Atrak - pulp and paper industries Atrak - pulp and paper industries Atrak - pulp and paper industries
Are paperboards dimensionally unstable?
Paperboards are made of cellulose fibers. These cellulose fibers are hygroscopic in nature. They absorb or release moisture in to the atmosphere depending on the conditions in the ambient. This release or absorption of moisture makes the paperboards dimensionally unstable.

What is the ideal atmospheric condition for printing and converting of boards ?
Temperature 23 ± 1 ºC and RH of 50 ± 2

Does a glossy board surface ensures glossy print ?
Though a glossy boards surface helps to give a glossy print but it does not ensure a glossy print. More than the glossy surface the ink hold out of a substrate, roughness and the kind of ink used, and the press parameters play important role in print gloss.

What is Meant by Quality & what are its dimensions?
Quality means fitness for use
Quality is inversely proportional to variability
Dimensions of Quality are
(i) Performance
(ii) Reliability
(iii) Durability
(iv) Serviceability
(v) Aesthetics
(vi) Features
(vii) Perceived Quality
(viii) Conformance to Standards

What is the difference between whiteness and brightness?
Brightness measures the reflectance of light at a wavelength of 457 nm from a paperboard surface. Whiteness is a composite term used to define the visual impact of near white surface by means of a single

What is stiffness? How can two boards of the same grammage & caliper have different stiffness values? How does stiffness affect carton conversion?
Stiffness, also called "flexural resistance", is a resistance bending under applied load. The stiffness of the board is directly related to the compression strength of the carton. It plays an important role in the performance of cartons in Form Fill and Sealing Machines, storage & handling, and in carrying the load of the material being packed.

The modulus of elasticity (MOE) & moment of inertia (MOI) are the two factors which control stiffness. The MOE & MOI differ with stock furnish. Boards are of different density - a board with same grammage can have different caliper. Stiffness is directly proportional to the cube of caliper. Therefore, two boards with similar caliper or grammage have different stiffness values.

What is picking?
Picking is the fracture of coating layer. It occurs when tack of the ink exceeds the cohesive forces of coating on to the base paper or the printing pressure is too high to pick the coating or the paper surface.
Piling occurs if the paper coating is too sensitive to fountain solution and the coating dissolves and gets deposited on the blanket.
If number of impressions / hr is high, coating material can build up rapidly and interfere with ink transfer.
Piling is the result of the ink in the first units of the press, building tack on the surface of the paper and eventually causing paper failure on the blankets further down, in the press. Piling shows up immediately and is more concentrated at the tail of the print image. It can be controlled by increasing wet pick strength of coating and frequent wash-ups at the press.

What is the importance of grain direction in printing ?
Papers and paperboards are anisotropic i.e they show different values for a same property in their orientation for e.g they expand more across the grain than along the grain direction. So the feeding in the printing machine is such a way that the grain direction is perpendicular to the feeding direction. This facilitates good feeding. Also the print length can be adjusted by changing the packing under blanket or plate cylinder. By adjusting this the misregister caused due to the expansion or contraction of paper can be corrected

What are halftones?
Halftones refers to the screened portion of a image which often get affected by the reproduction quality of the dot. This could be due to density variations in the print area which is caused by the printing machine used., errors in scanning, halftone photography, plate making, substrate smoothness and ink absorbency of the paper used.

Where does the term paper come from?
In its technical form, paper is an aqueous deposit of any vegetable fiber in sheet form. The name comes from the Latin "papyrus", which in the hands of the early Egyptians (its first known users), comprised the pith of a grass-like plant which was sliced into layers and beaten or pressed into sheets. Paper, as we know it today, had its origins in China. Traditional Chinese records give the credit for its development to one T'sai Lun (about 105AD) who was even deified as the god of papermakers

What is paper made of?
The raw material for the manufacture of paper is cellulose fiber, which is obtained from trees, recovered paper and annual vegetable fibers like cereal straws. Kaolin, starch and other products are used as auxiliary materials in the paper production process

What are the advantages of paper?
Paper is a natural product because it is manufactured from a natural and renewable raw material, wood. It also has another big environmental advantage: it is 100% recyclable.

Where does the wood - or pulp for papermaking - come from?
Pulpwood once came from whole mature trees. Today, the papermaker usually uses the parts of the tree that are left after wood has been used for other commercial purposes. Nearly all the pulpwood used in northern Europe could be classed as secondary cuttings, for example, thinnings extracted from the forest so that the remaining trees can grow to healthy maturity.

What sort of wood is used for making paper and board?
The industry was once based almost entirely on softwoods such as spruce, pine, larch, fir and cedar. Now birch, aspen and other hardwoods occurring in temperate climates are used as an ideal raw material for processing into fluting for corrugated cases as well as printing and writing papers, whilst eucalyptus, originally occurring only in Australia and New Zealand, has been successfully cultivated in other warm climates (eg South America, Spain and Portugal) as raw material for high-quality pulp suitable for a wide range of papers. Nevertheless, softwoods provide longer fibers (average 3 mm compared with 1mm for hardwoods) and continue to be used for papers required to have the highest strength characteristics

Are we cutting down the world's trees just to make paper?
No. Forest surface is increasing by 340,000 hectares per year. In the developed world, advantage is taken of the massive research which has been devoted to developing the best strains and to planting and conservation techniques likely to produce the healthiest trees. The destruction of rainforests in South America and Indonesia is an ecological disaster, but has nothing to do with the papermaker. Fiber needed for papermaking does not come from tropical sources and 80% of the wood used by the European pulp and paper industry comes directly from Europe.

Why use paper and board packaging?
Paper and board forms the basis for about 40% of all packaging and comes in a variety of forms from functional brown cardboard boxes to beautiful handmade boxes, paper sacks, carrier bags, tubes, cartons and wrapping papers. There has been a significant increase in the use of paper and board packaging in the past 50 years for many reasons.
    • it is robust and adaptable -- corrugated board can be used to protect delicate porcelain or large electrical items
    • it is practical -- cartons can be delivered flat to the packager, reducing space and thus transport costs
    • it can be recycled everywhere in contrast to renewable packaging that usually will have to be sent to the original producer or packer of a product
    • it is made from renewable materials, recovered paper and wood pulp
Paper is generally called board when it is heavier than 220 grammes per square meter.

Is packaging unnecessary, expensive and wasteful?
No. Packaging prevents product waste, contamination and pilfering; all of which add cost to the product. Very often the environmental effect of avoided wastage of products outweighs the impact of increased packaging. If a package has more than one layer, each will be essential and will serve a particular purpose such as retaining moisture.

What is the importance of grain direction in printing ?
Papers and paperboards are anisotropic i.e. they show different values for a same property in their orientation for e.g. they expand more across the grain than along the grain direction. So the feeding in the printing machine is such a way that the grain direction is perpendicular to the feeding direction. This facilitates good feeding. Also the print length can be adjusted by changing the packing under blanket or plate cylinder. By adjusting this the misregister caused due to the expansion or contraction of paper can be corrected

What is TAPPI stands for?
Technical Association of the Pulp and Paper Industry

What is recycling?
Recycling is the concept of taking already used materials and then processing them into other materials to be reused. For example, the morning paper can be recycled for another morning's news or other paper products.

Why should I recycle?
Recycling reduces our reliance on landfills, saves energy, conserves natural resources and reduces climate change impacts.

Why recycle?
Recovered paper is a valuable raw material that can be reused to create new paper and board products. Paper recovery is preferable to landfill or incineration for energy recovery.

What can be recycled?
Almost any paper can be recycled, including used newspapers, cardboard, packaging, stationery, "direct mail", magazines, catalogues, greeting cards and wrapping paper. It is important that these papers are kept separate from other household waste -- as contaminated papers are not acceptable for recycling


The Production Process

Raw Materials
As can be seen from the above diagram, there are two main fibrous raw materials used in papermaking. These are wood pulp (chemical and mechanical) and recovered paper. In addition, a quantity of additives (mainly natural mineral fillers) and dyestuffs are used together with traces of auxiliary chemicals. A further raw material is water, which is used in large quantities during the papermaking process but is then recovered and reused, or returned to the watercourse from which it is extracted.

Wood pulp normally arrives at the paper mill in the form of very thick sheets and recovered paper normally arrives in the form of large, compressed bales. Both these materials have to be broken down so that the individual fibers they contain are completely separated from each other. This process is performed in large vessels known as pulpers where the raw materials are diluted with up to 100 times their weight of water and then subjected to violent mechanical action using steel rotor blades. The resulting slurry (known as papermaking stock) is then passed to holding tanks. During this preliminary stage, auxiliary chemicals and additives may be added. The auxiliary chemicals are usually combined with the fibrous raw materials at levels from below 1% to 2% and can be sizing agents, which reduce ink and water penetration, and process anti-foaming agents. Common additives consist of clay, chalk or titanium dioxide that are added to modify the optical properties of the paper and board or as a fiber substitute. The stock is then pumped through various types of mechanical cleaning equipment to the paper machine.

The Paper Production Line

There are other designs of paper machine but, in all cases, the basic principles are the same. Paper machines vary enormously in size and speed depending upon the type of product being made. For instance, a specialty filter paper might be manufactured in a machine only 1m wide and moving at less than 5km/h, whereas newsprint can be produced on machines of 10m width travelling at well over 100km.
On the paper machine, yet further water is added to produce a fiber suspension of as little as 1 to 10 parts fiber to 1000 parts water and the resulting mixture is passed into a head-box which squirts it through a thin, horizontal slit across the full machine width (typically 2 - 6 m) on to a moving, endless wire mesh.
The water is then removed on this wire section by a mixture of gravity and suction in a process known as sheet formation where the fibers start to spread and consolidate into a thin mat, which is almost recognizable as a layer of paper on top of the wire mesh.
This web of wet paper is then lifted from the wire mesh and squeezed between a series of presses where its water content is lowered to about 50%. It then passes around a series of cast-iron cylinders, heated to temperatures in excess of 100ºC, where drying takes place. Here the water content is lowered to between 5% and 8%, its final level. Throughout its passage from the wire mesh to the drying operation, the paper web is supported on various types of endless fabric belts moving at the same speed. After drying, some papers may also undergo surface treatments e.g. sizing and calendaring. The latter process consists of smoothing the surface of the paper by passing it between a series of rotating, polished, metal rollers. It is then wound into a reel.

Paper Finishing Operations
The reels from the paper machine are passed into a separate area where they are subjected to further operations. These may be either simple processes where the reel is slit into a number of more narrow reels or cut into sheets. In some cases, more complicated processes may be performed such as coating (often consisting of the application of clay-based materials for special printing finishes) or more calendaring may be performed. The final reels or sheets are then wrapped and dispatched to other companies which carry out converting and printing operations.

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