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Rotuba Extruders Inc.

Separator Improves Quality Of Plastic Pellets

A well made circular screen separator like the Kason VIBROSCREEN separator does a better job of minimizing dust and fines than a rectangular screener had been able to do, according to Rotuba Extruders Inc. Plant Supervisor Gil Carmichael. Because of Rotuba's strong commitment to providing customer with cellulose acetate pellets no smaller than 1880 microns and no longer than 4040 microns, the company managers decided to switch from rectangular screens to circular screen separators. Rotuba Extruder customers appreciate the onsize pellets since fines often cause surface imperfections and oversize pellets pose potential bridging problems during handling. Furthermore, uniformly on-size pellets heat more efficiently, thus contributing to higher productivity.

The first VIBROSCREEN unit performed so well that another unit was installed three months later. A third unit was ordered the following year. They are all 24 in. (610 mm) diameter separators, thus reducing the floor space requirements by about 65 percent for each rectangular screen that was replaced.

Another benefit of using the VIBROSCREEN unit results from their being designed better for more thorough cleaning, according to Mr. Carmichael. The pellets that Rotuba Extruders Inc. markets frequently have unique colors. Customers expect that color to meet their standards and if pellets from previous batches become entrained in their bag or other container, then color fidelity may be threatened. Thus, use of VIBROSCREEN units contributes to enhanced quality control. However, oversize pellets can be reground and the regrind combined with the fines for reuse for black or opaque pellets, explained Mr. Carmichael.

Like many processors, Rotuba Extruders had special needs. The circular screen separators required positioning at a somewhat higher level than a standard design would have allowed for. Kason engineers worked closely with Rotuba Extruder personnel to ensure that the VIBROSCREEN units fit into the processing line precisely where they are needed. Special interchangeable covers, and anti-static grounding lugs were also designed to meet Rotuba Extruders requirements.

Rotuba Extruders are manufacturers of cellulose acetate used for toothbrush handles, combs, and barrettes. It is used for screwdriver handles, face shields, safety goggles, toys and many other products that require color ability, impact strength and ease of fabrication.

Rotuba Extruders is poised for producing pellets for these products and others at higher capacities in the future since the circular separators are operating at less than half their capacity of about 2000 lbs/h (900 kg/h). The VIBROSCREEN reliability is essential, however, since these units operate 24 hours per day, five to six days a week. "The VIBROSCREEN units operate very well and service has been prompt and friendly," said Mr. Carmichael. To ensure that the right sized separators were installed, Rotuba Extruders sent samples to the Kason test lab. Results showed that the 24 in. diameter units equipped with 5 mesh and 10 mesh screens would serve best.

Screen Tips - Volume 11, Number 1


Separator Improves Quality of Plastic Pellets
VIBROSCREEN at Rotuba Extruders helps ensure that customers receive only on-size pellets.