Process for thermoforming cellulose ester foam articles

Abstract

A method of thermoforming a foamed cellulose ester sheet into a foamed tray. The methods and compositions used therein provide foam trays having desired skin integrity after thermoforming. One or more high heat capacity additives and / or melt strength enhancers may be used to provide improved skin integrity at higher thermoforming draw ratios.

Description

Background Art

[0001] Many foam products, such as food packaging, are disposable items that are intended to be disposed of after use. One commercially important material used to make foam products is polystyrene. However, polystyrene is neither compostable nor biodegradable. Furthermore, some cities, states, and countries have enacted or are considering enacting bans on the use of polystyrene-based foams. Therefore, it is desirable to find alternative materials for foam products, as well as viable compositions, methods, and systems for producing such products.

[0002] During the thermoforming of foam articles, a flat foam sheet is heated and stretched into a mold. The deeper the mold, the more the sheet material must be stretched, which can be characterized by its stretch ratio. However, if the stretch ratio is too high, the sheet may tear or crack. Therefore, it is desirable to find an acceptable stretch ratio for articles formed from cellulose ester foam sheets, and to find compositions and processes for increasing the stretch ratio while maintaining acceptable surface integrity in the foam article product. Summary of the Invention

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

[0004] In another embodiment or in combination with any other embodiment mentioned herein, a method of forming a foam article is provided. The method comprises: (a) producing a foam 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 foam sheet in a mold to form the foam article.

[0005] In another embodiment or in combination with any other embodiment mentioned herein, a method of forming a foam article is provided. The method comprises: (a) producing a foam sheet from a cellulose ester composition; and (b) thermoforming the foam sheet in a mold having a footprint (X) and a surface area of ​​at least 1.2X to 5.0X, thereby forming the foam article. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic diagram illustrating a process of forming a biodegradable article according to an embodiment of the present invention;

[0007] Figure 2is a schematic diagram illustrating another process for forming a biodegradable article according to an embodiment of the present invention;

[0008] Figure 3 is an example of a method for use in accordance with an embodiment of the present invention. Figure 1 and / or Figure 2 Schematic diagram of the extrusion section in the product formation process;

[0009] Figure 4 is an example of a method for use in accordance with an embodiment of the present invention. Figure 1 and / or Figure 2 A schematic diagram of another extrusion section in the product formation process;

[0010] Figure 5 is an example of a method for use in accordance with an embodiment of the present invention. Figure 1 and / or Figure 2 Schematic diagram of the sheet forming section in the product forming process. DETAILED DESCRIPTION

[0011] Embodiments generally relate to methods, systems, and compositions for forming biodegradable particulate materials (eg, pellets), foam sheets, and articles. Figures 1 to 5 Exemplary processes, including methods, systems, and compositions, are depicted in FIG and described in greater detail below.

[0012] Methods and systems

[0013] like Figure 1 and Figure 2 As shown, the raw materials can be introduced into a biodegradable polymer production process, which produces a biodegradable polymer material. In one embodiment or in combination with any other embodiment mentioned herein, the biodegradable polymer material comprises one or more cellulose esters. The one or more cellulose esters can include cellulose acetate. In such embodiments, the raw materials can include pulp, such as wood pulp and / or cotton pulp. The pulp can be a dissolving grade pulp and / or a papermaking grade pulp. The cellulose in the pulp can be esterified, for example, with acetic acid to form a biodegradable cellulose ester polymer, such as a cellulose acetate polymer.

[0014] The biodegradable polymer material can then be introduced into a compounding process where it can be mixed with a plasticizer and optionally one or more other additives (e.g., stabilizers) and formed into a compounded material comprising the plasticized biodegradable polymer. Other additives can also be mixed with the polymer and plasticizer. For example, Figure 2As shown, other materials (additives) may include, but are not limited to, stabilizers, physical blowing agents, chemical blowing agents (and / or precursors), nucleating agents, surface modification additives, pigments, fillers, and / or other additives. Mixing can be accomplished by any known mixing technique, including but not limited to rolling in a cylindrical container, overhead stirring, sigma blade mixing, and tumbling.

[0015] The compounding process may include a microgranulation process. The microgranulation process may generally include mixing a biodegradable polymer material, a plasticizer and other additives to form a mixed composition, and forming a microgranulate material from the composition. In particular, the microgranulation process may include a granulation process, and the microgranulate material may include a certain amount of granules. The term "compounded CE material" means a cellulose ester material formed during the compounding process, which may include a mixture of cellulose ester, plasticizer and other additives. In addition, such compounded CE material may be in the form of microgranulate material or granules. It should be understood that as used herein, the phrase "microgranulation" or "microgranulation process" may be the same as "granulation" or "granulation process", or may at least include "granulation" or "granulation process". In some embodiments, the microgranulation process may include granulation in a water bath, granulation on an air cooling belt, underwater granulation, solvent compounding, etc.

[0016] In one embodiment or in combination with any other embodiment mentioned herein, plasticizers and other additives can be mixed with cellulose esters by conventional melt compounding techniques, which involve combining cellulose esters with plasticizers and optional other additives in a twin-screw extruder with appropriate mixing elements and at appropriate temperature and pressure to achieve a molten, homogeneously combined cellulose ester mixture when the material leaves the extruder. The molten compounded cellulose ester mixture can then be extruded through a die having an orifice with a diameter of about 2-6 mm to extrude strands. The strands can then be cooled by water (e.g., via underwater pelletizing) or air, and cut at regular intervals to provide uniform and desired sizes and shapes, which are referred to as "pellets" or "granules." Although a process for forming a granulated compounded material is described herein, it should be understood that, according to some embodiments, the compounded material fed to the foam sheet production process can be in any physical shape (e.g., pellets, powders, granules, fibers). The term "compounded CE material" means a cellulose ester material formed during the compounding process, which may include a mixture of cellulose ester, plasticizer, and other additives. In addition, such compounded CE material may be in the form of a molten mixture or a particulate material (e.g., pellets, powder, granules, fibers, etc.).

[0017] The compounded CE material, which may include pellets of plasticized biodegradable polymer as described above, may then be introduced into a foam sheet production process, such as Figure 1 and Figure 2 The foam sheet production process may include one or more zones / steps for producing a foam sheet or film, which are described in more detail below. Although an exemplary foam sheet production process is described herein, it should be understood that certain aspects described herein may also be applicable to rigid (i.e., non-foam) materials and articles. Figure 1 As shown, in one embodiment or in combination with any other embodiment mentioned herein, various additives can be introduced into one or more zones of the foam sheet production process. Additives can include, but are not limited to, stabilizers, physical blowing agents, chemical blowing agents (and / or precursors), nucleating agents, surface modification additives, pigments, fillers, and / or other additives.

[0018] The foam sheet production process may generally include an extrusion stage and a sheet forming stage. Figure 3 An exemplary extrusion section is depicted in . As shown, the extrusion section may include a feed preparation zone in which solid additives may be combined with the compounded CE materials and introduced into the downstream extrusion zone. In one embodiment or in combination with any other embodiment mentioned herein, the feed preparation zone may include a feed hopper. Thus, the compounded CE materials and other solid additives may be placed into a feed hopper, which directs the combined feed composition into the extrusion zone. The feed preparation zone may also include a mixer in which the compounded CE materials and one or more additives may be mixed before being introduced into the hopper. Mixing may be accomplished by any known mixing technique, including but not limited to rolling in a cylindrical container, overhead stirring, sigma blade mixing, and tumbling. Exemplary solid additives that may be combined with the compounded materials may include chemical foaming agents, nucleating agents, surface modification additives, pigments, fillers, and / or other additives.

[0019] The combined feed composition from the feed preparation zone can then be introduced into the extrusion zone. The extrusion zone can typically include one or more extruders, which can include single-screw and / or twin-screw extruders. In the extruder, the feed composition can be introduced into the extruder barrel and conveyed through the die via the screw to form an extrudate from the feed composition. When the composition is conveyed toward the die through the extruder barrel, the composition can be heated and at least partially melted. Therefore, the term "CE melt composition" is used herein to refer to a cellulose ester-based feed composition that has been melted into a flowable molten resin by the extrusion section. Heating can be supplied by an external heater positioned along the outside of the extruder barrel. The shape of the extrudate will typically depend on the shape and size of the die. As described below, the extrudate can be further shaped by downstream processes.

[0020] While in the extruder, one or more additives may be introduced to the CE molten resin. For example, one or more physical blowing agents may be added to the CE molten resin by injecting the physical blowing agent into the composition as it is conveyed within the extruder barrel.

[0021] like Figure 4 As depicted, in one embodiment or in combination with any other embodiment mentioned 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 combined into an integral apparatus. In any event, the feed composition from the feed preparation zone is introduced into the primary extrusion vessel and is at least partially melted as it is conveyed through the extruder barrel as described above, thereby producing a CE molten resin. The CE molten resin exiting the primary extrusion vessel may have a temperature of about 220°C to about 240°C. One or more additives, such as a blowing agent, may be added to the CE molten resin as it is conveyed through the primary extrusion vessel.

[0022] The CE molten resin from the primary extrusion vessel is then 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 than the primary extrusion vessel. Within the cooling vessel, the CE molten resin may be further mixed to provide a substantially uniform mixture of molten polymer and other additives. The CE molten resin may then be directed through a die and exit the die to provide a cellulose ester-based extrudate that may be further processed in the sheet forming section of the foam sheet production process. In one embodiment or in combination with any other embodiment mentioned herein, the CE molten resin exiting the die 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, from about 150°C to about 220°C, and / or from about 170°C to about 200°C.

[0023] like Figure 4 As shown, one or more filtration devices may be installed within the extrusion section to filter and remove particulate matter from the CE molten resin. For example, a screen changer filtration device may be installed at the downstream end of the primary extrusion vessel and the secondary extrusion vessel. The screen changer filtration device can remove solid components from the CE molten resin before the CE molten resin is directed through the die to the sheet forming section.

[0024] The sheet forming section may include any of the various systems and processes for forming the extrudate into a sheet of cellulose ester material that can be used for article forming. The shape of the extrudate will typically depend on the shape of the die, and the shape of the sheet formed in the sheet forming section may depend on the shape of the die and other downstream processes. For example, the extrudate may have a generally flat shape, or it may be annular and further processed to form a flat sheet. In embodiments where the die has an annular shape, the die may have a diameter of 1 to 40 cm, 2 to 20 cm, 2 to 10 cm, and / or 3 to 8 cm. In addition, the thickness of the opening from which the extrudate is ejected (referred to herein as "die gap") may typically be 0.1 to 6.0 mm, 0.1 to 3.0 mm, and / or 0.1 to 1.0 mm.

[0025] Figure 5 An exemplary sheet forming section is depicted in FIG. As shown, the CE molten resin is extruded through an annular die and stretched on a forming mandrel. A cooling fluid (e.g., air) can be made to flow through the inside and / or outside of the extrudate to cool the extrudate material when it passes through the mandrel. For example, a cooling fluid can be blown from the mandrel to the die to cool the inner surface of the extrudate between the die and the mandrel. Additionally or alternatively, a cooling fluid can be made to flow through the mandrel to cool the outer surface of the extrudate when the extrudate passes through the mandrel.

[0026] A slicer (or slitting device) can be used to cut the tubular extrudate, which allows the tubular shape to be formed into a flat sheet. For example, the tubular extrudate passing over a mandrel can be cut and stretched to a tensioning station, which includes one or more rollers that flatten the extrudate and maintain the necessary tension on the extrudate to continue pulling the extrudate over the mandrel. The flattened extrudate will typically be in the form of a sheet, which can then be directed to a winding station where the material can be rolled up for packaging and shipping.

[0027] Reference again Figure 1 and Figure 2 The sheet produced by the sheet production process can be used to form foam products, which are described in more detail below. Such products are particularly useful in the food service industry. Exemplary products include meat trays. The products can have one or more particularly advantageous properties. For example, the products can be biodegradable and / or compostable, and / or the products can have excellent mechanical properties (e.g., strength, density, cell size, absorption, etc.).

[0028] Composition

[0029] The process described above may include preparing and extruding a composition that can be used for downstream processing to form a useful article. For example, in one embodiment or in combination with any other embodiment mentioned herein, the extrusion feed material may include a 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 mentioned herein, the feed material may be combined with one or more additives, such as those described herein, to provide a mixed composition comprising a biodegradable polymer and one or more additives. In one embodiment or in combination with any other embodiment mentioned herein, the biodegradable polymer comprises a cellulose ester.

[0030] In one embodiment or in combination with any other embodiment mentioned herein, the cellulose ester composition includes one or more polymers and / or other additives that can act to enhance the melt strength of the composition and / or otherwise increase the elasticity of the composition (and the resulting foam product). Compared to foam sheets without these polymers and / or additives, such polymers and other additives can allow the foam sheet to be thermoformed with a higher draw ratio. For example, in some embodiments, the composition includes 1% to 50% by weight or 2% to 20% by weight of one or more such polymers and / or other additives. In some embodiments, the composition includes 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), C12-C16 fatty acids, biodegradable polymers (such as polyethylene glycol (PEG) and other biodegradable polymers described herein) and / or melt strength enhancers (such as functional ionic components). In some embodiments, the composition includes at least one additive having a specific heat capacity of at least 2000 J / kg-C and a melt strength enhancer.

[0031] Additional details of the composition components, including the biodegradable polymer (eg, cellulose ester) and other additives, are provided below.

[0032] Cellulose esters

[0033] The cellulose esters utilized as described herein can be any cellulose ester known in the art. Cellulose esters useful in embodiments herein typically comprise repeating units of the following structure:

[0034]

[0035] wherein R1, R2, and R3 are independently selected from hydrogen, acetyl, propyl, or butyl. The substitution level of a cellulose ester is typically expressed as the degree of substitution (DS), which is the average number of non-OH substituents per anhydroglucose unit (AGU). If the DS involves an acetyl substituent, the DS may be expressed as DSAc. In some cases, the DS may be expressed as DSOH, which describes the average number of free hydroxyl groups. Generally, conventional cellulose contains three hydroxyl groups per AGU unit that can be substituted; therefore, the value of DS can range from zero to three. Natural cellulose is a large polysaccharide with a degree of polymerization of 250-5,000 even after pulping and purification, and therefore the assumption of a maximum DS of 3.0 is generally correct. Because the DS is a statistical average, a value of 1 does not guarantee that every AGU has a substituent. In some cases, there may be unsubstituted anhydroglucose units, some with two substituents and some with three substituents, and generally the value will be a non-integer. The total DS is defined as the average number of all substituents per anhydroglucose unit. The degree of substitution of each AGU may also relate to a specific substituent, such as, for example, a hydroxyl group or an acetyl group. 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.

[0036] In one embodiment or in combination with any other embodiment, the cellulose ester has at least 2 anhydroglucose rings and may have at least 50 to a maximum of 5,000 anhydroglucose rings, or at least 50 to less than 150 anhydroglucose rings. The number of anhydroglucose 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, the cellulose ester may have an intrinsic viscosity (IV) of from about 0.2 to about 3.0 deciliters per gram, or from about 0.5 to about 1.8, or from about 1 to about 1.5, as measured at a temperature of 25°C for a 0.25 gram sample in 100 ml of a 60 / 40 solution by weight of phenol / tetrachloroethane. In one embodiment or in combination with any other embodiment, the cellulose ester useful herein may have a DS / AGU of from about 1 to about 3.0, or from about 2.0 to 2.9, or from about 2.2 to about 2.8, or from 1 to less than 2.2, or from 1 to less than 1.5, and the substituted ester is an acetyl ester.

[0037] Cellulose esters can be produced by any method known in the art. Examples of processes for producing cellulose esters are taught in Kirk-Othmer, Encyclopedia of Chemical Technology, 5th edition, Volume 5, Wiley-Interscience, New York (2004), pages 394-444. Cellulose, the starting material for producing cellulose esters, can be obtained from different grades and sources, such as cotton linter, softwood pulp, hardwood pulp, corn fiber and other agricultural sources, and bacterial cellulose.

[0038] One method of producing cellulose esters is to esterify the cellulose by mixing it with an appropriate organic acid, anhydride, and a catalyst. The cellulose is then converted into a cellulose triester. The esters are then hydrolyzed by adding a water-acid mixture to the cellulose triester, which can then be filtered to remove any gel particles or fibers. Water is then added to the mixture to precipitate the cellulose ester. The cellulose ester can then be washed with water to remove reaction by-products, followed by dehydration and drying.

[0039] The cellulose triester to be hydrolyzed may have three acetyl substituents. These cellulose esters may be prepared by many methods known to those skilled in the art. For example, cellulose esters may be prepared by the presence of a catalyst such as H2SO 4) Cellulose triesters can also be prepared by homogeneous acylation of cellulose dissolved in a suitable solvent such as LiCl / DMAc or LiCl / NMP.

[0040] Those skilled in the art will appreciate that the commercial term cellulose triesters also encompass cellulose esters that are not fully 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.

[0041] After cellulose is esterified to a triester, some of the acyl substituents can be removed by hydrolysis or alcoholysis to produce a secondary cellulose ester. As previously mentioned, the distribution of the acyl substituents can be random or non-random, depending on the specific method used. Secondary cellulose esters can also be prepared directly without hydrolysis by using a limited amount of acylating agent. This process is particularly useful when the reaction is carried out in a solvent that will dissolve the cellulose. All of these methods produce cellulose esters useful in the present invention.

[0042] In one embodiment or in combination with any of the recited embodiments, the cellulose acetate is 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) according to ASTM D6474 using NMP as solvent and a polystyrene equivalent Mn. In one embodiment or in combination with any other embodiment, the cellulose acetate composition comprises cellulose diacetate having a polystyrene equivalent number average molecular weight (Mn) 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 10,000 to less than 60,000; or 10,000 to less than 55,000; or 10,000 to 50,000; or 10,000 to less than 50,000; or 10,000 to less than 45,000; or 10,000 to 40,000; or 10,000 to 30,000; or 20,000 to less than 60,000; or or 30,000 to less than 60,000; or 30,000 to less than 55,000; or 30,000 to 50,000; or 30,000 to less than 50,000; or 30,000 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 less than 60,000; or 30,000 to less than 55,000; or 30,000 to 50,000; or 30,000 to less than 50,000; or 30,000 to less than 45,000; or 30,000 to 40,000; or 30,000 to 35,000; as measured by gel permeation chromatography (GPC) using NMP as solvent and according to ASTM D6474.

[0043] The most common commercial secondary cellulose esters are produced by an initial acid-catalyzed heterogeneous acylation of cellulose to form cellulose triesters. After obtaining a homogeneous solution of the cellulose triesters in the corresponding carboxylic acid, the cellulose triesters are hydrolyzed until the desired degree of substitution is achieved. After separation, random secondary cellulose esters are obtained. That is, the relative degree of substitution (RDS) of each hydroxyl group is approximately equal.

[0044] The cellulose esters useful in the present invention can be prepared using techniques known in the art and can be selected from various types of cellulose esters, such as, for example, cellulose esters available from Eastman Chemical Company, Kingsport, TN, USA, e.g., Eastman TM Cellulose acetate CA 398-30 and Eastman TMCellulose acetate CA 398-10, Eastman TM CAP 485-20 Cellulose acetate propionate; Eastman TM CAB 381-2 Cellulose acetate butyrate.

[0045] In one embodiment or in combination with any other embodiment, cellulose esters can be prepared by converting cellulose into cellulose esters using reactants obtained from recycled materials (e.g., recycled plastic component syngas sources). In one embodiment or in combination with any other embodiment, such reactants can be cellulosic reactants that include organic acids and / or anhydrides used in esterification or acylation reactions of cellulose, for example, as discussed herein.

[0046] In one embodiment of the invention or in combination with any of the recited embodiments or in combination with any of the recited embodiments, there is provided a cellulose ester composition comprising at least one recycled cellulose ester, wherein the cellulose ester has at least one substituent on an anhydroglucose unit (AU) derived from a recycled component material (e.g., recycled plastic component syngas).

[0047] In one embodiment or in combination with any other embodiment, the cellulose ester composition comprises cellulose ester in an amount of 50% to 99% by weight, or 60% to 99% by weight, or 70% to 99% by weight, or 80% to 99% by weight, or 90% to 99% by weight, or 50% to 90% by weight, or 60% to 90% by weight, or 70% to 90% by weight, or 80% to 90% by weight, or 90% to 99% by weight, or 50% to 80% by weight, or 60% to 80% by weight, or 70% to 80% by weight, or 50% to 70% by weight, or 60% to 70% by weight, or 50% to 60% by weight, all based on the total weight of the cellulose ester composition. In some embodiments, the cellulose ester used herein may comprise a combination, blend, or mixture of two or more different types of cellulose esters. For example, in some embodiments, the cellulose esters used herein may consist of a blend of two or more cellulose esters having different DSACs; however, the blend may have a total DSAC between 2.2 and 2.8 or between 2.0 and 2.9.

[0048] plasticizers

[0049] In one embodiment or in combination with any other embodiment, the cellulose ester composition described herein may include at least one plasticizer. Plasticizers reduce the melting temperature, i.e., Tg, and / or melt viscosity, of the cellulose ester. Plasticizers for cellulose esters may include triacetin, diacetin, dibutyl terephthalate, dimethyl phthalate, diethyl phthalate, poly(ethylene glycol) MW 200-600, dibutyl tartrate, di-2-methoxyethyl phthalate, ethyl o-benzoylbenzoate, triethylene glycol dipropionate, and poly(ethylene glycol) MW 200-600. glycoldipropionate), 1,2-epoxypropylphenyl glycol, 1,2-epoxypropyl(m-tolyl) glycol, 1,2-epoxypropyl(o-tolyl) glycol, β-oxyethyl cyclohexenecarboxylate, diethylene glycol bis(cyclohexanoate), triethyl citrate, polyethylene glycol, propylene glycol, polysorbate, sucrose octaacetate, acetylated triethyl citrate, acetyl tributyl citrate, Admex, tripropionin, Scandiflex, poloxamer copolymers, polyethylene glycol succinate, diisobutyl adipate, polyvinyl pyrrolidone, and ethylene glycol tribenzoate, benzoate-containing plasticizers (such as Benzoflex TM plasticizer series), poly (alkyl succinates) (such as poly (butyl succinate)), polyether sulfone, o-tolyl p-toluenesulfonate, n-ethyl toluenesulfonamide, adipate-based plasticizers, epoxidized soybean oil (such as Paraplex TM Plasticizer series), sucrose-based plasticizer, dibutyl sebacate, tributyrin, sucrose acetate isobutyrate, Resolflex TM Series plasticizers, triphenyl phosphate (TPP), triethyl phosphate (TEP), glycolates (e.g., ethyl phthaloyl ethyl glycolate "EPEG" and methyl phthaloyl ethyl glycolate "MPEG"), methoxy polyethylene glycol, 2,2,4-trimethylpentane-1,3-diyl bis(2-methylpropionate) and polycaprolactone. In some embodiments, the plasticizer used herein may include a combination or mixture of two or more different types of plasticizers.

[0050] In one embodiment or in combination with any other embodiment, plasticizer is a food compliance plasticizer.Food compliance means meeting applicable food additives and / or food contact regulations, wherein plasticizer is approved for use or is considered safe by at least one (country or region) food safety regulatory agency (or organization), for example, listed in 21CFR food additive regulations or otherwise generally recognized as safe (GRAS) by U.S. FDA. In one embodiment or in combination with any other embodiment, food compliance plasticizer is triacetin or polyethylene glycol (PEG) with a molecular weight of approximately 200 to approximately 600. In one embodiment or in combination with any other embodiment, the example of the food compliance plasticizer that can be considered can include triacetin, triethyl citrate, polyethylene glycol, Benzoflex, propylene glycol, polysorbate, sucrose octaacetate, acetylated triethyl citrate, acetyl tributyl citrate, Admex, tripropionin, Scandiflex, poloxamer copolymer, polyethylene glycol succinate, diisobutyl adipate, polyvinyl pyrrolidone and ethylene glycol tribenzoate.

[0051] In one embodiment or in combination with any other embodiment, the plasticizer can be present in an amount sufficient to permit the cellulose ester composition to be melt processed (or thermoformed) in conventional melt processing equipment into useful articles, such as disposable plastic articles. In one embodiment or in combination with any other embodiment, for most thermoplastic processing, the plasticizer is present in an amount of 1% to 40% by weight; or in an amount of 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. In one embodiment or in combination with any other embodiment, profile extrusion, sheet extrusion, thermoforming, and injection molding can be achieved using plasticizer levels in the range of 10% to 30% by weight, or 12% to 25% by weight, or 15% to 20% by weight, or 10% to 25% by weight, based on the weight of the cellulose ester composition.

[0052] 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, benzoate-containing plasticizers such as Benzoflex, TM series of plasticizers), poly(alkyl succinates) such as poly(butyl succinate), polyethersulfones, adipate-based plasticizers, epoxidized soybean oils such as Paraplex TM Plasticizer series), sucrose-based plasticizer, dibutyl sebacate, tributyrin, Resolflex TMSeries of plasticizers, triphenyl phosphate, glycolate, polyethylene glycol, 2,2,4-trimethylpentane-1,3-diylbis(2-methylpropionate) and polycaprolactone.

[0053] In one embodiment or in combination with any of the other embodiments, the cellulose ester composition may contain a plasticizer selected from the group consisting of PEG and MPEG (methoxy PEG). The polyethylene glycol or methoxy polyethylene glycol composition has an average molecular weight of 200 to 600 Daltons, wherein the composition is melt processable, biodegradable, and disintegratable.

[0054] In one embodiment or in combination with any of the other embodiments, the composition comprises polyethylene glycol or methoxy PEG having an average molecular weight of 300 to 550 Daltons.

[0055] In one embodiment or in combination with any of the other embodiments, the composition comprises polyethylene glycol having an average molecular weight of 300 to 500 Daltons.

[0056] In one embodiment or in combination with any other embodiment, the cellulose ester composition comprises at least one plasticizer (as described herein) in an amount of from 1% to 40% by weight, or from 5% to 40% by weight, or from 10% to 40% by weight, or from 12% to 40% by weight, from 13% to 40% by weight, or from 15% to 40% by weight, or greater than 15% to 40% by weight, or from 17% to 40% by weight, or from 20% to 40% by weight. % to 40 wt %, or 25 wt % to 40 wt %, or 5 wt % to 35 wt %, or 10 wt % to 35 wt %, or 13 wt % to 35 wt %, or 15 wt % to 35 wt %, or greater than 15 wt % to 35 wt %, or 17 wt % to 35 wt %, or 20 wt % to 35 wt %, or 5 wt % to 30 wt %, or 10 wt % to 30 wt %, or 13 wt % to 30 wt %, or 15 wt % to 30 wt %. %, or greater than 15 wt % to 30 wt %, or 17 wt % to 30 wt %, or 5 wt % to 25 wt %, or 10 wt % to 25 wt %, or 13 wt % to 25 wt %, or 15 wt % to 25 wt %, or greater than 15 wt % to 25 wt %, or 17 wt % to 25 wt %, or 5 wt % to 20 wt %, or 10 wt % to 20 wt %, or 13 wt % to 20 wt %, or 15 wt % to 20 ... % to 20 wt %, or 17 wt % to 20 wt %, or 5 wt % to 17 wt %, or 10 wt % to 17 wt %, or 13 wt % to 17 wt %, or 15 wt % to 17 wt %, or greater than 15 wt % to 17 wt %, or 5 wt % to less than 17 wt %, or 10 wt % to less than 17 wt %, or 13 wt % to less than 17 wt %, or 15 wt % to less than 17 wt %, all based on the total weight of the cellulose ester composition.

[0057] In one embodiment or in combination with any other embodiment, at least one plasticizer comprises or is a food-compliant plasticizer or an FDA-approved plasticizer. In one embodiment or in combination with any other embodiment, the food-compliant plasticizer or FDA-approved plasticizer comprises or is triacetin or PEG MW 300 to 500.

[0058] Biodegradable polymers

[0059] In one embodiment or in combination with any other embodiment, the cellulose ester composition described herein comprises: a biodegradable cellulose ester (BCE) component comprising at least one BCE, which may comprise one or more 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 may be selected from polyhydroxyalkanoates (PHA and PHB), polylactic acid (PLA), polycaprolactone polymer (PCL), polybutylene adipate terephthalate (PBAT), polyethylene glycol succinate (PES), polyvinyl acetate (PVA), polybutylene succinate (PBS) and copolymers (such as polybutylene succinate-co-adipate (PBSA)), cellulose esters, cellulose ethers, starch, proteins, derivatives thereof, 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%, or 1% to 40%, or 1% to 30%, or 1% to 25%, or 1% to 20% by weight of 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%, or 1% to 40%, or 1% to 30%, or 1% to 25%, or 1% to 20% by weight of the total amount of BCE and biodegradable polymer. In one embodiment or in combination with any other embodiment, the at least one biodegradable polymer comprises a PHA having a weight average molecular weight (Mw) within the range of 10,000 to 1,000,000, or 50,000 to 1,000,000, or 100,000 to 1,000,000, or 250,000 to 1,000,000, or 500,000 to 1,000,000, or 600,000 to 1,000,000. or 10,000 to 50,000, or 10,000 to 250,000, or 10,000 to 100,000, or 10,000 to 50,000, as measured using gel permeation chromatography (GPC) with a refractive index detector and polystyrene standards using a dichloromethane solvent.In one embodiment or in combination with any of the other embodiments, the PHA can include polyhydroxybutyrate-co-hydroxyhexanoate.

[0060] Nucleating agent

[0061] Nucleating agents refer to chemical or physical materials that provide sites for the formation of cells in a molten formulated mixture (such as within a CE molten resin). As will be described in more detail below, nucleating agents can be added to the compounded CE material during the compounding process. Alternatively or in addition, nucleating agents can be added during the foam sheet production process. For example, the nucleating agent can be blended with the formulation introduced into the hopper of the extruder in the extrusion section. Alternatively, the nucleating agent can be added to the CE molten resin in the extruder itself. Nucleating agents can include physical nucleating agents and chemical nucleating agents. Physical nucleating agents are materials that are immiscible with the polymer matrix of the CE molten resin at the extrusion temperature of the extrusion section. Chemical nucleating agents are materials that react (e.g., decompose) during extrusion (e.g., at the extrusion temperature within the extruder) to form physical nucleating agents. Therefore, chemical nucleating agents can be considered (and referred to herein as) precursors to physical nucleating agents formed in situ.

[0062] Suitable physical nucleating agents will include fine particles of a desired size and / or shape to create cell nucleation sites within the CE molten resin. For example, in some embodiments, the physical nucleating agent will have 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, particles having nanometer sizes may be preferred. Furthermore, in some embodiments, the physical nucleating agent will preferably have a high aspect ratio (i.e., width:height). For example, in some embodiments, the physical nucleating agent will have 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. Still further, as described above, the physical nucleating agent should be immiscible with the polymer matrix of the CE molten resin at the extrusion temperature of the extrusion zone. Thus, in some embodiments, the physical nucleating agent should 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 can be selected such that, after melting, it has the ability to recrystallize upon cooling.

[0063] Examples of suitable inorganic physical nucleating agents include, but are not limited to, minerals such as talc, CaCO 3 , mica, and mixtures of at least two of the foregoing. A representative example is Heritage Plastics HT6000 linear low density polyethylene (LLDPE) based talc concentrate. Other inorganic physical nucleating agents include wollastonite, silica, silicon oxide, titanium oxide, 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 will include an oxide such as a metal oxide or mixed metal oxide such as an oxide 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 oxide, and titanium oxide. In other embodiments, the inorganic nucleating agent will include a silicate such as a silicate selected from one or more of the following: magnesium silicate and calcium silicate.

[0064] It has been found that biodegradable natural particulate materials (for example, organic nucleating agents) derived from renewable organic sources can also serve as effective physical nucleating agents. The natural materials that can be used as physical nucleating agents include materials consisting of cellulose fiber and / or cellulose starch. Examples include but are not limited to almond shell powder, animal fiber, apricot shell powder, bamboo powder, bark powder, clam shell powder, coconut shell powder, coconut chaff, cork powder, corn cob powder, corn cob crumbs, cotton seed shells, cotton linter and fiber, hazelnut shell powder, kenaf powder, natural fiber, nut shells and powder, oat fiber powder, olive kernel powder, peanut shell powder, pecan shell powder, pine nut shell powder, pistachio shell powder, plant fiber, rice husk powder, rice husk grains, rice husk, soy flour, starch powder (hydrophobicity), walnut shell powder, wheat bran, wheat husk and wood powder. Other organic physical nucleating agents include cellulose powder, chitin, chitosan, stearic acid metal salts, carbon black and dolomite.

[0065] As described above, suitable chemical nucleating agents (or precursors to in-situ formed physical nucleating agents) are configured to decompose upon reaching a threshold chemical reaction temperature to create cell nucleation sites in the CE molten resin. These small cells serve as nucleation sites for larger cell growth 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 extrusion of the particulate material.

[0066] Examples of chemical nucleating agents include, but are not limited to, acids such as citric acid or citric acid-based substances. Other acids may include lauric acid, stearic acid, tartaric acid, ascorbic acid, propionic acid, and caproic acid. A representative example is HYDROCEROL TMCF-40E (available from Clariant Corporation) contains citric acid and a crystal nucleating agent. In some embodiments, the chemical nucleating agent will include a combination of an acid and an alkali, such as a carbonate, which may include sodium bicarbonate, zinc bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, etc. For example, a representative 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 components of the nucleating agent are dispersed. For example, another representative 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 ingredients, such as various biopolymers (e.g., polybutylene succinate, Capa polyester, etc.), polyolefins, acrylate copolymers (e.g., ethylene methyl acrylate), etc. In some such embodiments, citric acid and sodium bicarbonate may constitute approximately half (in wt %) of the chemical nucleating agent, while the carrier constitutes the remaining half (in wt %). In addition, 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 as much sodium bicarbonate (in weight %) as citric acid in the chemical nucleating agent.It will also be understood that in some embodiments, a carrier may not be needed or used, such as where the nucleating agent is Hecofoam or Hydrocerol.

[0067] In one embodiment or in combination with any of the embodiments mentioned herein, the nucleating agent is present at 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, all based on the total weight of the cellulose ester composition. In some embodiments, the nucleating agent used herein may include a combination or mixture of two or more different types of nucleating agents.

[0068] It should be noted that, regardless of the form of a compounded CE material or a CE molten resin, the cellulose ester material will generally be able to accept a maximum amount of nucleating agent that can act to form nucleation sites. Any remaining nucleating agent added to the cellulose ester material will be retained as a filler. Based on the type of filler used, the filler can provide various properties to the resulting cellulose ester foam and / or product. For example, some fillers can provide increased / decreased density, ductility, Young's modulus, yield strength, heat distortion temperature, permeability, impact resistance, elongation at break, adhesion, biodegradability, etc. of the cellulose ester material. Fillers can also be used to change the visual properties (e.g., color, opacity, etc.) and tactile properties (e.g., material continuity, surface roughness, etc.) of the cellulose ester material.

[0069] foaming agent

[0070] A blowing agent refers to a physical or chemical material (or combination of materials) that acts to expand the nucleation sites. The blowing agent may include a chemical blowing agent, a physical blowing agent, a combination thereof, or several types of chemical and physical blowing agents. The blowing agent is used to reduce the density of the material by expanding the cells formed at the nucleation sites in the molten formulation. The blowing agent can be added to the CE molten resin in the extruder. It has been unexpectedly discovered that the hygroscopic properties of biodegradable particulate natural fillers allow them to absorb water and carry the absorbed water into the molten resin mixture, where the water can act as a physical blowing agent.

[0071] The example of physical foaming agent comprises H2O, N2, CO2, alkane, olefin, ether, ketone, argon, helium, air or mixture.In addition, it has been unexpectedly found that the hygroscopic property of biodegradable particulate natural filler allows them to absorb moisture and carry the absorbed water into the molten resin mixture, in which water can serve as a physical foaming agent.Hygroscopic biodegradable natural filler can be formulated into a composition and is allowed to absorb moisture before the foaming process, wherein water is then released to serve as a physical foaming agent.Beneficially, water can also be used as a plasticizer for cellulose ester resin.In addition, in some embodiments, the physical foaming agent can include hydrocarbons, such as pentane / isopentane or butane / isobutane.Other hydrocarbons can include propane, ethane, methane, hexane, cyclohexane, cyclopentane, cyclobutene etc.

[0072] Chemical foaming agents are materials that degrade or react to produce gases (e.g., CO2 or N2). Such gases expand the cells within the molten resin mixture and / or the resulting foam mixture to produce a structural material with a plurality of gas voids dispersed throughout. Chemical foaming agents can be endothermic or exothermic. Chemical foaming agents typically degrade at a specific temperature to decompose and release gases. Examples of chemical foaming agents include azodicarbonamide, acids (e.g., citric acid), and carbonates such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, zinc carbonate, and the like, and combinations thereof.

[0073] In one embodiment or in combination with any of the embodiments mentioned herein, the blowing agent is present at 0.3 wt% to 1.5 wt%, or 0.3 wt% to 2.0 wt%, or 0.3 wt% to 2.5 wt%, or 0.3 wt% to 3.0 wt%, or 0.3 wt% to 3.5 wt%, or 0.3 wt% to 4.0 wt%, or 0.3 wt% to 8 wt%, or 1.3 wt% to 1.5 wt%, or 1.3 wt% to 2.0 wt%, or 1.3 wt% to 2.5 wt%, or 1 ...1.3 wt% to 3.5 wt%. % to 3.5 wt%, or 1.3 wt% to 4.0 wt%, or 1.3 wt% to 4.5 wt%, or 1.3 wt% to 5.0 wt%, or 1.3 wt% to 5.5 wt%, or 1.5 wt% to 3.0 wt%, or 1.5 wt% to 4.0 wt%, or 1.5 wt% to 5.0 wt%, or 1.5 wt% to 6.0 wt%, or 2.0 wt% to 3.0 wt%, or 2.0 wt% to 4.0 wt%, or 2.0 wt% to 5.0 wt%, or 2.0 wt% to 6.0 wt%, or 2.5 % to 3.0 wt%, or 2.5 wt% to 4.0 wt%, or 2.5 wt% to 5.0 wt%, or 2.5 wt% to 6.0 wt%, or 3.0 wt% to 4.0 wt%, or 3.0 wt% to 5.0 wt%, or 3.0 wt% to 6.0 wt%, or 0.0 wt% to 9.0 wt%, or 0.5 wt% to 9.0 wt%, or 1.0 wt% to 9.0 wt%, or 1.5 wt% to 9.0 wt%, or 2.0 wt% to 9.0 wt%, or 2.5 wt% to 9.0 wt%, or 3.0 % to 9.0 wt %, or 3.5 wt % to 9.0 wt %, or 4.0 wt % to 9.0 wt %, or 4.5 wt % to 9.0 wt %, or 5.0 wt % to 9.0 wt %, or 5.5 wt % to 9.0 wt %, or 6.0 wt % to 9.0 wt %, or 6.5 wt % to 9.0 wt %, or 7.0 wt % to 9.0 wt %, or 7.5 wt % to 9.0 wt %, or 8.0 wt % to 9.0 wt %, or 8.5 wt % to 9.0 wt %, all based on the total weight of the cellulose ester composition. In some embodiments, the blowing agent used herein may include a combination or mixture of two or more different types of blowing agents.

[0074] Surface modification additives

[0075] Surface modification additives refer to materials that can be added to a cellulose ester composition to modify the structure of the composition (or the resulting foam product) to improve the processing of the cellulose ester composition. For example, the inventors of the present application have discovered that adding a surface modification additive to a compounded CE material (e.g., to pellets during the compounding process) or to a CE molten resin (e.g., during the extrusion process) can improve processing by reducing unnecessary adhesion of the CE molten resin to a die or mandrel (or other components of the foam sheet production process). This reduction in adhesion can be achieved by the surface modification additive inhibiting the fusion of the cellulose ester caused by the plasticizer. The addition of the surface modification additive can also reduce blockage of the cellulose ester foam sheet produced at the sheet forming section. In addition, the surface modification additive can also improve the foam sheet production process by allowing it to be carried out at a lower temperature.

[0076] Still further, in some embodiments, the surface modification additive can function as an antistatic additive, suppressing sparks or arcs in the CE molten resin. Spark or arc suppression can be particularly important when using hydrocarbons as blowing agents to reduce the potential for ignition of the hydrocarbons and fire. Advantageously, the surface modification additive can also reduce the diffusion of the blowing agent (such as the hydrocarbon) from the foam sheet or resulting article. In some embodiments, the hydrocarbon itself can function as a surface modification additive.

[0077] Nevertheless, according to embodiments of the present invention, more general examples of surface modification additives that can be used with compounded CE materials (e.g., during the compounding process) or CE melt resins (e.g., during the foam sheet production process) 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 modification additives may also include fatty acid amides such as erucamide, oleamide, stearamide, behenamide, secondary amides and bisamides.

[0078] The additional examples of surface modification additives may include glycerides and / or stearates, such as monoglycerides, diglycerides and triglycerides. Monoglycerides may include glyceryl monostearate or monoglyceride derivatives, such as diacetyl tartaric acid esters (DATEM) of monoglycerides and diglycerides, ethoxylated monoglycerides, succinyl monoglycerides and propylene glycol monoesters (PGME). The example of surface modification additives may also include metal stearates, such as aluminum stearate, calcium stearate, lithium stearate, magnesium stearate, sodium stearate, zinc stearate and / or its combination (e.g., calcium stearate / zinc). The example of surface modification additives may also include waxes, such as polyolefin waxes (polypropylene wax and polyethylene wax), oxidized olefin waxes, ethylene acrylic acid (EAA) copolymer waxes, ethylene methyl acrylate (EMA) copolymer waxes, EAA ionomer waxes, acrylic acid waxes and / or natural waxes, such as rice bran wax, sunflower wax, sugarcane wax, candelilla wax, soybean wax, beeswax, candelilla wax and carnauba wax.

[0079] Other non-exclusive examples of surface modification additives include aliphatic diesters (e.g., dioctyl adipate), polyethylene glycol diesters, alkyl alkyl ether diesters, aromatic triesters, polyester resins, chlorinated hydrocarbons, halogenated hydrocarbons, alkyl ether monoesters, and alkyl monoesters. In addition, various oils can be used as surface modification additives, such as aromatic oils, naphthenic oils, glyceride oils, silicone oils, and epoxidized oils (e.g., soybean oil and linseed oil). Therefore, in some embodiments, surface modification additives include plasticizers, such as aliphatic diester plasticizers, polyester plasticizers, etc. In addition, in some embodiments, surface modification additives can include polyhedral oligomeric silsesquioxanes (POSS).

[0080] More generally, the surface modification additives used in embodiments of the present invention can have a lower polarity than the cellulose ester in the compounded CE material (e.g., during the compounding process) or the CE melt resin (e.g., during the foam sheet production process). For example, the surface modification additive can have (based on Hansen solubility parameters): an overall solubility parameter δ that is less than 25 MPa 1 / 2 , less than 20MPa 1 / 2 , or less than 19.5MPa 1 / 2 ; Dispersion solubility parameter δ d , which is less than 18MPa 1 / 2 , less than 16MPa 1 / 2 , or less than 14MPa 1 / 2 ; Solubility parameter δ of dipole intermolecular force d , which is less than 12MPa 1 / 2 , less than 8MPa 1 / 2 , or less than 4MPa 1 / 2 ; and / or hydrogen bond solubility parameter δ h , which is less than 11MPa 1 / 2, less than 10MPa 1 / 2 , or less than 9MPa 1 / 2 However, in some other embodiments, the surface modification additive used in embodiments of the present invention may have a higher polarity than the cellulose ester in the compounded CE material (e.g., during the compounding process) or the CE melt resin (e.g., during the foam sheet production process). For example, the surface modification additive may have (based on Hansen solubility parameters): an overall solubility parameter δ that exceeds 21.5 MPa 1 / 2 , more than 23MPa 1 / 2 , or more than 25MPa 1 / 2 . Additionally, in some embodiments, the surface modification additive may have a boiling point greater than 200°C, greater than 220°C, greater than 240°C, greater than 260°C, greater than 280°C, or greater than 300°C. Additionally, the surface modification additive may have a molecular weight greater than 100 g / mol, greater than 150 g / mol, greater than 220 g / mol, greater than 260 g / mol, greater than 300 g / mol, or greater than 340 g / mol and / or no more than 1000 g / mol, no more than 2500 g / mol, or no more than 5000 g / mol. Still further, it may be preferred that the surface modification additive is insoluble in the plasticizer used in the cellulose ester composition. For example, it may be preferred that the surface modification additive is insoluble in triacetin. Finally, in some embodiments, the surface modification additive may be biodegradable and / or food compliant or FDA approved.

[0081] In one embodiment or in combination with any of the embodiments mentioned herein, the surface modification additive is present at 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, 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, all based on the total weight of the cellulose ester composition. In some embodiments, the surface modification additive used herein may include a combination or mixture of two or more different types of surface modification additives.

[0082] Melt strength enhancers

[0083] The elasticity of the cellulose ester composition, and particularly the elasticity during heating processes such as extrusion and thermoforming, can be improved by including one or more melt strength enhancers. Such melt strength enhancers can be in the form of functional ionic components. Various 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 gum arabic, sulfopolyesters, quaternary salts, ionomers, ionic liquids, ionic waxes, and mixtures thereof.

[0084] Products

[0085] Extruded sheets of cellulose ester foam can be formed using the extrusion sections and / or sheet forming sections described above. Such extruded sheets include a structural material having a plurality of gas voids disposed therein. Such gas voids are formed by the expansion of a foaming agent in the form of a gas in a cellulose polymer melt. The structural material is based on cellulose ester, wherein the specific amounts of the constituent components of the structural material (e.g., cellulose ester, plasticizer, nucleating agent, surface modification additive, etc.) have been described in more detail above. Articles can be formed from extruded sheets of foam according to the embodiments and may be particularly useful in the food service industry. Exemplary articles include meat trays. The articles may have one or more particularly advantageous properties. For example, the article may have preferential water absorption properties, be biodegradable and / or compostable, and / or the article may have excellent mechanical properties (e.g., strength, density, cell size, absorption, etc.).

[0086] Such cellulose ester foam articles can be formed from a cellulose ester foam sheet by thermoforming, wherein heat and, optionally, pressure are applied to the foam sheet within a mold to produce a three-dimensional article that retains its shape after being released from the mold. For example, in some embodiments, the foam sheet is heated to a surface temperature that is 40°C to 100°C, 50°C to 80°C, or 50°C to 70°C higher than the Tg of the foam sheet. In some embodiments, the Tg of the foam sheet will be about 120°C. Thus, the thermoforming process can heat the foam sheet to a surface temperature of 150°C to 210°C or 160°C to 200°C. In some embodiments, uniform heat distribution throughout the foam sheet can be achieved by heating at a lower temperature (e.g., a temperature 40°C to 70°C higher than the Tg, or 150°C to 180°C), which may require a longer heating time.

[0087] In more detail, embodiments of the present invention may include a foam article in the form of a foam tray. The foam tray can be configured as a food tray to hold one or more food items, such as meat. Optionally, the food item is a protein (e.g., animal, plant), vegetable, or fruit. As illustrated, the foam tray may include a substantially planar base and a rim that projects 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) within which an item (e.g., meat or another food item) may be held and held.

[0088] Foam trays formed according to embodiments of the present invention can be formed in a variety of sizes. For example, the tray can have a width "W" ranging from 2-12 inches, 3-10 inches, or 5-9 inches, and a length "L" ranging from 4-24 inches, 5-18 inches, or 6-15 inches. Thus, in some embodiments, the tray can have a length that is 1.2 to 4 times, 1.4 to 3 times, or 1.5 to 2 times the width of the tray.

[0089] The foam tray may include a substantially planar base and a rim that projects 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) in which items (e.g., meat, cheese, vegetables, fruit, or other food items) can be held and contained. The area of ​​the base may be 5-100 square inches, 10-75 square inches, or 20-50 square inches. The rim height (measured from the bottom of the tray to the top of the rim) may be 0.2-4 inches, 0.4-2 inches, or 0.5-1 inches, and the rim width (i.e., the lateral distance "Rw" measured from one side of the tray to the point where the rim meets the base) may be 0.06-0.75 inches, 0.10-0.05 inches, or 0.25-0.50 inches. Optionally, the rim width "Rw" may be approximately 0.03W to 0.06W. The ratio of the base area to the rim area can be 1-10, 1.5-6, or 2-4. In addition, the tray can have a depth (measured from the top of the rim to the top of the base) of 0.3 to 4 inches, 0.5 to 3 inches, 1 to 3 inches, 1 to 2 inches, 1.25 to 2 inches, about 1.25 inches, or about 1.5 inches. In addition, the tray can have a thickness (i.e., the thickness of the cellulose ester foam material) of 1 to 10 mm, 1 to 8 mm, 2 to 8 mm, 3 to 7 mm, 4 to 6 mm, about 4 mm, about 5 mm, or about 6 mm, and / or less than 5 mm, less than 4 mm, less than 3 mm, or less than 2 mm. Alternatively or additionally, the tray or other article can have a thickness (i.e., the thickness of the cellulose ester foam material) of 100-400 mils, 120-300 mils, 150-250 mils.

[0090] Advantageously, the foam tray may have a preferential water absorption property. For example, when using a foam tray to hold meat, it may be preferred that the tray not absorb liquid that seeps from the meat. The foam tray may be tested for water absorption using a "water absorption test" comprising the following steps: (1) weighing the foam tray to obtain an original tray weight; (2) filling the receiving area of ​​the tray 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., eighteen hours); (4) emptying the tray of water contained in the receiving area; (5) gently wiping the tray to remove any excess water remaining on the surface of the tray; (6) weighing the water-exposed tray to obtain a water-exposed tray weight; and (7) calculating the percent weight increase of the water-exposed tray weight relative to the original tray weight.

[0091] According to embodiments of the present invention, after the tray of the present invention is filled with water and allowed to equilibrate at room temperature for one hour, the tray (after removing the water from the receiving area of ​​the tray) may have a weight increase of 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 additionally, after the tray of the present invention is filled with water and allowed to equilibrate at room temperature overnight (e.g., 18 hours or 24 hours), the tray (after removing the water from the receiving area of ​​the tray) may have a weight increase of less than 20%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, and / or less than 10.5%.

[0092] abbreviation

[0093] ADR is the area draw ratio; BA is the blowing agent; d is the density; TA is triacetin; Pent is pentane; PBA is the physical blowing agent; cc or cm 3 is cubic centimeters; Pz is plasticizer; O / N is overnight; Wt is weight; Temp is temperature; h is hours

[0094] After the water absorption test, the foam tray can be further subjected to a "freeze-thaw test" to test the tray's 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., eighteen hours); (2) removing the frozen tray from the freezer; (3) allowing the frozen tray to thaw overnight (i.e., eighteen hours) at room temperature; (4) filling the receiving area of ​​the thawed foam tray with water; (5) allowing the filled tray to equilibrate at room temperature for twelve hours; (6) emptying the tray of water in the receiving area; (7) gently wiping the empty tray to remove any excess water remaining on the surface of the tray; (8) weighing the water-exposed tray to obtain the water-exposed tray weight; and (9) calculating the percent weight increase of the water-exposed tray weight relative to the original weight of the tray. According to embodiments of the present invention, after the tray has been tested for water absorption and further after the tray is frozen overnight (i.e., eighteen hours), thawed overnight (i.e., eighteen hours), filled with water, and allowed to equilibrate at room temperature for twelve hours, the tray may have a weight increase of less than 30%, less than 25%, less than 20%, and / or less than 15%.

[0095] Several sample trays were formed and tested using water absorption and freeze-thaw tests. The trays were formed from cellulose ester foam sheets extruded using a tandem extruder system. The extruded cellulose ester molten resin comprised cellulose diacetate with a degree of substitution of 2.52, a melting point of 230°C to 250°C, and a Tg of 189°C. The molten resin was plasticized with a loading of 15% to 20% by weight of triacetin. Talc was used as a nucleating agent and mixed into the molten resin along with a physical foaming agent within the twin-screw extruder of the tandem extruder system. The resulting molten resin was transferred to a single-screw extruder, from which a ring die was used to extrude the cellulose ester foam sheet. The foam sheet was stretched, cut, and thermoformed to form the foam trays. Table 1 shows the results of the one-hour water absorption test for four samples. Table 2 shows the results of the eighteen-hour water absorption test for four samples, and Table 3 shows the results of the freeze-thaw test for two samples. It should be noted that for each sample, at least three foam trays were used and the measurements were averaged to provide the results shown below.

[0096] Table 1.

[0097] sample Average 1 hour increase (weight %) 1 3.9 2 6.5 3 4.6 4 6.3

[0098] Table 2.

[0099] sample Average O / N increase (wt%) 5 10.5 6 11.8 7 13.3 8 13.3

[0100] Table 3.

[0101]

[0102]

[0103] Embodiments provide for forming the foam tray described above according to the processes described herein. Specifically, a mixed composition comprising a 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 can include a generally planar base and a rim extending upward from the base and around the perimeter of the tray.

[0104] The thermoforming process typically involves heating a foam sheet to a desired temperature and stretching the foam sheet into a mold having a size suitable for the foam tray product. The amount that a flat foam sheet extends in the mold can be characterized by an area stretch ratio. As used herein, "area stretch ratio" refers to the total top surface area of ​​a thermoformed tray (i.e., including the base and edges) divided by the area footprint of the tray (i.e., the two-dimensional area of ​​the tray when viewed from the top). For example, if a flat sheet is thermoformed into a tray having dimensions of 10 inches wide by 12 inches long by 2 inches deep, the total top area will be 208 square inches (2(10x2)+2(12x2)+(10x12)) and the area footprint will be 120 square inches (10x12). Therefore, the area stretch ratio for this tray is 1.7 (208 / 120). Conventional polystyrene meat trays typically have a stretch ratio of about 1.5 to about 1.7.

[0105] In one embodiment or in combination with any of the embodiments mentioned herein, the cellulose ester foam tray thus can 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 (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.

[0106] Several trays with different area stretch ratios were formed to test the effect of the stretch ratio on the surface integrity of the tray. For all examples and measurements, Eastman CA-398-30 or Eastman FE700 (cellulose diacetate; CDA) were the resins. The degree of substitution (DS) was 2.52. The melting point was 230°C to 250°C, and the Tg was 189°C. The formulations were plasticized with triacetin (TA) at 15% and 20% loadings. Talc (ABT-1000) was used as a nucleating agent. Extruded foam sheets were prepared using a tandem extruder apparatus. A physical foaming agent (CO2 or pentane) and talc were mixed in a twin-screw extruder (ZE 30), and the melt was subsequently transferred to a single-screw extruder (KE 60). An annular die was used to extrude the foam sheet tube, after which the sheet was stretched on a calibrator cylinder and cut. The samples were thermoformed by heating to approximately 330°F (320°F to 360°F) and stretching the sheet into a mold at area draw ratios of 1.97, 1.59, and 1.41.

[0107] The surface integrity of trays with different plasticizer concentrations and area stretch ratios was tested by measuring water absorption using the water absorption test described above. Each tray was filled to the brim with water and allowed to equilibrate in a laboratory environment for different amounts of time: 1 hour, 2 hours, 4 hours, 8 hours, 18 hours, and 24 hours. After the set time, the water was drained, and the tray was gently wiped and weighed.

[0108] The surface integrity of the trays was also tested using the freeze-thaw test described above. Each tray was frozen in a freezer overnight (approximately 18 hours) and then thawed overnight (approximately 18 hours) in a laboratory environment. The weight of the tray was measured and compared to the water absorption before the freeze-thaw cycle.

[0109] Table 4 shows the area stretch ratios for 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 3 trays were measured to calculate the average and standard deviation.

[0110] Table 4.

[0111]

[0112] Table 5 shows the area draw ratios of three different tray molds used to thermoform two formulations (15 wt% and 20 wt% plasticizer). Water absorption was measured after overnight (approximately 18 hours). At least three trays were measured to calculate the average and standard deviation.

[0113] Table 5.

[0114]

[0115]

[0116] Table 6 shows the water absorption of trays with different area stretch ratios after exposure to water overnight and after freeze-thaw cycles.

[0117] Table 6.

[0118]

[0119] The tray made with an area stretch ratio of 1.97 had visible defects (cracks) throughout the base of the tray. However, the trays with an area stretch ratio < 1.6 had no such defects.

[0120] The above results show that cellulose ester trays thermoformed with an intact surface layer absorbed approximately 10% to 25% by weight of water, or approximately 15% to 20% by weight of water, with absorption reaching a maximum after approximately one day. Importantly, if the outer layer on the tray is cracked / damaged during thermoforming, the tray can absorb up to approximately 40% to 50% by weight of water, or more. Additionally, for trays with an intact surface layer, trays subjected to freeze-thaw cycles did not show significant changes in water absorption. However, water absorption of trays thermoformed with an area stretch ratio greater than 1.9 (which exhibited cracking) increased further after freeze-thaw cycles. Thus, the cellulose diacetate trays produced herein with an area stretch ratio of 1.97 absorbed significantly more (>2X) water than trays with area stretch ratios of 1.59 and 1.41.

[0121] In one embodiment or in combination with any of the embodiments mentioned herein, the cellulose ester foam tray may thus 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 (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 to have no visible cracks and increased water absorption. Thus, in some embodiments, when the foam tray is filled with water and allowed to equilibrate at room temperature for one hour, the foam tray has a weight gain of less than 10%, or less than 5%, according to a water absorption test. In some embodiments, when the foam tray is filled with water and allowed to equilibrate at room temperature for 18 hours, the foam tray has a weight gain of less than 25%, or less than 15%, according to a water absorption test. In some embodiments, when the foam tray is frozen for 18 hours, thawed for 18 hours, filled with water, and allowed to equilibrate at room temperature for 12 hours, the foam article has a weight gain of less than 30%, or less than 15%, according to a freeze-thaw test.

[0122] However, in one embodiment or in combination with any embodiment mentioned 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 formed from different compositions can improve the ductility of the sheet during thermoforming to avoid cracking of the tray under a higher stretch ratio. For example, a composition comprising a polymer and / or additive that adjusts the elasticity, melt strength and / or glass transition temperature (Tg) of the composition can produce a foam that can achieve an increased stretch ratio. Such polymers and additives include melt strength enhancers (such as those described herein) and components with a specific heat capacity of at least 2000 J / (kg K). Such polymers and additives may 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., MW 200-600) and mixtures thereof.

[0123] In one embodiment or in combination with any of the embodiments mentioned herein, the foam article (eg, a pallet) can have a density of less than 0.20 g / cm 3 , less than 0.18g / cm 3 , less than 0.15g / cm 3 , less than 0.12g / cm 3 , less than 0.10g / cm 3 , less than 0.08g / cm 3 , less than 0.06g / cm 3 , or less than 0.04g / cm 3 , or 0.04 to 0.8 g / cm 3 , 0.04 to 0.6 g / cm 3 , 0.04 to 0.5 g / cm 3 , 0.04 to 0.4 g / cm 3 , 0.04 to 0.3 g / cm 3 , 0.04 to 0.2 g / cm 3 , 0.04 to 0.15 g / cm 3 , 0.04 to 0.12 g / cm 3 , 0.04 to 0.10 g / cm 3 , 0.04 to 0.08 g / cm 3 , 0.04 to 0.06 g / cm 3 , 0.06 to 0.8 g / cm 3 , 0.06 to 0.6 g / cm 3 , 0.06 to 0.5 g / cm 3 , 0.06 to 0.4 g / cm 3 , 0.06 to 0.3 g / cm 3, 0.06 to 0.2 g / cm 3 , 0.06 to 0.15 g / cm 3 , 0.06 to 0.12 g / cm 3 , 0.06 to 0.10 g / cm 3 , 0.06 to 0.08 g / cm 3 , 0.08 to 0.8 g / cm 3 , 0.08 to 0.6 g / cm 3 , 0.08 to 0.5 g / cm 3 , 0.08 to 0.4 g / cm 3 , 0.08 to 0.3 g / cm 3 , 0.08 to 0.2 g / cm 3 , 0.08 to 0.15 g / cm 3 , 0.08 to 0.12 g / cm 3 , 0.08 to 0.10 g / cm 3 , 0.1 to 0.8 g / cm 3 , 0.1 to 0.6 g / cm 3 , 0.1 to 0.5 g / cm 3 , 0.1 to 0.4 g / cm 3 , 0.1 to 0.3 g / cm 3 , 0.1 to 0.2 g / cm 3 , 0.1 to 0.15 g / cm 3 , 0.1 to 0.12 g / cm 3 , 0.2 to 0.8 g / cm 3 , 0.2 to 0.6 g / cm 3 , 0.2 to 0.5 g / cm 3 , 0.2 to 0.4 g / cm 3 , 0.2 to 0.3 g / cm 3 , 0.3 to 0.6 g / cm 3 , 0.3 to 0.5 g / cm 3 , 0.3 to 0.4 g / cm 3 , 0.4 to 0.6 g / cm 3 , 0.4 to 0.5 g / cm 3 , or 0.5 to 0.6 g / cm 3 .

[0124] In one embodiment or in combination with any embodiment mentioned 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, or 300μm to 600μm, or 400μm to 600μm, or 500μm to 600μm, or 40μm to 550μm, or 40μm to 500μm, or 40μm to 450μm, or 40μm to 400μm, or 40μm to 350μm, or 40μm to 300μm, or 40μm to 250μm, or 40μm to 200μm, or 40μm to 150μm, or 40μm to 100μm.

[0125] Furthermore, it should be understood that because the foam article (eg, a pallet) is formed from the cellulose esters described herein, the foam article can include any of the components and / or additives of the cellulose ester-based materials described herein, as well as any resulting properties.

[0126] definition

[0127] It should be understood that the following is not intended to be an exhaustive list of defined terms. Additional definitions may be provided in the foregoing description, such as, for example, where the context accompanies the use of a defined term.

[0128] As used herein, the terms "a," "an," and "the" mean one or more than one.

[0129] As used herein, the terms "comprising," "comprises," and "comprise" are open transition words that are used to transition from an object recited before the term to one or more elements recited after the term, where the one or more elements listed after the transition word are not necessarily the only elements making up the object.

[0130] To be considered "compostable", a material must meet the following four criteria: (1) the material should pass the biodegradation requirement in a high temperature (58°C) test under controlled composting conditions according to ISO 14855-1 (2012), which corresponds to an absolute 90% biodegradation or a relative 90% biodegradation relative to a control polymer; (2) the material must achieve 90% disintegration when tested under aerobic composting conditions according to ISO 16929 (2013); (3) the tested material must meet all requirements for volatile solids, heavy metals and fluorine as specified in ASTM D6400 (2012), EN 13432 (2000) and ISO 17088 (2012); and (4) the material should not have a negative impact on plant growth.

[0131] As used herein, the term "biodegradable" generally refers to the biological transformation and consumption of organic molecules. Biodegradability is an inherent property of the material itself, and materials can exhibit varying degrees of biodegradability, depending on the specific conditions to which they are exposed. The term "disintegrable" refers to the tendency of a material to physically break down into smaller pieces when exposed to specific conditions. The degree of disintegration depends on the material itself and the physical size and configuration of the article being tested. Ecotoxicity measures the effect of a material on plant life and is determined according to procedures specified in standard test methods.

[0132] According to French norm NF T 51-800 and Australian standard AS 5810, to be considered "biodegradable" under home composting conditions, a material must show a total biodegradation of at least 90% (e.g., compared to the initial sample), or at least 90% of the maximum degradation of the appropriate reference material after both the reference and test articles have reached a plateau. The maximum test duration for biodegradation under home composting conditions is one year.

[0133] According to ASTM D6400 and ISO 17088, to be considered "biodegradable" under industrial composting conditions, at least 90% of the organic carbon in the entire article (or for each component present in an amount exceeding 1% by dry mass) must be converted into carbon dioxide at the end of the test period when compared to a control or absolute value. According to European Standard ED 13432 (2000), a material must show a total biodegradation of at least 90%, or at least 90% of the maximum degradation of a suitable reference material after both the reference article and the test article have reached a stationary phase. The maximum test duration for biodegradability under industrial composting conditions is 180 days.

[0134] according to To be considered "biodegradable" under soil composting conditions, materials must demonstrate a total biodegradation of at least 90% (e.g., compared to the initial sample) or a biodegradation of at least 90% of the maximum degradation of a suitable reference material after both the reference and test articles have reached a plateau. The maximum test duration for biodegradability under soil composting conditions is 2 years.

[0135] In one embodiment or in combination with any of the embodiments mentioned herein, the biodegradable cellulose acetate foam or article is industrially compostable or home compostable. In a subclass of this class, the foam or article is industrially compostable. In a sub-subclass of this subclass, the foam or article has a thickness of less than 6 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 3 mm. In a sub-subclass of this subclass, the article has a thickness of less than 1.1 mm. In a subclass of this class, the foam or article is home compostable. In a sub-subclass of this subclass, the foam or article has a thickness of less than 6 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 3 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 1.1 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 0.8 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 0.6 mm. In a sub-subclass of this subclass, the foam or article has a thickness of less than 0.4 mm.

[0136] In one embodiment or in combination with any of the embodiments mentioned herein, the foam or article has a thickness of 1 to 10 mm, 1 to 8 mm, 2 to 8 mm, 3 to 7 mm, 4 to 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 can have other larger sizes. For example, in some embodiments, the foam or article can have a thickness of 0.5 to 24 inches, 1 to 15 inches, or 3 to 12 inches.

[0137] In one embodiment or in combination with any of the embodiments mentioned herein, the foam sheet or article (e.g., tray) exhibits greater than 90% disintegration after 12 weeks according to the disintegration test protocol as described below, or in an alternative according to ISO 16929 (2013). In some other embodiments, the foam sheet and / or article (e.g., tray) prepared thereby may disintegrate 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% in no more than 12, or no more than 11, or no more than 10, or no more than 9, or no more than 8 weeks according to the disintegration test protocol or according to ISO 16929 (2013).

[0138] The test method for disintegration (referred to herein as the "disintegration test protocol") is based on ISO 16929 Plastics - Determination of the Degree of Disintegration of Plastics Materials under Defined Composting Conditions in a Pilot-Scale Test (2013). The foam sheet or article (e.g., a tray) is formed into a film having a thickness of about 0.25 mm (10 mils). Such a film can be formed by cutting or tearing the foam sheet or article (e.g., a tray). The film will typically have the same density as the original foam sheet or article (e.g., tray), such as not more than 0.20 g / cm 3 The samples in their final form were mixed with fresh artificial bioresidues. Oxygen concentration, temperature and humidity were regularly controlled. After 12 weeks, the resulting compost was screened and the amount of material (if any) remaining with fragments larger than 2 mm was determined.

[0139] As used herein, "area stretch ratio" refers to the total top surface area of ​​a thermoformed tray (i.e., including the base and rims) divided by the tray's area footprint (i.e., the two-dimensional area of ​​the tray when viewed from the top). For example, if a flat sheet is thermoformed into a tray having dimensions of 10 inches wide by 12 inches long by 2 inches deep, the total top area would be 208 square inches (2(10x2)+2(12x2)+(10x12)) and the area footprint would be 120 square inches (10x12). Therefore, the area stretch ratio for this tray is 1.7 (208 / 120).

[0140] Foam sheet manufacturing

[0141] Foam sheet samples were produced on a tandem foam production line manufactured by KraussMaffei. The extrusion line included a ZE30 twin-screw extruder as a primary extruder coupled to a KE60 single-screw extruder as a secondary cooling extruder. A loss-in-weight feeder was used to feed the formulated additives into the KE30 twin-screw feeder. A physical foaming agent was injected into the barrel of the primary extruder, extending downward from approximately 1 / 2 to 2 / 3 of the way along the barrel. The material was extruded from a 50mm annular die and conveyed on a sizing mandrel. The annular film was then cut and converted into a flat film in the tensioning / winding station portion of the rollers.

[0142] The material composition includes cellulose acetate resin (Eastman CA-398-30 or Eastman FE700) with 15 to 20 wt% triacetin and stabilizers (1 wt% epoxidized soybean oil, 0.15 wt% Doverphos S9228T). The material is injected with n-pentane as the blowing agent. Additional additives for the process include 1 wt% ABT 1000 talc and 1% chemical blowing agent. The material is extruded between 200°C and 220°C in the primary extruder and between 170°C and 190°C in the secondary extruder. The line output is 40 kg / h.

[0143] Thermoforming of sheets

[0144] The materials were thermoformed on a Hydrotrim laboratory thermoforming machine. The equipment features an oven with top and bottom heated plates, a timer to set the hold time in the oven, a vacuum to draw the material into the mold, and a plug assist for use with complex parts. The materials evaluated for this study were made using only the vacuum, with the top and bottom plates heated to 260°C.

[0145] Foam quality

[0146] The sample with 20 wt% triacetin had an average cell size of 247 microns, a thickness of 3.9 mm, and an initial density of 0.105 g / cc. The sample with 15 wt% triacetin had an average cell size of 285 microns, a thickness of 4.3 mm, and an initial density of 0.94 g / cc.

[0147] Evaluate

[0148] To perform the weight gain assessment, a tray was formed from each material. The initial weight of the tray was determined, and then the tray was filled ¾ of the way with water for the designated time increments. Once the allotted time had elapsed, the water was removed from the tray, blotted dry to remove surface moisture, and weighed. The weight change between the initial sample and the test sample was recorded. The % weight gain was calculated using the following formula:

[0149] Weight % increase = ((sample weight increase - initial weight increase) / initial weight increase)

[0150] Ideally, the sample would be formed with good part definition and minimal moisture gain.

[0151] Table 7. Effect of temperature.

[0152] Tray: Tray dimensions are 8.61" long by 6.56" wide by 1.25" deep with a stretch ratio of 1.3.

[0153]

[0154] *Calculated and extrapolated based on data measured at 1, 2, 4, 8 and 24 hours.

[0155] The data shows that there is a temperature effect for Examples 1-5, where the ideal temperature for minimal water absorption is between 170° C. and 200° C. This temperature range also applies to Examples 6-8.

[0156] Table 8.

[0157] Tray - Tray dimensions are 8.62" long by 6.56" wide by 1.50" deep with a stretch ratio of 1.4.

[0158]

[0159] *The temperature is too low and the tray is not fully formed.

[0160] **Calculated and extrapolated based on data measured at 1, 2, 4, 8 and 24 hours.

[0161] The data shows a temperature effect for Examples 9-13, where the ideal temperature for minimal water absorption is <200°C. Example 9 did not fully form at the target temperature. This temperature range also applies to Examples 14-17, as the lowest water absorption was also <200°C. Example 14 also did not fully form at the target temperature.

[0162] Table 9. Effect of extension ratio.

[0163] Multi-chamber cup-thick foam

[0164]

[0165] *Calculated and extrapolated based on data measured at 1, 2, 4, 8 and 24 hours.

[0166] The claims are not limited to the disclosed embodiments

[0167] The preferred forms of the present invention described above will be used as examples only and should not be used in a limiting sense to interpret the scope of the present invention. Those skilled in the art can easily modify the exemplary embodiments set forth above without departing from the spirit of the present invention.

[0168] The inventors hereby declare that it is their intention to determine and assess the fair and equitable scope of the invention under the doctrine of equivalents as it relates to any device that does not materially depart from the literal scope of the invention as set forth in the following claims.

Claims

1. A method of forming a foam article, the method comprising: (a) producing a foam sheet from a cellulose ester composition, wherein the cellulose ester composition comprises: (i) cellulose acetate, wherein the cellulose acetate has a degree of substitution ("DSAc") of acetyl substituents of 2.2 to 2.8, (ii) 10 to 25 weight percent of a plasticizer, wherein the plasticizer is triacetin, poly(ethylene glycol) having a molecular weight of 200-600, triethyl citrate, or a combination thereof, and (iii) 0.3% to 8% by weight of a blowing agent, each based on the total weight of the composition; as well as (b) thermoforming the foam sheet in a mold having a footprint (X) and a surface area less than 1.9X to form the foam article, wherein the thermoforming heats the foam sheet to a surface temperature of 170°C to 205°C, Wherein when the foam sheet is formed into a foam tray and the foam tray is filled with water and allowed to equilibrate at room temperature for 18 hours, the foam tray has a weight increase of less than 15% according to the water absorption test described in the specification.

2. The method of claim 1, wherein said producing (a) comprises extruding said composition through a compression mold to form an extrudate, and processing said extrudate to form said foam sheet.

3. The method of any one of claims 1 to 2, wherein the thermoforming heats the foam 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 at 15 to 20 wt%.

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

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

7. The method of claim 6, wherein the foam tray is configured to hold food items.

8. The method of claim 7, wherein the food item is an animal or plant protein, a vegetable or a fruit.

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

10. The method of 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 foam tray has a thickness of 1 to 10 mm.

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

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

14. A method according to any one of claims 6 to 13, wherein the foam tray is compostable.

15. The method of any one of claims 1 to 14, wherein the foam article is free of wrinkles.

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

17. The method of claim 16, wherein the additive is present at 1 wt% to 20 wt% based on the total weight of the composition.

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

19. The method of claim 18, wherein the melt strength enhancer comprises a functional ionic component.

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