The present invention relates to novel composite fabrics having resistance to penetration by chemical agents, particularly organic chemical agents of a gaseous and/or liquid nature such as may be encountered in the chemical industry or in military situations where chemical warfare agents have been deployed. The fabrics of the invention have preferred application in the manufacture of protective clothing for use in chemically contaminated environments or in the manufacture of other items for protecting humans and their equipment, eg. casualty evacuation bags or respirator bags.

The protection a fabric affords the wearer against chemical agents in the surrounding environment is only one of the factors influencing its design and that of garments and containers made from it. It is also necef ^* Ty, inter alia, to consider the physiological load that will be impo. . on the user, the cost, and the inten ? conditions of its use. It is important that the protection afforded , maximised within the constraints imposed by other factors.

One approach adopted in providing such protection is by use of fabrics comprised of air permeable materials which are water repellent but which permit the wicking of neat chemical agent drops. Wicking serves two purposes: a) it encourages evaporative loss of agent from the surr _ce of the cloth to the atmosphere by increasing the exposed surface area; b) it subjects ingressing vapour to a larger area of antigas fabric below the wicking layer thereby maximising absorptive uptake by the carbon contained therein.

Other factors also play a part in the selection of the most appropriate outer material, such as repellency, durability, low flammability, low infrared emissivity, ability to take DP dyes etc.

At the present time the introduction of new materials and textile technologies such as microporous materials (Eg Goretex RTM) and/or

microfibres, textile laminates and coated fabrics, has provided a number of elaborate new approaches to the problems of provision of chemical agent protective fabrics.

A central requirement for any new fabric is the retention of breathability to minimise physiological load, an important requirement despite the constraints this imposes upon types of material which can be used and their construction. An understanding of liquid behaviour, particularly at the first barrier (ie that of the shell fabric) is considered to be of importance in providing maximum protection, whether the system be of improved air-permeable type or of breathable membrane construction. As an example of the importance of wicking, comparison of the natural weathering properties of Goretex and modified acrylic has shown there can be significant differences in liquid persistency arising from the choice of outer fabric.

Whilst a wicking fabric rapidly spreads the load and provides absorbency, a non-wicking fabric provides repellency thereby helping to protect underlying layers from free liquid penetration.

It is an object of the present invention to provide novel air permeable multi-layered (composite) fabrics having high resistance to penetration by chemical agents yet retaining the feature of modest weight with its advantages of light physiological load on the wearer. Preferred objects of the present invention are retention of the ability to release chemical agent by natural weathering and reducing the need for decontamination, providing relatively fast reducing contact and transfer hazard; or decreased penetration of outer layers.

Preferred fabrics of a first embodiment of the present invention provide higher liquid capacity than existing fabrics while retaining good water repellency and wind proofing, thus providing improved comfort in bad weather and restricting penetration of wind driven vapour.

Preferred fabrics of a second embodiment of the present invention provide higher liquid repellency than existing fabrics while retaining good water repellency and wind proofing, thus providing improved comfort in bad weather and restrietir^ penetration of wind driven vapour.

The present invention provides an air perme ble composite fabric having layers positioned innermost and outermost with respect to a body or object to be enveloped in by the fabric in use comprising:

an outermost woven fabric layer (a); an intermediate woven or fibrous non-woven fabric layer (b) and an innermost layer (c) based upon gas adsorbing carbon.

wherein layer (a) has an organic liquid wicking capability, or has organic liquid repellency of at least 4 on the 3M scale, as described below; layer (b) has organic liquid repellency of at least k on the 3M scale, as described below, and has little or no organic liquid wicking capability. Preferably (a) and/or (b) is water repellent.

The present invention further provides items of clothing or a container made from this fabric material wherein the layer (a) is positioned on the threat side of layer (b) and layer (c) is positioned on the protected or 'body' side.

In the first aspect of the present invention the fist layer (a) has an organic liquid wicking capability, preferably comprising a woven, preferably close woven, fabric of sufficient sorptive capacity to inhibit further ingress of neat and thickened liquid. Naturally the fabric will be selected to have sufficient strength and resilience for its intended purpose. Preferably the fabric is of weight over 150g/m ² , more preferably over 200g/m ² , most preferably about 215g/m ² . Preferred product of the Ends and Picks is less than 1000, more preferably less than 800 eg. suitably about 35 x 20. In its

most preferred form this layer is treated, eg. with fluorocarbon or silicone, in order to render it water repellent while retaining the wicking capability; treatment methods may vary with material selected as will be understood by those skilled in the art.

Although some circumstances will occur where it may be more appropriate to proof the first layer (a) against organic liquids to some degree, it must retain wicking capability in order to facilitate weathering and evaporation effects in removal of any wicked chemical agent to provide the specific advantage of this first aspect.

For this aspect, preferably second layer (b) comprises a fine woven fabric, eg product of Ends X Picks being over 1500, suitably about 60 x 30, and preferably being lighter in weight than layer (a), eg. less than 130g/m ² , suitably about 120g/m ² . This layer is conveniently calendered and most preferably water proofed by fluorocarbon treatment.

Preferably layer (c) is an activated carbon fabric typically being a strong fabric having sufficient vapour retention capacity to provide at least 24 hours protection.

A particular advantage of use of the wicking and non-wicking combination as provided for by this first aspect of the present invention is that it allows ommission of non-woven oil and water repellent layers and in turn this allows more carbon to be included in the carbon layer. Thus layer (c) may comprise only activated carbon padded through a support fabric.

In the second aspect of the present invention, the outermost layer (a) has organic liquid repellency of 4 or more on the 3M scale, as described below. Preferably the outermost layer (a) comprises a woven fabric but otherwise may be of open, close or fine weave. Preferably this fabric is both organic liquid repellent and water repellent.

Naturally the fabric will be selected to have sufficient strength and resilience for its intended purpose. Weight of the fabric should be as light as possible while being consistent with these objectives. --

The layer may be treated for proofing urposes by spraying or dipping with fluorocarbon, treatment methods iuay vary with material selected as will be understood by those skilled in the art.

The layer (b) preferably comprises a woven fibrous fabric. _s layer is conveniently calendered and preferably water proofed by fluorocarbon treatment and may be the same as the ayer (a).

Preferably layer (c) is an activated carbon fabric typically being a strong fabric having sufficient vapour retention capacity to provide at least 24 hours protection.

A particular advantage of use of the combination as provided for by the present invention is that it allows ommission of non-fibrous oil and water repellent layers and in turn this allows more carbon to be included in the carbon layer. Thus layer (c) may comprise only activated carbon padded through a support fabric.

The oil-repellency of layers (a) and/or (b) may be provided by a variety of known treatments. One such suitable treatment is by use of the known Meltonian Protector with Scotchguard and wherein typically fabric material is sprayed evenly on both sides until wet then dried at about 8θ°C for eg 30 minutes. A further suitable treatment providing still greater repellency uses Scotchguard Fabric Protector FX 3569 wherein typically the fabric is immersed in 3% FX 3 9 concentrate in 2% acetic acid for 30 minutes, dried at about 80°C for about 30 minutes and then heated at about 165°C for about 30 minutes. These two treatments are assessed at oil repellency rating numbers 4 and 6 respectively the 3M Oil Repellency Test system.

The 3M Oil Repellency Test is designed to detect the presence of a

fluorochemical finish on all types of fabrics and provides a simple, rapid method of measurement by evaluating the fabrics resistance to wetting by a selected series of hydrocarbon liquids of different surface tensions and is carried out as follows.

Test sample is placed on a smooth horizontal surface and a small drop of test liquid approximately 3 mm in diameter is gently placed on its surface using a pasteur pipette taking care not to contact the pipette with the sample. The lower oil repellency test liquids are applied first, the drop is observed for 30 seconds at an angle of approximately 45° and if no penetration or wetting of the fabric at the interface and no wicking around the drop occurs the procedure is repeated using a test liquid with a higher oil repellency number until wetting occurs. The oil repellency rating given to the fabric is that of the highest numbered test liquid which will not wet the fabric within 30 seconds.

3M Oil repellency ratings:

It is further found by the present inventors that carbon fabrics, (eg. the layer (c)) may usefully be provided as a multiple, eg double carbon fabric layer construction wherein the activated carbon is divided, preferably equally, between two or more carbon fabric layers. In this arrangement it is found that penetration of chemical agent

under pressure is resisted more effectively than if an equal amount of carbon is placed in a single layer. This effect holds true for other fabric arrangements as well as those of the composite fabric referred to above as the fabric of the present invention.

Details of the preferred component layers of the composite fabrics < . the invention will now be exemplified by reference to the Figures the following details of fabrics, comparative fabrics and non-limitmg Examples and Comparative Examples of the composite fabrics themselves. Further fabrics of the invention may occur to those skilled in the art in the light of these Examples without departing from the sec; of the claims of the present specification.

FIGURES.

Figure 1: shows a diagrammatic cross-section through a composite fabric of the first apsect of the present invention.

Figure 2: shows a diagrammatic cross-section through a composite fabric of the second aspect of the esent invention.

FIRST ASPECT

EXAMPLE 1: ORGANIC WICKING FABRIC AS LAYER ( R) .

In a fabric of the present invention as illustrated in Figure 1 a non-wicking layer (8) is interposed between the outer wicking layer (3) and carbon layer (5) together with an associated air spaces (4), (6) and (9). In this arrangement the carbon layer (5) does not have the previously commonly incorporated integral fluorocarbon layer and thus the amount of carbon in said layer (5) is optionally increased. Applied organic agent (1) is wicked by the outer wicking layer (3) thus increasing its surface area to volume ratio and facilitating evaporation into the surrounding air (2) .

Studies .

The following studies were carried out to determine fabric types having optimal properties for functioning as either one of the first (a) or second (b) woven fabric layers and provide an indication of performance possible using various arrangements. Eight different candidate shell fabrics, offering a range of materials and finishes, based upon materials which might be appropriate to military use, were selected for study. From past experience, the greatest difficulties with exploiting a non-wicking approach have been found with low surface tension liquids such as nerve agents which readily wet all but the most repellent surfaces.

Neat liquids were chosen to span a range of surface tensions from water (72.6 mN/m at approx. 20°C) to heptane (20.3 mN/m at approx. 20°C) , with nerve agent GD representing a low tension CW agent (24.5 mN/m at approx. 20°C) . Loadings of up to 2. kg/cm ² were applied as representative of realistic localised wearing pressures typified by actions such as crawling and kneeling on hard surfaces. In this way factors important in controlling liquid penetration were determined under conditions likely to be found in the field.

Experimental.

Fabric Samples (see Table 1 for details)

A range of shell fabrics, A to H, were provided.

Test Liquids: Chemical Warfare (CW) Agents used were neat Nerve Agent (GD) and neat Sulphur Mustard Agent (HD) . Dimethyl Methylphosphonate (DMMP) was supplied by Aldrich Chemical Company Ltd. Methyl Salicylate (MS), Triethyl Phosphate (TEP) , and n-Heptane (all GPR grade) were supplied by BDH Chemicals Ltd.

Drop Spreading Behaviour: The full range of test liquids were used in these studies. Samples of test fabric were cut to the size of a standard 75mm x 51mm glass microscope slide, and placed on top of the same. The test liquid was then applied to the fabric surface as 2 separate lμl drops using a Hamilton PB-600-1 Repeating Dispenser equipped with a 50μl capacity Hamilton Syringe. The behaviour of the droplets was then observed with time for up to 2 hours.

Wicking Behaviour: Pieces of test fabric were cut into strips measuring 2.0 cm by approximately 12 cm, with the long axis cut in either warp or weft direction and the strips were then attached in turn to a Lauda automatic tensiometer. Wicking rates were measured by

bringing the fabric strip in contact with the liquid surface (MS or TEP), arresting it in position, and then monitoring liquid uptake via the change in force at a transducer.

Visual Observations of Liquid Penetration: A sample of test fabric with the longer side cut parallel to the warp direction was placed over a piece of single-ply Crestex paper tissue dyed in Cracet Scarlet 2B (an indicator used to visualise breakthrough) . The complete assemblage was supported on a horizonal plate glass surface which could be viewed from below. A single 2μl drop of test liquid (MS or TEP) was dispensed from a microlitre syringe onto the centre of the fabric and immediately after application of the drop a known loading was applied by means of a weight. The assembly was then left for a fixed time interval before dismantling and the dyed paper removed for measurement of penetration by image analysis. The pattern of spreading was recorded and measurements were made of area, perimeter, maximum length and maximum breadth.

Quantitative Measurement of Liquid Penetration: An identical assembly to that for the above visual observations was used, substituting a plain piece of the same cellulose tissue to collect penetrating liquid (either MS or TEP) . The paper was extracted into 25ml of propan-2-ol for quantitative analysis, MS being determined by UV/Vis Spectrophoto -metry and TEP by Gas Chromatography. For selected cloths, effects of increased loading and duration of applied load were also measured.

Experiments with Thickened Liquid: Methyl salicylate, thickened with K125 and dyed red with 0.5% Orasol Red, was used as a substitute for thickened Mustard. A similar assembly to that for visual observations was used, with a plain piece of tissue placed beneath the piece of test cloth on which to observe breakthrough. Both single layers of cloth and paired layers were evaluated and the paper visually examined from below during the run (or after a set time interval in the case of a heavier loading) .

TABLE 2. RESULTS OF DROP SPREADING EXPERIMENTS

+ indicates spreading; (+) denotes delayed spreading

Thus non-proofed fabrics (Group 1) wicked immediately with water and all of the organic liquids, while proofed fabrics (Groups 2-4) did not wick with water. Group 2 fabrics wicked with all of the organic liquids whilst Group 3 fabrics did not wick with HD but wicked with GD. and only two fabrics, (Group 4), did not wick with Chemical warfare (CW) agents GD and HD.

There was a close correlation between wicking behaviour and the liquid surface tension; low tension liquids such as GD were able to wet a wider selection of cloths. Heptane, which is a very low surface tension alkane, exhibited wicking behaviour on all of the cloths tested. TEP is an acceptable wicking simulant for GD, and MS likewise for HD.

A marked orientation to the pattern of liquid spread was observed in many cases, most noticeably with low surface tension liquids, usually running parallel to one or other of the filament directions resulting in an elongated shape and occasionally in a cruciform pattern (eg. GD on A) . The CW agents soaked most quickly into C giving a circular spot of relatively small diameter: results appeared to be the same regardless of the side of the material challenged.

Wicking behaviour: TEP and MS were used as CW agent simulants where it was impracticable to use toxic liquids as was the case in wicking rate measurement. The following observations were observed: Wicking is more rapid in the weft than in the warp direction; differences being more pronounced in unproofed fabrics; where wicking occurs the effect is the same for proofed and unproofed fabrics with MS and TEP. Uptake capacity for the wicking fabrics correlated with cloth weight.

Three fabrics resisted wetting by TEP: F, G and H, in order of degree of repellency; this confirms visual observation on droplets. Drop spreading results thus were in agreement with the wicking rate results whilst the latter clearly picked up delayed wetting behaviour.

Image analysis: Those fabrics exhibiting the least penetration (H, G, F and E) were those which demonstrated little or no wicking behaviour (Table 2) . Sample H was the only one to resist penetration at 5.6lg/cm ² but this was overcome at a higher loading of 117.75g/cm ² . The higher loading also increased the area of spreading in the other fabrics.

Differences in patterns of drop spread in wicking fabrics were most evident with low tension liquids and were found to relate to the fibre selection and weave used in the respective cloths . Thus an X-shaped wetted area obtained with GD and A reflected the offset in the weave whilst a cross shape with GD and B matched a more ordered plain weave. Elongated wicking along one axis in E followed differences in the

twill pattern warp and weft.

Whilst image analysis revealed the pattern of breakthrough, it could not be used to quantify the total amount of liquid which had penetrated, hence the need to correlate these results with chemical analysis. The same conditions were used as for image analysis and the percentage recovery of liquid was determined on undyed paper

Results for TEP and MS show that five cloths, all proofed, yielded penetration of 1% or less at 5-6g/cm ² , being identical to those exhibiting the smallest area of penetration. With MS the remaining cloths exceeded 10% penetration. The effect of increasing the load from 5-6 to 117.5g/cm ² with the top five fabrics was found to be marginal with MS but greater with TEP whilst prolonged application of load (exceeding 60 minutes) could lead to significant breakthrough.

Experiments with Thickened Liquid: Visual observat ons were used to study the effects of drop size and to compare neat and thickened MS. Whilst increasing the drop size with neat MS shortened the time to breakthrough under an applied load of l89-3kg/cr ^? , thickened MS gave an immediate and heavy breakthrough under the sa _^ e conditions eve with small drop izes. Two fabrics, F and G were identified as offering the best resistance to penetration and . now as good resistance to wicking as H but the latter fared less well in the TMS experiments. The main distinguishing feature of F and G is their being calendered.

Whilst either orien-_. ition of wicking/non-wicking layers pro " ^α d effective in use of the preferred materials there are certε_ _^ advantages in placing the wicking layer outermost, as stated above, that make this arrangement the most appropriate ιe for CW applications; this arrangement was thus used in further tests on the effects of increased load, duration of applied load and drop size. The effect of drop size was particularly important and the dual layer

system provided good attenuation even where penetration was found. Performance was found to be significantly better than tests on the individual layers might suggest.

IMAGE ANALYSIS RESULTS - TEP

(2μl TEP for 10 min approx 5.6lg/cm ² )

Order of wicking capability:

B>D>A>C>E>F>G>H range of Areas cm ² 6.87 to 0.13.

IMAGE ANALYSIS RESULTS - MS

(2μl MS for 10 min approx 5«6lg/cm ² )

Order of wicking capability:

B>D>A>OF>G>E>H range of Areas cm ² 0 to 3.71.

IMAGE ANALYSIS RESULTS - MS

(2μl MS for 10 min approx. H7.75g/cm ² )

Order of wicking capability: F>G>OE>H

TEP PENETRATION THROUGH FABRICS - QUANTITATIVE

2μl TEP for 10 min Mean of 2 replicates: (Control Recovery= 87.55%)

Order of organic liquid penetration resistance: H>G>OF>E>A>B>D at 5.6g/m ² OH>G>E>F at 120.4g/m ²

MS-PENETRATION THROUGH FABRICS - QUANTITATIVE

2μl MS for 10 min Mean of 2 replicates: (Control Recovery= 98.72%)

Order for organic liquid penetration resistance:

E>H>F>G>C>A>B>D at 6g/cm ² E>H>F>OG at 17.5g/m ² nb/ increasing load has no influence between 36 and 190g/cm ²

TABLE ^~ x \ TMS BREAKTHROUGH - SINGLE FABRIC LAYER

TABLE 4: TMS BREAKTHROUGH - TWO FABKIC LAYERS (Drop size approx. 45mg: result after 5 min unless stated)

nd = not determined

The combinations B-F, A-F, D-F, F-B and F-D were all penetrated in 3 minutes or less.

TABLE 5 TESTING OF COMPLETE ASSEMBLIES WITH TMS C = first layer (a) F = second layer (b) activated carbon layer = third layer (c) (Drop size approx.4θ-50mg) (EXAMPLE OF COMPOSITE OF THE INVENTION)

In manufacture of a composite fabric of the invention it is envisaged that a variety of mechanisms may be used to bind the layers together, eg. by use of a discontinuous or continuous applied adhesive layer, or by individual mechanical connection such as by threads. Most conveniently the fabric layers will be bound together by stitching applied at the least vulnerable parts of the garment or container, eg. shoulders, wrists and ankles.

SECOND ASPECT:

In a fabric of the present invention as illustrated in Figure 2 a fabric layer (8) is interposed between the outer woven layer (3) and carbon layer (5) together with an associated air spaces (4), (6) and (9). In this arrangement the carbon layer (5) does not have the previously commonly incorporated integral fluorocarbon layer and thus the amount of carbon in said layer (5) is optionally increased. Applied organic agent (1) penetrating layer (3) is arrested by contact with layer (8) and any penetrating vapour is adsorbed by activated carbon layer (5) •

EXAMPLE 2: ORGANIC LIQUID REPELLING LAYER AS LAYER fa).

A series of experiments was carried out using a 33% polyester-67% cotton mix (designated polyester-cotton) as the first and second layer. Fabric was assessed untreated (designated 0) or treated with a spray-on oil-repellent (designated 4) or dipped in oil-repellent treatment (designated 6) ; oil-repellency being determined using the 3M (RTM) system. _ _s

Carbon-loaded materials were scrim-reinforced, needled, non-woven fabrics padded through with activated carbon (designated Cxx: xx=carbon content g/m ² ).

Tests were carried out using a hollow brass cylinder 30cm long by 12cm diameter with a 5«5cm wide flattened section running along its longitudinal axis. Fabrics were applied to cover this section and any vapour penetrating was trapped in passive sampling tubes filled with adsorbent Tenax embedded in a 3 x 3 array of ho^s in the centre of the arm and open to the flattened section. The amount of vapour trapped was determined using a Perkin-Elmer 8600 gas chromatogram fitted with a 25m long 0.32 mm internal diameter polyimide-coated fused silica column (SGE) and a flame-ionisation detector. Oven temperature was 130°C and detector temperature was 250°C. Injection was via a Perkin-Elmer ATD 50 carousel system. Sampling tubes were placed in position and fabric under test wrapped around the cylinder.

A 30mg drop of thickened sulphur mustard (HD) was placed over each of the four corner tubes and a pressure of either 0.16 or 5Kg/cm ² was then applied to the drops for mins. Following removal of the load the cylinder was left undisturbed for 24 hrs, dismantled and the nine tubes contents analyzed.

Results are given as mean values from the four corner sampling tubes and are expressed in μg HD per tube. Data from other tubes was used

to determine the area covered by any contamination.

TABLE 6 Effect of increasing carbon layer beneath a single outer layer.

To establish the effect of dividing the carbon into two, equal, layers a similar set of experiments was carried out using the cylinder/nine tube arrangement.

TABLE 7 Effect of splitting carbon into two layers beneath a single outer layer.

TABLE 8 Effect of adding a second layer of non-carbon fabric to outer layer.

= Example of the invention.

TABLE 9 Effect of two non-carbon layers together with two carbon layers

Example of the invention.

While it may be seen that the most optimal configuration is that where both non-carbon fabric layers are oil-repellent, it may also be noted that where the optimal two non-carbon fabric layers are positioned

such that the oil-repellency of the innermost layer (layer 2- layer (b)) is rated 4 or 6 (spray-on or dipped treatment) and the outer layer (Layer 1- layer (a)) is untreated, less penetration occurs than if these layers are reversed. Such an arrangement is specifically the subject of the first aspect of this invention.

The results shown in Table 3 for use of a four layer composite fabric wherein the carbon is divided between two layers show that this difference may be largely reduced at relatively high pressure but may not be as good at lower pressures. This is presumed t„ ;:»e due to the formation of a physical barrier in the 5 Kg/cm ² situation caused by compression of materials.

Thus a particular application for the double carbon layered structure is in the provision of protection of parts of a suit or container which are subjected to comparatively high pr sures in use; eg. knee and elbow regions. Thus the parts of a suit in these regions might usefully be made of a fabric having a double layer of carbon fabric beneath the shell fabric, eg. (a) and (b) or be patched selectively therewith.

It should be noted that the layers of the composite fabrics of the invention may conveniently be held together in a variety of ways but most conveniently will be stitched together away from vulnerable regions of the suit or conatiner; ie. stitched at the shoulder wrist or ankle. Other known ways of holding the layers together will occur to a person skilled in the art.