Flame Retardant Polymer Composition

Abstract

The present invention relates to a flame retardant polymer composition comprising at least the following components A) 2.0 to 49.8 wt.-% based on the overall weight of the polymer composition of a copolymer comprising ethylene units and units selected from the group consisting of methyl acrylate, methyl methacrylate and mixtures thereof; B) 0.1 to 6.0 wt.-% based on the overall weight of the polymer composition of a polyethylene and/or polypropylene containing units originating from maleic acid anhydride; C) 0.1 to 5.0 wt.-% based on the overall weight of the polymer composition of a silicone fluid and/or a silicon gum; D) 50.0 to 70.0 wt.-% based on the overall weight of the polymer composition of a magnesium hydroxide; and E) 0 to 17.0 wt.-% based on the overall weight of the polymer composition of a copolymer of ethylene and a C4 to C10 alpha olefin comonomer having a density in the range of 860 kg/m3 to 950 kg/m.sup.3 determined according to ISO 1183; wherein the weight proportions of components A) to E) add up to 100 wt.-%. In addition, the present invention refers to a wire or cable comprising at least one layer comprising the polymer composition according to the present invention and to the use of the polyolefin composition according to the present invention as a flame retardant layer of a wire or cable.

Claims

1. A flame retardant polymer composition comprising at least the following components A) 2.0 to 49.8 wt.-% based on the overall weight of the polymer composition of a copolymer comprising ethylene units and units selected from the group consisting of methyl acrylate, methyl methacrylate and mixtures thereof; B) 0.1 to 6.0 wt.-% based on the overall weight of the polymer composition of a polyethylene and/or polypropylene containing units originating from maleic acid anhydride; C) 0.1 to 5.0 wt.-% based on the overall weight of the polymer composition of a silicone fluid and/or a silicon gum; D) 50.0 to 70.0 wt.-% based on the overall weight of the polymer composition of a magnesium hydroxide; and E) 0 to 17.0 wt.-% based on the overall weight of the polymer composition of a copolymer of ethylene and a C.sub.4 to C.sub.10 alpha olefin comonomer having a density in the range of 860 kg/m.sup.3 to 965 kg/m.sup.3 determined according to ISO 1183; wherein the weight proportions of components A) to E) add up to 100 wt.-%.

2. The flame retardant polymer composition according to claim 1, characterized in that, component A) is a copolymer comprising and preferably consisting of ethylene units and methyl acrylate units, more preferably the content of methyl acrylate units is in the range of 10 to 35 wt.-% and preferably in the range of 20 to 30 wt.-% based on the overall weight of component A); and/or component A) has a density determined according to ISO 1183 in the range of 920 to 960 kg/m.sup.3 and preferably in the range of 935 to 950 kg/m.sup.3; and/or component A) has a MFR.sub.2 determined according to ISO 1133 in the range of 0.1 to 10 g/10 min and preferably in the range of 0.2 to 0.7 g/10 min; and/or component A) comprise units with hydrolysable silane-groups, wherein the units with hydrolysable silane-groups are preferably represented by formula (I):
R.sup.1SiR.sup.2.sub.qY.sub.3-q   (I) wherein R.sup.1 preferably is an ethylenically unsaturated hydrocarbyl, hydrocarbyloxy or (meth)acryloxy hydrocarbyl group, each R.sup.2 preferably is independently an aliphatic saturated hydrocarbyl group, Y which may be the same or different, is preferably a hydrolysable organic group and q is 0, 1 or 2.

3. The flame retardant polymer composition according to claim 1, characterized in that, component B) is a obtained by copolymerising and/or grafting polyethylene with maleic acid anhydride, whereby a grafted linear low density polyethylene is preferred, more preferably the content of maleic acid anhydride is in the range of 0.3 to 2.0 wt.-%; and/or component B) has a density determined according to ISO 1183 in the range of 910 to 950 kg/m.sup.3 and preferably in the range of 920 to 940 kg/m.sup.3, and/or component B) has a MFR.sub.2 determined according to ISO 1133 in the range of 0.5 to 5 g/10 min and preferably in the range of 1.5 to 2.5 g/10 min.

4. The flame retardant polymer composition according to claim 1, characterized in that, component C) is a silicone fluid or silicone gum selected from the group consisting of polysiloxane, preferably polydimethylsiloxane, and siloxanes containing alkoxy or alkyl functional groups and mixtures thereof, preferably component C) is an organomodified siloxane.

5. The flame retardant polymer composition according to claim 1, characterized in that, component D) is a ground or precipitated magnesium hydroxide, preferably is a ground magnesium hydroxide, more preferably is a ground magnesium hydroxide having a median particle size d.sub.50 in the range of 1.0 to 10.0 □m, preferably in the range of 2.0 to 5.0 □m and still more preferably is a ground magnesium hydroxide surface-treated with stearic acid, preferably the content of stearic acid is 1.0 to 3.0 wt.-% and more preferably 1.5 to 2.5 wt.-% based on the weight of the ground magnesium hydroxide.6. The flame retardant polymer composition according to any one of the preceding claims, characterized in that, component D) is a ground or precipitated magnesium hydroxide having a BET surface area in the range of 1 to 20 m.sup.2/g and preferably in the range of 5 to 12 m .sup.2/g.

6. (canceled)

7. The flame retardant polymer composition according to claim 1, characterized in that, component E) is a copolymer of ethylene and 1-octene; whereby said copolymer preferably has a density in the range of 870 kg/m.sup.3 to 910 kg/m.sup.3, preferably in the range of 870 to 900 kg/m.sup.3 and more preferably in the range of 880 to 890 kg/m.sup.3 measured according to ISO 1183; and/or an MFR.sub.2 in the range of 0.1 to 10.0 g/10 min, preferably in the range of 0.5 to 5 g/10 min, more preferably in the range of 0.5 to 3 g/10 min and still more preferably in the range of 1.0 to 3.0 g/10 min measured according to ISO 1133 at 190° C. and a load of 2.16 kg; and/or component E) is a copolymer consisting of units of ethylene and 1-hexene, wherein the content of 1-hexene is in the range of 0.02 to 15.0 wt.-% and preferably in the range of 0.5 to 5.0 wt.-% based on the overall weight of component E), preferably the density of said copolymer is in the range a density in the range of 920 kg/m.sup.3 to 965 kg/m.sup.3, more preferably in the range of 930 to 960 kg/m.sup.3 and stilled more preferably in the range of 945 to 955 kg/m.sup.3 measured according to ISO 1183 and/or the MFR.sub.2 is in the range of 2.0 to 40.0 g/10 min, preferably in the range of 3.0 to 30.0 g/10 min, more preferably in the range of 4.0 to 20.0 g/10 min and still more preferably in the range of 5.0 to 15.0 g/10 min measured according to ISO 1133 at 190° C. and a load of 21.6 kg.

8. The flame retardant polymer composition according to claim 1, characterized in that, component E) is manufactured by using a single-site catalyst and preferably is a copolymer of ethylene and 1-octene manufactured by using a single-site catalyst.

9. The flame retardant polymer composition according to claim 1, characterized in that, the content of component A) in the polymer composition is in the range of 7.5 to 40.5 wt.%, preferably in the range of 15.5 to 32 wt.-% and more preferably in the range of 19.8 to 26.7 wt.-% based on the overall weight of the polymer composition; and/or the content of component B) in the polymer composition is in the range of 1.0 to 5.0 wt.%, preferably in the range of 2.0 to 4.5 wt.-% and more preferably in the range of 3.9 to 4.1 wt.-% based on the overall weight of the polymer composition; and/or the content of component C) in the polymer composition is in the range of 0.5 to 4.5 wt.%, preferably in the range of 1.0 to 4 wt.-% and more preferably in the range of 1.4 to 3.1 wt.-% based on the overall weight of the polymer composition; and/or the content of component D) in the polymer composition is in the range of 55.0 to 67.0 wt.%, preferably in the range of 60.0 to 66.0 wt.-% and more preferably in the range of 62.0 to 64.0 wt.-% based on the overall weight of the polymer composition; and/or the content of component E) in the polymer composition is in the range of 3.0 to 16.0 wt.%, preferably in the range of 5.0 to 10.0 wt.-%, more preferably in the range of 6 to 10 and still more preferably in the range of 6.0 to 9.0 wt.-% based on the overall weight of the polymer composition.

10. The polymer composition according to claim 1, characterized in that, the polymer composition comprises at least one additive, preferably selected from the group consisting of slip agents, UV-stabiliser, antioxidants, additive carriers, nucleating agents, mica and mixtures thereof, whereby these additives preferably are present in 0.01 to 5 wt.-% and more preferably in 0.1 to 4 wt.-% based on the overall weight of the polymer composition, still more preferably the polymer composition comprises mica, more preferably in 2.5 to 3.5 wt,.% based on the overall weight of the polymer composition.

11. The polymer composition according to claim 1, characterized in that, the weight ratio between components A) and E) is in the range from 0.8:1 to 4.0:1, preferably in the range from 1.8:1 to 3.0:1 and more preferably in the range from 1.9:1 to 2.8:1.

12. The polymer composition according to claim 1, characterized in that, the polymer composition comprises at least the following components: A) 15.5 to 32.0 wt.-% and preferably 19.8 to 26.7 wt.-% based on the overall weight of the polymer composition of a copolymer comprising and preferably consisting of ethylene units and units of methyl acrylate, more preferably having a density determined according to ISO 1183 in the range of 920 to 960 kg/m.sup.3 and preferably in the range of 935 to 950 kg/m.sup.3 and/or a MFR.sub.2 determined according to ISO 1133 in the range of 0.1 to 5 g/10 min and preferably in the range of 0.2 to 0.7 g/10 min; B) 2.0 to 4.5 wt.-% and preferably 3.9 to 4.1 wt.-% based on the overall weight of the polymer composition of a linear low density polyethylene grafted with maleic anhydride; C) 1.0 to 4.0 wt.-% and preferably 1.4 to 3.1 wt.-% based on the overall weight of the polymer composition of a silicone fluid and/or a silicon gum, preferably selected from the group consisting of polysiloxane, more preferably polydimethylsiloxane, and siloxanes containing alkoxy or alkyl functional groups and mixtures thereof; D) 60.0 to 66.0 wt.-% and preferably 62.0 to 64.0 wt.-% based on the overall weight of the polymer composition of a ground magnesium hydroxide having a median particle size d50 in the range of 1.5 to 5.0 μm and preferably in the range of 3.0 to 4.0 μm; and E) 5.0 to 10.0 wt.-% and preferably 6.0 to 9.0 wt.-% based on the overall weight of the polymer composition of a copolymer made of ethylene and 1-octene; whereby said copolymer preferably has a density in the range of 870 to 900 kg/m.sup.3 measured according to ISO 1183 and/or an MFR.sub.2 in the range of 0.5 to 5 g/10 min; wherein the weight proportions of components A) to E) add up to 100 wt.-%.

13. A wire or cable comprising at least one layer comprising the polymer composition according to claim 1.

14. The wire or cable according to claim 13, characterized in that, the wire ore cable comprises an insulation layer, preferably comprising or consisting of a material selected from the group consisting of crosslinked or thermoplastic polyethylenes, thermoplastic polypropylenes or flame retardant polyolefins.

15. Use of a polyolefin composition according to claim 1 as a flame retardant layer of a wire or cable.

Description

EXPERIMENTAL PART

A. Measuring Methods

[0098] The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

Melt Flow Rate (MFR)

[0099] The MFR was measured according to ISO 1133 (Davenport R-1293 from Daventest Ltd). MFR values were measured at two different loads 2.16 kg (MFR.sub.2) and 21.6 kg (MFR.sub.21) at 190° C.

Density

[0100] The density was measured according to ISO 1183-1-method A (2019). Sample preparation was done by compression moulding in accordance with ISO 1872-2:2007.

Comonomer Content in Component A)

Quantification of Microstructure by NMR Spectroscopy

[0101] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content of the polymer.

[0102] Quantitative .sup.1H NMR spectra recorded in the molten-state using a Bruker Avance III 500 NMR spectrometer operating at 500.13 MHz. All spectra were recorded using a .sup.13C optimised 7 mm magic-angle spinning (MAS) probehead at 150° C. using nitrogen gas for all pneumatics. Approximately 200 mg of material was packed into a 7 mm outer diameter zirconia MAS rotor and spun at 4 kHz. This setup was chosen primarily for the high sensitivity needed for rapid identification and accurate quantification {klimke06, parkinson07, castignolles09}. Standard single-pulse excitation was employed using a recycle delay of 2s {pollard04, klimke06}. A total of 16 transients were acquired per spectra.

[0103] Quantitative .sup.1H NMR spectra were processed, integrated and quantitative properties determined using custom spectral analysis automation programs. All chemical shifts were internally referenced to the bulk ethylene methylene signal at 1.33 ppm.

[0104] Assignment for methylacrylate (MA) incorporation {brandolini01}:

##STR00001##

[0105] Characteristic signals resulting from incorporation of methyl acrylate, in possible various comonomer sequences, were observed. The overall methylacrylate incorporation was quantified using the integral of the signal at 3.6 ppm assigned to the 1MA site, accounting for the number of reporting nuclei per comonomer:

MA=I.sub.1MA/3

[0106] The ethylene content was quantified using the integral of the bulk aliphatic (I.sub.bulk) signal between 0.00-3.00 ppm. The total ethylene content was calculated based on the bulk integral and compensating for the observed comonomer:

E=(1/4)*[I.sub.bulk−3*MA]

[0107] The total mole fractions of methylacrylate in the polymer was calculated as:

fMA=MA/(E+MA)

[0108] The total comonomer incorporations of methylacrylate in mole percent was calculated from the mole fraction in the standard manner:

MA [mol %]=100*fMA

[0109] The total comonomer incorporations of methylacrylate in weight percent was calculated from the mole fractions in the standard manner:

MA [wt %]=100*(fMA*86.09)/((fMA*86.09)+((1−fMA)*28.05))

[0110] klimke06

[0111] Klimke, K., Parkinson, M., Piel, C., Kaminsky, W., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2006; 207:382.

[0112] parkinson07

[0113] Parkinson, M., Klimke, K., Spiess, H. W., Wilhelm, M., Macromol. Chem. Phys. 2007; 208:2128.

[0114] pollard04

[0115] Pollard, M., Klimke, K., Graf, R., Spiess, H. W., Wilhelm, M., Sperber, O., Piel, C., Kaminsky, W., Macromolecules 2004; 37:813.

[0116] castignolles09

[0117] Castignolles, P., Graf, R., Parkinson, M., Wilhelm, M., Gaborieau, M., Polymer 50 (2009) 2373.

[0118] brandolini01

[0119] A. J. Brandolini, D. D. Hills, “NMR spectra of polymers and polymer additives”, Marcel Deker Inc., 2000.

Median Particle Size (d.sub.50)

[0120] Median particle size of metal hydroxide can be measured by laser diffraction (ISO13320), dynamic light scattering (ISO22412) or sieve analysis (ASTMD1921-06). For the metal hydroxides used in the working examples, the determination of the median particle size d.sub.50 was conducted by laser diffraction. Any limitation of the claims shall refer to values obtained from laser diffraction (ISO13320).

BET Surface

[0121] The Bet surface is determined in accordance with ISO 9277 (2010).

Manufacturing of Tape used for Determination of Tensile Strength and Elongation at Break

[0122] For determining the tensile strength and elongation at break, tapes (1.8 mm) were produced on a Collin TeachLine E20T tape extruder with a 4.2:1, 20D compression screw with a 20 mm diameter. The temperature profile was 150/160/170° C. and the screw speed was 55 rpm.

Tensile Testing

[0123] Tensile testing was executed in accordance with ISO 527-1 and ISO 527-2 using an Alwetron TCT 10 tensile tester. Ten test specimen were punched from a plaque using ISO 527-2/5A specimen and placed in a climate room with relative humidity of 50±5% at a temperature of 23° C. for at least 16 hours before the test. The test specimen were placed vertically between clamps with a distance of 50±2 mm, extensometer clamps with a distance of 20 mm and a load cell of 1 kN. Before the test was carried out, the exact width and thickness for every sample was measured and recorded. Each sample rod was tensile tested with a constant speed of 50 mm/min until breakage and at least 6 approved parallels were performed. In highly filled systems, there is generally a big variation of the results and therefore the median value was used to extract a single value for elongation at break (%) and tensile strength (MPa).

Compression Moulding

[0124] Plaques were prepared for the limiting oxygen index and vertical burning tests with compression moulding (Collin R 1358, edition: 2/060510) according to ISO 293. The pellets were pressed in between two Mylar film sheets and positioned in a specific frame with the correct shape and dimensions (140×150×3 mm). The samples were pressed by applying 20 bar for a minute at 170° C., followed by 200 bars pressure for 5 minutes at the same temperature. The remaining compression was done at the same high pressure for 9 minutes at a cooling rate of 15° C./min. The amount of pellets used for each plaque was calculated using the density of the material with an excess of 10 wt.-%.

Limiting Oxygen Index

[0125] Limiting oxygen index (LOI) was performed by following a test method based on ASTM D 2863-87 and ISO 4589 [38]. 10 test specimens for LOI were stamped out of previously mentioned pressed plaques. The test specimens were 12.5±0.5 mm long. Lines were drawn at 50 mm, measured from the top of the sticks. The samples sticks were placed vertically in a glass container with a predetermined atmosphere of oxygen and nitrogen. The samples were exposed to the predetermined atmosphere for at least 30 seconds before ignition. The sticks were ignited on the very top of the specimen during contact with an external flame for five seconds. If the stick was still burning after three minutes or if the flame had burned down past the measured 50 mm, the test had failed. Different ratios of oxygen and nitrogen were tested until the specimen passed the test and the current percentage of oxygen was recorded.

Vertical Burning Test

[0126] A small-scale fire test method was developed in this study to recreate real fire behaviour. In this test method vertical specimens are burned by their lower ends and thereby heating the area right above the pyrolysis zone. Ignition on the lower part of specimens is therefore more severe in testing the dripping ability and may aid in predicting the results from full-scale testing. Studying the char stability against melt dripping is important because it increases the burning surface area, which can lead to faster fire spread. The test specimen were the same dimensions as the LOI sticks and were ignited by a Bunsen burner to be classified according to their remaining compound and breakage/flaming droplets. The flame conditions were the same as in IEC 60332-1 vertical flame test for FR dripping test, with a butane gas flow rate of 650±30 ml/min and air 1000±50 ml/min. The outer part of the blue section of the flame is applied to the lower end of the vertically 18 cm suspended test specimen for 15 seconds and burning times are measured from the time of contact with the flame. If dripping occurs this is reported. The sample weight is measured before and after flame exposure and the remaining sample weight calculated in weight percent.

B. Materials Used

[0127] Component A) “EMA” is a copolymer of ethylene and methyl acrylate (weight ratio=75:25) having a MFR.sub.2 of 0.4 g/10 min and a density of 944 kg/m.sup.3, commercially available from DuPont (USA) under the name Elvaloy® AC 1125.

Component B)

[0128] “LLDPE-MAH” is a linear low density polyethylene grafted with maleic acid anhydride (maleic acid anhydride content=0.5 to 1.0 wt.-%, MFR.sub.2=2.0 g/10 min, density=930 kg/m.sup.3), commercially available from HDC Hyundai EP Co., Ltd. under the tradename Polyglue® GE300C.

Component C)

[0129] “OMS-1” is a masterbatch containing 50 wt.-% of an organo modified siloxane in 50 wt.-% in a LDPE matrix, commercially available from Evonik Nutrition & Care GmbH (Germany) as Tegomer® 6264.

[0130] “PDMS-1” is a masterbatch containing a high molecular weight polydimethylsiloxane mixed into LDPE, commercially available from DuPont as DOW CORNING™ AMB-12235 MASTERBATCH.

[0131] “PDMS-2” is a masterbatch consisting of 40 wt.-% ultrahigh molecular weight polydimethyl siloxane polymer available from Dow Corning and 60 wt.-% ethylene butyl acrylate copolymer having a butyl acrylate content of 13 wt.-% and a MFR.sub.2 of 0.3 g/10 min, commercially available from Borealis AG (Austria) as FR4897.

Component D)

[0132] “MDH-1” is a brucite (ground magnesium hydroxide) (Ecopiren® 3.5C) produced and commercially available by Europiren B.V (Netherlands) having a d.sub.50 of 3.5 μm, a specific surface area in the range of 7 to 10 m.sup.2/g and is coated with 2 wt.-% of stearic acid. The chemical composition is: Mg(OH).sub.2>92.8 wt.-%, CaO<2,3 wt.-%, SiO.sub.2<1.3 wt.-% and Fe.sub.2O.sub.3<0.13 wt.-%.

Component E)

[0133] “VLDPE-1” is a very low density copolymer of polyethylene and 1-octene having a density of 883 kg/m.sup.3 and a MFR.sup.2 of 1.1 g/10 min, commercially available as Queo 8203 from Borealis AG (Austria).

[0134] “VLDPE-2” is a very low density copolymer of polyethylene and 1-octene having a density of 883 kg/m.sup.3 and a MFR.sup.2 of 3.0 g/10 min, commercially available as Queo 8201 from Borealis AG (Austria).

Further Components

[0135] “Mica” is a potassium aluminium silicate, commercially available as Micafort SX 300 from Mocayco.

[0136] AO1 is a high molecular weight sterically hindered phenolic antioxidant, commercially available from BASF SE as Irganox 1010.

C) Preparation of the Polymer Compositions

[0137] The polymer compositions according to the inventive examples (IE1 to IE10 and for comparative examples (CE1 and CE2) were produced by mixing the components together in a BUSS-co-kneader (46 mm) at a screw speed of 225 rpm and at a set temperature of 180° C. in zone 1 and 160° C. in zone 2. The mixer screw was heated to 120° C. The extruder screw temperature was 160° C., the barrel heated to 170° C. and the speed 4 rpm. Component C) was always added in port 2, while all other components were added in port 1. The amounts of the different components in the polymer compositions and the properties of the polymer compositions according to the inventive examples and the comparative examples can be gathered from below Tables 1a and 1b.

TABLE-US-00001 TABLE 1a Composition and properties of the polymer compositions. Unit CE1 IE1 IE2 IE3 IE4 IE5 Component EMA (A) wt.-% — 29.8 21.8 19.8 17.8 13.8 LLDPE-MAH (B) wt.-% 4 4 4 4 4 4 OMS-1 (C) wt.-% 3 3 3 3 3 3 MDH-1 (D) wt.-% 63 63 63 63 63 63 VLDPE-1 (E) wt.-% 29.8 — 8 10 12 16 AO1 wt.-% 0.2 0.2 0.2 0.2 0.2 0.2 Properties LOI % 35.0 44.5 49.0 46.0 52.0 49.0 Dripping — yes no no no yes yes Remaining wt.-% 57 75 61 73 53 60 sample Tensile Strength MPa 10.6 8.9 10.6 8.8 11.1 12.1 Elongation at % 200 128 173 278 203 195 Break

TABLE-US-00002 TABLE 1b Composition and properties of the polymer compositions. Unit CE2 IE6 IE7 IE8 IE9 IE10 Component EMA (A) wt.-% 24.8 16.8 23.3 20.3 23.3 20.3 LLDPE-MAH (B) wt.-% 4 4 4 4 4 4 OMS-1 (C) wt.-% — 3 — 3 — 3 PDMS-1 (C) wt.-% — — 1.5 1.5 — — PDMS-2 (C) wt.-% — — — — 1.5 1.5 MDH-1 (D) wt.-% 63 63 63 63 63 63 VLDPE-1 (E) wt.-% — 10 — — — — VLDPE-2 (E) wt.-% 8 — 8 8 8 8 Mica wt.-% — 3 — — — — AO1 wt.-% 0.2 0.2 0.2 0.2 0.2 0.2 Properties LOI % 31.5 45.0 37.5 54.5 47.5 43.5 Dripping — no no yes yes no yes Remaining wt.-% 51 75 40 31 61 0 sample Tensile Strength MPa n.d. 9.4 n.d. 9.7 n.d. n.d. Elongation at % n.d. 180 n.d. 12.7 n.d. n.d. Break MFR.sub.2 g/10 min n.d. 7.0 n.d. 9.1 n.d. n.d. n.d. = not determined.

D) Discussion of the Results

[0138] The polymer composition according to Comparative Example CE1 is containing only component E) (=a very low density copolymer of polyethylene and 1-octene) as polymer base, but does not contain component A) (=a copolymer of ethylene and methyl acrylate). As can be gathered from Table 1a the polymer compositions according to the invention (IE1 to IE5) have compared to the polymer composition according to CE1 better flame retardant properties.

[0139] From Table 1b can be seen that component C) has a very positive effect on the flame retardant properties. Even if the polymer composition according to CE2 comprises component A) as polymer base the flame retardant properties of the polymer compositions according the inventive examples IE6 to IE10 are much better. The comparison of inventive example IE6 with the remaining inventive examples shows that the addition of mica is significantly increasing the char strength, the polymer composition acceding to IE6 shows the highest remaining sample weight.