Patent Application
20080187728
This application relates to multilayer film assemblies useful to prevent frosting, their method of manufacture, and articles formed from the film assemblies.
When a cooler surface comes in contact with warmer moist air, condensation may occur on the cooler surface. Depending on temperature differences, the condensation may take the form of fog or frost on the surface and, particularly with substantially transparent surfaces, affect light transmission and impair visibility.
Anti-frost films find utility in a number of different applications. For example, the marketing and sales of refrigerated merchandise often includes consumer selection directly from the refrigerated unit. To ensure effective marketing, the items within the case should remain visible and discernible to a patron looking into the case through a light transmitting, usually substantially transparent, panel, or door. When a patron chooses an item and opens the door to the case, the door may frost due to condensation as the cool, inside surface of the door comes in contact with the moist, ambient atmosphere outside the case. Typically, this frost remains even after closing the door, and impairs the view into the case for subsequent patrons. The inability to see into the case can result in loss of sale for the store. In addition, increased energy costs may incur, as patrons hold the door open longer to see the items inside the case.
One method used to reduce this problem includes a heated door that un-frosts the door after some length of time. These heated doors may be both expensive to purchase and costly to operate due to energy consumption to maintain the heated door, while the refrigerator is cooling/freezing the food inside the case. The lower the temperature within the case, the greater the costs of maintaining frost and frost resistant doors.
Another remedy is to provide anti-frost coatings. However, typical permanent anti-frost coatings do not provide effective frost resistance over a wide temperature gradient. Most noticeably, the lower temperature storage and display cases (0° C. and below) often develop frost and frost and therefore do not achieve optimum visibility with current anti-frost coatings.
Therefore, there is a need for new, low temperature anti-frost systems to enhance visibility into refrigerator and freezer cases by preventing or inhibiting frosting of the door when the door is exposed to cool air and then exposed to moist warmer air when opened.
In one embodiment, an anti-frost film assembly comprises a substantially transparent film having a first surface and a second surface opposite the first surface; and a substantially transparent anti-frost layer formed from a polyurethane-film forming composition effective to provide the layer with anti-frost properties at temperatures that alternate between about −23° C. and about 65° C., wherein the anti-frost layer is disposed on an area of the first surface of the film.
In one embodiment, a condensation-resistant article comprises a substantially transparent substrate having a first surface; and the above-described anti-frost film assembly wherein the second surface of the film is disposed on an area of the first surface of the substrate.
In one embodiment, a refrigerated panel comprises a substantially transparent refrigerator panel having a first surface, and the above-described anti-frost film assembly, wherein the second surface of the film is disposed on an area of the first surface of the door panel.
In one embodiment, a method of producing an anti-frost film assembly comprises: applying a substantially transparent anti-frost layer formed from a polyurethane-film forming composition to a first surface of a film, and applying an adhesive to a second surface of the film. The substantially transparent anti-frost layer is effective to provide the layer with anti-frost properties at temperatures that alternate between −23° C. and 65° C.
The above-described and other features will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
Refer now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike.
The anti-frost film assemblies disclosed herein are substantially transparent, multilayer films useful in the production of condensation-resistant articles such as refrigerator and freezer doors (e.g., that are for exposure to temperatures below freezing) and panels, or reflective surface (e.g., bathroom mirrors), but they are not limited to these specific products or applications. The anti-frost properties of the film assemblies are effective at temperatures as low as about −17° C., or even about −23° C., without use of external heaters. These temperatures are significantly lower than those enabled by prior art antifrosting films. Since heaters are not required, use of such films can provide a significant energy savings. In an advantageous optional feature, the assemblies are manufactured to be repositionable and/or to allow the inclusion of a graphic.
The anti-frost film assemblies comprise a substantially transparent anti-frost layer and a substantially transparent film. As used herein, “substantially transparent” refers to optical clarity, and means that enough light is transmitted through the layer(s) to allow visualization through the film assembly by an observer. Thus, while some haze or coloration may be present in the individual layer(s), such haze or coloration does not significantly interfere with visualization.
It has been shown by the inventors hereof that when this anti-frost film assembly is applied to a substrate, the formation of condensation (water droplets) on the substrate surface is reduced or prevented when the present assemblies are exposed to temperatures that alternate between about 65° C. and about −23° C. compared to other anti-frost solutions. While reference is made herein to “anti-frost film assembly,” this term is merely for convenience in discussion, and it is to be understood that the term encompasses film assemblies used to prevent visual impairment due to the formation of water droplets and/or water crystals.
Substantially transparent anti-frost layers that are effective at temperatures below about −17° C. are formed from a polyurethane-film forming composition. In one embodiment the film-forming composition further comprises a surfactant having a hydrophobic region and a hydrophilic region. Appropriate selection of the number, length, and type, and relative ratio of hydrophilic to hydrophobic groups allows adjustment of the anti-frost properties of the layer. Without being bound by theory, it is believed that such a structure allows a reduction in the interfacial tension between the surface of the layer and the condensing moisture, which enhances anti-frosting. Desirably the surfactant is also selected so as to not significantly adversely affect desirable physical properties of the polyurethane film, for example chemical resistance, scratch resistance, ultraviolet (UV) radiation resistance, and the like.
In addition, the surfactant may also comprise an isocyanate-reactive functionality. Such surfactants co-react to provide a polyurethane having the surfactant covalently bound and attached as a pendant group to the polyurethane polymer, or desirably, the surfactant attaches at the end of the polyurethane polymer. Suitable isocyanate-reactive functionalities include groups having an active hydrogen atom, for example a hydroxyl group, a carboxyl group, a primary or secondary amino group, or a sulfhydryl group. A compound having a combination comprising at least one of the foregoing types of groups may also be used.
Suitable surfactants comprising an isocyanate-reactive functionality and having a hydrophilic region and a hydrophobic region are disclosed, for example, in U.S. Pat. No. 5,877,254 to LaCasse, and may be nonionic, anionic, cationic, amphiphilic, or a mixture of the foregoing types of surfactants. Suitable nonionic surfactants include ethoxylated or propoxylated alcohols, phenols, amides, and amines.
Suitable ionic surfactants include quaternary cationic surfactants as well as anionic surfactants, for example cationic or anionic surfactants having a non-ethoxylated hydrocarbon chain with greater than or equal to 16 carbon atoms.
A non-limiting list of examples of suitable anionic surfactants includes monoethanolamine salts of sulfonic acids, diethanolamine salts of sulfonic acids, triethanolamine salts of sulfonic acids and combinations comprising at least one of the foregoing.
Examples of hydroxyl-containing cationic-surfactants include, without limitation, ricinoleamidopropyl dimethylethyl ammonium ethylsulfate, (12-hydroxy-1-oxo-9-octadecenyl)amino)-N,N-dimethyl, ethyl sulfate (salt)); stearamidopropyl dimethylethanolammonium methyl sulfate, and octadecylmethol diethanolammonium chloride.
Typical anionic surfactants rarely contain free reactive hydroxyl groups in their structure, and so may be made “hydroxyl bearing” by incorporating the free hydroxyl or other isocyanate-reactive groups in their countercation. Such modification can be accomplished by neutralizing a hydroxyl bearing quaternary ammonium base such a choline hydroxide with an acid such as dodecylbenzene sulfonic acid, as described in LaCasse. Other hydroxyl-bearing ammonium compounds include but are not limited to triethylethanol-, diethyldiethano-, and ethyltriethanolammonium salts. A non-limiting list of sulfonic acids from which the salts are prepared includes dodecylbenzene sulfonic acid, napthalene sulfonic acid, lignin sulfonic acids, petroleum sulfonic acids, and paraffin sulfonic acids. In this embodiment, the countercation becomes covalently bound to the polyurethane, and the anionic portion of the surfactant is associated with the polyurethane by virtue of the electrostatic attraction between the anion and countercation.
Combinations of reactive hydroxyl-bearing anionic and cationic surfactants are particularly useful, for example a combination of choline dodecylbenzene sulfonate with ricinoleamidopropyl ethyldimonium ethosulfate.
The surfactants may be used in concentrations of about 10% to about 40% by weight of total solids of the polyurethane-forming composition.
Formulations for the formation of polyurethane films generally include an isocyanate-containing component and an active hydrogen-containing component reactive with the isocyanate-containing component. Suitable isocyanate-containing components include, for example, hexamethylene diisocyanate, diphenylmethane diisocyanate, bis(methylcyclohexyl)diisocyanate and toluene diisocyanate. The isocyanate-containing component may be a prepolymer, for example a biuret or an isocyanurate of a diisocyanate, e.g., a prepolymer of diisophorone diisocyanate. Combinations comprising at least one of the foregoing isocyanate-containing compounds may be used. Blocking of the isocyanate group, for example with an oxime or phenol, and later removal of the protective group prior to reaction is also contemplated. When blocked isocyanates are used, it is possible to use solvents or other compounds which, but for the protective group in the isocyanate, would react with and consume the isocyanate groups.
The isocyanate-containing component is reacted with a hydrophilic component having an active hydrogen, particularly a hydroxyl hydrogen as is found in polyols. In order to provide the desired anti-frost characteristics, hydrophilic polyols are used, such as polyethylene glycol, ethylene glycol/propylene glycol copolymers, and combinations comprising at least one of the foregoing. Other suitable hydrophilic polyols include polybutylene glycol, polyethylene imine, amine-terminated polyethers, and certain polyester polyols. A combination of hydrophilic polyols may be used, for example, a polyethylene oxide/propylene oxide random triol having a weight average molecular weight of about 4,500 and containing approximately 70% by weight ethylene oxide combined with an ethylene oxide/propylene oxide block copolymer of weight average molecular weight about 2,100 and containing about 20% by weight ethylene oxide based upon a total weight of the polyols; e.g., 47% by weight of Visguard® Part A, 19% by weight of Visguard® part B (both commercially available from Film Specialties, Inc. Hillsborough, N.J.), and 33% by weight of a solvent (comprising 75% by weight of butinol and 25% by weight of diacetone alcohol). Such a combination provides enhanced hydrophilicity to the polyurethane backbone without substantially compromising scratch-resistance or interfering with the incorporation of the surfactant.
The hydrophilic polyol may be present in the composition in amount of about 10% to about 35% by weight of the total solids, and specifically about 15% to about 65% by weight.
In practice, the isocyanate-containing component, active hydrogen-containing component, and reactive surfactant may be combined in a suitable organic solvent. The organic solvent may be a number of materials that do not react rapidly with isocyanates, including ketones, esters, glycol esters, and tertiary alcohols, as well as combinations comprising at least one of the foregoing. Minor amounts of inert diluents such as aliphatic hydrocarbons and esters may also be used. Water and alcohols may be used if commercially available blocked isocyanates are used. Other components may be present, for example UV inhibitors, stabilizers, and catalysts.
For example, in one manner of proceeding, a polyisocyanate prepolymer having free isocyanate groups is mixed with an organic solvent solution of a hydrophilic polyol and a hydroxyl-bearing surfactant having a hydrophilic region and a hydrophobic region. The mixture is then allowed to heat cure at appropriate temperatures, e.g. between about 20° C. to and about 200° C. for a sufficient amount of time, e.g., about five minutes to about 24 hours. Cure time and temperature will vary depending on the components and application.
The anti-frost layer is disposed on a substantially transparent film. The film is selected to provide support to the layer. The film may also be selected so as to provide the desired level of flexibility, adhesion between the anti-frost layer and the film (with or without an adhesive), adhesion between the film and substrate (with or without an adhesive), and/or the desired compatibility with an adhesive. As such the choice of film composition will vary depending on the desired properties, including flexibility and transferability as described below. Suitable film materials that may be made substantially transparent include, for example, polycarbonate, acrylic, vinyl, styrene-based films, polyvinylchloride, polybisallyl carbonate, polyethylene terephthalate, and substantially transparent polyethylene naphthenate, as well as combinations comprising at least one of the foregoing types of polymers. Various polyolefins or fluorinated polymers may also be used with appropriate pretreatments.
The surface of the film may be treated to improve adhesion of the anti-frost layer to the film, for example with an adhesive, by mechanical roughening, plasma treatment, chemical etching, an/or other known treatment(s).
The anti-frost layer can be disposed on the substantially transparent film by a variety of methods, for example casting, coating (e.g., wire wound rod coating, gravure coating, slot die coating, pan fed reverse roll coating, and nip fed coating), and the like. The technique is selected so as to provide a uniform and thick coating, e.g, a coating having a thickness of about 0.0001 to about 0.1 inches (about 2.5 to about 2,540 micrometers (μm)), more specifically about 0.001 to about 0.01 inches (about 25.4 micrometers to about 254 micrometers), even more specifically, about 0.003 to about 0.008 inches (about 76.2 micrometers to about 203 micrometers). Where an organic solvent is used, the solvent may be removed during or after cure by evaporation, for example in an oven, in a one- or two-stage process. Cure and solvent removal, in particular time, temperature, and airflow during cure and solvent removal, is optimized to provide a uniform coating with low temperature anti-frost properties.
Several embodiments of anti-frost film assemblies and articles formed therefrom are described below with reference to individual drawing figures. In
Optionally, anti-frost film assembly 110 further comprises an adhesive layer 140 for temporarily or permanently adhering the assembly to a substrate (not shown). In one embodiment, adhesive layer 140 allows for repositioning of anti-frost film assembly 110. Adhesive layer 140 is disposed on an area of second surface 134 of film 130. Exemplary adhesives for use with the anti-frost film assemblies include pressure sensitive adhesives, silicone adhesives, acrylic adhesives (including ultraviolet cured and thermally cured adhesives, wet applied and dry applied adhesives), rubber adhesives, heat-seal adhesives, laminating adhesives, high temperature adhesives, and/or other adhesives that will achieve the intended result. Wet-applied acrylic adhesives sometimes known as “window adhesives” are of particular utility. Desirably, the adhesive bonds to glass with a bond strength of greater than or equal to about 3 pounds force per linear inch (lb/in) (e.g., about 8 lb/in to about 10 lb/in). Some exemplary adhesives include National Starch and Chemical Duro-Tak 80-1070, Toyo Color America LLC, Oribain BPS5160.
With or without optional adhesive layer 140, anti-frost film assembly 110 is substantially optically clear, providing visibility from an area 150, through optional adhesive layer 140, film 130, and anti-frost layer 120 to area 160.
In another embodiment, shown in
As shown in
Suitable substrates include, but are not limited to, substantially transparent glass, plastic, and substitutes suitable for a desired application. Specific substrates include polycarbonate (e.g., LEXAN® from GE Advanced Materials), polyester (for example, poly(cyclohexanedimethanol terephthalate)-co-poly(ethylene terephthalate), abbreviated as PETG when the polymer comprises greater than or equal to about 50 mole % of poly(ethylene terephthalate), acrylic, polyvinylchloride, polybisallyl carbonate, polyethylene naphthenate, as well as combinations comprising at least one of the foregoing, e.g., polycarbonate/poly(1,4-cyclohexylene dimethylene 1,4-cyclohexanedicarboxylate) (also known as polycarbonate/PCCD) (e.g., XYLEX from GE Advance Materials).
As the applications may be varied, so is the selection of substrate. For instance, substrates considered suitable for a refrigerated door may be determined by the presence or absence of heating devices, type, and design of refrigeration unit, and proposed use and life span. The film assemblies are designed to be positioned in operational relation to a substrate and/or form a transferable, non-permanent bond at the surface of a substrate and provide at least a substantially nonfrosting area of the substrate surface. Therefore, the film assemblies are particularly suited for use in refrigerated units, including refrigerators and freezers. And, while reference is made to refrigerated units and components such as refrigerated doors throughout this disclosure, it is to be understood that the anti-frost films disclosed herein can be used in other applications without undue experimentation. Other applications include, for example, building windows (such as house windows), windshields of vehicles (such as cars, trucks, motorcycles, boats, airplanes, and the like), reflective surfaces (such as bathroom mirrors, automotive mirrors, and the like), scientific equipment (for example on the face of displays, gauges, and the like), face shields (for example medical face shields, sporting equipment face shields, and the like), and instrument surface.
The anti-frost film may be applied onto a substrate in a non-permanent fashion, or placed in operative relation to a substrate to provide anti-frost properties to the substrate without becoming permanently affixed to the substrate. Thus, in one embodiment the film and/or the adhesive applied to the second surface of the film is selected so as to allow repositioning, transferability, and/or easy removal of the anti-frost film assembly. For example, the anti-frost film assembly may be wet applied so that the film can be repositioned until satisfactorily positioned, and form a bond upon drying. For example, a typical application includes applying a solution of about 99% or more of water and about 1% or less of soap to a room temperature substrate. Application of the solution onto the substrate surface may be by various methods, such as spraying the solution using an atomizer. The adhesive portion of the anti-frost film is placed against the solution-wet substrate. The film may be repositioned into satisfactory position, any air bubbles are squeezed out with a squeegee, and allowed to dry. In this manner, the anti-frost coating adheres to the surface of the substrate but the coating does not molecularly bond at its interface with the substrate. Alternatively, the anti-frost film assembly can be applied to the substrate by spraying the adhesive side of the film and applying this side, wet with solution, to the substrate.
Alternatively, the anti-frost film assembly may be held in place by mechanical devices, including tracks in a frame, or other methods. The anti-frost film is thus removable, repositionable, and transferable away from the substrate, if desired.
Turning to
The anti-frost film assembly 410 may be used on new or existing refrigerated panels, including those with or without heaters. As used herein the term “refrigerator panel” refers to any substrate used as a door or window for a refrigerated unit having an internal temperature less than or equal to about −10° C., or, more specifically less than or equal to about −17° C., and yet more specifically about −17° C. to about −23° C. The internal temperature and temperature range will be determined by the application of the cooled unit, and the items the unit is designed to store, display and preserve. For instance, food, medical supplies, and transplant organs have refrigerated units and temperature requirements designed to serve the specific storage needs of these items.
When incorporated into existing refrigerated panels, prevention of frost formation between the anti-frost film and the glass is desirable. This frost formation can be inhibited using an installation solution that is applied between the glass and the film. The installation solution comprises about 50 volume percent (vol. %) to about 70 vol % water (e.g., deionized water), or, more specifically, about 60 vol % to about 70 vol % water; about 10 vol % to about 40 vol % alcohol (e.g., isopropyl alcohol), or, more specifically, about 20 vol % to about 30 vol % alcohol; about 2 vol % to about 8 vol % surfactant, or, more specifically, about 2 vol % to about 5 vol % wetting solution; and less than or equal to about 3 vol % salt (e.g., sodium chloride such as in the form of deionized salt, or another salt that readily dissolves in the solution), or, more specifically, about 0.5 vol % to about 2 vol % salt. The volume percent is based upon the total volume of the installation solution. Exemplary wetting solution include Madico 30-1-1 Window Solution Concentrate (WSC) (commercially available from Madico, Woburn, Mass.), Right-On (commercially available from Avery Dennison, Pasadena, Calif.), dishwashing liquid (e.g., Joy dishwashing liquid), as well as others.
For example, 1 liter of solution can be prepared by combining 23 ounces (oz.) water, 9 oz. isopropyl alcohol, 1.5 oz. Madico 30-1-1 WSC, and 1 tablespoon salt. This installation solution has enabled good optics through the film after installation on the glass, even when the glass is cold, e.g., 0° C.
In refrigerated units, the anti-frost film assembly may be used in conjunction with low-emissivity (low-E) glass or coatings. The low-E glass may be selected to meet two primary criteria: high reflective capability as to the infrared spectrum (thereby rejecting invisible radiant heat); and high visibility transmittance (so that is does not obscure or cloud visibility through it). There are a large number of glass materials having varying low-emissivity properties. Low-E glass and low-E coated glass or plastics as discussed herein are meant to refer to glasses or plastics that are designed not to emit (and thus reflect) radiation above about 0.7 micrometers, and more particularly about 0.7 to about 2.7 micrometers. Typically several layers are used to reflect greater percentage in the about 0.7 to about 2.7 micrometer range. The low-E surfaces or coatings may have visible transmittance of about 70% to about 90%.
The anti-frost film assemblies described herein are useful for preventing condensation on substrates that are alternately exposed to temperatures down to −23° C., and then exposed to a higher temperature for about 1 second to about 5 minutes, in the presence of air having a relative humidity (RH) of about 1% to about 90%. In particular, the anti-frost film assemblies prevent condensation on substrates that are alternately held at temperatures as low as about −23° C., specifically about −17° C. to about −23° C., and then exposed to temperatures greater than or equal to about −17° C., greater than or equal to about 0° C., greater than or equal to about 10° C., or greater than or equal to about 20° C., up to about 65° C., for up to about 3 minutes or so, in the presence of air having a relative humidity (at room temperature; the temperature outside of the cooler) of about 3% to about 80%, or more specifically about 5% to about 70%, and even more specifically about 10% to about 50%.
In one embodiment the anti-frost film assemblies are useful for preventing condensation on substrates that are alternately held at temperatures of 0° C. to −23° C., and then exposed to moist ambient air at temperatures of about 18° C. to about 30° C. for up to about 2 minutes. The relative humidity of ambient air is generally about 40% to about 70%. As used herein “moist ambient air” refers to the temperatures and relative humidity within the ranges stated above that are most typically associated with the humid ambient conditions in a grocery store, convenience store, supermarket, or the like, or the area adjacent to a cooler (e.g., beverage cooler). Thus, in another embodiment, the anti-frost film assemblies prevent significant condensation on substrates that are alternately held temperature of about −17° C. to about −23° C., then exposed to a temperature of about 20° C. to about 25° C., specifically about 21° C. to about 24° C., for up to about one minute, in the presence of air having a relative humidity of about 40% to about 50% at the temperature of about 20° C. to about 25° C.
The fact that condensation is minimized or prevented at these low temperatures without use of external heaters represents a significant advance over the prior art. For example, approximately 1.4 amps are required to heat a refrigerated display door. Use of the above-described assemblies allows the owner to eliminate such heating. In a facility, e.g, a store, having about 100 to about 140 doors per store and about 120 volt power, this translates to about a 60 amp savings for the store owner. Heat is still applied to the doorframe but the majority of the heat can be turned off completely with the use of the film assemblies. Store owners and other users of refrigerated units can thus realize a significant energy savings.
The anti-frost filer and system are further illustrated by the following non-limiting examples.
An anti-frost assembly comprising an anti-frost layer disposed on a polycarbonate film was manufactured using a polyurethane anti-frost layer formed from a composition comprising the formulation in the Table I below (% by volume).
A wire wound rod coating technique was used to apply the formulation to the film, and the film formulation was cured and the solvent removed in a chamber oven with active airflow to form a coating on the film. Coating thickness was 0.005 to 0.0065 inches (127 to 165 micrometers) and curing temperature was about 235° F. (113° C.) (between 230° F. and 250° F. (110° C. to 121° C.)) for 3 to 5 minutes. Fan speed was adjusted so that very low air flow (fan speed of about 500 revolutions per minute (rpm)) was present for the first 1 to 2 minutes of cure and high airflow (fan speed of about 1,500 rpm) was present for the last 2 to 3 minutes of cure. A high polish polyester mask (e.g., Dupont KL1, 1 mil mask) was used on the coated side of the polycarbonate.
The other side of the polycarbonate film was coated with a window film wet applied repositionable acrylic adhesive. The assembly was applied to a glass substrate by spraying the glass with a solution of 99% water/1% detergent, then pressing the adhesive of the assembly against the glass, squeezing out any air bubbles with a squeegee, and allowing to completely dry.
The anti-frost effectiveness of the assembly was tested by equilibrating the assembly and a window substrate for 2 hours prior to testing. Substrates with and without the anti-frost coating were then exposed to ambient conditions (21° C., 50% RH) for 60 seconds, and then returned to the indicated temperature. The window was then watched at an observer distance between 1 to 3 feet at a normal viewing angle under normal fluorescent lighting conditions and the time for the window to become frost free was recorded.
The results are shown in the Table II below. In each instance the substrate without the anti-frost coating showed condensation. Time for the condensation to clear was measured and is shown below.
As may be seen from the above data, the surface area of a substrate at a temperature of about 0° C. to about −23° C. with the anti-frost assembly remains clear and substantially without frosting. The anti-frost film assemblies disclosed herein therefore allow a refrigerator door to be opened and closed throughout the course of the day, substantially without frosting when exposed to moist air equal to or greater than the surface temperature of the substrate, and thus not obscuring the view of the items within the refrigerated unit.
The above described antifrosting film assembly was applied to refrigeration units in an actual grocery store. The refrigeration units were set at −29° C., the air temperature inside the unit was −23° C. and the air in the store was 21° C. to 24° C. at 40 to 50% RH. Under these conditions there was no frosting observed on doors with the anti-frost material applied, even after 1 minute of being opened. Doors without the anti-frost material frosted within 10 to 15 seconds. No difference was seen between doors that were heated and had the anti-frost film assembly and those that were not heated and had the anti frost film assembly. This would allow the average store with 100 to 140 doors to run without heated doors and save approximately 60 amps for the store.
Anti-frost film assemblies were produced utilizing various masking film materials for the purpose of evaluating the effect of masking film surface finish and material. Haze values and frost times (i.e., duration until panel frosted, measured in seconds) were evaluated for three masking films: polyethylene masking film comprising a smooth surface (Smooth PE), polyethylene masking film comprising a fine textured surface (Fine Texture PE), and a polyester masking film comprising a smooth surface (Smooth PET). Haze was measured utilizing ASTM D1003 and time to frost was evaluated at an observer distance of 1 to 3 feet at a normal viewing angle under normal fluorescent lighting conditions.
From the data generated, it can be seen that the smooth polyester masking film (Smooth PET) produced the optimal frost resistance from the samples tested. In addition, comparing the Smooth PE to the Fine Texture PE masking films, it is shown that the fine textured surface on the Fine Texture PE sample produces a shorter time to frost duration. Further, the Fine Texture PE sample exhibits higher haze compared to the Smooth PE sample.
Presented in Table IV below are experimental results from an experiment conducted for the purpose of evaluating the effects of cure time, fan speed, and film thickness on appearance and frost resistance. Appearance was measured at an observer distance of 1 to 3 feet at a view angle of 45° under normal fluorescent lighting conditions.
From the data presented above, it can be seen that shorter cure times (e.g., less than 1.25 minutes) combined with high fan speeds and non-polished masks can result in time to frost values of less than 2 minutes. The surface finish of these articles was mottled, having an orange peel appearance. When longer cure times (e.g., greater than 1.5 minutes) were employed in combination with lower fan speeds, the articles produced exhibited good surface appearance and time to frost values were increased to greater than 2 minutes. Hence, a fan speed of less than or equal to about 1,000 rpm, or, more specifically, less than or equal to about 750 rpm, or, more specifically, less than or equal to about 500 rpm, can be employed to attain good appearance as well as time to frost of greater than 2 minutes. Additionally, cure times of great than or equal to about 1.5 minutes, or, more specifically, greater than or equal to about 1.75 minutes are desireable to attain the good appearance and the longer time to frost, e.g., at a film thicknesses of less than or equal to about 1,000 μm, or, more specifically, about 180 μm to about 510 μm.
The present anti-frost layer was used on a freezer door that had previously employed glass heaters to avoid frosting. The freezer was set for −25° C. (−13° F.) and −18° C. (0° F). As is evident from Table V, energy consumption reduced by greater than 40%. Prior to starting the tests A TES-3600 unit was attached to the inlet power cord for the freezer and the single phase 3 wire set up was used to measure the energy used by the system over time. In each set of tests the first test was conducted with the door heaters plugged in to establish the total energy usage of the system. The freezer contained 18 five gallon water bottles to create a thermal mass in the freezer (3 on each shelf). Subsequent tests of the set were conducted with the door heaters disconnected from the freezer's system. A set of tests were conducted at the minimum possible setting for the freezer (−13° F. set −5 to −8° F. measured) and with the freezer set for 0° F. The doors were left closed during all tests.
Table V shows the results for a chamber temperature of −8° F. (−22° C.). As can be seen from Table V, the reduction in energy usage was greater than 40%, and averaged 43% with a standard deviation of 1%.
Table VI shows the results for a Chamber temperature of 0° F. (−18° C.). As can be seen from Table VI, the reduction in energy usage was greater than 40%, and even greater than or equal to about 43% reduction compared to a freezer with a door heater on.
The film was also tested to assess the performance of the film mounted on glass freezer doors (a 3 door freezer) through three standard food distribution industry specifications:
As used in the following Tables VI and VII, sheathing refers to when sheathing moisture began, droplets at “ ” sec refers to when droplets formed on the door, and w/d refers to with droplets.
In each of the tests performed the film slowed or reduced the onset of door frosting when the door was opened. On the 900 second door open test at higher surrounding humidity values significant frosting, sheathing of moisture, and condensate droplets formed on both the film and non-film doors. In these cases of significant condensation forming the films took a slightly longer time than the heated non-filmed doors to come clear.
As disclosed herein, substantially transparent, multilayer films useful in the production of condensation-resistant articles (such as refrigerator and freezer doors and panels, bathroom mirrors, and the like), offer effective frost-resistance to temperatures below previously attainable, as low as about −17° C., or even as low as −23° C. Furthermore, these films offer effective frost resistance without use of external heaters, which are common in glass freezer door applications. This results in a significant savings in energy costs. In addition, articles produced from these films can be retrofit into many applications and/or assembled to existing articles, offering merchants several anti-frost solutions (e.g., adhesion coating can be put on the film In an advantageous optional feature, the assemblies are manufactured to be repositionable and/or allow the inclusion of a graphic.
The terms “first,” “second,” “outer”, “internal,” “external,” and the like as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” as used herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. Furthermore, all ranges directed to the same property or quantity are inclusive and independently combinable. Reference throughout the specification to “one embodiment”, “another embodiment”, “an embodiment”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the element(s) are not necessarily all referring to the same embodiment, and particular elements may be combined in any suitable manner in the various embodiments. If ranges are disclosed, the endpoints of all ranges directed to the same component or property are inclusive and independently combinable (e.g., ranges of “up to about 25 wt. %, or, more specifically, about 5 wt. % to about 20 wt. %,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 wt. % to about 25 wt. %,” etc.). The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the colorant(s) includes one or more colorants). Furthermore, as used herein, “combination” is inclusive of blends, mixtures, alloys, reaction products, and the like.
While the invention has been described with reference to several embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
The present application is a continuation-in-part of U.S. patent application Ser. No. 11/241,629, filed on Sep. 30, 2005, which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11241629 | Sep 2005 | US |
| Child | 11534427 | US |
