Bio-based adhesive composition for nonwoven materials

Abstract

The present invention relates to a bio-based adhesive composition that is environmentally friendly, renewable, compostable and / or biodegradable. A bio-based composition includes chitosan, an acid, and a plasticizer. By treating a nonwoven material with the bio-based adhesive according to the present invention, it is possible to provide a nonwoven material exhibiting excellent mechanical properties. The adhesive compositions according to the present invention are readily useful for treating different types of nonwoven materials, and can be adapted to provide certain properties to certain nonwoven materials and applications.

Description

Technical Field

[0001] The present invention relates to an environmentally friendly, renewable, compostable and / or biodegradable bio-based adhesive composition. The bio-based composition comprises chitosan, an acid and a plasticizer, wherein the plasticizer is a linear polyol and / or a non-macrocyclic sugar. The present invention also relates to a method for treating a nonwoven material with the bio-based adhesive composition according to the present invention.

[0002] Composition according to the present invention is suitable as the adhesive for dissimilar nonwoven materials.Handling various nonwoven materials with adhesive composition according to the present invention provides the nonwoven material with excellent mechanical properties.In addition, adhesive composition according to the present invention is easy to be used for handling dissimilar nonwoven materials, and can be suitable for providing specific properties for some nonwoven material and application. Background Art

[0003] Nonwoven materials are fabric-like materials made of long or short fibers, bonded together by chemical, mechanical, thermal or solvent treatment. Nonwoven fabrics are also defined as sheet or web structures bonded together by mechanical, thermal or chemical entanglement of fibers or filaments (as well as by perforated films). The term is used in the textile manufacturing industry to refer to fabrics that are neither woven nor knitted, such as felt. They are flat or tufted porous sheets made directly from individual fibers, molten plastic or plastic film.

[0004] Nonwovens can provide specific functionality such as absorbency, water repellency, softness, strength, flame retardancy, cushioning, thermal insulation, acoustic insulation, filtration, bacterial barrier, and sterility. These properties are often combined to create fabrics that are suitable for specific applications while achieving a good balance between product life and cost. They can mimic the look, texture, and strength of woven fabrics and can be as bulky as thick padding. Combined with other materials, they provide a range of products with different properties and can be used alone or as components of apparel, home furnishings, healthcare, engineering, industrial, and consumer products. Airlaid, Wetlaid, and Carded Nonwovens

[0005] The production of nonwoven materials begins with arranging fibers into a web. There are different technologies for arranging fibers, thereby producing nonwoven materials with different properties, suitable for different applications. The example of nonwovens produced by different technologies is wet-laid, air-laid, carded, spunlaid and air-laid nonwovens. The web may have a limited initial strength after the web is formed, and generally needs to be consolidated by applying an adhesive to the web, by thermal treatment or by mechanical treatment. By a series of finishing processes, further diversity can be added to the nonwoven material.

[0006] The principle of producing wet-laid nonwovens is similar to that of papermaking. A thin slurry of water and fibers is deposited on a moving wire screen, where the water is drained off and the fibers form a web. The web is further dewatered and dried by pressing between rolls. Binders are often included in the process, such as using a size press, spraying, or adding to the pulping process to increase the strength of the nonwoven material.

[0007] In the air-laid process, air is used as a medium to form a continuous web. Typically, fibers are dispersed in an air stream and deposited on, for example, a moving wire. The resulting deposit is then compressed, for example, by pressure or vacuum. However, due to the hydrogen bonds formed during the wet process, the material is completely unbonded at this stage because it cannot build up internal strength like, for example, wet-laid nonwovens or paper. In order to achieve bonding or other mechanical improvements in air-laid nonwovens, adhesives are typically added and can be introduced at different stages of the manufacturing process depending on the type of adhesive used.

[0008] The production of carded nonwovens is a dry-laid nonwoven process, i.e., dry fibers are mixed and then conveyed onto a moving metal wire. They are then combed into a web by a carding machine, which is a rotating drum or a series of drums covered with card wires (toothed strips). The exact configuration of the carding machine will depend on the type of fiber to be produced and the basis weight. The fiber bonding of the carded nonwoven usually involves hydroentanglement (spunlacing) of the fibers with a high-pressure water jet. Binders are also often added to carded nonwoven materials to increase strength and / or other properties.

[0009] Traditionally, liquid adhesives, slurries, suspensions, foams or powder adhesives have been used in the manufacture of nonwoven materials. The most common bonding technology is to add a liquid adhesive to the nonwoven material, such as by dipping, coating or spraying.

[0010] Binders are added to various nonwoven materials to improve the strength of the material, but may also provide or improve other properties that are desired in a particular nonwoven material or application, such as softness, flexibility, water repellency, or antimicrobial properties.

[0011] The properties desired for a particular nonwoven material or a particular application of the nonwoven material can be further tailored by adjusting the amount of binder composition added (ie, application level).

[0012] An example of desired performance is the softness of airlaid nonwoven materials used to make different sanitary products such as disposable diapers, feminine hygiene products, industrial or consumer wipes, wet wipes and napkins. Sanitary products are usually characterized by their large volume, softness and high water absorption. Elongation is a key requirement for these soft airlaid nonwoven materials. If it is too hard, i.e., does not have the flexibility of a soft feel, the airlaid nonwoven will be considered to be unpleasant for the user. In the production process of airlaid nonwoven materials and in the step of converting to the final product (for example, converting the airlaid nonwoven material into a napkin), elongation is also crucial because the machine causes high tension in the material, which requires the material to have a high elongation so as not to break. In addition, if the airlaid nonwoven material is not strong and flexible enough, the material may break when used. Therefore, when developing airlaid nonwoven materials for these applications, it is crucial to combine strength, soft feel and elongation. Treating an airlaid nonwoven material with a composition according to the present disclosure will provide an airlaid nonwoven material having the desired softness, strength, and elongation.

[0013] An example of the desired properties of the adhesive composition itself is the good applicability of the adhesive to different nonwoven materials. The nonwoven material of the carding is relatively dense, and it may be challenging to achieve satisfactory application of the adhesive in the nonwoven material of the carding. An alternative method of applying the adhesive in more challenging materials is to use foam impregnation. This requires that the adhesive is easy to foam with a common blowing agent.

[0014] In an attempt to reduce the use of synthetic binders (i.e., plastic binders), attention has been paid to bio-based polymers that can replace synthetic polymers used in nonwovens. However, to date, no alternative has been able to achieve nonwoven articles with such excellent mechanical properties in different types of nonwoven materials, while being so suitable for providing the properties required in a specific type of nonwoven material or application.

[0015] Attempts have previously been made to reduce or eliminate the use of synthetic binders in nonwovens, for example in WO2020068151A1. However, the articles disclosed in WO2020068151A1 still contain synthetic fibers and / or wet strength agents.

[0016] Previously, for example in WO2012015863A1, the use of chitosan as a binder component in nonwoven materials has been studied. However, as clearly stated in WO2012015863A1, chitosan as the only binder does not provide a sufficiently good level of mechanical properties, such as tensile strength. Therefore, a synthetic component, namely vinyl acetate ethylene, is provided to improve these properties as well as strength and elongation properties.

[0017] Bio-based polyelectrolyte complexes (PECs) are also being studied as environmentally friendly adhesive alternatives for materials such as fiber-based materials, textiles, woven and nonwoven fabrics. PECs are association complexes formed between oppositely charged polycations and polyanions, which are formed due to electrostatic interactions between oppositely charged polyions. Such adhesives are described, for example, in WO2018038671A1. However, nonwovens treated with PEC adhesive compositions will not work, for example, in air-laid nonwovens that require high softness, because they only show an elongation of about 3%, i.e., elongation at break. Such applications typically require an elongation of about 5-9%.

[0018] Therefore, there is still a need for a bio-based adhesive composition that is suitable for different nonwoven materials and different applications, provides excellent mechanical properties to the material, and also provides other properties required in a specific nonwoven material or application. Summary of the invention

[0019] It is an object of the present invention to provide a bio-based adhesive composition suitable as an adhesive for nonwoven materials.

[0020] It is an object of the present invention to provide a bio-based adhesive composition suitable for treating different types of nonwoven materials.

[0021] Another object of the present invention is to provide a bio-based adhesive composition that provides excellent mechanical properties to different types of treated nonwoven materials.

[0022] Another object of the present invention is to provide a bio-based adhesive composition that provides further properties to the treated nonwoven material.

[0023] Another object of the present invention is to provide a bio-based adhesive composition that imparts sufficiently high elongation to the treated nonwoven material.

[0024] Another object of the present invention is to provide a bio-based adhesive composition that imparts sufficiently high elongation to the treated airlaid nonwoven material.

[0025] Another object of the present invention is to provide an airlaid nonwoven material which exhibits strength and sufficiently good elongation, preferably an elongation of at least 4%.

[0026] Another object of the present invention is to provide a bio-based adhesive composition that is easily applicable to different nonwoven materials.

[0027] Another object of the present invention is to provide a bio-based adhesive composition that provides excellent strength to the treated carded nonwoven material.

[0028] Another object of the present invention is to provide a bio-based adhesive composition that is environmentally friendly, renewable, compostable and / or biodegradable.

[0029] Any combination of the above objects is also possible.

[0030] In a first general aspect, the present invention is directed to an aqueous bio-based binder composition for nonwoven materials, the composition comprising an acid, a plasticizer, and a cationic polyelectrolyte comprising chitosan, and wherein;

[0031] - the chitosan has a degree of deacetylation of 66-100%, and wherein the composition comprises 0.005-20% by weight of chitosan,

[0032] - the acid in the aqueous adhesive composition is a Bronsted acid and / or a Lewis acid, wherein the Bronsted acid is selected from any organic and / or inorganic acid, wherein the Lewis acid is selected from any cationic monovalent or polyvalent atom, and wherein the aqueous adhesive composition comprises preferably 0.01-30% by weight of the acid,

[0033] - the aqueous adhesive composition comprises at least 0.5 wt % and less than 15 wt % of a plasticizer, wherein the plasticizer is a linear polyol and / or a sugar, wherein the linear polyol is selected from one or more of mannitol, maltitol, xylitol and sorbitol, and the sugar is a non-macrocyclic sugar selected from one or more of glucose, mannose, fructose, sucrose, sucralose, sucrose ester, hydrolyzed starch or dextrin,

[0034] - the pH of the adhesive composition is less than 7,

[0035] And wherein the cationic polyelectrolyte is not complexed with an anionic polyelectrolyte.

[0036] Using the aqueous bio-based adhesive composition according to the present disclosure, an adhesive for nonwoven materials containing a large amount of renewable materials or made entirely of renewable materials is achieved. It has been found that the adhesive composition according to the present disclosure provides excellent mechanical properties in wet-laid as well as air-laid and carded nonwoven materials.

[0037] According to IUPAC standards, "macrocycle" refers to a cyclic macromolecule or a macrocyclic portion of a macromolecule. An example of a macrocyclic compound is cyclodextrin.

[0038] Plasticizer is selected from linear polyol and / or non-macrocyclic sugar.Not being bound by theory, this type of plasticizer is more flexible in its structure, thus resulting in softer nonwoven material and more effective application in nonwoven fiber structure.Macrocyclic plasticizer will result in harder material.In addition, macrocyclic compound has the tendency of showing increased hydrophobicity, which may be undesirable in some nonwoven applications.

[0039] The linear polyol is selected from one or more of mannitol, maltitol, xylitol and sorbitol. The sugar as non-macrocyclic sugar is selected from one or more of glucose, mannose, fructose, sucrose, sucralose, sucrose ester, hydrolyzed starch or dextrin.

[0040] In the context of plasticizers, hydrolyzed starch is the product of chemical or enzymatic treatment of starch from various natural sources. Hydrolyzed starch may be hydrogenated and contain a mixture of polyols. Hydrolyzed starch is a source of sorbitol.

[0041] In addition, surprisingly found that, compared with the conventional synthetic adhesive used in industry, aqueous adhesive composition according to the present invention can serve as the adhesive in airlaid nonwoven material, causes material to show sufficiently high intensity and elongation.Compared with other cationic polyelectrolytes, chitosan gives the material higher dry tensile index and especially wet tensile index processed with adhesive composition.Preferably, adhesive composition comprises at least 50 % by weight of bio-based (i.e. natural origin) components, more preferably at least 60 % by weight, more preferably at least 70 % by weight, even more preferably at least 80 % by weight, most preferably at least 90 % by weight.

[0042] Experiments have shown that adhesive compositions according to the present disclosure comprising chitosan (cationic polyelectrolyte) without the presence of anionic counterions in the composition can provide better flexibility and softness to nonwoven materials compared to adhesive compositions comprising polyelectrolyte complexes comprising cations and anions.

[0043] It has been found that in adhesive compositions according to the present disclosure, cationic polyelectrolytes comprising chitosan, and substantially free of anionic polyelectrolyte counterions in the composition, can be better spread in nonwoven materials, thereby resulting in more uniform distribution. Without being bound by theory, it is believed that the lack of electrostatic interaction between cationic polyelectrolytes and anionic polyelectrolytes causes cationic polyelectrolytes to be in a more expanded shape. If cationic polyelectrolytes interact with anionic countering components, the resulting polyelectrolyte complex will show a more curled structure. By obtaining a more expanded shape, it is believed that cationic polyelectrolytes can be better spread in nonwoven structures. Compared with if using PEC adhesive compositions, this results in stronger and more flexible nonwoven materials, because chitosan will serve as a bonding component connected to the fibers in the air-laid nonwoven material and itself. The synergistic effect between the cationic polyelectrolytes comprising chitosan and the plasticizer produces a composition suitable as a nonwoven adhesive, which can achieve strength and elongation of the treated material comparable to the conventional synthetic adhesive used.

[0044] In one aspect, the aqueous adhesive composition is substantially free of anionic polyelectrolytes. If a large amount of anionic polyelectrolytes are present in the composition, the cationic and anionic polyelectrolytes will form polyelectrolyte complexes (PECs), resulting in impaired functionality of the adhesive composition as described above.

[0045] It is important that the pH in the aqueous adhesive composition is below 7, as chitosan in its cationic form requires an acidic environment. Preferably, the pH of the composition is below 6.5, preferably, the pH of the composition is between 1.8-5.

[0046] In one aspect, the aqueous adhesive composition may further comprise a solvent selected from the group consisting of distilled water, tap water, and deionized water.

[0047] The amount of each component of the aqueous bio-based adhesive composition depends on the intended use of the composition and the properties required for that use, such as strength, softness, elongation, water repellency, absorbency, cushioning, insulation and / or filtration properties.

[0048] In one aspect, the aqueous adhesive composition comprises 0.01-11 wt %, eg, 0.01-8 wt %, 0.01-5 wt %, or 0.01-2 wt % of the acid.

[0049] In one aspect, the aqueous adhesive composition comprises at least 0.05 wt % and less than 15 wt % of a plasticizer. In one aspect, the aqueous adhesive composition comprises 0.05-14 wt % of a plasticizer.

[0050] In one aspect, the aqueous adhesive composition comprises 2-14 wt%, preferably 5-14 wt%, preferably 5-10 wt% plasticizer.

[0051] In one aspect, the aqueous adhesive comprises at least 1 wt%, such as at least 2 wt% and less than 15 wt% plasticizer. In one aspect, the aqueous adhesive comprises 1-10 wt% plasticizer.

[0052] In one aspect, the cationic polyelectrolyte in the aqueous adhesive composition consists of chitosan.

[0053] In one aspect, the aqueous adhesive composition comprises 0.005-10 wt%, preferably 0.005-5 wt%, even more preferably 0.5-2.5 wt% chitosan. The weight % of chitosan is optimized based on the desired viscosity.

[0054] In one aspect, the acid is selected from one or more of acetic acid, acetylsalicylic acid, adipic acid, benzenesulfonic acid, camphorsulfonic acid, citric acid, citric acid monohydrate, dihydroxyfumaric acid, formic acid, glycolic acid, glyoxylic acid, hydrochloric acid, lactic acid, malic acid, malonic acid, maleic acid, mandelic acid, oxalic acid, p-toluenesulfonic acid, phthalic acid, pyruvic acid, salicylic acid, sulfuric acid, tartaric acid and succinic acid, preferably lactic acid.

[0055] In one aspect, the aqueous adhesive composition comprises chitosan as a cationic polyelectrolyte, lactic acid as an acid, and at least one of sorbitol, hydrolyzed starch, xylitol, and maltitol as a plasticizer. Preferably, the plasticizer comprises hydrolyzed starch.

[0056] In one aspect, the aqueous adhesive composition further comprises at least one or more additives selected from defoamers, foaming agents, wetting agents, coalescing agents, catalysts, surfactants, emulsifiers, preservatives, rheology modifiers, fillers, nonionic polymers, dyes and pigments, wherein the concentration of the additive is 0-50% by weight, more preferably 0-30% by weight of the total weight of the composition. The additive is selected according to the application method and the expected final material properties.

[0057] Adhesive compositions according to the present disclosure can be easily applied to different nonwoven materials, such as wet-laid, air-laid and carded nonwoven materials. For relatively dense carded nonwoven materials, foam impregnation is a suitable and energy-saving alternative method for applying adhesive. This requires that adhesive is easy to foam with common foaming agents. It has been proved that adhesive compositions according to the present disclosure are easy to foam with common foaming agents, and are easy to be applied to carded nonwovens by foam impregnation. Therefore, carded nonwoven materials can be provided with excellent strength by processing carded nonwoven materials according to compositions disclosed herein, which is owing to adhesive being effectively applied to the material with foam impregnation.

[0058] In one aspect, the aqueous adhesive composition comprises at least one blowing agent selected from one or more of anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants.

[0059] The catalyst may be selected from Lewis bases and acids such as clays, colloidal or non-colloidal silica, dialdehydes, organic amines, organic amides, quaternary amines, metal oxides, metal sulfates, metal chlorides, urea sulfates, urea chlorides and silicate-based catalysts.

[0060] The preservative may be selected from one or more of a fungicide, a bactericide, a pharmaceutical preservative, a cosmetic preservative, and a food preservative. The inclusion of a preservative helps inhibit the growth of mold in the adhesive composition.

[0061] The filler may be selected from one or more of gum arabic, konjac glucomannan, organic fillers such as wood flour, starch soy flour, olive seed flour, cork flour, corn cobs, rice husks and inorganic fillers such as calcium carbonate, glass fiber, kaolin, talc and mica and other fillers known to those skilled in the art.

[0062] In one aspect, the aqueous adhesive composition comprises 0.5-2.5 wt % chitosan, at least 2 wt % and less than 15 wt % plasticizer, 0.05-3 wt % acid and optionally 0.05-10 wt % at least one or more additives selected from defoamers, foaming agents, wetting agents, coalescing agents, catalysts, surfactants, emulsifiers, preservatives, crosslinking agents, rheology modifiers, fillers, nonionic polymers, dyes and pigments. In a further aspect, the plasticizer is present in an amount of 2-14 wt %.

[0063] In a second general aspect, the present invention is directed to a method of treating a nonwoven material with a bio-based adhesive composition, wherein the method comprises the steps of:

[0064] a) providing an adhesive composition comprising an acid, a plasticizer and a cationic polyelectrolyte comprising chitosan, wherein the chitosan has a degree of deacetylation of 66-100%, the acid in the adhesive composition being a Bronsted acid and / or a Lewis acid, wherein the Bronsted acid is selected from any organic and / or inorganic acid, wherein the Lewis acid is selected from any cationic monovalent or polyvalent atom, and wherein the cationic polyelectrolyte is not complexed with an anionic polyelectrolyte;

[0065] b) optionally, diluting the adhesive composition provided in step a);

[0066] c) applying the composition of step a) or step b) to the nonwoven material by applying the adhesive composition to the formed nonwoven web, wherein the applied composition is a composition comprising 0.005-20 wt% chitosan, at least 0.5 wt% and less than 15 wt% plasticizer, 0.01-30 wt% acid and optionally 0.05-10 wt% of at least one or more additives, wherein the plasticizer is a linear polyol and / or a sugar, the linear polyol is selected from one or more of glycerol, mannitol, maltitol, xylitol and sorbitol, the sugar is a non-macrocyclic sugar selected from one or more of glucose, mannose, fructose, sucrose, sucralose, sucrose esters, hydrolyzed starch or dextrin, and the additive is selected from one or more of a defoamer, a foaming agent, a wetting agent, a coalescing agent, a catalyst, a surfactant, an emulsifier, a preservative, a cross-linking agent, a rheology modifier, a filler, a nonionic polymer, a dye and a pigment;

[0067] d) optionally curing the treated nonwoven material, preferably wherein the curing is carried out at 20°C to 200°C.

[0068] The applied bio-based adhesive composition may be any bio-based adhesive composition according to the first aspect.

[0069] In one aspect, the nonwoven material treated according to the method disclosed herein is selected from one or more of an air-laid nonwoven material, a wet-laid nonwoven material, and a carded nonwoven material.

[0070] In one aspect, the nonwoven material is substantially based on natural fibers, such as wood fibers (eg, pulp), fluff pulp, hemp, or man-made bio-based fibers, such as viscose, lyocell, and PLA.

[0071] By using the method according to the invention, a nonwoven material is achieved which exhibits improved strength and elongation properties comparable to nonwovens bonded with conventional synthetic adhesives. This enables the replacement of conventional synthetic adhesives with more environmentally friendly bio-based alternatives without compromising the mechanical properties of the nonwoven material.

[0072] In one aspect of the invention, the adhesive composition in step b) is diluted to an aqueous adhesive composition, the aqueous adhesive composition comprising 0.5-2.5 wt % of chitosan, at least 2 wt % and less than 15 wt % of a plasticizer, 0.05-3 wt % of an acid and optionally 0.05-10 wt % of at least one or more additives selected from defoamers, foaming agents, wetting agents, coalescing agents, catalysts, surfactants, emulsifiers, preservatives, crosslinking agents, rheology modifiers, fillers, nonionic polymers, dyes and pigments. In a further aspect, the adhesive composition is diluted so that the composition comprises 2-14 wt % of a plasticizer.

[0073] The adhesive composition can be applied by, for example, spraying the adhesive composition on the nonwoven material, by coating the adhesive composition on the nonwoven material, by dipping the adhesive composition on the nonwoven material, or by foam-dipping the adhesive composition on the nonwoven material.

[0074] In one aspect, curing is carried out at 20 to 200°C. Preferably, curing is carried out at above 135°C, preferably above 150°C.

[0075] In one aspect, the method results in a higher elongation of the treated nonwoven, preferably the method results in an elongation of at least 4%, preferably at least 5%. As used herein, elongation refers to the total elongation at break measured according to standard Edana 20.2-89.

[0076] In a third general aspect, the present invention relates to a nonwoven material treated according to the method defined in any one of the preceding aspects.

[0077] In one aspect, the nonwoven material exhibits an elongation of at least 4% after treatment with the aqueous binder composition as defined in any of the preceding aspects. Preferably, the elongation is at least 5%. The elongation is measured according to Edana 20.2-89.

[0078] In another general aspect, the present invention relates to the use of an aqueous binder composition according to any one of the preceding aspects for treating nonwoven materials. The use of the aqueous composition is preferably used to provide excellent mechanical properties and other preferred properties to different kinds of nonwoven materials. DETAILED DESCRIPTION

[0079] Hereinafter, a detailed description of the present invention is provided.

[0080] As used herein, "wt%" refers to the weight percentage of one or more ingredients based on the total weight of a compound or composition.

[0081] As used herein, "about" refers to a measurable value, such as an amount, and is intended to encompass variations of + / -5% or less, even more preferably + / -1% or less, and still more preferably + / -0.1% or less of the specified value, as far as the skilled artisan understands such variations to be suitable for making in the disclosed invention. However, it should be understood that the value to which "about" refers is itself also specifically disclosed.

[0082] As used herein, wet-laid nonwoven material is a nonwoven material produced by wet-laid process. Wet-laid nonwovens can be produced with natural fibers such as wood fiber (e.g. pulp), fluff pulp or hemp fiber or artificial bio-based fibers such as viscose, lyocell, PLA, etc. A small amount or a large amount of synthetic fibers such as PES, PET, PP, etc. and inorganic fibers such as glass fiber may also be present in wet-laid nonwovens. Wet-laid nonwovens can be used for but not limited to the following applications: desktop products such as napkins, notes or tablecloths, wipes and wet wipes, sanitary products such as diapers or feminine hygiene products, agricultural nonwovens such as ground films, air filter materials, tea bags, coffee filters, food mats, geotextiles (geotextiles) and wallpaper.

[0083] As used herein, air-laid nonwovens are nonwovens produced by air-laid (dry-laid) processes. Air-laid nonwovens can be produced by natural fibers such as wood fibers (e.g., pulp), fluff pulp or hemp fibers or artificial bio-based fibers such as viscose fibers, lyocell fibers, PLA, etc. A small amount or a large amount of synthetic fibers such as PES, PET, PP, etc. may also be present in air-laid nonwovens. Air-laid nonwovens can be used for, but are not limited to, the following applications: sanitary applications, such as baby diapers, feminine hygiene products, and sex care products; desktop products, such as napkins or notes, tablecloths; filter materials; automotive nonwovens; tea bags and coffee filters; medical nonwovens for masks, surgical gowns, and hair covers; food packaging materials and food pads; wipes and wet wipes; and geotextiles.

[0084] As used herein, a carded nonwoven material is a nonwoven material produced by a carded process. Carded nonwovens can be produced by natural fibers such as wood fibers (e.g., pulp), fluff pulp or hemp fibers or artificial bio-based fibers such as viscose fibers, lyocell fibers, PLA, etc. A small amount or a large amount of synthetic fibers such as PES, PET, PP, etc. can also be present in carded nonwovens. Carded nonwovens can be used for, but are not limited to, the following applications: sanitary applications, such as baby diapers, feminine hygiene products, and adult care products; filter materials; automotive nonwovens; tea bags and coffee filters; medical nonwovens for masks, surgical gowns, and hair covers; food packaging materials and food pads; wipes and wet wipes; geotextiles; building materials for thermal insulation and roofing; carpets, wallpapers, mattresses, and agricultural nonwovens.

[0085] As used herein, a surfactant is a molecule that comprises a hydrophilic "head" and a hydrophobic "tail".

[0086] As used herein, a polyelectrolyte is a polymer whose repeating units carry charged groups.

[0087] The present invention is further illustrated in the following examples, which do not limit the scope of the invention described in the claims.

[0088] Experimental Section

[0089] Prepare two different adhesive compositions as defined in Table 1.

[0090] Adhesive A Adhesive B raw material weight% weight% Tap water 61.41 60.61 Hydrolyzed starch syrup (70%) 35.00 35.40 Chitosan 2.10 2.20 Lactic acid (80%) 1.40 1.40 Acticide AB6 0.09 0.09 NaCl 0.00 0.30 total 100 100

[0091] Table 1. Adhesive Compositions

[0092] Example 1: Apply Adhesive A to a wet-laid nonwoven material by spraying

[0093] Use a wet-laid material of unbonded cellulose mixed fibers as the substrate. Add the material to the top of a conveyor belt running at different speeds (3, 5, and 7 m / min). Dilute Adhesive A from 26 wt% dry weight (measured with a moisture analyzer from VWR) to 2.5 wt% dry weight and spray it on the wet-laid nonwoven material. Then cure the wet-laid nonwoven material through an oven that is 2 m long and heated to 160 °C. After treatment, condition the material overnight at 23 °C and 50% RH. Then perform tensile tests on 50 mm × 250 mm cut samples using a Testometric M250-2.5AT tensile testing machine. Measure seven samples for each test. Perform dry tensile tests and wet tensile tests. As a comparison, perform dry tensile tests and wet tensile tests on wet-laid nonwoven materials to which no adhesive has been applied. For the wet tensile test, use a Finishcup, in which the samples are immersed in water for 15 seconds. The results of the dry tensile tests are shown in Table 2, and the results of the wet tensile tests are shown in Table 3. All values are averages.

[0094] Test Points Whether to add adhesive Conveyor belt speed [m / min] <![CDATA[Grammage [g / m 2 > Elongation [%] Tensile index [Nm / g] 1 no - 52.1 6.56 6.80 2 yes 3 62.8 6.81 11.54 3 yes 5 60.0 6.03 11.06 4 yes 7 54.0 6.04 10.06

[0095] Table 2. Dry Tensile Tests. Test No. 1 refers to the material without adhesive.

[0096] Test No. Whether to add adhesive Conveyor belt speed [m / min] Weight[g / m2] Elongation [%] Tensile index [Nm / g] 1 no - 52.6 8.96 2.43 2 yes 5 55.8 8.82 7.05 3 yes 7 53.0 8.45 5.26

[0097] Table 3. Wet Tensile Tests. Test No. 1 refers to the material without adhesive.

[0098] It can be concluded from Example 1 that the binder improves the mechanical properties of wet-laid nonwoven materials in both wet-laid and dry-laid conditions. By adjusting the addition of the binder composition, the increase in tensile index required for a particular application can be easily adjusted.

[0099] Example 2 - Application of Binder B to Airlaid and Wetlaid Nonwovens by Impregnation

[0100] Adhesive B was diluted from 27 wt% dry weight (measured with a moisture analyzer from VWR) to 14 wt% dry weight and added between two compression rollers of a horizontal padder from Wichelhaus GmbH. The speed of the rollers was set to 11.6 m / min and the pressure between the rollers was set to 0.1 MPa. The materials used in this study were air-laid nonwovens (fluff pulp fibers) and wet-laid nonwovens (mixed cellulose fibers). After impregnation, the materials were placed on a conveyor belt at a speed of 5 m / min, which passed through a 3 m long oven heated to 160°C. The materials were adapted overnight at 23°C and 50%. 50 mm × 250 mm cut samples were then tensile tested using a Testometric M250-2.5AT tensile testing machine. As a comparison, tensile tests were also performed on wet-laid and air-laid nonwoven materials to which no adhesive was applied. Ten specimens were measured for each test, and the results of the tensile tests are shown in Table 4. All values ​​are average values.

[0101] <![CDATA[Grammage [g / m 2 > Elongation [%] Tensile index [Nm / g] Wet-laid web 58.1 3.4 12.9 Wet-laid with adhesive 71.4 4.9 20.5 Airlaid 56.4 4.5 3.1 Airlaid with adhesive 66.8 5.4 13.4

[0102] Table 4. Dry tensile testing of wet-laid and air-laid nonwoven materials

[0103] As can be seen in Table 4, flexibility (elongation) and strength (tensile index) are significantly increased in both wet-laid and air-laid nonwoven materials. For the air-laid nonwoven material, it should be noted that the elongation after application of the adhesive composition is 5.4%, so this material meets the high flexibility requirements required in many applications where air-laid nonwovens are used.

[0104] Example 3: Foamability of Adhesive A with two different blowing agents.

[0105] The foaming properties of Adhesive A with two different blowing agents were evaluated. A nonionic blowing agent (Glucopone 215UP) and a zwitterionic (amphoteric) blowing agent (Ammonyx LO) were tested.

[0106] Adhesive A is diluted to 14 % by weight of dry weight (measured with a moisture analyzer from VWR) from 26 % by weight. 100 g of the diluent of adhesive A and 1 g of each blowing agent are added to a 250 mL beaker. The mixture is mixed for 5 minutes at 1500 rpm with a stirring paddle. The height of the foam phase is measured directly and after the mixing ends in 5 minutes. The results are shown in the following table 5.

[0107]

[0108] Table 5. Foaming test of binder A and different foaming agents

[0109] The experiments showed that Adhesive A could be foamed with both tested blowing agents and the foam remained stable for at least 5 minutes, which allowed smooth application of the adhesive with foam impregnation.

[0110] Example 4: Foam Impregnation of Binder A on Carded Nonwoven

[0111] Adhesive A was diluted to 10% dry weight from 26% by weight (measured with a moisture analyzer from VWR). 1.67g Glucopon 215UP (foaming agent, nonionic surfactant) was added to 200g of diluent, and the mixture was vigorously stirred at 2000rpm for 60 seconds with a disperser assembled on an overhead stirrer from IKA Werke. Dense and stable foam was observed. The foam was added between two compression rollers of a horizontal mill from Wichelhaus GmbH. The speed of the roller was set to 11.6m / min, and the pressure between the rollers was set to 0.1MPa. The carded viscose nonwoven was passed through a roller. The nonwoven was then dried for 3 minutes in an oven set to 170°C from Termaks. The material was adapted to spend the night at 23°C and 50%RH. Then a 50mm×250mm cut sample was subjected to a tensile test using a TestometricM250-2.5AT tensile testing machine. As a comparison, a carded nonwoven material to which no adhesive was applied was also subjected to tensile testing. Eight specimens were measured for each test and the results of the tensile testing are shown in Table 6. All values ​​are average values.

[0112]

[0113] Table 6. Dry tensile testing of carded nonwoven materials

[0114] The carded viscose nonwoven itself is very elastic due to the long staple fibers of the material. By applying the adhesive composition, a harder but stronger material can be obtained, which is clearly illustrated by the increase in the tensile stiffness index in the carded nonwoven treated with the foamed adhesive composition.

Claims

1. An aqueous bio-based adhesive composition for nonwoven materials, the adhesive composition comprising an acid, a plasticizer, and a cationic polyelectrolyte comprising chitosan, and wherein; - the chitosan has a degree of deacetylation of 66% to 100%, and wherein the adhesive composition comprises 0.005% to 20% by weight of chitosan; - the acid in the aqueous adhesive composition is a Bronsted acid and / or a Lewis acid, wherein the Bronsted acid is selected from any organic acid and / or inorganic acid, wherein the Lewis acid is selected from any cationic monovalent or polyvalent atom, and wherein the aqueous adhesive composition preferably comprises 0.01 wt% to 30 wt% of the acid; - the aqueous adhesive composition comprises at least 0.5 wt % and less than 15 wt % of a plasticizer, wherein the plasticizer is a linear polyol and / or a sugar, wherein the linear polyol is selected from one or more of mannitol, maltitol, xylitol and sorbitol, and the sugar is a non-macrocyclic sugar selected from one or more of glucose, mannose, fructose, sucrose, sucralose, sucrose ester, hydrolyzed starch or dextrin; - the pH of the adhesive composition is less than 7, And wherein the cationic polyelectrolyte is not complexed with an anionic polyelectrolyte.

2. The aqueous adhesive composition according to claim 1, in, The composition is substantially free of anionic polyelectrolytes.

3. The aqueous adhesive composition according to any one of the preceding claims, in, The composition comprises 0.01 wt% to 11 wt%, for example 0.01 wt% to 5 wt% or 0.01 wt% to 2 wt% of the acid.

4. The aqueous adhesive composition according to any one of the preceding claims, in, The composition comprises at least 1 wt %, such as at least 2 wt % and less than 15 wt % plasticizer.

5. The aqueous adhesive composition according to any one of the preceding claims, in, The composition comprises 0.005 wt% to 10 wt% chitosan, preferably 0.005 wt% to 5 wt% chitosan, or even more preferably 0.5 wt% to 2.5 wt% chitosan.

6. The aqueous adhesive composition according to any one of the preceding claims, in, The acid is selected from one or more of acetic acid, acetylsalicylic acid, adipic acid, benzenesulfonic acid, camphorsulfonic acid, citric acid, dihydroxyfumaric acid, formic acid, glycolic acid, glyoxylic acid, hydrochloric acid, lactic acid, malic acid, malonic acid, maleic acid, mandelic acid, oxalic acid, p-toluenesulfonic acid, phthalic acid, pyruvic acid, salicylic acid, sulfuric acid, tartaric acid and succinic acid, preferably lactic acid.

7. An aqueous adhesive composition according to any one of the preceding claims, in, The composition further comprises at least one additive selected from one or more of defoamers, foaming agents, wetting agents, coalescing agents, catalysts, surfactants, emulsifiers, preservatives, crosslinking agents, rheology modifiers, fillers, nonionic polymers, dyes and pigments, and wherein the concentration of the additive is 0 wt %-50 wt %, more preferably 0 wt %-30 wt %.

8. An aqueous adhesive composition according to any one of the preceding claims, in, The composition further comprises at least one foaming agent, which is selected from one or more of anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants.

9. The aqueous adhesive composition according to any one of the preceding claims, in, The composition comprises 0.5 wt % to 2.5 wt % of chitosan, at least 2 wt % and less than 15 wt % of a plasticizer, 0.05 wt % to 3 wt % of an acid and optionally 0.05 wt % to 10 wt % of at least one or more additives selected from defoamers, foaming agents, wetting agents, coalescing agents, catalysts, surfactants, emulsifiers, preservatives, crosslinking agents, rheology modifiers, fillers, nonionic polymers, dyes and pigments.

10. A method of treating a nonwoven material with a bio-based adhesive composition, in, The method comprises the following steps: a) providing an adhesive composition comprising an acid, a plasticizer and a cationic polyelectrolyte comprising chitosan, wherein the chitosan has a degree of deacetylation of 66% to 100%, the acid in the adhesive composition is a Bronsted acid and / or a Lewis acid, wherein the Bronsted acid is selected from any organic and / or inorganic acid, wherein the Lewis acid is selected from any cationic monovalent or multivalent atom, and wherein the cationic polyelectrolyte is not complexed with an anionic polyelectrolyte; b) optionally, diluting the adhesive composition provided in step a); c) applying the composition of step a) or step b) to the nonwoven material by applying an adhesive composition to the formed nonwoven web, wherein the applied composition is a composition comprising 0.005 wt% to 20 wt% chitosan, at least 0.5 wt% and less than 15 wt% plasticizer, 0.01 wt% to 30 wt% acid, and optionally 0.05 wt% to 10 wt% of at least one or more additives, wherein the plasticizer is a linear polyol and / or a sugar, the linear polyol is selected from one or more of glycerol, mannitol, maltitol, xylitol and sorbitol, the sugar is a non-macrocyclic sugar selected from one or more of glucose, mannose, fructose, sucrose, sucralose, sucrose esters, hydrolyzed starch or dextrin, and the additive is selected from a defoamer, a foaming agent, a wetting agent, a coalescing agent, a catalyst, a surfactant, an emulsifier, a preservative, a cross-linking agent, a rheology modifier, a filler, a nonionic polymer, a dye and a pigment; d) optionally curing the treated nonwoven material, preferably wherein the curing is carried out at 20°C to 200°C.

11. The method according to claim 10, in, The nonwoven material is selected from one or more of an air-laid nonwoven material, a wet-laid nonwoven material and a carded nonwoven material.

12. The method according to any one of claims 10 to 11, in, The nonwoven materials are essentially based on natural fibers, such as wood fibers (eg pulp), fluff pulp, hemp, or artificial bio-based fibers, such as viscose, lyocell and PLA.

13. The method according to any one of claims 10 to 12, in, The adhesive composition is applied to the nonwoven material by spraying the adhesive composition on the nonwoven material, by coating the adhesive composition on the nonwoven material, by dipping the adhesive composition on the nonwoven material, or by foam-dipping the adhesive composition on the nonwoven material.

14. The method according to any one of claims 10 to 13, in, The method results in a higher elongation of the treated nonwoven material, preferably the method results in an elongation of the nonwoven material of at least 4%, preferably at least 5%, said elongation being the elongation at break measured according to standard Edana 20.2-89.

15. A nonwoven material treated according to the method defined in any one of claims 10 to 14.

16. The nonwoven material according to claim 15, in, The material exhibits an elongation at break of at least 4%, preferably at least 5%, measured according to standard Edana 20.2-89.

17. Use of the aqueous adhesive composition according to any one of claims 1 to 9 for treating nonwoven materials.

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