Barefoot resin

Resins without additives are sometimes referred to as barefoor resins. The process of blending the master batch with the barefoot resin to achieve the desired additive concentration is known as letting down the additive. 

Anti-blocking agents may be incorporated into the polymer resin either by direct addition at the final concentration, or via a concentrate or master-batch that is added to barefoot resin to achieve the final concentration. 

Three homopolymers and one diblock copolymer were used. A barefoot resin of high-density polyethylene (HOPE 3000) was supplied by Petromont. Polypropylene PP PD702 was supplied by Eased, while polystyrene PS 615APR was supplied by the Dow Chemical Company. SEE CAP4741, a 1,4-hydrogenated styrene-ethylene-butylene diblock copolymer, was supplied by Shell. The materials characteristics are listed in Table 1. 

Exxon LL5202.09 LLDPE, a barefoot 12 melt index, 0.924 density polyethylene was used as the carrier resin for preparation of all concentrate formulations. Exxon LL1001.09 LLDPE, a barefoot 1.0 melt index, 0.918 density film resin was selected as the matrix material for the preparation of all letdown compounds. Additive-lree resins were used throughout this trial to minimize potential interactions with additive packages and to simplify the analysis task. 

Generally, the anti-blocks are dry blended with other additives and stabilizers in a carrier resin. The concentration of anti-block may range from 5 to 10% for synthetic silica to 30-50% for DE or talc. The other additives will be in concentrations that yield the proper final additive levels when let down. To achieve the most thorough mixing, the blended materials are then fed into a mixer/compounder which may be batch equipment, such as a Banbury or Henschel or into a twin-screw compounding extruder and melt compounded. The pelletized concentrate will be blended with barefoot pellets and let down to the desired final concentration. 

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