Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/3001—Extrusion nozzles or dies characterised by the material or their manufacturing process
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/30—Extrusion nozzles or dies
  • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
  • B29C48/31—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets being adjustable, i.e. having adjustable exit sections
  • B29C48/313—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets being adjustable, i.e. having adjustable exit sections by positioning the die lips
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/25—Component parts, details or accessories; Auxiliary operations
  • B29C48/92—Measuring, controlling or regulating

Definitions

• slot dies useful for continuous manufacture of a product, along with assemblies and methods thereof.
• Slots dies are commonly used by manufacturers for processing molten polymers, reactive mixtures, and other fluids, often on an industrial scale. Slot dies can be used for coatings, where a liquid is extruded onto a moving flexible substrate, such as a backing or release liner. When material is applied to a substrate, the process is generally referred to as extrusion coating. In other cases, the extruded material can cast onto a chilled roller and released to obtain a free-standing film directly without need for a backing. In some cases, two or more extrusions can be carried out simultaneously and integrated to obtain multilayered structures.
• Coating materials can be extruded at ambient temperature or an elevated temperature. Extrusions where extrudate temperature is elevated to melt or liquify feed stock material for processing are commonly referred to as hot melt coating or film extrusion. Extrusions made at room temperature can include solvent diluents. Suitable solvents include water, organic solvents, or any suitable fluid that dissolves or disperses components of a coating. Solvents are typically removed in subsequent processing such as by heat or vacuum drying.
• slot dies include a pair of opposing die lips that come together to form an applicator slot.
• the applicator slot extends along the width of a moving web or the width of a roller that receives the extruded product, such as a film.
• width corresponds to the cross-web dimension of a slot die and its components. Thickness of the extruded web is generally adjusted by altering the shape of one or both die lips, or by adjusting a choker bar located upstream from the die lips.
• Adjustment of the cross-web profile on film extrusion or extrusion coating dies can be made using a series of longitudinal actuators integrated into the slot die assembly. These actuators are coupled to the die lip or choker bar at various locations across its width to make precise adjustments to its shape. Local actuator settings can be adjusted using mechanical means, such as using a threaded connection, by heat based on thermal expansion and contraction, or a combination thereof.
• the draw zone length is defined as the distance between where the molten extrudate exits the slot die and where it contacts a chilled roller or other quenching surface. This parameter is important in extrusion, extrusion coating, and extrusion replication operations — a draw zone length that is too large can result in undesired process defects resulting from draw resonance, edge weave, and corrugation. Minimizing draw zone distance can also reduce the amount of neck-in, enabling a wider extruded width. Draw zone distance is also relevant because it influences the polymeric orientation in the film itself. Polymer orientation influences many film properties including mechanical properties such as tensile strength and optical properties such as birefringence, and even adhesion. For these reasons, it is often desired to run an extrusion process at a minimum draw zone length, while avoiding risk of collision between the slot die and the quenching surface.
• the slot die can include a spindle for adjustment of the flexible die lip (or “flex lip”) or choker bar that has a tuned bending stiffness.
• flex lip or “flex lip”
• choker bar that has a tuned bending stiffness.
• having a controlled amount of deflection in the spindle can actually reduce the force required to bend an associated flexible die lip or choker bar while preserving sufficient stiffness to attain precise cross direction caliper control in the extruded web.
• the need for spindle deflection arises out of the significant spatial separation between the actuator and the adjustment mechanism.
• An actuator spindle having intermediate levels of stiffness was found to provide surprising technical efficiency advantages.
• a slot die assembly is provided.
• the slot die assembly comprises: 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 comprising 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 defining a lip length and a force application point defining a moment arm length, wherein a ratio of the moment arm length to the lip length is from 0.8 to 10.
• a slot die assembly comprising: a slot die body; an applicator slot extending across a width of the slot die body, wherein the applicator slot is in fluid communication with a fluid flow path through the slot die body and further wherein the slot die body comprises 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 a width of applicator slot, each actuator operatively coupled to the adjustment mechanism to provide a local adjustment of the cross-sectional height of the fluid flow path at its respective location, wherein each actuator is a linear actuator comprising a motor and a spindle coupled to the motor, and further wherein either (i) the spindle displays a bending stiffness of from 5 kN/m to 350 kN/m, or (ii) each actuator further comprises a bearing for coupling the spindle to the adjustment mechanism.
• a method of using an aforementioned slot die assembly comprising: positioning the slot die assembly adjacent to a nip defined between two counter-rotating rollers; extruding an extrudate through the applicator slot of the slot die assembly and into the nip, wherein a draw zone distance between the flexible die lip and the nip is from 15 percent to 100 percent of a radius of one or both of the two counter-rotating rollers.
• FIG. 1 is cross-sectional view showing a slot die assembly according to an exemplary embodiment.
• FIGS. 2-5 are fragmentary cross-sectional views showing slot dies according various exemplary embodiments.
• FIGS. 6 and 7 are perspective views showing exemplary flexible die lip configurations.
• FIG. 8 is a cross-sectional view showing a slot die assembly according to an alternative embodiment.
• FIGS. 9A and 9B are side views of spindles useful in an exemplary slot die assembly.
• FIG. 10 is a slot die assembly incorporating spindles having the general characteristics of the spindle of FIG. 9A.
• FIGS. 11 and 12 are fragmentary cross-sectional views showing exemplary couplings between components of slot die assemblies according to exemplary embodiments.
• FIG. 13 and 14 are perspective views showing, in an exaggerated manner, the cooperative deflection of slot die components in response to an actuator adjustment.
• the terms “preferred” and “preferably” refer to embodiments described herein that can afford certain benefits, 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 and is not intended to exclude other embodiments from the scope of the invention.
• FIG. 1 illustrates a slot die assembly according to an exemplary embodiment, the slot die assembly hereinafter referred to by the numeral 100.
• the assembly 100 includes a slot die body 102, which is in turn comprised of opposing upper die block 104 and lower die block 105.
• the upper and lower die blocks 104, 105 combine to form a fluid flow path 108 through the slot die body 102 that is in fluid communication with a comparatively narrower applicator slot 110.
• the slot die body 102 includes an adjustment mechanism, embodied here as a flexible die lip 106.
• the flexible die lip 106 is integral with the upper die block 104 as shown in FIG. 1 and represents one of the two opposing sides of the applicator slot 110.
• the flexible die lip 106 could also be provided as a separate component that is flexibly coupled to the slot die body 102.
• the machining of an integral flexible die lip is generally preferred, however, for improved strength, robustness, and precision.
• An actuator 120 is fastened to a mounting bracket 122 that is fixed relative to the upper die block 104. While not visible in FIG. 1, the actuator 120 is one of a plurality of actuators disposed along the width of slot die assembly 100.
• the actuator 120 is itself an assembly including a drive unit 124 and a cylindrical spindle 126 operatively 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 aperture in the upper die block 104 as shown and contacts the flexible die lip 106 at its distal end 128.
• the actuator 120 can apply pushing and/or pulling forces against the flexible die lip 106.
• the actuator 120 can adjust a height of the fluid flow path 108 at a particular location along the width of assembly 100 thereby providing a local adjustment of fluid flow through applicator slot 110.
• the actuator 120 represented here is generalized and operates based on any known principle, such as a differential screw mechanism or thermal expansion/contraction. While not shown, it can be advantageous to use a primary and secondary actuator in tandem to provide coarse and fine positional adjustments, respectively, as described in co-pending International Patent Application No. PCT/IB2021/053172 (Yapel et al.), filed on April 16, 2021.
• an extrudate such as a molten polymer enters the assembly 100 through the inlet 112, passes through the fluid flow path 108, is shaped by the applicator slot 110 and expelled through the outlet 114, and finally deposited onto a chilled roller.
• any of a number of downstream converting processes can then occur. Such processes can include, for example, stretching, coating, texturing, printing, cutting, rolling, and laminating steps.
• production release liners can be removed and release liners added, or one or more additional layers can be added.
• curing steps could also occur, such as exposure to e-beam, an oven, or an ultraviolet (UV) chamber.
• the controller can receive position inputs from both a motor and a sensor.
• the motor may be a stepper motor that provides 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 more precise position information to the controller than that provided by the motor.
• the controller can further provide instructions to the motor to drive the spindle 126 of the actuator 120 to a preselected position.
• the controller can monitor the position of the spindle 126 of the actuator 120 using the sensor while operating motor 210 in order to position the spindle 126 of the actuator 120 according to a preselected position.
• the controller can control a set of actuators 108, either simultaneously or sequentially.
• the actuator 120 can incorporate a zero-backlash coupler.
• the sensor is comprised of a linear voltage displacement transducer, digital scale, capacitance gauge, optical displacement gauge, laser displacement gauge, or combination thereof, enabling the spindle 126 to be adjusted to a precise position.
• a conventional differential bolt mechanism can have a backlash of more than 100 micrometers
• a zero-backlash coupler can significantly reduce this backlash to less than 10 micrometers, or even less than 5 micrometers, such as about 3 micrometers. While not examined here, further details of this actuator assembly are described in greater detail in, for example, co-pending International Patent Application No. PCT/IB2020/061685 (Yapel, et al.).
• the primary actuators could be driven by a mechanical, thermally- adjustable bolts, piezoelectric, hydraulic, or pneumatic device.
• the applicator slot can be adjusted by applying a pressing load or tensile load to a flexible die lip using a lever supported by a rotating shaft as a fulcrum, along with an operating rod displaced in an axial direction by the body of the slot die. Rotational force of the lever is converted into a force in the axial direction of the operating rod, and the force in the axial direction becomes a pressing load or a tensile load exerted on the flexible die lip.
• the lever directly can apply a force to the operating rod at the point of action of the lever.
• thermally adjustable bolts automatically regulate the applicator slot using a plurality of adjusting pins, coupled to respective thermoelements disposed on a flexible die lip.
• the thermoelements can be controllable by the controller to adjust the applicator slot through the action of mechanical force applied to the flexible die lip by the corresponding adjusting pin through expansion or contraction of the thermoelements.
• the actuation mechanism can include providing at least two adjusting pins and/or thermoelements that are simultaneously adjusted.
• Operation of the actuators in adjusting the applicator slot can be implemented semi- automatically or automatically through operator input and the use of computer hardware, software, firmware or any combination thereof.
• various examples of the techniques may be implemented within 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 circuitry, as well as any combinations of such components, embodied in controllers, user interfaces or other devices.
• DSPs digital signal processors
• ASICs application specific integrated circuits
• FPGAs field programmable gate arrays
• controller may generally refer to any of the foregoing logic circuitry, alone or in combination with other logic circuitry, or any other equivalent circuitry.
• the functionality ascribed 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, or the like.
• RAM random access memory
• ROM read-only memory
• NVRAM non-volatile random access memory
• EEPROM electrically erasable programmable read-only memory
• FLASH memory magnetic media, optical media, or the like.
• the methods and assemblies described can also be adapted for strip coating, a film slot die, a multilayer slot die, a hot melt extrusion coating die, a drop die, a rotary rod die, an adhesive slot die, a solvent coating slot die, a water-based coating die, a slot fed knife die, an extrusion replication die, a vacuum contact die, or other slot die.
• FIGS. 2-5 show various slot die assemblies in fragmentary view and collectively show the geometric effects of flexible die lip shape and actuator orientation.
• the upper die block, flexible die lip, and actuator spindle are shown in isolation, along with an inset plot showing certain mechanical parameters associated with the depicted configuration.
• FIG. 2 shows a slot die assembly 200 including an upper die block 204 having an integral flexible die lip 206 and a spindle 226 that extends through the upper die block 204 and has a distal end 228 mechanically coupled to the flexible die lip 206.
• the flexible die lip 206 has a generally elongated shape in cross-sectional view and is aligned approximately parallel to an acutely angled front face 230 of the upper die block 204.
• the flexible die lip 206 is connected to the rest of upper die block 204 by a relatively thin strip of material defining a hinge 232.
• the hinge 232 represents a pivot point for the flexible die lip 206 when pushing or pulling forces are applied by the spindle 226.
• the depicted integral flexible die lip 206 can be conveniently manufactured by cutting a groove 234 into a single block of metal to create the hinge 232.
• the bottom of the groove 234 can be radiused, as shown, to minimize stress concentrations when adjusting the flexible die lip 206.
• the bottom of the groove 234 could have a relatively flat configuration.
• a bottom surface 235 of the flexible die lip 206 along the applicator slot is characterized by a lip length L, defined as the distance between the outermost tip of the flexible die lip 206 and hinge point H.
• Hinge point H is defined as the point along the bottom surface 235 where the perpendicular cross-section of hinge 232 is thinnest.
• the hinge point H can be defined as the point along that cross-section furthest from the distal end of the flexible die lip 206.
• a moment arm length MA corresponding to the force application created by the spindle 226 against the flexible die lip 206.
• This moment arm length MA is defined as the shortest distance between the hinge point H and longitudinal axis 207 of the spindle 226 as shown.
• the line segment corresponding to the arm length MA is orthogonal to the longitudinal axis 207 of the spindle 226.
• the ratio of the moment arm length MA to the lip length L can be from 0.8 to 10, from 0.8 to 6.5, from 0.8 to 3.25, or in some embodiments, 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 benefit of having a higher MA/L ratios derive from increased mechanical advantage to adjust the flexible die lip 206 through force applied by linear translation of the spindle 226.
• the flexible die lip 206 can have any suitable lip length L that facilitates bringing the slot die assembly 200 in close proximity to the nip roller 236. In this case, it is reasonably approximated that the nip roller 236 is tangent to the parting line dividing 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 from 3 centimeters to 10 centimeters, from 3 centimeters to 9 centimeters, from 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.
• the parting line dividing the upper die block and lower die block can be vertically offset upwards or downwards. In other embodiments, the orientation angle of the parting line might be different than zero, where a horizontal parting line is defined as having zero degree orientation angle.
• the hinge 232 can also have any suitable thickness, where such thickness is measured perpendicular to the bottom surface 235.
• This thickness can be from 3 percent to 40 percent, from 4 percent to 30 percent, from 6 percent to 25 percent, or 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.
• the front-facing surface of the flexible die lip 206 can have an angled section 238 that is oriented at an acute tip angle a relative to the bottom surface 235.
• the tip angle a can be from 10 degrees to 90 degrees, from 10 degrees to 60 degrees, from 10 degrees to 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.
• the angled section 238 need not be contiguous with the distal tip of the flexible die lip 206, although it is preferably extends across at least 30 percent, at least 35 percent, or at least 40 percent of the lip length L. If desired, two or more contiguous angled sections, as described above, may be used to assist to help conform the flexible die lip 206 to the curvature of the nip roller 236.
• the angled section 238 allows the slot die assembly 200 to approach the nip roller 236 as closely as possible, assuming some margin of safety 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 extrudate draw down during an extrusion.
• the draw zone distance separating the flexible die lip 206 and the nip point N can be from 15 percent to 100 percent, from 20 percent to 90 percent, from 20 percent to 50 percent, or 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 a radius of one or both nip rollers.
• the longitudinal axis of the spindle 226 is oriented at a certain actuator angle 0 relative to the bottom surface 235.
• This actuator angle 0 can vary over a wide range, such as from 0 degrees to 90 degrees, from 0 degrees to 70 degrees, from 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.
• this actuator angle 0 can be adjusted as needed to accommodate different shapes for the upper die block 204 and provide leverage to rotate the flexible die lip 206 about the hinge 232.
• FIG. 2 further depicts an inset plot showing various combinations of lip length L and moment arm length MA superimposed on a two-dimensional force budget map.
• the shaded region represents combinations of L and MA that enable 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 Ibf, or 15.6 kilonewtons. From the inset, it can be shown that the depicted configuration of the slot die assembly 200 satisfies its force budget based on its combination of moment arm length MA and lip length L.
• the longer moment arm length MA can be attributable to its unique geometry, and especially its extended lip segment height S, as shown in FIG. 2.
• the lip segment height S which is measured perpendicular to the bottom surface 235, can be considerably longer than the lip length L.
• the lip segment height S can exceed the lip length L by a factor of 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 relative to the lip length L.
• FIG. 3 shows a slot die assembly 300 according to an alternative embodiment.
• the upper part of the assembly 300 like that of the prior assembly 200, includes an upper die block 304 having an integral flexible die lip 306, and a spindle 326 that extends through the upper die block 304 and engages a top portion of the flexible die lip 306.
• the assembly 300 differs from the prior embodiment in that the spindle 326 is oriented horizontally, resulting in an actuator angle 0 of approximately zero degrees.
• the slot die assembly 300 does not satisfy the force budget criteria represented by the shaded region in the inset of FIG. 3. This outcome can be attributed to the increase in lip length L relative to the last embodiment. Reducing the actuator angle 0 did have the effect of increasing the moment arm length MA, but the increase in lip length resulted in a net decrease in the MA/L ratio such that the force budget was exceeded.
• FIG. 4 shows still another slot die assembly 400 in analogous view, bearing some similarities to the assembly 300 but incorporating a somewhat taller flexible die lip 406.
• the actuator angle 0 was approximately zero degrees given the horizontal orientation of the spindle 426 through the upper die block 404.
• this configuration satisfies the force budget criterion.
• the significantly greater height of the flexible die lip 406 resulted in a greater MA/L ratio.
• FIG. 5 shows yet another variant represented by slot die assembly 500, characterized by an upper die block 504 and a spindle 526 extending horizontally through the upper die block 504 and a flexible die lip 506 having a height similar to that of the assemblies 200, 300 and having a flex lip length L similar to that of assembly 200.
• this configuration easily satisfies the requisite force budget, as shown in the inset plot.
• FIGS. 6 and 7 each show optional features that could be incorporated into a flexible die lip to increase further its flexibility. For clarity, these features are shown with the die slot assembly in perspective view.
• a slot die assembly 600 includes a flexible die lip 604 containing 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 a plurality of die lip segments 633 and have the effect of reducing the overall bending stiffness of the flexible die lip 604.
• the reduction in the stiffness of the flexible die lip 604 primarily results from a reduction in the cross-sectional area of the flexible die lip 604 in a side view (such as shown in FIGS. 1-5) within each notch 630.
• the side cross-sectional view of the flexible die lip 604 beyond the hinge 632 can be reduced by 1 percent to 100 percent, from 25 percent to 100 percent, from 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 side cross-sectional area of the flexible die lip 604 beyond the hinge 632 along an unnotched section.
• the notches 630 have a width W and a depth D that is consistent across the width of the flexible die lip 604. Inclusion of the notches 630 creates open area within the portion of the flexible die lip 604 extending beyond the hinge 632, as defined along a plane perpendicular to the fluid flow direction. Based on the embodiment depicted in FIG. 6, this open area can be approximated as follows:
• % oven area - Overall width of die lip x (D + NT)
• the open area can be from 1 percent to 90 percent, from 2 percent to 85 percent, from 3.5 percent to 80 percent, or in some embodiments, 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. It is also possible for either or both of the width W and depth D to vary, in which case the degree of flexibility can similarly vary across its width.
• the notches 630 can also be characterized by an associated notch thickness NT, shown in FIG. 6, which is defined as the distance between bottom surface 635 and the lowest point of a given notch 630.
• the hinge thickness HT also represented in FIG. 6, can be from 2 percent to 100 percent, 10 percent to 100 percent, from 20 percent to 100 percent, from 25 percent to 75 percent, or in some embodiments, 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 of the notch thickness NT.
• the depth D of the notches 630 can also be characterized relative to the depth of the groove 634 extending across the width of the slot die 600 and defining the flexible die lip.
• 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 is approximately equal to D+NT-HT in the depicted embodiment.
• Each notch can have a depth that is from 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.
• FIG. 7 shows another slot die assembly 700 comprised of 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 prior embodiment in that the notches 730 have a generally semi-circular profile, while the notches 630 have a generally rectilinear profile. While each notch 730 has a similar width W and depth D, the % open area associated with this notch shape is plainly smaller than in the prior embodiment, resulting in a comparatively stiffer flexible die lip 704.
• FIG. 8 is directed to a slot die assembly 800 that displays an alternative spindle coupling that can also function to extend the moment arm length achievable between an actuator spindle and a flexible die lip.
• the slot die assembly 800 includes an actuator 820 mounted to an upper die block 804 with an attached flexible die lip 806.
• the actuator 820 is outfitted with a spindle 826, which is driven linearly along its longitudinal axis 807.
• the actuator 820 and spindle 826 have an offset position relative to a flexible die lip 806 such that axis 807 does not intersect with the flexible die lip 806.
• a pair of bends 827 in the spindle 826 allow it to be securely engaged to the flexible die lip 806.
• the bends 827 are orthogonal bends.
• the spindle 826 may comprise one part or an assembly of two or more parts as shown to create the bends 827.
• the spindle can optionally be guided using a guide bushing 828.
• the engagement of the spindle to flexible lip 806 can be secured using a clip 829 (as shown), bolt, or other fastener.
• this configuration can provide a mechanical equivalent to extending the lip segment height of the flexible die lip 806.
• This use of an offset actuator/spindle can be particularly beneficial when retrofitting an existing slot die assembly or when the location or orientation of the actuator is otherwise constrained.
• FIG. 9A illustrates an exemplary spindle 926 suitable for use with various slot die assemblies previously described.
• the spindle 926 shown here in isolation, is comprised of multiple cylindrical sections connected to one other in series.
• the multiple segments are integral portions of a unitary structure. Included amongst these are an end section 950, flexure 952, and end section 954.
• the flexure 952 represents the longest segment of the spindle 926. It is also possible that essentially the entire length of the spindle 926 can be dimensioned to function as a flexure.
• the flexure 952 can extend along any portion of the overall 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 thereof.
• the spindle 926 additionally includes a fourth section 956 for engagement with a flexible die lip, as will be described later.
• the flexure 952 is a flexure that provides for both predictable and resilient deflection of the spindle 926.
• the flexure has a cross-section area that is smaller than that of either or both of the end sections 950, 954. Pin, blade, notch flexures, and combinations thereof, can all be advantageously employed.
• a flexure can be optimized to enable bending at a particular location, avoid interference, minimize the amount of force required. Since these flexures do not require relative sliding between surfaces, backlash and associated dead bands in the control scheme can be avoided or minimized.
• it can be possible to have various degrees of freedom — for example 1, 2, or more.
• the flexure 952 can be of any length relative to overall length of the spindle 926, depending on where bending is desired.
• the flexure 952 can have a diameter that is from 15 percent to 100 percent, from 30 percent to 100 percent, or from 40 percent to 100 percent, or in some embodiments, less than, equal to, or greater than 15 percent, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent that of one or both end sections 950, 954.
• flexure 952 having a cross-sectional area (defined along a plane normal to the longitudinal axis of the spindle) that is from 2 percent to 100 percent, from 9 percent to 99 percent, or from 16 percent to 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 that of one or both end sections 950, 954.
• the reduction in diameter within the flexure 952 can, for some cases, provide significant and unexpected technical benefits. It was discovered that there is an optimal range of bending stiffness associated with the spindle when adjusting the shape of an adjustment mechanism, such as a flexible die lip. This phenomenon is based on a problem presented by a metaphysically stiff spindle, which is only capable of a pure translation along its longitudinal axis. As can be visualized in FIGS. 2-5, such a spindle would tend to stretch the flexible die lip material instead of bending to allow rotation of the flexible die lip along its hinge as intended. The amount of force required to stretch the die lip material (typically steel) is excessive and can overwhelm the actuator.
• FIG. 9B shows an alternative spindle 926’ according to an alternative embodiment.
• the spindle 926’ in FIG. 9B is comprised of a plurality of segments — namely, a section 950’, flexure 952’, section 954’, and section 956’ corresponding to those of FIG. 9 A.
• the spindle 926’ has a much shorter flexure 952’, which localizes bending of the spindle 926’ over a relatively short portion of the overall length of the spindle 926’.
• Such a configuration could potentially be beneficial, for instance, where deflection of the spindle might be limited over certain regions by interference issues or other geometric constraints.
• the length of the flexures relative to the overall length of the spindle need not be particularly restricted. Based on the particulars of the application, the flexure 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 overall length of the spindle.
• FIG. 10 shows a simplified view of a slot die assembly 900 that includes an upper die block 904 and series of spindles 926, each having the configuration shown in FIG. 9A, to adjust the shape of a flexible die lip 906.
• the nearest spindle 926 is shown in cross-section within the die block 904, illustrating how a small degree of bending of the spindle is desirable to enable a slight rotation of the flexible dip lip 906 about its hinge 932.
• an optimal spindle was generally found to display a bending stiffness of from 5 kN/m to 350 kN/m, from 10 kN/m to 263 kN/m, from 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.
• Eulerian buckling is problematic because force is not efficiently transmitted through the column. When such buckling occurs, the forces imparted also tends to be unpredictable, making the overall control scheme less effective.
• FIGS. 11 and 12 show the coupling between actuator spindles and respective adjustment mechanisms in respective slot die subassemblies 1000, 1100.
• Adjustment mechanisms can be any flexible elongated structure capable of locally restricting fluid flow through an applicator slot within a given slot die assembly.
• FIG. 11 shows engagement between spindle 1026 and a flexible die lip 1006 within an upper die block 1004, while FIG. 12 shows engagement between a spindle 1126 and choker bar 1106 within an upper die block 1104.
• the choker bar 1106, which is also referred to as a restrictor bar differs from the flexible die lip 1006 in that it restricts flow at a location within the upper die block 1104 that is remote and upstream from the outlet of the slot die assembly.
• each enlarged end section 1050, 1150 of the spindle 1026, 1126 is mechanically coupled to the drive unit of its respective actuator by coupling 1060, 1160 and to its respective adjustment mechanism 1006, 1106 (e.g., flexible die lip or choker bar) through direct contact between these bodies by a shoulder bolt coupling, which is a rigid coupling.
• shoulder bolt couplings are created by the reduced-diameter treaded end sections 1056, 1156 on the opposite end of each spindle 1026, 1126.
• each spindle could use a ball joint coupling the spindle to the adjustment mechanism.
• each spindle could include a clevis joint for coupling the spindle to the adjustment mechanism.
• a proper bearing can also facilitate proper and efficient pivoting of the adjustment mechanism during an extrusion.
• a zero-backlash coupler 1060, 1160 could 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.).
• the spindles 1026, 1126 can be coupled to the drive unit of an actuator by a threaded connection. If a threaded connection is used, it can be beneficial for the spindle to have a minimum spindle diameter along any of its segments that is at least as large as its minor thread diameter to avoid unduly comprising the flexural strength of the spindle. Aspects of these connections can be further applicable to the sections 952, 956 in FIG. 9A and the coupling between the spindles 1026, 1126 to the flexible die lip 1006 or choker bar 1106 in FIGS. 11 and 12, respectively.
• FIG. 13 and 14 show how an exemplary series of spindles 1126 can both individually and collectively engage with a choker bar 1106.
• FIG. 13 shows the spindles 1126 and choker bar 1106 in a neutral position
• FIG. 14 shows these same components in an adjusted position.
• the adjusted configuration exaggerates the degree of deflection in the spindles 1126 and the choker bar 1106.
• a lone spindle 1126 actively presses against the choker bar 1106 as shown in FIG. 14
• a curvature is created in the choker bar 1106 such that neighboring spindles 1126 must cooperatively bend towards the single spindle 1126 as shown.
• flexibility in the spindles 1126 can greatly facilitate the efficient operation of the choker bar 1106 when making localized adjustments to fluid flow within a slot die assembly.
• the spindle segments and coupling attachments should be strong enough to withstand tensile and compression loads over its serviceable lifetime without cyclic failure.
• the spindle is made of a steel, such as a 4140 or 15-5PH steel, and has a tensile yield strength of at least 15.6 kN.
• the spindle could be fully metallic, fully non-metallic, or a combination of both.
• Non-metallic materials include composite materials such as fiber-reinforced composites. Where anisotropic properties are desired, embedded fibers within a composite can stiffen the spindle along some directions but not others.
• the spindle could be an assembly comprised of multiple segments in series, where the segments are made from different materials and/or geometries. Different materials could also be used in parallel — for example, in a core sheath configuration.
• an inline ceramic component can be provided as a thermal insulator to reduce heat transfer from the slot die body to the actuator drive unit.
• the rotation stiffness can be an issue.
• rotational stiffness should be sufficient to enable assembly and further the minimum spindle diameter should exceed the minimum torsional yield diameter of the spindle.

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• 2021
  • 2021-10-08 CN CN202180103045.XA patent/CN118055840A/zh active Pending
  • 2021-10-08 WO PCT/US2021/054108 patent/WO2023059333A1/en active Application Filing
  • 2021-10-08 MX MX2024004082A patent/MX2024004082A/es unknown
  • 2021-10-08 EP EP21801774.7A patent/EP4412814A1/en active Pending

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