MXPA01006782A - Multi-ply wipe - Google Patents

Abstract

A basesheet for a wet wipe which includes multiple fibrous layers. At least one of the fibrous layers of the basesheet includes either 1) polyethylene fibers formed by a blend of polyethylene and an additive or 2) polypropylene fibers formed by a blend of polypropylene and an additive. For example, a fully hydrogenated hydrocarbon resin may be used as an additive with polyethylene to form polyethylene fibers which have a lower melting temperature of about 87 degrees Celsius. Polyethylene layers produced with such fibers may have an enhanced strength, produce less lint and be more securely attached to an adjacent fibrous layer. Polybutylene may be used as an additive with polypropylene to form polypropylene fibers to produce a more flexible layer with an increased attachment to an adjacent fibrous layer. The polyethylene and polypropylene layers may also include natural fibers such as cellulosic fibers. These polyethylene and polypropylene layers may both be present ina basesheet or may be combined with other fibrous layers. One or both of the major exterior surfaces of the generally planar basesheet may be formed by a polyethylene layer to provide the basesheet with a relatively soft exterior wiping surface. The polypropylene layer may be advantageously combined with a softer layer to provide strength and resiliency to the basesheet. A three ply basesheet may include an inner polypropylene layer and two outer polyethylene layers to thereby take advantage of the different properties of these layers. The use of an additive with either the polyethylene or polypropylene fibers allows the properties of the basesheet to be further controlled to suit the basesheet for its intended purpose.

Description

MULTI-STRATE CLEANING CLOTH BACKGROUND OF THE INVENTION 1. Field of the invention The present invention relates to multi-layer cleaning wipes. The invention particularly concerns wet wiping cloths which include a lower sheet of multiple layers. 2. Description of the related art Wet cleaning cloths are well known and have been produced in many forms. One of the most common forms of wet cleaning cloths is a stack of wet sheets packed in a plastic container. Wet cleaning cloths have been made from a variety of materials and have been moistened with a variety of appropriate cleaning solutions. Such cleaning cloths have been used as baby wipes, hand wipes, wipes for cleaning the home, industrial wipes and the like.

Typically, conventional wet wiping cloths have included a single layer of a substantially homogeneous material. For example, such conventional wet wipes have been formed by an air-laid fabric of fibers which are distributed or mixed uniformly through the fabric. The cleaning cloths have been formed by a variety of natural, synthetic and polymeric fibers such as polyester, polyethylene, polypropylene and cellulosic fibers. Other conventional wet wipes have included a coform of cellulosic fiber and polypropylene where the fibers are uniformly mixed through the fabric.

The balance of physical properties, such as softness, flexibility, strength, integrity, and elasticity, of cleaning cloths is difficult to optimize when using only a single type of fiber or fibers which are uniformly mixed through the thickness of the lower sheet material. This has been particularly true for those users who want improved smoothness. For example, certain fibers which can be used as wet cleaning cloths are rigid and can provide strength and elasticity but are not as soft or flexible as other fibers. While other fibers, which can also be used for wet cleaning cloths, are softer but can not have sufficient moisture resistance to withstand the forces exerted by the user and can produce more fluff than other fibers.

Synthesis of the Invention The present inventors have recognized the difficulties and problems of the prior art and in response to it have developed a lower sheet for a multi-layer wet cleaning cloth with improved physical properties by including an additive in either the polyethylene fibers or the polyethylene fibers. polypropylene used to form one of the layers or layers of the lower sheet of the wet cleaning cloth. The use of such an additive in the lower layer sheet allows the physical properties of the lower sheet to be modified to fit the intended purpose of the cleaning cloth. For example, the cleaning cloth which is intended to be used in contact with the skin, the layers of the lower sheet of a cleaning cloth according to the present invention can be combined to provide a soft and flexible cleaning cloth while still maintaining the resistance, integrity and elasticity of the cleaning cloth.

In one embodiment, the present invention provides a bottom sheet with layers for a wet cleaning cloth having a polyethylene layer and a polypropylene layer in mutual contact. In some embodiments, two outer layers of polyethylene are bonded to an inner layer of polypropylene. An additive is present in either the polyethylene or polypropylene fibers and therefore modifies one or more of the physical properties of the fibers and the resulting cleaning cloth. The natural fibers can also be included in one, several, or in all the lower leaf layers.

In some embodiments, an additive that lowers the melting temperature of the polyethylene and which functions as an adherent is added to the polyethylene fibers. A complete hydrogenated hydrocarbon resin additive can be used as an adherent and to lower the melt temperature of linear low density polyethylene by more than 40 degrees from about 130 degrees Celsius to about 87 degrees Celsius.

In other embodiments of the invention, an additive, for example a polybutylene such as a polybutene-1 copolymer, is present in the polypropylene fibers to increase the strapping of the stratum or the flexibility of the polypropylene layer. Another additive which can be used with polypropylene fibers to increase its adhesion is polyethylene acrylic acid.

Other embodiments of the present invention provide a wet cleaning cloth with a lower sheet having at least two fibrous layers wherein one of the layers includes fibers formed by a mixture which includes both an additive and a polyethylene. The polyethylene fiber layer may also include natural fibers while the other fibrous layer may include natural fibers, synthetic fibers or both synthetic and natural fibers.

Further embodiments of the present invention provide a wet cleaning cloth with a lower sheet having at least two fibrous layers wherein one of the layers includes fibers formed by a mixture which includes both an additive and a polypropylene. The polypropylene fiber layer may also include natural fibers while the other fibrous layer may include natural fibers, synthetic fibers or both synthetic and natural fibers.

Embodiments of the present invention may take the form of a lower sheet of wet cleaning cloth with non-woven layers which includes a first layer including polypropylene fibers and which has a first and a second major surface disposed opposite each other; a second layer which includes polyethylene fibers and has a main surface facing inwardly and an opposingly facing outwardly facing major surface area where the surface faces inwardly and is oriented towards and makes contact with the first major surface of the first layer and the surface facing away from the second layer defines an outer surface of the lower sheet; and an additive which is presented in either polypropylene fibers or polyethylene fibers.

The embodiments of the present invention can also take the form of a lower sheet of wet cleaning cloth with non-woven layers which includes an inner layer including polypropylene fibers and having a first and a second major surface arranged oppositely; the first and second outer layers each of which includes polyethylene fibers and has a major surface that faces inwardly and an opposingly disposed facing major surface, the major surfaces facing inwardly of the first and of the second outer layers are in respective contact with the first and second major surfaces of the inner layer, the major surfaces facing outwardly of the first and second outer layers define two principal outer surfaces arranged oppositely of the lower sheet; and an additive which is present in either the polypropylene fibers of the inner layer or polyethylene fibers of the first and second outer layers.

Further embodiments of the present invention may take the form of a wet cleaning cloth having a lower nonwoven sheet which includes a first fibrous layer and a second layer; The first fibrous layer has an opposing first and second surface arranged; the second layer includes a plurality of fibers and has a main surface that faces inwardly and an opposingly facing outwardly facing major surface area, the main surface facing inward is oriented toward and contacting the first major surface of the first layer and the outward facing major surface defining an outer surface of the lower sheet and wherein the fibers of the second layer include fibers formed by a mixture of polyethylene and an additive; and a solution arranged in the lower sheet.

In still further embodiments of the present invention, they may take the form of a wet cleaning cloth having a lower non-flowing sheet which includes a first layer and a second fibrous layer; the first layer including a plurality of fibers and having opposite first and second surfaces and wherein the fibers of the first layer includes fibers formed by a mixture of polypropylene and an additive; and the second fibrous layer having a main surface facing inwardly and an opposingly facing outward facing major surface, the inwardly facing surface is oriented toward and connecting to the first major surface and the surface main facing outward defining an outer surface of the lower sheet; and a solution arranged in the lower sheet.

The present invention, in its various embodiments, provides several advantages. It allows different materials, which include either polyethylene or polypropylene, to be combined to form a lower sheet of wet cleaning cloth in a manner in which it outweighs the different physical properties of the different materials. For example, the layers of the lower sheet can be combined to take advantage of the relative strength provided by the polypropylene fibers, the relative softness provided by the polyethylene fibers, or both of these properties. Additionally, the use of an additive, either in the polypropylene or polyethylene fibers, allows the properties of the lower sheet to be further controlled to better adapt the properties of the lower sheet to the intended purpose of the cleaning cloth.

Detailed Description of the Invention The present invention relates to the lower sheets with layers or multiple layers for wet cleaning cloths. The lower sheets according to the present invention can be used to form baby wipes, face and hand wipes, cosmetics wipes, household wipes, industrial wipes and other wet wipers products .

The bottom sheet layers of the wet wiping cloths can be made from a variety of materials including melt blown materials, coform materials, air laid materials, bonded web materials, hydroentangled materials, bonded materials by spinning and the like, and may comprise natural or synthetic fibers. The lower sheet with layers may include a relatively soft layer which may include relatively flexible and / or soft synthetic fibers such as linear low density polyethylene fibers. The lower sheet with layers may also include a relatively resilient, resilient layer which may include relatively high strength and elastic tensile strength synthetic fibers such as isotactic polypropylene fibers.

The lower sheets of the present invention are multi-layer lower sheets which include at least two fibrous layers wherein one of the layers includes either polypropylene fibers or polyethylene fibers. The present invention can also advantageously combine two fibrous layers wherein a first layer includes polypropylene fibers and a second layer includes polyethylene fibers. Additional fibrous layers which do not include polypropylene or polyethylene fibers can also be used in the lower sheets.

A lower sheet which includes both a layer of polyethylene and polypropylene can take advantage of the different properties of both fibers. Polyethylene fibers are generally more flexible and therefore softer than polypropylene fibers. This is due to the inherent differences between polyethylene and polypropylene in the viscosity, structural chemistry and fiber solidification. A lower sheet produced with polyethylene fibers may, therefore, generally be softer than a similar lower sheet produced with polypropylene fibers.

The same properties may increase the softness, however, they may also negatively and impact other properties of the lower sheet such as tensile strength, strapping, fluff, and fiber accumulation. An inner sheet produced with polypropylene will generally be able to play a lower polyethylene sheet with these subsequent properties but will not be able to have the softness provided by a lower polyethylene sheet.

The lower leaves are generally flat with two main outer surfaces arranged opposite each other. The lateral edges of the lower sheets have a limited surface area and are not generally used as cleaning or cleaning surfaces by the end user of the cleaning cloth. Therefore, by taking advantage of the softness provided by a polyethylene layer, the polyethylene layer can be used to define one or both of the major outer surfaces of the lower sheet. In a lower sheet of two layers, for example, a polyethylene layer can define a main outer surface of the lower sheet while a lower sheet of three layers, the polyethylene layers can be used to define both major outer surfaces of the sheet lower.

Similarly, a polypropylene layer can be combined with a layer having the greatest softness to provide improved strength of the inner sheet. As used herein and unless otherwise explicitly disclosed otherwise, a layer or layer of polyethylene refers to a bottom sheet layer which includes blended polyethylene or polyethylene fibers. The polyethylene fibers may be homopolymer fibers or bicomponent fibers. The polyethylene layer may also include non-polyethylene fibers such as natural fibers. In a similar manner, a polypropylene layer includes by propylene or blended polypropylene fibers. The polypropylene fibers can be bicomponent or homopolymer fibers. The polypropylene layer may also include polypropylene fibers such as natural fibers.

The additives can be mixed in the polyethylene or in the polypropylene used to form the fibers. The presence of an additive in the polypropylene or polyethylene fibers can affect the properties of the polypropylene or polyethylene layer and provides another means by which the properties of the lower sheet can be modified to adapt the lower sheet to a use in particular.

In accordance with an embodiment of the present invention, a layer of polypropylene and polyethylene can be combined together to form a lower sheet of two layers.

In such a lower sheet, where the first layer includes polypropylene fibers and the second layer includes polyethylene fibers, the first polypropylene layer has opposite first and second major surfaces disposed. Similarly, the second polyethylene layer has a major surface facing inwardly and a major surface facing outwardly. The main surface facing inward of the polyethylene layer contacts the first major surface of the polypropylene layer. The main surface facing outwardly of the polyethylene layer defines an outer surface of the lower sheet and provides a relatively smooth surface for cleaning while the polypropylene layer increases the strength of the lower sheet.

Either or both of the polypropylene and polyethylene layers may also include natural fibers. For example, the polypropylene layer can be a coform layer of melt blown polypropylene microfibers and wood pulp fibers wherein the weight ratio of the pulp to the polymer is about 50/50 about 75/25 and, advantageously, about 65/35. A suitable polypropylene is an isotactic polypropylene obtained from Montell USA Inc. of Wilmington, Delaware under the trademark designation MONTELL PF015. The polyethylene layer can be a coform layer of melt blown linear low density polyethylene microfibers and wood pulp fibers where the weight ratio of the pulp to the polymer is about 25/75 about 75 / 25 and, advantageously, around either 50/50 or 65/35. A suitable polyethylene is available from Dow Chemical Co. under the brand name ASPUN 683ÍA.

Additional embodiments of the present invention may include additional fibrous layers. For example, a lower sheet of three layers may advantageously include either an inner polypropylene layer and two outer polyethylene layers. In this manner, the facing surfaces facing away from the two layers of polyethylene can define both of the main outer surfaces arranged oppositely of the bottom sheet. The major surfaces facing inward of the polyethylene layers that are arranged in contact with the two major surfaces of the polypropylene layer by which the polypropylene layer can provide strength to the bottom sheet without having a negative impact on the smoothness of the main outer surfaces of the lower sheet. Natural fibers may also be included in one or more of the layers of such lower sheet.

The polypropylene and polyethylene fibers are thermally incompatible and generally do not bond well with one another. The polypropylene and polyethylene fibers, however, can become entangled with one another resulting in proper securing between the layers. For example, in a lower sheet, layers containing a coform layer of polyethylene and cellulosic fibers and a coform layer of polypropylene and cellulosic fibers, the polypropylene and polyethylene fibers can entangle with each other and the cellulosic fibers and can at least partially join the cellulosic fibers which results in an assurance between the layers. Such bonding of the interlaced layers and the entanglement can be improved by a thermomechanical process wherein in the lower sheet with layers is passed between a heated soft anvil roller and a heated pattern roller.

The incorporation of an additive in either the polypropylene or polyethylene fibers can also improve the level of clamping between the adjacent layers of polypropylene and polyethylene. The use of an adherent, an additive can provide such results.

Various adherents are known in the art and can be used to improve the bonding or adhesive properties of the fibers in which they are incorporated. Adherents can be effectively added to the materials with which the adherent has limited compatibility. Adherents often have molecular weights which have a wide distribution and fall within the range of 500 to 2000. The softness points of such adherents can vary from 50 to 150 degrees Celsius.

Adhesives can improve the adhesion of an elastomeric material by reducing the resistance of the material to deformation at low rates of deformation (thereby facilitating the formation of contact bonding) while increasing the deformation resistance at higher rates of deformation (by which provides a stronger resistance to separation). By reducing the elastic recovery and facilitating the plastic deformation, the adherent can allow the adhesive mass to contact the surface more intimately, thereby improving the strength of the joint. This functionality of the adherents is well known and can be quantified or verified for a particular elastomeric material and the adherent by comparing the shear storage modulus of the elastomeric material with and without the adherent.

It has been found that when polyethylene fibers for a lower sheet of wet cleaning cloth using a mixture of polyethylene and a hydrogenated hydrocarbon resin additive complete, such as the adherent REGALREZ 1126® produced by Hercules Inc. having offices in Wilmington , Delaware, the peel strength of the adjacent polypropylene and polyethylene layers can be significantly improved. The strapping, or peel strength, of the adjacent layers can be measured in a manner described below in the description of the examples.

Additionally, it has been found that a polyethylene mixture containing 80% polyethylene and 20% REGALREZ 1126® produces fibers having a melting temperature of about 87 degrees Celsius. This compares to a melting temperature of approximately 130 degrees Celsius for the virgin polyethylene used in the mixture.

By reducing the melting temperature of the polyethylene fibers, and in the absence of a corresponding drop in processing temperature, it is believed that the fibers will probably remain in a semi-molten state for a longer period of time during the formation of the layer of polyethylene compared to virgin polyethylene. It is also believed that this may allow for the formation of more bonds between the individual polyethylene fibers. It has been postulated that the presence of additional bonds may increase the tensile strength of the layer, reduce the amount of lint and improve the clamping between the polyethylene layer and the adjacent fibrous layer. Therefore, while the "adherent" attributes of REGELREZ® 1126 are considered to be primarily responsible for any increase in the number of fiber-to-fiber bonding, it is also believed that the reduction in the melting temperature of the mixture of resulting polyethylene can have an increased and potentially beneficial effect on the number of such unions.

It can be easily appreciated that an increased number of fiber-to-fiber bonds can increase the tensile strength of the layer. It is thought that an increased number of fiber to fiber joints within the polyethylene layer reduces two types of lint. All polyethylene layers are capable of producing polyethylene fluff, for example, polyethylene fibers which are separated from the bottom sheet. When the polyethylene layer also includes natural or other fibers, the loss of these other fibers may also produce fluff. It follows that when there is an increase in the fiber for the bonding of fiber to polyethylene fiber, there are very few polyethylene fibers and the individual polyethylene fibers are generally more securely bonded to the layer. Therefore, few polyethylene fibers are likely to become loose and produce polyethylene fluff. An increase in fiber-to-fiber bonding also follows for the polyethylene fibers will be able to provide a tighter network of fibers which will improve the mechanical capture of any non-polyethylene fibers present in the layer thereby also reducing this second source of fiber. fluff.

The increase in the fiber to fiber bond between the polyethylene fibers is also believed to improve the strapping hold. The individual polyethylene fibers which bind to, or become entangled with, the fibers in the adjacent layer are likely to be more strongly secured to the other fibers within the polyethylene layer when there are more fiber-to-fiber bonds between the fibers of the polyethylene layer. polyethylene and therefore provide a relatively stronger hold between the layers.

Increasing the number of fiber to fiber joints, however, may also reduce the softness of the polyethylene layer. The lower sheet layers containing (by weight) 65% cellulose pulp and 35% polyethylene fibers formed with a mixture containing 80% polyethylene and 20% REGALREZ 1126® can be perceived by some individuals to be less smooth than a layer formed with 65% cellulose pulp and % virgin polyethylene. It is thought that an increased number of polyethylene fiber meetings may reduce the flexibility of polyethylene fibers and therefore affect the tactile properties of fibers in a manner in which it is perceptible by some individuals.

It was also found that the use of an additive with polypropylene fibers can improve the level of clamping between the adjacent polypropylene and polyethylene fibers. For example, the use of polybutylene as an additive can increase the adhesion of polypropylene fibers, and, at levels of 20% and 50%, it was found to have a positive effect on the subjection of the stratum.The use of polybutylene as an additive is also controlled which is capable of reducing the stiffness of the lower sheet.

A reduction in stiffness, for example, an increase in flexibility, of the lower sheet generally has a positive influence on the tactile perception of the lower sheet.

Moreover, an increase in flexibility can occur in an inner layer which does not form one of the major outer surfaces and the lower sheet and still produces this positive influence on the perception of the lower sheet.

Polyethylene acrylic acid is another additive which can be incorporated into polypropylene fibers, either by itself or in combination with polybutylene, to improve the adhesion of polypropylene fibers. The mixing of a polyethylene acrylic with polypropylene is described in U.S. Patent No. 4,797,318 which is incorporated herein by reference.

In a further embodiment of the present invention, a bottom sheet having a polyethylene layer and at least one additional fibrous layer is provided. Fibers of the polyethylene layer includes polyethylene fibers formed with a mixture containing both polyethylene and an additive. The polyethylene layer may also include natural fibers. The fibers of the additional fibrous layer may be either synthetic, natural or a mixture of natural and synthetic fibers.

Similarly, in yet another embodiment of the present invention, a bottom sheet having a layer of polypropylene and at least one additional fibrous layer is provided. The fibers of the polypropylene layer include polypropylene fibers formed with a mixture containing both polypropylene and an additive. The polypropylene layer may also include natural fibers. The fibers of the additional fibrous layer may be either synthetic, natural or a mixture of natural and synthetic fibers.

Natural fibers such as cellulosic fibers can be used in a lower sheet of a wet cleaning cloth to provide improved wetness and thickness. Natural fibers can also provide a volume of vacuum within the lower sheet which can increase the moisture capacity of the lower sheet. Examples of natural fibers suitable for use in the present invention include not only cellulosic fibers such as wood pulp fibers, but also cotton fibers, flax fibers, jute fibers, silk fibers. and similar. In addition to polyolefins such as polypropylene and polyethylene, examples of thermoplastic polymer fibers suitable for use with the present invention include polyamides, and polyesters such as polyethylene terephthalate. Alternative synthetic fibers which may be appropriate include basic rayon and nylon fibers.

If a layer of the lower multi-layer sheet is a combination of natural and synthetic fibers, such as the cellulosic and polypropylene fibers, the relative percentages of the synthetic fibers and the natural fibers in the layer can vary over a wide range depending on in the desired characteristics of the wet cleaning cloths. For example, the layer may comprise from about 20 to about 95 percent by weight, desirably from about 20 to about 60 percent by weight, and more desirably from about 30 to about 40 percent by weight of synthetic fibers based in the dry weight of the layer. Such a layer of natural and synthetic fibers can be manufactured by methods well known to those of skill in the art.

Generally, it is desirable that a layer containing both synthetic natural fibers be formed by a coform process which provides a generally uniform distribution of the natural and synthetic fibers within the individual layer. The manufacture of coform layers is described in the patent of the United States of America No. granted to Anderson et al. Issued on July 11, 1978; U.S. Patent No. 4,604,313 issued to McFarland et al. which was issued on August 5, 1986; and U.S. Patent No. 5,350,624 which was issued on September 27, 1994; the descriptions of which are here incorporated by reference. Typically, such coform layers comprise a binder of blown microfiber thermoplastic polymer melts, such as polypropylene microfibers, and cellulosic fibers, such as wood pulp fibers. A coform layer is formed by initially forming at least one primary air stream containing the synthetic fibers and fusing the primary stream with at least one secondary stream of natural fibers. The primary and secondary currents are fused under turbulent conditions to form an integrated stream that contains a homogenous distribution of the fibers. The integrated air stream is directed in a forming surface to form a layer of material with air. A multiplicity of these coform layers can be formed in succession to provide a fabric of multiple coform layers.

As mentioned above, the clamping of layers in the form of polypropylene and polyethylene can be improved by a thermomechanical process when the bottom sheet with layers is passed between a heated soft anvil roller and a heated pattern roller. The pattern roller can have any raised pattern which provides the desired entanglement and interlayer bonding. Desirably, the patterned roller defines an elevated pattern which defines a plurality of bonding locations which define a bonding area of between about 4 and about 30 percent of the total area of the roll.

The pressure between the rollers and the temperature of the rollers must be balanced to produce an inner sheet that has adequate strength and integrity while maintaining the softness of the outer layers. The temperature and pressure may vary depending on the types of fibers that are used to provide the desired wet cleaning cloth. In a particular embodiment wherein the layers comprise at least one layer of polyethylene fibers and at least one other layer of polypropylene fibers, the pressure between the rolls may be between about 50 and about 900 Newtons per linear centimeter. and the temperature of at least one of the rolls may be between about 40 and about 150 degrees Celsius of bonding and improved entanglement. Under such conditions of temperature and pressure, the polyethylene fibers are deformed to provide mechanical entanglement with and possible bonding with the polypropylene fibers. As a result, the layers become entangled and joined in discrete areas arranged in a pattern which corresponds to the pattern raised on the patterned roller.

A lower sheet of multiple layers may have a total basis weight to form about 25 to about 120 grams per square meter and desirably from about 40 to about 90 grams per square meter. The basis weight of the lower sheet may also vary depending on the desired end use of the wet cleaning cloth. For example, a lower sheet suitable for cleaning the skin can have a basis weight of from about 60 to about 80 grams per square meter and desirably about 75 grams per square meter. In other embodiments the lower sheet with layers may include coform layers of polypropylene and cellulosic fibers and polyethylene and internal cellulosic fibers and a basis weight of from about 60 to about 90 grams per square meter and desirably about 80 grams per square meter. square meter.

Each layer of the lower sheet may or may not have the same basis weight depending on the desired properties of the cleaning cloth. For example, in a three layer coform lower sheet which includes an inner layer of polypropylenes and wood pulp fibers and two outer layers of polyethylene and wood pulp fibers, the base weight of the layers may define a weight ratio of outer / inner / outer layer of from about 10/80/10 to about 40/20/40, desirably about 25/50/25 to about 33/33/33 and more desirably about 30/40 / 30 based on the total weight of the lower sheet.

The lower sheet must have sufficient strength to withstand the forces exerted by the user when it is moistened with solution. In a lower sheet which includes layers of both layers of polyethylene and polypropylene, the layer which includes polypropylene fibers will generally be able to provide the majority of the strength to the bottom sheet while the polyethylene fibers can be used to provide a surface Soft exterior for the wet cleaning cloth. Therefore, the tensile strength of such a bottom sheet with layers may be higher than the tensile strength of a single layer containing polyethylene fibers and provides smoother outer surfaces than a single layer containing polypropylene fibers.

The lower sheets of multiple layers according to the present may be manufactured in a simple manufacturing line to which includes multiple individual forming banks. Each bank form is configured to provide a single layer or stratum. For example, the first and last training benches may be configured to provide the outer layers while the inner or middle forming benches may be configured to provide one or more inner layers. The mechanical entanglement of fibers in adjacent layers during the forming process subject to adjacent layers. The joints can also be formed between fibers of adjacent layers to provide additional clamping of the adjacent layers of the lower sheet. Subsequent thermomechanical bonding can also be used to improve clamping between adjacent layers.

Each training bank may include the appropriate equipment to provide the desired type of fabric. For example, if each layer comprises in a coform layer of melt blown microfibers and natural fibers such as wood pulp fibers, each forming bank may include a plurality of confusing blow matrices to extrude a molten polymeric material into fine streams. . The fine streams are then attenuated by gas converging streams at high speed to break the polymer streams into small diameter discrete microfibers. Such puffed-up confusion matrices are well known to those with a skill in the art. The current or currents of natural fibers which converge with melt blown microfiber streams can be provided by a conventional pulp picker roll process as is well known to those of skill in the art.

Alternatively, one or more layers of the lower sheet of wet cleaning cloth may be made from a different type of material such as a blown sheet with polymeric microfiber melting. For example, a resilient, internal and resilient layer can be formed with a layer of meltblown polypropylene fibers while the soft outer layers can be formed with coform polyethylene layers and wood pulp fibers as described above. The flexible and soft outer layers may also be provided by different types of materials such as meltblown, carded, or airlaid materials which are manufactured by processes well known to those of skill in the art.

The lower sheet of the present invention is used to form a wet cleaning cloth by adding an appropriate solution to the lower sheet. The solution can be any liquid which can be absorbed into the inner sheet of the wet cleaning cloth and can include a variety of different components which provide the desired cleaning properties. For example, the components may include water, emollients, surfactants, fragrances, preservatives, chelating agents, pH buffers or combinations thereof as are well known to those of skill in the art. The solution may also contain lotions and / or medications.

The amount of solution contained within each wet cleaning cloth may vary depending on the type of material that forms the lower sheet, the type of solution that is used, the type of container that is used to store the wet cleaning cloths, and the use intentional wet cleaning cloth. Generally, each wiper blade may contain from about 150 to about 600 percent by weight and desirably from about 250 to about 450 percent by weight of solution based on the dry weight of the bottom sheet. It is generally desirable that the amount of solution contained within the wet cleaning cloth be from about 300 to about 400% by weight and, advantageously, about 330 percent by weight based on the dry weight of the lower sheet.

If sufficient solution is not added to the lower sheet, the resulting wet cleaning cloth may be very dry and may not perform adequately. If excess solution is added to the sheet and lower, the cleaning cloth resulting means may be over saturated and pasty and the solution may be flooded in the bottom of the container.

The lower sheets, and the resulting wet cleaning cloths, are generally rectangular in shape and can have any length and width without proper bending. For example, the wet cleaning cloth may have an unfolded length of from about 2.0 to about 80.0 centimeters and desirably from about 10.0 to about 25.0 centimeters and an unfolded width of from about 2.0 to about 80.0 centimeters and desirably from about 10.0 to about 25.0 centimeters. Typically, the individual wet cleaning cloths are arranged in a folded configuration and an enzyme is stored from the other to provide a stack of wet cleaning cloths. Such bent configurations are well known to those with an art skill and include bending c, bending z, bending in similar rooms and configurations.

A stack of folded wet cleaning wipes can be placed inside a container, such as a plastic tube, to provide a package of wet cleaning wipes for eventual sale to the consumer. If the stack is interfolded, the cleaning cloths can be conveniently supplied using what is commonly referred to as a "pop-up" dispenser. Alternatively, the lower sheets of wet wipers can form a continuous strip of material which has perforations between each of the individual wipers. A continuous strip of lower sheet material can be arranged in a pile or wound on a roll for delivery.

And emplos The following examples are presented to provide a more detailed understanding of the invention. The particular materials and parameters are exemplary and are not intended to limit the scope of the invention.

The binder of additives and fibrous layers was developed to compare the efficacy and properties of the different additives. Samples separated according to each code were prepared and compared. Each of the samples has two-layer material having a coform polyethylene layer and a polypropylene coform layer. To facilitate the comparison of the different samples, each of the lower leaf samples has a target weight of 54 grams per square meter (gsm) and each layer shows 65% of cellulose pulp by weight.

The different samples are listed in the following table: PE = polyethylene PP = polypropylene The hydrocarbon resin added to the polyethylene of codes 2, 3 and 7 was REGALREZ 1126® which is a complete hydrogenated hydrocarbon resin produced by Hercules Inc. having offices in Wigton, Delaware. This resin is produced by the polymerization and hydrogenation of hydrocarbon supplies of pure monomer and is highly stable, lightly colored, of low molecular weight, non-polar resin.

When forming the polyethylene fibers which included complete hydrogenated hydrocarbon resins (codes 2 and 3), it was found that the hydrocarbon resin pellets were relatively "sticky". To improve processing, the hydrocarbon resin pellets composed in the polyethylene and the resulting mixture was abrupt in a twin screw extrusion process. The mixed pellets were then used to form the polyethylene fibers. For the codes that use a hydrocarbon resin additive, for example, codes 2 and 3, the polyethylene and the hydrocarbon layer was formed in a process where the extrusion temperature was 243 ° C (470 ° F), the air temperature of the primary air stream transporting the polyethylene fibers was from 277 to 282 ° C (530 to 540 ° F); and the height formed was from 25.4 to 27.9 centimeters (10 to 11 inches). When strata containing polyethylene fiber without an additive are formed, the extrusion temperature was 249 ° C (480 ° F), the air temperature of the primary air stream carrying the polyethylene fibers was 277 to 282 ° C (530 to 540 ° F), and the height formed was 25.4 to 30.5 centimeters (10 to 12 inches) .

Polybutylene was obtained under the brand name Shell DP 8911 from Shell Chemical Co. It has offices in Houston, Texas and since then is available under the brand name DURAFLEX 8911 from Montell USA Inc. The atactic polypropylene was obtained under the brand name REXTAC-211 from Huntsman, Inc. which has offices in Houston and in Odessa, Texas. For codes that use a polybutylene additive, for example, codes 4 and 5, the polypropylene and polybutylene layers were formed in a process where the extrusion temperature was 243 ° C (470 ° F), the temperature The air of the primary air stream transporting the polypropylene fibers was 268 to 288 ° C (515 to 550 ° F), and the height formed was 25.4 to 30.5 centimeters (10 to 12 inches). When strata containing polypropylene fibers are formed without an additive, the extrusion temperature was 260 ° C (500 ° F) and the height formed was 27.9 centimeters (11 inches).

Polyethylene was a linear low density polyethylene and was obtained under the brand name ASPUN 6831 from Dow Chemical having offices in Midland, Michigan. Polypropylenes was obtained under the brand name Montell PF015 from Montell USA Inc. which has offices in Wilmington, Delaware.

Code 1 did not include an additive in any of the polyethylene fibers of or in the polypropylene fibers and was used as a control. Two versions of code 1 were produced; a "PE control" in which a polyethylene coform layer was formed in a coform layer of propylene already present in the tissue former; and a "PP control" in which a polymorphine coform layer was formed in a polyethylene coform layer already present in the fabric former.

Codes 2 and 3 were formed in the same manner as the PE control, for example, the polyethylene coform layer was formed in the polypropylene coform layer. Therefore, the effectiveness of the additives used in codes 2 and 3 is more directly determinable by comparison with the PE control. Codes 4 through 6, on the other hand, were formed in the same manner as the PP control, for example, the polypropylene layer, coform was formed in the coform polyethylene layer. Therefore, the effectiveness of the additives used in codes 4 a is more directly determinable by a comparison with the PP control.

The peeling strength, the fluff, the cup crushing and the tensile strength (in both the machine direction "MD" and the cross machine direction "CD") of the samples were tested to provide a relative comparison of the different samples for these physical parameters.

Resistance to (T-Bark) Debarking 180 ' Before the debarking test, the samples were each joined with a similar pattern. The binding pattern bound approximately 13% of the surface area of the sample. The joint was conducted with a pressure of about 131.3 Newtons per linear centimeter (75 pounds per linear inch). The temperature of the average hot oil core of the linker was about 77 ° C (170 ° F), and the bonding temperature was estimated to be about 68 to 71 ° C (155 to 160 ° F).

The debarking sample tests were prepared by first cutting a 7-inch section through 7 inches of cloth cleaner and add solution to the cloth cleaner so the cloth cleaner contains solution in an amount of 330% of the dry weight of the cloth cleaner. The solution is the same solution as it is used in the Huggies® Wet Wipes that are commercially produced by Kimberly-Clark Corp. that have offices in Neenah, Wl (deionized water can be used as an alternative solution). A sample of 2 ± 0.04 inches (13 ± 1 millimeters) by 7 + 0.04 inches (152 + 1 millimeters) is then cut from the saturated cleaning cloth with the larger side parallel to the machine direction. The edges of the sample should be cut flush and parallel.

A constant rate extension unit (or voltage tester) equipped with an appropriate load cell and a computerized data acquisition system is used to perform the peel strength test. Suitable voltage testers and load cells can be obtained from Instron Corp. of Canton, MA or Sintech, Inc. of Research Triangle Park, NC.

The tension tester grips are parallel to one another. The voltage tester settings are as follows: the crosshead speed is set at 20 ± 0.04 inches per minute (508 ± 10 millimeters per minute); the gauge length is set at 1.0 + 0.04 inches (25 + 1 millimeters); the starting measure is placed at 0.5 ± 0.04 inches (13 + 1 millimeters); and the termination measurement is placed at 6 ± 0.4 inches (152 + 1 millimeter).

The test is conducted by first manually separating the polypropylene and polyethylene layers at one end of the sample. The strata are separated by a length of approximately 1 inch and not more than 2 inches. The two layers are then placed on opposite grips of a test device so that the sample is straight and without flexibility. The test device is then used to pull apart the layers (so that the separated layers form an angle of 180 °) at the specified rate while simultaneously recording the force required to separate the layers in grams of force.

Pelusado For the measurement of the lint sheet, a unit Gelbo modified was used. An appropriate test unit can be obtained from US Testing Co. , Inc. PO Box 3189, 1415 Park Avenue, Hoboken, NJ 07030. This test is used to determine the relative amount of particles released from a fabric when subjected to a twisting and continuous bending motion.

At least five lower sheets are used for any sample determination. At least seven lower leaves must be initially collected, reserving the upper and lower lower leaves as protection samples only. The test samples must be clean, dry, and free of environmental contamination. The test samples must also be free of bends, wrinkles, and any other distortion which may constitute an abnormality. Performing the test in six of ten samples is typically sufficient to provide a reasonable degree of confidence to obtain an average sample value. Contour values can be excluded when computing the average sample value.

To perform the test, a dry bottom sheet of 9 inches by 9 inches (23 centimeters by 23 centimeters) is placed in the modified Gelbo flexing unit where the blade is tied between two discs which keep the blade in a tubular configuration. The blade is carefully mounted, and with minimal handling, while the flexing heads are extended to their maximum distance. The sample must have a separation in the upper position of the tube formed by the sheet and the machine direction of the sheet should correspond to the long axis of the tube.

The blade is then rotated and flexed to emit fluff for a period of five minutes. The two handles have a bending stroke of 4.7 inches (119.8 millimeters) and there is a twist to the axle of 180 ° and a strike rate of around 60 cycles per minute. After five minutes, the sheet is removed and the amount of lint emitted is determined.

Due to the amount of lint produced, the measurement of the lint is made by measuring the basis weight of the sheet before and after bending on the sheet instead of using a particle counter. Weighing the samples instead of using a particle counter also counteracts the need to perform the test on a laminar flow cover or a room cleaned class 100, or enclose the flexure unit inside a Plexiglas® chamber which has been cleaned and purged with filtered air.

The test equipment should be located in, and the samples conditioned to, a common test atmosphere.

The test atmosphere should conform to either ASTM conditions (65 ± 2% RH and 72 ± 2 ° F) or TAPPI conditions (50 ± 2% RH and 72 ± 1.8 ° F).

The individual lint test results can be quite variable, therefore, the lint test described above can provide results that have a reproducibility which, in terms of absolute numbers, is only fair. In relative terms of gasification, however, the reproducibility of such tests has been found to be very good and therefore provide a relatively valuable measure of fabrics and their tendency to generate fluff.

Total Energy or "Cup Compression" The total energy of a non-woven fabric can be measured according to the "cup compression" test. The cup compression test and evaluates the stiffness of the fabric by measuring the peak load (also called "cup compression") required for a spherically formed foot foot of 4.5 centimeters in diameter to compress a piece of cloth 23 centimeters by 23 inches. centimeters formed in an inverted cup of approximately 6.5 centimeters in diameter by 6.5 centimeters in height while the cup-shaped fabric is surrounded by a cylinder of approximately 6.5 centimeters in diameter to maintain a uniform deformation of the cup-shaped fabric. An average of between 5 and 10 readings can be used to determine the final value, a smaller number of readings is appropriate when there is little or no variability in individual readings while a higher number of readings is preferred when there is greater variability in the readings. The foot and cup are aligned to avoid contact between the walls of the cup and the foot which can affect the readings. The foot descends at a rate of about 0.25 inches per second (380 millimeters per minute).

The cup compression test yields a value for the total energy required to compress a sample (the "compressed energy") which is the total energy from the beginning of the test to the peak load point. The compression energy or total energy is calculated by determining the area under the curve formed by the load in grams on one axis and the distance that the foot moves in millimeters in the other from the beginning of the test to the peak load. The compression energy is, therefore, reported in grams - millimeters.

Lower rate compression values indicate a less rigid fabric which is also generally considered a softer fabric. A suitable device for measuring cup compression is a load cell model TD-G-500 (range of 500 grams) available from Schaevitz Company, Pennsauken, NJ.

Peak Voltage Resistance The tensile strength of a peak of the samples was determined using a strip tension test well known in the art. The samples are prepared by first cutting a 7-inch by 7-inch section of the cleaning cloth and adding solution to the cleaning cloth by which the cleaning cloth contains solution in an amount of 330% of the dry weight of the cleaning cloth. The solution is the same solution as it is used in the Huggies® Wet Wipes which is commercially produced by Kimberly-Clark Corp. which has offices in Neenah, Wl (deionized water can be used as an alternative solution). A sample of 1+ 0.04 inches (25 + 1 millimeters) by 6+ 0.04 inches (150 + 1 millimeters) is then cut from the cleaning cloth saturated with the test direction (machine or transverse direction) running parallel to the larger side of the screen. strip. The edges of the sample should be cut flush and parallel.

A constant rate extension unit (or voltage tester) equipped with an appropriate load cell and a computerized data acquisition system is used to perform the test. Suitable voltage testers and load cells can be obtained from Instron Corp. of Canton, MA or Sintech, Inc. of Research Triangle Park, NC.

The tension tester grips are installed parallel to each other. The voltage tester settings are as follows: the crosshead speed is set to 12+ 0.04 inches per minute (300 ± 10 millimeters per minute); the graph is set to 12+ 0.04 inches per minute (300+ 10 millimeters per minute); The measurement length (measured from the center of the horizontal line clamp upper to the center of the lower horizontal line clamp) is set to 3. O ± 0.04 inches (76 + 1 mm); and the failure (breaking criterion) is 65%.

The test is conducted by placing the sample symmetrically on the clamps or the longest dimension and being parallel to the direction of the load application. The crosshead is then turned on and allowed to continue until the sample fails. The maximum measured load recorded as the peak voltage resistance. The peak voltage energy and the peak stretch can also be determined using the information from this test.

The peak voltage resistance of the tested codes was determined in both the machine direction (MD) and the cross machine direction (CD) of the material.

Comparison of Samples Several samples were compared using the test procedures described above. The results of these tests are presented below. 1 Actual basis weight in grams per square meter (GSM) 2 Amount of fluff loss in milligrams / 300 seconds 3 Compression value of cup in gram-millimeters (g-mm) 4 Load in grams 5 Debarking resistance in grams / 5.08 centimeters in width (grams / 2 inches in width) * E1 value of resistance for code 2 may not be determined for the failure of the stratum before separation.

As demonstrated by the results presented above, codes 2 and 3 provided reduced lint while code 3 demonstrated significantly higher peel strength than control codes. A debarking resistance for code 2 was not determined because the strata failed before debarking. This was interpreted as an indication of a very high resistance to debarking. (Once the peel strength exceeds the failure load of the strata that are clamped, additional increases in peel strength are of limited value). These results also indicate that the incorporation of the tested additive in the polyethylene fibers provided a greater capture of pulp and an increase in the subjection of the stratum. These results, however, were also accompanied by an increase in the cup compression value for codes 2 and 3. An increase in the cup compression value indicates an increase in the hardness of the lower sheet which is generally translated as a decrease in softness. Subjective touch comparisons also indicate that increased pulp capture and debarking resistance values were accompanied by reduced softness for codes 2 and 3.

These test results show that the use of additives with polypropylene fibers can be effective in adjusting the physical parameters of the lower sheet. As can be seen from a comparison of the cup compression values, codes 4 to 6 all had a lower stiffness than the control code PP (which was transformed in the same way as codes 4 to 6) and two of these samples still had a lower stiffness than the PE control code. These results, however, were also generally accompanied by a decrease in tensile strength.

The results of the sample presented above provided a demonstration of the incorporation of additives into either polypropylene or single-ply polyethylene fibers and a wet multi-layer cleaning cloth provides the ability to modify the physical properties that resulted from the lower sheet of multiple layers. The layers can then be chosen and combined to produce a lower sheet having the appropriate balance of properties desired for the intended use resulting from the wet cleaning cloth.

While the invention has been described in detail with respect to specific aspects thereof, it may be appreciated by those with a skill in the art, by achieving an understanding of the foregoing, it can easily conceive of alterations to, variations of, and equivalents. to these aspects.

Claims (44)

R E I V I N D I C A C I O N S

1. A base sheet of wet cleaning cloth in non-woven layers, said base sheet comprises a first layer including polypropylene fibers, said first layer having the first and second major surfaces placed in opposite form; a second layer including the polyethylene fibers, said second layer having an inwardly facing major surface and an outward facing major surface facing away, said inwardly facing surface facing and contacting said first surface and said outward facing surface defining an outer surface of said base sheet; Y an additive, said additive is present in one of said polypropylene fibers or said polyethylene fibers.

2. The base sheet as claimed in clause 1 characterized in that said additive is present in said polypropylene fibers of said first layer.

3. The base sheet as claimed in clause 2 characterized in that said first layer also comprises natural fibers.

4. The base sheet as claimed in clause 3 characterized in that said natural fibers and said polyethylene fibers are homogeneously mixed and said natural fibers comprise at least about 50%, by dry weight, of said second layer.

5. The base sheet as claimed in clause 2 characterized in that said second layer also comprises natural fibers.

6. The base sheet as claimed in clause 2 characterized in that said first and second layers each comprise natural fibers.

7. The base sheet as claimed in clause 6 characterized in that said natural fibers of said first and second layers are mixed homogeneously with said polypropylene fibers and said polyethylene fibers.

8. The base sheet as claimed in clause 7 characterized in that said natural fibers comprise at least about 50%, by dry weight, of each of said first and second layers.

9. The base sheet as claimed in clause 2 characterized in that said additive includes atactic polyethylene or polypropylene.

10. The base sheet as claimed in clause 1 characterized in that said additive is present in said polyethylene fibers of said second layer.

11. The base sheet as claimed in clause 10 characterized in that said first layer further comprises natural fibers.

12. The base sheet as claimed in clause 10 characterized in that said natural fibers and said polyethylene fibers are homogeneously mixed and said natural fibers comprise at least about 50%, by dry weight, of said second layer.

13. The base sheet as claimed in clause 10 characterized in that said second layer further comprises natural fibers.

14. The base sheet as claimed in clause 10 characterized in that said first and second layers each comprise natural fibers.

15. The base sheet as claimed in clause 14 characterized in that said natural fibers of said first and second layers are homogenously mixed with said polypropylene fibers and said polyethylene fibers.

16. The base sheet as claimed in clause 15 characterized in that said natural fibers comprise at least about 50%, by dry weight, of each of said first and second layers.

17. The base sheet as claimed in clause 10 characterized in that said additive includes the fully hydrogenated hydrocarbon resin.

18. The base sheet as claimed in clause 17 characterized in that said second layer further comprises natural fibers.

19. The base sheet as claimed in clause 10 characterized in that said polyethylene fibers having said additive present there have a melting temperature which is at least about 40 ° C lower than the melting temperature of the polyethylene. virgin polyethylene.

20. The base sheet as claimed in clause 19 characterized in that said second layer further comprises natural fibers.

21. The base sheet as claimed in clause 20 characterized in that said first layer further comprises natural fibers.

22. The base sheet as claimed in clause 10 characterized in that said polyethylene fibers have said adhesive present therein and have a melting temperature of about 87 ° C.

23. The base sheet as claimed in clause 1 characterized in that each of said first and second layers further comprise natural fibers blended homogeneously within said respective first and second layers.

24. The base sheet as claimed in clause 23 characterized in that said natural fibers present in said first and second layers comprise at least about 50%, by dry weight, of each of said first and second layers.

25. A base sheet of wet cleaning cloth in non-woven layers, said base sheet comprising an inner layer including polypropylene fibers, said inner layer having the first and second major surfaces positioned opposite; the first and second outer layers, each of said outer layers includes polyethylene fibers, each of said outer layers having an inwardly facing major surface and an opposingly facing outwardly facing major surface, said inwardly facing major surface of said first and second outer layers respectively being in contact with said first and second major surfaces of said inner layer, said main surfaces facing outwardly of said first and second outer layers define two main exterior surfaces positioned in opposite form of said sheet base, and an additive, said additive is present in said polypropylene fibers of said inner layer or said polyethylene fibers of said first and second outer layers.

26. The base sheet as claimed in clause 25 characterized in that said additive is present in said polypropylene fibers of said inner layer.

27. The base sheet as claimed in clause 26 characterized in that said additive includes polybutylene or tactical polypropylene.

28. The base sheet as claimed in clause 25 characterized in that said additive is present in said polyethylene fibers of said first and second outer layers.

29. The base sheet as claimed in clause 28 characterized in that said additive includes a fully hydrogenated hydrocarbon resin.

30. The base sheet as claimed in clause 29 characterized in that said first and second outer layers further comprise natural fibers.

31. The base sheet as claimed in clause 30 characterized in that said inner layer further comprises natural fibers.

32. The base sheet as claimed in clause 29 characterized in that said polyethylene fibers have said additive present therein and have a melting temperature which is at least about 40 ° C lower than the melting temperature of the polyethylene. virgin polyethylene.

33. The base sheet as claimed in clause 29 characterized in that said polyethylene fibers have said additive present there having a melting temperature of about 87 ° C.

34. The base sheet as claimed in clause 25 characterized in that each of said inner and outer layers further comprise natural fibers blended homogeneously within said respective inner and outer layers.

35. The base sheet as claimed in clause 34 characterized in that said natural fibers present in said inner and outer layers comprise at least about 50%, by dry weight, of said inner and outer layers.

36. A damp cleaning cloth comprising: a nonwoven base sheet having a first fibrous layer and a second layer; said first fibrous layer has the first and second major surfaces positioned opposite; and said second layer includes a plurality of fibers, said second layer having an inwardly facing major surface and an outward facing major surface facing away, said inwardly facing major surface facing and contacting the first. The main surface and said outward facing main surface define an outer surface of said base sheet, and wherein said plurality of fibers are formed by a mixture including polyethylene and an additive; Y a solution placed on said base sheet.

37. The wet cleaning cloth as claimed in clause 36 characterized in that said additive includes a fully hydrogenated hydrocarbon resin.

38. The wet cleaning cloth as claimed in clause 36, characterized in that said mixture has a melting temperature of less than about 90 ° C.

39. The wet cleaning cloth as claimed in clause 36 characterized in that each of said first and second layers further comprise natural fibers blended homogeneously within said respective first and second layers.

40. The wet cleaning cloth as claimed in clause 39 characterized in that said natural fibers present in said first and second layers comprise at least about 50%, by dry weight, of each of said first and second layers.

41. A damp cleaning cloth comprising: a nonwoven base sheet having a first layer and a second fibrous layer; said first layer includes a plurality of fibers, said first layer having the first and second main surfaces supposedly positioned, and wherein said plurality of fibers are formed with a mixture including polypropylene and an additive; said second fibrous layer have a main surface facing inwardly and a main surface facing away from the opposite side, said main surface facing inwardly facing towards and in contact with said first main surface and said main surface facing towards outside defining an outer surface of said base sheet; Y a solution arranged in said base sheet

42. The wet cleaning cloth as claimed in clause 41 characterized in that said additive includes polybutylene or atactic polypropylene.

43. The wet cleaning cloth as claimed in clause 41 characterized in that each of said first and second layers further comprises natural fibers blended homogeneously within said first and second respective layers.

44. The wet cleaning cloth as claimed in clause 43 characterized in that said natural fibers present in said first and second layers comprise at least about 50%, by dry weight, of each of said first and second layers. SUMMARY A lower sheet for a wet cleaning cloth which includes multiple fibrous layers. At least one of the fibrous layers of the lower sheet includes either 1) polyethylene fibers formed by a polyethylene blend and an additive or 2) polypropylene fibers formed by a mixture of polypropylene and an additive. For example, a fully hydrogenated hydrocarbon resin can be used as an additive with polyethylene to form polyethylene fibers which have a lower melting temperature of about 87 degrees Celsius. The polyethylene layers produced with such fibers can have an improved strength, produce less lint and be more securely fastened to an adjacent fibrous layer. Polybutylene can be used as an additive with polypropylene to form polypropylene fibers to produce a more flexible layer with an increased grip with an adjacent fibrous layer. The polypropylene and polyethylene layers may also include natural fibers such as cellulosic fibers. These layers of polypropylene and polyethylene can both be present in a lower sheet or can be combined with other fibrous layers. One or both of the main exterior surfaces of the generally flat bottom sheet can be formed by a polyethylene layer to provide the bottom sheet with a relatively smooth exterior cleaning surface. The polypropylene layer can be advantageously combined with a softer layer to provide strength and elasticity to the lower sheet. A lower sheet of three layers may include an inner polypropylene layer and two outer polyethylene layers to thereby take advantage of the different properties of these layers. The use of an additive with either polypropylene or polyethylene fibers allows the properties of the lower sheet to be further controlled to suit the lower sheet to its intended purpose.