LAYER

Technical field

The invention relates to a method of increasing hydrophobic properties of planar layer of polymeric nanofibres, by which a hydrophobic agent is applied to surface of the layer or into its entire structure.

The invention also relates to planar layer of polymeric nanofibres with increased hydrophobic properties.

Apart from that, the invention also relates to layered textile composite.

Background art

Nowadays many so called outdoor textiles are know, which prevent penetration of water from external environment and are permeable for vapour at the same time. Most of them are based on principle of using hydrophobic material and/or subsequent hydrophobic surface treatment, or on layering of several identical or different layers onto each other. However, outdoor textiles based on advantageous properties of nanofibrous layer start to appear, where their inter-fibrous spaces are due to their small dimensions hardly permeable for water, but which allow vapour to permeate freely on principle of diffusion. Examples of such textiles are described in US 2011092122 or US2008184453.. Their disadvantage is, that nanofibres mutually move - slip when hydrostatically loaded by water column of approx. 300 mm, as result of which the spaces between them grow larger, and the layer of nanofibres progressively becomes relatively easily permeable for water. Although the achieved value of hydrostatic load is higher than with some outdoor textiles without layer of nanofibres, it is not sufficient for many applications. Partial solution of this problem are, for example textiles proposed in US 2008220676 or US 2009176056, having hydrophobic material deposited on their nanofibrous layer. Their disadvantage is that the hydrophobic material is deposited in droplets solely on their surface or on surface of their nanofibres, so their inter-fibrous spaces are mostly free, and thus allowing the nanofibres to mutually slip when hydrostatically loaded by water column of approx. 1300 mm, and the layer thus becomes permeable for water again.

The goal of the invention is to remove or at least to eliminate disadvantages of the prior art by proposing a method of increasing hydrophobic properties of a layer of polymeric nanofibres, which would lead to increase its hydrostatic resistance, maintaining its very good permeability for vapour at the same time, and which would also secure protection of the layer of polymeric nanofibres from clogging with impurities.

Principle of the invention

The goal of the invention is achieved by employing the method according to the invention, the principle of which consists in that during applying of hydrophobic agent and/or after it, is on the layer of polymeric nanofibres acted from at least one side by a stream of air, which removes the hydrophobic agent from surface of the layer of polymeric nanofibres on this respective side into inter-fibrous spaces in its inner structure, while during this and/or after this is on the layer of polymeric nanofibres acted by increased temperature, which is lower than the melting temperature of the polymer of the nanofibres, as a result of which the hydrophobic agent contained in the layer dries out and coagulates, by means of which at least some inter-fibrous spaces of the layer of polymeric nanofibres are entirely filled up with the hydrophobic agent in solid state and polymeric nanofibres get fixed against mutual slipping. By this way, the hydrostatic resistance of the planar layer of polymeric nanofibres is increased by several tens to hundreds of percent. Further increase of hydrostatic resistance can be achieved, if on the layer of polymeric nanofibres is acted by means of temperature, which is higher than the glassy temperature of polymer of the nanofibres, by means of which shrinking of the layer of polymeric nanofibres and the inter-fibrous spaces occur, causing their more effective filling.

Even higher increase of hydrostatic resistance can be achieved, if the hydrophobic agent applied to the layer of polymeric nanofibres is simultaneously cross-linked upon action of increased temperature.

For removing as much as possible of the hydrophobic agent into the inter-fibrous spaces it is advantageous to expose the layer of polymeric nanofibres with applied hydrophobic agent to increased pressure before dry-out and coagulation of the agent, this advantageously by means of a calender.

Depending on requirements on the rate of shrinkage of the layer of polymeric nanofibres, the ^! layer is either in stretched posture or, on the contrary, in loose posture, when the shrinkage rate is higher, when acted on it by the increased temperature.

For subsequent use of the layer of polymeric nanofibres is further advantageous if the layer is during increasing its hydrophobic properties deposited on a layer of parrying textile. Suitable carrying textile is for example bi-component spunbond comprising polypropylene fibres covered by polyethylene coating, because it allows thermal lamination with the layer of nanofibres to be performed without the necessity of additional applying of bonding agent.

In terms of applying , of hydrophobic agent to the layer of nanofibres and its subsequent removal into its inner structure, it is advantageous to apply the hydrophobic agent to the layer of polymeric nanofibres in the form of water emulsion, the viscosity of which is lower than the viscosity of the concentrated hydrophobic agent.

The goal of the invention is also achieved by means of planar layer of polymeric nanofibres with increased hydrophobic properties, the principle of which is based on entire filling of at least some of its inter-fibrous spaces with hydrophobic agent in solid state.

Suitable hydrophobic agent is agent based on silicone or fluor-carbon or paraffin. Further on, the goal of the invention is achieved by means of layered textile composite, the principle of which consists in that it contains at least one layer of polymeric nanofibres, at least some of inter-fibrous spaces of which are entirely filled with hydrophobic agent in solid state.

Examples of embodiment

By the method of increasing hydrophobic properties of a layer of polymeric nanofibres according to the invention, emulsion of a hydrophobic agent is applied to the layer of polymeric nanofibres in the first step, advantageously of hydrophobic agent based on silicone, fluor-carbon or other suitable material containing long hydrocarbon chains, e.g. paraffin, etc. in distilled water. Its application can be performed _, by any known method, for example by immersing the layer of polymeric nanofibres into the emulsion, spraying the emulsion onto at least one of the surfaces of the layer of polymeric nanofibres, spreading it by means of rollers, etc.

After application of the emulsion of the hydrophobic agent and/or during it is on the layer of polymeric nanofibres acted from at least one side by an air stream. This removes the emulsion of the hydrophobic agent applied to surface of the layer of polymeric nanofibres into inter-fibrous spaces deeper in its inner structure thus supporting their filling. Thereat, the air stream used as the carrying one for application of the emulsion of the hydrophobic agent by means of its spraying in the form of aerosol, or eventually at least one more supporting air stream can be used.

During action of the air stream and/or after it, is on the layer of polymeric nanofibres acted, e.g. in a hot air chamber, by increased temperature, which is lower than the melting temperature of the polymer of the nanofibres, as a result of which dry-out and coagulation of the emulsion of the hydrophobic agent and filling of the inter-fibrous spaces (pores) of the layer of polymeric nanofibres with the hydrophobic agent in solid state occur. At least some of the inter-fibrous spaces are entirely filled with the agent and thus become completely impermeable for water in liquid state, surprisingly remaining permeable for vapour, as numerous tests have proved. In addition to that, individual polymeric nanofibres are fixed by means of the solid hydrophobic agent preventing their mutual slipping, due to which the layer of polymeric nanofibres modified in that way is able to withstand significantly higher levels of hydrostatic load, compared to layers of polymeric nanofibres known in the prior art. According to the need, the increased temperature and/or duration of its action can be selected in order to provide simultaneous cross-linking of the hydrophobic agent, which results in further increase of the hydrostatic resistance already achieved. Further on, it is advantageous to act on the layer of polymeric nanofibres by means of temperature higher than the glassy temperature of the polymer of the nanofibres, as in that case simultaneous shrinking of the layer of polymeric nanofibres and size-reduction of the inter-fibrous spaces (pores) occur, and the pores are thus easily filled with the hydrophobic agent in solid state. Thereat, the rate of shrinking can be influenced not only by means of increased temperature and duration of its action, but also by that, if the layer is exposed to increased temperature in stretched posture, when the shrinkage rate occurring after its release is smaller or, on the contrary, by exposing it to the same condition in loose posture, achieving higher shrinkage rate. In addition to that, filling the inter-fibrous spaces of the layer of polymeric nanofibres with the hydrophobic agent prevents them from being clogged with undesirable impurities, which could negatively influence the permeability of the layer of polymeric nanofibres for vapour and/or its impermeability for liquid water.

As suitable supplement to the action of the air stream, it is also possible to calender the layer of polymeric nanofibres, which, due to increased pressure between the rollers, supports further penetration of the emulsion of the hydrophobic agent into the inter-fibrous spaces of the layer of polymeric nanofibres and their filling, simultaneously providing complete or at least partial dry-out of the emulsion. In case of need, final drying stage and/or cross-linking of the hydrophobic agent can follow, for example in a hot air chamber. Apart from the calender, other devices can be employed, acting on the layer of polymeric nanofibres by means of pressure, such as foulard, etc.

It is advantageous for the intended applications, including in particular the use in textile industry, the layer of polymeric nanofibres to be as even as possible, breadthwise as well as lengthwise. The highest evenness in both directions, can be currently achieved by employing device for electrostatic spinning, by which is the liquid polymer matrix spun in an electric field created between a collecting electrode and a spinning electrode of an oblong shape - for instance a cylinder (see e.g. EP 1673493) or a string (see e.g. EP 2059630 or EP 2173930). This principle has been commercially applied in Nanospider™ technology of Elmarco company.

The layer of polymer nanofibres produced in this way is then subject to increase of its hydrophobic properties according to any of variants described above, either individually or in combination with carrying textile formed of a substrate textile onto which it has been deposited during electrostatic spinning, e.g. polypropylene spunbond. Thereat, it is advantageous to bind the layer of polymeric nanofibres to the substrate textile during deposition onto it or after that by means of lamination, using suitable bonding agent. In another variant is the layer of polymeric nanofibres deposited on the substrate textile transferred onto another suitable carrying textile, such as fabric or knitted fabric used for manufacture of outdoor clothing, either made of synthetic fibres (e.g. polyamide (PA), polyester (PES), etc.) or of natural fibres (e.g. cotton (CO)). The transfer can be performed by overlaying the layer of polymeric fibres with that carrying layer, their joining through lamination and subsequent removal of the original substrate textile. In both variants it is advantageous to bind the layer of polymeric fibres to the carrying textile during its deposition on it, or after that, through lamination employing suitable bonding agent, which is applied to the carrying textile for example; by means of gravufe printing method, or which is embedded in it as part of its fibres or otherwise. Example of the bonding agent embedded in the carrying textile is the bi-component spunbond, the fibres of which are made of polypropylene core covered by polyethylene coating, which melts during the lamination and thus binds the layer of polymeric nanofibres with that carrying textile. Thereat, the lamination of the layer of polymeric nanofibres with the carrying textile can be performed before the start of the process of increasing their hydrophobic properties or during it, during exposing the layer of polymeric nanofibres to increased temperature or after it. After increasing the hydrophobic properties of the layer of polymeric nanofibres, the two-layer textile composite produced in that way is used as the upper layer of the outdoor textile, while its carrying textile forms its outer surface. It is advantagedus to protect the layer of polymeric nanofibres from mechanical damage, especially abrasion, by supplementing the textile composite by suitable inner layer (inside lining) on the side of the open surface of the layer of polymeric nanofibres, which can be bound to it in case of need for example by means of lamination and/or suturation, or any other suitable method. In other embodiments, the two-layer or three-layer textile composite can be faced inside by the carrying textile, or supplemented by other textile or non-textile layers to achieve the required thickness and/or other parameters.

Suitable material of nanofibres is particularly polyamide 6 (PA 6), polyamide 6.6 (PA 6.6), polyurethane (PUR), polyvinyl alcohol (PVA), polyester (PES) or polyvinylidene fluoride (PVDF), etc., while their surface weight before application of the emulsion of the hydrophobic agent varies according to the needs and intended applications usually from 1 to 20 g/m ² , or is even higher. As hydrophobic agents some of commercially available agents can be advantageously used, which is applied to the layer of polymeric fibres either in concentrated state or advantageously in the form of emulsion in (distilled) water, where, based on its nature, it can be optionally supplemented by organic acid, such as for example acetic acid, with suitable catalyst added for stabilization purposes, such as the C48 or C43 substances.. .

Example 1

By means of electrostatic spinning using spinning electrode comprising spinning elements in shape of a string according to EP 2173930 a layer of nanofibres of polyamide 6 (PA 6) with surface weight of 5 g/m ² deposited on substrate textile formed by polypropylene spunbond with surface weight of 18 g/m ² was prepared. At the electrostatic spinning, the distance between the spinning elements of the spinning electrode and the substrate textile was 18 cm and the voltage difference between the spinning electrode and the collecting electrode formed of metal plate was 100 kV. Both layers were bound by means of lamination. To a sample of the two-layer textile composite, with dimensions 20x20 cm, produced in the way mentioned above, an emulsion of hydrophobic agent in distilled water containing 6 g of hydrophobic agent based on silicone, commercially available under designation Lukofix™, 0,1 ml of acetic acid and 1 ,5 g of C48 as a catalyst in 100 ml was applied from the side of layer of polymeric nanofibres by means of commercially available SATA minijet® spray- gun. The application of the emulsion was performed under action of pressure of 5 bar, the spot of application on the layer of polymeric nanofibres having diameter of 1 cm, the movement of the spray-gun being tractive. Thereat, the quantity of 0,37 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres.

Subsequently, the produced textile composite was exposed in the loose posture to a temperature of 160 °C for a period of 5 minutes in a hot air chamber, resulting in shrinking the layer of polymeric fibres by approx. 5%.

Hydrostatic resistance of produced textile composite was then measured according to the European standard EN 811. It, reached value of 6126 mm of water column, which is, value approx. 5 times higher than that of similar composites known in the prior art.

Example 2

A two-layer textile composite was produced in the same manner as in example 1 and the same emulsion of Lukofix™ hydrophobic agent was applied to it in the same way. However, the quantity of the emulsion applied to 1 g of the layer of polymeric nanofibres was 0,45 g. Further on, the composite was exposed to increased temperature in the same manner as in example 1.

Achieved value of hydrostatic resistance of this composite was 4222 mm of water column. ^{1 :}

Example 3

A two-layer textile composite was produced in the same manner as in example 1. An emulsion of hydrophobic agent in distilled water containing 12 g of hydrophobic agent based on silicone, commercially available under designation Lukofix™, 2 ml of acetic acid and 3 g of C48 as a catalyst in 00 ml was applied to it in the same manner. Thereat, the quantity of 0,06 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres. The composite prepared in that way was exposed to increased temperature in the same manner as in example 1. ,

Achieved value of hydrostatic resistance of this composite was 8089 mm of water column.

Example 4

A two-layer textile composite was produced in the same manner as in example 3, the same emulsion of Lukofix hydrophobic agent was applied to it in the same way. However, the quantity of the emulsion applied to 1 g of the layer of polymeric nanofibres was 0,08 g. Further on, the composite was exposed to increased temperature in the same manner as in example 3.

Achieved value of hydrostatic resistance of this composite was 8029 mm of water column.

Example 5

A two-layer textile composite was produced in the same manner as in example 3, the same emulsion of Lukofix hydrophobic agent was applied to it in the same way. However, the quantity of the emulsion applied to 1 g of the layer of polymeric nanofibres was 0,09 g. Further on, the composite was exposed to increased temperature in the same manner as in example 3.

Achieved value of hydrostatic resistance of this composite was 9027 mm of water column. >

Example 6

A two-layer textile composite with layer of polymeric nanofibres of surface weight of 12 g/m ² was produced in the same manner as in example 1. An emulsion of hydrophobic agent was applied to it in the same manner as in example 3, with 0,08 g of the emulsion applied to 1 g of the layer of polymeric nanofibres. Further on, the composite was exposed to increased temperature in the same manner as in example 3. Achieved value of hydrostatic resistance of this composite was 11058 mm of water column.

Example 7

A two-layer textile composite was produced in the same manner as in example 6, the same emulsion of Lukofix hydrophobic agent was applied to it in the same way. However, the quantity of the emulsion applied to 1 g of the layer of polymeric nanofibres was 0, 17 g. Further on, the composite was exposed to increased temperature in the same manner as in example 6.

Achieved value of hydrostatic resistance of this composite was 14377 mm of water column, which is value over 10 times higher than that of similar composites known in the prior art.

Example 8

A two-layer textile composite was produced in the same manner as in example 6, the same emulsion of Lukofix hydrophobic agent was applied to it in the same way. However, the quantity of the emulsion applied to 1 g of the layer of polymeric nanofibres was 0,21 g. Further on, the composite was exposed to increased temperature in the same manner as in example 6.

Achieved value of hydrostatic resistance of this composite was 12180 mm of water column. Example 9

A two-layer textile composite was produced in the same manner as in example 3. An emulsion of the same hydrophobic agent was applied to it by means of immersing it in a bath, while 0,17 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres. Before acting on it by increased temperature, the prepared composite was passed through a foulard by speed of 1 m/s, where was acted on it by a pressure of 4 bar.

Hydrostatic resistance of produced textile composite was then measured in accordance with the European standard EN 81 1 , reaching value of 3590 mm of water column in this case. Example 10

A two-layer textile ' composite was produced in the same manner as in example 6. An emulsion of the same hydrophobic agent was applied to it in the same manner, the application was carried out until complete surface wetting of the layer of polymeric nanofibres by the emulsion was achieved. Thereat, the quantity of 0,09 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres. Subsequently, on the layer of polymeric nanofibres was acted by means of commercially available SATA minijet® spray-gun producing an air stream of a pressure of 6 bar for 90 seconds, removing the emulsion of the hydrophobic agent applied to surface of the layer of polymeric nanofibres deeper into the inter-fibrous spaces in the inner structure of the layer. Further on, the composite was exposed to increased temperature in the same manner as in example 6. The hydrostatic resistance of produced textile composite was then measured in accordance with the European standard EN 811 , reaching the value of 14100 mm of water column in this case, exceeding the value achieved with comparable example Without employing the action of air - i.e. example 6 - by over 20%.

Example 11

A two-layer textile composite was produced in the same manner as in example 1. An emulsion of- hydrophobic agent in distilled water containing 50 g of hydrophobic agent based on fluorine-carbon, commercially available under designation Nuva™ in 100 ml was applied to it in the same manner. Thereat, the quantity of 0,24 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres.

Hydrostatic resistance of produced textile composite was then measured in accordance with the European standard EN 811 , reaching the value of 7000 mm of water column in this case.

Example 12

In the same manner as in example 1 , a layer of polymeric nanofibres of polyamide 6 (PA6) with surface weight of 12 g/m ² deposited on the same substrate textile was produced. An emulsion of hydrophobic agent in distilled water containing 50 g of the hydrophobic agent based on fluorine-carbon, commercially available under designation Sevophob NTF™ in 100 ml was applied to the textile composite in the same manner as in example 1. Thereat, the quantity of 0,24 g of the emulsion was applied to 1 g of the layer of polymeric nanofibres.

Hydrostatic resistance of produced textile composite was then measured in accordance with the European standard EN 811 , reaching the value of 6790 mm of water column in this case.

Example 13

By means of electrostatic spinning using a spinning electrode in the shape of cylinder according to EP 1673493 a layer of nanofibres of polyurethane (PUR) with surface weight of 5 g/m ² deposited on substrate textile comprising polypropylene spunbond of surface weight of 18 g/m ² was prepared. At the electrostatic spinning, the distance between the spinning electrode and the substrate textile was 17 cm and the voltage difference between the spinning electrode and the collecting electrode formed of metal plate was 75 kV. The two layers were bound by lamination in the same manner as in example .

To a sample, of the two-layer textile composite, with dimensions of 20x20 cm, produced in the way mentioned above, an emulsion of hydrophobic agent in distilled water containing 5 g of the hydrophobic agent based on fluorine- carbon, commercially available under designation Nuva™, in 100 ml was applied from the side of layer of polymeric nanofibres by means of commercially available SATA minijet® spray-gun. The application of the emulsion was performed under pressure of 5 bar, the spot of application on the layer of polymeric nanofibres having diameter of 1 cm. The application was performed continually, the movement of the spray-gun being tractive.

Subsequently, the produced textile composite was in loose posture exposed to temperature of 140 °C for period of 5 minutes in a hot air chamber, resulting in shrinking the layer of polymeric fibres by approx. 10%. Hydrostatic resistance of produced textile composite was then measured in accordance with the European standard EN 811 , reaching the value of 1750 mm of water column in this case.

The above mentioned, examples demonstrate that levels of hydrostatic resistance achieved when employing the method of increasing the hydrophobic properties of layer of polymeric fibres according to the invention are significantly higher than the ones achieved by means of the methods known in the prior art. In some cases, those values were exceeded more than 10 times.