % of DI water.
[0182] Coverage of the coating was observed visually which was
easily achieved as the coating was colored and had a high contrast
to the white background of the pipe. Complete coverage of the top
and bottom half of the pipe was achieved up to a certain depth
which are summarized in Table 6. Even the small gaps between the
two half-pipes where completely covered with coating up to a
certain depth into the pipe as presented in the table. This example
illustrates that the invention can also be used to coat partly
closed, concave or hard-to-reach surfaces such as pipes and drains.
TABLE-US-00006 TABLE 6 Pipe properties and penetration of coating
formulation Pipe properties and coating results Pipe #1 Pipe #2
Inner diameter (mm) 51 71 Wall thickness (mm) 4 6 Length (mm) 800
700 Material PVC PVC Pipe orientation during spraying horizontal
horizontal Penetration length to yield complete 390 430 coating on
top half of pipe (mm) Penetration length to yield complete 700 550
coating on bottom half of pipe (mm) Penetration length to yield
complete 700 320 coating in gaps between half-pipes (mm)
Example 13
[0183] This example illustrates how rheology modifiers provide a
removable antimicrobial coating composition with a shear thinning
behavior. Such behavior enables easy (good sprayability), efficient
(no drip) and effective (homogeneous antimicrobial activity)
application of the composition to the surface. The example also
illustrates that the antimicrobial efficacy can be fully retained
after the addition of a rheology modifier.
[0184] The compositions used in this examples are based on a
solution of PVOH (5 wt %) in water and a selection of additives.
Addition order and formulation methods (mixing, scale etc.) vary
for specific formulations.
[0185] Here we report the viscosity in centipoise (cP) at a shear
rate of 5 and 190 s.sup.-1. High viscosities mean less waste from
dripping. The ratio of the two viscosities is a measure for the
shear thinning effect. A higher ratio points towards better shear
thinning and good sprayability.
[0186] The formulation itself was used to assess the antimicrobial
activity of the composition containing the rheology modifier by
means of the zone-of-diffusion (ZOD) test described earlier using
Staphylococcus aureus ATCC 6358. It was found that the tested
rheology modifiers were either neutral or contributing positively
to the antimicrobial activity of the coating.
[0187] The composition in this example was obtained by adding
benzalkonium chloride (0.6 wt %), Silwet.RTM. L-77 (0.15 wt %),
BYK.RTM.425 (0.1 wt %) and erythrosine B (0.05 wt %) to a solution
of PVOH (5 wt %, Elvanol.RTM. 71-30) in the balance to 100 wt % of
DI water. In a second formulation step the rheology modifiers were
added (see Table 7). TABLE-US-00007 TABLE 7 Rheological properties
of rheology modifiers in a composition containing 5 wt % PVOH in DI
water and antimicrobial activity according to the ZOD method using
Staphylococcus aureus ATCC 6358. Rheology Level Viscosity at
Viscosity at Viscosity Antimicrobial modifier (wt %) 5 s.sup.-1
(cP) 190 s.sup.-1 (cP) ratio activity (ZOD) None 0 <50 <50 NA
+ Guar 8/22 2 520 337 1.5 ND Carrageenan 2 2760 491 5.6 ND Alcogum
L520 4 300 134 2.2 + Alcogum L251 2 140 126 1.1 ND Alcogum L251 4
560 371 1.5 + Viskalex HV100 1 240 127 1.9 ND + indicates that the
area of the zone of diffusion (ZOD) was equal or larger than the
area of coated coupon used in the experiment. ND denoted "not
determined". NA denoted "not applicable".
Example 14
[0188] This example illustrates that rheology agents can be used to
provide shear-thinning properties to the coating formulation based
on polyvinyl alcohol grades of different degrees of hydrolysis. The
example also illustrates that the degree of shear thinning
(viscosity ratio) can be adjusted by varying the level of rheology
modifier added to the formulation. The rheology agent used in this
example is Alcogum.RTM. L251.
[0189] The composition in this example was prepared by loading
water (total of all ingredients 100 wt %) into a flask with
magnetic stir bar, followed by Silwet.RTM. L-77 (0.1 wt %),
benzalkonium chloride (0.05 wt %), PEG (M.about.300) (0.2 wt %),
Alcogum.RTM. L251 (various levels in Table 8), PVOH (5 wt %,
Elvanol.RTM. 71-30 in water) and indigo carmine dye (0.03 wt %).
TABLE-US-00008 TABLE 8 Rheological properties of rheology modifiers
in aqueous compositions containing 5 wt % PVOH (Elvanol .RTM.)
Elvanol Alcogum Viscosity at Viscosity at Viscosity grade L251 (wt
%) 5 s.sup.-1 (cP) 190 s.sup.-1 (cP) ratio 71-30 0 104 78 1.3 71-30
1 829 336 2.5 71-30 2 6567 570 12 52-22 0 <50 <50 NA 52-22 1
352 197 1.8 52-22 2 2839 549 5.2 NA denoted "not applicable".
Example 15
[0190] This example illustrates the use of coating formulations
according to this invention to prevent fungi from growing on
surfaces.
[0191] Fungal spores (Aspergillus niger and Penicillium expansium)
were prepared by growing stock plates (malt extract agar) for 2
weeks at 25.degree. C., and harvesting spores by flooding plates
with 15 mL of filter-sterilized saline solution (0.85% NaCl plus
0.05% Triton.RTM. X-100). Plates were then scraped with a sterile
plastic cell scraper and the liquid is pipetted off, vortexed and
filtered through 3-4 layers of sterile cheesecloth. 400 microliters
of the coating formulation was spread onto 1 inch.times.1 inch
stainless steel coupons with a sterile pipet tip.
[0192] The coating formulation #109 of this example consisted of 5
wt % Elvanol.RTM. 71-30, 0.2 wt % PEG (M.about.300), 0.2 wt %
benzalkonium chloride, 0.1 wt % Silwet.RTM. L-77, 0.05 wt %
BYK.RTM.425, 0.01 wt % erythrosine B and the balance to 100 wt % of
DI water. The coating formulation #115 used for the negative
control experiments was identical to formulation #109 except that
no benzalkonium chloride was added.
[0193] The surface was completely covered and the coatings were
allowed to dry completely (3-4 hours or overnight) in a vertical
flow biohood. A 10 mL aliquot of the spore suspension was
centrifuged and the supernatant was discarded. Spores were
re-suspended in the same volume of Czapek Dox Broth. 100
microliters of this inoculum was added to each coupon and allowed
to dry for 5 minutes. Coupons were placed with the coated side up
on water agar plates and incubated at room temperature in a
dessicator with the bottom filled with water for 2-4 weeks and
observed daily for fungal growth.
[0194] Table 9 illustrates that no fungal growth was observed for
coating formulation #109 whereas uncoated coupons or coupons coated
with a coating formulation lacking the QAC active ingredient showed
excessive growth of fungi. TABLE-US-00009 TABLE 9 Fungistatic
activity of antimicrobial coating #109 and control experiments QAC
Inoculum Coated with conc. Fungal growth after week Fungal strain
(spores/mL) formulation (ppm) 1 2 3 4 Aspergillus niger 10.sup.6
#109 2000 - - - - Aspergillus niger 10.sup.6 #115 0 +++ +++ +++ +++
Aspergillus niger 10.sup.6 No coating 0 +++ +++ +++ +++ P.
expansium 10.sup.6 #109 2000 - - - - P. expansium 10.sup.6 #115 0
+++ +++ +++ +++ P. expansium 10.sup.6 No coating 0 ++++ +++ +++ +++
- indicates that no fungal growth was observed. +++ indicates
excessive fungal growth.
Example 16
[0195] This example illustrates the use of coating formulations
according to this invention to allow antimicrobial efficacy over
extended periods of time. The example also demonstrates continued
antimicrobial efficacy after multiple reinoculations of the
antimicrobial coating with microorganisms. The example also
demonstrates the residual antimicrobial efficacy of coatings formed
from the formulation. The example also illustrates that the
antimicrobial coating is efficacious against Gram-positive
(Staphylococcus aureus) and Gram-negative (Klebsiella pneumoniae)
organisms.
[0196] To test for effect of multiple bacterial contaminations on
the efficacy of antimicrobial coatings the following method was
used. Microorganisms tested included Staphylococcus aureus ATCC
6358 and Klebsiella pneumoniae ATCC 4352. An overnight culture of
the selected microorganism was prepared by taking a single colony
from a refrigerated stock plate by loop and inoculating 25 mL of
tryptic soy broth or other liquid medium in a 250 mL sterile
plastic Erlenmeyer flask. The flask was incubated overnight at
30.degree. C. while shaking at 150 RPM. Then, 0.4 mL of coating
formulation was spread onto a 1 inch.times.1 inch stainless steel
(SS316) coupons with a sterile pipet tip. The entire surface was
covered and the coating was allowed to dry completely (3-4 hours or
overnight) in a vertical flow biohood. Besides the antimicrobial
containing formulations, coupons were also coated with formulations
lacking the antimicrobial as a control. The overnight culture was
then diluted 1:10 with phosphate dilution buffer. Five percent
sterile fetal bovine serum may be added to the culture at this time
as an additional challenge to the coating. 10 microliters of this
1:10 dilution were used each time to contaminate the coupon
surfaces by dotting on with a pipet tip in at least 20 locations
and waiting for 5 minutes. Then, two coupons for each coating
formulation and two control coupons were placed in sterile plastic
50 mL centrifuge tubes containing 20 mL of Letheen neutralization
broth. The tubes were sonicated for 10 seconds and shaked for 10
minutes (200 RPM at 25.degree. C.). These samples were then diluted
serially and plated onto LB agar plates for colony forming unit
(CFU) determination. Plates were incubated at 35.degree. C.
overnight and colonies were counted the following day. The
remaining coupons were incubated at room temperature in a
dessicator with the bottom filled with water. After one hour, the
remaining coupons are all reinoculated with 10 microliters of
diluted culture as above. After 5 minutes, two coupons for each
formulation are removed and treated as above. The process is
repeated after 2 and 3 hours after the first inoculation of the
coupons.
[0197] The coating formulation #119 used in this example consisted
of 5 wt % Elvanol.RTM. 71-30, 0.2 wt % PEG (MW.about.300), 0.05 wt
% benzalkonium chloride, 0.1 wt % Silwet.RTM. L-77, 0.01 wt %
indigo carmine dye and the balance to 100 wt % of DI water. Tables
10 and 11 show that no viable cells of the two organisms used were
recovered for the coupons coated with formulation #119 whereas the
more the 10.sup.6 cells were recovered from the coupons coated with
the identical formulation lacking the QAC. TABLE-US-00010 TABLE 10
Effect of multiple inoculations with Staphylococcus aureus (ATCC
6358) on the efficacy of coating formulation #119 Sample QAC conc.
(ppm) Time (min) CFU 1 500 5 0 2 0 5 1.3 .times. 10.sup.6 3 500 60
0 4 0 60 1.4 .times. 10.sup.6 5 500 120 0 6 0 120 1.3 .times.
10.sup.6 7 500 180 0 8 0 180 1.5 .times. 10.sup.6
[0198] TABLE-US-00011 TABLE 11 Effect of multiple inoculations with
Klebsiella Pneumoniae (ATCC 4352) on the efficacy of coating
formulation #119 Sample QAC conc. (ppm) Time(min) CFU 1 500 5 0 2 0
5 6.2 .times. 10.sup.6 3 500 60 0 4 0 60 5.4 .times. 10.sup.6 5 500
120 0 6 0 120 5.6 .times. 10.sup.6 7 500 180 0 8 0 180 5.7 .times.
10.sup.6
Example 17
[0199] This example illustrates the use of surfactants to achieve
that the formulation spreads out into a film after application to a
surface.
[0200] In this example an organosilicone (Silwet.RTM.L-77) was used
as the surfactant. The formulations of this example consisted of 5
wt % polyvinyl alcohol (Elvanol.RTM. 52-22), 0.2 wt % PEG
(MW.about.300), 0.05 wt % benzalkonium chloride, varying
concentrations of Silwet.RTM.L-77 between 0 and 1 wt % (see Table
12) and a balance to 100 wt % of DI water.
[0201] The surface tensions of the samples were measured at
temperature of 26.3.degree. C. using a Kruess K11 tensiometer
(Kruess GmbH, Hamburg, Germany) using a wetted length of 40.2
mm.
[0202] A 100 .mu.L droplet of each sample was pipetted onto clean
test surfaces of stainless steel (SS316) and ultra-high-molecular
weight polyethylene (UHMWPE). Both SS316 and UHMWPE are key
materials of construction of industrial equipment, such as
equipment used for food processing. After application of the
droplets to the surfaces the droplets were allowed to spread for 5
minutes. Digital photographs of the test surfaces were taken and
the covered spreading area of the droplets on the test surfaces was
measured by image analysis (ImageJ Software, version 1.36b,
National Institute of Health, USA). The droplets' spreading area
was used as a measure of the spreading efficacy of each
formulation. Table 12 reports the results for two surface materials
and the formulations tested.
[0203] An improvement of spreading on SS316 was already observed by
the addition of 0.001 wt % of the organosilicone surfactant
resulting in a surface tension of 35.9 mN/m. When compared to the
formulation without added surfactant, the spreading area increased
by 16% for SS316.
[0204] A more pronounced increase of the spreading area was
observed when the surface tension was lowered to 22.5 mN/m or below
using an organosilicone concentration of at least 0.3 wt %. Under
these conditions, the spreading area was increased by more than
160% for SS316 and by more than 220% for UHMWPE when compared to
the formulation without added surfactant. TABLE-US-00012 TABLE 12
Effect of Silwet .RTM.L-77 surfactant addition to antimicrobial
coating formulations on surface tension and spreading ability on
SS316 and UHMWPE surfaces. Surfactant Surface Spreading area
(mm.sup.2) conc. tension of a 100 .mu.L droplet (wt %) (mN/m) on
SS316 on UHMWPE None 38.8 72 90 0.001 35.9 84 90 0.003 33.7 91 91
0.010 29.1 93 105 0.030 25.7 109 116 0.100 24.1 114 138 0.300 22.5
194 296 1.000 21.2 213 310
Example 18
[0205] This example illustrates the use of small gas bubbles in the
antimicrobial coating as a temporary opacifying agent. For some of
the intended uses of this invention it is not always desired to
have a permanent color of the coating. For example, for the coating
of walls a colored or opaque coating could be considered
unaesthetic and a transparent antimicrobial coating may be
preferred instead. Leaving out a permanent colorant or opacifying
agent has the disadvantage that the operator applying the coating
does not obtain feedback on what parts of the surface to be coated
have already been covered. To overcome this problem, the following
embodiment of this invention can be applied. At least one foaming
agent can be added to create small gas bubbles in the film that is
created on the target surface. The gas bubbles act as an opacifying
agent and turn the freshly applied film white. To prevent the gas
bubbles to get incorporated into the dry film, at least one
antifoaming agent is also added to the formulation. The antifoaming
agent aids the breakdown of the gas bubbles while the film is still
wet to yield a transparent coating after drying.
[0206] The formulation #134 used in this example consisted of 7 wt
% Elvanol.RTM. 52-22, 0.2 wt % PEG (MW.about.300), 0.05 wt %
benzalkonium chloride, 0.2 wt % Silwet.RTM. L-77, and the balance
to 100 wt % of DI water. The formulation #134a used in this example
was identical to formulation #134 except that it contained 120 ppm
active ingredient of Antifoam C emulsion in the formulation.
[0207] The surfactants benzalkonium chloride and Silwet.RTM. L-77
caused both of the above formulations to foam and gas bubbles
(>1,000,000 per square meter) were visible in the film obtained
directly after spraying of the formulations on a surface using an
high-volume/low-pressure (HVLP) spray gun (Devilbiss GTI spray gun;
air cap #2000; 1.5 mm fluid tip; E.I. DuPont Company spray booth,
Room 112, 377 Fairall Street, Ajax, ON, Canada.) The spray
conditions were as follows: 2-3 coat application totaling 5-20
microns film at 5.degree. C.-25.degree. C., 30-60% relative
humidity). Bubbles were counted visually using 4 inch.times.4 inch
square and are reported as bubbles per square meter. The gas
bubbles gave the films a white appearance after spraying. Many of
the gas bubbles disappeared as the film dried. The remainder was
approximately 15,000 bubbles/square meter for formulation #134
lacking the Antifoam C. For formulation #134a, however, only
100-500 very small bubbles per square meter were obtained after
drying of the film (see Table 14). TABLE-US-00013 TABLE 14 Gas
bubbles in film immediately after spraying and in dried coating,
respectively. Immediately after spraying Dried coating Gas bubbles
Gas bubbles (number (number Formulation per m.sup.2) Appearance per
m.sup.2) Appearance #134 >1,000,000 White film 15,000
Transparent (large) coating with visible bubbles #134a
>1,000,000 White film 100-500 Transparent (tiny) coating
Example 19
[0208] This example illustrates the impact of film thickness on
antimicrobial properties. The antimicrobial efficacy was measured
by the zone-of-diffusion (ZOD) method using Staphylococcus aureus
ATCC 6358. The composition of coating formulation #134 is described
in Example 18. Thicker films result in a larger zone-of diffusion
and thus improved biocidal properties of the coating.
TABLE-US-00014 TABLE 14 Antimicrobial efficacy as a function of
coating thickness for formulation #134. Antimicobial efficacy was
determined by zone of diffusion method using Staphylococcus aureus
ATCC 6358. Coating thickness Antimicrobial efficacy (ZOD)
(micrometers) (in coupon areas) 8 1.89 12 2.12 15 2.33
* * * * *