Technical Field of the Invention The present invention relates to polyamide/polyester antimicrobial microfiber compositions suitable for use in fabrics such as a cleaning cloth, mop cloth, towel, mask, clothing, etc. in the field of hygiene and disinfection and to a method for rendering said microfiber compositions antimicrobial with hypochlorous acid solutions. State of the Art

Fabrics such as cloths, mops, and towels made of microfiber yarns are often used for surface cleaning and disinfection. These fabrics particularly clean the surface by taking all the dirt on the surfaces upon themselves. However, the microorganisms they take on their surfaces accumulate and multiply, thus cause a bad odor. Also, such contaminated fabrics, increase the risk of cross contamination by contaminating this surface when applied to another surface. Several antimicrobial microfiber products are tried to be developed for all these aspects.

Microfiber cloths with antibacterial activity are commercially available in some countries. The antibacterial activity of these cloths can be ensured by adding silver ions to the polyester part of the fibers from the melt during fiber spinning, and similarly by using nano-silver technology. One of the applications found in the literature related to the subject is the utility model numbered CN208301607U. In the relevant utility model, it is aimed to obtain a self-cleaning cloth with antibacterial properties in order to kill bacteria through the silver ions containing therein. However, since silver is a heavy metal, its environmental effects are still discussed.

"Disinfectant Performance of a Chlorine Regenerable Antibacterial Microfiber Fabric as a Reusable Wiper" from 2018 was encountered during the research on the subject. In this study, the fibers were modified by grafting polymerization with 3-allyl-5,5-dimethylhydantoin (ADMH) to make the cloths antibacterial. The antibacterial activity was obtained by treating the modified cloths with NaOCI- sodium hypochlorite (bleach) and converting the N-H bonds on ADMH into N-CI form. In this study, where the clothes were made antibacterial using N-Halamine chemical, antibacterial activity was tried to be obtained by coating the polyester section with ADMH monomer. Grafting polymerization with ADMH is very difficult and difficult to commercialize.

Another study, “Rechargeable polyamide-based N-Halamine nanofibrous membranes for renewable, high-efficiency, and antibacterial respirators” was carried out in the year 2019. In this study, filters for air filtration were produced by drawing nanofibers from polyamide 6, 66, and 610 solutions. Also, the filters produced were treated with NaOCI so as to provide N-H --> N-CI conversion. In the relevant study, products for air filtration were aimed at chlorinating the polyamide surfaces produced with nano-spinning. It is not possible to use the surfaces obtained with nano-spinning in areas where mechanical strength such as cloth and towel etc. are required.

The chemistry of N-Halamine as can be understood from the above-mentioned examples comprises the following briefly; the conversion of structures with N-H bonds into N-CI bonds by treating them with a chlorine source and displaying an antibacterial activity of the N-CI bond. Polyamide polymer contains -N-H-C=0- bonds by nature. Herein, it is important to provide N-H --> N-CI conversion without damaging these bonds and dyes. Within this scope, NaOCI (sodium hypochlorite) is substantially used as a chlorine source in N-Halamine chemistry studies. On the one hand, while NaOCI is converting the N-H bonds into the N-CI form very slowly, on the other hand, it can break the polymer chains depending on color bleaching and high pH. There are statements such as "Do not use NaOCI" in the instructions for use of microfiber cloths due to these disadvantages of NaOCI. Yet, final users often try to disinfect such cloths with a NaOCI solution of 5000 ppm (diluting household NaOCI bleach 10 times). Consequently, the disadvantages existing in the state of the art and the insufficiency of available solutions regarding this matter necessitated making an improvement in the relevant technical field.

Objects of the Invention

The present invention relates to polyamide/polyester antimicrobial microfiber compositions suitable for use in fabrics such as cleaning cloth, mop cloth, towel, mask, clothing, etc. in the field of hygiene and disinfection and to a method for making said microfiber compositions antimicrobial with hypochlorous acid solutions, which fulfills the abovementioned requirements, eliminates all disadvantages and brings some additional advantages.

The primary object of the present invention is to make the fabrics antimicrobial obtained with polyamide/polyester microfiber yarns such as cleaning cloth, mop cloth, towel, mask, clothing, etc. used in the field of hygiene and disinfection.

Another object of the present invention is to enable that the polyamide/polyester microfiber fabrics, which are frequently used in domestic, industrial, medical, and veterinary fields and required antimicrobial activity thereon may be chlorinated easily and in a short time and become antimicrobial by means of storing high amounts of chlorine atoms. The halogenation process of N-H bonds described in the invention may be carried out in a very simple manner by means of a HOCI solution or HOCI tablet that is frequently used in domestic and industrial areas. The final consumer can make the produced microfiber composite polyamide (Nylon 6)/polyester cloths antimicrobial with a simple process.

Yet another object of the present invention is to ensure that the N-H bonds in the structure of microfiber cloths with Nylon 6 are rapidly converted into N-CI without any modification by means of using HOCI (hypochlorous acid) as the chlorine source at the pH range of 4-7. Therefore, the disadvantages of using NaOCI are eliminated by means of using HOCI as a chlorine source, and the effect of breaking polymer chains thereof is prevented due to bleach and high pH.

Yet another object of the present invention is to ensure that the strength is increased by means of the polyester, which is one of the fibers used in the microfiber structure obtained. Thus, products suitable for wiping, rubbing, and cleaning processes that require high mechanical strength may be obtained.

A similar object of the present invention is to ensure that the rate of chlorination and antimicrobial activity is increased by means of the polyamide, which is one of the fibers used in the microfiber composite structure, has a microfiber structure and due to the fact that the surface area and therefore the N-H bonds on the surface are high.

In order to achieve the aforementioned objects, a polyamide/polyester microfiber composition treated with hypochlorous (HOCI) acid solutions for the purpose of chlorinating the polyamide/polyester microfiber composition treated with hypochlorous (HOCI) acid solutions and a method rendering said composition antimicrobial, which comprises the process steps of; obtaining HOCI solution, treating the polyamide/polyester microfiber composition with the obtained HOCI solution, washing the polyamide/polyester microfiber composition loaded with chlorine, and drying the washed polyamide/polyester microfiber composition, has been developed.

Detailed Description of the Invention

In the detailed description provided herein, polyamide/polyester microfiber compositions that rendered antimicrobial by means of the hypochlorous acid solutions according to the invention and the preferred embodiments of the method for chlorinating said compositions with hypochlorous acid solutions are described only to provide a better understanding of the subject and without constituting any limiting effects.

The present invention is a polyamide/polyester microfiber composition rendered antimicrobial by means of treating with hypochlorous acid solutions.

Said polyester acts as the main carrier polymer that improves mechanical properties.

The polyamide used in the relevant composition is the main element in which the invention is realized. Preferably, Nylon 6 is used which has a microstructure. The N-H bonds in the amide groups contained in this polymer are converted into N-CI form with HOCI (hypochlorous acid) without damaging the polymer. N-CI bonds, on the other hand, exhibit antimicrobial activity by oxidizing microorganisms. It is very important in terms of contributing to the speed of chlorination and antimicrobial activity due to the microfiber structure of this polyamide, its surface area, and thus the high N-H bonds on the surface.

In the composite according to the invention, it is sufficient to have at least 5% polyamide content for antimicrobial activity. Preferably, it is used such that the polyamide/polyester ratio is 20-80 and 30-70 or 50-50.

In the following, the chlorination process carried out for making the fabrics obtained with polyamide/polyester microfiber yarns antimicrobial such as cleaning cloth, mop cloth, towel, mask, clothing, etc. used in the field of hygiene and disinfection is given in detail. Polyamide/polyester microfiber fabrics are materials, which are frequently used in domestic, industrial, medical, and veterinary (pet) fields and where antimicrobial activity is required.

HOCI converts the N-H bonds in the polyamide structure to the oxidative N-CI bond structure without excessively damaging the structure and dyes of polyamide/polyester microfiber fabrics. N-CI bonds exhibit antibacterial activity by oxidizing microorganisms. The HOCI used herein may be obtained from ready made HOCI solutions, as well as with HOCI solutions formed by chlorine tablets based on NaDCC (Sodium dichloroisocyanurate) dissolved in water.

Said chlorination method for rendering said polyamide/polyester microfiber composition antimicrobial comprises the following process steps; obtaining HOCI solution, treating the polyamide/polyester microfiber composition with the obtained HOCI solution, washing the polyamide/polyester microfiber composition loaded with chlorine, drying the washed polyamide/polyester microfiber composition. Said treatment may be optionally keeping the polyamide/polyester microfiber composition in HOCI solution for 2 to 12 hours or spraying the same. After spraying, the polyamide/polyester microfiber composition is kept at room temperature for 2 hours. After said processes, the drying process is carried out in the furnace at 54 °C for 1 hour. Drying can also be carried out by leaving the microfiber cloths dry on their own at room temperature. A furnace at 54 °C was preferred in the study so as to make the experimental studies faster.

In general, it is known that fabrics containing at least 0.05% Cl ⁺ in N-Halamine chemistry exhibit sufficient antimicrobial activity. Therefore, a polyamide/polyester microfiber structure containing at least 5% polyamide is sufficient for the present invention. However, studies were made with a ratio of 20/80 for cleaning cloths that are expected to have intensive washing and high antimicrobial effect in this study.

In a preferred chlorination method of the present invention, 40 g microfiber cloth (polyamide/polyester ratio 20/80) was chlorinated by keeping the same in 2000 g HOCI solution (200 ppm, pH5,5, Resteril Hygiene Spray, a product of Dr. KOCHERS Company under licencing) for 4 hours. The microfiber cloth was purified from free chlorine after chlorination by rinsing thoroughly with tap water and distilled water and drying in a furnace at 54 °C for 1 hour. The Cl ⁺ on the fabric was determined as 0.40% by weight via iodometric titration.

In another preferred chlorination method of the present invention, it was determined that microfiber cloths can also be chlorinated by spraying with a 200ppm HOCI solution. The cloths, which were sprayed with 200ppm HOCI solution until they become wet, were kept at room temperature for 2 hours. Then, it was washed with distilled water and dried in a furnace at 54°C for 1 hour, and purified from free chlorine thereon. The Cl ⁺ on the fabric was determined as 0,05% by weight via iodometric titration. The CI+ on the fabric was increased up to 0.21 % by weight by means of this process carried out five times.

A series of chlorination processes that can be easily performed by the final consumer are applied to microfiber cloths so as to compare the invention with the conventional chlorination with NaOCI and are summarized in the following table. All chlorination processes were carried out at a fabric/solution ratio of 1/50 (g/g) and for 4 hours. As can be observed from the results, HOCI solutions were loaded 20 to 40 times more chlorine (CI ⁺ %) than NaOCI solutions at a similarly active chlorine concentration. It has been shown in many studies that at least 0.05, preferably 0.20 CI ⁺ % oxidative chlorine amount is required for effective antimicrobial activity in N-Halamine chemistry. * Ready-to-use HOCI solution produced with the HOCI generator.

** A commercial tablet containing 50% NaDCC by weight.

*** A commercial bleach containing 5.25% NaOCI by weight.

In order to measure the repeatability of the chlorination process of microfiber fabrics, the amount of Cl ⁺ on the fabrics was determined by chlorinating the same with HOCI solution - 200 ppm at a weight ratio of 1/50 for 4 hours, then the whole fabric was neutralized with sodium thiosulfate and the amount of Cl ⁺ thereon was determined again. This repetitive chlorination-neutralization process was repeated 8 times and the results are summarized in the table. It was observed that the chlorine-storing properties of microfiber fabrics exposed to a repetitive chlorination-neutralization process did not change.

The resistance of chlorine to washing on chlorinated microfiber fabrics (HOC solution - 200 ppm for 4 hours) was tested according to AATCC Method 61-2A. This method includes an accelerated washing for 45 minutes at 49 °C and 42 rpm in a container including 50 steel balls with a standard detergent. Each 45-minute cycle corresponds to 5 machine washes. It was determined that chlorinated fabrics contain sufficient oxidative chlorine Cl ⁺ even after 50 washing cycles.

Chlorinated firstly (HOCI solution - 200 ppm for 4 hours) and then washed (AATCC 61-2A) microfiber fabrics were tested for antibacterial activity in an independent laboratory according to the ASTM 2149:2020 method. The ASTM 2149 test method is a method, which is developed to measure the effectiveness of fabrics and surfaces that do not release antimicrobial agents from their structure. It was observed that these fabrics were effective against 4 different types of bacteria.

The stability of fabrics chlorinated with HOCI solution - 200 ppm at a ratio of 1/60 was measured on the bench under fluorescence and sunlight. It was observed that chlorinated fabrics lost only 39% of the chlorine thereon for 6 weeks. Chlorinated, rinsed, and dried fabrics were kept on the bench for 6 weeks and subsequently, an antibacterial activity test was performed with Gram-negative Escherichia coli (ATCC 25922), which is one of the most resistant species, and the activity was observed.

The above-mentioned chlorination processes may be carried out optionally between 20-60°C and at a pH of 4-7. The HOCI solutions used may also contain salts such as NaCI. HOCI solutions can be used in concentrations of 200-2000 ppm. Chlorination can also be carried out by steady solution or by shaking.