Fifty years ago in ... Plastic Technology: September 1955.

Modernizing Old Injection Machines

In reply to the request for information on modernizing old injection machines, we have done a great deal of work on this problem because more presses were produced during 1944-46 than in any other period in our history. A stopwatch analysis of older injection machine cycles reveals that the clamping time is typically two seconds to open and two seconds to close on the mechanical type press, and somewhat longer on the full hydraulic unit. The injection time of the mechanical clamp machine requires approximately 8-10 seconds, and the plunger return time about the same. We can safely estimate, therefore, that the best complete cycle on an older 8-12 ounce machine is 20-22 seconds.

A.R. Morse, Injection Molders Supply Co.

Melamine Dinnerware

The first "patterned" melamine dinnerware has been introduced on the market by International Molded Plastics, Inc. The line consists of a pair of three-color patterns called Fantasy and Champagne. Heat-fixed decorations are sealed beneath the translucent surface and, being molded from chip- and break-resistant Melmac, assure permanence of design.

The Dry Offset Process For Decorating

We decided to do research on the dry offset method because it is our belief that only dry offset offers a means of applying multiple colors in close register at good production rates to surfaces which might vary considerably in contour, firmness, and fragility. In May of 1954, a prototype machine was put out for a production test in decorating polystyrene molded items with two colors applied to compound cylindrical contours. That machine has been in constant use by the purchaser since it first went to his plant. Machines using three or more colors are now under development.

Carl B. Johnson, Markem Machine Co.

NPE '56

The seventh National Plastics Exposition will be held next June 11-15 at the new Coliseum in New York City. A conference on plastics will be held simultaneously, featuring talks on new markets and applications and new processes such as vacuum forming, plastic pipe, and plastics for packaging.

Plastics at Disneyland

Monsanto is the sole exhibitor among chemical firms at Disneyland, Calif. Wall displays depict the manufacture and use of plastics. (Editor's note: The plastics industry sponsored the Fantastic Plastic Works exhibit, which opened a year ago at Walt Disney World's Epcot Center in Orlando, Fla.)

Low Pressure Polyethylene

Of all the plastics exhibited at the Hanover Industrial Fair in Germany, probably none drew more attention than Hostalen, the low-pressure polyethylene produced by the Farbwerke Hoechst A.G. using the Ziegler process and shown for the first time in various applications. There were foils, tubes, pipe, and household articles made by extrusion and injection molding. Hostalen, which is made in the form of a powder, has a specific gravity of 0.94 and is claimed to be more wear-resistant and rigid than high-pressure polyethylene, and also has a higher molecular weight, higher crystallinity, and higher softening point.

Non-Toxic Tin Stabilizers

The use of dibutyl tin compounds to stabilize PVC is limited by the fact that they are toxic to some extent. Although work on the problem is still in an early stage of development, it has been found that di-n-octyl tin maleate and di-n-octyl tin laurate have stabilizing effects of the same order as the corresponding butyl compounds but are not at all toxic.

New Injection Machine

A dry cycle time of ten seconds reportedly assures a high production rate with the new 300TA-12/16-ounce plastic injection molding machine introduced by Reed-Prentice Corp. Double shear toggle develops 300 tons positive mold locking pressure, which makes it possible to mold large-area parts without flash. The new Reed-Speed heating cylinder with 3 in. plunger diameter plasticizes 115 lb/hr.