Expandable thermoplastic polymer particles containing recycled material and method for producing same

Abstract

The invention relates to expandable polymer particles having a recovered material content based on styrene polymers, to a method for the production thereof and to the use of the expandable polymer particles in moulding foam parts. The expandable polymer particles contain from 10 wt.% to 99 wt.%, based on the total weight, of at least one recycled material (A) comprising at least one styrenic polymer (A-1) and consisting essentially of a styrenic polymer, from 1 wt.% to 10 wt.%, based on the total weight, of at least one propellant (C) and optionally at least one protopolymer (B), at least one nucleating agent (D) and / or at least one additive (E).

Description

manual

[0001] The invention relates to expandable polymer particles containing recyclate based on styrene polymers, a process for their production and the use of the expandable polymer particles in foamed molded parts. Prior art

[0002] For many years, particle foams have been used in a variety of applications, including thermal insulation in the construction industry, packaging in the automotive industry and structural lightweight wall materials. Particle foams usually consist of many foamed polymer beads that are welded to each other. Particle foams generally have the advantage of being lighter and having better mechanical properties than solid materials.

[0003] Particle foams made of polyolefins (e.g. polyethylene) have been known for decades and are described, for example, in US 6,028,121. CN 107501595A describes a method for producing expanded polypropylene particles. The disadvantage of particle foams made of polyolefins is that they need to be fully foamed during the production process, because the blowing agent does not stay in the polymer material for a long time. It is impossible to produce polyolefin particles loaded with blowing agents that can still expand after a certain storage time. Therefore, the production and processing (foaming) of particles cannot be separated in time and space, although this is expected to be achieved in practice. Only foamed polyolefin particles can be produced and processed. Due to the huge total volume, the transportation of such particles is more expensive than the transportation of unfoamed products / particles.

[0004] Therefore, it is desirable to provide expandable polymer particles that can be stored for longer periods of time and can optionally be transported at lower costs. Furthermore, it is desirable that these expandable polymer particles consist largely of recycled materials and are preferably also easily recyclable themselves, allowing them to be supplied to the circular economy.

[0005] EP-A 2 384 355 describes expandable thermoplastic polymer particles comprising a styrene polymer and a polyolefin.

[0006] Since the polymers used are not miscible with one another, compatibilizers are required to adjust the morphology. In order to obtain particle foams with high stiffness and good elasticity, polyolefins and compatibilizers must be used, which is not possible with particle foams consisting only of polystyrene.

[0007] However, the use of polyolefins with compatibilizers requires at least one additional process step, namely the production of a mixture of at least three components: polystyrene, polyolefin and compatibilizer. In addition, suitable compatibilizers are often complicated or expensive to produce. In addition, in the case of simplified recycling of particle foams at the end of their working life, a material consisting of only one polymer type is advantageous, which can be reintroduced into the corresponding material cycle.

[0008] US 4,108,806 describes a process for producing expanded and expandable polymer particles based on a polyolefin matrix into which expandable microspheres are incorporated. The microspheres consist of a thermoplastic shell and a core of a volatile liquid blowing agent which, upon heating, expands the polymer composition. This production process is costly and produces a polymer mixture of two or more polymer types.

[0009] Polymer foams comprising styrene polymers and copolymers and methods for their production are also described in the literature.

[0010] WO 2013 / 085742 describes providing an extruded polymer foam composed of a styrene-acrylonitrile copolymer (SAN) and using 74-78 wt % of 1,1,1,2-tetrafluoroethane, 13-16 wt % of CO 2 The invention discloses a foaming agent mixture of 7-9 wt. % water and expandable polymer particles.

[0011] US 7,919,538 claims a particle foam consisting of SAN and an additive which screens infrared radiation and thus increases the thermal insulation effect. Expandable polymer particles are not described.

[0012] US 3,945,956 describes a method for producing expandable polymer particles in which a volatile liquid blowing agent is encapsulated in hollow spheres of styrene-acrylonitrile copolymer. The blowing agent is encapsulated in the polymer particles but is not uniformly distributed in the polymer matrix. Therefore, expansion of such polymer particles produces a polymer foam having unevenly distributed cavities.

[0013] US 5,480,599 describes a process for producing particle foams, in particular from styrene polymers. The process makes it possible to at least partially recover the blowing agent after the particles have expanded. However, the process only provides expanded polymer particles, not expandable particles.

[0014] US 5,049,328 describes a method for producing foam without using organic blowing agents. Only inert gases (such as CO 2 , nitrogen or air) as a blowing agent. This method is not suitable for providing expandable polymer particles that can be stored for a period of time because the gas composed of small molecules will quickly escape from the polymer composition.

[0015] EP-A 0712885 claims expandable beads of acrylonitrile-butadiene-styrene copolymer (ABS). These beads are produced in a batch process, wherein the ABS beads are impregnated with a blowing agent in an autoclave. It is necessary to modify the surface of the beads with an electrolyte so that the beads can be loaded with the blowing agent in an aqueous medium. This is disadvantageous because the electrolyte will remain on the surface and will impair the weldability of the beads. In addition, the production volume is limited by the complex coating process, the size of the required autoclave, the batch operation mode and the long loading time of the blowing agent.

[0016] EP 2 614 111 discloses expandable vinyl aromatic polymers containing 0.5 to 2% by weight of talc and 1 to 5% by weight of carbon black. The vinyl aromatic polymers mentioned include polystyrene (PS), styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS) or copolymers of styrene and butadiene.

[0017] US2013 / 059933 teaches a method for producing an expandable pelletized polymer material, which consists of a styrene polymer component having a glass transition temperature of ≥130° C. and one or more thermoplastic polymers selected from the group consisting of aromatic polyethers, polyolefins, polyacrylates, polycarbonates, polyesters, polyamides, polyethersulfones, polyetherketones and polyether sulfides. Since the polymer material contains at least two different polymer classes, the expandable pellet material obtained is difficult to recycle even if it can be recycled mechanically.

[0018] DE 10 2012 217668 discloses an expandable polymer pellet material obtained from: P) 100 parts by weight of a polymer component consisting of: PS) 90 wt% to 100 wt% (based on P) of a styrene copolymer component, which consists of: PS1) one or more styrene-acrylonitrile copolymers (SAN) or PS2) a mixture of one or more styrene-acrylonitrile copolymers (SAN) and one or more styrene-maleic anhydride copolymers (SMA) and / or PS3) one or more styrene-acrylonitrile-maleic anhydride copolymers (SANMA) and PT) 0 to 10 wt. % (based on P) of one or more thermoplastic polymers selected from the group consisting of aromatic polyethers; polyolefins; polyacrylates; polycarbonates (PC); polyesters; polyamides; polysulfones; polyethersulfones (PES); polyetherketones (PEK) and polystyrenes; T) 2 to 8 parts by weight (based on P) of a physical blowing agent component (T) containing 80 to 100% by weight (based on T) of one or more hydrocarbons having 2 to 7 carbon atoms, F) a flame retardant system containing 1 to 10 parts by weight (based on P) of one or more brominated trialkyl phosphates as flame retardants (F1). The addition of flame retardants and the use of polymers from different polymer classes significantly reduce the recyclability of the expandable polymer pellet material.

[0019] DE 10 2012 217665 teaches a process for producing expandable polymer particles from styrene-acrylonitrile copolymers (SAN) mixed with 3.11% to 3.91% by weight of a physical blowing agent.

[0020] DE 103 58 801 discloses a particle foam molded part obtainable by welding pre-foamed foam particles, wherein the pre-foamed foam particles consist of an expandable thermoplastic polymer pellet material, which contains 5% to 100% by weight of a styrene copolymer A), 0% to 95% by weight of a polystyrene B) and 0% to 95% by weight of a thermoplastic polymer C) (different from a) and b)), and is characterized in that the density of the particle foam is in the range of 8 to 100 g / l.

[0021] DE 10 2008 023702 teaches a method for the continuous production of expandable polymer particles by incorporating a polymer stream into a second polymer stream containing an expandable system and additives. The addition of additives can impair the recyclability of the polymer foam at the end of its use or working life.

[0022] DE 103 58 804 discloses expandable styrene polymer pellet materials having at least a bimodal or multimodal molecular weight distribution.

[0023] WO 2022 / 090403 also describes expandable thermoplastic polymer particles with low blowing agent losses and high expansion capacity, which can be processed into particle foams with high stiffness and good elasticity. However, when using ABS, good results can only be achieved with the addition of nucleating agents.

[0024] In many applications, foamed materials are combined with unfoamed materials. With regard to good recyclability, it is desirable that the foamed and unfoamed materials consist of the same thermoplastic polymer matrix. At the end of its working life, the item can then be shredded and remelted without any impairment of the mechanical properties of the material.

[0025] In many industrial applications, styrene polymers or copolymers are used as unfoamed materials. It is therefore desirable to also have a compatible material in foamed form so that when both materials are combined in one article, good recyclability can be ensured. This can be achieved, for example, by particle foams of styrene polymers or copolymers.

[0026] Furthermore, it is also desirable to reintroduce a large part of the recycled material into the particle foam and to contribute to the circular economy. In particular, recyclates from end-of-life plastics (e.g. from EE waste) are used, with the desire to reintroduce this material into the cycle.

[0027] However, a common feature of all the above disclosures is that they always relate to materials produced from petrochemical primary raw materials. They do not contain recycled plastics, in particular post-consumer recyclate.

[0028] In recent years, efforts have been increasingly made to recycle plastic products at the end of their working life. The use of plastic recyclates offers various advantages over the production of plastics from fossil sources, such as energy savings, less waste and lower resource consumption. However, in order not to suffer a loss in quality compared to virgin plastic when using recyclates and to compensate for variations in the quality of the recyclates used, it is best to adjust the properties of the recyclates by means of suitable additives, as described in WO 2021 / 074084.

[0029] KR 101789704 describes the production of expandable polystyrene granules using recycled materials, but the recycled materials used are exclusively post-industrial waste, ie waste generated, for example, during the trimming of molded parts. No post-consumer waste is used.

[0030] EP 1 694 753 discloses a process for producing an expandable granular thermoplastic polymer material made from a mixture of 50 to 90% by weight of polystyrene and 10 to 50% by weight of a styrene copolymer selected from styrene-butadiene block copolymers, styrene-α-methylstyrene copolymers, acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), acrylonitrile-styrene acrylate (ASA), methacrylate-butadiene-styrene (MBS) and methyl methacrylate-acrylonitrile-butadiene-styrene (MABS). The document teaches that the styrene polymer melt can also be mixed with polymer recyclate, but the proportion does not exceed 50% by weight, in particular 1 to 20% by weight. The mechanical properties of expanded polymer compositions with a high polystyrene content are generally poor. This also applies to the expandable styrene polymer pellet materials described in EP 1 694 755, which materials comprise at least 70% by weight of polystyrene and 0.1% to 30% by weight of a low molecular weight styrene copolymer composed of styrene, acrylic acid and α-methylstyrene.

[0031] There is a high demand for expandable polymer granules and processes for providing expandable polymer granules which can be stored for a period of time and optionally transported at minimal cost and which consist of only a single polymer class in order to simplify recycling. The polymer granules should also include a high proportion of recycled polymer material so that the material flow remains largely closed loop. Furthermore, after expansion, the cavities in the expanded polymer granules should be largely uniformly distributed and exhibit a fine-porous foam structure. It should also be possible to produce molded parts from the expandable polymer granules having sufficiently good mechanical properties and good thermal insulation efficiency.

[0032] The object of the present invention is therefore to provide expandable thermoplastic polymer particles with low blowing agent losses and high expansion capacity, which particles are made from a high proportion of recycled material and can themselves also be easily recycled again and can be processed into particle foams with high stiffness and good elasticity. Another object is to provide a method for producing such expandable thermoplastic polymer particles.

[0033] Surprisingly, it has been found that this object can be achieved by producing expandable thermoplastic polymer particles according to the invention, which particles are explained in more detail in the claims, the subsequent description and the examples.

[0034] The expandable thermoplastic polymer particles of the present invention contain: A) 10 to 99 wt. % of at least one recyclate (A) comprising at least one styrene polymer (A-1), based on the total weight of (A), (B), (C), (D) and (E), and consisting essentially of a styrene polymer; B) 0 to 89 wt.-%, based on the total weight of (A), (B), (C), (D) and (E), of at least one virgin polymer (B) comprising at least one styrene polymer (B-1), C) 1 to 10 wt. % of at least one blowing agent (C), based on the total weight of (A), (B), (C), (D) and (E); D) 0 wt % to 3 wt % of at least one nucleating agent (D), based on the total weight of (A), (B), (C), (D), and (E); and E) 0 to 8 wt % of at least one additive (E), based on the total weight of (A), (B), (C), (D) and (E); wherein the sum of (A) and (B) accounts for 79 to 99 wt % based on the total weight of (A), (B), (C), (D) and (E), and

[0035] The expandable thermoplastic polymer particles contain substantially no other polymers besides at least one recyclate (A) and at least one virgin polymer (B). This means that, based on the total weight of (A), (B), (C), (D) and (E), the expandable thermoplastic polymer particles contain no more than 5% by weight, preferably no more than 3% by weight, usually no more than 1% by weight of polymers that do not meet the definition of recyclate (A) and virgin polymer (B). Based on the total weight of (A), (B), (C), (D) and (E), the expandable thermoplastic polymer particles preferably contain 0% by weight of polymers that do not meet the definition of recyclate (A) and virgin polymer (B). Small amounts of foreign polymers improve the recyclability of the expandable polymer particles according to the invention.

[0036] The term "styrene polymer" is to be understood as meaning a polymer which incorporates repeating units of styrene monomers in its polymer chain. The styrene polymer according to the invention is in particular selected from the group consisting of styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), acrylate-styrene-acrylonitrile copolymers (ASA), styrene-butadiene block copolymers (SBC), methyl methacrylate-acrylonitrile-butadiene-styrene copolymers (MABS), methyl methacrylate-butadiene-styrene copolymers (MBS), alpha (alpha)-methylstyrene-acrylonitrile copolymers (AMSAN), styrene-methyl methacrylate copolymers (SMMA), amorphous polystyrene (PS) and impact-modified polystyrene (HIPS).

[0037] The expandable thermoplastic polymer particles contain at least 10% by weight, typically at least 20% by weight, preferably at least 30% by weight, in particular at least 40% by weight, typically more than 50% by weight, of at least one recyclate (A), said recyclate comprising at least one styrene polymer (A-1) and consisting essentially of a styrene polymer, based on the total weight of (A), (B), (C), (D) and (E). The expandable thermoplastic polymer particles contain not more than 99% by weight, typically not more than 98% by weight, typically not more than 89% by weight, preferably not more than 84% by weight, typically not more than 79% by weight, of at least one recyclate (A), based on the total weight of (A), (B), (C), (D) and (E). The expandable thermoplastic polymer particles typically contain from 40% to 79% by weight, preferably from 45% to 74% by weight, typically from 51% to 72% by weight, of at least one recyclate (A), based on the total weight of (A), (B), (C), (D) and (E).

[0038] The expandable thermoplastic polymer particles optionally contain at least 1% by weight, typically at least 10% by weight, preferably at least 15% by weight, typically at least 20% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one virgin polymer (B), said polymer (B) comprising at least one styrene polymer (B-1) or consisting of at least one styrene polymer (B-1). The expandable thermoplastic polymer particles contain not more than 89% by weight, typically not more than 79% by weight, typically not more than 69% by weight, preferably not more than 59% by weight, typically less than 49% by weight, of at least one virgin polymer (B), based on the total weight of (A), (B), (C), (D) and (E). The expandable thermoplastic polymer particles typically contain from 20% to 59% by weight, preferably from 25% to 54% by weight, typically from 27% to 48% by weight, of at least one virgin polymer (B), based on the total weight of (A), (B), (C), (D) and (E).

[0039] The expandable thermoplastic polymer particles preferably contain less than 5% by weight, in particular less than 3% by weight, of polymers containing no styrene-derived repeating units, based on the total weight of (A), (B), (C), (D) and (E). However, when obtaining the recyclate (A), a small amount of impurities in the form of polymers containing no styrene-derived repeating units may be introduced by incomplete single species separation during the recycling process.

[0040] In the context of the present invention, recyclate (A) is defined as plastics, the origin of which is plastic articles sent for recycling and processing at the end of their working life. Recyclate can be processed by various processes known in the industry, see for example R. (2014): "PS- and ABS-Fraktionen as Gemischtem Elektronikschrott", in DGKarl J.Thomé-Kozmiensky (Ed.), Recycling and Rohstoffe, volume 7 (pp. 379–400), TK Verlag Karl Thomé-Kozmiensky, Neuruppin. The production of recyclates can include, in particular, the addition of additives and / or primary materials in order to achieve the desired material quality.

[0041] Thus, the recyclate (A) differs from the virgin polymer (B) in particular in that the recyclate (A) has been subjected to at least one separate thermal compounding step, such as an extrusion process or an injection molding process, before being used in the expandable thermoplastic polymer granules according to the invention. Unlike the virgin polymer (B), the recyclate (A) is therefore mechanically stressed at least once by mixing, in particular by shear forces, for example in an extruder, such as a single-screw or twin-screw extruder, or in other conventional plasticizing equipment, such as a Brabender mill or a Banbury mixer, at a temperature above the melting range temperature of the recyclate (A), for example in the range of 180° C. to 320° C., typically in the range of 200° C. to 300° C., for example in the range of 220° C. to 280° C., as determined according to ISO 294. The recyclate (A) may also be subjected to further process steps in which the recyclate (A) is mechanically stressed at a temperature below the melting range temperature, such as calendering.

[0042] At least one recyclate (A) comprises at least one styrene polymer (A-1) and consists essentially of a styrene polymer. Preferably, the recyclate (A) consists of at least 80% by weight, typically at least 85% by weight, preferably at least 90% by weight or at least 92% by weight, based on the recyclate (A).

[0043] In addition to styrene polymer (A-1), recyclate (A) may also contain other components usually, which have been added to the composition of recyclate for main purposes, or enter recyclate (A) due to insufficient separation in the recovery process. In addition to styrene polymer, recyclate (A) may also contain other components (A-2), such as additives, pigments, foreign polymers or pollutants, such as metal parts, especially aluminum particles. Recyclate (A) preferably does not contain substances that have an adverse effect on further use according to the present invention. These substances especially include halogen-containing flame retardants. Based on recyclate (A), the component (A-2) of recyclate (A) is usually no more than 20 weight %, usually no more than 15 weight %, preferably no more than 10 weight % or no more than 8 weight %. Recyclate (A) preferably does not substantially include other polymers. This means that, based on the gross weight of recyclate (A), recyclate (A) contains no more than 5 weight %, preferably no more than 3 weight %, usually no more than 1 weight % of polymers that do not meet the definition of styrene polymer (A-1). Preferably, the recyclate (A) contains 0 wt. % of polymers not meeting the definition of styrene polymer (a-1), based on the total weight of the recyclate (A). Small amounts of foreign polymers improve the recyclability of the expandable polymer particles according to the invention. Small amounts of foreign polymers improve the recyclability of the expandable polymer particles according to the invention.

[0044] In the context of the present invention, the terms "virgin material" and "virgin polymer" refer to plastics which have been produced from fossil raw materials and have not been recycled during their working life.

[0045] At least one virgin polymer (B) comprises or is composed of at least one styrene polymer (B-1). Preferably, based on the virgin polymer (B), the virgin polymer (B) comprises at least 80% by weight, usually at least 85% by weight, preferably at least 90% by weight or at least 92% by weight of at least one styrene polymer (B-1). The virgin polymer (B) may also contain component (B-2), which is usually used when producing styrene polymers and is used, for example, to improve processing properties. Examples of component (B-2) include additives, such as lubricants and release agents. In one embodiment of the present invention, the virgin polymer comprises at least one styrene polymer (B-1) based on 100% by weight of the virgin polymer (B). Accordingly, the virgin polymer of this embodiment comprises component (B-2) based on 0% by weight of the virgin polymer (B). Preferably, the virgin polymer (B) is substantially free of other polymers. This means that, based on the gross weight of the virgin polymer (B), the virgin polymer (B) contains no more than 5% by weight, preferably no more than 3% by weight, and usually no more than 1% by weight of polymers that do not meet the definition of styrene polymer (B-1). Preferably, the virgin polymer (B) contains 0 wt. % of polymers not meeting the definition of styrene polymer (B-1), based on the total weight of the virgin polymer (B). Small amounts of foreign polymers improve the recyclability of the expandable polymer particles according to the invention.

[0046] In one embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A) and at least one blowing agent (C). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one virgin polymer (B), and at least one blowing agent (C). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one blowing agent (C), and at least one nucleating agent (D). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), and at least one nucleating agent (D). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one blowing agent (C), and at least one additive (E).

[0047] In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), and at least one additive (E). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one blowing agent (C), at least one nucleating agent (D), and at least one additive (E). In a further embodiment, the expandable thermoplastic polymer particles consist of at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), at least one nucleating agent (D), and at least one additive (E).

[0048] In a particularly preferred embodiment, at least one recyclate (A) and at least one virgin polymer (B) comprise or consist of polymers belonging to the same polymer class. In this embodiment, the expandable polymer particles according to the invention are particularly easy to recycle, for example in a mechanical recycling process. In a further embodiment, at least one recyclate (A) and at least one virgin polymer (B) comprise or consist of polymers belonging to the class of miscible polymers. This also ensures good recyclability, for example in a mechanical recycling process. "Polymer class" is to be understood as polymers consisting of repeating units of the same monomer.

[0049] In this context, "miscible" is understood to mean that no domains of the first polymer are formed in a continuous matrix of the second polymer, ie the first polymer dissolves in the second polymer.

[0050] In the context of the present application, the term "miscible polymer classes" is also understood to mean polymers forming a polymer blend, wherein a continuous phase and a discontinuous phase are formed, but the discontinuous phase has domains with an average domain size of less than 5 μm. Preferably, the virgin polymer (B) is dispersed in the continuous phase of the recyclate (A) in the form of discontinuous phase domains, wherein the discontinuous phase domains of the virgin polymer (B) contain at most domains with an average diameter of ≤ 2 μm, more preferably ≤ 200 nm, typically ≤ 100 nm.

[0051] The expandable thermoplastic polymer particles contain 79 wt % to 99 wt % of at least one recycled material (A) and optionally at least one virgin polymer (B) based on the total weight of (A), (B), (C), (D) and (E), wherein the virgin polymer comprises a styrene polymer (A-1) or a styrene polymer (B-1), wherein the styrene polymer (A-1) and the styrene polymer (B-1) are preferably selected from styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), acrylate-styrene-acrylonitrile copolymers (ASA), styrene-butadiene block copolymers (SBC), methyl methacrylate-acrylonitrile-butadiene The styrene polymer (A-1) / styrene polymer (B-1) is selected from the group consisting of styrene-acrylonitrile copolymer (SABS), methyl methacrylate-butadiene-styrene copolymer (MBS), α-methylstyrene-acrylonitrile copolymer (AMSAN), styrene-methyl methacrylate copolymer (SMMA), styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile-maleic anhydride copolymer (SANMA), styrene-N-phenylmaleimide copolymer, styrene-acrylonitrile-N-phenylmaleimide copolymer, styrene-imide-maleic anhydride copolymer, styrene-imide-acrylonitrile-maleic anhydride copolymer, amorphous polystyrene (PS) and impact-modified polystyrene (HIPS). Preferably, the styrene polymer (A-1) / styrene polymer (B-1) is selected from the group consisting of styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS) or acrylonitrile-styrene-acrylate copolymer (ASA).

[0052] In one embodiment, the expandable thermoplastic polymer particles contain at least 86% by weight, typically at least 91.5% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one virgin polymer (B). In one embodiment, the expandable thermoplastic polymer particles contain up to 98.5% by weight, typically at least 98% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one virgin polymer (B). The expandable thermoplastic polymer particles typically contain 91% to 98% by weight, particularly preferably 93.5% to 97% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one virgin polymer (B).

[0053] In one embodiment, based on the recyclate (A) and the virgin polymer (B), the recyclate (A) and the virgin polymer (B) contain less than 50% by weight, preferably less than 25% by weight, more preferably less than 10% by weight of styrene homopolymers. In one embodiment, the recyclate (A) and the virgin polymer (B) do not contain styrene homopolymers. In one embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain styrene homopolymers.

[0054] In one embodiment, based on the recyclate (A) and the virgin polymer (B), the recyclate (A) and the virgin polymer (B) contain less than 50% by weight, preferably less than 25% by weight, more preferably less than 10% by weight of copolymers containing maleic anhydride and / or maleimide. In one embodiment, the recyclate (A) and the virgin polymer (B) do not contain copolymers containing maleic anhydride and / or maleimide. In a further preferred embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain copolymers containing maleic anhydride and / or maleimide.

[0055] In one embodiment, the recyclate (A) and the virgin polymer (B) contain less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. % of styrene-maleic anhydride copolymer (SMA), based on the recyclate (A) and the virgin polymer (B). In a further embodiment, the recyclate (A) and the virgin polymer (B) do not contain styrene-maleic anhydride copolymer (SMA). In a further preferred embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain styrene-maleic anhydride copolymer (SMA).

[0056] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. % of α-methylstyrene-acrylonitrile copolymer (AMSAN), based on the recyclate (A) and the virgin polymer (B). In a further embodiment, the recyclate (A) and the virgin polymer (B) do not contain α-methylstyrene-acrylonitrile copolymer (AMSAN). In a further preferred embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain α-methylstyrene-acrylonitrile copolymer (AMSAN).

[0057] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain less than 50 wt.%, preferably less than 25 wt.%, more preferably less than 10 wt.% of styrene-isoprene-styrene block copolymer (SIS), based on the recyclate (A) and the virgin polymer (B). In a further embodiment, the recyclate (A) and the virgin polymer (B) do not contain styrene-isoprene-styrene block copolymer (SIS). In a further preferred embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain styrene-isoprene-styrene block copolymer (SIS).

[0058] In one embodiment, the recyclate (A) and the virgin polymer (B) contain less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. % of styrene-acrylonitrile copolymer (SAN), based on the recyclate (A) and the virgin polymer (B). In one embodiment, the recyclate (A) and the virgin polymer (B) do not contain styrene-acrylonitrile copolymer (SAN). In a further embodiment, the expandable thermoplastic polymer particles do not contain other polymers besides the recyclate (A) and the optional virgin polymer (B), and the recyclate (A) and the virgin polymer (B) preferably do not contain styrene-acrylonitrile copolymer (SAN).

[0059] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain only styrene polymers of the same polymer class, wherein the styrene polymer is selected from the group consisting of styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS), acrylate-styrene-acrylonitrile copolymer (ASA), styrene-butadiene block copolymer (SBC), methyl methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS), methyl methacrylate-butadiene-styrene copolymer (MBS), α-methylstyrene-acrylonitrile copolymer (AMSAN), styrene-methyl methacrylate copolymer (SMMA), styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile-maleic anhydride copolymer (SANMA), styrene-N-phenylmaleimide copolymer, styrene-acrylonitrile-N-phenylmaleimide copolymer, styrene-imide-maleic anhydride copolymer, styrene-imide-acrylonitrile-maleic anhydride copolymer, amorphous polystyrene (PS) and impact modified polystyrene (HIPS).

[0060] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain only styrene polymers of the same polymer class, selected from the group consisting of styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), acrylate-styrene-acrylonitrile copolymers (ASA) and α-methylstyrene-acrylonitrile copolymers (AMSAN).

[0061] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain only styrene polymers of the same polymer class, selected from the group consisting of acrylonitrile-butadiene-styrene copolymers (ABS) and acrylate-styrene-acrylonitrile copolymers (ASA), preferably acrylonitrile-butadiene-styrene copolymers (ABS).

[0062] In a further alternative embodiment, the recyclate (A) and the virgin polymer (B) contain a polymer blend comprising styrene-acrylonitrile copolymer (SAN) and acrylonitrile-butadiene-styrene copolymer (ABS); styrene-acrylonitrile copolymer (SAN) and acrylate-styrene-acrylonitrile copolymer (ASA); α-methylstyrene-acrylonitrile copolymer (AMSAN) and acrylonitrile-butadiene-styrene copolymer (ABS); or α-methylstyrene-acrylonitrile copolymer (AMSAN) and acrylate-styrene-acrylonitrile copolymer (ASA). Particularly preferred are polymer blends comprising styrene-acrylonitrile copolymer (SAN) and acrylonitrile-butadiene-styrene copolymer (ABS).

[0063] In one embodiment of the present invention, the expandable thermoplastic polymer particles contain less than 5 wt.-%, preferably less than 3 wt.-%, typically less than 2 wt.-%, based on the total weight of (A), (B), (C), (D) and (E), of other thermoplastic polymers, in particular selected from the group consisting of polyamides (PA), polyolefins such as polypropylene (PP) or polyethylene (PE), polyacrylates such as polymethyl methacrylate (PMMA), polycarbonates (PC), polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyether sulfones (PES), polyether ketones (PEK), polyether sulfides (PES), polylactic acid esters, polyphenylene oxides (PPO / PPE), ethylene-vinyl acetate copolymers (EVA), styrene-ethylene-butylene-styrene copolymers (SEBS), styrene-ethylene-propylene copolymers (SEP) and styrene-butyl acrylate copolymers. Preferably, the expandable thermoplastic polymer particles do not contain a thermoplastic polymer selected from the group consisting of polyamide (PA), polyolefins such as polypropylene (PP) or polyethylene (PE), polyacrylates such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyether sulfone (PES), polyether ketone (PEK), polyether sulfide (PES), polylactic acid, polyphenylene oxide (PPO / PPE), ethylene-vinyl acetate copolymer (EVA), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene copolymer (SEP) and styrene-butyl acrylate copolymer.

[0064] The weight average molecular weight Mw of the styrene polymers of the invention is generally in the range of 10 000 g / mol to 1 000 000 g / mol, preferably in the range of 50 000 to 500 000 g / mol, typically in the range of 80 000 to 250 000 g / mol. The molecular weight Mw can be determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as eluent and calibrated with polystyrene.

[0065] In one embodiment of the present invention, the weight average molecular weight Mw of the styrene polymer of the recyclate (A) differs from the weight average molecular weight Mw of the styrene polymer of the virgin polymer (B) by no more than 75%, preferably no more than 50%, and usually no more than 30%. This means that, for example, when the weight average molecular weight Mw of the styrene polymer of the recyclate (A) is 100,000 g / mol, the weight average molecular weight Mw of the virgin polymer (B) is in the range of 25,000 g / mol to 175,000 g / mol, preferably 50,000 g / mol to 150,000 g / mol, and usually 70,000 g / mol to 130,000 g / mol.

[0066] The styrene polymers according to the invention generally have a diameter of 1 to 30 cm 3 / 10min, preferably 10 to 25cm 3 Melt volume flow rate MVR (220° C. / 10 kg) according to ISO 1133 of 100 Å / 10 min.

[0067] Preferably, the blowing agent (ingredient C) is homogeneously distributed in the expandable thermoplastic polymer particles in the polymer matrix consisting of one or more recyclates (A) and optionally at least one virgin polymer (B).

[0068] As blowing agent (component (C)), the expandable thermoplastic polymer particles contain 1 to 10 wt. %, preferably 1.5 to 7 wt. %, particularly preferably 2 to 5 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one physical blowing agent, for example an inorganic physical blowing agent (e.g. CO 2 or nitrogen) and / or an organic physical blowing agent (such as an aliphatic C3 to C8 hydrocarbon, alcohol, ketone, ether or halogenated hydrocarbon, preferably CO 2 or alternatively isobutane, n-butane, isopentane, n-pentane, cyclopentane or a mixture thereof). The blowing agent preferably comprises at least one organic physical blowing agent.

[0069] In a preferred embodiment, the blowing agent comprises less than 5 wt. %, more preferably less than 2 wt. % water, based on the total weight of ingredient (C). Preferably, the blowing agent is substantially free of water, i.e., it comprises no more than 0.5 wt. %, preferably no more than 0.1 wt. % water, based on the total weight of ingredient (C).

[0070] As optional component D, the expandable thermoplastic polymer particles contain 0 to 3% by weight, preferably 0 to 2% by weight, particularly preferably 0 to 0.5% by weight, of at least one nucleating agent, such as talc, aluminum oxide or silicon dioxide, based on the total weight of (A), (B), (C), (D) and (E).

[0071] In a preferred embodiment, the expandable thermoplastic polymer particles do not add talcum powder, aluminum oxide or silicon dioxide as component (D) during production. In a further embodiment, the expandable thermoplastic polymer particles do not add nucleating agent as component (D) during production, i.e. 0% by weight based on the total weight of (A), (B), (C), (D) and (E). However, the expandable thermoplastic polymer particles may contain nucleating agent, in particular from recyclate (A). It has been found that the optional additives and impurities present in the recyclate (A) are usually sufficient to induce the required pore formation in the expandable thermoplastic polymer particles.

[0072] The expandable thermoplastic polymer particles according to the invention may optionally contain further additives (E) in an amount which does not impair the cell formation and the foam structure produced thereby. The expandable thermoplastic polymer particles according to the invention generally contain at least one additive (E) in an amount of 0 to 8% by weight, preferably 0 to 5% by weight, more preferably 0 to 3% by weight, for example 0.1 to 3% by weight, based on the total weight of (A), (B), (C), (D) and (E).

[0073] Suitable additives (E) are known to those skilled in the art and include, for example, plasticizers, flame retardants (preferably non-halogenated flame retardants), soluble and insoluble inorganic and / or organic dyes and pigments, fillers or reinforcing agents (glass fibers, carbon fibers, etc.), co-foaming agents, antioxidants, heat stabilizers, UV stabilizers, peroxide scavengers, antistatic agents, lubricants, mold release agents, antiblocking agents, processing aids, and combinations of two or more thereof.

[0074] In a preferred embodiment, the expandable thermoplastic polymer particles do not contain halogenated flame retardants. Preferred flame retardants include in particular components based on phosphorus compounds known for this application.

[0075] Examples of antioxidants and heat stabilizers include halides of metals of Group I of the Periodic Table of the Elements, such as sodium, potassium and / or lithium halides, optionally in combination with copper (I) halides (e.g. chloride, bromide, iodide), sterically hindered phenols, hydroquinone, various substituted representatives of these groups and mixtures thereof, in concentrations up to 1% by weight, based on the total weight of the expandable thermoplastic polymer particles.

[0076] UV stabilizers are typically present in amounts up to 2 wt %, typically 0.1 wt % to 1.5 wt %, based on the total weight of the expandable thermoplastic polymer particles, and include various substituted resorcinols, salicylates, benzotriazoles, and benzophenones.

[0077] The thermoplastic polymer particles may also contain organic dyes (e.g. aniline black), pigments (e.g. titanium dioxide, phthalocyanine, ultramarine blue and carbon black) and fibrous and powdered fillers and reinforcing agents. Examples of the latter include carbon fibers, glass fibers, amorphous silica, calcium silicate (wollastonite), aluminum silicate, magnesium carbonate, kaolin, chalk, quartz powder, mica and feldspar.

[0078] Lubricants and mold release agents are typically used in amounts up to 1 wt %, typically 0.1 wt % to 0.8 wt %, based on the total weight of the expandable thermoplastic polymer particles, and include, for example, long chain fatty acids such as stearic acid or behenic acid, their salts such as calcium or zinc stearate, or esters such as stearyl stearate or pentaerythritol tetrastearate, and amide derivatives such as ethylene bisstearamide.

[0079] Mineral-based antiblocking agents can be present in a content of up to 0.1% by weight, based on the total weight of the expandable thermoplastic polymer particles. Examples that may be mentioned include amorphous or crystalline silicon dioxide, calcium carbonate or aluminum silicate.

[0080] Processing aids that may be present may include, for example, mineral oil (preferably medicinal white oil) in an amount of up to 5% by weight, preferably up to 2% by weight, especially 0.1% to 2% by weight, based on the total weight of the expandable thermoplastic polymer particles.

[0081] Examples of the plasticizer include dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oil, N-(n-butyl)benzenesulfonamide, and o- and p-tolylethylsulfonamide.

[0082] Production method

[0083] The present invention provides a method for producing expandable thermoplastic polymer particles, comprising the following steps: a) mixing at least one recyclate (A) or a mixture of at least one recyclate (A) and at least one virgin polymer (B) with at least one blowing agent (C) and optionally at least one nucleating agent (D) and / or at least one additive (E) to form a polymer mixture (I); b) pelletizing the blowing agent-loaded polymer mixture (I) to obtain expandable polymer particles; and c) optionally pre-expanding the expandable polymer particles.

[0084] The above descriptions on the selection of components (A), (B), (C), (D) and (E) and the amounts used apply accordingly to the method of the present invention.

[0085] In one embodiment, the method of the present invention uses only at least one recyclate (A) and at least one blowing agent (C) as starting materials. In a further embodiment, the method uses only at least one recyclate (A), at least one virgin polymer (B) and at least one blowing agent (C) as starting materials. In a further embodiment, the method uses only at least one recyclate (A), at least one blowing agent (C) and at least one nucleating agent (D). In a further embodiment, the method uses only at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C) and at least one nucleating agent (D). In a further embodiment, the method uses only at least one recyclate (A), at least one blowing agent (C), at least one nucleating agent (D) and at least one additive (E). In a further embodiment, the method uses only at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), at least one nucleating agent (D) and at least one additive (E). In a further embodiment, the method uses only at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), at least one nucleating agent (D) and at least one additive (E). In a further embodiment, the method uses only at least one recyclate (A), at least one blowing agent (C) and at least one additive (E). In a further embodiment, the method employs only at least one recyclate (A), at least one virgin polymer (B), at least one blowing agent (C), and at least one additive (E).

[0086] Preferably, process step a) is carried out at a temperature above the glass transition temperature of the at least one recyclate (A) or the mixture of at least one recyclate (A) and at least one virgin polymer (B). The temperature in process step a) is typically in the range of 150° C. to 250° C., typically in the range of 170° C. to 220° C.

[0087] Preferably, at least process step b), typically process steps b) and c) are carried out at a temperature around the glass transition temperature of the at least one recyclate (A) or a mixture of at least one recyclate (A) and at least one virgin polymer (B). The temperature in process step b) and optionally c) is typically in the range of 50° C. to 250° C.

[0088] Preferably, at least process step a), particularly preferably process steps a) and b), are carried out under a pressure above atmospheric pressure.

[0089] Process step c) is preferably carried out at a pressure not exceeding atmospheric pressure.

[0090] In one embodiment of the present invention, process steps a) and b) are carried out in an extruder, followed by underwater pelletizing at a water pressure in the range of 1.5 to 11 bar. The water temperature during underwater pelletizing is below the glass transition temperature of the at least one recyclate (A) or the mixture of at least one recyclate (A) and at least one virgin polymer (B), typically in the range of 20° C. to 80° C. The extruder temperature is above the glass transition temperature of the at least one recyclate (A) or the mixture of at least one recyclate (A) and at least one virgin polymer (B), typically in the range of 170° C. to 250° C.

[0091] In a further embodiment, process steps a) and b) are carried out in an autoclave. At least one granulated recyclate (A) or a granulated mixture of at least one recyclate (A) and at least one virgin polymer (B), optionally mixed with at least one nucleating agent (D) and / or at least one additive (E), is impregnated with a blowing agent (C) under pressure to provide expandable thermoplastic polymer particles. These can then be separated by decompression or pre-foamed foam particles can be obtained directly.

[0092] Particular preference is given to continuous processes in which, in process step a), recyclate (A), for example recycled SAN (rSAN), recycled ABS (rABS) or recycled ASA (rASA), and optionally virgin polymer (B), for example SAN, ABS or ASA, optionally mixed with nucleating agents (D) and / or additives (E), are melted in a twin-screw extruder and impregnated with a blowing agent (C). A preferred embodiment is the use of a mixture of recyclate (A) and virgin polymer (B) which has been produced separately and which has optionally been adjusted to the desired material quality by adding additives.

[0093] In process step b), the melt loaded with the blowing agent can then be extruded through a suitable die and cut to provide foam sheets, strands or particles. A preferred embodiment is extrusion through a microperforated plate to form particles, the microperforated plate comprising one or more holes with a diameter of 0.1 to 2.4 mm, preferably 0.2 to 1.2 mm, particularly preferably 0.5 to 0.8 mm. In a preferred embodiment, the melt flowing out of the microperforated plate is fed into a water stream, where the melt is cut into individual particles by a suitable device. Adjusting a suitable back pressure and a suitable temperature in this so-called underwater granulation water stream allows the targeted production of expandable polymer particles.

[0094] In an alternative embodiment, process steps a) and / or b) can be carried out completely or partly in suspension. The recyclate (A) and optionally the virgin polymer (B), the nucleating agent D and / or the additive (E) can be converted into a suspension, preferably an aqueous suspension, and then loaded with at least one gaseous blowing agent (C) (e.g. CO 2or nitrogen). The pressure at which the blowing agent (C) is introduced is, for example, in the range of 1 bar to 20 bar, and typically in the range of 1.2 bar to 15 bar or 1.5 bar to 10 bar. Once the desired blowing agent (C) loading is reached, the resulting polymer particles are isolated, for example by filtration and / or centrifugation, and optionally washed.

[0095] The optional pre-expansion step c) can be carried out by reducing the ambient pressure and / or increasing the ambient temperature.

[0096] In the non-pre-foamed state, the average particle size of the expandable thermoplastic polymer particles according to the invention with a recyclate content is preferably in the range of 0.1 to 5 mm, preferably in the range of 0.3 to 3 mm, particularly preferably in the range of 0.5 to 2 mm. Expandable polymer particles with a narrow particle size distribution and an average particle size in the range lead to better filling of the mold during the welding of the polymer particles to provide a molded part. They allow the design of finer molded parts and improve the surface of the molded parts.

[0097] In a further preferred embodiment, the expandable thermoplastic polymer particles with recycled content are pre-foamed. The resulting expandable polymer particles are preferably foamed to an average diameter in the range of 0.2 to 10 mm, preferably 0.3 to 5 mm, particularly preferably 0.5 to 4 mm. The final foaming of the pre-foamed (pre-expanded) polymer particles can then be carried out in a downstream processing step.

[0098] The specific gravity of the pre-expanded polymer particles having a recycled content is preferably in the range of 10 to 250 g / L, particularly preferably 20 to 200 g / L, particularly preferably 25 to 150 g / L, particularly preferably 30 to 100 g / L.

[0099] In the pre-expanded state, the expandable thermoplastic polymer particles preferably have an average cell size of between 50 and 400 μm, more preferably between 100 and 300 μm.

[0100] The expandable thermoplastic polymer particles with recyclate content according to the present invention can be introduced into a mold, which is then closed and heated by hot air or steam passing through the mold. Heating can also be carried out by radio waves or infrared radiation. This will cause the polymer particles to expand further, ideally until the cavity is completely filled, thereby forming a foam molded article. The selected processing pressure is low enough to maintain the pore structure in the cellular film. The pressure is usually in the range of 0.5 to 1.0 bar.

[0101] The expandable thermoplastic polymer particles according to the invention can be further processed (e.g. foamed) immediately after production, or stored and then only provided for the intended use. It is not necessary to apply a coating on the surface of the expandable thermoplastic polymer particles according to the invention, but if necessary, for example, an antistatic coating, it can be optionally carried out. Antistatic coatings are known to those skilled in the art. Examples of antistatic coatings include quaternary ammonium salts, polyoxyethylene-alkylphenol ethers, glycerides, stearic acid monoglyceride, stearic acid triglyceride, ethylene-bisstearamide, polyethylene glycol sorbitan monooleate, zinc stearate, sodium alkyl sulfonates, bis(2-hydroxyethyl)octylmethylammonium p-toluenesulfonate, polyvinyl propionate and surfactants. Suitable antistatic coatings are commercially available, for example under the trade name (BASF, Germany), (Peter H. Urdahl GmbH, Germany) or (PCC Chemax Inc., Poland).

[0102] use

[0103] The invention also provides the use of the expandable thermoplastic polymer particles of the invention with recycled content in the production of molded parts (e.g. foam molded articles), which are preferably formed by expanding and welding the expandable polymer particles using hot air, steam, radio waves and / or infrared radiation. The obtained molded parts can be used in a variety of application scenarios, in particular as insulating materials, damping materials, packaging materials or lightweight building materials, for example in the automotive field.

[0104] The specific gravity of the molded part is preferably less than 250 g / L, preferably less than 200 g / L, particularly preferably less than 150 g / L.

[0105] The compressive strength of the molded part at 10% elongation is preferably greater than 250 kPa.

[0106] The flexural modulus of the molded part is preferably greater than 15 MPa.

[0107] The invention will now be illustrated by the following examples, figures and claims.

[0108] Examples

[0109] In a co-rotating twin-screw extruder (model ZK25P, Collin GmbH) with a screw diameter of 30 mm and an aspect ratio of 42, recycled acrylonitrile-butadiene-styrene copolymer (rABS) (e.g., sold under the trade name A polymer mixture consisting of ECO (available from INEOS Styrolution) and virgin polymer acrylonitrile-butadiene-styrene copolymer (ABS) was melted at 200-240° C. with a blowing agent n-pentane and optionally a nucleating agent talc and thus homogeneously mixed. Table 1 reports the experiments performed.

[0110] The resulting polymer mixture (I) was then cooled in a single screw extruder (E 45M model, Collin GmbH) having a screw diameter of 45 mm and an aspect ratio of 30 and extruding the melt through a heated perforated plate. The polymer strands were subjected to underwater pelletization to obtain a microgranular material loaded with a blowing agent having a narrow particle size distribution. The back pressure in the underwater pelletization was adjusted to 8 to 11 bar.

[0111] The micropellet material loaded with blowing agent was then pre-foamed in an X-line 3 pre-foaming machine (Kurtz GmbH). The pre-foamed polymer particles were welded in a TVZ 162 / 100 PP molding machine (Teubert Maschinenbau GmbH) at about 120-125° C. to produce test specimens for measuring thermal and mechanical properties.

[0112] The density of the pre-expanded particles was determined according to ISO 1183 using an AG245 density balance (Mettler Toledo).

[0113] Cell size was measured using a profilometer (Keyence) and ImageJ software measuring the cell diameter on foam particles cut in half by freeze-fracture. In each case, 50 cells per particle of three particles of each material were evaluated.

[0114] The thermal properties of the samples were tested according to DIN EN 12667 using an HMF Lambda Small heat flow meter (Netzsch) with a sample size of 200 x 200 x 20 mm and a temperature gradient of 20 K.

[0115] The mechanical properties of the samples were tested by three-point bending tests, using a 1485 universal testing machine (Zwick Roell) according to ISO 1209 on test samples with dimensions of 120×25×20 mm, a preload of 1 N, and a test speed of 10 mm / min. Static compression tests were performed according to DIN EN ISO 844 on test samples with dimensions of 40×20×20 mm and with a foam skin, using a Z050 universal testing machine (Zwick Roell) with a preload of 10 N.

[0116] The results are reported in Table 1. The pairs of examples 1 and 2 and 3 and 4 each have the same recycled content, but different degrees of foaming, which can be specifically adjusted by changing the process parameters. The degree of foaming is reflected in the foam density. The comparison of mechanical and thermal properties should in each case be made with foams of the same density, since these properties are strongly influenced by the foam density. The degree of foaming of examples 1 and 3 and comparative examples 5 and 6 is greater than that of examples 2 and 4.

[0117] Table 1: Example results

[0118] Comparing Inventive Examples 1 and 3 (recycled content of 50 wt % and 70 wt % of the total weight of the polymer composition, respectively) with Comparative Examples 5 and 6 (no recycled content), the results show that:

[0119] The thermal conductivity of the inventive examples 1 and 3 is significantly lower than that of the non-inventive comparative examples 5 and 6, that is, when the polymer composition contains recycled content, the thermal insulation effect of the inventive examples is much better (see Figure 1 ). The foam in Comparative Example 5 was produced without a nucleating agent, thus resulting in an uneven foam structure in the case of a polymer composition without recycled material. The use of a nucleating agent can improve the foam structure (Comparative Example 6), but the thermal conductivity is still higher than that of foams with recycled material (and thus the thermal insulation effect is worse) (Examples 1 and 3). When the polymer composition contains a high recycled content, it is easy to produce insulating foam even without a nucleating agent.

[0120] In addition, Examples 1 and 3 of the present invention showed finer and more uniform cell structures than Comparative Example 5 (see Figure 4 and 5 ). Figure 4 The cell structure of the polymeric foam of the present invention having 50 wt% recycled content in Example 1 is shown. Figure 5 The cell structure of the non-inventive foam without recycled content in Comparative Example 5 is shown. The foam without recycled content is not uniform and has larger cells. In the non-inventive foam, a good cell structure can only be achieved by using a nucleating agent, such as Figure 6 shown. Figure 6 The foam structure of Comparative Example 6 is shown; it is a non-inventive foam with no recycled content but containing a nucleating agent. The average cell size of Inventive Example 1 is significantly smaller than the cell size of Non-inventive Comparative Example 5 which does not contain a nucleating agent, thus indicating that the cell structure in the inventive example is much better than the cell structure in the non-inventive example.

[0121] The test specimens made from the compositions according to the invention (Examples 1 and 3) have better compressive strength than the test specimens made according to the non-inventive comparative examples 5 and 6 (see also Figure 2). Comparative Example 5 (without nucleating agent) shows only very low compressive strength. Adding a nucleating agent in Comparative Example 6 does increase the compressive strength, but does not reach the good values ​​of the inventive examples with recycled content. Here too it is shown that the inventive compositions with high recycled content are suitable for producing foams with very good compressive strength, even without the addition of a nucleating agent.

[0122] The measured data of the flexural modulus of the test samples also clearly show that the foams of the invention with recycled content have significantly improved properties compared to the non-inventive foams. In the case of the latter, the addition of a nucleating agent does improve the flexural modulus (Comparative Example 6), but still does not reach the good values ​​of the inventive examples with recycled content (see also Figure 3 ).

[0123] Therefore, even without the addition of nucleating agents, the use of high recycled content can produce foams with superior mechanical and thermal properties than those produced using virgin material alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0124] Figure 1 Shown is a graphical representation of experimentally obtained thermal conductivity data for Examples 1 and 3 and Comparative Examples 5 and 6 at 25°C in units of W / m*K.

[0125] Figure 2 Shown is a graphical representation of experimentally obtained compressive strength data for Examples 1 and 3 and Comparative Examples 5 and 6 at 10% elongation in kPa.

[0126] Figure 3 A graphical representation of the experimentally obtained flexural modulus data for Examples 1 and 3 and Comparative Examples 5 and 6 is shown in units of MPa.

[0127] Figure 4 An electron micrograph of the pre-expanded particles of the present invention obtained in Example 1 is shown.

[0128] Figure 5 An electron micrograph of pre-expanded particles not according to the invention obtained in Comparative Example 5 is shown.

[0129] Figure 6 An electron micrograph of pre-expanded particles not according to the present invention obtained in Comparative Example 6 is shown.

Claims

1. An expandable thermoplastic polymer particle, comprising, preferably consisting of: A) 10 to 99 wt. % of at least one recyclate (A) comprising at least one styrene polymer (A-1), based on the total weight of (A), (B), (C), (D) and (E), and consisting essentially of a styrene polymer; B) 0 to 89 wt.-%, based on the total weight of (A), (B), (C), (D) and (E), of at least one virgin polymer (B) comprising at least one styrene polymer (B-1), C) 1 to 10 wt. % of at least one blowing agent (C), based on the total weight of (A), (B), (C), (D) and (E); D) 0 wt % to 3 wt % of at least one nucleating agent (D), based on the total weight of (A), (B), (C), (D), and (E); and E) 0 to 8 wt % of at least one additive (E), based on the total weight of (A), (B), (C), (D) and (E); wherein the sum of (A) and (B) accounts for 79 to 99 wt % based on the total weight of (A), (B), (C), (D) and (E), and Therein, the expandable thermoplastic polymer particles contain substantially no other polymers besides at least one recyclate (A) and at least one virgin polymer (B).

2. The expandable thermoplastic polymer particles according to claim 1, characterized in that At least one recyclate (A) and at least one virgin polymer (B) comprise at least one polymer selected from the group consisting of styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS), acrylate-styrene-acrylonitrile copolymer (ASA), methyl methacrylate-acrylonitrile-butadiene-styrene copolymer (MABS), methyl methacrylate-butadiene-styrene copolymer (MBS), α-methylstyrene-acrylonitrile copolymer (AMSAN), styrene-methyl methacrylate copolymer (SMMA), styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile-maleic anhydride copolymer (SANMA), styrene-N-phenylmaleimide copolymer, styrene-acrylonitrile-N-phenylmaleimide copolymer, styrene-imide-maleic anhydride copolymer, styrene-imide-acrylonitrile-maleic anhydride copolymer, amorphous polystyrene (PS) and impact modified polystyrene (HIPS).

3. The expandable thermoplastic polymer particles according to claim 1 or 2, characterized in that: The at least one recyclate (A) and the at least one virgin polymer (B) are at least one polymer selected from the group consisting of styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS) and acrylate-styrene-acrylonitrile copolymer (ASA).

4. The expandable thermoplastic polymer particles according to any one of claims 1 to 3, characterized in that In the non-prefoamed state, the average particle size of the expandable thermoplastic polymer particles is in the range of 0.1 to 5 mm, preferably in the range of 0.3 to 3 mm, particularly preferably in the range of 0.5 to 2 mm.

5. The expandable thermoplastic polymer particles according to any one of claims 1 to 4, characterized in that The polymer particles are pre-expanded to an average diameter of 0.2 to 10 mm, preferably 0.3 to 5 mm, particularly preferably 0.5 to 4 mm.

6. The expandable thermoplastic polymer particles according to any one of claims 1 to 5, characterized in that The expandable thermoplastic polymer particles contain two or more recycled materials (A) and virgin polymer (B), and the two or more recycled materials (A) and virgin polymer (B) are miscible with each other.

7. The expandable thermoplastic polymer particles according to any one of claims 1 to 6, characterized in that The average cell size of the pre-expanded particles is between 50 and 400 μm, preferably between 100 and 300 μm.

8. A method for producing expandable thermoplastic polymer particles according to any one of claims 1 to 7, comprising the following steps: a) mixing a mixture of at least one recyclate (A) and at least one virgin polymer (B) with at least one blowing agent (C) and optionally at least one nucleating agent (D) and / or at least one additive (E) to form a polymer mixture (I); b) granulating the blowing agent-loaded polymer mixture (I) to obtain expandable polymer particles; and c) optionally pre-expanding the expandable polymer particles.

9. The method according to claim 8, characterized in that At least step a), preferably steps a) and b), are carried out at a pressure exceeding atmospheric pressure.

10. The method according to claim 8 or 9, characterized in that: Process steps a) and b) are carried out in an extruder, followed by underwater pelletizing at a water pressure of 1.5 to 11 bar.

11. The method according to claim 8 or 9, characterized in that: Process steps a) and b) are carried out in an autoclave.

12. The method according to any one of claims 8 to 11, characterized in that Process steps a) and b) are carried out in suspension.

13. Use of expandable thermoplastic polymer particles according to any one of claims 1 to 7 in molded parts formed by welding pre-expanded thermoplastic polymer particles using hot air, steam, radio waves and / or infrared radiation, wherein the molded parts preferably have a specific gravity of less than 250 g / L, preferably less than 200 g / L, particularly preferably less than 150 g / L.

14. Use of expandable thermoplastic polymer particles according to any one of claims 1 to 7 in molded parts formed by welding pre-expanded thermoplastic polymer particles using hot air, steam, radio waves and / or infrared radiation, wherein the compressive strength at 10% elongation of the molded part is preferably greater than 250 kPa.

15. Use of expandable thermoplastic polymer particles according to any one of claims 1 to 7 in molded parts formed by welding pre-expanded thermoplastic polymer particles using hot air, steam, radio waves and / or infrared radiation, wherein the molded parts preferably have a flexural modulus greater than 15 MPa.

Images