WO2001012414A1

WO2001012414A1 - Die head having movable lip

Info

Publication number: WO2001012414A1
Application number: PCT/US2000/022690
Authority: WO
Inventors: Kenneth Douglas Vinson
Original assignee: The Procter & Gamble Company
Priority date: 1999-08-19
Filing date: 2000-08-17
Publication date: 2001-02-22
Also published as: AU6915200A

Abstract

A die head (10) for extruding a chemical additive comprises an interior channel (25) for receiving the chemical additive and a pair of mutually opposite discharge lips (21, 22) forming at least one discharge mouth (20) therebetween, which discharge mouth (20) is in fluid communication with the interior channel (25). At least one of the discharge lips (21, 22) is movable relative to the other in a direction substantially parallel to the movement of the chemical additive through the discharge mouth (20). By reciprocally moving the discharge lip (21), one can remove contamination build-up in the discharge mouth (20).

Description

DIE HEAD HAVING MOVABLE LIP

FIELD OF THE INVENTION

The present invention generally relates to extrusion processes and apparatuses therefor. More specifically, the present invention is concerned with processes and apparatuses for extruding chemical additives onto substrates, such as those used in making disposable items, such as paper toweling, napkins, toilet tissue, facial tissue, etc.

BACKGROUND OF THE INVENTION

Die heads for depositing a chemical additive onto a substrate 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 Die heads, Inc. Several other types of extrusion apparatuses are disclosed, for example, in the following U. S. patents: 5,607,726 issued on March 1997 to Flattery et al.; 5,522,931 issued to Iwashita et al. on June 4, 1996; 5,740,963 issued to Riney on April 21 , 1998; 5,511 ,962 issued to Lippert.

One of the concerns relating to die heads of prior art has been plugging of a die's discharge mouth, i. e., the outlet through which the extrudate, such as, for example, a chemical additive, exits the die head. Die heads are frequently used in dusty environments. In papermaking, for example, some paper webs tend to be particularly prone to release surface fibers. A dust comprising primarily papermaking fibers may cause contamination of a chemical functional additive, such as, for example, a topical tissue softener, which is routinely extruded onto the paper web. Other common contaminants may include degradation products of the chemical additive itself, which particularly may occur in stagnant areas around the walls of the die head. Build up of these degradation products can form over a period of time, harden and eventually separate from the walls of the die, thereby becoming a contaminant. More generally, particulate soil, sand, dirt, and grit tend to become airborne in the vicinity of the extrusion operation and settle into the supply of the chemical additive feeding the die head.

If the chemical additive, such as, for example, softener, is deposited onto a substrate by extrusion, the contaminants, which have found their way into the softener being extruded, may with time build up therein and eventually plug the discharge outlet of the die head. A process of cleaning of the die heads is usually costly, because it involves stoppage of a production line and/or a substantial effort. The cleaning may be further complicated in die heads designed to extrude very thin layers of extrudates and therefore comprising the discharge mouths having very small (in the range of 0.0002-0.00450 inches) dimensions requiring maintenance of high-precision tolerances.

Accordingly, the present invention advantageously provides a novel die head structured to allow one to quickly and efficiently remove the contamination build-ups from the discharge mouth. The present invention also provides an advantage of an extrusion process which substantially eliminates plugging of the discharge mouth of the extrusion apparatus.

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

The present invention provides a die head and a process for applying an extrudable material onto a surface of a web substrate or other working surface. A preferred extrudable material comprises a chemical additive commonly used in making consumer-disposable articles, such as paper toweling, napkins, toilet tissue, facial tissue, sanitary napkins, diapers, etc. The chemical additive may comprise a functional composition (i. e., the composition influencing strength, softness, or absorbency), or aesthetic composition (i. e., the composition conveying aesthetic impression, such as, for example, color, fragrance, and the like), or a combination thereof. The chemical additive is preferably selected from the group consisting of softeners, emulsions, emollients, lotions, topical medicines, soaps, antimicrobial and anti-bacterial agents, moisturizers, coatings, inks and dies, binders, and fragrances. The preferred chemical additive of the present invention comprises a chemical softening composition. More preferably, the chemical softening composition comprises quaternary compounds

having the formula: (Rl )4__m - N - [R2lm *^~ _> wherein m is from 1 to 3; each Rι is a C-\ -CQ alkyl group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; each R2 is a C14-C22 a' group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; and X^" is any softener-compatible anion.

A preferred web substrate comprises a fibrous web, such as, for example, a paper web. It is to be understood, however, that the die head and the process of the present invention may be beneficially used with other types of the extrudable fluids, such as, for example, polymer melts or adhesives, and other types of the substrates, such as, for example, non- wovens. The die head and the process of the present invention may also be used to form extrudates free of an underlying substrate, as, for example, a polymer film.

The die head of the present invention has an interior channel for receiving the chemical additive, and comprises a pair of mutually opposite discharge lips forming therebetween at least one discharge mouth in fluid communication with the interior channel. At least one of the discharge lips is movable relative to the other in a first direction substantially parallel to the movement of the extrudable material through the discharge mouth. The discharge lip is movable by a lip actuator in operable communication therewith. In one embodiment, the lip actuator comprises a screw. In another embodiment, the lip actuator comprises a piston driven by hydraulics or pneumatics. The lip actuator may also comprise a variety of devices known in the art. For example, it can be driven by a spring or by thermally expanding or contracting elements using heating or cooling devices. Other examples of the lip actuator include those comprising a cam mechanism and devices using application of an energy field, such as, for example, a magnetic field.

The die head may have the discharge mouth which is flared in at least one cross-section. Preferably, the discharge mouth is flared in at least two mutually perpendicular cross-sections. The preferred discharge mouth has a substantially circular shape.

The die head may have a plurality of discharge mouths consecutively spaced one from the other, or alternatively - one elongated discharge mouth. The die head may further have one or plurality of lip persuaders in operable communication with at least one discharge lip, for moving the lip in a second direction substantially different from the first direction. One preferred lip persuader comprises a screw. Another preferred lip persuader comprises a heating device inducing a change in position by selectively thermally expanding the elements of the persuader. The screw lip persuader and the heating means may be combined to provide coarse and fine adjustments.

In one preferred embodiment, the die head further comprises a knife- edge tip formed by at least one of the discharge lips. More preferably, the knife-edge tip is formed by two converging outer surfaces of the discharge lips.

The process of the present invention comprises the following steps:

(a) providing an extrudable material;

(b) providing a die head of the present invention described herein above;

(c) extruding the material through the discharge mouth of the die head; and

(d) moving, from time to time, at least one of the discharge lips, thereby removing contamination build-ups in the discharge mouth.

The process further preferably comprises the step of providing a working surface and continuously moving the working surface in front of the discharge mouth of the die head, whereby the step (c) further comprises depositing the extrudable material onto the working surface. The working surface is preferably the surface of the web substrate or the surface of the roll which will later in the process contact the surface of the web and thereby transfer the extrudable material thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of a die head of the present invention, having a moving lip. FIG. 2 is a schematic cross-sectional side view of another embodiment of the die head of the present invention, having a knife-edge discharge tip. FIG. 2A is a partial and schematic cross-sectional side view of an embodiment of a lip actuator comprising a cam mechanism. FIG. 2B is a partial and schematic cross-sectional side view of an embodiment of the lip actuator comprising an elctromagnetic device. FIG. 3 is a schematic representation of a process using the die head of the present invention. FIG. 4 is a schematic frontal view of the die head shown in FIG. 1. FIG. 5 is a schematic frontal view an another embodiment of the die head having a plurality of discharge mouths. FIG. 6 is a schematic partial view similar to that shown in FIG. 5, showing another embodiment of the discharge mouth having a plurality of discharge mouths.

DETAILED DESCRIPTION OF THE INVENTION

A die head 10 of the present invention comprises a body having an interior channel 25, best shown in FIGs. 1 and 2, for receiving an extrudable material. As used herein, the term "extrudable material" includes any substance, preferably liquid, which can be forced under pressure through the extrusion die of the present invention, resulting in an extrudate. Preferred extrudable materials comprise a "chemical additive", a term which, as used herein, refers to substances that may be added to the paper web to improve the web's functional and/or aesthetic characteristics, such as, for example, softness, strength, absorbency (functional characteristics) or inks and dyes (aesthetic characteristics). The chemical additives include, but are not limited to fluid comprising: water; alcohol; softeners (polysiloxanes, cationic surface active agents including quaternary ammonium compounds, non-cationic surface active agents, oils, waxes, and others), emulsions, emollients, lotions, topical medicines, soaps, various anti-microbial and anti-bacterial agents, and moisturizers (for example, glycols); 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.

One of the preferred chemical additives that can be beneficially used with the apparatus of the present invention comprises a chemical softening composition. More preferably, the chemical softening composition comprises quaternary compounds having the formula:

(Rl)₄-m - N⁺ - [R2]_m X^~ wherein: m is 1 to 3; each R-j is a Ci-Cβ alkyl group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; each R2 is a C14-C22 alkyl group, hydroxyalkyl group, hydrocarbyl or substituted hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; and

X^" is any softener-compatible anion

Preferably, each R1 is methyl and X' is chloride or methyl sulfate. Preferably, each R2 is C16-C-I8 ^alky' ^{or a|}kenyl, most preferably each R2 is straight-chain C18 alkyl or alkenyl. Optionally, the R2 substituent can be derived from vegetable oil sources. Several types of the vegetable oils (e.g., olive, canola, safflower, sunflower, etc.) can used as sources of fatty acids to synthesize the quaternary ammonium compound. Branched chain actives (e.g., made from isostearic acid) are also preferred.

Such structures include the well-known dialkyldimethylammonium salts (e.g. ditallowdimethylammonium chloride, ditallowdimethylammonium methyl sulfate, di(hydrogenated tallow)dimethyl ammonium chloride, etc.), in which Ri are methyl groups, R2 are tallow groups of varying levels of saturation, and X" is chloride or methyl sulfate. Commonly assigned patent applications Serial Number 08/947,422, filed 10/8/97 in the name of Ficke, et al., and Serial Number 60/103,371 (provisional), filed 10/15/98 in the name of Vinson, et al. are incorporated herein by reference for the purpose of disclosing preferred softening chemical compositions.

Depending on a particular process, chemical additives may be added to papermaking fibers during formation of the paper web, or/and by applying the additive to one or both surfaces of the web after the web has generally been formed. If the chemical additive is to applied to at least one surface of the web, it may be desirable to apply the additive, such as a softener, in such a way that the additive remains on the surface of the web and does not significantly penetrate the web's thickness. The present invention is primarily concerned with, but not limited to, applying the chemical additive such as a softener to the surface of the web substrate. Exemplary art includes U. S. Patent 5,215,626, issued to Ampulski, et. al. on June 1 , 1993; U. S. Patent 5,246,545, issued to Ampulski, et. al. on September 21 , 1993; U. S. Patent 5,525,345, issued to Warner, et. al. on June 11 , 1996, and U.S. Patent application Serial No. 09/053,319 filed in the name of Vinson, et al. on April 1 , 1998, all incorporated herein by reference. The die head 10 further comprises a pair of mutually opposite discharge lips: a first lip 21 and a second lip 22. The first lip 21 has a first edge 21a, and the second lip 22 has a second edge 22a. The discharge lips 21 , 22 are elongated elements extending in a widthwise direction W of the die 10, FIGs. 4-5. The discharge lips 21 , 22 form at least one discharge mouth 20 therebetween, FIGs. 1, 2, 4, 5, and 6. The discharge mouth 20 is in fluid communication with the interior channel 25. In an embodiment shown in FIG. 4, the discharge lips 21, 22 form one elongated discharge mouth 20, extending in the widthwise direction W. In embodiments shown in FIGs. 5 and 6, the discharge lips 21, 22 having cavities, or "grooves" therein form a plurality of discharge mouths 20 consecutively spaced one from another in the widthwise direction W.

According to the present invention, at least one of the discharge lips 21, 22 is movable relative to the other of the discharge lips 21, 22. Preferably, at least one of the discharge lips 21, 22 is slidably movable in the direction substantially parallel to the direction of the chemical additive's flow through the discharge mouth 20. FIGs. 1 and 2 show that the first lip 21 is in operable communication with, and preferably connected to, lip actuator 30. As used herein, the term "lip actuator" refers to a device structured and designed to cause at least one of the lips 21, 22 to move in a direction substantially parallel to the direction of the chemical additive's movement through the discharge mouth 20. This direction is termed herein as "first direction" and designated by a symbol "B" in FIGs. 1 and 2. In the embodiments of FIGs. 1, 2, 2A, and 2B, the lip actuator 30 preferably comprises a shaft 39.

The lip actuator 30 may comprise a variety of devices. In FIG. 1, for example, the lip actuator 30 comprises a screw rotatably fixed to the body of the die head and to the first lip 21 such that as the screw rotates, it causes the first lip 21 to move in the first direction B. In the embodiment shown in FIG. 2, the lip actuator 30 comprises a piston. During operation, the piston is actuated by means of a pressurized fluid, such as hydraulics or pneumatics to induce a compressive force causing first lip 21 to move in a first direction B.

Other embodiments of the lip actuator 30 may include a device structured to move the lips 21 and 22 in relation to one another by energizing and releasing a spring 33 (FIGs. 2, 2A, and 2B). In FIG. 2, the shaft 39 is movable by a fluid pressure developed by a medium contained in a chamber 31. Such a medium may comprise air or any suitable liquid. The spring 33 biases the shaft 39 against a wall of the chamber 31 when the fluid pressure is released. FIG. 2A shows the lip actuator 30 comprising the shaft 39 in operative communication with a rotatable cam 32. In FIG. 2B, the lip actuator 30 comprises an electromagnetic, or magnet, device 34. As the magnet device 34 is energized, it causes the shaft 39 to move to or from (depending on the embodiment) the device 34. Other embodiments of the lip actuator 30 may utilizes thermal expansion using heating or cooling devices, or micro-wave radiation, to induce tensile and compressive forces in lip actuator 30.

It is believed that shearing forces created when lips 21 and 22 are moved relative to one another are effective at dislodging contaminants by increasing the force vector applied to the contaminant particle directed in direction B, in addition to the force created by the head pressure of the extrudable fluid in the discharge mouth 20. This additional force is sufficient to induce the contaminant to overcome frictional or other forces binding the contaminant to one or both of the die lips 21 and 22.

FIGs. 1 and 2 show an embodiment of the die 10 in which both the first and second lips 21 , 22 are also flexibly movable relative to each other in the direction substantially perpendicular to the first direction B. The lips 21 , 22 in FIGs. 1 and 2 are flexibly adjustable such that the distance D between the leading edge 21a and the trailing edge 22a can be effectively controlled by a lip persuader 40 comprising at least one screw 41 , preferably having a fine-pitch thread, engaging a nut fixedly secured to the body of the die 10. A face end of the screw 41 is abutting a shoulder formed at an opposite side of the lip 21 or/and 22. When the screws 41 are rotated, their face ends extend forward and engage (and push) the respective lips 21 , 22 — and consequently the edges 21a, 22a - towards each other, thereby adjusting the distance D therebetween. Preferably, the lip persuader 40 comprises a plurality of the screws 41 and the corresponding nuts, equally distributed along the outlet width W - to provide a necessary precision of controlling the distance D along the outlet width W, FIG. 4. The screw 41 of the lip persuader 40 may be complemented by a heating device 45 (FIG. 1), for a more accurate adjustment of the distance D. In the latter instance, a coarse adjustment of the distance D may be accomplished by rotating the screw 41 within the nut, and then a fine adjustment of the distance D may be made by heating the screw 41 which preferably causes a minimal and finely-tuned longitudinal expansion of the screw 41. It is to be understood that depending on specific embodiments of the lip persuader 40 and the heating device 45, the heating device 45 may be utilized for a coarse adjustment, while the screw 41 - for a fine adjustment. It should also be understood that while FIGs. 1 and 2 show, for the illustration purposes, that the lip persuader 40 engaging both lips 21 and 22, only one of the lips 21 or 22 may be made to be flexibly-adjustable.

In FIG. 5, each of the plurality of the discharge mouths, formed by the first and second lips 21 , 22, has a discharge orifice in the shape of a circle. In FIGs. 5 and 6, the discharge mouths 20 are formed by semicircular cavities, or "grooves," in at least one of the discharge lips 21, 22. Mutually opposite portions of the lips 21, 22, which portions are located intermediate the discharge mouths 20, contact, or abut, each other such as to form a seal therebetween. Preferably, a knife-edge tip 29 is formed in the areas of abutting portions of the lips 21, 22. One (upper) half of the discharge orifice is formed by a portion of the first lip 21 , and the other (lower) portion of the discharge orifice is formed by the portion of the second lip 22. It is to be understood that while the circular/oval shape of the discharge orifice(s) is preferred, other shapes, for example, semicircular (FIG. 6), oval (not shown) or rectangular (not shown), are also contemplated in the present invention.

The reference is made herein to the "machine direction" designated in FIG. 3 as a directional arrow "MD." As used herein, the term "machine direction" indicates a direction which is parallel to the flow of the substrate (or the working surface) 50 through the equipment. The term "cross- machine direction" (or "CD," not shown) indicates a direction which is perpendicular to the machine direction and lies in the general plane of the substrate or working surface 50. In some embodiments of the process according to the present invention, the cross-machine direction may coincide with the widthwise direction W of the die 10, FIGs. 4-6. Preferably, in the process of the present invention, the working surface 50 is continuously moving in the machine direction in front of the discharge mouth 20 of the die head 10, in a close proximity thereto. Depending on a specific process, the working surface 50 may comprise the surface of the web substrate, or a sur ace of a rotating roll which later comes into contact with the surface of the substrate thereby transferring the chemical additive thereto. The die head may also be used for making cast films or blown films, in which instance, the working surface may comprise a chilled roller, water bath, etc., or be absent altogether.

In some embodiments, it may be beneficial to provide for the discharge mouth 20 with a passage cross-section having a variable open area which increases in the direction towards the discharge orifice, as disclosed in commonly-assigned patent application entitled "Extrusion Die," Serial No. 09/258,497, filed on February 26, 1999 in the name of Kenneth D. Vinson, which application is incorporated herein by reference. In such embodiments, an exit open area Ax of the discharge mouth 20 is greater than an entry open area Ae thereof, FIGs. 1 and 2. This ensures that at least some of the relatively large contaminants contained in the chemical additive disposed in the interior channel 25 will be precluded from entering the discharge mouth 20. At the same time, at least some of relatively small contaminants contained in the chemical additive will pass from the interior channel 25 through the discharge mouth 20 without being obstructed therein. In other words, if a particular contaminant is small enough to enter the discharge mouth 20 through the entry open area thereof, it is will certainly pass through the exit open area which is greater than the entry open area. Thus, plugging of the discharge mouth 20 may be substantially avoided. Preferably, a ratio Ax/Ae is between 1 and 10, more preferably the ratio Ae/Ax is between about 1.2 and 5, and most preferably the ratio Ae/Ax in between 1.5 and 2. As used herein and schematically shown in FIG. 2, the term "entry open area" Ae is an area through which the chemical additive enters the discharge mouth 20; and the term "exit open area" Ax is an area through which the chemical additive exits the discharge mouth 20 - and hence the die head 10. Stated differently, the entry open area Ae and the exit open area Ax refer to areas through which the chemical additive consecutively passes when entering and exiting, respectively, the discharge mouth 20. The open areas Ae and Ax are typically measured in square units in a plan defined by a perimeter of a given open area - either a plan defined by the perimeter of the entry orifice, or a plan defined by the perimeter of the exit orifice, respectively. If the discharge mouth 20 is desired, which has a passage cross-section having a variable open area, then preferably, the discharge mouth 20 is divergently flared in at least one cross-section (not shown). More preferably, the discharge mouth 21 flared in at least two mutually perpendicular cross- sections (not shown).

In FIGs. 2, 5, and 6, the die head 10 has a knife-edge tip 29, formed between two outer surfaces of the lips 21, 22. The outer surfaces of the lips 21, 22 form an angle α therebetween (FIG. 2). The tip extends between individual discharged mouths 20, which, if viewed in the frontal view of FIG. 5, have a circular shape. As one skilled in the art will appreciate, the circular shape of the discharge mouth 21 may appear as a semi-elliptical shape in each of the plans of the outer surfaces which form the angle α. The knife-edge tip 29 is characterized by a relatively sharp edge formed by two outer surfaces. During the extrusion process, the edge tip 29 preferably (but not necessarily) contacts a surface of the working surface 50, such as, for example, a surface of the web substrate. The preferred knife-edge tip 29 is especially suited for applications wherein it can beneficially provide attenuation of the chemical additive by causing the web substrate to pass in the direction substantially parallel to and in contact with the outer surface of either lip 21, 22, or both.

Claims

What is claimed is:

1. A die head for extruding an extrudable material, the die head having an interior channel for receiving the extrudable material, the die head comprising a pair of mutually opposite discharge lips forming therebetween at least one discharge mouth in fluid communication with the interior channel, wherein at least one of the discharge lips is movable relative to the other in a first direction substantially parallel to the movement of the extrudable material through the discharge mouth.

2. The die head according to Claim 1, further comprising a lip actuator in operable communication with the movable discharge lip for controlling the movement thereof, wherein the lip actuator preferably comprises a screw, a piston movable by fluid pressure, a shaft in operable communication with a cam, a magnet device, or any combination thereof.

3. The die head according to Claims 1 and 2, wherein the discharge mouth is flared in at least one cross-section, and preferably in at least two mutually perpendicular cross-sections.

4. The die head according to Claims 1, 2, and 3, wherein the die head has a plurality of discharge mouths consecutively spaced one from the other.

5. The die head according to Claims 1, 2, 3, and 4, wherein at least one discharge lip further has at least one lip persuader in operable communication therewith for moving said at least one lip in a second direction substantially different from the first direction.

6. The die head according to Claims 1, 2, 3, 4, and 5, further comprising a knife-edge tip formed by at least one of the discharge lips.

7. The die head according to Claims 1, 2, 3, 4, 5, and 6, wherein the at least one discharge mouth is formed by a cavity in at least one of the discharge lips, wherein mutually opposite portions of the discharge lips sealably abut each other.

8. A process for extruding a chemical additive used in making a disposable paper product, the process comprising steps of:

(a) providing a chemical additive, preferably selected from the group consisting of softeners, emulsions, emollients, lotions, topical medicines, soaps, anti-microbial and anti-bacterial agents, moisturizers, coatings, inks and dies, and binders;

(b) providing a die head having an interior channel for receiving the chemical additive, the die head comprising a pair of mutually opposite discharge lips forming therebetween at least one discharge mouth in fluid communication with the interior channel, wherein at least one of the discharge lips is movable relative to the other in a first direction substantially parallel to the movement of the chemical additive through the discharge mouth;

(c) extruding the chemical additive through the discharge mouth of the die head; and (d) moving, from time to time, at least one of the discharge lips, thereby removing contamination build-ups in the discharge mouth.

9. The process according to Claim 8, further comprising a step of providing a working surface and continuously moving the working surface in front of the discharge mouth of the die head, whereby the step (c) further comprises depositing the extruded chemical additive onto the working surface.

10. A process for applying a softening composition to a surface of the substrate, the process comprising steps of:

(a) providing a softening composition selected from the group comprising polysiloxane, cationic and non-cationic surface active agents, and mixtures thereof;

(b) providing a die head comprising a pair of mutually opposite discharge lips forming therebetween at least one discharge mouth, wherein at least one of the discharge lips is movable relative to the other in a first direction substantially parallel to the movement of the softening composition through the discharge mouth;

(c) providing the substrate and continuously moving the substrate in front of the discharge mouth of the die head;

(d) supplying the softening composition into the die head and extruding the softening composition through the discharge mouth of the die head onto the substrate; and (d) moving, from time to time, at least one of the discharge lips of the die head, thereby removing contamination build-ups from the discharge mouth of the die head.