Note: Descriptions are shown in the official language in which they were submitted.
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1
CaCO3 in polyester for nonwoven and fibers
The invention relates to a nonwoven fabric, a process for preparing a nonwoven
fabric,
articles containing said nonwoven fabric, and the use of said nonwoven fabric
as well as
to the use of fibers for the manufacture of nonwoven fabrics and the use of
calcium
carbonate as fillers for nonwoven fabrics.
Nonwoven fabrics are sheets or web structures made by bonding together fibers
or
filaments. They can be flat or bulky and, depending upon the process by which
they are
produced and the materials used, can be tailored for a variety of
applications. In
contrast to other textiles such as woven fabrics or knitted fabrics, nonwoven
fabrics
need not to go through the preparatory stage of yarn spinning in order to be
transformed into a web of a certain pattern. Depending on the strength of
material
needed for the specific use, it is possible to use a certain percentage of
recycled fabrics
in the nonwoven fabric. Conversely, some nonwoven fabrics can be recycled
after use,
given the proper treatment and facilities. Therefore, nonwoven fabrics may be
the more
ecological fabric for certain applications, especially in fields and
industries where
disposable or single use products are important such as hospitals, schools or
nursing
homes.
Today, nonwoven fabrics are mainly produced from thermoplastic polymers such
as
polypropylene, polyethylene, polyamides, or polyesters. The advantage of
polyester
fibers or filaments is their high crystallinity, high strength and high
tenacity. Polyethylene
terephthalate (PET) is the most widely used polyester class and is
characterized by
high modulus, low shrinkage, heat set stability, light fastness and chemical
resistance
account for the great versatility of PET. One major drawback of PET is its
slow
crystallization rate, which does not allow reasonable cycle times for
manufacturing
processes such as injection molding. Therefore nucleating agents such as talc
are often
added. However, these heterogeneous particles can act as stress concentrators,
and
thereby, may affect the mechanical properties of the polymer. Therefore,
nucleated PET
is often reinforced with glass fibers.
A talc filled PET is disclosed in the article of Sekelik et al. entitled
"Oxygen barrier
properties of crystallized and talc-filled poly(ethylene terephthalate)"
published in
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Journal of Polymer Science: Part B: Polymer Physics, 1999, 37, 847 to 857.
US 5,886,088 A is concerned with a PET resin composition comprising an
inorganic
nucleating agent. A method for producing a thermoplastic polymer material,
which is
filled with calcium carbonate is described in WO 2009/121085 A1. WO
2012/052778 A1
relates to tearable polymer films comprising a polyester and calcium carbonate
or mica
fillers. The spinning of PET fibers containing modified calcium carbonate was
studied by
Boonsri Kusktham and is described in the article entitled "Spinning of PET
fibres mixed
with calcium carbonate", which was published in the Asian Journal of Textile,
2011,
1(2), 106 to 113.
Extruded fibers and nonwoven webs containing titanium dioxide and at least one
mineral filler are disclosed in US 6,797,377 B1. WO 2008/077156 A2 describes
spunlaid fibers comprising a polymeric resin and one filler as well as
nonwoven fabrics
containing said fibers. Nonwovens of synthetic polymers with an improved
binding
composition are disclosed in EP 2 465 986 A1. WO 97/30199 relates to fibers or
filaments suitable for the production of a nonwoven fabric, the fibers or
filaments
consisting essentially of a polyolefin and inorganic particles.
In view of the foregoing, improving the properties of polyester based nonwoven
fabrics
remains of interest to the skilled man.
It is an object of the present invention to provide a nonwoven fabric having
an improved
soft touch and a higher stiffness. It would also be desirable to provide a
nonwoven
fabric which can be tailored with respect to its hydrophobic or hydrophilic
properties. It
would also be desirable to provide a nonwoven fabric containing a reduced
amount of
polymer without affecting the quality of the nonwoven fabric significantly.
It also an object of the present invention to provide a process for producing
a nonwoven
fabric from a polyester based polymer composition, especially a PET
composition,
which allows short cycle times during melt processing. It is also desirable to
provide a
process for producing a nonwoven fabric which allows the use of recycled
polyester,
especially recycled PET.
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According to one aspect of the present invention, a nonwoven fabric comprising
at least
one polymer comprising a polyester, and at least one filler comprising calcium
carbonate is provided.
According to another aspect, the present invention provides a non-woven fabric
comprising at least one polymer comprising a polyester, and at least one
filler
comprising calcium carbonate, wherein the calcium carbonate is present in the
non-
woven fabric in an amount from 0.1 to 50 wt.-%, based on the total weight of
the non-
woven fabric, and wherein the non-woven fabric comprises at least one polymer
and the
at least one filler in form of fibers and/or filaments having a diameter from
0.5 to 40 pm,
and wherein the polyester is a polyethylene terephthalate, and the calcium
carbonate
has an average particle size d80 from 1.2 to 1.8 pm, and a top cut particle
size of d98
from 4 to 7 pm.
According to still another aspect, the present invention provides a process
for producing
a nonwoven fabric comprising the steps of
a) providing a mixture of at least one polymer comprising a polyester and at
least
one filler comprising calcium carbonate,
b) forming the mixture into fibers, filaments and/or film-like filamentary
structures,
and
c) forming a nonwoven fabric from the fibers, filaments and/or film-like
filamentary structures.
According to still another aspect, the present invention provides a process
for producing
a nonwoven fabric comprising the steps of
a) providing a mixture of at least one polymer comprising a polyester and at
least
one filler comprising calcium carbonate,
b) forming the mixture into fibers and/or filaments having a diameter from 0.5
to
40pm, and
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c) forming a non-woven fabric from the fibers and/or filaments wherein the
calcium carbonate is present in the non-woven fabric in an amount from 0.1 to
50 wt.-%, based on the total weight of the non-woven fabric,
wherein the polyester is a polyethylene terephthalate, and the calcium
carbonate has an
average particle size d50 from 1.2 to 1.8 pm, and a top cut particle size of
d98 from 4 to 7
pril=
According to still another aspect, the present invention provides an article
comprising
the inventive nonwoven fabric, wherein said article is selected from
construction
products, consumer apparel, industrial apparel, medical products, home
furnishings,
protective products, packaging materials, cosmetic products, hygiene products,
or
filtration materials.
According to still another aspect, the present invention provides the use of
calcium
carbonate as filler in a nonwoven fabric comprising at least one polymer
comprising a
polyester.
According to still another aspect, the present invention provides the use of
fibers for the
manufacture of a non-woven fabric, wherein the fibers comprise at least one
polymer
comprising a polyester and at least one filler comprising calcium carbonate.
According to still another aspect, the present invention provides the use of
calcium
carbonate as filler in a nonwoven fabric comprising at least one polymer
comprising a
polyester, wherein the calcium carbonate is present in the non-woven fabric in
an
amount from 0.1 to 50 wt.-%, based on the total weight of the non-woven
fabric, and
wherein the non-woven fabric comprises at least one polymer and the at least
one filler
in form of fibers and/or filaments having a diameter from 0.5 to 40 pm, and
wherein the
polyester is a polyethylene terephthalate, and the calcium carbonate has an
average
particle size d50 from 1.2 to 1.8 pm, and a top cut particle size of d98 from
4 to 7 pm.
According to still another aspect, the present invention provides the use of
the inventive
nonwoven fabric in construction products, waterproofing, thermal insulation,
soundproofing, roofing, consumer apparel, upholstery and clothing industries,
industrial
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apparel, medical products, home furnishings, protective products, packaging
materials, cosmetic products, hygiene products, or filtration materials.
According to one embodiment the polyester is selected from the group
consisting of
a polyglycolic acid, a polycaprolactone, a
polyethylene ad ipate, a
polyhydroxyalkanoate, a polyhydroxybutyrate, a polyethylene terephthalate, a
polytrimethylene terephthalate, a polybutylene terephthalate, a polyethylene
naphthalate, a polylactic acid, or a mixture thereof, or copolymers thereof,
preferably
the polyester is a polyethylene terephthalate. According to another embodiment
the
polyester has a number average molecular weight from 5000 to 100000 g/mol,
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preferably from 10000 to 50000 g/mol, and more preferably from 15000 to
20000 g/mol.
According to one embodiment the calcium carbonate is ground calcium carbonate,
precipitated calcium carbonate, modified calcium carbonate, surface-treated
calcium
carbonate, or a mixture thereof, preferably surface-treated calcium carbonate.
According to another embodiment the calcium carbonate has an average particle
size
d50 from 0.1 to 3 gm, preferably from 0.4 to 2.5 gm, more preferably from 1.0
to
2.3 gm, and most preferably from 1.2 to 1.8 gm. According to still another
embodiment the calcium carbonate has an top cut particle size d98 from 1 to 10
gm,
preferably from 5 to 8 gm, more preferably from 4 to 7 gm, and most preferably
from 6 to 7 gm. According to still another embodiment the calcium carbonate is
present in the nonwoven fabric in an amount from 0.1 to 50 wt.-%, preferably
from
0. 2 to 40 wt.-%, and more preferably from 1 to 35 wt.-%, based on the total
weight
of the nonwoven fabric.
According to one embodiment of the inventive process, in step b) the mixture
is
formed into fibers, preferably by an extrusion process, and more preferably by
a melt
blown process, a spunbond process, or a combination thereof According to
another
embodiment of the inventive process, the nonwoven fabric is formed by
collecting
the fibers on a surface or carrier. According to still another embodiment of
the
inventive process, steps b) and c) are repeated two or more times to produce a
multilayer nonwoven fabric, preferably a spundbonded-meltblown-spunbonded
(SMS), a meltblown-spunbonded-meltblown (MSM), a spundbonded-meltblown-
spunbonded-meltblown (SMSM), a meltblown-spunbonded-meltblown-spunbonded
(MSMS), a spundbonded-meltblown- meltblown-spunbonded (SMMS), or a
meltblown-spunbonded-spunbonded-meltblown (MSSM) nonwoven fabric.
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It should be understood that for the purpose of the present invention, the
following
terms have the following meaning:
The term "degree of crystallinity" as used in the context of the present
invention
refers to the fraction of the ordered molecules in a polymer. The remaining
fraction is
designated as "amorphous". Polymers may crystallize upon cooling from the
melt,
mechanical stretching or solvent evaporation. Crystalline areas are generally
more
densely packed than amorphous areas and crystallization may affect optical,
mechanical, thermal and chemical properties of the polymer. The degree of
crystallinity is specified in percent and can be determined by differential
scanning
calorimetry (DS C).
"Ground calcium carbonate" (GCC) in the meaning of the present invention is a
calcium carbonate obtained from natural sources, such as limestone, marble,
calcite
or chalk, and processed through a wet and/or dry treatment such as grinding,
screening and/or fractionation, for example by a cyclone or classifier.
The term "intrinsic viscosity" as used in the context of the present invention
is a
measure of the capability of a polymer in solution to enhance the viscosity of
the
solution and is specified in dl/g.
"Modified calcium carbonate" (MCC) in the meaning of the present invention may
feature a natural ground or precipitated calcium carbonate with an internal
structure
modification or a surface-reaction product, i.e. "surface-reacted calcium
carbonate".
A "surface-reacted calcium carbonate" is a material comprising calcium
carbonate
and insoluble, preferably at least partially crystalline, calcium salts of
anions of acids
on the surface. Preferably, the insoluble calcium salt extends from the
surface of at
least a part of the calcium carbonate. The calcium ions forming said at least
partially
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crystalline calcium salt of said anion originate largely from the starting
calcium
carbonate material. MCCs are described, for example, in US 2012/0031576 Al,
WO 2009/074492 Al, EP 2 264 109 Al, EP 2 070 991 Al, or 2 264 108 Al.
For the purpose of the present invention, the term "nonwoven fabric" refers to
a flat,
flexible, porous sheet structure that is produced by interlocking layers or
networks of
fibers, filaments, or film-like filamentary structures.
Throughout the present document, the "particle size" of a calcium carbonate
filler is
described by its distribution of particle sizes. The value dx represents the
diameter
relative to which x % by weight of the particles have diameters less than dx.
This
means that the d20 value is the particle size at which 20 wt.-% of all
particles are
smaller, and the d98 value is the particle size at which 98 wt.-% of all
particles are
smaller. The d98 value is also designated as "top cut". The d50 value is thus
the
weight median particle size, i.e. 50 wt.-% of all grains are bigger or smaller
than this
particle size. For the purpose of the present invention the particle size is
specified as
weight median particle size d50 unless indicated otherwise. For determining
the
weight median particle size d50 value or the top cut particle size d98 value a
Sedigraph
5100 or 5120 device from the company Micromeritics, USA, can be used.
As used herein the term "polymer" generally includes homopolymers and co-
polymers such as, for example, block, graft, random and alternating
copolymers, as
well as blends and modifications thereof.
"Precipitated calcium carbonate" (PCC) in the meaning of the present invention
is a
synthesized material, generally obtained by precipitation following a reaction
of
carbon dioxide and calcium hydroxide (hydrated lime) in an aqueous environment
or
by precipitation of a calcium- and a carbonate source in water. Additionally,
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precipitated calcium carbonate can also be the product of introducing calcium
and
carbonate salts, calcium chloride and sodium carbonate for example, in an
aqueous
environment. PCC may be vaterite, calcite or aragonite. PCCs are described,
for
example, in EP 2 447 213 Al, EP 2,524,898 Al, EP 2 371 766 Al, or unpublished
European patent application no. 12 164 041.1.
In the meaning of the present invention, a "surface-treated calcium carbonate"
is a
ground, precipitated or modified calcium carbonate comprising a treatment or
coating layer, e.g. a layer of fatty acids, surfactants, siloxanes, or
polymers.
Where the term "comprising" is used in the present description and claims, it
does
not exclude other elements. For the purposes of the present invention, the
term
"consisting of" is considered to be a preferred embodiment of the term
"comprising
of'. If hereinafter a group is defined to comprise at least a certain number
of
embodiments, this is also to be understood to disclose a group, which
preferably
consists only of these embodiments.
Where an indefinite or definite article is used when referring to a singular
noun,
e.g. "a", "an" or "the", this includes a plural of that noun unless something
else is
specifically stated.
Terms like "obtainable" or "definable" and "obtained" or "defined" are used
interchangeably. This e.g. means that, unless the context clearly dictates
otherwise,
the term "obtained" does not mean to indicate that e.g. an embodiment must be
obtained by e.g. the sequence of steps following the term "obtained" even
though
such a limited understanding is always included by the terms "obtained" or
"defined"
as a preferred embodiment.
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The inventive nonwoven fabric comprises at least one polymer comprising a
polyester and at least one filler comprising calcium carbonate. In the
following
details and preferred embodiments of the inventive product will be set out in
more
detail. It is to be understood that these technical details and embodiments
also apply
to the inventive process for producing said nonwoven fabric and the inventive
use of
the nonwoven fabric, fibers, compositions, and calcium carbonate.
The at least one polymer
The nonwoven fabric of the present invention comprises at least one polymer
comprising a polyester.
Polyesters are a class of polymers which contain the ester functional group in
their
main chain and are generally obtained by a polycondensation reaction.
Polyesters
may include naturally occurring polymers such as cutin as well as synthetic
polymers
such as polycarbonate or poly butyrate. Depending on their structure
polyesters may
be biodegradable.
According to one embodiment, the polyester is selected form the group
consisting of
a polyglycolic acid, a polycaprolactone, a polyethylene adipate, a
polyhydroxyalkanoate, a polyhydroxybutyrate, a polyethylene terephthalate, a
polytrimethylene terephthalate, a polybutylene terephthalate, a polyethylene
naphthalate, a polylactic acid, or a mixture thereof, or copolymers thereof.
Any of
these polymers may be in pure form, i.e. in form of a homopolymer, or may be
modified by copolymerization and/or by adding one or more substituents to the
main
chain or side chains of the main chain.
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According to one embodiment of the present invention, the at least one polymer
consists of a polyester. The polyester may consist of only one specific type
of
polyester or a mixture of one or more types of polyesters.
The at least one polymer can be present in the nonwoven fabric in an amount of
at
least 40 wt.-%, preferably of at least 60 wt.-%, more preferably of at least
80 wt.-%,
and most preferably of at least 90 wt.-%, based on the total weight of the
nonwoven
fabric. According to one embodiment, the at least one polymer is present in
the
nonwoven fabric in an amount from 50 to 99 wt.-%, preferably from 60 to 98 wt.-
%,
and more preferably from 65 to 95 wt.-%, based on the total weight of the
nonwoven
fabric.
According to a preferred embodiment of the present invention, the polyester is
a
polyethylene terephthalate.
Polyethylene terephthalate (PET) is a condensation polymer and may be
industrially
produced by condensating either terephthalic acid or dimethyl terephthalate
with
ethylene glycol.
PET may be polymerized by ester interchange employing the monomers diethyl
terephthalate and ethylene glycol or direct esterification by employing the
monomers
terephthalic acid and ethylene glycol. Both ester interchange and direct
esterification
processes are combined with polycondensation steps either batch-wise or
continuously. Batch-wise systems require two reaction vessels; one for
esterification
or ester interchange and one for polymerization. Continuous systems require at
least
three vessels; one for esterification or ester interchange, another for
reducing excess
glycols, and still another for polymerization.
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Alternatively, PET may be produced by solid-phase polycondensation. For
example,
in such a process a melt polycondensation is continued until the pre-polymer
has an
intrinsic viscosity of 1.0 to 1.4 dl/g, at which point the polymer is cast
into a solid
film. The pre-crystallization is carried out by heating, e.g. above 200 C,
until the
desirable molecular weight of the polymer is obtained.
According to one embodiment, PET is obtained from a continuous polymerization
process, a batch-wise polymerization process or a solid phase polymerization
process.
According to the present invention, the term "polyethylene terephthalate"
comprises
unmodified and modified polyethylene terephthalate. The polyethylene
terephthalate
may be a linear polymer, a branched polymer, or a cross-linked polymer. For
example, if glycerol is allowed to react with a diacid or its anhydride each
glycerol
will generate a branch point. If internal coupling occurs, for example, by
reaction of
a hydroxyl group and an acid function from branches at the same or a different
molecule, the polymer will become crosslinked. Optionally, the polyethylene
terephthalate can be substituted, preferably with a C1 to Cio alkyl group, a
hydroxyl,
and/or an amine group. According to one embodiment, the polyethylene
terephthalate is substituted with a methyl, ethyl, propyl, butyl, tert.-butyl,
hydroxyl
and/or amine group. The polyethylene terephthalate can also be modified by co-
polymerization, e.g, with cyclohexane dimethanol or isophthalic acid.
Depending on its processing and thermal history, PET may exist both as an
amorphous and as a semi-crystalline polymer, i.e. as a polymer comprising
crystalline and amorphous fractions. The semi-crystalline material can appear
transparent or opaque and white depending on its crystal structure and
particle size.
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According to one embodiment, the polyethylene terephthalate is amorphous.
According to another embodiment, the polyethylene terephthalate is semi-
crystalline,
preferably the polyethylene terephthalate has a degree of crystallinity of at
least 20%,
more preferably of at least 40%, and most preferably of at least 50%.
According to
still another embodiment, the polyethylene terephthalate has a degree of
crystallinity
from 10 to 80%, more preferably from 20 to 70%, and most preferably from 30 to
60%. The degree of crystallinity may be measured with differential scanning
calorimetry (D S C).
According to one embodiment of the present invention, the polyethylene
terephthalate has an intrinsic viscosity, IV, from 0.3 to 2.0 dl/g, preferably
from
0.5 to 1.5 dl/g, and more preferably from 0.7 to 1.0 dl/g.
According to another embodiment of the present invention, the polyethylene
terephthalate has a glass transition temperature, Tg, from 50 to 200 C,
preferably
from 60 to 180 C, and more preferably from 70 to 170 C.
According to one embodiment of the present invention, the polyethylene
terephthalate has a number average molecular weight from 5000 to 100000 g/mol,
preferably from 10000 to 50000 g/mol, and more preferably from 15000 to
20000 g/mol.
The polyethylene terephthalate may be a virgin polymer, a recycled polymer, or
a
mixture thereof. A recycled polyethylene terephthalate may be obtained from
post
consumed PET bottles, preform PET scrap, regrained PET, or reclaimed PET.
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According to one embodiment, the polyethylene terephthalate includes 10 wt.-%,
preferably 25 wt.-%, more preferably 50 wt.-%, and most preferably 75 wt.-%
recycled PET, based on the total amount of polyethylene terephthalate.
According to one embodiment, the at least one polymer consists of a
polyethylene
terephthalate. The PET may consist of only one specific type of PET or a
mixture of
two or more types of PET.
According to one embodiment, the at least one polymer comprises further
polymers,
preferably polyolefines, polyamides, cellulose, polybenzimidazols, or mixtures
thereof, or copolymers thereof Examples for such polymers are
polyhexamethylene
diadipamide, polycaprolactam, aromatic or partially aromatic polyamides
("aramids"), nylon, polyphenylene sulfide (PPS), polyethylene, polypropylene,
polybenzimidazols, or rayon.
According to one embodiment, the at least one polymer comprises at least 50
wt.-%,
preferably at least 75 wt.-%, more preferably at least 90 wt.-%, and most
preferably
at least 95 wt.-% of a polyethylene terephthalate, based on the total amount
of the at
least one polymer.
The at least one filler
According to the present invention, the nonwoven fabric comprises at least one
filler
comprising a calcium carbonate. The at least one filler is dispersed within
the at least
one polymer.
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The use of at least one filler comprising calcium carbonate in polyester-based
nonwoven fabrics has certain advantages compared to conventional nonwoven
fabrics. For example, the hydrophobic or hydrophilic properties of the
nonwoven
web can be adapted to the intended application by using an appropriate calcium
carbonate filler. Furthermore, the use of calcium carbonate fillers allows for
the
reduction of polyesters in the production of nonwoven fabrics without
affecting the
quality of the nonwoven significantly. Moreover, the inventors surprisingly
found
that if calcium carbonate is added as filler to PET, the polymer exhibits a
higher
thermal conductivity, which leads to a faster cooling rate of the polymer.
Furthermore, without being bound to any theory it is believed that calcium
carbonate
acts as nucleating agent for PET, and thus, increases the crystallization
temperature
of PET. As a result the crystallization rate is increased, which, for example,
allows
shorter cycling times during melt processing. The inventors also found that
nonwoven webs manufactured from PET including calcium carbonate fillers have
an
improved soft touch and a higher stiffness compared to nonwoven webs made from
PET only.
According to one embodiment, the calcium carbonate is ground calcium
carbonate,
precipitated calcium carbonate, modified calcium carbonate, surface-treated
calcium
carbonate, or a mixture thereof. Preferably the calcium carbonate is surface-
treated
calcium carbonate.
Ground (or natural) calcium carbonate (GCC) is understood to be a naturally
occurring form of calcium carbonate, mined from sedimentary rocks such as
limestone or chalk, or from metamorphic marble rocks. Calcium carbonate is
known
to exist as three types of crystal polymorphs: calcite, aragonite and
vaterite. Calcite,
the most common crystal polymorph, is considered to be the most stable crystal
form
of calcium carbonate. Less common is aragonite, which has a discrete or
clustered
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needle orthorhombic crystal structure. Vaterite is the rarest calcium
carbonate
polymorph and is generally unstable. Ground calcium carbonate is almost
exclusively of the calcitic polymorph, which is said to be trigonal-
rhombohedral and
represents the most stable of the calcium carbonate polymorphs. The term
"source"
of the calcium carbonate in the meaning of the present application refers to
the
naturally occurring mineral material from which the calcium carbonate is
obtained.
The source of the calcium carbonate may comprise further naturally occurring
components such as magnesium carbonate, alumino silicate etc.
According to one embodiment of the present invention the source of ground
calcium
carbonate (GCC) is selected from marble, chalk, calcite, dolomite, limestone,
or
mixtures thereof Preferably, the source of ground calcium carbonate is
selected from
marble. According to one embodiment of the present invention the GCC is
obtained
by dry grinding. According to another embodiment of the present invention the
GCC
is obtained by wet grinding and subsequent drying.
"Precipitated calcium carbonate" (PCC) in the meaning of the present invention
is a
synthesized material, generally obtained by precipitation following reaction
of
carbon dioxide and lime in an aqueous environment or by precipitation of a
calcium
and carbonate ion source in water or by precipitation of calcium and carbonate
ions,
for example CaC12 and Na2CO3, out of solution. Further possible ways of
producing
PCC are the lime soda process, or the Solvay process in which PCC is a by-
product
of ammonia production. Precipitated calcium carbonate exists in three primary
crystalline forms: calcite, aragonite and vaterite, and there are many
different
polymorphs (crystal habits) for each of these crystalline forms. Calcite has a
trigonal
structure with typical crystal habits such as scalenohedral (S-PCC),
rhombohedral
(R-PCC), hexagonal prismatic, pinacoidal, colloidal (C-PCC), cubic, and
prismatic
(P-PCC). Aragonite is an orthorhombic structure with typical crystal habits of
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twinned hexagonal prismatic crystals, as well as a diverse assortment of thin
elongated prismatic, curved bladed, steep pyramidal, chisel shaped crystals,
branching tree, and coral or worm-like form. Vaterite belongs to the hexagonal
crystal system. The obtained PCC slurry can be mechanically dewatered and
dried.
According to one embodiment of the present invention, the calcium carbonate
comprises one precipitated calcium carbonate. According to another embodiment
of
the present invention, the calcium carbonate comprises a mixture of two or
more
precipitated calcium carbonates selected from different crystalline forms and
different polymorphs of precipitated calcium carbonate. For example, the at
least one
precipitated calcium carbonate may comprise one PCC selected from S-PCC and
one
PCC selected from R-PCC.
A modified calcium carbonate may feature a GCC or PCC with an internal
structure
modification or a surface-reacted GCC or PCC. A surface-reacted calcium
carbonate
may be prepared by providing a GCC or PCC in form of an aqueous suspension,
and
adding an acid to said suspension. Suitable acids are, for example, sulphuric
acid,
hydrochloric acid, phosphoric acid, citric acid, oxalic acid, or a mixture
thereof. In a
next step, the calcium carbonate is treated with gaseous carbon dioxide. If a
strong
acid such as sulphuric acid or hydrochloric acid is used for the acid
treatment step,
the carbon dioxide will form automatically in situ. Alternatively or
additionally, the
carbon dioxide can be supplied from an external source. Surface-reacted
calcium
carbonates are described, for example, in US 2012/0031576 Al, WO 2009/074492
Al, EP 2 264 109 Al, EP 2 070 991 Al, or EP 2 264 108 Al.
A surface-treated calcium carbonate may feature a GCC, PCC, or MCC comprising
a
treatment or coating layer on its surface. For example, the calcium carbonate
may be
treated or coated with a hydrophobising surface treatment agent such as, e.g.,
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aliphatic carboxylic acids, salts or esters thereof, or a siloxane. Suitable
aliphatic
acids are, for example, C5 to C28 fatty acids such as stearic acid, palmitic
acid,
myristic acid, lauric acid, or a mixture thereof. The calcium carbonate may
also be
treated or coated to become cationic or anionic with, for example, a
polyacrylate or
polydiallyldimethylammonium chloride (polyDADMAC). Surface-treated calcium
carbonates are, for example, described in EP 2 159 258 Al.
According to one embodiment, the modified calcium carbonate is a surface-
reacted
calcium carbonate, preferably obtained from the reaction with sulphuric acid,
hydrochloric acid, phosphoric acid, citric acid, oxalic acid, or a mixture
thereof, and
carbon dioxide.
According to another embodiment, the surface-treated calcium carbonate
comprises a
treatment layer or surface coating obtained from the treatment with fatty
acids, their
salts, their esters, or combinations thereof, preferably from the treatment
with
aliphatic C5 to C28 fatty acids, their salts, their esters, or combinations
thereof, and
more preferably from the treatment with ammonium stearate, calcium stearate,
stearic acid, palmitic acid, myristic acid, lauric acid, or mixtures thereof.
According to one embodiment, the calcium carbonate has an average particle
size d50
from 0.1 to 3 gm, preferably from 0.4 to 2.5 gm, more preferably from 1.0 to
2.3 gm,
and most preferably from 1.2 to 1.8 gm. In addition or alternatively, the
calcium
carbonate has an top cut particle size d98 from 1 to 10 gm, preferably from 5
to 8 gm,
more preferably from 4 to 7 gm, and most preferably from 6 to 7 gm.
The calcium carbonate can be present in the nonwoven fabric in an amount from
0.1
to 50 wt.-%, preferably from 0.2 to 40 wt.-%, and more preferably from 1.0 to
wt.-%, based on the total weight of the nonwoven fabric. According to another
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embodiment, the calcium carbonate is present in the nonwoven fabric in an
amount
from 0.5 to 20 wt.-%, from 1.0 to 10 wt.-%, from 5.0 to 40 wt.-%, from 7.5 to
30 wt.-%, or from 10 to 25 wt.-%, based on the total weight of the nonwoven
fabric.
According to one embodiment, the calcium carbonate is dispersed within the at
least
one polymer and is present in an amount from 0.1 to 50 wt.-%, preferably from
0.2 to
40 wt.-%, and more preferably from 1 to 35 wt.-%, based on the total weight of
the at
least one polymer. According to another embodiment, the calcium carbonate is
dispersed within the at least one polymer and is present in an amount from 0.5
to
20 wt.-%, from 1.0 to 10 wt.-%, from 5.0 to 40 wt.-%, from 7.5 to 30 wt.-%, or
from
10 to 25 wt.-%, based on the total weight of the at least one polymer.
According to one embodiment, the at least one filler consists of calcium
carbonate.
The calcium carbonate may consist of only one specific type of calcium
carbonate or
a mixture of two or more types of calcium carbonates.
According to another embodiment, the at least one filler comprises further
mineral
pigments. Examples for further pigment particles comprise silica, alumina,
titanium
dioxide, clay, calcined clays, talc, kaolin, calcium sulphate, wollastonite,
mica,
bentonite, barium sulfate, gypsum, or zinc oxide.
According to one embodiment, the at least one filler comprises at least 50 wt.-
%,
preferably at least 75 wt.-%, more preferably at least 90 wt.-%, and most
preferably
at least 95 wt.-% calcium carbonate, based on the total amount of the at least
one
filler.
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According to one embodiment, the at least one filler is present in the
nonwoven
fabric in an amount from 0.1 to 50 wt.-%, preferably from 0.2 to 40 wt.-%, and
more
preferably from 1 to 35 wt.-%, based on the total weight of the nonwoven
fabric.
According to another embodiment, the at least one filler is dispersed within
the at
least one polymer and is present in an amount from 1 to 50 wt.-%, preferably
from
2 to 40 wt.-%, and more preferably from 5 to 35 wt.-%, based on the total
weight of
the at least one polymer.
According to one aspect of the present invention, the use of calcium carbonate
as
filler in a nonwoven fabric comprising at least one polymer comprising a
polyester is
provided. According to another aspect of the present invention, the use of
calcium
carbonate as filler in a nonwoven fabric is provided, wherein the filler is
dispersed
within at least one polymer comprising a polyester.
According to one preferred embodiment of the present invention, the use of
calcium
carbonate as filler in a nonwoven fabric comprising a polyethylene
terephthalate is
provided. According to another preferred embodiment of the present invention,
the
use of calcium carbonate as filler in a nonwoven fabric is provided, wherein
the filler
is dispersed within at least one polymer comprising a polyethylene
terephthalate.
Preferably, the calcium carbonate is a surface-treated calcium carbonate.
According to a further aspect of the present invention, the use of calcium
carbonate
as filler in a nonwoven fabric fiber, filament and/or film-like filamentary
structure
comprising at least one polymer comprising a polyester, preferably a
polyethylene
terephthalate, is provided. According to a further aspect of the present
invention, the
use of calcium carbonate as filler in a nonwoven fabric fiber, filament and/or
film-
like filamentary structure comprising at least one polymer comprising a
polyester,
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preferably a polyethylene terephthalate, is provided, wherein the filler is
dispersed
within at least one polymer.
The nonwoven fabric
A nonwoven fabric is a flat, flexible, porous sheet structure that is produced
by
interlocking layers or networks of fibers, filaments and/or film-like
filamentary
structures.
According one aspect of the present invention a nonwoven fabric fiber,
filament
and/or film-like filamentary structure comprising at least one polymer
comprising a
polyester and at least one filler comprising calcium carbonate is provided.
According to one embodiment, the nonwoven fabric comprises at least one
polymer
comprising a polyester and at least one filler comprising calcium carbonate,
wherein
the at least one filler is dispersed within the at least one polymer.
According to
another embodiment the nonwoven fabric comprises the at least one polymer and
the
at least one filler in form of fibers, filaments and/or film-like filamentary
structures,
wherein the at least one filler is dispersed within the at least one polymer.
The fibers and/or filaments may have a diameter from 0.5 to 40 gm, preferably
from
5 to 35 gm. Furthermore, the fibers and/or filaments can have any cross-
section
shape, e.g., a circular, oval, rectangular, dumpbell-shaped, kidney-shaped,
triangular,
or irregular. The fibers and/or filaments can also be hollow and/or bi-
component
and/or tri-component fibers.
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In addition to the at least one polymer and the at least one filler, the
nonwoven fabric
may comprise further additives, for example, waxes, optical brighteners, heat
stabilizers, antioxidants, anti-static agents, anti-blocking agents,
dyestuffs, pigments,
luster improving agents, surfactants, natural oils, or synthetic oils. The
nonwoven
fabric may also comprise further inorganic fibers, preferably glass fibers,
carbon
fibers, or metal fibers. Alternatively or additionally, natural fibers such as
cotton,
linen, silk, or wool may be added. The nonwoven fabric may also be reinforced
by
reinforcement threads in form of a textile surface structure, preferably in
form of a
fabric, laying, knitted fabric, knitwear or nonwoven fabric.
According to one embodiment, the nonwoven fabric consists of the at least one
polymer comprising a polyester and the at least one filler comprising calcium
carbonate. According to another embodiment, the nonwoven fabric comprises at
least
one polymer comprising a polyethylene terephthalate and at least one filler
comprising calcium carbonate. According to still another embodiment, the
nonwoven
fabric consists of a polyethylene terephthalate and calcium carbonate.
According to an exemplary embodiment, the nonwoven fabric comprises the at
least
one polymer in an amount from 50 to 99 wt.-%, and the at least one filler in
an
amount from 1 to 50 wt.-%, based on the total weight of the nonwoven fabric,
preferably the at least one polymer in an amount from 60 to 98 wt.-%, and the
at least
one filler in an amount from 2 to 40 wt.-%, and more preferably the at least
one
polymer in an amount from 65 to 95 wt.-%, and the at least one filler in an
amount
from 5 to 35 wt.-%. According to another exemplary embodiment, the nonwoven
fabric consists of 90 wt.-% of a polyester, preferably a polyethylene
terephthalate,
and 10 wt.-% calcium carbonate, preferably a ground calcium carbonate, based
on
the total weight of the nonwoven fabric. According to still another exemplary
embodiment, the nonwoven fabric consists of 80 wt.-% of a polyester,
preferably a
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polyethylene terephthalate, and 20 wt.-% calcium carbonate, preferably a
ground
calcium carbonate, based on the total weight of the nonwoven fabric.
According to one aspect of the present invention, a process for producing a
nonwoven fabric is provided comprising the steps of
a) providing a mixture of at least one polymer comprising a polyester and at
least one filler comprising calcium carbonate,
b) forming the mixture into fibers, filaments and/or film-like filamentary
structures, and
c) forming a nonwoven fabric from the fibers, filaments and/or film-like
filamentary structures.
According to a preferred embodiment, the polyester is a polyethylene
terephthalate
and/or the calcium carbonate is surface-treated calcium carbonate.
The mixture of the at least one polymer comprising a polyethylene
terephthalate and
at the least one filler comprising calcium carbonate provided in process step
a) can
be prepared by any method known in the art. For example, the at least one
polymer
and the at least one filler may be dry blended, melt blended and optionally
formed
into granulates or pellets, or a masterbatch of the at least one polymer and
the at least
one filler may be premixed, optionally formed into granulates or pellets, and
mixed
with additional polymer or filler.
According to one embodiment, in step b) the mixture is formed into fibers,
preferably
by an extrusion process, and more preferably by a melt blown process, a
spunbond
process, or a combination thereof. However, any other suitable process known
in the
art for forming polymers into fibers may also be used.
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Any melt blown process, spunbond process, or a combination thereof, known in
the
art may be employed to form the mixture of at least one polymer and at least
one
filler into fibers. For example, melt blown fibers may be produced by melting
the
mixture, extruding the mixture through a die or small orifices to form fibers,
and
attenuating the molten polymer fibers by hot air. Surrounding cool air can
then be
induced into the hot air stream for cooling and solidifying the fibers. In a
spundbond
process, the mixture can be melt-spun into fibers by pumping the molten
mixture
through a multitude of capillaries arranged in a uniform array of columns and
rows.
After extrusion, the fibers can be attenuated by high velocity air. The air
creates a
draw force on the fibers that draws them down to a desired denier. The
spunbond
process may have the advantage of giving nonwovens greater strength. A second
component may be co-extruded in the spunbond process, which may provide extra
properties or bonding capabilities.
Two typical spunbond processes are known in the art as the Lurgi process and
the
Reifenhauser process. The Lurgi process is based on the extrusion of molten
polymer
through spinneret orifices followed by the newly formed extruded filaments
being
quenched with air and drawn by suction through Venturi tubes. Subsequent to
formation, the filaments are disbursed on a conveyor belt to form a nonwoven
web.
The Reifenhauser process differs from the Lurgi process in that the quenching
area
for the filaments is sealed, and the quenched air stream is accelerated, thus
inducing
more effective entrainment of the filaments into the air stream.
The fibers formed in process step b) may be drawn or elongated to induce
molecular
orientation and affect crystallinity. This may result in a reduction in
diameter and an
improvement in physical properties.
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According to one embodiment of the present invention, in step b) the mixture
is
formed into fibers by combining a melt blown process and a spunbond process.
By combining a meltblown and a spunbond process, a multilayer nonwoven fabric
can be produced, for example, a nonwoven fabric comprising two outer layers of
spunbond fabric and an inner layer of meltblown fabric, which is known in the
art as
spundbonded-meltblown-spunbonded (SMS) nonwoven fabric. Additionally either or
both of these processes may be combined in any arrangement with a staple fiber
carding process or bonded fabrics resulting from a nonwoven staple fiber
carding
process. In such described laminate fabrics, the layers are generally at least
partially
consolidated by one of the optional bonding methods described further below.
The nonwoven fabric produced by the inventive process can be a multilayered
nonwoven fabric, preferably a spundbonded-meltblown-spunbonded (SMS), a
meltblown-spunbonded-meltblown (MSM), a spundbonded-meltblown-spunbonded-
meltblown (SMSM), a meltblown-spunbonded-meltblown-spunbonded (MSMS), a
spundbonded-meltblown-meltblown-spunbonded (SMMS), or a meltblown-
spunbonded-spunbonded-meltblown (MSSM) nonwoven fabric. Said nonwoven
fabric may be compressed in order to ensure the cohesion of the layers, for
example,
by lamination.
According to one embodiment, steps b) and c) of the inventive process are
repeated
two or more times to produce a multilayer nonwoven fabric, preferably a
spundbonded-meltblown-spunbonded (SMS), a meltblown-spunbonded-meltblown
(MSM), a spundbonded-meltblown-spunbonded-meltblown (SMSM), a meltblown-
spunbonded-meltblown-spunbonded (MSMS), a spundbonded-meltblown-
meltblown-spunbonded (SMMS), or a meltblown-spunbonded-spunbonded-
meltblown (MSSM) nonwoven fabric.
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According to one embodiment, in step c) the nonwoven fabric is formed by
collecting the fibers on a surface or carrier. For example, the fibers can be
collected
on a foraminous surface such as a moving screen or a forming wire. The fibers
may
be randomly deposited on the foraminous surface so as to form a sheet, which
may
be held on the surface by a vacuum force.
According to an optional embodiment of the inventive process, the obtained
nonwoven fabric is subjected to a bonding step. Examples of bonding methods
include thermal point bonding or calendering, ultrasonic bonding,
hydroentanglement, needling and through-air bonding. Thermal point bonding or
calendering is a commonly used method and involves passing nonwoven fabric to
be
bonded through a heated calender roll and an anvil roll. The calender roll is
usually
patterned in some way so that the entire fabric is not bonded across its
entire surface.
Various patterns can be used in the process of the present invention without
affecting
the mechanical properties of the web. For instance, the web can be bonded
according
to a ribbed knit pattern, a wire weave pattern, a diamond pattern, and the
like.
However, any other bonding method known in the art may also be used.
Optionally,
binding agents, adhesives, or other chemicals may be added during the binding
step.
According to another optional embodiment of the inventive process, the
obtained
nonwoven fabric is subjected to a post-treatment step. Examples for post-
treatment
processes are direction orientation, creping, hydroentanglement, or embossing
processes.
According to one aspect of the present invention the use of fibers for the
manufacture
of a non-woven fabric is provided, wherein the fibers comprise at least one
polymer
comprising a polyester and at least one filler comprising calcium carbonate.
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According to one preferred embodiment of the present invention the use of
fibers for
the manufacture of a non-woven fabric is provided, wherein the fibers comprise
at
least one polymer comprising a polyethylene terephthalate and at least one
filler
comprising calcium carbonate.
According to another aspect of the present invention the use of a polymer
composition for the manufacture of a non-woven fabric is provided, wherein the
polymer composition comprises at least one polymer comprising a polyester and
at
least one filler comprising calcium carbonate. According to another preferred
embodiment of the present invention the use of a polymer composition for the
manufacture of a non-woven fabric is provided, wherein the polymer composition
comprises at least one polymer comprising a polyethylene terephthalate and at
least
one filler comprising calcium carbonate.
The nonwoven fabric of the present invention can be used in many different
applications. According to one aspect of the present invention, the inventive
nonwoven fabric is used in construction products, waterproofing, thermal
insulation,
soundproofing, roofing, consumer apparel, upholstery and clothing industries,
industrial apparel, medical products, home furnishings, protective products,
packaging materials, cosmetic products, hygiene products, or filtration
materials.
According to another aspect of the present invention, an article comprising
the
inventive nonwoven fabric is provided, wherein said article is selected from
construction products, consumer apparel, industrial apparel, medical products,
home
furnishings, protective products, packaging materials, cosmetic products,
hygiene
products, or filtration materials.
Examples for construction products are house wrap, asphalt overlay, road and
railroad beds, golf and tennis courts, wallcovering backings, acoustical wall
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coverings, roofing materials and tile underlayment, soil stabilizers and
roadway
underlayment, foundation stabilizers, erosion control products, canals
construction,
drainage systems, geomembranes protection and frost protection products,
agriculture mulch, pond and canal water barriers, or sand infiltration
barriers for
drainage tile. Other examples for construction products are fixations or
reinforcements for earth fillings.
Examples for consumer apparel are interlinings, clothing and glove insulation,
bra
and shoulder paddings, handbag components, or shoe components. Examples for
industrial apparel are tarps, tents, or transportation (lumber, steel)
wrappings.
Examples of medical products are protective clothing, face masks, isolation
gowns,
surgical gowns, surgical drapes and covers, surgical scrub suits, caps,
sponges,
dressings, wipes, orthopedic padding, bandages, tapes, dental bibs,
oxygenators,
dialyzers, filters for IV solutions or blood, or transdermal drug delivery
components.
Examples for home furnishings are pillows, cushions, paddings in quilts or
comforters, dust covers, insulators, window treatments, blankets, drapery
components, carpet backings, or carpets.
Examples for protective products are coated fabrics, reinforced plastic,
protective
clothing, lab coats, sorbents, or flame barriers. Examples of packaging
materials are
desiccant packing, sorbents packaging, gifts boxes, files boxes, various
nonwoven
bags, book covers, mailing envelopes, express envelopes, or courier bags.
Examples
of filtration materials are gasoline, oil and air filters, including
filtration
liquid cartridge and bag filters, vacuum bags, or laminates with non woven
layers.
The scope and interest of the invention will be better understood based on the
following examples which are intended to illustrate certain embodiments of the
present invention and are non-limitative.
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Examples
1. Measurement methods and materials
In the following, measurement methods and materials implemented in the
examples are
described.
Particle Size
The particle distribution of the calcium carbonate filler was measured using a
SedigraphTM 5120 from the company Micromeritics, USA. The method and the
instruments are known to the skilled person and are commonly used to determine
grain
size of fillers and pigments. The measurement was carried out in an aqueous
solution
comprising 0.1 wt.-% Na4P207. The samples were dispersed using a high speed
stirrer
and supersonics.
Intrinsic viscosity
The intrinsic viscosity or IV is a measure of the molecular mass of the
polymer and is
measured by dilute solution viscosimetry. All IVs were measured in 60/40 ratio
by
weight of phenol/tetrachloroethane solution, at 25 C according to ASTM D4603
in a
Ubbelohde capillary viscometer. Typically, about 8-10 chips were dissolved to
make a
solution with a concentration of about 0.5%.
Tensile test
The tensile test was carried out in accordance with ISO 527-3 using a 1 BA
(1:2) testing
sample at a speed of 50 mm/min. The properties that were determined via the
tensile
test are the yield stress, the break-strain, the break-stress, and the e-
modulus of the
polymer or polymer composition.
Charpy impact test
The charpy impact test was carried out in accordance with ISO 179-2:1997(E)
using
notched and unnotched testing samples having a size of 50 x 6 x 6 mm.
Materials
Polymer 1: LighterTM S98 PET, commercially available from Equipolymers GmbH,
Germany.
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Intrinsic viscosity: 0.85 0.02; Tg: 78 C; Trn: 247 C; crystallinity: min.
50.
Polymer 2: LighterTM C93 PET, commercially available from Equipolymers GmbH,
Germany.
Intrinsic viscosity: 0.80 0.02; Tg: 78 C; Tm: 247 C; crystallinity: min. 50.
Filler:
OmyafilmTM 707-0G (ground calcium carbonate), commercially available
from Omya AG, Switzerland.
Particle size d80: 1.6 pm; top cut d98: 6 pm.
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2. Examples
Example 1
Testing samples containing polymer 1 only as well as a composition of 90 wt.-%
polymer 1 and 10 wt.-% filler, based on the total weight of the composition,
were
prepared.
The mechanical properties of the testing samples were determined using the
tensile
test described above at a tension of 5 N with a 500 N tester. The results of
the tensile
test are shown in Table 1 below.
Sample A (comparative) Sample B (inventive)
Amount polymer (wt.-%) 100 90
Amount filler (wt.-%) - 10
Thickness (pm) 206 205
Yield stress (N/mm2) 55.9 58.8
Break-strain (%) 600 500
Break-stress (N/mm2) 58.2 46.2
E-modulus (N/mm2) 10 064 11 125
Table 1: Mechanical properties of samples A and B.
The inventive sample B showed a higher yield stress and e-modulus compared to
the
comparative sample A, while the break-strain and break-stress of the inventive
sample B was reduced. Thus, the inventive polymer composition (sample B) had a
higher elasticity and softness compared to the pure PET polymer (sample A).
This
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has a positive effect on the haptic properties of nonwoven fabrics produced
from
such a polymer composition, especially with respect to the softness of the
material.
For example, such a material is more pleasant to wear.
Example 2
Testing samples containing polymer 2 only as well as compositions of 90 wt.-%
polymer 2 and 10 wt.-% filler, and 80 wt.-% polymer 2 and 20 wt.-% filler,
based on
the total weight of the composition, were prepared.
The mechanical properties of the testing samples were determined using the
tensile
test described above at a tension of 4 N with a 20 kN tester and the Charpy
impact
test. The results of the tensile test are shown in Table 2 below.
Sample C Sample D Sample E
(comparative) (inventive) (inventive)
Amount polymer (wt.-%) 100 90 80
Amount filler (wt.-%) - 10 20
Thickness (mm) 2.09 2.08 2.09
Yield stress (N/mm2) 54.1 55.2 68.2
Break-strain (%) 830 578 242
Break-stress (N/mm2) ¨60 ¨50 ¨35
E-modulus (N/mm2) 2280 2640 3070
Charpy (kJ/m2) notched 2.9 1.6 1.0
Charpy (kJ/m2) unnotched 150 72 62
Table 2: Mechanical properties of samples C, D, and E.
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The inventive samples D and E showed a higher yield stress and e-modulus
compared to the comparative sample C, while the break-strain, the break-
stress, and
the impact resistance of the inventive samples C and D was reduced. Thus, the
inventive polymer compositions (samples D and E) had a higher elasticity and
softness compared to the pure PET polymer (sample C). This has a positive
effect on
the haptic properties of nonwoven fabrics produced from such a polymer
composition, especially with respect to the softness of the material. For
example,
such a material is more pleasant to wear.
