METHOD FOR PRODUCING WOVEN FABRIC OF RECYCLED PET AND MODIFIED WITH CARBON NANTUBES AND SUCH A FABRIC

Abstract

 The subject-matter of the invention is a production method of a technical fabric from 100% recycled PET modified with carbon nanotubes, characterized in that it comprises steps where a warp of yarn obtained from 100% recycled PET filaments is warped, with a thickness ranging from 40 to 334, the warp is tied on the loom, a weft obtained from 100% recycled PET filament yarn with a thickness ranging from 58 to 668 dtex is threaded on a loom, after loom activation, the fabric pattern is established and weaving is carried out, an aqueous suspension of carbon nanotubes which contains carbon nanotubes in an amount of 0.05 to 2% by weight, based on the fabric weight, and surfactants, preferably anionic surfactants in an amount of 0.1 to 5% by weight, based on the fabric weight, is prepared, preferably in a homogenizer, then the process of carbon nanotube application is carried out with the use of retention devices in hermetic conditions, under appropriate pressure of 1 to 5 bar, at 30 to 70°C, wherein during this process, the fabric is rewound in the nanotube suspension at a speed of 150 to 500 m/min, and then the fabric is dried at 160°C to 220°C, with a fabric web feed rate from 10 m/min to 30 m/min, the fabric is rinsed with water and a part of the suspension is recovered for its reuse, the rinsed fabric is subjected to thermal stabilization in order to maintain its physicochemical parameters, and drying, the dried fabric is rolled on rollers, labeled and subjected to a final quality control; and then the fabric is cut into smaller batches, wherein the stabilization of the fabric is carried out by annealing the fabric strip at 180°C to 220°C, with a fabric web feed rate of 15 to 30 m/min.

Description

[0001] The subject-matter of the invention is a production method of a conductive 100% recycled PET fabric modified with carbon nanotubes and an electrically conductive 100% recycled PET fabric obtained by this method.

Background of the Invention

[0002] Many currently produced technical fabrics are enriched with admixtures meant to ensure their durability, resistance to using conditions, as well as new additional properties such as thermal or electrical conductivity, and biocidal properties, while maintaining an appropriate quality-price ratio. The admixtures introduced into the material structure are usually in the form of synthetic threads woven together with natural fibers or cheaper synthetic fibers woven with other, more expensive threads with higher technological parameters. In case of fabric surface modification, the admixing can also be effected as a downstream process. A common method of applying various apertures to textile surfaces is the padding method (Makowski T, Grala M, Fortuniak W, Kowalczyk D, Brzezinski S (2016) Electrical properties of hydrophobic polyester and woven fabrics with conducting 3D network of multiwall carbon nanotubes. Mater Design 90:1026-1033. http://dx.doi.org/10.1016/j.matdes.2015.11.049; Makowski T, Kowalczyk D, Fortuniak W, Brzezinski S, Kregiel D (2015) Electrochemical deposition of silver nanoparticle and polymerization of pyrrole on fabrics via conducting multiwall carbon nanotubes. Cellulose 22:3063-3075. http://dx.doi.org/10.1007/s10570-015-0725-9). This technique makes it possible to obtain coatings in a repeatable and uniform manner. Other methods of applying apertures used in industry are spraying, printing or injection with materials which are meant to impart desired features to the surface. However, the padding method is the most common wet method used in the textile industry to apply apertures to the surface of fabrics imparting various desirable properties such as bioactivity, hydrophobicity or hydrophilicity. (Makowski T, Kowalczyk D, Fortuniak W, Brzezinski S, Kregiel D (2015) Electrochemical deposition of silver nanoparticle and polymerization of pyrrole on fabrics via conducting multiwall carbon nanotubes. Cellulose 22:3063-3075. http://dx.doi.org/10.1007/s10570-015-0725-9; Makowski T, Kowalczyk D, Fortuniak W, Jeziorska D, Brzezinski S, Tracz A (2014) Superhydrophobic properties of cotton woven fabrics with conducting 3D networks of multiwall carbon nanotubes, MWCNTs. Cellulose 21:4659-4670. http://dx.doi.org/10.1007/s10570-014-0422-0). A frequently used process is the application of suspensions based on nanoparticles, such as silver nanoparticles, the bactericidal properties of which are known and persist for a long time. (Ghosh S, Yadav S, Reynolds N (2010) Antibacterial properties of cotton fabric treated with silver nanoparticles. J Text I 101:917-924. http://dx.doi.org/Pii 926971188 10.1080/00405000903031053). Modifications to yarns intended to make them conductive, e.g. coating with polyaniline (Kim B, Koncar V, Dufour C (2006) Polyaniline-coated PET conductive yarns: Study of electrical, mechanical, and electro-mechanical properties. J Appl Polym Sci 101:1252-1256. http://dx.doi.org/10.1002/app.22799) or metals (Han EG, Kim EA, Oh KW (2001) Electromagnetic interference shielding effectiveness of electroless Cu-plated PET fabrics. Synthetic Metals 123:469-476. http://dx.doi.org/https://doi.org/10.1016/S0379-6779(01)00332-0) are known in the literature.

[0003] There is a global constant search for conductive materials based on fabrics (textile materials) that do not contain metallic particles, which limit the possibilities of replacing these materials in various areas of life, where their presence has a negative impact on the environment and waste disposal. Another approach is to use carbon yarns that can be employed to produce materials with electromagnetic shielding ability (Jagatheesan K, Ramasamy A, Das A, Basu A (2017) Investigation on Shielding and Mechanical Behavior of Carbon/Stainless Steel Hybrid Yarn Woven Fabrics and Their Composites. Journal of Electronic Materials 46:5073-5088. http://dx.doi.org/10.1007/s11664-017-5498-5). However, modified yarn application makes traditional weaving methods difficult and often requires modification of production lines. Another negative factor, which occurs during weaving, is dusting, which in case of modified yarns, can pose a threat to weaving machine operators. There is a significant need in the field for fabrics modified with nanomodifiers for a variety of applications.

[0004] Thus, Chinese patent application CN107419537 relates to functional fabric field, discloses a production method of a polyester fabric using titania (TiO₂) nanotubes to obtain electric conductivity. The preparation method comprises the following steps: 1) a warp knit fabric with a twill weave is prepared from a selected polyester fiber yarn with an appropriate linear density on a latch needle knitting machine; 2), the polyester fabric is first covered with a polyurethane coating and then with a rather thin titanium layer; 3) an electrolyte is prepared; 4), the polyester fabric is introduced into the electrolyte as an anode and a graphite as a cathode, the power is turned on for 4-6 h, and the voltage is set to 45-55 V. The polyester fabric is used as a base layer, which is covered with a titanium layer, and as a result of the electrolytic reaction, a layer of TiO₂ nanotubes is formed on the fabric, which causes a good electrical conductivity of the polyester fabric. Another Chinese patent application, CN106939465 A, discloses a textile fabric for infants and its production method. The textile fabric for infants consists of the following parts by weight: 50 to 80 parts of plant fibers, 50 to 80 parts of animal fibers, 1 to 3 parts of carbon nanotubes and 0.1 to 1 part of an antibacterial agent. The textile fabric for infants prepared by the method disclosed in that invention is prepared by mixing natural plant fibers and animal fibers, and is immersed in a suspension of carbon nanotubes and antibacterial agent, has a soft, breathable and smooth surface, strong antibacterial properties, not only can be resistant to common daily encountered bacteria, but also can effectively kill pathogenic Gram-negative bacteria such as Escherichia coli 0157, Gram-positive Staphylococcus aureus, Trichophyton mentagrophytes and the like.

[0005] Another Chinese patent application CN106758159 A discloses a preparation method of carbon nanotube conductive composite polyester fabric which comprises the following steps: (1) dissolving phenol in ethanol; (2) dispersing carbon nanotubes in ethanol/phenol mixed solution and performing ultrasonic treatment to obtain a black dispersion solution; (3) putting the polyester fabric in a dyeing bath, performing oscillation heating to raise the temperature to 40-60°C, and maintaining the temperature for 5-30 minutes; (4) finally, carrying out multiple washes with ethanol, by taking out the polyester fabric and drying it at 80°C, respectively, so as to obtain the carbon nanotube conductive polyester fabric. US patent application US2014349536 AA discloses a heat storage textile. In one embodiment, a textile is prepared by applying a coating containing carbon nanotubes to a side of a textile. The coating solution comprises, by weight, at least 0.1% carbon nanotubes, 0.01% dispersant, 9.89% resin binder and 10% solvent. The carbon nanotube surface may be modified to improve the adhesive properties. The carbon nanotubes can be single wall nanotubes, multi-wall nanotubes such as double wall nanotubes (DWNT), or thin multi-wall nanotubes. The coating may cure while transferring the coated heat storage textile with a constant velocity at a room temperature or in a heated chamber.

[0006] In turn, another US patent application US2013302605 AA discloses method of making a carbon nanotube fiber by providing a polyethylene terephthalate (PET) substrate; contacting the polyethylene terephthalate substrate with a polyvinyl alcohol polymer solution to form a polyvinyl alcohol polymer layer on the polyethylene terephthalate substrate; contacting the polyvinyl alcohol polymer layer with a carbon nanotube solution, wherein the carbon nanotube solution comprises one or more carbon nanotubes; forming a nanotube layer on the polyvinyl alcohol polymer layer; delaminating the polyvinyl alcohol polymer layer from the polyethylene terephthalate substrate to release a composite fiber layer; stretching the composite fiber layer; and drying the composite fiber layer.

[0007] The next US patent application US2013137324 AA discloses carbon nanotube coated fabric compositions for the purpose of tuning the optical properties of fabric, in particular the optical transmittance, absorption, and reflectance in the visible, NIR and mid-IR ranges. The carbon nanotube coated fabrics of that invention exhibit relatively uniform absorptivity and reflectivity of light across visible and IR spectral ranges and are ideal for use in stealth operations for counteracting night vision detection devices. The carbon nanotube coatings are thin, flexible coatings exhibiting high thermal and chemical stability, strong adhesion, low weight, and high tensile strength. In one embodiment, the composition includes an insulator layer for thermally insulating the CNT coating and establishing thermal equilibrium with the surrounding environment through the absorption of the thermal IR emitted from hot objects. Processes for preparing the carbon nanotube coated fabrics are also described therein.

[0008] Another US patent application US2011171413 AA discloses carbon nanotube embedded textiles and methods for production of carbon nanotube embedded textiles. Initially, carbon nanotubes, a cationic surfactant, and distilled water are mixed to form a stabilized carbon nanotube mixture. A textile is then soaked in a solution of the stabilized carbon nanotube mixture and an electrolyte to form a carbon nanotube adsorbed textile. The carbon nanotube adsorbed textile is then dried. Next, the dried carbon nanotube textile is treated in a solution of a crosslinking agent and a catalyst to form a carbon nanotube embedded textile. The carbon nanotube embedded textile is then dried.

[0009] In turn, Chinese patent application CN109457466 A discloses a functional functionalized carbon nanotube and its application in antistatic antibiotic fabric finishing liquor. The functional carbon nanotube is prepared by pre-treating conventional carbon nanotube to react with diluted ammonia water and aloe emodin. Compared with prior art, the functionalized carbon nanotube is applied on the antistatic antibiotic fabric finishing liquor, enabling the finishing fluid to protect the textile from bacteria attack, so that the fabric has characteristics such as sterility, lack of odor, static resistance and good comfort in addition to the cold protection and heat retention function.

[0010] As showed above, numerous solutions are known that use carbon nanotubes and other types of nanotubes to modify fabrics, composites and other polymeric substrates. Due to their useful properties, carbon nanotubes can provide fabrics with electrical conductivity, bactericidal properties, constitute a specific heat barrier, provide special optical properties, as well as odorlessness, static resistance and comfort of use. Carbon nanotubes are applied on fabrics in various ways, from aqueous and non-aqueous solutions or suspensions, with various additives such as surfactants and bactericides. Fabrics can be immersed in a solution/suspension of carbon nanotubes or sprayed or coated with such solutions or suspensions. The fabrics used are textile materials made of natural and artificial fibers, including 100% recycled PET.

[0011] However, none of the prior art documents discloses fabric modification of 100% recycled PET yarn which is used as both weft and warp to produce conductive technical fabrics with a wide spectrum of applications as eco-materials and composite and nanostructured biomimetic, bionic and biodegradable, multifunctional composite nanomaterials with a warp or reinforcement made of nanostructured carbon materials and other nanofibers, nanowires and nanotubes, as well as in personal electronics and as intelligent textiles. The aim of the present invention was to develop a one-step method for the production of a conductive composite material based on a polyester fabric made of 100% recycled PET using carbon nanotubes.

[0012] The electrically conductive composite obtained in a one-step production process, based on multi-wall inert (chemically unmodified) carbon nanotubes (MWCNT), the support of which is a polyester fabric, is a desirable material that is easy to implement for production while reducing dusting. Another important aspect when using multi-wall carbon nanotubes is their impact on human health, so one should use nanotubes that have no or very little negative impact (Ma-Hock et al., 2009; Murphy, Poland, Duffm, & Donaldson, 2013) on humans. Carbon nanotubes NC7000 from Nanocyl (Belgium) used by the Applicant meet the safety requirements, while at the same time there is great interest in the world markets in intelligent materials based on carbon nanoparticles on textile materials.

[0013] Out of concern for the natural environment, author of the present invention has been conducting for many years research on the possibility of using yarn obtained from 100% recycled PET and, unexpectedly, found that due to the use of yarn obtained from 100% recycled PET filaments, it is not only possible to use the same yarn as weft and warp, but also a technical fabric is obtained with high performance parameters and strength, which are at least equal to that of fabrics obtained from virgin polyester, as well as with improved absorption of various types of additives or modifiers, such as dyes, achieving a homogeneous distribution of additive/modifier in the final fabric.

[0014] It was also found that the use of yarn obtained from 100% recycled PET filaments results in a smoother, high absorbent fabric. As a result, the obtained fabric is free from the drawback of fabrics obtained from shorter 100% recycled PET fibers with cotton twist. Namely, cotton twist fibers were not suitable for use as a warp (a more durable element of the fabric), but only as wefts. Accordingly, it was not possible to obtain a technical fabric exclusively from 100% recycled PET since it was necessary to use fibers other than those of 100% recycled PET with better strength as the warp. For this purpose, for example, virgin polyester fibers with better mechanical/strength properties were used. In addition, fabrics containing 100% recycled PET cotton twist fibers dyed non-uniformly, resulting in fabrics with non-uniform dyeing, which limited their utility as decorative utility fabrics of suitable aesthetic appeal. However, due to the use of yarn obtained from 100% recycled PET filaments, durable technical fabrics were obtained with excellent absorbent properties, uniformly dyed, smoother, and most importantly, environmentally friendly. The use of 100% recycled PET is crucial in relation to the protection of the natural environment, as it ensures the effective and efficient use of used components made of PET, such as, for example, mass-produced bottles for the storage of water and other beverages.

[0015] Moreover, the use of yarn obtained from twisting shorter fibers obtained from 100% recycled PET with cotton twist was associated with increased dusting during production - a nuisance in the production halls. In addition, the resulting fabric was more prone to pilling and quickly lost its aesthetic appeal.

[0016] And finally, the use of yarn obtained from 100% recycled PET filaments made it possible to obtain durable technical fabrics with excellent absorbent properties for carbon nanotubes, resulting in a conductive fabric with a uniform structure of embedded nanotubes.

Summary of the invention

[0017] Thus, the subject-matter of the present invention is a production method of conductive 100% recycled PET fabrics modified with carbon nanotubes.

[0018] The production method of technical fabric from 100% recycled PET modified with carbon nanotubes is characterized in that it comprises the steps where:

• a warp of yarn obtained from 100% recycled PET filaments is warped with a thickness ranging from 40 to 334, preferably 84 to 334 dtex and more preferably 84 to 167 dtex;
• the warp is tied on a loom, preferably using an automatic warp-tying machine;
• a weft of yarn obtained from 100% recycled PET filaments, with a thickness ranging from 58 to 668 dtex, preferably 78 to 501 dtex, and preferably 167 to 334 dtex is threaded on the loom;
• after loom activation, a fabric pattern is established and weaving is carried out;
• an aqueous suspension of carbon nanotubes is prepared, which contains carbon nanotubes in an amount from 0.05 to 2% by weight, based on the fabric weight, preferably 0.1% to 1% by weight, and most preferably 0.125% to 0.5% by weight, and surfactants, preferably anionic surfactants, in an amount from 0.1 to 5% by weight, based on the fabric weight, preferably 0.25% to 3% by weight, and most preferably 0.5% to 1.5% by weight, preferably in a homogenizer;
• the process of carbon nanotube application is carried out using retention devices in hermetic conditions, under suitable pressure from 1 to 5 bar, preferably 2 to 4 bar, most preferably 2 to 3 bar, at 30 to 70°C, preferably 40 to 60°C, most preferably 45 to 55°C, wherein during this process the fabric is rewound in the nanotube suspension at a speed of 150 to 500 m/min, preferably 250 to 350 m/min, most preferably about 300 m/min;
• the fabric is dried at 160°C to 220°C, with a fabric web feed rate of 10 m/min to 30 m/min;
• the fabric is rinsed at least once with water and a part of the suspension is recovered for its reuse;
• the rinsed fabric is subjected to thermal stabilization in order to maintain its physicochemical parameters, and drying;
• the dried fabric is rolled on rollers, labeled and subjected to a final quality control; then the fabric is cut into smaller batches;

wherein the stabilization of the fabric is carried out by annealing the fabric strip at 180°C to 220°C, with a fabric web feed rate of 15 to 30 m/min.

[0019] Preferably, weaving is performed on a loom selected from an air-jet loom, a rapier loom, a water loom, a gripper loom or a hydraulic loom.

[0020] Preferably, the aqueous suspension of carbon nanotubes is prepared in an ultrasonic homogenizer in a continuous process.

[0021] Preferably, after the stabilization step, the fabric is subjected to coating with a coating dispersion in an amount of 10 to 80 g/m², and the coated fabric is then annealed at 160°C to 200°C with a fabric feed of 10 to 30 m/min.

[0022] Preferably, the fabric is coated with dispersions selected from such as an acrylic dispersion, a styrene-acrylic dispersion, a polyurethane dispersion or an aqueous styrene-butadiene latex dispersion.

[0023] Preferably, the coating is carried out on one side, preferably with a spreading bar, or on both sides, preferably by dip padding.

[0024] Preferably, the fabric is subjected to additional refinement processes through the application of enriching additives, such as bioactive, antibacterial, antiviral substances, nanomodifiers, flame-retardants and/or anti-moisture substances, as well as water- and oil-repellent substances.

[0025] Preferably, the fabric is subjected to additional refinement processes during its coating.

[0026] The subject-matter of the invention is also a conductive fabric, characterized in that it is made of yarn obtained from 100% recycled PET filaments, wherein the yarn used for the warp has a thickness of 40 to 334, preferably 84 to 334 dtex and more preferably 84 to 167 dtex and the yarn used for the weft has a thickness of 58 to 668 dtex, preferably 78 to 501 dtex, and more preferably 167 to 334 dtex, and is modified with carbon nanotubes, 0.05 to 2% by weight, based on the fabric weight, preferably 0.1% to 1% by weight, and most preferably 0.125% to 0.5% by weight.

[0027] Preferably, the fabric is coated at least on one side with a dispersion selected from such as an acrylic dispersion, a styrene-acrylic dispersion, a polyurethane dispersion or an aqueous styrene-butadiene latex dispersion, wherein the coating dispersion is used in an amount of 10 to 80 g/m².

[0028] Preferably, the fabric is additionally enriched with enriching additives, such as bioactive, antibacterial, antiviral substances, nanomodifiers, flame retardants and/or anti-moisture substances, as well as water- and oil-repellent substances.

[0029] Dtex means the weight in grams of 10000 m of yarn, therefore 334 dtex means that 10000 m of yarn with this thickness has a weight of 334 g.

[0030] The method according to the present invention allows achieving the effect of conductive PET-type polyester fabrics by introducing carbon nanotubes in a continuous hermetic process using an aqueous suspension.

[0031] It is possible to achieve this effect due to physicochemical processes occurring on the polyester fiber surface, i.e. strong adhesion to the hydrophobic fiber surface while the carbon nanotubes simultaneously wrap around the fibers. The effect is so beneficial that the nanotubes position themselves on the fiber surface, rendering the fabric both hydrophobic and electrically conductive by creating a conductive 3D network. For the production of conductive fabrics with predetermined parameters, a mixture containing carbon nanotubes, water and a surfactant which is also a detergent prepared in vats is used. The essence of obtaining high-quality conductive fabrics is the appropriate preparation of an aqueous suspension with carbon nanotubes, preferably using an ultrasonic homogenizer with the possibility of continuous operation.

[0032] The method of the present invention enables using less water, energy, and carbon nanoparticle raw material during production and to impart conductive properties to the fabric, the same as is the case with traditional coating techniques.

[0033] The fabrics obtained by this method have electricity- and heat-conducting properties and show very good strength parameters.

[0034] The fabrics according to the invention are obtained in a single-step technological process. Their production method allows reducing the negative impact on the natural environment, because 100% of the raw material used in the fabric comes from PET recyclate, which enables reusage of the raw material that has already been used. Water consumption per one cycle was reduced 6 times, which firstly has an ecological aspect, and additionally enables a fully automatically controlled process of hermetic pressure application with a reduced temperature of the process.

[0035] In addition, the method according to the present invention enables carrying out the process of nanotube application from an aqueous suspension in hermetic conditions, which prevents contamination of the working environment with nanotubes that may show a harmful effect on human health (Anna Maria Świdwińska-Gajewska et al., Medycyna Pracy 2017; 68(2): 259-276).

[0036] A fabric made of 100% recycled PET yarn, straight from the loom, after inspection for significant defects, is placed in a retention device. The nanotube solution with the detergent surfactant is then poured into the device and the retention process performed. In the retention process, the fabric is rewound in the suspension at a speed of 150 to 500 m/min in order to uniformly saturate the fabric in its entire volume with nanotubes and to uptake the maximum number of nanotubes from the suspension. After the deposition of the nanotubes on the fabric is completed, the soaked fabric is removed and dried/subjected to stabilization. The fabric is then rinsed and optionally the excess nanotubes are washed out. No additional washing agents are added as the detergent is already added in the retention process. Fabrics with applied nanotubes are no longer dyed because the fabric is black or almost black after nanotube application. Optionally, it can be coated with a colored coating layer to impart a different color. The fabric is then again dried/subjected to stabilization. In order to obtain specified electrical parameters, dried fabric is subjected to a control electrical resistance measurement. The process of nanotube application can be repeated until the required physicochemical parameters are achieved.

[0037] In order to impart additional properties to the fabric the resulting fabrics can be subjected to other refining processes, such as coating with substances of a bactericidal, fungicidal, virucidal, hydro and oleophobic nature. The fabric can also be coated on one or both sides with different dispersions selected from an acrylic dispersion, an styrene-acrylic dispersion, a polyurethane dispersion or an aqueous styrene-butadiene latex dispersion. Due to the special electrical properties of the fabric according to the invention, it can be used as an electrode and other elements can be applied to it by means of electrolysis processes.

[0038] Mainly NC700 nanotubes are used in the embodiments due to their high quality.

[0039] The fabric stabilization process was each time carried out at 180 to 220°C with a fabric feed of 15 to 30 m/min.

EXAMPLES

[0040] The method of technical fabric production entirely from 100% recycled PET according to the present invention is shown in the drawing, in which Fig. 1 depicts a block diagram of the production process.

Example 1

[0041] A 100% recycled PET technical fabric according to the present invention was obtained as follows. The warp was warped from a yarn obtained from 100% recycled PET filaments with a thickness of 84 dtex, which was then tied on the loom using an automatic warp-tying machine. A weft of 100% recycled PET filaments with a thickness of 668 dtex is threaded on the loom. After loom activation, the weaving was carried out, with the weft shot between the individual edges of the fabric being effected by means of compressed air without mechanical participation of the rapier. The fabric produced was wound on a roller and quality control was performed.

[0042] In the meantime, an aqueous suspension of carbon nanotubes was prepared containing an anionic surfactant also acting as a detergent, in this case sodium lauryl sulfate (SDS), and carbon nanotubes NC7000 in a weight ratio of 3:1. The suspension used contained, by weight, 0.5% nanotubes, based on the fabric weight. The mixture was placed in a homogenizer and the prepared suspension was dispersed. Then, the process of carbon nanotube application was carried out with the use of computer-controlled retention devices in hermetic conditions, under appropriate pressure (2-3 bar) and at 50°C for 30 min. In this process, the fabric was rewound in the suspension at a speed of 300 m/min in order to uniformly saturate the fabric throughout its entire volume with nanotubes and to uptake the maximum amount of substance from the suspension.

[0043] After the adhesion process was completed, the obtained fabric was dried at 130°C and then rinsed with water to remove excess carbon nanotubes and surfactant.

[0044] The dried fabric was wound on rollers, labeled, submitted to final quality control, and then cut into smaller batches.

Example 2

[0045] A 100% recycled PET technical fabric according to the present invention was obtained in the same manner as in Example 1, except that for the warping a yarn obtained from twisting filaments of 100% recycled PET with a thickness of 167 dtex was used. The warp was tied on a loom using an automatic warp-tying machine. A weft of 100% recycled PET filament yarn with a thickness of 668 dtex was threaded on the loom. After loom activation, weaving was carried out, with the weft shot between the individual edges of the fabric being effected by means of compressed air without mechanical participation of the rapier. The fabric produced was wound on a roller and quality control was performed.

[0046] In the meantime, an aqueous suspension of carbon nanotubes was prepared containing an anionic surfactant also acting as a detergent, in this case sodium lauryl sulfate (SDS), and carbon nanotubes NC7000 in a weight ratio of 3:1. The suspension used contained, by weight, 0.125% nanotubes, based on the fabric weight. The mixture was placed in a homogenizer and the prepared suspension was dispersed. Then, the process of carbon nanotube application was carried out with the use of computer-controlled retention devices in hermetic conditions, under appropriate pressure (4 bar) and at 55°C for 25 min. In this process, the fabric was rewound in the suspension at a speed of 350 m/min. After the application process was completed, the obtained fabric was dried and then rinsed with water and some of the carbon nanotubes were recovered for their reuse. The coated fabric was inserted into a stabilizer and annealed at 165°C with a fabric feed of 20 m/min. The dried fabric was subjected to electrical conductivity quality tests, then wound on rollers, labeled, subjected to final quality control, and then cut into smaller batches.

Example 3

[0047] A 100% recycled PET technical fabric according to the present invention was obtained in the same manner as in Example 1, except that after the thermal stabilization, fabric coating was performed by spreading layer of an aqueous styrene-butadiene latex dispersion by the spreading bar of the coater. The amount of suspension dispensed per 1 m² of fabric was 80 g/m², giving 40 g/m² of coating after drying.

Example 4

[0048] A 100% recycled PET technical fabric according to the present invention was obtained in the same manner as in Example 1, except that for the warping a yarn obtained from 100% recycled PET filaments with a thickness of 40 dtex was used. The warp was tied on a loom using an automatic warp-tying machine. A weft of 100% recycled PET filament yarn with a thickness of 56 dtex was threaded on the loom. After loom activation, weaving was carried out, with the weft shot between the individual edges of the fabric being effected by means of compressed air without mechanical participation of the rapier. The fabric produced was wound on a roller and quality control was performed.

[0049] In the meantime, an aqueous suspension of carbon nanotubes was prepared containing an anionic surfactant also acting as a detergent, in this case sodium lauryl sulfate (SDS), and carbon nanotubes NC7000 in a weight ratio of 3:1. The suspension used contained, by weight, 0.125% nanotubes, based on the fabric weight. The mixture was placed in a homogenizer and the prepared suspension was dispersed. Then, the process of carbon nanotube application was carried out with the use of computer-controlled retention devices in hermetic conditions, under appropriate pressure (2 bar) and at 45°C for 35 min. In this process, the fabric was rewound in the suspension at a speed of 250 m/min. After the application process was completed, the obtained fabric was dried and then rinsed with water and some of the carbon nanotubes were recovered for their reuse. The coated fabric was inserted into a stabilizer and annealed at 160°C with a fabric feed of 25 m/min. The dried fabric was subjected to electrical conductivity quality tests, then wound on rollers, labeled, subjected to final quality control, and then cut into smaller batches.

Example 5

[0050] A 100% recycled PET technical fabric according to the present invention was obtained in the same manner as in Example 1, except that the warp and weft yarns were made of filaments obtained from 100% recycled PET with a thickness of 167 dtex. In the meantime, an aqueous suspension of multi-wall carbon nanotubes was prepared as in Example 1. Then, the process of carbon nanotube application was carried out with the use of computer-controlled retention devices under pressure (2-3 bar) and at 50°C for 30 min. In this process, the fabric was rewound in the suspension at a speed of 300 m/min. In order to obtain a conductive fabric with different conductivity from 100% recycled PET, a suspension of carbon nanotubes with a different weight concentration of NC7000 Cw = 0.5 was used: 0.25; 0.125%.

[0051] The effect of the number of cycles of dispersed aqueous carbon nanotube suspension applications on the conductivity was also investigated, and so - one retention (dip1), and two retentions (dip2).

[0052] The textile materials in the form of wovens, after applying the conductive layer of carbon nanotubes from the suspension dispensed with the addition of a surfactant, were dried at 50°C in order to completely bind the nanotubes to the fiber surface. Electrical measurements were carried out at 20°C.

[0053] Imaging studies of the fabric surface were carried out using a scanning electron microscope (SEM) by JEOL 5500 (Japan). Before imaging, the samples were sputtered with a layer of gold with a thickness of 20 nm. The electron beam acceleration voltage was 15 kV.

[0054] The resistance tests of the samples were carried out with current/voltage source Keithley model 2400c (USA) using 2-electrode method. The resistance measurement was carried out in the voltage range 0-12V in order to determine the current-voltage characteristics, and then the resistance of the sample per surface square (sq) was determined. The distance between the electrodes was 1 cm. The voltage range chosen has been selected with regard to the suitability of the material in the automotive industry.

[0055] The results obtained for each fabric test are shown in the figures (Figs. 2-7).

[0056] The results of the surface morphology and conductivity tests for 100% recycled PET fabric not modified with carbon nanotubes are shown in Fig. 2.

[0057] Fig. 3 shows the surface morphology and conductivity test results for a 100% recycled PET fabric that was subjected once to a procedure of multi-wall carbon nanotube application (dip1) using a 0.5% concentration of NC7000 carbon nanotube suspension.

[0058] Fig. 3 shows an image from a stereoscopic light microscope equipped with a digital camera as well as a SEM micrograph of the conductive coating of multi-wall carbon nanotubes.

[0059] Fig. 4 shows the surface morphology and conductivity test results for a 100% recycled PET fabric that was subjected twice to a procedure of multi-wall carbon nanotube application (dip2) using a 0.5% concentration of NC7000 carbon nanotube suspension.

[0060] Fig. 4 shows an image from a stereoscopic light microscope equipped with a digital camera as well as a SEM micrograph of the conductive coating of multi-wall carbon nanotubes.

Example 6

[0061] A 100% recycled PET technical fabric according to the present invention was obtained in the same manner as in Example 1, except that the warp and weft yarns were made of filaments obtained from 100% recycled PET with a thickness of 167 dtex. In the meantime, an aqueous suspension of multi-wall carbon nanotubes was prepared as in Example 1. Then, the process of carbon nanotube application was carried out with the use of computer-controlled retention devices under pressure (2-3 bar) and at 50°C for 30 min. In this process, the fabric was rewound in the suspension at a speed of 300 m/min. In order to obtain a conductive fabric with different conductivity from 100% recycled PET, a suspension of NC7000 carbon nanotubes with different weight concentrations was used.

[0062] In the carbon nanotube application procedure a 0.5% suspension of NC7000 carbon nanotubes (cO.S; cO.S_1) was used. A 10 cm x 10 cm 100% recycled PET fabric was tested. The obtained results are presented in digital microscope images and SEM micrographs showing the conductive coatings of multi-wall carbon nanotubes, the images of which are shown in Fig. 5.

[0063] The same procedures for the application of carbon nanotubes to fabric made of 100% recycled PET were carried out, using a suspension of NC7000 carbon nanotubes with concentrations of 0.25% (cO.25) and 0.125% (cO.125). The test results in the form of digital microscope images and SEM micrographs of the conductive coating of multi-wall carbon nanotubes are shown in Fig. 6 (0.25% concentration) and Fig. 7 (0.125% concentration), respectively.

[0064] The results of the electrical conductivity measurements are shown in Fig. 8.

Final conclusion:

[0065] The obtained results show that the conductivity values can be controlled by changing the concentration of carbon nanotube suspensions while maintaining the same process parameters such as temperature, time and pressure. Images from the optical microscope and from the scanning electron microscope show good adhesion to the polyester fabric fibers. The research results also show that the nanotube suspension used is very well dispersed and that the conductive networks of nanotubes in the form of monolayers are formed on the surface, which is especially important in industrial applications where the cost of the substrates used is important.

[0066] All tests were performed with fabrics rinsed several times with distilled water and then dried in a laboratory dryer at 50°C.

Claims

1. A production method of a technical fabric from 100% recycled PET modified with carbon nanotubes, characterized in that it contains steps in which:

- a warp of yarn obtained from 100% recycled PET filaments is warped with a thickness ranging from 40 to 334 dtex, preferably 84 to 334 dtex and more preferably 84 to 167 dtex;

- the warp is tied on the loom, preferably using an automatic warp-tying machine;

- a weft of yarn obtained from 100% recycled PET filaments, with a thickness ranging from 58 to 668 dtex, preferably 78 to 501 dtex, and preferably 167 to 334 dtex is threaded on a loom;

- after loom activation, a fabric pattern is established and weaving is carried out;

- an aqueous suspension of carbon nanotubes is prepared, which contains carbon nanotubes in an amount from 0.05 to 2% by weight, based on the fabric weight, preferably 0.1% to 1% by weight, and most preferably 0.125% to 0.5% by weight, and surfactants, preferably anionic surfactants in an amount from 0.1 to 5% by weight, based on the fabric weight, preferably 0.25% to 3% by weight, and most preferably 0.5% to 1.5% by weight, preferably in a homogenizer;

- a process of carbon nanotube application is carried out with the use of retention devices in hermetic conditions, under appropriate pressure from 1 to 5 bar, preferably 2 to 4 bar, most preferably 2 to 3 bar, at 30 to 70°C, preferably 40 up to 60°C, most preferably 45 to 55°C, wherein during this process the fabric in the nanotube suspension is rewound at a speed of 150 to 500 m/min, preferably 250 to 350 m/min, most preferably about 300 m/min;

- the fabric is dried at 160°C to 220°C, with a fabric web feed rate of 10 m/min to 30 m/min;

- the fabric is rinsed at least once with water and a part of the suspension is recovered for its reuse;

- the rinsed fabric is subjected to a thermal stabilization in order to maintain its physicochemical parameters, and drying;

- the dried fabric is rolled on rollers, labeled and subjected to a final quality control; then the fabric is cut into smaller batches;

wherein the fabric stabilization is carried out by annealing the fabric strip at 180°C to 220°C, with a fabric web feed rate of 15 to 30 m/min.

2. The method according to claim 1, characterized in that the weaving is carried out on a loom selected from such as an air-jet loom, a rapier loom, a water loom, a gripper loom or a hydraulic loom.

3. The method according to claim 1 or claim 2, characterized in that the aqueous suspension of carbon nanotubes is prepared in an ultrasonic homogenizer in a continuous process.

4. The method according to any of the claims 1 to 3, characterized in that, after the stabilization step, the fabric is subjected to coating with a coating dispersion in an amount of 10 to 80 g/m², and the coated fabric is then heated at 160°C to 200°C with a fabric feed of 10 to 30 m/min.

5. The method according to claim 4, characterized in that, the fabric is coated with dispersions selected from such as an acrylic dispersion, a styrene-acrylic dispersion, a polyurethane dispersion or an aqueous styrene-butadiene latex dispersion.

6. The method according to claim 4 or claim 5, characterized in that the coating is carried out on one side, preferably with a spreading bar, or on both sides, preferably by dip padding.

7. The method according to any of the claims 1 to 6, characterized in that the fabric is subjected to additional refinement processes by applying enriching additives, such as bioactive, antibacterial, antiviral substances, nanomodifiers, flame-retardants and/or anti-moisture substances, as well as water- and oil-repellent substances.

8. The method according to claim 7, characterized in that the fabric is subjected to additional refinement processes during its coating.

9. A conductive fabric characterized in that it is made of a yarn obtained from 100% recycled PET filaments, wherein the yarn used for the warp has a thickness of 40 to 334, preferably 84 to 334 dtex and more preferably 84 to 167 dtex, and the yarn used for the weft has a thickness of 58 to 668 dtex, preferably 78 to 501 dtex, and preferably 167 to 334 dtex, and is modified with carbon nanotubes in an amount of 0.05 to 2% by weight, based on the fabric weight, preferably 0.1% to 1% by weight, and most preferably 0.125% to 0.5% by weight.

10. The conductive fabric according to claim 9, characterized in that it is coated on at least one side with a dispersion selected from such as an acrylic dispersion, a styrene-acrylic dispersion, a polyurethane dispersion or an aqueous styrene-butadiene latex dispersion, wherein the coating dispersion is used in an amount of 10 to 80 g/m².

11. The conductive fabric according to claim 9 or claim 10, characterized in that the fabric is additionally enriched with enriching additives, such as bioactive, antibacterial, antiviral substances, nanomodifiers, flame-retardants and/or anti-moisture substances, as well as water- and oil-repellent substances.

Drawing