Ultra-fiine Kaolin extenders for pigment extension in colour masterbatch

Pigment efficiency is determined by the degree to which the pigment particles are spaced out from one another. These KaMin kaolin grades have a plate-like morphology, with a median particle size of 400-800 nm. This allows these extender particles to get in between the other pigments, such that they are better spaced from one another.

Whilst the results presented in this article focus on the extension of titanium dioxide in plastics, the same principle can be applied to other colour pigments – although some fine-tuning of the masterbatch will be required for a colour match. Whilst this might be difficult to do for existing colours, why not incorporate KaMin kaolin into new colour matches - to gain that competitive edge?

What are the physical characteristics of ULTREX® 96 and ASP® 170?

The salient physical characteristics of these grades are shown in Table 1. You can see that they have an ultra-fine particle size with high brightness values. ASP® 170 has one of the smallest particle size distributions in the KaMin range of pigment extenders, which is why it is so effective at maintaining opacity and colour when partially replacing titanium dioxide. Ultrex® 96 is a unique calcined kaolin that has the highest brightness of any commercially available kaolin, making it excellent at maintaining colour.

Table 1: Overview of the physical characteristics of Ultrex® 96 and ASP® 170. These kaolin grades are engineered for pigment extension in the colour masterbatch.

Extending titanium dioxide in injection moulding"

For injection moulding, a 10% replacement of titanium dioxide with Ultrex® 96 shows both excellent colour and opacity. Even at 20% replacement, very good colour retention is obtained with a slight drop in opacity. ASP® 170 showed equal colour at lower levels of titanium dioxide extension but did not provide the same opacity of Ultrex® 96 at any extension level (Table 2).

A letdown ratio of 50:1 was used during injection moulding. Colour and opacity data for Ultrex® 96 and ASP® 170 were generated from 23 mm press-outs. The experimental setup is outlined below in the summary at the end of this article.

Table 2: Opacity and colour measurements when using KaMin kaolin to extend titanium dioxide in colour masterbatch, subsequently used for injection moulding.

Extending titanium dioxide in blown film

For film applications, a 5% and 10% replacement of titanium dioxide with ASP® 170 showed equal colour and opacity to that of the control. At 20% there is excellent colour, with only a slight drop in opacity at both letdown levels (Table 3).

Two letdown ratios were used during the production of blown film, 25:1 and 100:1. Opacity was measured on a 1.0 mm film. The experimental setup is outlined below in the summary at the end of this article.

Table 3: Opacity and colour measurements when using KaMin kaolin to extend titanium dioxide in colour masterbatch, subsequently used for blown film.

Summary

KaMin kaolin is engineered to be an effective extender of titanium dioxide in a white colour masterbatch. These pigment extenders can be used to improve efficiency and reduce costs in other colour masterbatch formulations as well. Their high brightness and fine particle size offer excellent colour and opacity retention, with the possibility for large cost savings. Our recommendations are as follows:

Injection Moulding: Replace 10-20% titanium dioxide with Ultrex® 96. At 10% you have comparable optical properties with parts that have no cost-reducing extender. 20% replacement has very good colour retention with a slight drop in opacity.

Film applications: We recommend replacing 10-20% titanium dioxide with ASP® 170. Optical properties are maintained at 10% whilst only a slight drop in opacity is observed at 20%.

Ultrex® 96 and ASP® 170 provide the manufacturer of colour masterbatch with a less expensive alternative to titanium dioxide and other colour pigments, whilst maintaining performance properties. Even a modest level of extension can prove very cost-effective, so why not get in touch with the technical sales team at Lawrence Industries and see how much you could save! Call us on 01827 314151 or request a sample on the ASP® and Ultrex® product pages.

Experimental Setup

Ultrex® 96 and ASP®-170 were evaluated in a linear low-density polyethylene (LLDPE) based white colour masterbatch. A portion of the titanium dioxide in the colour masterbatch was replaced with Ultrex® 96 and ASP® 170. Various levels of replacement were used for the injection moulding with Ultrex® 96 and the blown film work with ASP® 170. Samples were then generated at a 50:1 let down ratio.

Colour masterbatch:

50% - LLDPE

50% - titanium dioxide + kaolin extender

Resin: Dowlex LLDPE 2553 Dow

Titanium dioxide: Ti-Pure R101 Chemours

Specialty Extender:

Ultrex® 96 Specialty calcined pigment – 0.8μm particle size.

ASP®- 170 Specialty hydrous pigment – 0.4μm particle size.

Compounding Equipment and Conditions:

Leistritz twin screw extruder: 34mm

Barrel temperature: 240-250°C

Screw speed: 200 rpm

Injection Molding:

Base resin: Dowlex LLDPE 2553

Letdown ratio: 50:1

Battenfeld press: 85 ton

Barrel temperature: 230-250°C

Blown Film:

Base resin: Dowlex LLDPE 2553

1.0”, 24:1 L/D: Davis standard single screw

Barrel temperature: 190-246°C

Die diameter: 2” spiral

Blown up ratio: 3:1