Paper (rolls)
| Infobox on Paper (rolls) | |
|---|---|
| Example of Paper (rolls) |  |
| Facts | |
| Origin | This table shows only a selection of the most important countries of origin and should not be throught of as exhaustive
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| Stowage factor (in m3/t) | 1.78 m³/t (paper rolls wrapped in 6 layers of packing paper). Package dimensions are variable, the important factor being that the rolls within one cargo stack must exhibit uniform dimensions, to prevent distortion. |
| Humidity / moisture |
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| Ventilation | Recommended ventilation conditions: air exchange rate: 6 changes/hour (airing), if the dew point of the external air is lower than the dew point of the hold air. On voyages from cold to hot climates (Scandinavian ports, Continental ports - tropical unloading ports in Africa, Asia), every possible opportunity for warming the paper must be used to avoid cargo sweat. |
| Risk factors | Self-heating / spontaneous combustion, contamination, wet damage, mechanical influences; see text. |
Paper (rolls)
Description
Paper (and board) are manufactured from paper pulp. This material is first repulped in water and, after passing through various intermediate operations, such as straining to remove particulate matter, the aqueous slurry of fibres (about 0,5% cellulose fibres) is deposited as a continuous film on a recirculating wire mesh or a moving felt band. The belt passes over suction boxes which removes water from the film to produce a continuous ‘paper’ strip containing about 35% of cellulose. This is sufficiently strong to be stripped off the belt and threaded through a battery of heated rollers where it is further dried so that the paper or board emerging from the end of the machine has a moisture content of about 5%. The warm paper is reeled and possibly slit simultaneously into predetermined sized rolls, by means of continuous reeling equipment.
There are a large number of different types of paper which can be produced by using different types of paper pulp and by various treatments during the paper making operation, such as sizing, opacifying, treatment to produce wet strength, polishing (calendaring), coating etc. It is evident that more complex papers are commercially more valuable than less complex papers. It is also evident that sophisticated paper products which are unacceptable for the intended purpose must either be sold for scrap or returned for repulping. The pulp produced will inevitably be used for low grade products.
Major uses of paper are for newsprint and the manufacture of corrugated fibre board. The paper products used for each application are similar in as much as they are almost always in large, very heavy rolls over half a tonne in weight. Unbleached kraft rolls used for carton board are only slightly less valuable. Because of their weight they must be mechanically handled.
Newsprint rolls are used on high speed printing presses. Any interruption in the printing process, due to a fault in the paper, results in a substantial financial loss. Users take particular care to ensure that only sound rolls which can easily be handled to make them sound, are accepted.
Although the users of kraft paper are not constrained by time in the same way as newspaper publishers, they also employ high speed machinery of high capital cost and take the utmost care to prevent any interruption on a production line.
Applications
Paper may be classified into seven categories:
- Printing papers of wide variety.
- Wrapping papers for the protection of goods and merchandise. This includes wax and kraft papers.
- Writing paper suitable for stationary requirements. This includes ledger, bank, and bond paper.
- Blotting papers containing little or no size.
- Drawing papers usually with rough surfaces used by artists and designers, including cartridge paper.
- Handmade papers including most decorative papers, Ingres papers, Japanese paper and tissues, all characterized by lack of grain direction.
- Specialty papers including cigarette paper, toilet tissue, and other industrial papers.
Newsprint, which belongs to the first group, is used for daily and weekly newspapers, magazines, catalogs, newspaper supplements, direct mail items and for advertising flyers.
Shipment / storage / usage
Newsprint is a machine-finished printing paper, predominantly for web offset printing. Its basis weight is 40 - 56 g/m2. Since damage to the rolls of paper leads to considerable losses, the demands made of transport and storage of such rolls are high.
Fewer demands are made of newsprint with regard to visual characteristics and printability, because, of all the types of paper, newspapers are the shortest-lived sources of information. To keep the retail price low, they must be inexpensive, which is why the waste paper or mechanical pulp content is high.
Newsprint must have good printability, good pressroom runnability (tear resistant), sufficient opacity (reverse must not show through), good recyclability, optimum water content 7% and good dimensional stability.
Newsprint is transported in rolls up to 300 cm wide and with total weight of up to 4.5 t.
The circumferential packaging for the paper rolls wound ultratightly onto paperboard or metal cores is up to 3,5 mm thick and, as a rule, consists of several plies of kraft paper. To provide protection from moisture, a waterproof ply (e.g. of asphalt paper) is often incorporated therein. The circumferential packaging is folded over the ends by approximately 20 cm. The ends of the rolls are protected with corrugated board covers. In many cases, the final kraft paper cover is plastic-coated and stuck to the folded-over circumferential packaging. Core stability is ensured by a wooden or metal plug driven in at each end.
As there is a risk of losses caused by swelling and tearing of individual layers, paper (rolls) should be protected from extraneous wetness and handled carefully resp. professionally (with special cargo handling gear and forklift trucks with paper roll clamps).
Incorrect cargo handling may result in distortion of paper rolls (ovalization). Rolls exhibiting marked ovality can no longer be used for printing and have to be rewound.
Cargo spaces must be clean and smooth, to prevent any possibility of damage to the ends. The goods must be protected from any possible leakage from hydraulic lines. In addition, paper must be protected from all moisture, such as rain, snow, condensation water, seawater, extremely high levels of relative humidity or damp stacking surfaces.
The most favorable travel temperature range is 0 - 25°C. Optimum travel temperature: 20°C ± 5°C (relative humidity 60-70%).
During cargo handling, temperatures below 0°C are also permissible for short periods. The goods must be protected from heat sources.
Paper rolls are very sensitive to mechanical influences such as pressure, impact and friction. The risk of damage is greatest during cargo handling (i.e. distortion / ovalization, telescoping, indentations, edge damage, tearing, chafing).
Rolls which are landed heavily may be flattened and in some cases the cores may be crushed. While it may be possible to force the core back into shape any flattening of the rolls can cause jerking during the printing operation. With high speed presses, jerking or uneven running of the roll results in breaks in the paper, thereby slowing down the operation. Where the cores cannot be pressed out it becomes necessary to rewind the damaged roll. This operation can only be carried out by a skilled operator as the roll must be rewound at the same tension as existed before rewinding.
Damage may take place during loading on board vessels but occurs chiefly during discharge due to careless handling of winches and cranes when lifting from holds. Damage can arise from bad stowage, e.g. with case goods or other sharp volumes, or by forcing rolls behind ladders, shaft tunnels or similar hindrances.
If wet, newsprint may be unfit for printing purposes but may possibly be used for pulp, manufacturing paper bags, shop wrapping paper, etc.
Should a roll come into contact with steelwork, be rolled over an uneven surface or dropped unevenly on its end, damage may be found in the form of cuts and tears on the face or edge of the newsprint. There are two methods of establishing the amount of damage to newsprint rolls. One is to have the damage cut off the reel and the amount of paper thus cut off weighed. The alternative is to measure the depth that the cut or tear has penetrated the roll, and calculate the amount of loss by use of a formula :
