Note: Descriptions are shown in the official language in which they were submitted.
WO 2022/237925 1
PCT/CZ2022/050052
Nonwoven fabric with enhanced strength
Field of the Invention
The invention relates to thermally bonded nonwoven fabrics of spunmelt type,
containing
aliphatic polyesters with an increased efficiency of thermal bonding,
resulting in an increased
strength of the fabric.
Background Art
Strength or mechanical resistance of a nonwoven fabric is determined
particularly by two
principal factors. The first factor is given by the fiber itself (polymeric
composition and
characteristics of its crystallization, type of distribution, thickness of the
fiber). As to
biopolymers, particularly aliphatic polymers such as polylactic acid (PLA),
e.g. a Kimberly
Clark patent is known, which was filed in USA and granted under the number
US7994078 and
which describes suitable mixtures of aliphatic polyesters (combination of
multitude of
crystalline and amorphous polymers) for achieving a better quality of the
fiber and subsequently
of the nonwoven fabric. The above-mentioned mixtures can be used in
monocomponent fibers
or in various combinations in bicomponent fibers, where the use of a more
amorphous
constituent with a lower melting point on the surface of the fiber is
desirable.
The second factor, which fundamentally influences the resulting mechanical
properties of a
nonwoven fabric, is the mutual bonding of fibers. For purpose of this
disclosure, description of
thermal bonding will be limited to thermal bonding, in which a part of fibers
is melted, wherein
the softened or even melted parts of the fibers join and create a bonding
area. A very common
type of bonding is e.g. by means of a pair of calender rollers, which, in
addition to the effect of
temperature, makes use of pressure, wherein the protrusions on one or both of
the calender
rollers provide so-called bonding impressions. Another known method is for
example hot-air
bonding, in which a hot-air passes through the entire fabric, wherein the
bonding points are
created at fiber to fiber contact points. Methods of bonding and various
advantages are disclosed
e.g. in documents W02012130414 or W02017190717, which underline the advantages
of
various shapes and distributions of bonding impressions, created by a pair of
a smooth bonding
roller and a roller with protrusions. Hot-air bonding and its advantages is
disclosed for example
CA 03218433 2023- 11- 8
WO 2022/237925
PCT/CZ2022/050052
in the document W02020103964 or in the Czech application no. PV 2020-591 (no
yet
published).
Summary of the Invention
The aim of the invention is an enhancement of the strength of nonwoven fabrics
which contain
fibers with aliphatic polyesters, this goal being achieved by a nonwoven
fabric containing
endless fibers and bonding impressions or bonding points,
the endless fibers contain at least 80 wt. % of aliphatic polyesters,
the endless fibers contain a first component, which makes up at least 55 % of
the surface
of the fiber,
the first component contains at least one aliphatic polyester and at least 0.1
wt. % of an
additive,
the additive contains an amide group,
the additive corresponds to the general formula (i) or (ii) or (iii)
(i) R1-(C0)-NT-T2
(ii) R1-CO-NH-R2
(iii) R1-(C0)-NH-R3-NH-(C0)-R2,
wherein R1, R2, R3 are aliphatic hydrocarbon chains.
Preferably
a. R1 is an aliphatic hydrocarbon chain having a length of at least 10
carbons, more
preferably at least 12 carbons, preferably at least 15 carbons; and/or
b. R2 is an aliphatic hydrocarbon chain having a length of at least 10
carbons, more
preferably at least 12 carbons, preferably at least 15 carbons; and/or
c. R3 is an aliphatic hydrocarbon chain having a length of at least 1 to 7
carbons,
preferably 1 to 3 carbons.
Furthermore, it is preferred when
CA 03218433 2023- 11- 8
WO 2022/237925 3
PCT/CZ2022/050052
a. R1 is an aliphatic hydrocarbon chain having a length of no more than 30
carbons,
better yet no more than 25 carbons, preferably no more than 20 carbons; and/or
b. R2 is an aliphatic hydrocarbon chain having a length of no more than 30
carbons,
better yet no more than 25 carbons, preferably no more than 20 carbons.
Furthermore, it is preferred when
a. R1 is a straight aliphatic chain, and/or
b. R2 is a straight aliphatic chain; and/or
c. R3 is a straight aliphatic chain.
According to a preferred embodiment:
a. R1 is a saturated aliphatic chain; and/or
b. R2 is a saturated aliphatic chain; and/or
c. R3 is a saturated aliphatic chain.
It is furthermore preferred when the first component contains at least 0.15
wt. % of an additive,
better yet at least 0.20 wt. % of an additive, preferably at least 0.25 wt. %
of an additive.
In a preferred embodiment, the first component contains no more than 10% of an
additive,
better yet no more than 5% of an additive, preferably no more than 1% of an
additive.
The additive is preferably N,N'-ethylenebis(stearamide).
The component makes up preferably at least 70 % of the fiber surface, better
yet at least 85 %
of the fiber surface, better yet at least 90 % of the fiber surface,
preferably at least 95 % of the
fiber surface.
Preferably, in a bicomponent fiber of a core-sheath type, the first component
forms the sheath.
In another embodiment, the first component constitutes one of the sides in a
bicomponent fiber
of a side/side type.
The endless fibers contain preferably at least 90 wt. % of polymeric
constituents, better yet at
least 95 wt. % of polymeric constituents, preferably at least 99 % of
polymeric constituents.
CA 03218433 2023- 11- 8
WO 2022/237925 4
PCT/CZ2022/050052
It is furthermore preferable when the first component contains a mixture of
aliphatic polyesters
with differing values of heat of cold crystallization.
It is also preferable when the first component contains PLA or combinations of
at least two
types of PLA with differing values of heat of cold crystallization, eventually
when the first
component is comprised of PLA and another aliphatic polyester.
In a particularly preferred embodiment, the fibers of the nonwoven fabric
contain a second
component, wherein the first component has lower melting temperature than the
second
component.
The second component preferably contains at least one aliphatic polyester,
preferably PLA or
a mixture of different types of PLA with differing values of heat of cold
crystallization.
The above aim is achieve also by a method of production of a nonwoven fabric,
which contains
following steps:
a) preparation of a material for production of endless fibers, the material
containing at least 80
wt. % of polymeric constituents, wherein this material contains constituents
of a first
component of the endless fibers, the first component containing at least one
aliphatic polyester
and an additive in the amount of at least 0.1 wt. % of the total amount of the
first constituent,
wherein the additive contains an amide group and corresponds to the general
formula (i) or (ii)
or (iii)
(i) R1-(C0)-NH2
(ii) R1-(C0)-NH-R2
(iii) R1-(C0)-NH-R3-NH-(C0)-R2,
b) at least the constituents of the first component are melted and mixed,
c) at least the first component is fed to nozzles of a spinneret through which
the endless fibers
are formed, wherein at least 55 % of the surface is made up by the first
component.
Subsequently, the fibers formed in such a way are cooled down and drawn and
then they are
deposited on a moving belt, wherein
d) a batt formed in such a way is then thermally bonded
Preferably, in the step d), the batt is bonded by calendering and/or by using
hot air.
CA 03218433 2023- 11- 8
WO 2022/237925 5
PCT/CZ2022/050052
Definitions
A "bate is used herein to refer to fiber materials prior to being bonded to
each other. A "batt"
comprises individual fibers, which are usually unbonded to each other,
although a certain
amount of pre-bonding between fibers may be performed, and this pre-bonding
may occur
during or shortly after the lay-down of fibers in a spun-melt process, for
example. This pre-
bonding, however, still permits a substantial number of the fibers to be
freely movable such
that they can be repositioned. A "batt" may comprise several layers, resulting
by depositing
fibers from several spinning heads in a spun-melt process, and distributions
of a fiber diameter
thickness and a porosity in the "sub layers" laid-down from individual heads
do not differ
significantly. Adjacent layers of fibers need not be separated from each other
by sharp
transition, individual layers may blend partly in the area around the
boundary.
A "filament" designates an essentially endless fiber, whereas the term "staple
fiber" relates to
a fiber that has been cut to a defined length. The terms "fiber" and
"filaments", as used herein,
are mutually interchangeable.
To express a "fiber diameter" the SI length units ¨ micrometres (Am) or
nanometres (nm) are
used. The terms "fiber diameter" or "fiber thickness" are interchangeable for
the purpose of this
document. In the case where the fibers do not have a circular diameter, a
fiber diameter
corresponding to an equivalent fiber with a circular diameter is considered.
The terms "number
of grams of fiber per 9000 m" (also titr denier or Tden or den) or "number of
grams of fiber per
10000 m" (dTex) are used to express the level of fineness or coarseness of the
fiber.
A "monocomponent fiber" designates a fiber, formed by a single polymeric
constituent or by
a single mixture of polymeric components, as distinguished from a bicomponent
or a
multicomponent fiber.
A "mixture" or "blend" herein typically refer to polymeric materials contained
in a fiber, e.g.
when multiple polymers are mixed together. This does not exclude additions of
other materials,
typically in a smaller amount (for example colorants, process additives,
additives for adjusting
surface properties etc.). A blend can be used in monocomponent fibers as well
as in
bicomponent or multicomponent fibers.
A "bicomponent fiber" designates a fiber, the diameter of which comprises two
discrete
polymeric constituents, two discrete mixtures of polymeric constituents or a
discrete polymeric
constituent and a discrete mixture of polymeric constituents. A "bicomponent
fiber" is covered
CA 03218433 2023- 11- 8
WO 2022/237925 6
PCT/CZ2022/050052
by a general term "multicomponent fiber". A cross-section of a bicomponent
fiber can be
divided into two or more parts, made up by different constituents of any shape
or arrangement,
including for example a coaxial arrangement, core-sheath arrangement, side-
side, "segmented
pie" etc. The term "main constituent" describes a constituent, which makes up
a larger weight
proportion in the fiber.
A "first component" represents a polymer or a mixture of polymers which is a
single
component in the case of monocomponent fiber and which is one of the
components in the case
of a multicomponent fiber.
A bicomponent filament having "sheath-core structure" is a filament, the cross-
section of
which comprises two individual partial cross-sections, each one of them
consisting of different
polymeric constituent or a different mixture of polymeric constituents,
wherein the polymeric
constituents or the mixture of polymeric constituents forming the core is
surrounded by the
polymeric constituent or the mixture of polymeric constituents forming the
sheath. For
example, the term "C/S 70/30" describes a bicomponent fiber in a core-sheath
arrangement,
wherein the core makes up 70 wt. % of the fiber and the sheath makes up 30 wt.
% of the fiber.
A "nonwoven fabric" is a web or fiber layer produced of directionally or
randomly oriented
fibers which are first formed into a bait and then consolidated and bonded
together by friction,
cohesion, adhesion or one or more patterns of bonds and bonding impressions
created through
localized compression and /or application of pressure, heat, ultrasonic, or
heating energy, or a
combination thereof'. The term does not include fabrics which are woven,
knitted, or stitch-
bonded with yarns or filaments. The fibers may be of natural or manmade origin
and may be
staple or continuous filaments or be formed in situ. Commercially available
fibers have
diameters ranging from about 0.0005 mm to about 0.25 mm and they come in
several different
Forms: short fibers (known as staple, or chopped), continuous single fibers (-
filaments or
monofilaments), untwisted bundles of continuous filaments (tow), and twisted
bundles of
continuous filaments (yarn). Nonwoven fabrics can be formed by many processes
including but
not [United to melt-blowing, spun-bonding, spun-melting, solvent spinning,
electro-spinning,
carding, film fibrillation, melt-film fibrillation, air-laying, dry-laying,
wet-laying with staple
fibers and combinations of these processes as known in the art. The basis
weight of nonwoven
fabrics is usually expressed in grams per square meter (gsm).
A "spunbond" process is a process of production of nonwoven fabrics which
comprises a direct
conversion of a polymer to filaments, the conversion being immediately
followed by laying
CA 03218433 2023- 11- 8
WO 2022/237925 7
PCT/CZ2022/050052
thus produced filaments to form a nonwoven batt comprising randomly arranged
filaments.
This nonwoven batt is subsequently strengthened in such a way that a nonwoven
fabric is
formed by forming bonds between the fibers. The strengthening process can be
carried out in
various ways, for example by air-through-bonding, by passing between bonding
rollers etc.
"Filament to filament bonds" or "bonding points" refer to bonds which connect
usually two
filaments in an area, in which the filaments cross each other or locally meet
or abut on each
other. The bonding points/strengthening bonds may connect more than two
filaments or may
connect two parts of the same filament. The term "bonding point" thus here
represents a
connection between two fibers/filaments at a contact point by interconnecting
their constituents
with a lower melting point (see Fig. 1B). In the bonding point, the
constituent with a higher
melting point is neither damaged nor shaped. In contrast, the term "bonding
impression"
represents an area, on which a protrusion of a calender roller has acted (see
Fig. 1V). A bonding
impression has a defined area, given by the size of the protrusion of the
bonding roller and
typically the bonding impression has lower thickness than its surroundings.
Typically, during
bonding, a significant mechanical pressure arises in the area of the bonding
impression, wherein
the mechanical pressure can affect the shape of all of the constituents in the
area of the bonding
impression.
The expressions "bonding roller", "calender roller" and "roller" are herein
mutually
interchangeable.
"Hygienic absorbent article" refers herein to devices or aids that absorb and
contain body
exudates, and, more specifically, refers to devices or aids that are placed
against or in proximity
to the body of the wearer to absorb and contain the various exudates
discharged from the body.
Absorbent articles may include disposable diapers, training pants, underwear,
and adult
incontinence undergarments and pads, feminine hygiene pads, breast pads, care
mats, bibs,
wound dressing products and the like. As used herein, the term "exudates"
includes, but is not
limited to, urine, blood, vaginal discharges, breast milk, sweat and faecal
matter.
With respect to the making of a nonwoven web material and the nonwoven web
material itself
"cross direction" (CD) refers to the direction along the web material
substantially perpendicular
to the direction of forward travel of the web material through the
manufacturing line in which
the web material is manufactured. With respect to a ban moving through the nip
of a pair of
calender rollers to form a bonded nonwoven web, the cross direction is
perpendicular to the
direction of movement through the nip, and parallel to the nip.
CA 03218433 2023- 11- 8
WO 2022/237925 8
PCT/CZ2022/050052
With respect to the making of a nonwoven web material and the nonwoven web
material itself,
"machine direction" (MD) refers to the direction along the web material
substantially parallel
to the direction of forward travel of the web material through manufacturing
line in which the
web material is manufactured. With respect to a nonwoven batt moving through
the nip of a
pair of calender rollers to form a bonded nonwoven web, the machine direction
is parallel to
the direction of movement through the nip and perpendicular to the nip.
The term "aliphatic polyester" represents any biodegradable polymer (homo- as
well as
copolymer) based on an aliphatic polyester. Examples of biodegradable
aliphatic polyesters
useful for this invention comprise, without being limited to the following
list, for example:
polyhydroxy butyrate (PUB), polyhydroxy butyrate-co-valerate (PHBV),
polycaprolactone
(PCL), polybutylene succinate (PBS, polybutylene succinate-co-adipate (PBSA),
polyglycolic
acid (PGA), polylactide or polylactic acid (PLA), polybutylene oxalate,
polyethylene adipate,
polydioxanone (PDO) or polyoxalates (described e.g. in the patent application
US20050027081
from 2004) in general. Given the availability and the price, the most
preferable is now the
polylactide group, particularly PLA and its derivatives.
The term "polar central part" or "central polar part" represents the
functional group ¨(C0)-
NH-, which is the polar centre of the additive molecule. The central polar
part can be at the
edge of the molecule in the form of ¨(C=0)-NH2, as in the example of amides
(i), or in the
centre of the molecule, surrounded by a plurality of aliphatic residues R1,
R2, as in the example
of N-substituted amides (ii). In the additive molecule, the central polar part
can be contained
once or multiple times. The neighbouring central polar parts are then
connected by the aliphatic
chain R3.
A "bonding protrusion" or "protrusion" is a feature of a bonding roller at its
radially
outermost portion, surrounded by recessed areas. Relative the rotational axis
of the bonding
roller, a bonding protrusion has a radially outermost bonding surface with a
bonding surface
shape and a bon.cling surface shape area, which generally lies along an outer
cylindrical surface
with a substantially constant radius from the bonding roller rotational axis;
however,
protrusions having bonding surfaces of discrete and separate shapes are often
small enough
relative the radius of the bonding roller that the bonding surface may appear
flat/planar; and the
bondinv, surface shape area is closely approximated by a planar area of the
same shape. A
bonding protrusion may have sides that are perpendicular to the bonding
surface, although
usually the sides have an angled slope, such that the cross section of the
base of a bonding
CA 03218433 2023- 11- 8
WO 2022/237925 9
PCT/CZ2022/050052
protrusion is larger than its bonding surface. A plurality of bonding
protrusions may be arranged
on a calender roller in a pattern. The plurality of bonding protrusions has a
bonding area per
unit surface area of the outer cylindrical surface which can be expressed as a
percentage, and is
the ratio of the combined total of the bonding shape areas of the protrusions
within the unit, to
the total surface area of the unit.
Brief Description of Drawings
Fig. 1: Schematic comparison of a section of a fabric bonded using bonding
impressions (V)
and a fabric bonded using bonding points (B)
Fig. 2 A: SEM image of a bonding impression of a comparative nonwoven fabric
according to
Example 1
Fig. 2 B: SEM image of a bonding impression of a comparative nonwoven fabric
according to
the invention according to Example 2
Fig. 3: Schematic layout of a spunmelt-type production line for nonwoven
fabrics
Fig. 4: Schematic layout for thermal bonding using two heated rollers
(calender roller)
Fig. 5A is a top view photo of a nonwoven fabric according to Example 13,
Fig. 5B is a top view photo of a nonwoven fabric according to Example 12,
Fig. 5C is a photo of the cross-section of the nonwoven fabric according to
Fig. 5A and
Fig. 5D is a photo of the cross-section of the nonwoven fabric according to
Fig. 5B.
Exemplifying Embodiments of the Invention
The subject-matter of the invention is a thermally bonded nonwoven textile
made of spunmelt-
type endless fibers which contains an aliphatic polyester or a mixture of
aliphatic polyesters in
combination with a non-polymeric additive which alters the dynamics of
crystallization of the
material in the fibers and enhances the efficiency of the thermal bonding.
Aliphatic polyesters exhibit a characteristic behaviour during thermal
bonding. When exposed
to a heat flow, a change in the volume of the polymers occurs after absorption
of a certain
amount of heat (for example in the zone of so-called cold crystallization).
This phenomenon is
known as shrinkage Shrinkage is generally regarded as an undesirable
phenomenon and there
CA 03218433 2023- 11- 8
WO 2022/237925 10
PCT/CZ2022/050052
is a clear tendency within the field of art to use an aliphatic polyester with
a high portion of
amorphous constituent at least on a part of the surface of thermally bonded
fibers (aliphatic
polyesters with a high portion of amorphous constituent are characterized by a
low value of
heat of cold crystallization and, typically, they have a lower melting
temperature than the
crystalline constituents). Without intending to be bound by theory, we believe
that a certain
degree of exothermal cold crystallization is desirable. In case of a very
amorphous polymer, a
rapid melting of its surface can take place without heating and softening of
the entire fiber, or
at least of its entire bonding component. The melted part of the polymer on
the surface of the
fiber is adhesive and readily sticks to a surface of any of the components of
the line. Releasing
such a fiber requires higher force than releasing of a fiber freely laid on
the belt. When multiple
fibers get stuck, the total adhesiveness of the fibrous layer to the belt
increases, which can cause
tearing of the fibrous layer and an undesirable winding of the fiber belt on
an element of the
production line.
At the same time, even a relatively low degree of shrinkage can cause problems
during
production. It is important to be aware that during the production, the batt
is located on the
moving belt, drum or roller, which do not tend to be perfectly flat. Before
consolidation, the
nonwoven fabric batt represents a relatively open structure with partially
moving fiber parts.
Therefore, a fiber or its part, which comes into an immediate vicinity of a
protrusion or a
depression may easily stick or wind on it even at a first low shrinkage of the
material. Similarly
to the example above, release requires a higher force and causes a risk of
breaking the batt.
Such a scenario typically occurs when in contact with a hot roller with
protrusions, when the
batt passes from one element to another, when n contact with a drum in a drum
dryer or a hot-
air bonding unit etc.
Aliphatic polyesters are available in a varying degree of crystallinity, in
other words with
varying values of latent heat of cold crystallization, and both described
effects can blend into
one another, support one another and narrow down process window for thermal
bonding of a
nonwoven fabric. The described behaviour was observed for example in PLA
fibers with a
substantially amorphous polymer on the surface of the fiber at temperatures
exceeding 140 C
and at the speed of 150 m/min or for example at temperatures exceeding 110 C
at the speed of
7m/min.
Without intending to be bound by theory, it is believed that the additive
altering the dynamics
of the crystallization contributes to a more homogeneous softening and to a
subsequent melting
CA 03218433 2023- 11- 8
WO 2022/237925 11 PC
T/CZ2022/050052
of the polymer in such a way that a sintering of the fibers or a sintering of
the bonding
components of the fibers occurs and at the same time the additive shifts the
temperature of the
start of softening of the aliphatic polyester so that it allows for a proper
thermal interconnection
of the fiber surfaces.
The additive according to the invention represents a non-polymeric organic
compound
consisting of a central part and one or more non-polar ends. The polar central
part is generally
compatible with the structure of aliphatic polyesters, whereas the relatively
short and with
respect to their 3D structure relatively flexible non-polar ends locally
affect the dynamic of the
crystallization of the polymer. Ends which are too short do not ensure the
desired effect and
ends which are too long will tend to make clusters and decrease the
homogeneity of the mixture
in a polar environment of the aliphatic polyester.
According to a preferred embodiment of the invention, the central polar part
is made up of a
combination of a positive and a negative partial electrical charge on elements
of the central part.
Preferably the central part contains amides (i) or N-substituted amides (ii),
wherein the nitrogen
is bonded by a single bond to the carbon of the ketone group C=0 and by a
further single bond
on a further carbon of a continuing aliphatic chain R1-(C0)-(NH)-R2.
In the embodiment in accordance with the invention, the additive is made up by
a central polar
part, formed by a ¨(C0)-(NH2) and a hydrocarbon residue R1 (i).
In a particularly preferable embodiment, RI is a straight saturated aliphatic
chain containing 10
to 30 carbons, preferably 15 to 25 carbons.
In another embodiment in accordance with the invention, the additive is made
up by a central
polar part made up by ¨(C0)-(NH)- and hydrocarbon residues RI, R2 (ii).
(i) amides (ii) N-substituted
amides
0
R1
N
R2
CA 03218433 2023- 11- 8
WO 2022/237925 12
PCT/CZ2022/050052
0
R1
N -H
With an acceptable degree of simplification, it can be said that this
arrangement of the atoms in
the molecule leads to a creation of a partial negative charge on the oxygen
and a partial positive
charge on the carbon of the keto group or at the adjacent amide nitrogen as
well by effect of
resonance, and as such is well compatible with polar chains of aliphatic
esters, wherein the
effect can be further enhanced if the group ¨(C0)-(NH)- in the core of the
additive is repeated
in the combination R1-(C0)-(NH)-R3-(NH)-R1 (iii). The additive molecule can
thus contain
two or more central polar parts, connected by the aliphatic chain R3.
Aliphatic chains R1, R2
and R3 can be of different lengths.
(i) R1 - (C )- (NH)-R3 -(NH)-R
0
R 11,1 .................................................. \= R2
R3 .ge
N N
0 According to a preferred embodiment of the invention, R1 represents
an aliphatic hydrocarbon
residue having a length of at least 10 carbons, better yet at least 12
carbons, preferably at least
carbons.
According to a preferred embodiment of the invention, R1 represents an
aliphatic hydrocarbon
residue having a length of no more than 30 carbons, better yet no more than 25
carbons.
CA 03218433 2023- 11- 8
WO 2022/237925 13 PCT/CZ2022/050052
According to a preferred embodiment of the invention, R2 represents an
aliphatic hydrocarbon
residue having a length of at least 10 carbons, better yet at least 12
carbons, preferably at least
15 carbons.
According to a preferred embodiment of the invention, R2 represents an
aliphatic hydrocarbon
residue having a length of no more than 30 carbons, better yet no more than 25
carbons.
R3 preferably corresponds to a portion of the polymer between ester bonds.
Preferable
embodiments are shown in the Table 1:
Polymer Length of the Additive:
Additive:
aliphatic chain of the Suitable length of R3 Most
preferred
polyester between (carbons) length
of R3
the ester bonds in the
(carbons)
portion of the chain
containing keto
groups (number of
carbons)
PLA, PGA 2 1-3 2
PHB, PHBV 3 2-4 3
PBS, PBSA 4 3-5 4
Polyethylene adipate 6 5-7 6
Table /
According to a preferred embodiment of the invention, for use with PLA R3
represents an
aliphatic hydrocarbon residue having a length of 1 to 3 carbons, preferably 2
carbons.
According to a preferred embodiment of the invention, R1 and/or R2 and/or R3
is formed by a
straight aliphatic chain.
According to a preferred embodiment of the invention, R1 and/or R2 and/or R3
is formed by a
saturated aliphatic chain.
According to a particularly preferred embodiment of the invention, R1 and/or
R2 is a straight
saturated aliphatic chain, containing 10 to 30 carbons, more preferably 15 to
25 carbons.
According to a preferred embodiment of the invention, R1 and/or R2 and/or R3
is formed by a
straight saturated aliphatic chain.
According to a preferred embodiment of the invention, R1 and R2 are formed by
aliphatic
saturated straight hydrocarbon residues having the same length.
CA 03218433 2023- 11- 8
WO 2022/237925 14
PCT/CZ2022/050052
An example of a suitable non-polymeric additive from the group of amides (i)
is represented
for example by erucamide, behenamide (which is docosanamide) or oleamide
(structural
formulas are depicted below and described in Table 2).
Erucamide Behenamide
0
0
I
k
NH2
Oleamide
0
1
`-.- NH.2
Compound Erucamide Behenamide Oleamide
ILIPAC
(Z)-docos-13-enamide docosanamide
(9Z)-oktadec-9-enamid
name
Formula C221-143N0 C T71-145NO C I 81-
135NO
R1 length 21 C 21 C 17
C
R1 type straight straight straight
R1 bond 1 unsaturated (double saturated
1 unsaturated (double
from C12) from C8)
Table 2: description of erucamide, behenaniide and oleamide compounds
CA 03218433 2023- 11- 8
WO 2022/237925 15
PCT/CZ2022/050052
An example of a suitable non-polymeric additive from the group of N-
substituted amides is
represented by N,N'-ethylenebis(stearamide) known under the abbreviation EBS
with the
formula C38H76N202. The structural formula is depicted below.
N,N' -ethylenebi s( stearamide) = EB S
0
N N
0
EBS is an additive for a nonwoven fabric according to the invention, wherein
the hydrophobic
residues R1 and R2 are aliphatic saturated straight chains having an identical
length, the length
being 17 carbons, and R3 is an aliphatic saturated straight chain having a
length of 2 carbons.
According to a preferred embodiment of the invention, the nonwoven fabric
monocomponent
fiber contains at least 0.10 wt. % of a non-polymeric additive, better yet at
least 0.20 wt. % of
a non-polymeric additive, preferably at least 0.25 wt. % of a non-polymeric
additive.
According to a preferred embodiment of the invention, the amount of the non-
polymeric
additive according to the invention does not exceed 10 %, better yet 5 %,
preferably 1 %.
For thermal bonding of a batt into a nonwoven fabric, it may be preferable to
use bi- or
multicomponent fibers, wherein the first component contains in at least a part
of the fiber
surface (for example the sheath in a sheath/core combination or one of the
sides in a side/side
combination) is formed by a material with a lower melting temperature than the
other
component. During the bonding, primarily a softening of the first component
takes place and a
bond is formed at contact points of the fiber surfaces with a content of the
first component.
When using aliphatic polyesters, the first component contains preferably a
higher portion of
amorphous polyesters than the second component.
According to a preferred embodiment of the invention, the first component
covers at least 55
% of the fiber surface, better yet at least 70 % of the fiber surface, better
yet at least 85 % of
the fiber surface, better yet at least 90 % of the fiber surface, preferably
at least 95 % of the
fiber surface.
CA 03218433 2023- 11- 8
WO 2022/237925 16
PCT/CZ2022/050052
According to a preferred embodiment of the invention, the first component
contains at least
0.10 wt. % of the non-polymeric additive according to the invention, better
yet at least 0.20 wt.
% of the non-polymeric additive according to the invention, preferably at
least 0.25 wt. % of
the non-polymeric additive according to the invention.
According to a preferred embodiment of the invention, the amount of the non-
polymeric
additive according to the invention does not exceed 10 %, better yet 5 %,
preferably 1 %.
The behaviour of pure PLA in comparison with a mixture of PLA-EBS was tested
using
differential scanning calorimetry (DSC). The results are listed in Tables 3
and 4.
Second heating 100 % PLA1 90 % PLA1 + 10 %
EBS
(crystalline type)
Glass transition temperature
(ISO midpoint) 58 C 58 C
Cold crystallization
- Start 101 C
105 C
Peak 134 C 119 C
- End 157 C
137 C
- Heat 34 J/g
21 J/g
Melting
- Start 163 C
141 C
Peak 170 C 145 C
End 177 C 148 C
- Heat -34 J/g
-36 J/g
Table 3: DSC PLA 1 with and without an addition of EBS
The above data for the crystalline-type PLA1 make clear that the presence of
the additive did
not significantly affect the glass transition temperature, though significant
changes are
observable in the zone of dynamics of cold crystallization (with respect to
the start, end and the
amount of heat received) together with the zone melting (decrease of the start
of softening by
20 % and shortening of the temperature interval by half).
The zone of cold crystallization was markedly shortened by the addition of EBS
(from an
interval of 56 C to an interval of 31 C) and the amount of exothermic heat
decreased as well
CA 03218433 2023- 11- 8
WO 2022/237925 17
PCT/CZ2022/050052
(from 34 J/g to 21 J/g). Without intending to be bound by theory, it is
believed that the change
in the dynamics of cold crystallization due to the described non-polymeric
additive leads to a
decrease in the degree of shrinkage and thus leads to a restriction of the
undesired entrapment
of the fibers on the production line components. A further increase will
likely lead to undesired
effects on the production line (risk of entrapment of the fabric and breaking
of the batt
increases).
A decrease in the temperature of start of melting is another benefit that
helps to better
interconnect the nonwoven fabric for example in the form of bonding
impressions formed by
pressure in the case of calender bonding as well as bonding points formed in
fiber contact points
in the case of hot-air bonding.
Second heating 100 % PLA2 96 % PLA2 96 %
PLA2
(amorphous type) + 3,6 % PBAT + 3,6 %
PLA1
+ 0,4 % EBS + 0,4 %
EB S
Glass transition
temperature (ISO 57 C 59 C
60 C
midpoint)
Cold crystallization
- Start
107 C 106 C
- Peak Not observed
118 C 117 C
- End
131 C 130 C
- Heat
30 J/g 31 J/g
Melting
Start 139 C 145 C
144 C
- Peak 147 C
150 C 150 C
- End 157 C
157 C 159 C
Heat -1 J/g -31 J/g -
34 Jig
Table 4: DSC PLA2 with and without an addition of EBS and other materials
The above data for the amorphous-type PLA2 make clear that in this case, too,
the presence of
an additive did not affect the glass transition temperature, though it has a
significant influence
in the zones of cold crystallization and melting temperature. However, the
data shown in Table
4 show also that the additives of other polyesters (aromatic PBAT, crystalline
aliphatic PLA1)
CA 03218433 2023- 11- 8
WO 2022/237925 18
PCT/CZ2022/050052
do not interfere with the described desired effect of the additive according
to the invention. The
zone of cold crystallization was markedly strengthened by the addition of EBS.
While the
amorphous PLA2 does not exhibit any, a cold crystallization in a similar zone
can be observed
in both mixtures of polymers (from about 106 C to about 130 C), the amount
of exothermic
heat being also comparable (about 30 J/g). The amount of EB S is herein
optimized for achieving
the maximum effect during the thermal bonding for a particular type of polymer
¨ without
intending to be bound by theory, it was observed that the heats of cold
crystallization and the
heat of melting get closer to each other in the optimum zone.
Unlike the case of crystalline-type PLA1, a light increase in melting
temperature can be
observed, the temperature reaching 144-145 C which is similar to the above-
mentioned value
of 141 C. A significant change is present in the melting temperature, where
an increase from
1 J/g to 31-34 J/g was observed. Without intending to be bound by theory, it
is believed that the
above-mentioned increase in the melting temperature retards the melting of the
polymer
surface, in other words it contributes to the homogenization of melting of the
entire component,
which allows for the desired sintering of the fibers or their parts during the
thermal bonding and
reduces the risk of entrapment of the fabric on a production line component
and of breaking the
fibrous batt.
Without intending to be bound by theory, it is believed that an addition of an
aromatic polyester,
better yet of a biodegradable aromatic polyester, can be advantageous. Benzene
nuclei with
their specific distribution of free electrons and a relatively solid spatial
structure may enhance
crystallization, especially of amorphous parts of polymers, while the non-
polymeric additive
keeps the crystallization at a desired level.
In a preferred embodiment, addition of an aromatic polyester, preferably of a
biodegradable
aromatic polyester may be of advantage. According to a preferred embodiment,
the addition of
the aromatic polyester does not exceed 10 wt. % of the first component, better
yet does not
exceed 7 wt. % of the first component, preferably does not exceed 5 wt. % of
the first
component. According to a preferred embodiment of the invention, the
biodegradable aromatic
polyester is e.g. PBAT (polybutylene adipate terephthalate).
The above-mentioned changes, described using the DSC method are also
observable directly
on the nonwoven fabric, e.g. in the character of the bonding impressions. For
example a SEM
photograph of a bonding impression of pure PLA (produced according to the
description of
Example 1) shows bonding impressions with unsatisfactorily interconnected
fibers. The covers
CA 03218433 2023- 11- 8
WO 2022/237925 19
PCT/CZ2022/050052
of the used bicomponent fibers did not interconnect properly and it rather
appears as though
they stuck together only with their surfaces or merely by the effect of
pressure (Fig. 2 A). Such
created connections do not have the necessary strength and the fibers can be
disjoined relatively
easily. The second photograph represent a PLA bonding impression with a
content of 0.3 % of
EBS (produced in accordance with the description of Example 2), where a full
interconnection
of fibers is visible (Fig. 2 B). The nonwoven fabric depicted in this picture
exhibits a markedly
higher strength and surface resistance against abrasion. During the production
of both samples,
the same temperature and the same pressure of identical calender rollers was
used. When
attempting to increase the bonding temperature in the case of pure PLA, the
fabric entrapped
on the roller, which caused a risk of winding of the fabric belt and
interrupting the production
process.
Similarly, the above-mentioned changes can be seen in Fig. 5 as well, wherein
the SEM photos
of the nonwoven fabric, produced according to the description of Examples 12
and 13 on the
laboratory production line of the Centre of polymer systems UTB Zlin, are
depicted. Herein it
is made clear as well that comparative sample without an additive is not
properly
interconnected. From a top view (5B) it is evident that the bonding
impressions bulge out and
twirl. The cause is clear form a cross-section view (5D) ¨ the nonwoven fabric
is not properly
interconnected across its entire thickness and the bonding impressions are
present solely on the
surface of the fabric. However, when viewing the sample according to the
invention (5A and
5C), straight bonding impressions are seen, interconnected across the entire
thickness of the
fabric in a cross-section. The strength of both samples corresponds to the
described structural
changes as well, as shown in Table 6.
The spunbond process is based on polymeric melt spinning under a nozzle. The
production line
(Fig. 3) may comprise one or more spinnerets 1, adapted for the production of
spunbond-type
fibers. Each of the spinnerets is connected to at least one extruder, into
which the required
polymeric mixture is fed. The mixture in the extruder is melted and
transported into a spinning
nozzle 5. A person skilled in the art knows well that in order to obtain
fibers of different cross-
section shapes and diameters, various configurations of spinning nozzles can
be used which can
form monocomponent or multicomponent fibers in various configurations (e.g.
core/sheath,
side/side, islands in the sea etc). Initial fibers 4 of the spunbond type,
formed by the spinneret
5, are cooled and drawn in a cooling and drawing chamber 7 using an airflow
(the airflow being
fed by supply 6 of cooling and drawing air), then they are vibrated in the
diffuser 8 and
deposited on moving surface 2, which can be a permeable belt. If necessary,
the batt can be pre-
CA 03218433 2023- 11- 8
WO 2022/237925 20
PCT/CZ2022/050052
strengthened by one or more preconsolidation units 9, Q. In the case of using
more consecutive
spinnerets, the fibers from the second and subsequent spinnerets! fall on the
batt, formed by
preceding spinnerets 1. A different polymeric composition and/or different
process settings of
the spinnerets 1 (e.g. power, cooling rate and drawing rate) lead to different
characteristics of
the batt deposited by given spinneret on the bed ¨ various multilayer
composites with specific
properties can be formed.
A person skilled in the art will as well recognize the possibility of
installing one or more
spinnerets between the spunbond spinnerets, e.g. a meltblown, an advanced
meltblown or a
melt fibrillation spinneret, and thus insert typically a barrier layer with a
significantly smaller
fiber diameter between the spunbond layers. These composites are known as SMS
materials.
A batt, formed by all of the used spinnerets comprises individual fibers,
between which a mutual
solid bond is usually not yet formed, even though the fibers can be bonded in
a certain way,
whereas this pre-bonding can take place during the deposition of the layer
formed by free fibers
or shortly after in the preconsolidation units 9, 10 e.g. by using rollers,
hot-air, heat radiation
etc. However, this preconsolidation still allows a free movement of a
substantial quantity of
fibers, which may thus be moved. This batt can be bonded thermally (e.g. by
using rollers, flow
of a hot medium etc.) to form a nonwoven fabric.
The polymeric component or the mixture contained in the fibers of the nonwoven
fabric
according to the invention can be formed from one or more granulates based on
polymer
materials such as, in particular, aliphatic polyesters, more specifically e.g.
polylactic acid
polymer (PLA). According to a preferred embodiment of the invention, the
aliphatic polyesters
represent at least 80 wt. % of the fiber, better yet at least 90 wt. % of the
fiber, better yet at least
95 wt. % of the fiber, preferably at least 99 wt. % of the fiber. It is worth
mentioning that the
proportion of the polymeric constituents or the proportion of the aliphatic
polyesters is
calculated from the entire fiber irrespective of whether the fiber is mono- or
multicomponent.
According to a preferred embodiment of the invention, one aliphatic polyester
represents the
base constituent which makes up at least 60 wt. % of the aliphatic polyesters
content.
According to a preferred embodiment of the invention, an aliphatic polyester
based on
polylactide represents the base constituent which makes up at least 60 wt. %
of the aliphatic
polyesters content.
CA 03218433 2023- 11- 8
WO 2022/237925 21
PCT/CZ2022/050052
The nonwoven fabric fibers according to the invention may contain other
additives such as
colour pigments, materials increasing pleasantness of the touch (soft-touch,
cotton-touch etc.),
process additives etc.
The nonwoven fabric fibers according to the invention can contain further
additional materials
such as aromatic polyesters, thermoplastic polysaccharides and other
materials. These further
additional materials are preferably biodegradable. A person skilled in the art
will recognize the
advantages of the aliphatic polyester mixtures. For example, the advantages of
the combination
of PLA and PBS in different ratios and crystalline states are explained in a
number of prior
documents.
The nonwoven fabric fibers according to the invention can contain a mixture of
at least two
aliphatic polyesters, at least one of which is characterized by a lower value
of heat of cold
crystallization than the others. A preferable solution according to the
invention is represented
by a mixture of at least two aliphatic polyesters, at least one of which has a
heat of cold
crystallization by at least 1 J/g, better yet by at least 2 J/g, preferably by
at least 3 J/g lower than
at least one another aliphatic polyester in the composition, wherein even
chemically identical
aliphatic polyester having a differing grade is regarded as another aliphatic
polyester.
The nonwoven fabric fibers according to the present invention may contain
further additional
materials such as e.g. aliphatic polyolefins, e.g. polypropylene or
polyethylene, eventually
copolymers thereof.
The individual fibers can be monocomponent or bicomponent. Multicomponent
fibers comprise
particularly bicomponent fibers, for example fibers of the core-sheath type or
side-side type.
The individual constituents can often be separated into a first component ¨
binding constituent
with a lower melting point ¨ and a second component. In the case of aliphatic
polyesters, a more
amorphous form of polyester can be used as the first component with a lower
melting point so
that during the thermal bonding, the first component will act as a binder.
Fibers of the side-side
type or the eccentric core/sheath type may be used with advantage for example
in production
of highly voluminous materials. The use of suitable polymers in individual
constituents of a
bicomponent fiber can lead e.g. to so-called self-crimped fibers which
significantly increase
bulkiness of the nonwoven fabric. It is preferable for the solution according
to the invention
when the first component with a lower melting point is the above-mentioned
mixture containing
at least one aliphatic polyester and an additive. A person skilled in the art
will easily recognize
various other possibilities and advantages of the use of different types of
fibers. It is preferable
CA 03218433 2023- 11- 8
WO 2022/237925 22
PCT/CZ2022/050052
for the solution according to the invention when the difference between the
melting
temperatures of the first and the second components in a bicomponent fiber is
at least 5 C,
better yet at least 10 C and when the first component with a lower melting
temperature makes
up at least 55 % of the fiber surface, better yet at least 70 % of the fiber
surface, better yet at
least 85 % of the fiber surface, better yet at least 90 % of the fiber
surface, preferably at least
99 % of the fiber surface.
It is preferable for the solution according to the invention when the first
component represents
at least 5 wt. % of the fiber, better yet at least 10 wt. % of the fiber,
preferably at least 15 wt. %
of the fiber.
The solution according to the invention may be implemented as a spunlaid
nonwoven fabric
mostly containing bicomponent spunbond fibers with a proportion of the first
component of at
least 5 wt. % of the fiber, the first component making up at least 55 % of the
fiber surface.
A fabric prepared in such a way is subjected to a thermal bonding in the
bonding unit 3 which
can be implemented in various ways ¨ e.g. by using a pair of heated calender
rollers 50, 51 or
a flow of hot medium (e.g. air).
The solution according to the invention may be preferably realized by using a
thermal bonding
of a nonwoven fabric by a pair of calender rollers 50, 51. The technological
procedure of this
type of thermal bonding comprises a step of forming bonds between the fibers
which form a
batt, during which the fibers unite and interconnect to a certain degree to
form a fabric, while
at the same time, the mechanical properties, e.g. tensile strength, increase,
which can be
necessary for the material to maintain a sufficient structural integrity and
dimensional stability
during subsequent production processes as well as when using the final
product. As apparent
from Fig. 4, bonding by calendaring can be carried out so that the batt 21a
passes through the
clearance between a pair of rotating calender rollers 50, 51, which results in
a compression and
uniting of the fibers to form a nonwoven fabric 21. One or both of the
calendaring rollers 50,
51 can be heated such that they support heating, plastic deformation, blending
and/or thermal
melting/bonding of fibers layer on top of each other during the compression in
the clearance
between the rollers. The rollers can make up functional parts of the binding
mechanism, wherein
they are pressed towards one another by a force with a controllable magnitude
so that they apply
the required compression force/required pressure in the clearance. In some
processes, the
bonding mechanism may incorporate an ultrasonic source that allows a
transmission of the
CA 03218433 2023- 11- 8
23
WO 2022/237925
PCT/CZ2022/050052
ultrasound vibrations into the fibers, which again generate thermal energy
that improves the
bonding
A bonding pattern consisting of bonding protrusions and recessed areas can be
formed on the
outer surface of one or both calender rollers 50, 51 by machining, etching or
in other way, which
makes the bonding pressure acting on the batt during its passage through the
clearance 52
concentrate on the bonding surfaces of the bonding protrusions, whereas it is
decreased or
significantly limited in the recessed areas. The shapes of bonding surfaces
are predetermined.
As a result, a nonwoven fabric 21 with a pattern is formed, the pattern
consisting of bonding
impressions V (see Fig. 1) between the fibers which make up the nonwoven
fabric 21 whose
shape corresponds to the shape of the bonding impressions arranged in an
identical pattern as
on the surface of the calender roller 50, 51. The first roller, e.g. roller
51, may have a flat
cylindrical surface without a pattern, thus representing a pressure or
abutting roller, whereas
the second roller 50 may be provided with the above-mentioned pattern and thus
may represent
a roller which forms a bonding impression in the processed material; the
pattern created on the
nonwoven fabric by this combination of rollers will then correspond precisely
to the pattern on
said second roller 50. In some cases, both of the rollers 50, 51 can be
provided with patterns,
and the patterns may be different. In such a case, a combined pattern is
created by the action of
these patterns on the nonwoven fabric, such a pattern being disclosed for
example in the patent
document US 5,370,764.
It is preferable for the solution according to the invention when the total
bond area (total area
of the bonding impressions) makes up at least 8% of the total area of the
nonwoven fabric,
preferably at least 11% of the total area of the nonwoven fabric.
It is preferable for the solution according to the invention when the total
bond area does not
exceed 30% of the total area of the nonwoven fabric, better yet does not
exceed 25% of the total
area of the nonwoven fabric, preferably it does not exceed 20% of the total
area of the nonwoven
fabric.
The calender rollers bond the fibers together by using a combination of
temperature and
pressure. Therefore, it is preferable to set the temperature of the rollers on
a temperature closely
below the melting temperature of the bonding polymer. The temperature is
preferably set so as
to be 1-15 C lower than the melting temperature of the bonding polymer, more
preferably
1-10 C lower than the melting temperature of the bonding polymer. Said
bonding temperatures
are suitable for sufficiently rapid production lines, markedly lower
temperatures are adequate
CA 03218433 2023- 11- 8
WO 2022/237925 24
PCT/CZ2022/050052
particularly in slow laboratory lines having a belt speed in the range of
meters. The
recommended limit value of the temperature of rollers corresponds to a
production speed of at
least 50 m/min.
The solution according to the invention may be preferably implemented by using
thermal
bonding of a nonwoven fabric with the use of hot medium. Generally, the heat
transfer to the
batt can take place in various stages of the production process, e.g.
immediately after the
filaments have been deposited on the belt to preconsolidate the structure,
during the thermal
activation process, during the bonding process (final consolidation) etc.
Hot liquid enters the surface of the filamentary batt, flows around the
filaments, and a part of
the heat being transferred by the hot liquid passes to cooler filaments. It is
worth mentioning
that the creation of filament-to-filament bonds depends also on the local
intensity of the fluid
resistance pressure, i.e. the filaments may be in mutual contact or cross each
other and will not
form a bond (bonding point) or will form only a weak bond (bonding point),
while the filaments
in a more intense contact will form stronger bonds (bonding points) formed by
melted polymer
with a lower melting temperature. It is preferable for the solution according
to the invention
when the flow of the hot medium passes through the fabric which results in a
heat transfer
across the entire volume of the nonwoven fabric.
The preferred embodiment according to the invention comprise a bonding process
(final
consolidation), which is conducted using at least three different
consolidating sections. The air
flow is substantially perpendicular to the fabric and maintains a uniform
temperature and flow
rate with small fluctuations.
The first consolidating section preheats the fabric to a temperature nearly
below the temperature
of the bonding polymer. The temperature is preferably set to be 5-20 'V lower
than the melting
temperature of the bonding polymer, more preferably the temperature is set to
be 5-15 C than
the melting temperature of the bonding polymer, preferably the temperature is
set to be 5-10 C
lower than the melting temperature of the bonding polymer. The first
consolidating section
preferably comprises alternating directions of the heat flow entering the
first and the second
outer surface of the fabric.
The second consolidating section is set to achieve a narrow range of melting
temperature of the
polymer composition with a lower melting temperature in such a way to allow a
fusion bond to
be formed. On the other hand, with respect to the basis weight of the fabric,
the size of the fibers
and the ratios of the cross-sections of the polymer constituents, the set
temperature should not
CA 03218433 2023- 11- 8
WO 2022/237925 25
PCT/CZ2022/050052
be in a range broader than 5.0 C below up to at the most 3.0 C above the
melting temperature
of the bonding polymer. For example, when the melting temperature is 130 C,
the set
temperature should be in the range of 5 C below the melting temperature of
the bonding
polymer to a temperature equal to the melting temperature of the bonding
polymer, preferably
the temperature is set in the range of 4 C to 1 C below the melting
temperature of the bonding
polymer. The second consolidating section preferably comprises alternating
directions of the
heat flow entering from the first and the second outer surface of the fabric.
The third consolidating section is a cooling section providing a significantly
cooler air,
preferably at a temperature of 10-40 C, more preferably 20-30 C. Ambient air
may be used.
The cooling section contributes to the solidification of the filaments or at
least of the filaments
on the surface of the fabric and to a stabilisation of the formed fabric
strata structure. Preferably,
no additional tension is applied immediately before and during the cooling
process. Further
cooling can be provided by an additional air flow, a cooling roller etc. The
additional cooling
is preferably carried out when the temperature of the fabric exiting the third
consolidating
section does not yet reach the ambient temperature. The fabric should
preferably reach ambient
temperature, preferably the fabric should reach a temperature of 40-10 C,
more preferably the
fabric should reach a temperature of 20-30 C. For economically advantageous
reasons, the
process described herein is used to produce bulky, soft, nonwoven fabrics with
a low tendency
to felting at a high production capacity and a high production speed.
For example, in an embodiment according to the invention, a consolidation
device containing
4 drums can be used, the device using the effect of passing hot air. This
device enables a process
with short idle periods even at high speeds but also with sufficient exposure
to the hot air flow
and the hot air volume along the maximized path of the fibers, in order to
reach a necessary
melt flow with a low viscosity for forming fusion bonds in a defined narrow
parameter range.
In the machine direction, the drums allow for contact angles with the nonwoven
fabric of at
least 1000, preferably at least 130 , more preferably at least 150 ,
preferably at least 160 .
The precise parameter settings range for a given device depends on the
selected bonding
polymer as well as the size of the filaments, filament cross-section and the
weight-ratio between
the formulations of the polymer constituent.
The device, containing 4 drums, can also allow for an intense, alternating,
essentially vertical
air flow through the substrate of the nonwoven fabric in a short time. The
first pair of drums is
set to preheat the fabric structure immediately below the melting temperature
of the polymer
CA 03218433 2023- 11- 8
26
WO 2022/237925
PCT/CZ2022/050052
composition with a low melting temperature. The second pair of drums is set to
reach the range
of melting temperatures of the polymer composition with a low melting
temperature to allow
for forming fusion bonds. For the purpose of maintaining the structure of the
fabric and to
ensure that the fusion bonds are maintained intact, the last drum comprises a
hot section and a
cooling section along its circumference in the machine direction. It is
preferable when the fabric
structure, or at least the surface of the fabric structure, is solidified
before the release of the
fabric from the consolidation device. A separate additional cooling roller
with a high flow rate
of the cooling air across the fabric is located in the shortest distance
possible form the last drum
of the consolidation device which makes use of the air-through bonding which
finishes the
solidification of the fabric with an immediate cooling.
The interconnected nonwoven fabric 21 is in the final stage wound up on a
winder H. In the
case where it is necessary to modify the surface characteristics of the
nonwoven fabric, e.g. to
achieve improved fluid transfer or to increase the fluid drainage capability,
a spraying device
or a soaking roller is located either between the moving belt and the final
consolidation device
or between the final consolidation device and the bobbin.
The nonwoven fabric according to the invention may be, if necessary, adjusted
in other known
ways. For example, a use of a water jet called "hydroengorgement" is known for
softening of
the nonwoven fabric (described for example in the patent document US 8093163)
or "hydro-
patterning" which is intended directly for a modification of a nonwoven fabric
containing
bonding impressions (described in yet unpublished patent application US
63/183,148). The
fabric according to the invention can be for example perforated using various
methods
(overbonding, hot needles, water jet etc.)
The nonwoven fabric according to the invention may be produced having any
basis weight. A
person skilled in the art will recognize that higher basis weight is generally
associated with a
higher caliper and an improved touch of the final fabric, although this
entails correspondingly
higher costs. In contrast, even though a lower basis weight is associated with
correspondingly
lower costs, at the same time it makes difficult e.g. formation of a covering
outer layer of
hygienic absorbent products, where a specific level of covering ability or
other barrier
properties are required. In accordance with this foreknowledge, in such cases
a nonwoven fabric
according to the invention may be used, having a basis weight of no more than
60 gsm, better
yet no more than 40 gsm, better yet no more than 30 gsm, preferably no more
than 26 gsm. A
person skilled in the art will recognize that to achieve the desired
properties it is necessary that
CA 03218433 2023- 11- 8
27
WO 2022/237925
PCT/CZ2022/050052
the nonwoven fabric according to the invention comprises at least a minimum
amount of
material. In accordance with this presumption, in such cases a nonwoven fabric
according to
the invention may be used, having a basis weight of at least 6 gsm, better yet
8 gsm, preferably
at least 10 gsm.
In other cases, at least when using the nonwoven fabrics according to the
invention to produce
articles such as disposable clothing articles, parts of absorbent cores of
diapers, wipers or
dusters, higher basis weights of no more than 150 gsm, preferably no more than
100 gsm, may
be used. The optimum basis weight is determined by various necessities
associated with the
individual methods of use as well as by material costs.
In the following examples 1-11 of the production of nonwoven fabric, one layer
of bicomponent
fibers of the core/sheath type having an average thickness of 14-17 microns
with a weight ratio
of components core:sheath = 80:20 was prepared using a spunbond-type spinneret
using a
REICOFIL 4 technology at a nozzle output of 220-225 kg/h/m on a pilot line in
at STFI
(Sachsisches Textilforschunginstitut e.V.). The type of aliphatic polyester
used in the individual
components and the type and amount of additive is shown in Table 5 for
individual examples.
The Ingeo type represents products of the company Nature Works and the Lumina
type
represents products of the company Total Corbion. Examples 1,3 and 9 represent
comparative
compositions without an addition of the additive according to the invention.
The sheaths of
Examples 4-8 and 10-11 include PBAT (Polybutylene adipate terephthalate) ¨ an
aromatic
polyester ¨ in an amount not exceeding 5 wt. % of the component (sheath) in
addition to an
aliphatic polyester and an additive according to the invention. The batt was
thermally bonded
using a pair of hot calender roller 50, 51 (flat roller, patterned roller),
one of which is provided
with an elevated pattern known as gravure U 2888 (by Ungricht) with a total
bonding area of
18.1 %. The values of the temperature of the rollers and the compression are
also shown in
Table 5 and the measured properties of the produced nonwoven fabric are shown
in following
Table 6.
CA 03218433 2023- 11- 8
WO 2022/237925 28
PCT/CZ2022/050052
"z $ c u i 4-I 0 .
o ,-,,, ti=z,' c7,i
ci) ,i) '' '
2
2
CD
.71-,' ¨ -i= O ¨
:, O O
.õ ._. ,c
," o-. o
g 3.
7
0 0
-.7_., g c
' 5 8 ¨2 6> = -8 = u , ' ; -, -.5
ci..) g _ .4,2, ;--i ..--
cu (6,.), Az-, c) -,,=, cu
w 8 :¨ sLI., `) = (-
7)' --(uct ;¨, 0 70 ;--,Z 70
7:$ .Fi''
8 ct = t =
=
E- .3
1 PLA-Luminy L130 PLA-Luminy L175
145 25 50 140 138
2 PLA-Luminy L130 PLA-Luminy L175
0.3 % EBS 145 25 50 140 138
3 PLA-Ingeo 6100 D PLA-Ingeo 6752 D -
148 25 50 140 138
4
PLA-Ingeo 6100 D PLA-Ingeo 6752 D 0.2 % EBS 148 25 50 140 138
PLA-Ingeo 6100 D PLA-Ingeo 6752 D 0.3 % EBS 148 25 50 140 138
6
PLA-Ingeo 6100 D PLA-Ingeo 6752 D 0.3 % EBS 175 20 50 140 138
7
PLA-Ingeo 6100 D PLA-Ingeo 6752 D 0.3 % EBS 230 15 50 140 138
8
PLA-Ingeo 6100 D PLA-Ingeo 6752 D 0.5 % EBS 148 25 50 140 138
9 PLA-Luminy L130 PLA-Luminy LX930 -
147 25 50 138 135
PLA-Luminy L130 PLA-Luminy LX930 0.2 % EBS 148 25 50 140 138
11 PLA-Luminy L130 PLA-Luminy LX930 0.3 % EBS 148 25 50 140 138
Table 5: Polymer composition and process settings of Examples 1-11
9 --- 9 -;-
t._, V2 ,õ--,-:
7
CD 7
, ct '¨' El = =A' ¨ =
.''.
.c)
1=1
a) -,a, ,......, _. ,_. ,. -,.,
1= c,c:
,,,.., _.., -, c,,, ,,,,. anii "8 E 2.a.) Q 0 E
cl.a) L)
Tn.' '-------,;,,, 7
,D0E¨ oE
L.) v¨
g - 8
, = n ' g
g
2 =¨ =
w
0-2, =F_, uci, 15,-, 2 =F_, u
._
,.., ,..,
¨ ¨ 0 õ õ
t,0 =
=--, to,_= __., =
to,_2
0 ,_0
ci)
1 PLA-Luminy L175 27 6
7 18
2 PLA-Luminy L175 0,3 % EBS 38
41 % 9 64% 12 15
3 PLA-Ingeo 6752 D - 14 - 3
- 3 13
4 PLA-Ingeo 6752 D 0,2 % EBS 37
165% 10 269% 6 8
5 PLA-Ingeo 6752 D 0,3 % EBS 38
177 % 10 271 % 6 9
6 PLA-Ingeo 6752 D 0,3 % EBS 29
N/A 7 N/A 5 6
7 PLA-Ingeo 6752 D 0,3 % EBS 17
N/A 4 N/A 3 6
8 PLA-Ingeo 6752 D 0,5 % EBS 39
184% 10 266% 6 8
9 PLA-Luminy LX930 - 18 - 10
- 9 21
10 PLA-Luminy LX930 0,2 % EBS 55 200%
25 138% 21 26
11 PLA-Luminy LX930 0,3 % EBS 57 210%
27 156% 21 27
Table 6: Properties of the nonwoven fabric produced according to Examples 1-11
(columns
1-3 from the Table 5 are shown again for better orientation)
5
CA 03218433 2023- 11- 8
WO 2022/237925 29
PCT/CZ2022/050052
All examples represent a combination of various differing types of PLA from
two different
producers with the type with a lower melting temperature always being included
in the sheath.
The strength of the nonwoven fabric according to the invention always
exhibited a significant
increase, ranging from an increase of a half (+41 % in Example 2) to a three-
fold increase
(+200 % in Examples 10 and 11). A varying degree of increase indicates that
different
commercially available types of polymers are at a varying distance from the
desired state,
which is achieved using the described additive.
Examples 1 and 2 represent the effect of an additive (in this case EBS) on the
strength of a
thermally bonded (in this case by calender) nonwoven fabric produced from an
aliphatic
polyester (in this case PLA). Comparative example 1 represents a composition
with 100 % of
PLA arranged in the bicomponent fiber such that the constituent with a lower
melting point
makes up the sheath. Example 2 represents the same polymer composition except
that EBS
additive is added to the sheath. A marked increase of strength is immediately
observed (+41
% in MD and +64 % in CD direction). Fig. 2A, 2B also shows a clear difference
in the
appearance of the bonding impressions, where the fibers in bonding impression
on the
nonwoven fabric according to Example 1 look like merely stuck to each other,
while the
fibers in the bonding impression on the nonwoven fabric according to Example 2
are sintered
in the bonding impression and form a significantly stronger unit.
Examples 4-8 and 9-10 show a material with an addition of an aromatic
polyester (PBAT) in
the sheath, namely in a concentration of about 2 % to almost 5 %. In none of
the cases has the
addition increased to a value of 5 %. It is clear from the results that the
described addition of
aromatic polyester does not limit the positive effect of the additive. On the
contrary, a
possible synergistic effect is shown.
Examples 6 and 7 show a nonwoven fabric according to the invention with a
lower basis
weight (20 and 15 gsm). Even though standards without an additive for a
calculation of the
strength increase are not available, a comparison with Example 3 (25 gsm)
makes clew that a
significant increase in strength must have occurred. The nonwoven fabric
according to the
invention having a basis weight of 15 gsm (Example 7) has a higher strength
than the
comparative nonwoven fabric without additives having a basis weight of 25 gsm
(Example 3).
The nonwoven fabric in accordance with the invention can be prepared e.g. on a
laboratory
production line of UTB Zlin University. This laboratory production line with a
model label
LBS-300 allows for production of monocomponent or bicomponent fibers for
nonwoven
CA 03218433 2023- 11- 8
WO 2022/237925 30
PCT/CZ2022/050052
fabrics of the spunbond or meltblown type. Its extrusion system which consists
of two
extrusion machines can heat up polymers to temperatures up to 450 C. Fibers
for nonwoven
spunbond-type fabrics can be produced using a spunbond-type extrusion machine
containing
72 orifices (having a diameter of 0.35 mm and a length of 1.4 mm) on a square
area of 6x6
cm. There are several possible arrangements of the extrusion tool for
processing of
bicomponent fibers ¨ core/sheath, components arranged in parallel, segmented
pie or islands
in the sea. The system is open; in the inlet system, the pressure of the
extrusion air is available
up to the level of 150 kPa. The filaments can be retrieved in the original
state or laid on a belt,
moving at a speed in the range of 0.7 to 12 m/min. The final length of the
product is 10 cm at
the maximum. The total output of the line can be set in the range of 0.02 to
2.70 kg/h. The
final basis weight can be set within a range of 30 to 150 g/m2. The laboratory
production line
was used for producing layers described in Examples 12-13.
In the following Examples 12-13, one layer of bicomponent fibers was produced,
the layer
being of the core/sheath type and having an average diameter of 16 microns
with a mass ratio
of the components core:sheath equal to 80:20 with the output of the nozzle
being 0.44
g/min/capillary and the air pressure set to 85 kPa. The core was made up of
PLA polymer
(type Ingeo 6100D of Nature Works) and the sheath made up of a composition of
PLA (type
Ingeo 6752 of Nature Works) and an additive. The fibre layer was laid on a
moving porous
belt and thermally bonded at the speed of 7 m/min using a pair of hot calender
rolls 50, 51
(flat roller 102 C, patterned roller 102 C), one of them being provided with a
raised oval-
shaped pattern with a bonding surface of 25% (see Fig. 5).
Example 12 represents a comparative sample, wherein the sheath composition
does not
contain any additives.
Examples 13 represents a solution in accordance with the invention, wherein
the sheath
composition contains 0.2% of behenamide.
Both samples were produced with a basis weight of 125 g/m2.
Example Additive for the Strength MD % increase of
Elongation MD
first component [N] MD strength
(sheath) compared to the
wt. % comparative
sample
CA 03218433 2023- 11- 8
WO 2022/237925 31
PCT/CZ2022/050052
12 3.2
5.1
13 0.23 % 8.4 + 163 %
4.9
behenamide
Table 7: Properties of the produced nonwoven fabric according to Examples 12-
13
Behenamide, the selected representative of the amide group (i), exhibits an
effect similar to
the one observed in EBS. The additive significantly increases the strength of
the nonwoven
fabric (by 163 % in this case). Fig. 5 depicts SEM photos of Examples 12 and
13, wherein the
cause of this increase can be clearly seen. While in Example 12 it is clear
that the bonding
impressions do not interconnect the fabric properly and across its entire
thickness, Example
13 (according to the invention) displays bonding impressions across the entire
thickness of the
nonwoven fabric (particularly in the cross-sectional view).
Measurement methodology
-Basis weight" of a nonwoven fabric is measured using a measurement
methodology in
accordance with the standard EN ISO 9073-1:1989 (corresponding to a
methodology
according to WSP130.1). Ten layers of nonwoven fabric are used for the
measurement, the
size of a sample being 10x10 cm2.
-Strength and elongation of material" is measured using a standard method
EDANA
defined in the specification WSP 110.4.R4 (12), wherein the width of the
sample is 50 mm,
the distance of jaws is 100 mm, the speed is 100 mm/min and the preloading has
a value of
0,1 N.
"Crystallinity", "(latent) heat of crystallization", "temperature of cold
crystallization",
"heat of melting" and "melting temperature" are measured using the measurement
method
ASTM D3417 by means of DSC, wherein the rate of temperature change is 10
C/min in the
measured zone of 25-230 C and with a sample weight of 7.0-7.5 mg.
Industrial applicability
The invention is applicable wherever a nonwoven fabric containing aliphatic
polyesters is
required ¨ for example in the hygienic industry in the form of various
constituents of hygienic
products with absorption capabilities (e.g. baby diapers, incontinence
products, hygienic
products for women, disposable baby changing pads etc.) or in healthcare, e.g.
as a part of
sponges for treatment of wounds and/or protective garments, surgical cover
sheets, underlays
and other products made of barrier materials. Another possible application is
in industrial
CA 03218433 2023- 11- 8
WO 2022/237925 32
PCT/CZ2022/050052
applications, e.g. in the form of parts of protective garments, in filtration,
insulation,
packaging, sound adsorption, shoe industry, automotive industry, furniture
industry etc. The
invention is preferably applicable particularly in applications, for which
renewable resources
origin and partial or full biodegradability are required.
CA 03218433 2023- 11- 8
