WO1999065962A1

WO1999065962A1 - Grafted copolymers with good low-temperature impact resistance

Info

Publication number: WO1999065962A1
Application number: PCT/EP1999/003735
Authority: WO
Inventors: Michael Fischer; Heiner GÖRRISSEN; Hartmut Heinen
Original assignee: Basf Aktiengesellschaft
Priority date: 1998-06-12
Filing date: 1999-05-29
Publication date: 1999-12-23
Also published as: DE19826135A1; EP1097178A1

Abstract

The invention relates to grafted copolymers P with a defined core-shell morphology and a mean particle size (d50) of between 300 and 750 nm, containing, in relation to P, A) between 0,05 and 2.5 weight % of a stage A having a glass transition temperature of at least 25 °C on the basis of a vinyl aromatic monomer; B) between 9.8 and 30 weight % of a stage B having a glass transition temperature of at least 25 °C and a mean particle size (d50) of between 100 and 350 nm on the basis of a polymer made of a vinyl aromatic compound and several cross-linking agents; C) between 30 and 70 weight % of a stage C having a glass transition temperature of no more than 0 °C, on the basis of an alkyl acrylate; and D) between 20 and 60 weight % of a stage D having a glass transition temperature of at least 25 °C, on the basis of a vinyl aromatic monomer.

Description

Graft copolymers with good low-temperature impact strength

description

The present invention relates to graft copolymers P with a defined core-shell morphology and an average particle size (dso) of 300 to 750 nm, containing, based on P,

A) 0.05 to 2.5% by weight of stage A with a glass transition temperature of at least 25 ° C., based on A,

al) 50 to 99.9% by weight of at least one vinylaromatic monomer, a2) 0 to 49.9% by weight of at least one monomer copolymerizable with the monomers al), and a3) 0.1 to 25% by weight at least a crosslinking monomer,

B) 9.8 to 30% by weight of a stage B with a glass transition temperature of at least 25 ° C. and an average particle size (dso) of 100 to 350 nm, based on B,

bl) 50 to 99.8% by weight of at least one vinyl aromatic monomer, b2) 0 to 49.8% by weight of at least one monomer copolymerizable with the monomers bl), b3) 0.1 to 10% by weight a crosslinker component based on b3),

α) 0.1 to 100% by weight of dihydrodicyclopentadienyl acrylate, β) 0 to 99.9% by weight of at least one further crosslinking agent with two or more functional groups of different reactivity, and

b4) 0.01 to less than 0.5% by weight of at least one crosslinking agent with two or more functional groups of the same reactivity,

C) 30 to 70% by weight - a stage C with a glass transition temperature of at most 0 ° C., based on C,

cl) 50 to 100% by weight of at least one C ₈ -C ₈ alkyl acrylate c2) 0 to 50% by weight of at least one monomer copolymerizable with the monomers cl), and c3) 0.01 to 20% by weight of at least one crosslinking agent α or β or a mixture thereof,

D) 20 to 60% by weight of a stage D with a glass transition temperature of at least 25 ° C., based on D,

dl) 50 to 100% by weight of at least one vinyl aromatic monomer d2) 0 to 50% by weight of at least one monomer copolymerizable with the monomers dl).

Furthermore, the present invention relates to mixtures M containing the graft copolymers P and further graft copolymers P ', and thermoplastic molding compositions F containing P or M. Furthermore, the invention relates to the use of P or M as impact modifier for thermoplastic molding compositions. Finally, the invention relates to moldings or films containing P or M, and moldings or films made from F. Preferred embodiments can be found both in the subclaims and in the description. It goes without saying that the sum of the individual components of the graft copolymers P, mixtures M or molding compositions F each add up to 100% by weight.

Graft copolymers, which are often also referred to as “core-shell” particles, are known, for example, as impact modifiers for plastics such as styrene-acrylonitrile copolymers, polyvinyl chloride (PVC), polymethyl methacrylate or polycarbonate. They can be structured in two or more stages. The graft base, the "core", can be made of elastomeric "soft" material, i.e. those with glass transition temperatures of less than approx. 25 ° C, e.g. less than 0 ° C, or non-elastomeric, "hard" material, i.e. those with glass transition temperatures greater than about 25 ° C, e.g. more than 50 ° C. The graft pads, "shell" or "shell", can be correspondingly hard or soft or alternately hard or soft in the case of multi-stage graft copolymers.

The glass transition temperature of the individual stages can in each case be influenced by the choice of the monomers and additionally by adding one or more crosslinking agents. Monomers, for example, have a crosslinking action and have two or more functional groups which can react with the monomers forming the graft base or supports. If all functional groups of the polyfunctional monomer react at the same rate, these monomers only have a crosslinking effect. However, if the crosslinkers contain functional groups of different reactivity, the unreacted functional groups can be used as grafting sites, for example for attaching a graft to the graft base. nen. Such crosslinkers therefore not only have a crosslinking action but also have a grafting action.

The purposes for which graft copolymers can be used and how they influence optical quality, colorability, weather stability or crack formation in molding compositions depends on their structure but also on their size and morphology.

So far it has not been possible to produce graft copolymers (for example, those composed of a polystyrene core, a first shell made of polybutyl acrylate and a second shell made of styrene-acrylonitrile copolymers) of large particle size with a real core-shell structure, if core and Shell materials were incompatible with one another (see, for example, H. Okubo, Makromol. Chem.,

Macromol. Sym. 35/36 (1990) 307-325). From certain particle diameters of the graft base (from approx. 100 to 150 nm and total particle sizes from approx. 200 nm) it is shown in such graft copolymers that the graft base and coatings do not form a defined core-shell structure. The core is not completely and essentially concentrically enveloped by the graft. The graft base and overlays are partially mixed or the core material partially forms the outer phase boundary of the "core-shell" particle. This creates a raspberry-like morphology.

Therefore, the previously known graft copolymers with a defined core-shell structure whose core and shell materials are incompatible with one another have only small or only small core diameters in relation to the total size of the graft copolymers or they contain a graft base made of material which is compatible with that of the graft pads is.

The compatibility of two polymer components is generally understood to mean the miscibility of the components or the tendency of one polymer to dissolve in the other polymer component (see B. Vollmert, floor plan of macromolecular chemistry, Volume IV, p. 222 ff, E. Vollmert- Verlag 1979).

The lower the difference in their solubility parameters, the better tolerated two polymers are. Such parameters and the enthalpy of mixing cannot be determined uniformly for all polymers, so that the solubility can only be determined indirectly, for example by torsional vibration or DTA measurements. A miscible, ie compatible, system consisting of two or more polymers can be assumed at least if it meets at least one of the following criteria:

- optical clarity

A film made of mutually compatible polymers appears optically clear, but if they are incompatible, the film appears optically cloudy. If in doubt, an electron microscopic examination can determine the degree of segregation.

- Glass temperature:

Miscible with each other, i.e. Compatible polymers show only a glass temperature at thermal loads (DTA or DSC measurements), which lies between those of the starting polymers. In the case of partially compatible polymers, two different glass temperatures can be detected, but these move towards each other.

Nuclear Magnetic Resonance (NMR) Relaxation:

A very sensitive method is the determination of polymer miscibility by means of NMR relaxation time measurements. In the case of immiscible polymers, the spin-spin or spin-lattice relaxation times of the pure polymers are measured; in the case of miscible polymers, other relaxation times occur.

other methods:

Other applicable methods that can be used to determine the miscibility of polymers are turbidity measurements, scattering methods (light scattering), IR spectroscopy and fluorescence techniques (LA Utracki "Polymer Alloys and Blends", pp. 34-42, New York 1989). .

Examples of miscible polymers are extensively documented in various monographs (e.g. J. Brandrup, E.H. Immergut: Polymer Handbook, 3rd Edition, 1989).

For example, US Pat. No. 4,108,946 shows a graft base with a particle size of up to 240 nm made from crosslinked monomer mixtures of styrene / acrylonitrile or styrene / acrylonitrile / methyl ethacrylate, which is provided with a graft coating of acrylic esters. Pure polystyrene as a graft base is said to be undesirable. From DE-A 33 00 526 graft copolymers were known, each of which is composed of a non-elastic core with diameters up to 500 nm, preferably up to 200 nm, and a cross-linked acrylic ester shell. Methyl ethacrylate is preferably predominantly used for the monomer material of the core.

Likewise, US Pat. No. 3,793,402 graft copolymers were disclosed, the graft bases of which are crosslinked. Polyvinylbenzenes such as divinylbenzene or trivinylbenzene are described as crosslinking agents for graft bases, which preferably consist of styrene or substituted styrenes.

In addition, DE-A-22 44 519 graft copolymers were found which each contain a graft base based on vinyl aromatic compounds and up to 10% by weight of crosslinking monomers. Furthermore, DE-A-41 32 497 published graft copolymers whose graft bases are predominantly composed of vinylaromatic monomers and which can contain crosslinking agents which have a crosslinking and grafting action. According to the process described there, either graft copolymers can be obtained which contain small cores (up to approx. 150 nm) or those which have no defined core-shell morphology.

From DE-A 195 23 080 graft copolymers were known which contain a hard graft base with a particle size dso ^of at least 150 nm, a soft graft layer made from alkyl acrylate, and at least one further graft layer made from alkyl acrylate, and at least one further graft layer. The hard graft base contains, as crosslinking agent, monomers with two or more functional groups of different reactivity, and 0.1 to 25, preferably 0.5 to 10, particularly preferably 1 to 5% by weight of monomers with two or more functional groups same reactivity.

From DE-A 196 39 360 graft copolymers with a hard segment were known which, as crosslinking agents, had monomers with two or more functional groups of different reactivity, and 0.1 to 25, preferably 0.5 to 10 and particularly preferably 1 to 7% by weight. % Contains monomers with two or more functional groups of the same reactivity. The concentration of the crosslinker in the hard segment varies (crosslinker gradient along the segment).

The object of the present invention was to provide graft copolymers which consist of a crosslinked graft base and a graft overlay which is incompatible therewith have better impact strengths, especially at low temperatures, regardless of the processing temperature and which lead to low-temperature impact molding compounds. In addition, these graft copolymers should have large particle diameters and have a real core-shell structure with a defined phase boundary between the graft base and layers.

This object is achieved by the graft copolymers defined at the outset which, compared to the prior art, in particular DE-A 195 23 080 and DE-A 196 39 360, have significantly smaller amounts of crosslinking monomer with two or more functional groups contain the same reactivity.

Level A

According to the invention, the graft copolymers P contain 0.05 to 2.5, preferably 0.1 to 1 and particularly preferably 0.1 to 0.2% by weight, based on stages A to D, of a “hard” stage A. Material of stage A has a glass transition temperature Tg of at least 25 ° C, preferably at least 50 ° C, particularly preferably 80 to 130 ° C. Stage A is also called seed.

The glass transition temperatures were determined using differential scanning calorimetry (DSC). Details of this measurement method are described in Mark (ed.), Encyclopedia of Polymer Science and Engineering, Suppl. Vol., Wiley, New York, 1989, pp. 702-706. There were: T _Ξt a _r t: -100 ° C, T p _st0: + 180 ° C, heating rate: 10 ° C / min, Bestim ^¬ mung the Tg in the second run.

Stage A is composed of 50 to 99.5, preferably 70 to 99.9 and particularly preferably 90 to 99.9% by weight, based on A, of at least one vinylaromatic monomer a1). Examples of vinyl-aromatic monomers are styrene, α-methylstyrene or nuclear-alkylated styrenes such as p-methylstyrene or p-t-butylstyrene. Styrene, α-methylstyrene or p-methylstyrene or mixtures thereof are particularly preferably used. Styrene is very particularly preferably used.

In addition to the monomers a1), stage A can also contain monomers a2) which can be copolymerized therewith. Examples of such monomers are acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, methyl methacrylate, glycidyl methacrylate, maleic anhydride or vinyl methyl ether. Mixtures of different monomers a2) can of course also be used. The preferred monomers a2) include acrylonitrile and methyl methacrylate. According to the invention, the proportion of the mono- meren a2) from 0 to 49.9, preferably from 0 to 39% by weight, in particular from 0 to 38% by weight, based on A.

Furthermore, the graft base is made up of a crosslinking component a3). This is from 0.1 to 25% by weight, preferably from 0.5 to 10% by weight, particularly preferably from 1 to 5% by weight, based on A.

Crosslinking monomers a3) are bifunctional or polyfunctional comonomers, for example butadiene and isoprene, divinyl esters of

Dicarboxylic acids such as succinic acid and adipic acid, diallyl and divinyl ethers of bifunctional alcohols such as ethylene glycol and butane 1,4-diol, diesters of acrylic acid and methacrylic acid with the bifunctional alcohols mentioned, 1,4-divinyl benzene and triallyl cyanurate. The acrylic acid ester of tricyclodecenyl alcohol of the formula I below is particularly preferred

which is known under the name dihydrodicyclopentadienyl acrylate (DCPA), and the allyl esters of acrylic acid and methacrylic acid.

A particularly preferred seed level A consists of 95 to

99% by weight of styrene and 1 to 5% by weight of crosslinking agent, in particular DCPA. Very particularly preferably a seed stage A sus is 98 wt -.% Sty ^¬ rol and 2 wt .-% DCPA.

Stage A is prepared in a manner known to the person skilled in the art, for example in suspension, mass, solution or emulsion, preferably in emulsion and particularly preferably in aqueous emulsion. Details of the emulsion polymerization are further described in step C. The emulsion polymerization of stage A provides an aqueous dispersion of the smallest polymer particles, also called seed latex. The process conditions are set in a known manner so that stage A has particle sizes dso of usually 20 to 100, preferably 20 to 40 and particularly preferably 20 to 30 nm.

Level B

According to the invention, the graft copolymers P contain 9.8 to 30, preferably 9.8 to 20 and particularly preferably 9.8 to 17% by weight, based on A to D, of a “hard” stage B. Stage B consists of a material , which has a glass transition temperature of at least at least 25 ° C, preferably at least 50 ° C, in particular from 80 to 130 ° C. Level B is also known as the graft base.

Stage B is composed of from 50 to 99.8% by weight, preferably from 60 to 99% by weight, particularly preferably from 60 to 98% by weight, based on B, of at least one vinylaromatic monomer b1), such as it has already been described for the monomers a1). As with al), styrene, α-methylstyrene or p-methylstyrene or mixtures thereof are particularly preferably used. Styrene is particularly preferably used.

In addition to the monomers b1), stage B can also contain monomers b2) which are copolymerizable therewith, as have already been described for the monomers a2). Mixtures of different monomers b2) can of course also be used. As with a2), the preferred monomers b2) include acrylonitrile and methyl methacrylate. According to the invention, the proportion of monomers b2) is from 0 to 49.8, preferably from 0 to 39% by weight, in particular from 0 to 38% by weight, based on B.

Furthermore, stage B is made up of a crosslinker component b3). This is from 0.1 to 10% by weight, preferably from 0.1 to 5% by weight, particularly preferably from 0.1 to 2.5% by weight, based on B. The crosslinker component can be dihydrodicyclopentadienyl acrylate (α) of the formula (I) already given, alone or in combination with at least one other crosslinker with two or more functional groups of different reactivity (β). According to the invention, the crosslinking component consists of 0.1 to 100, preferably from 25 to 100% by weight, based on b3), of α and from 0 to 99.9, preferably from 0 to 75% by weight, based on α and ß, from ß. The crosslinking component particularly preferably contains from 50 to 100% by weight of α and from 0 to 50% by weight of β.

Examples of suitable crosslinkers β are ethylenically unsaturated monomers which carry epoxy, hydroxyl, carboxyl, amino or acid anhydride groups. These include hydroxyalkyl acrylates or hydroxyalkyl methacrylates such as hydroxy-Ci to Cio-alkyl acrylates or hydroxy-Ci- to Cio-alkyl methacrylates, especially hydroxyethyl acrylate or hydroxy-n-propyl acrylate. Also come allyl methacrylate, methallyl methacrylate, acryloylalkoxysilanes or methacryloylalkyloxysilanes of the general formula (II)

OH ₂ C = CR ² -C-0- (CH2) p-SiR ¹ 0 ( _3rd _n ) / ₂ ^(II) into which R ^{1 is} C ¹ -C ₃ -alkyl or phenyl, preferably methyl, R ^{2 is} hydrogen or methyl, n is an integer from 0 to 2 and p is an integer from 1 to 6, preferably from 1 to 4 represents. Examples are given

.beta.-methacryloyloxyethyldimethoxymethylsilane, γ-methacryloyloxy-n-propyImethoxydimethylsilan, γ-methacryloyloxy-n-propylmethoxymethylsilan, γ-methacryloyloxy - ropy1trimethoxysilan, γ-methacryloyloxy-n-propyldimethoxymethylsilane, γ-methacryloyloxy-n-propyldiethoxymethylsilan, δ-methacryloyloxy-n-butyldiethoxymethylsilan .

The preferred mixtures of the crosslinkers α and β include dihydrodicyclopentadienyl acrylate and hydroxy hylacrylate;

Dihydrodicyclopentadienyl acrylate and allyl methacrylate; Dihydrodicyclopentadienyl acrylate, hydroxyethyl acrylate and allyl methacrylate; Dihydrodicyclopentadienyl acrylate, allyl methacrylate and β-methacryloyloxyethyldimethoxymethylsilane; Dihydroxydicyclopenta - dienyl acrylate and ß-methacrylolyloxyethyldimethoxymethylsilane.

In addition, stage B is constructed according to the invention from 0.01 to below 0.5, preferably 0.01 to 0.4, particularly preferably 0.03 to 0.3 and very particularly preferably 0.04 to 0.28% by weight. %, based on B, of at least one crosslinker b4) with two or more functional groups of the same reactivity.

In principle, components b3) and b4) can be in any relation to one another. Preferred stages B, however, contain components b3) and b4) in a ratio of 1: 0.75 to 1: 5. The proportion of component b4) can, however, also be less, for example up to 1: 0.5. Higher proportions of b4) are also possible. The ratios from b3) to b4) can be up to 1:10. The ratios of b3) to b4) are particularly preferably from 1: 0.8 to 1: 3, or 1: 1 to 1: 3, in particular from 1: 0.9 to 1: 2, for example 1: 1 or 1: 1.5.

Suitable crosslinkers b4) are, for. B .:

Mono-, di-, tri- or tetra -Alkylenglycoldiacrylate, preferably C _l - to C mono-alkylene glycol such as ethylene glycol diacrylate, n-propylene glycol, 1, 3-n-butylene glycol or 1, 4-n-butylene glycol diacrylate, Mono-, di-, tri- or tetra-alkylene glycol dimethacrylates, preferably C ₁ -C ₄ -mono-alkylene glycol dimethacrylates such as ethylene glycol dimethacrylate, n-propylene glycol dimethacrylate, 1, 3-n-butylene glycol dimethacrylate or 1, 4-n-butylene glycol dimethacrylate,

Acrylates or methacrylates of glycerol, trimethylolpropane, pentaerythritol, inositol or similar sugar alcohols,

Acrylic or methacrylamides of ethylenediamine or other aliphatic diamines or polyamines,

Diallyl maleate, diallyl fumarate or diallyl phthalate,

Triacrylamides or trimethacrylamides,

Trially cyanurate or triallyl isocyanurate,

Vinylbenzenes such as divinylbenzene or trivinylbenzene. Divinylbenzene is particularly preferably used as crosslinker b4).

The choice of crosslinker b4) depends on the type of network that stage B should have. A compact network results, for example, when crosslinker α is used together with divinylbenzene, while a relatively loose network is obtained, e.g. Crosslinker α is used together with tetraethylene glycol diacrylate or dimethacrylate. The particularly preferred crosslinker mixtures include DCPA and butanediol diacrylate; DCPA and divinylbenzene; DCPA and diethylene glycol diacrylate as well as DCPA and tetraethylene glycol dimethacrylate. A crosslinker mixture of DCPA and divinylbenzene is very particularly preferred.

Further preferred DCPA, butanediol and allyl methacrylate ^¬; DCPA, butanediol diacrylate and hydroxyethyl acrylate; DCPA, butanediol diacrylate and divinylbenzene; DCPA, hydroxyethyl acrylate and divinylbenzene or diethylene glycol diacrylate or tetraethylene glycol diacrylate; DCPA, hydroxyethyl acrylate, allyl methacrylate and divinylbenzene or diethylene glycol diacrylate or tetraethylene glycol dimethacrylate; DCPA, allyl methacrylate, β-methacryloyloxyethyldimethoxymethylsilane and divinylbenzene or diethylene glycol diacrylate or tetraethylene glycol dimethacrylate; DCPA, β-methacryloyloxyethyldimethoxymethylsilane and divinylbenzene or diethylene glycol diacrylate or tetraethylene glycol dimethacrylate. Stage B is prepared by methods which are known, such as suspension, mass, solution or emulsion, preferably in emulsion. Details of emulsion polymerization are given below at level C.

According to the invention, stage B has a particle size (dso) of 100 to 350 nm, preferably 150 to 350 nm and particularly preferably 180 to 300 nm. The process conditions, in particular the polymerization time and temperature, and the type, amount and mode of addition of the emulsifier, are described in the Those skilled in the art are chosen in such a way that corresponding particle sizes result.

In all cases, the average particle size is the weight average of the particle size, as determined using an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z. and Z. Polymers 250 (1972), pages 782 to 796. The ultracentrifuge measurements provide the integral mass distribution of the particle diameter of a sample. From this it can be seen what percentage by weight of the particles have a diameter equal to or smaller than a certain size. The average particle diameter, which is also referred to as the dso value of the integral mass distribution, is defined as the particle diameter at which 50% by weight of the particles have a smaller diameter than the diameter which corresponds to the dso value. Likewise, 50% by weight of the particles then have a larger diameter than the dso value.

Stage B generally has a gel content of at least 90%, preferably at least 95%, the gel content being defined as the ratio of the mass insoluble in the solvent (toluene) to the total mass. The swelling index is the ratio of swollen to unswollen mass in the solvent (toluene) and is generally from 7 to 15 for stage B.

Level C

According to the invention, the graft copolymers P contain 30 to 70, preferably 40 to 60 and particularly preferably 45 to 55% by weight, based on stages A to D, of a “soft” stage C. Stage C is distinguished by the fact that their glass transition temperature is at most 0 ° C, preferably at most -20 ° C, in particular from -100 to -30 ° C.

For the grafting of stage B, at least one Ci-Ciβ-alkyl acrylate cl) and, if desired, at least one monomer c2) and copolymerizable with the monomers cl) are used in the presence of stage B and polymerized at least one crosslinker α or β or their mixtures c3). According to the invention, the proportion of the alkyl acrylates cl) is from 50 to 100% by weight, that of the monomers c2) from 0 to 50% by weight and that of the crosslinking agent c3 is 0.01 to 20% by weight. Preferred stages C are composed of from 60 to 99.9, in particular from 65 to 99% by weight of cl), from 0 to 39.9, in particular from 0 to 30% by weight of c2) and from 0.1 to 10, in particular from 1 to 5 wt. c3). The weights given relate to C.

As monomers cl), acrylic acid alkyl esters, acrylic acid phenylalkyl esters or acrylic acid phenoxyalkyl esters with up to 18 C atoms, in particular those with 2 to 8 C atoms in the alkyl radical, alone or as a mixture, come into consideration. In particular, n-butyl acrylate and ethylhexyl acrylate, e.g. Acrylaurethyl-n-hexyl ester as well as acrylic acid phenyl-n-propyl ester or acrylic acid phenoxy-ethyl ester are suitable.

Examples of the monomers c2) are acrylic acid or methacrylic acid derivatives different from cl), including preferably their esters or amides. In addition, styrene, nucleus-substituted styrenes, α-methylstyrene, acrylonitrile, and further rubber-forming monomers such as 1,3-butadiene, isopes, chloroprene and organosiloxanes such as dimethylsiloxanes are possible as copolymerizable monomers c2). Mixtures of different monomers c2) can of course also be used.

For the preparation of stage C, at least one crosslinker α or β or a mixture thereof is used according to the invention as component c3), the same crosslinkers β being used as for the preparation of stages A and B. However, others can also be used independently of stages A and B. Crosslinker ß can be used.

The graft copolymers according to the invention are produced, for example, in suspension, mass, solution or emulsion, preferably in emulsion and particularly preferably in aqueous emulsion. The process conditions (see also step B) are adjusted in a known manner so that step C has particle sizes dso of usually 250 to 600, preferably 350 to 550 and particularly preferably 350 to 500 nm.

The usual emulsifiers such as alkali metal salts of alkyl or alkylarylsulphonic acids, alkyl sulphates, fatty alcohol sulphonates, salts of higher fatty acids with 10 to 30 carbon atoms or resin soaps can be used for the production in aqueous emulsion. Sodium salts of alkyl sulfonates or of fatty acids with 10 to 18 carbon atoms are preferably used. To be favoured Emulsifiers in amounts of 0.3 to 5% by weight, in particular 1 to 2% by weight, based on the total weight of the monomers.

The usual persulfates, such as potassium peroxodisulfate, are used in particular as polymerization initiators; however, redox systems which allow lower polymerization temperatures are also suitable. The amount of initiators (e.g. from 0.1 to 1% by weight, based on the total weight of the monomers used for the preparation of the graft base A) depends in a known manner on the desired molecular weight.

The usual buffer substances, by means of which pH values of preferably 6 to 9 are set, can be used as polymerization aids, e.g. Sodium bicarbonate or sodium pyrophosphate, and molecular weight regulators such as mercaptans, terpinols or dimeric α-methylstyrene can be used. The molecular weight regulators are generally used in amounts of up to 3% by weight, based on the total weight of the monomers used for the preparation of the graft base A.

For the production of stage B, stage A, ie a cross-linked seed latex made of vinyl aromatic and a cross-linking agent, is first produced. The seed latex is then reacted to stage B with further monomers, crosslinking agents, emulsifiers, polymerization auxiliaries and initiators.

The emulsifiers, initiators and polymerization auxiliaries can each be introduced independently of one another or can be added independently during the polymerization at once, in several portions, as a gradient (e.g. ascending, descending, step function) or as a uniform feed. Mixed forms of these methods of addition are also possible.

It is advantageous to again carry out the graft copolymerization of the monomers forming stage C to stage B in an aqueous emulsion.

It is preferably carried out in the same system as the polymerization in stage B, it being possible for further emulsifier and initiator to be added. These may, but need not be identical to the emulsifiers or initiators used to prepare B. Emulsifier, initiator and polymerization auxiliaries can each be introduced alone or in a mixture together with the emulsion of stage B. However, they can also be added to the emulsion of B alone or in a mixture together with the monomers used for stage C. It can be used for Example of the initiator and as a polymerization aid, a buffer substance is presented together with the emulsion of stage B, and then the monomers for the graft pads C are added dropwise together with the emulsifier. 5

Stage B (graft base) and stage C are preferably polymerized in succession in a one-pot process.

The graft copolymerization is generally controlled so that a mass ratio of stage B to stage C of preferably 1: 0.5 to 1:20, particularly preferably 1: 1 to 1:10 results. Very particularly preferred graft copolymers according to the invention have mass ratios of B to C of 1: 3 to 1: 8.

15 level D

According to the invention, the graft copolymers P contain 20 to 60, preferably 25 to 50 and particularly preferably 28 to 45% by weight, based on A to D, of a “hard” stage D. The material of stage 20 has a glass transition temperature of at least 25 ° C, preferably at least 50 ° C, particularly preferably at least 90 ° C.

Stage D is composed of 50 to 100, preferably 60 to 99, particularly preferably 65 to 85 and very particularly preferably 70 to 25 80% by weight of at least one vinylaromatic monomer dl), as already mentioned in al). Styrene or α-methylstyrene are preferably used, particularly preferably styrene.

In addition to the monomers d1, stage D can also contain monomers d2) copolymerizable therewith, as have already been mentioned for a2). Mixtures of different monomers d2) can of course also be used. Preferred monomers d2) are acrylonitrile and methacrylonitrile, in particular acrylonitrile. According to the invention, the proportion of d2) is 0 to 50, preferably 1 35 to 40, particularly preferably 15 to 35 and in particular 20 to 30% by weight, based on D.

Stage D preferably contains no crosslinking monomers. D particularly preferably consists of styrene (and / or α-methylstyrene) and 40 acrylonitrile.

It is advantageous to carry out the graft copolymerization of stage D again in an aqueous emulsion in the presence of the graft copolymer from A, B and C which serves as the graft base. However, the graft polymerization can also take place in suspension, in bulk or in solution. It can be carried out in the same system as the polymerization of the graft copolymer from A, B and C, where further emulsifier and initiator can be added. These may, but do not need to be identical to those used to prepare stages A, B and C. For the rest, what has been said in the preparation of stage C applies to the choice and combination of emulsifiers and polymerization auxiliaries.

The graft copolymers P according to the invention have average particle sizes (dso) from 300 to 750, preferably from 400 to 600 nm. Particularly preferred graft copolymers of the invention have average particle diameters (dso) i ^m the range of 450 to 550 nm. The graft copolymers of the invention may auweisen both a narrow and broad particle size distribution. They preferably have a narrow particle size distribution. The particle size distribution is defined as the quotient Q = (dgo-dio) / dso. The dχo or dgo value is defined analogously to the dso value, with the difference that it is based on 10 or 90% by weight of the particles. Particularly preferred graft copolymers according to the invention have Q values of 0.3 or less, in particular 0.15 or less.

Even with large particle sizes of the graft base or a large ratio of stage B to stage C, the graft copolymers according to the invention have an almost perfect core-shell morphology. Stage B forms a core with a defined phase boundary to the stage C graft. It is essentially concentrically enveloped by the stage graft C. As a rule, the distance between the phase boundary B to C and that from C to D is on average at least 5, preferably at least 10 nm over the entire essentially concentric graft layer C, the distance being able to be determined by electron microscopy. For this purpose, sections with a thickness of less than 100 nm are made using a cryo-ultramicro and these are steamed with ruthenium tetroxide at 30 ° C. for 20 minutes. Only the particles cut at the equator are measured and the mean value of the distance between the phase boundary B / C and C / D of 10 particles is determined.

The graft copolymers P according to the invention can be used both alone and as a mixture with other graft copolymers or copolymers. They are suitable as impact modifiers for thermoplastic molding compositions. The graft copolymers according to the invention are particularly suitable as impact modifiers for thermoplastics which have a glass transition temperature of 25 ° C. or above, preferably above 60 ° C., in particular above 80 ° C. Examples are polyvinyl chloride (PVC), poly ethyl methacrylate, and copolymers of vinyl aromatic monomers and polar, copolymerizable ethylenically unsaturated monomers. Particularly preferred copolymers are Styrene-acrylonitrile copolymers or α-methylstyrene-acrylonitrile copolymers. In addition, the thermoplastic molding compositions can contain other thermoplastics, in particular polycarbonates.

The mixtures M according to the invention contain, based on M, 5 to 95, preferably 10 to 60 and particularly preferably 10 to 40% by weight of the graft copolymers P and 5 to 95, preferably 40 to 90 and particularly preferably 60 to 90% by weight at least one further graft copolymer P 'with a defined core-shell morphology. The further graft copolymer P 'consists of at least three stages, at least one of the stages having a glass transition temperature of at least 25 ° C (ie "hard") and at least one of the stages having a glass transition temperature of at most 0 ° C (ie "soft") ).

Seven further graft copolymers P'-1 to P '-7 are mentioned as examples. The monomers used for the individual stages, their proportions and the particle diameters are shown in Table 1 below. In the "Comonomers" line, the numerical ranges below one another indicate the% by weight, preferred% by weight and particularly preferred% by weight, in each case based on the particular stage. In the line "proportion of P '", the numerical ranges below one another indicate the% by weight, preferred% by weight and particularly preferred% by weight, in each case based on the further graft copolymer P'.

The line "dso" indicates the particle sizes d ₅₀ , the preferred d ₅₀ and the particularly preferred dso one below the other. The dso values given relate to the mean diameters of the corresponding stages of the graft polymer.

It means:

AN acrylonitrile S styrene DVB divinylbenzene n-BA n-butyl acrylate DCPA dihydrodicyclopentadienyl acrylate

First pure styrene, then S / AN, whereby the styrene is not allowed to polymerize before adding S / AN (smeared transition). The styrene seg makes 1/3, S / AN makes 2/3 of the level.

b) styrene / AN mixture (no homopolystyrene segment)

As can be seen from the table, the further graft copolymers P 'can have, for example, the following step sequences (H hard, W soft, H * hard with a smeared transition within the hard step):

P '- 1 H W H *

P '- 2 H H W H *

P '- 3 H W H

P '- 4 H H W H

P '- 5 W H W H

P '- 6 H W H

P '- 7 H H W H

The further graft copolymers P 'can be prepared in the same way as the graft copolymers P.

Particularly preferred mixtures M contain, for example, P and one of the graft copolymers P 'selected from P'-1, P'-2, P'-3, P'-4, P'-5, P'-6 and P'-7.

The themoplastic molding compositions F according to the invention contain

i) 5 to 95% by weight of at least one graft copolymer P as described above,

ii) 5 to 95% by weight of at least one copolymer CP

iia) 50 to 100 wt .-% of at least one vinyl aromatic monomer, C] _- to Ciβ-alkyl acrylate, Ci bis

Ci ₈ alkyl methacrylates or mixtures thereof and

ü) 0 to 50 wt .-% acrylonitrile, methacrylonitrile, maleic anhydride, N-substituted maleimides or mixtures thereof, and

iii) 0 to 50% by weight of additives.

Component ii)

In addition to component i), the molding compositions F contain, as component ii), one or more copolymers in amounts of 5 to 95% by weight, based on F. Preferred molding compositions contain from 20 to 79.9, in particular from 40 to 74.9,% by weight .-%, based on F, of component ii). Particularly preferred copolymers ii) contain from 60 to 80% by weight, based on ii), of monomers iia) and from 20 to 40% by weight, based on ii), of monomers)). Preferred copolymers ii) are those of at least one monomer from the group styrene, α-methylstyrene, nucleus-substituted styrenes such as p-methylstyrene and methyl methacrylate, copolymerized with at least one monomer from the group acrylonitrile, methacrylonitrile and maleic anhydride.

Particularly preferred copolymers ii) are those made from styrene, acrylonitrile and optionally methyl methacrylate. Other particularly preferred copolymers ii) contain α-methylstyrene, acrylonitrile and optionally methyl methacrylate. In addition, copolymers III of styrene and α-methylstyrene and acrylonitrile and optionally methyl methacrylate are particularly preferred. Furthermore, copolymers of styrene and maleic anhydride are among the particularly preferred copolymers ii). The copolymers ii) are generally resin-like, thermoplastic and rubber-free.

The copolymers ii) are known per se or can be prepared by methods known per se, such as free-radical polymerization, in particular by emulsion, suspension, solution or bulk polymerization. They generally have viscosity numbers in the range from 40 to 160, preferably from 60 to 100 (ml / g). This corresponds to molecular weights (weight average) M _w between 15,000 and 2,000,000 g / mol.

The copolymers ii) are also frequently formed in the graft copolymerization to produce the graft copolymers P according to the invention or the graft copolymers P 'as by-products, particularly when large amounts of monomers are grafted onto small amounts of a graft base.

Component iii)

The thermoplastic molding compositions F may contain additives as component iii). Their proportion is generally from 0 to 50, preferably from 0.1 to 20,% by weight, based on F.

Common additives are, for example, glass fibers, flame retardants, stabilizers and oxidation retardants, agents against heat decomposition and decomposition by ultraviolet light, lubricants and mold release agents, dyes and pigments or plasticizers. Glass fibers made of E, A or C glass can be used. The glass fibers are usually equipped with a size and an adhesion promoter. The diameter of the glass fibers is generally between 6 and 20 μm. Both continuous fibers (rovings) and chopped glass fibers with a length of 1 to 10 mm, preferably 3 to 6 mm, can be incorporated.

Pigments and dyes are generally present in amounts of up to 6, preferably from 0.5 to 5 and in particular from 0.5 to 3% by weight, based on F.

The pigments for coloring thermoplastics are generally known, see e.g. R. Gächter and H. Müller, Taschenbuch der Kunststoffadditive, Carl Hanser Verlag, 1983, pp. 494 to 510.

Oxidation retarders and heat stabilizers which can be added to the thermoplastic molding compositions according to the invention are e.g. Group I metals of the Periodic Table, e.g. Sodium, potassium, lithium halides, optionally in combination with copper (I) halides, e.g. Chlorides, bromides or iodides. The halides, especially of copper, can also contain electron-rich π ligands. Examples of such copper complexes are Cu halide complexes with e.g. Called triphenylphosphine. Zinc fluoride or zinc chloride can also be used. Sterically hindered phenols, hydroquinones, substituted representatives of this group, secondary aromatic amines, optionally in combination with phosphorus-containing acids or their salts, and mixtures of these compounds, preferably in concentrations of up to 1% by weight, based on F, can be used.

Examples of UV stabilizers are various substituted resorcinols, salicylates, benzotriazoles and benzophenones, which are generally used in amounts of up to 2% by weight, based on F.

Lubricants and mold release agents, which are generally added in amounts of up to 1% by weight of the thermoplastic molding compositions, are stearic acid, stearyl alcohol, alkyl stearates and amides, and esters of pentaerythritol with long-chain fatty acids. Salts of calcium, zinc or aluminum of stearic acid and dialkyl ketones, e.g. Distearyl ketone can be used.

Examples of plasticizers are dialkyl phthalates such as dioctyl phthalate. The thermoplastic molding compositions F can be prepared by processes known per se by mixing the components in conventional mixing devices such as screw extruders, Brabender mills or Banbury mills at temperatures of usually 150 to 5 350 ° C., preferably 200 to 280 ° C. and then extruded. After the extrusion, the extrudate is cooled and crushed.

The thermoplastic molding compositions are notable for high impact strength, particularly at low temperatures. At the same time, the thermoplastic molding compositions have a high resistance to weathering and aging. They can also be colored well.

They can be processed into shaped bodies, films or fibers.5 They can also be used, for example, by means of known coextrusion processes in the form of layers (preferably in layer thicknesses in the range from 100 μm to 10 mm) on surfaces, preferably on thermoplastics such as styrene-acrylonitrile copolymers , Acrylonitrile-butadiene-styrene terpolymers (ABS), polystyrene, impact-resistant polystyrene (HIPS) or PVC. The molding compounds can be used, for example, in the automotive sector, household sector and for leisure articles. So you can e.g. into automotive parts, street signs, window profiles, lamp covers, garden furniture, boats, surfboards or children's toys.

Examples

Application tests 0

The particle sizes (weight average values dso) were determined using an analytical ultracentrifuge according to the method described in W. Scholtan, H. Lange, Kolloid-Z. and Z.-Polymers 250 (1972) pages 782 to 796. 5

The ultracentrifuge measurement provides the integral mass distribution of the particle diameter of a sample. From this it can be seen what percentage by weight of the particles have a diameter equal to or smaller than a certain size. The mean particle diameter, which is also referred to as the d ₅₀ value of the integral mass distribution, is defined as the value at which 50% by weight of the particles have a smaller diameter and 50% by weight of the particles have a larger diameter than the dso Have value. 5 The notched impact strengths (a * [kJ / m ² ]) were measured at 0 ° C according to ISO 179 / leA on standard small bars injected at 270 ° C and then milled (A-notch). The mean value from the test of 10 samples is given in each case.

The solids content of the emulsions denotes the content of all solids contents in percent by weight based on the total mass of the respective emulsion.

Production of the graft copolymers P

a) Production of stage A: seed latex from cross-linked polystyrene

4500 g of water, 30 g of the Na salt of a Cχ ₂ - to cis paraffinsulfonic acid, 9 g of potassium peroxodisulfate, 12 g of sodium hydrogen carbonate and 1 g of sodium pyrophosphate were heated to 70 ° C. with stirring and under nitrogen. A mixture of 2940 g styrene and 40 g dihydrodicyclopentadienyl acrylate (DCPA) was added over 3 hours. After the monomer addition had ended, the emulsion was kept at 60 ° C. for 1 hour. The PS seed latex thus obtained had an average particle diameter dso of 85 nm. The solids content of the PS seed latex emulsion was 15%.

b) Production of stage B: hard stage from cross-linked polystyrene

3200 g of water, 2 g of sodium hydrogen carbonate, 1.5 g of sodium persulfate and 127 g of the polystyrene seed latex from a) were heated to 70 ° C. with stirring and under nitrogen. Inlets 1 and 2 were then added simultaneously at 70 ° C. within one hour. After the monomer addition had ended, the mixture was kept at 70 ° C. for one hour.

Feed 1: styrene: see table 2 DCPA: 11 g

Divinylbenzene: see Table 2 Feed ₂ : sodium salt of a Cχ ₂ bis cis paraffinsulfonic acid,

40% by weight solution in water: 8 g

The average particle size dso was 250 nm. The dispersion had a solids content of 15%.

c) Preparation of stage C: soft stage from crosslinked polybutyl acrylate 360 g of water, 6 g of sodium hydrogen carbonate and 5 g of sodium persulfate were added to the dispersion obtained in b), the mixture being stirred and kept at 65.degree. Feeds 3 and 4 were then added simultaneously at 65 ° C. over the course of 2 hours. After the monomer addition had ended, the mixture was kept at 65 ° C. for a further 2 hours.

Feed 3: n-butyl acrylate: 1730 g

DCPA: 35 g feed 4: as feed 2, but 26 g

10

The average particle size dso was 380 nm and the solids content of the dispersion was 39%.

d) Preparation of stage D: hard stage from uncrosslinked poly-15 styrene acrylonitrile

The dispersion obtained in c) was 2600 g of water, 4 g of sodium persulfate and 13 g of a 40 wt. -% solution of the sodium salt of a Cχ ₂ - to C ^ -paraffinsulfonic acid in water with stirring at 20 65 ° C. Feed 5 was then added at 65 ° C. in the course of 2 hours. After the monomer addition had ended, the mixture was kept at 65 ° C. for a further 2 hours.

Feed 5: styrene: 785 g 25 acrylonitrile: 260 g

The mean particle size dso was 480 nm and the solids content was 35%.

30 Isolation of the graft copolymers P

The graft copolymers were precipitated from the dispersion obtained in d) by adding CaSO solution. The separated polymer was washed with water and dried with warm air.

35

Production of the thermoplastic molding compounds F

A styrene / acrylonitrile copolymer with 35% by weight acrylonitrile and a viscosity number VZ of

40 81 ml / g used. The dried graft copolymer P was mixed with the copolymer CP on a twin-screw extruder ZSK 30 (Werner and Pfleiderer) in such a way that the resulting molding composition F had a graft copolymer P content of 29% by weight. Moldings were made from this molding compound by injection molding

45 manufactured. Table 2 below summarizes the results. The "DVB share" corresponds to the weight percent of component b4), based on B.

Table 2:

a) Share of divinylbenzene in the monomers of stage B

The table shows that graft copolymers whose stage B contains no crosslinker b4) (here divinylbenzene) copolymerized with two or more functional groups of the same reactivity give molding compositions with low cold impact strength (comparative experiment IV).

Graft copolymers which - not according to the invention - contain the crosslinking agent b4) in a proportion of 0.5% by weight or more, based on stage B, also have low a _κ values (comparative experiments 6V to 8V).

In contrast, graft copolymers according to the invention which contain the crosslinker b4) in a proportion of 0.01 to less than 0.5% by weight, based on B, give molding compositions with excellent notched impact strength in the cold (tests 2 to 5).

Claims

claims

1. Graft copolymers P with a defined core-shell morphology and an average particle size (dso) of 300 to 750 nm, containing, based on P,

al) 50 to 99.9% by weight of at least one vinylaromatic

Monomers, a2) 0 to 49.9% by weight of at least one monomer copolymerizable with the monomers al), and a3) 0.1 to 25% by weight of at least one crosslinking monomer,

bl) 50 to 99.8% by weight of at least one vinyl aromatic

Monomers, b2) 0 to 49.8% by weight of at least one monomer copolymerizable with the monomers b1), b3) 0.1 to 10% by weight of a crosslinking component, based on b3),

C) 30 to 70% by weight of a stage C with a glass transition temperature of at most 0 ° C., based on C,

cl) 50 to 100% by weight of at least one -C ₈ alkyl acrylate, c2) 0 to 50% by weight of at least one monomer copolymerizable with the monomers cl), and c3) 0.01 to 20% by weight of at least one crosslinking agent α or β or a mixture thereof,

dl) 50 to 100% by weight of at least one vinyl aromatic

Monomers d2) 0 to 50% by weight of at least one monomer copolymerizable with the monomers dl).

2. Graft copolymers according to claim 1, in which styrene or α-methylstyrene or a mixture thereof is used as the vinyl aromatic monomer al), bl) and / or dl).

3. Graft copolymers according to Claims 1 to 2, in which n) butyl acrylate or 2-ethylhexyl acrylate or a mixture thereof is used as monomer cl).

4. Graft copolymers according to claims 1 to 3, in which acrylonitrile or methacrylonitrile or a mixture thereof is used as monomer d2).

5. Graft copolymers according to Claims 1 to 4, in which divinylbenzene is used as crosslinker b4).

6. Mixtures containing M, based on M,

P) 5 to 95% by weight of the graft copolymers P according to claims 1 to 5, and

P ') 5 to 95% by weight of at least one further graft copolymer P' with a defined core-shell morphology which contains at least three stages, at least one of the stages having a glass transition temperature of at least 25 ° C. and at least one of the stages having a glass transition temperature of at most 0 ° C.

7. Thermoplastic molding compositions F containing, based on F,

i) 5 to 95% by weight of graft copolymers P according to claims 1 to 5 or mixtures M according to claim 6, ii) 5 to 95% by weight of at least one copolymer CP based on CP,

iia) 50 to 100% by weight of at least one vinylaromatic monomer, Ci-Cis-alkyl acrylate, Ci-Cia-alkyl methacrylate or mixtures thereof, ü) 0 to 50 wt .-% acrylonitrile, methacrylonitrile, maleic anhydride, N-substituted maleimides or mixtures thereof, and

iii) 0 to 50% by weight of additives.

8. Use of the graft copolymers P according to claims 1 to 5 or the mixtures M according to claim 6 as an impact modifier for thermoplastic molding compositions.

10

9. Shaped bodies or films containing graft copolymers P according to claims 1 to 5 or mixtures M according to claim 6.

15 10. Shaped bodies or films, made of thermoplastic molding compositions F according to claim 7.

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