Dispensing device and method thereof

Abstract

An apparatus for dispensing a composition is provided, the apparatus comprising a barrel having an inlet and an outlet, an extrusion screw, and a drive mechanism operably coupled to the extrusion screw. The extrusion screw comprises a shaft having a shank end for connecting to the drive mechanism and a distal end opposite the shank end. A first helical flight extends around a first section of the shaft, and a second helical flight extends around a second section of the shaft. The second section is located distal to the first section, the first helical flight having a nominal outer radius smaller than the nominal outer radius of the second helical flight, and optionally the first helical flight having a pitch shorter than the pitch of the first helical flight.

Description

[Technical field]

[0001] SUMMARY OF THE DISPOSITION A dispenser for a polymer composition, particularly one capable of continuously dispensing the polymer composition, is provided along with an associated method and dispensing system. [Background technology]

[0002] Single screw dispensers are commonly used as a mechanism for delivering polymeric materials in continuous manufacturing and converting operations. These machines use a rotating screw received within a cylindrical barrel. The barrel typically includes an inlet located at the top of the barrel and an outlet located at the distal end of the barrel. The barrel may include one or more resistive heating elements along its length that may be precisely controlled in heating the contents of the barrel.

[0003] Typically, these dispensers accept and convert a feedstock, which is typically a polymer pellet or powder. The feedstock may include one or more thermoplastic resins that are solid at ambient temperature. After the feedstock is fed into the dispenser through an inlet, it is heated above its melting temperature by a combination of heat conduction along the heated walls of the barrel and the high pressure and friction generated by the screw rotation. Thus, the feedstock is metered, melted, mixed, and finally discharged from the distal end of the barrel through an outlet as it is conveyed along the length of the barrel by the rotating screw.

[0004] The screw can be operated by a motorized drive assembly and gearbox, and temperature controllers are connected to heating and / or cooling elements along one or more control zones along the barrel to maintain a desired temperature profile based on the properties of the composition being dispensed and the application at hand. Summary of the Invention

[0005] The use of a dispensing device to receive a filament composition provides many technical advantages. The use of filaments as a feedstock is particularly convenient when dispensing adhesive compositions, including pressure-sensitive adhesive compositions. In these applications, to simplify handling and feeding into the dispenser, the filaments can have a core-sheath form factor in which a tacky first component is contained within a non-tacky second component. The tacky and non-tacky components are melted and mixed in the dispenser, and ultimately discharged at the distal end of the dispenser as a homogenous composition.

[0006] Filaments are significantly different from pellets in the manner in which they are fed. Filaments are much larger than pellets and do not fit between inlet flights. The filament form factor presents several technical challenges, at least some of which are unexpected. The process requires that the filament be firmly gripped and consistently drawn into the dispenser. If this is not the case, inadequate throughput or the external motorized feeding mechanism may become clogged. Feed wheel clogs have been found to be a common malfunction in conventional filament dispensers. Even with consideration given to metering the filament into the dispenser, clogs can occur from time to time. From a customer standpoint, even intermittent clogs can be a significant barrier to adoption.

[0007] Another failure mode can be when the filament supply to the dispenser stops unexpectedly. This can happen, for example, if the screw does not adequately grip the filament. In some cases, the filament may even fall out of the inlet, requiring operator intervention to restore proper supply to the inlet.

[0008] Provided herein is a dispensing device that uses an extrusion screw with a reduced radius (i.e., screw flight height) and, optionally, a reduced pitch along the inlet section. The reduced diameter creates a properly sized gap between the screw and the barrel that optimally matches the filament diameter and can act to actively pinch soft to medium soft thermoplastic filaments as they are drawn into the dispenser. The reduced pitch at the inlet allows the rate at which the filament is drawn into the barrel to slow down and match the extrusion rate of the dispenser, thereby avoiding a rolling ball at the inlet that would impede further feeding.

[0009] A rotating ball condition occurs when material enters the inlet and is partially masticated but does not continue down the length of the screw. Instead, the material flows back out of the inlet, creating a ball-shaped mass of masticated material. This mass of material can act as a barrier between the screw and the incoming filament. New material stops feeding properly as the ball of material does not enter the inlet or the filament does not get drawn in. In some cases, the filament can fall out of the dispenser, causing feeding to stop even though the screw continues to consume material from the rotating ball.

[0010] The present dispensing device provided can reduce or eliminate the need for an external motorized feed mechanism, simplifying the dispensing system while increasing reliability and economy.

[0011] In a first aspect, an extrusion screw is provided comprising a shaft having a shank end for connecting to a drive mechanism and a distal end opposite the shank end, a first helical flight extending about a first section of the shaft, and a second helical flight extending about a second section of the shaft, the second section being distal to the first section, the first helical flight having a nominal outer radius that is smaller than a nominal outer radius of the second helical flight.

[0012] In a second aspect, an apparatus for dispensing a composition is provided, the apparatus comprising a barrel having an inlet and an outlet, an extruder screw, and a drive mechanism operably coupled to the shank end.

[0013] In a third aspect, there is provided a method of dispensing a composition using an apparatus, the method comprising providing the composition to an inlet of a barrel; rotating the extruder screw such that a first helical flight draws the composition into a first section of the barrel through an inlet and a second helical flight conveys the composition through a second section where the composition is melted and discharged through a dispensing outlet. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of a dispensing system according to one exemplary embodiment. [Diagram 2] 2 is a cross-sectional view of a dispensing device that can be used in the dispensing system of FIG. 1 in an exemplary embodiment. [Diagram 3] FIG. 3 is an elevated side view of a screw according to one embodiment used in the dispensing device of FIG. 2. [Figure 4] 13 is a photograph showing a side view of a screw according to an alternative embodiment.

[0015] Repeat use of reference characters in the specification and drawings is intended to represent the same or similar features or elements of the present disclosure. It is to be understood that those skilled in the art can 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. definition

[0016] "Ambient temperature" means a temperature of 22 degrees Celsius.

[0017] "Nominal" refers to the average.

[0018] "Non-tacky" refers to a material that passes a "self-adhesion test," in which the force required to peel the material from itself without fracturing the material is below a predetermined maximum threshold. The self-adhesion test is described in WO 2019 / 164678 (Nyaribo et al.) and is typically performed on a sample of the sheath material to determine whether the sheath is non-tacky. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] As used herein, the terms "preferred" and "preferably" refer to embodiments described herein that may offer certain advantages, under certain circumstances, although other embodiments may also be preferred, under the same or other circumstances.

[0020] 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.

[0021] As used in this specification and 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 followed by "a" or "the" may include one or more of the element and equivalents thereof known to those skilled in the art. Furthermore, 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.

[0022] 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, where such terms are 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 present invention.

[0023] 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.

[0024] Dispensing devices for continuously dispensing polymeric feedstocks in molten form are described herein along with systems and methods thereof. The compositions dispensed can have a Shore A hardness ranging from 10 to 70, and in some cases can have a Shore A hardness of less than 10. These compositions are optionally pressure sensitive adhesives. The dispensing devices can be made very compact.

[0025] 1 is a schematic diagram of an exemplary dispensing system, hereinafter broadly referred to by the numeral 100. Dispensing system 100 includes a dispensing device 102 mounted on the end of a movable arm 104. The movable arm 104 is fixed to a base 106, which may be part of a table or other platform. The movable arm 104 may have any number of joints 105 that allow the dispensing device 102 to translate and rotate with up to six degrees of freedom. The movable arm 104 may be manually or robotically controlled, enabling the dispensing device 102 to dispense an extruded composition with precision and repeatability over a wide range of positions relative to the base 106.

[0026] Optionally, and as shown, dispensing system 100 includes a filament adhesive 108 that can be continuously supplied into dispensing device 102, as shown in FIG. The filament adhesive 108 can be continuously unwound from a spool 114, as shown. The location of spool 114 relative to other components of dispensing system 100 is not critical and can be mounted wherever convenient. For example, spool 114 can be secured to base 106 or to a structure to which base 106 is typically mounted.

[0027] The dispensing device 102 of Figure 1 is shown dispensing a molten composition 110 in hot melt form onto a bonding surface of an exemplary substrate 112. The substrate 112 need not be limited and may be, for example, an industrial part for adhesive bonding into an assembly. Optionally, the substrate 112 may be mounted on a base 106 to provide a spatial reference point for positioning the dispensing device 102. This may be particularly useful in an automated process that uses a computer to control the position and orientation of the dispensing device 102.

[0028] Advantageously, the dispensing of the molten composition 110 can be automated or semi-automated, thus requiring little or no intervention by a human operator. For example, the molten composition 110 can be dispensed onto the substrate 112 according to instructions provided by a computer based on a predetermined pattern. The predetermined pattern can be two-dimensional (along a planar surface) or three-dimensional (along a non-planar surface). The predetermined pattern can be represented by a digitized model on a computer, allowing the predetermined pattern to be customized for any number of substrates.

[0029] Examples of applications in which dispensing system 100 or dispensing device 102 may be used include those described in International Patent Publication No. WO 2020 / 174396 (Napierala et al.).

[0030] The dispensing system 100 of FIG. 1 is particularly adapted to receive a filament adhesive. A filament adhesive is a sticky substance provided in a continuous, string-like configuration. The filament adhesive preferably has a uniform cross-sectional area. Advantageously, the filament adhesive can be continuously fed from a spool into a dispensing device, such as a dispensing device.

[0031] Particularly useful filament adhesives have a core-sheath filament configuration. Core-sheath filament materials have a configuration in which a first material (i.e., the core) is surrounded by a second material (i.e., the sheath). Preferably, the core and sheath are concentric and share a common longitudinal axis. The ends of the core need not be surrounded by the sheath. Advantageously, the non-sticky sheath prevents the filament adhesive 108 from sticking to itself, thereby allowing for convenient storage and handling of the filament adhesive 108 on the spool 114.

[0032] The diameter of the core-sheath filament is not particularly limited. Factors influencing the selection of the filament diameter include size constraints for the adhesive dispenser, the desired adhesive throughput, and the accuracy requirements for the application of the adhesive. The core-sheath filament can have an average diameter of 1 millimeter to 20 millimeters, 3 millimeters to 13 millimeters, 6 millimeters to 12 millimeters, or in some embodiments, an average diameter less than, equal to, or greater than 1 millimeter, 2 millimeters, 3 millimeters, 4 millimeters, 5 millimeters, 6 millimeters, 7 millimeters, 8 millimeters, 9 millimeters, 10 millimeters, 11 millimeters, 12 millimeters, 13 millimeters, 14 millimeters, 15 millimeters, 16 millimeters, 17 millimeters, 18 millimeters, 19 millimeters, or 20 millimeters. The filament adhesive 108 may be a stock item and may be provided in any composition and length suitable for the application.

[0033] The dispensing methods described herein have many potential technical advantages, including retention of adhesive properties after dispensing, low volatile organic compound (VOC) characteristics, avoidance of die cutting, design flexibility, enabling complex non-planar bonding patterns, printing on thin and / or delicate substrates, and printing on irregular and / or complex topologies.

[0034] Core-sheath filament adhesives according to the present disclosure can be made using any known method. In an exemplary embodiment, these filament adhesives are made by extruding molten polymer through a coaxial die. Technical details, options, and advantages of the above-mentioned core-sheath filament adhesives are described in International Patent Publication No. WO 2019 / 164678 (Nyaribo et al.).

[0035] It should be understood that the dispensing apparatus 102 provided need not be limited to the dispensing system 100 shown in Figure 1. In other embodiments, the dispensing apparatus 102 may have a fixed position and / or orientation. Additionally, the dispensing apparatus 102 can accept feedstocks other than filament adhesive, for example, the dispensing apparatus 102 can accept polymer pellets, flakes, or granules via a hopper or other feeding mechanism known to those skilled in the art.

[0036] Figure 2 shows the dispensing device 102 of Figure 1 in more detail. As shown, the dispensing device 102 includes a barrel 120 and a rotatable screw 122 received therein. A gearbox 124 and a motor 126 together provide a drive mechanism operatively coupled to the screw 122. The drive mechanism powers the rotation of the screw 122 within the barrel 120 when the device 102 is operated. The motor 126 advantageously has a high torque limit that stalls the motor above a set torque level to avoid damage to the screw 122 if there is a sticking during operation.

[0037] The barrel 120 contains one or more heating elements for heating a feedstock composition, such as a thermoplastic composition, above its melting temperature. Adjacent one end of the screw 122 is an inlet 128 where the filament adhesive 108 can enter the apparatus 102 and melt due to thermal contact with the heated barrel 120 and shear action imparted by rotation of the screw 122 within the barrel 120. At the opposite end of the screw 122, the barrel 120 has an outlet 129 aligned with the longitudinal axis 148 of the screw 122 (shown in FIG. 4 ) where the molten composition is continuously dispensed from the apparatus 102.

[0038] For effective operation, it is desirable for the screw 122 to closely mate with the inner surface of the barrel 120 while having sufficient clearance to allow the screw 122 to be inserted and removed from the barrel 120 by its rotation. During operation, this clearance accommodates a small amount of the molten composition, thereby providing a liquid seal for the barrel 120. As shown, the screw 122 is subdivided into several sections, including a first section 130 adjacent an inlet 128 of the barrel 120 and a second section 132 located distal to the first section 130 and extending toward an outlet 129 of the barrel 120. Optionally, and as shown, the screw 122 further includes a mixing section 133 connected to a distal end of the second section 132 and adjacent to the outlet 129.

[0039] Further details regarding the structure of the screw 122 are described below with reference to FIG. 3, which shows the screw 122 exploded from the remaining components of the device 102. This figure shows, in the order presented, the shank end 134 of the screw 122 for connection to the motor 126 and the gearbox 124, the first section 130 and the second section 132, and the mixing section 133. The first section 130 is comprised of a first shaft 140 having a first helical flight 142 disposed thereon. The second section 132 is comprised of a second shaft 144 having a second helical flight 146 disposed thereon. The first helical flight 142 and the second helical flight 146 may or may not be connected to each other. Furthermore, in some embodiments, there may be more than one helical flight in either or both of the first section 130 and the second section 132. If a larger pitch is desired, and if one wishes to keep the gap between flights to a minimum, a combination of multiple helical flights may be advantageous.

[0040] The first shaft 140 and the second shaft 144 are generally axially symmetric about a common longitudinal axis 148. The radius or circumference of the shafts 140, 144 may be approximately constant along some portions of the sections 130, 132 and generally increase over other portions of the sections 130, 132. In the embodiment shown in FIG. 3, the radius of the first shaft 140 is approximately constant along its length. In contrast, the radius of the second shaft 144 is approximately constant over a first portion of its length, increases to a significantly larger radius over a second portion of its length, and then is approximately constant at the larger radius over a third portion of its length. The tapered second shaft 144 may force the mixing and melting of the composition to increase pressure within the barrel to aid in expelling the melt from the spout.

[0041] Each of the first helical flight 142 and the second helical flight 146 has a substantially constant radius along the length of the respective section 130, 132. However, as shown, the first helical flight 142 has a radius that is significantly smaller than the radius of the second helical flight 146. The first helical flight 142 can have a nominal outer radius that is 50%-90%, 60%-85%, 70%-80% of the nominal outer radius of the second helical flight 146, or in some embodiments, can have a nominal outer radius that is less than, equal to, or greater than 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%. If the percentage difference is too low, the pinching phenomenon will not be observed. If the percentage difference is too high, the inlet flight will be too shallow, which may compromise screw strength and make it more susceptible to breakage.

[0042] Depending on the size of the screw 122, the absolute difference in radius between the first helical flight 142 and the second helical flight 146 may be between 0.5 millimeters and 19 millimeters, between 3 millimeters and 15 millimeters, between 5 millimeters and 12 millimeters, or in some embodiments may be less than, equal to, or greater than 0.5 millimeters, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 millimeters.

[0043] In some embodiments, the first helical flight 142 has a pitch that is shorter than the pitch of the second helical flight 146, where the pitch is defined as the center-to-center distance along a direction parallel to the longitudinal axis 148 between two successive revolutions of the same flight. The first helical flight 142 can have a pitch that is 10%-99%, 25%-75%, or 40%-60% of the pitch of the second helical flight 146, or in some embodiments, can have a pitch that is less than, equal to, or greater than 10%, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or 100%. If the inlet pitch is too small, the filament may be drawn in too slowly, limiting maximum throughput. If the inlet pitch is too large, the rest of the screw cannot keep up, causing an overfeed of filament and the formation of a rotating ball that can halt the feeding process.

[0044] The screw 122 need not be comprised solely of the first section 130 and the second section 132. For example, although not shown here, the screw 122 may further include a transition section connecting the first and second sections to one another. In an exemplary embodiment, the first and second sections each have a substantially constant flight radius, and the screw further includes a third section having a flight radius that is tapered to provide a smoother transition from the flights of the first section to the flights of the second section.

[0045] The first section 130 generally extends along most or all of the section of the screw 122 adjacent the inlet 128 of the barrel 120. In a preferred embodiment, the first section 130 extends somewhat beyond the inlet 128 so that it can function to sheathe the filament within the barrel. Optionally, the inlet 128 allows the filament to ride on the screw without being sheathed. The first section 130 is generally shorter than the second section 132 and can have a length of 2% to 25%, 5% to 20%, 9% to 15% of the total length of the screw 122, or in some embodiments, a length that is less than, equal to, or greater than 2%, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25% of the total length of the screw 122. The length of the first section 130 may be at least 80%, at least 90%, or at least 100% of the length of the inlet 128 .

[0046] The radius of the first helical flight 142 is generally sized such that a continuous feedstock, such as a filament composition, can be effectively gripped between the outer surface of the first helical flight 142 and the inner surface of the barrel 120 as the screw 122 rotates within the barrel 120. In the apparatus 102, the clearance or gap between these opposing surfaces is preferably smaller than the diameter of the filament composition being fed into the inlet 128 of the barrel 120. This gap allows the filament composition to be actively drawn into the inlet 128 at a consistent rate as the screw 122 rotates during operation of the apparatus 102.

[0047] The appropriate sizing of the first helical flight 142 generally depends on the dimensions of the feedstock. It may be advantageous for the gap between the first helical flight 142 and the barrel 120 to be between 5% and 100%, between 10% and 75%, between 20% and 50%, or in some embodiments, less than, equal to, or greater than 5%, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% of the filament diameter.

[0048] Control of the rate at which the filament composition is drawn into the barrel 120 by the screw 122 can be achieved by optimizing the pitch of the first helical flight 142. A primary advantage of the described configuration of the screw 122 and the device 102, more generally, is that it allows for the filament composition to be actively drawn into the device 102 at a highly controlled rate while minimizing or eliminating the risk of accidental severing or losing grip of the filament composition. Because the device 102 is self-metering, no external motorized feed system is required. It has also been found that this configuration significantly reduces the rate at which the filament adhesive becomes clogged near the inlet 128 as a result of a mismatch between the feed rate and the consumption rate.

[0049] FIG. 4 shows a screw 222 according to an embodiment similar to that shown in FIG. 1, except that the screw 222 uses another Maddock-type mixing section 233. As with the previously described mixing section 133, this component is intended to completely melt the composition before it is discharged from the dispenser. However, it is understood that any other type of mixing section may be used alternatively or in combination. For example, the mixing section may be based on a screw section with multiple cylindrical posts or high-density flights, with cross-cuts (as found in the Saxton mixer) or any of a variety of known post patterns, including those used in the Pineapple Mixer. Optionally, posts or pins may be placed on the interior sidewall of the barrel to aid in the mixing process. There may be cross-cuts in the flights of the screw to avoid interference. Other aspects of the screw 222 are essentially similar to those already shown and described with respect to the screw 122, and will not be repeated here.

[0050] Other variations are possible. For example, the screw can have a hollow configuration as described in co-pending U.S. Provisional Patent Application No. 62 / 994,633 (Chastek et al.). The screw can also be modified to include gripping lugs formed on the flights of the first section as described in WO 2020 / 174394 (Napierala et al.). Various coatings, including metallic coatings composed of steel, chromium, or aluminum, are known in the art and can be placed on the screw surface as known in the art to provide crack and corrosion resistance. EXAMPLES

[0051] Objects and advantages of the present disclosure are further illustrated by the following non-limiting examples, but the specific materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit the disclosure.

[0052] Unless otherwise stated, all parts, percentages, ratios, etc. in the examples and elsewhere in this specification are by weight. [Table 1]

[0053] Test Method: Throughput measurement test The dispenser temperature was set to 200°C and allowed to equilibrate for at least 10 minutes. The dispenser was oriented with the inlet orifice facing down and unobstructed, and the filament was fed from a barrel located below the dispenser. Filament feeding was initiated by manually inserting the filament into the inlet orifice while the screw was rotating at 80 revolutions per minute. Dispensing was carried out for at least 1 minute to ensure that the barrel was filled with adhesive. The molten adhesive exiting the distal end of the dispenser was collected in an aluminum pan and weighed. Samples were collected for 30 seconds. Between collected samples, the dispenser was stopped for 30 seconds. A total of five samples were collected consecutively, with the screw stopped for 30 seconds between collections, and the throughput was reported in kilograms per hour (kg / h). The standard deviation among the five throughput samples was also reported in kilograms per hour. To ensure that the throughput rate of the dispenser was adequately reproducible, the standard deviation should be less than 10% of the throughput.

[0054] Feed grip test The dispenser temperature was set to 200°C and allowed to equilibrate for at least 10 minutes. The dispenser was oriented so that the inlet orifice was facing down and unobstructed, and 1.45 meters above the weight holding platform. A 2 meter long piece of filament was prepared by tying a 10 cm radius loop in the filament at one end. A 1 kilogram weight was attached to this loop and placed on the weight holding platform. With the screw rotating at 80 RPM, filament feeding was started by manually pushing the knot-free, weight-free end of the filament into the inlet orifice. Once enough filament had been fed into the dispenser to the point where all slack was removed between the 1 kilogram weight and the dispenser, a timer was started. Feeding continued and was monitored for 60 seconds. A pass condition was deemed if the dispenser was successful in continuing to draw filament into the inlet while maintaining a throughput rate of at least 50%. A pass condition may involve lifting the 1 kilogram weight off the weight holding platform or the filament may stretch. It is understood that a pass condition may consist of a combination of both lifting the weight and stretching the filament, with the exact result depending on the durometer and diameter of the filament. On the other hand, if the filament falls out of the dispenser within 60 seconds, it is a fail. A fail may be caused by the screw being unable to grip the filament or the formation of a rolling ball. In some cases, the screw grips the filament too weakly to remove the filament slack, but the tackiness of the filament may prevent it from falling off. In this situation, the feeding of the filament was manually assisted until the 1 kilogram weight was 30 centimeters above the weight holding platform with no filament slack. The 1 kilogram weight was slowly released to tension the filament and the test was started. No external feeding or gripping mechanisms were used during the feed grip test. The test was performed in triplicate, and three consecutive passing values ​​were required to deem a screw design to have desirable feed grip strength.

[0055] Preparatory Example 1 (PE1): Preparation of Polymodal Asymmetric Block Copolymer (PASBC) Multimodal asymmetric star block copolymers ("PASBC") were prepared according to Example 1 of U.S. Pat. No. 5,393,787 (Nestegard et al.), the subject matter of which is incorporated herein by reference in its entirety. The polymers had number average molecular weights of about 4,000 and about 21,500 Daltons for the two endblocks, 127,000-147,000 Daltons for the arms, and about 1,100,000 Daltons for the star, as measured by SEC (size exclusion chromatography) calibrated with polystyrene standards. The polystyrene content was 9.5-11.5 weight percent. The mole percentage of the high molecular weight arms was estimated to be about 30%.

[0056] Preparation of core-sheath filaments The composition of the filaments (weight percent material amounts) is shown in Table 2. Further description of the techniques and processes for assembling the filament structures is included in PCT Patent Application Publication No. 2019 / 1646798 (Nyaribo et al.). The core adhesive raw materials were compounded in a 30 mm Steer twin screw dispenser operating at 212°C. A Zenith gear pump was used to force the molten adhesive through a heated hose having an inner diameter of 25 mm and a length of 2.4 meters. The molten adhesive was dispensed through the central orifice of a coaxial die into a 30°C water bath and manually wound onto a fiber drum. Core-sheath filaments were made with a diameter of 8 mm ± 1 mm. The sheath material was fed using a 30 mm single screw dispenser set at 204°C and dispensed through the outer ring orifice of the coaxial die. [Table 2]

[0057] Example 1 and Comparative Example 1 (EX1 and CE1) Adhesive dispensing The core-sheath filaments assembled with PE1 were fed directly from the fiber drum into the dispensing head. The dispensing head contained either a screw (EX1) or a comparative screw (CE1), both manufactured as further defined below. Throughput measurement tests were performed with both the EX1 and CE1 screws loaded into the dispensing head. The results of the throughput measurement tests are recorded in Table 3.

[0058] Dispensers with EX1 and CE1 were also subjected to feed grip testing, the results of which are reported in Table 3. [Table 3]

[0059] EX1 screw manufacturing The 262 millimeter (mm) long and 9.5 mm radius screw as depicted in Figures 3 and 4 was machined in a computer numerical controlled (CNC) four-axis vertical end mill. The machining process was performed on a solid cylinder of aluminum 6061 with a radius of 9.5 mm. A single channel was created with an end mill cutter with a radius of 1.55 mm (0.0625 inch) for the first section 130 and the Maddock mixer, and a radius of 4.75 mm (0.0187 inch) for the second section 132 to define the flights, defining the channel width. The pitch (i.e., the apex-to-apex distance between the flights) of the first section was 6 mm, and the pitch of the second section was 12.5 mm. The screw shank was 35 mm long and had a radius of 6 mm. The first section extended from 45 mm to 77 mm from the shank end and had an outer radius (height of the flights) of 7 mm. The screw root radius of the first section (radius minus flight height) was 4.45 mm. The second section had an outer flight radius of 9.5 mm. The root radius of the second section was 4.45 mm from 77 mm to 140 mm, measured from the shank end, and increased to 6.7 mm from 140 mm to 190 mm. Between 190 mm and 232 mm, the root radius of the second section was 6.7 mm. The spiral Maddock mixer was located from 232 to 257 mm. The pitch was 100 mm. The flights were defined by a single 3.1 mm channel, forming a root radius of 6.7 mm. As expected for the spiral Maddock mixer design, the openings alternated between the shank and the distal end, creating eight equally spaced parallel spiral channels. The Maddock mixer had an outer flight radius of 9 mm.

[0060] CE1 Comparative Screw Production For comparison, a comparative screw was manufactured, which had a similar design to EX1, with the main difference being that it did not have the flights of the first section 130, i.e. it was made in a conventional manner with only the second section 132.

[0061] The screw was machined in a computer numerically controlled (CNC) four-axis vertical end mill with a length of 262 mm and a radius of 9.5 mm. The machining process was performed on a solid cylinder of aluminum 6061 with a radius of 9.5 mm. A single channel was created with an end mill cutter with a radius of 1.55 mm (0.0625 inch) for the Maddock mixer and a radius of 4.75 mm (0.0187 inch) for the second section 132 to define the flights, defining the channel width. The pitch of the second section 132 is 12.5 mm. The screw shank was 35 mm long with a radius of 6 mm. The second section 132 extended from 45 mm to 232 mm from the shank end. The second section 132 had an outer radius of flight of 9.5 mm. The root radius of the second section 132 was 4.45 mm from 45 mm to 107 mm, measured from the shank end, and increased to 6.7 mm from 107 mm to 170 mm. Between 170 mm and 232 mm, the root radius of the second section 132 remained at 6.7 mm. The spiral Maddock mixer was located from 232 to 257 mm. The pitch was 100 mm. The flights were defined by a single 3.1 mm channel, forming a root radius of 6.7. As expected for the spiral Maddock mixer design, the openings alternated between the shank and the distal end, creating eight equally spaced parallel spiral channels. The Maddock mixer had an out-of-flight radius of 9 mm.

[0062] Barrel manufacturing An aluminum block (63.5 mm x 38.1 x 76.2 mm) representing the shank end of the barrel was used for the inlet section of the barrel. A 9.5 mm radius hole was cut through the central longest axis to establish the main barrel axis. The block was threaded to receive a schedule 80 aluminum 3 / 4 inch NPT pipe nipple. The NPT pipe nipple was 152.4 mm long along the main barrel axis. A second aluminum block (38.1 mm x 38.1 mm x 25 mm) was fabricated to represent the distal end of the barrel and also had a 9.5 mm radius hole cut through the central shortest axis. The shortest axis was threaded to connect to the other end of the NPT pipe nipple. The distal end of the second block had a 1.6 mm radius orifice to act as the outlet nozzle. Additional machining was performed to drill the main barrel axis to an inside diameter of 9.6 mm. An inlet orifice was cut directly above the main barrel axis of block 1. A 4.8 mm radius end mill cutter was used to create a channel 9.5 mm wide and 19.1 mm long. The channel began 12.5 mm to 31.6 mm from the distal end of the barrel. The inlet orifice had straight sides and no bevel. The long axis of the inlet orifice was centered directly above the main barrel axis.

[0063] The barrel was attached to a 200W AC servo motor and 25:1 planetary gearbox combination using two aluminum plates (9.5mm x 38.1mm x 100mm). The extruder screw shank was connected to the gearbox shaft using a motor coupler. A resistance band heater and thermocouple in combination with a PID temperature controller was used to bring the dispenser to 200°C.

[0064] Manufacturing of the dispensing system components: Other dispensing system components were assembled according to the manufacturing techniques described in co-pending US Provisional Patent Application No. 62 / 810,248 (Napierala et al.).

[0065] All documents, patent documents or patent applications cited in the above patent application on Letters Patent are incorporated herein by reference in their entirety in a consistent manner. 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.

Claims

1. An extrusion screw comprising: a shaft having a shank end for connecting to a drive mechanism and a distal end opposite the shank end; a first helical flight extending around a first section of the extrusion screw; a second helical flight extending around a second section of the extrusion screw, the second section being distal to the first section, the first helical flight having a nominal outer radius smaller than a nominal outer radius of the second helical flight. Extrusion screw.

2. 2. The extrusion screw of claim 1, wherein the first helical flight has a nominal outer radius that is 50% to 90% of the nominal outer radius of the second helical flight.

3. 3. The extrusion screw of claim 1 or 2, wherein the difference in radius between the first and second helical flights is between 1 millimeter and 19 millimeters.

4. 4. The extrusion screw according to claim 1, wherein the first helical flight has a pitch that is shorter than the pitch of the first helical flight.

5. 5. The extrusion screw of claim 4, wherein the first helical flight has a pitch that is 10% to 99% of the pitch of the second helical flight.

6. 6. The extrusion screw of claim 1, wherein each of the first and second sections has a substantially constant flight radius, the shaft further comprising a third section and a third helical flight on the third section having a flight radius that is tapered to provide a transition from the helical flight of the first section to the second helical flight.

7. 7. The extrusion screw according to any one of claims 1 to 6, wherein the first section has a length of between 2% and 25% of the total length of the extrusion screw.

8. a barrel having an inlet and an outlet; The extrusion screw according to any one of claims 1 to 7, the drive mechanism operably coupled to the shank end; 16. An apparatus for dispensing a composition comprising:

9. 9. A method of dispensing a composition using the device of claim 8, comprising the steps of: providing the composition to the inlet of the barrel; rotating the extrusion screw such that the first helical flight draws the composition through the inlet into the first section of the barrel and the second helical flight conveys the composition through the second section where the composition is melted and discharged through the outlet; A method comprising:

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