Poly(meth)acrylate impact modifiers having reduced metal ion content and methods for their preparation

Abstract

The present invention is directed to a poly(meth)acrylate impact modifier comprising at least one multiphase alkyl(meth)acrylate emulsion polymer with reduced, particularly low, amounts of cationic metal ions, particularly very low concentrations of alkali metal ions, such as sodium. The impact modifier according to the present invention comprises 4.5 mmol / kg or less of alkali metal ions based on the solids content of the impact modifier. The impact modifier or the molding composition produced therefrom has improved optical properties, particularly high transparency after hot water storage.

Description

[Technical field]

[0001] The present invention is directed to a poly(meth)acrylate impact modifier comprising at least one multiphase alkyl(meth)acrylate emulsion polymer having a specific low amount of cationic metal ions, particularly a very low concentration of alkali metal ions, such as sodium. The impact modifier according to the present invention and the molding composition produced therefrom have improved optical properties, particularly high transparency after hot water storage.

[0002] Furthermore, the present invention is directed to a method for the preparation of poly(meth)acrylate impact modifiers comprising the preparation of at least one multiphase alkyl(meth)acrylate polymer by emulsion polymerization, followed by an ion exchange step of the resulting latex, e.g., using cation and / or anion exchange materials in combination with coagulation and mechanical dewatering, resulting in a reduced amount of cationic metal ions, such as alkali ions, in the dehydrated alkyl(meth)acrylate emulsion polymer.

[0003] The present invention also relates to impact-modified molding compositions, in particular impact-modified poly(methyl methacrylate) (PMMA) compositions, having an improved property profile, including good optical properties, in particular high transparency after hot water storage. The molding compositions are preferably used to produce molded articles and semi-finished products, such as films and sheets, in particular transparent articles and semi-finished products, or products with good optical appearance.

[0004] Background technology It is known that the impact resistance of relatively brittle synthetic resins, such as molding compositions, especially poly(meth)acrylate molding compositions, can be improved by incorporating an appropriate amount of so-called impact modifiers. It is an established practice in the industry to use impact modifiers produced by emulsion polymerization, known as core, core-shell or core-shell-shell particles. These generally comprise an elastomeric phase, for example as the core or as an intermediate shell grafted to the core, and a hard outer phase, which typically ensures good incorporation of the impact modifier particles into the matrix polymer. Such multiphase emulsion polymers and their preparation are described, for example, in WO 2004 / 056893.

[0005] Typically, such impact modifiers produced by emulsion graft polymerization are obtained as aqueous polymer dispersions (latexes) and must be post-processed by coagulation and isolation of the emulsified polymer. Several methods of coagulation (also called precipitation) of polymer latexes are well known and described in the prior art.

[0006] For example, it has been described that emulsified polymers, such as the poly(meth)acrylate impact modifiers of the present invention, can be coagulated by known physical coagulation processes, such as shear coagulation, thermal shear coagulation, spray drying, freeze coagulation or pressure coagulation processes, or by chemical coagulation processes involving the addition of electrolytes, particularly polyvalent cations, such as alkaline earth metal salts, aluminum salts or zinc salts, or inorganic or organic acids.

[0007] For example, coagulation of aqueous polymer dispersions by continuous or semi-continuous freeze coagulation and subsequent mechanical dewatering, for example using a centrifugation step, is described in WO 2015 / 074883. Coagulation and dewatering of emulsion polymers by thermal shear coagulation in an extruder line is described, for example, in WO 2002 / 184539, EP 0 683 028 and EP 0 187 715.

[0008] Another common method for coagulating emulsion polymers is to mix the emulsion polymer (latex) with a coagulant, which is often selected from aqueous solutions of metal salts, especially divalent or trivalent metal ions, and / or acids such as sulfuric acid, acetic acid, phosphoric acid, etc. For example, aqueous solutions of alkali metal salts, alkaline earth metal salts, zinc salts or aluminum salts, such as magnesium sulfate, calcium chloride and aluminum chloride, are used as coagulants.

[0009] The document EP 2942360 describes a thermoplastic resin powder obtained by coagulating a polymer latex produced by emulsion polymerization using a phosphoric ester as an emulsifier, the content of free acid in the resin being 500 ppm or less. For example, aluminum sulfate or sulfuric acid is used as the coagulant. EP 2942360 describes that the amount of coagulant should be as low as possible, since the presence of polyvalent metal ions in the thermoplastic resin powder reduces the flowability of the thermoplastic resin powder. The thermoplastic resin powder is described as containing less than 50 ppm calcium, preferably less than 50 ppm calcium and magnesium in total, as well as 60 to 300 ppm aluminum, and more than 50 ppm phosphorus. The amount of alkali metal ions is not discussed in EP 2942360.

[0010] The document GB 2226324(A) describes a transparent, viscous molding composition comprising 10-90% of a hard phase made of methyl methacrylate and 1-90% of a viscous phase distributed in the hard phase, for example made of a crosslinked butyl acrylate polymer, the molding composition comprising not more than 0.05% by weight of water-soluble components. It is described that the aqueous phase is separated in liquid form from the coagulate to such an extent that not more than 0.05% by weight of water-soluble components remain in the composition in order to ensure permanent transparency, especially under the influence of moisture.

[0011] The document US 2021 / 054113(A1) describes a multi-layer acrylic polymer coagulum characterized by its bulk density, particle size, and the amount of alkali and alkaline earth metals N (mmol / kg) is defined by the formula Σ(N / a)*(120-Tg)≦100 based on the glass transition temperature Tg (° C.) of the acetone soluble portion of the coagulum, and the valence a of the alkali and alkaline earth metals. The multi-layer acrylic polymer coagulum of D1 will exhibit excellent transparency, resistance to hot water whitening and stress whitening.

[0012] The document Korean Patent Application Publication No. 20180069421(A) describes an impact modifier that can impart impact strength to epoxy resins and a method for preparing the impact modifier, which involves reducing the content of residual emulsifier and metal ions, and adding hydrochloric acid to lower the pH to 3 or less to perform coagulation. The content of metal ions should be reduced to a level of 90 ppm or less through a post-treatment process. The impact modifier described in Korean Patent Application Publication No. 20180069421(A) contains a specific polyalkylene glycol-based comonomer, such as polyethylene glycol methacrylate (PEGMA). In addition, a specific phosphate ester-based emulsifier is used in the method for preparing the impact modifier.

[0013] Furthermore, the prior art describes subjecting polymer latexes, such as fluoropolymer latexes, to an ion exchange process, for example to reduce the metal ion content in the polymer latex.

[0014] DE 2046220 A describes the size separation of polydisperse particle dispersions by passing the dispersion through a bed of solid particles larger than the particles to be separated and eluting the bed with a dispersing medium to remove the particles from the bed according to their size. The bed of solid particles may be a bed of glass beads or crosslinked polystyrene beads. Ion exchange materials are also used in this connection.

[0015] EP 0 591 888 A1 describes a process for post-treating an aqueous dispersion of a fluorinated thermoplastic, which comprises substantially replacing the cations in the aqueous dispersion with hydrogen ions, optionally after dilution with water, compressing the dispersion and coagulating the dispersion by decompressing it through a small opening. Optionally, the coagulated dispersion is filtered, washed, mechanically dewatered, broken down into a free-flowing product and dried. The technical teaching of EP 0 591 888 A1 focuses on the continuous post-treatment of an aqueous dispersion of a fluorinated thermoplastic at high throughput, and optical properties are not taken into account.

[0016] EP 0 571 069 A2 discloses a process for improving the water-whitening resistance of pressure-sensitive adhesives by removing water-soluble ions and adjusting the pH of the pressure-sensitive adhesive formulation to at least about 6.0. Deionized adhesives that are not readjusted to a pH above about 6.0 do not show improved resistance to water-whitening. The water-soluble ions are removed by contacting the aqueous latex or adhesive formulation with an ion exchange resin, preferably the cations (e.g. using a sulfonic acid type cation exchanger) and anions (e.g. using a quaternary anion exchange resin) should be removed, for example using a so-called mixed bed ion exchanger. The amount of cations and anions in the pressure-sensitive adhesive is not described in EP 0 571 069 A2.

[0017] WO 2001 / 57100 A1 describes the preparation of ultra-clean, i.e. salt-free, fluoropolymers by aqueous emulsion polymerization, which removes essentially all ions different from NH4+, H+ and OH-, and coagulates the fluoropolymer without adding ions. The focus is on avoiding metal-free acid acceptors, i.e. strong organic bases, for applications such as curable compounds and coatings. Optical properties are not considered.

[0018] WO 2013 / 160029 describes a polymer composition containing at least a graft polymer produced by emulsion polymerization, and optionally a thermoplastic polymer, a rubber-free vinyl (co)polymer, and other polymers or polymer additives. The emulsion graft copolymer is precipitated in a basic medium by at least one alkaline earth metal salt, and comprises at least one sodium salt and at least one alkaline earth metal salt with a molar ratio Na / (Mg+Ca) of at least 0.10 and at most 1.0. It is described that molded articles prepared from said emulsion graft copolymer exhibit improved surface quality after storage under hot and humid conditions. In contrast to the present invention, it is recommended to increase the amount of sodium by adding sodium salt during the emulsion polymerization and / or coagulation process.

[0019] Particularly important properties of impact-modified PMMA molding compositions are advantageous mechanical properties such as high toughness (impact resistance, notched impact resistance), high elasticity (modulus of elasticity), as well as good processability (thermoplastic flowability, MVR), as well as good weathering and heat resistance. Furthermore, a fundamental requirement imposed on PMMA molding compositions and articles is that they are optically transparent, even after exposure to high temperatures or hot water. In general, products considered to be optically transparent are those with a haze value of less than or equal to 15.0%, in particular less than 10.0%, very particularly less than 6.0%, measured by a BYK Gardner Hazegard-plus haze meter at 23°C on test specimens with a thickness of 1 mm according to standard ASTM D1003 (2013).

[0020] Impact modified PMMA molding compositions and articles made therefrom often suffer from reduced transparency and milky white color after storage in hot water, especially after 10-24 hours in water at 80° C. Thus, there is a great need to provide impact modified PMMA molding compositions that exhibit reduced haze and high light transmission after hot water storage.

[0021] Summary of the Invention One object of the present invention is to provide poly(meth)acrylate impact modifiers, as well as molding compositions, moldings and semi-finished products, such as films and sheets, comprising poly(meth)acrylate impact modifiers, with improved optical properties, in particular with high transparency and high transmission. In particular, the impact modifiers should produce lower haze values ​​in accordance with ASTM D 100-13, in comparison with prior art modifiers, in particular after hot water storage at 70°C to 80°C. Furthermore, the impact modifiers should show high light transmission values, even after hot water storage at 70°C to 80°C, for example for 4 to 24 hours. In particular, the object of the present invention is to provide impact modifiers or semi-finished products, preferably transparent semi-finished products, with a haze of 40% or less, preferably 30% or less, preferably 20% or less, after hot water storage at 70°C, for example for 4 to 24 hours, preferably after hot water storage at 80°C, measured at 23°C on test specimens having a thickness of 1 mm according to standard ASTM D1003 (2013).

[0022] Another object of the present invention is to provide a cost-effective and easy process for producing the improved poly(meth)acrylate impact modifiers and / or impact-modifying polymer compositions.

[0023] Means for solving the problem Surprisingly, it has been found that the haze of the impact modifier or transparent article made therefrom after hot water storage is adversely affected by the presence of ionic species, particularly alkali metal ions.It has been found that the haze after hot water storage is reduced when the total amount of cationic metal ions, particularly alkali metal ions, in the impact modifier, especially after coagulation and dehydration, is reduced below a critical value of about 4.5 mmol / kg for dry impact modifier, preferably below 3.0 mmol / kg, more preferably below 1.0 mmol / kg.Furthermore, typically, the impact modifier of the present invention and test pieces containing it exhibit high light transmission values ​​even after hot water storage.

[0024] Preferably, the reduction of ionic species, especially alkali metal ions, can be achieved by an ion exchange process. Furthermore, it is possible to reduce the amount of metal ions, especially alkali metal ions, by known washing, dilution and / or dehydration processes. Surprisingly, it has been found that it is possible to add a defined amount of alkaline earth salts as coagulants after the ion exchange process to aid coagulation without compromising the haze after hot water storage.

[0025] Typically, said cationic metal ions, such as alkali metal ions or polyvalent metal ions (e.g., alkaline earth metals, zinc and aluminum), originate from additives such as emulsifiers, initiators and buffers used in emulsion polymerization. In general, the content of ionic species in the coagulated polymer can be reduced by washing and / or a higher degree of dehydration. However, such washing procedures are time-consuming and expensive and generate large amounts of washing water. In this context, it has been surprisingly found that such desired small amounts of cationic metal ions, in particular alkali metal ions, can be easily and advantageously obtained, for example, by an ion exchange step using a cation exchange material (typically containing acidic groups, e.g., sulfonic acid groups) and optionally an anion exchange material (typically containing basic groups, e.g., quaternary ammonium groups). It has been found that the polymer latex of the multiphase alkyl (meth)acrylate polymer obtained after emulsion polymerization remains stable during such an ion exchange step and does not show coagulation. Thus, if an additional ion exchange step is performed before coagulation, the hot water storage stability of the impact modifier or its composition can be improved.

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a poly(meth)acrylate impact modifier (hereinafter also referred to as impact modifier) ​​comprising (preferably consisting essentially of) at least one multiphasic alkyl(meth)acrylate emulsion polymer (hereinafter also referred to as emulsion polymer), wherein the total amount of alkali metal ions, preferably sodium and / or potassium, in the impact modifier is 4.5 mmol / kg or less, preferably 3.0 mmol / kg or less, more preferably 2.0 mmol / kg or less, based on the solids content of the impact modifier.

[0027] In a preferred embodiment, the poly(meth)acrylate impact modifier comprises less than or equal to 1.0 mmol / kg, preferably less than or equal to 0.9 mmol / kg, more preferably less than or equal to 0.5 mmol / kg of alkali metal ions, preferably sodium and / or potassium, based on the solids content of the impact modifier.

[0028] More preferably, the poly(meth)acrylate impact modifier comprises 0 to 4.5 mmol / kg, preferably 0 to 3.0 mmol / kg, more preferably 0 to 1.0 mmol / kg, preferably 0.01 to 4.5 mmol / kg, also preferably 0.01 to 3.0 mmol / kg, also preferably 0.01 to 1.0 mmol / kg of alkali metal ions based on the solids content of the impact modifier.

[0029] Preferably, the poly(meth)acrylate impact modifier of the present invention contains no more than 20.0 mmol / kg, preferably no more than 10.0 mmol / kg, more preferably no more than 9.0 mmol / kg of cationic metal ions (i.e., the sum of all cationic metal ions, e.g., alkali metal ions and polyvalent ions, e.g., alkaline earth metal ions, aluminum ions and / or zinc ions) based on the solids content of the impact modifier. Typically, the total amount of cationic metal ions (e.g., alkali metal ions, alkaline earth metal ions, aluminum ions and / or zinc ions) is in the range of 0.1 to 20.0 mmol / kg, preferably 0.4 to 10.0 mmol / kg.

[0030] Preferably, the poly(meth)acrylate impact modifiers of the present invention contain less than 6.5 mmol / kg, preferably less than 5.0 mmol / kg, more preferably less than 5.0 mmol / kg, of sulfur (calculated as sulfate) based on the solids content of the impact modifier.Typically, the impact modifiers contain less than 6.5 mmol / kg, preferably less than 5.0 mmol / kg, of sulfur-containing anions (calculated as sulfate) based on the solids content of the impact modifier.

[0031] Typically, the metal ions (e.g., alkali metal ions and / or polyvalent metal ions selected from alkaline earth metals, zinc and aluminum) contained in the impact modifier of the present invention originate from the auxiliaries, such as initiators, surfactants and buffer salts, used in the emulsion polymerization process of the multiphase alkyl (meth)acrylate emulsion polymer. In addition, the metal ions may originate from additives, such as stabilizers, added to the impact modifier. In particular, the alkali metal ions contained in the impact modifier of the present invention originate from the initiators and / or surfactants used in the emulsion polymerization.

[0032] Typically, a significant amount of metal ions in the impact modifier may come from the coagulant used in the isolation of the emulsion polymer from the aqueous latex dispersion. Therefore, the multi-phase alkyl (meth)acrylate emulsion polymer of the impact modifier of the present invention is preferably coagulated without adding a coagulant, such as a metal salt. Typically, coagulation is carried out by physical coagulation. Furthermore, it is possible to carry out coagulation together with physical coagulation by adding at least one coagulant selected from multivalent metal ions, such as calcium salts, magnesium salts and / or aluminum salts.

[0033] According to a preferred embodiment, the coagulation of the multi-phase alkyl (meth)acrylate emulsion polymer is carried out by physical coagulation without the addition of a coagulant, for example a coagulant selected from polyvalent metal ions. For example, the poly(meth)acrylate impact modifier contains 4.5 mmol / kg or less, preferably 3.0 mmol / kg or less, more preferably 2.0 mmol / kg or less, also preferably 1.0 mmol / kg or less of cationic metal ions (i.e. the sum of all cationic metal ions, for example alkali metal ions and polyvalent ions, for example alkaline earth metal ions) based on the solid content of the impact modifier. For example, the poly(meth)acrylate impact modifier may contain sodium ions and / or potassium ions, and the amount of all other cationic metal ions is below the detection limit of the respective analytical method.

[0034] According to another preferred embodiment, at least one polyvalent metal salt (e.g., alkaline earth metal salt, aluminum salt and / or zinc salt) is added as a coagulant, and the poly(meth)acrylate impact modifier comprises a total of less than 4.5 mmol / kg, preferably less than 3.0 mmol / kg, more preferably less than 1.0 mmol / kg of alkali metal ions based on the solid content of the impact modifier, and 0.4 to 15.0 mmol / kg, preferably 0.5 to 10.0 mmol / kg of polyvalent metal ions (e.g., alkaline earth metal ions, aluminum ions and / or zinc ions) based on the solid content of the impact modifier.

[0035] The term "polyvalent metal" or "polyvalent metal ion" refers to a metal ion having two or more ionic charges, preferably two or three. Preferably, the polyvalent metal ion can be selected from metals in IUPAC Group 2 (alkaline earth metals) and IUPAC Groups 8-14, more preferably from metals in IUPAC Group 2 (alkaline earth metals), IUPAC Group 12 (zinc group) and IUPAC Group 13 (boron group).

[0036] The term "alkali metals" or "alkali metal ions" includes elements in IUPAC Group 1 of the Periodic Table of the Elements, particularly lithium (Li), sodium (Na) and potassium (K). The term "alkaline earth metals" or "alkaline earth metal ions" includes elements in IUPAC Group 2 of the Periodic Table of the Elements, particularly magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba).

[0037] As used herein, the term "(meth)acrylate" is meant to include methacrylates, acrylates, and mixtures thereof.

[0038] The term "alkyl (meth)acrylate polymer" means a polymer that contains at least 30% by weight, preferably at least 40% by weight, and more preferably at least 50% by weight, of alkyl (meth)acrylate monomer units, including copolymers of alkyl (meth)acrylate monomers with one or more other copolymerizable monomers.

[0039] The term "alkyl (meth)acrylate emulsion polymer" means a multiphase emulsion polymer comprising at least 30% by weight, preferably at least 40% by weight, and more preferably at least 50% by weight, of alkyl (meth)acrylate monomer units in an outer shell, which may comprise a copolymer of alkyl (meth)acrylate monomers with one or more other copolymerizable monomers, such as styrene.

[0040] The terms "aqueous" or "aqueous solution" mean that the medium or solvent consists of or contains water as a major component. For example, a polar water-miscible co-solvent, such as an alcohol, may be included in the medium or solvent.

[0041] The term "latex" as used in connection with the present invention means a water-insoluble polymer dispersed in an aqueous phase, preferably stabilized by one or more surfactants, and prepared by conventional polymerization techniques, preferably emulsion polymerization.

[0042] Unless otherwise defined, the term ppm according to the present invention means ppm by weight, e.g. mg / kg, e.g. the term ppm means mg / kg of solids of the poly(meth)acrylate impact modifier.

[0043] The content of metal ions, such as alkali metals and alkaline earth metals, in emulsion polymers or impact modifiers is typically determined by atomic emission spectroscopy after chemical digestion of polymer samples, for example microwave-assisted digestion of polymer samples in nitric acid. The amount of alkali metals and polyvalent metals, such as alkaline earth metals or aluminum, is given taking into account the typical detection limit of the respective analytical method. For example, amounts given as 0% by weight, 0 ppm or 0 mmol / kg are understood to be below the detection limit of the respective analytical method.

[0044] Preferably, the polyvalent metal ion is selected from metal ions from IUPAC Group 2 (alkaline earth metals), IUPAC Group 12 (zinc group) and IUPAC Group 13 (boron group). More preferably, the polyvalent metal ion is selected from alkaline earth metals, preferably magnesium (Mg) and / or calcium (Ca), and metals from IUPAC Group 13, preferably aluminum. Most preferably, the polyvalent metal ion is selected from alkaline earth metals, zinc (Zn) and aluminum (Al). In a further preferred embodiment, at least one polyvalent metal ion is selected from magnesium (Mg), calcium (Ca), zinc (Zn) and aluminum (Al), more preferably magnesium (Mg), calcium (Ca) and aluminum (Al).

[0045] In particular, the total amount of cationic metal ions refers to the sum of all metal ions present in the poly(meth)acrylate impact modifier. In particular, the total amount of cationic metal ions includes alkali metal ions and polyvalent metal ions, such as alkaline earth metal ions and / or aluminum ions. In particular, the amount of alkali metal ions refers to the sum of all alkali metal ions present in the poly(meth)acrylate impact modifier. Preferably, the alkali metal ions are sodium ions and / or potassium ions, and the amount of alkali metal ions refers to the sum of sodium ions and potassium ions.

[0046] The cationic metal ions, e.g., alkali metal ions, may be present in the impact modifier in any form, such as a solid salt, or in the form of a salt content dissolved in the aqueous phase and bound or adsorbed to other components or groups of the emulsion polymer, e.g., anionic groups.

[0047] Typically, the impact modifier comprises or essentially consists of polymer particles prepared by emulsion polymerization. After emulsion polymerization, said impact modifier is in the form of an aqueous polymer dispersion at the end of the synthesis process. This aqueous polymer dispersion, also called latex, contains not only the polymer fraction but also polar water-soluble auxiliary materials such as surfactants, buffer substances, initiators and other redox components added during the polymerization process.

[0048] Multiphase alkyl (meth)acrylate emulsion polymer Preferably, the multiphasic alkyl (meth)acrylate emulsion polymer is an emulsion polymer obtained by emulsion polymerization, preferably by sequential emulsion polymerization, of alkyl (meth)acrylate monomers and optionally other copolymerizable monomers, the emulsion polymer having a multiphasic structure comprising at least one core and at least one, preferably one or two shells.

[0049] For example, the multiphase alkyl (meth)acrylate emulsion polymer may be formed by crosslinked particles having a core-shell structure or a core-shell-shell structure. Typically, the particles have an average particle size of 20 nm to 500 nm, preferably 50 nm to 450 nm, more preferably 100 nm to 400 nm, most preferably 150 nm to 350 nm. The average particle size can be determined by methods known to those skilled in the art, for example by static or dynamic light scattering, such as laser diffraction measurements or photon correlation spectroscopy according to DIN ISO 13321:1996. Typically, the volume average particle size can be obtained from light scattering measurements.

[0050] In a preferred embodiment, the multiphasic alkyl (meth)acrylate emulsion polymer comprises a soft elastomeric core and a hard non-elastomeric outer phase, typically produced in the presence of the core by graft emulsion polymerization, said multiphasic alkyl (meth)acrylate emulsion polymer being hereinafter referred to as a core-shell emulsion polymer.

[0051] In another preferred embodiment, the multiphasic alkyl (meth)acrylate emulsion polymer comprises a hard, non-elastomeric core, a soft, elastomeric intermediate shell formed in the presence of the core, typically by graft emulsion polymerization, and a hard, non-elastomeric outer shell formed in the presence of the intermediate core-shell particles, typically by graft emulsion polymerization, said multiphasic alkyl (meth)acrylate emulsion polymer being hereinafter referred to as a core-shell-shell emulsion polymer.

[0052] Preferably, the outer shell of the multi-phase emulsion polymer is a hard phase comprising at least 80% by weight of at least one C1-C6 alkyl methacrylate relative to the outer shell, preferably at least 80% by weight of methyl methacrylate relative to the outer shell.

[0053] Preferably, at least 50% by weight, more preferably at least 55% by weight, more preferably at least 80% by weight of the outer layer, based on the total weight of the emulsion polymer, is covalently bonded to the soft phase, i.e., the soft core of the core-shell emulsion polymer or the intermediate shell of the core-shell-shell emulsion polymer. Typically, the amount of covalently bonded outer layer (grafted polymer) (also called the degree of grafting) is determined as the amount insoluble in acetone.

[0054] To determine the degree of grafting, the water of the emulsion polymer dispersion is removed in a drying cabinet to obtain the pure modifier solid. 1.5 g of the multiphase emulsion polymer is mixed with 40 g of acetone and stirred at 40 °C until a turbid solution is obtained (2-3 h). The insoluble grafted polymer is separated by centrifugation (e.g., 9000 rpm, 2-5 h) and the clear supernatant is dried to a constant weight to obtain the amount of the soluble fraction. This allows the calculation of the degree of grafting by applying equation (1). Grafting degree = 100% - acetone solubles (1)

[0055] Preferably, the degree of grafting of the emulsion polymer is in the range of 50 to 100% by weight, preferably 52 to 99% by weight, based on the solid content of the emulsion polymer.

[0056] Preferably, the alkyl (meth)acrylate emulsion polymer comprises at least 60% by weight, preferably at least 75% by weight, of at least one C1-C alkyl (meth)acrylate copolymer based on the total emulsion polymer. 20 Alkyl (meth)acrylates, more preferably methyl methacrylate and / or n-butyl acrylate.

[0057] Generally, the (meth)acrylate is a C1-C 10 -Alkyl (meth)acrylate, C2-C 20 -Alkenyl (meth)acrylate, C6-C 20 Aryl (meth)acrylate, C6-C 20 Aralkyl (meth)acrylates, C1-C 10Included are hydroxyalkyl (meth)acrylates, glycol di(meth)acrylates, and multifunctional (meth)acrylates.

[0058] Preferably, the emulsion polymer is at least one C1-C 10 an alkyl methacrylate, preferably at least one C1-C methacrylate selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, isooctyl methacrylate, and ethylhexyl methacrylate; 10 These include alkyl methacrylates, as well as cycloalkyl methacrylates such as cyclohexyl methacrylate.

[0059] Preferably, the emulsion polymer is at least one C1-C 10 at least one C1-C alkyl acrylate selected from methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, isooctyl acrylate, and ethylhexyl acrylate; 10 These include alkyl acrylates, as well as cycloalkyl acrylates such as cyclohexyl acrylate.

[0060] Additionally, the emulsion polymer may include at least one conjugated diene, such as butadiene, particularly as a soft core.

[0061] In particular, the multi-phase alkyl (meth)acrylate emulsion polymer is At least 10% by weight, preferably at least 20% by weight, preferably 10 to 70% by weight of at least one of C1 to C 10, preferably a C1 to C6 alkyl methacrylate, preferably methyl methacrylate; 5 to 80% by weight, preferably 20 to 80% by weight, of at least one of C1 to C 10 an alkyl acrylate (preferably n-butyl acrylate) or at least one conjugated diene (preferably butadiene); 0 to 2% by weight, preferably 0.1 to 2% by weight, more preferably 0.5 to 1% by weight of at least one crosslinkable monomer, preferably a polyfunctional (meth)acrylate and / or an allyl (meth)acrylate; 0 to 15% by weight, preferably 0.5 to 10% by weight, more preferably 0.5 to 5% by weight, optionally further monomers, preferably different from the above mentioned monomers, such as vinyl aromatic monomers, e.g. styrene, α-methylstyrene or benzyl methacrylate, preferably styrene; The composition comprises (preferably consists of)

[0062] More specifically, the multi-phase alkyl (meth)acrylate emulsion polymer comprises: At least 40% by weight, preferably 40 to 70% by weight, of at least one of C1 to C 10 , preferably a C1 to C6 alkyl methacrylate, preferably methyl methacrylate; 5 to 45% by weight, preferably 20 to 45% by weight, preferably 25 to 42% by weight of at least one of C1 to C 10 Alkyl acrylate, preferably C1-C6 alkyl acrylate, preferably C1-C6 alkyl acrylate selected from ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate and butyl methacrylate (more preferably C1-C 10 Alkyl acrylates include n-butyl acrylate) and 0 to 2% by weight, preferably 0.1 to 2% by weight, more preferably 0.5 to 1% by weight of at least one crosslinkable monomer, preferably a polyfunctional (meth)acrylate and / or an allyl (meth)acrylate; 0-15% by weight, preferably 0-12% by weight, more preferably 0.5-10% by weight, optionally further monomers, preferably different from the above mentioned monomers, such as vinyl aromatic monomers, e.g. styrene, benzyl methacrylate, The composition comprises (preferably consists of)

[0063] The amounts are given relative to the total mass of the monomers.

[0064] Multi-phase alkyl (meth)acrylate emulsion polymers may contain vinyl aromatic monomers, such as styrene and / or C7-C acrylates, to adjust the refractive index difference between the hard and soft phases. 20 It is preferred to include aralkyl (meth)acrylates, such as benzyl methacrylate. Styrenes that may be used are styrene, substituted styrenes having alkyl substituents on the side chain, such as α-methylstyrene and α-ethylstyrene, substituted styrenes having alkyl substituents on the ring, such as vinyltoluene and p-methylstyrene, and halogenated styrenes, such as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrabromostyrene.

[0065] Typically, the crosslinking monomer has two or more polymerizable double bonds in the molecule. The crosslinking monomer may be selected from difunctional (meth)acrylates, trifunctional or multifunctional (meth)acrylates, and other known crosslinkers such as allyl methacrylate, allyl acrylate, and divinylbenzene.

[0066] For example, difunctional (meth)acrylates are diesters of (meth)acrylic acid with polyfunctional alcohols, such as di(meth)acrylates of propanediol, butanediol, hexanediol, octanediol, nonanediol, decanediol, eicosanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dodecaethylene glycol, tetradecaethylene glycol, propylene glycol, dipropyl glycol, and tetradecapropylene glycol. For example, trifunctional or polyfunctional (meth)acrylates are tri- or multi-esters of (meth)acrylic acid with polyfunctional alcohols, such as trimethylolpropane tri(meth)acrylate and pentaerythritol tetra(meth)acrylate.

[0067] Suitable cross-linking monomers are described, for example, in WO 02 / 20634 and EP 0522351.

[0068] Preferably, the alkyl (meth)acrylate emulsion polymer comprises at least one crosslinking monomer selected from ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, divinylbenzene, and allyl (meth)acrylate. More preferably, the crosslinking monomer is allyl methacrylate.

[0069] The alkyl (meth)acrylate emulsion polymer may contain 0 to 15% by weight, preferably 0 to 10% by weight, more preferably 0.5 to 5% by weight, of further components, such as auxiliaries or residues of auxiliaries added during polymerization and / or further processing, such as emulsifiers, initiators, buffers or molecular weight regulators, as described below, based on the solids content of the emulsion polymer. In particular, the alkyl (meth)acrylate emulsion polymer may contain 0 to 15% by weight, preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight, of molecular weight regulators, as described below, based on the solids content of the emulsion polymer.

[0070] Core-shell emulsion polymer For example, the impact modifiers are based on two-phase emulsion polymers consisting of a soft elastomeric core and a hard shell, as described for example in EP 0 528 196, DE 3 842 796 and DE 10 2005 062 687. In particular, said core-shell emulsion polymers can be obtained by a two-step emulsion polymerization in water, as described for example in DE 3 842 796 (A). In a first step, the core particles are prepared by emulsion polymerization and the shell is prepared by emulsion polymerization of a monomer mixture in the presence of the core particles.

[0071] Typically, the hard phase has a glass transition temperature T above 70° C. g and contains 80-100% by weight of methyl methacrylate relative to the hard phase. Typically, the soft core has a glass transition temperature T g With respect to the soft core, 50 to 99.5% by weight of C1 to C 10 The soft core comprises an alkyl acrylate and 0.5 to 5% by weight of a crosslinking monomer. Further, the soft core has a glass transition temperature T g and may contain 50 to 100% by weight of at least one conjugated diene, such as butadiene, based on the soft core.

[0072] In a preferred embodiment, the multi-phase alkyl (meth)acrylate emulsion polymer comprises: A1) 10 to 95% by weight of the total emulsion polymer has a glass transition temperature T g having A1.1) At least one of C1 to C, which is 50 to 99.5% by weight based on A1 10 an alkyl acrylate, preferably n-butyl acrylate; A1.2) 0.5 to 5% by weight, based on A1, of at least one crosslinking monomer having two or more ethylenically unsaturated groups, and A1.3) 0 to 10% by weight, based on A1, of at least one further ethylenically unsaturated free-radically polymerizable monomer. A soft elastomeric core A1, B1) 5 to 90% by weight of the total emulsion polymer, the glass transition temperature T g having B1.1) 80-100% by weight, based on B1, of at least one C1-C6 alkyl methacrylate, preferably methyl methacrylate, and B1.2) 0-20% by weight, based on B1, of at least one further ethylenically unsaturated free-radically polymerizable monomer, for example an ethylenically unsaturated free-radically polymerizable monomer selected from C1-C6 alkyl acrylates, such as butyl acrylate or ethyl acrylate. and a rigid shell B1 constructed from The core-shell emulsion polymer is a polymer comprising (preferably consisting of)

[0073] In another preferred embodiment, the multi-phasic alkyl (meth)acrylate emulsion polymer comprises A1) 50 to 90% by weight of the emulsion polymer has a glass transition temperature T of less than -10 ° C. g having A1.1) 90 to 100% by weight of at least one conjugated diene, preferably butadiene, based on A1; A1.2) 0 to 5% by weight, based on A1, of at least one crosslinking monomer having two or more ethylenically unsaturated groups, and A1.3) 0 to 10% by weight, based on A1, of at least one further ethylenically unsaturated free-radically polymerizable monomer, such as at least one vinyl aromatic monomer, preferably styrene and / or α-methylstyrene. A soft elastomeric core A1, B1) 10 to 50% by weight of the total emulsion polymer, a glass transition temperature T g having B1.1) 70 to 90% by weight, based on B1, of at least one C1 to C6 alkyl methacrylate, preferably methyl methacrylate, and B1.2) 10 to 30% by weight, based on B1, of at least one further ethylenically unsaturated free-radically polymerizable monomer, for example an ethylenically unsaturated free-radically polymerizable monomer selected from vinyl aromatic monomers, preferably styrene and / or α-methylstyrene. and a rigid shell B1 constructed from The core-shell emulsion polymer is a polymer comprising (preferably consisting of)

[0074] Preferably, the degree of grafting of the core-shell emulsion polymer is at least 50% by weight, preferably 50-60% by weight, based on the total solids content of the emulsion polymer.

[0075] In general, the glass transition temperature T of a polymer or a phase of a multiphase emulsion polymer g The glass transition temperature T can be determined in a known manner by differential scanning calorimetry (DSC). g can also be calculated as an approximation using the Fox formula.

[0076] Core-Shell-Shell Emulsion Polymer For example, the impact modifier may have a hard core constructed from, for example, crosslinked methyl methacrylate and a crosslinked C1-C 10 It is based on a three-phase emulsion polymer composed of a soft intermediate shell constructed from an alkyl acrylate, preferably n-butyl acrylate, and a hard outer shell constructed, for example, from non-crosslinked methyl methacrylate. Typically, said core-shell-shell emulsion polymers are prepared as described in EP 1 332 166 B1, WO 02 / 20634 and EP 0 522 351.

[0077] In particular, the poly(alkyl)methacrylate impact modifier may include a methacrylate / butadiene / styrene copolymer or an acrylate / methacrylate copolymer.

[0078] In a preferred embodiment, the multi-phase alkyl (meth)acrylate emulsion polymer comprises: A2) 5 to 40% by weight of the total emulsion polymer, a glass transition temperature T g having A2.1) 80-100% by weight of at least one C1-C6 alkyl methacrylate, preferably methyl methacrylate, based on A2; A2.2) 0 to 20% by weight, based on A2, of at least one further ethylenically unsaturated free-radically polymerizable monomer, and A2.3) 0-5% by weight, based on A1, of at least one crosslinking monomer having two or more ethylenically unsaturated groups. a hard non-elastomeric core A2 constructed from B2) 20 to 75% by weight of the total emulsion polymer, with a glass transition temperature T g having B2.1) At least one of C1 to C, which is 45 to 99.5% by weight based on B2 10 an alkyl acrylate, preferably n-butyl acrylate; B2.2) 0.5 to 5% by weight, based on B2, of at least one crosslinking monomer having two or more ethylenically unsaturated groups, and B2.3) 0 to 50% by weight, based on B2, of at least one further ethylenically unsaturated free-radically polymerizable monomer, preferably a monomer having an aromatic group. a soft elastomeric intermediate shell B2 constructed from C2) 15 to 60% by weight of the emulsion polymer having a glass transition temperature T g having C2.1) 80 to 100% by weight, preferably 90 to 100% by weight, based on C2, of at least one C1 to C6 alkyl methacrylate, preferably methyl methacrylate, and C2.2) 0 to 20% by weight, preferably 0 to 10% by weight, based on C2, of at least one further ethylenically unsaturated free-radically polymerizable monomer with a rigid outer shell C2 constructed from The core-shell-shell emulsion polymer comprises:

[0079] Preferably, at least 15% by weight, more preferably at least 25% by weight, of the hard outer shell C2 is covalently bonded to the soft elastomeric intermediate shell B2.

[0080] Preferably, the degree of grafting of the core-shell-shell emulsion polymer is at least 50% by weight, preferably 70-99% by weight, based on the total solids content of the emulsion polymer.

[0081] Method for producing poly(meth)acrylate impact modifiers Furthermore, the present invention relates to a method for producing a (i) preparation of at least one multiphasic alkyl (meth)acrylate emulsion polymer by emulsion polymerization, in particular by sequential emulsion polymerization, in which the multiphasic alkyl (meth)acrylate emulsion polymer is obtained in the form of a latex, (ii) removing cations and optionally anions in an ion exchange step by contacting the latex obtained in step (i) with an ion exchange material, preferably a cation exchange material, more preferably a cation exchange material in protonated form; (iii) coagulation and dehydration, preferably mechanical dehydration, of the latex obtained in step (ii), wherein the coagulation is carried out by physical coagulation to obtain a dehydrated alkyl (meth)acrylate emulsion polymer, the dehydrated alkyl (meth)acrylate emulsion polymer containing not more than 4.5 mmol / kg, preferably not more than 3.0 mmol / kg, more preferably not more than 2.0 mmol / kg, even more preferably not more than 1.0 mmol / kg of alkali metal ions, e.g. sodium and / or potassium, based on the solid content of the impact modifier. The present invention is directed to a method for making a poly(meth)acrylate impact modifier comprising at least one multi-phase alkyl (meth)acrylate emulsion polymer comprising:

[0082] The preferred embodiments mentioned above in relation to the impact modifier of the present invention apply accordingly to the process of the present invention.

[0083] In particular, the dehydrated poly(meth)acrylate emulsion polymer obtained in step (iii) contains not more than 20.0 mmol / kg, preferably not more than 10.0 mmol / kg, more preferably not more than 9.0 mmol / kg of cationic metal ions based on the solid content of the impact modifier.

[0084] In particular, the poly(meth)acrylate impact modifier comprising, or preferably consisting essentially of, a multi-phase alkyl (meth)acrylate emulsion polymer can be obtained as a dry polymer powder, especially after dehydration and drying.

[0085] In particular, the poly(meth)acrylate impact modifier comprising or preferably essentially consisting of a multi-phase alkyl (meth)acrylate emulsion polymer can be obtained in the form of polymer granules.For example, the polymer powder obtained after drying can be granulated, for example by a commonly known melt extrusion process, optionally with the addition of one or more additives and / or one or more additional polymer components.Furthermore, the impact modifier can be obtained in the form of polymer granules, and the solidification and dehydration in step (ii) can be carried out by thermal shear solidification in an extruder.

[0086] In a preferred embodiment, coagulation is performed by freeze coagulation and the aqueous phase of the coagulated emulsion polymer is at least partially removed by mechanical dewatering, for example in a centrifugation step. Typically, the water content of the dewatered emulsion polymer is in the range of 5-40% by weight, preferably 7-30% by weight, based on the dewatered emulsion polymer. In a preferred embodiment, the coagulation and dewatering in step (ii) is performed as described in WO 2015 / 074883.

[0087] Preferably, step (ii) may include a sintering step as described below. Additionally, the method of the present invention may include one or more washing steps (iii) and / or one or more drying steps (iv) as described below.

[0088] In a preferred embodiment, the coagulation and dewatering in step (ii) is carried out by extrusion. Typically, the latex obtained by emulsion polymerization is introduced into an extruder, which typically includes a coagulation zone, a dewatering zone and a devolatilization zone. Preferably, the coagulation and dewatering by extrusion can be carried out as described in WO 02 / 18453, EP 0683028 or EP 0187715.

[0089] In another preferred embodiment, the coagulation and dehydration in step (ii) is carried out by freeze coagulation. Preferably, the coagulation and dehydration by freeze coagulation can be carried out as described in WO 2015 / 074883.

[0090] Emulsion polymerization step (i) The process of the present invention includes an emulsion polymerization step (i) in which at least one multiphasic alkyl(meth)acrylate polymer is prepared by emulsion polymerization, in particular by sequential emulsion polymerization, the multiphasic alkyl(meth)acrylate emulsion polymer being obtained in the form of a latex.

[0091] The multiphase emulsion polymers are prepared in the aqueous phase in the usual manner by two-stage, three-stage or multi-stage emulsion polymerization. Typically, the emulsion polymerization stages are carried out at temperatures in the range of 20 to 100°C, preferably 60 to 90°C.

[0092] Generally, the core is prepared by emulsion polymerization in a first stage. Typically, the core has an average particle size of 50-150 nanometers (nm) for core-shell emulsion polymers and 100-300 nanometers (nm) for core-shell-shell emulsion polymers. Methods for adjusting the desired particle size are known to those skilled in the art. Advantageously, the particle size control is performed according to the seed latex method, for example, as described in US 2007 / 0123610 A1 and WO 2004 / 056893.

[0093] In the case of core-shell emulsion polymers, the hard outer phase is prepared in a second polymerization stage, after completion of the first polymerization stage, in the presence of the soft core.

[0094] In the case of core-shell-shell emulsion polymers, the elastomeric mesophase is prepared in a second polymerization stage in the presence of the core after the first polymerization stage has been completed. Finally, in a third stage, after the second polymerization stage has been completed, the final rigid phase is also made in the presence of the emulsion polymer of the second stage.

[0095] Emulsion polymerization is preferably carried out in the presence of anionic emulsifier.Generally known anionic emulsifiers are, for example, alkyl sulfates, alkyl sulfonates, alkyl sulfonic acids, aralkyl sulfonates, soaps of saturated or unsaturated fatty acids.Preferably, anionic emulsifiers are used that are selected from sulfonates, alkyl sulfosuccinates, and alkoxylated and sulfated paraffins, and mixtures thereof.

[0096] Preferably, the emulsion polymer latex is polymerized by aqueous free radical emulsion polymerization. The reaction is typically initiated via a water- or oil-soluble free radical polymerization initiator.

[0097] For example, suitable polymerization initiators are selected from inorganic or organic peroxides such as dilauroyl peroxide, tert-butyl peroctoate, tert-butyl perisononanoate, dicyclohexyl peroxydicarbonate, dibenzoyl peroxide and 2,2-bis(tert-butylperoxy)butane; azo compounds such as 2,2'-azobis(isobutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile), and redox initiator systems.Examples of suitable redox systems are the combination of tertiary amines and peroxides, or the combination of sodium disulfite and potassium, sodium or ammonium persulfates, or preferably peroxides.

[0098] In order to keep the flow of free radicals constant during the course of the polymerization or at different polymerization temperatures, it is also preferred to carry out the polymerization using a mixture of different polymerization initiators with different half-life times, for example dilauroyl peroxide and 2,2-bis(tert-butylperoxy)butane.

[0099] The polymerization initiator is typically used in an amount of 0.01 to 2% by weight based on the monomer mixture. Typically, the polymerization initiator is used in the range of 0.01 to 0.5% by weight based on the aqueous emulsion polymerization mixture.

[0100] Preferably, an alkali metal peroxydisulfate or ammonium peroxydisulfate is used as a polymerization initiator, for example 0.01 to 0.5% by weight based on the aqueous phase of the polymerization mixture, and the polymerization is preferably initiated at a temperature of 20°C to 100°C.

[0101] Preferably, a redox system is used as polymerization initiator, for example 0.01-0.05 wt. % of an organic hydroperoxide and 0.05 wt. %-0.15 wt. % of sodium hydroxymethylsulfinate (e.g. Rongalite®), each relative to the aqueous phase of the polymerization mixture, and the polymerization is preferably initiated at a temperature in the range of 20° C. to 80° C.

[0102] The chain length of the polymer, especially in the outer hard phase, can be adjusted by polymerizing the monomer mixture in the presence of a molecular weight regulator. In particular, known mercaptans such as n-butyl mercaptan, n-dodecyl mercaptan, 2-mercaptoethanol, or 2-ethylhexyl thioglycolate, or pentaerythritol tetrathioglycolate, can be used for this purpose. Typically, the amount of molecular weight regulator is 0.05-5% by weight relative to the monomer mixture, preferably 0.1-2% by weight relative to the monomer mixture, particularly preferably 0.2-1% by weight. Preferably, n-dodecyl mercaptan is used as the molecular weight regulator.

[0103] Furthermore, it is possible to use salts, acids and bases in the emulsion polymerization, in particular to adjust the pH or to buffer the reaction mixture. For example, solutions of sodium and potassium salts of sulfuric acid, phosphoric acid, sodium hydroxide, potassium hydroxide, carbonate, bicarbonate, sulfate and / or phosphoric acid (e.g. tetrasodium pyrophosphate) can be used. Typically, the emulsion polymer latex obtained in step (i) has a pH value in the range of 2 to 7, preferably 2.5 to 6.

[0104] Typically, the emulsion polymer latex obtained in step (i) has a solid content in the range of 20 to 60% by weight based on the total weight of the emulsion polymer latex. The solid content can be adjusted as necessary.

[0105] Ion exchange step (ii) The process for preparing the impact modifier of the present invention comprises contacting the latex obtained in step (i) with an ion exchange material, preferably a cation exchange material, more preferably a strong acid cation exchange material, in particular in the protonated form (H form), in step (ii). Preferably, after the ion exchange step, the amount of cationic metal ions is reduced to 1.0 mmol / kg or less. The latex is then typically coagulated without the addition of ions (i.e. salts and / or acids), preferably without the addition of cations such as alkali metal salts and alkaline earth metal salts.

[0106] In general, the ion exchange material used in step (ii) can be at least one cation exchange material (i.e., a material containing an anionic group capable of being loaded with a proton H+), and / or at least one amphoteric exchange material (i.e., a material containing an anionic group and a cationic group), and optionally at least one anion exchange material (i.e., a material containing a cationic basic group). Different ion exchange materials can be used as a mixture in one contact step with the emulsion polymer latex and / or consecutively in two or more contact steps with the emulsion polymer latex. For example, it is possible to contact the latex obtained in step (i) with an anion exchange material in a first step, and then contact the latex with a cation exchange material in a second step. Furthermore, it is possible to use mixed ion exchange materials containing anion exchange groups and cation exchange groups.

[0107] When the emulsion polymerization in step (i) is carried out in the presence of an anionic surfactant, preferably at least one cation exchange material is used, more preferably as the only ion exchange material.

[0108] In order to avoid latex coagulation and clogging of the ion exchange material, a non-ionic surfactant can be added in the ion exchange step (ii). In a preferred embodiment, at least one non-ionic surfactant is added to the latex before and / or during the ion exchange step (ii). In particular, coagulation of the latex may occur when an anion-stabilized latex (i.e. a latex prepared by emulsion polymerization using an anionic surfactant) is contacted with an anion exchange material. Suitable non-ionic surfactants are, for example, alkylaryl polyethoxy alcohols and alkyl polyethoxy alcohols, such as p-octylphenol-oxethylate (TRITON® X 100, Rohm & Haas) or fatty alcohols (GENAPOL X 080, Clariant GmbH). Typically, the non-ionic surfactant is added in an amount of 0.001 to 3.0% by weight based on the solid content of the emulsion polymer latex. Such ion exchange processes are described, for example, in WO 2001 / 57100(A1), WO 99 / 62830(A) and WO 99 / 62858(A).

[0109] In a preferred embodiment, the latex obtained in step (i) is contacted in step (ii) with at least one cation exchange material, more preferably a strong acid cation exchange material, especially in the protonated form (H-form). Suitable cation exchange materials contain at least one acid group, such as a carboxylic acid group (-COOH) or a sulfonic acid group (-S(=O)2OH), preferably a strong acid group, such as a sulfonic acid group. If the cation exchange material is not in the protonated form, e.g. the Na-form, it can be treated with an aqueous acid, such as hydrochloric acid or sulfuric acid, to obtain the protonated H-form of the exchanged material.Suitable examples of commercially available cation exchange materials are available from Dow Chemical under the trade names / trademarks DOWEX® MARATHON C, DOWEX® MONOSPHERE C-350, DOWEX® HCR-S / S, DOWEX® MARATHON MSC, DOWEX® MONOSPHERE 650C, DOWEX® HCR-W2, DOWEX® MSC-1, DOWEX® HGR NG(H), DOWEX® DR-G8, DOWEX® 88, DOWEX® MONOSPHERE 88, DOWEX® MONOSPHERE C-600 B, DOWEX® MONOSPHERE M-31, DOWEX® MONOSPHERE DR-2030, DOWEX® M-31, DOWEX® G-26(H), DOWEX® 50 W-X4, DOWEX® 50W-X8, DOWEX® 66. ion exchange resins manufactured by Rohm and Haas under the trade names / trade names Amberlyst® 131, Amberlyst® 15, Amberlyst® 16, Amberlyst® 31, Amberlyst® 33, Amberlyst® 35, Amberlyst® 36, Amberlyst® 39, Amberlyst® 40, Amberlyst® 70, Amberlite® FPC11, Amberlite® FPC22, Amberlite® FPC23; ion exchange resins manufactured by Brotech Corp. under the trade names / trade names Purofine® PFC150, Purolite® C145, Purolite® C150, Purolite® C160, Purolite® PFC100, Purolite® C100; and Monoplus® S100 and Tulsion® T42 is an ion exchange resin manufactured by Thermax Limited Corp. Other acidic cation exchange resins known to those skilled in the art may also be used.Preferably, Dowex® Marathon C manufactured by Dow Chemical is used.

[0110] Furthermore, the latex obtained in step (i) can be contacted with at least one anion exchange material, preferably in addition to contacting the latex with a cation exchange material. In this way, it is typically possible to reduce the amount of anions, such as sulfur-containing anions, to 6.5 mmol / kg or less (calculated as sulfate). When an anion exchange material is used and when an anion-stabilized emulsion polymer latex is used, preferably at least one nonionic surfactant is added before and / or during step (ii).

[0111] Typically, weakly basic, medium basic and strong basic anion exchange materials can be used. Typically, the basic groups can be selected from primary amino groups (-NH2), secondary amino groups (-NHR) and tertiary amino groups (-NR2), with the basic capacity increasing in this order from weak to medium. Typically, the functional groups of the anion exchange material can be selected from quaternary ammonium groups (also called Quat). Suitable anion exchange materials contain at least one functional cationic group, such as trimethylamine groups, trimethylbenzylammonium groups, or quaternary ammonium. If the anion exchange material is not loaded with hydroxy ions (i.e., Cl form), it can be treated with a basic aqueous solution, such as sodium hydroxide solution or potassium hydroxide solution, to obtain the deprotonated form (OH form) of the exchange material. Suitable examples of commercially available anion exchange materials are DOWEX® 1X2, 1X4 and 1X8 series resins (Dow Chemical), AMBERLITE IRA 402 type resins, OAMBERJET 4200 (Rohm and Haas), OPUROLITE A 845 (Purolite GmbH), LEWATIT MP-500 (Bayer AG).

[0112] In step (ii), the latex obtained in step (i) is contacted with at least one ion exchange material in any suitable manner, for example, the ion exchange step (ii) can be carried out by dispersing the ion exchange material in the latex or in a column ion exchange process.

[0113] According to one embodiment, the ion exchange step (ii) can be carried out as a batch process by adding the ion exchange material to the latex in a stirred vessel and stirring the dispersion. After this treatment, the ion exchange material is typically removed from the latex, for example by filtration.

[0114] According to another embodiment, the ion exchange step (ii) is carried out as a column ion exchange process, preferably continuously. Typically, in said embodiment, the latex obtained in step (i) is passed through a column packed with an ion exchange material. Typically, the latex can be passed through the column by any means known from chromatographic procedures, such as gravity feed, static siphon or an automated pumping system. Typically, the elution rate is 2-10 times (in some cases up to 46 times) the bed volume / hour. Typical mass flow rates are 1.0-10 g / min.

[0115] Preferably, the ion exchange step (ii) is carried out using a latex obtained in step (i) having a solids content in the range of 20-60% by weight, relative to the total weight of the latex, and / or a pH value in the range of 2-7, preferably 2.5-6. If necessary, the solids content of the latex obtained in step (i) can be reduced to 10-30% by weight, preferably below 20% by weight, before the ion exchange step, in particular to avoid coagulation of the latex. If necessary, depending on the selected ion exchange material, the pH value can be adjusted before the ion exchange step.

[0116] Coagulation and mechanical dewatering step (iii) The method of the present invention includes coagulation and dehydration in step (iii), preferably mechanical dehydration, and the latex obtained in step (ii) is coagulated by physical coagulation, preferably physical coagulation selected from shear coagulation, thermal shear coagulation, spray drying, freeze coagulation and pressure coagulation, more preferably by freeze coagulation, shear coagulation or thermal shear coagulation, to obtain a dehydrated alkyl (meth)acrylate emulsion polymer containing 4.5 mmol / kg or less, preferably 3.0 mmol / kg or less, more preferably 1.0 mmol / kg or less of alkali metal ions based on the solid content of the alkyl (meth)acrylate emulsion polymer.

[0117] According to the present invention, "coagulation by physical means" or "physical coagulation" refers to the aggregation and precipitation of polymer particles in an emulsion polymer latex by applying a physical process, typically reducing the repulsive forces between the polymer particles, which results in the separation and stabilization of the polymer particles in the latex. On the other hand, "chemical coagulation" refers to the aggregation and precipitation of polymer particles in an emulsion polymer latex, typically by the addition of a chemical agent (coagulant) that neutralizes some or all of the stabilizing charges located on the polymer particles.

[0118] According to the process for preparing the poly(meth)acrylate impact modifier of the present invention, the coagulation is carried out by physical coagulation. Furthermore, it may be advantageous to add at least one coagulant, such as a salt of a polyvalent metal ion, before and / or during the coagulation.

[0119] Coagulation can also be carried out without the addition of ionic species, preferably without the addition of cationic metal ions.

[0120] Physical coagulation of the emulsified polymer latex can be carried out by spray drying, by freeze coagulation (as described, for example, in WO 2015 / 07488), or by mechanical and / or thermal stress, especially using a degassing extruder (as described, for example, in WO 2002 / 18453, EP 0 979 162(A), EP 0 683 028(A)).

[0121] Typically, the pH value of the coagulation mixture during the coagulation step (iii) is in the range of 3-8, preferably 2-7, more preferably 3-5, also preferably 2-4.

[0122] As a coagulant in the coagulation step (iii), it is possible to add at least one salt of a polyvalent metal ion, preferably at least one salt of a polyvalent metal ion selected from alkaline earth metals, zinc and aluminum. For example, suitable alkaline earth metal salts here are magnesium sulfate (e.g., kieserite (Mg[SO4]·H2O), pentahydrite (Mg[SO4]·5H2O), hexahydrite (Mg[SO4]·6H2O) and epsomite (Mg[SO4]·7H2O, Epsom salts)), magnesium chloride, calcium chloride, calcium hydroxide, calcium acetate, calcium formate, magnesium formate or mixtures thereof. For example, suitable aluminum salts are aluminum sulfate (Al2(SO4)3), aluminum sulfate hydrate, aluminum chloride (AlCl3), aluminum chloride hydrate, aluminum chlorhydrate, and polyaluminum chloride. For example, suitable zinc salts are zinc chloride (ZnCl2), zinc sulfate (ZnSO4), zinc sulfate hydrate (eg, ZnSO4·7H2O), and zinc oxalate.

[0123] Dewatering of the coagulated latex can be accomplished by mechanical dewatering (e.g., centrifugation and / or filtration) and / or by thermal dewatering (e.g., by evaporation of the aqueous phase of the emulsified polymer, such as by spray drying). Additionally, coagulation and dewatering of the emulsified polymer latex can occur in one step, such as in the case of spray drying or coagulation and dewatering in a degassing extruder.

[0124] Preferably, dewatering of the coagulated emulsion polymer is accomplished by mechanical dewatering, such as by centrifugation, decantation or filtration. Preferably, the coagulated emulsion polymer is dewatered by batch or continuous centrifugation. The coagulated emulsion polymer is typically centrifuged for 90 seconds to 10 minutes.

[0125] According to another embodiment of the invention, the dewatering of the coagulated emulsion polymer is carried out by means of a degassing extruder, in particular in at least one dewatering zone of the extruder used for the shear or hot shear coagulation of the emulsion polymer.

[0126] Typically, the dehydrated emulsion polymer obtained in step (iii) has a water content of 40% by weight or less, preferably in the range of 2 to 35% by weight, more preferably 5 to 20% by weight.

[0127] The water content of the multi-stage emulsion polymer after dehydration (also called residual water content) is the water content in weight percent relative to the wet polymer obtained after dehydration. The water content is determined in particular using a suitable analytical device (e.g. drying and weighing device) and the sample is dried until a constant weight of the sample is achieved over a defined period of time. As an example, the water content of the emulsion polymer can be determined with a moisture analyzer and the sample is dried at a temperature in the range of 80-180°C. In particular, the water content can be determined using a Halogen Moisture Analyzer from Mettler Toledo at 160°C until a constant weight is achieved for 30 seconds.

[0128] Preferably, the dehydrated alkyl (meth)acrylate emulsion polymer obtained in the dehydration step (iii) or optionally after the washing step (iv) comprises less than 4.5 mmol / kg, preferably less than 3.0 mmol / kg, more preferably less than 1.0 mmol / kg of alkali metal ions (e.g. sodium and / or potassium) and less than 20.0 mmol / kg, preferably less than 10.0 mmol / kg of cationic metal ions, respectively based on the solids content of the emulsion polymer, based on the solids content of the impact modifier.

[0129] Optional sintering In particular, step (iii) of the process of the present invention involves a sintering step after coagulation of the emulsion polymer and prior to dewatering.

[0130] Preferably, step (iii) may include a sintering step, and the solidified multi-stage alkyl (meth)acrylate emulsion polymer has a glass transition temperature, T g Near or below the sintering temperature (T s Preferably, the optional sintering step is carried out after solidification and before dehydration. In particular, the optional sintering step is carried out at a temperature of T s ≧T g -50K, preferably T s ≧T g -30K, more preferably T g -15K≦T s ≦T g It is carried out at a temperature of +5K.

[0131] Preferably, the coagulation mixture, after coagulation of the emulsion polymer, is kept at a temperature (sintering temperature) in the range of 60° C. to 140° C., preferably 70° C. to 135° C., more preferably 75° C. to 130° C. In particular, the coagulated emulsion polymer is kept at said sintering temperature T2 for a period of 2 minutes to 24 hours, preferably 2 to 15 minutes, preferably 3 to 10 minutes, more preferably 5 to 10 minutes.

[0132] In a preferred embodiment, the coagulated emulsion polymer may be treated with steam after coagulation during the sintering process.

[0133] In a preferred embodiment, the coagulated emulsion polymer may be diluted with water prior to the sintering step. For example, the volume of the coagulated emulsion polymer composition may be increased by 1.5 to 5 times, preferably 2 to 4 times, by adding water prior to sintering.

[0134] The process for making the poly(meth)acrylate impact modifier may include one or both of the following optional steps: (iv) optionally washing the dehydrated alkyl (meth)acrylate emulsion polymer; (v) optionally drying the dehydrated alkyl (meth)acrylate emulsion polymer obtained in step (iii) or (iv).

[0135] Optional washing step (iv) In a preferred embodiment, mechanical dehydration of the emulsion polymer in step (iii) is followed by a washing step (iv), the dehydrated emulsion polymer being preferably treated with water or a mixture of water and a polar water-miscible organic solvent. The water or mixture is preferably removed after treatment by filtration or centrifugation. Preferably, in the downstream washing step (iv), an emulsion polymer is obtained having a water content of 40% by weight or less, preferably in the range of 2-35% by weight, more preferably 5-20% by weight.

[0136] For example, the washing step (iv) can be carried out by adding water, or a mixture of water and a polar water-miscible organic solvent, during the centrifugation, especially during a continuous centrifugation process.

[0137] Preferably, the dehydrated emulsion polymer obtained after the optional washing step (iv) exhibits amounts of alkali metal ions and polyvalent metal ions, such as alkaline earth metal ions, zinc ions or aluminium ions, as described above for the dehydrated emulsion polymer obtained after step (iii).

[0138] Optional drying step (v) The process for preparing the poly(meth)acrylate impact modifiers of the present invention may include one or more optional drying steps (v).

[0139] For example, the dehydrated emulsion polymer can be dried by a hot drying gas, such as air, or by an air dryer. Drying can be carried out, for example, in a cabinet dryer or other commonly known drying equipment, such as a flash dryer or a fluidized bed dryer. Typically, the optional drying step (v) is carried out at a temperature in the range of 50 to 160°C, preferably 55 to 155°C, particularly preferably 60 to 150°C.

[0140] In another embodiment, the coagulated and dewatered emulsion polymer is dried in a degassing extruder, particularly in an additional degassing section of the extruder used for coagulation and dewatering.

[0141] Typically the resulting dry emulsion polymer has a water content of less than 5%, preferably less than 2%, preferably in the range of 0.05 to 2% by weight, preferably 0.1 to 1.5% by weight, particularly preferably 0.1 to 1% by weight.

[0142] Preferably, the dried emulsion polymer, e.g. obtained as a powder or granules, exhibits the same amount of cationic metal ions, e.g. alkali metal ions, and polyvalent metal ions, e.g. alkaline earth metal ions, zinc ions and aluminium ions, as the dehydrated and optionally washed emulsion polymer obtained after step (iii) or (iv).

[0143] In a preferred embodiment of the present invention, in step (iii), the coagulation is carried out by freeze coagulation, and the mechanical dewatering of the coagulated emulsion polymer is carried out by centrifugation, and the water content of the dehydrated emulsion polymer is not more than 40% by weight based on the dehydrated emulsion polymer, and the process comprises: (iv) optionally washing the dehydrated alkyl (meth)acrylate emulsion polymer; (v) drying the dehydrated alkyl (meth)acrylate emulsion polymer obtained in step (iii) or (iv), wherein the poly(meth)acrylate impact modifier is obtained as a polymer powder.

[0144] According to another preferred embodiment of the present invention, in step (iii), coagulation and mechanical dewatering are carried out by thermal shear coagulation, the latex obtained in step (ii) is introduced into an extrusion line comprising at least one coagulation zone, at least one dewatering zone and at least one degassing zone, and the poly(meth)acrylate impact modifier is obtained as polymer granules.

[0145] Further, a method for producing a poly(meth)acrylate impact modifier includes the steps of: (vi) adding one or more additives to the multi-phase alkyl (meth)acrylate emulsion polymer; The method may include the optional steps of:

[0146] At each stage of the process for making the poly(meth)acrylate impact modifiers of the present invention, for example, before or during dehydration of the coagulated emulsion polymer, suitable conventional additives can be mixed in. Among these are dyes, pigments, stabilizers, lubricants, UV protection agents, and the like.

[0147] The optional additive may be selected from the commonly known additives and / or auxiliaries for plastic materials.For conventional auxiliaries and additives, refer to "Plastics Additives Handbook", Hans Zweifel, 6th edition, Hanser Publ., Munich, 2009, for example.For example, the at least one additive may be selected from fillers, reinforcing agents, dyes, pigments, lubricants or release agents, stabilizers, especially light and heat stabilizers, antioxidants, UV absorbers, plasticizers, impact modifiers, antistatic agents, flame retardants, bactericides, fungicides, optical brighteners, and foaming agents.

[0148] For example, the impact modifier may contain 0 to 15% by weight, preferably 0 to 10% by weight, more preferably 0.5 to 5% by weight of at least one of the additives described above, based on the solid content of the impact modifier.

[0149] Thermoplastic molding composition and method for its preparation In another aspect, the present invention is directed to a thermoplastic molding composition (hereinafter also called molding composition) comprising the poly(meth)acrylate impact modifier of the present invention and optionally at least one resin based on a thermoplastic (meth)acrylate polymer. For example, such impact-modified poly(meth)acrylate molding compositions are described in WO 2004 / 056893.

[0150] In particular, the thermoplastic molding composition 1 to 100% by weight, preferably 5 to 100% by weight, of at least one poly(meth)acrylate impact modifier as defined above, based on the total molding composition; 0 to 99% by weight, preferably 0 to 95% by weight, of at least one thermoplastic (meth)acrylate polymer, preferably at least one poly(methyl methacrylate), based on the total molding composition; 0 to 50% by weight, preferably 0 to 10% by weight, based on the total molding composition, of one or more additives, preferably two or more additives, selected for example from UV absorbers, UV stabilizers, heat stabilizers, antioxidants, lubricants, dyes and processing agents, and / or one or more additional polymer components; The composition comprises (preferably consists of)

[0151] Typically, the thermoplastic (meth)acrylate polymers here preferably comprise, in each case relative to their total weight, 50.0 to 100.0% by weight, preferably 60.0 to 100.0% by weight, particularly preferably 75.0 to 100.0% by weight, particularly preferably 85.0 to 99.5% by weight of an alkyl methacrylate monomer (each a repeating unit) having 1 to 20, preferably 1 to 12, more preferably 1 to 8, particularly preferably 1 to 4 carbon atoms in the alkyl group; 0.0 to 40.0% by weight, preferably 0.0 to 25.0% by weight, in particular 0.1 to 15.0% by weight of alkyl acrylate monomers having 1 to 20, preferably 1 to 12, advantageously 1 to 8, in particular 1 to 4 carbon atoms in the alkyl group (respective repeat units), 0.0 to 30% by weight, preferably 0.0 to 8.0% by weight of a styrene monomer (each a repeating unit), The composition comprises (preferably consists of)

[0152] In particular, the thermoplastic (meth)acrylate polymer comprises, relative to its total weight, at least 50.0% by weight, advantageously at least 60.0% by weight, preferably at least 75.0% by weight and in particular at least 85.0% by weight of methyl methacrylate.

[0153] For example, the molding composition may include one or more additives and / or one or more additional polymeric components selected from dyes, pigments, and crosslinked polymer beads.

[0154] In a preferred embodiment, the above-mentioned inventive thermoplastic molding composition comprises up to 50% by weight, preferably from 0.0001% by weight to 50% by weight, based on the total thermoplastic molding composition, of at least one dye and / or pigment, for example selected from perinone dyes, quinophthalone dyes, anthraquinone dyes, azo dyes, inorganic pigments, phthalocyanine pigments and carbon black.

[0155] Furthermore, the above-mentioned inventive thermoplastic molding composition may contain from 0.01% by weight to 50% by weight, based on the total thermoplastic molding composition, of at least one crosslinked polymer bead, preferably chosen from crosslinked polymer beads (scattering beads) having a refractive index different from that of the polymer matrix formed by the thermoplastic molding composition. Suitable crosslinked polymer beads are described below.

[0156] Typically, the thermoplastic (meth)acrylate polymers have a number-average molar mass in the range of 1000 to 100,000,000 g / mol, preferably in the range of 10,000 to 1,000,000 g / mol, in particular in the range of 50,000 to 500,000 g / mol, which can be determined, for example, by gel permeation chromatography using a calibration based on polymethyl methacrylate.

[0157] Furthermore, the present invention is directed to a process for the preparation of a thermoplastic molding composition, in which the components, typically in the form of a melt or in the form of powder or pellets, are mixed and homogenized, for example in a single-screw or multi-screw extruder or a roll mill.

[0158] In particular, the process for the preparation of a thermoplastic molding composition comprises xi) mixing 5-100% by weight, based on the total molding composition, of at least one poly(meth)acrylate impact modifier according to the invention as described above, 0-95% by weight, based on the total molding composition, of at least one thermoplastic (meth)acrylate polymer, and optionally 0-10% by weight of another additive and / or one or more additional polymeric components, xii) melt-kneading the mixture obtained in step xi) at a temperature preferably in the range of 200-280° C.; Includes.

[0159] Conventional additives may be mixed in at any processing stage suitable for this purpose, including dyes, pigments, fillers, reinforcing fibers, lubricants, UV stabilizers, organic or inorganic scattering particles, etc.

[0160] Furthermore, the present invention relates to moulded articles or semi-finished products such as foils, films or sheets produced from the above-described thermoplastic moulding compositions.

[0161] The thermoplastic molding compositions can be used for the production of any kind of moldings and semi-finished products such as sheets, films, fiber foams, etc. The processing can be carried out using known methods for thermoplastic processing, in particular the production can be carried out by thermoforming, (co)extrusion, injection molding, calendaring, blow molding, compression molding, press sintering, deep drawing or sintering, preferably by injection molding.

[0162] Molded or semi-finished products The present invention also relates to molded articles or semi-finished products produced from the inventive thermoplastic molding compositions described above.

[0163] For example, the molded article or semi-finished product may comprise the inventive thermoplastic molding composition as described above and further one or more additives as described above and / or one or more additional polymer components, for example the additives may be selected from dyes, pigments and crosslinked polymer beads.

[0164] Preferably, the molded article or semi-finished product comprises up to 50% by weight, preferably 0.0001% to 50% by weight, of at least one additive, preferably selected from dyes, pigments, organic scattering particles (in particular crosslinked polymer beads as described below) and inorganic scattering particles, based on the weight of the entire molded article or semi-finished product.

[0165] Preferably, the molded article or semi-finished product comprises up to 50% by weight, preferably 0.0001% to 50% by weight, of at least one dye and / or pigment, preferably selected from perinone dyes, quinophthalone dyes, anthraquinone dyes, azo dyes, inorganic pigments, phthalocyanine pigments and carbon black, based on the total weight of the molded article or semi-finished product.

[0166] Preferably, the moulded article or semi-finished product comprises from 0.01% to 50% by weight, relative to the total moulded article or semi-finished product, of at least one organic or inorganic scattering particle, preferably selected from crosslinked polymer beads, more preferably selected from crosslinked polymer beads (scattering beads) having a different refractive index compared to the refractive index of the polymer matrix formed by the thermoplastic moulding composition.

[0167] In a preferred embodiment, the semi-finished product is a film or sheet.

[0168] In a preferred embodiment, the molded or semi-finished product is transparent. In particular, the molded or semi-finished product has a haze value of 30.0% or less, preferably 20.0% or less, more preferably 10% or less, in particular 6.0% or less, measured by a BYK Gardner Hazegard-plus haze meter in accordance with ASTM D1003-13 for a material thickness of 40 μm to 1000 μm, determined after 4 h to 24 h water storage at 80 ° C. In particular, the molded or semi-finished product has a haze value of 40.0% or less, preferably 30% or less, more preferably 25.0% or less, also preferably 20.0% or less, measured at 23 ° C. on a test piece having a thickness of 1 mm, determined after 24 h water storage at 80 ° C. in accordance with standard ASTM D1003 (2013).

[0169] In particular, the molded article or semi-finished product is produced by providing a thermoplastic molding composition as described above, adding at least one additive, in particular at least one additive selected from the dyes, pigments and crosslinked polymer beads described above, and mixing the thermoplastic molding composition and the at least one additive, preferably via melt kneading, for example during a film-forming process or an injection molding process.

[0170] Typically, said dyes and / or pigments can be added to the above-described inventive thermoplastic molding composition in the form of a color preparation, a liquid composition comprising said color preparation or a masterbatch.

[0171] In some embodiments of the present invention, the molding composition may contain organic or inorganic scattering particles dispersed in the polymer matrix. The low haze value of the impact-modified thermoplastic molding composition of the present invention after hot water storage may be advantageous in combination with scattering particles, since it allows to obtain a more uniform opaque and matte appearance even after hot water storage. The choice of scattering particles is not particularly limited, but is typically selected such that the refractive index of the scattering particles differs from that of the copolymer matrix by at least 0.01. The refractive index can be measured at 23° C. at Na D radiation at 589 nm, as specified in standard ISO 489 (1999).

[0172] The scattering particles usually have a weight-average particle size of 0.01 μm to 100.0 μm. The weight-average particle size of the scattering particles is indicated as the so-called volume average d50 value (i.e. 50 volume percent of the particles have a particle size less than the stated average particle size) and can be measured according to the standard ISO 13320-1 (2009) for laser diffraction measurements. Typically, the size of the scattering particles is determined by laser light scattering using a Beckman Coulter LS 13 320 laser diffraction particle size analyzer, for example at room temperature, 23° C.

[0173] The inorganic scattering particles may include conventional inorganic opacifiers such as barium sulfate, calcium carbonate, titanium dioxide or zinc oxide.

[0174] The organic scattering particles are typically spherical scattering beads made of cross-linked polymeric materials such as polyalkyl(meth)acrylates, silicones, polystyrene, etc. Preferably, at least 70%, in particular at least 90%, of the scattering beads are spherical, relative to the number of scattering beads.

[0175] Preferred scattering beads comprised of cross-linked polystyrene are commercially available from Sekisui Plastics Co., Ltd. under the trademarks Techpolymer® SBX-4, Techpolymer® SBX-6, Techpolymer® SBX-8 and Techpolymer® SBX-12.

[0176] Other particularly preferred spherical plastic particles for use as scattering agents include crosslinked silicones. Particularly preferred silicone scattering agents for use in the present invention are available from Momentive Performance Materials Inc. as TOSPEARL® 120 and TOSPEARL® 3120.

[0177] The invention is explained in more detail by the following examples and claims.

[0178] Working Example The emulsion polymer EP1 (Examples 1-7) having a core-shell structure, and the emulsion polymer EP2 (Examples 8-9) and EP3 (Examples 10-12) having a core-shell-shell structure were prepared and freeze-coagulated. According to the examples of the present invention, the emulsion polymer latex was conveyed through an ion exchange material before freeze-coagulation.

[0179] I. Preparation of PMMA latex emulsion polymer Examples 1-6: Core-shell emulsion polymer EP1 Into a polymerization vessel equipped with an agitator, a feed vessel and external cooling was placed an aqueous phase containing sodium hydroxymethyl sulfate, acetic acid, iron(II) sulfate (FeSO4), and an aqueous seed latex solution having 5% solids by weight.

[0180] At a temperature of 55° C. (outside the vessel) emulsion I described in Table 1 was added continuously over a period of 20 minutes. After 10 minutes emulsion II described in Table 1 was added successively within 2 hours. The reaction mixture was stirred for 60 minutes, cooled to 45° C. and filtered through VA steel (mesh size 90 μm). Emulsion I was obtained by emulsifying the monomers and components shown in Table 1.

[0181] The amounts are summarized in Table 1 below.

[0182] [Table 1]

[0183] The resulting aqueous polymer dispersion EP1 had a solids content of 40-42 wt % and an average particle size of about 124 nm, as determined by laser light scattering at room temperature, 23° C., using a Beckman Coulter LS 13 320 laser diffraction particle size analyzer.

[0184] Examples 7-9: Core-shell-shell emulsion polymer EP2 In a polymerization vessel equipped with stirrer, feed vessel and external cooling was placed an aqueous phase containing acetic acid, iron(II) sulfate (FeSO4) and seeds, and 10 weight percent PMMA. At a temperature of 52° C. (external vessel temperature), emulsion I as described in Table 2 was added over 1 hour. In parallel, 0.69 g of sodium metabisulfite in 20 g of water was added (first 10 minutes).

[0185] After 15 minutes, 1.94 parts by weight of sodium metabisulfite in 100 parts by weight of water were added within 10 minutes, in parallel with the start of the addition of emulsion II described in Table 2. Emulsion II (Table 2) was added within 2 hours, followed by a pause of 50 minutes. Emulsion III described in Table 2 was added simultaneously with 0.62 parts by weight of sodium metabisulfite in 50 parts by weight of water. The addition of sodium metabisulfite was completed within 10 minutes, and emulsion III after 1 hour. The reaction mixture was then stirred for 30 minutes, cooled to 35° C. and filtered through VA steel (mesh size 100 μm).

[0186] Emulsions I, II and II were obtained by emulsifying the monomers and components shown in Table 2, respectively.

[0187] [Table 2]

[0188] The resulting aqueous polymer dispersion EP2 had a solids content of 46-48 wt % and an average particle size of about 340 nm as determined by laser light scattering at room temperature, 23° C., using a Beckman Coulter LS 13 320 laser diffraction particle size analyzer.

[0189] Examples 10-12: Core-shell-shell emulsion polymer EP3 In a polymerization vessel equipped with a stirrer, a feed vessel and external cooling, water, sodium carbonate and seeds containing 10 weight percent PMMA were placed. At a temperature of 83°C (vessel temperature), emulsion I, as described in Table 3, was added over 90 minutes (10 minutes addition, 10 minutes pause, 80 minutes addition). After a 10 minute pause, the addition of emulsion II, as described in Table 3, was started. Emulsion II was added within 2 hours, followed by a pause of 30-45 minutes. Emulsion III was added within 1 hour. The reaction mixture was then stirred for 30 minutes, cooled to room temperature (approximately 30 minutes) and filtered through VA steel (mesh size 100 μm).

[0190] Emulsions I, II and II were obtained by emulsifying the monomers and components shown in Table 3, respectively.

[0191] [Table 3]

[0192] The resulting aqueous polymer dispersion EP3 had a solids content of 49-51 wt % and an average particle size of about 250 nm as determined by laser light scattering at room temperature, 23° C., using a Beckman Coulter LS 13 320 laser diffraction particle size analyzer.

[0193] II. Ion exchange The aqueous polymer dispersions of Examples 3-6 (core-shell emulsion polymer EP1), Examples 8 and 9 (core-shell-shell emulsion polymer EP2) and Examples 11 and 12 (core-shell-shell emulsion polymer EP3) were subjected to an ion exchange step prior to coagulation, as described below.

[0194] For Examples 3, 5, 6 and 9, a 16 mm inner diameter glass column was packed with 25 mL of a strong acid cation exchanger (Dowex® Marathon C, Dow Chemical) provided in the protonated form (H-form). The free volume above the ion exchange bed was then manually packed with the respective dispersion. The dispersion was then pumped from top to bottom through the column at a mass flow rate of 3.7 g / min (Example 3), 2.5 g / min (Example 5), 2.4 g / min (Example 6) or 3.5-5 g / min (Example 9).

[0195] For Examples 4, 8 and 12, a glass column with an internal diameter of about 50 mm was packed with about 200 mL of a strong acid ion exchanger (Dowex® Marathon C, manufactured by Dow Chemical). The free volume above the ion exchange bed was then manually packed with the respective dispersion. The dispersion was then passed through the column under slight nitrogen pressure.

[0196] For Examples 5.1, 5.2 and 11, a 107 mm internal diameter stainless steel column was packed with 1000 mL of a strong acid ion exchanger (Dowex Marathon C). The free volume above the ion exchange bed was then manually packed with the respective dispersion. The dispersion was then pumped from top to bottom through the column at a mass flow rate of 285 g / min (Examples 5.1 and 5.2) or 230-240 g / min (Example 11).

[0197] The procedures for Examples 1-12 are summarized in Table 4.

[0198] Samples were taken at regular intervals at the column outlet and analyzed for their sodium content by AAS.

[0199] III. Freezing, sintering and dehydration The aqueous polymer dispersions of Examples 1-10 and 12 (some after ion exchange treatment) were frozen at -18°C for 24 hours. The mixtures were then sintered at 80°C for 24 hours. The latexes were cooled to room temperature and the particles were separated from the water by centrifugation at 1800 rpm. Centrifugation times were varied between 1.5 and 10 minutes to obtain different residual water contents (w(H2O)) in the coagulated and dehydrated emulsion polymer. In Examples 4, 8 and 12, instead of centrifugation, the polymer was separated from the water by vacuum filtration.

[0200] After centrifugation or filtration, the polymer was washed with deionized water and centrifuged or filtered again. This procedure was performed three times and the resulting polymer powder was dried at 50°C for about 16-48 hours to obtain a final moisture content of less than 1%. Test specimens of 1 mm thickness were prepared from the dried material as described below.

[0201] In examples 5.1, 5.2 and 11, the outlet material of the ion exchange column (as described above) was continuously fed to a continuous flake ice machine (HIGEL HEC400) and continuously frozen at a roller temperature of -20 °C, the roller speed was 1.2 rpm and the filling level was 140 mm. The resulting ice was then transferred to a 5 L continuous stirred tank reactor (CSTR) and mixed with 110 g / min water (ambient temperature), 150 g / min water and steam (160 °C) and continuously thawed at temperatures between 85 °C and 95 °C. The outlet material of the CSTR was collected and centrifuged in batch mode at 2800 rpm for 10 min. The resulting dehydrated polymer was then dried in an oven at 46 °C for 96 h (examples 5.1 and 11) or 72 h (example 5.2).

[0202] The procedures for Examples 1-12 are summarized in Table 4.

[0203] The water content after centrifugation (w(H2O)) was determined using an electronic moisture analyzer (Sartorius MA45). The results are given in the table below.

[0204] The metal ion content (e.g., sodium content, calcium content, and magnesium content) of the dehydrated and dried impact modifiers (emulsion polymers) of Examples 1-12 was determined as follows, and the results are summarized in the table below.

[0205] [Table 4]

[0206] IV. Preparation of Molding Compositions and Test Specimens The polymer powders EP1 obtained as described above in Examples 1 to 6 were hot pressed to prepare test pieces having a thickness of 1 mm and a diameter of 5 cm.

[0207] The impact modifiers (polymer powders) according to Examples 7-12 (based on emulsion polymers EP2 and EP3) were blended with PMMA_1 (a copolymer of about 96% by weight of methyl methacrylate (MMA) and 4% by weight of methyl acrylate, having a weight average molecular weight of about Mw=110.000) to obtain the impact modifier (w IM The amounts of 100000 15 ...

[0208] Further, a 53 μm film was produced by extrusion, and the haze and transmittance of the film were measured as follows.

[0209] V. Results The haze and transmittance of the specimens (1 mm) and films (53 μm) were determined as follows, and the results are summarized in the table below.

[0210] The water content of the emulsion polymer obtained after coagulation and dehydration is indicated as w(H2O). The amount of impact modifier (emulsion polymer) in the respective molding composition in the test pieces used for haze and transmittance is indicated as w(IM) given in weight %. The amounts of metal ions and sulfur (calculated as sulfate) in the impact modifier (dry emulsion polymer) are given in mmol / kg (impact modifier).

[0211] Tables 5-6 (Examples 1-6) contain the results for core-shell emulsion polymer EP1 that was partially processed by acidic ion exchanger, freeze coagulation and mechanical dehydration.

[0212] Tables 7-8 summarize the results for core-shell-shell emulsion polymers EP2 (Examples 7-9) and EP3 (Examples 10-12) that were partially processed by acidic ion exchange, freeze coagulation and mechanical dehydration and subsequently blended with PMMA_1.

[0213] [Table 5]

[0214] According to Example 5.3 (see Table 5a), an aqueous solution of calcium acetate (CaAc2) (coagulant) was added to the emulsion polymer EP1 after the ion-exchange step. Ion-exchange, coagulation and dehydration were carried out as described in Example 5 (see Section III above). It was shown that the haze after hot water storage can be further improved by adding a certain amount of calcium salt as a coagulation aid.

[0215] [Table 6]

[0216] [Table 7]

[0217] [Table 8]

[0218] [Table 9]

[0219] It has been shown that reducing the amount of metal ions, especially sodium ions, to less than 4.5 mmol / kg, preferably less than 1 mmol / kg, results in improved hot water storage stability in terms of haze and transmittance.

[0220] VI. Testing Method a. Hydrothermal haze Test specimens (obtained by hot pressing, 1 mm thick, 5 cm diameter) were stored for 24 h in deionized water at 80° C. Haze values ​​were determined before and after hot water storage according to ASTM D1003-13 using a haze meter BYK Gardner haze-gard i.

[0221] These specimens, prepared as described above, were tested at 23°C using a BYK Gardner haze-gard i haze meter in accordance with ASTM D1003-13, both in their original state ("pre-haze") and after 24 hours of hydrothermal storage in 80°C deionized water. It is noted that materials with haze values ​​greater than 30% (according to ASTM D1003-13) are considered "diffuse" and should be tested in accordance with the Goniometric Optical Scattering Measurement Practice (E2387). As the focus of this study is on transparent materials with haze values ​​less than 30%, haze values ​​greater than 30% are reported to illustrate trends.

[0222] These haze values ​​and the difference in haze values ​​before and after storage in hot water (haze / Δ) (haze / 24h-haze / 0h) are summarized in the table above.

[0223] The transmittance (given in %) before and after hot water storage was determined accordingly according to ASTM D1003-13.

[0224] b. Metal ion content To determine the metal ion content (e.g., Na and Ca), microwave-assisted digestion of the dried emulsion polymer with nitric acid was performed, after which the content of related ions was determined by atomic absorption spectroscopy.

[0225] To determine the sulfate content of the modifier, the polymer was digested by the Wickbold method. Ion chromatography was then used to determine the sulfur content, which was then used to calculate the final sulfate ion (SO 2- The sulfur content m S is given calculated as sulfate.

[0226] c. Water content Unless otherwise specified, moisture content (residual water) was determined using an electronic moisture analyzer (Sartorius MA45) heated to 85°C.

Claims

1. A poly(meth)acrylate impact modifier comprising at least one multilayer alkyl(meth)acrylate emulsion polymer, wherein the total amount of alkali metal ions in the impact modifier is 4.5 mmol / kg or less, preferably 3.0 mmol / kg or less, more preferably 2.0 mmol / kg or less, and even more preferably 1.0 mmol / kg or less, relative to the solid content of the impact modifier.

2. The poly(meth)acrylate impact modifier according to claim 1, characterized in that it contains 20.0 mmol / kg or less, preferably 10.0 mmol / kg or less, and more preferably 9.0 mmol / kg or less, cationic metal ions relative to the solid content of the impact modifier.

3. The poly(meth)acrylate impact modifier according to claim 1, characterized in that the polyphase alkyl (meth)acrylate emulsion polymer is obtained by emulsion polymerization and comprises a core and at least one, preferably one or two, shells.

4. The aforementioned polyphase alkyl (meth)acrylate emulsion polymer At least 10% by weight, preferably at least 20% by weight, of at least one C1-C10 alkyl methacrylate, 5 to 80% by weight, preferably 20 to 80% by weight, at least one C1 to C10 alkyl acrylate or at least one conjugated diene, 0 to 2% by weight, preferably 0.1 to 2% by weight, at least one crosslinkable monomer, A further monomer, preferably vinyl aromatic monomer, in the case of 0 to 15% by weight, preferably 0.5 to 10% by weight. The poly(meth)acrylate impact modifier according to claim 1, characterized by containing the following.

5. The aforementioned polyphase alkyl (meth)acrylate emulsion polymer A1) 10 to 95% by weight of the total emulsion polymer, with a glass transition temperature T of less than -10°C. ｇ It has, A1.1) At least one type of C in an amount of 50 to 99.5% by weight relative to A1. １ ~C １０ Alkyl acrylate, preferably n-butyl acrylate, A1.2) 0.5 to 5% by weight of A1, at least one crosslinkable monomer having two or more ethylenically unsaturated groups, and A1.3) 0 to 10% by weight of at least one further ethylenically unsaturated free radical polymerizable monomer relative to A1. A soft elastomer core A1 is constructed from, B1) 5 to 90% by weight of the total emulsion polymer, with a glass transition temperature T above 70°C ｇ It has, B1.1) At least one type of C in an amount of 80 to 100% by weight relative to B1 １ ~C ６ Alkyl methacrylate, preferably methyl methacrylate, and B1.2) At least one further ethylenically unsaturated free radical polymerizable monomer in an amount of 0 to 20% by weight relative to B1. The rigid shell B1 is constructed from and The poly(meth)acrylate impact modifier according to claim 1, characterized in that it is a core-shell emulsion polymer containing the above.

6. The aforementioned polyphase alkyl (meth)acrylate emulsion polymer A2) 5 to 40% by weight of the total emulsion polymer, with a glass transition temperature T above 50°C ｇ It has, A2.1) At least one kind of C in an amount of 80 to 100% by weight with respect to A2 １ ~C ６ alkyl methacrylate, preferably methyl methacrylate, A2.2) At least one further ethylenically unsaturated free radical polymerizable monomer in an amount of 0 to 20% by weight relative to A2, and A2.3) At least one crosslinkable monomer having two or more ethylenically unsaturated groups, in an amount of 0 to 5% by weight relative to A1. A rigid non-elastomer core A2 is constructed from, B2) 20 to 75% by weight of the total emulsion polymer, with a glass transition temperature T of less than 0°C. ｇ It has, B2.1) At least one type of C in an amount of 45 to 99.5% by weight relative to B2. １ ~C １０ Alkyl acrylate, preferably n-butyl acrylate, B2.2) 0.5 to 5% by weight of B2, at least one crosslinkable monomer having two or more ethylenically unsaturated groups, and B2.3) 0 to 50% by weight of at least one further ethylenically unsaturated free radical polymerizable monomer, preferably a monomer having an aromatic group, relative to B2. A soft elastomer intermediate shell B2 is constructed from, C2) 15 to 60% by weight of the total emulsion polymer, with a glass transition temperature T above 50°C ｇ It has, C2.1) At least one C2 in an amount of 80 to 100% by weight, preferably 90 to 100% by weight. １ ~C ６ Alkyl methacrylate, preferably methyl methacrylate, and C2.2) At least one further ethylenically unsaturated free radical polymerizable monomer in an amount of 0 to 20% by weight, preferably 0 to 10% by weight, relative to C2. The rigid outer shell C2 is constructed from and The poly(meth)acrylate impact modifier according to claim 1, characterized in that it is a core-shell-shell emulsion polymer containing the above.

7. (i) A preparation step of at least one polyphase alkyl (meth)acrylate emulsion polymer by emulsion polymerization, wherein the polyphase alkyl (meth)acrylate emulsion polymer is obtained in the form of latex, (ii) A step of removing cations and optionally anions in an ion exchange step, wherein the latex obtained in step (i) is brought into contact with an ion exchange material, and the removal of the latex. (iii) Coagulation and dehydration of the latex obtained in step (iii), preferably a mechanical dehydration step, wherein the coagulation is carried out by physical coagulation, and a dehydrated alkyl (meth)acrylate emulsion polymer is obtained, wherein the dehydrated alkyl (meth)acrylate emulsion polymer contains alkali metal ions in an amount of 4.5 mmol / kg or less, preferably 3.0 mmol / kg or less, more preferably 2.0 mmol / kg or less, and even more preferably 1.0 mmol / kg or less, relative to the solid content of the impact modifier. A method for producing a poly(meth)acrylate impact modifier according to any one of claims 1 to 6, comprising at least one polyphase alkyl (meth)acrylate emulsion polymer that includes

8. The method according to claim 7, characterized in that at least one cation exchange material and / or at least one amphoteric exchange material and optionally at least one anion exchange material are used in the ion exchange step (ii).

9. The method according to claim 7, characterized in that at least one nonionic surfactant, preferably selected from alkylaryl polyethoxy alcohols and alkyl polyethoxy alcohols, is added to the latex before and / or during the ion exchange step (ii).

10. In step (iii), the solidification is carried out by freeze-solidification, the mechanical dehydration of the solidified emulsion polymer is carried out by centrifugal separation, and the water content of the dehydrated emulsion polymer is in the range of 5 to 40% by weight, preferably 7 to 30% by weight, relative to the dehydrated emulsion polymer. (iv) Depending on the circumstances, wash the dehydrated alkyl (meth)acrylate emulsion polymer. The method according to claim 7, comprising (v) drying the dehydrated alkyl (meth)acrylate emulsion polymer obtained in step (iii) or (iv), characterized in that the poly (meth)acrylate impact modifier is obtained as a polymer powder.

11. The method according to claim 7, characterized in that in step (iii), the coagulation and mechanical dehydration are carried out by thermal shear coagulation, the latex obtained in step (ii) is introduced into an extrusion line having at least one coagulation zone, at least one dehydration zone and at least one degassing zone, and the poly(meth)acrylate impact modifier is obtained as polymer granules.

12. A thermoplastic molding composition, The molding composition contains 1 to 100% by weight, preferably 5 to 100% by weight, of at least one poly(meth)acrylate impact modifier according to claim 1, The molding composition contains 0 to 99% by weight, preferably 0 to 95% by weight, of at least one thermoplastic (meth)acrylate polymer, preferably at least one poly(methyl methacrylate), The molded composition contains 0 to 50% by weight, preferably 0 to 10% by weight, of one or more additives and / or one or more additional polymer components. A thermoplastic molding composition containing the following:

13. xi) Mixing 1 to 100% by weight, preferably 5 to 100% by weight, of the entire thermoplastic molding composition with at least one poly(meth)acrylate impact modifier according to claim 1, 0 to 99% by weight, preferably 0 to 95% by weight, of at least one thermoplastic (meth)acrylate polymer, and optionally 0 to 50% by weight, preferably 0 to 10% by weight, of one or more additives and / or another additional polymer component. xi) Melt kneading of the mixture obtained in step xi) A method for producing the thermoplastic molding composition according to claim 12, including the method described in claim 12.

14. A molded article or semi-finished product manufactured from the thermoplastic molding composition described in claim 12.

15. The molded article or semi-finished product according to claim 14, characterized in that it contains, up to 50% by weight, preferably 0.0001% to 50% by weight, of at least one additive selected from dyes, pigments, organic scattering particles, and inorganic scattering particles, relative to the entire molded article or semi-finished product.

16. The molded article or semi-finished product according to claim 14, characterized in that, after being stored in water at 80°C for 24 hours according to standard ASTM D1003 (2013), and measured at 23°C on a test piece having a thickness of 1 mm, it has a haze value of 40.0% or less, preferably 30% or less, more preferably 25.0% or less, and also preferably 20.0% or less.