Fiber-forming process

Method of manufacturing fiber

<p>10. . . Extrusion head</p><p>11. . . hopper</p><p>12. . . Extruder</p><p>13. . . Pump</p><p>15. . . Filament</p><p>16. . . Long machine</p><p>17. . . distance</p><p>18. . . gas</p><p>18a, b. . . Cold airflow</p><p>19. . . Collector</p><p>20. . . Fibrous body</p><p>twenty one. . . distance</p><p>twenty two. . . Drive roller</p><p>twenty three. . . Storage volume</p><p>twenty four. . . Processing tank</p><p>25. . . Horizontal length</p><p>27. . . Entrance wall</p><p>28. . . The main part</p><p>29. . . Recessed area</p><p>30. . . gap</p><p>31. . . catheter</p><p>32. . . Air knife (indicated by arrow)</p><p>33. . . Gap width</p><p>34. . . Exit opening</p><p>35. . . Inclined tube length</p><p>37. . . Assembly pulley</p><p>38. . . Bearing</p><p>39. . . Rod</p><p>41. . . Feed pipe</p><p>43a, b. . . Air column</p><p>44. . . Connecting rod</p><p>46. . . Second shot</p><p>47. . . Device board</p><p>48. . . Nut</p><p>50. . . arrow</p><p>52. . . Fiber end</p><p>53. . . Middle part of fiber</p><p>55,55'. . . High temperature melting point spike</p><p>56,56'. . . Low temperature melting point spike</p><p>57,57'. . . Higher cold-crystal spike</p><p>58,58'. . . Higher cold-crystal spike</p><p> 59. . . T _g point </p><p> 60. . . T _g point </p>

Figure 1 is an overall schematic diagram of the device of the present invention, which is used to form a non-woven fiber web.

Figure 2 is an enlarged side view of a processing tank that can be used in the present invention, with assembly elements not shown for the tank.

Fig. 3 is a partial top view of the processing tank shown in Fig. 2, showing the assembly and other assembly devices at the same time.

Figure 4 is a scanning electron micrograph of the mesh fabric prepared in Example 5.

Figures 5, 6, 7 and 7a are diagrams obtained by differential scanning calorimeters of various exemplary meshes of the present invention.

In many fiber manufacturing methods, the filament material extruded from the spinneret is guided through a processing tank, for example, the filament material is stretched, oriented, and/or reduced in diameter. This treatment or elongated groove is generally used in the spunbonding process (refer to US Patent No. 3,502,763; No. 3,692,618; No. 4,064,605; No. 4,217,387; No. 4,812,112; No. 4,820,459; No. 5,270,107; No. 5,292,239; No. 5,571,537 No. 5,648,041; and No. 5,688,468). But it can also be used in other methods, such as melt-blown method (refer to U.S. Patent Nos. 4,622,259 and 4,988,560), filament and yarn melt spinning method (refer to U.S. Patent No. 4,202,855), And the instantaneous spinning of plexifilamentary film-fibril materials.

The use of processing tanks imposes limitations on the method of integral fiber formation-these restrictions ensure that the fiber effectively traverses the tank without causing clogging. These restrictions include limiting the speed of the fiber as it moves through the groove; restricting the structure of the groove so that the fiber passes through the groove and re-threading when the fiber breaks; and restrictions on the degree of melting or liquid extruding the fiber into the groove.

At present, various efforts have been made to improve the treatment tank and reduce the limitation of the treatment tank on the fiber forming method. There is a study that the trough uses a wide-mouth entrance and a movable wall is used to form the trough. The wall moves into position after the polymer starts to flow, and can move away from the position if clogging occurs; refer to U.S. Patent Nos. 4,405,297 and No. 4,405,297 No. 4,340,563 and No. 4,627,811. Or U.S. Patent No. 6,136,245 proposes to start the fiber forming method slowly, using the treatment tank and the extrusion die with a distance greater than the required operating distance; the method is slowly accelerated, and the treatment tank moves to the spinning hole until the end Located in this operating position.

In different attempts to achieve uniform fiber velocity in the width direction of the elongated groove, the wall of the groove is made of flexible material, and a pressure sensor grid is used to initiate local changes in the geometric shape of the wall to try to pass the groove width Balance the pressure; refer to U.S. Patent No. 5,599,488. US Patent No. 4,300,876 describes a blower structure, which has only one wall that is bent to provide Coanda air flow, and conveys the extruded filaments inside.

All these studies still have important limitations on the fiber formation method using the treatment tank.

The present invention proposes a novel fiber formation method, which not only reduces many restrictions on the use of processing tanks, but also greatly expands the opportunities for fiber formation and fiber web formation. In this novel fiber forming method, the extruded filaments of the fiber forming material are oriented through a processing slot defined by two parallel walls, at least one of the two parallel walls can be moved to and away from the other wall instantaneously; Both walls can be moved closer to and away from each other instantaneously. The term "momentary movement" means that the movement is extremely rapid, so that the fiber formation process is substantially uninterrupted; for example, the process does not need to be stopped and restarted. For example, if the non-woven net structure is collected, the collection of the net can be continued without stopping the collector, and the uniform net cloth can be collected substantially.

The wall can be moved by various mobile devices. In a specific example, at least one movable wall is elastically biased against another wall; the biasing force is selected to establish a dynamic balance between the fluid pressure and the biasing force in the groove. Therefore, the wall can move away from the other wall due to the increase in the pressure in the tank, but when the original pressure in the tank is restored, the biasing force will quickly return to the equilibrium position. If the extruded filament material adheres or accumulates on the wall, causing the pressure in the tank to increase, at least one wall is quickly moved away from the other wall to release the accumulated extrudate, and the pressure quickly returns to the original pressure. And the movable wall returns to its original position. Although the operating parameters of the program may partially change temporarily, the process is not stopped, but the fibers are continuously formed and collected.

In a different embodiment of the present invention, the moving device is a swinger, which rapidly swings the wall between the original position defining the slot space and the second position away from another wall. The oscillation is carried out quickly, so the fiber formation process is basically not interrupted, and any extrudates accumulated in the processing tank and may block the tank are regularly released by pulling the wall apart.

Generally, the novel fiber forming method of the present invention includes a) extruding filaments of a fiber-forming material; b) guiding the filaments through a processing slot defined by two parallel walls, at least one of which can be moved instantaneously Move to and away from another wall and connect to a moving device to cause instantaneous movement while the filament passes; and c) Collect the processed filament.

The processing tank with the instantaneously movable wall makes a huge change in the fiber formation method. The methods and parameters that were in danger of blocking the processing tank are now available. The fiber speed, polymer flow rate, and degree of melting or liquefaction of the polymer as it enters the processing tank can be changed to produce an improved and essentially novel method. The present invention is particularly useful for improving the method of direct mesh formation, that is, the method in which the fiber-forming material is directly converted into a non-woven mesh structure without forming fibers individually, and then combined into a mesh in a different process.

The present invention also provides and uses a novel device. In short, it includes a) an extrusion head for extruding filaments of a fiber-forming material through a spinning nozzle located in the extrusion plate, b) a groove, Align to accept the extruded filaments so that they pass through the groove, the groove is defined by two parallel walls, at least one of which can be moved to and away from the other wall instantaneously; and c) a moving device for Moving the at least one wall, for example, elastically biasing the wall against another wall, or causing the wall to swing toward and away from the other wall. The wall moves towards and away from the other wall very easily, making it possible to move as described quickly or instantaneously. For example, the wall will move away from the other wall due to the increase in the pressure in the tank, but when the pressure in the tank returns to the original value At this time, the biasing device will quickly return to its original position; or the oscillating device will cause the wall to oscillate rapidly between the nearer and the farther interval.

The present invention also proposes novel products. As discussed in detail later in the present invention, the fiber collection from the fiber forming method of the present invention may include fibers that are interrupted along the length, for example, due to fiber breakage or entanglement. The important properties of the segment where the fiber is interrupted may be different from the main part of the fiber, such as morphological characteristics, such as showing different melting points, cold crystallization temperature, glass transition temperature, crystallization index (representing the proportion of fiber crystals), or Crystal type. These differences can be detected by differential scanning calorimeter or X-ray scattering. The fiber assembly system is a better result of the novel fiber forming method of the present invention; in addition, the novel mesh fabric itself provides better properties. One of the useful products of the present invention includes a binder in the form of a mesh. The fiber system includes fibers that are randomly interrupted in the length direction due to fibrous segments, the diameter is less than 300 microns, but the diameter is larger than the main part of the fiber.

Schematic description

Figure 1 is an overall schematic diagram of the device of the present invention, which is used to form a non-woven fiber web.

Figure 2 is an enlarged side view of a processing tank that can be used in the present invention, with assembly elements not shown for the tank.

Fig. 3 is a partial top view of the processing tank shown in Fig. 2, showing the assembly and other assembly devices at the same time.

Figure 4 is a scanning electron micrograph of the mesh fabric prepared in Example 5.

Figures 5, 6, 7 and 7a are diagrams obtained by differential scanning calorimeters of various exemplary meshes of the present invention.

Figure 1 shows an exemplary device for carrying out the invention. By introducing the fiber-forming material into the hopper 11, the material is melted in the extruder 12, and the melted material is pumped into the extrusion head 10 through the pump 13, and the fiber-forming material is put into the extruder Head 10-in this example device. Although solid polymer materials in the form of pellets or other particles are generally used to melt them into a liquid, pumpable state, other fiber-forming liquids such as polymer solutions can also be used.

The extrusion head 10 can be a conventional spinning plate or spinning assembly, and usually includes multiple spinning ports arranged in a regular pattern, such as a straight line. The filaments 15 of the fiber-forming liquid are extruded from the extrusion head and conveyed to the processing tank or the drawing machine 16. The distance 17 that the extruded filament 15 travels before reaching the length drawing machine 16 may vary depending on the exposure conditions. Generally, a quenching flow of air or other gas 18 is applied to the extruded filaments by conventional methods and devices to reduce the temperature of the extruded filaments 15. Or the air or other gas stream can be heated to help stretch the fibers. There can be one or more air (or other fluid) streams. For example, the first air stream 18a is blown laterally to the filament stream to remove unwanted gas materials or fumes released during extrusion; and the second step The cold air flow 18b achieves the main required temperature reduction effect. Depending on the method used or the desired form of the final product, the quench air can fully solidify the extruded filament 15 before it reaches the lengthening machine 16. In other cases, the extruded filaments are still in a soft or molten state during the drawing machine. Or no quenching flow is used; in this case, ambient air or other fluid between the extrusion head 10 and the lengthening machine 16 can be used for any changes to the extruded filaments before entering the lengthening machine Medium.

The filament 15 passes through the length drawing machine 16 discussed in detail below, and then leaves. As shown in Figure 1, it most often leaves and arrives at the collector 19, where it is collected as a fibrous body 20, which may or may not be bonded, and is in the form of a handleable mesh. The present invention is particularly useful as a direct-mesh fabric forming method, in which the fiber-forming polymer material is converted into a mesh fabric in a single basic direct operation, such as done in a spunbond method or a meltblown method. Or the fiber leaving the drawing machine can be in the form of monofilament, tow or yarn, which can be wound on a storage spool or further processed.

The collector 19 is usually porous, and a gas-unwinding device 14 can be arranged below the collector to help the fibers to be stored on the collector. The distance 21 between the exit of the length extractor and the collector can be changed to obtain different effects. The collection body 20 can be transported to other devices such as a calender, embossing machine, laminator, cutting machine, etc.; or it can be wound into a storage roll 23 through a driving drum 22. After passing through the treatment tank of the present invention, but before being assembled, the extruded filaments or fibers can be subjected to several additional treatment steps not illustrated in FIG. 1, such as further stretching, spraying, and the like.

Fig. 2 is an enlarged side view of an individual processing device, that is, the length-extracting machine 16, which includes two separate and movable halves or sides 16a and 16b, which define the processing tank 24 therebetween; the sides 16a and 16b The long surface forms the side wall of the groove. Figure 3 is a schematic top view of different scales, showing the individual length extension machine 16, its configuration and supporting structure. As shown in the upper view in Figure 3, the processing or drawing groove 24 is usually a long slit with a transverse length 25 (transverse to the path of the filament passing through the drawing machine), which can vary depending on the number of filaments to be processed .

Although there are two half-types or sides, the length extractor is operated as a single unit device, which is first discussed under its combined form. (The structures shown in FIGS. 2 and 3 are only representative, and various structures can be used.) The representative length drawing machine 16 includes an inclined entrance wall 27 that defines the entrance interval or the throat 24a of the drawing groove 24. The inlet wall 27 is preferably curved at the edge or surface 27a of the inlet so as to make the air inlet with the extruded filaments 15 smooth. The wall 27 is connected to the main body 28 and may have a recessed area 29 to establish a gap 30 between the main body 28 and the wall 27. Air can be introduced into the gap 30 through the duct 31 to generate an air knife (indicated by the arrow 32), which increases the speed of the filament passing through the elongator, and also has an additional quenching effect on the filament. The extractor body 28 is preferably bent at 28a, so that the air passage from the air knife 32 into the passage 24 is smooth. The angle (α) of the surface 28b of the length drawing machine body can be selected to determine the angle required by the air knife to drive the filaments through the length drawing machine. The air knife may not be close to the entrance of the groove, but is arranged inside the groove.

The longitudinal length of the elongation slot 24 passing through the elongation machine (the direction along the long axis 26 passing through the elongation slot is called the axial length) can have a uniform gap width (between two on the page of Figure 2). The horizontal distance between the sides of the length extractor, here referred to as the gap width 33). Or as illustrated in Figure 2, the gap width can vary along the length of the elongated groove. The elongation groove is preferably narrower inside the elongation machine; for example, as shown in Figure 2, the gap width 33 on the air knife is the narrowest width, and the elongation groove is closer along its length direction The width of the outlet opening 34 is greater, for example, at an angle β. The inside of the elongated groove 24 is reduced and then widened, producing a venturi effect, increasing the volume of air introduced into the groove, and increasing the speed of the filaments through the groove. In different specific examples, the elongation groove is defined by a straight line or flat wall; in this specific example, the interval between the walls can be a fixed value in its length, or the wall can be in the elongation groove The axial length is slightly expanded (preferably) or cohesive. In these cases, the wall defining the elongated trough is considered to be parallel because the deviation from the actual parallel is relatively small. As shown in FIG. 2, the wall defining the main part of the longitudinal length of the channel 24 may be in the form of a plate 36 which is separated from and connected to the main part 28.

The length of the elongated slot 24 can be changed to achieve different effects; especially, it can be changed to be used in the part between the air knife 32 and the outlet opening 34, which is sometimes referred to as the inclined tube length 35 herein. The angle between the trough wall and the shaft 26 can be wider as it approaches the outlet 34 to change the distribution of fibers on the collector; or structures such as deflection surfaces and Coanda curved surfaces can be used on the outlet. , And uneven wall length to achieve the required distribution or other fiber distribution. The gap width, the length of the inclined tube, the shape of the elongated groove, etc. are usually selected together with the material to be processed and the processing mode that is expected to achieve the desired effect. For example, a longer oblique tube length can be used to increase the crystallinity of the prepared fiber. The conditions are selected and can be greatly changed to process the extruded filaments into the required fiber form.

As shown in FIG. 3, the side edges 16 a and 16 b of the representative length drawing machine 16 are each carried by the assembly pulley 37 connected to the linear bearing 38 sliding on the rod 39. The bearing 38 is arranged to surround the rod in a radial direction through a device such as an axially extending ball bearing row, and has a low friction slip on the rod, so that the side edges 16a and 16b can be moved closer to and away from each other easily. The assembly pulley 37 is connected to the elongated body 28 and the housing 40, and the air from the feeding pipe 41 is distributed to the duct 31 and the air knife 32 through this location.

In this specific example for illustration, the air columns 43a and 43b are connected to the sides 16a and 16b of the length extractor via the connecting rod 44, and a clamping force is applied to press the sides 16a and 16b of the length extractor close to each other. The clamping force is selected together with other operating parameters to balance the pressure existing in the elongated groove 24. In other words, the clamping force and the force acting on the inside of the elongation slot are due to the gas pressure in the elongation machine being in a balanced or balanced state under better operating conditions, and the sides of the elongation machine are pressed open. The filament material can be extruded and pressed through the lengthening machine to gather into the final fiber. At the same time, the lengthening machine parts maintain their established equilibrium or stable position, and the lengthening groove or channel 24 maintains the established position. The width of the balance or steady-state gap.

During the operation of the individual devices shown in Figures 1-3, the movement of the side of the length extractor or the trough wall usually only occurs when there is system interference. This interference may occur when the filament breaks or becomes entangled with other filaments or fibers. This kind of rupture or entanglement is often accompanied by an increase in the pressure inside the elongated groove 24, for example, because the forward end of the filament from the extrusion head or the entanglement is enlarged, the groove 24 is partially blocked. This increased pressure is sufficient to cause the sides or trough walls 16a and 16b of the length extractor to move away from each other. During the movement of the trough wall, the end or entanglement of the input filament will pass through the lengthening machine. At this time, the pressure in the lengthening trough 24 returns to its steady-state value before the disturbance, and the air column 43 generates The clamping force makes the side of the length-extracting machine return to its steady-state position. Other disturbances that cause the pressure increase in the elongation groove include "injection", that is, when the extruded filament is interrupted, the spherical liquid mass of fiber-forming material falling from the exit of the extruder, or the accumulation of extruded filament material , May be glued and adhered to the wall of the elongated groove or pre-stored fiber-forming materials.

In fact, one or both of the sides 16a and 16b of the length-extracting machine are "floating", that is, they are not fixed in position by any structure, but are arranged so that they can be free in the lateral direction in the direction indicated by the arrow 50 in FIG. 1 And move easily. In the preferred configuration, in addition to friction and power, the only force acting on the side of the elongation machine is the biasing force exerted by the air column and the internal pressure developed in the elongation groove 24. In addition to the air column, other clamping devices can be used, such as springs, spring deformation, or cams; but the air column provides the required control and variability. In other devices that can be used in the present invention, one or both of the sides of the length extension machine are driven in an oscillating manner, for example, a servo motor, a vibration type or an ultrasonic drive device. The vibration rate can vary over a wide range, including, for example, at least 5,000 cycles per minute to 60,000 cycles per second. In another variation, the moving device adopts the negative air pressure form (for example, relative to the ambient air pressure) developed by the Venturi airflow in the processing tank.

In the specific example illustrated in FIGS. 1-3, the gap width 33 of the elongated groove 24 is related to the pressure existing in the groove, or is related to the flow rate and temperature of the fluid passing through the groove. The clamping force is consistent with the pressure in the elongated groove and varies depending on the gap width of the elongated groove; for a specific fluid flow rate, the narrower the gap width, the higher the pressure in the elongated groove, and the greater the clamping force needs to be . The lower clamping force produces a wider gap width. Mechanical stoppers, such as stop structures located on one or two sides 16a and 16b of the length extractor, can be used to determine the minimum or maximum gap to be maintained.

In a usable configuration, the air column 43a exerts a greater clamping force than the column 43b, for example, using an air column 43a with a diameter larger than the piston of the user of the air column 43b. When interference occurs during operation, a difference in force is established, and the side 16b of the length extractor becomes the easiest side to move. The applied force difference is approximately equal to and compensates for the frictional force preventing the bearing 38 from moving on the rod 39. The restricting device is connected to the larger air column 43a to restrict the lengthening side 16a from moving toward the lengthening machine side 16b. The one shown in Figure 3 illustrates the use of a double-bar type air column as the air column 43a with the restricting device. The second rod 46 is threaded and extends through the device plate 47. A nut 48 is worn. The nut can be adjusted. To adjust the position of the air column. By, for example, rotating the nut 48 to adjust the restricting device, the elongated groove 24 can be aligned with the extrusion head 10.

Because during the interference period of the fiber forming operation, the side edges 16a and 16b of the lengthening machine have the aforementioned instant separation and reclosing, the operating parameters of the fiber forming operation can be detailed. The conditions that originally made the method inoperable--for example, because the filaments that need to be shut down for re-threading are broken--can be used because of the method and device of the present invention; when the filaments are broken, the rethreading of the input filament ends is usually automatic To proceed. For example, higher speeds that cause frequent breakage of the filaments can be used. In the same way, a narrow gap width can be used-resulting in the air knife being more neutral, and giving greater external force and greater speed to the filaments passing through the length of the drawing machine. Or the filaments can be introduced into the elongation groove under higher melting conditions to better control the fiber properties, because the risk of the elongation groove being blocked is reduced. The lengthening machine can be moved closer to or away from the extrusion head to specifically control the temperature of the filament when it enters the lengthening groove.

Although the groove wall of the length extraction machine 16 is usually an integral structure, it can also be in the form of a combined body in which individual parts are assembled for the aforementioned floating movement. The individual parts including a wall are joined to each other through a sealing device to maintain the internal pressure in the processing tank 24. In different configurations, a flexible sheet of material such as rubber or plastic forms the wall of the processing tank 24, so that the tank can be locally deformed when the pressure changes locally (for example, due to the breakage of a single filament or a group of filaments). block). The flexible wall can be joined with a series or grid of biasing devices; sufficient biasing devices are used to respond to local deformation and bias the deformed part of the wall back to its undeformed position. Or a series or grid of oscillating devices can join the flexible wall to oscillate a local area of the wall.

As shown in the text, in the preferred embodiment of the processing tank illustrated in FIGS. 2 and 3, the end of the transverse length of the tank does not have side walls. The result is that the fibers passing through the groove will spread out to the outside of the groove when they approach the outlet of the groove. This kind of dispersion is required to widen the fiber body collected on the collector. In other specific examples, the processing tank does include a side wall, and a single side wall on one of the lateral ends of the tank is not connected to the sides 16a and 16b of the two tanks, because the connection with respect to the sides of the two tanks will be as discussed above Generally prevent the side from separating. Conversely, the side wall can be connected to the side of a groove and move when the side wall moves with changes in the pressure in the channel. In other specific examples, the side wall is divided, one part is connected to the side of one tank, and the other part is connected to the side of another tank. If it is desired to confine the processed fiber flow in the processing tank, It is better to overlap the side wall part.

Various fiber-forming materials can be used to make fibers using the method and device of the present invention. Organic polymer materials, or inorganic materials such as glass or ceramic materials can be used. Although the present invention can particularly use fiber-forming materials in molten form, other fiber-forming liquids such as solutions or suspensions can also be used. Any fiber-forming organic polymer material can be used, including polymers commonly used for fiber formation, such as polyethylene, polypropylene, polyethylene terephthalate, nylon, and urethane ester. Some polymers or materials that are more difficult to form into fibers by spunbonding or meltblown techniques can be used, including amorphous polymers such as cyclic olefins (which have high melt viscosity that limits their application in conventional direct extrusion techniques) , Block copolymers, styrene-based polymers, and adhesives (including pressure sensitive types and hot melt types). The specific polymers listed here are for illustration only, and various other polymers or fiber-forming materials can be used. Interestingly, the fiber forming method of the present invention using molten polymer is often performed at a temperature lower than that of the conventional direct extrusion technique, providing many advantages.

Fibers can also be formed from blends of materials, including materials blended with specific additives such as pigments or dyes. Two-component fibers can be prepared, such as core-sheath or side-by-side two-component fibers (here "two-component" includes fibers with more than two components). In addition, different fiber-forming materials can be extruded through different spinning nozzles of the extrusion head to prepare a mesh fabric including a mixture of fibers. In other specific examples of the present invention, other materials are introduced into the fiber stream prepared by the present invention before or during the fiber assembly to prepare a blended mesh. For example, other short fibers may be blended in the manner disclosed in U.S. Patent No. 4,118,531; or specific materials may be introduced and captured in the mesh in the manner disclosed in U.S. Patent No. 3,971,373; or U.S. Patent No. The microscopic mesh taught in No. 4,813,948 is blended into the mesh. Or, the fibers prepared by the present invention can be introduced into other fiber streams to prepare fiber blends.

The fiber forming method of the present invention can be controlled to achieve different effects and different mesh forms. For example, the method of the present invention can be controlled to control the curing of the filaments in the treatment tank (for example, move the treatment tank closer to or away from the extrusion head, or increase or decrease the volume or temperature of the quenching fluid). In some cases, at least a large portion of the extruded filaments of the fiber-forming material are assimilated before entering the processing tank. The curing changes the nature of the effect of impacting the hollowness of the filament in the processing tank, and the effect produced in the filament, and changes the properties of the collected mesh. In other methods of the present invention, the method is controlled so that at least most of the filaments are cured after entering the processing tank, and at this time they are cured in the tank or after leaving the tank. Sometimes, the method is controlled so that at least most of the filaments or fibers are solidified after being assembled, so the fibers are sufficiently melted so that when they are assembled, adhesion is formed at the intersection of the fibers.

By changing the method, various mesh properties can be obtained. For example, when the fiber-forming material solidifies substantially before it reaches the lengthening machine, the mesh is taller and has less or no inter-fiber adhesion. On the contrary, when the fiber-forming material is still in a molten state when it enters the lengthening machine, the fibers may still be soft when collected, so as to achieve the adhesion between the fibers.

The present invention has the following advantages. The filaments can be processed at a fast speed not known by the previous method of directly forming a mesh. The role of the processing tank in this method is the same as that of the typical role of the processing tank of the present invention, that is, in the extended fiber The silk material provides the main draw length. For example, polypropylene has never been known to be processed at an apparent filament speed of 8000 meters per minute, but the present invention can use this apparent speed (the term "apparent speed" is used because the speed is, for example, from the polymer flow rate). , Polymer density and average fiber diameter calculation). Faster apparent filament speeds have been achieved, such as 10,000 meters per minute, or even 14,000 or 18,000 meters per minute, and these speeds can be achieved using a variety of polymers. In addition, each spinning nozzle in the extrusion head can process a large volume of polymer, and these large volumes can be processed while moving the extruded filaments at a high speed. This combination produces a high productivity index-the polymer flux rate (for example, grams per spin per minute) multiplied by the superficial velocity of the extruded filaments (for example, meters per minute). The method of the present invention can be easily performed with a productivity index of 9000 or higher, even when producing filaments with an average diameter of 20 microns or less.

Various methods conventionally used as auxiliary methods of fiber formation methods can be combined with the filaments entering or leaving the lengthening machine, such as spraying finishing agents or other materials on the filaments, applying static charges to the filaments, and applying water. Fog and so on. In addition, various materials can be added to the assembled mesh, including adhesives, adhesives, finishing agents, and other meshes or films.

Although there is generally no reason to do this, the filaments can be blown out of the extrusion head by the main air flow in the usual manner used in conventional melt-blowing operations. The main airflow causes the initial elongation and stretching of the filament.

The diameter of the fiber prepared by the method of the present invention can vary greatly. Microfiber sizes (about 10 microns or less in diameter) can be obtained and provide several advantages; however, larger diameter fibers can also be prepared and used for specific applications; the fibers are often 20 microns or less in diameter. Fibers with a circular cross-section are most commonly prepared, but other cross-sectional shapes can also be used. Depending on the selected operating parameters, such as solidification in a self-melting state before entering the lengthening machine, the collected fibers can be continuous or substantially discontinuous. The orientation of the polymer chains in the fiber is affected by the choice of operating parameters, such as the degree of solidification of the filaments entering the lengthening machine, the speed and temperature of the airflow introduced into the lengthening machine by an air knife, and the lengthening machine channel The axial length, gap width and shape (because, for example, the shape affects the Venturi effect).

The invention achieves unique fibers and fiber properties, and unique fiber mesh cloth. For example, in some of the collected meshes, it is found that the fibers are broken, that is, broken, or are entangled with other fibers, or deformed by joining the walls of the processing tank. The fiber section at the break-the fiber section at the break point of the fiber, and the fiber section where entanglement or deformation occurs-here are called the interrupted fiber section, or simply, often referred to as the "fiber end" ": Among these, the fiber segment forms the end or the end of the unaffected length of the fiber, even if it is entangled or deformed, it often does not actually break or detach the fiber. The fiber ends have a fiber form (as opposed to the spherical shape sometimes obtained in meltblown or other previous methods), but the diameter is usually enlarged along the middle of the fiber: its diameter is usually less than 300 microns. The fiber ends--especially the broken ends--often have a curved or helical shape, causing the end to become entangled with itself or with other fibers. The fiber ends can be bonded side by side with other fibers, for example, by the spontaneous coalescence of the fiber material.

Figure 4 is a scanning electron micrograph of the polypropylene fiber web prepared in Example 5 at 150X magnification. As shown in the figure, the net includes fiber ends 52, which, although in the form of fibers, have a larger diameter than the middle or mid-section 53. The interrupted fiber sections or fiber ends are usually very small. The main part of the fiber is unaffected (in short, the main unaffected part of the fiber is referred to herein as the "middle section"). Moreover, the interruption is separated and in arbitrary positions, that is, it is not repeated regularly or occurs in a predetermined manner.

The fiber ends described are due to the unique characteristics of the fiber forming method of the present invention. Although there are breaks and interruptions in the formation of individual fibers, they are still continuous fibers. The fiber end may not occur in all the fabrics collected in the present invention, but it does occur at least in part of the operating program parameters that can be used (for example, if the extended filaments of the fiber-forming material reach high curing before entering the processing tank Degree, it may not happen). Individual fibers may be interrupted, for example, they may break when stretched in the processing tank, or they may become entangled with themselves or other fibers due to deflection from the processing tank wall or turbulence in the processing tank, and may still be melted: However, the fiber forming method of the present invention is still sustainable when it cannot withstand such interruption. The net cloth collected by the result amount includes a clearly detectable number of fiber ends or interrupted fiber sections, and there are fiber discontinuities in this area. Because the interruption generally occurs in or after the treatment tank, and the fiber is generally tied here to receive the tensile force, the fiber is under tension when it is broken, entangled or deformed. The break or entanglement usually leads to the interruption or release of tension, which causes the diameter of the fiber end to shrink and increase. Moreover, the broken end moves freely in the fluid flow in the treatment tank, causing the end to be wound into a spiral shape and entangled with other fibers, at least in some cases.

Analytical studies and comparisons of fiber ends and middle parts, such as parts 52 and 53 in Figure 4, generally show that there are different morphologies between the end and middle parts. The polymer chains in the end of the fiber are usually oriented, but not to the extent that the middle part of the fiber is oriented. This difference in orientation leads to differences in crystal ratios and crystal types or other morphological structures. And these differences will be reflected in the different nature.

Figures 5 and 6 respectively show the drawings obtained by differential scanning calorimetry (DSC) for representative fibers and fiber ends of the PET webs prepared in Examples 27 and 29. The solid line graph is the middle or middle part of the fiber, and the dashed line is the fiber end. The solid line graph shows the double melting point peaks, points 55 and 56 in Figure 5, and points 55' and 56' in Figure 6. The high temperature peaks 55 and 55' show the crystalline parts induced by chain extension or strain; while the other peaks 56 and 56' show the non-chain extension or low-order crystalline parts. (The term "peak" at this time refers to the part of the heating curve that causes a single process, such as the melting of a specific molecular part of the fiber, such as chain extension; sometimes the peaks are very close to each other, so that the peaks have a curve that defines another peak. The appearance of the shoulder, but it is still regarded as individual spikes because it represents the melting points of different molecular parts). The presence of chain-extended crystalline parts usually means that the fiber has superior properties, such as tensile strength, durability, and dimensional stability.

According to the comparison between the solid line and the dotted line, it is found that in the sample, the end of the fiber indicated by the dotted line has a lower melting point than the middle part of the fiber; this difference in melting point is caused by the difference in the crystal structure and orientation between the middle and the end . Moreover, in the sample, the fiber end has a higher cold-crystalline peak (individually points 57 and 57' in Figures 5 and 6; the crystallization of amorphous or semi-crystalline materials when heated is called cold crystallization), It shows that compared with the middle part, the end of the fiber contains more amorphous or semi-crystalline materials, and less high-order materials. The middle part has cold crystals represented by sharp peaks 58 and 58', but the temperature range is wider than the fiber end and different from it.

In the process of thermal analysis, it is often found that the glass transition temperature (T _g )difference. This difference is more clearly shown in Figures 7 and 7a, which are the middle (solid line) and end (dashed line) diagrams of another sample, that is, Example 16; Figure 7a shows the occurrence of T ₈ A magnified view of part of it. T in the middle ₈ , Point 59 is 9.74°C, and the T at the end _g , Point 60, is -4.56°C.

The middle and end of the fiber prepared by the present invention are usually evaluated by a properly calibrated differential scanning calorimeter (DSC). The middle and end of the fiber are different from each other, so the lowest resolution (0.1°C) of the test instrument is one or more A common thermal transformation, because there are differences in the mechanism of operation in the middle of the fiber and the internal operation of the fiber end. For example, during experimental observation, the difference in the thermal transformation is as follows: 1) The glass transition temperature T in the middle _g It can be slightly higher than the temperature at the end, and this feature can reduce the height when the crystal content or orientation in the middle of the fiber increases; 2) When observed, the starting temperature Tc of cold crystallization and the peak area measured during the cold crystallization process are in the fiber The middle part is lower than the fiber end, 3) the melting peak temperature T in the middle of the fiber _m Or higher than the terminal T _m , Or become a composite nature, showing multiple lowest endothermic points (ie, multiple melting peaks, indicating different melting points of different molecular parts, for example, their crystalline structure is completely different). One of the molecular parts of the middle part of the fiber is higher than The molecular part of the fiber ends melts at the temperature. The fiber ends and the middle of the fiber are most often different in one or more of the parameters glass transition temperature, cold crystallization temperature, and melting point, and the melting point differs by at least 0.5 or 1°C.

The net cloth with enlarged fiber ends has the advantage that the fiber ends can be softened more easily to increase its adhesion to the net cloth; and the spiral shape can increase the adhesion of the net cloth.

Example

The apparatus shown in Figure 1 was used to prepare fibers from several different polymers listed in Table 1. The specific parts and operating conditions of the device were changed as described below and are also listed in Table 1. Table 1 also includes a description of the properties of the prepared fibers.

Examples 1-22 and 42-43 were prepared from polypropylene; Examples 1-13 were prepared from polypropylene (Exxon 3505G) with a self-melt flow index (MFI) of 400, and Example 14 was prepared from polypropylene with an MFI of 30 (Fina 3868), Examples 15-22 were prepared from polypropylene (Fina 3860) with MFI of 70, and Examples 42-43 were prepared from polypropylene (Fina 3960) with MFI of 400. Polypropylene has a density of 0.91 g/ml.

Examples 23-32 and 44-46 were prepared from polyethylene terephthalate; Examples 23-26, 29-32 and 44 were prepared from PET (3M 651000) with an intrinsic viscosity (IV) of 0.61, Example 27 was prepared from PET with an IV of 0.36, Example 28 was prepared from PET with an IV of 0.9 (low molecular weight PET, which can be used as a high tenacity spinning fiber, prepared by Crystar 04003 provided by Dupont Polymers, and Example 45 and 46 is made from PETG (AA45-004 manufactured by Paxon Polymer Company, Baton Rouge, LA). The density of PET is 1.35, while PETG has a density of about 1.30.

Examples 33 and 41 were prepared from nylon 6 polymer (Ultramid PA6 B-3 of BASF) with an MFI of 130 and a density of 1.15. Example 34 was prepared from polystyrene (Crystal PS 3510 provided by Nova Chemicals) with an MFI of 15.5 and a density of 1.04. Example 35 was prepared from polyurethane (Morton PS-440-200) with an MFI of 37 and a density of 1.2. Example 36 was prepared from polyethylene (Dow 6806) with an MFI of 30 and a density of 0.95. Example 37 was prepared from a block copolymer (Shell Kraton G1657) having an MFI of 8 and a density of 0.9, containing 13% styrene and 87% ethylene butene copolymer.

Example 38 is a two-component core-skin fiber, with the polystyrene inner core (89 weight percent) used in Example 34 and the outer sheath of the copolymer used in Example 37 (11 weight percent). Example 39 is a two-component side-by-side fiber prepared from polyethylene (Exxact 4023 with an MFI of 30; 36 weight percent) and a pressure-sensitive adhesive 64 weight percent) prepared from polyethylene (Exxon Chemicals, Exxact 4023 with an MFI of 30; 36 weight percent). The adhesive contains 92 weight percent isooctyl acrylate, 4 weight percent styrene, and 4 weight percent acrylic terpolymer, and has an intrinsic viscosity of 0.63, which is provided by a Bonnot adhesive extruder.

In Example 40, each fiber is a single component, but fibers with two different polymer compositions-polyethylene used in Example 36 and polypropylene used in Examples 1-13. The extruding head has four rows of spinning nozzles, each row has 42 spinning nozzles; and the feed provided to the extrusion head is to provide different polymers of the two polymers in the adjacent spinning nozzles in a row to achieve ABA ...form.

In Example 47, the fiber mesh fabric was prepared by a single self-pressure-sensitive adhesive, which was prepared as a component of the two-component fiber in Example 39; a Bonnot adhesive extruder was used.

In Embodiments 42 and 43, the air column used to bias the side or wall of the movable length extractor is replaced with a spiral spring. In Example 42, the spring was deflected by 9.4 mm on each side during the operation of the example. The spring constant of the spring is 4.38 Newton/mm, so the clamping force applied by each spring is 41.1 Newton. In Embodiment 43, the spring deflects 2.95 mm on each side, the spring constant is 4.9 Newtons/mm, and the clamping force is 14.4 Newtons.

In Example 44, the extrusion head is a melt-blown extrusion plate with a diameter of 0.38 mm spinning orifice, and the center-to-center spacing is 1.02 mm. The spinning line is 101.6 mm long. The main melt blown air at a temperature of 370°C is introduced at a rate of 0.45 cubic meters per minute (CMM) through the 203 mm wide air day on each side of the spinneret row for the combined use of two air knives.

In Embodiment 47, a pneumatic rotating ball vibrator that oscillates at about 200 cycles per second is connected to each side or each wall of the movable length drawing machine; the air column is kept in place and aligned in the extrusion The elongated groove under the head is used to make the side of the elongated machine return to its original position when the pressure builds up to cause the side to separate. During the operation of the embodiment, compared with the time when the vibrator is not in operation, a smaller amount of pressure-sensitive adhesive is glued to the wall of the length extension machine when the vibrator is in operation. In Examples 7 and 37, the clamping force is zero, but the secondary air pressure developed by the Venturi airflow in the processing tank causes the movable side wall to return to its original position after interference.

In each embodiment, the polymer formed into fibers is heated to the temperature listed in Table 1 (in the extruder 12, it is close to the temperature measured at the outlet of the pump 13), where the polymer melts, and the melted polymer Provide to the extrusion spout at the rate listed in the table. The extrusion head usually has four rows of spinnerets, but the number of spinnerets, spinneret diameter, and the length-to-diameter ratio of spinnerets vary as listed in the table. In Examples 1-2, 5-7, 14-24, 27, 29-32, 34, and 36-40, each row has 42 spinning ports, so there are 168 spinning ports in total. In other embodiments-except for Example 44, each row has 21 spinning ports, so there are 84 spinning ports in total.

The parameters of the length extraction machine also change as listed in the table, including the air knife gap (dimension 30 in Figure 2); the length of the length extraction machine body angle (α in Figure 2); the temperature of the air passing through the length extraction machine; The rate of quenching air; the clamping pressure and the force applied to the length-extracting machine by the air column; the total volume of air passing through the length-extraction machine (in actual cubic meters per minute, or ACMM; the listed volume About half of it passes through each air knife 32); the gap between the top and bottom of the length extraction machine (dimensions 33 and 34 in Figure 2 respectively); the length of the oblique pipe of the length extraction machine (dimension 35 in Figure 2); The distance from the exit edge of the extrusion plate to the length extractor (dimension 17 in Figure 2); and the distance from the exit of the length extractor to the collector (dimension 21 in Figure 2). The air knife has a lateral length of about 120 mm (the slot length 25 direction in FIG. 3); and the elongated body 28 forming the recess for the air knife has a lateral length of about 152 mm. The lateral length of the wall 36 connected to the elongated body is changed: in Examples 1-5, 8-28, 33-35, and 37-47, the lateral length of the wall is 254 mm; Examples 6, 26, In 29-32 and 36, it is about 406 mm; and in Example 7, it is about 152 mm.

Record the properties of the collected fibers, including the average fiber diameter, digital image measurement obtained from a scanning electron microscope, using the image analysis program UTHSCSAIMAGE Tool for Windows, 1.28 of the University of Texas Health Science Center in San Antonin (copyright 1995-1997) Version. The image is from 500 to 1000 times magnification, depending on the fiber size.

The apparent filament velocity of the collected fiber is calculated from the following formula, V _Appearance =4M/pπd _f² , Where M is the polymer flow rate of each spinning port, g/m3, p is the polymer density, and d _f It is the average fiber diameter measured, in meters.

The toughness and elongation at break of the fiber are measured by placing the fiber in a paper frame under magnification and separating a single fiber. The fiber was tested for breaking strength by the method listed in ASTM D3822-90. Eight different fibers were used to determine the average breaking strength and average breaking elongation. The toughness is calculated from the average breaking strength, and the average denier of the fiber is calculated from the fiber diameter and the polymer density.

The cut sample from the prepared mesh includes the part containing the end of the fiber, that is, the fiber segment in which the break or entanglement occurs, and the part in the middle of the fiber, that is, the fiber is mainly unaffected. Partly, the sample was analyzed by differential scanning calorimetry, specifically Modulated DSC ^TM , Use the 2920 device provided by TA Instruments Inc, New Castle, DE, and use a heating rate of 4°C/min, the interference amplitude is positive or negative 0.636°C, and the period is 60 seconds. The melting point of both the end and the middle of the fiber was measured; the highest melting point peak on the DSC chart of the middle and the end of the fiber was recorded in Table 1.

Although the melting point difference between the middle and the end is not detected in some cases, other differences, such as the difference in glass transition temperature, are often found in these examples.

The samples at the middle and end of the fiber are also subjected to X-ray diffraction analysis. Using Bruker micro-diffraction meter (provided by Bruker AXS, Inc. Madison, WI), copper K _a HI-STAR 2D position sensor registration method for radiation and scattered radiation to collect data. The diffractometer device has a 300-micron collimator and a graphite-incident-beam monochromator. The X-ray generator includes a rotating anode surface that operates at 50 kilovolts and 100 mA settings and uses a copper target. After 60 minutes of collecting data using the transmission geometric pattern, the detector is concentrated at 0 degrees (2θ). Use BrukerGADDS data analysis software to calibrate the sample for detector sensitivity and spatial irregularity. The calibrated data are averaged in azimuth angles and converted into Xy pairs of scattering angle (2θ) and intensity values. Use the data analysis software ORIGIN to evaluate crystallinity ^TM (Provided by Microcal Software, Inc. Northhampton, MA) Perform the compact distribution map method.

The Gaussian spike shape model is used to describe the contribution of individual crystalline spikes and amorphous spikes. For some data sets, a single amorphous spike cannot adequately represent the overall amorphous scattering intensity. In these cases, an additional maximum width is used to fully represent the observed amorphous scattering intensity. The crystallinity index is calculated as the ratio of the crystalline peak area to the overall scattering peak area (crystalline plus amorphous) in the scattering angle range of 6 to -36 degrees (2θ). A value of one indicates 100 percent crystallinity, and a value of zero corresponds to a completely amorphous material. The values obtained are recorded in Table 1.

Five examples of mesh fabrics made from polypropylene, examples 1, 3, 13, 20 and 22. X-ray analysis shows that the middle and the ends are different in that the ends include β-crystalline forms, which are below 5.5 angstroms. Measured.

The stretched area ratio is determined by dividing the cross-sectional area of the spout of the extruded plate by the cross-sectional area of the finished fiber-calculated by the average fiber diameter. The productivity index is also calculated.

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Symbol description of main components

10. . . Extrusion head

11. . . hopper

12. . . Extruder

13. . . Pump

15. . . Filament

16. . . Long machine

17. . . distance

18. . . gas

18a, b. . . Cold airflow

19. . . Collector

20. . . Fibrous body

twenty one. . . distance

twenty two. . . Drive roller

twenty three. . . Storage volume

twenty four. . . Processing tank

25. . . Horizontal length

27. . . Entrance wall

28. . . The main part

29. . . Recessed area

30. . . gap

31. . . catheter

32. . . Air knife (indicated by arrow)

33. . . Gap width

34. . . Exit opening

35. . . Inclined tube length

37. . . Assembly pulley

38. . . Bearing

39. . . Rod

41. . . Feed pipe

43a, b. . . Air column

44. . . Connecting rod

46. . . Second shot

47. . . Device board

48. . . Nut

50. . . arrow

52. . . Fiber end

53. . . Middle part of fiber

55,55'. . . High temperature melting point spike

56,56'. . . Low temperature melting point spike

57,57'. . . Higher cold-crystal spike

58,58'. . . Higher cold-crystal spike

59. . . T _g point

60. . . T _g point