Food Packaging Technology Interview Questions and Answers for Experienced people on “Paper Making – 2”.
1. Which of the following was the first paper making machine?
a) Fourinder machine
b) Cylinder machine
c) Twin-Wire Formers
d) Roller Presses
Answer: a
Clarification: The first paper making machine was Fourdrinier machine of 1804, named after its financiers Henry and Sealy Fourdrinier, two prosperous London stationers who purchased the patent interests of the Frenchman Didot Frères. In this, paper is made by depositing a very dilute suspension of fibers from a very low consistency aqueous suspension (greater than 99% water) on to a relatively fine woven screen, over 95% of the water being removed by drainage through the wire. The fibers interlace in a generally random manner as they are deposited on the wire and become part of the filter medium.
2. Paper greater than ________ is considered paperboard.
a) 300 μm
b) 200 μm
c) 500 μm
d) 400 μm
Answer: a
Clarification: Paper greater than -2 (i.e., grams per square meter or GSM).
3. _________ are used to produce heavy multi-ply boards.
a) Fourinder machine
b) Cylinder machine
c) Twin-Wire Formers
d) Roller Presses
Answer: b
Clarification: Cylinder machines are used to produce heavy multi-ply boards. They produce a sheet that is much stronger in the direction of flow than that produced on Fourdrinier machines. A cylinder covered with a wire cloth is rotated partially submerged in a stock suspension. Because of a vacuum applied inside the cylinder, water drains inward through the wire cloth, and the paper web is formed on the outside. The web is picked up by a felt, which is pressed onto the top of the cylinder by a rubber roll. A series of vats provide individual plies of fiber which are subsequently matted together.
4. ___________ are particularly used for lightweight sheets, corrugated media and linerboard grades.
a) Fourinder machine
b) Roller Presses
c) Twin-wire formers
d) Cylinder machine
Answer: c
Clarification: Twin-wire formers are particularly used for lightweight sheets, corrugated media and linerboard grades. In this, the paper web is formed between two converging forming screens by means of a flow box and the water is drained from the slurry by pressure and later by vacuum. A typical twin-wire forming unit is the inverform, which was designed to provide a new method for the manufacture of single and multi-ply sheets at high speeds. Successive layers of fiber are laid down sequentially on the felt, with water being removed upwardly, overcoming the difficulty experienced in the conventional downward removal of water through several layers of board at high speed.
5. The moisture content of the paper sheet before entering the dryer is _______
a) 35%–40%
b) 35%–50%
c) 45%–60%
d) 75%–90%
Answer: d
Clarification: After leaving the forming fabric of the papermaking machine, the sheet (which has a moisture content of 75%–90% depending on type) passes to the press and dryer sections for further water removal.
6. The moisture content of the paper sheet after passing through the rotary presses is _______
a) 80%–90%
b) 60%–70%
c) 40%–50%
d) 10%–20%
Answer: b
Clarification: Rotary presses (which may have solid or perforated rollers, often with internal suction) receive the sheets on continuous felts, which act as conveyers and porous receptors of water. On leaving the press, the moisture content is typically 60%–70%, again depending on type.
7. The final moisture content of paper after pressing and drying is __________
a) 4%–10%
b) 10%–20%
c) 1%–5%
d) 40%–50%
Answer: a
Clarification: The paper is after passing through a series of steam-heated rollers is dried to a final moisture content between 4% and 10%. Other types of dryers are used for special products or situations. For example, the Yankee dryer is a large, steam-heated cylinder, which dries the sheet from one side only, and is used extensively for tissues and to produce machine glazed (MG) papers, the latter having a glazed or shiny surface from intimate contact with the polished dryer surface.
8. The application of chemicals to the surface of a paper web is done with _______
a) Stew press
b) Scaling press
c) Screw press
d) Size press
Answer: d
Clarification: The application of chemicals to the surface of a paper web is done with a size press. In a size press, the dry paper is passed through a flooded nib, where a dispersion of functional chemical contacts both sides of the paper. Excess liquid is then squeezed out in the press and the paper is re-dried.
9. An optimum concentration of coating solution for improving water resistance of paperboard is _____
a) 1.5 w/v%
b) 2.5 w/v%
c) 3 w/v%
d) 1 w/v%
Answer: c
Clarification: An optimum concentration of coating solution for improving water resistance of paperboard was 3 w/v %. It gives a coating thickness of 28 μm equivalent to 49.5 GSM. There is an increase in the water resistance of paperboard when it is coated with PLA. A coating thickness between 4.7 to 42.7 μm decreases water vapor permeability from 4.8 to 25.5 times, while decreasing water absorptiveness from 11.9 to 17.9 times.
10. __________ are widely used in paper coatings for oil and moisture resistance in microwave popcorn bags.
a) Chlorochemicals
b) Hydrogen peroxide
c) Fluorochemicals
d) Polyphenols
Answer: c
Clarification: Fluorochemicals are widely used in paper coatings for oil and moisture resistance in microwave popcorn bags. It is also used in fast-food paper packaging for muffin and french-fry bags, sandwich/burger wrappers and small pizza and burger boxes. The perfluorocarbon moiety in these classes of products has the effect of lowering the surface energy of the individual paper fibers which greatly contributes to the holdout of low surface energy liquids such as greases and oils.
11. Pigments are added at the wet end of the paper machine and serve to fill the sheet.
a) True
b) False
Answer: b
Clarification: The given statement is false. Though functionally and chemically similar, fillers and pigments are distinguished from one another in that fillers are added at the wet end of the paper machine and serve to fill the sheet; pigments are added at the size press and serve to alter the surface of the sheet.
12. Pigments comprise ______ of the dry solids in paper coatings.
a) 10%–30%
b) 70%–90%
c) 40%–50%
d) 60%–90%
Answer: b
Clarification: Pigments comprise 70%–90% of the dry solids in paper coatings. They are generally designed to mask or change the appearance of the base stock, improve opacity, impart a smooth and receptive surface for printing or provide special properties for particular purposes.
13. Paper has a definite caused by the greater orientation of fibers.
a) Yield
b) Strain
c) Stretch
d) Grain
Answer: d
Clarification: Paper has a definite grain caused by the greater orientation of fibers, in the direction of travel of the paper machine, and the greater strength orientation that results partly from the greater fiber alignment and partly from the greater tension exerted on the paper in this direction during drying.
14. The grain direction is known as the machine direction (MD), while the cross direction (CD) is the direction of the paper at right angles to the MD.
a) True
b) False
Answer: a
Clarification: The given statement is true. The grain direction is known as the machine direction (MD), while the cross direction (CD) is the direction of the paper at right angles to the MD. The grain of paper must be taken into account in measuring all physical properties. Most of the physical properties of paper depend on direction, that is, the MD, CD and thickness direction (z-direction).
15. Usually, there is less variation in paper properties in the MD than in the CD.
a) True
b) False
Answer: a
Clarification: The given statement is true. Usually, there is less variation in paper properties in the MD than in the CD. It is because variations occur slowly in the MD, whereas in the CD they may occur quite suddenly for a variety of process related reasons. In addition, the CD strength normally varies depending on how far the sample was taken from the edge of the sheet.