FI20226068A1

FI20226068A1 - Antimicrobial synthetic textile and a method for manufacturing thereof

Info

Publication number: FI20226068A1
Application number: FI20226068A
Authority: FI
Inventors: Kari Holopainen; Haydn Kriel; Ville Tieaho; Sedigheh Borandeh; Stefan Sandås
Original assignee: Nordic Biotech Group Oy
Priority date: 2022-11-30
Filing date: 2022-11-30
Publication date: 2024-05-31
Also published as: WO2024115816A1

Abstract

The present disclosure relates to antimicrobial synthetic textiles and a method for manufacturing antimicrobial synthetic textiles. The present disclosure further concerns the use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile.

Description

ANTIMICROBIAL SYNTHETIC TEXTILE AND A METHOD FOR MANUFACTURING

THEREOF

FIELD OF THE DISCLOSURE

BACKGROUND OF THE DISCLOSURE

Antimicrobial textiles offer several benefits in professional, health care and home environments such as reduction of microbe growth and odor control. Home textiles have always been a major part of the global textile trade. Also, the exponential spread of COVID- 19 across the globe along with a rising requirement for smart medical textiles in healthcare facilities has boosted the antimicrobial textile market. Synthetic polyester fabrics dominate the consumption of antimicrobial fabrics with almost half of the global market share and are likely to showcase a compound annual growth rate (CAGR) of over 9.2% through 2027.

Antimicrobials used in textiles range from synthetic organic compounds such as triclosan, quaternary ammonium compounds (QACSs), polybiguanides, brominated phenols and N- halamines to metals such as silver, copper and zinc. Many of these commonly used antimicrobial agents have some undesired properties. For example, silver ions and QACs are poorly biodegradable and when released into the environment they are very toxic to aquatic organisms. Also, some of the commonly used antimicrobial chemicals potentially contribute to the emergence of antimicrobial resistance (AMR), i.e. antibiotic-resistant bacteria and other types of multidrug-resistant microbes. It is known that silver, copper and zinc are released in high amounts from antimicrobial coatings to the aquatic ecosystems.

Studies have shown that of the antimicrobial substances triclosan, triclocarban and silver

N 25 in textiles, on average 60 % of the antibacterial substance was washed out after 10 washes

N and even up to 100 % of the substance was washed out over time. 5 An antimicrobial treatment performed on a textile needs to satisfy different requirements

O besides being efficient against microorganisms. These include being suitable for textile

E processing, presenting durability to laundering, dry cleaning and hot pressing, presenting © 30 a favorable safety and environmental profile, and not harming textile quality or appearance. 3 There is a longstanding need for a synthetic textile treatment composition which permits a

N durable and safe antimicrobial finish and can be applied simply and inexpensively.

N

BRIEF DESCRIPTION OF THE DISCLOSURE

An object of the present disclosure is to provide a method for manufacturing an antimicrobial synthetic textile, an antimicrobial synthetic textile obtainable by the method, a synthetic textile comprising an antimicrobial finish, and use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile to alleviate the above disadvantages.

The object of the disclosure is achieved by a method for manufacturing an antimicrobial synthetic textile, an antimicrobial synthetic textile obtainable by the method, a synthetic textile comprising an antimicrobial finish, and use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

DETAILED DESCRIPTION OF THE DISCLOSURE

Polycarboxylic acids such as citric acid (CA) are organic compounds having multiple carboxylic acid functional groups. There are plenty of free hydroxyl (-OH) groups in cellulose and cellulosic fibers such as cotton. When polycarboxylic acids are applied to produce a finish to textiles comprising cellulosic fibers, a stable covalent bond is formed via esterification of hydroxide groups and carboxylic groups. On such textiles, an antimicrobial finishing comprising esterified polycarboxylic acids is therefore automatically relatively durable.

In textile manufacturing, finishing refers to processes that convert the textile such as fiber, yarn, fabric or woven or knitted cloth into a more usable material to improve the look, performance, or "hand" (feel) of the finished textile or for example an item of clothing made from the textile. An antimicrobial finish causes the textile to inhibit growth of microbes.

N Infestation of textiles by microbes can cause pathogenic infection and development of odor

N 25 where the textile is worn next to the skin. In addition, stains and loss of fiber guality of

DN textile substrates can also take place. With an aim to protect the wearer and the textile 5 substrate itself, an anti-microbial finish may be applied to textile materials. = Esterification is a conventionally used method in green wood modification technology.

E Esterification of hydroxyl groups of cellulose with a polycarboxylic acid such as citric acid 2 30 is an inexpensive and environmentally friendly cellulose modification method. Previously,

O polycarboxylic acids have been used in different applications on cotton fabric. These

N conventional methods include impregnating cotton fabric with CA and sodium s hypophosphite (SHP) solution and thermally treating the fabric to bring about esterification where CA forms ester bonds with cellulose hydroxyls trough the formation of anhydrides. (Vukusic et al. Croat Med J 2011, 52: 68-75).

Since synthetic textiles lack free OH-groups on the surface compared to the naturally derived textile cotton, these synthetic materials cannot be esterified with polycarboxylic acids. Thus, it is challenging to produce an antimicrobial synthetic textile having a durable polycarboxylic acid finish.

The present invention relates to a method for manufacturing an antimicrobial synthetic textile, an antimicrobial synthetic textile obtainable by to the method and a synthetic textile comprising an antimicrobial finish. The present invention further relates to use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile.

As used herein, the term “textile” refers to various fiber-based materials, including, but not limited to, fibers, yarns, filaments, threads and different fabric types such as woven fabric, non-woven fabric and cloth. Also as used herein, the term “fabric” is defined as any thin, flexible material made from yarn, directly from fibers, polymeric film, foam, or any combination of these techniques. Also as used herein, the term “cloth” refers to a fabric that consists of a fine, flexible network of yarns.

Typically, the smallest component of a fabric is fiber. As used herein, the term “natural fiber” refers to fiber obtained from plants or animals, whereas the term “synthetic fiber” is used of fiber manufactured with chemical synthesis and covers also semi-synthetic fibers synthesized from natural polymers. Similarly, a “natural textile” is a textile based on plant or animal fiber(s), and a “synthetic textile” is a textile based on fiber(s) manufactured with chemical synthesis and covers also semi-synthetic fiber(s) synthesized from natural polymers.

N In an aspect, the invention relates to a method for manufacturing an antimicrobial synthetic

S 25 textile, comprising the steps of a) providing a treatment solution comprising a = polycarboxylic acid and a catalyst; b) applying the treatment solution on a synthetic textile o to produce a polycarboxylic acid treated synthetic textile; and c) curing the polycarboxylic - acid treated synthetic textile. Optionally, curing is performed at a temperature in the range & of 150°C to 180°C.

O 30 In a further aspect, the invention relates to an antimicrobial synthetic textile obtainable by said method. & In another aspect, the invention relates to a synthetic textile comprising an antimicrobial finish comprising a polycarboxylic acid cured in the presence of a catalyst. Optionally, curing is performed at a temperature in the range of 150°C to 180°C.

We have surprisingly found that polycarboxylic acids can be applied in finishing synthetic textiles, resulting in a very strong antimicrobial effect with good washability. Manufacturing the durable antimicrobial finish involves use of a catalyst that, without being bound to any one theory, is believed to crosslink and/or polymerize the polycarboxylic acid molecules, producing a layer or network of crosslinked and/or polymerized polycarboxylic acid molecules on the surface of the textile. The antimicrobial finish represents non-leaching technology and thus no or only a minimal amount of active substance is released to the environment during washing of the textile. Crosslinking and/or polymerization of polycarboxylic acid molecules is induced by curing the synthetic textile treated with one or more polycarboxylic acid(s) at an elevated temperature in the presence of the catalyst.

As used herein, the term “curing” refers to cross-linking and/or polymerizing polycarboxylic acid molecules on the surface of a synthetic textile by applying heat to said polycarboxylic acid. The curing reaction is enhanced by a catalyst and is believed to produce the toughening or hardening of the polycarboxylic acid by cross-linking and/or polymerization.

As used herein, the term "or" has the meaning of both "and™ and "or" (i.e. "and/or").

Furthermore, the meaning of a singular noun includes that of a plural noun and thus a singular term, unless otherwise specified, may also carry the meaning of its plural form. In other words, the term "a" or "an" may mean one or more.

As used herein, the term “comprising” includes the broader meanings of “including”, “containing”, and “comprehending”, as well as the narrower expressions “consisting of and “consisting only of’.

Synthetic textiles that can used in all aspects of the invention including antimicrobial finishing by the method of the disclosure include, but are not limited to, textiles made of

N polyester; polyamide such as nylon; polyacrylonitrile such as acrylic and modacrylic; olefin;

O 25 vinyon; polyethylene such as ultra-high-molecular-weight polyethylene (UHMWPE,

A UHMW), Dyneema and Spectra; elastane; vinylon; aramid such as Kevlar, Nomex and

TY Twaron; polybenzimidazole (PBI); polyphenylene sulfide (PPS); polylactic acid (PLA); & poly(p-phenylene-2,6-benzobisoxazole (PBO); Vectran; and glass fiber or any mixture

E thereof. In other words, the synthetic textile is made of a polymer material having no free o 30 hydroxyl groups in their structure except optionally at the end(s) of the polymer chain. In 3 yet other words, each polymer molecule may have up to one free hydroxyl group at each

N end or terminus of the molecule such as a hydroxyl of a carboxyl acid group.

N Polycarboxylic acids that may be used in all aspects of the invention including the method or the antimicrobial synthetic textile or the synthetic textile comprising an antimicrobial finish disclosed herein include, but are not limited to, citric acid (CA; CAS 77-92-9), isocitric acid (ICA; CAS 320-77-4), tricarballylic acid (TCA; CAS 99-14-9), 1,2,4-butanetricarboxylic acid (BTRCA; CAS 923-42-2), 1,2,3,4-butanetetracarboxylic acid (BTCA; CAS 1703-58- 8), oxalic acid (CAS 144-62-7), tartaric acid (L(+)-tartaric acid CAS 87-69-4, and other 5 isomers), succinic acid (CAS 110-15-6), malic acid (CAS 6915-15-7), malonic acid (CAS 141-82-2), glutamic acid (L-isomer CAS 56-86-0, and other isomers), aspartic acid (L- isomer CAS 56-84-8, and other isomers), glutaric acid (CAS 110-94-1) and 1,3,5- pentanetricarboxylic acid (CAS 6940-58-5). The polycarboxylic acids may also be in any isomer, salt or hydrate form including, but not limited to, sodium citrate, anhydrous (CAS 13742-35-0) and citric acid monohydrate (CAS 5949-29-1).

The antimicrobial synthetic textile and the synthetic textile comprising an antimicrobial finish and the method of the invention involve a catalyst that is believed to enhance the rate of a crosslinking and/or polymerization reaction between the polycarboxylic acid molecules. In all aspects of the invention, sodium hypophosphite, anhydrous CAS 7681- 53-0 (SHP; NaH:PO,), or SHP hydrates like CAS 123333-67-5 or monohydrate CAS 10039-56-2; or monosodium phosphate, anhydrous CAS 7558-80-7 (MSP; NaH2PO.), or

MSP hydrates like monohydrate CAS 10049-21-5 or dihydrate CAS 10049-21-5, or any mixture thereof may be used as a catalyst.

In an embodiment, the polycarboxylic acid and the catalyst are provided dissolved in a solvent. Suitable solvents include but are not limited to one or more solvent(s) selected from an aqueous solvent, water, alcohol, ether, ethyl acetate, ketone or DMSO. That is, any one of the listed solvents or any mixture of the listed solvents that is suitable for dissolving the polycarboxylic acid in question is also suitable for use in the antimicrobial synthetic textile and the synthetic textile comprising an antimicrobial finish and the method

N 25 of the invention. Preferably, the solvent is water or an agueous solvent such as a water-

S alcohol mixture. = Polycarboxylic acids, particularly citric acid and isocitric acid begin to disintegrate at 2 temperatures exceeding 175*C. Because of this, a textile treated with a polycarboxylic acid

E such as CA or ICA has a strong tendency to turn yellow due to degradation of the + 30 polycarboxylic acid into for example unsaturated acids such as aconitic acid, particularly

O at high temperatures and/or during an extended time heat treatment. Therefore, it is also important to maintain a short curing time to avoid disintegration.

A In an embodiment, curing is performed in the method or the antimicrobial synthetic textile or the synthetic textile comprising an antimicrobial finish as disclosed herein at a temperature of 150°C to 180°C, or 150°C to 175°C, or 160°C to 175°C, or 160° to 170°C, or 150° to 170°C.

In another embodiment, curing is performed in the method or the antimicrobial synthetic textile or the synthetic textile comprising an antimicrobial finish as disclosed herein for a period of time ranging from 30 to 180 seconds, or 30 to 150 seconds, or 30 to 120 seconds, or 60 to 120 seconds.

Also, we have surprisingly discovered that a one-step treatment of curing may also be used to simultaneously dry the synthetic textile. In other words, a two-step treatment involving a separate drying step and curing step is not required to achieve a durable antimicrobial finishing. As used herein, the term “drying” refers to applying heat to the synthetic textile to achieve a reduced moisture content. Typically, drying is performed at a lower temperature than curing for example to avoid disintegration of polycarboxylic acid and to avoid occurrence or onset of the curing reaction. A one-step curing provides a fast and energy-efficient process as compared to a conventional two-step drying and curing.

In an embodiment, no drying step by applying heat to the polycarboxylic acid treated synthetic textile is performed before the curing step in the method or the antimicrobial synthetic textile or the synthetic textile comprising an antimicrobial finish as disclosed herein. In other words, drying is achieved in a single curing step performed at a temperature of 150°C to 180°C, or 150°C to 175°C, or 160°C to 175°C, or 160° to 170°C, or 150° to 170°C. Preferably, the single curing step is performed for a period of time ranging from 30 to 180 seconds, or 30 to 150 seconds, or 30 to 120 seconds, or 60 to 120 seconds.

As used herein, the term “wet pick-up” refers to the amount of fluid or solution by percent

N weight picked up by a textile during a method step. Wet pick-up is influenced by factors

N 25 such as textile characteristics and solution properties. As used herein, the term “dry pick-

DN up” refers to the amount of treatment chemicals by percent weight left on a textile after 5 evaporating a solution or solvent liquid. = A combination of wet pick-up, polycarboxylic acid concentration such as citric acid

E concentration and catalyst concentration such as SHP concentration that results in dry

O 30 pick-up of polycarboxylic acid and catalyst in the range of 3% - 12% produces the most © durable and antimicrobially effective finish. Preferably, the dry pick-up of polycarboxylic

N acid and catalyst may be in the range of 4% to 10% or 5% to 9%. As readily understood s by those skilled in the art, regulating dry pick-up of the textile may be performed by adjusting wet pick-up or concentrations of treatment chemicals. As exemplified in the working examples herein, using in treatment of synthetic textile a 10 wt% CA solution, a 10 wt% SHP solution and wet pick-up of 70%, dry pick-up for both CA and SHP is 7%.

In a further aspect, the present invention relates to use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile. The polycarboxylic acid is one or more selected from citric acid (CA), isocitric acid (ICA), tricarballylic acid (TCA) 1,2,4-butanetricarboxylic acid (BTRCA), 1,2,3,4-butanetetracarboxylic acid (BTCA), oxalic acid, tartaric acid, succinic acid, malic acid, malonic acid, glutamic acid, aspartic acid, glutaric acid, 1,3,5- pentanetricarboxylic acid or a salt or a hydrate or an isomer thereof.

In an embodiment, in the use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile, the polycarboxylic acid is cured in the presence of a catalyst selected from sodium hypophosphite (SHP), monosodium phosphate (MSP), or any mixture thereof.

In a yet further aspect, the present invention relates to any item and/or product manufactured from the antimicrobial synthetic textile obtainable by the method of the invention or the synthetic textile comprising an antimicrobial finish. These include, but are not limited to items of clothing, furnishings, upholsteries, and products for healthcare and hospital use.

As regards discoloration of textiles treated with polycarboxylic acids due to formation of colored degradation products, use of a polyol in the treatment solution may prevent yellowing of the textile. This is because the presence of a polyol may be expected to prevent the unwanted side-reaction producing unsaturated acids such as aconitic acid.

Such polyols include, but are not limited to xylitol, sorbitol, glycerol and pentaerythritol.

Also, use of BTCA, TBA and/or BTRCA as the polycarboxylic acid is believed to prevent

N or reduce formation of the yellow-colored side-products because these polycarboxylic

O 25 acids form anhydrides upon heating without producing significant amounts of unsaturated < acids. 5 In an embodiment, the antimicrobial synthetic textile and the synthetic textile comprising = an antimicrobial finish and the method of the invention involve a polyol selected from xylitol, & sorbitol, glycerol and pentaerythritol. The polyol may be included in the treatment solution 3 30 comprising polycarboxylic acid and catalyst i.e. the polyol is applied to the synthetic textile

O with the polycarboxylic acid and before curing to produce the antimicrobial finish.

S The treatment solution may comprise further auxiliary components including essential oils that contain terpenes for antimicrobial efficacy and odor control (e.g. peppermint oil). Odor control may also be achieved by metal oxides. As readily appreciated by those skilled in the art, further auxiliary components may include surfactants to decrease surface tension of water, rheology modifiers to alter the rheology of the solution, antifoaming additives such as polydimethylsiloxanes to reduce foaming and additional biocides approved for use in textile industry. Surfactants can alleviate problems caused by hardness of water.

Preferably, the surfactant is a bio-sourced surfactant such as a green non-ionic surfactant.

A water-soluble polymer may act as a rheology modifier.

Polycarboxylic acids have several carboxylic groups each having their own pKa value. For example, citric acid is a tricarboxlic acid having with pKa values of 3.128, 4.761, and 6.396 at 25 °C. The antimicrobially most efficient range for citric acid is below pH 3.1 where at least half of CA molecules have all three carboxylic groups are protonated i.e. CA is in

H3A form. For example, at pH 4.7 none of CA is in H3A form but half of it is in H2A form and half in HA form. The same applies to other polycarboxylic acids at their own specific pKa values.

We have surprisingly discovered that pH of the treatment solution affects quality of the resulting antimicrobial finish. Using a pH in the range of 2 to 7 in the treatment solution that is applied on a synthetic textile to manufacture a polycarboxylic acid treated synthetic textile produces the most durable finish. Optionally, the pH may be in the range of 2 to 6, or 2 to 5, or 2 to 4, or 2 to 3. As readily understood by those skilled in the art, regulating pH of the treatment solution may be performed with acids and/or bases.

GRAS (Generally-Recognized-as-safe) additives can safely be used for odor reduction and bacterial control on a textile material. A GRAS substance is a food substance that is not subject to premarket review and approval by FDA because it is generally recognized, by qualified experts, to be safe under the intended conditions of use. These are for instance citric acid, malic acid and their derivatives. Among GRAS substances there is a group of

N 25 those which are listed as minimum risk pesticides, and which can therefore be claimed to

N have antimicrobial efficacy when used in textiles. Citric acid is included in this group. Also, - other nature-derived GRAS substances such as chitosan and chitosan derivatives are 2 considered safe and green antimicrobial substances. Chitosan has a wide-spectrum

E antimicrobial activity based on quaternary nitrogen and is particularly effective at pH values + 30 below 6. Chitosan may produce a synergistic antimicrobial effect when combined with a

O polycarboxylic acid in all aspects of the invention such as the method for manufacturing an antimicrobial synthetic textile or antimicrobial textile or use according to the invention.

N Citric acid is an Annex I (EU) listed active substance that is identified as a low-risk substance. Biocidal products containing such substances with low toxicity are eligible for a simplified authorization procedure in the EU. For instance, silver-based technologies are not considered as low risk substances as their mode of action is based on leaching which is basically “foxic-by-design’. Developing an antimicrobial textile finish is required to meet the adequate level of “Safe-by-Design” (SbD) strategy. The SbD concept refers to identifying the risks and uncertainties concerning humans and the environment at an early phase of the innovation process to minimize uncertainties, potential hazards and/or exposure. The SbD approach addresses the safety of the material/product and associated processes through the whole life cycle: from the Research and Development (R&D) phase to production, use, recycling and disposal. Citric acid is safe to environment and does not pose a danger to humans. It can be found naturally in fruits and vegetables, particularly in citrus fruits.

Water solubility among GRAS substances differs, which affects washing durability. For example, benzoic acid and sorbic acid having water solubility of 0,29 % and 0,16 % (20 °C), respectively, are likely to produce a durable antimicrobial finish solely based on their low solubility. However, citric acid having high water solubility (59 %, 20 °C) will not provide washing durability and thus the antimicrobial efficacy against gram positive or negative bacteria may be more short-lived unless a way to efficiently cure citric acid is established.

EXAMPLES

Example 1

Example 1 presents a method of antimicrobially finishing a synthetic textile with citric acid employing sodium hypophosphite as catalyst. The method involves a two-step heat treatment of separately drying and curing the textile.

Water-soluble treatment solution was prepared as follows. Citric acid (CAS No. 77-92-9)

N and sodium hypophosphite (SPH) monohydrate (CAS No. 10039-56-2) were in solid form

N 25 when dissolved in distilled water in room temperature. The final concentrations were 10 = wt% for citric acid and 10 wt% for SPH. Citric acid was dissolved first in and after all of the

RS citric acid had visibly dissolved, SPH was added.

E Polyester fabric samples were immersed in the 10 wt% citric acid, 10 wt% SPH working © solution, swirled around for a minute and after that either padded to approximately 70%

O 30 pick-up or dried straight after dipping. Wet samples were placed to stenter frame and firstly

N dried completely in 100 *C for 10 minutes and then cured in 150 *C for 90 seconds. After

N curing fabric samples were left to rehydrate overnight in room temperature and were then ready for further processing. The materials were rinsed thoroughly with tap water and then subjected to laundering. Laundering included either Ox or 10x wet-on-wet domestic laundering cycles at 40 °C. Laundering was carried out according to 4N program of the

ISO 6330 standard in an Electrolux Professional Wascator FOM71 CLS using the ECE-2 reference detergent. All samples were rinsed well in deionized water prior to analysis.

Determination of durability and resultant antibacterial protection of the treated fabrics was carried out through screening tests based on standard ISO 20743. In brief, pieces of treated polyester fabric (0.4 g) were inoculated with 3.6 x10* cells of Staphylococcus aureus. After 21-hour contact time, the surviving S. aureus cells were shaken-out from the sample pieces with 20 ml of tryptone soy broth supplemented with 0.07% lecithin and 0.5%

Tween®. S. aureus cells were quantitated by plating a dilution series of the shake-out liquid on tryptone soy agar plates and counting colonies after 24-hour incubation.

Antibacterial activity value (A) was calculated according to formula [1]:

A = (lgCi- 1900) — (IgT: —IgTo) = F -G [1] where F is the growth value on the control specimen (F = (IgC:- 19Co); G is the growth value on the antibacterial testing specimen (G = (IgT: —IgTo); Ig Ci is the common logarithm of the number of bacteria obtained from control specimen after an 18 h to 24 h incubation; lg Co is the common logarithm of the number of bacteria in the inoculum; Ig Ti is the common logarithm of the number of bacteria obtained from antibacterial testing specimen after an 18 h to 24 h incubation; Ig To is the common logarithm of the number of bacteria in the inoculum. A values and data used for calculation of A is presented in Table 1.

Table 1. Data for antibacterial activity value (A) calculation for citric acid and sodium hypophosphite (SPH) treated polyester fabric.

N Ox washed sample 10x washed sample

N oO

I

O

A

O

N

The result was that both treated samples, both 0x and 10x washed, had an A value of 5.8 i.e. gave >5 log (> 99.999 %) reduction in S. aureus colony count compared to untreated control polyester fabric. The ISO 20743 (2021) standard gives the following reference values for efficacy of antibacterial property: log reduction <2 = low antibacterial property; log reduction 2-3 = significant antibacterial property; log reduction >3 = strong antibacterial property. Therefore, the treated fabric had strong antibacterial property against

Staphylococcus aureus even after 10 washing cycles.

Example 2

Example 2 presents preparation of water-soluble treatment solution based on crosslinking agent, citric acid, and catalyst, sodium hypophosphite monohydrate; manufacture of polyester material with antimicrobial properties; and demonstration of antimicrobial properties of the manufactured polyester textile against Gram-positive and Gram-negative bacteria after various washing cycles.

To prepare the water-soluble treatment solution, solid form citric acid, anhydrous, (CA;

CAS No. 77-92-9) and sodium hypophosphite monohydrate (SHP; CAS No. 10039-56-2) were dissolved in tap water at room temperature. The final concentrations were 9 wt% for

CA and 9 wt% for SHP. Citric acid was dissolved first and after all CA had visibly dissolved,

SHP was added. To investigate the effect of citric acid alone, a similar CA solution was prepared without adding SHP in the solution.

Polyester material with antimicrobial properties was manufactured by immersing polyester fabric samples in two different working solutions containing a) 9 wt% citric acid and 9 wt% sodium hypophosphite monohydrate or b) 9 wt% citric acid, swirled around for one minute

N and thereafter padded to approximately 70 % pick-up. Wet samples were placed to stenter

S 25 frame and dried and cured in one step, 90 seconds at 160 *C. After curing fabric samples = were left to rehydrate overnight at room temperature. The treated textile materials were o rinsed thoroughly with tap water and then subjected to laundering. Laundering included - either Ox, 10x, or 25x wet-on-wet domestic laundering cycles at 40 *C. Laundering was & carried out according to 4N program of the ISO 6330 standard (2021) in an Electrolux 3 30 Professional Wascator FOM71 CLS using the ECE-2 reference detergent. All samples

O were rinsed well in deionized water prior to analysis.

O Determination of durability and resultant antibacterial protection of the treated fabrics was carried out through screening tests based on the standard ISO 20743 (2021). Briefly, pieces of treated polyester fabric (0.4 g) were inoculated with either 4.5 x10* cells of Gram-

positive Staphylococcus aureus (ATCC 6538) or 4.7 x10 cells of Gram-negative Klebsiella pneumoniae (ATCC 4352). After overnight contact time, the surviving bacterial cells were shaken-out from the sample pieces with 20 ml of tryptone soy broth supplemented with 0.07 wt% lecithin and 0.5 vol% Tween®. Bacterial cells were quantitated by plating a dilution series of the shake-out liquid on tryptone soy agar plates and counting colonies after overnight incubation.

Antibacterial activity value (A) was calculated similarly as in Example 1. A values and data used for calculation of A are presented in Tables 2 and 3.

Table 2. Data for antibacterial activity value (A) calculation for Staphylococcus aureus (ATCC 6538). CA = citric acid; SHP = sodium hypophosphite; Ox = Ox washed; 10x = 10x washed; 25x = 25 x washed.

Value Ox Ox 10x 10x 25x 25x

CA+SHP CA CA+SHP CA CA+SHP CA

O

N o

O

I

Za o 00 © o ©

N

O

N

Table 3. Data for antibacterial activity value (A) calculation for Klebsiella pneumoniae (ATCC 4352). CA = citric acid; SHP = sodium hypophosphite; Ox = Ox washed; 10x = 10x washed; 25x = 25 x washed.

Value 0x 0x 10x 10x 25x 25x

CA+SHP CA CA+SHP CA CA+SHP CA

Clams) | 39] SO] Be] s] =] %

The ISO 20743 standard (2021) gives the following reference values for efficacy of antibacterial property: log reduction <2 = low antibacterial property; log reduction 2-3 = significant antibacterial property; log reduction >3 = strong antibacterial property. The result with Gram-positive S. aureus was that the samples treated with citric acid and sodium hypophosphite monohydrate had strong antimicrobial property (log reduction > 3) as rinsed and also after 10 or 25 washing cycles. With CA alone, the rinsed sample had significant antimicrobial property (log reduction 2-3) but after 10 or 25 washing cycles there

N was only low antimicrobial property left in the samples. With the Gram-negative bacterium

O Klebsiella pneumoniae, the results were essentially the same except after 25 washing —- cycles, the samples treated with CA and SHP had significant, not strong, antimicrobial o 15 property.

O

I

Za o © Example 3 ©

O Example 3 presents the effect of drying and curing temperature on the formation of

N antimicrobial properties on polyester textile.

N

CAS No. 77-92-9) and sodium hypophosphite monohydrate (SHP; CAS No. 10039-56-2)

were dissolved in tap water at room temperature. The final concentrations were 9 wt% for

CA and 9 wt% for SHP. Xylitol (CAS 87-99-0) was added in the treatment solution to a final concentration of 0.5 wt% to reduce yellowing of the textile samples. pH of the treatment solution was 3.0.

Polyester material with antimicrobial properties was manufactured by immersing polyester fabric samples in the treatment solution, swirling around for one minute and after that, padding to approximately 70% pick-up. Wet samples were placed to stenter frame and dried and cured in one step, 90 seconds at either 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C. After curing, fabric samples were left to rehydrate overnight at room temperature. The treated textile materials were rinsed thoroughly with tap water and then subjected to laundering. Laundering included 10x wet-on-wet domestic laundering cycles at 40°C. Laundering was carried out according to 4N program of the ISO 6330 standard (2021) in an Electrolux Professional Wascator FOM71 CLS using the ECE-2 reference detergent. All samples were rinsed well in deionized water prior to analysis.

Determination of durability and resultant antibacterial protection of the treated fabrics was carried out through screening tests based on the standard ISO 20743 (2021). Briefly, pieces of treated polyester fabric (0.4 g) were inoculated with 4.8 x10* cells of Gram- positive Staphylococcus aureus (ATCC 6538). After overnight contact time, the surviving bacterial cells were shaken-out from the sample pieces with 20 ml of tryptone soy broth supplemented with 0.07 % lecithin and 0.5 % Tween®. Bacterial cells were quantitated by plating a dilution series of the shake-out liquid on tryptone soy agar plates and counting colonies after overnight incubation.

Antibacterial activity value (A) was calculated similarly as in Example 1. A values and data used for calculation of A are presented in Table 4.

N

O

N o

O

I

= 00 ©

O

©

N

O

N

Table 4. Data for antibacterial activity value (A) calculation at different curing temperatures. Co and Ci were determined for untreated control polyester fabric and To and

Ti for the sample. 120°C | 130°C | 140°C | 150°C | 160°C | 170°C | 180°C

According to the results, strong antimicrobial activity (log reduction >3) against Gram- positive S. aureus was achieved when drying and curing step was done at either 160°C or 170°C. Additionally, significant antimicrobial activity was achieved when drying and curing step was done at 150°C and low antimicrobial activity was achieved when drying and curing step was done at 180°C. As per visual inspection, no yellowing of the textile was observed even at 180°C. This is assumed to be influenced by the presence of the polyol xylitol in the samples.

N

N o Example 4 = Example 4 presents preparation of water-soluble treatment solution based on citric acid 2 15 and either a) sodium hypophosphite monohydrate, or b) monosodium phosphate dihydrate

T as a reaction catalyst; manufacture of polyester material with antimicrobial properties; and

Za a demonstration of antimicrobial properties of the manufactured polyester textile against

N Water-soluble treatment solution was prepared as follows: citric acid, anhydrous, (CA;

N 20 CAS No. 77-92-9) and either a) sodium hypophosphite (SHP) monohydrate (CAS No. 10039-56-2), or b) monosodium phosphate (MSP) dihydrate (NaH>PO4-2H;0;

CAS No. 13472-35-0) were in solid form when dissolved in deionized water at room temperature. The final concentrations were 9 wt% for citric acid and either a) 9 wt% for

SHP, or b) 13.5 wt% for NaH2PO4-2H20. pH of the treatment solution a) was 2.88 and b) 2.99.

Polyester material with antimicrobial properties was manufactured by immersing polyester fabric samples in two different working solutions containing a) 9 wt% citric acid (CA) and either a) 9 wt% SHP or b) 13.5 wt% NaH,PO2H;0O, swirled around for one minute and after that, padded to approximately 70 % pick-up. Wet samples were placed to stenter frame and dried and cured in one step, 90 seconds at 160 *C. After curing fabric samples were left to rehydrate overnight in room temperature and were then ready for further processing. The materials were rinsed thoroughly with tap water and then subjected to laundering similarly to Example 4.

Determination of durability and resultant antibacterial protection of the treated fabrics was carried out similarly to Example 4. The treated textile pieces were inoculated with 4.3 x10* cells of Gram-positive Staphylococcus aureus (ATCC 6538). After overnight contact time, the surviving bacterial cells were shaken-out from the sample pieces with 20 ml of tryptone soy broth supplemented with 0.07 wt% lecithin and 0.5 vol% Tween®. Bacterial cells were quantitated by plating a dilution series of the shake-out liquid on tryptone soy agar plates and counting colonies after overnight incubation.

Antibacterial activity value (A) was calculated similarly as in Example 1. A values and data used for calculation of A are presented in Table 5.

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Table 5. Data for antibacterial activity value (A) calculation. CA = citric acid; SHP = sodium hypophosphite; MSP = monosodium phosphate; Ox = Ox washed; 10x = 10x washed.

Value 0x Ox 10x 10x

CA+SHP CA+MSP CA+SHP CA+MSP >99.999 >99.999 >99.999 >99.999

The polyester fabric samples treated with citric acid and with either SHP or MSP as a reaction catalyst had strong antimicrobial property (log reduction > 3) both before washing and after 10 washing cycles. Both catalysts therefore have similar activity.

Example 5

Example 5 presents the effect of adding low molecular weight chitosan to the treatment solution on antimicrobial properties against Gram-positive bacteria.

N

O The treatment solution was prepared essentially as in Example 2 except the final < concentrations were 10 wt% for CA and 10 wt% for SHP, and additionally low molecular 5 weight chitosan (LMW-CS; CAS No. 9012-76-4) was added to final concentration of

O 1 wt%. Treatment of polyester fabric samples and testing of their antimicrobial property

E 15 was done essentially as described in Example 2, except in this case wet pick-up was 00 approximately 63 %, and the samples were dried and cured in two steps, first at 100 °C © 3 for 10 min and then at 160 °C for 90 seconds.

N

S Antibacterial activity value (A) was calculated similarly as in Example 1. A values and data used for calculation of A is presented in Table 6.

Table 6. Data for antibacterial activity value (A) calculation. 0x washed sample 10x washed sample

The result was that the treated samples, both Ox and 10x washed, gave >5 log (> 99.999%) reduction in S. aureus colony count compared to untreated control polyester fabric. The presence of chitosan did not weaken the antimicrobial activity of CA. Chitosan may have an additive effect on antimicrobial activity of the treatment solution because it is known to be an antimicrobial agent against fungi and both Gram-negative and Gram-positive bacteria, and particularly chitosan derivatives also have activity against viruses.

It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

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Claims

1. A method for manufacturing an antimicrobial synthetic textile, comprising the steps of: a) providing a treatment solution comprising a polycarboxylic acid and a catalyst; b) applying the treatment solution on a synthetic textile to produce a polycarboxylic acid treated synthetic textile; and ¢) curing the polycarboxylic acid treated synthetic textile; wherein the polycarboxylic acid is one or more selected from citric acid (CA), isocitric acid (ICA), tricarballylic acid (TCA) 1,2,4-butanetricarboxylic acid (BTRCA), 1,2,3,4- butanetetracarboxylic acid (BTCA), oxalic acid, tartaric acid, succinic acid, malic acid, malonic acid, glutamic acid, aspartic acid, glutaric acid, 1,3,5-pentanetricarboxylic acid or a salt, a hydrate or an isomer thereof, and wherein the catalyst is one or more selected from sodium hypophosphite (SHP), an SHP hydrate, monosodium phosphate (MSP), an MSP hydrate or any mixture thereof.

2. The method of claim 1, wherein curing is performed at a temperature ranging from 150°C to 180°C, or 150°C to 175°C, or 160°C to 175°C, or 160° to 170°C, or 150° to 170°C.

3. The method of claim 1 or claim 2, wherein curing is performed for a period of time ranging from 30 to 180 seconds, or 30 to 150 seconds, or 30 to 120 seconds, or 60 to 120 seconds. N 20

4. The methodof any one of the preceding claims, wherein the treatment solution has a S pH in the range of 2 to 7, or 2 to 6, or 2 to 5, or 2 to 4, or 2 to 3.

5 5. The method of any one of the preceding claims, wherein dry pick-up of polycarboxylic O acid and/or catalyst is in the range of 3% to 12%, preferably in the range of 4% to 10% E or 5% to 9%. 00 " " " " " " 8 25

6. The method of any one of the preceding claims, wherein the synthetic textile is selected from polyester; polyamide such as nylon; polyacrylonitrile such as acrylic and S modacrylic; olefin; vinyon; polyethylene such as ultra-high-molecular-weight polyethylene (UHMWPE, UHMW), Dyneema and Spectra; elastane; vinylon; aramid such as Kevlar, Nomex and Twaron; polybenzimidazole (PBI); polyphenylene sulfide

(PPS); polylactic acid (PLA); poly(p-phenylene-2,6-benzobisoxazole (PBO); Vectran; glass fibre or any mixture thereof.

7. The method of any one of the preceding claims, wherein to produce the treatment solution, the polycarboxylic acid and catalyst are dissolved in a solvent selected from an aqueous solvent, water, alcohol, ether, ethyl acetate, ketone, DMSO or any mixture thereof.

8. An antimicrobial synthetic textile produced according to the method of any one of claims 1 to 7.

9. A synthetic textile comprising an antimicrobial finish comprising a polycarboxylic acid cured in the presence of a catalyst, wherein the polycarboxylic acid is one or more selected from citric acid (CA), isocitric acid (ICA), tricarballylic acid (TCA) 1,2,4- butanetricarboxylic acid (BTRCA), 1,2,3,4-butanetetracarboxylic acid (BTCA), oxalic acid, tartaric acid, succinic acid, malic acid, malonic acid, glutamic acid, aspartic acid, glutaric acid, 1,3,5-pentanetricarboxylic acid or a salt, a hydrate or an isomer thereof, and wherein the catalyst is one or more selected from sodium hypophosphite (SHP), a SHP hydrate, monosodium phosphate (MSP), an MSP hydrate or any mixture thereof.

10. The synthetic textile of claim 9, wherein curing is performed at a temperature ranging from 150°C to 180°C, or 150°C to 175°C, or 160°C to 175°C, or 160° to 170°C, or 150° to 170°C, optionally wherein curing is performed for a period of time ranging from to 180 seconds, or 30 to 150 seconds, or 30 to 120 seconds, or 60 to 120 seconds.

11. The synthetic textile of claim 9 or claim 10, wherein dry pick-up of polycarboxylic acid N and/or catalyst is in the range of 3% to 12%, preferably in the range of 4% to 10% or DN 5% to 9%. o 25

12. The synthetic textile of any one of claims 9 to 11, wherein the synthetic textile is I selected from polyester; polyamide such as nylon; polyacrylonitrile such as acrylic and - modacrylic; olefin; vinyon; polyethylene such as ultra-high-molecular-weight O polyethylene (UHMWPE, UHMW), Dyneema and Spectra; elastane; vinylon; aramid such as Kevlar, Nomex and Twaron; polybenzimidazole (PBI); polyphenylene sulfide S 30 (PPS); polylactic acid (PLA); poly(p-phenylene-2,6-benzobisoxazole (PBO); Vectran; glass fibre or a mixture thereof.

13. Use of a polycarboxylic acid as an antimicrobial finish on a synthetic textile, wherein the polycarboxylic acid is one or more selected from citric acid (CA), isocitric acid (ICA), tricarballylic acid (TCA) 1,2,4-butanetricarboxylic acid (BTRCA), 1,2,3,4- butanetetracarboxylic acid (BTCA), oxalic acid, tartaric acid, succinic acid, malic acid, malonic acid, glutamic acid, aspartic acid, glutaric acid, 1,3,5-pentanetricarboxylic acid or a salt, a hydrate or an isomer thereof.

14. The use of claim 13, wherein the polycarboxylic acid is cured in the presence of a catalyst, wherein the catalyst is one or more selected from sodium hypophosphite (SHP), a SHP hydrate, monosodium phosphate (MSP), an MSP hydrate or any mixture thereof.

15. The use of claim 13 or 14, wherein the synthetic textile is selected from polyester; polyamide such as nylon; polyacrylonitrile such as acrylic and modacrylic; olefin; vinyon; polyethylene such as ultra-high-molecular-weight polyethylene (UHMWPE, UHMW), Dyneema and Spectra; elastane; vinylon; aramid such as Kevlar, Nomex and Twaron; polybenzimidazole (PBI); polyphenylene sulfide (PPS); polylactic acid (PLA); poly(p-phenylene-2,6-benzobisoxazole (PBO); Vectran; glass fibre or a mixture thereof. N N O N o O I = 00 © o © N N O N