Title:
Tissue product with silk fibers and method of making the same
Kind Code:
A1


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)
Application Number:
11/231214
Publication Date:
05/25/2006
Filing Date:
09/20/2005
Primary Class:
Other Classes:
162/141, 162/162
International Classes:
D21H13/34
View Patent Images:



Primary Examiner:
FORTUNA, JOSE A
Attorney, Agent or Firm:
THE PROCTER & GAMBLE COMPANY (CINCINNATI, OH, US)
Claims:
What is claimed is:

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

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

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.

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.

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.

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.

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.

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.

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.

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.

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

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

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.

FIG. 2 represents a piece of tissue paper of the invention.

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.

FIG. 4 represents a multi-ply article comprising the tissue of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Definitions:

The following terms are used in the present document with the following meaning:

Tissue: a sheet comprising a plurality of interconnected fibers.

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.

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.

Toilet tissue: an article comprising tissue and primarily intended for the cleaning of human body from solid or liquid human waste.

Handkerchiefs and facial tissue: articles comprising tissue and primarily intended for cleaning the human nasal area and/or removing human nasal waste.

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.

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.

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

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

The panellists for the assessment are selected and qualified according to DIN 10961 “Schulung von Prüfpersonen für sensorische Prüfungen” (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.

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 Prüfung” [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.

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.

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%.

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.

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).

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.

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.

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.

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.

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

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

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.

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.

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.