Acrylate and non-acrylate chemical compositions for selectively coating fiber-based food containers

Abstract

A method and apparatus for vacuum forming and subsequent application of a topical coating to a fiber-based food container, the method comprising: forming a slurry containing an embedded moisture barrier, a vapor barrier, and / or an oil barrier; and applying a topical coating containing a vapor barrier, a moisture barrier, an oil barrier, and / or an oxygen barrier, such as polyvinyl alcohol, a sugar alcohol, citric acid, and / or cellulose nanofibrils.

Description

【Technical Field】 【0001】 Cross - reference to related applications This application is a continuation - in - part of U.S. Patent Application No. 15 / 220,371, filed on July 26, 2016, and U.S. Patent Application No. 16 / 726,180, filed on December 23, 2019, and claims priority, the entire contents of which are incorporated herein by reference. 【0002】 The present invention generally relates to spray coatings for use with vacuum - formed fibrous food containers, and more specifically to a selective combination of slurry chemistries and surface coatings for creating a desired oil, water, vapor, and / or oxygen barrier. 【Background Art】 【0003】 Pollution caused by single - use plastic containers and packaging materials is prevalent, marring the global landscape and threatening delicate ecosystems and the living organisms that inhabit them. Single - use containers, in the form of foam styrene and expanded polystyrene (EPS) packaging, take - out containers, bottles, thin - film bags, and photodegraded plastic pellets, migrate into the ocean along waterways. 【0004】 This marine debris accumulates in vast sections of the highly concentrated plastic islands located in each of our ocean gyres. Sunlight and waves break down the floating plastic into progressively smaller particles, which do not completely disappear or biodegrade. Furthermore, plastic particles function as sponges for water - soluble contaminants such as pesticides. Fish, turtles, and even whales can eat plastic objects, which can sicken or kill them. Smaller marine animals ingest microscopic plastic particles, and when we eat seafood, they come back to us. 【0005】 Sustainable solutions to reduce plastic pollution are gaining momentum. However, for continued adoption, these solutions need to be not only environmentally friendly but also competitive with plastics in terms of both performance and cost. This invention involves replacing plastics with innovative molded fiber technology without compromising product performance, while providing a competitive cost structure within an ecologically responsible framework. 【0006】 As a brief background, molded paper pulp (molded fibers) has been used since the 1930s to make containers, trays, and other packaging, but experienced a decline in the 1970s with the introduction of plastic foam packaging. Paper pulp can be manufactured from old newspaper printing paper, corrugated cardboard boxes, and other plant fibers. Today, molded pulp packaging is widely used for electronic components, household goods, automotive parts, and medical products, as well as as edge / corner reinforcement or pallet trays for shipping electronic components and other fragile components. The mold is formed as a mirror image of the finished packaging, with a screen attached to its surface. Vacuum is drawn across the screen, and the fiber particles accumulate in the shape of the finished product. 【0007】 The two most common types of molded pulp are classified as Type 1 and Type 2. Type 1 has walls of 3 / 16 inch (4.7 mm) to 1 / 2 inch (12.7 mm) and is commonly used for support packaging applications. Type 1 molded pulp production is also known as “dry” production and uses a fiber slurry made from crushed newspaper printing paper, kraft paper, or other fibers dissolved in water. A mold mounted on a platen is immersed or submerged in the slurry, and a vacuum is applied to the roughly convex back surface. The vacuum pulls the slurry onto the mold to form the shape of the packaging. While under vacuum, the mold is removed from the slurry tank, allowing water to be drained from the pulp. Air is then blown through a tool to extrude the molded fiber pieces. The pieces are typically piled up on a conveyor in a drying oven. 【0008】 Type 2 molded pulp production, also known as "wet" production, is typically used for packaging electronic devices, mobile phones, and household goods with containers having walls of 0.02 inches (0.5 mm) to 0.06 inches (1.5 mm). Type 2 molded pulp uses the same materials and follows the same basic process as Type 1 production up to the point where vacuum pulls the slurry onto the mold. After this step, the transfer mold is fitted with the fiber packaging and moves the formed "wet part" to a hot press machine, where the fiber material is compressed and dried to increase density and provide a smooth external surface finish. For example, see stratasys.com / solutions / additive-manufacturing / tooling / molded-fiber, keiding.com / molded-fiber / manufacturing-process / , European Patent Publication No. EP1492926B1 of Grenidea Technologies PTE Ltd., published on April 11, 2007, with the title "Improved Molded Fiber Manufacturing," and afpackaging.com / thermoformed-fiber-molded-pulp / . All of the above content is incorporated herein by this reference. 【0009】 Textile packaging products are biodegradable, compostable, and, unlike plastics, do not migrate into the ocean. However, currently known textile technologies are not well-suited for use with meat and poultry, cooked foods, agricultural products, microwaveable foods, or as lids for beverage containers such as hot coffee. In particular, selectively integrating one or more oil, water, steam, and / or oxygen barriers into a slurry, and / or selectively applying one or more barrier layers to all or part of the surface of the finished packaging product, can be laborious, time-consuming, and expensive. 【0010】 Therefore, methods, devices, spray systems, and chemical formulations are needed to overcome the limitations of conventional technology. 【0011】 Various features and characteristics will also become apparent from the subsequent detailed description and the attached claims, in conjunction with the attached drawings and this background section. [Overview of the project] 【0012】 Various embodiments of the present invention relate to the manufacture of vacuum-formed, fibrous packaging and container products and methods, chemical formulas, spray systems, and nozzle configurations for selectively applying barrier coatings to selected surfaces thereof, including, in particular, i) meat, agricultural, horticultural, and utility containers embodying novel geometric features that promote structural rigidity; ii) meat, agricultural, and horticultural containers having embedded and / or local moisture, oil, oxygen, and / or vapor barriers; iii) microwaveable and oven-heatable containers for frozen foods, ready-to-eat foods, yogurt, salads, cooked foods, macaroni and cheese, and other foods, embodying embedded and / or local moisture, oil, oxygen, and / or vapor permeability barriers, and / or yield enhancers for improving chemical bonding within the fibrous matrix; and iv) meat containers embodying moisture / vapor barriers that maintain structural rigidity over long shelf life. 【0013】 It should be noted that the various inventions described herein are illustrated in the context of, but are not limited to, conventional slurry-based vacuum forming processes. Those skilled in the art will understand that the inventions described herein may be intended for any fiber-based manufacturing method, including 3D printing technology, and including drying or fluffing processes that may or may not involve vacuum forming. 【0014】 Various other embodiments, aspects, and features are described in more detail below. [Brief explanation of the drawing] 【0015】 Exemplary embodiments are described below in conjunction with the attached drawings, and similar figures refer to similar elements. [Figure 1]This is a schematic block diagram of an exemplary vacuum forming process using a fibrous slurry according to various embodiments. [Figure 2] This is a schematic block diagram of an exemplary closed-loop slurry system for controlling the chemical composition of a slurry, according to various embodiments. [Figure 3] This is a perspective view of the bottom surface of an exemplary meat tray according to various embodiments. [Figure 4] Figure 3 shows a side elevation view of a meat tray according to various embodiments. [Figure 5] Figures 3 and 4 are top plan views of meat trays according to various embodiments. [Figure 6] Figure 5 shows end views of meat trays according to various embodiments. [Figure 7] This is a schematic perspective view of various embodiments of a spray coating system for meat trays. [Figure 8] This is a schematic perspective view of a spray coating system using a full-cone and hollow-cone dual nozzle system for use in microwave ovens, frozen foods, cooked meals, and other food containers with deep side walls, according to various embodiments. [Modes for carrying out the invention] 【0016】 The following detailed description of the present invention is essentially illustrative and is not intended to limit the present invention or its uses and applications. Furthermore, it is not intended to be bound by the background described above or any theories presented in the following detailed description. 【0017】 Various embodiments of the present invention relate to fibrous or pulp-based products for use both within and outside the food and beverage industry. In non-limiting examples, the disclosure relates to specific chemical formulations of slurries and localized films or coatings adapted to address the unique challenges faced by the food industry, including oil barriers, moisture barriers, vapor barriers, water vapor barriers, oxygen barriers, strength additives, and yield enhancers, the lack of which has so far limited the range of fibrous products that can effectively replace single-use plastic containers in the food industry. By combining novel slurry chemicals with surface coating technologies (e.g., spray coating, dipping), textile products can be used for, for example, frozen, chilled, and non-chilled foods, medical, pharmaceutical, and biological applications, microwaveable and oven-safe food containers, beverage cups and lids, edible and non-edible liquids, substances that release water, oil, and / or water vapor during storage, shipping, and preparation (e.g., cooking), consumable and horticultural applications including landscape / garden plants, flowers, herbs, shrubs, and trees, chemical storage and dispensing equipment (e.g., paint trays), agricultural products (including human and animal food such as fruits and vegetables), salads, cooked foods, meat, poultry, and fish, packaging, lids, etc. It will be possible to replace plastic equivalents in a wide range of applications, such as industrial, automotive, marine, aerospace, and military components, including buckets, tubes, gaskets, spacers, sealants, cushions, and similar items, as well as related molds, wire mesh forms, recipes, spray systems and spray nozzle configurations and processes, chemical formulas, tools, slurry distributions, chemical monitoring, chemical injection, and related systems, apparatus, methods, and technologies for manufacturing the aforementioned components. 【0018】 Various embodiments of spray coating technology surround an oil barrier and / or a vapor barrier around a bowl for a microwave oven and a tray for meat to address the phenomenon where water and / or oil penetrates through the tray surface and peels off with the meat after freezing. Additionally, spray coating may have applicability to the lid of a beverage, for example, to mitigate unwanted staining (e.g., lipstick). 【0019】 In some embodiments, the bowl for a microwave oven, steamer, or tray is spray-coated only on the inner surface, while other embodiments contemplate spray coating on both the inner and outer surfaces. For spray applications, the spray nozzle may be configured to apply a spray pattern (e.g., circular, annular, rectangular, and the like) that approximates the surface to be coated. 【0020】 Various spray, dip, or other coating styles use chemicals adapted to produce the desired performance characteristics in the finished product. Various chemical formulations are mixed with a polyester emulsion and applied to the surface of a container (e.g., the bottom surface) to mitigate the permeation of water vapor through the container wall (e.g., during heating using a microwave oven or a conventional oven), and include alginates (e.g., algae derivatives). Various chemical formulations may also include a calcium carbonate component to promote the bonding of the coating to the surface of a fibrous container. In many applications, the coating also effectively mitigates the permeation of oil. 【0021】 These coating chemicals may be used instead of (or in addition to) incorporating TG8111-based fluorochemicals into a slurry, as described elsewhere in this specification. In some embodiments, the surface coating may have a secondary oil barrier attribute in addition to the primary vapor barrier and / or water barrier attributes, although there may be cases where it is desirable to embed an oil barrier component in the slurry. 【0022】 Various surface coating embodiments contemplate both chemical aspects as well as process aspects (e.g., the manner in which the formulation is applied to the surface to achieve the desired coverage objectives). Process considerations include, but are not limited to, the size of the spray droplets, the configuration and orientation of the sprayer, the spray geometry, and “fill and transfer” techniques where containers (e.g., yogurt) are filled with the coating formulation and quickly emptied to create a film on the inner surface. 【0023】 In this regard, vapor barriers (e.g., to prevent drying of frozen foods during freezing) and oxygen barriers (e.g., to maintain freshness and shelf life during freezing) typically require complete (e.g., 100%) coverage of the protective surface, while moisture (e.g., water) barrier coatings (e.g., to prevent meat from sticking to meat trays or starch from sticking to microwave bowls after one or more freeze / thaw cycles) can be effective at substantially less than complete surface coverage. 【0024】 In various embodiments, spray and other coating processes may be used to apply vapor, oxygen, moisture, and / or oil barriers to the surface of the finished container, in addition to or instead of incorporating one or more barrier chemicals into the slurry used to vacuum form the container. In a preferred embodiment, for example, when only the inner surface is coated (e.g., in the case of a non-sticky barrier), the moisture barrier component is mixed into the slurry and the oil and / or vapor barrier is applied to the formed container. 【0025】 Spray coating applications are intended, among others, for microwave bowls, frozen foods, and meat trays. Depending on the application, it may be desirable to spray coat one or more of the following barriers: water, steam, oil, and oxygen. In the case of microwave bowls, 100% coverage is not necessarily required, as long as the issue is shelf life. Spray technology can be used to apply water and / or steam barriers, but it can also be used to prevent "sticking" (which does not require 100% coverage) so that meat does not tear paper fibers when removed from the tray in a frozen state (after one or more freezing / thawing cycles). Yogurt and other applications use spray coating for water vapor and oxygen barriers, which typically requires nearly 100% coverage. 【0026】 The use cases of spray coatings generally involve i) the chemical composition of the coating to be applied, ii) the thermophysical, fluidic, and viscoelastic properties, iii) the equipment for applying the coating to one or more surfaces (or portions of surfaces) of a container, packaging, or other workpiece, and iv) process parameters such as drying time and temperature. 【0027】 A typical use case involving spray coating is to surround the coating of a meat tray with a moisture barrier to help prevent meat from sticking to the fiber tray after freezing. After freezing, a top (surface) coating may be applied (via spray or otherwise) to reduce the degree to which meat sticks to the tray. The coating also helps maintain the strength and rigidity of the tray without freezing, for example, while meat and secretions are placed in the tray in a refrigerator. 【0028】 An exemplary method for manufacturing spray-coated meat trays may begin with an aqueous fiber-based slurry containing up to 100% OCC, or any desired combination of OCC and double-backed kraft (DLK) paper. (Alternatively, the various slurry bases described herein may contain a mixture of recycled and virgin fibers, or the slurry base may contain 100% virgin fibers (e.g., hardwood, softwood, or a combination thereof), as considered below in conjunction with microwave bowls.) 【0029】 A water / moisture barrier (e.g., 2-5%, preferably about 4% AKD), a dry strength additive (e.g., 0.5-4.5%, preferably about 4% starch, Hercobond 6950, or modified starch), and a wet strength additive (e.g., Kymene) may be added to the slurry. After the trays are vacuum-formed (e.g., after being dried in a hot press for about 55 seconds), the trays are transferred to a stacker, and the stack of trays is transferred to a spray coating station, where they are uncontained and dropped into their respective pockets on a conveyor, after which an auxiliary moisture coating is applied to each tray in either a continuous or parallel manner. 【0030】 In various embodiments, the auxiliary coating may be applied using a system including two fixed nozzles positioned above the tray, each nozzle outputting a spray pattern in the form of a wall or curtain (very similar to an air knife) as the tray passes underneath. Thus, each nozzle (or combination of nozzles) generates a spray pattern that terminates in a line preferably perpendicular to the direction of workpiece movement. In one embodiment, one nozzle may be angled forward (towards the direction of tray movement) to ensure complete coating of inclined sidewalls, structural ribs, and any other geometric features, while the other nozzle may be angled backward. 【0031】 Alternatively, a substantially flat tray with limited sidewall depth, or a single curtain-type spray configuration, may be used for applications where film uniformity is not particularly important. 【0032】 One criterion for evaluating whether a tray has received sufficient coverage (e.g., whether it is adequately coated) involves comparing the weight of the tray before and after coating to determine whether the weight of the coating material applied to the tray meets a predetermined threshold (or range). Alternatively or additionally, the thickness of the applied film may be measured to determine whether the coating thickness meets a predetermined threshold (or range of values). 【0033】 In some embodiments, the uniformity of the applied coating may also be measured, and process parameters may be adjusted as necessary to facilitate uniformity of future tray applications, in which case uniformity involves at least two considerations, namely i) whether the film layer is too thin at local points or areas, so that an effective barrier is not formed, and ii) whether the film layer is too thick at local points or areas, so that the finished tray at that point cannot dry completely, resulting in stains or peeling (the upper layer of the film sliding off or otherwise peeling away from the film). 【0034】 Next, the coated trays are dried in an oven at a temperature of 70-180°C, preferably about 80-110°C, most preferably about 95°C, for about 1 minute to remove moisture from the film layer and to cure as appropriate by other means. An infrared (IR) sensor may be used to check the temperature of the meat tray at one or more points to ensure that the appropriate curing temperature has been achieved. 【0035】 With respect to meat trays, the coating composition may contain 25% acrylic and 75% water, and the acrylic may include acrylic copolymer latex or similar material, such as Rhobarr 110 binder available from DOW Chemical Corporation. In this context, the coating functions as an anti-stick layer to prevent the top layer of the meat tray from peeling off when frozen meat is removed from the tray. 【0036】 In some embodiments, some or all of the opposite sides of the tray (including the bottom surface and / or outer sidewalls) may also be coated. This reduces to some extent the possibility of frozen secretions from the meat (e.g., blood, oil, water) adhering to the outside of the tray, for example, if secretions leak around the seal between the tray and the outer plastic wrap when the packaging is stored on its side. 【0037】 Meat trays typically do not require a separate oil barrier, but a steam and / or anti-fouling barrier can also effectively inhibit oil permeation. 【0038】 Pea emulsion and alginate can also be used as a substitute for acrylic, or in addition to acrylic, for meat trays, microwave bowls, and / or other packaging components. 【0039】 After drying, the trays are stacked, boxed, and shipped. 【0040】 The term "ready to eat" (RTE) tray refers to a container in which salads, fruits, cooked meals, and other foods are packaged using a sealed plastic membrane around the perimeter of the tray and are often stored in a refrigerator. RTE trays may be coated to provide an oxygen barrier to improve freshness and shelf life. 【0041】 RTE trays without localized membrane barriers can be prepared by adding to an OCC / DLK slurry containing 30-100% OCC / DLK and 0-70% virgin pulp, preferably about 100% OCC / DLK, i) an oil barrier containing 1-5%, preferably about 4%, Daikin 8111, ii) a moisture / water barrier containing 2-5%, preferably about 3.5%, AKD, and iii) a reinforcing component containing 3% starch such as Hercobond. 【0042】 RTE trays with localized membrane barriers may be prepared in substantially the same manner as described above (but with the oil barrier omitted and / or the AKD increased to 4%), and a localized oxygen barrier containing acrylic in an aqueous solution (e.g., 25% Robar 110 and 75% water) may also be added. With respect to RTE trays and containers (e.g., yogurt cups), the membrane is typically thicker than that described above in the context of meat trays to ensure a more complete (e.g., 100%) coverage. 【0043】 Uncoated microwave bowls may be made using a slurry containing up to 100% virgin fibers (softwood, hardwood, or a combination thereof). In one embodiment, the slurry base contains about 45% bleached hardwood, about 35% bleached softwood, and about 25% unbleached softwood. The slurry may also contain an oil barrier (e.g., 2.5% 8111), a water barrier (e.g., 3% AKD), a drying strength additive (e.g., 2.5% starch), a yield additive (e.g., 0.15% Nalco), and a defoaming component to remove entrained air (e.g., 1.5% Expair). 【0044】 Coated microwave bowls and other food packaging products may be made using a substantially virgin fiber slurry base as described above in relation to uncoated microwave bowls, further containing about 3% water barrier (AKD) and about 2.5% starch, but without oil barriers, yield additives, and defoamers. The coating formulation may contain about 27.5% solid in aqueous solution. The 27.5% solid may contain all or a preferred combination of the following 5(5) components (sometimes referred to as the DWP formulation): i) 25% acrylate, ii) 1.8% rice bran wax (may reduce tackiness), iii) 0.4% pectin (may promote the formation of a vapor barrier and may reduce tackiness to facilitate the un-nesting of stacked bowls), iv) 0.3% pea protein (may promote the emulsion of rice bran wax), and v) 0.2% liquid ammonium or other additive to adjust the pH and thereby promote acrylate curing. 【0045】 For bowls and other packaging components with deep sidewalls, curtain-type spray output terminating at the line is insufficient. To address this challenge, the inventors have developed two nozzle spray paradigms, one with a hollow cone spray pattern and the other with a full cone spray pattern, which together provide adequate coverage of the bottom surface and sidewall features without over-spraying the bottom surface. 【0046】 In a preferred embodiment, the coating is applied to microwave bowls using a two-nozzle system positioned above a conveyor that carries the bowls through a spray coating station. A first "full cone" nozzle is configured to cover the center (bottom) of each bowl, and a second "hollow cone" nozzle is configured to cover the inner side walls of each bowl. The full cone and hollow cone spray patterns are preferably configured to ensure complete coverage while minimizing excess film thickness in areas where the full cone pattern overlaps with the hollow cone pattern. 【0047】 In a preferred embodiment, as the bowl or other packaging component moves along the conveyor, the nozzle system also moves along the same path for a predetermined period of time, so that the nozzle or multiple nozzles do not translate relative to the bowl during spraying. Thus, the nozzles can remain "stationary" relative to each bowl without impairing processing capacity. 【0048】 Other coating technologies for use in the items discussed herein may include non-acrylate coating formulations that exhibit barrier (e.g., hot water / oil and water vapor transmission rate (WVTR)) performance and microwave water (MW) performance equivalent to the acrylate coatings described above. In particular, the dry coating composition may be included in an amount of 3% of the total weight of the bowl (or other container), for example: 【0049】 Non-acrylate coating example 1: i) A solid in the range of 6.5% to 8.5% by weight (e.g., 7.4% by weight), e.g., a target coat weight of 8.5 to 9.5 grams (e.g., a dry weight of 0.6 to 0.7 grams), ii) Polyvinyl alcohol (PVOH) in the range of 30-40% (for example, 36%), iii) Sugar alcohols in the range of 30% to 50% (e.g., 45%) (e.g., xylitol), iv) Citric acid in the range of 9% to 18% (for example, 13.5%), and v) Cellulose nanofibrils (CNF) in the range of 3% to 12% (e.g., 5.5%). 【0050】 Non-acrylate coating example 2: i) A solid in the range of 6% to 8% by weight (e.g., 7.0% by weight), for example, a target coat weight of 9 to 11 grams (e.g., 10 grams dry weight), ii) PVOH in the range of 30% to 40% (for example, 38%) iii) Sugar alcohols (xylitol) in the range of 30% to 50% (for example, 38%) iv) Citric acid in the range of 9% to 18% (for example, 14%), and v) Cellulose nanofibril (CNF) in the range of 3% to 12% (e.g., 10%). 【0051】 In some embodiments, the following ranges may be used for various components: [Table 1] 【0052】 The coated yogurt cups may be made using a substantially virgin fiber slurry base, as described above in relation to uncoated microwave bowls, further containing about 4% water barrier (AKD) and 3% starch. Instead of (or in addition to) the spray method described above, the localized oxygen barrier layer may be applied using either i) a full immersion step in which the cup is immersed in a pool of coating solution, thereby coating both the inner and outer surfaces, or ii) a “fill and discard” technique in which the coating solution is poured into the cup until it is full, and then discarded to coat the inner surface of the cup. In this context, the same or more diluted (lower acrylate concentration) versions of the aforementioned DWP formulations may be used. In addition, the poured solution may be recycled in an open-loop or closed-loop system to reduce waste. 【0053】 The coated cups may then be dried in an oven at approximately 95°C for about 1 minute, after which they may be stacked, boxed, and shipped. 【0054】 In a traditional macaroni and cheese (mac and cheese) bowl, the pasta is dry and the cheese is typically packaged separately in plastic or foil envelopes, so an oxygen barrier layer may or may not be required. If an oxygen layer is desired, it can be applied, for example, using either the full immersion or pour-and-dispose technique (or both) described above. If an oxygen layer is not required, an anti-stick coating can be applied, as described above. 【0055】 An alternative version of the DWP formulation would involve omitting 0.3% pea protein (which is in powder form) and using 0.05% Tween 80 (emulsifier) ​​to perform substantially the same function as emulsifying rice wax. 【0056】 In addition, instead of using powdered pectin, we use an aqueous version that is easier to mix. 【0057】 Formulations for localized coatings may include the following: [Table 2] [Table 3] [Table 4] 【0058】 In general, DWP spray coatings can be described as aqueous formulations containing total solids in the range of 15–40% by weight, preferably 25–30% by weight, most preferably about 27.5% by weight. One component in the formulation may include an acrylic polymer that crosslinks and polymerizes to facilitate the formation of a desired moisture, oil, and / or oxygen barrier layer during curing. The formulation also contains rice bran wax to provide non-stick properties and a non-glossy surface finish of the coated surface. The wax is emulsified with pea protein for stable aqueous dispersion. The formulation also contains pectin as a viscosity modifier for optimal adhesion to hydrophobic fiber surfaces during spray coating. The pH of the formulation is about 9.0 with the addition of ammonia to maintain the solubility of the acrylic polymer. 【0059】 An exemplary method for preparing a solution to be applied as a local coating will be described in the context of a 75(75) gallon batch using the following definitions: RBW: Rice Bran Wax PP: Pea Protein PEC: Pectin G: Gallon L: liter kg: kilogram 【0060】 Heat 35.6 gallons of water to at least 185°F and mix 5.1 kg of RBW at high speed for about 12 minutes until the wax pellets are completely dissolved and the solution temperature returns to 185°F. Add 0.85 kg of PP to the mixture over about 1 minute. Mix the PP for another 10 minutes or longer until no lumps are visible. Add 1.14 kg of Pec over 5 minutes and mix the contents for another 15 minutes or longer until no lumps are visible. Continue mixing at low speed until the batch temperature reaches about 120°F. While mixing, add 37.5 gallons of Rhobarr 110 to the batch and continue mixing for 10 minutes. Slowly pour 2.15 L of 4% ammonia into the batch and continue mixing for another 10 minutes. 【0061】 Referring here to Figure 1, an exemplary vacuum forming system and process 100 using a fibrous slurry includes a first step 101 in which a mold (not shown for clarity) in the shape of a mirror image of the product to be manufactured is wrapped in a fine wire mesh form 102 to match the contour of the mold. A supply 104 of the fibrous slurry 104 is introduced at a pressure (P1) 106 (typically ambient pressure). By maintaining a lower pressure (P2) 108 inside the mold, the slurry is drawn out through the mesh form, trapping the fibrous particles in the shape of the mold and discharging the excess slurry 110 for recirculation into the system. 【0062】 Continuing to refer to Figure 1, the second stage 103 involves accumulating a fiber layer 130 around the wire mesh in the shape of the mold. When the layer 130 reaches the desired thickness, the mold enters a third stage 105 for either wet curing or dry curing. In the wet curing process, the formed part is transferred to a heated press (not shown), where the layer 130 is compressed and dried to the desired thickness, thereby producing a smooth external surface finish for the finished part. In the dry curing process, heated air passes directly over the layer 130 to remove moisture from it, resulting in a more textured finish similar to that of a conventional egg carton. 【0063】 According to various embodiments, the vacuum forming process operates as a closed-loop system in that unused slurry is recirculated into the liquid tank where the product is formed. Therefore, some of the chemical additives (discussed in more detail below) are absorbed by the individual fibers, while some remain in the aqueous solution. During vacuum forming, only the fibers (that have absorbed some of the additives) are trapped in form, while the remaining additives are recirculated into the tank. As a result, since the remaining additives are recirculated with the slurry in the solution, only the additives trapped within the forming section need to be replenished. As described below, the system maintains a steady state of chemicals in the vacuum tank at predetermined volume ratios of components, including the slurry. 【0064】 Referring here to Figure 2, there is a closed-loop slurry system 200 for controlling the chemical composition of the slurry. In the illustrated embodiment, a tank 202 is filled with a fibrous slurry 204 having a specific desired chemical, and then a vacuum forming mold 206 is immersed in the slurry tank to form a molded part. After the molded part is formed to the desired thickness, the mold 206 is removed for subsequent processing 208 (e.g., forming, heating, drying, top coating, and so on). 【0065】 In a typical wet pressing process, the hot pressing temperature range is approximately 150-250°C, and the hot pressing pressure range is approximately 140-170 kg / cm². 2 The density of the final product is approximately 0.5-1.5 g / cm³. 3 Therefore, the most likely range is approximately 0.9 to 1.1 g / cm³. 3 The final product thickness is approximately 0.3 to 1.5 mm, preferably approximately 0.5 to 0.8 mm. 【0066】 Continuing to refer to Figure 2, a fibrous slurry containing pulp and water is introduced into tank 202 at slurry inlet 210. In various embodiments, a pulverizer may be used to pulverize the pulp fibers and create additional bonding sites. One or more additional components or chemical additives may be supplied at their respective inlets 212-214. The slurry may be recirculated using a closed-loop conduit 218 to which additional pulp and / or water is added as needed. To maintain a steady-state balance of desired chemical additives, a sampling module 216 is configured to dynamically or periodically adjust the levels of each additive by measuring or otherwise monitoring the components of the slurry and controlling their respective inlets 212-214. Typically, the slurry concentration is about 0.1-1%, most ideally about 0.3-0.5%, and preferably about 0.4-0.5%. In one embodiment, various chemical components are maintained at predetermined desired volume percentages, and alternatively, chemicals may be maintained based on weight percentages or any other desired mode of control. 【0067】 The pulp fibers used in 202 may also be mechanically crushed to improve interfiber bonding and the bonding of chemicals to the fibers. In this way, the slurry undergoes an improvement process that alters the water filtration rate or discharge rate of the fibrous material. Physical improvement modifies the fibers to make them smaller and more flexible, thereby achieving better bonding. The improvement process can also increase the tensile strength and burst strength of the final product. In various embodiments, water filtration rate is related to the surface condition and swelling of the fibers. The water filtration rate (CSF) is preferably in the range of 200 to 700, more preferably about 350 to 550, with respect to many of the processes and products described herein. 【0068】 Various chemical formulations (sometimes referred to herein as "chemicals"), spray coating and immersion systems, as well as nozzle and product configurations for various textile packaging and containers, and various methods for applying topical coatings will be further described in conjunction with Figures 3 to 8. 【0069】 Figure 3 is a perspective view of the meat tray 300 illustrating the lower surface 302 of the bottom surface and the outer surface of the side wall 304. 【0070】 Figure 4 is a side elevation view of the meat tray 402 shown in Figure 3. 【0071】 Figure 5 is a top plan view of the meat trays shown in Figures 3 and 4, illustrating the upper surface 502 of the bottom region of the tray, as well as the respective side walls 504 and 506. 【0072】 Figure 6 is an end view of the meat tray 602 shown in Figure 5. 【0073】 Figure 7 is a schematic perspective view of a spray coating system 700 useful for spray coating meat trays according to various embodiments. 【0074】 More specifically, the system 700 includes a conveyor 708 having pockets 710 for holding trays as the trays are transported along the direction indicated by the arrow 730. The trays include a bottom panel 704 having structural features (e.g., ribs) 706 and are surrounded by side walls 702. 【0075】 Continuing with reference to Figure 7, the illustrated spray system comprises a first spray nozzle 712 and a second spray nozzle 718, respectively. Nozzle 712 is configured to discharge a substantially planar spray pattern 715 bounded by a side edge 714 and terminating at a line 716 substantially perpendicular to direction 730. Nozzle 718 is configured to discharge a substantially planar spray pattern 721 bounded by a side edge 720 and terminating at a line 716 substantially perpendicular to direction 722. As the tray passes under the spray nozzles, the spray lines 716 and 722 apply the coating to all or selected portions of the inner surfaces of the bottom surface 704 and / or the side walls 702. 【0076】 Figure 8 is a schematic perspective view of a spray coating system 800, which includes a full-cone nozzle 810 configured to discharge a full-cone spray pattern and a hollow-cone nozzle 814 configured to discharge an annular (or "donut") shaped spray pattern. In particular, the system 800 is configured to apply a full-cone spray pattern 812 to the inner bottom surface 802 of a workpiece (bowl). The system 800 is further configured to apply a hollow-cone spray pattern 816 to the inner surface of the workpiece sidewall 804. 【0077】 Continuing to refer to Figure 8, the conveyor 806 is configured to transport trays along the direction defined by arrow 830 (right side in Figure 8). In one embodiment, the conveyor 806 may be configured to sequentially index in the direction of arrow 830, thereby positioning a series of trays under stationary nozzles 810, 814 lowered from the stationary pressure plate 820. At this position, the right-hand bowl can be spray-coated on its sidewalls, while the left-hand bowl can be spray-coated on its bottom. After indexing to the next position, the bowl that was previously under nozzle 810 is then positioned under nozzle 814, and so on. 【0078】 In an alternative embodiment, the total workpiece processing capacity may be increased by operating the conveyor 806 in a continuous manner (as opposed to sequential indexing). To maintain alignment between the nozzle system and the workpieces below during the application of spray coating, the pressure platen 820 may be configured to move to the right with the conveyor 830 to temporarily interrupt the relative motion between the nozzles, and then shift to the left to align the nozzles with the next series of workpieces to be coated. 【0079】 Figure 8 illustrates two workpieces, as well as one of each of a full-cone and a hollow-cone nozzle, but those skilled in the art will understand that, for each reciprocating motion of the pressure plate 820, the system can be estimated to accommodate any number of nozzles and workpieces. 【0080】 As briefly described above, the present invention provides various slurries used for vacuum forming containers, comprising pulp and water fiber mixtures to which chemical components are added to impart desired performance characteristics tailored for each specific product application. The base fibers may include at least one or a combination of the following materials: softwood (SW), bagasse, bamboo, old corrugated cardboard (OCC), and newspaper printing paper (NP).Alternatively, the base fiber may be selected according to the following resources, the entire contents of which are incorporated herein by reference: “Lignocellulosic Fibers and Wood Handbook: Renewable Materials for Today's Environment,” edited by Mohamed Naceur Belgacem and Antonio Pizzi (copyright protected 2016 by Scrivener Publishing, LLC), and available at https: / / books.google.com / books?id=jTL8CwAAQBAJ&printsec=frontcover#v=onepage&q&f=false; and “Efficient Use of Fluorescent Whitening Agents and Shading Colorants in the Production of” by Liisa Ohlsson and Robert Federe, published on October 8, 2002, at African Pulp and Paper Week, and available at tappsa.co.za / archive / APPW2002 / Title / Efficient_use_of_fluorescent_w / efficient_use_of_fluorescent_w.html. "White Paper and Board," copyrighted 200 by Woodhead Publishing Ltd. and available at books.google.com / books?id=xO2iAgAAQBAJ&printsec=frontcover#v=onepage&q&f=false, is edited by JF Kennedy, GO Phillips, and P.A. Williams, and is titled "Application of Enzymes and Flocculants for Enhancing the Freeness of Paper Making Pulp," U.S. Patent No. 5,169,497A, issued December 8, 1992. 【0081】 With respect to vacuum-formed product containers manufactured using either a wet or dry press, fiber systems of OCC or OCC / DLK and NP may be used, wherein the OCC / DLK component is 50% to 100%, preferably about 70% OCC / DLK and 30% NP or VNP, and has an added moisture / water repellent in the range of 1 to 10% by weight, preferably about 1.5% to 4% by weight, most preferably about 4% by weight. In preferred embodiments, the moisture / water barrier may comprise alkyl ketene dimers (AKD) (e.g., Hercon 79, Hercon 80) and / or long-chain diketenes, available from FOBCHEM at fobchem.com / html_products / Alkyl-Ketene-Dimer%EF%BC%88AKD-WAX%EF%BC%89.html#.V0zozvkrKUk and Yanzhou Tiancheng Chemical Co., Ltd. at yztianchengchem.com / en / index.php?m=content&c=index&a=show&catid=38&id=124&gclid=CPbn65aUg80CFRCOaQod0JUGRg. 【0082】 To produce specific colors for molded pulp products, cationic dyes or fiber-reactive dyes may be added to the pulp. Fiber-reactive dyes, such as Procion MX, bond to the fibers at a molecular level and chemically become part of the fabric. Additionally, adding salt, soda ash, and / or increasing the pulp temperature helps to further trap the absorbed dye within the fabric, preventing color bleeding and improving color depth. 【0083】 To improve structural rigidity, liquid starch components may be added to the slurry, such as Topcat® L98 cationic additive (or Hercobond 6950 available from Solenis LLC), Hercobond, and Topcat® L95 cationic additive (available from Penford Products Co., Cedar Rapids, Iowa). Alternatively, liquid starch may also be combined with low-charge liquid cationic starch, such as Penbond® cationic additive and PAF 9137 BR cationic additive (also available from Penford Products Co., Cedar Rapids, Iowa). 【0084】 For dry pressing processes, Topcat L95 or Hercobond 6950 may be added in the range of 0.5% to 10% by weight, preferably about 1% to 7% by weight, most preferably about 6.5% by weight for products that need to maintain strength, especially in high-humidity environments, and otherwise most preferably about 1.5% to 2.0% by weight. For wet pressing processes, dry strength additives such as Topcat L95 or Hercobond 6950 are made from modified polyamines that form both hydrogen and ionic bonds with fibers and fine particles. Dry strength additives increase dry strength, as well as improve drainage and yield, and are also effective in fixing anions, hydrophobic substances and sizing agents to textile products. These additives may be added in the range of 0.5% to 10% by weight, preferably about 1% to 6% by weight, most preferably about 3.5% by weight. In addition, both wet and dry processes can benefit from the addition of wet strength additives, such as polyamide-epichlorohydrin (PAE) resins like Kymene 920A or 1500, or solutions formulated with similar components available from Ashland Specialty Chemical Products at ashland.com / products. In preferred embodiments, Kymene 920A or 1500 may be added in the range of 0.5% to 10% by volume, preferably about 1% to 4% by volume, most preferably about 2% by volume, or in an amount equal to the dose of the dry strength additive. Kymene 920A or 1500 belongs to a class of polycationic materials containing an average of two or more amino groups and / or quaternary ammonium bases per molecule. Such amino groups tend to protonate in acidic solutions to generate cationic species. Other examples of polycationic materials include polymers derived from the modification of amino-containing polyamides with epichlorohydrin, such as those prepared from condensed adipic acid and dimethylentriamine, which are commercially available as Hercosett 57 from Hercules and Catalyst 3774 from Ciba-Geigy. 【0085】 The inventors have found that molded fiber containers can be suitable as single-use food containers suitable for use in microwave ovens, convection ovens, and conventional ovens by embedding barrier chemicals in a slurry, adding a localized coating to a finished vacuum-formed container, or both. In particular, the slurry and / or localized coating chemicals should advantageously avoid condensation caused by placing a hot container on a surface having a lower temperature than the container, corresponding to one or more of the following three performance metrics: i) moisture barrier, ii) oil barrier, and iii) water vapor (condensation) barrier. 【0086】 In this context, the degree to which water vapor penetrates a container is related to the porosity of the container, which is what the present invention seeks to reduce. That is, even if the container is effectively impermeable to oil and water, water vapor penetration into the container can impair the user experience, especially if water vapor condenses on a cold surface, leaving a moisture ring. The inventors further determined that the condensation problem is inherently present in textile applications, as water vapor typically does not penetrate plastic barriers. 【0087】 Therefore, with respect to microwaveable containers, the present invention envisions a fibrous or pulp-based slurry comprising a water barrier, an oil barrier, and a water vapor barrier, as well as an optional yield enhancer. In one embodiment, a softwood (SW) / bagasse fiber base may be used in the range of about 10% to 90%, preferably in a ratio of about 7:3. As a water barrier, AKD may be used in the range of about 0.5% to 10%, preferably about 1.5% to 4%, most preferably about 3.5%. As an oil barrier, greases and oil-repellent additives are often aqueous fluorine emulsions containing compositions of fluororesins or other fluorine-containing polymers such as UNIDYNE TG 8111 or UNIDYNE TG-8731, available from Daikin or World of Chemicals at worldofchemicals.com / chemicals / chemical-properties / unidyne-tg-8111.html. The oil barrier component of the slurry (or local coating) may be present in a weight percentage of 0.5% to 10% by weight, preferably about 1% to 4% by weight, and most preferably about 2.5% by weight. As a yield enhancer, an organic compound such as Nalco 7527, available from Nalco Company in Naperville, Ill., may be used in a volume of 0.1% to 1% by volume, preferably about 0.3% by volume. Finally, to strengthen the finished product, a dry strength additive such as an inorganic salt (e.g., Hercobond 6950, available at solenis.com / en / industries / tissue-towel / innovations / hercobond-dry-strength-additives / , and see sfm.state.or.us / CR2K_SubDB / MSDS / HERCOBOND_6950.PDF) may be used in the range of 0.5% to 10% by weight, preferably about 1.5% to 5% by weight, and most preferably about 4% by weight. 【0088】 As mentioned above, vapor barrier performance is directly affected by the porosity of the fiber tray. Reducing the porosity of the fiber tray, and therefore improving the vapor barrier performance, can be achieved using at least two approaches. One is by improving the filtration efficiency of the tray material by grinding the fibers. The second method is by localized spray coating using, for example, Daikin S2066, an aqueous long-chain fluorine-containing polymer. The spray coating can be implemented using a concentration in the range of about 0.1% to 3% by weight, preferably about 0.2% to 1.5% by weight, and most preferably about 1% by weight. 【0089】 Meat trays as they are known today, such as those used in grocery stores for displaying poultry, beef, pork, and seafood, are typically made from plastic materials such as polystyrene and polystyrene foam, primarily due to their excellent moisture barrier properties. The inventors have determined that modifications of the aforementioned chemicals used for microwaveable containers can be adapted for use in meat trays, particularly with respect to moisture barriers (oil and porous barriers are typically less important in meat trays than in microwaveable containers). 【0090】 Accordingly, with respect to meat containers, the present invention envisions a fibrous or pulp-based slurry comprising a water barrier and an optional oil barrier. In one embodiment, a softwood (SW) / bagasse and / or bamboo / bagasse fiber base may be used in the range of about 10% to 90%, preferably in a ratio of about 7:3. As a moisture / water barrier, AKD may be used in the range of about 0.5% to 10%, preferably about 1% to 4%, most preferably about 4%. As an oil barrier, an aqueous emulsion, such as UNIDYNE TG 8111 or UNIDYNE TG-8731 may be used. The oil barrier component of the slurry (or local coating) may be contained in the range of 0.5% to 10% by weight, preferably about 1% to 4% by weight, most preferably about 1.5% by weight, as a weight percentage. Finally, to enhance the finished product, a dry strength additive such as Hercobond 6950 may be used in the range of 0.5% to 10% by weight, preferably about 1.5% to 4% by weight, and most preferably about 4% by weight. 【0091】 As discussed above in relation to agricultural product containers, slurry chemicals and / or spray coating chemicals, in combination with structural features, can provide long-term rigidity over time by preventing moisture / water from penetrating the tray. 【0092】 Therefore, a method for manufacturing a meat tray is provided. The method includes providing a wire mesh mold that approximates the shape of a meat tray; preparing an aqueous fiber slurry containing at least one of old cardboard boxes (OCC) and double-backed kraft (DLK) paper; adding an embedded moisture barrier to the slurry; immersing the mold in the slurry; vacuuming the mold in the slurry until fiber particles of a desired thickness accumulate on the surface of the mold; removing the accumulated particles from the mold; drying and pressing the accumulated particles in a press to thereby form a meat tray; transferring the meat tray from the press to a coating station; and applying an auxiliary moisture barrier layer to the surface of the meat tray at the coating station. 【0093】 In one embodiment, the embedded moisture barrier contains 2% to 5% alkyl ketene dimer (AKD). 【0094】 In one embodiment, the method further includes adding a drying strength additive to the slurry. 【0095】 In one embodiment, the drying strength additive contains 0.5% to 4.5% starch. 【0096】 In one embodiment, the coating station comprises a spray system and a conveyor configured to move meat trays along the direction of travel and engage with the spray system. 【0097】 In one embodiment, the spray system comprises a first nozzle configured to discharge a first predetermined spray pattern onto a meat tray. 【0098】 In one embodiment, a first predetermined spray pattern includes a substantially vertical curtain terminating at a line in a meat tray, the line having a predetermined thickness and oriented substantially perpendicular to the direction of travel. 【0099】 In one embodiment, the spray system further includes a second nozzle configured to discharge a second predetermined spray pattern onto a meat tray, wherein the first spray pattern is angled toward the direction of travel and the second spray pattern is angled toward the direction of travel. 【0100】 In one embodiment, the auxiliary moisture barrier layer contains an acrylic copolymer latex in an aqueous solution. 【0101】 In one embodiment, the auxiliary moisture barrier layer comprises a solution of acrylic and water in a ratio of approximately 1:3. 【0102】 The method is also provided for manufacturing a microwave bowl of a type characterized by a substantially flat circular bottom region bounded by circumferential side walls. The method comprises providing a wire mesh mold that approximates the shape of a bowl; preparing an aqueous fibrous slurry containing at least one of hard virgin fibers and soft virgin fibers; adding an embedded moisture barrier to the slurry; immersing the mold in the slurry; vacuuming the mold in the slurry until fibrous particles of a desired thickness accumulate on the surface of the mold; removing the accumulated particles from the mold; drying and pressing the accumulated particles in a press to thereby form a bowl; transferring the bowl from the press to a coating station; and applying a localized oil barrier layer to at least a portion of the bowl at the coating station. 【0103】 In one embodiment, the embedded moisture barrier contains 2% to 5% alkyl ketene dimer (AKD). 【0104】 In one embodiment, the method further comprises adding a drying strength additive to the slurry, the drying strength additive containing 0.5% to 4.5% starch. 【0105】 In one embodiment, the local oil barrier layer contains about 27.5% solid in an aqueous solution. 【0106】 In one embodiment, the solid comprises acrylate, rice bran wax, pectin, and pea protein. 【0107】 In one embodiment, the coating station includes a spray system and a conveyor configured to move a bowl along the direction of travel below the spray system. 【0108】 In one embodiment, the spray system includes a first nozzle configured to discharge a full cone spray pattern onto the bottom region of a bowl, and a second nozzle configured to discharge a hollow cone spray pattern onto the inner surface of the circumferential side wall. 【0109】 In one embodiment, the method further includes the step of moving the spray system along the direction of travel, so that i) a first nozzle is positioned above the bowl and remains stationary relative to the bowl for a first predetermined period of time, and ii) a second nozzle is positioned above the bowl and remains stationary relative to the bowl for a second predetermined period of time. 【0110】 In one embodiment, the first period is one of the following: i) greater than the second period, ii) equal to the second period, and iii) less than the second period. 【0111】 The method is provided for manufacturing a type of fibrous microwave bowl including a substantially circular bottom portion bounded by inclined circumferential sidewalls. The method may include the steps of: providing a wire mesh mold approximating the shape of the bowl; preparing an aqueous fibrous slurry containing up to 100% virgin fibers; adding an embedded moisture barrier to the slurry; immersing the mold in the slurry; vacuuming the mold in the slurry until fibrous particles of a desired thickness accumulate on the surface of the mold; removing the accumulated particles from the mold; drying and pressing the accumulated particles in a press to form the bowl; transferring the bowl from the press to a coating station; and applying an acrylic oil barrier layer to the surface of the bowl at the coating station. 【0112】 In one embodiment, the embedded moisture barrier contains 2% to 5% alkyl ketene dimer (AKD). 【0113】 In one embodiment, the oil barrier layer includes a calcium carbonate component to promote bonding to the bowl surface. 【0114】 In one embodiment, the oil barrier layer contains a pea emulsion. 【0115】 In one embodiment, the oil barrier layer contains an alginate. 【0116】 In one embodiment, the oil barrier layer comprises an aqueous solution containing about 25% acrylate and a first auxiliary component configured to reduce tackiness. 【0117】 In one embodiment, the first auxiliary component contains approximately 1.8% rice bran wax. 【0118】 In one embodiment, the first auxiliary component contains about 0.4% pectin. 【0119】 In one embodiment, the oil barrier layer includes a second auxiliary component configured to promote the emulsification of a first auxiliary component. 【0120】 In one embodiment, the second auxiliary component contains approximately 0.3% pea protein. 【0121】 In one embodiment, the oil barrier layer includes a third auxiliary component configured to adjust the pH level of the oil barrier coating, thereby promoting acrylate curing. 【0122】 In one embodiment, the third auxiliary component contains about 0.2% liquid ammonium. 【0123】 In one embodiment, the coating station comprises a spray system and a conveyor configured to move a bowl along the direction of travel and engage with the spray system. 【0124】 In one embodiment, the spray system comprises a first nozzle configured to discharge a full-cone spray pattern onto the bottom of a bowl. 【0125】 In one embodiment, the spray system includes a second nozzle configured to discharge a hollow conical spray pattern onto the inner surface of the side wall. 【0126】 In one embodiment, the oil barrier layer comprises a solution of acrylic and water in a ratio of approximately 1:3. 【0127】 The method is also provided for manufacturing a microwave bowl of a type characterized by a substantially flat circular bottom region bounded by circumferential sidewalls, and comprises the steps of: providing a wire mesh mold approximating the shape of the bowl; preparing an aqueous fiber-based slurry containing at least one of hard virgin fibers and soft virgin fibers; adding an embedded moisture barrier to the slurry; immersing the mold in the slurry; vacuuming the mold in the slurry until fiber particles of a desired thickness accumulate on the surface of the mold; removing the accumulated particles from the mold; drying and pressing the accumulated particles in a press to thereby form the bowl; transferring the bowl from the press to a coating station; and applying a localized oil barrier layer to at least a portion of the bowl at the coating station, the localized oil barrier layer containing about 27.5% solids in an aqueous solution. 【0128】 In one embodiment, the solid comprises acrylate, rice bran wax, pectin, and pea protein. 【0129】 A microwave bowl may be manufactured using any of the methods described herein. 【0130】 Although the present invention has been described in the context of the embodiments described above, it will be understood that the present invention is not limited in that way. For example, various spray systems and nozzle configurations, slurry chemicals, and spray coat chemicals can be adapted to suit additional applications based on the teachings of the present invention. 【0131】 As used herein, the term “exemplary” means “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferable or advantageous to other embodiments, nor is it intended to be construed as a model that must be literally replicated. 【0132】 While the detailed description above provides a useful roadmap for implementing various embodiments of the invention for those skilled in the art, it should be understood that the specific embodiments described above are merely examples and are not intended to limit the scope, applicability, or configuration of the invention in any way. Conversely, various modifications can be made to the function and arrangement of the described elements without departing from the scope of the invention.

Claims

[Claim 1] A method for manufacturing a microwave bowl, A process for providing a wire mesh mold that approximates the shape of a meat tray, A step of preparing an aqueous fiber slurry containing at least one of old corrugated cardboard (OCC) and double-lined kraft (DLK) paper, A step of adding the embedded moisture barrier to the aqueous fiber-based slurry, A step of immersing the wire mesh mold in the aqueous fiber slurry, A step of vacuuming the wire mesh molding die within the aqueous fiber slurry until fiber particles of a desired thickness accumulate on the surface of the wire mesh molding die, The steps include removing the accumulated particles from the wire mesh mold and A step of drying and pressing the accumulated particles in a press machine to form the microwave oven bowl, The process of transferring the microwave oven bowl from the press machine to the coating station, The coating station includes the step of applying a non-acrylate moisture barrier layer to the surface of the microwave bowl, The non-acrylate moisture barrier layer contains 6.5% to 8.5% non-acrylate particulate solid in an aqueous solution, and the non-acrylate moisture barrier layer contains polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF). The total amount of the polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF) is 100% by weight. The non-acrylate moisture barrier layer comprises 30% to 40% polyvinyl alcohol, 30% to 50% sugar alcohol, 9% to 18% citric acid, and 3% to 12% CNF. method. [Claim 2] The method according to claim 1, wherein the embedded moisture barrier comprises 2% to 5% by weight of an alkyl ketene dimer (AKD). [Claim 3] The method according to claim 1, further comprising adding a dry strength additive to the aqueous fiber slurry. [Claim 4] The method according to claim 3, wherein the drying strength additive contains 0.5% to 4.5% by weight of starch. [Claim 5] The aforementioned coating station spray system and The method according to claim 1, further comprising: a conveyor configured to move the microwave bowl along the direction of travel and engage with the spray system. [Claim 6] The method according to claim 5, wherein the spray system comprises a first nozzle configured to discharge a first predetermined spray pattern onto the bottom of the microwave oven bowl. [Claim 7] The method according to claim 6, wherein the first predetermined spray pattern comprises a substantially vertical curtain terminating at a line in the microwave bowl. [Claim 8] The method according to claim 6, wherein the spray system further comprises a second nozzle configured to discharge a second predetermined spray pattern onto the side wall of the microwave oven bowl. [Claim 9] The method according to claim 1, wherein the non-acrylate moisture barrier layer comprises a 1:3 solution of fine particles and water. [Claim 10] A method for manufacturing a microwave oven bowl of a type characterized by a substantially flat circular bottom region bounded by circumferential side walls, A step of providing a wire mesh mold that approximates the shape of the aforementioned microwave oven bowl, A step of preparing an aqueous fiber slurry containing at least one of hard virgin fibers and soft virgin fibers, A step of adding the embedded moisture barrier to the aqueous fiber-based slurry, A step of immersing the wire mesh mold in the aqueous fiber slurry, A step of vacuuming the wire mesh molding die within the aqueous fiber slurry until fiber particles of a desired thickness accumulate on the surface of the wire mesh molding die, The steps include removing the accumulated particles from the wire mesh mold and A step of drying and pressing the accumulated particles in a press machine to form the microwave oven bowl, The process of transferring the microwave oven bowl from the press machine to the coating station, The coating station includes the step of applying a local barrier layer to the inner surface of the microwave oven bowl, The local barrier layer comprises 6.5% to 8.5% non-acrylate particulate solid in an aqueous solution, and the local barrier layer comprises polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF). The total amount of the polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF) is 100% by weight. The local barrier layer comprises 30% to 40% polyvinyl alcohol, 30% to 50% sugar alcohol, 9% to 18% citric acid, and 3% to 12% CNF. method. [Claim 11] The method according to claim 10, wherein the embedded moisture barrier comprises 2% to 5% alkyl ketene dimer (AKD). [Claim 12] The method according to claim 10, further comprising adding a drying strength additive to the aqueous fiber slurry, wherein the drying strength additive contains 0.5% to 4.5% starch. [Claim 13] The method according to claim 10, wherein the local barrier layer comprises 30% to 40% polyvinyl alcohol, 30% to 50% sugar alcohol, 9% to 18% citric acid, and 4.5% to 6.5% CNF. [Claim 14] The method according to claim 10, wherein the local barrier layer comprises 36% polyvinyl alcohol, 45% sugar alcohol, 13.5% citric acid, and 5.5% CNF. [Claim 15] A method for manufacturing a microwave oven bowl of a type characterized by a substantially flat circular bottom region bounded by circumferential side walls, A step of providing a wire mesh mold that approximates the shape of the aforementioned microwave oven bowl, A step of preparing an aqueous fiber slurry containing at least one of hard virgin fibers and soft virgin fibers, A step of adding the embedded moisture barrier to the aqueous fiber-based slurry, A step of immersing the wire mesh mold in the aqueous fiber slurry, A step of vacuuming the wire mesh molding die within the aqueous fiber slurry until fiber particles of a desired thickness accumulate on the surface of the wire mesh molding die, The steps include removing the accumulated particles from the wire mesh mold and A step of drying and pressing the accumulated particles in a press machine to form the microwave oven bowl, The process of transferring the microwave oven bowl from the press machine to the coating station, The coating station includes the step of applying a local barrier layer to the inner surface of the microwave oven bowl, The local barrier layer comprises 6% to 8% non-acrylate particulate solid in an aqueous solution, and the local barrier layer comprises polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF). The total amount of the polyvinyl alcohol, sugar alcohol, citric acid, and cellulose nanofibril (CNF) is 100% by weight. A method wherein the local barrier layer comprises 30% to 40% polyvinyl alcohol, 30% to 50% sugar alcohol, 9% to 18% citric acid, and 3% to 12% CNF. [Claim 16] The method according to claim 15, wherein the local barrier layer comprises 38% polyvinyl alcohol, 38% sugar alcohol, 14% citric acid, and 10% CNF.

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