EQUIPMENT Paper Stretches Two Ways Stretchable kraft p a p e r is ready for makes strong bags, sacks with less paper To
Clupak:
from lab model
t o paper machine t o finished bag
THE PAPER INDUSTRY comes a
new
invention of Sanford Cluett, originator of the Sanforizing process. T h e i n vention: extensible paper—or, in. other words, p a p e r with a stretch. West Virginia Pulp & Paper began developing the product from a p a t e n t held by Cluett, Peabody & Co. T o d a y , three years and 2.5 million research dollars later, the paper is ready for marketing. Initially West Virginia will make only extensible kraft, although bleached papers can b e m a d e stretchable, too. T h e kraft, called Kraftsman Clupak, i s aimed primarily a t multiwall b a g s and grocery sacks. Sacks made of t h e new material can take rough treatment such as dropping. In drop tests m a d e b y West Virginia, regular and stretchable kraft grocery bags of identical size and weight w e r e filled with a load of canned and boxed food. The sacks, hung on ropes, dropped t h r e e feet where they snapped to a halt i n midair. The regular kraft sack invariably ruptures after the first or second drop; Kraftsman Clupak withstands t h e test an average of 20 times before breaking, the company reports. • Mechanical Process. Putting stretch into paper is purely a mechanical process. Chemical treatment of the fibers is the same as it is for regular felted papers. T h e processing change comes in t h e middle of the drying chain. Paper feeds onto a r u b b e r belt and is expanded along with the belt a s it runs beneath a dryer roll. When t h e pressure is released, the rubber belt r e turns to its original state, t h e paper follows. Result is a pushing a n d twisting back of the fibers. P r o p e r temperature a n d moisture at this point keep the paper smooth, prevent i t s wrinkling. Regular kraft has a greater tensile strength than t h e new p a p e r . B u t when a b a g drops, it is subject to a n impact load far greater than its tensile strength. Therefore, says W e s t Virginia, it's important to have a paper
market;
tough enough t o withstand sudden imp a c t and to yield with t h e shock. Yet it shouldn't dissipate all its energyabsorption qualities in yielding t o its limit before all the "stretch" is pulled out. T h e amount of stretch p u t into the p a p e r can be varied. But West Virginia has found that about 1 0 % stretch in the direction of the machine and a b o u t 5% stretch in the cross direction gives the optimum toughness for industrial use. The company is currently producing extensible kraft on a n e w $25-million paper machine at its plant in Charleston, S. C. T h e machine makes a sheet of p a p e r 20 feet -wide, puts out a b o u t 225 tons a day. Cost of t h e paper will be 10 to 15% above regular kraft. • N e w C o m p a n y Formed. With appearance of the new product comes the formation of Clupak, Inc.—an organization created jointly by W e s t Virginia and Cluett, P e a b o d y to license p a p e r process. Although not i n a position t o license immediately, the company expects to b e ready b y late spring or early summer. Patent design o n t h e machine is not yet frozen b u t should b e b y the time Clupak gets a staff together and is ready to start licensing. West Virginia is actually a licensee of t h e process. But t h e company figures it will only b e able to fill a small p a r t of t h e expected demand. I t s goal is 10% of the current 4 million-ton-a-year market for coarse paper, t h e company says. Besides multiwall bags a n d grocery sacks, a lot of other uses h a v e been suggested, says West Virginia: wrappings, impregnated with rust inhibitor, to protect machined parts; wrappers for mail order catalogs; containers of the p a p e r laminated with asphalt, polyethylene, or wax; cable wrapping a n d auto tire wrapping. T h e process can make p a p e r soft and pliable. So other uses could be: disposable wearing apparel, masking tape, and shotgun shells. E1
