NL1043320B1 - High-performance multi-filament yarns with an electroconductive coating and items made from such yarns - Google Patents

Abstract

The present invention relates to high performance multi-filament yarn with an electroconductive coating wherein essentially each filament of the multi-filament yarn is coated individually. Furthermore, the invention relates to high-dexterity electroconductive protective gloves and other wearable items made from such coated high-performance multi-filament yarns. The electroconductivity enables the wearer of a glove according to the invention to operate a device with a touchscreen. The electroconductive glove according to the invention combines a high degree of dexterity and comfort for the wearer of the glove with a high degree of protection by the glove. Moreover, several embodiments of the yarns with the electroconductive coating according to the invention add good gripping properties to a glove without compromising the breathability of the glove.

Description

HIGH-PERFORMANCE MULTI-FILAMENT YARNS WITH AN ELECTROCONDUCTIVE COATING AND ITEMS MADE FROM SUCH YARNS

FIELD OF THE INVENTION The present invention relates to an electroconductive coating for high-performance yarns and to items, including for example protective gloves, that are made from high- performance yarns with such an electroconductive coating.

BACKGROUND OF THE INVENTION The use of touchscreens in people’s daily live is increasing steadily, both privately and professionally, and is not imited ta smartphones and tablets. Many machines and control systems in industry are operated through touchscreens. At the same time there is more focus on safety in work environments and the use of personal protective equipment, such as protective gloves have become the standard in a wide variety of industries.

Hence, there is a need for protective gloves that are electroconductive to enable a wearer of the gloves to use a touchscreen without taking the gloves off. In addition to being electroconductive such gloves shall provide the required level of protection against heat, cuts, abrasion, chemicals, etcetera. Protection against such potential threats can be achieved by selecting the right materials. For example: UHMWPE {Dyneema)/p-Aramid {Twaren/Kevlar) for cut resistance and meta/para-aramid/Woal {nomex/Kevlar) for heat protection, Although the wearing comfort of gloves is very subjective, in general, a textile glove that is thin and soft on the skin and breathable is considered to be comfortable, The softness of the textile is largely related to the thickness and flexibility of the individual filaments in a yarn bundle.

In gloves according to the prior art the functionality of electroconductivity Is obtained by adding either a metallic {steel or copper} yarn or a carbon fiber to the high performance yarn, comprising for example UHMWPE/p-Aramid, since UHMWPE yarns are electric insulators. The stiffness of the metallic yarns will reduce the flexibility of the yarn and will hence have a negative effect on the comfort level of a glove. When such a glove is worn for prolonged periods, this may result in hand fatigue. The use of carbon fiber in gloves is also problematic since it is very brittle and will break in the knitting process or during the use of the glove, which may cause skin irritation.

Another disadvantage of gloves that comprise metallic or carbon fiber yarns is the fact that they may cause scratching of touchscreens.

Most working gloves have a distinctive color, typically not white. Since most high performance yarns, such as for example UHMWPE/p-Aramids/LCP, are difficult to dye, it is common practice to add an extra end of colored Nylon or Polyester to the yarn that is used for the knitting of a protective glove. So, in the case of an elecro- conductive protective glove according to the prior art the combinational yarn that is used typically comprises UHMWPE {or p-Aramid) for cut and/or heat protection, steel/copper for electroconductivity and a black Nylon {or Polyester) to give the glove a dark color, for example to hide dirt. Processing of such a combinational yarn is expensive and may damage the processing equipment due to the high rigidity and abrasiveness of the metallic/carbon yarns.

A significant percentage of the working gloves according to the prior art have a PU {Polyurethane) ar Nitrile coating on the palm side of the glove. This coating is applied as a separate process step during which the palm side of the glove is dipped into a solvent based PU bath, followed by curing and drying in an oven for over 45 minutes, This PU coating provides grip to the glove which is required for certain applications. Unfortunately, such a coating reduces the breathability of the glove significantly as it forms an impermeable layer of PU on the surface of the textile glove. Since the entire glove is dipped into a PU bath the yarn bundles inside the textile glove are completely impregnated which causes the individual filaments to lose their freedom to move, resulting in a negative effect on both the degree of wearing comfort and cut protection.

SUMMARY OF THE INVENTION The present invention relates to high performance multi-filament yarn with an electroconductive coating wherein essentially each filament of the multi-filament yarn is coated individually. Furthermore, the invention relates to high-dexterity etectroconductive protective gloves and other wearable items made from such coated high-performance multi-filament yarns. The electroconductivity enables the wearer of a glove according to the invention to operate a device with a touchscreen. The electroconductive glove according to the invention combines a high degree of dexterity and comfort for the wearer of the glove with a high degree of protection by the glove. Moreover, several embodiments of the yarns with the electroconductive coating according to the invention add good gripping properties to a glove without compromising the breathability of the glove.

DETAILED DESCRIPTION OF THE INVENTION The first step in the search for a suitable novel electroconductive coating comprising a suspension of a liquid binder and electroconductive particles, involved identifying electroconductive particles with attractive characteristics/properties.

With respect to the electroconductive particles, preliminary exploratory tests that have been performed with various types of electroconductive particles including metallic powders, revealed that conductive allotropes of carbon would most probably be the most attractive choice to provide electroconductivity to a high performance yarn without or with a minimum of concessions to other attractive features of the yarn, Within the group of allotropes of carbon, graphite was a possible choice, for example in the form of carbon black, However, graphene seemed more preferable, but eventually the preliminary tests revealed that carbon nanotubes would be the preferred choice, Also, intermediate morphologies, like for example the materials offered commercially by the company CarbonX with its main office located in Amsterdam, The Netherlands, appeared to be an option. A special grade of carbon

& nanotubes, hereinafter also referred to as ONT or CNTs, was selected and mixed with a PU (Polyurethane) based matrix to a homogenous blend in a first experiment and with a PU and Folyolefin matrix in a further experiments, since this combined matrix appeared ta exhibit some unforeseen benefits.

The CNTs should provide the electroconductivity.

However, a wide variety of liquid binders can be used for bonding the carbon allotropes to the fibers.

Film forming water-based polymer dispersions are preferred, especially if combined with water-based dispersions of the carbon allotropes, Evaporation of water during the coating process is non-polluting. if a solvent-based dispersion would be used, that would require the recycling of solvents, i0 thus increasing the complexity and cost of the coating process.

Examples of suitable water-based hinders are dispersions of polyursthane, acrylics, epoxies, polyesters and preferably polyoletins, if combined with UHMWPE fibers.

Also, several mixtures of different dispersions appeared to be an option.

Dispersions of block copolymers such as the block copolymer commercially known as Kraton® or similar materials with a low glass-transition temperature {Tg} polymer in one block appear to be attractive for providing grip to a glove that is knitted from a high performance yarn that is casted with such a material.

Yet, other methods of grip improvement are possible as wall Following the, with respect to some aspects, surprising outcome of the preliminary exploratory tests, the dispersion coating method of applying CNT's was applied to multi-filament UHMWPE yarn on a filament level.

Because most of the individual filaments were coated separately, the total varn bundle remained flexible, and therefore comfortable when in contact with the skin of a person, while cut resistance is kept at its maximum, In various embodiments of the multi-flament yarn with a CNT containing electroconductive coating only a minority of the individual filaments appeared fo stick together after drying of the coating, Coating of the varns was performed by unwinding it from a bobbin, feeding it through a bath containing a liquid dispersion of the conductive carbon allotrope and the polymeric binder.

Subsequently, the yarn was fed through an oven where the liguid is evaporated.

This coating method according to the invention includes the option to use multiple heating methods in the oven, including for example contact heat and/or MITO waves, in a preferred embodiment of the heating method a combination of infrared radiation 5 and hot air is used.

After drying, the yarn is wound on another bobbin and ready for use, for example in a glove knitting machine.

Due to the black color of the ONT, the polymeric matrix has a silver grey color, which results in coated yam with a silver grey color, From tests with yarns that were coated hy this method it became clear that already a very low concentration of CNT's provides sufficient conductivity to the yarn for one of the intended uses, being the production of knitted gloves that enable the operation of a touchscreen.

This characteristic is also confirmed hy the light grayness of sufficiently electroconductive CNT coated yarns.

The development of blackness, which would be expected at higher concentrations of CNTs, is not complete yet while the conductivity is already sufficient.

Other carbon allotropes than CNT may provide less conductivity if not applied in larger amounts that cause more developed blackness.

Due to the absence of hard/inflexible metallic yarns or carbon fibers, electroconductive high performance yarns according to the invention will be easier to process on a knitting machine than the prior art electroconductive yarns that do contain metallic and/or carbon fibers.

The following has been observed with respect to the effective embodiments of the CNT containing electroconductive coating according to the invention.

The concentration of the carbon allotrope, for example CNT, in the total mixture comprising the carbon allotrope and polymer binder may vary within wide ranges while still assuring an effective functional coating.

Only one percent and in some cases even ong half of a percent percent of carbon allotrope relative to the amount of polymer hinder may already be sufficient for some applications if highly electroconductive carbon allotropes like CNT's are used.

This percentage refers to the coating in the solid state, so, after evaporation of the liquid.

Depending on the desired properties of an item, for example a glove, that will be made from the coated yarn

& according to the invention, the percentage of the carbon allotrope shall preferably be at least two percent and more preferable at least three percent. The percentages mentioned in this section comprise weight percentages.

For certain applications the yarn will have to be provided with a coating according to the invention in which the carbon allotrope percentage constitutes as much as sixty percent of the coating. However, in several preferred embodiments of the coating the carbon allotrope percentage does not exceed forty five percent and preferably does not exceed thirty percent.

The coating comprising a mixture of carbon allotrope and polymer binder as a weight percentage of the fiber of a coated yarn may be as low as two percent if highly conductive carbon allotropes are used. For some applications it should be higher than three percent and preferably higher than four percent. In an embodiment in which the amount of carbon allotrope relative to the amount of binder is very law, for example essentially three percent and the amount of coating (i.e. the combination of the carbon allotrope and binder) relative to the fiber is four percent, the weight of the carbon sllotrope relative to the weight of the fiber is only three percent of four percent, so only approximately one thousandth. So, a very low amount of carbon allotrope surprisingly can already provide functionality for operating touchscreens and the like, On the other hand the weight of the coating comprising a mixture of carbon allotrope and polymer binder as a percentage of the weight of fiber may be as high as forty percent. Such a high percentage may be especially suitable for providing grip. For most applications a percentage below thirty percent is preferred and a percentage below twenty percent is often even more preferred. For items, such as for example gloves, the lower the concentration of carbon allotrope particles in the coating and the lower the weight percentage of the coating relative to the weight of the fiber the better fram a wearing comfort point of view. If gripping properties of a glove are not important a CNT concentration of three percent or sometimes even less in the coating and a coating weight percentage of four percent relative to the weight of the fiber is sufficient. As observed in embodiments of multi-filament yarns with such low CNT concentrations in the coating and a low coating to fiber weight ratio the percentage of individually coated freely movable filaments of a multi-filament yarn can be very high.

This provides a high degree of wearing comfort.

Optimal concentrations of CNT's in an electroconductive coating and optimal coating thicknesses (i.e. weight) depend on the desired/required application and the selection of the coating composition, including carbon allotrope and polymer hinder, and the type of yarn.

Some high performance polymeric yarns comprising for example HMWPE have a low strength in the transverse direction of the yarn, This low transverse strength of these yarns may lead to contamination of parts of the machines in which such yarns are used, particularly the machine parts that come into contact with yarn that moves (partially) in a transverse direction of the yarn.

This causes wear at the outer surface of the yarn and deposition of the wear products on the machine parts, for example knitting machine parts, resulting in the need to clean the machine frequently.

Application of the CNT coating according to the invention to yarns with a low transverse strength has the added benefit, in addition to providing electroconductivity, that it will increase the transverse strength at the surface of the yarn filaments, thus reducing wear of the yarn upon transverse movements while in contact with machine parts.

Experimental results Several gloves and T-shirts were knitted with a prototype of the high-performance multi-filament yarn with an electroconductive CNT containing coating according to the invention and tested for comfort, aesthetics, and functionality with the following, preliminary, findings:

- Easy to knit; - Very flexible and comfortable on the skin; - Smartphone touchscreens can be operated with it;

~ Increased level of grip, The advantages of electroconductive gloves made from coated yarn according to the present invention over electroconductive gloves according to the prior art can be summarized as follows:

1. No risk of damaging sensitive touchscreens {thanks to the absence of metallic/carbon yarn);

2. Higher comfort level / less hand-fatigue thanks to the absence of metallic yarns;

3. Increased longevity of a knitting machine thanks to the absence of metallic yarns;

4. Better dexterity of the glove since the total yarn combination used for the glove will be thinner thanks to the absence of colored Nylon {or Polyester) and/or metallic yarns; 5, Better cut resistance because individual filaments keep their freedom to move;

6. Better comfort/softness on the skin, hereinafter also referred to as high wearing comfort, which is due to the observable and measurable characteristic that a large percentage, meaning at least thirty percent and preferably at least fifty percent, of the individual filaments of the multi-filament yarn keep their freedom to move, in spite of the presence of the electroconductive coating;

7. Improved breathability since the yarn is coated and the open structure of the fabric remains intact in contrast to the prior art gloves in which the surface is closed by dip coating and the release of body heat and perspiration through the glove is essentially blacked completely; The experiments that yielded the above-mentioned results were performed with a multi-filament yarn comprising three hundred and ninety filaments. However, multi- filament yarn according to the invention may comprise any number of filaments. in the context of this invention the term ‘high performance Tiber’ or ‘high performance synthetic fiber’ shall be construed to comprise UHMWPE fibers and/or any other fiber a with exceptional physical and/or mechanical properties.

A high performance fiber is considered to actually deserve the designation high performance if it has a tenacity of at least S cN/Dtex {covering high tenacity Nylon and Polyester), preferably at least 10 cN/Dtex {covering HDPE) or at least 20cN/Dtex {covering meta and para aramids)and most preferably at least 30 cN/Dtex {covering LCP - Vectran ®, PBO Zylon®). The polymer binders that can be used in the electroconductive coating for the production of electroconductive multi-filament yarn according to the invention are not limited to examples of suitable polymers that are given in the above description and may comprise any polymer or combination of polymers that will result in a dry coating matrix with the required/desired properties.

In the above description gloves are mentioned as examples of items for which it will be beneficial to make them from an electroconductive multi-filament yarn according to the invention.

However, there is an almost unlimited number of other wearable items for which the multi-filament electroconductive yarn according to the invention may be the ideal yarn to provide the item with the most attractive functional features, The invention envisions that the items made from the electroconductive multi- filament according to the invention can comprise knitted items, woven items and tems made from unidirectional non-woven fabrics comprising electroconductive coating according to the invention, By analogy with the multi-filarment yarn according to the invention, the electroconductive coating according to the invention can also be applied to individual strands of a rope ta provide the rope with electroconductive properties.

Among several other possible benefits of an electroconductive, but still highly flexible, rope a rope with individually coated strands can for example be monitored automatically for broken strands by measuring the electroconductivity of the rope.

As strands of the rope break, the electroconductivity will decrease, thus acting as a warning sign for a loss of strength of the rope.

The term “essentially” herein, such as in “essentially in line”, will be understood by the person skilled In the art, The term “essentially” may also include embodiments with

“entirely”, “completely”, etc. Hence, in embodiments the adjective essentially may also be removed. Where applicable, the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 29% or higher, even mare especially 39.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the S term “comprises” means “consists of”. The term “comprising” may in an embodiment refer to “consisting of" but may in another embodiment also refer to "containing at least the defined species and optionally one or mare other species”. Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim, 10 The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or tem 2” and similar phrases may relate to one or more of iter 1 and item 2.

While only certain features of the invention have been described herein, many modifications and changes will occur to those skilled in the art, It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention, it should be noted that the above-mentioned embodiments ijlustrate rather than limit the Invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardwars comprising several distinct elements. The mere fact that certain measures ars regited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage, The invention further pertains to a method or process comprising one or more of the characterizing features described in the description.

The various aspects discussed in this application can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined.

Furthermore, some of the features can form the basis for one or more divisional applications.

Claims (16)

CONCLUSIONS A high-performance synthetic fiber multi-filament yarn, characterized in that the mut filament yarn comprises an electrically conductive cover layer, the cover layer consisting of at least half a weight percent of a carbon allotrope. A high performance synthetic fiber comprising multi-filament yarn, characterized in that at least twenty percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer comprising at least half weight percent of a carbon allotrope. exists. Multi-filament yarn according to claim 2, characterized in that at least thirty percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer being at least half a weight percent of carbon in the dry state. allotrope exists. Multifilament yarn according to claim 2 or 3, characterized in that at least forty percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer in the dry state for at least half a weight percent of a carbon allotrope exists, Multi-filament yarn according to one or more of claims 2-4, characterized in that at least fifty percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer being in the dry state for at least half a weight percent consists of a carbon allotrope, Multi-filament yarn according to one or more of claims 2-5, characterized in that at least sixty percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer for at least half weight percent consists of a carbon allotrope. Multi-filament yarn according to one or more of claims 2-6, characterized in that at least seventy percent of the number of filaments in the bundle is freely movable and comprises an electrically conductive cover layer, the cover layer for at least half weight percent consists of a carbon allotrope. Multi-filament yarn according to one or more of the preceding claims, characterized in that the cover layer in the dry state consists of at least two and at most sixty percent by weight of a carbon allotrope. Multi-filament yarn according to one or more of the preceding claims, characterized in that the cover layer in the dry state consists of at least three and at most five percent by weight of a carbon allotrope. Multi-filament yarn according to one or more of the preceding claims, characterized in that the carbon allotropic comprises carbon nanotubes. Multi-filament yarn according to one or more of the preceding claims, characterized in that the weight of the cover layer in the dry state is at least two and at most sixty percent of the weight of the filament on which the cover layer is applied, 12. An optionally protective garment, characterized in that the garment is made of a multi-filament yarn according to one or more of the preceding claims. A garment according to claim 12, comprising a glove, characterized in that the glove is electrically conductive to a sufficient degree to enable it to operate a touchscreen and that the glove has high wearing comfort. Glove according to claim 13, characterized in that the material of the glove comprises an open fabric structure only. Glove according to claim 13 or 14, characterized in that at least thirty percent of the number of filaments of the multi-filament yarn processed in the glove is freely movable. Glove according to claim 15, characterized in that at least fifty percent of the number of filaments of the multi-filament yarn incorporated in the glove is freely movable. 17. A glove according to claim 13, characterized in that the glove contains multi-filament yarn comprising an electrically conductive cover layer, which cover layer consists for a minimum of ten and a maximum of sixty percent by weight of a carbon allotrope,