ANTIOXIDANTS AND STABILISERS | ADDITIVES
of melt flow rate (MFR) and colour. Tests involving multiple extrusion of a BOPP film
grade material at 270°C, one containing AddWorks PKG 118 and the other a standard commodity AO package, have shown that the new product can cut the increase in MFR by more than half over five passes (Figure 3). Multiple heat histories can also induce yellowing in BOPP resin. Addworks PKG 118 has been shown to reduce this (Figure 4). Another negative effect of multiple extrusion is
formation of gels in the polymer. AddWorks PKG 118 is also claimed to reduce this with the com- pany claiming that at equal concentrations (typi- cally 0.12%) it halves the number of gels compared with a standard AO package. Clariant has recently started offering its Ad-
dWorks PKG 171, saying it provides outstanding colour retention during multiple extrusion and shows very good colour fastness to burnt-gas fumes. It is said to be particularly effective in peroxide vis-broken PP. “Using only 1,000 ppm of AddWorks PKG 171 versus 1,500 ppm of the market standard results in a significant lower YI increase after oven ageing,” says Hartmut Siebert, Global Technical Segment Manager Polymer Producers in Clariant’s additives business. Germany’s Baerlocher says it is continuing to build on its Resin Stabilization Technology (RST) platform for applications in recycling and com- pounding of recycled polyolefins. RST is said to act synergistically with traditional antioxidants, so expanding the performance window, and can also be used to work around solubility or cost con- straints with certain additive formulations – this includes minimising or excluding phosphites. “With the RST-Technology now having gained a
steady foothold in LDPE-film recycling, where it reduces gels and counteracts mechanical property deterioration, Baerlocher also seeks to expand the success into HDPE recycling,” says Henrik Eriksson, Technical Product Manager at Baerlocher. An increasing amount of blow moulded packag- ing for detergents and personal care products contains recycled HDPE. Eriksson says that with increasing competition for sources of high-quality material, converters are looking to use more HDPE from post-consumer recyclate (PCR). “However, with this sort of raw material the processing properties mostly turn out to be insufficient for producing high quality packaging on a larger scale,” he says. This is because degraded PCR-HDPE has poorer melt strength and can lead to flow issues, such as sag or swell, and uneven distribution of material in the part. Tests have shown that when one of Baerlocher’s RST-based products — Baeropol T-Blend 1111 TX
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— is included in regranulated HDPE-regrind, it improves both the quality and consistency of the extrusion blow moulding process. Eriksson says that, compared with a standard phosphite/phenol stabiliser blend, Baeropol T-Blend 1111 TX is better at maintaining tight tolerances for bottle weight and in reducing flash. Mechanical properties also benefit (Figure 5).
Baerlocher is also introducing Baeropol formula- tions with additional functionalities. One example is a chain extender aimed at what the company has identified as a supply/demand mismatch between low melt strength HDPE from post-consumer waste streams and high melt strength HDPE needed for pipes and large blow mouldings. “This additive allows a compounder to upcycle low value HDPE for implementation in higher value
Figure 3: Chart
showing the increase in melt flow rate of BOPP after multiple extrusions comparing Clariant’s Addworks PKG 118 (blue bars) with a standard AO package (grey bars) Source: Clariant
Figure 4: Colour stability of BOPP over multiple extrusions determined by yellowing index (YI) comparing AddWorks PKG 118 at two different addition levels with a standard antioxidant (base resin was unstabilised commercial BOPP grade with 300ppm Hycite 713 acid scavenging co-stabiliser) Source Clariant
September 2021 | COMPOUNDING WORLD 85
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