pulp and paper industry calendering

1. Super calendar
Kumar shantnu (121416)
Pankaj nishant (121420)

2. calender
 A Calender is employed, usually to smooth, coat, or thin a material. With
textiles, fabric is folded in half and passed under rollers at high temperatures
and pressures
 Calanders come in various forms including a machine calender, (soft calenders
and super calenders).
 . Calanders are made up of steel roller sets, between which the paper passes

3. Super calendar
 supercalender gives paper a high-gloss finish
 A supercalender is a stack of calenders consisting of alternating steel and
fiber-covered rolls through which paper is passed to increase its density,
smoothness and gloss.
 It is similar to a calender except that alternate chilled cast iron and softer
rolls are used.
 A supercalender is a vertical alternating stack of hard polished steel and soft
cotton (or other resilient material) rolls.
 The hard roll is pressed heavily against the soft roll, compressing the
material.

4. calendering
 Calendering is a mechanical finishing process used on cloth where fabric is
folded in half and passed under rollers at high temperatures and pressures.
 Calendering is used on fabrics such as moire to produce its watered.
 Calendaring is a high speed ironing process that primarily imparts lustre and is
usually the final treatment for the fabrics in the finishing sequence.
 The basic principle of calendaring is to expose the cloth to the combined
effect of moisture, heat and pressure until the fabric acquires a very smooth
and light reflecting surface and gets a good lustre.

5. Calendering
OBJECTIVS:
To compress the fabric and reduce its thickness.
 To upgrade the fabric handle and to impart a smooth silky touch
to the fabric
 To improve the Opacity of the fabric.
 To reduce the Air Permeability of the fabric by changing its
porosity.
 To impart different degree of Lustre to the fabric.

6. Super calendering
 A paper finishing operation consisting of an additional degree of calendering
performed on a special machine not connected to the main papermaking
machine.
 The supercalender gives paper a high-gloss finish, the extent of
supercalendering determining the extent of the gloss.
 Supercalendering, in enhancing some paper properties, diminishes others in
the same way the regular calendering does.

7. History of Calendering
 The calendering processes that we know today are the finishing methods
developed from the early 1800s mainly to make machine-made papers
sufficiently smooth for printing and writing and to give some grades a glossy
appearance.
 These two properties are quite distinct.
 the former being related to the ability of a paper surface to receive ink
satisfactorily and uniformly.
 the latter referring to its light reflecting characteristics.
 the methods employed since well before 1000 AD to increase smoothness
invariably also increased gloss, they used to be called 'glazing'

9.  The embossing unit is used to imprint special features on the film
 The winding station includes cutting devices for edge trimming of rolls .
 The extrusion process converts plastic powder or pellets into a continuous uniform melt and
forces this melt through a die, which upon cooling yields a desired shape. The end products
are custom profiles, sheet, pipe, tubing, fibers, film, coatings, and pellets.
 To begin the process the polymer must go through blending and fluxing before it goes through
the calender. Blending is a process that creates the desired polymer and fluxing heats and
works this blended polymer to make it a consistency easier for the calender to handle
 The polymer is then ready to go through the calender and will leave it at a thickness
dependent mainly on the gap between the last two rollers. The last set of rollers also dictate
the surface finish; for example, they can influence the glossiness and texture of the surface.
 That is why calenders typically end with a smaller roller at a higher speed to peel the sheet
off. It is also why the middle roller is normally kept cooler so that the sheet won't stick to the
other rollers nor will it split by sticking to both rollers which can happen.

10. types of calender
 7- bowl calendar
 Chasing calendar
 Friction calendar
 Schreiner calender
 Felt calender

11. 7 BOWL CALENDER:
.

12. 7 BOWL CALENDER:
 Generally the compressed material bowls are made from either
Cotton or Wool paper, Linen paper or Flax paper.
 The hard bowl is made up of either Chilled Iron or Close
Grained Cast Iron or Steel.
 Iron bowls are made with highly polished surface and are
heated from inside by steam or gas.
 The fabric is passed through the machine in between the bowls
and as the result Gloss is developed in the calendered fabric.

13.  They run at a speed of 8 mts / min.
 In this machine, there are 3 iron bowls, and 4 cotton bowls.
 In between two metallic bowls, one cotton bowl is arranged.
 Care should be taken in such a way that no two iron bowls are arranged
together to avoid damage to the fabric.

14. CHASING CALENDER
 ,

15. CHASING CALENDER
 It is also a 7 bowl calendar. A chasing calendar finish is
obtained with all the bowls of the calendaring machine running
with the same surface speed, and the cotton fabric is passed
through the nips of the calendar fro several times, each layer of
the cloth overlapping one another
 Chasing gives a Thready – Linen appearance and a special soft
handle to the fabric. Here, all rollers are run at the same
speed. The fabric is passed through the nips of rollers for
several times.

16. FRICTION CALENDER

17. FRICTION CALENDER:
 For producing this effect, the top four bowls of a 7bowl calendar can be
lifted up, disconnecting the contact between the third and the fourth
bowls so as to use only three bowls.
 The Friction calendar with a 7 bowl calendar after disconnecting the top
four bowls.
 The three bowl calendar, one of which is cotton and the other two are of
chilled iron.
 Friction calendaring gives a higher Gloss and greater closing of the yarns,
it is produced by bringing the cloth in contact with a heated polished
chilled iron bowl which is rotating at a faster speed than the cloth itself.
 The polished chilled iron bowl is heated by steam or gas and using gear
wheels, the top chilled bowl is rotated at double the speed of the fabric
and of the lower two bowls.

18. FRICTION CALENDER:
 As a variation, the top bowl may be run at 1&1/2 times the speed of
the lowest bowl, with the middle bowl running at an intermediate
speed.
 The top bowl with its higher surface speed produces the friction
effect by polishing the cloth.
 This finish is generally imparted to loose construction cloth such as
binding cloth, low quality printed cloth etc.It is generally run at a
speed of 32 mts/min.
 The speed of the calendar when used in friction calendaring is
determined by the amount of finish desired on the fabric and by the
number of bowls used.

19. SCHREINER CALENDER

20. SCHREINER CALENDER
 The usual schreiner calendar consists of two bowls, the upper bowl is made up of
specially polished steel bowl and the lower bowl is made of compressed cotton.
 The top metallic bowl is engraved with parallel lines normally 200 lines / inch2 at
20 angle. For some special cases it maybe drawn at an angle of 45.
 The metallic bowl is heated by gas usually at 150 C.
 The two bowls are in contact with each other when the machine is running and are
kept separated when not in use. Otherwise the cotton bowl may get destroyed.
 The top bowl is fixed and the lower is movable.
 Very high pressure of100 tons or more is exerted on the fabric as it passes through
the nip by hydraulic means.

21. SCHREINER CALENDER
 The lower bowl, in some cases is set at an angle by
Skewing arrangement to give enhanced brilliancy.
 Mercerized fabric when treated in this calendar gives Silk
finish. Like other calendar finishes, it is also not
permanent.
 It is destroyed while washing the fabrics.
 Generally Umbrella cloth and Aniline Black dyed cloth are
finished by this calendar.
 Speed is 10 to 25 mts/min.

22. FELT CALENDER
 Light weight cotton goods like super fine Dhoti's, Sarees,etc.,
are finished on this machine.
 This is also employed for the finishing of knitted goods. Blanket
drying is a special method of cylinder drying. Here the cylinder
is used for both drying and finishing.
 The main cylinder is 6 to 8 feet in diameter made up of Tinned
Sheet Iron or Stainless steel.
 The cylinder is heated by steam and rotates freely.
 An endless wollen felt blanket passes around the major part of
the cylinder.
 The cylinder is rotated along with the endless blanket.

23. FELT CALENDER
 Before feeding the fabric to the machine, the fabric is passed through a
padding mangle for applying the finishing mixture and then passed over
an expander or a small stenter.
 Then the fabric is fed between the blanket and the cylinder and is kept
against the hot surface by the pressure of the blanket during drying.
 In this manner, there is no undue tension on warp. In addition to drying,
it gives an attractive finish with soft feel and a smooth surface.
 In another type of felt finish, the fabric is finished on hot air stenter,
damped on a damping machine and then passed through felt calendar to
get required feel.
 Speed of this machine is30 to 40 mts/min.Fabric width of 1 to 2.5 cm can
be reduced by this machine.

24. Calendering effects on paper properties
 Positive effect
 Smoothness
 Gloss
 Absorption and porosity
 Caliper control
 Two-sidedness control (printing
papers
 Negative Effects
 Bulk and stiffness
 Strength properties
 Opacity and brightness
 Light scattering
 Costs

25. Following attentions should be paid for
maintenance
 Calendar roll should be inspected with utmost care and defect causing any
unusual sound should be found and rectified
 All bearing of calendar rolls should be lubricated frequently
 Rolls should be ground to proper finish and crown
 Calendar rolls should be periodically changed and sent for grinding