Flame-retardant polyamides with pale color

Abstract

Thermoplastic molding compositions comprising A) from 10 to 99.8% by weight of a thermoplastic polyamide, B) from 0.1 to 60% by weight of red phosphorus, C) from 0.01 to 4% by weight of a Cu(I) salt or Ag(I) oxide or Cu(I) complex or Ag(I) salt or Cu(I) oxide or Ag(I) complex, or a mixture of these, D) from 0 to 40% by weight of an impact modifier, and E) from 0 to 60% by weight of further additional substances, where the total of the percentages by weight of A) to E) is 100%.

Claims

1. A method for producing a molding composition consisting of A) from 20 to 98% by weight of a thermoplastic polyamide, B) from 0.5 to 40% by weight of red phosphorus, C) from 0.1 to 3% by weight of a Cu(I) salt or Ag(I) oxide or Cu(I) complex or Ag(I) salt or Cu(I) oxide or Ag(I) complex selected from the group consisting of Cu.sub.2O, Ag.sub.2O, CuSCN, AgSCN, CuCl, AgCl, CuBr, AgBr, CuI, and mixtures of these, D) from 1 to 30% by weight of an impact modifier, and E) from 0 to 50% by weight of further additional substances, the method comprising mixing with components A), B), D) and optionally E) with component C), wherein the thermoplastic molding compositions, with L color values at least 15% lower than those of PA molding compositions without component C) in accordance with DIN 53236 and ISO 7724-3, CieLab method wherein component E) is selected from the group consisting of carbon fibers, glass fibers, glass beads, amorphous silica, calcium silicate, calcium metasilicate, magnesium carbonate, kaolin, chalk, powdered quartz, mica, barium sulfate, feldspar, lubricants, ZnO, Zn borate, Zn stannate, MgO, Mg(OH).sub.2, ZnCO.sub.3, MgCO.sub.3, CaCO.sub.3, Mg Ca carbonates, AlOOH, sterically hindered phenols, nigrosins, melamine compounds, phosphites, amines, hydroquinones, aromatic secondary amines, resorcinols, salicylates, benzotriazoles, benzophenones, inorganic pigments, sodium phenylphosphinate, aluminum oxide, silicon dioxide, talc powder, and mixtures thereof; and wherein component D) is one or more elastomeric polymers.

2. The method according to claim 1, wherein the composition further comprises an alkali metal halide, and in which component C) is in a mixture with the alkali metal halide.

3. The method according to claim 2, where the alkali metal halide is potassium bromide or potassium iodide, or a mixture of these.

4. The method according to claim 1, wherein component C) is present with an alkali metal halide in a mixing ratio of from 1:10 to 1:1.

5. The method according to claim 1 for the production of a molding composition which, wherein the thermoplastic molding compositions have, with phosphorus release values at 28 days/70 C. of less than 200 g of phosphorus/specimen.

6. The method according to claim 1, wherein the composition contains from 0.2 to 1.0% by weight of component C.

7. The method according to claim 6, wherein the composition contains 1 to 15% by weight of component B.

Description

EXAMPLES

(1) The following components were used:

(2) Component A/1

(3) Nylon-6,6 with intrinsic viscosity IV 150 ml/g, measured as a 0.5% by weight solution in 96% by weight sulfuric acid at 25 C. in accordance with ISO 307. (Ultramid A27 from BASF SE was used.)

(4) Component A/2

(5) PA 66 with IV 125 ml/g (Ultramid A24 from BASF SE)

(6) Component B/1

(7) 50% strength concentrate of red phosphorus with average particle size (d.sub.50) from 10 to 30 m in an olefin polymer of: 59.8% by weight of ethylene, 35% by weight of n-butyl acrylate, 4.5% by weight of acrylic acid, and 0.7% by weight of maleic anhydride (component D) with melt flow index MFI 10 g/10 min (190/2.16). The copolymer was produced via copolymerization of the monomers at elevated temperature and elevated pressure.

(8) Component B/2

(9) P.sub.red (see above) without elastomer D)

(10) Component C/1

(11) Copper iodide

(12) Component C/2

(13) bis(Triphenylphosphine)copper iodide complex CAS No.: 16109-82-3

(14) Component E/1:

(15) Standard chopped glass fiber for polyamides, length=4.5 mm, diameter=10 m.

(16) Component E/2:

(17) N,N-Hexamethylenebis-3,5-di-tert-butyl-4-hydroxhydrocinnamide (Irganox 1098)

(18) Component E/3:

(19) Ca stearate

(20) Component E/4

(21) ZnO

(22) Production of the Molding Compositions

(23) In order to provide evidence of the phosphorus stability improvements described in the invention, appropriate plastics molding compositions were manufactured via compounding. To this end, the individual components were mixed in a ZSK 26 (Berstorff) twin-screw extruder with throughput 20 kg/h and a flat temperature profile at about 270 C., extruded in the form of strand, cooled until pelletizable, and pelletized.

(24) The test specimens for the studies set out in table 1 were injection-molded in an Arburg 420 C injection-molding machine at a melt temperature of about 270 C. and mold temperature of about 80 C. In the examples of the invention, component C) was applied to the dried pellets in the form of powder in a drum.

(25) Testing of Plastics Parts for Phosphorus Release:

(26) A specimen of plastic (12512.51.6 mm) was halved, and each half was placed in a 10 ml glass beaker. A silver contact material (10500.125 mm) was placed in a short test tube. The three specimens were then placed in a 100 ml screw-cap bottle, 5 ml of water were added, and the sealed system was placed in a drying oven at 70 C. After 28 days, the test tube was removed and filled to the top with water, and the entire contents were placed in a glass beaker. 5 ml of conc. hydrochloric acid were added, and the mixture was evaporated almost to dryness. The metal specimen was then removed and rinsed with water; 1 ml of sulfuric acid was admixed with the residue, and the mixture was again evaporated almost to dryness. 20 ml of water are then used for dilution, 4 ml of 5% strength potassium peroxodisulfate solution are added, and the mixture is heated for 30 minutes. The phosphorus was then determined photometrically by using molybdenum blue, in g of phosphorus/specimen of plastic.

(27) Color Measurement:

(28) Color was measured in accordance with DIN 53236:1983, method B. The calculation method used was in accordance with DIN 6174:1979, which is identical with ISO 7724-3, this being what is known as the CieLab method: L*=Lightness; +is whiter; is blacker a*=Color components; +redder; greener b*=Color components; +yellower; bluer. The value zero means no color=uncolored=colorless. C*ab=Chroma (uncolored/colored); h ab=Hue angle (from 0 to 360). Evaluation of all of L*, a*, and b* produces the color difference E*.

(29) The CTI value was determined in accordance with IEC 60112.

(30) Table 1 shows the constitutions of the uncolored molding compositions and the results of the measurements.

(31) TABLE-US-00004 TABLE 1 Component comp 1* INV1 INV2 INV3 INV4 INV5 INV6 A/1 60.6 60.4 60.1 59.6 60.4 60.1 59.6 B/1 12 12 12 12 12 12 12 C/1 0.2 0.5 1.0 C/2 0.2 0.5 1.0 E/1 26 26 26 26 26 26 26 E/2 + E/3 (50:50) 0.7* 0.7* 0.7* 0.7* 0.7* 0.7* 0.7* E/4 0.7 0.7 0.7 0.7 0.7 0.7 0.7 Color measurement/delta L 31.3 26.5 24.0 19.7 20.4 18.0 17.3 Color measurement/delta a 29.1 19.1 14.1 6.7 9.5 2.3 0.54 Color measurement/delta b 22.8 15.1 10.6 4.0 6.3 0.8 0.10 Modulus of elasticity/[MPa] 8090 8050 8041 8073 8080 8101 8204 Tensile stress at break/[MPa] 130 132 134 133 131 133 136 Tensile strain at break/[%] 3.6 3.2 3.1 3.2 3.6 3.6 3.5 CTI/[V] open open open open open open open Phosphorus release after 28 480 150 60 54 8 5 2 days/70 C. in g of phosphorus/specimen *for comparison

(32) The data in table 1 show that the compositions of the invention exhibit much better phosphorus stability than the prior art (reduced phosphorus release). The compositions of the invention are also found to have a darker color (delta L value smaller) and to have less red/yellow coloring (delta a and delta b values smaller).

(33) Pale-colored PA Molding Compositions

(34) Basic Formulation for Table 2

(35) TABLE-US-00005 Component A/2 44.1 [% by weight] B/2 2 D 10 E/1 25 E/2 0.35 E/3 0.35 E/4 0.7 E/5 5 E/6 12.5 Component E/5: Titanium dioxide Component E/6: Melamine polyphosphate

(36) The respective components C) (see table 2) were incorporated in the abovementioned formulation, in each case at 1% by weight (PA content being correspondingly 43.1% by weight).

(37) Mini Extrusion

(38) The specimens were incorporated by means of mini extrusion, using a Micro 15 extruder from DSM. The processing took place at 280 C.

(39) Color measurement: see table 1.

(40) Daylight Aging

(41) Exposure to light in accordance with DIN EN ISO 11341 Method 2:0.35 W/m.sup.2nm) at 340 nm, exposure time 24 h; exposure temperature 38 C. (+2 C.), exposure humidity 50% (+/10%).

(42) TABLE-US-00006 TABLE 2 color fastness Delta color measurement after Color measurement weathering L* a* b* L* a* b* E Basic formulation 72 12 10 3.4 7.5 6.4 10.43 (for comparison) +Ag(I)Cl 63 1 3 0.22 0 0.13 0.25 C/2 with KI (1:2) 67 2 1 0.58 0.91 0.31 1.12 +Cu(I) acetate 64 +1 1 0.9 0.23 0.14 0.94 +Cu(I)Br 62 1 4 0.21 0.2 0.1 0.30 +Cu(I)Cl 62 1 3 0.25 0.04 0.16 0.30 +Cu(I)I 64 1 3 0.31 0.28 0.35 0.68 +Cu(I).sub.2O 59 1 3 0.78 0.02 0.16 0.80 +Cu(II)O 67 5 4 1.23 1.71 0.22 2.12 (for comparison) +Cu(I) oxalate 61 1 3 0.62 0.11 0.24 0.67 Cu(I)SCN 64 1 2.2 0.04 0.02 0.02 0.05
Production of the Molding Compositions for Table 3

(43) The thermoplastic material was processed by means of a Leistritz ZSK 25-F41 twin-screw extruder with throughput 30 kg/h. Extrusion temperature was 300 C. The polymer strand was cooled by means of a waterbath and then pelletized and dried. Injection molding to give the test specimens used took place at 320 C.

(44) Mechanical Properties were Measured in Accordance With

(45) Tensile modulus of elasticity: DIN EN ISO 527-1/-2 Tensile strain at break: DIN EN ISO 527-1/-2 Tensile stress at break: DIN EN ISO 527-1/-2 Charpy impact resistance: DIN EN ISO 179.

(46) Flame retardancy was tested in accordance with UL 94.

(47) TABLE-US-00007 TABLE 3 Components comp1 1 2 3 A/2 36.75 36.5 36.25 35.75 B/2 1.85 1.85 1.85 1.85 C/2 with KI (1:2) 0.25 0.5 1 D 10 10 10 10 E/1 25 25 25 25 E/2 0.35 0.35 0.35 0.35 E/3 0.35 0.35 0.35 0.35 E/4 0.7 0.7 0.7 0.7 E/5 12.5 12.5 12.5 12.5 E/6 12.5 12.5 12.5 12.5 Mechanical properties Modulus of elasticity/MPa 8353 7539 7373 7205 Tensile stress at break/MPa 91 90 90 84 Tensile strain at break/% 1.8 2.4 2.2 1.9 Charpy without notch at 42 43 43 38 23 C./kJ/m.sup.2 UL 94 0.8 mm 2 d/23 C. Classification V-0 V-0 V-0 V-0 CTI measurement/V not measured 400 400 400 Color measurement L* 77 76 72 70 a* 7 6 3 1 b* 6 6 2 0 Color fastness after 24 h of dry weathering L* 79 78 73 70 a* 3 3 2 0.24 b* 4 4 2 2 E* 4.7 3.5 1.0 2.5