What are the major categories of chemical additives used for papermaking? - Answers retention aids,
sizing agents, fillers, strength agents, alum
What is so special about "alkaline papermaking?" - Answers It allows the use of calcium carbonate as a
filler.
What are the three broad goals of the stock prep area? - Answers Achieve desired product properties,
set/control sheet basis weight, increase sheet strength
How is the stock prep area set up? - Answers A collection of tile-lined tanks called "chests." The dump
chest contains the raw pulp. The mix (or blend) chest receives from the dump chest and the furnish
components and feeds the refiners. The machine chest receives the refined stock and feeds the stuff
box.
Why do we refine? - Answers It decreases yield loss at lower-cost grades
What physical changes occur to a papermaking fiber when it goes through refining? What changes occur
to the stock? - Answers They collapse into flat ribbons, fibrillate, become more conformable, and can be
shortened.
Where do fines come from? - Answers Refining
What things get better with refining? What things get worse? - Answers Tensile and burst strength,
formation, smoothness, and printability get better. Tear strength, freeness, yield, opacity, bulk, and air
porosity get worse.
What is the nature of the refining action? What type of equipment has been used to induce this action
into papermaking stock? - Answers It is a "rolling friction." Equipment that has been used to induce this
include the beater, Jordan, Claflin, and disk.
What is freeness? How is it measured? - Answers Describes how freely water drains from a fiber slurry.
It is measured by the CSF test.
What relative refining energy level is required for various grades? - Answers tissue < linerboard base <
multiwall bag < bleached board < fine papers < linerboard top < glassine
Why are some grades NOT refined? - Answers Market pulp is normally not refined because the customer
will do it themselves.
What are the major goals of this area? - Answers To deliver the right amount of fiber to the paper
machine in order to meet basis weight specs, and to distribute that stock uniformly.
, What is the role of the basis weight valve? - Answers It sets the average basis weight of the sheet by
metering thick stock to the fan pump.
Why is the stuff box important? - Answers It dampens pulsations from the thick stock pump that could
cause sheet barring.
How is thick stock converted to thin stock? - Answers The fan pump dilutes thick stock with white water
from the fourdrinier
What is the deculator? - Answers It is a vacuum header that removes air after centrifugal cleaning prior
to the headbox.
What is the headbox screen used for? - Answers Pulses stock against a screen to stop fiber flocs from
getting through
What does the headbox manifold do? - Answers Deliver stock to the headbox with absolute even fiber
distribution across the machine width
Why is a headbox named that? - Answers It provides pressure, or "head"
What is the slice? - Answers The opening at the lip of the headbox where stock jets out onto the wire
What are the major purposes of the headbox? - Answers To provide the pressure necessary to deliver
the correct amount of thin stock to the forming wire
What are the three major types of headboxes, and why we have to move to a different type as the
machine speeds increase. - Answers Atmospheric, air-padded, and hydraulic. We need to use a different
type as machine speed increases in order to maintain the rush/drag ratio.
What is rush/drag ratio? - Answers The ratio of jet speed to wire speed, usually 1.0 plus or minus 5%
What are three major water removal zones/forces on a typical fourdrinier wet end? - Answers Gravity,
vacuum, press
What are the major types of wet end machines used for papermaking? - Answers Fourdrinier, top-wire,
gap former
What might be some typical consistency values at different points of the wet end? - Answers headbox:
0.5%
gravity: 2-3%
vacuum: 20-25%
press: 40-50%
What is "two-sidedness" and how do we try to minimize it? - Answers When filler and fines are removed
from one side only. Minimize using a top-wire or gap former.