Plastic free wet wipes with high bulk and wet strength

A wet wipe is provided. The wet wipe includes a sheet formed from non-plastic materials. The sheet has a weight of between 40-90 gsm. The sheet comprises a blend of wood pulp fluff fiber and cellulosic staple fibers and/or cross-linked curly pulp. The wood pulp fluff fiber has a weight percent of between 60-95%. The cellulosic staple fibers and/or cross-linked curly pulp has a weight percent of between 40-5%. A plastic free binder is included. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

FIELD OF THE INVENTION

This invention generally relates to wet wipes.

BACKGROUND OF THE INVENTION

This invention generally relates to wet wipes such as for hygiene or cleaning applications. The disposable consumer wipes market is being faced with challenges related to the disposal and degradation of products after use. Plastics in the marine environment and in beach litter are further highlighting this issue. In the European Union, a legislative directive has been approved for the control of single use plastics. See EU Single Use Plastics Directive 2019/904 Jun. 5, 2019. In North America and other geographies, such legislation is being considered. See California Circular Economy and Plastics Pollution Reduction Act June 2019.

Consumer wipes have been specifically identified as one such material that would be regulated by such types of legislation. Most consumer wipes utilize plastic based fibers (typically polyester or polypropylene) as a component of the structure. These plastic fibers may be up to 80% of the structure in some baby wipes and surface cleaning wipes in order to produce a functionally effective wipe material.

The elimination and substitution of these fibers for natural based, non-plastic fibers creates challenges to develop successfully both the wet strength and the thickness (bulk) that the plastic fibers provide. It is possible to produce structures that are based of wood pulp and natural, non-plastic binders, such as starch, CMC & sugar based chemistries. However these products tend to, by themselves, be low in wet strength and very dense/flat such that they do not meet the functional or aesthetic needs of the product.

As such, there is a need in the art for an improved wet wipe that uses natural materials and is plastic free, but that provides sufficient bulk and wet strength.

SUMMARY OF THE INVENTION

The disclosure provides new and improved material for wet wipes with improved strength and/bulk characteristics while being plastic free as well as method of forming the material.

In an example, a wet wipe formed from a sheet formed from non-plastic materials is provided. The sheet has a weight of between 40-90 gsm. The sheet includes a blend of wood pulp fluff fiber and cellulosic staple fibers. The wood pulp fluff fiber has a weight percent of between 60-95%. The cellulosic staple fibers have an average fiber length of between 3-12 mm. The cellulosic staple fibers have a weight percent of between 40-5%. The sheet includes a plastic free binder. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

The cross-direction being perpendicular to a direction in which the sheet travels when it is being formed, e.g. along a width of a belt upon which the fibers are laid during the forming process.

In one example, the cellulosic staple fibers are formed from one or more of fine denier/decitex, shaped lyocell, or viscose.

In one example, the wet thickness of the sheet is between 0.7 mm and 1.8 mm for a 50 gsm product.

In one example, the cellulosic staple fibers have a modified cross-sectional shape.

In one example, the cellulosic staple fibers have a trilobal cross-sectional shape.

In one example, the cellulosic staple fibers have a flat cross-sectional shape.

In one example, the fibers have been compacted under pressure of between 4-8 Bar and the wet thickness has been maintained at between 0.7-1.5 mm.

In an example, a wet wipe formed from a sheet formed from non-plastic materials is provided. The sheet has a weight of between 40-90 gsm. The sheet includes a blend of wood pulp fluff fiber and cross-linked curly pulp. The wood pulp fluff fiber has a weight percent of between 60-95%. The cross-linked curly pulp have a weight percent of between 40-5%. The sheet includes a plastic free binder. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

In an example, a wet wipe formed from a sheet formed from non-plastic materials is provided. The sheet has a weight of between 40-90 gsm. The sheet includes a blend of wood pulp fluff fiber and a blend of cellulosic staple fibers and cross-linked curly pulp. The wood pulp fluff fiber has a weight percent of between 60-95%. The blend of cellulosic staple fibers and cross-linked curly pulp have a weight percent of between 40-5%. The sheet includes a plastic free binder. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

In one example, the cellulosic staple fibers of the blend of cellulosic staple fibers and cross-linked curly pulp has an average fiber length of between 3-12 mm.

In one example, the cross-linked curly pulp has been treated with a sawmill system.

In one example, the blend of cellulosic staple fibers and cross-linked curly pulp has a weight percentage of 5-40% of cellulosic staple fibers and a weight percentage of 5-40% of cross-linked curly pulp.

In one example, the cross-linked curly pulp has a knots level of less than 10% and preferably less than 5% and more preferably less than 3%.

In one example, the cross-linked curly pulp has a dust level of less than 10% and more preferably of less than 5%.

In one example, the cross-linked curly pulp has a saline capacity of at least 10 grams per gram and at least 15 grams per gram.

In one example, the forming process is airlaid.

In one example, the plastic free binder is natural.

In one example, the plastic free binder is any one or more of carboxymethyl cellulose, modified starch and/or modified sugars.

In one example, the wet thickness of the sheet is between 0.7 mm and 1.8 mm for a 50 gsm product.

In an example, a method of forming a wet wipe includes forming a sheet from non-plastic materials, the sheet having a weight of between 40-90 gsm. The step of forming includes blending wood pulp fluff fiber and cellulosic staple fibers. The wood pulp fluff fiber has a weight percent of between 60-95%. The cellulosic staple fibers have an average fiber length of between 3-12 mm. The cellulosic staple fibers has a weight percent of between 40-5%. The step of forming includes air laying the blend of wood pulp fluff fiber and cellulosic staple fibers to form a web. The step of forming includes applying a plastic free binder to the web. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

In one example, the method includes compressing the web under pressure from 4-8 Bar while the wet thickness after compression is between 0.7-1.5 mm. The step of compression occurs prior to the step of applying the plastic free binder.

In an example, a method of forming a wet wipe includes forming a sheet from non-plastic materials, the sheet having a weight of between 40-90 gsm. The step of forming includes blending wood pulp fluff fiber and cross-linked curly pulp. The wood pulp fluff fiber has a weight percent of between 60-95%. The cross-linked curly pulp has a weight percent of between 40-5%. The step of forming includes air laying the blend of wood pulp fluff fiber and cellulosic staple fibers to form a web. The step of forming includes applying a plastic free binder to the web. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

In one example, the method includes compressing the web under pressure from 4-8 Bar while the wet thickness after compression is between 0.7-1.5 mm. The step of compression occurs prior to the step of applying the plastic free binder.

In an example, a method of forming a wet wipe includes forming a sheet from non-plastic materials, the sheet having a weight of between 40-90 gsm. The step of forming includes blending wood pulp fluff fiber and a blend of cellulosic staple fibers and cross-linked curly pulp. The wood pulp fluff fiber has a weight percent of between 60-95%. The blend of cellulosic staple fibers and cross-linked curly pulp has a weight percent of between 40-5%. The step of forming includes air laying the blend of wood pulp fluff fiber and cellulosic staple fibers to form a web. The step of forming includes applying a plastic free binder to the web. The sheet has an effective wet strength of at least 150 grams per linear inch in the cross-direction.

In one example, the method includes compressing the web under pressure from 4-8 Bar while the wet thickness after compression is between 0.7-1.5 mm. The step of compression occurs prior to the step of applying the plastic free binder.

DETAILED DESCRIPTION OF THE INVENTION

A wet wipe formed in accordance with the application uses non-plastic materials. In one implementation, the wet wipe is an airlaid pulp based nonwoven. The wet wipe uses standard wood pulp fiber in combination with cellulosic fibers to provide 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 Nonwovem Materials (Strip Method) and wet bulk of at least 0.7 mm for 50 gsm product as measured by INDA/EDANA Nonwovens Standard Procedures Edition 2015, Standard Procedure: NWSP 120.6.R0 (15) Nonwoven Thickness (EDANA Method).

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.

For example, low diameter (decitex or denier) fibers with an average fiber length from 3 mm to 12 mm may be employed. These fibers have the capability to form a network 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 dtex and preferably approximately 1.15 dtex 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 dtex and preferably approximately 0.9 dtex such as that distributed by Kelheim Fibres of Kelheim Germany under the DANUFIL trademark.

Other 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.1is a viscose fiber with a modified cross-sectional shape to having a trilobal shape distributed by Kelheim Fibres under the GALAXY tradename.FIG.2is 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.FIG.5illustrates ultrafine lyocell fibers that may be incorporated. To be considered ultrafine, the lyocell fibers have a fineness of below 1.3 dtex.

Further, cross-linked wood pulp fiber also referred to as “cross-linked curly wood pulp fiber” or “cross-linked curly pulp” can be used to retain the wet bulk or wet strength (e.g. resiliency) of the wet wipe structure. For example, International Paper grades CMC530/CMF530/GMF530/TR195/TR195A may be incorporated.FIG.3illustrates representative cross-linked wood pulp fiber.

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 these cellulosic staple fibers to be admixed successfully with standard fluff wood pulp allowing the resulting blend of materials to obtain the desired functional wet strength and bulk.

In the case of the cross-linked curly pulp fibers, a specific low speed sawmill treatment is required to open these fibers without breaking the fibers and creating dust and destroying their effectiveness to enhance bulk. A representative sawmill treatment system for processing the cross-linked curly pulp fibers is illustrated inFIG.4. The sawmill process would be carried out prior to admixing with the wood pulp fluff.

Preferably, the cross-linked curly pulp fibers have a knots level of less than 10% and even more preferably less than 5% and even more preferably less than 3%. The knots level is measured by way of Scandinavian Pulp & Paper Board Testing Method SCAN 37-8. Typically knots level relates to the amount of dense clumps in the product. A clump is defined as assembly of fibers that is denser in nature than about 1-4 mm in diameter.

Preferably, the dust level of the cross-linked curly pulp fibers is less than 10% and more preferably less than 5%. The dust level is the amount of dust that the product has. Dust is defined as fibers having a fiber length of less than 0.2 mm. High levels of dust make the product difficult to process and reduces yield.

Preferably, the saline capacity of the cross-linked curly pulp fibers is at least 10 grams per gram and more preferably at least 15 grams per gram. This is measured using the International Paper test which measures the amount of saline liquid that the cross-linked curly pulp absorbs and retains under pressure. It is a measure of the products wet resilience prior to the product being admixed with the wood pulp fluff.

FIG.6is a chart of characteristics of cross-linked curly pulp before and after different types of treatment. More particularly, after being sawmill treated or hammermill treated. While hammer mill treatment provides decent knots levels, it has a high dust content and low saline capacity. Conversely, sawmill treatment provides good knots levels, dust levels and saline capacity.

The above identified fibers can be blended with wood pulp formed during an airlaid process. The airlaid fibers can then be compressed, such as by way of compaction rolls, to help develop strength. Typically, compaction reduces product thickness, which undesirably reduces bulk. However, the use of cellulosic staple fibers or cross-linked curly pulp mitigates the reduction in thickness while maintaining strength properties.

The desired fiber blend for achieving desired wet strength and bulk is 60% to 95% by weight wood pulp fluff and 40% to 5% by weight cellulosic staple fibers or cross-linked curly pulp. More preferably, the blend is 70-90% by weight wood pulp fluff at 70 to 90% and 30-10% by weight cellulosic staple fibers or cross-linked curly pulp.

In some implementations, the portion of the blend formed from cellulosic staple fibers or cross-linked curly pulp is a mixture of both cellulosic staple fibers and cross-linked curly pulp.

After forming the fiber blends above, the fiber blends are sprayed with a natural, plastic free chemical binder. The binder may be carboxymethyl cellulose (CMC), modified starch or modified sugars. Typically, the modified starch or modified sugars are modified with some kind of crosslinking system. These binders migrate to the crossover points of the fibers on heating and drying and form an insoluble bond during the crosslinking process.

In a preferred wet wipe, the structure of the wet wipe has a weight of 40-90 grams per square meter and preferably a wet strength of at least 150 grams per linear inch in the cross-direction. The cross-direction is defined as a direction perpendicular to the direction the product flows as it is being manufactured.

While the structure described above finds particular use in wet wipes and particularly wet wipes used as baby wipes, the structure may find additional use in feminine hygiene or diaper products (both children and adult).

FIG.7is a schematic illustration of a system100for forming the structure of the material to be formed into the sheets for wet wipes.

The system100includes a source of wood pulp fluff fiber102. The wood pulp fibers may be added through the use of hammer mills.

The system100includes a second source of fibers104for supplying cellulosic staple fibers and/or cross-linked curly pulp. These fibers may be added into the system through fiber bale breakers and fiber dosing units. In some implementations, such as when cross-linked curly pulp is used, the second source of fibers104may include a sawmill treatment system for manipulating the cross-linked curly pulp prior to mixing with the wood pulp fluff fibers.

These wood pulp fluff fibers and the cellulosic staple fibers and/or cross-linked curly pulp fibers are transported and mixed in transport fans106and sent to the web forming sections108that include airlaid forming heads which can include forming drums.

The mixed fibers enter the forming drums from the side and vacuum is pulled at the bottom of the airlaid forming heads. The mixed fibers are distributed by perforations in the forming drums and needle rolls. The needle rolls turn in opposite directions.

As the mixed fibers are dispensed from the forming drums, the fibers are deposited on a belt107to form a web of the mixture of the fibers. After being deposited on the belt107, the web and its associated fibers may be compressed by compaction rolls109. The compression by compaction rolls109increases strength within the resulting material. However, the particular composition of fibers helps mitigate the typical associated reduction in bulk.

In one example, the compaction rolls109compact the web of the mixture of fibers under pressure of between 4-8 Bar and the wet thickness has been maintained at between 07-1.5 mm.

A web bonding region110can provide chemical and thermal bonding as well as apply the plastic free binder.

Thereafter, the web may be exposed to finishing processes and then removed from the belt and wound into a roll. When forming sheets for wet wipes, the web may be directly supplied to a cutting arrangement or the roll of web may be shipped to another location for forming the wet wipe sheets.

In one example, it was determined that the use of 1.15 denier lyocell fibers at mix levels of 10% and 20% enhanced both wet strength and wet thickness of wet wipe products. The following chart provides experimental data related to testing:

In one example, it was illustrated that by using lyocell, such as 20% lyocell, the amount of compression could be increased to 6 Bar while maintaining or even increasing the resulting wet thickness value as compared to pulp only. Using Lycoell, also resulted in increased strength in both the machine and cross-directions due, in part, to the ability to increase the pressure. The following chart illustrates the effect on wet thickness, machine direction and cross-direction strength with increased pressure as well with increased pressure and the use of lyocell: