CN118043145A

CN118043145A - Enzymatic degradation method for absorbent structures of hygiene articles

Info

Publication number: CN118043145A
Application number: CN202280065993.3A
Authority: CN
Inventors: R·罗萨蒂; J·C·加西亚-加西亚
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 2021-10-04
Filing date: 2022-09-29
Publication date: 2024-05-14

Abstract

The present invention relates to a method of enzymatic degradation of an absorbent structure, the absorbent structure being adapted to provide an absorbent core of a hygiene article, wherein the method comprises the step of contacting the absorbent structure with a solution comprising an enzyme; wherein the absorbent structure comprises a polysaccharide superabsorbent polymer, such as a cellulose-based or starch-based superabsorbent polymer.

Description

Enzymatic degradation method for absorbent structures of hygiene articles

Technical Field

The present invention relates to a method of enzymatic degradation of an absorbent structure suitable for providing an absorbent core for sanitary articles, avoiding the need to send the used absorbent structure to a landfill site.

Background

Most disposable diapers are currently made of a substantial proportion of petroleum derived materials such as polypropylene and/or polyethylene. These materials are typically present in the form of spun fibers forming a cloth-like nonwoven web material, or alternatively or in addition, in the form of films. In recent years, people have begun focusing on the "environmental footprint" of all kinds of human activities. The manufacture and use of diapers is no exception, especially in view of the ever-increasing population, i.e. the increasing number of infants. Most disposable diapers are not typically reused or recycled and many are disposed of in landfills after use. An alternative is a reusable cloth diaper. However, the use of cloth diapers requires the use of energy (e.g., for operating equipment, heating wash water, and treating waste water) and chemicals (e.g., detergents and water treatment agents) that are necessary to wash soiled diapers at the rates they are typically used, and the treatment of the associated waste water presents its own pressure to the environment.

Several designs of diapers including reusable cloth outer covers and reusable or disposable absorbent inserts have been manufactured and marketed. However, disposable absorbent inserts are typically not flushable and can clog household plumbing and sewage systems if flushed into a toilet. Thus, these designs still present at least some of the disadvantages of conventional cloth diapers to the user without providing some of the advantages that can be obtained from current disposable diaper designs.

It would be advantageous to provide a method for degrading an absorbent structure, preferably a soiled absorbent structure after use, which can be easily disposed of while avoiding the need to send the used absorbent structure to a landfill.

Disclosure of Invention

Drawings

Fig. 1A is a front view of an apparatus suitable for use with the present invention. FIG. 1B is a perspective view of a rotating blade associated with the apparatus of FIG. 1A;

FIG. 2 is a schematic cross-sectional view of the apparatus shown in FIG. 1A;

FIG. 3 is a perspective view of a disposable absorbent insert shown separately from an outer cover, which may be in a stand-alone, relaxed state;

FIG. 4 is a plan view of the disposable absorbent insert shown in an extended and laid flat configuration with the body facing surface facing the viewer;

FIG. 5A is a cross-sectional view of an example of an insert such as shown in FIG. 4, taken along line 5A-5A in FIG. 4;

FIG. 5B is a cross-sectional view of an example of an insert such as shown in FIG. 4, taken along line 5B-5B in FIG. 4;

FIG. 5C is a cross-sectional view of another example of an insert such as shown in FIG. 4, taken along line 5C-5C in FIG. 4;

FIG. 5D is a cross-sectional view of another example of an insert such as shown in FIG. 4, taken along line 5D-5D in FIG. 4;

FIG. 5E is a cross-sectional view of another example of an insert such as shown in FIG. 4, taken along line 5E-5E in FIG. 4;

FIG. 5F is a cross-sectional view of another example of an insert such as shown in FIG. 4, taken along line 5F-5F in FIG. 4;

Fig. 5G is a cross-sectional view of another example of an insert, such as shown in fig. 4, taken along lateral axis 70 in fig. 4.

Fig. 6 is a graph showing storage modulus versus temperature for certain adhesives.

Detailed Description

The present invention relates to a method of enzymatic degradation of an absorbent structure suitable for providing an absorbent core of a hygiene article.

The absorbent structure comprises superabsorbent polymers, optionally in combination with cellulosic fibers such as wood pulp and other plant-based fibers.

The term "superabsorbent polymer" (abbreviated herein in singular and plural as "SAP") generally refers to an absorbent material that is at least 7 times, and preferably at least 10 times its weight in a 0.9% saline solution (referred to herein as capacity) as measured using the Centrifuge Retention Capacity (CRC) test (EDANA method NWSP.0.r2 (19)). SAPs are water insoluble but water swellable crosslinked polymers capable of absorbing large amounts of fluids. Most commonly, conventional SAPs are polyacrylate polymers, however polyacrylate polymers are often difficult to reduce by enzymatic degradation.

Thus, for the purposes of the present invention, preferred SAPs are polysaccharide polymers and derivatives of polysaccharide polymers, such as cellulose or starch based polymers. Polysaccharides are carbohydrates that can be broken down into two or more monosaccharide molecules by hydrolysis. Polymers suitable for use as SAPs include cellulose-based polymers, such as carboxymethyl cellulose. Examples are manufactured by Magic S.r.L, oleggio, italy Cellulose-based materials, which are crosslinked and/or reinforced mainly by inorganic fillers of natural origin. Suitable starch-based superabsorbent polymers and methods for their synthesis are described in DE 19619680 published 11, 20 in 1997.

The polysaccharide SAP is degradable by glucose hydrolase. For example, cellulose-based absorbent polymers such as carboxymethyl cellulose (including crosslinked carboxymethyl cellulose) may be degraded by cellulases. The starch-based particulate absorbent polymer material is degradable by amylase.

Other suitable polysaccharides include polyaluminates and carrageenans which are degradable by alginate lyase and carrageenan enzymes, respectively. Carrageenan is a general description of a group of sulfated polysaccharides. Different polysaccharide SAPs may be used in combination.

Preferably, the cellulase is selected from the group consisting of cellulases, beta-glucosidases and hemicellulases. For example, the cellulase may be selected from the group consisting of endo-1, 4-glucanases, exo-1, 4-glucanases I and II, and beta-glucosidase. Without wishing to be bound by theory, first, the 1, 4-glycosidic bond of cellulose may be broken down by endocellulases (e.g., endo-1, 4-glucanases). The cellulose chain may then be further cleaved by an exo-1, 4-glucanase to produce cellobiose molecules, which are then hydrolyzed by the glucosidase to release the two monomeric carbohydrate units.

The cellulase is preferably provided in the form of a solution dissolved in water. The enzyme solution may also contain a pH buffer, such as sodium citrate, sodium citrate-phosphate, sodium acetate or sodium phosphate, to control the pH within the recommended range for the particular enzyme or enzyme blend of interest.

Suitable cellulase blends are commercially available under the designation Cellulase from Millipore-Sigma, enzyme mixtures, catalog number SAE0020-50 ML. The optimum pH range is 3.8 to 6.5, preferably 4.5 to 5.5. A suitable pH buffer concentration is 50mM. An example of a cellulase is a fungal beta-glucan hydrolase. An example of a pH buffer is 50mM sodium citrate buffer pH 5. Where the used absorbent article contains a mixture of bodily substances, such as urine and feces, a specific pH buffer may be required, which may lead to the production of pH altering metabolites, such as ammonia: for these cases, it may be preferable to use a pH buffer with a molar concentration higher than 100mM, more preferably higher than 200mM, even more preferably higher than 250 mM.

The enzyme solution may comprise different types of enzymes. Optionally, the enzyme solution may also contain different types of degradation enhancing active substances, such as peroxides.

Although the process of the present invention may be carried out on an industrial scale, it is envisioned that the process is particularly well suited for carrying out on a relatively small scale, such as a community or home scale. For example, the method may be performed in a maternal care facility; in a caretaker's house or other child care facility; or in the home. This method provides a means of handling absorbent articles but does not have the complexity of the sorting and collection system required for large-scale reprocessing of used absorbent articles. It is a preferred embodiment of the present invention that once the absorbent structure is at least partially liquefied by contact with the enzyme solution, the liquefied waste may preferably be discharged into a municipal sewage system, wherein the liquefied waste may be accepted and easily treated in the same manner as conventional sewage treatment.

An apparatus suitable for use in the method of the present invention is shown in FIG. 1A. The apparatus comprises a collecting unit, which is shown in fig. 1A as a container 2 with a lid 4. A rotary blade mechanism 6 is provided within the container 2. An enlarged and more detailed view of the blade mechanism is shown in fig. 1B.

According to the method of the invention, one or more absorbent structures are loaded into a drum. The absorbent structure may be an absorbent core or diaper "insert" as described in more detail below. According to this method, the absorbent structure is intended to be used and thus contains urine, faeces and other body fluids. The enzyme-containing solution is added to the absorbent structure in the container 2 and the container is closed with a lid 4. The absorbent structure is then degraded by the enzymes in the solution and optionally mechanically reduced by the stirring and/or cutting action of the rotary blade mechanism 6. The process may be programmed to open and close the blade mechanism as desired. The process may also be programmed to control the temperature of the enzyme solution as desired.

This process may take several hours to degrade and liquefy the absorbent structure to a degree sufficient to allow for treatment in a municipal sewage system. The process may be conducted for at least 2 hours, at least 4 hours, at least 8 hours, or at least 12 hours.

As shown in fig. 1A, the apparatus may include a closable chamber, such as a container 2 and a lid 4. The cover 4 is attachable to and detachable from the container 2. The chamber should be closed during operation for several reasons: 1) the cover will avoid spillage of the contents of the compartment, 2) the closed compartment will avoid accidental contact of children, people or household pets with the liquid and soiled diapers contained in the compartment, 3) the cover will limit the heat dissipation and water evaporation required for effective degradation activity carried by the enzymes on the absorbent structure material, 4) the cover will limit the emission of bad odors from the used absorbent structure.

As shown in fig. 1B, the rotating element 6 may be a sharp blade to facilitate tearing and shredding of the used absorbent structure and mixing of the used absorbent structure with enzyme solution: increasing the contact of the used absorbent structure with the enzyme solution may improve the enzymatic activity of degrading the used absorbent structure. The rotating element 6 may also be a mixing element or blade without sharp cutting edges. The rotating element 6 is connected to a rotating shaft, which is connected to a motor. The rotating element and the rotating shaft may also be absent. The device may be provided with an interface such as an operation panel to allow a user to turn the device on/off and to set operating conditions such as temperature, rotational speed and duration of the process. The container 2 is detachable from the apparatus to simplify the emptying and cleaning of the container 2 by the user.

The apparatus may also be programmed to follow a particular rotational speed over time, for example it may be preferred to use a greater rotational speed for the first 5 minutes or 10 minutes or 20 minutes or 30 minutes or 60 minutes and then a lower speed for the remaining processing duration. A greater rotational speed may be preferred initially to facilitate shredding of the used absorbent article. The rotation speed may be in the range of 50rpm to 10000rpm, for example it may be in the range between 100rpm and 1000 rpm. Too low a speed may not be sufficient to chop the used absorbent article. Too high a speed will consume more energy and can lead to air entrapment and foam formation, which can reduce enzyme activity. An antifoaming agent may be added to the enzyme solution to prevent or at least reduce foam formation.

In one embodiment, the container 2 itself may be rotated using a motor. In this case, the container may not be provided with a rotating element, since stirring is provided by the rotation of the chamber itself.

The apparatus may also be provided with a heating system and a temperature control system to control the temperature of the enzyme solution contained in the container 2. For optimal activity of the enzyme, there may be an optimal temperature. Too low a temperature may result in low enzyme activity, whereas too high a temperature may result in irreversible degradation and inactivation of the enzyme. The optimum temperature may be in the range between about 15 ℃ and about 80 ℃, preferably in the range between about 40 ℃ and about 60 ℃. The optimum operating temperature depends on the particular enzyme used, as indicated, for example, by the enzyme manufacturer. The apparatus may be programmed to follow a specific temperature that varies over time, for example, a lower temperature may be preferred for a first duration of time required for dissolution of the used absorbent article by the enzyme solution, followed by a higher temperature for a second duration of time; if the slurry must be treated, for example, in a composter or in an open environment, a higher temperature treatment may be required for a second duration to sterilize or reduce the concentration of viable bacteria in the slurry. An additional benefit of using a specific temperature that varies over time may be to use a lower temperature and for a first duration that is required to optimize the activity of a first enzyme type (which is optimal at a first temperature), and then to use a higher temperature and for a second duration that is required to optimize the activity of a second enzyme type (which is optimal at a second temperature).

As shown in fig. 2, the treatment device may be provided with a filter 8, a pump 10 and an outlet for evacuating the container. The container 2 can be opened and closed using a cover 4, which can be attached and detached from the container 2. The used absorbent structure is loaded into the container 2. The rotary element 6 is connected to a rotary shaft driven by a motor. The container 2 may have an outlet connected to the pump 10. At the end of the treatment, the pump 10 may discharge the solution via an outlet to a tank located at the location of the treatment apparatus. The tank may be attached to a grey or black water system at that location. The outlet may be provided with a filter 8 to filter out undegraded parts of the used absorbent article, e.g. parts larger than a given size. The pump may be manually operated via a panel or automatically programmed in the device. The cleaning procedure may also be performed via simply loading water with optional chemicals to perform the cleaning and then emptying the container 2 via the pump 10. The container 2 may be provided with an inlet for automatic supply of water, the amount of water being metered by the pump 12. The water may already contain enzymes and/or pH buffers. Alternatively, the enzyme and/or pH buffer may be loaded directly into the container 2, while the used absorbent article is loaded via the opening of the lid 4. The pump 10 may be used to circulate fluid in the chamber by pumping the fluid back through a separate inlet, thereby providing fluid agitation. Fluid agitation may also be achieved by multiple inlets connected to pumps 10 and/or 12, thereby creating multiple fluid jets.

Enzyme solution is added to contact the used absorbent structure in the treatment device. The weight ratio of the used absorbent structure to enzyme solution may preferably be in the range of 1:1 to 1:100, more preferably in the range of 1:10 to 1:50. For example, if a dry absorbent structure is known to have a mass of 30g, 300g of solution may be added.

Another parameter is the actual amount of enzyme added via the enzyme solution. The representative ratio of enzyme amount per gram of dry absorbent structure material is preferably in the range of 0.001g to 10g enzyme per gram of dry absorbent structure material, more preferably in the range of 0.1g to 1g enzyme per gram of dry absorbent structure material.

In the following description, the absorbent structure is described with reference to "absorbent inserts". The absorbent insert may be suitable for use in a hybrid incontinence article, wherein a disposable absorbent insert is used in combination with a reusable, washable outer cover (such as a cloth outer cover). Examples of suitable features of the absorbent insert 50 will be described with reference to fig. 3, 4, and 5A-G.

Fig. 3 depicts a disposable absorbent insert 50 that may form the internal components of a wearable absorbent article as described herein, which is shown in perspective view as it may appear separate from the outer cover in a separate manner. Fig. 4 depicts one example of an insert 50, which is shown stretched out and laid flat with the body facing surface facing the viewer. Fig. 5A-5G depict cross-sections of the insert 50 as shown in fig. 4 in various possible examples.

The insert 50 may have a topsheet 51 and a backsheet 52 that form a cuff-like closure for absorbent structures such as those further described below. The absorbent structure described with reference to the absorbent insert comprises a top sheet 51 and a bottom sheet 52. The topsheet 51 and backsheet 52 may be attached together along a longitudinal seam 64 and along a lateral seam 69.

Top sheet

The topsheet 51 may be formed of a liquid permeable nonwoven web material. It may be desirable that the material forming the topsheet 51 be compliant, soft feeling, and non-irritating to the wearer's skin. It may be desirable that at least a portion of the topsheet 51 be liquid permeable, allowing liquid to readily penetrate through its thickness. Suitable topsheets can be made from a wide range of biodegradable materials, such as woven or nonwoven materials of natural fibers (e.g., softwood pulp, hardwood pulp, cotton, bamboo pulp, abaca pulp, viscose, lyocell, hemp, flax, kapok, kenaf, jute, cuprammonium, ramie, sisal, and the like). If the topsheet 51 comprises fibers, the fibers may be treated by spunbonding, carded web, wet-laid, melt-blown, hydroentangled, or other methods known in the art. The preferred fibers of the top sheet 51 and bottom sheet 52 are viscose, pulp and blends of viscose and pulp. Even more preferred are viscose fibres having a flat cross-sectional shape such that the average fibre thickness is less than 7 microns, such as the Viloft viscose fibres commercially available from Kelheim Fibers GmbH. Another preferred embodiment of the top sheet 51 may be a spunlaced fabric made of a mixture of viscose and pulp. Without being bound by theory, it is believed that the enzymatic dissolution of the fibers depends on a variety of factors, such as the thickness of the fibers, the crystallinity of the polymers comprising the fibers, the type of treatment to which the natural fibers are subjected. For example, natural fibers containing hemicellulose polymers may be more soluble. For example, fibers having a thinner thickness may be more soluble because they provide a larger specific surface area for enzymes to contact the fibers, degrade the polymer and impair the mechanical stability of the fibers. For example, fibers with higher lignin content may be more difficult to degrade. For example, pulp fibers or viscose fibers made from dissolving wood pulp in a sulfite process are more susceptible to enzymatic degradation than pulp fibers or viscose fibers made from dissolving wood pulp in a sulfate or kraft process.

In some cases, it may be desirable for at least a portion of the topsheet 51 to be made of a hydrophobic material or to be treated to be hydrophobic in order to isolate the wearer's skin from liquids contained in the absorbent core 71. Suitable hydrophobic cellulosic fibers are, for example, viscose fibers with hydrophobic additives, such as the Olea fibers commercially available from Kelheim Fibres GmbH. If the topsheet 51 is typically made of a hydrophobic material, it may be desirable for at least a portion of the upper surface of the topsheet 51 to be treated to be hydrophilic so that liquid will transfer through the topsheet more quickly. The topsheet 51 may be rendered hydrophilic by treatment with a surfactant or by incorporating a surfactant into the topsheet. Suitable methods for treating the topsheet 51 with a surfactant include spraying the topsheet material with a surfactant and/or immersing the material in a surfactant. A more detailed discussion of such treatments and hydrophilicities is contained in U.S. Pat. nos. 4,988,344 and 4,988,345. A more detailed discussion of some suitable methods for incorporating surfactants into topsheets can be found in U.S. patent No. H1670. However, in another example, the topsheet 51 may comprise a hydrophobic apertured web. This may be accomplished by eliminating the hydrophilization treatment step from the production process and/or applying a hydrophobic treatment agent, such as a polytetrafluoroethylene compound, e.g., SCOTCHGUARD, or a hydrophobic lotion composition, to the top sheet material, as described below. In such examples, it may be desirable for the pores to be large enough to allow the permeation of aqueous fluids (e.g., urine) without significant resistance otherwise attributable to hydrophobicity. It may also be desirable for the apertures to have sufficient effective open area and/or aperture size to allow penetration of low viscosity fecal matter. Examples of topsheets meeting these requirements are described in U.S. Pat. nos. 5,342,338, 6,414,215 and 6,010,491. Alternatively, hydrophobic and hydrophilic fibers may be mixed in the topsheet 51 to allow for rapid acquisition while reducing fluid retention. For example, hydrophobic viscose and hydrophilic viscose fibers may be blended in a ratio of 10:90 to 90:10, depending on the level of hydrophilicity and hydrophobicity of those fibers. The level of hydrophilicity and hydrophobicity can be determined via the water contact angle.

Any portion of the topsheet 51 may be coated with a lotion or skin care composition, as is known in the art. Examples of suitable lotions include those described in U.S. Pat. nos. 5,607,760, 5,609,587, 5,635,191, 5,643,588, 5,968,025 and 6,716,441. The lotion can be used as the above-mentioned water repellent agent alone or in combination with another agent. Lotions and hydrophobic treatments may be biodegradable.

The topsheet 51 may also include or be treated with an antimicrobial agent, some examples of which are disclosed in U.S. patent application Ser. No. 08/212,441, published as U.S. Law registered invention H1732.

The topsheet 51, backsheet 52, or any portion of the topsheet or backsheet may be embossed and/or matte finished to provide a more cloth-like appearance.

Negative film

The backsheet 52 is generally the outer liner portion of the insert 50 forming the garment-facing surface thereof and prevents exudates absorbed and contained within the insert 50 from wicking through and soiling the outer cover. In some instances, it may be desirable for the backsheet 52 to be substantially liquid impermeable.

The backsheet 52 may be formed of a substantially liquid impermeable nonwoven web so as to contain and isolate liquid exudates from the outer cover, garment and/or environment of the wearer. At the same time, the backsheet 52 may be vapor permeable to provide breathability of the insert and the wearable absorbent article, thereby reducing wetness in the area between the insert and the wearer's body and helping to reduce the likelihood of skin irritation and/or rash that may be caused by excessive hydration of the skin. Alternatively, the backsheet 52 may be a hydrophilic nonwoven material, however, it would be desirable to construct a liquid impermeable material in a launderable reusable cover.

In certain embodiments, the backsheet may have a Water Vapor Transmission Rate (WVTR) of greater than about 2000g/24h/m ², greater than about 3000g/24h/m ², greater than about 5000g/24h/m ², greater than about 6000g/24h/m ², greater than about 7000g/24h/m ², greater than about 8000g/24h/m ², greater than about 9000g/24h/m ², greater than about 10000g/24h/m ², greater than about 11000g/24h/m ², greater than about 12000g/24h/m ², greater than about 15000g/24h/m ², as measured according to WSP 70.5 (08) at 37.8 ℃ and 60% relative humidity. In this particular application, a higher WVTR may be desirable because the insert backsheet 52 will not form the outer surface of the wearable article as a conventional disposable diaper backsheet, but rather will be covered by one or more layers of the outer cover material, which may itself act to reduce the WVTR of the composite structure in some cases.

The backsheet 52 may be joined to the topsheet 51, absorbent core 71, or any other element of the insert 50 by any suitable attachment mechanism known in the art. For example, the attachment mechanism may comprise a continuous line or layer of adhesive, a patterned layer of adhesive, or a series of separate lines, spirals, or spots of adhesive. One example of an attachment device includes an open pattern network of adhesive filaments, as disclosed in U.S. patent No. 4,573,986. Other suitable attachment mechanisms include a number of adhesive filament strands wound in a spiral pattern, as exemplified by the apparatus and methods shown in the following patents: U.S. patent No. 3,911,173;4,785,996; and 4,842,666.

The presence of the binder in the absorbent article can lead to problems with the formation of tacky aggregates at the treatment temperature in the treatment equipment. Such viscous aggregates tend to stick to the shaft and blade system in the treatment apparatus and significantly increase the dissolution time of the used absorbent structure. To address this problem, it is preferred that some or preferably all of the adhesive used in the absorbent article have a storage modulus G' of greater than 300,000pa, as measured at a frequency of 1Hz according to the oscillatory rheology test method described herein. Most preferably, an adhesive is used having a storage modulus G' measured at 1Hz of greater than 300,000Pa when measured at 50 ℃.

Without wishing to be bound by theory, it is believed that adhesives having a storage modulus G' above 300,000pa measured at 1Hz at the processing temperature in the processing equipment will be less tacky, thus reducing the effect of bonding the residual fibers together and to the components of the processing equipment. This finding is consistent with the Dahlquist criteria. Considering that the treatment apparatus is to be cooled to about room temperature, it may be preferable to use an adhesive having a storage modulus G' measured at 1Hz of higher than 300,000pa in a temperature range between an ambient temperature at which the treatment apparatus is used and an operating temperature of the treatment apparatus (e.g., 20 ℃ to 50 ℃). The storage modulus G' in the temperature range between the ambient temperature at which the treatment device is used and the operating temperature of the treatment device may be below 10,000,000pa.

FIG. 6 plots the storage modulus G' of two commercially available adhesives over a temperature range of-10℃to 100 ℃. Sample a is DM538, which is commercially available from Henkel. Sample a has a storage modulus G' of the Dahlquist criterion between 20 ℃ and 50 ℃ above 300,000 pa. Sample B is H2031F, which is commercially available from Bostik. Sample B has a storage modulus G' between 20 ℃ and 50 ℃ below the Dahlquist criterion. Sample a represents a preferred adhesive for this application.

Alternatively, the attachment mechanism may include thermal bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable attachment mechanism or combination of such attachment mechanisms as known in the art.

It should be appreciated that the outer cover described above may be constructed of a variety of materials and be configured to bear and maintain a number of structural loads commonly imposed on disposable diapers by: by stretching and adapting to the anatomical features and body movements of the wearer; and by absorbing, swelling and increasing the weight exuded by the wearer's faeces. Thus, the use of such outer covers may present less requirements for the structural strength of the insert than is required for the interior components of the disposable diaper. Thus, articles such as described herein may include disposable absorbent inserts made from materials other than those typically used to make disposable diapers, such as petroleum derived materials, for example, polyethylene and polypropylene. For example, in addition to the materials described above, disposable absorbent inserts are also contemplated that have one or more of a topsheet, a backsheet, and/or other components formed from: wood, cotton, flax (linen), hemp, bamboo or other cellulosic fibers (e.g., paper). If resistance to aqueous liquid penetration or significant liquid impermeability is desired, for example, for a backsheet, a material typically formed of hydrophilic fibers, such as paper, may be coated or impregnated with a hydrophobic material, such as a skin-compatible oil or wax, to impart the desired resistance to aqueous liquid penetration. Each material forming the insert may be selected so as to be dispersible, flushable, biodegradable and/or compostable in water or aqueous solution (preferably an agriculturally acceptable humus or soil conditioner).

Absorbent core

Referring to fig. 5A-G, the insert 50 may have an absorbent core 71 positioned within the envelope-like structure formed by the topsheet 51 and the backsheet 52. The absorbent core 71 may comprise any absorbent material that is generally compressible, conformable, non-irritating to the wearer's skin, and capable of absorbing and retaining liquids such as urine and other certain body exudates. The absorbent core 71 may comprise various liquid-absorbent materials commonly used in disposable diapers and other absorbent articles, such as comminuted wood pulp, which is generally referred to as air felt. Examples of other suitable absorbent materials include creped cellulose wadding; coform comprising wood pulp and a meltblown polymer; tissue, including tissue wraps and tissue laminates; an absorbent foam; absorbing the sponge; a superabsorbent polymer; an absorbent gelling material; or any other known absorbent material or combination of materials.

The absorbent core 71 may include a liquid acquisition/distribution material 65 and a storage material 66. Generally, the acquisition/distribution material 65 may have relatively rapid absorbent and wicking properties, but may also have limited absorbent capacity. Conversely, in general, the storage material 66 may have relatively slow absorption and wicking properties, but may also have a greater absorption capacity. Thus, the acquisition/distribution material 65 may be used to quickly absorb and distribute a gush of liquid (e.g., urine), whereas the storage material 66 having a larger absorbent capacity may be used to absorb such liquid from the acquisition/distribution material and store it for the time required until the insert is replaced.

The absorbent core 71 may be manufactured in a variety of sizes and shapes (e.g., rectangular, hourglass, "T" -shaped, etc.). The configuration and construction of the absorbent core 71 may also vary (e.g., the absorbent core or other absorbent structure may have various caliper zones, a hydrophilic gradient, a superabsorbent gradient, or lower average density and lower average basis weight acquisition zones; or may include one or more layers or structures). Examples of absorbent structures for use as absorbent core 71 may include those described in U.S. Pat. nos. 4,610,678, 4,673,402, 4,834,735, 4,888,231, 5,137,537, 5,147,345, 5,342,338, 5,260,345, 5,387,207, and 5,625,222.

In order to reduce the overall size and/or thickness of the absorbent core and thereby improve the comfort of the wearer and reduce the volume of disposable waste formed by soiled inserts, it may be desirable to construct the absorbent core using as little volume of core material as possible with performance constraints. Generally, the absorbent core construction that minimizes or eliminates the need for airfelt or other forms of cellulosic fibers in combination with particles of superabsorbent polymer is referred to as a "substantially airfelt-free core". Airfelt and other cellulosic fibers have been used as absorbent fillers in the absorbent cores of disposable diapers. Such fibers have absorbent properties and impart some absorbent capacity to the absorbent core, and are included to provide a structural matrix to retain dispersed particles of superabsorbent polymer and/or absorbent gelling material. While inclusion of such particles improves absorbent capacity, maintaining such particles properly dispersed may be critical to prevent the particles from forming "gel-blocking" when swollen with absorbed liquid in use, resulting in a compromise in absorbent capacity. The inclusion of airfelt or other cellulosic fibers as the matrix of the superabsorbent particles can function to reduce or prevent gel blocking. However, this also results in the absorbent core having a large volume even before any liquid is absorbed.

Referring to the examples depicted in fig. 5C and 5E herein, an absorbent core 71 having a portion that is substantially free of airfelt may be disposed between the topsheet 51 and the backsheet 52. The core 71 may include a layer formed at least in part from a substrate, a superabsorbent polymer, or a distribution of absorbent particles 66 of absorbent gelling material, and a thermoplastic adhesive composition that entraps the distribution of absorbent particles 66 and adheres to at least a portion of the substrate, thereby securing the absorbent particles 66 on or near the substrate and relative to the substrate. The core may have channels, i.e. areas substantially free of absorbent material such as pulp and SAP. The% cellulose-based SAP as part of the cellulose/SAP mixture may be less than 70%, less than 50%, less than 35%, less than 25%: for cellulose-based SAPs having reduced absorbent properties under pressure, it may be preferable to reduce the% of cellulose-based SAPs.

Sublayer (sublayer)

The insert 50 may also include a sublayer disposed between the topsheet 51 and the backsheet 52. The sublayer may be any material or structure capable of receiving, storing or immobilizing bodily exudates. Thus, the sub-layer may comprise a single material or multiple materials operably associated with each other. Further, the sublayer may be integral with another element of the insert 50, or may be one or more separate elements directly or indirectly joined with one or more elements of the insert 50. Further, the sublayer may comprise a structure separate from core 71, or may comprise at least a portion of core 71 or may be a component of at least a portion of the core.

Suitable materials for use as the sublayer may include macroporous open cell foams, macroporous compression resistant high loft nonwoven structures comprising a plurality of vertically oriented looped fiber strands, absorbent core structures as described above with punched holes or depressions, and the like. Further, the sublayer or any portion thereof may include or be coated with a lotion or other known substance to increase, enhance or alter the performance or other characteristics of the element.

Insert asymmetry

Referring to fig. 4, the insert 50 will have an insert lateral axis 70 equally dividing its longitudinal length. The insert 50 may have a configuration that is asymmetric across the insert lateral axis 70. For purposes of this specification, "asymmetric" and "asymmetry" as used with respect to an insert means that the features, geometries (e.g., shapes), materials, and/or configurations on one side of the insert lateral axis 70 are substantially different in some respects from those on the other side of the insert lateral axis 70. Such asymmetric configurations result from having various features of the insert 50 designed to accommodate the physical features and functions of the intended wearer (as they differ front to back, i.e., body contours, excretory and elimination functions), thereby enhancing the containment/absorption performance, comfort, fit and/or appearance of the wearable absorbent article, thereby conserving the use of materials and/or reducing the volume of disposable waste. "asymmetric" and "asymmetry" do not refer to differences across the insert lateral axis that may be attributed to features that may be included on the insert for the following purposes only: pure cosmetic coloring or surface finishing; fastened to an outer cover (such as the fastener components described herein); a user grasps an insert (such as the grasping structures described herein); as indicia for orienting the insert within the outer cover (such as orientation indicia described herein); or for other purposes that are substantially unrelated to the physical characteristics and function of the intended wearer (as they differ front to back), thereby affecting the performance, comfort, fit, and/or physical appearance of the wearable absorbent article, conserving material usage, and/or reducing the volume of disposable waste.

As one example, the topsheet 51 may have one or more apertures 63 therethrough, primarily in the crotch and/or rearward region 55, as set forth in fig. 4. The apertures 63 may allow liquid or low viscosity feces to penetrate the topsheet 51 and reach the absorbent material in the absorbent core 71 faster than would occur without such apertures, thereby enhancing the liquid feces absorption and containment capacity of the insert 50.

In another example, the fecal management features may be disposed in the back of the article, including one or more pockets, spacers, low viscosity fecal management elements, openings in the suspended topsheet, and the like, for example, as described in co-pending U.S. application Ser. Nos. 11/224,779, 11/786,890 and 11/894,087. Thus, the topsheet 51 may include one or more larger apertures in the rear region to provide unrestricted or relatively less restricted movement of solid or higher viscosity waste therethrough. The size of the pores may be important in achieving the desired fecal waste encapsulation performance. If the aperture is too small, waste may not pass through the aperture because the point of exudation is not aligned with the aperture or because the fecal matter has a size greater than the aperture. However, if the aperture is too large, the area of skin that can be exposed to "rewet" from the contained waste increases.

The insert may have an asymmetry in its absorbent core (absorbent core asymmetry). The asymmetry of the absorbent core may be caused by the arrangement of materials and features within the absorbent core to position particular materials and features of the absorbent core in their most desirable and/or most efficient locations depending on the features and functions of the wearer's anatomy (as they differ front to back).

For example, all or a portion of the rear region 55 of the insert 50 may include acquisition/distribution material 71, but less or no storage material 66 than the front region 54, as seen in fig. 5A and 5B, 5C and 5D, and 5E and 5F, respectively. With this particular absorbent core asymmetry, the storage material 66 may be primarily located in the front of the wearable absorbent article when worn. This may provide a substantial portion of the urine storage capacity of the insert closer to the wearer's urine insult point to reduce the likelihood of leakage and remove potentially uncomfortable and/or unsightly dimensions and volumes from between the wearer's legs or back regions of the wearer, particularly when the storage material 66 swells with absorbed liquid. In addition, this particular asymmetry provides for savings in the amount of storage material 66 used by locating the storage material 66 only in a portion of the insert, rather than along substantially the entire insert. The liquid storage capacity of the front region of the absorbent core may be greater than the liquid storage capacity of the rear region of the absorbent core as measured by the tea bag centrifuge capacity test (Teabag Centrifuge CAPACITY TEST) disclosed in U.S. patent 6,278,037. The liquid storage capacity of the front region of the absorbent core may be at least about 10%, 20%, 50% or even 100% or more greater than the liquid storage capacity of the back region. With such an arrangement, the acquisition/distribution material 65 located in both the front region 54 and the rear region 55 can be used to acquire liquid (typically urine) and move the liquid to the storage material 66 located primarily in the front region 54. Alternatively or in addition, the area and/or basis weight of the acquisition system or component material in the front region of the insert may be at least about 10%, 20%, 50% or even 100% or more greater than the area and/or basis weight of the rear region. Alternatively or in addition, the surface area, cross-sectional area, and/or lateral width of the absorbent core 71 may be greater in the front region 54 as compared to the back region 55. For example, the surface area, cross-sectional area, and/or lateral width of the absorbent core 71 in the front region 54 may be greater than the back region 55 to accommodate a greater proportion of the acquisition/distribution and/or storage material present in the front region of the absorbent core.

Referring to fig. 5A, 5C, and 5E, in other examples, the absorbent material 66 in the front region 54 may be dispersed within the acquisition/distribution material 65 (fig. 5A), respectively, contained within a separate liquid permeable structure or cuff 67 (fig. 5C) in fluid communication with the acquisition/distribution material 65; or dispersed on or within the adhesive matrix of the retention material 68 and in fluid communication with the acquisition/distribution material 65 (fig. 5E). Conversely, the rear region 55 may contain primarily acquisition/distribution material 65, but less storage material 66 than the front region 54, or no storage material (fig. 5B, 5D, 5F). The material in the front region 54 may also be provided according to the configurations described in one or more of U.S. patent application US2008/312617、US 2008/312618、US2008/312619、US2008/312620、US2008/312621、US 2008/312622、US2008/312623、US2008/312624、US2008/312625、 and US2008/312628, where the rear region 55 has a different configuration.

In another example, the storage material 66 and the acquisition/distribution material 65 may occupy separate distinct layers of the absorbent core 71, as shown in fig. 5C. In some cases, it may be desirable to have the surface area of the layer containing the acquisition/distribution material 65 (i.e., the planar chart area relative to a flat-laid insert, as shown in fig. 4) be greater than the layer containing the storage material 66, or vice versa. For example, if the layer containing acquisition/distribution material 65 is formed so as to have a larger surface area laterally across the insert in the front region 54, this may be used to provide a greater amount of space for acquisition/distribution material in the front region. This may impart greater capacity in the front region to quickly absorb and distribute relatively large gushes of urine discharged toward the front region, as may be desirable for wearable absorbent articles such as for elderly men, infants, and toddlers-enhancing the containment capacity of the insert.

In another example, as shown in fig. 5G, the absorbent core 71 is wrapped in core wraps 73, 74. The wrapped core is enclosed between the top sheet 51 and the bottom sheet 52. In one example, the core wraps 73, 74 may be made of nonwoven paper (e.g., tissue paper); the topsheet 51 and the backsheet 52 may be manufactured from regenerated cellulose, such as viscose.

However, in another example, such as for newborns and infants, a large gush of urine may not be expected, but rather a relatively large amount of liquid or low viscosity fecal matter may be expected. Thus, wearable absorbent articles for the group of intended wearers can include a larger sized acquisition/distribution layer in the rear region 55 of the insert, which occupies a larger surface area. This may impart more capacity in the rear region to quickly absorb liquid surges or low viscosity fecal material discharged toward the rear region and thereby enhance the containment capacity of the insert.

The difference between the front and rear regions may also be included for the purpose of the sleeping insert. While an insert designed for awake use may have a substantial portion of its liquid storage capacity in the front region 54 as described above, an insert designed for use, for example, by infants sleeping may have a substantial portion of its liquid storage capacity in the rear region 55 to accommodate infants sleeping supine by locating a substantial portion of the storage capacity where fluid effluent will flow under the influence of gravity.

It may also be desirable to locate the thickener in the absorbent core in the rear region 55 of the insert. Thickeners may be used to provide additional assurance that liquid or low viscosity fecal matter will be thickened and thus more secure and more likely to be contained within the insert. The thickener may be biodegradable.

The insert 50 may also have an overall shape/backsheet asymmetry. For example, the insert 50 may occupy a greater surface area on one side of the insert lateral axis 70 than on the other side, as viewed in the laid-down position as shown in fig. 4. This may be useful for comfort, body cover, appearance, performance, and/or for the purpose of saving backsheet materials. For example, in combination with comprising a majority of the storage material 66, the front region 54 of the insert 50 may occupy a greater surface area, which is associated with a greater space within the insert to receive the storage material, e.g., to improve overnight absorption and containment capacity of a prone sleeping wearer, and to allow the insert to remain flatter, particularly relevant when the absorbent material swells with absorbed liquid. Such a larger surface area may be greater on one side of the insert lateral axis 70 than the surface area occupied by the rear region 55 on the other side of the insert lateral axis 70.

The insert 50 may also have a narrow region in the region located in the crotch region of the outer cover. This narrowing in the crotch region can be used to enhance wearing comfort by eliminating the size and volume between the legs. Referring to fig. 2B, it may also be used to better enable the crotch region 26 of the outer cover 20 to accommodate and retain the laterally centered position of the insert 50 by ensuring that the insert 50 (by having a limited amount of absorbent material and a limited width therein) does not swell beyond the spatial capacity of the crotch region 26 of the outer cover 20. Such narrowing may, for example, continue into the rear portion of the insert, creating an overall shape/backsheet asymmetry.

The insert 50 may also be otherwise asymmetric across the insert lateral axis 70 for the same, related or other purposes as those described above.

Thus, it should be appreciated that if the design fit, comfort, performance, and appearance of the insert 50 were to be fully achieved, the insert asymmetry across the insert lateral axis 70 would be a result of the design and construction of the insert so as to have only one front region and only one rear region, i.e., the front region and the rear region are not interchangeable.

Gripping structure

Referring to fig. 2F, 3 and 4, the insert 50 may also include respective forward user gripping structures 59 and rearward user gripping structures 61. User gripping structures 59, 61 may be provided to enable a user to quickly and easily grasp the insert 50 proximate the respective ends of the gripping members.

The gripping structures as shown and/or suggested may enable a user to more quickly grip and stretch the insert 50 from a contracted position similar to that depicted in fig. 3 to an extended position similar to that depicted in fig. 4, which may be desirable for installing the insert 50 into an outer cover. As shown, if the user grasps the structure 59, 61 centered near the respective end of the insert 50, this may also provide visual assistance to the user to co-locate the respective centered pair of fastener components, as described in more detail below.

In addition, the user gripping structures 59, 61 may be used to enable a user to quickly and easily grasp the insert 50 near its respective ends, with less likelihood of being soiled when replacement of the insert 50 becomes necessary or desirable due to their distance from the exudation point on the wearer's body. Thus, the user may better avoid contacting the wearer's exudates with the user's hands when removing the soiled insert 50 from the outer cover 20.

Referring to the example depicted in fig. 2F, it may be desirable in some cases to include more than one gripping structure 59 on the insert. This may be considered useful in examples such as that depicted in fig. 2F, where more than one fastener component 56 is disposed on an end of the insert. In this case, the inclusion of separate gripping structures 59 associated with and proximate to each fastener component 56 may enable a user to manipulate portions of the insert to more easily accurately position and install them within the outer cover, with the fastener components 59, 33 properly co-located and/or aligned. When it is desired to remove the insert from the outer cover, it may also be possible to more easily enable the user to pull fastener members 56 away from the pair of fastener members 33 to separate them by locating or concentrating the user's drag force at the location where they are desired to achieve such separation.

The user gripping structures 59, 61 may include tab-like extensions as shown in fig. 2F, 3 and 4, with free ends that are not attached to the outer cover 20 when the insert 50 is installed in the outer cover 20, which may be easily gripped. The user gripping structure may also have different forms. As non-limiting examples, the user gripping structures may take the form of annular protrusions (not shown) extending from the ends of the insert 50, finger holes (not shown) through the insert 50 near the ends of the insert 50, pockets having openings facing the lateral centerline 70 of the insert, and other structures that facilitate gripping and pulling of the insert 50 at locations near the ends of the insert 50.

Additionally, the gripping structures 59, 61 may be formed of a material having a high coefficient of friction (e.g., at least about 0.5), an elastically compressible material, and/or a surface having a three-dimensional relief to facilitate a user's firm grip and pull on the insert.

The gripping structures 59, 61 may also be configured or adapted to enable folding over or under the respective ends of the insert towards the lateral centerline of the insert. This can be used to hide the gripping structures behind other materials and protect them from contamination by body exudates. Alternatively or in addition, it may be used to add convenience to the user.

Insert/outer cover fastener component; orientation marks; other possible features

Referring back to fig. 2B, 3 and 4, as previously described, the outer cover 20 may have one or more insert fastener components disposed thereon, such as a front insert fastener component 33 and/or a rear insert fastener component 32. Insert 50 may have front and/or rear fastener components 56, 57 disposed thereon. The respective front and/or rear fastener components 56, 57 on the insert 50 may be selected and/or adapted to cooperate to enable fastening with the respective front and/or rear insert fastener components 33, 32 provided on the outer cover 20.

Examples

Example 1

The absorbent article was a two-piece hybrid diaper made of a reusable cloth diaper made of Charlie Banana and a disposable biodegradable insert, 5 months 2021. The disposable biodegradable insert was made of two identical laminates, glued to each other with 5gsm spiral construction glue, 95mm wide in CD and 350mm long in MD.

The disposable insert comprises a CMC based AGM,Commercially available from Magic s.r.l., oleggio, italy. The disposable biodegradable insert has about the following overall composition: 7 g/>25G of pulp fiber, 8.3g of bamboo viscose glue thorn cloth, 1.8g of thin paper and 0.6g of glue. Each laminate contained in the disposable biodegradable insert has the same design as the commercially available Charlie Banana disposable insert.

The two-piece hybrid diaper described above is then used by the infant in consumer testing and subsequently treated according to the degradation process in a treatment apparatus in the presence of an enzyme solution.

The treatment device was Kcook Multi CCL401,401 WH, commercially available from Kenwood. The machine comprises a container which is removable from the body of the machine and which can be closed with a lid. The empty container weighed approximately 2120g, without blade and cap. The height of the vessel was 22cm, whereas the inner diameter of the vessel was 21cm. Kcook machines allow control of the temperature of the solution and the rotational speed of the inserts and blades used within the container. A schematic of the apparatus is shown in fig. 1A, and a schematic of the blade is shown in fig. 1B.

The temperature was set to 50 ℃ and the rotational speed was set to a level/value of '4'. Three used disposable inserts were loaded into the barrels of Kcook machines: 1 of them is loaded with urine and faeces, while the other two are loaded with urine only. The total amount of urine and feces for the three used inserts was about 302g. Three disposable inserts were filled into a bucket and 1350g enzyme solution was added. The initial pH was 5.0 prior to starting the treatment apparatus.

The following were mixed to prepare an enzyme solution:

135g of cellulase blend commercially available from Sigma-Aldrich under the trade name SAE0020-50ML

6755 G of 0.5M buffer ph 5.0 liquid, commercially available from ALFA AESAR from ThermoFisher GmbH

And 540g of deionized water.

The vessel was closed with a lid and the device was started and operated for 32 hours. The lid was opened every 8 hours to visually check the degradation state of the insert used. At the end of the experiment, the machine was shut down and after 8 hours the contents of the barrels were visually analyzed and analyzed using the test methods described herein. The pH was measured at the end of the experiment to be 4.8.

Visually, the three used inserts appeared to dissolve with only some residual fibers present in the liquid. The degree of dissolution was quantified using a 20mm sized screen. The solution was poured from Kcook machine through a 20mm screen. The screen is pre-weighed prior to the operation of passing the solution through the screen to determine the initial weight w0. After the operation of passing the solution through the screen was completed, the screen was evaporated in an environment of 23 ℃ and 50% rh until the weight was constant, thus determining the final weight wf. The actual insert mass wr left on the screen is determined to be wf-w0. The amount of used inserts (wr) left on the screen was 1.0g of residue on a 20mm screen.

Example 2

The same two-piece hybrid diaper as described in example 1 was used with the same disposable biodegradable insert. The two-piece hybrid diaper described above is then used by the infant in consumer testing and subsequently treated according to the degradation process in a treatment apparatus in the presence of an enzyme solution. Three used disposable inserts were loaded into the barrels of Kcook machines: one of them carries urine and faeces, while the other two carry urine only. The total amount of urine and feces for the three used inserts was about 291g. The treatment apparatus was Kcook Multi CCL WH 401 as in example 1. Three used inserts were loaded into the barrels of the processing equipment and 1350g enzyme solution was added to the barrels. The initial pH was 5.0 prior to starting the treatment apparatus. The following were mixed to prepare an enzyme solution:

135g of cellulase blend commercially available from Sigma under the trade name 3AE0020-50ML

1215G of a 0.1M buffer solution pH 5.0 liquid, commercially available from MERCK KGAA

Once the three used inserts and 1350g enzyme solution were loaded into the barrel of the Kcook apparatus, the barrel was closed with a lid and the apparatus was started and operated for a total of 16 hours. After 8 hours, the lid was opened to visually check the degradation status of the used insert, when a large amount of material fragments were not degraded and still present in the solution in the bucket. This is still the case when the experiment is stopped after 16 hours. The pH was measured at the end of the experiment to be 5.85.

Without being bound by theory, it is believed that the mixing of urine and feces results in the formation of ammonia and an increase in pH to a level that is no longer optimal for the enzyme. This supports the findings in example 1 that increased molar concentrations of pH buffer have resulted in better control of pH and better degradation of used absorbent article inserts.

Oscillating rheology test method

The oscillatory rheology test method is used to measure the storage modulus G' of a hot melt adhesive or polymer composition at a temperature of interest. A controlled stress rotary rheometer (such as Discovery HR-3 (TA Instruments, NEW CASTLE, DE, USA), or equivalent instrument) is capable of controlling sample temperature (using a combination of Peltier cooler and resistive heater) with an accuracy equal to or exceeding 0.5 ℃ over a range of at least-10 ℃ to 150 ℃. The rheometer was operated in a parallel plate configuration and a 20mm stainless steel parallel plate tool.

The method initially uses a parallel plate gap of 1000 μm. To compensate for thermal expansion of the tool, the gap was set at 1000 μm and a mapping of the actual plate gap (as measured using a suitable standard test fluid) was performed as a function of temperature in the range of-10 ℃ to 150 ℃. This mapping is then used throughout the process of determining storage modulus at the temperature of interest.

The rheometer was heated to 150 ℃, the adhesive or polymer composition was introduced into the rheometer, the gap was set at 1050 μm, the excess protruding sample was trimmed, and then the gap was set at 1000 μm. The axial force control of the rheometer was set to 0N and maintained within ±0.1n of force during the experiment, thereby compensating for thermal expansion/contraction of the sample itself by adjusting the gap in addition to the compensation of the tool described above, so as to avoid overfilling or underfilling. The rheometer was then cooled to 130 ℃, at which time the temperature was reduced from 130 ℃ to-10 ℃ at a constant cooling rate of 2 ℃/min (hot to cold temperature ramp), starting the measurement. The applied strain amplitude was 0.1% and the oscillation frequency was 1Hz (i.e., one cycle per second). The resulting oscillating stress was recorded.

After this step, the sample temperature was set to 23 ℃ (the temperature was raised to this set point at a rate of 10 ℃/min) and the sample was allowed to stand at 23 ℃ for 4.0 hours. At the end of this period, the temperature was set to-10 ℃ (the temperature was reduced to the set point at a rate of 10 ℃/min), the sample was equilibrated at-10 ℃ for 300 seconds, and a second oscillatory rheology measurement (0.1% strain, 1Hz oscillation frequency) was started while the temperature was raised to 130 ℃ (cold to hot temperature ramp) at a constant rate of increase of 2 ℃/min. The applied strain amplitude was 0.1% and the oscillation frequency was 1Hz (i.e., one cycle per second). The resulting oscillating stress was recorded. Duplicate replicates were performed for each sample.

From the second ramp of rising temperature (cold to hot), the arithmetic mean storage modulus G' of two replicates at each of 20 ℃ and 50 ℃ was calculated and recorded, and these values were recorded in pascals (Pa) to 1Pa as the storage modulus at 20 ℃ and the storage modulus at 50 ℃, respectively.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Rather, unless otherwise indicated, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40mm" is intended to mean "about 40mm".

Claims

1. A method of enzymatic degradation of an absorbent structure suitable for providing an absorbent core of a hygiene article, wherein the method comprises the step of contacting the absorbent structure with a solution comprising an enzyme;

Wherein the absorbent structure comprises a superabsorbent polymer; and

Characterized in that the superabsorbent polymer comprises a polysaccharide.

2. The method of claim 1, wherein the polysaccharide comprises a cellulose-based polymer, and wherein the enzyme solution comprises a glycoside hydrolase enzyme.

3. The method of claim 2, wherein the cellulose-based polymer is carboxymethyl cellulose.

4. A method according to claim 2 or 3, wherein the superabsorbent polymer comprises at least 90 wt%, preferably at least 95 wt%, still more preferably at least 99 wt% of the cellulose-based polymer.

5. The method of any one of claims 1 to 4, wherein the polysaccharide comprises a starch-based polymer, and wherein the enzyme solution comprises an amylase.

6. The method of any of the preceding claims, wherein the absorbent structure comprises less than 1 wt% acrylic polymer.

7. The method of any of the preceding claims, wherein the absorbent structure further comprises wood pulp.

8. The method of any of the preceding claims, wherein the absorbent structure is partially or fully encapsulated by a core wrap, wherein the core wrap comprises regenerated cellulose fibers.

9. The method of claim 8, wherein the regenerated cellulose fibers comprise viscose fibers.

10. The method of claim 8 or 9, wherein the regenerated cellulose fibers have an average fiber thickness of less than 7 microns.

11. The method of any one of the preceding claims, wherein the enzyme solution further comprises a peroxide.

12. The method of any one of the preceding claims, wherein the enzyme solution further comprises an antifoaming agent.

13. The method according to any of the preceding claims, wherein the pH is maintained between 3.8 and 6.5, preferably between 4.5 and 5.5.

14. The method of any of the preceding claims, wherein the absorbent structure comprises one or more binders, and wherein at least one of the binders has a storage modulus G' of greater than 300,000pa measured according to the oscillatory rheology test method at 1Hz and 50 ℃.

15. The method according to any of the preceding claims, wherein the absorbent structure is at least partially liquefied by contacting the absorbent structure with the enzyme solution and the liquefied waste is preferably discharged into a municipal sewage system.