Process for preparation of thermoplastic moulding compositions with good color stability

Abstract

The present application relates to a method for preparing a thermoplastic molding composition based on an ABS copolymer, in which two or more compounds selected from the group consisting of A2: octadecyl 3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate; a3: phenylpropionic acid, 3, 5-bis (1, 1-dimethylethyl)-4-hydroxy-, 1, 1 '-(thiodi-2, 1-ethylidene) ester, and A5: 4, 5-bis (1, 1-dimethylethyl)-4-hydroxy-, 1, 1'-(thiodi-2, 1-ethylidene) ester; and A4: a phenolic stabilizer A of 2, 4, 6-tri (3 ', 5'-di-tert-butyl-4 '-hydroxybenzyl) mesitylene, and a thio-co-stabilizer B. The invention further discloses a preparation method of the stabilizer. The ABS molding composition obtained by the method provided by the invention has good color stability.

Description

TECHNICAL FIELD

[0001] The present invention relates to a process for the production of a thermoplastic molding composition based on acrylonitrile-butadiene-styrene copolymer (ABS) having good color stability, and an ABS molding composition obtained by the process.

[0002] Polymer dispersions obtained by emulsion polymerization, in particular so-called emulsion rubbers or polymer latices, have very wide applications, for example in latex paints, paper coatings, leather finishes, textile finishing, adhesives raw materials. It is well known to incorporate isolated solid emulsion graft rubber copolymers as impact modifiers into thermoplastic molding compositions.

[0003] Furthermore, it is known from the prior art to incorporate emulsion graft rubber copolymers, for example grafted polybutadiene rubbers, into styrene-acrylonitrile copolymers (SAN) or alpha-methylstyrene-acrylonitrile copolymers (AMSAN) to produce ABS polymers, or into blends of SAN and AMSAN, or into polymer blends of SAN or AMSAN with other polymers such as polycarbonates (PC), polyestercarbonates (PEC) or polyamides (PA), in order to increase the impact strength of the thermoplastic compositions. Such acrylonitrile-butadiene-styrene copolymers (ABS) and acrylonitrile-butadiene-alpha-methylstyrene copolymers (also commonly referred to as ABS) and blends with ABS polymers have been used for many years to produce molded parts for a variety of applications, for example in the automotive sector. Generally, such impact strength-modified ABS molded parts can be produced by free-radical emulsion graft polymerization of styrene and acrylonitrile in the presence of a polybutadiene latex, or by mixing a polybutadiene latex grafted with styrene and acrylonitrile, which is prepared by free-radical emulsion polymerization and is isolated separately, with a thermoplastic SAN matrix. The terms "emulsion polymerization" and "free-radical emulsion polymerization" have the same meaning in this document.

[0004] In addition to the particularly advantageous mechanical properties of ABS compositions, such as high impact strength and notched impact strength, high elasticity and good processability (melt flow index), the ability to withstand the effects of heat and ultraviolet (UV) radiation is of particular importance. In order to stabilize ABS polymer compositions or other polymers produced by graft emulsion polymerization on a polybutadiene latex, it is generally necessary to add stabilizers, in particular in the form of dispersions, in order to prevent oxidative decomposition of the polymers, for example decomposition promoted by light, ultraviolet (UV) radiation, thermal stress. Thermoplastic ABS compositions and stabilized ABS compositions and processes for their production are described, for example, in WO 2001 / 62848, WO 2008 / 020012 and WO 2009 / 071537.

[0005] EP-A 038876 discloses polymer compositions (e.g. ABS terpolymers, SAN copolymers) comprising a stabilizer composition comprising a combination of a phenolic antioxidant with 2,6-di-tert-butylphenyl pentaerythrityl spiro-bis- phosphite. Among a long list of exemplary phenolic antioxidants, thiodiglycol bis-(3,5-di-t-butyl-4-hydroxyphenyl propionate) and stearyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate are mentioned.

[0006] Examples 24, 25 and 31 to 35 show PP or HDPE compositions comprising 0.1 or 0.3 parts by weight of one of the above antioxidants.

[0007] WO 2015 / 078877 discloses a stabilizing composition for a polymer composition, preferably polyethylene, comprising a first stabilizing component comprising at least one fully hindered phenolic antioxidant (a); a second stabilizing component comprising at least one partially hindered phenolic antioxidant (b); and a third stabilizing component comprising at least one sulfur containing antioxidant (c). Among a list of 13 suitable antioxidants (a), octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl) propionate (ANOX® PP18 - CAS 2082-79-3), 2,2'-thiodiethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl) propionate] (ANOX® 70 - CAS 41484-35-9) and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl) benzene (ANOX® 330 - CAS 1709-70-2) are mentioned. A mixture of octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl) propionate (a), dilauryl thiodipropionate (c) and triethylene glycol bis-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)-propionate] or, alternatively, a mixture of 2,2'-thiodiethylene bis 3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate and distearyl thiodipropionate (c) is exemplified. In all examples two or more antioxidants (a) are not used. The stabilizing composition is used for a polyolefin-based polymeric material, i.e. LDPE. No ABS compound is mentioned.

[0008] CN 102181123 A discloses a flame retardant ABS (acrylonitrile-butadiene-styrene) material comprising 0.3 to 0.6 parts by weight of at least one antioxidant selected from the group consisting of antioxidant 1076, antioxidant 1010, antioxidant 300, antioxidant 245, antioxidant 1035, antioxidant 1222, antioxidant 168, BHT. In all examples a combination of antioxidant 1010 and antioxidant 168 or antioxidant 245 is used.

[0009] CN 101824202 A and CN 102040798 A disclose a composite processing stabilizer for ABS and HIPS resins consisting of bisphenol monoacrylate antioxidant, phenolic antioxidant and auxiliary antioxidant. The phenolic antioxidant is preferably antioxidant 1076 (octadecyl-3,5-bis(l,l-dimethylethyl)-4-hydroxyphenylpropionate), antioxidant 1010, antioxidant WSL (Wingstay L), antioxidant 300, antioxidant 245, antioxidant 1035 (2,2'-thiodiethanol bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and antioxidant 1222. Preferably, the auxiliary antioxidant is TNPP, antioxidant 168, P-EPQ, antioxidant 626, DLTP, DSTP. In each example ABS composition, only one phenolic antioxidant is used.

[0010] CN102643508 A describes a flame-retardant ABS material comprising 0.5 - 1.5 parts by weight of an antioxidant. Suitable antioxidants are antioxidant 1010, antioxidant 1330, antioxidant 1076, antioxidant 1034, antioxidant 168, antioxidant 618, antioxidant 300, antioxidant DSTP and antioxidant DMTDP. No specific mixture of the antioxidants is mentioned or used in the examples.

[0011] CN 109825025 A discloses a heat and light resistant ABS composition comprising 0.15 to 1 wt% of an antioxidant. The antioxidant is one or a combination of components selected from a long list, including phenolic antioxidants (including β-(octadecan-3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and 2,2'-thiodiethyl bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]) and phosphite antioxidants. In the examples, none of the aforementioned phenolic antioxidants is used.

[0012] JP 02103253 A relates to a vinyl aromatic diene block copolymer and blends thereof with thermoplastic polymers or rubbers stabilized with 0.5 to 5 parts by weight of at least one specific phenolic compound. In the examples, the block copolymer is extrusion granulated in the presence of a phenolic antioxidant AO1 to AO13 (e.g. AO-6: n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxy-phenyl)propionate, or AO-8: 1,3,5-trimethyl-2,4,6-(3,5-di-tert-butyl-4-hydroxy-benzyl)benzene). No block copolymer stabilized with a mixture comprising both antioxidants AO6 and AO8 is disclosed.

[0013] WO 2018 / 202791 relates to a stabilizing composition for stabilizing polymers, such as polyolefins. The stabilizing composition comprises at least one antioxidant comprising one or more of: i. a phenolic antioxidant; ii. a phosphite antioxidant; iii. a sulfur-containing antioxidant; and iv. an amine antioxidant. In a long list of suitable (hindered) phenolic antioxidants, 2,2'-thiodiethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (ANOX™ 70 - CAS 41484-35-9); octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate (ANOX™ PP18 - CAS 2082-79-3); and 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (ANOX™ 330 - CAS 1709-70-2) are mentioned. The polymeric material is preferably based on polyolefins, i.e. PE and / or PP, or styrenic block copolymers. All examples show PP polymers stabilized with a composition comprising only one phenolic stabilizer.

[0014] WO 1995 / 02639 discloses a method for stabilizing recycled styrene-containing plastic materials, such as expanded PS, ABS waste, wherein a mixture of 0.01 to 10 wt.-% of a) at least one sterically hindered phenol and b) an inorganic compound, such as a metal oxide, is used. One of the most preferred components a) is octadecyl beta-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (AO-2).

[0015] In a long list of representative examples of such sterically hindered phenols, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene is mentioned. In a second list, as one of the further preferred compounds, (thiodi-2,1-ethylene-3,5-bis(1,1-dimethyl)-4-hydroxyphenyl propionate) is disclosed. In all example expanded PS compositions, only one phenolic stabilizer a) (such as AO-2) is used. No thio co-stabilizer B is used in all examples.

[0016] Emelyanova et al. (Zhurnal Prikladnoi Khimii, (1979), 52(9), 2055-60) tested 15 stabilizers, including phenols (including benzenepropanoic acid 3,5-bis(l,l-dimethylethyl)-4-hydroxy-, 1,1 '-(thiodi-2,1- ethylene) ester; 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene; octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (preferred), thiophenols, etc., to improve the thermal stability of ABS copolymers. No mixture of the stabilizers was used in this study.

[0017] Stabilizers are typically used in the form of dispersions. Typically, such stabilizer dispersions comprise phenolic antioxidants to stabilize the polymer against oxidative phenomena. Phenolic antioxidants are typically used in combination with a co-stabilizer, such as an organic sulfur compound (organic sulfur compound) or an organic phosphorus compound (organic phosphorus compound). In the production of stabilizer dispersions and / or thermoplastic compositions, further additives are typically also used, such as light stabilizers, antistatic agents, and other commonly used additives. In particular, silicone oils, such as polydimethylsiloxanes, are used as additives in ABS compositions, in particular to improve the resistance to compounds and to improve the impact strength.

[0018] Typically, a dispersion is a system consisting of at least one internal phase (also called dispersed phase), which is uniformly and finely distributed in a so-called external or continuous phase. Typically, dispersions are prepared by introducing the required dispersion energy into the system, for example by mechanical energy. Typically, in common dispersions, so-called coarse dispersions, the average size of the dispersed phase particles is in the range from 100 nm to 1 mm. Macroemulsions are thermodynamically unstable and typically separate within a certain time depending on the conditions, such as stabilization, temperature, and pH value. Several methods and devices for preparing dispersions are known to the person skilled in the art. Surface-active substances, so-called surfactants or dispersants, which typically facilitate the formation of dispersed phase particles, such as droplets or solid particles, and counteract phase separation, are an important component of dispersions.

[0019] Aqueous stabilizer dispersions for stabilizing ABS compositions against thermal and ultraviolet (UV) decomposition, which comprise a phenolic stabilizer and a co-stabilizer, such as an organic sulfur compound (organic sulfur compound) or an organic phosphorus compound, typically have to be prepared using an expensive multistage process to ensure a homogeneous distribution of the components.

[0020] DE 199 46 519 A1 and WO 2001 / 23498 disclose a continuous process for the preparation of an aqueous stabilizer dispersion S for stabilizing a polymer dispersion, i.e. an emulsion graft copolymer. The stabilizer dispersion S comprises preferably a phenolic antioxidant C, a thio co-stabilizer D and a surfactant A. Stabilizer dispersions S are exemplified, wherein the phenolic antioxidant C is CI : octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No.: 2082-79-3), C2: butylated reaction product of p-cresol and dicyclopentadiene (Wingstay L), C3: 1,1,3,-tris-(2'-methyl-4'-hydroxy-5'-tert-butylphenyl)butane (Topanol CA) and C4: mixture of 4,4'-thiobis-(3-methyl-6-tert-butylphenol).

[0021] WO 2017 / 211783 discloses a process for the preparation of a homogeneous aqueous stabilizer dispersion S which is suitable for the production of stabilizing compositions based on acrylonitrile-butadiene-styrene copolymers (ABS). The stabilizer dispersion S comprises at least one phenolic stabilizer A, at least one thio co-stabilizer B (i.e. dilaurylthiodipropionate (DLTP)), at least one surfactant C (i.e. potassium stearate or oleic acid) and at least one silicone oil D. Preferably, the phenolic stabilizer A is a butylated reaction product of p-cresol and dicyclopentadiene according to formula (la) with n = 1-3 (CAS No.: 68610-51-5, i.e. Wingstay L) (Ia). In addition to the phenolic stabilizer A of formula (la), other conventional antioxidants can be comprised in the stabilizer dispersion S. In the list of 15 preferred phenolic stabilizers A, the stabilizer A of formula (la) is mentioned as well as including 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene (CAS 1709-70-2) or octadecyl 3-(3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl)propionate (CAS 2082-79-3). In all exemplified stabilizer dispersions, only one phenolic stabilizer A is used, i.e. the stabilizer of formula (la).

[0022] In many of the above prior art ABS molding compositions, Wingstay L is used as phenolic stabilizer, which in the future can not be allowed anymore for use in ABS polymers due to regulatory reasons.

[0023] Therefore, there is a need to provide an improved acrylonitrile-butadiene-styrene copolymer (ABS) molding composition and a process for its preparation, which has a good base color, a good color stability during the process of processing (injection molding), and a good long-term stability during the life cycle of the injection molded article, while also meeting the (future) regulatory requirements. SUMMARY

[0024] It is an object of the present invention to provide a process for the preparation of an acrylonitrile-butadiene-styrene copolymer (ABS) molding composition, which has a good, or, compared to the prior art compositions comprising the phenolic stabilizer A of formula (la) described above, an improved base color, a good or improved color stability during the process of processing (injection molding), and a good or improved long-term stability during the life cycle of the injection molded article. Furthermore, the ABS molding composition obtained by the process should only comprise phenolic stabilizers (antioxidants) which meet the (future) regulatory requirements.

[0025] It is an object of the present invention to provide a process for the preparation of an acrylonitrile-butadiene-styrene copolymer (ABS) molding composition, which has a good, or, compared to the prior art compositions comprising the phenolic stabilizer A of formula (la) described above, an improved base color, a good or improved color stability during the process of processing (injection molding), and a good or improved long-term stability during the life cycle of the injection molded article. Furthermore, the ABS molding composition obtained by the process should only comprise phenolic stabilizers (antioxidants) which meet the (future) regulatory requirements. 0 to 94.996 wt.-%, preferably 5 to 80 wt.-%, based on the total weight of the thermoplastic molding composition, of a rubber-free thermoplastic copolymer CA comprising at least 50 wt.-% of one or more vinyl aromatic monomers CA11, preferably selected from the group consisting of styrene and alpha-methylstyrene, and mixtures of monomers CA11 with at least one further comonomer CA12, in particular at least one vinyl cyano monomer; 5 to 99.996 wt.-%, preferably 15 to 60 wt.-%, based on the total weight of the thermoplastic molding composition, of a graft copolymer CB comprising: 5 to 95 wt.-%, based on the weight of the graft base CB1, of at least one graft base CB1 obtained by emulsion polymerization of: CB11: 50 to 100 wt.-%, based on the weight of the graft base CB1, of at least one conjugated diene B11, in particular 1,3-butadiene, CB12: 0 to 50 wt.-%, based on the weight of the graft base CB1, of at least one further monomer CB12 selected from the group consisting of styrene, alpha-methylstyrene, acrylonitrile, methacrylonitrile and methyl methacrylate, in particular styrene; and 5 to 95 wt.-%, based on the weight of the graft copolymer CB, of at least one graft shell CB2 obtained by emulsion polymerization of the following monomers in the presence of the at least one graft base CB1: CB21 : 50 to 95 % by weight, based on the graft shell CB2, of monomers CB21 selected from the group consisting of styrene, alpha-methylstyrene, and mixtures of styrene with at least one monomer selected from the group consisting of alpha-methylstyrene, para-methylstyrene and (meth)acrylic acid C1-C8-alkyl ester, in particular styrene; CB22: 5 to 50 % by weight, based on the graft shell CB2, of monomers B22 selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one monomer selected from the group consisting of methacrylonitrile, maleic anhydride, phthalic anhydride, N-phenylmaleimide, N-cyclohexylmaleimide, in particular acrylonitrile, wherein the sum of CB11 + CB12 is 100 % by weight; the sum of CB21 + CB22 is 100 % by weight, and the sum of graft base CB1 and graft shell CB2 is 100 % by weight; 0.002 to 5 % by weight, preferably 0.01 to 3 % by weight, more preferably 0.1 to 1 % by weight, based on the total weight of the thermoplastic molding composition, of two or more phenolic stabilizers A selected from the group consisting of: A2: octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No.: 2082-79-3); A3: benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 1,1 '-(thiodi-2,1- ethenyl) ester (CAS No.: 41484-35-9); and A4: 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene (CAS No.: 1709-70-2); wherein the phenolic stabilizers A are preferably a combination of phenolic stabilizers A2 and A3, or A2 and A4, or A2, A3 and A4, in a weight ratio A2:A3, or A2:A4, or A2:(A3+A4) of 90 to 55 : 10 to 45, preferably 85 to 60 : 15 to 40, more preferably 80 to 65 : 20 to 35; 0.002 to 5 % by weight, preferably 0.01 to 3 % by weight, more preferably 0.1 to 1 % by weight, based on the total weight of the thermoplastic molding composition, of at least one thio co-stabilizer B; Optionally, up to 2 % by weight, preferably 0.001 to 1 % by weight, more preferably 0.01 to 0.2 % by weight, based on the total weight of the thermoplastic molding composition, of at least one silicone oil component D; 0 to 30 % by weight, preferably 0 to 10 % by weight, more preferably 0.01 to 1 % by weight, based on the total weight of the thermoplastic molding composition, of at least one further component K selected from the group consisting of: different from additives and / or adjuvants A, B and D, with the proviso that phenolic stabilizer A1 - butylated reaction product of p-cresol and dicyclopentadiene (CAS No.: 68610-51 -5) is excluded, residues of said at least one surfactant C used for producing the stabilizer dispersion S, and / or at least one further polymer selected from the group consisting of polycarbonates PC, polyester carbonates PEC and polyamides PA; The method comprises the following steps: x) adding a stabilizer dispersion S to the graft copolymer CB after its emulsion polymerization, said stabilizer dispersion S being obtained by a method comprising the following steps ii) to v) in which the order of steps ii) to v) can be varied: i) providing an aqueous composition, preferably water; ii) adding at least one surfactant C to the aqueous composition; iii) optionally adding at least one thio co-stabilizer B to the aqueous composition, wherein the temperature of the aqueous composition is higher than or equal to the melting point of the at least one thio co-stabilizer B; iv) adding at least one, typically two or more, of said phenolic stabilizers A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferably the phenolic stabilizer A2 alone, to the aqueous composition, wherein the temperature of the aqueous composition is higher than or equal to the melting point of the optional at least one thio co-stabilizer B, at least 40 °C; v) optionally adding at least one silicone oil component D to the aqueous composition; vi) homogenizing the aqueous composition obtained in steps ii) to v) to yield a stabilizer dispersion S; xi) precipitating the graft copolymer CB obtained in step x) including the stabilizer dispersion S by adding a precipitation solution comprising at least one salt; xii) subjecting the precipitated graft copolymer CB obtained in step xi) to mechanical dewatering, optionally washing and / or optionally drying; prexiii) optionally providing a thermoplastic copolymer CA; prexiii') optionally providing a stabilization premix of the thermoplastic copolymer CA with at least one, typically two or more, of said phenolic stabilizers A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferably the phenolic stabilizer A3 or A4 alone, and the at least one thio co-stabilizer B, and optionally the at least one silicone oil component D; xiii) optionally mixing the graft copolymer CB obtained in step xii) with the thermoplastic copolymer CA, and optionally with further components K, or xiii') optionally mixing the graft copolymer CB obtained in step xii) with the stabilized premix obtained in step prexiii'), and optionally with further components K; and xiv) mixing the composition obtained in step xii) or xiii) with at least one, typically two or more, of said phenolic stabilizer A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferred a phenolic stabilizer A3 or A4 alone, and said at least one thio co-stabilizer B, and optionally said at least one silicone oil component D.

[0026] In a preferred embodiment, the amounts of components CA, CB, A, B, D and optionally K add up to 100 wt.-%. In particular, the amount of graft copolymer CB can be adjusted such that the sum of compounds is 100 wt.-%.

[0027] The optional at least one thermoplastic copolymer CA, the at least one graft copolymer CB, the two or more phenolic stabilizers A, the at least one thio co-stabilizer B, the optional at least one silicone oil component D, the optional at least one further component K, the stabilizer dispersion S, and suitable methods for producing the stabilizer dispersion S, as well as preferred embodiments of the process according to the present application, will be described in detail hereinafter.

[0028] Graft copolymer CB Preferably, the graft copolymer CB comprises: 5 to 95 wt.-%, preferably 40 to 85 wt.-%, based on the graft copolymer CB, of at least one graft base CB1, which is obtained by emulsion polymerization of: CB11: 50 to 100 wt.-%, preferably 79 to 100 wt.-%, based on the weight of the graft base CB1, of at least one conjugated diene CB11, in particular 1,3-butadiene, CB12: 0 to 50 wt.-%, preferably 0 to 21 wt.-%, based on the weight of the graft base CB1, of at least one further monomer CB12 selected from styrene and a-methylstyrene, in particular styrene; and 5 to 95 wt.-%, preferably 15 to 60 wt.-%, based on the graft copolymer CB, of at least one graft shell CB2, which is obtained by emulsion polymerization of: CB21 : 50 to 95 wt.-%, preferably 70 to 90 wt.-%, based on the weight of the graft shell CB2, of monomers CB21 selected from the group consisting of styrene, alpha-methylstyrene, and mixtures of styrene with at least one monomer selected from the group consisting of alpha-methylstyrene and methyl methacrylate, preferably styrene and / or alpha-methylstyrene, more preferably styrene; CB22: 5 to 50 wt.-%, preferably 10 to 30 wt.-%, based on the weight of the graft shell CB2, of monomers B22 selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one monomer selected from the group consisting of methacrylonitrile, maleic anhydride, N-phenylmaleimide, in particular acrylonitrile.

[0029] The average particle size of the graft copolymer CB can vary between 50 nm and 10,000 nm, preferably between 80 nm and 3,000 nm, more preferably between 100 nm and 2,000 nm.

[0030] The particle size distribution of the graft copolymer CB can be unimodal, bimodal or multimodal. According to one particularly preferred embodiment of the present application, the particle size distribution is bimodal.

[0031] Suitable as the at least one conjugated diene CB11 are 1,3-butadiene and isoprene, preferably 1,3-butadiene.

[0032] Preferably, the monomers CB11 are 1,3-butadiene and the monomers CB12 are preferably styrene and / or alpha-methylstyrene, in particular styrene.

[0033] Preferably, the monomers CB21 are styrene and / or alpha-methylstyrene, in particular styrene, and the monomers CB22 are preferably acrylonitrile.

[0034] In one preferred embodiment, the monomers CB11 are 1,3-butadiene.

[0035] The graft base CB1 can be obtained, for example, by reacting 0 to 10 wt.-% of styrene and 90 to 100 wt.-% of butadiene.

[0036] In one preferred embodiment, the graft copolymer CB is an ABS graft copolymer, which consists of a graft base CB1 obtained by emulsion polymerization of monomers CB11 (i.e. 1,3-butadiene) and monomers CB12 (i.e. styrene) and a graft shell CB2 obtained by emulsion polymerization of monomers CB21 (selected from the group consisting of styrene, alpha-methylstyrene and mixtures thereof) and monomers B22 (i.e. acrylonitrile) in the presence of the graft base CB1.

[0037] The graft copolymer CB usually has a complex structure and essentially consists of a graft base CB1 and a graft shell CB2. The graft copolymer CB is polymerized by emulsion polymerization, wherein the graft base CB1 is first obtained by emulsion polymerization of monomers CB11 and optionally CB12, and the graft shell CB2 is then obtained by emulsion polymerization of monomers CB21 and CB22 in the presence of the graft base CB1. Preferably, the graft copolymer CB is polymerized by aqueous radical emulsion polymerization. The reaction is usually initiated by water-soluble or oil-soluble radical polymerization initiators, such as inorganic or organic peroxides, like peroxydisulfates or benzoyl peroxide, or by means of redox initiator systems. Suitable polymerization processes are described in documents WO 2002 / 10222, DE-A 28 26925 and EP-A 022 200.

[0038] Graft latices described in EP-B 0 845 496, WO 2009 / 071537 and WO 2014 / 170407 can be preferred for use in the process of the present application.

[0039] Preferably, the graft base CB1 having a multimodal or bimodal, more preferably bimodal, particle size distribution can be obtained after its emulsion polymerization using an agglomerated copolymer, in particular an agglomerated latex, as described in WO 2008 / 020012, wherein the graft shell CB2 is obtained by emulsion polymerization of monomers CB21 and CB22 in the presence of the agglomerated graft base after agglomeration.

[0040] In a preferred embodiment, the graft copolymer CB comprises: CB1 : 40 to 85 % by weight, based on the graft copolymer CB, of at least one graft base CB1 obtained by emulsion polymerization of monomers CB11 and optionally CB12: CB11 : 79 to 100 % by weight, based on the weight of the graft base CB1, of at least one conjugated diene CB11, preferably 1,3-butadiene; CB12: 0 to 21 % by weight, based on the weight of the graft base CB1, of at least one further monomer CB12 selected from styrene and a-methylstyrene, in particular styrene; wherein the sum of CB11 + CB12 is 100 % by weight; and the obtained graft base CB1 is agglomerated by adding: 0.01 to 5 parts by weight, based on 100 parts by weight of the graft base CB1 (both based on the solid content), of an agglomerated copolymer CP consisting of: CP1 : 80 to 99.9 % by weight of one or more hydrophobic C1 to C12 alkyl acrylates or C1 to C 12alkyl methacrylates, and CP2: 0.1 to 20 wt.-% of one or more hydrophilic comonomers selected from the group consisting of methacrylamide, acrylamide, methacrylamide, ethyl acrylamide and n-butyl acrylamide, wherein the sum of CP1 and CP2 is 100 wt.-%; and CB2: 15 to 60 wt.-%, based on the graft copolymer CB, of at least one graft shell CB2, which is obtained by emulsion polymerization of the following monomers in the presence of the agglomerated at least one graft base CB1 : CB21 : 70 to 90 wt.-%, based on the graft shell CB2, of monomers CB21 selected from the group consisting of styrene, alpha-methylstyrene, and mixtures of styrene with at least one monomer selected from the group consisting of alpha-methylstyrene and methyl methacrylate, in particular styrene and / or alpha-methylstyrene; CB22: 10 to 30 wt.-%, based on the graft shell CB2, of monomers CB22 selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one monomer selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one monomer selected from the group consisting of methacrylonitrile, maleic anhydride, N-phenylmaleimide, in particular acrylonitrile; wherein the sum of CB21 + CB22 is 100 wt.-%; and wherein the sum of the graft base CB1 and the graft shell CB2 is 100 wt.-%; and wherein the agglomerated graft base CB1 has a bimodal particle size distribution comprising a fraction of particles having a D 50 value in the range of 80 to 330 nm, preferably in the range of 80 to 150 nm, and a fraction of particles having a D 50 value in the range of 340 to 550 nm, preferably in the range of 340 to 480 nm.

[0041] particle size distribution, the weight average particle size D W and the weight median average particle size D 50 can be determined using an ultracentrifuge (as described for example in W. Scholtan, H. Lange: Kolloid Z. u. Z. Polymere 250, pp. 782 to 796, 1972) or a disc centrifuge (for example a DC 24000 of CPS Instruments Inc.). The weight average particle size D W (or the Debye average particle size) is based on the average size of the particles per unit weight. The weight average particle size D W can be given as definition: D W = sum ( n i * D i4 ) / sum ( n i * D i 3 ) n i : number of particles having a diameter D i

[0042] (see G. Lagaly, O. Schulz, R. Ziemehl: Dispersionen und Emulsionen: Eine Einführung in die Kolloidik feinverteilter Stoffe einschließlich der Tonminerale, Darmstadt: Steinkopf-Verlag 1997, ISBN 3-7985-1087-3, pages 279 to 283, equation 8.3b). The weight median diameter D 50 represents the diameter at which 50% by weight of the particles are smaller than this size.

[0043] In particular, preferred embodiments of the graft base CB1 are described in DE-A 10 2005 022 632 (Examples S 11 to S 13 ) and WO 2014 / 170406 (Example B1 ). In particular, preferred embodiments of the agglomerated copolymer CP are described in WO 2008 / 020012 (Examples 3.1 a to 3.1 h) and WO 2014 / 170406 A1 (Examples C-1 and C-2). Preferably, the graft copolymer CB described in WO 2014 / 170406 is used according to the present application, see "Pfropfcopolymer B, Allgemeine Vorgehensweise", pages 34-35.

[0044] The molding composition can also comprise two or more different graft copolymers CB. In a preferred embodiment, the graft copolymer CB is a mixture of at least two graft copolymers CB-I and CB-II, wherein The graft copolymer CB-I is obtained by emulsion polymerization of a mixture of monomers CB21 and CB22 in the presence of a graft base CB1 -I having a particle size D 50 in the range of 80 to 330 nm, and the graft copolymer CB-II is obtained by emulsion polymerization of a mixture of monomers CB21 and CB22 in the presence of a graft base CB1 -II having a particle size D 50 in the range of 340 to 480 nm.​

[0045] The at least one graft copolymer CB is present in the thermoplastic molding composition in an amount of at least 5 wt.-%, preferably at least 15 wt.-%, more preferably at least 25 wt.-%, most preferably at least 30 wt.-%, based on the total weight of the thermoplastic molding composition.

[0046] Thermoplastic copolymer CA The thermoplastic copolymer CA is free of any latex type polymer (rubber free) and comprises at least 50 wt.-% of one or more vinyl aromatic monomers CA11, in particular styrene and / or a-methylstyrene, and a mixture of monomers CA11 with at least one further comonomer CA12, in particular at least one vinyl cyano monomer.

[0047] Preferably, the vinyl aromatic monomers CA11 are selected from styrene and a-methylstyrene, in particular styrene.

[0048] Preferably, the at least one further comonomer CA12 is at least one vinyl cyano monomer (as comonomer CA12).

[0049] Preferably, the thermoplastic copolymer CA comprises at least 50 wt.-% of one or more vinyl aromatic monomers CA11, in particular styrene and / or a-methylstyrene, and at most 50 wt.-% of one or more further comonomers CA12, in particular vinyl cyano monomers.

[0050] In particular, the at least one thermoplastic copolymer CA can be selected from polystyrene, styrene copolymers such as styrene-acrylonitrile copolymers, a-methylstyrene copolymers such as a-methylstyrene-acrylonitrile copolymers.

[0051] Preferably, the thermoplastic copolymer CA comprises (or consists of) at least one vinyl aromatic monomer CA11, preferably selected from styrene and a-methylstyrene, in an amount of 69 to 81 wt.-%, preferably 70 to 76 wt.-%, more preferably 72 to 76 wt.-%, and at least one vinyl cyano monomer CA12, preferably acrylonitrile and / or methacrylonitrile, in an amount of 19 to 31 wt.-%, preferably 24 to 30 wt.-%, more preferably 24 to 28 wt.-%.

[0052] In a preferred embodiment, the thermoplastic copolymer CA is a SAN copolymer (CA-1) consisting of monomers CA11 and CA12, wherein the at least one vinyl aromatic monomer CA11 is selected from styrene, a-methylstyrene and mixtures thereof, and the at least one vinyl cyano monomer CA12 is acrylonitrile.

[0053] Generally, the thermoplastic copolymer CA has a number average molar mass (Mn) of 10,000 to 200,000 g / mol, preferably 20,000 to 150,000 g / mol, more preferably 30,000 to 100,000 g / mol, and a weight average molar mass (Mw) of 50,000 to 500,000 g / mol, preferably 100,000 to 400,000 g / mol, more preferably 150,000 to 350,000 g / mol.n ) from 15,000 to 100,000 g / mol (determined by GPC with UV detection). The viscosity (Vz) of the thermoplastic copolymer CA can be, for example, in the range from 50 to 120 ml / g (measured according to DIN 53726 at 25 °C in a 0.5 wt.-% solution in DMF).

[0054] The thermoplastic copolymer CA can be prepared by all known methods, for example mass polymerization, solution polymerization, suspension polymerization and emulsion polymerization or hybrid processes, for example mass / suspension polymerization, with or without further components. More preferably, the thermoplastic copolymer CA is prepared from the components acrylonitrile and styrene and / or a-methylstyrene by mass polymerization or in the presence of one or more solvents, for example toluene or ethylbenzene. Polymerization processes are described, for example, in Kunststoff-Handbuch [Plastics Handbook], Vieweg-Daumiller, Volume V, (Polystyrol) [Polystyrene], Carl-Hanser-Verlag, Munich 1969, page 122 and following pages.

[0055] Phenolic stabilizer A and thio co-stabilizer B The two or more phenolic stabilizers A are selected from the following group: A2: octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No.: 2082-79-3), with the proviso that A3 and / or A4 must always be present when A2 is applied; A3: benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 1,1 '-(thiobis-2,1- ethenyl) ester (CAS No.: 41484-35-9); A4: 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene (CAS No.: 1709-70-2).

[0056] A preferred phenolic stabilizer A is a combination of the phenolic stabilizers A2 and A3.

[0057] A further preferred phenolic stabilizer A is a combination of the phenolic stabilizers A2 and A4.

[0058] Furthermore, a preferred phenolic stabilizer A is a combination of the phenolic stabilizers A2, A3 and A4.

[0059] According to another embodiment, the phenolic stabilizer A is a combination of the phenolic stabilizers A3 and A4.

[0060] In the context of the present application, the combination of stabilizers (i.e. the combination of phenolic stabilizers A, the combination of thio co-stabilizers B, and / or the combination of phenolic stabilizers A and thio co-stabilizers B) has the following meanings: a) mixtures of two or more stabilizer components, and / or b) combinations of stabilizers obtained by adding two or more stabilizer components in separate feed streams at different points of the production or processing step to the graft copolymer CB, the ABS polymer compound (graft copolymer CB and optional thermoplastic copolymer CA) and / or the blend of the ABS polymer compound with PC, PEC and / or PA, or c) combinations of both meanings.

[0061] When a combination of phenolic stabilizers is applied, for example A2 with A3, or A2 with A4, or A2 with A3 and A4, then the preferred amount of A2 is always higher than the sum of A3 or A4, or A3 and A4.

[0062] Preferred is a combination of phenolic stabilizers A2 and A3 in a weight (percent) ratio A2 : A3 of 95 to 55 : 5 to 45, preferably 90 to 60 : 10 to 40, more preferably 85 to 65 : 15 to 35. Furthermore, often a combination of phenolic stabilizers A2 and A3 in a weight (percent) ratio A2 : A3 of 80 to 65 : 20 to 35 is used.

[0063] Furthermore, preferred is a combination of phenolic stabilizers A2 and A4 in a weight (percent) ratio A2 : A4 of 95 to 55 : 5 to 45, preferably 90 to 60 : 10 to 40, more preferably 85 to 65 : 15 to 35. Furthermore, often a combination of phenolic stabilizers A2 and A4 in a weight (percent) ratio A2 : A4 of 80 to 65 : 20 to 35 is used.

[0064] Furthermore, preferred is a combination of phenolic stabilizers A2, A3 and A4 in a weight ratio A2 : (A3 + A4) of 95 to 55 : 5 to 45, preferably 90 to 60 : 10 to 40, more preferably 85 to 65 : 15 to 35. Furthermore, often a combination of phenolic stabilizers A2, A3 and A4 in a weight (percent) ratio A2 : (A3 + A4) of 80 to 65 : 20 to 35 is used.

[0065] According to another embodiment, a combination of phenolic stabilizers A3 and A4 is used in a weight ratio A3 : A4 of 90 to 10 : 10 to 90, preferably 80 to 20 : 20 to 80, more preferably 70 to 30 : 30 to 70.

[0066] The phenolic stabilizer A is used in combination with at least one thio co-stabilizer B, which is preferably a sulfide compound selected from the following group: B1 : dilaurylthiodipropionate (CAS No.: 123-28-4); B2: distearylthiodipropionate (CAS No.: 693-36-7); B3: dimyristylthiodipropionate (CAS No.: 16545-54-3); B4: 2,4-bis(n-octylthio)-6-(4'-hydroxy-3',5'-di-tert-butylanilino)-1,3,5-triazine (CAS No.: 991 -84-4); B5: trimethylolpropane tri(octylthiodipropionate); B6: trimethylolethane tri(octylthiodipropionate); B7: ethylene glycol bis(dilaurylthiodipropionate); B8: didecyl monosulfide.

[0067] Preferred thio co-stabilizers B are B1 and / or B2, particularly preferred is B1.

[0068] The phenolic stabilizer A and the at least one thio co-stabilizer B as described above for the stabilizer combination can be added separately, partially mixed or fully mixed in at least one or more feed streams to the graft rubber copolymer CB, the ABS polymer compound (graft copolymer CB and optional thermoplastic copolymer CA) and / or the blend of the ABS polymer compound with PC, PEC and / or PA in the production and processing steps.

[0069] Preferred combinations of phenolic stabilizer A and thio co-stabilizer B are: A2 and A3 and B1 and / or B2, preferably A2 and A3 and B1 ; A2 and A4 and B1 and / or B2, preferably A2 and A4 and B1 ; A2 and A3 and A4 and B1 and / or B2, preferably A2 and A3 and A4 and B1.

[0070] A stabilizer dispersion is required to stabilize the graft copolymer CB against oxidation and discoloration during post-treatment including: precipitation of the graft copolymer CB by adding a precipitation solution comprising at least one salt, mechanical dewatering (e.g. by filtration or centrifugation), optional washing and / or optional drying of the precipitated graft copolymer CB.

[0071] A suitable method to dry the precipitated graft copolymer CB is drying in a flash dryer or fluidized bed dryer using hot air, or a combination of both to achieve a dried graft copolymer CB, or drying the wet graft copolymer CB together with a SAN copolymer melt in a kneader or extruder.

[0072] The preparation of the stabilizer dispersion S can be carried out according to DE 199 46 519 A1 or WO 2017 / 211783 A1, but is not limited to the methods or procedures described there.

[0073] According to the present application, the stabilizer dispersion S is obtained by a process comprising the following steps, the order of steps ii) to v) can be changed: i) providing an aqueous composition, preferably water; ii) adding at least one surfactant C to the aqueous composition obtained in step i); iii) optionally adding at least one thio co-stabilizer B to the aqueous composition obtained in step ii), wherein the temperature of the aqueous composition is higher than or equal to the melting point of the at least one thio co-stabilizer B; iv) adding at least one, typically two or more, of the phenolic stabilizers A2, A3 or A4, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferred the phenolic stabilizer A2 alone, to the aqueous composition obtained in step ii) or iii), wherein the temperature of the aqueous composition is higher than or equal to the melting point of the optional at least one thio co-stabilizer B, at least 40 °C; v) optionally adding at least one silicone oil component D; vi) homogenizing the aqueous composition obtained in steps ii) to v) to produce the stabilizer dispersion S.

[0074] The homogenization of the aqueous composition obtained in steps ii) to v) can be achieved by, for example, passing the aqueous composition at least once through at least one homogenization device, preferably at least once through at least one homogenization nozzle, whereby the stabilizer dispersion S is obtained, which consists of a continuous phase and at least one dispersed phase. Alternatively, any other suitable homogenization device that is capable of providing high shear forces can be applied, such as a rotor-stator mixer or a bead mill. If the dispersed phase is solid under the processing conditions, a bead mill process can be preferred.

[0075] Typically, a rotor-stator mixer is used as homogenization device.

[0076] The following stabilizer dispersions S are preferred: 1) a stabilizer dispersion of component A2.

[0077] 2) a stabilizer dispersion of component A3.

[0078] 3) a stabilizer dispersion of component A4.

[0079] 4) a stabilizer dispersion of a mixture of components A2 and A3.

[0080] 5) stabilizer dispersion of a mixture of components A2 and A4.

[0081] 6) stabilizer dispersion of a mixture of components A2, A3 and A4.

[0082] 7) stabilizer dispersion of a mixture of components A2 and B1 and / or B2, preferably A2 and B1.

[0083] 8) stabilizer dispersion of a mixture of components A3 and B1 and / or B2, preferably A3 and B1.

[0084] 9) stabilizer dispersion of a mixture of components A4 and B1 and / or B2, preferably A4 and B1.

[0085] 10) stabilizer dispersion of a mixture of components A2 and A3 and B1 and / or B2, preferably A2 and A3 and B1.

[0086] 11) stabilizer dispersion of a mixture of components A2 and A4 and B1 and / or B2, preferably A2 and A4 and B1.

[0087] 12) stabilizer dispersion of a mixture of components A2, A3 and A4 and B1 and / or B2, preferably A2, A3 and A4 and B1.

[0088] The at least one phenolic stabilizer A contained in the stabilizer dispersion S is preferably used in an amount of 0.1 to 65 wt.-%, preferably 1 to 60 wt.-%, particularly preferably 10 to 30 wt.-%, most preferably 15 to 30 wt.-%, based on the total weight of the stabilizer dispersion S.

[0089] The at least one thio co-stabilizer B, if present, is preferably used in an amount of 0.1 to 65 wt.-%, preferably 1 to 60 wt.-%, particularly preferably 10 to 40 wt.-%, most preferably 20 to 40 wt.-%, based on the total weight of the stabilizer dispersion S.

[0090] Optionally, at least one silicone oil component D is used during the preparation of the stabilizer dispersion S.

[0091] The amount of water in the stabilizer dispersion S can be adjusted so that the sum with the other components amounts to 100 wt.-%.

[0092] For the preparation of the stabilizer dispersion S, at least one surfactant C is used.

[0093] A surfactant is a compound which reduces the surface tension of an aqueous phase and / or protects colloids, which helps to stabilize dispersions, in particular suspensions, emulsions or suspoemulsions against sedimentation.

[0094] The at least one surfactant C is preferably used in an amount of 0.1 to 20 % by weight, preferably 0.5 to 15 % by weight, particularly preferably 1 to 10 % by weight, most preferably 1 to 5 % by weight, based on the total weight of the stabilizer dispersion S.

[0095] Suitable surfactants C are surfactants or protective colloids which are generally known for the preparation of emulsions and suspensions, in particular aqueous emulsions and suspensions. Mixtures of surfactants and / or protective colloids can also be used.

[0096] Examples of suitable protective colloids are polyvinyl alcohol, cellulose derivatives and copolymers containing vinylpyrrolidone. A detailed description of other suitable protective colloids is found in Houben-Weyl, Methoden der organischen Chemie, Vol. XIV / 1, Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 411-420.

[0097] The surfactants used as surfactants C are preferably exclusively compounds which, unlike the protective colloids, generally have a relative molecular mass of less than 2,000 g / mol. They can be anionic, cationic or non-ionic. When mixtures of surfactants are used, the individual components must be compatible with one another, which can be checked by some preliminary experiments if in doubt. Examples of suitable surfactants are ethoxylated mono-, di- and trialkylphenols, the alkyl groups of which have 4 to 9 carbon atoms and the degree of ethoxylation (EO index) is 3 to 50; ethoxylated fatty alcohols, the alkyl groups of which have 8 to 36 carbon atoms and the EO index is 3 to 50; fatty alcohol sulfonates, sulfosuccinates, ether sulfonates, resin soaps, and alkali metal or ammonium salts of alkyl sulfonic acids having 8 to 12 carbon atoms, and salts of higher fatty acids having 10 to 30 carbon atoms. Other suitable emulsifiers are found in Houben-Weyl, Methoden der organischen Chemie, Vol. XIV / 1, Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pp. 192-206.

[0098] Other suitable anionic surfactants are bis(phenylsulfonic acid)ethers and their alkali metal or ammonium salts, which carry C4-C 24 -alkyl groups on one or both aromatic rings. These compounds are disclosed, for example, in US 4,269,749.

[0099] Preferably, the at least one surfactant C is a compound selected from sodium or potassium salts of arylalkyl sulfonates or alkyl sulfonates, or salts of fatty acids having 10 to 18 carbon atoms.

[0100] In a preferred embodiment, the surfactant C is selected from alkyl sulfonates, arylalkyl sulfonates, fatty acids and their sodium and potassium salts. More preferably, the at least one surfactant C is selected from fatty acids, in particular fatty acids having an aliphatic hydrocarbon chain of 10 to 30, preferably 10 to 18 carbon atoms, and their sodium and potassium salts. More preferably, the surfactant C is at least one fatty acid selected from oleic acid, stearic acid, palmitic acid and their sodium and potassium salts.

[0101] In another preferred embodiment, the surfactant C or the active form of the surfactant C is prepared in situ by converting an alkyl sulfonate, arylalkyl sulfonate or fatty acid with an alkali metal hydroxide by converting into the corresponding salt, which acts as surfactant in the dispersion. Instead of an alkali metal hydroxide, also an alkali metal carbonate or bicarbonate can be used. Preferably, the at least one surfactant C is at least one fatty acid, preferably selected from oleic acid, stearic acid and palmitic acid, which is converted into the corresponding sodium or potassium salt.

[0102] The two or more phenolic stabilizers A comprised in the molding composition obtained according to the process of the present application are added in step x) (i.e. iv)) and, optionally, in step prexiii') or step xiv).

[0103] The total amount of the two or more phenolic stabilizers A is 0.002 to 5 wt.-%, preferably 0.01 to 3 wt.-%, more preferably 0.1 to 1 wt.-%, based on the total weight of the thermoplastic molding composition. The amount of phenolic stabilizers A used in each of the process steps x) (i.e. iv)) and prexiii'), or, x) (i.e. iv)) and xiv), respectively, adds up to 100 wt.-%, based on the total amount of phenolic stabilizers A.

[0104] The at least one thio co-stabilizer B comprised in the molding composition obtained according to the process of the present application is optionally added to the aqueous composition used for obtaining the stabilizer composition S in step x) (i.e. iii)) and further in the optional step prexiii') or step xiv).

[0105] The total amount of the at least one thio-prostabiiizer B is 0.002 to 5 wt.-%, preferably 0.01 to 3 wt.-%, more preferably 0.1 to 1 wt.-%, based on the total weight of the thermoplastic molding composition. The amount of thio-prostabiiizer B used in each of the process steps x) (i.e. iii) ) and prexiii') or, x) (i.e. iii) ) and xiv) above, adds up to 100 wt.-%, based on the total amount of thio-prostabiiizer B.

[0106] Preferably, in steps xiii) and xiv) of the process according to the present application, at least one phenolic stabilizer A and optionally the at least one silicone oil component D are mixed in the extrusion or knead process of the graft copolymer CB stabilized with the stabilizer dispersion S as dry or wet powder with the rubber-free thermoplastic copolymer CA (e.g. SAN copolymer) or other components K (e.g. other polymers such as PC, PEC and / or PA or blends of ABS polymer compounds with PC, PEC and PA).

[0107] Further preferably, in steps xiii) and xiv) of the process according to the present application, at least one phenolic stabilizer A and at least one thio-prostabiiizer B and optionally at least one silicone oil component D are mixed in the extrusion or knead process of the graft copolymer CB stabilized with the stabilizer dispersion S as dry or wet powder with the rubber-free thermoplastic copolymer CA (e.g. SAN copolymer) or other components K (e.g. other polymers such as PC, PEC and / or PA or blends of ABS polymer compounds with PC, PEC and PA).

[0108] The at least one phenolic stabilizer A, thio-prostabiiizer B and, if present, silicone oil component D can be added to the extrusion or knead process individually or in combination.

[0109] According to the process of the present application (step prexiii') it is also possible and preferred to provide a stabilized pre-mixture of the rubber-free thermoplastic copolymer CA (e.g. SAN copolymer) with at least one stabilizer A, the at least one thio-prostabiiizer B and optionally a silicone oil component D, which is then added (step xiii') to the extrusion or knead process of the graft copolymer CB stabilized with the stabilizer dispersion S as dry or wet powder with optional other components K (e.g. other polymers such as PC, PEC and / or PA).

[0110] In step prexiii') of the inventive process, it is also possible to first provide a mixture of stabilizer A, B and optionally the silicone oil component D with the rubber-free thermoplastic copolymer CA (e.g. SAN copolymer) to produce a stabilizer masterbatch, and then mix this masterbatch with further rubber-free thermoplastic copolymer CA (e.g. SAN copolymer) to obtain a stabilized pre-mixture of the rubber-free thermoplastic copolymer CA. The stabilized pre-mixture can be produced by an extrusion or kneading process.

[0111] Silicone oil component D Silicone oil means a polymeric siloxane with organic side chains, which can be in particular of the formula [R a R b SiO] o described, wherein R a and R b are organic groups, e.g. alkyl groups. Preferably, the silicone oil component is selected from polydimethylsiloxanes, which can be linear or branched.

[0112] If present, the at least one silicone oil component D is preferably used in an amount of 0.1 to 40 wt.-%, preferably 0.5 to 30 wt.-%, particularly preferably 1 to 10 wt.-%, most preferably 2 to 8 wt.-%, based on the total weight of the stabilizer dispersion S.

[0113] In a preferred embodiment, the silicone oil component D is a polydimethylsiloxane of the general formula (V) (CH3)2Si-[O-Si(CH3)2-] p O-Si(CH3)2(V), wherein p = integer > 1, preferably p = 1 to 5,000.

[0114] Preferably, the kinematic viscosity of the silicone oil component D is in the range of 100 mm 2 / s to 1,000,000 mm 2 / s, preferably in the range of 500 to 100,000 mm 2 / s.

[0115] Preferably, the silicone oil component used in the inventive process is a polydimethylsiloxane, CAS Registry Number 63148-62-9, with a kinematic viscosity of 1,000 to 60,000 mm 2 / s.

[0116] For example, a suitable silicone oil component D used in the inventive process is one or more of the commercially available products Wacker Silicone Fluids AK 1000 (kinematic viscosity 1,000 mm 2 / s) and Wacker Silicone Fluids AK 60,000 (kinematic viscosity 60,000 mm 2 / s) and Wacker Silicone Fluids AK 60,000 (kinematic viscosity 60,000 mm 2 / s).

[0117] The at least one silicone oil component D comprised in the molding composition obtained according to the inventive process is optionally added in step x) (i.e. v)) to the process for obtaining the stabilizer composition S and / or is optionally added in optional step prexiii) or in step xiv).

[0118] The total amount of the at least one silicone oil component D is at most 2 wt.-%, preferably 0.001 to 1 wt.-%, more preferably 0.01 to 0.2 wt.-%, based on the total weight of the thermoplastic molding composition. The amount of silicone oil D used in each of the process steps x) (i.e. v)) and prexiii), or x) (i.e. v)) and xiv) above adds up to 100 wt.-%, based on the total amount of silicone oil component D.

[0119] Further components K In particular, the thermoplastic molding composition obtained according to the inventive process can comprise 0 to 30 wt.-%, preferably 0 to 10 wt.-%, of at least one further component K, based on the total weight of the thermoplastic molding composition. More preferably, the at least one further component K is present in an amount of 0.001 to 10 wt.-%, more preferably 0.01 to 5 wt.-%, based on the total weight of the thermoplastic molding composition.

[0120] The optional further component K can be selected from additives and / or auxiliaries commonly used in plastic materials. With regard to conventional auxiliaries and additives, reference is made to, for example, "Plastics Additives Handbook", Ed. Gächter and Müller, 4thedition, Hanser Publ., Munich, 1996. For example, the at least one further component K can be selected from fillers, reinforcing agents, dyes, pigments, lubricants or release agents, stabilizers for increasing hydrolysis resistance and chemical resistance, light stabilizers, UV absorbers, plasticizers, impact resistance modifiers, antistatic agents, flame retardants, bactericides, fungicides, optical brighteners and blowing agents.

[0121] The optional at least one further component K is preferably selected from dyes, pigments, lubricants or release agents, light stabilizers, antistatic agents, flame retardants and fillers, in particular mineral fillers.

[0122] Furthermore, the thermoplastic composition can comprise as further component K a residue of the at least one surfactant C used for producing the stabilizer dispersion S as described above, selected from the group consisting of surfactants and protective colloids.

[0123] In another embodiment, the at least one further component K can be at least one further polymer selected from the group consisting of polycarbonates and polyamides.

[0124] Preferably, the further component K is at least one aromatic polycarbonate and / or at least one aromatic polyester carbonate. Aromatic polycarbonates and / or aromatic polyester carbonates suitable for use in the present application are described in the prior art and can be prepared by known methods. In particular, the preparation of aromatic polycarbonates / aromatic polyester carbonates is carried out by reacting a diphenol, preferably bisphenol A, a carbonic halide, preferably phosgene, and optionally an aromatic dicarboxylic acid halide, preferably a benzenedicarboxylic acid halide, to yield. For example, suitable aromatic polycarbonates and aromatic polyester carbonates and methods for 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.

[0125] Preferably, the further component K is at least one polyamide selected from the group consisting of homopolymers, copolymers and mixtures of such polyamides. Suitable polyamides and methods for their production are known in the prior art. In particular, suitable semi-crystalline polyamides are polyamide-6, polyamide-6,6, mixtures of these components and corresponding copolymers.

[0126] Also included are polyamides whose acid component consists wholly or in part of terephthalic acid and / or isophthalic acid and / or suberic acid and / or sebacic acid and / or azelaic acid and / or adipic acid and / or cyclohexane dicarboxylic acid, and whose diamine component consists wholly or in part of meta- and / or para-xylylenediamine and / or hexamethylenediamine and / or 2,2,4-trimethylhexamethylenediamine and / or 2,2,4-trimethylhexamethylenediamine and / or isophorone diamine. In particular, amorphous polyamides can be used as further component K, which are obtained by polycondensation of diamines, such as ethylenediamine, hexamethylenediamine, decanediamine, 2,2,4- and / or 2,4,4-trimethylhexamethylenediamine, meta- and / or para-xylylenediamine, bis-(4-aminocyclohexyl)-methane, bis-(4-aminocyclohexyl)-propane, 3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 2,5- and / or 2,6-bis-(aminomethyl)-norbornane and / or 1,4-diaminomethylcyclohexane, with dicarboxylic acids, such as oxalic acid, adipic acid, azelaic acid, sebacic acid, heptanedicarboxylic acid, 2,2,4- and / or 2,4,4-trimethyladipic acid, isophthalic acid and terephthalic acid.

[0127] Examples of fillers which can be mentioned, which can be chosen from particulate fillers or reinforcing agents, for example silicates, amorphous silica, 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 silk roving, chopped glass or glass beads). In particular, at least one particulate filler, preferably a mineral filler, can be used as further component K.

[0128] Examples of suitable pigments are titanium dioxide, phthalocyanines, ultramarine blue, iron oxide or carbon black, and the entire group of organic pigments.

[0129] Common stabilizers for thermoplastic polymers include light stabilizers (stabilizers for increasing light resistance) and stabilizers for increasing hydrolysis resistance and chemical resistance. Examples of suitable light stabilizers are various substituted resorcinols, salicylates, benzotriazoles and benzophenones. HALS stabilizers (hindered amine light stabilizers), benzophenones, resorcinols, salicylates and benzotriazoles are also suitable.

[0130] Examples of suitable antistatic agents are amine derivatives, such as N,N-bis(hydroxyalkyl)alkylamines or -alkyleneamines, alkyl sulfonates, polyethylene glycol esters, copolymers consisting of ethylene oxide diols and propylene oxide diols (in particular diblock or triblock copolymers consisting of ethylene oxide blocks and propylene oxide blocks), diols, and glycerol mono- and distearates, and mixtures of these.

[0131] Suitable lubricants or release agents are fatty acids having 12 to 30 carbon atoms, their salts and derivatives, such as stearic acid and stearates, stearyl alcohol, stearates, amide waxes (such as stearamide, in particular ethylene bis(stearamide) (EBS)) and polyolefin waxes. Particularly suitable lubricants and release agents are stearic acid, stearates (such as magnesium stearate), ethylene bis(stearamide) (such as Irgawax® 599, Ciba, Switzerland) and mixtures thereof. Preferably, the thermoplastic molding composition comprises 0.05 to 5 wt.-%, preferably 0.1 to 3 wt.-%, of at least one lubricant or release agent, more preferably ethylene bis(stearamide) and / or magnesium stearate, based on the total weight of the thermoplastic molding composition. In a preferred embodiment, the thermoplastic molding composition comprises 0.1 to 5 wt.-% of ethylene bis(stearamide) and 0.05 to 1 wt.-% of magnesium stearate, based on the total weight of the thermoplastic molding composition. ®

[0132] Thermoplastic molding composition ​A further aspect of the present application is the thermoplastic molding composition obtained by the process according to the present application.

[0133] The thermoplastic molding composition preferably obtained by the process according to the present application comprises: 5 to 80 wt.-% of the thermoplastic copolymer CA; 15 to 60 wt.-% of the graft copolymer CB; 0.01 to 3 wt.-%, preferably 0.1 to 1 wt.-% of the two or more phenolic stabilizers A; 0.01 to 3 wt.-%, preferably 0.1 to 1 wt.-% of the at least one thio- co-stabilizer B; 0.001 to 1 wt.-%, preferably 0.01 to 0.2 wt.-% of the at least one silicone oil component D, based on the total weight of the thermoplastic molding composition; 0 to 10 wt.-%, preferably 0.01 to 1 wt.-% of the at least one further component K, based on the total weight of the thermoplastic molding composition.

[0134] In a preferred embodiment, the amounts of components CA, CB, A, B, D and optional K add up to 100 wt.-%. In particular, the amount of graft copolymer CB can be adjusted such that the sum of compounds is 100 wt.-%.

[0135] The thermoplastic molding composition obtained according to the process of the present application can be based on the common blends of ABS polymer compounds (blends of rubber-free thermoplastic copolymers CA and graft copolymers CB) with polycarbonates PC, polyestercarbonates PEC or polyamides PA, such as ABS / PC or ABS / PEC or ABS / PA.

[0136] Process for producing a thermoplastic molding composition The process according to the present application for producing a thermoplastic molding composition comprises the step x) of adding the stabilizer dispersion S to the graft copolymer CB after its emulsion polymerization. In particular, this means that the aqueous stabilizer dispersion S is added to the graft copolymer CB in the form of an aqueous latex.

[0137] Preferably, in step x), the stabilizer dispersion S is added to the graft copolymer CB after its emulsion polymerization in an amount of typically 0.05 to 3 wt.-%, preferably 0.1 to 1.5 wt.-%, based on the solid content of the stabilizer dispersion S / solid content of the graft copolymer latex CB (i.e. solid wt.-% of the stabilizer dispersion S / solid wt.-% of the graft copolymer CB).

[0138] Corresponding to the definition of the solids content of the stabilizer dispersion S, the solids content of the graft copolymer (i.e. of the graft copolymer latex or of the precipitated graft copolymer obtained in step xi)) means and equals the weight content of non-volatile compounds in the graft copolymer. In particular, the solids content equals the solids content determined after removal of volatile compounds, in particular water, for example by evaporation in a drying cabinet at 150 to 180 °C for about 10 to 120 minutes.

[0139] Generally, the at least one aqueous stabilizer dispersion S as described above is mixed with the emulsion-polymerized graft copolymer CB under stirring.

[0140] The process for producing a thermoplastic molding composition according to the present application comprises the step xi) of precipitating the graft copolymer CB (comprising the stabilizer dispersion S) obtained in step x) by adding a precipitation solution comprising at least one salt. Generally, the graft copolymer CB obtained in step x) is precipitated using a precipitation solution comprising at least one salt or at least one salt and at least one acid. Preferred salts are selected from the group consisting of magnesium sulfate, calcium chloride, magnesium sulfate monohydrate (kieserite Mg[SO4]•H2O), magnesium sulfate pentahydrate (pentahydrate Mg[SO4]•5H2O), magnesium sulfate hexahydrate (hexahydrate kieserite Mg[SO4]•6H2O) and magnesium sulfate heptahydrate (Epsom salt (Mg[SO4]•7H2O)). Preferred acids are selected from the group consisting of sulfuric acid, phosphoric acid and acetic acid.

[0141] In a preferred embodiment, step xi) comprises precipitating the graft copolymer CB obtained in step x) by adding a precipitation solution comprising at least one salt and at least one acid. Preferably, the precipitation solution is first provided, for example in a precipitation tank, and subsequently the graft copolymer CB (a mixture of the graft copolymer CB and the stabilizer dispersion S) is added to the precipitation solution under stirring, and the obtained precipitation mixture is then heated.

[0142] Generally, the precipitation solution used in the process according to the present application is prepared by mixing water with at least one salt or a saturated solution of the salt and / or at least one acid. Generally, the precipitation solution comprises 0.1 to 5 wt.-%, preferably 0.2 to 1 wt.-%, of the at least one salt and / or at least one acid.

[0143] Preferably, the amount of the at least one salt and / or at least one acid (e.g., magnesium sulfate and / or sulfuric acid (96% by weight)) is used in such a way that, based on the total aqueous phase of the precipitation mixture, the concentration of the at least one salt and / or the at least one acid is in the range of 0.01 to 1% by weight, preferably 0.05 to 0.7% by weight. More preferably, the amount of the at least one salt is used in such a way that, based on the total aqueous phase of the precipitation mixture, the concentration of the at least one salt is in the range of 0.1 to 1% by weight, preferably 0.2 to 0.75% by weight. More preferably, the amount of the at least one acid is used in such a way that, based on the total aqueous phase of the precipitation mixture, the concentration of the at least one acid is in the range of 0.01 to 0.5% by weight, preferably 0.02 to 0.1% by weight. The precipitation mixture generally refers to the mixture of the graft copolymer CB (i.e., a mixture of graft copolymer CB and stabilizer dispersion S) obtained in step x) and the precipitation solution.

[0144] Typically, precipitation in step xi) is carried out at a temperature range of 40°C to 150°C, preferably 60 to 95°C. In a preferred embodiment, step xi) is carried out by adding the graft copolymer CB (including the stabilizer dispersion S) obtained in step x) to the precipitation solution under stirring.

[0145] Preferably, the solids content of the graft copolymer CB (including the stabilizer dispersion S) used in the precipitation step xi) is in the range of 5 to 30% by weight, preferably 10 to 25% by weight, and more preferably 15 to 20% by weight.

[0146] Preferably, the solids content of the precipitated dispersion (which can be considered as a mixture of graft copolymer CB, including stabilizer dispersion S, and precipitated solution) obtained in precipitation step xi) is in the range of 5 to 20% by weight, more preferably 10 to 15% by weight.

[0147] The method for producing a thermoplastic molding composition according to the present invention includes step xii): mechanically dehydrating, optionally washing and / or optionally drying the precipitated graft copolymer CB obtained in step xii).

[0148] Typically, the precipitated graft copolymer CB is at least partially dehydrated by centrifugation and / or filtration. Preferably, a centrifuge is used to at least partially mechanically dehydrate the precipitated graft copolymer CB and separate it from the aqueous phase.

[0149] Typically, the residual moisture level of the graft copolymer CB obtained after mechanical dehydration is in the range of 10 to 50% by weight, preferably 20 to 40% by weight, and more preferably 25 to 35% by weight.

[0150] The residual moisture level refers to the amount of water, based on the total weight of the wet grafted copolymer CB, expressed in weight %. Typically, the residual moisture level can be determined using a suitable equipment, such as a drying balance. Typically, the sample is dried for a given time until a constant weight level is maintained. For example, the residual moisture level can be determined in a Mettler-Toledo Halogen Moisture Analyzer HR73 at 180 °C, for 30 seconds, maintaining a constant weight.

[0151] In another preferred embodiment, the grafted copolymer CB is subjected to one or more washing steps after the mechanical dewatering, wherein the separated grafted copolymer CB is contacted with water or a mixture of water and a polar organic solvent miscible with water (optional washing step). After washing, the grafted copolymer CB is typically separated from the water by centrifugation.

[0152] Optionally, the grafted copolymer CB after dewatering or dewatering and washing can be subjected to drying, for example using a box dryer or other commonly used drying equipment, such as a flash dryer or a fluidized bed dryer. The grafted copolymer CB can also be dried as described in DE-A 19907136. Typically, the optional drying step is carried out at a temperature in the range of 50 to 160 °C.

[0153] Preferably, after step xii), the grafted copolymer CB is in the form of a dry polymer latex powder having a residual moisture level of less than 5 wt.%, preferably less than 2 wt.%, more preferably less than 1 wt.%.

[0154] It is also possible to mix the grafted copolymer CB in step xiii) in the form of a moist crumb having a residual moisture level of 1 to 40 wt.%, in particular 20 to 40 wt.%, and then the grafted copolymer is fully dried during the mixing process (step xiii).

[0155] The process for producing a thermoplastic molding composition according to the present application comprises the optional step prexiii) of providing a thermoplastic copolymer CA, or the optional step prexiii') of providing a stabilized premix of the copolymer CA with at least one, typically two or more, of said phenolic stabilizer A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferred a phenolic stabilizer A3 or A4 alone, and said at least one thio co-stabilizer B, and optionally said at least one silicone oil component D; The process for producing a thermoplastic molding composition according to the present application further comprises the optional step xiii) of mixing the grafted copolymer CB obtained in step xii) with the thermoplastic copolymer CA provided in the optional step prexiii), and optionally with further components K.

[0156] The process for producing a thermoplastic molding composition according to the present application further comprises the optional step xiii') mixing the graft copolymer CB obtained in step xii) with the stabilized premix obtained in step prexiii'), and optionally with further components K.

[0157] Preferably, if the thermoplastic copolymer CA is present, step xiii) according to the present application comprises the mixing of the thermoplastic copolymer CA and the graft copolymer obtained in step xii), and optionally the addition of further components K.

[0158] Preferably, if the thermoplastic copolymer CA is present in the form of the stabilized premix obtained in step prexiii'), step xiii') according to the present application comprises the mixing of the stabilized premix of the thermoplastic copolymer CA and the graft copolymer obtained in step xii), and optionally the addition of further components K.

[0159] Methods and devices for mixing the graft copolymer CB with further polymers and / or further components selected from the above-mentioned additives and auxiliaries are known to the person skilled in the art. Typically, steps xiii) and xiii') comprise melt compounding and / or melt extrusion, and can typically be carried out using one or more kneaders, extruders and / or twin-screw extruders.

[0160] Preferably, the mixing in step xiii) or xiii'), in particular the mixing of the dry graft copolymer CB, the thermoplastic copolymer CA or the stabilized mixture of the thermoplastic copolymer CA and optionally further components K, is carried out in a temperature range of 200 to 300 °C.

[0161] The mixing in step xiii) or xiii'), in particular the mixing of the dry graft copolymer CB, the thermoplastic copolymer CA or the stabilized mixture of the thermoplastic copolymer CA and optionally further components K, can be carried out sequentially or simultaneously. Furthermore, it is suitable to mix part or all of the components in a first step at 15 to 40 °C, in particular at room temperature, and then to increase the temperature to 200 to 300 °C in a second step, optionally with the addition of further additives.

[0162] In step xiv) of the process according to the present application, the composition obtained in step xii) or xiii) is mixed with at least one, typically two or more, of said phenolic stabilizers A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferably a single phenolic stabilizer A3 or A4, and said at least one thio co-stabilizer B, and optionally said at least one silicone oil component D.

[0163] Step xiv), which is carried out in the absence of step xiii'), can be a separate step, but can also be included in step xiii) of the process according to the application. Thus, reference is made to the process conditions (i.e. temperature) of step xiii) as previously described herein.

[0164] According to another embodiment, no silicone oil D is added in optional step prexiii') or step xiv) of the process according to the application. Thus, if present, the total amount of silicone oil D is added in step x) by adding the stabilizer dispersion S. In a further embodiment of the application, a further compounding step can be reduced.

[0165] The thermoplastic composition obtained by the process according to the application can be used for the production of shaped parts by any commonly used method, such as injection molding, extrusion, blow molding. For example, the shaped parts can be selected from the group consisting of plates, semi-finished products, films, fibers and foams. In particular, the molded articles can be used, for example, in the automotive sector, for example for the manufacture of the body of a vehicle, for automotive interior trim. The molded articles obtained by the process according to the application can be used in particular in the construction of ships, aircraft or trains, in particular as interior lining parts, underbody panel assemblies, instrument panels, seat shell structures, bulkheads. Furthermore, non-automotive applications of the molded articles obtained by the process according to the application are also conceivable, such as formwork, lining elements, support shells and housing parts.

[0166] The present application is further illustrated by the examples and claims.

[0167] Experimental examples Example I. Preparation of the stabilizer dispersion S The stabilizer dispersion S was produced using the following components: A: phenolic stabilizer A, see list C: surfactant, potassium stearate, E: deionized water.

[0168] The solids content of the stabilizer dispersion S was measured by evaporation of the sample in a drying cabinet at 180 °C for 25 minutes.

[0169] List of phenolic stabilizers A: A1 : butylated reaction product of p-cresol and dicyclopentadiene according to formula (la), n = 1-3 (CAS No.: 68610-51-5); A2: octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS No.: 2082-79-3); A3: benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 1,1 '-(thiodi-2,1- ethylene) ester (CAS No.: 41484-35-9); A4: 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene (CAS No.: 1709-70-2).

[0170] A5: Pentaerythrityl tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (CAS No.: 6683-19-8); A6: 1,2-bis[-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS No.: 32687-78-8); A7: N,N'-hexane-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamide] (CAS No.: 23128-74-7); A8: Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, C7-9 branched alkyl esters (CAS No.: 125643-61-0); A9: 2,4-dimethyl-6-(1-methylpentadecyl)phenol (CAS No.: 134701-20-5); WL8 = A4 A10: Triethylene glycol bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate (CAS No.: 36443-68-2); A11: 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (CAS No.: 27676-62-6); A12: 6,6'-di-tert-butyl-4,4'-butylidenebis-m-cresol (CAS No.: 85-60-9); A13: 4-[[4,6-bis(n-octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol (CAS No.: 991-84-4); A14: 2-methyl-4,6-bis(octylthiomethyl)phenol (CAS No.: 110553-27-0); A15: 2,2'-dihydroxy-3,3'-di(alpha-methylcyclohexyl)-5,5'-dimethyl-diphenylmethane (CAS No.: 77-62-3); A16: Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, C13-C15 branched and linear alkyl esters (CAS No.: 171090-93-0); A17: 1,3,5-tris[[4-tert-butyl-3-hydroxy-2,6-dimethylphenyl]methyl]-1,3,5- triazine-2,4,6(1 H,3H,5H)-trione (CAS No.: 40601 -76-1 ); A18: 4,4',4''-(1 -methylpropane-3-ylidene)tris(6-tert-butyl-m-cresol) (CAS No.: 1843-03-4).

[0171] b. Stabilizer dispersions S, general description According to DE 199 46 519 A1, the stabilizer dispersion S was prepared using a rotor-stator mixer with a tip speed of 21 m / s.

[0172] First, 55 parts of deionized water and 5 parts of potassium stearate C were provided in a glass beaker at 60°C and mixed with a stirrer. At 80°C, 40 parts of A were added to the mixture of water and soap provided and mixed with a stirrer and then for 3 minutes with a rotor-stator mixer with a tip speed of 21 m / s.

[0173] Total batch: 200.0 g Theoretical solids content: 45.0 wt.-% The solids content was measured and then adjusted to 45.0 wt.-% by adding deionized water. Under the optical microscope, particles in the range of 1 to 5 pm and a small amount of some large particles in the range of 20 pm were visible.

[0174] The stabilizer dispersions S1 contain A1, S2 contain A2, and so on (see Table 1 ).

[0175] Table 1 : Stabilizer dispersions S1 to S18

[0176]

[0177] Example II: Preparation of ABS graft copolymer CB As graft copolymer CB, a mixture of the following two ABS rubber latices was used: 2352.9 g of a first graft rubber latex with a solids content of 34.0 wt.-%, obtained by emulsion polymerization of a mixture of 50 wt.-% of styrene and acrylonitrile in a weight ratio of 73:27 on 50 wt.-% of a polybutadiene latex (calculated on the solids of the polybutadiene latex), said polybutadiene latex having a D 50 a size of 125 nm, using potassium persulfate as initiator and tert-dodecyl mercaptan as chain transfer agent, and 3191.5 g of a second graft rubber latex having a solid content of 37.6 wt%, obtained by emulsion polymerization of a mixture of 41 wt% of styrene and acrylonitrile in a weight ratio of 73:27 on 59 wt% of a polybutadiene latex (calculated on the solids of the polybutadiene latex), said polybutadiene latex having a D 50 The size was 340 nm, using potassium persulfate as initiator and tert-dodecyl mercaptan as chain transfer agent.

[0178] The mixing ratio of the first graft rubber latex to the second graft rubber latex was 40:60 (weight ratio) based on the solid content.

[0179] The latex of graft copolymer CB was mixed with each stabilizer dispersion S1 to S18. The stabilizer dispersion was added to the graft copolymer CB, which was an aqueous emulsion polymer, and stirred for 1 hour. Then the stabilization of the latex was performed by adding the latex under stirring to a magnesium sulfate / sulfuric acid solution and heating to 95 °C. The final solid content of the precipitated dispersion was 12.5 wt%.

[0180] The amounts of magnesium sulfate (100 wt%) and sulfuric acid (96 wt%) were such that the concentration of magnesium sulfate was 0.5 wt%, based on the total aqueous phase (in the precipitation mixture), and the concentration of sulfuric acid (96 wt%) was 0.07 wt%, based on the total aqueous phase (in the precipitation mixture).

[0181] For the precipitation of ABS graft copolymer CB1 the following specific values were used: First deionized water (10,981 g) was provided, then 55.23 g of magnesium sulfate (100 wt%) and 7.74 g of sulfuric acid (96 wt%) were added and dissolved. After that, the mixture of graft rubber latex and stabilizer dispersion S1 (0.444 g) was added under stirring and heated to 95 °C.

[0182] ABS graft copolymers CB2 to CB18 were precipitated in the same way using stabilizer dispersions S2 to S18.

[0183] The mixture of graft copolymer CB and stabilizer dispersion was centrifuged, washed with water and dried to reach a residual humidity of less than 1.0 wt%. ABS graft rubber powder was obtained and used as graft copolymer CB in Example III. The composition of the ABS graft copolymers is summarized in Table 2.

[0184] The present invention is not limited to the use of graft copolymer CB according to the preceding examples. Another example of a suitable graft copolymer CB can be found in WO 2022 / 229335 (component B2 / B, page 40, line 9 to page 42, line 26), but with the exception that instead of adding a dispersion of 72.9 parts of stabilizer Wingstay L (CAS No.: 68610-51-5), a stabilizer dispersion S according to the present invention is added.

[0185] The results are summarized in the following table 2.

[0186] Table 2: Composition of ABS graft copolymers CB1 to CB18

[0187] Example III: Preparation and characterization of thermoplastic molding compositions a. Styrene-acrylonitrile copolymer CA (SAN copolymer) A statistical copolymer from styrene (monomer CA11) and acrylonitrile (monomer CA12) with a polymerized styrene to acrylonitrile ratio of 76:24 was produced by free radical solution polymerization. The SAN copolymer (thermoplastic copolymer CA) exhibits a melt flow rate (MVR) of 56 mL / 10 min, determined according to ISO 1133 at 220 °C and a load of 10 kg.

[0188] b. Compounding of thermoplastic molding compositions The thermoplastic molding compositions TC1 to TC18 were produced by compounding and pelletizing using a twin-screw extruder ThermoFischer Process 11 (11 mm twin-screw, 40 L / D, 220 rpm).

[0189] The temperature of the twin-screw extruder was set to 240 °C using 2 gravimetric dosing devices (one for the graft copolymer CB, one for the premix of all other components).

[0190] The following components were used: Thermoplastic copolymer CA: SAN copolymer prepared according to example IIIa, 64.74 wt.-%; Graft copolymer CB: one of the stabilized ABS graft copolymer powders CB1 to CB18 obtained according to example II, 34.86 wt.-% Phenolic stabilizer A: one of the phenolic stabilizers A1 to A18, 0.15 wt.-%; Thio co-stabilizer B1 : dilauryl thiodipropionate, 0.150 wt.-%; Silicone oil D: polydimethylsiloxane with a kinematic viscosity of 1,000 mm² / s; 0.1 wt.-%.

[0191] The total weight of all components is 3000 g.

[0192] Graft copolymer CB1 and phenolic stabilizer A1 are used for thermoplastic molding composition TC1 ; CB2 and A2 for TC2, and so on.

[0193] Injection molding is performed on an Engel e-mac 50 equipment using a mold with a single-sided polished plate (80 x 80 x 2 mm dimensions) and using the thermoplastic compositions TC1 to TC18.

[0194] For the evaluation of the short-term stability, test specimens are injection molded at elevated temperatures (240 °C, 260 °C, 280 °C) and extended residence times (see Table 3) and the yellowness index and 20° gloss are investigated.

[0195] For the evaluation of the long-term stability, test specimens are injection molded under standard conditions (see Table 3) and the plaques are stored in an oven at 80 °C.

[0196] After 0 h, 200 h, 400 h, 600 h, 800 h, 1000 h of storage at 80 °C, the yellowness index and 20° gloss are investigated.

[0197] Table 3: Injection molding conditions for short-term and long-term stability tests

[0198] Measurement parameters for the yellowness index YI: Color measurements are performed using a spectrophotometer Konica Minolta Cm-2600d; The investigation is performed using standard illuminant C and the 1964 standard observer (10°); The XYZ color of 4 samples at 4 similarly placed positions per injection molding temperature is investigated; The XYZ values of the 4 measurement points per sample are averaged according to ASTM E313 and the yellowness index (YI) of each sample is calculated using the following formula: YI = 100 * (1.2871 * X - 1.0781 * Z) / Y; The following values represent the average of the respective yellowness indices at each injection molding temperature (240 °C, 260 °C, 280 °C).

[0199] The difference of the thermoplastic molding compositions TC (TC2 to TC20) to TC1 (containing phenolic stabilizer A1, reference composition) is calculated.

[0200] For the short-term test: AYI = [YI(TC 240°C) + YI(TC 260°C) + YI(TC 280°C)] - [YI(TC1 240°C) - YI(TC 260°C) - YI(TC 280°C)] For short term testing: AYI = [YI(TC 0h) + YI(TC 200h) + YI(TC 400h) + YI(TC 600h) + YI(TC 800h) + YI(TC 1000h)] - [YI(TC1 0h) + YI(TC1 200h) + YI(TC1 400h) + YI(TC1 600h) + YI(TC1 800h) + YI(TC1 1000h)] Surface gloss was measured according to ISO 2813 by reflectance measurements at 20° angle (reported as gloss units (GU)), using the same panel as for the measurement of the yellowness index.

[0201] Table 4: 20° gloss measurements and rating for short term testing

[0202] [*] ++ Much better than TC1 with A1 (reference sample) + Better than TC1 with A1 (reference sample) 0 Similar to TC1 with A1 (reference sample) - Worse than TC1 with A1 (reference sample) Table 5: 20° gloss measurements and rating for long term testing

[0203] [*] + Better than TC1 with A1 (reference sample) 0 Similar to TC1 with A1 (reference sample) - Worse than TC1 with A1 (reference sample) Table 6: AYI measurements, AYI rating and 20° gloss rating for short and long term testing and overall rating

[0204] [*] ++ Much better than TC1 with A1 (reference sample) + Better than TC1 with A1 (reference sample) 0 Similar to TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) [**] ++ better than TC1 with A1 (reference sample): ΔY < 0 + similar to TC1 with A1 (reference sample): 0 < ΔY < 2 0 slightly worse than TC1 with A1 (reference sample): 2 < ΔY < 4 - much worse than TC1 with A1 (reference sample): ΔY > 4 [***] ++ much better than TC1 with A1 (reference sample) + better than TC1 with A1 (reference sample) 0 similar to TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) [****] ++ much better than TC1 with A1 (reference sample) + better than TC1 with A1 (reference sample) 0 similar to TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) As a surprising result of testing such a large number of phenolic stabilizers A, only a few phenolic stabilizers, namely phenolic stabilizers A2, A3 and A4, were superior to the reference stabilizer A1.

[0205] Mixtures of phenolic stabilizers A2, A3 and A4 were then tested: A2 with A3 and A2 with A4.

[0206] According to the general description of Example I, the following stabilizer dispersions S19 to S24 were produced using a mixture of phenolic stabilizers A2 and A3 or a mixture of phenolic stabilizers A2 and A4.

[0207] Table 7: Stabilizer dispersions S19 to S24

[0208] ABS graft copolymers CB19 to CB24 were prepared according to Example II and precipitated in the same manner using the stabilizer dispersions S19 to S24.

[0209] Table 8: Composition of ABS graft copolymers CB19 to CB24

[0210] The stabilized graft copolymer CB19 to CB24 obtained and the mixture of the phenolic stabilizer A2 and A3 or A2 and A4 are used for the thermoplastic molding compositions TC19 to TC24. The details of the compositions are given in Table 9. The thermoplastic molding compositions TC19 to TC24 are produced and tested according to the thermoplastic molding compositions TC1 to TC18.

[0211] Thermoplastic copolymer CA: SAN copolymer prepared according to example IIIa, 64.74 wt.-%; Graft copolymer CB: ABS graft rubber powder CB19 to CB24, 34.86 wt.-%; Phenolic stabilizer A2 and A3 or A2 and A4: 0.150 wt.-%; Thio co-stabilizer B1 : dilaurylthiodipropionate, 0.150 wt.-%; Silicone oil D: polydimethylsiloxane with a kinematic viscosity of 1,000 mm² / s; 0.100 wt.-%. The total weight of all components is 3000 g.

[0212] Table 9: Composition of the thermoplastic molding compositions TC19 to TC24

[0213] Table 10: 20° gloss measurements and rating of the short-term test

[0214] [*] + similar or better than TC1 with A1 (reference sample) 0 slightly worse than TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) Table 11 : 20° gloss measurements and rating of the long-term test

[0215] [*] + better or similar than TC1 with A1 (reference sample) 0 slightly worse than TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) Table 12: ΔYI measurements, ΔYI rating and 20° gloss rating and overall rating of the short-term and long-term test

[0216] [*] + better or similar than TC1 with A1 (reference sample) 0 slightly worse than TC1 with A1 (reference sample) - worse than TC1 with A1 (reference sample) [**] ++ better than TC1 with A1 (reference sample): ΔY < 0 + similar to TC1 with A1 (reference sample): 0 < ΔY < 2 0 slightly worse than TC1 with A1 (reference sample): 2 < ΔY < 4 - much worse than TC1 with A1 (reference sample): ΔY > 4 [***] ++ better than TC1 with A1 (reference sample): ΔY < 0 + similar to TC1 with A1 (reference sample): 0 < ΔY < 7.5 0 slightly worse than TC1 with A1 (reference sample): 7.5 < ΔY < 15 - much worse than TC1 with A1 (reference sample): ΔY > 15 [****] ++ much better than TC1 with A1 (reference sample) + better or similar to TC1 with A1 (reference sample) 0 slightly worse than TC1 with A1 (reference sample) - much worse than TC1 with A1 (reference sample) The experimental results (compare Tables 10 and 12) show that the molding compositions TC21 to TC24 comprising the combination of the phenolic stabilizers A2 and A3 or A2 and A4 have a better color stability in the short-term and long-term tests than the molding composition TC1 comprising the phenolic stabilizer A1.

[0217] The experimental data further show (compare Table 12) that, especially in the long-term ΔY test, a better color stability is obtained when the thermoplastic molding compositions TC19 to TC24 are produced using the combination of A2 and A3 or A2 and A4 compared to TC2 to TC4 using only one phenolic stabilizer A2, A3 or A4.

[0218] The best long-term ΔY test results were obtained using the compositions TC22 to TC24 using a mixture of the phenolic stabilizers A2 and A4.

[0219] An additional experiment was carried out in which the stabilizer dispersion S2 was applied to the graft polymer CB25 according to Example II. The following amounts were applied.

[0220] Table 13: Composition of the ABS graft copolymer CB25

[0221] The stabilized graft copolymer CB25 and the phenolic stabilizer A3 or A4 are used in the thermoplastic molding compositions TC25 to TC28. The following components are used; details are given in Table 14.

[0222] Thermoplastic copolymer CA: SAN copolymer prepared according to Example IIIa, 64.74 wt.-%; Graft copolymer CB: ABS graft copolymer powder CB25, 34.86 wt.-%; Phenolic stabilizer A3 or A4: see Table 14; Thio co-stabilizer B1 : dilaurylthiodipropionate, 0.150 wt.-%; Silicone oil D: polydimethylsiloxane with a kinematic viscosity of 1,000 mm² / s; 0.100 wt.-%.

[0223] The total weight of all components is 3000 g.

[0224] The thermoplastic molding compositions TC25 to TC28 are produced and tested according to the thermoplastic molding compositions TC1 to TC18.

[0225] Table 14: Composition of the thermoplastic molding compositions TC25 to TC28

[0226] Table 15: ΔYI measurements and ΔYI ratings of short-term and long-term tests and overall ratings

[0227] [*] ++ better than TC1 with A1 (reference sample): ΔY < 0 + similar to TC1 with A1 (reference sample): 0 < ΔYI < 20 slightly worse than TC1 with A1 (reference sample): 2 < ΔYI < 4 - much worse than TC1 with A1 (reference sample): ΔYI > 4 [**] ++ better than TC1 with A1 (reference sample): ΔYI < 0 + similar to TC1 with A1 (reference sample): 0 < ΔYI < 7.5 0 slightly worse than TC1 with A1 (reference sample): 7.5 < ΔYI < 15 - much worse than TC1 with A1 (reference sample): ΔYI > 15 [***] ++ much better than TC1 with A1 (reference sample) + better or similar to TC1 with A1 (reference sample) 0 slightly worse than TC1 with A1 (reference sample) - much worse than TC1 with A1 (reference sample) The thermoplastic molding compositions TC25 to TC28, in particular TC25 and TC28, show an improved color stability compared to the reference composition TC1 as indicated by their ΔYI values as well as the ΔYI ratings and overall ratings of the short-term and long-term tests.

Claims

1. A process for preparing a thermoplastic molding composition, comprising: 0 to 94.996 wt.-%, based on the total weight of the thermoplastic molding composition, of a rubber-free thermoplastic copolymer CA comprising at least 50 wt.-% of one or more vinyl aromatic monomers CA11, preferably selected from the group consisting of styrene and alpha-methylstyrene, and mixtures of monomers CA11 with at least one further comonomer CA12, in particular at least one vinyl cyano monomer; 5 to 99.996 wt.-%, based on the total weight of the thermoplastic molding composition, of a graft copolymer CB comprising: 5 to 95 wt.-%, based on the weight of the graft copolymer CB, of at least one graft base CB1 obtained by emulsion polymerization of: CB11: 50 to 100 wt.-%, based on the weight of the graft base CB1, of at least one conjugated diene B11, CB12: 0 to 50 wt.-%, based on the weight of the graft base CB1, of at least one further monomer CB12 selected from the group consisting of styrene, alpha-methylstyrene, acrylonitrile, methacrylonitrile and methyl methacrylate; and 5 to 95 wt.-%, based on the weight of the graft copolymer CB, of at least one graft shell CB2 obtained by emulsion polymerization of: CB21: 50 to 95 wt.-%, based on the weight of the graft shell CB2, of monomers CB21 selected from the group consisting of styrene, alpha-methylstyrene, and mixtures of styrene with at least one monomer selected from the group consisting of alpha-methylstyrene, para-methylstyrene and (meth)acrylic acid C1-C8-alkyl ester; CB22: 5 to 50 wt.-%, based on the weight of the graft shell CB2, of monomers B22 selected from the group consisting of acrylonitrile and mixtures of acrylonitrile with at least one monomer selected from the group consisting of methacrylonitrile, maleic anhydride, phthalic anhydride, N-phenylmaleimide, N-cyclohexylmaleimide; wherein the sum of CB11 + CB12 is 100 wt.-%; the sum of CB21 + CB22 is 100 wt.-%, and the sum of graft base CB1 and graft shell CB2 is 100 wt.-%; 0.002 to 5 wt.-%, based on the total weight of the thermoplastic molding composition, of two or more phenolic stabilizers A selected from the group consisting of: A2: octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); A3: benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 1,1'-(thiodi-2,1- ethylene) ester; and A4: 2,4,6-tris(3',5'-di-tert-butyl-4'-hydroxybenzyl)mesitylene; 0.002 to 5 wt.-%, based on the total weight of the thermoplastic molding composition, of at least one thio co-stabilizer B; optionally, up to 2 wt.-%, based on the total weight of the thermoplastic molding composition, of at least one silicone oil component D; 0 to 30 % by weight, based on the total weight of the thermoplastic molding composition, of at least one further component K selected from the group consisting of additives and / or auxiliaries different from A, B and D, with the proviso that the phenolic stabilizer A1 - butylated reaction product of p-cresol and dicyclopentadiene (CAS No.: 68610-51-5) is excluded; residues of the at least one surfactant C used for producing the stabilizer dispersion S; and / or at least one further polymer selected from the group consisting of polycarbonates PC, polyestercarbonates PEC and polyamides PA; The process comprises the following steps: x) adding a stabilizer dispersion S to the graft copolymer CB after its emulsion polymerization, the stabilizer dispersion S being obtained by a process comprising the following steps ii) to v) in which the order of the steps can be changed: i) providing an aqueous composition, preferably water; ii) adding at least one surfactant C to the aqueous composition; iii) optionally adding at least one thio co-stabilizer B to the aqueous composition, wherein the temperature of the aqueous composition is higher than or equal to the melting point of the at least one thio co-stabilizer B; iv) adding at least one, typically two or more, of the phenolic stabilizers A to the aqueous composition, wherein the temperature of the aqueous composition is higher than or equal to the melting point of the optional at least one thio co-stabilizer B, at least 40 °C; v) optionally adding at least one silicone component D to the aqueous composition; vi) homogenizing the aqueous composition obtained in steps ii) to v) to yield a stabilizer dispersion S; xi) precipitating the graft copolymer CB obtained in step x) including the stabilizer dispersion S by adding a precipitation solution comprising at least one salt; xii) subjecting the precipitated graft copolymer CB obtained in step xi) to mechanical dewatering, optionally washing and / or optionally drying; prexiii) optionally providing a stabilization pre-mix of the thermoplastic copolymer CA with at least one, typically two or more, of the phenolic stabilizers A, the at least one thio co-stabilizer B, and optionally the at least one silicone component D; prexiii') optionally providing a stabilization pre-mix of the thermoplastic copolymer CA with at least one, typically two or more, of the phenolic stabilizers A, preferably a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or further preferred a phenolic stabilizer A3 or A4 alone, and the at least one thio co-stabilizer B, and optionally the at least one silicone component D; xiii) optionally mixing the graft copolymer CB obtained in step xii) with the copolymer CA, and optionally with further components K, or xiii') optionally mixing the graft copolymer CB obtained in step xii) with the stabilization pre-mix obtained in step prexiii'), and optionally with further components K; and xiv) mixing the composition obtained in step xii) or xiii) with at least one, typically two or more, said phenolic stabilizer A, said at least one thio co-stabilizer B, and optionally said at least one silicone oil component D.

2. The process for the preparation of a thermoplastic molding composition according to claim 1, comprising: 5 to 80 wt.-% of a rubber-free thermoplastic copolymer CA; 15 to 60 wt.-% of a graft copolymer CB; 0.01 to 3 wt.-%, preferably 0.1 to 1 wt.-%, of two or more phenolic stabilizers A; 0.01 to 3 wt.-%, preferably 0.1 to 1 wt.-%, of at least one thio co-stabilizer B; 0.001 to 1 wt.-%, preferably 0.01 to 0.2 wt.-%, of at least one silicone oil component D, based on the total weight of the thermoplastic molding composition; 0 to 10 wt.-%, preferably 0.01 to 1 wt.-%, of at least one further component K, based on the total weight of the thermoplastic molding composition.

3. The process for the preparation of a thermoplastic molding composition according to claim 1 or 2, wherein the two or more phenolic stabilizers A are a combination of phenolic stabilizers A2 and A3, or A2 and A4, or A2, A3 and A4, in a weight ratio A2:A3, or A2:A4, or A2:(A3+A4) of 95 to 55 : 5 to 45.

4. The process for the preparation of a thermoplastic molding composition according to claim 3, wherein the weight ratio A2:A3, or A2:A4, or A2:(A3+A4) is: 90 to 60 : 10 to 40, preferably 85 to 65 : 15 to 35.

5. The process for the preparation of a thermoplastic molding composition according to any one of claims 1 to 4, wherein the at least one thio co-stabilizer B is selected from B1 : dilaurylthiodipropionate and B2: distearylthiodipropionate.

6. The process for the preparation of a thermoplastic molding composition according to any one of claims 1 to 5, wherein in step iv) a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or the phenolic stabilizer A2 alone is added to the aqueous composition.

7. The process for the preparation of a thermoplastic molding composition according to any one of claims 1 to 6, wherein in step prexiii') or xiv) a combination of phenolic stabilizers A2 and A3, or a combination of phenolic stabilizers A2 and A4, or the phenolic stabilizer A3 or A4 alone is used as phenolic stabilizer A.

8. The process for the preparation of a thermoplastic molding composition according to any one of claims 1 to 7, wherein optional steps prexiii') and xiii') are present.

9. The process for the preparation of a thermoplastic molding composition according to any one of claims 1 to 8, wherein the at least one conjugated diene B11 is 1,3-butadiene and the at least one further monomer CB12 is styrene and / or a-methylstyrene, in particular styrene.

10. The process for the preparation of a thermoplastic molding composition according to any of claims 1 to 9, wherein monomer CB21 is styrene and / or alpha-methylstyrene, in particular styrene, and monomer CB22 is acrylonitrile.

11. The process for the preparation of a thermoplastic molding composition according to any of claims 1 to 10, wherein the vinyl aromatic monomer CA11 is selected from styrene and alpha-methylstyrene, in particular styrene, and the at least one further comonomer CA12 is at least one vinyl cyano monomer, in particular acrylonitrile.

12. The thermoplastic molding composition obtained according to the process of any of claims 1 to 11.

13. Use of the thermoplastic molding composition obtained according to the process of any of claims 1 to 11 for the preparation of a molded part.

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