Layer fiber product

Abstract

The layer fibrous product comprises at least one layer selected from the group consisting of a nonwoven layer and a tissue layer wherein the at least one layer selected from the group consisting of a nonwoven layer and a tissue layer comprises cellulosic fibers comprising an organic polycarboxylic acid, and wherein the organic polycarboxylic acid has at least one carboxyl group and at least one free carboxyl group covalently bound to the cellulosic fibers. Since there is a covalent chemical bond between the carboxyl group of the polycarboxylic acid and the hydroxyl groups of the cellulosic fibers present in all substrates, the layered fiber product exhibits a lasting acidic pH even after having been rinsed with water. In some embodiments, a persistent acidic pH may be achieved in a nonwoven treated with an organic polycarboxylic acid even after washing with a detergent.

Description

[0001] This application is a divisional application of the PCT international application PCT / SE2020 / 050182 filed on February 17, 2020, which entered the Chinese national phase on July 11, 2022, and the invention patent application with Chinese patent application number 202080092676.1 and invention name “Layer Fiber Product”. Technical Field

[0002] The present disclosure relates to ply fibrous products and processing thereof. Background Art

[0003] Layer fiber products (such as products based on tissue (tissue) and nonwoven (nonwoven)) are widely used in modern society.For example, nonwoven is used as cleaning wipes (cleaning wipe), wound care dressing (woundcare dressing) or can be used for other wipes of sanitary products.Nonwoven is a flexible porous fiber product usually produced by a blend of synthetic textile fiber or synthetic textile fiber and cellulose fiber.For example, nonwoven can be produced by entanglement of cellulose fiber (such as natural fiber or semi-synthetic cellulose fiber) and synthetic textile fiber (such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) or polyester) and / or by cohesion and / or adhesion bonding of cellulose fiber (such as natural fiber or semi-synthetic cellulose fiber) and synthetic textile fiber (such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) or polyester).

[0004] Disposable hygiene products, such as tissue and nonwovens, consume resources and cause environmental damage. Reusable nonwoven-based products offer a sustainable and environmentally friendly alternative to commonly used disposable hygiene products, which are disposable.

[0005] The most important physical properties of nonwoven-based products include their strength, their softness, their absorbency, mainly towards aqueous systems, and their linting and dust resistance. These physical properties are usually adjusted to meet the needs of the average consumer.

[0006] Cleaning wipes are used in many different environments, such as as food service wipes in the kitchen to clean workbenches where food is prepared, or in offices, schools and hospitals to clean furniture and surroundings. In many use cases, they remain damp for a long time. Therefore, it may be important to prevent and / or reduce bacterial growth in the wipes during storage and use. Typically, bacterial growth can be caused by an increase in moisture, warm temperatures, and a neutral or slightly elevated pH. For example, many bacteria show optimal growth at a pH of about 7. For this reason, reducing pH is an effective way to limit undesirable bacterial growth. The spread of undesirable bacteria is particularly dangerous in hospital environments, thereby causing the risk of promoting nosocomial infections. In order to prevent the spread of nosocomial infections, it may be important to prevent and / or reduce bacterial growth in the cleaning wipes used in these sensitive environments. Some of the most relevant nosocomial pathogens are gram-negative bacteria such as enterobacteria (e.g., E. coli, E. cloacae, and Klebsiella) and gram-positive bacteria such as Staphylococcus aureus (S. aureus). Furthermore, preventing and / or reducing bacterial growth can allow the formation of unpleasant odors to be avoided.

[0007] Tissue paper products are often in contact with human skin and body fluids, for example when applied as personal hygiene wipes (e.g., toilet paper, pre-moistened toilet paper, baby wipes, feminine hygiene wipes, handkerchiefs, facials) or wound care dressings. However, the presence of body fluids in tissue products can cause undesirable effects such as microbial growth, odor, and disturbance of natural skin pH. Generally, a slightly acidic pH can be beneficial to skin health due to increased barrier properties and balanced skin microflora. Bacterial growth can also lead to different forms of skin irritation and primary or secondary skin infections.

[0008] In order to solve these problems, it has been proposed to locally treat layer fiber products (such as nonwovens) with antimicrobial silver or other metal-based antimicrobial agents. However, the supply of silver is limited, and the method for obtaining and processing silver has negative environmental impact. There is also a general concern about the potential formation of resistant bacteria. In addition, after the layer fiber product (particularly nonwoven fabric) is subjected to multiple washing cycles, the content of silver particles in the product will decrease, which will eventually lead to limited reusability.

[0009] Furthermore, there are currently tissue-based handkerchiefs on the market that have been treated with benzalkonium chloride as an antibacterial agent ( Benzalkonium chloride was not strongly bonded to the cellulose fibers of the tissue layer.

[0010] Viscose-based nonwoven wipes for cleaning hard surfaces treated with zinc pyrithione, which is not necessarily permanently attached, are also known. Zinc pyrithione is a coordination complex of zinc with fungistatic and bacteriostatic properties which, if released, is toxic to aquatic life.

[0011] In addition, due to bacterial metabolism, odorous byproducts (such as volatile sulfonyl compounds or amine compounds) can be formed (see Hughes et al.; Oral malodour-a review, Archives of oral biology 53, suppl. I (2008) S1-S7). For example, Escherichia coli is known to convert L-tryptophan into malodorous compounds (such as indole and ammonia) (see Han et al., Environmental Factors Affecting Indole Production in Escherichia coli, Res Microbiol. 2011; 162 (2): 108-116). For example, the formation of odors in cleaning wipes can cause unsanitary conditions and discomfort to users.

[0012] It is therefore desirable to provide a layer fiber product, in particular a nonwoven product or a tissue product, which provides a skin-friendly and durable antimicrobial treatment and is safe for the environment and the user. It is also desirable to use an antimicrobial agent with zero or very limited risk of developing resistant bacteria.

[0013] It would also be desirable to provide a sheet fabric product that exhibits a persistent antimicrobial effect even after rinsing with water, and / or a sheet fabric product that provides a higher level of hygiene relative to conventional sheet fabric products. Summary of the invention

[0014] This disclosure relates to:

[0015] 1. A layer fiber product comprising at least one layer selected from a nonwoven layer and a tissue layer, wherein at least one layer selected from the nonwoven layer and the tissue layer comprises cellulosic fibers containing an organic polycarboxylic acid, and wherein the organic polycarboxylic acid has at least one carboxyl group covalently bonded to the cellulosic fibers and at least one free carboxyl group.

[0016] The present disclosure includes the following embodiments ("projects"):

[0017] 2. The layer fiber product according to item 1, wherein the organic polycarboxylic acid has two to ten carboxyl groups, preferably three to five carboxyl groups, more preferably three carboxyl groups.

[0018] 3. A layer fiber product according to item 1 or 2, wherein the organic polycarboxylic acid has 2 to 12 carbon atoms in the main chain, for example, 4 to 6 carbon atoms in the main chain, wherein the compound is preferably selected from citric acid, isocitric acid, citraconic acid, tartaric acid, itaconic acid, 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, glutaric acid, α-ketoglutaric acid, malic acid, malonic acid, 2-hydroxymalonic acid, oxalic acid, oxalosuccinic acid, succinic acid, carboxysuccinic acid, 1,2-dimethylsuccinic acid, adipic acid, pimelic acid, 2-methylpropanetricarboxylic acid, aconitic acid, 1,2,4-butanetricarboxylic acid, polymers of acrylic acid, and mixtures thereof, wherein the acid is preferably citric acid.

[0019] 4. The layer fiber product according to any one of items 1 to 3, wherein at least one carboxyl group is covalently bonded to the cellulose fibers by forming an ester group with a cellulose hydroxyl group.

[0020] 5. The layer fiber product according to any one of items 1 to 4, wherein at least one layer is a nonwoven layer comprising:

[0021] (A) cellulose fibers, the cellulose fibers being selected from the group consisting of:

[0022] (A1) natural fibers, preferably pulp fibers or natural fibers derived from cotton, bagasse, hemp, linen, sisal, straw, flax, kapok, millkweed, sisal, abaca, pineapple, flax, hemp, jute or kenaf, more preferably pulp fibers, wherein the pulp fibers may be selected from softwood fibers and hardwood fibers, and

[0023] (A2) semisynthetic fibers, preferably viscose, rayon or lyocell, more preferably viscose or lyocell,

[0024] Wherein the weight proportion of the cellulose fibers is preferably 10 wt % to 100 wt %, more preferably 10 wt % to 80 wt %, in particular 25 wt % to 75 wt %, such as 40 wt % to 70 wt %, based on the total weight of the layer fiber product, and

[0025] wherein the nonwoven layer optionally comprises:

[0026] (B) synthetic fibers, which are selected from polyethylene, polypropylene, polyethylene terephthalate and polyester, wherein the weight proportion of non-cellulosic fibers is preferably 0% to 90% by weight, more preferably 20% to 90% by weight, in particular 25% to 75% by weight, such as 30% to 60% by weight, based on the total weight of the layer fiber product.

[0027] 6. The layer fiber product according to any one of items 1 to 5, wherein the layer fiber product is a multi-ply tissue product, the multi-ply tissue product preferably comprising 2 to 6 superimposed plies, more preferably 2 to 4 plies.

[0028] 7. The layer fiber product according to any one of items 1 to 6, wherein the product is selected from handkerchiefs, napkins, paper hand towels, facial tissues, wound care dressings and cleaning wipes.

[0029] 8. The layer fiber product according to any one of items 1 to 7, wherein the cellulose fibers containing organic polycarboxylic acid are obtained by treating cellulose fibers with an organic polycarboxylic acid, preferably with an organic polycarboxylic acid as defined in any one of items 2 to 3, in the presence of an activating agent.

[0030] 9. The layer fiber product according to any one of items 1 to 8, wherein the surface of the layer fiber product has a post-rinsing pH of 2.0 to 5.5, preferably 2.5 to 5.5, more preferably 3.0 to 5.0, and / or a post-washing pH of 2.0 to 5.0, preferably 2.5 to 4.5, more preferably 3.0 to 4.5.

[0031] 10. A method for producing a layer fiber product, the method comprising the steps of:

[0032] (a) treating the cellulosic fibers with a treatment solution comprising one or more organic polycarboxylic acids or optionally a mixture of one or more organic polycarboxylic acids and their salts, preferably an organic polycarboxylic acid as defined in any one of items 2 to 4, and an activator;

[0033] (β) optionally drying; and

[0034] (γ) curing to obtain the layer fiber product.

[0035] 11. The method according to item 10, wherein at least one, preferably all, of the following conditions are met:

[0036] (i) based on the total weight of the treatment solution, the concentration of the organic polycarboxylic acid in the treatment solution is 2 wt % to 80 wt %, preferably 2.5 wt % to 50 wt %, more preferably 10 wt % to 20 wt %,

[0037] (ii) the treatment time is from 10 seconds to 2 hours, preferably from 30 seconds to 1 hour and 15 minutes, in particular 5 minutes,

[0038] (iii) a curing time of 1 to 10 minutes, preferably 2 to 8 minutes, in particular 5 minutes,

[0039] (iv) The curing temperature is 100°C to 200°C, preferably 110°C to 180°C, more preferably 140°C to 170°C.

[0040] 12. The layer fiber product according to item 8 or the method according to item 10 or 11, wherein the activator is selected from sodium hypophosphite monohydrate, N-N'-carbonyldiimidazole, p-toluenesulfonyl chloride, and a combination of N,N'-dicyclohexylcarbodiimide and 4-pyrrolidinopyridine or 4-dimethylaminopyridine.

[0041] 13. Use of the layer fiber product according to any one of items 1 to 9 as:

[0042] (I) antibacterial wipes for personal hygiene, preferably handkerchiefs, paper towels, toilet paper, pre-moistened toilet paper, baby wipes, feminine hygiene wipes,

[0043] (II) Wound care dressings,

[0044] (III) antimicrobial wipes for use in food service cleaning, household and food production,

[0045] (IV) Cleaning wipes suitable for cleaning surfaces, preferably hard surfaces in a domestic environment or a hospital environment.

[0046] 14. Use of a layer fiber product as defined in any one of items 1 to 9 for reducing the amount of undesirable bacteria or inhibiting the growth of said undesirable bacteria, wherein said undesirable bacteria are selected from Escherichia coli, Enterococcus faecalis, Staphylococcus epidermidis, Staphylococcus aureus and Klebsiella pneumoniae.

[0047] 15. Use of a layer fiber product according to item 14, wherein the log CFU / ml of undesirable bacteria is reduced by at least 5%, such as 10-20%, in particular 15%.

[0048] In case the present description mentions “preferred” embodiments / features, combinations of these “preferred” embodiments / features shall also be considered disclosed, insofar as this combination of “preferred” embodiments / features makes technical sense.

[0049] In the following, the use of the terms "comprising / including / containing" should be understood as disclosing also the term "consisting of" as a more restricted embodiment, insofar as this makes technical sense. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 (ab) : Bacterial counts of Staphylococcus aureus and Klebsiella pneumoniae after 6 hours of contact in viscose-based nonwovens and viscose-PET-based nonwovens treated with organic polycarboxylic acids compared to untreated material.

[0051] Figure 2 (ac) : Escherichia coli in pulp / PP-based nonwovens and viscose-based nonwovens treated with organic polycarboxylic acids compared to untreated materials , Enterococcus faecalis and Staphylococcus epidermidis Bacterial counts after 6 hours of contact. DETAILED DESCRIPTION

[0052] 1 Definition

[0053] The term "layer" as used herein refers to a distinguishable and generally separable cut-to-size tissue web obtained after processing ("converting") one or more base (original) tissue webs. Each individual layer may comprise one or more plies (e.g., one, two, three or four plies). In the case of nonwovens, the term "layer" as used herein refers to a distinguishable and generally separable cut-to-size nonwoven web.

[0054] A "multi-ply tissue product" is defined as a tissue preferably comprising 2 to 6 superimposed plies (eg 2 to 4 plies).

[0055] Also for purposes of the present disclosure, the term "nonwoven" is conventional in the art and may be further defined in the manner described in ISO 9092:2011.

[0056] "Tissue" is defined as base paper produced by a paper machine and comprising natural fibers. We understand by "tissue layer" a single-layer based tissue obtained from a tissue machine. The tissue layer is made by a process comprising the steps of forming an aqueous suspension of pulp fibers (i.e. the so-called "furnish"), depositing the aqueous suspension onto a wire to form a wet web, dewatering the web, drying and creping.

[0057] With respect to the tissue layer, the term "ply" refers to a stratum with a defined fiber composition within the web. One or more plies are formed by depositing one or more pulp furnish streams onto a wire using a pressurized single or multi-layer headbox. This technique is well known to those skilled in the art. This makes it possible to use different kinds of fibers in each layer of the web.

[0058] According to the definition of ISO 4046-2, we understand "pulp" as a fibrous material that is usually of plant origin and has been prepared for further manufacturing methods. "Pulp fibers" used herein include pulp fibers from chemical pulp (such as kraft pulp, sulfate pulp or sulfite pulp), mechanical pulp, thermomechanical pulp, chemical mechanical pulp and / or chemical thermomechanical pulp (abbreviated as CTMP). Pulps derived from both deciduous plants (hardwood) and conifers (softwood) can be used. Fibers can also come from non-woody plants (for example, cereal straw, bamboo, jute or sisal). The pulps used can be primary fiber materials ("virgin fibers"). Optionally, they can be secondary fiber materials ("recycled pulp").

[0059] "Filaments" are fibers that are very long (in principle infinite) in proportion to their diameter. "Staple fibers" are fibers of discrete lengths.

[0060] "Decitex" is a unit of linear density of fibers and yarns, and provides the weight in grams of 10 km of fiber or yarn.

[0061] "Cellulosic fibers" contain carbohydrate units comprising, for example, β(1→4) linked D-glucose units with free cellulose hydroxyl groups allowing for the attachment of organic polycarboxylic acids via covalent bonds.

[0062] "Cellulose hydroxyl groups" are to be understood as hydroxyl groups that are capable of reacting with an acid (preferably an organic polycarboxylic acid) to form a covalent bond (ester carbonyl bond).

[0063] We understand "covalent bonding" as a covalent ester bond formed between cellulose hydroxyl groups and at least one (preferably 1 or 2) of the carboxyl groups of the organic polycarboxylic acid. Thus, a permanent connection of the organic polycarboxylic acid to the cellulose fibers in the nonwoven is achieved.

[0064] A "free carboxyl group" is understood to be a carboxyl group which is able to release a proton.

[0065] The term "substituted" as used herein means substituted by one or more groups selected from the group consisting of halogen groups, carbonyl groups, alkyl groups, alkenyl groups, alkoxy groups, cycloalkyl groups, arylalkenyl groups, aryl groups, aryloxy groups, heteroaryl groups, aryl groups, nitrile groups, hydroxyl groups and heterocyclic groups, and combinations of these groups.

[0066] The term "oxo" as used in this disclosure shall be understood as oxygen attached to another atom via a double bond.

[0067] "Natural fibers" are defined as fibers derived from natural sources such as plant materials.

[0068] "Semisynthetic fibers" (also sometimes called "regenerated fibers") are fibers derived from natural sources (such as plant materials) that are regenerated into cellulosic fibers.

[0069] "Synthetic fibers" are fibers derived from synthetic materials, and are equivalently described as "non-cellulosic fibers" in this disclosure.

[0070] As used in this disclosure, "dry weight of substrate" should be understood as the weight of the substrate (layer fiber product) measured after conditioning at 50% relative humidity and 20°C.

[0071] "Washing" is to be understood as temporarily exposing the layer fiber product to water by immersing the layer fiber product in, for example, warm water.

[0072] "Washing" is to be understood as cleaning a layer fiber product, such as a nonwoven, in a domestic washing machine. Layer fiber products, in particular nonwovens, can thus be subjected to an aqueous solution containing a detergent without losing their structural characteristics.

[0073] "Activators" are defined as compounds that are capable of activating carboxylic acid groups to render them sufficiently reactive toward cellulose hydroxyl groups to form ester bonds between the carboxylic acid groups and the cellulose OH groups. In one embodiment, the activator is capable of dehydrating the carboxylic acid groups, which can result in the formation of internal anhydrides of organic polycarboxylic acids, which are anhydrides formed by the elimination of water from a single molecule.

[0074] "Curing" is defined as the step of promoting a chemical reaction between the organic polycarboxylic acid and the cellulose hydroxyl groups to form covalent ester bonds. In one embodiment, curing also includes drying of the fiber product.

[0075] By the term "treatment solution" we understand a solution containing an organic polycarboxylic acid and optionally a salt of said organic polycarboxylic acid, wherein the optional salt of the organic polycarboxylic acid is a salt corresponding to the selected acid, which may be an activator of the carboxylic acid groups. The treatment solution may be an aqueous solution.

[0076] The unit "CFU / ml" (colony forming units / ml) relates to the number of viable bacterial cells per milliliter of sample. "Unwanted bacteria" are to be understood as bacteria which may be pathogenic or nosocomial. In one embodiment, the unwanted bacteria are associated with the formation of odors. In another embodiment, the unwanted bacteria are resistant bacteria.

[0077] 2 Implementation Plan

[0078] The nonwoven of the present disclosure can be manufactured by any method suitable for comprising a composition of cellulose in the form of natural fibers, semisynthetic fibers or their combination. The nonwoven can comprise natural fibers or semisynthetic fibers having a fiber length between 1 mm and 25 mm. The nonwoven in the present disclosure can also comprise substantially continuous filaments. Natural fibers or semisynthetic fibers and / or continuous filaments can have a homogeneous composition, or can be composed of multicomponent types (including but not limited to sheath / core bicomponent, core / skin / skin bicomponent or tricomponent and side-by-side bicomponent). The nonwoven can be wet-laid, air-laid, carded or directly spun into a web. They can also be composite materials made of different fiber layers, and those layers can be produced using different methods. Examples include but are not limited to layer combinations with meltblown and spun-laid composite materials.

[0079] Nonwovens can be stabilized by many different methods including, but not limited to, thermal bonding by calendering or hot air or steam or ultrasonic energy, mechanical entanglement using needle punching or hydroentanglement, or chemical bonding using adhesives or solvents and pressure. Nonwovens can also contain staple fibers, pulp fibers and / or filaments.

[0080] The linear density of the filaments can be 0.3 to 3 dtex, for example 0.5 to 2.4 dtex, specifically 0.8 to 2.0 dtex. They can be produced by melting the thermoplastic polymer and extruding through a fine nozzle. Thereafter, the polymer is cooled, for example, by an air stream blown at the polymer stream and along the polymer stream, and hardened into a strand that can be processed by drawing, stretching or curling. Chemicals for additional functions can be added to the surface.

[0081] Any thermoplastic polymer with cohesive properties suitable for allowing itself to be stretched in a molten state can be used to produce meltblown fibers or spun-web fibers. Exemplary fibers that can be used as non-cellulose fibers (synthetic fibers) are fibers made of polyolefins (such as polyethylene (PE) and polypropylene (PP)), or polyesters (such as polylactide and polyethylene terephthalate (PET) or polybutylene terephthalate), or polyamides. Copolymers of these polymers and natural polymers with thermoplastic properties can also be used. Based on the gross weight of the layer fiber product, the weight proportion of non-cellulose fibers can be 0 weight % to 90 weight %, specifically 20 weight % to 90 weight %, particularly 25 weight % to 75 weight %, such as 30 weight % to 60 weight %.

[0082] Long filament can also use natural fiber to produce by chemical treatment the solution that comprises cellulose.After this, long filament can be spun into semi-synthetic viscose filament by cellulose xanthate solution and subsequent sulfur treatment.Another kind of method for producing semi-synthetic filament is to use cellulose-containing NMMO (N-methylmorpholine N-oxide) solution to produce lyocell fiber filament, and described solution is extruded through spinneret hole to form latent filament (latent filament), and described latent filament is hardened into filament after this.Depend on the type of fiber product and its manufacturing technology, these long filaments can be cut into certain length then, to provide suitable fiber.

[0083] Cellulose fibers according to the present disclosure can be produced, for example, from virgin pulp raw materials. In one embodiment, the cellulose fibers are produced from recycled pulp materials. Depending on the storage conditions of the recycled pulp materials, some types may be contaminated by bacteria. The embodiments described herein can be used to inhibit such bacterial contamination. The recycled pulp materials can be derived from recycled office paper.

[0084] Suitable cellulose fibers to be used according to the present disclosure may contain long-chain fibrous cellulose fractions as the main structural building components, which are present in naturally occurring cellulose-containing cells, particularly those of lignified plants. The fibers may be isolated from lignified plants by a digestion step to remove or reduce the content of lignin and other extractables and an optional bleaching step.

[0085] The weight proportion of cellulose fibers, based on the total weight of the layer fiber product, can be 10 to 100 wt%, specifically 10 to 80 wt%, in particular 25 to 75 wt%, such as 40 to 70 wt%.

[0086] Cellulosic fibers can be selected from natural fibers, especially those with water absorption capacity and a tendency to contribute to the formation of cohesive sheets. In a specific embodiment, natural fibers are derived from seed hair fibers (such as cotton, kapok or milkweed), leaf fibers (such as sisal, abaca, pineapple or hemp (for example, New Zealand hemp); bast fibers, such as flax, bagasse, hemp, jute, kenaf, flax, straw, or woody plants (pulp). Pulp fibers can be more desirable. Wood pulp fibers are particularly well suited for use, and both softwood fibers (which are generally derived from conifers) and hardwood fibers (generally from deciduous trees) are suitable. A portion or all of the natural staple fibers may comprise pulp having a fiber length between 1 mm and 7.5 mm. Pulp fibers may account for at least 25% by weight of the cellulose fiber content, such as 40% to 98% by weight, specifically 60% to 98% by weight, more specifically 75% to 95% by weight, particularly 83% to 90% by weight.

[0087] The pulp fiber length can be 1 mm to 5 mm, such as 2 mm to 4 mm, specifically 3 mm for softwood fibers, and can be 0.5 mm to 4 mm, specifically 1 mm to 3 mm (e.g., 1 mm to 2 mm), more specifically about 1.2 mm for hardwood fibers. The pulp fiber length of recycled fibers is a mixture of these lengths and can be even shorter.

[0088] The cellulosic fibers may also be selected from semi-synthetic fibers as described above (eg derived from viscose, rayon, or lyocell), whereby the use of viscose and lyocell may be desirable in certain embodiments.

[0089] The cutting of the semisynthetic fiber bundle is usually performed to produce a single cut length, which can be modified by changing the distance between the knives of the cutting wheel. Depending on the intended use, different fiber lengths are used, for example 2 mm to 25 mm, specifically 5 mm to 25 mm, more specifically 5 mm to 15 mm, and particularly 6 mm to 12 mm. The cellulose staple fibers can all have the same or substantially the same length, or a variety of different lengths can be used. Based on the total weight of the cellulose fibers, the weight proportion of the semisynthetic fibers can be 2% to 50% by weight, specifically 5% to 50% by weight, more specifically 2% to 40% by weight, for example 5% to 25% by weight, and particularly 10% to 17% by weight.

[0090] The basis weight of the tissue layer in the present disclosure is 8 g / m 2 Up to 50g / m 2 , specifically 10g / m 2 Up to 30g / m 2 , more specifically 12g / m2 Up to 25g / m 2 The same applies to the nonwoven and the resulting layers.

[0091] Based on the potential compatibility of the production methods (wet forming), "tissue" production is included in papermaking technology. Tissue production is distinguished from paper production by its extremely low basis weight and its much higher tensile energy absorption index. Paper and tissue also usually differ in the elastic modulus, which as a material parameter characterizes the stress-strain properties of these planar products.

[0092] The high tensile energy absorption index of tissue paper is caused by external or internal creping. The former is caused by compression of the paper web attached to the drying cylinder due to the action of the creping blade or, in the latter case, by the speed difference between the two wires ("fabrics"). This causes the still moist, plastically deformable paper web to break up internally by pressing and shearing, making it more stretchable under load than uncreped paper. A high tensile energy absorption index can also be achieved by giving the tissue paper a 3D structure through the wires themselves. Most of the typical functional properties of tissue paper and tissue products are derived from the high tensile energy absorption index (see DIN EN 12625-4 and DIN EN 12625-5).

[0093] Tissue paper can be produced from papermaking fibers according to the "conventional process", such as in the manufacture of "dry-laid creped tissue paper" or "wet-laid creped tissue paper" or in the "structured tissue paper process", such as the Through Air Drying (TAD) manufacturing process, the manufacture of uncreped through air drying (UCTAD) tissue paper or alternative manufacturing processes, such as Voith's Advanced Tissue Molding System (ATMOS), or Georgia Pacific's Energy Efficient Technologically Advanced Drying eTAD, or MetsoPaper's Structured Tissue Technology SST. It is also possible to use hybrid processes, such as NTT (New Textured Tissue), which is a variation of the conventional process.

[0094] The conventional dry creping manufacturing method comprises the following steps:

[0095] - Pressing and drying the wet paper fibers into a sheet on a large diameter heated cylinder (also called a Yankee dryer); and

[0096] - The sheet of dried paper fibres is subsequently separated and creped by metal blades applied against the cylinder, crosswise to the direction of rotation of the cylinder.

[0097] The creping operation creates undulations in the sheet in a direction that crosses the direction of travel of the sheet. The creping operation increases the thickness of the sheet and imparts elasticity and touch (soft touch) properties to the sheet.

[0098] The TAD manufacturing method includes the following steps:

[0099] - molding a sheet of wet paper fibers on a fabric; and

[0100] The sheet is then at least partially dried by a stream of hot air passing through the sheet.

[0101] The dried sheet may then be creped.

[0102] Furthermore, in the manufacture of the tissue web to be used, the method described in PCT / EP2015 / 059326 (filing date: April 29, 2015; invention name: "Tissue paper comprising pulp fibers originating from Miscanthus and method for manufacturing the same", the entire contents of which are incorporated herein by reference for the sole purpose of providing details of such methods) can be used. Specifically, reference is made to the description of item 3 on pages 22 to 27 of the application and the details of the TAD method disclosed therein (e.g., 3D-shaped fabrics, permeable drying cylinders). The parameters described in this paragraph are also valid for the use of ATMOS technology.

[0103] Once tissue has been manufactured, a unique manufacturing operation known as a converting operation is typically employed to form tissue products such as paper towels, toilet tissue, bathroom tissue or toilet paper, wiping tissue, handkerchiefs.

[0104] The polycarboxylic acid in the present disclosure may have 2 to 12 carbon atoms in the main chain, for example 4 to 6 carbon atoms in the main chain, in particular 5 carbon atoms in the main chain. In one embodiment, the organic polycarboxylic acid is a compound represented by the following formula (I):

[0105]

[0106] in

[0107] n is 0 to 11, such as 1, 2 or 3, and

[0108] R1 is selected from the group consisting of a hydrogen atom, an alkyl group which may be substituted, an alkylene group which may be substituted, an oxo group and a hydroxyl group,

[0109] R2 is a hydrogen atom or a hydroxyl group,

[0110] R3 and R4 are each independently selected from a hydrogen atom, an alkyl group which may be substituted, a carboxyl group, an oxo group and a hydroxyl group, provided that at least one of R3 and R4 is a carboxyl group.

[0111] According to another embodiment, the organic polycarboxylic acid is selected from citric acid, isocitric acid, citraconic acid, tartaric acid, itaconic acid, 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, glutaric acid, α-ketoglutaric acid, malic acid, malonic acid, 2-hydroxymalonic acid, oxalic acid, oxalosuccinic acid, succinic acid, carboxysuccinic acid, 1,2-dimethylsuccinic acid, adipic acid, pimelic acid, 2-methyltricarboxylic acid, aconitic acid, 1,2,4-butanetricarboxylic acid, polymers of acrylic acid, and mixtures thereof, wherein the acid may, for example, be citric acid.

[0112] In the present disclosure, the content of the organic polycarboxylic acid in the treatment solution may be 2 wt % to 80 wt %, specifically 2.5 wt % to 50 wt %, more specifically 10 wt % to 20 wt %, based on the total amount of the solution. The pKa value of the organic polycarboxylic acid may be between 1 and 6.5.

[0113] In one embodiment, the organic polycarboxylic acid exhibits a water solubility (at 20°C) of at least 2.0 wt%, specifically at least 2.5 wt%, or at least 10 wt% (for reference, the solubility of citric acid in water at 20°C is known to be 59.2% w / w).

[0114] In one embodiment, one carboxyl group of the organic polycarboxylic acid is covalently bound to the cellulose fiber by forming an ester group with the cellulose hydroxyl group. In another embodiment, at least one (such as 1 to 9, specifically 2 to 4, especially 2) free carboxyl groups provide acidic properties.

[0115] The layer fiber product of the present disclosure (wherein the cellulose fiber is covalently bonded to the organic polycarboxylic acid) is obtained by treating the cellulose fiber with the organic polycarboxylic acid in the presence of an activator. At least 1 (specifically 1 or 2, especially 1) carboxyl group is required to allow the organic polycarboxylic acid to covalently bond to the cellulose hydroxyl groups on the cellulose fiber, and at least 1 (specifically 1 to 9, more specifically 2 to 4, especially 2) free carboxyl groups provide acidic properties. The presence of a few remaining free carboxyl groups after bonding causes a further reduction in pH on the surface of the layer fiber product.

[0116] When measured according to the method described in the experimental part of the present disclosure, the surface layer of the layer fiber product in the present disclosure can have a post-rinsing pH of 2.0 to 5.5, specifically 2.5 to 5.5, more specifically 3.0 to 5.0; and / or when measured according to the method described in the experimental part of the present disclosure, the surface layer of the layer fiber product in the present disclosure can have a post-washing pH of 2.0 to 5.0, specifically 2.5 to 4.5, more specifically 3.0 to 4.5. Low pH inhibits or limits bacterial growth, and thus prevents the spread of pathogenic bacteria and the development of nosocomial infections. In addition, the formation of odorous byproducts can also be inhibited.

[0117] In the present disclosure, the layer fiber product may be one of a handkerchief, a napkin, a paper towel, a facial tissue, a wound care dressing, or a cleaning wipe.

[0118] In one aspect of the present disclosure, the application fields of the layer fiber product include but are not limited to the use of the layer fiber product as:

[0119] (I) antibacterial wipes for personal hygiene, such as handkerchiefs, paper towels, toilet paper, pre-moistened toilet paper, baby wipes, feminine hygiene wipes,

[0120] (II) Wound care dressings,

[0121] (III) antimicrobial wipes for use in food service cleaning, household and food production,

[0122] (IV) Cleaning wipes suitable for cleaning surfaces such as hard surfaces in a domestic or hospital environment.

[0123] The present disclosure also relates to a method for producing a layer fiber product, the method comprising the steps of:

[0124] (a) treating the cellulosic fibers with a treatment solution comprising one or more organic polycarboxylic acids or optionally a mixture of one or more organic polycarboxylic acids and their salts, preferably an organic polycarboxylic acid as defined in the present disclosure, and an activator,

[0125] (β) optionally drying, and

[0126] (γ) curing to obtain the layer fiber product.

[0127] In a specific embodiment, the organic polycarboxylic acid is mixed with its salt, wherein the salt is a salt corresponding to the selected acid. When the organic polycarboxylic acid and its corresponding salt are mixed in a 1:1 molar ratio, the mixture exhibits a buffering capacity that stabilizes the pH of the resulting treatment solution.

[0128] In another embodiment, the treatment with the treatment solution according to the present disclosure is performed by soaking, spraying, slot coating, or foam coating, whereby soaking or spraying may be desirable.

[0129] In another embodiment, the method for producing a layer fiber product is further specified by one or more, or even all, of the following conditions:

[0130] (i) based on the total weight of the treatment solution, the concentration of the organic polycarboxylic acid in the treatment solution is 2 wt % to 80 wt %, specifically 2.5 wt % to 50 wt %, more specifically 10 wt % to 20 wt %,

[0131] (ii) the treatment time is 10 seconds to 2 hours, specifically 30 seconds to 1 hour and 15 minutes, especially 5 minutes,

[0132] (iii) a curing time of 1 to 10 minutes, specifically 2 to 8 minutes, especially 5 minutes,

[0133] (iv) The curing temperature is 100°C to 200°C, specifically 110°C to 180°C, more specifically 140°C to 170°C.

[0134] In a specific embodiment, the treatment time mentioned above should be understood as the soaking time.

[0135] The activator in the present disclosure can be selected from sodium hypophosphite monohydrate, N-N'-carbonyldiimidazole (CDI), p-toluenesulfonyl chloride (TosCl), a combination of N,N'-dicyclohexylcarbodiimide and 4-pyrrolidinylpyridine or 4-dimethylaminopyridine. The organic polycarboxylic acid and the activator are dissolved in the treatment solution at a molar ratio (acid: activator) of 0.8 to 1.2 (specifically 0.9 to 1.1, such as 1.0).

[0136] According to another aspect of the present disclosure, the treatment solution comprising an organic polycarboxylic acid may further comprise a surfactant. The surfactant reduces the surface tension of the treatment solution in which it is dissolved. This is particularly suitable for materials containing synthetic fibers (e.g., fibers comprising PE, PP, etc.) that exhibit high hydrophobicity.

[0137] The present disclosure also relates to the use of the layer fiber product for reducing the amount of undesirable bacteria or inhibiting the growth of undesirable bacteria. In one embodiment, the undesirable bacteria are selected from Escherichia coli, Enterococcus faecalis, Staphylococcus epidermidis, Staphylococcus aureus and Klebsiella pneumoniae. According to another aspect of the present disclosure, the log CFU / ml of the bacteria is reduced by at least 5%, such as 10-20%, in particular 15%.

[0138] 3 Examples

[0139] 3.1 Raw materials and chemicals

[0140] Substrate for treatment (fiber products)

[0141] Different types of nonwovens are used:

[0142] Viscose-based nonwovens (pure viscose, TORK Long-lasting, 70 g / m 2 )

[0143] Viscose / PET-based nonwoven (60% by weight of viscose and 40% by weight of polyester, Suominen, 70 g / m 2 )

[0144] Pulp / PP based nonwoven (65 wt% pulp fibers and 35 wt% polypropylene fibers, TORK industrial cleaning cloth (520), 65 g / m 2 )

[0145] Chemicals

[0146] For modification of layer fiber products, the following chemicals are used:

[0147] Citric acid (Thermo Fisher GmbH, Karlsruhe, Germany)

[0148] Sodium hypophosphite monohydrate (NaH2PO2·H2O, Thermo Fisher GmbH,

[0149] Karlsruhe, Germany)

[0150] Ammonium citrate (Acros Organics BVBA, Loughborough, United Kingdom)

[0151] · Lactic acid (Acros Organics BVBA, Loughborough, United Kingdom).

[0152] 3.2 Nonwovens treatment using organic polycarboxylic acids

[0153] The dry weight of the substrate to be treated is determined after conditioning it at 50% relative humidity and 20°C.

[0154] The nonwoven was soaked in a treatment solution containing (i) citric acid or an equimolar mixture of citric acid and ammonium citrate, and (ii) sodium hypophosphite monohydrate as an activator (molar ratio organic polycarboxylic acid: activator = 1:1). The treated nonwoven was wrung out, dried, and cured at 160° C. for 5 minutes.

[0155] 3.3 pH measurement on nonwoven surfaces

[0156] The pH of the surface of the nonwoven viscose-based, viscose-PET-based or pulp / PP-based wipes was evaluated after rinsing and / or after washing.The samples treated with organic polycarboxylic acids were compared with untreated samples and samples treated with organic monocarboxylic acids.

[0157] Use a pH meter (VWR TM The pH of the nonwoven sample surface was measured using a sympHony, SB80PI) and a flat end pH electrode (HAMILTON Flattrode). The nonwoven sample was rinsed once in tap water and wrung out before measurement. The pH meter rod was rinsed with deionized water and immersed in a 0.9% NaCl solution. A small drop of saline solution (0.9% NaCl) was added to the electrode head. Then, the electrode head was contacted with different nonwoven materials to wet the nonwoven sample at the measuring point. pH was measured at three different spots on the nonwoven and the average value was recorded.

[0158] 3.4 Rinse or wash nonwovens with water

[0159] After solidification (referring to item 3.2), the nonwoven material is rinsed in warm water, and pH is measured according to the above method. The rinsing of treated material is carried out as follows: the nonwoven material is immersed in a 7L plastic beaker with warm water, and wrung out. Then, fresh water is added to the beaker, and the process is repeated once. After rinsing, before pH measurement, the nonwoven is wrung out completely. In one embodiment, "warm" water can have a temperature of 30 to 40 ℃ (e.g., 35 ℃).

[0160] If applicable, detergent was also used at 40°C in a household detergent (model: WKG130 NDS TDos, Miele) Grumme) washing the treated nonwoven. The amount of detergent can be determined by the automatic dosing system contained in the washing machine. After a laundry washing cycle, the pH of the nonwoven surface is measured again using the above method.

[0161] Example 1-1

[0162] As described in item 3.2, the sample treatment with organic polycarboxylic acid was carried out. A viscose fiber material was used as nonwoven material and treated with a treatment solution containing 20% ​​by weight of citric acid (molar mass: 192.12 g / mol) and 10% by weight of sodium hypophosphite monohydrate (105.99 g / mol), based on the total weight of the solution, i.e. a molar ratio (polycarboxylic acid / activator) of about 0.9. The soaking time was 5 minutes.

[0163] Washing was performed according to the general method described in item 3.4.

[0164] As determined by the method in item 3.3, the pH value of the nonwoven surface after washing was 3.7.

[0165] Examples 1-2 to 6-3 and Reference Examples 1 to 6

[0166] Sample preparation was performed in the same manner as set forth in Example 1-1, except for the differences shown in Table 1 and explained further below. The reference examples were not subjected to any treatment with an organic polycarboxylic acid prior to rinsing and / or washing with water.

[0167] In Examples 1-2, 2-2, and 3 to 6, the soaking time was reduced to 30 seconds.

[0168] In Examples 2-1, 2-2 and Reference Example 2, a viscose / PET-based nonwoven was used.

[0169] In Examples 4-1 to 4-3, 6-1 to 6-3, and Reference Examples 4 and 6, a pulp / PP-based nonwoven was used. In addition, for comparative purposes, 10 wt% of lactic acid (an organic monocarboxylic acid) was used in Examples 3-3 and 4-3.

[0170] In Examples 3-2 and 4-2, a mixture of 5 wt % of citric acid and 5 wt % of an acid ammonium salt was used.

[0171] In Examples 3-1, 5-1 and 6-1, 10% by weight of citric acid was used. In Examples 5-2 and 6-2, 5% by weight of citric acid was used. In Examples 5-3 and 6-3, 2.5% by weight of citric acid was used.

[0172]

[0173] *In addition, antimicrobial testing was performed using standard test method AATCC 100 (see also item 3.5).

[0174] The test data in Table 1 confirm that all nonwovens treated with organic polycarboxylic acids (such as citric acid) show lasting acidic pH even after being rinsed with water. In contrast, treatment with lactic acid (Comparative Example 3-3 or 4-3) causes pH value to be very close to the pH value of the corresponding reference example. This difference can only be explained by forming a covalent chemical bond (ester bond) between the carboxyl group of the polycarboxylic acid (citric acid) and the hydroxyl group of the cellulose fibers present in all substrates. Incidentally, the presence of a covalent bond (ester carbonyl bond) can also be shown by FTIR analysis (see Bing Li, et al in Cellulose, April 2015, Volume 22, Issue 2, pp 1295-1309 "Preparation and catalytic performance of Fe (III) -citric acid-modified cotton fiber complex as a novel cellulose fiber-supported heterogeneous photo-Fenton catalyst").

[0175] It can also be seen that in most cases, especially if the amount of polycarboxylic acid (e.g., citric acid) is at least 5 wt. %, in particular at least 10 wt. % (based on the total weight of the solution), a persistent acidic pH can be achieved in the nonwoven treated with the organic polycarboxylic acid even after washing with a detergent when compared to an untreated nonwoven. Thus, a persistent antimicrobial effect of the nonwoven-based layer fiber product is also given after washing the product. Therefore, the nonwoven-based layer fiber product of the present disclosure can be reused after washing without losing its antimicrobial activity.

[0176] 3.5 Antibacterial effect

[0177] To determine whether the acid treatment has an antimicrobial effect, treated nonwovens (rinsed or washed) and untreated nonwovens as reference materials were examined. The antibacterial effect was measured using a modified version of the standard method AATCC 100 "Assessment of Antibacterial Finishes on Textile Materials" (see https: / / antimicrobial.specialtytesting.com / products / aatcc-100-assessment-of-anti bacterial-finishes-on-textile-materials).

[0178] Examples 1-1, 2-1, 2-2 and Reference Example 2

[0179] Bacterial strains of Staphylococcus aureus (P5) and Klebsiella pneumoniae (P119) were mixed into 100% nutrient broth (tryptic soy broth, TSB 211825, Difco). The initial concentration was 10 5 CFU / ml. 1 ml of bacterial suspension was added to different nonwoven samples and incubated at 35°C for 6 hours. After incubation, bacteria were taken out from the nonwoven using a homogenizer and Letheen broth (Acumedia) and spread on trypticase Soy Agar (TSA, 211043, from BBL).

[0180] Figure 1 (ab) The bacterial counts after 6 hours of incubation (35°C) are shown.

[0181] The results clearly show that the presence of organic polycarboxylic acids covalently bound to the cellulose fibers within the layer inhibits bacterial growth. No Staphylococcus aureus was observed for the treated viscose-based nonwovens and viscose / PET-based nonwovens. ( Figure 1 a) After 30 seconds of immersion time, only Klebsiella pneumoniae was observed ( Figure 1 b) Slight growth of (Example 2-2).

[0182] In contrast, with 10 5 The bacteria in the untreated material were able to grow by 2-3 log units up to 10 CFU / ml compared to the initial concentration. 7 -10 8 CFU / ml (see Example 2).

[0183] By inhibiting or limiting bacterial growth of E. coli and Klebsiella pneumoniae, the risk of pathogenic bacteria transmission and development of nosocomial infections can be reduced. In addition, the permanent slightly acidic pH inhibits or limits bacterial growth and reduces the formation of odorous byproducts caused by bacterial metabolism in the layer fiber products of the present disclosure.

[0184] Examples 5-1, 6-1 and Reference Examples 5 and 6

[0185] Bacterial strains of Escherichia coli (P2), Enterococcus faecalis (P120), and Staphylococcus epidermidis (P136) were mixed into 5% nutrient broth (TSB and saline, 0.9%). The initial concentration was 10 5CFU / ml. 1 ml of bacterial suspension was added to different nonwoven samples and incubated at 35°C for 6 hours. After incubation, bacteria were removed from the nonwoven using a homogenizer and Letheen broth and plated on TSA.

[0186] Figure 2 (ac) Shown are bacterial numbers after 6 hours incubation in 5% TSB at 35° C. The limit of detection in this experiment was 200 bacteria / ml (ie, 2.3 log CFU / ml).

[0187] Compared with the initial concentration, the E. coli bacteria in Reference Examples 5 and 6 ( Figure 2 a) It was able to grow about 3 log CFU / ml, while the layer fiber product of the present disclosure exerted a growth inhibition effect of 1 log CFU / ml. ( Figure 2 b) and Staphylococcus epidermidis ( Figure 2 c) No growth was possible at all in the ply fiber products of the present disclosure, whereas in the case of reference examples 5 and 6 bacterial growth was still observed.

[0188] Thus, it is clearly shown that the presence of the organic polycarboxylic acid covalently bonded to the cellulose fibers within the layer fiber product inhibits or limits bacterial growth. Thus, the risk of the spread of unwanted bacteria (e.g., pathogenic bacteria or nosocomial bacteria) and the associated odor formation is reduced.

Claims

1. A layer fiber product comprising at least one layer selected from a nonwoven layer and a tissue layer, wherein at least one layer selected from the nonwoven layer and the tissue layer comprises cellulosic fibers containing an organic polycarboxylic acid, and wherein the organic polycarboxylic acid has at least one carboxyl group covalently bonded to the cellulosic fibers and at least one free carboxyl group.

2. The layer fiber product according to claim 1, wherein the organic polycarboxylic acid has two to ten carboxyl groups, preferably three to five carboxyl groups, more preferably three carboxyl groups.

3. A layer fiber product according to claim 1 or 2, wherein the organic polycarboxylic acid has 2 to 12 carbon atoms in the main chain, for example 4 to 6 carbon atoms in the main chain, wherein the compound is preferably selected from citric acid, isocitric acid, citraconic acid, tartaric acid, itaconic acid, 1,2,3-propanetricarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, glutaric acid, α-ketoglutaric acid, malic acid, malonic acid, 2-hydroxymalonic acid, oxalic acid, oxalosuccinic acid, succinic acid, carboxysuccinic acid, 1,2-dimethylsuccinic acid, adipic acid, pimelic acid, 2-methylpropanetricarboxylic acid, aconitic acid, 1,2,4-butanetricarboxylic acid, polymers of acrylic acid, and mixtures thereof, wherein the acid is preferably citric acid.

4. The layer fiber product according to any one of claims 1 to 3, wherein at least one carboxyl group is covalently bonded to the cellulose fibers by forming an ester group with a cellulose hydroxyl group.

5. The layer fiber product according to any one of claims 1 to 4, wherein at least one layer is a nonwoven layer, the nonwoven layer comprising: (A) cellulose fibers, the cellulose fibers being selected from the group consisting of: (A1) natural fibers, preferably pulp fibers or natural fibers derived from cotton, bagasse, hemp, flax, sisal, straw, flax, kapok, milkweed, sisal, abaca, pineapple, flax, hemp, jute or kenaf, more preferably pulp fibers, wherein the pulp fibers may be selected from softwood fibers and hardwood fibers, and (A2) semisynthetic fibers, preferably viscose fibers, rayon fibers or lyocell fibers, more preferably viscose fibers or lyocell fibers, Wherein the weight proportion of the cellulose fibers is preferably 10 wt % to 100 wt %, more preferably 10 wt % to 80 wt %, in particular 25 wt % to 75 wt %, such as 40 wt % to 70 wt %, based on the total weight of the layer fiber product, and wherein the nonwoven layer optionally comprises: (B) synthetic fibers, which are selected from polyethylene, polypropylene, polyethylene terephthalate and polyester, wherein the weight proportion of non-cellulosic fibers is preferably 0% to 90% by weight, more preferably 20% to 90% by weight, in particular 25% to 75% by weight, such as 30% to 60% by weight, based on the total weight of the layer fiber product.

6. The layer fiber product according to any one of claims 1 to 5, wherein the layer fiber product is a multi-ply tissue product, the multi-ply tissue product preferably comprising 2 to 6 superimposed plies, more preferably 2 to 4 plies.

7. The layer fiber product according to any one of claims 1 to 6, wherein the product is selected from handkerchiefs, napkins, paper towels, facial tissues, wound care dressings and cleaning wipes.

8. The layer fiber product according to any one of claims 1 to 7, wherein the cellulosic fibers containing organic polycarboxylic acid are obtainable by treating cellulosic fibers with an organic polycarboxylic acid, preferably with an organic polycarboxylic acid as defined in any one of claims 2 to 3, in the presence of an activating agent.

9. The layer fiber product according to any one of claims 1 to 8, wherein the surface of the layer fiber product has a post-rinsing pH of 2.0 to 5.5, preferably 2.5 to 5.5, more preferably 3.0 to 5.0, and / or a post-rinsing pH of 2.0 to 5.0, preferably 2.5 to 4.5, more preferably 3.0 to 4.

5.

10. A method for producing a layer fiber product, the method comprising the steps of: (a) treating the cellulosic fibers with a treatment solution comprising one or more organic polycarboxylic acids or optionally a mixture of one or more organic polycarboxylic acids and their salts, preferably an organic polycarboxylic acid as defined in any one of claims 2 to 4, and an activator; (β) optionally drying; and (γ) curing to obtain the layer fiber product.

11. The method according to claim 10, wherein at least one, preferably all, of the following conditions are met: (i) based on the total weight of the treatment solution, the concentration of the organic polycarboxylic acid in the treatment solution is 2 wt % to 80 wt %, preferably 2.5 wt % to 50 wt %, more preferably 10 wt % to 20 wt %, (ii) the treatment time is from 10 seconds to 2 hours, preferably from 30 seconds to 1 hour and 15 minutes, in particular 5 minutes, (iii) a curing time of 1 to 10 minutes, preferably 2 to 8 minutes, in particular 5 minutes, (iv) The curing temperature is 100°C to 200°C, preferably 110°C to 180°C, more preferably 140°C to 170°C.

12. The layer fiber product according to claim 8 or the method according to claim 10 or 11, wherein the activator is selected from sodium hypophosphite monohydrate, N-N'-carbonyldiimidazole, p-toluenesulfonyl chloride, and a combination of N,N'-dicyclohexylcarbodiimide and 4-pyrrolidinopyridine or 4-dimethylaminopyridine.

Images