ES2927918B2 - COMPOSITE MATERIAL BASED ON THE DISPERSION OF POLYMERS FROM THE PAEK FAMILY IN ASA, ABS AND DERIVED BLENDS - Google Patents

Description

DESCRIPTION

COMPOSITE MATERIAL BASED ON THE DISPERSION OF POLYMERS OF THE

PAEK FAMILY IN ASA, ABS AND DERIVED BLENDS

TECHNIQUE SECTOR

The invention is based on the development of polymer-polymer composite materials. In these composites, the dispersing phase is acrylonitrile styrene acrylate (ASA), acrylonitrile butadiene styrene (ABS) terpolymers or derivative mixtures, and the dispersed phase is a polymer from the polyaryletherketone (PAEK) family. The result is a material that combines the good mechanical properties of the dispersant phase and incorporates the flame retardant behavior of the dispersed phase. The composites derived from the present invention are of interest in the construction sector (aerospace, naval, rail and automotive transport, furniture, etc.) as well as in polymer engineering, since the materials, due to their thermoplastic nature, are fully processable both by conventional plastics processing techniques (injection, extrusion, thermoforming, rotational molding, etc.) and by additive manufacturing technologies based on the extrusion of material.

BACKGROUND OF THE INVENTION

Additive manufacturing (AM) brings together a compendium of manufacturing techniques for three-dimensional parts, based on layer-by-layer deposition of material, from a wide range of technologies governed by various physicochemical principles (Guo, N.; Leu MC Front. Mech. Eng. 2013, 8, 215). The parts manufactured in this way result from the addition of the aforementioned layers in a process that involves 3D-CAD design, transfer to an AM machine and addition of material (Gibson, I.; Robsen, DW; Stucker. Additive Manufacturing technologies: 3D Printing , Rapid Prototyping and Direct Digital Manufacturing; Springer, 2015). AM evolved from its initial application in rapid prototyping to cover the needs of very varied manufacturing sectors (medicine (Giannatsis, J.; Dedoussis, V. Int. J. Adv. Manuf. Technol. 2009, 40, 116), aeronautics and shipbuilding (Najmon, JC; Raeisi, S.; Tovar, A. Additive Manufacturing for the Aerospace Industry; Elsevier, 2019), (Moreno Nieto, D.; Casal Lopez, V.; Molina, SI Addit. Manuf. 2018, 23, 79), automotive (Bassoli, E. et al. Rapid Prototyp. J. 2007 13, 148), (Leal, R. et al. Int. J. Adv. Manuf. Technol. 2017, 92, 1671 ), etc.), while facilitating rapid production of parts that, due to their complex geometry and high added value, require short runs (T ofail, SM et al. Mater. Today, 2018, 21, 22), (Hague , R., Campbell, I. Dickens, P. Proc. Inst. Mech. Engrs. Part C.

2003, 217, 25) favoring energy savings, operating costs and minimizing emissions (Tang, Y.; Mak, K.; Zhao, Y. F. J. Clean Prod. 2016, 137, 1560), (Yang, Y.; Li , L. J. Clean Prod. 2018, 170, 1268), (Ullah, A. M. M. S. et al. Int. J. Sustain. Manuf. 2015, 3, 20), (Weller, C.; Kleer, R.; Piller, F. T. Int. J. Prod. Econ. 2015, 164, 43).

Within the generic group of AM techniques known as fused filament manufacturing (FFF), polymers (or polymer-based composites) in molten form are forced through a heated die. These material extrusion techniques are one of the most widespread uses in the context of AM due to the easy processing of polymers in comparison with ceramics or metals, which usually require higher operating temperatures and more sophisticated technologies (Lee, J. Y.; An , J.; Chua, C. K. Appl. Mater. Today. 2017, 7, 120). However, in the industrial context, the FFF would suffer from a relatively reduced manufacturing capacity, therefore, in order to build industrial-sized parts, large-scale manufacturing devices are required. In recent years, larger machines have been built by modifying the feeding system (replacing polymeric filament with polymeric pellets or composite) and the size of the nozzles has been increased so that manufacturing volumes of the order of several meters have been achieved. cubic. These techniques are generically called large format additive manufacturing (LFAM) fed by pellets (Sánchez, D. M. et al. Mater. Des. 2020, 191, 108577).

Among the materials used in the previously described techniques, ASA and ABS terpolymers are used, as well as their potential mixtures with polycarbonate (PC), polyvinyl chloride (PVC) and polymethylmethacrylate (PMMA), among others (Du, YG et al. J Polym. Res. 2012, 19, 9993), (Akay, M.; Ozden, SJ Mater. Sci. 1995, 30, 3358). ABS has excellent properties that, however, suffer deterioration over time (loss of mechanical resistance, color change) when the material is exposed to the elements due to exposure to UV radiation. The substitution of the butadiene block by acrylate it eliminates the olefinic bond of the structure, susceptible to degradation (Liang, YL; et al. Polymer. 2012, 53, 604).

A common denominator in the transport sector, regarding the use of plastic materials, is the need to produce parts with the highest possible flame retardance, when not fireproof behavior, considering the catastrophic thermal degradation that polymers generally suffer when increasing temperature. The traditional solution to mitigate the consequences of said thermal degradation is to incorporate flame retardants as additives to the polymers. These retardants are organic and inorganic substances that through different mechanisms interfere with the fire cycle (air-heat-fuel). At present, a great research effort is focused on displacing the traditional halogenated retardants and those that incorporate other toxic elements (due to their negative environmental implications) by different families of materials, both on a micro and nanoscopic scale (phosphorous, metallic particles, based on carbon, etc.) (Vahidi, G. et al. J. Appl. Polym. Sci. 2021, 138, 1).

There are polymers with high resistance to thermal degradation, particularly PAEK. This family of polymers shares the presence of aromatic groups (aryls) with different formulations. Polyaryletheretherketone (PEEK) exhibits a glass transition at 143 °C, a melting point around 343 °C and a degradation interval between 575-580 °C. These properties translate into an increase in the temperature necessary for the material to ignite, increasing the limiting oxygen limit and providing superior flame retardant behavior, compared to other polymers (Patel, P. et al. Polym. Degrad. Stab 2011, 96, 12), so that they would not burn in the presence of fire when they are serving in a conventional air atmosphere; the percentage of oxygen in the air is not sufficient for the sustained combustion process of these polymers to take place.

In short, the combination of ASA and ABS materials in LFAM, as well as derivative mixtures, with PAEK-based polymers, turns out to be a convenient compromise solution in order to improve the flame retardant properties of the former. The additivation of PAEK polymers, which do not melt during the processing of ASA and ABS (in the range 220-250 °C), can be considered analogous to the dispersion of materials ceramics within thermoplastic polymers, which implies an interaction that would hinder the flow of the polymer chains of the dispersant phase (Peponi, L. et al. Mater. Sci. Eng. R Reports. 2014, 85, 1), thus so that materials with improved mechanical resistance are obtained. Additionally, ASA and ABS can be functionalized, for example, by grafting with maleic anhydride (Liu, Z. et al. Ind. Eng. Chem. Res.

2012, 51, 9235), (Ma, H. et al. Polym. Degrad. Stab. 2006, 91, 2951), so the compatibilization of the dispersant phase in ASA, ABS and derivatives can eventually be facilitated by following functionalization procedures as those described. Since the price of PAEK is high (Sánchez, D. M. et al. Mater. Des. 2020, 191, 108577), the application in the form of mixtures would reduce costs through ASA and ABS-based composites, which would provide structural parts useful not only for the field of transport, but also for interior and exterior furniture and, in general, in situations in which the required products must exhibit flame retardant behavior or high combustion retardation in the presence of fire. The use of the polymer-polymer composites described in the present invention in the form of functional coatings should not be ruled out.

From the foregoing it can be deduced that the novelty of the present invention lies in improving the mechanical properties and flame resistance of ASA or ABS-based composites by adding small amounts of a high-cost technical polymer, particularly from the family of PAEK or PEI, although the concept could be extended to other technical polymers with a high limiting oxygen index (polytetrafluoroethylene PTFE, polyphenylenesulfone PPSU, polyimide, PI, etc). The foregoing is the core of the invention, without prejudice to being able to use ASA or ABS-based mixtures with other widely used thermoplastics (polypropylene, PP, polyethylene, PE, polyethylene terephthalate, PET, polystyrene, PS, or the aforementioned PC , PVC, PMMA, etc.), including those from recycled and renewable sources. In this way, an intrinsically non-fireproof dispersant phase would be obtained. The addition of the above technical polymers would provide an improvement in mechanical and flame retardant properties and the eventual functionalization of the matrix based on ASA or ABS (or their described mixtures) using techniques described in the literature, such as maleic anhydride grafts, would facilitate dispersion. of the flame retardant additives in the dispersed phase.

Regarding the bibliographic search, there is no previous contribution in the academic literature such as the one referred to in this invention. The articles referenced in this section provide a vision of the state of the art around the families of materials involved. Patent databases have also been consulted, finding a good number of these for ASA and ABS-based fire retardant materials, although most make use of inorganic compounds, halogenated in particular, in any case moving away from the concept of mixing technical polymers in low proportion in ASA and ABS or their eventually functionalized mixtures. More interesting would be the discussion of some patents that make use of similar materials. The use of polyesters based on resorcinol containing PEI and PC functionalized with siloxane (US2007100088A1) stands out. This patent does not make use of PAEK but of functionalized PEI or PC to introduce fire retardant character to the mixtures, although the polymer base is polyesters, differing from ASA and ABS that are the object of the present invention. It should be considered that in this patent the functionalization would not be performed on the dispersing phase but on the additives, in an approach with a different chemical basis. Additionally, the patent does not claim use in additive manufacturing, as other patents do (WO2015134316A1), (CN106700411A). In these, materials for additive manufacturing are claimed, although PAEK is not used in the first and they are used as a dispersing phase in the second, instead of as a dispersed phase in a low proportion, as described in the present invention with the consequent savings in costs. cost. Additionally, in both cases use is made of other additives to improve the flame retardant character (halogenated in the first, fibers in the second), moving away from the concept of the invention described.

In short, although there are patents that seek to improve flame resistance with approaches that may seem similar due to the use of materials such as those described in the present invention, an identical concept has not been found in terms of the manufacture of ASA-based composites. , ABS or any of its derivative mixtures, functionalized if applicable, including materials from the PAEK family (or other polymers that are intrinsically flame retardant in the presence of air) to achieve a flame retardant polymer-polymer composite with improved mechanical resistance, designed for its use in additive manufacturing by extrusion of material and without prejudice to its manufacture by conventional thermoplastic production techniques.

EXPLANATION OF THE INVENTION

The invention consists of the production of polymer-polymer composites where the dispersant phase is ASA, ABS, any of its derivative mixtures, whose main component is ASA or ABS, with other thermoplastics such as PP, PE, PET, PS, PC, PVC and PMMA, or other thermoplastics, including variants of these materials from their recycling, as well as the chemical functionalization of said thermoplastics, for example through the use of maleic anhydride grafts. The dispersed phase would be any material from the PAEK family (PEEK, PEK, PEKK, etc.), also including PEI and any technical polymer that does not melt during the extrusion and mixing process of the base thermoplastic polymer (ASA, ABS, etc. .). The dispersed phase is added as an additive in proportion to the weight of the dispersing phase, up to 10% by weight.

The procedure for obtaining the composite consists of hot dispersion of the dispersed phase in the dispersing phase with subsequent extrusion using a device for this purpose ( infernal mixer, single/double screw extruder). The heating profile of the equipment with which the synthesis is carried out must seek to melt the dispersant phase. Shear mixing must also be guaranteed to ensure an adequate level of dispersion of the additives. Where appropriate, if chemical functionalization is performed using maleic anhydride grafts, maleic anhydride and an initiator (dicumyl peroxide or benzoyl peroxide) must be added together with the additives to allow the anhydride grafts to be incorporated into the ASA chain or ABS. The materials must be dried prior to processing and the resulting mix would be well suited for use in FFF printers, in filament form; It would either be reduced to pellets for use in LFAM printers fed in this format, or it would be adapted to a suitable format for use in other conventional polymer transformation and manufacturing technologies.

The FA would make use of these polymer blends. Since the dispersed phase, due to its physical-chemical nature, does not melt during the mixing process with the dispersing polymer, the resulting material can be referred to as a polymer-polymer composite (for example, ASA-PEEK). The filament fed to an FFF machine, or, where appropriate, the pellets, conveniently dried prior to feeding to an LFAM machine, allow the deposition of molten material layer by layer until the final parts or coatings are obtained. The heating profile of the nozzle must be analogous to that used in the preparation of the materials, so that it melts the dispersant phase and can be deposited on the construction platform of the machine. Said platform must also be conditioned at a temperature that minimizes the possible thermal shrinkage ( warping) of the first deposited layers.

The preparation of the composites described in the present invention can be carried out following the following generic sequence:

1. Weighing of the dispersant phase and the dispersed phase. The second will be added as an additive in percentage proportion to the weight of the first. If the dispersing phase is functionalized, an additional 3% and 0.3% by weight of maleic anhydride dispersing phase and dicumyl peroxide or benzoyl peroxide initiator, respectively, are weighed.

2. Drying of the materials. To prevent inadequate dispersion of the additives within the dispersing polymer, the formation and accumulation of moisture in the materials must be avoided. For this, they will be conveniently placed in an oven at a temperature between 60-80 °C and kept for a time of no less than 3 h. If applicable, the maleic anhydride and the initiator should not be heated.

3. Pre-mixing of materials. Whenever they cannot be dosed together with a device for this purpose, all the heavy and dried materials in the previous steps will be mixed by manual shaking (if applicable, maleic anhydride and the initiator), as a step prior to extrusion. of the composites.

4. Hot mixing with melting of the dispersing phase. The premix is subjected to a heating profile so that the melting and subsequent shear mixing will provide adequate dispersion of the dispersed phase in the dispersant.

5. Final conditioning. The composite will be suitable for the final use for which it is intended. Depending on the format obtained in the previous step, it will be necessary to reduce to pellets if composite filaments have been obtained from an extrusion process and the composite in this format is required for its subsequent manufacture using LFAM or any other conventional technology. On the contrary, if pellets have been obtained and filament is required for its application in FFF machines, the eventual pellet of The composite obtained in the previous step would be melted again and extruded until the necessary filaments were formed, taking care of the proper dispersion of the additive in the dispersing polymer.

6. Use of composites. These will be used to manufacture structural parts or coatings through additive manufacturing technologies by material extrusion or conventional thermoplastic processing.

The manufactured parts or coatings are applicable in various construction sectors. For example, in the naval environment, interior construction elements can be manufactured in ABS/PAEK, while any element that is exposed to the elements should be manufactured in ASA/PAEK. The parts manufactured from the materials subject of the present invention exhibit improved fire retardant behavior and mechanical resistance with respect to the pristine dispersant phase. This has been demonstrated through the pertinent flammability and tensile behavior tests of the aforementioned materials.

As can be seen from the state of the art, AF is in an expansive phase that is expected to maintain sustained growth in the coming years. The proliferation of new manufacturing techniques goes hand in hand with the need for research activity that supplies the different AM processes with useful materials to satisfy a wide variety of industrial and private consumer demands.

In this sense, the materials that the invention develops are focused on providing an innovative economic solution to a problem that has aroused a considerable volume of research, in the form of academic articles and the generation of patents. Said problem consists of having parts with personalized geometries for rapid construction in sectors such as naval, aerospace, automotive, etc. More specifically, the invention provides starting materials for the manufacture of parts or coatings from the mixture of conventional polymeric materials that improve the flame retardant behavior and mechanical resistance of the pristine dispersant phase, providing a solution to the need for structural parts. Designed for use both indoors and outdoors, in the case of exposure to severe temperature conditions.

Although the application of the materials proposed in AM stands out, their properties (halogen-free flame retardants, improvement in mechanical resistance) also make them materials that can be applied in other polymer transformation technologies, such as injection, extrusion, rotational molding, etc., greatly expanding its scope of technical application.

In the background of the invention, various approaches have been provided that improve the flame retardant behavior of polymers such as ASA and ABS, widely used in FA, most of them based on the dispersion of different families of flame retardant materials. For its part, the present invention is a simple approach that allows combining the good mechanical properties of the dispersant phase and the fire retardant properties of the dispersed phase. Both phases are polymers whose large-scale mixing is simple and economical with conventional procedures, where the bibliographical citations consulted refer to laboratory-scale processes, without clear scalability. Additionally, thanks to the use of ASA and ABS as a dispersing phase, the composites resulting from the mixture with PAEK or PEI exhibit good mechanical properties and resistance to environmental degradation of the former and incorporate the flame retardant character of the latter. Considering the high price of technical polymers that are used as a dispersed phase, their use as an additive (up to a maximum of 10% by weight of the dispersing polymer) is an adequate economic solution to obtain materials with sufficient fire retardant behavior and mechanical resistance. .

To justify this new concept of producing fire-retardant composites with improved mechanical properties, improvements have been demonstrated in composites of 3, 6 and 10% (w/w) of PEEK in ASA of up to 25% tensile strength and up to 50% rigidity, obtaining materials that do not ignite when exposed to flame. For example, in the case of a composite with 3% (w/w) PEEK in ASA, a breaking strength of 43.5 MPa is achieved compared to 35.6 MPa for pure ASA, and a Young's modulus, as a measure of rigidity, 1960 MPa compared to 1400 MPa presented by pure ASA. Furthermore, this composite does not ignite when exposed to a flame, unlike pure ASA which burns completely, according to the UL-94 standard. The 6 and 10% composites have Young's modulus around 2000 MPa and a similar breaking strength of 45 MPa. Similarly, they resist exposure to flame.

In conclusion, the concept of using technical polymers as additives in ASA and ABS-based composites is novel for two reasons. In the first place, it was not evident that the dispersion of PAEK and other polymers with a high limiting oxygen index would provide an improvement in the fire retardant behavior of the composites and even less in the low relative proportion (up to 10%) in which have added. Secondly, it was also not obvious that the introduction of the additives would not appreciably worsen the mechanical properties, all of which was caused by difficulties in making the dispersant and dispersant phases compatible. The achievement of the improvement in flame resistance and mechanical properties converts the idea of the invention into a simple method of producing composites with improved mechanical and functional properties at a reduced cost and with viable use in conventional and additive manufacturing.

BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a set of drawings is attached as an integral part of said description, where, with an illustrative and non-limiting nature, what has been represented has been following:

- Figure 1: Two comparative graphs of the measurements of breaking strength and Young's modulus for the pure ASA polymer and for composites with different percentages by weight of PEEK (3, 6 and 10%) are shown.

PREFERRED EMBODIMENT OF THE INVENTION

By way of example, the preparation of ASA-PEEK filaments is described in a proportion of PEEK of 3% by weight with respect to ASA.

1. For the preparation of the composite, 1 kg of ASA and 30 g of PEEK were weighed.

2. The materials were dried in an oven overnight at 60 °C.

3. ASA and PEEK were mixed by hand shaking.

4. The above mixture was fed into a laboratory Noztek Pro Filament Extruder single screw extruder which produced a filament with an average diameter of 1.75 mm, at a temperature of 240 °C. To improve the degree of mixing, the filament obtained was pelletized and introduced again into the extruder (at the same temperature) and the final filament was obtained.

5. The filament obtained could be used in an FFF machine and also pelletized again for use in an LFAM and in conventional injection (in both cases after prior drying as in step 2).

6. The filament was fed into a FFF Raise 3D Pro 2 machine that melted the material at 240°C and deposited it on a build platform at 100°C for the construction of mechanical test specimens.

To prepare the same composite, including the functionalization by means of maleic anhydride grafts, 30 g of maleic anhydride and 3 g of dicumyl peroxide initiator would be weighed in addition to what was referred to in step 1, and they would be incorporated into the manual mixture in step 3. or they would be fed together with the powder with a dispenser for this purpose. The rest of the steps (4 to 6) would be analogous to obtain the functionalized composite in this case.

INDUSTRIAL APPLICATION

The materials manufactured according to the sequence described would eventually have a high degree of industrial interest, considering the advanced degree of development of the capacities of the materials, the feasibility of both synthesis and manufacturing in AM and other conventional manufacturing techniques having been demonstrated in the laboratory. with thermoplastics. The improvement of fire retardant and mechanical properties has also been demonstrated.

In short, the present invention would provide materials that, after being appropriately processed by conventional techniques or by FA material extrusion techniques, can be immediately applied as final products in the form of structural parts or coatings. Given the ease of processing, the interest industrial in the materials subject of the present invention would lie both in the processing of the material, and in its subsequent manufacture using the technologies described. The commercialization of the final products would be another potentially viable economic activity that would arise as a result of the invention.

Claims (13)

1. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, characterized in that it is made up of: - A dispersant phase based on ASA or any of its derivative mixtures with other thermoplastics, provided that the majority component is ASA, and - A dispersed phase based on any material from the PAEK family (PEEK, PEK, PEKK,... ), also including other technical polymers that would not melt at the processing temperature of the dispersant phase, the proportion of dispersed phase with respect to the dispersing polymer being a maximum of 10% (w/w). 2. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to claim 1, characterized in that the dispersant phase is ASA. 3. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to claim 1, characterized in that the dispersant phase is a mixture of ASA with another thermoplastic selected from the list: PP, PE, PET, PS , PC, PVC and PMMA; as well as the variants of these materials from their recycling. 4. Composite material based on the dispersion of polymers of the PAEK family in ASA and derivative mixtures, according to claim 1, characterized in that the dispersed phase is a polymer selected from the following list: PEEK, PEK, PEKK, PEI, PPSU , PTFE and PI. 5. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to claim 1, characterized in that the dispersed phase is PEEK. 6. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to claim 1, characterized in that the dispersant phase is chemically functionalized with grafts of maleic anhydride. 7. Composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to previous claims, characterized in that the proportion of PEEK is between 3-6% (w/w) with respect to ASA. 8. Use of composite materials based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to previous claims, with modulus of elasticity of up to 2090 MPa, breaking strength of 44.9 MPa and improved flame resistance according to standard. UL-94, for obtaining structural parts or coatings in various construction sectors (aerospace, naval, automotive, furniture, etc.). 9. Use of composite materials based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to previous claims, with modulus of elasticity of up to 2090 MPa, breaking strength of 44.9 MPa and improved flame resistance according to standard. UL-94, for obtaining structural parts or coatings in the polymer engineering sector. 10. Use of composite materials based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to previous claims, with modulus of elasticity of up to 2090 MPa, breaking resistance of 44.9 MPa and improved flame resistance according to standard. UL-94, for obtaining structural parts or coatings in various construction sectors (aerospace, naval, automotive, furniture, etc.) that are exposed to the elements. 11. Use of the composite material based on the dispersion of polymers of the PAEK family in ASA and derivative mixtures, according to previous claims, in the form of pellets for large format additive manufacturing (LFAM). 12. Use of the composite material based on the dispersion of polymers of the PAEK family in ASA and derivative mixtures, according to previous claims, in the form of a filament for additive manufacturing with fused filament (FFF). 13. Use of the composite material based on the dispersion of polymers from the PAEK family in ASA and derivative mixtures, according to previous claims, for manufacturing by means of conventional thermoplastic production techniques, such as injection, extrusion, thermoforming and rotational molding.