Note: Descriptions are shown in the official language in which they were submitted.
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CELLULOSE-BINDING FIBRES
FIELD OF THE INVENTION
The present invention relates to drylaid nonwoven materials
comprising polyolefin bicomponent fibres having excellent
bonding affinity for natural fibres such as cellulose fibres.
BACKGROUND OF THE INVENTION
Hygienic absorbent products such as disposable diapers con-
tain, in addition to a water-permeable coverstock, a water-
impermeable backsheet and one or more layers for distribution
of liquid, an absorbent core typically comprising natural fi-
tires such as cellulose fluff pulp fibres, synthetic fibres
based on e.g. polyolefin and/or polyester and a superabsorb-
ent polymer (SAP) material. In absorbent cores of this type,
the synthetic fibres, which often are bicomponent fibres of
e.g. polypropylene/polyethylene or polyester/polyethylene,
are thermobonded to each other to form a supporting network
for the core. Ideally, the synthetic fibres should be able to
not only bond to each other, but also to the natural fibres
and the SAP, so as to result in a core structure which is as
strong and coherent as possible, and in which the natural fi-
tires and the SAP are locked into place within the structure.
However, the existing synthetic fibres that are used for the
production of drylaid, e.g. airlaid, nonwovens suffer from
the disadvantage of suboptimal bonding to e.g. cellulose fi-
tires. The problem is made worse by the fact that the natural
fibres are typically relatively short, e.g. fluff pulp fibres
with a length of not more than about 3 mm, as compared to the
synthetic fibres, which are normally (although not necessar-
ily) considerably longer. As a result, dust problems are cre-
ated in the manufacturing process, and the performance of the
resulting nonwovens is also suboptimal, since a large propor-
.___..v____ __._. ~_ ~._..~.__~ .~_._.._. ~
p I II
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tion of the natural fibres is not bonded to any of the syn-
thetic fibres or otherwise held in place by means of the
structure formed by bonding of the synthetic fibres.
It is therefore an object of the present invention to provide
a bicomponent synthetic fibre which has an improved bonding
affinity for natural fibres such as cellulose fluff pulp fi-
bres and which therefore is particularly suitable for the
production of drylaid nonwovens comprising a mixture of syn-
thetic fibres and natural fibres.
EP 0465203-Bl discloses thermally bonded fibrous wet laid
webs containing bicomponent fibres comprising a first compo-
nent of polyester, polyamide or polypropylene and a second
component of linear low density polyethylene (LLDPE) with a
density of 0.88-0.945 g/cc and a grafted high density poly-
ethylene (HDPE) with a density of 0.94-0.965 g/cc which has
been grafted with malefic acid or malefic anhydride to provide
succinic acid or succinic anhydride groups along the HDPE
polymer.
EP 0421734-Bl discloses thermobondable bicomponent fibres
composed of two different polyolefins having melting points
which differ by at least 20°C, the lower melting polyolefin
containing 3-loo by weight of a monoglyceride of a fatty acid
of 12 or more carbon atoms incorporated therein. The fibres
are reported to be easily processable without the need for an
oiling agent to be applied during spinning or drawing.
US 4,950,541 discloses succinic acid and succinic anhydride
grafts of linear ethylene polymers obtained by grafting
malefic acid or malefic anhydride onto a LDPE (low density
polyethylene), LLDPE or HDPE polymer. The grafted polymers
are dyeable and can be used e.g. as the sheath component of a
bicomponent fibre.
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US 4,684,576 discloses the production of blends of grafted
HDPE with ungrafted LLDPE or LDPE, the HDPE having been
grafted with malefic acid or malefic anhydride to provide suc-
cinic acid or succinic anhydride groups along the HDPE poly-
mer. The blends are disclosed for use in producing laminate
structures.
It has now unexpectedly been found that polyolefin bicompo-
nent fibres whose low melting component comprises a non-
grafted polyolefin component and a grafted polyolefin compo-
nent which has been grafted with an unsaturated dicarboxylic
acid or an anhydride thereof have advantageous properties
when used in the production of drylaid nonwoven materials,
including improved bonding to cellulose pulp fibres and im-
proved strength properties in the resulting nonwovens.
BRIEF DISCLOSURE OF THE INVENTION
In one aspect, the present invention relates to a drylaid
nonwoven material comprising bicomponent fibres comprising a
low melting polyolefin component and a high melting polyole-
fin component, wherein the low melting polyolefin component
has a melting point at least 4°C lower than the melting point
of the high melting polyolefin component, the low melting
polyolefin component constituting at least a part of the sur-
face of the fibre and comprising a non-grafted polyolefin
component and a grafted polyolefin component, wherein the
grafted polyolefin component has been grafted with an unsatu-
rated dicarboxylic acid or an anhydride thereof.
Another aspect of the invention relates to a method for pro-
ducing a drylaid nonwoven material, comprising forming a fi-
brous web using dry lay nonwoven equipment, the web compris-
ing bicomponent fibres comprising a low melting polyolefin
component and a high melting polyolefin component, wherein
the low melting polyolefin component has a melting point at
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least 4°C lower than the melting point of the high melting
polyolefin component, the low melting polyolefin component
constituting at least a part of the surface of the fibre and
comprising a non-grafted polyolefin component and a grafted
polyolefin component, wherein the grafted polyolefin compo-
nent has been grafted with an unsaturated dicarboxylic acid
or an anhydride thereof, and bonding the fibrous web to re-
sult in the drylaid nonwoven material.
A further aspect of the invention relates to a bicomponent
fibre as described above for the production of drylaid non-
woven materials.
DETAILED DISCLOSURE OF THE INVENTION
The term "polyolefin component" for the purpose of this in-
vention means a polyolefin-containing polymeric material of
which the largest part (by weight) consists of homo- or co-
polymers of monoolefins such as ethylene, propylene, 1-bu-
tene, 9-methyl-1-pentene, etc. Examples of such polymers are
isotactic or syndiotactic polypropylene, polyethylenes of
different densities, such as high density polyethylene, low
density polyethylene and linear low density polyethylene and
blends of the same. The polymeric material may be mixed with
other non-polyolefin polymers such as polyamide or polyester,
provided that polyolefins still constitute the largest part
of the composition. The melts used to produce the polyolefin-
containing fibres may also contain various conventional fibre
additives, such as calcium stearate, antioxidants, process
stabilizers, compatibilizers and pigments, including whiten-
ers and colourants such as TiOz, etc.
Although the present description will for the sake of sim-
plicity generally refer to "fibres", i.e. cut staple fibres,
it is to be understood that the present invention will also
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be applicable to the production of continuous polyolefin
filaments, e.g. spunbonded filaments.
The term "drylaid" nonwoven refers to a nonwoven material
5 produced by a dry process, including airlaid nonwovens,
carded nonwovens., etc.
The bicomponent fibres may be of the sheath-core type with
the core being located either eccentrically (off-center) or
concentrically (substantially in the center), or of the side-
by-side type, in iahich each of the two components typically
has a semi-circle cross section. Bicomponent fibres having
irregular fibre profiles are also contemplated, e.g. an oval,
ellipse, delta, star, multilobal, or other irregular cross
section, as well as splittable fibres. The bicomponent fibres
will typically have a high melting and low melting polyolefin
component which comprise, respectively, polypropyl-
ene/polyethylene (the polyethylene comprising HDPE, LDPE
and/or LLDPE), high density polyethylene/linear low density
polyethylene, polypropylene random copolymer/polyethylene, or
polypropylene/polypropylene random copolymer.
In certain cases, e.g. when the two components of the fibres
comprise high density polyethylene/linear low density poly-
ethylene or polypropylene/polypropylene random copolymer, the
difference in melting points the difference in melting points
between the two polyolefin components may be quite small,
e.g. about 7-8°C and in some cases even as low as about 4-
5°C. However, it is generally preferred that the two
components have melting points which differ by at least about
20°C, preferably at least about 25°C, more preferably at
least about 28°C, e.g, at least about 30°C.
As mentioned above, a presently preferred aspect of the in-
vention relates to a drylaid nonwoven material containing
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polyolefin bicomponent fibres in which the low melting poly-
olefin component comprises a non-grafted component and a
grafted component, the grafted component having been grafted
with an unsaturated dicarboxylic acid or an anhydride
thereof. Examples of such acids and anhydrides are malefic
acid, malefic anhydride and derivatives thereof such as citra-
conic acid, citraconic anhydride and pyrocinchonic anhydride;
fumaric acid and derivatives thereof; unsaturated derivatives
of malonic acid such as 3-butene-l,l-dicarboxylic acid,
benzylidene malonic acid and isopropylidene malonic acid; and
unsaturated derivatives of succinic acid such as itaconic
acid and itaconic anhydride.
Malefic acid and malefic anhydride are particularly preferred
as the dicarboxylic acid or anhydride thereof. When these
compounds are grafted onto a polyolefin chain, the resulting
chain is provided with succinic acid or succinic anhydride
groups, respectively, grafted onto it. The grafting of the
dicarboxylic acid or anhydride thereof onto the polyolefin
may be performed in a manner that is known per se, see e.g.
the above-mentioned EP 0465203, US 4,950,541 and US
4, 684, 576.
The weight ratio of grafted polyolefin to non-grafted poly-
olefin in the low melting polyolefin component of the bicom-
ponent fibres will be within the range of about 1:99 to
50:50, typically about 1.5:98.5 to 30:70, more typically
about 2:98 to 20:80, e.g. about 3:97 to 15:85, such as about
5:95 to 10:90.
Within the grafted polyolefin, the content of carboxylic acid
or anhydride thereof is typically in the range of about 1-30
(by weight), typically about 2-20~, more typically about
3-150, such as about 5-10°.
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The weight ratio between the high melting and low melting
polyolefin components will be in the range of from 10:90 to
90:10, typically about 20:80 to 80:20, more typically about
30:70 to 70:30, e.g. 35:65 to 65:35.
As mentioned above, drylaid nonwovens according to the inven-
tion comprising polyolefin bicomponent fibres and natural fi-
bres may be characterised by an improved bonding of the bi-
component fibres to the natural fibres as determined by a
standardised dust test whose result reflects the quality of
the bonding between the two types of fibres. In this stan-
dardised test, drylaid nonwoven samples having a base weight
of about 85 g/m~ and a thickness of about 1.1 mm are prepared
using a line speed of 20 or 40 m/min from a mixture of 25~~ by
weight of the synthetic fibres being tested and 75o by weight
of a cellulose pulp fibre (e. g. NB 416 from Weyerhauser).
Nonwovens to be tested are generally prepared using a series
of different bonding temperatures (e. g. using hot air or cal-
ender bonding, typically a hot air oven) in order to optimise
the properties of a given nonwoven.
The determination of the dust value of a nonwoven is per-
formed as follows. Before the measurement is carried out, the
nonwoven samples to be tested are conditioned for at least 12
hours to ensure that all of the samples have been subjected
to the same temperature and humidity conditions. Since, as
described below, the results are often expressed as a rela-
tive value compared to a control, the exact temperature and
relative humidity for the conditioning of the samples is not
critical, as long as all samples to be compared have been
subjected to the same conditions. Ambient temperature and hu-
midity conditions may therefore be used. Prior to condition-
ing, the nonwovens are cut into individual samples with a
size of 12 x 30 cm. After conditioning, a cardboard strip
with a width of 5 mm is attached to the short sides of the
sample, after which the sample with the attached cardboard
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strips is weighed on a laboratory scale with an accuracy of
~0.1 mg. The nonwoven sample to be tested is then fixed with
two clamps having a length of 12 cm, each of which is mounted
on an arm. The exposed area of the fixed nonwoven is about
310 cm', which is about the size of a piece of A4 paper. One
of the arms is stationary, while the other arm is rotatable
and is attached to a spring.
The test is performed by rotating the rotatable arm 45°, so
that the nonwoven sample goes from a "stretched out" condi-
tion to a "relaxed" condition, after which the rotatable arm
is released, whereby the action of the spring returns the ro-
tatable arm to its original position. The movement of the arm
is stopped by the nonwoven sample, which thus is subjected to
a small vibration and stretching effect designed to be simi-
lar to the conditions a nonwoven roll is subjected to when it
is unrolled at the converter, the vibration and stretching
resulting in a loss of loose fibres at the fibre surface.
This action is repeated 50 times. The stretching force the
sample is subjected to must of course lie within the non-
woven's elasticity limit, so that the nonwoven is not sub-
stantially deformed or damaged during the test. For the same
reason, and taking into consideration that the tensile
strength of different nonwovens can vary considerably, the
force provided by the spring must obviously be compatible
with the nonwoven to be tested, so that the nonwoven is on
the one hand returned to its original stretched out position
and subjected to a slight vibration and stretching, but is on
the other hand not excessively stretched so as to become de-
formed or damaged.
After having been subjected to the vibration/stretching ac-
tion 50 times, the sample is again weighed, and the differ-
ence between the two values is calculated and expressed as mg
of dust.
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In this standardised dust test, the result in mg will often
be no more than about 15 mg, typically no more than about 10
mg, preferably no more than about 5 mg, more preferably no
more than about 4 mg, still more preferably no more than
about 3 mg, most preferably no more than about 2 mg. For non-
wovens with a particularly good affinity between the syn-
thetic fibres and the natural fibres, the result can be as
low as abort 1 mg of dust.
An alternative and often preferred way of defining the dust-
reducing properties of a given fibre in the standardised dust
test is in terms of reduction of the amount of dust (in mg)
in a standard nonwoven prepared from fibres of the invention
compared to a similar nonwoven prepared from similar fibres
without the grafted polyolefin component. In this case, the
nonwoven prepared from the fibres of the invention should
show a dust reduction of at. least about 40o by weight com-
pared to the control nonwoven prepared with the control fi-
bres, typically at least about 50o by weight. Preferably, the
dust reduction is at least about 600, more preferably at
least about 700, and still more preferably at least about
800. For fibres with particularly good cellulose-binding
properties, the dust reduction can be as much as about 90=~ or
more. Since the dust properties of a given nonwoven can vary
greatly depending on factors such as the nature of the bicom-
ponent fibres and the nature of the cellulose or other fibres
as well as e.g. the particular webforming and bonding proc-
ess, it will often be preferred to compare the performance of
a given fibre in terms of i.ts dust reduction percentage com-
pared to a similar control fibre rather than in terms of an
absolute value in mg.
It is furthermore contemplated that the fibres of the inven-
tion will also show an improved bonding and fixation of not
only cellulosic fibres but also different superabsorbent
polymers (SAP) that are commonly used in hygiene absorbent
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products in the form of particles or fibres. Such SAPS, e.g.
a crosslinked polyacrylic acid salt, are typically used in
the form of superabsorbent particles in the absorbent core of
e.g. disposable diapers, since they are able to absorb many
5 times their weight in liquid and form a gel that holds onto
the liquid upon wetting. Even if the fibres of the invention
are not directly bonded to the SAP particles, it is contem-
plated that the improved bonding of the fibres of the inven-
tion to the cellulosic fibres will result in an improved
10 structure that in itself serves to ensure that the SAP parti-
cles are maintained in the desired location in the absorbent
product, whereby the function of the SAP will be improved.
The spinning of the fibres is preferably accomplished using
conventional melt spinning (also known as "long spinning"),
with spinning and stretching being performed in two separate
steps. Alternatively, other means of manufacturing staple fi-
bres, in particular "compact spinning", which is a one step
operation, may be used to carry out the invention. Methods
for the spinning of bicomponent fibres and filaments are
well-known in the art. Such methods generally involve extru-
sion of the melts to produce filaments, cooling and drawing
of the filaments, treatment of the filaments with an appro-
priate spin finish to result in desired surface properties,
e.g. using a spin finish to provide hydrophilic properties
when the fibres are to be used in an absorbent core and/or to
provide antistatic properties, stretching the filaments,
typically, treating with a second spin finish, texturizing
the filaments, drying the filaments and cutting the filaments
to result in staple fibres.
As indicated above, the drylaid nonwovens of the present in-
vention typically comprise, in addition to the polyolefin bi-
component fibres, at least one additional fibrous material,
in particular natural fibres or regenerated fibres, e.g.
selected from cellulose fibres, viscose rayon fibres and
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Lyocell fibre ~. The cellulose fibres may e.g. be pulp fibres
or cotton fib res and are in particular pulp fibres such as
CTMP (chemi-thermo-mechanical pulp), sulfite pulp or kraft
pulp.
The fibrous web comprising the bicomponent fibres and the ad-
ditional fibrous material will typically comprise 5-50$ by
weight of the bicomponent fibres and 50-95$ by weight of the
additional fibrous material, more typically 10-40$ by weight
of the bicomponent fibres and 60-90$ by weight of the addi-
tional fibrous material, e.g. 15-25~ by weight of the bicom-
ponent fibres and 75-85$ by weight of the additional fibrous
material.
EXAMPLES
EXAMPLE 1
Trials were run with different polyolefin bicomponent fibres
to evaluate their bondability to cellulose pulp fibres.
The cellulose fibres were NB 416 from Weyerhauser. The weight
ratio of between the bicomponent fibres and the'cellulose fi-
bres was 25:75.
The tested bicomponent fibres had the following composition,
fibre No..l being according to the present invention:
l: Core: polypropylene; sheath: loo grafted LLDPE (5$ malefic
acid grafted onto 95$ LLDPE), 90$ LLDPE.
Z. Control fibre; core: polypropylene; sheath: 100$ LLDPE.
3. AL-Speci ~ -C from Danaklon A/S; polypropylene core, HDPE
sheath. ~
4. Hercules 449 from Hercules Inc., length 5 mm, fineness 1.5
dtex; polypropylene core/polyethylene sheath.
~ Tr~dem~
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Bicomponent fibres 1, 2 and 3 all had a fineness of 1.7 dtex,
a length of 6 mm and a weight ratio between core and sheath
of 35:65.
The fibres were run at a very low speed of 8.33 m/min on an
airlaid apparatus (Dan-Web, Denmark), since the primary pur-
pose of these trials was to determine the fibres' ability to
bond to cellulose. During the trials, an airlaid nonwoven
product having a basis weight of 80 g/m2 was aimed at, and
the trials were started at the lowest possible bonding tem-
perature, after which the temperature in the oven was in-
creased in increments of 5 or 10°C.
Results:
The cross direction (CD) dry strength, machine direction (MD)
dry strength and MD wet strength were determined an samples
produced at different temperatures as indicated below (EDANA
test method No. 20.2-89, tested at a speed of 100 mm/min).
Furthermore, the thickness and the basis weight (g/m2) of
each sample was determined, and this information (not listed
below) was used to adjust the strength values to result in
normalised values that are comparable in spite of minor
differences in thickness and base weight of the individual
samples tested. The results are shown below.
Tm~t~
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BondingStrength Strength Strength
MD MD,
SampleTemp. CD wet
No. ~C N/5cm N/5cm N/5cm
1 125 25.9 25.2 25.4
1 130 20.9 20.5 18.3
1 135 23.5 22.4 20.6
1 140 23.1 22.3 20.1
1 145 23.9 22.5 18.0
2 125 17.46 15.43 15.13
2 130 13.63 13.32 11.62
2 135 15.17 15.06 12.66
2 140 16.25 15.72 13.99
2 145 12.77 7.3.08 9.78
2 150 11.28 7Ø77 6.77
2 155 4.15 4.26 2.23
3 130 24.01 23.37 23.59
3 140 19.34 7.8.08 18.57
3 150 15.59 1.6.66 14.92
4 130 7.98 7.78 7.98
4 140 9.23 7.93 8.73
4 150 8.83 8.93 8.83
4 160 4.21 4.31 2.26
4 170 3.24 3.14 1.27
The results of the dust test were as follows (average of 2
trials, except for fibre No. 3, which is the range of results
obtained in a larger number of test runs with this fibre):
Fibre number Dust (mg)
1 1.7
2 7.4
3 12-30
4 14.0
Compared to the control PP/PE fibres 2, 3 and 4, fibre 1 ac-
cording to the invention gave a significantly improved result
in the dust test, the greatly reduced dust generation re-
flecting a significantly improved bonding of the bicomponent
fibres of the invention to the cellulose fluff pulp fibres.
Observation of the samples by microscope also revealed bond-
ing of the bicomponent fibres of the invention to the cellu-
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lose fibres. It was also found that fibre 1 gave a bulkier
nonwoven compared to fibres 2 and 3 (fibre 4 was not compared
in this regard). Furthermore, as shown by the strength values
given in the table above, the fibres of the invention re-
suited in nonwovens with improved strength and elongation
characteristics.
EXAMPLE 2
A test of the ability of two different fibres to bind cellu-
lose was performed in a test on a commercial airlaid line.
Airlaid nonwovens with a basis weight of about 80 g/m- and a
thickness of about 1 mm were produced. The nonwovens con-
tained 25o by weight of bicomponent fibres and 75o by weight
of cellulose pulp fibres. The bicomponent fibres tested had a
fineness of 1.7 dtex and a length of 6 mm. In addition to
(control) fibre No. 3 described above, a bicomponent fibre
(referred to as No. 5) with the same cellulose-binding addi-
tive as in fibre No. 1 but a higher melting polyethylene
sheath component (HDPE) was tested. This fibre thus had the
following composition:
5: Core: polypropylene; sheath: 10o grafted LLDPE (5o malefic
acid grafted onto 95o LLDPE), 90o HDPE.
The individual nonwoven samples were bonded at different tem-
peratures with intervals of 3°C in order to ascertain the op-
timum bonding temperature for the individual fibres.
It was found that the nonwovens containing bicomponent fibres
of the invention (fibre 5) resulted in an improved binding of
the cellulose fibres as evidenced by a reduced generation of
dust during processing compared to the control fi-
bre(quantitative measurements were not performed in this
case). Furthermore, the fibres of the invention resulted in
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nonwovens with improved strength characteristics as evidenced
by the following test results:
MD tensile strength, dry (N/5 cm)
Bonding Fibre
Temp. °C Control 5
137 13.96 15.08
140 15.77 19.01
143 ~ 12.56 19.40
146 - 15.41
EXAMPLE 3
Tests were performed to illustrate the influence of varying
the amount of additive (malefic acid grafted LLDPE with an ac-
15 tine content of 50) in the sheath component.
The bicomponent fibres tested all had a fineness of 1.7 dtex
and a length of 6 mm. The core/sheath weight ratio for fibres
6-9 was 35:65, and 50:50 for fibre No. 10. The core was in
all cases of polypropylene. Nonwovens were produced on a com-
mercial airlaid line using technology from Dan-Web, Denmark,
the nonwovens having a basis weight of about 80 g/m', a
thickness of about 1 mm, and weight ratio of bicomponent
fibres to cellulose fibres of 25:75. Samples with each of the
bicomponent fibres were tested at 3 different bonding
temperatures, 137, 140 and 143°C.
The sheath composition of the individual fibres was as fol-
lows:
6: 5o grafted LLDPE (5o malefic acid grafted onto 95o LLDPE),
95o LLDPE.
7: 5o grafted LLDPE (5o malefic acid grafted onto 95o LLDPE),
95 o HDPE .
8: 10o grafted LLDPE (5° malefic acid grafted onto 95o LLDPE),
9 0 ° HDPE .
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9: 12.50 grafted LLDPE (5% malefic acid grafted onto 950
LLDPE), 87.50 HDPE.
10. 13° grafted LLDPE (5o malefic acid grafted onto 950
LLDPE ) , 8 7 o HDPE .
As a control, AL-Special-C from Danaklon A/S (polypropylene
core, HDPE sheath; No. 3 above), was used.
The wet and dry tensile strength and the elongation of the
various nonwovens was tested. As the results below show, the
nonwovens containing the fibres of the invention showed a
substantially improved dry and wet tensile strength compared
to the control nonwovens. In addition, some of the fibres of
the invention, notably Nos. 6, 7 and 8, showed elongation
values above those of the control fibres, while fibre 10 and
to a certain extent fibre 9 showed elongation values lower
than for the control fibres. The suboptimal results for fi-
bres 9 and 10 in terms of elongation are believed to be re-
lated to the fact that some difficulties were experienced in
spinning these fibres with a relatively large amount of the
grafted component in the sheath. It is believed that with
further tests and optimisation of the spinning process and
other process parameters, it will be possible to obtain im-
proved results for these and other fibres with a relatively
large content of the grafted polyolefin component as well.
Tensile
strength,
dry (N/5
cm)
Bonding Fibre
No.
Temp . Control 6 7 8 9 10
C
137 8.54 21.58 17.65 16.91 18.68 12.75
140 9.85 18.58 20.98 17.00 17.95 14.40
143 8.53 18.59 19.25 30.63 18.18 16.38
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Elongation,
dry (o)
Bonding Fibre No.
Temp . Control 6 7 8 9 10
C
137 185.25 190.25 154.50 199.67 174.25 133.50
140 175.00 184.75 188.25 195.67 169.00 119.00
143 178.67 189.25 185.78 184.25 185.75 144.75
Tensile
strength,
wet (N/5
cm)
Bonding Fibre
No.
Temp . Control 6 7 8 9 10
C
137 8.24 17.57 15.21 16.03 17.11 9.39
140 9.32 13.64 17 - 13.78 16.31 10.19
143 8.01 15.34 15.2 24.08 17.04 16.31
E1 ion,
wet (o)
Bonding Fibre
No.
Temp . Control 6 7 8 9 10
C
137 175.25 220.75 161.50 179.67 205.25 118.75
140 159.50 194.25 177.75 186.75 189.00 132.50
143 142.50 196.00 179.67 177.00 188.50 123.75
A visual assessment of the dust properties of the nonwovens
indicated that all of the tested bicomponent fibres of the
invention had an improved bonding to the cellulose fibres
compared to the control bicomponent fibres. Fibres 7 and 8
ran particularly well on the production line, and, as the re-
sults above show, excellent strength values were also
obtained for nonwovens containing these fibres.
The results of the fibres of this example in the dust test
were as follows (fibre 10 was not tested):
CA 02281802 19,99-08-24
WO 98/45519 PCT/DK98/00131
18
Fibre number Dust (mg)
6 6.6
7 14.9
8 5.8
9 6.7
Control 29.9
It can be concluded from the above that good results were ob-
tained with all levels of additive addition, although there
appeared to be a tendency for better results with additions
of about 5-100.