Manufacture of pet expanded cellular foams

Abstract

A method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET) from a polyethylene terephthalate component in particulate form. The polyethylene terephthalate in the polyethylene terephthalate component comprises or consists of recycled polyethylene terephthalate, and has a melt flow rate (MFR) within the range of from 10 to 35 g / 10 min; and an intrinsic viscosity within the range of from 0.70 to 1.0 dl / g. The polyethylene terephthalate component is blended with a chain extender, nucleating agent(s) and physical blowing agent(s) to form a molten expandable polyethylene terephthalate composition which is extruded through a die to form an expanded cellular foam, formed from polyethylene terephthalate, having improved fire-retardant properties.

Description

[0001] Manufacture of PET Expanded Cellular Foams

[0001] The present invention relates to a method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET), and to an expanded cellular foam composed of polyethylene terephthalate (PET).

[0002] It is well-known to those skilled in the art of manufacturing thermoplastic polymer expanded cellular foams to produce such foams from polyethylene terephthalate (PET). PET expanded cellular foams are used for a variety of different industrial applications, for example for use in the transport and construction industries, in particular for use as a core layer in sandwich structures, for use in thermal and / or acoustic insulation panels, for use in vibration damping, and for use in building and construction applications, for example in walls, floors, ceilings, roofs or panels and / or supports or structural insulation, for example in vessels, containers, pipes, tanks, tubes, and ducts.

[0003] For many of these applications, the PET expanded cellular foam is required to exhibit fire-retardant properties.

[0004] It is known to produce PET foams for industrial applications from virgin PET or from recycled post-consumer or industrial PET. When manufacturing PET foam from recycled post- consumer or industrial PET, the PET material is provided in the form of flakes, which have been formed by granulating or shredding post-consumer PET products such as bottles, packaging, etc, or by granulating or shredding industrial PET waste, or in the form of pellets which have been obtained from the flakes. As is well-known to those skilled in the art, the recycled PET is subjected to additional processing, such as washing. The recycled PET may also be subjected to thermal treatments to modify the material properties of the recycled PET.

[0005] In the manufacture of PET structural foams which are required to exhibit fire-retardant properties, it is well known to add various fire-retardant additives to the PET composition. However, the need for such fire-retardant additives increases the cost and complexity of the manufacture of the PET foam, and can reduce the mechanical properties of the resultant fire- retardant PET foam.

[0006] Some commercially available PET foams are produced from virgin PET and do exhibit some fire-retardant properties in the absence of the addition of any specific fire-retardant additives, such as halogen-containing additives and phosphorous-containing additives. For example, some commercially available PET foams which are produced from virgin PET can achieve a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of at least fire class C. 1 420203GB

[0007] However, there is a need in the art for PET foams which are produced from recycled post-consumer or industrial PET and which can exhibit similar fire-retardant properties to PET foams which are produced from virgin PET even in the absence of the addition of any specific fire-retardant additives, such as halogen-containing additives and phosphorous-containing additives. The Applicant is not aware that any such recycled PET fire-retardant foams, exhibiting such a fire performance classification in the absence of any fire-retardant additives, are currently available in commerce.

[0008] Moreover, it is believed that the PET recycling process generally degrades the mechanical properties of the PET resin, which makes the recycled PET resin less suitable than virgin PET resin for the manufacture of structural foams having fire-retardant properties.

[0009] Accordingly, there is a need in the art for the production of PET foams which are produced from recycled PET, which is recycled from post-consumer PET and / or industrial PET, and exhibit good fire-retardant properties, without the addition of any specific fire- retardant additives, such as halogen-containing additives and / or phosphorous-containing additives.

[0010] There is also a need in the art to produce PET foams which exhibit good fire-retardant properties, without the addition of any specific fire-retardant additives, such as halogen- containing additives and / or phosphorous-containing additives, and can be produced using known PET foam manufacturing techniques from recycled PET, which is recycled from post- consumer or industrial PET.

[0011] Furthermore, there is a need in the art for the production of PET foams which are produced from recycled PET and can exhibit similar or improved fire-retardant properties as compared to PET foams produced from virgin PET, without the addition of any specific fire- retardant additives, such as halogen-containing additives and / or phosphorous-containing additives.

[0012] The present invention aims to meet these needs in the art and to overcome the problem of achieving good or improved fire-retardant properties of PET foams produced from recycled PET, and articles incorporating such PET foams, even when such PET foams do not comprise any specific fire-retardant additives, such as halogen-containing additives and / or phosphorous- containing additives.

[0013] In accordance with a first aspect of the present invention, there is provided a method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET), the method comprising the steps of: 2 420203GB a. providing a polyethylene terephthalate component in particulate form, wherein the polyethylene terephthalate in the polyethylene terephthalate component comprises or consists of recycled polyethylene terephthalate, and the polyethylene terephthalate component has the following properties: i. a melt flow rate (MFR) within the range of from 10 to 35 g / 10 min; and ii. an intrinsic viscosity within the range of from 0.70 to 1.0 dl / g; b. blending the polyethylene terephthalate component with at least one chain extender and at least one nucleating agent to form a polyethylene terephthalate blend; c. heating the polyethylene terephthalate blend and at least one physical blowing agent to form a molten expandable polyethylene terephthalate composition in an extruder; and d. extruding the molten expandable polyethylene terephthalate composition through a die of the extruder to form an expanded cellular foam composed of polyethylene terephthalate.

[0014] The recycled polyethylene terephthalate is a post-consumer and / or industrial PET resin which has been collected and then treated, for example by washing, using recycling processes well-known to those skilled in the art of polymer processing.

[0015] Preferably, the polyethylene terephthalate in the polyethylene terephthalate component consists of recycled polyethylene terephthalate. Typically, the particulate form comprises pellets of recycled polyethylene terephthalate, and for example the pellets have been obtained from flakes of recycled polyethylene terephthalate.

[0016] In preferred embodiments of the present invention, the polyethylene terephthalate component comprises one or more contaminants selected from (i) polyvinyl chloride (PVC) at a concentration of up to 7.5 ppm by weight, typically up to 5 ppm by weight; (ii) polyethylene terephthalate glycol (PETG) at a concentration of up to 20 ppm by weight, typically up to 15 ppm by weight; (iii) one or more polyolefins (PO) at a concentration of up to 80 ppm by weight, typically up to 55 ppm by weight; and (iv) one or more low melting point polymer resins having a melting point of lower than 100 °C at a concentration of up to 40 ppm by weight, typically up to 30 ppm by weight, each concentration being based on the weight of the polyethylene terephthalate component.

[0017] The contaminants, PVC, PETG, PO, and low melting point polymer resins, and potentially also other organic species, are typically present in recycled polyethylene terephthalate, obtained from post-consumer or industrial sources, and are present as a result of 3 420203GB not having been completely eliminated during the recovery and recycling process of the post- consumer or industrial polyethylene terephthalate. In this specification these organic and polymeric constituents are also considered to constitute unavoidable and undesired contaminants of the recycled post-consumer polyethylene terephthalate. In this specification, the concentration of these contaminants, PVC, PETG, PO, and low melting point polymer resins, in the recycled polyethylene terephthalate is measured by an analysis conducted on the flakes of the recycled polyethylene terephthalate, which are produced in the conventional PET recycling process.

[0018] In this specification, the term “polyethylene terephthalate blend” is intended to mean the polyethylene terephthalate-containing composition prior to addition of the physical blowing agent(s) to form an expanded cellular foam, i.e. the polymer and its additives apart from the physical blowing agent. The polyethylene terephthalate blend comprises not only the polyethylene terephthalate component, but also the chain extender(s), the nucleating agent(s) and (if present) any fire-retardant additive(s), and any masterbatch ingredients, such as a polyester (e.g. virgin PET) carrier, which may have been used to incorporate the chain extender(s), the nucleating agent(s) and (if present) any fire-retardant additive(s) as one or more masterbatches into the polyethylene terephthalate-containing composition prior to addition of the physical blowing agent(s) to form an expanded cellular foam.

[0019] In preferred embodiments of the present invention, the at least one chain extender comprises pyromellitic dianhydride (PMDA) at a concentration of from 0.15 to 0.35 wt%, preferably from 0.2 to 0.3 wt%, based on the weight of the polyethylene terephthalate blend.

[0020] In preferred embodiments of the present invention, the at least one nucleating agent comprises an organic nucleating agent, in particular a thermoplastic fluoropolymer, preferably an irradiated thermoplastic fluoropolymer, for example polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), at a concentration of from 0.075 to 0.25 wt% based on the weight of the polyethylene terephthalate blend.

[0021] In preferred embodiments of the present invention, the at least one nucleating agent comprises an inorganic nucleating agent which is an inorganic particulate, preferably talc, at a concentration of from 1 to 3 wt% based on the weight of the polyethylene terephthalate blend.

[0022] In preferred embodiments of the present invention, the at least one physical blowing agent comprises a hydrocarbon having from 4 to 7 carbon atoms, preferably an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, more preferably cyclopentane (i.e. C5H10), wherein the hydrocarbon physical blowing agent is at a concentration of from 1 to 3 4 420203GB wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0023] In preferred embodiments of the present invention, the at least one physical blowing agent further comprises an inorganic gas, preferably wherein the inorganic gas is selected from nitrogen or carbon dioxide or a mixture thereof, wherein the inorganic gas physical blowing agent is at a concentration of from 0.02 to 0.7 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0024] In preferred embodiments of the present invention, the inorganic gas comprises or consists of nitrogen, wherein the nitrogen is at a concentration of from 0.02 to 0.06 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0025] In preferred embodiments of the present invention, the at least one physical blowing agent comprises a mixture of an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, preferably cyclopentane, and nitrogen.

[0026] In preferred embodiments of the present invention, the inorganic gas comprises or consists of carbon dioxide, wherein the carbon dioxide is at a concentration of from 0.2 to 0.6 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0027] In preferred embodiments of the present invention, the molten expandable polyethylene terephthalate composition is halogen-free and / or free of any fire-retardant additive, preferably free of any halogen-containing additive and / or phosphorous-containing additive functioning as a fire-retardant additive, more preferably free of a polyphosphonate polymer.

[0028] In preferred embodiments of the present invention, the molten expandable polyethylene terephthalate composition consists of a mixture of polyethylene terephthalate, the at least one chain extender, the at least one nucleating agent and the at least one physical blowing agent, and optionally any organic contaminants up to a total contaminant concentration of 100 ppm by weight based on the weight of the polyethylene terephthalate component. As described above, the contaminant concentration was measured on flakes of the recycled polyethylene terephthalate produced using the conventional PET recycling process.

[0029] In preferred embodiments of the present invention, the molten expandable polyethylene terephthalate composition is heated in the extruder to a temperature within the range of from 260 to 300 °C and the temperature of the die is within the range of from 260 to 290 °C.

[0030] In preferred embodiments of the present invention, the die is a strand die which comprises an array of holes which form a plurality of extruded strands composed of the 5 420203GB expanded cellular foam, and wherein the extruded foam strands are bonded together by fusion bonding to form an elongate board composed of the expanded cellular foam.

[0031] In preferred embodiments of the present invention, the expanded cellular foam has a density of from 80 to 250 kg / m3, for example from 105 to 200 kg / m3.

[0032] In accordance with a second aspect of the present invention, there is provided an expanded cellular foam composed of polyethylene terephthalate (PET), wherein the expanded cellular foam comprises chain-extended polyethylene terephthalate in which polyethylene terephthalate molecules have been chain-extended by at least one chain extender, at least one nucleating agent, and at least one physical blowing agent, wherein the at least one physical blowing agent comprises a mixture of an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, and nitrogen,, and wherein the expanded cellular foam is free of any fire retardant additives, including any halogen-containing additive and phosphorous-containing additive functioning as a fire retardant additive, wherein the expanded cellular foam has a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of at least C-s2-d0, which is a fire class C, a smoke class s2 and a flaming droplets / particles class d0.

[0033] In preferred embodiments of the second aspect of the present invention, the alicyclic hydrocarbon compound comprises cyclopentane,

[0034] In preferred embodiments of the second aspect of the present invention, the at least one chain extender comprises pyromellitic dianhydride (PMDA).

[0035] In preferred embodiments of the second aspect of the present invention, the at least one nucleating agent comprises (i) a first organic nucleating agent which comprises a thermoplastic fluoropolymer, preferably an irradiated thermoplastic fluoropolymer, for example polyvinylidene fluoride or polytetrafluoroethylene, and (ii) a second inorganic nucleating agent which comprises an inorganic particulate, preferably talc.

[0036] In preferred embodiments of the second aspect of the present invention, the expanded cellular foam is in the form of an elongate board formed by fusion bonding a plurality of extruded foam strands.

[0037] In preferred embodiments of the second aspect of the present invention, the expanded cellular foam has a density of from 80 to 250 kg / m3, for example from 105 to 200 kg / m3.

[0038] During the devising of the present invention by the inventors, a number of experiments were carried out. Various properties of the PET resins, and the resultant PET foams, were tested. 6 420203GB

[0039] Before testing the polyethylene terephthalate resins, the PET resins were dried for a period of at least 12 hours at a temperature of 140°C in a conventional drier.

[0040] In this specification, the weight average molecular weight (Mw) and the dispersity (Đ) were measured by Gel Permeation Chromatography using a Malvern / Viscotek TDA 301 with associated pump and autosampler equipped with PL HFIPgel guard plus 2 x PL HFIPgel 300 x 7.5mm, 9μm Agilent HPLC columns and differential refractive index detector. Samples were dissolved in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) at a concentration of 2 mg / mL and eluted with HFIP with 25 mM NaTFAc at a flow rate of 0.8 mL / minute at 40 °C. The GPC system was calibrated using a series of Agilent Technologies EasiVial polymethylmethacrylate (PMMA) calibrants and the Mw results were expressed as PMMA equivalent molecular weights.

[0041] In this specification, the melt flow rate (MFR) was measured according to the test protocol of International Standard ISO 1133-2. In particular, the measurement test used an extrusion plastometer available in commerce under the trade name MFlow from ZwickRoell GmbH, Germany. In the measurement test, 8.5 grams of dried PET granules were extruded at a temperature of 275 °C after a preheating period of 3 minutes, and the applied weight to cause extrusion through a capillary tube in this standard test was 2.16 kg.

[0042] In this specification, the intrinsic viscosity was measured according to the test protocol of the American standard ASTM D4603-18, the test using a glass capillary viscometer at a temperature of 30 °C to test a solution having a 0.5 wt% concentration of PET dissolved in a 60 / 40 (by weight) mixture of phenol and 1,1,2,2-tetrachloroethane.

[0043] In this specification, the term “free of any fire-retardant additive(s)” is defined as meaning that the total concentration of any conventional functional fire-retardant additive(s), which are known to those skilled in the art as primarily functioning to provide fire-retardant properties to thermoplastic polymer resins, in the polyethylene terephthalate resin composition is less than 100 ppm by weight (i.e. less than 0.01 wt%), based on the total weight of the polyethylene terephthalate resin composition.

[0044] In this specification, the resultant extruded cellular PET foams were subjected to fire- testing to determine the fire performance classification according to the Single Burning Item (SBI) fire test of the EU standard EN-13823. The various classification criteria for the (SBI) fire test of the EU standard EN-13823 are set out below in Table 1. 7 420203GB

[0045] Table 1 8 420203GB

[0046] The present invention is predicated on the finding of the present inventors that by providing a recycled PET resin with specific material properties, a PET expanded cellular foam, produced by extrusion, for example reactive extrusion, can be produced from a recycled PET resin, from post-consumer or industrial sources, and the foam can have good fire- retardance properties even though no conventional functional fire-retardant additive(s) have been added to the PET resin.

[0047] Furthermore, by combining the recycled PET resin having the specific material properties with a chain extender, such as PMDA, one or more nucleating agents, and one or more physical blowing agents, the PET foam, particularly when made from a recycled PET starting material for example in the form of pellets, can exhibit improved fire-retardance performance as compared to some commercially available recycled PET resins known for the production of PET foams and can exhibit similar or improved fire-retardance performance as compared to some commercially available virgin PET resins known for the production of PET foams.

[0048] The present invention is particularly predicated on the finding of the present inventors that by providing a recycled PET resin with specific material properties, in particular a specific melt flow rate (MFR) and intrinsic viscosity, and preferably also a particular average molecular weight and dispersity, and providing that the contaminant concentration in the recycled PET resin is very low, and therefore the recycled PET resin has a high purity, the recycled PET resin can achieve fire-retardant properties of the resultant PET foam that are similar to, or even better than, the fire-retardant properties achieved using virgin PET.

[0049] Also, the present invention is particularly predicated on the additional finding of the present inventors that by providing a particular combination of physical blowing agents, in particular a combination of an alicyclic hydrocarbon such as cyclopentane in combination with a small concentration, relative to the concentration of the alicyclic hydrocarbon, of nitrogen, the fire-retardant properties of the PET foam can be significantly enhanced as compared to the use of a physical blowing agent consisting only of an alicyclic hydrocarbon, or a physical blowing agent consisting only of a blend of an alicyclic hydrocarbon and carbon dioxide. The improved fire-retardant properties associated with the combination of an alicyclic hydrocarbon such as cyclopentane and nitrogen can be achieved using recycled PET.

[0050] The Examples and Comparative Examples described hereinafter show the unexpectedly enhanced fire-retardant properties of the PET foams produced by the method of the preferred embodiments of the present invention.

[0051] Embodiments of the present invention will now be described by way of example only. 9 420203GB

[0052] The present invention provides a method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET).

[0053] A starting material is provided, which is a polyethylene terephthalate component in particulate form. The polyethylene terephthalate component comprises or consists of recycled polyethylene terephthalate. In the preferred embodiments of the present invention, the polyethylene terephthalate component consists of recycled polyethylene terephthalate. Typically, the particulate form comprises pellets of recycled polyethylene terephthalate, and for example the pellets have been obtained from flakes of recycled polyethylene terephthalate. However, the recycled polyethylene terephthalate composition may be in the form of flakes which have been produced by granulating or shredding articles composed of polyethylene terephthalate, which may be post-consumer articles such as bottles or may be industrial waste from an industrial source, and using washing processes known to those skilled in the art of polymer processing.

[0054] In this specification, the term “recycled post-consumer or industrial polyethylene terephthalate” is herein defined as meaning that the polyethylene terephthalate comprises at least 90 wt% of post-consumer or industrial polyethylene terephthalate which has been recovered, in a recycling process, from consumer articles such as bottles, packaging, etc or from an industrial source, and up to 10 wt% of virgin polyethylene terephthalate, each based on the total weight of the polyethylene terephthalate.

[0055] However, in other less preferred embodiments the polyethylene terephthalate composition can comprise a small proportion of added virgin polyethylene terephthalate in the form of pellets. For example, in alternative embodiments the polyethylene terephthalate in the polyethylene terephthalate component consists of a mixture of recycled polyethylene terephthalate and virgin polyethylene terephthalate, wherein the mixture comprises at least 50 wt% recycled polyethylene terephthalate and up to 50 wt% virgin polyethylene terephthalate, each based on the total weight of the polyethylene terephthalate, optionally at least 70 wt% recycled polyethylene terephthalate and up to 30 wt% virgin polyethylene terephthalate, each based on the total weight of the polyethylene terephthalate.

[0056] In accordance with the present invention, the polyethylene terephthalate component has the following properties: a melt flow rate (MFR) within the range of from 10 to 35 g / 10 min, typically from 20 to 23 g / 10 min; and an intrinsic viscosity within the range of from 0.70 to 1.0 dl / g, typically from 0.70 to 0.85 dl / g, more typically from 0.77 to 0.82 dl / g.

[0057] The polyethylene terephthalate component preferably also has a weight averaged molecular weight (Mw) within the range of from 35,000 to 38,000 g / mol; and a dispersity (Đ) 10 420203GB within the range of from 3.8 to 4.2. These various properties are measured using the measurement protocols described hereinabove.

[0058] The polyethylene terephthalate component preferably comprises very low concentrations of contaminants. Contaminants are often present in recycled PET as a result of the PET having been recovered from post-consumer or industrial PET-containing waste. However, the present inventors have found that by utilising a recycled PET which has a very low contaminant concentration, the resultant PET foam may have enhanced fire-retardant properties as compared to a recycled PET which has a higher contaminant concentration. As described above, the contaminant concentration was measured on flakes of the recycled polyethylene terephthalate produced using the conventional PET recycling process.

[0059] The polyethylene terephthalate component typically comprises one or more contaminants selected from: (i) polyvinyl chloride (PVC) at a concentration of up to 7.5 ppm by weight, typically up to 5 ppm by weight; (ii) polyethylene terephthalate glycol (PETG) at a concentration of up to 20 ppm by weight, typically up to 15 ppm by weight; (iii) one or more polyolefins (PO) at a concentration of up to 80 ppm by weight, typically up to 55 ppm by weight; and (iv) one or more low melting point polymer resins having a melting point of lower than 100 °C at a concentration of up to 40 ppm by weight, typically up to 30 ppm by weight, each concentration being based on the total weight of the polyethylene terephthalate component.

[0060] The polyethylene terephthalate component is blended with at least one chain extender, and at least one nucleating agent to form a polyethylene terephthalate blend.

[0061] The at least one chain extender typically comprises or consists of pyromellitic dianhydride (PMDA), which has CAS Number 89-32-7, at a concentration of from 0.15 to 0.35 wt%, preferably from 0.2 to 0.3 wt%, based on the weight of the polyethylene terephthalate blend.

[0062] The at least one nucleating agent typically comprises or consists of a mixture of a nucleating agents, for example a mixture of an organic or polymeric nucleating agent and an inorganic nucleating agent.

[0063] For example, typically the at least one nucleating agent comprises a thermoplastic fluoropolymer, preferably an irradiated thermoplastic fluoropolymer, for example 11 420203GB polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), at a concentration of from 0.075 to 0.25 wt% based on the weight of the polyethylene terephthalate blend. Additionally, the at least one nucleating agent typically comprises an inorganic particulate, preferably talc, which has CAS Number 14807-96-6, at a concentration of from 1 to 3 wt% based on the weight of the polyethylene terephthalate blend.

[0064] In preferred embodiments of the present invention, the at least one chain extender and the at least one nucleating agent are added to the polyethylene terephthalate component in the form of respective masterbatches to form the polyethylene terephthalate blend, using masterbatch technology well known to those skilled in the art.

[0065] The polyethylene terephthalate blend is mixed with at least one physical blowing agent, and the mixture of the polyethylene terephthalate blend and the at least one physical blowing agent is heated to form a molten expandable polyethylene terephthalate composition in an extruder.

[0066] Typically, the polyethylene terephthalate blend is pre-heated to form a molten state in the extruder and then the at least one physical blowing agent is introduced into the molten polyethylene terephthalate blend, and mixed into the molten polyethylene terephthalate blend, to form the molten expandable polyethylene terephthalate composition. Then, the molten expandable polyethylene terephthalate composition is extruded through a die of the extruder to form an expanded cellular foam composed of polyethylene terephthalate.

[0067] Preferably, the at least one physical blowing agent comprises a hydrocarbon having from 4 to 7 carbon atoms, preferably an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms. A particularly preferred alicyclic hydrocarbon compound for the physical blowing agent is cyclopentane. The hydrocarbon physical blowing agent is typically at a concentration of from 1 to 3 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0068] More preferably, the at least one physical blowing agent further comprises an inorganic gas. The inorganic gas is typically selected from nitrogen or carbon dioxide or a mixture thereof. The inorganic gas physical blowing agent is typically at a concentration of from 0.02 to 0.7 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0069] In a particularly preferred embodiment of the present invention, the inorganic gas comprises or consists of nitrogen, wherein the nitrogen is at a concentration of from 0.02 to 0.06 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition. 12 420203GB

[0070] In alternative embodiments of the present invention, the inorganic gas may comprise or consist of carbon dioxide. The carbon dioxide is typically at a concentration of from 0.2 to 0.6 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

[0071] Most preferably, the molten expandable polyethylene terephthalate composition consists of a blend of polyethylene terephthalate, the at least one chain extender, the at least one nucleating agent and the at least one physical blowing agent, and any unavoidable organic contaminants up to a total contaminant concentration of 100 ppm by weight based on the weight of the polyethylene terephthalate. As described above, the contaminant concentration was measured on flakes of the recycled polyethylene terephthalate produced using the conventional PET recycling process. Consequently, the resultant expanded PET foam consists of chain extended PET, residual nucleating agent(s) and a residual concentration of the physical blowing agent(s) which remain trapped in any cells, for example closed cells, within the cellular matrix of the expanded PET foam.

[0072] Typically, the expandable polyethylene terephthalate composition is heated in the extruder to a temperature within the range of from 260 to 300 °C and the temperature of the die is within the range of from 260 to 290 °C.

[0073] Preferably, the die is a strand die which comprises an array of holes which form a plurality of extruded strands composed of the expanded cellular foam. After the strands have been extruded, the extruded foam strands are bonded together by fusion bonding to form an elongate board composed of the expanded cellular foam. The elongate board may be sized and shaped using techniques well known to those skilled in the art.

[0074] Any suitable extruder known to those skilled in the art for use in extruding thermoplastic foams may be used to form the extruded foam. For example, the extruder may be a co-rotating twin screw extruder.

[0075] In preferred embodiments of the present invention, the molten expandable polyethylene terephthalate composition, and consequently the resultant expanded PET foam, is halogen-free and / or free of any fire-retardant additive(s), preferably free of any halogen-containing additive and / or phosphorous-containing additive functioning as a fire-retardant additive, more preferably free of a polyphosphonate polymer.

[0076] The resultant expanded cellular foam typically has a density of from 80 to 250 kg / m3, for example from 105 to 200 kg / m3.

[0077] In addition to providing a method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET), the present invention also provides, in 13 420203GB accordance with a second aspect, as a product, an expanded cellular foam composed of polyethylene terephthalate (PET).

[0078] In accordance with the second aspect of the present invention, the expanded cellular foam comprises chain-extended polyethylene terephthalate in which polyethylene terephthalate molecules have been chain-extended by at least one chain extender, at least one nucleating agent, and at least one physical blowing agent, wherein the at least one physical blowing agent comprises a mixture of an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, and nitrogen, and wherein the expanded cellular foam is free of any fire retardant additives, including any halogen-containing additive and phosphorous-containing additive functioning as a fire retardant additive, wherein the expanded cellular foam has a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of at least C-s2-d0, which is a fire class C, a smoke class s2 and a flaming droplets / particles class d0.

[0079] In preferred embodiments of the second aspect of the present invention, the alicyclic hydrocarbon compound comprises cyclopentane,

[0080] In preferred embodiments of the second aspect of the present invention, the at least one chain extender comprises pyromellitic dianhydride (PMDA).

[0081] In preferred embodiments of the second aspect of the present invention, the at least one nucleating agent comprises (i) a first nucleating agent which comprises a thermoplastic fluoropolymer, preferably polytetrafluoroethylene (PTFE), more preferably irradiated polytetrafluoroethylene (PTFE), and (ii) a second nucleating agent which comprises an inorganic particulate, preferably talc.

[0082] In preferred embodiments of the second aspect of the present invention, the expanded cellular foam is in the form of an elongate board formed by fusion bonding a plurality of extruded foam strands.

[0083] In preferred embodiments of the second aspect of the present invention, the expanded cellular foam has a density of from 80 to 250 kg / m3, for example from 105 to 200 kg / m3.

[0084] The expanded cellular foam consists of the reaction product from the reactive extrusion of an expandable molten composition comprising or consisting of polyethylene terephthalate, at least one chain extender, at least one nucleating agent and at least one physical blowing agent. The chain extender(s), nucleating agent(s) and physical blowing agent(s) are described above with respect to the method of the present invention.

[0085] The expanded cellular foam may further comprise, as unavoidable contaminants, any organic contaminants up to a total contaminant concentration of 100 ppm by weight based on 14 420203GB the total weight of the expanded cellular foam. The contaminants are described above with respect to the method of the present invention.

[0086] As described above, in the resultant expanded PET foam, a residual concentration of the physical blowing agent(s) may remain trapped in any cells, e.g. closed cells, within the cellular matrix of the expanded PET foam. Therefore, typically in the expanded PET foam, the weight ratio of plural physical blowing agents would remain in the cellular matrix. The expanded PET foam typically comprises the physical blowing agent(s) as described above with respect to the method of the present invention, and the physical blowing agent comprises a mixture of (i) a first physical blowing agent which comprises an alicyclic hydrocarbon compound, for example cyclopentane, and (ii) a second physical blowing agent which comprises nitrogen.

[0087] The expanded cellular foam is preferably in the form of an elongate board formed by fusion bonding a plurality of extruded foam strands. The expanded cellular foam typically has a density of from 80 to 250 kg / m3, for example from 105 to 200 kg / m3.

[0088] The present invention will now be described in greater detail with reference to the following non-limiting Examples and Comparative Examples. Example 1

[0089] In this example, a co-rotating twin screw extruder was provided. The extruder had, in order from the input to the output, a feeding zone, a melting zone and a metering zone A strand die was provided at the output of the extruder. The foam extrudate was subjected to a dimensional calibration after exiting the strand die so that the plurality of extruded foam strands coalesced and bonded by fusion bonding and then were shaped to form a rectangular board.

[0090] A feedstock comprising a recycled post-consumer polyethylene terephthalate (rPET) resin, a chain extender and a nucleating agent was fed to the extruder. The feedstock was melted and mixed within the extruder, and the chain extender reacted with the PET molecules to increase the chain length, cross-linking and average molecular weight of the PET molecules, as is well known to those skilled in the art.

[0091] The recycled polyethylene terephthalate was in the form of pellets derived from flakes, and had the following material properties (measured using the respective measuring techniques described above): a weight averaged molecular weight (Mw) within the range of from 35,000 to 38,000 g / mol; a dispersity ((Đ)) within the range of from 3.8 to 4.2; a melt flow rate (MFR) within the range of from 20 to 23 g / 10 min; and an intrinsic viscosity (IV) within the range of from 0.78 to 0.81 dl / g. 15 420203GB

[0092] In addition, the recycled polyethylene terephthalate had a low contaminant concentration, in particular: a polyvinyl chloride (PVC) concentration of 5 ppm, a polyethylene terephthalate glycol (PETG) concentration of 15 ppm, a polyolefins (PO) concentration of 55 ppm, and a low-melting (lower than 100 °C) products concentration of 30 ppm, each based on the weight of the polyethylene terephthalate. As described above, the contaminant concentration was measured on flakes of the recycled polyethylene terephthalate produced using the conventional PET recycling process.

[0093] Such a recycled polyethylene terephthalate is available in commerce from Gurit Italy PET Recycling S.r.l. under the trade name “Valplastic K PET 8000 light blue”.

[0094] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.21 wt%, based on the weight of the polyethylene terephthalate blend. The chain extender was added as a typical PMDA masterbatch known to those skilled in the art. The wt% concentration value applies to the PDMA active rather than to the entire masterbatch.

[0095] The nucleating agent comprised irradiated polytetrafluoroethylene (PTFE) at a concentration of 0.2 wt% based on the weight of the polyethylene terephthalate blend. The nucleating agent was added as a typical thermoplastic fluoropolymer masterbatch known to those skilled in the art. The wt% concentration value applies to the PTFE active rather than to the entire masterbatch.

[0096] A physical blowing agent was introduced into the feedstock within the extruder to form a molten foamable composition within the extruder which exited the strand die as an extruded PET foam. The PET foam continuously exited the strand die as a plurality of strands which coalesced and were fusion bonded and dimensioned to be formed into a rectangular board. The physical blowing agent comprised cyclopentane at a concentration of 2.1 wt% based on the weight of the molten foamable composition.

[0097] The process parameters of the extrusion process are listed in Table 2.

[0098] Table 2 Feature Parameter Temperature of feeding zone (°C) 280-300 Temperature of melting zone (°C) 270-290 Temperature of metering zone (°C) 260-280 16 420203GB Temperature of die (°C) 260-290 Melt throughput (kg / h) 180 Screw speed (rpm) 13-15

[0099] The resultant rPET expanded cellular foam material exhibited a fine and uniform cell structure and had a foam density of 118 kg / m3.

[0100] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0101] The expanded cellular foam of Example 1 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of D-s2-d1, which is a fire class D, a smoke class s2 and a flaming droplets / particles class d1. The expanded cellular foam of Example 1 exhibited a Fire Growth Rate (FIGRA), measured according to EN- 13823, of 432 W / s.

[0102] The results are summarised in Table 3. 17 420203GB

[0103] Table 3 PET Composition Nucleating Physical FIGRA – W / s Agent(s) Blowing Class Agent(s) Fire-retardant additive Example 1 rPET – Mw 35-38k g / mol, Đ 3.8- PTFE C5H10432 4.2, MFR 20-23 g / 10min, IV 0.78- D-s2-d1 0.81, Low contaminants None Comp. rPET – Mw 30-34k g / mol, Đ 3.0- PTFE C5H101426 Example 1 3.7, MFR 35-42 g / 10min, IV 0.64- NC-s3-d2 0.67, High contaminants None Comp. vPET – Mw 38-41k g / mol, Đ 3.8- PTFE C5H10450 Example 2 4.2, MFR 19-21 g / 10min, IV 0.78- D-s2-d0 0.82, Low / no contaminants None Example 2 rPET – Mw 35-38k g / mol, (Đ) 3.8- PTFE+ C5H10227 4.2, MFR 20-23 g / 10min, IV 0.78- Talc + C-s2-d0 0.81, Low contaminants N2None Example 3 rPET – Mw 35-38k g / mol, Đ 3.8- PTFE+ C5H10183 4.2, MFR 20-23 g / 10min, IV 0.78- Talc + C-s1-d0 0.81, Low contaminants N2None Comp. rPET – Mw 30-34k g / mol, Đ 3.0- PTFE+ C5H10948 Example 3 3.7, MFR 35-42 g / 10min, IV 0.64- Talc + NC-s3-d2 0.67, High contaminants N2Polyphosphonate Comp. vPET – Mw 38-41k g / mol, Đ 3.8- PTFE+ C5H10548 Example 4 4.2, MFR 19-21 g / 10min, IV 0.78- Talc + D-s2-d0 0.82, Low / no contaminants N2None Example 4 rPET – Mw 35-38k g / mol, (Đ) 3.8- PTFE C5H10278 4.2, MFR 20-23 g / 10min, IV 0.78- + D-s2-d0 0.81, Low contaminants CO2None Comp. rPET – Mw 30-34k g / mol, Đ 3.0- PTFE C5H101581 Example 5 3.7, MFR 35-42 g / 10min, IV 0. + NC-s3-d2 0.64-0.67, High contaminants CO2None Comp. vPET – Mw 38-41k g / mol, Đ 3.8- PTFE C5H10371 Example 6 4.2, MFR 19-21 g / 10min, IV 0.78- + D-s2-d0 0.82, Low / no contaminants CO2None

[0104] Accordingly, the expanded cellular foam of Example 1 exhibited a good fire performance even though no conventional fire-retardant additives, such as halogen-containing 18 420203GB additive and / or phosphorous-containing polymers, had been added to the polyethylene terephthalate composition. Comparative Example 1

[0105] In this comparative example, a different polyethylene terephthalate resin was used as compared to Example 1.

[0106] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0107] The feedstock comprised a recycled post-consumer polyethylene terephthalate (rPET) resin, a chain extender and a nucleating agent. The recycled polyethylene terephthalate was in the form of pellets derived from flakes, and had the following material properties (measured using the respective measuring techniques described above): a weight averaged molecular weight (Mw) within the range of from 30,000 to 34,000 g / mol; a dispersity ((Đ)) within the range of from 3.0 to 3.7; a melt flow rate (MFR) within the range of from 35 to 42 g / 10 min; and an intrinsic viscosity (IV) within the range of from 0.64 to 0.67 dl / g.

[0108] In addition, the recycled post-consumer polyethylene terephthalate had a higher contaminant concentration than the PET resin used in Example 1, in particular: a polyvinyl chloride (PVC) concentration of 50 ppm, a polyethylene terephthalate glycol (PETG) concentration of 30 ppm, a polyolefins (PO) concentration of 330 ppm, and a low-melting (lower than 100 °C) products concentration of 30 ppm, each based on the weight of the polyethylene terephthalate. As described above, the contaminant concentration was measured on flakes of the recycled polyethylene terephthalate produced using the conventional PET recycling process.

[0109] Such a recycled polyethylene terephthalate is available in commerce from Gurit Italy PET Recycling S.r.l. under the trade name “Valplastic K PET 6000 millefiori”.

[0110] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.3 wt%, based on the weight of the polyethylene terephthalate blend. The chain extender was added in a masterbatch having a PET carrier.

[0111] The nucleating agent comprised irradiated polytetrafluoroethylene (PTFE) at a concentration of 0.2 wt% based on the weight of the polyethylene terephthalate blend. The nucleating agent was added in a masterbatch having a PET carrier.

[0112] As for Example 1, a physical blowing agent was introduced into the feedstock within the extruder to form a molten foamable composition within the extruder. Again, the physical blowing agent comprised cyclopentane at a concentration of 2.1 wt% based on the weight of the molten foamable composition. 19 420203GB

[0113] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 118 kg / m3.

[0114] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0115] The expanded cellular foam of Comparative Example 1 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of NC-s3-d2, which is a fire class NC (i.e. not classified as not compliant with the test), a smoke class s3 and a flaming droplets / particles class d2. The expanded cellular foam of Comparative Example 1 exhibited a Fire Growth Rate (FIGRA), measured according to EN- 13823, of 1426 W / s.

[0116] Accordingly, the expanded cellular foam of Comparative Example 1 exhibited a poor fire performance, significantly worse than that of Example 1. Comparative Example 2

[0117] In this comparative example, a different polyethylene terephthalate resin was used as compared to Example 1.

[0118] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0119] The feedstock comprised a virgin polyethylene terephthalate (vPET) resin, a chain extender and a nucleating agent. The virgin polyethylene terephthalate was in the form of pellets, and had the following material properties (measured using the respective measuring techniques described above): a weight averaged molecular weight (Mw) within the range of from 38,000 to 41,000 g / mol; a dispersity ((Đ)) within the range of from 3.8 to 4.2; a melt flow rate (MFR) within the range of from 19 to 21 g / 10 min; and an intrinsic viscosity (IV) within the range of from 0.78 to 0.82 dl / g.

[0120] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.22 wt%, based on the weight of the polyethylene terephthalate blend. The chain extender was added in a masterbatch having a PET carrier.

[0121] The nucleating agent comprised irradiated PTFE at a concentration of 0.2 wt% based on the weight of the polyethylene terephthalate blend. The nucleating agent was added in a masterbatch having a PET carrier.

[0122] As for Example 1, a physical blowing agent was introduced into the feedstock within the extruder to form a molten foamable composition within the extruder. Again, the physical blowing agent comprised cyclopentane at a concentration of 2.1 wt% based on the weight of the molten foamable composition. 20 420203GB

[0123] The resultant vPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 114 kg / m3.

[0124] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0125] The expanded cellular foam of Comparative Example 2 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of D-s2-d0, which is a fire class D, a smoke class s2 and a flaming droplets / particles class d0. The expanded cellular foam of Comparative Example 2 exhibited a Fire Growth Rate (FIGRA), measured according to EN-13823, of 450 W / s.

[0126] Accordingly, the expanded cellular foam of Comparative Example 2 exhibited a good fire performance, but the Fire Growth Rate (FIGRA) value was worse than that of Example 1.

[0127] A comparison of the results of Example 1, and Comparative Examples 1 and 2 shows that by selecting a specific recycled PET composition, having a high purity and a specific weight averaged molecular weight, dispersity, melt flow rate and intrinsic viscosity, the recycled PET can exhibit improved fire performance, in particular an improved FIGRA value, as compared to other recycled PET compositions having lower purity and different specific weight averaged molecular weight, dispersity, melt flow rate and intrinsic viscosity values, and also which is improved as compared even to virgin PET compositions having similar molecular properties.

[0128] The present inventors believe that this improved fire performance of a recycled PET expanded cellular foam, even in the absence of any additional conventional fire-retardant additives such as halogen-containing additive and / or phosphorous-containing polymers, is unexpected.

[0129] The present invention therefore solves the problem of how to use recycled PET resins to make expanded cellular foams exhibiting good fire-retardance. Example 2

[0130] In this example, the same polyethylene terephthalate resin was used as compared to Example 1. The resin system also comprised talc as an additional nucleating agent and nitrogen as an additional physical blowing agent.

[0131] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0132] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.27 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised a mixture of irradiated PTFE at a concentration of 0.1 wt% and talc at a 21 420203GB concentration of 2.5 wt%, each based on the weight of the polyethylene terephthalate blend. The chain extender and nucleating agents were added in respective masterbatches, each having a PET carrier.

[0133] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.6 wt% and nitrogen at a concentration of 0.04 wt%, each based on the weight of the molten foamable composition.

[0134] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 121 kg / m3.

[0135] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0136] The expanded cellular foam of Example 2 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of C-s2-d0, which is a fire class C, a smoke class s2 and a flaming droplets / particles class d0. The expanded cellular foam of Example 2 exhibited a Fire Growth Rate (FIGRA), measured according to EN- 13823, of 227 W / s.

[0137] Accordingly, the expanded cellular foam of Example 2 exhibited a very good fire performance, better than that of Example 1. Example 3

[0138] In this example, the same polyethylene terephthalate resin was used as compared to Example 1. The resin system also comprised talc as an additional nucleating agent and nitrogen as an additional physical blowing agent.

[0139] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0140] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.24 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised a mixture of irradiated PTFE at a concentration of 0.1 wt% and talc at a concentration of 2.5 wt%, each based on the weight of the polyethylene terephthalate blend. The chain extender and nucleating agents were added in respective masterbatches, each having a PET carrier.

[0141] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.13 wt% and nitrogen at a concentration of 0.03 wt%, each based on the weight of the molten foamable composition.

[0142] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 192 kg / m3. 22 420203GB

[0143] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0144] The expanded cellular foam of Example 3 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of C-s1-d0, which is a fire class C, a smoke class s1 and a flaming droplets / particles class d0. The expanded cellular foam of Example 3 exhibited a Fire Growth Rate (FIGRA), measured according to EN- 13823, of 183 W / s.

[0145] Accordingly, the expanded cellular foam of Example 3 exhibited a very good fire performance, better than that of Example 1. Comparative Example 3

[0146] In this comparative example, a different polyethylene terephthalate resin was used as compared to Example 2 and Example 3 and was the same polyethylene terephthalate resin that was used in Comparative Example 1, and also the expanded cellular foam comprised a fire- retardant additive.

[0147] The same extruder system, and the same process parameters, as used in Examples 2 and 3 were used to produce an extruded foam board.

[0148] The recycled polyethylene terephthalate was the product available in commerce from Gurit Italy PET Recycling S.r.l. under the trade name “Valplastic K PET 6000 millefiori”.

[0149] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.375 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised a mixture of irradiated PTFE at a concentration of 0.1 wt% and talc at a concentration of 2.5 wt%, each based on the weight of the polyethylene terephthalate blend. The chain extender and nucleating agents were added in respective masterbatches, each having a PET carrier.

[0150] The polyethylene terephthalate resin further comprised a fire-retardant additive, in particular a polyphosphonate homopolymer having a phosphorus content of 10.5 wt%. The polyphosphonate homopolymer is available in commerce under the trade name Nofia® HM1100 from FRX Polymers Inc, USA. The polyphosphonate homopolymer fire-retardant additive had a concentration of 2.0 wt%, based on the weight of the polyethylene terephthalate blend.

[0151] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.7 wt% and nitrogen at a concentration of 0.04 wt%, each based on the weight of the molten foamable composition. 23 420203GB

[0152] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 117 kg / m3.

[0153] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0154] The expanded cellular foam of Comparative Example 3 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of NC-s3-d2, which is a fire class NC, a smoke class s3 and a flaming droplets / particles class d2. The expanded cellular foam of Comparative Example 3 exhibited a Fire Growth Rate (FIGRA), measured according to EN-13823, of 948 W / s.

[0155] Accordingly, the expanded cellular foam of Comparative Example 3 exhibited a poor fire performance, significantly worse than that of Examples 2 and 3, which is surprising since the expanded cellular foam of Comparative Example 3 additionally comprised a phosphorous- containing fire-retardant additive. Comparative Example 4

[0156] In this comparative example, a different polyethylene terephthalate resin was used as compared to Examples 2 and 3.

[0157] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0158] The feedstock comprised a virgin polyethylene terephthalate (vPET) resin, a chain extender and a mixture of nucleating agents. The virgin polyethylene terephthalate was the same resin as used in Comparative Example 2.

[0159] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.36 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised a mixture of irradiated PTFE at a concentration of 0.1 wt% and talc at a concentration of 2.0 wt%, each based on the weight of the polyethylene terephthalate blend. These ingredients were added in masterbatches having a PET carrier.

[0160] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.5 wt% and nitrogen at a concentration of 0.04 wt%, each based on the weight of the molten foamable composition.

[0161] The resultant vPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 124 kg / m3.

[0162] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823. 24 420203GB

[0163] The expanded cellular foam of Comparative Example 4 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of D-s2-d0, which is a fire class D, a smoke class s2 and a flaming droplets / particles class d0. The expanded cellular foam of Comparative Example 4 exhibited a Fire Growth Rate (FIGRA), measured according to EN-13823, of 548 W / s.

[0164] Accordingly, the expanded cellular foam of Comparative Example 4 exhibited a worse fire performance, with a higher Fire Growth Rate (FIGRA) value, than those of Examples 1, 2 and 3.

[0165] A comparison of the results of Examples 2 and 3, and Comparative Examples 3 and 4 shows that by selecting a specific recycled PET composition, having a high purity and a specific weight averaged molecular weight, dispersity, melt flow rate and intrinsic viscosity, and employing a mixture of physical blowing agents which comprises not only an alicyclic hydrocarbon such as cyclopentane but also a small proportion by weight of an inorganic gas such as nitrogen, the recycled PET can exhibit improved fire performance, in particular an improved FIGRA value, as compared to other recycled PET compositions having lower purity and different specific weight averaged molecular weight, dispersity, melt flow rate and intrinsic viscosity values which may even comprise an additional conventional fire-retardant additive such as a phosphorous-containing polymer, and also can exhibit improved fire performance as compared even to virgin PET compositions having similar molecular properties. These improved fire performance properties can be achieved across a wide range of densities for the recycled PET expanded cellular foam.

[0166] The present inventors believe that this improved fire performance of a recycled PET expanded cellular foam, even in the absence of any additional conventional fire-retardant additives such as halogen-containing additive and / or phosphorous-containing polymers, is unexpected.

[0167] These results confirm that the present invention solves the problem of how to use recycled PET resins to make expanded cellular foams exhibiting good fire-retardance. Example 4

[0168] In this example, the same polyethylene terephthalate resin was used as compared to Example 1. The resin system also comprised carbon dioxide as an additional physical blowing agent.

[0169] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board. 25 420203GB

[0170] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.27 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised irradiated PTFE at a concentration of 0.1 wt%, based on the weight of the polyethylene terephthalate blend. These ingredients were added in masterbatches having a PET carrier.

[0171] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.3 wt% and carbon dioxide at a concentration of 0.3 wt%, each based on the weight of the molten foamable composition.

[0172] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 110 kg / m3.

[0173] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0174] The expanded cellular foam of Example 4 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of D-s2-d1, which is a fire class D, a smoke class s2 and a flaming droplets / particles class d1. The expanded cellular foam of Example 4 exhibited a Fire Growth Rate (FIGRA), measured according to EN- 13823, of 278 W / s.

[0175] Accordingly, the expanded cellular foam of Example 4 exhibited a good fire performance, and with regard to the FIGRA value similar to that of Example 1. Comparative Example 5

[0176] In this comparative example, a different polyethylene terephthalate resin was used as compared to Example 4 and was the same polyethylene terephthalate resin that was used in Comparative Example 1.

[0177] The same extruder system, and the same process parameters, as used in Example 4 were used to produce an extruded foam board.

[0178] The recycled polyethylene terephthalate was the product available in commerce from Gurit Italy PET Recycling S.r.l. under the trade name “Valplastic K PET 6000 millefiori”.

[0179] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.33 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised a mixture of irradiated PTFE at a concentration of 0.15 wt%, based on the weight of the polyethylene terephthalate blend. These ingredients were added in masterbatches having a PET carrier. 26 420203GB

[0180] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.0 wt% and carbon dioxide at a concentration of 0.5 wt%, each based on the weight of the molten foamable composition.

[0181] The resultant rPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 125 kg / m3.

[0182] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823.

[0183] The expanded cellular foam of Comparative Example 3 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of NC-s3-d2, which is a fire class NC, a smoke class s3 and a flaming droplets / particles class d2. The expanded cellular foam of Comparative Example 3 exhibited a Fire Growth Rate (FIGRA), measured according to EN-13823, of 1581 W / s.

[0184] Accordingly, the expanded cellular foam of Comparative Example 5 exhibited a poor fire performance, significantly worse than that of Example 4. Comparative Example 6

[0185] In this comparative example, a different polyethylene terephthalate resin was used as compared to Example 4.

[0186] The same extruder system, and the same process parameters, as used in Example 1 were used to produce an extruded foam board.

[0187] The feedstock comprised a virgin polyethylene terephthalate (vPET) resin, a chain extender and a mixture of nucleating agents. The virgin polyethylene terephthalate was the same resin as used in Comparative Example 2.

[0188] The chain extender comprised pyromellitic dianhydride (PMDA) at a concentration of 0.27 wt%, based on the weight of the polyethylene terephthalate blend. The nucleating agent comprised irradiated PTFE at a concentration of 0.1 wt%, based on the weight of the polyethylene terephthalate blend. These ingredients were added in masterbatches having a PET carrier.

[0189] The physical blowing agent comprised a mixture of cyclopentane at a concentration of 1.33 wt% and carbon dioxide at a concentration of 0.33 wt%, each based on the weight of the molten foamable composition.

[0190] The resultant vPET expanded cellular foam material again exhibited a fine and uniform cell structure and had a foam density of 128 kg / m3.

[0191] The expanded cellular foam was subjected to a fire performance test, in particular the Single Burning Item (SBI) fire test of the EU standard EN-13823. 27 420203GB

[0192] The expanded cellular foam of Comparative Example 6 had a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN- 13823, of D-s2-d0, which is a fire class D, a smoke class s2 and a flaming droplets / particles class d0. The expanded cellular foam of Comparative Example 6 exhibited a Fire Growth Rate (FIGRA), measured according to EN-13823, of 371 W / s.

[0193] Accordingly, the expanded cellular foam of Comparative Example 6 exhibited a worse fire performance, with a higher Fire Growth Rate (FIGRA) value, than that of Example 4.

[0194] A comparison of the results of Example 4, and Comparative Examples 5 and 6 shows that by selecting a specific recycled PET composition, having a high purity and a specific melt flow rate and intrinsic viscosity, and preferably weight averaged molecular weight and dispersity, and employing a mixture of physical blowing agents which comprises not only an alicyclic hydrocarbon such as cyclopentane but also a small proportion by weight of an inorganic gas such as carbon dioxide, the recycled PET can exhibit improved fire performance, in particular an improved FIGRA value, as compared to other recycled PET compositions having lower purity and different specific melt flow rate and intrinsic viscosity values, and preferably weight averaged molecular weight and dispersity values, which may even comprise an additional conventional fire-retardant additive such as phosphorous-containing polymers, and also improved fire performance as compared even to virgin PET compositions having similar molecular properties.

[0195] The present inventors believe that this improved fire performance of a recycled PET expanded cellular foam, even in the absence of any additional conventional fire-retardant additives such as phosphorous-containing polymers, is unexpected.

[0196] These results again confirm that the present invention solves the problem of how to use recycled PET resins to make expanded cellular foams exhibiting good fire-retardance. 28 420203GB

Claims

Claims 1. A method of manufacturing an expanded cellular foam composed of polyethylene terephthalate (PET), the method comprising the steps of: a. providing a polyethylene terephthalate component in particulate form, wherein the polyethylene terephthalate in the polyethylene terephthalate component comprises or consists of recycled polyethylene terephthalate, and the polyethylene terephthalate component has the following properties: i. a melt flow rate (MFR) within the range of from 10 to 35 g / 10 min; and ii. an intrinsic viscosity within the range of from 0.70 to 1.0 dl / g; b. blending the polyethylene terephthalate component with at least one chain extender and at least one nucleating agent to form a polyethylene terephthalate blend; c. heating the polyethylene terephthalate blend and at least one physical blowing agent to form a molten expandable polyethylene terephthalate composition in an extruder; and d. extruding the molten expandable polyethylene terephthalate composition through a die of the extruder to form an expanded cellular foam composed of polyethylene terephthalate.

2. A method according to claim 1 wherein the polyethylene terephthalate in the polyethylene terephthalate component consists of recycled polyethylene terephthalate.

3. A method according to claim 1 or claim 2 wherein the polyethylene terephthalate in the polyethylene terephthalate component consists of a mixture of recycled polyethylene terephthalate and virgin polyethylene terephthalate, wherein the mixture comprises at least 50 wt% recycled polyethylene terephthalate and up to 50 wt% virgin polyethylene terephthalate, each based on the total weight of the polyethylene terephthalate, optionally at least 70 wt% recycled polyethylene terephthalate and up to 30 wt% virgin polyethylene terephthalate, each based on the total weight of the polyethylene terephthalate.

4. A method according to any one of claims 1 to 3 wherein the particulate form comprises pellets of recycled polyethylene terephthalate, optionally wherein the pellets have been obtained from flakes of recycled polyethylene terephthalate.

5. A method according to any one of claims 1 to 4 wherein the polyethylene terephthalate component has a weight averaged molecular weight (Mw) within the range of from 35,000 to 38,000 g / mol. 29 420203GB6. A method according to any one of claims 1 to 5 wherein the polyethylene terephthalate component has a dispersity (Đ) within the range of from 3.8 to 4.

2.

7. A method according to any one of claims 1 to 6 wherein the polyethylene terephthalate component has a melt flow rate (MFR) within the range of from 20 to 23 g / 10 min.

8. A method according to any one of claims 1 to 7 wherein the polyethylene terephthalate component has an intrinsic viscosity within the range of from 0.70 to 0.85 dl / g.

9. A method according to claim 8 wherein the polyethylene terephthalate component has an intrinsic viscosity within the range of from 0.77 to 0.82 dl / g.

10. A method according to any one of claims 1 to 9 wherein the polyethylene terephthalate component comprises one or more contaminants selected from (i) polyvinyl chloride (PVC) at a concentration of up to 7.5 ppm by weight, optionally up to 5 ppm by weight; (ii) polyethylene terephthalate glycol (PETG) at a concentration of up to 20 ppm by weight, optionally up to 15 ppm by weight; (iii) one or more polyolefins (PO) at a concentration of up to 80 ppm by weight, optionally up to 55 ppm by weight; and (iv) one or more low melting point polymer resins having a melting point of lower than 100 °C at a concentration of up to 40 ppm by weight, optionally up to 30 ppm by weight, each concentration being based on the weight of the polyethylene terephthalate component.

11. A method according to any one of claims 1 to 10 wherein the at least one chain extender comprises pyromellitic dianhydride (PMDA) at a concentration of from 0.15 to 0.35 wt%, optionally from 0.2 to 0.3 wt%, based on the weight of the polyethylene terephthalate blend.

12. A method according to any one of claims 1 to 11 wherein the at least one nucleating agent comprises an organic nucleating agent, optionally a thermoplastic fluoropolymer, further optionally an irradiated thermoplastic fluoropolymer, at a concentration of from 0.075 to 0.25 wt% based on the weight of the polyethylene terephthalate blend.

13. A method according to any one of claims 1 to 12 wherein the at least one nucleating agent comprises an inorganic particulate, optionally talc, at a concentration of from 1 to 3 wt% based on the weight of the polyethylene terephthalate blend.

14. A method according to any one of claims 1 to 13 wherein the at least one physical blowing agent comprises a hydrocarbon having from 4 to 7 carbon atoms, optionally an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, further optionally cyclopentane, wherein the hydrocarbon physical blowing agent is at a 30 420203GBconcentration of from 1 to 3 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

15. A method according to claim 14 wherein the at least one physical blowing agent further comprises an inorganic gas, optionally wherein the inorganic gas is selected from nitrogen or carbon dioxide or a mixture thereof, wherein the inorganic gas physical blowing agent is at a concentration of from 0.02 to 0.7 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

16. A method according to claim 15 wherein the inorganic gas comprises or consists of nitrogen, wherein the nitrogen is at a concentration of from 0.02 to 0.06 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

17. A method according to claim 16 wherein the at least one physical blowing agent comprises a mixture of an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, optionally cyclopentane, and nitrogen.

18. A method according to claim 15 wherein the inorganic gas comprises or consists of carbon dioxide, wherein the carbon dioxide is at a concentration of from 0.2 to 0.6 wt%, based on the total weight of the molten expandable polyethylene terephthalate composition.

19. A method according to any one of claims 1 to 18 wherein the molten expandable polyethylene terephthalate composition is halogen-free and / or free of any fire- retardant additive, preferably free of any halogen-containing additive and / or phosphorous-containing additive functioning as a fire-retardant additive, more preferably free of a polyphosphonate polymer.

20. A method according to any one of claims 1 to 19 wherein the molten expandable polyethylene terephthalate composition consists of a mixture of polyethylene terephthalate, the at least one chain extender, the at least one nucleating agent and the at least one physical blowing agent, and optionally any organic contaminants up to a total contaminant concentration of 100 ppm by weight based on the weight of the polyethylene terephthalate component.

21. A method according to any one of claims 1 to 20 wherein the molten expandable polyethylene terephthalate composition is heated in the extruder to a temperature within the range of from 260 to 300 °C and the temperature of the die is within the range of from 260 to 290 °C.

22. A method according to any one of claims 1 to 21 wherein the die is a strand die which comprises an array of holes which form a plurality of extruded strands composed of 31 420203GBthe expanded cellular foam, and wherein the extruded foam strands are bonded together by fusion bonding to form an elongate board composed of the expanded cellular foam.

23. A method according to any one of claims 1 to 22 wherein the expanded cellular foam has a density of from 80 to 250 kg / m3, optionally from 105 to 200 kg / m3.

24. An expanded cellular foam composed of polyethylene terephthalate (PET), wherein the expanded cellular foam comprises chain-extended polyethylene terephthalate in which polyethylene terephthalate molecules have been chain-extended by at least one chain extender, at least one nucleating agent, and at least one physical blowing agent, wherein the at least one physical blowing agent comprises a mixture of an alicyclic hydrocarbon compound having from 4 to 7 carbon atoms, and nitrogen, and wherein the expanded cellular foam is halogen-free and free of any fire retardant additives, including any halogen-containing additive and phosphorous-containing additive functioning as a fire retardant additive, wherein the expanded cellular foam has a fire performance classification, according to the Single Burning Item (SBI) fire test of the EU standard EN-13823, of at least C-s2-d0, which is a fire class C, a smoke class s2 and a flaming droplets / particles class d0.

25. An expanded cellular foam according to claim 24 wherein the at least one chain extender comprises pyromellitic dianhydride (PMDA).

26. An expanded cellular foam according to claim 24 or claim 25 wherein the at least one nucleating agent comprises (i) a first organic nucleating agent which optionally comprises a thermoplastic fluoropolymer, further optionally an irradiated thermoplastic fluoropolymer, and (ii) a second inorganic nucleating agent which comprises an inorganic particulate, optionally talc.

27. An expanded cellular foam according to any one of claims 24 to 26 wherein the alicyclic hydrocarbon compound comprises cyclopentane.

28. An expanded cellular foam according to any one of claims 24 to 27 which is in the form of an elongate board formed by fusion bonding a plurality of extruded foam strands.

29. An expanded cellular foam according to any one of claims 24 to 28 wherein the expanded cellular foam has a density of from 80 to 250 kg / m3, optionally from 105 to 200 kg / m3. 32 420203GB

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