HK1086286B - Core and shell particle for modifying impact resistance of a mouldable poly(meth)acrylate material - Google Patents

Description

Core-shell particles for impact-modifying poly (meth) acrylate molding compositions

The invention relates to core-shell particles, to a method for producing said core-shell particles, to molding compositions containing core-shell particles and to the use thereof. The invention relates in particular to core-shell particles which can be used for impact-modifying poly (meth) acrylate molding compositions. It has been known for a long time that: the notched impact strength of the molding compositions, in particular of poly (meth) acrylate molding compositions, can be increased by adding appropriate amounts of so-called impact modifiers to the molding compositions. For this purpose, the use of core-shell particles having 1 or 2 shells has been practiced industrially. These particles generally have an elastomer phase, wherein in the case of core-shell particles having 1 shell, the core is in most cases the elastomer phase, and in the case of core-shell particles having two shells, the first shell grafted onto the core is in most cases the elastomer phase.

For example, U.S. Pat. No. 4, 3793402 discloses impact-resistant molding compositions, in particular based on poly (meth) acrylates, which contain 90 to 4% by weight of multi-stage core-shell particles, wherein the particles have a hard core, an elastomeric first shell and a hard second shell. Typical main components of the core and the second shell are alkyl methacrylates having 1 to 4 carbon atoms in the alkyl group, in particular methyl methacrylate. The first shell is composed predominantly of butadiene, substituted butadienes and/or alkyl acrylates having 1 to 8 carbon atoms in the alkyl radical. It may however still contain from 0 to 49.9% by weight, in particular from 0.5 to 30% by weight, of copolymerizable monomer units, such as copolymerizable, monoethylenically unsaturated monomer units. The presence of from 10 to 25% by weight of copolymerizable, monoethylenically unsaturated monomer units, in particular styrene, is very particularly advantageous here, in accordance with U.S. Pat. No. 3, 3793402. The total diameter of the core-shell particle is 100-300 nm.

Similarly, German patent application DE 4121652A 1 describes impact modifiers for thermoplastics such as polymethyl methacrylate, which are composed of an at least three-phase emulsion polymer containing:

A) a hard core composed of a crosslinked homopolymer or copolymer of free-radically polymerizable ethylenically unsaturated monomers;

B) an elastomeric phase having a glass transition temperature of not greater than 10 ℃ generated in the presence of the core material, the elastomeric phase consisting of:

a) alkyl acrylates containing 1 to 8 carbon atoms in the alkyl group;

b) at least one crosslinking comonomer having two or more polymerizable double bonds in the molecule;

c) aralkyl acrylate or methacrylate;

d) a hard phase consisting of a homopolymer or copolymer of free-radically polymerizable, ethylenically unsaturated monomers, formed in the presence of an elastomeric phase, having a glass transition temperature of at least 50 ℃.

The moulding compositions exemplified in this publication (example 3) have a melt viscosity of 6.2kJ/m at room temperature²Having a temperature of-10 ℃ of 4.7kJ/m²And has a melting point of 3.7kJ/m at-20 DEG C²Izod notched impact strength of (a). The Vicat softening temperature of the molding composition was 97 ℃.

German patent application DE 4136993 a1 discloses an impact-modified molding composition which contains 10 to 96% by weight of a polymethyl methacrylate-based polymer and 4 to 90% by weight of multi-stage core-shell particles, wherein monomer mixtures which contain predominantly methyl methacrylate are used for the preparation of the core and the second shell layer, respectively. The monomer mixture for the first shell layer contains 60 to 89.99% by weight of an alkyl acrylate having 1 to 20 carbon atoms in the alkyl group and/or a cycloalkyl acrylate having 5 to 8 carbon atoms in the cycloalkyl group, and 10 to 39.99% by weight of a phenylalkyl acrylate having 1 to 4 carbon atoms in the alkyl group, and, where appropriate, other components. The average particle diameter of the core-shell particles is from 50 to 1000nm, in particular from 150 to 400 nm.

European patent EP 0828772B 1 describes impact-modifying poly (meth) acrylates by means of multi-stage core-shell particles which are composed of a core, a first shell and, if appropriate, a second shell and are free of ethylenically unsaturated compounds having at least two double bonds of the same reactivity. In this case, the core contains a first (meth) acrylic polymer. The first shell comprises a polymer having a low glass transition temperature comprising from 0 to 25 wt%, particularly from 5 to 26 wt% of a styrenic monomer and from 75 to 100 wt% of a (meth) acrylic monomer that can form a homopolymer having a glass transition temperature of from-75 to-5 ℃. The second shell layer, if present, contains a second (meth) acrylic polymer which may be the same or different from the first (meth) acrylic polymer. The total diameter of the core-shell particle was 250-320 nm.

In addition to emulsion polymers, suspension polymers are occasionally also used for impact modification of molding compositions. Here, the rubber, for example grafted by polymethyl methacrylate, has a relatively fine distribution in the matrix of the molding composition, for example polymethyl methacrylate. The elastomeric phase consists of a mostly crosslinked copolymer having a low glass transition temperature of less than 25 ℃ which generally contains alkyl acrylate units having from 1 to 8 carbon atoms in the alkyl radical, in particular butyl acrylate units, as the main constituent. Occasionally, polybutadiene or polybutadiene copolymers are also used as the ductile phase.

Although a significant improvement in notched impact strength can be achieved with the above-described impact modifier application, this is still not entirely satisfactory for many applications. Impact modification, for example at low temperatures, requires, in particular, relatively large amounts of these impact modifiers, which in turn also leads to a significant impairment of other properties of the molding compositions which are important for the application, in particular the modulus of elasticity, the melt viscosity, the Vicat temperature and the die swell.

Accordingly, there is a need in the industry for impact modifiers wherein the use of a minimum amount of impact modifier can substantially increase the notched impact strength of the molding composition, particularly at low temperatures, without at the same time having a significant penalty on other important properties of the molding composition, particularly the modulus of elasticity, melt viscosity, vicat temperature and die swell. The molding compositions here need to have a melt viscosity of preferably more than 6.0kJ/m at 23 DEG C²Preferably an elastic modulus of more than 1450MPa, preferably a melt viscosity of more than 2000Pa · s and advantageously less than 4500Pa · s, preferably a vicat temperature of more than 93 ℃ and preferably a die swell of 0-20%.

In view of the prior art, the object of the invention is: impact modifiers for molding compositions, in particular for poly (meth) acrylate molding compositions, are provided which can increase the notched impact strength, in particular at low temperatures, of the molding compositions without at the same time significantly impairing other properties of the molding compositions which are important for the application, in particular the modulus of elasticity, the melt viscosity, the Vicat temperature and the die swell. Here, the molding compositions need to have a melt viscosity of preferably more than 6.0kJ/m at 23 DEG C²Preferably an elastic modulus of more than 1450MPa, preferably a melt viscosity of more than 2000Pa · s and advantageously less than 4500Pa · s, preferably a vicat softening temperature of more than 93 ℃ and preferably a die swell of 0-20%.

Another object of the invention is: there is provided a method for preparing the impact modifier of the present invention, which can be simply prepared on an industrial scale and at low cost.

Another object on which the invention is based is: the field of application and possible uses of the impact modifier of the invention are provided.

These objects are achieved by the core-shell particles of the present invention, as well as other objects which, although not explicitly mentioned, may be readily derived or inferred from the context of the discussion incorporated herein. Advantageous improvements of the core-shell particles of the present invention are also claimed. The invention also claims preferred ways of preparing the core-shell particles of the invention. Impact-modified poly (meth) acrylate molding compositions containing the core-shell particles according to the invention are also claimed, as well as preferred fields of application of these molding compositions.

By providing a core-shell particle consisting of a core, a first shell layer and optionally a second shell layer, wherein:

i) the core comprises at least 75.0 wt%, based on its total weight, of (meth) acrylate repeat units;

ii) the first shell has a glass transition temperature of less than 30 ℃;

iii) an optionally present second shell layer located outside the first shell layer, comprising at least 75.0 wt% based on its total weight of (meth) acrylate repeating units;

iv) the first shell layer comprises the following components based on its total weight:

E)92.0 to 98.0 wt% of (meth) acrylate repeating units, and

F)2.0 to 8.0 wt.% of styrenic repeat units of formula (I)

Wherein R is¹-R⁵Each independently of the others being hydrogen, halogen, C₁-C₆-alkyl or C₂-C₆-alkenyl, and R⁶The radical is hydrogen or alkyl having 1 to 6 carbon atoms,

wherein the weight percentages of E) and F) add up to 100.0 wt%;

v) the radius of the core-shell particle, including the optionally present second shell layer, is greater than 160.0 to 240.0nm as determined by the Coulter method,

impact modifiers for molding compositions, in particular for poly (meth) acrylate molding compositions, are successfully obtained in an unpredictably predictable manner, wherein the impact modifiers improve the notched impact strength, in particular at low temperatures, of the molding compositions without at the same time significantly impairing other properties of the molding compositions which are important for the application, in particular the modulus of elasticity, the melt viscosity, the Vicat temperature and the die swell. The molding compositions which are particularly suitable according to the invention here preferably have a viscosity of more than 6.0kJ/m at 23 ℃²Preferably an elastic modulus of more than 1450MPa, preferably a melt viscosity of more than 2000Pa · s and advantageously less than 4500Pa · s, preferably a vicat softening temperature of more than 93 ℃ and preferably a die swell of 0-20%.

By using the core-shell particles of the invention, a series of important advantages can be obtained simultaneously. These advantages include in particular:

by using the core-shell particles of the invention, it is possible to obtain molding compositions having significantly improved notched impact strength values, in particular at low temperatures below 0 ℃ and advantageously according to ISO180, of more than 3.7kJ/m at-20 ℃²The Izod notched impact strength of (1).

When compared with conventional impact modifiers, significantly smaller amounts of the core-shell particles of the invention are sufficient to obtain molding compositions having comparable notched impact strength at low temperatures, in particular at-20 ℃.

The core-shell particles of the invention can be prepared in a simple manner on an industrial scale and at low cost.

The molding compositions impact-modified by the process of the invention are distinguished by a distinctly improved property profile at low temperatures, in particular at-20 ℃. This makes them useful for applications at low temperatures, especially at temperatures below 0 ℃.

The present invention relates to core-shell particles comprising a core, a first shell layer and optionally a second shell layer. Furthermore, the core-shell particles of the invention may, where appropriate, comprise further shells, although core-shell particles which have proven particularly successful for the purposes of the invention are those which are composed of a core, a first shell layer and preferably a second shell layer.

The term "core-shell particles" is well known in the art and within the scope of the present invention denotes polymers obtainable by multistage emulsion polymerization. This method has long been known in the prior art and is listed and explained, for example, in Houben-Weyl, volume E20, part 2 (1987), page 1150 and the following pages. The person skilled in the art may also find further valuable teachings from the publications US 3793402, DE 4121652 a1, DE 4136993 a1, EP 828772 a1, the disclosures of which are expressly incorporated herein by reference.

Within the scope of the present invention, the core has at least 75 wt% of (meth) acrylate repeating units, based on its total weight.

Within the scope of the present invention, the expression "(meth) acrylate" here denotes acrylate, methacrylate and mixtures of the two. Thus, they include compounds having at least one group of the formula,

wherein R is hydrogen or methyl. They include in particular alkyl acrylates and/or alkyl methacrylates.

The core preferably comprises the following components, based in each case on its total weight:

A) from 50.0 to 99.9% by weight, advantageously from 60.0 to 99.9% by weight, preferably from 75.0 to 99.9% by weight, particularly preferably from 80.0 to 99.0% by weight, in particular from 85.0 to 99.0% by weight, of alkyl methacrylate repeating units, where the alkyl group contains from 1 to 20, preferably from 1 to 12, in particular from 1 to 8, carbon atoms,

B)0.0 to 40.0% by weight, preferably 0.0 to 24.9% by weight, advantageously 1.0 to 29.9% by weight, in particular 1.0 to 14.9% by weight, of alkyl acrylate repeat units, where the alkyl groups contain 1 to 20, preferably 1 to 12, particularly preferably 1 to 8, in particular 1 to 4 carbon atoms,

C)0.1 to 2.0 wt% of crosslinking repeating units, and

D)0.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the weight percentage is preferably supplemented to 100.0 wt%.

These compounds A), B), C) and D) naturally differ from one another, and in particular the compounds A) and B) do not contain a crosslinking monomer C).

R¹-R⁵The radicals are each, independently of one another, hydrogen, halogen, in particular fluorine, chlorine or bromine, or alkyl having 1 to 6 carbon atoms, preferably hydrogen. R⁶The radical is hydrogen or an alkyl radical having 1 to 6 carbon atoms, preferably hydrogen. Particularly suitable alkyl radicals having 1 to 6 carbon atoms are methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl and cyclopentyl and cyclohexyl.

Thus, the styrenic repeat units of formula (I) comprise repeat structural units obtainable by polymerization of monomers of formula (Ia).

In particular, suitable monomers of formula (Ia) include: styrene; substituted styrenes having alkyl substitution in the side chain, such as α -methylstyrene and α -ethylstyrene; substituted styrenes having an alkyl substitution on the ring, such as vinyltoluene and p-methylstyrene; and halogenated styrenes such as monochlorostyrene, dichlorostyrene, tribromostyrene, and tetrabromostyrene.

The alkyl methacrylate repeating unit (a) refers to a repeating structural unit obtainable by polymerization of an ester of methacrylic acid. In particular, suitable esters of methacrylic acid include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-octyl methacrylate, ethylhexyl methacrylate, nonyl methacrylate, 2-methyloctyl methacrylate, 2-tert-butylheptyl methacrylate, 3-isopropylheptyl methacrylate, decyl methacrylate, undecyl methacrylate, 5-methylundecyl methacrylate, dodecyl methacrylate, 2-methyldodecyl methacrylate, tridecyl methacrylate, dodecyl methacrylate, n-butyl methacrylate, n-, 5-methyltrodecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, 2-methylhexadecyl methacrylate, heptadecyl methacrylate, 5-isopropylheptadecyl methacrylate, 5-ethyloctadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, cycloalkyl methacrylate, for example cyclopentyl methacrylate, cyclohexyl methacrylate, 3-vinyl-2-butylcyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, bornyl methacrylate and isobornyl methacrylate.

In a particularly preferred embodiment of the invention, the core comprises at least 50 wt.%, advantageously at least 60 wt.%, preferably at least 75 wt.%, in particular at least 85 wt.%, based on its total weight, of methyl methacrylate repeat units.

The above-mentioned alkyl acrylate repeating unit (B) means a repeating structural unit obtainable by ester polymerization of acrylic acid. In particular, suitable esters of acrylic acid include: methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-octyl acrylate, ethylhexyl acrylate, nonyl acrylate, 2-methyloctyl acrylate, 2-tert-butylheptyl acrylate, 3-isopropylheptyl acrylate, decyl acrylate, undecyl acrylate, 5-methylundecyl acrylate, dodecyl acrylate, 2-methyldodecyl acrylate, tridecyl acrylate, 5-methyltrodecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, tert-butyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, decyl acrylate, ethylhexyl acrylate, nonyl acrylate, dodecyl acrylate, 2-methyldodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadec, 2-methylhexadecyl acrylate, heptadecyl acrylate, 5-isopropylheptadecyl acrylate, 5-ethyloctadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, cycloalkyl acrylates, for example cyclopentyl acrylate, cyclohexyl acrylate, 3-vinyl-2-butylcyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, bornyl acrylate and isobornyl acrylate.

The above-mentioned crosslinking repeating unit (C) means a repeating structural unit obtainable by polymerization of a crosslinking monomer. In particular, suitable crosslinking monomers include all compounds which are capable of initiating crosslinking under the polymerization conditions of the present invention. In particular, these compounds include:

(a) difunctional (meth) acrylates, preferably

A compound of the formula:

wherein R is hydrogen or methyl and n is a positive integer greater than or equal to 2, preferably from 3 to 20, in particular di (meth) acrylates of propylene glycol, butylene glycol, hexylene glycol, octylene glycol, nonylene glycol, decylene glycol and di (meth) acrylates of eicosanediol;

a compound of the formula:

wherein R is hydrogen or methyl, and n is a positive integer from 1 to 14; in particular the di (meth) acrylates of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dodecaethylene glycol, tetradecylene glycol, propylene glycol, dipropylene glycol and tetradecylene glycol.

Glycerol di (meth) acrylate, 2 '-bis [ p- (gamma-methacryloxy-beta-hydroxypropoxy) phenylpropane ] or bis GMA, bisphenol a dimethacrylate, neopentyl glycol di (meth) acrylate, 2' -bis (4-methacryloxypolyethoxyphenyl) propane having 2 to 10 ethoxy groups per molecule, and 1, 2-bis (3-methacryloxy-2-hydroxypropoxy) butane;

(b) tri-or polyfunctional (meth) acrylates, in particular trimethylolpropane tri (meth) acrylate and pentaerythritol tetra (meth) acrylate.

(c) Graft crosslinkers having at least two C ═ C double bonds of different reactivity, in particular allyl methacrylate and allyl acrylate;

(d) aromatic crosslinking agents, in particular 1, 2-divinylbenzene, 1, 3-divinylbenzene and 1, 4-divinylbenzene.

The weight percentages of the components A) to D) of the core are preferably selected in such a way that: so that the core has a glass transition temperature Tg of at least 10 c, preferably at least 30 c. The glass transition temperature Tg of the polymers can be determined here in a known manner by Differential Scanning Calorimetry (DSC). The glass transition temperature Tg can also be approximately pre-calculated by the Fox equation. According to foxt.g., bull.am.physics soc.1, 3, page 123 (1956):

wherein x is_nIs the mass fraction (based on 100% by weight) of the monomer n, and Tg_nIs the glass transition temperature in degrees Kelvin of the homopolymer of the monomer n. From Polymer Handbook, second edition, J.Wiley&Sons, New York (1975), the person skilled in the art is given more useful teachings which give the Tg values of the most commonly used homopolymers.

The first shell layer of the core-shell particles of the present invention has a glass transition temperature of less than 30 ℃, preferably less than 10 ℃, in particular from 0 to-75 ℃. The glass transition temperature Tg of the polymers here can be determined by Differential Scanning Calorimetry (DSC) as described above and/or approximately pre-calculated by the Fox equation.

The first shell layer comprises the following components based on its total weight:

E)92.0 to 98.0 wt% of (meth) acrylate repeating units, and

F)2.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the weight percentages add up to 100 wt%.

Within the scope of a very particularly preferred embodiment of the present invention, the first shell layer comprises:

e-1)90.0 to 97.9% by weight of alkyl acrylate repeating units having 3 to 8 carbon atoms in the alkyl radical and/or alkyl methacrylate repeating units having 7 to 14 carbon atoms in the alkyl radical, in particular butyl acrylate repeating units and/or dodecyl methacrylate repeating units, and

e-2)0.1 to 2.0% by weight of crosslinking repeating units,

F)2.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

among them, the parts by weight are preferably added up to 100.0 parts by weight.

These compounds E-1), E-2) and F) naturally differ from one another, and in particular the compound E-1) does not contain a crosslinking monomer E-2).

The optionally present second shell layer comprises at least 75 wt% of (meth) acrylate repeating units based on its total weight. It preferably comprises:

G) from 50.0 to 100.0% by weight, advantageously from 60.0 to 100.0% by weight, particularly preferably from 75.0 to 100.0% by weight, in particular from 85.0 to 99.5% by weight, of alkyl methacrylate repeat units in which the alkyl group contains from 1 to 20, preferably from 1 to 12, in particular from 1 to 8, carbon atoms;

H)0.0 to 40.0 wt.%, preferably 0.0 to 25.0 wt.%, and especially 0.1 to 15.0 wt.% of alkyl acrylate repeat units, wherein the alkyl group contains 1 to 20, preferably 1 to 12, especially 1 to 8 carbon atoms;

I)0.0 to 10.0 wt.%, preferably 0.0 to 8.0 wt.% of styrenic repeat units of formula (I);

wherein the sum of the weight percentages is preferably 100.0 wt%.

In a particularly preferred embodiment of the present invention, the second shell comprises at least 50 wt.%, advantageously at least 60 wt.%, preferably at least 75 wt.%, in particular at least 85 wt.%, based on its total weight, of methyl methacrylate repeating units.

Furthermore, the components of the second shell are advantageously selected in such a way that the second shell has a glass transition temperature Tg of at least 10 ℃, preferably of at least 30 ℃. The glass transition temperature Tg of the polymers can be determined here as described above by Differential Scanning Calorimetry (DSC) and/or approximately pre-calculated by the Fox equation.

The total radius of the core-shell particle, including the optionally present second shell layer, is more than 160 to 240nm, preferably 170-220nm, in particular 175-210 nm. The total radius is determined by the Coulter method. This is known in the literature that methods for particle size determination are based on the measurement of the electrical resistance, which changes in a characteristic manner when particles pass through a narrow measuring aperture. More details can be found, for example, in Nachr. chem. Tech. Lab, 43, 553-566 (1995).

For the purposes of the present invention, it has furthermore proved very particularly advantageous if the particles have the following characteristics, in each case based on the total weight of the particles,

i) the core constitutes 5.0-50.0 wt.%, preferably 15.0-50.0 wt.%, advantageously 25.0-45.0 wt.%, in particular 30.0-40.0 wt.%,

ii) the first shell constitutes 20.0 to 75.0 wt.%, preferably 30.0 to 60.0 wt.%, advantageously 35.0 to 55.0 wt.%, in particular 40.0 to 50 wt.%, and

iii) the second shell constitutes from 0.0 to 50.0% by weight, preferably from 5.0 to 40.0% by weight, advantageously from 10.0 to 30.0% by weight, in particular from 15.0 to 25.0% by weight,

wherein the sum of the weight percentages is preferably 100.0 wt%.

The core-shell particles of the invention can be prepared in a known manner, for example by multistage emulsion polymerization. This polymerization is advantageously carried out by a process in which water and an emulsifier are used to form the initial charge. This initial charge preferably comprises from 90.0 to 99.99 parts by weight of water and from 0.01 to 10.00 parts by weight of emulsifier, the stated parts by weight adding advantageously being 100.00 parts by weight.

Then, this initial charge was gradually fed in the following order

b) The monomers for the core are added in the desired proportions and polymerized until a conversion of at least 85.0% by weight, preferably at least 90.0% by weight, advantageously at least 95.0% by weight, in particular at least 99% by weight, based in each case on their total weight,

c) the monomers for the first shell are added in the desired proportions and polymerized until a conversion of at least 85.0% by weight, preferably at least 90.0% by weight, advantageously at least 95.0% by weight, in particular at least 99% by weight, based in each case on their total weight,

d) the monomers for the second shell are optionally added in the desired proportions and polymerized until a conversion of at least 85.0% by weight, preferably at least 90.0% by weight, advantageously at least 95.0% by weight, in particular at least 99% by weight, based in each case on their total weight.

For the purposes of the present invention, polymers are here understood to mean compounds whose molecular weight is at least 10 times the molecular weight of the respective starting compounds A) to I), the so-called monomers.

The progress of the polymerization reaction in each step can be monitored by known methods, for example gravimetrically or by gas chromatography.

According to the invention, the polymerization in steps b) to d) is preferably carried out at a temperature of from 0 to 120 ℃, preferably from 30 to 100 ℃.

Very particularly advantageous polymerization temperatures have proven to be here from above 60 ℃ to below 90 ℃, advantageously from above 70 ℃ to below 85 ℃, preferably from above 75 ℃ to below 85 ℃.

The polymerization is initiated using the initiators usually used for emulsion polymerization. Examples of suitable organic initiators are hydroperoxides, such as tert-butyl hydroperoxide or cumene hydroperoxide. Suitable inorganic initiators are the alkali metal and ammonium salts of hydrogen peroxide and peroxodisulfuric acid, in particular sodium peroxodisulfate and potassium peroxodisulfate. Suitable redox initiator systems are, for example, combinations of tertiary amines with peroxides or alkali metal and ammonium salts of sodium metabisulfite and peroxodisulfuric acid, in particular sodium and potassium peroxodisulfate, or particularly preferably peroxides. Can be found in the professional literature, particularly in H.Rauch-Puntigam, Th."Acryl-und Methacryl VerbindungenAcrylic and methacrylic compounds), ", Springer, Heidelberg, 1967 or Kirk-Othmer, Encyclopedia of chemical Technology, first volume, pages 386 and later, J.Wiley, New York, 1978 to find more detail. The use of organic and/or inorganic initiators is particularly preferred within the scope of the present invention.

The initiators mentioned may be used individually or in mixtures. They are preferably used in amounts of from 0.05 to 3.0% by weight, based on the total weight of the monomers used in each step. In order to keep the radical flow constant throughout the polymerization or at various polymerization temperatures, it is also preferred to carry out the polymerization using a mixture of polymerization initiators of various half-lives.

The reaction mixture is preferably stabilized by emulsifiers and/or protective colloids. In order to obtain low dispersion viscosities, stabilization by emulsifiers is preferred. The total amount of emulsifiers is preferably from 0.1 to 5% by weight, in particular from 0.5 to 3% by weight, based on the total weight of the monomers A) to I). Particularly suitable emulsifiers are anionic or nonionic emulsifiers, or mixtures thereof, in particular:

alkyl sulfates, preferably alkyl sulfates having from 8 to 18 carbon atoms in the alkyl radical, alkyl and alkylaryl ether sulfates having from 8 to 18 carbon atoms in the alkyl radical and from 1 to 50 ethylene oxide units;

sulfonates, preferably alkylsulfonates having 8 to 18 carbon atoms in the alkyl radical, alkylarylsulfonates having 8 to 18 carbon atoms in the alkyl radical, esters and half-esters of sulfosuccinic acid with monohydric alcohols or with alkylphenols having 4 to 15 carbon atoms in the alkyl radical; where appropriate, it is also possible to ethoxylate these alcohols or alkylphenols with from 1 to 40 ethylene oxide units;

partial esters of phosphoric acid and their alkali metal and ammonium salts, preferably alkyl phosphates and alkylaryl phosphates containing from 8 to 20 carbon atoms in the alkyl or alkylaryl radical and having from 1 to 5 ethylene oxide units;

alkyl polyglycol ethers, preferably those having 8 to 20 carbon atoms in the alkyl radical and 8 to 40 ethylene oxide units;

alkylaryl polyglycol ethers, preferably alkylaryl polyglycol ethers having from 8 to 20 carbon atoms in the alkyl or alkylaryl radical and from 8 to 40 ethylene oxide units;

ethylene oxide-propylene oxide copolymers, preferably block copolymers, advantageously have from 8 to 40 ethylene oxide units or propylene oxide units, respectively.

According to the invention, mixtures of anionic emulsifiers and nonionic emulsifiers are preferred. Mixtures which have proven very particularly advantageous here are: mixtures of esters or half-esters of sulfosuccinic acid with monohydric alcohols or with alkylphenols having from 4 to 15 carbon atoms in the alkyl radical as anionic emulsifiers and alkyl polyglycol ethers, preferably having from 8 to 20 carbon atoms in the alkyl radical and from 8 to 40 ethylene oxide units, as nonionic emulsifiers in a weight ratio of from 8: 1 to 1: 8.

Emulsifiers mixed with protective colloids may also be used, where appropriate. Suitable protective colloids include in particular: partially hydrolyzed polyvinyl acetate, polyvinyl pyrrolidone, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, starch, protein, poly (meth) acrylic acid, poly (meth) acrylamide, polyvinyl sulfonic acid, melamine formaldehyde sulfonate, naphthalene formaldehyde sulfonate, styrene-maleic acid copolymer, and vinyl ether-maleic acid copolymer. If protective colloids are used, they are preferably used in amounts of from 0.01 to 1.0% by weight, based on the total weight of the monomers A) to I). The protective colloid can be used to form the initial charge before the polymerization is initiated, or it can be metered in.

The initiator can be used to form the initial charge or it can be metered in. Furthermore, it is also possible for a portion of the initiator to be used to form the initial charge and for the remainder to be metered in.

The polymerization is preferably initiated by heating the reaction mixture to the polymerization temperature and by metering in the initiator, preferably in aqueous solution. The metered addition of the emulsifier and the monomers can be carried out separately or in the form of a mixture. In the case of metering in a mixture consisting of emulsifier and monomers, the procedure is carried out as follows: the emulsifier and the monomers are premixed in a mixer upstream of the polymerization reactor. The remaining emulsifier and the remaining monomers which are not used to form the initial charge are preferably metered in separately from one another after the polymerization has been initiated. The metered addition is preferably started from 15 to 35 minutes after the initiation of the polymerization.

Furthermore, it is particularly advantageous for the purposes of the present invention for the initial charge to contain a so-called "seed latex" which is preferably obtainable by polymerization of alkyl (meth) acrylates and advantageously has a particle radius of from 3.0 to 20.0 nm. After defined polymerization onto the seed latex, a shell is formed around the periphery of the seed latex during the polymerization, and the radii of the particles formed are measured by the Coulter method, it being possible to calculate these small radii. This method known in the literature for particle size measurement is based on the measurement of the electrical resistance, which changes in a characteristic manner when particles pass through a narrow measurement aperture. More details can be found, for example, in Nachr. chem. Tech. Lab, 43, 553-566 (1995).

The monomer component of the actual core, i.e. the first composition, is preferably added to the seed latex under conditions that avoid the formation of new particles. As a result, the polymer formed in this first process step is deposited in the form of a shell around the seed latex. Similarly, the monomer component of the first shell material (the second composition) is added to the emulsion polymer under conditions that avoid the formation of new particles. As a result, the polymer formed in the second step is deposited in the form of a shell around the existing core. Accordingly, this operation is repeated to form each additional shell.

In another preferred embodiment of the present invention, the core-shell particles of the present invention are obtained by emulsion polymerization, wherein long-chain aliphatic alcohols, preferably having from 12 to 20 carbon atoms, are used in an emulsified manner instead of seed latices for forming the initial charge. In a preferred embodiment of this process, stearyl alcohol is used as the long-chain aliphatic alcohol. Similar to the procedure described above, the core-shell structure is obtained by stepwise addition and polymerization of the corresponding monomers under conditions which avoid the formation of new particles. The person skilled in the art can find more details about the polymerization process in patent documents DE 3343766, DE 3210891, DE 2850105, DE 2742178 and DE 3701579.

However, it has proven very particularly advantageous within the scope of the present invention to meter in the second and third monomer mixtures, independently of the particular operating procedure, in dependence on the amount consumed.

The chain length, in particular of the (co) polymer of the second shell, can be adjusted by polymerization of the monomer or of the monomer mixture in the presence of molecular weight regulators, in particular mercaptans which are known for this purpose, such as n-butyl mercaptan, n-dodecyl mercaptan, 2-mercaptoethanol or 2-ethylhexyl thioglycolate, pentaerythritol tetrathioglycolate; wherein the molecular weight regulator is generally used in an amount of 0.05 to 5% by weight, preferably 0.1 to 2% by weight, and particularly preferably 0.2 to 1% by weight, based on the monomer mixture (see, for example, H.Rauch-Puntigam, Th."acrylic-und Methacrylverbindungen (acrylic and methacrylic compounds)", Springer, Heidelberg, 1967; Houben-Weyl, Methoden der organischen Chemie (methods of organic chemistry), volume XIV/1, page 66, Georg Thieme, Heidelberg, 1961, or Kirk-Othmer, Encyclopedia of Chemical Technology (Encyclopedia of Chemical Technology), volume 1, page 296 and the following pages, J.Wiley, New York, 1978). The molecular weight regulator used is preferably n-dodecyl mercaptan.

After the polymerization has ended, the post-polymerization can be carried out to remove residual monomers using known methods, for example by means of an initiated post-polymerization reaction.

Since the process of the invention is particularly suitable for preparing aqueous dispersions having a high solids content of more than 50% by weight, based on the total weight of the aqueous dispersion, the relative proportions of all substances are chosen in such a way that the total weight of the monomers is more than 50.0% by weight, advantageously more than 51.0% by weight and preferably more than 52.0% by weight, based on the total weight of the aqueous dispersion. Substances to be considered in this context include, besides the monomers, all other substances used, such as water, emulsifiers, initiators, optionally regulators and protective colloids, etc.

The aqueous dispersions obtainable by the process of the present invention are characterized by a low content of coagulum, which is preferably less than 5.0% by weight, advantageously less than 3.0% by weight, in particular less than 1.5% by weight, based on the total weight of the aqueous dispersion. In a very particularly preferred embodiment of the invention, the aqueous dispersion contains less than 1.0% by weight, preferably less than 0.5% by weight, advantageously less than 0.25% by weight, in particular 0.10% by weight or less, of coagulate, based on its total weight.

The term "coagulate" in this context means water-insoluble components which can preferably be filtered off by filtration, advantageously by passing the dispersion through a filter housing equipped with a tight filter cloth, numbered 0.90 DIN 4188.

The core-shell particles of the invention can be obtained from a dispersion by the following process: for example spray drying, freeze coagulation, precipitation by electrolyte addition or by mechanical or thermal loading, as it is carried out by vented extruders according to DE 2750682A 1 or US 4110843. The spray-drying process is the most common, although the other processes mentioned have the advantage that the water-soluble polymerization auxiliaries are at least partially separated from the polymer here.

The core-shell particles according to the invention are used to improve the notched impact strength of hard thermoplastics which are compatible with the hard phase, preferably of poly (meth) acrylate molding compositions, in particular of polymethyl methacrylate.

For a suitable improvement of the properties, the poly (meth) acrylate molding compositions preferably contain further polymers. In particular, these polymers include polyacrylonitrile, polystyrene, polyethers, polyesters, polycarbonates, and polyvinyl chloride. These polymers may be used individually or in mixtures, wherein in a very particularly preferred embodiment of the present invention copolymers of the invention which can be derived from the abovementioned polymers are added to the molding compositions. In particular, these copolymers include styrene-acrylonitrile copolymers (SAN), which are preferably added to the molding compositions in amounts of up to 45% by weight.

Particularly preferred styrene-acrylonitrile copolymers are obtainable by polymerizing a mixture consisting of:

70.0 to 92.0 wt.% of styrene

8.0 to 30.0 wt.% of acrylonitrile and

from 0.0 to 22.0% by weight of further comonomers, based in each case on the total weight of the monomers to be polymerized.

In general, from 10 to 60 parts of impact modifier are incorporated into 100 parts of the molding composition to be modified.

According to the invention, particularly preferred molding compositions comprise, based in each case on their total weight:

A)1.0 to 50.0 wt% of at least one core-shell particle of the invention;

B)1.0 to 99.0 wt.% of at least one (meth) acrylic polymer,

C)0.0 to 45.0 wt%, preferably 1.0 to 45 wt%, of a styrene-acrylonitrile copolymer, and

D)0.0 to 10.0 wt.% of other additives

Wherein the sum of the weight percentages is 100.0 wt%.

The (meth) acrylic polymer preferably comprises, based in each case on its total weight,

a) from 50.0 to 100.0% by weight, advantageously from 60.0 to 100.0% by weight, particularly preferably from 75.0 to 100.0% by weight, in particular from 85.0 to 99.5% by weight, of alkyl methacrylate repeating units in which the alkyl radical contains from 1 to 20, preferably from 1 to 12, advantageously from 1 to 8, in particular from 1 to 4, carbon atoms,

b)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 repeat units in which the alkyl group contains 1 to 20, preferably 1 to 12, advantageously 1 to 8, in particular 1 to 4, carbon atoms, and

c)0.0 to 8.0 wt.% of styrenic repeat units of formula (I);

wherein the sum of the weight percentages is 100.0 wt%.

According to a particularly preferred embodiment of the present invention, the (meth) acrylic polymer comprises at least 50.0 wt.%, advantageously at least 60.0 wt.%, preferably at least 75.0 wt.%, in particular at least 85.0 wt.%, based on its total weight, of methyl methacrylate repeating units.

Furthermore, preferably the (meth) acrylic polymer has a number average molecular weight of 1000-. Such molecular weights can be determined, for example, by gel permeation chromatography with polystyrene calibration.

Mixtures of this type can be prepared in various ways. For example, a dispersion of core-shell particles is mixed with an aqueous dispersion of the blending components, and the mixture may be coagulated, the aqueous phase separated, and the coagulum melted to obtain the molding composition. This method makes it possible in particular to achieve a homogeneous mixing of the two materials. The individual components can also be prepared separately and separated off, and mixed in the form of their melts or in the form of powders or granules, and homogenized in a multi-screw extruder or on a roll mill.

Conventional additives may be incorporated in any processing step suitable for this purpose. These additives include, in particular, dyes, pigments, fillers, reinforcing fibers, lubricants, UV stabilizers and the like.

In a very particularly preferred embodiment of the present invention, the molding composition comprises from 0.1 to 10% by weight, preferably from 0.5 to 5.0% by weight, in particular from 1.0 to 4.0% by weight, based in each case on its total weight, of a further polymer (AP) whose weight average molecular weight is at least 10%, preferably at least 50%, in particular at least 100%, higher than the weight average molecular weight of the (meth) acrylic polymer. The molecular weight can be determined here, for example, by gel permeation chromatography with polystyrene calibration.

Particularly suitable polymers (AP) according to the invention preferably comprise, based in each case on their total weight,

a) from 50.0 to 100.0% by weight, advantageously from 60.0 to 100.0% by weight, particularly preferably from 75.0 to 100.0% by weight, in particular from 85.0 to 99.5% by weight, of alkyl methacrylate repeating units in which the alkyl radical contains from 1 to 20, preferably from 1 to 12, advantageously from 1 to 8, in particular from 1 to 4, carbon atoms,

b)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 repeat units in which the alkyl group contains 1 to 20, preferably 1 to 12, advantageously 1 to 8, in particular 1 to 4, carbon atoms, and

c)0.0 to 8.0 wt.% of styrenic repeat units of formula (I);

wherein the sum of the weight percentages is 100.0 wt%.

In a particularly preferred embodiment of the present invention, the polymer (AP) contains at least 50.0% by weight, advantageously at least 60.0% by weight, preferably at least 75.0% by weight, in particular at least 85.0% by weight, based on its total weight, of methyl methacrylate repeat units.

Furthermore, the polymer (AP) preferably has a weight average molecular weight of 10000-. Such molecular weights can be determined, for example, by gel permeation chromatography with polystyrene calibration.

Blends of core-shell particles, in particular with polymethyl methacrylate, are particularly suitable for producing moldings advantageously having a wall thickness of greater than 1mm, for example extruded coils (Bahnen) of 1 to 10mm thickness, which can be punched well and are useful, for example, for producing printable panels for electrical apparatus or for producing high-quality injection moldings, for example windshields for motor vehicles. They can also be used to make thinner films, for example 50 μm.

The mouldings obtainable according to the invention are characterized in that:

according to ISO 306(B50), the vicat softening temperature is preferably at least 85 ℃, preferably at least 90 ℃, and particularly preferably at least 93 ℃,

preferred notched impact strengths KSZ (Izod 180/1eA) according to ISO180 of at least 5.8kJ/m at 23 DEG C²Advantageously greater than 6.0kJ/m²The KSZ is preferably at least 3.7kJ/m at-20 DEG C²And are and

preferred elastic modulus is at least 1450MPa according to ISO 527-2.

In a particularly preferred embodiment of the invention, the moldings of the invention are used as mirror housings or spoilers for motor vehicles, as tubes, as films for sports articles, or as protective coverings or as refrigerator components.

The following examples and comparative examples serve to illustrate the invention without thereby restricting the inventive concept.

I. Core-shell particles

A. Preparation of seed latex

The seed latex was prepared by emulsion polymerization of a monomer composition containing 98 wt% ethyl acrylate and 2 wt% allyl methacrylate. The content of these particles in water is about 10% by weight and their diameter is about 20 nm.

B. Preparation of core-shell particles

All of the core-shell particles described below were prepared by emulsion polymerization according to the following general preparation protocol. The emulsions I to III given in Table 1 were used here.

19.416kg of water were formed into an initial charge in the polymerization vessel and under stirring at 83 ℃ (vessel internal temperature). 16.2g of sodium carbonate and 73g of seed latex were added. Then, emulsion I was metered in over 1 hour. 10 minutes after the end of the addition of emulsion I, emulsion II is metered in over about 2 hours. Then, about 90 minutes after the end of the addition of emulsion II, emulsion III is metered in over about 1 hour. 30 minutes after the end of the addition of emulsion III, the mixture was cooled to 30 ℃.

The dispersion was frozen at-20 ℃ for 2 days to isolate the core-shell particles, then thawed again, and the coagulated dispersion was isolated via filter cloth. The solid was dried in a drying oven at 50 ℃ (for about 3 days).

The particle size of the core-shell particles (see table 2) was determined by a Coulter N4 apparatus, wherein these measurements were made on the particles in the dispersion.

Table 1: composition of Each emulsion (all data in [ g ])

	VB1	VB2	B1	B2	B3
						Emulsion I
Water (W)	8109.65	8109.65	8109.65	8109.65	8109.65
						Sodium persulfate	8.24	8.24	8.24	8.24	8.24
Aerosol OT 75	65.88	65.88	65.88	65.88	65.88
						Methacrylic acid methyl ester	14216.72	14216.72	14216.72	14216.72	14216.72
Acrylic acid ethyl ester	593.6	593.6	593.6	593.6	593.6
						Allyl methacrylate	29.68	29.68	29.68	29.68	29.68
Emulsion II
						Water (W)	7081.18	7081.18	7081.18	7081.18	7081.18
Sodium persulfate	18.59	18.59	18.59	18.59	18.59
						Aerosol OT 75	84.71	84.71	84.71	84.71	84.71
Acrylic acid butyl ester	15454.8	18793.8	17839.8	17744.4	17649
						Styrene (meth) acrylic acid ester	3453.48		954	954	954
Allyl methacrylate	171.72	286.2	286.2	381.6	477
						Emulsion III
Water (W)	2992.59	2992.59	2992.59	2992.59	2992.59
						Sodium persulfate	8.24	8.24	8.24	8.24	8.24
Aerosol OT 75	10.59	10.59	10.59	10.59	10.59
						Methacrylic acid methyl ester	7632	7632	7632	7632	7632
Acrylic acid ethyl ester	848	848	848	848	848

Molding compositions

A. Blending of moulding compositions

The moulding composition based on polymethyl methacrylate, PLEXIGLAS, is extruded through an extruder7N(GmbH &Kg, Darmstadt) was mixed with the corresponding core-shell particles. The compositions of the examples and comparative examples are reported in table 2.

B. Testing of the Molding compositions

Test specimens were prepared from the mixed molding compositions. The molding compositions or the corresponding test specimens, respectively, were tested according to the following test methods:

● melt viscosity η s (220 ℃/5 MPa): DIN 54811(1984)

● die swell B: DIN 54811(1984)

● Vicat softening temperature (16h/80 ℃): DIN ISO 306(1994.8)

● notched Izod impact strength: ISO180 (1993)

● Charpy notched impact: ISO 179(1993)

● modulus of elasticity: ISO 527-2

The test results can also be seen in table 2.

The advantages of the mixtures according to the invention with respect to conventional impact-modified molding compositions (comparative examples A and B) can be clearly seen:

the notched impact strength at-20 ℃ of the molding compositions according to the invention is markedly higher than that of the comparative molding compositions in the case of comparable contents (< 40% by weight) of core-shell particles. All mixtures here have comparable notched impact strengths at room temperature.

In addition, the styrene-free tough phase does not improve the low-temperature notched impact strength of the corresponding molding compositions.

Excellent low-temperature notched impact strengths can be achieved without impairing the other important properties of the molding compositions, in particular the viscosity, the Vicat softening temperature and the modulus of elasticity.

When compared with the molding compositions disclosed in the patents DE 2253689, DE 4121652 and DE 4136993, a comparable low-temperature notched impact strength can be achieved with significantly smaller amounts of core-shell particles.

Table 2: test results for impact-modified moulding compositions

Claims (19)

1. A core-shell particle having a core, a first shell layer, and optionally a second shell layer, wherein:

i) the core comprises at least 75.0 wt%, based on its total weight, of (meth) acrylate repeat units;

ii) the first shell has a glass transition temperature of less than 30 ℃;

iii) an optionally present second shell layer located outside the first shell layer comprising at least 75.0 wt% of (meth) acrylate repeating units based on its total weight;

the method is characterized in that:

iv) the first shell layer comprises the following components based on its total weight;

E)92.0 to 98.0 wt% of (meth) acrylate repeating units, and

F)2.0 to 8.0 wt.% of styrenic repeat units of formula (I)

Wherein R is¹-R⁵Each independently of the others being hydrogen, halogen, C₁-C₆-alkyl or C₂-C₆-alkenyl, and R⁶The radical is hydrogen or alkyl having 1 to 6 carbon atoms,

wherein the sum of the weight percentages of E) and F) is 100.0 wt%,

and

v) the radius of the core-shell particle, including the optional second shell layer, is from more than 160.0 to 240.0nm, measured by the Coulter method.

2. Core-shell particles according to claim 1, characterized in that: in each case based on the total weight of the particles,

i) the core is 5.0-50.0 wt%,

ii) the first shell layer constitutes 20.0 to 75.0 wt%, and

iii) the second shell constitutes 0.0-50.0 wt%,

wherein the sum of the weight percentages is 100.0 wt%.

3. Core-shell particle according to claim 1 or 2, characterized in that: the core comprises, based in each case on its total weight,

A)50.0 to 99.9% by weight of alkyl methacrylate repeat units having 1 to 20 carbon atoms in the alkyl group,

B)0.0 to 40.0 wt.% of alkyl acrylate repeating units having 1 to 20 carbon atoms in the alkyl group,

C)0.1 to 2.0 wt% of crosslinking repeating units, and

D)0.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the sum of the weight percentages is 100.0 wt%.

4. Core-shell particle according to claim 1 or 2, characterized in that: the core comprises, based in each case on its total weight, from 80.0 to 99.9% by weight of methyl methacrylate repeating units and from 1.0 to 20.0% by weight of alkyl acrylate repeating units having from 1 to 4 carbon atoms in the alkyl radical, where the percentages by weight add up to 100.0% by weight.

5. Core-shell particle according to claim 1 or 2, characterized in that: the first shell comprises, based in each case on its total weight,

e-1)90.0 to 97.9% by weight of alkyl acrylate repeat units having 3 to 8 carbon atoms in the alkyl radical and/or alkyl methacrylate repeat units having 7 to 14 carbon atoms in the alkyl radical,

e-2)0.1 to 2.0% by weight of crosslinking repeating units, and

F)2.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the sum of the weight percentages is 100.0 wt%.

6. Core-shell particles according to claim 5, characterized in that: the alkyl acrylate repeat units having 3 to 8 carbon atoms in the alkyl group and/or the alkyl methacrylate repeat units having 7 to 14 carbon atoms in the alkyl group are butyl acrylate repeat units and/or dodecyl methacrylate weight units.

7. Core-shell particle according to claim 1 or 2, characterized in that: the particles have a second shell comprising, in each case based on their total weight,

G)50.0 to 100.0 wt.% of alkyl methacrylate repeating units having 1 to 20 carbon atoms in the alkyl group,

H)0.0 to 40.0 wt.% of alkyl acrylate repeating units having 1 to 20 carbon atoms in the alkyl group, and

I)0.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the sum of the weight percentages is 100.0 wt%.

8. Core-shell particle according to claim 1 or 2, characterized in that: the core has a glass transition temperature of at least 30 ℃.

9. Core-shell particle according to claim 1 or 2, characterized in that: the particle has a second shell layer having a glass transition temperature of at least 30 ℃.

10. A method for preparing core-shell particles according to any of the preceding claims 1 to 9, characterized in that: a multi-step emulsion polymerization is carried out using the monomers for the core, the first shell and optionally the second shell and using an emulsifier.

11. A molding composition comprising, based in each case on its total weight,

A)1.0-50.0 wt% of at least one core-shell particle according to any one of claims 1-9;

B)1.0 to 99.0 wt% of at least one (meth) acrylic polymer,

C)0.0 to 45 wt% of a styrene-acrylonitrile copolymer, and

D)0.0 to 10.0 wt.% of other additives,

wherein the sum of the weight percentages is 100.0 wt%.

12. A molding composition according to claim 11, characterized in that: the (meth) acrylic polymer comprises, based in each case on its total weight,

a)50.0 to 100.0 wt.% of alkyl methacrylate repeating units having 1 to 20 carbon atoms in the alkyl group,

b)0.0 to 40.0 wt.% of alkyl acrylate repeating units having 1 to 20 carbon atoms in the alkyl group, and

c)0.0 to 8.0 wt.% of styrenic repeat units of the general formula (I),

wherein the sum of the weight percentages is 100.0 wt%.

13. A molding composition according to claim 11 or 12, characterized in that: the molding composition contains a styrene-acrylonitrile copolymer, wherein the styrene-acrylonitrile copolymer is obtained by polymerizing a mixture consisting of:

from 70 to 92% by weight of styrene,

8 to 30% by weight of acrylonitrile, and

from 0 to 22% by weight of further comonomers, based in each case on the total weight of the monomers to be polymerized.

14. A molding composition according to claim 11 or 12, characterized in that: it comprises 0.1 to 10% by weight, based on its total weight, of a further polymer having a weight average molecular weight which is at least 10% higher than the weight average molecular weight of the (meth) acrylic polymer as component B.

15. A molded article obtainable from the molding composition according to any of claims 11 to 14.

16. The molded article according to claim 15, characterized in that: the moldings have a Vicat softening temperature according to ISO 306B 50 of at least 85 ℃ and a notched impact strength KSZ according to ISO180, i.e. Izod 180/1eA, of at least 5.8kJ/m at 23 DEG C²And at least 3.7kJ/m at-20 DEG C²The modulus of elasticity according to ISO 527-2 is at least 1500 MPa.

17. The molded article according to claim 16, characterized in that: the moldings have a Vicat softening temperature according to ISO 306B 50 of at least 90 ℃.

18. The molded article according to claim 17, characterized in that: the moldings have a Vicat softening temperature according to ISO 306B 50 of at least 93 ℃.

19. The molded article according to claim 15, characterized in that: the moldings are mirror housings or spoilers for motor vehicles, tubes, membranes for sports equipment, protective covers or parts of refrigerators.