Biocidal and photoluminescent treatment of viscose fiber immediately after addition of carbon disulfide (xanthation) in conversion of cellulose to viscose

Abstract

The invention relates to the biocidal and photoluminescent treatment of viscose fibers immediately after the addition of carbon disulfide (xanthation) in the conversion of cellulose into viscose, comprising a biocidal composition and an additive allowing the presence of the biocidal composition to be recognized by the luminescent effect, the biocidal composition is added in an amount of 0.1 wt%-5 wt% of the material and comprises 3%-5% of silver-loaded phosphate glass, 1%-3.5% of silicone, 0.1%-0.3% of aliphatic hydrocarbon and 90%-95% of water, and the luminescent additive is added in an amount of 0.1 wt%-5 wt% of the material. The luminescent additive comprises 20-40% of silica gel oxide, 10-30% of alumina gel, 30-50% of calcium fluoride, 0.5-3% of erbium (III) fluoride, 5-15% of ytterbium (III) fluoride, up to 5% of thulium (III) fluoride and up to 1% of europium (III) fluoride, relative to the total weight of the luminescent additive.

Description

Technical Field

[0001] The present invention relates to a biocidal treatment of viscose fibers with a biocidal composition based on silver ions, the biocidal treatment allowing antimicrobial protection, which is applied immediately after the addition of carbon disulphide (xanthation) in the conversion of cellulose into viscose, and, in addition, the addition of a luminescent additive, which allows ensuring that the fibers have been previously treated with said biocidal product, which allows providing confidence to the user and ensuring the presence of the product. Background Art

[0002] Rayon or viscose is a cellulose fiber that was previously dissolved and then regenerated. It is a very versatile fiber that has the same properties as other natural fibers in terms of comfort in use, it can imitate the feel of silk, wool, cotton or linen. The fiber can be easily dyed in other colors. Rayon fabrics are soft, lightweight, cool, comfortable and highly absorbent, but they do not insulate the body, allowing perspiration. For this reason, they are ideal for hot and humid climates. Rayon is mainly used in textile manufacturing (blouses, dresses, jackets, underwear, linings, suits, ties, etc.), decoration (quilts, blankets, decorations, coverings, etc.), industry (surgical materials, nonwoven products, tire cords, etc.) and other uses (feminine hygiene products).

[0003] In the production of viscose, a continuously moving web of cellulose pulp is treated with caustic soda to form alkali cellulose, the alkali cellulose web thus treated is transferred to a sealed chamber and uniformly impregnated with carbon disulfide to form cellulose xanthate, and the cellulose xanthate is discharged from the sealed chamber to be converted into viscose. The web may be a single web or several overlapping webs of dry cellulose pulp, which, after being treated with caustic soda to form alkali cellulose, is treated with gaseous or liquid carbon disulfide.

[0004] In order to keep the viscose fibers free of microorganisms, fungi, viruses, etc., the fibers are impregnated with a biocide product, as described in patent application WO / 1998 / 017165, which relates to a cellulose-based sponge material impregnated with a biocide to eliminate the microorganisms present in the material, which is achieved by a regenerated cellulose-based sponge fabric, which is equipped with an internal reinforcement, characterized in that the internal reinforcement consists of viscose fibers with a cut fiber length of 5 mm to 50 mm, and characterized in that the internal reinforcement consists of viscose fibers impregnated with a biocide. Ammonium salts (especially benzalkonium chloride) as biocides lose their effectiveness in the presence of cotton fibers, so the invention combines biocides, which can be derivatives of isothiazolone, benzisothiazolone or benzimidazole, quaternary ammonium salts. The biocide impregnation can also be carried out by treatment with glycerol or 1,2-propylene glycol (propylene glycol). In order for them to be effective, they must be present in the sponge fabric in an amount sufficient to reduce the water activity. Many of the compounds mentioned are active not only against fungi and bacteria, but also against yeasts, algae and other microorganisms.

[0005] However, viscose fibers impregnated with biocides in this way do not remain protected for a long time, so it is necessary to incorporate a biocidal product in a step of the process after xanthation that allows obtaining a final product that remains free of fungi, bacteria, yeasts, algae and other microorganisms for a longer time.

[0006] In the process of producing a cellulose xanthate solution, cellulose fibers are mixed and stirred with an aqueous caustic soda solution in an amount sufficient to produce a fiber suspension substantially free of lumps or fiber aggregates in the caustic soda solution, and the resulting fiber suspension in the caustic soda solution is then mixed with carbon disulfide in the presence of an emulsifier, which acts to induce in the initial step of the mixture the emulsification of carbon disulfide in the caustic soda solution, which must have a microscopically fine particle size, thereby promoting xanthation of the cellulose fibers and dissolution of the cellulose xanthate in the caustic soda solution. Summary of the invention

[0007] The present invention shows a change in the step of manufacturing viscose or rayon fibers immediately after the addition of carbon disulfide (xanthation) in the conversion of cellulose into viscose, in which a biocidal product with a source of silver ions and a luminescent additive are combined, allowing to keep the resulting fibers protected from different microorganisms, fungi, yeasts, bacteria, viruses much longer than conventional methods, and the luminescent additive allows to ensure that the fibers maintain protection. DETAILED DESCRIPTION

[0008] The present invention relates to a method for antimicrobial protection by incorporating a biocidal product based on a controlled source of Ag+ ions during the xanthation process, the biocidal product allows for longer protection than conventional biocides used in conventional impregnation methods. In addition, the biocidal composition incorporates a luminescent additive in the process that allows for proof that the part has been treated and is free of microorganisms, pathogens, viruses, etc. The biocidal product will provide the final viscose or rayon fiber with a protective capability against microbial growth that will last for at least 200 washes in garments made from rayon fibers treated by this method.

[0009] The method for making viscose or rayon has the following steps:

[0010] 1) Digestion of cellulose,

[0011] 2)xanthation,

[0012] 3) Neutralization, dissolution and liquefaction,

[0013] 4) Spinning.

[0014] The present invention improves the neutralization, dissolution and liquefaction steps by adding a biocidal product with a luminescent additive, wherein the biocidal formulation consists of an aqueous dispersion that will allow it to chemically adsorb on the viscose in dispersion after pre-cutting, which is verified immediately after the xanthation process, and when most of the excess carbon disulfide from the xanthation process has been removed. The process needs to be carried out under constant stirring.

[0015] Cellulose from cotton fibers is treated with sodium hydroxide and then mixed with carbon disulfide to form cellulose xanthate, which is then dissolved in more sodium hydroxide. The resulting viscose is extruded in an acid bath or through a small opening to make rayon (also sometimes called viscose). The acid converts the viscose back into cellulose.

[0016] The biocidal product of the invention allows the silver Ag+ ions from the phosphate glass with the silver source to bind to the free S- ions of the cellulose coordinated with carbon disulfide CS2 before forming the viscose, since it is added in a step immediately after xanthation, in competition with the ionic sodium in the solution, it is essential that there is no excess carbon disulfide, since in equilibrium it interferes with the coordination of the silver ions present in the medium that are bound to the cellulose coordinated with disulfide, in addition, there should be no excess sodium hydroxide in the medium, so the step must be quantitatively controlled. This allows the formation of a stable composition capable of maintaining the presence of the Ag+ ions associated with the product formed from the cellulose coordinated with sulfide, thus activating the antimicrobial protection in the resulting product.

[0017] To provide antimicrobial protection to viscose fibers for at least 200 washes, the concentration of the biocide should be about 0.1 wt % to 5 wt % relative to the viscose material treated.

[0018] The biocidal composition comprises: 3-5% silver loaded phosphate glass, 1-3.5% silicone, 0.1-0.3% aliphatic hydrocarbon and 90-95% water. The composition is added in the process in an amount of 0.1 wt%-5 wt% of the viscose treated. The biocidal composition provides a sufficient amount of silver ions to maintain the biocidal effect of the Ag(+) ions throughout the service life of the material. It is important to eliminate excess carbon disulfide due to the possible occurrence of undesirable chemical reactions of silver sulfide formation, which will contaminate the fibers, and to control the amount of hydroxide added in the rayon manufacturing process itself. The total contact time between the biocide and the viscose should be not less than 5 minutes, preferably between 5 and 10 minutes.

[0019] Furthermore, a luminescent additive is incorporated which allows indicating that the viscose or rayon fibers have been previously treated with the biocidal composition. A luminescent additive formed of a metal oxide (aluminosilicate glass containing rare earth ions in the form of a dopant) is incorporated into the biocidal composition, which allows the coating of said composition to be detected and identified by infrared light inducing an easily detectable luminescence (green light). This luminescent additive exhibits a pattern of emitted light which allows the compounds to be unforgeably coded, which distinguishes them relative to other similar products on the market.

[0020] The luminescent additive acting as a marker allowing the identification of the biocidal composition is added in an amount of 0.1-5 wt% of the material, including a combination of 20-40% silica gel with 10-30% alumina gel and 30-50 wt% calcium fluoride. To this mixture is added a material doped with luminescent "rare earth" ions, such as 0.5%-3% erbium (III) fluoride, 5%-15% ytterbium (III) fluoride, up to 5% thulium (III) fluoride, and up to 1% europium (III) fluoride. All these percentages are relative to the total weight of the luminescent additive.

[0021] Silica gel is used as a luminescent coating, i.e. it does not involve heat generation and is particularly useful in the main physical phenomena that allow the generation of light with characteristics such as phosphorescence and fluorescence. In addition, it is used as an insulating coating, forming a thin layer similar to a laminate on the coated surface, protecting and preserving the surface from the action of water, from scratches or other wear damage. Alumina is used as a selective adsorbent, allowing the level of fluoride in the mixture to be adjusted downward.

[0022] Calcium fluoride doped with luminescent "rare earth" ions significantly increases its fluorescence, with a broad emission that appears within the acceptable target range. Erbium fluoride increases the transmittance of infrared light and the remaining luminescent material in the marking composition. Erbium-doped silica glass fibers are active elements that amplify the luminescence effect, and in addition, their homogenization is increased due to the presence of aluminum oxide. Ytterbium fluoride also increases the amplification of the material as a luminescent marker, and thulium (III) fluoride is used to improve infrared emission and improve the upconversion of fluorescence to ultraviolet and visible light in fluoride glasses. The fluorescence of europium is used to increase the effect of marker additives.

[0023] The luminescent additive, which acts as an identification marker for the biocidal composition, is applied at between 0.1 wt % and 5 wt % of the material treated during the hardening process.

[0024] This luminescent additive (visible under IR) is formulated to be integrated into the formulation of the material being treated and acts as a marker when illuminated by IR light in the 900 to 990 nanometer range.

[0025] Different tests have established that the luminescent additive of the product presents emission only under invisible infrared light with high intensity brightness, due to the lack of background noise due to zero autofluorescence of the fabric matrix or the surface to which it has been applied. Moreover, the luminescence intensity ratios between the different visible emission bands (blue, green and red) observed after the conversion of the invisible infrared reading light can be adjusted as desired (by varying the concentration level and type of doping "rare earth" ions). In other words, by designing and synthesizing on demand at the source, encoding the emitted light with an unforgeable code, a novel and disruptive proof of concept for a security mode with optical encryption is provided.

[0026] The tests applied in the results obtained by this method are:

[0027] UNE-EN ISO 20743:2013 Determination of antimicrobial activity of textiles

[0028] UNE-EN ISO 18184:2019 Determination of antimicrobial activity of textiles

[0029] ASTM E2149-20: Standard Test Method for Determining the Antimicrobial Activity of Immobilized Antimicrobials Under Dynamic Contact Conditions

[0030] - UNE-EN ISO 18184 - Test methods for determining the antiviral activity of products against specific viruses.

[0031] The resulting composition was analyzed based on the biocidal activity comparing a range of product concentrations to evaluate the efficacy of the product against bacteria. This concentration range is based on guidelines for chemical preservatives and disinfectants. The assay demonstrated that its antimicrobial activity lasted for a period of at least 30 days. It eliminates those microorganisms that may cause infection, the presence of mites or similar problems. It prevents the growth of algae, fungi, viruses, mold and other potential pathogens. It prevents side effects such as odor, discoloration or damage to fabrics due to the presence of microorganisms.

[0032] The antimicrobial activity of textiles is usually evaluated using the standard protocol for textiles with antimicrobial activity, JIS L1902 (JIS stands for Japanese Industrial Standard), which is equivalent to the international method ISO 20743. It is a reference method in the industry and is carried out worldwide. The method attempts to simulate the real conditions of the material. The R value defines whether a product or material is considered to have antimicrobial properties. Each sample is inoculated with about 1*105 CFU (colony forming units) and incubated at 37°C, 100% RH for 24 hours.

[0033] The antimicrobial activity value of the sample tested by JIS L1902 standard is determined by applying the following formula: R = log (B / C)

[0034] Where B is the average number of viable bacterial cells on the untreated samples after 24 hours of incubation, and C is the average number of viable bacterial cells on the samples treated with the antimicrobial agent after 24 hours of incubation.

[0035] When R>2.0, the sample is considered to have biocidal properties.

[0036] In the application of the product of the present invention, the process of washing contaminated clothing caused by infection in a hospital is performed.

[0037]

[0038] In view of these results, it is shown that the treatment with the product of the invention in the indicated materials not only increases the antimicrobial effect, but also shows an enhancement of this effect depending on the number of washes performed. In order to provide antimicrobial protection to viscose fibers for at least 200 washes, the concentration of the biocide should be between about 0.1 wt% and 5 wt% relative to the treated viscose material.

[0039] As an added value, the luminescent feature of the invention clearly distinguishes the invention with respect to the prior art, as it allows the user to visualize where the product has been applied, as well as to identify the coded light pattern to indicate that the product is authentic. Using a simple and compact portable handheld device (pocket spectrometer), it will allow the end user to illuminate with a low-cost commercial infrared laser pointer to detect the custom-coded, unforgeable luminescent pattern, thus verifying that the applied product is protected by the biocidal composition. This luminescent technology using infrared light and color coding using "rare earth" ions are at the forefront of anti-counterfeiting light technology in terms of the technological line used for document authentication (passports, security inks) and for secure encryption of legal tender banknotes. Therefore, its application in the original identification of biocidal products undoubtedly constitutes an absolute novelty, which defines a clear and significant difference from other products with similar characteristics on the market. The biocidal product is formulated in an aqueous base, thus obtaining a good drying time ranging from 2 to 3 minutes. The product is easy to apply. Using an atomizer, it allows effective application on the surface with the help of a cloth.

Claims

1. A biocidal and photoluminescent treatment of viscose fibers followed by the addition of carbon disulfide (xanthation) in the conversion of cellulose to viscose, characterized in that A biocidal composition is combined in the neutralization, dissolving and liquefaction steps, the amount of the biocidal composition is 0.1-5wt% of the material, and includes: 3-5% silver-loaded phosphate glass, 1-3.5% silicone, 0.1-0.3% aliphatic hydrocarbon and 90-95% water. In addition, the added amount of a luminescent additive is 0.1-5wt% of the material, and the luminescent additive includes 20-40% silica gel, 10-30% alumina gel, 30-50% calcium fluoride, 0.5-3% erbium (III) fluoride, 5-15% ytterbium (III) fluoride, up to 5% thulium (III) fluoride and up to 1% europium (III) fluoride relative to the total weight of the luminescent additive.

2. Biocidal and photoluminescent treatment of viscose fibers followed by addition of carbon disulfide (xanthation) in the conversion of cellulose to viscose according to claim 1, characterized in that The total contact time between the biocidal composition and the viscose should be no less than 5 minutes, preferably between 5 minutes and 10 minutes.

3. Biocidal and photoluminescent treatment of viscose fibers followed by addition of carbon disulfide (xanthation) in the conversion of cellulose to viscose according to claim 1, characterized in that The luminescent additive acts as a marker when illuminated by IR light in the range of 900 to 990 nanometers.

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