Note: Descriptions are shown in the official language in which they were submitted.
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DISPOSABLE CONTAINERS COATED WITH A LATEX COATING
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to disposable
containers. More particularly, the present
invention relates to molded foam containers that a re
made from thermoplastic particles, e.g. expandable
polystyrene particles (EPS), and that are coated
with a latex coating. The containers are used to
retain liquids, e.g. coffee or foods containing of 1
and/or fatty components, e.g. precooked fat-
containing foods, e.g. instant noodles, soups, fried
chicken, sauces, and the like. The invention also
relates to a method for forming a container, an
article of manufacture, and an improved method for
storing liquid and food substances.
2. Background Art
The manufacture of molded foam containers, e.g.
cups, bowls, etc. from expanded thermoplastic
particles is well known. The most commonly used
thermoplastic particles are expandable polystyrene
(EPS) particles.
Typically, polystyrene beads are impregnated
with hydrocarbon, e.g. pentane as a blowing agent
that boils below the softening point of the
polystyrene and causes the beads to expand when
heated.
The formation of molded containers from
impregnated polystyrene beads is generally done in
two steps. First, the impregnated beads are pre-
expanded to a density of from about 2 to 12 pounds
per cubic foot. Second, the pre-expanded beads are
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heated in a closed mold to further expand the pre-
expanded beads to form a fused article having the
shape of the mold.
The expandable polystyrene particles used to
make foam containers are generally prepared by an
aqueous suspension polymerization process, which
results in beads that can be screened to relatively
precise bead sizes. Typically, the raw bead
diameters for making containers, such as cups, range
from about 0.008 to about 0.02 inch. It has been
known to produce cups from beads having a diameter
of about 0.03 inches.
In spite of careful bead size control, one
problem that continues to plague the container
industry is that after a period of time the
containers, especially those made from EPS
particles, have a tendency to leak. That is,
liquids, especially hot liquids, e.g. coffee, water,
oil and/or fat, permeate around the fused
polystyrene beads and leak onto the outer surface of
the container. Generally, this results in an unsafe
condition for the person holding the container
and/or results in stains appearing on the outer
surface of the container. It is known that leakage
resistance is dependent on temperature. That is,
hot liquid and food substances tend to penetrate
around the fused beads faster than cold substances.
Several approaches have evolved over the years
in an attempt to reduce leakage in containers that
retain cold and hot liquids and/or pre-cooked foods.
Amberg et al., U.S. Patent 4,036,675 discloses
a container made from foamed plastic material,
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preferably foamed polystyrene, which is lined on one
or both sides with unoriented polyolefin film,
preferably polypropylene. The film is secured to
the foamed plastic base material using as a heat-
sensitive adhesive a vinylic polymer or polyamide
resin. The film is coated with a wet adhesive and
dried before laminating the film to the foam
material. Laminating is done by heating the foam
material to 250-275°F, preheating the coated film to
100-180°F, and pressing the coated film surface
against the heated foam for 10 to 15 seconds by
using a cold platen or roller.
Sonnenberg U.S. Patent Nos. 4,703,065 and
4,720,429 disclose thermoplastic polymer foam cups
for retaining coffee that are molded from
thermoplastic polymer particles whose surfaces are
coated with a fluorosurfactant before molding.
Sonnenberg U.S. Patent No. 4,785,022 discloses
a method for enhancing the coffee retention of
molded foam cups, which involves coating the
expandable polystyrene particles with various rubber
polymers and copolymers. The rubber can be
polybutene, polyisobutylene, isobutylene-butene
copolymer and butene-ethylene copolymer.
Arch, et al. U.S. Patent No. 4,798,749
approaches the problem of coffee leakage by
replacing conventional blowing agents such as
butanes, n-pentane, hexanes, and the halogenated
hydrocarbons with isopentane in the expandable
styrene polymer particles.
Ikeda, et al., U.S. Patent No. 4,698,367
discloses expandable thermoplastic resin particles
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in which the thermoplastic resin, composed of
fluorinated vinyl polymer and hydrophilic vinyl
polymer, covers or is included on the surface or in
the surface layer of the expandable thermoplastic
particle. The resin particles are useful for
producing package containers for oily or fatty
foods.
Sakoda et al., U.S. Patent No. 6,277,491 B1 is
directed to preventing oil from penetrating into a
molded container made from expandable thermoplastic
resin beads. The resin beads are coated or
incorporated with a fluorine-containing block
copolymer comprising a fluorine-containing vinyl-
type polymer segment derived from a fluorine-
containing vinyl-type monomer and a lipophilic
vinyl-type polymer segment derived from a lipophilic
vinyl-type monomer.
The above prior art containers are addressed to
polystyrene containers, such as cups or bowls. The
following patents pertain to paper cups that are
either spray coated or that contain a thermoplastic
resin film either for heat insulating purposes or
for producing a high impermeability to liquids.
For example, Suzuki et al., U.S. Patent No.
4,206,249 discloses a process for producing a paper
container having a high impermeability to liquids
which involves spray coating a polymerizable
solution containing a pre-polymer onto a wall
surface of the paper container and irradiating the
coated wall with ultraviolet light to set the pre-
polymer onto the wall surface thereof. This forms a
coating that is impermeable to liquids, such as
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water, milk, soft drinks, oils, etc. This patent
teaches in column 2, lines 45-62, a method in which
the interior wall surface of the Container is lined
with a thermoplastic film. The thermoplastic film
is first laminated onto a blank and the blank is
formed into a container.
Iioka, U.S. Patent No. 4,435,344 discloses a
heat-insulating paper container where the outer and
inner surfaces are extrusion coated or laminated
with a thermoplastic synthetic resin film. The
resin film is converted into a foamed layer on the
paper substrate and the container is formed. The
result is a container with good thermo-insulation
properties. This film preferably is polyethylene
and as taught in column 3, lines 50-55, this resin
film can be polypropylene, polyvinyl chloride,
polystyrene, polyester, nylon and the like.
Iioka et al., U.S. Patent No. 5,490,631
discloses a heat insulating paper container
comprising a body member wherein a thick foamed heat
insulating layer made of a thermoplastic synthetic
resin film is formed in the printed area of the
outer surface and a less thick foamed heat-
insulating layer that can be made of the same
thermoplastic synthetic resin film is formed in the
non-printed area of the outer surface. The
thermoplastic synthetic resin film is typically
polyethylene.
Breining, et al., U.S. Patent No. 6,416,829 B2
discloses a heat insulating paper cup where the body
member is coated on its outside surface with a
foamed low density polyethylene, and on. its inside
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surface with an unfoamed modified low density
polyethylene.
None of these prior art containers pertain to
thermoplastic containers that are coated with a
latex coating and are used to retain and/or store
liquid and food substances, such as coffee, soups,
stews, pre-cooked foods and the like.
SUMMARY OF THE INVENTION
The invention has met the above need. A
thermoplastic container is molded from expandable
thermoplastic particles and a latex. coating is
applied to a portion of at least one of the inner
and outer surfaces of the container; preferably to
the inner surface; and more preferably to both the
inner and outer surfaces. The container is
relatively impenetrable thereby substantially
reducing or eliminating leakage, and therefore,
stains from forming on the surfaces of the
container.
The latex coating, if applied to the outer
surface of the container can also be used for
labeling and/or printing purposes.
The latex coating may be selected from the
group consisting of latex of methyl methacrylate and
styrene copolymer, latex of methyl acrylate and
styrene copolymer, latex of acrylic acid and styrene
copolymer, and latex of butadiene and styrene
copolymer.
The thickness of the coating may range from
about 0.10 mils (0.27 mg dry coating weight per
square centimeter cup surface) to about 5.0 mils
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(13.4 mg dry coating weight per square centimeter
cup surface), and preferably may be about 0.9 mils
(about 0.25 mg dry coating weight per square
centimeter cup surface). The coating may be applied
to a portion of or to the entire inner and/or outer
surface of the container. In an embodiment of the
invention, the coating is applied substantially to
the entire inner and/or outer surface of the
container.
The latex coating is applied to the containers
surfaces via a brushing process, a dipping process,
or a spraying process, e.g. via an airless spraying
device or devices.
The container is made from expandable
thermoplastic resin beads, and in some embodiments,
this expandable thermoplastic resin is expandable
polystyrene (EPS).
Some embodiments of the invention involve a
molded thermoplastic container that exhibits
improved resistance to leakage and/or stain and
improved insulation properties.
Some embodiments of the invention involve a
latex coating that is applied to the inner and/or
outer surface of a molded thermoplastic container.
Other embodiments of the invention involve a
method for applying a latex coating to the surfaces
of a molded thermoplastic container.
And still other embodiments involve an article
of manufacture comprising a molded thermoplastic
container that is coated with a latex coating and
that contains a liquid or food substance, and which
container has improved storage longevity, improved
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stain resistance, and/or improved leakage
resistance.
These and other aspects of the invention will
be more fully appreciated and understood from the
following description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
In the invention, containers, e.g., cups,
bowls, and the like are molded from expandable
thermoplastic particles. The expandable
thermoplastic particles are made from any suitable
thermoplastic homopolymer or copolymer.
Particularly suitable for use are homopolymers
derived from vinyl aromatic monomers including
styrene, isopropylstyrene, alpha-methylstyrene,
nuclear methylstyrenes, chlorostyrene, tert-
butylstyrene, and the like, as well as Copolymers
prepared by the copolymerization of at least one
vinyl aromatic monomer with monomers such as
divinylben~ene, butadiene, alkyl methacrylates,
alkyl acrylates, aCrylonitrile, and malefic
anhydride, wherein the vinyl aromatic monomer is
present in at least 50% by weight of the Copolymer.
Styrenic polymers are preferred, particularly
polystyrene. However, other suitable polymers may
be used, such as polyolefins (e. g. polyethylene,
polypropylene), and polycarbonates, polyphenylene
oxides, and mixtures thereof.
Preferably, the expandable thermoplastic
particles are expandable polystyrene (EPS)
particles. The particles can be in the form of
beads, granules, or other particles convenient for
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expansion and molding operations. Particles
polymerized in an aqueous suspension process are,
essentially spherical and are preferred for molding
the foam container of the invention. The particles
are screened so that their diameter ranges from
about 0.008 to about 0.02 inch.
The expandable thermoplastic particles are
impregnated with a suitable blowing agent using any
conventional method. For example, the impregnation
can be achieved by adding the blowing agent to the
aqueous suspension during the polymerization of the
polymer, or alternatively by re-suspending the
polymer particles in an aqueous medium and then
incorporating the blowing agent as taught in U.S.
Patent No. 2,983,692 to D. Alelio.
Any gaseous material or material which will
produce gases on heating can be used as the blowing
agent. Conventional blowing agents include
aliphatic hydrocarbons containing 4 to 6 carbon
atoms in the molecule, such as butanes, pentanes,
hexanes, and the halogenated hydrocarbons, e.g.
CFC's and HCFC'S, which boil at a temperature below
the softening point of the chosen polymer. Mixtures
of the aliphatic hydrocarbons blowing agents can
also be used.
Alternatively, water can be blended with these
aliphatic hydrocarbons blowing agents or water can
be used as the sole blowing agent as taught in U.S.
Patent Nos. 6,127,439; 6,160,027; and 6,242,540
assigned to NOVA Chemicals (International) S.A. In
the aforesaid patents, water-retaining agents are
used. The weight percentage of water for use as the
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blowing agent can range from 1 to 20%. The teachings
of U.S. Patent Nos. 6,127,439, 6,160,027 and
6,242,540 in their entirety are incorporated herein
by reference.
The impregnated thermoplastic particles are
generally pre-expanded to a density of from about 2
to about 12 pounds per cubic foot. The pre-
expansion step is conventionally carried out by
heating the impregnated beads via any conventional
heating medium, such as steam, hot air, hot water,
or radiant heat. One generally accepted method for
pre-expanding impregnated thermoplastic particles is
taught in U.S. Patent No. 3,023,175 to Rodman.
The impregnated thermoplastic particles can be
foamed cellular polymer particles as taught in Arch
et al. U.S. Patent Application Serial No. 10/021,716
assigned to NOVA Chemicals Inc, the teachings of
which in their entirety are incorporated herein by
reference. The foamed cellular particles are
preferably polystyrene that are pre-expanded to a
density of from about 12.5 to about 34.3 pounds per
cubic foot, and that contain a volatile blowing
agent level less than 6.0 weight percent, preferably
from about 2.0 wt % to about 5.0 wt %, and more
preferably ranging from about 2.5 wt % to about 3.5
wt o based on the weight of the polymer.
In a conventional manner, the pre-expanded
particles ("pre-puff") are heated in a closed mold
to further expand the particles and to form the foam
molded container of the invention.
In general, the latex coating suitable for use
in the invention is of the type that will not be
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detrimental to the thermoplastic particles forming
the container. That is, the latex coating of the
invention will be devoid of any chemicals that tend
to dissolve or react with the thermoplastic
particles, particularly polystyrene particles. For
example, most solvent-based polymeric coatings would
not be feasible in the invention.
"Latex" can be defined as a colloidal
dispersion of polymer particles in an aqueous
medium, such as water. The phase ratio (polymer
phase to aqueous phase) may range from 40:60 to
60:40 by weight. In the latex coating industry, a
more common term is "solids content". "Solids
content" as used herein refers to the dry matter
that comprises the polymer, emulsifiers, inorganic
salts, etc. in the latex coating. A typical range
for the solids content is between 40 and 60 percent
weight. This measurement is derived by drying a
latex coating sample to a constant mass at a
temperature between 100 and 140°C. The solids
content is then expressed as the percentage ratio of
the dry matter to the total mass of the sample.
The latex used in the invention may contain
surfactants and/or other minor components. The
surfactant, which generally is used for stability
purposes, may be any of the commonly known
surfactants used in latex coatings such as sodium
octyl sulfonate, sodium decyl sulfonate, sodium
dodecyl sulfonate, sodium tetradecyl sulfate, sodium
hexadecyl sulfate, sodium dodecyl sulfate, branched
sodium alkyl sulfate, sodium dodecyl ethoxylate
(2E0), dodecyl alcohol ethoxylate (5E0), dodecyl
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alcohol ethoxylate (7E0), dodecyl alcohol ethoxylate
(8E0), etc.
A particularly suitable polymer of the latex
coating of the invention may be a monomer selected
from the group consisting of butadiene, n-butyl
acrylate, i-butyl acrylate, 2-ethylhexyl acrylate,
methyl acrylate, ethyl acrylate, octyl acrylate,
vinyl acetate, vinyl chloride, vinylidene chloride,
vinyl pivalate, vinyl neo-decanoate, acrylonitrile,
methyl acrylonitrile, acrylamide, styrene, cx-methyl
styrene, methyl methacrylate, ethyl methacrylate, n-
butyl methacrylate, i-butyl methacrylate; or the
polymer may be selected from the group consisting of
a homopolymer or the copolymer of two or more of the
above monomers or the copolymer of two or more of
the above monomers with the following functional
monomers including acrylic acid, methacrylic acid,
itaconic acid, fumaric acid, hydroxyethyl acrylate,
hydroxyethyl methacrylate, diethylaminoethyl
methacrylate, tent-butylaminoethyl methacrylate,
acrylamide, dimethyl meta-isopropenyl benzyl
isocyanate, N-methylolacrylamide, N-methylol
methacrylamide, N-(iso-butoxymethyl)acrylamide,
glycidyl acrylate, glycidyl methacrylate, sodium
styrene sulfonate.
The latex coating may be comprised of a polymer
selected from the group consisting of acrylate,
ethyl acrylate, methyl methacrylate, methacrylate,
acrylic acid, methacrylic acid, monomers or the
copolymers of these monomers combined with vinyl
acetate or styrene.
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S Preferred latex coatings are latex of methyl
methacrylate and styrene copolymer, latex of methyl
acrylate and styrene copolymer, latex of acrylic
acid and styrene copolymer, and latex of butadiene
and styrene copolymer.
The molecular weight for the latex coating may
range from about 100 to about 1 million units (500
to about 200 million g/mol). The molecular
polydispersity for the latex coating may be defined
as ranging from very narrow to very broad, i.e. from
about 1.0 to about 20.
The thermoplastic container may be a
polystyrene cup that is fabricated by a conventional
cup-forming machine that has an inner shell and an
outer shell. A conventional cup-forming machine is
Cup Production MODEL 6-VLC-125 machine, made by
Autonational B.V. or is MODEL M10 cup machine, made
by Master Machine & Tool Co.
In the invention, after the container is
formed, the latex coating is applied to a portion of
at least one of the inner and outer surfaces,
preferably, the inner surface, and more preferably,
both the inner and outer surfaces. Preferably, the
latex coating is applied to substantially the entire
inner and/or outer surface.
The latex coating may be applied to the surface
or surfaces of the container via any suitable
process, including a dipping process, a brushing
process, or a spraying process via any suitable
means. A spraying process may be preferred from
both an economic and production standpoint.
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The type of latex coating particularly suitable
for the invention is comprised of polymers in solid
particulate form and water. The initial solids
content of the polymer may be about 48o to about 500
by weight, which can be adjusted to change the
viscosity so that the process equipment, such as the
spraying system, can adequately handle the
application of the coating onto the container.
The solids content of the latex prior to being
applied to the container's surface generally will
depend on the process being used to apply the latex
to the container. For example, if a spraying
process or a brushing process is used, preferably
the solid contents will range from about 40% to
about 47o by weight, based on the weight of the
latex. If a dipping process is used, preferably the
solid contents will range from about 8% to about 200
by weight.
After the latex is applied to the surface or
surfaces of the container, the container may then be
carried via a transport belt to a drying chamber or
oven. The drying oven may be a conventional oven
and the heating medium may be hot air, radiant heat,
or heat plus vacuum. Preferably, the heating medium
is hot air. A typical drying oven is obtained from
Blue M Electric Company, Blue Island, Illinois. The
drying time is dependent on the drying temperature,
the solids content of the coating, and the coating
thickness. For example if the coating is 1.5 mils,
the drying temperature will be about 90°C with a
drying time of about 60 seconds. Typically, the
drying temperature will range from about 50°C to
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about 100°C and the drying time will range from
about 5 seconds to about 3000 seconds for coatings
with a solids content ranging from about 8% to about
47o by weight.
As stated herein, the thickness of the latex
coating on the surface or surfaces of the container
may range from about 0.10 mils (0.27 mg dry coating
weight per square centimeter cup surface) to about
5.0 mils (13.4 mg dry coating weight per square
centimeter cup surface), and preferably may be about
0.9 mils (0.25 mg dry coating weight per square
centimeter cup surface). This coating thickness may
extend on a portion of or substantially on the
entire inner and/or outer surface of the container.
In a preferred embodiment of the invention, the
latex is applied to the container via a spraying
process. The production rate for a single spraying
device for spray coating the latex onto the inner
surface of a 16-ounce cup may range from about 50 to
about 600 cups per minute. It is apparent that
several spraying devices can be used to accommodate
the desired production rate of the cups.
A spraying device that may be useful in the
invention is an airless spraying device available
from Nordson Corporation. An example of a spraying
device provided by Nordson Corporation is disclosed
in the aforesaid Suzuki et al., U.S. Patent No.
4,206,249. In this instance, it is preferable that
the airless spraying device applies the latex at
room temperature instead of at the elevated
temperatures taught in U.S. Patent No. 4,206,249.
It is understood that minor modifications can be
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made to the spraying device of the '249 patent when
spraying the latex coating of the invention.
The coating rate can be defined as "the dry
weight of the coating sprayed onto the unit surface
area of the container". As stated herein, the
coating rate may range from about 0.27 milligrams to
about 13.4 milligrams dry coating weight per square
centimeter cup surface.
The latex is applied to a portion of or
substantially onto at least one of the inner and
outer surfaces of the container to form a coating;
preferably to the inner surface; and more preferably
to both inner and outer surfaces.
The latex coating may be applied to the outer
surface for leakage resistance purposes and/or for
labeling and printing purposes. It is to be
understood that the container has both a sidewall
and a bottom section and that the "inner surface"
and the "outer surface" generally will refer to both
the sidewall and bottom section of the container.
The invention is further illustrated, but not
limited by, the following examples.
Examples
Example 1
This example illustrates the preparation of
latex coated containers. Expandable polystyrene cup
beads (DYLITE~ beads from NOVA Chemicals, Inc.,
which comprise polystyrene and pentane) were blended
with zinc stearate and pre-expanded in an 11-gallon
(about 1.5 cubic foot) Rodman Steam pre-expander
(Artisan Industries Inc.) at atmospheric pressure.
The pre-expansion was operated batch wise. 3.5
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pounds of cup beads having a diameter distribution
of about 0.008 inches to about 0.02 inches were used
to make pre-puff with a density of about 3.5 pounds
per cubic foot. The newly prepared pre-puff was air
dried for 5 minutes to remove the moisture and aged
for about 4 hours before molding.
Sixteen-ounce cups were molded from the aged
pre-puff beads. The steam header pressure was 80
pounds per square inch and the total cycle time was
in the range of 6 to 15 seconds. The molded foam
cups were allowed to age overnight.
Latex (Roymal 45526 product manufactured. and
marketed by Roymal Incorporated, which is a latex of
methyl acrylate, acrylic acid, and styrene
copolymer), was sprayed onto the inner surface, i.e.
both the sidewall and the bottom, of the cups at a
coating rate of 1.7 to 4.3 mg dry coating weight per
square centimeter cup surface, using an airless
spray device manufactured and sold by the Nordson
Corporation. For this latex product, the ratio of
styrene to methyl acrylate may range from about 5:95
percent weight to about 95:5 percent weight based on
the weight of the polymer segments, and the acrylic
acid may range from about 0 to 10% by weight in the
total polymer weight. The latex contained 48% by
weight solids.
Prior to applying the latex to the inner
surface, the latex was diluted with de-ionized water
to produce a latex containing 46o by weight solids.
The coated cups were then dried in an oven
using a combination of hot air circulation and
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radiant heat at 90°C for 1 minute. The coated cups
were stored overnight before being. tested.
The coated cups were tested by the following
method: Spicy oil at room temperature was poured
into each container to fill the cup up to about 800
of its capacity. The outer surface of each
container was observed for oil stains and leakage
every 10 minutes for the first..l.5 hours, every 30
minutes in the time frame from 1.5 hours to 6 hours,
and, then, every hour thereafter for a total of 48
hours .
The average time to failure (ATF) for each cup
group sampling was calculated by adding the time to
failure for each container, and dividing the total
time to failure by the number of containers tested.
Typically, ten cups in each group were tested. A
maximum ATF value of 48 hours means that none of the
cups in that group exhibited any stain or leakage.
A minimum ATF value of 0.17 hours means that all of
the cups in that group failed within the first 10
minutes.
The results for the oil retention (ATF) are
shown in Table 1. As indicated, the cups with the
latex coating had an increased ATF compared to the
cups without the latex coating (control).
Table 1
Coating rate ~ 0 1.7 2.5 3.8 4.3
( mg / cm2
)
ATF (hour) 0.83 38.9 48 48 48
Remark Control
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Example 2
The EPS cups were 6 ounce cups. The oil
retention test (ATF) for these EPS cups having a
pre-puff density of 3.5 pounds per cubic foot was
performed in a manner similar to that for Example 1.
The type of latex coating was the same as that
used in Example 1. The coating was first diluted
with water to produce coatings with varying solids
content. The molded foam cups were coated via a dip
coating process with the diluted latex so that both
the inner and the outer surfaces of the cups were
coated. The coated cups were dried at room
temperature overnight before being tested. The
results are shown in Table 2.
The cups with the latex coating have an
increased ATF compared to those cups without the
latex coating (control).
Table 2
Coating 6.OU 9. Op 12.0
Thickness
Solid - 8.08 12.13 16.17
content (%)
ATF (hr) 0.83 16.4 48 48
Remark Control
Example 3
The procedure of Example 1 was repeated except
the testing method was replaced by the following
method.
Four coated cups were tested by the following
method: 1) Oil fried pre-shaped cup noodles, such as
those available in the market, were placed in each
cup. 2) Three grams of red pepper powder were spread
evenly onto the noodle surfaces. 3) Each cup was
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tightly sealed with an adhesive label and plastic
stretch film, and placed in the oven at a
temperature of 149°F (65°C). 4) Each sample was
checked for stains first every hour during a 7 hour.
period and then once every 8 hours until failure for
a total of 72 hours or 3 days.
The average time to failure (ATF) was
calculated similar to that set forth in Example 1.
The maximum ATF value of 72 hours represents that
none of the cups for the cup group sampling
exhibited any stain or leakage. The minimum ATF
value of 1 hour represents that all of the cups in
the cup group sampling failed within the first 1
hour.
The results for the stain resistance, in terms
of ATF, are shown in Table 3.
Table 3
Coating rate (mg/cm2) 0 3.8
ATF (hour) 1.8 72.0
Remark Control
As indicated in Table 3, the cups with the
latex coating had an increased ATF for the mixture
of fried noodles and red pepper powder compared to
the cups without the latex coating (control).'
Example 4
The procedure of Example 1 was repeated except
the testing method was replaced by the following
method .
The coated cups were tested by the following
method: Salsa sauce, which is a spicy sauce, was
poured at room temperature into each container to
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fill the cup up to about 900 of its capacity. The
outer surface of each container was observed for
stains and leakage every one hour for a total of 48
hours.
The average time to failure (ATF) for each cup
group sampling was calculated by adding the time to
failure for each container, and dividing the total
time to failure by the number of containers tested.
Typically, five cups in each group were tested. A
maximum ATF value of 48 hours means that none of the
cups in that group exhibited any stain or leakage.
A minimum ATF value of 1 hour means that all of the
cups in that group failed within the first hour.
The results for the stain resistance, in terms
of ATF, are shown in Table 4.
Table 4
Coating rate (mg/cm~) 0 3.8
ATF (hour) 2.0 48.0
Remark Control
As indicated in Table 4, the cups with the
latex coating had an increased ATF for salsa sauce
compared to the cups without the latex coating
( control ) .
While the present invention has been
particularly set forth in terms of specific
embodiments thereof, it will be evident to those
skilled in the art that numerous variations and
details of the invention may be made without
departing from the instant invention as defined in
the appended claims. For instance, different types
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of latex coatings can be applied in one or more
layers to one or more surfaces of the container.
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