Method for producing graft copolymer powder composition and thermoplastic resin composition

Abstract

The present invention relates to a method for producing a graft copolymer composition based on acrylonitrile-styrene-acrylate (ASA) or acrylonitrile-butadiene-styrene (ABS) graft copolymers. The graft copolymer composition is obtained by emulsion polymerization and subsequent precipitation, dehydration, drying, and optionally cold drying of a graft copolymer powder, wherein the obtained graft copolymer B powder is mixed with an aeration gas (preferably air and / or nitrogen), wherein during the entire aeration step, the bulk density of the graft copolymer B powder is equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B. The graft copolymer powder exhibits high powder flowability and a reduced tendency to agglomerate during storage (e.g., in a silo).

Description

[0001] The present invention relates to a method for producing a graft copolymer composition based on an acrylonitrile-styrene-acrylate (ASA) or acrylonitrile-butadiene-styrene (ABS) graft copolymer. The graft copolymer composition is obtained by emulsion polymerization and subsequent precipitation, dehydration, drying and optionally cold drying of a graft copolymer powder, wherein the obtained graft copolymer B powder is mixed with an aeration gas (preferably air and / or nitrogen), wherein the bulk density of the graft copolymer B powder during the entire aeration step is equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B. The graft copolymer powder exhibits high powder flowability and a reduced tendency to agglomerate during storage, for example in a silo.

[0002] Furthermore, the present invention relates to a process for producing a thermoplastic molding composition comprising at least one thermoplastic styrene copolymer, in particular a styrene-acrylonitrile copolymer; the graft copolymer composition obtainable by the process of the invention; and optionally further components.

[0003] For decades, ABS copolymers and ASA copolymers have been widely used as thermoplastic molding compositions for producing various types of molded articles. It is known that styrene-acrylonitrile (SAN) and / or α-methylstyrene-acrylonitrile (AMSAN) copolymers can be modified to improve impact resistance by incorporating one or more grafted rubbers (hereinafter also referred to as graft copolymers, such as grafted polybutadiene rubber or grafted cross-linked acrylates). These impact-modified SAN molding compositions can be produced by polymerizing styrene and acrylonitrile in the presence of, for example, polybutadiene rubber, and / or by subsequent blending of the graft copolymers with a separately produced styrene-acrylonitrile matrix.

[0004] A wide range of variations in the property profiles of the molding compositions and the moldings produced therefrom is possible. Particularly important properties of ABS and ASA molding compositions are excellent mechanical properties, such as high toughness and impact resistance, good processability and relatively high heat resistance.

[0005] Typically, grafted rubber copolymers are produced by preparing a crosslinked acrylate latex or butadiene latex as a graft base by emulsion polymerization, and subsequently grafting, for example, styrene and acrylonitrile or a mixture of corresponding monomers by graft emulsion polymerization to produce one or more graft shells. WO 2015 / 078751 describes the effect of the particle size of the graft copolymer latex on the mechanical properties of impact-modified thermoplastic compositions.

[0006] After emulsion polymerization, the graft copolymer latex is typically precipitated using salt and / or acid solutions to produce a coarse particle suspension, e.g., particles with an average diameter D 50 In the range of 500 to 1500 μ m (for example, measured by sieve analysis). Using metal cations to precipitate polymer latex (being called coagulation) is well-known and described in many documents, for example in DE-A 2 021398, DE-A 2 815 098 and EP-B 0 459 161. Usually, most of water is removed from this suspension by centrifugation or filtration. The gained rubber is a wet powder, which can be directly fed to an extruder to carry out primary mixing and dehydration (see for example EP-A 0 734 825) subsequently. Alternatively, the gained rubber wet powder can be dried using a conventional method.

[0007] ASA and ABS graft copolymers are typically used in the subsequent mixing steps in dry powder form. Typically, the graft copolymer powder needs to be stored in, for example, silos containing several tons of polymer prior to subsequent processing. Generally speaking, the powder tends to clump and solidify over time in the storage silo. As a result, it is difficult or even impossible to discharge the graft copolymer powder from the silo. This situation is a serious problem in production because it makes it difficult to transport and add rubber powder to the extruder. The present invention describes a method for overcoming these shortcomings.

[0008] Surprisingly, it has been found that by cooling the graft copolymer powder after the drying step in a cooling air stream at a temperature of 50° C. or less, preferably 40° C. or less, the agglomeration and consolidation of the powder over time can be significantly reduced or even prevented. Furthermore, it has been found that aeration of the graft copolymer powder during storage, preferably at a temperature of 50° C. or less, significantly prevents agglomeration and consolidation over time. For example, aeration can be performed by external recirculation, wherein a certain amount of graft copolymer powder is conveyed by air from the outlet of the storage silo back to the top of the storage silo.

[0009] The present invention relates to a method for producing a graft copolymer composition comprising (preferably consisting of) the following monomers:

[0010] B: 90 to 100% by weight, preferably 95 to 100% by weight, of at least one graft copolymer B comprising:

[0011] B1: 50 to 90% by weight, preferably 55 to 90% by weight, more preferably 55 to 65% by weight, based on the graft copolymer B, of at least one graft base B1 obtained by emulsion polymerization of the following monomers:

[0012] B11: 50 to 100% by weight, preferably 87 to 99.5% by weight, based on the graft base B1, of at least one monomer B11 selected from C1-C8 alkyl (meth)acrylates (preferably n-butyl acrylate) and butadiene;

[0013] B12: 0 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 1 to 2.5 wt % of at least one multifunctional crosslinking monomer B12, based on the graft group B1; the multifunctional crosslinking monomer B12 is preferably selected from allyl (meth)acrylate, divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and dihydrodicyclopentadienyl acrylate (DCPA).

[0014] B13: 0 to 50% by weight, preferably 0 to 20% by weight, more preferably 0 to 10% by weight, based on the graft base B1, of at least one other monomer B13, the other monomer B13 being selected from styrene, α-methylstyrene, C1-C4 alkylstyrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, chloroprene, methyl methacrylate, alkylene glycol di(meth)acrylate and vinyl methyl ether;

[0015] wherein the sum of B11, B12 and B13 equals 100 wt %; and

[0016] B2: 10 to 50% by weight, preferably 10 to 45% by weight, more preferably 30 to 45% by weight, based on the graft copolymer B, of at least one graft shell B2, obtained by emulsion polymerization of the following monomers in the presence of at least one grafting base B1:

[0017] B21: 50 to 100% by weight, preferably 50 to 95% by weight, more preferably 65 to 80% by weight, most preferably 75 to 80% by weight, based on the graft shell B2, of at least one vinylaromatic monomer B21 selected from styrene, α-methylstyrene or a mixture of styrene with at least one further monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl(meth)acrylates, preferably C1-C4 alkyl(meth)acrylates, for example methyl methacrylate or ethyl methacrylate; and

[0018] B22: 0 to 50% by weight, preferably 5 to 50% by weight, more preferably 20 to 35% by weight, most preferably 20 to 25% by weight, based on the graft shell B2, of at least one monomer B22 chosen from acrylonitrile or a mixture of acrylonitrile with at least one further monomer chosen from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids, for example maleic anhydride or phthalic anhydride, and imides of unsaturated carboxylic acids, for example N-substituted maleimides, such as N-cyclohexylmaleimide or N-phenylmaleimide;

[0019] The total of the graft base B1 and the graft shell B2 is 100% by weight,

[0020] K1: 0 to 10% by weight, preferably 0 to 5% by weight, of at least one further component K1,

[0021] The method comprises the following steps:

[0022] a) preparing at least one graft copolymer B, which comprises the emulsion polymerization of monomers B21 and B22 in the presence of at least one grafting base B1 to form at least one graft shell B2, wherein the graft copolymer B is obtained in the form of a latex;

[0023] b) precipitating at least one graft copolymer B latex after the emulsion polymerization in step a), wherein the graft copolymer B latex is mixed with at least one precipitation solution PS, thereby producing a precipitation mixture;

[0024] c) mechanically dewatering the precipitated graft copolymer B, wherein a graft copolymer B having a water content of equal to or less than 50% by weight, preferably equal to or less than 40% by weight, is obtained;

[0025] d) optionally washing the dehydrated graft copolymer B;

[0026] e) drying the dehydrated graft copolymer B obtained in step c) or d) using a drying gas having a temperature in the range of 50° C. to 160° C., wherein a graft copolymer B powder is obtained;

[0027] f) optionally cooling the dried graft copolymer B powder obtained in step e) using a cooling gas, wherein the temperature of the cooling gas is equal to or less than 50° C., preferably equal to or less than 40° C.; more preferably equal to or less than 30° C., and wherein the cooling gas passes through the graft copolymer B powder;

[0028] g) aerating the graft copolymer B, wherein the graft copolymer B powder obtained in step e) or f) is mixed with an aerating gas, wherein during the entire aerating step g) the bulk density of the graft copolymer B powder is equal to or less than 98.5%, preferably 97.5%, of the bulk density of the unaerated graft copolymer B;

[0029] h) Optionally adding one or more optional components K1, preferably selected from stabilizers, release agents, plasticizers and pigments.

[0030] Preferably, the graft copolymer composition obtained by the process is a graft copolymer B powder having a water content of less than 5 wt%, preferably less than 1 wt%, preferably in the range of 0.05 to 0.8 wt%, preferably 0.1 to 0.5 wt%, particularly preferably 0.1 to 0.3 wt%.

[0031] Preferably, the graft copolymer composition obtained by the process of the present invention is a powder having a Jenike flow factor (FFC) value (fluidity) equal to or greater than 2, preferably equal to or greater than 3, preferably greater than 2, preferably greater than 3, as measured according to ASTM 6773-2008. Preferably, this fluidity is maintained throughout the aeration step g). Preferably, this fluidity is maintained during storage (without aeration) for up to 24 hours, preferably for up to 12 hours. In particular, the fluidity is maintained after storage at a temperature equal to or less than 50° C., preferably equal to or less than 40° C., more preferably equal to or less than 30° C.

[0032] Graft copolymer B

[0033] The graft copolymer composition comprises at least 90% by weight, preferably at least 95% by weight, based on the total graft copolymer composition, of at least one graft copolymer B. Preferred embodiments are described below.

[0034] Preferably, the graft copolymer B is selected from ASA graft copolymers and ABS graft copolymers. ASA graft copolymers generally contain a crosslinked poly(meth)acrylate rubber as the graft base B1, in particular a crosslinked polybutyl acrylate graft base B1. ABS graft copolymers generally contain one or more polybutadiene rubbers and / or styrene-butadiene rubbers as the graft base B1.

[0035] Typically, the graft base B1 consists of a polymer (preferably an at least partially crosslinked polymer) having a glass transition temperature below 0°C, preferably below -20°C, more preferably below -40°C, wherein the glass transition temperature T g The measurement was performed by dynamic mechanical analysis (DMA) using a frequency of 1 Hz.

[0036] The at least one graft shell B2 generally consists of monomers which copolymerize to give a polymer having a glass transition temperature of greater than +20° C., preferably greater than +60° C. Preferred monomers of the graft shell B2 (monomers B21 and B22) are selected from styrene, α-methylstyrene, (meth)acrylonitrile, methyl (meth)acrylate, ethyl acrylate, N-phenylmaleimide and maleic anhydride.

[0037] Preferred monomers B11 for producing the graft base B1 are butadiene, alkyl acrylates and / or alkyl methacrylates (also known as alkyl (meth)acrylates), wherein the alkyl group has 1 to 8, preferably 4 to 8, carbon atoms. Preferably, monomer B11 is at least one monomer selected from C4-C8 alkyl acrylates, preferably butyl acrylate, ethylhexyl acrylate and cyclohexyl acrylate. Typically, n-butyl acrylate and / or 2-ethylhexyl acrylate are used as monomer B11, more preferably n-butyl acrylate alone or in mixtures with other monomers B11.

[0038] In order to crosslink the C1-C8 alkyl (meth)acrylate monomers B11 and thus the graft groups B1, monomers B11 are polymerized in the presence of 0.1 to 10% by weight, preferably 0.1 to 5% by weight, preferably 0.5 to 3% by weight, preferably 1 to 4% by weight, and more preferably 1 to 2.5% by weight, based on the graft groups B1, of one or more polyfunctional crosslinking monomers B12. Suitable monomers B12 are polyfunctional crosslinking monomers that are copolymerizable, in particular, with the aforementioned monomers, especially B11 and B13. Suitable polyfunctional crosslinking monomers B12 contain two or more, preferably two or three, more preferably exactly two, olefinic double bonds, which are preferably not 1,3-conjugated. Examples of suitable polyfunctional crosslinking monomers B12 are allyl (meth)acrylate, divinylbenzene, diallyl esters of dicarboxylic acids, such as, for example, diallyl maleate, diallyl fumarate, and diallyl phthalate. Acrylic esters of tricyclodecenol (tricyclodecenyl acrylate; dihydrodicyclopentadienyl acrylate, DCPA), as described in DE-A 1 260135, also represent preferred polyfunctional crosslinking monomers B12.

[0039] In particular, the multifunctional crosslinking monomer B12 (preferably used for crosslinking polyalkyl (meth)acrylate rubber) is at least one monomer selected from the group consisting of allyl (meth)acrylate (AMA), divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate and dihydrodicyclopentadienyl acrylate (DCPA), preferably allyl (meth)acrylate, divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate and DCPA, preferably selected from the group consisting of allyl (meth)acrylate and DCPA.

[0040] In a preferred embodiment, 1 to 2.5% by weight, preferably 1.5 to 2.2% by weight, based on the graft base B1, of dihydrodicyclopentadienyl acrylate (DCPA) is used as monomer B12, alone or in a mixture with at least one other of the above-mentioned monomers B12, in particular with allyl (meth)acrylate.

[0041] Furthermore, at least one graft group B1 may optionally comprise one or more copolymerizable monoethylenically unsaturated monomers B13 different from B11 and B12. Monomer B13 may, for example, be selected from butadiene, isoprene, styrene, acrylonitrile, methyl (meth)acrylate and vinyl methyl ether.

[0042] Preferably, the other monomer B13 is at least one monomer selected from styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, methyl (meth)acrylate, isoprene, chloroprene and C1-C4 alkylstyrene.

[0043] In a preferred embodiment, the vinyl aromatic monomer B21 (specifically, each of monomers B21, B21′ and B21″) is styrene and / or α-methylstyrene, and the at least one ethylenically unsaturated monomer B22 (specifically, each of monomers B22 and B22″) is acrylonitrile or a mixture of acrylonitrile and at least one monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, maleic anhydride, phthalic anhydride, N-cyclohexylmaleimide and N-phenylmaleimide. More preferably, the monomers B21 and B22 used in the emulsion polymerization of the graft copolymer B are a mixture of styrene and acrylonitrile, wherein the weight ratio of styrene to acrylonitrile is in the range of 95:5 to 50:50, more preferably in the range of 80:20 to 65:35.

[0044] In a preferred embodiment, at least one grafting group B1 is obtained by emulsion polymerization of the following monomers:

[0045] B11: 70 to 99.9% by weight, preferably 87 to 99.5% by weight, based on the graft base B1, of at least one C1-C8 alkyl (meth)acrylate as monomer B11, preferably n-butyl acrylate and / or 2-ethylhexyl acrylate;

[0046] B12: 0.1 to 10 wt %, preferably 0.1 to 5 wt %, more preferably 1 to 2.5 wt %, based on the graft group B1, of at least one multifunctional crosslinking monomer B12; the multifunctional crosslinking monomer B12 is preferably selected from allyl (meth)acrylate, divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate and dihydrodicyclopentadienyl acrylate (DCPA);

[0047] B13: 0 to 29.5% by weight, preferably 0 to 25% by weight, more preferably 0 to 10% by weight, based on the graft base B1, of at least one other monomer, preferably selected from styrene, α-methylstyrene, C1-C4-alkylstyrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, chloroprene, methyl methacrylate, alkylene glycol di(meth)acrylates and vinyl methyl ether,

[0048] The sum of B11, B12 and B13 is 100% by weight.

[0049] In another preferred embodiment, the at least one grafting group B1 is obtained by emulsion polymerization of the following monomers:

[0050] B11: 90 to 99.9% by weight, preferably 97 to 99.5% by weight, more preferably 97.5 to 99% by weight, of at least one C1-C8 alkyl (meth)acrylate as monomer B11, based on the graft base B1, preferably at least one C4-C8 alkyl (meth)acrylate, more preferably n-butyl acrylate and / or 2-ethylhexyl acrylate, most preferably n-butyl acrylate; and

[0051] B12: 0.1 to 10 wt %, preferably 0.5 to 3 wt %, more preferably 1 to 2.5 wt %, based on the graft group B1, of at least one multifunctional crosslinking monomer B12; the multifunctional crosslinking monomer B12 is selected from allyl (meth)acrylate, divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate and dihydrodicyclopentadienyl acrylate (DCPA), in particular from allyl (meth)acrylate and / or dihydrodicyclopentadienyl acrylate (DCPA);

[0052] The sum of B11 and B12 is 100% by weight (based on all monomers of the graft group B1).

[0053] In particular, further suitable compositions of the graft base B1 comprising monomers B11, B12 and optionally B13 and general processes for their preparation are described, for example, in DE-A 28 26 925, DE-A 31 49 358 and DE-A 34 14 118.

[0054] In a preferred embodiment, the at least one graft shell B2 is obtained by emulsion polymerization of the following monomers in the presence of at least one grafting base B1:

[0055] B21: 50 to 95% by weight, preferably 65 to 80% by weight, more preferably 70 to 80% by weight, based on the graft shell B2, of at least one vinylaromatic monomer B21, wherein monomer B21 is selected from styrene, α-methylstyrene or a mixture of styrene with one further monomer selected from α-methylstyrene, p-methylstyrene, C1-C4 alkyl(meth)acrylates (e.g. methyl(meth)acrylate, ethyl(meth)acrylate), preferably selected from styrene, α-methylstyrene or a mixture of styrene with α-methylstyrene or methyl(meth)acrylate, and

[0056] B22: 5 to 50% by weight, preferably 20 to 45% by weight, more preferably 20 to 40% by weight, further preferably 20 to 36% by weight, further preferably 20 to 33% by weight, based on the graft shell B2, of at least one ethylenically unsaturated monomer B22, where monomer B22 is chosen from acrylonitrile or a mixture of acrylonitrile with at least one further monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids (for example maleic anhydride, phthalic anhydride) and imides of unsaturated carboxylic acids (for example N-substituted maleimides, such as N-cyclohexylmaleimide and N-phenylmaleimide), preferably from acrylonitrile or a mixture of acrylonitrile with methacrylonitrile.

[0057] In particular, the graft copolymer B comprises a graft base B1, preferably a crosslinked polyalkyl (meth)acrylate rubber as described above, and one or more graft shells B2, in particular one, two or three graft shells B2, which differ in the selection and amount of monomers B21 and B22 and are obtained by stepwise graft emulsion polymerization of monomers B21 and / or B22 in the presence of the graft base B1 in the presence of the already grafted graft base.

[0058] In a preferred embodiment, the graft copolymer B comprises at least one graft base B1, preferably the above-mentioned crosslinked polybutyl acrylate rubber, and exactly one graft shell B2, which is obtained by emulsion polymerization of the monomers B21 and B22 as described above, in particular styrene and acrylonitrile, in the presence of the graft base B1 (single-stage grafting).

[0059] In another preferred embodiment, the graft copolymer B comprises at least one grafting base B1, preferably the above-mentioned crosslinked polybutyl acrylate rubber, and two graft shells B2' and B2", wherein B2' is obtained by emulsion polymerization of monomers B21 (especially styrene) in the presence of the grafting base B1, and the graft shell B2" is obtained by subsequent emulsion polymerization of monomers B21 and B22 (especially styrene and acrylonitrile) as described above in the presence of the grafting base B1 grafted to B2' (two-stage grafting).

[0060] In a preferred embodiment (single-step grafting), the graft copolymer B comprises:

[0061] B1: Based on the graft copolymer B, 50 to 70% by weight, preferably 55 to 65% by weight, more preferably 58 to 65% by weight of at least one, preferably exactly one, graft base B1 as described above, wherein preferably the particle size (especially the average particle size D w ) in the range of 60 to 200 nm, preferably 60 to 150 nm, more preferably 60 to 100 nm;

[0062] B2: 30 to 50% by weight, preferably 35 to 45% by weight, more preferably 35 to 42% by weight, based on the graft copolymer B, of one or more, preferably exactly one, graft shell B2, obtained by emulsion polymerization of the following monomers in the presence of at least one grafting base B1:

[0063] B21: 50 to 95% by weight, preferably 65 to 80% by weight, more preferably 70 to 80% by weight, based on the graft shell B2, of at least one vinylaromatic monomer B21, wherein monomer B21 is selected from styrene, α-methylstyrene or a mixture of styrene with at least one further monomer selected from α-methylstyrene, p-methylstyrene and C1-C4 alkyl(meth)acrylates (e.g. methyl(meth)acrylate, ethyl(meth)acrylate), preferably selected from styrene, α-methylstyrene or a mixture of styrene with α-methylstyrene or methyl(meth)acrylate; and

[0064] B22: 5 to 50% by weight, preferably 20 to 35% by weight, more preferably 20 to 30% by weight, based on the graft shell B2, of at least one ethylenically unsaturated monomer B22, wherein monomer B22 is selected from acrylonitrile or a mixture of acrylonitrile with at least one further monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids (for example maleic anhydride, phthalic anhydride) and imides of unsaturated carboxylic acids (for example N-substituted maleimides, such as N-cyclohexylmaleimide and N-phenylmaleimide), preferably from acrylonitrile or a mixture of acrylonitrile with methacrylonitrile;

[0065] The total of the graft base B1 and the graft shell B2 is 100% by weight, and the particle size (especially the average particle size D) of the graft copolymer B latex obtained in step a) is w ) is in the range of 60 to 140 nm. In another preferred embodiment (two-step grafting B2' and B2"), the graft copolymer B comprises:

[0066] B1: Based on the graft copolymer B, 50 to 70% by weight, preferably 55 to 65% by weight, more preferably 58 to 65% by weight of at least one, preferably exactly one, graft base B1 as described above, wherein preferably the particle size (especially the average particle size D w ) in the range of 200 to 800 nm, preferably 300 to 600 nm, more preferably 350 to 550 nm;

[0067] B2′: 10 to 30% by weight, preferably 10 to 20% by weight, more preferably 10 to 15% by weight, based on the graft copolymer B, of at least one graft shell B2′, obtained by emulsion polymerization of the following monomers in the presence of the graft base B1:

[0068] B21′: 100% by weight, based on the graft shell B2′, of at least one vinylaromatic monomer B21′, the vinylaromatic monomer B21′ being selected from styrene, α-methylstyrene or a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C4 alkyl(meth)acrylates (e.g. methyl(meth)acrylate, ethyl(meth)acrylate); and

[0069] B2": 20 to 40% by weight, preferably 20 to 30% by weight, more preferably 25 to 30% by weight, based on the graft copolymer B, of at least one graft shell B2", obtained by emulsion polymerization of the following monomers in the presence of the graft base B1 to which B2' is grafted:

[0070] B21": 50 to 95% by weight, preferably 65 to 80% by weight, more preferably 70 to 80% by weight, based on the graft shell B2", of at least one vinylaromatic monomer B21", selected from styrene, α-methylstyrene or a mixture of styrene with at least one further monomer selected from α-methylstyrene, p-methylstyrene and C1-C4 alkyl(meth)acrylates (e.g. methyl(meth)acrylate, ethyl(meth)acrylate), preferably selected from styrene, α-methylstyrene or a mixture of styrene with α-methylstyrene or methyl(meth)acrylate; and

[0071] B22": 5 to 50% by weight, preferably 20 to 35% by weight, more preferably 20 to 30% by weight, based on the graft shell B2", of at least one ethylenically unsaturated monomer B22", chosen from acrylonitrile or a mixture of acrylonitrile with at least one further monomer chosen from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids (for example maleic anhydride, phthalic anhydride) and imides of unsaturated carboxylic acids (for example N-substituted maleimides, such as N-cyclohexylmaleimide and N-phenylmaleimide), preferably chosen from acrylonitrile or a mixture of acrylonitrile with methacrylonitrile;

[0072] The total of the graft base B1, the graft shell B2′ and the graft shell B2″ is 100% by weight, and the particle size (especially the average particle size D) of the graft copolymer B latex obtained in step a) is w ) in the range of 300 to 700nm.

[0073] According to a preferred embodiment, the graft copolymer B is a mixture of the above-mentioned single-step graft copolymer B and the two-step graft copolymer B (comprising grafts B2′ and B2″).

[0074] More preferably, monomers B21, B21′ and B21″ are styrene or a mixture of styrene and α-methylstyrene.

[0075] More preferably, monomers B22 and B22" are acrylonitrile or a mixture of acrylonitrile and at least one other monomer selected from methacrylonitrile, maleic anhydride, N-cyclohexylmaleimide, N-phenylmaleimide, more preferably acrylonitrile or a mixture of acrylonitrile and at least one other monomer selected from methacrylonitrile and maleic anhydride. In a more preferred embodiment of the present invention, monomers B21, B21' and B21" are styrene, and monomers B22 and B22' are acrylonitrile.

[0076] In a preferred embodiment of the present invention, the process according to the invention comprises the synthesis of at least two, preferably two, three or four different graft copolymers BI and B-II, wherein the particle sizes of the graft copolymers BI and B-II differ. In this preferred embodiment, the graft copolymer B comprises in particular at least two graft copolymers BI and B-II, preferably based on a crosslinked C1-C8 alkyl (meth)acrylate graft group B1 as described above, wherein:

[0077] The particle size of the graft copolymer BI (small size ASA rubber) (especially the average particle size D w ) is in the range of 60 to 200 nm, preferably 80 to 150 nm, more preferably 90 to 100 nm, and

[0078] The particle size (average particle size D w ) is in the range of 300 to 800 nm, preferably 300 to 700 nm, more preferably 400 to 600 nm.

[0079] The graft copolymer BI (small-scale ASA rubber) is preferably obtained by emulsion polymerization of the monomers B21 and B22 as described above (especially styrene or α-methylstyrene as B21 and acrylonitrile as B22) in the presence of a previously prepared graft base B1 as described above, for example for the single-step graft copolymer B.

[0080] In a preferred embodiment, the graft copolymer B is a graft copolymer having a core-shell structure produced by emulsion polymerization, wherein the core-shell structure comprises a core B1 and three layers B2 to B4 in the order B1 to B4 from the inside to the outside (for example, as described in PCT / EP2019 / 069698), wherein the graft copolymer is composed of the following monomers:

[0081] B1: 6 to 19% by weight of a core B1 comprising at least one copolymer consisting of the following monomers:

[0082] B11: 95.0 to 99.9 weight percent of at least one vinyl aromatic monomer, and

[0083] B12: 0.1 to 5.0 wt. % of at least one difunctional or polyfunctional crosslinking monomer;

[0084] B2: 41 to 54% by weight of an outer core layer B2 grafted onto B1, said outer core layer consisting of at least one copolymer comprising the following monomers:

[0085] B21: up to 99.0% by weight of at least one C2-C8 alkyl acrylate;

[0086] B22: 1.0 to 5.0 wt. % of one or more difunctional or polyfunctional crosslinking monomers;

[0087] B3: 1 to 19% by weight of a first graft shell B3 consisting of at least one vinylarene polymer; and

[0088] B4: 21 to 39% by weight of a second graft shell B4 consisting of at least one copolymer comprising at least one vinylarene monomer B41 and at least one nitrile monomer B42;

[0089] wherein B1, B2, B3 and B4 add up to 100% by weight; and

[0090] The weight average particle size d of the graft copolymer B is wIn the range of 280 to 450 nm, preferably 310 to 370 nm, more preferably 320 to 360 nm.

[0091] Preferably, the graft copolymer B-II (large-size ASA rubber) needs to have a narrow particle size distribution, wherein the particle size distribution Q=(D 90 -D 10 ) / D 50 Less than 0.3, preferably less than 0.2.

[0092] In another embodiment, the graft copolymer B may be an ABS graft copolymer comprising the following monomers:

[0093] B1: 40 to 80% by weight, preferably 50 to 70% by weight, more preferably 55 to 65% by weight, based on the graft copolymer B, of at least one graft base B1 obtained by emulsion polymerization of butadiene as monomer B1; and

[0094] B2: 20 to 60% by weight, preferably 30 to 50% by weight, more preferably 35 to 45% by weight, based on the graft copolymer B, of at least one graft shell B2 as described above, preferably obtained by emulsion polymerization of up to 65 to 80% by weight, based on the graft shell B2, of styrene as monomer B21, and 20 to 35% by weight, based on the graft shell B2, of acrylonitrile as monomer B22, in the presence of at least one grafting group B1;

[0095] The total weight of the graft base B1 and the graft shell B2 is 100 wt %; and the particle size of the ABS graft copolymer B latex (particularly the average particle size D w ) in the range of 100 to 500 nm.

[0096] Generally, the particle size of the graft copolymer B latex can be given as the weight average particle size D w For example, the weight average particle size D w The turbidity measurement can be used as described in H. Lange, "Colloid-Zeitschrift und Zeitschrift für Polymere", Vol. 223, No. 1. The weight-average particle size D w (or De Broucker average particle size), also known as average particle size D w , is the average size per unit weight of the particles.

[0097] Alternatively, the particle size can be given as the median particle size D 50, for example, determined from the particle size distribution obtained by ultracentrifuge measurement (as described in W. Scholtan, H. Lange, Journal of Colloids and Polymers, 250, pp. 782-796, 1972), electron microscopy or hydrodynamic chromatography (HDC) (as described, for example, in W. Wohlleben, H. Schuch, Measurement of Particle Size Distribution of Polymer Latexes, 2010, ed.: L. Gugliotta, J. Vega, pp. 130-153). The median particle size D 50 It means that 50% by volume of the particles (such as polyacrylate latex particles) have a particle size less than D 50 The diameter of the value and the other 50% by volume have a diameter greater than D 50 In a similar manner, for example, D 90 The value provides the particle size where 90% by volume of all particles have a smaller diameter.

[0098] Preferably, the particle size mentioned in the present invention for the graft copolymer B refers to the weight average particle size D determined using turbidity measurement as described, for example, in H. Lange, Journal of Colloids and Polymers, Vol. 223, No. 1. w value.

[0099] Suitable crosslinked C1-C8 alkyl (meth)acrylate polymer graft bases B1 (referred to as B1-II) of the graft copolymer B-II can be conveniently produced by seed polymerization as described in DE 1 911 882 for producing ASA polymers according to known procedures for producing large-scale dispersions. According to this method, a particle size (especially an average particle diameter D of 50 to 180 nm, preferably less than 120 nm) is obtained. w In the present invention, a small-sized cross-linked acrylate latex (seed latex) obtained by emulsion polymerization of a C1-C8 alkyl (meth)acrylate as monomer B11, a cross-linking monomer B12, and optionally other comonomers B13 is subjected to another polymerization reaction. In particular, the reaction conditions are adjusted so as to allow only the seed latex particles of the present invention to grow further without forming new latex particles (described in the Journal of Applied Polymer Science, Vol. 9, 1965, pp. 2929-2938). Typically, an initiator is used in the process.

[0100] The particle size of the resulting graft copolymer B-II (large-size rubber) can be adjusted by varying the ratio of seed latex to monomer. Graft copolymer B-II is preferably obtained by emulsion polymerization of monomers B21 and B22 as described above (especially styrene or α-methylstyrene as B21 and acrylonitrile as B22) in the presence of previously prepared graft base B1-II.

[0101] Preferably, the graft copolymers BI and B-II are prepared, precipitated, and dehydrated separately in steps a) to c) and optionally d) to f). It is also possible to separately produce the graft copolymer latexes BI and B-II in step a) and then mix them and precipitate them together in step b). Subsequent steps, such as the dehydration in step c) and the washing in step d), can be carried out as described.

[0102] The weight ratio of graft copolymer BI to B-II can vary within a wide range. Preferably, graft copolymer B is a mixture of graft copolymer BI and B-II, wherein the weight ratio of BI:B-II is 90:10 to 10:90, preferably 80:20 to 20:80, and more preferably 70:30 to 35:65.

[0103] Graft copolymers B having different particle sizes, in particular a bimodal particle size distribution of 60 to 200 nm and 300 to 800 nm, can also be obtained by known agglomeration procedures. Graft copolymers having large and small particles are described, for example, in DE-A 3615 607.

[0104] Furthermore, graft copolymers B having two or more different graft shells B2 can be used as described above. Furthermore, graft copolymers having a multilayer graft shell are described, for example, in EP-A 0111260 and WO 2015 / 078751.

[0105] Step a)—Preparation of graft copolymer B by emulsion polymerization

[0106] The process comprises preparing at least one graft copolymer B, which comprises the emulsion polymerization of monomers B21 and B22 in the presence of at least one grafting base B1 to form at least one graft shell B2, wherein the graft copolymer B is obtained in the form of a latex.

[0107] The graft copolymer B generally has a complex structure and is essentially composed of one or more graft groups B1 and one or more graft shells B2. Typically, the graft copolymer B is produced in the form of a latex (rubber) by emulsion polymerization in step a), wherein the one or more graft groups B1 are first obtained by emulsion polymerization of monomers B11, B12, and optionally B13, and then the one or more graft shells B2 are obtained by graft emulsion polymerization of monomers B21 and B22 in the presence of one or more of the graft groups B1.

[0108] Preferably, the graft copolymer B latex is polymerized by aqueous free-radical emulsion polymerization. The reaction is typically initiated by a water-soluble or oil-soluble free-radical polymerization initiator (e.g., an inorganic or organic peroxide, such as peroxodisulfate or benzoyl peroxide) or with the aid of a redox initiator system. Suitable polymerization processes are described in WO 2002 / 10222, DE-A 28 26 925, and EP-A 022 200.

[0109] The initiator used to produce the graft base B1 and / or the emulsion polymerization of the at least one graft copolymer B can be any desired initiator. Preference is given to using at least one organic and / or inorganic peroxide compound (containing at least one peroxide group ROOH and / or ROOR) as an initiator, for example hydrogen peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, p-methane hydroperoxide, ammonium persulfate, potassium persulfate or sodium persulfate. Inorganic peroxide salts are particularly useful, examples being ammonium, sodium or potassium peroxodisulfates (persulfates), perphosphates and perborates. Sodium persulfate and potassium persulfate are particularly preferred.

[0110] In a preferred embodiment, inorganic peroxide salts, in particular inorganic peroxodisulfate salts, preferably sodium peroxodisulfate and / or potassium peroxodisulfate, are used in the emulsion polymerization of the graft copolymer B.

[0111] The emulsifier used to produce the graft base B1 and / or the emulsion polymerization to produce at least one graft copolymer B may generally comprise conventional anionic emulsifiers. Preference is given to using the following as emulsifiers: alkyl sulfates, alkyl sulfonates, alkyl sulfonic acids, aryl sulfonates, soaps of saturated or unsaturated fatty acids, and alkaline disproportionated or hydrogenated abietic acid or tall oil acid or mixtures thereof. Preference is given to using emulsifiers having carboxyl groups (e.g., disproportionated abietic acid, C 10 -C 18 salts of fatty acids, emulsifiers according to DE-A 36 39904 and DE-A 39 13 509). In a preferred embodiment, C 10 -C 20 Alkyl sulfonic acid and / or C 10 -C 20 Alkyl sulfonates, such as C12 -C 18 Paraffin sulfonic acid is used as an emulsifier.

[0112] In a further preferred embodiment, the emulsifier used may comprise alkaline soaps of sodium and potassium salts of disproportionated and / or dehydrogenated and / or hydrogenated and / or partially hydrogenated resins (rosins) with a content of at least 30% by weight of dehydroabietic acid and a content of at most 1% by weight of abietic acid.

[0113] Furthermore, salts, acids, and bases can be used during the emulsion polymerization of the graft base B1 and the graft shell B2, in particular to adjust the pH or buffer the reaction mixture. For example, solutions of sulfuric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, sodium salts of carbonates, bicarbonates, sulfates, and / or phosphates (e.g., tetrasodium pyrophosphate) can be used. In a preferred embodiment, at least one carbonate and / or bicarbonate, such as sodium bicarbonate, is used as a buffer.

[0114] The polymerization temperature in the emulsion polymerization of the graft copolymer B is generally from 25° C. to 160° C., preferably from 40° C. to 90° C. Conventional temperature control, for example isothermal, can be used here; however, the graft polymerization reaction is preferably carried out so that the temperature difference between the start and the end of the reaction is at least 10° C., preferably at least 15° C. and particularly preferably at least 20° C.

[0115] Typically, the production of the graft copolymer B is achieved in the present invention by means of emulsion polymerization. The common implementation of emulsion polymerization in batch operation or in continuous operation is known to those skilled in the art.

[0116] In particular, the monomers of the graft shell B2 (i.e., monomers B21 and B22, either individually or as a monomer mixture) are added continuously to the graft base B1 in the specified amounts and ratios and polymerized. The monomers are generally added to at least one graft base B1 in a manner known to those skilled in the art. In particular, the graft copolymer B may comprise two or more graft shells B2 prepared by stepwise polymerization of monomers B21 and / or B22.

[0117] Step b) - Precipitation of the Graft Copolymer B Latex Using Precipitation Solution PS

[0118] The process according to the invention comprises precipitation of at least one graft copolymer B after emulsion polymerization in step a), wherein the graft copolymer B latex is mixed with at least one precipitation solution PS, thereby producing a precipitation mixture, wherein preferably the at least one precipitation solution PS comprises at least one salt and / or acid. In particular, the precipitation solution PS comprises at least one alkaline earth metal salt, preferably at least one salt of magnesium and / or calcium; more preferably at least one magnesium salt.

[0119] In particular, the at least one alkaline earth metal salt is selected from alkaline earth metal halides (such as chlorides), alkaline earth metal sulfates, alkaline earth metal phosphates (such as orthophosphates or pyrophosphates), alkaline earth metal acetates and alkaline earth metal formates. Preferably, the at least one alkaline earth metal salt is selected from chlorides and sulfates.

[0120] Preferred alkaline earth metal salts herein are magnesium sulfate (e.g., kieserite (Mg[SO4]·H2O), magnesium sulfate pentahydrate (Mg[SO4]·5H2O), magnesium sulfate hexahydrate (Mg[SO4]·6H2O), and epsomite (Mg[SO4]·7H2O, Epsom salt), magnesium chloride, calcium chloride, calcium formate, magnesium formate, or mixtures thereof. In particular, magnesium sulfate is preferably used.

[0121] In particular, the solids content of the precipitation mixture obtained in step b) is in the range of 5 to 20% by weight, preferably 7 to 18% by weight, more preferably 10 to 18% by weight, still preferably 12 to 20% by weight.

[0122] Preferably, the pH of the precipitation mixture obtained in step b) is in the range of 5 to 10, preferably in the range of 6 to 9, and further preferably in the range of 8 to 9. For example, the pH can be adjusted by adding buffer salts, acids and / or bases, wherein, for example, solutions of sulfuric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, sodium and potassium carbonates (e.g. sodium carbonate Na2CO3 and / or sodium bicarbonate NaHCO3 or mixtures thereof), sodium and potassium sulfates or sodium and potassium phosphates (e.g. tetrasodium pyrophosphate) can be used. For example, it is preferred to add at least one buffer salt selected from the group consisting of sodium salts, in particular sodium carbonate, sodium sulfate and sodium phosphate, preferably sodium carbonate Na2CO3 and sodium bicarbonate NaHCO3,

[0123] Buffer salts, acids and / or bases can be added during steps a) and / or b), preferably during the preparation of the at least one graft copolymer B (emulsion polymerization, step a).

[0124] Typically, the precipitation solution PS and the graft copolymer B latex are mixed in step b) within a period ranging from 5 to 30 minutes, preferably from 5 to 20 minutes.

[0125] The precipitation in step b) can be carried out in a temperature range of 20° C. to 150° C., preferably 40° C. to 100° C., particularly preferably 45° C. to 99° C., and further preferably 60° C. to 90° C. Preferably, the graft copolymer B latex is mixed with at least one precipitation solution PS at a temperature T1 (precipitation temperature) in the range of 30° C. to 80° C., preferably 35° C. to 75° C., and more preferably 40° C. to 65° C.

[0126] Preferably, after mixing the graft copolymer B latex with at least one precipitation solution PS, the precipitation mixture is kept at a temperature T2 (sintering temperature) in the range of 70° C. to 140° C., preferably 75° C. to 135° C., more preferably 90° C. to 135° C. In particular, the precipitation mixture is kept at said temperature T2 for a period of 2 to 90 minutes, preferably 5 to 80 minutes, more preferably 10 to 70 minutes.

[0127] In a preferred embodiment, in step b), the graft copolymer B latex is mixed with at least one precipitation solution PS at a temperature T1 (precipitation temperature) in the range of 30° C. to 70° C., preferably 40° C. to 65° C., and the precipitation mixture is subsequently kept at a temperature T2 (sintering temperature) in the range of 70° C. to 120° C., preferably 80° C. to 100° C., for at least 5 minutes.

[0128] Step c) - Mechanical dehydration of the precipitated graft copolymer B

[0129] The process comprises mechanical dehydration of the precipitated graft copolymer B (obtained in step b), wherein a graft copolymer B having a water content equal to or less than 50% by weight, preferably equal to or less than 40% by weight, is obtained.

[0130] The water content of the graft copolymer B after dehydration (also referred to as the residual moisture content) is the water content in percent by weight, based on the wet graft copolymer B obtained after dehydration. The water content is determined, in particular, using a suitable analytical instrument (e.g., a drying and weighing instrument), wherein the sample is dried until a constant sample weight is achieved over a defined period of time. For example, the water content of the graft copolymer B can be determined in a halogen moisture analyzer HR73 from Mettler Toledo at 180° C. for 30 seconds until a constant weight is achieved.

[0131] In particular, the water content of the dehydrated graft copolymer B obtained in step c) is in the range of 10 to 50 wt %, preferably 20 to 40 wt %, more preferably 20 to 30 wt % (based on the total dehydrated graft copolymer B).

[0132] Typically, step c) of the present invention comprises mechanical dehydration of the precipitated graft copolymer B by means of continuous or batch centrifugation and / or filtration. Preferably, mechanical dehydration of the precipitated graft copolymer B is preferably achieved by means of continuous centrifugation. The precipitated graft copolymer B is typically centrifuged at a centripetal acceleration of 200 to 1500 g (wherein g is the acceleration due to gravity, 1 g = 9.81 m / s), preferably 500 to 1300 g, for a period of 1 second to 5 minutes, preferably 1 second to 120 seconds.

[0133] Step d) - Optional washing of the dehydrated graft copolymer B

[0134] In another embodiment, the mechanical dehydration of the graft copolymer B in step c) is combined with a washing step (e.g. on a centrifuge) or is followed by a washing step, wherein the dehydrated graft copolymer B is preferably treated with water. In addition, mixtures of water and polar organic solvents miscible with water, such as alcohols, can be used.

[0135] The water or mixture is preferably removed after treatment by filtration and / or centrifugation. Preferably, in the downstream washing step d), a graft copolymer B is obtained having a water content in the range of 10 to 50% by weight, preferably 20 to 40% by weight, particularly preferably 20 to 30% by weight. It is also preferred to obtain a graft copolymer B having a water content as described above for step c).

[0136] For example, the washing step can be performed by adding water or a mixture of water and a polar organic solvent miscible with water during centrifugation, in particular, during continuous centrifugation.

[0137] Step e) - Drying of the Dehydrated Graft Copolymer B

[0138] The process of the present invention comprises drying the dehydrated graft copolymer B obtained in step c) or d) using a drying gas having a temperature in the range of 50° C. to 160° C., preferably 55° C. to 155° C., more preferably 60° C. to 150° C., further preferably 100° C. to 160° C., wherein a powder of the graft copolymer B is obtained. Typically, the temperatures of the drying gas given above are the inlet temperatures of the drying gas.

[0139] Preferably, the temperature of the graft copolymer B during the drying step e) is less than 50° C., preferably in the range of 20° C. to 49° C., more preferably in the range of 35° C. to 45° C. Typically, the temperature of the graft copolymer is the maximum temperature during the drying step e), i.e. the temperature of the graft copolymer does not exceed the values ​​given above.

[0140] In one embodiment, the method comprises drying the dehydrated graft copolymer B obtained in step c) or in the optional washing step d) in a known manner. For example, the dehydrated graft copolymer B can be dried by a hot drying gas (e.g., air or nitrogen). Drying can be carried out, for example, in a box dryer (laboratory oven), a fluidized bed dryer, a flash dryer, or other commonly known drying devices.

[0141] The drying gas used preferably comprises air, nitrogen or any desired mixture thereof.

[0142] In a preferred embodiment, the drying in step e) can be carried out by moving the graft copolymer B in at least one drying gas, and the inlet temperature of the drying gas is in the range of 50°C to 160°C, preferably 60°C to 150°C.

[0143] In a preferred embodiment, the drying of the dehydrated graft copolymer B in step e) is achieved using a fluidized bed dryer and / or a flash dryer (pneumatic dryer). Fluidized bed dryers and flash dryers are known to those skilled in the art. In particular, these are described in the literature for flowable granular materials. Drying devices of the type described in "Drying Technology" (Volume 2, Dryers and Drying Processes, Springer-Verlag, 1959). Fluidized bed dryers are described by way of example on pages 275 to 282 of the aforementioned document. Pneumatic dryers or flash dryers, as mentioned, are described by way of example on page 282 of the aforementioned document. The average residence time of the graft copolymer B in the pneumatic dryer is generally 1 to 300 seconds, preferably 1 to 120 seconds, particularly preferably 5 to 60 seconds. In particular, the average residence time of the graft copolymer B in the fluidized bed dryer is 1 to 60 minutes, preferably 5 to 50 minutes, particularly preferably 10 to 40 minutes.

[0144] Further details of drying the dehydrated graft copolymer using a fluidized bed dryer and / or a flash dryer are described in WO 2017 / 093468 and WO 2018 / 060111.

[0145] Typically, the water content of the dried graft copolymer B obtained in step e) is below 5% by weight, preferably below 1% by weight, preferably in the range from 0.05 to 0.8% by weight, preferably 0.1 to 0.5% by weight, particularly preferably 0.1 to 0.3% by weight.

[0146] Step f) - Optionally cooling the dried graft copolymer B powder

[0147] Optionally, the method of the present invention comprises cooling the dried graft copolymer B powder obtained in step e) using a cooling gas (preferably air and / or nitrogen), wherein the temperature of the cooling gas is equal to or less than 50° C., preferably equal to or less than 40° C.; more preferably equal to or less than 30° C., and wherein the cooling gas passes through the graft copolymer B powder. For example, the cooling gas may pass through the graft copolymer B powder or pass over the surface of the graft copolymer B powder.

[0148] Preferably, the dried graft copolymer B powder obtained in step e) is cooled using cooling gas, wherein the temperature of the cooling gas is in the range of 0°C to 50°C, preferably in the range of 5°C to 40°C, more preferably in the range of 10°C to 30°C, further preferably in the range of 10°C to 25°C.

[0149] Preferably, during the cooling step f), the temperature of the graft copolymer B is less than 40° C., preferably from 5° C. to 40° C., more preferably from 10° C. to 30° C., and even more preferably in the range of 10° C. to 25° C. Typically, the temperature of the graft copolymer is the maximum temperature during the cooling step f), i.e., the temperature of the graft copolymer does not exceed the values ​​given above. Typically, the temperature of the graft copolymer B is within the stated range throughout the cooling step e).

[0150] In a preferred embodiment, the cooling gas is passed through the powder of the graft copolymer B, wherein a continuous or discontinuous gas flow, preferably a flow of air and / or nitrogen, is maintained. For example, the cooling gas can be passed through the powder of the graft copolymer B in the dryer (e.g., a fluidized bed dryer) used in step e) by means of a conveying stream or circulation, e.g., in a pipe, silo, or tank.

[0151] Preferably, the cooling gas is passed through the graft copolymer B powder in step f) to obtain a fluidized powder. Generally, a fluidized powder is understood to be a heterogeneous mixture of a fluid and a solid that exhibits fluid-like properties. For example, the upper surface of the fluidized powder is relatively horizontal, and the fluidized powder can be represented by a single bulk density. The terms fluidized bed or flotation bed are also commonly used. Generally, fluidization is understood to be a process for preparing the heterogeneous mixture. Generally, a fluidized powder is obtained when a fluid (usually a gas) passes through a granular medium upward (i.e., relative to the direction of gravity) and the particles are in a constant upward and downward motion, thereby generating a fluidized state. The flow conditions of the corresponding system must generally be adjusted to produce the desired fluidized layer.

[0152] In a preferred embodiment, cooling step f) is performed using a fluidized bed dryer. In particular, cooling step f) is performed after drying step e), wherein a fluidized bed dryer is used, in particular, both steps are performed using the same fluidized bed dryer. In this preferred embodiment, step f) comprises cooling the dried graft copolymer B powder obtained in step e) using a cooling gas, wherein the cooling gas is passed through the graft copolymer B powder to obtain a fluidized powder.

[0153] Typically, the water content of the graft copolymer B obtained in cooling step f) is below 5% by weight, preferably below 1% by weight, preferably in the range of 0.05 to 0.8% by weight, preferably 0.1 to 0.5% by weight, particularly preferably 0.1 to 0.3% by weight.

[0154] Step g) - Aeration of the dried graft copolymer B

[0155] The process according to the invention comprises aeration of the graft copolymer B, wherein the graft copolymer B powder obtained in step e) or f) is mixed with an aeration gas, preferably air and / or nitrogen, wherein during the entire aeration step g), the bulk density of the graft copolymer B powder is equal to or less than 98.5%, preferably equal to or less than 97.5%, of the bulk density of the unaerated graft copolymer B.

[0156] Preferably, during the entire aeration step g), the bulk density of the graft copolymer B powder is in the range of 80% to 98.5%, preferably 85% to 97.5%, of the bulk density of the unaerated graft copolymer B powder.

[0157] In particular, the bulk density of the unaerated graft copolymer B is the density of the graft copolymer B powder obtained in step e) or f) after storage (unaerated) for at least 48 hours, preferably at least 36 hours, more preferably at least 24 hours in, for example, a drum or silo. In particular, the density of the unaerated graft copolymer B is the density of the graft copolymer B powder obtained in step e) or f) after storage (unaerated) for at least 48 hours, preferably at least 36 hours, more preferably at least 24 hours at a storage temperature of 50°C or less, preferably 40°C or less, more preferably 30°C or less, and preferably at least 20°C, preferably in the range of 20°C to 30°C.

[0158] Preferably, the bulk density of the unaerated graft copolymer B is the density of the graft copolymer B powder obtained in step e) or f) after storage (unaerated) for 48 hours. Preferably, the bulk density of the unaerated graft copolymer B is the density of the graft copolymer B powder obtained in step e) or f) after storage (unaerated) at a storage temperature of 30° C. for 48 hours.

[0159] Preferably, the bulk density of the un-aerated graft copolymer B is between 200 and 600 kg / m 3 , preferably 250 to 500 kg / m 3 , also preferably 300 to 450 kg / m 3 within the range.

[0160] Typically, the inflation gas is not released completely immediately after the graft copolymer B powder is mixed with the inflation gas, but is generally released over time until the bulk density of the unaerated graft copolymer B powder reaches a saturation level. According to the present invention, the bulk density of the graft copolymer B in step g) is equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B powder, wherein this bulk density is maintained throughout the duration of the inflation step g).

[0161] Preferably, the graft copolymer B powder obtained in step e) or f) is mixed with the aeration gas, wherein the mixing is carried out for the entire duration of step g), or is carried out one or more times during the duration of step g). Preferably, the mixing can be carried out one or more times during the duration of step g), as long as a bulk density equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B powder is maintained.

[0162] Preferably, the temperature of the inflation gas is equal to or lower than 40° C., preferably equal to or lower than 30° C.; more preferably equal to or lower than 25° C. Preferably, the temperature of the inflation gas is in the range of 0° C. to 40° C., preferably in the range of 5° C. to 40° C., more preferably in the range of 10° C. to 30° C., further preferably in the range of 10° C. to 25° C. More preferably, the temperature of the inflation gas is equal to or lower than the temperature of the graft copolymer B after the cooling step f).

[0163] Preferably, during the aeration step g), the temperature of the graft copolymer B powder is less than 40° C., preferably from 5° C. to 40° C., more preferably from 10° C. to 30° C., and even more preferably from 10° C. to 25° C. Typically, the temperature of the graft copolymer is the maximum temperature during the aeration step g). Typically, the temperature of the graft copolymer B powder is within the aforementioned range throughout the aeration step g).

[0164] Preferably, the graft copolymer B powder obtained in step e) or f) is mixed with the aerating gas by stirring and / or by passing the aerating gas through the graft copolymer B powder.

[0165] In a preferred embodiment, the mixing of the graft copolymer B powder obtained in step e) or f) with the inflation gas in step g) is carried out by passing the inflation gas through the graft copolymer B powder, wherein a continuous or discontinuous gas flow, preferably an air and / or nitrogen flow, is maintained. For example, the inflation gas can be passed through the graft copolymer B powder by a continuous or discontinuous conveying flow or a continuous or discontinuous circulating conveying, for example in a pipe, silo or tank.

[0166] In a preferred embodiment, the graft copolymer B powder obtained in step e) or f) is mixed with the aeration gas in step g) by delivering air via continuous or discontinuous external circulation, wherein a portion of the graft copolymer B powder is conveyed from the outlet of the storage container (e.g., a silo) back to the inlet of the storage container (e.g., at the top of the silo).

[0167] Furthermore, the graft copolymer B powder obtained in step e) or f) can be mixed with the aeration gas by stirring (e.g. in a stirred vessel). Furthermore, in step g), the mixing can be carried out by passing the aeration gas through the graft copolymer B powder to obtain a fluidized powder (fluidized bed), for example using a fluidized bed dryer.

[0168] Typically, the aeration step g) is carried out during storage of the graft copolymer B powder (graft copolymer composition) before subsequent processing, for example before compounding the graft copolymer composition with a thermoplastic copolymer A as described below. In particular, the average storage time may last for a period ranging from 1 hour to 3 weeks, preferably for a period ranging from 2 hours to 10 days.

[0169] Step h) - Optionally adding one or more optional components K1

[0170] In general, the process according to the invention can comprise the addition of one or more optional components K1 (step h), preferably selected from additives and auxiliaries.

[0171] In particular, the graft copolymer composition obtained by the process of the present invention may contain 0 to 10% by weight, preferably 0 to 5% by weight, typically 0.001 to 5% by weight, and more preferably 0.01 to 2% by weight, based on the total graft copolymer composition (preferably based on the solids content of the total graft copolymer composition), of at least one further component K1. Preferably, at least one component K1 is not a polymeric compound.

[0172] At least one further component K1 can optionally be added at each stage of the process according to the invention (step h). In a preferred embodiment, optional step h) comprises adding at least one stabilizer as component K1, in particular selected from the group consisting of light stabilizers and heat stabilizers, before or during the dehydration of the precipitated graft copolymer B (step c). In a preferred embodiment, at least one stabilizer, such as a heat stabilizer, UV stabilizer or light stabilizer, is added after or during the preparation of the graft copolymer by emulsion polymerization in step a).

[0173] Optional other components K1

[0174] For example, the at least one further component K1 can be selected from conventional additives and / or auxiliaries for plastic materials. For conventional auxiliaries and additives, reference is made, for example, to the Plastics Additives Handbook, Hans Zweifel, 6th edition, Hanser Publishers, Munich, 2009.

[0175] For example, the at least one additive K1 can be selected from fillers, reinforcing agents, dyes, pigments, lubricants or mold release agents, stabilizers (especially light stabilizers and heat stabilizers), antioxidants, UV absorbers, plasticizers, impact modifiers, antistatic agents, flame retardants, bactericides, fungicides, optical brighteners and blowing agents. For example, the optional additive K1 can be selected from the additives K2 described below in connection with the method for producing the thermoplastic molding composition.

[0176] In a preferred embodiment, the additive K1 is selected from conventional stabilizers for thermoplastic polymers (primary stabilizers), such as stabilizers for increasing thermal stability (which are generally agents for counteracting thermal decomposition), light stabilizers (stabilizers for increasing light resistance), and stabilizers for increasing resistance to hydrolysis and chemical substances. Examples of suitable light stabilizers are various substituted resorcinols, salicylates, benzotriazoles, benzophenones and phenolic antioxidants (such as 1076 or TBM-6).

[0177] Examples of suitable stabilizers are hindered phenols, vitamin E and compounds having similar structures thereto. Hindered amine light stabilizers (HALS stabilizers), benzophenones, resorcinols, salicylates, benzotriazoles and phenolic antioxidants are also suitable.

[0178] Furthermore, at least one further component K1 can be selected from the additives and auxiliaries described above for producing the graft copolymer B in step a), for example from surfactants, buffer salts, stabilizers and initiators.

[0179] Preparation of thermoplastic molding compositions

[0180] The present invention further relates to a process for producing a thermoplastic molding composition by mixing components, said thermoplastic molding composition comprising a graft copolymer B composition as described above (or, respectively, a graft copolymer composition obtained by the process of the invention) and at least one thermoplastic styrene copolymer A, optionally at least one further polymeric component C and optionally at least one further component K2.

[0181] In this context, the present invention relates to a process for producing a thermoplastic molding composition comprising (preferably consisting of) the following monomers:

[0182] A: 5 to 95% by weight, preferably 30 to 95% by weight, more preferably 40 to 90% by weight of at least one thermoplastic copolymer A derived from the following monomers:

[0183] A1: 50 to 95% by weight, preferably 60 to 90% by weight, more preferably 60 to 85% by weight, based on the copolymer A, of a monomer A1 selected from styrene, α-methylstyrene and a mixture of styrene with at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl (meth)acrylates,

[0184] A2: 5 to 50% by weight, preferably 10 to 40% by weight, more preferably 15 to 40% by weight, based on the copolymer A, of at least one monomer A2 selected from acrylonitrile and a mixture of acrylonitrile with at least one further monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids (for example maleic anhydride or phthalic anhydride) and imides of unsaturated carboxylic acids (for example N-substituted maleimides, such as N-cyclohexylmaleimide or N-phenylmaleimide),

[0185] B: 5 to 95% by weight, preferably 5 to 70% by weight, more preferably 10 to 60% by weight of at least one graft copolymer B as defined above;

[0186] C: 0 to 90% by weight, preferably 0 to 80% by weight, more preferably 20 to 60% by weight of at least one other polymeric component C, and

[0187] K2: 0 to 10% by weight, preferably 0 to 5% by weight, typically 0.1 to 5% by weight, of at least one further component K2, preferably selected from additives and auxiliaries;

[0188] The method comprises the following steps:

[0189] a), b), c), e), g) and optionally d), f) and / or h) as described above; and

[0190] i) Thermoplastic copolymer A, at least one graft copolymer B and optionally one or more further polymeric components C and / or optionally one or more further components K2 are mixed.

[0191] The methods and devices for mixing the graft copolymer B with the thermoplastic polymer A and optionally further polymer components C and / or additives K2 are known to those skilled in the art. Possible mixing devices for compounding are, for example, discontinuously operated heated internal mixers with or without a die, continuous kneaders (e.g., continuous internal mixers), screw kneaders with axially oscillating screws, Banbury mixers, continuous extruders and roll mills, open mills with heated rolls and calenders.

[0192] Typically, the mixing step i) comprises melt compounding and / or melt extrusion and can typically be performed using one or more kneaders, extruders and / or twin screws. For melt extrusion, for example, single-screw or twin-screw extruders are particularly suitable. Preferably, a twin-screw extruder is used. In some cases, the mechanical energy introduced by the mixing device during mixing already causes the mixture to melt, so that heating of the mixing device is not required.

[0193] The mixing in step i) can be carried out successively or simultaneously. In addition, in the first step, it is suitable to mix some or all of the components at a temperature of 15°C to 40°C, for example at room temperature, and then in the second step, optionally with the addition of further additives, increase the temperature to up to 200°C to 300°C.

[0194] Preferably, in step i), mixing is carried out at a temperature in the range of 100° C. to 400° C., preferably 180° C. to 300° C. In general, the temperature depends on the chemical and physical properties of the components. In general, the temperature should be selected so as to achieve a substantially molten polymer mixture. In this context, the term "melting" means that all components (in particular polymeric components) are melted, except for those components that should not be melted (for example glass fibers or pigment particles). On the other hand, the temperature should not be unnecessarily high in order to avoid thermal damage to the polymer mixture. The mechanical energy introduced can be so high that even the mixing device must be cooled. The mixing device is usually operated at a temperature of 150° C. to 400° C., preferably 180° C. to 300° C., and has generally different temperature zones known to those skilled in the art.

[0195] The mixing of the thermoplastic copolymer A, the at least one graft copolymer B and the optional further component K can be effected in a known manner successively or simultaneously. Furthermore, some components can be mixed initially at a temperature of 15° C. to 40° C., in particular at room temperature (about 20° C.), and the temperature can subsequently be increased to 200° C. to 300° C. and further components can optionally be added.

[0196] Thermoplastic Copolymer A

[0197] Preferably, the thermoplastic copolymer A comprising at least one vinylarene monomer is a resin that does not contain any latex-type polymer (rubber-free resin).

[0198] Preferably, the thermoplastic copolymer A comprises at least 50% by weight of one or more vinylaromatic monomers A1, preferably selected from styrene, α-methylstyrene, p-methylstyrene, and optionally at least one further ethylenically unsaturated monomer A2.

[0199] Furthermore, preferred thermoplastic copolymers A are prepared from mixtures of styrene and other comonomers A2. In particular, at least one thermoplastic copolymer A can be selected from polystyrene, copolymers of styrene (e.g., styrene acrylonitrile copolymers (SAN)), copolymers of α-methylstyrene (e.g., α-methylstyrene acrylonitrile copolymers (AMSAN)). Generally speaking, any SAN and / or AMSAN copolymer known in the art can be used as thermoplastic copolymer A within the scope of the present invention.

[0200] In particular, the thermoplastic copolymer A is chosen from SAN and / or AMSAN copolymers containing less than 36% by weight of acrylonitrile as monomer A2, based on the copolymer A. Preferably, the thermoplastic copolymer A contains at least one vinyl aromatic monomer A1, preferably styrene, in an amount of 50 to 99% by weight, preferably 60 to 95% by weight, further preferably 65 to 90% by weight, more preferably 65 to 70% by weight, and at least one vinyl cyanide monomer A2, preferably acrylonitrile, in an amount of 1 to 50% by weight, preferably 5 to 40% by weight, further preferably 10 to 35% by weight, more preferably 30 to 35% by weight.

[0201] In a preferred embodiment, the at least one thermoplastic copolymer A comprises (preferably consists of) the following monomers:

[0202] A1: 50 to 99% by weight, preferably 50 to 95% by weight, more preferably 60 to 90% by weight, still preferably 60 to 85% by weight, based on the copolymer A, of at least one vinylaromatic monomer A1, the vinylaromatic monomer A1 being selected from styrene, α-methylstyrene or a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl(meth)acrylates,

[0203] A2: 1 to 50% by weight, 50 to 99% by weight, preferably 5 to 50% by weight, more preferably 10 to 40% by weight, still preferably 15 to 40% by weight, based on the copolymer A, of at least one further ethylenically unsaturated monomer A2, the further ethylenically unsaturated monomer A2 being selected from acrylonitrile or a mixture of acrylonitrile and at least one further monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids and imides of unsaturated carboxylic acids.

[0204] In particular, it is preferred that the thermoplastic copolymer A contains 35% by weight or less of acrylonitrile based on the total copolymer A.

[0205] In a preferred embodiment of the present invention, the at least one vinylaromatic monomer A1 is styrene or α-methylstyrene, and the at least one other ethylenically unsaturated monomer A2 is acrylonitrile.

[0206] In another preferred embodiment of the present invention, monomer A1 is a mixture of styrene and α-methylstyrene, and monomer A2 is acrylonitrile, wherein the mixture preferably comprises at least 10% by weight, preferably at least 50% by weight and more preferably at least 90% by weight of styrene, based on the total amount of monomer A1.

[0207] In a preferred embodiment, the thermoplastic copolymer A is composed of monomers A1 and A2, wherein the at least one aromatic vinyl monomer A1 is selected from styrene, α-methylstyrene and mixtures thereof; and the at least one other ethylenically unsaturated monomer A2 is acrylonitrile or a mixture of acrylonitrile and methacrylonitrile.

[0208] Particularly preferred thermoplastic copolymers A are copolymers comprising (preferably consisting of) the following monomers:

[0209] A1: 60 to 95% by weight, preferably 60 to 90% by weight, more preferably 60 to 85% by weight, and still more preferably 65 to 80% by weight, based on the total copolymer A, of at least one vinyl aromatic monomer A1, the vinyl aromatic monomer A1 being selected from styrene, α-methylstyrene, or a mixture of styrene and α-methylstyrene; and

[0210] A2: 5 to 40% by weight, preferably 10 to 50% by weight, more preferably 15 to 40% by weight, and still more preferably 20 to 35% by weight, based on the total copolymer A, of at least one further ethylenically unsaturated monomer A2, the ethylenically unsaturated monomer A2 being selected from acrylonitrile or a mixture of acrylonitrile and methacrylonitrile.

[0211] In a preferred embodiment, the thermoplastic copolymer A is produced from (preferably consists of) the following monomers:

[0212] A1: 64 to 95% by weight of monomer A1, based on copolymer A, selected from styrene and mixtures of styrene with at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl (meth)acrylates,

[0213] A2: 5 to 36 wt% of monomer A2, based on copolymer A, wherein monomer A2 is selected from acrylonitrile.

[0214] In a preferred embodiment, the thermoplastic copolymer A is produced from (preferably consists of) the following monomers:

[0215] A1: based on the copolymer A, 67 to 95% by weight of monomer A1, wherein the monomer A1 is selected from styrene or α-methylstyrene,

[0216] A2: 5 to 33 wt% of monomer A2, based on copolymer A, wherein monomer A2 is selected from acrylonitrile.

[0217] In particular, the weight average molecular weight (M w ) is in the range of 15,000 to 200,000 g / mol, preferably in the range of 30,000 to 150,000 g / mol. Typically, the number average molar mass (M n ) in an amount of 15,000 to 100,000 g / mol. Preferably, the average molecular weight can be determined by gel permeation chromatography (GPC) using polystyrene as a standard and, for example, UV detection. Preferably, the thermoplastic copolymer A exhibits a viscosity number (VN) of 50 to 120 ml / g, preferably 50 to 100 ml / g, more preferably 55 to 85 ml / g (determined according to DIN 53726 at 25° C., 0.5% by weight in dimethylformamide).

[0218] In a preferred embodiment, the thermoplastic copolymer A is a SAN (styrene acrylonitrile copolymer) or an AMSAN (α-methylstyrene acrylonitrile copolymer) copolymer, which has an average molecular weight and / or viscosity within the above ranges.

[0219] Copolymer A can be prepared by all known methods, such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization or hybrid processes (e.g. bulk / suspension polymerization), with or without other components. It is possible to synthesize thermoplastic copolymer A by thermal initiation or by adding initiators (especially free radical initiators, such as, for example, peroxides). Suitable thermoplastic copolymers A are preferably produced by bulk or solution polymerization.

[0220] More preferably, the thermoplastic copolymer A is prepared from the components acrylonitrile and styrene and / or α-methylstyrene by bulk polymerization or in the presence of one or more solvents, such as toluene or ethylbenzene. The polymerization processes are described, for example, in "Plastics Handbook", Vieweg-Daumiller, Volume V (Polystyrol), Carl-Hanser-Verlag, Munich, 1969, pages 122 et seq.

[0221] Details on the production of SAN and / or AMSAN resins by bulk or solution polymerization are described, for example, in US 4,009,226 and US 4,181,788. Furthermore, the synthesis of thermoplastic copolymers A is described, for example, in DE-A 24 20 358 and DE-A 2724 360. Suitable thermoplastic copolymers are also described in DE-A 19713509.

[0222] Other polymer components C

[0223] Optionally, the thermoplastic molding composition comprises 0 to 90% by weight, preferably 0 to 60% by weight, typically 0.5 to 30% by weight, in a further embodiment 30 to 90% by weight, preferably 30 to 60% by weight, based on the total molding composition, of at least one further polymer component C. Preferably, the optional polymer component C is selected from polycarbonates (including aromatic polycarbonates and aromatic polyester carbonates), polyamides and polyesters, more preferably from polycarbonates and polyamides.

[0224] In a preferred embodiment, the thermoplastic molding composition comprises 5 to 60% by weight, preferably 20 to 60% by weight, more preferably 30 to 60% by weight, based on the total molding composition, of at least one further polymer component C selected from the group consisting of polycarbonates, polyamides and polyesters, preferably from the group consisting of polycarbonates and polyamides.

[0225] Preferably, the at least one further polymer component C is at least one aromatic polycarbonate and / or at least one aromatic polyester carbonate. Suitable aromatic polycarbonates and / or aromatic polyester carbonates are described in the state of the art and can be prepared by known processes. For example, the preparation of aromatic polycarbonates is described in Schnell, "Chemistry and Physics of Polycarbonates", Interscience Publishers, 1964, and in DE-AS 1 495 626, DE-A 2 232 877, DE-A 2 703 376, DE-A 2 714 544, DE-A 3 000 610, and DE-A 3 832 396. For example, the preparation of aromatic polyester carbonates is described in DE-A 3 077 934. In particular, the preparation of aromatic polycarbonates and / or aromatic polyester carbonates is carried out by reacting a diphenol (preferably bisphenol A), a carbonic acid halide (preferably phosgene) and optionally an aromatic dicarboxylic acid halide (preferably a phthalic acid halide). Suitable aromatic polycarbonates and aromatic polyester carbonates and their preparation are described in DE-A 2 714 544, DE-A 3 000 610, DE-A 3 832 396 and DE-A 3 077 934, in particular.

[0226] The aromatic polycarbonates and / or aromatic polyester carbonates used as component C can be linear or branched in a known manner. Branching agents which can be used are trifunctional or more trifunctional carboxylic acid chlorides (as described, for example, in DE-A 2 940 024 and DE-A 3 007 934) or trifunctional or more trifunctional phenols.

[0227] Typically, the average weight average molecular weight (M) of aromatic polycarbonates and polyester carbonates suitable for use as component C is W , measured for example by ultracentrifuge or scattered light) is from 10,000 to 200,000 g / mol, preferably from 15,000 to 80,000 g / mol, particularly preferably from 24,000 to 32,000 g / mol.

[0228] Relative solution viscosity (η) of aromatic polycarbonate and polyester carbonate used as component C rel ) is generally in the range of 1.18 to 1.4, preferably 1.20 to 1.32 (measured at 25° C. on a solution of 0.5 g of polycarbonate or polyester carbonate in 100 ml of dichloromethane). Thermoplastic aromatic polycarbonates and polyester carbonates can be used alone or in any desired mixture of one or more thereof, preferably one to three or one or two. More preferably, only one type of polycarbonate is used.

[0229] Preferably, the aromatic polycarbonates used as component C are polycarbonates based on bisphenol A and phosgene, which comprise polycarbonates which have been prepared via corresponding precursors or synthetic building blocks of bisphenol A and phosgene.

[0230] Furthermore, the at least one further polymer component C may preferably be at least one polyamide selected from homopolyamides, copolyamides, and mixtures thereof. Suitable polyamides and methods for their production are known from the prior art. In particular, suitable semi-crystalline polyamides are polyamide-6, polyamide-6,6, mixtures thereof, and corresponding copolymers. Also included are polyamides wherein the acid component is entirely or partially composed of terephthalic acid, isophthalic acid, suberic acid, sebacic acid, azelaic acid, adipic acid and / or cyclohexanedicarboxylic acid, and the diamine component is entirely or partially composed of m- and / or p-xylenediamine, hexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine and / or isophoronediamine. In particular, amorphous polyamides can be used as further component C, wherein the amorphous polyamides are prepared by diamines (such as ethylenediamine, hexamethylenediamine, decanediamine, 2,2,4- and / or 2,4,4-trimethylhexamethylenediamine, m- and / or p-xylenediamine). The invention can be obtained by polycondensation of xylene-diamine, bis(4-aminocyclohexyl)-methane, bis(4-aminocyclohexyl)-propane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, 3-aminomethyl-3,5,5-trimethyl-cyclo-hexyl-amine, 2,5- and / or 2,6-bis(aminomethyl)-norbornane and / or 1,4-diamino-methylcyclohexane) with dicarboxylic acids such as oxalic acid, adipic acid, azelaic acid, azelaic acid, decanedicarboxylic acid, heptadecanedicarboxylic acid, 2,2,4- and / or 2,4,4-trimethyladipic acid, isophthalic acid and terephthalic acid.

[0231] The polyamides suitable as component C preferably have a relative viscosity (measured at 25° C. as a 1% (w / v) solution in 1% by weight m-cresol or 96% by weight sulfuric acid) of 2.0 to 5.0, particularly preferably 2.5 to 4.0.

[0232] One or more additives K2

[0233] In particular, the thermoplastic molding composition obtained by the process of the invention may contain 0 to 10% by weight, preferably 0 to 5% by weight, and typically 0.1 to 5% by weight, of at least one additive K2, based on the total thermoplastic molding composition. More preferably, the at least one additive K2 is present in an amount of 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, based on the total thermoplastic molding composition. In particular, the additive K is not a polymeric compound.

[0234] The optional additives K2 can be selected from conventional additives and / or auxiliaries for plastic materials. For conventional auxiliaries and additives, reference is made, for example, to the "Handbook of Plastic Additives", and ed., 4th edition, Hansen-Verlag, Munich, 1996. By way of example, the at least one additive K may be selected from fillers, reinforcing agents, dyes, pigments, lubricants or mold release agents, stabilizers (in particular, light stabilizers and heat stabilizers), antioxidants, UV absorbers, plasticizers, impact modifiers, antistatic agents, flame retardants, bactericides, fungicides, optical brighteners and blowing agents.

[0235] The optional additives K2 are preferably selected from dyes, pigments, lubricants or release agents, stabilizers (especially light stabilizers), antistatic agents, flame retardants and fillers (especially mineral fillers).

[0236] Examples of fillers (which may be selected from particulate fillers) or reinforcing agents that may be mentioned are silicates, amorphous silicon dioxide, calcium silicate (such as wollastonite), powdered quartz, mica, metal oxides, metal hydroxides, carbon black, graphite, barium sulfate, calcium carbonate, magnesium carbonate, bentonite, talc, kaolin, carbon fibers or glass fibers in the form of glass fabric, glass mat or glass yarn, chopped glass or glass beads. In particular, at least one particulate filler (preferably a mineral filler) can be used as additive K.

[0237] Examples of suitable pigments are titanium dioxide, phthalocyanine, ultramarine, iron oxide or carbon black, and the entire class of organic pigments, preferably titanium dioxide and carbon black.

[0238] Common stabilizers for thermoplastic polymers include stabilizers for improving thermal stability (which are generally agents for counteracting thermal decomposition), light stabilizers (stabilizers for increasing light resistance), and stabilizers for improving hydrolysis resistance and resistance to chemical substances. Examples of suitable light stabilizers are various substituted resorcinols, salicylates, benzotriazoles, and benzophenones.

[0239] Examples of suitable stabilizers are hindered phenols, vitamin E and compounds structurally similar thereto. Hindered amine light stabilizers (HALS stabilizers), benzophenones, resorcinols, salicylates and benzotriazoles are also suitable.

[0240] Suitable lubricants or mold release agents are fatty acids having 12 to 30 carbon atoms, their salts and derivatives thereof, for example stearic acid and stearates, palmitic acid and palmitates, stearyl alcohol, stearates, amide waxes (for example stearamide, in particular ethylene bis(stearamide) (EBS)) and polyolefin waxes. Particularly suitable lubricants and mold release agents are stearic acid, stearates (for example magnesium stearate), palmitic acid, palmitates (for example sodium palmitate), ethylene bis(stearamide) (for example Ciba, Switzerland), and mixtures thereof. Preferably, the thermoplastic molding composition comprises 0.05 to 5% by weight, preferably 0.1 to 3% by weight, based on the total thermoplastic molding composition, of at least one lubricant or mold release agent, more preferably ethylene bis(stearamide), at least one alkali metal or alkaline earth metal stearate, and / or at least one alkali metal or alkaline earth metal palmitate. In a preferred embodiment, the thermoplastic molding composition comprises 0.1 to 5% by weight, based on the total thermoplastic molding composition, of potassium stearate and / or potassium palmitate.

[0241] In particular, the thermoplastic molding composition may optionally comprise 0 to 2% by weight, preferably 0.01 to 2% by weight, of at least one customary processing aid, for example selected from lubricants and release agents and antistatic agents.

[0242] In particular, the thermoplastic molding composition may optionally comprise 0 to 10% by weight, preferably 0.1 to 10% by weight, of pigments and / or colorants, in particular selected from titanium dioxide, phthalocyanines, ultramarine blues, iron oxides or carbon black, and the entire class of organic pigments.

[0243] Furthermore, the thermoplastic composition may comprise, as component K2, residues of at least one additive K1 selected from surfactants, buffer salts, stabilizers, initiators, used to produce the graft copolymer B as described above.

[0244] The present invention also provides a graft copolymer composition obtained by the method of the present invention as described above. In particular, the present invention provides a graft copolymer composition obtained by the method of the present invention as described above, wherein the bulk density of the graft copolymer composition is equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B. The preferred embodiments describing the bulk density of the graft copolymer B in the aeration step g) apply accordingly.

[0245] Furthermore, the present invention provides a thermoplastic molding composition and a molding produced therefrom, wherein the thermoplastic molding composition is obtained by the process according to the invention for producing a thermoplastic molding composition comprising a graft copolymer B composition as described and at least one thermoplastic styrene copolymer A.

[0246] The thermoplastic molding composition can be used to prepare molded articles, such as sheets or semi-finished products, films, fibers, or foams, and corresponding molded articles, such as sheets, semi-finished products, films, fibers or foams. The known processes for thermoplastic processing can be used for processing, in particular, the preparation can be achieved by thermoforming, extrusion, injection molding, calendering, blow molding, compression molding, press sintering, deep drawing (deepdrawing) or sintering, preferably by injection molding.

[0247] The molding compositions of the present invention can be used to prepare any type of molded article. These can be produced by injection molding, extrusion, and blow molding processes. Another type of processing is the production of molded articles by thermoforming from previously prepared sheets or films, and by film overmolding processes. Examples of these molded articles are any type of film, profile, housing component, for example, for household appliances such as juicers, coffee machines, mixers; for office equipment such as monitors, printers, copiers; exterior and interior parts for automobiles; sheets, pipes, electrical installation ducts, windows, doors, and other profiles in the construction sector (finishing for indoor and outdoor applications); and components for electrical and electronic applications such as switches, plugs, and sockets.

[0248] In particular, the molding compositions of the invention can be used, for example, to produce the following moldings:

[0249] Parts for the interior of rail vehicles, ships, aircraft, buses and other motor vehicles, body components for motor vehicles, housings for electrical equipment including small transformers, housings for equipment for processing and transmitting information, housings and cladding for medical equipment, massage equipment and their housings, children's toy cars, sheet wall units, housings for safety equipment, insulated transport containers, devices for holding or caring for small animals, moldings for sanitary and bathing equipment, protective grilles for ventilator openings, moldings for garden sheds and tool rooms, housings for garden equipment.

[0250] The present invention is described in more detail by the following examples and claims. Example

[0251] 1. Preparation of Styrene-co-Acrylonitrile Grafted Polybutyl Acrylate Latex (Graft Copolymer B)

[0252] The following graft copolymer B latex was prepared:

[0253] a. Preparation of Graft Base B1-1

[0254] The reaction vessel was charged with 90.2 parts of demineralized water, 0.61 parts of C 12 -C 18 The sodium salt of paraffin sulfonic acid and 0.23 parts of sodium bicarbonate. When the temperature in the reaction vessel reached 59 ° C, 0.16 parts of sodium persulfate dissolved in 5 parts of demineralized water were added. 59.51 parts of butyl acrylate and 1.21 parts of the mixture were added over a period of 210 minutes. The reaction was then continued for 60 minutes. Finally, the polymer dispersion (graft base B1-1) had a total solids content of 39.6% and the latex particles had an average particle size D of 75 nm. w (determined by turbidity).

[0255] b. Preparation of Graft Base B1-2

[0256] The reaction vessel was charged with 70.66 parts of demineralized water, 0.3 parts of graft base B1-1 (obtained as described above, particle size 75 nm) and 0.23 parts of sodium bicarbonate. After heating the reaction vessel to 60° C., 0.16 parts of sodium persulfate dissolved in 5 parts of demineralized water were added to the reaction mixture. A mixture of 59.51 parts of butyl acrylate and 1.21 parts of tricyclodecenyl acrylate was added over a period of 210 minutes. In parallel with the first feed, 0.36 parts of C 12 -C 18 A solution of the sodium salt of paraffin sulfonic acid in 16.6 parts of demineralized water was prepared. After 200 minutes from the start of the feed, the temperature was gradually increased to 65°C. The reaction was then continued at 65°C for 60 minutes. Finally, the polymer dispersion (graft base B1-2) had a total solids content of 39.4% and the latex particles had an average particle size D of 440 nm. w (determined by turbidity).

[0257] c. Preparation of graft shell B2

[0258] 154 parts of the graft base B1-2 as described above were mixed with 88.29 parts of demineralized water, 0.11 parts of C 12 -C 18 The sodium salt of paraffin sulfonic acid and 0.14 parts of sodium persulfate (dissolved in 5.61 parts of demineralized water) are added to the reaction vessel. The reaction mixture is heated to 61°C. Over a period of 60 minutes, 13.16 parts are added at a temperature of 61°C, followed by a post-polymerization time of 90 minutes, in which the temperature is increased from 61°C to 65°C. Subsequently, a mixture of 20.5 parts of styrene and 6.83 parts of acrylonitrile is added to the reactants over a period of 150 minutes. The reaction is continued at 65°C for a further 60 minutes. A polymer dispersion having a total solids content of 35.2% is obtained. The latex particles have an average particle size D of 500 nm. w (determined by turbidity).

[0259] d. Precipitation, Dehydration and Drying of Graft Copolymer B Latex

[0260] 112.5 g of MgSO4 solution (19.9 wt%) was mixed with 2143.1 g of demineralized water. 451.1 g of this solution was used as a pre-charge and heated to 60° C. 900 g of the polymer latex from step b) and 1804.5 g of the remaining diluted MgSO4 solution were added separately over 10 minutes, while maintaining the temperature at 60° C. The resulting mixture was then heated to 92° C. for 5 minutes.

[0261] The resulting slurry was filtered off and washed once with 500 ml of demineralized water. The dehydrated graft copolymer B was dried in a laboratory oven at 70° C. to obtain graft copolymer B powder after 2 days. The water content of the dried graft copolymer B was about 0.25% by weight.

[0262] 2. Powder flow analysis

[0263] The flowability was determined using a ring shear tester according to ASTM 6773-2008 with a consolidation stress σ1 of approximately 12 kPa. The consolidation stress σ1 was constant for all samples and was measured for a 100 m diameter 3.5 m steel pipe. 3 Silo and average graft copolymer B powder density calculations.

[0264] The actual determination of flow properties can be carried out in an annular shear tester. In general, a uniaxial compression test can be used as a model to define the flow properties of a powder. The powder is placed in a container with walls that are assumed to be frictionless and consolidated for a short period of time with a normal stress σ1 (consolidation stress). After the walls are removed, a constantly increasing normal stress σ is applied. At failure, the normal stress σ is measured. c (Unrestrained yield strength). Ratio FFC=σ 1 / σ c This value indicates the flowability of the powder. Generally speaking, the larger the FFC (Jenneke Flow Factor), the better the powder's flowability. When comparing different powders, the consolidation stress must be constant.

[0265] When bulk solids are stored for a period of time, the unconstrained yield strength of some powders typically increases relative to their original value. This behavior is known as consolidation over time. Consolidation over time can also be measured in a ring shear tester when a powder is stored for a period of time (after shear failure and before shear failure) at a consolidation stress σ1.

[0266] The initial flowability FFC (0 hours) of the graft copolymer B powder obtained in Example 1 above (after drying) was measured at different temperatures T of 60°C, 40°C, 21°C and 15°C according to ASTM 6773-2008 as described above. In addition, the flowability FFC (6 hours) was measured at temperature T (60°C, 40°C, 21°C or 15°C) after 6 hours under a positive load of 12 kPa (according to ASTM 6773-2008). The results of Table 1 below are given.

[0267] Table 1: Fluidity of graft copolymer B powder at different temperatures FFC (0 hours) and FFC (6 hours)

[0268]

[0269]

[0270] The higher the FFC value, the better the flowability of a particular powder. Generally, powders with FFC values ​​above 4 are considered easy to flow. It can be clearly seen that cooling (below 40°C, preferably at 15°C to 21°C) significantly improves the flowability of the graft copolymer B powder. Furthermore, consolidation over time is also reduced at temperatures below 40°C. Compared to the flowability FFC (6 hours) at 40°C and above, the flowability FFC (6 hours) at temperatures below 40°C is 33 to 43% higher.

[0271] 3. Inflation test

[0272] a. Aeration in bubble towers

[0273] The graft copolymer B powder obtained in Example 1 (after drying) was filled in an acrylic glass cylinder. The filling level was determined by the volume increase ratio of the cylinder. The initial filling height (unaerated state) was measured after a curing time of 10 minutes. Then, at a temperature in the range of 11° C. to 12.5° C. and at atmospheric pressure (977 to 987 mbar), 3-4 m 3 The powder in the cylinder is aerated with an air flow of 1 / h until bubbles are visible on the powder surface. The filling height (aerated state) is measured again.

[0274] The inflation was stopped and the filling height was measured after different waiting times (1 to 30 minutes). The test was repeated with samples of different amounts of graft copolymer B. The results are summarized in Table 2. The filling level and mass of the graft copolymer samples were used to determine the bulk density (kg / m 3 ).

[0275] Table 2: Aeration in Bubble Columns

[0276]

[0277] The bulk density after inflation remains approximately 5% lower than the bulk density in the uninflated state before inflation.

[0278] b. Liquidity test

[0279] A glass cylinder (1 L) was filled with approximately 600 ml of the graft copolymer B powder obtained in Example 1 (after drying) and stored for a period of 24 hours at a certain temperature (20 or 40° C.). After storage, the powder was considered to be fully aerated (unaerated state). The cylinder was brought to a 45° tilt angle and the time it took for the powder to completely flow out of the cylinder was measured. This powder was again filled into the cylinder and aerated by stirring the cylinder for 5 minutes. After stirring, the powder was considered to be fully aerated. After stirring, the "flow time" was measured again.

[0280] This procedure was repeated, with different storage times after aeration (stirring). The temperature of the powder and cylinder was controlled by a laboratory oven. The results are summarized in Table 3 below. It can be clearly seen that the fully fluidized powder has the best flow characteristics (short "flow time"). As the storage time increases (bulk density increases, see Table 2), the fluidity decreases (longer "flow time"). The two temperatures (20°C and 40°C) show the same overall profile. However, at the lower temperature, the initial fluidity is higher.

[0281] Table 3: Flow properties test results measured at 20°C and 40°C

[0282]

Claims

1. A method for producing a graft copolymer composition comprising: B: 90 to 100% by weight of at least one graft copolymer B comprising: B1: 50 to 90% by weight, based on the graft copolymer B, of at least one graft base B1 obtained by emulsion polymerization of the following monomers: B11: 50 to 100% by weight of at least one monomer B11, based on the graft base B1, wherein the monomer B11 is selected from C1-C8 alkyl (meth)acrylates and butadiene; B12: 0 to 10 wt% of at least one multifunctional crosslinking monomer B12, based on the graft group B1; B13: Based on the graft base B1, 0 to 50% by weight of at least one other monomer B13, the monomer B13 is selected from styrene, α-methylstyrene, C1-C4 alkylstyrene, acrylonitrile, methacrylonitrile, isoprene, chloroprene, alkylene glycol di(meth)acrylate and vinyl methyl ether; wherein the sum of B11, B12 and B13 equals 100 wt %; and B2: 10 to 50% by weight, based on the graft copolymer B, of at least one graft shell B2, obtained by emulsion polymerization of the following monomers in the presence of the at least one grafting base B1: B21: 50 to 100% by weight, based on the graft shell B2, of at least one vinylaromatic monomer B21, the vinylaromatic monomer B21 being selected from styrene, α-methylstyrene or a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl (meth)acrylates; and B22: 0 to 50% by weight, based on the graft shell B2, of at least one monomer B22, the monomer B22 being selected from acrylonitrile or a mixture of acrylonitrile and at least one other monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids and imides of unsaturated carboxylic acids; wherein the at least one graft shell B2 consists of monomers which copolymerize to produce a polymer having a glass transition temperature greater than +20°C; wherein the sum of the graft base B1 and the graft shell B2 is equal to 100 wt %; K1: 0 to 10% by weight of at least one other component K1; The method comprises the following steps: a) preparing the at least one graft copolymer B, which comprises emulsion polymerization of the monomers B21 and B22 in the presence of the at least one graft base B1 to form the at least one graft shell B2, wherein the graft copolymer B is obtained in the form of a latex; b) precipitating the at least one graft copolymer B latex after the emulsion polymerization in step a), wherein the graft copolymer B latex is mixed with at least one precipitation solution PS, thereby producing a precipitation mixture; c) mechanically dewatering the precipitated graft copolymer B, wherein said graft copolymer B is obtained having a water content of equal to or less than 50% by weight; d) optionally washing the dehydrated graft copolymer B; e) drying the dehydrated graft copolymer B obtained in step c) or d) using a drying gas having a temperature in the range of 50° C. to 160° C., wherein a graft copolymer B powder is obtained; f) cooling the dried graft copolymer B powder obtained in step e) using a cooling gas, wherein the temperature of the cooling gas is equal to or less than 50° C., and wherein the cooling gas passes through the graft copolymer B powder; and wherein during the cooling step f), the temperature of the graft copolymer B is in the range of 10° C. to 25° C.; g) aerating the graft copolymer B, wherein the graft copolymer B powder obtained in step e) or f) is mixed with an aerating gas, wherein the temperature of the aerating gas is less than 25° C., and wherein during the entire aerating step g), the bulk density of the graft copolymer B powder is equal to or less than 98.5% of the bulk density of the unaerated graft copolymer B; h) Optionally adding one or more optional components K1.

2. The method according to claim 1, characterized in that The at least one grafting base B1 is obtained by emulsion polymerization of the following monomers: B11: 70 to 99.9% by weight of at least one C1-C8 alkyl (meth)acrylate as monomer B11, based on the graft base B1; B12: 0.1 to 10 wt% of at least one multifunctional crosslinking monomer B12, based on the graft base B1; B13: 0 to 29.5% by weight of at least one other monomer, based on the graft group B1, selected from styrene, α-methylstyrene, C1-C4 alkylstyrene, acrylonitrile, methacrylonitrile, isoprene, chloroprene, alkylene glycol di(meth)acrylate and vinyl methyl ether; The sum of B11, B12 and B13 is 100% by weight.

3. The method according to claim 1 or 2, characterized in that The at least one graft copolymer B comprises: B1: 50 to 70% by weight, based on the graft copolymer B, of precisely one graft group B1; and B2: 30 to 50% by weight, based on the graft copolymer B, of precisely one graft shell B2, obtained by emulsion polymerization of the following monomers in the presence of the graft base B1: B21: 50 to 95% by weight, based on the graft shell B2, of at least one vinyl aromatic monomer B21, the vinyl aromatic monomer B21 being selected from styrene, α-methylstyrene, or a mixture of styrene and α-methylstyrene or methyl (meth)acrylate; and B22: 5 to 50% by weight, based on the graft shell B2, of at least one ethylenically unsaturated monomer B22, the ethylenically unsaturated monomer B22 being selected from acrylonitrile or a mixture of acrylonitrile and methacrylonitrile; The total weight of the graft base B1 and the graft shell B2 is 100 wt %, and the particle size of the graft copolymer B latex obtained in step a) is in the range of 60 to 140 nm.

4. The method according to claim 1 or 2, characterized in that The graft copolymer B comprises: B1: 50 to 70% by weight, based on the graft copolymer B, of at least one graft group B1; and B2′: 10 to 20% by weight, based on the graft copolymer B, of at least one graft shell B2′, obtained by emulsion polymerization of the following monomers in the presence of the graft base B1: B21': 100% by weight, based on the graft shell B2', of at least one vinylaromatic monomer B21', the vinylaromatic monomer B21' being selected from styrene, α-methylstyrene or a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C4 alkyl (meth)acrylates; and B2": 20 to 30% by weight, based on the graft copolymer B, of at least one graft shell B2", obtained by emulsion polymerization of the following monomers in the presence of the graft base B1 grafted to B2': B21": 70 to 80% by weight, based on the graft shell B2", of at least one vinylaromatic monomer B21", the vinylaromatic monomer B21" being selected from styrene, α-methylstyrene or a mixture of styrene and alpha-α-methylstyrene or methyl (meth)acrylate; and B22": 20 to 30% by weight, based on the graft shell B2", of at least one ethylenically unsaturated monomer B22", the ethylenically unsaturated monomer B22" being selected from acrylonitrile or a mixture of acrylonitrile and methacrylonitrile; The total of the graft base B1, the graft shell B2' and the graft shell B2" is 100% by weight, and the particle size of the graft copolymer B latex obtained in step a) is in the range of 300 to 700 nm.

5. The method according to claim 1 or 2, characterized in that The graft copolymer composition obtained by the method is a graft copolymer B powder having a water content of less than 5% by weight.

6. The method according to claim 1 or 2, characterized in that The cooling step f) is performed after the drying step e), wherein both steps are performed using a fluidized bed dryer.

7. The method according to claim 1 or 2, characterized in that During the entire aeration step g), the bulk density of the graft copolymer B powder is within a range from 98.5% to 80% of the bulk density of the non-aerated graft copolymer B powder.

8. The method according to claim 1 or 2, characterized in that The graft copolymer B powder obtained in step e) or f) is mixed with the aerating gas in step g) by stirring and / or by passing the aerating gas through the graft copolymer B powder.

9. The method according to claim 1 or 2, characterized in that The graft copolymer B powder obtained in step e) or f) is mixed with the inflation gas in step g) by delivering air through continuous or discontinuous external circulation, wherein a portion of the graft copolymer B powder is conveyed from the outlet of the storage container back to the inlet of the storage container.

10. A method for producing a thermoplastic molding composition, the thermoplastic molding composition comprising: A: 5 to 95% by weight of at least one thermoplastic copolymer A derived from: A1: 50 to 95% by weight of monomer A1, based on the copolymer A, wherein the monomer A1 is selected from styrene, α-methylstyrene, and a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene, and C1-C8 alkyl (meth)acrylates; A2: 5 to 50% by weight, based on the copolymer A, of at least one monomer A2, the monomer A2 being selected from acrylonitrile and a mixture of acrylonitrile with at least one other monomer selected from methacrylonitrile, acrylamide, vinyl methyl ether, anhydrides of unsaturated carboxylic acids, and imides of unsaturated carboxylic acids; B: 5 to 95% by weight of at least one graft copolymer B as defined in any one of claims 1 to 9; C: 0 to 90% by weight of at least one other polymeric component C; and K2: 0 to 10% by weight of at least one further component K2; The method comprises the following steps: a), b), c), e), g) and optionally d), f) and / or h) according to any one of claims 1 to 9; as well as i) mixing the thermoplastic copolymer A, the at least one graft copolymer B and optionally one or more further polymeric components C and / or optionally one or more further components K2.

11. The method according to claim 10, characterized in that The thermoplastic copolymer A is produced from: A1: 64 to 95% by weight of monomer A1, based on the copolymer A, the monomer A1 being selected from styrene and a mixture of styrene and at least one other monomer selected from α-methylstyrene, p-methylstyrene and C1-C8 alkyl (meth)acrylates; and A2: based on the copolymer A, 5 to 36 wt% of monomer A2, wherein the monomer A2 is selected from acrylonitrile.

12. The method according to claim 10 or 11, characterized in that The thermoplastic molding composition comprises: C: 20 to 60% by weight, based on the total molding composition, of at least one further polymer component C selected from the group consisting of polycarbonates, polyamides and polyesters.

13. The method according to claim 10 or 11, characterized in that Said mixing in step i) is carried out at a temperature in the range of 180°C to 300°C.

14. A graft copolymer composition obtained by the method according to claim 1 or 2.

15. The graft copolymer composition according to claim 14, characterized in that The graft copolymer composition has a bulk density equal to or less than 98.5% of the bulk density of the non-aerated graft copolymer B.

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