Improved Processability and Productivity of Wire Cable Compounds Using SP2 Scorch Protected Organic Peroxides

摘要

To address the compounding and manufacturing challenges of the wire & cable industry, we commercialized two "SP2" (Enhanced Scorch Protected) organic peroxide grades. The "SP2" technology was applied to the two major organic peroxides used to crosslink wire & cable compounds. Luperox DC40P-SP2 is a scorch protected dicumyl peroxide formulation. Luperox F40P-SP2 is a scorch protected di(t-butylperoxy)diisopropylbenzene formulation.Scorch is the unwanted crosslinking of polymers and elastomers that occurs during compounding and extrusion. To avoid scorch when melt mixing organic peroxides into polymers and elastomers, a two-step process is used. In the first step, all the ingredients are added, except for the reactive peroxide. The next day, in a second step, the organic peroxide is added to the compound in a final mixing operation. This second mixing step is conducted to lower mixing temperatures in an attempt to slow down the generation of free radicals from the peroxide, that cause scorch during compounding.In several commercial operations, the "SP2" peroxides eliminated the need for the less efficient two-pass mixing process. One-pass compounding increased productivity, lowered costs and doubled the mixing capacity, without the fear of scorch. One-pass mixing is possible with the "SP2" peroxides, as free radicals are efficiently trapped during compounding, thus allowing higher mixing temperatures while protecting the elastomer from scorch. Wire & cable manufacturing productivity is further improved as these peroxides reduce die fouling, thus lengthening the time between maintenance shutdowns.There is another major challenge to increasing the productivity of cable manufacture when using organic peroxides: improved productivity requires faster line speeds. As a result, faster curing compositions are required as the cable spends less time in the CV (Continuous Vulcanization) tube of fixed length and temperature, due to the faster line speed. Faster curing cable formulations are more prone to scorch. Furthermore, faster line speeds to increase the productivity of cable manufacture will increase compounding temperatures due to heat shear caused by higher extruder RPM. The superior scorch protective ability of the SP2 peroxides meets this contradictory challenge of providing greater compounding scorch safety in the extruder, while processing a more reactive cable compound at higher melt temperatures.Several polymers and elastomers used by the wire & cable industry were evaluated: EPDM, EOM, EVA, AEM, LDPE, HNBR, and CPE. The SP2 peroxides provided up to six times longer scorch times at compounding extrusion temperatures, as measured using a RPA rheometer, MDR rheometer and/or Mooney viscometer. By using these SP2 peroxides with reactive crosslinking coagents in cable formulations, significantly increased productivity without fearof scorch was obtained. Faster curing, more reactive wire & cable formulations can be created which possess much greater compounding safety than with the standard organic peroxides.