AU2021101113A4 - Open cell polymer foam - Google Patents

Abstract

Methods of producing an open-cell polymer foam from a thermoplastic polymer are disclosed. Articles formed from the produced open-cell thermoplastic polymer foam are also disclosed and the use of the articles, for example, in the construction industry are described.

Description

"Open cell polymer foam"

Technical Field

[0001] The present invention relates to polymer foams, and in particular to thermoplastic polymer foams. The present invention further relates to methods and systems for producing open-cell polymer foams including rod, sheet, pipe and custom profiles.

Background

[0002] Polymer foams are formed of polymer materials comprising bubbles or cells of gas dispersed through the polymer material. Polymer foams are used to produce a range of products that find use in a number of applications.

[0003] Polymer foams are typically formed from either thermoplastic polymers or thermosetting polymers. The choice of polymer in forming a polymer foam product will depend on the desired properties of the product in which the foam is to be used.

[0004] Thermosetting polymers, once set, cannot be heat moulded or melted in order to reform the polymer. As such, once a foam has been formed from a thermosetting polymer, additional processing is required to form the foam into the shape required for the intended purpose. This may include mechanical processing to cut or otherwise remove any excess material. Furthermore, as any material offcuts resulting from the shaping of the foam cannot be reworked (e.g. melted and reshaped), the ability to recycle and reuse such waste materials is limited.

[0005] In contrast to thermosetting polymer, thermoplastic polymers are plastics that can be moulded in a specific temperature range. The solidification or setting of thermoplastic polymers is reversible and therefore thermoplastic polymers can be reheated and reshaped as required.

[0006] Polymer foams can be closed-cell foams which are formed by thermoplastic polymers or open-cell foams formed by thermoplastic polymers. In closed-cell foams, the gas forms discrete pockets that are completely surrounded (i.e. closed) by the solid thermoplastic polymer material. In open-cell foam, the cell walls are broken or "open", however there is sufficient rigidity in the cell walls to retain the shape.

[0007] Due to the configuration of the cells, closed-cell foams and open-cell foams have different physical properties. For example, closed-cell foams are generally more rigid, have a relatively high tensile strength and are substantially waterproof, whereas open-cell foams are typically softer, more flexible, have a lower compression set, and allow for more flow of fluid or gas through than closed cell foams.

[0008] It will be appreciated that the term "open-cell foam" does not require that each and every cell in the foam is open and an open-cell foam may comprise a portion of closed cells therein.

[0009] Polymer foam products, and particularly open-cell polymer foam products formed of polyurethane, are used extensively in the construction and other industries.

[0010] In one application, polyurethane open-cell foam backing rods, flexible lengths of profile or sheeting foam that are used as "backing" in joints or cracks, may be inserted into joints prior to filling the remainder of the joint with a sealant in order to reduce the consumption of sealant.

[0011] The properties associated with open-cell foams, such as the excellent rebound characteristics, low density and flexibility, make them the foam of choice for the above described building applications. Furthermore, due to the open-cell nature of the polyurethane foams, a quick cure of the sealant or concrete can be achieved in the backing rod and expansion joint applications due to the flow of moisture through the open cells.

[0012] Polyurethane open-cell foams are further used in the formation of acoustic foams for use in buildings, either applied to internal surfaces of a room, or to be secured around various building fittings such as water and waste pipes. Acoustic foam is generally formed of a polymer foam where one side is provided with an uneven surface, for example having a pattern of pyramidal, wave or conical shaped extrusions, and a backing material provided on the other, planar side of the sheet made of a composite barrier. Open-cell foams reduce noise levels by dissipating soundwaves in the open-cell structure of the foam.

[0013] Open-cell polyurethane foam also dominates the bedding market due to its excellent rebound characteristics and its ability to breathe. Closed-cell polyethene foam finds a limited use in bedding in providing frame support, with the limited rebound and inability to breathe due to the closed-cell nature of the foam limits its wider use in the field of bedding.

[0014] While open-cell polyurethane foam finds use in a number of applications such as those described above, manufacturing polyurethane products presents certain manufacturing difficulties in that the process requires specialty infrastructure to accommodate the toxic chemicals (e.g. toluene diisocyanate) used in the manufacturing process. In addition, as described above, open-cell polyurethane recycling is costly due to the polymer being thermosetting, therefore recycling requires a granulating and secondary bonding process to create higher density shapes. Additional processing steps are also required to form open-cell polyurethane foam into a desired shape adds a costly additional processing step and increases waste output.

[0015] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

[0016] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary

[0017] According to the present disclosure, there is provided a method of producing an open cell thermoplastic polymer foam, the method comprising:

providing a thermoplastic polymer feedstock;

heating the thermoplastic polymer feedstock to form a flow of molten thermoplastic polymer material;

introducing a gas to the flow of molten thermoplastic polymer material to form a molten polymer-gas mixture and extruding the molten polymer-gas mixture to form a closed-cell thermoplastic polymer foam; and mechanically perforating closed-cells of the closed-cell thermoplastic polymer foam thereby to produce the open-cell polymer thermoplastic polymer foam.

[0018] According to the present disclosure, there is further provided an open-cell thermoplastic polymer foam produced by a method disclosed herein.

[0019] According to the present disclosure, there is further provided an article comprising a thermoplastic open-cell thermoplastic polymer foam disclosed herein.

[0020] According to the present disclosure, there is further provided a system for producing an open-cell thermoplastic polymer foam, the system comprising:

means for providing a thermoplastic polymer feedstock;

a heater for heating the thermoplastic polymer feedstock to form a flow of molten thermoplastic polymer material;

a pressurised gas source for introducing a gas to the flow of molten thermoplastic polymer material to form a molten polymer-gas mixture;

an extruder for extruding the molten polymer-gas mixture to form a closed-cell thermoplastic polymer foam; and

mechanical perforation means for mechanically perforating closed-cells of the closed cell thermoplastic polymer foam thereby to produce the open-cell polymer thermoplastic polymer foam.

Definitions

[0021] Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or groups of compositions of matter. Thus, as used herein, the singular forms "a", "an" and "the" include plural aspects unless the context clearly dictates otherwise. For example, reference to "a" includes a single as well as two or more; reference to "an" includes a single as well as two or more; reference to "the" includes a single as well as two or more and so forth.

[0022] Each example of the present disclosure described herein is to be applied mutatis mutandis to each and every other example unless specifically stated otherwise. The present disclosure is not to be limited in scope by the specific examples described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the disclosure as described herein.

[0023] The term "and/or", e.g., "X and/or Y" shall be understood to mean either "X and Y" or "X or Y" and shall be taken to provide explicit support for both meanings or for either meaning.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0025] The term "about" as used herein means within 5%, and more preferably within 1%, of a given value or range. For example, "about 3.7%" means from 3.5 to 3.9%, preferably from 3.66 to 3.74%. Wnthte term "about" is associated with a range of values, e.g., "about X% to Y%", the term "about" is intended to modify both the lower (X) and upper (Y) values of the recited range. For example, "about 20% to 40%" is equivalent to "about 20% to about 40%".

Description of Embodiments

[0026] A method of producing an open-cell thermoplastic polymer foam is provided.

[0027] The method comprises providing a thermoplastic polymer feedstock from which the open-cell thermoplastic polymer foam is to be formed. The production of the thermoplastic polymer feedstock may be incorporated as a process step in the overall method for producing the open-cell thermoplastic polymer foam. In a preferred embodiment, however, the thermoplastic polymer feedstock is pre-manufactured and stored as a solid for use in the described method. As the feedstock material is a thermoplastic polymer, the stored solid feedstock can be heated and melted as required for use in the method.

[0028] In an embodiment, the thermoplastic polymer feedstock is in the form of beads and stored in a hopper from which they are fed into the process as required.

[0029] It will be appreciated that excess or waste thermoplastic polymer material from this or other manufacturing processes can be recycled and re-used as the thermoplastic polymer feedstock for the described method. For example, off-cuts from the final foam product can be refed to the hopper for re-use.

[0030] The thermoplastic polymer feedstock maybe formed of any thermoplastic polymer material suitable for forming a foam, in particular by an extrusion process.

[0031] For example, the thermoplastic polymer feedstock comprises one or polymers selected from the group comprising: thermoplastic polyamides (TPE-A); thermoplastic copolyesters (TPE-E); styrenic block copolymers (TPE-S); thermoplastic polyurethanes; thermoplastic polyolefinelastomers (TPE-0), not classified thermoplastic elastomers (TPZ); polyolefin plastomers (POP); polyolefin elastomers (POE); silicone elastomers (TPSiV) and combinations thereof.

[0032] In a particular embodiment, the polymer feedstock comprises one or more polymers selected from polyolefin elastomers (POE) and/or polyolefin plastomers (POP) or a combination thereof. Such compositions have been found to provide a high degree of elasticity, compression set, UV stability and desired thermal properties in addition to the being suitable for processing on standard thermoplastic extruder equipment

[0033] For example, the polymer feedstock may comprise an elastomeric polypropylene which has the molecular structure of propylene and ethylene monomer integrated in the molecular chain. The ethylene content can be varied to provide a desired degree of flexibility, elasticity, and/or compression.

[0034] The thermoplastic polymer feedstock may be heated as required to form a flow of molten thermoplastic polymer material. The temperature to which the thermoplastic polymer feedstock is heated will vary depending on the particular composition of the thermoplastic polymer.

[0035] Prior to or during the heating process, one or more additives may introduced to the molten thermoplastic polymer material. In an embodiment, dye or pigment is introduced to provide a coloured thermoplastic polymer foam such that formed products can be distinguished based on a number of characteristics, for example to indicate the manufacturer of the foam, to indicate the intended use, or to indicate different physical characteristics of the foam product to a user.

[0036] Gas is introduced to the flow of molten thermoplastic polymer material to form a molten polymer-gas mixture. Preferably the gas is introduced in a manner such that the gas is substantially homogenously dispersed throughout the molten thermoplastic polymer material. In an embodiment, the gas comprises butane, propane isobutane or a combination thereof.

[0037] The molten polymer-gas mixture is then extruded through the opening of a die to form a closed-cell thermoplastic polymer foam. The opening of the die is configured to provide the desired shape (e.g. rod, tube, sheet, or other custom shape) to the final product.

[0038] It will be appreciated that the gas is introduced into the molten thermoplastic polymer material under pressure and that, as the molten thermoplastic polymer material is extruded through the die to an area of lower pressure, the gas within the thermoplastic polymer material expands forming bubbles, i.e. cells, in the thermoplastic polymer material to produce a thermoplastic polymer foam comprising predominantly closed cells. These cells, as a result of their closed nature preventing the flow of the expanding gas, are typically of a larger size than is achievable in the production of thermosetting polymer foams with open cells, leading to a lower density foam.

[0039] In order to provide a foam that suitable for use in applications commonly requiring the use of open-cell thermosetting polymer foams, the above described closed-cell thermoplastic polymer foam undergoes further processing in order to convert the closed-cell thermoplastic polymer foam to an open-cell polymer foam. In particular, the walls of the closed cells are mechanically perforated to convert the closed cells to open cells.

[0040] This mechanical "opening" of the cells may be achieved by any method that acts to mechanically disrupt the closed cell walls to convert the closed cells to open cells.

[0041] It will be appreciated that not all of the closed cells forming the extruded closed-cell thermoplastic need be converted for the resulting foam to be considered an open-cell thermoplastic foam. For example, the mechanical perforation may provide an open-cell thermoplastic foam comprising at least 30% open cells, for example around 40%, around 50%, around 60%, or around 70% or more open cells in order to provide the open-cell thermoplastic polymer foam. The degree of opening will vary depending on the desired final physical properties of the final product, which in turn will be determined based on the intended use of the final product.

[0042] In an embodiment, mechanically perforating closed cells of the closed-cell thermoplastic polymer foam comprises inserting an array of pins into the extruded closed-cell thermoplastic polymer foam. The height, diameter and density of the pins will depend on a number of factors. For example the height of the pins may depend on the thickness of the foam to be mechanically perforated and the desired depth of penetration of the pins. The diameter of the pins may be smaller than the diameter of the closed cells to be perforated, and may be sized and spaced in a manner that allows for multiple pins to perforate a single closed cell.

[0043] In an embodiment, the diameter of the pins may be from about 0.1 mm to about 5 mm, for example the pin diameter may be about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4.0 mm, 4.5 mm or 5.0 mm. However, it will be appreciated that for certain applications such as the production of bedding, larger diameter pins may be used to achieve the desired flexibility, for example a pin diameter of about 50 mm or even up to about 80 mm.

[0044] The pins in the array of pins may be regularly or irregularly spaced from one another or a combination of regularly and irregularly spaced. In an embodiment, the pins in the array of pins are spaced in a way to form a particular pattern.

[0045] The disclosed method is preferably run in a continuous manner so as to provide a continuous production of extruded, perforated foam. In this manner, the array of pins is configured to continuously perforate the flow of extruded closed-cell thermoplastic polymer foam exiting the extrusion die. In an embodiment, the array of pins are radially ourwardly extending from a roller such that the flow of extruded closed-cell thermoplastic polymer exiting the extrusion die is continuously mechanically perforated by the array of pins as the roller rotates.

[0046] The resulting open-cell thermoplastic polymer foam provides the combined benefits of traditional closed-cell foams which are recyclable, relatively cheaper, more efficient and safer to produce, and improved stability in wet and humid environments, with the physical characteristics of traditional thermosetting open-cell foams. Such products may be used to replace the use of polyurethane foams typically used in, for example, backing rods, acoustic foams and bedding.

[0047] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (5)

CLAIMS:

1. A method of producing an open-cell thermoplastic polymer foam, the method comprising

providing a thermoplastic polymer feedstock;

heating the thermoplastic polymer feedstock to form a flow of molten thermoplastic polymer material;

introducing a gas to the flow of molten thermoplastic polymer material to form a molten polymer-gas mixture and extruding the molten polymer-gas mixture to form a closed-cell thermoplastic polymer foam; and

mechanically perforating closed cells of the closed-cell thermoplastic polymer foam thereby to produce the open-cell polymer thermoplastic polymer foam.

2. The method according to claim 1, wherein the thermoplastic polymer feedstock comprises one or polymers selected from the group comprising: thermoplastic polyamides (TPE A); thermoplastic copolyesters (TPE-E); styrenic block copolymers (TPE-S); thermoplastic polyurethanes; thermoplastic polyolefinelastomers (TPE-0), not classified thermoplastic elastomers (TPZ); polyolefin plastomers (POP); polyolefin elastomers (POE); silicone elastomers (TPSiV) and combinations thereof.

3. The method according to claim 2, wherein the thermoplastic polymer feedstock comprises one or more polymers selected from polyolefin elastomers (POE) and/or polyolefin plastomers (POP) or a combination thereof.

4. The method according to any one of the preceding claims, wherein mechanically perforating closed cells of the closed-cell thermoplastic polymer foam comprises inserting an array of pins into the extruded closed-cell thermoplastic polymer foam.

5. An open-cell thermoplastic polymer foam produced by a method according to any one of claims 1 to 4.