RU2769362C1 - Biodegradable nonwoven fabric containing wood pulp and the method for its manufacture - Google Patents

Abstract

FIELD: personal hygiene products.

SUBSTANCE: present invention relates to a method for manufacturing biodegradable nonwoven fabric and a napkin. A method for manufacturing biodegradable nonwoven fabric, including steps in which a fibrous web is formed from a mixture of fibers containing biodegradable fibers and wood pulp fibers, or a layer of biodegradable fibers is formed with a layer of sanitary and hygienic paper. Next, at least part of the biodegradable fibers are woven together by water-jet treatment of a fibrous web or a fibrous web combined with a layer of sanitary and hygienic paper, and the woven fibrous web is dried. A biodegradable binder is applied to the woven fibrous web before drying the woven fibrous web, a biodegradable agent that gives strength in a wet state is added to the fiber mixture, a biodegradable binder is mixed with a fiber mixture.

EFFECT: invention makes it possible to increase the strength, softness and elasticity of non-woven material.

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Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention relates to a biodegradable nonwoven fabric, a method for making a biodegradable nonwoven fabric, and tissues or tissue paper containing a biodegradable nonwoven fabric. In particular, the biodegradable nonwoven material may be a plastic-free, fully compostable nonwoven material or a backing suitable for disposable use, such as napkins or tissue paper.

BACKGROUND OF THE INVENTION

Disposable wipes, such as wet wipes or personal care wipes such as baby wipes, face wipes, etc., are very popular for cleaning human skin or household items due to consumer comfort and cleaning efficiency. However, growing concerns about plastic pollution are driving an increase in demand for plastic-free, fully compostable/biodegradable bases for disposable wipes and similar products.

Spunlace (also referred to as hydroentangling) and needle punching techniques are commonly used to make a nonwoven fabric or backing suitable as wipes. Spunlace technology is a method of bonding wet or dry fibrous webs, during which thin jets of water under high pressure penetrate the fibrous web and cause the fibers to intertwine, thereby giving the fabric integrity. Needling is a bonding method in which the fibers are mechanically intertwined with each other using needles.

Spunlace technology using only compostable fibers made from regenerated cellulose, such as viscose/rayon, tencel or cellulose acetate, or natural fibers, such as cotton, provides a solution for plastic-free, compostable/biodegradable disposable wipes However, there is a problem of a significant increase in the cost of materials due to the replacement of PET fibers, widely used in the bases of disposable wipes (for example, baby wipes), with compostable fibers, which can reach 50% of the cost of materials. Due to the high cost of materials, these products have so far only been used in the premium segment and have not been able to replace standard products such as baby wipes.

A common approach to reduce the cost of the materials of such spunlace bases is to replace some of the viscose fibers with wood pulp, which imparts the required hydrophilic properties to the base of the wipes. This approach to the production of nonwovens consists in the combined weaving of a certain amount of relatively short and thin fibers and a certain amount of longer fibers.

In general, the wet-laid/air-laid technology of fibers and wood pulp combined with spunlace technology for bonding without the use of binders, widely used for the manufacture of dissolvable wipes (wet toilet tissue), described in EP 2 985 375 A1, the contents of which incorporated herein by reference, or an insoluble wipes (airlaid) backing faces three limitations in the mechanical integrity of the nonwoven structure, especially after exposure to liquid, which is critical for the use of such a backing in baby wipes and personal care wipes requiring more high mechanical strength and elasticity:

(i) Poor material strength compared to standard spunlace materials, even with increased fiber content compared to the formulation used for dissolving wipes. Because the wood pulp fibers are too short and too stiff to be hydrowoven, they become trapped in the structure of the hydrowoven viscose/tencel fibers but do not significantly contribute to the mechanical strength of the web. Therefore, such materials require a significant increase in areal density compared to standard spunlace materials in order to achieve similar mechanical strength.

(ii) Because wood pulp fibers are woven into the structure of viscose/tencel hydrowoven fibers but do not themselves have bonding points, they can move and clump after exposure to liquid/water and mechanical stress and wrinkling of the web, disrupting the fabric structure, unlike materials obtained using spunlace and air laying technology, in which most of the fibers are connected by bonding points, resulting in a three-dimensional structure that retains the fabric structure even after exposure to liquid/water and mechanical stress/collapse. Consumers rate this behavior as "paper-like behavior" or "normal toilet paper-like behavior" and consider the tissue to be of poor quality. In addition to this perceived lack of comfort, the sticking/clumping of the wood pulp fibers negatively impacts the functionality of the wipe, as the movement of the wood pulp fibers in the structure randomly changes the local composition of the web. The formation of low woodpulp areas results in thin spots that limit the desired insulating and holding capacity of the tissue, while areas of high woodpulp content develop increased thickness or even clumps, detracting from the desired smooth surface and tactile properties of the tissue.

(iii) The separation of the wood pulp fibers occurs due to the lack of integration of the wood pulp fibers into the nonwoven matrix by means of bonding points, causing the fibers to fall out of the napkin during rolling and use when the web is subjected to mechanical stresses (bending, stretching, wrinkling etc.). The shedding of wood pulp fibers when using a wipe for cleaning purposes limits the scope of potential applications and is perceived by users as a disadvantage of the product.

Thus, hitherto known technologies are characterized by cost and performance problems.

OBJECTS OF THE INVENTION

The present invention aims to overcome the problems and disadvantages described above. Thus, it is an object of the present invention to provide a biodegradable, compostable nonwoven material suitable for single use, such as wipes, having customized or adjustable properties, in particular in terms of strength and resilience (when wet), and low cost.

SUMMARY OF THE INVENTION

The inventor of the present invention has carried out thorough research and found that the mechanical properties (such as strength and/or resilience) of a nonwoven material obtained by mechanically weaving a mixture of wood pulp fibers and biodegradable fibers can be improved by (i) adding a biodegradable binder, optionally containing softening agents, for example, glycerin, after forming a woven fabric structure of biodegradable fibers and wood pulp fibers, by ii) adding a preferably compostable wet strength agent before the headbox to form a fabric structure of biodegradable fibers and wood pulp fibers, and /or by (iii) blending biodegradable binder fibers (particularly biodegradable thermal bonding fibers) with a fiber blend containing biodegradable fibers and wood pulp fibers, these objectives can be solved. Without wishing to be bound by any theory, the inventor of the present invention believes that, by any of the measures (i) to (iii) above, bonding points (particularly covalent bonds) can be formed on the wood pulp fibers to bond them together and combine them. into an integrated structure in the fiber structure obtained according to the spunlace technology. As a result, a wood pulp web structure can be obtained that is integrated (or embedded) in the structure of woven biodegradable fibers, so that a structure is formed in which the wood pulp fibers are essentially unable to move in the structure of woven fibers even after exposure to a liquid, such as water. , as well as wrinkling of the web or mechanical impact on the web. As a result, the wood pulp fibers can be prevented from falling out and clumping, which maintains the functionality of the nonwoven fabric. In addition, by selecting the ratio of biodegradable fibers and wood pulp fibers, as well as the content of the wet strength agent, binder and/or binder fiber, it is possible to properly adjust the material properties in a wide range, to prevent movement and clumping of wood pulp fibers after exposure to the liquid / water base and obtain the desired strength and elasticity of the web. This makes it possible to obtain a tissue base with similar properties to spunlace materials in the wet state and to replace the high content of compostable fibers with cheaper wood pulp fibers.

Accordingly, the present invention relates to a biodegradable nonwoven fabric containing biodegradable fibers and wood pulp fibers, in which at least a portion of the biodegradable fibers are woven together (with at least a partial capture of the wood pulp fibers), and in which at least a portion of the fibers wood pulp is covalently bonded (attached, glued) to each other by at least one element from the group consisting of a biodegradable binder, a biodegradable wet strength agent, and a biodegradable binder fiber (resulting in the formation of a wood pulp web structure embedded into a structure of woven biodegradable fibers, so that a structure is formed in which the wood pulp fibers themselves form an integrated structure and/or essentially cannot move separately in the structure of woven fibers even after exposure to a liquid, such as water).

The present invention also relates to a method for manufacturing a biodegradable nonwoven fabric, comprising the steps of (a) forming a fibrous web from a mixture of fibers containing biodegradable fibers and wood pulp fibers, or forming a layer of biodegradable fibers on tissue paper, (b) woven over at least a portion of the biodegradable fibers with each other (which captures at least a portion of the wood pulp fibers) by water-jetting the fibrous web (or layer of tissue paper and fibers), and (c) drying the woven fibrous web (at a temperature sufficient to curing the applied binders), the method further comprising at least one (e.g., one, any two, or all three) of the following steps: (i) applying a biodegradable binder to the woven fibrous web prior to step (c) drying, (ii ) adding a biodegradable wet strength agent to the fiber blend, and (iii) mixing the biodegradable binder fiber with the mixture of fibers.

In addition, the present invention relates to a biodegradable nonwoven fabric obtained by the process for manufacturing a biodegradable nonwoven fabric described herein.

In addition, the present invention relates to a napkin or tissue paper containing or consisting of biodegradable nonwoven material described in this document.

Further, the present invention relates to the use of a biodegradable binder, a biodegradable wet strength agent and/or a biodegradable binder fiber to provide resilience to a tissue or tissue containing a biodegradable nonwoven material.

Other objects and many accompanying advantages of the embodiments of the present invention will become clearer and more apparent from the following detailed description of the embodiments and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows photographs of a control sample subjected to a crush test, where the left photo illustrates a flat wetted sample before crushing, the middle photo illustrates the sample crumpled in a fist, and the right photo illustrates the sample after crushing.

Figure 2 shows photographs of a sample of a biodegradable nonwoven fabric in accordance with an embodiment of the present invention, subjected to a wrinkle test, where the left photo illustrates a flat wetted sample before crumpling, the middle photo illustrates the sample crumpled in a fist, and the right photo illustrates the sample after crumpling.

Figure 3 shows an exemplary device for measuring two-point bending stiffness.

Figure 4 shows an exemplary apparatus for measuring bending stiffness. The device is not illustrated to scale.

DETAILED DESCRIPTION OF THE INVENTION

Below will be described the details of the present invention, as well as other features and advantages. However, the present invention is not limited to the following specific description, which is provided for purposes of illustration only.

It should be noted that features described in relation to one exemplary embodiment or exemplary aspect may be combined with any other exemplary embodiment or exemplary aspect, in particular, features described in relation to any exemplary embodiment of a biodegradable nonwoven material may be combined with any other exemplary embodiment of a biodegradable nonwoven fabric, with any exemplary embodiment of a process for making a biodegradable nonwoven fabric, with any exemplary embodiment of a tissue or tissue paper, and with any exemplary use case, and vice versa, unless specifically noted otherwise.

The use of the indefinite or definite article with a singular term such as "a", "an", or "the" also includes the plural, and vice versa, unless specifically stated otherwise, while the word "one" or the number "1 " in this context usually means "only one" or "exactly one".

The expression "comprising" in this context not only includes the meaning of "comprising", "including" or "comprising", but can also include the meaning of "essentially consisting of" and "consisting of".

Unless specifically stated otherwise, the expression "at least part" in this context can mean at least 5%, in particular at least 10%, in particular at least 15%, in particular at least 20% , in particular at least 25%, in particular at least 30%, in particular at least 35%, in particular at least 40%, in particular at least 45%, in particular at least 50%, in particular at least 55%, in particular at least 60%, in particular at least 65%, in particular at least 70%, in particular at least 75%, in particular at least 80%, in particular at least 85%, in particular at least 90%, in particular at least 95%, in particular at least 98%, and may also mean 100 %.

In a first aspect, the present invention relates to a biodegradable nonwoven fabric.

The expression "non-woven fabric" in this context can, in particular, mean a web of individual fibers that are at least partially intertwined, but without a regular pattern, as in a knitted or woven fabric.

The expression "biodegradable" (which may also be used instead of the expression "compostable") in this context may specifically mean that the material in question, e.g. , biodegradable binder and the like, meets at least the requirements of industrial composting, for example, according to EN 13432, and preferably also the requirements of domestic composting, and even more preferably also biodegradable in the marine environment. The expression "biodegradable in the marine environment" in this context may, in particular, mean that the material degrades by more than 90% by weight within 12 months in sea water at a minimum temperature of 15°C and under the influence of daylight.

The biodegradable nonwoven fabric contains biodegradable fibers and wood pulp fibers.

In one embodiment, the biodegradable fibers comprise cellulose fibers. The expression "cellulose fibers" in this context may in particular mean fibers based on cellulose, in particular modified or regenerated cellulose fibers, for example fibers derived from cellulose or cellulose derivatives such as ethyl cellulose, cellulose acetate and the like. The expression "regenerated cellulose fibers" in this context can, in particular, mean artificial cellulose fibers obtained by spinning from a solution.

In one embodiment, the regenerated cellulose fibers may be selected from the group consisting of viscose (rayon) or lyocell (tencel).

Viscose is a type of solution-spun fiber produced by the viscose process, typically involving the intermediate dissolution of cellulose as cellulose xanthate and subsequent spinning of the fibers.

Lyocell is a type of solution-spun fiber made by the amine oxide process, typically involving dissolving cellulose in N-methylmorpholine-N-oxide and then spinning the fibers.

In one embodiment, the biodegradable fibers may have an average fiber length of 1 mm to 100 mm, such as an average fiber length of 3 mm to 80 mm, such as an average fiber length of 5 to 70 mm, such as an average fiber length of 10 to 65 mm, for example an average fiber length of 15 to 60 mm, for example an average fiber length of 18 to 50 mm, for example an average fiber length of 20 to 40 mm.

In one embodiment, the biodegradable fibers may have an average fiber length of 1 mm to 12 mm, in particular 3 mm to 10 mm. This may be advantageous in particular when airlaid nonwoven fabric is produced.

In one embodiment, the biodegradable fibers may have an average fiber length of 1 mm to 12 mm, in particular 3 mm to 8 mm. This may be advantageous, in particular, in the production of a nonwoven fabric by the wet lay process.

In one embodiment, the biodegradable fibers may have an average fiber length of 10 mm to 100 mm, in particular 10 mm to 80 mm. This may be advantageous, in particular, in the production of a non-woven fabric by a dry-air spinning process.

In one embodiment, the biodegradable fibers may have an average fiber length of 15 mm to 60 mm. This may be advantageous, in particular, in the production of a nonwoven material by the carding process.

In one embodiment, the biodegradable fibers may have a fiber coarseness of 0.5 to 10 dtex, such as 0.5 to 4.0 dtex, or 1.0 to 10 dtex, such as 1.0 to 2.5 dtex. .

In one embodiment, biodegradable fibers may be present in an amount of 10 to 80% by weight, such as 15 to 70% by weight, such as 20 to 60% by weight, such as 25 to 50 wt.%, for example, in an amount of from 30 to 40 wt.%, based on the total weight of the nonwoven material.

In one embodiment, the wood pulp fibers may be natural wood pulp fibers, in particular wood pulp fibers of natural origin, such as softwood pulp fibers or hardwood pulp fibers. Wood pulp can in particular mean a (lignocellulosic) fibrous material obtained by chemically or mechanically separating the cellulose fibers of wood or the like, for example by the kraft pulping process (sulphate process).

In one embodiment, the wood pulp fibers may have an average fiber length of 1.0 mm to 4.0 mm, such as 1.5 mm to 3.5 mm, such as 2.0 mm to 3.2 mm.

In one embodiment, the wood pulp fibers may have a fiber coarseness of 0.3 to 3.5 dtex, such as 0.6 to 2.5 dtex.

In one embodiment, the wood pulp fibers may be present in an amount of 20 to 90% by weight, such as 30 to 85% by weight, such as 40 to 80% by weight, such as 50 to 75 wt.%, for example, in an amount of from 60 to 70 wt.%, based on the total weight of the nonwoven material.

In a biodegradable nonwoven material, at least a portion of the biodegradable fibers are woven together. In particular, at least a portion of the biodegradable fibers may be woven together such that at least a portion of the wood pulp fibers are entrapped in the woven biodegradable fibers.

The expression "woven" in this context may, in particular, mean that the biodegradable fibers are at least partially intertwined with each other, which gives strength to the nonwoven material, for example, tear strength or tensile strength. Interlacing of biodegradable fibers can in particular be achieved by treating the fibrous web with water jets, as will be explained in more detail below, which may also be referred to as "hydro-entanglement" or "spunlace", and the interlaced fibers may thus also be referred to as "hydro-entangled fibers" or "fibers obtained using spunlace technology". Alternatively, weaving of biodegradable fibers can be achieved by needling, in which biodegradable fibers are mechanically intertwined with needles. As an alternative to blending biodegradable fibers and wood pulp into an airlaid layer, or carding, or airlaid dry forming for feeding into spunlace equipment, a layer of biodegradable fibers can also be formed on top of the tissue paper layer by carding technology, or dry-formed, or air-laid, and then fed into a spunlace machine in which the tissue is broken down to form a web of at least partially woven biodegradable fibers trapping at least a portion of the wood pulp fibers.

In a biodegradable nonwoven fabric, at least a portion of the wood pulp fibers are covalently bonded (bonded, glued) to each other (resulting in an integrated layer of wood pulp in the spunlace biodegradable fiber structure) by at least one element from the group consisting of of a biodegradable binder, a biodegradable wet strength agent, and a biodegradable binder fiber. By at least partially covalently bonding the wood pulp fibers, a wood pulp web structure can be obtained that is integrated (or incorporated) into the structure of the woven biodegradable fibers so that a structure is formed in which the wood pulp fibers are essentially unable to move in the structure of the woven biodegradable fibers. fibers even after exposure to a liquid such as water. Further, clumping of wood pulp fibers can be substantially prevented. In this regard, the bonding of wood pulp fibers is preferably initiated by applying heat after weaving the biodegradable fibers by hydroentangling or needle punching.

In addition to bonding wood pulp fibers, at least one member of the group consisting of a biodegradable binder, a biodegradable wet strength agent, and a biodegradable binder fiber, optionally but not necessarily, can also bind biodegradable fibers, in particular woven biodegradable fibers. , and, optionally, but not necessarily, can also bind wood pulp fibers with biodegradable fibers, in particular with woven biodegradable fibers. However, without wishing to be bound by theory, it is believed that most of at least one of the group consisting of biodegradable binder, biodegradable wet strength agent, and biodegradable binder fiber binds the wood pulp fibers to each other (and not to biodegradable fibres) resulting in a wood pulp web structure that can also be (and in fact should be) associated with a woven biodegradable fiber structure. In addition, the increase in volume due to the formation of the structure of the web from the wood pulp and its subsequent integration or incorporation into the structure of the woven biodegradable fibers is considered sufficient (even without binding to the biodegradable fibers) in essence to limit the free movement of the wood pulp in the structure of the woven fibers even after exposure liquid, such as water, and essentially to prevent falling out and/or clumping. In addition, the formation of a layer of interconnected fibers of wood pulp in the structure of woven biodegradable fibers can lead to an increase in the elasticity of the material.

In one embodiment, at least a portion of the wood pulp fibers are bonded to each other with a biodegradable binder fiber. The expression "bonding fiber" in this context may, in particular, mean a fiber capable of bonding (for example, by thermal bonding, covalent bonding, ionic interactions, or the like) with each other or with other fibers. Preferably, the biodegradable binder fiber is a biodegradable thermobonding (or thermally activated) fiber. The biodegradable binder fiber may in particular be a biodegradable thermoplastic fiber. The expression "thermoplastic fibers" in this context may in particular mean fibers that soften and/or partially melt under the influence of heat and are able to bond with each other or with other non-thermoplastic fibers, for example cellulose fibers, when cooled and re-solidified.

In one embodiment, the biodegradable binder fiber comprises a multi-component fiber, in particular a bi-component fiber, such as bi-component fibers having a sheath-core configuration. Bicomponent fibers consist of two types of polymers having different physical and/or chemical characteristics, in particular different melting characteristics. A bicomponent fiber having a sheath-core configuration typically has a core of a higher melting point component and a sheath of a lower melting point component.

For example, the biodegradable binder fiber may contain polylactic acid (PLA), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT), and other biodegradable thermoplastic polymers. A combination of two or more components may also be used.

In one embodiment, the biodegradable binder fiber may be present in an amount of from 0.1 to 30 wt.%, for example, in an amount of from 0.2 to 20 wt.%, for example, in an amount of from 0.2 to 10 wt.%, for example , in an amount of from 0.2 to 7.5 wt.%, for example, in an amount of from 0.35 to 5 wt.%, for example, in an amount of from 0.5 to 4 wt.%, based on the total weight of the nonwoven material.

In one embodiment, at least a portion of the wood pulp fibers are bonded together with a biodegradable wet strength agent. The expression "wet strength agent" in this context can, in particular, mean a substance that increases the tensile strength of the nonwoven fabric in the wet state, for example, through the formation of covalent bonds. In particular, it may be preferred that the wet strength agent be biodegradable. However, it is also possible to use a non-biodegradable wet strength agent (eg, in small amounts that do not adversely affect biodegradability/compostability), which can significantly increase the wet tensile strength of the nonwoven fabric.

For example, the biodegradable wet strength agent may be selected from the group consisting of chitosan, modified starch, cellulose derivatives, and other components. A combination of two or more components may also be used. The expression "cellulose derivatives" in this context may, in particular, mean chemically modified (for example, methylated, ethylated, hydroxypropylated, acetylated and/or carboxylated) cellulose compounds, and may, in particular, contain cellulose ethers and cellulose esters, for example , methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose or cellulose acetate.

In one embodiment, the biodegradable wet strength agent may be present in an amount of 0.1 to 3% by weight, such as 0.2 to 2% by weight, such as 0.35 to 1.5 wt.%, for example, in an amount of from 0.5 to 1 wt.%, based on the total weight of the nonwoven material.

In one embodiment, the biodegradable nonwoven fabric may contain an additional wet strength agent, in particular a non-biodegradable wet strength agent. An example of an additional wet strength agent may be an epichlorohydrin resin, such as a polyamide-polyamine-epichlorohydrin resin.

In one embodiment, at least a portion of the wood pulp fibers are held together with a biodegradable binder. The expression "binder" in this context may, in particular, refer to a chemical compound capable of bonding (for example, by forming covalent bonds, ionic interactions, or the like) with two or more fibers, thereby connecting the fibers to each other, which leads to increase the tensile strength of the canvas or fabric.

For example, the biodegradable binder may be selected from the group consisting of chitosan, modified starch, cellulose derivatives, in particular mixtures of carboxymethyl cellulose and citric acid, protein-based binders such as casein, and other components. A combination of two or more components may also be used. Other suitable biodegradable binders are described in WO 2014/117964 A1, the disclosure of which is incorporated herein by reference.

In one embodiment, the biodegradable binder may be present in an amount of 0.05 to 5% by weight, such as 0.1 to 4% by weight, such as 0.25 to 3% by weight, such as in an amount of 0.5 to 2 wt.%, based on the total weight of the nonwoven material.

In one embodiment, the Biodegradable Binder further comprises an additive, such as glycerin, (intended to) serve as a softening agent to increase the flexibility and drape of the (dried) nonwoven fabric. In other words, glycerin or similar emollients may be added to the biodegradable binder or wet strength agent to increase the flexibility and drape of the dried nonwoven.

The wet strength agent in the context of the present application and the binder in the context of the present application may, in particular, differ in application times. The wet strength agent is typically added to the fiber blend prior to forming the fibrous web structure or fabric structure. For example, a wet strength agent may be added to or before the headbox of the paper machine. The binder is usually applied after the fibrous web structure or fabric structure has been formed, and it may also be applied even after the fibrous web has been woven. For example, the binder may be applied or added to the woven fibrous web, but preferably before the woven web is dried. It is also possible to apply the binder after drying the hydrowoven web, but this will be less effective due to the need to dry the web twice. The binder fiber may be added to the blend of other fibers prior to forming the fibrous web structure or fabric structure.

In one embodiment, at least a portion of the wood pulp fibers may be bonded together with a biodegradable wet strength agent and/or a biodegradable binder and, optionally, an additional biodegradable binder fiber. In particular, at least a portion of the wood pulp fibers can only be bonded together with a biodegradable wet strength agent; at least part of the fibers of the wood pulp can be bonded to each other only with a biodegradable binder; at least a portion of the wood pulp fibers can be bonded together with a biodegradable wet strength agent and a biodegradable binder; at least a portion of the wood pulp fibers can be bonded together with a biodegradable wet strength agent and a biodegradable binder fiber; at least a portion of the wood pulp fibers can be bonded together with a biodegradable binder and a biodegradable binder fiber; and/or at least a portion of the wood pulp fibers may be bonded together with a biodegradable binder, a biodegradable wet strength agent, and a biodegradable binder fiber.

In one embodiment, substantially all of the fibers contained in the biodegradable nonwoven material may be biodegradable fibers, in particular, substantially all of the fibers contained in the biodegradable nonwoven material may be biodegradable fibers, wood pulp fibers and, optionally, a biodegradable binder. fiber as described herein. In other words, the biodegradable nonwoven material may essentially contain no fibers other than biodegradable fibers, in particular no fibers other than biodegradable fibers, wood pulp fibers, and optionally a biodegradable binder fiber as described herein. With respect to embodiments "essentially containing no other fibers other than biodegradable fibers", other fibers other than biodegradable fibers, if any, may be present in relatively small amounts of up to 10, up to 5, up to 3, up to 2, or up to 1 wt.% of the total weight of the nonwoven material.

In one embodiment, the biodegradable nonwoven material may have a grammage or basis weight of 20 to 150 g/m ² , such as 30 to 125 g/m ² , such as 40 to 100 g/m ² , such as 50 to 80 g/m ² .

In one embodiment, the nonwoven fabric is water insoluble. The expression "soluble" may specifically refer to the property of the nonwoven fabric to disintegrate or decompose in water upon the application of relatively low mechanical energy, such as in a situation that typically occurs in a toilet flush. In particular, when washed, the soluble nonwoven material may lose its integrity, for example, some individual fibers or collections of fibers may be released from the fabric, and/or the fabric may break into several pieces. The expression "insoluble" in this context can accordingly mean the property of the nonwoven fabric to resist disintegration in water when relatively low mechanical energy is applied, such as in a situation that typically occurs in a toilet flush.

In one embodiment, the nonwoven fabric may be treated (impregnated) with a liquid or lotion. In other words, the nonwoven material may further comprise a liquid or lotion. In this case, the nonwoven material may in particular be a wet wipe or wet tissue paper. The liquid or lotion is not particularly limited, and any liquid or lotion commonly used in the field of wet wipes or wet tissue paper can be used. Typically, the liquid or lotion may contain a solvent such as water, alcohol or mixtures thereof, surfactants or detergents, skin care agents, emollients, humectants, fragrances, preservatives, and the like. depending on the intended use.

In one embodiment, the biodegradable nonwoven material exhibits an increase in material resiliency, as measured by bending stiffness, as determined by modification of the ASTM D 4032-94 test, as further described below, by greater than 25%, preferably greater than 50%, and most preferably more than 75% compared to nonwoven fabric without biodegradable binder fiber, biodegradable wet strength agent or biodegradable binder.

In one embodiment, the biodegradable nonwoven material exhibits material resilience, characterized by flexural stiffness in machine direction (MD) and/or in cross direction (CD), determined according to a modification of the ISO 5628 (DIN 53 121) test, as further described below. , more than 25%, preferably more than 50%, and most preferably more than 75% compared to a nonwoven fabric without a biodegradable binder fiber, a biodegradable wet strength agent, or a biodegradable binder.

In a second aspect, the present invention relates to a method for manufacturing a biodegradable nonwoven material, in particular, a biodegradable nonwoven material described herein.

The method contains steps in which:

(a) forming a fibrous web from a mixture of fibers containing biodegradable fibers and wood pulp fibers, or alternatively forming a layer of biodegradable fibers combined with a layer of tissue/paper;

(b) weaving at least a portion of the biodegradable fibers together by water jetting the fibrous web or the fibrous web combined with the tissue paper layer; and

(c) drying the woven fibrous web.

The method further comprises at least one (for example, one, any two, or all three) of the following steps, wherein:

(i) applying a biodegradable binder to the woven fibrous web prior to drying the woven fibrous web,

(ii) adding a biodegradable wet strength agent to the fiber blend, and

(iii) mixing the biodegradable binder fiber with the mixture of fibers.

In step (a), the fibrous web can be produced, for example, by a conventional wet-laid process using a wet-laid machine, such as an oblique needle machine or a flat needle machine, or a nonwoven dry air forming process. A conventional wet-lay method is described, for example, in US 2004/0129632 A1, the description of which is incorporated herein by reference. A suitable process for dry-air forming a nonwoven material is described, for example, in US 3,905,864, the disclosure of which is incorporated herein by reference. Thus, the fibrous web can be obtained, for example, by wet laying or air laying.

In one embodiment, the fibrous web is wet laid. In another embodiment, the fibrous web is air laid. Also suitable for forming a layer of biodegradable fibers combined with a layer of wood pulp fibers is a combination of a carding method or a dry air forming method combined with an air laying method. Instead of an airlaid process, the wood pulp fibers can also be subjected to a process in which the tissue/paper layer is combined with the fibrous layer before entering the hydroentangling section where the tissue/wood pulp is disintegrated and mixed with biodegradable fibers.

The fiber blend used to form the fibrous web contains biodegradable fibers and wood pulp fibers and optionally may further contain a biodegradable binder fiber and/or a biodegradable wet strength agent.

In step (b), at least a portion of the biodegradable fibers are intertwined with each other by water jet treatment of the fibrous web. In particular, at least a portion of the biodegradable fibers can be woven together so that at least a portion of the wood pulp fibers can be entrapped in the woven biodegradable fibers (woven fibrous web of biodegradable fibers).

The expression "water jetting" in this context can, in particular, mean a method of mechanically interlacing fibers by exposing the fibrous web to jets of water. Water jetting may also be referred to as hydroweaving or spunlacing. Water jetting typically involves applying thin, high pressure jets of water from a plurality of nozzles to a fibrous web that is on a conveyor belt or needle belt. The jets of water pass through the web, hit the tape, from which they can be reflected, and pass through the web again, which leads to the interlacing of the fibers. Thus, by water-jetting the fibrous web, the fibers become woven, in particular hydro-woven.

In one embodiment, a biodegradable binder may be applied to the woven fibrous web. The biodegradable binder may be applied to the woven fibrous web as a solution or dispersion. For example, the biodegradable binder may be applied by spraying or other liquid application means such as a size press, padding, or others. It may be beneficial to remove excess water prior to application of the binder, especially in the case of spray application, by applying vacuum, pressure, or other method to remove excess water to prevent dilution of the binder.

In one embodiment, a softening agent, such as glycerin, is added to the biodegradable binder to impart increased flexibility/drapeability (reduction of stiffness) to the finished nonwoven fabric, especially when dry.

In step (c), the drying of the woven fibrous web can preferably be carried out so that the biodegradable binder fiber softens and/or partially melts, in particular thermally activated, and/or so that the biodegradable wet strength agent and/or biodegradable the binder is cured, in particular subjected to a chemical reaction. In particular, the drying is preferably carried out at a (sufficiently high) temperature to thermally activate the biodegradable binder fiber and/or initiate a chemical reaction between the biodegradable wet strength agent and/or the biodegradable binder, for example at a temperature above 80°C, for example, above 100°C, for example, above 120°C, for example, above 140°C, for example, above 180°C, depending on the particular biodegradable binder fiber, biodegradable wet strength agent, and/or biodegradable binder used.

In a third aspect, the present invention relates to a biodegradable nonwoven fabric obtained by the process for manufacturing a biodegradable nonwoven fabric described herein. In particular, the biodegradable nonwoven fabric produced by the method for manufacturing the biodegradable nonwoven fabric described herein may have any of the properties or characteristics of the biodegradable nonwoven fabric according to the first aspect as described above.

In a fourth aspect, the present invention relates to a tissue or tissue paper containing or consisting of the biodegradable nonwoven material described herein. In particular, the nonwoven material according to the present invention can be used as a napkin or tissue paper.

In one embodiment, the tissue or tissue paper may be a dry tissue or dry tissue paper. Dry wipes can be used in particular as kitchen tissue/towels, floor towels and absorbent paper towels.

In one embodiment, the tissue or tissue paper may be a wet wipe or wet tissue paper. For example, the wipe may be treated with a liquid or lotion, as described in more detail above. Wet wipes, in particular, can be used as personal care products to clean the skin, including intimate areas. Thus, wet wipes can in particular be used as personal care products, such as facial wipes or baby wipes.

In one embodiment, the wipe is selected from the group consisting of facial wipes, facial wipes, baby wipes, sanitary napkins, kitchen towels, paper towels, handkerchiefs (facial tissue paper), cleaning tissue paper, cleaning tissue paper, sanitary paper, cleaning wipes for floors and hard surfaces.

In a fifth aspect, the present invention relates to the use of a biodegradable binder, a biodegradable wet strength agent, and/or a biodegradable binder fiber to bounce a tissue or tissue containing a biodegradable nonwoven material (or to increase the elasticity of a tissue or tissue paper). paper containing biodegradable non-woven material). A biodegradable binder, a biodegradable wet strength agent, and/or a biodegradable binder fiber, in particular, may refer to the examples illustrated above. The inventors of the present invention have found that by using a biodegradable binder, a biodegradable wet strength agent, and/or a biodegradable binder fiber in a biodegradable nonwoven fabric, the resulting nonwoven fabric, as well as the tissue or tissue paper containing it, can be resilient. The expression "elasticity" in this context can, in particular, mean a property of the tissue structure, for example, elasticity or the ability to at least partially return to its original shape after collapse. The resilience can be characterized, for example, by bending stiffness determined according to a modification of the test according to ASTM D 4032-94, and/or bending stiffness in machine direction (MD) and/or in the transverse direction (CD) determined according to a modification of the test according to ISO 5628 (DIN 53 121), as described in more detail below.

The present invention is further described with reference to the following examples, which are provided solely for the purpose of illustrating specific embodiments and should in no way be construed as limiting the scope of the invention.

Examples

A blend ^of 20 wt. % viscose fibers and 80 wt. 985 375 B1.

Because the wet laid material does not contain a binder, a base is used as a "base stock" to demonstrate the effect of using different binders. Due to the lack of a binder, the base can be "reactivated" by applying an aqueous binder system that simulates the process.

The woven fiber layer was treated in three different ways:

a) An aqueous solution of carboxymethyl cellulose (0.4 wt.%), citric acid (0.1 wt.%) and sodium dihydrogen phosphate (0.06 wt.%) was sprayed at room temperature (25°C) onto the surface of the original base described above, so that the solution is evenly distributed over the surface of the original base and absorbed into the material due to capillary force. The sample was dried in a laboratory oven at 120°C without direct contact with the hot surface (air drying). The amount of an aqueous solution of carboxymethyl cellulose and citric acid was chosen so that after drying the material to constant weight at a temperature of 120°C, the following composition of the material was obtained:

19.6 wt.% viscose fibers,

78.2 wt.% wood pulp fibers,

1.5 wt.% carboxymethyl cellulose,

0.5 wt% citric acid,

0.25 wt% sodium dihydrogen phosphate.

b) An aqueous solution of carboxymethyl cellulose (0.4 wt%), citric acid (0.1 wt%), sodium dihydrogen phosphate (0.06 wt%) and glycerol (1 wt%) was sprayed at room temperature (25° C) on the surface of the original base described above, so that the solution is evenly distributed over the surface of the original base and absorbed into the original base due to capillary force. The sample was dried in a laboratory oven at 120°C without direct contact with the hot surface (air drying). The amount of an aqueous solution of carboxymethyl cellulose, citric acid and glycerol was chosen so that after drying the material to constant weight at a temperature of 120°C, the following composition of the material was obtained:

18.8 wt.% viscose fibers,

75 wt.% wood pulp fibers,

1.5 wt.% carboxymethyl cellulose,

0.5 wt% citric acid,

0.25 wt% sodium dihydrogen phosphate,

4 wt.% glycerol.

c) Aqueous solution of carboxymethyl cellulose (0.4 wt%), citric acid (0.1 wt%), sodium dihydrogen phosphate (0.06 wt%) and epichlorohydrin wet strength agent (Kymmene GHP 20, 0 05 wt.%) was sprayed at room temperature (25°C) onto the surface of the original base described above, so that the solution was evenly distributed over the surface of the original base and absorbed into the original base due to capillary force. The sample was dried in a laboratory oven at 120°C without direct contact with the hot surface (air drying). The amount of an aqueous solution of carboxymethyl cellulose, citric acid and a wet strength agent was chosen so that after drying the material to constant weight at a temperature of 120°C, the following composition of the material would be obtained:

19.5 wt.% viscose fibers,

78 wt.% wood pulp fibers,

1.5 wt.% carboxymethyl cellulose,

0.5 wt% citric acid,

0.25 wt% sodium dihydrogen phosphate,

0.25 wt% epichlorohydrin wet strength agent.

In order to determine the effect of the treatment of a hydrowoven mixture of viscose fibers and wood pulp fibers on the mechanical properties, especially on the flexibility and resilience of the original substrate and the treated samples a), b) and c), the following material properties were measured, which are shown in Table 1:

1) Tensile strength according to ASTM D5035, measured at 200% moisture content.

2) Elongation at break (ASTM D5035) measured at 200% moisture content.

3) Circular bending stiffness as modified from ASTM D 4032-94 test at 200% moisture content (see below).

4) Bursting strength (ASTM D774) measured at 200% moisture content.

5) Two-point bending stiffness according to a modification of the ISO 5628 (DIN 53 121) test at 200% moisture content.

The two-point bending stiffness measurement is used to determine the resilience of a material, which is a measure of the material's ability to resist collapse.

Two-point bending stiffness measurement according to a modification of the ISO 5628 (DIN 53 121) test:

The two-point bending stiffness was measured according to a modification of the ISO 5628 (DIN 53 121) test. On FIG. 3 shows an exemplary device for making measurements on samples. The measurement can be done either by measuring the force required to bend the test specimen to a given angle, or by measuring and determining the bending stiffness, which characterizes the elastic properties of the material.

A test specimen (38 mm × 50 mm) with a defined moisture content is placed in the clamp. After starting the measurement, the clamp is slowly turned to move the free end of the test specimen in contact with the load cell. The test specimen is bent at the chosen angle of 30°. The tool registers force throughout the measurement process. The clamp is then returned to its original position and the test piece can be removed.

To determine the bending force and bending stiffness, a Lorentzen-Wettre bending test machine model 016-94281 was used using the following parameter settings: Bending angle α = 30°; Bend length L = 1 mm; Bending speed: 5°/s;

The width of the test specimen is 38 mm.

Using the appropriate formula, the bending stiffness S _{b 30-1} was calculated:

The measurement was repeated 6 times and the average of these measurements was taken.

The bending stiffness measurement is used to determine the resilience of a material, which is a measure of the material's ability to recover from collapse.

Circular bending stiffness measurement according to ASTM D 4032-94 test modification:

Circular bending stiffness was measured according to a modification of the ASTM D 4032-94 test. On FIG. 4 shows an exemplary apparatus for making bending stiffness measurements (not to scale).

Bending stiffness is measured as the force required to push a sample (38 mm × 38 mm) with a moisture content of 200 wt.%, located on top of the hole, into the hole using a piston for a certain penetration distance (see Fig. 3).

The piston is made of smooth polished stainless steel 72 mm long and 6.3 mm in diameter, has a free end of a round shape with a radius of 3 mm and is used to push the sample into a hole with a diameter of 18.75 mm in a smoothly polished stainless steel plate measuring 102 mm × 102 mm × 6.4 mm. The overlapping edge of the hole is located at an angle of 45° at a depth of 4.8 mm.

The force required to push a sample lying on the flat surface of the hole with a piston centered over the hole into the hole is measured by a load cell located between the piston and the actuator that moves the piston into the hole. A Zwick model Z.2.5/TN1S testing machine was used to move the piston and measure the force.

Circular bending stiffness was defined as the maximum force measured while pushing the sample with a piston at a speed of 500 mm/min into a 6.4 mm deep hole. The measurement was repeated 5 times and the average of these measurements was taken.

Table 1

Sample Wet Tensile Strength in MD*
(N/50mm) Wet CD Tensile Strength* (N/50mm) Elongation at Break in MD Wet* (%) Elongation at Break in CD Wet* (%) Flexural stiffness in MD wet* (µNm) Flexural stiffness in CD wet* (µNm) Wet bending stiffness* (H) Wet Burst Strength*
(kPa) Control sample 7.5 5.4 30.0 48.7 0.48 0.31 0.020 32.8 a) 8.3 4.9 34.6 57.0 1.44 0.62 0.033 36.7 b) 13.1 7.3 27.8 53.0 1.31 0.75 0.025 34.2 c) 16.3 10.8 23.8 46.5 1.59 0.67 0.045 41.2

*Samples have a water content of 200 wt.%

Sample Dry tensile strength in MD**
(N/50mm) Tensile strength in CD dry**
(N/50mm) Elongation at break in MD dry**
(%) Elongation at Break in CD Dry**
(%) Flexural stiffness in MD dry** (µNm) Flexural stiffness in dry CD** (µNm) Dry bending stiffness
(H) Control sample 16.57 8.42 11.96 31.70 8.71 2.95 0.195 a) 29.28 15.48 8.60 32.49 23.12 7.46 0.452 b) 30.28 16.30 8.22 26.61 19.75 8.51 0.398 c) 29.52 15.13 7.53 28.18 19.07 8.29 0.400

** Samples have a moisture content of 8%

MD - pattern machine direction

CD - transverse direction of the sample

The data in Table 1 demonstrates the increasing value of web resilience relative to mechanical strain, measured as both bending stiffness and circular bending stiffness. The positive effect of adding a wet strength agent is also evident (sample c)), as evidenced by the increased values at the same binder content.

Comparison of bending stiffness and bending stiffness (dry) of the control sample and sample a) shows a significant increase in the stiffness of the dry material after application of the binder and the softening effect of the addition of glycerin, reducing the stiffness of the material, which is important when used as a dry wipe. When applied as a wet wipe, the added solution/lotion serves as a moisturizing agent, so the addition of glycerin may not be necessary.

Currently, there are no standardized measurement methods that describe the quantitative determination of the ability of the web to resist wrinkling. However, this effect can be easily demonstrated by wetting samples with water to a water content of 400 wt.% and crushing a sample of 20 cm × 20 cm in a fist.

Figure 1 shows photographs of a control sample subjected to a crush test, where the left photo illustrates a flat wetted sample before crushing, the middle photo illustrates the sample crumpled in a fist, and the right photo illustrates the sample after crushing.

Figure 2 shows photographs of a sample of a biodegradable nonwoven fabric in accordance with an embodiment of the present invention, subjected to a wrinkle test, where the left photo illustrates a flat wetted sample before crumpling, the middle photo illustrates the sample crumpled in a fist, and the right photo illustrates the sample after crumpling.

While the control remains in a wad like tissue paper without a wet strength agent, as shown in FIG. 1, other samples have the ability to spread, as shown in Fig. 2, which becomes more pronounced as the bonding of the wood pulp fibers increases, which correlates with an increase in bursting strength and bending stiffness.

A simple crush test demonstrates a significant increase in the resilience of a hydrowoven blend of biodegradable fibers and wood pulp fibers by adding a binder after hydro entangling, which holds the wood pulp fibers together to form an integral layer within the woven biodegradable fiber structure. This is clearly seen in the increase in bending stiffness, which characterizes the ability of the material to resist crushing, when trying to return the sheet to its original flat shape before crushing. Comparison of the tensile strength and elongation at break of the sample a) and the control sample shows that these properties by themselves are not suitable for determining/evaluating the resilience effect.

Although the present invention has been described in detail with reference to specific embodiments and examples, the present invention is not limited thereto, and various changes and modifications are possible without deviating from the scope of the present invention.

Claims (14)

1. A method for manufacturing a biodegradable nonwoven material, including the steps in which: (a) forming a fibrous web from a mixture of fibers containing biodegradable fibers and wood pulp fibers, or forming a layer of biodegradable fibers with a layer of tissue paper; (b) weaving at least a portion of the biodegradable fibers together by water-jetting the fibrous web or the fibrous web combined with the tissue paper layer; and (c) drying the woven fibrous web, wherein the method further comprises at least one of the following steps, wherein: applying a biodegradable binder to the woven fiber web prior to drying the woven fiber web, adding a biodegradable wet strength agent to the fiber blend, mixing the biodegradable binder fiber with the mixture of fibers. 2. The method of claim 1, wherein in step (a) the fibrous web is formed by a wet-laid process or an air-laid process, or the fibrous web combined with the tissue layer is formed by a dry-laid process such as carding or air-laying. 3. Biodegradable non-woven material obtained by the method according to claim 1 or 2. 4. A napkin or tissue paper comprising or consisting of a biodegradable nonwoven fabric according to claim 3. 5. Napkin or tissue paper according to item 4, wherein the wipe or tissue is a dry wipe or wet wipe, and/or wherein the tissue or tissue paper is selected from the group consisting of facial tissues, cosmetic tissues, baby wipes, sanitary napkins, kitchen tissue paper, paper towels, handkerchiefs, cleaning tissue paper, cleaning tissue paper , cleaning wipes for floors and hard surfaces.

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