Process for improving carbon black dispersion

An injection molded article produced by a process comprising preparing injection molding a coloured polymer composition by melt-mixing, wherein the coloured polymer composition comprises a melt-mixed coloured polycarbonate composition, comprising:

• a) from 40 to 99.96 wt. % of at least one thermoplastic polymer (a), wherein polymer (a) is at least one selected from the group consisting of aromatic polycarbonates and aromatic polyester carbonates, wherein the polymer (a) has a weight average molecular weight of 15,000 to 80,000 g/mol, and wherein the polymer (a) is a homopolycarbonate or copolycarbonate containing bisphenol A;
• b) from 0.1 to 3 wt. % of at least one pigment component (b);
• c) from 0.1 to 3 wt. % of at least one demoulding agent (c) selected from the group consisting of pentaerythritol tetrastearate, glycerol monostearate, and stearyl stearate;
• d) from 0 to 60 wt. % of one or more thermoplastic polyesters (d);
• e) from 0 to 40 wt. % of one or more elastomers (e) other than component f;
• f) from 0 to 40 wt. % of one or more optionally rubber-modified vinyl (co)polymers (f);
• and
• g) from 0 to 10 wt. % one or more further additives;
• the process comprising using a masterbatch, wherein the melt-mixed coloured polycarbonate composition comprises a masterbatch consists consisting of the at least one pigment (b) and the at least one demoulding agent (c) in compounding prepared using a shear and mixing unit in a single-shaft extruder, a multi-shaft extruder, an internal mixer, a co-kneader, or a shear roller device,
• wherein the demoulding agent is at least one selected from the group consisting of pentaerythritol tetrastearate, glycerol monostearate and stearyl stearate,
• wherein the at least one pigment is (b) comprises a carbon-based pigment and the content of pigment in the masterbatch is from 40 to 60 wt. %, based on the total weight of the masterbatch,
• wherein the carbon-based pigment is selected from the group consisting of:
• a) carbon black;
• b) graphite;
• c) fullerene;
• d) graphene;
• e) activated charcoal;
• and f) carbon nanotubes, and
• wherein the process additionally comprises preparing the masterbatch by using a shear and mixing unit in a single-shaft extruder, multi-shaft extruder, internal mixer, co-kneader or a shear roller device,
• wherein the pigment is homogeneously distributed and present in finely dispersed form in the polymer composition,
• wherein the produced coloured polymer composition is a polycarbonate composition comprising
• a) from 40 to 99.96 wt. % of at least one thermoplastic polymer (a), wherein polymer (a) is at least one selected from the group consisting of aromatic polycarbonates and aromatic polyester carbonates, wherein the polymer has a weight average molecular weight of 15,000 to 80,000 g/mol and is a homopolycarbonate or copolycarbonate containing bisphenol A
• b) from 0.1 to 3 wt. % of at least one pigment component (b),
• c) from 0.1 to 3 wt. % of at least one demoulding agent (c) selected from the group consisting of pentaerythritol tetrastearate, glycerol monostearate and stearyl stearate,
• d) from 0 to 60 wt. % of one or more thermoplastic polyesters (d),
• e) from 0 to 40 wt. % of one or more elastomers (e) other than component f,
• f) from 0 to 40 wt. % of one or more optionally rubber-modified vinyl (co)polymers (f), and
• g) from 0 to 10 wt. % one or more further additives.