Processors of rigid PVC pipe, window profiles, siding, fencing, and doors can save money and speed compound mixing by using a new grade of white mineral oil as an external lubricant in place of the usual paraffin wax.
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Processors of rigid PVC pipe, window profiles, siding, fencing, and doors can save money and speed compound mixing by using a new grade of white mineral oil as an external lubricant in place of the usual paraffin wax. That's the word from Crompton Corp., Greenwich, Conn., whose Hydrobrite PVC Oil is a highly refined, free-flowing liquid paraffin that reportedly does not agglomerate in storage or handling as is typical of wax. The liquid form is also said to result in more uniform coating of PVC particles and improved productivity in high-intensity mixers. Hydrobrite is also believed to be slightly more compatible with PVC, which potentially could reduce plate-out. Most important, vinyl compounders can save up to 15% on lubricant cost with no sacrifice in performance, Crompton says.
Compared with paraffin wax, white mineral oil reportedly offers advantages of long-term price and supply stability. While there is no shortage of paraffin wax today, changes in petroleum production have reduced paraffin wax production in North America, and no new capacity is scheduled any time soon.
This liquid lubricant has been approved by the Plastic Pipe Institute (PPI) and the National Sanitation Foundation (NSF) as a functional equivalent to paraffin wax for high-pressure PVC water pipe when used in range formulations at 1 to 2 phr. Chemically inert, colorless, odorless, and tasteless, it is also food grade (per 21 CFR 172.878 and 21 CFR 178.3620a) and boasts excellent uv and color stability.
As an external lubricant, the oil helps reduce friction between the polymer and metal surfaces and delays fusion of the PVC powder, just as wax does. To perform equivalently to 165 F paraffin wax, Hydrobrite PVC Oil must be used at up to 25% higher levels. However, lubricant cost savings of 6% to 15% can be achieved by switching to this alternative, as its cost is typically 25% to 36% lower than paraffin wax. One of the top North American PVC pipe producers reportedly saved over $300,000/yr by replacing paraffin wax with Hydrobrite PVC Oil.
Rheological data show Hy-drobrite to have processing characteristics similar to those of paraffin wax (see table). Crompton market manager Roy Seib points out that all rheology comparisons were done using 165 F paraffin wax, which used to be the workhorse product in the industry. However, availability constraints in recent years have forced many processors to use lower-melting paraffin waxes (140 to 158 F). Seib says that relative to these lower-melting waxes, the comparative use levels for Hydrobrite PVC Oil would be only 0% to 15% higher.
According to Seib, there is an insignificant reduction (about 1° C) in HDT when replacing paraffin wax with Hydrobrite oil. Hydrobrite also provides Izod impact test results equivalent to those obtained with paraffin wax.
Weathering characteristics of Hydrobrite oil also have been shown to be equivalent to wax. As shown in the accompanying graph, differences in color shift (E) for both white and dark-gray siding are negligible under accelerated weathering. Slightly improved performance with Hydrobrite in white siding can be attributed to the higher levels of lubricant, which causes less "wear and tear" on the polymer during processing.
Seib notes that Hydrobrite is used commercially in pressure pipe of 1.5 to 24 in. and larger diam., pressure fittings of 1.5 to 24 in., gravity-flow pipe of 8 to 24 in., gravity sewer pipe of 4 to 36 in., and other sewer pipe.
|HYDROBRITE OIL VS. PARAFFIN WAX
IN TYPICAL NSF PVC PIPE COMPOUND
|Use level, phr||1.2||1.5|
|Fusion time, min||6:08||6:08|
|Initial fusion Torque, mg||1017||982|
|Torque at Fusion, mg||2098||2144|
|Equilibrium Torque, mg||1450||1450|
|Degradation Time, min||28:08||28:04|