HEAT-AGING RESISTANT POLYAMIDE MOLDING COMPOSITIONS

Abstract

Disclosed herein is a thermoplastic molding composition, including: a) 30 to 99.85 wt % of at least one thermoplastic polyamide as component A; b) 0.1 to 10 wt % of at least one polyhydric alcohol having more than 6 hydroxyl groups, and having a number average molecular weight M.sub.n of more than 2000 g/mol as component B; c) 0.05 to 3 wt % of at least one sterically hindered phenol antioxidant as component C; d) 0 to 3 wt % of at least one polycarboxylic compound having more than 3 carboxylic acid groups and/or carboxylate groups, and having a number average molecular weight M.sub.n of more than 300 g/mol as component D; e) 0 to 50 wt % of at least one fibrous and/or particulate filler as component E; and f) 0 to 25 wt % of further additives as component F; where the total of wt % of components A to F is 100 wt %.

Claims

1. A thermoplastic molding composition, comprising a) 30 to 99.85 wt % of at least one thermoplastic polyamide as component A; b) 0.1 to 10 wt % of at least one polyhydric alcohol having more than 6 hydroxyl groups, and having a number average molecular weight M.sub.n of more than 2000 g/mol as component B; c) 0.05 to 3 wt % of at least one sterically hindered phenol antioxidant as component C; d) 0.01 to 3 wt % of at least one polycarboxylic compound having more than 3 carboxylic acid groups and/or carboxylate groups, based on polyethylenimine which is N-substituted by acetic acid or acetate groups, and having a number average molecular weight M.sub.n of more than 300 g/mol as component D; e) 0 to 50 wt % of at least one fibrous and/or particulate filler as component E; and f) 0 to 25 wt % of further additives as component F; wherein the total of wt % of components A to F is 100 wt %.

2. The thermoplastic molding composition according to claim 1, wherein component B has more than 8 hydroxyl groups.

3. The thermoplastic molding composition according to claim 1, wherein component B has a number average molecular weight M.sub.n of more than 3000 g/mol.

4. The thermoplastic molding composition according to claim 1, wherein component B is an ethylene-vinyl alcohol copolymer having a content of 10 to 60 mol % of ethylene units.

5. The thermoplastic molding composition according to claim 1, wherein component C has a molecular weight of more than 500 g/mol.

6. The thermoplastic molding composition according to claim 1, wherein component D has a number average molecular weight M.sub.n of more than 500 g/mol.

7. The thermoplastic molding composition according to claim 1, wherein component C has at least one phenol group substituted by at least one branched C.sub.3-12-alkyl group.

8. The thermoplastic molding composition according to claim 1, wherein component D is present in an amount of from 0.01 to 3 wt %.

9. The thermoplastic molding composition according to claim 1, wherein component E comprises glass fibers, and is present in an amount of from 10 to 50 wt %.

10. A process for preparing the thermoplastic molding composition according to claim 1 by mixing the components A to F.

11. A method of using the thermoplastic molding composition according to claim 1 for producing fibers, foils, and moldings of any type.

12. A fiber, foil or molding, made of the thermoplastic molding composition according to claim 1.

13. A mixture comprising of b) 0.1 to 10 parts by weight of at least one polyhydric alcohol having more than 6 hydroxyl groups, and having a number average molecular weight M.sub.n of more than 2000 g/mol as component B; c) 0.05 to 3 parts by weight of at least one sterically hindered phenol antioxidant as component C; and d) 0.01 to 3 parts by weight of at least one polycarboxylic compound having more than 3 carboxylic acid groups and/or carboxylate groups, based on polyethylenimine which is N-substituted by acetic acid or acetate groups, and having a number average molecular weight M.sub.n of more than 300 g/mol as component D.

14. The mixture according to claim 13, wherein the amount of component D is from 0.1 to 2 parts by weight.

15. A method of using the mixture according to claim 13 in thermoplastic molding compositions comprising polyamides for improving the heat-aging resistance.

16. (canceled)

17. The mixture according to claim 13, consisting of b) 0.1 to 10 parts by weight of at least one polyhydric alcohol having more than 6 hydroxyl groups, and having a number average molecular weight M.sub.n of more than 2000 g/mol as component B; c) 0.05 to 3 parts by weight of at least one sterically hindered phenol antioxidant as component C; and d) 0.01 to 3 parts by weight of at least one polycarboxylic compound having more than 3 carboxylic acid groups and/or carboxylate groups, based on polyethylenimine which is N-substituted by acetic acid or acetate groups, and having a number average molecular weight M.sub.n of more than 300 g/mol as component D.

18. The thermoplastic molding composition according to claim 1, wherein component B has more than 10 hydroxyl groups.

19. The thermoplastic molding composition according to claim 1, wherein component B has a number average molecular weight M.sub.n of more than 5000 g/mol.

20. The thermoplastic molding composition according to claim 1, wherein component C has a molecular weight of more than 1000 g/mol.

21. The thermoplastic molding composition according to claim 1, wherein component D has a number average molecular weight M.sub.n of more than 1000 g/mol.

Description

EXAMPLES

[0381] The following components were used: [0382] PA1: Polyamide-6 having a viscosity number of 150 ml/g, measured on a 0.5% strength by weight solution in 96% strength by weight of sulfuric acid at 25° C. to ISO 307, melting point: 220° C. (Ultramid® B27 from BASF SE) [0383] PA2: Polyamide-66 having a viscosity number of 150 ml/g, measured on a 0.5% strength by weight solution in 96% strength by weight of sulfuric acid at 25° C. to ISO 307, melting point: 260° C. (Ultramid® A27 from BASF SE) [0384] PA3: Polyamide 66/6 having a viscosity number of 150 ml/g, measured on a 0.5% strength by weight solution in 96% strength by weight of sulfuric acid at 25° C. to ISO 307, melting point: 195° C. (Ultramid® C.sub.27 from BASF SE) [0385] GF: Standard E glass fiber, NEG E T249H [0386] Lubricant: Ethylene bis stearamide (EBS) from Lonza Cologne GmbH [0387] Stabilizer 1a: Cuprous iodide (CAS: 7681-65-4) [0388] Stabilizer 1b: Potassium iodide (CAS: 7681-11-0) [0389] Stabilizer 2: EVOH (ethylene vinyl alcohol copolymer; CAS: 25067-34-9) having an ethylene content of 20% to 50% [0390] Stabilizer 3: Irganox® 1010 from BASF SE [0391] Stabilizer 4: Trilon® P from BASF SE [0392] Stabilizer 5: DPE (dipentaerythritol, CAS: 126-58-9) [0393] Stabilizer 6: Iron powder (CAS: 7439-89-6) [0394] Colorant: Solvent Black 7 (CAS: 8005-02-5)

[0395] Preparation of the Granules

[0396] The nature-colored polyamide granules were dried in a drying oven at 100° C. for 4 hours so that the humidity was below 0.1%. Afterwards, the molding compositions were prepared by melt compounding. The components were mixed in a twin-screw extruder having a diameter of 25 mm and a L/D ratio of 36. Processing conditions were set for 16 kg/h and 260 to 330° C., employing a flat temperature profile depending on the base resin. The obtained extrudates were cooled and granulated.

[0397] The granules obtained were used for injection-molding tensile bars or plaques, according to ISO 527-2 and Charpy sticks according to ISO 179-1. The molding temperature depending on the base resin was between 280 and 330° C. melt temperature and 80 to 120° C. mold temperature. Compositions and mechanical data for inventive (INV) and comparative (COMP) examples are listed in below Tables 1 and 2.

[0398] Tensile modulus of elasticity, tensile stress at break and tensile strain at break are determined according to ISO 527. The Charpy (notched) impact strength is determined according to ISO 179-2/1eU and ISO 179-2/1eAf, respectively. Melting point and crystallization temperature are determined according to ISO 11357. All of the norms refer to the version valid in 2020.

[0399] Heat aging experiments were conducted in a standard laboratory oven at elevated temperatures and air as indicated in the tables below. Retention of tensile strength and elongation at break after heat aging in comparison with the value of the virgin specimens, the non-heat-aged control specimens were considered as being 100%.

[0400] Example COMP2 is based on US 2010/0028580 A. For Example COMP2, a migration of low molecular weight additive is reported in the literature (EP 2 896 656 A1). For Examples COM P1, INV1 and INV2, no migration was observed under test conditions. Migration or bleed-out of additives was tested by injection molding of 60×60×2 mm plaques at respective temperatures of 280° C./80° C. for PA6 and 290° C./80° C. for PA66. The resultant plaques where stored at 100° C. and 144 h in an oven at atmospheric pressure. Migration took place and in case of low molecular weight additives like DPE a white powder could be observed on the surface of the plaque.

[0401] The soot formation was determined visually after heat aging at the given conditions. For a more quantitative approach, the weight loss of a molded plaque of 60×60×2 mm and 60×60×1 mm dimension was determined with a balance before after accelerated heat aging at 200° C. and 1000 h.

TABLE-US-00003 TABLE 1 COMP1 INV1 INV2 COMP2 PA1 69.22 66 65.5 66.5 GF 30 30 30 30 Lubricant 0.2 0.2 0.2 0.2 Stabilizer 1a 0.06 Stabilizer 1b 0.22 Colorant 0.3 0.3 0.3 0.3 Stabilizer 2 3 3 Stabilizer 3 0.5 0.5 Stabilizer 4 0.5 Stabilizer 5 3 Mechanical properties (dry), 23° C.: Modulus of elasticity 9357 9714 9687 9540 (ISO 527) [MPa] Tensile strength 173 171 175 175 (ISO 527) [MPa] Elongation at break 3.9 4.0 4.0 3.4 (ISO 527) [%] Impact strength 96 98 101 72 (ISO 179/1eU) [kJ/m.sup.2] Notched impact 12.8 12.6 13.7 10.8 strength Aging 150° C.: Tensile strength 159 183 186 177 (2000 h) [MPa] Tensile strength 150 178 183 N.N. (3000 h) [MPa] Retention of tensile 87 104 104 N.N. strength after 3000 h [%] Elongation at break 2.0 2.9 3.,1 2.3 (2000 h) [%] Elongation at break 1.8 2.6 2.8 N.N. (3000 h) [%] Retention of elongation 46 65 70 N.N. at break after 3000 h [%] Sooting (visual) high low low low Aging 180° C.: Tensile strength 146 172 179 191 (2000 h) [MPa] Tensile strength 141 165 168 N.N (3000 h) [MPa] Retention of tensile 81 97 96 N.N. strength after 3000 h [%] Elongation at break 1.7 2.2 2.4 2.5 (2000 h) [%] Elongation at break 1.6 2.1 2.1 N.N. (3000 h) [%] Retention of elongation 40.8 52.5 52.5 N.N. at break after 3000 h [%] Sooting (visual) high medium medium medium Weight loss after aging at 200° C./1000 h: 1 mm [%] 9 8 6 N.N. 2 mm [%] 5 5 4 N.N.

TABLE-US-00004 TABLE 2 COMP3 INV3 INV4 INV5 PA2 54.2 51 50.5 50.3 PA3 15 15 15 15 GF 30 30 30 30 Lubricant 0.2 0.2 0.2 0.2 Stabilizer 1a 0.075 Stabilizer 1b 0.225 Colorant 0.3 0.3 0.3 0.3 Stabilizer 2 3 3 3 Stabilizer 3 0.5 0.5 0.5 Stabilizer 6 Stabilizer 4 0.5 0.5 Stabilizer 6 0.25 Mechanical properties (dry), 23° C.: Modulus of elasticity 9786 9912 9984 9967 (ISO 527) [MPa] Tensile strength 182 179 185 182 (ISO 527) [MPa] Elongation at break 3.7 3.74 3.75 3.5 (ISO 527) [%] Impact strength 87 95 94 86 (ISO 179/1eU) [kJ/m.sup.2] Notched impact 9.48 9.85 10.5 9.37 strength Aging 190° C.: Tensile strength 139 148 163 172 (2000 h) [MPa] Retention of tensile 77 83 88 95 strength after 2000 h [%] Elongation at break 1.6 1.7 1.94 2.19 (2000 h) [MPa] Retention of elongation 42 46 52 63 at break after 2000 h [%]

[0402] The above examples illustrate that by employing stabilizer 2 (a polyhydric alcohol according to component B) and stabilizer 3 (a sterically hindered phenol antioxidant according to component C) polyamide molding compositions can be obtained which show a high retention of tensile strength and elongation at break after prolonged heat treatment. The heat aging resistance of the polyamide molding compositions can be further increased by additionally employing stabilizer 4 which is a polycarboxylic compound of component D, see Examples INV2, INV4 and INV5.