HK1021998B - Wet wipes with improved softness - Google Patents

Description

Wet wipes having improved softness

Background

Technical Field

The present invention relates to wet wipes having improved softness. And more particularly to wet wipes including a multi-layer substrate sheet for enhancing softness and flexibility of the wet wipe while maintaining strength and resiliency thereof.

Description of the Related Art

Wet wipes are well known commercial consumer products and have many forms. Perhaps the most common wet wipe is a stack of wetted sheets packaged in a plastic container. Such wet wipes are made from a wide variety of materials by soaking in a suitable wiping solution. Such wet wipes have been used for baby wipes, hand wipes, household cleaning wipes, industrial wipes, and the like.

Typically, such prior wet wipes have included a layer of substantially homogeneous material. For example, existing wet wipes comprise a web of air-laid fibers that are uniformly mixed or distributed throughout the web. The wipes have included polymeric fibers such as polyester, polyethylene, polypropylene, and natural or synthetic fibers such as cellulose fibers. Other prior wet wipes have included a fibrous web of polypropylene fibers and cellulosic fibers wherein the fibers are uniformly mixed throughout the web.

However, the balance between various physical properties, such as softness, flexibility, strength, overall retention, and resiliency, of the wet wipe having fibers uniformly mixed throughout its thickness has not been fully optimized. This is particularly true for those users who require increased softness. For example, certain fibers that can be used in wet wipes are relatively stiff and provide strength and resiliency to the wet wipes, but these fibers are not as soft or flexible as other fibers. While other fibers that may be used in wet wipes are softer but may not have sufficient wet strength to withstand the force applied by the user. The softness of the wiping surface of the wipe is considered to be most important for babies, since the wiping surface of the wipe is intended to contact the tender skin of the baby. Furthermore, it is difficult to combine different types of fibres that provide the desired properties, such as fibres that provide strength and fibres that provide softness, in one homogenous layer due to their incompatibility with each other. Accordingly, there is a need for a wet wipe having improved softness and flexibility while maintaining the strength, overall retention, and resiliency of the wipe.

Summary of The Invention

In response to the above difficulties and problems, the present invention provides new wet wipes having improved softness and flexibility while having sufficient strength, overall retention and resiliency.

In one aspect, the present invention is also directed to a multi-layer wet wipe comprising a liquid, a first nonwoven outer layer, a second nonwoven outer layer, and a nonwoven inner layer. The second nonwoven outer layer is disposed in facing relation to the first nonwoven outer layer, and the nonwoven inner layer is disposed in facing relation between the two nonwoven outer layers. At least the outer layer is formed from a mixture of natural and polymeric fibers and the inner layer includes fibers having a higher tensile strength than the outer layer. Thus, the structure of the outer layer can provide different physical properties, such as softness, to the wet wipe, while the structure of the inner layer provides additional properties, including strength, to the wet wipe. For example, the first and second outer layers may comprise a mixture of polyethylene fibers and natural fibers to provide softness, while the inner layer may comprise polypropylene fibers for providing strength. In a specific embodiment, the outer layer comprises a mixture of polyethylene fibers and natural fibers, while the inner layer comprises a mixture of polypropylene fibers and natural fibers.

In another aspect, the present invention is directed to a method of producing wet wipes, the method comprising: a) providing a continuously moving first layer of nonwoven material; b) providing a continuously moving second layer of nonwoven material, said second layer of nonwoven material and first layer of nonwoven material being positioned relative to each other, wherein the second layer comprises fibers having a higher tensile strength than the first layer; c) providing a continuously moving third layer of nonwoven material, which is arranged opposite the second layer of nonwoven material, sandwiching the second layer of nonwoven material between the first and third layers of nonwoven material to form a layered nonwoven substrate sheet, wherein the fibers of the third layer have a lower tensile strength than said second layer. d) Passing said layered base sheet between a pair of rotating nip rollers to at least partially secure said first and second layers together; e) applying a liquid to the layered base sheet; f) the continuously moving layered substrate sheet is cut into individual sheets to form the wet wipes. The first and third layers of nonwoven material may comprise layers (coformlayer) formed from polyethylene fibers and natural fibers together, and the third layer of nonwoven material may comprise layers formed from polypropylene fibers and natural fibers together.

In various aspects of the present invention, an improved wet wipe is preferably provided that includes a layered nonwoven substrate sheet. The use of one layered base sheet enables different fibers to be incorporated in different layers of the base sheet to provide different properties. Thus, the different layers can be configured to provide an optimized balance of physical properties for the wet wipe, such as softness, flexibility, strength, overall retention, and resiliency. Thus, the present invention provides wet wipes having improved performance and consumer acceptance over prior wet wipes comprising a single homogenous layer.

Detailed Description

The present invention relates to a new wet wipe having improved softness while maintaining sufficient strength and resiliency, and a method of producing the same. The wet wipes of the present invention can be used in baby wipes, hand wipes, facial wipes, cosmetic wipes, household wipes, industrial wipes, and the like.

The wet wipes of the present invention include a layered base sheet containing a liquid. The liquid can be any solution capable of being absorbed by the wet wipe substrate sheet and can comprise any suitable composition that provides the desired wiping properties. For example, the component may be water, an emollient, a surfactant, a fragrance, a preservative, a chelating agent, a ph buffering agent, or combinations thereof, as are well known to those of ordinary skill in the art. The liquid may also contain lotions and/or medicaments.

The amount of liquid contained in each wet wipe can vary depending on the type of material used to produce the wet wipes, the type of liquid used, the type of container used to store the wet wipes, and the end use of the wet wipes. Typically, to improve wiping performance, each wet wipe can contain from about 150% to about 600%, desirably from about 250% to about 450%, by weight of the dry weight of the wipe, of liquid. Specifically, the amount of liquid contained in the wet wipes is about 300% to 400%, desirably about 330% of the dry weight of the wet wipes. If the amount of liquid is less than the above range, the wet wipe may be excessively dry and may not perform adequately. If the amount of liquid is greater than the above range, the wet wipes may become overly saturated or soaked and the liquid may collect at the bottom of the container.

Each wet wipe is generally rectangular and can have any suitable unfolded width and length. For example, the wet wipes can have an unrolled length of about 2.0 to 80.0 centimeters, desirably about 10.0 to 25.0 centimeters, and an unrolled width of about 2.0 to 80.0 centimeters, desirably about 10.0 to 25.0 centimeters. Generally, each individual wet wipe is arranged in a folded configuration and stacked one on top of the other to form a stack of wet wipes. Such folded configurations are well known to those skilled in the art and include C-fold, Z-fold, 1/4-fold configurations, and the like. The folded stack of wet wipes can be placed inside a container, such as a plastic tub, to form a package of wet wipes that is ultimately sold to a consumer. Alternatively, the wet wipes can comprise a continuous strip of material having perforations between each wipe, which can be provided as a stack or wound into a roll for dispensing.

The layered base sheet of the wet wipes of the present invention comprises at least two outer layers of material having different physical properties relative to a third layer. By selecting an appropriate material configuration, the layers impart various physical properties to the wet wipe including softness, elasticity, strength, flexibility, overall retention, toughness, absorbency, liquid retention, caliper, tear resistance, surface texture, drape, hand, wettability, wicking, and the like, or combinations thereof. Desirably, the material used for the layered base sheet can be configured to provide softness and flexibility while maintaining sufficient strength, overall retention, and elasticity, particularly when wetted. For example, a wet wipe can include at least one layer of material configured to provide strength and resiliency to the wet wipe and at least two additional layers of material configured to provide a soft, gentle wiping surface to the wet wipe. Thus, the wet wipe has a soft layer on each side of a strength and resiliency layer so that both exposed surfaces of the wipe have a soft, gentle skin contacting surface.

Each layer of the wet wipes can be made from a variety of materials including: meltblown materials, coform materials, airlaid materials, bonded-carded webs, hydroentangled materials, spunbond materials, etc., each layer of the wipe may comprise synthetic or natural fibers. Desirably, all of the layers of the layered base sheet comprise fibrous materials that impart an improved look and feel to the wet wipe. Examples of natural fibers suitable for use in the present invention include cellulosic fibers such as wood pulp fibers, cotton fibers, flax fibers, jute fibers, silk fibers, and the like. Examples of thermoplastic polymer fibers suitable for use in the present invention include polyolefins such as polypropylene and polyethylene, polyamides, and polyesters such as polyethylene terephthalate. Other synthetic fibers suitable for the present invention include nylon and staple fibers. A major advantage of the present invention is that the fiber type of each layer of the layered base sheet may be varied to obtain a specific combination of physical properties in the final layered base sheet that is not possible to obtain in a single layer of material. Thus, the layered base sheet obtained according to the different aspects of the invention may comprise different layers comprising different fibers which are incompatible with each other in one single layer.

For example, the layered base sheet of the present invention may comprise at least two soft and flexible layers comprising soft polymeric fibers, such as linear low density polyethylene fibers and/or other polymeric fibers having similar properties. The soft fibers are used in combination with natural fibers such as cellulose fibers. The layered base sheet may comprise at least one strong elastic layer, which may comprise elastic polymer fibers having a relatively high tensile strength, such as polypropylene fibers and/or other polymer fibers having similar properties. These strong polymeric fibers may be used in combination with or without natural fibers such as cellulose fibers. Desirably, at least one of the layers contains natural fibers, such as cellulosic fibers, to improve the thickness and wettability of the base sheet. Natural fibers may also impart void volume to the base sheet, which may improve its water retention properties.

For a layer of the layered base sheet formed from a combination of polymeric fibers and natural fibers, for example, polypropylene fibers and cellulosic fibers, the relative percentages of the polymeric fibers and natural fibers in the layer can vary over a wide range depending on the desired characteristics of the wet wipe. For example, the layer may comprise polymer fibers in an amount of about 20% to 95%, more desirably about 20% to 60%, or even more desirably about 30% to 40% by weight of the dry weight of the layer. Such a layer of polymer fibres and natural fibres may be produced by any method known to the person skilled in the art.

Generally, it is desirable to form a layer by a coform process to obtain a more uniform distribution of polymer fibers and natural fibers in the layer. Such coform layers are commonly produced as disclosed in U.S. patent No. US4100324 issued to Anderson et al on 7/11 of 1978; U.S. patent US4604313 issued to Mcfarland et al at 8/5 in 1986; and US patent No. US5350624, published on 9/27 of 1994, which patents are incorporated herein by reference. Generally, such coform layers include a matrix of thermoplastic polymer meltblown microfibers, such as polypropylene microfibers, and cellulosic fibers, such as wood pulp fibers, formed by the gas. A co-formed layer is formed by: at least one primary air stream containing synthetic or polymeric fibers is initially formed and then combined with at least one secondary air stream of natural or cellulosic fibers. The primary and secondary air streams merge under turbulent conditions to form a unitary air stream having a thorough and uniform distribution of the different fibers. The integrated air flow is directed onto a forming surface so that air forms the layer of material. A plurality of such coform layers can be successively formed to form a web of multiple coform layers.

In one particular embodiment, the wet wipe of the present invention includes a base sheet having three co-formed layers including a strong resilient inner layer disposed between two soft and flexible outer layers. The tough, resilient inner layer comprises a coform layer formed from meltblown polypropylene microfibers and wood pulp fibers in a weight ratio of wood pulp to polymer from about 50/50 to 75/25, desirably about 65/35. Suitable polypropylenes are available from Montel, Inc. under the trade designation MONTEL PF 015. The flexible outer layer comprises a coform layer formed from meltblown linear low density polyethylene microfibers and wood pulp fibers in a weight ratio of wood pulp to polymer of from about 50/50 to about 75/25, desirably about 65/35. One suitable polyethylene is available from Dow under the trade designation Dow 6831A.

The different fibers in the different layers of the layered base sheet of the present invention, such as the polypropylene microfibers and polyethylene microfibers described above, are generally not compatible and bondable to each other. However, these different fibers may be entangled with each other to obtain a proper fixation between the layers. For example, in a layered base sheet comprising a co-formed layer of polyethylene fibres and cellulose fibres and a co-formed layer of polypropylene fibres and cellulose fibres, the polyethylene fibres and polypropylene fibres may be entangled with each other and with the cellulose fibres and may at least partly bind the cellulose fibres together, whereby the anchoring between the layers is obtained.

This bonding and entanglement between the layers can be enhanced by a thermal deformation process in which the layered base sheet is passed between a heated smooth anvil roll and a heated patterned roll. The patterned roll may have any raised pattern that provides the desired entanglement and bonding between the layers. Desirably, the patterned roll has a raised pattern thereon for enhancing the bonding between the layers. A plurality of bond sites are formed between the plies by the raised pattern, the bond sites defining a bond region that occupies between about 4% and 30% of the total area of the roll.

The pressure and temperature between the rolls must be equalized to form a base sheet having sufficient strength and overall retention while maintaining softness of the outer layer. The temperature and pressure can vary depending on the type of fibers employed to form the desired wet wipe. In a particular embodiment in which at least one of the layers is a polyethylene fiber layer and at least one other layer is a polypropylene fiber layer, the pressure between the rolls may be about 5 to 90 kilograms per centimeter in the linear direction and the temperature of at least one of the rolls may be about 65 to 95 degrees celsius, all to achieve an improved entanglement and bonding. Under such conditions of temperature and pressure, the polyethylene fibres deform and obtain mechanical entanglement with the polypropylene fibres and possibly also adhesion with the polypropylene fibres. The layers are thereby entangled and bonded between the discrete regions arranged in a pattern corresponding to the raised pattern on the patterned roll.

The layered base sheet for wet wipes can have a basis weight of from about 25 to 120 grams per square meter, desirably from about 40 to 90 grams per square meter. The basis weight can also vary depending on the end use of the wet wipe. For example, a suitable base sheet for wiping the skin may have a basis weight of about 60 to 80 grams per square meter, desirably about 75 grams per square meter. In a particular embodiment, the layered base sheet of this embodiment comprises a coform layer of polypropylene fibers and cellulosic fibers and a coform layer of polyethylene fibers and cellulosic fibers having a basis weight of about 60 to 90 grams per square meter, desirably about 80 grams per square meter, for improved softness and sufficient strength.

Each layer may have a different basis weight or may have the same basis weight depending on the different properties desired for the wet wipe, such as strength and softness. For example, in a base sheet having three coform layers including an inner layer of polypropylene fibers and wood pulp fibers and two outer layers of polyethylene fibers and wood pulp fibers, the basis weight of the laminate may have a weight ratio of outer layer/inner layer/outer layer of about 10/80/10 to 40/20/40, desirably about 25/50/25 to 33/33/33, and more desirably about 30/40/30, all in proportions to the total weight of the base sheet, for improved performance.

In one particular embodiment, it is desirable that the wet wipes of the present invention have sufficient strength to withstand the force applied by a user when wetted with a solution. For example, for a layered base sheet of wet wipes having improved performance, it may have the following tensile strength, namely: at least about 1.23 newtons per centimeter in the machine direction and at least about 0.70 newtons per centimeter in the cross-machine direction. Here, the machine direction refers to the direction in which the material is produced, and the cross-machine direction refers to the direction perpendicular to the machine direction. In one particular embodiment, the layered base sheet comprises a coform layer of polypropylene fibers and cellulosic fibers and a coform layer of polyethylene fibers and cellulosic fibers, the layered base sheet having a tensile strength of about 1.31 to 3.50 newtons per centimeter in the machine direction, about 0.84 to 1.40 newtons per centimeter in the cross-machine direction, desirably about 1.58 to 1.93 newtons per centimeter in the machine direction, and about 0.93 to 1.11 newtons per centimeter in the cross-machine direction. In such a structure, the coform layer comprising polypropylene fibers plays a major role in the strength of the base sheet, while the coform layer comprising polyethylene fibers provides a soft surface for contacting the skin of the user. Such a layered base sheet thus has a higher tensile strength than a monolayer comprising polyethylene fibres and provides a softer surface than a monolayer comprising polypropylene fibres.

The layered base sheet of wet wipes according to various aspects of the present invention can be produced on a manufacturing line that includes a plurality of individual forming assemblies. Each forming assembly is configured to form a single layer having the desired properties. For example, the structure of the first and last forming assemblies can form a soft outer layer, while the structure of the intermediate or inner forming assembly can form at least one strong and resilient inner layer. During formation, the mechanical entanglement between the fibers of each layer provides the bonding between the layers and bonds may be formed between adjacent layers, thus forming the layered base sheet. Thermal deformation bonding may also be subsequently performed on the layered base sheet to improve the bonding between the layers.

Each forming train may contain suitable equipment to form the desired type of web. For example, if each layer comprises a coform layer of meltblown microfibers and natural fibers such as wood pulp fibers, each forming block may include a plurality of meltblown dies, as is well known to those skilled in the art. Typically, the melt-blowing process involves a melt-blowing die that is structured to extrude molten polymer into a fine stream. The polymer stream is then attenuated by the converging high velocity gas stream to turn the polymer stream into small diameter discontinuous microfibers. The stream of natural fibers agglomerated with the stream of meltblown microfibers may be obtained by treatment with an existing pulp picker roll, as is well known to those skilled in the art.

Additionally, one or more layers of the wet wipes of the various aspects of the present invention can be made from different types of materials, such as meltblown sheets of polymer microfibers. For example, the inner layer, which is strong and resilient, may comprise a layer of meltblown polypropylene fibers, while the outer layer, which is soft, may comprise a coform layer of polyethylene and wood pulp fibers, as described above. The soft and flexible outer layer may additionally be obtained from different types of materials, such as air laid carded webs or the previously described meltblown materials, which may be produced by methods well known to those skilled in the art.

Examples

The following examples are presented to provide a more detailed understanding of the invention. Specific materials and parameters are given by way of example and are not intended to limit the scope of the invention.

Example 1

Wet wipes were made according to the present invention. Each wet wipe comprises a base sheet having three co-formed layers including a strong resilient inner layer disposed between two soft, flexible outer layers. The tough, resilient inner layer comprises a coform layer formed from meltblown polypropylene microfibers and wood pulp fibers in a weight ratio of wood pulp to polymer of about 65/35. Polypropylene is available from Montel corporation under the trade designation monteff 015. The soft outer layer comprises a coform layer formed from meltblown linear low density polyethylene microfibers and wood pulp fibers, wherein the weight ratio of wood pulp to polymer is about 65/35. Polyethylene is available from Dow under the trade designation Dow 6831A. The wet wipe has an inner layer/outer layer/inner layer weight ratio of about 30/40/30. The wet wipe comprises a solution similar to that now used in Kleenex^Huggies^Unstrained Classic Baby tapes, available from Kimberly-Clark corporation, Neenah, Wisconsin is provided with a office. The wet wipes contained about 330% solution by dry weight of the wipe.

The wet wipes described above were subjected to a grab tensile strength test well known to those skilled in the art. The wipe is placed between a pair of jaws which are pulled apart. The force required to pull the wipe apart is recorded as the tensile strength. The tests were conducted in both the Machine Direction (MD) and the cross-machine direction (CD). The wet wipe has an average MD tensile strength of 1.67 newtons per centimeter (0.95 pounds per inch) and an average CD tensile strength of 1.05 newtons per centimeter (0.60 pounds per inch).

Comparative example 1

Product Kleenex^Huggies^Unsented Classic Baby wires are available from Kimberly-Clark corporation, having an office in Neenah, Wisconsin. Each of the wet wipes includes a co-formed base sheet having about 65% by weight cellulosic fibers and 35% by weight polypropylene microfibers based on the dry weight of the base sheet. The polypropylene is available from Montel under the trade designation MONTEL PF 015. The wet wipe comprises about 330% solution by dry weight of the base sheet.

The wet wipe was subjected to the grab tensile test described above. The wet wipe has an average MD tensile strength of 3.16 newtons per centimeter (1.80 pounds per inch) and an average CD tensile strength of 1.45 newtons per centimeter (0.83 pounds per inch).

Comparative example 2

A wet wipe similar to that of comparative example 1 was made, except that the polymer was different. Each of the wipes contained a coform basesheet containing about 65% by weight cellulosic fibers and 35% by weight polyethylene microfibers based on the dry weight of the basesheet. The polyethylene is available from Dow under the trade designation Dow 6831A. The wet wipes contained about 330% solution by dry weight of the base sheet.

The wet wipe was subjected to the grab tensile strength test described previously. The wet wipe has an average MD tensile of 0.38 newtons per centimeter (0.22 pounds per inch) and an average CD tensile of 0.28 newtons per centimeter (0.16 pounds per inch).

The wet wipes of example 1 and comparative example 1 were also tested for use by 55 participants who used the wet wipe for a period of 5 days. The participants were then asked questions related to the performance of the wipes. The softness of the wet wipe of example 1 (invention) is more satisfactory than that of comparative example 1.

Exemplary example 1 illustrates that the layered basesheet of the present invention provides wet wipes having improved softness while also having sufficient strength to perform as a wet wipe. Accordingly, various aspects of the present invention provide better wet wipes having softer performance and adequate strength and overall retention than prior wet wipes. Such wet wipes have increased consumer acceptance and can be better used for baby wipes, hand wipes, facial wipes, beauty wipes, household wipes, industrial wipes, and the like.

While the invention has been described in detail with respect to specific aspects thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily produce alterations to, variations of, and equivalents to these aspects. Accordingly, the scope of the invention should be determined with reference to the appended claims, along with any equivalents thereof.

Claims (22)

1. A multi-ply wet wipe comprising:

a) a liquid;

b) a first nonwoven outer layer;

c) a second nonwoven outer layer disposed opposite the first nonwoven outer layer;

d) a nonwoven inner layer positioned in facing relation between said first nonwoven outer layer and said second nonwoven outer layer; the method is characterized in that:

at least the outer layer is formed from a mixture of natural and polymeric fibers and the fibers of the inner layer have a higher tensile strength than the outer layer.

2. The wet wipe of claim 1 wherein said first and second outer layers include polyethylene fibers.

3. The wet wipe of claim 1 or 2 wherein said inner layer includes polypropylene fibers.

4. The wet wipe of any of the preceding claims wherein said layers each include a blend of natural fibers and polymeric fibers.

5. The wet wipe of any one of claims 1 through 4 wherein a weight percentage of said natural fibers to said polymeric fibers in each of said outer layers is from about 50/50 to about 65/35.

6. The wet wipe of claim 4 or 5 wherein a weight percentage of said natural fibers to said polymeric fibers in said inner layer is from about 50/50 to 75/25.

7. The wet wipe of any one of the preceding claims wherein at least one of said layers includes a coform layer formed from natural fibers and polymeric fibers.

8. The wet wipe of claim 1 further comprising said liquid in an amount corresponding to about 150% to about 600% by weight of a dry weight of said wet wipe.

9. The wet wipe of any one of the preceding claims wherein a weight ratio of said first outer layer, said inner layer, said second outer layer is from about 10/80/10 to about 40/20/40.

10. The wet wipe of claim 1 wherein said wet wipe has a tensile strength in the machine direction of at least about 1.23 newtons per centimeter.

11. The wet wipe of any of the preceding claims wherein said wet wipe has a total dry basis weight of from about 50 to about 90 grams per square meter.

12. The wet wipe of any one of the preceding claims wherein said outer layer is at least partially entangled with said inner layer at a plurality of bond sites, said bond sites forming a bond area comprising between about 4% and 30% of the surface area between respective layers.

13. A method of producing a multi-layer wet wipe comprising:

a) providing a continuously moving first layer of nonwoven material;

b) providing a continuously moving second layer of nonwoven material disposed opposite said first layer of nonwoven material;

c) providing a continuously moving third layer of nonwoven material opposing said second layer of nonwoven material sandwiching said second layer of nonwoven material between said first and third layers of material to form a layered nonwoven substrate sheet;

d) at least partially securing the first layer, the second layer, and the third layer together;

e) adding a liquid to said layered base sheet; and

f) cutting said continuously moving layered substrate sheet into individual sheets to form said wet wipes, forming at least first and third layers of a mixture of natural and polymeric fibers and forming a second layer of nonwoven material with fibers having a higher tensile strength relative to said first and said third layers of nonwoven material.

14. The method of claim 13, wherein said first layer and said third layer comprise a coform layer of polymeric fibers and natural fibers.

15. A method according to claim 13 or 14, wherein the second layer comprises a co-formed layer of polymeric fibres and natural fibres.

16. The method of any of claims 13 to 15, wherein said first layer and said third layer comprise polyethylene fibers and said second layer comprises polypropylene fibers.

17. A method according to any one of claims 14 to 16, wherein the first and third layers comprise co-formed layers of polyethylene fibres and natural fibres and the second layer comprises a co-formed layer of polypropylene fibres and natural fibres.

18. A method according to any one of claims 13 to 17, wherein said first, second and third layers are secured together locally at least at some bond sites, said bond sites forming a bond area which comprises between about 4% and 30% of the total surface area between said layers.

19. A method according to any one of claims 13 to 18, wherein the laminar substrate sheet is passed between a pair of rotating rollers to at least partially secure the first, second and third layers together.

20. The method of claim 19 wherein one of said nip rollers is heated so that the fibers of one of said layers are at least partially deformed and entangled with the fibers of said other layer.

21. A method as claimed in claim 19 or 20, wherein said one roll is heated to a temperature of about 65 to 95 degrees celsius.

22. The method of any of claims 13 to 21, wherein the liquid is added to the layered base sheet in an amount equal to about 150% to about 600% by dry weight of the layered base sheet.