DESC:TECHNICAL FIELD OF THE INVENTION
The present invention relates to the field of light weight flame retardant thermal protective fabrics.
BACKGROUND OF THE INVENTION
A flame retardant personal protective wear is typically used to safeguard a person from a risk of electric arcs and/or flash fires. However, when fabrics and garments are manufactured using flame resistant fibers of low tensile strength, the fabrics or garments break open easily on exposure to the intense thermal stress induced by electrical arcs, thereby rendering the wearer vulnerable to fatal injury. Electrical arcs typically involve thousands of volts and thousands of amperes of electrical current. To offer protection to a wearer, a garment or fabric must resist the transfer of the arc energy through the fabric to the wearer. If the garment breaks open when electrical arcs incident on it, a hole is formed in the garment which exposes skin of the wearer to the incident arc energy.
Currently, cotton or cotton and Nylon 66 flame retardant solution treated fabrics are used to safeguard a wearer from electrical arcs. However, such fabrics are heavy in weight. Such fabrics typically have weight more than 250 gsm to 450 gsm. Another type of conventional flame retardant fabric comprises cotton and Modacrylic flame retardant fibers. Such fabrics are also heavy having weight more than 220 gsm to 300 gsm. Yet other conventional flame retardant fabrics involve use of Modacrylic or Polyacrylic Nitrile (PAN) carbon fibers and aramid fibers. Such fabrics have very limited color options. Thus, conventional flame retardant fabrics either have high weight, limited color options, limited bleach resistance, or requires special care during washing.
Hence, there is a need of a flame retardant fabric that alleviates the aforementioned drawbacks of conventional flame retardant fabrics, and can confer better protection compared to the conventional protective fabrics.
SUMMARY OF THE INVENTION
The present invention provides a flame retardant fabric and a method of manufacturing the fabric. The flame retardant fabric comprises at least 40% w/w cellulosic fibers, at least 25% w/w modacrylic fibers, and at least 10% w/w flame-retardant vinylon fibers. In an embodiment, the fabric comprises 40% to 60% w/w cellulosic fibers. In another embodiment, the fabric comprises 25% to 40% w/w modacrylic fibers. In another embodiment, the fabric comprises 10% to 25% w/w flame-retardant vinylon fibers.
In another embodiment, the fabric comprises 0% to 8% w/w para aramid fibers. In yet another embodiment, the fabric comprises 0% to 2% w/w antistatic fibers.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
The detailed description is described with reference to the accompanying figures. In the figures, the reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.
Figure 1 shows process flow chart of production of a flame retardant fabric, in accordance with an embodiment of the present invention.
Figure 2 shows process flow chart of wet processing of the flame retardant fabric manufactured by the process of Figure 1, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Although specific terms are used in the following description for sake of clarity, these terms are intended to refer only to particular structure of the invention selected for illustration in the drawings, and are not intended to define or limit the scope of the invention.
References in the specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
The present invention provides a flame retardant fabric that comprises at least 40% w/w cellulosic fibers, at least 25% w/w modacrylic fibers, and at least 10% w/w flame-retardant vinylon fibers,
In an embodiment, the fabric comprises 40% to 60% w/w cellulosic fibers. In another embodiment, the fabric comprises 25% to 40% w/w modacrylic fibers. In another embodiment, the fabric comprises 10% to 25% w/w flame-retardant vinylon fibers.
In another embodiment, the fabric comprises 0% to 8% w/w para aramid fibers.
In yet another embodiment, the fabric comprises 0% to 2% w/w antistatic fibers.
The cellulosic fibers are selected from the group consisting of cotton, rayon, Viscose, Modal, Cuprammonium, and Lyocell. The presence of cellulosic fibers confers higher thermal stability to the fabric.
The Modacrylic and cotton fibers decompose during arc flash, thereby giving higher Arc Thermal Protective Value (ATPV) and comfort to wearer.
The Vinylon alone or with Para Aramid fibers provide good Energy Break-Open Threshold (EBT) and durability. The para aramid fibers are used to prevent break open phenomena observed in the fabric at high temperature flash fire. In case the fabric is to be used in an environment having limited flash fire hazard, the fabric of the present invention is manufactured without para aramid content.
The antistatic fibers remove any static charge development on the fabric. The antistatic fibers are typically useful in case the humidity of environment in which the fabric is to be used is less than 60%. If humidity is more than 60%, no static charge develops on the fabric as the moisture content in the surrounding atmosphere acts as antistatic agent. The antistatic fibers are used in the fabric in case the fabric is to be used in an environment where humidity can go below 60%.
In the context of the present invention, the aforementioned values of fiber contents are determined to achieve optimum performance by the fabric. If the amount of the modacrylic fibers is reduced below 25% and that of cotton fibers is increased above 40% of the total weight of the fabric, the Limit of Oxygen Index (LOI) rating of the fabric reduces drastically. If the amount of the cotton fibers is kept constant, i.e., between 40% to 60% of the total weight of the fabric, and the amount of vinylon and/or aramid fibers is increased respectively above 25% and 8% of the total weight of the fabric, the cost of manufacturing the fabric increases. If the amount of vinylon and/or aramid fibers is reduced respectively below 10% and 5% of the total weight of the fabric, the Energy Break-Open Threshold (EBT) reduces drastically resulting in lower arc rating value.
The vinylon fibers reduce the deterioration of the cotton and modacrylic part. More specifically, vinylon fibers are dyed with same reactive dyes group and similar processes as that of cotton fibers. Thus, vinylon fibers do not deteriorate the cotton and modacrylic fibers. The deterioration of the cotton and modacrylic fibers is typically observed when amount of aramid fibers is more. If the fabric has more aramid fibers content, the solvent used for dyeing the aramid content deteriorates the cotton and modacrylic fibers. In the present invention, either the aramid content is completely removed and is replaced with vinylon fibers or the content of the aramid fibers is kept as small as possible and fire retardant vinylon fibers are used to replace whole aramid fibers or a part of aramid fibers. Further, use of vinylon fibers also solves the problem of limited color options faced in conventional fabrics as the vinylon fibers can be dyed with same dyes as cotton fibers. Thus, a lot of color options which suits the cotton and other fibers are available for the fabric of the present invention.
The Modacrylic fibers are dyed with basic dyes. The cellulosic and vinylon fibers are dyed with reactive or Vat dyes, which gives very good fastness properties and allow to dye the fabric with any color including high visible color like high visible yellow, red and Orange color as per ISO 20471. Further, the fabric may be optionally treated with other functional durable finishes such as an anti-microbial finish, water and oil repellant coatings, stain release coatings and the like, without affecting protective performance.
Now referring to Figure 1, a process flow chart for production of flame retardant fabric of the present invention is shown.
The process (100) of manufacturing the fabric of the present invention comprises an initial step of preparation of a blend of at least 40% cellulosic fibers, at least 25% modacrylic fibers, and at least 10% flame-retardant vinylon fibers of total weight of the fabric to be manufactured.
In an embodiment, the blend comprises 40% to 60% cellulosic fibers of the total weight of the fabric to be manufactured. In another embodiment, the blend comprises 25% to 40% modacrylic fibers of the total weight of the fabric to be manufactured. In yet another embodiment, the blend comprises 10% to 25% flame-retardant vinylon fibers of the total weight of the fabric to be manufactured.
In yet another embodiment, the blend comprises 0% to 8% para aramid fibers of the total weight of the fabric to be manufactured. In yet another embodiment, the fabric comprises 0% to 2% antistatic fibers of the total weight of the fabric to be manufactured.
In next step, the blend is subjected to a spinning process (102) in which the blend is spun in a ring spinning machine to obtain yarns of the aforementioned fibers wherein the yarn count of the yarns varies from about 2/50 Ne to about 2/20 Ne (double yarn). In the next step, the spun yarns are subjected to a sizing process (104) wherein water soluble threads of the yarns are removed by washing the yarns with water having temperature of 70°C along with lubricant and softener. This also improves the weavability properties, especially lubrication, binding and antistatic properties of the yarns. In further step, the sized yarns are subjected to a weaving process (106) to obtain the fabric of the present invention wherein weaving of the yarns is facilitated in weft and warp fashion. The finished fabric typically weighs between 130 to 250 GSM.
Referring to Figure 2, the woven fabric so obtained is further subjected to a wet processing process (108) wherein the fabric is subjected to a Singeing (202) process in which the fibers protruding from the fabric are burnt out by singeing machine through gas burner. This improves the resistance to pilling and imparts luster to the fabric. In next step, the fabric is subjected to an exhaust pre-treatment and modacrylic part dyeing process (204). In this step, added impurities like spinning oil etc. and natural impurities are removed by exhaust pre-treatments. Further, Modacrylic part is dyed with basic dyestuff in HTHP jigger or soft-flow or jet dyeing machine. In further step, the fabric is subjected to a Cellulosic/PVA part dyeing (206) process wherein both the cellulosic and PVA fibers are dyed with same dyestuff. Typically, the fibers are dyed with vat or reactive dyes as per requirement with any color shade including High-Visible colors. In next step, the fabric is subjected to a finishing process (208) wherein the fabric is treated with hydrophilic softener on a stenter machine to provide the fabric a soft hand feel. The fabric can be treated with other durable features like anti-microbial finish, water and oil repellants, and stain release agents during the finishing process (208). In last step, the fabric is subjected to a sanforising process (210) in which the fabric is allowed to shrink in length as well as in width, to provide a permanent dimension. Referring to Figure 1, the fabric is subjected to a garmenting process (110) after subjecting the fabric to the wet processing (108) in which a garment is manufactured using the flame retardant fabric.
The fabric and methods of production of fabric described herein can provide ATPV of <8 cal/cm2 (HRC 1) below 165 GSM and ATPV >8 cal/cm2 (HRC 2) above 165 GSM.
The fabric of the present invention is air permeable and moisture vapour permeable which helps in reducing perspiration and provides greater comfort to a wearer for longer periods of time. The Moisture Vapour Transmission Rate (MVTR) of the fabric as per ASTM E-96-05 is more than 2000 gm/m2/Day. The fabric of the present invention has high abrasion resistance of more than 100000 revolutions in an abrasion test as per ISO 12947-2/ASTM D4966. The fabric is dimensionally stable i.e., display reduced stretching or shrinking.
The fabric of the present invention is lightweight. In an embodiment, the weight of the fabric ranges from 130 GSM to 250 GSM.
In another embodiment, the yarn count of the fabric varies from 2/50 Ne to 2/20 Ne.
Few examples of the fabric of the present invention are provided below.
Example 1:
The fabric comprises 33% w/w Protex M (Modacrylic) fibers, 42% w/w Pima Cotton (Cellulosic) fibers, 15% w/w Vinal HL (Vinylon) fibers, 8% w/w Para aramid fibers, and 2% w/w anti-static fibers.
The properties of the fabric having aforementioned fibers are provided below.
Yarn Count: 2/40s Ne
Finish Const: EPI 75 X PPI 60, GSM: 165, Weave: Twill Rip stop
Tensile Strength (ISO 13934-1): warp: 800N, Weft: 600N
Tear Strength (ISO 13937-2): warp:40 N, Weft: 40N
Abrasion (ISO 12947-2): more than 100000 (no thread break)
Pilling (ASTMD3512): 4 (out of scale 5)
Vertical Flame Test (ASTM D 6413 WEFT): Damage Length 74 mm (Requirement is the damage length should be less than 100 mm for NFPA2112 and less than 152 mm for ASTM 1590 standards)
MVTR (ASTM E-96-05): 2200 gm/m2/Day
HRC: 2

Example 2:
The fabric comprises 35% w/w Protex M (Modacrylic) fibers, 45% w/w Pima Cotton (Cellulosic) fibers, 20% w/w Vinal HL (Vinylon fibers).
The properties of the fabric having aforementioned fibers are provided below.
Yarn: 2/40s Ne
Finish Const: EPI 75 X PPI 60, GSM: 165, Weave: Twill Rip stop
Tensile Strength (ISO 13934-1): warp: 790N, Weft: 580N
Tear Strength (ISO 13937-2): warp: 38 N, Weft: 40N
Abrasion (ISO 12947-2): more than 100000 (no thread break)
Pilling (ASTMD3512): 4 (out of scale 5)
Vertical Flame Test (ASTM D 6413 WEFT): Damage Length 78 mm (Requirement is the damage length should be less than 100 mm for NFPA2112 and less than 152 mm for ASTM 1590 standards)
MVTR (ASTM E-96-05): 2200 gm/m2/Day
HRC: 2
The fabric of the present invention confers good thermal protection against flash fires, and also against electrical arcs. Further, the fabric reduces the risk of static charge development and consequent fire hazards associated with static energy. The fabric resists the transfer of energy when exposed to the intense thermal stress of an electrical arc. The fabric reduces energy transfer by absorbing a portion of the incident energy and through charring which allows for a reduction in transmitted energy.
“Arc Thermal Protective Value” (ATPV) refers to the maximum incident energy (in calories per centimeter squared) that protective equipment can be exposed to and prevent onset of a second-degree burn. Ratings are based upon the total weight of the fabric.
A Hazard Risk Category (HRC) level is determined by the minimum amount of calories per square centimeter (ATPV or Cal/cm2). Any treated garment must pass through with a 50% probability of a 2nd or 3rd degree burn occurring, which is how the protective level of the treated clothing is determined. The higher the ATPV, the higher the HRC level attained and greater is the protection that is needed. Typical HRCs are given below.
HRC 1: 4 Cal/cm2 = ATPV < 8 Cal/cm2
HRC 2: 8 Cal/cm2 = ATPV < 25 Cal/cm2
HRC 3: 25 Cal/cm2 = ATPV < 40 Cal/cm2
HRC 4: 40 Cal/cm2 = ATPV
The protective wear described herein complies with standards such as ISO 20471, NFPA 2112, ISO 15025, EN 1149/5, ASTM F1959/F1959M – 13, EN 61482-1-1. The NFPA 2112 standard provides minimum requirements for the design, construction, evaluation, and certification of flame-resistant garments for use by industrial personnel, with the intent of not contributing to the burn injury of the wearer, providing a degree of protection to the wearer, and reducing the severity of burn injuries resulting from short-duration thermal exposures or accidental exposure to flash fires.
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

,CLAIMS:
1. A flame retardant fabric comprising:
at least 40% w/w cellulosic fibers;
at least 25% w/w modacrylic fibers; and
at least 10% w/w flame-retardant vinylon fibers.
2. The fabric as claimed in claim 1, wherein said fabric comprises 40% to 60% w/w cellulosic fibers.
3. The fabric as claimed in any one of the preceding claims 1-2, wherein said fabric comprises 25% to 40% w/w modacrylic fibers.
4. The fabric as claimed in any one of the preceding claims 1-3, wherein said fabric comprises 10% to 25% w/w flame-retardant vinylon fibers.
5. The fabric as claimed in any one of the preceding claims 1-4, wherein said fabric comprises 0% to 8% w/w para aramid fibers.
6. The fabric as claimed in any one of the preceding claims 1-5, wherein said fabric comprises 0% to 2% w/w antistatic fibers.
7. The fabric as claimed in claim 1 or claim 2, wherein said cellulosic fibers are selected from the group consisting of cotton, rayon, Viscose, Modal, Cuprammonium, and Lyocell.
8. The fabric as claimed in claim 1, wherein said modacrylic fibers are dyed with basic dyes, and said cellulosic and vinylon fibers are dyed with reactive dyes or Vat dyes.
9. The fabric as claimed in claim 1, wherein Moisture Vapour Transmission Rate (MVTR) of said fabric is more than 2000 gm/m2/Day.
10. The fabric as claimed in claim 1, wherein said fabric has abrasion resistance of more than 100000 revolutions.
11. The fabric as claimed in claim 1, wherein yarn count of said fabric varies from 2/50 Ne to 2/20 Ne.
12. The fabric as claimed in claim 1, wherein weight of said fabric ranges from 130 GSM to 250 GSM.
13. A method of manufacturing a flame retardant fabric, said method comprising following steps:
preparing a blend of at least 40% cellulosic fibers, at least 25% modacrylic fibers, at least 10% flame-retardant vinylon fibers of total weight of a fabric to be manufactured;
spinning said blend in a ring spinning machine to obtain yarns;
washing said yarns in water having temperature of 70°C along with lubricant and softener;
weaving said yarns to obtain a fabric;
burning protruding fibers of said fabric in a singeing machine;
dyeing modacrylic part of said fabric of said fabric; and
dyeing cellulosic part and PVA part of said fabric.
14. The method as claimed in claim 13, wherein said method includes following steps:
treating said fabric with hydrophilic softener on a stenter machine; and
shrinking said fabric in length.
15. The method as claimed in claim 13, wherein said blend includes 0% to 8% para aramid fibers and 0% to 2% antistatic fibers of total weight of a fabric to be manufactured.