AU2010202211A1 - Polyster Foam Material having Flame-Resistant Behaviour - Google Patents

Description

P/00/011 28/5/91 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Name of Applicant: Armacell Enterprise GmbH Actual Inventors Dr Horst Grste Dr Jie Li Address for service is: WRAYS Ground Floor, 56 Ord Street West Perth WA 6005 Attorney code: WR Invention Title: Polyster Foam Material having Flame-Resistant Behaviour The following statement is a full description of this invention, including the best method of performing it known to me: 1 2 5 Polyester foam material having flame-resistant behaviour Field of the Invention The present invention relates to an expanded polyester material having a better flame resistant behaviour than the foamed product of polyester resins, wherein at least one of halogen-free flame retardants is added into the formulation of foamed polyester and the 10 mixture is able to be foamed through an expansion process. Background Art Polyester materials, particularly polyethylene terephthalate, exhibit a very high mechanical strength (compression/shear strength and modulus) and an excellent temperature 15 resistance. Foamed polyesters can be used in many applications where light-weight and high mechanical loading are requested. However, foamed cellular materials of polyester resin show no or poor flame-resistance, when exposed to fire. This averts applications of such foamed materials in e.g. construction, yacht or ship building, automotive, wagon building and furniture. In addition, 20 the fire classification of polyester foam materials according to Single Burning Item (SBI, prEN 13823) is not available up to date. Therefore, fire-resistant polyester foams should be produced by foam extrusion and tested according to prEN 13823 (SBI) in the current invention. The SBI classification of foamed polyester resins tested according to prEN 13823 is not 25 very promising: PET foam without any flame retardancy shows e.g. a total heat release

(THR

6 oos) of 19.2MJ, a fire growth rate (FIGRA) over 745W/s and a total smoke production (TSP 6 oos) about 349MJ (Comparable example 1). Production of foamed polyesters is nowadays more and more practiced by a reactive process comprising upgrading or increasing of molecular weight and extensional viscosity 30 of aromatic polyester resins during the extrusion process with help of chain-extenders such as multifunctional tetracarboxylic dianhydrides or/and polyepoxides.

3 The reactive extrusion to produce polyester foams is, however, a very sensitive process. The chemicals used for upgrading of polyester resins therefore also may react with chemical groups of the fire retardants and so allow only very limited reaction for the necessary polymer chain enhancement, which is essential for the foaming process. 5 In addition, most fire retardants can not be incorporated into the foaming process due to processing conditions of the polyester foams, which in general exceed 290'C and more than 100 bar pressures. At or even far below that high temperature and high pressure, such flame retardants start to degrade and further react. This releases water or produces substances which react with the most sorts of chain-extenders, thus interferes the reactive 10 foaming process. Furthermore, production of physically blown foams is very sensitive to additives others than resins, because these additives act in many cases as nucleates and result in an over nucleation, and no acceptable cell structure is achievable. Most flame retardants having a melting point above 280*C belong to this kind of additives. 15 On the other hand, most flame-resistant additives, which may work in process of polyester for compact products, are not necessarily feasible for the reactive foaming extrusion of polyesters. In a series of screening trials with flame retardants (FR) which target to improve the flame behaviour of polyester foam materials, halogen-containing or -free flame retardants are 20 added into the foaming recipes of polyester and run on a pilot extrusion line to produce foamed polyester materials. For instance, a Br/Sb 2

O

3 combination containing a brominated diphenyl derivative is tested for processability of a reactive foam extrusion by melt blending this kind of FR in form of granulates with PET and chain-extending masterbatch with a twin-screw extruder. The 25 mixture is charged with a physical blowing agent. The addition of this Br/Sb 2

O

3 containing FR even at a loading of 2wt% of the mixture leads already to a dramatic pressure decrease in the extruder so that no stable foaming process was possible. The invention EP0908488 Al (Al Ghatta, H., et al.) describes flame retardant compositions comprising polyester resin and a flame retardant compound, which are extruded with help 30 of a chain-extending additive PMDA or PMDA-containing masterbatch and physical blowing agents. The foam products containing brominated FR are tested successfully for BI or MI according to EP0908488. The most effective flame retardant compound (Example 3 of EP0908488) consists of 3.Owt% ethylenebistetra-bromophthalimide and 4 0.3wt% sodium antimonate according to the inventors. The PET foam implying this compound is classifiable with BI according to DIN 4102, as claimed in EP0908488. This foam composition is repeated in the current invention and the trial confirmed that this PET composition is able to be foamed by a reactive extrusion. But, the SBI classification of the 5 foamed product according to prEN 13823 is worse than the PET foam containing no FR in terms of fire growth rate (FIGRA), smoke production and max. smoke growth rate (SMOGRA) (s. Tab. 2). Besides, the halogen-containing flame retardants used in polymers cause problems, in case of fire, recycling or disposal of wastes, such as: 10 1) Aggressive corrosion due to generation of aggressive gases (HC, HBr) and formation of acids (Hydrochloric acid), 2) Toxicity due to production of toxic substances like chloric and bromine-containing dioxins, furans and other halogen-containing toxic products. The disadvantages of halogen-containing flame retardants give motivations for searching 15 for and application of halogen-free alternatives. One of them is phosphorus-based flame retardant compositions which form an intumescent system. In the event of fire, the intumescent systems having a phosphor content of 0.5% to 10% by weight of the mixture, preferably from 2.0% to 6.0%, form, as a result of the temperature increase, an accelerated carbonization of the polymer at the surface resulting in char-forming. 20 Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application, or patent cited in this text is not repeated in this text merely for reasons of conciseness. 25 Reference to cited material or information contained in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in Australia or any other country. Disclosure of the Invention 30 According to a first aspect of the invention there is provided a flame-resistant, expanded cellular material from aromatic polyester resins, obtained by extrusion foaming polyester resins, wherein the polyester foam has a total heat release (THR 6 00s) less than 6.0 MJ, a fire 5 growth rate (FIGRA) less than 430.0 W/s, a total smoke production (TSP 6 oos) less than 165.0 MJ and no flaming droplets/particles within 600s, wherein all parameters thereof are tested according to prEN 13823. According to a second aspect of the invention the polyester resin of the expanded material 5 is an aromatic polyester homo- and/or copolymer having an intrinsic viscosity of 0.4 to 1.4 dl/g, preferably selected from virgin and/or post-consumer resins of PET and/or PBT and/or PEN in form of granules, agglomerates, powders or flakes. According to a third aspect of the invention the expanded material comprises one or a mixture of fusible zinc phosphinates of the following formula, O 10 Zn 0 - P - RI

.

R2 -2 15 where R, and R 2 are identical or different and are hydrogen, Ci-Cis-alkyl, linear or branched, and/or aryl, preferably CI-C 6 -alkyl, linear or branched, and/or phenyl, particularly preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tertubutyl, n-pentyl or 20 phenyl, most preferably zinc dimethylphosphinate, zinc methylethylphosphinate, zinc diphenylphosphinate, zinc diethylphosphinate, zinc ethylbutylphosphinate or zinc dibutylphosphinate. According to a fourth aspect of the invention there is provided a process for production of an expanded material according to the first aspect comprising melt blending of a mixture 25 containing the polyester resin of the second aspect and one or a mixture of fusible zinc phosphinates of the third aspect and an expansion process characterized by a decompression induced by a change in thermodynamic state such as pressure or temperature of the melt mixture. The invention extends to an article obtained from the expanded material of any of the first 30 to third aspects. The invention further extends to the use of materials according to any of the first to third aspects as a core such as highly loaded structures (e.g. wagon building, aviation parts, automotive components or construction components) or as thermal and/or acoustic insulation or building and construction applications or as wall/floor/ceiling/roof panels 35 and/or supports or structural insulation where the flame retardancy is of use.

6 Best Mode(s) for Carrying out the Invention In the current invention, a series of phosphor-containing flame retardants which are currently availabe for polyester application has been reviewed through the reactive foam 5 exrrusion process. However, most of them impair the foaming process such that no polyester foam can be manufactured, e.g.: 1) Micronized aluminium tris(diethylphosphinate) even in an amount of 1% by weight of total foam composition results in a much lower pressure (about 80bar lower) in comparison to the composition containing no FR and a process instability, whereas no 10 foamed product with fine cell is possible. 2) Addition of 2wt% oxaphospholane glycol ester shows similar process impairment like above. No acceptable PET foam can be produced. 3) Ammonium polyphosphate worsens the foam extrusion already in an amount of lwt%, so that no PET foam is producible. 15 However, it has been surprisingly found in this invention that unlike the flame retardants mentioned above addition of meltable zinc phosphinates up to 1Owt% does not impair the foamability of polyester resin, wherein the mixture of polyester resin, FR and a chain extending masterbatch is melt blended by using an extruder (preferably a twin-screw extruder). The melt mixture is charged in the extruder with a physical blowing agent and 20 foamed. The foamed polyester resin shows a uniform and fine cell structure. The fire resistance of foamed polyesters can be improved by addition of fusible zinc phosphinates: The foamed material comprising an aromatic polyester resin and 5wt% zinc diethylphosphinate is characterized with a total heat release (THR 6 00s) less than 6.0 MJ, a fire growth rate (FIGRA) less than 430.0 W/s, a total smoke production (TSP 6 oos) less than 25 165.0 MJ and no flaming droplets/particles within 600s (Example 1). All parameters are tested according to prEN 13823. The meltable zinc phosphinates described in this invention have the following formula, O Zn0-P-R1

-

R2 -2 30 7 where R, and R 2 are identical or different and are hydrogen, CI-C 18 -alkyl, linear or branched, and/or aryl. The fusible zinc phosphinates have a melting point of 40 to 250*C, preferably a melting point higher than 200*C, and a decomposition point preferably not lower than 300'C. 5 R, and R 2 are preferably Ci-C 6 -alkyl, linear or branched, and/or phenyl. Ri and R 2 are particularly preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tertubutyl, n-pentyl or phenyl. The zinc phosphinates are most preferably zinc dimethylphosphinate, zinc methylethylphosphinate, zinc diphenylphosphinate, zinc diethylphosphinate, zinc 10 ethylbutylphosphinate or zinc dibutylphosphinate. The phosphorus content of preferred meltable zinc phosphinates ranges from 10 to 35% by weight, particularly preferably from 15 to 25% by weight. The fusible zinc phosphinates are incorporated into the foaming equipment in form of powder or granulates. The granulates are manufactured by extrusion compounding of the 15 flame retardants with up to Swt% wax such as polyolefin or acrylate copolymers. The chain-extending additives needed for the reactive extrusion process are in general multifunctional compounds selected from one or more of chain-extending/branching ingredients, preferably from a group consisting of tetracarboxylic dianhydride, polyepoxides, oxazolines, oxazines, acyllactams and antioxidant containing sterically 20 hindered phenolic end groups or mixtures thereof. In foaming processes for production of fire-resistant polyester cellular materials, a physical or chemical blowing agent can be chosen for expansion, while a physical blowing agent is typically selected from carbon dioxide (CO 2 ), Nitrogen (N 2 ), ketons, hydrofluorocarbon, a hydrocarbon (such as n-hexane, n-octane, iso-butane, isopentane, cyclopentane and n 25 heptane) or a mixture of above gases. A nucleate is generally applied in the foaming process, whereas commonly used nucleate types are talc, TiO 2 , MgO, BaSO 4 , SiO 2 , A1 2 0 3 , CdO, ZnO, mica filler, fluor polymers, diatomaceous earth or the like alone or in combination. Beside nucleation and blowing agents, it is also possible to additionally use further 30 additives such as process/thermal stabilizers, fluor-polymers and UV stabilizers etc. in the recipes. Preferred aromatic polyesters for production of cellular foamed products include those derived from terephthalic acid, isophthalic acid, naphthalenedicarboxyl acid, 8 cyclohexanedicarboxylic acid and the like or the alkyl esters. Particularly preferred is DMT- or PTA-based PET with I.V. of about 0.4 - 1.4dl/g (according to ASTM 4603) including homo- and copolymers. A process of foaming virgin polyester resins, post-consumer polyester materials or a 5 mixture thereof (to increase for instance the overall molecular weight) in form of granules, agglomerates, powders or flakes is also possible in combination with above said group of flame retardants. The term "post-consumer" is defined as material being brought back into the process - i.e. being recycled - after its prior processing and/or use, e.g. as PET bottles, PET articles, polyester scraps, recycling polyesters. 10 The process applied for foaming fire-resistant polyesters is in general foam extrusion, wherein an extrusion line is used. The extrusion line for the reactive extrusion foaming of polyester consists basically of an extruder, dosing equipment, gas injector, heat exchanger, static mixer and die for extrudate shaping. The extrusion line is followed by downstream equipment such as puller, conveying rolls with air cooling, sawing unit, further cooling and 15 grinding and packaging etc. All types of foaming extruders can be used for the reactive foam extrusion in the current invention: single screw or co-/counter-rotating twin screw extruder, tandem extrusion line consisting of a primary extruder (twin or single screw extruder) and a secondary/cooling single screw extruder. 20 Other foaming processes such as injection molding or batch process are also possible to produce the polyester cellular materials charged with said flame retardants. This invention is illustrated by the following examples given for illustrative purpose. Comparative example 1: 25 In this example, a co-rotating twin screw extruder having a screw diameter of 75 mm and L/D=32, followed by a static mixer and a strand die, was applied. The foam extrudate underwent a calibration after leaving the strand die to be shaped to a rectangular board. PET copolymer (I.V.=0.78dl/g) was dried at 165'C for 6h and the concentrate, disclosed in Example 4 of European Patent Application 09 006 678.8, at 80'C for 8h. The PET resin 30 composed with 0.3% of PMDA and effectively 0.6% of a nucleating agent each by weight of the total throughput was continuously extruded and foamed at a throughput of 45 kg/h. The mixture was extruded and foaming took place with help of a hydrocarbon as physical blowing agent. The process parameters are listed in Tab. 1: 9 Tab. 1: Process parameters Feature Parameter Temperature of feeding zone ('C) 120-260 Temperature of melting zone ('C) 280-285 Temperature of metering zone (*C) 275-280 Temperature of static mixer (*C) 275-285 Temperature of die (*C) 285-290 Melt throughput (kg/h) 45 Gas injection (g/min) 17.5 PET foam material with fine and uniform cell structure was obtained at a foam density of 112kg/m 3 and tested for SBI fire classification according to prEN 13823 (s. Tab. 2). 5 Comparative example 2: The comparative example I was repeated with the difference that the melt system was charged with 2% of a Br/Sb 2

O

3 combination containing a brominated diphenyl derivative by weight of total mixture. 10 The addition of the brominated diphenyl derivative decreased the melt strength and pressure of polyester so much, that no foam was obtainable. Comparative example 3: The comparative example I was repeated with the difference that a flame retardant 15 compound (Example 3 of EP0908488) consisting of 3% ethylenebistetra bromophthalimide and 0.3% sodium antimonate by weight of the mixture was incorporated into the extruder. PET foam material with fine and uniform cell structure was obtained at a foam density of 113kg/m 3 and tested for SBI fire classification according to prEN 13823. The testing 20 results except total heat release and flaming droplets/particles were much worse than the PET foam without any flame retardancy (s. Tab. 2).

10 Comparative example 4: The comparative example I was repeated with the difference that micronized aluminium tris(diethylphosphinate) in an amount of 1% by weight of total throughput was added into the foam recipe. 5 However, the addition of aluminium tris(diethylphosphinate) resulted in a decrease in melt strength and pressure of polyester. No foam was obtainable. Comparative example 5: The comparative example I was repeated with the difference that 2% oxaphospholane 10 glycol ester by weight of total throughput was added in the foam recipe. The trial showed a decrease in melt strength and pressure. No foam could be produced. Comparative example 6: The comparative example I was repeated with the difference that ammonium 15 polyphosphate was added into the extruder in an amount of 1% by weight of total throughput. The foaming process was impaired so much, that no foam is obtainable. Example 1: The comparative example 1 was repeated with the difference that 5% of zinc 20 diethylphosphinate by weight of the total throughput, having a phosphorus content of about 20% (m/m) and a melting point of 200*C, were added into the extruder. The extrusion process was stable and PET foam with fine and uniform cell structure was obtained at a foam density of 113 kg/m 3 . The extruded foam board was prepared for SBI testing and the results of the fire testing are 25 summarised in Tab. 2. The testing results show a clear improvement of the fire-resistance of PET foam. Tab. 2: Results of SBI fire testing according to prEN 13823 Fire testing item Comparative Comparative Example I example I example 3 Total heat release (THR 6 oos) [MJ] 19.2 18.9 6.0 Fire growth rate (FIGRA) [W/s] 745.38 3625.96 428.51 Total smoke production (TSP 6 00s) [MJ] 349.1 375.3 164.0 11 Max. smoke growth rate (SMOGRA 106.8 772.93 108.49 max) [m 2 /s 2 ] Flaming droplets/particles (within 600s) d2 dO (none) dO (none) Example 2: The comparative example 2 was repeated with the difference that 9% of zinc diethylphosphinate by weight of the total throughput was added into the extruder. 5 The extrusion process was stable and a PET foam with fine and uniform cell structure was obtained at a foam density of 112 kg/m 3 . Throughout this specification, unless the context requires otherwise, the word "comprise"or variation such as "comprises" or "comprising" will be understood to imply 10 the inclusion of a stated integer or group of integers but not the exclusion of any other intger or group of integers.

Claims (13)

1. A flame-resistant, expanded cellular material from aromatic polyester resins, obtained by extrusion foaming polyester resins, wherein the polyester foam has a total heat release (THR 6 00s) less than 6.0 MJ, a fire growth rate (FIGRA) less than 5 430.0 W/s, a total smoke production (TSP 6 oos) less than 165.0 MJ and no flaming droplets/particles within 600s, wherein all parameters thereof are tested according to prEN 13823.

2. The expanded material according to claim 1, wherein the polyester resin is an 10 aromatic polyester homo- and/or copolymer having an intrinsic viscosity of 0.4 to 1.4 dl/g, preferably selected from virgin and/or post-consumer resins of PET and/or PBT and/or PEN in form of granules, agglomerates, powders or flakes.

3. The expanded material according to claim I comprising one or a mixture of fusible 15 zinc phosphinates of the following formula, O Zn O0- P- R - R2 - 2 where Ri and R 2 are identical or different and are hydrogen, Ci-C 18 -alkyl, linear or branched, and/or aryl, preferably Ci-C 6 -alkyl, linear or branched, and/or phenyl, 20 particularly preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tertubutyl, n pentyl or phenyl, most preferably zinc dimethylphosphinate, zinc methylethylphosphinate, zinc diphenylphosphinate, zinc diethylphosphinate, zinc ethylbutylphosphinate or zinc dibutylphosphinate. 25

4. The expanded material according to claim 3, wherein the fusible zinc phosphinates have a melting point of 40 to 250*C, preferably a melting point above 200*C and a decomposition temperature preferably not lower than 300'C. 13

5. The expanded material according to any of claim 3 to 4, wherein the phosphorus content of the fusible zinc phosphinates ranges from 10 to 35% by weight, particularly preferably from 15 to 25% by weight. 5

6. The expanded material according to any of claims I to 5 having a density below 300 kg/m.

7. A process for production of an expanded material according to claim 1, comprising melt blending of a mixture containing the polyester resin of claim 2 and one or a 10 mixture of fusible zinc phosphinates of claims 3 and an expansion process characterized by a decompression induced by a change in thermodynamic state such as pressure or temperature of the melt mixture.

8. An article obtained from the expanded material of any of claims I to 6. 15

9. The use of materials according to any of claims I to 6 and 8 as a core such as highly loaded structures (e.g. wagon building, aviation parts, automotive components or construction components) or as thermal and/or acoustic insulation or for building and construction applications or as wall/floor/ceiling/roof panels 20 and/or supports or structural insulation where the flame retardancy is of use.

10. A flame-resistant, expanded cellular material from aromatic polyester resins according to claim I substantially as herein described with reference to the examples. 25

11. A process for production of an expanded material according to claim 7, substantially as herein described with reference to the examples.

12. An article obtained from the expanded material according to any of claims 1 to 6, 30 substantially as herein described with reference to the examples.

13. The use of materials according to any one of claims I to 6 substantially as herein described with reference to the examples.