MXPA06007127A - Disposable containers coated with a latex coating. - Google Patents

Abstract

A molded thermoplastic container e.g. cup, bowl made from expandable thermoplastic particles e.g. expandable polystyrene, has a latex coating, e.g. 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, applied to at least its inner surface via dipping, brushing or spraying processes for improved leakage and/or stain resistance and/or storage longevity. The coating may be applied to the outer surface of the container for leak resistance and printing purposes. A related method for forming the container, an article of manufacture, and an improved method for storing liquid and food substances are also disclosed.

Description

DISPOSABLE CONTAINERS COATED WITH A LATEX COVER FIELD OF THE INVENTION The present invention relates to disposable containers. More particularly, the present invention relates to molded foam containers which are made of thermoplastic particles, for example expandable polystyrene (EPS) particles, and which are coated with a latex coating. The containers are used to contain liquids, for example coffee or foods containing oil and / or fatty components, for example 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 liquids and food substances.

BACKGROUND OF THE INVENTION The manufacture of molded foam containers, for example cups, bowls, ect. of expanded thermoplastic particles is well known. The most commonly used thermoplastic particles are expandable polystyrene (EPS) particles. Typically, the polystyrene beads are impregnated with hydrocarbon, for example pentane as a Ref. 173885 blowing agent which boils below the softening point of the polystyrene and causes the beads to expand when heated. The formation of molded containers of impregnated polystyrene beads is generally given in two stages. First, the impregnated beads are pre-expanded to a density of approximately 2 to 12 pounds per cubic foot (0.032 to 0.192 g / cm3). Second, the pre-expanded beads are 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 sifted to relatively accurate bead sizes. Typically, bead diameters for making containers, such as cups, vary from about 0.008 (0.020 cm) to about 0.02 inches (0.050 cm). It has been known to produce cups from pearls having a diameter of approximately 0.03 inches (0.076 cm). In addition to the pearl size control, a problem that continues to plague the container industry is that after a period of time the containers, especially those made of EPS particles, have a tendency to leak. That is to say, liquids, especially hot liquids, for example coffee, water, oil and / or grease, penetrate around the fused polystyrene beads and filter on the external surface of the container. Generally, this results in an unsafe condition for the person holding the container and / or resulting in spots appearing on the external surface of the container. It is known that the resistance to filtration is dependent on temperature. That is, hot food and liquid substances tend to penetrate around the fused beads faster than cold substances. Various procedures have been developed over the years in an attempt to reduce leakage in containers containing hot and cold liquids and / or precooked foods. Amberg et al. , US Pat. No. 4,036,675 discloses a container made of foamed plastic material, preferably foamed polystyrene, which is coated 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 vinyl polymer or polyamide resin. The film is coated with a wet adhesive and dried before lamination of the film to the foam material. Lamination is done by heating the foam material to 250-275 ° F (119.9-133.65 ° C), preheating the coated film to 100-180 ° F (37.4-81.4 ° C), and pressing the coated film surface against the foam warm for 10 to 15 seconds using a roller or cold plate. Sonnenberg, Patents of the United States Nos. 4,703,065 and 4,720,429 disclose cups of thermoplastic polymer foam to contain coffee that are molded of thermoplastic polymer particles whose surfaces are coated with a fluorosurfactant prior to molding. Sonnenberg, Patent of the United States No.

No. 4,785,022 discloses a method for improving coffee retention of molded foam cups, which involves coating the expandable polystyrene particles with various copolymers and rubber polymers. The rubber can be polybutene, polyisobutylene, isobutylene-butene copolymer and butene-ethylene copolymer. Arch, et al, U.S. Patent No. 4,798,749 proposes the problem of coffee filtration by replacing conventional blowing agents such as butanes, n-pentane, hexanes, and hydrocarbons halogenated with isopentane in the expandable styrene polymer particles. Ikeda, et al., U.S. Patent No. 4,698,367 discloses expandable thermoplastic resin particles in which the thermoplastic resin, composed of fluorinated vinyl polymer and hydrophilic vinyl polymer, covers or is included on the surface or in the layer surface of the expandable thermoplastic particle. The resin particles are useful for producing packaging containers for oily or fatty foods. Sakoda et al., U.S. Patent No. 6,277,491 Bl is directed to prevent oil from entering a molded container made of expandable thermoplastic resin beads. The resin beads are coated or incorporated with a fluoro-containing block copolymer comprising a vinyl-type polymer segment containing fluoro derivative of a fluoro-containing vinyl monomer and a lipophilic vinyl-type polymer segment derived from a vinyl-type monomer lipophilic The prior art containers are directed to polystyrene containers, such as cups and bowls. The following patents pertain to paper cups that are either spray coated or contain a thermoplastic resin film either for heat insulation purposes or to produce high liquid impermeability. For example, Suzuki et al., U.S. Patent No. 4,206,249 discloses a process for producing a paper container having a high liquid impermeability which involves spraying a polymerizable solution containing a pre-polymer onto a surface. of wall of the paper container and irradiate the wall coated with ultraviolet light to place the prepolymer on the wall surface thereof. This forms a coating that is impervious to liquids, such as water, milk, non-alcoholic beverages, oils, etc. This patent teaches in column 2, lines 45-62, a method in which the inner wall surface of the container is coated with a thermoplastic film. The thermoplastic film is first laminated on a white and the white is formed in a container. Iioka, U.S. Patent No. 4,435,344 discloses a thermal insulation paper container wherein the outer and inner surfaces are laminated or extrusion coated 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 thermal insulation properties. This film is preferably 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 thermal insulation paper container comprising a body member wherein a thick foamed thermal insulation layer made of a thermoplastic synthetic resin film is formed in the printed area of the outer surface and a less thick foamed thermal insulation layer that can be made of the same thermoplastic synthetic resin film is formed in the unprinted 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 paper cup of thermal insulation wherein the body member is coated on its outer surface with a foamed low density polyethylene, and on its inner surface with a polyethylene of modified low density non-foamed. None of these prior art containers belong to thermoplastic containers that are coated with a latex coating and are used to contain and / or store food and liquid substances, such as coffee, soups, stews, precooked foods and the like.

BRIEF DESCRIPTION OF THE INVENTION The invention has satisfied the above need.

A thermoplastic container is molded of 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 both to the inner and outer surfaces. The container is relatively impenetrable whereby filtration is substantially reduced or eliminated, and therefore, stains are formed on the surfaces of the container. The latex coating, if applied to the outer surface of the container may also be used for labeling and / or printing purposes. The latex coating may be selected from the group consisting of styrene and methyl methacrylate copolymer latex, styrene copolymer latex and methyl acrylate, styrene copolymer latex and acrylic acid latex, and styrene-butadiene copolymer latex. The thickness of the coating may vary from about 0.10 mils (0.000254 cm) (0.27 mg dry coating weight per square centimeter of cup surface) to about 5.0 mils (0.0127 cm) (13.4 mg dry coating weight). per square centimeter of cup surface), and preferably it can be approximately 0.9 mils (0.0022 cm) (approximately 0.25 mg dry coating weight per square centimeter of cup surface). The coating can be applied to a portion or to the internal and / or external surface of the container. In one embodiment of the invention, the coating is applied substantially to the entire internal and / or external surface of the container. The latex coating is applied to the surfaces of containers via a brush process, an immersion process, or a spray process, for example via a device or airless spray devices. The container is made of 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 filtration and / or stain resistance 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 containing a food or liquid substance, and the container has improved storage longevity, improved stain resistance, and / or strength. to improved filtration. 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, for example, cups, bowls, and the like are molded from expandable thermoplastic particles. The expandable thermoplastic particles are made of any suitable thermoplastic copolymer or homopolymer. 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 divinylbenzene, butadiene, alkyl methacrylates, alkyl acrylates, acrylonitrile, and maleic 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 can be used, such as polyolefins (for example polyethylene, polypropylene), and polycarbonates, polyphenylene oxides, and mixtures thereof. Preferably, the expandable thermoplastic particles are expandable polystyrene (EPS) particles. The particles may be in the form of beads, granules, or other suitable particles for expansion and molding operations. The 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 varies from about 0.008 (0.020 cm) to about 0.02 inches (0.050 cm). The expandable thermoplastic particles are impregnated with a suitable blowing agent using any conventional method. For example, impregnation can be achieved by adding the blowing agent to the aqueous suspension during the polymerization of the polymer, or alternatively re-suspending the polymer particles in an aqueous medium and then incorporating the blowing agent as taught in the US Pat. the United States No. 2,983,692 of D. Alelio. Any gaseous material or material which will produce gases in the 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 halogenated hydrocarbons, for example CFCs and HCFCs, which boil at a temperature below the softening point of the chosen polymer. Mixtures of aliphatic hydrocarbon blowing agents can also be used. Alternatively, water can be mixed with these aliphatic hydrocarbon blowing agents or water can be used as the blowing agent only 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 above patents, agents that retain water are used. The weight percentage of water for use as the blowing agent can vary 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 about 2 to about 12 pounds per cubic foot (0.032 g / cm3 to approximately 0.192 g / cm3). The pre-expansion step is conventionally performed by heating the impregnated beads via any conventional heating means, such as steam, hot air, hot water, or radiant heat. A generally accepted method for pre-expanding the impregnated thermoplastic particles is taught in U.S. Patent No. 3,023,175 to Rodman. The impregnated thermoplastic particles may 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 are incorporated in their entirety in the present for reference. The foamed cellular particles are preferably polystyrene which are pre-expanded to a density of about 12.5 to about 34.3 pounds per cubic foot (0.2 to about 0.549 g / cm3), and which contain a level of volatile blowing agent of less than 6.0 percent by weight, preferably from about 2.0% by weight to about 5.0% by weight, and more preferably ranges from about 2.5% by weight to about 3.5% by weight based on the weight of the polymer. In a conventional manner, the pre-expanded ("pre-swollen") particles 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 detrimental to the thermoplastic particles forming the container. That is, the latex coating of the invention will be free of some chemicals that have to dissolve or react with the thermoplastic particles, particularly polystyrene particles. For example, most polymeric solvent-based coatings could 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) can vary from 40:60 to 60:40 by weight. In the latex coating industry, a more common term is "solids content". The "solids content" as used herein refers to the dry matter comprising the polymer, emulsifiers, inorganic salts, etc. in the latex coating. A typical range for the solids content is between 40 and 60 weight percent. This measurement is derived by drying a sample of latex coating at 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 is generally used for stability purposes, can 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, hexadecyl sodium sulfate, sodium dodecyl sulfate, branched sodium alkyl sulfate, sodium dodecyl ethoxylate (2E0), dodecyl alcohol ethoxylate (5E0), dodecyl 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, acrylate. of octyl, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl pivalate, vinyl neo-decanoate, acrylonitrile, methyl acrylonitrile, acrylamide, styrene, a-methyl styrene, methyl methacrylate, ethyl methacrylate, methacrylate -butyl, i-butyl methacrylate; or the polymer can 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, tert-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. Preferred latex coatings are styrene-methyl methacrylate copolymer latex, styrene-methyl acrylate copolymer latex, styrene-acrylic acid copolymer latex, and styrene-butadiene copolymer latex. The molecular weight for the latex coating may vary from about 100 to about 1 million units (500 to about 200 million g / mol). The molecular polydispersity for the latex coating can be defined to vary from very narrow to very broad, i.e. from about 1.0 to about 20. The thermoplastic container can be a polystyrene cup which is manufactured by a conventional cup making machine which It has an inner cover and an outer cover. A conventional cup forming machine is the Cup Production MODEL 6-VLC-125 machine, made by Autonatíonal B.V. or is machine for MY MODEL cups, 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 can be applied to the surface or surfaces of the container via any suitable process, including an immersion process, a brush process, or a spray process via any suitable means. A spray process can be preferred both from an economic and production point of view. 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 can be about 48% to about 50% by weight, which can be adjusted to change the viscosity so that the process equipment, such as the spray system, can properly handle the coating application over the container. The solids content of the latex prior to being applied to the surface of the container will generally depend on the process that is used to apply the latex to the container. For example, if a spray process or a brush process is used, preferably the solid contents will vary from about 40% to about 47% by weight, based on the weight of the latex. If a dip process is used, preferably the solids contents will vary from about 8% to about 20% by weight. After the latex is applied to the surface or surfaces of the container, the container can then be transported via a conveyor belt to a drying chamber or oven. The drying oven may be a conventional oven and the heating means may be hot air, radiant heat, or more vacuum heat. Preferably, the heating means is hot air. A typical drying oven is obtained from the Blue M Electric Company, Blue Island, Illinois. The drying time is dependent on the drying temperature, the solids content of the coating, and the thickness of the coating. For example if the coating is 1.5 mils (0.0038 cm), the drying temperature will be approximately 90 ° C with a drying time of approximately 60 seconds. Typically, the drying temperature will vary from about 50 ° C to about 100 ° C and the drying time will vary from about 5 seconds to about 3000 seconds for coatings with solids content ranging from about 8% to about 47% by weight.

As set forth herein, the thicknesses of the latex coating on the surface or surfaces of the container may vary from about 0.10 mils (0.000254 cm) (0.27 mg dry coating weight per square centimeter of cup surface) to about 5.0 mils (0.0127 cm) (13.4 mg dry coating weight per square centimeter of cup surface), and can preferably be approximately 0.9 mils (0.0022 cm) (0.25 mg dry coating weight per square centimeter of cup surface). This coating thickness may extend in a portion or substantially in the entire internal and / or external 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 spray device for latex spray coating on the inner surface of a 16-ounce cup (0.4730 L) can vary from about 50 to about 600 cups per minute. It is evident that various spray devices can be used to accommodate the desired production speed of the cups. A spraying device that may be useful in the invention is an airless spray device available from Nordson Corporation. An example of a spray device provided by Nordson Corporation is described in the above Suzuki et al., U.S. Patent No. 4,206,249. In this case, it is preferable that the airless spray device applies the latex at room temperature instead of the elevated temperatures taught in U.S. Patent No. 4,206,249. It is understood that minor modifications can be made to the spraying device of the '249 patent when spraying the latex coating of the invention. The coating speed can be defined as "the dry weight of the powder coating on the unit surface area of the container". As set forth herein, the coating speed can vary from about 0.27 milligrams to about 13.4 milligrams dry coating weight per square centimeter of cup surface. The latex is applied to a portion or substantially on at least one of the inner and outer surfaces of the container to form a coating; preferably to the inner surface; and more preferably both to the inner and outer surfaces. The latex coating can be applied to the external surface for filtration resistance purposes and / or for labeling and printing purposes. It will be understood that the container has both a bottom section and a side wall and that the "inner surface" and the "outer surface" will generally refer to both the bottom section and the side wall of the container. The invention is further illustrated, but not limited, by the following examples.

Examples Example 1 This example illustrates the preparation of containers coated with latex. Expandable polystyrene cup beads (DYLITE beads from NOVA Chemicals, Inc., which comprise polystyrene and pentane) were mixed with zinc stearate and pre-expanded in an 11-gallon (about 1.5 cubic feet) Rodman Steam pre-expander ) (42475.5 cm3) (Artisan Industries Inc.) at atmospheric pressure.

The pre-expansion was operated in the form of batches. They were used 3. 5 pounds (1.58 kg) of cup beads having a distribution diameter of approximately 0.008 inches (0.020 cm) to approximately 0.02 inches (0.050 cm) to make pre-swollen with a density of approximately 3.5 pounds per cubic foot (0.056 g) / cm3). The freshly prepared pre-swelling was air-dried for 5 minutes to remove moisture and cured for approximately 4 hours before molding. 17 ounce cups (0.5026 L) were molded from the cured pre-swollen beads. The pressure of the steam heater was 80 pounds per square inch (5.6 kg / cm2) and the total cycle time was in the range of 6 to 15 seconds. The molded foam cups were left to cure overnight. The latex (Roymal 45526 product manufactured and sold by Roymal Incorporated, which is a latex of methyl acrylate, acrylic acid, and styrene copolymer), was sprayed on the inner surface, that is, both on the side wall with the bottom , of the cups at a coating speed of 1.7 to 4.3 mg dry coating weight per square centimeter of the surface of the cup, using an airless spray device manufactured and sold by Nordson Corporation. For this latex product, the ratio of styrene to methyl acrylate can vary from about 5:95 weight percent to about 95: 5 weight percent based on the weight of the polymer segments, and the acrylic acid may vary from about 0 to 10% by weight in the total polymer weight. The latex contains 48% by weight solids. Prior to the application of the latex to the inner surface, the latex was diluted with deionized water to produce a latex containing 46% by weight solids. The coated cups were then dried in an oven using a combination of hot air circulation and 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: aromatic oil was poured at room temperature into a container to fill the cup to approximately 80% capacity. The outer surface of each container was observed by spotting and filtering oil every 10 minutes for the first 1.5 hours, every 30 minutes in the time frame from 1.5 hours to 6 hours, and then every hour after that for a total 48 hours The average time to failure (TPF) for each group of sample cups was calculated by adding time to failure for each container, and dividing the total time of failure by the number of containers tested. Typically, ten cups in each group were tested. A maximum TPF value of 48 hours means that none of the cups in this group exhibits any staining or filtering. A minimum TPF value of 0.17 hours means that all cups in this group failed within the first 10 minutes. The results for oil retention (TPF) are shown in Table 1. As indicated, the cups with the latex coating had an increased TPF compared to the cups without the latex coating (control).

Table 1 Example 2 The EPS cups were 6 ounce cups (0.1774 L). The oil retention test (TPF) for these EPS cups having a pre-inflation density of 3.5 pounds per cubic foot (0.056 g / cm3) 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 contents. The molded foam cups were coated by a deep coating process with the diluted latex so that both the inner and 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 TPF compared to those cups without the latex coating (control).

Table 2 Example 3 The procedure of Example 1 was repeated except that the test method was replaced by the following method. Four coated cups were tested by the following method: 1) Pre-formed cup noodles fried in oil, such as those available in the market, were placed in each cup. 2) Three grams of red pepper powder was sprayed evenly onto the surfaces of noodles. 3) Each cup was hermetically sealed with an adhesive label and tough plastic film, and placed in the oven at a temperature of 149 ° F (65 ° C). 4) Each sample was verified by spots first every hour for a period of 7 hours and then once every 8 hours until failure for a total of 72 hours or 3 days. The average time to failure (TPF) was calculated similar to that described in Example 1. The maximum TPF value of 72 hours represents that none of the cups for group sampling of cups exhibited any staining or filtration. The minimum TPF value of 1 hour represents that all cups in the group of cups sample failed within the first hour. The results for stain resistance, in terms of TPF, are shown in Table 3.

Table 3 As indicated in Table 3, the cups with the latex coating had increased TPF 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 that the test method was replaced by the following method. The coated cups were tested by the following method: which is a hot sauce, was poured at room temperature in each container to fill the cup to approximately 90% capacity. The outer surface of each container was observed for staining and filtering every hour for a total of 48 hours. The average time to failure (TPF) for each group sample of cups was calculated by adding the time to failure of each container, and dividing the total time for failure by the number of containers tested. Typically, five cups in each group were tested. A maximum TPF value of 48 hours means that none of the cups in this group exhibits any staining or filtration. A minimum TPF value of 1 hour means that all cups in this group fail within the first hour. The results for stain resistance, in terms of TPF, are shown in Table 4.

Table 4 As indicated in Table 4, the cups with the latex coating had an increased TPF for sauce compared with the cups without the latex coating (control). Although the present invention has been particularly described in terms of specific embodiments thereof, it will be apparent to those skilled in the art that numerous variations and details of the invention can be made without departing from the present invention as defined in the appended claims. For example, different types of latex coatings can be applied in one or more layers to one or more surfaces of the container. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention is that which is clear from the present description of the invention.

Claims (24)

1. CLAIMS Having described the invention as above, the contents of the following claims are claimed as property: 1. Thermoplastic container molded to contain liquid and food substances and having internal and external surfaces, characterized in that it comprises: a latex coating applied to at least a portion of at least one of the internal and external surfaces of the molded thermoplastic container for coating the container . 2. Molded thermoplastic container according to claim 1, characterized in that it is made of expandable thermoplastic particles. 3. Molded thermoplastic container according to claim 2, characterized in that the expandable thermoplastic particles are expandable polystyrene particles. Molded thermoplastic container according to claim 1, characterized in that the latex coating is comprised of a monomer selected from the group consisting of butadiene, n-butyl acrylate, i-butyl acrylate, 2-ethylhexyl acrylate, acrylate of methyl, ethyl acrylate, octyl acrylate, vinyl acetate, vinyl chloride, vinylidene chloride, vinyl pivalate, vinyl neo decanoate, acrylonitrile, methyl acrylonitrile, acrylamide, styrene, a-methyl styrene, methyl methacrylate , ethyl methacrylate, n-butyl methacrylate, i-butyl methacrylate. Molded thermoplastic container according to claim 4, characterized in that the latex coating is comprised of a polymer selected from the group consisting of a homopolymer, a copolymer of two or more of the monomers, and a copolymer of two or more of monomers with the following functional monomers including acrylic acid, methacrylic acid, itaconic acid, fumaric acid, hydroxyethyl acrylate, hydroxyethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, acrylamide, dimethyl meta-isopropenyl benzyl isocyanate, N -methyl methacrylamide, N-methylol methacrylamide, N- (iso-butoxymethyl) acrylamide, glycidyl acrylate, glycidyl methacrylate, sodium styrene sulfonate. Molded thermoplastic container according to claim 1, characterized in that the latex coating is comprised of a polymer selected from the group consisting of acrylate, ethyl acrylate, methyl methacrylate, methacrylate, acrylic acid, methacrylic acid, and monomers or copolymers of the monomers combined with vinyl acetate or styrene. 7. Molded thermoplastic container according to claim 1, characterized in that the latex coating is selected from the group consisting of styrene-methyl methacrylate copolymer latex, styrene-methyl acrylate copolymer latex, styrene copolymer latex and acrylic acid, and butadiene-styrene copolymer latex. 8. Molded thermoplastic container according to claim 7, characterized in that the latex coating is styrene copolymer latex and methyl acrylate latex. 9. Molded thermoplastic container according to claim 1, characterized in that the latex coating has a thickness ranging from about 0.10 mils (0.000254 cm) to about 5.0 mils (0.0127 cm). 10. Molded thermoplastic container according to claim 1, characterized in that the latex coating is applied to the surfaces of the container via a spraying process, and wherein the latex coating when diluted has a solids content ranging from about 40% to about 47% by weight. 11. Molded thermoplastic container according to claim 1, characterized in that the latex coating is applied to the surfaces of the container via an immersion process, and wherein the latex coating when diluted has a solids content ranging from about 8% to about 20% by weight. 12. Molded thermoplastic container according to claim 1, characterized in that the latex coating is applied to the surfaces of the container via a brush process, and wherein the latex coating when diluted has a solids content ranging from about 40% to about 47% by weight. 13. Molded thermoplastic container according to claim 1, characterized in that the latex coating is comprised of a solids phase and an aqueous phase, and wherein the solids phase is approximately 50% by weight based on the weight of the solids coating. latex. 14. Method for forming a container for containing liquid and food substances, characterized in that it comprises the steps of: forming a molded thermoplastic container having an internal surface and an external surface, and applying a latex coating to at least a portion of the less one of the internal surface and the outer surface of the container to make the container resistant to seepage and / or staining of liquid and food substances. 15. Method according to claim 14, characterized in that the steps further comprise: applying the latex coating to the internal surface of the container. 16. Method according to claim 14, characterized in that the steps further comprise: applying the latex coating to the external surface of the container. Method according to claim 14, characterized in that the latex coating is selected from the group consisting of styrene-methyl methacrylate copolymer latex, styrene-methyl acrylate copolymer latex, styrene-acid copolymer latex acrylic, and butadiene-styrene copolymer latex. Method according to claim 14, characterized in that the latex coating is copolymer latex of styrene and methyl acrylate. 19. Method according to claim 14, characterized in that the latex coating is applied to the container via a spraying process. 20. Method according to claim 14, characterized in that the latex coating is applied to the container via an immersion process. 21. Method according to claim 14, characterized in that the latex coating is applied to the container via a brush process. 22. An article of manufacture having improved storage longevity, improved stain resistance, and / or improved filtration resistance, characterized in that it comprises: a molded thermoplastic container coated with a latex coating and containing a liquid substance or a food substance . 23. Manufacturing article according to claim 22, characterized in that the container has improved stain resistance. 24. Improved method characterized in that it is for storing liquid or food substances using the container according to claim 1.