Patent Application
20170022634
The present disclosure relates to textile fibers. In particular, but not by way of limitation, the present disclosure relates to articles and methods for incorporating active particles into meta-aramid and para-aramid fibers for improving the physical characteristics of flame-resistant textiles.
Meta-aramid and para-aramid fibers are used in protective textiles to protect objects and/or humans from excessive heat exposure and burning caused by open flames. These fibers are adapted to self-extinguish when they are exposed to a flash fire or heat event. Various industry-standard test methods are used to determine the heat resistance, flame resistance, and self-extinguishing characteristics of such protective textiles. Examples of common tests include the methods found in ASTM D6413, ASTM F2700, and ASTM 2703, as well as the PyroMan™ test method, developed by Ansell Protective Solutions AB, Johan Kocksgatan 10, SE-231 81 Trelleborg, Sweden. The benefits of protection that meta-aramids and para-aramids provide allow meta-aramids and para-aramid fibers to be used in a wide range of applications where flame resistance is required.
Wearing garments comprising meta-aramid and para-aramid fibers provide the benefits of protecting the wearer from flame exposure, but these benefits come at a cost of human comfort, since moisture is unable to move through meta-aramid and para-aramid fiber material. Similarly, meta-aramid and para-aramid materials used to protect industrial components have the benefit of protecting the parts from flame exposure, but moisture build-up between the textile and the industrial component can cause other problems. The movement of water vapor or liquid water is important in either extending the comfort range for a human or to keep an industrial part at an optimum moisture level.
These materials have a need to have improved moisture function to extend the usage capability. It is desirable to improve on the functionality of these products against a flame and other thermal events. One embodiment of an invention providing these improvements comprises a textile comprising a plurality of synthetic fibers. In such a textile, the plurality of synthetic fibers comprise a plurality of meta-aramid and/or para-aramid fibers. A plurality of active particles are physically embedded in the plurality of synthetic fibers, with the plurality of active particles comprising a higher heat stability temperature than the plurality of synthetic fibers.
Another embodiment of the invention comprises a fire-resistant garment. One such fire-resistant garment comprises a plurality of synthetic fibers and a plurality of active particles physically embedded in the plurality of synthetic fibers. The plurality of synthetic fibers comprises a plurality of meta-aramid and/or para-aramid fibers and the plurality of active particles are physically embedded in the plurality of synthetic fibers. Furthermore, the plurality of active particles comprises a higher heat stability temperature than the plurality of synthetic fibers.
Yet another embodiment of the invention comprises a method of creating a composite polymer textile. One such method comprises creating a solution by dissolving meta-aramid and/or para-aramid polymers into a solvent and dispersing active particles into the solution. The solution is then spun using a spinneret, polymerizing or precipitating the solution into a meta-aramid and/or para-aramid fiber material and physically incorporating the active particles into the meta-aramid and/or para-aramid fiber material.
Various objects and advantages and a more complete understanding of the present invention are apparent and more readily appreciated by reference to the following Detailed Description and to the appended claims when taken in conjunction with the accompanying Drawings wherein:
The term “or” as used in this specification and the appended claims is meant to be an exclusive identification between two terms, meaning “either”. Therefore, when the “or” term is used with reference to items A and B, for example, as in “items A or B”, the phrase should be viewed as “either of item A and item B, not both of item A and B.” The term “and” as used in the appended claims and the specification is mean to be inclusive. In using the item A and B example above, the phrase “item A and item B” should be viewed as “both of item A along with item B.” If the term “and/or” is used in the claims and specification, the term should be viewed as inclusive and exclusive. Therefore, in the example above, the phrase “A and/or B” should be viewed as “either ‘A or B’ or ‘A and B’”.
References in the specification to “one embodiment”, “an embodiment”, “a preferred embodiment”, “an alternative embodiment”, “a variation”, “one variation”, and similar phrases mean that a particular feature, structure, or characteristic described in connection with at least one embodiment of the invention. The appearances of phrases like “in one embodiment”, “in an embodiment”, or “in a variation” and similar phrases in various places in the specification are not necessarily all meant to refer to the same embodiment or variation and may refer to multiple embodiments or variations. Similarly, the word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any use of the term “exemplary” herein is not necessarily to be construed as preferred or advantageous over other embodiments.
An aramid fiber comprises a manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide where at least 85% of the amide linkages (CO—NH—) in the polyamide are attached directly to two aromatic rings. Meta-aramid and para-aramid fibers differ slightly in their chemical composition as compared to purely aramid fibers. Specifically, the position on the aromatic rings to which the meta-aramid and para-aramid fibers bond differs as compared to purely aramid fibers.
Fibers comprising the meta-aramid 150 and para-aramid 100 structure seen in
As stated, meta-aramid and para-aramid fibers are also useful in protecting structures and objects from heat and flame. In industrial settings, pipes, tanks, pumps, and other structures and equipment can be protected from damage with hoses or wraps comprised of meta-aramid or para-aramid fibers surrounding the equipment/structures. However, many pieces of industrial equipment or structures also create condensation during operation and this water buildup between the flame-resistant material and the equipment can introduce additional problems. Meta-aramid and para-aramid textiles are also further used in building materials as a substitute for asbestos and/or other construction materials in walls and ceilings. Building materials that include meta-aramid and para-aramid textiles can cause humidity buildup within buildings. In nearly every application of meta-aramid and para-aramid materials, in order to alleviate the effects of humidity buildup, some kind of ventilation is usually implemented. However, depending on how various methods of ventilation are implemented, the ventilation may compromise the effectiveness of the flame-resistance system.
In order to alleviate this compromised effect of ventilation, yet still provide decreased humidity in meta-aramid and para-aramid materials, an embodiment of the invention comprises a textile in which active particles are integrated into meta-aramid and para-aramid fibers. One type of textile may comprise a woven material, a non-woven material, or a performance-enhanced material. The term “active particle” may be defined as a material with a specific set of physical properties that interact with the environment to achieve particular performance characteristics. One type of active particle textile may comprise a polymer composite comprising meta-aramid and/or para-aramid fibers and one or more active particles. For ease of reference, textiles in accordance with embodiments of the present disclosure comprising active particles and either meta-aramid or para-aramid fibers may be referred to as “composite textiles” or “composite polymer textiles.”
The active particles in composite textiles achieve two desired performance characteristics: First, the active particles may provide moisture management characteristics in the form of a decreased or a substantial elimination of humidity and liquid between the skin of the textile wearer and the textile; Second, the particles may enhance the flame-resistant performance (i.e., increased resistance to burning when in contact or near a direct flame) of the textile, beyond the existing characteristics if the textile contains only meta-aramid and para-aramid fibers. For example, to meet the requirements of ASTM D6413, the material must not melt or drip, have less than 2 seconds of afterglow and after flame, and less than 4 inches of char length. In order to achieve these characteristics, the active particles themselves have particular properties.
Providing desired moisture management properties to a textile may be obtained through adding to the textile active particles that 1) absorb infrared light in the 8 to 12 micron wavelength region, 2) have the ability to adsorb and desorb (i.e., eject or emit) water at temperatures between 10 and 40° C., and 3) have a surface area greater than 10 m2/g. Water is absorbed by the active particles when the person begins to perspire while wearing the garment. The active particles desorb the adsorbed liquid or vapor when infrared light is absorbed by the active particle, comprising enough energy to cause the water to desorb from the particle. It is contemplated that the infrared light may be emitted by the person wearing the garment. In one embodiment, the amount of active particles in the textile may comprise from about 0.01% to about 3% by weight. However, the active particle loading level may be determined based on the strength of the fiber. In some embodiments, increased active particle loading may occur with increased tensile strength. The amount of water that is absorbed and desorbed from the active particles may comprise an evaporation rate. One or more of these particular properties may be collectively referred to throughout the disclosure as the “moisture management properties.” The specific moisture management properties described herein provide certain advantages which result in the desired characteristics of the composite textile. For example, one advantage that the capturing of infrared energy in the 8 to 12 micron wavelength region provides is an increase of the evaporation rate of water as compared to its normal evaporation rate. For example, woven fabric comprising Nomex® material without active particles comprises an AATCC 200 drying rate of about 0.73 ml/h and the same Nomex® fabric material with active particles comprises a drying rate of about 3.5 ml/h. Such woven fabric may comprise of 15% polyethylene terephthalate (PET) doped with 1% active particles blended with 85% Nomex® fibers. Additionally, the ability to adsorb and desorb water while wearing the garment ensures that moisture can pass through the composite textile at body temperature and at normal ambient environmental temperatures. The surface area property of greater than 10 m2/g generally indicates that a particle has high porosity. High porosity can be advantageous in active particles of the present disclosure because the large surface area created by pores allows a relatively large amount of water to be adsorbed to the surface of a particle in comparison to its overall size, thereby creating a flow of perspiration from the wear of the garment to the ambient environment, as described above.
In order to enhance the flame-resistant characteristics of the textile, the active particles may have a heat (thermal) stability of greater than 300° C. and a specific heat of less than 1.3 J/gK at 293K. Many existing meta-aramid and para-aramid fibers have a heat stability (otherwise known as a thermal degradation temperature) of between 200 and 260° C. Incorporating active particles with a higher heat stability temperature than the meta-aramid and para-aramid fibers is advantageous because it is likely that the composite textile will be exposed to temperatures of at least 200 to 260° C. In order to preserve the moisture management functionality of the active particles, they should not degrade (e.g., decomposition and volatilization) at temperatures that the meta-aramid and para-aramid fibers are designed to be exposed to. Further, adding the active particles as described in the present disclosure may increase the overall heat stability of the textile to a higher temperature threshold than existing meta-aramid and para-aramid fibers. Several types of active particles can be utilized in embodiments of the present disclosure, including zeolite and activated carbon. In many embodiments, active particles may be minerals that may absorb and desorb water with human infrared energy. Any type of active particle having one or more of the properties listed herein may be used without departing from the scope of the present disclosure.
As seen in
Another aspect of the present disclosure provides a method by which active particles and meta-aramid or para-aramid fibers may be formed into a composite polymer textile. One method of manufacturing meta-aramid and para-aramid fibers is wet-spinning. Wet-spinning comprises a process in which a polymer/monomer is dissolved into a solvent, and the solution is spun using a spinneret, which precipitates or polymerizes the solution into a relatively flat fiber material. The material is eventually quenched into its solid form.
The method of the present disclosure may comprise dissolving polymers of meta-aramid or para-aramid into a solvent. Solutions of such dissolved polymers may be used in the process of wet-spinning to manufacture meta-aramid and para-aramid fibers, rather than heat-based extrusion methods of manufacturing, because once a meta-aramid or para-aramid polymer is formed, it does not melt into a liquid. One example of a solvent that may be used with the presently disclosed method includes sulfuric acid. Those skilled in the art can appreciate that solvents require particular characteristics in order to allow the polymer to dissolve into a solvent during the wet spinning process. Furthermore, an aspect of the present disclosure is that the active particles are insoluble and physically unaffected (not damaged) by the solvent. Therefore, in addition to the physical properties of active particles listed throughout the present disclosure, in some embodiments, the active particles may also have the additional property of being insoluble in certain known solvents. Alternatively, or additionally, in various embodiments of the method, a particular solvent may be chosen because it does not adversely impact the physical properties of a desired active particle.
One method may further comprise dispersing active particles into the solution. This dispersal may occur before or while the solution is being spun through a spinneret. The particles can be directly dispersed into the solution. Alternatively, the active particles may be dispersed using a dispersing agent. One type of dispersing agent may comprise Carbowet® from Air Products and Chemicals, Inc. 7201 Hamilton Blvd. Allentown Pa. 18195. Advantages to using a dispersing agent may be to achieve a higher level of uniformity of particle distribution, prevent particles from agglomerating, and prevent the particles from falling out of the dispersion. Falling out of a dispersion comprises a particle settling to the bottom of solution volume, preventing proper mixing of the solution. As another alternative, the active particles may be dispersed using a removable protective layer, such as an encapsulant, as described in U.S. Pat. No. 7,247,374, which is hereby incorporated by reference in its entirety. For example, when an active particle is coated with a protective layer, the protective layer may comprise a dispersing agent. Upon removal of the encapsulant from the active particle, or before, the encapsulant acts as a dispersing agent.
Upon dispersing the active particles in the solvent and then subsequently wet-spinning the solution, active particles may become physically incorporated and/or enmeshed with the meta-aramid or para-aramid fibers. Though the active particles may not form chemical bonds with the fibers, the two become physically intertwined. In the art, the dispersion of insoluble particles into a wet-spinning solution has not been pursued due to the knowledge that (i) active particles would not form chemical bonds with the tightly-aligned meta-aramid and para-aramid fibers and that (ii) the active particles would have a negative impact on the formation of the fibers. However, the method of the present disclosure results in the physical entanglement of the particles with the polymer fibers without negatively impacting the spinning process or the formation of the fibers. In fact, dispersion forces or van der Waals forces may also hold the active particles and meta-aramid or para-aramid fibers together. Seen in
The active particles that are dispersed into the solution may be between 100 nm (0.1 microns) and 10 microns in size (e.g. average diameter). It is contemplated that in some embodiments, a given supply of active particles dispersed in a solution may be non-uniform in size. The 100 nm to 10 micron size range of active particles allows them to achieve certain properties. For example, activated carbon particles in the size range of at least 100 nm to may have a surface area greater than 10 m2/g, which allows for optimal moisture management characteristics of the resulting composite textile. Active particles of less than 10 microns in size may be sufficiently large to provide the desired characteristics while also being small enough to become entangled or enmeshed with the meta-aramid and para-aramid fibers during the wet-spinning manufacturing process.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
This application claims priority to U.S. Provisional Application No. 62/138,325, filed Mar. 25, 2015 and entitled “Enhanced Meta-Aramid and Para-Aramid Fibers”, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62138325 | Mar 2015 | US |
