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Bez nadpisu

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Nonwoven is a sheet, web, or batt of natural and/or man-made fibers or filaments, ... machined on the drum to provide a variety of different stitch patterns and looks. ... – PowerPoint PPT presentation

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Title: Bez nadpisu


1
THERMAL AND CHEMICAL TECHNOLOGIES OF NONWOVENS
PRODUCTION Klára Kalinová Katedra netkaných
textilií - 2006 -
2
NONWOVENS IN GENERAL
Definition of nonwovens Nonwoven is a sheet,
web, or batt of natural and/or man-made fibers or
filaments, excluding paper, that have not been
converted into the yarns, and that are bonded to
each other by any of several means...
3
Production of nonwovens
4
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5
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6
POLYMERIC AND FIBROUS PROPERTIES WITH RESPECT TO
THERMAL PROCESS
Bicomponent fiber. Sheath/core 50/50 PE/PP.
Bicomponent fiber. Islands in a sea.
7
Thermal constants
Physical states of polymers. Tg is glass
temperature and Tf is plastic flow temperature.
8
() - semicrystallic polymers () -
evaporated heat
9
Crystallization kinetics of polymers
Equilibrium of polymerization
10
Detection of polymeric structural changes and
thermal constants
DSC method
11
DSC measurement arrangement
The DSC consists of a furnace containing two
identical crucibles, each of which rests on a
thin plate located inside the measurement head.
Directly beneath the center of each crucible is
the junction of a differential thermocouple
12
DTA method
DTA diagram. T0 is opening temperature, Tm
maximal or minimal temperature, T1 temperature of
return to zero line, Tx temperature of exothermic
process start, Ty temperature of exothermic
process end
13
TMA method
14
TMA instrument
15
TMA instrument. A range of typical probes.
16
Heat flow sensors- Thermoelectric couples
Heat flow sensors- thermometers
  • Dilatation thermometer
  • Gas expansion thermometer
  • Resistance thermometer
  • Radiation thermometer ...

17
POLYMERIC AND FIBROUS PROPERTIES WITH RESPECT TO
CHEMICAL PROCESS
Dispersion
18
Monomer Tg(0C) Ethylene - 125 Butadiene -
78 Butyl Acrylate - 52 Ethyl Acrylate -
22 Vinyl Acetate 30 Vinyl Chloride
80 Methyl Methacrylate 105 Styrene 105
Acrylonitrile 130
19
Polymer and co-polymer dispersions
20
Acrylic Acid Derivatives - structural elements
21
Vinyl Copolymers - structural elements
22
Crosslinking polymers
23
Crosslinking with Organic Peroxide
Step1) Peroxide thermal decomposition
Step 2) Hydrogen abstraction with radical
formation on the polymer chain
Step3) Crosslinking reaction by free macroradical
recombination
24
The binders containing the substituted acrylamide
groups have self-crosslinking properties and the
possible reaction as follows
25
Coagulation methods
1. Removing water by evaporation 2. Freezing of
dispersion 3. Change in acidity 4. Creating of
non-dissociating salts 5. Using of
thermosensibilizers
3.
4.
5.
26
WEB FORMING METHODS
Wet-laid methods
27
Raw material
Natural fibers other than wood pulp remain of
interest because they have valuable properties
for specialized end-uses. They suffer from
unstable pricing and supply due to variations in
climate, worldwide demand, and availability of
competing fibers. Some natural fibers - such as
cotton linters, manila hemp and cellulose staple
fibers - are also used in wet-laid
process. Synthetic fibers provide specialized
properties, uniformity, and constancy of supply
which cannot be achieved by natural fibers.
Crimped fibers require special dispersion and
bonding techniques, but make a very soft and
bulky product. Usually 2-30 mm fibers are used in
wet laid process use of rayon and polyester
textile fibers with lengths exceeding 1.5 inches
has been reported sporadically.
28
Flocculation increases with increase in length to
diameter ratio which is given as
L length of fibers in mm D diameter of fibers
in mm Tt fiber fineness in dtex
Flocculation occurs when concentration of
dispersion exceeds critical concentration of
dispersion Cw defined as percentage of fibers in
dispersion and given as
Dispersion volume per 1 gram of fibers
29
Spunbond
Spunbond fabrics are produced by depositing
extruded, spun filaments onto a collecting belt
in a uniform random manner followed by bonding
the fibers.
30
Extruder
It consists of a heated barrel with a rotating
screw inside. Its main function is to melt the
polymer pellets or granules and feed them to the
next step/element.
31
Gear pump
The metering pump typically has two intermeshing
and counter-rotating toothed gears. 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.
32
Spinneret
The molten polymer mix is pumped through a heated
conduit to a resin filter system and then to a
distributor section that leads to the spinnerette
units.
33
Pneumatic jet for spunbonding
The web is formed by the pneumatic deposition of
the filament bundles onto the moving belt.
34
Pneumatic jet for spunbonding
In order for the web to achieve maximum
uniformity and cover, individual filaments must
be separated before reaching the belt.
35
Rotating deflector plane to separate the
filaments
Filaments are also separated by mechanical or
aerodynamic forces.
36
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37
Melt blown
The Melt blowing is process in which
high-velocity air blows a molten thermoplastic
resin from an extruder die tip onto a conveyor or
take up screen to form a fine fibrous and
self-bonding web.
38
Melt blown die
39
Two types of die nosepiece capillary and drilled
hole
40
Melt blown - bicomponent fibers
Bicomponent melt blown systems produce
sheath/core, side-by-side, tipped trilobal and
tipped cross fibers with approximately 2 micron
diameters
41
Flash spinning
In flash-spinning, pure solvent droplets and
highly saturated polymer/solvent mixtures are
decompressed through a spin orifice.
42
Spunbond and melt blown modification
SMS
43
Typical products of spunbond and meltblown
technologies
Product Fabric
Disposable Diaper, Incontinence Largest single
market segment in nonwovens for cloth-like
backsheet, leg cuff and cover stock
Durable Papers Almost exclusively Tyvek
polyethylene spunbond fabric (Tyvek is a
registered trademark of E.I. DuPont de Nemours
Co.)
Disposable, Protective Apparel Dominated by
Tyvek polyethylene spunbond fabric, although
growing use of polypropylene spunbond and
composite materials
Bedding, Pillows, Furnishings Competitive market
segment using polypropylene and polyester
spunbonds
Geotextiles Heavyweight polypropylene and
polyester spunbonds, and needlepunch
polypropylene and woven fabrics
44
Typical products of spunbond and meltblown
technologies
Product Fabric
Furniture Polypropylene spunbond fabric,
polypropylene needlepunch and polyester spunbond
fabric
Filtration Spunbond and meltblown fabric for
liquid and air filtration
Automotive, Carpet, Trim Heavyweight polyester
spunbond fabrics
Carpet Underlayment Carpet backings consisting
of PET, polyamide and polypropylene spunbond
fabrics
Medical Products Spunbond and spunbond/meltblown
composite fabrics
Roofing Typically polyester spunbonds
45
This technology consists depositing the polymer
onto a conveyer of heated wires giving a high
voltage potential.
Electrostatic spinning
46
Electrostatic spinning
The process makes use of electrostatic and
mechanical force to spin fibers from the tip of a
fine orifice or spinneret. The spinneret is
maintained at positive or negative charge by a DC
power supply.
47
Solution spinning
1 polymer solution, 2 rotating charged
electrode, 3 - counter electrode, 4 container,
5 - supporting material, 6 - unreeling device, 7
- reeling device, 8 - formation of the
nanofibers, 9 - vacuum chamber
48
Polymer solvent systems used in electrospinning
49
THERMAL BONDING METHODS
where D is diffusion coefficient and .
concentration gradient.
Diffusion
where j is electric current, specific
conductivity and potential gradient
Transport of electric charge
where is thermal energy flow, thermal
conductivity and thermal gradient.
Thermal energy flow
Temperature distribution T in the time and in the
space
where is time and x distance from the heat
transfer surface
50
Heating of 2D layers
Let s have a fiber layer of area S, surface
density of Ms ant thickness of h. The total mass
of this textile is
Temperature difference between the two surfaces
of textile
51
a is heat transfer coefficient, dt is a time of
textile heating and c is a specific heat
52
Figure of temperature growing in time.
53
Heating of 3D layers
Temperature distribution in the thickness of
textile in times t 1 ,, t ? , where h is
thickness of textile.
54
Heating special cases of fibrous layers
Through air heating
55
Structure and properties of thermoplastic agents
bonded web - fibers, powder, grating, foil
Agglomerate structure
56
Structure and properties of bicomponent fibers
bonded web
Point structure
57
Powder bonding
In powder bonding, the adhesive powder of
thermoplastic polymers is applied onto webs by
heat and pressure.
58
Through air thermobonding
59
Through-air bonding technology can be ideal for
process heating a wide range of air-permeable
nonwovens.
Through-air bonding with horizontal belt
60
Through-air bonding with a drum
61
Calender bonding
Smooth roll calendering
62
Embossed roll calendering
The Embossing method is a figured or sculptured
area-bond hot calendering. In this case, though,
the area bonding is three dimensional.
63
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64
Modified rollers for prevention of their
deformation
Constant material width and adjustable line force
through x-crossing of the rolls are
characteristics of the CX-Calenders. They are
used for thermo-bonding as well as laminating and
flat embossing
CX-Calenders offset axes rollers
65
The Swimming Roll makes it possible to compensate
for the deflection of the roll over a wide line
pressure area and to carry out edge corrections.
They are an essential component when large
material widths need to be run at high speeds.
Swimming Roll
66
Deflection compensation by Swimming Roll
67
Deflection compensation by HyCon-Roll
The advantages of the HyCon-Roll with
hydro-static pressure control are variable line
force, variable pressing width to suit change of
fabric width, and the option of edge relief of
the FlexRoll Sleeve, which prevents overheating
of the edges at high temperatures of the steel
roll.
68
Support elements installed in axle of HyCon-Roll
69
The vertical arrangement of the hydro-static
pressure controlled rolls in the HyCon-I Calender
allows for precision embossing.
HyCon-I Calender
70
HyCon-L Calender
By the L-shaped arrangement of its rolls, the
HyCon-L Calender enables two very different line
forces in the top and in the rear nip that can be
adjusted infinitely and independently of each
other. Thus two different effects can be achieved
in one passage of the fabric, e.g. density and
high lustre in one nip and excellent handle in
the soft nip.
71
Ultrasound bonding
Two or more layers of material are continuously
fed between the vibrating horn and rotating drum.
Patterns can be machined on the drum to provide a
variety of different stitch patterns and looks.
72
Infrared bonding
A combination of infrared and convection heating
is achieved by forcing air through the holes
73
Microwave bonding
In comparison to conventional high-frequency
technology, microwave technology requires special
elements for generating and transporting energy
due to the considerably higher frequency and the
frequency dependent modification of the
electromagnetic wave transport.
74
Microwave bonding - Molecule polarisation due to
the microwave heating
Microwave heating, a form of dielectric heating,
is understood as the generation of heat in
materials of low electrical conductivity by the
action of a high-frequency electric field.
75
Water molecule polarisation due to the microwave
heating
At the other end of the microwave heating
spectrum, around 3000 MHz, the energy absorption
is primarily due to the existence of permanent
dipole molecules which tend to re-orientate under
the influence of a microwave electric field.
76
Multimode resonant applicators
Multimode resonant applicators consist of a
metallic enclosure into which a microwave signal
is coupled through a slot and suffers multiple
reflections. The superposition of the incident
and reflected waves gives rise to a standing wave
pattern or mode. In a given frequency range such
an applicator will support a number of resonant
modes.
77
Radio-frequency bonding
Scientifically speaking, there are several ways
that a dielectric material absorbs energy from
the oscillating electric field. The two most
important mechanisms are molecular rotation and
electrical conduction.
78
Thermal constants of choice polymers
79
Thermal Conductivity of Polyamide
80
Effect of Temperature on Thermal Conductivity of
Polymers
81
CHEMICAL BONDING METHODS
Structure and properties of latex and foamed
latex bonded webs
Segment structure
82
Dispersion preparation
83
B - Polymer Dispersion-Injector
84
Activation Chamber
The Activation Chamber consists of a clear
synthetic housing filled with synthetic media
specifically designed to produce a gentle, yet
effective mixing action it does not contain any
moving parts.
85
Device for saturation of latex, foamed latex,
solution and paste
Print bonding - Rotary screen printer
86
Rotogravure printer
87
Spray bonding
In spray bonding, binders are sprayed onto moving
webs. The binder is atomized by air pressure,
hydraulic pressure, or centrifugal force and is
applied to the upper surfaces of the web in fine
droplet form through a system of nozzles.
88
Froth bonding
Foam bonding is a means to apply binder at low
water and high binder-solids concentration
levels.
89
Inclined padder
Saturation bonding is used in conjunction with
processes which require rapid binder addition,
such as card-bond systems, and for fabric
applications which require strength, stiffness,
and maximum fiber encapsulation, such as carrier
fabrics.
90
Saturation bonding
91
Felting
The physical structure of the outer scaly layer
of the wool fiber contributes to wools unique
property of felting.
92
Cylindrical felting machine
93
WEB CONVERSION METHODS
Thermoplastic adhesives Typical formula of hot
melt adhesives is following Resin 35
50 Polymer (EVA) 25 35 Wax   20 30
94
Thermoplastic adhesives - hand gun
95
Polymers
96
Hot-melt shapes
97
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98
Hot-melt applicators - hand gun
99
Hot-melt applicators
dots
100
spiral
101
Hot-melt applicators - ITW Dynatec Melt On Demand
Adhesive Hopper
102
Hot-melt applicators - nozzles
103
Coating and laminating - Powder
104
Coating and laminating
105
Coating and laminating - Coating by rotary screen
printing
Coating is a basic and exceptionally important
form of finishing for non-woven bonded fabrics.
The way in which the coating is carried out
depends on the substrate, the machinery
available, the substance that is to be applied
and, also on the effect desired.
106
Roll laminating
Roll laminating is influenced by this factors
Heat laminating occurs at the surface of the
metal roll, which obtains its heat by conduction
from heated oil circulated through its center or
from restrictive heating. The composition rolls
obtain their heat from contact with the heated
metal roll. Pressure laminating occurs through
simultaneous application of heat and pressure.
The heat causes the adhesive to become
thermoplastic. The pressure ? mechanical bonding
by forcing the binder polymer to flow in the
carrier fibers. Speed The speed at which the
nonwoven passes between the rolls, combined with
heat and pressure conditions, determines the
degree of bonding in the nonwoven. The faster the
rate, the lower the cost. Cooling rolls A set
of two cooling rolls placed immediately after the
laminating stage eliminates shrinkage of web and
subsequent wrinkles.
107
Hot and cold laminating
One of laminators is the "Roll Laminator". Among
these laminators there are two types, which are
"Hot" or "Cold". Hot laminators heat the roller
or rollers up to temperatures that can exceed 240
degrees
108
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109
Principle of laminating calender
In Küsters' Thermo-laminating Ranges two or more
fabric webs are bonded by temperature and
pressure between two rolls. This can be done
either all-over with smooth rolls or partially
with an engraved roll. If, additional to pressure
and temperature, a bonding agent is used,
different kinds of materials can be laminated.
Various speeds and variable line forces are
possible.
110
Various types of coater/laminators, a solventless
adhesive laminator are available. The
complementary silicone coaters are intended for
paper production and extrusion coater/laminators
focused primarily on producing coated and
laminated nonwovens in rollstock and sheets for
medical, automotive and related applications.
Plastic Extrusion Coating
111
Solventless Adhesive Laminating
112
Plastic Extrusion Laminating
113
Non-contact DispensJet module
The non-contact DispensJet module dispenses small
dots onto a variety of substrates at cycle rates
of 12 to 15 milliseconds. Adhesive or coating
material is fed into a chamber where it is
temperature conditioned for optimal
machinability.
114
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115
Spray coating/laminating
A reactive polyurethane glue is heated untill it
becomes liquid. This requires a temerature of
about 150C. the liquid glue is pumped to a
number of specially designed spray nozzles
116
Laminating flame - One burner using
By flame-lamination one understands the making of
a compound of 2, resp. 3 components
singlelamination, resp. sandwichlamination by
using the adhesion characteristics of the foam
which is melted by the line-gasburner.
117
Laminating flame - Two burners using
A line-gasburner which is installed across the
whole working width, is melting the foam,
resulting in an adhesive film. Inside the
calander,
118
Laminating - IR heating
119
Laminating - US
Herrmann Ultrasonics company has developed a
system especially for Ultrasonic Laminating.
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