Polymer foam article and method of making a polymer foam

Abstract

Molded polymeric foam articles are described as having a novel foam structure. The polymeric foam articles include a continuous polymeric matrix throughout the article in which a plurality of cells are defined, the plurality of cells including a surface region extending 500 microns below a surface of the article. The surface region is further characterized as having compressed cells. The novel foam structure is achieved even when the molded polymeric foam article includes a thickness greater than 2 cm, a volume greater than 1000 cm 3 , or both a volume greater than 1000 cm 3 and a thickness greater than 2 cm. Methods of making the molded polymeric foam articles are also described.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 867,516, filed June 27, 2019, entitled “Method for Molten Foam Injection, Molding of Foamed Parts”. U.S. Provisional Patent Application No. 62 / 867,516 is incorporated herein by reference in its entirety, as fully set forth herein. Background Technology

[0003] Foamed polymer products are widely used in industry due to their highly desirable properties, such as providing the high strength associated with solid polymer articles while simultaneously achieving a reduction in density and thus a reduction in the amount of polymer used to form articles of a given volume. Furthermore, the industry enjoys the benefits of the weight reduction provided by foamed articles compared to their solid counterparts, while still obtaining the strength, toughness, and impact resistance inherent in the polymer itself.

[0004] Therefore, the industry has developed several currently conventional methods for entraining gas into thermoplastic polymers to manufacture such foamed articles. For molding foamed thermoplastic polymer articles using gas, commercial guidelines and industrial practice employ melt-mixing equipment operable to maintain pressure within the equipment while melt-mixing a gas or gas source with the thermoplastic polymer, and further, at a temperature above the melting temperature of the thermoplastic polymer, to limit gas expansion within the equipment. Such methods and equipment are designed to minimize the formation of air bladders or gas pockets, which would otherwise be formed by the expansion of gas in the molten thermoplastic polymer. Thus, when residing within and arranged within a melt-mixing equipment, the thermoplastic polymer may contain a gas source or the gas itself dissolved or dispersed therein, without or substantially without air bladders. A mixture of molten thermoplastic polymer and gas at or above a temperature at which air bladders would form at atmospheric pressure, without or substantially without air bladders, can be referred to as a molten pneumatic mixture. The temperature at which a gas or pneumatogen will form a gas pocket in a melt-aerated mixture at atmospheric pressure can be called the critical temperature. Therefore, melt-mixing equipment known in the art is designed and adapted to manufacture and dispense melt-aerated mixtures. Furthermore, such equipment is suitable for manufacturing melt-aerated mixtures by adding primary gases, latent gases, or potential gases that are released at a characteristic temperature or formed through exothermic or endothermic chemical reactions at a characteristic temperature. The critical temperature of a primary gas, latent gas, or potential gas is the temperature at which the reaction occurs or the gas is released into the thermoplastic polymer. All such materials and methods are well known, and for this purpose, melt-mixing equipment of various designs is commercially available. Commonly used melt-mixing equipment is a single-screw or twin-screw extruder modified to have a pressure chamber at the distal end of the screw to receive the melt-aerated mixture propelled toward the pressure chamber during mixing by operating the screw in a predetermined amount or "injection amount".

[0005] After a predetermined amount or injection volume has been accumulated in the pressurized chamber, the molten aerated mixture is dispensed from the melt mixing equipment and guided through fluid-connected pipes, conduits, etc., into the cavity of a mold to obtain the desired shape. Dispensing is typically performed to maximize the amount of foaming (bladder formation) that occurs in the mold cavity by releasing pressure while the thermoplastic polymer is still molten. The expanded foam in the cavity is then cooled to produce a foamed article. Foamed parts molded using this method are referred to in the art as injection-molded foamed plastic parts. This technique is generally limited to manufacturing parts with a thickness of about 2 cm or less.

[0006] Injection molding, which uses a foaming agent source to induce foam structure in molded parts, can be understood from the recent peer-reviewed journal article by Bociaga et al., “The influence of foaming agent addition, talc filler content, and injection velocity on selected properties, surface state, and structure of polypropylene injection molded parts.” Cellular Polymers 2020, 39(1) 3-30. In this publication, the process conditions typically used for molding a standard injection-molded ISO test bar of 4.1 mm thickness are systematically varied to create 16 different combinations of process settings and formulation variables (concentration of foaming agent source, filler content, injection velocity, injection time, holding time, and holding pressure). The authors teach that controlling the process and formulation produces some variations in terms of the foam structure in the resulting foamed parts, but all variables produce parts with a “surface,” a technical term describing a highly characteristic region of the surface of injection-molded foamed plastic articles that are close to or substantially free of air pockets.

[0007] Inspection of the surface of injection-molded foamed articles, and examination of a region extending approximately 500 micrometers below the surface in any direction, revealed solid thermoplastic regions—that is, regions without or substantially without air pockets. Foamed parts produced by injection molding according to conventional injection molding methods include surface features. Furthermore, depending on the method, equipment, and materials used, the surface layer of most such parts is significantly thicker than 500 μm, and can be 1 mm, 2 mm, 3 mm, or even thicker.

[0008] For manufacturing large foamed components (such as pallets or trolley bodies), the conventional methods described above are insufficient because the large mold cavity causes excessive pressure drop during filling as the molten aerated mixture flows and expands, and air pockets may form during filling, which subsequently merge from the viscous polymer flow or leak. Therefore, in some cases of “structural foam” molding, multiple nozzles are used simultaneously to rapidly fill large or thick mold cavities. In other cases, significant back pressure can be applied within the mold cavity to prevent air pocket formation during filling; the pressure is then released after filling to allow air pockets to form essentially within the mold cavity. Both methods are typically used in a single process.

[0009] However, the aforementioned structural foam molding methods do not solve the problem that actually hinders the industrial development of very large components. It is well known that regions near the surface of a molten material cool faster than its interior, creating a temperature gradient within the material. The cooling rate is slowest at the deepest points within the material. In the case of large mold cavities filled with large amounts of molten polymer or aerated mixtures, the interior regions of the material may cool so slowly that the viscous flow of the thermoplastic allows air pockets to coalesce, forming large, polymer-free bags and disrupting the intended continuous polymer matrix defining such a foam. This effect can be exacerbated by the shrinkage of the polymer volume when the polymer cools below its melt transition temperature. For large foamed components, this effect can even lead to the complete collapse of the foam structure within the component.

[0010] Without a continuous polymer matrix throughout the component, it is impossible to achieve the strength and density reduction associated with foamed articles. Foamed components with large areas or voids lacking polymer compromise the structural integrity of the component, making it unsuitable for its intended use. These serious technical problems limit the industrial application of polymer foams to many other applications that are highly useful and beneficial. Therefore, there is a continuous need for improved methods for manufacturing foamed articles, especially large or thick ones. There is a continuous need to obtain components that always maintain a continuous foam structure. In particular, there is a need to obtain components with a thickness greater than 2 cm that always maintain a continuous foam structure. In industry, there is a continuous need to address these needs using conventional equipment and materials. Summary of the Invention

[0011] This document describes a method for manufacturing molten polymer foam. The method includes: adding a thermoplastic polymer and a foaming agent source to an extruder; heating and mixing the thermoplastic polymer and the foaming agent source under pressure in the extruder to form a molten aerated mixture, wherein the temperature of the molten aerated mixture exceeds the critical temperature of the foaming agent source; collecting a portion of the molten aerated mixture in a collection zone of the extruder; defining an expansion volume in the collection zone to reduce the pressure in the collection zone; allowing an expansion period of a certain time after defining the expansion volume; and dispensing molten polymer foam from the collection zone. In an embodiment, the expansion volume is selected to provide 10% to 300% of the total desired molten foam volume in the collection zone. In an embodiment, the expansion period is 5 seconds to 600 seconds. In an embodiment, the molten aerated mixture is undisturbed or substantially undisturbed during the expansion period.

[0012] In some embodiments, the dispensing is directed to a forming element; in others, the forming element is a die. In some embodiments, a fluid connection exists between the extruder's collection zone and the die. In some embodiments, the dispensing is an unimpeded flow of molten polymer foam. In some embodiments, the dispensing is a linear flow of molten polymer foam.

[0013] In some embodiments, the method further includes cooling the dispensed molten polymer foam to a temperature below the melt transition temperature of the thermoplastic polymer. In some embodiments, for one or more additional materials of the extruder, one or more materials are selected from colorants, stabilizers, brighteners, nucleating agents, fibers, granules, and fillers. In some embodiments, the foaming agent source is a foaming agent and the addition is pressurized. In other embodiments, the foaming agent source includes bicarbonates, polycarboxylic acids or their salts or esters, or mixtures thereof.

[0014] This document also discloses polymer foam articles manufactured using the methods, materials, and apparatus described herein. In one embodiment, the polymer foam article has a foam structure characterized throughout as a continuous polymer matrix defining multiple air pockets. In another embodiment, the surface region of the polymer foam article includes compressible air pockets. In yet another embodiment, the surface region is a region extending 500 micrometers from the surface of the article.

[0015] This document also discloses thermoplastic polymer foam articles having a foam structure throughout their entirety, the foam structure being a continuous polymer matrix defining a plurality of air pockets therein, and further wherein the surface region of the article includes compressible air pockets. In some embodiments, the surface region is a region of the article extending 500 micrometers from its surface. In some embodiments, the article includes compressible air pockets greater than 500 micrometers from its surface. In embodiments, the polymer foam article includes a thickness greater than 2 cm; in other embodiments, the polymer foam article includes a thickness greater than 1000 cm. 3 1000 cm 3 Up to 5000 cm 3 or even greater than 5000 cm 3 The volume; and in yet another embodiment, the polymer foam article comprises a volume greater than 1000 cm³. 3 Volume and thickness greater than 2 cm, 1000 cm 3 Up to 5000 cm 3 The volume and thickness are greater than 2 cm, or greater than 5000 cm. 3 Its volume and thickness are greater than 2 cm.

[0016] In the embodiments, the materials used to manufacture polymer foam articles are not particularly limited and include thermoplastic polymers selected from: polyolefins, polyamides, polyimides, polyesters, polycarbonates, poly(lactic acid), acrylonitrile-butadiene-styrene copolymers, polystyrene, polyurethanes, polyvinyl chloride, tetrafluoroethylene copolymers, polyethersulfones, polyacetals, polyarylamides, polyphenylene ethers, polybutene, polybutadiene, polyacrylates and polymethacrylates, ionomeric polymers, polyether-amide block copolymers, polyaryletherkeytones, polysulfones, polyphenylene sulfide, polyamide-imide copolymers, poly(butylene succinate), cellulose articles, polysaccharides, and copolymers thereof, alloys, blends, and compound blends. In some embodiments, the thermoplastic polymer is a mixed stream of plastic waste. The continuous polymer matrix optionally also includes one or more additional materials selected from: colorants, stabilizers, brighteners, nucleating agents, fibers, particles, and fillers.

[0017] Other purposes and features will be partly apparent and partly indicated below. Attached Figure Description

[0018] Figures 1A to 1B A melt mixing apparatus that can be used to perform the methods described herein is shown.

[0019] Figure 2-1 These are photographic images of parts molded according to the standard foam molding method as described in Example 1. Figure 2-2 These are photographic images of parts molded using the molten-foam injection molding (MFIM) method as described in Example 1. Figure 2-3 and 2-5 These are photographic images of blocks cut from a component manufactured according to the standard foam molding method as described in Example 1. Figure 2-4 and 2-6 These are photographic images of blocks cut from a component manufactured according to the MFIM method as described in Example 1.

[0020] Figure 3A It is a photographic image of the cross-section of component A, which is manufactured according to the standard foam molding method as described in Example 2 and cut into two pieces to show the cross-section. Figure 3B It is a photographic image of the cross-section of component B, which was manufactured according to the MFIM method and cut into two pieces to show the cross-section, as described in Example 2.

[0021] Figure 4A It is a photographic image of the cross-section of component C, which is manufactured according to the MFIM method and cut into two pieces to show the cross-section, as described in Example 2. Figure 4BIt is a photographic image of the cross-section of component D, which is manufactured according to the standard foam molding method as described in Example 2 and cut into two pieces to show the cross-section.

[0022] Figure 5 It is a graph of component density versus decompression volume for different decompression times, including Test B as described in Example 3.

[0023] Figure 6 It is a graph that includes strain versus time for components manufactured in tests A, B and C as described in Example 4.

[0024] Figure 7 Photographs showing different views of components A, B, and C as described in Embodiment 4.

[0025] Figure 8 Photographed image views of cross sections of components A', B', C' and D' as described in Embodiment 4 are shown.

[0026] Figure 9 This is a diagram of the two components as described in Example 5.

[0027] Figure 10 It is an isometric image of a tomographic scan of a first component manufactured according to the MFIM method as described in Example 6.

[0028] Figure 11 As described in Example 6 Figure 10 The image shown is of the cross-sectional plane.

[0029] Figure 12 It is a graph showing the average hole size and hole count of the first component manufactured as described in Example 6, relative to the hole roundness.

[0030] Figure 13 It is a diagram of an X-ray tomographic image of a cross-section of the second (spherical) component as described in Example 6.

[0031] Figure 14 It is a graph showing the average hole size and hole count of the second (spherical) component manufactured as described in Example 6, relative to the hole roundness.

[0032] Figure 15 The image shows a micrograph of the fracture surface of a fractured three-inch diameter composite sphere manufactured according to the MFIM method as described in Example 7.

[0033] Figure 16 The image shows a microscopic photograph of the fracture surface of a fractured three-inch diameter composite sphere manufactured according to the MFIM method as described in Example 7.

[0034] Figure 17 The image shows a microscopic photograph of the fracture surface of a fractured three-inch diameter composite sphere manufactured according to the MFIM method as described in Example 7.

[0035] Figure 18 The image shows a microscopic photograph of the fracture surface of a fractured three-inch diameter composite sphere manufactured according to the MFIM method as described in Example 7.

[0036] Figure 19 Microscopic images of cross sections of ISO rod components manufactured according to standard foam molding processes 10, 11, 14 and 15 as described in Example 8 are shown.

[0037] Figure 20 Microscopic images of cross sections of ISO bar components manufactured according to MFIM processes 9, 10, 15, and 16 as described in Example 8 are shown.

[0038] Figure 21 Micrographs of cross sections of ISO bar components manufactured according to MFIM method 9 as described in Example 8 are shown, as well as stress-strain diagrams of repeating components manufactured according to MFIM method 9.

[0039] Figure 22 This includes micrographs of cross sections of ISO rod components manufactured according to standard foam molding operation 10 as described in Example 8, and stress-strain diagrams of repeating components manufactured according to standard foam molding operation 10.

[0040] Figure 23 Includes two images from X-ray tomography of an ISO rod component manufactured according to the standard foam molding process as described in Example 8.

[0041] Figure 24 This includes two images from X-ray tomography of an ISO rod component manufactured according to the MFIM method as described in Example 8.

[0042] Figure 25 These are X-ray scan images of a large tensile bar component manufactured according to the MFIM method as described in Example 9.

[0043] Figure 26 This includes the cross-sections of eight large tensile bar components manufactured according to the MFIM method, as described in Example 9.

[0044] Figure 27 The image is an X-ray tomographic image of a large tensile bar component manufactured according to the MFIM method as described in Example 9.

[0045] Figure 28 This includes a series of X-ray tomographic images at different depths within a tensile rod component manufactured according to the MFIM method as described in Example 10, and a series of images at different depths within a tensile rod component manufactured according to the standard foam molding method.

[0046] Figure 29 It includes a graph showing the hole count versus depth for a stretching bar component manufactured according to the MFIM method as described in Example 10, and a graph showing the hole count versus depth for a stretching bar component manufactured according to the standard foam molding method.

[0047] Figure 30 It includes diagrams of hole roundness versus depth for a drawn bar component manufactured according to the MFIM method as described in Example 10, and diagrams of hole roundness versus depth for a drawn bar component manufactured according to the standard foam molding method.

[0048] Figure 31 It includes diagrams of hole dimensions versus depth for a stretching rod component manufactured according to the MFIM method as described in Example 10, and diagrams of hole dimensions versus depth for a stretching rod component manufactured according to the standard foam molding method.

[0049] Figure 32 This is a photograph of sample 20 manufactured according to the reverse MFIM method as described in Example 12.

[0050] Figure 33 This is a photograph of sample 10 manufactured according to the MFIM method as described in Example 12.

[0051] Figure 34 This is a photograph showing a cross-section of sample 20 manufactured according to the reverse MFIM method as described in Example 12.

[0052] Figure 35 This is a photograph showing a cross-section of sample 10 manufactured according to the MFIM method as described in Example 12.

[0053] Figure 36 This is a graph showing the hole count versus depth (distance from the surface) for samples 10 (MFIM) and 20 (reverse MFIM) as described in Example 12.

[0054] Figure 37 This is a graph showing the hole size versus depth (distance from the surface) of samples 10 (MFIM) and 20 (reverse MFIM) as described in Example 12.

[0055] Figure 38 It is a graph including the average stress versus strain graph of sample 10 (MFIM) from the compression modulus measurement as described in Example 12, and a graph of sample 20 (reverse MFIM).

[0056] Figure 39 It is a graph including the average stress versus strain graph of sample 10 (MFIM) from flexural modulus measurement as described in Example 12, and a graph of sample 20 (reverse MFIM).

[0057] Figure 40 It is a graph of stress versus strain from compression modulus measurements, made from three metallocene polyethylene (mPE) materials of different densities and manufactured according to the MFIM method, as described in Example 14.

[0058] Figure 41 A mold configuration that can be used to perform the methods described herein is shown.

[0059] Throughout the accompanying drawings, corresponding reference numerals indicate the corresponding parts. Detailed Implementation

[0060] While this disclosure provides reference to preferred embodiments, those skilled in the art will recognize that changes in form and detail may be made without departing from the spirit and scope of the invention. Several embodiments will be described in detail with reference to the accompanying drawings, which are referenced throughout several views, and the same reference numerals denote the same parts and components. Reference to the various embodiments does not limit the scope of the appended claims. Furthermore, any examples set forth in this specification are not intended to be limiting and merely illustrate some of the many possible embodiments of the appended claims.

[0061] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, this document (including definitions) shall prevail. Preferred methods and materials are described below, but similar or equivalent methods and materials may be used in the practice or testing of the invention. All publications, patent applications, patents and other references mentioned herein are incorporated herein by reference in their entirety. The materials, methods and examples disclosed herein are illustrative only and are not intended to be limiting.

[0062] As used herein, “polymer matrix” (including “continuous polymer matrix”, “thermoplastic polymer matrix”, “molten polymer matrix” and similar terms) means a continuous solid or molten thermoplastic polymer phase or a defined amount of solid or molten thermoplastic polymer defining a continuous phase.

[0063] As used herein, "melt mixture" means a molten thermoplastic polymer or a mixture of molten thermoplastic polymers, optionally comprising one or more additional materials mixed with the molten thermoplastic polymer or a mixture thereof.

[0064] As used herein, "melt-aerated mixture" means a mixture of a thermoplastic polymer and a gas-generating agent source, wherein the polymer is at a temperature above its melting temperature and the temperature of the mixture exceeds the critical temperature of the gas-generating agent source; furthermore, the mixture is characterized by the absence or substantial absence of air pockets. Melt-aerated mixtures exist at pressures sufficient to prevent, or substantially prevent, air pocket formation, or to dissolve or disperse the gas-generating agent source as a gas or supercritical liquid within the thermoplastic polymer. The terms "substantially prevents air pocket formation," "substantially absent air pockets," and similar terms for melt-aerated mixtures mean that while pressure conditions can be used to prevent air pocket formation in the melt mixture, defects in the processing equipment, component wear, etc., may lead to unintentional pressure losses that do not affect the overall composition when obtaining and maintaining a pressurized melt mixture.

[0065] As used herein, “foam,” “polymer foam,” “thermoplastic polymer foam,” “molten foam,” “molten polymer foam,” and similar terms generally refer to a continuous polymer matrix in which multiple air pockets, which are dispersed as a discontinuous phase, are defined.

[0066] As used herein, the term "airbag" refers to a discrete void defined and surrounded by a continuous thermoplastic polymer matrix.

[0067] As used herein, the term "gas generator" refers to a gaseous compound that can define an air pocket within a molten thermoplastic polymer matrix.

[0068] As used in this article, the term "critical temperature" refers to the temperature at which a gas-generating agent source produces a gas-generating agent at atmospheric pressure.

[0069] As used herein, the term "effervescent source" refers to a latent effervescent agent, potential effervescent agent, or nascent effervescent agent that is added to or present in a thermoplastic polymer matrix, for example, dissolved in the matrix and / or present therein as a supercritical fluid; or in the form of an organic compound that generates an effervescent agent through a chemical reaction; or a combination of these; or wherein the effervescent source is an effervescent agent, becomes an effervescent agent, or generates an effervescent agent at the critical temperature characteristic of the effervescent source.

[0070] As used herein, the terms “comprising,” “including,” “having / has,” “may,” “containing,” and variations thereof are intended as open-ended transitional phrases, terms, or words that do not exclude the possibility of additional actions or structures. Unless the context clearly indicates otherwise, the singular form “a / an / the” includes plural references. Whether explicitly stated or not, this disclosure also considers “comprising” the embodiments or elements presented herein, “consisting of” the embodiments or elements presented herein, and other embodiments “substantially constitute” the embodiments or elements presented herein.

[0071] As used herein, the terms “optional” or “optionally” mean that an event or situation described below may occur but does not have to occur, and that the description includes both the scenario in which the event or situation occurs and the scenario in which the event or situation does not occur.

[0072] As used herein, the term "about," used to describe the amount, concentration, volume, process temperature, process time, yield, flow rate, pressure, and similar values ​​and ranges of components in a composition, refers to variations in numerical quantities that may occur, for example, through typical measurement and processing steps used to manufacture the compound, composition, concentrate, or formulation; through unintentional errors in these steps; through differences in the manufacture, origin, or purity of the starting materials or components used to carry out these methods; and similar similar considerations. The term "about" also covers amounts that differ due to aging of formulations having a particular initial concentration or mixture, and amounts that differ due to mixing or processing formulations having a particular initial concentration or mixture. In cases modified by the term "about," the appended claims include equivalents of these amounts. Furthermore, unless specifically limited by the context, when "about" is used to describe a range of values, such as "about 1 to 5," the statement means "1 to 5" and "about 1 to about 5" and "1 to about 5" and "about 1 to 5."

[0073] As used herein, the term “substantially” means “consistent primarily of” as interpreted in U.S. patent law, and includes “consistent of” as interpreted in U.S. patent law. For example, a composition that is “substantially free” of a particular compound or material may be free of that compound or material, or may have a small amount of that compound or material present, for example, due to unintentional contamination, side reactions, or incomplete purification. “Small amount” can be trace, immeasurable, non-interfering with values ​​or properties, or some other amount as provided in the context. A composition that is “substantially only” having the components of the provided list may consist only of those components, or have trace amounts of some other components present, or have one or more additional components that do not materially affect the properties of the composition. Furthermore, “substantially” as used in describing embodiments of this disclosure, such as the type or amount, property, measurable amount, method, value, or range of an ingredient in a composition, means a variation that does not affect the overall listed composition, property, amount, method, value, or range in a manner that negates the intended composition, property, amount, value, or range. Where modified by the term "substantially", the appended claims include equivalents according to that definition.

[0074] As used herein, any enumerated range of values ​​considers all values ​​within that range and should be interpreted as supporting any claim that enumerates a subrange having endpoints that are real values ​​within the enumerated range. As an illustrative example of assumption, the disclosure of ranges 1 to 5 in this specification should be considered to support claims of any of the following ranges: 1 to 5; 1 to 4; 1 to 3; 1 to 2; 2 to 5; 2 to 4; 2 to 3; 3 to 5; 3 to 4; and 4 to 5.

[0075] In the embodiments disclosed herein, a method for extruding molten polymer foam comprises, primarily, or comprises: adding a thermoplastic polymer and a foaming agent source to an inlet located at a first end of an extruder; heating and mixing the thermoplastic polymer and the foaming agent source in the extruder to form a molten aerated mixture, wherein the temperature of the molten aerated mixture exceeds the critical temperature of the foaming agent source; collecting a portion of the molten aerated mixture in a barrel region located adjacent to a second end of the extruder; forming an expanded volume in the barrel region, wherein the formation causes a pressure drop in the barrel region; allowing a certain time to pass after the pressure drop; and dispensing the molten polymer foam from the extruder.

[0076] In embodiments, an extruder is any machine designed and adapted to melt, mix, and dispense thermoplastic polymers and mixtures thereof, optionally with one or more other materials (e.g., fillers, nucleating agents, diluents, stabilizers, brighteners, etc.); and furthermore, the extruder includes a collection zone for collecting large quantities of the mixed molten material, and is also capable of forming an expanded volume in the collection zone accompanied by a pressure drop. Extruders are industrially known and widely used for melting, mixing, and controlling molten thermoplastic polymers. In embodiments, an extruder is adapted and designed for melting, mixing, and dispensing mixtures of thermoplastic polymers and a source of a foaming agent. Such an extruder is suitable for obtaining molten aerated mixtures at pressures sufficient to prevent or substantially prevent the formation of air pockets in the molten aerated mixture.

[0077] In an embodiment, the extruder used to perform this method includes an internal volume, referred to in the art as the "barrel" of the extruder, designed and adapted to receive a solid thermoplastic polymer, and also adapted to melt and mix the solid thermoplastic polymer. In an embodiment, the extruder defines an internal volume designed to receive a solid thermoplastic polymer and a foaming agent or foaming agent source, and also for melting at least the polymer and for mixing the foaming agent or foaming agent source with the molten polymer to obtain a molten aerated mixture. In an embodiment, the extruder further includes a collection zone for collecting a large quantity of the molten aerated mixture material. In an embodiment, the extruder further includes means for forming an expanded volume in the collection zone accompanied by a pressure drop.

[0078] In one embodiment, the extruder is an injection molding machine. In another embodiment, the extruder is a SODICK™ molding machine sold by Plustech Inc. of Schaumburg, Illinois. In yet another embodiment, the extruder includes one or two members, referred to in the art as “screws”, arranged within an internal volume (referred to in the art as a “barrel”). In one embodiment, the screw generally has a cylindrical shape and includes one or more protruding threaded members referred to as “flight”. In some embodiments, the extruder is a single-screw extruder defined as including a screw movably arranged within the barrel for rotating the barrel about its axis, for moving the barrel laterally along its axis, or for a combination of rotational and lateral movement. In other embodiments, the extruder is a twin-screw extruder, defined as comprising two screws movably arranged within a barrel in a substantially parallel and adjacent relationship relative to each other. Furthermore, each screw is movably arranged within the barrel for rotating the barrel about its axis, for moving the barrel laterally along its axis, or for a combination of rotational and lateral movement. The screws of the twin-screw extruder are further arranged such that the action of the screws when rotating in an anti-rotational manner defines a designed mixing and transport pattern of the molten thermoplastic polymer disposed within the barrel.

[0079] In embodiments, the extruder is also adapted and designed to receive solid thermoplastic polymers. In embodiments, the barrel of the extruder is also adapted and designed to receive solid thermoplastic polymers via inlets positioned near a first end of the extruder and adapted to add solid thermoplastic polymers into the barrel. The solid thermoplastic polymer is added to the inlets in any suitable form, such as beads, pellets, powders, strips, or blocks (all forms familiar to those skilled in the art). In embodiments, the extruder includes a second, third, or even a fourth or higher number of inlets designed and adapted to add or introduce one or more additional materials (including one or more solid, liquid, or gaseous materials) into the internal volume of the extruder, and is also adapted to mix one or more additional materials with the thermoplastic polymer. The internal volume of the extruder is adapted to receive, contain, and melt the thermoplastic polymer and optionally one or more additional materials; and to subject the thermoplastic polymer and optionally one or more additional materials to heating, shearing, and mixing to form a molten mixture, while conveying the molten mixture in a direction generally traveling from its first end to its second end. In embodiments where the extruder is a single-screw extruder or a twin-screw extruder, shearing, mixing, and transport are achieved by rotating the screw or by rotating the two screws in opposite directions.

[0080] In embodiments, the internal volume of the extruder, or a portion thereof, is surrounded or partially surrounded by one or more heat sources. In several embodiments, heat sources suitably suited for heating the internal volume of the extruder include heated water jackets, heated oil jackets, resistance heaters, open flames or jacketed flames, or other heat sources. The heat sources are operable to raise the temperature within the internal volume of the extruder. The temperature is suitably selected by the operator for melting the thermoplastic polymer and / or maintaining a desired temperature within a portion of the internal volume of the extruder. In embodiments, the extruder is suitable to include more than one heat source, wherein the heat sources are independently operable to allow a technician to provide a series of temperature “zones” within the internal volume. Additional temperature zones may be included in some extruders associated with adding one or more materials to the extruder inlet or dispensing more materials from the extruder outlet. In embodiments, the temperatures within one or more temperature zones are set by the operator for increased control and optimization of the melting, mixing, shearing, and transport of the thermoplastic polymer and optionally one or more other materials.

[0081] Extruders are conventionally designed and adapted to apply and maintain pressure within the internal volume of the extruder during the heating, mixing, and transport of the molten mixture. In embodiments, the extruder is designed and adapted to apply and maintain a first pressure within the internal volume or barrel during the heating, mixing, and transport of the molten aerated mixture. In embodiments, the pressure within the barrel during the heating, mixing, and transport of the molten aerated mixture is sufficient to prevent or substantially prevent leakage of the molten aerated mixture from the barrel. In embodiments, the pressure within the barrel is sufficient to prevent the formation of air pockets in the molten aerated mixture when the temperature within the barrel exceeds the critical temperature of the gas-generating agent source. In embodiments, the pressure within the barrel is substantially sufficient to prevent the formation of air pockets in the molten aerated mixture when the temperature within the barrel exceeds the critical temperature of the gas-generating agent source. In such embodiments described in this paragraph, "substantially" means unintentional leakage of material or unintentional loss of pressure from the barrel due to the manufacture, aging, or use of the extruder and / or screw, as is well known to those skilled in the art. Furthermore, in such an implementation, "substantially" in the context of "sufficient to prevent the formation of air pockets in the molten aerated mixture" means that while maintaining pressure on the molten aerated mixture, a small percentage (e.g., up to 10%) of the gas-generating agent may unintentionally form air pockets; however, the operator's goal is to maintain sufficient pressure to prevent air pocket formation.

[0082] In one embodiment, the extruder barrel includes a collection zone for collecting a quantity of molten mixture in preparation for dispensing the molten mixture from the extruder. The quality of the molten mixture is selected by the user. In another embodiment, the molten mixture is a molten aerated mixture. In such an embodiment, the technical term used to describe the collection of a large quantity of molten aerated mixture in the collection zone of the extruder barrel is called "building up the injection." As those skilled in the art of injection molding will understand, to build up the injection, a large quantity of molten aerated mixture is collected by: conveying the molten aerated mixture from a first end of the extruder toward a second end—that is, toward and into the collection zone—via the rotation of one or more screws (or additional mixing elements), and by further accumulating the molten aerated mixture in the collection zone until the desired quantity of molten aerated mixture is collected and disposed in the collection zone of the barrel. The collection zone is located between the second end of the extruder and one or more screws and is in pressurized communication with the rest of the barrel.

[0083] In conventional injection molding for forming thermoplastic polymer foams, a molten aerated mixture is conveyed toward and into a collection zone via the rotation of one or more screws (or additional mixing elements), where a large quantity of the molten aerated mixture or "filler" is collected or "built up." When a selected mass of the molten aerated mixture is arranged within the collection zone, it is referred to as filling up. Those skilled in the art will understand that the foregoing description of the melt mixing equipment (e.g., the mechanical components and features of an extruder or other melt mixing equipment) and, furthermore, the foregoing description of the methods for manufacturing and collecting the molten aerated mixture into filler, are consistent with conventional equipment and methods for manufacturing and filling molten aerated mixtures using such equipment.

[0084] According to these known methods and apparatuses, the formation of air pockets in the injection of the molten aerated mixture is generally prevented or substantially prevented when present in the barrel (including during mixing, heating, conveying, and collection), and further when arranged within a collection zone. Conventionally, when collecting the desired injection in the collection zone, a gate or valve located between the collection zone and the outlet located at the second end of the extruder is opened, thereby providing a fluid connection from the barrel to the outlet for dispensing the injection from the extruder. In some embodiments, when the gate or valve is opened, a mechanical plunger is applied to push the molten aerated mixture from the barrel and through the outlet. In embodiments, one or more screws are suitably employed for lateral movement in the direction toward the second end of the extruder, which in turn pushes the molten aerated mixture from the collection zone of the barrel and through the outlet.

[0085] We have found that, after the injection of the molten aerated mixture into the collection zone of the extruder, it is advantageous to form, provide, or define an expansion volume in the collection zone of the extruder, wherein a pressure drop is defined accompanying the expansion; allowing a period of time, referred to herein as the expansion period, to pass after the definition; and dispensing the injection from the extruder after the expansion period. In such embodiments, the injection is dispensed in the form of a molten polymer foam. In embodiments, the expansion volume is defined by the injection disposed adjacent to the collection zone of the extruder. In embodiments, the injection is not mixed or subjected to applied shear or stretching while the expansion volume is being defined. In embodiments, the injection is not transported during the expansion period. In embodiments, the injection is allowed to remain or reside undisturbed or substantially undisturbed in the collection zone during the expansion period. In any of the foregoing embodiments, the injection may be heated during the expansion period; however, in some embodiments, no heat is added to the injection during the expansion period.

[0086] After the expansion period, molten polymer foam can be dispensed from the second end of the extruder. The molten polymer foam comprises multiple air pockets. Without being theoretically limited, we assume that air pockets are formed when the molten aerated mixture is subjected to an expanded volume accompanied by a pressure drop (secondary pressure). Based on known principles of physics, air pocket formation is likely caused by the limitation of the expanded volume in the collection zone of the barrel and the accompanying pressure drop, as well as the expansion period in which air pockets are formed by the action of a gas-generating agent. In some embodiments, the limitation of the expanded volume after injection is attributed to the superior properties of the dispensed molten polymer foam. In other words, we find that forming a molten aerated mixture under pressure and then reducing the pressure before dispensing the mixture (e.g., into a mold cavity) and accompanied by the formation of a defined volume produces molten polymer foam that, upon cooling, provides a solidified polymer foam article with unexpected and highly beneficial physical properties.

[0087] We have found significant technical benefits in molten polymer foam dispensed from an extruder according to the aforementioned method. These benefits are observed in solidified polymer foam produced by cooling the molten polymer foam to a temperature below the melt transition temperature of the thermoplastic polymer. Articles manufactured using molten polymer foam dispensed from an extruder after the expansion period exhibit structures that differ both macroscopically and microscopically from polymer foams manufactured by conventional methods; and demonstrate superior properties, for example, suitable for structural components. Polymer foam articles manufactured using the methods, equipment, and materials described herein are characterized by a continuous thermoplastic matrix throughout the entire article and multiple air pockets distributed throughout the polymer foam article. This characteristic is met for articles with a thickness greater than 2 cm and a volume greater than 1000 cm³. 3 Or except for volumes greater than 1000 cm³ 3 At 1000 cm3 Up to 5000 cm 3 Between, or even greater than 5000 cm 3 In addition, articles with a thickness greater than 2 cm; and furthermore, including those with a thickness greater than 1000 cm. 3 Volume and thickness greater than 2 cm, 1000 cm 3 Up to 5000 cm 3 The volume and thickness are greater than 2 cm, or greater than 5000 cm. 3 Products with a volume greater than 2 cm in thickness.

[0088] In an embodiment, defining the expansion volume in a single-screw extruder is suitably achieved by laterally moving the screw toward the first end of the extruder and away from the collection area of ​​the extruder's feed collection region. In an embodiment, defining the expansion volume in a twin-screw extruder is achieved by laterally moving both screws toward the first end of the extruder and away from the collection area of ​​the extruder's feed collection region. The lateral movement is optionally accompanied by rotation of one or more screws. That is, one or both screws may be rotated during the lateral movement, or rotation may be stopped during the lateral movement. It will be understood that defining the expansion volume by the lateral movement of one or two screws is advantageously selected by the extruder operator to provide a selected expansion volume. That is, the distance of the lateral movement of one or more screws is suitably selected by the operator to define the selected expansion volume.

[0089] Therefore, in the implementation scheme, the operator adds sufficient volume to the collection area to accommodate the total expected molten polymer foam volume, or some percentage thereof, with the expansion volume as the target. The total expected molten polymer foam volume of the injection can be calculated based on the amount of thermoplastic polymer and gas-generating agent source added to build the injection, plus any other materials, further assuming that all gas-generating agent sources will help form air pockets in the molten polymer foam to be obtained. Those skilled in the art will understand that industrially available gas-generating agent sources provide information suitable for calculating the total expected molten polymer foam volume based on the amount of gas-generating agent source added to manufacture the injection, as well as other processing conditions. In the implementation scheme, the expansion volume is the difference between the injection volume and the expected molten polymer foam volume. In the implementation scheme, the expansion volume is targeted to provide 10% to 100% of the total expected molten polymer foam volume in the collection area, for example, 15% to 100%, or 20% to 100%, or 25% to 100%, or 30% to 100%, or 35% to 100%, or 40% to 100%, or 45% to 100%, or 50% to 100%, or 55% to 100%, or 60% to 100%, or 65% to 100%, or 70% to 100%, or 75% to 100%, or 80% to 100%, or 85% to 100%, or 90% to 100%, or 10% to 95%, or 10% to 90%, or 10% to 85%, or 10% to 80%, or 10%. Up to 75%, or 10% to 70%, or 10% to 65%, or 10% to 60%, or 10% to 55%, or 10% to 50%, or 10% to 45%, or 10% to 40%, or 10% to 35%, or 10% to 30%, or 10% to 25%, or 10% to 20%, or 10% to 15%, or 15% to 20%, or 20% to 25%, or 25% to 30%, or 30% to 35%, or 35% to 40%, or 40% to 45%, or 45% to 50%, or 50% to 55%, or 55% to 60%, or 60% to 65%, or 65% to 70%, or 70% to 75%, or 75% to 80%, or 80% to 85%, or 85% to 90%, or 90% to 95%, or 95% to 100%. In some other embodiments, the expansion volume is 100% to 300% of the difference between the injection volume and the expected molten polymer foam volume, for example, 100% to 105%, or 100% to 110%, or 100% to 115%, or 100% to 120%, or 105% to 110%, or 110% to 115%, or 115% to 120%, or 120% to 125%, or 120% to 150%, or 150% to 200%, or 200% to 250%, or 250% to 300%.

[0090] After the expansion volume is defined, a period of time is allowed to pass or elapse before the molten polymer foam is dispensed from the extruder. In some embodiments, during the expansion period, no mixing, conveying, shearing, or other physical operations or additional volume changes are performed in the collection zone. Instead, in such embodiments, the feedstock is allowed to stand in the collection zone during the expansion period. At the end of the expansion period, the molten polymer foam is dispensed from the extruder outlet. In some embodiments, the molten polymer foam is dispensed into a die cavity and cooled to a temperature below the melt transition temperature of the thermoplastic polymer to obtain a solidified polymer foam article.

[0091] In the implementation scheme, the expansion period is selected by the operator from approximately 5 to 600 seconds, depending on the sample quality, the source and amount of the gas-generating agent, and any other materials present in the infill. In the implementation scheme, the expansion period is 5 to 600 seconds, or 5 to 500 seconds, or 5 to 400 seconds, or 5 to 300 seconds, or 20 to 600 seconds, or 20 to 500 seconds, or 20 to 400 seconds, or 20 to 300 seconds, or 10 to 200 seconds, or 20 to 200 seconds, or 30 to 200 seconds, or 40 to 200 seconds, or 50 to 200 seconds, or 5 to 190 seconds, or 5 to 180 seconds, or... 5 to 170 seconds, or 5 to 160 seconds, or 5 to 150 seconds, or 5 to 140 seconds, or 5 to 130 seconds, or 5 to 120 seconds, or 5 to 110 seconds, or 5 to 100 seconds, or 5 to 90 seconds, or 5 to 80 seconds, or 5 to 70 seconds, or 5 to 60 seconds, or 5 to 50 seconds, or 5 to 40 seconds, or 5 to 30 seconds, or 5 to 20 seconds, or 5 to 10 seconds, or 10 to 15 seconds, or 15 seconds Up to 20 seconds, or 20 to 25 seconds, or 25 to 30 seconds, or 30 to 35 seconds, or 35 to 40 seconds, or 40 to 45 seconds, or 45 to 50 seconds, or 50 to 55 seconds, or 55 to 60 seconds, or 60 to 70 seconds, or 70 to 80 seconds, or 80 to 90 seconds, or 90 to 100 seconds, or 100 to 110 seconds, or 110 to 120 seconds, or 120 to 130 seconds, or 130 to 140 seconds 0 seconds, or 140 to 150 seconds, or 150 to 160 seconds, or 160 to 170 seconds, or 170 to 180 seconds, or 180 to 190 seconds, or 190 to 200 seconds, or 200 to 250 seconds, 250 to 300 seconds, or 300 to 350 seconds, or 350 to 400 seconds, or 400 to 450 seconds, or 450 to 500 seconds, or 500 to 550 seconds, or 550 to 600 seconds.

[0092] When molten polymer foam is cooled to a temperature below the melt temperature of the thermoplastic polymer to obtain solidified polymer foam, the aforementioned method causes the formation of molten polymer foam, as described in the following sections, which yields several significant technical benefits. Polymer foam articles are typically characterized as integral articles having a continuous polymer matrix defining a plurality of air pockets dispersed throughout the article. In embodiments, polymer foam articles are particularly characterized as having a continuous polymer matrix defining a plurality of air pockets dispersed in a surface region of the article, wherein the surface region is defined as the area between the article's surface (polymer foam-air interface) and a distance of 500 micrometers from the interior of the surface.

[0093] Figure 1A A representative implementation of an apparatus that is effectively used to perform the above-described method is shown in the figure. Figure 1A This is a schematic diagram of an exemplary single-screw injection molding apparatus 20 according to embodiments disclosed herein, which can be used to perform the methods described herein to manufacture molten polymer foam and polymer foam articles also disclosed herein. Figure 1A As shown, the injection molding system 20 includes a barrel 21 attached to a motor or drive section 24 and a mold section 26. The barrel 21 includes a first end 21a, a second end 21b, and defines a hollow internal barrel portion 22. The barrel portion 22 also defines a nozzle 36 adjacent to the second end 21b of the barrel. A screw 30 is disposed within the barrel portion 22 and includes a screw tip portion 34. The screw 30 is operatively connected to the motor section 24 for rotation about its central axis; or for lateral movement indicated by arrow Z. The lateral movement of the screw 30 can be in a direction generally from the first end 21a of the barrel toward the second end 21b of the barrel; or in a direction from the second end 21b of the barrel toward the first end 21a of the barrel. The lateral movement of the screw 30 in either direction may optionally be further combined with rotational movement. The screw 30 also includes one or more threads 31, which are mixing elements for mixing and transporting material present in the barrel portion 22, typically from the first end 21a of the barrel towards the second end 21b of the barrel. Through the screw threads 31 within the barrel 21 and also through the location of the check valve 32, the screw 30 is arranged within the barrel portion 22 in a pressurized-sealing relationship, allowing a pressure exceeding atmospheric pressure to be maintained within the barrel portion 22. A shut-off valve 37 is connected to the barrel 21 near the second end 21b and is operable to control a fluid connection, a pressurized connection, or both between the nozzle 36 and the mold section 26. The check valve 32, arranged within the barrel portion 22 and surrounding the screw 30, is operable to prevent back pressure from pushing material residing in the barrel portion 22 towards the first end 21a of the barrel, and thus provides a pressurized-sealing, fluid-sealing, or pressurized-fluid-sealing relationship between the shut-off valve 37 and the check valve 32.

[0094] In addition regarding Figure 1A The mold section 26 includes two mold portions 38 as shown. The mold portions 38 are removably engaged together to define a cavity 39. In some embodiments, one or more of the mold portions 38 are movable to allow the release of solidified polymer foam articles therefrom. In some embodiments, the mold portions 38 are in contact with each other; in other embodiments, the mold portions 28 are spaced apart by a gap.

[0095] In the implementation plan, using such as Figures 1A to 1B The apparatus of system 20 shown herein appropriately performs the methods disclosed herein. Figure 1AAs indicated by arrow A, a mixture 42A comprising a selected amount of thermoplastic polymer, a gas-generating agent source, and optionally one or more other materials is added to the barrel portion 22 through inlet 28 by a selected mass. In some embodiments, the gas-generating agent source is a gas-generating agent, and inlet 28 or another inlet (not shown) is a gas inlet pressurized to the barrel portion 22; and the gas-generating agent is added to the gas inlet at a selected pressure while non-gaseous materials are added to inlet 28. During the addition of mixture 42A to the barrel portion 22 through inlet 28, a motor 24 is operable to rotate a screw 30. The rotation of the screw 30 transports and mixes mixture 42A to the screw tip 34. A heat source (not shown) is suitably employed to add heat to the mixture 42A within the barrel portion 22. The motor 24 rotates the screw 30 to transport the mixture 42A present in the barrel portion 22 in a direction generally traveling from the first end 21a to the second end 21b of the barrel 21 until it reaches the screw tip 34. Furthermore, the rotation of the screw 30 during transport provides mixing of the mixture 42A. As the mixture 42A is transported and mixed by the rotation of the screw 30, a heating element or heating band (not shown) adjacent to the barrel section 22 is operated to heat the mixture 42A. Multiple heating zones may be present adjacent to the barrel section 22 to vary the temperature inside the barrel section 22 between the first end 21a and the second end 21b of the barrel 21. During transport, the screw 30, which rotates within the barrel section 22, is operable to mix the mixture 42A; and heat is added to the mixture as it is transported, thereby raising the temperature of the mixture above the melting point of the thermoplastic polymer at least before reaching the second end 21b of the barrel 21 to transform the mixture 42A into a molten aerated mixture 42B. Furthermore, the screw 30 is arranged within the barrel section 22, and the thread 31 contacts the barrel 21 during the rotation of the screw 30; combined with the check valve 32, the shut-off valve 37 in the closed position, or both, a pressurized seal is provided within the barrel section 22, thereby allowing the molten gas-filled mixture 42B to exist within the barrel section 22 at pressures exceeding atmospheric pressure. Even if the gas-generating agent source is above its critical temperature, the pressure within the barrel section 22 is sufficient to prevent or substantially prevent gasbag formation.

[0096] Furthermore, the rotation of the operating screw 30 conveys the pressurized molten aerated mixture toward the screw tip 34, thereby conveying or accumulating a selected mass of the pressurized molten aerated mixture 42B within the collection zone 40 of the barrel section 22. The collection zone 40 is defined as follows: Figure 1AThe region within the volume extending between the check valve 32 and the shut-off valve 37 of the cylindrical portion 22 is further defined as the region of the cylindrical portion 22 located along the X distance of the cylindrical portion 21. A selected mass or "injection volume" of pressurized molten aerated mixture 42B is collected or accumulated in the collection zone 40 of the cylindrical portion 22. The pressure within the collection zone 40 is sufficient to prevent or substantially prevent the formation of air pockets in the molten aerated mixture. In an embodiment, the injection substantially fills the collection zone 40.

[0097] The preparation of the molten aerated mixture 42B is achieved using conventional methods familiar to those skilled in the art. Conventional and known variations in the methods and materials used to prepare the injection molding compound are covered by the methods described herein. After preparation, the compound can be subjected to the methods disclosed herein to obtain all the technical benefits disclosed herein regarding the formation of polymer foams and polymer foam articles. For example, to form the compound, the MUCELL® high-pressure process method, employed, for example, by Trexel Inc. of Wilmington, Massachusetts, is suitably used, in which a gas-generating agent source is added directly to the extruder under pressure mixing to prevent or substantially prevent air pocket formation, followed by compound collection. Various patented technologies and trade publications also describe specialized melt mixing and conveying designs for obtaining the molten aerated mixture and forming the compound, such as specialized screw designs for mixing and recirculation modes; any of these can be effectively combined with the aforementioned compound forming methods and equipment to form the compound as described herein and collect the compound under pressure in the collection zone of the melt mixing equipment.

[0098] After the injection material is formed and collected in the collection zone, an expansion volume is defined therein, and the expansion is accompanied by a decrease in pressure in the collection zone and near the injection material. Therefore, Figure 1A A melt-aerated mixture apparatus 20 is depicted, wherein a screw 30 is positioned to collect the infeed in a collection zone 40. The infeed comprises a selected mass of melt-aerated mixture 42B and is disposed under pressure within the collection zone 40. Further relative to this process stage... Figure 1A , Figure 1B A device 20 is depicted in which a screw 30 is positioned to define an expansion volume 44 within a collection area 40. Slightly more detailed... Figure 1B The image shows the screw 30 in the position created by the lateral movement of the screw 30 toward the first end 21a of the cylinder; that is, the screw 30 in Figure 1B relative to Figure 1ARetraction. The retraction of screw 30 from collection zone 40 and the resulting partial displacement define the expansion volume 44 within collection zone 40 and also cause a pressure drop within collection zone 40. In some embodiments, rotation of screw 30 stops before retraction. In some embodiments, rotation of screw 30 stops during retraction or after retraction is complete. The retraction distance of screw 30 (i.e., the distance by which screw 30 moves laterally toward the first end 21a of the cylinder) is selected by the operator to provide a suitable expansion volume 44.

[0099] exist Figure 1B In some embodiments, the operator selects the expansion volume 44 to provide a collection zone 40 with a total volume matching the total expected molten polymer foam volume of the injection; in such embodiments, the total volume in the collection zone 40 after adding the expansion volume 44 is Figure 1B The total expected molten polymer foam volume of the molten aerated mixture 42B. In other embodiments, the operator selects the expansion volume 44 to provide a collection zone 40 with a total volume that is a certain percentage of the total expected molten polymer foam volume of the molten aerated mixture or injection material residing in the collection zone 40; that is, after adding the expansion volume 44, the total volume in the collection zone 40 is equal to about 50% to 120% of the total expected molten polymer foam volume. In some embodiments, the expansion volume is set to provide a total volume in the collection zone to accommodate 100% of the total expected molten polymer foam volume. The total expected molten polymer foam volume of the injection material can be calculated based on the amount of thermoplastic polymer and gas-generating agent source added to build the injection material, plus any other materials, further assuming that all gas-generating agent sources contribute to the formation of air pockets in the molten polymer foam to be obtained.

[0100] In such Figure 1B As shown, after the screw 30 retracts to define the expansion volume 44, the injection is held as... Figure 1B While within the collection zone 40 shown (specifically, where the collection zone 40 includes the expansion volume 44), a period of time (referred to as the "expansion period") is permitted. The expansion period is selected by the operator from 5 seconds to 200 seconds. In an embodiment, during the expansion period, the injection material is allowed to remain undisturbed or substantially undisturbed within the collection zone 40. In an embodiment, "undisturbed" means that the injection material is not subjected to any processes that cause mixing, shearing, or transport (flow) of the injection material during the expansion period. In an embodiment, "substantially undisturbed" means that the injection material is not intentionally disturbed by mixing, shearing, or transport processes that occur during the expansion period, but, for example, thermal differences, leaks, and other manufacturing problems may cause unintentional stress or strain on the injection material residing in the collection zone during the expansion period.

[0101] After the expansion phase, open as... Figure 1BThe nozzle shut-off valve 37 shown dispenses molten polymer foam from the cylinder 22. In such a way... Figures 1A to 1B In the illustrated embodiment, molten polymer foam flows into chamber 39. Dispensing can be done mechanically, for example, by pushing in using the lateral movement of a screw, or by pressurized dispensing by applying pressurized gas to the collection area; however, in some embodiments, applying pressure is not necessary for dispensing the molten polymer foam. In some embodiments, without adding an external pressure source, for example... Figures 1A to 1B In the case where the molten polymer foam is pushed by the additional lateral movement of the screw 30 toward the second end 21b of the cylinder, during the dispensing of the molten polymer foam, as... Figures 1A to 1B The pressure at nozzle 36 shown is 1 psi to 20 psi above gravity, for example 3 psi to 20 psi, 5 psi to 20 psi, 7 psi to 20 psi, 10 psi to 20 psi, 15 psi to 20 psi, 1 psi to 15 psi, 1 psi to 10 psi, 1 psi to 7 psi, 1 psi to 5 psi, 2 psi to 5 psi, 5 psi to 10 psi, 10 psi to 15 psi, or 15 psi to 20 psi. In embodiments, distribution is achieved by maintaining a fluid connection between nozzle 36 and cavity 39. In some such embodiments, the fluid connection is further a pressurized connection.

[0102] In the arrangement Figures 1A to 1B After being placed within the cavity 39 defined by the mold portion 38 as shown, the molten polymer foam is cooled or allowed to cool until it reaches a temperature below the melt transition temperature of the thermoplastic polymer, such as the temperature in the current ambient conditions. In some embodiments where the expansion volume is set to provide a total volume in the collection area less than 100% of the total expected molten polymer foam volume, the air bladder may continue to nucleate and / or develop (size growth) after the molten polymer foam has been dispensed and before the temperature has been sufficiently cooled to reach the melt transition temperature of the thermoplastic polymer. Cooling of the molten polymer foam is achieved using conventional methods for cooling injection-molded articles and includes, without limitation, immersing the mold in a liquid coolant at a set temperature, or spraying the mold with a liquid coolant such as liquid water; impinging an airflow onto the mold; ambient air cooling; and so on.

[0103] In an alternative implementation of the aforementioned method, using, for example Figure 1B The device 20 configured as shown is used to form molten polymer foam. Figure 1B The image shows the screw 30 in the position created by the lateral movement of the screw 30 toward the first end 21a of the cylinder; that is, the screw 30 in Figure 1B relative to Figure 1ARetraction. The retraction of screw 30 from collection zone 40 and the resulting partial displacement define an expansion volume 44 within collection zone 40, and also cause a pressure drop within collection zone 40. (Using as...) Figure 1B The device 20 shown is configured to mix, heat, and transfer the molten aerated mixture 42B toward the second end 21b of the cylinder 21 in substantially the same manner as described above. Furthermore, a screw 30 is arranged within the cylinder portion 22, wherein the thread 31 contacts the cylinder 21 during rotation of the screw 30; combined with a check valve 32, a shut-off valve 37 in the closed position, or both, a pressurized seal is provided within the cylinder portion 22, thereby allowing the molten aerated mixture 42B to exist within the cylinder portion 22 at pressures exceeding atmospheric pressure. Even if the gas-generating agent source is above its critical temperature, the pressure within the cylinder portion 22 is sufficient to prevent or substantially prevent gasbag formation. However, in this alternative embodiment, the molten aerated mixture is transferred through the check valve 32 and into a collection zone 40 further supplemented with an expansion volume 44.

[0104] The advantage of the method disclosed herein is that conventional materials and equipment used for extrusion and injection molding can be used to carry out the method. No specialized equipment or material requirements are necessary to carry out the disclosed method. Therefore, any thermoplastic polymer or mixture thereof that can be used for injection molding and / or for forming polymer foams can be efficiently used with conventional techniques such as standard injection molding equipment and any industrially available foaming agent source, optionally together with one or more additional material combinations as selected by the equipment operator.

[0105] In embodiments, the thermoplastic polymers that can be used in conjunction with the methods, apparatus, and articles described herein include any thermoplastic plastic or mixtures thereof known in industry for use in injection molding or injection molding of polymer foam articles; and mixtures of such polymers. The available polymers are characterized by having a melt flow viscosity suitable for injection molding (e.g., for injection forming). Therefore, the thermoplastic polymers may include a degree of crosslinking that is thermally reversible or does not otherwise impede sufficient viscous melt flow for use in the injection molding process.

[0106] In embodiments, thermoplastic polymers that can be used in conjunction with the methods, apparatus, and articles described herein include olefin polymers such as polyethylene, polypropylene, polyalphaolefins, and their various copolymers and branched / crosslinked variants, said branched / crosslinked variants including, but not limited to, low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), thermoplastic polyolefin elastomers (TPE), ultra-high molecular weight polyethylene (UHMWPE), etc.; polyamides (PA), polyimides (PI), polyesters such as polyester terephthalate (PET), and... Polybutylene terephthalate (PBT), polyhydroxyalkanoates (PHAs) such as polyhydroxybutyrate (PHB), polycarbonate (PC), polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polystyrene, polyurethanes (including thermoplastic polyurethane elastomers (PU, TPU)), polycaprolactone, polyvinyl chloride (PVC), tetrafluoroethylene copolymers, polyethersulfone (PES), polyacetal, polyarylamide, polyphenylene ether (PPO), polybutene, polybutadiene, polyacrylates and polymethacrylates (acrylic), ionomers (SURLYN) ® Similar ion-functionalized olefin copolymers), polyether-amide block copolymers (PEBAX®), polyaryletherketones (PAEK), polysulfones, polyphenylene sulfides (PPS), polyamide-imide copolymers, poly(butylene succinate), cellulose products, polysaccharides, and their copolymers, alloys, blends, and blends may be used in combination with the methods described herein without limitation.

[0107] Regarding the unrestricted use of polymer blends and mixtures, we have found that in the embodiments, mixed streams of recycled plastics can be used as thermoplastic polymers. Therefore, in the embodiments, marine waste plastics are mixed streams of polymer waste collected from the ocean and beaches and having the following exemplary contents: 10% to 90% polyolefin contents, 10% to 90% PET contents, 1% to 25% polystyrene contents, and 1% to 50% unknown polymer contents. Such mixed plastic streams and waste plastic streams (not limited to those collected from the ocean and beaches) can also be used to form molten polymer foams and polymer foam articles using the methods and equipment described herein.

[0108] Gas-generating agent sources are widely available in industry, and the conditions under which gas-generating agents can be formulated during melt mixing are well understood and widely reported. Therefore, any gas-generating agent source that can be used in injection molding, reaction injection molding, or other methods for manufacturing polymer foams may be used herein to form molten polymer foams and solidified polymer foam articles according to the methods, apparatus, and polymer foam articles described herein. Gas-generating agents that can be used in conjunction with the methods and apparatus described herein include air, CO2, and N2, each encapsulated in the form of beads, pellets, etc., or in a latent form within a thermoplastic, wherein a chemical reaction produces CO2 or N2 when heated within the melt mixing apparatus. Such chemical reactions are suitably exothermic or endothermic, and there are no limitations regarding their use in conjunction with the methods and apparatus disclosed herein. Suitable sources of effervescent agents include sodium bicarbonate, compounds based on polycarboxylic acids such as citric acid, or their salts or esters, such as sodium citrate or trimethyl citrate; mixtures of sodium bicarbonate and polycarboxylic acids such as citric acid; sulfonyl hydrazides, including p-toluenesulfonyl hydrazide (p-TSH) and 4,4'-oxobis(benzenesulfonyl hydrazide) (OBSH), pure and modified azodicarbonamide, aminourea, tetrazolium, and diazinone. In any of the foregoing, the effervescent agent source may optionally be further encapsulated in a carrier resin designed to melt during heating, mixing, and collection of the injection.

[0109] In the implementation scheme, available sources of vaporizing agents include commercially available compositions, such as HYDROCEROL® BIH 70, HYDROCEROL® BIH CF-40-T, or HYDROCEROL® XH-901, all available from Clariant AG, Switzerland; FCX 7301 available from RTP Company, Winona, Minnesota; FCX 27314 available from RTP Company, Winona, Minnesota; CELOGEN® 780 available from CelChem LLC, Naples, Florida; ACTAFOAM® 780 available from Galata Chemicals, Southbury, Connecticut; ACTAFOAM® AZ available from Galata Chemicals, Southbury, Connecticut; ORGATER MB.BA.20 available from ADEKA Polymer Additives Europe, Millouse, France; and ENDEX available from Endex International, Rockford, Illinois. 1750™; and FOAMAZOL™ 57, available from Bergen International in East Rutherford, New Jersey.

[0110] In some embodiments, the gas-generating agent source is a gas-generating agent, which is applied as a gas to the melt mixing apparatus, such as a gaseous mixture. Figures 1A to 1B The extruder equipment shown is described. In such embodiments, the gas is dissolved in the thermoplastic polymer by direct pressurization and addition into and mixing within the melt-mixing apparatus. In some embodiments, the gas is pressurized to become a supercritical fluid before or simultaneously with dissolution into the molten thermoplastic polymer. Applying a gas-generating agent directly to injection molding equipment is industrially known as the MUCELL® process, as employed by Trexel Inc. of Wilmington, Delaware. This process requires specialized equipment, such as a regulated pressurized fluid connection from a gas reservoir (tank, cylinder, etc.) to the extruder inlet to establish a pressurized relationship with the barrel as the thermoplastic polymer is also added to and melted. Where such specialized equipment is available, the gas-generating agent can be effectively used as a gas-generating agent source in combination with the methods described herein by directly applying the gas-generating agent to the thermoplastic polymer and one or more other materials to form a melt-inflated mixture.

[0111] Based on conventional techniques related to the formation of thermoplastic polymer foams with desired polymer foam density and the operation of the foaming agent and foaming agent source, the foaming agent source is added to the thermoplastic polymer and any optional one or more other materials in an amount targeting a selected density reduction of the thermoplastic polymer. There is no particular limitation on the amount of foaming agent source added to the thermoplastic polymer; therefore, we have found that density reductions of up to 85% are achieved without the use of polymer bubbles or glass bubbles, thus providing polymer foam articles with unique and unexpected properties reported below, and also with a target density reduction of up to 85%. As used herein, “density reduction” means the percentage reduction in mass of the polymer foam article compared to the same article manufactured without the addition of a foaming agent (source) (i.e., a polymer article excluding or substantially excluding air pockets). Therefore, in embodiments, the molten polymer foams and polymer foam articles described herein appropriately exclude glass bubbles or polymer bubbles while providing the following selected density reductions: up to 85%, for example 30% to 85%, for example 35% to 85%, 40% to 85%, 45% to 85%, 50% to 85%, 55% to 85%, 60% to 85%, 65% to 85%, 70% to 85%, 75% to 85%, 30% to 35%, 35% to 40%, 40% to 50%, 50% to 55%, 55% to 60%, 60% to 65%, 65% to 70%, 70% to 75%, 75% to 80%, or 80% to 85%. Including glass bubbles or polymer bubbles further expands the achievable density reduction of the polymer foam articles manufactured according to the methods herein. In some embodiments, a density reduction greater than 85% can be achieved. Nevertheless, polymer foam articles benefiting from reduced density are characterized by a pervasive, continuous polymer matrix in which air pockets are dispersed, said polymer foam articles comprising volumes greater than 1000 cm³. 3 1000 cm 3 Up to 5000 cm 3 or even greater than 5000 cm 3 Molded articles; and articles with a volume greater than 1000 cm² 3 And its thickness is greater than 2 cm and its volume is 1000 cm³. 3 Up to 5000 cm 3 Between and with a thickness greater than 2 cm, or a volume greater than 5000 cm³. 3 And molded products with a thickness greater than 2 cm.

[0112] As mentioned above, there is no particular limitation on the amount of gas-generating agent source added to the thermoplastic polymer; therefore, we found that up to 70% of the total volume of the polymer foam article includes air pockets. The percentage of the total volume of the air pockets to the total volume of the polymer foam article is called the "void fraction" of the article; thus, a void fraction of up to about 70% was achieved without containing polymer bubbles or glass bubbles, etc., thereby providing a polymer foam article that has the unique and unexpected properties reported below and also has the target void fraction of up to 70% of the volume of the polymer foam article. Therefore, in embodiments, the molten polymer foams and polymer foam articles described herein appropriately exclude glass bubbles or polymer bubbles while providing the following void fractions: up to 70%, for example 5% to 70%, for example 10% to 70%, 15% to 70%, 20% to 70%, 25% to 70%, 30% to 70%, 35% to 70%, 40% to 70%, 45% to 70%, 50% to 70%, 55% to 70%, 60% to 70%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, 35% to 40%, 40% to 50%, 50% to 55%, 55% to 60%, 60% to 65%, or 65% to 70%. Including glass bubbles or polymer bubbles further expands the achievable void fraction of polymer foam articles manufactured according to the methods herein. In some embodiments, a void fraction greater than 70% can be achieved. Nevertheless, polymer foam articles having a 70% porosity fraction are characterized by having a pervasive, continuous polymer matrix in which air pockets are dispersed, said polymer foam articles comprising having a porosity greater than 5000 cm⁻¹ 3 The volume is greater than 2 cm in thickness, or greater than 5000 cm³. 3 The molded product has both a volume and a thickness greater than 2 cm.

[0113] In some embodiments, the thermoplastic polymer and the gas-generating agent source are blended before the blend is applied to the melt-mixing apparatus for heating and mixing. In other embodiments, the thermoplastic polymer and the gas-generating agent source are added to the melt-mixing apparatus separately, for example, through two different inlets or ports that can be used to add materials to the melt-mixing apparatus. In still other embodiments, a solid mixture comprising both the thermoplastic polymer and the gas-generating agent source is added as a single input to the melt-mixing apparatus for heating and mixing.

[0114] In embodiments, one or more additional materials are included in or added to the melt-mixing apparatus along with the thermoplastic polymer and the gas-generating agent source; such additional materials are suitably mixed or blended with the thermoplastic polymer, the gas-generating agent source, or both; or one or more additional materials are added separately to the melt-mixing apparatus, for example, through a separate port or inlet. Examples of suitable additional materials include colorants (dyes and pigments), stabilizers, brighteners, nucleating agents, fibers, granules, and fillers. Specific examples of some suitable materials include talc, titanium dioxide, glass bubbles or glass beads, thermoplastic polymer granules, thermoplastic polymer fibers, thermoplastic polymer beads or thermoplastic polymer bubbles, and thermosetting polymer granules, thermosetting polymer fibers, thermosetting polymer beads or thermosetting polymer bubbles. Other examples of suitable materials include fibers such as glass fibers, carbon fibers, cellulose fibers and fibers containing cellulose, natural fibers such as cotton or wool fibers, and synthetic fibers (e.g., polyester fibers, polyamide fibers, or aramid fibers); and include microfibers, nanofibers, crimped fibers, shredded fibers or chopped fibers, phase-separated mixed fibers such as bicomponent fibers containing any of the aforementioned polymers, and thermosetting plastics formed from any of the aforementioned polymers. Further examples of suitable additional materials are waste materials that are further shredded or chopped where appropriate and include: woven or nonwoven fabrics, cloth or paper; sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates; and other biological waste streams, organic waste streams and mineral waste streams and their mixtures. Other suitable materials include minerals such as calcium carbonate and dolomite, clays such as montmorillonite, sepiolite, and bentonite, mica, wollastonite, hydromagnesia / calcium magnesium carbonate mixtures, synthetic minerals, silica aggregates or colloids, aluminum hydroxide, alumina-silica composite colloids and particles, halloysite nanotubes, magnesium hydroxide, basic magnesium carbonate, precipitated calcium carbonate, and antimony oxide. Other suitable materials include carbonaceous fillers such as graphite, graphene, graphene quantum dots, carbon nanotubes, and C2O4. 60 Buckkeyballs. Other suitable materials include thermally conductive fillers such as boron nitride (BN) and surface-treated BN.

[0115] In the embodiments, one or more additional materials are included in or added to the melt mixing apparatus along with the thermoplastic polymer and the foaming agent source in the following amounts to form a casting: about 0.1% to 50% by mass of the thermoplastic polymer, for example, 0.1% to 45%, 0.1% to 40%, 0.1% to 35%, 0.1% to 30%, 0.1% to 25%, 0.1% to 20%, 0.1% to 15%, 0.1% to 10%, 0.1% to 9%, 0.1% to 8%, 0.1% to 7%, 0.1% to 6%, 0.1% to 5%, 0.1% to 4%, 0.1% to 3%, 0.1% to 2 ... 1%, 1% to 50%, 2% to 50%, 3% to 50%, 4% to 50%, 5% to 50%, 6% to 50%, 7% to 50%, 8% to 50%, 9% to 50%, 10% to 50%, 11% to 50%, 12% to 50%, 13% to 50%, 14% to 50%, 15% to 50%, 20% to 50%, 25% to 50%, 30% to 50%, 35% to 50%, 40% to 50%, 45% to 50%, 0.1% to 2%, 2% to 5%, 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25%, 25% to 30%, 30% to 35%, 35% to 40%, 40% to 45%, or 45% to 50%.

[0116] Therefore, in melt mixing equipment that is not an extruder, those skilled in the art will understand that the following methods will produce molten polymer foams with the significant technical benefits described in the following sections. The method for forming and collecting molten polymer foam includes: heating and mixing a thermoplastic polymer and a foaming agent source to form a molten aerated mixture, wherein the temperature of the molten aerated mixture exceeds the critical temperature of the foaming agent source and the pressure applied to the molten aerated mixture is sufficient to substantially prevent air pocket formation; collecting a selected amount of the molten aerated mixture in a collection zone; defining an expansion volume in the collection zone adjacent to the molten aerated mixture that results in a pressure drop; maintaining the expansion volume for an expansion period; and collecting the molten polymer foam from the collection zone. In embodiments, the molten aerated mixture is undisturbed or substantially undisturbed during the expansion period.

[0117] In some embodiments, collecting molten polymer foam includes applying the molten polymer foam into a cavity defined by a mold; and cooling the molten polymer foam to a temperature below the melt temperature of the thermoplastic polymer to obtain a polymer foam article. In embodiments where the molten polymer foam is applied into the cavity of the mold, the cooled polymer foam article acquires the shape and size of the mold, and furthermore, the polymer foam is characterized by a continuous polymer matrix having air pockets distributed throughout the article. In embodiments, the molten polymer foam is applied into the mold cavity by allowing the molten polymer foam to flow and enter the mold cavity by gravity; in some such embodiments, the flow is unimpeded and allowed to fall into an open cavity. In other embodiments, the molten polymer foam is applied to the forming element under pressurized flow. In embodiments, the molten polymer foam is delivered from the collection area of ​​a melt mixing device to the mold cavity via a nozzle fluidly connected to the mold cavity or other means for delivering the molten polymer foam.

[0118] For example, in one embodiment, the extruder is adapted and designed to dispense a molten mixture from an outlet into a forming element, the forming element being a mold that defines a cavity and is designed and adapted to receive a molten polymer mixture, such as a molten aerated mixture. In another embodiment, the forming element is a mold configured and adapted to receive molten thermoplastic polymer dispensed from an outlet, further wherein the mold is characterized by typically defining a cavity or cavity having a selected shape and size of a desired article.

[0119] In some embodiments, dispensing from the extruder is achieved by mechanical actuation, by applying gas pressure from within the extruder barrel, or a combination thereof. In other embodiments, after the expansion period, only the outlet, valve, gate, nozzle, or door of the collection zone is opened, allowing the molten polymer foam to flow unimpeded through the outlet; the molten flow is then directed to cooling equipment or other processing equipment, or allowed to be poured into a molding element. In still other embodiments, the molding element is fluidly connected to the outlet and is further designed and adapted to be filled with the molten mixture such that the molten mixture acquires a selected shape upon cooling and solidification. In some embodiments, the molding element is fluidly connected to the extruder outlet, such that a pressure is maintained between the collection zone, the outlet, and the molding element or die. Any conventional thermoplastic molding or forming process associated with injection molding of polymer articles (e.g., polymer foam articles) is suitable for molding the molten polymer foam described herein.

[0120] In embodiments where molten polymer foam is allowed to flow unimpeded through the outlet, or where molten polymer foam is propelled under pressure from the outlet without additional flow resistance, the molten flow ultimately impacts a surface, for example, a surface typically perpendicular to the direction of the molten flow. We have observed that, during sustained molten flow, the flow in such cases then acquires generally cylindrical (coiled) and planar (folded) patterns, as reported, for example, by Batty and Bridson, “AccurateViscous Free Surfaces for Buckling, Coiling, and Rotating Liquids” Symposium on Computer Animation, Dublin, July 2008. In embodiments, molten polymer foam is allowed to flow unimpeded from the outlet of the melt mixing apparatus or to be “poured” unimpeded from the outlet of the melt mixing apparatus into a mold configured as an open container. In some embodiments, the open container mold is completely filled with molten polymer foam; in others, the open container mold is partially filled with molten polymer foam.

[0121] In some embodiments related to the aforementioned coiled melt flow, a substantially shear-free melt flow, or a substantially linear melt flow, or a substantially linear and shear-free melt flow, is provided via a fluid connection between the extruder outlet and the die cavity. In some such embodiments, the melt flow can be obtained by impinging on its vertical surface or by flowing downwards along the substantially vertical walls or sides of the die cavity and collecting at the bottom of the die cavity. Figure 41 The diagram illustrates one such implementation. Figures 1A to 1B A variant of the extruder, wherein the die 26 of the device 20 is located on a substantially horizontal surface 100. See also... Figures 1A to 1B The component shown does not have a shut-off valve 37 at the distal end 21b of the cylinder 21; instead, in Figure 41 In this configuration, the collection area 40 extends to a mold valve 137 positioned adjacent to a mold cavity 39 defined within the mold 26. Therefore, the mold valve 137 is operable to define the collection area 40 or to provide an outlet for dispensing molten polymer foam into the mold cavity 39 via a substantially linear horizontal flow 110. The mold valve 137 is located at a height H above the horizontal surface 100, and at a height H2 above the bottom or bottom 120 of the mold 26 when located on the horizontal surface 100. (See reference...) Figure 41The mold valve 137 is selectively opened to provide a fluid connection between the collection area 40 and the mold cavity 39. Thus, the mold valve 137 is selectively opened to provide a substantially linear horizontal flow 110 of molten polymer foam entering the mold cavity 39. Upon entering the mold cavity 39, the linear flow flows downwards over a distance H2, and in some embodiments, as it continues to fill the mold cavity 39, a coiled molten flow is obtained. Other relevant variations of the method and apparatus are considered to provide a coiled molten flow as described herein.

[0122] In the implementation plan, from such Figure 41 When the polymer foam article is cooled and removed from the mold or open container as shown in the illustration, coiled and folded flow patterns are visible on the surface of the article. Examples of such visible flow patterns can be found in, for example... Figure 2-2 and 2-4 As observed in the text, when performing low-temperature fracture and microscopic examination on the interior of polymer foam articles formed using coiling and folding flows, the interior of the article contains no or substantially no flow patterns, interfaces, or other evidence of coiling and folding. For example, low-temperature fracture of such polymer foam articles does not result in fracture at any identifiable interface between coiling and folding; and both macroscopic and microscopic examinations of the interior of such polymer foam articles yield a uniform appearance relative to the flow pattern. The physical properties of such polymer foam articles are consistent with those obtained by subjecting the molten polymer foam to directional fluid flow or pressurized directional fluid flow via a fluid connection between the outlet of the melt mixing equipment and the mold.

[0123] In some embodiments, the method herein includes substantially filling a mold with molten polymer foam formed according to the foregoing method, then cooling the molten polymer foam to form a solidified polymer foam; and in some embodiments, further removing the solidified polymer foam article from the mold. In some embodiments, cooling is cooling to a temperature below the melt transition temperature of the thermoplastic polymer. In some embodiments, cooling is cooling to a temperature equal to the ambient temperature. In some embodiments, the mold also includes one or more vents for pressure equalization within the mold during filling with the molten polymer foam, but in other embodiments, no vents are present. After cooling, the polymer foam article can be removed from the mold for further finishing or use.

[0124] According to any of the foregoing descriptions, Table 1 provides available, but not limiting, examples of processing conditions for using conventional single-screw extruder-type reaction injection molding equipment to further manufacture molten polymer foams by employing one or more representative thermoplastic polymers as shown and a citric acid-based foaming agent source.

[0125] Table 1 Representative thermoplastic polymers and conditions that can be used to manufacture and mold molten polymer foams.

[0126]

[0127] In the implementation, the dimensions of a mold effectively used to form a polymer foam article manufactured using the methods and materials disclosed herein include molds that define cavities that can be filled by a single injection of molten polymer foam, or a series of cavities that can be filled by a single injection of molten polymer foam. Therefore, the size of the mold cavity is limited only by the injection volume that can be established in the melt-mixing equipment used by the user. With a maximum size of 1×10⁻⁶... 5 cm 3 Representative mold cavities of a given volume can be used to manufacture large components, such as automotive cabs or exterior parts, I-beam structural components, and other large plastic articles suitably employing polymer foam. Furthermore, the shape of the mold cavity is not particularly limited and can be complex in terms of overall shape and even surface patterns and features, for example, shapes recognizable as dumbbells, cutlery, decorative spheres with raised geographic features; human, animal, or insect shapes; frame or packaging shapes for framing or packaging, such as electronics, appliances, automobiles, etc.; shapes for later placement and installation of screws, bolts, and other non-thermoplastic articles into or through polymer foam articles; and so on—all suitable mold shapes for molding polymer foam articles as described herein. In some embodiments, the cavity includes a thickness gradient of up to 300% over one or more regions of the cavity.

[0128] According to any of the foregoing descriptions, Table 2 provides available, but not limiting, examples of mold cavity volumes and mold dimensions that can be used to mold molten polymer foam by pressurized flow or unobstructed flow of molten polymer foam into a mold. Furthermore, larger mold volumes (e.g., up to 100,000 cm³) are possible when the injection mass is appropriately increased. 3 (or larger) is useful.

[0129] Table 2 Representative mold cavity volumes and dimensions that can be used to mold molten polymer foams.

[0130]

[0131] Any of the methods, processes, uses, machines, equipment, or individual features described above can be freely combined with each other to form polymer foams and polymer foam articles with unique and unexpected properties. Therefore, in embodiments, polymer foam articles are formed using the methods, materials, and equipment described above. Polymer foam articles are discrete, monolithic objects manufactured by forming or molding molten polymer foam according to any of the methods and materials disclosed above, and variations thereof that can be combined in any part and in any way to form the molten polymer foam as described above.

[0132] Therefore, the terms used in the foregoing discussion to refer to methods, materials and equipment shall, in the following text, refer to articles manufactured using one or more of the methods, materials and equipment covered in the foregoing discussion.

[0133] In embodiments, any combination of the foregoing methods results in the formation of a polymer foam article comprising a continuous thermoplastic polymer matrix defining a plurality of air bladders, primarily composed of, or consisting of, a continuous thermoplastic polymer matrix defining a plurality of air bladders. The continuous thermoplastic polymer matrix comprises, consists of, or primarily consists of a solid thermoplastic polymer (i.e., a thermoplastic polymer present below its melt transition temperature). In embodiments, the continuous thermoplastic polymer matrix further comprises one or more additional materials dispersed within the solid thermoplastic polymer.

[0134] Based on the amount of gas-generating agent source added to the injection, the polymer foam article achieves a selected percentage density reduction based on the density of the thermoplastic polymer and any other materials added to form the polymer foam. In embodiments, density reductions include 30%, 40%, 50%, 60%, 70%, and even as high as 80% to 85%, selected by the user. In embodiments, density reductions up to 85% are achieved solely through the presence of discontinuously distributed air pockets within the polymer matrix. In embodiments, prior to forming the polymer foam article using the methods and equipment described herein, the polymer foam article does not contain hollow particles, such as polymer bubbles or glass bubbles, added to the injection.

[0135] Furthermore, considering the reduced density, as described above, the polymer foam articles described herein are characterized by having a continuous thermoplastic polymer matrix throughout or substantially throughout their entirety. We have found that large polymer foam articles can suitably be formed from the molten polymer foams disclosed herein to include a continuous polymer matrix defining multiple air pockets. A “large” article is one that has a diameter of 1000 cm³. 3Or larger, for example, 2000 cm 3 Or larger, 3000 cm 3 Or larger, 4000cm 3 Or larger, or 5000 cm 3 Or larger volumes, or in the 1000 cm³ range 3 Up to 5000 cm 3 Any volume between; and including heights up to 10,000 cm. 3 Up to 20,000 cm tall 3 Up to 50,000 cm tall 3 Or even as high as 100,000 cm 3 Or even larger volumes. Therefore, large polymer foam articles can be suitably shaped into a continuous polymer matrix comprising multiple defined air pockets throughout. The volume of the article is limited only by the size of the mold cavity and the injection volume that can be collected in the melt mixing equipment. In an embodiment, large articles are formed by a single injection from a single outlet of the melt mixing equipment; that is, there is no method of separating the molten polymer foam flow into multiple simultaneous distribution pipes, nozzles, or other methods of simultaneously directing multiple molten flows into a single mold cavity.

[0136] Furthermore, we have found that thick polymer foam articles can be suitably formed as a continuous polymer matrix comprising multiple defined air pockets. Thickness, as used herein, refers to the straight-line distance through the interior of any two points on the surface of a polymer foam article. A “thick” article is defined as having a thickness of 2 cm or greater, such as 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, 15 cm, 20 cm, 25 cm, 30 cm, 35 cm, 40 cm, 45 cm, or even 50 cm or greater. In some embodiments, the polymer foam article is formed using the methods and materials described herein, characterized by both large size and thickness, further wherein the large, thick polymer foam article is still characterized by having a continuous polymer matrix comprising multiple defined air pockets throughout the article. In embodiments, the large, thick article is formed by a single injection from a single outlet of a melt-mixing apparatus, i.e., without separating the molten polymer foam flow into multiple simultaneous distribution pipes, nozzles, or other methods of simultaneously directing multiple molten flows into a single mold cavity.

[0137] The manufacture of large, thick, or large and thick polymer foam articles is problematic in industry due to the cooling gradient of the molten foam after it is distributed into cavities of such size. The interior of such articles tends to cool very slowly, and some of the thermoplastic polymer disposed in the mold cavity may remain above its melt temperature, resulting in significant bladder coalescence before the thermoplastic solidifies (reaching temperatures below its melt transition temperature). In stark contrast, we have found that large, thick, and large thick articles are suitably formed using the methods, materials, and equipment disclosed herein, and the polymer foam articles formed therein are characterized by a continuous polymer matrix with bladders distributed throughout the article. The slower cooling interior of the larger articles shows very little or no evidence of bladder coalescence during cooling. Regardless of the size, thickness, or volume of the polymer foam article formed, the bladders remain intact or substantially intact during the cooling of the molten polymer foam and do not coalesce during cooling, thus producing a continuous polymer matrix.

[0138] The characteristic of the polymer foam articles described herein is unexpected and unforeseen: prior art methods produce foams that tend to undergo blister coalescence during cooling. Therefore, conventional molten polymer foams located within the mold's internal volume may cool so slowly that the blister coalesces completely, resulting in very large gaps or even completely collapsed structures within large or thick articles formed using conventional polymer foaming methods. In stark contrast, the molten polymer foams formed according to this method do not undergo significant blister coalescence or collapse of the continuous polymer matrix during cooling. Therefore, large and thick polymer foam articles with a pervasive continuous polymer matrix are achieved using the methods, materials, and apparatus described herein.

[0139] A characteristic of the continuous polymer matrix that forms the structural features of a polymer foam article according to the aforementioned methods, apparatus, and materials is its presence throughout the entire polymer foam article (including its surface area). The surface area can be suitably characterized as an internal region of the polymer foam article 500 micrometers or less from the surface. As defined herein, the surface area is part of a region conventionally referred to as the “surface” of the foam article, which is a region in a polymer foam article manufactured using conventional methods that is free of or substantially free of air pockets. Conventionally formed foam articles include a surface layer at least as thick as the surface area (i.e., 500 micrometers thick); however, the surface layer is typically much thicker and can extend as far as 1 mm, 1.5 mm, 2 mm, 2.5 mm, or even 3 mm from the surface of the article. However, polymer foam articles formed using the methods of this disclosure achieve a true foam structure extending from their surface and throughout their entire thickness and volume. In embodiments, microscopic examination reveals evidence of air pockets on the surface of polymer foam articles formed using the conditions, processes, and materials disclosed herein. Therefore, the method disclosed herein yields unexpected results in terms of the continuity of the polymer matrix structure throughout the polymer foam article in any direction of the polymer foam article and in every region (including inside very large and / or thick polymer foam articles and at and on the surface of the article).

[0140] The following examples include an analysis of surface regions of several polymer foam articles manufactured using the methods disclosed herein and exhibiting this continuous foam structure. Macroscopically, polymer foam articles manufactured using the methods disclosed herein can appear to have a surface layer: that is, the surface regions of the article can appear different from the interior regions of the article. However, we found that, in stark contrast to a surface layer characterized by the absence of air pockets, the surface regions of polymer foam articles manufactured by this method include multiple compressed air pockets. Macroscopically, the compressed air pockets produce the appearance of a surface layer; however, microscopic examination reveals that the significant visual difference is caused by the “planarization” or compressed arrangement of the continuous polymer matrix near the surface of the article.

[0141] Therefore, for example, as in Figure 17 and Figure 18As can be seen, there is a gradual transition from spherical air bladders to compressed air bladders as the polymer foam article is formed using the conditions, processes, and materials disclosed herein moves toward the surface. Therefore, in embodiments, the surface region of the polymer foam article manufactured using the methods disclosed herein includes multiple compressed air bladders. In embodiments, compressed air bladders are present in the surface region of the polymer foam article manufactured using the methods disclosed herein. In some such embodiments, compressed air bladders are present in an internal region of the polymer foam article at a distance of 500 micrometers or less from the surface. In some such embodiments, compressed air bladders are present in an internal region of the polymer foam article at a distance as far as 2 cm from the surface. A compressed air bladder is defined as an air bladder with a roundness value less than 1, where a roundness value of zero indicates a completely non-spherical air bladder, and a value of 1 indicates a perfectly spherical air bladder. In the embodiments, air bladders with a roundness of less than 0.9 are observed in the surface area of ​​the foamed polymer article, and furthermore, 10% to 90%, or 10% to 80%, or 10% to 70%, or 10% to 60%, or 10% to 50%, or 10% to 40%, or 10% to 30%, or 10% to 20%, or 20% to 80%, or 20% to 70%, or 20% to 60%, or 20% to 50%, or 20% to 40%, or 20% to 30%, or 30% to 70%, or 30% to 60%, or 30% to 50%, or 30% to 40% of the air bladders in the surface area have a roundness of 0.9 or less. In the embodiments, the average roundness of the surface region of the foamed polymer article is 0.70 to 0.95, for example, 0.75 to 0.95, or 0.80 to 0.95, or 0.85 to 0.95, or 0.90 to 0.95, or 0.70 to 0.90, or 0.70 to 0.85, or 0.70 to 0.80, or 0.70 to 0.75, or 0.70 to 0.75, or 0.75 to 0.80, or 0.80 to 0.85, or 0.85 to 0.90, or 0.90 to 0.95.

[0142] In some embodiments, the compressed air bladder is present at a distance greater than 500 micrometers from the surface of the polymer foam article. For example, in some embodiments, the compressed air bladder is present at a height of up to 1 mm above the surface of the polymer foam article, or at a height of 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 1 cm, or greater above the surface of the polymer foam article. In some embodiments, the area of ​​the compressed air bladder in the polymer foam article corresponds to 0.01% to 70% of the total volume of the article, for example, 0.1% to 70%, or 0.5% to 70%, or 1% to 70%, or 2% to 70%, or 3% to 70%, or 4% to 70%, or 5% to 70%, or 6% to 70%, or 7% to 70%, or 8% to 70%, or 9% to 70%, or 10% to 70%, or 15% to 70%, or 20% to 70%, or 30% to 70%, or 40% to 70%, or 50% of the total volume of the article. Up to 70%, or 60% to 70%, or 0.01% to 60%, or 0.01% to 60%, or 0.01% to 50%, or 0.01% to 40%, or 0.01% to 30%, or 0.01% to 20%, or 0.01% to 10%, or 0.01% to 9%, or 0.01% to 8%, or 0.01% to 7%, or 0.01% to 6%, or 0.01% to 5%, or 0.01% to 4%, or 0.01% to 3%, or 0.01% to 2%, or 0.01% to 1%, or 0.01% to 0.1%.

[0143] Figure 12 and 14 The diagram shows a graph of the average airbag size and average airbag count versus the average airbag roundness for two polymer foam articles manufactured using the methods of this disclosure. Quantitative analysis of airbag size and distribution reveals an inverse relationship between average airbag size and airbag roundness, as well as an inverse relationship between average airbag size and airbag number.

[0144] Figure 18 Additionally, visual evidence of air pockets on the surface of polymer foam articles formed using the methods, materials, and equipment described herein is presented. Figure 18Furthermore, visual evidence is shown of the presence of multiple compressed air bladders approximately 500 micrometers from the surface of a polymer foam article formed using the methods, materials, and apparatus described herein. In this sense, the polymer foam article of this disclosure achieves a significant difference from prior art foam articles. While the “surface” or the initial 500 micrometers of thickness of foam articles manufactured by conventional methods does not contain or substantially does not contain air bladders, prior art foam articles are typically characterized by their spherical shape regardless of the location of the air bladders. Therefore, at the thickness where air bladders are observed in conventional foam articles, the air bladders are typically spherical with a roundness close to or about 1. Compressed air bladders cannot be formed when foam articles are manufactured using conventional methods, and therefore no distribution of air bladder roundness is observed in such conventional foam articles. Moreover, no air bladders are formed even in the initial 500 micrometers of thickness of foam articles manufactured by conventional methods, so no comparison regarding air bladders can be obtained for the surface areas of foamed polymer articles as described herein and foam articles manufactured using conventional injection molding methods.

[0145] Furthermore, the conditions, processes, and materials disclosed herein are appropriately optimized according to the target end use or application to form polymer foam articles with different physical properties. For example, the density of the polymer foam article varies appropriately as a function of the expansion volume. By reducing the expansion volume, the density of the resulting polymer foam article decreases in a generally linear manner, for example, as... Figure 5 As shown. Furthermore, as from... Figure 5 As can be seen, increasing the expansion period results in a denser polymer foam product. Such conditions and other variables can be appropriately used within the full range of conditions, methods, and materials disclosed herein to modify the physical properties of the resulting polymer foam products.

[0146] In one variation of the conditions, processes, and materials disclosed herein, the molten polymer foam is appropriately distributed to form multiple polymer foam articles by a single injection by separating the flow of the molten polymer foam into two, three, four, or more paths toward multiple molds or mold segments. In another variation of the conditions, processes, and materials disclosed herein, a single mold is filled using two injections, wherein the first injection differs from the second injection in terms of the thermoplastic polymer content or the ratio of blended polymers, the foaming agent source, optionally one or more other materials, density, void fraction, depth of the region of the air pocket, or some other material or physical property difference.

[0147] In another variation of the conditions, processes, and materials disclosed herein, polymer foam articles manufactured using the methods disclosed herein are subjected to a fastener pull-out test according to ASTM D6117. The polymer foam articles exhibit superior pull-out strength compared to foam articles manufactured using conventional foaming methods. Furthermore, polymer foam articles formed using the materials, methods, and equipment disclosed herein do not require pre-drilling, tapping, or designing of fastener locations.

[0148] In yet another variation of the conditions, processes, and materials disclosed herein, polymer foam articles manufactured using the methods disclosed herein were subjected to ballistic testing. Using guidance from the National Institute of Justice (NIJ) "Ballistic Resistance of Body Armor NIJ Standard-0101.06," a series of 3-inch thick polymer foam articles were formed from polyether-amide block copolymer (PEBAX®), linear low-density polyethylene (LLDPE), and polypropylene using a citric acid-based gas-generating agent source. Polymer foam articles made using all three of these thermoplastic polymers were found to stop .22 LR pistol bullets, passing NIJ Level I; and polymer foam articles made using all three of these thermoplastic polymers were found to stop 9 mm LUGER® pistol bullets, passing NIJ Levels II and IIA.

[0149] Experimental Section

[0150] The following examples are intended to further illustrate the invention and are not intended to limit the scope of the invention in any way. Examples 1 and 11 were performed on an Engel Duo 550 Ton injection molding machine (available from Engel Machinery Inc., York, Pennsylvania, USA). Examples 2 through 4 were performed on a Van Dorn 300 injection molding machine (available from Van Dorn Demag, Strongsville, Ohio, USA). Unless otherwise stated, the remaining examples were performed on an Engel Victory 340 Ton injection molding machine (available from Engel Machinery Inc., York, Pennsylvania, USA).

[0151] In the embodiments described herein, "cc" means "cubic centimeter" (cm). 3 ), "sec" means "second".

[0152] Standard foam molding and MFIM

[0153] In the embodiments described herein, two direct injection expanded foam molding techniques, referred to herein as "standard foam molding" and "molten foam injection molding" ("MFIM"), are employed.

[0154] In standard foam molding, the following general steps are used: A) A mixture is prepared by blending a polymer (which may be in the form of pellets, powder, beads, granules, etc.) with a foaming agent and any other additives (e.g., fillers). According to standard injection molding, the mixture is introduced into the injection unit, and the rotating screw of the injection unit moves the mixture forward within the injection unit barrel, thus forming a heated fluid material. B) A set volume of material is fed to the front of the injection unit barrel by the rotation of the screw, thus moving the set volume from the feed zone to the front of the screw. During this feeding step, the screw is rotated to translate the molten mixture forward into the space between the screw and the nozzle within the barrel, thereby providing the set volume. C) The molten mixture is injected into the mold cavity by the forward translation of the screw and / or the rotation of the screw.

[0155] In fused foam injection molding (MFIM), the following general steps are used: A) A mixture is prepared by blending a polymer (which may be in the form of nurrets, pellets, powders, beads, granules, etc.) with a chemical foaming agent and any other additives (e.g., fillers). According to standard injection molding, the mixture is introduced into the injection unit, and the rotating screw of the injection unit moves the material forward within the injection unit barrel, thus forming a heated fluid material. B) A set volume of material is fed to the front of the injection unit barrel by the rotation of the screw, thus moving the set volume from the feed zone to the front of the screw. During this feed step, the screw is rotated to move the material between the screw and the nozzle, thereby providing the set volume. C) After the material has moved to the front of the screw, in a step referred to herein as “decompression,” the screw is moved backward away from the nozzle without rotation or substantially without rotation to avoid moving more material to the front of the screw.

[0156] A mixture-free space is created within the barrel between the screw and the nozzle; this intentional space has a volume referred to herein as the "decompression volume". D) The material is held within the barrel between the screw and the nozzle for a period of time referred to herein as the "decompression time". During the decompression time, the material foams due to the pressure drop created by the space added in step (C). E) The molten foam is injected into the mold cavity by the forward translation and / or rotation of the screw.

[0157] Example 1

[0158] Two parts were foam molded using a blend of low-density polyethylene and 2% by weight of Hydrocerol® BIH 70 blowing agent, available from Clariant AG of Muttens, Switzerland. Molding was performed using an Engel Duo 550 Ton injection molding machine (available from Engel Machinery Inc., York, Pennsylvania, USA). The mold cavity was a (approximately) spherical shape with a diameter of six inches (15.24 cm). The first part was molded using standard foam molding, and the second part using MFIM. An aluminum mold with a cold gate and runner system for feeding a 6-inch diameter spherical cavity was used for both parts. The melt delivery system and most processing conditions were identical for both parts. The process settings for MFIM and the standard foam molding method used as a control are detailed in Table 3. Depending on the process, the parts were made from approximately equal masses.

[0159]

[0160] Photograph the first and second components. Figure 2-1 This is a photographic image of the first part molded using the standard foam molding method. As can be seen in the image, the standard foam method does not produce a part that fills the mold cavity, and the part does not match the shape of the spherical cavity of the mold.

[0161] Figure 2-2 This is a photographic image of a second part molded using the MFIM method. As can be seen in the image, the MFIM method produces a part that completely or substantially fills the spherical mold cavity, and that the part matches or substantially matches the shape of the spherical cavity of the mold.

[0162] The first part, molded using standard foam molding, is cut into two pieces. Figure 2-3 and 2-5 This is a photographic image of one of the components manufactured according to the standard foam molding method. As can be seen in the image, the first component includes a large hollow cavity.

[0163] The second part, molded according to the MFIM method, is cut into two pieces. Figure 2-4 and 2-6 This is a photographic image of one section of the second component. As can be seen in the image, the second component lacks the large hollow cavity found in standard foam-process components. MFIM components have a pervasive porous structure.

[0164] Example 2

[0165] Two parts are formed by foam injection molding: part A according to the standard foam molding method and part B according to the MFIM method. In both methods, LDPE / talc pellets are dry-mixed with a foaming agent and then mixed during loading into the molding machine.

[0166] For component B, a mixture of low-density polyethylene (LDPE), talc, and Hydrocerol® BIH 70 is formed and fed into a Van Dorn 300 injection molding machine to provide polymer injection inside the barrel. After the injection material accumulates in front of the screw, the screw is translated backward away from the injection nozzle without rotation according to the MFIM method to create a space with a depressurized volume between the screw and the nozzle. The mixture is then foamed into this space before being injected into the mold.

[0167] The same procedure is used for part A, except that after the filler material accumulates in front of the screw, the screw does not move backward away from the nozzle, i.e., the depressurization volume is zero. The filler material is metered to fill the mold cavity with a target of 10% less weight relative to the solid part under standard foam molding conditions.

[0168] Tables 4 to 7 below show the polymers, molds, machines, and processing setups used in Example 2.

[0169]

[0170]

[0171]

[0172]

[0173] Cut component A and component B in half to show the cross-section. Figure 3A and Figure 3B The resulting cross-sections of component A and component B are shown respectively. For example... Figure 3A As shown, part A has an outer region nearly 0.8 inches (20.3 mm) thick extending from the surface, indicating that more than 50% of the molded part is completely solid. Part A has a density of 0.84 g / cc.

[0174] Figure 3B The cross-section of part B, molded using the MFIM method with the settings shown in Tables 4 and 5, is shown. Figure 3B As can be seen, component B has a foam structure with a distribution including pore size and shape. Component B has almost no solid, unfoamed outer regions. The density of component B is 0.35 g / cc.

[0175] Two additional parts (part C and part D) were formed by foam injection molding using a spherical cavity mold. Parts C and D were formed using the same mixture of LDPE, talc, and Hydrocerol® BIH 70. Part C was manufactured using the MFIM method, and part D was manufactured using the standard foam molding method. Both methods produced spherical or near-spherical parts with a diameter of six inches (15.24 cm). Parts C and D were cut in half from the middle (widest part) to expose the cross-section of the parts. Figure 4A This is a photographic image of a cross-section of part C (471 g, requiring 160 seconds of cooling) manufactured by the MFIM method. Figure 4B It is a photographic image of a cross-section of part D (1360 g, requiring 800 seconds of cooling time), which was molded using a standard foaming process.

[0176] Similar results were obtained as with the block mold method. Part C, manufactured using the MFIM method, exhibits pores throughout the part, while part D, manufactured using the standard foam molding method, shows areas adjacent to the outer surface of the part that are pore-free or substantially pore-free (“solid”). Part C is less dense than part D.

[0177] Example 3

[0178] In Example 3, the MFIM method was used to mold block parts under different decompression volumes (Experiment A) and different decompression volumes and decompression times (Experiment B).

[0179] Tables 8 to 10 show the material composition, mold geometry information, and processing settings used for tests A and B.

[0180]

[0181]

[0182] The composite LDPE / talc pellets are mixed with the foaming agent just before molding.

[0183] Experiment A

[0184] In Experiment A, all variables remained constant except for the volume ratio of the polymer to the depressurized volume (empty space) in the barrel prior to injection. Table 10 shows the setup for each sample run in Experiment A:

[0185]

[0186] The volume of molten foam injected into the polymer cavity is constant, but the density of the molten foam is a function of the polymer charge / decompression volume ratio. Changing the polymer charge / decompression volume yields parts with the weight and density shown in Table 11:

[0187]

[0188] The results in Table 11 show that the density of the resulting component can be altered by reducing the mass and volume of the polymer in the molten foam injection and correspondingly increasing the decompression volume.

[0189] Test B

[0190] In Experiment B, five molding processes were performed three times under the same conditions as in Experiment A: once with a decompression time of 20 seconds (the same as in Experiment A), once with a decompression time of 70 seconds, and once with a decompression time of 120 seconds. Fifteen resulting foam molded parts were weighed, and their density was calculated using the volume of the mold cavity. For each of the three decompression times, the part density was plotted as a function of the decompression volume. Figure 5 The figure is shown in [the image]. For example, in [the image]... Figure 5 As can be seen, the component density varies as a function of the decompression volume. Furthermore, as... Figure 5 As shown, the longer the decompression time, the denser the component.

[0191] Example 4

[0192] In Example 4, two series of tests (Series I and Series II) were run using the MFIM method. In Series I, a constant injection speed was used, but the mold closing height was varied. In Series II, the mold closing height increased with increasing injection speed. In Series II, all conditions were kept constant except for the injection speed (cc / s) and the mold closing height. In these tests, LDPE / talc pellets were dry-mixed with a foaming agent and then mixed during loading into the molding machine.

[0193] Tables 12 and 13 below show the material composition and basic mold configuration of the injection blends used in these tests.

[0194]

[0195]

[0196] Series I

[0197] In Series I, an injection speed of 394 cubic centimeters per second was used, and three tests were run: Test A produced part A with a mold closing height of 1.02 mm; Test B produced part B with a mold closing height of 0.76 mm; and Test C produced part C with a mold closing height of 0.51 mm. The setup for the Series I tests is shown in Table 14.

[0198]

[0199] During each molding cycle (each of Test A, Test B, and Test C), a strain gauge (Kistler Surface Strain Sensor Type 9232A) will be used. Available from Winterthur, Switzerland Kistler Holding AG acquired) Installed directly above or inside the mold cavity. The strain sensor comprises two piezoelectric sensors that measure the strain of the aluminum cavity as a function of time during the molding cycle. The strain measurement is used as an indirect measure of the forces acting on the mold cavity surface by the injection of molten foam and any subsequent additional foaming occurring within the mold cavity. The cavity strain measurement results for Test A, 1.02 mm gap height (line A); Test B, 0.76 mm mold closure height (line B); and Test C, 0.51 mm mold closure height (line C) are shown in... Figure 6 In. Figure 6 In the figure, strain (unit extension per unit length) is plotted against time in seconds. The strain curves show that the pressure in test C is higher than that in test B, and that in test B it is higher than that in test A.

[0200] Figure 7 The document includes photographic images showing side, top, oblique, and bottom views of components A, B, and C. Components A and B show evidence of collapse because they do not fully conform to the shape of the mold cavity. Component A shows more collapse than component B. Component C is more fully formed than either component A or B because its edges are better defined, it better conforms to the shape of the mold cavity, and its interior appears more uniform.

[0201] It is believed that if sufficient pressure is not applied during solidification to stabilize the foam in the cavity, the part may partially collapse within the cavity during molding. Therefore, in Series II, the mold is closed more tightly at a slower injection rate to maintain sufficient pressure and prevent the part from collapsing during molding.

[0202] Series II

[0203] In Series II, the gap between the two mold halves (mold closure height) decreases systematically as the injection rate decreases. The molding conditions used are the same as in Series I, except that the injection rates and mold closure heights used are those shown in Table 15:

[0204]

[0205] Four components (component A', component B', component C', and component D') were produced in experiments A', B', C', and D', respectively.

[0206] Parts A', B', C', and D' were each cut into two pieces, and their cross-sections were photographed. The photographs are shown below. Figure 8 In order to produce parts that do not collapse before solidification, the two halves of the mold must be gradually closed, as shown in Table 15, until they are actually pressed together (as indicated by the negative dimension).

[0207] Parts A', B', C', and D' showed no evidence of collapse, had well-defined edges and surfaces, and appeared fairly uniform. Therefore, the MFIM method was used to manufacture parts by controlling the pressure within the cavity during injection (e.g., by varying the mold closure height) using significantly different injection rates.

[0208] Example 5

[0209] In Example 5, the same LDPE composite material as in Examples 1 to 3 was used in a non-standard dual-cavity mold, wherein the molding parameters are shown in Tables 16 to 18.

[0210]

[0211]

[0212]

[0213] Example 5 produced Figure 9 Part 51 is shown in the diagram. During injection, molten foam is introduced through gate 52 and separated into two separate channels to fill part 51 substantially simultaneously. Therefore, the MFIM method can be used to form parts by separating the melt into multiple paths in a mold.

[0214] Example 6

[0215] The first part was molded using a formulation in which 15 wt% talc / 85 wt% polycarbonate composite was blended with 3 wt% Hydrocerol® XH-901 before being loaded into the injection molding machine. The first part was formed using the MFIM method. Process details are provided in Tables 19 and 20. The part was manufactured using a 4×2×2 block mold (5.08×10.16×10.16 cm) with a mold cavity volume of 524.4 cc and a gate volume of 17.4 cc. The gate was cut off from the part, and the part was then subjected to X-ray tomography to quantify the porous structure formed within the 5.08×10.16×10.16 cm geometry.

[0216]

[0217]

[0218] X-ray computed tomography was performed using a Zeiss Metrotom 800 130 kV imaging system (available from Carl Zeiss AG, Oberkochen, Germany). This instrument measures the attenuation of X-ray radiation due to component geometry and the density of materials used. Column data were calculated using the Feldkamp reconstruction algorithm (a standard technique used in industry). The instrument features a 1536 × 1920 pixel flat panel detector with a final resolution of 3.5 μm under these measurement conditions.

[0219] Figure 10 The image shows an isometric image of a full Zeiss 3D tomographic scan of the first component, in which the solid polymer portion is shown as transparent, the holes are masked for visualization, and the cutting plane AA is indicated for a single cross-section. Figure 11 The single-plane section AA is selected from X-ray data, where threshold analysis is applied to allow discrete hole identification and subsequent quantitative analysis.

[0220] The roundness of the cross-sections of the holes was obtained. The roundness of these cross-sections is used as a measure of the sphericity of the holes. Therefore, roundness and sphericity are used interchangeably in the embodiments. Figure 12 The quantitative analysis shown reveals the hole distribution as a function of both the count and the average size of each hole. A roundness value of 0 indicates a completely non-spherical hole, and a value of 1 indicates a perfectly spherical hole. The data show the distribution of hole size and shape. Except for the most deformed holes (represented by 0.1 to 0.2 on the roundness scale), there is an inverse relationship between the average hole size and the number of holes for a given roundness. Furthermore, there is an inverse relationship between the average hole size and the number of holes.

[0221] Using the MFIM method, second spherical parts with a diameter of six inches (15.24 cm) were molded from low-density polyethylene (LDPE) using the polymer formulations and processing parameters outlined in Tables 21 and 22. LDPE / talc pellets were dry-mixed with the foaming agent Hydrocerol® BIH 70 and mixed during loading into the molding machine.

[0222]

[0223]

[0224] Figure 13 It is an X-ray tomographic image of a cross-section of a sphere. For example, in... Figure 13 As can be seen, the outer region contains too many smaller holes, while the central region has larger holes.

[0225] Figure 14A graph showing the average hole size and average hole count against the average hole roundness is presented, revealing the inverse relationship between average hole size and roundness, as well as the inverse relationship between average hole size and hole count.

[0226] Example 7

[0227] LDPE composite spheres (92 wt% polymer, 5 wt% talc, and 3 wt% Hydrocerol® BIH 70) with a diameter of three inches (7.62 cm) were molded using the MFIM method, and the resulting foam pore structure was... Figures 15 to 18 The details are as follows. Table 23 provides the molding conditions. The part was molded in a custom-designed water-cooled aluminum mold on an Engel Victory 340 Ton injection molding press. The mold cavity volume was 15.38 inches. 3 (252 cc), injection volume for 5 inches 3 (82 cc), and the decompression volume in the cylinder is 5 inches. 3 (82 cc). The decompression time was 77 seconds. The weight of the molded part was 80.31 g, resulting in a final part density of 0.32 g / cc.

[0228]

[0229] After being removed from the mold, the part was aged under ambient conditions for 24 hours, then scored and immersed in liquid nitrogen for two minutes. After being removed from the liquid nitrogen, the ball was broken along the scored surface line, and the fracture surface was imaged using an environmental scanning electron microscope (ESEM) (FEI Quanta FEG 650). Figures 15 to 18 The images shown are photomicrographs of the fractured surface of the spherical component taken using a large field-of-view detector, 5.0 kV and 40 Pa pressure at different magnifications.

[0230] Figure 15 The white box in the middle indicates Figure 16 The area detailed in the text. Figure 16 The white box in the middle indicates Figure 17 The area detailed in the text.

[0231] exist Figure 17 In the image, the holes on the left are larger and relatively spherical, while those on the right appear to gradually flatten as they approach the surface of the sphere.

[0232] Figure 18 The images in the text detail the work of... Figure 17 The area indicated by the white box in the image. (As shown in...) Figure 18 It can be seen that there is a gradual transition from spherical to "flattened" or compressed holes that move toward the surface of the component.

[0233] Example 8

[0234] To establish baseline differences between standard thickness parts manufactured under standard foam molding conditions, a baseline for molding parameters was established using a 16-run Design of Statistical Analysis (DOE) approach with a recently published study on standard foam injection molding (Paultkiewicz et al., Cellular Polymers 39, 3-30 (2020)). Materials (standard molding grade polypropylene with 0 wt%, 10 wt%, and 20 wt% talc; and 0 wt%, 1 wt%, and 2 wt% Hydrocerol® BIH 70 (blowing agent)) were compounded to the specifications outlined in the publication to closely simulate the baseline study. The study aimed to investigate the effects of blower concentration, talc content, and process conditions on selected properties of the injection-molded foam parts. A standard ISO stretch bar mold with a cavity size of 4.1 mm thickness, 10 mm width (gauge length), and 170 mm length was used. No special venting was developed for the ISO bar mold. After ensuring that the injection molding machine, material formulation, and process window could replicate the results published by Paultkiewicz et al., a second study was conducted using MFIM-specific process variables (especially decompression volume and decompression time) while setting the pressure and holding time (important variables in the published study) to constant values ​​of zero kN and zero seconds, respectively.

[0235] Molding was performed using an Engel Victory 340 Ton machine equipped with water cooling. The constant and variable process conditions used for both the "standard" foam molding method and the MFIM molding method are shown in Table 24.

[0236]

[0237] For each standard molding study and MFIM molding study, the designed studies required 16 combinations of processing conditions / polymer formulations (16 runs). Each run was repeated multiple times, thus producing duplicate parts for each run. Table 25 summarizes the variations between the standard design runs and the MFIM design runs. These runs were performed in a randomized order to avoid bias. The L / T ratio for the ISO stretch bar was 40.5.

[0238]

[0239] After molding 32 unique process combinations from two 16-run DOE studies, mechanical tensile strength tests were performed on five samples from each series, and the fracture surfaces were imaged after fracture. Representative ISO bar cross-sections from runs 10, 11, 14, and 15 of the standard foam molding process are shown below. Figure 19 The selection of representative ISO bar sections from Operations 9, 10, 15, and 16 of the MFIM method is shown in the figure. Figure 20 middle.

[0240] When examining cross-sectional images, the differences between standard foam molding techniques and MFIM, as seen in recent literature, are evident. The structure in the standard process bar consists of relatively few but well-defined spherical pores located on all sides of a pore-deficient, thick region of the polymer. The cross-sectional images obtained by the standard foam molding method are in good agreement with those in the publications of Paultkiewicz et al., and represent the current industry standard. In contrast, typical cross-sections of ISO bars molded by MFIM show a pore structure with more asymmetrical deformable pores.

[0241] Similar to the embodiments described herein, and despite being much thinner parts with a much larger L / T ratio (40.5) than previously described, in almost all cases the holes in the MFIM cross-section also extend to the region adjacent to the surface. The results clearly demonstrate that employing the decompression step in MFIM, combined with eliminating the variables of holding pressure and holding time in standard foam molding, results in a significantly different hole structure in the molded parts.

[0242] Tensile tests were performed on five repeating parts from MFIM Run 9. Figure 21 Representative cross sections and a series of stress / strain diagrams from five tested components from MFIM Run 9 are shown.

[0243] Tensile tests were performed on five repeating parts from Run 10, which were manufactured using standard foam molding methods. Figure 22 Representative cross sections and a series of stress / strain diagrams from five tested components from standard foam method run 10 are shown.

[0244] The average tensile strength of the five parts from MFIM run 9 was lower than that of the five parts from standard foam molding run 10. However, the MFIM parts exhibited greater breakage strain (elongation).

[0245] More holes are visible in the cross-section of the MFIM part from Run 9 (102 holes) than in the standard foam molding part from Run 10 (19 holes).

[0246] For randomly selected repeating parts from run 15 of the standard foam molding method (shown in...) Figure 23 (in the middle) and for randomly selected repeating parts produced during the MFIM process (shown in 9) Figure 24 X-ray tomography was performed (under the conditions described in Example 5). Figure 23 and Figure 24 Both show a "top" view taken at 50% depth and a "side" view taken at the same 50% depth.

[0247] In standard foam molding method ISO rod ( Figure 23 In the hole structure formed by the rod, the hole is circular in shape, and the area adjacent to the rod surface lacks holes.

[0248] In comparison, such as Figure 24 The ISO rod shown is produced by the MFIM process and includes numerous elongated holes, with holes found in the region adjacent to the surface of the part.

[0249] Example 9

[0250] To explore the dependence of the final pore structure on MFIM processing conditions, eight LDPE stretch bars were molded using the MFIM method on an Engel Victory 340 Ton injection molding machine. The mold comprised an aluminum-modified stretch bar cavity with dimensions including a gradually tapering flange to a width of 3.5 cm, a length of 24 cm, a thickness of 2.54 cm, and a variable width with a gauge length of 6 cm and a gauge width of 2.54 cm. The large stretch bars were fed from a cold gate and runner system through a 1.0 cm diameter gate. The material formulation contained LDPE with or without talc, always containing 2% by weight of the blowing agent Clariant Hydrocerol® BIH 70. The melt temperature was set to the configuration detailed in Table 26, and the residence time in the barrel was 13 minutes prior to building up the filler for injection. After the filling process is completed, the screw is retracted to obtain a reduced volume of 4.0 cubic inches (66 cc) or 6.0 cubic inches (98 cc), and the LDPE foaming agent mixture is foamed for 15 or 45 seconds before injection into the empty barrel space. Studies were completed for both unfilled LDPE and LDPE filled with 15% talc. Detailed process conditions are shown in Table 26.

[0251]

[0252] Figure 25 An X-ray scan of one of the components from the study is shown, revealing the overall shape of the components.

[0253] Figure 26 The cross-sections of each test bar molded in the study, cut from the middle of the gauge length, are depicted under the indicated variable parameters. The sample set comprises two main groups: samples made with talc and samples made without talc. Figure 26 In the left-hand sample set, we see components made without talc. These components exhibit a smaller pore structure within the core, and the integrity of the formed pore structure is largely unaffected by variations in the decompression ratio and decompression time, indicating that both the decompression ratio and decompression time are within acceptable ranges.

[0254] The sample set on the right describes those bars containing 15% talc by weight. Some tailing on the part surface is caused by damage to the low-modulus LDPE by the tool and does not represent part quality. The pore structure in the talced parts is consistently larger, and the pore roundness is slightly lower than that of the talc-free equivalents.

[0255] The X-ray tomographic images were taken from a cross-section approximately 50% of the MFIM component at the main surface, where the MFIM component is located at 15% talc and 6 inches. 3 It was manufactured with a (98 cc) decompression volume and a decompression time of 15 seconds. The image is shown below. Figure 27 middle.

[0256] Example 10

[0257] A stretch bar component was manufactured using standard foam molding with the processing parameters described in Example 9, but without the decompression step of the MFIM method, from LDPE loaded with 15 wt% talc and 2 wt% Hydrocerol® BIH 70. This standard foam molded component was compared with that from Example 9, using LDPE loaded with 15 wt% talc and 6 inches... 3 A comparison was made between MFIM parts manufactured with a decompression volume of (98 cc) and a decompression time of 15 seconds. X-ray tomographic images of the central portions of each part (MFIM molding and standard foam molding) at different depths from the main surface were taken using the method described in Example 6. Cross-sectional images were also recorded. The images are shown in... Figure 28 middle.

[0258] X-ray tomographic analysis of hole count, hole roundness, and average hole size (longest hole dimension) was performed on images at various depths from the main surface for each tensile bar component (MFIM material and standard process material). Hole count, hole roundness, and average hole size were plotted relative to the depth of the cross-section; and each plot is shown separately. Figures 29 to 31 middle.

[0259] like Figure 29As shown, the hole count of the MFIM-molded part is high at all depths. As can be seen throughout the embodiments and figures, parts molded using standard foam molding appear to have no or substantially no holes in the area adjacent to the surface or the “surface layer” (e.g., at a depth of about 2.5 mm from the main surface), while parts molded using the MFIM method have holes in the area about 2.5 mm below the surface and between the surface and the surface.

[0260] like Figure 30 As shown, typically, the roundness of the holes in standard foam molding samples is greater than that in MFIM molded parts (except for the part facing the center of the MFIM part), where the roundness is also high in MFIM molded samples.

[0261] like Figure 31 As shown, the hole size of a standard foam-molded stretch bar component is typically large, but drops rapidly to zero in areas near the outer surface (e.g., within 2.5 mm of the surface). In contrast, the hole size is more uniform throughout the depth of the MFIM-molded component, and the hole extends all the way to the surface.

[0262] Visual inspection Figure 28 The cross-sections shown exhibit the same trend. Within 2.5 mm of any outer surface, standard foam molded parts appear to lack pores, while in MFIM parts, pores are visible up to the outer surface.

[0263] Example 11

[0264] A large sample of recycled marine plastics was analyzed using differential scanning calorimetry and estimated to contain approximately 85% by weight HDPE, with the remainder consisting of polypropylene and contaminants.

[0265] Two parts (a 4”×4”×2” brick and a 15.24 cm diameter sphere) were successfully molded from marine plastics using the MFIM method. Molding was performed using an Engel Duo 550 Ton injection molding machine (available from Engel Machinery Inc., York, Pennsylvania, USA). Both parts are center-gate and filled using a viscous, coiled, folded flow.

[0266] The processing parameters and characteristics of the obtained parts are listed in Tables 27 and 28, respectively:

[0267]

[0268]

[0269] Example 12

[0270] A sphere with a diameter of nine inches (22.86 cm) was molded using the MFIM method described herein (“Sample 10”). Furthermore, a second sphere with a diameter of nine inches (22.86 cm) was molded using a variant method (Sample 20). The variant method referred to herein as the “reverse MFIM” method is as follows:

[0271] A) A mixture is prepared by blending a polymer (which may be in the form of pellets, powders, beads, granules, etc.) with a chemical foaming agent and any other additives (e.g., fillers). According to conventional injection molding, the mixture is introduced into the injection unit, and the rotating screw of the injection unit moves the material forward within the injection molding machine barrel, thus forming a heated fluid material. B) The screw is moved backward toward the hopper, thereby creating an intentional space within the barrel between the screw and the nozzle. C) A set volume of material is fed to the front of the injection unit barrel by the rotation of the screw, thus moving the set volume from the feed area to the front of the screw and into the intentional space created in step B. During this feeding step, the screw is rotated to move the molten material into the space between the screw and the nozzle within the barrel, thereby providing the set volume. However, this set volume only occupies a portion of the intentional space, thus providing volume for injection foaming and expansion (reduced pressure volume). D) The material is allowed to remain within the barrel between the screw and the nozzle for a period of time, referred to herein as the "reduced pressure time". During the decompression time, the material expands due to foaming, thus filling or partially filling the space created in step (B). E) Molten foam is injected into the mold cavity by the forward translation and / or rotation of the screw.

[0272] Therefore, the difference between the regular MFIM method and the reverse MFIM method is that in the MFIM method, the screw is rotated to introduce the material into the front of the barrel before being moved backward to allow for the use of the decompression space; while in the reverse method, the screw is moved backward to allow for the use of the decompression space before being rotated to introduce the material into the intentionally created space.

[0273] Both Sample 10 and Sample 20 were molded from virgin LDPE containing 2% Hydrocerol® BIH 70, 2% talc, and 1% yellow colorant. Molding was performed on an Engel Duo 550 Ton injection molding machine (available from Engel Machinery Inc., York, Pennsylvania, USA). The mold was a spherical cavity fed through a cold runner and gate within an aluminum mold.

[0274] The processing parameters are shown in Table 29:

[0275]

[0276] The component density of both Sample 10 and Sample 20 was 0.214 g / cc, with a density reduction of 77% in both cases.

[0277] Photograph of sample 20 is shown Figure 32 The photos of sample 10 and sample 10 are shown in Figure 33 In the figure, each spherical component is mounted on a support. As can be seen from the figure, sample 20, fabricated using the "reverse MFIM method," exhibits an inhomogeneous surface, while the surface of sample 10, fabricated using the MFIM method, is much more uniform. The average wrinkle depth was estimated using optical microscopy and X-ray tomography. The average wrinkle depth was measured to be less than 50 micrometers for sample 10, but 565 micrometers for sample 20.

[0278] Samples 10 and 20 were each cut in half to provide cross-sections at their maximum diameter. The cross-sections of all four pieces were photographed. One half of sample 20, fabricated using the inverse MFIM method, is shown below. Figure 34 In the middle, and half of sample 10 is shown. Figure 35 Careful examination of the edges revealed that, unlike the parts produced elsewhere using standard foaming methods, pores were found up to 2.5 mm from the surface in samples 10 and 20.

[0279] X-ray tomography was performed on samples 10 and 20 at a depth of the first inch, and the pore count and pore size were measured at different distances from the surface of each sample using the method described in Example 6. (Figure in...) Figure 36 and 37 As given, “MFIM” refers to sample 10, and “reverse MFIM” refers to sample 20.

[0280] Two additional spherical components (component 6 and component 7) were prepared under the same conditions as sample 10 and using the same polymer / talc / colorant / foaming agent mixture (i.e., by MFIM). Five cuboid components, each approximately 2 inches by 2 inches by 1 inch, were cut from each of components 6 and 7, and the compressive modulus (stress versus strain) was tested. The mean stress versus mean strain (MFIM method) was plotted and shown. Figure 38 middle.

[0281] Two additional spherical components (component 22 and component 24) were prepared under the same conditions as sample 20 and using the same polymer / talc / colorant / foaming agent mixture as sample 20. Five cuboid components, each approximately 2 inches by 2 inches by 1 inch (approximately 5.1 cm by 5.1 cm by 5.1 cm), were cut from each of components 22 and 24, and the compressive modulus (stress versus strain) was tested. The mean stress versus mean strain (inverse MFIM method) was plotted and also shown in... Figure 38 In the middle. For example, in Figure 38 It can be seen that the compression modulus of the parts manufactured by the MFIM method (the average of parts 6 and 7) is similar to that of the parts manufactured by the reverse MFIM method (the average of parts 22 and 24).

[0282] Five strips were cut from each of parts 6 and 7 (MFIM) and parts 22 and 24 (reverse MFIM). Each strip was approximately 1 inch by 1 inch by 8 inches. The flexural modulus (stress versus strain) was tested for all strips, and the results were averaged for ten MFIM-produced strips, and the results for ten reverse MFIM strips were averaged. The results are plotted on... Figure 39 middle.

[0283] Example 13

[0284] Components of various shapes and materials, as shown in Table 30, were manufactured using the MFIM method described herein. The components were cross-sectionally viewed. In all cases, the regions near the surface comprised smaller-sized holes, but the hole size increased as the component moved away from the surface. The decreasing hole size in the regions closer to the surface transitioned to a larger hole size further away. Although the transition was gradual and therefore there was no distinct layer between smaller and larger holes, the relative areas of the smaller or “compressed” holes and the larger holes were estimated by eye and confirmed by light microscopy using microscopy, and are shown in Table 30. While the figures are only estimates, examination of the images indicates that the depth and percentage area occupied by the “compressed” holes varied considerably and could depend on the component shape, material, and / or operating conditions.

[0285]

[0286] Example 14

[0287] The first part was molded using a formulation in which 98 wt% metallocene polyethylene was blended with 2 wt% Hydrocerol® BIH 70 before being loaded into the injection molding machine. The first part was formed using the MFIM method. Process details are provided in Tables 31 and 32. The part was manufactured using a 2”×4”×4” block mold (5.08×10.16×10.16 cm) with a mold cavity volume of 524.4 cc and a gate volume of 17.4 cc. The gate was cut off from the part, and the part was then subjected to a compression load test to quantify the compressive strength characteristics of the porous structure formed within the 2”×4”×4” geometry.

[0288]

[0289]

[0290] Compression tests were performed on the Instron Universal Testing System (available from Instron USA, Norwood, Massachusetts, USA). Prior to testing, each molded foam block was placed between test plates and stabilized in an ambient chamber at 30°C for five minutes. The instrument is equipped with a 250 kN load sensor. The compression test rate was 5 mm / min.

[0291] The results showed that the compressive modulus was 19 MPa for sample A (0.37 g / cc), 39 MPa for sample B (0.45 g / cc), and 55 MPa for sample C (0.57 g / cc). Figure 40 As shown, the compressive strength of metallocene polyethylene (mPE) blocks increases with increasing density.

Claims

1. A method for forming a polymer foam article, the method comprising: In the barrel of an injection molding machine, a thermoplastic polymer and a gas-generating agent source are heated and mixed to form a molten aerated mixture, wherein the temperature of the molten aerated mixture exceeds the temperature at which the gas-generating agent source generates gas at atmospheric pressure, and wherein the pressure applied to the molten aerated mixture is sufficient to substantially prevent airbag formation. A selected amount of the molten aerated mixture is collected in the collection area of ​​the cylinder; An expansion period is defined in the collection area near the molten aerated mixture, which causes an expansion volume that results in a pressure drop and maintains the expansion volume for a certain period of time to form molten polymer foam from the molten aerated mixture; The molten polymer foam is dispensed from the collection area into a cavity defined by a mold, wherein the molten polymer foam is in contact with the surface of the mold defining the cavity; as well as The molten polymer foam in the mold cavity is cooled to below the melt transition temperature of the thermoplastic polymer to form a solidified polymer foam article in the cavity.

2. The method of claim 1, wherein the dispensing comprises partially filling the mold cavity.

3. The method of claim 1, wherein the dispensing comprises substantially filling the mold cavity.

4. The method of claim 1, wherein the dispensing comprises completely filling the mold cavity.

5. The method according to any one of claims 1 to 4, wherein the gas-generating agent source is a latent gas-generating agent, potential gas-generating agent, or nascent gas-generating agent added to or present in the thermoplastic polymer matrix.

6. The method according to any one of claims 1 to 4, wherein the gas-generating agent source is an organic compound that generates a gas-generating agent through a chemical reaction.

7. The method according to any one of claims 1 to 4, wherein the gas-generating agent source is a gas-generating agent.

8. The method according to claim 6, wherein the gas-generating agent is CO2 or N2.

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