DESC:Field of the Invention
The present invention relates to flame retardant fabrics and more particularly to a treatment method for a lightweight flame retardant, thermal and arc protective fabric and a method of manufacturing said fabric.
Background of the Invention
The fabrics and garments as manufactured by known process using flame resistant fiber of low tensile strength and the fabrics or garments of known process break open easily up on exposure to the intense thermal stress of an electrical arc, rendering the wearer vulnerable to additional injury as a result of the incident energy. Electrical arcs typically involve thousands of volts and thousands of amperes of electrical current. The electrical arc is much more intense than incident energy such as from a flash fire. To offer protection to a wearer a garment or fabric must resist the transfer of the arc energy through the fabric to the wearer. During break open a hole forms in the fabric directly exposing the surface or wearer to the incident energy.
Currently cotton or cotton/ Nylon 66 flame retardant solution treated fabrics are available but these are heavier in weight (e.g., more than 250 gsm (250 to 450 gsm) in twill, plain or rip stop weave). Cotton/Modacrylic flame retardant polymer blended fabric is also heavy (e.g., more than 220 gsm (220 to 300 gsm) in twill, plain or rip stop weave). There are fabrics blended with Modacrylic or Polyacrylic Nitrile (PAN) carbon fibre with aramid but they have limited colour options and deteriorated with UV light, in the 150 to 250 gsm range in twill, plain or rip stop weave. Currently known fabrics either have high weight or limited colour options and limited bleach resistance and/or very stringent wash / care instructions and poor UV resistance.
In light of the above, there exists a need to provide a light weight flame retardant, thermal and arc protective fabric conferring better protection against electric arcs and / or flash fires and excellent resistance to UV radiations offering ease and flexibility in terms of weight, bleaching, colour, wash care and not compromising to properties like breathability and/or durability.
Summary of the Invention
In an embodiment, the present invention provides a treatment method for a light weight flame retardant, thermal and arc protective fabric that comprises an initial step of coating the fabric with poly (hydroxyorgano) phosphonium polymer followed by step of drying the coated fabric to a residual moisture content in the range of 6 to 8% and treating the dried coated fabric with ammonia gas followed by oxidative washing and drying.
In another embodiment, the present invention provides a method of manufacturing the light weight flame retardant, thermal and arc protective fabric that comprises an initial step of spinning of fibers into yarns thereby selecting fiber blends / polymer blends followed by the step of weaving of said yarns to form a double cloth structure with twill derivative weave fabric. In next step, the weaved fabric is subjected to wet processing followed by treatment with tetrakis (hydroxyalkyl) phosphonium polymer (THPX) and sanforising. In final step, the sanforised fabric is utilized for making garment with flame retardant thermal and arc protective trims therefrom.
Brief Description of Drawings
FIG. 1 is an illustration of a double cloth weave structure obtained after weaving for light weight flame retardant, thermal and arc protective fabric of the present invention.
Detailed Description of the invention
The foregoing objectives of the present invention are accomplished, and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
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 “preferred embodiment” means that a particular feature, structure, characteristic or function described in detail thereby omitting known constructions and functions for clear description of the present invention.
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention.
The present invention relates to a lightweight flame retardant, thermal and arc protective fabric comprising cotton / cellulosic fiber, polyamide and antistatic fiber and also relates to method for producing said fabric having flame-retardant properties.
In one aspect, the present invention provides a method of preparing a lightweight flame retardant, thermal and arc protective fabric has been provided.
In a preferred embodiment, the method of preparing a lightweight flame retardant, thermal and arc protective fabric is provided wherein said properties are imparted by treating the fabric with poly (hydroxyorgano) phosphonium compound.
In an embodiment, the method of treatment of the fabric with poly (hydroxyorgano) phosphonium compound comprising the steps of:
(a) coating the fabric with poly (hydroxyorgano) phosphonium polymer;
(b) drying the coated fabric to a residual moisture content in the range of 6 to 8%;
(c) treating the dried coated fabric with ammonia gas; and
(d) oxidative washing and drying the fabric.
In an embodiment, the poly(hydroxyorgano) phosphonium polymer may be selected from group comprising of a tetrakis(hydroxyalkyl) phosphonium salt (THPX), preferably tetrakis(hydroxyalkyl) phosphonium polymer.
In an embodiment, the tetrakis(hydroxyalkyl) phosphonium polymer (THPX) may be selected from group comprising of tetrakis(hydroxymethyl) phosphonium chloride (THPC) and tetrakis(hydroxymethyl) phosphonium sulfate (THPS).
In an embodiment, the tetrakis(hydroxymethyl) phosphonium polymer (THPX) may be selected from condensate reaction product of tetrakis(hydroxymethyl) phosphonium chloride (THPC) with nitrogen comprising compound selected from urea along with monomers selected from the group comprising of amines, phenols and polybasic and anhydrides.
In context of the present invention, THPX has industrial importance in the production of crease-resistant and flame-retardant finishes on cotton textiles and other cellulosic fabrics. A flame-retardant finish can be prepared from THPX by the Proban Process, in which THPC is treated with urea. The urea condenses with the hydroxymethyl groups on THPX. The phosphonium structure is converted to phosphine oxide as the result of this reaction. This reaction proceeds rapidly, forming insoluble high molecular weight polymers.
In an embodiment, drying of the impregnated fabric, in step (b), may be to a residual moisture content in the range of 6 to 8%.
In an embodiment, oxidative washing, in step (d), may suitably be carried out in the presence of an oxidizing agent or wetting agent wherein the oxidizing agent is Hydrogen peroxide and the wetting agent is Isopropyl alcohol.
In another embodiment, a fabric comprises cotton / cellulosic fibre, polyamide and antistatic fiber.
In an embodiment, a light weight flame retardant, thermal and arc protective fabric of the present invention comprising: about 80% to about 90% weight of total fabric weight of cotton / cellulosic fiber, about 10% to about 20% by weight thermoplastic fiber and about 0.1 % to about 3% by weight of total fabric weight of an antistatic fiber.
In this embodiment, the thermoplastic fiber is selected from polyamide fiber and antistatic fiber.
In this embodiment, the presence of lower amounts of thermoplastic fibre (e.g., from about 10 % to about 20 % by weight of total fabric weight of Polyamide) confers higher thermal stability compared to other fabrics.
In an embodiment, the fabric comprises a double structure twill derivative weave of 150 gsm to 250 gsm. In this embodiment, due to this weave structure fabric is having more air pocket and blocks more energy and gives more arc rating compared to same gsm with blend with other weave.
In an embodiment, the fabric is having moisture vapor transmission rate of more than 2000 gm/m2/day and abrasion resistance of more than 100000 revolutions.
In an embodiment, the Arc Thermal Protection Value (ATPV) of the fabric of the present invention is of more than 8 cal/cm2 at 200 gsm.
In an embodiment, the fabric is a lightweight flame-retardant fabric.
According to the present invention, the presence of lower amounts of thermoplastic fibre (e.g., from about 10 % to about 20 % by weight of total fabric weight of Polyamide) confers higher thermal stability compared to other fabrics. The fabric of the present invention is dyed with vat dyes thereby allowing for fastness of colours. As the colours are fast, there are no limitations on wash care like oxidative bleaching or drying. Further, the vat dyeing process overcomes limits on colours of fabrics when compared to other processes for making fabrics. The fabrics of the present invention are breathable (air permeable, moisture vapour permeable) which helps reduce perspiration and provides greater comfort to the user for longer periods of time. The MVTR (Moisture Vapour Transmission Rate) 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.
The fabric of the present invention are dimensionally stable (i.e., display reduced stretching or shrinking), and optionally further comprise other functional durable finishes such as an anti-microbial finish, water and oil repellent coatings, stain release coatings and the like, without affecting protective performance. The low weight synthetic blended of the prior known fabric (Example - Aramid, Modacrylic fabric) the initial strength is deteriorated by sun light due to contain of UV rays, but the fabric of the present invention is not deteriorated. The tensile strength and tear strength reduce 50 to 80% if the synthetic blended fabric is exposed to sun light in a year time with normal expose two to three hour in a day. But fabric of the present invention clothing is not affected by UV rays of sun light.
In an embodiment, the detailed process for preparation of light weight flame retardant, thermal and arc protective fabric is described hereinafter. The said process comprising the steps of:
a) spinning of fibers into yarns thereby selecting fiber blends / polymer blends;
b) weaving of yarns in step a) to form a double cloth structure with twill derivative weave fabric;
c) wet processing of the weaved fabric followed by THPX Treatment and sanforising; and
d) garmenting of sanforised fabric for making garment with flame retardant thermal and arc protective trims therefrom.
In an initial step, the fibers are converted into yarn by a spinning process wherein different types of fiber blends / polymer blends are selected in said spinning process according to the end use requirements for the yarn. In one example, fibers comprising of about 80 % to about 100 % by weight of total fabric weight of Cotton / Cellulosic fiber, from about 10 % to about 20 % by weight total fabric weight of Polyamide and from about 0 % to about 3 % by weight of total fabric weight of an antistatic fiber by weight of the total weight of the fibers. The yarn count varied from about 2/30 Ne to about 2/60 Ne (double yarn) but the twist multiplier of 4.5 remains constant for any count of yarn (single yarn). It is understood here that spinning process is conducted in a ring spinning system. The spinning process involves processing the fibers through a blow room wherein opening and blending of the different fibers in specific proportion is conducted, then the blended fibers are sent to the next machine by a chute feed system thereby adding spinning oil to reduce antistatic charge and increase fiber cohesive force. Thereafter, the fibers treated in the blow room are sent through a carding machine wherein all the impurities, naps etc. are cleaned and provided output sliver. The fibers treated in the blow room are subjected to draw frame wherein the fibers are made more parallel by drafting and removing hooks. The fibers treated in the draw frame are subjected to speed frame that is used to make roving which is the input material of ring frame to form a single yarn. The yarn is then subjected to winding to make a bigger package and remove objectionable faults like thick and thin segments from the ring yarn. Thereafter, the yarn is subjected to steaming that is used to remove the snarling by eliminating any tendency for undesirable torqueing. The yarn is made to relax till it is stable. In this step, the steam treatment to yarn is given at 90 0C in an autoclave and subjected to parallel winding wherein two yarns are wound as required for double yarn followed by twisting to give a required twist to the double yarn. The double yarn gives good luster and strength while having the same resultant count of single yarn.
In next step, the double yarn treated under spinning is subjected to weaving that includes warping, sizing and weaving. The warping is facilitated to make warp sheet for loom. The sizing is facilitated such that starch with softener and thickener is given to enhance the weavability properties, especially lubrication, binding and antistatic properties. The weaving is facilitated such that a double cloth structure with twill derivative weave fabric is made according to the in an air jet loom with 16 shaft drafting at 800 rpm loom speed. The typical double cloth structure obtained after weaving is shown in FIG. 1.
In next step, the woven yarn of earlier step is subjected to wet processing that includes a primary step of singeing wherein the protruding fibers are burnt out by singeing machine through gas burner which improves the resistance to pilling and imparts luster to the fabric. Thereafter, the fabric subjected to desizing wherein the added impurities like size, spinning oil etc. are removed by oxidative desizing. In this process fabric is treated with a reaction mixture over a predefined reaction time. In one preferred embodiment, the reaction mixture includes 25 g/lit of H2O2, 30 g/lit of NaOH, 2 g/lit of sequestering agent and 2 g/lit of wetting agent. The predefined reaction time is 8 hours. After desizing the fabric is washed with hot water to remove impurities. Thereafter, the fabric is subjected to steaming to accelerate the reaction and complete in 10 minutes, followed by washing. In next step, the fabric is subjected to continuous scouring and Bleaching: mercerization. In this process fabric is treated with 310 gm/ lit Caustic in tight mode for 56 sec. This process makes the cotton rod like structure from twisted ribbon like structure which gives luster and dimensional stability to the fabric. In further step, the fabric is subjected to vat dyeing through PDPS (Pad dry - pad steam) process. In this process, the fabric is padded with vat dye and auxiliary, afterward the fabric is dried at 140°C. Thereafter, the fabric is developed on a continuous dyeing range (CDR) machine by padding with a reducing agent and then steaming for 1 minute, followed by oxidation with H2O2. Thereafter, the fabric is washed and dried at a vertical drying range (VDR) at 80°C. The fabric is then subjected to THPX Treatment wherein the fabric is initially coated with THPX chemical by padding and dry to moisture contain up to 8% and secondly the fabric is given ammonia treatment followed by oxidative washing. Finally, the fabric is subjected to sanforising that allows the fabric to shrink in length as well as width, to provide a permanent dimension to the fabric.
In final step, the sanforised fabric is subjected to garmenting process for making flame retardant trims.
Examples
Examples and implementations are provided herein below for the illustration of the invention. Variations, modifications, and enhancements to the described examples and implementations and other implementations can be made based on what is disclosed.
Examples are set forth herein below and are illustrative of different amounts and types of reactants and reaction conditions that can be utilized in practicing the disclosure. It will be apparent, however, that the disclosure can be practiced with other amounts and types of reactants and reaction conditions than those used in the examples, and the resulting devices various different properties and uses in accordance with the disclosure above and as pointed out hereinafter.
Example- 1
Abrasion Resistance Test as per ISO 12947/2:
The fabric being tested was pulled taut and loaded onto the lower plates of the Martindale machine. Small discs of worsted wool or wire mesh (the abradant) were continually rubbed against the test specimens in a Lissajous oscillating circle with a lode of 12 kpa or more / less as per fabric gsm. The fabric was continually inspected for wear and tear, and the test ended when two yarns broke. In said test, the fabric was observed to have high abrasion resistance of more than 100000 revolutions in the abrasion test.
Example-2
Tensile strength test as per ASTM D 5034 / Tear strength test as per ASTMD 1424
Tensile strength” refers to the maximum amount of stress that can be applied to a material before rupture or failure. The “tear strength” is the amount of force required to tear a fabric. In general the tensile strength of a fabric relates to how easily the fabric will tear or rip. The tensile strength may also relate to the ability of the fabric to avoid becoming permanently stretched or deformed. The tensile and tear strengths of a fabric should be high enough so as to prevent ripping, tearing, or permanent deformation of the garment in a manner that would significantly compromise the intended level of protection of the garment.
The fabric was tested for tensile strength and tear strength. In 200 gsm fabric, the tensile strength was 67 LBS on warp way and 55 LBF in weft way. In 200 gsm fabric, the tear strength was 7 LBF warp way and 6 LBF in weft way.
Example-3
Arc Thermal Protective Value (ATPV) Test
Arc Thermal Protective Value” (ATPV) refers to the maximum incident energy (in calories per centimeter square) 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 was 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 was how the protective level of the treated clothing was determined. The higher the ATPV, the higher the HRC level attained, the greater the protection that was 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 fabrics and methods of production of fabrics of the present invention provided ATPV of more than 8 cal/cm2 (HRC 2) at 200 gsm.
The protective wear described herein complies with standards such as NFPA 2112, ISO 11612, ISO 11611, 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 foregoing description of specific embodiments of the present invention has been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.
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 method for treatment of a lightweight flame retardant fabric, said method comprising the steps of:
(b) coating the fabric with poly (hydroxyorgano) phosphonium polymer;
(b) drying the coated fabric to a residual moisture content in the range of 6 to 8%;
(c) treating the dried coated fabric with ammonia gas; and
(d) oxidative washing of the fabric followed by drying the fabric.
2. The method as claimed in claim 1, wherein the poly (hydroxyorgano) phosphonium polymer is tetrakis (hydroxyalkyl) phosphonium polymer (THPX).
3. The method as claimed in claim 2, wherein the tetrakis (hydroxyalkyl) phosphonium polymer (THPX) comprises tetrakis (hydroxymethyl) phosphonium chloride (THPC) and tetrakis (hydroxymethyl) phosphonium sulfate (THPS).
4. The method as claimed in claim 3, wherein the tetrakis (hydroxymethyl) phosphonium polymer (THPX) is selected from condensate reaction product of tetrakis (hydroxymethyl) phosphonium chloride (THPC) along with a nitrogen comprising compound.
5. The method as claimed in claim 4, wherein the nitrogen comprising compound is selected from urea along with monomers selected from the group comprising of amines, phenols and polybasic and anhydrides.
6. The method as claimed in claims 3 and 4, wherein THPC is treated with urea that condenses with the hydroxymethyl groups on THPX such that phosphonium structure is converted to phosphine oxide allowing the reaction to proceed rapidly thereby forming insoluble high molecular weight polymers.
7. The method as claimed in claim 1, wherein the oxidative washing is carried out in the presence of an oxidizing agent Hydrogen peroxide
8. The method as claimed in claim 1, wherein the oxidative washing is carried out in the presence of a wetting agent Isopropyl alcohol.
9. The method as claimed in claim 1, wherein the fabric comprises cotton/ cellulosic fiber, thermostatic fiber and antistatic fiber in a predetermined proportion.
10. The method as claimed in claim 9, wherein the weight of cotton / cellulosic fiber is 80 % to 90% by weight of total fabric.
11. The method as claimed in claim 9, wherein the weight of thermoplastic fiber is 10% to 20% by weight of total fabric.
12. The method as claimed in claim 9, wherein the weight of the antistatic fiber is 0.1 % to 3% by weight of total fabric.
13. The method as claimed in claim 9, wherein the thermoplastic fiber is selected from polyamide fiber and antistatic fiber.
14. The method as claimed in claim 1, wherein the fabric has a double structure with twill derivative weave of 150 gsm to 250 gsm.
15. The method as claimed in claim 1, wherein the fabric has a moisture vapor transmission rate above 2000 gm/m2/day
16. The method as claimed in claim 1, wherein the fabric has an abrasion resistance of more than 100000 revolutions.
17. The method as claimed in claim 1, wherein the fabric has an Arc Thermal Protection Value (ATPV) more than 8 cal/cm2 at 200 gsm.
18. The method as claimed in claim 1, wherein the fabric is dimensionally stable and optionally comprises functional durable finishes such as an anti-microbial finish, water and oil repellent coatings, stain release coatings and the like.
19. A method of manufacturing the light weight flame retardant, thermal and arc protective fabric as claimed in claim 1, wherein said method comprising the steps of:
a) spinning of fibers into yarns thereby selecting fiber blends / polymer blends;
b) weaving of yarns in step a) to form a double cloth structure with twill derivative weave fabric;
c) wet processing of the weaved fabric followed by THPX Treatment and sanforising; and
d) garmenting of sanforised fabric for making garment with flame retardant thermal and arc protective trims therefrom.
20. The method as claimed in claim 19, wherein the step of spinning of fibers comprising the steps of:
a) processing the fibers through a blow room by conducting opening and blending of the different fibers in a predefined proportion;
b) treating the blended fibers in a machine by a chute feed system thereby adding spinning oil to reduce antistatic charge and increase cohesive force of said fibers;
c) treating the fibers through a carding machine wherein all the impurities are cleaned and provided output sliver;
d) subjecting the fibers to draw frame wherein the fibers are made more parallel by drafting and removing hooks therein;
e) subjecting the fibers treated in the draw frame to form a single yarn;
f) subjecting the yarn for winding to remove objectionable faults like thick and thin segments therein;
g) subjecting the yarn to steaming to remove the snarling by eliminating any tendency for undesirable torqueing therein; and
h) relaxing the yarn by subjecting to steam treatment at a temperature of 90 0C in an autoclave followed by parallel winding and twisting to give a required twist to the double yarn.
21. The method as claimed in claim 19, wherein the step of weaving includes warping, sizing and weaving.
22. The method as claimed in claim 19, wherein the step of wet processing comprising the steps of:
a) subjecting the fabric to singeing wherein the protruding fibers are burnt out by a singeing machine through a gas burner which improves the resistance to pilling and imparts luster to the fabric;
b) subjecting the fabric to desizing wherein the added impurities are removed by oxidative desizing by treating with a reaction mixture including 25 g/lit of H2O2, 30 g/lit of NaOH, 2 g/lit of sequestering agent and 2 g/lit of wetting agent for a reaction time of 8 hours;
c) washing the fabric with hot water to remove impurities therein;
d) subjecting he fabric to steaming followed by washing;
e) subjecting the fabric to continuous scouring and bleaching by treating with 310 gm/ lit Caustic in tight mode for 56 sec. to facilitate luster and dimensional stability to the fabric;
f) subjecting the fabric to vat dyeing through PDPS (Pad dry - pad steam) process wherein the fabric is padded with vat dye and auxiliary followed by drying at 140°C;
g) subjecting the fabric to a continuous dyeing range (CDR) machine by padding with a reducing agent followed by steaming for 1 minute and by oxidation with H2O2;
h) washing the fabric is and drying at a vertical drying range (VDR) at 80°C;
i) subjecting the fabric to THPX Treatment wherein the fabric is initially coated with THPX chemical by padding and dry to moisture contain up to 8% ;
j) subjecting the fabric to ammonia treatment followed by oxidative washing; and
k) subjecting the fabric to sanforising that allows the fabric to shrink in length as well as width, to provide a permanent dimension to the fabric.