Method for thermoforming cellulose ester foam articles

Abstract

A method for thermoforming a foamed cellulose ester sheet into a foam tray. This method and the composition used therein provide a foam tray with desired surface preservation after thermoforming. By using one or more high heat capacity additives and / or melt strength improvers, improved surface preservation can be provided at a higher thermoforming stretch ratio.

Description

Background Art

[0001] Many foamed products, such as food packaging supplies, are intended to be disposable items that are discarded after use. One commercially important material used to make foamed products is polystyrene. However, polystyrene cannot be composted or biodegraded. Further, some municipalities, states, and countries have implemented or are considering implementing bans on the use of polystyrene foam. Thus, it is desirable to find alternative materials for use in foamed products, as well as promising compositions, methods, and systems for manufacturing such products.

[0002] During the thermoforming of a foamed article, a flat foamed sheet is heated and stretched into a mold. The deeper the mold, the more the sheet material needs to be stretched, which can be characterized by its draw ratio. However, if the draw ratio is too high, the sheet can tear or crack. Thus, it is desirable to find an acceptable draw ratio for articles formed from cellulose ester foamed sheets, as well as compositions and processes for increasing the draw ratio while maintaining acceptable skin integrity of the foamed article product.

Summary of the Invention

[0003] In one embodiment, or in combination with any other embodiment mentioned herein, a method of forming a foamed article is provided. The method includes (a) manufacturing a foamed sheet from a cellulose ester composition, and (b) thermoforming the foamed sheet in a mold having a footprint area (X) and a surface area less than 1.9X, thereby forming a foamed article.

[0004] In another embodiment, or in combination with any other embodiment referred to herein, a method of forming a foamed article is provided. The method includes (a) producing a foamed sheet from a composition comprising a cellulose ester and an additive having a specific heat capacity of at least 2000 J / (kg K), and (b) thermoforming the foamed sheet in a mold, thereby forming a foamed article.

[0005] In another embodiment, or in combination with any other embodiment referred to herein, a method of forming a foamed article is provided. The method includes (a) producing a foamed sheet from a cellulose ester composition, and (b) thermoforming the foamed sheet in a mold having a footprint area (X) and a surface area of at least 1.2X to 5.0X, thereby forming a foamed article.

Brief Description of the Drawings

[0006] [Figure 1] It is a schematic diagram showing a biodegradable product molding process according to an embodiment of the present invention. [Figure 2] It is a schematic diagram showing another biodegradable product molding process according to an embodiment of the present invention. [Figure 3] It is a schematic diagram showing an extrusion section that can be used in the article molding process of FIG. 1 and / or FIG. 2 according to an embodiment of the present invention. [Figure 4] It is a schematic diagram showing another extrusion section that can be used in the article molding process of FIGS. 1 and 2 according to an embodiment of the present invention. [Figure 5] It is a schematic diagram showing a sheet molding section that can be used in the article molding process of FIG. 1 and / or FIG. 2 according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0007] The embodiments generally relate to methods, systems, and compositions for forming biodegradable particulate materials (e.g., pellets), foamed sheets, and articles. Figures 1 to 5 show exemplary processes including methods, systems, and compositions, which are described in further detail below.

[0008] Methods and Systems As shown in Figures 1 and 2, raw materials are introduced into a biodegradable polymer manufacturing process for producing biodegradable polymer materials. In one embodiment, or in combination with any other embodiment referred to herein, the biodegradable polymer material comprises one or more cellulose esters. The one or more cellulose esters may include cellulose acetate. In such embodiments, the raw materials may include pulp such as wood pulp and / or cotton pulp. The pulp may be dissolvable grade pulp and / or paper grade pulp. The cellulose in the pulp can be esterified, for example with acetic acid, to form biodegradable cellulose ester polymers such as cellulose acetate polymers.

[0009] Next, the biodegradable polymer material can be introduced into the compounding process. In this process, the biodegradable polymer material can be mixed with a plasticizer and optionally one or more other additives (e.g., stabilizers) to form a compound material containing a plasticized biodegradable polymer. Other additives may also be mixed with the polymer and plasticizer. For example, as shown in Figure 2, other materials (additives) may include, but are not limited to, stabilizers, physical blowing agents (multiple), chemical blowing agents (multiple) (and / or precursors), nucleating agents (multiple), surface modifying additives (multiple), pigments (multiple), fillers (multiple), and / or other additives (multiple). Mixing can be achieved by any known mixing technique, including but not limited to rolling in a cylindrical vessel, overhead stirring, sigma blade mixing, and tumbling.

[0010] The compounding process may include a particle formation process. The particle formation process may generally include mixing biodegradable polymer materials, plasticizers, and other additives to form a mixed composition, and forming particulate material from that composition. Specifically, the particle formation process may include a pelletizing process, and the particulate material may contain a number of pellets. The term “compounded CE material” means a cellulose ester material formed during the compounding process, which may include a mixture of cellulose esters, plasticizers, and other additives. Furthermore, such compounded CE material may take the form of particulate material or pellets. It should be understood that, as used herein, the terms “particle formation” or “particle formation process” may be the same as, or at least include, “pellet formation” or “pelletizing process.” In some embodiments, the particle formation process may include pelletizing in a water tank, pelletizing on an air-cooled belt, water pelletizing, solvent compounding, and the like.

[0011] In one embodiment, or in combination with any other embodiment referenced herein, plasticizers and other additives(s) may be mixed with cellulose esters by conventional melt compounding techniques. This technique involves mixing the cellulose esters with plasticizers and optionally other additives at appropriate temperatures and pressures in a twin-screw extruder equipped with appropriate mixing elements, to obtain a molten, uniformly combined cellulose ester mixture by the time the material is discharged from the extruder. The molten, compounded cellulose ester mixture may then be extruded through a die having an orifice approximately 2–6 mm in diameter to extrude strands. These strands may then be cooled with water (e.g., via underwater pelletizing) or air and cut at regular intervals to obtain uniform, desirable sizes and shapes called “pellets” or “granules.” While this specification describes a process for forming pelletized compounding materials, it will be understood that the compounding materials supplied to the foam sheet manufacturing process may be in any physical form (e.g., pellets, powders, granules, fibers) according to some embodiments. The term "compounded CE material" refers to a cellulose ester material formed during the compounding process, which may include a mixture of cellulose esters, plasticizers, and other additives. Furthermore, such compounded CE material may take the form of a molten mixture or particulate material (e.g., pellets, powders, granules, fibers, etc.).

[0012] Next, as described above, formulated CE materials containing pellets of plasticizable biodegradable polymers can be introduced into a foamed sheet manufacturing process, as shown in Figures 1 and 2. The foamed sheet manufacturing process may include one or more zones / steps for producing a foamed sheet or film, which are described in further detail below. While exemplary foamed sheet manufacturing processes are described herein, it should be understood that certain embodiments described herein may also be applicable to rigid (i.e., non-foamed) materials and articles. As shown in Figure 1, various additives can be introduced into one or more zones of the foamed sheet manufacturing process in one embodiment or in combination with any other embodiments referred to herein. Additives may include, but are not limited to, stabilizers, physical foaming agents (or more), chemical foaming agents (or more) (and / or precursors), nucleating agents (or more), surface modifying additives (or more), pigments (or more), fillers (or more), and / or other additives (or more).

[0013] A foamed sheet manufacturing process may generally include an extrusion section and a sheet forming section. An exemplary extrusion section is shown in Figure 3. As shown, the extrusion section may include a feed preparation zone where solid additives may be combined with the compounded CE material and introduced into the downstream extrusion zone. In one embodiment, or in combination with any other embodiment referred to herein, the feed preparation zone may include a feed hopper. Thus, the compounded CE material and other solid additives may be deposited in the feed hopper, which directs the combined feed composition towards the extrusion zone. The feed preparation zone may further include a mixer where the compounded CE material and one or more additives may be mixed before being introduced into the hopper. Mixing can be achieved by any known mixing technique, including but not limited to rolling in a cylindrical vessel, overhead stirring, sigma blade mixing, and tumbling. Examples of solid additives that can be combined with the formulation materials include chemical blowing agents, nucleating agents, surface modifying additives, pigments, fillers, and / or other additives.

[0014] Next, the combined feed composition from the feed preparation zone may be introduced into the extrusion zone. The extrusion zone may generally include one or more extruders, which may include single-screw and / or twin-screw extruders. Within the extruder(s), the feed composition may be introduced into the extruder barrel and conveyed by a screw(s) through a die that forms an extruder from the feed composition. As the composition is conveyed through the extruder barrel toward the die, it may be heated and at least partially melted. Thus, the term “CE molten composition” is used herein to mean a cellulose ester-based feed composition melted into a fluid molten resin through the extrusion section. Heating may be supplied by an external heater positioned along the outside of the extruder barrel. The shape of the extruder is generally determined by the shape and size of the die head. The extruder may be further shaped by downstream processes as described below.

[0015] One or more additives can be introduced into the CE molten resin while it is in the extruder. For example, one or more physical blowing agents can be added to the CE molten resin by injecting a physical blowing agent into the composition being conveyed in the extruder barrel.

[0016] As shown in Figure 4, in one embodiment, or in combination with any other embodiment referred to herein, the extrusion zone may include a primary extrusion vessel and a cooling vessel. The primary extrusion vessel and the cooling vessel may be separate devices or may be combined as an integrated device. In any case, the supply composition from the supply preparation zone is introduced into the primary extrusion vessel and at least partially melts as it is conveyed through the extruder barrel as described above, thereby producing molten CE resin. The molten CE resin exiting the primary extrusion vessel may have a temperature of about 220°C to about 240°C. One or more additives, such as blowing agents, may be added to the molten CE resin as it is conveyed through the primary extrusion vessel.

[0017] Next, the molten CE resin from the primary extrusion vessel is introduced into a cooling vessel. The cooling vessel may be a secondary extrusion vessel that operates similarly to the primary extrusion vessel but at a lower temperature. In the cooling vessel, the molten CE resin can be further mixed to provide a substantially homogeneous mixture of the molten polymer and other additives(s). The molten CE resin can then be passed through a die and directed outward from the die head to obtain a cellulose ester-based extruder, which can be further processed in the sheet forming section of a foamed sheet manufacturing process. In one embodiment, or in combination with any other embodiment referred to herein, the molten CE resin exiting the die head may have a temperature of at least 150°C, at least 160°C, at least 170°C, at least 180°C, at least 190°C, at least 200°C, about 150°C to about 220°C, and / or about 170°C to about 200°C.

[0018] As shown in Figure 4, one or more filtration devices may be installed within the extrusion section to filter and remove particulate matter from the molten CE resin. For example, a screen changer filtration device may be installed downstream of the primary and secondary extrusion vessels, thereby removing solid components from the molten CE resin before it passes through the die head to the sheet molding section.

[0019] The sheet forming section may include any of a variety of systems and processes for forming extruded sheets from cellulose ester material that can be used for article forming. The shape of the extruded sheet is generally determined by the shape of the die head, but the shape of the sheet formed in the sheet forming section may be determined by the shape of the die head and other downstream processes. For example, the extruded sheet may generally have a flat shape, or it may be annular and subject to further processing to form a flat sheet. In embodiments where the die is annular, the die may have diameters of 1 to 40 cm, 2 to 20 cm, 2 to 10 cm, and / or 3 to 8 cm. Furthermore, the thickness of the opening from which the extruded sheet is discharged, referred to herein as the “die gap,” may generally be 0.1 to 6.0 mm, 0.1 to 3.0 mm, and / or 0.1 to 1.0 mm in size.

[0020] An exemplary sheet molding section is shown in Figure 5. As illustrated, the molten CE resin is extruded through an annular die and stretched on a molding mandrel. A cooling fluid (e.g., air) can be flowed inside and / or outside the extruded material to cool it as it passes over the mandrel. For example, the cooling fluid can be blown from the mandrel towards the die to cool the inner surface of the extruded material between the die and the mandrel. Additionally or alternatively, the cooling fluid can be flowed across the mandrel to cool the outer surface of the extruded material as it passes over the mandrel.

[0021] A slicer (or cutting device) can be used to open up a tubular extruder, which allows the tubular shape to be formed into a flat sheet. For example, a tubular extruder passing over a mandrel may be cut open and pulled to a tension station containing one or more rollers. These rollers flatten the extruder and maintain the amount of tension required to keep the extruder pulled over the mandrel. The flattened extruder is generally in the form of a sheet, which may then be directed to a winding station, where the material may be wound for packaging and transport.

[0022] Referring again to Figures 1 and 2, the sheets produced by the sheet manufacturing process can be used to form foamed products. Foamed products will be described in more detail below. Such articles are particularly useful in the food service industry. An exemplary article is a meat tray. This article may have one or more particularly advantageous properties. For example, the article may be biodegradable and / or compostable, and / or may have excellent mechanical properties (e.g., strength, density, cell size, absorption, etc.).

[0023] composition The process described above may include the preparation and extrusion of compositions that can be used in downstream processing to form useful articles. For example, in one embodiment, or in combination with any other embodiment referred to herein, the extrusion feed material may include particulate material comprising a biodegradable polymer and optionally one or more additives, such as those described herein. In one embodiment, or in combination with any other embodiment referred to herein, the feed material may provide a mixed composition comprising a biodegradable polymer and one or more additives, such as those described herein. In one embodiment, or in combination with any other embodiment referred to herein, the biodegradable polymer comprises a cellulose ester.

[0024] In one embodiment, or in combination with any other embodiments referenced herein, the cellulose ester composition comprises one or more polymers and / or other additives that function to enhance the melt strength of the composition and / or, conversely, to increase the elasticity of the composition (and the resulting foamed article). Such polymers and other additives may cause the foamed sheet to be thermoformed at a higher stretch ratio compared to a foamed sheet that does not contain these polymers and / or additives. For example, in some embodiments, the composition comprises one or more such polymers and / or other additives in an amount of 1% to 50% by weight, or 2% to 20% by weight. In some embodiments, the composition comprises at least one additive having a specific heat capacity of at least 2000 J / kg-C. In some such embodiments, one or more additives are selected from C20-C40 hydrocarbons (e.g., paraffin wax), C12-C16 fatty acids, biodegradable polymers (such as polyethylene glycol (PEG) and others described herein), and / or melt strength improvers (such as functional ionic components). In some embodiments, the composition comprises at least one additive having a specific heat capacity of at least 2000 J / kg-C, and a melt strength improver.

[0025] Further details of the composition components, including biodegradable polymers (e.g., cellulose esters) and other additives, are shown below.

[0026] Cellulose ester The cellulose esters used as described herein may be any known in the art. Cellulose esters that can be used in the embodiments herein generally contain repeating units of the following structure: [ka] In the formula, R1, R2, and R3 are independently selected from the group consisting of hydrogen, acetyl, propyl, or butyl. The substitution level of a cellulose ester is usually expressed in terms of the degree of substitution ("DS"), which is the average number of non-OH substituents per anhydrous glucose unit ("AGU"). When DS refers to an acetyl substituent, DS may be expressed as DSAc. In certain circumstances, DS may be expressed as DSOH, describing the average free hydroxyl group. Generally, conventional cellulose contains three hydroxyl groups in each substituteable AGU unit. Therefore, DS can have a value of 0 to 3. Natural cellulose is a large polysaccharide with a degree of polymerization of 250 to 5,000 even after pulping and purification, and therefore the assumption that the maximum DS is 3.0 is approximately correct. Since DS is a statistical mean, a value of 1 does not guarantee that every AGU has only one substituent. In some cases, unsubstituted anhydrous glucose may be present, some with two substituents, some with three, and the value is usually a non-integer. Total DS is defined as the average number of all substituents per anhydrous glucose unit. The degree of substitution per AGU can also refer to specific substituents, such as hydroxyl or acetyl. In one embodiment, or in combination with any other embodiment, n is an integer in the range of 25 to 250, or 25 to 200, or 25 to 150, or 25 to 100, or 25 to 75.

[0027] In one embodiment, or in combination with any other embodiment, a cellulose ester may have at least two anhydrous glucose rings and at least 50 to a maximum of 5,000 anhydrous glucose rings, or at least 50 to less than 150 anhydrous glucose rings. The number of anhydrous glucose units per molecule is defined as the degree of polymerization (DP) of the cellulose ester. In one embodiment, or in combination with any other embodiment, a cellulose ester may have an intrinsic viscosity (IV) of about 0.2 to about 3.0 deciliters / gram, or about 0.5 to about 1.8, or about 1 to about 1.5, measured at a temperature of 25°C for 0.25 grams of sample in 100 ml of a 60 / 40 wt solution of phenol / tetrachloroethane. In one embodiment, or in combination with any other embodiment, cellulose esters useful herein may have a DS / AGU of about 1 to about 3.0, or about 2.0 to 2.9, or about 2.2 to about 2.8, or less than 1 to 2.2, or less than 1 to 1.5, where the substituted ester is acetyl.

[0028] Cellulose esters can be produced by any method known in the art. An example of a cellulose ester production process is taught in Kirk-Othmer, Encyclopedia of Chemical Technology, 5th Edition, Vol. 5, Wiley-Interscience, New York (2004), pp. 394-444. Cellulose, the starting material for producing cellulose esters, can be obtained from a variety of grades and sources, including, among others, cotton linters, softwood pulp, hardwood pulp, corn fiber, and other agricultural sources, as well as bacterial cellulose.

[0029] One method for producing cellulose esters involves esterification of cellulose by mixing it with a suitable organic acid, acid anhydride, and catalyst. The cellulose is then converted to cellulose triester. Next, the cellulose triester can be hydrolyzed by adding a water-acid mixture, and then filtered to remove gel particles or fibers. Water is then added to the mixture to precipitate the cellulose ester. The cellulose ester may then be washed with water to remove reaction by-products, followed by dehydration and drying.

[0030] The hydrolyzed cellulose triesters may have three acetyl substituents. These cellulose esters can be prepared by a number of methods known to those skilled in the art. For example, cellulose esters can be prepared by heterogeneous acylation of cellulose in a mixture of carboxylic acid and anhydride in the presence of a catalyst such as H2SO4. Cellulose triesters can also be prepared by homogeneous acylation of cellulose dissolved in a suitable solvent such as LiCl / DMAc or LiCl / NMP.

[0031] Those skilled in the art will understand that the commercial term "cellulose triester" also includes cellulose esters that are not completely substituted with acyl groups. For example, cellulose triacetate commercially available from Eastman Chemical Company, Kingsport, TN, USA typically has a DS of about 2.85 to about 2.99.

[0032] After esterification of cellulose to triester, some of the acyl substituents may be removed by hydrolysis or alcohol decomposition to obtain a secondary cellulose ester. As mentioned earlier, the distribution of acyl substituents may be random or non-random depending on the specific method used. Alternatively, the secondary cellulose ester may be prepared directly without hydrolysis by using a limited amount of acylation reagent. This process is particularly useful when the reaction is carried out in a solvent that dissolves cellulose. All of these methods yield cellulose esters useful in the present invention.

[0033] In one embodiment, or in combination with any of the embodiments mentioned, the cellulose acetate is a cellulose diacetate having a polystyrene-equivalent number-average molecular weight (Mn) of about 10,000 to about 100,000, as measured by gel permeation chromatography (GPC) using NMP as the solvent and polystyrene-equivalent Mn according to ASTM D6474. In one embodiment, or in combination with any other embodiment, the cellulose acetate composition, when measured by gel permeation chromatography (GPC) according to ASTM D6474 using NMP as the solvent, has a range of 10,000 to 90,000, or 10,000 to 80,000, or 10,000 to 70,000, or 10,000 to 60,000, or less than 10,000 to 60,000, or less than 10,000 to 55,000, or 10,000 to 50,000, or less than 10,000 to 50,000, or less than 10,000 to 45,000, or 10,000 to 40,000, or 10,000 to 30,000, or 20,000. 00 to less than 60,000, or 20,000 to less than 55,000, or 20,000 to less than 50,000, or 20,000 to less than 50,000, or 20,000 to less than 45,000, or 20,000 to 40,000, or 20,000 to 35,000, or 20,000 to 30,000, or 30,000 to 60,000 It contains cellulose diacetate having a polystyrene-equivalent number-average molecular weight (Mn) of less than 00, or between 30,000 and less than 55,000, or between 30,000 and less than 50,000, or between 30,000 and less than 45,000, or between 30,000 and 40,000, or between 30,000 and 35,000.

[0034] The most common commercially available secondary cellulose esters are produced by forming cellulose triesters through the initial heterogeneous acylation of cellulose using an acid catalyst. After obtaining a homogeneous solution of the cellulose triester in the corresponding carboxylic acid, the cellulose triester is then subjected to hydrolysis until the desired degree of substitution is obtained. After isolation, random secondary cellulose esters are obtained, i.e., the relative degree of substitution (RDS) at each hydroxyl group is approximately equal.

[0035] The cellulose esters useful in the present invention can be prepared using techniques known in the art, and can also be selected from various types of cellulose esters available from, for example, Eastman Chemical Company, Kingsport, TN, USA, such as Eastman® Cellulose Acetate CA398-30 and Eastman® Cellulose Acetate CA398-10, Eastman® CAP485-20 Cellulose Acetate Propionate, and Eastman® CAB381-2 Cellulose Acetate Butyrate.

[0036] In one embodiment, or in combination with any other embodiment, cellulose esters can be prepared by converting cellulose to cellulose esters using a reactant obtained from a recycled material, such as a recycled plastic-containing synthesis gas source. In one embodiment, or in combination with any other embodiment, such reactant may be a cellulose reactant comprising an organic acid and / or acid anhydride used in a cellulose esterification or acylation reaction, such as those discussed herein.

[0037] One embodiment of the present invention provides a cellulose ester composition comprising at least one regenerated cellulose ester, or in combination with any of the embodiments described herein, wherein the cellulose ester has at least one substituent on anhydrous glucose units (AU) derived from a regenerated material (e.g., recycled plastic-containing synthesis gas).

[0038] In one embodiment, or in combination with any other embodiment, the cellulose ester composition contains 50-99% by weight, or 60-99% by weight, or 70-99% by weight, or 80-99% by weight, or 90-99% by weight, 50-90% by weight, or 60-90% by weight, or 70-90% by weight, or 80-90% by weight, or 90-99% by weight, or 50-80% by weight, or 60-80% by weight, or 70-80% by weight, or 50-70% by weight, or 60-70% by weight, or 50-60% by weight, based on the total weight of the cellulose ester composition. In some embodiments, the cellulose ester used herein may include a combination, blend, or mixture of two or more different types of cellulose esters. For example, in some embodiments, the cellulose ester used herein may consist of a blend of two or more cellulose esters having different DSACs, provided that this blend has a total DSAC of 2.2-2.8, or 2.0-2.9.

[0039] plasticizer In one embodiment, or in combination with any other embodiment, the cellulose ester compositions described herein may contain at least one plasticizer. The plasticizer reduces the melting temperature, i.e., Tg, and / or melt viscosity of the cellulose ester. Cellulose ester plasticizers include glycerol triacetate (triacetin), glycerol diacetate (diacetin), dibutyl terephthalate, dimethyl phthalate, diethyl phthalate, poly(ethylene glycol) (molecular weight 200-600), dibutyl tartrate, di-2-methoxyethyl phthalate, ethyl o-benzoyl benzoate, triethylene glycol dipropionate, 1,2-epoxypropylphenylethylene glycol, 1,2-epoxypropyl(m-cresyl)ethylene glycol, 1,2-epoxypropyl(o-cresyl)ethylene glycol, β-oxyethylcyclohexene carboxylate, bis(cyclohexanate)diethylene glycol, triethyl citrate, polyethylene glycol, propylene glycol, polysorbate, sucrose octaacetate, acetylated triethyl citrate, tributyl acetyl citrate, Admex, trippropionine, Scandiflex, poloxamer copolymer, and more. Polyethylene glycol succinate, diisobutyl adipate, polyvinylpyrrolidone, and glycol tribenzoate, benzoate-containing plasticizers such as the Benzoflex® plasticizer series, poly(alkyl succinates) such as poly(butyl succinate), polyethersulfone, o-cresyl p-toluenesulfonate, n-ethyltoluenesulfonamide, adipate-based plasticizers, soybean oil epoxides such as the Paraplex® plasticizer series, sucrose-based plasticizers, Possible materials include dibutyl sebacate, tributylline, sucrose acetate isobutyrate, Resolflex® series plasticizers, triphenyl phosphate (TPP), triethyl phosphate (TEP), glycolates (ethylphthalyl ethyl glycolate "EPEG" and methylphthalyl ethyl glycolate "MPEG"), methoxypolyethylene glycol, 2,2,4-trimethylpentane-1,3-diirbis(2-methylpropanoate), and polycaprolactone.In some embodiments, the plasticizers used herein may include a combination or mixture of two or more different types of plasticizers.

[0040] In one embodiment, or in combination with any other embodiment, the plasticizer is a food-compatible plasticizer. Food compatibility means that it complies with applicable food additive and / or food contact regulations, and the plasticizer is permitted for use or recognized as safe by at least one (national or regional) food safety regulatory authority (or organization), for example, listed in the 21 CFR Food Additive Regulations, or otherwise recognized by the U.S. FDA with a Certificate of Gravity for Use (GRAS). In one embodiment, or in combination with any other embodiment, the food-compatible plasticizer is triacetin or polyethylene glycol (PEG) having a molecular weight of about 200 to about 600. In one embodiment, or in combination with any other embodiment, possible examples of food-compatible plasticizers include triacetin, triethyl citrate, polyethylene glycol, Benzoflex, propylene glycol, polysorbate, sucrose octaacetate, acetylated triethyl citrate, tributyl acetyl citrate, Admex, trippropionine, Scandiflex, poloxamer copolymer, polyethylene glycol succinate, diisobutyl adipate, polyvinylpyrrolidone, and glycol tribenzoate.

[0041] In one embodiment, or in combination with any other embodiment, the plasticizer may be present in an amount sufficient to enable the cellulose ester composition to be melt-processed (or thermoformed) in a conventional melt-processing apparatus to produce useful articles, such as disposable plastic products. In one embodiment, or in combination with any other embodiment, the plasticizer may be present in an amount of 1 to 40% by weight, or 5 to 25% by weight, or 10 to 25% by weight, or 12 to 20% by weight, based on the weight of the cellulose ester composition, for most thermoplastic processing. In one embodiment, or in combination with any other embodiment, profile extrusion, sheet extrusion, thermoforming, and injection molding can be achieved with plasticizer levels ranging from 10 to 30%, or 12 to 25%, or 15 to 20%, or 10 to 25% by weight, based on the weight of the cellulose ester composition.

[0042] In one embodiment, or in combination with any other embodiment, the plasticizer is a biodegradable plasticizer. Some examples of biodegradable plasticizers include triacetin, triethyl citrate, acetyl triethyl citrate, polyethylene glycol, benzoic acid-containing plasticizers such as the Benzoflex® plasticizer series, poly(alkyl succinates) such as poly(butyl succinate), polyethersulfone, adipic acid-based plasticizers, soybean oil epoxides such as the Paraplex® plasticizer series, sucrose-based plasticizers, dibutyl sebacate, tributylin, plasticizers in the Resolflex® series, triphenyl phosphate, glycolic acid, polyethylene glycol, 2,2,4-trimethylpentane-1,3-diirbis(2-methylpropanoate), and polycaprolactone.

[0043] In one embodiment, or in combination with any other embodiment, the cellulose ester composition may contain a plasticizer selected from the group consisting of PEG and MPEG (methoxyPEG). The polyethylene glycol or methoxy polyethylene glycol composition has an average molecular weight of 200 to 600 daltons, and the composition is melt-workable, biodegradable, and disintegrable.

[0044] In one embodiment, or in combination with any other embodiment, the composition comprises polyethylene glycol or methoxyPEG having an average molecular weight of 300 to 550 daltons.

[0045] In one embodiment, or in combination with any other embodiment, the composition comprises polyethylene glycol having an average molecular weight of 300 to 500 daltons.

[0046] In one embodiment, or in combination with any other embodiment, the cellulose ester composition contains at least one plasticizer (as described herein) in an amount based on the total weight of the cellulose ester composition of 1-40% by weight, or 5-40% by weight, or 10-40% by weight, or 12-40% by weight, 13-40% by weight, or 15-40% by weight, or more than 15-40% by weight, or 17-40% by weight, or 20-40% by weight, or 25-40% by weight, or 5-35% by weight, or 10-35% by weight, or 13-35% by weight, or 15-35% by weight, or more than 15-35% by weight, or 17-35% by weight, or 20-35% by weight, or 5-30% by weight, or 10-30% by weight. , or containing in amounts of 13-30% by weight, or 15-30% by weight, or more than 15-30% by weight, or 17-30% by weight, or 5-25% by weight, or 10-25% by weight, or 13-25% by weight, or 15-25% by weight, or more than 15-25% by weight, or 17-25% by weight, or 5-20% by weight, or 10-20% by weight, or 13-20% by weight, or 15-20% by weight, or more than 15-20% by weight, or 17-20% by weight, or 5-17% by weight, or 10-17% by weight, or 13-17% by weight, or 15-17% by weight, or more than 15-17% by weight, or less than 5-17% by weight, or less than 10-17% by weight, or less than 13-17% by weight, or less than 15-17% by weight.

[0047] In one embodiment, or in combination with any other embodiment, at least one plasticizer includes or is a food-grade plasticizer or an FDA-approved plasticizer. The food-grade plasticizer or FDA-approved plasticizer includes or is triacetin or PEG (MW300-500).

[0048] Biodegradable polymers In one embodiment, or in combination with any other embodiment, the cellulose ester composition described herein comprises a BCE component comprising at least one biodegradable cellulose ester (BCE) which may comprise one or more of the cellulose esters described herein, and a biodegradable polymer component comprising at least one other biodegradable polymer (other than BCE). In one embodiment, or in combination with any other embodiment, the other biodegradable polymer can be selected from polyhydroxyalkanoates (PHA and PHB), polylactic acid (PLA), polycaprolactone polymer (PCL), polybutylene adipate terephthalate (PBAT), polyethylene succinate (PES), polyvinyl acetate (PVA), polybutylene succinate (PBS) and copolymers (such as polybutylene succinate-co-adipate (PBSA)), cellulose esters, cellulose ethers, starch, proteins, their derivatives, and combinations thereof. In one embodiment, or in combination with any other embodiment, the cellulose ester composition comprises two or more biodegradable polymers. In one embodiment, or in combination with any other embodiment, the cellulose ester composition contains a biodegradable polymer (other than BCE) in an amount of 0.1 to less than 50% by weight, or 1 to 40% by weight, or 1 to 30% by weight, or 1 to 25% by weight, or 1 to 20% by weight, based on the cellulose ester composition. In one embodiment, or in combination with any other embodiment, the cellulose ester composition contains a biodegradable polymer (other than BCE) in an amount of 0.1 to less than 50% by weight, or 1 to 40% by weight, or 1 to 30% by weight, or 1 to 25% by weight, or 1 to 20% by weight, based on the total amount of BCE and biodegradable polymer.In one embodiment, or in combination with any other embodiment, at least one biodegradable polymer has a weight-average molecular weight (Mw) measured by gel permeation chromatography (GPC) with methylene chloride as the solvent using a refractive index detector and a polystyrene standard, which is 10,000 to 1,000,000, or 50,000 to 1,000,000, or 100,000 to 1,000,000, or 2 The PHA comprises a range of 50,000 to 1,000,000, or 500,000 to 1,000,000, or 600,000 to 1,000,000, or 600,000 to 900,000, or 700,000 to 800,000, or 10,000 to 500,000, or 10,000 to 250,000, or 10,000 to 100,000, or 10,000 to 50,000. In one embodiment, or in combination with any other embodiment, the PHA may comprise polyhydroxybutyrate-co-hydroxyhexanoate.

[0049] Nuclear agent A nucleating agent refers to a chemical or physical material that provides sites for cell formation in a mixture of molten formulations, such as within a molten CE resin. As will be described in more detail below, nucleating agents can be added to the formulated CE material during the formulation process. Alternatively, or in addition, nucleating agents may be added during the manufacturing process of the foamed sheet. For example, a nucleating agent may be blended with the formulation introduced into the hopper of the extruder in the extrusion section. Alternatively, a nucleating agent may be added to the molten CE resin in the extruder itself. Examples of nucleating agents include physical nucleating agents and chemical nucleating agents. A physical nucleating agent is a substance that is immiscible with the polymer matrix of the molten CE resin at the extrusion temperature of the extrusion section. A chemical nucleating agent is a substance that reacts (e.g., decomposes) during extrusion (e.g., at the extrusion temperature in the extruder) to form a physical nucleating agent. Thus, a chemical nucleating agent may be considered (referred to herein as a precursor) of a physical nucleating agent formed in situ.

[0050] Suitable physical nucleating agents include fine particles having a desired particle size and / or shape to create cell nucleation sites within the CE molten resin. For example, in some embodiments, the physical nucleating agent has an average particle size of less than 1000 microns, less than 500 microns, less than 100 microns, less than 50 microns, less than 25 microns, less than 20 microns, less than 10 microns, less than 5 microns, less than 2 microns, less than 1.5 microns, and / or less than 1.0 micron. However, in some other embodiments, it may be preferable to have nanoscale-sized particles. Furthermore, in some embodiments, the physical nucleating agent preferably has a high aspect ratio (i.e., width:height). For example, in some embodiments, the physical nucleating agent has an average aspect ratio greater than 1:1, greater than 2:1, greater than 5:1, greater than 10:1, greater than 20:1, greater than 30:1, greater than 40:1, greater than 50:1, greater than 75:1, and / or greater than 100:1. Furthermore, as described above, the physical nucleating agent must be immiscible with the polymer matrix of the CE molten resin at the extrusion temperature of the extrusion section. Therefore, in some embodiments, the physical nucleating agent needs to have a melting temperature of at least 220°C, at least 230°C, at least 240°C, at least 250°C, at least 275°C, at least 300°C, at least 325°C, or at least 350°C. However, the physical nucleating agent may be selected to have the ability to recrystallize after cooling following melting.

[0051] Examples of suitable inorganic physical nucleating agents include, but are not limited to, talc, minerals such as CaCO3 and mica, and mixtures of at least two of the above. One representative example is Heritage Plastics HT6000 Linear Low Density Polyethylene (LLDPE) Based Talc Concentrate. Other inorganic physical nucleating agents include wollastonite, silica, silicon dioxide, titanium dioxide, magnesium oxide, aluminum oxide and calcium silicate, barium sulfate, kaolin, aluminum trihydrate ATH (Al(OH)3), MDH (Mg(OH)2), diatomaceous earth, magnetite / hematite, halloysite, zinc oxide, and titanium dioxide. In some embodiments, the inorganic nucleating agent includes oxides such as metal oxides or mixed metal oxides, selected from one or more of the following: aluminum oxide, antimony oxide, arsenic oxide, bismuth oxide, boron oxide, calcium oxide, gallium oxide, iron oxide, lithium oxide, magnesium oxide, silicon dioxide, and titanium dioxide. In other embodiments, the inorganic nucleating agent includes silicates such as magnesium silicate and calcium silicate, selected from one or more of the following:

[0052] Biodegradable natural particulate matter derived from renewable organic sources (e.g., organic nucleating agents) has also been found to function as effective physical nucleating agents. Natural substances that can be physical nucleating agents include substances composed of cellulose fibers and / or cellulose starch. Examples, but not limited to, include almond husk powder, animal fiber, apricot husk powder, bamboo powder, bark powder, shell powder, coconut husk powder, coconut fiber, cork powder, corn cob powder, corn cob grit, cottonseed husks, flocs and fibers, hazelnut husk powder, kenaf powder, natural fiber, nut shells and powders, oat fiber powder, olive stone powder, peanut shell powder, pecan husk powder, pine nut husk powder, pistachio nut husk powder, plant fiber, rice husk powder, rice husk grit, rice husks, soybean powder, starch powder (hydrophobic), walnut husk powder, wheat husk, wheat hull, and wood powder. Other organic physical nucleating agents include cellulose powder, chitin, chitosan, metal stearate, carbon black, and dolomite.

[0053] As described above, a suitable chemical nucleating agent (or a precursor to a physical nucleating agent formed in situ) is configured to decompose when a threshold chemical reaction temperature is reached, generating cell nucleating sites in the CE molten resin. These small cells serve as nucleating sites for the proliferation of larger cells from physical or other types of blowing agents. In some embodiments, the precursor is configured to form a gas such as CO2 or N2 during the extrusion of the particulate material.

[0054] Examples of chemical nucleating agents include, but are not limited to, acids such as citric acid or citric acid-based materials. Other acids may include lauric acid, stearic acid, tartaric acid, ascorbic acid, propionic acid, and hexanoic acid. A typical example is HYDROCEROL™ CF-40E (available from Clariant Corporation), which contains citric acid and a nucleating agent. In some embodiments, the chemical nucleating agent includes a combination of acid and base, such as a carbonate, and examples of carbonates include sodium bicarbonate, zinc bicarbonate, potassium bicarbonate, sodium carbonate, and potassium carbonate. For example, a typical example of a chemical nucleating agent is a combination of citric acid and sodium bicarbonate. In some embodiments, the chemical nucleating agent may include a carrier in which the active ingredient of the nucleating agent is dispersed. For example, yet another typical example of a chemical nucleating agent is a combination of citric acid, sodium bicarbonate, and a carrier. In some embodiments, the carrier may include polystyrene. However, the carrier may include other compositions such as various biopolymers (e.g., polybutylene succinate, Capa polyester, etc.), polyolefins, and acrylic copolymers (e.g., ethylene methyl acrylate). In some such embodiments, citric acid and sodium bicarbonate may constitute about half (by weight) of the chemical nucleating agent, while the carrier constitutes the remaining half (by weight). Furthermore, in some such embodiments, there may be more sodium bicarbonate than citric acid in the chemical nucleating agent. For example, there may be about three times (by weight) more sodium bicarbonate than citric acid in the chemical nucleating agent. It should also be understood that in some embodiments, such as when the nucleating agent is hecofoam or hydrocerol, a carrier may not be required or used.

[0055] In one embodiment or in combination with any of the embodiments referenced herein, the nucleating agents are present in amounts of 0.1 to 10% by weight, 0.1 to 5.0% by weight, at least 0.1% by weight, at least 0.25% by weight, at least 0.5% by weight, at least 1.0% by weight, at least 1.25% by weight, at least 1.5% by weight, at least 1.75% by weight, at least 2.0% by weight, at least 2.25% by weight, at least 2.5% by weight, at least 2.75% by weight, or at least 3.0% by weight, or at least 3.5% by weight, or at least 4.0% by weight, or at least 4.5% by weight, and / or less than 7.5% by weight, less than 5% by weight, less than 4% by weight, less than 3% by weight, less than 2% by weight, or less than 1.0% by weight, based on the total weight of the cellulose ester composition. In some embodiments, the nucleating agents used herein may include combinations or mixtures of two or more different types of nucleating agents.

[0056] It should be noted that cellulose ester materials, whether in the form of compounded CE material or CE molten resin, can generally tolerate a maximum amount of nucleating agent that can function to form nucleating sites. Any remaining nucleating agent added to the cellulose ester material remains as a filler. Depending on the type of filler used, the filler can provide various properties to the resulting cellulose ester foam and / or article. For example, some fillers can increase / decrease the density, ductility, Young's modulus, yield strength, thermal deflection temperature, permeability, impact resistance, elongation to break, adhesive properties, and biodegradability of the cellulose ester material. Fillers can also be used to alter the visual properties (e.g., color, opacity, etc.) and tactile properties (e.g., material continuity, surface roughness, etc.) of the cellulose ester material.

[0057] foaming agent A blowing agent refers to a physical or chemical material (or combination of materials) that acts to expand nucleating sites. Blowing agents may include chemical blowing agents, physical blowing agents, combinations thereof, or several types of chemical and physical blowing agents. Blowing agents function to reduce the density of the material by expanding the cells formed in the molten mixture at the nucleating sites. Blowing agents may be added to the CE molten resin in the extruder. It has been surprisingly discovered that the hygroscopic nature of biodegradable particulate natural fillers allows them to absorb moisture, carrying the absorbed water into the molten resin mixture, where it can act as a physical blowing agent.

[0058] Examples of physical blowing agents include H2O, N2, CO2, alkanes, alkenes, ethers, ketones, argon, helium, air, or mixtures thereof. Furthermore, it has been surprisingly discovered that the hygroscopic nature of biodegradable particulate natural fillers allows them to absorb moisture, transport the absorbed water into the molten resin mixture, where it can act as a physical blowing agent. Hygroscopic and biodegradable natural fillers can be incorporated into the composition to allow them to absorb moisture before the foaming process, after which the water is released and acts as a physical blowing agent. Beneficially, water can also be used as a plasticizer for cellulose ester resins. Additionally, in some embodiments, the physical blowing agent may include hydrocarbons such as pentane / isopentane or butane / isobutane. Other hydrocarbons may include propane, ethane, methane, hexane, cyclohexane, cyclopentane, or cyclobutene.

[0059] Chemical blowing agents are materials that decompose or react to produce gases (e.g., CO2 or N2). Such gases expand cells in the molten resin mixture and / or the resulting foam mixture, creating a structural material with multiple gaseous voids that are dispersed throughout. Chemical blowing agents can be endothermic or exothermic. Chemical blowing agents typically decompose and release gases at a certain temperature. Examples of chemical blowing agents include azodicarbonamides, acids (e.g., citric acid), and carbonates (e.g., sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, zinc carbonate, etc.), and combinations thereof.

[0060] In one embodiment, or in combination with any of the embodiments referenced herein, the foaming agent is present in an amount of 0.3 to 1.5% by weight, or 0.3 to 2.0% by weight, or 0.3 to 2.5% by weight, or 0.3 to 3.0% by weight, or 0.3 to 3.5% by weight, or 0.3 to 4.0% by weight, or 0.3 to 8%, or 1.3 to 1.5% by weight, or 1.3 to 2.0% by weight, based on the total weight of the cellulose ester composition. 1.3-2.5% by weight, or 1.3-3.0% by weight, or 1.3-3.5% by weight, or 1.3-4.0% by weight, or 1.3-4.5% by weight, or 1.3-5.0% by weight, or 1.3-5.5% by weight, or 1.5-3.0% by weight, or 1.5-4.0% by weight, or 1.5-5.0% by weight, or 1.5-6.0% by weight, or 2.0-3.0% by weight, or 2.0-4.0% by weight, or 2.0-5 0.0% by weight, or 2.0-6.0% by weight, or 2.5-3.0% by weight, or 2.5-4.0% by weight, or 2.5-5.0% by weight, or 2.5-6.0% by weight, or 3.0-4.0% by weight, or 3.0-5.0% by weight, or 3.0-6.0% by weight, or 0.0-9.0% by weight, or 0.5-9.0% by weight, or 1.0-9.0% by weight, or 1.5-9.0% by weight, or 2.0-9.0% by weight , or present in amounts of 2.5-9.0% by weight, or 3.0-9.0% by weight, or 3.5-9.0% by weight, or 4.0-9.0% by weight, or 4.5-9.0% by weight, or 5.0-9.0% by weight, or 5.5-9.0% by weight, or 6.0-9.0% by weight, or 6.5-9.0% by weight, or 7.0-9.0% by weight, or 7.5-9.0% by weight, or 8.0-9.0% by weight, or 8.5-9.0% by weight. In some embodiments, the blowing agent used herein may include a combination or mixture of two or more different types of blowing agents.

[0061] Surface modification additives Surface modifiers refer to materials that can be added to cellulose ester compositions to improve their processability, thereby modifying the structure of the composition (or the resulting foamed article). For example, the inventors of this application have found that adding surface modifiers to compounded CE materials (e.g., pellets in the compounding process) or CE molten resin (e.g., in the extrusion process) can improve processing by reducing undesirable adhesion of the CE molten resin to the die or mandrel (or other components in the foamed sheet manufacturing process). Such reduction in adhesion can be achieved by the surface modifier suppressing the fusion of cellulose esters caused by plasticizers. The addition of surface modifiers can also reduce blocking of cellulose ester foamed sheets produced in the sheet molding section. Furthermore, surface modifiers can also improve the foamed sheet manufacturing process by enabling the process to be carried out at lower temperatures.

[0062] Furthermore, in some embodiments, the surface modification additive may function as an antistatic additive to suppress electrical sparks or arc discharges in the molten CE resin. Suppression of electrical sparks or arc discharges can be particularly important to reduce the possibility of hydrocarbons igniting and causing a fire when hydrocarbons are used as blowing agents. Beneficially, the surface modification additive may also reduce the diffusion of blowing agents, such as hydrocarbons, from the foamed sheet or the resulting article. In some embodiments, hydrocarbons themselves can be used as surface modification additives.

[0063] Nevertheless, more common examples of surface modifiers that can be used with the compounded CE material (e.g., during the compounding process) or with the CE molten resin (e.g., during the foam sheet manufacturing process) according to embodiments of the present invention include fatty acids such as palmitic acid, tallow acid, stearic acid, oleic acid, linoleic acid and linolenic acid, arachidic acid / behenic acid, behenic acid, and erucic acid. Surface modifiers may also include fatty acid amides such as erucamide, oleoamide, stearamide, benamide, secondary amide, and bisamide.

[0064] Examples of additional surface modification additives may include glycerol esters and / or stearate esters such as monoglycerides, diglycerides, and triglycerides. Examples of monoglycerides include glycerol monostearate or monoglyceride derivatives (such as diacetyltartrate esters of mono and diglycerides (DATEM), ethoxylated monoglycerides, succinyl monoglycerides, and propylene glycol monoesters (PGME)). Examples of surface modification additives may also include metal stearate salts such as aluminum stearate, calcium stearate, lithium stearate, magnesium stearate, sodium stearate, zinc stearate, and / or combinations thereof (e.g., calcium stearate / zinc stearate). Examples of surface modifying additives include waxes such as polyolefin waxes (polypropylene wax and polyethylene wax), olefin oxide waxes, ethylene acrylic acid (EAA) copolymer waxes, ethylene methyl acrylate (EMA) copolymer waxes, EAA ionomer shafts, acrylic waxes, and / or natural waxes (such as rice bran wax, sunflower wax, sugarcane wax, candelilla wax, soybean wax, beeswax, caddelilla wax, and carnauba wax).

[0065] Other non-exclusive examples of surface modification additives include aliphatic diesters (e.g., dioctyl adipates), polyglycol diesters, alkylalkyl ether diesters, aromatic triesters, polyester resins, chlorinated hydrocarbons, halogenated hydrocarbons, alkyl ether monoesters, and alkyl monoesters. Furthermore, various oils such as aromatic oils, naphthenic oils, glyceride oils, silicone oils, and epoxidized oils (e.g., soybean oil and linseed oil) can be used as surface modification additives. Thus, in some embodiments, the surface modification additive includes plasticizers such as aliphatic diester plasticizers and polyester plasticizers. Furthermore, in some embodiments, the surface modification additive may include polyhedral oligomeric silsesquioxanes (POSS).

[0066] More generally, the surface modification additive used in the embodiments of the present invention may be less polar than the cellulose ester in the compounded CE material (e.g., during the compounding process) or the CE molten resin (e.g., during the foamed sheet manufacturing process). For example, the surface modification additive may have (based on the Hansen solubility parameter) a total solubility parameter δ of less than 25 MPa 1 / 2 less than 20 MPa 1 / 2 less than or 19.5 MPa 1 / 2 less than; a dispersion force solubility parameter δ of less than 18 MPa 1 / 2 less than 16 MPa 1 / 2 less than or 14 MPa 1 / 2 less than; a bipolar intermolecular force solubility parameter δ d ; of less than 12 MPa 1 / 2 less than 8 MPa 1 / 2 less than or 4 MPa 1 / 2 less than; a hydrogen bond solubility parameter δ d ; and / or less than 11 MPa 1 / 2 less than 10 MPa 1 / 2 less than or 9 MPa 1 / 2 less than; a hydrogen bond solubility parameter δ h may have. On the other hand, in some other embodiments, the surface modification additive used in the embodiments of the present invention may be more polar than the cellulose ester in the compounded CE material (e.g., during the compounding process) or the CE molten resin (e.g., during the foamed sheet manufacturing process). For example, the surface modification additive may have (based on the Hansen solubility parameter) a total solubility parameter δ greater than 21.5 MPa 1 / 2 greater than 23 MPa 1 / 2 greater than or 25 MPa 1 / 2The total solubility parameter δ may be greater than or equal to 200°C, 220°C, 240°C, 260°C, 280°C, or 300°C. Furthermore, the surface modification additive may have a molecular weight greater than 100 g / mol, 150 g / mol, 220 g / mol, 260 g / mol, 300 g / mol, or 340 g / mol, and / or less than or equal to 1000 g / mol, less than or equal to 2500 g / mol, or less than or equal to 5000 g / mol. Furthermore, it may be preferable that the surface modification additive is insoluble in the plasticizer(s) used in the cellulose ester composition. For example, it may be preferable that the surface modification additive is insoluble in triacetin. Finally, in some embodiments, the surface modification additive may be biodegradable and / or food-safe or FDA-approved.

[0067] In one embodiment, or in combination with any of the embodiments referenced herein, the surface modifiers are all present in amounts of 0.05 to 0.75% by weight, or 0.05 to 1.0% by weight, or 0.05 to 2.5% by weight, or 0.05 to 5.0% by weight, or 0.75 to 1.0% by weight, or 0.75 to 2.5% by weight, or 0.75 to 5.0% by weight, or 0.1 to 1.0% by weight, or 0.1 to 2.5% by weight, or 0.1 to 5.0% by weight, or 1.0 to 2.5% by weight, or 1.0 to 5.0% by weight, or 2.5 to 5.0% by weight, based on the total weight of the cellulose ester composition. In some embodiments, the surface modifiers used herein may include combinations or mixtures of two or more different types of surface modifiers.

[0068] Melt strength improver The elasticity of a cellulose ester composition, particularly its elasticity during heating processes such as extrusion and thermoforming, can be increased by including one or more melt strength improvers. Such melt strength improvers may be in the form of functional ionic components. A variety of compounds and materials can be used, as long as they contain ionic functional groups. For example, in some embodiments, the functional ionic component is selected from the group consisting of acacia rubber, sulfopolyesters, quaternary salts, ionomers, ionic liquids, ionic waxes, and mixtures thereof.

[0069] Goods Extruded sheets of cellulose ester foam can be formed using the extrusion and / or sheet molding sections described above. Such extruded sheets comprise a structural material having a plurality of gas voids arranged throughout. Such gas voids are formed by the expansion of a foaming agent in the form of a gas within a cellulose polymer molten. The structural material is cellulose ester-based, and specific amounts of the constituent components of the structural material (e.g., cellulose ester, plasticizer, nucleating agent, surface modifying additive, etc.) are described in more detail above. Articles can be molded from extruded sheets of foam according to embodiments and may be particularly useful in the food service industry. An exemplary article is a meat tray. This article may have one or more particularly advantageous properties. For example, the article may have selective water absorption, be biodegradable and / or compostable, and / or have excellent mechanical properties (e.g., strength, density, cell size, absorption, etc.).

[0070] Such cellulose ester foams can be formed from cellulose ester foam sheets by thermoforming, in which heat and optionally pressure are applied to the foam sheet in a mold, producing a three-dimensional article that retains its shape after being removed from the mold. For example, in some embodiments, the foam sheet is heated to a surface temperature 40-100°C, 50-80°C, or 50-70°C higher than the Tg of the foam sheet. In some embodiments, the Tg of the foam sheet is about 120°C. Therefore, in the thermoforming process, the foam sheet can be heated to a surface temperature of 150-210°C or 160-200°C. In some embodiments, a uniform heat distribution across the foam sheet can be achieved by heating at a lower temperature (e.g., 40-70°C higher than the Tg, or 150-180°C), which may require a longer heating time.

[0071] More specifically, embodiments of the present invention may include foam articles in the form of foam trays. A foam tray may be configured as a food tray for supporting one or more food items, such as meat. Alternatively, the food items may be proteins (e.g., animal, plant), vegetables, or fruits. As shown in the figure, a foam tray may comprise a substantially flat base and a rim that rises above the base and extends around the foam tray. The top surface of the base and the surrounding rim define a receiving area (e.g., a bowl) that can hold and support an article (e.g., meat, or other food item).

[0072] The foam trays molded according to embodiments of the present invention can be molded to a variety of sizes. For example, a tray may have a width "W" ranging from 2 to 12 inches, 3 to 10 inches, or 5 to 9 inches, and a length "L" of 4 to 24 inches, 5 to 18 inches, or 6 to 15 inches. Thus, in some embodiments, the length of the tray may be 1.2 to 4 times, 1.4 to 3 times, or 1.5 to 2 times the width of the tray.

[0073] A foam tray may comprise a substantially flat base and a rim that rises above the base and extends around the perimeter of the foam tray. The top surface of the base and the surrounding rim define a receiving area (e.g., a bowl) that can hold and support items (e.g., meat, cheese, vegetables, fruits, or other foods). The base area can be 5 to 100 square inches, 10 to 75 square inches, or 20 to 50 square inches. The rim height (measured from the bottom of the tray to the top of the rim) can be 0.2 to 4 inches, 0.4 to 2 inches, or 0.5 to 1 inch, and the rim width (i.e., the lateral distance "Rw" measured from the side of the tray to the point where the rim touches the base) can be 0.06 to 0.75 inches, 0.10 to 0.05 inches, or 0.25 to 0.50 inches. Alternatively, the rim width "Rw" may be approximately 0.03W to 0.06W. The ratio of base area to rim area can be 1–10, 1.5–6, or 2–4. Furthermore, the tray depth (measured from the top of the rim to the top of the base) may be 0.3–4 inches, 0.5–3 inches, 1–3 inches, 1–2 inches, 1.25–2 inches, approximately 1.25 inches, or approximately 1.5 inches. Furthermore, the tray thickness (i.e., the thickness of the cellulose ester foam material) may be 1–10 mm, 1–8 mm, 2–8 mm, 3–7 mm, 4–6 mm, approximately 4 mm, approximately 5 mm, or approximately 6 mm, and / or less than 5 mm, less than 4 mm, less than 3 mm, or less than 2 mm. Alternatively or additionally, trays or other articles may have a thickness of 100–400 mils, 120–300 mils, or 150–250 mils (i.e., the thickness of the cellulose ester foam material).

[0074] Beneficial in some cases, foam trays may have selective water absorption. For example, when a foam tray is used to support meat, it may be preferable that the tray does not absorb liquid released from the meat. A foam tray may be tested for water absorption using a “water absorption test.” This test includes the following steps: (1) weighing the foam tray to obtain the original tray weight; (2) filling the tray’s support with water until the water reaches the top of the rim; (3) allowing the water-filled foam tray to equilibrate at room temperature for one hour or overnight (i.e., 18 hours); (4) removing the water supported in the support to empty the tray; (5) lightly wiping the tray to remove any excess water remaining on the surface of the tray; (6) weighing the immersed tray to obtain the tray weight after immersion; and (7) calculating the percentage increase in weight of the tray after immersion relative to the original tray weight.

[0075] According to embodiments of the present invention, after filling the tray of the present invention with water and allowing it to equilibrate at room temperature for 1 hour, the weight increase of the tray (after removing the water from the tray's receiving portion) may be less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, and / or less than 4%. Alternatively, or in addition, after filling the tray of the present invention with water and allowing it to equilibrate at room temperature overnight (e.g., 18 or 24 hours), the weight increase of the tray (after removing the water from the tray's receiving portion) may be less than 20%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, and / or less than 10.5%.

[0076] Abbreviation ADR is the area stretch ratio, BA is the blowing agent, d is the density, TA is triacetin, Pent is pentane, PBA is the physical blowing agent, and cc or cm 3 is cubic centimeters, Pz is the plasticizer, O / N is overnight, Wt is the weight, Temp is the temperature, and h is the hour (multiple hours are possible).

[0077] After the water absorption test, the foam tray can be subjected to a further "freeze-thaw test" to test its ability to absorb water after undergoing a freeze-thaw cycle. The freeze-thaw test includes the following steps: (1) freezing the tray in a freezer overnight (i.e., 18 hours); (2) removing the frozen tray from the freezer; (3) thawing the frozen tray at room temperature overnight (i.e., 18 hours); (4) filling the receiving compartment of the thawed foam tray with water; (5) allowing the water-filled foam tray to equilibrate at room temperature for 12 hours; (6) removing the water supported in the receiving compartment to empty the tray; (7) lightly wiping the empty tray to remove any remaining water from the surface of the tray; (8) weighing the tray after immersion to obtain the weight of the tray after immersion; and (9) calculating the percentage increase in the weight of the tray after immersion relative to its original weight. According to embodiments of the present invention, if a tray is subjected to a water absorption test, and then the tray is frozen overnight (i.e., 18 hours), thawed overnight (i.e., 18 hours), filled with water, and allowed to equilibrate at room temperature for 12 hours, the weight increase of the tray may be less than 30%, less than 25%, less than 20%, and / or less than 15%.

[0078] Several sample trays were molded and tested using water absorption and freeze-thaw tests. The trays were molded from cellulose ester foam sheets extruded using a tandem extruder system. The extruded cellulose ester molten resin contained cellulose diacetate with a degree of substitution of 2.52, a melting point of 230-250°C, and a Tg of 189°C. The molten resin was plasticized by adding 15-20% by weight of triacetin. Talc was used as a nucleating agent and mixed with a physical blowing agent into the molten resin in the twin-screw extruder of the tandem extruder system. The resulting molten resin was transferred to a single-screw extruder, and a cellulose ester foam sheet was extruded using an annular die in the single-screw extruder. The foam sheet was stretched, cut, and thermoformed to form foam trays. The results of four samples subjected to a 1-hour water absorption test are shown in Table 1. The results of four samples subjected to an 18-hour water absorption test are shown in Table 2. The results of two samples subjected to a freeze-thaw test are shown in Table 3. Please note that each sample used at least three foam trays, and the measurements were averaged to obtain the results shown below. [Table 1] [Table 2] [Table 3]

[0079] Embodiments provide the foam tray described herein, formed according to the process described herein. Specifically, a mixed composition containing cellulose ester can be extruded through an extruder and processed to form a cellulose ester foam sheet. The foam sheet can then be thermoformed to form a tray, which may include a generally flat base and a rim extending upward from the base along the perimeter of the tray.

[0080] The thermoforming process generally involves heating a foam sheet to a desired temperature and stretching the foam sheet into a mold having appropriate dimensions for a foam tray article. The amount a flat foam sheet stretches in the mold can be characterized by the area stretch ratio. As used herein, “area stretch ratio” means the total top surface area of ​​a thermoformed tray (i.e., including the base and rim) divided by the tray’s area footprint (i.e., its two-dimensional area when viewed from above). For example, if a flat sheet is thermoformed into a tray with dimensions of 10 inches wide × 12 inches long × 2 inches deep, the total top surface area is 208 square inches (2(10 × 2) + 2(12 × 2) + (10 × 12)), and the area footprint is 120 square inches (10 × 12). Therefore, the area stretch ratio of this tray is 1.7 (208 / 120). Conventional polystyrene meat trays typically have a stretch ratio of about 1.5 to about 1.7.

[0081] Accordingly, in one embodiment, or in combination with any of the embodiments referred to herein, the cellulose ester foam tray may have a stretch ratio of 1.2 to 5.0, 1.3 to 4.0, 1.4 to 3.0, or 1.5 to 2.0. That is, the foam sheet can be thermoformed in a mold having a footprint area (X) and a surface area of ​​1.2X to 5.0X, 1.3X to 4.0X, 1.4X to 3.0X, or 1.5X to 2.0X.

[0082] To test the effect of the stretch ratio on the surface preservation of the trays, several trays with different area stretch ratios were molded. The resin used for all examples and measurements was Eastman CA-398-30 or Eastman FE700 (cellulose diacetate, CDA). The degree of substitution (DS) was 2.52. The melting point was 230-250°C and the Tg was 189°C. The formulations were plasticized with 15% and 20% triacetin (TA). Talc (ABT-1000) was used as a nucleating agent. Extruded foam sheets were produced using a tandem extruder setup. A physical blowing agent (CO2 or pentane) and talc were mixed in a twin-screw extruder (ZE30), and the molten material was then transferred to a single-screw extruder (KE60). The foam sheet tube was extruded using an annular die, and then the sheet was stretched on a calibrator cylinder, cut, and opened. The samples were heated to approximately 330°F (320°F~360°F), and the sheets were thermoformed by stretching them in a mold at area stretching ratios of 1.97, 1.59, and 1.41.

[0083] The surface preservation properties of trays with different plasticizer concentrations and area stretch ratios were tested by measuring the amount of water absorbed using the water absorption test described above. Each tray was filled with water up to the rim and allowed to equilibrium in the experimental environment for different periods of time (1 hour, 2 hours, 4 hours, 8 hours, 18 hours, 24 hours). After the set time, the water was drained, the trays were lightly wiped, and their weight was measured.

[0084] The surface preservation of the trays was also tested using the freeze-thaw test described above. Each tray was frozen overnight (approximately 18 hours) in a freezer, and then thawed overnight (approximately 18 hours) in the experimental environment. The weight of the trays was measured and compared to the amount of water absorbed before the freeze-thaw cycle.

[0085] Table 4 shows the area stretch ratios of three different tray molds (with different stretch ratios) used to thermoform two diacetate formulations (15% and 20% plasticizer). Water absorption was measured after 1 hour. At least three trays were measured, and the mean and standard deviation were calculated. [Table 4]

[0086] Table 5 shows the area stretch ratios of three different tray molds used to thermoform two formulations (15 wt% and 20 wt% plasticizer). After one night (approximately 18 hours), water absorption was measured. At least three trays were measured, and the mean and standard deviation were calculated. [Table 5]

[0087] Table 6 shows the amount of water absorbed after being exposed to water overnight and after a freeze-thaw cycle, using trays with different area stretching ratios. [Table 6]

[0088] Trays fabricated with an area-to-stretch ratio of 1.97 had visible defects (cracks) throughout the entire base of the tray. However, trays with an area-to-stretch ratio of less than 1.6 did not have such defects.

[0089] The above results suggest that thermoformed cellulose ester trays with intact surface absorbed approximately 10–25 wt% or 15–20 wt% of water, with absorption maximizing after approximately one day. Importantly, if the tray surface was damaged during thermoforming, the tray could absorb approximately 40–50 wt% or more of water. Furthermore, when the trays were subjected to freeze-thaw cycles, no significant change in water absorption was observed in trays with intact surface. However, the water absorption of thermoformed trays with an area-to-stretch ratio greater than 1.9 (indicating cracking) increased further after the freeze-thaw cycle. Therefore, the cellulose diacetate tray manufactured herein with an area-to-stretch ratio of 1.97 absorbed significantly more water (more than twice as much) than trays with area-to-stretch ratios of 1.59 and 1.41.

[0090] Accordingly, in one embodiment, or in combination with any of the embodiments referred to herein, the cellulose ester foam tray may have a stretch ratio of less than 1.9, less than 1.8, less than 1.7, or less than 1.6. That is, the foam sheet can be thermoformed in a mold having a footprint area (X) and a surface area of ​​less than 1.9X, less than 1.8X, less than 1.7X, or less than 1.6X. Such trays can be formed without visible cracking and increased water absorption. Accordingly, in some embodiments, when the foam tray is filled with water and equilibrated at room temperature for 1 hour, according to a water absorption test, the weight increase of the foam tray is less than 10% or less than 5%. In some embodiments, when the foam tray is filled with water and equilibrated at room temperature for 18 hours, according to a water absorption test, the weight increase of the foam tray is less than 25% or less than 15%. In some embodiments, when a foam tray is frozen for 18 hours, thawed over 18 hours, filled with water, and allowed to equilibrate at room temperature for 12 hours, freeze-thaw tests show that the weight increase of the foamed material is less than 30% or less than 15%.

[0091] On the other hand, in one embodiment, or in combination with any of the embodiments referred to herein, a stretch ratio of at least 1.6, at least 1.7, at least 1.8, at least 1.9, or even higher can be achieved. For example, foam sheets molded from different compositions may have improved stretchability during thermoforming to avoid cracking of the tray at a higher stretch ratio. For example, a composition comprising polymers and / or additives that adjust the elasticity, melt strength, and / or glass transition temperature (Tg) of the composition can result in a foam that can increase the stretch ratio. Such polymers and additives include melt strength improvers as described herein, as well as components having a specific heat capacity of at least 2000 J / (kg K). Such polymers and additives include, but are not limited to, functional ionic components, C20-C40 hydrocarbons (e.g., paraffin wax), C12-C16 fatty acids, polyethylene glycol (PEG) (e.g., MW200-600), and mixtures thereof.

[0092] In one embodiment, or in combination with any of the embodiments referred to herein, the foamed article, for example, the tray, is 0.20 g / cm³. 3 Less than 0.18 g / cm³ 3 Less than 0.15 g / cm³ 3 Less than 0.12 g / cm³ 3 Less than 0.10 g / cm³ 3 Less than 0.08 g / cm³ 3 Less than 0.06 g / cm³ 3 Less than 0.04 g / cm³ 3 Less than 0.04-0.8 g / cm³ 3 , 0.04~0.6 g / cm³ 3 , 0.04~0.5 g / cm³ 3 , 0.04~0.4 g / cm³ 3 , 0.04~0.3 g / cm³ 3 , 0.04~0.2 g / cm³ 3 , 0.04~0.15 g / cm³ 3 , 0.04~0.12 g / cm³ 3 , 0.04~0.10 g / cm³ 3 , 0.04~0.08 g / cm³ 3 , 0.04~0.06 g / cm³ 3 , 0.06~0.8 g / cm³ 3 , 0.06~0.6 g / cm³ 3 , 0.06~0.5 g / cm³ 3 , 0.06~0.4 g / cm³ 3 , 0.06~0.3 g / cm³ 3 , 0.06~0.2 g / cm³ 3 , 0.06~0.15 g / cm³ 3 , 0.06~0.12 g / cm³ 3 , 0.06~0.10 g / cm³ 3 , 0.06~0.08 g / cm³ 3 , 0.08~0.8 g / cm³ 3 , 0.08~0.6 g / cm³ 3 , 0.08~0.5 g / cm³ 3 , 0.08~0.4 g / cm³ 3 , 0.08~0.3 g / cm³ 3 , 0.08~0.2 g / cm³ 3 , 0.08~0.15 g / cm³3 , 0.08~0.12 g / cm³ 3 , 0.08~0.10 g / cm³ 3 , 0.1~0.8 g / cm³ 3 , 0.1~0.6 g / cm³ 3 , 0.1~0.5 g / cm³ 3 , 0.1~0.4 g / cm³ 3 , 0.1~0.3 g / cm³ 3 , 0.1~0.2 g / cm³ 3 , 0.1~0.15 g / cm³ 3 , 0.1~0.12 g / cm³ 3 , 0.2~0.8 g / cm³ 3 , 0.2~0.6 g / cm³ 3 , 0.2~0.5 g / cm³ 3 , 0.2~0.4 g / cm³ 3 , 0.2~0.3 g / cm³ 3 , 0.3~0.6 g / cm³ 3 , 0.3~0.5 g / cm 3 , 0.3~0.4 g / cm³ 3 , 0.4~0.6 g / cm³ 3 , 0.4~0.5 g / cm 3 , or 0.5~0.6 g / cm³ 3 It may have a density of .

[0093] In one embodiment, or in combination with any of the embodiments referred to herein, the average foam cell size is 40 μm to 600 μm, or 50 μm to 600 μm, or 60 μm to 600 μm, or 70 μm to 600 μm, or 80 μm to 600 μm, or 90 μm to 600 μm, or 100 μm to 600 μm, or 150 μm to 600 μm, or 200 μm to 600 μm, or 250 μm to 600 μm. m, or 300μm~600μm, or 400μm~600μm, or 500μm~600μm, or 40μm~550μm, or 40μm~500μm, or 40μm~450μm, or 40μm~400μm, or 40μm~350μm, or 40μm~300μm, or 40μm~250μm, or 40μm~200μm, or 40μm~150μm, or 40μm~100μm.

[0094] Furthermore, since foamed articles, such as trays, are molded from the cellulose esters described herein, it should be understood that foamed articles may contain any components and / or additives of the cellulose ester-based materials described herein, as well as any resulting properties.

[0095] definition It should be understood that the following is not intended to be an exclusive list of the terms to be defined. Other definitions, for example, when used in context, may be provided in the explanations above.

[0096] As used herein, the terms "a," "an," and "the" mean one or more.

[0097] As used herein, the terms “comprising,” “comprises,” and “comprise” are open-ended transitional clauses used to move the subject listed before the term to one or more elements listed after the term, the elements listed after the transitional clause are not necessarily the only elements that constitute the subject.

[0098] To be considered "compostable," the material must meet the following four criteria: (1) The material must pass the biodegradation requirements in tests conducted under controlled composting conditions at high temperature (58°C) according to ISO 14855-1 (2012), equivalent to 90% absolute biodegradation or 90% relative to the control polymer; (2) The material tested under aerobic composting conditions according to ISO 16929 (2013) must reach 90% disintegration; (3) The test material must meet all requirements regarding volatile solids, heavy metals, and fluorine as specified by ASTM D6400 (2012), EN 13432 (2000), and ISO 17088 (2012); (4) The material must not adversely affect plant growth.

[0099] As used herein, the term “biodegradability” generally refers to the biological transformation and consumption of organic molecules. Biodegradability is an inherent property of the material itself, and materials may exhibit different degrees of biodegradability depending on the specific conditions to which they are exposed. The term “disintegrability” refers to the tendency of a material to physically decompose into smaller fragments when exposed to specific conditions. Disintegration depends on both the material itself and the physical size and composition of the article being tested. Ecotoxicity measures the effect of a material on plants, and the heavy metal content of a material is determined according to the procedures presented in standard test methods.

[0100] For a material to be considered "biodegradable," it must exhibit at least 90 percent biodegradation in total under household composting conditions, according to French standard NFT51-800 and Australian standard AS5810 (for example, compared to the initial sample), or at least 90 percent of the maximum biodegradation of a suitable reference material after reaching a plateau for both the reference and test items. The maximum test period for biodegradation under household composting conditions is one year.

[0101] Under industrial composting conditions in accordance with ASTMD6400 and ISO17088, for an article to be considered "biodegradable," at least 90% of the organic carbon in the whole article (or each component present in amounts exceeding 1% by dry mass) must be converted to carbon dioxide by the end of the test period, compared to a control or absolute value. According to European standard ED13432 (2000), the material must exhibit at least 90 percent biodegradation in total, or at least 90 percent of the maximum biodegradation of a suitable reference material after reaching a plateau for both the reference and test items. The maximum test period for biodegradability under industrial composition conditions is 180 days.

[0102] To be considered "biodegradable" under soil composting conditions compliant with Vincotte's OK Biodegradable Soil Conformity Mark and DIN CERTCO's DIN Geprueft Biodegradable Soil Certification Scheme, the material must exhibit at least 90% biodegradation in total (e.g., compared to the initial sample), or at least 90 percent of the maximum degradation of a suitable reference material after reaching a plateau for both the reference and test items. The maximum test period for biodegradability under soil composting conditions is two years.

[0103] In one embodiment, or in combination with any of the embodiments referenced herein, the biodegradable cellulose acetate foam or article is industrially compostable or household compostable. In one subclass of this class, the foam or article is industrially compostable. In one subclass of this class, the foam or article has a thickness of less than 6 mm. In one subclass of this class, the foam or article has a thickness of less than 3 mm. In one subclass of this class, the article has a thickness of less than 1.1 mm. In one subclass of this class, the foam or article is household compostable. In one subclass of this class, the foam or article has a thickness of less than 6 mm. In one subclass of this class, the foam or article has a thickness of less than 3 mm. In one subclass of this class, the foam or article has a thickness of less than 1.1 mm. In one subclass of this class, the foam or article has a thickness of less than 0.8 mm. In one subclass of this subclass, the foam or article has a thickness of less than 0.6 mm. In another subclass of this subclass, the foam or article has a thickness of less than 0.4 mm.

[0104] In one embodiment, or in combination with any of the embodiments referenced herein, the thickness of the foam or article is 1–10 mm, 1–8 mm, 2–8 mm, 3–7 mm, 4–6 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, or about 8 mm. However, it should be noted that the foam or article may have other, larger sizes. For example, in some embodiments, the foam or article may have a thickness of 0.5–24 inches, 1–15 inches, or 3–12 inches.

[0105] In one embodiment, or in combination with any of the embodiments referred to herein, a foamed sheet or article (e.g., a tray) exhibits more than 90% collapse after 12 weeks according to the collapse test protocol described below, or according to the alternative ISO 16929 (2013). In some further embodiments, the foamed sheets and / or articles (e.g., trays) produced thereby may collapse by at least 91, or at least 92, or at least 93, or at least 94, or at least 95, or at least 96, or at least 97, or at least 98, or at least 99, or at least 99.5 percent, according to the collapse test protocol or ISO 16929 (2013), within 12 weeks or less, or 11 weeks or less, or 10 weeks or less, or 9 weeks or less, or 8 weeks or less.

[0106] The test method used for disintegration (referred to herein as the “disintegration test protocol”) is based on ISO 16929 Plastics – Determination of the degree of disintegration of plastic materials under specified composting conditions in a pilot scale (2013). A foamed sheet or article (e.g., a tray) is formed into a film having a thickness of approximately 0.25 mm (10 mils). Such a film can be formed by cutting or crushing the foamed sheet or article (e.g., a tray). The film generally has the same density as the original foamed sheet or article (e.g., a tray), e.g., 0.20 g / cm³. 3The process includes the following: The final sample is mixed with fresh artificial bioresidue. Oxygen concentration, temperature, and humidity are regularly controlled. After 12 weeks, the resulting compost is sieved, and the amount of material remaining, if any, that is larger than 2 mm, is measured.

[0107] As used herein, “area stretch ratio” refers to the total top surface area of ​​a thermoformed tray (i.e., including the base and rim) divided by the tray’s area footprint (i.e., its two-dimensional area when viewed from above). For example, if a flat sheet is thermoformed into a tray with dimensions of 10 inches wide x 12 inches long x 2 inches deep, the total top surface area is 208 square inches (2(10×2) + 2(12×2) + (10×12)), and the area footprint is 120 square inches (10×12). Therefore, the area stretch ratio of this tray is 1.7(208 / 120).

[0108] Manufacturing of foam sheets Foamed sheet samples were prepared using a Kraus Maffei tandem foaming line. The extrusion line consists of a ZE30 twin-screw extruder as the primary extruder and a KE60 single-screw extruder as the secondary cooling extruder to which the ZE30 is coupled. Compounding additives are fed into the KE30 twin-screw feeder using weight-reducing and gravimetric feeders. Physical foaming agent is added from approximately half the barrel of the primary extruder. 2 / The material is injected downwards into the primary extruder up to 3. The material is extruded from a 50 mm annular die and transported on a sizing mandrel. The annular film is then cut and converted into a flat film at the tension / winding station section of the roll.

[0109] The material composition includes cellulose acetate resin (Eastman CA-398-30 or Eastman FE700) containing 15-20% by weight of triacetin, and stabilizers (1 wt% epoxidized soybean oil, 0.15 wt% Doverphos S9228T). n-pentane is injected into the material as a blowing agent. Additional additives to the process include 1 wt% ABT1000 talc and 1% chemical blowing agent. The material was extruded in a primary extruder at 200-220°C and in a secondary extruder at 170-190°C. The line production rate was 40 kg / hour.

[0110] Thermoformable sheet The material was thermoformed using a Hydrotrim Lab thermoforming machine. This unit features upper and lower heating plates inside the oven, a timer for setting the holding time inside the oven, a vacuum for drawing the material into the mold, and a plug assist for use with complex parts. The material evaluated for this study was fabricated using vacuum only, with the upper and lower mounting plates heated to 260°C.

[0111] Foam quality The average cell size of the sample containing 20 wt% triacetin was 247 microns, the thickness was 3.9 mm, and the initial density was 0.105 g / cc. The average cell size of the sample containing 15 wt% triacetin was 285 microns, the thickness was 4.3 mm, and the initial density was 0.94 g / cc.

[0112] evaluation To evaluate the weight increase, trays were molded from each material. The initial weight of the trays was measured, and then the trays were filled with water to 3 / 4 capacity at specified time intervals. Once the time allocation was reached, the water was removed from the trays, the surface of the trays was wiped dry, and the weight was measured. The weight change of the initial and test samples was recorded. The w% increase was calculated using the following formula.

[0113] w% increase = ((Increase in sample weight - Increase in initial weight) / Increase in initial weight) Ideally, the sample is molded to have good site differentiation and minimal moisture increase. [Table 7]

[0114] The data shows the temperature effect in Examples 1-5, and the ideal temperature for minimizing absorption is 170-200°C. This temperature range also applies to Examples 6-8. [Table 8]

[0115] The data shows the temperature effect in Examples 9-13, and the ideal temperature for minimizing absorption is 200°C. ℃ It was less than 200°C. Example 9 was not fully molded at the target temperature. This temperature range also applies to Examples 14-17, where the minimum water absorption was also less than 200°C. Example 14 was not sufficiently molded at the target temperature. [Table 9]

[0116] Claims not limited to the disclosed embodiments The preferred embodiments of the present invention described above are for illustrative purposes only and should not be used to limit the meaning of the interpretation of the scope of the invention. Modifications to the exemplary embodiments described above can be readily made by those skilled in the art without departing from the spirit of the invention.

[0117] The inventors hereby express their intention to determine and evaluate the reasonably fair scope of the invention on the basis of the doctrine of equivalents whenever the invention relates to any device that does not substantially deviate from, but falls outside, the literal scope of the invention as set forth in the following claims.

Claims

1. A method for molding a foamed article, wherein the method is (a) comprising producing a foamed sheet from a cellulose ester composition, The cellulose ester composition is (i) comprising cellulose acetate, wherein the cellulose acetate has a degree of substitution of acetyl substituents of 2.2 to 2.8 ("DSAc"), and the cellulose ester composition further comprises (ii) comprising 10 to 25% by weight of a plasticizer, wherein the plasticizer is triacetin, poly(ethylene glycol) with a molecular weight of 200 to 600, triethyl citrate, or a combination thereof, the cellulose ester composition further comprises (iii) Contains 0.3 to 8% by weight of a foaming agent, Each is based on the total weight of the composition, and the method further, (b) The process includes thermoforming the foamed sheet in a mold having a footprint area (X) and a surface area of ​​less than 1.9X, thereby forming the foamed article. The aforementioned thermoforming involves heating the foam sheet to a surface temperature of 170°C to 205°C. When the foam sheet is molded into a foam tray, the foam tray is filled with water, and allowed to equilibrate at room temperature for 18 hours, the foam tray exhibits a weight increase of less than 15% according to the water absorption test described herein. The aforementioned method.

2. The method according to claim 1, wherein the manufacturing (a) includes passing the composition through a die to form an extruded product and processing the extruded product to form the foamed sheet.

3. The method according to any one of claims 1 to 2, wherein the thermoforming is performed by heating the foamed sheet to a surface temperature of 175°C to 200°C.

4. The method according to any one of claims 1 to 3, wherein the plasticizer is present in an amount of 15 to 20% by weight.

5. The method according to any one of claims 1 to 4, wherein the foamed article is a foamed tray, and when the foamed tray is filled with water and allowed to equilibrate at room temperature for 24 hours, the foamed tray exhibits a weight increase of less than 10% or less than 5% according to the water absorption test described herein.

6. The method according to any one of claims 1 to 5, wherein the foamed article is a foamed tray.

7. The method according to claim 6, wherein the foam tray is configured to support food.

8. The method according to claim 7, wherein the food is animal or plant protein, vegetables or fruits.

9. The method according to any one of claims 6 to 8, wherein the foam tray has a width in the range of 2 to 14 inches (5.08 cm to 35.56 cm) and a length of 4 to 24 inches (10.16 cm to 60.96 cm).

10. The method according to any one of claims 6 to 9, wherein the foam tray has a depth of 0.5 to 3 inches (1.27 to 7.62 cm).

11. The method according to any one of claims 6 to 10, wherein the thickness of the foam tray is 1 to 10 mm.

12. The foam tray has a density of 0.20 g / cm³. ３ Less than 0.18 g / cm³ ３ Less than 0.15 g / cm³ ３ Less than 0.12 g / cm³ ３ , 0.10 g / cm³ ３ Less than 0.08 g / cm³ ３ Less than 0.06 g / cm³ ３ Less than 0.04 g / cm³ ３ The method according to any one of claims 6 to 11, having a density less than

13. The method according to any one of claims 6 to 12, wherein the foam tray is biodegradable.

14. The foam tray is compostable, according to any one of claims 6 to 13.

15. The method according to any one of claims 1 to 14, wherein the foamed article is free of corrugations.

16. The method according to any one of claims 1 to 15, further comprising an additive selected from the group consisting of C20 to C40 hydrocarbons (paraffin wax), C12 to C16 fatty acids, and mixtures thereof.

17. The method according to claim 16, wherein the additive is present in an amount of 1 to 20% by weight based on the total weight of the composition.

18. The method according to any one of claims 1 to 17, wherein the composition further comprises a melt strength improver.

19. The method according to claim 18, wherein the melt strength improver comprises a functional ionic component.

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