Patent Grant
7811952
Protective garments are often constructed from high-strength, inherently flame resistant fabrics, such as fabrics comprising aramid materials. Although such fabrics are strong and, therefore, can provide the desired degree of protection to the wearer, the strength of these fabrics can be compromised through exposure to ultraviolet (UV) rays, such as those emitted by the sun and other light sources. In fact, it is not unusual for the fabrics of such garments to lose 50% or more of theft original strength after repeated exposure to daylight.
Unfortunately, protective garments of the type described above are often worn outdoors. For example, such garments are used by various utility personnel and other industrial workers. In such cases, the strength of the protective garment can decline as use of the garment continues, even over a relatively short period of time. This results in decreased protection for the wearer, as well as increased costs in replacing compromised garments.
In addition to reducing the strength of protective garments, UV exposure can further adversely affect the color of the garments. Specifically, UV exposure can reduce the colorfastness of such garments, causing their color to fade as the duration of UV exposure increases. Such fading is undesirable from an aesthetics point of view. In some cases, however, such fading can decrease the visibility of the garment, and therefore the wearer. This phenomenon is especially undesirable for high-visibility garments used near roadways and other hazardous areas in which failure to see the wearer may result in harm to that wearer.
In view of the above, it would be desirable to be able to produce protective fabric that has greater resistance to UV radiation.
Disclosed are protective fabrics and methods for making protective fabrics. In one embodiment, a protective fabric includes a plurality of inherently flame resistant fibers, and at least one ultraviolet-resistant additive incorporated into the inherently flame resistant fibers through a dye process using a carrier, wherein the ultraviolet-resistant additive significantly increases at least one of the strength retention and the colorfastness of the fabric when exposed to ultraviolet radiation.
In one embodiment, a method includes immersing a fabric in a mixture comprising a carrier and a ultraviolet-resistant additive, the fabric comprising a plurality of inherently flame resistant fibers, solubilizing the ultraviolet-resistant additive with the carrier so that the ultraviolet-resistant additive is absorbed by the inherently flame resistant fibers, wherein absorption of the ultraviolet-resistant additive into the inherently flame resistant fibers significantly increases at least one of the strength retention and the colorfastness of the fibers when exposed to ultraviolet radiation.
The fabrics and methods of the present disclosure can be better understood with reference to the following drawings. Features shown in these drawings are not necessary drawn to scale.
As is described above, the strength and/or colorfastness of fabrics used to construct protective garments can be significantly reduced due to ultraviolet (UV) exposure. As is described in the following, however, the resistance of such fabrics to UV radiation can be significantly improved by incorporating UV-resistant additives into the fibers of such fabrics. When such additives are incorporated into the fabric fibers, the strength loss and/or color fading that can occur due to UV exposure can be reduced.
It is noted that, although a firefighter turnout coat and lineman vest are shown in the figures and described herein, other garments may benefit from the fabrics and methods described herein. Such garments may include one or more of shirts, pants, jackets, coveralls, vests, and the like that are intended for use in various different applications. Moreover, the present disclosure is not limited to garments. More generally, the present disclosure pertains to UV-resistant fabrics irrespective of their application.
The fabrics used to make the outer shell 12 of the garment 10 and the outer layer 20 of the garment 18 can comprise a high-strength, flame-resistant fabric. In some embodiments, the fabric comprises inherently flame resistant fibers that form the fabric body. Examples of such inherently flame resistant fibers include aramid (aromatic polyamide) fibers, such as meta-aramid fibers and para-aramid fibers.
Example meta-aramid fibers include those sold under the trademark Nomex® by DuPont, and fibers that are currently available under the trademark Conex by Teijin.
Example para-aramid fibers include those that are currently available under the trademarks Kevlar by DuPont, and Technora® and Twarong by Teijin.
Other inherently flame resistant fibers suitable for construction of the fabric include, for example, polybenzoxazole (PBO), polybenzimidazole (PBI), melamine, polyamide, polyimide, polyimideamide, and modacrylic.
One or more other types of fibers may be blended with the inherently flame resistant fibers to construct the fabric. Examples of such fibers include cellulosic fibers, such as rayon, acetate, triacetate, and Iyocell. These cellulosic fibers, although not naturally resistant to flame, can be rendered flame resistant through application with an appropriate flame retardant. Generally speaking, cellulosic fibers that contain one or more flame retardants are given the designation “FR”. Accordingly, the preferred flame resistant cellulosic fibers include FR rayon, FR acetate, FR triacetate, and FR lyocell.
Of the many blends conceivable using the above-described fibers, specific examples include 100% Nomex T-455®, 100% Nomex T-462®, 100% Nomex E114® (Z-200), a 65/35 blend of Nomex T-462® and FR rayon, a 60/40 blend of Nomex T-462® and FR rayon, a 60/40 blend of Kevlar T-970® and Nomex T-462®, a 60/40 blend of Kevlar T-970® and PBI, an 80/20 blend of Nomex T-462® and PBI, a 60/20/20 blend of Kevlar T-970®, PBO, and Nomex T-462®, a 50/50 blend of meta-aramid and modacrylic, a 60/40 blend of Kevlar Nomex T-970® and Basofil® (melamine), a 60/40 blend of meta-aramid and para-aramid, and 90/10 blend of meta-aramid and para-aramid. It is to be understood that these specific constructions are mere examples and are not intended to limit the scope of the present disclosure.
The fabric can be dyed to a desired shade of color using customary dyeing equipment. Typically, a dye, a dye assistant (or “carrier”), and a flame retardant for the non-inherently flame resistant fibers (if applicable), are combined to form a mixture, (e.g., a dyebath, solution, dispersion, or the like). Carriers aid in the absorption of dyestuff into the fibers of the fabric. In addition, some carriers aid in the solubilization of various WV-resistant additives that, as is discussed below, increase the UV resistance of the fibers and, therefore, the fabric. As an alternative to adding carrier to the mixture (e.g., dyebath), the carrier can instead be imbibed into the fibers during fiber production. When the fibers are imbibed with carrier, dyeing is conducted in the typical manner, except that additional carrier may not be needed in the mixture.
Once the mixture is formed, the fabric is contacted with the mixture, typically by immersion, and the mixture is heated to fix the dye in the fibers. Although the fabric has to been described as being dyed in the piece, dyeing can be performed during other stages of the production process. Therefore, dyeing can be performed on the fibers, on yarn, or on substantially any fibrous textile, including sliver. Suitable equipment for dyeing a textile include, for example, jig dyeing machines, pad dyeing machines, beck dyeing machines, and jet dyeing machines.
In addition to dye, UV-resistant additives can be incorporated into the fibers to increase the fibers' resistance to UV radiation. One type of UV-resistant additive is UV light absorbers. UV light absorbers are materials that absorb UV radiation to reduce the deleterious effects of that radiation on the medium (fibers in this case) in which the absorber is incorporated. Such UV light absorbers include, for example, benzophenone compounds, triazsole compounds, and benzoic acid compounds. Specific examples, of UV light absorbers include Uvinul 3000 (2,4-dihydroxy-benzophenone), Uvinul 3049 (2,2′-dihydroxy-4,4′-dimethoxybenzophenone), Uvinul 3050 (2,2′-4,4′-tetrahydroxy-benzophenone), and Uvinul 3088 (2-propenoic acid,3-(4Omethoxyphenyl)-2-ethylhexylester), all from BASF; Surftech 4500 (benzotriazole) from American Textile, LLC; and Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol), Tinuvin 327 (2-(3,5,Di-(tert)-butyl-2-hydoxyphenyl)-5-chlorobenzotriazole) and Tinuvin 328 (2-hydroxy-3,5-di-(ter)-amylphenyl)benzotriazole) from Ciba Specialty Chemicals
Another type of UV-resistant additive that can be incorporated into the fibers are hindered amine light (HAL) stabilizers. Such HAL stabilizers include, for example, amide compounds and piperidine compounds. Specific examples include Uvinul 4050H (N,N′-1,6-hexanediylbis(N-(2,2,6,6-tetramethyl-piperidinyl-formamide) from BASF, and
Sanduvor 3058 Liquid(1-acetyl-4-(3-dodecyl-2,5-dioxo-1-pyrrolidinyl)-2,2,6,6-tetramethyl-piperidine from Clariant.
Tests suggest that UV light absorbers are particularly effective in improving fabric strength retention, while HAL stabilizers are particularly effective in improving fabric colorfastness. Although they can be used separately, incorporation of both a UV light absorber and a HAL stabilizer into a given fabric can yield improved results in terms of strength retention and/or colorfastness. Specific examples of UV light absorber/HAL stabilizer blends include Chimasrob 119FL (Chimasorb 119 (complex triazine) and Tinuvin 622 (sucinate polymer with piperidineethanol)) and Tinuvin 783LD (Tinuvin 622 and Chimasorb 944 (complex triazine)).
The UV-resistant additives can be incorporated into the fibers of the fabric at nearly any stage in the production process. Given that carriers that may be used as dye assistants in the dyeing process, it may be desirable to add the UV-resistant additives to the fibers during the dyeing process (assuming dyeing is performed). In such a case, the UV light absorber(s) can, for example, be provided in the mixture in a concentration of about 0.5% on weight of fabric (owl) to about 6% owf, and the HAL stabilizer(s) can, for example, be provided in the dyebath in a concentration from about 0.5% to about 3% owf. In some embodiments, concentrations of about 2% to 4% and 2% to 3% owf for UV light absorber and HAL stabilizer, respectively, are preferred. Examples of carriers that have been determined to solubilize UV light absorbers and/or HAL stabilizers include aryl ether, benzyl alcohol, N-cyclohexylpyrrolidone (CHP), N,N-diethyl-m-toluamide (DEET), dimethylformamide (DMF), dibutyl acetamide (DBA), Isophorone, Acetophenone, Dimethylacetamnide, and Dibutylformamide.
A flame retardant compound can also be included in the mixture, applied as an after-dyeing surface treatment, or otherwise incorporated in the fibers of the fabric to enhance flame resistance or to counteract any deleterious effects of the carrier contained within the inherently flame resistant fibers. Furthermore, other chemicals can be applied to the fibers (e.g., added to the mixture) including lubricants, wetting agents, leveling agents, and the like.
Testing was performed to examine the effectiveness of UV light absorbers and HAL stabilizers that were incorporated in the fibers of fabric during the dye process. In that testing, various samples of fabric were tested for strength according to test methods described in ASTM D5733-99 and ASTM D1424-96 both before and after exposure to UV radiation (daylight). Some of those samples had been treated with a UV light absorber, a HAL stabilizer, or both, while others (the “controls”) were left untreated.
Table I provides strength retention data for this testing.
Various phases of testing were conducted. In one such phase (Phase A), various samples of 100% Nomex T-462® were tested for strength after 14 days of exposure to UV radiation in the form of sunlight using the trap tear test described in ASTM D5733-99, which is hereby incorporated by reference. Each sample was dyed or treated using a carrier, which comprised one of DEET, CHP, benzyl alcohol, and aryl ether. A control sample and a sample treated with a benzophenone compound (Uvinul 3049) were prepared using each carrier.
As can be appreciated from Table I, the samples that were treated with the benzophenone compound UV light absorber typically exhibited greatly improved strength retention in both the warp and fill directions after WV exposure. On average, each treated sample exhibited 7.8% greater strength retention as compared to the controls (i.e., 85.9% average for treated samples, 78.1% average for non-treated samples), and strength retention differences as high as 12.9% were observed.
In a second phase of the testing (Phase B), samples of a 65/35 blend of Nomex T-462® and FR rayon were tested for strength after 30 days of exposure to sunlight using the Elmendorf test described in ASTM D1424-96, which is hereby incorporated by reference. Each sample was dyed or treated using a CHP carrier, and each sample was treated with a different concentration of UV light absorber ranging from zero (i.e., for the control) to 6%. As is evident from the test data, significant strength retention increases were observed when the fabric was treated with levels of UV light absorber as low as 1% owf. In particular, the strength retention for the sample treated with 1% benzophenone compound (Uvinul 3049) was 14.9% greater in the warp direction and 8.8% greater in the fill direction as compared to the control sample. Greater strength retention was generally observed as the percentage of UV light absorber was increased.
In a third phase of the testing (Phase C), samples of a 60/40 blend of Kevlar T-97® and Nomex T-462® were tested for strength after 14 days, and in two cases 30 days, of exposure to sunlight. The samples were treated with various carriers and UV light absorbers. In addition, two samples were treated with a HAL stabilizer (in the 30 day exposure cases). Again, the samples that were treated with the UV light stabilizers exhibited increased strength retention. The testing conducted for the samples containing a HAL stabilizer appeared to indicate that similar results are possible in cases in which the concentration of UV light absorber was reduced and the concentration of HAL stabilizer was increased.
Further testing was performed to examine the effectiveness of UV light absorbers and HAL stabilizers in improving colorfastness of fabrics that are exposed to UV radiation. In this testing, various samples of fabric were tested for colorfastness according to AATCC Test Method 16-2003 (Option 3). Some of those samples had been treated with a UV light absorber, a HAL stabilizer, or both, while others (i.e., the controls) were left untreated. Table II provides colorfastness data for this testing.
According to AATTCC Test Method 16-2003, colorfastness is rated from a scale of 1 to 5, with “1” being the poorest colorfastness and “5” being the best colorfastness. As can be appreciated from Table II, the colorfastness of the fabrics treated with UV light absorbers and/or HAL stabilizers performed markedly better in terms of colorfastness as compared to the control fabrics.
While particular embodiments of the protective garments have been disclosed in detail in the foregoing description and drawings for purposes of example, it will be understood by those skilled in the art that variations and modifications thereof can be made without departing from the scope of the disclosure.
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