Expandable thermoplastic polymer particles with a content of recycled material, and method for producing same

Abstract

The invention relates to expandable polymer particles with a content of recycled material based on styrene polymers, to a method for producing same, and to the use of the expandable polymer particles in a molded foam part. The expandable polymer particles contain 10 to 99 wt.%, based on the total weight, of at least one recycled material (A), which comprises at least one styrene polymer (A-1) and which largely consists of styrene polymers, 1 to 10 wt.%, based on the total weight, of at least one propellant (C), and optionally at least one primary polymer (B), at least one nucleating agent (D), and / or at least one additive (E).

Description

[0001] Expandable, thermoplastic polymer particles with recycled content and process for their production

[0002] Description

[0003] The invention relates to expandable polymer particles with a recycled content based on styrene polymers, a process for their production and the use of the expandable polymer particles for foam moldings.

[0004] State of the art

[0005] Particle foams have been used for years in numerous applications, including insulation in construction, packaging, and structural, lightweight wall materials in the automotive sector. Particle foams typically consist of many expanded polymer beads that are welded together. Particle foams typically offer the advantage of weight reduction while maintaining good mechanical properties over solid materials.

[0006] Particle foams made from polyolefins, such as polyethylene, have been known for decades and are described, for example, in US Pat. No. 6,028,121. CN 107501595A describes a process for producing particles from expanded polypropylene. A disadvantage of particle foams made from polyolefins is that they must be fully foamed during production, as the blowing agent does not remain in the polymer material for an extended period. It is not possible to produce polyolefin particles loaded with blowing agent that can still be expanded after a certain storage time. Therefore, a temporal and spatial separation of particle production and processing (foaming) is not possible, although this is desirable in practice. Only already foamed polyolefin particles can be produced and processed. Due to the high overall volume, the transport of such particles is more complex than the transport of unfoamed products or particles.

[0007] It is therefore desirable to provide expandable polymer particles that can be stored for extended periods and, if necessary, transported with minimal effort. Furthermore, it is desirable that these expandable polymer particles consist largely of recycled material and, preferably, are themselves easily recyclable, thus enabling them to be fed into a circular economy.

[0008] EP-A 2384355 describes expandable, thermoplastic polymer particles containing a styrene polymer and a polyolefin. Since the polymers used are immiscible with each other, a compatibilizer must be used to adjust the morphology. The use of polyolefins and compatibilizers is necessary to achieve particle foams with high stiffness and good elasticity, which cannot be achieved with a particle foam consisting solely of polystyrene.

[0009] However, the use of polyolefins with a compatibilizer requires at least one additional process step: the production of a blend of at least three components: polystyrene, polyolefin, and compatibilizer. Furthermore, suitable compatibilizers are often complex to produce or expensive. Furthermore, in order to simplify the recycling of particle foams at the end of their lifespan, a material consisting of only one polymer type is advantageous, as it can be reintroduced into the corresponding material cycle.

[0010] 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 made of a volatile liquid blowing agent, which causes the polymer mass to expand upon heating. This production method is complex and results in a polymer mixture of two or more polymer types.

[0011] Polymer foams, including styrene polymers and copolymers, as well as processes for their production are also described in the literature.

[0012] WO 2013 / 085742 describes the provision of an extruded polymer foam made of styrene-acrylonitrile copolymer (SAN) produced using a blowing agent mixture of 74-78 wt.% 1,1,1,2-tetrafluoroethane, 13-16 wt.% CO2, and 7-9 wt.% water. The provision of expandable polymer particles is not disclosed.

[0013] US Pat. No. 7,919,538 claims a particle foam consisting of SAN and an additive that shields infrared radiation for the purpose of improved thermal insulation. No expandable polymer particles are described.

[0014] US 3,945,956 describes a process for producing expandable polymer particles in which a volatile liquid blowing agent is enclosed in a hollow sphere made of a styrene-acrylonitrile copolymer. The blowing agent is enclosed in a polymer particle but not homogeneously distributed in a polymer matrix. Upon expansion of such polymer particles, a polymer foam with inhomogeneously distributed voids is formed. US 5,480,599 describes a process for producing particle foams, including from styrene polymers. The process allows the blowing agent to be at least partially recovered after expansion of the particles. However, the process only produces expanded polymer particles, not expandable particles.

[0015] US Pat. No. 5,049,328 describes a process for foam production without organic blowing agents. Only inert gases such as CO2, nitrogen, or air are used as blowing agents. This process is not suitable for producing expandable polymer particles that can be stored for a certain period of time, because the gases, consisting of small molecules, quickly escape from the polymer mass.

[0016] EP-A 0712885 claims expandable beads made of acrylonitrile-butadiene-styrene copolymers (ABS). These are produced in a batch process in which ABS beads are impregnated with a blowing agent in an autoclave. It is necessary to modify the bead surface with electrolytes so that the beads can be loaded with the blowing agent in an aqueous medium. This is disadvantageous because the electrolytes remain on the surface and can impair the weldability of the beads. Furthermore, the producible quantities are limited by the complex coating process, the size of the required autoclave, the discontinuous operation, and the long loading time with the blowing agent.

[0017] EP 2 614111 discloses expandable vinylaromatic polymers containing 0.5 to 2 wt.% talc and 1 to 5 wt.% carbon black. Vinylaromatic polymers mentioned include polystyrene (PS), styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), or copolymers of styrene and butadiene.

[0018] US 2013 / 059933 teaches a process for producing an expandable, pelletized polymer material consisting of a styrene polymer component with 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; polyether ketones; and polyether sulfides. Since the polymer material comprises at least two different polymer classes, the resulting expandable granules are difficult or impossible to recycle mechanically.

[0019] DE 10 2012 217668 discloses an expandable polymer granulate obtainable from:

[0020] P) 100 parts by weight of a polymer component consisting of PS) 90-100 wt.% (based on P) of a styrene copolymer component consisting of PS1) one or more styrene-acrylonitrile copolymers (SAN) or

[0021] 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

[0022] PT) 0 to 10 wt.% (based on P) of one or more thermoplastic polymers from the group consisting of aromatic polyethers; polyolefins; polyacrylates; polycarbonates (PC); polyesters; polyamides; polysulfones; polyethersulfones (PES); polyether ketones (PEK) and polystyrene;

[0023] T) 2 to 8 parts by weight (based on P) of a physical blowing agent component (T) containing 80 to 100 wt. % (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 granules.

[0024] DE 10 2012 217665 teaches a process for producing expandable polymer particles from styrene-acrylonitrile copolymers (SAN), which are mixed with 3.11 to 3.91 wt.% of a physical blowing agent.

[0025] DE 103 58 801 discloses particle foam moldings obtainable by welding pre-foamed foam particles made of expandable, thermoplastic polymer granules containing 5 - 100 wt.% of a styrene copolymer A), 0 to 95 wt.% of polystyrene B) and 0 to 95 wt.% of a thermoplastic polymer C) different from a) and b), characterized in that the particle foam has a density in the range of 8 to 100 g / l.

[0026] DE 10 2008 023702 teaches a process for the continuous production of expandable polymer particles by incorporating a polymer stream into a second polymer stream containing the expanding system and additives. The addition of additives complicates the recycling of the polymer foam at the end of its use or service life.

[0027] DE 103 58 804 discloses expandable styrene polymer granules with at least bimodal or multimodal molecular weight distribution. Expandable, thermoplastic polymer particles with low blowing agent loss and high expansion capacity, which can be processed into particle foams with high stiffness and good elasticity, are also described in WO 2022 / 090403. However, when using ABS, good results are only achieved with the addition of nucleating agents.

[0028] In many applications, foamed materials are combined with non-foamed materials. For good recycling, it is desirable for the foamed and non-foamed materials to consist of the same thermoplastic polymer matrix. This allows the object to be shredded and remelted at the end of its service life without any loss of mechanical properties.

[0029] In many industrial applications, a styrene polymer or copolymer is used as a non-foamed material. It would therefore be desirable to have a compatible material in foamed form as well, so that overall recycling is good when both materials are combined in one product. This is possible, for example, with a particle foam made from a styrene polymer or copolymer.

[0030] Furthermore, it would be desirable to incorporate a large proportion of recycled material back into the particle foam to contribute to the circular economy. In particular, the utilization of recycled plastics, such as electrical and electronic waste, would be desirable so that this material can be reintroduced into the cycle.

[0031] However, all of the above-mentioned disclosures have in common that they always refer to materials made from primary petrochemical raw materials. They do not contain any recycled plastics, especially post-consumer recyclates.

[0032] In recent years, there have been increased efforts to recycle plastic products at the end of their service life. The use of plastic recyclates offers several advantages over the production of plastics from fossil sources, such as energy savings, waste reduction, and lower resource consumption. However, in order to avoid quality losses when using recyclates compared to primary plastics and to compensate for quality fluctuations in the recyclates used, it is advantageous to adjust the properties of the recyclates using suitable additives, as described in WO 2021 / 074084. KR 101789704 describes the use of recyclates to produce expandable polystyrene particles; however, only post-industrial waste is used as recyclate, i.e. waste that arises, for example, from cutting molded parts. Post-consumer waste is not used.

[0033] EP 1 694 753 discloses a process for producing expandable, politized thermoplastic polymer materials from a mixture of 50 to 90 wt.% polystyrene and 10 to 50 wt.% 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 polymer recyclates can also be added to the styrene polymer melt, but specifies a maximum proportion of 50 wt.%, in particular 1 to 20 wt.%. The mechanical properties of expanded polymer compositions with a high polystyrene content are generally disadvantageous. This also applies to the expandable styrene polymer granules described in EP 1 694 755, which contain at least 70 wt.% polystyrene and 0.1 to 30 wt.% polystyrene.-% of a low molecular weight styrene copolymer consisting of styrene, acrylic acid and alpha-methylstyrene.

[0034] There is a high demand for expandable polymer particles and for processes for producing expandable polymer particles that can be stored for a certain period of time and, if necessary, transported with minimal effort, and that consist of only a single polymer class to simplify recycling. Furthermore, the polymer particles should contain a high proportion of recycled polymer material to keep the material flows largely in a closed loop. Furthermore, after expansion, the voids in the expanded polymer particles should be largely homogeneously distributed and exhibit a fine-cell foam structure. Furthermore, the expandable polymer particles should be capable of producing molded parts with sufficiently good mechanical properties and good thermal insulation.

[0035] An object of the present invention is therefore to provide expandable, thermoplastic polymer particles with low blowing agent loss and high expansion capacity, which consist of a high proportion of recycled materials and can also be easily recycled themselves, and which can be processed into particle foams with high rigidity and, at the same time, good elasticity. A further object is to provide a process for producing such expandable, thermoplastic polymer particles. Surprisingly, it has been found that this object can be achieved by producing the expandable, thermoplastic polymer particles according to the invention, which are explained in more detail in the claims, the following description, and the examples.

[0036] The expandable, thermoplastic polymer particles according to the invention contain:

[0037] A) 10 to 99 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) which comprises at least one styrene polymer (A-1) and consists predominantly of styrene polymers;

[0038] B) 0 to 89% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one primary polymer (B) which comprises at least one styrene polymer (B-1),

[0039] C) 1 to 10 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one blowing agent (C);

[0040] D) 0 to 3 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one nucleating agent (D); and

[0041] E) 0 to 8 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one additive (E); where the sum of (A) and (B) amounts to 79 to 99 wt. %, based on the total weight of (A), (B), (C), (D) and (E), and where the expandable, thermoplastic polymer particles contain essentially no further polymers besides the at least one recyclate (A) and the at least one primary polymer (B). This means that the expandable, thermoplastic polymer particles contain no more than 5 wt. %, preferably no more than 3 wt. %, often no more than 1 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of polymers which do not correspond to the definition of the recyclate (A) and the primary polymer (B). The expandable, thermoplastic polymer particles preferably contain 0 wt.-%, based on the total weight of (A), (B), (C), (D), and (E), of polymers that do not meet the definition of recyclate (A) and primary polymer (B). The low amount of foreign polymers improves the recyclability of the expandable polymer particles according to the invention.

[0042] Styrene polymers are polymers in whose polymer chain repeat units of styrene monomers are incorporated. In particular, the styrene polymers according to the invention are 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), α(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN), styrene-methyl methacrylate copolymers (SMMA), amorphous polystyrene (PS), and impact-modified polystyrene (HIPS).

[0043] The expandable, thermoplastic polymer particles contain at least 10 wt. %, frequently at least 20 wt. %, preferably at least 30 wt. %, in particular at least 40 wt. %, often more than 50 wt. %, based on the total weight of (A), (B), (C), (D), and (E), of at least one recyclate (A), which comprises at least one styrene polymer (A-1) and consists predominantly of styrene polymers. The expandable, thermoplastic polymer particles contain no more than 99 wt. %, usually no more than 98 wt. %, frequently no more than 89 wt. %, preferably no more than 84 wt. %, often no more than 79 wt. %, based on the total weight of (A), (B), (C), (D), and (E), of the at least one recyclate (A). Frequently, the expandable, thermoplastic polymer particles contain 40 to 79 wt.%, preferably 45 to 74 wt.%, often 51 to 72 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of the at least one recyclate (A).

[0044] The expandable, thermoplastic polymer particles optionally contain at least 1 wt.%, frequently at least 10 wt.%, preferably at least 15 wt.%, often at least 20 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one primary polymer (B), which comprises at least one styrene polymer (B-1) or consists of at least one styrene polymer (B-1). The expandable, thermoplastic polymer particles contain no more than 89 wt.%, usually no more than 79 wt.%, frequently no more than 69 wt.%, preferably no more than 59 wt.%, often less than 49 wt.%, based on the total weight of

[0045] (A), (B), (C), (D) and (E), of the at least one primary polymer (B). Frequently, the expandable, thermoplastic polymer particles contain 20 to 59 wt.%, preferably 25 to 54 wt.%, often 27 to 48 wt.%, based on the total weight of (A),

[0046] (B), (C), (D) and (E), of the at least one primary polymer (B).

[0047] The expandable, thermoplastic polymer particles preferably comprise less than 5 wt. %, in particular less than 3 wt. %, based on the total weight of (A), (B), (C), (D), and (E), of polymers that do not have repeat units derived from styrene. However, small amounts of impurities from polymers that do not have repeat units derived from styrene can be introduced due to incomplete separation in the recycling process when obtaining the recyclates (A). For the purposes of this invention, recyclate (A) is defined as plastics that originate from plastic articles that were recycled and processed at the end of their service life. Processing into recyclates can be carried out using various methods known in the industry, see, for example, Köhnlechner, R. (2014): “Generation of clean PS and ABS fractions from mixed electronic scrap,” in DG Karl J. Thome-Kozmiensky (Ed.), Recycling and Raw Materials, Volume 7 (pp. 379-400), TK Verlag Karl Thome-Kozmiensky, Neuruppin. In particular, additives and / or primary materials may have been added during the production of the recyclates to achieve the required material quality.

[0048] The recyclates (A) therefore differ in particular from the primary polymers (B) in that the recyclates (A) have undergone 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 particles according to the invention. The recyclates (A) have therefore, in contrast to the primary polymers (B), been mechanically stressed at least once by mixing at a temperature above the melting range temperature of the recyclate (A), for example at a temperature in a range from 180 °C to 320 °C, frequently in a range from 200 °C to 300 °C, such as 220 °C to 280 °C, determined in accordance with ISO 294, in particular by shear forces, e.g. in an extruder, e.g. B. single-screw or twin-screw extruders, or in other conventional plasticizing devices, such as Brabender mills or Banbury mixers.In addition, the recyclates (A) may also have been subjected to other processing steps in which the recyclate (A) was mechanically stressed at temperatures below the melting range temperature, such as calendering.

[0049] The at least one recyclate (A) comprises at least one styrene polymer (A-1) and consists predominantly of styrene polymers. Preferably, the recyclate (A) consists of at least 80 wt.%, frequently at least 85 wt.%, preferably at least 90 wt.% or at least 92 wt.%, based on the recyclate (A), of at least one styrene polymer (A-1).

[0050] In addition to the styrene polymer (A-1), the recyclate (A) can often contain further components that were added to the composition of the recyclate for primary use or that have entered the recyclate (A) due to inadequate separation during the recycling process. In addition to the styrene polymers, the recyclates (A) can contain further components (A-2) such as additives, pigments, foreign polymers, or contaminants such as metal particles, in particular aluminum particles. Preferably, the recyclate (A) does not contain any substances that have a negative impact on the further use according to the invention. These include, in particular, halogen-containing flame retardants. The components (A-2) generally make up no more than 20 wt. %, frequently no more than 15 wt. %, preferably no more than 10 wt. % or no more than 8 wt. %, based on the recyclate (A), of the recyclate (A). Preferably, the recyclate (A) contains essentially no further polymers.This means that the recyclate (A) contains no more than 5 wt. %, preferably no more than 3 wt. %, often no more than 1 wt. %, based on the total weight of the recyclate (A), of polymers that do not meet the definition of the styrene polymer (A-1). Preferably, the recyclate (A) contains 0 wt. %, based on the total weight of the recyclate (A), of polymers that do not meet the definition of the styrene polymer (A-1). The low amount of foreign polymers improves the recyclability of the expandable polymer particles according to the invention.

[0051] For the purposes of this invention, primary materials and primary polymers refer to plastics that are made from fossil raw materials and have not yet been recycled during their lifetime.

[0052] The at least one primary polymer (B) comprises or consists of at least one styrene polymer (B-1). The primary polymer (B) preferably comprises at least 80 wt. %, frequently at least 85 wt. %, preferably at least 90 wt. % or at least 92 wt. %, based on the primary polymer (B), of at least one styrene polymer (B-1). In addition, the primary polymer (B) may contain components (B-2), which are typically used during the production of the styrene polymers and serve, for example, to improve processability. Examples of component (B-2) include additives such as lubricants and mold-release agents. In one embodiment of the invention, the primary polymer comprises 100 wt. %, based on the primary polymer (B), of at least one styrene polymer (B-1). Accordingly, the primary polymer of this embodiment comprises 0 wt. %, based on the primary polymer (B), of a component (B-2).The primary polymer (B) preferably contains essentially no other polymers. This means that the primary polymer (B) contains no more than 5 wt. %, preferably no more than 3 wt. %, often no more than 1 wt. %, based on the total weight of the primary polymer (B), of polymers that do not correspond to the definition of the styrene polymer (B-1). The primary polymer (B) preferably contains 0 wt. %, based on the total weight of the primary polymer (B), of polymers that do not correspond to the definition of the styrene polymer (B-1). The small amount of foreign polymers improves the recyclability of the expandable polymer particles according to the invention. In one embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A) and the at least one blowing agent (C).In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one primary polymer (B), and the at least one blowing agent (C). In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one blowing agent (C), and the at least one nucleating agent (D). In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one primary polymer (B), the at least one blowing agent (C), and the at least one nucleating agent (D). In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one blowing agent (C), and the at least one additive (E).

[0053] In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one primary polymer (B), the at least one blowing agent (C), and the at least one additive (E). In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate (A), the at least one blowing agent (C), the at least one nucleating agent (D), and the at least one additive (E). In a further embodiment, the expandable, thermoplastic polymer particles consist of the at least one recyclate

[0054] (A), the at least one primary polymer (B), the at least one blowing agent (C), the at least one nucleating agent (D) and the at least one additive (E).

[0055] In a particularly preferred embodiment, the at least one recyclate (A) and the at least one primary polymer (B) comprise polymers belonging to the same polymer class or consist thereof. In this embodiment, the expandable polymer particles according to the invention can be recycled particularly well, for example in mechanical recycling processes. In a further embodiment, the at least one recyclate (A) and the at least one primary polymer

[0056] (B) Polymers that belong to or consist of miscible polymer classes. Even in this case, good recycling capability is ensured, e.g., in mechanical recycling processes. "Polymer classes" are understood to mean polymers composed of repeating units of the same monomers. In this context, miscible means that no domains of a first polymer form in a continuous matrix of a second polymer, i.e., the first polymer is dissolved in the second polymer.

[0057] For the purposes of this application, the term "miscible polymer classes" also includes polymers that form polymer blends in which 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 primary polymer (B) is dispersed in the form of discontinuous phase domains in a continuous phase of the recyclate (A), wherein the discontinuous phase domains of the primary polymer (B) comprise at most phase domains with an average diameter of <2 μm, more preferably <200 nm, frequently <100 nm.

[0058] The expandable, thermoplastic polymer particles contain a total of 79 to 99 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one primary polymer (B), which comprise styrene polymers (A-1) and styrene polymers (B-1), respectively, wherein the styrene polymers (A-1) and styrene polymers (B-1) are preferably 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), a(alpha)-methylstyrene- Acrylonitrile copolymers (AMSAN), styrene-methyl methacrylate copolymers (SMMA), styrene-maleic anhydride copolymers (SMA), styrene-acrylonitrile

[0059] Maleic anhydride copolymers (SANMA), styrene-N-phenylmaleimide copolymers, styrene-acrylonitrile-N-phenylmaleimide copolymers, styrene-imide-maleic anhydride copolymers, styrene-imide-acrylonitrile-maleic anhydride copolymers, amorphous polystyrene (PS), and impact-modified polystyrene (HIPS). Preferably, the styrene polymers (A-1) or styrene polymers (B-1) are selected from the group consisting of styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), or acrylonitrile-styrene-acrylate copolymers (ASA).

[0060] In one embodiment, the expandable, thermoplastic polymer particles comprise at least 86 wt. %, frequently at least 91.5 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one primary polymer (B). In one embodiment, the expandable, thermoplastic polymer particles comprise up to 98.5 wt. %, frequently at least 98 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one primary polymer (B). Often, the expandable, thermoplastic polymer particles comprise 91 to 98 wt. %, particularly preferably 93.5 to 97 wt. %, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) and optionally at least one primary polymer (B).

[0061] In one embodiment, the recyclate (A) or the primary polymer (B) contains less than 50 wt.%, preferably less than 25 wt.%, more preferably less than 10 wt.%, based on the recyclate (A) or the primary polymer (B), of styrene homopolymer. In one embodiment, the recyclate (A) and the primary polymer (B) do not contain any styrene homopolymer. In one embodiment, the expandable, thermoplastic polymer particles do not contain any polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain any styrene homopolymer.

[0062] In one embodiment, the recyclate (A) or the primary polymer (B) contains less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. %, based on the recyclate (A) or the primary polymer (B), of copolymers comprising maleic anhydride and / or maleimide. In one embodiment, the recyclate (A) and the primary polymer (B) do not contain any copolymers comprising maleic anhydride and / or maleimide. In a further preferred embodiment, the expandable, thermoplastic polymer particles do not contain any polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain any copolymers comprising maleic anhydride and / or maleimide.

[0063] In one embodiment, the recyclate (A) or the primary polymer (B) contains less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. %, based on the recyclate (A) or the primary polymer (B), of styrene-maleic anhydride copolymer (SMA). In a further embodiment, the recyclate (A) and the primary polymer (B) do not contain any styrene-maleic anhydride copolymer (SMA). In a further preferred embodiment, the expandable, thermoplastic polymer particles contain no polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain any styrene-maleic anhydride copolymer (SMA).

[0064] In a further alternative embodiment, the recyclate (A) and the primary polymer (B) contain less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. %, based on the recyclate (A) and the primary polymer (B), respectively, of α(alpha)-methylstyrene-acrylonitrile copolymer (AMSAN). In a further embodiment, the recyclate (A) and the primary polymer (B) do not contain α(alpha)-methylstyrene-acrylonitrile copolymer (AMSAN). In a further preferred embodiment, the expandable, thermoplastic polymer particles do not contain any polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain α(alpha)-methylstyrene-acrylonitrile copolymer (AMSAN).

[0065] In a further alternative embodiment, the recyclate (A) and the primary polymer (B) contain less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. %, based on the recyclate (A) and the primary polymer (B), respectively, of styrene-isoprene-styrene block copolymer (SIS). In a further embodiment, the recyclate (A) and the primary polymer (B) do not contain any styrene-isoprene-styrene block copolymer (SIS). In a further preferred embodiment, the expandable, thermoplastic polymer particles do not contain any polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain any styrene-isoprene-styrene block copolymer (SIS).

[0066] In one embodiment, the recyclate (A) or the primary polymer (B) contains less than 50 wt. %, preferably less than 25 wt. %, more preferably less than 10 wt. %, based on the recyclate (A) or the primary polymer (B), of styrene-acrylonitrile copolymer (SAN). In one embodiment, the recyclate (A) and the primary polymer (B) do not contain any styrene-acrylonitrile copolymer (SAN). In a further embodiment, the expandable, thermoplastic polymer particles contain no polymers other than the recyclate (A) and optionally the primary polymer (B), which preferably do not contain any styrene-acrylonitrile copolymer (SAN).

[0067] In a further alternative embodiment, the recyclate (A) and the primary 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), styrene-butadiene block copolymers (SBC), methyl methacrylate-acrylonitrile-butadiene-styrene copolymers (MABS), methyl methacrylate-butadiene-styrene copolymers (MBS), a(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN), styrene-methyl methacrylate copolymers (SMMA), styrene-maleic anhydride copolymers (SMA), styrene-acrylonitrile-maleic anhydride copolymers (SANMA), styrene-N-phenylmaleimide copolymers, Styrene-acrylonitrile-N-phenylmaleimide copolymers, styrene-imide-maleic anhydride copolymers, styrene-imide-acrylonitrile-maleic anhydride copolymers, amorphous polystyrene (PS) and impact-modified polystyrene (HIPS).

[0068] In a further alternative embodiment, the recyclate (A) and the primary 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 a(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN).

[0069] In a further alternative embodiment, the recyclate (A) and the primary 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).

[0070] In a further alternative embodiment, the recyclate (A) and the primary polymer (B) contain polymer blends comprising styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS); styrene-acrylonitrile copolymers (SAN) and acrylate-styrene-acrylonitrile copolymers (ASA); α(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN) and acrylonitrile-butadiene-styrene copolymers (ABS); or α(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN) and acrylate-styrene-acrylonitrile copolymers (ASA). Particularly preferred are polymer blends comprising styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS).

[0071] In one embodiment of the invention, the expandable, thermoplastic polymer particles comprise less than 5 wt.%, preferably less than 3 wt.%, often 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), polycarbonate (PC), polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyethersulfone (PES), polyether ketones (PEK), polyether sulfides (PES), polylactates, polyphenylene ethers (PPO / PPE), ethylene-vinyl acetate copolymers (EVA), styrene-ethylene-butylene-styrene copolymers (SEES), styrene-ethylene-propylene copolymers (SEP), and styrene-butyl acrylate copolymers.Preferably, the expandable, thermoplastic polymer particles do not comprise thermoplastic polymers 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), polyethersulfone (PES), polyether ketones (PEK), polyether sulfides (PES), polylactates, polyphenylene ethers (PPO / PPE), ethylene-vinyl acetate copolymers (EVA), styrene-ethylene-butylene-styrene copolymers (SEES), styrene-ethylene-propylene copolymers (SEP), and styrene-butyl acrylate copolymers.

[0072] The styrene polymers according to the invention typically have a weight-average molecular weight Mw in a range from 10,000 g / mol to 1,000,000 g / mol, preferably in a range from 50,000 to 500,000 g / mol, frequently in a range from 80,000 to 250,000 g / mol. The molecular weight Mw can be determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the eluent and with polystyrene calibration.

[0073] In one embodiment of the invention, the styrene polymer of the recyclate (A) has a weight-average molecular weight Mw that differs by no more than 75%, preferably no more than 50%, frequently no more than 30%, from the weight-average molecular weight Mw of the styrene polymer of the primary polymer (B). This means that, for example, with a weight-average molecular weight Mw of the styrene polymer of the recyclate (A) of 100,000 g / mol, the weight-average molecular weight Mw of the primary polymer (B) is in a range from 25,000 g / mol to 175,000 g / mol, preferably 50,000 g / mol to 150,000 g / mol, frequently 70,000 g / mol to 130,000 g / mol.

[0074] The styrene polymers according to the invention usually have a melt volume flow rate MVR (220 °C / 10 kg) according to ISO 1133 of 1 to 30 cm 3 / 10 min, preferably 10 to 25 cm 3 / 10 min.

[0075] Preferably, the blowing agent (component C) in the expandable, thermoplastic polymer particles is homogeneously distributed in a polymer matrix comprising the one or more recyclates (A) and the optional at least one primary polymer (B).

[0076] 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 such as CO2 or nitrogen, and / or an organic, physical blowing agent such as aliphatic C3 to C8 hydrocarbons, alcohols, ketones, ethers or halogenated hydrocarbons, preferably CO2 or alternatively isobutane, n-butane, isopentane, n-pentane, cyclopentane, or mixtures thereof. The blowing agent preferably comprises at least one organic, physical blowing agent. In a preferred embodiment, the blowing agent comprises less than 5 wt. %, more preferably less than 2 wt. %, based on the total weight of component (C), of water. Preferably, the propellant is substantially free of water, ieit comprises not more than 0.5% by weight, preferably not more than 0.1% by weight, of water, based on the total weight of component (C).

[0077] As optional component D, the expandable, thermoplastic polymer particles contain 0 to 3 wt.%, preferably 0 to 2 wt.%, particularly preferably 0 to 0.5 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one nucleating agent, for example talc, aluminum oxide or silicon dioxide.

[0078] In a preferred embodiment, no talc, aluminum oxide, or silicon dioxide is added as component (D) to the expandable, thermoplastic polymer particles during production. In a further embodiment, no nucleating agent is added as component (D) to the expandable, thermoplastic polymer particles during production, i.e., 0 wt. %, based on the total weight of (A), (B), (C), (E), and (E). Nevertheless, it is possible for the expandable, thermoplastic polymer particles to contain nucleating agents, which originate in particular from the recyclate (A). It has been found that the additives and impurities optionally present in the recyclate (A) are generally sufficient to induce the desired pore formation in the expandable, thermoplastic polymer particles.

[0079] Optionally, the expandable, thermoplastic polymer particles according to the invention can comprise further additives (E) in amounts that do not impair pore formation and the resulting foam structure. Frequently, the expandable, thermoplastic polymer particles according to the invention comprise at least one additive (E) in amounts of 0 to 8 wt. %, preferably 0 to 5 wt. %, more preferably 0 to 3 wt. %, for example 0.1 to 3 wt. %, based on the total weight of (A), (B), (C), (D), and (E).

[0080] Suitable additives (E) are known to the person skilled in the art and include, for example, plasticizers, flame retardants, preferably non-halogen-containing flame retardants, soluble and insoluble inorganic and / or organic dyes and pigments, fillers or reinforcing agents (glass fibers, carbon fibers, etc.), co-blowing agents, antioxidants, heat stabilizers, UV stabilizers, peroxide destructors, antistatic agents, lubricants, mold release agents, antiblocking agents, processing aids, and combinations of two or more thereof. In a preferred embodiment, the expandable, thermoplastic polymer particles do not comprise halogen-containing flame retardants. Preferred flame retardants include components based on phosphorus compounds that are known, in particular for this application.

[0081] Examples of antioxidants and heat stabilizers include halides of metals of group I of the periodic table, e.g. sodium, potassium and / or lithium halides, optionally in combination with copper(I) halides, e.g. chlorides, bromides, iodides, sterically hindered phenols, hydroquinones, various substituted representatives of these groups and mixtures thereof in concentrations of up to 1 wt.%, based on the total weight of the expandable, thermoplastic polymer particles.

[0082] Various substituted resorcinols, salicylates, benzotriazoles and benzophenones are mentioned as UV stabilizers, which are generally contained in amounts of up to 2 wt.%, often 0.1 to 1.5 wt.%, based on the total weight of the expandable, thermoplastic polymer particles.

[0083] Furthermore, organic dyes such as nigrosine, pigments such as titanium dioxide, phthalocyanines, ultramarine blue, and carbon black can be included as colorants in the thermoplastic polymer particles, as well as 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, powdered quartz, mica, and feldspar.

[0084] Lubricants and mold release agents, which can generally be used in amounts of up to 1% by weight, often 0.1 to 0.8% by weight, based on the total weight of the expandable, thermoplastic polymer particles, are, for example, long-chain fatty acids such as stearic acid or behenic acid, their salts (e.g. Ca or Zn stearate) or esters (e.g. stearyl stearate or pentaerythritol tetrastearate) and amide derivatives (e.g. ethylenebisstearylamide).

[0085] Furthermore, mineral-based antiblocking agents may be included in amounts of up to 0.1 wt.%, based on the total weight of the expandable, thermoplastic polymer particles. Examples include amorphous or crystalline silica, calcium carbonate, or aluminum silicate.

[0086] As a processing aid, for example, mineral oil, preferably medical

[0087] White oil, in amounts of up to 5 wt.%, preferably up to 2 wt.%, in particular 0.1 to 2 wt.%, based on the total weight of the expandable, thermoplastic polymer particles.

[0088] Examples of plasticizers include dioctyl phthalate, dibenzyl phthalate, butylbenzyl phthalate, hydrocarbon oils, N-(n-butyl)benzenesulfonamide and o- and p-tolylethylsulfonamide.

[0089] Manufacturing process

[0090] The invention provides a process for producing expandable, thermoplastic polymer particles, comprising the steps of: a) adding the at least one recyclate (A) or a mixture of the at least one recyclate (A) and the at least one primary polymer (B) with the at least one blowing agent (C) and optionally the at least one nucleating agent (D) and / or the 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.

[0091] The information given herein regarding the selection of components (A), (B), (C), (D) and (E) as well as the amounts to be used apply accordingly to the process according to the invention.

[0092] In one embodiment, only the at least one recyclate (A) and the at least one blowing agent (C) are used as starting materials in the process according to the invention. In a further embodiment, only the at least one recyclate (A), the at least one primary polymer (B) and the at least one blowing agent (C) are used as starting materials in the process. In a further embodiment, only the at least one recyclate (A), the at least one blowing agent (C) and the at least one nucleating agent (D) are used in the process. In a further embodiment, only the at least one recyclate (A), the at least one primary polymer (B), the at least one blowing agent (C) and the at least one nucleating agent (D) are used in the process.In a further embodiment, only the at least one recyclate (A), the at least one blowing agent (C), the at least one nucleating agent (D) and the at least one additive (E) are used in the process. In a further embodiment, only the at least one recyclate (A), the at least one primary polymer (B), the at least one blowing agent (C), the at least one nucleating agent (D) and the at least one additive (E) are used in the process. In a further embodiment, only the at least one recyclate (A), the at least one blowing agent (C) and the at least one additive (E) are used in the process. In a further embodiment, only the at least one recyclate (A), the at least one primary polymer (B), the at least one blowing agent (C) and the at least one additive (E) are used in the process.

[0093] Process step a) preferably takes place at a temperature above the glass transition temperature of the at least one recyclate (A) or the mixture of the at least one recyclate (A) and the at least one primary polymer (B). The temperature in process step a) is frequently in a range from 150°C to 250°C, frequently in a range from 170 to 220°C.

[0094] Preferably, at least process step b), and often process steps b) and c), take place at a temperature around the glass transition temperature of the at least one recyclate (A) or the mixture of the at least one recyclate (A) and the at least one primary polymer (B). The temperature in process step b) and optionally c) is often in a range from 50°C to 250°C.

[0095] Preferably, at least process step a), particularly preferably process steps a) and b), takes place under a pressure which exceeds atmospheric pressure.

[0096] Preferably, process step c) takes place under a pressure which does not exceed atmospheric pressure.

[0097] In one embodiment of the invention, process steps a) and b) take place in an extruder with subsequent underwater granulation at a water pressure in the range from 1.5 to 11 bar. The water temperature during underwater granulation is below the glass transition temperature of the at least one recyclate (A) or the mixture of the at least one recyclate (A) and the at least one primary polymer (B), frequently in a range from 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 the at least one recyclate (A) and the at least one primary polymer (B), frequently in a range from 170°C to 250°C. In a further embodiment, process steps a) and b) take place in an autoclave. In this case, the at least one granulated recyclate (A) orThe granulated mixture of the at least one recyclate (A) and the at least one primary polymer (B), which have optionally been admixed with at least one nucleating agent (D) and / or at least one additive (E), is impregnated under pressure with the blowing agent (C) to form expandable, thermoplastic polymer particles. These can then be isolated or obtained directly as prefoamed foam particles by pressure release.

[0098] Particularly preferred is a continuous process in which, in process step a), a recyclate (A), for example recycled SAN (rSAN), recycled ABS (rABS), or recycled ASA (rASA), and optionally a primary polymer (B), for example SAN, ABS, or ASA, optionally mixed with the nucleating agent (D) and / or additives (E), is melted in a twin-screw extruder and impregnated with the blowing agent (C). A preferred embodiment is the use of a separately prepared mixture of the recyclate (A) and the primary polymer (B), which has optionally already been adjusted to a desired material quality by adding additives.

[0099] The blowing agent-laden melt can then be extruded through a suitable nozzle to form foam sheets, strands or particles and cut into them in process step b). A preferred embodiment is extrusion through a micro-hole plate with one or, as a rule, several holes with a hole diameter of 0.1 to 2.4 mm, preferably 0.2 to 1.2 mm, particularly preferably 0.5 to 0.8 mm, so that particles are formed. In a preferred embodiment, the melt emerging from the micro-hole plate is fed into a water stream, where the melt is cut into individual particles by a suitable device. Setting the appropriate counterpressure and a suitable temperature in the water stream for this so-called underwater granulation enables the targeted production of expandable polymer particles.

[0100] In an alternative embodiment, process steps a) and / or b) can take place wholly or partly in a suspension. The recyclate (A), and optionally primary polymer(s) (B), nucleating agent (D) and / or additive(s) (E), can be transferred into a suspension, preferably an aqueous suspension, which is then loaded with at least one gaseous blowing agent (C) such as CO2 or nitrogen under increased pressure. The pressure at which the blowing agent (C) is introduced is, for example, in the range from 1 bar to 20 bar, often in the range from 1.2 bar to 15 bar, or 1.5 bar to 10 bar. As soon as the desired loading with blowing agent (C) is reached, the resulting polymer particles are isolated, for example by filtration and / or centrifugation, and optionally washed.

[0101] The optional pre-expansion step c) can be carried out by reducing the ambient pressure and / or increasing the ambient temperature.

[0102] The expandable, thermoplastic polymer particles with a recycled content according to the invention preferably have an average particle diameter in the non-prefoamed state in the range of 0.1 to 5 mm, preferably 0.3 to 3 mm, and particularly preferably 0.5 to 2 mm. Expandable polymer particles with a narrow particle size distribution and an average particle diameter in the stated range lead to better mold filling when the polymer particles are welded together to form a molded part. They enable a more delicate molded part design and a better molded part surface.

[0103] In a further preferred embodiment, the expandable, thermoplastic polymer particles containing recycled material are prefoamed. 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, and particularly preferably 0.5 to 4 mm. The final foaming of the prefoamed (preexpanded) polymer particles can then take place in a subsequent processing step.

[0104] The specific density of the pre-foamed polymer particles with recycled content is preferably in the range from 10 to 250 g / L, particularly preferably from 20 to 200 g / L, particularly preferably from 25 to 150 g / L and particularly preferably from 30 to 100 g / L.

[0105] The expandable, thermoplastic polymer particles in the pre-foamed state preferably have an average cell size between 50 and 400 pm, more preferably between 100 and 300 pm.

[0106] The expandable, thermoplastic polymer particles according to the invention with a recycled material content can be filled into a mold, which is then closed and heated by hot air and / or steam. Alternatively, heating can be achieved using radio waves or infrared radiation. The polymer particles expand further, ideally until the cavity is completely filled, and thus form a foam molded article. The processing pressure is selected to be low enough that the pore structure in the cell membranes is retained. The pressure is usually in the range of 0.5 to 1.0 bar. The expandable, thermoplastic polymer particles according to the invention can be further processed (e.g. foamed) immediately after production, or they can be stored first and only later put to their intended use.The application of a coating to the surface of the expandable, thermoplastic polymer particles according to the invention is not required, but can be optional if, for example, an antistatic finish is desired. Antistatic coatings are known to those skilled in the art. Examples of antistatic coatings include quaternary ammonium salts, polyoxyethylene alkylphenol ethers, glycerol esters, stearic acid monoglyceride, stearic acid triglyceride, ethylene-bis-stearamide, polyethylene glycol sorbitan monooleate, zinc stearate, sodium alkanesulfonate, bis-(2-hydroxyethyl)-octyl-methyl-ammonium p-toluenesulfonate, polyvinyl propionate, and surfactants. Suitable antistatic coatings are commercially available, for example, under the trade names Larostat® (manufacturer: BASF, Germany), Neostatic® (manufacturer: Peter H. Urdahl GmbH, Germany), or Chemstat® (manufacturer: PCC Chemax Inc., Poland).

[0107] use

[0108] The invention further relates to the use of the inventive expandable, thermoplastic polymer particles with a recycled content for the production of molded parts such as foam bodies, which are preferably formed by expanding and welding the expandable polymer particles using hot air, steam, radio waves, and / or infrared radiation. The resulting molded parts can be used in numerous applications, in particular as insulation material, damping material, packaging material, or as lightweight construction material, for example, in the automotive sector.

[0109] Preferably, the molded part has a specific density of less than 250 g / L, preferably less than 200 g / L, particularly preferably less than 150 g / L.

[0110] Preferably, the molded part has a compressive strength at 10% elongation of more than 250 kPa.

[0111] Preferably, the molded part has a flexural modulus of more than 15 MPa.

[0112] The invention is illustrated by the following examples, figures, and claims. Examples

[0113] In a co-rotating twin-screw extruder (type ZK25P, manufacturer Collin GmbH) with a screw diameter of 30 mm and a length-to-diameter ratio of 42, polymer mixtures consisting of a recycled acrylonitrile-butadiene-styrene copolymer (rABS), available, for example, under the brand name Terluran® ECO (manufacturer INEOS Styrolution), and the primary polymer acrylonitrile-butadiene-styrene copolymer (ABS), were melted with the blowing agent n-pentane and, optionally, the nucleating agent talc at 200-240 °C and thus homogeneously mixed. The experiments conducted are listed in Table 1.

[0114] The resulting polymer mixture (I) was then cooled in a single-screw extruder (type E 45 M, manufacturer Collin GmbH) with a screw diameter of 45 mm and a length-to-diameter ratio of 30, and the melt was extruded through a heated die plate. The polymer strand was cut off by underwater pelletizing to obtain blowing agent-loaded mini-granules with a narrow particle size distribution. The counterpressure in the underwater pelletizing system was set at 8 to 11 bar.

[0115] The blowing agent-loaded mini-granules were then pre-expanded in an X-Line 3 pre-expander (manufacturer Kurtz GmbH). The pre-expanded polymer particles were welded in a TVZ 162 / 100 PP molding machine (manufacturer Teubert Maschinenbau GmbH) at approximately 120-125 °C to produce test specimens for measuring the thermal and mechanical properties.

[0116] The density of the pre-expanded particles was determined using an AG245 density balance (manufacturer Mettler Toledo) according to ISO 1183.

[0117] Cell size was measured by measuring the cell diameters of foam particles cut in half by cryogenic fracturing using a Keyence profilometer and ImageJ software. Fifty cells per particle, each of three particles per material, were evaluated.

[0118] The thermal characterization of the test specimens was carried out in accordance with DIN EN 12667 using a heat flow measuring plate apparatus type HMF Lambda Small (manufacturer Netzsch) using test specimens measuring 200 x 200 x 20 mm and a temperature gradient of 20 K. The mechanical characterization of the test specimens was carried out using a 3-point bending test using a universal testing machine 1485 (manufacturer Zwick Roell) in accordance with ISO 1209 on test specimens measuring 120 x 25 x 20 mm, with a preload of 1 N and a test speed of 10 mm / min. Static compression tests were carried out in accordance with DIN EN ISO 844 using a universal testing machine Z050 (manufacturer Zwick Roell) on test specimens measuring 40 x 20 x 20 mm with foam skin, with a preload of 10 N.

[0119] The results are shown in Table 1. Example pairs 1 and 2, as well as 3 and 4, each have the same recycled content but differ in their degree of foaming, which is specifically adjusted by varying the process parameters. The degree of foaming is reflected in the foam density. To compare mechanical and thermal properties, foams of the same density should be used, as these properties are strongly influenced by the foam density. Examples 1 and 3 and Comparative Examples 5 and 6 are more highly foamed than Examples 2 and 4.

[0120] Table 1 : Results of the examples

[0121] Comparing Examples 1 and 3 according to the invention (with a recycled content of 50 and 70 wt.% of the total weight of the polymer composition, respectively) with Comparative Examples 5 and 6 (no recycled content), the following becomes clear:

[0122] The thermal conductivity of inventive examples 1 and 3 is significantly lower than that of non-inventive comparative examples 5 and 6, i.e. the insulating effect of the inventive examples is significantly better when the polymer mass contains a recycled content (see also Fig. 1). The foam from comparative example 5 was produced without nucleating agents, which leads to inhomogeneous foam structures in the polymer masses without a recycled content. The use of nucleating agents improves the foam structure (comparative example 6), but the thermal conductivity is still higher (and the insulating effect thus poorer) than that of the foams with a recycled content (examples 1 and 3). Even without nucleating agents, very well-insulating foams can be produced if the polymer mass contains a high recycled content.

[0123] Inventive Examples 1 and 3 also exhibit a finer and more homogeneous cell structure than Comparative Example 5 (see Figs. 4 and 5). Fig. 4 shows the cell structure of an inventive polymer foam with 50 wt. % recycled content according to Example 1. Fig. 5 shows the cell structure of a non-inventive foam without recycled content according to Comparative Example 5. The foam without recycled content is inhomogeneous, with large cells. In the non-inventive foams, a good cell structure can only be achieved through the use of nucleating agents, as Fig. 6 shows. Fig. 6 shows the foam structure of Comparative Example 6; this is a non-inventive foam without recycled content, but with nucleating agent.The mean cell size of Example 1 according to the invention is significantly smaller than the cell size in Comparative Example 5 not according to the invention without nucleating agent, thus the cell structure in the examples according to the invention is significantly better than in the examples not according to the invention.

[0124] Test specimens produced from the compositions according to the invention (Examples 1 and 3) exhibit better compressive strength than test specimens according to the non-inventive Comparative Examples 5 and 6 (see also Fig. 2). Comparative Example 5 (without nucleating agent) exhibits only very low compressive strength. The addition of nucleating agents in Comparative Example 6 improves 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 a high recycled content are suitable for producing foams with very good compressive strength even without the addition of nucleating agents.

[0125] The measured flexural modulus data of the test specimens also clearly demonstrate that the inventive foams with recycled content have significantly improved properties compared to the non-inventive foams. Although the addition of nucleating agents improves the flexural modulus in the latter (Comparative Example 6), the good values ​​of the inventive examples with recycled content are still not achieved (see also Fig. 3).

[0126] By using a high proportion of recycled material, foam bodies can be produced that have better mechanical and thermal properties than foam bodies made only from primary material, even without the addition of nucleating agents.

[0127] Explanation of the figures

[0128] Fig. 1 shows the graphical representation of the experimentally obtained data of thermal conductivity at 25 °C in W / m*K of Examples 1 and 3 and Comparative Examples 5 and 6.

[0129] Fig. 2 shows the graphical representation of the experimentally obtained compressive strength data at 10% elongation in kPa of Examples 1 and 3 and Comparative Examples 5 and 6.

[0130] Fig. 3 shows the graphical representation of the experimentally obtained data of the flexural modulus in MPa of Examples 1 and 3 and Comparative Examples 5 and 6.

[0131] Fig. 4 shows an electron microscope image of a prefoamed particle according to the invention, which was obtained from Example 1. Fig. 5 shows an electron microscope image of a non-inventive prefoamed particle, which was obtained from Comparative Example 5.

[0132] Fig. 6 shows an electron microscope image of a non-inventive prefoamed particle obtained from Comparative Example 6.

Claims

Patent claims 1. Expandable, thermoplastic polymer particles containing, preferably consisting of A) 10 to 99 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one recyclate (A) which comprises at least one styrene polymer (A-1) and consists predominantly of styrene polymers; B) 0 to 89% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one primary polymer (B) comprising at least one styrene polymer (B-1), C) 1 to 10 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one blowing agent (C); D) 0 to 3 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one nucleating agent (D); and E) 0 to 8 wt.%, based on the total weight of (A), (B), (C), (D) and (E), of at least one additive (E); wherein the sum of (A) and (B) amounts to 79 to 99 wt.%, based on the total weight of (A), (B), (C), (D) and (E), and wherein the expandable, thermoplastic polymer particles contain essentially no further polymers besides the at least one recyclate (A) and the at least one primary polymer (B).

2. Expandable, thermoplastic polymer particles according to claim 1, characterized in that the at least one recyclate (A) and the at least one primary polymer (B) are at least one polymer selected from the group consisting of styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), acrylate-styrene-acrylonitrile copolymers (ASA), methyl methacrylate-acrylonitrile-butadiene-styrene copolymers (MABS), methyl methacrylate-butadiene-styrene copolymers (MBS), a(alpha)-methylstyrene-acrylonitrile copolymers (AMSAN), styrene-methyl methacrylate copolymers (SMMA), styrene-maleic anhydride copolymers (SMA), styrene-acrylonitrile-maleic anhydride copolymers (SANMA), styrene-N-phenylmaleimide copolymers, Styrene-acrylonitrile-N-phenylmaleimide copolymers, styrene-imide-maleic anhydride copolymers, styrene-imide-acrylonitrile-maleic anhydride- Copolymers, amorphous polystyrene (PS), and impact-modified polystyrene (HIPS). Expandable, thermoplastic polymer particles according to claim 1 or 2, characterized in that the at least one recyclate (A) and at least one primary polymer (B) are at least one polymer selected from the group consisting of styrene-acrylonitrile copolymers (SAN), acrylonitrile-butadiene-styrene copolymers (ABS), and acrylate-styrene-acrylonitrile copolymers (ASA). Expandable, thermoplastic polymer particles according to one of claims 1 to 3, characterized in that the average particle diameter of the expandable, thermoplastic polymer particles in the non-prefoamed state is in the range from 0.1 to 5 mm, preferably from 0.3 to 3 mm, particularly preferably from 0.5 to 2 mm.Expandable, thermoplastic polymer particles according to one of claims 1 to 4, characterized in that the polymer particles are prefoamed to an average diameter of 0.2 to 10 mm, preferably 0.3 to 5 mm, particularly preferably 0.5 to 4 mm. Expandable, thermoplastic polymer particles according to one of claims 1 to 5, characterized in that the expandable, thermoplastic polymer particles contain a plurality of recyclates (A) and primary polymers (B), and the plurality of recyclates (A) and primary polymers (B) are miscible with one another. Expandable, thermoplastic polymer particles according to one of claims 1 to 6, characterized in that the average cell size of the prefoamed particles is between 50 and 400 pm, preferably between 100 and 300 pm.A process for producing expandable, thermoplastic polymer particles according to any one of claims 1 to 7, comprising the following steps: a) adding the at least one blowing agent (C) and optionally the at least one nucleating agent (D) and / or the at least one additive (E) to a mixture of the at least one recyclate (A) and the at least one primary polymer (B), so that a polymer mixture (I) is formed;. 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 process according to claim 8, characterized in that at least step a), preferably steps a) and b), takes place under a pressure which exceeds atmospheric pressure.

10. Process according to claim 8 or 9, characterized in that process steps a) and b) take place in an extruder with subsequent underwater granulation at a water pressure in the range of 1.5 to 11 bar.

11. Process according to claim 8 or 9, characterized in that process steps a) and b) take place in an autoclave.

12. Process according to one of claims 8 to 11, characterized in that process steps a) and b) take place in a suspension.

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

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

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

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