POLYAMIDE COMPOSITION COMPRISING CARBON BLACK

Abstract

Disclosed herein is a polyamide composition (PC) including at least one polyamide (A) and at least one carbon black (B), where the surface layer of the at least one carbon black (B) includes not more than 2% by weight of oxygen, based on the total weight of the surface layer of the at least one carbon black (B), and where the weight of oxygen in the surface layer is measured by X-ray photoelectron spectroscopy at an X-ray penetration depth of 2 to 10 nm. Further disclosed herein are a process for producing the polyamide composition (PC), a process for producing a moulded article by forming the polyamide composition (PC), a moulded article including the polyamide composition (PC), and a method of using the at least one carbon black (B) in a polyamide composition (PC) for increasing the shrinkage of moulded articles made from the polyamide composition (PC).

Claims

1. A polyamide composition (PC) comprising the following components (A) and (B) (A) at least one polyamide, and (B) at least one carbon black, wherein the surface layer of component (B) comprises not more than 2% by weight of oxygen, based on the total weight of the surface layer of component (B), and wherein the weight of oxygen in the surface layer is measured by X-ray photoelectron spectroscopy at an X-ray penetration depth of 2 to 10 nm, wherein the polyamide composition (PC) comprises in the range from 55 to 99.9% by weight of the at least one polyamide (A) and in the range from 0.1 to 4% by weight of the at least one carbon black (B), based on the total weight of the polyamide composition (PC).

2. The polyamide composition (PC) according to claim 1, wherein the polyamide composition (PC) comprises in the range from 60 to 99.7% by weight of component (A) and in the range from 0.3 to 3% by weight of component (B), based in each case on the total weight of the polyamide composition (PC).

3. The polyamide composition (PC) according to claim 1, wherein the surface layer of component (B) comprises not more than 1% by weight of nitrogen, based on the total weight of the surface layer of component (B), and wherein the weight of nitrogen in the surface layer is measured by X-ray photoelectron spectroscopy at an X-ray penetration depth of 2 to 10 nm.

4. The polyamide composition (PC) according to claim 1, wherein component (B) is a partial combustion carbon black.

5. The polyamide composition (PC) according to claim 1, wherein component (B) has an average diameter in the range from 5 nm to 70 nm.

6. The polyamide composition (PC) according to claim 1, wherein the at least one polyamide (A) present in the polyamide composition (PC) is selected from the group consisting of PA 4, PA 6, PA 7, PA 8, PA 9, PA 11, PA 12, PA 46, PA 66, PA 69, PA 510, PA 610, PA 612, PA 613, PA 1212, PA1313, PA 6T, PA MXD6, PA 61, PA 6-3-T, PA 6/6T, PA 6/66, PA 66/6, PA 6/12, PA 66/6/610, PA 61/6T, PA PACM 12, PA 61/6T/PACM, PA 12/MACMI, PA 12/MACMT, PA PDA-T and copolyamides composed of two or more of the abovementioned polyamides.

7. The polyamide composition (PC) according to claim 1, wherein the at least one polyamide (A) present in the polyamide composition (PC) is selected from the group consisting of polyamide 6 (PA 6), polyamide 66 (PA 66), polyamide 6/66 (PA 6/66), polyamide 66/6 (PA 66/6), polyamide 610 (PA 610), polyamide 6/6T (PA 6/6T), polyamide 12 (PA12) and polyamide 1212 (PA1212).

8. The polyamide composition (PC) according to claim 1, wherein the polyamide composition (PC) further comprises at least one additive (C) selected from the group consisting of stabilizers, dyes, pigments, fillers, reinforcers, impact modifiers and plasticizers.

9. The polyamide composition (PC) according to claim 8, wherein the polyamide composition (PC) comprises in the range from 0 to 55% by weight of the at least one additive (C), based on the total weight of the polyamide composition (PC).

10. The polyamide composition (PC) according to claim 1, wherein component (B) has a 325 mesh sieve residue of less than 50 ppm

11. The polyamide composition (PC) according to claim 1, wherein component (B) has a volume resistivity of less than 100 Ω*cm.

12. The polyamide composition (PC) according to claim 1, wherein component (B) has a pour density of less than 300 g/l.

13. A process for producing a polyamide composition (PC) according to claim 1, wherein component (A), a masterbatch (MB) and optionally component (C) are compounded in a twin-screw extruder, wherein the masterbatch (MB) comprises component (A) and component (B).

14. The process according to claim 13, wherein the masterbatch (MB) comprises from 60 to 80% by weight of component (A) and in the range from 20 to 40% by weight of component (B), based in each case on the total weight of the masterbatch (MB).

15. A process for the production of a moulded article, the method comprising forming the polyamide composition (PC) according to claim 1.

16. A moulded article comprising the polyamide composition (PC) according to claim 1.

17. The moulded article according to claim 16, wherein the moulded article has a volume resistivity of at least 5*10.sup.11 Ω*m.

18. A method of using at least one carbon black (B) in a polyamide composition (PC), the method comprising using the at least one carbon black (B) in a polyamide composition (PC) for increasing the shrinkage of moulded articles made from said polyamide composition (PC), wherein the surface layer of the at least one carbon black (B) comprises not more than 2% by weight of oxygen, based on the total weight of the surface layer of the at least one carbon black (B), and wherein the weight of oxygen in the surface layer is measured by X-ray photoelectron spectroscopy at an X-ray penetration depth of 2 to 10 nm.

Description

EXAMPLES

[0123] The following components were employed:

[0124] Polyamide (A):

TABLE-US-00003 (A1) Polyamide 6 (PA 6) (Ultramid ® B27E; BASF SE)

[0125] Carbon Black (8):

TABLE-US-00004 (B1) Ensaco ®250G (Imerys Graphite & Carbon Switzerland Ltd.) (B2) Ensaco ®360G (Imerys Graphite & Carbon Switzerland Ltd.) (B3) Black Pearls ® (Cabot Corporation) 880

[0126] Additive (C)

[0127] (C1) Glass Fiber ECS 03 T-249 (Nippon Electric Glass)

[0128] (C2) N,N′-Ethylenebis(stearamide)

[0129] (C3) Masterbatch comprising CuI and KI

[0130] Table 1 states the essential parameters of the polyamide used (component (A)) and table 2 states the essential parameters of the carbon blacks used (component (B)).

TABLE-US-00005 TABLE 1 Zero shear rate viscosity η.sub.0 at AEG CEG T.sub.M T.sub.G 240° C. Type [mmol/kg] [mmol/kg] [° C.] [° C.] [Pas] (A1) PA 6 36 54 220.0 53 399

[0131] AEG indicates the amino end group concentration. This is determined by means of titration. For determination of the amino end group concentration (AEG), 1 g of the component (semicrystalline polyamide) was dissolved in 30 mL of a phenol/methanol mixture (volume ratio of phenol:methanol 75:25) and then subjected to potentiometric titration with 0.2 N hydrochloric acid in water.

[0132] The CEG indicates the carboxyl end group concentration. This is determined by means of titration. For determination of the carboxyl end group concentration (CEG), 1 g of the component (semicrystalline polyamide) was dissolved in 30 mL of benzyl alcohol. This was followed by visual titration at 120° C. with 0.05 N potassium hydroxide solution in water.

[0133] The melting temperature (T.sub.M) of the semicrystalline polyamides and the glass transition temperature (T.sub.G) were each determined by means of differential scanning calorimetry.

[0134] For determination of the melting temperature (T.sub.M), as described above, a first heating run (H1) at a heating rate of 20 K/min was measured. The melting temperature (T.sub.M) then corresponded to the temperature at the maximum of the melting peak of the heating run (H1).

[0135] For determination of the glass transition temperature (T.sub.G), after the first heating run (H1), a cooling run (C) and subsequently a second heating run (H2) were measured. The cooling run was measured at a cooling rate of 20 K/min; the first heating run (H1) and the second heating run (H2) were measured at a heating rate of 20 K/min. The glass transition temperature (T.sub.G) was then determined as described above at half the step height of the second heating run (H2).

[0136] The zero shear rate viscosity η.sub.0 was determined with a “DHR-1” rotary viscometer from TA Instruments and a plate-plate geometry with a diameter of 25 mm and a plate separation of 1 mm. Unequilibrated samples were dried at 80° C. under reduced pressure for 7 days and these were then analysed with a time-dependent frequency sweep (sequence test) with an angular frequency range of 500 to 0.5 rad/s. The following further analysis parameters were used: deformation: 1.0%, analysis temperature: 240° C., analysis time: 20 min, preheating time after sample preparation: 1.5 min.

TABLE-US-00006 TABLE 2 Particle 325 mesh size sieve residue Oxygen Nitrogen [nm] [ppm] [wt %] wt %] (B1) <30 2 1.0 0.5 (B2) <30 10 1.0 0.5 (B3) >100 <100 6.7 1.6

[0137] The 325 mesh sieve residue was determined according to ASTM D1514-00

[0138] The weight percentages of the oxygen and nitrogen are determined by X-ray photoelectron spectroscopy at a X-ray penetration depth of 2 to 10 nm.

[0139] Production of the Masterbatch (MB)

[0140] The components reported in table 3 were compounded in the ratio reported in table 3 in a twin-screw extruder (ZE25A UXTI) at 280 rpm, a barrel temperature of 260° C. and a throughput of 11.2 kg/h with subsequent extrudate pelletization.

TABLE-US-00007 TABLE 3 (A1) (B1) (B2) (B3) Example [wt %] [wt %] [wt %] [wt %] (MB1) 70 30 — — (MB2) 70 — 30 — (MB3) 70 — — 30

[0141] Production of the Polyamide Composition (PC)

[0142] The components reported in table 3 were compounded in the ratio reported in table 4 in a twin-screw extruder (ZE25A UXTI) at 280 rpm, a barrel temperature of 260° C. and a throughput of 11.2 kg/h with subsequent extrudate pelletization.

TABLE-US-00008 TABLE 4 Example E1 E2 E3 C4 C5 C6 (A1) 62.34 60.68 60.68  64.01 62.34 60.68 [wt %] (M1) 1.67 3.33 — — — — [wt %] (M2) — — 3.33 — — — [wt %] (M3) — — — — 1.67 3.33 [wt %] (C1) 35.00 35.00 35.00  35.00 35.00 35.00 [wt %] (C2) 0.30 0.30 0.30 0.30 0.30 0.30 [wt %] (C3) 0.69 0.69 0.69 0.69 0.69 0.69 [wt %]

[0143] Production of Moulded Parts

[0144] The above obtained pellets were injection-moulded on an injection molding machine at a melt temperature of 280° C. to give moulded parts of a thickness of 2 mm, and of dimensions of 60×60 mm.

[0145] Subsequently, the properties of the moulded parts obtained were determined. The moulded parts obtained were tested in the dry state after drying at 80° C. for 336 h under reduced pressure. The results are shown in table 5.

[0146] The shrinkage was determined according to ISO 294.

[0147] To measure Δ creep, the moulded parts were drawn up to a yield stress of 70% and the elongation of the moulded parts was determined. After 12 hours, the elongation of the moulded parts was determined again. The difference of the two elongation values corresponds to Δ creep.

[0148] Tensile strength, tensile modulus of elasticity and elongation at break were determined according to ISO 527-1:2012.

[0149] The volume resistivity was determined by first determining the electrical conductivity as volume conductivity as the volume resistivity is the reciprocal value of the volume conductivity. The volume conductivity was determined using a 4-point measuring apparatus. For each moulded article, the measurement was carried out on five specimens having the dimensions 77×12×4 mm.sup.3 which had been sawn from moulded articles. To achieve good contact between specimen and electrodes, four silver electrodes were painted directly on the specimen using a conductive silver paste (Leitsilber 200 from Hans Wohlbring GmbH). A Current Source 225 was used as current source, a Programmable Electrometer 617 was used as voltage measuring instrument and a Multimeter 1000 was used as current measuring instrument, in each case from Keithley Instruments.

TABLE-US-00009 TABLE 5 Example E1 E2 E3 C4 C5 C6 Shrinkage 0.27 0.28 0.29 0.24 0.24 0.24 Parallel [%] Shrinkage 0.88 0.91 0.90 0.75 0.79 0.80 Perpendicular [%] Tensile 11 090     11 140     11 150     10 990     10 790     11 560     modulus of elasticity [MPa] Tensile 177    176    186    182    173    177    strength [MPa] Elongation at 3.0  3.0  3.4  3.8  3.4  3.4  break [%] Δ Creep[%] 0.79 0.81 1.07 1.03 Volume 3.2 * 10.sup.12 8.2 * 10.sup.11 3.4 * 10.sup.12 3.4 * 10.sup.12 resistivity [Ω * m]

[0150] It is clearly apparent from table 5 that the use of at least one carbon black (B), wherein the surface of the at least one carbon black (B) comprises not more than 2% by weight of oxygen, based on the total weight of the surface of the at least one carbon black (B), in a polyamide composition results in a higher shrinkage of the mouldings comprising this polyamide composition (PC). The mouldings show, despite the high shrinkage, a high creep resistance as well as good mechanical properties like a high tensile modulus of elasticity and a high tensile strength.