Spun Laid Process, Melt Blown Process, Differences between spun laid Process and Melt Blown Process

1. Assignment Submission on the Spun Laid Process, Melt Blown Process,
Differences between spun laid Process and Melt Blown Process
Textile Process Experiment
Submitted By-
Md.Sajjadul Karim Bhuiyan
Id No.-1715226027
School of Textile Science and Engineering
Wuhan Textile University.
Sc

2. Spun Laid Process
In the spun bond technology, usually a thermoplastic fiber forming polymer is extruded to form
fine filaments fibers of around 15–35 micrometer diameter. The filaments are attenuated
collected on a conveyor belt in the form of a web. The filaments in web are then bonded to
make spun bond nonwoven fabric.
Raw materials of Spun Laid Process
Spun bond technology uses preferably thermoplastic polymers with high molecular weight and
broad molecular weight distribution such as polypropylene (PP) and polyester (PET). To a small
extent, other polyolefin such as polyethylene of high density (HDPE) and linear polyethylene of
low density (LLDPE) as well as a variety of polyamides (PA), mainly PA 6 and PA 6.6 are found.
The fiber grade polypropylene (mainly isotactic) is the principal type of polypropylene which is
used in spun bond technology. Spun bond nonwovens are exclusively made from crystalline
polyester. Nowadays, the bicomponents are found in spun bond fabrics. Sometimes the
bicomponent filaments are splitted or fibrillated into microfibers by means of hydro entangling
energy. In addition, bicomponent fibers with eccentric sheath core arrangement are used to
develop crimp in spun laid fabrics by differential thermal shrinkage of the two polymer
components.
Process Sequence
The spun bond technology, sequence of processes is as follows:
polymer preparation ---> polymer feeding, melting, transportation and filtration ---> Extrusion --
-> Quenching ---> Drawing ---> Laydown ---> Bonding ® Winding.

3. Spun bonding combines fiber spinning with web formation by placing the bonding device in line
with spinning. In some arrangements the web is bonded in a separate step which, at first
glance, appears to be less efficient. However, this arrangement is more flexible if more than
one type of bonding is applied to the same web.
Figure 1- Schematic of spun bonding process
Figure 2- Deflector plane for separation of filaments
Spun bonding is one of the most popular methods of producing polymer-laid nonwovens. This process is
based on the melt spinning technique. The melt is forced by spin pumps through a spinneret having a
large number of holes. The quench air ducts, located below the spinneret block, continuously supply the
conditioned air to cool the filaments. There is also a continuous supply of auxiliary room temperature air.
Over the line's entire working width, ventilator generated under-pressure sucks the filaments and mixed
air down from the spinnerets and cooling chambers.

4. The through a venture (high velocity low pressure zone) to a distributing chamber, which affects fanning
and entanglement of the filaments. Finally, the filaments are deposited as a random web on a moving
sieve belt. The randomness is imparted by the turbulence in the air stream, but there is a small bias in the
machine direction due to some directionality imparted by the moving belt. The section below the sieve
belt enhances the lay down of the filaments. The conveyor belt then carries the spun bonded web to the
bonding zone. The web is then bonded either thermally, mechanically or chemically, depending on the
material and the desired properties in the final fabric. Thermal point bonding is the most commonly used
technique for many applications.
Advantages of Spun Laid Process
 From an energy point of view, modern Spun bonding requires no heat for water elimination,
which is very proficient.
 Production lines for thermal-bonded nonwovens also require less floor space & operator.
Also the production rates of fabric production are very high.
 Thermal-bonded nonwovens are usually softer and drier, have superior strength per unit
weight, and are permeable and absorbent for the reason that of very smaller bonding
points.
Application
The spun bond nonwovens are finding applications in a variety of end uses. Today they are used
both for durable and disposable applications. The main applications for spun bond nonwovens
are in automobiles, civil engineering, hygiene, medical, packaging, and agriculture.

5. Melt Blown Process
The melt blown technology is based on melt blowing process, where, usually, a thermoplastic
fiber forming polymer is extruded through a linear die containing several hundred small
orifices. Convergent streams of hot air (exiting from the top and bottom sides of the die
nosepiece) rapidly attenuate the extruded polymer streams to form extremely fine diameter
fibers (1–5 micrometer). The attenuated fibers are subsequently blown by high-velocity air onto
a collector conveyor, thus forming a fine fibered self-bonded melt blown nonwoven fabric.
Raw materials of Melt Blown Process
Polypropylene has been the most widely used polymer for melt blown technology. Besides, a
variety of different polymers including polyamide, polyester, and polyethylene are used. It is
known that polyethylene is more difficult to melt blow into fine fiber webs than polypropylene,
but polyamide 6 is easier to process and has less tendency to make shot (particles of polymers
that are larger than fibres) than polypropylene. In general, the requirements of polymers for
melt blown technology are high MFR or MFI (300-1500 gm/10 min), low molecular weight, and
narrow molecular weight distribution.
Process Sequence
A typical melt blowing process consists of the following elements: extruder, metering pumps,
die assembly, web formation, and winding
Figure 3-Schemetic Diagram of Melt Blowing Process

6. 1.1.Extruder
The polymer pellets or granules are fed into the extruder hopper. Gravity feed supplies pellets
to the screw, which rotates within the heated barrel. The pellets are conveyed forward along
hot walls of the barrel between the flights of the screw, as shown in Figure 2. As the polymer
moves along the barrel, it melts due to the heat and friction of viscous flow and the mechanical
action between the screw and barrel. The screw is divided into feed, transition, and metering
zones. The feed zone preheats the polymer pellets in a deep screw channel and conveys them
to the transition zone. The transition zone has a decreasing depth channel in order to compress
and homogenize the melting polymer. The molten polymer is discharged to the metering zone,
which serves to generate maximum pressure for extrusion. The pressure of molten polymer is
highest at this point and is controlled by the breaker plate with a screen pack placed near the
screw discharge. The screen pack and breaker plate also filter out dirt and infused polymer
lumps. The pressurized molten polymer is then conveyed to the metering pump.
1.2.Metering pump
The metering pump is a positive-displacement and constant-volume device for uniform melt
delivery to the die assembly. It ensures consistent flow of clean polymer mix under process
variations in viscosity, pressure, and temperature. The metering pump also provides polymer
metering and the required process pressure. The metering pump typically has two intermeshing
and counter-rotating toothed gears. The positive displacement is accomplished by filling each
gear tooth with polymer on the suction side of the pump and carrying the polymer around to
the pump discharge, as shown in Figure 2. The molten polymer from the gear pump goes to the
feed distribution system to provide uniform flow to the die nosepiece in the die assembly (or
fiber forming assembly).
1.3.Die Assembly
The die assembly is the most important element of the melt blown process. It has three distinct
components: polymer-feed distribution, die nosepiece, and air manifolds.
1.3.1. Feed Distribution
The feed distribution in a melt-blown die is more critical than in a film or sheeting die for two
reasons. First, the melt-blown die usually has no mechanical adjustments to compensate for
variations in polymer flow across the die width. Second, the process is often operated in a
temperature range where thermal breakdown of polymers proceeds rapidly. The feed
distribution is usually designed in such a way that the polymer distribution is less dependent on
the shear properties of the polymer. This feature allows the melt blowing of widely different
polymeric materials with one distribution system. The feed distribution balances both the flow

7. and the residence time across the width of the die. There are basically two types of feed
distribution that have been employed in the melt-blown die: T-type (tapered and untapered)
and coat hanger type. Presently, the coathanger type feed distribution is widely used because it
gives both even polymer flow and even residence time across the full width of the die.
1.3.2. Die Nosepiece
From the feed distribution channel the polymer melt goes directly to the die nosepiece. The
web uniformity hinges largely on the design and fabrication of the nosepiece. Therefore, the die
nosepiece in the melt blowing process requires very tight tolerances, which have made their
fabrication very costly. The die nosepiece is a wide, hollow, and tapered piece of metal having
several hundred orifices or holes across the width. The polymer melt is extruded from these
holes to form filament strands which are subsequently attenuated by hot air to form fine fibers.
In a dies nosepiece, smaller orifices are usually employed compared to those generally used in
either fiber spinning or spunbond processes. A typical die nosepiece has approximately 0.4-mm
diameter orifices spaced at 1 to 4 per millimeters (25 to 100 per inch). There are two types of
die nosepiece used: capillary type and drilled hole type. For the capillary type, the individual
orifices are actually slots that are milled into a flat surface and then matched with identical slots
milled into a mating surface. The two halves are then matched and carefully aligned to form a
row of openings or holes as shown in Figure 3. By using the capillary type, the problems
associated with precise drilling of very small holes are avoided. In addition, the capillary tubes
can be precisely aligned so that the holes follow a straight line accurately. The drilled-hole type
has very small holes drilled by mechanical drilling or electric discharge matching (EDM) in a
single block of metal, as shown in Figure 3. During processing, the whole die assembly is heated
section-wise using external heaters to attain desired processing temperatures. It is important to
monitor the die temperatures closely in order to produce uniform webs. Typical die
temperatures range from 2l5oC to 340OC.
Figure 4- Schematic Diagram of Die Nosepiece

8. 1.3.3. Air Manifolds
The air manifolds supply the high velocity hot air (also called as primary air) through the slots
on the top and bottom sides of the die nosepiece, as shown in Figure 4. The high velocity air is
generated using an air compressor. The compressed air is passed through a heat exchange unit
such as an electrical or gas heated furnace, to heat the air to desired processing temperatures.
They exits from the top and bottom sides of the die through narrow air gaps, as shown in Figure
4. Typical air temperatures range from 230oC to 360oC at velocities of 0.5 to 0.8 the speed of
sound.
1.4. Web Formation
As soon as the molten polymer is extruded from the die holes, high velocity hot air streams
(exiting from the top and bottom sides of the die nosepiece) attenuate the polymer streams to
form microfibers. As the hot air stream containing the microfibers progresses toward the
collector screen, it draws in a large amount of surrounding air (also called secondary air) that
cools and solidifies the fibers, as shown in Figure 4. The solidified fibers subsequently get laid
randomly onto the collecting screen, forming a self-bonded nonwoven web. The fibers are
generally laid randomly (and also highly entangled) because of the turbulence in the air stream,
but there is a small bias in the machine direction due to some directionality imparted by the
moving collector. The collector speed and the collector distance from the die nosepiece can be
varied to produce a variety of melt-blown webs. Usually, a vacuum is applied to the inside of
the collector screen to withdraw the hot air and enhance the fiber laying process.
1.5. Winding
The melt-blown web is usually wound onto a cardboard core and processed further according
to the end-use requirement. The combination of fiber entanglement and fiber-to-fiber bonding
generally produce enough web cohesion so that the web can be readily used without further
bonding. However, additional bonding and finishing processes may further be applied to these
melt-blown webs.
1.6 Bonding
Additional bonding, over the fiber adhesion and fiber entanglement that occurs at lay down, is
employed to alter web characteristics. Thermal bonding is the most commonly used technique.
The bonding can be either overall (area bonding) or spot (pattern bonding). Bonding is usually
used to increase web strength and abrasion resistance. As the bonding level increases, the web
becomes stiffer and less fabric like.

9. 1.7.Finishing
Although most nonwovens are considered finished when they are rolled up at the end of the
production line, many receive additional chemical or physical treatment such as calendaring,
embossing, and flame retardance. Some of these treatments can be applied during production,
while others must be applied in separate finishing operations.
Characteristics of Melt blown fabrics are:
The main desired characteristics expected for melt blown nonwoven fabrics are:
 Adjustable Pores And Capillary Structure
 Excellent barrier properties
 Filament size 1 -3 µm
 High Elasticity
 High Filtration capability
 Isotropic formation- this means that the fibers are randomly distributed in the machine
direction (MD) and cross-machine direction (CD).
 Large Area-to-weight ratio
 Self-bonding
 The weight of the melt-blown fabrics in gram per square meter (GSM) should range
from 4 g/m2 to over 1000 g/m2.
 Very good thermal insulation for apparel application
 Weak tensile properties
 Wicking Properties
Application
Owing to the smaller fibers and larger surface area occupied by the fibers the melt blown
nonwovens offer enhanced filtration efficiency, good barrier property, and good wicking
property. They are finding applications in filtration, insulation, and liquid absorption.

10. Spun laid Process versus Melt Blown Process
It is interesting to note the differences between the spun bonds and melt blown technologies
and products thereof. The melt blown technology requires polymers with considerably lower
melt viscosity as compared to the spun bond technology. The initial investment for spun bond
technology is three to four times higher than that for melt blown technology. The melt blown
technology consumes more energy than the spun bond technology because of the usage of
compressed hot air. The melt blown nonwoven is generally found to be costlier than the spun
bond nonwoven.
A melt-blown process uses large amounts of high-temperature air to attenuate the filaments.
The air temperature is typically as high as or higher than the temperature of the polymer. In
contrast, the spun bond process generally uses a smaller volume of air close to ambient
temperature to apply the attenuation force

11. Assignment Submission on the Needle Punching Process, Dry Laid
Carding Process
Textile Process Experiment
Submitted By-
Md. Sajjadul Karim Bhuiyan
Id No.-1715226027
School of Textile Science and Engineering
Wuhan Textile University.
Sc

12. Needle Punching Process
A physical method of mechanically interlocking fibers webs by using barbed needles to
reposition some of the fibers from a horizontal to a vertical orientation. Thousands of needles
interlock fibers in a web.
Principle of Needle Punching Process
A needle punched nonwoven is a fabric made from webs or batts of fibers in which some of the
fibers have been driven upward or downward by barbed needles. This needling action binding
point is a set of fibers with various orientation, which are bonded by friction forces.
Figure 5- Principle of Needle Punching Process
The needle board is the base unit into which the needles are inserted and held. The needle
board then fits into the needle beam that holds the needle board into place. The feed roll and
exit roll are typically driven rolls and they facilitate the web motion as it passes through the
needle loom. The web passes through two plates, a bed plate on the bottom and a stripper
plate on the top. Corresponding holes are located in each plate and it is through these holes the
needles pass in and out. The bed plate is the surface the fabric passes over which the web
passes through the loom. The needles carry bundles of fiber through the bed plate holes. The
stripper plate does what the name implies; it strips the fibers from the needle so the material
can advance through the needle loom.
Appearance and degree of compression of a needle felt are mainly influenced by:
 Needle arrangement in the needle board
 Needle parameters (gauge, form of barb, number of barbs)
 Needling parameters (penetration depth and density, draft)
 Direction of needling (from top, from bottom or from both sides)

13. The number of needles in the needle board varies from 1500 to 5000 needles per meter and
per board of 200 mm width. The needle selection should be depends upon the fineness of the
fibrate proper selection of gauge, barb, point type and blade shape (pinch blade, star blade,
conical) can often give the needle punch the added edge needed in this competitive industry.
Influence of needling conditions on the needle felt’s characteristics:
The characteristics of the needle felts depend on the fibres used, the technological conditions
of web formation and above all on the consolidation.
Important values for the formation of pores and channels are:
 Fiber diameter: derived value of fiber density and fineness
 Amount of fibers per area: derivable value of web mass, fibre length and fineness
 Needle diameter: determines the space required by the barbs for the fibre
transport. It depends on the fibre fineness,i.e. coarser fibers mean coarser
needles(smaller gauge number) and vice versa
 Penetration depth: penetration depth of the needle point out of the felt underside
and the number of barbs penetrating the felt cross section
 Stitching density: important value for the number of penetrations (hollow spaces) in
the needle felt and their size.
Direction of Needling
When the needle boards are arranged “opposite to each other”, two needling modes
“simultaneous” and “alternating” are possible. The needling “simultaneous” mode means that
both boards penetrate the felt at the same time. Therefore only half the needles can be
inserted in alternating rows in each board to prevent confrontation of the needles. To reach
certain and higher compression, the necessary total penetration density is shared between
several needle looms. The needle looms are arranged one behind the other in so-called
needling lines.
The different needling directions are as follows:
 double boards (down stroking)
 double boards (up stroking)
Figure 6- Direction of needle penetration

14.  Twin board (two boards up stroking and down stroking in the same vertical
plane).
 Tandem or twin boards (up and down stroking in alternation in two sequential
needle punching zones).
 Four boards or quad punch (up and down stroking for simultaneous double
sided needle punching with two sets of up- and down-stroking boards, each set
arranged in the same vertical plane).
Characteristics of Needle Punched Nonwovens Fabric:
Generally important characteristics of needle felts are the degree of felt compression, the
strength-elongation ratio and the permeability characteristics.

 Longer fiber lengths result in higher strength, higher felt density and less air
permeability.
 Finer fibers lead to smaller felt thickness and to lower air permeability. The needling of
finer fibers requires inevitably also the use of finer needles to achieve sufficient strength
characteristics
 Higher crimp results in a higher tear resistance and elongation and a better dimensional
stability of the needle felts.
 The characteristics and the structure of needle felts also depend on the web structure
and the area mass. Machine oriented web results in a high strength in the longitudinal
direction and predominantly cross oriented webs result in a high strength in cross
direction.
 The web area mass has a great influence on air permeability.
 The area ratio of the fiber plugs in the needle felt is in the range of 2–12%.
Applications of Needle punching process:
Needle punched structures have a wide range of applications in both domestic and industrial
markets. The applications of needle punched fabrics are extensive and listed as follows:
 Geotextiles
 Automotive
 Filter media
 Floor coverings
 Blankets
 Insulation padding
 Tennis Court Surfaces
 Wall coverings
 Trunk Liners
 Interlinings
 Papermaker Felts
 Felts
 Padding
 Kevlar Bullet Proof Vests

15. Dry Laid Carding Process
This method commonly referred to as “Dry Laid, “is utilized for staples fibers, whether natural,
synthetic or blends. Fibers are conventionally carded to form a web, which then can be cross
lapped to attain desired thickness and mass. It is a relatively slow and more expensive method
to convert fibers into a continuous web of certain integrity. It is commonly under the term dry
laid process.
Fiber Preparation Processes
The staple-fiber based processes include fiber preparation processes (opening and mixing
processes), web formation by carding or by air-lay or by wet-lay processes and then web
stacking by parallel-lay, cross-lay, and perpendicular-lay processes. The raw materials in the
form of staple fibers are converted into a web or batt structure with a given basis weight
(weight per unit area). Virtually any staple fiber that can be carded or dispersed in air or water
can be used in these processes.
Process of Dry Laid Carding Process
1. Bale Opening: The fiber preparation processes basically perform the following
functions: fiber opening and fiber mixing. It can be noted that the cleaning of fibers
(separation of foreign matters) in not usually followed by the nonwoven industry. The
natural fibers such as cotton are generally purchased in a pre-cleaned form, and for
medical application, bleached cotton is used. Above all, as the manmade fibers are
mostly used they do not require intensive cleaning. The fiber preparation processes in
the nonwoven industry closely resembles to that of the conventional blow room
process.
Figure shows the diagram of a bale opening machine. The wide bale opening machine is
used which can accommodate several bales side by side. The individual bales may
consist of the same raw material or several different components to make up the blend.
The fibers from such bales are opened and mixed together. There exist three types of
openers for bale opening machine: universal opener, single roll opener, and multi-roll

16. opener. The universal opener has three different rollers and it is suitable for all fibers. It
is also known as high performance opener. The single roll opener is suitable for man-
made fibers and it gives maximum protection to the fibers from damage. The multi-roll
opener provides progressive opening action and it is suitable for all difficult-to-pen
fibers like bleached cotton. The intensity of opening of these openers can be calculated
by the amount of fiber mass per one spike or teeth of the opener for a given rate of
production and angular speed of the opener.
2. Blending : The multi-mixer is used to mix and blend (homogenize) different varieties of
same fiber or different types of fibers. Figure shows the diagram of a multi-mixer.
1 2 3 4 5
6
7
8 9 10
3. Course Opening: The blending Conveyor feeds fiber into an opening roll, which has a
three-lag pin beater where coarse opening of the fiber tufts take place.
4. Fine Opening: The fiber opened by the opening roll is transported by air to the feed box
of the fine opener. The fine opener consists of two opening rolls, one evener roll and a
cylinder roll all of which are wound with metallic clothing. The opener reduces the tuft
size by using the principle of carding points between rolls. The reduced tufts are
transferred to the cylinder roll which delivers the opened fibre into an air stream to the
web-former.
5. Web Forming Feeding: The feed system to the web-forming machine is selected based
on the type of the fiber and the type of the web-former. Chute feeding machine is
normally used to feed fibers up to 60 millimeters in length. For longer fibers, a hopper
feed with a shaker-type chute is used.

17. 5.1. Web Forming (Carding Action): This process follows the initial opening of the
raw material. It is particularly important process because it is responsible for the
separating, still further, the tufts of the fiber fed into the machine and reducing
them to an individual fiber state. The individualization of fibers allows the removal
of the much of the impurities. Finally the carding machine reduces the overall
thickness of the material into the form of light web.
The surfaces move at relative speed to each other and the fibers gets disentangled. The
distance between two surfaces decides the degree of opening and cleaning. The action
carried out between the clothed surfaces is also known as “carding action”.
The carding action is carried out on machine known as “card”. There are mainly two
types of cards viz. roller and clearer card (for medium and long staple fibers) and the
revolving flat card (for short staple fibers up to 5-65mm).
5.2. WEB LAYING: There are mainly three types of web laying techniques or dry-laid
webs:
1. Parallel laid webs
2. Cross laid webs
3. Randomly laid webs or air laid webs
5.2.1. Parallel laid webs: Several carding machines are placed one behind another in a
long line. The web from the first card is allowed to fall on a conveyor which runs along
the full length of the production line underneath the cards. As the web from the first
card passes from the second card, the web from second card is superimposed upon it.
This process is repeated along the line until a fleece of the correct mass per unit area is
achieved.

18. The parallel laid web system is used extensively in the production of fleeces for relative
light weight adhesive bonded nonwovens, such as cleaning cloths.
5.2.2. Cross-laid webs : The cross laying, the web deposited on an inclined lattice as it leaves
the card and is subsequently laid in cross wise manner on a wider lattice which is moving in a
direction at right angle to the original direction of laying.
This cross layer enables three important characteristics of resulting fleece to be controlled. The
width of the fabric, with cross laid fleece of up to the meters in width being possible.
The mass per unit area of the fleece, which is dependent on the take up speed, so that slow
take off allows many layers to be superimposed and produce heavy fabrics, while fast take off
produces fewer layers and a more open zigzag of lay to create lighter fabrics
The strength characteristics of the fleece as cross direction than in the machine direction
though the ratio can be varied by altering the angle of lay and the subsequent drafting of the
cross laid fleece.
The cross laid web techniques overcomes the difficulties encountered with parallel laid webs
and has an added advantages. By stretching the cross laid webs the ratio of strengths of the
fleece in the machine and cross directions can be controlled to suit the requirements of the end
product.

19. 5.2.3. Randomly-laid webs: In alternative means of producing fleeces is offered by machines
using aerodynamic feed of the fibers. In this case, those fibers from a carding cylinder are
carried in air currents and deposited onto a condenser cage, from which they are drawn off in
sheet form. The condenser cage is usually a hollow cylinder formed from a mesh; this enables it
to be drawn through the mesh into the center of cylinder, but fibers into the air current cannot
pass through mesh and is collected on a surface.
The air or random laying techniques allows fabrics with a wide range of mass per unit area to be
produced, in which fiber orientation can be made very much more random than is the case with
traditional web layering. Short fibers can be processed easily, allowing textile waste materials
to be used in nonwovens.
Random laid webs are made as a single layer and are claimed to have equal properties in all
directions. However they are the most expansive to produce, when compared to parallel laid
webs, which are the cheapest and cross laid webs, which lie between the two from the
production cost point of view.