1. The term ECF in chlorine bleaching stands for _________ bleaching.
a) Elemental chromium free
b) Estimated chlorine free
c) Essential chlorine free
d) Elemental chlorine free
Discussion
Explanation: The term ECF in chlorine bleaching stands for elemental chlorine free bleaching. Chlorine bleaching was identified as the major source of polychlorinated dioxins and dibenzofurans compounds. In addition to dioxins and furans, a host of other chlorinated organic compounds (known collectively as adsorbable organic halides or AOX) are formed during chlorine bleaching. Strict regulations now limit the production of these chlorinated compounds, resulting in a move away from molecular chlorine bleaching to chlorine dioxide, so-called ECF or elemental chlorine free bleaching.
2. ________ is the mostly used chemical for bleaching of chemical pulp.
a) Sodium Hydroxide
b) Potassium Iodide
c) Hydrogen Peroxide
d) Sodium Disulphite
Discussion
Explanation: Hydrogen Peroxide (H2O2) is the mostly used chemical for bleaching of chemical pulp. The reaction typically requires 3 h at 40°C and is followed by neutralization and destruction of excess peroxide with SO2. Peroxide bleaching allows brightness to be increased by nearly 20%.
3. Recycled paper requires more chemicals and causes more harm to environment than new paper.
a) True
b) False
Discussion
Explanation: The given statement is false. Recycled paper uses lesser chemicals than new paper. Recycling of paper is an example of the sustainable use of resources. Recycled or secondary fibers are an important raw material in terms of volume and utilization for the paper industry in many countries, due to market pressures resulting from government legislation, increasing public awareness of issues like sustainability and a dwindling supply of virgin fibers in some regions.
4. __________ is the interface between the pulp mill and the papermaking process.
a) Stew preparation
b) Stock preparation
c) Dew preparation
d) Stall preparation
Discussion
Explanation: Stock preparation is the interface between the pulp mill and the papermaking process in which pulp is treated mechanically and, in some instances, chemically by the use of additives and is thus made ready for forming into a sheet or board on the paper machine. During the stock preparation steps, the pulps are most conveniently handled as aqueous slurries.
5. The separation of all the fibers from one another and their dispersion in water is called ________
a) Slushing
b) Sheeting
c) Wetting
d) Mashing
Discussion
Explanation: The separation of all the fibers from one another and their dispersion in water is called slushing or repulping. In the papermaking process utilizing purchased pulps and waste paper which are received as dry sheets, the first step is the separation of all the fibers from one another, and their dispersion in water with a minimum of mechanical work to avoid altering the fiber properties. This process is known as slushing or repulping and is carried out in a machine such as the hydrapulper, so called because of the hydraulic forces that are developed. When the pulping and papermaking operations are adjacent to one another, pulps are usually delivered to the paper mill in slush form directly from the pulping operation.
6. The object of beating is _________ of the fibers by assisting them to imbibe water.
a) To increase the surface area
b) To decrease the surface area
c) To increase the volume
d) To decrease the volume
Discussion
Explanation: The object of beating is to increase the surface area of the fibers by assisting them to imbibe water. As a result, additional bonding opportunities are provided for between cellulose molecules of neighboring fibers.
7. After beating, the mixture of pulp is brought to a consistency of ______
a) 3%–5%.
b) 1%–7%.
c) 5%–7%.
d) 6%–9%.
Discussion
Explanation: The mixture of pulp (known as the furnish) is passed into the beater and brought to a consistency of 5%–7%. The beating makes the fibers more flexible, causing them to become relatively mobile and to deform plastically on the paper machine.
8. In many paper mills, beaters have been replaced by ________
a) Continuous refiners
b) Continuous disks
c) Continuous sheets
d) Continuous templates
Discussion
Explanation: In many paper mills, beaters have been replaced by continuous refiners, such as disk refiners (where rotary disks rotate against a working surface) and conical refiners. However, the batch beater is a convenient vessel for adding chemicals and mixing them intimately with the pulp in order to give special properties to the final paper.
9. Which of the following is not a filler used in paper?
a) Titanium dioxide
b) Sodium hydroxide
c) Kaolin clay
d) Calcium carbonate
Discussion
Explanation: Sodium hydroxide is not a filler used in paper. Calcium carbonate is the most important papermaking filler followed by kaolin clay, with limited use of titanium dioxide. Fillers can improve brightness, opacity, softness, smoothness and ink receptivity, and are essentially insoluble in water under the conditions of use. Filler particles are often 0.5 to 3 mm in diameter, which is much smaller than the fibers used in making paper. Hence, fillers help in making the paper smooth. Not only this, fillers also increase papers’ opacity and brightness as it increases light scattering efficiency.
10. Which of the following is used to increase water resistance of paper?
a) Filling
b) Sizing
c) Stretching
d) Sheeting
Discussion
Explanation: Sizing is the process of adding materials to the paper in order to render the sheet more resistant to penetration by liquids, particularly water. Rosin is the most widely used sizing agent, but starches, glues, caseins, synthetic resins and cellulose derivatives are also used. The sizing agents may be added directly to the stock as beater additives to produce internal or engine sizing.