EP1154890A1

EP1154890A1 - Extrusion apparatus for extruding continuous layer of extrudate

Info

Publication number: EP1154890A1
Application number: EP00907224A
Authority: EP
Inventors: Bruce J. Solberg; Gerald Tatera; Jonathan Ficke
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1999-02-26
Filing date: 2000-02-09
Publication date: 2001-11-21
Also published as: JP2002537153A; BR0008333A; WO2000050217A1; PE20001604A1; AU2875400A; CA2363110A1; AR032581A1

Abstract

A process for extruding and depositing an extrudate having a substantially continuous flow profile onto a substrate comprises dividing the extrudable fluid into a plurality of individual streams consecutively spaced along the width of the substrate, and then causing the individual streams of the extrudable fluid to widen widthwise and preferably connect just prior to being deposited onto the substrate. An extrusion apparatus, has an inlet and an outlet and comprises, in its preferred embodiment, a housing having a cavity and a removable shim having a plurality of slits therethrough and sized for insertion into the cavity of the housing for a close-fitting relationship therewith such that the plurality of the slits form the plurality of flow channels structured to transport the individual streams of the extrudable fluid from the inlet to the outlet. The slits of the shim are divergently flared at the outlet to facilitate widening of the individual streams of the extrudable fluid. Preferably, the shim is recessed relative to the outlet.

Description

EXTRUSION APPARATUS FOR EXTRUDING CONTINUOUS LAYER OF EXTRUDATE

FIELD OF THE INVENTION

The present invention generally relates to extrusion processes and apparatuses therefor. More specifically, the present invention is concerned with an extrusion process and an extrusion apparatus for continuously extruding a thin and substantially continuous layer of an extrudable material onto a substrate.

BACKGROUND OF THE INVENTION Extrusion apparatuses for forming sheet-like continuous extrudates of fluid materials on substrates are known in the art. Dies of a type generally known in the art as a coat-hanger die are described, for example, in the following U. S. patents: 4,043,739 issued on August 23, 1997 to Appel and assigned to Kimberly-Clark Corporation; 4,372,739 issued on February 8, 1983 to Vetter et al. and assigned to Rom GmbH of Darmstadt, Germany; 5,234,330 issued on August 10, 1993 to Billow et al. and assigned to Eastman Kodak Company; 5,494,429 issued on February 27, 1996 to Wilson et al. and assigned to Extrusion Dies, Inc.

The extrusion apparatuses for forming discontinuous patterns of extrudates having relatively high viscosity, such as, for example, hot melt adhesives or foams, are also known. U.S. Patents 4,774,109, issued on Sep. 27, 1988 and 4,844,004, issued on Jul. 4, 1989, to Hadzimihalis at el. and assigned to Nordson Corporation, disclose a method and an apparatus for applying narrow, closely spaced beads of viscous liquid, such as hot melt adhesive, to a substrate. The apparatus comprises a shim sandwiched between a pair of blades and having a plurality of closely spaced slots terminating with narrow exit openings for emitting beads of the viscous material. The narrow exit openings of the slots are located at a substantial distance above the substrate such that the multiple beads of the viscous fluid emitted from the openings are not sheared as they emitted from the slots' exit openings. The multiple beads of the emitted viscous material are narrow in width and are separated from one another across the substrate's width.

Coat-hanger dies have been used primarily to provide a uniform thickness of the extrudates of a relatively high viscosity, such, for example, as thermoplastics or solvent-plasticized materials. At the same time, coat-hanger dies known in the art are not well suited for materials having relatively low viscosity (less than about 1000 centipoise), especially when low flow rates (less than about 100 millimeter per minute per inch) are required. It is so mostly because the low-rates extrusion of materials having low viscosity requires maintaining a very high level of precision and tolerances with respect to the coat- hanger's nozzle opening throughout an entire width of the die. Therefore, many of the low-viscosity materials used in papermaking, such as, for example, water- based solutions, moisturizers, chemical softeners, anti-microbial and anti- virusoidal agents, various functional coatings, etc., typically have been deposited on substrates by techniques using spraying or printing operation, such as, for example, printing with Gravure rolls or reverse rolls. At the same time, spray-on methods of application of the low-viscosity substances to substrates have several disadvantages, such as, for example, a relatively low transfer efficiency rate (about 50%), difficulty and sometimes even impossibility of maintaining a reclaiming system and mist containment, high requirements of nozzle maintenance, and relatively high chemical losses. Printing methods also have several disadvantages, such as: relatively high cost and difficulty of maintaining and controlling an equipment - due to a relatively large number of moving parts and - typically - necessity to use active filtering. Moreover, typically each Gravure roll should be specially designed for a given rate and viscosity of the material being deposited. Roll cleaning is usually also required as fibers from the webs build up on the roll.

Now it has been found that the materials having relatively low viscosity can be beneficially extruded at very low flow rates using a capillary-type process, by utilizing a novel process and an extrusion apparatus of the present invention. Moreover, the extrusion process and the extrusion apparatus of the present invention allow one to avoid many of the problems associated with the spraying and printing processes and the processes using the coat-hanger dies of the prior art. This benefit has been achieved by separating the extrudable fluid into a plurality of individual, preferably capillary, streams, delivering the individual streams of the extrudable fluid to the proximity of a continuously moving substrate such that the individual streams are consecutively spaced across a width of the substrate at a desired frequency, and then causing the individual streams of the extrudable fluid to widen and preferably connect just prior to being deposited onto the substrate, thereby forming a substantially continuous, and preferably uniform, widthwise flow profile of the extrudate.

Accordingly, the present invention advantageously provides a novel extrusion apparatus and a process for forming a substantially continuous widthwise profile of the extrudate.

Another advantage of the present invention is that it provides an extrusion apparatus and a process allowing one to extrude a variety of low-viscosity materials at very low flow rates, especially when using the inventive process under conditions effectuating capillary forces. A further advantage of the present invention is that it provides an extrusion apparatus and a process for extruding a low-viscosity extrudate at very low flow rates and yet having a substantially continuous widthwise flow profile.

Another advantage of the present invention is that it provides an extrusion apparatus and a process for extruding a low-viscosity extrudate having a substantially uniform profile at very low flow rates.

Still another advantage of the present invention is that it provides an extrusion apparatus that one can easily disassemble for inspection, cleaning and/or adjustment, and then re-assemble with a minimal effort while still maintaining precise clearances of the discharge opening(s). Further advantage of the present invention is that it provides an easy and expeditious way of changing or adjusting parameters of an extrusion process, without necessity of substituting one extrusion apparatus for another. Other objects, features, and advantages of the present invention will be readily apparent from the following description taken in conjunction with accompanying drawings, although variations and permutations may be had without departing from the spirit and scope of the disclosure.

SUMMARY OF THE INVENTION An extrusion apparatus of the present invention comprises an inlet portion and an outlet portion. The inlet portion comprises an inlet for receiving an extrudable fluid, and the outlet portion comprises at least a first lip. The first lip has a first edge defining an elongate outlet for discharging the extrudable fluid, the outlet having an outlet width. As used herein, the "first lip" may be a leading lip or a trailing lip, depending on a specific embodiment of the extrusion apparatus. The extrusion apparatus further comprises a plurality of flow channels extending from the inlet portion to the outlet portion. The flow channels are structured to provide movement of individual streams of the extrudable fluid from the inlet portion to the outlet portion of the extrusion apparatus. Preferably, each of the flow channels has a discharge end associated with the first lip. The discharge ends of at least some of the flow channels are consecutively spaced along at least a portion of the first lip and preferably recessed relative to the first edge of the first lip such as to allow the individual streams of the extrudable fluid to widen "widthwise" (i. e., in a direction parallel to the outlet width) after exiting the flow channels. Preferably, the discharge ends of at least some of the flow channels are consecutively spaced in a close proximity from one another such as to provide a substantially continuous profile of the extrudable fluid along at least the portion of the outlet width. The discharge ends of the flow channels may be spaced from one another at substantially equal distances - to provide a substantially uniform profile of the extrudable fluid.

According to the present invention, at least some of the flow channels are divergently flared at the discharge ends to facilitate widening of the individual streams of the extrudable fluid in the outlet portion of the extrusion apparatus. In a preferred embodiment, the discharge ends of the flow channels are disposed relative to one another and relative to the first edge such that at least some of the individual streams of the extrudable fluid connect after exiting the flow channels. It is believed that because of the capillary action existing between the extrudable fluid and flared surfaces of the flow channels, an increase in a widthwise dimension, or width, of the flow channels facilitates widening of the individual streams of the extrudable fluid as the individual streams exit the flow channels through the discharge ends thereof. Preferably, the discharge ends of the flow channels are so closely spaced that at least some of the adjacent widened streams of the extrudable fluid eventually connect with one another.

Preferably, at least one distribution channel is provided in the inlet portion of the extrusion apparatus. The distribution channel is in fluid communication with the plurality of the flow channels, and may be used to equalize pressure applied to individual streams of the extrudable fluid. Preferably, the movement of the extrudable fluid within the flow channels is facilitated by pressure applied to the extrudable fluid. In its preferred embodiment, the extrusion apparatus of the present invention comprises a housing having a cavity therein intermediate the inlet and the outlet, and a relatively thin shim shaped for insertion into the cavity of the housing for a close-fitting relationship therewith. The preferred shim is removable, i. e., can be removed for inspection, cleaning, etc., and replaced by another shim, if desired. The shim has a first end, a second end opposite to the first end, a shim width, and a shim thickness, which is preferably substantially uniform. In one preferred embodiment, the thickness of the shim is from about 0.0005 inches to about 0.0450 inches, preferably from about 0.001 inches to about 0.015 inches, and more preferably, from about 0.002 inches to about 0.010 inches. Preferably, the shim is substantially planar. However, embodiments are contemplated in which the shim may have differential thickness and/or is not planar - depending on desired characteristics of the process and the extrusion apparatus. The shim is preferably made from a material selected from the group consisting of metal, plastic, glass, wood, paper, and any combination thereof. The shim is made from a material chosen to be chemically non-reactive to the extrudable fluid. The shim further has a plurality of relatively narrow slits, or cuts, therethrough, each of the slits having a discharge end terminating at (or flushing with) the second end of the shim. Thus, the discharge ends of the slits are open ends. The slits preferably form individual "capillaries" for the extrudable fluid. In the preferred embodiment, the slits are "cut" through the entire thickness of the shim. The slits, or cuts, are structured such that when the shim is disposed within the cavity of the housing in a close-fitting, preferably sealing, relationship therewith, the plurality of the slits form a plurality of flow channels providing fluid communication between the inlet and the outlet and structured to direct individual streams of the extrudable fluid to the outlet. Preferably, the discharge ends of the slits are consecutively spaced at predetermined distances therebetween along the shim width.

In its most preferred embodiment, the housing comprises a leading section and a trailing section, the leading and trailing sections being spaced apart and structured to receive the shim therebetween for a close-fitting relationship. The leading and trailing sections are fixedly, and preferably separably, joined to each other, with the shim disposed therebetween. When the shim is clamped between the leading and trailing sections of the housing, the slits of the shim and the surfaces of the housing contacting the shim form the plurality of the flow channels. Preferably, each of the discharge ends is in association with the first lip.

Preferably, a second lip, opposite to the first lip, is provided, the second lip having a second edge. The first edge and the second edge define an outlet therebetween for discharging the extrudable fluid, the outlet having an outlet width, which is measured along the first lip (and/or second lip). Preferably, at least one of the first lip and the second lip is movable relative to the other such that a distance, or clearance, between the first lip and the second lip is adjustable. A distance between the first and second lips is measured in a direction perpendicular to the outlet width. In the embodiment comprising both the first and second lips (or both the leading and trailing lips), the discharge ends of the slits are preferably disposed between the first and second lips. In such an embodiment, the discharge ends are preferably recessed relative to both the first edge of the first lip and the second edge of the second lip.

Preferably, the discharge ends of the slits are consecutively spaced in close proximity from one another so that adjacent individual streams of the extrudable fluid, after exiting the flow channels, form a substantially continuous profile of the extrudable fluid along the shim width. If desired, at least some of the discharge ends of the slits may be spaced from one another at substantially equal distances. Such an embodiment may provide a substantially uniform flow profile of the extrudate. A widthwise frequency of the discharge ends of the shim's slits may vary depending upon viscosity of the extrudable fluid, geometry of the extrusion apparatus, including the shim, and other desired characteristics and parameters of a given process. Typically, however, a widthwise frequency of the discharge ends of the slits is preferably from 1 to 11 per inch of the width of the shim, and more preferably from 2 to 5 per inch of the width of the shim. According to the present invention, each of the slits has a first portion comprising the inlet end and a second portion comprising the discharge end, the second portions being divergently flared towards the second end of the shim, and having a second length. Preferably, the first portions of the slits are substantially parallel to one another and have a substantially uniform first width. A width of the discharge ends is designated herein as a second width. The first width of the first portions of the slits is in the range of approximately 0.0005- 0.0500 inches, preferably in the range of approximately 0.001-0.025 inches, and more preferably in the range of approximately 0.010-0.015 inches. A ratio of the second width to the first width is preferably from about 2 to about 100, more preferably from about 5 to about 50, and most preferably from about 10 to about 35. A ratio of the second width to the second length is preferably from about 0.1 to about 5.0, more preferably from about 0.4 to about 1.5, and most preferably from about 0.6 to about 1.1.

A process of the present invention comprises the following steps: providing a substrate having a width; providing a source of the extrudable fluid; dividing the extrudable fluid into a plurality of individual streams and transporting the plurality of individual streams of the extrudable fluid to the proximity of the substrate such that the individual streams are consecutively spaced along the width of the substrate; preferably causing the individual streams of the extrudable fluid to widen widthwise; continuously moving the substrate; and depositing the extrudable fluid onto the substrate. The preferred process of the present invention is conducted under conditions effectuating capillary forces between the extrudable fluid and those surfaces of the extrusion apparatus which contact the extrudable fluid, especially in the preferred step of causing the individual streams of the extrudable fluid to widen widthwise.

The process further preferably comprises the steps of providing at least a first lip having a first edge and a width, the first lip being structured to receive the extrudable fluid. The step of dividing the extrudable fluid into a plurality of individual streams preferably comprises providing a plurality of flow channels extending from the source of the extrudable fluid to the first lip. Each of the flow channels is structured to provide movement of an individual stream of the extrudable fluid from the source of the extrudable fluid to the first lip. Each of the flow channels has a discharge end associated with the first lip. The discharge ends of the flow channels are consecutively spaced at predetermined distances from one another along the first lip. Preferably, the substrate is continuously moving in a close proximity from the first edge of the first lip such that the discharge ends of the flow channels are consecutively spaced across the width of the substrate. Preferably, the substrate contacts the first lip of the extrusion apparatus. The individual streams of the extrudable fluid move within the flow channels and discharge onto the at least first lip. The step of depositing the extrudable fluid onto the substrate comprises contacting the substrate with the extrudable fluid, preferably while the extrudable fluid is associated with the first lip. The process further preferably comprises providing a second lip opposite to the first lip, the second lip having a second edge. In such an embodiment, the discharge ends of the flow channels are preferably disposed between the first and second lips. The first and second lips are also termed herein as "leading" and "trailing" lips, depending on the direction of relative movement of the substrate. One preferred substrate comprises a fibrous web, such as, for example, a paper web. The extrudable fluid may comprise a variety of substances, including but not limited to functional additives, such as, for example, softeners, emulsions, emollients, lotions, topical medicines, soaps, various anti-microbial and anti- bacterial agents, moisturizers, coatings, inks and dies, binders, and strength agents. The extrudable fluid may also comprise reactive and non-reactive vapors, such as, for example, oxygen and nitrogen.

Preferably, the process further comprises a step of causing the individual streams of the extrudable fluid to widen laterally, or widthwise, i. e., in the direction parallel to the first edge and/or second edge, or in the direction parallel to the outlet width. This step is performed prior to the extrudate being deposited onto the substrate. As explained above, the flow channels may be beneficially flared at the discharge ends, and/or recessed relative to at least one of the first and second edges, to facilitate widening of the individual streams of the extrudable fluid after the individual streams exit the flow channels through the discharge ends. It is believed that under the capillary forces, the extrudable fluid follows a widthwise expansion of the divergently flared discharge ends of the flow channels, thereby spreading in the widthwise direction. More preferably, the process further comprises causing the individual streams of the extrudable fluid to connect after exiting the flow channels. It can be accomplished by spacing the discharge ends of the flow channels in close proximity from one another. In some embodiments, it may be desirable that the discharge ends of the flow channels are spaced from one another at substantially equal distances - to form the extrudate that has a substantially uniform widthwise flow profile. In the process of the present invention, the extrudate has an average flow rate that is preferably less than 1000 milliliter per minute per inch of the width of the first lip, more preferably from about 0.1 milliliter per minute per inch to about 100 milliliter per minute per inch of the width of the first lip, and still more preferably from about 1 milliliter per minute per inch to about 10 milliliter per minute per inch of the width of the first lip. The process may also include a step of adjusting a distance between the first lip and the second lip by moving at least one of the first lip and the second lip relative to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of one preferred embodiment of an extrusion apparatus of the present invention, shown in a partially disassembled arrangement. FIG. 2 is a schematic perspective view of a process of the present invention, showing the extrusion apparatus of the present invention extruding an extrudable fluid onto a substrate moving in a machine direction. FIG. 3 is a schematic cross-sectional view of one embodiment of the extrusion apparatus comprising a housing formed by a trailing section and a leading section, and a replaceable shim of the present invention interposed between the trailing and leading sections in a close-fitting relationship therewith. FIG. 4 is a schematic cross-sectional view of the extrusion apparatus, taken along lines 4-4 of FIG. 3. FIG. 4A is a schematic cross-sectional view taken along lines 4A-4A of FIG. 4. FIG. 5 is a schematic plan view of the shim of the present invention.

FIG. 6 is a schematic side-elevational view of another embodiment of the extrusion apparatus of the present invention. FIG. 7 is a schematic cross-sectional view of still another embodiment of the extrusion apparatus of the present invention. FIG. 8 is a schematic partial plan view of the extrusion apparatus of the present invention, showing comparative diagrams of a velocity distribution of the extrudable fluid within flow channels of the extrusion apparatus. FIG. 9 is a schematic and partial cross-sectional view of the extrusion apparatus, showing an extrudate contacting the extrusion apparatus's lip, the extrudate having a continuous profile along a width of an outlet of the extrusion apparatus. FIG. 10 is a schematic cross-sectional view similar to that shown in FIG. 9, and showing an extrudate which is substantially continuous and non-uniform along a portion of the width of an outlet of the extrusion apparatus. FIG. 11 is a schematic cross-sectional view similar to that shown in FIGs. 9 and 10, and showing an extrudate which is substantially uniform along a portion of the width of an outlet of the extrusion apparatus of the present invention. FIG. 12 is a schematic side elevational view of another embodiment of the extrusion apparatus of the present invention, comprising a trailing lip recessed relative to a leading lip.

FIG. 13 is a schematic side elevational view of the extrusion apparatus of the present invention, comprising a shim having a non-uniform thickness. FIG. 14 is a schematic plan view of the shim of the present invention having differential spacing between the slits. FIG. 15 is a schematic side elevational view of an embodiment of the extrusion apparatus having adjustable lips. FIG. 16 is a schematic and partially cut-away plan view of an embodiment of the extrusion apparatus structured to form two areas of a substantially continuous widthwise flow profile. FIG. 17 is a schematic side view of an embodiment of the extrusion apparatus comprising a trailing section, a leading section, and a plurality of replaceable shims interposed therebetween. FIG. 18 is a schematic plan view of two shims of the present invention mutually juxtaposed in a side-by-side arrangement. The housing of the extrusion apparatus is not shown for clarity.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process and an apparatus for forming a substantially continuous profile of an extrudable fluid, or extrudate, and depositing it onto a substrate, such as, for example, a fibrous web. FIGs. 1 and

2 schematically show a perspective view of one preferred embodiment of the apparatus of the present invention, an extrusion apparatus 10. For illustrative purposed, FIG. 1 shows the preferred extrusion apparatus 10 in a partially disassembled arrangement, while FIG. 2 shows the extrusion apparatus 10 which is fully assembled. FIG. 2 shows the extrusion apparatus 10 in combination with a substrate 70, thereby schematically illustrating the process of the present invention. The process of the present invention comprises several steps some of which may be performed simultaneously, and/or in an order at least partially different from the order described herein below, as one skilled in the art will appreciate.

The first step of the process of the present invention comprises providing a substrate 70 having a width. A variety of materials may be used as the substrate 70. Examples include but are not limited to: paper, fabric, plastic, including film, metal, wood, woven and non-woven materials. Structured papers, as well as non-structured papers, may be used as the substrate 70. Several examples of the structured papers may be found in the following commonly assigned U. S. patents: 4,529,480 issued July 16, 1985 to Trokhan; 4,637,859 issued Jan. 20, 1987 to Trokhan; 5,364,504 issued Nov. 15, 1994 to Smurkoski, et al.; 5,529,664 issued June 25, 1996 to Trokhan, et al.; and 5,679,222 issued Oct. 21 , 1997 to Rasch, et al. Other examples of the papers that may be used as the substrate 70 are described in the following U. S. patents: 3,301 ,746 issued Jan. 31 , 1967 to Sanford, et al.; 3,974,025 issued August 10, 1976 to Ayers; 4,191 ,609 issued March 04, 1980 to Trokhan; and 5,366,785 issued Nov. 22, 1994 to Sawdai. One-ply, as well as multi-ply webs may be used as the substrate 70 in the present invention.

Preferably the substrate 70 is continuously moving relative to the extrusion apparatus 10. More preferably, the substrate 70 is continuously moving in close proximity to the extrusion apparatus 10. As used herein, the term "close proximity" in the present context refers to a nearness in space between the extrusion apparatus 10 and the substrate 70, which nearness allows the extrudate to contact the substrate 70, thereby being transferred from the extrusion apparatus 10 onto the substrate 70, as described below. The term "close proximity" includes, but does not require, the substrate 70 to contact the extrusion apparatus 10. Preferably, however, the substrate 70 does contact the extrusion apparatus 10 during the process of the present invention, thereby the transferal of the extrudate from the extrusion apparatus 10 to the substrate 70 is conducted under conditions effectuating what is known in the art as a "capillary" transferal, as will be explained in more detail below. The next step comprises providing an extrudable fluid 80. As used herein, the term "extrudable fluid" refers to any fluid, including liquid, as well as gaseous material, which is capable of being extruded using the apparatus 10 and the process of the present invention. The examples of the extrudable fluid 80 include but are not limited to: water and various water-based solutions; alcohol and various alcohol-based solutions; functional additives, such as softeners (siloxanes, oils, quaternary ammonium, waxes, and others), emulsions, emollients, lotions, topical medicines, soaps, various anti-microbial and antibacterial agents, and moisturizers (for example, glycol); fillers, such, for example, as clay slurry; a variety of resins; coatings, such, for example, as clay and latex, and various opacifiers; inks and dies; binders; reactive and non-reactive vapors, such, for example, as oxygen and nitrogen. According to the present invention, the extrudable fluid 80 may have a wide range of viscosity. Preferably, the viscosity of the extrudable fluid is less than 5000 centipoise, more preferably from 1 to 500 centipoise, and most preferably from 10 to 200 centipoise. As used herein, the term "extrudate" designated by a reference numeral 80a refers to the extrudable fluid 80 which has been extruded using the extrusion apparatus 10 of the present invention but not yet deposited onto the substrate 70, i. e., the extrudate 80a is the extrudable fluid 80 just prior to being deposited to the substrate 70. The extrudate 80a retains sufficient fluidity. In the present application, the terms "extrudable fluid" 80 and "extrudate" 80a may be used interchangeably.

The next step comprises dividing the extrudable fluid 80 into a plurality of individual streams and transporting the individual streams of the extrudable fluid 80 to the proximity of the substrate 70 such that in the proximity of the substrate 70 the individual streams of the extrudable fluid 80 are consecutively spaced along the width of the substrate 70. Referring now to FIG. 7, this step may be performed by providing a plurality of flow channels 40, each having an inlet end 41 associated with a source 15 of the extrudable fluid 80 and a discharge end 42 located in the proximity of the substrate 70. The discharge ends 42 are consecutively spaced along the width of the substrate 70 at predetermined distances from one another. It should be understood that the discharge ends 42 need not form a straight line in plan view. Nor the discharge ends 42 need to form a line that is parallel to the width of the substrate 70 (or, stated differently, perpendicular to the direction of the movement of the substrate 70).

Preferably, the discharge ends 42 are associated with at least one lip 36 (either a leading lip or a trailing lip) having an edge 37, and more preferably the discharge ends 42 contact at least one lip 36. As used herein, the term "associated" and permutations thereof refer to a close relationship between two or more elements, with respect to movement of the extrudable fluid 80. For example, the inlet ends 41 are associated with the source 15 of the extrudable fluid 80 in that the extrudable fluid 80 from the source 15 enters the flow channels 40 through the first ends 41 ; analogously, the discharge ends 42 are associated with the lip 36 in that the extrudable fluid 80 contacts the lip 36 when exiting the flow channels 40 through the discharge ends 42. The substrate 70 preferably contacts the edge 37 of the lip 36.

The next step comprises causing the individual streams of the extrudable fluid 80 to widen laterally, or widthwise, such as to form a substantially continuous widthwise profile of the extrudable fluid 80, or extrudate 80a. It should be emphasized that the substantially continuous widthwise profile of the extrudable fluid 80 is formed, in accordance with the preferred embodiment of the present invention, prior to the extrudable fluid 80 having been deposited onto the substrate 70, while the extrudable fluid 80 is still associated with the extrusion apparatus 10. More preferably, at least some of the adjacent individual streams of the extrudable fluid 80 widen sufficiently to connect, as best shown in FIG. 8. The ways of accomplishing this step will be sufficiently described below, in the context of a detailed description of the extrusion apparatus 10 of the present invention. The extrudate 80a has an average flow rate of less than 1000 milliliters per minute per inch (ml/min/in), preferably - from 0.1 to 100 ml/min/in, and more preferably - from about 1 to about 10 ml/min/in. As used herein the term "average" flow rate refers to an average arithmetic flow rate measured in the area of a substantially continuous flow profile, as defined herein below.

The next step of the process comprises depositing the extrudable fluid 80, which at this point have a substantially continuous widthwise profile, onto the substrate 70. This step is accomplished by contacting the continuously moving substrate 70 with the extrudate 80a. Preferably, the substrate 70 contacts the lip 36, and more preferably, the edge 37 of the lip 36. It is believed that the extrusion apparatus 10 of the present invention may be beneficially used in a "free-jet" process, i. e., the process in which the extrudable fluid 80 is propelled, or impinged, from the extrusion apparatus 10 onto the substrate 70 through a gap formed therebetween, in which instance the substrate 70 does not contact the lip 36. It should be recognized, however, that a preferred embodiment of the process of the present invention comprises a "capillary" transferal of the extrudable fluid 80 to the substrate 70, i. e., the transferal by way of the substrate 70 contacting the extrudate 80a while the extrudate 80a is still in association with, or contacts, the lip 36. Stated differently, in the preferred embodiment of the process, the extrudate 80a does not separate from the lip 36 (hence the extrusion apparatus 10) before the extrudate 80a contacts the continuously moving substrate 70. Therefore, in the preferred embodiment of the process, there is no gap between the extrusion apparatus 10 and the web substrate 70.

It should be recognized that depending on a surface texture of the substrate 70, a coating formed by the extrudate 80a having the substantially continuous widthwise profile may or may not be substantially continuous on a surface of the substrate 70. In this regard, it is important to recognize a difference between the terms "extrudate" and "coating" in the context of the present application. As used herein, the term "coating" refers to the extrudate 80a which has been deposited to the substrate 70, while the term "extrudate" 80a refers to the extrudable fluid 80 disposed upon at least one lip 36, and preferably contacting the edge 37, just prior to being deposited onto the substrate 70. This distinction may be significant for the following reasons. First, when a very thin layer of the extrudate 80a having very low rates is being transferred from the lip 36 onto the substrate 70, interruptions in the layer of the extrudate 80a may occur, which interruptions may be tolerable as long as they do not adversely affect intended performance of the product being made. Second, the surface of some of the structured papers referred to herein above, may have differential planes, one of which may be formed by "pillows" and the other by "knuckles" formed in the paper. In this instance, the coating may also be disposed in the differential planes corresponding to the knuckles and the pillows, respectively, and may appear to be interrupted throughout the surface of the paper, even though just prior to having been deposited onto the substrate 70, the extrudate 80a has a substantially continuous profile in the widthwise direction. In addition, possible surface irregularities of the substrate 70 may also interfere with the continuity of the extrudate 80a being transferred to the substrate 70, and - consequently - with the continuity of the coating.

A preferred extrusion apparatus 10 shown in FIGs. 1-4A preferably comprises a housing 13 and a shim 50 disposed in the housing 13 in a close- fitting relationship therewith. The shim 50 has a first end 51 and a second end 52 opposite to the first end 51. The shim 50 further comprises a plurality of slits, or cuts, 60 through the shim 50 and generally extending intermediate the first and second ends 51 , 52 of the housing 50, as shown in FIGs. 4, 5, and 14. FIGs. 3 and 4 show in more detail two mutually perpendicular cross-sections of the preferred embodiment of the extrusion apparatus 10 principally shown in FIGs. 1 and 2. The preferred housing 13 comprises at least two sections: a leading section 11 and a trailing section 12. In an assembled arrangement, the leading and trailing sections 11 , 12 are joined together, with the shim 50 interposed between the leading and trailing sections 11 , 12. In the embodiment shown in FIGs. 6 and 12, the leading and trailing sections 11 , 12 of the housing 13 are fixedly joined together and spaced apart at a distance which is defined by a thickness H of the shim 50. One skilled in the art will appreciate that in some embodiments of the housing 13 at least some portions of the leading section 11 and the trailing section 12 may not be spaced apart, but instead contact each other. In the latter instance, the leading portion 11, or the trailing portion 12, or both the leading and trailing portions 11 , 12 may have a depression for receiving the shim 50. FIG. 4A schematically shows such an embodiment of the housing 13 in which both the leading section 11 and the trailing section 12 have corresponding depressions which are sized and structured to receive the shim 50 when the housing 13 is assembled.

Regardless of its specific embodiment, the housing 13, when viewed as a whole in the assembled arrangement, has a "cavity" formed by opposite inner surfaces 11a, 12a (FIG. 4A) of the leading and trailing sections 11 , 12, respectively, the cavity being sized and structured to receive the shim 50 for the close-fitting relationship between the shim 50 and the housing 13. As used herein, the term "cavity" is generic and refers to a spacing between the leading portion 11 and the trailing portion 12 (FIGs. 6 and 12) or between corresponding portions thereof (FIGs. 3-4A), as well as to the depression in at least one of the leading and trailing portions 11 , 12, sized to receive the shim 50. In the preferred embodiment, the opposite inner surfaces 11a, 12a of the leading and trailing sections 11 , 12 comprise straight and mutually parallel surfaces, and the "cavity" is formed only when the shim 50 is interposed between the sections 11 , 12, thereby spacing them apart.'

By "close-fitting relationship" it is meant that the opposite inner surfaces 11a, 12a (FIG. 4A) of the leading and trailing sections 11 , 12 (i. e., the surfaces forming the cavity) contact opposite surfaces of the shim 50, thereby preventing the shim 50 from moving in at least a direction from one of the leading and trailing sections 11 , 12 to the other. The shim 50 is structured and disposed within the housing 13 such that a sufficiently tight and secure contact between corresponding juxtaposed surfaces of the shim 50 and the housing 13 prevent the extrudable fluid 80 to leak therebetween. Preferably, the shim 50 is fixed between the leading and trailing sections 11 , 12 by virtue of a sufficient clamping force imparted on the shim 50 by the leading section 11 and the trailing section 12 joined together. More preferably, the clamping force is sufficient to "seal" the shim 50 within the housing 13. Thus, when the shim 50 is clamped within the housing 13, flow channels 40 formed by the slots 60 of the shim 50, as described below in detail, provide the only way for the extrudable material 80 to move within the housing 13. The leading and trailing sections 11 , 12 may be joined by any means known in the art, for example: by a plurality of bolts, screws, pins, or clamp(s); by adhesive; by welding, including ultrasonic and laser welding; by magnetic force; by vacuum force; and by any other suitable means known in the art, none of which are shown in the drawings to avoid obscuring clarity. It should be understood that the leading and trailing sections 11 , 12 may be joined indirectly: each of the leading and trailing sections 11, 12 may, independently of the other, be joined (for example, by adhesive) to the shim 50. For example, the leading section 11 may be attached to one side of the shim 50, and the trailing section 12 may be attached to the opposite side of the shim 50.

The preferred housing 13 has an inlet portion 20 and an outlet portion 30. The inlet portion 20 is in fluid communication with the outlet portion 30. As used herein, two or more elements are said to be in "fluid communication" when these elements are capable or adapted to be capable of transmitting (either one-way or reciprocally) various fluids, including liquid and gaseous substances. The inlet portion 20 of the housing 13 comprises an inlet 21 for receiving an extrudable fluid 80, and preferably a distribution channel 15 in fluid communication with the inlet 21 , as shown in FIGs. 3 and 4. The preferred inlet 21 generally comprises an opening through which the extrudable fluid 80 can be supplied, preferably under pressure, into the housing 13. The preferred distribution channel 15 comprises a slot extending in a widthwise direction. The distribution channel 15 may be formed in one or both of the leading section 11 and the trailing section 12. The distribution channel 15 accumulates the extrudable fluid 80 supplied through the inlet 21 and thus functions as a source of the extrudable fluid 80. The distribution channel 15 also equalizes pressure among the flow channels 40.

The outlet portion 30 has an outlet 31 through which the extrudable fluid

80 can be discharged onto the substrate 70. As used herein, the outlet 31 is an area through which the extrudable fluid 80 exits the extrusion apparatus 80. The preferred outlet portion 30 comprises a leading lip 32 and a trailing lip 36 (FIGs. 3 and 6). As used herein, the terms "leading lip" and "trailing lip," or a generic term a "lip," refer to those surfaces (or portions thereof) which contact the extrudable fluid 80 as the extrudable fluid 80 exits flow channels 40 (defined herein below) of the extrusion apparatus 10 and prior to the extrudable fluid 80 being deposited onto the substrate 70. Preferably, the leading lip 32 has a leading edge 33, and the trailing lip 36 has a trailing edge 37. Preferably, the leading edge 33 and the trailing edge 37 are substantially parallel to each other. As used herein the term "substantially parallel" indicates that minor deviations from absolute parallelism may be tolerable, while not preferred, as long as these minor deviations do not significantly affect the performance of the extrusion apparatus 10. Preferably, both the leading and trailing lips 32, 36 contact the extrudable fluid 80 when the extrudable fluid 80 exits the flow channels 40, whereby a clearance between the leading lip 32 and the trailing lip 36 define a "thickness" of the layer of the extrudate 80a.

In the preferred embodiment of the extrusion apparatus 10, the extrudable fluid 80 contacts both the leading lip 32 and the trailing lip 36 just prior to being deposited onto the substrate 70. Preferably, the leading lip 32 is disposed in the leading section 12, and the trailing lip 36 is disposed in the trailing section 13, as best shown in FIGs. 3 and 6. The leading and trailing lips 32, 36 may comprise an integral (i. e., structurally inseparable) portion of the respective opposite surfaces of the leading and trailing sections 11 , 12, which opposite surfaces clamp the shim 50 therebetween, as shown in FIG. 3. Alternatively, the leading and trailing lips 32, 36 may comprise surfaces that are separable from the opposite surfaces of the leading and trailing sections 11 , 12 which clamp the shim 50 therebetween, as shown in FIG. 6. FIG. 15 shows an embodiment of the extrusion apparatus 10 in which the leading and trailing lips 32, 36 are flexibly movable relative to each other such that the distance D between the leading edge 33 and the trailing edge 37 can be effectively controlled by a pair of thread mechanisms 90. In FIG. 15, the thread mechanism 90 comprises at least one screw 91 , preferably having a fine-pitch thread. The screw 91 is engaging a nut 92 fixedly secured to the body of the housing 13. A face end of the screw 91 is abutting a shoulder formed at an opposite side of the flexible lip 36 or 37. When the screws 91 are rotated such that their face ends extend forward, the face ends of the screw 91 engage and push the respective flexible lips 32, 36 - and consequently the edges 33, 37 - towards each other, thereby adjusting the distance N between the edges 33, 37. Preferably, the tread mechanism comprises a plurality of the screws 91 and the nuts 92, equally distributed along the outlet width W - to provide a necessary precision of controlling the distance N along the outlet width W. The thread mechanism may be complemented by a heating device 95, for a more accurate adjustment of the distance D. In the latter instance, a coarse adjustment of the distance N may be accomplished by rotating the screw 91 within the nut 92, and then a fine adjustment of the distance N may be made by heating the screw 91 which preferably causes a minimal and finely- tuned longitudinal expansion of the screw 91. It is to be understood that depending on specific embodiments of the thread mechanism 90 and the heating device 95, the heating device 95 may be utilized for a coarse adjustment, while the thread mechanism 90 - for a fine adjustment. It should also be understood that while FIG. 15 shows, for the illustration purposes, the thread mechanisms 90 and the heating devices 95 engaging both the leading lip 32 and the trailing lip 36, only one of the lips 32, 36 may be made to be flexibly-adjustable. In some embodiments, only one - either the thread mechanism 90 or the heating device 95 - may be desirable.

The housing 13 comprising the mutually separable leading and trailing sections 11 , 12 is preferred because separability of the housing 13 provides an easy access, when needed, to the shim 50 and the inner surfaces 11a, 12a of the housing 13 -- for example, for inspection, cleaning, and replacement. One can easily disassemble such extrusion apparatus 10 for inspection, cleaning and/or adjustment, and then re-assemble it with a minimal effort, while still maintaining precise clearances of the discharge outlet between the leading lip 32 and the trailing lip 36 -- due to the existence of the shim 50, "automatically" spacing apart the leading and trailing sections 11 , 12. However, an embodiment is possible, while not preferred, in which the housing 13 comprises an integral member, in which case the leading and trailing sections may be mutually inseparable. In the latter instance, the cavity in the housing 13 may be formed by a machining operation, such, for example, as grooving, or as part of a molding operation, or by any other suitable means known in the art, including but not limited to laser-cutting and chemical or electrochemical etching. The latter embodiment of the integral housing 13 is not illustrated but can be easily visualized by one skilled in the art.

Another embodiment of the extrusion apparatus 10 according to the present invention, which embodiment can be easily visualized by one skilled in the art and therefore is not illustrated herein, comprises a housing 13 formed by at least the leading section 11 and the trailing section 12 mutually juxtaposed. One of the leading section 11 and the trailing section 12 has grooves formed in one of the inner surface 11a or 12a, respectively (FIG. 4A). In the assembled housing 13, when the leading and trailing sections 11 , 12 are joined together such that their inner surfaces are mutually abutting, the grooves in one of the leading and trailing sections 11 , 12 and the corresponding inner surface of the other of the leading and trailing sections 11 , 12 form the flow channels 40 providing fluid communication between the inlet portion 20 and the outlet portion 30. The latter embodiment may be complimented by the shim 50 according to the present invention, and/or have a spacer interposed between the leading section 11 and the trailing section 12 to space apart the sections 11 , 12, in which instance the inner surfaces of the leading and trailing section 11 , 12 having the grooves therein abut against the opposite surfaces of the shim 50 and/or spacer. It should also be understood that the shim 50 and the spacer may be used in combination, by being interposed side-by-side between the leading and trailing section 11 , 12 (not shown).

Analogously, more than one shim 50 may be used in the extrusion apparatus 10 of the present invention, as shown in FIGs. 17 and 18. Two or more shims 50 could be interposed side-by-side between the leading and trailing sections 11 , 12. The slits 60 of a plurality of the shims 50 interposed between the sections 11 , 12 may or may not coincide. In the embodiment of the extrusion apparatus 10 comprising the plurality of the shims 50, one can effectively control widthwise distribution of the flow profile of the extrudable fluid 80 by laterally moving at least one of the shims 50 relative to at least another shim 50, thereby changing relative location and/or a resulting widthwise frequency of the flow channels 40 formed by the slits 60. In FIG. 17, for example, a first shim 50a and a second shim 50b are disposed between the leading and trailing sections 11 , 12. In FIG. 17, a spacer 55 is interposed between the two shims 50a and 50b, but it is to be understood that the spacer 55 may not be needed in some embodiments, in which the shims 50 contact one another in a side-by-side arrangement. In FIG. 18 (in which the spacer 55 is not shown for clarity) the first shim 50a has a first widthwise frequency a of the slits 60, which may or may not be equal to a second frequency b of the slits 60 of the second shim 50b. Similarly, the width of the slits of one shim may be different from the width of the slits of the other.

In a preferred embodiment of the housing 30, the leading edge 33 and the trailing edge 37 define the discharge outlet 31 therebetween. The outlet 31 has an outlet width W schematically shown in FIGs. 1 and 4. As used herein, terms "width," "widthwise," and permutations thereof refer to those dimensions that are parallel to at least one of the leading and trailing edges 33, 37; and the term "lateral" and permutations thereof refer to a direction that is parallel to at least one of the leading and trailing edges 33, 37. The reference is also made to a "machine direction" designated in several drawings as a directional arrow "MD" and a "cross-machine direction" designated as a directional arrow "CD." As used herein, the term "machine direction" indicates a direction which is parallel to the flow of the substrate 70 through the equipment. The term "cross-machine direction" indicates a direction which is perpendicular to the machine direction and lies in the general plane of the substrate 70. In some embodiments of the process according to the present invention, the extrusion apparatus 10 may be disposed relative to the substrate 70 such that the outlet width W is parallel to the cross-machine direction CD, as schematically shown in FIGs. 2 and 4. It should be noted, however, that embodiments are possible, and may be even desirable, in which the outlet is disposed such that the widthwise direction is not parallel to the cross-machine direction CD, i. e., the direction of the outlet width W and the cross-machine direction CD form an acute angle therebetween (not shown).

While the extrusion apparatus 10 comprising both the leading and trailing lips 32, 36 is preferred, in some embodiments the extrusion apparatus 10 does not necessarily require an existence of both leading and trailing lips 32, 36 (and consequently an existence of both leading and trailing edges 33, 37). In the extrusion apparatus 10 comprising a single lip -- either the leading lip 32 having the leading edge 33, or the trailing lip 36 having the trailing lip 37 - the outlet 31 is defined as an area adjacent to the leading edge 33 or the trailing edge 37, through which area the extrudable fluid 80 exits the extrusion apparatus 10 and is being deposited onto the substrate 70. Stated differently, in the extrusion apparatus 10 comprising a single lip, the outlet 31 is defined in one direction by the width of the lip, and in the other direction - by a thickness of the extrudate, the two directions being mutually perpendicular. In the latter instance, either the leading lip 32 or the trailing lip 36 may be defined herein as a "first lip" or "at least one lip." The extrusion apparatus 10 having a single lip - the trailing lip 36, for example - is schematically illustrated in FIG. 7 and discussed in greater detail below. While the leading and trailing edges 33, 37 are shown in FIGs. 3 and 4 as straight lines, it should be understood that one or both of the lips 33, 37 may be curved (not shown), if desired. One of the leading edge 33 and the trailing edge 37 may be recessed relative to the other. As used herein, one of the edges 33, 37 is "recessed" relative to the other when during the process of the present invention a distance between the surface of the substrate 70, onto which the extrudate 80a is being deposited, and one of the leading and trailing edges 33, 37 is greater than a distance between the surface of the substrate 70 and the other of the leading and trailing edges 33, 37. FIG. 12, for example, shows a fragment of an exemplary embodiment of the extrusion apparatus 10 and the process of the present invention, in which the leading edge 33 contacts a surface 70a of the substrate 70, while the trailing edge 37 does not; consequently, there is a distance formed between the trailing edge 37 and the substrate 70, and it is said that the trailing edge 37 is recessed relative to the leading edge 11. Without being limited by theory, applicants believe that such or similar embodiments may facilitate continuity of contact between the extrudate 80a and the substrate 70 and may be beneficial in some processes requiring increased contact time, as well as beneficially provide a zone of pressure to enhance the fluid's penetration into and/or absorption by the substrate 70. An extent of the recess (as well as an alignment, as appropriate) of one of the leading and trailing edges 33, 37 relative to the other may be controlled by a first spacer 19, as schematically shown in FIGS. 3, 6, and 15.

As defined above, the shim 50 has the first end 51 and the second end 52 opposite to the first end 51 , and the plurality of slits 60, as shown in FIGs. 1 , 4, and 8. Preferably, the general orientation of the slits 60 is orthogonal relative to the second end 52. In the preferred shim 50, each slit 60 has an inlet end 61 and a discharge end 62. As used herein, the inlet end 61 is defined as a point/area from which the individual stream of the extrudable fluid 80 begins its movement within the flow channel 40 towards the outlet 21. Preferably, the inlet ends 61 are defined by an upstream boarder of the distribution channel 15, as best shown in FIGs. 7 and 8. The discharge ends 62 of the slits 60 terminate at (or flush with) the second end 52 of the shim 50 and therefore are open. The shim 50 and the housing 13 are sized such that when the shim 50 is within the housing 13, the discharge ends 62 of the slits 60 are associated with the outlet portion 30 of the housing 13, and are preferably disposed between the leading and trailing lips 32, 36, as shown in FIG. 3. Due to the close-fitting relationship between the shim 50 and the housing 13, the plurality of the slits 60 and areas of the inner surfaces of the housing 13 corresponding thereto form a plurality of flow channels 40 which are structured to provide fluid communication between the distribution channel 15 of the inlet portion 20 and the outlet 31 of the outlet portion 30.

The shim 50 has a thickness H, as shown in FIG. 3. The thickness H may be uniform from the inlet end 51 to the second end 52 (FIGs. 3, 6, and 12), or - alternatively - the thickness H may differentiate, for example, from a first thickness "e" at the first end 51 to a second thickness "E" at the second end 52, the second thickness E being greater than the first thickness e, as schematically shown in FIG. 13. The preferred shim 20 is "removable" and preferably "replaceable" in that it can be removed, if needed, from the housing 13 and replaced, as appropriate, with a new shim which may or may not be identical or similar to the shim 20 being removed. The specific shim 50 can be designed and/or chosen, based on a rheology of the extrudable fluid 80, desirable characteristics of the process and the product to be made, and other relevant factors. For example, the extrudable fluid 80 having a relatively low viscosity, such, for example, as softeners used in making paper products and having viscosity from about 10 to about 30 centipoise, may require the shim 50 having a relatively smaller thickness H (from about 0.0005 inches to about 0.0450 inches), while the extrudable fluid having a relatively high viscosity, such, for example, as a silicone oil having viscosity from about 100 to about 300 centipoise, may require the shim 50 having a relatively greater thickness H (from about 0.002 inches to about 0.010 inches). That is so because, as best shown in FIGs. 3 and 6, the thickness H of the shim 50 defines a distance between the leading section 11 and the trailing section 12 of the housing 13, as well as a cross-sectional clearance of the flow channels 40. One of the essential advantages of the present invention is that the extrusion apparatus 10 provides high flexibility with respect to changing and/or adjusting parameters of a given process. The housing 13 comprising the leading and trailing sections 11 , 12 is capable of receiving a variety of the replaceable shims 50, based on the desired characteristics of the process. One shim can be easily and expeditiously replaced with another, thereby avoiding the necessity of substituting one extrusion apparatus for another.

As used herein, the term "flow channel" 40 refers to a passageway sized and structured to provide a continuous movement of a relatively thin, preferably "capillary," individual stream of the extrudable fluid 80 to the outlet portion 30. One skilled in the art will appreciate that in the embodiment of the extrusion apparatus 10 comprising the shim 50, a cross-sectional shape of the flow channel 40 is defined by a cross-sectional shape of the slit 60, which may, in turn, be limited, among other considerations, by a particular technological process employed of making the shim 50 and/or slits 60. Various shapes of the cross-section of the flow channels 40 may be used. The examples include but are not limited to: circle, oval, rectangular, and any combinations thereof. In the preferred embodiment of the shim 50, the slits 60 may be "cut" through the body of the shim 50 by a variety of machining operations, chemical and electrochemical etching, laser beam, electrical discharge machining (EDM), and other means known in the art. If the shim 50 is substantially flat and uniform, the individual flow channel 40 may have a substantially rectangular configuration in a cross-section.

Regardless of their specific shape, the flow channels 40 posses certain characteristics. The open discharge ends 42 of the flow channels 40 are associated with the outlet portion 30 of the extrusion apparatus 10. Preferably, the discharge ends 42 are associated with at least one of the leading and trailing lips 32, 36 such that when the extrudable fluid 80 exits the flow channels 40 through the discharge ends 42, the extrudable fluid 80 is in contact with at least one of the leading and trailing lips 32, 36, as best shown in FIG. 8. Preferably, the discharge ends 42 of the flow channels 40 are consecutively spaced along the outlet width W in a close proximity from one another such as to provide a substantially continuous profile of the extrudable fluid along the outlet width W. As used herein, the term "substantially continuous profile" refers to a widthwise pattern of the extrudate 80a just prior to being deposited onto the substrate 70, preferably when the extrudate 80a reaches one or both of the leading and trailing edges 33, 37. The profile is said to be "substantially" continuous to indicate that some minor deviations from the absolute continuity may be tolerable as long as these deviations do not adversely affect the intended characteristics of the extrudate 80a. Specifically, the "substantially continuous profile" means the pattern of the extrudate 80a which is either continuous (i. e., uninterrupted) in the widthwise direction - as shown in FIG. 9, or insignificantly interrupted in the widthwise direction - as shown in FIG. 10. In the latter instance (FIG. 10), a resulting widthwise dimension f1+f2+... of "interruption" areas 80b, in which the widthwise continuity of the flow profile is interrupted, is less than 50%, preferably less than 10%, more preferably less than 5%, and most preferably less than 2%, relative to the outlet width W or to a relevant fraction (or portion) thereof. It should be understood that in some applications of the process of the present invention, it may be desirable to intentionally create the interruption areas adjacent to the area or areas having the substantially continuous widthwise profile of the extrudable fluid 80. In this instance, of course, the intentionally created interruption areas should be excluded from consideration when estimating substantial widthwise continuity of the flow profile, and only those fractions, or portions, of the outlet width W should be taken into consideration, which fractions are designed and/or intended to have a substantially continuous profile, as one skilled in the art will readily understand. FIG. 16 shows an example of the extrusion apparatus 10 having the shim 50 designed to create a first widthwise area "A1" and a second widthwise area "A2", each area having a substantially continuous widthwise profile of the extrudate 80a, two areas A1 , A2 being separated by an area "A3" having no extrudate 80a. In the example of FIG. 16, the widthwise continuity of the flow profile is estimated relative to the areas A1 and/or A2, excluding the area A3 from consideration. Various permutations of the embodiment of the extruder 10 shown in FIG. 16 are contemplated by the present invention.

One skilled in the art should understand that, with respect to the "substantial continuity" of the flow profile of the extrudate 80a, the characteristics of the flow profile may vary, depending on the surface texture of the substrate 70, purpose and effect of the extrudate 80a being deposited onto the substrate, desirable characteristics of a coating formed by the extrudate 80a on the substrate 70, and other relevant considerations. For example, the extrudate 80a comprising a softener or topical medicine being deposited onto a paper web may be allowed to form the widthwise flow profile having a relatively low level of continuity (i. e., relatively more frequent and/or wide interruption areas), without losing the effect of introducing the softener or topical medicine onto/into the paper. At the same time, the extrudate 80a comprising silicon or resin intended to form a substantially uninterrupted coating layer throughout the surface of the substrate 70 may require a relatively high continuity (i. e., relatively less frequent and/or relatively narrow interruption areas) of its widthwise flow profile. Analogously, the structured papers having a relatively high surface texture, such, for example, as CHARMIN® toilet tissue and BOUNTY® paper towel, produced by the current assignee, may require a relatively low level of the widthwise continuity of the extrudable fluid 80a comprising functional additives. At the same time, papers having a relatively smooth surface, such, for example, as those intended for the photographic or printing purposes will require an uninterrupted photosensitive coating layer thereon formed by the extrudable material 80a.

To provide a substantially continuous profile of the extrudate 80a, preferably the discharge ends 42 of the flow channels 40 are positioned relative to one another such that after the individual streams of the extrudable fluid 80 exit the flow channels 40 through the second ends 42, at least some of the adjacent individual streams of the extrudable fluid 80 connect, as best shown in FIG. 8. A distance Wc (FIG. 5) separating two adjacent discharge ends 42 along the second end 52 of the shim 50 is very small, preferably less than 0.1 inches. In one preferred embodiment of the shim 50 used for the extrudable fluid 80 having viscosity in the range of from about 10 to about 40 centipoise, the distance Wc in less than 0.065 inches was found to produce good results. It is to be understood that depending on the properties of the extrudable fluid 80, specific design of the leading and trailing sections 11 , 12 and the shim 50, relative velocities of the substrate 70 and the extrudate 80a, and other relevant factors, the distance Wc may be less than 0.05 inches and in some instances the distance Wc may equal 0, i. e., the side walls 63 (FIGs. 5 and 8) connect (not shown) at a certain point. In most cases, however, some minimal distance Wc between the adjacent discharge ends 42 is desirable to provide a sufficient structural support for the mutually opposite leading and trailing lips 32 and 36, such that a required precision clearance therebetween along the outlet width W may be maintained.

In FIG. 8 a point at which the two adjacent individual streams of the extrudable fluid 80 connect is schematically indicated by a symbol "X." Preferably, the individual streams of the extrudable fluid 80 connect prior to or at the point of reaching either one or both of the leading edge 33 and the trailing edge 37. In the preferred embodiment of the extrusion apparatus 10 of the present invention, the discharge ends 42 of the flow channels 40 are recessed relative to at least one of the leading and trailing edges 33, 37, as best shown in FIGs. 4 and 8, in which figures an extent of the recess is indicated by a symbol "Z." The recess Z is a distance between the discharge ends 42 of the flow channels 40 and one or both of the leading and trailing edges 33, 37. The recess Z allows the individual streams of the extrudable fluid 80 to have a space within which the individual streams, while contacting at least one of the leading and trailing lips 32, 36, can laterally widen after having exited the flow channels 40 through the discharge ends 42. The recess Z may be controlled by a second spacer 19a supporting (or spacing) the shim 50 within the housing 13, as shown in FIGs. 3 and 4. Preferably, an extent of lateral widening of the individual streams of the extrudable fluid 80 should be sufficient to create a substantially continuous flow profile along the outlet width W.

If desired, the extruder 10 of the present invention can be structured such as to provide a substantially uniform flow along the outlet width W. As used herein, the term "substantially uniform flow" refers to that widthwise profile of the extrudate 80a just prior to being deposited into the substrate 70, which profile is characterized by a uniform flow rate along the outlet width W, as schematically shown in FIG. 11. It should be understood that minor deviations from absolute uniformity of the flow rate may be tolerable, while not preferred, as long as these deviations do not adversely affect a desirable characteristics of the flow profile, including the widthwise distribution of the extrudate 80a. The discharge ends 42 of the flow channels 40 may be spaced from one another at substantially equal distances along the outlet width W. Equal spacing between the discharge ends 42 of the flow channels 40 may be essential for the purposes of providing a substantially uniform flow of the extrudate 80a. Furthermore, in one highly preferred embodiment of the extrusion apparatus 10, the flow channels 40 are divergently flared at the discharge ends 42, laterally expending in the widthwise direction, as best shown in FIGs. 4, 5, 7, and 8. Without being limited by theory, applicants believe that because of the capillary action existing between the extrudable fluid 80 and the flared surfaces of the flow channels 40, an increase in a widthwise dimension, or width, of the flow channels 40 facilitates widening of the individual streams of the extrudable fluid 80 as the individual streams exit the flow channels 40 through the discharge ends 42 thereof. This feature of the present invention is especially beneficial in the "capillary" process, as opposed to the "free-jet" process, as defined above. In FIG. 8, showing a partial and more detailed plan view of the exemplary shim 50 in conjunction with the trailing lip 36, symbols "La" and "Lb" designate lengths of a first portion 60a and a second potion 60b, respectively, of the slits 60 which form the flow channels 40. In FIG. 8, the first portions 60a of the slits 60 are parallel to one another and have a substantially uniform first width Wa. It should be understood, however, that the shim 50 having the first portions 60a which are not parallel to one another and/or which have differential widths is also contemplated by the present invention. As shown in FIG. 5, a width of the discharge ends 42 of the slits 60, or a second width, is designated as Wb. The first width Wa and the second end Wb are selected based on a variety of factors, including but not limited to: material of the housing 13 and the shim 50, geometry of the shim 50 including spacing between and frequency of the discharge ends 62 of the slits 60, rheology, including viscosity, of the extrudable fluid 80, amount of pressure applied to the extrudable fluid 80, desirable characteristics and parameters of the profile of the extrudate 80a, velocity of the moving substrate 70, and other relevant factors. Technological limitations may also influence a choice of the first width Wa. The slits 60 may be created by a variety of means, including but not limited to: machine cutting; cutting with a laser beam, fluid, and ultra-sound; chemical etching; molding; and other methods known in the art. For the shim 50 used for extruding the extrudable fluid 80 having viscosity from 10 to 300 centipoise, the first width Wa is from about 0.0005 inches to about 0.0500 inches, preferably from about 0.001 inches to about 0.025 inches, and most preferably from about 0.010 inches to about 0.015 inches, depending on specific requirements of the process and rheology of the extrudable fluid 80. The factors mentioned above with respect to the first width Wa and the second width Wb may also be relevant for the purposes of designing the shape of the second portion 62 of the slits 60. Preferably, the second portion 60b gradually and continuously diverges towards the second end 52 of the shim 50, as shown in FIG. 8. The second portion 60b has walls 63 which may have a variety of shapes, including but not limited to curvatures (FIGs. 4, 5, and 8), straight lines (similar to walls 43 shown in FIG. 4), and combinations thereof (not shown). The curved shapes of the walls 63 (or 43) may comprise circular, parabolic, and other shapes.

A ratio Wb Wa is preferably from about 2 to about 100, more preferably from about 5 to about 50, and most preferably from about 10 to about 35. A ratio Wb/Lb is preferably from about 0.1 to about 5, more preferably from about 0.4 to about 1.5, and most preferable from about 0.6 to about 1.1. The shim 50 having the first width Wa of about 0.013 inches and the second width of about 0.320 inches (the ratio Wb/Wa being about 25) and the second length Lb of about 0.380 inches (the ratio Wb/Lb being about 0.8) was found to produce satisfactory results when used in the extrusion apparatus 10 for extruding the extrudable fluid having viscosity in the range of from about 10 to about 40 centipoise.

While denying to be limited by theory, the applicants believe that in a preferred laminar and capillary process, gradual widening of the second portions 40b of the flow channels 40 (or the second portions 60b of the slits 60 of the shim 50) equalizes velocity-distribution profile of the individual streams of the extrudable fluid 80, as the extrudable fluid 80 exits the flow channels 40. FIG. 8 schematically shows what is believed to be illustrative diagrams of a changing velocity-distribution profile, from V1 to V2 to V3, and further to V4 and to V5, as the extrudable fluid 80 advances from the source of the extrudable fluid, i. e., the distribution channel 15, towards the outlet 21 , within the flow channels 40 formed by the slits 60 of the shim 50. As one skilled in the art will recognize, for a laminar flow within the flow channel 40 the velocity distribution is generally parabolic (V1), with a maximal velocity at the center equal to about two times the average velocity, provided the extrudable fluid completely fills the cross-section of the flow channel 40, i. e., forms what is known in the art as "duct flow." Preferably, at least a sufficient part of the first portion 40a immediately preceding the second portion 40b is substantially straight - to facilitate forming a laminar flow within the first portion 40a of the flow channel 40. The substantially straight part immediately preceding the second portion 40b preferably has a length equal to or greater than at least two equivalent diameters of the first portion 40a. The term "equivalent diameter" is used herein to define the cross-sectional area of the first portion 40a of the flow channel 40b having a non-circular shape, in relation to the equal cross-sectional area of the first portion 40a having a circular geometrical shape. An area of any geometrical shape can be described according to the formula: S=1/4(πD²), where "S" is the area of any geometrical shape, π = 3.14159, and "D" is the equivalent diameter. For example, the cross- sectional area of the first portion 40a having a rectangular shape can be expressed as a circle of an equivalent area "s" having a diameter "d." Then, the diameter d can be calculated from the formula: s=1/4(πd²), where s is the known area of the rectangle. In the foregoing example, the diameter d is the equivalent diameter D of this rectangular. Of course, the equivalent diameter of a circle is the circle's real diameter. It should be noted that, while the duct flow is highly preferred, it is believed that the extrusion apparatus 10 and the process of the present invention may produce satisfactory results even in an instance of an "open-channel flow," i. e., when the extrudable fluid 80 does not completely fill the cross-section of the flow channel 40. As the diagrams of FIG. 8 show, once the preferred laminar flow is established within the flow channels 40, the velocity distribution profile (V1) within the first portion 40a of the flow channel 40 does not appreciably change as the individual streams of the extrudable fluid 80 move towards an intermediate portion 44 of the flow channel 40. The "intermediate portion" 44 (or 66 in the context of the shim 60) is used herein primarily for illustration purposes to designate a point (or an area) between the first portion 40a (60a) and the second portion 40b (60b). After the individual streams of the extrudable fluid 80 pass the intermediate portion 44 and enter the second portion 40b having an increasing width, an average velocity decreases within the flow channels 40, and the extrudable fluid's velocity profile (V2, V3, and V4) changes to become more and more "flat" thereby equalizing the flow rate across the width of each of the individual flow channels 40. Preferably, the width of the second portion 40b increases gradually, and the extrudable fluid's velocity profile also changes gradually, as shown in FIG. 8. Without being limited by theory, the applicants believe that within the second portion 40b of the flow channel 40 the individual stream decelerates due to an adverse pressure gradient created by a friction between the extrudable fluid 80 and the surface of the lip 36 - which is caused by an increase in a flow area and internal shear forces, depending on the viscosity of the extrudable fluid 80 and/or surface energy of the lip 36. It is believed that lateral widening of the individual streams of the extrudable fluid 80 within the second portions 40b of the flow channels 40 is at least partially attributed to a capillary action existing between the extrudable fluid 80 and surfaces of the leading and/or trailing lips 32, 36 and the walls 43 (or 63). Therefore, it is believed that lateral widening of the streams of the extrudable fluid 80 can be beneficially controlled by providing the above-mentioned surfaces 32, 36, and 43 having certain predetermined "wetability" characteristics. As used herein, the term "wetability" refers to an ability of the surfaces 32, 36, 43 to cause the extrudable fluid 80 to adhere to the surfaces 32, 36, 43 of the extrusion apparatus 10. The wetability is defined primarily by a combination of a surface tension of the extrudable fluid 80 and a surface energy of the surfaces contacting the extrudable fluid 80. At the same time, the capillary action preferably prevents the extrudable fluid 80 from draining out of the flow channels 40. The extrudable fluid 80 is preferably transferred to the substrate 70 while the extrudable fluid 80 is in association with the lip 36 of the extrusion apparatus 10, i. e., a "capillary" transfer.

It is again pointed out that the preferred embodiment of the process comprises capillary, as opposed to free-jet, or impinging, forces. This may be accomplished by having the shim 50 which is very thin - having the thickness H from about 0.0005 to about 0.0450 inches, and the slits 60 having a very narrow first width W (in the range of approximately 0.0005-0.0500 inches), and a relatively long first length La (in the range of approximately 0.05-10.00 inches and greater). As one skilled in the art will understand, the capillary action is due to surface tension, cohesion of molecules of the extrudable fluid 80, and the adhesion of the molecules of the extrudable fluid 80 to the surfaces 32, 36, 43 defined herein above. Eugene A. Avallone & Theodore Baumeister 111, Marks' Standard Handbook for Mechanical Engineers, Ninth Edition, 1987, page 3-38, which book is incorporated herein by reference for the purpose of describing mechanics of fluids, and especially the capillary action. To maintain the capillary action at different flow rates and viscosity of the extrudable fluid 80, the geometry and spacing/density of the flow channels 40 may be changed as desired.

When the individual streams of the extrudable fluid 80 reach the discharge ends 42 of the flow channels 40, the velocity profile (V4) is significantly "flattened" and equalized relative to the velocity profile (V1) within the first portion 40a of the flow channel 40. After the individual streams of the extrudable fluid 80 exit the flow channels 40 through the discharge ends 42, the individual streams further widen due to a capillary action between the extrudable fluid 80 and the surface of at least the lip 36, until the adjacent streams of the extrudable fluid 80 preferably connect at the point "X" to form a combined (or resulting) velocity profile which - after the extrudable fluid 80 having reached the point "X" -- is believed to be substantially equalized. The area defined between the intermediate portion 44 of the flow channels 40 and one if the leading and trailing edges 33, 37, in which area the extrudable fluid 80 is being laterally redistributed is defined herein as a "redistribution area" 39. It is also believed that lateral widening of the extrudable fluid 80 beneficially causes thinning of a layer of the extrudable fluid 80. This thinning of the layer of the extrudate 80a further facilitates conditions favorable for the extrudable fluid 80 to be deposited onto the substrate at very flow rates. Preferably, the shim 50 is substantially straight and planar. It is to be understood, however, that an embodiment of the extrusion apparatus 10 is contemplated in which the shim 50 or any part thereof has a non-planar configuration, for example, curved (not shown). In the latter instance, the inner surfaces 11a, 12a of the sections 11 , 12 are preferably also correspondingly curved. The thickness H of the shim 50 is defined based on a desirable cross- sectional clearance of the flow channels 40, which in turn is based on a type of the extrudable fluid 80 (including its viscosity), velocity of the moving substrate 70, other desirable characteristics of the process, geometry of the shim 50, and various other factors that may be relevant. For the extrudable fluid 80 having viscosity from 10 to 200 centipoise, the thickness H is from about 0.0005 inches to about 0.0450 inches, preferably from about 0.001 inches to about 0.015 inches, and more preferably from 0.002 inches to 0.010 inches. It should be noted, however, that the preferred ranges of the thickness H and the first width W are especially beneficial if a certain appropriate level of removal of contaminants from the extrudable fluid 80 is maintained such that contamination particles, if any, do not substantially obstruct flow of the extrudable fluid 80 through the flow channels 40.

As used herein, the term "widthwise frequency" or simply "frequency" (or "density") of the discharge ends 62 of the slits 60 of the shim 50 refers to a number of the discharge ends 62 per one inch of the width of the shim 50. One skilled in the art will understand that the frequency of the discharge ends 62 is dictated by the viscosity of the extrudable fluid 80, geometry of the flow channels 40, and other relevant parameters of the process, mentioned above. For the extrudable fluid 80 having viscosity from 10 to 200 centipoise, the widthwise frequency of the discharge ends 62 of the slits 60 is preferably from 1 to 11 , and more preferably from 2 to 5 per inch of the width of the shim 50. It should be noted that in some embodiments the substantially uniform flow of the extrudate 80a is not required, and may even be undesirable. In some embodiments of the process it may be desirable to differentiate the flow rate of the extrudate 80a along the outlet width W. In such instances, the flow rate profile may be controlled by differentiating frequency (i. e., spacing therebetween) of the discharge ends 42 of the flow channels 40 (or the slits 60 of the shim 50), and/or by differentiating the width of the channels 40 (or the slits 60), such as to cause a relatively greater amount of the extrudate 80a to be extruded and thus deposited onto pre-selected areas of the substrate 70, preferably - the substrate's areas differentiated in the cross-machine direction. FIG. 14 shows an exemplary embodiment of the shim 50 in which the slits 60 has differential spacing therebetween. The slits 60c which are disposed close to the center of the shim 50 are spaced at a distance "c" from one another; and the slits 60n which are disposed at the periphery of the shim 50 are spaced at a distance "n" from one another. In FIG. 14, the distance n is greater than the distance c. Thus, the flow channels formed by the slits 60c provide a combined flow rate which is greater than that provided by the flow channels formed by the slits 60n, all other characteristics of the process being equal with respect to the slits 60c and the slits 60n. Such principal embodiment may be beneficially used in making various consumer disposable articles, such as, for example, diapers, sanitary napkins, and other items, in which it may be desirable to provide differential distribution of the functional additives across the article's area, including creating the interruption areas onto which no extrudate 80a is deposited.

An embodiment of the extrusion apparatus 10 in which the flow channels 40 have differential widths is not shown herein but can be easily visualized by one skilled in the art. It should also be appreciated that the second length Lb may differentiate among the slits 60, as shown in FIG. 14, in which the slits 60n have a relatively greater second length Lb1 , while the slits 60c have a relatively shorter second length Lb2. The extrusion apparatus 10 may comprise various combinations and permutations of the differential spacing between the second ends 42 of the flow channels 40, the differential shapes and widths of the flow channels 40 (including both the first portion 40a and the second portion 40b), differential first lengths La, and differential second length Lb, all of which are included in the scope of the present invention.

While the extrusion apparatus 10 having the housing 13 is preferred, an embodiment of the extrusion apparatus 10 is possible, which has no housing 13. One example of such an embodiment is shown in FIG. 7. The extrusion apparatus 10 shown FIG. 7 has a plurality of the flow channels 40 comprising a plurality of tubes, or conduits. Each of the flow channels comprises a first portion 40a having the inlet end 41 , and a second portion 40b having the second end 42. The second portions 40a are preferably divergently flared towards the discharge ends 42. The distribution channel 15 is in fluid communication with the flow channels 40. The discharge ends 42 of the flow channels 40 are in close relationship with, and preferably contact, a lip 36a having an edge 37a. The discharge ends 42 of the flow channels 40 are preferably recessed relative to the edge 37a of the lip 36a. Divergent flaring of the second portions 40b preferably comprises gradual widening of the second portions 40b in a plan which is parallel to the edge 37a, and preferably parallel to the lip 36a. The gradual widening of the second portion 40b may comprise a straight, circular, hyperbolic, or any other suitable configuration, or a combination thereof. The edge 37a defines the outlet 31 for discharging the extrudable fluid 80. The outlet has the outlet width W. The embodiment of FIG. 7 has no housing 13 and is used to illustrate that the housing 13, while highly preferred, is not necessary for the present invention. It also should be understood that the flow channels 40 shown in FIG. 7 need not be identical or even parallel. For example, one skilled in the art will easily recognize that a plurality of the flow channels 40 shown in FIG. 7 may comprise a plurality of flexible tubes, or hoses, having a variety of shapes and cross-sections. Preferably, at least a sufficient part of the first portion 40a immediately preceding the second portion 40b is substantially straight - to allow a laminar flow to form within the first portion 40a of the flow channel 40, as discussed above.

In the preferred embodiment of the process of the present invention, the movement of the extrudable fluid from the inlet portion 20 to the outlet portion 30 of the extrusion apparatus 10 is caused, or at least facilitated, by a pressure, preferably positive, applied to the extrudable fluid 80. Preferably, the pressure is applied to the extrudable fluid 80 disposed in the distribution channel 15, i. e., the extrudable fluid 80 is continuously supplied and maintained under required pressure in the distribution channel 15. An amount of the pressure is dictated by a variety of factors, including but not limited to: type (including viscosity) and a desirable flow rate of the extrudable fluid 80, a geometry of the flow channels 40, a velocity of the substrate 70, and other considerations. For the extrudable fluid 80 having viscosity from 10 to 30 centipoise (such as silicon, for example), the pressure from about 2 pounds per square inch (psi) to about 5 psi was found to produce good results. For the extrudable fluid 80 having viscosity from about 100 to about 300 centipoise, the pressure is preferably from about 50 psi to about 150 psi.

Preferably, each of the flow channels 40 provides a substantially equal pressure drop between the inlet end 41 and the second end 42. One of the purposes of the distribution channel 15 is to equalize the pressure among the flow channels 15. In this respect, it should be noted that the extrusion apparatus 10 of the present invention may have more than one distribution channels 15, which embodiment is not shown but may be easily visualized by one skilled in the art. Preferably, the pressure drop is greater than about one pound per square inch (1 psi). More preferably, the pressure drop is from about 2 psi to 1000 psi, and more preferably, between 3 psi to 300 psi.

If desired, the viscosity of the extrudable fluid 80 may be influenced by heating/cooling of the extrusion apparatus 10, or portions thereof. Alternatively or additionally, the extrudable fluid 80a may be heated and/or cooled. Differential heating or cooling of the pre-determined widthwise portions of the extrusion apparatus 10 may be beneficially used to control the widthwise flow rate of the extrudate 80a. A variety of materials may be used for the shim 50. The examples include but are not limited to: metals (including but not limited to brass and stainless steel and their alloys), plastics, wood, glass, and paper (including paper board). Preferably, the material of the shim 50, as well as the material of the housing 13, should be chosen to be chemically non-reactive to the extrudable fluid 80. Compressible materials, as well as non-compressible materials, may be used for the shim 50 and/or the spacer 55 (FIG. 18). As used herein, the term "compressible shim" refers to the shim 50 that is capable of appreciably changing its thickness H under application of a pressure imparted by the clamping force between the leading and pressing sections 11 , 12. More specifically, the shim 50 is compressible if the shim 50 or any part thereof can reduce its thickness H more than 3%, preferably more than 10%, and more preferably more than 25%, under the pressure of from 0 to 4000 pounds per square inch imparted by the leading and trailing sections 11 , 12. The compressible materials include elastomers, i. e., the materials that can at least partially regain their initial thickness after the compressive force has been removed or decreased.

Such compressible materials as rubber, plastic, paper, foam, and others known in the art, alone or in combination may be used for the compressible shim 50. It is to be understood that the compressible shim 50 may comprise a composite structure, i. e., the structure formed with two or more layers of the material. For example, the shim 50 can be made from a layer of a compressible material interposed between two layers of a non-compressible material. Various permutations of the shim 50 comprising more than one material are included in the scope of the invention.

The compressible shim 50 may beneficially provide an easy way of adjusting the thickness H of the shim or shims 50 and/or the spacer 55, and consequently -- the clearance between the leading and trailing sections 11 , 12. One, by changing the clamping force between the sections 11 , 12, can influence the flow rate of the extrudable fluid through the extrusion apparatus 10. It is noted that as a result of an increased pressing force between the sections 11 , 12, the slits 60 of the shim 50 may change their width ad/or configuration, depending on a specific material and design of the shim 50.

The process and the apparatus 10 of the present invention provide an inexpensive, easy and expeditious way of changing or adjusting parameters of an extrusion process, without necessity of changing the extrusion apparatus. By partially disassembling the housing 13, one can easily clean the extrusion apparatus 10 when necessary, and by substituting one shim 50 for another, one can efficiently and with a minimal effort change parameters of the extrusion process.

Claims

What is claimed is:

1. An extrusion apparatus comprising: an inlet portion and an outlet portion, the inlet portion comprising an inlet for receiving an extrudable fluid and preferably at least one distribution channel, and the outlet portion comprising at least a first lip having a first edge defining an elongate outlet for discharging the extrudable fluid and preferably a second lip having a second edge, the outlet having an outlet width; and a plurality of flow channels, preferably in fluid communication with at least one distribution channel, and extending from the inlet portion to the outlet portion, the flow channels being structured to provide movement of individual streams of the extrudable fluid therebetween, each of the flow channels having a discharge end associated with the first lip, the discharge ends of the flow channels being consecutively spaced along at least a portion of the first lip, the discharge ends of at least some of the flow channels being divergently flared to allow the individual streams of the extrudable fluid to widen in a direction generally parallel to the outlet width while exiting the flow channels, preferably the discharge ends of at least some of the flow channels being sufficiently recessed relative to the first edge of the first lip such that at least some of the individual streams of the extrudable fluid connect after exiting the flow channels, and more preferably the discharge ends of at least some of the flow channels being consecutively spaced in a close proximity from one another such as to provide a substantially continuous profile of the extrudable fluid along at least a portion of the outlet width.

2. An extrusion apparatus for extruding an extrudable fluid onto a substrate, the extrusion apparatus comprising: a housing comprising a leading section and a trailing section, the leading and trailing sections being separably joined together and spaced apart, the housing further having an inlet portion and an outlet portion, the inlet portion having an inlet for receiving the extrudable fluid and a distribution channel in fluid communication with the inlet, and the outlet portion having a leading lip and a trailing lip opposite to the leading lip, the leading lip having a leading edge, and the trailing lip having a trailing edge, the leading and trailing edges defining an outlet therebetween for discharging the extrudable fluid, the outlet having an outlet width; and at least one removable shim having a plurality of slits therethrough, each slit having an open discharge end, the shim being interposed between the leading and trailing sections of the housing in a close-fitting relationship therewith such that the plurality of the slits form a plurality of the flow channels extending from the distribution channel to the outlet portion thereby providing fluid communication therebetween, the discharge ends of the slits being disposed between the leading and trailing lips of the outlet portion of the housing and preferably recessed relative to at least one of the leading edge and the trailing edge, the slits of the shim being divergently flared at the discharge ends to facilitate widening of the extrudable fluid.

3. A removable shim for use in an extrusion apparatus comprising a housing having an inlet for receiving an extrudable fluid, at least a first lip having the first edge defining an outlet for discharging the extrudable fluid, and a cavity within the housing intermediate the inlet and the outlet, the cavity being shaped to receive the shim for a close-fitting relationship with the housing, the shim having a first end, a second end opposite to the first end, a shim width, and a shim thickness, the shim further having a plurality of slits therethrough, each of the slits having a first portion comprising an inlet end and a second portion comprising a discharge end terminating at the second end of the shim, the second portions of the slits being divergently flared, the slits being structured such that when the shim is disposed within the cavity of the housing in a close-fitting relationship therewith, the plurality of the slits of the shim form a plurality of flow channels providing fluid communication between the inlet and the outlet and structured to direct individual streams of the extrudable fluid to the outlet, the discharge ends of the slits being consecutively spaced at predetermined distances therebetween along the shim width.

4. The extrusion apparatus according to Claims 1, 2, and 3, wherein at least some of the discharge ends of the flow channels are spaced from one another at substantially equal distances.

5. The extrusion apparatus according to Claims 1 , 2, 3, and 4, further comprising a housing having a cavity therein intermediate the inlet and the outlet, and at least one shim shaped for insertion into the cavity of the housing for a close-fitting relationship therewith, the shim having a plurality of slits therethrough such that when the shim is inserted into the cavity the plurality of the slits form the plurality of the flow channels, the housing preferably comprising a leading section and a trailing section separable from and fixedly joined to the leading section.

6. The extrusion apparatus according to Claims 1, 2, 3, 4, and 5, wherein at least one of the first lip and the second lip is movable relative to the other.

7. The extrusion apparatus according to Claims 1, 2, 3, 4, 5, and 6, wherein a distance between the first lip and the second lip is adjustable.

8. The extrusion apparatus according to Claims 1, 2, 3, 4, 5, 6, and 7, wherein the discharge ends of the slits are spaced in close proximity from one another and are sufficiently recessed relative to the first edge of the first lip such that at least two adjacent individual streams of the extrudable fluid connect after exiting the flow channels, such that adjacent individual streams of the extrudable fluid after exiting the flow channels form a substantially continuous profile of the extrudable fluid along at least a portion of the shim width.

9. The extrusion apparatus according to Claims 1 , 2, 3, 4, 5, 6, 7, and 8, wherein at least one removable shim comprises a plurality of removable shims interposed between the leading and trailing sections in a side-by- side arrangement.

10. The extrusion apparatus according to Claims 1 , 2, 3, 4, 5, 6, 7, 8, and 9 wherein at least one of the removable shims has a first widthwise frequency of the discharge ends, and at least one another of the removable shims has a second widthwise frequency of the discharge ends, the first frequency being greater than the second frequency.

11. The extrusion apparatus according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10, further comprising at least one spacer interposed between at least two adjacent shims or between the shim and one of the leading and trailing sections.

12. The shim according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 , wherein the thickness of the shim is from about 0.0005 inches to about 0.045 inches, preferably from about 0.001 inches to about 0.015 inches, and more preferably from about 0.002 inches to about to about 0.010 inches.

13. The shim according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, wherein the first portions of the slits are substantially parallel to one another, and preferably have a substantially uniform first width Wa, which is preferably from about 0.0005 inches to about 0.0500 inches, more preferably from about 0.001 inches to about 0.025 inches, and most preferably from about 0.010 inches to about 0.015 inches.

14. The shim according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, and 13, wherein the discharge ends of the slits have a second width Wb, a ratio Wb/Wa comprising preferably from about 2 to about 100, more preferably from about 5 to about 50, and most preferably from about 10 to about 35.

15. The shim according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and

14, wherein at least some of the discharge ends of the slits are spaced from one another at substantially equal distances, a distance separating two adjacent discharge ends along the second end of the shim being less than 0.1 inches.

16. The shim according to Claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, and 15, wherein a widthwise frequency of at least some of the discharge ends of the slits is from 1 to 11 per inch of the width of the shim, and preferably from 2 to 5 per inch of the width of the shim.

17. The shim according to Claims 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

15, and 16, wherein the shim is made from a material selected from the group consisting of metal, plastic, glass, wood, paper, and any combination thereof.

18. The shim according to Claims 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,

15, 16, and 17, wherein the shim is made from a compressible material.