Recycled heat-resistant polystyrene composition and method for providing excellent heat resistance in mechanical recycling of polystyrene

Abstract

The present invention relates to a recycled polystyrene composition A comprising at least one polystyrene A-1 produced by thermally initiated and / or radical polymerization initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, and a recycled heat-resistant polystyrene composition P comprising at least one sterically hindered phenolic antioxidant as component B. The present invention also relates to a method for imparting excellent heat resistance to polystyrene in a mechanical recycling process. Furthermore, the recycled heat-resistant polystyrene composition P, a method for producing the recycled heat-resistant polystyrene composition P, and the use of the recycled heat-resistant polystyrene composition P for producing molded articles are described.

Description

[Technical Field]

[0001] explanation The present invention relates to a recycled heat-resistant polystyrene composition and a method for imparting excellent heat resistance to polystyrene in a mechanical recycling process. Furthermore, the present invention deals with a method for producing a recycled heat-resistant polystyrene composition. Compared to conventional polystyrene (PS) compositions, the recycled heat-resistant polystyrene composition P contains and releases less residual monomers. [Background technology]

[0002] Plastic products or products incorporating plastics are part of almost every workplace or residential environment. Most of these plastics are virgin polymers produced from petroleum. In recent years, there has been a growing movement to recycle and reuse petrochemical products such as plastics, in addition to metal materials. The recycling process of plastics from waste plastic materials offers various advantages compared to the production of crude oil-derived plastics, such as requiring less energy, reducing the need for waste disposal, and reducing the use of limited geological resources such as petroleum. Typically, waste plastic materials include post-consumer and post-industrial waste and plastic scrap. Some of the most common polymer types in waste plastic materials from recycled sources are high impact polystyrene (HIPS), acrylonitrile-butadiene-styrene copolymer (ABS), polypropylene (PP), and polycarbonate (PC).

[0003] The quest for polystyrene compositions with low residual monomer content requires grades that do not release monomers (e.g., styrene) due to the decomposition of polystyrene during processing. Processing of polystyrene compositions often results in the degradation of polystyrene due to a combination of mechanical stress, thermal degradation, and oxidation. High temperatures significantly promote the production of styrene monomer. The upper limit behavior of commercial polystyrene materials typically results in a residual monomer content of about 400 ppm styrene at 220°C and 1500 ppm at 260°C. It has previously been reported that thermally initiated polystyrene is more stable compared to radically initiated polystyrene (Non-Patent Document 1).

[0004] So-called "weak links" in the polymer chain are known to play an important role in the initiation of thermal degradation of polystyrene. It is also known that the initial rate of degradation is a function of the initiation mechanism (anionic vs. radical) and, in the case of radical-initiated polystyrene, the specific initiator. Graeme Moad, David H. Solomon, and R. Ian Willing (Department of Applied Organic Chemistry, Melbourne, Australia) have reported on the nature of initiator-derived end groups in polystyrene prepared with benzoyl peroxide as the initiator and speculated on the possible role of these end groups in the thermal and photochemical degradation of the polymer (Non-Patent Document 2).

[0005] Examination of the NMR spectra of the degraded polymers showed that after only 10 minutes, all resonances due to secondary benzoate end groups had disappeared, and the primary benzoate resonances appeared essentially unchanged in both appearance and relative intensity. Thus, end groups formed by head addition to monomer, transfer to initiator, or primary radical termination are significantly more thermally unstable than end groups formed from tail addition to normal monomers.

[0006] However, no information is given on alternative methods to benzoyl peroxide by initiation methods that result in superior heat resistance. Furthermore, no methods are known so far for improving the properties of polystyrene compositions for their repeated use in post-consumer recycled food packaging, with respect to the content of residual monomers.

[0007] For example, to use recycled polystyrene compositions in food packaging, it is essential to minimize the residual styrene content in the recycled polystyrene compositions, since the styrenic monomer may migrate from the packaging material into, for example, the food. Recycled polystyrene compositions tend to contain and / or release increased amounts of residual styrenic monomer due to the repeated thermal and / or mechanical treatments they undergo during the recycling process. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] M. Singh, US Naudi, J. Polym. Sci. Polym. Lett. 17, 121, 1979 [Non-patent document 2] Graeme Moad, David H. Solomon, and R. Ian Willing, Macromolecules 21, 855-857 (1988) Summary of the Invention [Problem to be solved by the invention]

[0009] Surprisingly, it has been found that when recycled polystyrene is used that is (or was) produced by thermally initiated and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiated radical polymerization and that is further mixed with at least one sterically hindered phenolic antioxidant, a heat-resistant polystyrene composition P is obtained. Furthermore, it has been found that processing properties such as viscosity can be improved according to the present invention. [Means for solving the problem]

[0010] Description of the Invention The present invention: A: Component A: A-1: as component A-1, at least one polystyrene, where the polystyrene A-1 is obtained by thermally initiated and / or radical polymerization initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; A-2: Optionally, component A-2 may include styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C3-C 12 at least one impact-modified polymer comprising polymer particles derived from at least one monomer selected from alpha-olefins, and combinations thereof; and A-3: Optionally, as component A-3, at least one additive at least one recycled polystyrene composition comprising: B: as component B, at least one sterically hindered phenolic antioxidant; and C: Optionally, as component C, at least one additive The present invention relates to a recycled heat-resistant polystyrene composition P comprising (or consisting of)

[0011] According to the present invention, component A-1 can be, for example, a polystyrene component originally obtained (long ago) by thermally initiated and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiated radical polymerization, used in polymer products for some time, and then reused in a new process for producing the recycled heat-resistant polystyrene composition P.

[0012] Preferably, the recycled heat-resistant polystyrene composition P comprises: A: as component A, at least one recycled polystyrene composition in an amount of 95 to 99.9% by mass based on the recycled heat-resistant polystyrene composition P; B: as component B, 0.1 to 1% by weight of at least one sterically hindered phenolic antioxidant based on the recycled heat-resistant polystyrene composition P; and C: As component C, 0 to 4% by mass of at least one additive based on the recycled heat-resistant polystyrene composition P Contains (or consists of).

[0013] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P preferably comprises: A: 97.5 to 99.9% by mass of recycled heat-resistant polystyrene composition P as component A, A-1: as component A-1, at least one polystyrene, [wherein said polystyrene A-1 is prepared by thermally initiated radical polymerization]; A-2: Component A-2 includes styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C3-C 12 at least one impact-modified polymer comprising polymer particles derived from at least one monomer selected from alpha-olefins, and combinations thereof; and A-3: Optionally, as component A-3, at least one additive at least one recycled polystyrene composition comprising: B: As component B, 0.1 to 0.5 mass% based on the recycled heat-resistant polystyrene composition P is octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS number: 2082-79-3, Irganox (R) 1076), 2,6-di-tert-butyl-p-cresol (CAS No. 87-97-8, Kerobit (R) at least one sterically hindered phenolic antioxidant selected from TBK, and mixtures thereof; and C: As component C, 0 to 2% by mass of at least one additive based on the recycled heat-resistant polystyrene composition P Contains (or consists of).

[0014] In the context of the present invention, recycled polystyrene refers to polystyrene-based polymers, including general purpose polystyrene (GPPS) and high impact polystyrene (HIPS), that are typically obtained from waste plastic materials, especially recycled materials, in a recycling and separation process.

[0015] In the context of this invention, "recycled goods" refers to items such as packaging, especially food packaging, appliances, machinery, sporting goods, consumer electronics, and automobiles.

[0016] In the context of the present invention, recycled polymers (e.g., recycled polystyrene A) are defined as polymers derived from polymer articles that have been recycled and reprocessed at the end of their useful life. The processing to obtain recycled polymers can be carried out by various processes known in the industry, see, for example, Koehnlechner, R. (2014): "Erzeugung sauberer PS- and ABS-fractionen aus gemischtem ektronikschrott", DG Karl J. Thome-Kozmiensky (ed.), Recycling und Rohstoffe, Vol. 7 (pp. 379-400), TK Verlag Karl Thome-Kozmiensky, Neurouppin.

[0017] Recycled polystyrene A is characterized in that it has been processed into an article (e.g., a molded article) at least once after its production as a primary polymer (virgin polymer). Recycled polystyrene A therefore typically differs from primary polymers (virgin polymers) in that the recycled polymer has undergone at least one additional thermal compounding step, such as extrusion or injection molding, before being used in the recycled heat-resistant polystyrene composition P according to the present invention.

[0018] Thus, in contrast to the primary polymer (virgin polymer), recycled polystyrene A has typically been subjected to at least one thermal compounding step at a temperature higher than the melting temperature of recycled polystyrene A, e.g., in the range of 180°C to 320°C, often in the range of 200°C to 300°C, for example, in the range of 220°C to 280°C, as measured according to ISO 294, and / or has been subjected to mechanical stress by mixing, in particular by shear forces, for example in an extruder, e.g., a single- or twin-screw extruder, or in other conventional plasticizing equipment such as a Brabender mixer or a Banbury mixer.

[0019] Additionally, recycled polystyrene A may have been subjected to other processing steps, such as calendering, in which the recycled polymer is mechanically compressed below its melting range temperature.

[0020] The components of recycled high temperature polystyrene composition P, particularly components A, B, and C, are further defined below.

[0021] Recycled polystyrene composition (component A) The polystyrene composition P comprises, as component A, a recycled polystyrene composition, which comprises: A-1: at least one polystyrene as component A-1; A-2: optionally, at least one impact-modifying polymer as component A-2; and A-3: Optionally, at least one additive as component A-3 Includes:

[0022] At least one polystyrene A-1 contained in recycled polystyrene composition A is produced by thermally initiated and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiated radical polymerization.

[0023] Preferably, the recycled polystyrene composition A is a recycled material obtained from the recycling process of post-consumer products, preferably selected from food packaging, office supplies, cosmetic packaging, automotive supplies, household appliances and electrical equipment.

[0024] In a preferred embodiment, the recycled polystyrene composition A is: A-1: at least one polystyrene A-1; A-2: Styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C3-C 12 at least one impact-modified polymer A-2 comprising polymer particles derived from at least one monomer selected from alpha-olefins, and combinations thereof; and A-3: optionally at least one additive A-3 as component A-3 Contains (or consists of).

[0025] In one embodiment of the present invention, polystyrene A-1 is produced by a thermally initiated radical polymerization process.

[0026] In one embodiment of the present invention, polystyrene A-1 is produced by a radical polymerization process initiated by 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

[0027] In one embodiment of the present invention, polystyrene A-1 is produced by a radical polymerization process that is thermally initiated and initiated by 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

[0028] As used herein, the term "polystyrene" refers to a polymer containing monomer residues derived from one or more monomers selected from styrene, p-methylstyrene, tertiary butylstyrene, dimethylstyrene, their nuclear brominated or chlorinated derivatives, and combinations thereof.

[0029] According to a preferred embodiment, polystyrene A-1 comprises at least 30% by weight, more preferably at least 60% by weight, and particularly preferably at least 85% by weight, of one or more monomers selected from styrene, p-methylstyrene, tert-butylstyrene, dimethylstyrene, their nuclear brominated or chlorinated derivatives, and combinations thereof, based on polystyrene A-1. Preferably, polystyrene A-1 comprises 30% by weight, more preferably at least 60% by weight, and particularly preferably at least 85% by weight, of styrene, based on polystyrene A-1.

[0030] According to one embodiment, recycled polystyrene composition A may be selected from standard polystyrene (also called general-purpose polystyrene GPPS). In this embodiment, polystyrene A-1 is selected from standard polystyrene, and impact-modified polypolymer A-2 is absent. Optionally, recycled polystyrene composition A may contain at least one additive as component A-3.

[0031] Suitable standard polystyrene (also called general purpose polystyrene (GPPS)) is produced by the radical polymerization process of styrene or a styrene derivative as described above, initiated by thermal initiation and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiation. Preferably, GPPS is produced by the polymerization of styrene or a mixture of styrene with any of the other copolymerizable monomers described above. Preferably, GPPS is produced by the polymerization of styrene or a mixture of styrene with one or more monomers selected from p-methylstyrene, tertiary butylstyrene, dimethylstyrene, their nuclear brominated or chlorinated derivatives, and combinations thereof. In general, the heterogeneity of the polymer, which may be affected by the polymerization process, is of little importance here.

[0032] According to an alternative embodiment, recycled polystyrene composition A may be selected from high impact polystyrene (also called HIPS). In this embodiment, polystyrene A-1 may be selected from standard polystyrene, and at least one impact-modifying polymer A-2 is present. Optionally, recycled polystyrene composition A may contain at least one additive as component A-3. In one embodiment, recycled polystyrene composition A consists of 100% by weight HIPS, based on A.

[0033] According to a further embodiment, recycled polystyrene composition A may comprise a mixture of high impact polystyrene (HIPS) and standard polystyrene (GPPS).

[0034] In a preferred embodiment, the recycled polystyrene composition A is selected from high impact polystyrene (HIPS). The production, structure, and properties of the polystyrenes are described in detail and extensively in the literature, for example, in Echte, Haaf, Hambrecht in Angew. Chem. (Int. Ed. Engl.) 20, 344-361 (1981); and Kunststoffhandbuch, Vieweg and Daumiller, eds., Vol. 4 "Polystyrol", Carl-Hanser-Verlag Munich (1996).

[0035] As used herein, the term "high-impact polystyrene" or "HIPS" refers to a rubber-modified polystyrene comprising polystyrene A-1 as a matrix material and at least one impact-modifying polymer A-2, described below, as an elastomeric material. For example, HIPS can be produced by adding polybutadiene rubber or other elastomeric material to styrene monomer during polymerization, thereby chemically bonding the elastomeric material to the polystyrene to form a graft copolymer, which facilitates the incorporation of the impact-modifying polymer A-2 into the final resin composition. According to the present invention, polymerization is carried out by radical polymerization of styrene or one of the above-mentioned styrene derivatives in the presence of at least one impact-modifying polymer A-2, initiated by thermal initiation and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiation.

[0036] As used herein, the term "elastomeric material" refers to a material that deforms when pressure is applied and returns to its original shape when the pressure is removed.

[0037] Typically, elastomeric materials that can be used to make high impact polystyrene (HIPS) include styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C3-C6 12 One or more impact-modified polymers A-2 comprising monomer residues derived from alpha olefins, and combinations thereof.

[0038] As used herein, the term "monomer residue" or "polymer made from" or "polymer comprising" a particular monomer refers to a monomer repeat unit in a polymer derived from the polymerization of a particular monomer containing a polymerizable unsaturated group. As used herein, the term "polymer" is intended to encompass homopolymers, copolymers, and graft copolymers.

[0039] In some embodiments of the present invention, the impact-modifying polymer A-2 may be a rubbery polymer containing ethylenic unsaturation. In some cases, the impact-modifying polymer A-2 may be one or more C olefins such as polybutadiene. 4-6 It may be a copolymer or homopolymer of a conjugated diolefin.

[0040] In some particular embodiments, polystyrene composition A is selected from high impact polystyrenes comprising polystyrene A-1 and at least one impact modifying polymer A-2 selected from butadiene rubber (BR) and styrene-butadiene rubber (SBR).

[0041] The butadiene rubber is particularly a medium or high cis-polybutadiene. Typically, high cis-polybutadiene contains cis-configured monomer units in an amount of 90% or more, and in some cases greater than about 93% by weight, based on the polybutadiene. In many cases, medium cis-polybutadiene has a cis content of about 30-50% by weight, and in some cases about 35-45% by weight, based on the polybutadiene.

[0042] Suitable butadiene rubbers that can be used in the present invention are commercially available from a variety of sources, such as Buna CB 550 available from Arlanxeo Corporation (Pittsburgh, PA); SE PB 5800-Schkopau available from Trinseo LLC (Berwyn, PA); Diene rubber available from Lion Elastomers LLC (Orange, Texas). (R) 55AC15, and KBR 710S available from Kumho Petrochemical Co. (Seoul, Republic of Korea).

[0043] Furthermore, the impact-modifying polymer A-2 may be selected from certain structurally modified butadiene rubbers, for example, in which the proportion of 1,4-cis and / or 1,4-trans or the proportion of 1,2- and 1,4-linkages has been modified compared to conventional rubbers.

[0044] Furthermore, instead of butadiene rubber, other diene rubbers, and also elastomers of the ethylene-propylene-diene copolymer (EPDM rubber) type, and hydrogenated diene rubbers can also be used as impact-modifying polymer A-2.

[0045] Recycled polystyrene A can be obtained from recycling previously produced polystyrene by polymerizing one or more of the above-mentioned styrene monomers selected from styrene, p-methylstyrene, tertiary butylstyrene, dimethylstyrene, their nuclear brominated or chlorinated derivatives, and combinations thereof, optionally in the presence of impact-modified polymer A-2, provided that: (i) The polymerization reaction is thermally initiated; (ii) the polymerization reaction is initiated by radical initiation using 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane as the initiator; or (iii) The polymerization reaction is thermally initiated and initiated by radical initiation using 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane as the initiator.

[0046] Thermal initiation can be induced by subjecting a reaction mixture containing one or more of the above-mentioned styrene monomers selected from styrene, p-methylstyrene, tertiary butylstyrene, dimethylstyrene, their nuclear brominated or chlorinated derivatives, and combinations thereof, optionally in the presence of impact-modified polymer A-2, to an elevated temperature, for example, a temperature between 100° C. and 180° C., preferably 110-150° C. At this temperature, the polymerization reaction is initiated without the addition of an initiator.

[0047] When 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane is used as the initiator, the initiator is preferably used in an amount of 50 to 500 ppm, more preferably 100 to 250 ppm, based on the total reaction mixture.

[0048] For example, methods for production are disclosed in US2011 / 0054123, US5,543,461 (see column 5, lines 3-42), US5,861,455 (see column 3, line 42 to column 4, line 17), and US6,613,837 (column 3, line 55 to column 4, line 23), the relevant portions of which are incorporated herein by reference.

[0049] In one embodiment, recycled polystyrene composition A is an impact polystyrene comprising 80 to 99% by weight, preferably 85 to 98% by weight, of a styrene matrix (polystyrene A-1), preferably polystyrene, and 1 to 20% by weight, preferably 2 to 15% by weight, of at least one impact-modifying polymer A-2, preferably polybutadiene and / or styrene-butadiene copolymer.

[0050] When present, the impact-modified polymer A-2 is typically in the form of particles, often having an average particle size (as measured by conventional methods) of at least about 0.25 μm, in some cases at least about 0.5 μm, and in other cases at least about 1 μm. Preferably, the average particle size (by volume) of the impact-modified polymer A-2 particles can be up to about 12 μm, in some cases up to about 11 μm, and in other cases up to about 10 μm. Often, the average particle size of the impact-modified polymer A-2 particles can be in the range of 1 μm to 10 μm, e.g., 2, 4, or 7 μm. The average particle size of the impact-modified polymer A-2 particles can be any value or range between any of the values indicated above. The particle size of the impact-modified polymer A-2 is typically measured by analyzing a spectrum obtained from light scattering through a solution of the particles in a polystyrene solvent such as methyl ethyl ketone or ethyl acetate. Suitable instruments for this measurement include the Horiba model LA-960V2 or the Beckman Coulter LS 13 320.

[0051] Typically, the weight average molecular weight (M w ) is in the range of 50,000 to 500,000 g / mol, preferably 120,000 to 250,000 g / mol, and more preferably 130,000 to 240,000 g / mol. In particular, the weight average molecular weight (M w ) ranges from 170,000 to 250,000 g / mol, preferably from 180,000 to 207,000 g / mol, and more preferably about 190,000 g / mol. In particular, the weight average molecular weight (M w ) ranges from 120,000 to 240,000 g / mol, preferably from 132,000 to 207,000 g / mol, and more preferably about 165,000 g / mol. Typically, molecular weight values are determined by gel permeation chromatography (GPC) using appropriate polystyrene standards. Unless otherwise indicated, molecular weight values given herein are weight average molecular weights (Mw).

[0052] Typically, the recycled polystyrene composition A may comprise (or consist of) GPPS or HIPS having a viscosity number VN (measured in accordance with DIN 53726) in the range of 50 to 100 ml / g, preferably 60 to 80 ml / g.

[0053] In particular, GPPS and / or HIPS with one or more additives A-3 (typically unknown due to the often unknown origin of the recycled material) such as, for example, mineral oil (e.g., medical white oil), lubricant (e.g., metal stearate), stabilizer, antistatic agent, flame retardant, or wax can be used as recycled polystyrene composition A.

[0054] Phenolic antioxidant (ingredient B) According to the invention, the polystyrene composition P comprises at least one sterically hindered phenolic antioxidant B. The phenolic antioxidant component B preferably has the general formula (I): [ka] wherein R1 to R5 independently represent a hydrogen atom or an alkyl group having 1 to 70 carbon atoms, wherein the hydrocarbon group optionally contains at least one heteroatom selected from O and S, and wherein at least one of the substituents R1 and R5 represents a hydrocarbon group having at least 3 carbon atoms. and mixtures thereof.

[0055] In a further preferred embodiment, at least one of the substituents R1 and R5 represents a hydrocarbon group having 3 to 6 carbon atoms, preferably an iso-propyl group, a sec-butyl group, a tert-butyl group, a neo-pentyl group and / or a cyclohexyl group.

[0056] In one embodiment, at least one of the substituents R2, R3 and R4 represents a hydrogen atom.

[0057] In one embodiment, at least one of the substituents R2, R3 and R4 represents a hydrocarbon group having at least 1 carbon atom.

[0058] In one embodiment, at least one of the substituents R1 and R5 represents a tert-butyl group; at least two of the substituents R2, R3, and R4 represent a hydrogen atom; and one of the substituents R2, R3, and R4 represents a hydrocarbon group having at least one carbon atom.

[0059] In one embodiment, the at least one sterically hindered phenolic antioxidant B has the general formula (Ia): [ka] wherein R3 represents a hydrocarbon group having 1 to 70 carbon atoms, wherein the hydrocarbon group optionally contains at least one heteroatom selected from O and S; and R2, R4, and R5 independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and wherein at least one of the substituents R2, R3, and R4 is not hydrogen. The compound is selected from the group consisting of:

[0060] In one embodiment of the present invention, the at least one sterically hindered phenolic antioxidant B is octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS number: 2082-79-3, Irganox (R) 1076), 2,6-di-tert-butyl-p-cresol (CAS No. 87-97-8, Kerobit (R) TBK), 2-(1,1-dimethylethyl)-6-[(3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl-4-methylphenyl acrylate (CAS number 61167-58-6, Irganox (R) 3052), and mixtures thereof.

[0061] Further examples of compounds that can be used as component B include oxygen radical scavengers, such as pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (CAS number 6683-19-8, Irganox (R) 1010, BASF SE), tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate]methane (CAS no. 6683-19-8, Songnox (R) 1010, Songwon), 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenyl (CAS number 991-84-4, Irganox (R) 565, BASF SE) and blends thereof, carbon radical scavengers such as 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate (CAS No. 123968-25-2, Sumilizer (R) GS, Sumitomo), 2-(1,1-dimethylethyl)-6-[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]-methyl]-4-methylphenyl acrylate (CAS no. 61167-58-6, Sumilizer (R) GM, Sumitomo) and blends thereof.

[0062] In one embodiment of the present invention, component B is 2,6-di-tert-butyl-p-cresol (CAS number 87-97-8), a compound of the following formula (Ib): [ka] The present invention comprises or consists of a sterically hindered phenolic antioxidant of the formula:

[0063] In one embodiment of the present invention, component B is 2-(1,1-dimethylethyl)-6-[(3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl-4-methylphenyl acrylate (CAS number 61167-58-6), a compound of the following formula (Ic): [ka] The present invention comprises or consists of a sterically hindered phenolic antioxidant of the formula:

[0064] In one embodiment of the present invention, component B is octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS number: 2082-79-3), a compound of the following formula (Id): [ka] The present invention comprises or consists of a sterically hindered phenolic antioxidant of the formula:

[0065] In one embodiment of the present invention, component B comprises a mixture of sterically hindered phenolic antioxidants of formula (Ib), (Ic) and / or (Id).

[0066] Preferably, the heat resistance of the polystyrene composition is improved by mixing the recycled polystyrene composition A with 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, and often 0.1 to 1% by weight of at least one sterically hindered phenolic antioxidant B based on the total recycled heat-resistant polystyrene composition P.

[0067] Additive (Component C) The recycled heat-resistant polystyrene composition P may contain up to 10% by weight, preferably up to 5% by weight, of one or more further additives C different from component B, based on the total recycled heat-resistant polystyrene composition P.

[0068] Preferably, the recycled heat-resistant polystyrene composition P may contain one or more additives C in an amount of 0.01 to 10 mass %, preferably 0.1 to 5 mass %, and more preferably 0.1 to 2.5 mass %, based on the total mass of the recycled heat-resistant polystyrene composition P. The additives C may be mixed with the polystyrene composition A and the sterically hindered phenolic antioxidant B during the production of the recycled heat-resistant polystyrene composition P.

[0069] However, recycled polystyrene composition A often contains a significant amount of additive A-3, which may be the same as additive C. In this case, the addition of additional additive C is not necessary, or only a reduced amount of C is required. Thus, recycled heat-resistant polystyrene composition P may contain the commonly known additive A-3 derived from recycled polystyrene composition A, but this is not included in the amount described for additive C.

[0070] The further additive C is typically selected from additives generally known for polystyrenes and their copolymers and compositions. Substances that can be used as additives or auxiliaries are polymer additives known to those skilled in the art and described in the prior art (e.g., Plastics Additives Handbook, edited by Schiller et al., 6th edition, 2009, Hanser). The additives and / or auxiliaries can be added before the compounding procedure (mixing the polymer components A and B in the molten state) or during the compounding procedure.

[0071] The recycled heat-resistant polystyrene composition P may contain, as component C, 0.01 to 5 mass % of conventional additives such as processing aids, stabilizers, antioxidants, UV absorbers, lubricants, flame retardants, colorants, pigments, and plasticizers.

[0072] Examples of antioxidants and heat stabilizers are sterically hindered phenols, various substituted representatives of these groups, and mixtures thereof, in concentrations of up to 1% by weight based on the total recycled heat-resistant polystyrene composition P.

[0073] UV stabilizers that may be mentioned, which are commonly used in amounts of up to 2% by weight based on the total recycled heat-resistant polystyrene composition P, are various substituted resorcinols, salicylates, benztriazoles and benzophenones different from component B. In addition, tris(2,4-di-tert-butylphenol) phosphite (CAS number 31570-04-4, Irgafos from BASF SE, Germany) is also available. (R)A secondary stabilizer such as (168) may also be used. These secondary stabilizers are commercially available. The stabilizer is preferably used in an amount of 0.01 to 0.5% by weight, more preferably 0.1 to 0.3% by weight, based on the total weight of the recycled heat-resistant polystyrene composition P.

[0074] Examples of processing aids that can be used in an amount of 0.1 to 5% by weight, preferably 0.5 to 4% by weight, based on the total recycled heat-resistant polystyrene composition P are homogeneously miscible oils or oil mixtures, in particular selected from mineral oils (medical-grade mineral oils), vegetable oils (also called plant oils), and silicone oils. In particular, medical-grade mineral oil (e.g., bg. DAB 70) can be used as additive C in an amount of 1 to 4% by weight, based on the recycled heat-resistant polystyrene composition P.

[0075] Preferred lubricants are long chain fatty acids such as stearic acid or behenic acid, salts of fatty acids (e.g., calcium stearate or zinc stearate), fatty acid esters (e.g., stearyl stearate or pentaerythrityl tetrastearate), amide derivatives of fatty acids (e.g., ethylene bisstearylamide, erucic acid amide, Acrawax (R) ), phosphates (e.g., tricalcium phosphate), hydrocarbon waxes, e.g., microcrystalline wax and paraffin wax (e.g., Besquare (R) ), and fumed silica (e.g., Aerosil (R) Typical fatty acids may be selected from linear or branched, saturated or unsaturated C5-C 25 It is a carboxylic acid with an alkyl chain.

[0076] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P contains, as additive C, 4,4'-(1,6-hexamethylenebis(formylimino))bis(2,2,6,6-tetramethyl-1-oxylpiperidine), a polystyrene having a general formula (II-a): [ka] Polymerization inhibitor (Uvinul (R) 4040P from BASF).

[0077] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P contains, as additive C, 5,7-bis(1,1-dimethylethyl)-3-[2,3-dimethylphenyl]-2(3H)-benzofuranone (CAS number 201815-03-4), a compound of general formula (II-b): [ka] Antioxidant (Irganox (R) HP-136 (available from BASF).

[0078] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P contains, as additive C, 2,3-dimethyl-2,3-diphenylbutane (CAS number 1889-67-4), a polystyrene having the general formula (II-c): [ka] Flame retardant synergist (Perkadox (R) 30 from Akzo Nobel).

[0079] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P contains, as additive C, N-butyl-5,15-bis(2,4,4-trimethylpentan-2-yl)-9,11-dioxa-2-thia-10-nickelatricyclo[10.4.0.0 3,8 ]Hexadeca-1(16),3,5,7,12,14-hexaen-10-aminium (CAS number 14516-71-3), general formula (II-d): [ka] Light stabilizer (Chimassorb (R) N-705 from BASF).

[0080] In one embodiment of the present invention, the recycled heat-resistant polystyrene composition P may contain, as additive C, a mixture of components of general formula (II-a), (II-b), (II-c) and / or (II-d).

[0081] Preferably, the components of general formula (II-a), (II-b), (II-c) and / or (II-d) are each present in an amount of 0 to 2% by weight, more preferably 0 to 1% by weight, based on the total recycled heat-resistant polystyrene composition P.

[0082] Method for providing superior heat resistance in mechanical recycling of polystyrene compositions The present invention also relates to a method for imparting excellent heat resistance to polystyrene in a mechanical recycling process, the method comprising the steps of: (i) recycling a polystyrene composition A comprising at least one polystyrene as component A-1 and, optionally, at least one impact-modifying polymer A-2 as component A-2, wherein the at least one polystyrene A-1 is obtained from a thermally initiated and / or 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane initiated radical polymerization; (ii) mixing the recycled polystyrene composition A with at least one sterically hindered phenolic antioxidant as component B and optionally at least one further additive as component C; and (iii) extruding the resulting blend of recycled polystyrene composition A, at least one sterically hindered phenolic antioxidant B, and optionally at least one further additive C. Includes:

[0083] The recycling of polystyrene composition A in step (i) is preferably achieved by recycling waste polymer materials obtained from the recycling of used products selected from food packaging, office supplies, cosmetic packaging, automotive supplies, home appliances and electrical equipment.

[0084] The waste is preferably separated into polymer classes and optionally washed to reduce the amount of polymer class difference from component A. Preferably, the resulting fractionated waste polymer is pretreated, for example by homogenization, grinding, crushing, and / or pulverization, before being introduced into step (ii) or (iii). Polystyrene composition A is often subjected to one or more thermal compounding steps, such as extrusion or injection molding, before being used in the process according to the invention.

[0085] Often, before being used in the process according to the present invention, recycled polystyrene A has been subjected to at least one thermal compounding step at a temperature higher than the melting temperature of recycled polystyrene A, for example in the range of 180°C to 320°C, often in the range of 200°C to 300°C, for example in the range of 220°C to 280°C, as measured, for example, in accordance with ISO 294. Optionally, before being used in the process according to the present invention, recycled polystyrene A has been mechanically compressed by mixing, in particular by shear forces, for example in an extruder, for example a single- or twin-screw extruder, or other conventional plasticizing equipment such as a Brabender mixer or a Banbury mixer.

[0086] Steps (ii) and (iii) may be carried out separately or in combination with each other. Typically, components A and B, and optionally C, are melt-mixed at temperatures ranging from 180 to 300°C, preferably from 200 to 280°C. Suitable methods for steps (ii) and (iii) are known per se. For example, extruders, such as co-rotating or counter-rotating single- or twin-screw extruders, or other conventional kneading equipment, such as continuous or batch kneaders, Brabender mixers, or Banbury mixers, can be used to produce the recycled heat-resistant polystyrene composition P. The kneading elements should ensure sufficient homogenization of the components to ensure fine mixing. The recycled heat-resistant polystyrene composition P of the present invention can be obtained by mixing and homogenizing the components according to conventional methods in plastics technology, where the order of adding the components can be varied.

[0087] The characteristic of mechanically recycling polystyrene that provides excellent heat resistance can be found by measuring the heat resistance of polystyrene products when produced by the method described in this invention and comparing it with classical polystyrene recycling methods. For example, re-monomerization, which is caused by the decomposition of the polymer structure during extrusion (at high temperature), can be measured by determining the styrene level in the extruded product.

[0088] The present invention also relates to a method for providing a recycled heat-resistant polystyrene composition P, comprising steps (i) to (iii).

[0089] The constituents used in the process according to the invention, in particular components A, B and C and their preferred embodiments, are as defined herein above.

[0090] Process for producing recycled heat-resistant polystyrene composition P Furthermore, the present invention relates to a method for producing the inventive recycled heat-resistant polystyrene composition P. In particular, the present invention relates to a method for producing the inventive recycled heat-resistant polystyrene composition P described herein, in which components A and B, and optionally C, are melt-mixed at a temperature in the range of 180 to 300°C, preferably 200 to 280°C.

[0091] The recycled heat-resistant polystyrene composition P can be produced by methods known per se. For example, extruders, such as co-rotating or counter-rotating single- or twin-screw extruders, or other conventional kneading equipment, such as continuous or batch kneaders, Brabender mixers, or Banbury mixers, can be used to produce the recycled heat-resistant polystyrene composition P. The kneading elements should ensure sufficient homogenization of the components to ensure fine mixing. The recycled heat-resistant polystyrene composition P of the present invention can be obtained by mixing and homogenizing the components by methods conventional in plastics technology, where the order of adding the components can be varied.

[0092] Preferably, polystyrene composition A may be pretreated prior to melt mixing with component B, for example by homogenizing, grinding, crushing, and / or pulverizing.

[0093] Use of recycled heat-resistant polystyrene composition P Furthermore, the present invention relates to the use of the recycled heat-resistant polystyrene composition P of the present invention described herein for the production of molded articles (shaped articles) for various applications, such as in the automotive sector, electronics, household goods, construction, healthcare products, packaging, and sports and leisure goods. The recycled heat-resistant polystyrene composition P of the present invention can be used to produce any kind of molded article. These can be produced by injection-molded, extrusion-molded, and blow-molded processes. Another type of process is the production of molded articles by thermoforming from pre-manufactured sheets or films and by processing film-overmolded articles. In particular, the recycled heat-resistant polystyrene composition P of the present invention is used in extrusion processes to form molded articles. Examples of these molded articles are any kind of film, profile, or housing part. In particular, the recycled heat-resistant polystyrene composition P is used in extrusion processes to produce extruded sheets.

[0094] The recycled heat resistant polystyrene composition P may be used by itself or in combination with virgin materials, such as virgin polystyrene compositions.

[0095] For example, in one embodiment of the present invention, the recycled heat-resistant polystyrene composition P may be used in a polymer blend P* comprising 1 to 99% by weight, preferably 2 to 70% by weight, often 5 to 50% by weight of the recycled heat-resistant polystyrene composition P according to the present invention, based on the total weight of the polymer blend P*, and 1 to 99% by weight, preferably 30 to 98% by weight, often 50 to 95% by weight of a virgin polymer composition comprising polystyrene, high impact polystyrene, and mixtures thereof, based on the total weight of the polymer blend P*.

[0096] Furthermore, in an alternative embodiment, recycled heat-resistant polystyrene composition P can be used to construct a layered structure S comprising at least two layers, preferably at least three layers, where at least one layer corresponds to recycled heat-resistant polystyrene composition P according to the present invention, and at least one of the layers corresponds to a polymer composition P' different from recycled heat-resistant polystyrene composition P. In one preferred embodiment for this purpose, the layered structure comprises a three-layer extruded structure S having a P'-P-P' layer sequence, i.e., a three-layer structure S, where recycled heat-resistant polystyrene composition P corresponds to a central layer covering both expanded surfaces, and at least one of the layers covering the central layer is made from a polymer composition P' different from recycled heat-resistant polystyrene composition P according to the present invention. Often, polymer composition P' is a virgin polymer composition P' comprising polystyrene, high-impact polystyrene, or a mixture thereof.

[0097] Molded products made from recycled heat-resistant polystyrene composition P The present invention further relates to molded articles made from the inventive recycled heat-resistant polystyrene composition P described herein. The molded articles can be selected from any type of molded article, for example, as described herein. In particular, the molded articles can be, for example, packaging materials, especially packaging materials for food packaging, packaging materials for cosmetics, packaging materials for pharmaceuticals, housings for electrical equipment, housings and cladding for medical equipment, children's toys, sheet-like wall elements, insulated transport containers, sanitary and bathroom equipment.

[0098] According to the present invention, in addition to the recycled heat-resistant polystyrene composition P itself, the molded article may comprise 1 to 99% by weight, preferably 2 to 70% by weight, often 5 to 50% by weight, of the recycled heat-resistant polystyrene composition P according to the present invention, based on the total weight of the polymer blend P*, and 1 to 99% by weight, preferably 30 to 98% by weight, often 50 to 95% by weight, based on the total weight of the polymer blend P*, of a virgin polymer composition comprising polystyrene, high-impact polystyrene and mixtures thereof.

[0099] Furthermore, in an alternative embodiment, the molded article may be a layered structure S comprising at least two layers, preferably at least three layers, with at least one layer corresponding to the recycled heat-resistant polystyrene composition P according to the present invention and at least one layer corresponding to a polymer composition P' different from the recycled heat-resistant polystyrene composition P. In one preferred embodiment for this purpose, the layered structure is a three-layer extruded structure having a P'-P-P' layer arrangement, i.e., a three-layer structure S, in which the recycled heat-resistant polystyrene composition P corresponds to a central layer covering both expanded surfaces, and at least one of the layers covering the central layer is made from a polymer composition P' different from the recycled heat-resistant polystyrene composition P according to the present invention.

[0100] Often, the polymer composition P' is a virgin composition P' comprising polystyrene, high impact polystyrene or a mixture thereof.

[0101] The invention is further illustrated by the following examples and claims. [Example]

[0102] 1. Effect of the initiation process on the heat resistance of polystyrene compositions Impact-modified polystyrene (HIPS) was produced in a standard two-vessel, two-tower polymerization cascade, where the first vessel was a prepolymerization vessel, which was fed with a polybutadiene rubber solution and styrene. The second vessel was where the phase inversion to the final HIPS form occurred. The resulting HIPS contained polybutadiene rubber particles with an average diameter of 2 μm in a polystyrene matrix with a total polybutadiene content of 8% by weight.

[0103] Polymerization was initiated by various mechanisms: Example 1: Thermal start at a temperature between about 110°C and 140°C. Example 2: Radical initiation using 180 ppm of 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (CAS no. 6731-36-8) as initiator. Example 3 (comparison): Radical initiation using 180 ppm benzoyl peroxide (perbenzoic anhydride, CAS number 94-36-0) as initiator.

[0104] The HIPS obtained according to Examples 1 to 3 was mixed with 600 ppm of zinc stearate and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS number: 2082-79-3, Irganox (R) 1076, BASF) and further mixed with 400 ppm.

[0105] The regeneration of styrene monomer was then investigated by carrying out multiple extrusions at high temperatures using a high shear screw. The severe conditions allow for good differentiation between samples. Extrusion tests were carried out at high temperatures and shear to enhance the remonomerization. This process simulates the conditions during the (repeated) regeneration process of waste polymer materials. The following conditions were applied: Extruder: Coperion ZSK 30 Temperature: 260℃ Rotation speed: 200 l / min Processing capacity 10 kg / hour No degassing.

[0106] To determine the degradation of the polymer structure during the extrusion runs, the viscosity number VN of each composition was measured before the first extrusion run and after each extrusion run. The viscosity number VN was measured according to DIN 53726.

[0107] [Table 1]

[0108] The experimental data in Table 1 show that the viscosity number VN of a 0.5 wt. % solution of each polymer composition decreases for all HIPS polymer compositions after several extrusion runs. However, the thermally initiated HIPS of Example 1 is more stable than the radically initiated HIPS product. Among the radically initiated HIPS products, the HIPS product of Example 2 initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane is advantageous in terms of heat resistance.

[0109] 2. Effect of phenolic antioxidant B on the heat resistance of polystyrene compositions Polystyrene compositions according to Table 2 were prepared using the following ingredients: A: High impact polystyrene (HIPS) with a polybutadiene content of 8% by weight, a styrene content of 89% by weight, and a medical white oil (DAB70) content of 3% by weight. Polymerization was initiated using 180 ppm (based on the total weight of the reaction mixture) of 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (CAS No. 6731-36-8) as an initiator. Component A further contains 600 ppm (i.e., 0.06% by weight based on the total weight of the HIPS and medical white oil) of zinc stearate. B-1: Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS number: 2082-79-3, Irganox (R) 1076, BASF) B-2: 2,6-di-tert-butyl-p-cresol (CAS No. 87-97-8, Kerobit (R) TBK)

[0110] The compositions according to Table 2 were prepared using an extruder at an extrusion temperature of 260°C.

[0111] [Table 2]

[0112] The compositions according to Examples 4, 5 and 6 were repeatedly extruded. This process simulates the conditions during the (repeated) recycling process of waste polymeric materials. The following conditions were applied: Extruder: Coperion ZSK 30 Temperature: 260℃ Rotation speed: 200 l / min Processing capacity: 10 kg / hour No degassing.

[0113] To determine remonomerization due to degradation of the polymer structure during the extrusion run, styrene levels were measured for each composition before the first extrusion run and after the first, third, and fifth extrusion runs. Styrene levels were measured by capillary gas chromatography using headspace techniques and a styrene-based calibration curve.

[0114] [Table 3]

[0115] The data in Table 3 show that the addition of sterically hindered phenolic antioxidant B in accordance with the present invention reduces the formation and release of monomeric styrene during repeated extrusion runs.

[0116] Thus, the recycled heat-resistant polystyrene compositions and methods described herein allow for the production of polystyrene compositions and products with better quality, which can be used, for example, in food packaging. The methods are also ecologically advantageous.

Claims

1. A recycled heat-resistant polystyrene composition P is: A: As component A, A-1: Component A-1 is at least one recycled polystyrene [wherein the polystyrene is obtained by thermally initiated and / or radical polymerization initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane]; A-2: Depending on the circumstances, component A-2 may include styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C 3 ~C 12 At least one impact-improving polymer comprising polymer particles derived from at least one monomer selected from alpha-olefins and combinations thereof; and A-3: Depending on the case, at least one additive as component A-3. A recycled polystyrene composition comprising at least one such composition; B: Component B is at least one sterically hindrance phenolic antioxidant; and C: Depending on the case, at least one additive as component C; Includes, Here, recycled polystyrene is obtained from waste plastic material, as described above for the recycled heat-resistant polystyrene composition P.

2. A: Component A is at least one recycled polystyrene in an amount of 95 to 99.9% by mass based on recycled heat-resistant polystyrene composition P; B: As component B, at least one sterically hindrance phenolic antioxidant in 0.1 to 1% by mass based on recycled heat-resistant polystyrene composition P; and C: As component C, at least one additive in 0 to 4% by mass based on the recycled heat-resistant polystyrene composition P. The recycled heat-resistant polystyrene composition P according to claim 1, comprising:

3. As component B: Based on recycled heat-resistant polystyrene composition P, in an amount of 0.1 to 0.5% by mass, general formula (I): 【Chemistry 1】 [In the formula, R1 to R5 independently represent a hydrogen atom or an alkyl group having 1 to 70 carbon atoms, wherein the hydrocarbon group optionally contains at least one heteroatom selected from O and S, and wherein at least one of the substituents R1 and R5 represents a hydrocarbon group having at least 3 carbon atoms.] At least one sterically hindrance phenolic antioxidant selected from the compounds A recycled heat-resistant polystyrene composition P according to claim 1 or 2, comprising the above.

4. A: As component A, based on recycled heat-resistant polystyrene composition P, in an amount of 97.5 to 99.9% by mass, A-1: Component A-1 is at least one polystyrene [wherein polystyrene A-1 is produced by thermally initiated radical polymerization]; A-2: Component A-2 consists of styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C 3 ~C 12 At least one impact-improved polymer A-2 comprising polymer particles derived from at least one monomer selected from alpha-olefins and combinations thereof; and A-3: Depending on the case, at least one additive as component A-3. at least one recycled polystyrene, including; B: As component B, 0.1 to 0.5% by mass based on recycled heat-resistant polystyrene composition P, at least one sterically hindered phenolic antioxidant selected from 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid octadecyl (CAS No. 2082-79-3), 2,6-di-tert-butyl-p-cresol (CAS No. 87-97-8), and mixtures thereof; and C: As component C, at least one additive in 0 to 2% by mass based on the recycled heat-resistant polystyrene composition P. A recycled heat-resistant polystyrene composition P according to claim 1 or 2, comprising the above.

5. A method for providing excellent heat resistance in the mechanical regeneration process of polystyrene, and for providing a regenerated heat-resistant polystyrene composition P, wherein the method comprises the following steps: (i) A step of regenerating a polystyrene composition A obtained from waste plastic material, comprising as component A-1 at least one recycled polystyrene obtained by radical polymerization that is thermally initiated and / or initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; (ii) A step of mixing the recycled polystyrene composition A with at least one sterically hindered phenolic antioxidant as component B and optionally at least one further additive as component C; and (iii) A step of extruding a mixture obtained comprising recycled polystyrene composition A, at least one sterically hindered phenolic antioxidant B, and optionally at least one further additive C. The above method, including.

6. Polystyrene composition A is: A-1: Component A-1 is at least one polystyrene; A-2: Depending on the circumstances, component A-2 may include styrene, 1,3-butadiene, isoprene, acrylonitrile, ethylene, C 3 ~C 12 At least one impact-improved polymer comprising polymer particles derived from at least one monomer selected from alpha-olefins and combinations thereof; and A-3: Depending on the case, at least one additive as component A-3. The method according to claim 5, including the method described in claim 5.

7. The method according to claim 5 or 6, wherein the polystyrene of polystyrene A-1 is obtained by a thermally initiated radical polymerization process.

8. The method according to claim 5 or 6, wherein the polystyrene of polystyrene A-1 is obtained by a radical polymerization process initiated with 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane.

9. At least one sterically hindrance phenolic antioxidant B is defined by general formula (I): 【Chemistry 2】 [In the formula, R1 to R5 independently represent a hydrogen atom or an alkyl group having 1 to 70 carbon atoms, wherein the hydrocarbon group optionally contains at least one heteroatom selected from O and S, and wherein at least one of substituents R1 and R5 represents a hydrocarbon group having at least 3 carbon atoms. The method according to claim 5 or 6, selected from the compounds.

10. The method according to claim 5 or 6, wherein at least one sterically hindered phenolic antioxidant B is selected from octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No.: 2082-79-3), 2,6-di-tert-butyl-p-cresol (CAS No.: 87-97-8), 2-(1,1-dimethylethyl)-6-[(3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]-methyl-4-methylphenyl acrylate (CAS No.: 61167-58-6), and mixtures thereof.

11. A method for producing a molded article by extrusion molding of the recycled heat-resistant polystyrene composition P described in claim 1.

12. A method for producing a molded article by extrusion molding of a recycled heat-resistant polystyrene composition P obtained according to the method of claim 5.

13. The method according to claim 11 or 12 for manufacturing an extruded sheet.

14. A method for producing the recycled heat-resistant polystyrene composition P according to claim 1 or 2, wherein components A and B, and optionally C, are melt-mixed at a temperature in the range of 180 to 280°C.

15. A molded article manufactured from the recycled heat-resistant polystyrene composition P described in claim 1 or 2.

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