OBJECT OF THE INVENTION
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The main object of this invention consists of a double-cloth fabric made with fire-resistant fibres, with a high thermal and mechanical resistance, to be used in the confection of work protection garments.
BACKGROUND OF THE INVENTION
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Work protection garments, in particular protective garments against heat and flame, must pass a number of tested assays by an accredited body, in order to guarantee compliance with certain minimum requirements specified by the prevailing regulations.
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The requirements and risks to be met by said garments are the following:
- Flame resistance
- Radiant heat, convection heat
- Resistance to traction and tear
- Abrasion resistance
- Pilling resistance
- Water penetration resistance
- Resistance to chemical products
- Protection against melted metal splash
- Bad visibility
- Electric arc
- Static electricity dissipation
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In addition to complying with the requirements and demands specified in the prevailing regulations, users will value the following additional features:
- High protection level
- High mechanical resistance
- Ergonomy
- Comfort
- Light weight
- Durability
- Ease of maintenance
- Price
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In order to obtain textile products with said features, the textile industry uses threads that are basically obtained from meta-aramid and para-aramid fibres, thanks to their fire-resistant and mechanical properties.
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In contact with a heat source at a temperature greater than 300ºC, meta-aramid fibres contract and become denser, which subsequently leads to charring and cracking of the textile material. Their thermal contraction is approximately 24% at temperatures greater than 300ºC.
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On the contrary, para-aramid fibres undergo a low thermal contraction, of approximately 3% at temperatures greater than 300ºC.
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The combination of para-aramid and meta-aramid fibres prevents this breakage, which is called "non-break". This combination of fibres is capable of preventing the contraction, cracking and subsequent breakage of textile materials. This solution is disclosed in patents
US3063966 and
US3506990 .
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On the other hand, as compared to para-aramid fibres, colour-pigmented meta-aramid fibres have a greater colour fastness to light, washing and rubbing, under both dry and humid conditions.
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On the contrary, due to their molecular structure, para-aramid fibres have limited colour fastness to light and abrasion and, with use, exhibit progressive ageing in the form of the degradation of the fibres, which end up showing so-called fabric frosting, a blurred appearance in the form of discoloured, whitened fibres on the surface of the textile material.
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In the specific case of garments designed for protection against thermal attacks, such as, for example, flashovers, which are fortuitous flare-ups, they are composed of multi-layer solutions composed of:
- ● An external layer made of fire-resistant woven fabric. Approximate weight of 220-240 g/m2.
- ● A humidity barrier made of a fabric with a microporous water-repellent membrane. Approximate weight of 80-110 g/m2.
- ● A thermal barrier made of an unpunched non-woven fabric. Approximate weight of 100-150 g/m2.
- ● An inner lining. Approximate weight of 110-135 g/m2.
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This solution for protection garments with multi-layer fabrics has the disadvantage that they are very heavy garments that may cause physical and thermal stress. The factors that contribute to thermal stress are: the degree of transpiration of the garment, the thermal flow and the structure of the protection garment. In one intervention, humidity passes through the garment's different layers with the incidence of a radiant heat source, which may cause steam burns.
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Also well-known in the state of the art are protection garments obtained from a fabric equipped with a reinforcement grid, generally made of para-aramid, on the inner face, which is bound to the outer surface of the fabric. The disadvantage of this type of fabrics lies in that they have very restricted mechanical features, since they are limited to the properties of the reinforcement grid, and their binding stitches are visible from the outer surface of the fabric, which causes the latter to have a stippled appearance.
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Another factor that determines the useful life of the fabric is the level of pilling, which is considered to be a first sign of wear in a fabric. This is a physical process that basically develops on the outer face of the fabric due to friction between different parts of the garment, or between it and another different element. They appear on the surface of the fabric, in the form of small balls made up of fibres, bound to the fabric by means of other fibres, and give the fabrics an aged appearance. There are different assay methods to determine a level of "pilling" on a fabric. In this invention, a "Martindale" assay equipment has been used, following the method specified in standard UNE EN ISO 12945/2:01. The results of this assay are defined from level 1, which would indicate a very deficient level, to level 5, which would determine an excellent level, which a much lower wear.
DESCRIPTION OF THE INVENTION
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The double-cloth fabric proposed by the invention resolves the problems discussed above, since it offers very high resistance to traction and tear, as well as thermal protection, has a reduced weight, and an optimal appearance and durability.
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To this end, more specifically, the double-cloth fabric of the invention comprises: a first cloth, woven with threads that comprise an intimate mixture of between 25% and 99% of meta-aramid fibres, and between 1% and 75% of para-aramid fibres; and a second cloth woven with threads that comprise an intimate mixture of between 5% and 70% of meta-aramid fibres, and between 20% and 95% of para-aramid fibres. This second cloth comprises threads composed of para-aramid fibres, both cloths being bound by binding stitches with a concentration of between 5 and 50 binding stitches/cm2, made from the threads with the intimate mixture of meta-aramid fibres and para-aramid fibres. Thus, the binding of both cloths takes place by means of threads with the same characteristics as the first cloth; for this reason, the external finish and the appearance are homogeneous.
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Said para-aramid thread of the second layer may be arranged in weft and/or warp, preferably in weft and warp, in order to increase the double-cloth fabric's resistance to traction and tear.
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The binding stitches made from the threads with the intimate mixture of meta-aramid fibres and para-aramid fibres are preferably warp threads from the first cloth or the second cloth.
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Preferably, the binding stitches are uniformly distributed along the length of the fabric, with a concentration of between 10 and 30 stitches/cm2. Said concentration of binding stitches makes it possible to transmit the mechanical features from the second cloth to the first cloth.
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Preferably, the first cloth comprises between 50% and 98% of meta-aramid, more preferably between 70% and 95%; and between 2% and 50% of para-aramid, more preferably between 3% and 30%.
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Preferably, the second cloth comprises between 10% and 40% of meta-aramid, more preferably between 12% and 30%; and between 70% and 90% of para-aramid, more preferably between 72% and 88%. The percentages of para-aramid in the second cloth include the arrangement of the complementary para-aramid threads.
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The first cloth is made of intimate-mixture threads with different fibre contraction properties against thermal attacks. With a high percentage of meta-aramid, and a lower percentage of para-aramid, the first cloth has good thermal and mechanical resistance properties, and excellent resistance properties to ultraviolet light degradation, washing and rubbing under dry and humid conditions.
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The second cloth is made of intimate-mixture threads with different contraction properties at high temperatures, and para-aramid threads with a low contraction at those high temperatures. With a lower percentage of meta-aramid, and a higher percentage of para-aramid, the second cloth has excellent thermal and mechanical resistance properties, and acceptable resistance properties to ultraviolet light degradation, washing and rubbing under dry and humid conditions.
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Given that para-aramid fibres exhibit greater wear upon use as compared to meta-aramids, in order to prevent ageing and degradation of the fabric, the so-called fabric frosting, the first cloth has a high percentage of meta-aramid fibres, which have a good colour fastness behaviour and, in the second cloth, para-aramid fibres predominate, which have a high mechanical resistance and a lower contraction, thereby contributing to prevent the fabric's non-break.
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The double-cloth fabric comprises two simple, superimposed cloths and, therefore, consists of two warps and two wefts. Each warp is bound to its weft, forming a fabric that is independent from that formed by the other warp and the other weft. The two cloths are bound, along the entire length, by binding stitches with warp threads from the first or the second cloth. The binding stitches used to bind the two cloths, in a course of 14 warp threads and 14 runs, are between 1 and 6, which represents a concentration of between 10 and 30 stitches/cm2.
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Both the first and the second cloth may incorporate Rip Stop reinforcement threads, in weft and/or warp, in order to increase the mechanical resistance even more, and thereby prevent fabric tear as much as possible. The Rip Stop structure consists of arranging, in both warp and weft, additional threads that maintain the same evolution and form symmetric squares throughout the entire fabric.
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In order to dissipate the electrostatic charge, the double-cloth fabric may additionally comprise less than 5% of antistatic fibres, designed to discharge the charge by induction-conduction dissipation. These antistatic fibres may be incorporated into the different threads of the first cloth or the second cloth, or by means of supplementary threads.
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In addition to the high mechanical features described above, the double-cloth fabric of the invention improves the thermal resistance by creating, between both cloths, a continuous air chamber that acts as a thermal barrier and helps to prevent thermal stress. This contributes to preventing the passage of humidity toward the interior of the garment by capillarity, thereby preventing steam burns caused by contact of the humidity with the thermal flow of radiant heat.
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Depending on its final application, the double-cloth fabric additionally comprises one of the following finishes: ceramic, water-proof, micro-encapsulated, bactericidal, fungicidal, silicone, impregnated with insecticidal substances, and mixtures thereof.
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Another aspect of the invention is a garment that comprises any of the fabrics as defined above.
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Said garment is a work protection garment, preferably designed for fire-fighters, forestry workers, the military, the electrical industry, the chemical industry and the petrochemical industry.
DESCRIPTION OF THE DRAWINGS
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In order to complement the description being made and contribute to a better understanding of the characteristics of the invention, in accordance with a preferred practical embodiment example thereof, a set of drawings is attached as an integral part of said description, where the following has been represented for illustrative, non-limiting purposes:
- Figure 1 shows a grid design of the structure of the fabric binding presented in taffeta on the two cloths with Rip Stop.
- Figure 2 shows a section of the double-cloth fabric, where the configuration of a binding stitch and of the air chamber may be observed.
PREFERRED EMBODIMENT OF THE INVENTION
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Below we describe two practical embodiment examples of the double-cloth fabric:
Example 1:
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Composition first cloth (1):
- 75% of meta-aramid
- 23% of para-aramids
- 2% of antistatic fibre
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Composition second cloth (2):
- 18% of meta-aramid
- 81 % of para-aramids
- 1% of antistatic fibre
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Total composition of the double-cloth fabric:
- 42% of meta-aramid
- 57% of para-aramids
- 1% of antistatic fibre
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Concentration binding stitches (4): 22 stitches/cm2
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Weight of the double-cloth fabric: 240 g/m2
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Finish: water-proof.
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Results obtained:
- Resistance to traction in accordance with standard UNE EN ISO 13934/1:99.
- ○ Warp: 2,542.00 N
- ○ Weft: 2,793.00 N
- Resistance to tear in accordance with standard UNE EN ISO 13937/2:01.
- ○ Warp: 150.50 N
- ○ Weft: 225.00 N
- Resistance to abrasion in accordance with standard UNE EN ISO 12947/2:99. (cycles necessary to break 3 threads).
- Resistance to pilling formation UNE EN ISO 12945/2:01
- ○ Level 4-5 (4,000 cycles).
Example 2:
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Composition first cloth (1):
- 93% of meta-aramid
- 5% of para-aramids
- 2% of antistatic fibre
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Composition second cloth (2):
- 23% of meta-aramid
- 76% of para-aramids
- 1% of antistatic fibre
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Total composition of the double-cloth fabric:
- 52% of meta-aramid
- 47% of para-aramids
- 1% of antistatic fibre
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Concentration binding stitches (4): 22 stitches/cm2
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Weight of the double-cloth fabric: 240 g/m2
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Finish: water-proof.
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Results obtained:
- Resistance to traction in accordance with standard UNE EN ISO 13934/1:99.
- ○ Warp: 1,456.00 N
- ○ Weft: 1,434.00 N
- Resistance to tear in accordance with standard UNE EN ISO 13937/2:01.
- ○ Warp: 155.8 N
- ○ Weft: 144.7 N
- Resistance to abrasion in accordance with standard UNE EN ISO 12947/2:99 (cycles necessary to break 3 threads).
- Resistance to pilling formation UNE EN ISO 12945/2:01
- ○ Level 4-5 (4,000 cycles).
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In light of the results of the assays performed on the samples of the examples specified above, it may be observed that the values for resistance to traction and tear are very high; in the first example, they are above 100% of the fabrics currently in the market with high mechanical features for work protection.