MXPA98010103A - System for preparing glass fiber pellets - Google Patents

Abstract

A system for making densified glass fiber pellets from chopped segments of multi-filament glass strand is described. The densifiedpellets may be advantageously produced by hydrating chopped glass strands (24) and then pelletizing them by tumbling in a rotary drum (41), and densifying the resulting pellets by tumbling in a rotating zig-zag or undulating tube (42) for a period of time sufficient to increase their density but insufficient to degrade the fibers to a point where composite articles formed from such pellets have lower tensile or impact strengths than comparable composite articles formed from unpelletized strand segments.

Description

SYSTEM FOR PREPARING GRANULES OF GLASS FIBER DESCRIPTION Background and field of the invention The present invention relates to the manufacture of glass fiber granules. In particular, the present invention provides an apparatus for making densified fiberglass granules by combining multiple segments of a finely chopped multi-fiber glass yarn. The granules provide a convenient form for the storage and handling of finely cut glass fibers used as reinforcing materials in composite structures. Usually, finely cut glass fibers are used as reinforcing materials in thermoplastic articles. Typically, such fibers are formed by drawing fused glass into filaments through a nozzle or plate with holes and applying a gum or glue composition containing lubricants, coupling agents and film-forming binder resins to the filaments, joining the filaments into yarns, by thinly cutting the fiber strands into segments of the desired length, and drying the rubber composition. These segments of finely cut yarn are subsequently mixed with a polymeric resin, and the mixture is fed to an injection or compression molding machine to be formed into glass reinforced plastic articles. Typically, the finely cut yarns are mixed with granules of a thermoplastic polymer, and the mixture is fed to an extrusion machine where the resin is melted, the integrity of the glass fiber yarns is destroyed and the fibers are dispersed through of the molten resin, and the fiber / resin dispersion is formed into granules. These granules are then fed to the molding machine and formed into molded articles which have a virtually homogeneous dispersion of the glass fibers therethrough. Unfortunately, however, finely cut glass fibers made by such processes are typically bulky and do not flow well. Accordingly, such fibers are difficult to handle and have been problematic in automated processing equipment. An attempt to solve this problem has been to compact the finely cut yarns into denser rod configuration lumps or granules to improve the flowability of the finely cut yarns, and allow the use of automated equipment to weigh and transport the glass fibers to mix with thermoplastic resins.

Such a process is described in U.S. Patent No. 4,840,755, in which finely cut and wet yarns are rolled, preferably on a vibrating conveyor, to round the yarns and compact them into denser cylindrical granules. While such methods and apparatus tend to provide granules of cylindrical configuration more dense and exhibiting better fluidity, they are undesirably limited in certain aspects. For example, the size of the granule and the content of the fiber are generally limited by the size and number of fibers in the finely cut yarn, in which the process is designed to prevent multiple segments of finely cut yarn from adhering together to form granules that contain more fibers than those that are present in a single thread cut finely. Accordingly, to obtain granules having a suitable bulk density and a sufficient diameter to length ratio to exhibit good fluidity, the yarn from which the segments are thinly cut should normally be formed from a large number of filaments. However, increasing the number of filaments required to be formed and combined into a single yarn undesirably complicates the forming operation. In an effort to overcome these limitations, U.S. Patent No. 5,578,535 discloses glass fiber granules that are from about 20 to 30 percent denser than the individual glass strands from which they were made, and from approximately 5 to 15 times larger in diameter. These granules are prepared by hydrating segments of yarn cut to a sufficient level to avoid filamentization but insufficient to cause the yarn segments to agglomerate in a lump, and mixing segments of yarn hydrated for a sufficient time to form granules. Proper mixing includes a process that will keep the fibers moving on themselves, such as drumming, stirring, churning, mixing, stirring and intermixing. Although the described granules can be made by such various mixing processes, it has been found that many such processes are too inefficient to be used commercially, or can not be adequately controlled to produce a uniform granule product that provides the composite article. resulting with strength characteristics comparable to those made from finely-ground, ungranulated yarn fibers. For example, the use of a modified disc granulator frequently produces an excessive residence time of the granules formed within the mixer, which produces a degradation of the granules due to the abrasive nature of the glass fiber granules that are rubbed between yes. Such degradation of the granules finally reduces the strength characteristics of the molded articles made with them. Therefore, there is a need for an effective granulation process that controllably provides a uniform product of glass fiber granules that imparts strength characteristics equal to finely chopped non-granulated yarn in molded composite articles. Such a need is met by means of the present invention which is summarized and described in detail below.

An object of the present invention is to provide an efficient process and apparatus for the formation of granules which controllably provide virtually uniform fiberglass granules having a shape and density which provide good fluidity. Another object is to produce granules that can be used in the manufacture of a glass fiber reinforced composite article without appreciable loss in strength characteristics compared to comparable products made with finely grained non-granulated yarns. Such objects are achieved by means of a process in which fiberglass yarns comprised of a multiplicity of virtually continuous glass fibers are finely cut into segments of the desired length and hydrated to a sufficient moisture content to cause the segments of yarn are joined in granules when spinning on a rotating drum (tamboreación). After this, the yarn segments are subjected to a first tumbling action to distribute the hydrating solution substantially uniformly over the yarn segments and cause the yarn segments to combine to form pellets. The density of the granules is then increased by compacting the granules by means of a second tumbling action. The process of the invention can advantageously employ an apparatus comprising: (a) means for cutting the glass fiber yarns to form segments of finely cut yarn; (b) means for transporting the finely cut wire segments to a first drumming means; (c) means for applying a moisturizing solution to the segments of finely cut yarn; (d) first drumming means for imparting a drumming action to the finely cut yarn segments to disperse the moisturizing solution and cause the finely cut yarn segments to align and merge into granules; (e) means for transporting the granules to second drumming means; (f) second drumming means for tumbling the granules to compact them and increase their density; (g) means for transporting the densified granules to a dryer; and (h) drying means adapted to receive and dry the granules. Other objects, features, and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings in which similar reference numerals refer to similar elements.

Brief description of the drawings Figure la is an illustration of a rotary or rotary drum granulator system useful in the invention; and Figure Ib is a front view of a preferred embodiment of a granulation densification system useful in the invention. Figure 2 is a front view of a preferred embodiment of a mixing apparatus for performing the steps of granulation and densification. Figure 3 is a diagram of a preferred apparatus of the invention for forming fibers and processing them into densified granules. Figure 4 (a) is a longitudinal cross-sectional view of a baffle that can be used in the rotating drum of the invention; Figure 4 (b) is an end view of the baffle shown in Figure 4 (a) taken along line A-A; Figure 4 (c) is an end view of the baffle shown in Figure 4 (a) taken along line B-B; Figure 4 (d) is a longitudinal cross-sectional view of a rotating drum of the invention with the baffle of Figure 4 (a) installed therein; and Figure 4 (e) is an isometric section view of the rotating drum and deflector of Figure 4 (d) installed. Figure 5 (a) is a side edge view of an alternative baffle that can be used in the rotating drum of the invention; Figure 5 (b) is a radial cross-sectional view of a rotating drum of the invention with the baffle of Figure 5 (a) installed therein; and Figure 5 (c) is an isometric section view of the rotating drum and deflector of Figure 5 (b) installed.Detailed description and preferred modalities In the process of the invention, a yarn of substantially continuous glass fibers is formed by conventional techniques such as drawing of molten glass through a heated nozzle to form a multitude of virtually continuous glass fibers and collecting the fibers in a thread. In the present invention any convenient apparatus for producing such fibers and collecting them in a yarn can be used.

Suitable fibers are fibers having a diameter from about 3 microns to about 90 microns, and suitable threads contain from about 50 fibers to about 2000 fibers. Preferably, the yarns formed in the process of the invention contain from about 400 fibers to about 800 fibers having a diameter from about 3 microns to about 23 microns. After the fibers are formed, and prior to collection in a yarn, the fibers can be covered with a convenient aqueous gum composition, such as one known in the medium. Preferably, the rubber composition consists essentially of water, one or more coupling agents, and optionally, one or more lubricants and pH adjusters. Suitable coupling agents include organofunctional silanes, such as those sold by Witco under the following commercial designations: A-154 Methyl-trichlorosilane MeSiCl3 A-163 Methyl-trimethoxy-silane MeSi (OCH3) 3 A-189? -Mercaptopropyltrimethoxysilane HS (CH2) 3Si (OCH3) 3 A-143? -Coropropyltrimethoxy- silane C1 (CH2) 3 Si (OMe) 3 A-151 Vinyl-triethoxy-silane CH2 = CHSi (OC2H5) 3 A-172 Vinyl-tris- (2-methoxyethoxy) silane CH2 = CHSi (OCH2CH2OCH3) 3 A-188 Vinyl -triacetoxy-silane CH2 = CHSi (OOCCH3) 3 A-1100? - (Amino) -propyl-triethoxy-silane H2N (CH2) 3Si (OC2H5) 3 A-1120 n- (Trimethoxy-silyl-propyl-ethylene H2N (CH2) 2NH (CH2) 3Si (OCH3) 3 - diamine) A-174? - (Methacryloxy) propyl-triethoxy-silane (OCH3) 3 A-187? -Glycidoxy-propyltrimethoxy CH2-CH-CH20 (CH2) 3Si (OCH3) 3 -sylan O Preferred coupling agents for use in the invention are 3-aminopropyltriethoxy-silane and gamma-glycidoxypropyltrimethoxysilane sold commercially by Osi de Witco under the trade designations A-1100 and A-187, respectively. Preferably, organofunctional silanes are used in an amount from about 0.1 percent to about 1.0 percent of the gum composition. Any suitable lubricant may be used in the gum composition, such as water-soluble ethylene glycol stearates, ethylene glycol oleates, ethoxylated fatty amines, glycerin, emulsified mineral oil, and organopolysiloxane emulsions. Preferred lubricants include: polyethylene glycol monostearate; polyethylene glycol monooleate; butoxyethyl stearate; Stearic ethanolamide (Lubsize K12, sold by Alpha / Owens Corning); a lubricant described in U.S. Patent No. 3,597,265, the disclosure of which is incorporated herein by reference (sold by Emery Corp. under the trade designation of Emerlube 6760); and a mixture of 30% white oil, 30% polyethylene glycol monopelargonate 400, 30% polyoxyethylene (3) myristic alcohol, and 10% ethoxylated alkyl amine (Parastat S-2) (Emerlube 7607, sold by Emery Corp.). Preferably, the lubricant is present in the gum composition in an amount from about 0.05 percent to about 0.10 percent by weight. Additionally, small amounts of weak acids, such as acetic acid, can be added to the gum composition to lower the pH of the composition from about 3.5 to about 8. Preferably, the acids are present in the composition in an amount from about 0.15 per cent. one hundred to about 0.3 weight percent, and the pH of the composition is from about 6 to about 8. Rubber compositions suitable for the invention include: 1. A-1100 organofunctional silane (58% active content) 0.5% Deionized water Balance A-1100 organofunctional silane (58% active content) 0.5% Lubesize K12 (Alpha / Owens Corning) 0.07% Glacial acetic acid up to pH 6 to 8 Deionized water Balance A-100 organofunctional silane (58% active content) 0.5% Emerlube 7607 (Emery Corp.) 0.1% Deionized water Balance A-100 organofunctional silane (58% active content) 0.5% Monostearate polyethylene glycol 400 0.1% Deionized water Balance A-100 organofunctional silane (58% active content) 0.5% Emerlube 6760U (Emery Co.) 0.01% Deionized water Balance A 100 organofunctional silane (58% active content) 0.38% A-187 organofunctional silane 0.12% Deionized water Balance The aqueous gum composition can be applied any conventional means, including a kiss roller and spray applicator. Preferably, the rubber composition is applied by passing the fibers on top of a kiss roller applicator. Moreover, the gum is preferably applied to the fibers in an amount sufficient to provide the fibers with a moisture content of from about 8 percent to about 13 percent, more preferably about 11% (unless otherwise indicated, all percentages here are by weight). Once formed, the continuous yarns are finely cut into lengths from about one-eighth of an inch (3.175 mm) to one-quarter inch (31.75 mm). Any convenient means known in the medium for finely cutting fiberglass in such lengths can be used in the process. After this, the moisture content of the finely cut yarn segments is adjusted to a convenient level for granule formation when the finely cut yarn segments are forced to move on themselves, and the finely cut yarn segments are introduced. in first drumming or granulating means which imparts such movement to the yarn segments. While the moisture content of the yarn segments can be adjusted before they are introduced into the granulator, it is preferred that the glass fibers are hydrated to a moisture content suitable for granule formation in the granulator. Preferably, the moisture content of the fibers in the granulator is from about 12 percent to about 16 percent, more preferably from about 13 percent to about 14 percent. If the moisture content is too low, the yarns tend not to combine into granules and will remain in a typical yarn formation. Conversely, if the moisture content is too high, the yarns tend to agglomerate or bunch up or form granules of too large a diameter and of an irregular non-cylindrical shape. Additionally, it is preferred that the moisturizing fluid also contains a binder or second gum composition. The hydration fluid can therefore contain suitable components, such as those typically included in glass fiber gum compositions, for example, film formers, wetting agents, antistatic agents, and additional coupling agents and lubricants. By applying this second rubber composition in the granulator, an application efficiency of 100% can be achieved. Moreover, the application of this gum outside the fiber formation environment allows the inclusion of materials that are not desirable in the formation process due to toxicity, cleanliness, odor, high cost, or sensitivity to cutting.

Examples of suitable binder compositions that can be incorporated in the hydration fluid include the following compositions (unless otherwise indicated, all percentages are by weight): 1. EpiRez 3544 - epoxy aqueous dispersion at 53% resin solids (Shell Chem. Co). 12.58% Witco 290H - aqueous polyurethane dispersion at 62% resin solids (Witco Co.) 0.99% A-l 100 organofimcional silane to 58% active solids (Witco Co.) 0.10% Deionized Water Rest 2. The gum compositions described in U.S. Patent No. 5,236,982, its contents are incorporated herein by reference. 3. Terephthalic Acid 3.21% Ammonium hydroxide at 28% active content 3.89% GenFlo 559 - aqueous polyurethane dispersion at 50% resin solids 4.06% (General Tire and Rubber Co.) ChemCor 43N40 aqueous polypropylene dispersion at 40% resin solids 8.12% (Chemical Corporation of America) Deionized Water Rest . Z6020 - organofunctional silane (Dow Corning Corp.) 2.65% Pluronic 10R5 - block copolymer of ethylene oxide and propylene oxide 1.8% (BASF Corp.) Deionized water Rest 5. Z6020 .89% Maldene 286 - maleic anhydride copolymer and butadiene 13.3% (Lindau Chemicals, Inc.) Ammonium hydroxide at 28% active content 1.6% Deionized water Rest The above are examples of formulations of binders or adhesives that have been evaluated and found useful in the process of the invention. The person skilled in the art can select other suitable binder formulations or other components that can be used. In fact, an advantage of the invention is that almost all the aqueous gum formulations used in the glass fiber technology would be useful as binders for spraying onto the fibers in the drumming apparatus according to the process of the invention. To ensure a good coverage of the fiber strands, it is preferred that the rubber be applied to the yarn segments when they enter the granulator and before they begin to join in granules. If the gum is applied at other positions within the granulator, there is a tendency for the granules to be formed before the finely cut yarns are completely covered with the rubber composition, which produces granules formed of fibers that are not completely covered with rubber. the composition of rubber.

When such granules are used in the manufacture of fiber reinforced plastic articles, the uncoated fibers lack the interface coating required to provide good reinforcing characteristics, and the resulting article will have less optimal properties. Preferably, the granulator is provided with a spray nozzle located adjacent to the yarn segment inlet to spray the rubber composition onto the yarn segments when they enter the granulator. The granulator used in the present invention can be any apparatus capable of providing drumming to the yarn segments such that: (1) they are covered substantially uniformly with the aqueous binder / gum composition and (2) multiple segments of yarn cut finely align and join in granules of the desired size. Such a drumming apparatus must have a sufficient average residence time to ensure that the yarn segments are covered practically with the hydration fluid and the granules are formed, but insufficient for the granules to be damaged or degraded by abrasion by rubbing together. Preferably, the residence time in the drumming apparatus is from about 1 minute to about 10 minutes. More preferably, the residence time in the drumming apparatus is from about 1 minute to about 3 minutes. A preferred granulator is a rotating drum, such as the drum 41 shown in FIG. The granulator 41 receives finely cut wire segments 24 which can be prepared using a fiber forming nozzle 11, rubber applicator 13, collecting clamp 14 and the fine cutting device 20. In a preferred embodiment, the apparatus is provided with a system to monitor and / or adjust various parameters, which can be controlled automatically by means of a control board 70 such as an Alien Bradley PLC-5/40 PLC system. If desired, the moisture content of the incoming yarn segments can be measured 24 using convenient means 71. A yarn weigher 72 can be provided and located suitably, for example, before, after, or in association with the yarn carrier 30. A similar weigher can be used to monitor the weight of the granules on the conveyor 31. Measurement of the binder and water can be achieved by controlling the pumps 33 and 34. The drum 41 is adapted to house a spray head to apply the moisturizing solution to the wire segments 24 as they enter the drum. Preferably, an external air mixing nozzle 47 is mounted in the drum near its inlet for the mixing of an aqueous binder composition that can be provided by means of a Masterflex 33 pump from a supply of binder 35, with any additional water that it can be provided by means of a Masterflex pump 34 from a water supply 36, required to reach the moisture content of the finely cut yarn segments at the desired level and apply the mixture to the finely cut yarn segments in the drum. The binder composition and water are combined in a fluid stream through the orifice of the nozzle, which is then struck with two jets of air placed 180 degrees apart and at an angle of 60 degrees to the direction of flow of the stream. The air is fed as clean, dry air 52. This effectively creates a mist that is pushed over the surface of the yarn segments that move in the drum. The rotation of the drum causes the wet yarn segments to rotate on themselves while the surface tension created by the rubber or wet coating causes the yarn segments to contact each other over a significant portion of their length to align with each other and join in a cylindrical configuration granule. By such action, any single fines or fibers created during the shredding operation are recombined with and incorporated into the formation of the granules to virtually eliminate individual fine fibers from the resulting granules. Preferably, the drum is tilted slightly so that the end of the drum from which the pellets exit is lower than the end into which they enter to ensure that the pellets formed in the drum do not remain in the drum for an excessive period. In a preferred embodiment, the drum is tilted such that its axis of rotation is at an angle (q) from about 1 degree to about 3 degrees with respect to the horizontal. The angle of inclination can be adjusted manually or automatically using suitable adjustment means 43a. Mainly the moisture content of the yarn segments controls the size of the granules formed in the drum. If the moisture content is maintained at a high level, a greater number of yarn segments will be joined in a granule and the granule will thus be of larger diameter. Conversely, if the humidity is maintained at a lower level, few yarn segments will merge into a granule and in this way the granule will have a smaller diameter. Preferably the granules formed by the process of the invention have a diameter from about 20% to about 65% of their length. Such granules are typically formed by combining from about 70 yarn segments to about 175 yarn segments, each containing from about 500 individual filaments per yarn to about 2000 individual filaments per yarn. The size of the granules is also affected by the production capacity of the drum. If the production capacity of the drum is high, the yarn segments will have a shorter residence time in the drum, which will cause the formation of smaller granules because the application of fluid is not dispersed in the yarns and threads they will not join in a granule. Nevertheless, because the granules that form are in the drum for a shorter period of time, less compaction of the granules occurs. Although some compaction of the granules formed in the granulator invariably occurs, it is typically insufficient to increase the granule density to a level that provides an optimum level of fluidity. For this reason, after their formation in the granulator 41, the granules are fed in second drumming means or densifier 42 where the granules are further compacted and densified. Any low-impact drumming apparatus which compacts the granules without degrading them by abrasion or otherwise damaging them can be used. Preferably, the densifier has a less vigorous drumming action, smoother than that of the granulator to minimize such degradation of the granules. In addition, the densifier preferably has an average residence time of less than about 5 minutes to ensure that the granules do not degrade by abrasion. More preferably, the average residence time in the densifier is from about 1 minute to about 2 minutes. A preferred densifier is a zigzag tube adapted to be rotated about its longitudinal axis (x) as shown in Figure lb. The zigzag tube 42 is rotatably mounted in a frame 43 by means of pivoting sheave assemblies 44 and rotatably driven by means of the thrust motor 45. As the tube is rotated, the pellets in the tube are gently rotated in the drum by the Rotation of the tube when they are thrown 13 through the tube by gravity. As with the above rotating drum, the zigzag tube densifier is preferably inclined at a slight angle to ensure that the granules flow through the apparatus without excessive residence times. Preferably the longitudinal axis of the tube is at an angle from about 1 degree to about 3 degrees with respect to the horizontal, with the inlet of the tube 39 being higher than the outlet of the tube 49.

Although granule formation and densification can occur in separate apparatuses, such as a separate rotating drum 41 and a rotating zigzag tube 42 with a conveyor 31 therebetween as shown in FIG. 1a, the process of the present invention can be carried out using other suitable means. For example, granule formation and densification may occur in separate regions or drumming zones within a single apparatus. A preferred example of such an apparatus is a "Zig-Zag" blender commercially sold by Patterson Kelly which is illustrated in Figure 2 and in 40 in Figure 3. The blender 40 comprises a rotating drum 41 connected to a zigzag tube 42 at one end of the drum. Both the drum 41 and the tube 42 are rotatably mounted on a frame 43 by means of pivoting sheave assemblies 44 and are rotationally driven by means of a variable speed motor 45. The zigzag tube is attached to the drum in a radially spaced position of the center of rotation of the drum and is in fluid communication with it so that in each revolution of the drum, the material inside the drum will flow into the tube as the pipe joining site goes down the level of material in the drum. The finely cut wire segments 24 enter the granulation drum 41 through the inlet 46. The incoming yarn segments are sprayed with a moisturizing solution, preferably containing binders, film formers, lubricants, antistatics, and coupling agents, through the spray nozzle 47 located adjacent the inlet 46. The granulation drum rotation 41 causes the yarn segments inside the drum to turn on themselves, which distributes the moisturizing solution on the surface of the yarn segments and causes the wire segments to align and merge into granules 48. the granules found in the drum pass to the zigzag tube 42 through an opening 41a at the exit end of the drum and are further densified in the zigzag tube 42 In a preferred embodiment, the drum 41 has an inner baffle to reduce the distance of the free fall of the glass granules and segments of thread during drum rotation. By reducing this distance, there is less damage to glass fibers and granules by impact and abrasion which can provide improved physical properties in glass fiber reinforced molded articles made with such fibers. While suitable baffles can take many forms, particularly preferred configurations include generally cylindrical baffles as shown in Figure 4, and curved plate baffles as shown in Figure 5. Such baffles are preferably attached to the outlet end wall of the baffle plate. drum 41 and project in there from a distance of from about 10 to about 50 percent of the length of the drum. The deflectors can be made of any material that resists the operating conditions within the drum, for example, stainless steel, and can be attached to the drum wall, by means of rivets, screws, welding or other suitable means. When fixing means such as bolts or screws are used, the edges of the baffles adjacent to the drum wall preferably have flanges 83 formed therein to facilitate joining. As shown in Figure 4, the generally cylindrical baffle 80 is preferably hollow with sealed ends which prevent the glass from entering and being mounted on the exit end wall of the drum 41 so that its central longitudinal axis approximately corresponds to that of the drum . As used herein, "generally cylindrical" means to include true cylinders as well as pseudo-cylindrical members having planar, tapered or cut portions, or varying radii over portions of their length. Preferably the deflectors have a diameter from about 20 to about 35 percent of the diameter of the drum to provide a sufficient reduction in the free fall of the granules to reduce the deterioration of the fibers. further, the diameter of the baffle can advantageously decrease along at least a portion of the length of the baffle such that the end of the baffle extending internally is smaller in diameter than the end attached to the drum. Providing the deflector with such form serves to minimize its impedance or resistance to the longitudinal flow of glass through the drum. Preferably, the deflector end projecting inwardly has a diameter from about 25 to about 60 percent of the diameter of the drum. Additionally, the baffle is preferably mounted on the exit end wall of the drum so as to partially overlap the exit opening 41a of the drum to reduce the backward flow of the granules from the zigzag densifying tube 42 in the drum as unit rotates. This correspondingly reduces the average residence time of the granules in the drum and helps ensure that the granules are not damaged or degraded by excessive abrasion. Preferably, the deflector blocks from about 20 to about 30 percent of the area of the outlet opening. Moreover, as shown in FIG. 4, the portion of the baffle that overlaps the outlet opening can be flattened, tapering or otherwise modified as desired to improve its reverse flow reduction of granules while minimizing its obstruction to flow. granules in the zigzag densifying tube. As shown in Figure 5, preferred curved plate deflectors generally have a curved portion 84 and a linear portion 86 and are mounted on the exit wall of the drum perpendicular thereto to project inwardly into the interior of the drum. The curved portion of the baffle preferably has a substantially constant radius which will coincide with the radius of the outlet opening, and the linear portion is preferably of a height equivalent to the exit opening. Furthermore, as shown in Fig. 5, the baffle is preferably mounted on the drum wall with the linear portion being adjacent the rotatably loose edge of the outlet opening 41a such that, when the outlet opening is in the lower part of its rotation, the linear portion is oriented vertically and the curved portion curves towards the central axis of the drum on the exit opening. By orienting the baffle in this manner, not only is the free falling distance of the granules reduced during the rotation of the drum, but it also acts as a large ladle or guide to facilitate the flow of the granules through the outlet opening in the Zigzag tube densifier increasing the apparent head of glass granules available to flow in the densifier with each rotation of the drum. As such, this also helps reduce the average residence time of the granules in the drum and prevents excessive abrasion of the granules. It has been found that the inclusion of the above deflectors in the drum of the granulator reduces the average residence time of the granules in the drum from about 2 minutes and 35 seconds without a baffle to about 1 minute and 40 seconds for the generally cylindrical baffle and 1 minute and 20 seconds for the curved plate deflector. In addition, the apparent reduction in fiber degradation resulting from the inclusion of such baffles is evident by an increase in the physical properties of the molded articles with the resulting granules, which include average increases in tensile strength from about 2 to about about 3 percent, increases in flexural strength from about 1 to about 2 percent, and increases in impact resistance from about 4 to about 5 percent. After densification, the granules can be delivered to a conveyor belt 50 and can be dried, for example, using a covered oven provided with hot air 61 and cooling air 62 or any convenient drying means 60 with means for discharging 63.

To reduce the drying time to an acceptable level for commercial mass production, it is preferred that the fibers are dried at elevated temperatures from about 121 ° C (250 ° F) to about 293.3 ° C (560 ° F) in an oven of fluidized bed. After drying, the densified granules 48 can be sorted by size using a 65 mesh or other convenient device, and ordered in either a product continent 66 or a waste container 67. By varying the production capacity and the moisture content of the containers. glass fiber segments, fiberglass granules can be manufactured which are from about 13% to about 60% denser than the corresponding non-granular glass wire segments, and from about 10 times to about 65 times larger in diameter. For example, finely cut segments of 4 mm (in length) of a yarn of 2000 filaments composed of 14 micron (diameter) fibers have a bulk density typically from about 528.66 kg / m3 (33 lb / ft3) to 576.72 kg / m3 (36 lb / ft3). After they have been hydrated to a moisture content of about 13 percent to about 14 percent and formed into densified granules according to the process of the invention, the resulting dry granules typically have a bulk density of about 640.8 kg / m3 (40 lb / ft3) to approximately 881.1 kg / m3 (55 lb / ft3). As a result of their increased diameter to length ratio and increased density, the resulting granules show a significantly improved fluidity compared to the product of finely-ground, ungranched yarn. The process of the invention is preferably carried out with an apparatus as described in Figure 3, wherein the fiber strands are formed in the fiber forming apparatus 10, finely cut using a cutting device 20, and they convey by means of the conveyor 30 to the drumming apparatus 40 where the finely cut yarns are granulated and densified. The resulting granules are transported through the conveyor 50 to the drying device 60. The fiber forming apparatus 10 preferably includes a glass fiber forming furnace having fiber forming nozzles Ia, llb, and 11c from a multiplicity of filaments 12a, 12b, and 12c are drawn or thinned, and to which an aqueous rubber composition containing optional coupling agents and lubricants and pH adjusters is applied by means of rubber applicators such as rollers 13a, 13b, and 13c. The groups of filaments are then collected or assembled into separate threads 15a, 15b, and 15c by means of collector clamps 14a, 14b, and 14c, and then inserted into the cutting device 20. The cutting device 20 includes a guide roller 21 that has slots of a number that corresponds to the number of the threads, a feed roller that turns freely 22 having a surface made of an elastic material having a high coefficient of friction with respect to the glass fibers, for example, rubber or synthetic resin, and a cutting roller 23 elastically compressed against the feed roller 22 and positively driven by means of a motor, the cutting roller has a multiplicity of blades projecting there radially. The wet yarns 15a, 15b, and 15c inserted into the cutting device 20 are wound around the feed roll 22 beyond the groove of the guide roller 21, and cut at the point of contact between the feed roller 22 and the feed rollers 22. cutting roller blades 23, in pieces, that is, finely cut wires 24, of a length that is determined by means of the circumferential pitch of the blades. The finely cut yarns 24 are dropped onto a suitable conveying means such as a conveyor 30., and are brought to the drumming apparatus 40. The preferred conveyor for transporting the finely cut and wet yarn segments is a web conveyor having a non-tacky, wavy surface, such as that commercially sold by Sparks under the trade designation of Ultraline. Food Belt Monoflex WU220M (white polyurethane with mini diamond top cover). The drumming apparatus 40 comprises a granulation drum 41 rigidly secured at one end to a zigzag pellet densification tube and hollow 42 mounted on a frame 43 by means of pivoting sheave assemblies 44 and rotatably driven by means of an electric motor. impulse 45, for example, a 30 amp variable speed motor. The densification tube 42 is attached to the drum 41 at a position radially distant from the center of rotation of the drum and is in fluid communication therewith. Preferably, the working volume of the hydrous yarn segments and the granules within the drum is from about 20% to about 50% of the drum volume, more preferably about 50% of the drum volume, to ensure a retention time within the drum. drum to form granules but insufficient to degrade them by abrasion. The densified granules pass from the drum 41 through the densification tube 42, and exit the densification tube at its outlet 49. The density of the granules leaving the densification tube is preferably from about 736.92 kg / m3 (46 lb / ft3). ) to approximately 993.24 kg / m3 (62 lb / ft3) which includes a moisture content of about 14% by weight. The frame of the drumming apparatus 43 is preferably provided with elevation adjustment means 43a, to allow the drumming apparatus to be maintained at a slight angle of up to about 5 degrees from the horizontal to ensure an appropriate flow of material through of the granulation drum and the densification tube. In a preferred embodiment of the invention, the angle is from about 1 degree to about 3 degrees. The granules emerging from the densification tube fall on a conveyor 50 and are transported to an oven 60, where the hydrating solution is dried. Preferably, the conveyor 50 is a belt conveyor having a non-tacky, corrugated surface sold commercially by Sparks under the trade designation of Ultraline Food Belt Monoflex WV220M (white polyurethane with mini diamond top cap). Although the invention has been described in detail with reference to the preferred features and embodiments, various modifications will be readily apparent to those skilled in the art by the practice of the invention. Therefore, it is intended that the invention is not limited by the foregoing description, but is defined by the appended claims and their equivalents.

Claims (19)

1. An apparatus for producing glass fiber granules from finely cut segments of multi-filament glass strands characterized in that it comprises: a. means for applying an aqueous hydrating solution to the segments of finely cut yarn; b. first drumming means for providing a drumming action to the finely cut and hydrated yarn segments to supply the hydration solution and cause the finely cut yarn segments to be aligned and joined into granules; c. means for conveying granules to second drumming means; and d. second means of tamboreación to drum the granules to compact them and increase their density.

The apparatus according to claim 1, further characterized in that the first drumming means comprise a rotary drum driven around its longitudinal axis, the drum has a first and a second end, the first end has an inlet opening for receiving segments of finely cut wire and the second end has an outlet opening for discharging the granules, the center of the outlet opening being radially distant from the axis of rotation of the rotating drum.

The apparatus according to claim 2, further characterized in that the second drumming means comprises a hollow zigzag tube rotatably driven about a longitudinal axis, the tube having a first and a second open end, the first end open provides an inlet to receive the granules and the second open end provides an outlet for unloading the densified granules.

The apparatus according to claim 2, further characterized in that the means for applying a moisturizing solution to the finely cut wire segments comprises a spray nozzle located adjacent to the inlet opening of the drum.

The apparatus according to claim 2, further characterized in that the means for applying a moisturizing solution to the finely cut wire segments comprises a spray nozzle inside the drum.

6. The apparatus according to claim 2, further characterized in that it further comprises means positioned within the drum to reduce the free falling distance of the granules during the rotation of the drum.

The apparatus according to claim 6, further characterized in that the means for reducing the free fall comprises a generally cylindrical deflector attached at one end to the second end of the drum and extending inwardly into the drum.

The apparatus according to claim 7, further characterized in that the longitudinal axis of the deflector is substantially parallel to the axis of rotation of the drum.

The apparatus according to claim 8, further characterized in that the baffle overlaps a portion of the outlet opening in the drum.

The apparatus according to claim 6, further characterized in that the means for reducing the free fall comprises a curved plate attached at one edge of the second end of the drum and extending inwardly in the drum.

11. The apparatus in accordance with the claim 10, further characterized in that the curved plate comprises a curved portion and a linear portion, and is attached to the drum such that the linear portion is adjacent to the exit opening at its rotatably loose edge and the curved portion is bent toward the Drum rotational axis.

12. The apparatus according to claim 11, further characterized in that the curved portion has a substantially constant radius of curvature.

The apparatus according to claim 3, further characterized in that the entry of the second drumming means is connected to the outlet opening of the first drumming means and is in fluid communication with them.

14. An apparatus for producing glass fiber granules from finely cut segments of multi-filament glass wire characterized in that it comprises: a. means for applying a moisturizing solution to segments of finely cut yarn; b. a drum rotatably driven about its longitudinal axis, the drum has a first and a second end, the first end has an inlet opening for receiving the segments of finely cut wire and the second end has an outlet opening for unloading the wire. granules, the center of the outlet opening is radially distant from the axis of rotation of the drum; c. a zigzag hollow tube rotationally driven about a longitudinal axis, the tube having a first and a second end open, the first open end is joined to the exit opening of the drum in such a way that the material inside the drum can pass in the When the tube and the tube are rotated, the second open end provides an outlet to discharge the granules of the tube.

15. The apparatus according to claim 14, further characterized in that it further comprises means positioned within the drum to reduce the free falling distance of the granules during the rotation of the drum.

16. The apparatus according to claim 15, further characterized in that the means for reducing free fall comprises a generally cylindrical baffle attached at one end to the second drum end and extending inwardly into the drum.

The apparatus according to claim 16, further characterized in that the baffle overlaps a portion of the exit opening in the drum.

18. The apparatus according to claim 14, further characterized in that the means for reducing the free fall comprises a curved plate attached at one edge to the second end of the drum and extending inwardly in the drum. The apparatus according to claim 18, further characterized in that the curved plate comprises a curved portion and a linear portion, and is attached to the drum such that the linear portion is adjacent to the exit opening at its rotationally loose edge and the curved portion curves towards the axis of rotation of the drum.