Introduction
Surface sizing
Pigmenting
Coating
Reeling
Calendering
Winding
Sheeting
Roll handling
Introduction |
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Surface sizing |
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Pigmenting |
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Coating |
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Reeling |
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Calendering |
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Winding |
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Sheeting |
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Roll handling |
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Finishing after paper or board machine depends on grade requirements. Typical finishing methods for all grades are:
In addition, according to product can be:
Based on the coat weight being applied to the surface and the consistency of
the surface finishing agent, paper and board coating methods can be divided
into three different categories 
:
The target of surface sizing is to improve paper or paper board strength properties, like internal strength (bonding strength) or surface strength (low dusting). Applications of sizing are fine papers, coated base papers and paper boards.
Surface sizing improves paper properties by reinforcing the bonds between fibers
with a water-soluble binding agent, usually starch 
. The machines are located
past the predrying section, to ensure that the paper is dry enough to withstand
sizing. After adding surface size the web is dried. When the starch solution
dries, water evaporates, and extremely strong hydrogen bonds are formed between
the starch and other media. This is the manner in which starch functions as
a sizing agent.
In practice, size presses 
and
film size presses 
are used in surface sizing:
consists of two rotating rolls, a sizing
agent pool applyed between them. Paper web is routed through the pool to the
nip, where size is pressed to the web. The most important property of pool
size press is good penetration reached, which is the goal when increasing
internal strenght of paper. The size press seldom reaches speed over 1000
m/min. This method is used mainly with paper boards.
.
In a film size press, the surface size is applied with rod onto the nip roll
surface and then transferred to the paper web in the nip of the rolls. The
amount of the film is determined by the open cross-section of rod profile
and roll coating. This effects mostly the form of the slot rod, the roll coating
elastic modulus (~hardness) and load to the rod. The need for post-drying
is minor for film size press.
Pigments can be added to the sizing solution, then we talk about pigmentation. Pigmentation affects porosity by plugging paper pores. Surface size contains no pigments, and the coat weight being applied to the paper or board surface during pigmentation is very small (from 1.0 to 2.0 g/m2 ). In addition to surface sizing, pigmentation can also be performed with a size press.
The purpose of paper and board coating is to improve the appearance and printability of the product:
and opacity. In all, the quality of chosen base paper and coating formulation, as well as coating and printing methods affect the quality of the end product.
When coating the surface
of paper or board - either one or both sides - a coating color containing pigment
(such as kaolin, talc or carbonate) and binding agent (such as starch or latex)
is applied. The color is applied to the paper or board surface in excess. The
coat weight is corrected by removing the excess color. After correcting the
coat weight, it is dried .
Printability can be improved by coating the paper or board several times . High-grade printing
papers can be coated up to three times.
The most commonly used coating method is blade coating in
its various forms . In addition
to blade coaters, coating can also be done using rod coaters, film transfer
coaters and air brush coaters .
Pigment coating can be performed at the mill either with a:
The purpose of reeling is to render the planiform paper or board produced in
a form which is easier to handle. The continuous process of a paper machine
is interrupted first at the machine reel, also called Pope, whereafter the process
continues in sequences. The sequences are interlinked with maximum smoothness,
with an effort to avoid wasting work which has already been done .
The paper may be reeled several times after the paper machine before it is
a finished product. Types of reelers and winders :
Calendering has three main functions:
Moreover, calendering may be used for various special purposes, e.g., for stamping relief designs on the paper with patterned rolls.
Calendering is implemented by means of leading the web through a system of nips between two or more rolls.Tällöin raina mm. puristuu ja kiilloittuu. Mechanisms producing smoothness and gloss:
Most printing-specific properties of paper are improved at calendering, but, at the same time, many other properties related to runnability and usability are impaired.
The paper may be calendered at:
Types of calenders:
The paper web from a paper machine or a board machine as well as from a coater and/or a calender is wound up around a reel spool to a parent reel. The parent reel web is machine-wide and even over 90 km long, so it has to be slit into web sections of suitable width and length for the customer and wound up around cores before sending out from the mill.
At the same time, web runnability is also tested. Customer rolls must have good runnability on printing presses or during sheeting as well as durability and ease of handling during transportation and storage.
Early printing techniques made use of paper in sheets. As printing techniques
developed, roll printing was brought into use . The advantages of sheet printing are its
versatility and flexibility in relation to the grade of paper. Sheet printing
machines are used in the production of all sorts of printed items. Roll printing
is only more economical when used for high-volume printwork. The most typical
printwork is produced for commercial applications, such as brochures, annual
reports, specialty papers, catalogs, posters, etc. Sheeted paper is also used
in offices for a variety of copying , printout and report applications.
The sheeting plant can either be integrated with the paper
mill or completely independent, both as a process and company. The highest level
of integration is where paper rolls are brought to the sheeting plant unwrapped
and sheeting trim is pulped in the paper mill.
The base factors affecting cutter capacity are:
Sheet size and paper grade affect all the above base factors. The effective run time has the greatest effect on reducing the production capacity of the cutter. Limiting factors for this are:
As a result of these factors, the production capacity of folio cutters is significantly less than the theoretical capacity. The number of shutdowns caused by equipment faults and maintenance is minimal.
Roll handling involves all operations being carried out after the paper or
board has been cut into smaller rolls on the winder . Rolls
are either intended for customer delivery or finishing at the mill, such as
sheeting. Roll handling comprehends the transport of rolls from the winder to
the warehouse and protecting the rolls against damages caused by transportation
and climate changes, i.e. the packing of rolls in the appropriate wrapping materials.
In roll handling the roll is also assigned its own 'code', which is used to
ensure that the roll arrives in the right place at the right time.
Roll handling include:
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