MXPA06010451A - Modacrylic/aramid fiber blends for arc and flame protection - Google Patents

Abstract

A yarn, fabric and garment suitable for use in arc and flame protection contains modacrylic, p-aramid and m-aramid fibers.

Description

MIXES OF MODACRYLIC FIBER / ARAMIDA FOR PROTECTION AGAINST ARC FLASH AND FLAMES FIELD OF THE INVENTION This invention relates to a mixed yarn useful for the production of fabrics which possess protective properties against electric arc and flames. This invention also relates to garments produced with such fabrics.

BACKGROUND OF THE INVENTION Individuals who work near energized electrical equipment and emergency personnel who respond to incidents near electrical equipment are at risk of electric arc hazards and flames which may result from an arcing event. Electric arcs are extremely violent events typically involving thousands of. volts and thousands of amps of electricity. Electric arcs are formed in the air when the potential difference (ie, voltage) between two electrodes causes the atoms in the air to ionize and become able to conduct electricity. U.S. Patent 5,208,105 to Ichibori et al. discloses a blend of flame retardant composite fibers comprising a fiber containing halogen Ref. 174806 having a large amount of an antimony compound and at least one fiber selected from the list consisting of natural fibers and chemical fibers. The fiber mixture is woven into a cloth and tested for a Limited Oxygen Index as a measure of its flame resistance. What is needed is a thread, cloth and garment which have a high level of protection against electric arc and flames.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to a yarn for use in protective fabrics and garments against electric arc and flame comprising: (a) 40 to 70 weight percent modacrylic fiber, (b) 5 to 20 percent by weight of p-aramid fiber and (c) 10 to 40 weight percent of n-aramid fiber, the percentages based on components (a), (b), and (c). In addition, the fabric and garment can provide resistance to abrasion and breakage.

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the proportion of a yarn from which fabrics and garments can be produced that provide both electric arc protection and flame resistance. Fabrics and garments comprising flame resistant fabrics of low tensile strength when exposed to the intense thermal stress of an electric arc can be broken exposing the user to further injury as a result of the incident energy. Arcs typically involve thousands of volts and thousands of amperes of electrical current. The electric arc is much more intense than the incident energy such as instant fire. To offer protection to a user a garment or cloth must resist the transfer of energy through the user. It is believed that this occurs both by the fabric that absorbs a portion of the incident energy and by the fabric that resists breaking. During breakage a hole is formed in the fabric by directly exposing the surface or user to the incident energy. The yarns, fabrics and garments of this invention when exposed to the intense thermal stress of an electric arc resist the transfer of energy. It is believed that this invention reduces energy transfer by absorbing a portion of the incident energy and through carbonization allows a reduction in transmitted energy. The yarns of this invention comprise a mixture of modacrylic fiber, meta-aramid fiber, and para-aramid fiber. Typically, the yarns of this invention comprise 40 to 70 weight percent modracrylic fiber, 5 to 20 weight percent para-aramid fiber, and 10 to 40 weight percent meta-aramid fiber. Preferably, the yarns of this invention comprise 55 to 65 weight percent modacrylic fiber, 5 to 15 weight percent para-aramid fiber, and 20 to 30 percent of meta-aramid fiber. The above percentages are on the basis of the three named components. Additionally, an additional abrasion-resistant fiber can be added to the yarn to improve durability via improved abrasion resistance. By "yarn" is meant an association of spun or twisted fibers together to form a continuous filament, which may be used in weaving, knitting, braiding, or folding, or otherwise made into a fabric or textile material. By modacrylic fiber is meant acrylic synthetic fiber made of a polymer comprising mainly acrylonitrile. Preferably, the polymer is a copolymer comprising 30 to 70 weight percent of an acrylonitrile and 70 to 30 weight percent of a vinyl monomer containing halogen. The halogen-containing vinyl monomer is at least one monomer selected, for example, from vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, etc. Examples of copolymerizable vinyl monomers are acrylic acid, methacrylic acid, salts or esters of such acids, acrylamide, methylacrylamide, vinyl acetate, etc. Preferred modacrylic fibers of this invention are copolymers of acrylonitrile combined with vinylidene chloride, the copolymer further having an antimony oxide or antimony oxides for improved fire retardancy. Such useful modacrylic fibers include, but are not limited to, the fibers described in U.S. Patent No. 3,193,602 having 2 percent by weight of antimony trioxide, the fibers described in U.S. Patent No. 3,748,302. made with various antimony oxides which are present in an amount of at least 2 weight percent and preferably no greater than 8 weight percent, and the fibers described in U.S. Patent Nos. 5,208,105 and 5,506,042 having 8 to 40 weight percent of an antimony compound. Within the yarns of this invention, the modacrylic fiber provides a flame-resistant carbonization forming fiber with an IOL typically of at least 28 depending on the level of doping with the antimony derivatives. Modacrylic fiber is also resistant to the extension of fiber damage due to exposure to flames. Modacrylic fiber while being highly flame resistant does not by itself provide adequate tensile strength to a yarn or cloth made of the yarn to offer the desired level of tear strength when exposed to an electric arc. As used herein, "aramid" is understood to mean a polyamide wherein at least 85% of the amide bonds (-CONH-) are directly attached to two aromatic rings. The additives can be used with aramid and, in fact, it has been found that up to as much as 10 percent by weight of other polymeric material can be mixed with aramid or that copolymers having as much as 10 percent can be used of another substituted diamine for the diamine of the aramid or as much as 10 percent of another substituted diacid chloride for the diacid chloride of the aramid. Suitable aramid fibers are described in Man-Made Fibers-Science and Technology, Volume 2, Section entitled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers are also described in U.S. Patents Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127; and 3,094,511. The m-aramides are those aramides where the amide bonds are in the meta position relative to each other, and the p-aramides are those aramides where the amide bonds are in the para position relative to each other. In the practice of this invention, the most frequently used aramides are poly (paraphenylene terephthalamide) and poly (metaphenylene isophthalamide). Within the yarns of this invention the m-aramid fiber can provide a flame-resistant carbonization forming fiber with an IOL of about 26. The m-aramid fiber is also resistant to the extension of damage to the fiber due to the exposure to the flames. The m-aramid fiber also adds comfort to fabrics formed of fibers comprising yarn of this invention. The m-aramid fiber provides additional tensile strength of the yarn and formed fabrics of the yarn. The modacrilic fiber and m-aramid combinations are highly flame resistant but do not provide adequate tensile strength to a yarn or cloth made of the yarn to offer the desired level of tear resistance when exposed to an electric arc. Within the yarns of this invention the p-aramid fibers provide a fiber of high tensile strength which when added in adequate amounts improves the breaking strength of the fabrics formed of the yarn. Large amounts of p-aramid fibers in the yarns make garments comprising the yarns not comfortable to the wearer. The term tensile strength refers to the maximum amount of tension that can be applied to a material before rupture or failure. Tear strength is the amount of force required to tear a fabric. In general, the tensile strength of a fabric refers to how easily the fabric will tear or tear. The tensile strength can also refer to the ability of the fabric to avoid becoming permanently stretched or deformed. The tensile and tear strengths of a fabric should be sufficiently high to prevent tearing, tearing, or permanent deformation of the garment in a manner that could significantly compromise the proposed level of protection of the garment. Additionally an abrasion resistant fiber can be added to the yarn to improve durability via improved abrasion resistance. Abrasion resistant means the ability of a fiber or cloth to resist friction and surface wear. Preferably the abrasion resistant fiber is a nylon. "Nylon" means fibers made of aliphatic polyamide polymers; and polyhexamethylene adipamide (nylon 66) is the preferred nylon polymer. .Other nylons such as polycaprolactam (nylon 6), polybutyrolactam (nylon 4), poly (9-aminononanoic acid) (nylon 9), polyenantolactam (nylon 7), polycaprylactam (nylon 8), polyhexamethylene sebacamide (nylon 6, 10), and the like are suitable. The abrasion resistant fiber typically comprises 2 to 15 weight percent of the yarn. Yarns containing less than 2 weight percent abrasion resistant fiber do not show a marked improvement in abrasion resistance. Yarns containing fibers resistant to abrasion in excess of 15 weight percent may experience a reduction in the protective properties against electric arc and flame resistance of the yarn and formed fabrics of the yarn. Additionally, an antistatic component can be added to the yarn, fabric, or garment of this invention. Illustrative examples are steel fiber, carbon fiber, or a carbon coating to an existing fiber. The conductivity of the carbon or a metal such as steel when incorporated into a yarn, cloth or garment of this invention provides electrical conduit to assist in the dissipation of static electricity buildup. Static electric shocks can be dangerous for workers who work with sensitive electrical equipment or nearby flammable vapors. The antistatic component may be present in an amount of 1 to 5 weight percent of the total yarn. The yarns of this invention can be produced by any of the yarn spinning techniques commonly known in the art such as but not limited to ring spinning, core spinning, and air jet spinning or superior air spinning techniques such as like Murata air jet spinning where air is used to twist the fibers cut into a thread. Typically the single threads produced by any of the common techniques are then folded together to form a twisted cape thread comprising at least two unique threads prior to being converted into a fabric. To provide protection from the intense thermal stresses caused by electric arcs it is desirable that an electric arc protective cloth and garments formed of this fabric possess characteristics such as an IOL above the concentration of oxygen in air for flame resistance. , a short carbonization length indicative of slow propagation of damage to the fabric, and good breaking strength to prevent the incident energy from directly hitting the surfaces below the protective layer. Thermally protective garments such as firefighters' luggage typically provide protection from convection heat generated by an outdoor flame. Such protective garments when exposed to the intense energy generated by an electric arc can be broken (ie, a form of opening in the fabric) resulting in the penetration of energy into the garment and causing severe injury to the wearer. The fabrics of this invention preferably provide both protection against the convective heat of an outdoor flame and offer increased resistance to breakage and energy transfer when exposed to an electric arc. The term "fabric," as used in the specification and appended claims, refers to a desired protective layer that has been woven, knitted, or otherwise bonded using one or more different types of the yarn of this invention. Preferably the fabrics of this invention are woven fabrics. Most preferably the fabrics of this invention are a twist. The basis weight is a measure of the weight of a fabric per unit area. Typical units include ounces per square yard and grams per square centimeter. The base weights reported in this specification are reported in ounces per square yard (OPYC). When the amount of fabric per unit area increases the amount of material between a potential hazard and the subject to be protected increases. An increase in the base weight of a material suggests that a corresponding increase in protective performance will be observed. An increase in the basis weight of the fabrics of this invention results in increased breaking strength, increased thermal protection factor, and increased arc protection. The basis weights of the fabrics of this invention are typically greater than about 8.0 opyc (271.2 gpmc), preferably greater than about 8.7 opyc (294.9 gpmc), and most preferably greater than about 9.5 opyc (322.0 gpmc). It is believed that the fabrics of this invention with base weights greater than about 12 opyc (406.8 gpmc) could show increased stiffness and could thereby reduce the comfort of a garment produced from such a fabric. The carbonization length is a measure of the flame resistance of a textile. A carbonization is defined as a carbonaceous residue formed as the result of pyrolysis or incomplete combustion. The carbonization length of a fabric under the ASTM 6413-99 test conditions as reported in this specification is defined as the distance from the edge of the fabric, which is directly exposed to the flames to the furthest point of the damage of the fabric. visible fabric after a specified tear force has been applied. Preferably the fabrics of this invention have a carbonization length of less than 6 inches (15.24 cm).

The fabrics of this invention can be used as a single layer or as part of a multi-layer protective garment. Within this specification the protective value of a fabric is reported by a single layer of this fabric. This invention also includes a garment made of the fabrics of this invention. The yarns of this invention may be present in either the warp or fabric fill. Preferably the yarns of this invention are present in both the warp and the filling of the resulting fabric. Most preferably, the yarns of this invention are exclusively present in both the warp and the filling of the fabric.

TEST METHODS Abrasion Test The abrasion performance of the fabrics of this invention is determined in accordance with ASTM D-3884-01"Standard Guide for Abrasion Resistance of Textile Fabrics (Rotary Platform, Double Head Method)".

Arc Flash Resistance Test The electrical arc resistance of the fabrics of this invention is determined in accordance with ASTM F-1959-99"Standard Test Method for Determining the Are Thermal Performance Valué of Materials for Clothig". Preferably the fabrics of this invention have an electric arc resistance of at least 0.8 calories and more preferably at least 1.2 calories per square centimeter per opyc.

Grip Test The gripping resistance of the fabrics of this invention is determined in accordance with ASTM D-5034-95"Standard Test Method for Breaking Strength and Elongation of Fabrics (Grab Test)".

Limited Oxygen Index Test The limited oxygen index (IOL) of the fabrics of this invention is determined in accordance with ASTM G-125-00"Standard Test Method for Measuring Liquid and Solid Material Fire Limits in Gaseous Oxidants".

Tear Test The tear strength of the fabrics of this invention is determined in accordance with ASTM D-5587-03"Standard Test Method for Tearing of Fabrics by Trapezoid Procedure".

Thermal Protection Performance Test The thermal protection performance of the fabrics of this invention is determined in accordance with NFPA 2112"Standard on Flame Resistant Garments for Protection of Industrial Personnel Against Flash Fire".

Vertical Flame Test The carbonization length of the fabrics of this invention is determined in accordance with ASTM D-6413-99"Standard Test Method for Flame Resistance of Textiles (Vertical Method)". The term thermal protector performance (or FPT) refers to a capacity of the fabric to provide continuous and reliable protection to a user's skin under a fabric when the fabric is exposed to a radiant heat or direct flame.

IOL From ASTM G125 / D2863 The minimum concentration of oxygen, expressed as a percentage of volume, in a mixture of oxygen and nitrogen that will adjust the flaming combustion of a material initially at room temperature under the conditions of ASTM D2863. To illustrate the present invention, the following examples are provided. All parts and percentages are by weight and degrees in Celsius unless otherwise indicated.

EXAMPLES Modracrylic / Aramid / Nylon Fabric Example 1 A durable, thermally protective fabric was prepared having both warp and fill yarns spun with intimate ring blends of Nomex® type 450, Kevlar® 29, Modacrylic and nylon. Nomex® type 450 is poly (m-phenylene isophthalamide) (MPD-I), Modacrylic is copolymer of ACN / polyvinylidene chloride with 6.8% antimony (known as Protex®C), Kevlar® 29 is poly (p-phenylene terephthalamide) ) (PPD-T) and the nylon used was polyhexamethylene adipamide. A mixed wick of 30% by weight of Nomex® type 450, 5 wt.% Kevlar® 29, 50 wt.% Modacrylic and 15 wt.% Nylon was prepared and processed by the conventional cotton system in a spun yarn having a torsion multiplier of 3.7 using a loom with rings. The yarn thus made was a single yarn of 24.6 tex (24 cotton count). Two single strands were then bent in the folding machine to make a two-strand thread. Using similar process and same twist and bend ratio, a yarn of 28.1 tex (cotton count 21) was made to be used as filler yarn. The threads were then twofold to form a folded yarn. Nomex® / Kevlar® / Modacrylic / nylon yarns were used as the warp and fill in a shuttle loom in a 3 x 1 asadogado construction. The raw asadogado fabric had a construction of 26 ends x 17 passes per cm (66 ends by 42 passes per inch), and base weight of 240.7 g / m 2 (7.1 oz / yd 2). The raw roasting cloth prepared as described above was washed in hot water and dried under low tension. The washed cloth was then jet dyed using basic dye. The finished fabric of 311.9 g / m 2 (9.2 oz / yd 2) was then tested for its thermal and mechanical properties.

Example 2 A durable, thermal protective fabric having both warp and fill yarns is prepared with intimate ring blends of Nomex® type 450, Kevlar® 29, Modacrylic and nylon. Nomex® type 450 is poly (m-phenylene isophthalamide) (MPD-I), Modacrylic is copolymer of ACN / polyvinylidene chloride with 6.8% antimony (known as Protex®C), Kevlar® 29 is poly (p-phenylene terephthalamide) ) (PPD-T) and the nylon used was polyhexamethylene adipamide. A batch mixed in 25% by weight of Nomex® type 450, 5% by weight of Kevlar® 29, 60% by weight of Modacrylic and 10% by weight of nylon was prepared and processed by the conventional cotton system in a yarn that has a torsional multiplier of 3.7 using a ring loom. The yarn thus made was a single yarn of 21.1 tex (cotton count 28). Two single strands were then bent in the folding machine to make a two-strand thread. Using similar process and same torsion and bending ratio, a 22.7 tex thread (26 cotton count) was made to be used as filler yarn. The threads were then twofold to form a folded yarn. Nomex® / Kevlar® / Modacrylic / nylon yarns were used as the warp and filling in a shuttle loom in a 3-locker construction 1. The raw loosening fabric had a construction of 27 ends x 21 passes per cm (68 ends) by 52 passes per inch), and base weight of 223.7 g / m? 2 (6.9 oz / ydA2). The raw roasting cloth prepared as described above was washed in hot water and dried under low tension. The washed cloth was then jet dyed using basic dye. The finished fabric of 294.9 g / mA2 (8.7 oz / yd 2) was then tested for its thermal and mechanical properties.

EXAMPLE 3 A durable, thermally protective fabric having both warp and fill yarns is prepared with rings of intimate blends of Nomex® type N303, Kevlar® 29, Modacrylic and nylon. Nomex® type N303 is 92% poly (m-phenylene isophthalamide) (MPD-I), 5% Kevlar® 29 and 3% P140 (carbon-coated nylon for antistatic), Modacrylic is ACN / polyvinylidene chloride copolymer with 2 % Antimony, Kevlar® 29 is poly (p-phenylene terephthalamide) (PPD-T) and the nylon used was polyhexamethylene adipamide. A wick mixed in 20% by weight of Nomex® type 450, 10% by weight of Kevlar® 29, 60% by weight of Modacrylic and 10% by weight of nylon was prepared and processed by the conventional cotton system in a yarn that has a torsion multiplier of 3.7 using an air jet loom. The yarn thus made was a single yarn of 24.6 tex (24 cotton count). Two single strands were then bent in the folding machine to make a two-strand thread. Using similar process and same torsion and bending ratio, a 28.1 tex thread (cotton count 21) was made to be used as filler yarn. The threads were then twofold to form a folded yarn. The Nomex® / Kevlar® / Modacrylic / cotton yarn was used as the warp and Nomex® / Modacrylic yarn as the filling in a shuttle loom in a 3 x 1 asadogado construction. The raw asadogado fabric had a construction of 27 ends x 17 passes per cm (68 ends per 42 strokes per inch), and basis weight of 244.1 g / m 2 (7.2 oz / yd 2). The raw roasting cloth prepared as described above was washed in hot water and dried under low tension. The washed cloth was then jet dyed using basic dye. The finished fabric of 325.4 g / mA2 (9.6 oz / ydA2) was then tested for its thermal and mechanical properties.

EXAMPLE 4 A durable, thermal protective fabric having both warp and fill yarns was prepared with intimate ring blends of Nomex® type 450, Kevlar® 29, Modacrylic and nylon. Nomex® type 450 is poly (m-phenylene isophthalamide) (MPD-I), Modacrylic is ACN copolymer / polyvinylidene chloride with 15% antimony (known as Protex®M), Kevlar® 29 is poly (p-phenylene terephthalamide) ) (PPD-T) and the nylon used was polyhexamethylene adipamide. A mixed wick in 25% by weight of Nomex® type 450, 10% by weight of Kevlar® 29, 60% by weight of Modacrylic and 5% by weight of nylon were prepared and processed by the conventional cotton system into a spun yarn having a torsional multiplier of 3.7 using a ring loom. Two single strands were then folded into the folding machine to make a two-strand thread. Nomex® / Kevlar® / Modacrylic / nylon yarns were used as the warp and fill in a shuttle loom in a 3 x 1 twill construction. The raw twill fabric prepared as described above was washed in hot water and dried low low voltage. The washed cloth was then jet dyed using basic dye. The finished fabric of 295 g / m 2 (8.7 oz / ydA2) was then tested for its thermal and mechanical properties.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

CLAIMS Having described the invention as above, the contents of the following claims are claimed as property:

1. Thread for use in protection against electric arc and flame, characterized in that it comprises: (a) 40 to 70 weight percent modacrylic fiber, (b) 5 to 20 weight percent p-aramid fiber And (c) 10 to 40 weight percent m-ar fiber, percentages based on components (a), (b) and (c).

2. Thread according to claim 1, characterized in that it comprises: (a) 55 to 65 weight percent modacrylic fiber, (b) 5 to 15 weight percent p-aramid fiber and (c) 20 a 35 weight percent m-aramid fiber.

3. Thread according to claim 1, characterized in that it additionally contains (d) an abrasion-resistant fiber.

4. Thread according to claim 3, characterized in that the abrasion resistant fiber is present in an amount of 2 to 15 weight percent based on the components (a), (b), (c) and ( d).

5. Thread according to claim 3, characterized in that the abrasion-resistant fiber is nylon.

6. Thread according to claim 1, characterized in that it additionally contains an anti-static component.

7. Thread according to claim 6, characterized in that the anti-static component is present in an amount of 1 to 5 weight percent of the total yarn.

8. Thread according to claim 6, characterized in that the anti-static component comprises metal or carbon fiber.

9. Thread according to claim 8, characterized in that the anti-static component comprises carbon.

10. Fabric suitable for use in electric arc and flame protection, characterized in that it comprises: (a) 40 to 70 weight percent modacrylic fiber, (b) 5 to 20 weight percent p-aramid fiber And (c) 10 to 40 weight percent m-aramid fiber, percentages based on components (a), (b) and (c).

11. Fabric according to claim 10, characterized in that the yarn comprises: (a) 55 to 65 weight percent modacrylic fiber, (b) 5 to 15 weight percent p-aramid fiber And (c) 20 to 35 weight percent m-aramid fiber.

12. Fabric according to claim 10, characterized in that it additionally comprises (d) an abrasion-resistant fiber.

Fabric according to claim 12, characterized in that the abrasion-resistant fiber is present in an amount of 2 to 15 weight percent based on components (a), (b), (c) and ( d).

14. Fabric according to claim 12, characterized in that the abrasion-resistant fiber is nylon.

15. Fabric according to claim 10, characterized in that it additionally contains an anti-static component.

16. Fabric according to claim 10, characterized in that it has a carbonization length in accordance with ASTM D-6413-99 of less than 6 inches (15.24 cm).

17. Fabric according to claim 10, characterized in that it has electric arc resistance according to ASTM F-1959-99 of at least 0.8 calories per square centimeter per opyc.

18. Fabric according to claim 17, characterized in that the electric arc resistance is at least 1.2 calories per square centimeter per opyc.

19. Garment suitable for use in electric arc and flame protection, characterized in that it comprises: (a) 40 to 70 weight percent modacrylic fiber, (b) 5 to 20 weight percent fiber of p aramid Y (c) 10 to 40 weight percent of m-arami fiber, the percentages based on components (a), (b) and (c).

20. Garment in accordance with claim 19, characterized in that it comprises: (a) 55 to 65 weight percent modacrylic fiber, (b) 5 to 15 weight percent p-aramid fiber and (c) 20 a 35 weight percent m-aramid fiber.

21. Garment in accordance with claim 19, characterized in that it additionally comprises an abrasion-resistant fiber.

22. Garment in accordance with claim 19, characterized in that it additionally contains an anti-static component.