ADDITIVES | PROCESSING AIDS
Matthies says that while Montan wax derivatives
are used by preference in the processing of engineering plastics, their benefits can also be taken advantage of in PVC processing, particularly where demands on the quality of the end products are especially high. In terms of chemistry, for example, they are similar to fatty acid esters but benefit from considerably longer carbon chains. As a result, montanic esters display low volatility and this, together with their very good compatibility with PVC, means they exhibit a low tendency to migration. Even at high addition rates in PVC applications, he says they have a very low tendency to form a coating on the finished part.
Release and flow In PVC, montan waxes function primarily as release agents by providing external lubrication. They also improve the surface quality and smoothness and provide the final product with a superior gloss. Montanic esters are used in injection moulding and other applications where good melt flow is required, as they also reduce the melt viscosity – in- ternal lubrication. In high-speed cable extrusion they exhibit advantageous lubricating properties, especially at the tip of the processing screw. Völpker says that its Waradur OP grade tends to have a slightly lower external lubrication effect than Waradur E. The latter, on the other hand, lowers the melt viscosity slightly more, which results in lower extrusion pressures (Table 1). Matthies explains that montan waxes are particu- larly advantageous in PVC, where their effect on melt viscosity is much greater than that of glycerol monostearate and complex esters (Figure 1). He
says this performance advantage is particularly interesting in applications where high shear forces occur, for example in injection moulding or coextru- sion of window profiles. During extrusion of PVC window profiles, montan waxes improve gloss (Figure 2) and can also solve problems such as ‘chattering’ or ‘judder- ing’ if they are used to partially replace primarily external lubricants such as Fischer-Tropsch paraffins or PE waxes, Matthies says. This effect is attributed to the reduction of the polymer melt viscosity. “Experience has shown that the shrinkage of the extrudate during calibration is improved in this way,” he says.
Another advantage of montan waxes is their
relatively high melting point. This means that they reduce the Vicat softening point in, for example, PVC injection moulding applications by much less than common fatty acid esters, which have signifi- cantly lower melting points (Figure 3).
Newly renewed Velox is the exclusive distributor of Völpker’s waxes for plastics applications in various European countries, supplying not only montan waxes but also other types. The distributor highlights Voelp- ker Wax 4418, an organic ester based on renew- able plant waxes, saying that this new product optimally combines the characteristics of a multi- purpose plastics additive with the appeal of bio-based raw materials. This makes the grade particularly appropriate for use in thermoplastic polymers derived from renewable resources. The company says Voelpker Wax 4418 contains modified natural long-chain fatty acids. It is
Table 1: Chemical, physical and rheological data of typical Völpker lubricants (==> indicates fusion is delayed; ⇐: fusion is promoted; ⇑: torque or pressure increases; ⇓: torque or pressure decreases ⇔: insignificant influence. Two symbols indicates a more pronounced effect at the same dosage)
Lubricant
Waradur S Fatty acids, montan wax
Waradur E Fatty acids, montan wax, ethylene esters
Waradur GE Fatty acids, montan wax, glycerol esters
Waradur OP Fatty acids, montan-wax,
Average molecular Drop point weight [g/mol]
range [°C] approx. 425 approx. 900 approx. 900 approx. 900
1-methyl-1,3-propanediyl esters Source: Völpker Spezialprodukte
60 COMPOUNDING WORLD | April 2018
www.compoundingworld.com 82 – 88 82 – 88 80 – 88 99 – 105 Effect on ==>==> ==>==> ==>==> ==> Effect on fusion time extrusion torque ⇓⇓ ⇓⇓ ⇓⇓ ⇓⇓
Effect on extrusion pressure
⇓⇓ ⇓⇓ ⇓⇓ ⇓
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94
