Biodegradable, compostable, and recyclable injection-molded microporous flexible foam

Abstract

This application discloses a method for manufacturing recyclable injection-molded microcellular foams for footwear components, seating components, protective equipment components, and water sports accessories. The method includes the steps of: providing a thermoplastic polymer comprising at least one monomer derived from a depolymerized post-consumer plastic; injecting fluid into the barrel of a molding apparatus; introducing the fluid under temperature and pressure conditions to generate a supercritical fluid; the method further includes mixing the thermoplastic polymer and the supercritical fluid to generate a single-phase solution; and injecting the single-phase solution into a mold of an injection molding machine under gas back pressure; the method further includes foaming the single-phase solution by controlling the head and temperature conditions within the mold.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to U.S. Provisional Patent Application No. 63 / 119,691, filed December 1, 2020, which is incorporated herein by reference in its entirety.

[0003] background

[0004] This disclosure relates to a method for injection molding microporous foaming of various flexible foam compositions, such as footwear components, seating components, protective equipment components, and water sports accessories, from recyclable or biodegradable, industrially compostable bio-derived thermoplastic polymers.

[0005] Degradation through composting is an important method for recycling resources used in the production of manufactured goods. However, when these manufactured goods involve foam, decomposition can be problematic. In particular, conventional known methods of manufacturing flexible foam have several drawbacks. These drawbacks include, for example, the selection and use of non-renewable polymers, chemical blowing agents, and chemical additives, which, when used in the foam manufacturing industry and inherent processing procedures, are generally not biodegradable and are often considered harmful to the environment. This lack of biodegradability means that many conventional flexible foam materials and products containing them end up in landfills for decades to centuries.

[0006] This is also problematic because the overuse of landfills in the world today 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 aforementioned non-biodegradable polymers and chemicals used in traditional flexible foams are specifically derived from non-renewable resources.

[0007] These materials are not naturally renewable like bio-derived raw materials, and therefore, their generation is a net loss to the environment, as their materials are often unsustainably acquired, used, and then discarded. Furthermore, even when renewable polymers are chosen for conventionally known flexible foam manufacturing methods, the chemical blowing agents and crosslinking processes used in these methods can contaminate the renewable polymers with additives that are not biodegradable or compostable. This makes it a zero-sum game. In addition, the crosslinking of biopolymers may also prevent any end-of-life solutions suitable for biodegradation or composting because the precursor components cannot be separated, leading to more waste generation and more material ending up in landfills.

[0008] Therefore, while composting and recycling are important methods for providing a renewable and sustainable future, their integration in manufacturing is very limited. However, it would be extremely useful, for example, for the environment, if the materials being made could be compostable. For instance, the composting and biodegradation of flexible foam materials creates opportunities for waste management, thus representing net environmental and economic benefits. For example, composting these materials would allow for a reduction in the total amount of waste sent to landfills and large-scale incinerators.

[0009] Besides reducing waste, the composting process also produces a usable product that is nutrient-rich and can be used to improve poor soil for growing food or fertilizing gardens. Therefore, the concepts of composting and biodegradable soft foam, however novel, can fundamentally transform the entire value chain while maintaining the principles of a so-called circular economy. There are two typical forms of composting: industrial composting and home composting. Both methods have their advantages and disadvantages.

[0010] Industrial composting is a large-scale form of composting designed to process very large quantities of organic waste. It is carried out in large facilities at temperatures of 50 to 60°C. Home composting is a form of composting that processes organic waste from a single household. In particular, home composting refers to composting at relatively low temperatures, as seen in compost heaps in a home's backyard, hence the term "home." Compared to industrial composting, home composting involves the low-temperature aerobic decomposition of organic materials or waste such as patio decorations, kitchen waste, wood shavings, cardboard, and paper. The volume processed in home composting is much smaller than in industrial composting, and composting is often used in private gardens. This method is typically carried out in small composters and heaps. In this method, the temperature is typically in the range of psychrophilia (0–20°C) to thermophilia (20–45°C) (explained below). Therefore, different techniques exist, but the general process is the same: a controlled process of activating compost, followed by solidification.

[0011] The active composting stage typically lasts at least 21 days. Under these conditions, microorganisms grow on the organic waste, breaking it down into carbon dioxide and water, which they then use as nutrients. During composting, the organic waste piles up, and thus, some of the energy in the compost is released as heat. As the temperature of the compost pile rises, the microbial population changes: microorganisms adapted to ambient temperatures (e.g., thermophiles) cease activity, die, and are replaced by microorganisms adapted to surviving at higher temperatures (e.g., thermophiles). For hygiene purposes, for home composting, the temperature should be maintained above 60°C for at least one week to eliminate pathogenic microorganisms. In contrast, the solidification stage of industrial composting slows the decomposition rate to a uniform pace, and the compost matures at temperatures below 40°C within a lower thermophilic range.

[0012] A major challenge in industrial composting is ensuring the proper handling of input materials for effective processing. In other words, the logistical hurdle lies in the need for proper collection, sorting, and transportation to industrial composting facilities. The overall composting and recycling conversion rate in the United States is approximately 35%, indicating that society has a long way to go before most infrastructure achieves a "closed loop" in waste conversion. One way to overcome this shortcoming is to better educate end-users and establish a localized network of recycling programs that feed back into larger recycling initiatives. The goal is to develop sufficient convenience and accessibility to make industrial composting a regular and ubiquitous part of daily life.

[0013] Similarly, a common drawback of home composting is the amount of work involved. All the necessary composting materials need to be transported and / or transferred to the compost pile. Once the compost pile is large enough to begin generating energy and thus heat, it needs to be moved to make the decomposition faster and more thorough, which can be a daunting task. When the organic matter is fully decomposed, the home compost must be removed for soil amendment. Another disadvantage of home composting is the limited amount of usable compost that the average person can produce in a home environment. The limited amount of compost produced may give way to limited use, and therefore, the average person's motivation to commit to home composting may be low.

[0014] Because of these drawbacks, the manufacturing industry has traditionally avoided using raw materials and precursor ingredients with biodegradable or compostable potential. Furthermore, this has traditionally been avoided because the required technical performance characteristics of these materials are generally less desirable than those of traditionally non-biodegradable and non-compostable varieties. For example, a limiting factor for some (but not all) compostable precursor ingredients may be their tendency to decompose and / or degrade before the end of the product's lifespan. One example of this is in UV-sensitive products, where biodegradable and compostable precursors can be attacked and weakened by repeated exposure to sunlight, potentially leading to product failure well before the end user is ready to dispose of it.

[0015] In the context of plastics, thermoplastics, and other products manufactured using fossil fuels, recycling typically involves mechanically shredding the finished product, melting the shredded contents, and then granulating the resulting material for later use in manufacturing. While recycling reduces the need for fossil fuels and diverts products from landfills, it can lead to a loss of quality in the recycled polymers due to contamination or impurities added to the feedstock, and most plastics and thermoplastics can only be recycled a limited number of times. Furthermore, the chemical blowing agents, crosslinking polymers, and chemical additives used in the manufacture of conventional flexible foams prevent the final product from breaking down into its constituent polymers for later use in manufacturing recycled products. Therefore, conventionally manufactured flexible foam products are not recyclable when they reach the end of their service life.

[0016] Furthermore, current focus in modern manufacturing is on achieving net neutrality in terms of emissions and waste, sustainability in the materials used in the manufacturing process, and renewability at the end of the product and its materials' lifespan. Therefore, net neutrality, for example regarding CO2 emissions, becomes important not only in the compostability of the final product but also in the selection of appropriate materials for manufacturing consumer goods.

[0017] Therefore, compared to more traditional manufacturing methods currently in use, the key driver of the manufacturing method disclosed herein is that manufacturers produce environmentally conscious end products, and thus it is useful to carefully consider the materials used in the manufacture of said end products and balance them with the product's expected lifespan. An example of a challenging product whose production process should address these issues but has not been resolved is the use of standard manufactured goods with foam, such as the production of cushioning pads for furniture and / or foam products, such as those used in the manufacture of running shoes.

[0018] For example, running shoes are highly technical products exposed to repeated abuse, such as impact, abrasion, and prolonged exposure to various environments; this could be 1-3 years, depending on frequency of use. It is important to consider these requirements when considering using sustainable materials for furniture cushioning or for cushioning in shoe soles, midsoles, and / or running shoe insoles. Materials that cannot withstand repeated abuse before failure will not produce a satisfactory running shoe. Furthermore, any material that has the potential to decompose or weaken to its failure point during normal product use, before its expected end-of-life, is unacceptable.

[0019] Summary

[0020] To address this issue, specialized materials must be found that strike a proper balance between technical performance characteristics and sustainability, such as compostability and manageable end-of-life solutions—that is, net neutral (or negative) in terms of harmful emissions. In particular, due to the large volume of furniture cushioning and the demanding nature of running shoes, household compostable materials would not be a suitable solution for their manufacture, as the lower decomposition temperatures would result in furniture or running shoes easily falling off long before their intended end-of-life. In this case, industrial compostable materials are a better choice because they can withstand higher temperature challenges and offer superior technical performance characteristics close to or equal to their non-industrial compostable and non-biodegradable counterparts. Essentially, furniture or a pair of running shoes made from industrially compostable materials can function well throughout the product's lifespan, and only at the end of the product's lifespan can the material be selectively placed directly into an industrial composting environment for a "closed-loop" waste transformation.

[0021] Therefore, where possible, materials and manufacturing methods should be designed in a way that allows for compostability at the end of the product's lifespan, in order to reduce the destructive footprint often associated with manufacturing. However, as mentioned above, this is difficult because commercially available biodegradable and compostable precursors are very limited. Those that do exist are not necessarily designed and able to address all the combined challenges of performance and long-term usability, while also being readily compostable and biodegradable in a controlled environment at the end of their lifespan. Precursors that address some of the aforementioned challenges fail to address others, and this could lead to consumer panic and potentially negative reviews of products containing them. Despite these significant drawbacks, materials that can theoretically be composted in industrial facilities or at home could be useful starting points for renewable, sustainable, and green manufacturing.

[0022] Another aspect of this manufacturing method relates to the production of flexible foam. Flexible foam is a type of material formed by trapping air pockets in a liquid or solid; the resulting foam portion is called flexible due to its extensibility. Flexible foam is commonly used in cushioning applications such as footwear, furniture, bedding, and other sporting goods. Flexible foam is generally classified into two categories: closed-cell flexible thermoplastic polymer foam and open-cell flexible polyurethane foam. Each of these foam types has very different manufacturing methods.

[0023] Closed-cell flexible thermoplastic polymer foams are typically produced using a dry process, where suitable synthetic polymers are selected and mixed with various chemical additives, crosslinking agents, and chemical foaming agents to produce a "dough," which is then kneaded and extruded into flat sheets. These sheets are then stacked on top of each other and placed in a hot press under controlled pressure. The material mixture and chemical foaming agents react and expand within the hot press chamber. The result is a closed-cell flexible foam "bag" or "block," which is then sliced ​​to thickness. In contrast, open-cell flexible polyurethane foams are typically produced using a liquid casting or liquid molding process, where synthetic polyol chemicals, isocyanate chemicals, and other chemical additives react together when cast or injected into molded shapes such as "bags" or "blocks." The result is an open-cell flexible foam, which is then sliced ​​to thickness.

[0024] Consistent with the above, one of the problems with existing flexible foams on the market today is that they use almost entirely non-renewable materials and hazardous chemicals in their manufacturing process. Furthermore, partly due to the chemical cross-linking that occurs in the aforementioned methods of manufacturing conventional flexible foams, the physical structure of these foams cannot be composted, biodegraded, or recycled. This is largely due to their designed chemical composition and the inability to separate them back to their root precursor components. That is, at the end of the life of a conventional flexible foam, it has no further use and cannot be successfully reprocessed into new materials using any known commercially viable method.

[0025] Therefore, in light of the above, this document describes flexible foams and manufacturing methods that can be used to produce renewable, sustainable, and / or environmentally responsible end products. These materials and end products are designed for continuous use without decomposition, but rapidly degrade and compost at the end of their lifespan. Flexible foams and semi-flexible foams can both be classified as flexible foams because they are both derived from polymers with a glass transition (Tg) below their service temperature (typically room temperature). Details of one or more embodiments are set forth in the accompanying description below and with respect to the presented figures and their features. Other features and advantages will be apparent from the specification, figures, and claims.

[0026] This document describes a method for microcellular foaming various flexible foam compositions using injection molding dies modified with biodegradable and industrially compostable thermoplastic resins. Currently, almost all known flexible foams in the world are derived from non-renewable raw materials, and most (if not all) are neither biodegradable nor industrially compostable. One object of this invention is to produce flexible foams that minimize environmental harm while possessing significant technical performance characteristics equal to or greater than those of conventional non-biodegradable petrochemical flexible foams. By selecting plant-derived raw materials to produce biopolymers, this invention helps to insulate the atmosphere from greenhouse gases, significantly reduces dependence on non-renewable petroleum, and substantially reduces the amount of non-biodegradable waste that ultimately ends up in landfills each year.

[0027] In various implementations, the resulting flexible foam can be configured for industrial composting rather than household composting, although household composting may be useful in certain situations, depending on the market. Industrial composting is useful in various cases because it ensures that the flexible foam will continue its functionalization into the resulting product for its entire lifespan and will not decompose or separate midway through use of the finished product. For example, it would be harmful to a person to purchase a pair of shoes made from the flexible foam of this invention, only to have the foam degrade during normal use before the shoes reach the end of their lifespan.

[0028] As used herein, “biodegradable” generally refers to the ability to be broken down by biological activity, particularly microorganisms. In some embodiments, materials and foams described herein as biodegradable and / or industrially compostable meet or exceed the requirements of at least one of the following standards: European Standard EN 13432, ASTM D6400, or Australian Standard AS 4736. In some embodiments, materials and foams described herein as biodegradable and / or industrially compostable meet or exceed the requirements specified in at least European Standard EN 13432. In some embodiments, materials and foams described herein as industrially compostable are configured to exhibit at least 60% biodegradation within 180 days of composting in a commercial composting unit (at least 60% of the material must be decomposed by biological activity). In some embodiments, materials and foams described herein as industrially compostable are configured to exhibit at least 90% biodegradation within 180 days of composting in a commercial composting unit.

[0029] Therefore, in one aspect, this document provides a method for manufacturing biodegradable and industrially compostable flexible foams (whether open-cell or closed-cell), and may include one or more of the following steps: producing a thermoplastic biopolymer blend masterbatch for foaming; injection molding the thermoplastic biopolymer blend into a suitable mold shape using inert nitrogen; employing dynamic mold temperature control to ensure optimal cell structure; controlling the biopolymer melt, pressure, and time to form a desirable flexible foam; and utilizing gas back pressure during injection molding to ensure optimal foam structure, minimizing appearance defects, and resulting in a foam component with little or no plastic skin on the outside.

[0030] The manufacturing method disclosed herein, combined with carefully selected bio-derived, renewable, and recyclable raw materials, opens the door to an environmentally friendly closed-loop process. This closed-loop process begins with material selection. For example, selecting inert and rapidly renewable polymer raw materials that are certified by a third party as compostable ensures adherence to the principles of a circular economy. For these purposes, the selected rapidly renewable polymer raw materials begin their life cycle in the form of renewable plants or minerals. Once converted into suitable polymers, these environmentally responsible precursors can be combined with other environmentally responsible precursors and components to functionalize them into custom biopolymer compounds that can be used in the disclosed manufacturing method.

[0031] Specifically, once a suitable biopolymer compound is produced, it is processed in the chemical-free manufacturing method disclosed herein. The resulting flexible foam is non-crosslinked and, in many cases, biodegradable and compostable. Therefore, at the end of their service life, these resulting foams can be carefully ground into small pieces and industrially composted in a qualified facility to decompose their components, for example, 100% back into usable biomass. This usable biomass can then be used to grow more inert and rapidly renewable polymer feedstock materials, and the process continues in an indefinite cycle. Thus, this document describes a biodegradable and industrially compostable microporous flexible foam and a method for manufacturing the same. In some embodiments, the foam may be closed-cell foam, but in other embodiments it may also be formed as open-cell foam.

[0032] In various implementations, biodegradable and industrially compostable flexible foams can be formulated to have the same properties and characteristics as conventional petrochemical ethylene vinyl acetate (EVA) foams, and also contain a high percentage of biomass-carbon content. For example, flexible EVA foam is a widely used material in industry today. EVA foam is so popular because of its relatively low cost and ease of processing, while maintaining generally acceptable technical performance characteristics for a given product. However, the use of EVA foam has several drawbacks. The material is typically derived from non-renewable raw materials and chemically cross-linked with chemical foaming agents to produce flexible foams that are not easily biodegradable, non-compostable, or non-recyclable.

[0033] Depending on the required physical characteristics and the intended end use of the product, there are many possible configurations and implementations that should not be limited by this disclosure.

[0034] One factor that makes the advancements presented in this paper so useful is that biodegradable foams operate in a manner similar to EVA, and therefore their technical performance characteristics are similar to those of EVA without chemical additives and cross-linking. The result is a commercially acceptable flexible foam that can directly replace ubiquitous EVA, but offers a significantly reduced environmental impact and an environmentally responsible end-of-life management solution.

[0035] Therefore, in one aspect, a method is provided for manufacturing biodegradable and industrially compostable flexible foam molded articles. 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 further include introducing a fluid into the barrel under temperature and pressure conditions to generate a supercritical fluid that produces a thermoplastic foam melt upon contact with the thermoplastic biopolymer blend masterbatch. Furthermore, the method may include injecting the thermoplastic foam melt into a cavity of a suitable mold shape and applying a gas backpressure to the cavity. Finally, the cavity may be cooled to produce the molded article.

[0036] In various cases, the introduction of one or more thermoplastic biopolymer masterbatches is via a gate bushing, for example, where the thermoplastic biopolymer blend masterbatch is produced by a twin-screw extruder. In one embodiment, the thermoplastic biopolymer blend masterbatch comprises one or more of polylactic acid (PLA), polyhydroxyalkanoate (PHA), poly(butylene adipate-co-terephthalate) (PBAT), polyhydroxybutyrate (PHB), cellulose acetate (CA), starch, and petroleum-derived thermoplastics. In some embodiments, the thermoplastic biopolymer blend masterbatch comprises one or more polymers selected from or composed of polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), and polybutylene adipate (PBA). In some embodiments, the thermoplastic biopolymer blend masterbatch comprises or consists of one or more thermoplastic polymers derived from renewable resources (e.g., PBAT, PHB, or blends thereof). In some embodiments, the thermoplastic biopolymer blend masterbatch does not include any petroleum-derived thermoplastics. In various cases, fluid is introduced into the cylinder via a metering unit. In certain cases, the supercritical fluid comprises one or more of nitrogen and carbon dioxide. The supercritical fluid can be introduced at pressure and temperature, for example, where the pressure ranges from about 150 bar to about 300 bar, and the temperature ranges from about 150°C to about 350°C. Similarly, the gas backpressure ranges from about 5 bar to about 50 bar for an application duration of 1 second to 25 seconds. In some cases, the temperature can be controlled by dynamic mold temperature control.

[0037] Furthermore, in another aspect, an injection molding apparatus is provided for producing biodegradable and industrially compostable flexible foam molded articles. In various cases, the injection molding apparatus may include one or more of the following: It may include a hopper, for example, wherein the hopper is configured to receive and introduce a variety of thermoplastic biopolymers into the molding apparatus, for example, wherein the thermoplastic biopolymers form a masterbatch to be blended.

[0038] The device may include a metering unit, for example, configured to receive fluid and, under certain conditions, introduce the received fluid into a molding apparatus to generate a supercritical fluid upon introduction. The molding apparatus may include a barrel having a first cavity configured to receive a blend of thermoplastic biopolymer masterbatch and fluid, such that when introduced into the barrel, a thermoplastic foamed melt is generated when the supercritical fluid contacts the blended thermoplastic biopolymer masterbatch within the cavity of the barrel. A gas backpressure delivery unit may also be included, wherein a gas backpressure delivery unit (GCP) is configured to backpressure gas into the first cavity to control the expansion of the foamed melt. Furthermore, a mold having a cavity in fluid communication with the cavity of the barrel may be included, wherein the cavity of the mold is configured to receive the foamed melt and generate a flexible foam molded article upon melt cooling.

[0039] In various embodiments, the injection molding equipment may include a reciprocating screw configured to compress the foamed melt within the cavity of the barrel and deliver the compressed foamed melt to the cavity of the mold. Therefore, a conduit may exist between the cavity of the barrel and the cavity of the mold, wherein the conduit includes a nozzle with a gate bushing to form a seal between the barrel and the mold.

[0040] Therefore, injection molding equipment may include one or more of the following: a hopper, into which thermoplastic material is supplied in the form of small pellets. The hopper on the injection molding machine holds these pellets. The pellets can be gravity-fed from the hopper throat into the barrel and screw assembly. The equipment may also include a barrel, in which the barrel of the injection molding machine supports a reciprocating plasticizing screw, and can be heated by an electric heating element.

[0041] Reciprocating screws may also be present, used for compressing, melting, and conveying materials. A reciprocating screw may include three zones: a feed zone, a compression (or transition) zone, and a metering zone. Nozzles may also be present, connecting the barrel to the mold's sprue bushing and forming a seal between the barrel and the mold. The nozzle temperature can be set to the material's melting temperature or just below that temperature. When the barrel is in its fully forward machining position, the nozzle radius can be nested and sealed within the recessed radius of the sprue bushing with a locating ring. During barrel cleaning, the barrel can be withdrawn from the sprue, allowing the cleaning compound to fall freely from the nozzle.

[0042] In addition, molds and hydraulic systems can be provided. Mold systems may include tie rods, fixed and movable pressure plates, as well as receiving cavities, gating and runner systems, ejector pins, heating and cooling channels, and molding plates (bases) for temperature and pressure sensors. A mold is essentially a heat exchanger in which molten thermoplastic solidifies into the desired shape and dimensional details defined by the cavity. Hydraulic systems may also be present on injection molding machines to provide power to open and close the mold, build and hold the clamping tonnage, rotate the reciprocating screw, drive the reciprocating screw, and power the ejector pins and moving the mold core. Many hydraulic components are required to provide this power, including pumps, valves, hydraulic motors, hydraulic fittings, hydraulic lines, and hydraulic tanks.

[0043] Control systems can also be provided. These systems can be configured to provide consistency and repeatability in machine operation. They monitor and control processing parameters, including temperature, pressure, SCF dosing, injection speed, screw speed and position, and hydraulic position. Process control can have a direct impact on the quality of the final part and the economics of the process. The range of process control systems can be from simple relay on / off controls to extremely complex microprocessor-based closed-loop controls.

[0044] Mold clamping systems can also be provided. These systems can be configured to open and close the mold, support and carry its components, and generate sufficient force to prevent the mold from opening. Clamping force can be generated by mechanical (toggle) locks, hydraulic locks, or a combination of both. Delivery systems can also be provided. These systems provide a pathway for molten plastic from the machine nozzle to the part cavity and typically include: gates, cold slug wells, main runners, branch runners, and sprues.

[0045] Therefore, in another aspect, a system for producing biodegradable and industrially compostable flexible foam molded articles is provided. The system may include an injection molding apparatus for producing the biodegradable and industrially compostable flexible foam molded articles as described above. The system may also include a supercritical gas dispensing system configured to receive fluid and introduce the received fluid under certain conditions into a first cavity of a cylinder to generate a supercritical fluid upon introduction, which generates a foamed melt when it contacts a blended thermoplastic biopolymer masterbatch within the first cavity. The system may also include a dynamic temperature control system configured to control the temperature within one or more of the first and second cavities. A gas backpressure delivery unit may also be included, configured to backpressure gas into the first cavity to control the expansion of the foamed melt. Furthermore, a control unit having one or more microprocessors may be included, wherein the control unit is configured to control one or more of the injection molding apparatus, the supercritical gas dispensing system, the dynamic temperature control system, and the gas backpressure delivery unit according to one or more system parameters.

[0046] Specifically, system components may include an injection molding machine system comprising a hopper, barrel, reciprocating screw, nozzle, mold system, hydraulic system, control system, mold clamping system, and delivery system. An SCF gas dispensing system may be included, comprising an inert gas (e.g., nitrogen) tank, an air compressor, SCF metering and control equipment, an SCF injector, and a specially designed reciprocating screw, as well as front and rear check valves. A dynamic temperature control system may also be provided, comprising heating units, cooling units, sequence valves, and computer control. Furthermore, heating elements and cooling channels located within the mold body are supplied by the dynamic temperature control system, through which heating or cooling media circulate. Their function is to regulate the temperature on the mold surface. A gas backpressure system may also be provided, comprising a gas (e.g., inert gas, such as nitrogen) tank, an air compressor, an air pump, a gas safety valve, a gas pressure sensor, and computer control.

[0047] The system and / or any of its subsystems may include one or more sensors, such as temperature, pressure, accelerometers, gyroscopes, and orientation sensors, for example, one or more of which are configured to communicate with one or more other components of the injection molding apparatus, such as being located within one or more cavities of the injection molding apparatus. In various embodiments, the sensors may be smart sensors and include communication modules, for example, having network connectivity to perform wireless communication. Therefore, any of the various components of the system and / or its components may include a communication module that can be coupled to one or more of a control module, a supercritical gas dispensing system, a dynamic temperature control system, and a gas backpressure control unit, for example, wherein the communication module is configured to perform one or more wireless communication protocols, including Wi-Fi, Bluetooth, Bluetooth Low Energy, and 3G, 4G, and 5G cellular communication.

[0048] In another aspect, this disclosure describes a recyclable microporous flexible foam and a method for manufacturing the same. In some embodiments, the foam is a closed-cell foam. In other embodiments, the foam can be formed as an open-cell foam. The production of a recyclable microporous flexible foam structure begins with a suitable high-performance polymer, such as a polymer derived from polyamides. A non-limiting example of a suitable polymer is a polyamide 66 copolymer sold by Ascend Performance Materials, LLC, Houston, TX under the trade name Vydyne. Other non-limiting examples of suitable polymers include any number of polyamide block copolymers, such as polyether-block-amide (PEBA), PAE, TPA, TPE-A, COPA, etc. The aforementioned thermoplastic polymers exhibit advantageous technical properties in forming the microporous flexible foam structure of the present invention. Some enhanced technical properties include excellent aging properties, excellent elongation, tensile strength, and compression set. Furthermore, recycled materials can be used to manufacture suitable recyclable polymers or polymer blends of the present invention. For example, on one hand, recyclable flexible foam thermoplastic polymers contain at least one monomer or polymer derived from post-consumer or post-industrial recycled materials, such as caprolactam, recycled polyether block amide polymers, etc. For instance, caprolactam can be derived from such recycled materials obtained by depolymerizing post-industrial or post-consumer materials containing polyamides, such as fishing nets, carpet fibers, or industrial waste. Some examples of depolymerized post-consumer or post-industrial recycled caprolactam include those provided by Aquafil USA Inc., Cartersville, Georgia. Caprolactam, whether in flake, liquid, or molten form. Thermoplastic polymers may additionally or alternatively include polyamide polymers derived from post-industrial or post-consumer polyamide carpet fibers that have been 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 upgradable recyclable polyamide materials. An exemplary polyamide polymer derived from post-industrial carpet fibers is Econyl, manufactured by Aquafil USA Inc., Cartersville, Georgia. Furthermore, polyamide waste can be collected from or around the world's oceans in the form of fishing nets, etc., and then sorted, melted, and reprocessed into upgradable recyclable polyamide materials. An exemplary polyamide polymer derived from collected post-industrial fishing nets is Akulon Repurpused, manufactured by Koninklijke DSM NV, Heerlen, the Netherlands. One object of the present invention is to utilize recycled polymer raw materials as much as possible.

[0049] Without a suitable blowing agent and blowing process, optimal polyamide alone cannot produce recyclable flexible foam. 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 conventional injection molding foaming processes. Unfortunately, ADA is not environmentally friendly and is a suspected carcinogen. Furthermore, conventional foaming processes using ADA result in cross-linking during manufacturing, thus producing a class of non-recyclable flexible foams. To obtain recyclable flexible foam, inert nitrogen or carbon dioxide is used as a physical blowing agent in an improved injection molding process. The improved physical blowing process is used in conjunction with a suitable thermoplastic polymer or blend masterbatch, allowing the polymer or blend and the blowing agent to work harmoniously to produce recyclable flexible foam. The preferred injection molding process of this invention utilizes homogeneous cell nucleation that occurs when a single-phase solution of polymer and supercritical fluid (SCF) enters the mold cavity of an improved injection molding machine through an injection gating system. When the solution enters the mold, the pressure drops, causing SCF to escape from the solution and form cell nuclei. Cells then grow until the material fills the mold and the SCF's expansion capacity is exhausted. This manufacturing process runs on injection molding machines that have been modified to allow the metering, delivery, and mixing of SCF into the polymer to produce a single-phase solution. Dynamic mold temperature control (DMTC) is used to ensure a consistent cell structure within the expanding polymer melt. DMTC can be best described as heating elements and cooling channels located within the mold body, supplied by the dynamic temperature control system, through which the heating or cooling medium circulates. Their function is to regulate the temperature on the mold surface. Gas backpressure (GCP) is also used in this process to ensure optimal foam structure, resulting in a soft foam with little or no skin. GCP can be best described as a method involving a pressurized mold cavity injected with nitrogen to counteract the expansion of gases in the melt. As the backpressure is released, bubbles that would normally break through the surface become trapped inside, forming a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness.

[0050] Under carefully controlled process conditions, the generation of a single-phase solution in which SCF is completely dissolved and uniformly dispersed in the molten polymer occurs within the injection barrel: the SCF mass flow rate must be precisely metered to a continuous, fixed amount of time within the polymer. Furthermore, the correct temperature, pressure, and shear conditions must be established within the barrel during this dispensing period. Back pressure, screw speed, and barrel temperature control, as well as gas back pressure and the SCF delivery system, all play a role in establishing the process conditions for generating the single-phase solution.

[0051] Thermoplastic polymers used to manufacture recyclable and chemical-free flexible foams can optionally be produced from any number of 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 may contain any number of 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 requirements of hardness, moderate melt flowability, high elongation, and recyclability.

[0052] Furthermore, blends of two or more thermoplastic polymers offer a combination of properties and prices not available with a single polymer. There are several methods for successfully blending polymers together. One method uses a twin-screw extruder to melt two or more polymer resins together, then extrudes the molten polymer resin blend into a filament, cools the filament, and feeds it into a granulator to produce a large quantity of granulated blocks known as masterbatch. Another method of polymer resin blending is to use compatibilizers to incorporate different chemicals into the polymer blend. This can be done using twin-screw extruders, etc., to melt the compatibilizer and two or more polymers of the aforementioned non-limiting thermoplastic polymer types together.

[0053] In some embodiments, a method for manufacturing recyclable flexible foam molded articles includes providing a thermoplastic polymer precursor comprising at least one monomer derived from a depolymerized post-consumer plastic; injecting a fluid into the barrel of a molding apparatus under temperature and pressure conditions to generate a supercritical fluid; mixing the thermoplastic polymer and the supercritical fluid to generate a single-phase solution; injecting the single-phase solution into a mold of an injection molding machine, wherein the mold is under gas back pressure; and foaming the single-phase solution by controlling the heat and temperature conditions within the mold. In some embodiments, foaming the single-phase solution includes generating a plurality of bubble-containing pores in the solution by allowing at least a portion of the supercritical fluid to exit the single-phase solution, each bubble-containing pore being surrounded by a pore wall formed of a thermoplastic polymer; increasing the volume of each of the plurality of bubble-containing pores; and causing at least a portion of the pore wall to rupture to form an open-cell foam. In some embodiments, causing at least a portion of the pore wall to rupture includes increasing the volume of each of the plurality of bubble-containing pores such that at least a portion of the bubble-containing pores impacts adjacent bubble-containing pores. In some embodiments, such impact can cause rupture of the pore wall between adjacent bubble-containing pores. In some embodiments, causing at least a portion of the cell wall to rupture includes thinning that portion of the cell wall. In further embodiments, causing at least a portion of the cell wall to rupture includes applying ultrasound to rupture that portion of the cell wall. According to some embodiments, the ultrasound may be applied, for example, using an ultrasonic transducer or a sonicator, and may be applied within a mold.

[0054] In some embodiments, the method according to this disclosure may include the step of recycling flexible foam by depolymerizing the foam into one or more monomers. The depolymerization method includes the following steps: mechanically separating the thermoplastic polymer of the recyclable foam from waste; introducing a depolymerization catalyst into the separated thermoplastic polymer; heating the thermoplastic polymer and the catalyst to produce a distillate; separating water and the resulting monomers from other byproducts; 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 preparation of recyclable flexible foam. The resulting monomers may include caprolactam or other monomers that can be repolymerized into thermoplastic polymers.

[0055] In some embodiments, a method for manufacturing a biodegradable and / or compostable flexible foam molded article includes providing a biodegradable and / or compostable thermoplastic polymer; injecting a fluid into the barrel of a molding apparatus under temperature and pressure conditions to generate a supercritical fluid; mixing the thermoplastic polymer and the supercritical fluid to generate a single-phase solution; injecting the single-phase solution into a mold of an injection molding machine, wherein the mold is under gas back pressure; and foaming the single-phase solution by controlling the heat and temperature conditions within the mold. In some embodiments, foaming the single-phase solution includes generating a plurality of bubble-containing pores in the solution by allowing at least a portion of the supercritical fluid to exit the single-phase solution, each bubble-containing pore being surrounded by a pore wall formed of a thermoplastic polymer; increasing the volume of each of the plurality of bubble-containing pores; and causing at least a portion of the pore wall to rupture to form an open-cell foam. In some embodiments, causing at least a portion of the pore wall to rupture includes increasing the volume of each of the plurality of bubble-containing pores such that at least a portion of the bubble-containing pores impacts adjacent bubble-containing pores. In some embodiments, such impact can cause rupture of the pore wall between adjacent bubble-containing pores. In some embodiments, causing at least a portion of the pore wall to rupture includes thinning that portion of the pore wall. In further embodiments, causing at least a portion of the pore wall to rupture includes applying ultrasound to break that portion of the pore wall. According to some embodiments, the ultrasound can be applied, for example, using an ultrasonic transducer or sonicator, and can be applied within a mold. Flexible foams produced by such methods can be fully biodegradable and / or compostable. In some embodiments, the flexible foam is industrially compostable. In some embodiments, the flexible foam can be incorporated into articles such as footwear components (e.g., shoe insoles or midsoles), seating components, protective gear components, or water sports accessories.

[0056] In some embodiments, the thermoplastic polymer is a biopolymer. In some embodiments, the thermoplastic polymer is part of a blend of one or more biodegradable and / or compostable polymers. The thermoplastic polymer (or blends thereof) is or includes polymers selected from polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene adipate-co-terephthalate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS). In some embodiments, the thermoplastic polymer is PBAT, PHA, or PHB.

[0057] Depending on the application, additives can also be used in polymer formulations. For example, fillers such as precipitated calcium carbonate, oolitic aragonite, starch, and biomass can be used to reduce some costs while maintaining the recyclability and integrity of the finished flexible foam.

[0058] In addition, additional additives used in polymer formulations may include one or more of the following. These may include nucleating agents, such as microlayered talc or high aspect ratio oolitic aragonite. Such nucleating agents can significantly improve the key properties of the resulting flexible foam by preventing cell aggregation, reducing bulk density, and improving resilience, as well as other beneficial reinforcing properties. Several non-limiting examples of nucleating agents used in the production of recyclable and chemical-free injection-molded microcellular flexible foams are provided by Talc America Inc., Houston, Texas. Microlayered talc sold by Calcean Minerals & Materials LLC, Gadsden, Alabama High aspect ratio oolitic aragonite for sale.

[0059] Colorants, dyes, and pigments may also be included. For example, various colorants such as dyes or pigments can be used in the polymer formulations of this invention. Several non-limiting examples are pigments tailored for specific types of thermoplastic polymer applications, such as the wide range of products offered by Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or those offered by Holland Colours Americas Inc., Richmond, Indiana.

[0060] 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 claims. Brief description of the attached diagram

[0062] These and other aspects will now be described in detail with reference to the following figures.

[0063] Figure 1 A foamed footwear component, i.e., a shoe midsole, is shown according to an embodiment of the present disclosure;

[0064] Figure 2 The illustration shows a schematic diagram of an injection-molded microporous flexible foam system for producing biodegradable and industrially compostable flexible foam suitable for footwear.

[0065] Figure 3 This is a flowchart of a method for manufacturing injection-molded microporous flexible foam that is biodegradable and industrially compostable;

[0066] Figure 4 The illustration shows that a recyclable flexible foam according to this disclosure is injection molded to produce a midsole for athletic shoes;

[0067] Figure 5 Showing the production Figure 4 A schematic diagram of an injection molding machine for recyclable flexible foam is shown in the image.

[0068] Figure 6 It is used for manufacturing Figure 4 A flowchart of a method for recycling microporous flexible foam; and

[0069] Figure 7 It is shown that... Figure 6 The implementation plan of the method for manufacturing recyclable microporous flexible foam includes a flowchart of the steps related to the recycling of flexible foam.

[0070] The same reference numerals in the various figures denote the same elements.

[0071] Detailed description

[0072] This document describes a biodegradable and industrially compostable microporous flexible foam, a recyclable microporous flexible foam, and a method for manufacturing the same. In some embodiments, the foam is a closed-cell foam. In other embodiments, the foam can be formed as an open-cell foam. In various embodiments, the biodegradable, industrially compostable, and recyclable flexible foam can be formulated to have the same properties and characteristics as conventional petrochemical ethylene vinyl acetate (EVA) foam, and also contains a high percentage of biomass-carbon content.

[0073] Biodegradable and compostable injection-molded microporous flexible foam and its preparation method

[0074] This disclosure relates to methods for producing biodegradable and industrially compostable microporous flexible foams and methods for manufacturing the same. As described above, foaming describes a process involving the trapping of cavitation in a liquid or solid. Foaming is commonly used industrially to produce lightweight polymer materials. This is an advantageous solution for many types of products because foamed materials impart numerous added values, such as soft cushioning, comfort, and impact protection.

[0075] In various situations, foamed materials are useful within microporous foams. Microporous foams are a form of man-made plastic specifically designed to contain numerous, for example billions, of tiny bubbles, some smaller than about 50 micrometers. This type of foam is formed by dissolving gas into various types of polymers under high pressure, resulting in a uniform arrangement of bubbles, a process often referred to as nucleation. The primary driver for controlling and adjusting the density of microporous foams is the gas used to create them. Depending on the gas used, the density of the foam can range from about 5% to about 99% of that of pretreated bioplastics.

[0076] Therefore, closed-cell foam is useful in various situations. Closed-cell foam is generally referred to as a cell that is completely surrounded by its walls and therefore not interconnected with other cells. This type of material is useful because it effectively reduces the flow rate of liquids and gases through the cells. Closed-cell foams, such as those produced according to the methods disclosed herein, can be used in industries where liquid resistance is critical, such as cushioning, footwear, marine, HVAC, and automotive applications.

[0077] However, open-cell foams can be useful in various situations. Open-cell foams are generally classified as "open-cell" when more than half of their cells are open and interconnected with other cells. This type of foam, which can be produced and used in the methods disclosed herein, can be useful because it operates more like a spring than closed-cell foam, readily returning to its original state after compression. This "elasticity" is caused by unrestricted airflow and chemical composition. In some embodiments, open-cell thermoplastic foams can be produced using the same equipment and basic methods as those described herein for producing closed-cell thermoplastic foams, except that the open-cell foam structure develops when the walls between the cells become unstable and break, thus creating a pathway for the existence of open-cell foam structures.

[0078] This disclosure provides different methods for achieving open-cell foam structures. According to some embodiments, a first method is a cell impact or disturbance method. In some embodiments, to achieve the aforementioned cell wall rupture, cells are allowed to grow to the extent that adjacent or neighboring cells collide or interfere with each other, leading to cell wall rupture. In some embodiments, the microporous foam structure utilizes a critical nucleation density. In a non-limiting embodiment, for example, the cell size can be controlled to be from 10 μm to 50 μm, and the cell density can be controlled to be 5.0 × 10⁻⁶. 7 Up to 1.3×10 9 Number of bubbles / cm 3 Relatively uniform cells, or "bubbles," must be close enough to each other to form impact structures, and in some such embodiments, the impact of cells leads to the formation of open-cell foam structures. In some embodiments, the nucleus of each bubble should be able to grow sufficiently to collide with each other, causing cell weakening and rupture. Furthermore, a high cell cluster density may be required in some embodiments to generate impact structures.

[0079] According to some embodiments of this disclosure, another method for achieving an open-cell foam structure is to aggregate “bubbles” that cause the walls between the cells to spontaneously and uniformly rupture or break down, thus forming an open-cell foam structure. In some embodiments, as the cells grow, a thin film forms between each cell. This film is affected by the internal pressure of the “bubbles” as well as van der Waals separation pressure and electrostatic separation pressure. In some embodiments, if the pressure causing the film to thin or weaken exceeds the pressure causing the film to thicken or strengthen, the film between each cell will rupture or break down, and this can be understood as the force that determines the rupture or breakage of the cell walls. The increasing internal “bubble” pressure and van der Waals separation pressure act as forces that contribute to thinning the film present between each cell, while electrostatic separation acts as a force that contributes to thickening or strengthening the aforementioned film.

[0080] In some cases, the presence of polar groups in the polymer structure can actually thicken or reinforce the cell walls, making it difficult for them to rupture or break. Conversely, due to the general thermodynamic instability of the film, surface waves develop during impact in some embodiments, which greatly contributes to the rupture or breakdown of the cell walls, and this phenomenon causes the film to thin faster than the internal “bubble” pressure builds up, resulting in a faster cell wall rupture or breakdown mechanism. In some embodiments, it may be important that the cell walls rupture or break as quickly as possible to create an open-cell foam structure, as this helps overcome the growth of thermoplastic polymer foam viscosity, which is known to increase during mold cooling and the injection phase of foam production. In some embodiments, various foam molding parameters determine the optimal nucleation and cell growth in the formation of the final microporous injection-molded foam part. For example, the nucleation rate may be significantly affected by the injection rate and mold temperature, and therefore, in some embodiments, the processing window for producing the open-cell foam of the present invention is very narrow. In some embodiments, the method of producing open-cell foam according to the present disclosure may include steps for controlling one or more of these parameters.

[0081] In some non-limiting embodiments, for example, the gas saturation pressure is selected to be from 75 bar to 250 bar. In further non-limiting examples, the foam cell size can be from 10 to 50 μm, preferably from 15 to 25 μm. In some examples, the cell density can be 0.5 × 10⁻⁶. 8 Number of bubbles / cm 3 Up to 7×10 8 Number of bubbles / cm 3 1×10 is preferred 8 Number of bubbles / cm 3 Up to 3×10 8 Number of bubbles / cm 3 In some implementations, the foam expansion ratio is between 1.5 and 4.5.

[0082] In a further embodiment, the method for forming open-cell foam according to this disclosure may include using ultrasonic irradiation as a means of opening the pores of the foam structure. In some such embodiments, the duration and intensity of ultrasonic irradiation are factors in obtaining an open-cell foam structure. In some embodiments, applying ultrasound can cause at least a portion of the pore walls to rupture. According to some embodiments, ultrasound may be applied, for example, using an ultrasonic transducer or sonicator, and may be applied within an injection mold.

[0083] In certain cases, the foam produced according to the method and the product derived therefrom function in a manner similar to flexible ethylene vinyl acetate (EVA) foam. In particular, flexible EVA foam is a widely used material in manufacturing today. EVA foam is so popular because of its relatively low cost and ease of processing, while maintaining generally acceptable technical performance characteristics for a given product. Therefore, foam produced in the manner disclosed herein can be manufactured at a relatively low cost and is easy to manufacture, while maintaining not only acceptable but often superior technical performance, and is also environmentally friendly.

[0084] More specifically, as mentioned above, there are many disadvantages to using EVA foam. This material is derived from non-renewable raw materials and is chemically crosslinked with chemical foaming agents that are not easily biodegradable, compostable, or recyclable. However, unlike flexible EVA foam, the biodegradable and industrially compostable flexible foams of this disclosure do not contain chemicals or crosslinking agents, and are readily biodegradable and industrially compostable when suitable bio-derived polymers are used in their manufacture.

[0085] For example, in various embodiments, this document provides biodegradable and industrially compostable flexible foams that can be formulated to have similar properties and characteristics to conventional petrochemical ethylene vinyl acetate (EVA) foams, and also contain a high percentage of biomass-carbon content. Specifically, in various embodiments, biodegradable, net-neutral, and industrially compostable foam precursors are used to manufacture biodegradable and industrially compostable flexible foams, for example, in an environmentally friendly manner. To achieve these objectives, any amount of suitable bio-derived thermoplastic raw materials can be selected and can be derived from rapidly renewable raw materials that do not typically compete with animal feed or human food. Advantageously, as noted, carefully selected bio-derived thermoplastic foam precursors have technical performance characteristics that are close to or equivalent to those of conventionally used EVA.

[0086] Non-limiting examples of suitable thermoplastic raw materials for manufacturing the biodegradable and industrially compostable flexible foams of this disclosure are bio-derived PBAT copolyesters, which have technical performance characteristics that are nearly equivalent to or equivalent to conventional non-renewable EVA, as described below. Therefore, in various cases, the apparatus, systems, and methods of use of the present invention can be employed to produce biodegradable and industrially compostable microporous flexible foams, which can be generated from biodegradable and industrially compostable bio-derived thermoplastic resins.

[0087] More specifically, the foam precursor useful according to the disclosed method can be any suitable type of thermoplastic resin, such as a bio-derived thermoplastic resin or bio-derived thermoplastic compound produced from rapidly renewable raw materials. This thermoplastic resin is a raw, unformed polymer that melts and becomes liquid when heated, and hardens and becomes solid when cooled.

[0088] The production of thermoplastics is not a simple task. Complex chemical and mechanical processes are required to manufacture the final product. In its simplest form, thermoplastics consist of polymers, which in turn are composed of compounds. To produce the compounds needed to manufacture the polymers and then the thermoplastics, different types of molecules must be broken down and separated. Typically, foam precursors are used by feeding them in granular form into a suitable injection molding machine. The granules are processed by the injection molding machine, where they are liquefied and injected into a pre-formed mold cavity. After injection, the molded part is cooled and demolded from the mold in a solid state; the method implemented in this embodiment is discussed in more detail below.

[0089] Bio-derived thermoplastics can be described by category. One popular class is bio-based thermoplastic precursors and biomass. There are two types of biopolyesters: polylactic acid (PLA) and polyhydroxyalkanoates (PHA). PLA is a class of thermoplastics produced through bacterial fermentation. PLA is essentially a long chain of many lactic acid molecules. Many different bio-derived feedstocks can be used to produce PLA, such as sugarcane, corn, sugar beets, and lignin-rich wood waste, to name a few. PHA is typically produced from naturally occurring bacteria and food waste. There is a subclass of PHA called polyhydroxybutyrate (PHB), which is also a widely available type of PHA.

[0090] In some cases, starch or cellulose fillers can be optionally included in the formation of biopolyester blends because their inclusion makes the blends more economical, and in some cases, their use increases the decomposition rate. Another type of bio-derived thermoplastic is called cellulose acetate (CA). CA is a synthetic product derived from cellulose, which is found in various parts of plants. Currently, raw materials used to manufacture CA include cotton, wood, and agricultural waste, to name a few. Furthermore, starch is yet another type of thermoplastic. Typically, starch is heated, treated with water and plasticizers to produce thermoplastics. To impart strength, starch is often combined with fillers made from other materials. Currently, raw materials available for starch production include corn, wheat, potatoes, and cassava. Several biodegradable petroleum-derived thermoplastics are also known. Common types include polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene terephthalate (PBAT), and polyvinyl alcohol (PVOH / PVA). The aforementioned petroleum-derived thermoplastics can be produced in the form of bio-derived varieties. Thanks to technological advancements and breakthroughs, novel bio-derived feedstocks for the production of PBS, PCL, PBAT, and PVOH / PVA are being manufactured and are becoming increasingly commercially available. One or more of these precursors can be produced and used according to the methods disclosed herein.

[0091] Once the precursors are generated, they can be foamed and used to manufacture one or more end products, for example, via injection molding processes as disclosed herein. For instance, in various cases, bio-derived thermoplastic precursors can be foamed and used in the production of end products, such as via injection molding. In conventional foam injection molding (also known as direct injection foaming), the thermoplastic polymer is first melted. While the thermoplastic polymer is uniformly melted, a chemical foaming agent is dispersed into the polymer melt to make the injection molding compound foamable.

[0092] A homogeneous polymer compound is then injected into a mold to create the foam product. Typically, the injected polymer compound is not classified as foam until an endothermic reaction in the heated mold cavity activates the chemical blowing agent, resulting in an expanded foam part. Therefore, the mold cavity size must be smaller than the final part size. The actual part expansion occurs within the thermoplastic polymer formulation, causing the part to grow to the desired part size when it is demolded from the mold.

[0093] Once the desired part size is achieved, it will shrink or contract upon cooling, which typically requires a secondary molding operation to obtain accurate cooled part dimensions. Therefore, managing the expansion and contraction of conventional injection-molded foam can be considered tedious, time-consuming, and complex. As discussed herein, this injection molding technology can be used to produce precursors and foams, and the products derived from them. However, in specific cases, as disclosed herein, conventional injection molding machines can be modified to better enable the use of biodegradable, net-neutral foam precursors, which can be used in improved methods to produce environmentally friendly foams suitable for manufacturing foam products such as furniture cushioning, shoe components, and sports equipment.

[0094] Therefore, while conventional methods can be used to produce foam products, they may have drawbacks in certain situations, particularly in the production of compostable microporous flexible foams. For example, in various cases, typical injection molding processes can be flawed in different ways when using compostable bio-derived thermoplastic resins to produce compostable flexible foams. For instance, the aforementioned conventional unmodified foam injection molding process may be defective and unsuitable for producing biodegradable and compostable flexible foams. The main reason lies in the very nature of conventional unmodified foam injection molding, where polymer compounds undergo cross-linking during its manufacturing process.

[0095] As described above, crosslinking can be described as the formation of covalent bonds that randomly hold portions of several polymer chains together. The result is a random three-dimensional network of interconnected chains within the foam matrix. Such crosslinked foams cannot be easily decrosslinked, and therefore, the various precursor components cannot be easily separated back to their respective types and biodegradable or compostable. Therefore, the advantages currently disclosed are not easily realized without changing the foaming equipment and its method of use in manufacturing. Therefore, this paper proposes a manufacturing machine and a method for producing foams in a manner suitable for use with non-crosslinked precursors in injection molding processes.

[0096] Therefore, in one aspect, this paper presents a novel injection molding machine. The molding machine can be configured to employ various flexible foam compositions, including bio-derived thermoplastic precursors, which, by applying the precursors to the novel injection molding machine, can be foamed in a manner that produces compostable microporous flexible foam structures, which can then be used to produce one or more flexible foam products. Thus, in one aspect, this paper provides a novel injection molding machine.

[0097] Some factors that distinguish the manufacturing machinery of this disclosure are the use of specialized auxiliary equipment coupled to a microporous gas delivery system, which can be fixed to a standard injection molding machine, thereby modifying and improving the standard injection molding machine. Essentially, as presented herein, the standard injection molding machine has been thoroughly overhauled and modified to operate in a suitable manner for use according to this disclosure. A general approach to improvement begins with modifying the injection molding screw on the injection molding machine to handle supercritical inert gases, such as nitrogen, CO2, and / or non-reactive and / or inert gases.

[0098] A gas delivery system can then be fitted to the injection molding machine to deliver the appropriate amount of gas to the polymer melt within the screw, for example, before injection into a temperature-controlled mold cavity. Furthermore, specialized mold cavities can be used where the thermal cycling of the mold allows for better control of the resulting foam's outer skin texture and thickness, as well as reduced part production cycle time. Additionally, an auxiliary gas backpressure system can be fitted to the injection molding machine to force inert gas back into the mold to counteract the liquid polymer melt injected into the mold.

[0099] This back pressure is used to ensure that the molten injection jet substantially (if not completely) fills the mold cavity and prevents part warping and shrinkage, as well as to control cell distribution and cell density. Furthermore, proper back pressure has a beneficial effect on the skin texture and skin thickness of the part. Therefore, when the assembly is demolded from the mold cavity, there is no significant shrinkage, and no immediate auxiliary steps required for molding the foam assembly are needed. Advantageously, the assembly is not cross-linked, and therefore, if suitable bio-derived polymer compounds are used in foam production, it can be biodegradable or compostable.

[0100] In view of the foregoing, in one aspect, this disclosure relates to the production of biodegradable and compostable, e.g., industrially compostable, microporous soft foam structures. In particular, in one embodiment, the process begins with a suitable biopolymer or biopolymer blend. For example, in various cases, the biopolymer can be one or more polymers, such as those derived from natural sources, chemically synthesized from biomaterials, or entirely biosynthesized from living organisms. In some embodiments, the terms "bio-derived," "biopolymer," or "bioplastic" may be used herein to refer to polymers derived from a biological source (e.g., as opposed to petroleum-based sources) or made from precursor materials (e.g., monomers) derived from a biological source. In some such embodiments, the biological source can be a renewable plant source. Besides plants, in some embodiments, the biological source of "bio-derived," "biopolymer," or "bioplastic" materials includes, for example, microorganisms (e.g., bacteria), algae, animals (e.g., animal fats / lipids), and / or insects.

[0101] There are two main types of biopolymers: one obtained from living organisms, and the other produced from renewable resources but requiring polymerization. Those produced from living organisms include proteins and carbohydrates. Unlike synthetic polymers, biopolymers have a distinct structure. This type of polymer is distinguished based on its chemical structure. What makes the biopolymers of this disclosure particularly useful is their very close resemblance in technical performance properties to non-renewable EVA.

[0102] Similarly, in specific cases, biopolymer blends can be used to create foam structures, where the biopolymer blend can be a custom compound of two or more biopolymers. Several non-limiting types of biopolymers include sugar-based biopolymers, starch-based biopolymers, synthetic material-based biopolymers, and cellulose-based biopolymers. The typical proportions of a biopolymer blend will depend on the type of product being manufactured and the required technical characteristics of the resulting part.

[0103] More specifically, in certain embodiments, biopolymer blends that can be used as foam precursors include a variety of resins, such as one or more solid or viscous materials, which can be added to the polymer melt, for example, after curing. Thus, after polymerization or curing, the resin forms a polymer. For example, suitable resins can be one or more of the following: aliphatic and aliphatic-aromatic copolyester sources. Generally, aliphatic or aliphatic compounds refer to or represent organic compounds in which carbon atoms form open chains rather than aromatic rings. Similarly, suitable aliphatic-aromatic compounds are typically random combinations of open-chain carbon atoms (aliphatic moieties) and one or more stable atomic rings (aromatic moieties).

[0104] Typically, the amount of aromatic acids in the chain is below 49%, although recent technological advances show great promise in increasing this content and further aiding biodegradation. An example of aliphatic-aromatic compounds is aliphatic-aromatic copolyesters (AAPEs), which can be produced from any number of non-renewable and renewable feedstocks, but renewable sources of AAPE are particularly useful. Therefore, in various embodiments, one or more of these aliphatic and / or aliphatic compounds can be of copolyester origin. Such copolyesters are produced when the polyester is 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, combinations of precursor variations are made to substantially hybridize or “bridge” the aliphatic-aromatic chain and to incorporate more than one additional precursor during polymerization.

[0105] Non-limiting examples of suitable biopolymer blends are polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). PLA is a biodegradable thermoplastic aliphatic polyester derived from renewable biomass. Typical feedstocks used to manufacture PLA include fermented plant starches such as corn, cassava, sugarcane, beet pulp, and low-grade lignin-rich wood waste. Similarly, polybutylene adipate-terephthalate (PBAT) is a biodegradable random copolymer, particularly a copolyester typically derived from butylene adipate, 1,4-butanediol, and terephthalic acid. It is advantageous to use PBAT from renewable sources rather than from non-renewable petroleum sources. In various cases, one or more of these components can be blended.

[0106] Blends of two or more thermoplastic biopolymers offer a combination of properties and prices not available with single polymers or copolymers. Several methods exist for successfully blending biopolymers together. One common method involves using a twin-screw extruder to melt two or more biopolymer resins together, then extruding the molten biopolymer resin blend into a filament, cooling the filament, and feeding it into a granulator to produce a large quantity of granulated blocks known as masterbatch. Another method for blending biopolymer resins involves using compatibilizers to bind different chemicals together to form a biopolymer blend. Typically, this also uses twin-screw extrusion or similar methods to melt the compatibilizer and two or more biopolymers together in the aforementioned process.

[0107] Therefore, this document has determined that the aforementioned blended thermoplastic biopolymer resins exhibit advantageous technical properties in forming the optimal microporous flexible foam structure of this disclosure. Some of the enhanced technical properties include acceptable aging characteristics, excellent elongation and compression set, among other benefits. For example, as disclosed herein, one advantage of using biopolymer blends is the enhanced technical performance characteristics resulting from the formation and use of a given biopolymer blend. Specifically, all the enhanced properties, such as improved elongation, tensile strength, impact strength, and melt flow rate, can be achieved when the correct combination of biopolymers and / or biopolymer-compatibilizer blends is realized, to name a few.

[0108] Therefore, these resins can be used to produce foaming agents according to the methods and machines disclosed herein. Thus, in one aspect, this disclosure relates to a foaming process. As stated above, the machines and methods disclosed herein can be configured to perform a foaming operation, thereby trapping cavitation in a liquid or solid, which can be used to produce lightweight polymer materials. This is an advantageous solution for many types of products because foam materials impart numerous added values, such as soft cushioning, comfort, technical sports equipment, including shoe components and impact protection. However, in various cases, the aforementioned optimal aliphatic and aliphatic-aromatic copolyester biopolymers or biopolymer blends can be used alone to produce flexible foams, and in various cases, their use in the production of flexible foams can be enhanced by incorporating a suitable foaming agent during the foaming process.

[0109] For example, a well-known blowing agent used today is a chemical called azodicarbonamide (ADA). Azodicarbonamide is typically pre-impregnated into petrochemical thermoplastic masterbatch resins for conventional injection molding foam processes. In particular, the pre-impregnation of chemical blowing agents such as ADA is usually included in bioplastic blends before foaming. The reason for this is the need for pre-impregnation of chemical blowing agents, such as ADA, because conventional injection molding foaming does not allow for the customization of foam molding variability. That is, the ability of chemical blowing agents such as ADA to alter or influence the physical aspects of the foaming process during production is limited.

[0110] Conversely, the specialized foaming process of this disclosure benefits from physical foaming provided by rare or inert gases such as nitrogen. In this method, the concentration of the gas (e.g., nitrogen) supplied to the biopolymer melt can be adjusted, and this has a direct impact on the foaming result, which can be considered a major advantage for tailoring a specific aspect of the resulting foam. Although several known biodegradable and industrially compostable petrochemical-derived thermoplastics exist, such as PBAT copolyesters, the use of renewable source raw materials (e.g., pure PBAT copolyester series) is advantageous.

[0111] For example, in the production of foaming agents, it can be useful to first produce customized masterbatches, such as customized bioplastic blends for producing a given type of biodegradable and industrially compostable flexible foam for a given product type. For instance, different types of customized masterbatch compounds can be produced for different types of product applications. This can be explained by pointing to the method of making a specific type of foam in a pair of shoes, which may differ from what is needed to make a specific type of foam, such as for making a piece of furniture. Furthermore, customized masterbatches can each contain different colorants for a given product application. Similarly, different product types require different aspects of customization, and the ability to produce unique, individual masterbatches is highly advantageous for these specific applications.

[0112] Unfortunately, ADA is environmentally unfriendly and is a suspected carcinogen for human health. Therefore, its use in this method and the advantages of the resulting products are limited. Furthermore, conventional petrochemical thermoplastic masterbatch resins are neither biodegradable nor industrially compostable, thus limiting their advantages. In view of these drawbacks of using ADA and conventional petrochemical products to produce masterbatches, this paper proposes a biodegradable, industrially compostable thermoplastic biopolymer resin that can be used to produce masterbatches to generate biodegradable and industrially compostable microporous flexible foams.

[0113] In various cases, as described above, to obtain more optimized biodegradable and industrially compostable flexible foams for manufacturing final molded articles, for example in an environmentally neutral manner, supercritical fluids can be systematically injected into the molding process. Specifically, a supercritical fluid is a substance (liquid or gas) 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 unique properties that differ from those of liquids or gases, for example, 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 a supercritical fluid state, which can be used as foaming agents in the foaming process according to the methods disclosed herein.

[0114] The aforementioned supercritical fluid functions by dissolving in the polymer matrix within the injection molding machine barrel. Due to the specialized injection molding process, the liquid bioplastic compound is injected into the mold cavity under controlled pressure and temperature, forcing the polymer melt to fully expand to the cavity's maximum limit. During this process, the gas can be used to maximize the cell structure of the polymer matrix during foaming. This maximization of the specialized foaming process ensures that undesirable shrinkage or warping in the final foam component is minimized. This is very different from soft foams produced with conventional chemical blowing agents, as conventional blowing agents do not undergo the same type of supercritical state or pressure, and therefore conventionally produced foams lack consistency in the final foam component and may contain undesirable shrinkage and warping.

[0115] More specifically, in various cases, inert gases (such as nitrogen or carbon dioxide) can be formulated into a supercritical fluid state and then used as physical foaming agents, for example, in the novel injection molding machines and methods discussed herein. In this case, the disclosed improved physical foaming process can be used in conjunction with a suitable thermoplastic biopolymer or a biopolymer masterbatch, which may be a blend, such that the biopolymer or biopolymer blend and the foaming agent work in harmony to produce optimal biodegradable and industrially compostable flexible foam.

[0116] Suitable biopolymers, bioplastics, and bioplastic blends of this disclosure can be derived from renewable resources, such as those that do not compete with animal feed and human food, and those derived from renewable resource waste streams. Non-limiting examples of suitable biopolymers that can be used to produce biopolymers or biopolymer blends include polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene adipate-co-terephthalate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS). Suitable biopolymer blends of this disclosure are any combination of the biopolymer and bioplastic types listed above, and any hybrid biopolymer blend composed of biomass containing poly(butylene adipate-co-terephthalate) (PBAT). A non-limiting example of this is lignin containing a PBAT blend, wherein the lignin is derived from wood waste and the PBAT is derived from renewable resources.

[0117] Therefore, in various embodiments, the injection molding apparatus and methods of use disclosed herein can be used to produce foams with uniform cell nucleation. As discussed, the apparatus and methods of use disclosed herein can be used to generate uniform cell nucleation to produce foam, whereby foam nuclei are generated randomly and spontaneously, and thus grow irreversibly in a single-phase solution system that is virtually free of impurities. For example, as described below, one aspect provides a method for manufacturing soft and / or rigid foams. This method can be implemented to obtain open-cell or closed-cell foams, for example, wherein the foam has inherent compostable, antimicrobial, and / or flame-retardant properties.

[0118] In some cases, the method may include one or more steps of forming a masterbatch, such as blending one or more resins, such as copolymer carrier resins, and various foaming components. In subsequent steps, the method may include adding antimicrobial compounds, making the foam material suitable for the production of antimicrobial, antibacterial, and / or antiviral footwear components, furniture components, yoga mats, clothing, sporting goods components, medical devices, and / or flame-retardant articles, as well as other suitable applications. In particular, products produced according to the methods disclosed herein can be used in a wide range of mass applications, and their production typically involves three distinct stages. First, a bulk polymer product is formed. Next, the polymer is exposed to various processing steps. Finally, the polymer is transformed into its final product, such as clothing, antimicrobial carpets, furniture, automotive components, yoga mats, and shoe components, including soles, midsoles, insoles, etc.

[0119] In particular, such single-phase solutions can be used to generate nucleation sites where pores grow and expand by gas diffusion into the bubbles. The machines and methods disclosed herein are particularly suitable for initiating foaming processes that result in uniform pore nucleation in a manner where small bubbles are uniformly dispersed within a foam matrix. Specifically, unlike conventional foaming, the soft foams formed by the supercritical fluids of this disclosure benefit from significantly improved mechanical properties directly attributable to the size of the small bubbles. More specifically, the apparatus and methods disclosed herein are configured to produce bubbles with diameters on the order of 100 micrometers or larger to about 1 micrometer or smaller, such as about 50 micrometers to about 10 micrometers, or smaller, such as about 20 micrometers to about 40 micrometers, including about 30 micrometers, and these are generated using thermodynamic instabilities, and no conventional chemical foaming agents are used in the foam generation process.

[0120] For example, in one particular embodiment, the system can be configured to use the novel injection molding machine disclosed herein to produce biodegradable and industrially compostable microporous flexible foams with uniform cell nucleation, which can occur when a single-phase solution of a biopolymer or biopolymer blend and a supercritical fluid (SCF) enters the mold cavity of the injection molding machine through an injection gating. Specifically, as explained in more detail below, the injection molding machine is configured to produce molten material, for example, by injecting a mold precursor into a mold to produce finished parts or component parts. The injection molding machine may include a hopper, an injection pusher or screw plunger, and a heating unit. Such injection molding machines are rated by tonnage, which indicates the amount of clamping force that the machine can apply.

[0121] Therefore, the process can begin with granular bioplastic compound being forced into a heated cylinder by a pusher from a hopper. As the granules move slowly forward through a specialized reciprocating screw plunger, supercritical fluid is introduced via a syringe through a separate supercritical metering auxiliary unit, which can be directly connected to the injection molding equipment feeding the screw. Thus, the supercritical fluid saturates the biopolymer melt during screw rotation, resulting in a single-phase solution.

[0122] The molten mixture is then forced into a heated chamber with high back pressure, where it melts at a temperature controlled by a computer interface. As the plunger advances, the molten bioplastic compound is forced through a nozzle resting against the mold, allowing it to enter the mold cavity through a sprue. Thus, the foaming process of the present invention can be configured to subject the polymer material to a mechanical or physical process by which heat and pressure are applied to the polymer material in the presence of a foaming agent. The foaming agent can be chemically derived, as in the case of conventional closed-cell EVA foaming, or it can be inertly derived, as in the case of the biodegradable and industrially compostable flexible foam of this disclosure. Therefore, in view of the foregoing, when the solution enters the mold, the pressure drops, causing the SCF to emerge from the solution, creating cell nuclei.

[0123] Specifically, during screw rotation, the supercritical fluid saturates the biopolymer melt, resulting in a single-phase solution at specific temperatures and pressures. The molten blend is forced into a heated mold chamber with high back pressure, and the pressure of the single-phase solution drops from the micropore process pressure to atmospheric pressure, causing rapid pressure unloading. Nucleation occurs as gas separates from the mixture. At this point, the nuclei grow into stable bubbles. The bubble size is determined by saturation, micropore process pressure, and mixing temperature, all of which can be controlled by this system and method. Therefore, bubble growth begins when millions of nuclei are generated and are stable.

[0124] The bubble morphology is determined by the SCF concentration and injection molding process parameters. Therefore, these parameters can be selected for system control to produce a useful and / or defined bubble morphology. As part molding concludes, the mold cools and the melt temperature decreases, forcing the melt to freeze and solidify. Again, these parameters can be strictly controlled by the system, for example, depending on the final product to be produced. Specifically, at this point, bubble growth stops and the shape of the resulting part is fixed. Cells then grow until the material fills the mold and the expansion capacity of the SCF is exhausted.

[0125] Therefore, in this process, the molten biopolymer and SCF blend is controlledly injected into a heated mold cavity and undergoes a sudden pressure drop. Nucleation growth generates millions of tiny bubbles, which physically force the molten mixture to expand to the maximum limit of the mold cavity. When the molten blend expands to its maximum physical potential energy, the material cools rapidly within the mold, and bubble formation stops, the molten mixture stops expanding, and the final solidified part is formed. All of this happens within seconds in the injection molding system.

[0126] As noted, the manufacturing process operates on the aforementioned injection molding machines, which have been modified for precise control of metering, delivery, mixing, temperature, pressure, injection, speed, etc. For example, auxiliary metering units can be used to meter and control the precise delivery of SCF gas into the polymer melt. Specifically, a suitable gas dispensing auxiliary unit can be configured to convert inert gas into a supercritical fluid state and, for example, meter the SCF delivery into the injection molding machine via a computer control mechanism.

[0127] For example, an operator or a suitably configured microcontroller can program a gas metering auxiliary to dispense a predetermined amount of SCF gas. Essentially, a gas metering auxiliary is an SCF delivery system that can be electronically and / or physically coupled to an injection molding machine. In particular, a suitable SCF gas metering auxiliary for use in this disclosure can be configured to produce a series of gas metering systems designed to convert industrial-grade nitrogen or other inert gases into supercritical fluids. The gas metering device can be configured to precisely dispense SCF and inject it into the injection molding machine at pressures up to and even exceeding 275 bar.

[0128] To operate the gas dispensing equipment, the operator can use an associated computing device, such as a desktop or laptop computer, configured to generate a graphical user interface (GUI) to control the system equipment and corresponding control parameters, such as the dispensing equipment. For example, the operator can input selected parameters, such as the desired SCF gas dispensing injection parameters, into the GUI. The system's processing element then calculates all auxiliary parameters in real time and optimizes the SCF delivery in the injection molding machine. Thus, the system's control unit ensures that the gas dispensing system and the injection molding machine work together, for example, through a computer-controlled network. Therefore, this gas dispensing system is a unique property of this disclosure because supercritical inert gases can be effortlessly used as physical blowing agents to produce the biodegradable and industrially compostable flexible foams of this disclosure, replacing the chemically reactive blowing agents used in conventional flexible foams. This control over the mixing of SCF into the biopolymer is useful for producing single-phase solutions.

[0129] Furthermore, in the injection molding process of this disclosure, SCF is injected into the polymer melt. A single-phase polymer-SCF mixture is obtained within the screw and barrel of the injection molding machine under specific temperature and pressure. The temperature and pressure can be variably controlled and directly affect the type of flexible foam produced and the type of application the final product will be used for. At this stage, the SCF concentration is determined by saturation, microporous process pressure, and mixing temperature. An example can be provided for manufacturing the biodegradable and industrially compostable flexible foam of this disclosure for use in the manufacture of foamed furniture, automotive, sports, and / or footwear components, particularly shoe midsoles. A non-limiting example of a suitable biopolymer blend for this non-limiting example is a rapidly renewable PBAT biopolyester that forms the biopolymer compound.

[0130] Therefore, the granular biopolymer compound is first fed into the injection molding machine via a hopper. Next, as a specific SCF gas is introduced and uniformly mixed into the currently molten biopolymer compound until it is fully saturated, the biopolymer slowly moves through the screw and barrel of the injection molding machine. The molten biopolymer compound and SCF are now a single-phase solution. A non-limiting example of the initial SCF gas concentration can be Co = 0.25%, with a melting temperature of 176°C to 250°C, more preferably 180°C.

[0131] Furthermore, in various implementations, the temperature within the mold can be precisely controlled along with the pressure, for example, using a Dynamic Mold Temperature Control (DMTC) protocol. For instance, a DMTC approach can be employed to ensure consistent cell structure within the expanding biopolymer melt. Specifically, DMTC can be configured to include rapid changes and control of the mold temperature and / or pressure during the injection filling phase. This allows for dynamic control of the mold temperature and / or pressure in terms of hot and cold thermal cycling, with or without pressure.

[0132] For example, the system's control module can be configured to control the mold temperature during the injection filling stage; in this case, dynamic mold temperature control can be employed. More specifically, a key feature of the dynamic mold temperature control used in this paper, compared to conventional injection molding processes, is that the mold temperature itself can be dynamically controlled. Before melt injection of the single-phase solution, the mold can be heated to a preset upper limit. During the melt filling stage, the temperature of the mold cavity surface can be maintained above the upper limit to prevent premature melt solidification. When the melt filling process is complete, the mold is rapidly cooled to the lower limit (demolding temperature), and then the molded foam part is demolded from the mold cavity.

[0133] 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 in this disclosure consists of five main components: an air compressor, a valve switching device, a computer-controlled mold temperature control unit, an electrically heated mold, and a cooling tower. The cooling tower provides sufficient water cooling to the mold. The air compressor generates compressed air as the driving gas for pneumatic valves and removes residual cooling water after it has entered the mold for cooling. The valve switching device switches valves to deliver different media from the piping to the mold, such as hot and cold cycles.

[0134] Therefore, in various cases, the machines and methods described herein may include conduits and other conduits for the passage of reactive materials, which are associated with one or more heat exchange units to heat and / or cool the reactants as they are pumped into and / or through the conduits and pipes. In this case, the exchangers can be controlled to regulate the temperature to the reaction level. A dispensing head may be included at one end of the conduit, which may be associated with one or more valves. Furthermore, the dispensing head may be connected to a processing line. An electrically heated mold is used to mold the final shape of the foam part. The role of mold temperature control is to control the heating and cooling of the mold; all of this is coordinated with the injection molding machine via computer control.

[0135] Similarly, as shown, pressure can also be precisely controlled, for example, through a gas backpressure (GCP) protocol. For instance, a GCP protocol can be used during manufacturing to better ensure the optimal foam structure of the final product, resulting in a soft foam with little or no skin. For example, using this GCP process, the pressurized mold cavity can be filled with SCF, which, individually and together, counteracts the expansion of gas in the melt. In particular, as the backpressure is released, bubbles that would normally break through the surface are trapped inside, thus forming a smooth skin.

[0136] This gas backpressure process prevents bubbles from contacting and breaking through the surface of the foam material during the formation of the foam part. This is achieved by applying backpressure to the mold cavity simultaneously or approximately simultaneously with the injection jet and holding time of the molten single-phase solution using a GCP system. The inert bubbles are subjected to tremendous forces, and therefore the molten single-phase solution has no opportunity to release the trapped bubbles to the outside of the foam structure during formation. The result is a molded foam part with a beautiful, smooth skin on its exterior.

[0137] Therefore, as implemented herein, the system controller can implement a gas backpressure (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, through various components of the control system, the control system can be configured to apply varying screw-containing SCF single-phase solution pressure and GCP pressure, for example, in conjunction with appropriate jet size, jet holding time, melt temperature, and mold temperature.

[0138] In this way, a complete system is created that can produce high-quality and commercially acceptable biodegradable and industrially compostable flexible foam parts. Specifically, subtle variations in GCP pressure can affect the surface quality of the foam. For example, without GCP, bubbles formed in the polymer melt within the mold cavity may be released, and the resulting foam part may have an unacceptable appearance. Furthermore, without GCP, the skin thickness may be excessive because there is no back pressure to counteract the rapid cooling of the molten single-phase solution as it expands into the mold. In particular, the single-phase solution may impact the steel mold boundaries during injection and solidify immediately, forming a non-ideal thick skin, which is unacceptable for most commercial applications. In summary, process parameters have a significant impact on the quality of the final part. Therefore, in these ways, the GCP method can be implemented to control foaming, for example, through one or more of the following: surface quality, foam structure, skin thickness, etc.

[0139] Therefore, in various embodiments, the system can be configured to generate SCF in a manner that forms a single-phase solution. Specifically, in various embodiments, a single-phase solution is generated, wherein the SCF can be completely dissolved and uniformly dispersed in the molten biopolymer, which occurs within an injection chamber under carefully controlled process conditions. For example, as discussed, the formation of a single-phase solution is crucial for the production of consistent, mass-producible molded foam parts of this disclosure.

[0140] Therefore, 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 to ensure that the biopolymer compound and SCF are uniformly mixed into a single-phase solution, for example, in which the single-phase solution is fully saturated and dispersed within the biopolymer melt in the injection molding machine barrel. Once the single-phase solution is achieved, the system can reliably input the required jet weight, jet holding time, and GCP gas supply for customizing infinitely producible molded foam parts in a time-optimized and mass-producible manner.

[0141] Therefore, SCF should be precisely metered into the biopolymer at a mass flow rate over a fixed time period. For example, the system control module can be configured to establish the correct conditions—temperature, pressure, and shear force—within the barrel during the dispensing period. Similarly, back pressure, screw speed, and barrel temperature can be finely controlled via one or more control elements of the system. Furthermore, the SCF delivery system can be modulated to establish process conditions that produce optimal single-phase solutions.

[0142] 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 fluid flowing through one or more containers (e.g., pipes) of the system. Mass flow rate is the mass of fluid flowing through a fixed point per unit time. As per this disclosure, the principle of mass flow metering is implemented to ensure consistent repeatability during foam molding. Specifically, as described above, a specially designed injector is coupled to an injection molding cylinder that can be controlled by a computer control program of the system's processor. Thus, the system can be configured to deliver specific SCF gas feeds into the biopolymer melt, and the computer control program can optimize delivery based on real-time data collected from the mass flow rate, for example, through feedback from one or more system sensors. The use of this mass flow metering ensures optimal process control of the single-phase solution of the present invention.

[0143] Therefore, during the dispensing period, the temperature of the entire system, such as the temperature inside the cylinder, can be controlled to be between 100°C and 600°C, for example, 200°C to 500°C, for example, 300°C to 400°C, and more specifically, 320°C to 380°C, including 360°C to 380°C inside the cylinder. Similarly, the SCF delivery pressure can be finely controlled to be between 1,000 and 8,000 PSI, for example, 1,500 to 6,000 PSI, for example, 2,000 to 5,500 PSI, particularly 3,000 to 4,000 PSI, and more specifically, 2,600 to 2,800 PSI.

[0144] In this way, the control module can be configured such that temperature and pressure work together to generate optimal cores and resulting bubbles within the biopolymer melt and the resulting foam matrix. Furthermore, regarding shear force, shear forces are established within the barrel as the molten biopolymer layers flow relative to each other. Therefore, during injection, the molten biopolymer compound can flow through the melt delivery channel of the barrel nozzle, for example, before entering the mold like a fountain.

[0145] Shear is the stretching of a biopolymer between a rotating screw and a stationary barrel, resulting in heat generation within the material. Therefore, shear forces must be controlled during injection molding. Consequently, one or more control units of the system can be configured, for example, to control injection speed, filling time, and tolerances therein, to achieve the correct conditions for producing a given biopolymer compound given injection molding machine dimensions and given injection molding machine screw and barrel dimensions.

[0146] Back pressure can also be controlled. For example, back pressure is the pressure exerted by the biopolymer in the mold during injection molding. Specifically, back pressure is the resistance applied to the injection screw as it recovers to load the next biopolymer jet into the mold. As described above, various parameters of the system can be configured to control and / or adjust the back pressure.

[0147] Furthermore, the system's controller can be configured to control and regulate the screw speed. The screw speed can be controlled by a computer. As shown, in the initial stage of the injection molding operation, the screw rotates within the barrel to homogenize the molten biopolymer compound mixture together with the SCF gas. Non-limiting examples of the screw speed disclosed herein can be from 1 to 75 to 100 to 200 rpm, for example, from 20, 25, or 30 to 40, 50, or 60 rpm.

[0148] The system may include a heating and / or cooling control unit, which may be associated with the cylinder to control the temperature therein. Therefore, the control module can be configured to control the cylinder temperature. Thus, the cylinder temperature can be controlled to make it hotter or colder as needed for the foaming process.

[0149] Therefore, in light of the above, an SCF delivery system may include a control unit configured to control a combination of SCF delivery pressure and SCF dose weight, typically measured in grams. The SCF pressure and dose can be controlled in a manner that affects the single-phase solution. That is, a smaller SCF dose results in a lower required SCF saturation in the biopolymer melt, while a larger SCF dose results in a higher required SCF saturation in the melt. Similarly, a lower SCF delivery pressure results in a lower absorption saturation, and therefore less nucleus growth, which can form bubbles in the molten biopolymer melt. And a higher SCF delivery pressure results in a higher absorption saturation, and therefore faster nucleus growth, which can form bubbles in the molten melt.

[0150] Regarding saturation, the system and apparatus are configured to deliver gas into the melt chamber at controlled temperatures and pressures, causing supercritical fluid to form and saturate in the biopolymer melt, for example, during screw rotation. Thus, a single-phase solution is produced at controlled temperatures and pressures. Specifically, a single-phase polymer-SCF mixture can be obtained within the screw and barrel of an injection molding machine at controlled temperatures and pressures. More specifically, the system controller can variably control the temperature and pressure depending on the type of flexible foam being produced and the type of final product being produced.

[0151] At this stage, the concentration of SCF can be determined and controlled, for example through a feedback loop, thereby determining the saturation level, for example through a sensor that assesses the progress of the saturation process, and then adjusting the microporous process pressure and mixing temperature based on the determined setpoint for achieving the saturation level. In this case, the supercritical fluid (SCF) is controllably saturated in the biopolymer melt during screw rotation, which produces a single-phase solution at a given temperature and pressure. SCF is part of a two-part molten biopolymer compound mixture and acts as a physical foaming agent in this injection mold under certain pressure and temperature.

[0152] Therefore, in view of the foregoing, in one aspect, this document provides a machine and a method for producing biodegradable and industrially compostable microporous flexible foams using the machine. Specifically, in one case, the foam is produced and / or used in the production of foam products, for example by a microporous injection molding (MuCell) process, such as MuCell manufacturing. MuCell manufacturing employs a supercritical fluid as described above, which is subjected to extreme pressure and dissolved in a polymer melt within the screw barrel of a manufacturing tool, as described below, which is configured to optimize the SCF feed to produce a molten biopolymer melt that we heat to a liquid state.

[0153] Therefore, the core of an injection molding machine consists of the injection molding machine barrel and the screw contained within it, both typically made of tool steel. The barrel is the primary delivery inlet for the current single-phase solution before it is metered and then pressed or “injected” into a dynamically temperature-controlled mold assembly. Thus, the biopolymer melt is delivered into the barrel through the injection molding machine hopper. And as one of the first steps in the operation of the injection molding machine, the system controller feeds a given amount of granular bioplastic pellets into the hopper.

[0154] Specifically, during injection, SCF evaporates and transforms into bubbles, such as foam in the form of finished molded parts. Because the bubbles reach micron-sized dimensions, this process produces microporous foam. The method described in this paper is superior to conventional injection molding techniques because it produces end products that demonstrate one or more of the following: less shrinkage, lighter weight, virtually no shrinkage marks, and can be produced using low-cost precursors. More specifically, regarding shrinkage reduction, it can be controlled by understanding that volumetric shrinkage is caused by thermal shrinkage affecting all polymers, and therefore, shrinkage can be avoided by tracking the shrinkage process with system sensors and finely controlling barrel conditions to regulate the shrinkage process.

[0155] Essentially, shrinkage describes the degree of volume change of a material as it changes from a liquid to a solid. In traditional injection molding, the mold temperature is not controlled by pressure, so the molten polymer used in conventional methods shrinks upon contact with the cold tool steel of the injection mold, leading to shrinkage. In current machines and systems, shrinkage can be controlled and is generally not a problem because temperature-controlled pressurized molds ensure that the molten biopolymer fills the maximum surface area inside the mold without premature cooling, and the applied uniform stress further aids in this regard within the pressurized mold cavity itself.

[0156] Regarding the production of lightweight products, a general principle is that the more the polymer expands, the more weight is reduced. However, this system is configured to optimize single-phase solutions by applying appropriate pressure, temperature, and time to achieve optimal quality lightweight foam. This is beneficial for applications requiring lightweight foam, such as cushioning pads, footwear foam, and foams used in the production of sports equipment. Similarly, regarding the control of shrinkage marks in conventional flexible foam manufacturing, shrinkage marks and voids are caused by insufficient compensation for the localized shrinkage of the material at thick sections during component cooling.

[0157] In particular, shrinkage marks typically appear on surfaces opposite and / or adjacent to the legs or ribs. This is due to uneven heat dissipation and / or similar factors. After the material on the outer side of the foam component cools and solidifies, the core material begins to cool. Its shrinkage pulls the surface of the main wall inward, causing shrinkage marks. If the skin is rigid enough, the deformation of the skin may be replaced by the formation of voids in the core.

[0158] Unlike traditional flexible foam molding, which faces challenges such as shrinkage marks and voids, the machine configuration and existing system parameters are controllable to produce the biodegradable and industrially compostable flexible foam of this disclosure, minimizing the occurrence of these problems. Specifically, in this method, the SCF gas is controlled in a manner to regulate, for example, maximize the cell structure of the polymer matrix during the foaming process. This maximization of the specialized foaming process better ensures that there are no undesirable shrinkage marks or voids in the final foamed assembly.

[0159] Furthermore, as noted, a useful advantage of this system is that it uses low-cost materials and produces a final product with less warpage. In particular, for many reasons discussed above, this disclosure benefits from the process in which the SCF gas is responsible for maximizing the cell structure of the polymer matrix during the foaming process. This maximization of the specialized foaming process ensures minimal warpage within the final foamed assembly.

[0160] Another advantage of this system is its ability to be configured to control tolerances. For example, the system can be configured to perform tight-tolerance soft foam injection molding. In particular, tight-tolerance soft foam injection molding, as presented herein, can be used to produce parts that work smoothly together and help reduce the overall product failure rate.

[0161] For a product to function as intended and reliably, all its components must assemble smoothly. Therefore, this equipment and its components are designed with tolerances tightly controlled. Typically, these components are manufactured with the best possible tolerances. Acceptable tolerance ranges vary; for example, very tight tolerances are + / - 0.001". Sometimes, even a few thousandths of an inch can mean a difference between suitable and unsuitable parts.

[0162] Therefore, determining tight tolerances early in the design phase is useful. This is because design engineers must consider requirements for foam component geometry, overall foam component dimensions, and foam component wall thickness—all of which impact tolerance control, and all of these, if poorly managed, can exacerbate shrinkage marks, warpage, and inconsistent component tolerances. This system and apparatus overcomes most of these design challenges while still employing best design practices, as the SCF gas is responsible for maximizing the cell structure of the polymer matrix during foaming. Similarly, the system can be configured for faster cooling within the mold.

[0163] For the reasons mentioned above, shrinkage marks, warpage, and tolerance inconsistencies are significantly reduced. This is largely due to the uniformly sized and evenly distributed microcellular cells within the foam matrix. Therefore, to achieve these benefits, the microcellular foaming process should be precisely controlled. For example, as noted, when foaming occurs along the melt front, the advance can introduce streaks and flow marks on the molding surface, leading to defects.

[0164] In addition to the above, these drawbacks can be further minimized by employing one or more co-injection and in-mold texturing techniques. However, in many cases, this can be prohibitively costly. This system overcomes this cost constraint by selecting high-quality product opportunities where the added value of this disclosure is acceptable and appreciated.

[0165] It is important to note that SCF foaming can have drawbacks in various situations, as it can lead to changes in melt viscosity and other physical properties in some cases. In particular, when SCF diffuses uniformly into the polymer melt, the single-phase solution acts as a reversible plasticizer by increasing the free volume and thus reducing the polymer's viscosity. This effect also lowers the polymer's glass transition temperature and tensile strength. This can result in non-uniform bubble size.

[0166] Uneven bubble size can lead to inconsistent technical performance characteristics throughout the produced molded foam parts, and can also cause undesirable appearance issues. Both of these problems exist when attempting to produce a consistent, renewable, biodegradable, and industrially compostable flexible foam with uniform technical performance characteristics across all parts during mass production. This system is configured to overcome these difficulties.

[0167] Therefore, as described above, to overcome these drawbacks and achieve more precise control over the microporous foaming process, gas back pressure (GCP) as discussed above is employed. As mentioned above, precise control of the gas back pressure ensures that bubbles are regulated during the formation of the foam component to prevent them from contacting and breaking through the surface of the foaming material. This is achieved by applying a counteracting pressure to the mold cavity by the GCP system, which can be simultaneous with or approximately simultaneously with the injection of the molten single-phase solution, while simultaneously controlling the holding time within the mold. For these purposes, the mold temperature and pressure can also be precisely controlled.

[0168] After injection, the inert bubbles are subjected to tremendous forces, and therefore the molten single-phase solution has no opportunity to release the trapped bubbles to the outside of the foam structure during formation. Similarly, the tremendous forces applied to the single-phase solution help to better distribute the millions of tiny bubbles within the foam structure inside the mold, and help to maintain consistent bubble size. The result is molded foam parts with a beautiful, smooth outer skin, consistent foam size, and repeatable technical performance characteristics across all parts during mass production.

[0169] For example, the system can be configured to allow the introduction of a gas pressure control (GCP) to control the foaming process, for example, by applying different gas pressures and / or temperatures during the melt injection stage. Thus, the GCP is introduced into the foaming process within the mold cavity located inside the injection molding machine. First, inert gas is pumped into the mold cavity by a gas compressor and gas pump through a gas control valve. A gas pressure sensor feeds real-time data from the gas control valve back to the computer controller.

[0170] The system initiates the dispensing of GCP into the mold cavity by setting dispensing parameters and holding time within the computer system. The computer system then injects the appropriately dispensed inert GCP into the mold cavity. Without GCP, the biopolymer melt enters the mold cavity and immediately begins foaming, producing uneven bubbles that break through the surface and create undesirable swirl marks on the outside of the foam, which is problematic.

[0171] Similarly, the injection speed can be precisely controlled, for example, by adjusting the screw pressure (P). 螺杆 ) and gas pressure (P) 气体 The difference between P and P is used to determine the injection speed. Specifically, when P... 螺杆 Slightly higher than P 气体 When both parameters are sufficiently high, the melt from the SCF flows into the mold cavity without foaming. P 螺杆 Set to higher than P 气体 and P 气体 Setting the pressure below the critical pressure will result in partial foaming. Finally, P should be appropriately selected based on the dynamic mold temperature. 螺杆 P 气体 The pressure difference allows for more precise control of bubble size. Therefore, by fine-tuning these parameters, flow-induced streaks can be minimized, even if they cannot be completely eliminated.

[0172] Specifically, these parameters can be determined in part by taking into account flow behavior. For example, in one embodiment, rheological (flow) behavior of a polymer melt with 0.4 wt% N2 SCF dissolved was generated at different mold temperatures (185, 195, and 205 °C), injection speeds (5, 10, and 15 mm / s screw speeds), and GCP values ​​(50, 100, 200, and 300 bar). In this case, the measured shear rates were 3000–11000 s⁻¹. -1 Furthermore, when the GCP is 300 bar, the glass transition temperature (Tg) decreases from 96°C to 50°C. Similarly, in this case, compared to conventional injection molding, the melt viscosity decreases by approximately 30% when the GCP increases from 50 bar to 200 bar.

[0173] Specifically, at a GCP of 300 bar, the viscosity of a single-phase injection melt without any foaming can be reduced by up to 50%, depending on the injection conditions. This is useful because it reduces pressure and temperature requirements, thereby lowering manufacturing costs, particularly energy costs, and also reducing the cycle time of foamed parts during production. Therefore, these system parameters can all achieve greater energy savings by reducing pressure and temperature requirements and shorter cycle times, meaning more parts can be produced faster and at a lower cost, for example, by selecting suitable biopolymer compounds and customizing process temperature, pressure, and holding time to suit the material's mechanical properties.

[0174] Additionally, as noted, an important feature of this machine and system is that they can be configured to control bubble size for greater uniformity. As described above, this can be achieved in part by controlling temperature, pressure, SCF feed control, GCP, DMTC, and other parameters discussed above. All these properties work together to ensure optimal, most uniform bubble size and its best uniform dispersion within the foam matrix. Furthermore, surface quality can be improved by controlling the fluid offset along the melt front.

[0175] As the name suggests, the melt front is the point where the molten single-phase solution enters the mold cavity. The melt front velocity is the speed at which the melt front advances. For any mold with a complex cavity geometry, some areas may fill faster than others. By controlling the melt front velocity, for example by controlling temperature, pressure, and SCF (Superficial Fluid Content) dispensing, as well as other parameters, a more uniform cavity filling speed can be achieved, ensuring that the resulting foam parts have an acceptable surface quality.

[0176] Therefore, once a single-phase solution is generated, the improved injection molding machine, as described above, maintains the solution under pressure until injection begins. For example, as mentioned above, the machine can be configured to achieve this through the combined action of a throttling nozzle and screw position control. Specifically, the throttling nozzle can be configured as a connection between the plasticizing barrel (with a reciprocating screw) and the mold. Such throttling nozzles can be automated or externally controlled, and they can be used to prevent melt from flowing between melt jets, thereby preventing depressurization and premature foaming into the mold.

[0177] Therefore, the choke nozzle prevents decompression and premature foaming into the mold. For example, without a choke nozzle, the single-phase solution will not have sufficient pressure within the mold cavity and will not be able to produce the desired molded foam parts. Similarly, active or passive screw position control can be used to prevent decompression by the backward movement of the screw.

[0178] Specifically, the system can be configured to perform active screw position control, such as continuously monitoring the screw position and adjusting the pressure applied to the back of the screw to maintain a defined position setpoint or to maintain a constant pressure on the back of the screw. For example, in passive position control, oil used to regulate back pressure is prevented from draining into the oil tank at the end of screw recovery. This residual oil prevents the screw from moving backward due to the pressure of the single-phase solution.

[0179] Furthermore, as mentioned above, a suitable mold design helps maintain a single-phase solution. Specifically, in cases where the mold includes a hot runner system, one or more valve-type gates can be included and controlled to prevent material from dripping from the nozzle, for example, when the mold is open. More specifically, hot runner systems can be used herein in injection molding equipment and can include systems with physically heated components, making them more efficient for transferring molten plastic from the machine's nozzle into the mold cavity. For example, "cold runners" or "hot runners" can be used, where a cold runner is an unheated physical channel used to guide molten plastic into the mold cavity after it leaves the nozzle, while a hot runner is heated and a cold runner is not.

[0180] Similarly, in various cases, the device may include a nozzle break, configured to interrupt contact with the sprue bushing during normal operation. This configuration is useful in stacked or cascaded molds, where a shutdown device is used on the sprue bushing. Specifically, the sprue bushing may be configured to receive the machine nozzle and thus allow molten biopolymer compound to enter the mold. In events where the machine nozzle must disengage from the sprue bushing, molten biopolymer compound may flow backward from the sprue bushing, and mold decompression may occur. Any molten flow waste increases production costs, negatively impacts subsequent melt jets, and may even prevent proper mold closure, potentially causing even more problems.

[0181] To overcome this problem, a gate bushing with a shut-off device can be selected. Otherwise, pressure from the hot runner would be released through the gate bushing. In particular, when a gate bushing requires a shut-off device, in addition to the other benefits mentioned above, the shut-off device can also prevent the escape of pressure buildup within the mold. Any decompression of the mold could prevent foaming of the molten part, and therefore the desired molded part would not be formed.

[0182] As described above, various blowing agents can be used for the injection molding of biodegradable and industrially compostable microporous foams. In certain cases, these blowing agents may include inert and / or rare gases, such as inert nitrogen or carbon dioxide, or other gases capable of being converted into a supercritical fluid (SCF) state. According to the apparatus, systems, and methods of use disclosed herein, SCF can be introduced (e.g., injected) into a machine, such as into a melt barrel, for example, via a specially designed computer-controlled injector that can be coupled, for example, fixed to the injection molding machine barrel, for example, to feed the blowing agent into the molten biopolymer melt within the barrel. The injection molding machine controller can be programmed to deliver a specific SCF gas feed rate (whether nitrogen or carbon dioxide, etc.) into the biopolymer melt, and this delivery can be optimized by a system controller.

[0183] Therefore, each of the aforementioned SCF foaming agents has its place, depending on the technical requirements of the final component being produced. In particular, as noted, a useful SCF is carbon dioxide in its supercritical state, which is denser than nitrogen at the same pressure but has a much higher heat capacity. Experiments have shown that supercritical carbon dioxide produces dense foam, which can be used in certain cushioning applications. In contrast, supercritical nitrogen can be used to produce low-density foam components with smaller pores suitable for the footwear and sporting goods applications disclosed herein.

[0184] Therefore, a useful foaming agent for producing sporting goods (such as shoes) is SCF nitrogen, as it provides improved weight reduction and a finer cell structure at a much lower weight percentage than SCF carbon dioxide. However, for furniture and automotive applications, a useful foaming agent is carbon dioxide, which produces a much larger cell structure, despite its larger size and / or weight. Specifically, in various cases, enhanced weight reduction of foam components is a useful property for product applications requiring minimal weight. As a non-limiting example, running shoes have always required the inclusion of very lightweight, flexible foam capable of withstanding repeated abuse.

[0185] By providing enhanced weight reduction with a fine cellular structure in the examples above, injection-molded soft foam components will be relied upon to improve runner efficiency through the manufacture of acceptable lightweight shoes. Furthermore, the fine cellular structure of the aforementioned foam will ensure highly durable running shoes capable of handling the repetitive impact forces generated by runners constantly applying pressure and shock to the foam components of the shoe during acceleration.

[0186] In fact, the nitrogen content of SCF will typically be at least 75% lower than the carbon dioxide content of SCF required to achieve comparable components. Therefore, the significantly reduced nitrogen content requirement of SCF compared to carbon dioxide ensures optimal material and time savings when mass-producing the biodegradable and industrially compostable flexible foam of this disclosure for use in manufacturing shoe components. However, carbon dioxide SCF is a useful foaming agent in various specific situations, such as when viscosity reduction is the primary processing objective, and / or when the application cannot withstand the more intense foaming action of nitrogen SCF.

[0187] In some cases, SCF (carbon dioxide) is a suitable blowing agent, particularly in semi-flexible foams. Both flexible and semi-flexible foams can be classified as flexible foams because they are both derived from polymers with a glass transition (Tg) below their service temperature (typically room temperature). In physical foaming processes using physical blowing agents, a depression in the glass transition can be observed. The difference in effectiveness between nitrogen and carbon dioxide blowing agents stems from their behavior in biopolymer melts.

[0188] For example, carbon dioxide, which becomes an SCF fluid at 31.1 °C and 72.2 bar, is 4 to 5 times more soluble in biopolymers than nitrogen, which becomes a supercritical fluid at -147 °C and 34 bar. For instance, the saturation point of unfilled biopolymers is approximately 1.5 to 2% by weight of nitrogen, depending on temperature and pressure conditions, while the saturation point of carbon dioxide is close to 8% by weight. Carbon dioxide also exhibits greater fluidity in biopolymers, allowing it to migrate deeper into existing bubbles than nitrogen. From the perspective of cell nucleation, greater solubility and fluidity mean fewer nucleated pores, and the pores that do nucleate will tend to be larger.

[0189] However, solubility becomes an advantage when the goal is to reduce viscosity. SCF dissolved in biopolymers acts as a plasticizer, reducing the viscosity of the biopolymer. Because viscosity reduction depends in part on the amount of SCF added to the biopolymer, and because carbon dioxide has a higher solubility limit than nitrogen, its ability to reduce viscosity is even stronger. Carbon dioxide is also useful when the amount of nitrogen required to produce parts is so low that consistent part processing is not possible.

[0190] Because carbon dioxide is a less potent blowing agent, it is sometimes easier to use low concentrations. For example, 0.15% or 0.2% carbon dioxide is equivalent to extremely low concentrations of nitrogen, below 0.05%. The situations described in the previous examples primarily occur with soft materials and components 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 components and the final products that will contain them.

[0191] First, selecting a suitable compatibilizing biopolymer or biopolymer compound in combination with the associated SCF gas is useful. Second, proper use of the SCF gas through optimal feed weight and pressure is crucial to ensuring maximum saturation within the single-phase solution and optimal nucleation to generate millions of uniform bubbles within the foam matrix. Furthermore, the end result is a homogeneous injection-molded flexible foam part that depends on all aspects of the SCF and GCP gas feeding process operating in conjunction with the injection molding machine temperature, pressure, and holding time to achieve commercially acceptable molded foam parts, as explained above.

[0192] As noted, in one aspect, a method is provided for manufacturing biodegradable and industrially compostable flexible foams, whether open-cell or closed-cell. In various cases, the manufacturing method 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 reference masterbatch can be produced by a twin-screw extruder, wherein two or more biopolymers, fillers, and / or additives can be uniformly blended into a single polymer melt, for example, within an extrusion barrel. The molten biopolymer blend is then extruded in a strand, cooled, and granulated into particles referred to as masterbatch, 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 SCF such as inert nitrogen or carbon dioxide gas.

[0193] As described above, this injection molding can be used in a manufacturing method that produces parts by injecting molten material into a product mold. In this disclosure, a suitable biopolymer or biopolymer blend is selected, for example, in granular form. These granules can be pre-dried in an auxiliary pellet dryer to ensure the removal of any potential moisture. The pre-dried pellets can then be introduced into the hopper of the injection molding machine. The operator then selects the optimal barrel temperature, nozzle temperature, and mold temperature of the injection molding machine and inputs these values ​​via computer control.

[0194] Furthermore, the optimal SCF gas feed percentage and pressure, as well as the optimal GCP gas feed and pressure, can be adjusted proportionally, and these values ​​can be input to the system control unit or determined by the system control unit in other ways, such as dynamically. Once the system is configured correctly, the injection molding machine is ready to operate. Particles can be released into the screw and barrel of the injection molding machine in a specified amount under computer control, where they melt at a specific temperature or a set of temperatures.

[0195] SCF gas is introduced into the injection molding machine barrel under controlled pressure and dosage via a computer-controlled SCF injector. The SCF saturates the currently molten particles, generating a single-phase solution. Then, under appropriate back pressure and screw positioning, the injection molding machine delivers a measured jet of the single-phase solution into a dynamically temperature-controlled mold cavity. Nucleation growth occurs in the melt, forming millions of microporous bubbles within the biopolymer melt. Essentially simultaneously, a GCP system, controlled by a computer, delivers a pre-metered dose of backpressure gas into the mold, optimizing cell uniformity and adjusting surface texture for optimal appearance. The dynamically temperature-controlled mold temperature can then be switched to water cooling, and bubble formation and melt expansion cease. At this point, the soft foam molded part is formed and can be demolded.

[0196] Specifically, as described above, the system can be configured to perform dynamic mold temperature control, which can be used to produce optimal cell structure. For example, as described, Dynamic Mold Temperature Control (DMTC) performs rapid electric rod heating and rapid water cooling. More specifically, the DMTC program employed herein may include one or more of the following five main components: an air compressor, a valve switching device, 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 cooling operations, while a suitably configured air compressor generates compressed air to drive gas through pneumatic valves to expel any residual cooling water from the mold after cooling. One or more valve switching devices may be configured and used to switch valves to transfer different media from various machine pipes to the mold, for example, for hot and cold cycles. Electrically controlled heating elements may be included and configured to mold the final shape of the foam part. The water tower and heating elements together can provide fine control of the mold temperature, allowing the mold to be heated and / or cooled rapidly during the execution of the molding process.

[0197] All of these are coordinated with the injection molding machine via 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 could be from 15°C to 30°C, and a further non-limiting example of the heating element temperature range of the DMTC system could be from 60°C to 150°C, and could be from 90°C to 130°C, and could be any temperature in between. In these ways, the biopolymer melt, pressure, and time can be controlled to form a desirable soft foam.

[0198] Specifically, in the injection molding process of this disclosure, SCF is injected into the polymer melt. A single-phase polymer-SCF mixture is obtained within the screw and barrel of the injection molding machine under specific temperature and pressure. The temperature and pressure can be variablely controlled by a computer and are directly related to the type of flexible foam produced and its intended end-product application. By applying different screw-containing SCF single-phase solution pressures and GCP pressures, in conjunction with appropriate jet size, jet holding time, melt temperature, and mold temperature, a complete system is created that can produce high-quality and commercially acceptable biodegradable and industrially compostable flexible foam parts, for example, by utilizing gas back pressure during the injection molding process to ensure an optimal foam structure with minimal appearance defects and little or no plastic skin on the exterior of the foam parts.

[0199] As noted, a useful benefit of products produced according to the devices, systems, and methods disclosed herein is that they can be biodegradable and / or compostable, for example, in home or industrial composting programs. In particular, producing goods configured for decomposition in industrial composting ensures that the flexible foam will extend the lifespan of the resulting product, for example, by functionalizing it in a way that prevents it from decomposing or detaching during the intermediate use of the finished product. For example, it would be harmful for someone purchasing furniture, a pair of shoes, or other sporting equipment made from the flexible foam of this disclosure to experience foam degradation during normal use before the product reaches the end of its lifespan.

[0200] More specifically, this disclosure benefits from the use of inert physical foaming agents and biodegradable and industrially compostable biopolymers or biopolymer compounds. These two aspects combine to form a single-phase solution that is functionalized in a specialized flexible foam injection molding system. The result is a biodegradable and industrially compostable flexible foam suitable for a variety of end products; a non-limiting example is footwear foam for shoemaking. The resulting flexible foam is non-crosslinked, chemical-free, and environmentally friendly.

[0201] At the end of their lifespan, biodegradable and industrially compostable flexible foams can be redirected to appropriate industrial composting facilities via waste transfer, where the foams are ground and industrially composted into usable biomass. The end result is a system that adheres to various aspects of the so-called circular economy. The flexible foams disclosed herein begin and end “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 their technical performance characteristics or their environmentally friendly design throughout their lifespan.

[0202] As discussed above, the apparatus, systems, and methods of use described herein can be used for the purpose of producing one or more molded end products, such as components for footwear, seating, automobiles, protective equipment, and / or sporting goods. Therefore, in various embodiments, this document provides one or more components that can be used to construct a shoe, such as its sole, midsole, and / or insole, for example, wherein 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 and thereby provide cushioning and / or support.

[0203] In some embodiments, shoe components may include foam materials produced herein, which may be environmentally friendly, biodegradable, and compostable. In various cases, each individual component may consist of multiple layers, including a base layer and a cushioning layer, such as a buffer layer. For example, in certain embodiments, support members may be included, such as support members coupled to the base layer, and if the component is an insole, it may include one or more of an arch contact portion or a heel contact portion.

[0204] In particular, in various embodiments, foam materials can be produced, for example, in the manufacture of cushions, padded furniture, shoe components such as insoles, pads, fibers, and woven fabrics. Other useful products may include caulking materials, such as silicone caulking materials, silicone medical gloves, silicone tubing for drug delivery systems, silicone adhesives, silicone lubricants, silicone coatings, and other suitable silicone products, such as condoms. In various embodiments, foam products can be produced in a manner where the foam material can possess one or more antimicrobial, antibacterial, antifungal, antiviral, and / or flame-retardant properties.

[0205] More specifically, in one aspect, this disclosure may generally relate to a method for manufacturing furniture, such as decorative furniture and / or its cushions, including or otherwise comprising foam, for example, foam that is biodegradable and / or compostable. Therefore, the foam of this disclosure is advantageous for manufacturing furniture comprising foam inserts produced in this way. Resins and foams produced and used have proven advantageous as cushioning materials, for example, for pillows, sofas, beds, seat cushions, or for other decorative furniture, etc.

[0206] For example, according to the methods disclosed above, molds for producing small to large blocks of foam can be created, for example, to form foam inserts, such as for furniture or automotive parts components. The block foam can then be cut into smaller pieces of the desired size and shape based on the type and form of the furniture being produced. Specifically, the sized and cut pieces can then be applied to or otherwise assembled into furniture or vehicle frames or other edging materials, and they can be covered together to produce the final furniture product, whether it is a pillow, sofa, cushion, e.g., a sofa or car seat cushion. Furthermore, when needed, the outer shell or edging material can be attached to the frame material, for example by stapling and / or pins, or otherwise secured to the frame of the article to be decorated and covered with fabric or other materials.

[0207] Therefore, in various embodiments, when manufacturing decorative furniture such as sofas or car seats, a frame can be produced. Various internal components of the furniture (e.g., structural components), such as springs, can be installed within the frame, and then foam boards produced according to the methods disclosed above can be placed inside, above, and around the frame springs, for example, for cushioning and / or insulation. Of course, layers of other materials, such as cotton, wool, felt, rubber products, etc., can also be included, and then a covering material can be added to cover the frame and complete the product manufacturing.

[0208] Specifically, the foam of this invention, together with other materials disclosed herein, can be used as padding or filler that can be shaped, adjusted, and folded under the covering material when stretched on a frame. Furthermore, as noted, in various cases, for a variety of reasons, the foam products produced herein can be used to meet and exceed those known in the art, the most important of which is that typical PU and / or EVA foams are not biodegradable in any way, while the components of the foam produced herein are biodegradable. Therefore, in various embodiments, a method of constructing furniture on an open frame is provided. For example, in one case, the method may include one or more of the following steps.

[0209] Specifically, the method may include providing a frame defining a backrest, multiple sidewalls, and a seat portion, for example, wherein the backrest frame portion extends substantially vertically relative to each other while the seat portion extends substantially horizontally, such that the seat portion bisects the vertical portion. The method may also include cutting a flat foam board to suitable sizes and shapes to provide padding for the backrest and seat and / or sidewall portions; cutting a flat covering material to suitable sizes and shapes to complete the backrest, seat, and / or sidewall portions; attaching the foam board and covering material together at spaced positions; compressing the foam to form a predetermined profile on its outer surface; and forming a substantially flat sub-assembly, wherein the foam board and covering material are free to move relative to each other at the attachment positions; and shaping and attaching the sub-assembly to the frame. The covering of the foam cushion or cushioned article can be any suitable covering material commonly used for decorating furniture and covering decorative pillows, such as woven wool fabrics, woven nylon fabrics, or fabrics woven from various other synthetic fibers, as well as such materials as leather.

[0210] Furthermore, in another aspect, this disclosure generally relates to methods for manufacturing shoe components, such as soles, midsoles, and / or insoles of shoes, including or otherwise constructed of foam, such as compostable foam. Specifically, in certain embodiments, methods for manufacturing soles, midsoles, insoles, and / or other shoe inserts are provided. For example, the shoe inserts of the present invention may be in the form of cushioning devices adapted to be inserted into or otherwise installed in shoes, such as running shoes or athletic shoes, which may be configured to reduce the impact of the foot on surfaces, such as the ground during running or walking, thereby absorbing and / or damping vibrations to the foot.

[0211] Specifically, the shoe sole assembly, including the midsole and inserts, may include one or more layers. For example, in some cases, a base layer, a foam layer, and / or a fabric layer may be provided. Specifically, a base layer and / or a foam layer of relatively elastic material may be included, for example, disposed above the base layer, and / or a fabric layer disposed above the foam layer. Thus, the method may include integrally forming the base layer, foam layer, and fabric as a three-layer laminate. In various cases, a support layer may be provided at least in the heel area, and this support layer may be made of a rigid material, for example, having a higher density than the laminated material. Adhesives, glues, or other attachment mechanisms may be provided and used to attach and form the three-layer laminate with the support layer.

[0212] More specifically, in other cases, methods for manufacturing shoe components such as inserts may include the following steps: providing a foam layer and / or providing a fabric layer; heating the foam layer; bonding the foam layer and the fabric layer; providing a base layer, such as a base layer with the same, greater, or smaller density than the foam layer; and heating at least one of the base layer and the foam layer to couple the base layer to the foam layer to form a double or triple laminate.

[0213] The method may also include providing pre-formed support members, such as arch support members and / or heel members, whose density may be substantially equal to, less than, or greater than the density of the foam layer. In certain cases, the support members may be formed from compressed foam material to obtain greater density and therefore greater rigidity compared to the rigidity of the foam layer. Additionally, heat and / or pressure may be applied between the support members and / or heel members and the laminate to activate the adhesive. Molding pressure may then be applied to the composition to form and / or shape the three-layer laminate into support members and / or heel members to form an integral one-piece shoe insert, wherein the pre-formed heel member forms the rear portion and / or the support member forms the middle portion of the bottom surface of the finished shoe insert, for example, in its middle and / or heel region, and the base layer forms the bottom surface of the finished insole in its front region.

[0214] However, it should be noted that support members and / or heel members are not required, and in some cases, one or more laminated components may be excluded or additional laminated layers may be added. It should also be noted that in some embodiments, the foam layer may be more flexible and / or cushioning than the base layer, for example, having a greater durometer, while the base layer may be more flexible and / or cushioning, for example, having a greater durometer than the support members. Therefore, the more flexible foam and base layer can be relatively resilient and conform to the desired shoe size and configuration, while the support layer(s) can be relatively rigid.

[0215] Specifically, as noted, the foam layer and / or one or more support layers may be composed of biodegradable and / or environmentally friendly foam materials disclosed herein. Specifically, the support layer may be a denser foam, thereby making the support layer more rigid. Thus, in various embodiments, the foam layer may have a density of about 2, about 3, or about 5 to about 10 psi or greater, for example, a density of about 4-6 psi. Additionally, the foam layer may have a thickness of 1 / 8” + or -5%, for example, a thickness of about 3 / 32” to 5 / 32”.

[0216] Similarly, the base layer may also have a density of about 2, about 3, or about 5 to about 10 pounds per cubic foot or greater, for example, a density of about 4-6 pounds per 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". Regarding the support layer that may be formed primarily in the arch and / or heel area of ​​the insert, it may also be made of the biodegradable and / or compostable foam disclosed herein.

[0217] However, the support layer can be made through compression, resulting in a final density on the order of 22-23 psi or greater. The fabric layer can be made of any suitable material, such as cotton, polyester, or polypropylene knitted fabric. In various cases, the material layer and the foam layer can be laminated together using a flame lamination technique, which uses an open flame directed at the foam layer. The open flame generates sufficient heat on the surface to cause the flat sheet of foam layer to melt. Once melted, the fabric layer can be bonded to it, and the two layers sandwiched together can be run between chilling rollers while sufficient pressure is applied between the rollers to bond the two layers together.

[0218] At this point in the process, these layers remain in flat sheet form. These integrated layers can then be flame-laminated onto the base layer. The previously integrated material and foam layers can be bonded to the support layer, and then these multilayer laminates can be run between chilling rollers. At this stage of the process, these layers are still in flat sheet form. The laminated layers at this point are then ready for molding. This can be done by heating the laminated layers to a molding temperature of approximately 250℉ for approximately 1 to approximately 5 minutes or longer, such as a period of approximately 225 seconds. This sufficiently heats the previously laminated layers to allow them to be inserted into the mold.

[0219] The following is a description of various embodiments of the present disclosure with reference to the accompanying drawings. Therefore, in one aspect, a footwear assembly is provided. In particular, as... Figure 1 As shown, one embodiment of this disclosure is a footwear component, namely a microporous soft foam shoe midsole 100 made of a biodegradable and industrially compostable thermoplastic biopolymer blend 102.

[0220] Specifically, the injection-molded microporous flexible foam shoe midsole, which is biodegradable and industrially compostable, is made from one or more biopolymers and biopolymer blends, such as thermoplastic biopolymers. In particular, the thermoplastic biopolymers or biopolymer blends used to manufacture the injection-molded microporous flexible foam, which is biodegradable and industrially compostable, can optionally be produced from any number of aliphatic and aliphatic-aromatic copolyesters, etc.

[0221] Non-limiting examples of suitable biopolymers for producing biopolymers or biopolymer blends include polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene adipate-co-terephthalate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS). Furthermore, hybrid biopolymer blends can be used to manufacture biodegradable and industrially compostable injection-molded microporous flexible foams. One non-limiting example of a hybrid biopolymer blend includes algae-containing poly(butylene adipate-co-terephthalate) (PBAT).

[0222] In the provided examples, the algal portion of the hybrid biopolymer comprises any suitable class of algae in dried powder form. Several non-limiting examples of suitable algal classes include cyanobacteria, green algae, red algae, brown algae, and diatoms, and combinations thereof. The aforementioned dried algal powder can be extruded with PBAT biopolymer using a twin-screw extruder on standard equipment, causing the algal powder to be denatured into polymer chains of PBAT. This thereby forms a hybrid biopolymer for manufacturing the biodegradable and industrially compostable injection-molded microporous flexible foam of this disclosure.

[0223] The produced foam products may include or otherwise incorporate a variety of the following components: filler powder and / or one or more additives. In particular, depending on the application, additives may also be used in biopolymer formulations. For example, oligomer poly(aspartic-co-lactic acid) (PAL) may optionally be formulated into the masterbatch to accelerate biodegradation. Furthermore, fillers such as precipitated calcium carbonate from aragonite, starch, etc., may be used to reduce component costs while maintaining the renewable and biodegradable integrity of the finished flexible foam.

[0224] In addition, the additives used in biopolymer formulations may include one or more of the following: nucleating agents, such as microlayered talc or high aspect ratio oolitic aragonite. Such nucleating agents can significantly improve the key properties of the resulting flexible foam by preventing cell aggregation, reducing bulk density, and increasing resilience, as well as other beneficial reinforcing properties. Several non-limiting examples of nucleating agents used in the production of biodegradable and industrially compostable injection-molded microcellular flexible foams are provided by Imerys Talc America Inc., Houston, Texas. Microlayered talc sold by Calcean Minerals & Materials LLC, Gadsden, Alabama High aspect ratio oolitic aragonite for sale.

[0225] Colorants, dyes, and pigments may also be included. For example, various colorants, such as dyes, pigments, or bio-pigments, may optionally be used in the biopolymer formulations of the present invention. Several non-limiting examples are natural pigments of plant origin that have been tailored for use in biopolymers, such as the wide range of products available from Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or from Holland Colours Americas Inc., Richmond, Indiana.

[0226] There are many possible configurations and implementations, depending on the required physical characteristics and the intended end use of the shoe midsole 100, whether for work, recreation, water use, etc., and should not be limited by these examples.

[0227] A suitable device for this system can be found in Figure 2 The example illustrates this, and it can be used in the production of foam materials as disclosed above. For instance, in use, biopolymer masterbatch 202 is fed into the hopper 204 of any suitable injection molding machine 206. The biopolymer masterbatch is heated and liquefied while being conveyed through the screw 208 of the injection molding machine. Nitrogen or CO2 gas 210 is injected into the biopolymer melt and mixed 212. Furthermore, the biopolymer-gas mixture is injected under pressure into the injection molding tool 214. In conjunction with the biopolymer-gas injection, a gas backpressure system 216 delivers a metered dose of nitrogen or CO2 gas 218 into the pressure molding tool via a gas control valve 220.

[0228] Shortly thereafter, the Dynamic Mold Temperature Control System (DMTC) 222 is controlling and adjusting the temperature inside the molding tool 214. The molding tool 214 is then fully cooled, and the resulting biodegradable and industrially compostable injection-molded microporous flexible foam part is demolded from the injection molding machine.

[0229] Figure 3A flowchart illustrating method 300 for producing biodegradable and industrially compostable injection-molded microcellular flexible foam is provided. At 302, a biopolymer mixture is selected, and at 304, the mixture is drawn into an injection molding machine via a material hopper. At 306, the biopolymer mixture is liquefied and homogenized while being conveyed through the screw of the injection molding machine. At 308, nitrogen or CO2 gas is injected into the biopolymer melt. At 310, the biopolymer-gas mixture is injected under pressure into an injection molding tool. At 312, the temperature of the injection molding tool is dynamically controlled to ensure optimal cell structure. At 314, an optimal dose of gas backpressure is applied to the injection molding tool for a sufficient duration to ensure an ideal foam structure with minimal skin thickness. At 316, the injection molding tool is sufficiently cooled, and the resulting molded foam part is demolded from the injection molding machine.

[0230] In some embodiments, and without limiting the disclosure herein, the method for manufacturing biodegradable and industrially compostable flexible foam includes the steps outlined below. The process setup procedure revolves around establishing a controlled SCF feed into the injection chamber: under screw speed, temperature, and pressure conditions, thereby producing a single-phase solution.

[0231] To ensure that the basic conditions for SCF dispensing are met, seven process setpoints need to be adjusted: SCF delivery pressure: Set the bioplastic pressure relative to the pressure at which SCF is dispensed during screw rotation. This refers both to the specific biopolymer back pressure during screw recovery and to screw position control during screw idling. As a non-limiting example, the biopolymer delivery pressure setpoint can be 2,000 psi to 3,000 psi, more preferably 2,700 psi to 2,800 psi. This setpoint sets the screw position at the start of SCF dispensing, and the SCF injector can then be set to the open or closed position. This position should be set such that the pressure in the barrel has stabilized before dispensing begins during screw recovery. As a non-limiting example, the open position can be 0.3 to 0.4 inches.

[0232] The shot size and the percentage of SCF can also be controlled. This controls the actual mass of SCF dispensed during each cycle. As a non-limiting example, the injection volume can be from 100 g to 300 g, and more preferably 200 g. A non-limiting example of the SCF percentage can be from 0.45% to 0.75%, and more preferably 0.5%. The system can also be configured to optimize dispensing. This is achieved by maximizing dispensing time and minimizing the flow rate (the pressure difference between the expected amount pressure and the delivery pressure). A non-limiting example of dispensing time is 1-2 seconds, and more preferably 1.7 seconds.

[0233] Dynamic mold temperature control (DMTC) can also be implemented. This involves rapidly changing and controlling the mold temperature during the injection filling phase to dynamically control the mold temperature in terms of thermal cycling. Before melt injection, the mold is first heated to a preset upper limit. During the melt filling phase, the temperature of the mold cavity surface is maintained above the upper limit to prevent premature melt solidification.

[0234] When the melt filling process is complete, the mold is rapidly cooled to a lower limit known as the demolding temperature (i.e., the temperature at which the part is demolded from the mold cavity). A non-limiting example of the preferred mold temperature range of this disclosure is 40°C to 150°C, wherein the cooling rate is 1°C / second to 15°C / second, and more preferably 11°C / second. A non-limiting example of the mold cooling time of this invention is 80 seconds to 100 seconds.

[0235] Similarly, gas back pressure (GCP) can also be controlled. This involves a pressurized mold cavity filled with nitrogen to counteract the expansion of gases in the melt. As the back pressure is released, bubbles that typically break through the surface become trapped inside, creating a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness. Non-limiting examples of the gas back pressure of the present invention are 0 bar / 10 bar / 30 bar / 50 bar, wherein the holding time is from 1 second to 25 seconds, and more preferably 5 seconds. Non-limiting examples of the average micropore diameter of the present invention can be from 1 micrometer to 100 micrometers, measured in micrometers (μm), and more preferably 40 micrometers.

[0236] In view of the above, in some embodiments, a suitable thermoplastic biopolymer blend is produced. Once the thermoplastic blend is produced, it can be injection molded into a suitable mold shape, for example by adding an inert gas, such as nitrogen. Furthermore, the pressure can be precisely controlled.

[0237] For example, gas backpressure can be used in the injection molding process. This also helps to further ensure an optimal foam structure with minimal appearance defects and little or no plastic skin on the exterior of the foam component, which is important for manufacturing foamed products with multiple end uses based on the mold shape. The molding process may include implementing dynamic mold temperature control. For example, in various embodiments, dynamically controlling the temperature of the molding process is useful for achieving optimal cell structure. Other controllable elements of the molding process include controlling the biopolymer melt, pressure, and time to form a desirable soft foam.

[0238] Therefore, in view of the foregoing, this disclosure relates to a method for injection molding various flexible foam compositions of microporous foam from biodegradable and industrially compostable bio-derived thermoplastic resins for use in, for example, footwear components, seating components, protective equipment components, and water sports accessories.

[0239] The formation of biodegradable and industrially compostable microporous flexible foam structures begins with suitable biopolymers or biopolymer blends, such as those derived from aliphatic and aliphatic-aromatic copolyesters. Non-limiting examples of suitable biopolymer blends are polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). The aforementioned blends of thermoplastic biopolymer resins exhibit advantageous technical properties in forming the optimal microporous flexible foam structures of this invention. Some enhanced technical properties include acceptable aging properties, excellent elongation and compression set, among other benefits.

[0240] Without a suitable blowing agent and foaming process, optimal aliphatic and aliphatic-aromatic copolyester biopolymers or biopolymer blends cannot produce flexible foams on their own. 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 conventional injection molding foam processes. Unfortunately, ADA is environmentally unfriendly and is a suspected carcinogen for human health. Furthermore, conventional petrochemical thermoplastic masterbatch resins are neither biodegradable nor industrially compostable. To achieve the optimal biodegradable and industrially compostable flexible foam of the invention described above, inert nitrogen or carbon dioxide in a supercritical fluid state is used as a physical blowing agent in an improved injection molding process. The improved physical foaming process is used in conjunction with a suitable thermoplastic biopolymer or blended biopolymer masterbatch, allowing the biopolymer or biopolymer blend and the blowing agent to work synergistically to produce optimal biodegradable and industrially compostable flexible foam.

[0241] The injection molding process disclosed herein relies on uniform cell nucleation that occurs when a single-phase solution of a biopolymer or biopolymer blend and a supercritical fluid (SCF) enters the mold cavity through an injection gate. As the solution enters the mold, a pressure drop causes the SCF to escape from the solution, forming cell nuclei. Cells then grow until the material fills the mold and the expansion capacity of the SCF is exhausted. The manufacturing process is carried out on an injection molding machine modified to allow the metering, delivery, and mixing of SCF into the biopolymer to produce a single-phase solution. Dynamic mold temperature control (DMTC) is employed to ensure a consistent cell structure in the expanding biopolymer melt. DMTC is preferably described as rapidly changing and controlling the mold temperature during the injection filling phase; this thus dynamically controls the mold temperature in terms of thermal cycling. Gas backpressure (GCP) is also used in the manufacturing process to ensure an optimal foam structure with little or no skin on the resulting soft foam. GCP is preferably described as a process involving a pressurized mold cavity filled with SCF to counteract the expansion of gas in the melt. As the back pressure is released, bubbles that have broken through the surface are usually trapped inside, forming a smooth skin. GCP controls foaming through surface quality, foam structure, and skin thickness.

[0242] Under carefully controlled process conditions, a single-phase solution is generated within the injection barrel, in which the SCF is completely dissolved and uniformly dispersed in the molten biopolymer. The SCF must be a mass flow precisely metered into the biopolymer at fixed time intervals. Furthermore, suitable temperature, pressure, and shear conditions can be established within the barrel during the dispensing period. Back pressure, screw speed, barrel temperature control, and the SCF delivery system all play a role in establishing the process conditions for generating the single-phase solution.

[0243] Once a single-phase solution has formed, the improved injection molding machine maintains the solution under pressure until injection begins. This is achieved through the combined action of a throttling nozzle and screw position control. The throttling nozzle prevents decompression and premature foaming into the mold. Active or passive screw position control prevents decompression by the backward movement of the screw. 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 the position setpoint or keep a constant pressure on the back of the screw. In passive position control, the oil used to regulate back pressure is prevented from draining into the oil tank at the end of the screw recovery. Due to the pressure of the single-phase solution, this residual oil prevents the screw from moving backward.

[0244] Proper mold design also helps maintain a single-phase solution. Molds with hot runner systems require valved sprues to prevent material from dripping from the nozzle when the mold is open. Molds where the machine nozzle is out of contact with the sprue bushing during normal operation (e.g., stack molds or cascade molds) require the sprue bushing to be closed. Otherwise, pressure from the hot runner would be released through the sprue bushing.

[0245] The blowing agents used for injection molding biodegradable and industrially compostable microporous foams are inert nitrogen or carbon dioxide in a supercritical fluid (SCF) state. Each of these blowing agents has its own application, depending on the technical requirements of the final part being produced.

[0246] The blowing agent useful for this invention is SCF (nitrogen) because it provides improved weight reduction and a finer cell structure at a much lower weight percentage than SCF (carbon dioxide). In fact, the nitrogen content of SCF will typically be at least 75% lower than the SCF carbon dioxide content required to achieve comparable parts. However, SCF carbon dioxide is the preferred blowing agent in two cases: when reducing viscosity is the primary processing objective, or when the application cannot withstand the more intense foaming action of SCF nitrogen.

[0247] The difference in effectiveness between the two blowing agents stems from their behavior in biopolymer melts. Carbon dioxide, which becomes a supercritical fluid at 31.1 °C and 72.2 bar, is 4 to 5 times more soluble in biopolymers than nitrogen, which becomes a supercritical fluid at -147 °C and 34 bar. For example, the saturation point of unfilled biopolymers is about 1.5 to 2% by weight of nitrogen, depending on temperature and pressure conditions, while the saturation point of carbon dioxide is close to 8% by weight. Carbon dioxide also exhibits greater fluidity in biopolymers, allowing it to migrate deeper into existing bubbles than nitrogen. From the perspective of cell nucleation, greater solubility and fluidity mean fewer cells will nucleate, and the cells that do nucleate tend to be larger.

[0248] However, solubility becomes an advantage when the goal is to reduce viscosity. SCF dissolved in biopolymers acts as a plasticizer, reducing the viscosity of the biopolymer. Because viscosity reduction depends in part on the amount of SCF added to the biopolymer, and because carbon dioxide has a higher solubility limit than nitrogen, it is more effective at reducing viscosity.

[0249] Carbon dioxide is also preferred when the amount of nitrogen required to produce a part is so low that it is impossible to process the part consistently. Because carbon dioxide is a less potent foaming agent, it is sometimes easier to use lower concentrations. For example, 0.15% or 0.2% carbon dioxide is equivalent to extremely low concentrations of nitrogen, less than 0.05%. The examples cited above primarily occur with soft materials and parts with thick cross-sections.

[0250] Recyclable Injection Molded Microporous Flexible Foam and Its Manufacturing Method

[0251] Figure 4 and Figure 6 The illustration shows a recyclable injection-molded microporous flexible foam 402 according to the present disclosure and its manufacturing method. Reference Figure 4 Foam 402 is preferably a closed-cell foam, but it can also be formed as an open-cell foam. In various embodiments, foam 402 can be made to have properties and characteristics that are at least approximately similar to those of conventional non-recyclable ethylene vinyl acetate (EVA) foam, etc.

[0252] In some embodiments, the term "recyclable" may generally refer to the ability of a material or product to be collected, separated, or otherwise recovered from a waste stream for reuse or for the manufacture or assembly of another article. In some embodiments, polymers and foams described herein as recyclable refer to the ability of constituent materials to be recycled, for example, by mechanical, chemical, and / or biological or organic recycling. In some embodiments, polymers and foams described herein as recyclable refer to the ability of constituent materials to be recycled using standard plastics recycling methods, for example, as described in ISO 15270:2008. In some embodiments, the recycled materials, foams, and / or products described herein may be produced in accordance with the requirements set forth in the Textile Exchange Recycling Declaration Standard 2.0 (RCS, July 1, 2017) and / or the Textile Exchange Global Recycling Standard 4.0 (GRS, July 1, 2017).

[0253] As discussed in more detail below, recyclable foam 402 is achieved through the use of... Figure 5 The injection molding machine shown is made by processing thermoplastic polymers. The thermoplastic polymer used to manufacture the recyclable flexible foam 402 can optionally be produced from any number of polyamide-based thermoplastic polymers, polyamide copolymers, etc. Non-limiting examples of suitable polymers that can be used in this invention include polyamide 6, polyamide 6 / 6-6, polyamide 12. Alternatively, the thermoplastic polymer may contain any number of polyamide block copolymers, such as polyether block amides (PEBA), PAE, TPA, TPE-A, COPA, etc. Other non-limiting examples of suitable polymers and copolymers include polyamide 66 copolymers sold by Ascend Performance Materials, LLC, Houston, TX under the trade name Vydyne. The above-described thermoplastic polymer resins exhibit advantageous technical properties in forming the optimal microporous flexible foam structure of this invention. Some enhanced technical properties include excellent aging properties, excellent elongation, tensile strength, and compression set.

[0254] Furthermore, blends of two or more thermoplastic polymers offer a combination of properties and prices not found in single thermoplastic polymers. There are several methods for successfully blending thermoplastic polymers together. As discussed in more detail below, twin-screw extrusion melts two or more thermoplastic polymers together, then extrudes the molten polymer resin blend into a thread, cools it, and feeds it into a granulator to produce a large quantity of granulated blocks known as masterbatch. Another method of polymer resin blending is to use compatibilizers to bind the different chemicals together in the polymer blend. Typically, this is also done using twin-screw extrusion, etc., to melt the compatibilizer and two or more polymers together into the aforementioned non-limiting thermoplastic polymer types.

[0255] 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 include caprolactam, recycled polyether block amide polymers, etc. For instance, caprolactam may be derived from recycled materials obtained by depolymerizing post-industrial or post-consumer materials containing polyamides, such as fishing nets, carpet fibers, or industrial waste. Non-limiting examples of depolymerized post-consumer or post-industrial recycled caprolactam include those provided by Aquafil USA Inc., Cartersville, Georgia. Caprolactam, whether in flake, liquid, or molten form. Thermoplastic polymers may additionally or alternatively contain polyamide polymers derived from collected, sorted, melted, and reprocessed post-industrial or post-consumer polyamide carpet fibers. One such polyamide polymer derived from post-industrial carpet fibers is Econyl, manufactured by Aquafil USA Inc., Cartersville, Georgia. Furthermore, polyamide waste can be collected from or around the world's oceans in the form of fishing nets, etc., and then sorted, melted, and reprocessed into upscale recyclable usable polyamide materials. An exemplary polyamide polymer derived from collected post-industrial fishing nets is Akulon Repurpused, manufactured by Koninklijke DSM NV, Heerlen, the Netherlands.

[0256] Depending on the application, additives can also be used in polymer formulations. For example, fillers such as precipitated calcium carbonate, oolitic aragonite, starch, and biomass can be used to reduce component costs while maintaining the recyclable integrity of the finished flexible foam.

[0257] Furthermore, the additives used in polymer formulations may consist of one or more of the following: nucleating agents, such as microlayered talc or high aspect ratio oolitic aragonite. Such nucleating agents can significantly improve the key properties of the resulting flexible foam by preventing cell aggregation, reducing bulk density, increasing resilience, and other beneficial reinforcing properties. Several non-limiting examples of nucleating agents used in the production of recyclable injection-molded microcellular flexible foams are provided by Imerys Talc America Inc., Houston, Texas. Microlayered talc sold by Calcean Minerals & Materials LLC, Gadsden, Alabama High aspect ratio oolitic aragonite for sale.

[0258] 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. Several non-limiting examples are pigments tailored for specific types of thermoplastic polymer applications, such as the wide range of products available from Treffert GmbH & Co. KG, Bingen am Rhein, Germany, or from Holland Colours Americas Inc., Richmond, Indiana.

[0259] Using recycled materials to manufacture microporous flexible foam reduces the environmental impact typically associated with manufacturing expanded thermoplastic polymer foams from sustainably sourced materials. As discussed in more detail below, the method of producing microporous flexible foam disclosed herein increases the environmental benefits of using recycled materials because the resulting product can be further recycled into thermoplastic polymers, which can then be used to generate new products from microporous flexible foam or alternatively from other products that use thermoplastic polymers.

[0260] Figure 5 and Figure 6 It shows the manufacturing process. Figure 4 The injection molding machine 506 and method 600 for recycling flexible foam 402 are shown. Therefore, in one aspect, this disclosure relates to a method for foaming a thermoplastic polymer. As described in more detail below, this method can be used to manufacture any of a number of end products from foam 402, such as technical sports equipment including shoe components, and other products requiring features such as cushioning, impact protection, and comfort.

[0261] like Figure 5As shown, the injection molding apparatus 506 includes a hopper 504 configured to receive a plurality of thermoplastic polymers 502 and introduce them into the molding apparatus 506. A barrel 507 is connected to the hopper 504 and configured to receive the thermoplastic polymers 502 and includes a dedicated reciprocating screw plunger 508. The barrel 507 also includes a temperature control unit (not shown) for heating and cooling the contents of the barrel 507. Figure 5 As shown, a computer controller 503 with temperature and pressure measuring devices 505 is configured to sense the temperature and pressure within the cylinder 507. A gas dispensing system 509 is fluidly connected to the cylinder 507 and includes a metering unit 512 configured to receive fluid 510 and introduce it into the cylinder 507. The gas dispensing system 509 maintains the fluid 510 above the critical temperature and pressure (Tc and Pc, respectively) to produce supercritical fluid (SCF) 510. In the method of this disclosure, SCF 510 is used as a physical blowing agent to replace chemical blowing agents, such as azodicarbonamide (ADA), used in conventional flexible foam production methods. For example, SCF 510 may comprise inert or rare gases, such as nitrogen, carbon dioxide, helium, neon, argon, or xenon. Compared to conventional flexible foam molding methods, the method of this disclosure not only improves the environmental impact by eliminating the environmentally harmful and suspected carcinogen ADA from the process and replacing it with an inert or rare SCF, but also, as will be further detailed below, the flexible foam 402 of this disclosure can be recycled at the end of its service life due to the method described herein.

[0262] refer to Figure 6 A method for manufacturing recyclable flexible foam 102 may begin in step 602: selecting a thermoplastic polymer 502 and supplying it to the hopper 504 of an injection molding machine 506. Subsequently, in step 604, the thermoplastic polymer 502 is fed from the hopper 504 into a barrel 507 and heated. In step 606, as the screw plunger 508 moves the thermoplastic polymer 502 through the injection molding machine 506, the heated barrel 507 melts the thermoplastic polymer 502. Furthermore, a controller 503 may be configured to control and regulate the screw speed.

[0263] In step 608, SCF 510 is introduced into the barrel 507 via a syringe 511 through a metering unit 512 connected to the injection molding equipment 506, and SCF 510 dissolves in the molten thermoplastic polymer 502 to produce a single-phase solution. The concentration of SCF 510 in the melt can be adjusted, which affects the degree of foaming achieved. (Reference) Figure 5The metering system 512 is configured to dispense an appropriate amount of SCF into the molten thermoplastic polymer 502. A non-limiting example of the initial SCF gas concentration is Co = 0.25%, wherein the melting temperature is from 176°C to 250°C, and more preferably 180°C. Furthermore, the controller 503 controls the pressure of the SCF 510 introduced into the barrel 507 via the SCF injector. The SCF 510 saturates the molten thermoplastic polymer 502, thereby producing a single-phase solution. Additionally, a screw plunger 508 rotates within the barrel 507 at the speed required to homogenize the thermoplastic polymer 502 and SCF 510 and produce the single-phase solution. The screw 508 can rotate within the barrel 507 at a speed of 1 to 200 rpm, and preferably from about 20 rpm to about 60 rpm.

[0264] Regarding saturation, the injection molding machine 506 is configured to deliver gas to the barrel 507 at a certain temperature and pressure to saturate the molten thermoplastic polymer 502 during screw rotation. Specifically, the controller 503 is configured to control a combination of SCF delivery pressure and SCF dosage weight. The SCF pressure and dosage can be controlled in a manner that affects the single-phase solution. That is, the smaller the SCF dosage, the lower the required SCF saturation in the biopolymer melt, while the larger the SCF dosage, the higher the required SCF saturation in the melt. Similarly, the lower the SCF delivery pressure, the lower the saturation absorption, and therefore the lower the growth of nuclei that can grow in the molten biopolymer melt to form bubbles. Furthermore, the higher the SCF delivery pressure, the greater the saturation absorption, and therefore the faster the growth of nuclei that can grow in the molten melt to form bubbles.

[0265] The controller 503 variably controls the temperature and pressure in a manner that depends on the type of flexible foam being produced and the type of final product being produced. Specifically, the temperature of the entire system, for example within the cylinder 507, can be controlled from 100°C to 600°C, for example from 200°C to 500°C, for example from 300°C to 400°C, and more specifically from 320°C to 380°C, including 360°C to 380°C within the cylinder. Similarly, the SCF delivery pressure can be finely controlled from 1,000 to 8,000 PSI, for example from 1,500 to 6,000 PSI, for example from 2,000 to 5,500 PSI, particularly from 3,000 to 4,000 PSI, and more specifically from 2,600 to 2,800 PSI.

[0266] exist Figure 5In the illustrated embodiment, controller 503 uses a sensor that measures saturation to determine and control the concentration of SCF 510, assess the progress of the saturation process, and regulate pressure and temperature. SCF 510 controllably causes molten thermoplastic polymer 502 to form a single-phase solution at a defined temperature and pressure during the rotation of reciprocating screw 508. SCF is part of a two-part molten thermoplastic polymer composite mixture and acts as a physical foaming agent in this injection molding die under defined pressure and temperature.

[0267] As discussed in more detail below, the SCF 510 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 has a higher density than nitrogen at the same pressure, but also a higher heat capacity. Supercritical carbon dioxide produces dense foam, which can be used in certain cushioning applications. In contrast, supercritical nitrogen can be used to produce low-density foam components with smaller cores, which can be used in the production of foam 402 for footwear and sporting goods.

[0268] However, solubility becomes an advantage when the goal is to reduce viscosity. SCF dissolved in the recyclable thermoplastic polymer 502 acts as a plasticizer, reducing the viscosity of the thermoplastic polymer 502. Because viscosity reduction depends in part on the amount of SCF added to the recyclable thermoplastic polymer 502, and because carbon dioxide has a higher solubility limit than nitrogen, its ability to reduce viscosity is greater. Carbon dioxide is also useful when the amount of nitrogen required to produce the parts is too low to consistently process the final product.

[0269] Because carbon dioxide is a less potent blowing agent, it is sometimes easier to use low concentrations. For example, 0.15% or 0.2% carbon dioxide is equivalent to extremely low concentrations of nitrogen, below 0.05%. The examples cited above primarily occur with soft materials and components with thick cross-sections. Therefore, whether it is nitrogen, carbon dioxide, or one of the other inert and rare gases listed above, physical blowing agents play a useful role in the final foamed components and the final products containing them.

[0270] Choosing a compatible thermoplastic polymer or thermoplastic polymer compound with an appropriate combination of the associated SCF gas is useful. Secondly, proper utilization of the SCF gas through optimal feeding weight and pressure can provide preferred saturation in a single-phase solution and influence nucleation (the generation of numerous uniform bubbles in the foam matrix, as will be described in more detail below). Furthermore, the end result is a uniformly formed injection-molded flexible foam part, which depends on all aspects of the SCF gas feeding process and the coordinated operation of gas backpressure with the injection molding machine's temperature, pressure, and holding time to achieve commercially acceptable molded foam parts.

[0271] refer to Figure 5 The reciprocating screw 508 is also configured to compress and move the molten thermoplastic polymer 502 within the cavity of the barrel 507. A gas backpressure (GCP) system 516 is configured to deliver gas backpressure to the barrel 507 to control the expansion of the molten thermoplastic polymer 502. Figure 5 In the illustrated embodiment, 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. A reciprocating screw plunger 508 and a cylinder 507 are also configured to provide back pressure and deliver thermoplastic polymer 502 into a mold 514 having a cavity configured to fluidly communicate with the cylinder 507 and configured to receive molten thermoplastic polymer 502 (described in more detail below). Figure 5 In the illustrated embodiment, the screw plunger 508 and barrel 507 are configured to apply approximately 2,000 psi to approximately 3,000 psi, more preferably 2,700 psi to 2,800 psi. The configuration of the screw plunger 508 and barrel 507 also sets the position for the SCF 510 dispensing to begin, after which the SCF injector can be set to an open or closed position. The position should be set so that the pressure in the barrel stabilizes during screw recovery before the SCF 510 dispensing begins. As a non-limiting example, the open position can be 0.3 to 0.4 inches.

[0272] In addition to the GCP system Figure 5 The injection molding machine 506 shown also 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 a GCP system 516 to ensure a consistent cell structure within the expanding thermoplastic polymer 502. The DMTC 522 can be configured to influence and control rapid changes in mold temperature and / or pressure during the injection filling stage, and to dynamically control mold temperature and / or pressure with or without back pressure through thermal cycling.

[0273] Continue to refer to Figure 5 The controller 503 is configured to control the temperature of the mold 514 during the injection stage 610 via the DMTC 522. More specifically, a key feature of the dynamic mold temperature control employed in this paper, compared to conventionally known injection molding processes, is that the mold temperature itself can be dynamically controlled. Figure 5 The DMTC 522 shown uses rapid electric heating rods and rapid water cooling. Specifically, the DMTC 522 includes five main components: an air compressor (not shown), a valve changing device 526, a computer-controlled mold temperature control unit (located within a controller 503), electric heating rods (located within a mold 514), and a cooling tower 532. The cooling tower 532 is used to supply sufficient water cooling to the mold. The air compressor is used to generate compressed air as the driving gas for pneumatic valves and to remove residual cooling water that has entered the mold after cooling. Figure 5 The illustrated embodiment also includes a water heating unit 534 and a valve switching device 526 for switching valves to deliver different media from the pipeline to the mold 514, providing hot and cold circulation. For example, the DMTC 522 can provide water cooling of about 15°C to about 30°C, and the heating rod can heat the mold to about 60°C to about 150°C, and can optimally heat the mold to 90°C to 130°C.

[0274] Figure 5 The injection molding machine 506 depicted includes conduits and other conduits for the passage of reactive materials, said conduits being associated with one or more heat exchange units to heat and / or cool the reactants as they are pumped in and / or pass through the conduits and pipes. In this configuration, the exchangers can be controlled to regulate the temperature to the reactive level. A dispensing head may be included at one end of the conduit, which may be associated with one or more valves. Furthermore, the dispensing head may 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 via computer control.

[0275] Therefore, as implemented herein, controller 503 implements gas backpressure to improve control of the foaming process by applying different gas pressures during the injection phase as described below. Controller 503 is configured to manipulate GCP system 516 and DMTC 522 to regulate temperature and pressure, and thereby control nucleation and the resulting bubbles in the molten thermoplastic polymer 502 and the resulting foam matrix.

[0276] like Figure 6As shown, in step 610, the thermoplastic plunger 508 advances, forcing molten thermoplastic polymer 502 through a nozzle (not shown) that rests against the mold 514 and injects the thermoplastic polymer 502 into the mold 514. The injection molding machine 506 sends a measured jet of 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 this upper limit to prevent premature solidification of the molten thermoplastic elastomer 502. The GCP system 516 delivers gas backpressure within the mold 514 to control nucleus growth, preventing bubbles from contacting and breaking through the surface of the thermoplastic polymer 502 during the formation of the foam component. This is achieved by applying a counteracting pressure to the mold cavity by the GCP system 516 simultaneously or approximately simultaneously with the injection of the single-phase thermoplastic polymer 502 solution into the mold cavity 514. During injection step 610, the inert bubble is subjected to a force sufficient to hold the SCF 510 within the thermoplastic polymer 502.

[0277] refer 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. Although the steps of dynamically controlling the temperature of mold 612 and applying gas back pressure to mold 614 are... Figure 6 The flowchart shows these as separate steps, but steps 612 and 614 can be performed simultaneously or immediately afterward, causing the temperature and pressure within the mold controlled by controller 503 to change. In steps 612 and 614, nucleation occurs within the molten thermoplastic polymer 502, forming numerous microporous bubbles. With controller 503 ( Figure 5 In step 612, the temperature is raised and lowered, causing SCF 510 to evaporate and turn into bubbles, resulting in the foaming of thermoplastic polymer 502 within mold 514. In step 614, the GCP system 516, under computer control, delivers a pre-metered dose of backpressure gas into the mold to produce substantially uniform bubbles, and the gas backpressure modulates the surface texture for an optimal decorative appearance. Bubbles grow until the thermoplastic polymer 502 fills mold 514, and the expansion capacity of SCF 510 is consumed. As the bubbles reach a micron size, the process produces microporous foaming. The SCF 510 concentration can affect the bubble structure. Therefore, controller 503 selects temperature and gas backpressure parameters to produce a useful and / or defined bubble structure. With the completion of part molding, the mold cools and the thermoplastic polymer solidifies. Figure 6In the embodiment depicted, in step 616, the dynamically temperature-controlled mold temperature is switched to water cooling, and the formation of bubbles and the expansion of the thermoplastic polymer 502 are slowed down and stopped. DMTC 522 rapidly cools the mold 514 to a lower limit (demolding temperature), and now forms the soft foam molded part 402 and demolds it from the mold.

[0278] As previously mentioned, in some embodiments, the production of open-cell foam can utilize the same equipment and basic methods as those described herein for the production of closed-cell foam, except that the open-cell foam structure develops as the walls between the cells break, thereby creating pathways for the existence of the open-cell foam structure. Therefore, in some embodiments, Figure 5 The system 500 shown can be used to produce open-cell foam and closed-cell foam.

[0279] In some embodiments, one or more components of system 500 may be configured to cause cells to grow to a degree that leads to collisions or interference between adjacent or near-neighboring cells, resulting in cell wall rupture. In some embodiments, one or more components of system 500 may be configured to produce a critical nucleation density such that cells, or “bubbles,” are close enough to each other that they form impact structures. In some such embodiments, cell impacts lead to the formation of open-cell foam structures. In some embodiments, the nuclei of each bubble should be able to grow sufficiently to collide with each other to cause cell weakening and rupture. Furthermore, a high cell cluster density may be required in some embodiments to generate impact structures.

[0280] In some embodiments, for example, controller 503 is configured to control the temperature of mold 514 during injection phase 610 via DMTC 522 to generate a sufficiently high cell density to allow cell collision. In some embodiments, GCP system 516 may be configured to deliver different pre-metered doses of backpressure gas into mold 514 to generate open-cell foam.

[0281] According to some embodiments of this disclosure, another method for achieving an open-cell foam structure is to coalesce “bubbles,” thereby causing the walls between the pores to rupture spontaneously or uniformly, thus forming an open-cell foam structure. In some embodiments, system 500 may be specifically configured to form such coalesced bubbles. In some embodiments, as the pores grow, a film forms between each pore. This film is affected by the internal pressure of the “bubbles,” as well as van der Waals separation pressure and electrostatic separation pressure. In some embodiments, if the pressure causing the film to thin or weaken exceeds the pressure causing the film to thicken or strengthen, the film between each pore will rupture or break, and this can be understood as the force determining the rupture or breakage of the pore walls. The increasing internal “bubble” pressure and van der Waals separation pressure act as forces that contribute to thinning the film present between each pore, while electrostatic separation acts as forces that contribute to thickening or strengthening the aforementioned film.

[0282] In some cases, the presence of polar groups in the polymer structure can actually thicken or reinforce the cell walls, making it difficult for them to rupture or break down. Conversely, due to the general thermodynamic instability of the film, surface waves develop during impact in some embodiments, which greatly contributes to the rupture or breakdown of the cell walls, and this phenomenon causes the film to thin faster than the internal “bubble” pressure builds up, resulting in a faster cell wall rupture or breakdown mechanism. In some embodiments, it may be important for the cell walls to rupture or break down as quickly as possible to create an open-cell foam structure, as this helps overcome the viscosity increase of thermoplastic polymer foams, which is known to increase during the mold cooling and demolding stages of foam production.

[0283] In some embodiments, various foam molding parameters determine the optimal nucleation and cell growth in the formation of the final microporous injection-molded foam part. For example, the nucleation rate may be significantly affected by the injection rate of the gas delivery system 509 and / or the mold temperature controlled by the DMTC 522. In some embodiments, the method for generating open-cell foam according to this disclosure may include steps for controlling one or more of these parameters.

[0284] In a further embodiment, the method for forming open-cell foam according to this disclosure may include using ultrasound as a means of opening the pores of the foam structure. In some such embodiments, the duration and extent of ultrasonic irradiation are factors in obtaining an open-cell foam structure. In some embodiments, an ultrasonic energy source may be included in system 500 and configured to supply ultrasound to produce an open-cell foam structure. The ultrasonic energy source may be, for example, an ultrasonic instrument, an ultrasonic probe, or an ultrasonic transducer configured to convert electrical signals into ultrasound. In some embodiments, for example, the ultrasonic energy source may be included in mold 514 and used to apply ultrasonic irradiation to cause rupture of at least a portion of the pore walls.

[0285] Recyclable injection-molded microporous flexible foam products

[0286] Figure 4 The footwear components of this disclosure are shown. More specifically, a recyclable microporous soft foam midsole 400 is made of recyclable soft foam 402.

[0287] As briefly discussed above, the methods for manufacturing recyclable materials described above enhance the environmentally beneficial effects of utilizing monomers and polymers developed from recycled raw materials, because the resulting products can be further recycled into monomers, which can then be repolymerized into thermoplastic polymers for the manufacture of new, other plastic materials. In particular, the production of products configured for recycling ensures that the flexible foam will extend the lifespan of the resulting products, for example, by functionalizing it in some way so that it does not decompose or detach during the middle of the product's use. For example, for someone purchasing furniture, a pair of shoes, or other sporting equipment made from the recyclable flexible foam of this disclosure, it would be harmful if the foam degraded during normal use only before the product's end of its lifespan.

[0288] More specifically, this disclosure benefits from the use of inert physical blowing agents and the thermoplastic polymer compounds listed above that do not crosslink during the manufacturing process. The resulting recyclable flexible foam 402 is non-crosslinked, free of harmful chemical blowing agents such as ADA, and environmentally friendly. Furthermore, recyclable flexible foam 402 can be used in a variety of end products, such as footwear foam for shoemaking.

[0289] At the end of its product life, recyclable flexible foam 402 can be redirected to an appropriate recycling facility via waste transfer. Because recyclable flexible foam 402 does not use chemical blowing agents such as ADA, and because the methods described herein do not use crosslinked thermoplastic polymers during its manufacturing process, recyclable foam 402 can be milled, pretreated, and depolymerized into one or more monomers. One such depolymerizing monomer is caprolactam, for example, supplied by Aquafil USA Inc., Cartersville, Georgia. Caprolactam, whether in sheet, liquid or molten form, or depolymerized caprolactam, whether in sheet, liquid or molten form, supplied by DSM Engineering Plastics Americas, Troy Michigan.

[0290] refer to Figure 7 The method disclosed herein considers a method 700 for recycling recyclable foam 402 using a thermal and chemical depolymerization process, according to which the temperature of a polymer, such as PEBA, is raised above an upper limit temperature, and any of a number of chemical reagents or catalysts are used to depolymerize it into its constituent monomers. Figure 7In the illustrated embodiment, the depolymerization process begins at step 702, which involves the mechanical separation of the thermoplastic polymer from any waste into the recyclable foam 402. In step 704, a depolymerization catalyst is introduced into 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 to the above-mentioned material, for example, by superheated steam, which can be used to distill caprolactam and any other volatile compounds and produce a distillate containing caprolactam monomers. The applied temperature can be from about 100°C to about 325°C. In step 708, the distillate is fractionated to separate water and caprolactam from other byproducts of the depolymerization process. In step 710, an oxidant is introduced into the separated aqueous caprolactam. Some non-limiting examples of oxidants include potassium permanganate, hydrogen, oxygen, potassium dichromate, sodium or potassium hypochlorite, perchlorate, or perboric acid. 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.

[0291] Following purification of the caprolactam monomer in step 714, the depolymerized monomer can be repolymerized into a thermoplastic polymer and used to manufacture a more recyclable flexible foam 402. Therefore, the method of this disclosure establishes a circular process whereby the produced product can be broken down, manufactured into new products, and reintroduced into the commercial stream, rather than using new virgin fossil fuels or other non-renewable raw materials. Furthermore, the recyclable foam 402 of this disclosure does not compromise its technical performance characteristics or its environmentally conscious design during its service life.

[0292] As discussed above, the apparatus, system, and method of use thereof can be used for the purpose of producing one or more molded end products, such as components for footwear, seating, automobiles, protective equipment, and / or sports equipment. Therefore, in various embodiments, this document provides one or more components that can be used to construct a shoe, such as a sole, midsole, and / or insole, for example, 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 and thereby provide cushioning and / or support.

[0293] In some embodiments, the shoe component may include recyclable foam 402 produced according to method 600 disclosed herein, which may be environmentally friendly and recyclable. In various cases, each individual component may consist of multiple layers, including a base layer and a cushioning layer. For example, in a particular embodiment, a support member may be included, such as a support member coupled to the base layer, and the component is an insole having one or more of an arch contact portion or a heel contact portion.

[0294] In particular, in various embodiments, foam materials can be produced, for example, in the manufacture of cushions, cushioned furniture, shoe components such as insoles, pads, fibers, and woven fabrics. Other useful products may include caulking materials, such as silicone caulking materials, silicone medical gloves, silicone tubing for drug delivery systems, silicone adhesives, silicone lubricants, silicone coatings, and other suitable silicone products, such as condoms. In various embodiments, foam products can be produced in a manner in which the foam material can possess one or more antimicrobial, antibacterial, antifungal, antiviral, and / or flame-retardant properties.

[0295] More specifically, in one aspect, this disclosure may generally relate to a method for manufacturing furniture, such as decorative furniture and / or its cushions, including or otherwise comprising foam, such as biodegradable and / or compostable foam. Therefore, the recycled foam of this disclosure is advantageous for manufacturing furniture incorporating foam inserts produced in this manner. Recyclable foam produced according to the methods of this disclosure has proven advantageous for use as a cushioning material, for example, in pillows, sofas, beds, seat cushions, or other decorative furniture.

[0296] For example, method 600 can be used to produce small to large pieces of recyclable foam 402, such as forming foam inserts for furniture or automotive parts components. The block foam can then be cut into smaller pieces of the desired size and shape based on the type and form of the furniture being produced. Specifically, the sized and cut pieces can then be applied to or otherwise assembled into furniture or vehicle frames or other edging materials, and they can be covered together to produce the final furniture product, whether it is a pillow, sofa, cushion, such as a sofa or car cushion. Furthermore, when needed, the outer shell or edging material can be attached to the frame material, for example by stapling and / or pins, or otherwise secured to the frame of the article to be decorated and covered with fabric or other materials.

[0297] Therefore, in various implementations, the manufacture of decorative furniture, such as sofas or car seats, can involve producing a frame. Various internal components of the furniture (e.g., structural components), such as springs, can be installed within the frame, and then sheets of recyclable soft foam 402 can be positioned within, above, and around the springs, for example, for cushioning and / or insulation. Of course, layers of other materials, such as cotton, wool, felt, rubber products, etc., can also be included, and then a covering material is added to cover the frame and complete the product manufacturing.

[0298] Specifically, the recyclable foam disclosed herein, together with other materials disclosed herein, can serve as padding or filler that can be shaped, adjusted, and folded beneath the covering material when stretched on a frame. Furthermore, as noted, in various cases, for a variety of reasons, the recyclable foam produced herein can be used to meet or exceed those known in the art, the most important of which is the fact that typical PU and / or EVA foams are not recyclable, while the components of the foam produced herein are recyclable. Therefore, in various embodiments, a method for constructing furniture on an open frame is provided.

[0299] Furthermore, in another aspect, this disclosure generally relates to methods for manufacturing shoe components such as soles, midsoles, and / or insoles, including or otherwise comprising shoe components made of conventional foam. Specifically, in certain embodiments, methods for manufacturing recyclable soles, midsoles, insoles, and / or other shoe insoles are provided. For example, this shoe insert can be a cushioning device adapted to be inserted into or otherwise fitted into a shoe such as a running shoe or athletic shoe, configured to reduce the impact of the foot striking a surface such as the ground, for example, during running or walking, thereby absorbing and / or damping vibrations to the foot.

[0300] Specifically, the sole assembly, including the midsole and inserts, may include one or more layers. For example, in some cases, a base layer, a recyclable foam layer, and / or a fabric layer may be provided. Specifically, it may include a base layer of relatively elastic material, and / or a recyclable foam layer disposed above the base layer, and / or a fabric layer disposed above the recyclable foam layer. Thus, the method may include integrally molding the base layer, the recyclable foam layer, and the fabric into a three-layer laminate. In various cases, a support layer may be provided in the heel area, which may be made of a rigid material, for example, having a higher density than the other components of the laminate. Adhesives, glues, or other attachment mechanisms may be provided and used to attach and form the three-layer laminate with the support layer.

[0301] More specifically, in other cases, a method of manufacturing a shoe component, such as an insole, may include the following steps: providing a recyclable foam layer, providing a fabric layer, heating the recyclable foam layer, and bonding the recyclable foam layer and the fabric layer; providing a base layer, such as a base layer with the same, greater, or less density than the recyclable foam layer; and heating at least one of the base layer and the foam layer to couple the base layer to the recyclable foam layer, thereby forming a two- or three-layer press-fit.

[0302] The method may also include providing pre-formed support members, such as arch support members and / or heel members, whose density may be substantially equal to, less than, or greater than the density of the foam layer. In certain cases, the support members may be formed from compressed foam material to obtain a greater density and therefore greater rigidity compared to the rigidity of the recyclable foam layer. Additionally, a heat- and / or pressure-activated adhesive may be applied between the support members and / or heel members and the laminate. Molding pressure may then be applied to the composition to form and / or shape the three-layer laminate into the support members and / or heel members, thereby forming an integral, one-piece shoe insert, wherein the pre-formed heel member forms the rear portion and / or the support member forms the middle portion of the bottom surface of the finished shoe insert, for example, in its middle and / or heel region, and the base layer forms the bottom surface of the finished shoe insert in its front region.

[0303] However, it should be noted that support members and / or heel members are not required, and in some cases, one or more laminated components may be excluded or additional laminated layers may be added. It should also be noted that in some embodiments, the recyclable foam layer may be more flexible and / or cushioning than the base layer, for example, having greater rigidity, while the base layer may be more flexible and / or cushioning, for example, having greater rigidity than the support members. Therefore, the more flexible foam and base layer can be relatively elastic and conform to the desired shoe size and configuration, while the support layer(s) can be relatively rigid.

[0304] Specifically, the support layer can be a denser recyclable foam, making the support layer more rigid. Therefore, in various embodiments, the recyclable foam layer can have a density of about 2, about 3, or about 5 to about 10 pounds per cubic foot or greater, for example, a density of about 4-6 pounds per cubic foot. Additionally, the recyclable foam layer can have a thickness of about 1 / 8”, for example, a thickness of about 3 / 32”-5 / 32”.

[0305] Similarly, the base layer may also have a density of about 2, about 3, or about 5 to about 10 pounds per cubic foot or greater, for example, a density of about 4-6 pounds per 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 be about 1 / 4” or less to about 7 / 16”. Regarding the support layer that may be formed primarily in the arch and / or heel area of ​​the insert, it may also be made from the recyclable foam disclosed herein.

[0306] However, the support layer can be made by compressing recyclable foam 402, resulting in a final density on the order of 22-23 psi. The fabric layer can be made of any suitable material, such as cotton, polyester, or polypropylene knitted fabric. In various cases, the material and the recyclable foam layer can be laminated together using a flame lamination technique, which employs an open flame that generates sufficient heat to melt the surface of the recyclable foam layer. After melting, the fabric layer is bonded to the recyclable foam layer and a cooling roller to bond the two layers together.

[0307] At this point in the process, these layers remain in flat sheet form. These integrated layers can then be flame-laminated onto the base layer. The previously integrated material and foam layers can be bonded to the support layer, and then these multilayer laminates can be run between chilling rollers. At this stage of the process, these layers are still in flat sheet form. The laminated layers at this point are then ready for molding. This can be done by heating the laminated layers to a molding temperature of approximately 250℉ for approximately 1 to approximately 5 minutes or longer, such as a period of approximately 225 seconds. This sufficiently heats the previously laminated layers to allow them to be inserted into the mold.

[0308] As mentioned above, SCF physical blowing agents can be selected based on the desired properties of the final product. Carbon dioxide, which becomes an SCF fluid at 31.1°C and 72.2 bar, has a solubility in thermoplastic polymer 502 that is 4 to 5 times greater than that of nitrogen, which becomes a supercritical fluid at -147°C and 34 bar. The saturation point of unfilled recyclable thermoplastic polymers is approximately 1.5 to 2% by weight of nitrogen, depending on temperature and pressure conditions, while the saturation point of carbon dioxide is close to 8% by weight. Carbon dioxide also exhibits greater fluidity in biopolymers, allowing it to migrate deeper into existing bubbles than nitrogen. From the perspective of cell nucleation, greater solubility and fluidity mean fewer nucleated cells, while the cells that do nucleate will tend to be larger.

[0309] In the embodiments discussed above, where method 600 is used to produce sporting goods such as shoes, SCF 510 includes nitrogen gas in a critical state. Nitrogen gas provides improved weight reduction and a refined core at a much lower weight percentage than SCF carbon dioxide. The nitrogen content of SCF 510 is at least 75% lower than the SCF carbon dioxide content required to achieve comparable components. Therefore, the significantly reduced SCF nitrogen content requirement compared to SCF carbon dioxide ensures optimal material and time savings when mass-producing the biodegradable and industrially compostable flexible foam of this disclosure for manufacturing shoe components.

[0310] Although carbon dioxide is heavier, it can be a suitable foaming agent in certain applications, such as when viscosity reduction is the goal of the process, and / or when the final product cannot withstand the stronger foaming action of SCF nitrogen, or in semi-flexible foams. For example, when method 600 is used to produce furniture and automotive products, SCF 510 includes carbon dioxide in a critical state because carbon dioxide produces a larger cell structure, despite its larger size and / or weight. During physical foaming processes using physical foaming agents, depressions in the glass transition can be observed.

[0311] As briefly discussed above, supercritical carbon dioxide can be used as a physical foaming agent when the amount of nitrogen required to produce a part is too low to ensure consistent part processing. Because carbon dioxide is a less potent foaming agent, it is easier to use low concentrations in certain applications. For example, 0.15% or 0.2% carbon dioxide (comparable to less than 0.05% nitrogen) can be used to produce flexible materials and parts with thick cross-sections.

[0312] Although some embodiments have been described in detail above, other modifications are possible. Other embodiments are within the scope of the appended claims.

Claims

1. A method for manufacturing recyclable flexible foam molded products, comprising: Provides recyclable thermoplastic polymers; Supercritical fluid is generated by injecting fluid into the cylinder of a molding equipment under temperature and pressure conditions. The thermoplastic polymer and the supercritical fluid are mixed to produce a single-phase solution; The single-phase solution is injected into a mold of an injection molding machine, wherein the mold is under gas back pressure; The single-phase solution is foamed by controlling the heat and temperature conditions within the mold, wherein foaming the single-phase solution includes: A plurality of bubble-containing pores are generated in the single-phase solution by causing at least a portion of the supercritical fluid to exit from the single-phase solution, wherein each of the bubble-containing pores is surrounded by a pore wall formed of the thermoplastic polymer. Increase the volume of each of the plurality of bubble-containing pores; and The foam wall is broken up by applying ultrasound to break up at least a portion of the foam wall to form an open-cell foam.

2. The method of claim 1, wherein the thermoplastic polymer comprises at least one monomer derived from a depolymerized post-consumer plastic.

3. The method of claim 1, wherein the thermoplastic polymer comprises a polyamide or a polyamide copolymer.

4. The method of claim 1, wherein the thermoplastic polymer comprises a polymer selected from polyether-block-amide (PEBA), PAE, TPA, TPE-A or COPA.

5. The method according to claim 2, wherein the monomer comprises caprolactam.

6. The method according to any one of claims 1-5, wherein the thermoplastic polymer comprises a polyamide thermoplastic elastomer.

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

8. The method according to any one of claims 1-7, further comprising the step of recovering the flexible foam by depolymerizing the flexible foam into one or more monomers.

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

10. The method according to any one of claims 1-9, wherein the ultrasound is applied by an ultrasound instrument, an ultrasound probe, or an ultrasound transducer.

11. The method according to any one of claims 1-9, wherein the ultrasound is applied within the mold.

12. The method according to any one of claims 1-9, wherein the ultrasound is applied via an ultrasonic energy source in the mold.

13. The flexible foam produced by the method according to any one of claims 1-12.

14. The flexible foam according to claim 13, wherein the flexible foam is an open-cell foam.

15. An article comprising a flexible foam according to any one of claims 13 and 14.

16. The article of claim 15, wherein the article of claim 15 comprises a footwear assembly, a seat assembly, a protective equipment assembly, or a water sports accessory.

17. A method for manufacturing biodegradable and / or compostable flexible foam moldings, comprising: Provide biodegradable and / or compostable thermoplastic polymers; Supercritical fluid is generated by injecting fluid into the cylinder of a molding equipment under temperature and pressure conditions. The thermoplastic polymer and the supercritical fluid are mixed to produce a single-phase solution; The single-phase solution is injected into a mold of an injection molding machine, wherein the mold is under gas back pressure; The single-phase solution is foamed by controlling the heat and temperature conditions within the mold, wherein foaming the single-phase solution includes: A plurality of bubble-containing pores are generated in the single-phase solution by causing at least a portion of the supercritical fluid to exit from the single-phase solution, wherein each of the bubble-containing pores is surrounded by a pore wall formed of the thermoplastic polymer. Increase the volume of each of the plurality of bubble-containing pores; and The foam wall is broken up by applying ultrasound to break up at least a portion of the foam wall to form an open-cell foam.

18. The method of claim 17, wherein the thermoplastic polymer comprises a biopolymer.

19. The method of claim 17, wherein the thermoplastic polymer comprises a polymer selected from the group consisting of polylactic acid (PLA), poly(L-lactic acid) (PLLA), poly(butylene adipate-co-terephthalate) (PBAT), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), polycaprolactone (PCL), polybutylene adipate succinate (PBSA), polybutylene adipate (PBA), and thermoplastic starch (TPS).

20. The method of claim 19, wherein the thermoplastic polymer is PBAT.

21. The method of claim 19, wherein the thermoplastic polymer is PHA.

22. The method of claim 19, wherein the thermoplastic polymer is PHB.

23. The method according to any one of claims 17-22, wherein the ultrasound is applied by an ultrasound instrument, an ultrasound probe, or an ultrasound transducer.

24. The method according to any one of claims 17-23, wherein the ultrasound is applied within the mold.

25. The method according to any one of claims 17-23, wherein the ultrasound is applied via an ultrasonic energy source in the mold.

26. The flexible foam produced by the method according to any one of claims 17-25.

27. The flexible foam of claim 26, wherein the flexible foam is an open-cell foam.

28. The flexible foam according to claim 26 or claim 27, wherein the flexible foam is industrially compostable.

29. An article comprising a flexible foam according to any one of claims 26-28.

30. The article of claim 29, wherein the article of claim 29 comprises a footwear assembly, a seat assembly, a protective equipment assembly, or a water sports accessory.

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