SP and CST Technologies A new generation of cost saving curatives in rubber processing - Part 2(Paper No.14)

摘要

Improving the productivity of rubber compounding by increasing the mixer speed or replacing two-pass mixing with a one-pass mixing step has been a challenge when using organic peroxides. Attempting these productivity improvements can lead to higher mixing temperatures that could result in "scorch" or premature crosslinking. To address the issue of scorch during rubber compounding, peroxides with higher thermal stability have been used by the rubber industry. Unfortunately, these more thermally stable peroxides will also provide slower crosslinking rates that lower productivity for crosslinking operations, unless cure temperatures can be increased.Previously, to answer this contradictory challenge, Arkema Inc. introduced two new commercially available peroxide grades based on di(t-butylperoxy)diisopropylbenzene; Luperox F40M-SP and Luperox F-CST. These peroxides were designed specifically for crosslinking EPDM based upon novel "SP" Scorch Protected and "CST" Controlled Speed Technology. F40M-SP provides a two to three fold improvement in scorch time safety when compounding EPDM with no loss in cure rate, and significantly better elastomer flow properties with a 25% longer scorch time at cure temperatures for better mold-filling, compared to the standard peroxide. Thus F40M-SP provides increased productivity for EPDM compounding and crosslinking operations. The F-CST2 is a unique peroxide grade that provides the same superior scorch time as the SP, but with a 20% faster cure rate in EPDM without changing the cure temperature, compared to the standard peroxide.In this paper we review F40M-SP and F-CST and introduce three new SP peroxides: Luperox 231XL40-SP. Luperox 230XL40-SP and Luperox F40P-SP. 231XL40-SP and 230XL40-SP are two new "SP" peroxides designed for crosslinking EPDM and HNBR. Based on 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane and n-butyl-4,4-di(t-butyl peroxy)valerate respectively, these Peroxyketal peroxides offer significantly faster cure rates at lower temperatures while providing up to three times the ts5 Mooney scorch time at compounding temperatures. 231XL40-SP and 230XL40-SP provide improved elastomer flow during injection molding and prevent scorch during cure that results in poor tear-trim, poor hot-tear, and backrinding problems. The third new SP peroxide, Luperox F40P-SP, contains an enhanced SP package specifically designed for use in HNBR and CPE compounding and crosslinking. F40P-SP provides much longer scorch times during the compounding of chlorinated polyethylene (CPE) even when mixing very reactive crosslinking coagents to provide faster cure rates in continuous vulcanization (CV) steam tube lines, used extensively in wire & cable manufacture.