U.S. patent application number 17/286374 was filed with the patent office on 2021-11-04 for pulp-containing biodegradable non-woven fabric and method for producing the same.
The applicant listed for this patent is GLATFELTER GERNSBACH GMBH. Invention is credited to Henning Roettger.
Application Number | 20210340700 17/286374 |
Document ID | / |
Family ID | 1000005778174 |
Filed Date | 2021-11-04 |
United States Patent
Application |
20210340700 |
Kind Code |
A1 |
Roettger; Henning |
November 4, 2021 |
PULP-CONTAINING BIODEGRADABLE NON-WOVEN FABRIC AND METHOD FOR
PRODUCING THE SAME
Abstract
The present invention relates to a biodegradable non-woven
fabric, a method for producing a biodegradable non-woven fabric and
a wipe or tissue. The biodegradable non-woven fabric comprises
biodegradable fibers and pulp fibers. At least a part of the
biodegradable fibers is entangled with each other. At least a part
of the pulp fibers is covalently bonded to each other by at least
one of the group consisting of a biodegradable binder, a
biodegradable wet-strength agent and a biodegradable binder
fiber.
Inventors: |
Roettger; Henning;
(Kaltenkirchen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GLATFELTER GERNSBACH GMBH |
Gernsbach |
|
DE |
|
|
Family ID: |
1000005778174 |
Appl. No.: |
17/286374 |
Filed: |
October 16, 2019 |
PCT Filed: |
October 16, 2019 |
PCT NO: |
PCT/EP2019/078089 |
371 Date: |
April 16, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D06B 5/22 20130101 |
International
Class: |
D06B 5/22 20060101
D06B005/22 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2018 |
EP |
18200989.4 |
Claims
1. A biodegradable non-woven fabric comprising biodegradable fibers
and pulp fibers, wherein at least a part of the biodegradable
fibers is entangled with each other, and at least a part of the
pulp fibers is covalently bonded to each other by at least one of
the group consisting of a biodegradable binder, a biodegradable
wet-strength agent and a biodegradable binder fiber.
2. The biodegradable non-woven fabric according to claim 1, wherein
substantially all fibers comprised in the biodegradable non-woven
fabric are the biodegradable fibers, the pulp fibers and optionally
the biodegradable binder fiber.
3. The biodegradable non-woven fabric according to claim 1, wherein
the biodegradable fibers comprise cellulosic fibers, in particular
regenerated cellulose fibers.
4. The biodegradable non-woven fabric according to claim 3, wherein
the regenerated cellulose fibers are selected from the group
consisting of viscose or lyocell.
5. The biodegradable non-woven fabric according to claim 1, wherein
the pulp fibers are comprised in an amount of from 20 to 90 wt.-%
based on the total weight of the non-woven fabric, and/or wherein
the biodegradable fibers are comprised in an amount of from 10 to
80 wt.-% based on the total weight of the non-woven fabric.
6. The biodegradable non-woven fabric according to claim 1, wherein
at least a part of the pulp fibers is bonded to each other by a
biodegradable binder fiber, in particular wherein the biodegradable
binder fiber comprises a bicomponent fiber.
7. The biodegradable non-woven fabric according to claim 1, wherein
at least a part of the pulp fibers is bonded to each other by a
biodegradable wet-strength agent, in particular wherein the
biodegradable wet-strength agent is selected from the group
consisting of chitosan, modified starch and cellulose
derivatives.
8. The biodegradable non-woven fabric according to claim 1, wherein
at least a part of the pulp fibers is bonded to each other by a
biodegradable binder, in particular wherein the biodegradable
binder is selected from the group consisting of chitosan, modified
starch, cellulose derivatives, in particular blends of
carboxymethylcellulose and citric acid, and protein based binders,
such as casein.
9. The biodegradable non-woven fabric according to claim 8, wherein
the biodegradable binder further comprises an additive, such as
glycerol, acting as softening agent and/or improving the
flexibility and drapability of the non-woven fabric.
10. The biodegradable non-woven fabric according to claim 1,
showing an increase of material resiliency characterized by a
Circular Bend Stiffness Force determined in accordance with
modified ASTM D 4032-94 as described in the specification of more
than 25%, preferably more than 50% and most preferably more than
75%, compared to a non-woven fabric without any one of a
biodegradable binder fiber, a biodegradable wet-strength agent and
a biodegradable binder.
11. A method for producing a biodegradable non-woven fabric,
comprising the steps of: (a) forming a fibrous web from a fiber
blend comprising biodegradable fibers and pulp fibers or forming a
layer of biodegradable fibers with a layer of tissue; (b)
entangling at least a part of the biodegradable fibers with each
other by subjecting the fibrous web or the fibrous web combined
with a tissue layer to a water-jet treatment; and (c) drying the
entangled fibrous web, wherein the method further comprises at
least one of the following steps: applying a biodegradable binder
to the entangled fibrous web prior to drying the entangled fibrous
web, adding a biodegradable wet-strength agent to the fiber blend,
blending a biodegradable binder fiber to the fiber blend.
12. The method according to claim 11, wherein in step (a) the
fibrous web is formed by a wet-laid process or an air-laid process
or the fibrous web combined with a tissue layer is formed by a dry
laying process such as carding or air-laid.
13. A biodegradable non-woven fabric obtainable by a method
according to claim 11.
14. A wipe or tissue comprising or consisting of the biodegradable
non-woven fabric according to claim 1.
15. The wipe or tissue according to claim 14, wherein the wipe or
tissue is a dry wipe or a wet wipe and/or wherein the wipe or
tissue is selected from the group consisting of facial wipes,
cosmetic wipes, baby wipes, sanitary wipes, kitchen tissue, paper
towel, handkerchiefs, cleaning tissue, cleansing tissue, floor mop
and hard surface cleaning wipe.
16. Use of a biodegradable binder, a biodegradable wet-strength
agent and/or a biodegradable binder fiber for imparting resiliency
to a wipe or tissue comprising a biodegradable non-woven fabric.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a biodegradable non-woven
fabric, a method for producing a biodegradable non-woven fabric and
wipes or tissues comprising the biodegradable non-woven fabric. In
particular, the biodegradable non-woven fabric may be a
plastic-free, entirely compostable non-woven fabric or substrate
suitable for disposable applications, such as wipes or tissues.
BACKGROUND
[0002] Disposable wipes, such as wet toilet wipes or personal care
wipes like baby wipes, facial wipes etc. are very popular for
cleaning the skin of human bodies or facilities in the household
because of their comfort for consumers and efficacy in cleaning.
However, increasing concerns about plastic contamination of the
environment create an increasing demand for plastic-free and fully
compostable/biodegradable substrates for disposable wipes and
similar products.
[0003] Spunlacing (which may also be referred to as
hydroentanglement) and needle punching are technologies
conventionally used for producing non-woven fabric or substrates
suitable as wipes. Spunlacing is a bonding process for wet or dry
fibrous webs where fine, high pressure jets of water penetrate the
fibrous web and cause an entanglement of fibers, thereby providing
fabric integrity. Needle punching is a bonding process where fibers
are mechanically intertwined by needles.
[0004] Spunlace technology only using compostable fibers made of
regenerated cellulose like Viscose/Rayon, Tencel or Cellulose
Acetate or natural fibers like cotton provide a technical solution
for plastic-free and compostable/biodegradable disposable wipes but
is challenged by the significant increase of material cost by
replacing PET fibers commonly used in disposable wipe substrates
(e.g. baby wipes) by compostable fibers at an up to 50% increase of
material cost. Due to the too high material cost, such products so
far have only been used in a niche premium segment but could not
replace standard volume products like baby wipes.
[0005] An established approach to reduce material cost of such
spunlaced substrates is to replace part of the viscose fibers by
pulp providing the required hydrophilic properties of the wipe
substrate. This approach for providing non-woven fabrics resides in
the combined entanglement of a certain amount of relatively short
and fine fibers and a certain amount of longer fibers.
[0006] In general wetlaid/airlaid technology blending fibers and
pulp combined with spunlace technology for bonding without the
application of binders as it is commonly used for the production of
dispersible wipes (moist toilet tissue) as disclosed in EP 2 985
375 A1, the disclosure of which is incorporated herein by reference
or non-dispersible wipe substrates (airlaced) is facing two
limitations in the mechanical integrity of the non-woven structure
especially after exposure to liquid being critical for using such
substrates in applications like baby wipes and personal care wipes
requiring higher mechanical strength and resiliency:
[0007] (i) The material strength is low compared to standard
spunlace materials even if the fiber content is increased compared
to the recipe used for dispersible wipes. As the pulp fibers are
too short and too stiff to be entangled by the hydroentangling
process, they are only entrapped in the structure of the
hydroentangled viscose/tencel fibers but do not meaningfully
contribute to the mechanical strength of the web. Therefore such
materials require a significantly increased basis weight compared
to standard spunlace to achieve similar mechanical strength.
[0008] (ii) As the pulp fibers are only entrapped within the
structure of hydroentangled viscose/Tencel fibers and do not have
bonding points themselves, they can move and clump together after
exposure to liquid/water and mechanical stress and crumpling of the
web destroying the textile structure. Compared to spunlace and
airlaid materials where the majority of fibers are connected by
bonding points creating a 3-dimensional structure preserving a
textile like structure even after exposure to liquid/water and
mechanical stress/crumpling. This behavior is considered as "paper
like" or "similar to standard toilette tissue" and perceived by
consumers as poor performance of the wipe. In addition to this
perceived lack of comfort, the functionality of the wipe negatively
impacted by the clumping/shifting of the pulp fiber as the movement
of the pulp fibers within the structure changes the local
composition of the web in an uncontrolled manner. The creation of
pulp poor areas results in thin spots limiting the barrier and
containment capacity the wipe should provide while areas with an
increased pulp content create increased thickness or even clumps
destroying the desired even surface and textile touch of the
wipe.
[0009] (iii) Linting of pulp fibers results from the lack of
integration of pulp fibers by bonding points to the matrix of the
non-woven material resulting in fibers falling off the wipe during
converting and use when the web is exposed to mechanical stress
(bending, stretching, crunshing . . . ). The loss of pulp fibers
when using a wipe for cleaning purposes is limiting the field of
potential applications and is considered by users as a product
deficiency.
[0010] Thus, the hitherto known technologies face challenges on
cost and technical performance.
OBJECTS OF THE INVENTION
[0011] The present invention aims at overcoming the above described
problems and drawbacks. Thus, it may be an object of the present
invention to provide a biodegradable, compostable non-woven fabric
suitable for disposable applications, such as wipes, with tailored
or adjustable properties, in particular in terms of (wet) strength
and resiliency, and at low cost.
SUMMARY OF THE INVENTION
[0012] The present inventor has made diligent studies and has found
that the mechanical properties (such as strength and/or resiliency)
of a non-woven fabric made by mechanically entangling a blend of
pulp fibers and biodegradable fibers may be improved by (i) adding
a biodegradable binder potentially including softening agents like
glycerol after formation of an entangled textile structure from
biodegradable fibers and pulp fibers, by (ii) adding a preferably
compostable wet-strength agent prior to the head box before
formation of a textile structure from biodegradable fibers and pulp
fibers, and/or by (iii) blending biodegradable binder fibers (in
particular biodegradable thermobonding fibers) to a fiber blend
comprising biodegradable fibers and pulp fibers, these objects can
be solved. Without wishing to be bound by any theory, the present
inventor assumes that by any of the above measures (i) to (iii),
bonding points (in particular covalent bondings) at the pulp fibers
may be created bonding them together and fixing them to an
integrated structure within the structure of the spunlaced fibers.
As a result, a pulp-web-structure may be formed which is integrated
into (or embedded in) the structure of entangled biodegradable
fibers such that a structure is created where the pulp fibers may
not substantially move within the entangled fiber structure even
after exposure to a liquid, such as water, and crumpling the web or
applying mechanical strength to the web. As a result, an extraction
and clumping of pulp fibers may be avoided maintaining the
functionality of the non-woven material. In addition, by tailoring
the ratio of biodegradable fibers and pulp fibers as well as the
content of wet-strength agent, binder and/or binder fiber, it may
be possible to properly adjust the material properties in a wide
range and to avoid pulp fibers moving and clumping after exposing
the substrate to liquid/water and tailoring the desired
web-strength and resiliency. This may allow the design of wipe
substrates with similar properties like spunlace materials also in
the wet state and replacing a high content of compostable fibers by
much lower cost pulp fibers.
[0013] Accordingly, the present invention relates to a
biodegradable non-woven fabric comprising biodegradable fibers and
pulp fibers, wherein at least a part of the biodegradable fibers is
entangled with each other (at least partly entrapping pulp fibers),
and wherein at least a part of the pulp fibers is covalently bonded
(fixed, adhered) to each other (together) by at least one of the
group consisting of a biodegradable binder, a biodegradable
wet-strength agent and a biodegradable binder fiber (thereby
forming a pulp-web-structure integrated into the structure of
entangled biodegradable fibers such that a structure is created
where the pulp fibers form an integrated structure themselves
and/or may not substantially individually move within the entangled
fiber structure even after exposure to a liquid, such as
water).
[0014] The present invention further relates to a method for
producing a biodegradable non-woven fabric, comprising the steps of
(a) forming a fibrous web from a fiber blend comprising
biodegradable fibers and pulp fibers or forming a layer of
biodegradable fibers on a tissue carrier, (b) entangling at least a
part of the biodegradable fibers with each other (thereby enclosing
at least a part of the pulp fiber) by subjecting the fibrous web
(or layer of tissue/fibers) to a water-jet treatment, and (c)
drying the entangled fibrous web (at a temperature sufficient to
cure applied binders), wherein the method further comprises at
least one (such as one, any two or all three) of the following
steps: (i) applying a biodegradable binder to the entangled fibrous
web prior to the drying step (c), (ii) adding a biodegradable
wet-strength agent to the fiber blend, and (iii) blending a
biodegradable binder fiber to the fiber blend.
[0015] In addition, the present invention relates to a
biodegradable non-woven fabric obtainable by a method for producing
a biodegradable non-woven fabric as described herein.
[0016] Moreover, the present invention relates to a wipe or tissue
comprising or consisting of the biodegradable non-woven fabric as
described herein.
[0017] Furthermore, the present invention relates to the use of a
biodegradable binder, a biodegradable wet-strength agent and/or a
biodegradable binder fiber for imparting resiliency to a wipe or
tissue comprising a biodegradable non-woven fabric.
[0018] Other objects and many of the attendant advantages of
embodiments of the present invention will be readily appreciated
and become better understood by reference to the following detailed
description of embodiments and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 shows photographs of a reference sample subjected to
a crumpling test wherein the photograph on the left-hand side
illustrates a flat moistened sample prior to crumpling, the
photograph in the middle illustrates the sample crumpled in a first
and the photograph on the right-hand side illustrates the sample
after crumpling.
[0020] FIG. 2 shows photographs of a sample of a biodegradable
non-woven fabric according to an embodiment of the invention
subjected to a crumpling test wherein the photograph on the
left-hand side illustrates a flat moistened sample prior to
crumpling, the photograph in the middle illustrates the sample
crumpled in a first and the photograph on the right-hand side
illustrates the sample after crumpling.
[0021] FIG. 3 illustrates an exemplary set-up for the 2-point
bending stiffness measurements.
[0022] FIG. 4 illustrates an exemplary set-up for the Circular Bend
Force measurements. The set-up is not drawn to scale.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Hereinafter, details of the present invention and other
features and advantages thereof will be described. However, the
present invention is not limited to the following specific
descriptions, but they are rather for illustrative purposes
only.
[0024] It should be noted that features described in connection
with one exemplary embodiment or exemplary aspect may be combined
with any other exemplary embodiment or exemplary aspect, in
particular features described with any exemplary embodiment of a
biodegradable non-woven fabric may be combined with any other
exemplary embodiment of a biodegradable non-woven fabric, with any
exemplary embodiment of a method for producing a biodegradable
non-woven fabric, with any exemplary embodiment a wipe or tissue
and with any exemplary embodiment of a use and vice versa, unless
specifically stated otherwise.
[0025] Where an indefinite or definite article is used when
referring to a singular term, such as "a", "an" or "the", a plural
of that term is also included and vice versa, unless specifically
stated otherwise, whereas the word "one" or the number "1", as used
herein, typically means "just one" or "exactly one".
[0026] The expression "comprising", as used herein, includes not
only the meaning of "comprising", "including" or "containing", but
may also encompass "consisting essentially of" and "consisting
of".
[0027] Unless specifically stated otherwise, the expression "at
least a part of", as used herein, may mean at least 5% thereof, in
particular at least 10% thereof, in particular at least 15%
thereof, in particular at least 20% thereof, in particular at least
25% thereof, in particular at least 30% thereof, in particular at
least 35% thereof, in particular at least 40% thereof, in
particular at least 45% thereof, in particular at least 50%
thereof, in particular at least 55% thereof, in particular at least
60% thereof, in particular at least 65% thereof, in particular at
least 70% thereof, in particular at least 75% thereof, in
particular at least 80% thereof, in particular at least 85%
thereof, in particular at least 90% thereof, in particular at least
95% thereof, in particular at least 98% thereof, and may also mean
100% thereof.
[0028] In a first aspect, the present invention relates to a
biodegradable non-woven fabric.
[0029] The term "non-woven fabric", as used herein, may in
particular mean a web of individual fibers which are at least
partially intertwined, but not in a regular manner as in a knitted
or woven fabric.
[0030] The term "biodegradable" (which may also be referred to as
"compostable"), as used herein, may in particular mean that the
material concerned, such as the biodegradable non-woven fabric, the
biodegradable fibers, the biodegradable binder fiber, the
biodegradable wet-strength agent, the biodegradable binder and the
like, complies at least with the requirements for industrial
compostability, for instance in accordance with EN 13432, and
preferably also with the requirements for home compostability and
is most preferred also marine biodegradable. The term "marine
biodegradable", as used herein, may in particular mean that the
material biodegrades by more than 90% by weight within 12 month
storage in sea water at min. 15.degree. C. and exposure to
daylight.
[0031] The biodegradable non-woven fabric comprises biodegradable
fibers and pulp fibers.
[0032] In an embodiment, the biodegradable fibers comprise
cellulosic fibers. The term "cellulosic fibers", as used herein,
may in particular denote fibers based on cellulose, in particular
modified or regenerated cellulose fibers, such as fibers prepared
from cellulose, or cellulose derivates, such as ethyl cellulose,
cellulose acetate and the like. The term "regenerated cellulose
fibers", as used herein, may in particular denote manmade cellulose
fibers obtained by a solvent spinning process.
[0033] In an embodiment, the regenerated cellulose fibers may be
selected from the group consisting of viscose (rayon) or lyocell
(tencel).
[0034] Viscose is a type of solvent spun fiber produced according
to the viscose process typically involving an intermediate
dissolution of cellulose as cellulose xanthate and subsequent
spinning to fibers.
[0035] Lyocell is a type of solvent spun fiber produced according
to the aminoxide process typically involving the dissolution of
cellulose in N-methylmorpholine N-oxide and subsequent spinning to
fibers.
[0036] In an embodiment, the biodegradable fibers may have an
average fiber length of from 1 mm to 100 mm, for instance an
average fiber length of from 3 mm to 80 mm, for instance an average
fiber length of from 5 to 70 mm, for instance an average fiber
length of from 10 to 65 mm, for instance an average fiber length of
from 15 to 60 mm, for instance an average fiber length of from 18
to 50 mm, such as an average fiber length of from 20 to 40 mm.
[0037] In an embodiment, the biodegradable fibers may have an
average fiber length of from 1 mm to 12 mm, in particular of from 3
mm to 10 mm. This may be advantageous, in particular when the
non-woven fabric is prepared by an airlaid process.
[0038] In an embodiment, the biodegradable fibers may have an
average fiber length of from 1 mm to 12 mm, in particular of from 3
mm to 8 mm. This may be advantageous, in particular when the
non-woven fabric is prepared by a wetlaid process.
[0039] In an embodiment, the biodegradable fibers may have an
average fiber length of from 10 mm to 100 mm, in particular of from
10 mm to 80 mm. This may be advantageous, in particular when the
non-woven fabric is prepared by an airlay process.
[0040] In an embodiment, the biodegradable fibers may have an
average fiber length of from 15 mm to 60 mm. This may be
advantageous, in particular when the non-woven fabric is prepared
by a carding process.
[0041] In an embodiment, the biodegradable fibers may have a fiber
coarseness of from 0.5 to 10 dtex, in particular from 0.5 to 4.0
dtex or from 1.0 to 10 dtex, such as from 1.0 to 2.5 dtex.
[0042] In an embodiment, the biodegradable fibers may be comprised
in an amount of from 10 to 80 wt.-%, such as in an amount of from
15 to 70 wt.-%, such as in an amount of from 20 to 60 wt.-%, such
as in an amount of from 25 to 50 wt.-%, such as in an amount of
from 30 to 40 wt.-%, based on the total weight of the non-woven
fabric.
[0043] In an embodiment, the pulp fibers may be natural pulp
fibers, in particular pulp fibers of natural origin, such as
softwood pulp fibers or hardwood pulp fibers. Pulp may in
particular denote a (lignocellulosic) fibrous material prepared by
chemically or mechanically separating cellulose fibers from wood or
the like, such as by a kraft process (sulfate process).
[0044] In an embodiment, the pulp fibers may have an average fiber
length of from 1.0 mm to 4.0 mm, for instance from 1.5 mm to 3.5
mm, such as from 2.0 mm to 3.2 mm.
[0045] In an embodiment, the pulp fibers may have a fiber
coarseness of from 0.3 to 3.5 dtex, such as from 0.6 to 2.5
dtex.
[0046] In an embodiment, the pulp fibers may be comprised in an
amount of from 20 to 90 wt.-%, such as in an amount of from 30 to
85 wt.-%, such as in an amount of from 40 to 80 wt.-%, such as in
an amount of from 50 to 75 wt.-%, such as in an amount of from 60
to 70 wt.-%, based on the total weight of the non-woven fabric.
[0047] In the biodegradable non-woven fabric, at least a part of
the biodegradable fibers is entangled with each other. In
particular, at least a part of the biodegradable fibers may be
entangled with each other such that at least a part of the pulp
fibers is entrapped (with)in the entangled biodegradable
fibers.
[0048] The term "entangled", as used herein, may in particular mean
that the biodegradable fibers are at least partly intertwined with
each other, thereby imparting strength, such as tear strength or
tensile strength, to the non-woven fabric. Entangling of the
biodegradable fibers might in particular be achieved by a treatment
of a fibrous web with water jets, as will be explained in further
detail below, which may also be referred to as "hydroentanglement"
or "spunlacing" and the entangled fibers may thus also be referred
to as "hydroentangled fibers" or "spunlaced fibers". Alternatively,
entangling of the biodegradable fibers might be achieved by needle
punching where the biodegradable fibers are mechanically
intertwined by means of needles. Alternatively to blending the
biodegradable fibers and the pulp forming a layer by means of
airlaid or carding or airlay plus airlaid to be fed into the
spunlacing unit, the layer of biodegradable fibers may also be
formed on top of a layer of tissue using carding or airlay or
airlaid technology and then be fed into the spunlacing unit which
is disintegrating the tissue forming a web of at least partially
entangled biodegradable fibers enclosing at least part of the pulp
fibers.
[0049] In the biodegradable non-woven fabric, at least a part of
the pulp fibers is covalently bonded (fixed, adhered) to each other
(thereby forming an integrated pulp layer within the biodegradable
spunlaced fiber structure) by at least one of the group consisting
of a biodegradable binder, a biodegradable wet-strength agent and a
biodegradable binder fiber. As a result of this at least partial
covalent bonding of pulp fibers together, a pulp-web-structure may
be formed which is integrated into (or embedded in) the structure
of entangled biodegradable fibers such that a structure is created
where the pulp fibers may not substantially move within the
entangled fiber structure even after exposure to a liquid, such as
water. Moreover, a clumping of pulp fibers may be substantially
avoided. Therefore, the bonding of the pulp fibers is preferably
initiated by application of heat after entangling the biodegradable
fibers by means of hydroentangling or needle punching.
[0050] In addition to the bonding of the pulp fibers together, at
least one of the group consisting of a biodegradable binder, a
biodegradable wet-strength agent and a biodegradable binder fiber
may optionally, but not necessarily, also bond the biodegradable
fibers, in particular the entangled biodegradable fibers, together
and may optionally, but not necessarily, also bond pulp fibers to
the biodegradable fibers, in particular to the entangled
biodegradable fibers. However, without wishing to be bound by any
theory, it is believed that the (large) majority of the at least
one of the group consisting of a biodegradable binder, a
biodegradable wet-strength agent and a biodegradable binder fiber
bonds the pulp fibers together (rather than bonding to the
biodegradable fibers) thereby forming a pulp-web-structure which
may also (but does need to) bond to the structure of entangled
biodegradable fibers. In addition, the increase in bulkiness due to
the formation of a pulp-web-structure and the resulting integration
or embedding thereof within the structure of entangled
biodegradable fibers is believed sufficient (even without bonding
to the biodegradable fibers) for substantially limiting a free
movement of the pulp within the entangled fiber structure even
after exposure to a liquid, such as water, and for substantially
avoiding extraction and/or clumping. Furthermore, the formation of
a layer of inter-bonded pulp fibers within the structure of
entangled biodegradable fibers may increase the resiliency of the
material.
[0051] In an embodiment, at least a part of the pulp fibers is
bonded to each other by a biodegradable binder fiber. The term
"binder fiber", as used herein, may in particular denote a fiber
that is able to bind (e.g. by thermobonding, by forming covalent
bonds, by ionic interactions or the like) to each other or to other
fibers. Preferably, the biodegradable binder fiber is a
biodegradable thermobonding (or thermally activatable) fiber. The
biodegradable binder fiber may in particular be a biodegradable
thermoplastic fiber. The term "thermoplastic fibers", as used
herein, may in particular denote fibers that soften and/or partly
melt when exposed to heat and are capable to bind with each other
or to other non-thermoplastic fibers, such as cellulose fibers,
upon cooling and resolidifying.
[0052] In an embodiment, the biodegradable binder fiber comprises a
multicomponent fiber, in particular a bicomponent fiber, such as
bicomponent fibers of the sheath-core type. Bicomponent fibers are
composed of two sorts of polymers having different physical and/or
chemical characteristics, in particular different melting
characteristics. A bicomponent fiber of the sheath-core type
typically has a core of a higher melting point component and a
sheath of a lower melting point component.
[0053] For example, the biodegradable binder fiber may comprise
polylactic acid (PLA), polybutylene succinate (PBS),
polybutyratadipate terephthalate (polybutylene adipate
terephthalate, PBAT), and other biodegradable thermoplastic
polymers. Combinations of two or more thereof may also be
applied.
[0054] In an embodiment, the biodegradable binder fiber may be
comprised in an amount of from 0.1 to 30 wt.-%, such as in an
amount of 0.2 to 20 wt.-%, such as in an amount of from 0.2 to 10
wt.-%, such as in an amount of from 0.2 to 7.5 wt.-%, such as in an
amount of from 0.35 to 5 wt.-%, such as in an amount of from 0.5 to
4 wt.-%, based on the total weight of the non-woven fabric.
[0055] In an embodiment, at least a part of the pulp fibers is
bonded to each other by a biodegradable wet-strength agent. The
term "wet-strength agent", as used herein, may in particular denote
an agent that improves the tensile strength of the non-woven web in
the wet state, for instance by forming covalent bonds. In
particular, it may be preferred that the wet-strength agent is
biodegradable. However, it may also be possible to use a
non-biodegradable wet-strength agent (for instance in small amounts
not negatively impacting the biodegradability/compostability) which
may significantly increase the wet tensile strength of the
non-woven fabric.
[0056] For example, the biodegradable wet-strength agent may be
selected from the group consisting of chitosan, modified starch,
cellulose derivatives and others. Combinations of two or more
thereof may also be applied. The term "cellulosic derivatives", as
used herein, may in particular denote chemically modified (for
instance methylated, ethylated, hydroxypropylated, acetylated
and/or carboxylated) cellulose compounds, and may in particular
include cellulose ethers and cellulose esters, such as
methylcellulose, ethylcellulose, hydroxyethyl cellulose,
hydroxypropyl cellulose, carboxymethyl cellulose or cellulose
acetate.
[0057] In an embodiment, the biodegradable wet-strength agent may
be comprised in an amount of from 0.1 to 3 wt.-%, such as in an
amount of from 0.2 to 2 wt.-%, such as in an amount of from 0.35 to
1.5 wt.-%, such as in an amount of from 0.5 to 1 wt.-%, based on
the total weight of the non-woven fabric.
[0058] In an embodiment, the biodegradable non-woven fabric may
comprise a further wet-strength agent, in particular a
non-biodegradable wet-strength agent. An example of the further
wet-strength agent may include an epichlorhydrine resin, such as a
polyamine-polyamide-epichlorohydrine resin.
[0059] In an embodiment, at least a part of the pulp fibers is
bonded to each other by a biodegradable binder. The term "binder",
as used herein, may in particular denote a chemical compound that
is able to bind (e.g. by forming covalent bonds, by ionic
interactions or the like) to two or more fibers, thereby
interconnecting the fibers, resulting in an increased tensile
strength of the web or fabric.
[0060] For example, the biodegradable binder may be selected from
the group consisting of chitosan, modified starch, cellulose
derivatives, in particular blends of carboxymethylcellulose and
citric acid, protein based binders, such as casein, and others.
Combinations of two or more thereof may also be applied. Further
suitable biodegradable binders are disclosed in WO 2014/117964 A1,
the disclosure of which is incorporated herein by reference.
[0061] In an embodiment, the biodegradable binder may be comprised
in an in amount of from 0.05 to 5 wt.-%, such as in an amount of
from 0.1 to 4 wt.-%, such as in an amount of from 0.25 to 3 wt.-%,
such as in an amount of from 0.5 to 2 wt.-%, based on the total
weight of the non-woven fabric.
[0062] In an embodiment, the biodegradable binder further comprises
an additive, such as glycerol, (configured for) acting as softening
agent improving the flexibility and drapability of the (dried
treated) non-woven fabric. In other words, glycerol or similar
softening additives may be added to the biodegradable binder or
wet-strength agent in order to improve the flexibility and
drapability of the dried treated non-woven fabric.
[0063] A wet-strength agent within the meaning of the present
application and a binder within the meaning of the present
application may in particular be distinguished by the time of its
application. A wet-strength agent is typically added to a fiber
blend prior to formation of a fibrous web or textile structure. For
instance, a wet-strength agent may be applied into or prior to a
head box of a paper-making machine. A binder is typically applied
after formation of a fibrous web or textile structure, and may even
be applied after entanglement of the fibrous web. For instance, a
binder may be applied or added to an entangled fibrous web, but
preferable prior to drying the entangled web. It is also feasible
to apply the binder after drying the hydroentangled web but this
would be less efficient due to the necessity of drying the web
twice. A binder fiber may be added to the blend of the other fibers
prior to formation of a fibrous web or textile structure.
[0064] In an embodiment, at least a part of the pulp fibers may be
bonded to each other by a biodegradable wet-strength agent and/or
by a biodegradable binder, and optionally further by a
biodegradable binder fiber. In particular, at least a part of the
pulp fibers may be bonded to each other only by a biodegradable
wet-strength agent; at least a part of the pulp fibers may be
bonded to each other only by a biodegradable binder; at least a
part of the pulp fibers may be bonded to each other by a
biodegradable wet-strength agent and by a biodegradable binder; at
least a part of the pulp fibers may be bonded to each other by a
biodegradable wet-strength agent and by a biodegradable binder
fiber; at least a part of the pulp fibers may be bonded to each
other by a biodegradable binder and by a biodegradable binder
fiber; and/or at least a part of the pulp fibers may be bonded to
each other by a biodegradable binder, by a biodegradable
wet-strength agent and by a biodegradable binder fiber.
[0065] In an embodiment, substantially all fibers comprised in the
biodegradable non-woven fabric may be biodegradable fibers, in
particular substantially all fibers comprised in the biodegradable
non-woven fabric may be the biodegradable fibers, the pulp fibers
and optionally the biodegradable binder fiber described herein. In
other words, it may be possible that the biodegradable non-woven
fabric does substantially not comprise any other fibers than
biodegradable fibers, in particular no other fibers than the
biodegradable fibers, the pulp fibers and optionally the
biodegradable binder fiber described herein. With regard to
embodiments comprising "substantially no other fibers than
biodegradable fibers", other fibers than biodegradable fibers, if
any, may still be present in relatively minor amounts of up to 10,
up to 5, up to 3, up to 2, or up to 1 wt.-% based on the total
weight of the non-woven fabric.
[0066] In an embodiment, the biodegradable non-woven fabric may
have a grammage or basis weight of from 20 to 150 g/m.sup.2, such
as from 30 to 125 g/m.sup.2, such as from 40 to 100 g/m.sup.2, such
as from 50 to 80 g/m.sup.2.
[0067] In an embodiment, the non-woven fabric is non-dispersible in
water, rather than dispersible. The term "dispersible" may in
particular denote the property of a non-woven fabric to be capable
of disintegrating or decomposing in water by applying a relatively
low mechanical energy, such as a situation that typically occurs in
a toilet upon flushing. In particular, when being flushed, a
dispersible non-woven fabric may be no longer intact, for instance
a certain amount of individual fibers or of fiber aggregates may be
released from the fabric and/or the fabric may break to several
pieces. The term "non-dispersible", as used herein, may accordingly
denote the property of the non-woven fabric to be capable of
resisting to disintegration in water upon applying a relatively low
mechanical energy, such as a situation that typically occurs in a
toilet upon flushing.
[0068] In an embodiment, the non-woven fabric may be treated
(impregnated) with a liquid or a lotion. In other words, the
non-woven fabric may further comprise a liquid or a lotion. In such
situation, the non-woven fabric may in particular represent a wet
wipe or wet tissue. The liquid or the lotion is not particularly
limited, and any liquid or lotion customary in the field of wet
wipes or wet tissues may be applied. Typically, the liquid or the
lotion may comprise a solvent, such as water, an alcohol, or
mixtures thereof, surfactants or detergents, skin care agents,
emollients, humectants, perfumes, preservatives etc. depending on
the intended use.
[0069] In an embodiment, the biodegradable non-woven fabric shows
an increase of material resiliency characterized by a Circular Bend
Stiffness Force determined in accordance with modified ASTM D
4032-94 as described further below of more than 25%, preferably
more than 50% and most preferably more than 75%, compared to a
non-woven fabric without any one of a biodegradable binder fiber, a
biodegradable wet-strength agent and a biodegradable binder.
[0070] In an embodiment, the biodegradable non-woven fabric shows
an increase of material resiliency characterized by a bending
stiffness in machine direction (MD) and/or in cross direction (CD)
determined in accordance with modified ISO 5628 (DIN 53 121) as
described further below of more than 25%, preferably more than 50%
and most preferably more than 75%, compared to a non-woven fabric
without any one of a biodegradable binder fiber, a biodegradable
wet-strength agent and a biodegradable binder.
[0071] In a second aspect, the present invention relates to a
method for producing a biodegradable non-woven fabric, in
particular of a biodegradable non-woven fabric as described
herein.
[0072] The method comprises the steps of: [0073] (a) forming a
fibrous web from a fiber blend comprising biodegradable fibers and
pulp fibers or alternatively forming a layer of biodegradable
fibers combined with a tissue/paper layer; [0074] (b) entangling at
least a part of the biodegradable fibers with each other by
subjecting the fibrous web or the fibrous web combined with a
tissue layer to a water-jet treatment; and [0075] (c) drying the
entangled fibrous web.
[0076] The method further comprises at least one (such as one, any
two or all three) of the following steps: [0077] (i) applying a
biodegradable binder to the entangled fibrous web prior to drying
the entangled fibrous web, [0078] (ii) adding a biodegradable
wet-strength agent to the fiber blend, and [0079] (iii) blending a
biodegradable binder fiber to the fiber blend.
[0080] In step (a), the fibrous web may be prepared for instance by
a conventional wet-laid process using a wet-laid machine, such as
an inclined wire or flat wire machine, or a dry-forming air-laid
non-woven manufacturing process. A conventional wet-lay process is
described for instance in US 2004/0129632 A1, the disclosure of
which is incorporated herein by reference. A suitable dry-forming
air-laid non-woven manufacturing process is described for instance
in U.S. Pat. No. 3,905,864, the disclosure of which is incorporated
herein by reference. Thus, the fibrous web may be formed for
instance by a wet-laid process or an air-laid process.
[0081] In an embodiment, the fibrous web is formed by a wet-laid
process. In another embodiment, the fibrous web is formed by an
air-laid process. Also a combination of a carding process or an
airlay process combined with an airlaid process is suitable for
forming a layer of biodegradable fibers combined with a layer of
pulp fibers. Instead of the airlaid process the pulp fibers can
also be fed into the process as a tissue/paper layer getting
combined with the fiber layer prior to entering the hydroentangling
section where the tissue/pulp get disintegrated and blended with
the biodegradable fibers.
[0082] The fiber blend used for forming the fibrous web comprises
biodegradable fibers and pulp fibers and may optionally further
comprise a biodegradable binder fiber and/or a biodegradable
wet-strength agent.
[0083] In step (b), at least a part of the biodegradable fibers are
entangled with each other by subjecting the fibrous web to a
water-jet treatment. In particular, at least a part of the
biodegradable fibers may be entangled with each other such that at
least a part of the pulp fibers may be enclosed (with)in the
entangled biodegradable fibers (the entangled fibrous web of
biodegradable fibers).
[0084] The term "water-jet treatment", as used herein, may in
particular mean a process of mechanically entangling fibers by
giving the fibrous web an impact with jets of water. Water-jet
treatment may also be referred to as hydroentanglement or
spunlacing. Water-jet treatment typically involves the ejection of
fine, high pressure jets of water from a plurality of nozzles on a
fibrous web provided on a conveyor belt or forming-wire. The water
jets penetrate the web, hit the belt where they may be reflected
and pass again the web causing the fibers to entangle. Thus, by
subjecting the fibrous web to the water-jet treatment, the fibers
are entangled, in particular hydroentangled.
[0085] In an embodiment, a biodegradable binder may be applied to
the entangled fibrous web. The biodegradable binder may be applied
in the form of a solution or dispersion to the entangled fibrous
web. For instance, the biodegradable binder may be applied by
spraying or other means of liquid application like a size-press,
foulard or other. It may be favorable to remove excessive water
prior to application of the binder especially in case of spray
application by application of vacuum, pressure or other removing
excessive water to avoid dilution of the binder.
[0086] In an embodiment, a softening agent like glycerol is added
to the biodegradable binder providing an enhanced
flexibility/drapeability (reduced stiffness) of the finished
non-woven especially in the dry state.
[0087] In step (c), the drying of the entangled fibrous web may
preferably be carried out such that the biodegradable binder fiber
softens and/or partly melts, in particular is thermally activated,
and/or that the biodegradable wet-strength agent and/or the
biodegradable binder is cured, in particular undergoes a chemical
reaction. In particular, the drying is preferably carried out at a
(sufficiently high) temperature to thermally activate the
biodegradable binder fiber and/or to cause a chemical reaction of
the biodegradable wet-strength agent and/or the biodegradable
binder, for instance at a temperature of more than 80.degree. C.,
such as more than 100.degree. C., such as more than 120.degree. C.,
such as more than 140.degree. C., such as more than 180.degree. C.,
depending on the specific biodegradable binder fiber, biodegradable
wet-strength agent and/or biodegradable binder used.
[0088] In a third aspect, the present invention relates to a
biodegradable non-woven fabric obtainable by a method for producing
a biodegradable non-woven fabric as described herein. In
particular, a biodegradable non-woven fabric obtainable by a method
for producing a biodegradable non-woven fabric as described herein
may have any of the properties or features of a biodegradable
non-woven fabric according to the first aspect, as described in the
foregoing.
[0089] In a fourth aspect, the present invention relates to a wipe
or tissue comprising or consisting of the biodegradable non-woven
fabric as described herein. In particular, the non-woven fabric
according to the present invention may be usable as a wipe or a
tissue.
[0090] In an embodiment, the wipe or tissue may be a dry wipe or
dry tissue. Dry wipes may be particularly suitable for use as
kitchen tissue/towel, shop floor towel and paper towel, enabling
the soakage of liquids.
[0091] In an embodiment, the wipe or tissue may be a wet wipe or
wet tissue. For instance, the wet wipe may be treated with a liquid
or a lotion, as described in further detail above. Wet wipes may be
particularly suitable for personal care applications cleaning the
skin of a human body, including the private parts thereof. Thus,
wet wipes may be particularly suitable for personal care use such
as facial wipes or baby wipes.
[0092] In an embodiment, the wipe is selected from the group
consisting facial wipes, cosmetic wipes, baby wipes, sanitary
wipes, kitchen towel, paper towel, handkerchiefs (facial tissue),
cleaning tissue, cleansing tissue, floor mop and hard surface
cleaning wipe.
[0093] In a fifth aspect, the present invention relates to the use
of a biodegradable binder, a biodegradable wet-strength agent
and/or a biodegradable binder fiber for imparting resiliency to a
wipe or tissue comprising a biodegradable non-woven fabric (or for
increasing resiliency of a wipe or tissue comprising a
biodegradable non-woven fabric). The biodegradable binder, the
biodegradable wet-strength agent and/or the biodegradable binder
fiber may be in particular those exemplified above. The present
inventors have found that by using a biodegradable binder, a
biodegradable wet-strength agent and/or a biodegradable binder
fiber in a biodegradable non-woven fabric, the resulting non-woven
fabric as well as a wipe or tissue comprising the same may be
imparted with resiliency. The term "resiliency", as used herein,
may in particular denote a property of a textile like structure,
such as an elasticity or capability of at least partly reverting to
an original shape after crumpling. The resiliency may be
characterized for instance by a Circular Bend Stiffness Force
determined in accordance with modified ASTM D 4032-94 and/or a
bending stiffness in machine direction (MD) and/or in cross
direction (CD) determined in accordance with modified ISO 5628 (DIN
53 121) as described in further detail below.
[0094] The present invention is further described by the following
examples, which are solely for the purpose of illustrating specific
embodiments, and are not construed as limiting the scope of the
invention in any way.
EXAMPLES
[0095] A blend of 20 wt.-% of viscose fibers and 80 wt.-% of
natural pulp fibers have been processed on an inclined wire machine
with a basis weight of 60 g/m.sup.2 and hydroentangled by
application of water jets and dried as described in the patent EP 2
985 375 B1.
[0096] As this wetlaid material does not contain any binder, the
substrate is used as "base substrate" to demonstrate the effect of
different binder applications. Due to the lack of binder the
substrate can get "reactivated" by application of the aqueous
binder system simulating an in-line process.
[0097] This layer of entangled fibers has been treated in 3
different ways: [0098] a) An aqueous solution of carboxymethyl
cellulose (0.4 wt. %), citric acid (0.1 wt. %) and sodium
dihydrogenphosphate (0.06 wt. %) is sprayed at room temperature
(25.degree. C.) on the surface of the base substrate described
above so that the solution is evenly distributed on the surface of
base substrate and gets sucked into the material by capillary
force. The sample is dried in a lab oven at 120.degree. C. without
direct contact to a hot surface (air drying). The amount of aqueous
solution of carboxymethyl cellulose and citric acid is chosen to
achieve the following material composition after drying of the
material to constant weight at 120.degree. C. [0099] 19.6 wt. %
viscose fibers [0100] 78.2 wt. % pulp fibers [0101] 1.5 wt. %
carboxymethyl cellulose [0102] 0.5 wt. % citric acid [0103] 0.25
wt. % sodium dihydrogenphosphate [0104] b) An aqueous solution of
carboxymethyl cellulose (0.4 wt. %), citric acid (0.1 wt. %),
sodium dihydrogenphosphate (0.06 wt. %) and glycerol (1 wt. %) is
sprayed at room temperature (25.degree. C.) on the surface of the
base substrate described above so that the solution is evenly
distributed on the surface of the base substrate and gets sucked
into the base substrate by capillary force.
[0105] The sample is dried in a lab oven at 120.degree. C. without
direct contact to a hot surface (air drying). The amount of aqueous
solution of carboxymethyl cellulose and citric acid and glycerol is
chosen to achieve the following material composition after drying
of the material to constant weight at 120.degree. C. [0106] 18.8
wt. % viscose fibers [0107] 75 wt. % pulp fibers [0108] 1.5 wt. %
carboxymethyl cellulose [0109] 0.5 wt. % citric acid [0110] 0.25
wt. % sodium dihydrogenphosphate [0111] 4 wt. % glycerol [0112] c)
An aqueous solution of carboxymethyl cellulose (0.4 wt. %) citric
acid (0.1 wt. %), sodium dihydrogenphosphate (0.06 wt. %) and
epichlorohydrin based wet-strength agent (Kymmene GHP 20, 0.05 wt.
%) is sprayed at room temperature (25.degree. C.) on the surface of
the base substrate described above so that the solution is evenly
distributed on the surface of the base substrate and gets sucked
into the base substrate by capillary force. The sample is dried in
a lab oven at 120.degree. C. without direct contact to a hot
surface (air drying). The amount of aqueous solution of
carboxymethyl cellulose and citric acid and wet-strength agent is
chosen to achieve the following material composition after drying
of the material to constant weight at 120.degree. C. [0113] 19.5
wt. % viscose fibers [0114] 78 wt. % pulp fibers [0115] 1.5 wt. %
carboxymethyl cellulose [0116] 0.5 wt. % citric acid [0117] 0.25
wt. % sodium dihydrogenphosphate [0118] 0.25 wt. % epichlorohydrin
based wet-strength agent
[0119] In order to determine the impact of the treatment of the
hydroentangled blend of viscose and pulp fibers on the mechanical
properties, especially the flexibility and resilience of the base
substrate and the treated samples a), b) and c), the following
material properties got measured which are summarized in table 1
below:
1) Tensile strength ASTM D5035 measured at 200% moisture content 2)
Elongation at break (ASTM D5035) measured at 200% moisture content
3) Circular Bend Stiffness Force modified ASTM D 4032-94 at 200%
moisture content (see below) 4) Bursting pressure (ASTM D774)
measured at 200% moisture content 5) 2-point bending stiffness
modified ISO 5628 (DIN 53 121) at 200% moisture content
[0120] The measurement of the 2-point bending stiffness is used to
characterize the resiliency of the material describing the
capability of a material to resist to get crumpled up.
[0121] Measurement of the 2-point bending stiffness according to
modified ISO 5628 (DIN 53 121):
[0122] The 2-point bending stiffness has been measured according to
a modified ISO 5628 (DIN 53 121) test. FIG. 3 illustrates an
exemplary set-up for the sample measurements. This can be done
either by measuring the force needed to bend a test piece to a
predetermined angle, or by measuring and determining the bending
stiffness, which is an elastic property of the material.
[0123] A test piece (38 mm.times.50 mm) with a defined moisture
content is placed in the clamp. Upon starting the measurement, the
clamp turns slowly to move the free end of the test piece in
contact with the load cell. The test piece is bent to the selected
angle of 30.degree.. The instrument records the force throughout
the measurement process. The clamp then returns to the start
position and the test piece can be released.
[0124] A Lorentzen-Wettre bending tester 016-94281 has been used to
perform the determination of the bending force and the bending
stiffness, using the following parameter set-up: Bending angle
a=30.degree.; Bending length L=1 mm; Bending velocity:
5.degree./s;
Test piece width 38 mm.
[0125] The bending stiffness S.sub.b 30-1 has been computed using
the corresponding formula:
Bending .times. .times. stiffness = Bending .times. .times. force
.times. Bending .times. .times. length .times. .times. L 2 .times.
60 .pi. .times. Bending .times. .times. angle .times. .times.
.alpha. .times. Test .times. .times. piece .times. .times. width
##EQU00001##
[0126] The measurement is repeated 6 times and the mean value of
these measurements is used.
[0127] The measurement of the Circular Bend Force is used to
characterize the resiliency of the material describing the
capability of a material to recover after getting crumpled up.
[0128] Measurement of the Circular Bend Stiffness Force according
to modified ASTM D 4032-94:
[0129] The Circular Bend Stiffness Force has been measured
according to a modified ASTM D 4032-94 test. FIG. 4 illustrates an
exemplary set-up for the Circular Bend Force measurements (not to
scale).
[0130] The Circular Bend Stiffness Force is measured as the force
required to push a sample (38 mm.times.38 mm) with a moisture
content of 200 wt. % positioned on top of an orifice into the
orifice with a piston at a defined penetration distance (see FIG.
3).
[0131] The piston is made of smoothly polished stainless steel with
a length of 72 mm and a diameter of 6.3 mm having tip shaped as a
round-nose with a radius of 3 mm and is used to push the sample
into an orifice in a smoothly polished stainless-steel plate of the
dimensions 102 mm.times.102 mm.times.6.4 mm with a diameter of
18.75 mm. The lap edge of the orifice is at a 45.degree. angel to a
depth of 4.8 mm.
[0132] The force required to push the sample lying flat of the
surface of the orifice with the piston positioned central on top of
the orifice into the orifice is measured using a load cell
positioned between the piston and a drive moving the piston into
the orifice. A Zwick Z.2.5/TN1S has been used to move the piston
and to measure the force.
[0133] The Circular Bend Stiffness Force is defined as the max.
force measured when pushing the sample with the piston at a speed
of 500 mm/min into the orifice to a depth of 6.4 mm. The
measurement is repeated 5 times and the mean value of these
measurements is used.
TABLE-US-00001 TABLE 1 Circular Tensile Tensile Elongation
Elongation Bending Bending bend Bursting strength strength at break
at break stiffness stiffness stiffness pressure MD wet* CD wet* MD
wet* CD wet* MD wet* CD wet* force wet* wet* Sample (N/50 mm) (N/50
mm) (%) (%) (.mu.Nm) (.mu.Nm) (N) (kPa) Reference 7.5 5.4 30.0 48.7
0.48 0.31 0.020 32.8 a) 8.3 4.9 34.6 57.0 1.44 0.62 0.033 36.7 b)
13.1 7.3 27.8 53.0 1.31 0.75 0.025 34.2 c) 16.3 10.8 23.8 46.5 1.59
0.67 0.045 41.2 Circular Tensile Tensile Elongation Elongation
Bending Bending bend strength strength at break at break stiffness
stiffness stiffness MD dry** CD dry** MD dry** CD dry** MD dry** CD
dry** force dry sample (N/50 mm) (N/50 mm) (%) (%) (.mu.Nm)
(.mu.Nm) (N) Reference 16.57 8.42 11.96 31.70 8.71 2.95 0.195 a)
29.28 15.48 8.60 32.49 23.12 7.46 0.452 b) 30.28 16.30 8.22 26.61
19.75 8.51 0.398 c) 29.52 15.13 7.53 28.18 19.07 8.29 0.400
*Samples contain a water content of 200 wt. % **samples have a
moisture content of 8% MD = machine direction of the sample CD =
cross direction of the sample
[0134] The data in table 1 show an increasing value of resilience
of the web against mechanical deformation measured both by the
bending stiffness and the circular bend stiffness force. The
positive effect of adding a wet-strength agent (sample c)) is also
evident as reflected by the increased values at similar binder
content. Comparing both the bending stiffness and the Circular Bend
Stiffness Force (dry) of the reference material and sample a)
reveal the significant increase of material stiffness of the dry
material after application of the binder and the softening effect
of addition of glycerol reducing the material stiffness which is of
importance for the application as dry wipe. For applications as
wet-wipe the added solution/lotion is functioning as a wetting
agent, so that the addition of glycerol may not be required.
[0135] There are no standardized measurements available describing
quantifying the capability of a web to resist crumpling. However,
the effect can be easily demonstrated by soaking the samples to a
water content of 400 wt.-% and crumpling a sample of 20 cm.times.20
cm in the fist.
[0136] FIG. 1 shows photographs of a reference sample subjected to
a crumpling test wherein the photograph on the left-hand side
illustrates a flat moistened sample prior to crumpling, the
photograph in the middle illustrates the sample crumpled in a first
and the photograph on the right-hand side illustrates the sample
after crumpling.
[0137] FIG. 2 shows photographs of a sample of a biodegradable
non-woven fabric according to an embodiment of the invention
subjected to a crumpling test wherein the photograph on the
left-hand side illustrates a flat moistened sample prior to
crumpling, the photograph in the middle illustrates the sample
crumpled in a first and the photograph on the right-hand side
illustrates the sample after crumpling.
[0138] While the reference sample remains as a clump of material
similar to a tissue without wet-strength agent as shown in FIG. 1,
the other samples have the capability to unfold as shown in FIG. 2
which is more distinct the stronger the bonding of the pulp fibers
is which correlates with an increasing burst pressure and circular
bending force.
[0139] The simple crumpling test demonstrates the substantially
increased resiliency of the hydroentangled blend of biodegradable
fibers and pulp fibers by adding a binder after hydroentanglement
which bonds the pulp fibers together forming a layer with integrity
within the structure of the entangled biodegradable fibers. This is
clearly seen by an increase of the Circular Bend Stiffness Force
measuring the resistance of the material against getting crumpled
trying to move the sheet back into the original flat shape prior to
crumpling. Comparing the tensile strength and elongation at break
data of sample a) and the reference reveal that these properties
alone are not suitable to characterize/predict the effect of
increased resiliency.
[0140] While the present invention has been described in detail by
way of specific embodiments and examples, the invention is not
limited thereto and various alterations and modifications are
possible, without departing from the scope of the invention.
* * * * *