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Twin-screw compounders and reclaim extruders from new source.

Twin-Screw Compounders and Reclaim Extruders From New Source

A new line of reversible corotating/counterrotating, intermeshing, twin-screw compounders, as well as a new single-screw, dual-diameter extruder for scrap reclaim represent new departures for Davis-Standard Div. of Crompton & Knowles Corp., Pawcatuck, Conn. Both new machines were developed by Davis-Standard's recently formed Compounding/Recycling Business Area. Each will be on hand in the lab at the company's new Technical Center.

CONVERTIBLE TWIN SCREWS

As reported last month (see PT, Sept. '90, p. 14), Davis-Standard licensed the technology behind Japan Steel Works' TEX twin-screw extruders as the basis for a new line of 12 machines to range from 30 to 128 mm diameter. Davis-Standard already makes conical twin screws for PVC extrusion, but these will be its first parallel twins designed specifically for compounding.

The line, trade-named D-Tex, is equipped with a gearbox that will run the machine in either corotating or counterrotating mode. Significantly, the mode selection does not require mechanical changes in the gearbox configuration. The company claims that the machines will have high torque capability over a wide speed range and that desired shear characteristics can be achieved at high output rates.

Extruders are available with two-lobe and three-lobe kneading blocks, so screw elements can be selected for low or high shear. Basic screw length is 30:1 L/D. The biggest machine has an 800-hp motor and is rated for an output of 5000 lb/hr. The barrel includes multiple downstream ports for devolitilization or addition of solids. Barrel heating is from cast-aluminum electric heaters.

Initially, Davis-Standard will source the barrel, screw, and gearbox from JSW, however it expects to supply its own machine components in the future. The 10-yr license agreement with JSW includes transfer of processing technology for various materials, as well. Davis-Standard is offering delivery times from six to eight months and will supply turnkey compounding systems. It has not finalized pricing, but says the machines will be comparable in cost to higher-end twin-screw units.

Davis-Standard will market these machines in the U.S., Canada, and Mexico. It does not intend to compete directly with JSW, which sells twin-screw machines larger than 120 mm from an office in Houston. (CIRCLE 56)

OMNIVOROUS RECLAIM EXTRUDER

As reported previously, a dual-diameter single-screw extruder is also new to Davis-Standard's product line (see PT, July '90, p. 99). The machine is the first of a line called the Scrapper series, designed to handle a wide range of plant scrap and post-consumer waste, including off-grade rolls of film, granulated injection molding sprues, and foam and fiber fluff. The barrel is mounted on a moveable case to allow easy access for screw cleaning and replacement.

The feed section has a tangential feed opening that reportedly can ingest continuous web products directly into the extruder without first chopping the material. Adjustable knives between the screw flights cut material so it won't wrap around the screw, and push it forward. The 8-in.-diam. feed section, sized to accept low-bulk-density scrap, tapers to 4 1/2 in. diam. where the material is melted. Output rates are said to be in the 800-1200 lb/hr range. Price of the unit is $220,000. (CIRCLE 57)
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Title Annotation:Crompton and Knowles Corp.'s Davis-Standard Div.
Author:De Gaspari, John
Publication:Plastics Technology
Date:Oct 1, 1990
Words:529
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