FIELD OF INVENTION

This invention relates to a light-weight flame resistant fabric. In particular, this invention relates to a light-weight flame resistant fabric with a grid wave structure for use to protect human beings from thermal hazards of flame and electrical arc.

BACKGROUND OF THE INVENTION

Flame-resistant fabrics are used in making articles such as protective clothing, drapes, tents, tarps, and furniture upholstery. These articles are used against thermal hazards arising from exposure to heat, flame, and electric arc. The flame-resistant fabrics inhibit the propagation of flame, generate char, and prevent the generation of volatile gases to provide protection against thermal hazards. There are two types of flame-resistant fabrics known in the prior art. The first one is flame retardant-treated fabric and the second one is inherently flame-resistant fabric. The treated flame retardant fabric primarily consists of a cellulose-rich fabric blend including thermoplastic fibers and antistatic fibers. This fabric is treated with a phosphorous-based flame retardant chemical such as Pyrovatex® CP and Proban®. Inherently flame-resistant fabrics primarily consist of blends of inherent flame-resistant fibers along with cellulosic fibers, thermoplastic fibers, and anti-static fibers. Inherently flame-resistant fibers by their nature, do not need any additional flame retardant chemical finish. Examples of inherent flame-resistant fibers are asbestos, carbon, polyphenylene benzobisoxazole, polybenzimidazole, para-aramids, meta-aramids, fluorocarbons, acrylonitrile polyphenylene sulfides, melamines and polyimides.

The flame-resistant fabrics also need to provide thermal insulating property. Better thermal insulation will reduce or eliminate heat-related and burn- related injuries in human protection applications. Thermal insulation of the fabric is not solely dependent on the flame retardant chemicals or inherent flame-resistant fibers used in making the fabric. Other factors which improve thermal insulation are the weight of the fabric, the ability to trap air, and the physical contact area on the surface to be protected.

Thermal insulation of the fabric used in the thermal protective application is measured as per the EN ISO 11612. As per the standards, convective, contact, and radiant heat resistance are measured to determine the overall thermal performance of the flame-resistant fabric. Here the fabric is exposed to a standard source of heat and flame and the rise in temperature is measured by a sensor placed behind the fabric. The time required to increase the temperature by a certain degree Celsius is noted and the fabric is graded in different categories based on the recorded time.

Additionally, the flame-resistant fabrics also provide thermal insulation as tested per NFPA 21 12. Under this standard, the fabric is tested against a flame source with an exposure heat flux of 83.55 kW/m ² (2.0 cal/cm ² sec). A sensor containing a copper calorimeter is placed on top of the specimen and measures the heat transfer through the fabric specimen. The test measures the amount of heat passed through the specimen to cause a second-degree burn. TPP ratings are measured with the sensor both in "contact" with the specimen and "spaced" 6 mm away from the specimen.

The weight of the fabric is measured in grams per square meter (GSM). Increasing the weight of the fabric improves the thermal insulation performance of the fabric. Increased air trapping can be achieved by using a multi-layer fabric structure, use of non-woven fabric, use of fleece structure or imparting a three-dimensional structure to the fabric. A three- dimensional structure will also help in minimizing the contact area exposed to flame and the surface to be protected.

Increasing the weight of the fabric makes the protective clothing heavier and hinders the work performance of the user. The use of a multilayer system or a non-woven fabric will increase the bulkiness of the fabric and hinder the working performance of the user. Adding weight to the fabric or using a nonwoven fabric also adds to the cost of the fabric.

US patent publication no. US8501639B2 discloses a fabric consisting of a single layer of a non-woven substrate, wherein the non-woven substrate is treated with a finish comprising one or more flame retardant phosphorous compounds or nitrogen compounds, wherein the non-woven substrate is a non-woven fabric comprising cellulosic fibers and has a basis weight ranging from 3.0 to 8.0 ounces per square yard, wherein the finish is applied to the non-woven substrate in an amount ranging from 15 to 130 percent solids, based upon the weight of the non-woven substrate, wherein the single-layer, finished fabric has a thickness ranging from 0.01 to 0.15 inches and a contact thermal protective performance value of at least 4.5, wherein the non-woven substrate is a non-woven, stitch-bonded fabric, and wherein the non-woven substrate comprises polyester fibers.

US patent publication no. US20120270456A1 , disclose a flame retardant fabric for use in personal protective clothing which provides a high level of protection from flames or other sources of heat wherein said fabric is made from a mixture of a primary yarn which is a blend of FR cellulosic fibers with high-temperature resistant polymer fibers and a secondary yarn which is a twisted yarn containing a continuous synthetic filament yarn.

There are disadvantages associated with the prior art. One of the disadvantages is that the weight of the conventional fabric is increased to increase the thermal insulation of the fabric.

Another disadvantage associated with the prior art is that the air trapping in the fabric is less.

Yet another disadvantage associated with the prior art is that the contact surface of the fabric is high so that its contact area is highly exposed to flame and the surface to be protected. Still another disadvantage associated with the prior art is that adding weight to the fabric or using a non-woven fabric also adds to the cost of the fabric.

Thus, there is a need for a fabric wherein the thermal insulation, air trapping, and protection levels are enhanced, without increasing the fabric weight or bulkiness and without increasing any cost.

OBJECTIVE OF THE INVENTION

Therefore, an object of the present invention is to provide a light-weight flame resistant fabric which obviates the disadvantages associated with the prior art. Another object of the present invention is to provide a light-weight flame resistant fabric with reduced weight.

Yet another object of the present invention is to provide a light-weight flame resistant fabric which is capable to trap more amount of air between its wavy structure. Still another object of the present invention is to provide a light-weight flame resistant fabric which is capable to reduce the exposed contact area between the flame and the protected surface.

A further object of the present invention is to provide a light-weight flame resistant fabric which is cost-effective. Another object of the present invention is to provide a light-weight flame resistant fabric which provides a soft, flexible finish to the fabric that may be suitable for use in a wide range of products. In addition, the fabric is dyed to a variety of shades and/or patterns.

Yet another object of the present invention is to provide a light-weight flame resistant fabric which is durable enough for long-term usage and can withstand multiple wash cycles.

Still another object of the present invention is to provide a light-weight flame resistant fabric which is being used in protective garments applications, for example, fire-resistance suits, fire resistance gloves, fire blankets, blast blankets, welding suits, welding drapes, welding pads, and welding filters and also being used in other types of protective garments which required protection from multiple hazards.

A further object of the present invention is to provide a light-weight flame resistant fabric which is used in, for example, mattresses, chairs, sofas, and seats for home furnishing or that used in vehicles.

Another object of the present invention is to provide a light-weight flame resistant fabric which is used in fashion apparel, for example, shirts, trousers, skirts, blouses, jackets, frocks, and inner-wear.

Another object of the present invention is to provide a light-weight flame resistant fabric which includes containers, for example, fire resistant document pouches, fire-resistant safes, packaging containers for explosives, shipping containers for explosives, and fire-resistant ammunition cases.

Another object of the present invention is to provide a light-weight flame resistant fabric which improves thermal protection and ease of movement without increasing the weight or the cost of the fabric.

SUMMARY OF THE INVENTION

According to this invention, there is provided a light-weight flame resistant fabric comprising a base structure made of fiber yarns having a low boiling water shrinkage property, grid structures, made of filament yarns of a thermoplastic polymer having a high boiling water shrinkage property, being formed in the base structure at an interval of 3 - 20 mm and subsequently heat treated such that to create wave structure in the grid pattern at both sides of the fabric so as to allow entrapment of air in the fabric and minimized contact surface.

In another embodiment the yarns of the base structure are made of a blend of cellulosic fibers, for example, cotton, hemp, viscose, rayon, bamboo, jute, linen, and modal fiber wherein the percentage weight of one of the fibers present in the blend is not less than 60 %.

In another embodiment, the base yarn of the base structure is made of inherently flame-resistant fibers or a blend of inherent flame-resistant fibers, for example, meta-aramids, para-aramids, inherent fire-resistant viscose, modacrylic, acrylonitrile, asbestos, carbon, wool, polyphenylene benzobisoxazole, polybenzimidazole, fluorocarbons, polyphenylene sulfides, melamines and / or polyimide.

In one embodiment the grid yarn is made of a polyester, or a blend of the polyester, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and I or polytrimethylene terephthalate (PTT).

BRIEF DESCRIPTION OF THE DRAWINGS

Light-weight flame resistant fabric, according to a preferred embodiment, is herein described and illustrated in the accompanying drawings, wherein:

Figure 1 , illustrates a perspective view of a weave structure of the invented fabric, and

Figure 2, illustrates a perspective view of waves in the invented fabric.

DETAILED DESCRIPTION OF THE INVENTION

Light-weight flame resistant fabric is herein described with numerous specific details so as to provide a complete understanding of the invention. However, these specific details are exemplary details and should not be treated as the limitation to the scope of the invention. Throughout this specification the word “comprises” or variations such as “comprises or comprising”, will be understood to imply the inclusions of a stated element, integer or step, or group of elements, integers or steps, but not the exclusions of any other element, integer or step or group of elements, integers or steps.

Referring to the drawing, particularly figure 1 , a perspective view of a weave structure (100) of the invented fabric is shown. The light-weight flame resistant fabric comprises a base structure (1 10) made of fiber yarns (1 1 1 & 1 12) which have a less than 7 % (low) boiling water shrinkage property. Grid structures (120) are made of filament yarns (121 & 122) of a thermoplastic polymer which have a 9 - 25 % (high) boiling water shrinkage property. The grid structures (120) are formed in the base structure by weaving therewith at an interval of 3 - 20 mm. After that, the woven fabric is exposed to heat treatment at 60 - 150 °C temperature in a stenter for 1 - 5 minutes such that to create wave structure (200) (shown in fig. 2) in the grid structures I pattern on both sides of the fabric so as to allow air entrapment in the fabric and minimized contact surface.

The base structure (1 10) is weaved by warp yarns (1 1 1 ) and weft yarn (1 12). The yarns (1 1 1 & 112) are, for example, ring-spun yarn, compact yarn, siro spun yarn and open-end spun yarn, which has a low boiling water shrinkage, preferably below 7%. The yarns (11 1 & 1 12) have a linear density of 8's Ne to 100’s Ne, preferably between 10’s Ne and 40’s Ne.

The yarns (1 1 1 , 1 12) of the base structure (1 10) are made of cellulosic fiber or a blend of cellulosic fiber, for example, cotton, rayon, modal, viscose, hemp, bamboo, jute and / or linen. In another embodiment the yarns (1 1 1 , 1 12) of the base structure (110) are made of a blend of cellulosic fiber, for example, a blend of cotton, hemp, viscose, rayon, bamboo, jute and modal fiber wherein the percentage weight of one of the fibers presents in the blend is not less than 60 %. Examples of such blends are Cotton: Hemp blend in a ratio of 60:40; Cotton: Modal blend in a ratio of 80:20.

In another embodiment the base yarn (1 1 1 , 1 12) of the base structure (1 10) is made of a blend of cellulosic fiber with thermoplastic fibers wherein the percentage of cellulosic fiber is not less than 60% by weight. The thermoplastic fibers include but are not limited to polyester, polypropylene, and polyamide. An example of such a blend is Cotton: Nylon in a blend ratio of 88:12; Cotton: Polyester in a blend ratio of 75:25.

In another embodiment, the base yarn (1 1 1 , 1 12) of the base structure (1 10) is made of inherent flame resistant fibers or a blend of inherent flame resistant fibers, for example, meta-aramids, para-aramids, inherent fire- retardant viscose, modacrylic, asbestos, carbon, polyphenylene benzobisoxazole, polybenzimidazole, fluorocarbons, polyphenylene sulfides, melamines and / or polyimide. In one embodiment, antistatic fibers are used in the fiber blend to impart anti-static property to the fabric. Use of 1 to 5% antistatic fiber is preferred.

The grid structure (120) is woven with warp yarns (121 ) and weft yarn (122). The grid yarns (121 , 122) are continuous filament yarns of thermoplastic polymer, with high boiling water shrinkage. The filament yarns may be untwisted, twisted or intermingled. The boiling water shrinkage of grid yarn (121 , 122) ranges from 9% to 25%. The grid yarns have a tensile strength of at least 2.4 cN/Dtex and elongation to break of at least 25%. The grid yarns with a low initial modulus of 15 to 35 cN/Dtex is preferred. The grid yarn (121 ,122) has a linear density ranging from 20 deniers to 600 deniers.

In one embodiment the grid yarn (121 ,122) comprises a core yarn and sheath yarn. The core is made from a continuous filament yarn of thermoplastic polymer, with high boiling water shrinkage, whereas the sheath is made of a group of fibers like cellulosic fiber and inherent flame resistant fibers.

In one embodiment the grid yarn (121 ,122) is made of a polyester, or a blend of the polyester, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and I or polyurethane terephthalate (PTT).

The fabric (weaved base and grid structure) during the finishing process, is exposed to a temperature of more than 60 °C, more preferably at a temperature of 80 °C, the high shrinkage grid yarns (121 , 122) show higher shrinkage, compared to the base yarn (1 1 1 , 1 12). Considering a single component of a grid, the length of grid yarn on all four sides is smaller than the length of base yarn. This excess length cannot remain planar to the fabric surface creating a peak (211 ) or a valley (212) (shown in fig. 2). The subsequent grids surrounding a grid with a peak tend to form a valley. This results in a three-dimensional grid wave (210) and waves structure (200). The peak height of the wave (210) ranges from 1 mm - 6mm, more preferably in the range of 1 mm - 3 mm. The weight of the fabric is in the range of 60 to 500 GSM, more preferably in the range of 150 GSM to 350 GSM.

A testing and research data of the present invention of a light-weight flame resistant fabric are shown in the following table. 1 . Also, the testing data is compared with a conventional retardant fabric.

Table 1

Certain features of the invention have been described with reference to the example embodiments. However, the description is not intended to be construed in a limiting sense. Various modifications of the example embodiments as well as other embodiments of the invention, which are apparent to the persons skilled in the art to which the invention pertains, are deemed to lie within the spirit and scope of the invention.