U.S. patent application number 11/231214 was filed with the patent office on 2006-05-25 for tissue product with silk fibers and method of making the same.
Invention is credited to Sabine Bogdanski, Juergen Huegel, Siegfried Kurt Martin.
Application Number | 20060108082 11/231214 |
Document ID | / |
Family ID | 34927455 |
Filed Date | 2006-05-25 |
United States Patent
Application |
20060108082 |
Kind Code |
A1 |
Bogdanski; Sabine ; et
al. |
May 25, 2006 |
Tissue product with silk fibers and method of making the same
Abstract
A tissue product comprising a plurality of first fibers and a
plurality of silk fibers and a method of making the tissue product
wherein the silk fibers are a different color than the color of the
first fibers, as assessed by the human naked eye.
Inventors: |
Bogdanski; Sabine;
(Schwalbach, DE) ; Martin; Siegfried Kurt; (Bad
Soden, DE) ; Huegel; Juergen; (Liederbach,
DE) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
34927455 |
Appl. No.: |
11/231214 |
Filed: |
September 20, 2005 |
Current U.S.
Class: |
162/143 ;
162/141; 162/162 |
Current CPC
Class: |
D21H 13/34 20130101;
D21H 27/30 20130101; D21H 21/28 20130101 |
Class at
Publication: |
162/143 ;
162/162; 162/141 |
International
Class: |
D21H 13/34 20060101
D21H013/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2004 |
EP |
04027502.6 |
Claims
1. A tissue product, such as a handkerchief, a toilet tissue, a
facial tissue, a towel or a wet wipe comprising: a plurality of
first fibers having at least a first color; and a plurality of silk
fibers having a second color, wherein the second color of the silk
fibers is different than at least the first color of the first
fibers, as assessed by a human naked eye.
2. The tissue product of claim 1 wherein the first fibers are
cellulosic fibers.
3. The tissue product of claim 1 wherein the first fibers include
non-cellulosic fibers.
4. The tissue product of claim 1 wherein the tissue product
comprises the silk fibers up to about 5% (weight/weight) of total
fibers.
5. The tissue product of claim 1 wherein the tissue product
comprises the silk fibers up to about 0.1% (weight/weight) of total
fibers.
6. The tissue product of claim 1 wherein the silk fibers have an
average fiber length that is equal or less than about 8 mm.
7. The tissue product of claim 1 wherein the tissue product
includes at least one first zone comprising more of the silk fibers
than a second zone with quantitatively fewer of the silk
fibers.
8. The tissue product of claim 1 wherein the second color of at
least some of the silk fibers is blue, green or purple.
9. The tissue product of claim 1 wherein the tissue product further
includes synthetic fibers.
10. The tissue product of claim 9 wherein the synthetic fibers are
a different color than the second color of the silk fibers.
11. The tissue product of claim 9 wherein the first fibers are
cellulosic fibers and the synthetic fibers are a different color
than the first color of the first fibers.
12. The tissue product of claim 1 wherein the tissue product has a
thickness and the silk fibers are non-homogenously distributed
throughout the thickness of the tissue product.
13. The tissue product of claim 1 wherein the tissue product is
comprised in a multi-ply article.
14. A kit comprising the tissue product of claim 1, a packaging
structure in close proximity to the tissue product and graphical
indicia on the packaging structure or on the tissue product,
wherein the graphical indicia indicates the presence of silk within
the tissue product.
15. A process for making a tissue product comprising the steps of:
providing a slurry of first fibers having a first color; providing
silk fibers into the slurry, the silk fibers having a second color
that is different than the first color; depositing the slurry
including the first fibers and the silk fibers onto a paper making
belt; and dewatering the slurry to form a tissue product that
includes the first fibers and silk fibers such that the silk fibers
are visible in the tissue product, as assessed by the naked human
eye.
16. A process for making a tissue product comprising the steps of:
providing a slurry of first fibers having a first color; providing
a second slurry including silk fibers having a second color that is
different than the first color; depositing the first slurry and the
second slurry onto a paper making belt such that the silk fibers of
the second slurry are non-homogeneously distributed onto the paper
making belt; and dewatering the slurry to form a tissue product
that includes the first fibers and silk fibers such that the silk
fibers are visible in the tissue product, as assessed by the naked
human eye.
17. The process of claim 16 wherein the first and the second
slurries are directed into a multiple channel headbox, wherein the
first slurry is directed into a first channel of the multiple
channel headbox and the second slurry is directed into a second
channel of the multiple channel headbox prior to be deposited onto
the paper making belt.
18. The process of claim 16 wherein at least some silk fibers are
provided in the first slurry, wherein the first and the second
slurries are directed into a multiple channel headbox prior to
being deposited onto the paper making belt, and wherein the first
slurry comprises quantitatively fewer of the silk fibers than the
second slurry.
19. The process of claim 16 wherein the silk fibers having the
second color are deposited in onto the paper making belt in at
least a first zone and a second zone, wherein the first zone
includes quantitatively fewer of the silk fibers having the second
color than the second zone.
20. The process of claim 16 wherein the tissue product has a
thickness and the silk fibers having the second color are deposited
onto the papermaking belt such that the silk fibers having the
second color are non-homogeneously distributed throughout the
thickness of the tissue product.
Description
FIELD OF THE INVENTION
[0001] This invention relates to the field of paper and paper
making. In particular the present invention applies to tissue
products and the making of tissue products including silk
fibers.
BACKGROUND OF THE INVENTION
[0002] Paper products, and particularly tissue products, are widely
used by consumers for uses that include contact with the skin. For
example, toilet papers, paper handkerchiefs, paper towels, facial
tissue and wet wipes are all intended to help remove liquid or
solid residues from the human skin. Their conditions of use usually
induce an intimate contact between the article and the human skin.
Such contact can vary in duration, intensity of the forces applied,
and relative movements. In some cases, the contact can lead to
irritation, redness or damage to the skin, especially upon repeated
use.
[0003] Therefore, it is generally desired that the paper products
be soft and/or smooth. Other desired properties include the
strength of the tissue in a wet and/or dry state, and the
absorbency of the tissue.
[0004] Softness, however, is one of the most desired qualities for
such products. Generally, softness can include many interrelated
dimensions or aspects. For example, softness can result from a
tissue's ability to not erode, abrade, or irritate the skin,
ability to leave the skin in a smooth natural condition after use,
ability to enhance the (re-)hydration of the skin via the
deposition of a lotion onto the skin after use, ability to enhance
glide over the skin (low friction), and/or the ability to provide
the user with the feeling of a smooth texture.
[0005] In that regard, the perception of the user plays a key role
in the softness quality of a tissue. The softness perception can be
based on physical properties (such as the smoothness of the surface
of the tissue), or a mix of physical and visual properties (such as
the texture or embossment of the tissue), or on "soft signals"
delivered by the tissue. For example, a tissue having a neutral or
pastel color will often be perceived much softer than a tissue with
a red intense color. These "soft signals" often account as much as
physical properties to the perceived softness of the tissue and
lead to factually measurable better softness of the tissues, as
appreciated by the users.
[0006] Conventionally, softness of a tissue can be increased by the
use of additives in the fiber slurry during the paper making, by
the use of additives in the dry stage of the paper making, and/or
by various surface modifications during the converting phase of the
tissue paper (calendering for example is known to improve
softness). Also, various papermaking technologies can be tailored
to deliver a softer tissue. For example, the layering of slurries
of different fiber compositions or the creping conditions can
affect the softness of a tissue product.
[0007] The selection of fibers used for paper making also plays an
important role in the softness of the tissue paper. Conventionally,
the fiber mix for tissue paper comprises a selection of long or
short cellulosic fibers. Cellulosic fibers usually comprise most,
if not all, the fibers of tissue papers. Other fibers, however, can
be used, such as synthetic fibers. In certain embodiments, silk
fibers can be used in paper making. The silk fibers can be
incorporated into the paper making slurries, possibly in presence
of specific additives. Traditional Japanese silk paper can be made
by using silk fibers to make silk paper. Modified silk protein can
be used in the slurries for papermaking. Alternatively, gels or
coating solutions containing silk proteins can be added to the
surface of a tissue. Silk proteins, however, if not in a form of
naturally occurring fibers or fragments thereof, are not visible
and hence are not used alone for the purpose of the present
invention.
[0008] The use of silk protein and silk gels is described in EP
13060073A (Kawano Paper Co.). The use of modified silk proteins is
described in particular in EP0840824B1 (Kimberly Clark Worldwide
Inc.). Japanese paper containing silk is described in JP2002030593A
and in JP11050397A.
[0009] The use of silk fibers in industrial paper making processes
has been limited by at least two aspects. The silk fibers are
relatively expensive raw materials (several times more expensive
than conventional cellulosic pulp) and second the use of silk
fibers in paper making processes can modify the fine balance of
strength, absorbency and softness that is well controlled in
industrial paper making processes. As such, silk fibers have not
been used in tissue paper produced in large scale, such as for
toilet paper, wipes, paper towels, facial tissue and paper
handkerchiefs.
[0010] Thus, it would be desirable to provide a tissue product that
is perceived by the user as soft, while being suitably strong and
absorbent. It would also be desirable to provide a method of making
a tissue that is perceived as soft by the user. It would also be
desirable to provide a perception of softness in a tissue product
by the incorporation of at least some silk fibers that are visibly
distinct to the user.
SUMMARY OF THE INVENTION
[0011] The present invention provides tissue products such as
toilet tissues, towels, facial tissue, handkerchiefs and/or wipes
comprising a plurality of first fibers and a plurality of silk
fibers. The silk fibers are a different color than at least some of
the plurality of first fibers, as assessed by the human naked
eye.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows one embodiment of a tissue paper of the present
invention, a roll of tissue paper to be used as toilet paper,
comprising colored silk fibers and cellulosic fibers.
[0013] FIG. 2 represents a piece of tissue paper of the
invention.
[0014] FIG. 3 represents a piece of tissue paper of the invention
in a particular embodiment having three stripes comprising colored
silk fibers alternating with zones comprising no colored silk
fibers.
[0015] FIG. 4 represents a multi-ply article comprising the tissue
of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Definitions:
[0017] The following terms are used in the present document with
the following meaning:
[0018] Tissue: a sheet comprising a plurality of interconnected
fibers.
[0019] Tissue paper: a paper product comprising a majority of
cellulosic fibers and made by a paper-making process. Tissue paper
can be dry or impregnated with a limited amount of a lotion or
other substances.
[0020] Tissue product: a product similar in nature to a tissue
paper, as set forth above, but not limited to including at least
some cellulosic fibers and not limited to any particular process
for making the tissue product.
[0021] Toilet tissue: an article comprising tissue and primarily
intended for the cleaning of human body from solid or liquid human
waste.
[0022] Handkerchiefs and facial tissue: articles comprising tissue
and primarily intended for cleaning the human nasal area and/or
removing human nasal waste.
[0023] Towel: an article comprising tissue and primarily intended
for cleaning surfaces and/or objects in households. Towels can be
used as absorbent means in households and may include, for example,
paper towels.
[0024] Wet wipe: an article impregnated with a significant amount
of liquid and primarily intended to wipe the human body. Wipes may
comprise synthetic fibers and/or natural fibers, such as cellulosic
fibers. Wet wipes can comprise a tissue paper.
[0025] Naked eye: the term naked eye as used in this document
refers to uncorrected vision and to corrected vision (i.e. glasses
or contact lenses) but excludes the use of any magnification means
such as a magnifier or a microscope. It further excludes the use of
any means altering the perception of colors (such as substantially
colored glasses or lenses). The "human naked eye" performing the
evaluations is in any case subjected to the selection and
qualification described hereafter.
DESCRIPTION OF THE INVENTION
[0026] Different formation processes such as air-laid or wet-laid
substrate processes can be used to make the fibrous web of the
present invention. In a wet-laid process, tissue papers are
produced by laying a slurry of paper making fibers with high water
content onto a screen (or paper making belt) and gradually removing
the water from the native web, until obtaining an essentially dry
web of paper. The slurry of paper making fibers can be laid as a
homogeneous layer or as multiple sub-layers each comprising a
different fiber mix (so called "layering technology"). The water
removing operations can be of many different types and are widely
described in the art. This includes pressing the web in a nip,
possibly in presence of water absorbing felt, passing hot air
through the paper web (so called "through-air dried paper" (TAD),
elevating the temperature of the web to evaporate the humidity
(e.g. Yankee drier), moving the paper on a structured surface while
forcing the water out of the web, and many more technical options.
The above described phase of paper-making is the so-called "wet
stage" of paper-making. The wet-stage is generally considered to
end when the tissue paper is sufficiently dry to be rolled into a
roll of tissue paper. Any operation made before the creation of the
primary roll of tissue paper is generally considered to be part of
the wet-stage.
[0027] In a second phase ("converting", or "dry stage"), the paper
web, essentially dry, is usually converted into an article of
manufacture (such as a paper handkerchief or a roll of toilet
paper). The converting operations can include, but are not limited
to, calendering the web, structuring the web, embossing the web,
cutting it to the desired dimensions, applying a lotion or other
substance on the surface of the tissue paper, folding, printing the
tissue paper, winding the web, and packaging the article. This
second phase is also applicable to air-laid processes.
[0028] The wet-laid papermaking process is a very complex process
in which the fiber slurry composition drives many of the subsequent
process conditions to deliver a paper web of the desired
properties. For example, hardwood fibers will provide for a paper
web having different properties (such as softness and tensile
strength) than softwood fibers.
[0029] It is been found that all of the above operations are
compatible with the incorporation of silk fibers into the
papermaking slurry, without modification, adaptation or fine tuning
of the complex papermaking process. This finding is particularly
relevant with the relatively low amount of silk fibers of some
embodiments of the present invention. It has further been found
that the properties of the paper web induced by the fiber mix used
and the process condition are altered by the presence of silk
fibers. For example, it is known that silk fibers can be relatively
less absorbent than other fibers commonly used in tissue paper.
However, in all the embodiments of the present invention it has
been found that the absorbency remains substantially the same as
the absorbency of a corresponding paper web having no silk
fibers.
[0030] In one aspect, the present invention relates to the process
of making a tissue comprising silk fibers. The silk fibers are of a
color different from the color of at least some of the cellulosic
fibers. The process comprises the steps of providing silk fibers in
a dry or wet form. Providing the silk fibers in a wet form means
that the silk fibers are provided together with a liquid carrier.
The carrier can be water or any other suitable liquid, i.e. the
silk fibers are mixed with and/or diluted into an aqueous solution
or suspension. The aqueous solution or suspension can comprise
additional chemicals (such as softeners, strength agents or other
paper-making additives). The carrier can also be a non-aqueous
substance (for example a glue, an additive or a mixture of
chemicals). Providing the silk fibers in a dry form means that the
silk fibers are essentially dry when added to the tissue paper.
Typically, this will be done when the fibers of the tissue paper
have been formed into at least a precursor web and at least
partially dried (i.e. the fibers are no longer merely in a slurry,
but have been provided onto a forming member and at least partially
dewatered). The silk fibers can be provided in a dry form together
with other chemicals or additives, typically also in a dry form.
The silk fibers can be added at the wet stage of the paper making
process or in the dry end or converting part of the paper making
process.
[0031] In some embodiments of the present invention, the silk
fibers can be added to the paper-making slurry before or during the
transfer of the slurry to the headbox. Single-channel or multiple
channel headboxes can be used. A single channel headbox generally
leads to a homogeneous presence of silk fibers throughout the depth
of the native paper web. On the contrary, the process conditions
can be selected as to ensure that the silk fibers are
non-homogeneously distributed throughout the thickness of the
tissue paper. The fibers can be provided in quantitatively higher
amount on one side of the tissue paper compared to the second side
of the tissue paper formed or being formed in the process. For
example, a first conventional slurry (comprising silk fibers) can
be fed to a multiple channel headbox together with a second slurry
that does not comprise silk fibers or comprises quantitatively
fewer silk fibers than the first slurry. The configuration leads to
a non-homogeneous (i.e. heterogeneous) native paper web that
exhibits one first side with silk fibers (from the first slurry)
while the other side does not comprise silk fibers or comprises
quantitatively fewer silk fibers (from the second slurry) than the
first side. In some embodiments, the second slurry can comprise at
least about 25%, at least about 50%, or at least about 75% fewer
silk fibers than the first slurry. In another embodiment the second
slurry does not comprise silk fibers. Alternatively, this can be
done by adding the silk fibers on one side of the tissue being
formed, after the initial layering of the cellulosic fibers. In
another embodiment, the silk fibers are added (from example by
spraying, possibly with the addition of a binder and/or a glue)
when the paper is already in a dry or semi-dry stage. This addition
can be selectively on one side only of the tissue paper being
formed or quantitatively more on one side, and improve thereby
visibility of the silk fibers.
[0032] In one embodiment of the present invention the sides of the
tissue paper are positioned in the finished article so as to expose
the silk-containing side (or the side comprising quantitatively
more silk fibers) to the external side of the article (i.e. to the
skin-contacting surface of the article during regular use of the
article or to the most visible side in-use).
[0033] In one embodiment the tissue paper of the present invention
is of a basis weight of between about 10 gsm (grams per square
meter) and about 80 gsm or between about 20 and about 30 gsm.
[0034] It has been found that the present invention can achieve the
desired effect when using silk fibers having an average fiber
length of about 3 to about 4 mm (the "average fiber length" is the
average length of the fibers, according to known methods of the
art, when counting a representative sample of fibers). That length
is close to the usual length of softwood fibers. The range has been
found to combine a good compatibility with the equipment and
process conditions usually used (for example no special filter to
be used in the paper making process), with an adequate
noticeability of the fibers on the dry tissue, especially when the
fibers are colored and thus enhance the perception of softness. The
use of silk fibers lengths in the ranges of about 2 to about 5 mm,
or about 1 to about 8 mm is also contemplated.
[0035] The silk fibers are in most cases natural silk fibers and
can be so-called "Tussah" fibers that have been mechanically
processed to reach the desired length. Such fibers are, for
example, available from SEAL International Limited, Ladywell Mills,
Hall Lane, Bradford, West Yorkshire, BD4 7DF, England. The use of
other types of silk fibers is also contemplated, such as mulberry
silk or other silk types. More generally, the invention can be
reproduced with many other types of silk-like fibers of animal
origins. The other fibers of the present invention are typically
conventional cellulosic fibers such as common hardwood fibers or
industrial softwood fibers. The fibrous structure may also include
any suitable non-cellulosic fibers such as, for example, synthetic
fibers or other natural fibers. The synthetic fibers can be any
material, for example, those selected from the group consisting of
polyolefins, polyesters, polyethylene, polyamides,
polyhydroxyalkanoates, polysaccharides, and any combination
thereof. More specifically, the material of the synthetic fibers
can be selected from the group consisting of polypropylene,
polyethylene, poly(ethylene terephthalate), poly(butylene
terephthalate), poly(1,4-cyclohexylenedimethylene terephthalate),
isophthalic acid copolymers, ethylene glycol copolymers,
polycaprolactone, poly(hydroxy ether ester), poly(hydroxy ether
amide), polyesteramide, poly(lactic acid), polyhydroxybutyrate,
starch, cellulose, glycogen and any combination thereof.
Nonlimiting examples of suitable hydroxyl polymers include
polyvinyl alcohol, starch, starch derivatives, chitosan, chitosan
derivatives, cellulose derivatives, gums, arabinans, galactans and
mixtures thereof. Further, the synthetic fibers can be single
component (i.e. single synthetic material or mixture makes up
entire fiber), bi-component (i.e. the fiber is divided into
regions, the regions including two different synthetic materials or
mixtures thereof) or multi-component fibers (i.e. the fiber is
divided into regions, the regions including two or more different
synthetic materials or mixtures thereof) or any combination
thereof. Also, any or all of the synthetic fibers may be treated
before, during or after the process of the present invention to
change any desired property of the fibers. For example, in certain
embodiments, it may be desirable to treat the synthetic fibers
before or during the papermaking process to make them more
hydrophilic, more wettable, etc. In some embodiments the synthetic
fibers can be between about 10 and about 100 mm long, alternatively
between about 20 and about 80 mm, between about 40 and about 60 mm
long or between about 45 and about 55 mm long on average.
[0036] The silk fibers in the present invention are a different
color or tone than the general tone or color of at least some of
the cellulosic fibers. Usually, cellulosic fibers in tissue
products for use as toilet paper, paper towels, paper
handkerchiefs, facial tissue and wipes are relatively uniformly
white or a very light grey color. However, other colors can be
used, so long as the silk fibers remain visible.
[0037] The color of the silk fibers can originate from their native
color or from processes or treatments to which the silk is
submitted to in order to transform it into a suitable material. In
certain embodiments, the silk color can be white, grey, grayish,
brown or brownish, with many various tones and intensity. The color
of the silk fibers can originate (i) from de-colorizing the raw
fibers such as a bleach treatment, and/or (ii) from a specific
coloration process, intended to impart a specific color or tone to
the fibers and/or (iii) from a treatment preventing the fibers from
retaining a specific color or tone (or any combinations of the
above treatments). Other colors for the silk fibers of the present
invention are contemplated, without limiting the array of potential
other colors that can be used, such as blue, red, yellow, light
grey, light brown, pink, purple, black, green, turquoise, dark
brown, orange, white, beige, gold, silver, copper and violet.
Variations of tones and intensity as well as combinations of the
above are also contemplated. Additionally, one can also contemplate
the use of silk fibers that are of 2 or 3 (or more) different
colors, for example, red and blue silk fibers or gold and silver
silk fibers, etc. In another embodiment, the use of a population of
silk fibers that is divided into 2, 3 or more sub-populations is
contemplated. In this embodiment, each sub-population has a
different color or color intensity. For example, the population of
silk fibers used in the invention can be a mixture of red fibers
and blue fibers or a mixture of dark brown fibers with light purple
fibers.
[0038] The present invention may have silk fibers that are of an
intense color that contrasts with the white light tones of the
background cellulosic fibers. For example, the invention may be
practiced with the silk fibers being blue, green or purple and the
cellulosic fibers forming a white background. However, different
combination of colors can be practiced such as white or pale silk
fibers with dark-colored cellulosic fibers, cellulosic fibers in
one pale color and silk fibers in an intense different color, etc.
Similar color tones with different intensities are also
contemplated, for example, dark blue silk fibers with pale blue
cellulosic fibers. Importantly, however, the silk fibers should be
visually distinguished from the cellulosic background fibers by the
naked human eye. If synthetic fibers are present, they can be of
the same color as the cellulosic fibers or the silk fibers or of a
color different from the silk fibers and/or from the cellulosic
fibers.
[0039] The color differences are assessed by visual evaluation
using the human naked eye. The following normalized procedures
describe the test room conditions, the selection of panellists for
the assessment and the method applicable for this sensory
assessment. Generally, the conditions are as indicated in the
referenced test methods, which are incorporated by reference. Where
the methods provide a number of options and/or where the conditions
are not described in the methods, the options/conditions are to be
used as specified in the below.
[0040] The set-up of the room for the testing is as described in
ISO 8589 "General guidance for the design of test rooms", 1988
[first edition 1988-11-15]: Walls and furnishing are selected to be
of a matte off-white or light neutral light grey color. Lighting is
free from strong shadows. Direct sunlight is avoided. The lighting
is provided by a daylight lamp having a color temperature of 6500 K
without additional filter or other colored light source. The
lighting intensity is between 500 Lux and 1500 Lux.
[0041] The panellists for the assessment are selected and qualified
according to DIN 10961 "Schulung von Prufpersonen fur sensorische
Prufungen" (issued August 1996). A minimum of 10 panellists with
non-pathologic visual acuity and exempt of color-blindness are
qualified based on the following qualification processes and with
the qualification criteria indicated in the referenced method
DIN10961: (a) Qualification of color sense using 23 color charts
and "1 Florkontrast-Test", (b) Qualification for different color
intensities in liquids to differentiate color intensities (red,
orange, green), and to differentiate colors by mixing 2
complementary colors (yellow-green-blue/red-violet-blue), (c)
Qualification for color differences in a dry medium using a grey
scale.
[0042] The assessment on the color difference of silk fibers in the
tissue paper is performed using the test protocol described in DIN
10972 "A--nicht A Prufung" [2003-08]. At least 10 qualified
panellists are requested to make their assessment when looking at
the samples from a distance of 30 to 50 cm. Results are compiled
and reported as described in the DIN 10972 method.
[0043] The paper of the present invention can have silk fibers,
possibly colored, uniformly distributed at the surface of the
tissue. FIG. 2 is a representation of such an embodiment with a
uniform distribution of the colored silk fibers 3 at the surface of
the tissue 2. Alternatively, zones with silk fibers 11 and zones
without silk fibers 12 can be made on the tissue paper of the
present invention. In a further alternative, zones with a
relatively high density of silk fibers and zones with a relatively
lower density of silk fibers can be created on the surface of the
tissue paper 2. The zones (with relatively high density of silk
fiber) can be shaped as stripes, rectangles, squares, ovals,
circles, frames, or any combination thereof, or any other indicia
at the surface of the paper. In one embodiment of the invention,
such zones with silk fibers 11 extend along the machine direction
of the tissue 2 ("machine direction" as opposed to "cross
direction" relates to the orientation of the tissue paper as it
passes through the paper machine). One unique stripe can be present
or alternatively 2, 3, 4 or more stripes can be present. FIG. 3
shows an embodiment of the tissue paper 2 of the invention having
three stripes 5 comprising colored silk fibers 3 whereas the other
zones 11 comprise cellulosic fibers in a paler tone and are
substantially without colored silk fibers 3. In a further
embodiment, the zones comprising silk fibers 11 are shaped as to
represent a symbol or graphical indicia linked to the commercial
brand of the article or a text, such as the trademark of the
brand.
[0044] The amount of silk fibers in the present invention is
measured as a weight/weight % of the total amount of fibers. The
amount of silk fibers can be up to about 5%. In other embodiments
the amount of silk fibers is up to about 2%, up to about 1%, up to
about 0.5%, or up to about 0.1%.
[0045] In some embodiments of the present invention, it has been
found that silk fibers, especially when colored in a relatively
dark tone (while cellulosic fibers are in a relatively white tone),
can be noticeable even at a very low amount. Actually, a lower
limit for noticeability could not be easily defined, although it
has been observed that a level below 0.001% would be hardly
detectable by a human naked eye.
[0046] In general, the detectability of the silk fibers can be done
by microscopy. The singular appearance of silk fibers allows for an
easy detection, counting and measurement by conventional or
electronic microscopy. However, for the present invention, the
detectability of the silk fibers by a human naked eye is more
important, especially when the fibers are of a color different from
the color of the cellulosic fibers. Detectability by the human eye
enhances the perception of softness linked to the use of silk in
the product and also secures an amount of silk fibers that can
induce better physical surface characteristics for the tissue (such
as softness).
[0047] It has been found that the detectability by the naked human
eye is a trigger to enhance the perception of softness, bulkiness,
smoothness, luxuriousness, general quality and/or kindness to skin
of the tissue by the user. The perception is expressed by the users
as an increased of bulkiness, softness, smoothness. The
noticeability of the silk fibers interacts at, at least, two
levels. At intermediate or relatively low silk fiber amounts in the
tissue, a physiological sensation of softness is perceived. That
effect decreases with lower amounts of silk fibers incorporated in
the tissue. Importantly, it has been found that the physiological
signal of softness remains high whenever the silk fibers are
colored with a tone different from the background tone of the
cellulosic fibers. That enhancing effect is not to be considered as
an artifactual bias, but it measurably participates in the
perception of the softness, bulkiness, kindness to the skin quality
of the tissue. It has been found that the response of the users is
in fact more than the sum of all the sensory signals that he/she
perceives. Visual and physical signals blend together and the
tissue is actually felt as being softer when the physical
perception of a smooth surface is synergistically enhanced by the
visualization of colored silk fibers.
[0048] The invention may be practiced in the context of tissue
paper used in articles intended for human skin contact. The use for
human skin contact leads to particular characteristics of the paper
such as the general softness and absorbency, the use of skin
compatible chemical additives, the purity of the raw materials or
cleanliness of the process conditions. Such articles can be paper
handkerchiefs, wet wipes, paper towels, facial tissue or rolls or
stacks of toilet paper. Other types and forms of domestic wipes are
also contemplated.
[0049] The articles relating to the present invention can comprise
one single ply of the tissue paper of the present invention or be a
multi-ply article comprising for example 2, 3 or 4 (or more) plies
of tissue paper. All plies can be made of the same tissue paper or
alternatively some plies can be made of a different tissue paper
from the others. In some embodiments, at least one outer surface of
one outer ply of the articles comprises at least some of the silk
fibers of the present invention. The inner plies and/or the inner
surfaces may comprise significantly fewer silk fibers than the
outer ply and/or the outer surface or not at all. The various plies
of the article can be combined by any means, such as application or
glue and/or embossment of a pattern. Silk fibers have different
physical characteristics from cellulosic fibers and may require
adaptation of the combining means. However, it has been found that
the presence of silk fibers, according to invention, within one of
the ply of the article generally does not prevent the embossment of
the article to impart the desired pattern at the surface of the
tissue and/or help the combination of the plies.
[0050] FIG. 1 represents one embodiment of the present invention in
which a tissue paper 2 is rolled around a cardboard core 6 to form
a roll of toilet tissue paper 1. Colored silk fibers 3 are visible
among the white cellulose fibers 4 at the surface of the tissue
paper 2. FIG. 2 represents a piece of the tissue paper 2 of the
invention. The colored silk fibers 3 are visible at the surface of
the tissue paper 2. A multi-ply embodiment of the invention is
shown on FIG. 4. The article 10 of FIG. 4 comprises a first ply 8
and a second ply 9. The first ply 8 is a tissue paper of the
invention. The first ply 8 comprises silk fibers 3 and white
cellulosic fibers 4. According to the invention, the silk fibers 3
are of a color different from the color of the white cellulosic
fibers 4. The first and second plies have been combined together
and embossed at the embossing points 7 to form the article 10. For
representation purposes, the first and second plies 8, 9 are shown
in FIG. 4 being clearly separated one from another. The plies can
however be so closely combined together that they may not, at first
glance, be individually recognizable.
[0051] In one aspect, the invention also relates to tissue paper
together with its packaging structure (such as a box, container,
wrap film, labels), also referred to as a kit comprising a tissue
paper and its packaging structure. It has been found that the
synergistic effect herein described is further reinforced when a
graphical indicia is present on the packaging structure or on the
article. The graphical indicia can be any text or logo, icon or
representation. The graphical indicia can be printed on the
packaging structure, embossed to it or attached to it, or to the
tissue paper, or to the article itself or to one of its parts (for
example the core of a toilet paper roll). The graphical indicia can
comprise a piece of specific material (for example a piece of silk
tissue or silk fabric or a material comprising silk fibers).
Alternatively or additionally, the graphical indicia can comprise
the shape of the packaging structure (for example a carton box
having a specific smooth shape). In other embodiments the graphical
indicia comprise a transparent portion of the packaging structure,
through which the tissue paper can be seen. The graphical indicia
can increase the perception of softness/bulkiness/kindness to skin
by the user of the article. Such indicia can include for example
the word "silk" or its derivatives (such as "silky" or "silk-like")
or can indirectly and more graphically indicates softness, and/or
indicate the presence of soft fibers such as silk fibers or cotton
fibers.
EXAMPLE 1
[0052] Silk fibers (Tussah silk cut from SEAL International
Limited, Ladywell Mills, Hall Lane, Bradford, West Yorkshire, BD4
7DF, England; Silk cut) are first colored with a blue colorant
("Marabu-SilkArt azure" from Marabuwerke GmbH & Co. KG,
Asperger StraBe 4, 71732 Tamm, Germany). The silk fibers are then
added at a level of 0.1% (w/w) of the total amount of fibers used,
into the mixing vessel for the preparation of the papermaking
slurry. The hybrid slurry (cellulose fibers+silk fibers) is then
used in a usual papermaking process (for example as described in
U.S. Pat. No. 3,301,746 by Sanford et al, EP0536320B1 by Trokhan et
al, and U.S. Pat. No. 4,529,480 by Trokhan et al.). The web of
tissue paper is then converted into a roll of toilet paper by
conventional industrial processes. Pieces of issue papers are then
evaluated for the visibility of the silk fibers on the tissue paper
and for physical properties.
EXAMPLE 2
[0053] The same silk fibers as described in Example 1 are used at a
level of 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2% and 5% (w/w) of the total
amount of fibers, to form fiber mixes. The fiber mixes comprises
cellulosic fibers and silk fibers. In additional assays, synthetic
fibers (polypropylene) are also added to the fiber mixes, at a
level of 1%, 5%, 10%, and 20% (w/w) of the total amount of fibers.
The cellulosic fibers are usual cellulosic fibers commonly used for
paper-making. The fiber mixes are used as a base to form
hand-sheets of tissue paper as described in TAPPI method T-205
(TAPPI, Technical Association of the Pulp and Paper Industry,
published method T 205 sp-95, approved by the Pulp Committee of the
Process Quality Division TAPPI, ISBN 0-89852-334-6). The sheets of
tissue paper are then evaluated for the visibility of the silk
fibers on the tissue paper and for physical properties.
[0054] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated by reference herein;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of the term in this written
document conflicts with any meaning or definition of the term in a
document incorporated by reference, the meaning or definition
assigned to the term in this written document shall govern.
[0055] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *