Fire-retarding thermoplastic moulding compositions based on polymer blends of polypropylene and magnesium hydroxide.

The invention relates to magnesium hydroxide, optionally coated magnesium hydroxide, highly filled, flame-retardant thermoplastic molding compositions, the base material of which consists of polymer blends of polypropylene and ethylene-propylene terpolymer rubber.

The fire protection equipment of thermoplastic materials with combinations of halogen compounds and synergists, such as compounds of phosphorus, antimony, bismuth and boron is out<ul id="ul0001" list-style="none"><li>1. Vogel, "flame retarding plastics" Hüthig-Verlag, Heidelberg, 1966, pages 94-102</li><li>2nd Troitzsch, "Fire behavior of plastics" Hanser Verlag, Münschen, 1982, pages 1-63</li></ul> known.

In addition to the possibility of fire protection equipment of thermoplastic materials with halogen compounds, there is also the possibility of fire protection equipment with halogen-free flame retardants based on phosphorus compounds and nitrogen compounds, such as DE-OS 30 19 617, DE-OS 28 27 867 and DE-OS 34 01 835 can be seen.

It is also known from EP-PS 00 52 868 that styrene polymers can be flame-retarded with high amounts of magnesium hydroxide. However, the amounts of halogen-free flame retardants used are 50-70% by weight in order to achieve the test conditions UL 94 V-0 according to Underwriter's Laboratories. At the same time, the large amounts of filler greatly reduce the mechanical properties, in particular the elongation at break and the impact resistance, of the fire-resistant thermoplastic materials, so that they can only be used to a limited extent as materials.

The object was therefore to develop a thermoplastic molding compound which is highly filled with magnesium hydroxide and which is fire-protected in accordance with UL 94 V-0 and does not have the disadvantages of the deterioration in the mechanical properties, as shown above.

The invention relates to flame-retardant thermoplastic molding compositions with high impact strength and high elongation at break based on polymer blends. These polymer blends are characterized in that they consist of a mixture of polypropylene homo- and / or. Copolymer, ethylene-propylene terpolymer rubber and magnesium hydroxide and optionally polyethylene homo- and / or. Copolymer, polyacrylic acid ester homo- and / or -Copolymer and polyvinyl acetate homo- u./o. Copolymer. The composition of the polymer blends in the molding compositions consists of 1-40% by weight, preferably 20-35% by weight, polypropylene homo- and / or. Copolymer (component A), 0-10% by weight, preferably 2-5% by weight of polyethylene homo- and / or. Copolymer (component B), 0-5% by weight, preferably 0.8-3% by weight, polyacrylic acid ester homo- and / or. Copolymer (component C), 0-5% by weight, preferably 0.8-3% by weight, polyvinyl acetate homo- and / or. Copolymer (component D) and 0.5-10% by weight, preferably 2-5% by weight, of ethylene-propylene terpolymer rubber (component E), the sum of components A to E = 30-40% by weight -% and the magnesium hydroxide, optionally as a coated magnesium hydroxide, is 60-70% by weight of the total molding composition. In addition to components A and E, at least one of components C or D is preferably present in the polymer blend.

Particularly suitable components for the polymer blends are polypropylene homopolymer with an average molecular weight of 240,000-380,000 u./o. Polypropylene-ethylene random copolymer with an average molecular weight of 440,000-470,000, polyethylene homopolymer with an average molecular weight of 40,000-100,000 u./o. Ethylene acrylic acid copolymer with an average molecular weight of 100,000-250,000 u./o. Ethylene-vinyl acetate copolymers with an average molecular weight of 50,000-150,000, methacrylic acid ester and / or. Acrylic acid ester homopolymers with an average molecular weight of 200,000-800,000, polyvinyl acetate homopolymers with an average molecular weight of 300,000-1,000,000 and ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight propylene and about 5-11 double bonds per 1000 C atoms.

In principle, however, components with higher or lower molecular weights and other proportions of the components in the copolymers can also be used. It is crucial that the use of polymer blends instead of pure polypropylene, even with a high degree of filling with magnesium hydroxide, results in good elongation at break and impact strength with good fire behavior.

To produce the polymer blends according to the invention, the individual polymer masses, which consist of approximately 1-40% by weight, preferably 20-35% by weight, of component A. 0-10% by weight, preferably 2-5% by weight, of component B 0-5% by weight, preferably 0.8-3% by weight, of component C. 0-5% by weight, preferably 0.8-3% by weight, of component D. and 0.5-10% by weight, preferably 2-5% by weight, of component E. consist, homogeneously mixed in a Banburry mixer for a short time at a temperature of 190-200 ° C. Then 50-75% by weight, preferably 60-65% by weight, of magnesium hydroxide, optionally coated magnesium hydroxide, are added and the mixture is kneaded homogeneously at 200 ° C.

The homogeneous, thermoplastic molding compositions thus obtained are placed on a heated calender, drawn off as a film and granulated. The granules obtained are injected at 240 ° C on an injection molding machine to standard test specimens.

The following examples describe the preparation of the flame-retardant thermoplastic molding compositions which are highly filled with magnesium hydroxide.

example 1

In a Banburry mixer, 3.4 kg of polypropylene homopolymer with an average molecular weight of 350,000, 0.23 kg of polyethylene homopolymer with an average molecular weight of 65,000, 0.23 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight of polypropylene and about 7 double bonds per 1000 carbon atoms and 0.14 kg of ethylene-vinyl acetate copolymer with an average molecular weight of 80,000 at 190-200 ° C. were mixed homogeneously over 3 minutes. Then 6 kg of magnesium hydroxide coated with 2% by weight of silane with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are added and the entire mixture is kneaded homogeneously at 200 ° C. for 10 minutes.

Example 2

Analogously to Example 1, 2.9 kg of polypropylene homopolymer with an average molecular weight of 350,000, 0.45 kg of polyethylene homopolymer with an average molecular weight of 80,000, 0.45 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight -% propylene and about 7 double bonds per 1000 carbon atoms and 0.2 kg ethylene-vinyl acetate copolymer with an average molecular weight of 100,000 at 190-200 ° C for 3 minutes homogeneously mixed. Then 6 kg of magnesium hydroxide coated with 2% by weight of silane with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are added. Mixing and processing is carried out as described in Example 1.

Example 3

Analogously to Example 1, 3.0 kg of polypropylene homopolymer with an average molecular weight of 350,000, 0.2 kg of polyethylene homopolymer with an average molecular weight of 65,000, 0.2 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight -% propylene and about 7 double bonds per 1000 carbon atoms and 0.1 kg ethylene-vinyl acetate copolymer with an average molecular weight of 80,000 at 190-200 ° C homogeneously mixed for 3 minutes. Then 6.5 kg of magnesium hydroxide coated with 2% by weight of silane with a particle size distribution of 100% &lt;10 °, 90% &lt;5 μ are added. Mixing and processing is carried out as described in Example 1.

Example 4

Analogously to Example 1, 2.5 kg of polypropylene homopolymer with an average molecular weight of 350,000, 0.4 kg of polyethylene homopolymer with an average molecular weight of 80,000, 0.4 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% Propylene and about 7 double bonds per 1000 carbon atoms and 0.2 kg ethylene-vinyl acetate copolymer with an average molecular weight of 100,000 at 190-200 ° C homogeneously mixed for 3 minutes. Then 6.5 kg of magnesium hydroxide coated with 2% by weight of silane with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are added. Mixing and processing is carried out as described in Example 1.

Example 5

Analogously to Example 1, 2.9 kg of polyethylene-polypropylene copolymer with an average molecular weight of 450,000, 0.3 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight of propylene and about 7 double bonds per 1000 carbon atoms , 0.1 kg of ethylene-vinyl acetate copolymer with an average molecular weight of 80,000 and 0.2 kg of ethylene-acrylic acid ester copolymer with an average molecular weight of 650,000 at 190-200 ° C homogeneously mixed for 3 minutes. Then 6.5 kg of magnesium hydroxide coated with 2% by weight of silane with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are added. Mixing and processing is carried out as described in Example 1.

Example 6

Analogously to Example 1, 3.0 kg of polyethylene-polypropylene copolymer with an average molecular weight of 450,000, 0.3 kg of ethylene-propylene-ethylidene norbone terpolymer rubber with about 30% by weight of propylene and about 7 double bonds per 1000 carbon atoms , 0.07 kg of polyvinyl acetate with an average molecular weight of 800,000 and 0.13 kg of polymethyl methacrylate with an average molecular weight of 550,000 at 190-200 ° C. for 3 minutes. Then 6.5 kg of magnesium hydroxide coated with 2.5% by weight of silane with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are added. Mixing and processing is carried out as described in Example 1.

Example 7

(Comparative example)

In a Banburry mixer, 4.0 kg of polypropylene homopolymer with an average molecular weight of 35,000 and 6.0 kg with 2% by weight of silane-coated magnesium hydroxide with a particle size distribution of 100% &lt;10 μ, 90% &lt;5 μ are poured in and Kneaded to a homogeneous mass at 200 ° C for 10 minutes. Further processing is carried out analogously to example 1.

Example 8

(Comparative example)

Analogously to Example 7, 3.5 kg of polypropylene homopolymer with an average molecular weight of 350,000 and 6.5 kg with 2% by weight of silane-coated magnesium hydroxide with a particle size distribution of 100% &lt;100µ 90% &lt;5µ are mixed in a Banburry mixer. filled and kneaded at 200 ° C for 10 minutes to a homogeneous mass. Further processing is carried out analogously to example 1.

The standard test specimens produced from the mixtures according to Examples 1-8 were stored for 24 hours in a standard climate of 23 ° C./65% relative humidity and the fire behavior was tested according to UL 94 with a material thickness of 3.2 mm. In addition, the mechanical properties such as tensile strength, tensile strength, elongation at break, impact resistance and modulus of elasticity were determined. The dimensional stability under heat was also determined.

Tables 1 and 2 below list the formulations, or the fire behavior and the mechanical properties of the mixtures prepared in accordance with Examples 1-8.<tables id="tabl0001" num="0001"><img file="EP0249010A2_D0001.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0249010A2_D0002.tif" /></tables>