JP2024537095A - Slot die assembly with tailored stiffness, reduced stretch zone, and force budget - Google Patents

Abstract

Described herein is a slot die assembly having a slot die body and an applicator slot extending across a width of the slot die body, the applicator slot being in fluid communication with a fluid flow path through the slot die body, the slot die body having an adjustment mechanism for adjusting a cross-sectional height of the fluid flow path through the applicator slot. The adjustment mechanism can include a flexible die lip having a hinge point that defines a lip length and a force application point that defines a moment arm length, the ratio of the moment arm length to the lip length being between 0.8 and 10. Optionally, the adjustment mechanism can be operated by an actuator having a spindle with flexures or bearings that provide a predetermined bending stiffness for greater efficiency.

Description

A slot die useful for continuous manufacturing of products is provided, along with an assembly and method thereof.

Slot dies are commonly used by manufacturers to process molten polymers, reaction mixtures, and other fluids, often on an industrial scale. Slot dies can be used for coating, where a liquid is extruded onto a moving flexible substrate, such as a backing or release liner. When the material is applied to a substrate, the process is commonly called extrusion coating. In other cases, the extruded material can be cast onto a chilled roller and demolded to directly obtain a free-standing film without the need for a backing. In some cases, two or more extrusions can be performed simultaneously and combined to obtain a multilayer structure.

There are many ways in which slot die extrusion can be performed. Coating materials can be extruded at ambient or elevated temperatures. Extrusion in which the extrudate temperature is increased to melt or liquefy the feedstock material for processing is commonly referred to as hot melt coating or film extrusion. Extrudates made at room temperature can include a solvent diluent. Suitable solvents include water, organic solvents, or any suitable fluid that dissolves or disperses the components of the coating. The solvent is typically removed in subsequent processing, such as by heat or vacuum drying.

Slot dies generally include a pair of opposing die lips that together form an applicator slot. The applicator slot extends along the width of the moving web or the width of the roller that receives the extruded product, such as a film. As used herein, with respect to slot dies and slot die components, the term "width" corresponds to the cross-web dimension of the slot die and its components. The thickness of the extruded web is generally adjusted by changing the shape of one or both die lips or by adjusting a choker bar located upstream from the die lips.

Adjustments to the cross-web profile on a film extrusion or extrusion coating die can be made using a series of longitudinal actuators built into the slot die assembly. These actuators are coupled to the die lip or choker bar at various locations across the width of the die lip or choker bar to precisely adjust the shape of the die lip or choker bar. Local actuator settings can be adjusted using mechanical means, such as using threaded connections, thermally based on thermal expansion and contraction, or by a combination thereof. Some of these processes are described in co-pending International Patent Applications PCT/IB2020/061685 (Yapel et al.), PCT/IB2020/061687 (Yapel et al.), and PCT/IB2020/061688 (Secor et al.), and U.S. Provisional Patent Application No. 63/122,996 (Secor et al.), all of which were filed on December 9, 2020.

The stretch zone length is defined as the distance between where the molten extrudate exits the slot die and where it contacts the chilled roller or other quenching surface. This parameter is important in extrusion, extrusion coating, and extrusion replication operations, where a stretch zone length that is too large can result in undesirable process defects resulting from stretch resonance, edge weave, and waviness. Minimizing the stretch zone distance can also reduce the amount of neck-in, allowing for wider extrusion widths. The stretch zone distance is also relevant, since it affects the polymer orientation of the film itself. Polymer orientation affects many film properties, including mechanical properties such as tensile strength, and optical properties such as birefringence, as well as adhesion. For these reasons, it is often desirable to run the extrusion process with a minimum stretch zone length while avoiding the risk of collisions between the slot die and the quenching surface.

This can be accomplished by employing a die lip configuration that increases the moment arm length of the adjustment mechanism relative to the lip length. As a further option, the slot die can include a spindle for adjustment of a flexible die lip (or "flex lip") or choker bar with an adjusted bending stiffness. Counterintuitively, having a controlled amount of deflection in the spindle can actually reduce the force required to bend the associated flexible die lip or choker bar while maintaining sufficient stiffness to achieve precise transverse thickness control of the extruded web. The need for spindle deflection arises from the large spatial separation between the actuator and the adjustment mechanism. It has been found that an actuator spindle with an intermediate level of stiffness offers surprising technical efficiency advantages.

In one aspect, a slot die assembly is provided. The slot die assembly includes a slot die body and an applicator slot extending across a width of the slot die body. The applicator slot is in fluid communication with a fluid flow path through the slot die body, and the slot die body includes an adjustment mechanism including a flexible die lip for adjusting a cross-sectional height of the fluid flow path through the applicator slot. The flexible die lip has a hinge point that defines a lip length and a force application point that defines a moment arm length, the ratio of the moment arm length to the lip length being between 0.8 and 10.

In a second aspect, a slot die assembly is provided comprising: a slot die body; an applicator slot extending across the width of the slot die body and in fluid communication with a fluid flow path through the slot die body, the slot die body further comprising an adjustment mechanism for adjusting a cross-sectional height of the fluid flow path through the applicator slot; and a plurality of actuators spaced along the width of the applicator slot, each actuator operably coupled to an adjustment mechanism to provide local adjustment of the cross-sectional height of the fluid flow path at its respective location, each actuator being a linear actuator comprising a motor and a spindle coupled to the motor, and further comprising either (i) the spindle exhibiting a bending stiffness of 5 kN/m to 350 kN/m, or (ii) each actuator further comprising a bearing for coupling the spindle to the adjustment mechanism.

In a third aspect, a method of using the aforementioned slot die assembly is provided, the method including positioning the slot die assembly adjacent to a nip defined between two counter-rotating rollers and extruding an extrudate through an applicator slot of the slot die assembly into the nip, the stretch zone distance between the flexible die lip and the nip being between 15 percent and 100 percent of the radius of one or both of the two counter-rotating rollers.

FIG. 1 is a cross-sectional view of a slot die assembly according to an exemplary embodiment. 1A-1C are partial cross-sectional views illustrating a slot die, according to various exemplary embodiments. 1A-1C are partial cross-sectional views illustrating a slot die, according to various exemplary embodiments. 1A-1C are partial cross-sectional views illustrating a slot die, according to various exemplary embodiments. 1A-1C are partial cross-sectional views illustrating a slot die, according to various exemplary embodiments. FIG. 1 is a perspective view illustrating an exemplary flexible die lip configuration. FIG. 1 is a perspective view illustrating an exemplary flexible die lip configuration. FIG. 13 is a cross-sectional view showing a slot die assembly according to an alternative embodiment. FIG. 1 is a side view of a spindle useful in an exemplary slot die assembly. FIG. 1 is a side view of a spindle useful in an exemplary slot die assembly. 9B is a slot die assembly incorporating a spindle having the general characteristics of the spindle of FIG. 9A. 1 is a partial cross-sectional view illustrating an exemplary connection between components of a slot die assembly according to an exemplary embodiment. 1 is a partial cross-sectional view illustrating an exemplary connection between components of a slot die assembly according to an exemplary embodiment. FIG. 13 is a perspective view showing exaggerated cooperative deflection of slot die components in response to actuator adjustments. FIG. 13 is a perspective view showing exaggerated cooperative deflection of slot die components in response to actuator adjustments.

Repeat use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the present disclosure. It is to be understood that those skilled in the art may devise numerous other modifications and embodiments that are within the scope and spirit of the principles of the present disclosure. The figures may not be drawn to scale.

As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may provide certain advantages, under certain circumstances, however, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the invention.

As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to an element preceded by "a" or "the" may include one or more of the element and equivalents thereof known to those skilled in the art. Additionally, the term "and/or" refers to one or all of the listed elements or a combination of any two or more of the listed elements.

It should be noted that the term "comprises" and variations thereof do not have a limiting meaning when these terms appear in the accompanying description. Furthermore, "a," "an," "the," "at least one," and "one or more" are used interchangeably herein. Relative terms such as left, right, front, rear, top, bottom, side, above, below, horizontal, vertical, etc. may be used herein, when taken from the perspective seen in a particular drawing. However, these terms are used merely for ease of description and in no way limit the scope of the invention.

Throughout this specification, references to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described with respect to that embodiment is included in at least one embodiment of the invention. Thus, the appearances of phrases such as "in one or more embodiments," "in a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the invention. Where applicable, product names are written in all capital letters.

Figure 1 illustrates a slot die assembly according to one exemplary embodiment, hereinafter referred to by the numeral 100. The assembly 100 includes a slot die body 102, which in turn is comprised of opposing upper and lower die blocks 104 and 105. The upper and lower die blocks 104 and 105 combine to form a fluid flow passage 108 through the slot die body 102 in fluid communication with a relatively narrow applicator slot 110.

The slot die body 102 includes an adjustment mechanism, here embodied as a flexible die lip 106. Optionally, as shown, the flexible die lip 106 is integral with the upper die block 104 as shown in FIG. 1 and represents one of two opposing sides of the applicator slot 110. Alternatively, as described below, the flexible die lip 106 can be provided as a separate component flexibly coupled to the slot die body 102. However, machining of an integral flexible die lip is generally preferred for improved strength, robustness, and precision.

The actuator 120 is secured to a mounting bracket 122 that is fixed relative to the upper die block 104. Although not visible in FIG. 1, the actuator 120 is one of multiple actuators arranged along the width of the slot die assembly 100. The actuator 120 itself is an assembly that includes a drive unit 124 and a cylindrical spindle 126 operably coupled to the drive unit 124 that can be precisely translated along its longitudinal axis based on input provided by a controller (not shown). The spindle 126 passes through an opening in the upper die block 104 as shown and contacts the flexible die lip 106 at its distal end 128.

By precisely controlling the position of the spindle 126, the actuator 120 can apply a pushing and/or pulling force against the flexible die lip 106. By varying the shape of the flexible die lip 106 in this manner, the actuator 120 can adjust the height of the fluid flow passage 108 at specific locations along the width of the assembly 100, thereby providing localized adjustment of the fluid flow through the applicator slot 110. The actuator 120 shown here is generalized and operates based on any known principle, such as a differential screw mechanism or thermal expansion/contraction. Although not shown, it may be advantageous to use a primary actuator and a secondary actuator in tandem to provide coarse and fine positioning adjustments, respectively, as described in co-pending International Patent Application No. PCT/IB2021/053172 (Yapel et al.), filed April 16, 2021.

During a manufacturing operation, an extrudate, such as a molten polymer, enters the assembly 100 through the inlet 112, passes through the fluid flow passages 108, is shaped by the applicator slots 110, exits through the outlet 114, and is finally deposited on a cooled roller. Any of a number of downstream conversion processes, not germane to this disclosure, may then be performed. Such processes may include, for example, stretching, coating, texturing, printing, cutting, rolling, and laminating. In some processes, the manufacturing release liner may be removed and a release liner may be added, or one or more additional layers may be added. If the extrudate is a curable composition, a curing step may also be performed, such as exposure to an e-beam, oven, or ultraviolet (UV) chamber.

In a preferred embodiment, the controller can receive position inputs from both the motor and the sensor. For example, the motor can be a stepper motor, providing an indication of the number of "steps" the stepper motor has taken from a known reference position of the stepper motor. The sensor can provide the controller with more accurate position information than is provided by the motor. The controller can also provide commands to the motor to drive the spindle 126 of the actuator 120 to a preselected position. For example, the controller can use the sensor to monitor the position of the spindle 126 of the actuator 120 while operating the motor 210 to position the spindle 126 of the actuator 120 according to a preselected position. The controller can control the set of actuators 108 either simultaneously or sequentially.

In a preferred embodiment, the actuator 120 can incorporate a zero-backlash coupler. In an exemplary configuration, the sensor can be a linear voltage displacement transducer, a digital scale, a capacitance gauge, an optical displacement gauge, a laser displacement gauge, or a combination thereof, allowing the spindle 126 to be adjusted to a precise position. While conventional differential bolt mechanisms can have backlash in excess of 100 micrometers, the zero-backlash coupler can significantly reduce this backlash to less than 10 micrometers, or even less than 5 micrometers, for example, about 3 micrometers. Although not discussed here, further details of this actuator assembly are described in more detail, for example, in co-pending International Patent Application No. PCT/IB2020/061685 (Yapel et al.).

More broadly, the primary actuator may be driven by a mechanically or thermally adjustable bolt, a piezoelectric device, a hydraulic device, or a pneumatic device. In one exemplary primary actuation mechanism, the applicator slot may be adjusted by applying a compressive or tensile load to the flexible die lip using a lever supported by a rotating shaft as a fulcrum, with the actuation rod being axially displaced by the body of the slot die. The rotational force of the lever is translated into an axial force on the actuation rod, which becomes a compressive or tensile load acting on the flexible die lip. The lever may apply a force directly to the actuation rod at the point of application of the lever.

In another exemplary primary actuation mechanism, a thermally adjustable bolt automatically adjusts the applicator slot using multiple adjustment pins coupled to respective thermoelectric elements disposed on the flexible die lip. The thermoelectric elements may be controllable by a controller to adjust the applicator slot through the action of mechanical forces applied to the flexible die lip by corresponding adjustment pins through the expansion or contraction of the thermoelectric elements. As a further option, the actuation mechanism may include providing at least two adjustment pins and/or thermoelectric elements that are adjusted simultaneously.

Further aspects of the above, along with other variations, are described in U.S. Pat. No. 9,700,911 (Nakano) and WO 2019/219724 (Colell et al.).

The operation of the actuator in adjusting the applicator slot can be performed semi-automatically or automatically through the use of operator input and computer hardware, software, firmware, or any combination thereof. For example, various embodiments of the techniques can be implemented in one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or any other equivalent integrated or discrete logic circuits, and any combination of such components, embodied in a controller, user interface, or other device. The term "controller" may generally refer to any of the foregoing logic circuits alone or in combination with other logic circuits, or any other equivalent circuit.

When implemented in software, the functionality attributed to the systems and controllers described in this disclosure may be embodied as instructions on a computer-readable storage medium, such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, magnetic media, optical media, and the like. The instructions may be executed by one or more processors to support one or more embodiments of the functionality described in this disclosure.

In various embodiments, the methods and assemblies described can also be adapted for strip coating, film slot dies, multi-layer slot dies, hot melt extrusion coating dies, drop dies, rotating rod dies, adhesive slot dies, solvent coating slot dies, aqueous coating dies, slot fed knife dies, extrusion replication dies, vacuum contact dies, or other slot dies.

Figures 2-5 show various slot die assemblies in partial views, collectively illustrating the geometric effects of flexible die lip shape and actuator orientation. In each of the illustrated assemblies, the upper die block, flexible die lip, and actuator spindle are shown in isolation, with insets showing the specific mechanical parameters associated with the illustrated configuration.

2 shows a slot die assembly 200 including an upper die block 204 having an integral flexible die lip 206 and a spindle 226 having a distal end 228 extending through the upper die block 204 and mechanically coupled to the flexible die lip 206. As shown, the flexible die lip 206 has a generally elongated shape in cross section and is aligned approximately parallel to an acute angled front surface 230 of the upper die block 204.

The flexible die lip 206 is connected to the remainder of the upper die block 204 by a relatively thin piece of material that defines a hinge 232. The hinge 232 represents a pivot point for the flexible die lip 206 when a pushing or pulling force is applied by the spindle 226. The illustrated one-piece flexible die lip 206 may be conveniently manufactured by cutting a groove 234 into a single block of metal to form the hinge 232. The bottom of the groove 234 may be rounded as shown to minimize stress concentrations when adjusting the flexible die lip 206. Alternatively, the bottom of the groove 234 may have a relatively flat configuration.

2, the bottom surface 235 of the flexible die lip 206 along the applicator slot is characterized by a lip length L, which is defined as the distance between the outermost tip of the flexible die lip 206 and the hinge point H. The hinge point H is then defined as the point along the bottom surface 235 where the vertical cross section of the hinge 232 is thinnest. If the hinge 232 has a generally uniform cross section, the hinge point H can be defined as the point along the cross section furthest from the distal end of the flexible die lip 206.

Also related to the motion of the flexible die lip 206 is the moment arm length MA, which corresponds to the force applied to the flexible die lip 206 by the spindle 226. This moment arm length MA is defined as the shortest distance between the hinge point H and the longitudinal axis 207 of the spindle 226, as shown. The line segment corresponding to the arm length MA is perpendicular to the longitudinal axis 207 of the spindle 226.

In various embodiments, the ratio of the moment arm length MA to the lip length L (i.e., MA/L) may be 0.8-10, 0.8-6.5, 0.8-3.25, or in some embodiments may be less than, equal to, or greater than 0.8, 0.85, 0.9, 0.95, 1, 1.1, 1.2, 1.5, 1.7, 2, 2.5, 3, 3.25, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10. The advantage of having a higher MA/L ratio comes from the increased mechanical advantage to adjust the flexible die lip 206 via the force applied by the translation of the spindle 226. Further advantages come from the improved adjustment resolution of the die lip and the resulting die slot height. These relatively high MA/L ratios are made possible by the elongated cross-sectional shape of the flexible die lip 206.

The flexible die lip 206 can have any suitable lip length L that facilitates approximating the slot die assembly 200 to the nip roller 236. In this case, the nip roller 236 is reasonably approximated as tangent to the parting line that divides the upper die block 204 from the lower die block. This parting line is generally aligned with the bottom surface 235 of the flexible die lip 206. The lip length L can be 3 centimeters to 10 centimeters, 3 centimeters to 9 centimeters, 3 centimeters to 8 centimeters, or in some embodiments, less than, equal to, or greater than 3 centimeters, 4, 5, 6, 7, or 8 centimeters.

Optionally, the parting line dividing the upper and lower die blocks may be offset vertically upwards or downwards. In other embodiments, the orientation angle of the parting line may be different from 0, with a horizontal parting line being defined as having an orientation angle of 0 degrees.

The hinge 232 can also have any suitable thickness, such thickness being measured perpendicular to the bottom surface 235. This thickness may be between 3 percent and 40 percent, between 4 percent and 30 percent, between 6 percent and 25 percent, or may be less than, equal to, or greater than 3 percent, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 percent of the lip length.

To further minimize the distance between the slot die assembly 200 and the nip roller 236, the forward facing surface of the flexible die lip 206 can have an angled section 238 oriented at an acute tip angle α relative to the bottom surface 235. The tip angle α can be between 10 degrees and 90 degrees, between 10 degrees and 60 degrees, between 10 degrees and 40 degrees, or in some embodiments, less than, equal to, or greater than 10 degrees, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 degrees. Notably, the angled section 238 need not be contiguous with the distal tip of the flexible die lip 206, but preferably extends over at least 30 percent, at least 35 percent, or at least 40 percent of the lip length L. If desired, two or more consecutive angled sections can be used to assist in helping the flexible die lip 206 conform to the curvature of the nip roller 236, as described above.

The angled section 238 allows the slot die assembly 200 to get as close as possible to the nip rollers 236 while allowing for some safety margin to prevent collision between these two structures. Having a short draw zone distance, or distance between the distal end of the flexible die lip 206 and the nip point N where the opposing counter-rotating nip rollers come together (as shown), can help minimize drawdown of the extrudate during extrusion. The draw zone distance separating the flexible die lip 206 and the nip point N may be 15 percent to 100 percent, 20 percent to 90 percent, 20 percent to 50 percent, or may be less than, equal to, or greater than 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent of the radius of one or both nip rollers.

As shown, the longitudinal axis of the spindle 226 is oriented at a particular actuator angle β relative to the bottom surface 235. This actuator angle β can vary over a wide range, such as 0 degrees to 90 degrees, 0 degrees to 70 degrees, 0 degrees to 50 degrees, or in some embodiments, less than, equal to, or greater than 0 degrees, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 degrees. Advantageously, this actuator angle β can be adjusted as needed to accommodate different geometries for the upper die block 204 and provide leverage for rotating the flexible die lip 206 about the hinge 232.

2 further shows an inset showing various combinations of lip length L and moment arm length MA superimposed on a two-dimensional force budget map. In this coordinate system, the shaded areas represent combinations of L and MA that allow an actuator constrained by a maximum force rating to control the flexible die lip 206 at a given maximum extrudate flow rate. The maximum force rating can vary depending on the actuator, with a typical value being about 3500 lbf or 15.6 kilonewtons. From the inset, it can be seen that the illustrated configuration of the slot die assembly 200 meets its force budget based on its combination of moment arm length MA and lip length L.

The longer moment arm length MA can be attributed to its unique geometry, particularly its extended lip segment height S, as shown in FIG. 2. The lip segment height S, measured perpendicular to the bottom surface 235, can be significantly longer than the lip length L. In various embodiments, the lip segment height S can exceed the lip length L by 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, or 2.8 times the lip length L.

3 shows a slot die assembly 300 according to an alternative embodiment. The upper portion of the assembly 300 includes an upper die block 304 with an integral flexible die lip 306, similar to the upper portion of the previous assembly 200, and a spindle 326 that extends through the upper die block 304 and engages the top of the flexible die lip 306. The assembly 300 differs from the previous embodiment in that the spindle 326 is oriented horizontally, resulting in an actuator angle β of about 0 degrees. Unlike the previous slot die assemblies, the slot die assembly 300 does not meet the force budget criteria represented by the shaded region in the inset of FIG. 3. This result can be attributed to the increase in lip length L relative to the immediately preceding embodiment. Reducing the actuator angle β had the effect of increasing the moment arm length MA, but increasing the lip length resulted in a net decrease in the MA/L ratio, resulting in the force budget being exceeded.

Figure 4 shows in a similar view yet another slot die assembly 400 that has some similarities to assembly 300 but incorporates a somewhat taller flexible die lip 406. As previously mentioned, the actuator angle β was approximately 0 degrees considering the horizontal orientation of the spindle 426 through the upper die block 404. However, as revealed by the inset, this configuration meets the force budget criteria. If the flex lip length L is held constant, the significantly larger height of the flexible die lip 406 results in a larger MA/L ratio.

Figure 5 shows yet another variation represented by slot die assembly 500 characterized by an upper die block 504, a spindle 526 extending horizontally through the upper die block 504, and a flexible die lip 506 having a height similar to that of assemblies 200, 300 and a flex lip length L similar to that of assembly 200. Given both a relatively short lip length L and a long moment arm length MA, this configuration easily meets the required force budget, as shown in the inset.

6 and 7 each illustrate optional features that can be incorporated into the flexible die lip to further increase its flexibility. For clarity, these features are shown in perspective along with the die slot assembly. As shown in FIG. 6, the slot die assembly 600 includes a flexible die lip 604 that includes a series of regularly spaced notches 630. The notches 630 are spaced along the width of the slot die body to divide the flexible die lip into multiple die lip segments 633, which have the effect of reducing the overall bending stiffness of the flexible die lip 604.

The reduction in stiffness of the flexible die lip 604 is primarily due to a reduction in the cross-sectional area of the flexible die lip 604 in a side view (as shown in FIGS. 1-5) within each notch 630. The cross-sectional side view of the flexible die lip 604 beyond the hinge 632 can be reduced by 1 percent to 100 percent, 25 percent to 100 percent, 70 percent to 100 percent, or in some embodiments, less than, equal to, or greater than 1 percent, 2, 5, 7, 10, 12, 15, 17, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent relative to the cross-sectional side area of the flexible die lip 604 beyond the hinge 632 along the unnotched section.

開放面積は、同じ平面に沿って画定されるノッチのない可撓性ダイリップ面積に対して、１パーセント～９０パーセント、２パーセント～８５パーセント、３．５パーセント～８０パーセントであってもよく、又はいくつかの実施形態では、１、２、３．５、５、７、１０、２０、３０、４０、５０、６０、７０、８０、８５、若しくは９０パーセントより小さい、それに等しい、若しくはそれより大きくてもよい。幅Ｗ及び深さＤのいずれか又は両方が変化することも可能であり、その場合、可撓性の程度は、その幅にわたって同様に変化することができる。 In some embodiments, the notch 630 has a consistent width W and depth D across the width of the flexible die lip 604. The inclusion of the notch 630 creates an open area in the portion of the flexible die lip 604 that extends beyond the hinge 632, defined along a plane perpendicular to the fluid flow direction. Based on the embodiment shown in FIG. 6, this open area can be approximated as follows:

The open area may be between 1 percent and 90 percent, between 2 percent and 85 percent, between 3.5 percent and 80 percent, or in some embodiments may be less than, equal to, or greater than 1, 2, 3.5, 5, 7, 10, 20, 30, 40, 50, 60, 70, 80, 85, or 90 percent relative to an unnotched flexible die lip area defined along the same plane. Either or both of the width W and depth D can also vary, in which case the degree of flexibility can similarly vary across the width.

The notches 630 can also be characterized by an associated notch thickness NT, shown in FIG. 6, defined as the distance between the bottom surface 635 and the lowest point of a given notch 630. The hinge thickness HT, also depicted in FIG. 6, can be 2 percent to 100 percent, 10 percent to 100 percent, 20 percent to 100 percent, 25 percent to 75 percent of the notch thickness NT, or in some embodiments, can be less than, equal to, or greater than 10 percent, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent.

The depth D of the notch 630 can also be characterized relative to the depth of the groove 634, which extends across the width of the slot die 600 and defines the flexible die lip. As defined herein, the groove 634 has a depth measured from the bottom of the groove 634 to the top surface of the flexible die lip 604, and in the illustrated embodiment is approximately equal to D+NT-HT. Each notch can have a depth of 1 percent to 100 percent, 10 percent to 100 percent, 25 percent to 100 percent, or in some embodiments, less than, equal to, or greater than 1 percent, 2, 5, 7, 10, 12, 15, 17, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent of the groove depth.

Figure 7 shows another slot die assembly 700 constructed from a flexible die lip 704 having a plurality of regularly spaced notches 730 extending along the width of the slot die assembly 700. This embodiment differs somewhat from the previous embodiment in that the notches 730 have a generally semicircular profile and the notches 630 have a generally rectilinear profile. Each notch 730 has a similar width W and depth D, but the % open area associated with this notch shape is significantly smaller than in the previous embodiment, resulting in a relatively stiffer flexible die lip 704.

FIG. 8 is directed to a slot die assembly 800 illustrating an alternative spindle coupling that can also function to extend the moment arm length achievable between the actuator spindle and the flexible die lip. Here, the slot die assembly 800 includes an actuator 820 attached to an upper die block 804 having a flexible die lip 806 attached thereto. The actuator 820 is equipped with a spindle 826 that is linearly driven along its longitudinal axis 807. The actuator 820 and spindle 826 have an offset position relative to the flexible die lip 806 such that the axis 807 does not intersect the flexible die lip 806.

A pair of bends 827 on the spindle 826 allow the spindle to positively engage the flexible die lip 806. In this example, the bends 827 are right angle bends. The spindle 826 may comprise one piece or an assembly of two or more pieces as shown to form the bends 827. The spindle may optionally be guided using a guide bushing 828. The engagement of the spindle to the flexible lip 806 may be secured using a clip 829 (as shown), a bolt, or other fastener. Advantageously, this configuration may provide the mechanical equivalent of extending the lip segment height of the flexible die lip 806. This use of an offset actuator/spindle may be particularly beneficial when retrofitting an existing slot die assembly or when the position or orientation of the actuator is otherwise constrained.

9A illustrates an exemplary spindle 926 suitable for use with the various slot die assemblies described above. The spindle 926 is shown here in isolation and is comprised of multiple cylindrical sections connected in series with one another. In a preferred embodiment, the multiple segments are an integral part of a single structure. These include an end section 950, a flexure 952, and an end section 954. Optionally, as shown, the flexure 952 represents the longest segment of the spindle 926. It may also be the case that essentially the entire length of the spindle 926 can be dimensioned to function as a flexure. More broadly, the flexure 952 can extend along any portion of the length of the spindle, including less than, equal to, or greater than 1, 2, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 92, 95, 97, or 99 percent of the length of the spindle. In this illustration, the spindle 926 further includes a fourth section 956 for engaging a flexible die lip, as described below.

In some embodiments, the flexure 952 is a flexure that provides predictable and resilient deflection of the spindle 926. As shown, the flexure has a cross-sectional area that is smaller than the cross-sectional area of either or both of the end sections 950, 954. Pin, blade, notch flexures, and combinations thereof can all be used advantageously. The flexures can be optimized to allow bending at specific locations, avoid interference, and minimize the amount of force required. These flexures do not require relative sliding between surfaces, so backlash and associated dead zones in the control scheme can be avoided or minimized. Depending on the flexure used, it may be possible to have various degrees of freedom (e.g., one, two, or more). The flexure 952 may be any length relative to the overall length of the spindle 926, depending on where bending is desired.

The flexure 952 can have a diameter that is less than, equal to, or greater than 15 percent to 100 percent, 30 percent to 100 percent, or 40 percent to 100 percent of the diameter of one or both end sections 950, 954, or in some embodiments, 15 percent, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent. These values correspond to flexures 952 having a cross-sectional area (defined along a plane perpendicular to the longitudinal axis of the spindle) that is between 2 percent and 100 percent, between 9 percent and 99 percent, or between 16 percent and 98 percent, or in some embodiments, less than, equal to, or greater than 2 percent, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 98, 99, or 100 percent of the cross-sectional area of one or both end sections 950, 954.

The reduction in diameter within the flexure 952 can, in some cases, provide important and unexpected technical advantages. It has been discovered that when adjusting the geometry of an adjustment mechanism such as a flexible die lip, there is an optimal range of bending stiffness associated with the spindle. This phenomenon is based on the problem presented by a metaphysically rigid spindle that is only capable of pure translation along its longitudinal axis. As can be visualized in Figures 2-5, such a spindle tends to stretch the flexible die lip material instead of bending to allow for the intended rotation of the flexible die lip along its hinge. The amount of force required to stretch the die lip material (typically steel) can be excessive and overwhelm the actuator. Therefore, it is desirable to have some flexure in the spindle to allow this bending motion to occur. Also, having an overly flexible spindle is undesirable as it can result in buckling of the spindle and insufficient transfer of force from the actuator to the flexible die lip.

9B shows an alternative spindle 926' according to an alternative embodiment. Similar to the spindle 926 of FIG. 9A, the spindle 926' of FIG. 9B is composed of multiple segments, namely, a section 950', a flexure 952', a section 954', and a section 956' corresponding to those of FIG. 9A. The main difference, however, is that the spindle 926' has a much shorter flexure 952' that localizes the bending of the spindle 926' over a relatively short portion of the total length of the spindle 926'. Such a configuration can potentially be beneficial, for example, when the bending of the spindle may be limited over a certain region due to interference issues or other geometric constraints. The length of the flexure relative to the total length of the spindle need not be particularly limited. Depending on the specifics of the application, the flexures can extend along less than, equal to, or greater than 2, 3, 4, 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 97 percent of the total length of the spindle.

Figure 10 shows a simplified diagram of a slot die assembly 900 that includes an upper die block 904 and a series of spindles 926, each having the configuration shown in Figure 9A, to adjust the shape of the flexible die lip 906. At the foreground of this view, the nearest spindle 926 is shown in cross section within the die block 904, showing how a small degree of bending of the spindle is desirable to allow for a small degree of rotation of the flexible dip lip 906 about its hinge 932.

Given the above constraints, it has been found that optimal spindles generally exhibit bending stiffnesses of 5 kN/m to 350 kN/m, 10 kN/m to 263 kN/m, 15 kN/m to 175 kN/m, or in some embodiments less than, equal to, or greater than 5 kN/m, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 150, 175, 200, 225, 250, 275, 300, 325, or 300 kN/m. In any case, it is generally desirable to avoid any bending stiffness that is insufficient to prevent Euler buckling of the spindle when subjected to compression. Euler buckling is problematic because forces are not efficiently transferred through the column. When such buckling occurs, the applied forces also tend to become unpredictable, reducing the effectiveness of the overall control scheme.

11 and 12 show the coupling between the actuator spindle and the respective adjustment mechanism in each slot die subassembly 1000, 1100. An adjustment mechanism, as used herein, may be any flexible elongated structure capable of locally restricting fluid flow through the applicator slot in a given slot die assembly. FIG. 11 shows the engagement between the spindle 1026 and the flexible die lip 1006 in the upper die block 1104, and FIG. 12 shows the engagement between the spindle 1126 and the choker bar 1106 in the upper die block 1004. The choker bar 1106, also called a restrictor bar, differs from the flexible die lip 1006 in that it restricts flow at a location in the upper die block 1104 that is upstream away from the outlet of the slot die assembly.

11 and 12, each enlarged end section 1050, 1150 of the spindle 1026, 1126 is mechanically coupled to its respective actuator drive unit by a joint 1060, 1160 and to its respective adjustment mechanism 1006, 1106 (e.g., flexible die lip or choker bar) through direct contact between their bodies by a rigid shoulder bolt joint. As shown, the shoulder bolt joint is formed by a small diameter threaded end section 1056, 1156 at the opposite end of each spindle 1026, 1126.

Although not explicitly shown here, alternative joints are possible. Instead of a rigid joint between the spindle and the adjustment mechanism, bearings or joints that allow some degree of relative movement between these components can be used. For example, each spindle can use a ball joint that couples the spindle to the adjustment mechanism. Alternatively, each spindle can include a clevis joint to couple the spindle to the adjustment mechanism. As well as including a flexible spindle, suitable bearings can also facilitate proper and efficient pivoting of the adjustment mechanism during extrusion.

Optionally, as shown, a zero-backlash coupler 1060, 1160 can be used to connect the actuator to the spindle. Such couplers are described, for example, in co-pending International Patent Application No. PCT/IB2020/061685 (Yapel et al.). At the opposite end, the spindle 1026, 1126 can be coupled to the actuator's drive unit by a threaded connection. If a threaded connection is used, it may be beneficial for the spindle to have a minimum spindle diameter along any of its segments that is at least as large as its thread root diameter to avoid excessive bending strength of the spindle. These connection aspects may be further applicable to the coupling between the spindle 1026, 1126 and the flexible die lip 1006 or choke bar 1106 of sections 952, 956 of FIG. 9A and FIGS. 11 and 12, respectively.

In relation to the slot die assembly of FIG. 12, FIGS. 13 and 14 show how an exemplary series of spindles 1126 can individually and collectively engage with the choker bar 1106. FIG. 13 shows the spindles 1126 and choker bar 1106 in a neutral position, and FIG. 14 shows these same components in an adjusted position. For clarity, the adjusted configuration exaggerates the degree of deflection of the spindles 1126 and choker bar 1106. As shown in FIG. 14, when a single spindle 1126 actively presses against the choker bar 1106, a curvature is created in the choker bar 1106 such that adjacent spindles 1126 are forced to cooperatively bend toward the single spindle 1126 as shown. As with the flexible die lip embodiment, the flexibility of the spindles 1126 can greatly facilitate efficient operation of the choker bar 1106 when making localized adjustments to the fluid flow within the slot die assembly.

Additional engineering considerations may also apply with respect to the spindle used in the slot die assembly. For example, the spindle segments and coupling attachments should be strong enough to withstand tensile and compressive loads over their usable life without periodic failure. In a preferred embodiment, the spindle is made of steel, such as 4140 or 15-5PH steel, and has a tensile yield strength of at least 15.6 kN.

Alternative spindle materials and configurations are also possible. For example, the spindle may be entirely metallic, entirely non-metallic, or a combination of both. Non-metallic materials include composite materials, such as fiber-reinforced composite materials. If anisotropic properties are desired, fibers embedded within the composite material may stiffen the spindle along some directions but not others. Optionally, the spindle may be an assembly made up of multiple continuous segments, with the segments made from different materials and/or geometries. Different materials may also be used in tandem (e.g., in a core-sheath configuration). Various materials may provide complementary benefits. In some embodiments, an in-line ceramic component may be provided as insulation to reduce heat transfer from the slot die body to the actuator drive unit.

Rotational stiffness can be an issue if torque is required to couple the spindle to an adjustment mechanism (e.g., a flexible die lip or choke bar). For a given spindle diameter and length, rotational stiffness should be sufficient to allow assembly, and the minimum spindle diameter should exceed the minimum torsional yield diameter of the spindle.

Various implementations have been described in the preceding sections. These and other implementations are within the scope of the claims provided herein.

All references, patents, and patent applications cited in the above patent application for Letters Patent are incorporated herein by reference in their entirety for consistency. In the event of any inconsistency or contradiction between any of the incorporated references and this application, the information in the foregoing description shall prevail. The foregoing description is intended to enable one skilled in the art to practice the disclosure as set forth in the claims, and should not be construed as limiting the scope of the present disclosure, which is defined by the claims and all equivalents thereof.

All references, patents, and patent applications cited in the above patent application for Letters Patent are incorporated herein by reference in their entirety for consistency. In the event of any inconsistency or discrepancy between any of the incorporated references and this application, the information in the foregoing description shall prevail. The foregoing description is intended to enable a person skilled in the art to practice the disclosure as set forth in the claims, and should not be construed as limiting the scope of the present disclosure, which is defined by the claims and all equivalents thereof.
In addition to the respective embodiments, the following aspects are noted.
(Appendix 1)
A slot die body;
an applicator slot extending across a width of the slot die body, the applicator slot being in fluid communication with a fluid flow path through the slot die body;
Equipped with
the slot die body includes an adjustment mechanism having a flexible die lip for adjusting a cross-sectional height of the fluid flow path through the applicator slot;
the flexible die lip has a hinge point that defines a lip length and a force application point that defines a moment arm length, and further wherein the ratio of the moment arm length to the lip length is between 0.8 and 10;
Slot die assembly.
(Appendix 2)
2. The slot die assembly of claim 1, wherein the lip length is between 2 centimeters and 10 centimeters.
(Appendix 3)
3. The slot die assembly of claim 1 or 2, wherein the flexible die lip has a lip segment height, and a ratio of the lip segment height to the lip length is from 0.35 to 5.
(Appendix 4)
4. The slot die assembly of any one of claims 1 to 3, wherein the slot die body has a distal end characterized by a tip angle between 10 degrees and 90 degrees.
(Appendix 5)
5. The slot die assembly of any one of claims 1 to 4, wherein the flexible die lip has a lip segment height, and a ratio of the lip segment height to the lip length is from 0.35 to 5.
(Appendix 6)
6. The slot die assembly of any one of claims 1 to 5, wherein the flexible die lip has a hinge thickness defined at the hinge point, the hinge thickness being between 3 percent and 40 percent of the lip length.
(Appendix 7)
7. The slot die assembly of claim 6, wherein the flexible die lip has a particular height, and a ratio of the particular height to the hinge thickness is between 3.5 and 60.
(Appendix 8)
8. The slot die assembly of any one of claims 1 to 7, wherein the flexible die lip has a particular height, and a ratio of the height to the moment arm length is between 0.55 and 6.
(Appendix 9)
9. The slot die assembly of any one of claims 1 to 8, wherein the flexible die lip includes a plurality of notches along its length, the plurality of notches being spaced along the width of the slot die body so as to divide the flexible die lip into a plurality of die lip segments to reduce the overall stiffness of the flexible die lip.
(Appendix 10)
10. The slot die assembly of claim 9, wherein the flexible die lip is characterized by both a hinge thickness and a notch thickness, the hinge thickness being between 10 percent and 100 percent of the notch thickness.
(Appendix 11)
11. The slot die assembly of claim 9 or 10, wherein the hinge points are based on grooves extending across the width of the flexible die lip, the depth of each notch being between 1 percent and 100 percent of the depth of the groove.
(Appendix 12)
12. The slot die assembly of any one of claims 9 to 11, wherein the plurality of notches form an open area in the flexible die lip extending beyond the hinge point defined along a plane perpendicular to a direction of fluid flow through the fluid flow passage, the open area being between 1 percent and 90 percent of an unnotched flexible die lip area defined along the plane.
(Appendix 13)
13. The slot die assembly of any one of claims 1 to 12, further comprising a plurality of actuators spaced along a width of an applicator slot, each actuator operatively coupled to the flexible die lip at the force application point to adjust the cross-sectional height of the fluid flow passage at its respective location to provide localized adjustment of fluid flow through the applicator slot.
(Appendix 14)
14. The slot die assembly of claim 13, wherein each actuator is a linear actuator comprised of a motor and a spindle coupled to the motor, the spindle oriented at an actuator angle relative to a fluid flow direction through the fluid flow path, the actuator angle being between 0 degrees and 90 degrees.
(Appendix 15)
15. The slot die assembly of claim 14, wherein the spindle comprises a flexure.
(Appendix 16)
A slot die body;
an applicator slot extending across a width of the slot die body, the applicator slot being in fluid communication with a fluid flow path through the slot die body, the slot die body further comprising an adjustment mechanism for adjusting a cross-sectional height of the fluid flow path through the applicator slot;
a plurality of actuators spaced along a width of the applicator slot, each actuator operatively coupled to the adjustment mechanism to provide local adjustment of the cross-sectional height of the fluid flow passage at its respective location;
Equipped with
each actuator is a linear actuator comprising a motor and a spindle coupled to the motor, and further comprising either (i) the spindle comprising a flexure, or (ii) each actuator further comprising a bearing for coupling the spindle to the adjustment mechanism;
Slot die assembly.
(Appendix 17)
17. The slot die assembly of claim 16, wherein each actuator comprises a ball joint coupling the spindle to the adjustment mechanism.
(Appendix 18)
17. The slot die assembly of claim 16, wherein each actuator comprises a clevis joint coupling the spindle to the adjustment mechanism.
(Appendix 19)
A method of using the slot die assembly of any one of claims 1 to 18, comprising the steps of:
positioning the slot die assembly adjacent a nip defined between two counter-rotating rollers;
extruding extrudate through the applicator slot of the slot die assembly and into the nip;
Including,
A method wherein a draw zone distance between the flexible die lip and the nip is between 15 percent and 100 percent of the radius of one or both of the two counter-rotating rollers.
(Appendix 20)
20. The method of claim 19, wherein the stretch zone distance is between 20 percent and 90 percent of the radius of one or both of the two counter-rotating rollers.

Claims (20)

A slot die body;
an applicator slot extending across a width of the slot die body, the applicator slot being in fluid communication with a fluid flow path through the slot die body;
Equipped with
the slot die body includes an adjustment mechanism having a flexible die lip for adjusting a cross-sectional height of the fluid flow path through the applicator slot;
the flexible die lip has a hinge point that defines a lip length and a force application point that defines a moment arm length, and further wherein the ratio of the moment arm length to the lip length is between 0.8 and 10;
Slot die assembly. The slot die assembly of claim 1, wherein the lip length is between 2 centimeters and 10 centimeters. The slot die assembly of claim 1 or 2, wherein the flexible die lip has a lip segment height, and the ratio of the lip segment height to the lip length is between 0.35 and 5. The slot die assembly of any one of claims 1 to 3, wherein the slot die body has a distal end characterized by a tip angle between 10 degrees and 90 degrees. The slot die assembly of any one of claims 1 to 4, wherein the flexible die lip has a lip segment height, and the ratio of the lip segment height to the lip length is 0.35 to 5. The slot die assembly of any one of claims 1 to 5, wherein the flexible die lip has a hinge thickness defined at the hinge point, the hinge thickness being between 3 percent and 40 percent of the lip length. The slot die assembly of claim 6, wherein the flexible die lip has a specific height, and the ratio of the specific height to the hinge thickness is between 3.5 and 60. The slot die assembly of any one of claims 1 to 7, wherein the flexible die lip has a specific height, and the ratio of the height to the moment arm length is between 0.55 and 6. The slot die assembly of any one of claims 1 to 8, wherein the flexible die lip includes a plurality of notches along its length, the plurality of notches being spaced along the width of the slot die body so as to divide the flexible die lip into a plurality of die lip segments to reduce the overall stiffness of the flexible die lip. The slot die assembly of claim 9, wherein the flexible die lip is characterized by both a hinge thickness and a notch thickness, the hinge thickness being between 10 percent and 100 percent of the notch thickness. The slot die assembly of claim 9 or 10, wherein the hinge points are based on grooves that extend across the width of the flexible die lip, and the depth of each notch is between 1 percent and 100 percent of the depth of the groove. The slot die assembly of any one of claims 9 to 11, wherein the plurality of notches form an open area in the flexible die lip extending beyond the hinge point that is defined along a plane perpendicular to a direction of fluid flow through the fluid flow passage, the open area being between 1 percent and 90 percent of the area of the flexible die lip without the notches defined along the plane. The slot die assembly of any one of claims 1 to 12, further comprising a plurality of actuators spaced along a width of the applicator slot, each actuator operatively coupled to the flexible die lip at the force application point to adjust the cross-sectional height of the fluid flow passage at its respective location to provide localized adjustment of fluid flow through the applicator slot. The slot die assembly of claim 13, wherein each actuator is a linear actuator comprised of a motor and a spindle coupled to the motor, the spindle oriented at an actuator angle relative to a fluid flow direction through the fluid flow passage, the actuator angle being between 0 degrees and 90 degrees. The slot die assembly of claim 14, wherein the spindle includes a flexure. A slot die body;
an applicator slot extending across a width of the slot die body, the applicator slot being in fluid communication with a fluid flow path through the slot die body, the slot die body further comprising an adjustment mechanism for adjusting a cross-sectional height of the fluid flow path through the applicator slot;
a plurality of actuators spaced along a width of the applicator slot, each actuator operatively coupled to the adjustment mechanism to provide local adjustment of the cross-sectional height of the fluid flow passage at its respective location;
Equipped with
each actuator is a linear actuator comprising a motor and a spindle coupled to the motor, and further comprising either (i) the spindle comprising a flexure, or (ii) each actuator further comprising a bearing for coupling the spindle to the adjustment mechanism;
Slot die assembly. The slot die assembly of claim 16, wherein each actuator comprises a ball joint coupling the spindle to the adjustment mechanism. The slot die assembly of claim 16, wherein each actuator includes a clevis joint connecting the spindle to the adjustment mechanism. A method of using the slot die assembly according to any one of claims 1 to 18, comprising the steps of:
positioning the slot die assembly adjacent a nip defined between two counter-rotating rollers;
extruding extrudate through the applicator slot of the slot die assembly and into the nip;
Including,
a stretch zone distance between the flexible die lip and the nip that is between 15 percent and 100 percent of the radius of one or both of the two counter-rotating rollers;
method. The method of using the slot die assembly of claim 19, wherein the stretch zone distance is between 20 percent and 90 percent of the radius of one or both of the two counter-rotating rollers.

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