Thermoplastic moulding materials.

0001The invention relates to thermoplastic molding compositions containing as essential components<ul id="ul0001" list-style="none"><li>A) 45 to 85% by weight of a thermoplastic polyester composed of terephthalic acid or a predominant proportion of terephthalic acid and a diol,</li><li>B) 5 to 30% by weight of a graft copolymer with an average particle diameter of 50 to 200 nm, built up from<ul id="ul0002" list-style="none"><li>b1) 50 to 90% by weight of a graft core<ul id="ul0003" list-style="none"><li>b1.1) 75 to 99.9% by weight of a (C₂ to C₁₀ alkyl) acrylate</li><li>b1.2) 0.1 to 5% by weight of a monomer with at least two olefinic non-conjugated double bonds and</li><li>b1.3) up to 24.9% by weight of further copolymerizable monomers</li></ul></li></ul> and<ul id="ul0004" list-style="none"><li>b2) 10 to 50% by weight of a graft shell<ul id="ul0005" list-style="none"><li>b2.1) 50 to 90 wt .-% styrene or a polymerizable styrene derivative and</li><li>b2.2) 10 to 50% by weight of acrylonitrile or methacrylonitrile,</li></ul></li></ul></li><li>C) 5 to 30 wt .-% of a graft copolymer with an average particle diameter of 250 to 1000 nm, built up from<ul id="ul0006" list-style="none"><li>c1) 50 to 90% by weight of a graft core<ul id="ul0007" list-style="none"><li>c1.1) 75 to 99.9% by weight of a (C₂ to C₁₀ alkyl) acrylate</li><li>c1.2) 0.1 to 5% by weight of a monomer with at least two olefinic non- conjugated double bonds</li><li>c1.3) to 24.9% by weight of further copolymerizable monomers and</li></ul></li></ul> c2) 10 to 50% by weight of a graft shell<ul id="ul0008" list-style="none"><li>c2.1) 50 to 90 wt .-% styrene or a polymerizable styrene derivative and</li><li>c2.2) 10 to 50% by weight of acrylonitrile or methacrylonitrile,</li></ul></li></ul> and<ul id="ul0009" list-style="none"><li>D) 5 to 25% by weight of a copolymer<ul id="ul0010" list-style="none"><li>d1) 50 to 90% by weight of styrene or a polymerizable styrene derivative and</li><li>d2) 10 to 50% by weight of acrylonitrile or methacrylonitrile.</li></ul></li></ul>

0002In addition, the invention relates to the use of such molding compositions for the production of moldings and moldings which are obtainable as essential components from the molding compositions according to the invention.

0003DE-A 2 758 497 describes thermoplastic molding compositions based on mixtures of polyalkylene terephthalates and rubber-elastic copolymers, so-called ASA polymers, of various acrylic acid esters and α-methylstyrene which are grafted with styrene-acrylonitrile copolymers. These molding compounds are suitable for the production of moldings such as, in particular, foils and housings for electrical devices. However, the mechanical properties are still not entirely satisfactory overall, particularly with regard to toughness.

0004Mixtures are known from EP-A 6 503 which consist of ASA polymers with a bimodal particle size distribution and of copolymers of styrene and / or α-methylstyrene with acrylonitrile. These molding compositions are easier to color than molding compositions with a statistical particle size distribution and have better mechanical properties.

0005An important property of the plastic parts made from thermoplastic materials, such as device housings, is their resistance to mechanical stress such as impact or impact. The multiaxial toughness of the plastics is of particular importance for this. It is determined by measuring the energy required to vertically pierce a disk-shaped plastic test specimen.

0006The object of the present invention was to provide thermoplastic molding compositions based on polyesters and graft polymers, in particular ASA polymers, which have improved toughness. In particular, the multiaxial toughness should be improved without impairing the other mechanical and application properties of these molding compositions.

0007We have found that this object is achieved by the thermoplastic molding compositions defined at the outset.

0008The molding compositions according to the invention contain<ul id="ul0011" list-style="none"><li>A) 45 to 85, preferably 50 to 76 and in particular 60 to 70% by weight of a thermoplastic polyester (A) composed of terephthalic acid or dicarboxylic acids with a predominant proportion of terephthalic acid and a diol</li><li>B) 5 to 30, preferably 8 to 25 and in particular 10 to 20% by weight of a finely divided graft copolymer (B),</li><li>C) 5 to 30, preferably 8 to 25 and in particular 10 to 20% by weight of a coarse-particle graft copolymer (C) and</li><li>D) 5 to 25, preferably 8 to 20 and in particular 10 to 15% by weight of a copolymer (D) composed of styrene or styrene derivatives with acrylonitrile or methacrylonitrile.</li></ul>

Polyester (A)

0009The thermoplastic polyesters (A) are obtained in a manner known per se by polycondensation of a dicarboxylic acid or a functional derivative of the dicarboxylic acid with a diol. Dimethyl esters are particularly suitable as functional derivatives of dicarboxylic acids.

0010Only terephthalic acid is preferably used as the dicarboxylic acid. However, up to 50, preferably up to 20 mol% of the terephthalic acid can be replaced by further dicarboxylic acids such as the naphthalenedicarboxylic acids, isophthalic acid, phthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acids and the cyclohexanedicarboxylic acids and mixtures of these carboxylic acids.

0011The diols used are primarily butane-1,4-diol or ethylene glycol, but also other diols such as 1,6-hexanediol, neopentyl glycol, cyclohexane-1,4-diol, 1,4-bis (hydroxymethyl) cyclohexane and Butene-1,4-diol and 4,4'-dihydroxy-diphenyl-methane, and mixtures of 1 to 20 mol% of these diols and the rest of butane-1,4-diol or ethylene glycol.

0012The viscosity number of the polyester (A), measured on a 0.5% by weight solution in a phenol / o-dichlorobenzene mixture (weight ratio 1: 1) at 25 ° C., is preferably in the range from 50 to 250 cm 3 / g, preferably from 70 to 170 cm³ / g. This corresponds to a molecular weight of approximately 10,000 to 30,000.

Graft copolymers (B) and (C)

0013The structure and the production of both the coarse-particle and the fine-particle graft copolymers (B) and (C) and their mixtures are known per se (cf., for example, EP-A 6 503).

0014It is essential to the invention that the graft copolymers (B) and (C) have different average particle diameters and that the particle diameter distributions do not substantially overlap.

0015The finely divided graft copolymer (B) has an average particle diameter (abbreviated: d₅₀) from 50 to 200, preferably from 80 to 150 nm.

0016The average particle diameter (d₅₀) of the coarse-particle graft copolymer (C) is 250 to 1000, preferably 350 to 800 nm.

0017Here d₅₀ is defined as the particle diameter in which the proportion of particles with a particle diameter below d₅₀ is less than 50% by weight. This particle diameter can be determined using an analytical ultracentrifuge using the method of W. Scholtan and H. Lange, Kolloid-Z., And Z.-Polymerisate<u>250</u> (1972) pages 782 to 796.

0018It is advantageous if the particle size distribution of the respective fine and coarse fraction is narrow, which is of particular importance for the coarse fraction.

0019The particle size distribution can be determined by the quotient<maths id="math0001" num=""><math display="inline"><mrow><mtext>Q = (d₉₀ - d₁₀) / d₅₀</mtext></mrow></math><img file="EP0643104A2_D0001.tif" /></maths> express. The particle diameter d₉₀ and d₁₀ are defined accordingly d₅₀, with the difference that they are based on 10 and 90 wt .-% of the particles.

0020For the quotient Q, values ​​of less than 0.3, in particular less than 0.2, in the case of the finely divided graft copolymers (B) and values ​​of less than 0.5, particularly less than 0.35, are preferred in the case of the coarse-particle graft copolymers (C).

0021The same monomers and ranges for the gross composition are suitable for the graft copolymers (B) and (C). Both exist 50 to 90, preferably 50 to 70% of a graft core (b1) or (c1), a rubber-elastic polymer based on a (C₂ to C₁₀ alkyl) acrylate and 10 to 50, preferably 30 to 50% of a graft shell (b2) or (c2), a copolymer of styrene or a styrene derivative of acrylonitrile or methacrylonitrile.

0022For the rubber-elastic graft cores (b1) or (c1), preference is given to polymers whose glass transition temperatures T_G are below 10 ° C, preferably below 0 ° C. Above all, those monomers are copolymerized whose homopolymers have the preferred glass transition temperatures T_G have, however, monomers whose homopolymers have a higher glass transition temperature can also be used in minor amounts.

0023The graft cores (b1) and (c1) are made up of 75 to 99.9% by weight, preferably 90 to 99% by weight of a (C₂ to C₁₀ alkyl) acrylate (monomers b1.1 or c1.1) 0.1 to 5% by weight, preferably 1 to 4% by weight, of a monomer with at least two olefinic non-conjugated double bonds (monomers b1.2 or c1.2) and up to 24.9% by weight, preferably 10 to 20% by weight of further copolymerizable monomers (monomers b1.3 or c1.3).

0024Preferred monomers (b1.1) and (c1.1) are alkyl acrylates with 2 to 8 carbon atoms in the alkyl radical. It is particularly preferred to use n-butyl acrylate and / or 2-ethylhexyl acrylate and very particularly preferably only n-butyl acrylate.

0025Suitable monomers (b1.2) or c1.2) are, for example, divinylbenzene, divinylmaleate, diallyl fumarate, diallyl phthalate, triallylcyanurate and triallyl isocyanate and in particular the acrylate of tricyclodecenyl alcohol (cf. DE-A 1 260 135).

0026Further copolymerizable monomers (b1.3) or (c1.3) are isoprene, styrene, polymerizable styrene derivatives, for example α-methylstyrene, acrylonitrile, (C₁ to C₈-alkyl) methacrylates such as methyl methacrylate, methyl acrylate, vinyl methyl ether and mixtures of these monomers.

0027The graft shells (b2) and (c2) are made up of 50 to 90 wt .-%, preferably 60 to 80 wt .-%, styrene or a polymerizable styrene derivative (monomers b2.1 or c2.1) and 10 to 50% by weight, preferably 20 to 40% by weight, of acrylonitrile or methacrylonitrile (monomers b2.2 or c2.2).

0028In general, it is advisable to prepare the graft copolymers (B) and (C) separately and then to mix them in the proportions defined.

0029Secondarily, such bimodal mixtures of graft copolymers (B) and (C) come into consideration in which the polymer (C) is obtained by agglomeration of the polymer (B).

0030The graft copolymers (B) and (C) can be prepared, for example, by the method described in EP-A 6 503.

0031For this purpose, a graft core (b1) or (c1) is first produced using the emulsion polymerization process, onto which a graft shell (b2) or (c2) is grafted using the same process.

0032A graft core (b1) is obtained by copolymerizing the acrylic acid esters (b1.1) and a polyfunctional monomer which effects the crosslinking (b1.2), optionally together with other comonomers (b1.3), in an aqueous emulsion. The customary auxiliaries such as emulsifiers, polymerization initiators and regulators are advantageously also used. The average particle diameter of the graft core dispersion can be adjusted in a known manner by selecting the polymerization conditions, in particular the type, amount and dosage of the emulsifier.

0033It is advisable to assume a correspondingly coarse dispersion of the graft core (c1) when producing the coarse-particle graft copolymer (C). In principle, this can be produced by the known one-stage methods for producing coarse-particle dispersions.

0034The so-called seed latex method is generally particularly suitable for the production of graft copolymers (C) with a narrow particle size distribution. Here, a finely divided dispersion of the graft core (b1) prepared in the manner already described is presented as a seed latex which continues to grow by adding further monomers. The polymerization conditions can be set so that predominantly only the existing polymer particles of the seed latex continue to grow without new latex particles being formed (cf. DE-B 1 911 882).

0035To graft the graft shells (b2) or (c2) onto the corresponding graft cores, a monomer mixture of the monomers (b2.1) and (b2.2) is polymerized in the presence of the previously prepared dispersions of the copolymers (b1) or (c1). or (c2.1) and (c2.2) by the emulsion polymerization process in the usual manner. Since the desired grafting yield is almost always less than 100%, a somewhat larger amount of the monomer mixture must be added than corresponds to the desired amount of grafted polymer (b2) or (c2). The non-grafted copolymer formed from this monomer mixture belongs to the copolymer (D).

0036While the graft shells of the fine-particle copolymers (B) are preferably built up in one step, those of the coarse-particle copolymers (C) are preferably polymerized in several successive steps. In this way, the graft shell can be constructed in the manner of a block copolymer.

0037Here, the monomers selected for the graft shell of a desired gross composition are divided into several feeds with different monomer compositions, which are reacted in time sequence with the graft core dispersion in a graft copolymerization. The period between the respective feeds is to be dimensioned such that the graft polymerization of the previously added monomers has already progressed to a certain conversion.

0038In the case of a double-shell structure of the graft shell (c2), the proportion of the first shell is generally 20 to 70% by weight, in particular 25 to 50% by weight, in each case based on the entire graft shell (c2). In the first grafting stage, preferably only monomers (c2.1) are used, in the polymerization of the second stage predominantly mixtures of the styrene monomers (c2.1) and monomers (c2.2) are used in a weight ratio of (c2.1): (c2 .2) from generally 90:10 to 60:10, in particular 80:20 to 70:30.

Copolymers (D)

0039The copolymers (D) are resinous and thermoplastic. Particularly preferred copolymers (D) are those made from styrene or polymerizable styrene derivatives such as α-methylstyrene with acrylonitrile or methacrylonitrile. Several of the copolymers described can also be used simultaneously.

0040Such copolymers often arise in the graft polymerization for the production of component (B) or (C) in the grafting step as by-products, particularly when large amounts of the monomer are grafted onto small amounts of the graft core (b1) or (c1).

0041The copolymers (D) are known per se and can also be prepared in a targeted manner by radical polymerization, in particular by emulsion, suspension, solution and bulk polymerization. They have viscosity numbers in the range from 40 to 160, corresponding to average molecular weights M._w (Weight average) from 40,000 to 2,000,000.

0042Up to 50, in particular 7 to 45 and particularly preferably 10 to 40% by weight of glass fibers, based on the total weight of the glass fiber-reinforced molding compositions, can be incorporated into the molding compositions according to the invention.

0043The glass fibers are commercially available and preferably have a diameter of 6 to 20 μm. After kneading with the molding composition according to the invention, they generally have an average length of 0.1 to 0.5 mm, preferably 0.1 to 0.4 mm. Glass fibers made from E-glass, a type of glass which contains less than 0.8% alkali oxide, are particularly preferred. To achieve better adhesion, the glass fibers can be coated with organosilanes, epoxysilanes or other polymer coatings.

0044The molding compositions according to the invention can furthermore contain customary additives and processing aids.

0045Typical additives are, for example, stabilizers such as oxidation retardants, agents against thermal decomposition and decomposition by ultraviolet light, lubricants and mold release agents, colorants such as dyes and pigments, powdered fillers and reinforcing agents and plasticizers.

0046The stabilizers can be added to the mixtures at any stage in the preparation, but preferably at an early stage in order to counteract premature decomposition of the masses.

0047Oxidation retarders and heat stabilizers for the thermoplastic molding compositions are those which are generally added to polymers, such as halides of metals of group I of the periodic table, for example sodium, potassium, lithium halides in combination with copper (I) halides, for example chlorides , Bromides or iodides. Suitable stabilizers are also sterically hindered phenols, hydroquinones, variously substituted representatives of this group and mixtures of these agents in concentrations of up to 1% by weight, based on the weight of the total mixture.

0048The UV stabilizers used are also the substances which are generally active in polymers in amounts of up to 2.0% by weight, based on the total weight of the mixture. Examples of UV stabilizers are various substituted resorcinols, salicylates, benzotriazoles and benzophenones.

0049Suitable lubricants and mold release agents are incorporated into the thermoplastic composition, for example in amounts of up to 5% by weight, based on the total weight. These include stearic acids, stearyl alcohol, stearic acid esters and amides.

0050Colorants, for example organic dyes such as nigrosine, pigments, for example titanium dioxide, cadmium sulfide, cadmium silfide selenide, phthalocyanines, ultramarine blue or carbon black can also be added.

0051Nucleating agents for accelerating polyester crystallization, such as talc, calcium fluoride, sodium phenylphosphinate, aluminum oxide or finely divided polytetrafluoroethylene, can also be used in amounts of, for example, up to 5% by weight, based on the thermoplastic composition.

0052Plasticizers, such as dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, hydrocarbon oils, N- (n-butyl) benzenesulfonamide, o- and p-toluenesulfonamide are advantageously added in amounts of up to about 20% by weight, based on the molding composition.

0053Furthermore, 0.1 to 10, preferably 0.2 to 5% by weight, based on the total weight of the molding composition, of silicone oil can also be added to improve the surface quality. In principle, the commercially available types of silicone oils are suitable, preferably those with viscosities in the range from 25,000 to 250,000, preferably 50,000 to 200,000 mPa · s (at 25 ° C.), particularly preferably a silicone oil based on dimethylsiloxane with a Viscosity of approximately 100,000 mPa · s at 25 ° C.

0054The thermoplastic molding compositions according to the invention can be produced by kneading the components (A), (B), (C) and (D) and, if appropriate, the glass fibers and the further auxiliaries and additives in an extruder. Such methods are known per se and are described in the literature. The mixing temperatures in the extruder are generally in the range from 240 to 300 ° C.

0055The molding compositions according to the invention are notable for high strength combined with good ductility and toughness. The multiaxial toughness is particularly noteworthy.

0056Device housings for sensitive and high-quality electronic devices and tear-resistant films can be produced particularly advantageously from the molding compositions according to the invention by injection molding.

Examples:

0057The following mixture components were used:

Polyalkylene terephthalates (A)

0058<ul id="ul0012" list-style="none"><li>A / 1) Polybutylene terephthalate with a molecular weight M_n (Number average) of 25,000 and a viscosity number, determined according to DIN 53728, Part 2, of 130 ml / g (Ultradur B 4500 from BASF)</li><li>A / 2) Polyethylene terephthalate with a molecular weight Mn (number average) of 30,000 and a viscosity number, determined according to DIN 53728, part 2, of 73 ml / g (Ultralen SP 3700 S from BASF)</li></ul>

Fine-particle graft polymer (B)

0060Fine-particle graft polymer with an average particle size of 0.1 µm and a particle size distribution Q = 0.25<ul id="ul0013" list-style="none"><li>b1) a graft core<ul id="ul0014" list-style="none"><li>b1.1) 58.8% by weight of n-butyl acrylate</li><li>b1.2) 1.2% by weight of tricyclodecenyl acrylate</li></ul></li></ul> and<ul id="ul0015" list-style="none"><li>b2) a graft shell<ul id="ul0016" list-style="none"><li>b2.1) 30% by weight of styrene</li><li>b2.2) 10% by weight of acrylonitrile</li></ul></li></ul>

Production of the finely divided graft polymer (B) graft core (b1)

0061To a template of 16 g of butyl acrylate, 0.4 g of tricyclodecenyl acrylate, 1 g of the sodium salt of a C12 to C18 paraffin sulfonic acid mixture, 0.3 g of potassium persulfate, 0.3 g of sodium hydrogen carbonate, 0.15 g of sodium pyrophosphate and 150 ml of water was added after the Starting the polymerization reaction, a mixture of 82 g of butyl acrylate and 1.6 g of tricyclodecenyl acrylate was given over 3 h, the temperature of the reaction mixture being 60 ° C. Following the addition of monomers, polymerization was continued for 1 h. The dispersion obtained had a solids content of 40% by weight, an average particle diameter (d50) of 76 nm and a particle size distribution of Q = 0.29.

Graft bowl (b2)

0062A mixture of 150 g of the dispersion of the graft core (b1), 30 g of styrene, 10 g of acrylonitrile, 60 g of water, 0.03 g of potassium persulfate and 0.05 g of lauroyl peroxide was polymerized at 65 ° C. for 4 hours. The polymer was then precipitated from the dispersion using calcium chloride solution at 95 ° C., washed with water and dried. The degree of grafting of the graft copolymer was 35%.

coarse-particle graft polymer (C)

0063Coarse-particle graft polymer with an average particle size of 0.5 μm and a particle size distribution Q = 0.20<ul id="ul0017" list-style="none"><li>c1) a graft core<ul id="ul0018" list-style="none"><li>c1.1) 58.8% by weight of n-butyl acrylate</li><li>c1.2) 1.2% by weight of tricyclodecenyl sulfate</li></ul></li></ul> and<ul id="ul0019" list-style="none"><li>c2) a graft shell<ul id="ul0020" list-style="none"><li>c2.1) 33.25% by weight of styrene</li><li>c2.2) 6.75% by weight of acrylonitrile</li></ul></li></ul>

Preparation of the coarse-particle graft copolymer (C)

0064A mixture of 49 g of butyl acrylate and a solution of 0.5 g of the sodium salt of a C12 was added synchronously to an initial charge of 1.5 g of the latex from graft core (b1), 50 g of water and 0.1 g of potassium persulfate in the course of 3 h - Up to C18 paraffinsulfonic acid added at 60 ° C. Polymerization was then carried out for 2 hours. The latex had a solids content of 40%, an average particle size (d50) of 430 nm and a particle size distribution of Q = 0.1.

Graft bowl (c2)

0065A mixture of 150 g of the above graft core latex (c1), 20 g of styrene, 60 g of water, 0.03 g of potassium persulfate and 0.05 g of lauroyl peroxide was polymerized at 65 ° C. for 3 hours. A mixture of 15 g of styrene and 5 g of acrylonitrile was then added and the mixture was polymerized for a further 4 h. The polymer was then precipitated from the dispersion using calcium chloride solution at 95 ° C., washed with water and dried. The degree of grafting of the graft copolymer was 35%.

Copolymer (D)

0066Copolymer (D) built up from<ul id="ul0021" list-style="none"><li>d1) 65% by weight of styrene and</li><li>d2) 35% by weight of acrylonitrile</li></ul> with a viscosity number of 80 ml / g, measured in dimethylformamide, 0.5% at 25 ° C.

0067The preparation was carried out by continuous solution polymerization using a process as described in the plastics manual, Viehweg-Daumiller, Volume V (polystyrene), Carl-Hanser-Verlag, Munich 1969, p. 124, lines 12ff.

0068In addition, all mixtures still contained 0.2% by weight of carbon black, based on the sum of the mixture components (A), (B), (C) and (D).

0069The compositions described in the table were melted and extruded. After the extrusion, the test specimens required for determining the properties were produced by injection molding at 260 ° C.

0070The results of the tests are summarized in the table.

0071The viscosity number (VZ) was determined in accordance with DIN 53726, Part 2, with a 0.5% strength by weight solution in phenol / o-dichlorobenzene (weight ratio 1: 1) at 23 ° C. in an Ubbelohde viscometer.

0072The Melt Flow Index (MFI) serves as a reference value for the flow behavior in processing processes with higher shear rates such as injection molding and extrusion. A melted sample is pressed through the nozzle of the melt index tester according to DIN 53 735 at 260 ° C and a load of 10 kg. The MFI is given in g / 10 min and corresponds to the mass of the melt strand that was pressed out of the nozzle in 10 min.

0073The tensile test (tensile stress and elongation) was determined in accordance with DIN 53455 at 23 ° C. using test specimens which are designated as test specimen No. 3 in the DIN specification.

0074The modulus of elasticity was calculated from the results of the tensile tests according to DIN 54457-3.

0075The impact strength was determined according to DIN 53453 at 23 ° C. The percussion work is determined by breaking standard small bars measuring 50 mm x 6 mm x 4 mm with a notch of 3 mm in diameter in a Charpy pendulum impact tester.

0076The multiaxial toughness was determined according to DIN 53443 at 23 ° C. Circular test specimens with a diameter of 60mm and a thickness of 2mm are clamped in a clamping ring with a diameter of 40mm and pierced vertically with a rounded steel cylinder, the penetration work being determined.

0077The heat resistance according to Vicat was determined according to DIN 53460. A needle with a total of 10 N and a cross section of 1 mm loaded is placed on a test specimen and the test specimen is heated at a speed of 50 K / h. The Vicat temperature is reached when the needle is pressed 1 mm deep into the test specimen.<tables id="tabl0001" num="0001"><img file="EP0643104A2_D0002.tif" /></tables>