FILTER MATERIAL

Field of the Invention

The present invention relates to protective materials and particularly, although not exclusively, to materials suitable for use in CBRN (Chemical, Biological, Radiological and Nuclear) protective fabrics or filtration fabrics, and methods for manufacturing such materials.

Background

Activated carbon materials are known to be effective barriers to or filters of chemical agents. Such agents include agents designed to harm such as Mustard, Sarin, VX nerve agents and chlorine. The international community agrees that such toxins are currently available and in use by terror organisations and certain states. Activated Carbon is well known to be effective to filter toxic molecules from contaminated airstreams.

However, activated carbon is generally lacking in durability, being brittle and delicate. Most activated carbon is available loose in different forms such as powders, granules or as an unsupported textile which needs further processing to achieve a regular, consistent and [physically stable form with passable durability. Even a woven cloth activated carbon layer is relatively open, unstable and delicate, meaning it provides little in the way of barrier protection. It is thus difficult to utilise in protective clothing which needs to have sufficient flexibility, weight, comfort and so on to be practical, while also retaining their protective durable qualities.

Materials therefore which maximise the efficacy of activated carbon layers are desired. In particular, chemical warfare agent (CWA) adsorption performance is a vital property of many CBRN protective fabrics.

The present invention has been devised in light of the above considerations. The present invention provides products that may offer solutions when fabricated into filters or utilised in protective clothing and or other PPE for Chemical protection.

Summary of the Invention

In a general aspect, the present inventors have found that by control of the adhesive with which carbon particles are adhered to fabric layers which sandwich it, the efficacy of adhesion can be improved and thus the efficacy of the protective qualities of the material increased. In particular, the locations of dots of adhesive used has been found to be important in securing these advantages.

In a usual case, there are three ‘layers’ to consider, first and second fabrics with a carbon-based layer in between. A first adhesive adheres the carbon to the first fabric, immobilising it. A second adhesive adheres the second fabric to the first fabric and/or the carbon. The present inventors have found that the first and second adhesives properties, such as dot spacing, dot diameter and dot thickness, are important for achieving a good balance of properties. For example, carbon particle occlusion lowers the efficacy of the filter; excessive path blockages reduce fluid flow through the filter; incorrect adhesion reduces durability. Previous works have had to include further filtration layers, for example a second layer of activated carbon particles, in order to achieve desired performance. The present inventors have found that by careful control of the dot configuration such further layers are unnecessary. Accordingly a superior fabric can be obtained at lower cost and lower manufacturing burden, as well as improved physical properties stemming from having fewer layers.

It will be appreciated that the adhesive location(s) on the first fabric alter where the carbon is held and hence allows for control of the dispersion of carbon across the fabric. This allows close control of the weight of the laminated product.

The present inventors have identified adhesive properties which provide improvements in several of these areas.

Accordingly, a first aspect of the present invention provides a filter material comprising a first fabric; a second fabric; and carbon particles, optionally activated carbon spheres, sandwiched between the first and second fabrics; wherein the carbon particles are adhered to the first fabric by a first adhesive; and the first fabric and/or the carbon particles are adhered to the second fabric by a second adhesive; and wherein the first adhesive is in the form of discrete dots with a distance of 100-600 pm between adjacent dots; the second adhesive is in the form of discrete dots with a distance of 100-800 pm between adjacent dots, and the distance between the dots of the second adhesive is different from the distance between dots of the first adhesive. These materials perform well and achieve high carbon loading/coverage with a simple and effective manufacturing process. With a difference in distance between the dots of the first and second adhesives, excessive occlusion of the carbon can be avoided and air flow through the material is improved, increasing contact of contaminants with the carbon. Furthermore the adhesives can be better optimised, as the first adhesive is more for adhesion of the first fabric to the carbon and the second adhesive is more for adhesion of the second fabric to the first fabric.

So, it may generally be preferable for the dots of the first adhesive and the dots of the second adhesive to be offset in the filter material.

In some embodiments the distance between dots of the first adhesive is preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm. In some embodiments the distance between dots of the second adhesive is preferably 150-450 pm, more preferably 300-400 pm, or alternatively 300-600 pm.

The dots of the first adhesive may suitably have a diameter of 100-800 pm, preferably 450-650 pm, more preferably 500-600 pm, or alternatively 300-600 pm.

The dots of the second adhesive may suitably have a diameter of 100 to 800 pm, preferably 200-400 pm, more preferably 250-350 pm, or alternatively 300-600 pm.

In preferred embodiments, the dots of the first adhesive have a thickness of 100 to 500 pm, preferably 200-400 pm, more preferably 250-350 pm or 200-300 pm. In preferred embodiments, the dots of the second adhesive have a thickness of 100 to 500 pm, preferably 100 to 300 pm, more preferably 150 to 250 pm or 200-300 pm.

In embodiments suitable for use in, for example, CBRN protective applications, the first fabric is a knitted or woven fabric and/or the second fabric is a nonwoven or knitted fabric.

A second aspect of the present invention provides a method for manufacturing a filter material, comprising the steps of: (a) applying a first adhesive onto a first fabric; (b) applying a second adhesive onto a second fabric; (c) applying carbon particles, optionally activated carbon spheres, to the first adhesive; (d) laminating the second fabric and first fabric, sandwiching the carbon particles therebetween; wherein in step (a) the first adhesive is applied as discrete dots with a distance of 100-600 pm, preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm, between adjacent dots; wherein in step (b) the second adhesive is applied as discrete dots with a distance of 100-800 pm, preferably 150-450 pm, more preferably 300-400 pm or alternatively 300-600 pm, between adjacent dots, and wherein the distance between the dots of the second adhesive is different from the distance between dots of the first adhesive.

A third aspect of the present invention provides a material made by a method of the present invention.

One or both of the first and second adhesives is suitably printed (that is, applied by printing), for example using a screen-printing technique; rotary screen printing or gravure printing.

In step (a) the first adhesive may be applied as discrete dots with a diameter of 100-800 pm, preferably 450-650 pm, more preferably 500-600 pm or alternatively 300-600 pm; and/or in step (b) the second adhesive may be applied as discrete dots with a diameter of 100-800 pm, preferably 200-400 pm, more preferably 250-350 pm or alternatively 300-600 pm.

The first adhesive may be applied by screen printing using a screen with a thickness of 100 to 500 pm, preferably 200-400 pm, more preferably 250-350 pm or 200-300 pm, and/or the second adhesive may be applied by screen printing using a screen with a thickness of 100 to 500 pm, preferably 100-300 pm, more preferably 150-250 pm or 200-300 pm.

In order to obtain an advantageous adhesive deposition, in step (a) the screen may optionally have an open area of 25 to 35%; and in step (b) the screen may optionally have an open area of 15 to 25%.

In this method, steps (a) and (b) may be done in any order, or concurrently. Step (c) is of course done after step (a), but can be performed before, after or concurrently with step (b).

In some embodiments, there is a significant period of time between step (a) and step (c) which results in the adhesive applied in step (a) drying. In such cases, step (c) is carried out after the first adhesive has been reheated (melted) so that the carbon particles will stick to it. The same applies for step (b) and the second adhesive: there may be a significant period of time between step (b) and step (c) which results in the adhesive applied in step (b) drying. In such cases, step (c) is carried out after the second adhesive has been reheated (melted)

Because of the nature of the first and second fabrics, and the processing steps of the method, it may be suitable that the first and second adhesives are different. They may in particular have a different chemical composition, and/or a different melting temperature. Suitably the first adhesive has a higher melting temperature than the second adhesive.

In the present invention, the first fabric may suitably be a knitted fabric. Separately, the second fabric may suitably be a nonwoven fabric.

The invention includes the combination of the aspects and preferred features described except where such a combination is clearly impermissible or expressly avoided.

Summary of the Figures

Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

Figure 1 schematically shows steps of a method according to the present invention. As explained below, certain steps are omitted for brevity.

Detailed Description of the Invention

Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

As explained above, the present invention relates to layered laminated materials (filter materials). The layers of the laminated material are chosen to have particular properties. Adhesives are used to secure the layers, that is, the first fabric, the second fabric, and the carbon particles.

Fabrics

In the present invention, first and second fabrics sandwich carbon particles, and are laminated together by way of adhesive(s). These fabrics may be selected according to the desired end use of the material.

The first fabric may suitably be a knitted fabric. Suitable fabrics include knitted materials made from meta- or para-aramid, cotton, polyester, polyamide or blends of different fibres.

The first fabric may alternatively be a woven fabric. It may be a woven fabric such as a polyester, polyamide, or other such material. Natural materials, such as cotton, bast or viscose can also be used. Suitable choices include, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN) and polyethylene succinate). Polyethylene terephthalate (PET) is a particularly suitable choice, and especially polyethylene terephthalate (PET) woven in a plain, ripstop or twill weave. The second fabric may suitably be a nonwoven fabric. Suitable fabrics include nonwoven materials such as those spun from polyethylene, polypropylene, polyamide or polyester.

It is possible for an item, such as a garment or clothing item, to comprise the present material along with other non-laminated layers. That is, such an item may comprise the present laminated material along with one or more functional layers which are not laminated to the present laminated material and are thereby ‘loose’. Examples include an outer skin layer, also known as a shell layer, (present as an outermost layer farthest from the skin of a user or wearer of the clothing item or garment) or an inner lining layer, or liner, (present as an innermost layer closest to the skin of a user or wearer of the clothing item or garment).

Additional functional fabric layers can be added to the present materials as additional laminated layers, for example for moisture management or particulate filtration. However, the present invention is advantageous in that it provides good performance with the presence of only a single carbon-based filtration layer. Hence, further such layers can be excluded and the resultant fabric made more cheaply and easily. It furthermore has improved properties such as weight and flexibility since it can include fewer layers to achieve a comparable filtration performance.

Accordingly, in some embodiments of the present invention the filter material of the present invention is a laminated material including only a single carbon filtration layer; that is, only one layer of carbon particles is included in the laminated layers.

Suitable materials for a shell or outer layer include woven fabrics made from meta or para-aramid, cotton, polyester, polyamide or blends of different fibres; nonwoven materials such as those spun from polyethylene, polypropylene, polyamide or polyester; or knitted materials made from meta- or paraaramid, cotton, polyester, polyamide or blends of different fibres.

Such outer layer or shell materials may be dyed or printed; alternatively or additionally they may be treated with for example a coating to prevent penetration by particulate contaminants, liquid droplets or wet or dry aerosols. Suitable such coatings are known in the art. It will be apparent that more than one such treatment may be used depending on the desired usage and appearance of the fabric or garment in question.

Suitable materials for an inner layer or liner include soft knitted fabrics that offer a high level of comfort when in contact with the skin’s surface, for example those made from meta- or para-aramid, cotton, viscose, silk, polyester, polyamide or blends of different fibres.

Carbon layer

The carbon layer is laminated between the first and second fabrics and is held by an adhesive which has been applied to the first fabric. It may further be held by an adhesive which has been applied to the second fabric. In some embodiments, as mentioned above, the present filter material includes only a single carbon layer. The carbon layer comprises carbon particles dispersed across the fabric(s). Those carbon particles may suitable be activated carbon particles, for example spherical activated carbon particles. Such particles are known in the art.

The properties of the carbon particles may be chosen suitably. In the present invention, they may be spheres with an average particle diameter of 200-800 pm, or carbon granules with an average particle diameter of 100-1000 pm. They may have a specific surface area (measured by BET method) of 600- 2000 m ² g ^-1 , and preferably 1050-1500 m ² g ^-1 .

An advantage of the present methods observed by the inventors is that the specific surface area of the carbon particles is not degraded by the deposition process; that is, the specific surface area of the deposited carbon particles matches the theoretical specific surface area based on that property of the raw, undeposited particles.

The distribution of the carbon particles on the adhesive and thus on the fabric is controlled to give advantageous filtration and protective qualities. Of course the loading of the carbon particles is dependent on the adhesive distribution, discussed below.

Suitably, the present invention permits a carbon particle loading of about 120 to 230 gm ^-2 . The carbon may be deposited to give a specific coverage of about 500-700 m ² per gram of fabric, and/or about 150- 300 km ² per metre ² of fabric.

The present invention allows high levels of carbon deposition as mentioned above; in particular, an improvement in the area covered by carbon particles. In the present invention this may be 60% or greater, for example 62% or greater.

The present inventors have also found that the average distance between carbon particles is important for achieving an advantageous protective quality. Most preferably, there are no distances > 500 pm between carbon particles.

The carbon adsorbs toxic volatile molecules in gas or vapour phase. In order to maximise this effect, it is advantageous for the maximum surface area of the carbon particles to be exposed. As the first or second adhesive occludes the carbon surfaces where it adheres, there is significant advantage to the present invention in keeping such occlusion to a reduced level (for example by using a smaller amount of adhesive than has been done previously, or by offsetting at least some of the dots of the first and second adhesives so that no carbon particles are excessively occluded). Similarly, if carbon particles are too close they occlude one another. Again the present invention can address this with careful positioning of the carbon particles (for example by choice of adhesive position, the locations of carbon particles adhered by the adhesive is similarly controlled). The present invention improves the area of the functional media presented to the fluid stream for filtration/purification.

Adhesive

As explained above, adhesive is applied to each of the first and second fabrics to secure the carbon particles and the fabrics in a laminated fashion. The distribution of the adhesive is identified by the present inventors as important for obtaining the present advantages. In general, the distribution of the adhesive across the fabrics is suitably uniform.

Herein there is described a first adhesive, which is applied to the first fabric, and a second adhesive, which is applied to the second fabric. As mentioned above, the first adhesive may be optimised for adhesion of the first fabric to the carbon; the second adhesive may be optimised for adhesion of the second fabric to the first fabric.

The adhesive is applied to the fabric in the form of dots, that is, discrete, individual locations of deposition. It is the qualities of these dots which provide advantageous carbon loading and hence filtration and protection qualities.

The first adhesive, on the first fabric, is deposited as dots with a distance between adjacent dots of 100- 600 pm, preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm. The second adhesive, on the second fabric, is deposited as dots with a distance between adjacent dots of 100-800 pm, preferably 150-450 pm, more preferably 300-400 pm or 300-600 pm. Suitably, for both the first and second adhesives, the distances between adjacent dots across the fabric are substantially uniform.

It has been found that these spacings give an advantageous balance of fabric-fabric and fabric-carbon adhesion, while at the same time giving an advantageous level of material flexibility, filtration performance and so on.

The first adhesive may be deposited as dots with a diameter of 100-800 pm, preferably 450-650 pm, more preferably 500 to 600 pm or alternatively 300-600 pm. The second adhesive may be deposited as dots with a diameter of 100-800 pm, preferably 200-400 pm, more preferably 250 to 350 pm or alternatively 300-600 pm. It is found that, in combination with the above dot spacings, these dot sizes provide advantageous adhesion, filtration and general performance characteristics. This may be because of a reduce occlusion of the carbon particles, for example.

[The diameter and spacing can be measured by viewing an SEM image (200x magnification; 10kV; 1 .34 mm) of the adhesive dots on the fabric, and defining a circle around a given dot which is the smallest circle containing the entire dot. The diameter of that circle can then be taken as the effective diameter of the dot; the minimum distance between any point of that circle and a point on any adjacent circle can be taken as the distance between those dots. That is, it is the distance between the edges of the circles (dots), rather than the distance between their centres, which is considered. ] I n general dot diameter and spacing may be affected by factors such as specific adhesive type used and, where the dots are printed, the print screen selected.

It has been found that smaller dots are difficult to consistently form; in particular when screen printing a significant amount of adhesive will become stuck to the screen and thus not be properly deposited on the fabric. Accordingly, dots with a diameter of less than 200 pm are not preferred. In preferred embodiments, 80% or more of the total dots of the second adhesive are of diameter 250 to 450 pm. It is further found by the inventors that smaller dots provide more pathways for agents such as chemical warfare agents to be ‘intercepted’ by the carbon particles. Therefore it is preferred for the dots to have as small a diameter as the process reliably allows, while still giving sufficient adhesion of the carbon.

The dots of the first adhesive may preferably have a thickness of 100 to 500 pm, preferably 200 to 400 pm, more preferably 250-350 pm or 200-300 pm. This thickness provides good anchorage of the carbon spheres to the adhesive and good lamination strength. A preferred thickness for the dots of the first adhesive is 250-350 pm. The dots of the second adhesive may preferably have a thickness of 100 to 500 pm, preferably 100 to 300 pm, more preferably 150 to 250 pm or 200-300 pm, in view of the different materials for which the adhesive is primarily intended.

As explained herein, the present inventors have found that the distance between dots is important for achieving an advantageous carbon particle loading and distribution. Most preferably, there are no distances > 500 pm between dots.

It is preferred that both the first and second adhesives are provided as dots with one or more of the above properties.

The first and second adhesive materials can be selected from various known adhesives. As explained below, for processing reasons it may be preferred for the first and second adhesives to be different; in particular a different melting temperature between the first and second adhesives allows selective softening for carbon particle distribution and/or lamination.

This may help in view of possible different functions of the first and second adhesives. In some embodiments, the first adhesive is primarily responsible for carbon particle adhesion, and ‘control’ of the carbon particle dispersion. On the other hand, the second adhesive may be primarily responsible for lamination, that is, adhesion of the second fabric not only to the carbon particles but also to the first fabric and first adhesive. This may mean that processing conditions and adhesive properties are selected in view of these purposes.

Accordingly it may be preferred for the first adhesive to have a higher melting temperature than the second adhesive. This particularly helps in preventing or lessening spread of the first adhesive on the first fabric, which can result in loss of air permeability, flexibility and lamination strength. For example, the first adhesive may have a melting temperature of about 150°C to 180°C and the second adhesive a melting temperature of about 110°C to 140°C.

Additionally or alternatively, the first adhesive may advantageously include a cross-linking agent; these can also help in the control of dot adhesive spreading.

In general it is important that the dots remain discrete and do not spread across the fabric during, for example, drying or re-melting processing steps.

Suitable adhesive materials include, for example, polyurethanes; polyether/polyurethane dispersions; ethylene vinyl acetate (EVA); co-polyesters; co-polyamides; and thermoplastic polyurethane powders dispersed into a paste. Such adhesives are well known in the art, and may be applied as a mixture with a thickener or crosslinker. Where the manufacturing method will include re-melting one or more of the adhesives (see below), if is preferred that a crosslinker is not used. Polyurethanes are particularly preferred.

In some embodiments, the first adhesive is a polyurethane adhesive and the second adhesive is a polyether/polyurethane dispersion adhesive.

For example, the second adhesive may be a hot melt adhesive; that is, an adhesive that is applied in a melted (molten) form and then solidifies to provide adhesion. Re-heating permits an applied hot melt adhesive to be readied or primed for further adhesion. For example, the adhesive may be applied to the second fabric and cooled/solidified. Then, the second fabric may be applied to a first fabric to which carbon particles are already adhered, sandwiching the carbon between the fabric. The laminated fabrics may then be heated to re-melt the hot melt adhesive and give adhesion of the second fabric.

Alternatively the reheating may occur shortly before the application of the second fabric.

Suitable hot melt adhesives include polyurethanes. It may optionally include further components such as, for example, a thickener (such as an inverse emulsion thickener). The hot melt adhesive may be pH corrected. Accordingly the second adhesive may suitably be a two-component mix.

On the other hand, the first adhesive which is primarily for fixing the carbon particles may be different from the second adhesive. It may for example be a wet adhesive. It may too be polyurethane based, but it will be appreciated that a hot melt adhesive and a wet adhesive are different even if the base component (polyurethane) is the same or of the same chemical family.

The first adhesive may optionally include further components. It may include one or more of an emulsifier (preferably a non-ionic emulsifier, such as an aryl polyglycol or polyethylene glycol), a thickener (such as an acrylic resin/polyacrylate), a defoamer or antifoaming agent (such as a mix of aliphatic cations and a fatty acid), a pH modifier (such as ammonia), and a secondary adhesive (such as a blocked aliphatic isocyanate).

A suitable mix for the first adhesive may comprise, for example, (by wet wt%):

20-50%, preferably 25-35% of the primary adhesive (for example, a polyurethane) optionally, 0.5-2% pH modifier (for example, ammonia); optionally, 0.5-1 .5% secondary adhesive (for example, a dispersion of a blocked aliphatic isocyanate); optionally, 2-5% thickener (for example, an acrylic resin); optionally, 0.25-1% emulsifier (for example an aryl polyglycol non-ionic emulsifier); and optionally, 0.5-2% antifoaming agent (for example, a mixture of aliphatic cations and a fatty acid derivative); with the balance being water - generally, 50-70%.

As the second adhesive, an example of a suitable adhesive is a two-component mix of the following: AboBond™ LPU (hot melt polyurethane adhesive - a dispersion of polyurethane polymers in water; obtained from Bodewes Material Solutions) + Texipol™ 63-237 (inverse emulsion thickener). As the first adhesive, an example of a suitable adhesive is:

Manufacture

The present invention provides a method for manufacturing a filter material, comprising the steps of: (a) applying a first adhesive onto a first fabric; (b) applying a second adhesive onto a second fabric; (c) applying carbon particles, optionally activated carbon spheres, to the first adhesive; (d) laminating the second fabric and first fabric, sandwiching the carbon particles therebetween; wherein in step (a) the first adhesive is applied as discrete dots with a distance of 100-600 pm, preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm, between adjacent dots; wherein in step (b) the second adhesive is applied as discrete dots with a distance of 100-800 pm, preferably 150-450 pm, more preferably 300-400 pm or alternatively 300-600 pm, between adjacent dots, and wherein the distance between the dots of the second adhesive is different from the distance between dots of the first adhesive.

The order of steps (a) and (b) is not important, of course; step (a) may be before step (b); or step (b) before step (a); or steps (a) and (b) may overlap or be performed concurrently. Step (c) is done after step (a), but again step (b) is not necessarily before step (c). Step (b) may be before step (c); or step (c) before step (b); or steps (b) and (c) may overlap or be performed concurrently.

It is also noted that, for practical reasons, step (c) may be performed some significant time after step (a) or step (b). For example, the fabric and adhesive combination formed in step (a) may be transported to a different location for step (c) to be carried out. In step (c), the carbon particles are suitably applied to a ‘wet’ first adhesive. Therefore if there is some time between steps (a) and (c) the adhesive might dry. Accordingly before step (c) there may be an addition re-melting step, in which the first adhesive is heated to melt it so that the carbon particles can be applied to a wet adhesive.

Similarly, step (d) is carried out after steps (c) and (b). However suitably the first and second adhesives are ‘wet’ when this occurs, to enhance lamination. Thus, before step (d) there may be an additional remelting step, in which one or both of the first and second adhesives are heated to melt them. Of course if one or both of the adhesives is already ‘wet’ (i.e. melted) at the time of step (d) it does not need to be heated and re-melted in this way.

Indeed in some embodiments it may be preferred that the function of the first adhesive is primarily to hold the carbon particles securely after step (c), and the second adhesive functions to strongly laminated the first and second fabrics with the carbon particles between them in step (d).

In such embodiments, step (d) may be carried out at a temperature above the melting temperature of the second adhesive but below the melting temperature of the first adhesive. This means that the secure and controlled carbon particle distribution discussed above, by way of the first adhesive, is not altered or impacted by the lamination processing in step (d). It may be facilitated by using a hot melt adhesive as the second adhesive.

Steps (a) and (b) may suitably be carried out by printing, for example screen printing. The present inventors have found that this technique, using a screen having holes of a certain distribution therein, through which an adhesive is applied to the fabric by a squeegee or the like, allows for reliable dot formation and control without potential flow across the fabric.

Where a screen is used, it is generally removed before the adhesive is dried (if a drying step is present, for example where the intention is to re-melt one or more of the adhesives) and before the carbon particles are added.

Clearly the properties of the screen will affect the properties and pattern of the adhesive printed through it. It may therefore be desirable to use a first screen for the first adhesive (that is, in step (a)) and a second screen for the second adhesive (that is, in step (b)).

The first screen may have a hole pattern in which the holes have a maximum dimension of 100-800 pm, preferably 450-650 pm, more preferably 500-600 pm, or alternatively 300-600 pm. The second screen may have a hole pattern in which the holes have a maximum dimension of 100-800 pm, preferably 200- 400 pm, more preferably 250-350 pm or alternatively 300-600 pm. The holes themselves are not particularly limited herein; however it has been found that hexagonal holes provide consistent dot formation.

As explained herein, the distance between dots of adhesive contributes to the advantages of the invention. Accordingly it can be recognised that control/selection of the distances between the holes of the first and second screens can lead to the desired adhesive dot distributions. The first screen (for the first adhesive) may therefore preferably have a distance of 100-600 pm, preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm, between adjacent holes. The second screen (for the second adhesive) may preferably have a distance of 100-800 pm, preferably 150- 450 pm, more preferably 300-400 pm or alternatively 300-600 pm, between adjacent dots. The distance between the holes of the first and second screens is different.

Alternatively, if the adhesive is one for which the size of dots does not exactly correspond to the hole size, a screen may be selected such that in step (a) the first adhesive is applied as discrete dots with a distance of 100-600 pm, preferably 350-550 pm, more preferably 400-500 pm or 300-400 pm, between adjacent dots; in step (b) the second adhesive is applied as discrete dots with a distance of 100-800 pm, preferably 150-450 pm, more preferably 300-400 pm or alternatively 300-600 pm, between adjacent dots, and the distance between the dots of the second adhesive is different from the distance between dots of the first adhesive.

The screen thickness affects how thick the deposited adhesive is. However, it will be recognised that some adhesive volume is lost through drying; accordingly, to achieve a desired adhesive thickness the first screen may have a thickness of 100-500 pm, preferably 200-400 pm, more preferably 250-350 pm or 200-300 pm. The second screen may have a thickness of 100-500 pm, preferably 100-300 pm, more preferably 150-250 pm or 200-300 pm.

Similarly the open area of the screen affects the coverage of the adhesive over the fabric. This then affects the carbon loading (for the first adhesive and fabric) and the lamination strength (for the second adhesive and fabric). The open area of the screen can be suitably selected to achieve advantages in these areas. The present inventors have found that a screen open area of 25-35% is particularly useful for the first screen, and a screen open area of 15-25% is particularly useful for the second screen. One or both of these such screens may be used in embodiments of the invention.

In step (c), the carbon particles are applied to the first adhesive, on the first fabric. This may be done in any suitable manner, for example by scattering the particles over the fabric, or by applying the adhesive- treated face of the fabric to a bed of the particles. Carbon particles may be applied by a revolving brush; or an engraved roller; a knurled roller; or by a vibrating plate or sieve. Some such methods may result in excess (non-adhered) carbon particles being trapped on the first fabric. Accordingly the present methods may include a step, after step (c) and before step (d), or removing excess carbon particles from the first fabric, leaving only those carbon particles which are adhered to the first fabric by the first adhesive. Such removal may be achieved by, for example, a simple shaking or other agitation technique, or vacuum suction (at a level insufficient to remove carbon particles which are attached to the adhesive).

In step (d), the lamination preferably is done with the second adhesive ‘wet’, that is, partially or completely melted. As explained above, this may be achieved by heating, or by carrying out step (d) sufficiently quickly after step (b). It is optionally for the first adhesive to be ‘wet’ in this step; in preferred embodiments it is not.

The heating may involve heating both fabrics and the carbon particles, in view of the proximity of the fabrics in the lamination process; this leads to the above preference that the first and second adhesives have different melting temperatures and in particular that the second has a lower melting temperature than the first.

The lamination may be done by procedures known in the art, for example by laying the second fabric on top of the first fabric with the surfaces having the first and second adhesives on them facing one another, then applying pressure.

Steps of one embodiment of the present method are illustrated in Figure 1. In Figure 1(a), a screen mask 6 is placed onto a first fabric 1 (here a knitted fabric). Then, in Figure 1(b), a first adhesive 3 is applied to the first fabric 1 through the holes of the mask 6. Removal of the screen 6 leaves the first adhesive 3 dispersed on the first fabric 1 , as shown in Figure 1(c). These steps correspond to the step (a) described herein.

Carbon spheres of the type described above are then dispersed on the first adhesive and are stuck there. This dispersed structure is illustrated in Figure 1(d). This corresponds to the step (c) described herein.

Not illustrated are steps in which, using a similar screen and steps as in Figure 1(a)-(c), a second adhesive 4 is applied to a second fabric 2, here a nonwoven material. These steps correspond to the step (b) described herein.

The two fabrics 1 and 2 are then laminated as shown in Figure 1(e), with the respective adhesives 3 and 4 and the carbon spheres 5 sandwiched between them. This corresponds to the step (d) described herein.

***

The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described. Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example +/- 10%.

Experimental Explanation

REFERENCE SAMPLE PRODUCTION

A fabric samples was prepared. Fabrics measuring 20 cm x 20 cm were used.

The first fabric was a knitted fabric and the second fabric a nonwoven fabric.

The screens used were: for fabric layer 1 - 25 holes/inch mesh, 300 pm thick, 30 % open area, 555 pm hole diameter, 2530 mm wide - 64 cm circumference. for fabric layer 2 - 40 holes/inch mesh, 200 pm thick, 22 % open area, 300 pm hole diameter, 2530 mm wide - 64 cm circumference.

As the first adhesive there was used a mixture of ‘Adhero™ Prime TL’ from CHT™, a polyurethane adhesive, at 100 parts; a crosslinker ‘Adhero™ CL1 T from CHT™; and a thickener ‘Texipol™ 63-237’ from Scott Bader™, at 11 parts.

As the second adhesive there was used a mixture of ‘Impranil™ DAH’ from Covestro™, a polyurethane/polyether dispersion, at 100 parts; a crosslinker ‘Imprafix™ 2794’ from Covestro™; and a thickener ‘Texipol™ 63-237’ from Scott Bader™, at 11 parts.

The first adhesive was printed onto the first fabric through the screen for fabric layer 1 . Carbon spheres (Kureha A-BAC MP) were scattered onto the first adhesive; it was then dried for 5 minutes at 160°C. The second adhesive was printed onto the second fabric through the screen for fabric layer 2; it was then dried for 5 minutes at 50°C.

Excess carbon was removed by shaking. The two fabrics were then laminated in a hot press at a temperature of 120 °C for 3 minutes. Performance Testing

The laminated fabric made by the process above had added to it a standard cotton/nylon printed outer shell. Three swatches (A, B and C) of that combined material were taken. Each material swatch was set up in a test cell and challenged with droplets of a test chemical warfare agent (CWA) laid by means of a dispenser-syringe combination, with the droplets separated as widely as possible. Then the swatches were placed into a thermostated and humidified exposure room, where tubes on top of the cells served to present a laminar flow towards the cell surface. During the test thermostated and humidified nitrogen was drawn through the clothing with a velocity corresponding to a AP of 25 Pa across the swatches. The quantity of penetrated CWA was collected in a bubbler filled with Di-Ethyl Succinate (DES). At the end of the test, the quantity of CWA in the DES was determined by gas chromatography/flame photometric detector. The dose as reported was calculated by dividing the penetrated quantity of CWA (after test duration) by the flow in ml/min. This results in a dose with units mg.min/m ³ .

Testing was done with two different CWAs, CWA 1 (soman) and CWA 2 (mustard agent).

In this test, the surface area of the material swatches was 10 cm ² ; a contamination amount of 10 g/m ² was applied. 10 droplets were applied for CWA 1 and 8 droplets were applied for CWA 2. Each droplet had a volume of 1 pl. The tests were performed at a temperature of 32°C, and a relative humidity of 80%RH. The total test duration was 24 hours; measurements were taken at 6 hours, then 24 hours.

Results - CWA 1

Results - CWA 2 Existing products have 24-hour penetrated doses of, for example, around 350 mg.min/m ³ for CWA 1 and around 670 mg.min/m ³ for CWA 2. It is therefore apparent that the present invention provides products with a useful and even advantageous performance.