WO2020257481A1 - Agents d'expansion dans des systèmes de traitement de mousse polymère - Google Patents

Agents d'expansion dans des systèmes de traitement de mousse polymère Download PDF

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Publication number
WO2020257481A1
WO2020257481A1 PCT/US2020/038472 US2020038472W WO2020257481A1 WO 2020257481 A1 WO2020257481 A1 WO 2020257481A1 US 2020038472 W US2020038472 W US 2020038472W WO 2020257481 A1 WO2020257481 A1 WO 2020257481A1
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WO
WIPO (PCT)
Prior art keywords
blowing agent
hopper
polymeric material
physical blowing
mixture
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2020/038472
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English (en)
Inventor
Samuel Edward DIX
Levi A. Kishbaugh
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Trexel Inc
Original Assignee
Trexel Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US16/447,201 external-priority patent/US11332593B2/en
Application filed by Trexel Inc filed Critical Trexel Inc
Priority to EP20826773.2A priority Critical patent/EP3987004A4/fr
Publication of WO2020257481A1 publication Critical patent/WO2020257481A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/3442—Mixing, kneading or conveying the foamable material
    • B29C44/3446—Feeding the blowing agent
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
    • C08J9/08—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing carbon dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
    • B29C44/34—Auxiliary operations
    • B29C44/36—Feeding the material to be shaped
    • B29C44/38—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length
    • B29C44/42—Feeding the material to be shaped into a closed space, i.e. to make articles of definite length using pressure difference, e.g. by injection or by vacuum
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2201/00—Foams characterised by the foaming process
    • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
    • C08J2201/03—Extrusion of the foamable blend
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/02—CO2-releasing, e.g. NaHCO3 and citric acid
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/06—CO2, N2 or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/08—Supercritical fluid
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/18—Binary blends of expanding agents
    • C08J2203/184—Binary blends of expanding agents of chemical foaming agent and physical blowing agent, e.g. azodicarbonamide and fluorocarbon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2300/00—Characterised by the use of unspecified polymers
    • C08J2300/22—Thermoplastic resins

Definitions

  • the present application relates generally to polymer foam processing and, more particularly, to methods and systems that include introducing blowing agent into a hopper of a polymeric foam processing system.
  • Polymeric foams include a plurality of voids, also called cells, in a polymer matrix.
  • Polymeric foams are processed using a variety of techniques.
  • polymeric foams can be processed by injecting a physical blowing agent into the polymeric material within an extruder.
  • many conventional systems inject blowing agent through a blowing agent port in the barrel of the extruder into a fluid stream of polymeric material within the extruder.
  • the blowing agent may be mixed with the polymeric material to form a solution within the extruder.
  • the solution may be, for example, injected into a mold to form an injection molded polymeric foam article.
  • Such conventional systems may require modifications to standard extruder equipment (e.g., to extend length of the barrel to ensure sufficient mixing, to form a blowing agent port, etc.) and/or utilize relatively expensive equipment (e.g., blowing agent mass flow meter) to control the flow and introduction of blowing agent into the extruder.
  • a method comprising providing a hopper of a polymeric foam processing system.
  • the method further comprises supplying polymeric material to the hopper, supplying chemical blowing agent to the hopper and supplying physical blowing agent to the hopper.
  • the method further comprises supplying polymeric material, chemical blowing agent and physical blowing agent to an inlet of an extruder including a screw configured to rotate in a barrel.
  • the method further comprises conveying a mixture of polymeric material, chemical blowing agent and physical blowing agent in a downstream direction in the extruder.
  • the method further comprises accumulating a shot of the mixture of polymeric material and blowing agent and injecting the shot into a mold to form a molded polymeric foam article.
  • a system comprising an extruder including a screw configured to rotate in a barrel to convey a mixture of polymeric material and blowing agent in a downstream direction in a polymer processing space defined between the screw and the barrel.
  • the system further comprises a mold connected to an outlet of the extruder.
  • the screw is configured to periodically move in a downstream direction in the barrel to inject a shot of the mixture of polymeric material and blowing agent into the mold.
  • the system further comprises a hopper configured to hold polymeric material pellets and blowing agent in a chamber volume.
  • the hopper includes at least one inlet connectable to a source of the blowing agent.
  • the hopper includes an outlet connectable to the polymer processing space in the extruder.
  • the system further comprises a pressure regulator constructed and arranged to control the pressure of blowing agent supplied to the hopper.
  • the system further comprises at least one processor and at least one storage medium having encoded thereon executable instructions that, when executed by the at least one processor, cause the at least one processor to carry out a method which comprises controlling a pressure of the blowing agent supplied to the hopper to a desired pressure using the pressure regulator based, at least in part, on the desired weight percentage of blowing agent in the shot of the mixture of polymeric material and blowing agent.
  • a method comprises providing a hopper configured to hold polymeric material pellets and supplying blowing agent to the hopper at a desired blowing agent pressure based, at least in part, on a desired weight percentage of blowing agent in the shot.
  • the method further comprises supplying blowing agent and the polymeric material pellets to an inlet of an extruder including a screw configured to rotate in a barrel.
  • the method further comprises conveying a mixture of polymeric material and the blowing agent in a downstream direction in the extruder and accumulating a shot of the mixture of polymeric material and blowing agent.
  • the method further comprises injecting the shot into a mold to form a molded polymeric foam article.
  • a system includes an extruder including a screw configured to rotate in a barrel to convey a mixture of polymeric material and blowing agent in a downstream direction in a polymer processing space defined between the screw and the barrel.
  • the system further includes a mold connected to an outlet of the extruder.
  • the screw is configured to periodically move in a downstream direction in the barrel to inject a shot of the mixture of polymeric material and blowing agent into the mold.
  • the system further comprises a blowing agent introduction system including a source of blowing agent and a pressure regulator.
  • the system further comprises a hopper including a chamber volume having a port fluidly connected to the source of blowing agent.
  • the hopper is configured to hold polymeric material pellets and blowing agent in a chamber volume.
  • the hopper includes a first outlet configured to supply polymeric material pellets and blowing agent to the polymer processing space in the extruder.
  • the system is configured to recycle blowing agent in the chamber volume to a location in the blowing agent introduction system upstream of the pressure
  • a system in one aspect, includes an extruder including a screw configured to rotate in a barrel to convey a mixture of polymeric material and blowing agent in a downstream direction in a polymer processing space defined between the screw and the barrel.
  • the system further includes a mold connected to an outlet of the extruder.
  • the screw is configured to periodically move in a downstream direction in the barrel to inject a shot of the mixture of polymeric material and blowing agent into the mold.
  • the system further includes a blowing agent introduction system including a source of blowing agent and a hopper including at least a first chamber volume and a second chamber volume. At least one of the first or the second chamber volumes are configured to connect to the source of blowing agent and to hold polymeric material pellets and blowing agent.
  • FIG. 1 schematically illustrates a polymer foam processing system according to an embodiment.
  • FIG. 2 schematically illustrates a multi-chamber hopper assembly according to an embodiment.
  • FIG. 3 schematically illustrates a computing device suitable for use in connection with a polymer foam processing system according to an embodiment.
  • the methods and systems may include introducing blowing agent into a hopper of a polymeric foam system.
  • the methods and systems may include introducing chemical blowing agent, as well as physical blowing agent, into the hopper. It has been observed that introducing both chemical and physical blowing agents into the hopper may be particularly advantageous in some cases. For example, using physical blowing agent may reduce the amount of chemical blowing agent that otherwise would be used to achieve a certain density reduction in the resulting foamed article which can lead to cost savings. Also, using chemical blowing agent may reduce the pressure and/or amount of physical blowing agent required to achieve a certain density reduction and/or article quality (e.g., lack of warp).
  • blowing agent cost savings can lead to blowing agent cost savings and/or the ability to use less complicated and expensive equipment (e.g., gas seals).
  • the methods and systems are particularly well suited for processes that produce injection molded polymeric foam articles.
  • the methods may utilize a control system that enhances control over the amount of physical blowing agent (e.g., nitrogen, carbon dioxide) introduced into the polymeric material being processed by the system.
  • the system may control the amount of physical blowing agent introduced, in part, by controlling the pressure of blowing agent supplied to the hopper to a desired amount.
  • the desired pressure may be based, at least in part, on the desired weight percentage of physical blowing agent in the polymeric material being processed.
  • the methods may determine the desired blowing agent pressure from a variety of additional inputs which may relate to the blowing agent (e.g., blowing agent type), desired article characteristics (e.g., article weight), polymer characteristics (e.g., polymer type, polymer pellet bulk density) and equipment design (e.g., hopper chamber volume).
  • the methods and systems are designed to recycle blowing agent to reduce the amount of unused blowing agent.
  • the methods and systems may also include a multi-chamber hopper design that facilitates re-filling the chamber(s) with polymeric material pellets, for example, when a chamber is empty.
  • a blowing agent introduction system 10 is used to deliver physical blowing agent to a polymer processing system 12.
  • system 12 is an injection molding system that includes an extruder 14 and a mold 16.
  • Polymeric material e.g., in the form of pellets
  • chemical blowing agent is also provided to the hopper. The hopper supplies the chemical blowing agent, physical blowing agent and polymeric material to the extruder.
  • the extruder includes a screw 20 designed to rotate within a barrel 22 to process the polymeric material.
  • Heat e.g., provided by heaters on the extruder barrel
  • shear forces e.g., provided by the rotating screw
  • Such heat and shear forces also cause the chemical blowing agent to react (e.g., by decomposing) to form carbon dioxide which may be present in the fluid stream in the supercritical stale within the extruder.
  • the physical blowing agent e.g., nitrogen
  • the mixture is a single-phase solution with the physical blowing agent being dissolved in the polymeric material prior to injection into the mold.
  • a valve 29 is arranged between the outlet of the extruder and the inlet of the mold.
  • a shot of the mixture (e.g., single-phase solution) may be accumulated downstream of the screw within the extruder causing the screw to retract in an upstream direction within the barrel.
  • suitable conditions e.g., after a predetermined time period, at a
  • the screw stops retracting and rotating to end the plastication period of the molding cycle.
  • the screw may be forced downstream within the barrel to inject the mixture into a cavity of the mold when valve 29 opens.
  • the mixture is subjected to a pressure chop during injection which nucleates a large number of cells and a polymer foam article is formed in the mold.
  • the screw may begin to rotate once again to begin another molding cycle.
  • the method is typically repeated to produce multiple polymeric foam articles. It should also be understood that not all methods described herein involve formation of a single-phase solution and that certain methods may involve injection of a two-phase mixture (e.g., polymeric material and blowing agent) into the mold.
  • a two-phase mixture e.g., polymeric material and blowing agent
  • microcellular foam articles may be preferred in certain embodiments that produce microcellular foam articles, as described further below, to form a single-phase solution which is nucleated upon injection into the mold.
  • Suitable processes for forming single-phase solutions and nucleating upon injection into the mold have been described in commonly-owned U.S. Patent No. 6,884,823 which is incorporated herein by reference above in its entirety.
  • the polymer foam processing system may include a number of conventional components not illustrated in the figure.
  • the physical blowing agent introduction system is illustrated as being used in conjunction with an injection molding system, it should be understood that the blowing agent introduction system may be used in conjunction with any other polymer processing system into which blowing agent is introduced including blow molding systems.
  • suitable chemical blowing agent may be capable of producing carbon dioxide under conditions in the extruder.
  • the chemical blowing agent may undergo a reaction (e.g., a decomposition reaction) to form carbon dioxide upon being heated in the extruder.
  • Suitable chemical blowing agents may include acids and/or alkalis.
  • suitable chemical blowing agent may comprise citric acid, sodium bicarbonate, monosodium citrate, dinitroso pentamethylenetetramine (DPT), oxybis (benzenesulfonyl hydrazide) (OBSH), p- toluenesulfonyl hydrazide (TSH), p-toluenesulfonyl semicarbazide (TSS) and calcium carbonate.
  • DPT dinitroso pentamethylenetetramine
  • OBSH oxybis (benzenesulfonyl hydrazide)
  • TSH p- toluenesulfonyl hydrazide
  • TSS p-toluenesulfonyl semicarbazide
  • the inventors have appreciated that using certain amounts of chemical blowing agent (e.g., in combination with certain amounts of nitrogen physical blowing agent) may be preferred to form injection molding articles having desirable characteristics.
  • the weight percentage of chemical blowing agent may be between about 0.10 and 2.0 weight percent based on the total weight of the polymeric material.
  • the weight percentage of the chemical blowing agent may be greater than or equal to 0.3 weight percent or greater than or equal 0.50 weight percent based on the total weight of the polymeric material; and, in some embodiments, the weight percentage may be less than or equal to 2.0 weight percent and/or less than or equal to 1.0 and/or less than or equal to 0.5 weight percent based on the total weight of polymeric material. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 0.30 weight percent and 2.0 weight percent).
  • the chemical blowing agents used in the methods described herein may have any suitable form.
  • the chemical blowing agents may be in the form of pellets.
  • the chemical blowing agents may be in the form of particles.
  • Other forms may also be also suitable such as flakes, powder or liquid.
  • the pellets and/or particles (or other forms) may include other components (e.g., non-reactive components) in addition to the chemical blowing agent.
  • the particles may have small particle sizes such as less than 10 micron and/or less than 1 micron.
  • some such chemical blowing agent particles have been described in US Patent No. 8,563,621 which is incorporated herein by reference in its entirely.
  • the physical blowing agent introduction system includes a physical blowing agent source 26 connectable to one or more port(s) 28 that are connectable to a chamber volume in the hopper.
  • Conduit 36 is used to connect various components of the introduction system and to provide a pathway from the source to the blowing agent port(s).
  • the blowing agent introduction system upstream of the hopper, the blowing agent introduction system includes a pressure regulator 38 which, as described further herein, may be used to set the pressure of blowing agent supplied to the hopper at a desired level.
  • the blowing agent introduction system may include an accumulator 47 connected to an interchangeable bottle of blowing agent. In some embodiments, such as when a bottle does not supply blowing agent at a sufficiently high pressure, a pump may be connected to increase and/or maintain pressure of blowing agent in the introduction system.
  • a control system 44 of the physical blowing agent introduction system may receive one or more inputs (e.g., relating to the desired amount of physical blowing agent introduced into the polymeric material which may be selected by an operator) and can provide output(s) to control the pressure regulator to supply a desired physical blowing agent pressure to the hopper.
  • the blowing agent introduction system may include other standard components such as valves which may be used to selectively control blowing agent flow therepast.
  • the physical blowing agent introduction system may be configured to recycle residual blowing agent remaining in the hopper.
  • the physical blowing agent introduction system may have other designs and may not include all of the components (e.g., a control system) as described herein in all embodiments.
  • the control system may be any of the type known in the art such as a computing device, as described further below.
  • the control system is capable of receiving input signals (e.g., from a user, from other components of the polymer processing system) and sending appropriate output signals (e.g., to components of the blowing agent introduction system such as the pressure regulator and/or the polymer processing system).
  • techniques described herein may involve supplying physical blowing agent to the hopper at a desired pressure.
  • a desired amount of physical blowing agent into the polymeric material e.g., desired weight percentage of physical blowing agent in the shot of polymeric material injected into the mold
  • the desired pressure may be determined from a number of parameters in addition to the desired weight percentage of blowing agent in the polymeric material.
  • the parameters may include characteristics relating to the equipment design.
  • the hopper chamber volume may be used as a parameter.
  • the parameters may include characteristics relating to the polymeric material.
  • the type of polymer e.g., resin type such as polypropylene, polyethylene, etc.
  • weight of polymeric material and/or polymeric material density may be used as parameters.
  • the parameters may include characteristics relating to the injected molded article.
  • the weight e.g., mass of polymeric material
  • the weight of the injection molded article may be used.
  • the parameters may include characteristics relating to the physical blowing agent.
  • the type of physical blowing agent e.g., nitrogen, carbon dioxide
  • the type of physical blowing agent may be a parameter that is used in addition to the desired weight percentage of physical blowing agent in the polymeric material noted above.
  • one aspect of determining the desired physical blowing agent pressure supplied to the hopper involves a step of determining the volume of physical blowing agent in the chamber in the hopper. In some embodiments, one aspect of determining the desired physical blowing agent pressure supplied to the hopper involves a step of determining the amount of physical blowing agent that leaks out of the chamber volume of the hopper.
  • one aspect of determining the desired physical blowing agent pressure supplied to the hopper involves a step of determining the maximum number of shots that may be achieved when using a hopper having a certain chamber volume.
  • the systems and methods described herein system may be used to introduce physical blowing agent into polymeric material within the extruder over a wide range of desired amounts.
  • the desired physical blowing agent amount depends upon the particular process and is generally less than about 10% by weight of polymeric material and physical blowing agent.
  • the physical blowing agent level is less than about 5%, in others, less than about 3%, in others less than about 1%, in others less than about 0.5%, and still others less than about 0.1%, or even lower by weight of polymeric material and blowing agent mixture.
  • using low amounts of physical blowing agents has advantages such as cost savings.
  • the source provides physical blowing agent to the introduction system.
  • the source may supply any type of physical blowing agent known to those of ordinary skill in the art including nitrogen, carbon dioxide, hydrocarbons,
  • the blowing agent may be supplied in any flowable physical state such as a gas, a liquid, or a supercritical fluid.
  • the source provides nitrogen as a blowing agent.
  • the source provides carbon dioxide as a blowing agent.
  • solely carbon dioxide or nitrogen is used. Blowing agents that are in the supercritical fluid state after injection into the extruder, (optionally, before injection as well) and in particular supercritical carbon dioxide and supercritical nitrogen, are preferred in certain embodiments.
  • the system is designed to recycle unused blowing agent.
  • the system may be configured to recycle residual physical blowing agent remaining in the chamber volume in the hopper after the polymeric material in the hopper have been supplied to the extruder.
  • the residual blowing agent is removed from the hopper (e.g., via a port in the chamber volume) and re-circulated back into the blowing agent introduction system so that it may be used again.
  • the physical blowing agent may be re-circulated via conduit 46.
  • Conduit 46 for example, re-introduces the physical blowing agent into the physical blowing agent introduction system at a position upstream of the pressure regulator.
  • the physical blowing agent is re-introduced into an accumulator of the physical blowing agent introduction system.
  • recirculated physical blowing agent may be re-introduced into the chamber volume of the hopper that contains unused polymeric material (e.g., pellets).
  • the polymer foam processing system includes a hopper having multiple chambers.
  • FIG. 2 schematically illustrates a multi-chamber hopper assembly 100 according to an embodiment.
  • the multi-chamber hopper assembly includes a first chamber 102 and a second chamber 104.
  • the first and second chambers are connected to a source of polymeric material (e.g., pellets) and/or a source of chemical blowing agent.
  • the hopper assembly includes a loader 106 which is configured to contain polymeric material and chemical blowing agent upstream of the hopper chambers.
  • the assembly may include respective shut-off valves 108 arranged between the loader and inlets to the chambers which may be controlled to permit or prevent polymeric material and chemical blowing agent from entering the chambers.
  • the assembly may also include physical blowing agent inlets 112 which are fluidly connected to the blowing agent source.
  • Shut-off valves may be associated with inlets 112 to permit or prevent physical blowing agent from flowing into the chambers.
  • Shut-off valves 114 may also be positioned at respective outlets 115, 117 of the chambers. In the illustrative embodiment, the outlets are connected to a third chamber 116.
  • one of outlet shut-off valves is open to permit supply of polymeric material (and blowing agents) to the third chamber, while the other of the outlet shutoff valves is closed to prevent supply of polymeric material and blowing agents to the third chamber.
  • the appropriate outlet valve is closed and the other outlet valve is opened to enable the other chamber to supply polymeric material and chemical blowing agent to the third chamber.
  • the third chamber includes an outlet 118 that is connected to the polymer processing space so that polymeric material pellets and blowing agent may be supplied to the extruder.
  • the third chamber also includes a physical blowing agent inlet that is fluidly connected to the blowing agent source.
  • Pressure may be maintained within the chambers that are supplying the polymeric material and blowing agent to the extruder and reduced in the other chamber. That is, when the outlet of the first chamber is open and the outlet of the second chamber is closed, pressure may be maintained in the first chamber and the third chamber and may be reduced in the second chamber (e.g., to atmosphere, for example, to enable polymeric material to be added to the second chamber). Similarly, when the outlet of the second chamber is open and the outlet of the first chamber is closed, pressure may be maintained in the second chamber and the third chamber and may be reduced in the first chamber (e.g., to atmosphere, for example, to enable polymeric material pellets to be added to the second chamber). When pressure is reduced in one or more chambers, it may be accomplished by releasing the physical blowing agent from the chamber. In some cases, the released physical blowing agent may be recycled as described above.
  • blowing agent is not supplied to first chamber 102 or second chamber 104 and is only supplied to third chamber. In such embodiments, blowing agent is not supplied to first chamber 102 or second chamber 104 and is only supplied to third chamber. In such embodiments, blowing agent is not supplied to first chamber 102 or second chamber 104 and is only supplied to third chamber. In such embodiments, blowing agent is not supplied to first chamber 102 or second chamber 104 and is only supplied to third chamber. In such
  • the first chamber and second chamber may not include blowing agent ports, while the third chamber may include a physical blowing agent port. It also should be understood that not all embodiments utilize a multi-chamber hopper assembly and that a more conventional (e.g., single chamber) hopper assembly may be used in some cases.
  • polymeric material suitable for forming polymeric foams may be used with the methods described herein.
  • polymeric materials in some cases, are thermoplastics which may be amorphous, semicrystalline, or crystalline materials.
  • thermoplastics which may be amorphous, semicrystalline, or crystalline materials.
  • polymeric materials include polyolefins (e.g., polyethylene and polypropylene), styrenic polymers (e.g., polystyrene, ABS), fluoropolymers, polyamides, polyimides, polyesters, and/or mixtures of such polymeric materials.
  • polyolefin materials may be used.
  • the polyolefin material may be a mixture of more than one type of olefin, or a mixture of one or more types of polyolefin and one or more types of non-polyolefin polymeric materials.
  • the polymeric material used may depend upon the application in which the article is ultimately utilized.
  • the polymeric foam articles have a certain cell size.
  • the methods described herein may be used to produce foam articles having a small cell size.
  • the methods involve production of microcelluiar foam articles.
  • the microcellular foam article may have an average cell size of less than 100 microns.
  • the microcellular foam articles have an average cell size of less than 75 microns.
  • Average cell size may be determined by measuring a representative number of cells using microscopy (e.g., SEM) techniques.
  • the cell size may vary across the thickness of the injection molded article. For example, the cell size at or near the center of the article may be larger than the cell size approaching edges of the article and/or edges of the foamed region of the article.
  • the injection molded polymeric foam articles may have a range of void volume percentages.
  • the void volume percentage is the percentage of the volume of an article occupied by voids. It can be measured by the following equation:
  • Void volume % 100 x [1 - (density of the polymer foam article / density of solid polymer)]
  • the percentage void volume is 15%.
  • the particular void volume may depend upon the application. In some embodiments, the void volume percentage is relatively low. For example, the void volume percentage may be less than 20%, less than 15 %, less than 12%, less than 10% or less than 5%. In some embodiments, the void volume may be greater than 2%; greater than 5%, greater than 8%, greater than 10% or greater than 15%. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 2% and 15%, between 5% and 15%, between 8% and 12%, etc.).
  • the injection molded polymeric foam articles may have any suitable wall thickness.
  • wall thickness refers to the predominant cross-sectional dimension across the thickness of the article.
  • the article thickness may be less than 5.0 mm, less than 3.0 mm, less than 2.5 mm, less than 2.0 mm or less than 1.0 mm.
  • the article thickness may be greater than 0.5 mm, greater than 1.0 mm or greater than 1.5 mm. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 0.5 mm and 5 mm, between 0.5 mm and 3.0 mm, between 1.0 mm and 3.0 mm, etc.).
  • the injection molded polymeric foam articles may have unfoamed skin region(s) extending from the exterior surfaces of the article (e.g., article surfaces that are in contact with the injection mold).
  • the skin regions may surround (at least in part) a foamed interior region.
  • the total skin thickness and/or percentage of total skin thickness compared to total wall thickness may be characterized using visual techniques (e.g., by eye and/or microscopy).
  • the total skin thickness is the sum of the skin thicknesses across the cross- sectional thickness of the article.
  • the total skin thickness may be greater than 100 microns, greater than 200 microns, greater than 250 microns, greater than 300 microns, greater than 400 microns or greater than 500 microns. In some embodiments, the total skin thickness may be less than 700 microns, less than 600 microns, less than 500 microns or less than 300 microns. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 100 microns and 500 microns, between 250 microns and 700 microns, etc.).
  • the percentage of total skin thickness compared to total wall thickness may be greater than 15%, greater than 25%, greater than 40%, greater than 50% or greater than 60%. In some embodiments, the percentage of total skin thickness compared to total wall thickness may be less than 70%, less than 50%, less than 40% or less than 25%. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 25% and 70%, between 15% and 50%, etc.).
  • injection mold articles described herein have an identifiable skin. That is, such articles may comprise substantially entirely of a foamed structure.
  • the injection molded articles described herein can exhibit excellent properties including excellent mechanical properties such as high elongations.
  • the percent elongation at break (as measured by ASTM D638) may be greater than 5%, greater than 25%, greater than 50%, greater than 100%, or greater than 150%.
  • the percent elongation at break (as measured by ASTM D638) may be less than 200%, less than 150%, less than 100% or less than 50%. It should be understood that any suitable ranges defined by the above-noted minimum and maximum values may be used (e.g., between 5% and 200%, between 25% and 150%, etc.).
  • the desirable properties and characteristics enable the injection molded foam articles described herein to be used in a variety of applications.
  • the articles may be used in a variety of consumer and industrial goods including automotive components and packaging.
  • the techniques described herein may be embodied in computer- executable instructions implemented as software, including as application software, system software, firmware, middleware, embedded code, or any other suitable type of computer code.
  • Such computer-executable instructions may be written using any of a number of suitable programming languages and/or programming or scripting tools, and also may be compiled as executable machine language code or intermediate code that is executed on a framework or virtual machine.
  • A“functional facility,” however instantiated, is a structural component of a computer system that, when integrated with and executed by one or more computers, causes the one or more computers to perform a specific operational role.
  • a functional facility may be a portion of or an entire software element.
  • a functional facility may be implemented as a function of a process, or as a discrete process, or as any other suitable unit of processing. If techniques described herein are implemented as multiple functional facilities, each functional facility may be implemented in its own way; all need not be implemented the same way. Additionally, these functional facilities may be executed in parallel and/or serially, as appropriate, and may pass information between one another using a shared memory on the computer(s) on which they are executing, using a message passing protocol, or in any other suitable way.
  • functional facilities include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types.
  • the functionality of the functional facilities may be combined or distributed as desired in the systems in which they operate.
  • one or more functional facilities carrying out techniques herein may together form a complete software package.
  • These functional facilities may, in alternative embodiments, be adapted to interact with other, unrelated functional facilities and/or processes, to implement a software program application.
  • the functional facilities may be adapted to interact with other functional facilities in such a way as form an operating system.
  • the functional facilities may be implemented alternatively as a portion of or outside of an operating system.
  • Some exemplary functional facilities have been described herein for carrying out one or more tasks. It should be appreciated, though, that the functional facilities and division of tasks described is merely illustrative of the type of functional facilities that may implement the exemplary techniques described herein, and that embodiments are not limited to being implemented in any specific number, division, or type of functional facilities. In some implementations, all functionality may be implemented in a single functional facility. It should also be appreciated that, in some implementations, some of the functional facilities described herein may be implemented together with or separately from others (i.e., as a single unit or separate units), or some of these functional facilities may not be implemented.
  • Computer-executable instructions implementing the techniques described herein may, in some embodiments, be encoded on one or more computer-readable media to provide functionality to the media.
  • Computer-readable media include magnetic media such as a hard disk drive, optical media such as a Compact Disk (CD) or a Digital Versatile Disk (DVD), a persistent or non- persistent solid-state memory (e.g., Flash memory, Magnetic RAM, etc.), or any other suitable storage media.
  • Such a computer-readable medium may be implemented in any suitable manner, including as computer-readable storage media 806 of FIG. 3 described below (i.e., as a portion of a computing device 800) or as a stand-alone, separate storage medium.
  • “computer-readable media” refers to tangible storage media. Tangible storage media are non-transitory and have at least one physical, structural component.
  • at least one physical, structural component has at least one physical property that may be altered in some way during a process of creating the medium with embedded information, a process of recording information thereon, or any other process of encoding the medium with information. For example, a magnetization state of a portion of a physical structure of a computer-readable medium may be altered during a recording process.
  • these instructions may be executed on one or more suitable computing device(s) operating in any suitable computer system, including the exemplary computer system of FIG. 3, or one or more computing devices (or one or more processors of one or more computing devices) may be programmed to execute the computer-executable instructions.
  • a computing device or processor may be programmed to execute instructions when the instructions are stored in a manner accessible to the computing device or processor, such as in a data store (e.g., an on-chip cache or instruction register, a computer-readable storage medium accessible via a bus, a computer-readable storage medium accessible via one or more networks and accessible by the device/processor, etc.).
  • a data store e.g., an on-chip cache or instruction register, a computer-readable storage medium accessible via a bus, a computer-readable storage medium accessible via one or more networks and accessible by the device/processor, etc.
  • Functional facilities comprising these computer-executable instructions may be integrated with and direct the operation of a single multi-purpose programmable digital computing device, a coordinated system of two or more multi-purpose computing device sharing processing power and jointly carrying out the techniques described herein, a single computing device or coordinated system of computing devices (co-located or geographically distributed) dedicated to executing the techniques described herein, one or more Field-Programmable Gate Arrays (FPGAs) for carrying out the techniques described herein, or any other suitable system.
  • FPGAs Field-Programmable Gate Arrays
  • FIG. 3 illustrates one exemplary implementation of a computing device in the form of a computing device 800 that may be used in a system implementing techniques described herein, although others are possible. It should be appreciated that FIG. 3 is intended neither to be a depiction of necessary components for a computing device to operate in accordance with the principles described herein, nor a comprehensive depiction.
  • Computing device 800 may comprise at least one processor 802, a network adapter 804, and computer-readable storage media 806.
  • Computing device 800 may be, for example, a desktop or laptop personal computer, a personal digital assistant (PDA), a smart mobile phone, a server, a wireless access point or other networking element, or any other suitable computing device.
  • Network adapter 804 may be any suitable hardware and/or software to enable the computing device 800 to communicate wired and/or wirelessly with any other suitable computing device over any suitable computing network.
  • the computing network may include wireless access points, switches, routers, gateways, and/or other networking equipment as well as any suitable wired and/or wireless communication medium or media for exchanging data between two or more computers, including the Internet.
  • Computer-readable media 806 may be adapted to store data to be processed and/or instructions to be executed by processor 802.
  • Processor 802 enables processing of data and execution of instructions.
  • the data and instructions may be stored on the computer-readable storage media 806.
  • the data and instructions stored on computer-readable storage media 806 may comprise computer-executable instructions implementing techniques which operate according to the principles described herein.
  • computer-readable storage media 806 stores computer-executable instructions implementing various facilities and storing various information as described above.
  • Computer-readable storage media 806 may store the various processes/facilities discussed above.
  • a computing device may additionally have one or more components and peripherals, including input and output devices. These devices can be used, among other things, to present a user interface. Examples of output devices that can be used to provide a user interface include printers or display screens for visual presentation of output and speakers or other sound generating devices for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards, and pointing devices, such as mice, touch pads, and digitizing tablets. As another example, a computing device may receive input information through speech recognition or in other audible format.
  • Embodiments have been described where the techniques are implemented in circuitry and/or computer-executable instructions. It should be appreciated that some embodiments may be in the form of a method, of which at least one example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)

Abstract

L'invention concerne des procédés et des systèmes qui comprennent l'introduction d'un agent d'expansion dans une trémie d'un système de traitement de mousse polymère.
PCT/US2020/038472 2019-06-20 2020-06-18 Agents d'expansion dans des systèmes de traitement de mousse polymère Ceased WO2020257481A1 (fr)

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US16/447,201 2019-06-20
US16/447,201 US11332593B2 (en) 2018-03-01 2019-06-20 Blowing agents in polymer foam processing systems

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US4255368A (en) * 1979-07-18 1981-03-10 Union Carbide Corporation Structural foam molding process
US4406846A (en) * 1982-11-30 1983-09-27 Standard Oil Company (Indiana) Foamed thermoplastic resin comprising poly(p-methylenebenzoate)
US5393796A (en) * 1987-11-17 1995-02-28 Amesbury Industries, Inc. Method and apparatus for extruding a low density thermoplastic foam
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US6593384B2 (en) * 2000-05-25 2003-07-15 Trexel, Inc. Polymer foam processing with low blowing agent levels

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