KR20000016198A - System for preparing glass fiber pellets - Google Patents

Abstract

PURPOSE: A method and a device for an efficient pellet formation is provided to make an actually uniform glass fiber pellet having the shape and density supplying an excellent flowing property in a controllable method. CONSTITUTION: A system for making densified glass fiber pellets from chopped segments of multi-filament glass strand is described. The densified pellets 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

Apparatus for manufacturing glass fiber pellets

Cut glass fibers are commonly used as reinforcing materials in thermoplastic products. In general, these fibers are made by the following process, i.e. the molten glass is drawn through a bushing or orifice plate into filaments, and a sizing composition containing a lubricant, a coupling agent and a film-forming binder resin is described above. It is applied to the filaments, these filaments are gathered into strands, the fiber strands are cut into segments of the desired length and the sizing composition is dried. The chopped strand segments are then mixed with the polymer resin and the mixture is fed to a compression or injection molding machine to form a glass fiber reinforced plastic product. In general, the chopped strands are mixed with pellets of thermoplastic polymer, which mixture is fed to an extruder where the resin is dissolved, the identity of the fiberglass strands is lost and the fibers are dispersed throughout the molten resin, The resin dispersion is shaped into pellets. These pellets are then sent to a molding machine to form a molded article with the glass fibers substantially uniformly dispersed throughout.

However, chopped glass fibers made by the above method are generally bulky and poor in fluidity. Therefore, such fibers are difficult to handle and problematic in automated manufacturing machines.

In an attempt to solve the above problem, in order to improve the flowability of the cutting strands, the cutting strands are compacted into higher density rod-like bundles or pellets, and also the weight of the fiberglass for mixing with the thermoplastic resin. It is to enable automated equipment to measure and deliver the fiber. Such a method is disclosed in US Pat. No. 4,840,755. According to this, wet cutting strands are rolled on a vibrating carrier to round and compact these strands to create higher density cylindrical pellets. Such methods and apparatus can produce pellets that have a higher density and are more cylindrical and have better flowability, but are undesirably limited in some respects.

For example, since the method is intended to prevent multiple cut strand segments from sticking together to form pellets containing more fibers than in a single cut strand, the pellet size and fiber content will generally depend on the size of the fibers in the cut strand. You will be limited by the number. Thus, in order to obtain pellets with adequate volume density and sufficient diameter to length ratio to have good flowability, the strands cut into segments should generally consist of a large number of filaments. However, increasing the number of filaments needed to form and bond to a single strand undesirably complicates the molding operation.

In an attempt to overcome this drawback, US Pat. No. 5,578,535 introduces glass fiber pellets that are about 20 to 30% denser and about 5 to 15 times larger in diameter than individual glass strands. These pellets are prepared by the following process: hydrating the strand segments to a degree sufficient to prevent filamentation but insufficient to cause the chopped strand segments to clump together and pelletize the hydrated strand segments. Mix for a sufficient time. Suitable mixing methods include tumbling, stirring, blending, commingle, churning and intermingle, etc., thereby moving the fibers around each other.

The pellets disclosed above can be made with various blending methods as mentioned above, but many of these blends have strength properties that are too inefficient to be commercially available or comparable to those made from chopped strand fibers. It may not be properly controlled to produce a uniform pellet product that provides a final composite product having. For example, the use of an improved disk pelletizer results in an excessively long time for the formed pellets to reside in the mixer, resulting in damage to the pellets by rubbing and abrasion of the fiberglass pellets. As a result, damage to the pellets reduces the strength characteristics of the molded article made therefrom.

Therefore, there is a need for an efficient pellet forming method that can make a uniform glass fiber pellet product in a controllable manner that provides the same strength properties as unpellet chopped strand fibers in composite molded articles. This need can be met with the present invention, the gist and detailed description of which are described below.

The present invention relates to the production of glass fiber pellets, and in particular, according to the present invention, there is provided an apparatus for manufacturing density-reinforced glass fiber pellets by combining multiple segments of chopped multifiber glass strands. Such pellets would provide a convenient form for the storage and handling of chopped glass fibers used as reinforcement in composite structures.

FIG. 1A shows a rotary drum pellet forming system used in the present invention, and FIG. 1B is a front view showing one preferred embodiment of the pellet density enhancing system used in the present invention.

2 is a front view showing one preferred embodiment of a mixing apparatus for performing the pelletizing step and the density enhancing step.

FIG. 3 is a schematic representation of one preferred embodiment of the present invention for forming fibers and making those fibers into densified reinforced pellets.

4A is a longitudinal sectional view of a baffle that may be used in the rotary drum of the present invention, FIG. 4B is a cross sectional view of the baffle taken along the line AA in FIG. 4A, FIG. 4C is a cross sectional view of the baffle taken along the line BB in FIG. 4A, FIG. 4D is a longitudinal sectional view of the rotary drum with the baffle of FIG. 4A attached, and FIG. 4E is a partial cutaway isometric view of the drum and the baffle attached thereto.

FIG. 5A is a side view of another baffle that may be used in the rotary drum of the present invention, FIG. 5B is a radial cross-sectional view of the rotary drum of the present invention with the baffle of FIG. 5A attached, and FIG. 5C is a rotary drum of FIG. 5B and attached thereto Partial isometric isometric view of the baffle.

It is an object of the present invention to provide an efficient pellet forming method and apparatus capable of making substantially uniform glass fiber pellets having a shape and density providing good flowability in a controllable manner. Another object is to provide pellets that can be used in the production of glass fiber reinforced composite products without losing some of the strength properties compared to equivalent products made from unpellet cut strands.

The above object is achieved by a process of cutting a glass fiber strand consisting of a plurality of substantially continuous glass fibers into segments of a predetermined length and hydrating such strand segments to contain sufficient moisture to coalesce and pellet when tumbling. . The strand segment is then subjected to a first tumbling action in order to allow the hydration liquid to be distributed substantially uniformly over the strand segments and to allow the strand segments to join and form pellets. Then, the pellet becomes compact by the second tumbling action, thereby increasing the density of the pellet.

The method of the invention comprises the following means: (a) means for cutting glass fiber strands to make chopped strand segments; (b) means for transferring the chopped strand segments to the first tumbling means; (c) means for adding the hydration solution to the cut strand segment; (d) first tumbling means for imparting a tumbling action to the hydrated chopped strand segments to disperse the hydration solution to align and coalesce the chopped strand segments to pellets; (e) means for delivering said pellets to a second tumbling means; (f) second tumbling means for tumbling the pellets to make the pellets compact and increase their density; (g) means for delivering densified pellets to the dryer; And (h) drying means for receiving and drying the pellets. Other objects, features and advantages of the present invention will become apparent from the following detailed description with reference to the accompanying drawings in which like reference numerals designate like elements.

According to the method of the present invention, a strand made of substantially continuous glass fibers is drawn by drawing molten glass through a heated bushing to make a plurality of substantially continuous glass fibers and then gathering the fibers to become a single strand. Is formed. Appropriate devices for making these fibers and then gathering them into strands can be used in the present invention.

Suitable fibers are fibers having a diameter of about 3 to 90 microns, and suitable strands will also contain about 50 to 2000 fibers. Preferably, the strand formed by the rice method of the present invention will contain about 400 to 800 fibers having a diameter of about 3 to 23 microns.

After forming the fibers and prior to agglomeration into strands, the fibers may be coated with a suitable aqueous sizing composition known in the art. Preferably, this sizing composition comprises water, at least one coupling agent, and if necessary at least one lubricant and pH adjusting agent.

Suitable coupling agents include organofunctional silanes such as those produced by Witco and sold under the following trade names.

Preferred coupling agents used in the present invention may be purchased from Osi of Witco and are 3-aminopropyltriethoxy-silane and gamma-glycidoxypropyltrimethoxy-silane, each having the trade names A-1100 and A-187. to be. Preferably, the organofunctional silane is used in an amount of about 0.1 to 1.0% of the sizing composition.

Suitable lubricants may be used in sizing compositions such as water soluble ethylene glycol stearate, ethylene glycol oleate, ethoxylated fatty amines, glycerin, emulsified mineral oil and organic polysiloxane emulsions. Preferred lubricants include the following: polyethylene glycol monostearate, polyethylene glycol mono-oleate, butoxyethyl stearate, stearic ethanolamide (available from Lubsize K12, Alpha / Owens Corning), in the present invention Lubricant oil, introduced in US Pat. No. 3,597,265, which is incorporated by reference (trade name Emerlube 6760, manufactured by Emery Corp.), and 30% white oil, 30% polyethylene glycol 400 monofellargonate, 30% polyoxyethylene ( 3) a mixture of mystic alcohol and 10% ethoxylated alkyl amine (Parastat S-2) (manufactured by Emery Corp., trade name Emerlube 7607). The lubricant is preferably present in the sizing composition in an amount of about 0.05 to 0.10% by weight.

A small amount of a weak acid, such as acetic acid, may also be added to the composition to lower the pH of the sizing composition to about 3.5-8. Such weak acids are present in the sizing composition in an amount of about 0.15 to 0.3% by weight and the pH of the composition is preferably about 6-8.

Suitable sizing compositions used in the present invention include the following:

1.A-1100 organofunctional silane (58% active content) 0.5%

Deionized water rest

2. A-1100 organofunctional silane (58% active content) 0.5%

Lubesize K12 (Alpha / Owens Corning) 0.07%

Glacial acetic acid 6-8 pH

Deionized water rest

3. A-1100 organofunctional silane (58% active content) 0.5%

Emerlube 7607 (Emery Corp.) 0.1%

Deionized water rest

4. A-1100 organofunctional silane (58% active content) 0.5%

Polyethylene Glycol 400 Monostearate 0.1%

Deionized water rest

5. A-1100 organofunctional silane (58% active content) 0.5%

Emerlube 6760U (Emery Corp.) 0.01%

Deionized water rest

6.A-1100 organofunctional silane (58% active content) 0.38%

A-187 Organofunctional Silane 0.12%

Deionized water rest

The aqueous sizing composition can be added by conventional means, including kiss roll applicators and sprays. It is preferred to add the sizing composition by passing the fibers over the kiss roll applicator. Moreover, it is desirable to add a sufficient amount of sizing composition to the fibers to provide about 8-13%, more preferably 11%, of the moisture to the fibers (unless otherwise indicated, all percentages are expressed in weight ratios).

Once formed, the continuous strand is cut to a length of about 1/8 inch (3.175 mm) to 1/4 inch (31.75 mm). Any suitable means known in the art for cutting glass fiber strands to this length may be used in the present invention.

Then, when the chopped strand segments move around each other, the moisture content of these segments is adjusted to an appropriate level for pelleting, and the chopped strand segments are introduced into a first tumbling means or pellet forming machine to allow them to move as described above. Although the moisture content of the strand segments can be controlled prior to introduction into the pelletizer, it is desirable to hydrate the glass fibers to a moisture content suitable for pelleting in the pelletizer. The moisture content of the fibers in the pelletizer is preferably about 12-16%, more preferably about 13-14%. If the moisture content is too low, the strands tend not to bind into pellets and generally remain in strand form. Conversely, if the moisture content is too high, the strands will aggregate to form pellets that are non-uniform with too large a diameter and also have a non-cylindrical shape.

It is also preferable that the hydration solution also contains a binder or a second sizing composition. Thus, this hydration liquid may generally contain components contained in the glass fiber sizing composition, such as film forming agents, wetting agents, antistatic agents and suitable components such as additional coupling agents and lubricants. By adding the second sizing composition in the pelletizer, an application efficiency of 100% can be obtained. In addition, when the sizing composition is added outside the fibrous environment, it may contain undesired materials in the forming process for reasons of toxicity, cleanliness, odor, high cost or sensitivity to shear.

Examples of suitable binder compositions that can be used in the hydration are as follows (unless otherwise indicated, all percentages are by weight).

1.Epoxy water dispersion (Shell Chem. Co.) with EpiRez 3544-53% resin solids 12.58%

Polyurethane Water Dispersion (Witco Co.) with Witco 290H-62% Resin Solids 0.99%

A-1100-58% organofunctional silane with active solids (Witco Co.) 0.10%

Deionized water rest

2. Introduced in US Pat. No. 5,236,982, which is hereby incorporated by reference.

Size composition

3. Terephthalic acid 3.21%

3.89% ammonium hydroxide with 28% activity

GenFlo 559-50% Polyurethane Water Dispersion 4.06% with Resin Solids

(General Tire and Rubber Co.)

Polyurethane Water Dispersion with ChemCor 43N40-40% Resin Solids 8.12%

(Chemical Corporation of America)

Deionized water rest

Z6020-organic silane (Dow Corning Corp.) 2.65%

Block copolymer 1.8% of Pluronic 10R5-ethylene oxide and propylene oxide

(BASF Corp.)

Deionized water rest

5.Z6020 0.89%

Maldene 286-Copolymer of Maleic Unhydride and Butadiene 13.3%

Lindau Chemicals, Inc.

1.6% ammonium hydroxide with 28% activity

Deionized water rest

Presented above are the compositions of binders that have been evaluated and found useful in the methods of the present invention. Those skilled in the art will be able to select other suitable binder compositions or components that can be used. In fact, an advantage of the present invention is that almost all aqueous size compositions used in glass fiber forming techniques are useful as binders to be sprayed on fibers in a tumbling apparatus according to the method of the present invention.

In order for the sizing composition to be well applied to the fiber strands, it is desirable to add the sizing composition to the strand segments as they enter the pelletizer and also before they coalesce into pellets. When the sizing composition is applied at different locations within the pelletizer, the pellets tend to form before the cutting strands are completely covered with the sizing composition, which results in pellets made of fibers that are not all covered with the sizing composition. . If these pellets are used in the production of fiber reinforced plastic products, the uncoated fibers will lack the two-sided coating required for good reinforcement properties, and the final product will not have optimal properties. In order to apply the sizing composition to these segments as the strand segments enter the pelletizer, it is desirable to provide the pelletizer with a spray nozzle located adjacent the strand segment inlet.

The pelletizer used in the present invention is characterized in that (1) strand segments are substantially uniformly coated with an aqueous binder / sizing composition and (2) a plurality of cut strand segments are aligned and coalesced to pellet the desired size. Any device capable of tumbling strand segments may be used. Such a tumbling device should have an average residence time sufficient for the strand segments to be substantially covered with a hydrating fluid to form pellets, but not enough for the pellets to be damaged and worsened due to wear due to mutual contact. You have to have time. Preferably, the residence time in tumbling is about 1 minute to 10 minutes. More preferably, the residence time in tumbling is about 1 to 3 minutes.

Preferred pelletizers are rotary drums, such as drum 41 shown in FIG. 1A. The pellet forming machine 41 receives the chopped strand segments 24, which are prepared by the fiber forming bushing 11, the size applicator 13, the collecting shoe 14, and the cutting device 20.

In a preferred embodiment, the apparatus is provided with a system for monitoring and / or adjusting various parameters, which parameters are automatically controlled by a control panel 70 such as an Allen Bradley PLC-5 / 40 PLC system. If necessary, the moisture content of the incoming strand segment 24 can be measured by appropriate means 71. A strand weight gauge 72 may be provided, which may be suitably positioned in front of or behind the strand conveyor 30. Similar weighing devices may be used to weigh the pellets on the conveyor 31. Metering of the binder and water is carried out by controlling the pumps 33, 34.

The drum 41 is adapted to have a spray head which sprays hydration liquid onto the segments as the strand segments 24 enter the drum. Preferably, the external air mixture is mixed to mix the aqueous binder composition supplied from the binder supply 35 via the masterplex pump 33 with the additional water supplied from the water supply 36 via the masterplex pump 34. The nozzle 47 is installed near the inlet of the drum. The water is necessary to provide the desired amount of moisture to the chopped strand segments and also to add the mixture to the chopped strand segments in the drum. The binder composition and water mix into one fluid stream while mixing through the nozzle orifice. Two streams of air separated from each other by 180 degrees and positioned at an angle of 60 degrees to the flow direction of the stream impinge on the stream. The air is supplied as clean dry air 52. This air effectively produces mist, which is directed to the surface of the strand segments tumbling in the drum. Due to the rotation of the drum, the wet strand segments tumble around each other, and by the surface tension generated by the wet sizing or coating, the strand segments contacting each other over a significant part of their length are aligned and coalesced with each other. It becomes a cylindrical pellet. With this action, any fine, single fibers generated during the cutting operation are incorporated into the pellets which are recombined and formed so that individual fine fibers do not remain in the final pellet. Preferably the drum is tilted slightly, so that the end of the drum out of the pellets is lower than the end where the pellets come in so that the pellets formed in the drum do not remain in the drum for an excessive amount of time. According to a preferred embodiment, the drum is inclined such that its axis of rotation forms an angle q of about 1 to 3 degrees with the horizontal plane. The inclination angle can be adjusted manually or automatically by using an appropriate adjusting means 43a.

The size of pellets formed in the drum is basically controlled by the amount of moisture in the plant segments. If the moisture content is kept high, more and more strand segments are coalesced into pellets and thus the pellets have a larger diameter. Conversely, if the moisture content is kept low, fewer and fewer strand segments are coalesced into pellets, so that the diameter of the pellets is smaller.

Preferably, the pellets formed by the method of the present invention will have a diameter of about 20% to 65% of their length. Typically such pellets are formed by combining about 70 to 175 strand segments, each strand segment having about 500 to 2000 filaments per strand.

The size of the pellets is also influenced by the throughput of the drum. Larger throughput of the drum results in a shorter time for the strand segments to reside in the drum, which results in smaller pellets because the hydration liquid is not dispersed in the strands and the strands do not coalesce into pellets. However, the pellets formed are less dense because the pellets are in the drum for a short residence time.

The pellets formed are always compacted to some degree in the pelletizer, but are generally insufficient to increase the pellet density to a value that gives optimum fluidity. For this reason, after being formed in the pellet forming machine 41, the pellets are sent to the density enhancer 42, which is the second tumbling means, to be more compact there, thereby increasing the density. Any low-impact tumbling device that can compact the pellets without deteriorating or damaging the pellets with wear may be used. Preferably, the densifier is less violent than the pelletizer to minimize pellet deterioration. In addition, the density enhancer has an average residence time of about 5 minutes or less so that the pellets do not deteriorate due to wear. More preferably, the average residence time in the density enhancer is about 1 to 2 minutes.

Preferred density enhancers are zigzag tubes that are rotated about the longitudinal axis x as shown in FIG. The zigzag tube 42 is rotatably mounted on the frame 43 by the caster assembly 44 and rotated by the drive motor 45. When the tube is rotated, the pellets in the tube are gently tumbled by the rotation of the tube while passing through the tube by gravity. As with the rotary drums described above, the zigzag tube is also inclined at a slight angle so that the pellets can flow through the device without overly presenting it. Preferably, the longitudinal axis of the tube is at an angle of about 1 to 3 degrees with the horizontal plane, and the tube inlet 39 is higher than the tube outlet 49.

Pelletization and densification can be achieved in separate devices such as rotary drum 41 and rotary zigzag tube 42 sandwiching conveyor 31 as shown in FIG. It can also be done by means. For example, pelleting and densification may be made in separate tumbling regions within a single device. One example of such a device is a “zigzag” mixer, available from Patterson Kelly, as indicated by reference numeral “40” in FIGS. 2 and 3.

The mixer 40 has a rotary drum 41 connected to a zigzag tube 42 at one end. The drum 41 and the tube 42 are rotatably installed on the frame 43 by the caster assembly 44 and are rotated by the transmission motor 45. A zigzag tube attaches to and communicates with the drum at a distance radially away from the center of rotation of the drum, so that each time the drum is rotated, the tube connection becomes lower than the height of the material in the drum. Raw material flows into the tube. The cutting strand segments 24 enter the pelletizing drum 41 through the inlet 46. Preferably, a hydration solution containing a binder, film former, lubricant, antistatic agent and coupling agent is sprayed onto the incoming strand segments via a spray nozzle 47 located near the inlet 46. Rotation of the pelletizing drum 41 causes the strand segments in the drum to tumble around each other, and the hydration liquid is dispersed on the surface of the strand segments and the strand segments are aligned and coalesced into pellets 48. The pellets formed in the drum enter into the zigzag tube 42 through the holes 41a at the outlet end of the drum, whereby further densification is made in the zigzag tube 42.

According to a preferred embodiment, an internal baffle is provided in the drum 41 to reduce the free fall distance of the glass pellets and strand segments during rotation of the drum. By reducing this free fall distance, the deterioration of the glass fibers due to impact and abrasion is reduced and thus the physical properties of the glass fiber reinforced molded articles made from the glass fibers can be improved.

Suitable baffles may take various forms, but particularly preferred are the cylindrical baffles shown in FIG. 4 and the curved plate baffles shown in FIG. 5. This baffle is attached to the outlet end of the drum 41 and protrudes inwardly from this end by a distance of about 10 to 50% of the drum length. The baffle is made of a material that can withstand the working conditions in the drum, such as stainless steel, and can be attached to the drum by bolts, screws, welding or other suitable means. When fastening means such as bolts or screws are used, it is preferable to place the flange 83 at the edge of the baffle adjacent to the drum wall to facilitate attachment.

As can be seen in FIG. 4, the generally cylindrical baffle 80 is a hollow body having a sealed end to prevent the outflow of gas, and the longitudinal center axis thereof almost coincides with that of the drum 41. It is mounted at the outlet end of the drum. The term " generally cylindrical " mentioned above includes not only complete cylindrical but also similar cylindrical elements whose radius varies over a portion of the flat or tapered or cut-out portion or length. Preferably, the baffle will have a diameter that is about 20 to 35% of the drum diameter to sufficiently reduce the free fall distance of the pellets in order to reduce damage to the fibers. In addition, the diameter of the baffle may be reduced along at least a portion of the baffle length so that the end of the inwardly projecting baffle has a smaller diameter than the end attached to the drum. By providing this type of baffle it is possible to minimize the resistance to the longitudinal flow of glass through the drum. The end of the inwardly projecting baffle preferably has a diameter that is about 25 to 60% of the drum diameter.

Further, in order to reduce the reverse flow from the former to the latter when the zigzag tube density enhancer 42 and the drum rotate together, the baffle is mounted on the outlet end wall of the drum in a state partially surrounding the outlet 41a of the drum. It is preferable. This reduces the average residence time of the pellets in the drum and also prevents the pellets from being damaged or worsened by excessive wear. The baffle is preferably about 20-30% of the exit area. In addition, in order to improve the backflow reduction of the pellets while minimizing the resistance to pellet flow into the zigzag tube density enhancer, as shown in Figure 4, the portion surrounding the outlet in the baffle is flat, tapered or if necessary. You can modify it differently.

As shown in FIG. 5, the preferred curved plate baffles generally have a curved portion 84 and a straight portion 86 and are mounted thereon perpendicular to the outlet wall of the drum and project inwardly toward the interior of the drum. . Preferably, the curved portion of the baffle has a substantially constant radius that matches the radius of the outlet, and the straight portion has the same height as the outlet.

In addition, as shown in FIG. 5, the baffle is mounted on the drum wall such that its straight portion is adjacent to the rotating trailing edge of the exit 41a, whereby the straight portion is oriented vertically when the exit is under rotation and the curved portion is It will be curved over the exit toward the central axis of the drum. This arrangement of the baffles not only reduces the free fall distance of the pellets while the drum is rotating, but also causes the drum to rotate into the density enhancer with every revolution of the drum.

Increasing the apparent head of the incoming glass pellets also serves as a scoop or guide that allows the pellets to easily flow through the outlet into a zigzag tube density enhancer. This also reduces the average residence time in the drum and prevents excessive wear of the pellets.

By arranging the above baffles in the drum of the pellet forming machine, the average residence time of the pellets in the drum was 2 minutes and 35 seconds in the absence of baffles, but was generally 1 minute and 40 seconds in the case of the cylindrical baffles and also the curved surface. It was found to be 1 minute 20 seconds with plate baffles. In addition, the marked reduction in fiber degradation resulting from this baffle includes final pellets, including about 2-3% increase in average tensile strength, about 1-2% increase in bending strength, and about 4-5% increase in impact strength. It is evident from the increase in the physical properties of the molded article.

After densification, the pellets are transferred onto the conveyor belt 50 and for example other suitable drying means (60) with a hood-type oven or exhaust means (63) receiving hot air (61) and cooling air (62). Can be dried. To reduce the drying time to a level suitable for commercial mass production, it is desirable to dry the fibers in a fluidized bed oven at a high temperature of about 250 ° F. (121.1 ° C.) to 560 ° F. (293.3 ° C.). The densified pellets 48 can be sorted by size using a screen 65 or other suitable device after drying and are also sorted into product container 66 or waste container 67.

By varying the moisture content and throughput of the glass strand segments, it is possible to make glass fiber pellets that are about 13% to 60% denser and 10 to 65 times larger in diameter than unpelleted glass strand fibers. For example, a 4 mm cut segment of 2000 filament strands consisting of 14 micron (diameter) fibers may have a volume density of about 33 lb / ft ³ (528.66 kg / m ³ ) to 36 lb / ft ³ (576.72 kg / m ³ ). Have After molding into hydrated and densified pellets with a moisture content of about 13% to 14% according to the method of the present invention, the finally dried pellets are generally from about 40 lb / ft ³ (640.8 kg / m ³ ) to It has a volume density of 55 lb / ft ³ (881.1 kg / m ³ ). The final pellets have a significantly improved flowability compared to the unpelleted chopped strand products because the ratio of their diameter to length is increased and the density is also increased.

The method of the present invention may be preferably carried out with the apparatus shown in FIG. 3, wherein the fiber strands are made in the fiber forming apparatus 10 and cut by the cutting apparatus 20 so as to be tumbling apparatus by the conveyor 30. 40) where the cutting strands are pelletized and densified. The final pellets are sent to the drying apparatus 60 by the conveyor 50.

The fiber forming apparatus 10 includes a glass fiber forming furnace having fiber forming bushings 11a, 11b, 11c. A plurality of filaments 12a, 12b, 12c are drawn from the bushing and tapered, and an aqueous sizing composition containing a coupling agent and optionally a lubricant and a pH adjuster is applied to a sizing applicator such as rolls 13a, 13b, 13c. Is applied to the filament. The filament groups are then gathered by the collecting shoes 14a, 14b, 14c into individual strands 15a, 15b, 15c and then led to the cutting device 20.

The cutting device 20 includes a guide roller 21 grooved by the number of strands, a feed roller 22 freely rotatable having a surface made of an elastic material such as rubber or synthetic resin having a large coefficient of friction with respect to glass fibers, and And a cutter roller 23 driven by a motor while being elastically pressed against the feed roller 22. This cutter roller has a plurality of blades projecting in the radial direction. The wet strands 15a, 15b, 15c guided into the cutting device 20 are wound around the feed rollers 22 through the grooves of the guide rollers 21, and the feed rollers 22 and the cutter rollers 23 At the point of contact of the blades, they are cut off into fragments, ie cutting strands 24. The length of this cutting strand is determined by the circumferential pitch of the blades.

The cutting strands 24 are transferred to the tumbling apparatus 40 after falling into a suitable conveying water unit such as the conveyor 30. Preferred conveyors for transferring wet strand segments are conveyors having a non-adhesive surface with recesses. Such conveyors are those manufactured by Sparks and are branded Ultraline Food Belt Monoflex WU220M (white polyurethane with a small diamond top cover). The tumbling device 40 is provided with a pelletizing drum 41, which drum is firmly fixed at one end to a hollow zigzag pellet density-reinforcement tube 42, which is in turn framed by a caster assembly 44. 43) is rotatably mounted on and is also rotated by a drive motor 45, for example a 30-amp variable speed motor. The density reinforcing tube 42 is attached to and communicates with the drum at a point radially away from the center of rotation of the drum 41. Preferably, the working volume of the hydrated strand segments and the pellets in the drum should be sufficient to ensure the retention time in the drum required to form the pellets, while at the same time not sufficient to deteriorate the pellets due to wear. About 20-50% of the volume of the drum, more preferably about 50% of the volume of the drum.

The densified pellets pass from the drum 41 through the densification tube 42 and exit the densification tube at the outlet 49. The density of the pellets from the thickening tube is preferably about 46 lb / ft ³ (736.92 kg / m ³ ) to 62 lb / ft ³ (993.24 kg / m ³ ) and also contains 14% moisture by weight.

The height adjusting means 43a is provided on the frame 43 of the tumbling apparatus in order to keep the tumbling apparatus slightly tilted at an angle of about 5 degrees with the horizontal plane so that the raw material can properly flow through the pellet forming drum and the density-reinforced tube. It is. According to a preferred embodiment of the present invention the angle is about 1 degree to 3 degrees.

Pellets from the densification tube are dropped onto the conveyor 50 and transferred to the oven 60 where the hydration liquid is dried. Preferably, the conveyor 50 is a conveyor with a non-adhesive surface with concave portions, such a conveyor produced by Sparks, which is called Ultraline Food Belt Monoflex WV220M (white polyurethane with a small diamond top cover). There is.

While the invention has been described above in terms of preferred embodiments and features, it will be apparent to those skilled in the art that various modifications may be made to the invention. Accordingly, the present invention is not limited to the above embodiments but is defined by the following claims and their equivalents.

Claims (19)

a. Means for adding an aqueous hydration solution to the chopped strand segments, b. First tumbling means for imparting a tumbling action to the hydrated chopped strand segments to disperse the hydration solution to align and coalesce the chopped strand segments into pellets; c. Means for delivering the pellets to a second tumbling means, and d. And second tumbling means for tumbling the pellets in order to compress the pellets and increase their density. 2. An apparatus for producing fiberglass pellets from cut segments of multiple filament glass strands. 2. The device of claim 1, wherein the first tumbling means is a drum rotatable about a longitudinal axis, the drum having first and second ends, the first end having an inlet for receiving cutting strand segments. And a second end having an outlet for discharging pellets, the center of which is radially away from the axis of rotation of the drum. 3. The method of claim 2, wherein the second tumbling means is a hollow zig-zag tube that is rotated about a longitudinal axis, the tube having first and second open ends, the first open end receiving the pellets. Wherein the second inlet provides an inlet and the second open end provides an outlet for discharging the densified pellets. 3. An apparatus according to claim 2, wherein the means for applying the hydrating liquid to the chopped strand segments is a spray nozzle located adjacent the inlet of the drum. 3. An apparatus according to claim 2, wherein the means for applying the hydrating liquid to the chopped strand segments is a spray nozzle located in the drum. 3. An apparatus according to claim 2, further comprising means located in the drum to reduce the free fall distance of the pellets while the drum is rotating. 7. A device according to claim 6, wherein the drop-fall reduction means is a generally cylindrical baffle, one end of which is attached to the second end of the drum and extends inwardly into the drum. 8. The apparatus of claim 7, wherein the longitudinal axis of the baffle is substantially parallel to the axis of rotation of the drum. 10. The apparatus of claim 8, wherein the baffle covers a portion of the drum outlet. 7. A device according to claim 6, wherein the free fall distance reducing means is a curved plate attached at one edge to the second end of the drum and extending inwardly into the drum. The drum of claim 10, wherein the curved plate has a curved portion and a straight portion, and the plate further includes a curved portion and a straight portion, wherein the curved portion is adjacent to the rotating trailing edge of the outlet and the curved portion is curved toward the rotation axis of the drum. Apparatus characterized in that it is attached. 12. The apparatus of claim 11, wherein the curved portion has a substantially constant radius of curvature. 4. The device of claim 3, wherein the inlet of the second tumbling means is connected to the outlet of the first tumbling means to enable fluid flow. a. Means for applying the hydration solution to the cut strand segment; b. A drum rotatable about a longitudinal axis, the drum having first and second ends, the first end having an inlet for receiving the chopped strand segments and the second end having an outlet for discharging pellets, The center of the outlet is a drum radially away from the rotation axis of the drum, c. A hollow zig-zag tube that is rotatable about a longitudinal axis, the tube having first and second open ends, wherein the first open ends are drums so that the raw material in the drum can move into the tube when the drum and the tube are rotated. And a second open end providing an outlet for discharging pellets from the tube, wherein the second open end provides an outlet for discharging the pellets from the tube. 15. The apparatus of claim 14, further comprising means positioned in the drum to reduce the free fall distance of the pellets while the drum is rotating. 16. The apparatus of claim 15, wherein the means for reducing dropping distance is a generally cylindrical baffle having one end attached to the second end of the drum and extending inwardly into the drum. 17. The apparatus of claim 16, wherein the baffle covers a portion of the drum outlet. 15. The apparatus of claim 14, wherein the free fall distance reducing means is a curved plate attached at one edge to the second end of the drum and extending inwardly into the drum. 19. The drum according to claim 18, wherein the curved plate has a curved portion and a straight portion, and the plate further includes a curved portion and a straight portion, wherein the straight portion is adjacent to the rotating trailing edge of the outlet and the curved portion is curved toward the rotation axis of the drum. Apparatus characterized in that it is attached.