Plastic-Free and Binder-Free Wet Wipe

Abstract

A wet wipe includes a sheet formed from materials without plastics and without chemical or thermoplastic binders. The sheet has a weight of between 40-90 grams per square meter. The sheet has a blend of wood pulp fluff fiber between 50% - 80% by weight, fine denier lyocell or viscose of fiber length 5 to 12 millimeters between 10% - 30% by weight, and crosslinked curly pulp fibers between 3% - 15% by weight. The wet wipe is bonded with entangling water jets such that the wet wipe has a wet strength of at least 200 grams per linear inch in the cross direction, and a wet thickness between 0.4 and 1.5 millimeters.

Claims

1. A wet wipe comprising: a sheet formed from materials without plastics and without chemical or thermoplastic binders, the sheet having a weight of between 40 -90 grams per square meter, said sheet comprising: a blend of wood pulp fluff fiber between 50% -80% by weight, fine denier lyocell or viscose of fiber length 5 to 12 millimeters between 10% -30% by weight, and shaped cellulosic bulking fibers between 3% -15% by weight; wherein the blend of wood pulp fluff fiber, fine denier lyocell or viscose, and shaped cellulosic bulking fibers is bonded using entangling water jets, such that the wet wipe has a wet strength of at least 200 grams per linear inch in the cross direction, and a wet thickness between 0.4-1.5 millimeters.

2. The wet wipe of claim 1, wherein the sheet comprises a blend of wood pulp fluff fiber between 60% -80% by weight, fine denier lyocell or viscose of fiber length 5 to 12 millimeters between 15% -25% by weight, and shaped cellulosic bulking fibers between 5% -10% by weight.

3. The wet wipe of claim 1, wherein the shaped cellulosic bulking fibers include cellulosic staple fibers that have a trilobal cross-sectional shape.

4. The wet wipe of claim 1, wherein the shaped cellulosic bulking fibers include cellulosic staple fibers have a flat cross-sectional shape.

5. The wet wipe of claim 1, wherein the wet wipe has a wet strength of at least 400 grams per linear inch in the cross direction.

6. The wet wipe of claim 1, wherein the wet wipe has a wet strength of at least 500 grams per linear inch in the cross direction.

7. The wet wipe of claim 1, wherein the wet wipe has wet strength of at least 800 grams per linear inch in the machine direction.

8. The wet wipe of claim 1, wherein the wet wipe has wet strength of at least 1000 grams per linear inch in the machine direction.

9. The wet wipe of claim 1, wherein the thickness of the sheet, after converting, is at least 0.45 mm.

10. A wet wipe comprising: a sheet formed from materials without plastics or binders, the sheet having a weight of between 40 -90 grams per square meter, said sheet comprising: a blend of wood pulp fluff fiber between 50% -80% by weight, fine denier lyocell or viscose of fiber length 5 to 12 millimeters between 10% -30% by weight, and crosslinked curly pulp fibers between 3% -15% by weight; wherein the blend of wood pulp fluff fiber, fine denier lyocell or viscose, and crosslinked curly pulp fibers is bonded using entangling water jets, such that the wet wipe would have an effective wet strength of at least 200 grams per linear inch in the cross direction, and a wet thickness between 0.4 and 1.5 millimeters.

11. The wet wipe of claim 10, wherein the sheet comprises a blend of wood pulp fluff fiber between 60% -80% by weight, fine denier lyocell or viscose of fiber length 5 to 12 millimeters between 15% -25% by weight, and crosslinked curly pulp fibers between 5% -10% by weight.

12. The wet wipe of claim 10, wherein the wet wipe has a wet strength of at least 400 grams per linear inch in the cross direction.

13. The wet wipe of claim 10, wherein the wet wipe has a wet strength of at least 500 grams per linear inch in the cross direction.

14. The wet wipe of claim 10, wherein the wet wipe has wet strength of at least 800 grams per linear inch in the machine direction.

15. The wet wipe of claim 10, wherein the wet wipe has wet strength of at least 1000 grams per linear inch in the machine direction.

16. A method of manufacturing wet wipes, the method comprising the steps of: (i) opening and blending of wood pulp with fine denier lyocell or viscose and shaped cellulosic bulking fibers; (ii) airlaying this fiber blend into a homogeneous web and compacting and transferring this onto a hydroentangling belt; (iii) hydroentangling the formed web with high pressure water jets to bond the product; (iv) embossing the formed web to provide patterns; and (v) drying the web in through air bonding ovens.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0016] FIG. 1 is an illustration of a viscose fiber with a trilobal cross-sectional shape, according to an embodiment of the invention;

[0017] FIG. 2 is an illustration of a viscose fiber with a modified flat cross-sectional shape, according to an embodiment of the invention;

[0018] FIG. 3 is an illustration of exemplary cross-linked wood pulp fibers; and

[0019] FIG. 4 is a graphical illustration showing the wet strength of different converted fiber blends;

[0020] FIG. 5 is a graphical illustration showing the wet bulk thickness for different fiber blends after converting, including the two grades with shaped fibers (Galaxy and Helix).

[0021] While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0022] In general, many of the conventional airlaid nonwoven wet wipes which have been made without plastic also tend to be without cellulosic staple fiber or curly pulp, and tend to be very thin and low in wet strength. Additionally, it is typical for many of the conventional carded, hydroentangled nonwoven wet wipes to be much thinner, with less resiliency, and have embossment patterns that are less clear than conventional wet wipes.

[0023] Embodiments of the invention described herein show a plastic-free wet wipe that is made using predominantly low-cost wood pulp, but with a combination of specific, natural cellulosic fibers which can maintain their bulk and thickness, and which have a resilience such that the bulk and thickness will be maintained during processing and conversion to the finished product. A plastic-free wet wipe is described in U.S. Pat. No. 11,879,212, entitled Plastic Free Wet Wipes With High Bulk and Wet Strength, the entire teachings and disclosure of which is incorporated herein by reference thereto. A water-disintegrable cleaning sheet is disclosed in U.S. Pat. No. 5,281,306 (the '306 patent), the entire teachings and disclosure of which is incorporated herein by reference thereto.

[0024] As in the present invention, the wet wipe of U.S. Pat. No. 11,879,212 ('212 patent) is made using non-plastic materials. The wet wipe, disclosed in that patent, is an airlaid, wood-pulp-based nonwoven material. The wet wipe of the '212 patent uses standard wood pulp fiber in combination with cellulosic fibers to provide reasonably high wet strength and bulk. For example, the wet wipe may have a wet strength of at least 200 grams per linear inch in the cross direction as measured by INDA/EDANA Nonwovens Standard Procedures Edition 2015, Standard Procedure: NWSP 110.R0 (15) Breaking Force and Elongation of Nonwoven Materials (Strip Method) and may have a wet bulk of at least 0.7 mm for 50 grams per square meter as measured by INDA/EDANA Nonwovens Standard Procedures Edition 2015, Standard Procedure: NWSP 120.6.R0 (15) Nonwoven Thickness (EDANA Method).

[0025] The '212 patent further discloses low-diameter (decitex or denier) fibers with an average fiber length from 3 to 12 millimeters. These fibers have the capability to form a network when combined with a natural chemical binder and wood pulp to enhance wet strength. Examples of these fibers include lyocell in a range of between 0.8 -1.5 decitex and preferably approximately 1.15 decitex fiber such as that distributed by Lenzing Aktiengesellschaft of Lenzing Austria under the TENCEL tradename and viscose in a range of between 0.5 and 1.5 decitex and preferably approximately 0.9 decitex such as that distributed by Kelheim Fibres of Kelheim Germany under the DANUFIL trademark.

[0026] The use of these unique fiber blends and bonding through entangling water jets allows for the wet wipe to be created without the need for either chemical or thermoplastic binders, as practiced in the aforementioned '212 patent and '306 patent. This represents a notable improvement over the state of the art, as such binding systems have been found not to be stable in the lotion acidic environment that is required for skin health and preservative efficacy in baby wipe products.

[0027] In order to develop the desired wet strength and wet bulk in a finished wet wipe structure, wood pulp fluff may be combined with a number of different non-standard fiber types may be employed. Particular fibers that can be utilized to increase the wet bulk of the wet wipe structure are those that have a modified cross-sectional shape. FIG. 1 is a viscose fiber with a trilobal cross-sectional shape. This trilobal fiber is distributed by Kelheim Fibres under the GALAXY tradename.

[0028] FIG. 2 is a viscose fiber with a modified cross-sectional shape having a flat cross-sectional shape distributed by Kelheim Fibres under the VILOFT tradename. These modified cross-sectional shapes improve wet bulk by changing the way in which the fibers pack together and providing a modified resistance to pressure.

[0029] The above-identified fibers may undergo opening processing to allow them to be effectively processed using airlaid equipment. For example, in the case of the cellulosic staple fibers (e.g., lyocell or viscose as discussed above) undergo a series of mechanical combing and air conveying in order to break the product into their individual fibers. This allows the cellulosic staple fibers to be successfully admixed with standard fluff wood pulp so that the resulting blend of materials to obtain the desired functional wet strength and bulk.

[0030] Embodiments of the invention disclosed herein describe a product that utilizes shaped cellulosic fibers in addition to standard wood pulp fiber in order to develop a finished wet wipe which has high bulk/thickness and also resiliency against compression. In the context of this invention, shaped refers to fibers with cross-sections that are trilobal or flat in shape, though it can include other shapes beyond the conventional fibers with a circular cross-section. The method of web forming of these products uses air laid pulp-based nonwovens and this is then combined with bonding using high pressure water jets in a process called hydroentangling or spunlacing. This bonding system has been used before, but has typically resulted in more dense, thinner structures as the process typically reduces the thickness of the nonwoven material produced, this retention of bulk/thickness through this process is a key element of the invention.

[0031] In order to develop the desired bulk/thickness in a finished wet wipe structure while maintaining the necessary degree of wet strength, a critical blend of non-standard fiber types have been employed. For development of wet strength low-diameter (decitex or denier), fibers with a fiber length from 5 to 12 millimeters, which have the capability to form strong bond points or knots when entangled, have been employed. Examples of these fibers include Lenzing Lyocell 1.15 decitex fiber and Kelheim Viscose Danufil 0.9 decitex fiber.

[0032] These fibers are then combined with other non-standard cellulosic fibers to develop the wet bulk/thickness of the wet wipe structure and critically to retain this wet bulk and thickness during the production processes. Further, cross-linked wood pulp fiber also referred to as cross-linked curly wood pulp fiber or cross-linked curly pulp may be used to retain the wet bulk or wet strength (e.g., resiliency) of the wet wipe structure.

[0033] FIG. 3 illustrates an example of cross-linked wood pulp fibers. These fibers include those that have been modified through chemical treatment and caused to curl and remain resilient in a wet wipe. Such crosslinked curly wood pulp fibers (International Paper grades CMC530/CMF530/GMF530/TR195/TR195A) can be used to retain the bulk or resiliency of the wet wipe.

[0034] In order to successfully use fine denier lyocell or viscose successfully in the airlay forming system where the web is formed it has been shown that the use of novel antistatic treatments and fine fiber opening systems are required. In the case of crosslinked curly pulp fibers, a specific low-speed sawmill treatment is typically required to open these fibers and enhance bulk without breaking the fibers, creating dust, and destroying their effectiveness.

[0035] As explained above, in certain embodiments, the above-described fibers are blended with wood pulp and formed using an airlaid process. The effective blend ratios for achieving a wet wipe with sufficient wet strength and high bulk/thickness and resiliency are those with wood pulp from 50% to 80% by weight, fine denier lyocell/viscose from 10% to 30% by weight, and bulking fibers (modified cross section or curly fibers) from 3% to 15% by weight. More preferably, the blend ratios are in the range of wood pulp 60 to 80% by weight, and fine denier lyocell/viscose from 15 to 25% by weight, and bulking fibers from 5% to 10% by weight. Fiber blends such as these provide higher wet bulk/thickness and better resiliency than conventional plastic-free wet wipes. Additionally, these blends provide a binder-free and plastic-free formulation that is stable in both acidic and basic lotion environments.

[0036] FIG. 4 is a graphical illustration showing the wet strength of different converted fiber blends. The graph of FIG. 4 shows the converted product wet strength in the machine direction (MD) and in the cross direction (CD) perpendicular to the machine direction. As can be seen from FIG. 4, the wet wipe made using the process disclosed herein, e.g., Trial 2.0 Converted Galaxy fiber blend, shows enhanced wet strength compared a strictly lyocell fiber, and with wet strength as good or better than thermal bonding airlaid (TBAL) fibers. In the graph of FIG. 4, the Galaxy fiber blend shows a machine direction wet strength between 1150 and 1200 grams per linear inch, and a cross direction wet strength of approximately 600 grams per linear inch. As stated above, the machine direction is perpendicular to the cross direction.

[0037] FIG. 5 is a graphical illustration showing the wet bulk thickness for different fiber blends after converting, including the two grades with shaped fibers (Galaxy and Helix). As shown in FIG. 5, the Galaxy and Helix fiber blends maintain a high level of wet bulk thickness after converting, as compared to conventional TBAL and multi-bonding airlaid (MBAL) formulations.

[0038] To maintain the bulk/thickness of the above-described wet wipes, and to improve the aesthetic appeal of these products, many of these wipes have a pattern embossed upon them. In wet wipes that contain plastic, this embossing is easily achieved using heated calendar rollers with patterns on them. Alternatively, in some hydroentangled wet wipes, the embossed pattern is made during the water jet entanglement process.

[0039] In embodiments of the present invention, the embossing is performed using heated calendar rolls, but with the nonwoven fibers still in a wet state after the hydroentanglement process. This allows for a high-quality embossed pattern to be produced at the same level of quality as with thermoplastic-fiber-containing sheets, and in many cases with a significantly better level of definition than the embossed patterns achieved via hydroentanglement.

[0040] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0041] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0042] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.