Composite Fibers and Method of Producing Fibers

Abstract

Composite fibers created by a process including vertically texturizing and impregnating resin into the fibers at controlled viscosity results in stronger fibers in which virtually no microbubbles are trapped resulting in improved tensile strength for use in reinforcing concrete and other materials.

Claims

1. Composite fibers made by a method of producing composite fibers, said method comprising: feeding a plurality of fiber strands vertically down through a texturizer to obtain texturized fibers, wherein the texturized fibers are unstrained; vertically feeding the texturized fibers down through an injection device; injecting resin into the injection device at a viscosity of 5 mPa*S or less; rotating the plurality of fibers in the injection device, effective to twist the fibers into a bundle, wherein the twisting point is below the level of resin in the injection device, and wherein at least a portion of trapped gases rise to the surface of the resin; squeezing the bundle with squeezing rollers inside the injection device, wherein the trapped gases to rise to the surface of the resin; removing the bundle from the bottom of the device by pulling the bundle; pulling the bundle into a first curing station; pulling the bundle through shaping grips in which the shaping grips are adapted to: (i) pull the bundle from the first curing station, (ii) impart a shape to the bundle and (iii) push the bundle without tension out of the shaping grips; and pushing the bundle from the shaping grips through a second curing station without tensioning the bundle.

2. The composite fibers of claim 1, wherein the method further comprises the step of pushing the bundle from the second curing station to a cutter and cutting the bundle into fragments of a specified length.

3. The composite fibers of claim 2, wherein the fragments are cut to a length for use in at least one of: reinforcing concretes, mortars, soil stabilizing polymers, geo-polymers, or asphalts.

4. Concrete, mortar, soil stabilizing polymer, geo-polymer, or asphalt containing composite fibers of claim 3.

5. Fibers produced by a method comprising: vertically feeding a plurality of unstrained texturized fibers down through a device; injecting resin into the device at a viscosity of from 1 to 5 mPa*S; rotating the plurality of fibers effective to twist all the fibers into a bundle, wherein the twisting point is below the level of resin in the device, and wherein at least a portion of trapped gases rise to the surface of the resin; squeezing the bundle with squeezing rollers inside the device, wherein trapped gases rise to the surface of the resin; removing the bundle from the bottom of the device by pulling the bundle through tension rollers; pulling the bundle into a first curing station; pulling the bundle through shaping grips that pull the bundle from the first curing station, impart a shape to the bundle and push the bundle without tension out of the shaping grips; and pushing the bundle from the shaping grips through a second curing station without tensioning the bundle.

6. The fibers of claim 5, wherein the method further comprises the step of pushing the bundle from the second curing station to a cutter and cutting the bundle into fragments of a specified length.

7. The fibers of claim 5, wherein the method further comprises the step of rotating the bundle in the device effective to achieve a configuration of from about 5 plies per inch to about 25 plies per inch.

8. The fibers of claim 5, wherein the resin is supplied to the device at required viscosity by passing through a viscosity stabilizer that is directly connected to a resin metering mixing device.

9. The fibers of claim 5, wherein the bundle is partially cured in the first curing station to achieve a viscosity of about 10.sup.6 Pa*S.

10. The fibers of claim 5, wherein the shaping grips impart a wave structure to the bundle.

11. The fibers of claim 5, wherein the shaping grips impart a square wave structure to the bundle.

12. The fibers of claim 5, wherein the fragments are cut to a length for use in at least one of: reinforcing concretes, mortars, soil stabilizing polymers, geo-polymers, or asphalts.

13. The fibers of claim 5, wherein the fibers comprise at least one of: igneous rock fibers, carbon fibers, aramid, para-aramid or meta-aramid fibers or glass fibers.

14. The fibers of claim 5, wherein the fibers comprise igneous rock fibers selected from at least one of: feldspars, quartz, feldspathoids, olivines, pyroxenes, amphiboles, or micas.

15. The fibers of claim 5, wherein the fibers comprise basalt fibers.

16. The fibers of claim 5, wherein the fibers exhibit an intrabatch tensile strength with a variation of no more than 5%.

17. An apparatus for processing fibers in a continuous process, said apparatus comprising: one or more devices for holding a basalt fiber roving spool; a rotating table disposed below the one or more devices for holding a basalt roving spool; one or more air flow texturizers disposed below the rotating table; a resin injection device disposed below said texturizers; a resin stabilizer in fluid connection with said resin injection device; a resin mixing and metering device in fluid communication with said resin stabilizer; a tensioning roller disposed below the resin injection device; a first curing tunnel downstream of the tensioning roller; a second curing tunnel downstream of the first curing tunnel; shaping grips disposed between said first curing tunnel and said second curing tunnel, adapted to pull a bundle of fibers from the first curing station, impart a shape to the bundle and push the bundle into said second curing station without tensioning the bundle; and a cutting station downstream of said second curing tunnel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1A is an illustration of the weakening and breakage of conventionally pultruded fiber reinforced products due to microbubbles in the fibers.

[0017] FIG. 1B is a graph of tensile strength of 100 samples of conventionally pultruded basalt fiber from a single batch.

[0018] FIG. 2 is a flow diagram of a conventional pultrusion process in which all steps are practiced in a horizontal orientation.

[0019] FIG. 3A is a flow diagram of an embodiment of a pultrusion process according to the current disclosure.

[0020] FIG. 3B is a flow diagram of an embodiment of a second pultrusion process according to the current disclosure.

[0021] FIG. 4 is a diagram of an embodiment of an apparatus according to the current disclosure.

[0022] FIG. 5 is a graph of tensile strength of 100 samples of pultruded basalt fiber from a single batch according to the disclosure.

DETAILED DESCRIPTION

[0023] Process flow diagrams for the practice of embodiments of the disclosure are shown in FIGS. 3A and 3B. The process is similar to conventional pultrusion in that it is a continuous process for manufacturing a composite with a constant cross-section, but the process is improved and is effective to produce fibers with increased structural strength and consistency as compared to conventionally produced fibers. At least one difference in the disclosed methods and apparatus is that while conventional pultrusion processes and machines are completely horizontal, the disclosed improvements include solutions to the gas bubble problem that include at least in part, orienting at least part of the process vertically. Another aspect of the disclosure is that resin viscosity and fiber tension can be precisely controlled.

[0024] FIG. 3A illustrates an embodiment of the novel processes. As a first step, fiber strands from a roving spool (preferably with internal unwinding) are fed vertically down through a texturizer that separates individual filaments of the strand, to prevent their sticking together. As shown in FIG. 3A, the process can typically include two or more roving spools and texturizers. It is understood that the term vertical can include some variance from absolutely perpendicular to the horizontal plane, but that the fiber strands are texturized and coated with resin at a substantially vertical angle and at an angle that is effective to release entrapped microbubbles from the filaments and to allow the gas to rise to the surface of the resin. At level A of the process as shown in FIG. 3A, the texturized strands are tension free (unstrained).

[0025] At the next stage, shown as level B in FIG. 3A, two or more texturized fiber strands are fed down through a resin impregnationgas removaltension adjustment device. The resin injector injects resin into the device and saturates the texturized fibers with the resin previously prepared by metering mixing equipment. The viscosity of the resin injected into the resin impregnation device (Point C) does not exceed 5 mPa*S. The required viscosity is provided by a viscosity stabilizer that is directly connected to a resin metering mixing device.

[0026] During this process any previously trapped gases naturally surface. All the Roving SpoolTexturizer pairs are rotated around an axis Y twisting all the strands into a single bundle. The twisting point is below the resin level inside the device. Rotation can be chosen to provide 5 to 25 plies per inch. This arrangement improves the structural strength of the final product and improves gas removal from the fiberresin bond.

[0027] After complete saturation, gas removal and twisting, the bundle is pulled through tension rollers that remove excess resin before the bundle goes to a curing station. These rollers function as a tension buffer between unstrained fiber inside the resin impregnationgas removal device and the pulling device. In certain embodiments rollers downstream of the resin impregnation device can provide some pulling force in addition to the force provided by the shaping grips adapted so the bundle is under less stress. At the level shown as B of FIG. 3A the bundle of strands is twisted, impregnated with resin, free from gases, strained and uncured.

[0028] The bundle is subsequently pulled through curing station 1. It is understood that the curing stations are described herein primarily as heat curing stations, which are appropriate for thermoset resins such as polyurethanes, for example. It is understood, however, that in certain embodiments thermoset resins can be used and would require cooling curing stations. At the point shown as D in FIG. 3A, the resin is partially cured and has a viscosity of around 10.sup.6 Pa*S. The bundle then goes through shaping grips that provide a triple function pullshapepush. The process can be adapted such that the bundles are pushed from the shaping grips resulting in there being no tension after the bundle leaves the shaping zone to ensure that the desired shape of the bundle is not distorted. After the shaping zone, the bundle is pushed through curing station 2. At the end of the second curing the shaped bundle is completely polymerized, solidified, free from irregularities and shaped. The bundle can them be pushed into a cutter that cuts the continuous composite fibers into pieces of the required length. The process shown in FIG. 3B differs from that in FIG. 3A in that the bundle is rolled to a horizontal position for the steps of first curing, shaping, second curing and cutting.

Apparatus

[0029] An embodiment of an apparatus for making composite structural reinforcement fibers is presented in FIG. 4. The apparatus includes two internal unwinding fiber roving bobbins (10) located on a rotating table (180). Two compressed air blower texturizers (20) are attached under the table (180). In this configuration the fibers are fed downward through the air jet texturizer devices (20) and into a resin impregnator (40) with squeezing rollers inside. The resin is prepared in a resin metering-mixing device (80), that feeds into a resin injector with a resin viscosity stabilizer (50). A fiber bundle tensioning roller (70) is adapted to function as a tension buffer between unstrained fibers inside the resin impregnationgas removal device (40) and the pulling device (110). The bundle is pulled into a first tunnel curing station (90), through shaping pull-push gears (110), through a second tunnel curing station (120), over support roller (130), and into the cutter (150), where specified lengths of fibers (160) are cut and dropped into a bunker (170).

[0030] In FIG. 4, the fibers as shown at point (30) are texturized, unsaturated, tension free fiber strands. At point (60) the fibers are a resin saturated, gas free, twisted, and non-cured bundle. At point (100) the bundle is half cured unshaped continuous composite fiber. At point (140) the bundle is completely cured, shaped, gas free, continuous fibers. Part (160) is a final product that is a cut to length composite structural reinforcement fiber.

Results

[0031] Tensile testing of composite fibers made in accordance with the present disclosure showed that a hundred samples from the same batch had an average tensile strength of around 419.18 ksi with a variation of about 5% above and below the average line as shown in FIG. 5. This result is an almost 60% improvement over fibers made with conventional pultrusion (compare to FIG. 1B). The study of shape, size, texture and phase distribution of composite fibers made in accordance with the disclosed process shows that there are almost no gas microbubbles between filaments inside the set resin.

[0032] The average residual strength of a concrete slab (standard 4500 psi concrete) reinforced with fibers produced by the disclosed process (mix ratio of 12 pounds of fiber per 1 cubic meter of concrete) is 3,176 psi, which is about 50% better than conventionally produced fibers. The average flexural strength of the same type of slab without fiber reinforcement is 2,740 psi.

[0033] All of the apparatus, components and methods disclosed and claimed herein can be made and used without undue experimentation in light of the present disclosure. While the apparatus, components and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to the construction or components described herein without departing from the concept, spirit and scope of the invention. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.