CN119677802A - Expanded thermoplastic polymer particles containing recycled material and method of producing the same - Google Patents

Abstract

The present invention relates to expanded thermoplastic polymer particles having a recycled material content based on styrene polymer, a process for their production and the use of the expanded polymer particles in molding foam parts. The expanded thermoplastic polymer particles contain 10 to 99wt.%, based on the total weight, of at least one recycled material (a) comprising and consisting essentially of at least one styrene polymer (a-1), 1 to 90wt.%, based on the total weight, of at least one virgin polymer (B) and optionally at least one propellant (C), at least one nucleating agent (D) and/or at least one additive (E).

Description

Expanded thermoplastic polymer particles containing recycled material and method of producing the same

Description

The present invention relates to expanded polymer particles containing a styrene polymer-based recycle, a process for their production and the use of the expanded polymer particles in foam molded parts.

For many years, particulate foams have been used in a variety of applications including insulation in the construction industry, packaging in the automotive industry, and structural lightweight wall materials. The particulate foam is typically composed of a plurality of foamed polymer beads welded to one another (well). Particle foam generally has the advantage of being lighter in weight and better in mechanical properties than solid materials.

Particulate foams made from polyolefins (e.g. polyethylene) have been known for decades, for example as described in US 6,028,121. CN 107501595A describes a process for producing expanded polypropylene particles. A disadvantage of granular foams made of polyolefin is that they need to be fully foamed during production, since the foaming agent does not stay in the polymeric material for a long time. In these cases, the loading of the blowing agent is carried out immediately before the expansion of the particles, which are then welded together in a subsequent step to form the molded part.

US 4,108,806 describes a process for producing expanded and expandable polymer particles based on a polyolefin matrix incorporating expandable microspheres. The microspheres consist of a thermoplastic shell and a volatile liquid blowing agent core which, upon heating, expands the polymer composition. Such a production process is costly and may result in a polymer blend of two or more polymer types.

Expandable polymer particles comprising styrene polymers and copolymers and methods for their production are also described in the literature.

WO 2013/085742 describes providing extruded polymer foam composed of styrene-acrylonitrile copolymer (SAN) and produced using a blowing agent mixture of 74-78 wt.% 1, 2-tetrafluoroethane, 13-16 wt.% CO ₂ and 7-9 wt.% water. There is no disclosure of providing expanded polymer particles.

US 5,480,599 describes a process for producing particulate foam, in particular from styrene polymers and copolymers. The method makes it possible to recover the blowing agent at least partially after expansion of the particles.

EP-A2384355 describes expandable thermoplastic polymer particles containing styrene polymers and polyolefins. Because the polymers used are not miscible with each other, compatibilizers are required to adjust morphology. In order to obtain a high stiffness and good elasticity of the granular foam, polyolefin and compatibilizer must be used, which cannot be achieved with a granular foam consisting of polystyrene only.

However, the use of polyolefin with compatibilizer requires at least one additional process step of producing a mixture of at least three components, polystyrene, polyolefin and compatibilizer. In addition, suitable compatibilizers are often complex or expensive to produce. Furthermore, in the case of a simplified recovery of the particle foam at the end of its working life, a material consisting of only one polymer type is advantageous, which can be reintroduced into the corresponding material cycle.

US 7,919,538 claims a granular foam consisting of SAN and additives which shield infrared radiation, thereby improving the insulation.

US 3,945,956 describes a process 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 not uniformly distributed in the polymer matrix. Thus, this expansion of the polymer particles can produce a foam having unevenly distributed cavities.

EP-A0712885 claims expandable beads of acrylonitrile-butadiene-styrene copolymer (ABS). These beads were produced using a batch process in which ABS beads were impregnated with a blowing agent in an autoclave. It is necessary to modify the bead surface with an electrolyte so that the beads can be loaded with blowing agent in an aqueous medium. This is disadvantageous because the electrolyte can remain on the surface and can impair the weldability of the beads. In addition, the throughput is limited by the complex coating process, the size of the autoclave required, the batch mode of operation and the long loading time of the blowing agent.

EP-A2614111 discloses expandable vinylaromatic polymers containing from 0.5 to 2% by weight of talc and from 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.

US2013/059933 teaches a method for producing an expandable pelletized polymeric material consisting of a styrene polymer component having a glass transition temperature of greater than or equal to 130 ℃ 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 polymeric material comprises at least two different polymer classes, the obtained expandable pellet material is difficult, if not impossible, to recycle mechanically.

DE 10 2012 217668 discloses an expandable polymer pellet material, which is obtained from:

p) 100 parts by weight of a polymer component consisting of:

PS) 90% to 100% by weight (based on P) of a styrene copolymer component consisting of PS 1) one or more styrene-acrylonitrile copolymers (SAN) or

PS 2) a mixture of one or more styrene-acrylonitrile copolymers (SAN) and one or more styrene-maleic anhydride copolymers (SMA) and/or

PS 3) one or more styrene-acrylonitrile-maleic anhydride copolymers (SANMA) and

PT) 0 to 10wt% (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 polystyrene;

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 of different polymer classes significantly reduce the recyclability of the expandable polymer pellet material.

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.

DE 103 58 801 discloses a particulate foam molded part obtainable by welding pre-expanded foam particles consisting of an expandable thermoplastic polymer particulate material containing 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)), characterized in that the density of the particulate foam is in the range of 8 to 100 g/l.

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 an expandable system and additives. The addition of additives can impair the recyclability of the polymer foam after its end of its service or working life.

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

US 5,049,328 describes a foam production process without the use of organic blowing agents. Only inert gas (e.g., CO ₂, nitrogen, or air) is used 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 consisting of small molecules can rapidly escape from the polymer composition.

Expandable thermoplastic polymer particles with low blowing agent losses and high expansion capacity are also described in WO 2022/090403, which can be processed into a particle foam with high stiffness and good elasticity. However, when ABS is used, good results are obtained only with the addition of a nucleating agent.

In many applications, the foamed material is combined with unfoamed material. In terms of good recyclability, it is desirable that the foamed material and the unfoamed material consist of the same thermoplastic polymer matrix. At the end of its working life, the article may thereafter be crushed and remelted without any effect on the mechanical properties of the material.

Styrene polymers or copolymers are used as unfoamed materials in many industrial applications. It is therefore desirable to have a compatible material in the form of foam so that when the two materials are combined in one article, good recyclability is ensured. This can be achieved, for example, by a granular foam of styrene polymers or copolymers.

In addition, it is desirable to reintroduce a substantial portion of the recycled material into the granular foam to contribute to the recycling economy. In particular, using recyclates from scrap plastic (e.g. from EE waste), it is desirable to reintroduce such material into the cycle.

However, a common feature of all the above publications is that they always relate to materials produced from petrochemical primary feedstocks. They do not contain recycled plastics, in particular post-consumer recyclates.

In recent years, there has been an increasing effort to recycle plastic products at the end of their working life. The use of plastic recyclates has various advantages over the production of plastics from fossil sources, such as energy conservation, reduced waste and reduced resource consumption. However, in order not to suffer from a loss of quality compared to the original plastic and to compensate for the quality change of the used recyclates when using recyclates, it is preferable to adjust the properties of the recyclates by means of suitable additives, as described in WO 2021/074084.

KR 101789704 describes the use of recyclates for the production of expandable polystyrene particles, but the recyclates used are only waste materials after industrial use, i.e. waste materials produced, for example, during the trimming of molded parts. And waste materials after expense consumption are not adopted.

CN-a 110105677 teaches a process for producing expanded polypropylene particles using the recyclate. However, the proportion of recyclates is very low, at most 40% by weight, and the polypropylene foam produced is of very uneven structure.

EP-A1694753 discloses a process for producing expandable pelletized thermoplastic polymer materials made from a mixture of 50 to 90% by weight of polystyrene and 10 to 50% by weight of a styrene copolymer selected from the group consisting of styrene-butadiene block copolymers, styrene-alpha-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 the polymer recyclate, but the proportion does not exceed 50% by weight, in particular from 1% to 20% by weight. The mechanical properties of expanded polymer compositions with high polystyrene content are often poor. The same applies to the expandable styrene polymer pellet material described in EP 1694 755, which comprises at least 70% by weight of polystyrene and 0.1 to 30% by weight of a low molecular weight styrene copolymer consisting of styrene, acrylic acid and alpha-methylstyrene.

In order to simplify recycling, there is a great demand for a process that provides expanded polymer particles composed of only a single polymer class, but which also includes a high proportion of recycled polymer material, so as to largely maintain a closed cycle of material flow. Furthermore, after expansion, the cavities in the expanded polymer particles should be largely uniformly distributed and exhibit a fine-pore foam structure. It should also be possible to produce molded parts from expandable polymer particles with sufficiently good mechanical properties and good heat insulation efficiency.

It is therefore an object of the present invention to provide expanded thermoplastic polymer particles which are made from a high proportion of recyclates and which are themselves also easy to recycle and which can be processed to form a particle foam having high stiffness and good elasticity. It is another object to provide a method of producing such expanded thermoplastic polymer particles.

Surprisingly, it has been found that this object can be achieved by producing the expanded thermoplastic polymer particles according to the invention, which are set forth in more detail in the claims, in the following description and in the examples.

An expanded thermoplastic polymer particle comprising (or consisting of):

A) 10 to 99 wt% of at least one recycle (a) comprising and consisting essentially of at least one styrene polymer (a-1), based on the total weight of (a), (B), (C), (D) and (E);

b) 1 to 90% by weight, 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) 0 to 6 wt% of at least one blowing agent (C), based on the total weight of (a), (B), (C), (D) and (E);

d) 0 to 3% by weight of at least one nucleating agent (D), based on the total weight of (A), (B), (C), (D) and (E), and

E) 0 to 8wt% 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) comprises 83 to 100 weight percent based on the total weight of (a), (B), (C), (D) and (E), and wherein the expanded thermoplastic polymer particles are substantially free of other polymers except for the at least one recycle (a) and the at least one virgin polymer (B). This means that the expanded thermoplastic polymer particles contain not more than 5% by weight, preferably not more than 3% by weight, generally not more than 1% by weight, 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 virgin polymer (B). The expanded thermoplastic polymer particles preferably contain 0% by weight, based on the total weight of (A), (B), (C), (D) and (E), of a polymer which does not conform to the definition of the recyclate (A) and the virgin polymer (B). The small amount of foreign polymer improves the recyclability of the expanded polymer particles according to the invention.

The term "styrene polymer" is understood to mean a polymer incorporating in its polymer chain repeating units of styrene monomers. The styrene polymers according to the invention are selected in particular 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).

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

The expanded thermoplastic polymer particles contain at least 1 wt.%, typically at least 10 wt.%, preferably at least 15 wt.%, typically at least 20 wt.%, based on the total weight of (a), (B), (C), (D) and (E), of at least one virgin polymer (B) comprising or consisting of at least one styrene polymer (B-1). The expanded thermoplastic polymer particles contain not more than 90 wt.%, typically not more than 79 wt.%, typically not more than 69 wt.%, preferably not more than 59 wt.%, typically less than 49 wt.% of at least one virgin polymer (B), based on the total weight of (a), (B), (C), (D) and (E). The expanded thermoplastic polymer particles generally contain from 20 to 59% by weight, preferably from 25 to 54% by weight, generally from 27 to 48% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one virgin polymer (B).

The expanded 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 a polymer free of styrene-derived repeating units. However, in obtaining the recovery (A), a small amount of impurities in the form of polymers free of styrene-derived repeating units may be introduced during recovery by incomplete single species separation.

In the context of the present invention, recyclate (A) is defined as plastic, the source of which is the plastic articles that are sent to recycling and processing at the end of their working life. The recyclates may be processed by various processes known in the industry, see for exampleR.(2014):,,Erzeugung sauberer PS-und ABS-Fraktionen aus gemischtem Elektronikschrott",in D.G.Karl J.Thomé-Kozmiensky(Ed.),Recycling und Rohstoffe,volume 7(pp.379–400),TK Verlag Karl Thomé-Kozmiensky,Neuruppin. The production of recyclates may include, inter alia, the addition of additives and/or primary materials to achieve the desired material quality.

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, prior to use in the expanded thermoplastic polymer particles of the invention. Unlike virgin polymer (B), the recyclate (a) is thus subjected to mechanical stress at least once by mixing, in particular by shear forces, for example in an extruder, for example a single-screw or twin-screw extruder, or in other conventional plasticizing equipment, for example a Brabender mill or a Banbury mixer, at a temperature above the melting range of the recyclate (a), for example in the range 180 ℃ to 320 ℃, typically in the range 200 ℃ to 300 ℃, for example in the range 220 ℃ to 280 ℃, determined according to ISO 294.

The recyclate (a) may also undergo other process steps in which the recyclate (a) is subjected to mechanical stress, such as calendaring, at a temperature below the melting range temperature.

The at least one recycle (A) comprises and consists essentially of at least one styrene polymer (A-1). Preferably, the recovery (A) consists of at least one styrene polymer (A-1) to an extent of at least 80% by weight, generally to an extent of at least 85% by weight, preferably to an extent of at least 90% by weight or at least 92% by weight, based on the recovery (A).

In addition to the styrene polymer (A-1), the recycle (A) may often contain other components which have been added to the composition of the recycle for the main purpose or which have entered the recycle (A) due to insufficient separation during the recycling. In addition to the styrene polymer, the recyclate (A) may also contain other components (A-2), such as additives, pigments, foreign polymers or contaminants, such as metal parts, in particular aluminum particles.

The recyclate (A) preferably does not contain substances which adversely affect the further use according to the invention. These include, inter alia, halogen-containing flame retardants. Component (A-2) of recycle (A) is generally not more than 20% by weight, generally not more than 15% by weight, preferably not more than 10% by weight or not more than 8% by weight, based on recycle (A). The recovery (a) preferably contains substantially no other polymers.

This means that the recyclate (A) contains not more than 5% by weight, preferably not more than 3% by weight, generally not more than 1% by weight, based on the total weight of recyclate (A), of polymers which do not comply with the definition of styrene polymer (A-1). Preferably, the recycle (A) contains 0% by weight, based on the total weight of the recycle (A), of a polymer which does not conform to the definition of the styrene polymer (a-1). The small amount of foreign polymer improves the recyclability of the expanded polymer particles according to the invention.

In the context of the present invention, the terms "virgin material" and "virgin polymer" refer to plastics that are produced from fossil raw materials and that have not been recovered during their operational life.

The at least one virgin polymer (B) comprises or consists of the at least one styrene polymer (B-1). Preferably, the virgin polymer (B) comprises at least 80 wt.%, typically at least 85 wt.%, preferably at least 90 wt.% or at least 92 wt.% of at least one styrene polymer (B-1), based on the virgin polymer (B). The virgin polymer (B) may also contain component (B-2), which is generally used in the production of styrene polymers and is used, for example, to improve processability. Examples of the component (B-2) include additives such as lubricants and mold release agents. In one embodiment of the present invention, the virgin polymer comprises 100% by weight of at least one styrene polymer (B-1) based on virgin polymer (B).

Accordingly, the virgin polymer of this example contains 0 wt% of component (B-2) based on virgin polymer (B). Preferably, the virgin polymer (B) is substantially free of other polymers. This means that the virgin polymer (B) contains not more than 5% by weight, preferably not more than 3% by weight, generally not more than 1% by weight, of polymers which do not conform to the definition of the styrene polymer (B-1), based on the total weight of the virgin polymer (B). Preferably, the virgin polymer (B) contains 0% by weight, based on the total weight of virgin polymer (B), of a polymer that does not conform to the definition of the styrene polymer (B-1). The small amount of foreign polymer improves the recyclability of the expanded polymer particles according to the invention.

In one embodiment, the expanded thermoplastic polymer particles are comprised of at least one recycle (a) and at least one virgin polymer (B). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (a), at least one virgin polymer (B) and at least one blowing agent (C). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (a), at least one virgin polymer (B), and at least one nucleating agent (D). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (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 expanded thermoplastic polymer particles consist of at least one recycle (a), at least one virgin polymer (B) and at least one additive (E). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (a), at least one virgin polymer (B), at least one blowing agent (C) and at least one additive (E). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (a), at least one virgin polymer (B), at least one nucleating agent (D) and at least one additive (E). In a further embodiment, the expanded thermoplastic polymer particles consist of at least one recycle (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 particularly preferred embodiment, the at least one recycle (a) and the at least one virgin polymer (B) comprise or consist of polymers belonging to the same polymer class. In this embodiment, the expanded polymer particles according to the invention are particularly easy to recover, for example in a mechanical recovery process. In a further embodiment, the at least one recycle (a) and the 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 during mechanical recycling. The term "polymer class" is understood to mean polymers composed of repeating units of the same monomer.

In this context, "miscible" is understood to mean that domains of the first polymer are not formed in the continuous matrix of the second polymer, i.e. the first polymer is dissolved in the second polymer.

In the context of the present application, the term "miscible polymer class" is also understood to mean polymers forming a polymer blend 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 virgin polymer (B) is dispersed in the continuous phase of the recycle (A) in the form of discontinuous phase domains, wherein the discontinuous phase domains of virgin polymer (B) comprise phase domains having a maximum average diameter of 2 μm or less, more preferably 200nm or less, and typically 100nm or less.

The expanded thermoplastic polymer particles contain in total from 83 to 100% by weight of at least one recycle (A) and at least one virgin polymer (B) based on the total weight of (A), (B), (C), (D) and (E), said virgin polymer comprising styrene polymer (A-1) or styrene polymer (B-1), wherein the styrene polymer (A-1) and styrene polymer (B-1) are preferably 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), alpha-methylstyrene-acrylonitrile copolymer (AMSAN), styrene-methyl methacrylate copolymer (SMMA), styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile-maleic anhydride copolymer (SANMA), styrene-N-phenyl-maleimide-styrene-acrylonitrile copolymer, maleimide-styrene-acrylonitrile copolymer (MABS) and styrene-acrylonitrile-maleic anhydride copolymer (MANAMAMANAMAMANAMAN), 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).

In one embodiment, the expanded thermoplastic polymer particles comprise at least 89 wt%, typically at least 94.5 wt%, based on the total weight of (a), (B), (C), (D), and (E), of at least one recycle (a) and at least one virgin polymer (B). The expanded thermoplastic polymer particles generally comprise 93 to 99.5% by weight, particularly preferably 96 to 99% by weight, based on the total weight of (A), (B), (C), (D) and (E), of at least one recycle (A) and of at least one virgin polymer (B).

In one embodiment, the recycle (a) and virgin polymer (B) contain less than 50 wt%, preferably less than 25 wt%, more preferably less than 10 wt% of styrene homopolymer based on the recycle (a) and virgin polymer (B). In one embodiment, the recycle (a) and virgin polymer (B) do not contain a styrene homopolymer. In one embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably contain no styrene homopolymer.

In one embodiment, the recycle (a) and virgin polymer (B) contain less than 50wt%, preferably less than 25 wt%, more preferably less than 10 wt% of a copolymer comprising maleic anhydride and/or maleimide, based on the recycle (a) and virgin polymer (B). In one embodiment, the recycle (a) and virgin polymer (B) do not contain copolymers comprising maleic anhydride and/or maleimide. In a further preferred embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably contain no copolymers comprising maleic anhydride and/or maleimide.

In one embodiment, the recycle (a) and virgin polymer (B) contain less than 50 wt%, preferably less than 25 wt%, more preferably less than 10 wt% styrene-maleic anhydride copolymer (SMA) based on the recycle (a) and virgin polymer (B). In further embodiments, the recycle (a) and virgin polymer (B) do not contain styrene-maleic anhydride copolymer (SMA). In a further preferred embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably do not contain styrene-maleic anhydride copolymer (SMA).

In a further alternative embodiment, the recycle (a) and virgin polymer (B) contain less than 50wt%, preferably less than 25 wt%, more preferably less than 10wt% of an alpha-methylstyrene-acrylonitrile copolymer (AMSAN), based on the recycle (a) and virgin polymer (B). In further embodiments, the recycle (a) and virgin polymer (B) do not contain an alpha-methylstyrene-acrylonitrile copolymer (AMSAN). In a further preferred embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably do not contain an alpha-methylstyrene-acrylonitrile copolymer (AMSAN).

In a further alternative embodiment, the recycle (a) and 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 recycle (a) and virgin polymer (B). In further embodiments, the recycle (a) and virgin polymer (B) do not contain styrene-isoprene-styrene block copolymer (SIS). In a further preferred embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably do not contain styrene-isoprene-styrene block copolymer (SIS).

In one embodiment, the recycle (a) and 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 recycle (a) and virgin polymer (B). In one embodiment, the recycle (a) and virgin polymer (B) do not contain styrene-acrylonitrile copolymer (SAN). In a further embodiment, the expanded thermoplastic polymer particles contain no other polymer than the recycle (a) and virgin polymer (B), which preferably do not contain styrene-acrylonitrile copolymer (SAN).

In a further alternative embodiment, the recovery (a) and the virgin polymer (B) contain only styrene polymers of the same polymer class 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), alpha-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).

In a further alternative embodiment, the recycle (a) and virgin polymer (B) contain only styrene polymers of the same polymer class selected from the group consisting of styrene-acrylonitrile copolymer (SAN), acrylonitrile-butadiene-styrene copolymer (ABS), acrylate-styrene-acrylonitrile copolymer (ASA) and alpha-methylstyrene-acrylonitrile copolymer (AMSAN).

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

In a further alternative embodiment, the recycle (A) and virgin polymer (B) comprise a polymer blend comprising styrene-acrylonitrile copolymer (SAN) and acrylonitrile-butadiene-styrene copolymer (ABS), styrene-acrylonitrile copolymer (SAN) and acrylate-styrene-acrylonitrile copolymer (ASA), alpha-methylstyrene-acrylonitrile copolymer (AMSAN) and acrylonitrile-butadiene-styrene copolymer (ABS), or alpha-methylstyrene-acrylonitrile copolymer (AMSAN) and acrylate-styrene-acrylonitrile copolymer (ASA). Particular preference is given to polymer blends comprising styrene-acrylonitrile copolymers (SAN) and acrylonitrile-butadiene-styrene copolymers (ABS).

In one embodiment of the invention the expanded thermoplastic polymer particles comprise less than 5 wt.%, preferably less than 3 wt.%, typically less than 2wt.%, based on the total weight of (a), (B), (C), (D) and (E), of other thermoplastic polymers, in particular selected from the group 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), polyethersulfones (PEs), polyetherketones (PEK), polyethersulfides (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 expanded thermoplastic polymer particles do not comprise a thermoplastic polymer selected from the group 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), polyetherketone (PEK), polyethersulfide (PEs), polylactic acid esters, polyphenylene oxide (PPO/PPE), ethylene-vinyl acetate copolymers (EVA), styrene-ethylene-butylene-styrene copolymers (SEBS), styrene-ethylene-propylene copolymers (SEP) and styrene-butyl acrylate copolymers.

The weight average molecular weight Mw of the styrene polymers of the present invention is generally in the range from 10 to 1000 g/mol, preferably in the range from 50 to 500 g/mol, generally in the range from 80 to 250 g/mol. The molecular weight Mw can be determined by Gel Permeation Chromatography (GPC) using Tetrahydrofuran (THF) as eluent and calibrated with polystyrene.

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

The styrene polymers according to the invention generally have a melt volume flow rate MVR (220℃per 10 kg) according to ISO 1133 of from 1 to 30cm ³/10 min, preferably from 10 to 25cm ³/10 min.

Preferably, the blowing agent (component C) is homogeneously distributed in the expanded thermoplastic polymer particles in the polymer matrix consisting of one or more recyclates (A) and at least one virgin polymer (B).

As blowing agent (component (C)), the expanded thermoplastic polymer particles contain 0 to 6 wt.%, preferably 0 to 4 wt.%, generally preferably 0 to 2 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 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 mixtures thereof. The blowing agent preferably comprises at least one organic physical blowing agent.

In a preferred embodiment, the blowing agent comprises less than 5wt%, more preferably less than 2wt% water, based on the total weight of component (C). Preferably, the foaming agent is substantially free of water, i.e. it 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).

As optional component D, the expanded thermoplastic polymer particles contain 0 to 3 wt.%, preferably 0 to 2 wt.%, particularly preferably 0 to 0.5 wt.% of at least one nucleating agent, such as talc, alumina or silica, based on the total weight of (a), (B), (C), (D) and (E).

In a preferred embodiment, the expanded thermoplastic polymer particles are free of talc, alumina or silica as component (D) during the production process. In a further embodiment, the expanded thermoplastic polymer particles do not add a nucleating agent as component (D) during production, i.e. 0 wt. -%, based on the total weight of (a), (B), (C), (D) and (E). However, the expanded thermoplastic polymer particles may contain a nucleating agent, in particular from the recovery (A). It has been found that the optional presence of additives and impurities in the recycle (a) is generally sufficient to induce the desired pore formation in the expanded thermoplastic polymer particles.

The expanded thermoplastic polymer particles according to the invention may optionally contain other additives (E) in amounts which do not impair the cell formation and the foam structure produced thereby. The expanded thermoplastic polymer particles according to the invention generally comprise at least one additive (E) in an amount of from 0 to 8 wt. -%, preferably from 0 to 5 wt. -%, more preferably from 0 to 3 wt. -%, for example from 0.1 to 3 wt. -%, based on the total weight of (a), (B), (C), (D) and (E).

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-blowing 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.

In a preferred embodiment, the expanded thermoplastic polymer particles do not contain halogenated flame retardants. Preferred flame retardants include, inter alia, components based on phosphorus compounds known for this application.

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, optionally in combination with copper (I) halides (e.g., chloride, bromide, iodide), sterically hindered phenols, hydroquinones, various substituted representatives of these groups (REPRESENTATIVE) and mixtures thereof, in concentrations up to 1% by weight based on the total weight of the expanded thermoplastic polymer particles.

The uv stabilizer is typically present in an amount of up to 2wt%, typically 0.1 wt% to 1.5 wt%, based on the total weight of the expanded thermoplastic polymer particles, including various substituted resorcinol, salicylates, benzotriazoles, and benzophenones.

The thermoplastic polymer particles may also contain organic dyes (e.g., nigrosine), pigments (e.g., titanium dioxide, phthalocyanines, ultramarines, and carbon black), 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.

Lubricants and mold release agents are generally used in amounts of up to 1% by weight, typically from 0.1% to 0.8% by weight, based on the total weight of the expanded thermoplastic polymer particles, including, for example, long chain fatty acids (e.g., stearic or behenic acid), salts (e.g., calcium or zinc stearate) or esters (e.g., stearyl stearate or pentaerythritol tetrastearate), and amide derivatives (e.g., ethylene bis-stearamide).

The mineral-based antiblocking agent can be present in an amount of up to 0.1 weight percent based on the total weight of the expanded thermoplastic polymer particles. Examples which may be mentioned include amorphous or crystalline silica, calcium carbonate or aluminum silicate.

Processing aids which may be present may include, for example, mineral oils (preferably medical white oils) in amounts of up to 5% by weight, preferably up to 2% by weight, in particular from 0.1% to 2% by weight, based on the total weight of the expanded thermoplastic polymer particles.

Examples of plasticizers include dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils, N- (N-butyl) benzenesulfonamide and o-tolylethyl sulfonamide and p-tolylethyl sulfonamide.

Production method

The present invention provides a process for producing expanded thermoplastic polymer particles comprising the steps of:

a) Mixing a mixture of at least one recycle (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) Expanding the expandable polymer particles.

The foregoing description of the selection of components (A), (B), (C), (D) and (E) and the amounts employed applies correspondingly to the process according to the invention

In one embodiment, the process of the invention uses as starting materials only at least one recycle (A), at least one virgin polymer (B) and at least one blowing agent (C). In a further embodiment, the process employs only at least one recycle (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 process employs only at least one recycle (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 process employs only at least one recycle (a), at least one virgin polymer (B), at least one blowing agent (C) and at least one additive (E).

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

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

Preferably, at least process step a), particularly preferably process steps a) and b) are carried out at a pressure exceeding atmospheric pressure.

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

In one embodiment of the invention, the process steps a), b) and c) are carried out in an extruder, followed by underwater pelletization under water pressure in the range from 0 to 11bar, preferably from 0 to 5bar, particularly preferably from 0.5 to 1.5 bar. The water temperature during underwater pelletization is below the glass transition temperature of the at least one recycle (a) or the mixture of the at least one recycle (a) and the at least one virgin polymer (B), typically in the range of 20 ℃ to 80 ℃. The extruder temperature is above the glass transition temperature of the at least one recycle (a) or the mixture of the at least one recycle (a) and the at least one virgin polymer (B), typically in the range of 170 ℃ to 250 ℃.

In a further embodiment, the process steps a), b) and c) are carried out in an autoclave. The granulation mixture of the recovery (A) and the virgin polymer (B), optionally incorporating a nucleating agent (D) and/or other additives (E), is impregnated under pressure with a foaming agent (C). Then, the pressure is reduced to obtain foamed polymer particles.

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

In process step b), the melt loaded with the foaming 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 panel comprising one or more holes having a diameter of 0.1 to 2.4mm, preferably 0.2 to 1.2mm, particularly preferably 0.5 to 0.8mm, to form granules. In a preferred embodiment, the melt exiting the microperforated panel is fed into a water stream where it is cut into individual pellets by a suitable device. The targeted production of expandable or expanded polymer granules can be achieved by adjusting a suitable low back pressure and a suitable temperature in the water stream of such so-called underwater pelletization.

In alternative embodiments, process steps a) and/or b) may be carried out wholly or partly in suspension. The recyclate (A) and the virgin polymer (B), and optionally the nucleating agent D and/or the additive (E), may be converted into a suspension, preferably an aqueous suspension, followed by loading at least one gaseous blowing agent (C) (such as CO ₂ or nitrogen) under high pressure. The pressure at which the blowing agent (C) is introduced is, for example, in the range from 1 to 20bar, and generally in the range from 1.2 to 15bar or from 1.5 to 10 bar. Once the desired blowing agent (C) loading is achieved, the resulting polymer particles are isolated, for example by filtration and/or centrifugation, and optionally washed.

The expansion step c) may be performed by lowering the ambient pressure and/or increasing the ambient temperature.

The average particle diameter of the expanded thermoplastic polymer particles according to the invention having a recyclate content is preferably in the range from 0.1 to 10mm, preferably from 0.3 to 5mm, particularly preferably from 0.5 to 4 mm. Expanded polymer particles having a narrow particle size distribution and an average particle size within the range result in better filling of the mold during fusing of the polymer particles to provide a molded part. They allow for the design of finer molded parts and improved molded part surfaces.

The specific gravity of the expanded polymer particles having a recyclate content is preferably in the range from 10 to 250g/L, particularly preferably from 20 to 200g/L, particularly preferably from 25 to 150g/L, particularly preferably from 30 to 100g/L.

The expanded thermoplastic polymer particles preferably have an average cell size of between 50 and 400 μm, more preferably between 100 and 300 μm.

The expanded thermoplastic polymer particles having a recycle content according to the present invention may be introduced into a mold, which is then closed and heated by passing hot air or steam through the mold. Heating may also be by radio waves or infrared radiation. This will cause the polymer particles to weld together, thereby forming a foam molded article. The process pressure and temperature are selected to be low enough to maintain the pore structure in the cell membrane. The pressure is generally in the range from 0.5 to 1.0 bar.

The expanded thermoplastic polymer particles according to the invention may be further processed immediately after production. The application of a coating on the surface of the expanded thermoplastic polymer particles of the present invention is not necessary, but may optionally be performed if, for example, an antistatic coating 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, monoglycerides of stearic acid, triglycerides of stearic acid, ethylene-bis stearamide, polyethylene glycol sorbitol monooleate, zinc stearate, sodium alkyl sulfonate, bis (2-hydroxyethyl) octylmethylammonium p-toluene sulfonate, polyethylene 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., polish) are commercially available.

Use of the same

The present invention also provides the use of the expanded thermoplastic polymer particles of the present invention having a recycle content in the production of molded parts (e.g., foam molded articles), preferably formed by welding the expanded polymer particles using hot air, steam, radio waves and/or infrared radiation. The molded parts obtained can be used in a variety of applications, in particular as insulation, damping, packaging or lightweight construction materials, for example in the automotive sector.

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

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

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

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

Examples

In a corotating twin-screw extruder (model ZK25P, collin GmbH) having a screw diameter of 30mm and an aspect ratio of 42, an acrylonitrile-butadiene-styrene copolymer (rABS) (for example, under the trade nameECO (INEOS Styrolution)) and the virgin polymer acrylonitrile-butadiene-styrene copolymer (ABS) are melted at 200-240 ℃ with the blowing agent n-pentane and optionally the nucleating agent talc, thereby being homogeneously mixed. Table 1 reports the experiments performed.

The resulting polymer mixture (I) was then cooled in a single-screw extruder (E45M type, collin GmbH) having a screw diameter of 45mm and an aspect ratio of 30, and the melt was extruded through a heated perforated plate. The polymer strands are underwater granulated to obtain a blowing agent loaded microparticulate material having a narrow particle size distribution. The back pressure in the underwater pelletization was adjusted to 0.5 to 1.5bar.

The expanded polymer particles were welded in a TVZ/100 PP molding machine (Teubert Maschinenbau GmbH) at about 120-125 ℃ to produce test samples for measuring thermal and mechanical properties.

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

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

The thermal properties of the samples were tested according to DIN EN 12667 using an HMF Lambda Small thermal flow Meter (Netzsch), the dimensions of the test samples being 200X 20mm and the temperature gradient being 20K.

The mechanical properties of the samples were tested by a three-point bend test using a 1485 universal tester (Zwick Roell) according to ISO 1209 on a test sample of size 120x 25x20 mm with a preload of 1N and a test speed of 10mm/min. Test specimens having dimensions 40x 20mm and having a foam skin were subjected to static compression tests using a Z050 universal tester (Zwick Roell) according to DIN EN ISO 844, with a preload force of 10N. The results are reported in table 1.

Examples 1 and 2 and 3 and 4 each have the same recycle content, but differ in the degree of foaming, which can be specifically adjusted by varying the process parameters. The degree of foaming is reflected in the foam density. Comparison of mechanical and thermal properties foams of the same density should be used in each case, since these properties are strongly influenced by the foam density. Examples 1 and 3 and comparative examples 5 and 6 had a degree of foaming greater than examples 2 and 4.

TABLE 1 example results

Comparing inventive examples 1 and 3 (recovery content 50% and 70% by weight of the total weight of the polymer composition) with comparative examples 5 and 6 (no recovery content), the results show that:

inventive examples 1 and 3 have significantly lower thermal conductivities than non-inventive comparative examples 5 and 6, i.e., the inventive examples provide much better insulation when the polymer composition contains recycle levels (see fig. 1). The foam in comparative example 5 was produced without a nucleating agent, thus resulting in non-uniformity of the foam structure in the case of the polymer composition containing no recyclate. The use of a nucleating agent can improve the foam structure (comparative example 6), but the thermal conductivity is still higher than the foam with recyclates (and thus less effective insulation) (examples 1 and 3). When the polymer composition contains a high level of recyclates, it is easy to produce insulating foam even without nucleating agents.

In addition, inventive examples 1 and 3 showed finer, more uniform cell structures than comparative example 5 (see fig. 4 and 5). FIG. 4 shows the cell structure of the polymer foam of the invention containing 50% by weight of recyclate content in example 1. FIG. 5 shows the cell structure of a non-inventive foam containing no recyclate content of comparative example 5. The foam without the recycled material content is uneven and the foam holes are larger. In foams not according to the invention, a good cell structure can be achieved only by using nucleating agents, as shown in fig. 6. FIG. 6 shows the foam structure of comparative example 6, which is a non-inventive foam having no recyclate content but containing a nucleating agent.

The average cell size of inventive example 1 was significantly smaller than that of non-inventive comparative example 5, which did not contain a nucleating agent, thus indicating that the cell structure in inventive example was much better than that in non-inventive example.

The test samples made from the compositions of the invention (examples 1 and 3) have better compressive strength than the test samples made according to comparative examples 5 and 6, which are not according to the invention (see also fig. 2). Comparative example 5 (without nucleating agent) only shows very low compressive strength. The addition of the nucleating agent in comparative example 6 did increase the compressive strength, but did not reach the good value for the inventive example with the recyclate content. It is also shown here that the compositions according to the invention with a high recovery content are suitable for producing foams with very good compressive strength, even without the addition of nucleating agents.

The measured data of the flexural modulus of the test samples also clearly show that the inventive foam with the recyclate content has significantly improved properties compared to the non-inventive foam. In the latter case, the addition of the nucleating agent did improve the flexural modulus (comparative example 6), but still did not reach the good values for the inventive example with recycle content (see also fig. 3).

Thus, even without the addition of nucleating agents, the use of high recyclate levels can produce foams having mechanical and thermal properties superior to those produced using virgin materials alone.

Drawings

Fig. 1 shows a graphical representation of the thermal conductivity data obtained experimentally at 25 ℃ for examples 1 and 3 and comparative examples 5 and 6, in W/m K.

Figure 2 shows a graphical presentation of the compression strength data obtained experimentally at 10% elongation for examples 1 and 3 and comparative examples 5 and 6 in kPa.

Fig. 3 shows a graphical representation of the flexural modulus data obtained by experiments for examples 1 and 3 and comparative examples 5 and 6 in MPa.

Fig. 4 shows an electron micrograph of the expanded particles of the present invention obtained in example 1.

FIG. 5 shows an electron micrograph of the expanded particles of the invention obtained in comparative example 5.

FIG. 6 shows an electron micrograph of the expanded particles of the invention obtained in comparative example 6.

Claims (15)

1. An expanded thermoplastic polymer particle comprising, preferably consisting of:

A) 10 to 99 wt% of at least one recycle (a) comprising and consisting essentially of at least one styrene polymer (a-1), based on the total weight of (a), (B), (C), (D) and (E);

b) 1 to 90% by weight, 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) 0 to 6 wt% of at least one blowing agent (C), based on the total weight of (a), (B), (C), (D) and (E);

d) 0 to 3% by weight of at least one nucleating agent (D), based on the total weight of (A), (B), (C), (D) and (E), and

E) 0 to 8wt% 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) is 83 to 100% by weight based on the total weight of (A), (B), (C), (D) and (E), and

Wherein the expanded thermoplastic polymer particles are substantially free of other polymers than the at least one recycle (A) and the at least one virgin polymer (B).

2. The expanded thermoplastic polymer particles according to claim 1, wherein the at least one recycled (A) and the 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), alpha-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 styrene (PS) and impact polystyrene (HIPS).

3. Expanded thermoplastic polymer particles according to claim 1 or 2, characterized in that at least one recycle (a) and 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. Expanded thermoplastic polymer particles according to any of claims 1 to 3, characterized in that the average particle size of the expanded thermoplastic polymer particles is in the range of 0.1 to 10mm, preferably in the range of 0.3 to 5mm, particularly preferably in the range of 0.5 to 4 mm.

5. Expanded thermoplastic polymer particles according to one of claims 1 to 4, characterized in that the blowing agent (C) is homogeneously distributed in the polymer matrix consisting of at least one recycle (a) and at least one virgin polymer (B).

6. Expanded thermoplastic polymer particles according to any one of claims 1 to 5, characterized in that the expanded thermoplastic polymer particles comprise two or more recyclates (a) and virgin polymer (B), and that the two or more recyclates (a) and virgin polymer (B) are miscible with each other.

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

8. A method of producing expanded thermoplastic polymer particles according to any one of claims 1 to 7, comprising the steps of:

a) Mixing a mixture of at least one recycle (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) Expanding the expandable polymer particles.

9. The method according to claim 8, wherein at least step a) is performed at a pressure exceeding atmospheric pressure.

10. Process according to claim 8 or 9, characterized in that at least process steps a) and b), preferably process steps a), b) and c), are carried out in an extruder, followed by underwater pelletization under water pressure of 0 to 11 bar.

11. Process 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 method steps a) and b) are carried out in suspension.

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

14. Use of the expanded thermoplastic polymer particles according to any one of claims 1 to 7 in a molded part formed by welding the 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 250kPa.

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