Biodegradable, industrially compostable and recyclable injection-molded microcellular flexible foams

Abstract

To disclose a process for manufacturing a recyclable injection-molded microcellular foam for use in a footwear component, a seating component, a protective gear component, and a watersport accessory.SOLUTION: A process includes the steps of: providing a thermoplastic polymer containing at least one monomer derived from depolymerized post-consumer plastic; and inserting a fluid into a barrel of a molding apparatus. The fluid is introduced under a temperature and pressure condition to produce a super critical fluid. The process further includes: mixing the thermoplastic polymer and super critical fluid so as to create a single-phase solution; and injecting the single-phase solution into a mold of an injection molding machine under gas counter pressure. The process further includes foaming the single-phase solution by controlling the heat and temperature conditions within the mold.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 853,805, entitled "RECYCLABLE AND CHEMICAL-FREE INJECTION MOLDED MICROCELLULAR FLEXIBLE FOAMS, AND A METHOD OF MANUFACTURING THE SAME," filed May 29, 2019, and entitled "BIODEGRADABLE AND INDUSTRIALLY COMPOSTABLE INJECTION MOLDED MICROCELLULAR FLEXIBLE FOAMS, AND A METHOD OF MANUFACTURING THE SAME," filed May 21, 2019. Patent application Ser. No. 16 / 418,968 entitled "BIODEGRADABLE AND INDUSTRIALLY COMPOSTABLE INJECTION" This application is a continuation-in-part of U.S. Provisional Patent Application No. 62 / 674,544, filed May 21, 2018, entitled "MOLDED MICROCELLULAR FLEXIBLE FOAMS, AND A METHOD OF MANUFACTURING THE SAME," which claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 674,544, filed May 21, 2018, the entire disclosures of which are incorporated herein by reference in their entirety for all purposes. [Background technology]

[0002] The present disclosure relates to processes for injection-molded microcellular foaming of various flexible foam compositions from recyclable or biodegradable, industrially compostable, bio-based thermoplastic polymers for use, for example, in footwear components, seating components, protective gear components, and water sports accessories.

[0003] Decomposition through composting is an important process for regenerating resources used in the production of industrial products. However, when those industrial products contain foam, decomposition can be problematic. In particular, there are several disadvantages to previously known methods of flexible foam production. For example, such disadvantages include the selection and use of non-renewable polymers, chemical blowing agents, and chemical additives used in the foam manufacturing industry and in the inherent processing procedures, which are typically not biodegradable and are generally considered to be bad for the environment. This lack of biodegradation means that many conventional flexible foam materials and the products they are included in end up in landfills for periods ranging from decades to centuries.

[0004] This is also a problem because the overuse of landfills in today's world has direct negative impacts on both the environment and the economy. For example, landfills are the third largest source of methane emissions in the United States. Furthermore, the non-biodegradable polymers and chemicals used in conventional flexible foams are particularly derived from non-renewable resources.

[0005] These materials are not naturally renewable like bio-based raw materials, and therefore, their creation alone is a net loss to the environment because they are often unsustainably obtained, used, and then discarded. Furthermore, even if renewable polymers are selected for use in conventionally known methods of flexible foam production, the chemical blowing agents and crosslinking of these methods can contaminate the renewable polymer with additives that are not biodegradable or compostable, thus making it a zero-sum gain. Furthermore, crosslinking of biopolymers can also prevent suitable end-of-life solutions for biodegradation or composting because the precursor parts cannot be separated, thus creating more waste. This leads to more material going to landfills.

[0006] Therefore, composting and recycling are important processes in providing a renewable and sustainable future, but their integration in manufacturing is very limited. However, making manufactured materials compostable would be extremely beneficial, for example, to the environment. For example, composting and biodegradation of flexible foam materials creates waste disposal opportunities, which represent net benefits to the environment and the economy. For example, composting these materials would make it possible to reduce the overall amount of waste sent to landfills and mass incinerators.

[0007] In addition to reducing waste, the composting process will also produce usable products that are rich in nutrients and can be used to improve poor soil to grow food or to fertilize gardens. Thus, the very concept of composting and biodegradation of flexible foams, however novel, can revolutionize the entire value chain while following the principles of the so-called circular economy. There are two typical types of composting: industrial composting and home composting. Both of these composting methods have advantages and disadvantages.

[0008] Industrial composting is a type of large-scale composting designed to handle very large volumes of organic waste. It is carried out in large-scale facilities at temperatures of 50°C to 60°C. Home composting is a type of composting that handles organic waste from a single household. Specifically, home composting refers to composting at relatively low temperatures, such as those found in backyard compost piles, hence the "home" in the name. In contrast to industrial composting, home composting involves the low-temperature aerobic decomposition of organic materials or waste, such as yard waste, food scraps, wood waste, cardboard, and paper. The volumes processed in home composting are significantly smaller than in industrial composting, and the compost is usually used in private gardens. This process is typically carried out in small-scale composters and piles. In this method, temperatures typically range from psychrophilic (0-20°C) to mesophilic (20-45°C) (discussed below). Therefore, although different technologies exist, the general process is the same: active composting, followed by a controlled process of maturation.

[0009] The active composting phase typically lasts at least 21 days. Under these conditions, microorganisms grow on the organic waste, breaking it down into CO2 and water, which they use as nutrients. During composting, the organic waste accumulates in a pile, resulting in the release of some of the composting energy as heat. As the temperature of the compost pile increases, the microbial population shifts; microorganisms adapted to ambient temperatures, such as mesophiles, cease their activity, die off, and are replaced by microorganisms adapted to high temperatures, such as thermophiles. For sanitation purposes, in home composting, temperatures must be maintained above 60°C for at least a week to eliminate pathogenic microorganisms. In contrast, the maturation phase of industrial composting slows the rate of decomposition to a consistent rate, and compost matures at temperatures in the lower mesophilic range, below 40°C.

[0010] A key issue with industrial composting is that input materials must be properly located to be effectively processed. Logistical challenges pose a hurdle in that proper collection, sorting, and transportation to industrial composting facilities are required. The combined composting and recycling diversion rate in the United States is approximately 35%, indicating that society still has a long way to go before the majority of its infrastructure has "closed the loop" on waste diversion. One way to overcome this shortfall is to better educate end users and establish local networks of take-back schemes that feed into larger take-back schemes. The goal is to develop convenience and reach enough that industrial composting becomes the norm and a constant presence in everyday life.

[0011] Similarly, a common disadvantage of home composting is the amount of effort involved. All of the required compost-raw materials must be transported and / or transferred to the compost pile. Once the compost pile becomes large enough to begin producing energy, and therefore heat, decomposition must begin to occur more quickly and completely, which can be very arduous work. Once the organic matter has sufficiently decomposed, the home compost must be transported for use in soil improvement. Another drawback of home composting is the limited amount of usable compost that the average person can produce in a home setting. The limited amount of compost produced potentially goes to limited use, thus potentially reducing the average person's motivation to undertake the effort of home composting.

[0012] Because of these drawbacks, manufacturers have traditionally avoided using raw materials and precursor components that have the potential to biodegrade or compost. Additionally, this has traditionally been avoided because the required technical performance characteristics of these materials are often inferior to those of traditional non-biodegradable, non-compostable varieties. For example, a limiting factor for some, but not all, compostable precursor components may be their tendency to decompose and / or deteriorate before the end of the product's useful life. One example of this is UV-functionalized products, whereby biodegradable and compostable precursors are attacked and weakened by repeated sunlight exposure, ultimately resulting in product failure sooner than the end user can immediately dispose of the product.

[0013] In the context of plastics, thermoplastics, and other products made using fossil fuels, recycling traditionally involves mechanically shredding the manufactured product, melting the shredded contents, and then pelletizing the resulting material for later use in manufacturing. While recycling reduces the need for fossil fuels and diverts products from landfills, recycling can result in a loss of quality in the recycled polymer as a result of contamination or the addition of impurities to the raw materials, and most plastic and thermoplastic products can only be recycled a limited number of times. Furthermore, the chemical blowing agents, crosslinked polymers, and chemical additives used in the production of conventional flexible foams result in an end product that cannot be broken down into its constituent polymers for later use in the production of recycled products. As a result, conventionally produced flexible foam products are not recyclable when the product reaches the end of its usable life.

[0014] In addition, current concerns for modern manufacturing are to be net neutral with respect to emissions and disposal, sustainable with respect to the materials used in the manufacturing process, and renewable with respect to the end of life of the product and its materials, thus net neutral with respect to, for example, CO2 emissions. Additionally, compostability of the final product has become important in selecting appropriate materials for use in the manufacture of consumer goods products.

[0015] As a result, a key driver for the present manufacturing process disclosed herein is for manufacturers to produce an environmentally sound end product compared to more traditional manufacturing processes currently in existence, and therefore it is useful to carefully consider the materials used in the manufacture of said end product and balance this against the lifespan of the intended use of the product. One example of a challenging product in whose manufacture these concerns should be addressed, but are not, is a standard manufactured product that employs foam, such as in the manufacture of cushioning for furniture, and / or foam products, such as for the manufacture of running shoes.

[0016] For example, running shoes are highly technical products that are subject to repeated abuse, e.g., impacts, abrasion, and all kinds of environmental exposure over a significant amount of time; perhaps 1-3 years depending on frequency of use. Use in the manufacture of furniture or cushioning for soles, midsoles, and / or insoles for running shoes. It is important to consider the above requirements when considering sustainable materials for use in running shoes. A material that cannot handle repeated abuse before failure will not produce a satisfactory pair of running shoes. Additionally, a material that has the potential to degrade or weaken to the point of failure during routine product use before the end of its intended lifespan would be unacceptable. Summary of the Invention

[0017] To solve this problem, specialized materials must be sought that have the right balance of technical performance characteristics that are ultimately net-neutral (or negative) with respect to harmful emissions, and sustainability considerations, such as compostability with a controlled end-of-life solution. In particular, because furniture cushioning is bulky and running shoes are demanding products, home-compostable materials would not be a suitable solution for use in their manufacture, as lower decomposition temperatures would convert the furniture or running shoes into something that tends to disintegrate long before the end of its intended lifespan. In this example, industrially compostable materials are a much better option because they can address the higher temperature challenge and offer greater technical performance characteristics that are nearly equal to or even comparable to their industrially non-compostable and non-biodegradable counterparts. Essentially, furniture or a pair of running shoes manufactured using industrially compostable materials would perform very well throughout the product's useful life, and only at the end of the product's useful life would the materials have the option of being directed to an industrial composting setting for "closed-loop" waste diversion.

[0018] Therefore, if possible, materials and manufacturing processes should be designed to allow for easy composting after the end of a product's lifespan, in order to reduce the destructive footprint often associated with manufacturing processes. However, as noted above, this is difficult because commercially available biodegradable and compostable precursors are very limited. Those that exist are not necessarily designed or capable of solving all of the combined challenges of performance and long-term usability while being easily compostable and biodegradable in a controlled setting at the end of their useful life. Those precursors that solve some of the above challenges fail to solve others, which can dismay consumers and possibly lead to negative reviews of products containing them. Despite these significant drawbacks, materials that can be composted either in industrial facilities or at home would theoretically be a useful starting point for renewable, sustainable, and earth-friendly manufacturing.

[0019] Another aspect of the present manufacturing process relates to the production of flexible foams. Flexible foams are a type of object formed by trapping gas pockets in a liquid or solid, and the resulting foam is said to be flexible, in part, due to its malleability. Flexible foams are typically used in cushioning applications, such as footwear, furniture, bedding, and other sporting goods. Flexible foams typically fall into two categories: closed-cell flexible thermoplastic polymer foams and open-cell flexible polyurethane foams. Each of these foam types has very different manufacturing methods.

[0020] Closed-cell flexible thermoplastic polymer foams are typically produced in a dry process, where a suitable synthetic polymer is selected and blended with various chemical additives, crosslinkers, and chemical blowing agents to produce a "dough," which is then kneaded and extruded into a flat sheet. The sheets are then stacked on top of each other and placed in a heated press under controlled pressure. This mixture of materials and chemical blowing agents reacts and expands inside the heated press cavity. The result is a closed-cell flexible foam "bun" or "block," which is then sliced to thickness. In contrast, open-cell flexible polyurethane foams are typically produced in a liquid injection or liquid molding process, where synthetic polyol chemicals, isocyanate chemicals, and other chemical additives are poured or injected into a mold shape, such as a "bun" or "block." The mixture is reacted together in between. The result is an open-cell flexible foam, which is then sliced to thickness.

[0021] Consistent with the above, one of the problems with currently available flexible foams on the market today is that they almost exclusively use non-renewable materials and harmful chemicals in their manufacture. Furthermore, due in part to the chemical crosslinking that occurs in the above-described methods of manufacturing conventional flexible foams, the physical structure of these flexible foams cannot be composted, biodegraded, or recycled. This is primarily due to their design and the inability to separate back into their root precursors of chemical composition. That is, at the end of a conventional flexible foam's lifespan, it cannot be further used and cannot be successfully reprocessed into new materials by any known commercially viable method.

[0022] Therefore, in view of the above, presented herein are flexible foams and manufacturing processes that can be used to produce renewable, sustainable, and / or environmentally responsible end products, both of which can be used sustainably without decomposition, but which readily decompose and are composted at the end of their life. Both flexible and semi-flexible foams are included in the same category of flexible foams because they are both derived from polymers that have a glass transition (Tg) below their use temperature, which is typically room temperature. Details of one or more embodiments are set forth below in the accompanying description, with reference to the accompanying drawings and their features. Other features and advantages will become apparent from the description, drawings, and claims.

[0023] This document presents a process for the modified injection-molded microcellular foaming of various flexible foam compositions from biodegradable, industrially compostable thermoplastic resins. Currently, almost all known flexible foams worldwide are derived from non-renewable feedstocks, and most, if not all, are not biodegradable or industrially compostable. The goal of this invention is to produce flexible foams that cause minimal environmental harm while also possessing important technical performance characteristics that equal or exceed those of conventional non-biodegradable petrochemical flexible foams. By selecting plant-derived feedstocks to produce biopolymers, this invention contributes to sequestering greenhouse gases from the atmosphere, significantly reduces dependence on non-renewable petroleum, and significantly reduces the amount of non-biodegradable waste that ends up in landfills each year.

[0024] In various embodiments, the flexible foam produced thereby may be configured to be industrially composted rather than home composted, although it is contemplated that home composting may be used in some cases by the market. In various cases, industrial composting is useful because it ensures that the flexible foam will last the useful life of the resulting product into which it is functionalized and will not degrade or fall apart during use within the finished product. For example, it would be harmful for a person to purchase a pair of shoes made from the flexible foam of the present invention only to have the foam degrade during regular use before the end of the shoe's useful life.

[0025] Thus, in one aspect, a process for producing biodegradable, industrially compostable flexible foam, whether open-cell or closed-cell, is provided herein and may include one or more of the following steps: creating a thermoplastic biopolymer blend masterbatch for foaming; injection molding the thermoplastic biopolymer blend into a suitable mold shape using inert nitrogen gas; using dynamic mold temperature control to ensure optimal cell structure; controlling the biopolymer melt, pressure, and time to form the desired flexible foam; and using gas counter pressure in the injection molding process to ensure optimal foam structure with a minimum amount of surface defects and little to no plastic skin on the outside of the foam part.

[0026] The disclosed manufacturing process, in conjunction with carefully selected bio-based, renewable, and recyclable feedstocks, opens the door to an environmentally friendly, closed-loop process. This closed-loop process begins with material selection. For example, the selection of inert, rapidly renewable polymer feedstocks that are third-party certified as compostable ensures that circular economy principles are adhered to. To this end, the selected rapidly renewable polymer feedstocks begin their lifespan as renewable plant or mineral forms. Once converted into suitable polymers, these environmentally responsible precursors can be combined with other environmentally responsible precursors and material components for functionalization into custom biopolymer compounds that can be used in the disclosed manufacturing process.

[0027] In particular, once a suitable biopolymer compound is produced, it is processed in the chemical-free manufacturing method of this disclosure. The resulting flexible foams are non-crosslinked and often biodegradable and compostable. As a result, at the end of their usable life, these produced foams can be carefully ground into small pieces and industrially composted in a regular facility for decomposition, e.g., 100% of their composition can be returned to usable biomass. This usable biomass can then be used to grow more inert, rapidly renewable polymer feedstock, and the process continues in an endless loop. Thus, this document describes a biodegradable and industrially compostable microcellular flexible foam and a method for producing the same. The foam may be a closed-cell foam, but potentially also be formed as an open-cell foam.

[0028] In various implementations, biodegradable, industrially compostable flexible foams can be made to have the same properties and characteristics as traditional petrochemical ethylene vinyl acetate (EVA) foams, while also containing a high percentage of biomass-carbon content. For example, flexible EVA foam is a ubiquitous material used in industry today. What makes EVA foam so popular is its relatively low cost and ease of processing while maintaining generally acceptable technical performance characteristics for a given product. The downsides to using EVA foam are many. The material is generally derived from non-renewable sources, is chemically crosslinked with chemical blowing agents to produce flexible foam, and it is not easily biodegradable, compostable, or recyclable.

[0029] There are many configurations and embodiments that can be used depending on the desired physical properties and intended end use of the product, which should not be limited by this disclosure.

[0030] One factor that makes the advances presented herein so useful is that biodegradable foams perform in a manner similar to EVA, thus their technical performance characteristics are similar to those of EVA without chemical additives and crosslinking. The result is a commercially acceptable flexible foam that can be an immediate replacement for the ubiquitous EVA, but that offers a greatly reduced environmental impact and an environmentally responsible, managed end-of-life solution.

[0031] Thus, in one embodiment, a method for producing a biodegradable, industrially compostable molded flexible foam article is provided. In various cases, the method may include one or more of the following steps. For example, the method may include introducing a thermoplastic biopolymer blend masterbatch for foaming into the barrel of a molding apparatus. The method may additionally include introducing a fluid into the barrel under temperature and pressure conditions that produce a supercritical fluid, which, upon contact with the thermoplastic biopolymer blend masterbatch, produces a thermoplastic foamed melt. Furthermore, the method may include injecting the thermoplastic foamed melt into a cavity of a suitable mold shape and applying a gas counterpressure to the cavity. Finally, the cavity can be cooled to produce a molded article.

[0032] In various cases, one or more thermoplastic biopolymer masterbatches are introduced through a sprue bushing, e.g., a thermoplastic biopolymer blend masterbatch is produced using a twin-screw extruder. In one embodiment, the thermoplastic biopolymer blend masterbatch includes one or more of polylactic acid (PLA), polyhydroxyalkanoate (PHA), cellulose acetate (CA), starch, and petroleum-derived thermoplastics. In various cases, a fluid is introduced into the barrel through a metering unit. In particular, the supercritical fluid includes one or more of nitrogen and carbon dioxide. The supercritical fluid can be introduced under pressure and at a temperature, e.g., a pressure ranging from about 150 bar to about 300 bar and a temperature ranging from about 150°C to about 350°C. Similarly, a gas counterpressure ranging from about 5 bar to about 50 bar is applied for a time period ranging from 1 second to 25 seconds. In some cases, the temperature can be controlled by dynamic mold temperature control.

[0033] Additionally, in another aspect, an injection molding apparatus for producing biodegradable, industrially compostable flexible foam molded articles is provided. In various cases, the injection molding apparatus can include one or more of the following: A hopper can be included, for example, a hopper configured to receive and introduce a plurality of thermoplastic biopolymers into the molding apparatus, for example, the thermoplastic biopolymers form a blended masterbatch.

[0034] A metering unit may be included, for example, configured to receive a fluid and introduce the received fluid into the molding apparatus under conditions that generate a supercritical fluid upon said introduction. The molding apparatus may include a barrel having a first cavity configured to receive the blended thermoplastic biopolymer masterbatch and a fluid, whereby, upon introduction into the barrel, a thermoplastic foamed melt is generated when the supercritical fluid contacts the blended thermoplastic biopolymer masterbatch within the barrel cavity. A gas counterpressure delivery unit may also be included, where the GCP is configured to deliver gas counterpressure to the first cavity to control the expansion of the foamed melt. Also included may be a mold having a cavity fluidly connected to the barrel cavity, where the mold cavity is configured to receive the foamed melt and generate a flexible foam molded article upon cooling of the melt.

[0035] In various embodiments, the injection molding apparatus may include a reciprocating screw configured to compress the foamed melt in the barrel cavity and convey the compressed foamed melt into the mold cavity. Thus, there may be a conduit between the barrel cavity and the mold cavity, where the conduit includes a nozzle with a sprue bushing to form a seal between the barrel and the mold.

[0036] Thus, the injection molding apparatus may include one or more of the following: a hopper through which the thermoplastic material is fed to the molding machine in the form of small pellets. A hopper on the injection molding machine holds these pellets. The pellets may be gravity fed from the hopper through a hopper throat into a barrel and screw assembly. A barrel may also be included, in which case the barrel of the injection molding machine supports a reciprocating plasticizing screw and may be heated by electric heater bands.

[0037] A reciprocating screw may also be present, in which case the reciprocating screw is used to compress, melt, and convey the material. The reciprocating screw may include three zones: a feed zone, a compression (or transition) zone, and a metering zone. A nozzle may also be present, in which case the nozzle connects the barrel to the sprue bushing of the mold and forms a seal between the barrel and the mold. The nozzle temperature may be set at or just below the melting temperature of the material. When the barrel is in its full forward processing position, the nozzle radius can nest and seal within the concave radius of the sprue bushing using a locating ring. During barrel purging, the barrel may back out of the sprue, allowing the purging compound to fall freely from the nozzle.

[0038] Additionally, mold and hydraulic systems can also be provided. The mold system can include tie bars, stationary and movable platens, and a mold plate (base) that houses the cavity, sprue and runner system, ejector pins, heating and cooling channels, and temperature and pressure sensors. The mold is essentially a heat exchanger in which molten thermoplastic solidifies into the desired shape and dimensional details defined by the cavity. A hydraulic system may also be present in the injection molding machine, providing power to open and close the mold, build and maintain clamp tonnage, rotate the reciprocating screw, drive the reciprocating screw, and energize the ejector pins and moving mold core. Many hydraulic components are required to provide this power, including pumps, valves, hydraulic motors, hydraulic fittings, hydraulic piping, and oil tanks.

[0039] A control system can also be provided. The control system can be configured to provide consistency and repeatability in machine operation. It monitors and controls process parameters, including temperature, pressure, SCF dosing, injection speed, screw speed and position, and hydraulic position. Process control can have a direct impact on final part quality and process economics. Process control systems can range from simple relay on-off control to very sophisticated microprocessor-based, closed-loop control.

[0040] A clamping system may also be provided. The clamping system may be configured to open and close the mold, support and transport mold components, and generate sufficient force to prevent the mold from opening. The clamping force may be generated by a mechanical (toggle) lock, a hydraulic lock, or a combination of the two basic types. A delivery system may also be provided. The delivery system provides a path for molten plastic from the machine nozzle to the cavity section and generally includes the following: a sprue, a cold slug well, a main runner, branch runners, a gate, etc.

[0041] Thus, in a further aspect, a system for producing biodegradable, industrially compostable molded flexible foam articles is provided. The system may include the injection molding apparatus for producing biodegradable, industrially compostable molded flexible foam articles described above. The system may additionally include a supercritical gas dosing system configured to receive a fluid and introduce the received fluid into a first cavity of the barrel under conditions that generate a supercritical fluid upon said introduction, the supercritical fluid generating a foamed melt upon contact of the supercritical fluid with the blended thermoplastic biopolymer masterbatch in the first cavity. The system may further include a dynamic temperature control system configured to control the temperature within one or more of the first and second cavities. A gas counterpressure delivery unit configured to deliver gas counterpressure to the first cavity to control the expansion of the foamed melt may also be included. Additionally, a control unit having one or more microprocessors may be included, the control unit configured to control one or more of the injection molding apparatus, the supercritical gas dosing system, the dynamic temperature control system, and the gas counter pressure delivery unit according to one or more system parameters.

[0042] In particular, the system components may include an injection molding machine system, including a hopper, barrel, reciprocating screw, nozzle, mold system, hydraulic system, control system, clamping system, and delivery system. An SCF gas dosing system may be included, including a tank of inert gas, such as nitrogen, an air compressor, SCF metering and control equipment, an SCF injector, and a specially designed reciprocating screw, and both front and rear check valves. A dynamic temperature control system may also be provided, including a heating unit, a cooling unit, interlocking valves, and computer control. In addition, there may be heating elements and cooling channels located within the mold body, which are supplied by the dynamic temperature control system and through which the heating or cooling medium circulates. Their function is to regulate the temperature on the mold surface. A gas counterpressure system may also be provided. This includes a tank of gas, eg, an inert gas, eg, nitrogen, an air compressor, a gas pump, a gas safety valve, a gas pressure sensor, and a computer control.

[0043] The system and / or any of its subsystems may include one or more sensors, such as, for example, temperature, pressure, accelerometers, gyroscopes, and orientation sensors, where the one or more sensors are configured to be disposed in communication with one or more other components of the injection molding apparatus, e.g., within one or more cavities of the injection molding apparatus. In various embodiments, the sensors may be smart sensors and include a communication module, e.g., via a network connection, such that wireless communication is implemented. Thus, the system, and / or any of its various parts, may include a communication module, which may be coupled to one or more of the control module, the supercritical gas dosing system, the dynamic controlled temperature system, and the gas counterpressure control unit, where, for example, the communication module is configured to implement one or more wireless communication protocols, including WIFI, Bluetooth, low-energy Bluetooth, and 3G, 4G, and 5G cellular communications.

[0044] In another aspect, the present disclosure describes a recyclable microcellular flexible foam and a method for making the same. The foam is preferably a closed-cell foam, but may also potentially be formed as an open-cell foam. The creation of the recyclable microcellular flexible foam structure begins with a suitable high-performance polymer, such as one of polyamide origin. Non-limiting examples of suitable polymers include Ascend Performance A suitable example of a suitable thermoplastic polymer is a polyamide 66 copolymer sold under the trade name Vydyne by Materials, LLC, Houston, TX. Other non-limiting examples of suitable polymers include various polyamide block copolymers, such as polyether-block-amide (PEBA), PAE, TPA, TPE-A, COPA, and the like. The above-mentioned thermoplastic polymers exhibit advantageous technical properties in forming the microcellular flexible foam structures of the invention. Some of the enhanced technical properties include exceptional aging properties, excellent elongation, tensile strength, and compression set, among other benefits. Furthermore, recycled materials can be used in the manufacture of suitable recyclable polymers or polymer blends of the invention. For example, in one embodiment, the recyclable flexible foam thermoplastic polymer comprises at least one monomer or polymer derived from post-consumer or post-industrial recycled materials, such as caprolactam, recycled polyether block amide polymer, or the like. For example, caprolactam can be derived from such recycled materials by depolymerizing polyamide-containing post-industrial or post-consumer materials, such as fishing nets, carpet fibers, or post-industrial waste. Some examples of depolymerized post-consumer or post-industrial recycled caprolactam include ECONYL® caprolactam (whether flake, liquid, or melt) offered by Aquafil USA Inc., Cartersville, Georgia. The thermoplastic polymer can additionally or alternatively include polyamide polymers derived from post-industrial or post-consumer polyamide carpet fibers that are collected, sorted, melted, and reprocessed. One example of this is the use of post-industrial polyamide carpet fibers, etc., which are collected, sorted, melted, and reprocessed into upcycled, usable polyamide materials. An exemplary polyamide polymer derived from post-industrial carpet fibers is Econyl®, manufactured by Aquafil USA Inc., Cartersville, Georgia.Additionally, polyamide waste can be collected from or around the world's oceans in the form of fishing nets, or the like, which are then sorted, melted, and reprocessed into upcycled, usable polyamide material. An exemplary polyamide polymer derived from collected post-industrial fishing nets is Akulon Repurposed, manufactured by Koninklijke DSM NV, Heerlen, The Netherlands. The use of recycled polymer feedstocks whenever possible is an important aspect of this invention. This is the purpose.

[0045] Optimal polyamides alone cannot produce recyclable flexible foams without a suitable blowing agent and foaming process. The most widely known blowing agent used today is a chemical called azodicarbonamide (ADA). ADA is typically pre-impregnated into conventional thermoplastic masterbatch resins for use in conventional injection-molded foam processes. Unfortunately, ADA is not environmentally friendly and is a suspected carcinogen. Furthermore, conventional foaming processes using ADA crosslink during the manufacturing process, thereby creating non-recyclable flexible foam molds. To achieve recyclable flexible foams, inert nitrogen gas or carbon dioxide is used as a physical blowing agent in a modified injection-molding process. The modified physical blowing process is used in conjunction with a suitable thermoplastic polymer or blended polymer masterbatch, so that the polymer or blended polymer and blowing agent work in harmony to produce recyclable flexible foams. The preferred injection-molding process of this invention utilizes homogeneous cell nucleation, which occurs when a single-phase solution of polymer and supercritical fluid (SCF) passes through the injection gate into the mold cavity of a modified injection molding machine. As the solution enters the mold, pressure drops, causing the SCF to come out of solution and create bubble nuclei. The bubbles then grow until the material fills the mold and the SCF's expansion properties are exhausted. This manufacturing process proceeds in an injection molding machine, which has been modified to allow for the metering, delivery, and mixing of the SCF into the polymer to create a single-phase solution. Dynamic mold temperature control (DMTC) is used to ensure a consistent bubble structure within the expanding polymer melt. DMTC can best be described as heating elements and cooling channels located within the mold body, powered by a dynamic temperature control system, through which a heating or cooling medium circulates. Their function is to regulate the temperature on the mold surface. Gas counter pressure (GCP) is also used in the process to ensure optimal foam structure with little to no skin on the resulting flexible foam. GCP can best be described as a process involving a pressurized mold cavity, which is injected with nitrogen gas to counteract the expansion of the gas within the melt.As the counter pressure is released, gas bubbles that would traditionally break through the surface are trapped inside, creating a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness.

[0046] The creation of a single-phase solution in which the SCF is completely dissolved and uniformly dispersed in the molten polymer occurs inside the injection barrel under carefully controlled process conditions: the SCF must be accurately mass-metered into the polymer for a specific period of time, and during that dosing period, suitable conditions of temperature, pressure, and shear must be established within the barrel. Back pressure, screw speed, and barrel temperature control, as well as gas counter pressure and the SCF delivery system, all play a role in establishing the process conditions that create a single-phase solution.

[0047] The thermoplastic polymers used to produce the recyclable, chemical-free flexible foams can optionally be made from various polyamides or polyamide copolymers, etc. Non-limiting examples of suitable polymers include polyamide 6, polyamide 6 / 6-6, and polyamide 12. Alternatively, the thermoplastic polymer can include various polyamide block copolymers, such as polyether-block-amide (PEBA), PAE, TPA, TPE-A, COPA, etc. Any suitable polymer type can be used in this invention, provided it meets the required hardness, moderate melt flow, high elongation, and recyclability.

[0048] Additionally, blends of two or more thermoplastic polymers offer a combination of properties and price not found in a single polymer. There are many ways to successfully blend polymers together. One method is to use twin-screw extrusion to melt two or more polymer resins together, then extrude the molten polymer resin blend into strands that are cooled and then stamped. The mixture is then fed into a pelletizer to produce an array of pelletized pieces called a batch. Another method of polymer resin blending uses a compatibilizer to combine different chemicals in a polymer blend. This can be done using methods such as twin-screw extrusion to melt the compatibilizer and two or more polymers together into the non-limiting thermoplastic polymer types described above.

[0049] In one embodiment, a method includes recycling flexible foam by depolymerizing the foam into one or more monomers. The depolymerization process includes mechanically separating the thermoplastic polymer of the recyclable foam from the waste, introducing a depolymerization catalyst to the separated thermoplastic polymer, heating the thermoplastic polymer and catalyst to produce a distillate, separating water and the resulting monomers from other by-products, oxidizing the aqueous monomers, concentrating the oxidized aqueous monomers, purifying the concentrated monomers, and repolymerizing the monomers to produce a thermoplastic polymer for use in the method for producing recyclable flexible foam. The resulting monomers may include caprolactam or other monomers that can be repolymerized into a thermoplastic polymer.

[0050] Depending on the application, additives may also be used in the polymer formulation, for example, fillers such as precipitated calcium carbonate, roe-like aragonite, starch, biomass, etc. may be used to reduce part costs while maintaining the recyclable integrity of the finished flexible foam.

[0051] Additionally, additional additives for use in polymer formulations may include one or more of the following nucleating agents, such as microlamellar talc or high-aspect-ratio oolitic aragonite. Such nucleating agents can significantly improve the fundamental properties of the resulting flexible foam by inhibiting cell coalescence, reducing bulk density, and improving resilience, among other beneficially enhanced attributes. Some non-limiting examples of nucleating agents for use in producing recyclable, chemical-free, injection-molded microcellular flexible foams are microlamellar talc commercially available as Mistrocell® by Imerys Talc America Inc., Houston, Texas, and high-aspect-ratio oolitic aragonite commercially available as OceanCal® by Calcean Minerals & Materials LLC, Gadsden, Alabama.

[0052] Colorants, dyes, and pigments can also be included. Various colorants, such as dyes or pigments, can be used in the polymer formulations of the present invention. Some non-limiting examples are pigments customized for specific types of thermoplastic polymer applications, such as the wide range offered by Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or those offered by Holland Colors Americas Inc., Richmond, Indiana.

[0053] The details of one or more embodiments are set forth in the accompanying description below. Other features and advantages will be apparent from the description and from the claims.

[0054] These and other aspects will now be described in detail with reference to the following drawings. [Brief explanation of the drawings]

[0055] [Figure 1] 1 illustrates a foam footwear component, i.e., a shoe midsole, according to one implementation of the present disclosure. [Figure 2] FIG. 1 shows a schematic overview of an injection-molded microcellular flexible foam system for producing biodegradable and industrially compostable flexible foam suitable for footwear. [Figure 3] 1 is a flow chart of a method for producing biodegradable and industrially compostable injection-molded microcellular flexible foam. [Figure 4] 1 shows a recyclable flexible foam according to the present disclosure being injection molded to make a midsole for an athletic shoe. [Figure 5] 5 shows a schematic of an injection molding machine for producing the recyclable flexible foam shown in FIG. 4. [Figure 6] 5 is a flow chart of a method for producing the recyclable microcellular flexible foam of FIG. 4. [Figure 7] 7 is a flow chart illustrating steps for recycling flexible foam associated with one embodiment of the method for producing recyclable microcellular flexible foam of FIG. 6.

[0056] Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0057] This document describes biodegradable, industrially compostable, and recyclable microcellular flexible foams and methods for making the same. The foams are preferably closed-cell foams, but may also potentially be formed as open-cell foams. In various implementations, biodegradable, industrially compostable, and recyclable flexible foams can be made to have the same properties and characteristics as conventional petrochemical ethylene vinyl acetate (EVA) foams, while still containing a high percentage of biomass-carbon content.

[0058] Biodegradable and industrially compostable injection-molded microcellular flexible foam and method for producing same The present disclosure relates to a process for producing biodegradable and industrially compostable microcellular flexible foams and methods for producing the same. As mentioned above, foaming describes a process that involves trapping gas pockets in a liquid or solid. Generally, industry uses foaming to produce lightweight polymeric materials, which is an advantageous solution for many types of products, because foamed materials offer numerous added benefits, such as soft cushioning, comfort, and impact protection, among others.

[0059] In various cases, it is useful for the foam material to be a microcellular foam. Microcellular foam is a type of manufactured plastic, particularly one that is made to contain a large number of tiny bubbles, e.g., billions of bubbles (which may be less than about 50 microns in size). This type of foam is formed by dissolving a gas under high pressure into various types of polymers to cause a uniform arrangement of gas bubbles (commonly called nucleation). The primary driver for controlling and adjusting the density of microcellular foams is the gas used to create them. Depending on the gas used, the density of the foam can be anywhere from about 5% to about 99% of the pre-treated bioplastic.

[0060] Therefore, in various cases, it is useful for the foam to be a closed-cell foam. Closed-cell foams are generally known as cells that are completely enclosed by their walls and therefore not interconnected with other cells. This type of material is useful because it effectively reduces the flow of liquids and gases through the cells. For example, closed-cell foams produced according to the methods disclosed herein are useful in industries where liquid resistance is important, such as cushioning, footwear, marine, HVAC, and automotive applications.

[0061] However, in various cases, it may be useful for the foam to be an open-cell foam. An open-cell foam is typically classified as "open-cell" if the majority of its cells are open and interconnected with other cells. This type of foam, which may be produced and used in the methods disclosed herein, is advantageous because it has a tighter seal than closed-cell foam. It can be useful in that it behaves similarly to a rubber band and easily returns to its original state after being compressed. The "resilience" is caused by unrestricted air movement and chemical composition.

[0062] In particular, foams produced according to the described methods and products made therefrom perform in a manner similar to flexible ethylene vinyl acetate (EVA) foam. In particular, flexible EVA foam is a ubiquitous material used in manufacturing today. What makes EVA foam so popular is its relatively low cost and ease of processing, while maintaining generally acceptable technical performance characteristics for a given product. As a result, foams produced as disclosed herein can be produced at a relatively low cost and are easy to manufacture, while maintaining products of acceptable and often excellent technical performance, and at the same time are environmentally friendly.

[0063] More specifically, as noted above, the downsides to using EVA foam are numerous. The material is derived from non-renewable raw materials and is chemically crosslinked with chemical blowing agents that are not readily biodegradable, compostable, or recyclable. However, unlike flexible EVA foam, the biodegradable and industrially compostable flexible foams of the present disclosure do not contain chemicals or crosslinking agents, and they are readily biodegradable and industrially compostable when suitable bio-based polymers are used in their manufacture.

[0064] For example, in various implementations, biodegradable, industrially compostable flexible foams are presented herein that have similar properties and characteristics as conventional petrochemical ethylene vinyl acetate (EVA) foams, but can still be made to contain a high percentage of biomass-carbon content. In particular, in various embodiments, biodegradable, net-neutral, and industrially compostable foam precursors are used, e.g., in an environmentally friendly manner, in the manufacture of biodegradable, industrially compostable flexible foams. To achieve these goals, a variety of suitable bio-based thermoplastic feedstocks can be selected for use and can originate from rapidly renewable sources that typically do not compete with animal feed or human food. Conveniently, as shown, carefully selected bio-based thermoplastic foam precursors have technical performance characteristics that are nearly identical to or equal to those of conventionally used EVA.

[0065] A non-limiting example of such a suitable thermoplastic feedstock for use in producing the biodegradable, industrially compostable flexible foams of the present disclosure, having technical performance characteristics that are approximately equal to or equal to those of conventional non-renewable EVA, is the bio-based PBAT copolyester described herein below. Thus, in various cases, the present apparatus, systems, and methods of their use can be used to produce biodegradable, industrially compostable microcellular flexible foams that can be produced from bio-based, industrially compostable thermoplastics.

[0066] More specifically, foam precursors useful according to the disclosed methods can be any suitable type of thermoplastic resin, such as bio-based thermoplastics or bio-based thermoplastic compounds produced from rapidly renewable feedstocks. Such thermoplastics are raw, amorphous polymers that melt and become liquid when heated and harden and turn solid when cooled.

[0067] Making thermoplastics is not a simple task. Complex chemical and mechanical processes are required to produce the final product. In its simplest form, thermoplastics are formed from polymers, which are in turn formed from compounds. To make the polymers, the different types of molecules must then be broken down and separated to produce the compounds needed to make the thermoplastics. Typically, foam precursors are used by feeding them in granular form into a suitable injection molding machine. The granules are processed through an injection molding machine where they are liquefied and ejected into a pre-formed mold cavity. Once ejection is complete, the molded part is cooled and removed from the mold in a solid state; this process as carried out in this embodiment is described in more detail herein below.

[0068] Bio-based thermoplastics can be described by type. Common types of bio-based thermoplastic precursors and biomass. Two types of biopolyesters exist: polylactic acid (PLA) and polyhydroxyalkanoates (PHAs). PLA is a type of thermoplastic produced by bacterial fermentation. PLA is actually a long chain of many lactic acid molecules. There are many different bio-based feedstocks for producing PLA, including sugarcane, corn, sugar beet, and lignin wood waste, to name a few. PHAs are generally produced by naturally occurring bacteria and food waste. There is a subclass of PHA called polyhydroxybutyrate (PHB), which is one type of PHA that is also widely available.

[0069] In some cases, starch or cellulose fillers can be optionally included in the formation of biopolyester blends because their inclusion makes the blend more economical and, in some cases, their use enhances degradation rates. Another type of bio-based thermoplastic is known as cellulose acetate (CA). CA is a synthetic product derived from cellulose, which is found in various parts of plants. Current raw materials used to manufacture CA include cotton, wood, and agricultural waste, to name a few. Furthermore, starch is yet another type of thermoplastic material. Typically, starch is treated with heat, water, and plasticizers to produce a thermoplastic. To impart strength, starch is usually combined with fillers made from other materials. Currently available raw materials for producing starch include corn, wheat, potato, and cassava. Several petroleum-derived thermoplastics that can be biodegradable are also known. Common types are polybutylene succinate (PBS), polycaprolactone (PCL), and polybutyrate adipate terephthalate (PBAT), and polyvinyl alcohol (PVOH / PVA). The petroleum-derived thermoplastics can be produced in a variety of species of biological origin. New bio-based feedstocks for producing PBS, PCL, PBAT, and PVOH / PVA are being produced and are becoming increasingly commercially available due to technological advances and breakthroughs. One or more of these precursors can be made and employed according to the methods disclosed herein.

[0070] Once the precursors are made, they can be foamed, for example, via an injection molding process, as disclosed herein, and used to manufacture one or more end products. For example, in various cases, bio-based thermoplastic precursors can be foamed and used in the end product production process, for example, by injection molding. In traditional foam injection molding, also known as direct injection foam molding, a thermoplastic polymer is first melted. Once the thermoplastic polymer is homogeneously melted, a chemical blowing agent is dispersed in the polymer melt to make the injection compound foamable.

[0071] The homogeneous polymer compound is then injected into a mold to produce a foam product. Typically, the injected polymer compound is not classified as a foam until an endothermic reaction in the heated mold cavity activates a chemical blowing agent, resulting in an expanded foam part. As a result, the mold cavity size must be smaller than the final part size. The actual part expansion is created within the thermoplastic polymer formulation so that when the part is removed from the mold, it grows to the desired part size.

[0072] Once the desired part size is achieved, it also shrinks or contracts as it cools. However, this often requires a secondary molding operation to obtain the correct cooled part size. As a result, the process of managing the expansion-contraction of conventional injection-molded foams can be considered tedious, time-consuming, and complicated. Such injection molding techniques can be used to produce precursors and foams, and products produced therefrom, as described herein. However, in special cases, conventional injection molding machines can be modified as disclosed herein to better achieve the use of biodegradable, net-neutral foam precursors that can be used in the modified process, thereby producing environmentally friendly foams that can be used in producing foam products such as furniture cushioning, shoe components, sporting goods, and the like.

[0073] Thus, while conventional processes can be useful for producing foamed products, in some cases they may suffer from several drawbacks, particularly with respect to producing compostable microcellular flexible foams. For example, in various cases, typical injection molding processes may be deficient in a variety of different ways when using compostable bio-based thermoplastics to produce compostable flexible foams. For example, the conventional unmodified foam injection molding processes described above may be deficient and unsuitable for producing biodegradable and compostable flexible foams. The primary reason for this arises from the nature of conventional unmodified foam injection molding, in which polymer compounds are crosslinked during their manufacture.

[0074] As indicated above, crosslinking can be described as the random formation of covalent bonds that hold portions of some polymer chains together. The result is a random three-dimensional network of interconnected chains within the foam matrix. This crosslinked foam cannot be easily uncrosslinked, and thus the various precursor components cannot easily separate back into their individual forms and are not biodegradable or compostable. As a result, the presently disclosed advantages would not be easily achieved without modifying foaming equipment and its use in manufacturing. Thus, a manufacturing machine and process for using the same are presented herein to generate foam in a manner suitable for use with uncrosslinked precursors in an injection molding process.

[0075] As a result, in one aspect, a novel injection molding machine is provided herein. The molding machine can be configured to use a variety of flexible foam compositions, including bio-based thermoplastic precursors, which, upon application of the precursors into the novel injection molding machine, can be foamed in a manner to produce a compostable microcellular flexible foam structure, which can then be used to produce one or more flexible foam products. Thus, in one aspect, a novel injection molding machine is provided herein.

[0076] Some of the factors that set the manufacturing machine of the present disclosure apart are the use of specialized auxiliary equipment coupled with a microcellular gas dosing system, which can be added to a standard injection molding machine, thereby modifying and improving it. Essentially, as presented herein, a standard injection molding machine has been outfitted and refurbished to function in a manner suitable for use with the present disclosure. The general method for modification begins by converting the injection molding screw on the injection molding machine to be capable of handling supercritical inert gases, such as nitrogen, CO, and / or non-reactive and / or inert gases.

[0077] A gas dosing system may then be attached to the injection molding machine, for example, to dose the appropriate gas in the appropriate amount into the polymer melt in the screw prior to injection into the temperature-controlled mold cavity. Additionally, special mold cavities may be used where thermal temperature cycling of the mold can better control the resulting foam skin texture and skin thickness, as well as reduce cycle times for part production. Furthermore, an auxiliary gas counterpressure system may be attached to the injection molding machine to force inert gas back into the mold to counteract the ejection of the liquid polymer melt into the mold.

[0078] This counter pressure is useful for ensuring that the molten injection shot substantially, if not completely, fills the mold cavity, preventing the part from distorting and shrinking, and controlling cell distribution and cell density. Furthermore, proper counter pressure has a beneficial effect on the part's skin texture and skin thickness. As a result, there is no discernible shrinkage when the part is removed from the mold cavity, and no secondary processing is required for immediate use of the molded foam part. Advantageously, the part is not crosslinked, so that it is biodegradable or compostable, provided that suitable bio-based polymer compounds are used in making the foam.

[0079] In view of the above, in one aspect, the present disclosure relates to producing biodegradable and compostable (e.g., industrially) microcellular flexible foam structures. In particular, in one embodiment, the process begins with a suitable biopolymer or biopolymer blend. For example, in various cases, the biopolymer may be one or more polymers produced, for example, from natural sources, chemically synthesized from biological materials, or entirely biosynthesized by living organisms.

[0080] There are primarily two types of biopolymers: those derived from living organisms and those produced from renewable resources but requiring polymerization. Those produced by living organisms include proteins and carbohydrates. Unlike synthetic polymers, biopolymers have a distinct structure. This type of polymer is identified based on their chemical structure. What makes the biopolymers of the present disclosure particularly useful is that they closely mimic non-renewable EVA in terms of technical performance characteristics.

[0081] Similarly, in special cases, biopolymer blends can be used to create foam structures, for example, a biopolymer blend can be a custom compound of two or more biopolymers. Some non-limiting types of biopolymers are sugar-based biopolymers, starch-based biopolymers, synthetic material-based biopolymers, and cellulose-based biopolymers. Typical ratios of biopolymer blend combinations depend on the type of product being manufactured and the desired technical properties of the resulting part.

[0082] More specifically, in certain embodiments, biopolymer blends that can be used as foam precursors include multiple resins, such as one or more solid or viscous materials, that can be added to a polymer, for example, in a melt, after curing. Thus, after polymerization or curing, the resins form a polymer. For example, suitable resins can be one or more of the following: aliphatic and aliphatic-aromatic copolyesters. Generally speaking, aliphatic or aliphatic compounds refer to or refer to organic compounds in which carbon atoms form open chains instead of aromatic rings. Similarly, suitable aliphatic-aromatic compounds are generally random combinations of open chains of carbon atoms (aliphatic moieties) and one or more stable rings of atoms (aromatic moieties).

[0083] Typically, the amount of aromatic acid in the chain is less than 49%, but recent technological advances hold great promise for increasing this and further aiding biodegradation. One example of an aliphatic-aromatic is an aliphatic-aromatic copolyester (AAPE), which can be produced from a variety of non-renewable and renewable feedstocks, with renewable-source AAPE being particularly useful. Thus, in various embodiments, one or more of these aliphatic and / or aliphatic groups may originate from a copolyester. Such copolyesters are created when polyesters are modified. For example, copolyesters are produced when more than one diacid or diol is used in the polymerization process. In the case of aliphatic-aromatic copolyesters, the precursor combination is altered to essentially hybridize or "crosslink" the aliphatic-aromatic chains, combining more than one additional precursor in the polymerization process.

[0084] A non-limiting example of a suitable biopolymer blend is polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). Polylactic acid (PLA) is a biodegradable thermoplastic aliphatic polyester derived from renewable biomass. Typical raw materials used in the production of PLA include fermented plant starches, such as corn, cassava, sugarcane, sugar beet pulp, and, to a lesser extent, lignin wood waste. Similarly, polybutylene adipate terephthalate (PBAT) is a biodegradable random copolymer, specifically a copolyester commonly derived from adipic acid, 1,4-butanediol, and terephthalic acid. It is advantageous to use renewable PBAT rather than PBAT derived from nonrenewable petroleum sources. In various cases, one or more of these components may be blended.

[0085] Blends of two or more thermoplastic biopolymers offer a combination of properties and price points not found in single polymers or copolymers. There are many ways to successfully blend biopolymers together. A common method is to melt two or more biopolymer resins together using a twin-screw extruder, then extrude the molten biopolymer resin blend into strands, which are cooled and fed into a pelletizer to produce an array of pelletized pieces called a masterbatch. Another method of biopolymer resin blending is to use a compatibilizer to combine different chemicals together in a biopolymer blend. Typically, a compatibilizer and two or more biopolymers are melted together in the process, again using a twin-screw extruder or the like.

[0086] Thus, it has been determined herein that the blended thermoplastic biopolymer resins exhibit advantageous technical properties in forming the optimal microcellular flexible foam structures of the present disclosure. Some of the enhanced technical properties include: acceptable aging properties, excellent elongation, and excellent compression set, among other advantages. For example, benefits of using the biopolymer blends disclosed herein are the enhanced technical performance properties that result from the formation and use of a given biopolymer blend. Specifically, enhanced properties such as improved elongation, tensile strength, impact strength, and melt flow, to name a few, can all be realized when the appropriate combination of biopolymers and / or biopolymer-compatibilizer blends is achieved.

[0087] These resins can therefore be used in accordance with the methods and machines disclosed herein to produce blowing agents. Thus, in one aspect, the present disclosure relates to foaming processes. As described above, the machines and processes disclosed herein can be configured to perform a foaming operation, whereby gas pockets are trapped in a liquid or solid, and the foam can be used to produce lightweight polymeric materials. This is an advantageous solution for many types of products where foamed materials add multiple added value, such as soft cushioning, comfort items, technical athletic equipment such as shoe components, and impact protection. However, in various cases, the above-described optimal aliphatic and aliphatic-aromatic copolyester biopolymers or biopolymer blends alone are useful for producing flexible foams, and in various cases, their use in producing flexible foams can be enhanced by including a suitable blowing agent in the foaming process.

[0088] For example, a widely known blowing agent in use today is a chemical called azodicarbonamide (ADA). Azodicarbonamide is typically pre-impregnated into petrochemical thermoplastic masterbatch resins for use in conventional injection molded foam processes. In particular, pre-impregnation of chemical blowing agents such as ADA is typically included in bioplastic blends prior to foaming. The reason for this is that pre-impregnation of chemical blowing agents such as ADA is required because conventional injection molded foaming requires custom foam molding variability. That is, chemical blowing agents such as ADA are limited in their ability to modify or affect the physical aspects of the foaming process during the point of manufacture.

[0089] Conversely, the specialized foaming process of this disclosure benefits from the physical foaming provided by a noble or inert gas, such as nitrogen. In this process, the gas, e.g., nitrogen, dosage can be adjusted in concentration within the biopolymer melt, which has a direct effect on the foaming results, which may be considered a major advantage for customizing certain aspects of the resulting foam. While there are several petrochemical-derived thermoplastics known to be biodegradable and industrially compostable, such as PBAT copolyesters, it would be advantageous to use renewable-source raw materials, such as a line of pure PBAT copolyesters.

[0090] For example, in the production of blowing agents, it may be useful to first create a customized masterbatch, such as a bioplastic blend, tailored to produce a specific type of biodegradable, industrially compostable flexible foam for a specific product type. For example, different types of customized masterbatch compounds may be created for different types of product applications. This can be illustrated by noting that what is useful for producing a specific type of foam in a pair of shoes may be different from what is needed to produce a specific type of foam, such as for use in the manufacture of a piece of furniture. Furthermore, each customized masterbatch may contain different colorants for a specific product application. Again, different product types require different aspects of customization, and the ability to create uniquely distinct masterbatches is highly advantageous for these specific applications.

[0091] Unfortunately, ADA is not environmentally friendly and is a suspected carcinogen to human health. As a result, its use in the present method and the products produced thereby is limited in its benefits. Furthermore, conventional petrochemical thermoplastic masterbatch resins are not biodegradable or industrially compostable, and therefore their benefits are also limited. In view of these deficiencies in the use of ADA and conventional petrochemical products to produce masterbatches, a biodegradable, industrially compostable thermoplastic biopolymer resin is presented herein that can be used to produce a masterbatch for making biodegradable, industrially compostable microcellular flexible foam.

[0092] In various cases, as described above, a supercritical fluid can be injected into the molding process by a system to achieve a more optimal biodegradable and industrially compostable flexible foam for use in the production of molded end products, for example, in an environmentally emission-neutral manner. Specifically, a supercritical fluid is a substance (liquid or gas) that is in a state above its critical temperature (Tc) and critical pressure (Pc). At this critical point, gas and liquid coexist, and the supercritical fluid exhibits specific properties that are different from, for example, either a liquid or a gas under standard conditions. It is advantageous to use inert supercritical fluids, such as nitrogen, CO2, He, Ne, Ar, Xe, and other such inert gases, for example, in the supercritical fluid state, and these gases can be used as blowing agents in the foaming process according to the methods disclosed herein.

[0093] The supercritical fluid works by solubilizing in the polymer matrix in the barrel of the injection molding machine. When the specialized injection molding process injects the liquid bioplastic compound into the injection mold cavity under controlled pressure and temperature, the gas completely expands the polymer melt to the full extent of the mold cavity. In this process, the gas helps maximize the cellular structure of the polymer matrix during the foaming process. This maximization of the specialized foaming process ensures that undesirable sink marks or warpage in the final foamed part are minimized. This is because conventional blowing agents are not subjected to the same types of supercritical conditions or pressures, and therefore Conventionally produced foams are very different from conventional chemical blowing agent produced flexible foams in that they lack consistency in the final foamed part and they can contain undesirable sink marks and warpage.

[0094] More specifically, in various cases, inert gases such as nitrogen or carbon dioxide can be compounded in a supercritical fluid state, which can then be used as physical blowing agents, for example, in the novel injection molding machines and processes described herein. In such cases, the disclosed modified physical foaming process can be used in conjunction with a suitable thermoplastic biopolymer or blended biopolymer masterbatch, so that the biopolymer or biopolymer blend and blowing agent work in harmony to produce the most optimal biodegradable and industrially compostable flexible foam.

[0095] Suitable biopolymers, bioplastics, and bioplastic blends of the present disclosure can be derived from renewable resources, such as those that do not compete with animal feed and human food, and those derived from waste streams of renewable resources. Non-limiting examples of suitable biopolymers for use in producing biopolymers or biopolymer blends include polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoates (PHA), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene succinate adipate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS). Suitable biopolymer blends of the present disclosure are any hybrid biopolymer blends composed of any combination of the biopolymer and bioplastic types listed above and biomass-containing poly(butylene adipate-co-terephthalate) (PBAT), a non-limiting example of which is a lignin-containing PBAT blend, where the lignin originates from wood waste and the PBAT originates from renewable resources.

[0096] Thus, in various embodiments, the injection molding apparatuses and methods of use disclosed herein are useful for producing foams with uniform cell nucleation. As described, the apparatuses and methods of use disclosed herein can be used to produce uniform cell nucleation to produce foams whereby foam nuclei are randomly and naturally generated and thus irreversibly grown in a single-phase solution system with minimal or no impurities. For example, as specified herein below, in one aspect, a process for producing flexible and / or rigid foams is provided. The method can be carried out to induce open-cell or closed-cell foams, for example, foams with inherent compostable, antibacterial, and / or flame-retardant properties.

[0097] In some cases, the method may include one or more steps of forming a masterbatch, for example, by blending one or more resins, such as a copolymer carrier resin, and various foam material components. In a subsequent step, the method may include adding an antimicrobial compound, so that the foam material can be used in the manufacture of antimicrobial, antibacterial, and / or antiviral footwear components, furniture components, yoga mats, clothing, sporting goods components, medical devices, and / or flame-retardant articles of manufacture, and other suitable applications. In particular, products produced according to the methods disclosed herein can be used in a wide range of applications, and their production process can generally be broken down into three distinct phases: first, a bulk polymer product is produced; then, the polymer is subjected to various processing steps; and finally, the polymer is converted into its final product, such as clothing, antimicrobial carpet, furniture, automotive parts, yoga mats, shoe components including soles, midsoles, and insoles, etc.

[0098] In particular, this single-phase solution can be used to generate nucleation sites where bubbles can grow. The bubbles expand due to the diffusion of gas into the bubbles. The machines and processes disclosed herein are particularly useful for initiating the foaming process, resulting in the occurrence of uniform cell nucleation in a manner that results in small bubbles being uniformly dispersed within the foam matrix. Specifically, unlike conventional foaming, the flexible foams formed by the supercritical fluids of the present disclosure benefit from greatly improved mechanical properties that can be directly attributed to the small bubble size. More specifically, the apparatus and methods disclosed herein are configured to produce bubbles on the order of 100 microns or more to about 1 micron or less, e.g., about 50 microns to about 10 microns or less, e.g., about 20 to about 40 microns (including about 30 microns), which are produced by the use of thermodynamic instability, all without the use of conventional chemical blowing agents in the production of the foam.

[0099] For example, in certain embodiments, a system can be configured to use the novel injection molding machine disclosed herein to produce biodegradable, industrially compostable, microcellular flexible foams with uniform cell nucleation that can occur when a single-phase solution of a biopolymer or biopolymer blend and a supercritical fluid (SCF) passes through an injection gate and enters the mold cavity of the injection molding machine. Specifically, as described in more detail herein below, the injection molding machine is configured to produce molten material, for example, by injecting a molding precursor into a mold to produce a finished part or component. The injection molding machine can include a material hopper, an injection ram or screw-type plunger, and a heating unit. Such injection molding machines are rated in terms of tonnage, which represents the amount of clamping force the machine can exert.

[0100] Thus, the process can begin with a granular bioplastic compound being pumped from a hopper into a heated barrel by a force ram. As the granules are gradually moved forward by a special reciprocating screw-type plunger, a supercritical fluid is introduced via an injector by a separate supercritical metering accessory that can be directly connected to the injection molding machine, which flows into the screw. As a result, the supercritical fluid becomes saturated within the biopolymer melt as the screw rotates, creating a single-phase solution.

[0101] The molten mixture is then pumped into a heated chamber with high back pressure, where it is melted at a temperature controlled by a computer interface. As the plunger advances, the molten bioplastic compound is forced through a nozzle supported by the mold and can enter the mold cavity through a gate. Thus, the foaming process can be configured to subject the polymeric material to a mechanical or physical process, whereby heat and pressure are applied to the polymeric material in the presence of a blowing agent. The blowing agent can be of chemical origin, as in traditional closed-cell EVA foam, or it can be of inert origin, as in the biodegradable and industrially compostable flexible foam of the present disclosure. Therefore, with the above in mind, as the solution enters the mold, pressure drops, which causes the SCF to come out of solution and create bubble nuclei.

[0102] Specifically, the supercritical fluid saturates within the biopolymer melt during screw rotation, which creates a single-phase solution under certain temperature and pressure conditions. The molten mixture is forced into a heated mold chamber with high backpressure, causing the pressure of the single-phase solution to drop from the microcellular process pressure to atmospheric pressure, resulting in a rapid pressure drop. Nucleation occurs due to gas separating from the mixture. At this point, the nuclei grow into stable bubbles. Bubble size is determined by saturation, microcellular process pressure, and mixing temperature, all of which can be controlled by the present system and method. As a result, millions of nuclei are generated, and bubble growth begins when the nuclei are stable.

[0103] Foam morphology is determined by the SCF concentration as well as the injection molding process parameters. Thus, these parameters may be adjusted to produce a useful and / or determined foam morphology. , can be selected for control by the system. Once the part is formed, the mold is cooled, reducing the melt temperature, which causes the melt to freeze and solidify. Again, these parameters can be tightly controlled by the system, depending, for example, on the final product being produced. Specifically, at this point, the bubbles stop growing and the shape of the resulting part is fixed. The bubbles then grow until the material fills the mold, consuming the expansive properties of the SCF.

[0104] Thus, in this process, a molten biopolymer and SCF blend is controllably ejected into a heated mold cavity and experiences a sudden pressure drop. Millions of tiny bubbles are generated from nucleation growth, and these bubbles physically expand the molten mixture to the maximum constraints of the mold cavity. Once the molten mixture has expanded to its maximum physical potential, the material is rapidly cooled within the mold, bubble formation ceases, the molten mixture stops expanding, and the final solidified part is formed. All of this occurs within a few seconds within the injection molding system.

[0105] As shown, this manufacturing process operates on the injection molding machine, which has been modified to precisely control the following: metering, delivery, mixing, temperature, pressure, injection, speed, etc. For example, an auxiliary metering unit can be used to control metering to deliver precise SCF gas dosage into the polymer melt. Specifically, a suitable gas dosage accessory can be configured to convert the inert gas to a supercritical fluid state and meter the dosage of SCF delivery into the injection molding machine, for example, by a computer-controlled mechanism.

[0106] For example, an operator or a suitably configured microcontroller can program the gas dosing accessory to a predetermined SCF gas dosage. Essentially, the gas dosing accessory is an SCF delivery system that can be electronically and / or physically coupled to an injection molding machine. In particular, a suitable SCF gas dosing accessory for use in the present disclosure can be configured to generate lines of a gas dosing system designed to convert industrial-grade nitrogen or other inert gas into a supercritical fluid. The gas dosing device can be configured to accurately dose and inject SCF into an injection molding machine at pressures up to and even exceeding 275 bar.

[0107] To operate the gas dosing device, an operator can use an associated computing device, such as a desktop or laptop computing device, configured to generate a graphical user interface (GUI) for controlling the system and individual control parameters, such as the dosing device. For example, an operator can input selected parameters, such as desired SCF gas dosing shot parameters, into the GUI. The system's processing element then calculates all dependent parameters in real time to optimize SCF delivery into the injection molding machine. As a result, the system's control unit ensures that the gas dosing system and the injection molding machine work symbiotically together, for example, via a computer-controlled network. This gas dosing system is thus a unique attribute of the present disclosure, because supercritical inert gas can conveniently be used as a physical blowing agent to produce the biodegradable, industrially compostable flexible foams of the present disclosure, replacing the chemically reactive blowing agents used in conventional flexible foams. This control of SCF mixing into the biopolymer is useful for creating a single-phase solution.

[0108] Furthermore, during the injection molding process of the present disclosure, SCF is injected into the polymer melt. A single-phase polymer-SCF mixed solution is obtained in the injection molding machine screw and barrel under a defined temperature and pressure. The temperature and pressure can be variably controlled and can be directly related to the type of flexible foam produced and the type of application for which the final product will be used. At this stage, the concentration of SCF is determined by saturation, microcellular process pressure, and mixing temperature. An example can be provided for producing biodegradable and industrially compostable flexible foam of the present disclosure for use in the manufacture of foam furniture, automotive, athletic, and / or shoe components, particularly shoe midsoles. Suitable foams for use in this non-limiting example include: A non-limiting example of a suitable biopolymer blend is a rapidly renewable PBAT biopolyester formed into a biopolymer compound.

[0109] Thus, the granular biopolymer compound is first fed into the injection molding machine through a hopper. The biopolymer is then gradually moved through the injection molding machine screw and barrel, during which a specific SCF gas dosage is introduced into the now-molten biopolymer compound, uniformly mixing and completely saturating it. The molten biopolymer compound and SCF are now a single-phase solution. A non-limiting example of an initial SCF gas concentration can be Co=0.25%, with a melt temperature range of 176°C to 250°C, more preferably 180°C.

[0110] Additionally, in various embodiments, the temperature within the mold, along with the pressure, can be precisely controlled, for example, in a dynamic mold temperature control (DMTC) protocol. For example, a DMTC process can be used to ensure a consistent cell structure within the expanding biopolymer melt. In particular, DMTC can be configured to include rapid changes and control of mold temperature and / or pressure during the injection-filling stage. This therefore dynamically controls mold temperature and / or pressure in terms of both high- and low-temperature thermal cycling, with or without pressure.

[0111] For example, the system's control module may be configured to control the mold temperature during the injection-filling stage; for example, dynamic mold temperature control may be used in such cases. More particularly, compared to conventionally known injection molding processes, a key feature of the dynamic mold temperature control employed herein is that the mold temperature itself may be dynamically controlled. Prior to melt injection of the single-phase solution, the mold may initially be heated to a preset upper limit. During the melt-filling stage, the temperature of the mold cavity surface may be maintained above the upper limit to prevent the melt from prematurely solidifying. Upon completion of the melt-filling process, the mold is immediately cooled to a lower limit (ejection temperature), and then the molded foam part is removed from the mold cavity.

[0112] The dynamic mold temperature control (DMTC) implemented herein relies on a control method based on rapid electric rod heating and rapid water cooling. Specifically, the DMTC employed by this disclosure consists of five main components: an air compressor, a valve changer, a computer-controlled mold temperature control unit, an electrically heated mold, and a cooling tower. The cooling tower can be used to provide sufficient water cooling to the mold. The air compressor is used to generate compressed air as a driving gas for the air valve and to remove residual cooling water from entering the mold after cooling. The valve changer is used to switch valves to transfer different media (e.g., hot / cold thermal cycles) from the pipeline to the mold.

[0113] Thus, in various cases, the machines and processes herein may include pipes and other conduits for passing reactive materials, the conduits associated with one or more heat exchange units so that the reactants are heated and / or cooled as they are pumped into and / or through the conduits and pipes. In such cases, the exchangers may be controlled to regulate the temperature to reaction levels. A dispensing head may be included on one end of the pipe, which may be associated with one or more valves. Further, the dispensing head may be connected to a processing line. An electrically heated mold is used to mold the final shape of the foamed part. The function of the mold temperature control is to control the heating and cooling of the mold; all of this is computer-controlled and coordinated with the injection molding machine.

[0114] Similarly, as shown, pressure can also be finely controlled, for example, by a gas counter pressure (GCP) protocol. For example, a GCP protocol can be used in the manufacturing process to better ensure optimal foam structure in the final product, and to ensure little to no skin on the resulting flexible foam. For example, this GCP process can be used Using SCFs, they can be injected into a pressurized mold cavity, which can act alone and together to counteract the expansion of gases within the melt. In particular, as the counterpressure is released, gas bubbles that would normally break through the surface are trapped inside, creating a smooth skin.

[0115] This gas counterpressure process prevents gas bubbles from contacting and collapsing the surface of the foam material as the foam part is being formed. This is accomplished by a counterpressure applied by the GCP system into the mold cavity simultaneously, or nearly simultaneously, with the molten single-phase solution injection shot and during the hold period. The inert gas bubbles are subjected to enormous forces, so the molten single-phase solution is not given an opportunity to release bubbles trapped outside the foam structure during formation. The result is a molded foam part with a smooth-looking skin formed on the outside of the part.

[0116] Thus, as implemented herein, the system's controller can implement a gas counter pressure (GCP) procedure, which is configured to improve control of the foaming process by applying different gas pressures during the melt injection stage of foam injection molding. For example, by controlling various components of the system, the control system can be configured to apply various screw-inclusive SCF single-phase solution pressures and GCP pressures in conjunction with, for example, the proper shot size, shot hold time, melt temperature, and mold temperature.

[0117] In this way, an entire system is created that can produce high-quality, commercially acceptable, biodegradable, and industrially compostable flexible foam parts. Specifically, slight changes in the GCP pressure affect the surface quality of the foam. For example, without the use of GCPs, bubbles formed in the polymer melt located in the mold cavity would be released, resulting in an unacceptable surface appearance for the resulting foam part. In addition, without the use of GCPs, the skin thickness may be unnecessarily thick because there is no counterpressure to counteract the rapid cooling of the molten single-phase solution as it expands into the mold. In particular, the single-phase solution would impinge on the steel mold interface during the injection shot and immediately solidify with an undesirably thick skin, which would be unacceptable in most commercial applications. In short, process parameters have a clear impact on the quality of the final part. Thus, the GCP process can be implemented to control foaming through one or more of, for example, surface quality, foam structure, skin thickness, etc.

[0118] Thus, in various embodiments, the system can be configured to produce the SCF in a manner that forms a single-phase solution. In particular, in various embodiments, a single-phase solution is created in which the SCF can be completely dissolved and uniformly dispersed in the molten biopolymer, which occurs inside the injection barrel under carefully controlled process conditions. For example, as described, the formation of a single-phase solution is important for producing consistent, mass-producible molded foam parts of the present disclosure.

[0119] As a result, the injection molding system process should be configured to be controllable and repeatable in a highly consistent manner. To achieve this, the first line of defense is ensuring that the biopolymer compound and SCF are homogeneously mixed into a single-phase solution, e.g., a single-phase solution that is fully saturated and dispersed within the biopolymer melt in the injection molding machine barrel. Once a single-phase solution is achieved, the system can reliably input the desired shot weight, shot hold time, and GCP gas dosage to customize endlessly reproducible molded foam parts in a time-optimized, mass-producible manner.

[0120] Therefore, the SCF must be accurately mass-metered into the biopolymer for a certain period of time. For example, the system control module must monitor temperature, pressure, and flow rate during the administration period. The SCF delivery system can be configured to establish suitable conditions for shearing within the barrel. Similarly, back pressure, screw speed, and barrel temperature can be closely controlled by one or more control elements of the system. Additionally, the SCF delivery system can be adjusted to establish process conditions that create an optimal single-phase solution.

[0121] For example, as described above, the control module can be communicatively coupled to a system-associated mass flow metering device configured to measure the mass flow rate of a fluid moving through one or more vessels, e.g., tubing, of the system. Mass flow rate is the mass of fluid moving past a fixed point per unit time. As it relates to the present disclosure, the principles of mass flow metering are implemented to ensure consistent repeatability in the foam molding process. Specifically, as described above, a specially designed injector is coupled to the injection molding barrel, which can be controlled by computer-controlled programming of the system's processor. As a result, the system can be configured to perform a specific SCF gas dosage delivery into the biopolymer melt, and the computer-controlled program can optimize the delivery based on real-time data collection from the mass flow rate, e.g., via feedback from one or more system sensors. This use of mass flow metering ensures the most optimal process control for the single-phase solutions of the present invention.

[0122] Thus, during the administration period, the temperature throughout the system, such as within the barrel, can be controlled to be between 100° C. and 600° C., e.g., 200° C. and 500° C., e.g., 300° C. and 400° C., more particularly, between 320° C. and 380° C., inclusive. Similarly, the SCF delivery pressure can be closely controlled to be between 1,000 and 8,000 PSI, e.g., 1,500 and 6,000 PSI, e.g., 2,000 and 5,500 PSI, particularly, between 3,000 and 4,000 PSI, more particularly, between 2,600 and 2,800 PSI.

[0123] In this manner, the control module can be configured to coordinate temperature and pressure to generate an optimal nucleus and resulting bubble within the biopolymer melt and resulting foam matrix. Additionally, with regard to shear, shear is established within the barrel as layers of molten biopolymer flow past each other. Thus, during injection, the molten biopolymer compound can be caused to flow through the melt delivery channel of the barrel nozzle before entering the mold, e.g., like a fountain.

[0124] Shear is the stretching of the biopolymer between the rotating screw and the stationary barrel, generating heat within the material. Therefore, shear must be controlled during the injection molding process. As a result, one or more control units of the system can be configured to control, for example, the injection rate, fill time, and tolerances therein, to achieve suitable conditions for producing a given biopolymer compound with a given injection molding machine size and given injection molding machine screw and barrel sizes.

[0125] Backpressure can also be controlled. For example, backpressure is the pressure in an injection molding machine that exerts when a biopolymer is injected into a mold. Specifically, backpressure is the resistance applied to the injection screw as it returns to dispense the next shot of biopolymer into the mold. As indicated above, various parameters of the system can be configured to control and / or regulate backpressure.

[0126] Additionally, the system's controller can be configured to control and adjust the screw speed. The screw speed can be controlled by computer control. As shown, during the initial phase of the injection molding operation, the screw rotates within the barrel and cooperates with the SCF gas to homogenize the molten biopolymer compound mixture. Non-limiting screw speeds of the present disclosure Typical examples may be 1 or 5 or 10 to 75 or 100 or 200 rpm, for example 20, 25, or 30 to 40, 50 or 60 rpm.

[0127] The system may include a heating and / or cooling control unit that may be associated with the barrel to control the temperature therein. Accordingly, the control module may be configured to control the barrel temperature. Thus, the barrel temperature may be controlled to make the temperature therein hotter or cooler as needed for the foaming process.

[0128] Therefore, in view of the above, an SCF delivery system may include a control unit configured to control a combination of SCF delivery pressure and SCF dosage weight (typically measured in grams). The SCF pressure and dosage can be controlled in a manner that affects a single-phase solution. That is, the lower the SCF dosage, the less SCF saturation is required in the biopolymer melt, and the higher the SCF dosage, the more SCF saturation is required in the melt. Similarly, the lower the SCF delivery pressure, the lower the saturation uptake and therefore the lower the growth of nuclei that can grow to form bubbles in the molten biopolymer melt. The higher the SCF delivery pressure, the higher the saturation uptake and therefore the higher the growth of nuclei that can grow to form bubbles in the molten melt.

[0129] With respect to saturation, the system and apparatus are configured to deliver gas to the melt chamber under a temperature and pressure such that a supercritical fluid is formed and saturated within the biopolymer melt, for example, during screw rotation. As a result, a single-phase solution is produced under controlled temperature and pressure. Specifically, a single-phase polymer-SCF mixture solution can be obtained herein within the injection molding machine screw and barrel at a defined temperature and pressure. More specifically, the system controller can variably control the temperature and pressure in a manner that depends on the type of flexible foam to be produced and what type of final product is to be produced.

[0130] At this stage, the concentration of the SCF can be determined and controlled, for example, by a feedback loop, whereby the amount of saturation is determined, for example, by a sensor that evaluates the progress of the saturation process and then adjusts the microcellular process pressure and mixing temperature based on the achievement of a predetermined set point for the saturation level. In such cases, the supercritical fluid (SCF) controllably saturates within the biopolymer melt during screw rotation, which produces a single-phase solution under a defined temperature and pressure. The SCF is one component of a two-component molten biopolymer compound mixture, which is used as a physical blowing agent in the present injection mold under a defined pressure and temperature.

[0131]

[0006] Therefore, in one aspect, provided herein are machines and methods for the production of biodegradable, industrially compostable microcellular flexible foams. In particular, by way of example, the foams may be produced, for example, by a microcellular injection molding (MuCell) process, e.g., MuCell production, and / or used in the production of foamed products. MuCell production employs a supercritical fluid, as described above, that is subjected to extreme pressure and dissolved in a polymer melt within a screw barrel of a production tool, e.g., as described below, where the production tool is configured to optimize SCF dosing for the purpose of producing a molten biopolymer melt heated to a liquid state.

[0132] Thus, at the heart of the injection molding machine are the injection molding machine barrel and the screw contained therein, both of which are manufactured from ordinary tool steel. The barrel is the main delivery portal for this single-phase solution before it is metered and then forced, or "squirted," into a dynamically temperature-controlled mold part. As a result, the biopolymer melt is delivered into the barrel via the injection molding machine hopper. The system controller feeds a predetermined amount of granular bioplastic pellets into the hopper as one of the first steps in the injection molding machine operation.

[0133] Specifically, during injection, the SCF vaporizes and becomes gas bubbles, e.g., foam, in the form of a finished molded part. As the bubbles reach micron size, the process produces microcellular foam. The process described herein is advantageous over conventional injection techniques because it results in a final product that exhibits one or more of the following: less shrinkage, a lightweight product, few sink marks, and can be produced with low-cost precursors. More specifically, with regard to less shrinkage, shrinkage can be controlled by understanding that volumetric shrinkage is caused by thermal shrinkage, which affects all polymers; therefore, shrinkage can be avoided by tracking the progress of shrinkage with system sensors and by closely controlling barrel conditions to regulate the shrinkage process.

[0134] Essentially, shrinkage describes the degree to which a material's volume changes as it changes from a liquid to a solid. In conventional injection molding, the mold is not temperature controlled along with the pressure, so the molten polymer used by conventional methods shrinks upon contact with the cold tool steel of the injection mold, which causes shrinkage. In the present machines and systems, shrinkage is a negligible issue due to the controlled, typically temperature-controlled, pressure mold, which ensures that the molten biopolymer fills the maximum surface area inside the mold and there is no premature cooling, as well as the applied uniform stress of the pressure mold cavity itself further aiding in this regard.

[0135] Generally, for lightweight product manufacturing, the more the polymer is expanded, the greater the weight reduction. However, the present system can be configured to optimize the single-phase solution by adjusting the conditions through the application of appropriate pressure, temperature, and time, so that optimal quality of the lightweight foam can be achieved. This is good for product applications requiring lightweight foam, such as cushioning, footwear foam, and foam used to manufacture athletic equipment. Similarly, with regard to sink mark control in traditional flexible foam manufacturing, sink marks and voids are caused by localized shrinkage of the material in thick sections without sufficient compensation as the part cools.

[0136] In particular, sink marks typically occur on surfaces opposite and / or adjacent to legs or ribs. This occurs due to unbalanced heat removal and / or similar factors. After the outer material of a foam part cools and solidifies, the core material begins to cool. Its contraction pulls the main wall surfaces inward, causing sink marks. If the skin is sufficiently stiff, deformation of the skin can be displaced by the formation of voids in the core.

[0137] Unlike the sink marks and voids challenges faced by conventional flexible foam molding, the machine configuration and system parameters can be controlled to produce the biodegradable and industrially compostable flexible foam of the present disclosure, minimizing the occurrence of these problems. In particular, in the present process, the SCF gas is controlled to adjust, e.g., maximize, the cell structure of the polymer matrix during the foaming process. This maximization of the specialized foaming process better ensures that no undesirable sink marks or voids are present in the final foamed part.

[0138] Additionally, as shown, a useful benefit of the present system is that it uses lower cost materials and the resulting final product has less warpage. In particular, for many of the reasons described above, the present disclosure benefits from a process in which SCF gas contributes to maximizing the cellular structure of the polymer matrix within the foaming process. This maximization of the specialized foaming process ensures that warpage is minimized within the final foamed part.

[0139] Another benefit of the present system is that it can be configured to control tolerances. For example, the system can be configured to perform tight tolerance soft foam injection molding. In particular, the tight tolerance soft foam injection molding presented herein produces parts that work smoothly together. This can be used to create a lower overall defect rate for the product.

[0140] All of its parts must fit together smoothly to ensure the product works as intended. Therefore, the devices and their components are designed to tightly controlled tolerances. Typically, these parts are produced to the best tolerances possible. There are different ranges of acceptable tolerances; for example, a very tight tolerance is + / - 0.001". Sometimes even a few thousandths of an inch can mean the difference between a part that fits and one that doesn't.

[0141] As a result, it is useful to identify tight tolerances early in the design process, as design engineers must consider requirements for foam part shape, overall foam part size, and foam part wall thickness—all of which have an impact on tolerance control, and all of which, if not carefully managed, can exacerbate sink marks, warpage, and inconsistent part tolerances. The present system and apparatus overcomes most of these design challenges while still using best design practices, because the SCF gas contributes to maximizing the cell structure of the polymer matrix during the foaming process. Similarly, the system can be configured to cool more rapidly within the mold.

[0142] As a result of the above, sink marks, warpage, and tolerance inconsistencies are greatly reduced. This is primarily due to the uniformly sized, evenly distributed microscopic bubbles within the foam matrix. Therefore, to achieve these benefits, the microcellular foaming process must be closely controlled. For example, as shown, if foaming occurs along the melt front, advancement can introduce streaks and flow lines on the molded surface, causing defects.

[0143] In addition to the above, these defects may be further minimized herein by employing one or more of co-injection and in-mold decoration techniques. However, in many cases, this may be cost-prohibitive. Nevertheless, the present system overcomes such cost-prohibitive cases by selecting opportunities for high-quality products, in which case the added value of the present disclosure may be tolerated and appreciated.

[0144] It should be noted that SCF foaming can have disadvantages in various cases, as it can cause changes in melt viscosity and other physical properties. In particular, when SCF is dispersed uniformly throughout a polymer melt, the single-phase solution acts as a reversible plasticizer by increasing the free volume and thereby reducing the viscosity of the polymer. This effect also reduces the polymer's glass transition temperature and its tensile strength. This can result in non-uniform bubble sizes.

[0145] Non-uniform bubble size potentially leads to the production of molded foam parts with inconsistent technical performance characteristics across the part, as well as potentially undesirable cosmetic issues, both of which are problematic when attempting to produce consistently reproducible biodegradable and industrially compostable flexible foams containing the same technical performance characteristics from part to part during mass production. The present system is configured to overcome these challenges.

[0146] Therefore, as mentioned above, to overcome these disadvantages and to provide greater control over the microcellular foaming process, gas counter pressure (GCP) is employed. As mentioned above, the gas counter pressure is closely controlled so that the gas bubbles do not contact and penetrate the surface of the foam material as the foam part is being formed. This is achieved by applying a counter pressure into the mold cavity by the GCP system, It can be simultaneous, or nearly simultaneous, with the injection of the molten single-phase solution, while controlling the hold time within the mold. Mold temperature and pressure can also be closely controlled for these purposes.

[0147] Upon injection, the inert gas bubbles are subjected to enormous forces, so the molten single-phase solution is not given an opportunity to escape outside the foam structure while trapped bubbles are being formed. Similarly, the enormous forces acting on the single-phase solution help better distribute the millions of tiny bubbles within the foam structure inside the mold, as well as aid in bubble size consistency. The result is a molded foam part with a smooth-looking skin formed on the outside of the part, and consistent bubble size for repeatable technical performance characteristics from part to part during mass production.

[0148] For example, the system can be configured to allow the introduction of GCPs to control the foaming process, e.g., by applying different gas pressures and / or temperatures during the melt injection stage. As a result, the GCPs are introduced into the foaming process within a mold cavity present in an injection molding machine. First, an inert gas is introduced into the mold cavity through a gas control valve by a gas compressor and gas pump. A gas pressure sensor provides real-time data feedback from the gas control valve to a computer-controlled device.

[0149] The system initiates GCP dosing into the mold cavity by setting dosing parameters and hold times within the computer system. The computer system then initiates the proper dosing of inert GCP shots into the mold cavity. Without the use of GCPs, the biopolymer melt would enter the mold cavity and immediately begin to foam, creating uneven bubbles of gas that could break through the surface and create undesirable swirl marks on the outside of the foam, which is problematic.

[0150] Similarly, the injection rate can also be precisely controlled; for example, the injection rate can be determined by the difference between the screw pressure (Pscrew) and the gas pressure (Pgas). Specifically, if Pscrew is slightly higher than Pgas and both parameters are sufficiently high, the SCF melt will flow into the mold cavity without foaming. Setting Pscrew higher than Pgas and Pgas below the critical pressure will result in partial foaming. Finally, the appropriate selection of Pscrew, Pgas, and pressure differential in combination with the dynamic mold temperature allows for more precise control of bubble size. Thus, fine tuning of these parameters can minimize, if not eliminate, flow-induced streaks.

[0151] Specifically, these parameters can be determined in part by considering flow behavior. For example, in one embodiment, rheology (flow) was generated for a polymer melt containing 0.4 wt% SCF in N2 at different mold temperatures (185, 195, and 205°C), injection speeds (5, 10, and 15 mm / s screw speed), and ground pressures (50, 100, 200, and 300 bar). In these cases, the measured shear rates were in the 3000-11000 s-1 range, and the glass transition temperature, Tg, was reduced from 96 to 50°C when the ground pressure was 300 bar. Similarly, in this case, compared to conventional injection molding, the melt viscosity dropped by approximately 30% when the ground pressure was increased from 50 to 200 bar.

[0152] Specifically, when the GCP is 300 bar, the viscosity of the single-phase injection melt without foaming can be reduced by as much as 50% depending on the injection conditions. This is useful because it reduces the pressure and temperature requirements, thereby reducing production costs, particularly energy costs, and also reducing the foam part cycle time during production. As a result, all of these system parameters support greater energy savings due to lower pressure and temperature requirements and shorter cycle times, which can be used to manufacture, for example, suitable biopolymer compounds. Selecting the right tool and adjusting process temperature, pressure, and hold time to match the material's mechanical properties leads to more parts being produced faster and for less money.

[0153] Additionally, as shown, a key feature of the present machines and systems is that they can be configured to control bubble size for greater uniformity. As noted above, this can be achieved in part by controlling temperature, pressure, SCF dosing control, GCP, DMTC, and other parameters discussed above. All of these attributes work in concert to ensure optimal, most uniform bubble size and their optimal, uniform distribution within the foam matrix. Furthermore, surface quality can be improved by controlling fluid drift along the melt front.

[0154] As the name suggests, the melt front is the point at which the molten single-phase solution enters the mold cavity. Melt front velocity is the rate at which the melt front advances. For any mold with a complex cavity shape, some areas of the cavity may fill faster than other areas. By controlling the melt front velocity, for example, by controlling temperature, pressure, and SCF dosing control, among other parameters, a more uniform mold cavity fill rate can be achieved, which ensures that the surface quality of the resulting foam part is cosmetically acceptable.

[0155] Thus, once the single-phase solution is created, the modified injection molding machine described above maintains the solution under pressure until the start of injection. For example, the machine can be configured to achieve this through the cooperation of a shut-off nozzle and screw position control, as shown above. In particular, a shut-off nozzle can be configured to serve as a connection between the plasticizing barrel (with the reciprocating screw) and the mold. Such shut-off nozzles can be automatically or externally controlled, and they can be used to avoid melt dripping between melt shots, thereby preventing decompression and premature foaming into the mold.

[0156] As a result, the shut-off nozzle prevents decompression and premature foaming into the mold. For example, without the shut-off nozzle, the single-phase solution would not have sufficient pressure in the mold cavity and the desired molded foam part would not be produced. Similarly, either active or passive screw position control can be used to prevent decompression due to screw retraction.

[0157] In particular, the system can be configured to perform active screw position control, e.g., the position of the screw is continuously monitored and the pressure applied to the back of the screw is adjusted to maintain a determined position setpoint or so that a constant pressure is maintained at the back of the screw. For example, in passive position control, the oil used to control the back pressure is prevented from flowing to its reservoir at the end of the screw return. This residual oil keeps the screw from retracting due to the pressure of the single-phase solution.

[0158] Additionally, as noted above, proper mold design helps maintain a single-phase solution. Specifically, in these cases, the mold includes a hot runner system, which may include one or more valve gates and be controlled to prevent material drooling from the nozzle, for example, upon mold opening. More specifically, the hot runner system may be used in injection molding machines herein and may include a system of physically heated parts so that they can be used more efficiently to move molten plastic from the machine's nozzle into the mold cavity. For example, "cold" or "hot runners" may be used, where a cold runner is an unheated physical channel employed to guide molten plastic into the mold cavity after it leaves the nozzle; a hot runner is heated, while a cold runner is unheated.

[0159] Similarly, in various cases, the apparatus may include a nozzle brake configured to break contact with the sprue bushing during normal operation. This configuration is useful in stack or tandem molds, which employ a shutoff on the sprue bushing. In particular, the sprue bushing may be configured to receive a machine nozzle, thereby allowing molten biopolymer compound to enter the mold. If the machine nozzle must be removed from contact with the sprue bushing, the molten biopolymer compound may sag back from the sprue bushing, causing mold depressurization. All of this melt drip waste can increase production costs, adversely affect the next shot of melt, and prevent the mold from closing properly, potentially creating even more problems.

[0160] To overcome this, selecting a sprue bushing with a shutoff can be employed. Otherwise, pressure from the hot runner would be relieved through the sprue bushing. In particular, if the sprue bushing requires a shutoff, the shutoff prevents the escape of built-up in-mold pressure in addition to the other benefits mentioned above. Any decompression of the mold potentially prevents foaming of the molten part, resulting in the failure to form the desired molded part.

[0161] As indicated above, various blowing agents can be used for injection molding of biodegradable and industrially compostable microcellular foams. In particular cases, these blowing agents can include inert and / or noble gases, such as inert nitrogen gas or carbon dioxide or other gases that can be converted to a supercritical fluid (SCF) state. In accordance with the devices, systems, and methods of use disclosed herein, the SCF can be introduced, e.g., injected, into the machine, e.g., into the melt barrel, e.g., via a specially designed computer-controlled injector. The injector can be coupled, e.g., secured, to the injection molding machine barrel to deliver the blowing agent into the molten biopolymer melt in the barrel. The injection molding machine controller can be programmed to deliver a specific SCF gas dosage, whether nitrogen or carbon dioxide, into the biopolymer melt, and this delivery can be optimized by the system controller.

[0162] As a result, each of the above SCF blowing agents has its role depending on the technical requirements of the final part being produced. In particular, as shown, a useful SCF is carbon dioxide in its supercritical state, which is denser than nitrogen at the same pressure and also has a much higher heat capacity. Experiments have shown that carbon dioxide in its supercritical state produces dense foams that may be useful in certain cushioning applications. In contrast, supercritical nitrogen can be used to produce lower-density foam parts with smaller cells, which are useful in the footwear and sporting goods applications of the present disclosure.

[0163] Thus, a useful blowing agent for producing athletic equipment such as shoes is SCF nitrogen gas because it provides improved weight reduction and fine cell structure at a much lower weight percentage than SCF carbon dioxide, whereas in furniture and automotive applications, a useful blowing agent is carbon dioxide, which produces a much larger cell structure despite its larger size and / or weight. Specifically, in various cases, the enhanced weight reduction of foamed parts is a useful feature for product applications requiring minimal weight. As a non-limiting example, there is a continuing need for running shoes to contain flexible foams that are very lightweight and can withstand repeated abuse.

[0164] By providing enhanced weight reduction using microcellular structures in the above examples, injection molded flexible foam components may be relied upon for their ability to increase runner efficiency by producing acceptable lightweight shoes. This will ensure a highly durable running shoe with components that will be able to handle the repeated impact forces that result from the constant pressure and impact that a runner places on the foam components of the shoe during acceleration movements.

[0165] In fact, SCF nitrogen levels are typically at least 75 percent lower than the SCF carbon dioxide levels required to achieve comparable parts. Thus, the significantly reduced SCF nitrogen level requirements compared to SCF carbon dioxide ensure optimal material and time savings when mass-producing the biodegradable, industrially compostable flexible foams of the present disclosure for use in manufacturing shoe components. SCF carbon dioxide, however, is a useful blowing agent in a variety of special circumstances, such as when viscosity reduction is a primary process goal and / or when the application cannot tolerate the more aggressive foaming action of SCF nitrogen.

[0166] In some cases, SCF carbon dioxide is a suitable blowing agent, especially for semi-flexible foams. Both flexible and semi-flexible foams can be included in the same category of flexible foams because they are derived from polymers with glass transitions (Tg) lower than their use temperature, which is usually room temperature. During the physical foaming process using physical blowing agents, a decrease in the glass transition is observed. These differences in the effectiveness of nitrogen and carbon dioxide blowing agents arise from their behavior in biopolymer melts.

[0167] For example, carbon dioxide is four to five times more soluble in biopolymers than nitrogen, which becomes a supercritical fluid at 31.1°C and 72.2 bar and a supercritical fluid at -147°C and 34 bar. For example, the saturation point in unfilled biopolymers is approximately 1.5 to 2 weight percent nitrogen, depending on temperature and pressure conditions, while the saturation level for carbon dioxide is around 8 weight percent. Carbon dioxide also exhibits greater mobility in biopolymers, allowing it to migrate further into existing bubbles than nitrogen. From the perspective of bubble nucleation, greater solubility and mobility means that fewer nuclei are formed, and those that do tend to be larger.

[0168] Solubility, however, is an advantage when the goal is viscosity reduction. SCF dissolved in a biopolymer acts as a plasticizer, reducing the viscosity of the biopolymer. Because viscosity reduction is partially a function of the amount of SCF added to the biopolymer, and because carbon dioxide has a higher solubility limit than nitrogen, the ability to reduce viscosity using carbon dioxide is greater. Carbon dioxide is also useful when the amount of nitrogen required to produce a part is too low to consistently process the part.

[0169] Because carbon dioxide is a much less aggressive blowing agent, it can be easier to flow low levels of carbon dioxide. For example, 0.15 or 0.2 percent carbon dioxide compared to very low levels of nitrogen, less than 0.05 percent. The cases shown in the previous example occur primarily with soft materials and parts with thick cross sections. Therefore, physical blowing agents, whether SCF nitrogen, SCF carbon dioxide, or other SCFs, play a useful role in the final foamed parts and the end products that contain them.

[0170] First, selecting the appropriate combination of a compatible biopolymer or biopolymer compound and associated SCF gas is useful. Second, proper utilization of the SCF gas with optimal dosing weight and pressure is important to ensure maximum saturation within the single-phase solution and optimal generation of nuclei for generating millions of uniform bubbles within the foam matrix. Additionally, the end result of a uniformly formed injection-molded flexible foam part depends on all aspects of the SCF and GCP gas dosing process, as described above, working symbiotically with the injection molding machine temperature, pressure, and hold time to achieve a commercially acceptable molded foam part.

[0171] As shown, in one embodiment, a process for producing biodegradable, industrially compostable flexible foams, whether open-cell or closed-cell, is provided. In various cases, the manufacturing process includes one or more of the following steps: First, a thermoplastic biopolymer can be blended into a masterbatch for foaming. As a non-limiting example, the mentioned masterbatch can be produced by a twin-screw extruder, in which two or more biopolymers, fillers, and / or additives can be homogeneously blended into a single polymer melt, for example, in an extrusion barrel. The molten biopolymer blend is then extruded into strands, cooled, and pelletized into granules called masterbatches, which can then be processed as described above. Any combination of suitable biopolymers, bioplastics, fillers, additives, and colorants can be incorporated into the masterbatch production. Thus, once produced, the thermoplastic biopolymer blend can be injection molded into a suitable mold shape using an inert SCF, such as nitrogen or carbon dioxide gas.

[0172] As described above, injection molding can be used in manufacturing processes to produce parts by injecting molten material into a product mold. In this disclosure, a suitable biopolymer or biopolymer blend compound is selected, such as in granular form. The granules are pre-dried in an auxiliary pellet dryer to ensure that potential moisture is removed. The pre-dried pellets can then be introduced into the injection molding machine hopper. The operator then selects the optimal barrel temperature, nozzle temperature, and mold temperature for the injection molding machine and inputs these values through computer control.

[0173] Additionally, the optimum SCF gas dosage percentage and pressure, and the optimum GCP gas dosage and pressure can be determined, and these values can be input into or otherwise determined by, for example, a system control unit, dynamically. Once the system is properly configured, the injection molding machine is ready to operate. Granules can be discharged into the screw and barrel of the injection molding machine in amounts specified by computer control, where they are melted at a specific temperature or set of temperatures.

[0174] SCF gas is introduced into the injection molding machine barrel through an SCF injector under computer-controlled pressure and dose size. The SCF saturates the now-molten granules, creating a single-phase solution. Then, using the proper back pressure and screw positioning, the injection molding machine delivers a measured shot of the single-phase solution into a dynamically temperature-controlled mold cavity. Nucleation occurs within the melt, and millions of microcellular bubbles form within the biopolymer melt. Substantially simultaneously, the GCP system delivers a pre-metered dose of counter-pressure gas into the mold under computer control, optimizing bubble uniformity and surface texture conditions for optimal surface appearance. The dynamically temperature-controlled mold temperature can then be switched to water cooling, halting bubble formation and melt expansion. At this point, a flexible foam molded part is immediately formed and is removed from the mold.

[0175] In particular, as indicated above, the system may be configured to perform dynamic mold temperature control, which may be used to generate optimal foam structure. For example, as described, dynamic mold temperature control (DMTC) performs rapid electric rod heating and rapid water cooling. More specifically, the DMTC procedure employed herein may include one or more of the following five major components: an air compressor, a valve changer, a computer-controlled mold temperature control unit, an electrically heated mold, and a cooling tower. The cooling tower is configured to provide water cooling to the mold for performance of the cooling operation, while a suitably configured air compressor generates compressed air and drives the gas through an air valve to remove any residual cooling water from entering the mold after cooling. One or more valve changers are configured and employed to switch valves to move different media from various machine pipelines to the mold, for example, for hot / cold thermal cycling. An electrically controlled heating element may be included and configured to mold the final shape of the foam part. Both the water tower and heating element can function to precisely control the mold temperature so that the mold can be heated and / or cooled rapidly during the molding process.

[0176] All of this is coordinated with the injection molding machine by a suitably configured computer processor. For example, a non-limiting example of the cooling water temperature control of the DMTC system of the present invention can be 15-30°C, and a further non-limiting example of the heating element temperature range of the DMTC system can be in the range of 60-150°C, possibly in the range of 90-130°C, or any temperature therebetween. In this manner, the biopolymer melt, pressure, and time can be controlled to form the desired flexible foam.

[0177] In particular, during the injection molding process of the present disclosure, SCF is injected into a polymer melt. A single-phase polymer-SCF mixture solution is obtained under a defined temperature and pressure within the injection molding machine screw and barrel. The temperature and pressure may be variably controllable by computer control and are directly related to the type of flexible foam being produced and for which type of end-product application. By applying various screw-inclusive SCF single-phase solution pressures and GCP pressures in conjunction with the proper shot size, shot hold time, melt temperature, and mold temperature, an entire system is created by which high-quality, commercially acceptable biodegradable, and industrially compostable flexible foam parts can be produced, for example, by using gas counterpressure in the injection molding process to ensure optimal foam structure with minimal surface defects and little to no plastic skin on the exterior of the foam part.

[0178] As indicated, a useful benefit of the devices, systems, and products produced according to the methods disclosed herein is that they can be biodegradable and / or compostable, for example, in home or industrial composting protocols. In particular, producing items configured to degrade in an industrial composting regime ensures that the flexible foam will last the useful life of the resulting product, for example, by functionalizing it in a manner that prevents it from degrading or falling apart during use in the finished product. For example, it would be harmful to a person to purchase furniture, a pair of shoes, or other athletic equipment made from the flexible foam of this disclosure that would eventually result in the foam degrading during regular use before the end of the product's useful life.

[0179] More specifically, the present disclosure benefits from the use of an inert physical blowing agent and a biodegradable, industrially compostable biopolymer or biopolymer compound. These two aspects combine to form a single-phase solution that is functionalized within a specialized flexible foam injection molding system. The result is a biodegradable, industrially compostable flexible foam for use in many types of end products; a non-limiting example of which is footwear foam for use in shoe manufacturing. The resulting flexible foam is non-crosslinked, chemical-free, and environmentally friendly.

[0180] At the end of the biodegradable, industrially compostable flexible foam's lifespan, it can be redirected to an appropriate industrial composting facility through waste diversion, where the foam is ground into usable biomass and industrially composted. The end result is a system that adheres to aspects of the so-called circular economy. The flexible foams of the present disclosure begin and end as "dirt-to-dirt," meaning that natural biological processes have been adapted to produce materials and products for human use with minimal environmental impact. These flexible foams do not compromise either their technical performance characteristics during their useful life or their environmentally conscious design.

[0181] As described hereinabove, the devices, systems, and methods of their use herein can be used for the purpose of producing one or more molded end products, such as components for use in footwear, seats, automobiles, protective gear, and / or sporting goods. Thus, in various embodiments, provided herein are one or more components useful in the construction of shoes, such as soles, midsoles, and / or insoles thereof, e.g., the sole forms the base of the shoe and is configured to contact the ground, the midsole forms an intermediate structure and cushioning element, and the insole is configured to be inserted into the shoe, thereby providing cushioning and / or support to the shoe.

[0182] In some embodiments, a shoe component may include a foam material produced herein, which may be environmentally friendly, biodegradable, and compostable. In various cases, each individual component may be comprised of multiple layers, including a base layer and a cushioning layer, such as the cushioning layer here. For example, certain embodiments may include a support member, such as a support member coupled to the base layer, in which case the component is an insole in one or more of the arch-contacting or heel-contacting portions.

[0183] In particular, in various embodiments, foam materials can be produced, for example, foam materials can be used in the manufacture of cushions, cushioned furniture, shoe components such as insoles thereof, mats, fibers, textiles, etc. Other useful products can include caulks such as silicone caulk, silicone medical gloves, silicone tubing for drug delivery systems, silicone adhesives, silicone lubricants, silicone paints, and other suitable silicone products such as condoms. In various embodiments, foam products can be produced such that the foam materials can have one or more of antibacterial, antibacterial, antifungal, antiviral, and / or flame retardant properties.

[0184] More specifically, in one aspect, this disclosure can be generally directed to processes for the manufacture of furniture, such as upholstered furniture and / or its cushions, e.g., furniture that includes or is otherwise composed of biodegradable and / or compostable foam. Thus, the foams of the present disclosure are advantageous for use in the manufacture of furniture that includes foam inserts so produced. The resins and foams produced and employed have proven advantageous for use as cushioning materials for, for example, pillows, couches, beds, seat cushions, or other upholstered furniture.

[0185] For example, the methods disclosed herein above can produce molds for small to large blocks of foam, e.g., for forming foam inserts for use in, e.g., furniture or car accessory components. The block foam can then be cut into smaller blocks of desired size and shape based on the type and form of the furniture to be produced. Specifically, the sized and cut blocks can then be applied to or otherwise fitted within a furniture or automobile frame or other boundary material, and covered therewith to produce the final furniture product, whether a pillow, sofa, cushion, e.g., sofa or car cushion, etc. Additionally, if desired, an outer casing or boundary material can be attached to the frame material, e.g., by stapling and / or tacking, or otherwise secured to the frame of an article to be upholstered or covered with fabric or other material.

[0186] Thus, in various embodiments, when manufacturing upholstered furniture, such as a couch or car seat, a frame can be produced. Various interior, e.g., structural components of the furniture can be attached to the frame, e.g., springs, etc., and then foam sheets produced by the methods disclosed herein above can be placed in, on, and around the springs, e.g., for cushioning and / or insulation. Of course, other materials can be included, such as layers of cotton, wool, felt, rubber-based products, etc., and a cover material can then be placed over the springs. , can be added to cover the frame and complete the final product manufacturing.

[0187] Specifically, the foam, along with other materials disclosed herein, can function as padding or filler, allowing it to be shaped, adjusted, and tucked under the cover as the cover material is stretched over the frame. Additionally, as indicated, in various cases, the foam products produced herein are useful within and above those known in the art for a number of reasons, most notably the fact that typical PU and / or EVA foams are not biodegradable in any way, whereas the foam components produced herein are. Thus, in various embodiments, a method for constructing furniture on an open frame is provided. For example, by way of example, the method can include one or more of the following steps:

[0188] In particular, the method may include providing a frame defining a back, a plurality of sidewalls, and a seat portion, e.g., the back frame portion extending substantially vertically and the seat portion extending substantially horizontally relative to one another in a manner such that the seat portion transverses the vertical portion. The method may further include cutting a flat sheet of foam to an appropriate size and shape to provide padding for the back and seat and / or sidewall portions, cutting a flat cover material to an appropriate size and shape to complete the back, seat, and / or sidewall portions, adhering the foam sheet and cover material together at spaced locations, and compressing the foam to form a predetermined contoured design on its outer surface and to form a substantially flat subassembly, the foam sheet and cover material being free for relative movement intermediate the points of attachment and shaping the subassembly and attached to the frame. The cover for the foam cushion or cushioned article may be any suitable covering material commonly used in upholstered furniture and covered decorative pillows, such as wool, nylon, or various other synthetic fiber woven fabrics, and materials such as leather.

[0189] In yet another aspect, this disclosure is generally directed to processes for manufacturing shoe components, such as shoe soles, midsoles, and / or insoles, including or otherwise consisting of foam, e.g., compostable foam. Specifically, in certain embodiments, methods for manufacturing soles, midsoles, insoles, and / or other shoe inserts are provided. For example, the shoe inserts may be in the form of cushioning devices adapted to be inserted or otherwise fitted within shoes, e.g., running shoes or sneakers, that can be configured to reduce the impact of the foot striking a surface, e.g., the ground, during running or walking, thereby absorbing and / or attenuating impact to the foot.

[0190] In particular, sole components, including midsoles and inserts, may include one or more layers. For example, in some cases, a base layer, a foam layer, and / or a textile layer may be provided. Specifically, a base layer of a relatively elastic material may be included, and / or, for example, a foam layer disposed on the base layer, and / or a textile layer disposed on the foam layer. Thus, the method may include integrally forming the base layer, foam layer, and textile into a three-layer sheet. In various cases, a support layer may be disposed at least in the heel region, and the support layer may be constructed from a rigid material, for example, having a higher density than that of the laminate. Adhesives, glues, or other attachment mechanisms may be provided and employed to bond and form the three layers with the support layer.

[0191] More specifically, in other cases, a method for manufacturing a shoe component such as an insert may include the following steps: providing a foam layer and / or providing a textile layer; heating the foam layer; combining the foam layer and the textile layer; providing a base layer, e.g., Providing a base layer having a density that is the same as, greater than, or less dense than the foam layer; and heating at least one of the base layer and the foam layer to combine the base layer with the foam layer to form a two-layer or three-layer.

[0192] The method may further include providing a preformed support member, such as an arch support and / or heel member, which may have a density substantially the same as, less than, or greater than that of the foam layer. In particular cases, the support member may be formed from a compressed foam material to obtain a greater density, and thus greater rigidity, than that of the foam layer. In addition, a heat and / or pressure reactivatable adhesive may be applied between the support and / or heel member and the laminate. Molding pressure may then be applied to the composition, causing the formation and / or shaping of the three layers into a support and / or heel member to form a unitary, one-piece shoe insert, with the preformed heel member forming a rear portion and / or the support member forming a central portion of the bottom surface of the finished shoe insert, e.g., in the center and / or heel region thereof, and the base layer forming the bottom surface of the finished shoe insert in the front region thereof.

[0193] It should be noted, however, that the support and / or heel members need not be included, and in some cases, one or more laminate components may be eliminated or other laminate layers added. It should be further noted that in certain embodiments, the foam layer may be softer and / or more cushioned, e.g., having a greater durometer, than the base layer, which in turn may be softer and / or more cushioned, e.g., having a greater durometer, than the support member. Thus, the softer foam and base layer may be relatively resilient and able to shape and conform to the desired shoe size and configuration, while the support layer(s) may be relatively more rigid.

[0194] In particular, as indicated, the foam layer and / or one or more support layers can be composed of biodegradable and / or environmentally friendly foam materials disclosed herein. Specifically, the support layer can have a higher density foam, thereby making the support layer more rigid. Thus, in various embodiments, the foam layer can have a density of about 2, or about 3, or about 5 to about 10 lbs / cubic foot or greater, e.g., in the range of about 4-6 lbs / cubic foot. Additionally, the foam layer can have a thickness of 1 / 8" + or - 5%, e.g., in the range of about 3 / 32" - 5 / 32".

[0195] Similarly, the base layer may also have a density of about 2, or about 3, or about 5 to about 10 lbs / cubic foot or greater, for example, a density in the range of about 4-6 lbs / cubic foot. The thickness of the base layer may be on the order of about 5 / 16" + or -10%. However, in various cases, the thickness of the base layer may range from about 1 / 4" or less to about 7 / 16" thick. With regard to the support layer, it may be formed primarily in the arch and / or heel region of the insert, and it may also be made of the biodegradable and / or compostable foams disclosed herein.

[0196] However, the support layer may be manufactured by compressing it to a final density on the order of 22-23 lbs / ft3. The fabric layer may be constructed of any suitable material, such as cotton, polyester, or knit polypropylene. In various cases, the material and foam layer may be laminated together by a flame lamination technique employing an open flame directed at the foam layer. The open flame generates sufficient heat at the surface to cause the flat-sheet foam layer to melt. Once melted, the fabric layer may be joined to it, and the two sandwiched layers may be moved between chilled rollers while sufficient pressure is applied between the rollers to bond the two layers together.

[0197] At this point in the process, the layers are still maintained in flat sheet form. These combined layers can then be subsequently bonded to a base layer by flame lamination. The previously combined material and foam layer can be bonded to a support layer, and the multiple laminate layers are then moved between chill rollers. At this stage in the process, the layers are still in flat sheet form. The layers thus laminated to this point can then be molded. This can be done by heating the laminate layers to a molding temperature of approximately 250°F, for example, for a period of about 1 to about 5 minutes or more, e.g., about 225 seconds. This heats the previously laminated layers sufficiently to allow them to be inserted into a mold.

[0198] The following is a description of various implementations of the present disclosure, with reference to the accompanying drawings. Accordingly, in one aspect, a footwear component is provided. In particular, as shown in FIG. 1, one embodiment of the present disclosure is a footwear component, namely, a microcellular soft foam shoe midsole 100, made from a biodegradable and industrially compostable thermoplastic biopolymer blend 102.

[0199] Specifically, the biodegradable, industrially compostable injection-molded microcellular flexible foam shoe midsoles are made from one or more biopolymers and biopolymer blends, including, for example, thermoplastic biopolymers. In particular, the thermoplastic biopolymers or biopolymer blends used to make the biodegradable, industrially compostable injection-molded microcellular flexible foams can optionally be made from various aliphatic and aliphatic-aromatic copolyesters, and the like.

[0200] Non-limiting examples of suitable biopolymers for use in producing biopolymers or biopolymer blends include polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoates (PHAs), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene succinate adipate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS). In addition, hybrid biopolymer blends can be used to produce biodegradable, industrially compostable, injection-molded microcellular flexible foams. A non-limiting example of a hybrid biopolymer blend is comprised of algae-containing poly(butylene adipate-co-terephthalate) (PBAT).

[0201] In the example provided, the algae portion of the hybrid biopolymer is composed of any suitable algae species in dry powder form. Some non-limiting examples of suitable algae species include cyanobacteria, green algae, red algae, brown algae, and diatoms, as well as combinations thereof. The dry algae powder can be twin-screw extruded with the PBAT biopolymer on standard equipment, so that the algae powder degrades into PBAT polymer chains, thereby forming a hybrid biopolymer for use in manufacturing the biodegradable, industrially compostable, injection-molded microcellular flexible foams of the present disclosure.

[0202] The resulting foam product may contain or otherwise incorporate many of the following material components: filler powder and / or one or more additives. In particular, depending on the application, additives may also be used in the biopolymer formulation. For example, oligomeric poly(aspartic acid-co-lactide) (PAL) may optionally be compounded into a masterbatch to accelerate biodegradation. Additionally, fillers such as aragonite-derived precipitated calcium carbonate, starch, and the like may be used to reduce part costs while maintaining the renewable and biodegradable integrity of the finished flexible foam.

[0203] Additionally, additional additives for use in biopolymer formulations may consist of one or more of the following: nucleating agents, such as microlamellar talc or high aspect ratio oolitic aragonite, may be included. Such nucleating agents can significantly improve the fundamental properties of the resulting flexible foam by inhibiting cell coalescence, reducing bulk density, and improving rebound resilience, among other beneficially enhanced attributes. Some non-limiting examples of nucleating agents for use in producing biodegradable, industrially compostable injection-molded microcellular flexible foams are available from Imerys Talc America Inc., a microlamellar talc sold as Mistrocell® by Houston, Texas, and a high aspect ratio oolitic aragonite sold as OceanCal® by Calcean Minerals & Materials LLC, Gadsden, Alabama.

[0204] Colorants, dyes, and pigments may also be included. For example, various colorants, such as dyes, pigments, or biotins, may be optionally used in the biopolymer formulations of the present invention. Some non-limiting examples are natural pigments of plant origin tailored for biopolymer applications, such as the wide range offered by Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or those offered by Holland Colors Americas Inc., Richmond, Indiana.

[0205] There are many configurations and embodiments that can be used depending on the desired physical properties of the shoe midsole 100 and the intended end use, whether for work, recreation, water use, etc., which should not be limited by these examples.

[0206] A suitable apparatus for the system may be illustrated in FIG. 2 and used in the manufacture of the foam materials disclosed hereinabove. For example, in use, a biopolymer masterbatch 202 is fed into a hopper 204 of any suitable injection molding machine 206. The biopolymer masterbatch is liquefied by heating while being transported through an injection molding machine screw 208. Nitrogen or CO2 gas 210 is injected into the biopolymer melt and mixed 212. The biopolymer-gas mixture is then placed under pressure and injected into an injection mold 214. In cooperation with the biopolymer-gas injection, a gas counterpressure system 216 delivers a metered dose of nitrogen or CO2 gas 218 into the pressure mold via a gas control valve 220.

[0207] Shortly thereafter, a dynamic mold temperature control system (DMTC) 222 controls and regulates the temperature inside the mold 214. The mold 214 is then allowed to cool sufficiently and the resulting biodegradable, industrially compostable injection molded microcellular flexible foam part is removed from the injection molding machine.

[0208] FIG. 3 provides a flowchart illustrating a method 300 for producing biodegradable, industrially compostable injection-molded microcellular flexible foam. At 302, a biopolymer mixture is selected, and at 304, the mixture is drawn through a material hopper into an injection molding machine. At 306, the biopolymer mixture is liquefied and homogenized while being transported through the injection molding machine screw. At 308, nitrogen or CO2 gas is injected into the biopolymer melt. At 310, the biopolymer-gas mixture is placed under pressure and injected into an injection mold. At 312, the injection mold temperature is dynamically controlled to ensure optimal cell structure. At 314, an optimal dose of gas counterpressure is applied to the injection mold for a sufficient amount of time to ensure ideal foam structure with minimal skin depth. At 316, the injection mold is allowed to cool sufficiently, and the resulting molded foam part is removed from the injection molding machine.

[0209] In some implementations, without limiting the disclosure herein, a process for producing biodegradable, industrially compostable flexible foam includes the steps outlined below: The process setup procedure revolves around establishing controlled SCF dosing into an injection barrel under screw speed, temperature, and pressure conditions that result in a single-phase solution.

[0210] To ensure that the basic conditions for SCF dosing are met, there are seven primary process setpoints to adjust: SCF delivery pressure: This sets the bioplastic pressure to which SCF is administered during screw rotation. This refers to both the specific biopolymer backpressure during screw return and also the screw position control while the screw is not moving. As a non-limiting example, the pressure setpoint for biopolymer delivery may be in the range of 2,000 psi to 3,000 psi, more preferably in the range of 2,700 psi to 2,800 psi. This setpoint sets the screw position at which SCF dosing begins, which can then set the SCF injector to an open or closed position. The position should be set so that the pressure within the barrel during screw return stabilizes before dosing begins. As a non-limiting example, the open position may be in the range of 0.3 to 0.4 inches.

[0211] The shot size and SCF percentage can also be controlled. This controls the actual mass of SCF dispensed during each cycle. As a non-limiting example, the shot size can range from 100 grams to 300 grams, more preferably 200 grams. A non-limiting example of the SCF percentage can range from 0.45% to 0.75%, more preferably 0.5%. The system can also be configured to optimize dosing. This is achieved by maximizing the dosing time and minimizing the flow rate (the pressure difference between the pre-metering pressure and the delivery pressure). A non-limiting example of the dosing time is 1-2 seconds, more preferably 1.7 seconds.

[0212] Dynamic mold temperature control (DMTC) can also be implemented. This is a process that involves rapid change and control of mold temperature during the injection-filling stage, thus dynamically controlling mold temperature in terms of both high and low temperature thermal cycles. Prior to melt injection, the mold is first heated to a preset upper limit. During the melt-filling stage, the temperature of the mold cavity surface is maintained above the upper limit to prevent premature solidification of the melt.

[0213] Once the melt-fill process is complete, the mold is immediately cooled to a lower limit known as the ejection temperature, which is the temperature at which the part is removed from the mold cavity. A non-limiting example of an optimal mold temperature range for the present disclosure is 40°C to 150°C, with a cooling rate of 1°C / sec to 15°C / sec, more preferably 11°C / sec. A non-limiting example of a mold cooling time for the present invention is 80 seconds to 100 seconds.

[0214] Similarly, gas counter pressure (GCP) can also be controlled. This is a process involving a pressurized mold cavity into which nitrogen gas is injected to counteract the expansion of gas within the melt. As the counter pressure is released, gas bubbles that would traditionally break through the surface are trapped inside, creating a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness. Non-limiting examples of gas counter pressures of the present invention are 0 bar / 10 bar / 30 bar / 50 bar, with hold times of 1 second to 25 seconds, more preferably 5 seconds. Non-limiting examples of average microcellular cell diameters of the present invention can be measured in micrometers (μm), and are 1-micrometer to 100-micrometer, more preferably 40-micrometer.

[0215] With the above in mind, in some implementations, a suitable thermoplastic biopolymer blend is produced. Once the thermoplastic blend is produced, it can be injection molded into a suitable mold shape using the addition of an inert gas, such as nitrogen gas. In addition, pressure can also be finely controlled.

[0216] For example, the use of gas counter pressure in the injection molding process can be implemented. This is also useful to further ensure optimal foam structure with minimal surface defects and little to no plastic skin on the outside of the foam part, which is important when producing foamed products that may have multiple end uses based on mold geometry. The molding process can include implementing dynamic mold temperature control. For example, in various embodiments, dynamically controlling the temperature of the molding process is useful to achieve optimal cell structure. Other elements of the molding process that can be controlled include controlling the biopolymer melt, pressure, and time to form the desired flexible foam.

[0217] In view of the above, therefore, the present disclosure relates to a process for injection-molded microcellular foaming of various flexible foam compositions from biodegradable, industrially compostable, bio-based thermoplastic resins for use in, for example, footwear components, seating components, protective gear components, and water sports accessories.

[0218] Creating biodegradable, industrially compostable microcellular flexible foam structures begins with a suitable biopolymer or biopolymer blend, such as those derived from aliphatic and aliphatic-aromatic copolyesters. A non-limiting example of a suitable biopolymer blend is polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). The blended thermoplastic biopolymer resins exhibit advantageous technical properties in forming the optimal microcellular flexible foam structures of the invention. Some of the enhanced technical properties include acceptable aging properties, excellent elongation, and excellent compression set, among other benefits.

[0219] Optimal aliphatic and aliphatic-aromatic copolyester biopolymers or biopolymer blends alone cannot produce flexible foams without a suitable blowing agent and foaming process. The most widely known blowing agent used today is a chemical called azodicarbonamide (ADA). Azodicarbonamide is typically pre-impregnated into petrochemical thermoplastic masterbatch resins for use in conventional injection molding foam processes. Unfortunately, ADA is not environmentally friendly and is a suspected carcinogen to human health. Furthermore, conventional petrochemical thermoplastic masterbatch resins are neither biodegradable nor industrially compostable. To achieve the most optimal biodegradable and industrially compostable flexible foams for the above invention, inert nitrogen gas or carbon dioxide in a supercritical fluid state is used as a physical blowing agent in a modified injection molding process. The modified physical blowing process is used in conjunction with a suitable thermoplastic biopolymer or blended biopolymer masterbatch, so that the biopolymer or biopolymer blend and blowing agent work in harmony to produce the most optimal biodegradable and industrially compostable flexible foams.

[0220] The injection molding process of this disclosure relies on uniform bubble nucleation, which occurs when a single-phase solution of biopolymer or biopolymer blend and supercritical fluid (SCF) enters the mold cavity through an injection gate. As the solution enters the mold, pressure drops, causing the SCF to come out of solution and create bubble nuclei. The bubbles then grow until the material fills the mold, consuming the expansive properties of the SCF. This manufacturing process is carried out on an injection molding machine modified to allow for the metering, delivery, and mixing of the SCF into the biopolymer, creating a single-phase solution. Dynamic mold temperature control (DMTC) is employed to ensure a consistent bubble structure within the expanding biopolymer melt. DMTC can best be described as the rapid change and control of mold temperature during the injection and filling phase; it thus dynamically controls the mold temperature in terms of both high and low temperature thermal cycles. Gas counter pressure (GCP) is also used in the manufacturing process to obtain Ensures optimal foam structure with little to no skin on flexible foams. GCP can best be described as a process involving a pressurized mold cavity into which SCF is injected to counteract the expansion of gases in the melt. As the counter pressure is released, gas bubbles that would traditionally break through the surface are trapped inside, creating a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness.

[0221] The creation of a single-phase solution, in which the SCF is completely dissolved and uniformly dispersed in the molten biopolymer, occurs inside the injection barrel under carefully controlled process conditions: the SCF must be precisely mass-metered into the biopolymer for a specific period of time, and during the dosing period, the proper conditions of temperature, pressure, and shear can be established within the barrel. Backpressure, screw speed, and barrel temperature control, as well as the SCF delivery system, all play a role in establishing the process conditions that create a single-phase solution.

[0222] Once the single-phase solution is created, the modified injection molding machine maintains the solution under pressure until injection begins. The machine achieves this through the cooperation of a shutoff nozzle and screw position control. The shutoff nozzle prevents decompression and premature foaming into the mold. Either active or passive screw position control prevents decompression due to screw retraction. During active screw position control, the screw position is continuously monitored, and the pressure applied to the back of the screw is adjusted to maintain a position setpoint, or a constant pressure is maintained at the back of the screw. With passive position control, the oil used to control backpressure is prevented from flowing to its reservoir at the end of the screw retraction. This residual oil keeps the screw from retracting due to the pressure of the single-phase solution.

[0223] Proper mold design also helps maintain a single-phase solution. Molds with hot runner systems require valve gates to prevent material drooling from the nozzle at mold opening. Molds in which the machine nozzle breaks contact with the sprue bushing during normal operation, such as stack or tandem molds, require a shutoff on the sprue bushing. Otherwise, pressure from the hot runners is relieved through the sprue bushing.

[0224] The blowing agents used to injection mold biodegradable and industrially compostable microcellular foams are either inert nitrogen gas or carbon dioxide in the supercritical fluid (SCF) state. Each of these blowing agents has a role to play depending on the technical requirements of the final part being produced.

[0225] A useful blowing agent for this invention is SCF nitrogen gas because it provides improved weight reduction and fine cell structure at a much lower weight percentage than SCF carbon dioxide. In fact, SCF nitrogen levels are typically at least 75 percent lower than the SCF carbon dioxide levels required to achieve equivalent parts. SCF carbon dioxide, however, is the preferred blowing agent in two situations: when viscosity reduction is the primary processing goal or when the application cannot tolerate the more aggressive foaming action of SCF nitrogen.

[0226] The difference in effectiveness between the two blowing agents arises from their behavior in biopolymer melts. Carbon dioxide, which becomes a supercritical fluid at 31.1 degrees Celsius and 72.2 bar, is four to five times more soluble in biopolymers than nitrogen, which becomes a supercritical fluid at -147 degrees Celsius and 34 bar. For example, the saturation point in unfilled biopolymers is approximately 1.5 to 2 weight percent nitrogen, depending on the temperature and pressure conditions, while the saturation level for carbon dioxide is around 8 weight percent. Carbon dioxide also exhibits greater mobility in biopolymers, allowing it to migrate further into existing bubbles than nitrogen. From the perspective of bubble nucleation, greater solubility and mobility means that fewer bubbles nucleate and those that do not tend to be larger. do.

[0227] Solubility, however, is an advantage when the goal is viscosity reduction. SCF dissolved in a biopolymer acts as a plasticizer, reducing the viscosity of the biopolymer. Because viscosity reduction is, in part, a function of the amount of SCF added to the biopolymer, and because carbon dioxide has a higher solubility limit than nitrogen, the ability to reduce viscosity using carbon dioxide is superior.

[0228] Carbon dioxide is also preferred when the amount of nitrogen required to produce a part is too low to process the part consistently. Because carbon dioxide is a much less aggressive blowing agent, it can also be easier to flow low levels of carbon dioxide. For example, 0.15 or 0.2 percent carbon dioxide compared to very low levels of nitrogen, less than 0.05 percent. The case shown in the previous example occurs primarily with soft materials and parts with thick cross sections.

[0229] Recyclable injection-molded microcellular flexible foam and method for making same 4 and 6 illustrate a recyclable injection-molded microcellular flexible foam 402 and a method for producing the same in accordance with the present disclosure. Referring to FIG. 4, the foam 402 is preferably a closed-cell foam, but may also potentially be formed as an open-cell foam. In various implementations, the foam 402 can be made to have properties and characteristics that are at least generally similar to those of conventional non-recyclable ethylene vinyl acetate (EVA) foam, or the like.

[0230] As described in more detail below, the recyclable foam 402 is produced by processing a thermoplastic polymer using an injection molding machine as shown in FIG. 5. The thermoplastic polymer used to produce the recyclable flexible foam 402 can optionally be made from various polyamide-based thermoplastic polymers, polyamide copolymers, and the like. Non-limiting examples of suitable polymers for use in this invention are comprised of polyamide 6, polyamide 6 / 6-6, and polyamide 12. Alternatively, the thermoplastic polymer can include various polyamide block copolymers, such as polyether-block-amide (PEBA), PAE, TPA, TPE-A, COPA, and the like. Other non-limiting examples of suitable polymers and copolymers include polyamide 66 copolymers sold under the Vydyne trade name by Ascend Performance Materials, LLC, Houston, TX. The above-mentioned thermoplastic polymer resins exhibit advantageous technical properties in forming the optimal microcellular flexible foam structures of the invention. Some of the enhanced technical properties include, among other benefits, excellent aging properties, excellent elongation, tensile strength, and compression set.

[0231] In addition, blends of two or more thermoplastic polymers offer a combination of properties and price points not found in a single thermoplastic polymer. There are many methods for successfully blending thermoplastic polymers together. As described in more detail below, twin-screw extrusion melts two or more thermoplastic polymers together and then extrudes the molten polymer resin blend into strands that are cooled and fed into a pelletizer to produce an array of pelletized pieces called a masterbatch. Another method of polymer resin blending is to use a compatibilizer to combine different chemicals in a polymer blend. Generally, a compatibilizer and two or more polymers of the non-limiting thermoplastic polymer types described above are melted together, again using twin-screw extrusion or the like.

[0232] In one embodiment, the thermoplastic polymer comprises at least one monomer or polymer derived from post-consumer or post-industrial recycled materials. For example, the thermoplastic polymer may be caprolactam, recycled polyether block amide polymer, or the like. Caprolactam may include polymers, etc. By way of example, caprolactam can be derived from recycled feedstocks by depolymerizing post-industrial or post-consumer materials containing polyamides, such as fishing nets, carpet fibers, or industrial waste. A non-limiting example of depolymerized post-consumer or post-industrial recycled caprolactam is ECONYL® caprolactam (whether flake, liquid, or melt) offered by Aquafil USA Inc., Cartersville, Georgia. The thermoplastic polymer may additionally or alternatively include polyamide polymers derived from post-industrial or post-consumer polyamide carpet fibers that are collected, sorted, melted, and reprocessed. One such polyamide polymer derived from post-industrial carpet fibers is Econyl®, manufactured by Aquafil USA Inc., Cartersville, Georgia. Additionally, polyamide waste may be collected from or around the world's oceans in the form of fishing nets, or the like, which may then be sorted, melted, and reprocessed into upcycled usable polyamide material. An exemplary polyamide polymer derived from collected post-industrial fishing nets is Akulon Repurposed, manufactured by Koninklijke DSM NV, Heerlen, The Netherlands.

[0233] Depending on the application, additives may also be used in the polymer formulation, for example, fillers such as precipitated calcium carbonate, roe-like aragonite, starch, biomass, etc. may be used to reduce part costs while maintaining the recyclable integrity of the finished flexible foam.

[0234] Additionally, additives for use in polymer formulations may consist of one or more of the following: Nucleating agents, such as microlamellar talc or high-aspect-ratio oolitic aragonite, may be included. Such nucleating agents can significantly improve the fundamental properties of the resulting flexible foam by inhibiting cell coalescence, reducing bulk density, and improving resilience, among other beneficially enhanced attributes. Some non-limiting examples of nucleating agents for use in producing recyclable injection-molded microcellular flexible foams are microlamellar talc, commercially available as Mistrocell® by Imerys Talc America Inc., Houston, Texas, and high-aspect-ratio oolitic aragonite, commercially available as OceanCal® by Calcean Minerals & Materials LLC, Gadsden, Alabama.

[0235] Colorants, dyes, and pigments may also be included. For example, various colorants, such as dyes, pigments, or pigments, may optionally be used in the polymer formulations of the present invention. Some non-limiting examples include pigments tailored for specific types of thermoplastic polymer applications, such as the wide range offered by Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or Holland Colours. Provided by Americas Inc., Richmond, Indiana.

[0236] The use of recycled feedstocks to make microcellular flexible foam reduces the environmental impact typically associated with making expanded thermoplastic polymer foams by sourcing sustainable materials. As described in more detail below, the methods for making microcellular flexible foam of the present disclosure increase the environmental benefits of using recycled feedstocks because the resulting product can be further recycled into thermoplastic polymers, which can then be used to make new products from the microcellular flexible foam or, alternatively, other products using thermoplastic polymers.

[0237] Method for producing flexible foam Figures 5 and 6 show an injection molding machine 506 and method 600 for producing the recycled flexible foam 402 shown in Figure 4. Thus, in one aspect, the present disclosure relates to a method for foaming a thermoplastic polymer. As described in more detail below, the method can be used to make any of a number of end products from the foam 402, such as shoe components, and other products (where characteristics such as cushioning, impact protection, comfort, etc. are desired), such as specialty athletic equipment.

[0238] As shown in FIG. 5 , injection molding apparatus 506 includes a hopper 504 configured to receive and introduce a plurality of thermoplastic polymers 502 into molding apparatus 506. Barrel 507 is coupled to hopper 504 and configured to receive thermoplastic polymers 502 and include a specialized reciprocating screw-type plunger 508. Barrel 507 also includes a temperature control unit (not shown) for heating and cooling the contents of barrel 507. As shown in FIG. 5 , computer controller 503 having temperature and pressure measurement device 505 is configured to sense the temperature and pressure within barrel 507. Gas dosing system 509 is fluidly coupled to barrel 507 and includes a metering unit 512 configured to receive and introduce fluid 510 into barrel 507. Gas dosing system 509 maintains fluid 510 above a critical temperature and pressure (Tc and Pc, respectively) to generate a supercritical fluid (SCF) 510. In the presently disclosed method, SCF510 is used as a physical blowing agent to replace chemical blowing agents, such as azodicarbonamide (ADA), used in conventional methods of flexible foam production. By way of example, SCF510 may include an inert or noble gas, such as nitrogen, carbon dioxide, helium, neon, argon, or xenon. Not only does the disclosed method improve the environmental impact compared to conventional flexible foam molding methods by eliminating the environmentally hazardous and suspected carcinogen ADA from the process and replacing it with an inert or noble SCF, but, as described in more detail below, flexible foams 402 of the present disclosure may be recycled at the end of their useful life as a result of the methods described herein.

[0239] 6, a method for producing recyclable flexible foam 102 may begin in step 602: selecting a thermoplastic polymer 502 and feeding the thermoplastic polymer 502 into a hopper 504 of an injection molding machine 506. Thereafter, in step 604, the thermoplastic polymer 502 is then pumped from the hopper 504 into a barrel 507 and heated. In step 606, the heated barrel 507 melts the thermoplastic polymer 502 as a screw-type plunger 508 moves the thermoplastic polymer 502 through the injection molding machine 506. Additionally, a controller 503 may be configured to control and adjust the screw rotation speed.

[0240] In step 608, SCF 510 is introduced into barrel 507 through injector 511 via metering unit 512 connected to injection molding apparatus 506, where SCF 510 solubilizes in molten thermoplastic polymer 502 to form a single-phase solution. The SCF 510 may be adjusted in concentration within the melt, which affects the degree of foaming achieved. Referring to FIG. 5 , metering system 512 is configured to administer an appropriate amount of SCF into molten thermoplastic polymer 502. A non-limiting example of an initial SCF gas concentration may be Co=0.25%, with a melt temperature range of 176°C to 250°C, more preferably 180°C. Furthermore, controller 503 controls the pressure at which SCF 510 is introduced into barrel 507 through the SCF injector. SCF 510 saturates molten thermoplastic polymer 502, forming a single-phase solution. Additionally, screw-type plunger 508 rotates within barrel 507 at a speed necessary to homogenize thermoplastic polymer 502 and SCF 510 to produce a single-phase solution. Screw 508 rotates at a speed between 1 and 200 rpm, and preferably at a speed of approximately 20 rpm. ~It can rotate within barrel 507 at approximately 60 rpm.

[0241] Regarding saturation, the injection molding machine 506 is configured to deliver gas to the barrel 507 under a temperature and pressure that saturates the molten thermoplastic polymer 502 during screw rotation. Specifically, the controller 503 is configured to control a combination of the SCF delivery pressure and the SCF dosage weight. The SCF pressure and dosage can be controlled to affect a single-phase solution. That is, the smaller the SCF dosage, the less SCF saturation is required in the biopolymer melt, while the larger the SCF dosage, the greater the SCF saturation is required in the melt. Similarly, the lower the SCF delivery pressure, the lower the saturation uptake, and therefore the lower the growth of nuclei that can grow to form bubbles in the molten biopolymer melt. Furthermore, the higher the SCF delivery pressure, the greater the saturation uptake, and therefore the greater the growth of nuclei that can grow to form bubbles in the molten melt.

[0242] Controller 503 variably controls the temperature and pressure in a manner that depends on the type of flexible foam being produced and what type of final product is being produced. Specifically, the temperature throughout the system, for example within barrel 507, can be controlled to be in the range of 100°C to 600°C, for example, 200°C to 500°C, for example, 300°C to 400°C, more specifically, 320°C to 380°C, for example, 360°C to 380°C. Similarly, the SCF delivery pressure can be finely controlled to be in the range of 1,000 to 8,000 PSI, for example, 1,500 to 6,000 PSI, for example, 2,000 to 5,500 PSI, particularly, in the range of 3,000 to 4,000 PSI, more particularly, in the range of 2,600 to 2,800 PSI.

[0243] 5, controller 503 determines and controls SCF 510 concentration using sensors to determine the amount of saturation, evaluate the progress of the saturation process, and regulate pressure and temperature. SCF 510 controllably saturates molten thermoplastic polymer 502 during rotation of reciprocating screw 508 to create a single-phase solution under a defined temperature and pressure. SCF is one component of a two-component molten thermoplastic polymer compound mixture, which is used as a physical blowing agent in the presence of a defined pressure and temperature in the present injection mold.

[0244] As described in more detail below, the SCF510 blowing agent can be selected from the list of rare and inert fluids listed above based on the technical requirements of the final flexible foam 402 product. For example, carbon dioxide in its supercritical state is denser than nitrogen at the same pressure and has a higher heat capacity. Carbon dioxide in its supercritical state produces dense foams that may be useful in certain cushioning applications. In contrast, supercritical nitrogen can be used to produce lower-density foam parts with smaller cores, which can be used when making foam 402 for footwear and sporting goods.

[0245] However, solubility is an advantage when the goal is viscosity reduction. SCF dissolved in recyclable thermoplastic polymer 502 acts as a plasticizer, reducing the viscosity of thermoplastic polymer 502. Because viscosity reduction is in part a function of the amount of SCF added to recyclable thermoplastic polymer 502, and because carbon dioxide has a higher solubility limit than nitrogen, the ability to reduce viscosity using carbon dioxide is greater. Carbon dioxide is also useful when the amount of nitrogen required to produce a part is so low that it cannot consistently process the final product.

[0246] Because carbon dioxide is a less aggressive blowing agent, it can be easier to flow low levels of carbon dioxide. For example, 0.15 or 0.2 percent carbon dioxide compared to very low levels of nitrogen, less than 0.05 percent. The case shown in the previous example occurs primarily with soft materials and parts with thick cross sections. Therefore, whether it is nitrogen, carbon dioxide, or one of the other inert and noble gases listed above, the physical blowing agent plays a useful role in the final foamed parts and the final products containing them.

[0247] Selecting the appropriate combination of a compatible thermoplastic polymer or thermoplastic polymer compound and associated SCF gas is useful. Second, proper application of SCF gas with optimal dosing weight and pressure provides a favorable level of saturation within the single-phase solution, affecting nucleation (the generation of many uniform bubbles within the foam matrix, described in more detail below). Additionally, the end result of a uniformly formed injection-molded flexible foam part depends on all aspects of the SCF gas dosing process, and the use of gas counterpressure works symbiotically with injection molding machine temperature, pressure, and hold time to achieve a commercially acceptable molded foam part.

[0248] 5, the reciprocating screw 508 is further configured to compress and move the molten thermoplastic polymer 502 into a cavity of the barrel 507. A gas counter pressure (GCP) system 516 is configured to deliver gas counter pressure to the barrel 507 to control the expansion of the molten thermoplastic polymer 502. In the embodiment shown in FIG. 5, the GCP system 516 includes a gas pump 515, a gas reservoir 518 containing an inert gas such as nitrogen or carbon dioxide, a compressor 517, a pressure sensor 519, and a gas control valve 520. The reciprocating screw plunger 508 and barrel 507 are also configured to provide back pressure and to deliver the thermoplastic polymer 502 into a mold 514 (described in more detail below) that is disposed in fluid communication with the barrel 507 and has a cavity configured to receive the molten thermoplastic polymer 502. In the embodiment shown in FIG. 5, the screw plunger 508 and barrel 507 are configured to apply a pressure range of approximately 2,000 psi to approximately 3,000 psi, more preferably 2,700 psi to 2,800 psi. The placement of the screw plunger 508 and barrel 507 also sets the position at which SCF 510 dispensing begins, which can then set the SCF injector to an open or closed position. The position should be set so that the pressure within the barrel during screw return stabilizes before SCF 510 dispensing begins. As a non-limiting example, the open position may be in the range of 0.3 to 0.4 inches.

[0249] In addition to the GCP system, the injection molding machine 506 shown in Figure 5 includes a dynamic mold temperature control (DMTC) 522 configured to control the temperature within the mold 514. The DMTC 522 can be used in conjunction with the GCP system 516 to ensure a consistent cell structure within the expanding thermoplastic polymer 502. The DMTC 522 can be configured to affect rapid changes and control of mold temperature and / or pressure during the injection filling stage, and to dynamically control mold temperature and / or pressure with or without counter pressure through the use of hot and cold thermal cycles.

[0250] Continuing with FIG. 5, controller 503 is configured to control mold 514 temperature via DMTC 522 during injection stage 610. More specifically, compared to conventional injection molding processes, a key feature of the dynamic mold temperature control employed herein is that the mold temperature itself can be dynamically controlled. DMTC 522 shown in FIG. 5 uses rapid electric rod heating and rapid water cooling. Specifically, DMTC 522 includes five main components: an air compressor (not shown), a valve exchanger 526, a computer-controlled mold temperature control unit (disposed within controller 503), an electric heating rod (disposed within mold 514), and a cooling tower 532. Cooling tower 532 can be used to provide sufficient water cooling to the mold. The air compressor is used to generate compressed air as a drive gas for the air valve and to remove residual cooling water from entering the mold after cooling. In the embodiment shown in Figure 5, a water heating unit 534 is also included, and a valve changer 526 is used to switch valves to move different media from the pipeline to the mold 514 to provide high and low temperature thermal cycles. For example, the DMTC 522 can provide water cooling in the range of approximately 15°C to approximately 30°C, and the electric heating rods can provide metal cooling in the range of approximately 60°C to approximately 150°C. The mold can be heated and can be optimally heated in the range of 90℃ to 130℃.

[0251] The injection molding machine 506 shown in FIG. 5 includes pipes and other conduits for passing reactants, which are associated with one or more heat exchange units so that the reactants are heated and / or cooled as they are pumped into and / or through the conduits and pipes. In such cases, the exchangers can be controlled to regulate the temperature to reaction levels. A dispensing head can be included on one end of the pipe, which can be associated with one or more valves. The dispensing head can further be connected to a processing line. An electrically heated mold is used to mold the final shape of the foam part. The function of the mold temperature control is to control the heating and cooling of the mold; all of this is coordinated with the injection molding machine by computer control.

[0252] Thus, as implemented herein, the controller 503 implements gas counterpressure to improve control of the foaming process by applying different gas pressures during the injection phase, as described below. The controller 503 is configured to operate the GCP system 516 and the DMTC 522 to regulate the temperature and pressure, thereby controlling nucleation and the resulting foam within the molten thermoplastic polymer 502 and the resulting foam matrix.

[0253] As shown in FIG. 6 , in step 610, the thermoplastic plunger 508 advances, delivering the molten thermoplastic polymer 502 present therein through a nozzle (not shown), which injects the thermoplastic polymer 502 into a mold 514. The injection molding machine 506 delivers a measured shot of the single-phase thermoplastic polymer 502 into the dynamically temperature-controlled mold cavity 514. Prior to injection step 610, the DMTC 522 heats the mold 514 to a preset upper limit. During injection step 610, the DMTC 522 maintains the temperature of the mold cavity 514 above the upper limit to prevent the molten thermoplastic elastomer 502 from prematurely solidifying. The GCP system 516 delivers gas counterpressure into the mold 514 to control nucleation and prevent gas bubbles from contacting and breaking through the surface of the thermoplastic polymer 502 as the foam part is formed. This is accomplished by applying a counter pressure in the mold cavity by the GCP system 516 at or near the same time that the thermoplastic polymer 502 single-phase solution is injected into the mold cavity 514. The inert gas bubbles are subjected to sufficient force to hold the SCF 510 within the thermoplastic polymer 502 during the injection step 610.

[0254] Referring to Figure 6, in steps 612 and 614, controller 503 manipulates the pressure and temperature within mold 514 to control the physical foaming of thermoplastic polymer 502. While the steps of dynamically controlling the temperature of mold 612 and applying gas counterpressure to mold 614 are shown as separate steps in the flowchart of Figure 6, steps 612 and 614 may be performed simultaneously or in close succession, whereby controller 503 controls the temperature and pressure within the mold. In steps 612 and 614, nucleation occurs within molten thermoplastic polymer 502, and many microcellular bubbles are formed. As controller 503 (Figure 5) increases and decreases the temperature in step 612, SCF 510 vaporizes into gas bubbles, foaming thermoplastic polymer 502 within mold 514. In step 614, the GCP system 516 computer-controlled pumps a pre-metered dose of counter-pressure gas into the mold to generate a substantially uniform foam, and the gas counter-pressure conditions adjust the surface texture for optimal surface appearance. The gas bubbles grow until the thermoplastic polymer 502 fills the mold 514, consuming the expansive properties of the SCF 510. As the bubbles reach micron size, the process produces microcellular foam. The SCF 510 concentration can affect the gas bubble structure. Thus, the controller 503 selects the temperature and gas counter-pressure parameters to generate a useful and / or deterministic gas bubble structure. Once the part is molded, the mold cools and the thermoplastic polymer solidifies. In the embodiment shown in FIG. 6, step 61 At 6, the dynamic temperature controlled mold temperature is switched to water cooling, slowing and stopping the formation of gas bubbles and the expansion of the thermoplastic polymer 502. The DMTC 522 quenches the mold 514 to a lower limit (ejection temperature), and the flexible foam molded part 402 is now formed, which is removed from the mold.

[0255] Recyclable injection-molded microcellular flexible foam products 4 illustrates a footwear component of the present disclosure, more specifically a recyclable microcellular soft foam shoe midsole 400 made from recyclable soft foam 402.

[0256] As briefly described above, the methods for producing recyclable articles described above enhance the environmentally beneficial effects of using monomers and polymers developed from recycled raw materials, because the resulting products can be further recycled into monomers that can be repolymerized into thermoplastic polymers for use in producing new, other plastic materials. In particular, producing articles configured to be recycled ensures that the flexible foam lasts the useful life of the resulting product, for example, by functionalizing it so that it does not degrade or fall apart during use within the finished product. For example, it would be harmful to a person to purchase furniture, a pair of shoes, or other athletic equipment made from the recyclable flexible foam of this disclosure that would eventually result in the foam degrading during regular use before the end of the product's useful life.

[0257] More particularly, the present disclosure benefits from the use of the above-listed thermoplastic polymer compounds that are inert physical blowing agents and are not crosslinked during the manufacturing process. The resulting recyclable flexible foam 402 is non-crosslinked, does not contain harmful chemical blowing agents such as ADA, and is environmentally friendly. Furthermore, the recyclable flexible foam 402 can be used in many types of end products, such as footwear foam for use in shoe manufacturing.

[0258] The recyclable flexible foam 402 can be redirected to an appropriate recycling facility at the end of the product's useful life through waste diversion. Because the recyclable flexible foam 402 does not use chemical blowing agents such as ADA, and because the methods described herein do not use thermoplastic polymers that are crosslinked during its manufacture, the recyclable foam 402 can be ground, pretreated, and depolymerized into one or more monomers. One such depolymerized monomer is caprolactam, such as ECONYL® caprolactam (whether flake, liquid, or melt) offered by Aquafil USA Inc., Cartersville, Georgia, or DSM Engineering Plastics Americas, Troy, TX. Depolymerized caprolactam (whether flake, liquid, or melt) provided by Michigan.

[0259] Referring to FIG. 7, the disclosed method contemplates a method 700 for recycling recyclable foam 402 using a thermal and chemical depolymerization process in which the temperature of a polymer, such as PEBA, is raised above a ceiling temperature, and any of a number of chemical reagents or catalysts are used to depolymerize it into its constituent monomers. In the embodiment shown in FIG. 7, the depolymerization process begins in step 702, where the thermoplastic polymer of recyclable foam 402 is mechanically separated from the waste material. In step 704, a depolymerization catalyst is introduced to the separated thermoplastic polymer. Non-limiting examples of depolymerization catalysts include acids such as phosphoric acid and boric acid. In step 706, heat is applied, for example, via superheated steam, which can act to distill caprolactam and any other volatile compounds, producing a distillate containing caprolactam monomer. The applied temperature can range from about 100°C to about 325°C. In step 708, the distillate is fractionated to separate water and caprolactam from other by-products of the depolymerization process. In step 710, an oxidizing agent is introduced to the separated aqueous caprolactam. Some non-limiting examples of oxidizing agents include potassium permanganate, hydrogen, oxygen, potassium dichromate, hypochlorous acid, sodium or potassium perchlorate, or perborate. In step 712, the oxidized aqueous caprolactam is concentrated, for example, by evaporation. In step 714, the concentrated caprolactam monomer is purified, for example, by vacuum distillation.

[0260] After purification of the caprolactam monomer in step 714, the depolymerized monomer can be repolymerized into a thermoplastic polymer and used to produce a more recyclable flexible foam 402. Thus, the method of the present disclosure establishes a circular process whereby manufactured goods can be broken down, manufactured into new products, and re-entered into the commerce stream, as opposed to using new raw fossil fuels or other non-renewable feedstocks. Moreover, the recyclable foams 402 of the present disclosure do not compromise either their technical performance characteristics over their useful life or their environmentally conscious design.

[0261] As described hereinabove, the devices, systems, and methods of their use can be used for the purpose of producing components for use in one or more molded end products, such as footwear, seats, automobiles, protective gear, and / or sporting equipment. Thus, in various embodiments, provided herein are one or more components useful in the construction of shoes, such as soles, midsoles, and / or insoles thereof, where the sole forms the base of the shoe and is configured to contact the ground, the midsole forms an intermediate structure and cushioning element, and the insole is configured to be inserted into the shoe, thereby providing cushioning and / or support to the shoe.

[0262] In some embodiments, the shoe component may include recyclable foam 402 produced by the method 600 disclosed herein, which may be environmentally friendly and recyclable. In various cases, each individual component may be comprised of multiple layers, including a base layer and a cushioning layer. For example, certain embodiments may include a support member, such as a support member coupled to the base layer, and the component is an insole having one or more arch-contacting or heel-contacting portions.

[0263] In particular, in various embodiments, foam materials can be produced, for example, foam materials can be used in the manufacture of cushions, cushioned furniture, shoe components such as insoles thereof, mats, fibers, textiles, etc. Other useful products can include caulks such as silicone caulk, silicone medical gloves, silicone tubing for drug delivery systems, silicone adhesives, silicone lubricants, silicone paints, and other suitable silicone products such as condoms. In various embodiments, foam products can be produced such that the foam materials can have one or more of antibacterial, antibacterial, antifungal, antiviral, and / or flame retardant properties.

[0264] More specifically, in one aspect, this disclosure can be generally directed to a process for producing furniture, e.g., upholstered furniture and / or its cushions, e.g., furniture that includes or is otherwise composed of foam, e.g., biodegradable and / or compostable. Thus, the recycled foams of the present disclosure are advantageously used in the manufacture of furniture that includes the foam inserts so produced. Recyclable foams produced by the methods of the present disclosure have proven advantageous for use as cushioning material for, e.g., pillows, couches, beds, seat cushions, or other upholstered furniture.

[0265] For example, the method 600 may be used to generate small to large blocks of recyclable foam 402, e.g., foam inserts for use in furniture or car accessory components. The block foam can then be cut into smaller blocks of the desired size and shape based on the type and form of the furniture to be produced. Specifically, the sized and cut blocks can then be applied to or otherwise fitted within a furniture or automobile frame or other boundary material and covered therewith to produce the final furniture product, whether a pillow, sofa, cushion, e.g., sofa or car cushion, etc. Additionally, if desired, the outer casing or boundary material can be attached to the frame material, e.g., by stapling and / or tacking, or otherwise secured to the frame of the article to be upholstered and covered with fabric or other material.

[0266] Thus, in various embodiments, when manufacturing upholstered furniture, such as a couch or car seat, a frame may be created. Various interior, e.g., structural components of the furniture may be attached within the frame, e.g., springs, etc., and then sheets of recyclable flexible foam 402 may be placed within, over, and around the springs, e.g., for cushioning and / or insulation. Of course, other materials may be included, such as layers of cotton, wool, felt, rubber-based products, etc., and a cover material may then be added to cover the frame and complete the product manufacture.

[0267] Specifically, the recyclable foams of the present disclosure, along with other materials disclosed herein, can function as padding or filler, which can be shaped, adjusted, and tucked under the cover as the cover material is stretched over the frame. Additionally, as shown, in various cases, the recyclable foams produced herein are useful in and above those known in the art for a number of reasons, most notably the fact that typical PU and / or EVA foams are not recyclable, whereas the foam components produced herein are. Thus, in various embodiments, methods of constructing furniture on an open frame are provided.

[0268] In yet another aspect, this disclosure is generally directed to processes for manufacturing shoe components, such as shoe soles, midsoles, and / or insoles, e.g., shoe components including or otherwise consisting of conventional foam. Specifically, in certain embodiments, methods are provided for manufacturing recyclable soles, midsoles, insoles, and / or other shoe inserts. For example, the shoe inserts may be in the form of cushioning devices adapted to be inserted or otherwise fitted within shoes, e.g., running shoes or sneakers, which may be configured to reduce the impact of the foot striking a surface, e.g., the ground, while running or walking, thereby absorbing and / or attenuating impact to the foot.

[0269] In particular, sole components, including midsoles and inserts, may include one or more layers. For example, in some cases, a base layer, a recyclable foam layer, and / or a textile layer may be provided. Specifically, a base layer of a relatively elastic material may be included, and / or a recyclable foam layer disposed on the base layer, and / or a textile layer disposed on the recyclable foam layer. Thus, the method may include integrally forming the base layer, the recyclable foam layer, and the textile into a three-layer sheet. In various cases, a support layer may be disposed in the heel region, and the support layer may be constructed, for example, from a rigid material having a higher density than the other components of the laminate. Adhesives, glues, or other attachment mechanisms may be provided or employed to bond and form the three layers with the support layer.

[0270] More particularly, in other cases, a method for manufacturing a shoe component such as an insole comprises: The method may include the steps of: providing a recyclable foam layer, providing a fabric layer, heating the recyclable foam layer, and combining the recyclable foam layer and the fabric layer; providing a base layer, for example, a base layer having a density that is the same as, greater than, or less than that of the recyclable foam layer; and heating at least one of the base layer and the foam layer to combine the base layer with the recyclable foam layer to form a two-layer or three-layer.

[0271] The method may further include forming a preformed support member, e.g., an arch support and / or heel member, which may have a density substantially the same as, less than, or greater than that of the foam layer. In particular cases, the support member may be formed from a compressed foam material, achieving a greater density and thus greater rigidity than the recyclable foam layer. In addition, a heat and / or pressure reactivatable adhesive may be applied between the support and / or heel member and the laminate. Molding pressure may then be applied to the composition, causing it to form and / or shape the three-layer support and / or heel member to form a unitary, one-piece shoe insert, with the preformed heel member forming the rear portion and / or the support member forming the central portion of the bottom surface of the finished shoe insert, e.g., in the central and / or heel region thereof, and the base layer forming the bottom surface of the finished shoe insert in the front region thereof.

[0272] It should be noted, however, that support and / or heel members need not be included, and in some cases, one or more laminate components may be omitted or other laminates added. It should be further noted that in some embodiments, the recyclable foam layer may be softer and / or more cushioned, e.g., having a greater durometer, than the base layer, which in turn may be softer and / or more cushioned, e.g., having a greater durometer, than the support member. Thus, the softer foam and base layer may be relatively resilient and able to conform in shape to the desired shoe size and configuration, while the support layer(s) may be relatively more rigid.

[0273] Specifically, the support layer may have a higher density of recyclable foam, thereby making the support layer more rigid. Thus, in various embodiments, the recyclable foam layer may have a density of about 2, or about 3, or about 5 to about 10 lbs / cu ft or greater, e.g., in the range of about 4-6 lbs / cu ft. Additionally, the recyclable foam layer may have a thickness of approximately 1 / 8", e.g., in the range of about 3 / 32"-5 / 32".

[0274] Similarly, the base layer may also have a density of about 2, or about 3, or about 5 to about 10 lbs / cubic foot or greater, for example, a density in the range of about 4-6 lbs / cubic foot. The thickness of the base layer may be on the order of about 5 / 16" + or -10%. However, in various cases, the thickness of the base layer may range from about 1 / 4" or less to about 7 / 16" thick. With regard to the support layer, it may be formed primarily in the arch and / or heel region of the insert, and it may also be made of the recyclable foams disclosed herein.

[0275] However, the support layer may be manufactured by compressing the recyclable foam 402 to a final density on the order of 22-23 lbs / ft 3 . The fabric layer may be constructed of any suitable material, for example, cotton, polyester, or polypropylene knit. In various cases, the material and recyclable foam layer may be laminated together by a flame lamination technique that employs an open flame to generate sufficient heat to melt the surface of the recyclable foam layer. Once melted, the fabric layer becomes recyclable. The laminate is then bonded to the foam layer and cooled with a chill roller, thus joining the two layers together.

[0276] At this point in the process, the layers are still in flat sheet form. These combined layers can then be subsequently bonded to a base layer by flame lamination. The previously combined material and foam layer can be bonded to a support layer, and the multiple laminate layers are then moved between chill rollers. At this stage in the process, the layers are still in flat sheet form. At this point, the thus-laminated layers are then ready to be molded. This can be done by heating the laminate layers to a molding temperature of approximately 250°F, for example, for a period of about 1 to about 5 minutes or more, e.g., about 225 seconds. This heats the previously laminated layers sufficiently to allow them to be inserted into a mold.

[0277] As described above, the SCF physical blowing agent can be selected depending on the desired properties of the final product. Carbon dioxide, which becomes an SCF fluid at 31.1 degrees Celsius and 72.2 bar, is four to five times more soluble in thermoplastic polymer 502 than nitrogen, which becomes a supercritical fluid at -147 degrees Celsius and 34 bar. The saturation point in unfilled recyclable thermoplastic polymers is approximately 1.5 to 2 weight percent nitrogen, depending on temperature and pressure conditions, while the saturation level for carbon dioxide is around 8 weight percent. Carbon dioxide also exhibits greater mobility in biopolymers, allowing it to migrate further into existing bubbles than nitrogen. From a bubble nucleation perspective, greater solubility and mobility means that fewer bubbles nucleate, and those that do nucleate tend to be larger.

[0278] In the embodiment described above, where method 600 is used to produce athletic equipment such as shoes, SCF510 contains nitrogen in a critical state. Nitrogen provides improved weight reduction and fine nuclei at a much lower weight percentage than SCF carbon dioxide. SCF510 nitrogen levels are at least 75 percent lower than the SCF carbon dioxide levels required to achieve comparable parts. Thus, the significantly reduced SCF nitrogen level requirements compared to SCF carbon dioxide ensure more optimal material and time savings when mass-producing the biodegradable, industrially compostable flexible foams of the present disclosure used to manufacture shoe components.

[0279] Although carbon dioxide is heavier, it may be the preferred blowing agent in certain applications, such as when viscosity reduction is a process goal and / or when the final product cannot withstand the more aggressive blowing action of SCF nitrogen, or in semi-flexible foams. For example, when process 600 is used to produce furniture and automotive parts, SCF 510 contains carbon dioxide in a critical state because carbon dioxide produces a much larger cell structure despite its larger size and / or weight. During the physical foaming process using a physical blowing agent, a depression of the glass transition is observed.

[0280] As briefly described above, carbon dioxide in a supercritical state can be used as a physical blowing agent when the amount of nitrogen required to produce a part is too low to consistently process the part. Because carbon dioxide is a less aggressive blowing agent, it is easier to flow low levels of carbon dioxide in some applications. For example, 0.15 or 0.2 percent carbon dioxide (compared to nitrogen levels of less than 0.05 percent) can be used to produce parts with soft materials and thick cross sections.

[0281] Although several embodiments have been described in detail above, other modifications are possible and may fall within the scope of the following claims.

Claims

1. providing a thermoplastic polymer precursor comprising at least one monomer derived from depolymerized post-consumer plastic; introducing the fluid into the barrel of a molding device under temperature and pressure conditions that produce a supercritical fluid; mixing the thermoplastic polymer and the supercritical fluid to form a single-phase solution; injecting the single-phase solution into a mold of an injection molding machine, the mold being under gas counter pressure; foaming the SCF-impregnated single-phase solution by controlling the heat and temperature conditions in the mold; 1. A method for producing a recyclable molded flexible foam article, comprising:

2. 10. The method of claim 1, wherein the thermoplastic polymer comprises at least 40% monomers derived from the depolymerized post-consumer plastic.

3. 3. The method of claim 2, wherein the thermoplastic polymer comprises at least 60% monomers derived from the depolymerized post-consumer plastic.

4. 4. The method of claim 3, wherein the thermoplastic polymer comprises 90% or more of the monomers derived from the depolymerized post-consumer plastic.

5. The method of claim 1 , wherein the monomer comprises caprolactam.

6. The method of claim 1 , wherein the thermoplastic polymer comprises a polyamide-based thermoplastic elastomer.

7. The method of claim 6 , wherein the thermoplastic polymer comprises a copolymer comprising at least one caprolactam monomer.

8. 10. The method of claim 1, further comprising recycling the flexible foam by depolymerizing the flexible foam into one or more monomers.

9. 9. The method of claim 8, wherein the flexible foam is depolymerized to caprolactam.

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