Non woven Technology

1. IOT
DEPARTMENT OF TEXTILE AND GARMENT ENGINEERING
Non woven fabric manufacturing seminar on
wet-laid web preparation
HAWASSA,ETHIOPIA
To:Mr. Metasebia.G By peer-I members

2. TABLE OF CONTENTS:
R.No TITLE SLIDE
1 Introduction 3
2 Raw material 8
3 Production machineries
4 Process description 13
5 Process model 15
6 Special features of the wet laid process and
products
17
7 Miscellaneous Topics 20
8 Defects of wet-laid web fabric 23
9 Merits and demerits 26
10 Application 27
11 Conclusion 28
2

3. INTRODUCTION
Historical perspective:
 The wet-lay nonwoven process is known to be
derived from the wet-laid paper making process.
 H. Fourdrinier developed a papermaking machine
that has been the basis for the most modern
papermaking machines employing very short
fiber.
3

4. CONTINUED…
wet-laid paper making process:
 The wood pulp and water in the ratio of 0.003-
0.007 (w/w) are mixed to make a good quality
suspension of fibers and water.
 The suspension is then pumped to the headbox
which has a small opening, often called as slice.
 Through the slice, the fibre-water suspension is
dropped onto the moving perforated Fourdeinier
wires. These wires contain a lot of perforations
through which the water gets drained to the
vacuum and the fibres, deposited on the moving
wires, formed a web. In this way, the wet-laid
paper is formed 4

5. MODIFIED FORM OF THE MACHINE
 By using the previous version of the machine it
was not possible to process relatively long fibers
as the mentioned dilution ratio results in
inadequate fiber dispersion in water.
Measures taken to solve the problem:
 The ratio of weight of fiber pulp and weight of
water should be around 0.0005-0.00005.
 The inclination of the forming wire to the base
is required to be equal to 20°.
 The machine was made to have large headbox
(slice) opening
5

6. CONTINUED…
 This machine has been used to make papers from
long fibres and subsequently the basis for
making nonwovens also.
The modified:
6

7. NON WOVEN TEXTILES
Non woven production general sequence:
7
• Selecting
based on
compatibility
Fiber
preparation
•Wet laid
•Dry laid
•Spun laid
•Melt blown
Web
preparation • mechanical
• Thermal
• Chemical
Web bonding
• Mechanical
• Chemical
Finishing
We will see
wet laid
web here!

8. PAPER AND TEXTILES
Two fundamental reasons account for physical
property differences between paper and textiles:
1-difference in the raw materials each process uses.
Paper: fibers being short and fine are able to pack
together into a dense structure
Textiles : fibers tend to be longer, stronger, and
relatively inert
2-the structure and the way individual fibers are
arranged by the process to make a finished product.
Paper: the fibers overlap randomly and pack densely.
Textiles: there is a repeating unit structure which
provides some extensibility in all directions 8

9. CONTINUED…
 In light of the characteristics of these raw
materials and structure, one would expect
9
Paper to be
Textile to be
• weak
• Stiff
• Inextensible
• Smooth
• dense
• strong
• softer,
• bulkier
• more drape able,
• less smooth and
• more porous.

10. RAW MATERIALS
 In theory, any natural or synthetic fiber could
be used in the production of wet-laid nonwovens.
However, there are practical limitations on the
use of many fibers (cost, availability, priorities).
 wood pulp is used in virtually all wet-laid
nonwovens because of its ease of handling, low
cost, opacity, and chemical reactivity.
 Some natural fibers - such as cotton linters,
manila hemp and cellulose staple fibers - are also
used in wet-laid process(2-30 mm in length).
10

11. CONTINUED…
 Synthetic fibers provide specialized properties,
uniformity, and constancy of supply which cannot
be achieved by natural fibers.
Reasons for their limited application:
o They are 20 to 50% more expensive than the
same fiber in the form of textile staple.
o Flocculation(they entangle ).
11

12. CONTINUED…
Flocculation:
 is incapability to disperse in water due to longer
length and flexibility they have.
 Increases with an increase in length to diameter
ratio(L/D) of fiber.
Tt = fiber fineness in dtex
12

13. CONTINUED…
Several approaches have been developed to
overcome this problem:
o Synthetic fiber manufacturers offer fibers with
proprietary chemical surface treatments, which
improve dispersion.
o The general strategy for reducing flocculation
of synthetic fiber furnishes is to increase the
dilution (decrease the "consistency" of weight
percent of fiber in the suspension).
13

14. COMPATIBILITY OF THE MATERIAL
WITH THE PROCESS
 Whether or not a fiber is suitable for use in the
web process depends on its ability to disperse in
an aqueous medium.
The dispersion behavior of a fiber depends largely
on the following factors:
 The degree of fineness calculated from the
length and thickness of the fiber
 The stiffness of the fiber in an aqueous medium
(web modified)
 The kind of crimping
 The wettability
 The cutting quality of the fiber 14

15. PRODUCTION MACHINERIES
There are three characteristic stages in the process
• Swelling and dispersion of the fiber in water;
transport of the suspension on a continuous
traveling screen
• Continuous web formation on the screen as a
result of filtration
• drying and bonding of the web
15

16. CONTINUED…
Some of machines used in the process:
Web forming device with
inclined wire screen
Wet-laid web-making machine
with cylinder drier
16

17. PROCESS DESCRIPTION
 The fibres are mixed with water and it forms
fibre-water suspension.(two mixing tanks for
preparation of better fibre-water suspension.)
 This suspension is then pumped through the
headbox to the perforated wire.
 The water is drained through the perforations
and the fibres are laid on the moving wire to
form a web.
 The wet-laid web is then dried and bonded by
using binder. It is again dried and finally wound
on a roll.
17

18. CONTINUED…
• mixing
• Prepare
suspension
Stage
1
Suspension
via head
box to
perforated
wire
Stage
2
Dehydration
and web
formation.
Stage
3
18

19. CONTINUED…
The schematic diagram of a typical wet-lay process
for making nonwovens :
19

20. PROCESS MODEL
 It is often necessary to calculate process
parameters in advance with an aim to obtain a
specific structure of wet-laid nonwovens.
Because of this, it is often necessary to model
the wet- lay process.
20

21. CONTINUED…
21

22. CONTINUED…
The velocity of water in relation to the velocity
of wire determines the structure of the web.
 When both the velocities are equal then the
fibre lay-down is found to be practically
random.
 When the velocity of wire is higher than the
velocity of water then fibres are found to be
preferentially orientated in the machine
direction.
 when the velocity of wire is lower than the
velocity of water then fibres are found to be
preferentially orientated in the cross direction. 22

23. SPECIAL FEATURES OF THE WET-LAID
PROCESS AND ITS PRODUCTS:
Compared to dry web making process and its
product:
 Since short fibers are required the web
structure is closer, stiffer and less strong.
 The fibers in the web may be randomly or
longitudinally arranged.
 The basis weight (grams/square meter) can be
varied within broad limits.
 It’s highly productivity and have wide range of
application
23

24. MISCELLANEOUS TOPICS
Water removal from web:
 Water removal on drying is one of the most
important steps in the wet-laid process.
Pressure, vacuum, and heat are used to remove
water from the sheet.
 The efficiency of the methods are determined
by the machine speed, sheet weight, and fiber
compositions of the sheet
24

25. CONTINUED…
Calendaring:
 Calendars are often used on the product to make it
dense and smooth the sheet. Creping devices are used to
soften sheets by controlled bond breakage.
Aperturing and water-jet entanglement:
 Apertures are regularly spaced holes, and can
be selected for aesthetics or for performance.
 One method of aperturing uses a course forming
wire, so that the sheet is formed around the
protruding "knuckles" in a regular pattern.
 Another method uses high- pressure water
showers and patterned cylinders to rearrange
the fiber into the desired pattern.
25

26. FABRIC DEFECTS
There exist three types of defects in the wet-
laid nonwoven fabrics:
 logs, ropes, and dumbbells
26

27. CONTINUED…
Logs:
 are characterized by bundles of fibres with
aligned cut ends that are never dispersed.
 considered to be a fibre supply problem or can
be the result of remarkably low under agitation
of the initial dispersion.
Ropes:
 are characterized by assemblages of fibres, with
unaligned ends, that are clearly more
agglomerated than in the general dispersion.
 re formed when fibres are encountered a vortex
that facilitates in entangling the fibres to form
ropes.
27

28. CONTINUED…
Dumbbells:
 are characterized by paired clumps of fibres
connected by one or more long fibres.
 Their formation requires an excessively long
fibre and a snag in the system piping.
 The good quality of dispersion of fibres
in water is a key to the good quality of
wet-laid webs.
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29. MERITS AND DEMERITS
The merits of wet-lay nonwoven process are:
 High through-put rate.
 Isotropic as well as anisotropic structures can
be created.
 Too brittle fibres, generally not suitable for
textile applications, can be processed.
The demerits of wet-lay nonwoven process are:
 High capital intensive process.
 High energy intensive process.
 High fiber quality requirements.
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30. APPLICATIONS:
 They have applications in diversified areas,
namely surgical clothing and drapes, bed linen,
table linen, cloths, and napkins, towels, kitchen
wipes.
 In addition, the wet-laid technical nonwovens are
found to be used in many specialized
applications, including glass fibre roofing
substrate, glass fibre mat for flooring, glass
fibre mat for printed circuit boards, wall
covering, insulation materials, battery
separators, RFI shielding veils.
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31. CONCLUSION:
 The system was thought to be applied for any
types of fiber. However in practice the system is
found to be applied for those fibers capable of
dispersing in the fluid. Moreover the application
is constrained by different factors.
 To prepare the web different machineries are
applied having their own way of performing the
sub operations.
 The main advantage of the system is its
capability to process too brittle fibers that
mayn’t be processed in other systems. The high
energy intensives needed may make it limited.
 The products have application in different areas
including industrial and apparel uses.
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32. OUR SOURCES:
 Non woven manufacturing technology lecture,
NPTEL.
 Web formation methods, Textile school.
 Literatures of the same title prepared for
students, Bahir-Dar university, ETHIOPIA.
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33. PEER-I MEMBERS
R.No Name ID
1 Melkamu Kenito TECH/0750/09
2 Meron Tebikew TECH//09
3 Azeb Mekonin TECH//09
4 Abdulkerim Nesru TECH//09
5 Selamawit Asalfew TECH//09
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34. THIS IS ALL WE HAVE…
THANK YOU!34