WO2023220007A1

WO2023220007A1 - Sustainable foam

Info

Publication number: WO2023220007A1
Application number: PCT/US2023/021459
Authority: WO
Inventors: Drew V. Speer; Jingran YI; Eric ELLENBOGEN; Parimal Vadhar
Original assignee: Cryovac, Llc
Priority date: 2022-05-09
Filing date: 2023-05-09
Publication date: 2023-11-16

Abstract

A sustainable foam having 72-84 wt% cellulose acetate, 10-25 wt% plasticizer and 0.04-3 wt% of a chemical foaming agent. The foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505. The foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

Description

SUSTAINABLE FOAM

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims the benefit of U.S. Provisional Patent Application Serial No. 63/339,551, filed on May 9, 2022, and entitled “SUSTAINABLE FOAM.” The entire contents of this application are incorporated herein by reference.

BACKGROUND

[0002] The subject matter disclosed herein relates to sustainable foams. More particularly, the subject matter relates to low density foams having a small cell size in which the foam includes a cellulose acetate.

[0003] Polystyrene foams, including food trays made therefrom, are being banned in some regions. These foams are not widely collected or recycled. Foams contaminated with raw meats present additional difficulties in collecting and recycling.

[0004] Certain grades of cellulose acetate are known to be biodegradable and compostable. To form cellulose acetate-based foams, nucleating agents are used in combination with physical blowing agents. However, foams including certain nucleating agents, such as inert inorganic nucleating agent result in foams having higher densities, larger cell sizes or both. Furthermore, the presence of inert inorganic nucleating agent can be detrimental to being able to recycle or reuse foams.

[0005] The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION

[0006] A sustainable foam having 72-84 wt% cellulose acetate, 10-25 wt% plasticizer and 0.04-3 wt% of a chemical foaming agent. The foam having a density of less than any of 0 10, 0.08 or 0.06 g/cc as measured in accordance with ASTM DL505. The foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756. [0007] An advantage that may be realized in the practice of some disclosed embodiments of the use of a compostable and sustainable foam. The foam may be made into three- dimensional packaging articles.

[0008] In one exemplary embodiment, a foam is disclosed. The foam comprises 72-84 wt% cellulose acetate, 10-25 wt% plasticizer and 0.04-3 wt% of a chemical foaming agent. The foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM DI 505. The foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

[0009] In another exemplary embodiment, a method of making a foam is disclosed. The method comprises the steps of mixing a blend of 72-84 wt% cellulose acetate, 15-25 wt% of a plasticizer and 0.04-3 wt% of a chemical foaming agent, all wt% based on the total weight of the mixed blend. Heating the blend. Introducing a physical blowing agent to the blend. Extruding the blend and physical blowing agent to form a foam. The foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505. The foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

[0010] In another exemplary embodiment, a foam packaging article is disclosed. The foam packaging article comprises a comprises a foam formed into a three-dimensional packaging article and a product situated on the three-dimensional packaging article. The foam comprises 72-84 wt% cellulose acetate, 10-25 wt% plasticizer and 0.04-3 wt% of a chemical foaming agent. The foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM DI 505. The foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

[0011] This brief description of the invention is intended only to provide a brief overview of subject matter disclosed herein according to one or more illustrative embodiments, and does not serve as a guide to interpreting the claims or to define or limit the scope of the invention, which is defined only by the appended claims. This brief description is provided to introduce an illustrative selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of the invention. In the drawings, like numerals are used to indicate like parts throughout the various views. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which:

[0013] FIG. 1 is a block diagram showing an exemplary' process for making a foam according to embodiments;

[0014] FIG. 2 is an image of foam 3 as described herein;

[0015] FIG. 3 is a block diagram showing an exemplary' process for making a foam according to embodiments; and

[0016] FIG. 4 is a schematic cutaway view of an exemplary foam extruder according to embodiments herein.

DETAILED DESCRIPTION

[0017] In the United States standards defining test standards for labeling a product “biodegradable and compostable,” are conducted under ASTM D6400. This standard establishes a standard of industrial compostability. However, industrial compostability is performed at temperatures higher than are typically achieved in at home composting. Thus, products that satisfy this standard may not properly break down if consumers put them in their home compost heaps. The terms “biodegradable” and “compostable” currently have different standard in some jurisdictions. The term “biodegradable” generally refers to the biological conversion and consumption of organic molecules. Biodegradability is an intrinsic property of the material itself, and the material can exhibit different degrees of biodegradability, depending on the conditions (i.e. heat and pressure) to which the material is exposed.

[0018] For home consumers and composting the European Union has adopted EN 13432. EN 13432 requires that 90% of the product, by mass, is converted to CO2 within 6 months, and that after 3 months of composting and subsequent sifting through a 2 mm sieve no more than 10% residue, by mass, remains. As used herein the term “compostable” means a material that satisfies both (1) ASTM D-6400 and (2) EN 13432, the contents of both are incorporated herein by reference.

[0019] All references to (and incorporations by reference of) ASTM protocols are to the most-recently published ASTM procedure as of the priority (i.e., original) filing date of this patent application in the United States Patent Office unless stated otherwise.

[0020] Cellulose acetate composition

[0021] Cellulose acetate is an acetate ester derivative of cellulose. Cellulose can be obtained from many different sources such as, but not limited to wood pulp, cotton linters, plant fibers, and bacterial sources. Cellulose acetate is generally considered to be a nontoxic, non-irritant, and biodegradable material.

[0022] A method of producing cellulose acetates is esterification of cellulose. Cellulose is converted to a cellulose ester by mixing cellulose with acids, acid anhydrides, and catalysts. Hydrolysis process is then utilized to obtain cellulose acetates. The degree of esterification is expressed by acetyl value or as combined acetic acid. Fully acetylated cellulose acetate (cellulose triacetate) contains 44.8 percent combined acetyl or 62.5 percent as combined acetic acid. Cellulose triacetate is then hydrolyzed to give a cellulose acetate which contains approximately 39.4 percent combined acetyl or 55.0 percent combined acetic acid. In embodiments, the cellulose acetate has an acetyl content is between 36-44%. Acetyl content is measured according to ASTM D-817. Suitable cellulose acetate compositions are commercially available as CA398-30 from Eastman and CA398-10 available from Eastman.

[0023] In instances, cellulose acetate can be prepared by converting cellulose to a cellulose ester with reactants that are obtained from recycled materials, e.g., a recycled plastic content utilizing a syngas source. In embodiments, such reactants can be cellulose reactants that include organic acids and/or acid anhydrides used in the esterification or acylation reactions of the cellulose. In embodiments, the cellulose acetate is derived from a renewable source. For example, from wood or agriculture growth. In embodiments the cellulose acetate contains both recycled materials and is derived from a renewable source.

[0024] Cellulose acetate can have a major portion of biobased carbon content. In embodiments the cellulose acetate has a biobased content of at least any of 50%, 55%, 60% or 65% measured in accordance with ASTM D-6866. In embodiments, the cellulose acetate includes at least 10 wt%, 20 wt%, 30 wt%, 40 wt% or 50 wt% of recycled cellulose acetate. Recycled cellulose acetate may be recycled as part of a later processing scrap (such as skeleton recovery of thermoformed articles) or gathered from other sources. The recycled cellulose acetate can be ground, dried and reused along with, or instead of virgin cellulose acetate.

[0025] The cellulose acetate composition can include additional additives. Additional additives include carriers, fillers, plasticizers, stabilizers, waxes, compatibilizers, composability promoters, anti-oxidants, antifungal agents, colorants, anti-fogging agents, aging modifiers such as glycerol monostearate, anti-static, impact modifiers, antibacterial agents, flame retardants, processing aids, and combinations thereof. Such additional additives can be blended with and formed with the cellulose acetate material (e.g. as flake or pellet), or can be added as a separate component prior to extrusion.

[0026] Plasticizer

[0027] Plasticizers are used to improve processability of the cellulose acetate composition. Plasticizers can improve rheological, thermal, and mechanical properties. Plasticizer help the foam become thermoformable, reduces melt temperature (Tg of amorphous materials), or improves melt flow of the cellulose acetate.

[0028] The plasticizer may be formulated with the cellulose acetate or mixed into a blend prior to extrusion of the foam. The resin mixture may include the plasticizer as part of the cellulose acetate composition, the plasticizer may be added the extruder as a separate component, or both such that the plasticizer is distributed throughout the resin mixture in the extruder. In embodiments, the plasticizer is homogenously distributed throughout the resin mixture. [0029] Exemplary plasticizers include esters of saturated dibasic acids, esters of saturated polyhydric alcohols, fatty acid esters, low molecular weight polyethylene glycols and sulfonamide resins and more specifically a plasticizer selected from the group consisting of diethyl adipate, dicapryl adipate, dimethoxyethyl adipate, diethoxyethyl, dimethoxyethoxy adipate, triethyl citrate, tris-n-butyl citrate, acetyl triethyl citrate, glycerol monoacetate, glycerol diacetate, glycerol triacetate, (ethoxycarbonyl) methyl methyl phthalate, bis(2 methoxyethyl) phthalate, diethylene glycol diacetate, triethylene glycol diacetate, glycerol triisopropionate, ethylene glycol dipropionate, diethylene glycol dipropionate, dimethyl sebacate, diethyl succinate, dibutyl tartrate, polyethylene glycol (molecular weights 600 Daltons or below), isophthalic propylene glycol polyester, polyalkylene glycols and blends thereof.

[0030] In embodiments the plasticizer is a food-compliant plasticizer. Food-compliant means compliant with applicable food additive and/or food contact regulations where the plasticizer is cleared for use or recognized as safe by at least one (national or regional) food safety regulatory agency (or organization), for example listed in the 21 CFR Food Additive Regulations or otherwise Generally Recognized as Safe (GRAS) by the US FDA.

[0031] Plasticizer in included into the cellulose acetate composition such that composition will flow, can be processed and can be thermoformed into three dimensional objects. The cellulose acetate composition being either the dry cellulose acetate material with plasticizer contained therein as a flake or pellet, or as a mixture of cellulose acetate material with plasticizer as a separated component. In embodiments, the plasticizer is present in the cellulose acetate composition an amount from any of 10 to 25 wt%; or 15 to 25 wt%, or 13- 20 wt% based on the total weight of the cellulose acetate composition.

[0032] In embodiments the cellulose acetate, the plasticizer or both include compostable components. In embodiments, the plasticizer includes triacetin, triethyl citrate, or polyethylene glycol.

[0033] The plasticizer can include additional additives. Additional additives include carriers, fillers, stabilizers, waxes, compatibilizers, cellulose acetate, composability promoters, anti-oxidants, antifungal agents, colorants, anti-fogging agents, aging modifiers such as glycerol monostearate, anti-static, impact modifiers, antibacterial agents, flame retardants, processing aids, and combinations thereof. [0034] Chemical foaming agent

[0035] To form a foam the cellulose acetate composition is mixed with a chemical foaming agent. Chemical foaming agents refer to those compositions which when heated, decompose or react at a certain temperature to form a gas.

[0036] Chemical foaming agents are a class of foaming agents that are often utilized in solid (normally as powder, flake, or pellets) or as liquid. The chemical foaming agent is normally solid or liquid at room temperature. Upon heating beyond the decomposition temperature, the chemical foaming agent decomposes and releasing a gas into a mixture. Heating a blend allows the base matenal to flow and the chemical foaming agent to release gas. The gas forms bubbles or cells in the melt. The gas expands, and in turn causes the mixture to expand. On cooling and solidifying, the cell structure remains. Different chemical foaming agent release gas at different rates and temperatures, and the choice of chemical foaming agent depends on the processing conditions, type of foam material, and the desired phy sical properties of the foam. Chemical foaming agents tend to be dependent upon the temperature. Unlike physical blowing agents, chemical foaming agents can be added to a solid mixture before heating. In embodiments, the chemical foaming agent has a decomposition temperature of greater than any of 80°C, 100°C, 120°C or 140°C.

[0037] The cellulose acetate composition being at least cellulose acetate and 10-25 wt% plasticizer. Amounts of from 0.04 to 3 wt% of a chemical foaming agent is mixed with the cellulose acetate. The chemical foaming agent may be introduced as a masterbatch with a carrier resin and other additives commonly used. In embodiments the chemical foaming agent is an endothermic or exothermic chemical foaming agent. In embodiments the chemical foaming agent includes sodium bicarbonate, citric acid, or both.

[0038] Chemical foaming agents are a class of foaming agents that are often utilized in solid (normally as powder, flake, or pellets) or as liquid. The chemical foaming agent is normally solid or liquid at room temperature. Upon heating the chemical foaming agent decomposes and releasing a gas into a mixture. Heating a blend allows the base material to flow and the chemical foaming agent to release gas. The gas forms bubbles or cells in the melt. The gas expands, and in turn causes the mixture to expand. On cooling and solidifying, the cell structure remains. Different chemical foaming agent release gas at different rates and temperatures, and the choice of chemical foaming agent depends on the processing conditions, type of foam material, and the desired physical properties of the foam. Unlike physical blowing agents, chemical foaming agents can be added to a solid mixture before heating.

[0039] In embodiments the chemical foaming agent is 30-70 wt% sodium bicarbonate, citric acid, or both. The chemical foaming agent includes 10-30, 15-25 or 19-21 wt% sodium bicarbonate. The chemical foaming agent further includes 20-40, 25-35 or 29-31 wt% citnc acid. In embodiments the chemical foaming agent includes 10-30, 15-25 or 19-21 wt% sodium bicarbonate and 20-40, 25-35 or 29-31 wt% citric acid.

[0040] Sodium bicarbonate starts to decompose at around 160 °C, while citnc acid starts decomposing at around 210 °C. By utilizing a blend of sodium bicarbonate and citric acid, about 120 cm³/g of gas is produced.

[0041] In embodiments the chemical foaming agent further comprises a carrier resm, additives, nucleating agents or additional chemical foaming agents. Polyethy lene and polystyrene are known carrier resins. In embodiments the chemical foaming agent includes a biopolymer as a carrier resin. Biopolymer carrier resins include BioPBS FD92PM available from Mitsubishi Chemical and CAPA 6500 a poly caprolactone available from Ingevity. In an embodiment, the biopolymer is compostable as defined herein.

[0042] In embodiments the chemical foaming agent includes an alkaline earth metal combined with an acid such as citric acid or tartaric acid. In embodiments the chemical foaming agent further includes calcium carbonate.

[0043] The chemical foaming agent may further comprise nucleating agents. Nucleating agents produce more cells in the foam than would be produced without the nucleating agent. The nucleating agent selected from the group consisting of molecular sieve materials, titanium dioxide, perlite, and limestone. However, the inclusion of certain nucleating agents can be problematic in reusing and recycling foams without additional process steps. In certain embodiments, the mixture and the resulting foam includes less than any of 1.0 wt%, 0.8 wt%, 0.6 wt%, 0.4 wt%. 0.2 wt%. 0.1 wt%, 0.05 wt% or substantially no inert inorganic nucleating agent. As used herein, inert inorganic nucleating agents include molecular sieve materials, titanium dioxide, perlite, limestone, talc, silica, calcium carbonate, calcium fluoride, boron nitride, aluminum magnesium hydroxide, silica, silica gel, functionalized silica nanoparticles, silicon dioxide, titanium carbide, zirconium carbide, tungsten sulfide, zinc oxide, bentonite, or nucleating agents comprises a magnesium silicate, a silicon dioxide, a magnesium oxide, or combinations thereof.

[0044] In embodiments the chemical foaming agent include additional additives. Additional additives include carriers, fillers, stabilizers, waxes, compatibilizers, cellulose acetate, composability promoters, anti-oxidants, antifungal agents, colorants, anti-fogging agents, aging modifiers such as glycerol monostearate, anti-static, plasticizer, impact modifiers, antibacterial agents, flame retardants, processing aids, and combinations thereof.

[0045] Physical blowing agent

[0046] To produce a foam a physical blowing agent is introduced to the heated mixture of the cellulose acetate composition and chemical foaming agent. The physical blowing agent generates enough pressure to force the melt through an extruder. Upon introduction of the physical blowing agent the melt is cooled.

[0047] Physical blowing agents include, but are not limited to CO2, N2, supercritical CO2, unbranched or branched (C2- 6)alkane, propane, isobutane, N-butane, ethanol, cyclopentane or any combination thereof. The physical blowing agent is introduced into the mixture at a rate of less than 10 wt%, 9 wt%, 8 wt%, 7 wt%, 6 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt% based on the total weight of the mixture.

[0048] Forming a foam

[0049] A cellulose acetate composition and a plasticizer are provided, mixed and heated in an extruder. Screw type extruders are useful for introducing, mixing and heating materials. Screw type extruders include single screw, multiple single screw extruders in tandem, corotating twin screw, counter-rotating twin screw, parallel twin screw and conical twin screw. Screw type extruders utilize a pressure profile along the length of the screw to prevent blowing agent from backing up and exiting through upstream. Twin screw extruders may be utilized for improved heat transfer, shear mixing and pressure profile control.

[0050] The cellulose acetate composition may include the plasticizer as part of the composition, plasticizer may be added the extruder, or both such that the plasticizer is homogeneously distributed throughout the mixture. [0051] A chemical foaming agent is added to the mixture. The chemical foaming agent may be included in the main feed line, included with the cellulose acetate mixture, or may be added to separate feed port. The chemical foaming agent including sodium bicarbonate, citric acid or both. A physical blowing agent is introduced to the heated mixture generating sufficient pressure to force the melted mixture through an extruder. The physical blowing agent cools the melted blend during the process. A foam composition exits the extruder, which in embodiments is through a die. In embodiments, the foam composition includes less than 0.1 wt%, 0.05 wt%, 0.01 wt% or substantially inert inorganic nucleating agent.

[0052] The extruded foam has a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D-1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

[0053] In embodiments, the foam is extruded as a cylindrical rod. The cylindrical rod may be slit and then laid flat to form a laid flat sheet of the extruded foam. In other embodiments, the foam is extruded through an annular or sheet die. In embodiments, the foam sheet is then wound up and stored for later processing. The storage process ages the foam allowing for expansion to complete and allowing for foaming and blowing agents to dissipate. In embodiments, winding up the sheet is optional.

[0054] The foam sheet may then be sent to a thermoforming process. The thermoforming process utilizes heat and pressure to form the sheet into a three-dimensional packaging article. Tooling may be utilized to form the sheet into the desired shape. In an embodiment, the three-dimensional packaging article is a tray. In an embodiment the three- dimensional packaging article comprises a flange, a cavity and at least one wall. In embodiments foamed trays are manufactured in a two-step process. In a first step, foamed sheets are obtained in an extrusion process. In the second step, the foamed sheets are thermoformed into the desired shape. In another embodiment, these steps are combined into a single process.

[0055] Turning now to Fig. 1 is an exemplary embodiment of making a foam. The cellulose acetate composition and plasticizer are dried prior mixing. It is understood that the cellulose acetate and plasticizer may be integrated into the same material or be different components. The cellulose acetate and plasticizer are then mixed with a chemical foaming agent. This may be in a separate mixer or as part an extruder, for example a screw-type extruder. Once in the extruder, the materials melt and flow through the extruder. The heat activates the chemical foaming agent to begin the foaming process. Physical blowing agent is introduced into the extruder and a foam rod exits the extruder die. The foam may continue to expand once it leaves the die. To prevent over expansion, the foam should cool relatively quickly near the die exit.

[0056] Turning now to Fig. 3 is another exemplary embodiment of making a foam. The resin includes a cellulose acetate composition and plasticizer which are dried prior mixing. It is understood that the cellulose acetate and plasticizer may be integrated into the same material or be different components. The drying may not be required depending on the initial resin condition. The cellulose acetate and plasticizer are then mixed with a chemical foaming agent. This may be in a separate mixer or as part an extruder, for example a screw-type extruder. Once in the extruder, the materials melt and flow through the extruder. As the materials are heated in the extruder, the chemical foaming agent is activated to begin the foaming process. One or more physical blowing agents are introduced into the extruder and a foam exits the extruder die, such as a sheet or annular die. The foam may continue to expand once it leaves the die. To prevent over expansion, the foam should cool relatively quickly near the die exit. In the instance of an annular die, the annular foam may be pulled onto a cooling mandrel which cools and shapes the foam.

[0057] Referring now to FIG. 4, a schematic cutaway view of an exemplary foam extruder is shown. Resin 101 is fed into the extruder 110 via hopper 112. The resin 101 includes cellulose acetate along with plasticizer. The plasticizer may be added as a separate component or may be integrated with the cellulose acetate material as a pellet, flake or granular material. The resin may further include chemical foaming agent or other additives such as carriers, fillers, stabilizers, waxes, compatibilizers, composability promoters, antioxidants, antifungal agents, colorants, pigments, anti-fogging agents, aging modifiers such as glycerol monostearate, anti-static, impact modifiers, antibacterial agents, flame retardants, processing aids, and combinations thereof. Like the plasticizer, such additional additives can be blended with and formed with the cellulose acetate material, or can be added as a separate component to the mixture. While FIG. 4 depicts all of the resin 101 being loaded in a single hopper 112, it is understood that multiple hoppers may be utilized. And the resin may be split based on volume or composition. For example, the cellulose acetate and plasticizer may be loaded in a first hopper at a first point along the extruder, while a chemical foaming agent is loaded in at a second point along the extruder and further additives are loaded at a third point along the extruder. Alternatively, all materials can be mixed and loaded along multiple hoppers and loaded along multiple points along the extruder.

[0058] After the resin 101 enters the extruder, the material is heated and forced through the extruder 110 toward the mixing portion 113. The extruder 110 is depicted as a single screw type extruder. Other extruder types, such multiple single screw extruders in tandem, corotating twin screw, counter-rotating twin screw, parallel twin screw and conical twin screw may be employed. One or more heaters (not shown) are employed to raise the temperature of the resin. As the resin melts and reaches the decomposition temperature of the chemical foaming agent the chemical foaming agent begins to produce gas causing the melted resin to foam.

[0059] In embodiments, the resin can include additional additives. Additional additives include carriers, fillers, plasticizers, stabilizers, waxes, compatibilizers, composability promoters, anti-oxidants, antifungal agents, colorants, anti-fogging agents, aging modifiers such as glycerol monostearate, anti-static, impact modifiers, antibacterial agents, flame retardants, processing aids, and combinations thereof. Such additional additives can be blended with and formed with the resin material (e.g. as flake or pellet), or can be added as a separate component prior to extrusion. The total addition of additives can by 10% by weight as compared to the resin mixture.

[0060] In addition to chemical foaming agent, a blowing agent 102 is introduced into the mixing portion 113 of the extruder 110. As the physical blowing agents enter the extruder, the melted resin begins to cool and expand. The extruder 110 maintains a pressure profile along the length of the screw to prevent blowing agent from backing up and exiting through upstream points such as hopper 112. The pressure inside the extruder aids in moving the melted resin and blowing agents toward and through the die 130. To aid in controlling the expansion process, the melted resin and physical blowing agents move along a colling portion 116. The cooling portion aids in reducing overexpansion prior to the melt existing the die. The melted resin is further mixed in a mixer 120. In an embodiment the mixer is a static mixer. While mixer 120 is depicted as being located after the cooling portion 116, it is understood that in embodiments, the mixer 120 is placed before the cooling portion 116. In another embodiment, a first mixer is placed before the cooling portion 116 and a second mixer is placed after the cooling portion 116. In embodiments utilizing multiple mixers, the mixers may be the same or different mixing elements.

[0061] Examples

[0062] Table 1 Materials used in examples

[0063] Dried and cooled materials were provided to a screw type extruder. The material is dried at 60°C for at least 6 hours prior to processing. CAI and CFA were introduced in the main feed line. NA was added post melt. Physical blowing agent was introduced downstream of the NA and a foam was extruded from the die nozzle of a round die extruder to form a cylindrical shaped foam sample. Foams were made in a corotating twin screw type extruder in the composition as set forth in Table 2.

[0064] Table 2

[0065] It is noted that the amount of CFA included in Table 2 includes the carrier resin. The effective amount of chemical foaming agent being about 50% of the composition. The properties of the foams were measured and reported in Table 3 below

[0066] Table 3

[0067] Foams 1 and 2 had processing issues as noted in Table 3. Foam 3 continued to extrude foam for about 1 hour with no issues. It was surprising to see that removing talc from the formulation and only using the chemical foaming agent with the physical blowing agent would provide vastly superior density and cell size. Fig. 2 depicts an image of Foam 3.

[0068] Further foam compositions were made and extruded through an annular die such as described and depicted in reference to Figs. 3-4. The resulting foam properties and compositions shown in Tables 4 and 5. [0069] Table 4

[0070] Table 5

[0071] The foams identified in Table 6 where mixed and extruded through an annular die as described above in reference to Figs. 3-4. The extruder having a pressure of 4-5 MPa and maximum temperature from 210°C to 230°C and an exit temp is from 180°C to 195°C.

[0072] Table 6

[0073] Physical blowing agent level reported in Table 6 is stated as wt% based on the total weight of mixture excluding the physical blowing agent itself.

[0074] The foams of table 6 were conditioned for at least 1 day. Density measurements were made after thermoforming the foam. Table 7 reports properties of foams.

[0075] Table 7

[0076] As seen in Table 7, the foams described above exhibited low density measured in accordance with ASTM D-1505. Cell size was measured in accordance with ASTM D-3756.

[0077] Embodiment A. A foam comprising: a. 72-84 wt% cellulose acetate b. 10-25 wt% plasticizer c. 0.04-3 wt% of a chemical foaming agent the foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756. [0078] B. The foam of embodiment A wherein the cellulose acetate has a bio content of at least 50%, 55%, 60% or 65% measured in accordance with ASTM D-6866.

[0079] C. The foam of embodiments A-B wherein the cellulose acetate has an acetyl content of between 36-44%.

[0080] D. The foam of embodiments A-C wherein the foam comprises less than any of 1.0 wt%, 0.8 wt%, 0.6 wt%, 0.4 wt%. 0.2 wt%. 0.1 wt%, 0.05 wt% or substantially no inert inorganic nucleating agent.

[0081] E. The foam of embodiments A-D wherein the chemical foaming agent comprises any of 10-30, 15-25 or 19-21 wt% of sodium bicarbonate, measured based on the total weigh of the chemical foaming agent.

[0082] F. The foam of embodiments A-E wherein the chemical foaming agent further comprises any of 20-40, 25-35 or 29-31 wt% citric acid, measured based on the total weigh of the chemical foaming agent.

[0083] G. The foam of embodiments A-F further comprising calcium carbonate.

[0084] H. The foam of embodiments A-G further comprising a physical blowing agent.

[0085] I The foam of embodiments A-H wherein the foam is compostable as measured by one, the other or both of ASTM D-6400 and EN 13432.

[0086] J. A method for making a foam comprising the steps of: a. mixing a blend of 72-84 wt% cellulose acetate, 15-25 wt% of a plasticizer and 0.04- 3 wt% of a chemical foaming agent, all wt% based on the total weight of the mixed blend; b. heating the blend; c. introducing a physical blowing agent to the blend; d. extruding the blend and physical blowing agent to form a foam; the foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

[0087] K. The method of embodiment J wherein the chemical foaming agent comprises (i) any of 10-30, 15-25 or 19-21 wt% of sodium bicarbonate, measured based on the total weigh of the chemical foaming agent and (ii) any of 20-40, 25-35 or 29-31 wt% citric acid, measured based on the total weigh of the chemical foaming agent.

[0088] L. The method of embodiments J-K wherein the physical blowing agent is selected from the group consisting of carbon dioxide, supercritical carbon dioxide, ethanol, nitrogen, propane, isobutane and cyclopentane or combination thereof.

[0089] M. The method of embodiments J-L wherein the step of mixing is performed by a screw type extruder.

[0090] N. The method of embodiments J-M wherein the blend is heated to at least 165, 170, 175 or 180 °C.

[0091] O. The method of embodiments J-N wherein the foam is extruded as a cylindrical rod.

[0092] P. The method of embodiments O further comprising the steps of slitting the foam cylindrical rod and forming a laid flat sheet. [0093] Q. The method of embodiments P further comprising the step of thermoforming the laid flat sheet into a three-dimensional packaging article

[0094] R. The method of embodiments Q wherein the three-dimensional packaging article comprises a flange, a cavity and at least one wall.

[0095] S. The method of embodiments J-R wherein the foam comprises less than any of 0.1 wt%, 0.05 wt%, 0.01 wt% or substantially no talc-type nucleating agent.

[0096] T. A foam packaging article comprising: a. a foam formed into a three-dimensional packaging article, the foam comprising: i. 72-84 wt% cellulose acetate ii. 10-25 wt% plasticizer iii. 0.04-3 wt% of a chemical foaming agent (or define in amount of sodium bicarbonate the foam having a density of less than any of 0. 10, 0.08 or 0.06 g/cc as measured in accordance with ASTM DI 505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756 in any of the MD, TD or thickness; b. a product situated on the three-dimensional packaging article.

[0097] This written description uses examples to disclose the invention and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

What is claimed is:

1. A foam comprising: a. 72-84 wt% cellulose acetate; b. 10-25 wt% plasticizer; and c. 0.04-3 wt% of a chemical foaming agent; the foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756.

2. The foam of claim 1 wherein the cellulose acetate has a bio content of at least 50%, 55%, 60% or 65% measured in accordance with ASTM D-6866.

3. The foam of claim 1 wherein the cellulose acetate has an acetyl content of between 36-44%.

4. The foam of claim 1 wherein the foam comprises less than any of 1.0 wt%, 0.8 wt%, 0.6 wt%, 0.4 wt%. 0.2 wt%. 0.1 wt%, 0.05 wt% or substantially no inert inorganic nucleating agent.

5. The foam of claim 1 wherein the chemical foaming agent comprises any of 10-30, 15-25 or 19-21 wt% of sodium bicarbonate, measured based on the total weigh of the chemical foaming agent.

6. The foam of claim 1 wherein the chemical foaming agent further comprises any of 20-40, 25-35 or 29-31 wt% citric acid, measured based on the total weigh of the chemical foaming agent.

7. The foam of claim 1 further comprising calcium carbonate.

8. The foam of claim 1 further comprising a physical blowing agent.

9. The foam of claim 1 wherein the foam is compostable as measured by one, the other or both of ASTM D-6400 and EN 13432. A method for making a foam comprising the steps of: a. mixing a blend of 72-84 wt% cellulose acetate, 15-25 wt% of a plasticizer and 0.04-3 wt% of a chemical foaming agent, all wt% based on the total weight of the mixed blend; b. heating the blend; c. introducing a physical blowing agent to the blend; and d. extruding the blend and physical blowing agent to form a foam; the foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756. The method of claim 10 wherein the chemical foaming agent comprises (i) any of 10-30, 15-25 or 19-21 wt% of sodium bicarbonate, measured based on the total weigh of the chemical foaming agent and (ii) any of 20-40, 25-35 or 29-

31 wt% citric acid, measured based on the total weigh of the chemical foaming agent. The method of claim 10 wherein the physical blowing agent is selected from the group consisting of carbon dioxide, supercritical carbon dioxide, nitrogen, ethanol, propane, isobutane and cyclopentane or combination thereof. The method of claim 10 wherein the step of mixing is performed by a screw type extruder. The method of claim 10 wherein the blend is heated to at least 165, 170, 175 or 180 °C. The method of claim 10 wherein the foam is extruded as a cylindrical rod. The method of claim 15 further comprising the steps of slitting the foam cylindrical rod and forming a laid flat sheet. The method of claim 16 further comprising the step of thermoforming the laid flat sheet into a three-dimensional packaging article. The method of claim 17 wherein the three-dimensional packaging article comprises a flange, a cavity and at least one wall. The method of claim 10 wherein the foam comprises less than any of 0.1 wt%, 0.05 wt%, 0.01 wt% or substantially no talc-type nucleating agent. A foam packaging article comprising: a. a foam fonned into a three-dimensional packaging article, the foam comprising: i. 72-84 wt% cellulose acetate; ii. 10-25 wt% plasticizer; and iii. 0.04-3 wt% of a chemical foaming agent (or define in amount of sodium bicarbonate; the foam having a density of less than any of 0.10, 0.08 or 0.06 g/cc as measured in accordance with ASTM D1505; the foam having an average cell size of less than any of the following 300, 250, 200, 150, 120, 100, or 80 microns in accordance with ASTM D-3756; b. a product situated on the three-dimensional packaging article.