Flame-retardant polyamides

Abstract

Thermoplastic molding compositions containing A) from 30 to 97% by weight of at least one polyamide, B) from 1 to 20% by weight of a melamine compound, C) from 1 to 50% by weight of a mineral filler composed of a mixture of (crypto)crystalline silica (C1) and amorphous silica (C2) and of calcined kaolin (C3), D) from 0 to 20% by weight of a fibrous filler, E) from 0 to 25% by weight of talc powder, F) from 0 to 15% by weight of other additives, where the total of the percentages by weight of A) to F) is 100%.

Claims

1. A thermoplastic molding composition comprising A) from 40 to 80% by weight of at least one polyamide, B) from 2 to 13% by weight of a melamine compound comprising melamine cyanurate, C) from 10 to 40% by weight of a mineral filler comprising a mixture of (crypto)crystalline silica (C1) and amorphous silica (C2) and of calcined kaolin (C3), D) from 0 to 20% by weight of a fibrous filler, E) from 0 to 25% by weight of talc powder, F) from 0.1 to 1.5% by weight of at least one heat stabilizer selected from the group consisting of compounds of mono- and divalent copper, stabilizers based on secondary aromatic amines, stabilizers based on sterically hindered phenols, and mixtures of these and 0 to 15% by weight of other additives, comprising as mineral filler C) a mixture of from 53 to 65% by weight of C1 with from 7 to 12% by weight of C2 and from 25 to 35% by weight of C3, based on 100% of C, in which component C) has 3 to 8% by weight Al content and 38 to 45% by weight Si content, based on 100% of C) and where the total of the percentages by weight of A) to F) is 100%.

2. The thermoplastic molding composition according to claim 1, comprising D) from 0.5 to 20% by weight.

3. The thermoplastic molding composition according to claim 1, where the BET specific surface area of component C) in accordance with DIN ISO 9277 is from 5 to 15 m.sup.2/g.

4. The thermoplastic molding composition according to claim 3, where the oil absorption value of component C) in accordance with DIN ISO 787 Part 5 is from 50 to 60 g/100 g.

5. The thermoplastic molding composition according to claim 1 for use in the production of fibers, films, or moldings.

6. A molding of any type obtained from the thermoplastic molding composition according to claim 1.

7. A thermoplastic molding composition consisting of A) from 40 to 80% by weight of at least one polyamide, B) from 2 to 13% by weight of a melamine compound comprising melamine cyanurate, C) from 10 to 40% by weight of a mineral filler comprising a mixture of (crypto)crystalline silica (C1) and amorphous silica (C2) and of calcined kaolin (C3), D) from 0 to 20% by weight of a fibrous filler, E) from 0 to 25% by weight of talc powder, F) from 0.1 to 1.5% of at least one heat stabilizer selected from the group consisting of a compound of mono- or divalent copper, a copper compound in combination with a metal halide, a stabilizer based on a secondary aromatic amine, a stabilizer based on a sterically hindered phenol, and mixtures thereof, and 0 to 15% by weight of other additives, selected from the group consisting of a mold-release agent selected from the group consisting of calcium montanate, stearic acid, behenic acid, stearyl alcohol, an alkyl stearate, a stearamide, and an ester of pentaerythritol with a long-chain fatty acid, and a pigment, an impact modifier, a nucleating agent, and mixtures thereof, comprising as mineral filler C) a mixture of from 53 to 65% by weight of C1 with from 7 to 12% by weight of C2 and from 25 to 35% by weight of C3, based on 100% of C, in which component C) has 3 to 8% by weight Al content and 38 to 45% by weight Si content, based on 100% of C) and where the total of the percentages by weight of A) to F) is 100%.

Description

EXAMPLES

(1) The Following Components were Used:

(2) Component A:

(3) Polyamide 6 with intrinsic viscosity IV 125 ml/g, measured in 0.5% by weight solution in 96% by weight sulfuric acid at 25° C. in accordance with ISO 307 (Ultramid® B24 from BASF SE).

(4) Component B:

(5) Melamine cyanurate with average particle size d.sub.50˜2.6 μm (Melapur® MC25 from BASF SE).

(6) Component C/1a:

(7) Calcined mineral filler consisting, according to X-ray diffraction analysis using Rietveld evaluation, of a mixture of amorphous silica (10% by weight) and crystalline silica (60% by weight) and of calcined lamellar kaolin (30% by weight). (SILFIT® Z91 from Hoffmann Mineral)

(8) Specification and Test Methods:

(9) BET specific surface area: 8 m.sup.2/g (DIN ISO 9277),

(10) Oil absorption value: 55 g/100 g (DIN ISO 787 Part 5),

(11) Si content: 42%

(12) Al content: 4.8%

(13) Component C/1b:

(14) Calcined mineral filler consisting, according to X-ray diffraction analysis using Rietveld evaluation, of a mixture of amorphous silica (10% by weight) and crystalline silica (60% by weight) and of calcined lamellar kaolin (30% by weight). Surface sizing aminosilane (AKTIFIT® AM from Hoffmann Mineral)

(15) Specification and Test Methods:

(16) BET specific surface area: 7 m.sup.2/g (DIN ISO 9277),

(17) Oil absorption value: 55 g/100 g (DIN ISO 787 Part 5),

(18) Si content: 41%

(19) Al content: 5.6%

(20) Component C/1c:

(21) Commercially available talc powder (grade HP 325 from Pechel GmbH) with from 60 to 62% by weight silicon dioxide content and from 30 to 32% by weight magnesium oxide content, and average particle size d.sub.50 from 10 to 14 μm.

(22) Component D/1:

(23) Standard chopped glass fiber for polyamides, L=4.0 mm, D=10 μm

(24) Component D/2:

(25) Short glass fiber, average length (d.sub.50)˜210 μm, D=10 μm

(26) Components F: all of the formulations used the following as other additives: 0.3% by weight of 3,3′-bis(3,5-di-tert-butyl-4-hydroxyphenyl)-N,N′-hexamethylenedipropionamide (CAS No. 23128-74-7), 0.3% by weight of aluminum stearate (CAS No. 300-92-5), and 2.5% by weight of titanium dioxide (CAS No. 13463-67-7).

(27) Production of Molding Compositions

(28) The glow-wire resistance improvements described in the invention were demonstrated by compounding appropriate polyamide molding compositions. For this, the individual components were mixed in a ZSK 26 (Berstorff) twin-screw extruder at throughput 20 kg/h with a flat temperature profile at about 250-270° C., discharged in the form of strand, cooled until pellitizable and pelletized.

(29) Tests

(30) The test samples for the tests listed in table 1 were injection-molded in an Arburg 420C injection-molding machine at melt temperature about 250-290° C. and mold temperature about 80° C.

(31) The flame retardancy of the molding compositions was determined firstly by the UL 94 V method (Underwriters Laboratories Inc. Standard of Safety, “Test for Flammability of Plastic Materials for Parts in Devices and Appliances”, pp. 14-18, Northbrook 1998).

(32) Glow-wire resistance was determined by the GWFI (glow wire flammability index) in accordance with 60695-2-12. The GWFI test, carried out on 3 test samples (for example plaques measuring 60×60×1.0 mm or discs), used a glowing wire at temperatures of from 550 to 960° C. to determine the maximal temperature leading to no ignition during a time including the period of exposure to the glow-wire in 3 successive tests. The test sample was pressed by a force of 1 newton for a period of 30 seconds against a heated glow-wire. The penetration depth of the glow-wire was restricted to 7 mm. The test is considered passed if the afterflame time of the test sample after removal of the glow-wire is less than 30 seconds and if tissue paper placed under the test sample does not ignite.

(33) The proportions of components A) to F) in table 1 give a total of 100% by weight. The table shows the constitutions of the molding compositions and the results of the tests.

(34) TABLE-US-00002 TABLE 1 Component Test method 1 2 3 4 5 6 7 8 9 10 11 12 13 14 A 63.9 70.9 68.9 66.9 65.9 62.9 60.9 58.9 55.9 63.9 63.9 60.9 60.9 60.9 B 8 6 8 10 6 4 6 8 6 8 8 6 6 6 C/1a 25 C/1b 20 20 20 25 30 30 30 35 20 20 25 20 15 C/1c 5 10 15 D/1 5 D/2 5 F 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 Tensile 5122 4585 4547 4640 4943 5224 5335 5550 5828 5217 5644 5360 5727 5936 modulus of elasticity/MPa (ISO 527) Yield stress/ 77 82 82 81 80 82 81 80 82 81 87 77 76 74 MPa (ISO 527) Tensile strain 2.4 3.2 3.2 3.1 3.0 3.0 2.8 2.6 2.7 2.8 2.7 2.8 2.5 2.4 at break/% (ISO 527) Impact 38 96 64 53 69 72 62 50 55 41 33 47 37 36 resistance/ kJ/m.sup.2 (ISO 179/1eU) Notched impact 2.0 3.4 3.4 3.2 2.8 3.1 3.3 2.0 resistance/ kJ/m.sup.2 (ISO 179/1eA) MVR 186 230 215 206 207 193 179 155 134 184 173 186 183 186 275° C./5 kg (ISO 1133) HDT/A/° C. 83 77 81 83 89 93 87 140 93 93 97 DIN EN ISO 75 CTI/V 575 550 550 (DIN EN 60112) UL 94 V test V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 V-2 (0.8 mm) GWFI 960° C./ passed passed passed 0.5 mm GWFI 960° C./ passed passed passed passed passed passed passed passed passed passed passed 0.75 mm GWFI 960° C./ passed passed passed passed passed passed passed passed passed passed passed passed passed passed 1.0 mm GWFI 960° C./ passed passed passed passed passed passed passed passed passed passed passed passed passed passed 1.5 mm

(35) From the data in table 1 it is apparent that the compositions of the invention exhibit very good values not only in respect of flame retardancy and glow-wire resistance (UL 94 V-2 and GWFI 960° C. at 1.0 mm) but also in relation to mechanical properties.