EP4689275A1

EP4689275A1 - Process and system for foam forming webs

Info

Publication number: EP4689275A1
Application number: EP24781595.4A
Authority: EP
Inventors: Stephen A. Marrano; Eric R. HAASE; Kyle KRAUTKRAMER
Original assignee: Kimberly Clark Worldwide Inc; Kimberly Clark Corp
Current assignee: Kimberly Clark Worldwide Inc; Kimberly Clark Corp
Priority date: 2023-03-24
Filing date: 2024-03-21
Publication date: 2026-02-11
Also published as: WO2024206071A1; CN121039343A; MX2025011299A; AU2024244944A1; KR20250163946A

Abstract

A process and system for foam forming webs is disclosed. A foamed suspension of materials, such as fibers and other particles, is fed to one or more forming zones that are sequentially positioned along an inclined forming surface. A plurality of corresponding drain devices are positioned below the forming surface for draining excess fluids from the newly formed web. The flow rate of fluids being drained from the web is controlled in relation to the flow rate or pressure of a foamed suspension of fibers fed to the forming zones.

Description

PROCESS AND SYSTEM FOR FOAM FORMING WEBS

CROSS-REFERENCE TO RELATED APPLICATION

The present application is related and has right of priority to U.S. Provisional Patent Application No. 63/492,099 filed on March 24, 2023, which is incorporated by reference in its entireties for all purposes.

BACKGROUND

Many tissue products, such as facial tissue, bath tissue, paper towels, industrial wipers, and the like, are produced according to a wet laid process. Wet laid webs are made by depositing an aqueous suspension of pulp fibers onto a forming fabric and then removing water from the newly- formed web.

In order to improve various characteristics of tissue webs, webs have also been formed according to a foam forming process. During a foam forming process, a foamed suspension of fibers is created and spread onto a moving porous conveyor for producing an embryonic web. Foam formed webs can demonstrate improvements in bulk, stretch, caliper, and/or absorbency.

In addition to tissue webs, foam forming can be used to make all different types of webs and products. For example, relatively long fibers and synthetic fibers can be incorporated into webs using a foam forming process. Thus, foam forming processes can be more versatile than many wet laid processes.

Problems have been experienced in the past, however, in being able to control web formation in a foam forming process. For example, foamed suspensions containing fibers are three-phase mixtures containing solids, gases, and liquids. The gases represent compressible portions while the liquids are relatively incompressible. Thus, foamed suspensions are subject to changes in volume when experiencing changes in pressure or temperature. Moreover, these suspensions function as non-Newtonian fluids and are subject to changes in viscosity as the shear rate changes. Due to at least these characteristics of foamed suspensions, controlling the behavior of the foamed suspension fed to a porous forming surface during the formation of a web can be difficult. In addition, over-draining fluids or under-draining fluids from a web formed from a foamed suspension can subject the web to shear forces that cause defects and irregularities in the web. These problems can become exacerbated when attempting to form multi-layered structures.

Thus, a need currently exists for a system and process of producing foam formed webs in which there is better control over web formation as the process experiences natural variability in process conditions which will significantly affect how the fluid behaves. In addition, there is also a need for a system and process of producing multilayered foam formed webs in which the process and system allow control of the resulting web formation and layer mixing.

SUMMARY

In general, the present disclosure is directed to an improved process and system for forming webs from a foamed suspension of fibers. More particularly, the process and system of the present disclosure has been particularly designed in order to better control web formation. In general, the system and method of the present disclosure are directed to controlling the supply flow of a foamed suspension of fibers to a headbox in combination with controlling the drainage flow through a forming surface During the process, the drainage flow from one or more forming zones is controlled based upon the input flow rate and/or pressure to each forming zone. In this manner, possible detrimental effects caused by the suction force on the embryonic web and foam stock can be minimized.

In one aspect, a two phase fluid, such as a foam, is fed to a forming zone. The temperature, pressure, density and/or volumetric flow rate are monitored upstream from the forming zone. The temperature, pressure, density and/or volumetric flow rate are also monitored at the forming zone or downstream from the forming zone. Temperature or pressure changes, for example, can have an effect on the density/mass flow rate of the foam. In determining the drainage flow rate, the physical changes in the two phase fluid (e.g. density) can be calculated and accounted for. In this manner, drainage flow rates can be set to match flow rates fed to the forming zone for facilitating web formation.

Through the process of the present disclosure, webs can be produced with improved properties and characteristics. For example, webs made according to the present disclosure can display enhanced physical properties, including tensile strength properties, and particularly more uniform strength properties when comparing the properties of the webs in the machine direction in relation to the cross-machine direction.

In one embodiment, the present disclosure is directed to a process for producing a web. The process includes flowing a foamed suspension of materials, such as fibers, to one or more adjacent forming zones. The one or more forming zones include at least a first forming zone. The foamed suspension is fed to each forming zone independently of the other forming zones. The foamed suspension is fed to the first forming zone at a first flow rate. The foamed suspension of materials fed to the first forming zone is deposited onto a moving porous forming surface to form an embryonic web. Excess fluids are drained through the porous forming surface into one or more drain devices. Each forming zone includes a corresponding drain device positioned in alignment with each forming zone along the porous forming surface. The one or more drain devices includes at least a first drain device positioned opposite the first forming zone along the porous forming surface. The flow rate of drainage fluids is controlled through each drain device based on and in relation to at least one characteristic of the flow of the foamed suspension of materials being fed to the first forming zone. In one aspect, a flow rate of drainage fluids drained through the first drain device is controlled based on and in relation to the first flow rate of the foamed suspension of materials being fed to the first forming zone.

In one embodiment, the process further includes the step of flowing the foamed suspension of materials to a second forming zone positioned adjacent the first forming zone. The foamed suspension of materials can be fed to the second forming zone at a second flow rate. The foamed suspension of materials fed to the second forming zone is deposited onto the moving forming surface and onto the materials deposited onto the moving forming surface from the first forming zone to form a multilayered web. The flow rate of drainage fluids drained through a second drain device positioned opposite the second forming surface is controlled.

Similarly, the process can also include the step of flowing the foamed suspension of materials to a third forming zone positioned adjacent the second forming zone. The foamed suspension of materials is fed to the third forming zone at a third flow rate. The foamed suspension of materials is deposited onto the moving forming surface at the third forming zone onto the materials deposited onto the forming surface from the first forming zone and from the second forming zone. In accordance with the present disclosure, the flow rate of drainage fluids through a third drain device positioned opposite the third forming zone can be controlled based on the calculated third flow rate. In this manner, a three-layered web can be formed with controlled properties and optionally with fiber mixing between the adjacent layers.

Optionally, the drainage flow rate can be controlled such that the foamed suspension of materials being fed to the first forming zone can be caused to flow longitudinally outside a perimeter of the first forming zone for improving formation of the embryonic web in certain embodiments. The drainage flow rate through the second drain device and through the third drain device can also be controlled such that the foamed suspension of materials being fed to the second forming zone is caused to flow longitudinally outside a perimeter of the second forming zone and that the foamed suspension of materials being fed to the third forming zone is caused to flow longitudinally outside a perimeter of the third forming zone.

The embryonic web is then dried for forming a fibrous product.

In one aspect, the process can further include the step of flowing a fluid to a sealing zone. The sealing zone can be positioned adjacent to and upstream from the first forming zone. The fluid being fed to the sealing zone can be emitted onto the moving and porous forming surface for inhibiting air flow in an upstream longitudinal direction. The fluid fed to the sealing zone, in one aspect, can be non-fibrous and can comprise a liquid, such as water, or can comprise a foamed fluid.

Fluids can also be drawn through the embryonic web at a suction zone that is adjacent to and downstream from the one or more forming zones. The drainage flow rates of the foamed suspension of the materials being drained through the one or more forming zones can enter the suction zone. In one aspect, the drainage flow rate of the foamed suspension of materials being drained through the one or more drain devices can be controlled such that excess fluid from the one or more forming zones enters the suction zone for controlling the liquid and air mixture that is collected by the suction zone.

In one embodiment, the process is operated such that the flow rate of fluids through the first drain device is less than the first flow rate of the foamed suspension of materials being fed to the first forming zone. Similarly, the flow rate of fluids through the second drain device and/or the third drain device can also be less than the flow rate of the foamed suspension of materials being fed to the corresponding forming zone.

In one aspect, the foamed suspension of materials can be pumped to each of the one or more forming zones individually such that the fluid pressure within each supply line to each forming zone can be controlled independently of the other forming zones. In one aspect, for instance, the foamed suspension of materials is pumped to the first forming zone at a first pressure and the flow rate of drainage fluids drained through the first drain device is controlled based upon the first pressure. The flow rate of drainage fluids drained through the first drain device can be monitored by a flow meter and a pressure monitoring device downstream from the forming surface. The flow meter and the pressure monitoring device can send information to a controller that calculates a discharge flow rate at a reference pressure or flow rate. The controller, which can be any suitable microprocessor or programmable device, can be in communication with an adjustable flow control device for controlling the flow rate of drainage fluids drained through the first drain device based upon the calculated discharge flow rate. The flow control device, for instance, can be an adjustable valve.

In one embodiment, the moving forming surface is operated at an incline in relation to a horizontal. For instance, the forming surface can be at an angle of greater than about 10°, such as greater than about 20°, and generally less than about 60°, such as less than about 50°, in relation to the horizontal.

Webs can be made with high bulk characteristics or low bulk characteristics. The webs, for example, can have a bulk of greater than about 3 cc/g, such as greater than about 5 cc/g, such as greater than about 7 cc/g, such as greater than about 9 cc/g, such as greater than about 11 cc/g, such as greater than 14 cc/g and generally less than about 20 cc/g. Alternatively, the webs can have a bulk of less than about 3 cc/g, such as less than about 1 cc/g, such as less than about 0.5 cc/g, such as less than about 0.08 cc/g, and generally greater than about 0.03 cc/g.

Webs made according to the present disclosure can have all different types of basis weight. For instance, the basis weight can be from about 6 gsm to about 800 gsm, such as from about 10 gsm to about 200 gsm, such as from about 20 gsm to about 120 gsm. The webs can be made exclusively from pulp materials or can be made from pulp materials blended with other materials, such as synthetic fibers and/or superabsorbent particles or materials. The synthetic fibers, for instance, can be present in the web in an amount greater than about 5% by weight, such as in an amount greater than about 15% by weight, such as greater than about 20% by weight, such as in an amount greater than about 25% by weight and in an amount up to 100% by weight. The synthetic fibers can comprise polymer fibers, such as polyester fibers. Alternatively, the synthetic fibers can comprise regenerated cellulose fibers, such as rayon fibers, viscose fibers, and the like.

The foamed suspension of materials can be formed according to the present disclosure by combining a foam with a fiber furnish. The foam can have a density of from about 200 g/L to about 600 g/L, such as from about 350 g/L to about 600 g/L. The foamed suspension can be formed by combining a foaming agent with water. The foamed fiber suspension in can contain from about 40% to about 80% by volume air, such as from about 40% to about 65% by volume air.

The present disclosure is also directed to a system for producing webs. The system can include a plurality of adjacent forming zones positioned along a porous forming surface. Each forming zone can be in communication with a separate foamed fiber supply line. Each foamed fiber supply line can include a pumping device for pumping a foamed suspension of materials to a respective forming zone. Each foamed fiber supply line can further include a flow meter, a pressure monitoring device, a temperature monitoring device and/or a density monitoring device. Each foamed fiber supply line feeds a foamed suspension of materials to a corresponding forming zone for depositing the materials contained in the foamed suspension onto the porous forming surface at a determined flow rate (e.g. volumetric or mass flow rate) that can be calculated by a controller from receiving upstream flow rate, temperature, pressure and/or density information.

The system further includes a plurality of adjacent drain devices positioned along the porous forming surface opposite the plurality of adjacent forming zones. For each forming zone, there is a corresponding drain device positioned in alignment on an opposite side of the porous forming surface. Each drain device is in fluid communication with a corresponding drain line. Each drain line includes a flow control device for controlling a flow rate of a fluid being drained from each corresponding drain device. Each drain line can further include a flow meter, a temperature monitoring device, a density monitoring device, a pressure monitoring device, or combinations thereof. One or more controllers are placed in communication with each of the flow control devices associated with the drain lines. The one or more controllers are configured to control the flow rate of fluids being drained from the drain device in relation to a flow rate or pressure of the foamed suspension of materials being fed to each of the forming zones. For example, the one or more controllers can be configured to control the flow rate of fluids being drained from each drain device based on information received from the corresponding pressure monitoring devices associated with each forming zone. The system of the present disclosure can be used to produce single layer webs or multilayered webs.

In one embodiment, the system can further include a drying device positioned downstream from the forming zones for drying a web formed on the porous forming surface.

In one embodiment, the system can further include a separator tank in fluid communication with each of the drain lines for receiving a drain fluid from each drain device. The separator tank can separate free gases from foam and can be configured to recycle the foam in producing further amounts of the foamed suspension of materials. In one embodiment, the system can further include a suction zone adjacent to and downstream from the plurality of forming zones for drawing air through webs formed on the forming surface. The flow rate of fluids being drained from each drain device can be controlled by the one or more controllers in a manner that causes the suction zone to collect a liquid and air mixture from a web being formed. The liquid and air mixture collected from the suction zone can also be fed to the separator tank.

Other features and aspects of the present disclosure are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

Figure 1 is a schematic diagram of one embodiment of a process in accordance with the present disclosure for forming webs from a foamed suspension of materials;

Figure 2 is a schematic diagram of a system and process for depositing a foamed suspension of materials onto a forming surface in accordance with the present disclosure;

Figure 3 is another embodiment of a schematic diagram (partial view) of a system and process for depositing a foamed suspension of materials onto a forming surface in accordance with the present disclosure; Figure 4 is another embodiment of a schematic diagram of a system and process for depositing a foamed suspension of materials onto a forming surface in accordance with the present disclosure;

Figure 5 is another embodiment of a schematic diagram of a system and process for depositing a foamed suspension of materials onto a forming surface in accordance with the present disclosure; and

Figure 6 is a cross sectional view of one embodiment of a forming zone that may be incorporated into the process and system of the present disclosure.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DEFINITIONS

As used herein, the term “foam formed product” means a product formed from a suspension including a mixture of a solid, a liquid, and dispersed gas bubbles.

As used herein, the term “foam forming process” means a process for manufacturing a product involving a suspension including a mixture of a solid, a liquid, and dispersed gas bubbles.

As used herein, the term “foaming fluid” means any one or more known fluids compatible with the other components in the foam forming process. Suitable foaming fluids include, but are not limited to, water.

As used herein, the term “foam half life” means the time elapsed until the half of the initial foam mass reverts to liquid water.

As used herein, the term “layer” refers to a structure that provides an area of a substrate in a height direction of the substrate that is comprised of similar components and structure.

As used herein, the term "nonwoven web" means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted web.

As used herein, unless expressly indicated otherwise, when used in relation to material compositions the terms "percent", “%”, "weight percent", or "percent by weight" each refer to the quantity by weight of a component as a percentage of the total except as whether expressly noted otherwise.

The term “personal care absorbent article” refers herein to an article intended and/or adapted to be placed against or in proximity to the body (i.e., contiguous with the body) of the wearer to absorb and contain various liquid, solid, and semi-solid exudates discharged from the body. Examples include, but are not limited to, diapers, diaper pants, training pants, youth pants, swim pants, feminine hygiene products, including, but not limited to, menstrual pads or pants, incontinence products, medical garments, surgical pads and bandages, and so forth.

The term "superabsorbent material" as used herein refers to water-swellable, water-insoluble organic or inorganic materials including superabsorbent polymers and superabsorbent polymer compositions capable, under the most favorable conditions, of absorbing at least about 10 times their weight, or at least about 15 times their weight, or at least about 25 times their weight in an aqueous solution containing 0.9 weight percent sodium chloride.

The term "machine direction" as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a nonwoven web.

The term "cross-machine direction" as used herein refers to the direction which is perpendicular to the machine direction defined above.

The term "pulp" as used herein refers to fibers from natural sources such as woody and non- woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. Pulp fibers can include hardwood fibers, softwood fibers, and mixtures thereof.

The term "average fiber length" as used herein refers to an average length of fibers, fiber bundles and/or fiber-like materials determined by measurement utilizing microscopic techniques. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of fibers. The fibers are set up on a microscope slide prepared to suspend the fibers in water. A tinting dye is added to the suspended fibers to color cellulose-containing fibers so they may be distinguished or separated from synthetic fibers. The slide is placed under a Fisher Stereomaster II Microscope— S19642/S19643 Series. Measurements of 20 fibers in the sample are made at 20X linear magnification utilizing a 0-20 mils scale and an average length, minimum and maximum length, and a deviation or coefficient of variation are calculated. In some cases, the average fiber length will be calculated as a weighted average length of fibers (e.g . , fibers, fiber bundles, fiber-like materials) determined by equipment such as, for example, a Kajaani fiber analyzer Model No. FS-200, available from Kajaani Oy Electronics, Kajaani, Finland. According to a standard test procedure, a sample is treated with a macerating liquid to ensure that no fiber bundles or shives are present. Each sample is disintegrated into hot water and diluted to an approximately 0.001% suspension. Individual test samples are drawn in approximately 50 to 100 ml portions from the dilute suspension when tested using the standard Kajaani fiber analysis test procedure. The weighted average fiber length may be an arithmetic average, a length weighted average or a weight weighted average and may be expressed by the following equation: where k=maximum fiber length xrfiber length npnumber of fibers having length xi n=total number of fibers measured.

One characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not discriminate between different types of fibers. Thus, the average length represents an average based on lengths of all different types, if any, of fibers in the sample.

As used herein the term "staple fibers" means discontinuous fibers made from synthetic polymers such as polypropylene, polyester, post consumer recycle (PCR) fibers, polyester, nylon, and the like, and those not hydrophilic may be treated to be hydrophilic. Staple fibers may be cut fibers or the like. Staple fibers can have cross-sections that are round, bicomponent, multicomponent, shaped, hollow, or the like.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure.

In general, the present disclosure is directed to a system and process for forming webs, particularly nonwoven webs including tissue webs, absorbent cores, synthetic fiber mats, and the like. In accordance with the present disclosure, the webs are formed from a foamed suspension of fibers. In accordance with the present disclosure, both the supply flow and the drainage flow of a foamed suspension of fibers being deposited onto a porous forming surface are controlled. For instance, the web making system of the present disclosure includes at least one discrete zone of formation positioned adjacent the forming surface that receives a flow of a foamed suspension of fibers. The input pressure and/or input flow rate of the foamed suspension of fibers into the at least one discrete zone of formation is coordinated with drainage flow through the porous forming surface to control web formation. When producing multilayered webs, the process and system can result in layer mixing for creating multilayered webs with enhanced physical properties. In one aspect, a supply of a foamed suspension of fibers is fed to a headbox where the at least one discrete zone of formation is located and the drainage flow from the headbox can be converted to a pressure for optimizing sheet formation. Through the process and system of the present disclosure, the forming conditions of the web are controlled for avoiding underdrainage and/or overdrainage during changes in process conditions and raw material inputs. In one embodiment, the drainage flow from the porous forming surface is controlled with adjustable flow control devices, such as valves and/or pumps which, in turn, are controlled by a volumetric flow meter and/or a pressure transmitter and/or a temperature monitoring device. Using both a flow meter, pressure transmitter, and/or temperature monitoring device combination allows for a fully quantified two-phase discharge flow profile that then can be converted to a reference value. In this manner, the adjustable flow meter device can be controlled to achieve a calculated discharge flow at the reference value.

In one aspect, the process and system can be used to produce multilayered webs that include a plurality of discrete web forming zones that can be positioned adjacent to one another along the porous forming surface. When forming the multilayered web, the drainage flow rate in each of the discrete forming zones can be controlled in order to produce webs having stable sheet formation and enhanced structure and interface stability.

The system and process of the present disclosure can provide various advantages and benefits. For instance, during the process, fiber orientation can be controlled. Consequently, the system and process of the present disclosure can also be used to produce webs having tailored properties for a particular end use application. For instance, through the process of the present disclosure, webs can be formed having improved stretch properties, improved absorbency characteristics, increased bulk if desired, increased caliper if desired, and/or increased basis weight. Additionally, a combination of different properties can be enhanced and improved.

In addition to the above, the system and process of the present disclosure minimizes any detrimental effects that may occur due to applying vacuum or a suction force onto the foamed suspension of fibers or onto the embryonic web being formed. Overall, alignment of input pressure and drainage flow across multiple zones of formation can achieve a stable sheet formation.

As described above, the process and system of the present disclosure are particularly well suited for use in foam forming processes for producing fibrous webs. There are many advantages and benefits to a foam forming process as described above. During a foam forming process, water is replaced with foam as the carrier for the fibers that form the web. The foam, which represents a large quantity of air, is blended with fibers and optionally other materials, such as superabsorbent materials. Since less water is used to form the web, less energy is required in order to dry the web. Although foam forming processes and systems can offer various advantages, control over the foamed suspension during the process to produce webs is problematic. Foamed suspensions, for instance, are two-phase systems that include a compressible, gas phase and a substantially incompressible, liquid phase. Because foamed suspensions are non-Newtonian, the density and viscosity of the foam changes based upon the location and the process. In accordance with the present disclosure, various parameters of the foamed suspension are monitored or calculated during the process for determining the characteristics of the foamed suspension as it is deposited onto a forming surface and as fluids are drained from the forming surface. For instance, the foamed suspension being fed to the forming surface can be monitored for flow rate, such as volumetric flow rate, pressure, temperature, and/or density, which can be measured or calculated. Knowing at least some of the above parameters allows for calculating density changes and volumetric foam flow rate changes as the foamed suspension is fed through a headbox and deposited onto a forming surface. In accordance with the present disclosure, all or some of the above parameters can also be determined on the drainage side of the forming surface. In this manner, the drainage rate of fluids through the forming surface can be calculated and controlled based upon the flow rate of the foamed suspension to the forming surface for controlling and optimizing the formation of a web with uniform properties. In particular, monitoring parameters of the foam going to the forming surface and being drained from the forming surface can be used to prevent under-draining or over-draining of the web on the forming surface for producing webs without fiber mat disruptions, imperfections, or other irregularities that may be caused by unbalanced shear forces being exerted on the web.

Referring to FIGS. 1 and 2, one embodiment of a system and process in accordance with the present disclosure are shown. In general, during the process, solid material, such as fibers and/or superabsorbent particles, water, and a foam forming agent are added to a tank and mixed until the desired air content, bubble size/foam stability, and solid dispersion are achieved, such as a fiber dispersion. The fiber-containing foam may then optionally be diluted during the process, especially when a recycle stream is present. In one aspect, the air content of the foamed suspension is between about 30% and about 65% As will be described below, the process and system of the present disclosure are particularly directed to measuring certain parameters of the foamed suspension in line in order to calculate volumetric flow rate, air content, basis weight, and/or velocity of the foamed suspension at the forming surface. Beneath the moving forming surface are one or more drain devices which may apply vacuum to the web as it is formed and which pull excess foam through the forming surface for controlling formation of the sheet. Within drain lines positioned downstream from the forming surface, various parameters of the drained foam are also measured for calculating a volumetric flow rate of foam being drained from the surface. The volumetric flow rate of foam being drained from the forming surface is then controlled and adjusted based upon the volumetric flow rate of the foamed suspension being fed to the forming surface for carefully controlling the properties of the nonwoven web being formed. The process and system of the present disclosure are well suited to not only producing single layer webs but also producing multi-layer webs. When producing multi-layer webs, shear forces can be controlled and/or minimized for improving interlayer boundaries.

FIG. 1 illustrates a system and process for producing a foamed suspension of fibers and for forming webs from the foamed suspension of fibers. It should be understood that any suitable web forming system may be used in accordance with the present disclosure and FIG. 1 is provided for exemplary purposes only. As shown in FIG. 1 , the system can include a mixing tank 12 that is used to form the foamed suspension of fibers. The foamed suspension of fibers is then fed to a web forming system 10 or headbox that deposits the foamed suspension of fibers onto a porous forming surface 26 for forming a web 14. In accordance with the present disclosure, the web forming system or headbox 10 includes one or more adjacent forming zones in combination with one or more corresponding drain devices and drain lines for controlling and coordinating the inflow of the aqueous suspension of fibers with the drainage flow through the forming surface 26 to control web formation. The web forming system 10 is more particularly illustrated in FIG. 2.

In an alternative embodiment, the system for producing the web can be a twin-wire forming system. In a twin-wire former, two wires respectively form loops, and while they are traveling with stock pinched therebetween, fluids are removed from by means of drain devices, hence gradually a fiber mat grows and a web is formed. The twin-wire former is characterized in that by eliminating a free surface of stock as shown in FIG. 1 , faster running speeds may be possible.

Referring to FIG. 3, a partial view of one embodiment of a twin-wire forming system is shown. One or more layers from independent forming zones of a foamed suspension of fibers is jetted from a headbox 210 between two forming surfaces 226 and 228 to form a web 214. The two forming surfaces can be guided by a forming roll and a breast roll, respectively. The formed web 214 travels along an approximate curved line on a plurality of shoe blades spaced from one another on the side of the forming surface 226.

The foamed suspension of fibers can be subjected to dewatering at an equal rate almost simultaneously through both forming surfaces 226 and 228. For example, as will be described in greater detail below with respect to FIG. 2, drain devices having controls to control drainage rates can be positioned adjacent to the forming surface 226 and adjacent to the forming surface 228. Referring back to FIG. 1, the mixing tank 12 is in communication with a water supply 22 for feeding water to the tank and a foaming agent or surfactant supply 24 for feeding a surfactant to the tank 12. A fiber furnish is fed to the tank 12 and combined with the water and surfactant. The aqueous solution formed by combining the surfactant and water can be agitated and formed into a foam for forming a foamed suspension of fibers. As described above, in addition to fibers, various other materials can be combined in the tank 12. Such other materials, for instance, can include superabsorbent particles or the like.

The surfactant or foaming agent, for instance, may comprise any suitable surfactant. In one embodiment, for instance, the foaming agent may comprise sodium lauryl sulfate, which is also known as sodium laureth sulfate or sodium lauryl ether sulfate. Other foaming agents include sodium dodecyl sulfate or ammonium lauryl sulfate. In other embodiments, the foaming agent may comprise any suitable cationic and/or amphoteric surfactant. For instance, other foaming agents include fatty acid amines, amides, amine oxides, fatty acid quaternary compounds, and the like.

In one embodiment, a nonionic surfactant is used. The nonionic surfactant, for instance, may comprise an alkyl polyglycoside. In one aspect, for instance, the surfactant can be a C8 alkyl polyglycoside, a C10 alkyl polyglycoside, or a mixture of C8 and C10 alkyl polyglycosides.

The foaming agent is combined with water generally in an amount greater than about 0.1 % by weight, such as in an amount greater than about 0.5% by weight, such as in an amount greater than about 0.7% by weight. One or more foaming agents are generally present in an amount of from about 0.01 % by weight to about 5% by weight, such as in an amount up to about 2% by weight.

Once the foaming agent and water are combined, the mixture is blended or otherwise subjected to forces capable of forming a foam. A foam generally refers is an aggregate of hollow cells or bubbles.

The foam density can vary depending upon the particular application and various factors including the fiber furnish used. In one embodiment, for instance, the foam density of the foam can be greater than about 200 g/L, such as greater than about 250 g/L, such as greater than about 300 g/L. The foam density is generally less than about 600 g/L, such as less than about 500 g/L, such as less than about 400 g/L, such as less than about 350 g/L. In one embodiment, for instance, a lower density foam is used having a foam density of generally less than about 350 g/L, such as less than about 340 g/L, such as less than about 330 g/L. The foam will generally have an air content of greater than about 40%, such as greater than about 50%, such as greater than about 60% (at standard temperature and pressure (STP)). The air content is generally less than about 75% by volume, such as less than about 70% by volume, such as less than about 65% by volume. The foam can be formed in the presence of a fiber furnish or, alternatively, the foam can first be formed and then combined with a fiber furnish. In general, any fibers capable of making a basesheet, such as a tissue web or other similar type of nonwoven in accordance with the present disclosure may be used.

Fibers suitable for making webs comprise any natural or synthetic cellulosic fibers including, but not limited to nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and woody or pulp fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, and aspen. Pulp fibers can be prepared in high-yield or low-yield forms and can be pulped in any known method, including kraft, sulfite, high-yield pulping methods and other known pulping methods. Fibers prepared from organosolv pulping methods can also be used.

A portion of the fibers, such as up to 100% or less by dry weight, or from about 5% to about 30% by dry weight, can be synthetic fibers such as rayon, polyolefin fibers, polyester fibers, bicomponent sheath-core fibers, multi-component binder fibers, and the like. The fibers can be virgin fibers or recycled fibers. The fibers can be staple fibers and can have an average length of from about 3 mm to about 150 mm. An exemplary polyethylene fiber is Fybrel®, available from Minifibers, Inc. (Jackson City, Tenn.). When containing synthetic polymer fibers, the web can be thermally bonded where the fibers intersect.

Synthetic cellulose fiber types include rayon in all its varieties and other fibers derived from viscose or chemically-modified cellulose. Chemically treated natural cellulosic fibers can be used such as mercerized pulps, chemically stiffened or crosslinked fibers, or sulfonated fibers. For good mechanical properties in using papermaking fibers, it can be desirable that the fibers be relatively undamaged and largely unrefined or only lightly refined. While recycled fibers can be used, virgin fibers are generally useful for their mechanical properties and lack of contaminants. Mercerized fibers, regenerated cellulosic fibers, cellulose produced by microbes, rayon, and other cellulosic material or cellulosic derivatives can be used. Suitable papermaking fibers can also include recycled fibers, virgin fibers, or mixes thereof. In certain embodiments capable of high bulk and good compressive properties, the fibers can have a Canadian Standard Freeness of at least 200, more specifically at least 300, more specifically still at least 400, and most specifically at least 500.

Other papermaking fibers that can be used in the present disclosure include paper broke or recycled fibers and high yield fibers. High yield pulp fibers are those papermaking fibers produced by pulping processes providing a yield of about 65% or greater, more specifically about 75% or greater, and still more specifically about 75% to about 95%. Yield is the resulting amount of processed fibers expressed as a percentage of the initial wood mass. Such pulping processes include bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP), pressure/pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high yield sulfite pulps, and high yield Kraft pulps, all of which leave the resulting fibers with high levels of lignin. High yield fibers are well known for their stiffness in both dry and wet states relative to typical chemically pulped fibers.

The web can also be formed without a substantial amount of inner fiber-to-fiber bond strength. In this regard, the fiber furnish used to form the base web can be treated with a chemical debonding agent. The debonding agent can be added to the foamed fiber slurry during the pulping process or can be added directly to the headbox. Suitable debonding agents that may be used in the present disclosure include cationic debonding agents such as fatty dialkyl quaternary amine salts, mono fatty alkyl tertiary amine salts, primary amine salts, imidazoline quaternary salts, silicone quaternary salt and unsaturated fatty alkyl amine salts. Other suitable debonding agents are disclosed in U.S. Pat. No. 5,529,665 to Kaun which is incorporated herein by reference. In particular, Kaun discloses the use of cationic silicone compositions as debonding agents.

In one embodiment, the debonding agent used in the process of the present disclosure is an organic quaternary ammonium chloride and, particularly, a silicone-based amine salt of a quaternary ammonium chloride. For example, the debonding agent can be PROSOFT.RTM. TQ1003, marketed by the Hercules Corporation. The debonding agent can be added to the fiber slurry in an amount of from about 1 kg per metric tonne to about 10 kg per metric tonne of fibers present within the slurry.

In an alternative embodiment, the debonding agent can be an imidazoline-based agent. The imidazoline-based debonding agent can be obtained, for instance, from the Witco Corporation. The imidazoline-based debonding agent can be added in an amount of between 2.0 to about 15 kg per metric tonne.

Other optional chemical additives may also be added to the aqueous papermaking furnish or to the formed embryonic web to impart additional benefits to the product and process. The following materials are included as examples of additional chemicals that may be applied to the web. The chemicals are included as examples and are not intended to limit the scope of the invention. Such chemicals may be added at any point in the papermaking process.

Additional types of chemicals that may be added to the paper web include, but is not limited to, absorbency aids usually in the form of cationic, anionic, or non-ionic surfactants, humectants and plasticizers such as low molecular weight polyethylene glycols and polyhydroxy compounds such as glycerin and propylene glycol. Materials that supply skin health benefits such as mineral oil, aloe extract, vitamin E, silicone, lotions in general and the like may also be incorporated into the finished products.

In general, the products of the present disclosure can be used in conjunction with any known materials and chemicals that are not antagonistic to its intended use. Examples of such materials include but are not limited to odor control agents, such as odor absorbents, activated carbon fibers and particles, baby powder, baking soda, chelating agents, zeolites, perfumes or other odor-masking agents, cyclodextrin compounds, oxidizers, and the like. Superabsorbent particles may also be employed. Additional options include cationic dyes, optical brighteners, humectants, emollients, and the like.

Once the foamed suspension of fibers is formed in the tank 12, the foamed suspension of fibers can be fed to the web forming system as shown in FIG. 2. As illustrated in FIG. 2, the web forming system 10 includes one or more forming zones. In the embodiment illustrated in FIG. 2, three forming zones are shown including first forming zone 50, second forming zone 52, and third forming zone 54. The forming zones 50, 52, and 54 are positioned along the porous forming surface 26. In one embodiment, as shown in FIG. 2, the porous forming surface 26 can be at an incline with respect to the horizontal. For instance, the porous forming surface 26 can have an angle with the horizontal of greater than about 10°, such as greater than about 20°, such as greater than about 30°, and generally less than about 60°, such as less than about 50°. Each forming zone 50, 52, and 54 is designed to receive a separate and independent flow of the foamed suspension of fibers for depositing the foamed suspension of fibers onto the forming surface 26. For instance, the first forming zone 50 can deposit a foamed suspension of fibers directly onto the forming surface 26. The second forming zone 52, however, can be configured to deposit a second flow rate of the foamed suspension of fibers on top of the fibers deposited by the first forming zone 50. Similarly, the third forming zone 54 can deposit a flow of the aqueous suspension of fibers on top of the fibers deposited by the first forming zone 50 and the second forming zone 52. In this manner, a multilayered web is formed. It should be understood, however, that the system and process of the present disclosure may include only a single forming zone for forming single layered webs.

As shown in FIG. 2, each forming zone 50, 52, and 54 is in fluid communication with a separate and independent foamed fibrous supply line. For instance, first forming zone 50 is in communication with a first foamed fibrous supply line 56, the second forming zone 52 is in fluid communication with a second foamed fibrous supply line 58, and the third forming zone 54 is in fluid communication with a third foamed fibrous supply line 60. The supply lines 56, 58, and 60 are configured to feed a foamed suspension of fibers to each of the corresponding forming zones 50, 52, and 54 at a determined and selected flow characteristic, which can be, for instance, flow rate, such as volumetric flow rate, pressure, air content, and/or density. In this regard, each of the supply lines 56, 58, and 60 can be in fluid communication with the mixing tank 12 as shown in FIG. 1. For instance, the first supply line 56 can include a first injection line 62 that is connected to the mixing tank 12. Similarly, the second supply line 58 can include a second injection line 64, while the third supply line 60 can be in communication with a third injection line 66. The injections lines 62, 64, and 66 can all be in communication with the mixing tank 12 for feeding the foamed suspension of fibers to each of the forming zones 50, 52, and 54. Alternatively, the system can include separate mixing tanks wherein each injection line 62, 64, and 66 can be connected to a different mixing tank for feeding the foamed suspension of fibers to the web forming system 10.

As shown, each of the foamed fibrous supply lines 56, 58, and 60 can include a pumping device, a flow meter, such as a volumetric flow meter, a pressure monitoring device, and/or a temperature monitoring device. Each foamed fibrous supply line 56, 58, and 60 can also be in communication with a density monitoring device. The density monitoring device, for instance, can be part of one of the other devices, such as part of the flow meter. Alternatively, the density of the foamed suspension of fibers can be calculated using information received from the other instruments.

For example, the first foamed fibrous supply line includes a first pumping device 68, a first flow meter 74, a first pressure monitoring device 80, and a first temperature monitoring device 81 , the second foamed fibrous supply line 58 includes a second pumping device 70, a second flow meter 76, a second pressure monitoring device 82, and a second temperature monitoring device 83 and the third foamed fibrous supply line 60 includes a third pumping device 72, a third flow meter 78, a third pressure monitoring device 84 and a third temperature monitoring device 85. In accordance with the present disclosure, the pumping devices 68, 70, and 72 can be adjusted so that the foamed suspension of fibers can be independently fed to each forming zone 50, 52, and 54 at a desired flow rate and/or pressure. The flow meters 74, 76, and 78, the pressure monitoring devices 80, 82, and 84 (e.g. volumetric flow rate) and the temperature monitoring devices 81 , 83 and 85 can monitor flow rates, pressures, and temperatures upstream from the forming surface for calculating at least one characteristic of the flow of the foamed suspension of fibers at the forming surface.

In one embodiment, the flow meters 74, 76, and 78, the pressure monitoring devices 80, 82, and 84, the temperature monitoring devices 81 , 83 and 85 can be placed in communication with one or more controllers. The controllers can comprise microprocessors or any suitable programmable device. The pumping devices 68, 70, and 72 can also be placed in communication with the one or more controllers. The controllers can be configured to adjust the pumping devices 68, 70, and 72 based upon information received from the flow meters 74, 76, and 78, from the pressure monitoring devices 80, 82, and 84, and/or from the temperature monitoring devices 81 , 83 and 85. In this manner, the foamed suspension of fibers can be fed to each forming zone 50, 52, and 54 at a flow rate within desired set points and/or at a pressure within desired set points for optimizing formation of a web on the forming surface 26.

Information received from the flow meters 74, 76, and 78, from the pressure monitoring devices 80, 82, and 84, and/or from the temperature monitoring devices 81 , 83, and 85 can be used to determine the characteristics of the foamed suspension of fibers at the location of the measurements. In addition, the density of the foamed suspension of fibers can be measured or calculated from the information received from the various instruments. This information, in one embodiment, can be sent to the controllers for then calculating at least one characteristic of the foamed suspension of fibers at the forming surface. In particular, the controller can be programmed to correct the determined volumetric flow rate at the forming surface based upon changes in density, pressure, and temperature. For example, the foamed suspension can experience a pressure drop when being emitted from the supply line onto the forming surface that changes the density of the foamed suspension. One method for calculating downstream values of the foamed suspension, for instance, is disclosed in U.S. Patent No. 4,764,253, which is incorporated herein by reference.

As described above, in one embodiment, the density of the foamed suspension is determined either directly or calculated. In one aspect, a density monitoring device (e.g. density meter) can be incorporated into the system illustrated in FIG. 2. The density monitoring device, for instance, can be part of the flow meters 74, 76, and 78. The density monitoring device can measure the density directly. Alternatively, density can be measured in other ways. For instance, the air content of the foamed suspension can be first determined and density can be calculated based upon the measured pressure.

In one aspect, the measured characteristics of the foamed suspension within the supply lines 56, 58, and 60 can be combined with other known information to calculate one or more characteristics of the foamed suspension at the forming surface. For instance, in one embodiment, in addition to measuring or determining flow rate (mass flow rate and/or volumetric flow rate), density, temperature, and pressure of the foamed suspension, other information can be fed to the controller including the amount of solid material or concentration contained in the feedstock, the width of the forming surface, the speed of the forming surface, and the desired basis weight of the layer for calculating and/or determining at least one set point, such as the volumetric flow rate of the foamed suspension that is fed to the forming surface.

The foamed suspension is a two-phase fluid. The foamed suspension includes a liquid volume fraction and a gas volume fraction. The gas volume fraction can also be referred to as air content by volume. The air content by volume can be determined by dividing the weight of one liter of foam by the weight of one liter of water (e.g. 1 ,000 g). The air content by volume of the foamed suspension is dependent upon pressure. In other words, the air content by volume and the density of the foamed suspension change as the pressure changes.

In one aspect, when making calculations, the solid component of the foam can be neglected and assumed part of the liquid phase. The flow rate (L/min) of the foamed suspension can be represented as the sum of the liquid flow rate (L/min) combined with the flow rate of the gas phase (L/min). The liquid volume fraction of the foam is the percent volume of the total foam that is liquid and can be determined by dividing the liquid flow rate (L/min) by the foam flow rate (L/min). The liquid volume fraction can also be calculated from the measured or calculated density of the foamed suspension. The total foam flow rate (L/min) can then be calculated by dividing the flow rate (L/min) of the feedstock by the liquid volume fraction. The gas flow rate of the foamed suspension can be determined by subtracting from the foamed suspension flow rate (L/min) the liquid flow rate (L/min). All of the above determinations are at the location of the measurements in FIG. 2.

To calculate density changes and volumetric foam flow rate changes at other points in the system, such as at the forming surface, the difference in pressure must be accounted for due to the expansion or compression of the gas phase. The ideal gas law can be used to determine the changes in density and volumetric foam flow rate assuming no temperature change. Alternatively, temperature changes within the system can be measured, calculated or estimated and thus accounted for in the ideal gas law. In this manner, one or more characteristics of the foamed suspension, including density and volumetric flow rate, can be determined at the location of the flow meters 74, 76, and 78 illustrated in FIG. 2 and then calculated at the forming surface.

In addition to the above measurements and calculations, the basis weight of the formed web or layer on the forming surface can also be calculated. Basis weight calculations can be determined based upon the area formed per time and the weight of solid matter, such as fibers, delivered to the forming surface per time (e.g. fiber flow rate). The area of the web formed per time unit can be determined based upon the width of the forming surface and the velocity of the forming surface. The solid or fiber flow rate that is desired can be calculated by multiplying the target basis weight by the area formed per time. For determining the actual solid or fiber mass flow rate, one can assume that the weight of water is the total mass of fluid moving through the system. Density differences between the fiber and water and the effect of temperature on water density can be neglected. Thus, the mass flow rate can be calculated by dividing the mass flow rate of fiber being fed to the system divided by the amount of fiber contained in the liquid phase of the foamed suspension. Alternatively, the mass flow rate of the fiber can be directly measured.

In one aspect, the controller can be programmed to have predetermined or preselected reference values of at least one characteristic of the foamed suspension. For instance, the controller can be programmed with a desired volumetric flow rate value and/or mass flow rate value. These values can be calculated by the controller and compared to the preset value Based on comparisons between the preset value and the calculated or measured value, the controller can be configured to control the pumping devices 68, 70, and 72 in response to any departure from the preset value. In this manner, the controller can control the volumetric flow rate of the foamed suspension to the forming surface and/or the basis weight of the layer being formed.

In addition to controlling the flow characteristics of the foamed suspension fed to the forming surface, the system and process of the present disclosure also contains similar components for measuring and/or determining similar characteristics of the drainage fluids that are drained through the forming surface. For instance, the fluids drained from the forming surface are also in the form of a foam having a liquid phase and a gas phase. As shown in FIG. 2, the flow rate, temperature, pressure, and/or density of the drainage fluids can also be measured, determined and/or calculated. A flow control device can be placed on each drainage line for then controlling the amount of fluids being drained from the forming surface based upon the flow characteristics of the foamed suspension that is fed to the forming surface. In this manner, the formation of the web can be controlled for optimizing the properties of the web.

In the embodiment illustrated in FIG. 2, various characteristics of the drainage fluid are measured and/or calculated downstream from the forming surface. These measurements are taken downstream from the forming surface and then used to calculate flow rates at the forming surface taking into account changes in pressure, density, and/or temperature.

For example, as shown in FIG. 2, opposite each forming zone 50, 52, and 54 is a corresponding drain device in fluid communication with a corresponding drain line. In the embodiment illustrated in FIG. 2, each forming zone is in alignment with a single drain device.

As used herein, a drain device is “in alignment” with a forming zone when the drain device is positioned in relation to the length of the forming zone such that the drain device does not extend beyond the length of the forming zone by greater than about 20%. For instance, one embodiment of a forming zone 300 is shown in FIG. 6 for exemplary purposes and for purposes of explanation. As shown, the forming zone 300 includes a first layer of a foamed suspension of materials 302 being deposited adjacent to an inclined porous forming surface 26. The first foamed suspension of materials 302 can be emitted by a first headbox.

As shown in FIG. 6, a second foamed suspension of materials is also being fed into the process from a second headbox. In the embodiment illustrated in FIG. 6, two different flow streams are shown. The system and process, however, can include only a single flow stream or can include more than two flow streams.

The first flow stream of the foamed suspension of materials 302 is fed to the forming zone 300 by being deposited onto the moving porous forming surface 26. The first flow of the foamed suspension of materials 302 is separated from the second flow of the foamed suspension of materials 304 by a partition or lamella 306. As used herein, the length of the forming zone is the distance between where the foamed suspension of materials is deposited onto the moving porous forming surface 308 to where the partition or lamella 306 terminates. As shown in FIG. 6, the forming zone 300 has a length L.

In accordance with the present disclosure, a drain device is in alignment with the forming zone as long as the drain device does not extend greater than 20% beyond the length L of the forming zone. In other embodiments, the drain device or plurality of drain devices may all be positioned within the length of the forming zone. Alternatively, one or more drain devices can extend beyond the length of the forming zone by less than about 15%, such as less than about 10%, such as less than about 5%, such as less than about 2%.

Referring back to FIG. 2, opposite the first forming zone 50 along the forming surface 26 is a first drain device 86 in fluid communication with a first drain line 92. Opposite the second forming zone 52 is a second drain device 88 in fluid communication with a second drain line 94. Similarly, opposite the third forming zone 54 is a third drain device 90 in communication with a third drain line 96. As shown in FIG. 2, the forming zones 50, 52, and 54 are adjacent to each other along the forming surface 26 and are positioned on one side of the forming surface. The drain devices 86, 88, and 90 are also adjacent to each other and are positioned on the opposite side of the forming surface 26 in alignment with the forming zones 50, 52, and 54. As the foamed suspension of fibers is deposited onto the forming surface from each forming zone 50, 52, and 54, a web 14 is formed and excess fluids enter the corresponding drain devices 86, 88, and 90. The drain devices can be any suitable static or dynamic drain device capable of draining fluids from the web or from the forming surfaces. The drain device can be a static suction or vacuum box. Alternatively, the drain device can be a drum, such as a rotating drum that applies suction.

As shown in FIG. 2, each drain line 92, 94, and 96 includes a corresponding flow control device, flow meter, temperature monitoring device, and pressure monitoring device. For example, the first drain line 92 includes a first flow control device 98, a first flow meter 104, a first temperature monitoring device 105, and a first pressure monitoring device 110. The second drain line 94 includes a second flow control device 100, a second flow meter 106, a second temperature monitoring device 107, and a second pressure monitoring device 112. The third drain line 96 includes a third flow control device 102, a third flow meter 108, a third temperature monitoring device 109, and a third pressure monitoring device 114. The flow control devices 98, 100, and 102 can be any suitable device for controlling flow through the line and can be, an adjustable valve or a pump. Pumps, for instance, can be used to apply suction to the forming surface. Alternatively, draining can occur through gravity. In still another embodiment, each flow control device 98, 100, and 102 can be the combination of a pump and an adjustable valve.

In one embodiment of the present disclosure, each drain line 92, 94, and 96 is controlled independently of the other drain lines. The amount of flow or drainage from each drain device 86, 88, and 90 through each corresponding drain line 92, 94, and 96 can be adjusted and controlled based upon at least one characteristic of the foamed suspension of fibers that can be measured or calculated as described above and that is fed to each of the forming zones 50, 52, and 54. For instance, in one embodiment, the amount of flow or drainage from each drain device can be based upon the volumetric flow rate of the foamed suspension of fibers being fed to each of the forming zones. For example, the flow meters 104, 106, and 108 in combination with the pressure monitoring devices 110, 112, and 114, the temperature monitoring devices 105, 107, and 109, and/or optionally one or more density monitoring devices, can be used to quantify the fluids being drained which can be a two-phase discharge flow containing both liquids and gases. The two-phase discharge flow can be converted to a reference pressure based upon information received from the flow meters 104, 106, and 108, the pressure monitoring devices 110, 112, and 114, the temperature monitoring devices 105, 107, and 109 and/or density monitoring devices. The flow control devices 98, 100, and 102 can then be adjusted and controlled in order to achieve an optimum or desired discharge flow rate that is based upon the at least one characteristic of the foamed suspension of fibers fed to each of the forming zones 50, 52, and 54.

In one aspect, for instance, the characteristics of the two-phase drainage fluid flowing through drain lines 92, 94, and 96 can be measured or calculated downstream from the forming surface. The same calculations as described above can then be used to determine one or more characteristics of the foam being drained from the forming surface based upon the measured and calculated characteristics of the foam downstream from the forming surface.

In one embodiment, the system can further include one or more controllers 116. The controllers can be microprocessors or any suitable programmable devices. As shown in FIG. 2, each flow control device 98, 100, and 102, each flow meter 104, 106, and 108, each temperature monitoring device 105, 107, and 109, each density monitoring device, and/or each pressure monitoring device 110, 112, and 114 can be in communication with the controller 116. The controller can receive information from the flow meters 104, 106, and 108, the temperature monitoring devices 105, 107, and 109, the optional density monitoring devices, and/or the pressure monitoring devices 110, 112, and 114 for making adjustments to the flow control devices 98, 100, and 102 for controlling the flow rate in which fluids are drained from each of the drain devices 86, 88, and 90. The combination of receiving information from the flow control devices 98, 100, and 102, which can be volumetric flow meters, from the pressure monitoring devices 110, 112, and 114, from the temperature monitoring devices 105, 107, and 109, and/or from optional density monitoring devices can be used to quantify the fluid discharge flows containing both gases and liquids. In one embodiment, the controller 116 can use the above information to calculate a flow rate, such as a volumetric flow rate, at the forming surface and control the volumetric flow rate based upon at least one characteristic of the foamed suspension being fed to the forming surface. The controller 116 can then control the flow control devices 98, 100, and 102 to achieve a calculated discharge flow rate through each drain device and drain line.

In one aspect, the controller 116 can determine a volumetric flow rate of the foam being drained from the forming surface and can adjust the volumetric flow rate based upon the volumetric flow rate of the foamed suspension being fed to the forming surface. Alternatively, the drainage system can apply a vacuum to the forming surface at each of the drain devices. The controller 116, in this embodiment, can determine a reference pressure from the information received from all of the measuring devices and instruments positioned downstream. The controller 116 can then adjust the reference pressure at the forming surface based upon a characteristic of the foamed suspension, such as based upon the volumetric flow rate of the foamed suspension.

Through the process of the present disclosure, the drainage of foam from the forming surface can be carefully controlled based upon the amount of foam and fibers being fed to the forming surface for producing webs without over-draining or under-draining the webs during formation. In this manner, webs can be produced with uniform characteristics and with enhanced properties. In the embodiment illustrated in FIG. 2, the flow control devices 98, 100, and 102 are shown as valves. In other embodiments, however, the flow control devices 98, 100, and 102 can be pumping devices for pumping fluids through the drain lines at desired flow rates. In one aspect, each flow control device can be a combination of a pumping device and a valve.

In accordance with the present disclosure, the drainage flow rates through each drain line 92, 94, and 96 can be coordinated with the flow rates and/or pressures of the foamed suspension of fibers fed to each of the forming zones 50, 52, and 54. By controlling drainage flow rates based upon supply flow rates, web formation can be controlled for optimizing properties. When producing multilayered webs, such as shown in FIG. 2, the drainage flow rates can be controlled in relation to input pressures and/or flow rates in order to further enhance interlayer mixing for further improving the physical properties of webs while the webs are being formed.

For instance, as shown in FIG. 2, by controlling the discharge flow rates in relation to the input flow rates, the foamed suspension of fibers fed to each forming zone 50, 52, and 54 can be caused to spread out in a unique way onto the forming surface 26. For example, as shown by the arrows, the foamed suspension of fibers fed to each forming zone 50, 52, and 54 can be caused to flow laterally outside a perimeter of each forming zone for causing fiber reorientation and/or layer mixing. For example, in one embodiment, the drainage flow rates at the drain devices 86, 88, and 90 can be maintained at a flow rate that is less than the flow rate of the foamed suspension of fibers being fed to each of the forming zones 50, 52, and 54. Creating a pressure differential where the forming zones 50, 52, and 54 intersect with the forming surface 26 can create fiber mixing and reorientation and longitudinal flow as shown in FIG. 2.

In one embodiment, the process and system of the present disclosure can further include a sealing zone 120 positioned along the forming fabric 26 and in fluid communication with a sealing fluid supply line 122. As shown in FIG. 2, the sealing fluid supply line 122 can include a pumping device 124, a flow meter 126, a pressure monitoring device 128, and a temperature monitoring device 129. The sealing fluid supply line 122 is for feeding a fluid, particularly a liquid, to the sealing zone 120. Sealing fluid can be any suitable liquid. For instance, the sealing fluid can be water, a water and surfactant solution, or the like. In one embodiment, the sealing fluid is non-fibrous. A sealing fluid is fed to the sealing fluid zone 120 at a flow rate and/or at a pressure such that sealing fluid deposited onto the forming surface 26 forms a fluid seal that prevents air flow in an upstream longitudinal direction. Information received from the flow meter 126, the pressure monitoring device 128, the temperature monitoring device 129, and optionally a density monitoring device can be used to calculate volumetric flow rates of the foam at the forming surface. As shown in FIG. 2, the sealing zone 120 can be positioned upstream from and adjacent to the plurality of forming zones. The sealing zone 120 can also be placed opposite a sealing drain device 130 connected to a sealing drain line 132. The sealing drain line 132 can include a flow control device 134, a flow meter 136, a temperature monitoring device 137, and a pressure sensing device 138 that can all be in communication with the controller 116. In this manner, the flow rate of drainage of the sealing fluid can be carefully controlled based upon the flow rate or pressure at which the sealing fluid enters or exits the sealing zone 120. By including the sealing zone 120, better formation of the web 14 occurs opposite the first forming zone 50.

The web forming system 10 as shown in FIG. 2 can also include a suction zone 140 adjacent to the plurality of formation zones and positioned downstream from the formation zones. The suction zone 140 is in fluid communication with a drain line 142 which can include a pressure monitoring device 144. The suction zone 140 is for drawing fluids through the embryonic web 14 after the web has been formed. The suction zone 140 is for removing excess fluids, particularly liquids, from the web 14. In one aspect, the drainage flow rate of the foamed suspension of fibers being drained through the one or more drain devices is controlled such that excess fluid from the one or more forming zones enters the suction zone 140. Ideally, the suction zone 140 facilitates draining fluids from the web 14 without causing any detrimental effects.

In one embodiment, the one or more drain devices 86, 88, and 90 are operated such that the foamed suspension of fibers fed to the forming zones 50, 52, and 54 and particularly to the third forming zone 54 causes excess liquids to flow longitudinally outside a perimeter of the third forming zone 54 for being collected at the suction zone 140.

In one embodiment, as shown in FIG. 2, all of the drain lines 92, 94, 96, 132, and 142 can be fed to a separator tank 150. The separator tank 150 can be configured to separate free gases from foam. As shown, the separator tank 150 can include a gas outlet 152 that can be connected to a vacuum source and a liquid outlet 154. The liquid collected in the separator tank 150 can comprise a water and surfactant mixture. As shown in FIG. 2, a pumping device 156 can be used to pump liquids from the separator tank 150 to a liquid tank 158 which can also be placed in communication with a water source 160. The liquid tank 158 can be used to recycle the water and surfactant mixture back into the process through the supply lines 56, 58, 60, and 122.

The web forming system illustrated in FIG. 2 can offer various advantages and benefits when forming webs from foamed suspension of fibers. For instance, by controlling flow through the drain lines in relation to the flow of the foamed suspension of fibers to the forming zones, the detrimental effects of suction on the foam stock during formation of the web can be minimized. In addition, alignment of input pressure and drainage flow across the multiple zones of formation achieves a stable sheet formation and can produce multilayered webs with controlled and/or optimized mixing between the different layers of the web.

Referring to FIG. 1 , after the embryonic web 14 is formed from the web forming system or headbox 10, the web can be fed to various different downstream processes. FIG. 1 merely represents one embodiment of a process for drying the web after being formed. As shown, the web 14 is formed on the forming surface 26 and conveyed downstream. The endless traveling forming fabric 26, for instance, can be supported and driven by rolls 28.

Once formed on the forming fabric 26, the formed web can have a consistency of less than about 50%, such as less than about 20%, such as less than about 10%, such as less than about 5%. In fact, the forming consistency can be less than about 2%, such as less than about 1 .8%, such as less than about 1 .5%. The forming consistency is generally greater than about 0.5%, such as greater than about 0.8%.

Once the wet web is formed on the forming fabric 26, the web is conveyed downstream and optionally further dewatered. For instance, the process can optionally include a plurality of vacuum devices 16, such as vacuum and vacuum rolls. The vacuum boxes assist in removing moisture from the newly formed web 14.

As shown in FIG. 1 , the forming fabric 26 may also be placed in communication with a steambox 18 positioned above a pair of vacuum rolls 20. The steambox 18, for instance, can increase dryness and reduce cross-directional moisture variance. The applied steam from the steambox 18 heats the moisture in the wet web 14 causing the water in the web to drain more readily, especially in conjunction with the vacuum rolls 20. From the forming fabric 26, the newly formed web 14 is conveyed downstream and dried. The web can be dried using any suitable drying device. For instance, the web can be through-air dried or placed on a heated drying drum and creped or left uncreped. In FIG. 1 , for instance, the formed web 14 is placed in contact with two heated drying drums 38 and 40. In one embodiment, from the drying drums 38 and 40, the web can be fed to a through-air dryer prior to being wound into a roll.

The embodiment in FIG. 2 is for forming multilayer webs. In another aspect, the process of the present disclosure can be used to create single layer webs from a foamed suspension of materials.

Referring to FIG. 4, for instance, one embodiment of a web forming system made in accordance with the present disclosure is shown in which the system includes a single forming zone positioned in alignment with a drain device. Like reference numerals have been used to indicate similar elements.

As shown, the system includes an injection line 62 for injecting a foamed suspension of fibers into the system adjacent a pump 68. The pump 68 conveys the foamed suspension of fibers to a forming zone 50. A flow meter 74, a pressure monitoring device 80, and a temperature monitoring device 81 can monitor flow rates, pressures, and temperatures upstream from the forming surface for calculating at least one characteristic of the flow of the foamed suspension of fibers at the forming surface.

Opposite the forming zone 50 is positioned a drain device 86 that is in alignment with the forming zone. The drain device 86 is in communication with a corresponding drain line 92. The drain line 92 includes a corresponding flow control device 98, a flow meter 104, a temperature monitoring device 105, and a pressure monitoring device 110. All of the instruments can be in communication with a controller 116 which may comprise one or more microprocessors.

In the embodiment illustrated in FIG. 4, the drain device 86 can be operated to control drainage in a manner that controls formation of the web. Thus, as the foamed suspension of fibers is deposited on the forming surface, the amount of drainage occurring along the forming surface within the forming zone 50 can be controlled, adjusted and modified based upon any desired result.

The process and system as illustrated in FIG. 4 is generally for forming a single layer web. Referring to FIG. 5, another embodiment of a system in accordance with the present disclosure is shown that is designed to form multilayer webs using a single drain device.

In FIG. 5, like reference numerals have been used to indicate similar elements. As shown in FIG. 5, the system includes injection lines 62, 64, and 66 for injecting a foamed suspension of fibers into the process adjacent corresponding pumps or pumping devices 68, 70, and 72. The pumping devices 68, 70, and 72 feed the foamed suspension of fibers to corresponding forming zones 50, 52, and 54.

Each pumping device 68, 70, and 72 is in communication with a corresponding foamed fibrous supply line 56, 58, and 60. Each foamed fibrous supply line 56, 58, and 60 is in communication with a flow meter 74, 76, and 78, a pressure monitoring device 80, 82, and 84, a temperature monitoring device 81, 83, and 85, and optionally a density monitoring device (not shown). The three foamed fibrous supply lines 56, 58, and 60 are fed to the corresponding forming zones 50, 52, and 54 for forming a three-layer web. In one embodiment, for instance, the middle layer may comprise a superabsorbent material that is sandwiched between two outer layers. In the embodiment illustrated in FIG. 5, the forming zones 50, 52, and 54 are all in alignment with a single drain device 86. As shown, the drain device 86 is in fluid communication with corresponding a drain line 92. The drain line 92 is in communication with a flow control device 98, a flow meter 104, a temperature monitoring device 105, and a pressure monitoring device 110.

In the embodiment illustrated in FIG. 5, the amount of drainage through the drain device 86 can be based on all the information received by the controller 116 from the instruments associated with all three forming zones 50, 52, and 54. Further, adjustment of the drainage rate through the drain device 86 can also be controlled by the controller 116 in conjunction with information received from the flow control device 98, the flow meter 104, the temperature monitoring device 105, and/or the pressure monitoring device 110.

Webs made according to the present disclosure can be used in all different types of products. For instance, the tissue web can be used to produce bath tissue, facial tissue, paper towels, industrial wipers, and the like. In one embodiment, webs made according to the present disclosure can contain substantial amounts of superabsorbent particles. For instance, at least one layer of the web can contain superabsorbent particles in an amount greater than about 50% by weight and up to about 90% by weight, including all increments of 1% by weight therebetween. These types of webs are particularly well suited for incorporation into personal care absorbent articles. For instance, the webs can be used as absorbent cores positioned between a liquid permeable liner and a liquid impermeable outer cover.

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

What Is Claimed:

1 . A process for producing a web comprising: flowing a foamed suspension of materials to one or more forming zones, the one or more forming zones including at least a first forming zone, the foamed suspension being fed to the first forming zone at a first flow rate depositing the foamed suspension of materials fed to the first forming zone adjacent to at least one moving porous forming surface to form an embryonic web; draining excess fluids through the porous forming surface into at least one drain device; and controlling a flow rate of drainage fluids drained through the at least one drain device based on at least one characteristic of the flow of the foamed suspension of materials being fed to the first forming zone; and drying the embryonic web.

2. A process as defined in claim 1 , wherein the at least one characteristic of the flow of the foamed suspension of materials comprises a temperature, pressure, a mass flow rate, a volumetric flow rate, or a density of the foamed suspension of materials.

3. A process as defined in claim 1 , further comprising the step of flowing the foamed suspension of materials to a second forming zone positioned adjacent the first forming zone, the foamed suspension of materials being fed to the second forming zone at a second flow rate; depositing the foamed suspension of materials fed to the second forming zone onto the materials deposited adjacent the forming surface from the first forming zone to form a multilayered web; and controlling a flow rate of drainage fluids drained through at least one drain device positioned in alignment with the second forming zone.

4. A process as defined in claim 3, wherein the drainage flow rate through the at least one drain device positioned in alignment to the second forming zone is controlled such that the foamed suspension of materials being fed to the second forming zone is caused to flow longitudinally outside a perimeter of the second forming zone

5. A process as defined in claim 3 or 4, further comprising the step of flowing the foamed suspension of materials to a third forming zone positioned adjacent the second forming zone, the foamed suspension of materials being fed to the third forming zone at a third flow rate; depositing the foamed suspension of materials fed to the third forming zone onto the materials deposited adjacent the forming surface from the first forming zone and the second forming zone; and controlling a flow rate of drainage fluids drained through at least one drain device positioned in alignment with the third forming zone.

6. A process as defined in claim 5, wherein the drainage flow rate through the at least one drain device positioned in alignment to the third forming zone is controlled such that the foamed suspension of materials being fed to the third forming zone is caused to flow longitudinally outside a perimeter of the third forming zone.

7. A process as defined in claim 1 , wherein the process only includes the first forming zone for producing single layer webs.

8. A process as defined in any of the preceding claims, wherein a sealing zone is positioned adjacent to and upstream from the first forming zone for inhibiting air flow in an upstream longitudinal direction.

9. A process as defined in claim 8, wherein the sealing zone positioned adjacent to and upstream from the first forming zone emits a fluid in relation to the at least one porous forming surface for inhibiting air flow.

10. A process as defined in claim 9, wherein the fluid emitted by the sealing zone comprises a foam.

11. A process as defined in any of the preceding claims, wherein the flow rate of fluids through the first drain device is less than the first flow rate of the foamed suspension of materials being fed to the first forming zone.

12. A process as defined in any of the preceding claims, wherein the foamed suspension of materials is pumped to each of the one or more forming zones individually such that the fluid pressure upstream from each forming zone can be controlled independently of the other forming zones.

13. A process as defined in any of the preceding claims, wherein the foamed suspension of materials is pumped to the first forming zone, prior to the first forming zone, the temperature, pressure, flow rate, and density of the foamed suspension of materials is determined in order to calculate a flow rate at the forming surface, the flow rate of drainage fluids drained through the first drain device being controlled based upon the calculated flow rate.

14. A process as defined in any of the preceding claims, wherein the flow rate of drainage fluids drained through the first drain device is monitored by a flow meter and a pressure monitoring device, the flow meter and the pressure monitoring device sending information to a controller that calculates a discharge flow rate, the controller being in communication with an adjustable flow control device for controlling the flow rate of drainage fluids drained through the first drain device based upon the calculated discharge flow rate.

15. A process as defined in any of the preceding claims, further comprising the step of drawing fluids through the embryonic web at a suction zone that is downstream from the one or more forming zones and corresponding drain devices.

16. A process as defined in claim 15, wherein the drainage flow rate of the foamed suspension of materials being drained through the one or more drain devices is controlled such that excess fluid from the one or more forming zones enters the suction zone.

17. A process as defined in any of the preceding claims, wherein the forming surface is inclined in relation to a horizontal.

18. A process as defined in any of the preceding claims, wherein the foamed suspension of materials is formed by combining a foam with a fiber furnish, the foam having a density of from about 200 g/L to about 600 g/L, such as from about 350 g/L to about 600 g/L and/or containing from about 40% to about 80% by volume air, such as from about 40% to about 65% by volume air.

19. A process as defined in any of the preceding claims, wherein the materials contained in the web comprise at least about 5% by weight pulp fibers, such as at least about 10% by weight pulp fibers, such as at least about 15% by weight pulp fibers optionally combined with non-fibrous particles, such as super absorbent particles.

20. A process as defined in any of the preceding claims, wherein the materials contained in the web comprise at least about 5% by weight polymer synthetic fibers, such as at least about 10% by weight polymer synthetic fibers, such as at least about 15% by weight polymer synthetic fibers.

21 . A process as defined in claim 1 , wherein the dried web has a density of greater than about 0.03 g/cc, such as greater than about 0.05 g/cc, such as greater than about 0.1 g/cc, and less than about 0.7 g/cc, such as less than about 0.5 g/cc.

22. A process as defined in claim 1 , wherein the dried web has a basis weight of from about 6 gsm to about 800 gsm, such as from about 10 gsm to about 200 gsm, such as from about 20 gsm to about 120 gsm.

23. A process as defined in any of the preceding claims, wherein the fluids drained through the first drain device are monitored downstream from the forming surface by at least one of a flow meter, a temperature monitoring device, and a pressure monitoring device, and wherein information received from at least one of the flow meter, the pressure monitoring device, or the temperature monitoring device is used to calculate a flow rate of fluids being drained through the first forming zone at the forming surface.

24. A process as defined in any of the preceding claims, wherein the at least one drain device is positioned in alignment to the at least one forming zone along the at least one porous forming surface.

25. A process as defined in any of the preceding claims, wherein the first drain device comprises a vacuum box.

26. A process as defined in any of claims 1 through 23, wherein the first drain device comprises a drain roll.

27. A system for producing webs comprising: a forming zone positioned in relation to at least one porous forming surface, the forming zone being in communication with a foamed fibrous supply line, the foamed fibrous supply line including a pumping device for flowing a foamed suspension of materials to the respective forming zone, the foamed fibrous supply line further including a flow meter, a pressure monitoring device, a temperature monitoring device, or combinations thereof, the foamed fibrous supply line for feeding a foamed suspension of materials to the corresponding forming zone for depositing the materials contained in the foamed suspension adjacent to the at least one porous forming surface at a determined flow rate, a pressure or both; at least one drain device positioned to drain fluids from the porous forming surface, the at least one drain device being in fluid communication with a corresponding drain line, the drain line including a flow control device for controlling a flow rate of a fluid being drained into the drain device, the drain line further including a flow meter, a pressure monitoring device, a temperature monitoring device, or combinations thereof; and one or more controllers in communication with the flow control device associated with the drain line, the one or more controllers being configured to control the flow rate of fluids being drained into the at least one drain device in relation to a flow rate, a temperature, or a pressure of the foamed suspension of materials being fed to the forming zone.

28. A system as defined in claim 27, comprising a plurality of forming zones and a plurality of drain devices, each forming zone being in communication with a separate foamed fibrous supply line, each foamed fibrous supply line including a pumping device for flowing a foamed suspension of materials to a respective forming zone, each foamed fibrous supply line further including a flow meter, a pressure monitoring device, a temperature monitoring device, or combinations thereof, each foamed fibrous supply line for feeding a foamed suspension of materials to a corresponding forming zone for depositing the materials contained in the foamed suspension adjacent to the at least one porous forming surface at a determined flow rate, a pressure or both; each drain device being positioned in alignment with the at least one porous forming surface in coordination with the plurality of forming zones, wherein for each forming zone there is at least one corresponding drain device, each drain device being in fluid communication with a corresponding drain line, each drain line including a flow control device for controlling a flow rate of a fluid being drained into each corresponding drain device, each drain line further including a flow meter, a pressure monitoring device, a temperature monitoring device, or combinations thereof; and wherein the one or more controllers are in communication with each of the flow control devices associated with the drain lines, the one or more controllers being configured to independently control the flow rate of fluids being drained into each drain device in relation to a flow rate or a pressure of the foamed suspension of materials being fed to each of the forming zones.

29. A system as defined in claim 28, wherein the one or more controllers are configured to control the flow rate of fluids being drained from each drain device based on information received from the corresponding flow meter, pressure monitoring device, and/or temperature monitoring device associated with each forming zone.

30. A system as defined in claim 27, 28, or 29, further comprising a drying device positioned downstream for drying a web formed on the porous forming surface.

31 . A system as defined in claim 28 wherein the plurality of forming zones are positioned along the at least one porous forming surface in order to form multilayer webs.

32. A system as defined in claim 27, 28, 29, 30, or 31 wherein the moving forming surface is inclined in relation to a horizontal.

33. A system as defined in any of claims 27 through 32, further comprising a separator tank in fluid communication with the drain line for receiving a drain fluid from the drain device, the separator tank separating free gasses from foam for recycling the foam in producing the foamed suspension of materials.

34. A system as defined in any of claims 27 through 33, further comprising a suction zone adjacent to and downstream from the forming zone for drawing fluids through webs formed on the forming surface, the flow rate of fluids being drained into the drain device being controlled by the one or more controllers in a manner that causes the suction zone to collect a fluid from a web being formed.