Die with insert and gas purging method for die

A die assembly includes a die housing having a multiplicity of inner wall sections defining a die cavity, an inlet passageway passing through the die housing in fluid communication with the die cavity, and an outlet passageway passing through the die housing in fluid communication with the die cavity at a position distal from the inlet passageway. The die assembly also includes an insert removably received in the die cavity. The insert includes a body portion having a multiplicity of outer wall sections, and at least one flow channel is formed between at least one inner wall section of the die housing and each opposite outer wall section of the body portion of the insert; fluid communicates between the external supply and each of the flow channels and the outlet passageway. Also provided is a die insert and a method of purging gas from a die having an insert.

TECHNICAL FIELD

This disclosure relates to a die assembly for extrusion of fluids, and more particularly, to die inserts and methods useful in liquid coating processes using extrusion dies.

BACKGROUND

Fluid extrusion dies are used in manufacturing processes to make a variety of goods. Some dies, for example, are used to form thin films, bars or other elongated shapes of plastic material. Other dies are used to apply a coating of fluent material to a moving web. A number of different coating dies have been constructed to apply a liquid or semi-liquid material to a moving web. In general, such dies receive the liquid or semi-liquid material under pressure from a pump or other device, and distribute the material to regions across the width of the web as the web is advanced in directions along its longitudinal axis.

Many conventional dies have an inlet passageway, an outlet passageway and an inner cavity that extends between the inlet passageway and the outlet passageway. The outlet passageway is relatively wide and often approximates the width of the web in instances where the die has a slot-type outlet for discharging a ribbon of fluid onto the web. The inner cavity is also relatively wide, and serves as a manifold to distribute incoming fluid from the inlet passageway to various regions of the outlet passageway.

Some coating dies, known as slot dies, include an outlet passageway in the form of a transverse slot that discharges the fluid material in a sheet-like bead on a continuous substrate or web. A typical slot coating die has an internal cavity that is used to distribute liquid across the width of a moving web such that it can be uniformly coated with the liquid. The profile of the cavity is chosen to provide the necessary cross-web uniformity for a range of liquids and desired feed rates used in production of coated articles. Similarly, the width of the cavity is chosen so that the die is able to coat the widest webs that can be threaded through the coater head.

For some coating applications it is desirable to use the central portion of the slot to distribute liquid as a strip across a narrower width of a wider substrate web or alternatively, across the entire width of a web that is appreciably narrower than the nominal width of the die. In such cases, the effective width of the slot can be reduced with additional deckles or a cut shim positioned across the slot. Partial or full die inserts can also be used to reduce the effective slot width.

SUMMARY OF THE DISCLOSURE

In general, embodiments of the present disclosure relate to a die assembly including a die insert for use in forming a sheet of fluent material. Embodiments of the present disclosure also relate to a method of purging gas from a die assembly having a die insert, for example, during start-up of an extrusion die in a liquid coating process.

In one aspect, embodiments of the present disclosure provide a die assembly comprising a die housing having one or more inner wall sections defining a die cavity, an inlet passageway passing through the die housing in fluid communication with the die cavity, and an outlet passageway passing through the die housing in fluid communication with the die cavity at a position distal from the inlet passageway. An insert is removably received in the die cavity, the insert comprising a body portion having a plurality of outer wall sections, and at least one flow channel is formed between at least one inner wall section of the die housing and each opposite outer wall section of the body portion of the insert. The die assembly includes a means for providing fluid communication between an external supply of fluent material and each of the at least one flow channel and the outlet passageway. In exemplary embodiments, the inlet passageway is adapted to selectively connect to an external supply of fluent material.

In some exemplary embodiments, the means for providing fluid communication may include a first conduit passing through at least part of the body portion of the insert in fluid communication between the inlet passageway and the outlet passageway, and a second conduit passing through the die housing in fluid communication with each flow channel and the outlet passageway. The first and second conduits may each be adapted to selectively connect to the external supply of fluent material.

In another aspect, embodiments of the present disclosure provide a die assembly comprising an insert removably received within a die housing having at least one inner wall section defining a die cavity. An inlet passageway passes through the die housing in fluid communication with the die cavity, and an outlet passageway passes through the die housing in fluid communication with the die cavity at a position distal from the inlet passageway. In some embodiments, the inlet passageway is adapted to selectively connect to an external supply of fluent material.

In certain exemplary embodiments, the insert comprises a body portion having a plurality of outer wall sections, and at least one flow channel is formed between at least one inner wall section of the die housing and each opposite outer wall section of the body portion of the insert. A first conduit passes through at least part of the body portion of the insert, and the first conduit is in fluid communication between the inlet passageway and the outlet passageway. A second conduit passes through at least the die housing, and the second conduit is in fluid communication with each flow channel and the outlet passageway. In some embodiments, the first and second conduits are each adapted to selectively connect to the external supply of fluent material.

In some exemplary embodiments, each of the inlet passageway, the first conduit and the second conduit has a substantially cylindrical cross-section, and the second conduit extends through the inlet passageway of the die housing and at least a portion of the insert concentric with and coaxially around the first conduit. In other exemplary embodiments, the die assembly further comprises a vent passageway having a substantially cylindrical cross-section, and at least a portion of the vent passageway passes through the inlet passageway of the die housing and at least portion of the insert concentric with and coaxially around the first conduit. In certain exemplary embodiments, the second conduit is in fluid communication with the vent passageway and the at least one flow channel.

In another aspect, embodiments of the present disclosure provide an insert for use within a die assembly for forming a sheet of fluent material. The die assembly includes a die housing having a plurality of inner wall sections defining a die cavity, an inlet passageway passing through the die housing in fluid communication with the die cavity, and an outlet passageway passing through the die housing in fluid communication with the die cavity at a position distal from the inlet passageway. In some embodiments, the inlet passageway is adapted to selectively connect to an external supply of fluent material.

In certain exemplary embodiments, the insert comprises a body portion having a plurality of outer wall sections, and the body portion is adapted to be removably positioned within the die cavity. At least one flow channel is formed between at least one outer wall section of the body portion of the insert and each opposite inner wall section of the die housing upon positioning the body portion within the die cavity. The insert further comprises a first conduit passing through at least part of the body portion of the insert, and the first conduit is in fluid communication between the inlet passageway and the outlet passageway. The insert also comprises a second conduit passing through at least the die housing, and the second conduit is in fluid communication with each flow channel and the outlet passageway. In some embodiments, the first and second conduits are each adapted to selectively connect to the external supply of fluent material.

In certain exemplary embodiments, the insert further comprises at least one chamber formed within the insert body. In other exemplary embodiments, the insert further comprises at least one insert cavity formed in the insert body. In some exemplary embodiments, the at least one insert cavity is in fluid communication with one or more of the inlet passageway, the outlet passageway, the second conduit, and the at least one flow channel. In other exemplary embodiments, the at least one insert cavity is in fluid communication with a vent passageway.

In a further aspect, embodiments of the present disclosure provide a method of purging gas from a die assembly including an insert removably positioned within a die cavity of a die housing having a plurality of inner wall sections defining the die cavity, thereby defining at least one flow channel between at least one inner wall section of the die housing and each opposite outer wall section of the body portion of the insert. A first conduit passes through at least part of the body portion of the insert, and the first conduit is in fluid communication between an inlet passageway and an outlet passageway in the die housing. A second conduit passes through at least the die housing, and the second conduit is in fluid communication with each flow channel and the outlet passageway. In some embodiments, the first and second conduits are each adapted to selectively connect to an external supply of fluent material.

In certain embodiments, the method comprises:

(a) providing a first liquid flow from the external supply of fluent material through the second conduit;

(b) continuing the first liquid flow through the second conduit until the second conduit and each flow channel are substantially free of gas; and

(c) thereafter providing a second liquid flow from the external supply of fluent material through the first conduit, thereby providing a sheet of fluent material from the outlet passageway. In some embodiments, the method further comprises interrupting the first liquid flow through the second conduit while maintaining the second liquid flow through the first conduit.

The above summary is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The Figures and the Detailed Description that follow more particularly exemplify certain preferred embodiments utilizing the principles disclosed herein and within the scope of the claims.

DETAILED DESCRIPTION

With respect to the above discussion of extrusion dies, Applicants have discovered that the use of deckles or shims to reduce the width of the coating bead may create problems in installing, operating and maintaining the die in a continuous extrusion process, for example, a continuous extrusion coating process. For example, when the coating liquid contains particulates (e.g. for dispersions), these particulates tend to settle in the areas of the large die cavity where liquid flow is slow, leading to plugging of the die over time and requiring frequent interruptions in the coating process to clean the die. To correct for this, partial or full die inserts may be used to reduce the volume of the die cavity as well as the effective slot width. However, Applicants have also discovered that the use of die inserts may create additional problems in installing, operating and maintaining the die in a continuous extrusion coating process.

Extrusion dies and die inserts are typically built out of metals such as stainless steel for precise dimensional control, good chemical and corrosion resistance, and thermal stability. However, stainless steel dies and die inserts are often too heavy for unaided lifting and positioning within the coating system and the die cavity, respectively. The weight of a die insert and a die containing that insert may be reduced by machining chambers or cavities into the body portion of the insert. However, gases such as air that are temporarily retained within the body portion of the insert, may, during a subsequent coating operation, be entrained in the extruded fluid, producing a void or defect (e.g. a streak) in the resulting extrudate film or coating.

Difficulties may also arise when positioning a closely-fitting die insert inside the die cavity. Small gaps may be formed between the outer wall sections of the body of the die insert and the inner wall sections that define the die cavity within the die housing because of the significant mechanical challenges of providing a perfectly fitted insert for the die cavity. These gaps can trap gas bubbles (e.g. air bubbles) during installation of the insert within the die cavity. Typically with best machining, the gaps between the die and insert are less than 1 mil (25 micrometers). Nevertheless, gases (e.g. air bubbles) may be trapped between the inner walls of the die cavity and the outer wall sections of the insert, and gases trapped in this way may be released over time upon passage of a liquid through the die during extrusion or coating. The bubbles may partially block the entrance to the die slot, causing streaks or voids in the product.

The embodiments may take on various modifications and alterations without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the disclosure is not to be limited to the following described embodiments, but is to be controlled by the limitations set forth in the claims and any equivalents thereof. In particular, all numerical values and ranges recited herein are intended to be modified by the term “about”, unless stated otherwise. Various embodiments of the disclosure will now be described with reference to the Figures.

Referring toFIGS. 1A-1C,FIG. 1Ashows a perspective view of a die assembly8according to an illustrative embodiment of the present disclosure. The die assembly8includes a die housing10, an inlet passageway22passing through the die housing10, an outlet passageway14(e.g. a slot formed between first transverse side16and second transverse side18of the die housing10) passing through the die housing10at a position distal from the inlet passageway22, and a die cover12. The die assembly8also includes an insert (not visible inFIG. 1A) removably received in a die cavity (not visible inFIG. 1A) and forming at least one channel (not visible inFIG. 1A) within the die cavity. The die assembly8also includes a means for providing fluid communication between an external supply of fluent material and each of the at least one flow channel and the outlet passageway.

A first conduit (not visible inFIG. 1A) passes through at least part of the insert in fluid communication between the inlet passageway22and the outlet passageway14. A second conduit24in fluid communication with each flow channel and the outlet passageway14, passes through the die housing10. The first conduit (not shown inFIG. 1A) and second conduit24are each adapted to selectively connect to an external supply of fluent material20. Optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit (not shown inFIG. 1A). Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

FIG. 1Bshows a cross-sectional view of a die assembly8including an insert30according to an illustrative embodiment of the present disclosure. The die assembly8includes a die housing10having a plurality of inner cavity wall sections36defining die cavity32, an inlet passageway22passing through the die housing10in fluid communication with the die cavity32, an outlet passageway14passing through the die housing10in fluid communication with the die cavity32at a position distal from the inlet passageway22, and a die cover12forming a ceiling40over at least a portion of die cavity32.

The insert30includes a body portion having a plurality of outer wall sections38, and at least one flow channel34formed between at least one inner cavity wall section36of die cavity32in die housing10, and each opposite outer wall section38of the body portion of insert30. The die assembly8also includes an insert30removably received in the die cavity32, and a means for providing fluid communication between an external supply of fluent material20and each of the at least one flow channel34and the outlet passageway14. In some exemplary embodiments, the inlet passageway22is adapted to selectively connect to the external supply of fluent material20.

In some exemplary embodiments, the means for providing fluid communication may include a first conduit42passing through at least part of the body portion of the insert30in fluid communication between the inlet passageway22and the outlet passageway14, and a second conduit24passing through the die housing10in fluid communication with each flow channel34and the outlet passageway14. The first conduit42and second conduit24may each be adapted to selectively connect to the external supply of fluent material20. Optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

In some exemplary embodiments, a chamber58is formed within the body portion of the insert30. The chamber defines a void within the body portion of insert30. The chamber58is preferably not in fluid communication with outlet passageway14. In certain embodiments, the chamber58is not in fluid communication with the external supply of fluent material20. In some exemplary embodiments, the chamber58acts to reduce the weight of die insert30, thereby simplifying the task of installing and removing the insert within cavity32of die housing10, and in handling the die assembly8for installation in a coating apparatus or extruder.

In certain embodiments, the die insert30is made slightly undersized relative to the volume of the die cavity32, thereby creating at least one flow channel34having a controlled gap around at least a portion of the insert30when the insert30is placed within the die cavity32. In certain exemplary embodiments, the volume occupied by the body portion of the insert30is less than the volume of the die cavity32. In some preferred embodiments, the volume occupied by the body portion of the die insert30is at least about 30% of the volume of the die cavity32(before installation of the insert30). In other preferred embodiments, the volume occupied by the body portion of the die insert30is at most about 99% by volume of the die cavity32(before installation of the insert30).

In some exemplary embodiments, a portion of one or more of outer wall sections38of die insert30may have a surface including one or more supports or buttresses (not shown in the figures) which hold or support the insert30away from one or more of the opposing inner cavity wall sections36of die cavity32in die housing10, thereby defining at least one flow34channel defined in the gap between the supported outer wall section38and the opposing inner cavity wall section36. In other exemplary embodiments, a shim or other removable support (not shown inFIGS. 1A-1C) may be inserted between one or more of outer wall sections38of die insert30and the opposing inner cavity wall sections36of die cavity32in die housing10, thereby holding or supporting the insert30and defining at least one flow34channel formed as the gap between the supported outer wall section38and the opposing inner cavity wall section36.

In certain embodiments, each flow channel34defines a gap having a height of at least about 125 micrometers. In other embodiments, each flow channel34defines a gap having a height of at most about 12,500 micrometers. The controlled gap between the insert30and the plurality of inner cavity wall sections36defining die cavity32may, in some embodiments, allow liquid to purge gas (e.g. air bubbles) from the die cavity32(seeFIGS. 1B-1CandFIGS. 2A-2G).

FIG. 1Cshows a cross-sectional view of another exemplary embodiment of a die assembly8. The die assembly8includes a die housing10having a plurality of inner cavity wall sections36defining die cavity32, an inlet passageway22passing through the die housing10in fluid communication with the die cavity32, an outlet passageway14passing through the die housing10in fluid communication with the die cavity32at a position distal from the inlet passageway22, and a die cover12forming a ceiling40over at least a portion of die cavity32.

The die assembly8also includes an insert30positioned within die cavity32of die housing10on one or more shims44. Each shim44may be positioned between an outer wall section38of the body portion of insert30and the opposing inner wall section36of die cavity32, thereby defining at least one flow channel34. The die assembly8also includes an insert30removably received in the die cavity32, and a means for providing fluid communication between an external supply of fluent material20and each of the at least one flow channel34and the outlet passageway14. In some exemplary embodiments, the inlet passageway22is adapted to selectively connect to the external supply of fluent material20.

In some exemplary embodiments, the means for providing fluid communication may include a first conduit42passing through at least part of the body portion of the insert30in fluid communication between the inlet passageway22and the outlet passageway14, and a second conduit24passing through the die housing10in fluid communication with each flow channel34and the outlet passageway14. The first conduit42and second conduit24may each be adapted to selectively connect to the external supply of fluent material20. Optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

As shown inFIG. 1C, a first flow channel34is formed between the insert30, and each of inner cavity wall section36(e.g. the rear wall) of cavity32and ceiling40of die cover12. A second flow channel34′ is also shown between inner cavity wall section36(e.g. the floor) of cavity32, and insert30. In certain exemplary embodiments, each flow channel34and34′ is in fluid communication between the second fluid conduit24and the outlet passageway14.

In some exemplary embodiments, a chamber58is formed within the body portion of the insert30. The chamber defines a void within the body portion of insert30. The chamber58is preferably not in fluid communication with outlet passageway14. In certain embodiments, the chamber58is not in fluid communication with the external supply of fluent material20. In some exemplary embodiments, the chamber58acts to reduce the weight of die insert30, thereby simplifying the task of installing and removing the insert within cavity32of die housing10, and in handling the die assembly8for installation in a coating apparatus or extruder.

In other exemplary embodiments, an insert30for use within a die assembly8for forming a sheet of fluent material is provided.FIGS. 2A-2Gillustrate a die assembly8including an insert30according to an illustrative embodiment of the present disclosure. The die assembly8includes a die housing10having a plurality of inner cavity wall sections36defining die cavity32, an inlet passageway22passing through the die housing10in fluid communication with the die cavity32, an outlet passageway14passing through the die housing10in fluid communication with the die cavity32at a position distal from the inlet passageway22, and a die cover (not shown inFIGS. 2A-2G) forming a ceiling40over at least a portion of die cavity32.

The insert30is removably received in the die cavity32. The insert30includes a body portion having a plurality of outer wall sections38, and at least one flow channel34formed between at least one inner cavity wall section36of die cavity32in die housing10, and each opposite outer wall section38of the body portion of insert30. The die assembly8also includes an insert30removably received in the die cavity32, and a means for providing fluid communication between an external supply of fluent material20and each of the at least one flow channel34and the outlet passageway14. In some exemplary embodiments, the inlet passageway22is adapted to selectively connect to the external supply of fluent material20.

In some exemplary embodiments, the means for providing fluid communication may include a first conduit42passing through at least part of the body portion of the insert30in fluid communication between the inlet passageway22and the outlet passageway14, and a second conduit24passing through the die housing10in fluid communication with each flow channel34and the outlet passageway14. The first conduit42and second conduit24may each be adapted to selectively connect to the external supply of fluent material20. Optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

In some exemplary embodiments illustrated inFIGS. 2A-2G, first conduit42, in fluid communication between the inlet passageway22and the outlet passageway14, passes through at least part of the body portion of insert30. In certain exemplary embodiments, second conduit24, in fluid communication with each flow channel34and the outlet passageway14, passes through the die housing10. The insert30may include one or more optional insert cavity50. The insert cavity50may be in fluid communication between each flow channel34. The first conduit42and second conduit24may each be adapted to selectively connect to an external supply of fluent material20. For example, optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

In additional exemplary embodiments, the die assembly8includes a vent passageway54in fluid communication with the second conduit24and at least one flow channel34. In certain embodiments illustrated byFIGS. 2A-2G, the vent passageway54and the second conduit24each has a substantially cylindrical cross-section, and vent passageway54is positioned concentric with and coaxially around inlet passageway22. The vent passageway54may also be in fluid communication with outlet passageway14. Vent passageway54may be selectively vented to the external environment, for example, to purge gas from within the die cavity32. For example, optional vent valve29in fluid communication with the vent passageway54, may selectively regulate flow through the vent passageway54. Vent passageway54may be a separate vent passageway, or alternatively, may be formed as a passageway between the inlet passageway22and at least a portion of the first conduit42(as shown inFIGS. 2A-2G), or between a portion of the first conduit42and the second conduit24(as described below with respect toFIG. 3).

In certain exemplary embodiments, the insert30may include at least one chamber (not shown inFIGS. 2A-2G) within the body portion of the insert30. In some exemplary embodiments, the insert30may additionally or alternatively include at least one insert cavity50formed within the body portion of the insert30. In some embodiments, the at least one insert cavity50may be in fluid communication with one or more of the inlet passageway22, the outlet passageway14, the second conduit24, and the at least one flow channel34. In the illustrative embodiment shown inFIGS. 2A-2G, the insert cavity50is formed in the body portion of insert30in fluid communication with the vent passageway54, the outlet passageway14, the inlet passageway22, the second conduit24, and the flow channel34.

In some exemplary embodiments, the vent passageway54may provide a path for venting air from an insert cavity50formed in the body portion of the die insert30. In certain exemplary embodiments illustrated inFIGS. 2A-2G, the vent passageway54has an upper end proximate an upper body portion of the insert30, and the wall of the vent passageway54has at least one perforation52near the upper end, whereby fluent material may pass from the insert cavity50through the at least one perforation52and into the vent passageway54. This path may be open during die start-up while filling the die cavity32with fluent material, and may be closed after the purging of air is complete. For example, the die insert30and die assembly8shown inFIG. 2may enable liquid to be pumped into each flow channel34formed between at least one inner cavity wall section36of die cavity32in die housing10, and each opposite outer wall section38of the body portion of insert30, thereby displacing (i.e. purging) gas (e.g. air) from the die cavity32and any optional insert cavities50formed within the body portion of the insert30.

In other embodiments illustrated inFIG. 3, a conduit assembly60(e.g. a “lance” made of pipes or tubes) passes through the inlet passageway22in the die housing10and penetrates the die insert30and the exterior of the die to form a path that can vent gases such as air bubbles from around and within the insert30to outside of the die housing10. In certain embodiments, the use of a conduit assembly60in the form of a “lance” permits use of the existing inlet passageway22in the die housing10to provide fluent material from an external source of fluent material20to the first conduit42formed within the die insert30, and ultimately to the exit passageway14, without significant modification to the die housing10. In some embodiments, the conduit assembly60permits removal of trapped gases (e.g. air) between the outer wall sections38of body portion of insert30and the inner walls of the die cavity36, or within one or more cavity50formed in the body portion of insert30.

In one exemplary embodiment illustrated inFIG. 3, the die assembly8includes a die housing10having a plurality of inner cavity wall sections36defining die cavity32, an inlet passageway22passing through the die housing10in fluid communication with the die cavity32, an outlet passageway14passing through the die housing10in fluid communication with the die cavity32at a position distal from the inlet passageway22, and a die cover12forming a ceiling40over at least a portion of die cavity32. The die assembly8also includes an insert30positioned within die cavity32of die housing10on one or more shims44. Each shim44may be positioned between an outer wall section38of the body portion of insert30and the opposing inner wall section36of die cavity32, thereby defining at least one flow channel34.

The insert30is removably received in the die cavity32. The insert30includes a body portion having a plurality of outer wall sections38, and at least one flow channel34formed between at least one inner cavity wall section36of die cavity32in die housing10, and each opposite outer wall section38of the body portion of insert30. The die assembly8also includes a means for providing fluid communication between an external supply of fluent material20and each of the at least one flow channel34and the outlet passageway14. In some exemplary embodiments, the inlet passageway22is adapted to selectively connect to the external supply of fluent material20.

In some exemplary embodiments, the means for providing fluid communication may include a first conduit42passing through at least part of the body portion of the insert30in fluid communication between the inlet passageway22and the outlet passageway14, and a second conduit24passing through the die housing10in fluid communication with each flow channel34and the outlet passageway14. The first conduit42and second conduit24may each be adapted to selectively connect to the external supply of fluent material20. Optional first control valve26in fluid communication with the inlet passageway22selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24.

In exemplary embodiments, first conduit42, in fluid communication between the inlet passageway22and the outlet passageway14, passes through at least part of the body portion of insert30. In some exemplary embodiments, second conduit24, in fluid communication with each flow channel34and the outlet passageway14, passes through the die housing10. The insert30may include one or more optional insert cavity50as shown inFIG. 3. The insert cavity50may be in fluid communication between each flow channel34. In additional exemplary embodiments, the first conduit42and second conduit24are each adapted to selectively connect to an external supply of fluent material20. For example, optional first control valve26in fluid communication with the first conduit42selectively connects the external supply of fluent material20to the first conduit42. Optional second control valve28in fluid communication with the second conduit24selectively connects the external supply of fluent material20to the second conduit24. In some embodiments, control valve28is in fluid communication with the inlet passageway22, which is also in fluid communication with second conduit24.

In additional exemplary embodiments, the die assembly8includes a vent passageway54in fluid communication with the second conduit24and at least one flow channel34. In certain embodiments illustrated byFIG. 3, the vent passageway54and the second conduit24each has a substantially cylindrical cross-section, and vent passageway54is positioned concentric with and coaxially within inlet passageway22. The vent passageway54may also be in fluid communication with outlet passageway14. Vent passageway54may be selectively vented to the external environment, for example, to purge gas from within the die cavity32. For example, optional vent valve29in fluid communication with the vent passageway54, may selectively regulate flow through the vent passageway54. Vent passageway54may be a separate vent passageway, or alternatively, may be formed as a passageway between the inlet passageway22and at least a portion of the first conduit42(as shown inFIGS. 2A-2G), or between a portion of the first conduit42and the second conduit24(as described below with respect toFIG. 3).

In certain exemplary embodiments, each of the inlet passageway22, the first conduit42, and the second conduit24has a substantially cylindrical cross-section. In exemplary embodiments, the second conduit24extends through (e.g. within) the inlet passageway22of the die housing10and at least a portion of the insert30concentric with and coaxially around the first conduit42. In certain exemplary embodiments, the second conduit has a wall, and one or more perforations52,52′ providing fluid communication between the second conduit and at least one insert cavity50formed in the body portion of the insert30in fluid communication with the at least one flow channel34.

In certain exemplary embodiments, the insert30may additionally or alternatively include at least one chamber (not shown inFIG. 3) within the body portion of the insert30. In some exemplary embodiments, the insert30may additionally or alternatively include at least one insert cavity50formed within the body portion of the insert30, as shown inFIG. 3. In some embodiments, the at least one insert cavity50may be in fluid communication with one or more of the inlet passageway22, the outlet passageway14, the second conduit24, and the at least one flow channel34. In the illustrative embodiment shown inFIG. 3, the insert cavity50is formed in the body portion of insert30in fluid communication with the vent passageway54, the outlet passageway14, the second conduit24, and the flow channel34.

In another aspect, embodiments of the present disclosure provide a method of purging gas from cavity32defined in die housing10containing insert30. For example, the die insert30and die assembly8shown inFIG. 3may enable liquid to be pumped into each flow channel34formed between at least one inner cavity wall section36of die cavity32in die housing10, and each opposite outer wall section38of the body portion of insert30, thereby displacing (i.e. purging) gas (e.g. air) from the die cavity32and any optional insert cavities50formed within the body portion of the insert30. As one example, vent passageway54may be open during die start-up while filling the die cavity32with fluent material, and may be closed, in some embodiments, after the purging of gas (e.g. air) is complete.

Other embodiments of the present disclosure provide additional methods of purging gas, such as air, from a die assembly8including an insert30removably positioned within a die cavity32of a die housing10having a plurality of inner wall sections36defining the die cavity32, thereby defining at least one flow channel34between at least one inner wall section of the die housing36and each opposite outer wall section38of the body portion of the insert30. A first conduit42passes through at least part of the body portion of the insert30, and the first conduit42is in fluid communication between an inlet passageway22and an outlet passageway14in the die housing10. A second conduit24passes through at least the die housing10, and the second conduit24is in fluid communication with each flow channel34and the outlet passageway14. In some embodiments, the first conduit42and second conduit24are each adapted to selectively connect to an external supply of fluent material20using, for example, control valves26and28, respectively.

In one exemplary embodiment, the method includes the steps of:

(a) providing a first liquid flow from the external supply of fluent material through the second conduit;

(b) continuing the first liquid flow through the second conduit until the second conduit and each flow channel are substantially free of gas; and

(c) thereafter providing a second liquid flow from the external supply of fluent material through the first conduit, thereby providing a sheet of fluent material from the outlet passageway.

In some embodiments, the method further includes interrupting the first liquid flow through the second conduit while maintaining the second liquid flow through the first conduit.

One exemplary embodiment of the method is illustrated byFIGS. 2A-2G. InFIG. 2A, a flow of fluent material (e.g. a coating solution or dispersion, or a polymer melt for extrusion) from an external source20through second conduit24is initiated by opening control valve28. Vent valve29is preferably open during this step, and control valve26is preferably closed. InFIG. 2B, fluent material flows from second conduit24into at least one insert cavity50, thereby displacing gas (e.g. air) from within cavity50. Fluent material also begins to flow into a portion of flow channel34, fluent material rising within flow channel34with the rising level of fluent material within insert cavity50, thereby displacing gas from within flow channel34. InFIG. 2C, fluent material has displaced a substantial portion of the gas from within cavity50, and fluent material begins to flow through perforation52into vent channel54, thereby displacing gas from within vent channel54. InFIG. 2D, fluent material has displaced a portion of the gas within vent channel54.

InFIG. 2E, fluent material has displaced a substantial portion of the gas within vent channel54and flows out of vent valve29. After passage of sufficient time such that gas bubbles are no longer observed exiting vent valve29, vent valve29is closed, as shown inFIG. 2F. Fluent material continues to flow into flow channel34and out of outlet passageway14supplied by second conduit24through chamber50. After passage of sufficient time such that fluent material has displaced a substantial portion of gas from flow channel34and filled cavity32such that gas bubbles are no longer observed in the fluent material exiting outlet passageway14, control valve26may be opened, thereby permitting fluent material to flow through inlet passageway22and into first conduit42as shown inFIG. 2G. In some embodiments, control valve28may then be closed, while maintaining flow of fluent material through inlet passageway22, first conduit42, and out of outlet passageway14as a sheet of fluent material useful in coating an article or forming an extruded sheet or film.

Suitable dies useful in practicing the various embodiments of the present disclosure are known to those skilled in the art. Exemplary dies include, for example, extrusion dies used in extrusion coating or melt extrusion of polymer melts. One particularly well-suited die is an extrusion slot die wherein the exit passageway defines a generally rectangular transverse slot formed between the side walls of the die housing. Exemplary conduit materials include, but are not limited to, various pipes, ducts, pipes and tubing known to those skilled in the art. Exemplary die inserts according to the various embodiments of the present disclosure may be fabricated from a variety of materials, for example, metals, such as stainless steel or aluminum, polymers, such a polycarbonate and poly(methyl) methacrylate, and wood.

Some embodiments of the disclosure provide a die including a removable die insert that permits reduction of the cavity volume of the die while using the existing inlet and outlet passageways of the die housing to supply and emit fluent material from an external supply. Other embodiments provide an insert that narrows the width of the die outlet passageway (e.g., slot), thereby permitting application of a narrower strip of fluent material. In other embodiments, the insert fills a substantial portion of the die cavity, thereby reducing the dead volume within the die in which the fluent material may collect. This may be particularly advantageous for dispersions which may undergo sedimentation within the die chamber, or for reactive liquids. A removable die insert may also simplify cleaning of the die chamber.

Other embodiments of the disclosure provide a die insert comprising one or more internal cavities or chambers, thereby reducing the weight of the die insert, which may simplify the task of installing and removing the insert within the die, and in handling the die. Additional embodiments of the disclosure may provide an apparatus and method for purging a gas, such as air, from spaces around and within a die insert, thereby reducing or eliminating the release of gas bubbles into the fluent material exiting the die slot. This may provide the advantage of reducing or eliminating defects, for example, coating defects, caused by bubbles or voids in the extruded fluid material.

It is apparent to those skilled in the art from the above description that various modifications can be made without departing from the scope and principles of this disclosure, and it should be understood that this disclosure is not to be unduly limited to the illustrative embodiments set forth hereinabove. All publications and patents are herein incorporated by reference to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. Various embodiments of the disclosure have been described. These and other embodiments are within the scope of the following claims.