EDANA´S 2000 NONWOVENS SYMPOSIUM
Ultrafine Microfiber Spunbond for
Hygiene and Medical Application
Dieter Groitzsch
The Freudenberg Nonwovens Group, Germany
Introduction
Up to now there is no generally accepted definition for micro fibers. But normally the term is
linked to the fiber diameter and/or weight/ length of filament in dtex or denier and not with any
properties of the fiber. Due to the fact that cross section of fibers is not exclusively circular the
diameter should not be used for characterisation of fiber fineness. Most accepted definition for
micro fibers seems to be a fiber with 1 dtex in maximum.
This constribution is essentially focused on melt spun endless filament webs based on so
called ultra fine resp. ultra super fine microfibers with a level of around 0,09 — 0,13 dtex.
It is well known that such ultrafine fibers are not able to be spun out of a spinneret and would
not be able to be processed on carding machines. This problem had been overcome in the
past by providing conjugate and island in the sea fibers of more than 1 dtex splittable in
ultrafine segments by solvents, alkali treatment or - in the last 10 years more a more favorized
and from ecological point of view most friendly - high pressure water jets.
By far the most part of conjugate fibers splittable by hydroentanglement are produced in Far
East. They are offered as staple fibers for processing on carding machines and so all present
microfiber based nonwoven fabrics available on the market are composed of cut fibers, which
of course provide disadvantages compared to endless filaments.
Freudenberg has intensively been working since more than 5 years on a research and
development programm - internally called Omega-project - to create a new generation of
unique nonwoven spunwebs.
In Table I the most important differences in construction of staple fiber and spundbond
nonwoven fabrics are put together.
Table I
Construction principle of staple fiber and conventional spunbond nonwoven fabrics
Fiber
Staple fiber nw fabrics
Spunbond nw fabrics
Fiber length
38 — 90 mm
Continuous (endless)
Shape of fiber along its lenght
Crimped
Not crimped
Fiber orientation in the fabric
at high speed manufacturing
In md
anisotropic
isotropic (random)
(md/cd = 1/1 — 2/1)
Range of processable fiber fineness
0,8 — 50 dtex
0,5 — 10 dtex
(meltblown not included)
Fiber forming polymer
Whole range available
Restricted on melt spinnability
Carded nonwoven fabrics are composed of staple fibers with two dimensional or helical crimp,
anisotropically distributed with strong orientation in machine direction whereas conventional
spunwebs are constructed of non crimped continuous filaments with more or less isotropic
distribution in the fabric. Therefore both types of nonwoven fabrics have got their advantages
and disadvantages. In Table II the most relevant characteristics of carded versus
conventional spunbond nonwoven fabrics are collected.
Table II
Fabric characteristics staple fiber versus spunbond nw fabrics
Fabric characteristics
Staple fiber nw fabrics
Spunbond nw fabrics
Mechanical strengths over all
low
high
in md much higher than in cd
no big difference between cd and md
Elongation
in cd much higher than in md
no big difference between cd and md
Softness
high
low
Stiffness
low
high
Drapability
high
low
Loftiness
high
low
Resiliancy
high
low
Textile properties over all
high
low
Summerized over all conventional spunbond nonwoven fabrics provide much higher
mechanical strengths in md and cd than carded nonwoven fabrics but because of the non
crimped fibers all characteristics derived from such as softness, drapability, loftiness and the
like are uncomparably worse than with carded nonwoven fabrics. Expressed somewhat
simplified: the non-textile characteristics of conventional spunbonds has been so unfavorable
that huge areas of application such as garment industry or upper material for shoes and
luggage could not be covered by them.
The Omega-project has been focused on an unique new class of nonwovens which combine
the benefits of both the carded and the spunbond fabrics in an ideal way. Transferring textile
properties into a spunbond grade there are principally two possibilities:
a) evolute crimping during quenching and aerodynamical stretching, enhanced by
thermal post treatment
b) reduce the fiber fineness down to microfiber denier
and of course a combination of both.
The new process for the manufacture of Evolon Fabrics covers both. In order to provide spiral
(helical) crimping a fiber with bicomponental side-by-side or eccentric sheath-core
configuration and for ultra fine micro fibers a splittable multi-sector pie fiber has to be used. In
Figures 1 and 2 the cross sectional views of side-by-side bicomponental fibers are shown
whereas 16 segment pie fiber resp. hollow pie fibers are illustrated in Figures 3 and 4. Hollow
pie fibers are more preferred for better hydrodynamic splittability and pie fiber without hole for
better spinning properties and depositing onto the moving belt to form a nonwoven fabric of
uniform structure.
Fig. 1
Fig. 2
For most end uses ultrafine micro fiber denier spunbond is preferred by far.
Fig. 3
Fig.4
In-line-production is illustrated schematically in figure 5, starting from polymer granule and
ending with the ultrafine microfiber spunbond fabric. Two different polymers are transported
by extruders to the spinneret, leaving it as bicomponental endless filaments, which are
quenched and stretched by air streams with a very high speed up to sonic velocity. The
stretched filaments are finally laid down onto a moving belt to form a nonwoven fabric of
uniform structure. As demonstrated later in more detail the fiber distribution is more or less an
isotropical one. Mechanical strengths are practically the same in machine and cross direction
which might beneficial for most part of applications.
Afterwards the continuous filament web is subjected to an hydro-entanglement and fiber
splitting process.
Fig. 5
Splitting rate is normally performed in a range of at least 97%. In order to provide such high
degree of splitting many parameters had to be checked on their impact and to adapted one to
the other. Such parameters are the hole diameter in the spinneret, quenching, rate of
stretching and last not least the water pressure which has to be increased up to 400 bar.
Fiber polymer combinations and weight ratios
For splitting in single ultrafine microfibers an incompatibility of both fiber polymers on their
interphase is necessary. Suited polymer couples are polyesters (such as PET and PBT ) with
polyamides (such as polyamide 6.6 or 6), polyesters with polyolefins and polyamides with
polyolefins.
Weight ratio of both fiber polymer components can be varied from 20/80 to 80/20. Within the
Evolon ® fabric range the most common used polymer combination by far is PET / PA 6.6 18Pie-fiber in a weight ratio of 65/35. The lower raw material costs for polyester granule
compared to polyamide might be the driving force for the use of a higher part of polyester.
Up to now Freudenbergs investigations had been focused exclusively on rigid polymers and
of course they will be extended to thermoplastic elastomers (TPE) of at least one of both
components. Unbelievable fabrics features are expected thereby.
Hydrophilic and hydrophobic properties
Evolon ® fabrics can be adjusted hydrophillic or hydrophobic depending on the applications
or end uses posed on the nonwoven. In order to provide durable hydrophilic character usually
an add-on of a hydrophilic agent to the polyester fiber polymer is preferred to an external
application onto the fiber surface by methods such as spraying, padding and the like. Without
hydrophilic agent the Evolon PET/PA 6.6 65/35 fabrics are medium up to weak hydrophobic,
mainly due to the presence ot one third of polyamide 6.6. An external finishing of the
nonwoven fabric after hydroentanglement and splitting - the wet-in-wet method is the best
from economical point of view- is necessary in order to attain highest level of hydrophobic
performance.
Wear comfort properties
Different Evolon grades had been tested by the German Hohenstein Textile-Research
Institute. Its laboratory has developed a computerized skin simulator and it is the leading
authority on fabric comfort.
Wear comfort is determined by thermal insulation, drying time, water vapor transmission rate
wicking properties and the ability to buffer water vapor for short time. It is also influenced by
sensorial comfort characteristics such as the wet-cling index and the number of contact points
between the fabric and the skin. Most Evolon samples tested at Hohenstein were found to
provide very good wear comfort. In Table III the results of all tests conducted at Hohenstein
and by the Institue Textile de France (ITF) are compiled. Most samples obtained top rating 1
= very good for total wear comfort. For excellent wear comfort Evolon fabrics have to be
adjusted hydrophillic and to pass any mechanical softening treatment.
Table III
Type of fabric
Target Values; values for reference
Evolon type
OP-464
OP-602
OP-608
OP-711
OP-717
Heat insulation Ret
103 m2K/W
For Doppelripp-BW-Unter-hemd approx. 28
not measured
not measured
not measured
42,5
39,3
Water vapour transmission index imt
Good sportswear: >0,3
Maschenware sportswear: approx. 0,45
not measured
not measured
not measured
0,56
0,53
Humanity transport Fi-Value
(g/m2 h mbar)
Good sportswear: 20-24
22,6
16,8
21,6
15,2
14,6
Wetting Time sec
Cotton: 0,5
0,5
128
2,4
>600
>600
Drying time t min
Cotton: approx 37
18,0
34,5
21,0
25,0
24,5
Wet Cling Index iK
(skin sensoric)
Unacceptable >15
All evolution styles provide values of <4
Surface index Io
Length and number of Abstandshalter
(skin sensoric)
Io<3
Textile is too smooth and adheres
Io>15
Textile is too rauh and kratzig
All evolution fabrics lie between Io=4,8 - 8,2
Number of contact points nk
(skin sensoric)
nk>1500
Worse, klamm and humid
nk>1500
good
Evolon fabrics
1 measurement: 1059
4 measurement: 757 - 822
Stiffness S
Maschenware < 27
Evolon fabrics without any mechanical post treatment io 37,8 - 50,6
Resumee: mechanical post treatment for softening, such as tumbling is necessary
Sensorial wear comfort WCs
Measured at Hohenstein
Research Institute
1,5
2,1
1,8
3,0
3,2
Total wear comfort WC
1,0
3,5
1,0
1,0
1,0
Type of fabric
Target Values; values for reference
OP-464
OP-602
OP-608
OP-711
OP-717
Evolon type
Impact of different parameters on final fabric
As already mentioned Evolon fabrics can be adjusted hydrophillic respectively antistatic by an
add-on of hydrophilic agent. Mechanical strengths are also depending on fiber forming
polymer respectively the polymer combination of the bicomponental fiber and the number of
segment within the PIE-fiber. The impact of these parameters on tensile and tear strength of
the fabric after hydro entanglement and splitting is illustrated in Fig. 6. PIE 8 fiber comes off
the best in this respect. If normal polyethylenterephthalate is replaced 8 by a low pilling type
tensile strenght drops down dramatically and tear strenght only moderately. Fabrics
composed of PIE 8 provide somewhat higher strengths than PIE 16.
Fig. 6
The impact of dope dyeing on tensile strength is shown more detailled in Fig. 7 for fabrics
based exclusively on PIE 16. The concentration of the blue dyestuff - varied from 2 to 4 % exerts a small influence on tensile strength after hydro entanglement and splitting, i.e. the
higher the dyestuff concentration the lower the strengths. The negative effect on tensile
strength of black dyestuff (4 %) proved to be higher with the blue one.
Fig. 7
The impact of dyestuff concentration on decrease of tear strength is much less severe than
on decrease of tensile strength, as illustrated in Fig. 8.
Fig. 8
Of course any changements in mechanical strengths of final nonwoven fabric have got their
original cause in the tenacity of the endless filaments . In Fig. 9 tenacities of different filament
types are arranged. Comparing results of Fig. 6 with Fig. 9 there is obviously the same trend.
Fig. 9
Dope dyeing is the preferred kind of dyeing for Evolon fabrics based on PIE 16 or PIE 8
bicomponental filaments. Due to the extremly high fiber surface ultra fine microfibers needs
much more dyestuff compared to normal fine denier fabrics providing correspondingly much
less color fastness after texile dyeing, especially for darker shades.
The fiber surface of a 100 g/m 2 fabric composed of 100% polyethylene terephthalate is
calculated
for 1,7 dtex with 23,6 m2
for 0,8 dtex with 33,8 m2
for 0,2 dtex with 64,4 m2
for 0,1 dtex with 94,3 m2
In the case PIE-segmented filaments calculation is more difficult because the splitted
filaments are triangle like shaped in cross section providing much higher fiber surface
compared to fibers with circular cross section.
Calculation according to a formula not presentated here provides a fiber surface of 264 m 2 for
a PIE 16 fiber PET/PA 6.6 with weight ratio 65/35 and a fiber fineness of 1,6 dtex. In other
words fiber surface of this PIE 16 fiber is increased for approximately12 times after total
splitting in 16 segments.
Evolon for medical and hygiene applications
The unique new Evolon fabric range is highly versatile because practically all end-use
properties can be steered during the process. For example different grades can be converted
to sports- or workwear, shoe linings or window shades, clean room wipes , substrates for
tufting or automotive interior components. The fabrics properties, such as outstanding drape,
wear comfort and mechanical strengths are comparable to woven or knitted textiles.
First research and development efforts had been focused on such end-uses, requiring
durable or at least semi-durable nonwovens fabrics of higher weights.
The Evolon line is planned to go on stream around September of this year. Additional lines
will follow in 2002.
Challenge for the next future will be the creation of Evolon fabrics for hygiene and medical
market. They will differ from grades for other applications in some respect. Fabrics for such
kind of applications do not require extremely high durability because they are normally
disposed after single use and do normally not need high fabric weights.
First projects which have already been started are
- a rigid backing substrate for for medical plasters and wound dressings,
- an extensible, elastic backing substrate for for medical plasters and wound
dressings
- an extremly light weight apertured topsheet.
Further projects will follow. The extension of Evolon product range for hygiene/medical market
will be of highest priority.
The rigid backing substrate in white and beige has been focused on replacement of a rigid,
non extensible woven with weights of around 100 g/m 2. Target weight for the Evolon counter
part will 80-100 g/m2 too.
For soft, extensible and (at least partially) elastic backing materials for plasters the
incomparably high mechanical strenght of Evolon grades allows a reduction of fabric weight
down to around 35 g/m 2.
Nonwoven fabrics for backing substrates of wound dressings and plasters coated by pressure
sensitive adhesives (PSA) based on synthetic polymers, such as polyacrylic esters, are wide
spread. But nonwoven fabrics could not compete with woven fabrics if they are PSA coated
by natural rubber, providing much higher adhesive power to human skin than polyacrylics or
the like and requiring much higher web integrity in order to prevent delamination within the
fabric after removal of the plaster.
Evolon proved to be well suited not only in this repect but also with regard to other properties
such as softness of the surface and the suede like properties evolved by ultra-fine
microfibers.
In Fig. 10 Evolon PIE 16 PET/PA 6.6 post treated by fluorocarbon resin and thermosol
disperse dyed in one single step is compared to a neck stretched fabric on the same base.
Neck-in stretch was performed between a pair of rollers with different speeds and at room
temperature. It can be demonstrated how the orientation of the fiber can be changed from
random (isotropic) to machine direction (md) by this process. Elongation at break in md is
reduced from 52 to 11 % and in cross direction (cd) increased from 63 to 150 %.
Fig. 10
In Fig. 11 a and b Evolon fabrics before and after neck-in stretching are compared to other
nonwoven fabrics carded and binder bonded with different fiber blends and neck stretched
polyamide 6 spunbond, also binder bonded, which had been produced at Freudenberg up to
dismantling of the polyamide around 8 years ago.
Fig. 11a
Fig. 11b
Outlook for Evolon with regard to future medical-hygiene projects
The most part of end uses for hygiene-medical nonwoven fabrics by far can be covered by
low weights under 50 g/m 2 either for performance or cost reasons.
We have started investigations for such low fabric weights on our pilot plant at present mainly
focused on


single use Operating Room (OR) drapes and gowns in a weight range of around 30 45 g/m2 and
apertured fabrics for topsheets of baby diapers, diapers for adult incontinence and
sanitary napkins in fabric weights of around 10 - 20 g/m2.
Ultrafine micro fibers of Evolon fabrics might provide very good barrier properties with low
fabric weights. Actually Spunbond-Meltblown-Spunbond fabrics (SMS) based on
polypropylene are proved to generate best barrier properties due to the micro fiber meltblown
sheet. PP is used for performance (high water repellency) and cost reasons. Disadvantage of
this polymer in conjunction with a 3 sheet composite structure is the film like handle missing
any textile properties and the non sterilizability with gamma- or beta- irradiation.
Evolon process will have the benefit to apply hydrophobic polymer combinations such as
polyethylene terephthalate and polyolefine and the option to put a meltblown sheet on a ultra
fine microfiber spunbond or between two of such ultra fine microfiber spunbond layers.
As far as apertured topsheets are concerned we started around 2 years ago a project. The
high mechanical strengths, the soft micro fiber surface of Evolon fabrics and the fact that fiber
entanglement, splitting in ultrafine microfibers and aperturing are attained in one single step
by high pressure water jets are pleading for the Evolon process.
Samples in a weight of 15-17 g/m2 were manufactured on the pilot plant. In order to provide
water repellency the polymer combination PET/PA 6,6 weight ratio 65/35 PIE 16 had been
replaced by PET/PP weight ratio 78/22 PIE 16.
Apertured topsheets are already used in sanitary napkins. Vacuum perforated plastic films
with funnel like holes are wide spread in this field. But also nonwoven/film composites are
known.
There are different methods for perforation:
(1) Perforation by heat embossing at temperatures over the melting point of the fiber
(2) Perforation by friction calendering between an engraved and a smooth roller
(3) Perforation by slitting and extension perpenticular to the slits
(4) Perforation by passing male-/female rollers
(5) Hot needle perforation and last not least
(6) Perforation by water jets onto suitable supporting means such as coarse mesh
sreens or perforated drainage drums with projections in order to provide clear holes
In Fig. 12 tensile strength of a 16 g/m 2 Evolon fabric based on PET/PP = 78/22, perforated by
hydro entanglement is compared with further nonwoven fabrics, manucatured at different
methods - carded; carded//meltblown (CM) and spunbond//meltblown (SM) - apertured also
either by hydroentanglement or by heat embossing according to method (1). Tensile strenght
is again related to 1 g/m 2 in order to elaminate the impact of different fabric weights.
Fig. 12
Evolon PET/PP (actual fabric weight: 16,7 g/m 2) provides specific tensile strength of more
than 3 times compared to carded/perforated by melt-embossing, around 5 times compared to
PP//PP-SM=10/20, around 3 times compared to PP/PE//PP-SM=10/20, approx. 2,5 times
compared to PP//PP-SM=20/20 and 14 times compared to PP/PE//PP-CM=10/20. The
tremendous superiority of Evolon cannot be shown more effective than by these numbers.
With the unique new Evolon fabric range and manufacturing process Freudenberg has
contributed a further major technological breakthrough to the nonwoven industry. We are in
the very beginning with our investigations and are sure that the tremendous benefits of
Evolon fabrics will provide a lot of new application and open the hygiene and medical market
more and more in future.
This article is published on NT New Textiles, see the contents.
WHAT'S NEW

COMBEAU INDUSTRIES ANNOUNCES THE INSTALLATION OF A
NEW HIGH-SPEED, WIDE-WIDTH SLITTER/REWINDER FOR
NONWOVEN FABRICS

SYNTHETICS FINISHING OPENS NEW MEGA-WAREHOUSE AND
STORAGE FACILITY IN THE SOUTH

COMBEAU INDUSTRIES TO INSTALL NEW HIGH-SPEED WIDEWIDTH NONWOVEN FINISHING LINE

DEFEND™ FAMILY OF PROTECTIVE FINISHES
COMBEAU INDUSTRIES ANNOUNCES THE INSTALLATION OF A NEW
HIGH-SPEED, WIDE-WIDTH SLITTER/REWINDER FOR NONWOVEN FABRICS
HICKORY, NC – According to Ralph Krueger, Vice President for New Product
Development, “This is our third slitter/rewinder devoted almost exclusively to the
needs of the major nonwoven roll goods producers. It is capable of handling fabric
widths out to 180” and roll diameters up to 60” and, as such, will fulfill a growing
need in the wide commodity fabric business.” Combeau Industries has recently
experienced increased demand for nonwoven slitting and rewinding, which augments
it core service businesses, such as chemical coating, saturation, lamination, thermal
bonding, needling, calendering, and embossing of woven and nonwoven fabrics.
SYNTHETICS FINISHING OPENS NEW MEGA-WAREHOUSE
AND STORAGE FACILITY IN THE SOUTH
HICKORY, NC – Commission fabric finisher, Synthetics Finishing, Division of
TSG Incorporated, has just completed their largest expansion project in the
company’s 100-year history. Recently opened is a new 2,400,000 cubic foot
warehousing, shipping, and distribution center located on approximately six acres
adjacent to its main finishing plant in Hickory, North Carolina.
According to Darryl Grater, Vice President of Southern Operations, ?This facility, our
5th in North Carolina, represents the company’s continuing commitment to the
upholstery business and the southern furniture industry in general. For years many of
our top customers, including mills, jobbers, and overseas exporters, have complained
about the lack of fast, efficient warehousing, cutting, and shipping services available
in the south. This installation should finally answer that complaint.”
The high-bay warehousing section of this installation, nearly 40 feet from floor to
ceiling, reportedly contains the largest number of fabric storage tubes (all
manufactured by Sunoco Products Company) at any single location in the United
States. State-of-the-art material handling shuttles operating in seven 185 foot isles are
capable of picking and placing individual fabric roles into their own storage locations.
COMBEAU INDUSTRIES TO INSTALL NEW HIGH-SPEED
WIDE-WIDTH NONWOVEN FINISHING LINE
HICKORY, NC - Commission nonwoven finisher, Combeau Industries, a division of
TSG Incorporated, is in the process of installing a second high-speed wide-width
nonwoven finishing line at its North Carolina location. The new equipment is capable
of handling fabric widths out to 170” and roll diameters up to 60”.
According to Ralph Krueger, Vice President for New Business Development, “This
line should expand our well-known wide-width capabilities beyond low viscosity
saturation and spray application of light to medium weight nonwoven webs used
primarily in the medical, hygiene, and filtration markets. Utilization of ultra high
efficiency drying and curing technology, in addition to a newly developed multipurpose coating station, should position Combeau perfectly to service ever-growing
markets for high add-on single or double sided coating and high-viscosity
impregnation, used primarily in nonwovens for roofing, geotextiles, and automotive
applications.”
The new finishing line is expected to be fully operational in the second quarter of
2002.
DEFEND™ FAMILY OF PROTECTIVE FINISHES
HICKORY, NC - TSG Incorporated and its commission finishing division,
Synthetics Finishing offers its Defend™ family of specially modified protective
coatings for furnishing fabrics used mainly in commercial and institutional
environments.
Defend™ finishes impart a variety of protective features to textiles while still
retaining the original textured, fabric-like surface characteristics, breathability and
hand.
The Defend™ coating is suitable for use with a multitude of fabric constructions,
fibers, and weights. Many “loom state” high style fabrics can be successfully treated
with Defend™ to withstand the rigors of the institutional market. Defend™ treated
fabrics exhibit enhanced dirt, stain, and abrasion resistance in addition to
antimicrobial properties which inhibit the growth of bacteria or fungus.
Defend™ treated fabrics are ideal for use in restaurants and food service areas where
maximum abrasion resistance and easy removal of nasty food-born stains are of
primary importance. Outdoor upholstery and fabric for medical/incontinent
applications require the ultra-high liquid repellency of the Defend™ coating in order
to perform adequately. Defend™ finishes have also helped create a whole new
generation of “soft” fabric tote products (luggage, golf bags, backpacks, handbags)
that display the beauty and design possibilities of real woven fabric while not
sacrificing scrubability, scuff resistance and repellency.
Various Defend™ finishes are presently available, each individually tailored to
specific styles of fabric and performance requirements. Contact your sales
representative for more information.
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