Short fiber fluff pulp with reduced odor perception, fluff pulp panel, uses thereof and absorbent article

Abstract

The present invention relates to a short fiber fluff pulp, a fluff pulp panel and an absorbent article comprising the short fiber fluff pulp having a Runkel index below around 1.6 and pentosan content from about 10% to about 20% used to promote reduction on urine and menstrual fluids odor perception. The invention also refers to the use of the short fiber fluff pulp and of the fluff panel on sanitary napkins, diapers, pet pads, underpads and / or incontinence products.

Description

SHORT FIBER FLUFF PULP WITH REDUCED ODOR PERCEPTION, FLUFF PULP PANEL, USES THEREOF AND ABSORBENT ARTICLE FIELD OF THE S^VENTON

[0001] The present invention relates to a short fiber fluff pulp, a fluff pulp panel and an absorbent article comprising the short fiber fluff pulp having a Runkel index below around 1.6 and pentosan content from about 10% to about 20% used to promote reduction on urine and menstrual fluid odor perception. The invention also refers to the use of the short fiber fluff pulp and of the fluff panel on sanitary napkins, diapers, pet pads, underpads and / or incontinence products.BACKGROUND

[0002] Human urine is primarily composed of water, electrolytes, and nitrogenous waste products resulting from protein metabolism. During the breakdown of amino acids and peptides, excess of nitrogen is converted in the liver into urea through the urea cycle. Urea is highly water-soluble and constitutes the main nitrogenous component of urine. Although urea itself is odorless, its retention in warm and moist environments - such as absorbent hygiene products - creates favorable conditions for microbial activity.

[0003] Once urine is absorbed by these products, microorganisms, particularly urease-producing bacteria, metabolize urea and release ammonia, a volatile compound with a strong and unpleasant odor, perceptible even at low concentrations. Over time, secondary microbial and chemical processes generate additional malodorous substances, including low-molecular-weight amines, sulfur- containing compounds, and short-chain fatty acids. These compounds collectively intensify the characteristic odor associated with urine, especially during prolonged retention in absorbent materials.

[0004] Regarding menstrual odor, Trimethylamine (TMA) is the principal odorant in menstrual fluid because of its strong sensory impact, stability under menstrual conditions, and microbial pathways that favor its production. In sanitary napkins, the combination of blood chemistry, elevated pH, and bacterial metabolism creates anenvironment conducive to TMA generation. This explains why odor control strategies in feminine hygiene products often prioritize TMA capture or neutralization, alongside secondary odorants such as diacetyl and 3-methylbutanal.

[0005] Absorbent hygiene products such as diapers, sanitary pads, urinary incontinence articles, and sanitary napkins are predominantly manufactured using cellulose-based materials, commonly fluff pulp obtained from long cellulose fibers, due to their liquid absorption and distribution properties. However, cellulose fibers lack intrinsic mechanisms to inhibit microbial activity or retain volatile compounds. Their porous structure, while efficient for fluid uptake, facilitates the diffusion and release of odor-causing molecules into the surrounding environment. As a result, unpleasant odors become noticeable shortly after use, leading to discomfort and reduced user satisfaction.

[0006] This scenario presents a significant technical challenge: the need for absorbent materials that not only manage fluids effectively but also mitigate or neutralize odor perception. Conventional approaches, such as adding fragrances, superficial odor-masking agents or chemical additives to control odor, fail to address the root cause of odor and may introduce additional concerns related to skin sensitivity and chemical exposure.

[0007] Several prior art documents have attempted to address this issue by modifying fiber properties or incorporating additives into absorbent products. For example, JP2018115408 discloses fibers with a Runkel index lower than 1.5; however, these fibers are synthetic and not cellulose-based, which limits their applicability in conventional fluff pulp structures. Document JP2017192435 reveals fibers with a Runkel index of 0.8 or lower, but they are intended for toilet paper applications and exhibit high Canada Standard Freeness, making them unsuitable for absorbent hygiene products that require specific fluid retention and distribution characteristics. Additionally, BR122013022639-7 describes an absorbent article comprising modified fluff pulp combined with chemical additives to control odor. While this approach may reduce odor perception, it introduces complexity in manufacturing and potential concerns regarding chemical exposure, without addressing the structural optimization of cellulose fibers themselves.

[0008] Despite these efforts, none of the cited solutions fully resolve the technical challenge of providing effective, long-lasting odor control in absorbent products without relying on synthetic fibers and / or chemical additives. Consequently, these solutions have not fully met the technical need for effective, sustainable, long-lasting odor control without compromising absorbency or safety.

[0009] The present invention provides a novel and inventive solution to this problem by introducing a short cellulose-based fiber composition with specific characteristics designed to reduce odor perception. These fibers, derived from fluff¬ type cellulose, are processed and arranged in a way that optimizes fluid absorption while limiting the conditions that favor odor release. The unique configuration of the fibers enhances retention and distribution of urine, reducing the exposure of absorbed liquid to microbial activity and minimizing the volatilization of odor-causing compounds. Moreover, by controlling the fiber pH during the fluff production process, it is possible to obtain also an odor control specifically for menstrual fluid (Trimethylamine). This approach significantly improves odor control without compromising absorbency, softness, or safety, thereby enhancing hygiene, comfort, and overall user experience during extended wear.SUMMARY OF THE INVE TION

[0010] The present invention refers to a short fiber fluff pulp, wherein the fibers comprise a Runkel index below around 1.6, and wherein the fibers promote a reduction on odor perception. The odor is menstrual fluids odor and / or urine odor.

[0011] In a preferably embodiment of the invention, the fibers comprise a Runkel index from about 0.6 to about 1.1.

[0012] In another embodiment of the invention, the short fiber fluff pulp presents a pentosan content in the fibers from about 10% to about 20% of the total weight of the fibers.

[0013] In another embodiment of the invention, it refers to a fluff pulp panel comprising at least 10% by weight of the short fiber fluff pulp, wherein the % by weight is based on the total amount of fibers comprised in the panel. In an optionalembodiment of the invention, the fluff pulp panel comprises a superabsorbent additive, preferably a superabsorbent polymer and / or a superabsorbent fiber.

[0014] In another embodiment of the invention, it reveals an absorbent article comprising at least 10% by weight of the short fiber fluff pulp and, optionally, a superabsorbent additive, preferably a superabsorbent polymer and / or a superabsorbent fiber, in which the fluff pulp promotes a reduction on odor perception. The % by weight is based on the total amount of fibers comprised in the article.

[0015] In other embodiments of the invention, it is disclosed the use of the short fiber fluff pulp and use of the fluff pulp panel for absorbent products like diapers, urinary incontinence products, sanitary napkins, pet pads, and underpads.BRIEF DESCRIPTiOH OF THE DRAWiNGS

[0016] FIG. 1 shows the results obtained from measurements of the quantity of ammonia in the headspace air during an odor control study of Example 1.

[0017] FIG. 2 shows the results obtained from measurements of the quantity of volatilized ammonia content (ppm) during an odor control study of Example 2.

[0018] FIG. 3 shows the results obtained from measurements of the quantity of volatilized TMA content (%) during an odor control study of Example 3.PETAiLED DESCWPTIOH OF THE iNVEHTiON

[0019] The present invention discloses a short fiber fluff pulp, the short cellulose fibers with low Runkel index. The Runkel index is the ratio of twice the cell wall thickness to the fiber lumen diameter, and can be expressed as:2 x cell wall thicknessRunkel index = — - - - - - -f iber lumen diameter

[0020] The wall thickness and the fiber lumen diameter are measured according to ISO 16065-2, from which the Runkel index is calculated.

[0021] The lower the Runkel index, the thinner the fiber wall, improving the intertwining of short fibers, improving the tensile properties of the web composed ofsuch fibers. The tower index also results in smaller fibers accommodated closer to each other, which results in the panel lower porosity.

[0022] In consequence of the tower Runkel Index, there is a better consistency in the homogeneous defibration of the pulp web and better retention of superabsorbent additive (superabsorbent polymer (SAP) or superabsorbent fiber) particles along the formed core, when used. Hardwood fibers with a Runkel Index greater than 1.6 present difficulties, little integrity in the handling of the fluffy pulp web formed, as well as low retention of the integrity of the core formed with the individualized fibers, and migration of SAP in the core. The reduction of the Runkel Index can be achieved by the combination of specifically sourced wood and the pulp processing conditions.

[0023] In this sense, the present invention provides a short fiber fluff pulp wherein the fibers comprise a Runkel index below around 1.6, preferably from about 0.6 to about 1.1, that promotes reduction on perception of urine odor. Furthermore, in a embodiment of the invention, when occurs an acidification in the pulping process, the fluff pulp can also promote reduction on perception of menstrual fluids odor and even better odor control for urine.

[0024] The tow Runkel Index interferes in the porosity of the panel when using the fluff pulp of the present invention, which is lower than the porosity of the long fiber cellulose originated from softwood, that is usually used in the hygiene market. A lower porosity reduces the liquid / air interface area, thus hindering the ammonia desorption process. Thus, the higher proportion of the fluff pulp of the present invention reduces the release of ammonia.

[0025] Furthermore, the present invention provides a short fiber fluff pulp comprising a content of pentosan from about 10% to about 20% of the total weight of the fiber.

[0026] Pentosan content in fiber of a fluff pulp can influence odor reduction in absorbent products by modifying liquid retention and chemical interactions within the structure. Pentosan is highly hydrophilic, which enhances the ability of the pulp to retain urine and reduce free liquid surfaces where ammonia volatilization occurs.Additionally, its hydroxyl-rich structure can interact with ammonium ions, limiting their conversion to gaseous ammonia.

[0027] Furthermore, pentosan may contribute to localized pH modulation during use. Partial hydrolysis of pentosan can release weak acids, creating a slightly acidic environment that inhibits urease activity, the enzyme responsible for ammonia formation. Combined with improved fiber flexibility and network formation, these effects help reduce ammonia release and, consequently, odor in absorbent articles containing the pulp.

[0028] The short fiber fluff pulp of the present invention is obtained from hardwood trees, preferably from Eucalyptus trees. Usually, the pulp is produced by pulping processes, such as mechanical, chemical, or semi chemical.

[0029] The short fiber fluff pulp of the present invention is obtained through a method for producing fluff pulp derived from eucalyptus wood, wherein there is a selection of raw material and controlled chemical processing steps are employed to obtain fibers with defined morphological and chemical characteristics.

[0030] The process for obtaining the short fiber fluff pulp with odor control properties of the present invention comprises the selection of raw material, wherein the eucalyptus wood of interest is selected, according to the desired properties for the final product, and transforming it into wood chips, by using cutting equipment Then, the wood chips are subjected to a kraft pulping process under controlled conditions of temperature, pressure, and alkali concentration (Chemical Cooking Stage). Specific care is taken to minimize hemicellulose degradation while ensuring sufficient lignin removal. Process parameters are adjusted to maintain fiber integrity and uniformity, avoiding excessive fines generation. Subsequently, the cooked pulp undergoes a multi-stage bleaching process (e.g., oxygen, chlorine dioxide, peroxide), optimized to achieve high brightness while preserving fiber strength. Special attention is given to the control of pentosan content, ensuring that the final pulp maintains a defined percentage range. Finally, the pulp is dried to reduce the moisture content of the pulp through controlled heat and mass transfer, and it mayoccur by different ways, for example, via steam-heated cylinders or through through-air drying (TAD).

[0031] Optionally, after the last bleaching stage, an acid can be added in the aqueous extract of the pulp to achieve a pH value lower than 5.5. The pH value of the aqueous pulp is obtained according to the norm ABNT NBR NM ISO 6588- 1:2021. The pH control results in a fluff pulp with specific odor control property for menstrual fluid (TMA molecule). This fluff pulp with pH control also enhances the odor control for urine.

[0032] The obtained pulp is characterized by using analytical methods (e.g., fiber morphology analysis, carbohydrate profiling) to validate compliance with Runkel Index specification, ensuring that fibers remain within the desired collapsibility and Pentosan percentage specification, characteristics that synergically contribute to odor control and fiber performance. The resulting fluff pulp presents a high absorbency capacity, as well as a controlled odor profile.

[0033] In face of that, the short fiber pulp of the present invention is, therefore, processed and arranged in a way that optimizes fluid absorption while limiting the conditions that favor odor release. The unique configuration of the short fibers of the present invention enhances retention and distribution of urine, reducing the exposure of absorbed liquid to microbial activity and minimizing the volatilization of odor-causing compounds. Unlike prior solutions that rely on synthetic fibers or chemical additives, the short fiber fluff pulp of the present invention achieves odor control solely through its characteristics and physical properties, maintaining products safety, softness, and absorbency.

[0034] Moreover, by controlling the fiber pH during the fluff pulp production process, it is possible to obtain also an odor control specifically for menstrual fluid (Trimethylamine). This approach significantly improves odor control without compromising absorbency, softness, or safety, thereby enhancing hygiene, comfort, and overall user experience during extended wear.

[0035] These properties make the pulp particularly suitable for hygiene and absorbent products, such as diapers, sanitary pads, sanitary napkins, and related applications.

[0036] The present invention also relates to a fluff pulp panel that comprises at least 10% by weight of the short fiber fluff pulp disclosed herein. The % by weight is based on the total amount of fibers comprised in the panel. The panel can comprise other types of fiber, for example, synthetic or man made fibers.

[0037] The use of the short fiber fluff pulp and use of the fluff panel of the present invention can be on diapers, urinary incontinence products, pet pads and / or underpads, that will release less ammonia than the usual absorbent products, besides being thinner due to the lower Runkel index. The short fiber fluff pulp and the fluff panel can be also used in sanitary napkins to reduce the TMA release.

[0038] The present invention also refers to an absorbent article that comprises at least 10% by weight of the short fiber fluff pulp, wherein the % by weight is based on the total amount of fibers comprised in the article. The absorbent article can be diapers, urinary incontinence products, sanitary napkins, underpads, and pet pads.

[0039] Optionally, the fluff pulp panel and / or the absorbent article of the present invention comprise a superabsorbent additive, preferably a superabsorbent polymer or a superabsorbent fiber. Due to their ionic nature and interconnected structure, the superabsorbent polymers (SAPs) absorb large amounts of water and other aqueous solutions without dissolving by solving water molecules through hydrogen bonding. The factors that provide absorption power to polymers are osmotic pressure, based on mobile counterions, and the affinity between the polymer electrolyte and water. The factor that suppresses the absorption power, on the contrary, is found in the elasticity of the gel resulting from their network structure. Not only do they have high fluid absorption capacity, but the absorbed fluid is difficult to release, as they only immobilize the fluid by trapping it rather than retaining it in the structure.EXAMPLES

[0040] The examples presented herein illustrate the characteristics and performance of the short fiber fluff pulp and confirm that this inventive short fiber fluff pulp delivers superior odor control without compromising other essential properties of the final products.

[0041] The examples are non-exhaustive, they have the purpose of illustrating the invention and should not be used as a basis to limit it.Example 1

[0042] In this example, odor control for urine was measured by incubating fiber fluff pulp samples comprising 100% long fiber (Sample A, Pine), 50% short fiber and 50% long fiber (Sample B, Eucalyptus) and 100% short fiber (Sample C, Eucalyptus) in 120 m L of synthetic urine supplemented with yeast extract and peptone. The short fiber fluff pulp used on Samples B and C is the one revealed on this invention.

[0043] The medium was inoculated with defined microbial consortia under controlled conditions at 37 °C for a period of 7 hours. Two inoculation mixes were employed: Mix 1 including Enterobacter cloacae, Escherichia coll ATCC 8739, Staphylococcus aureus ATCC 6538, Staphylococcus xylosus ATCC 29971, and Proteus mirabilis ATCC 25933; and Mix 2 comprising the same organisms except Proteus mirabilis. Positive control contained Proteus mirabilis only, and negative control contained no bacteria. Inoculum concentrations were adjusted to approximately 109CFU / mL for Enterobacter cloacae, Escherichia coil, Staphylococcus aureus, and Staphylococcus xylosus, and 107CFU / mL for Proteus mirabilis.

[0044] Ammonia generation was quantified by hourly measurements of gaseous emissions. The quantification of ammonia emissions from the different absorbent panels was performed through hourly air sampling in the headspace of each specimen, with the samples confined in sealed beakers to prevent external interference. In this study, ammonia concentration was determined using a portable ammonia sensor, which provided direct readings of gaseous NH3levels. The application of such sensors represents a methodology in laboratory-scale studies involving ammonia generation, which has a high resolution in the parts-per-million (ppm) range and low operational cost, while maintaining adequate accuracy and reproducibility for comparative analysis.

[0045] The typical operation of portable ammonia sensors relies on different detection principles, including:

[0046] Electrochemical sensors: Ammonia present in the air diffuses into an electrochemical cell, where a redox reaction occurs, generating an electrical current proportional to the NH3concentration.

[0047] Photoacoustic or non-dispersive infrared (NDIR) sensors: Ammonia molecules absorb radiation at specific wavelengths, and the sensor detects this absorption as a measure of concentration.

[0048] Semiconductor (metal-oxide) sensors: The presence of NH3modifies the electrical conductivity of a metal-oxide film, and this variation is converted into a concentration signal.

[0049] These methodologies enable direct readings in parts per million (ppm), with sufficient resolution for laboratory-scale emission studies.

[0050] Table 1 and Figure 1 show the Results of the tests demonstrating the reduction of ammonia emissions and, consequently, reduction of odor when using the Samples B and C (Samples of the present invention).Table 1Quantity of Ammonia in ppmSample TO T1 T2 T3 T4 T5 T6 T7100% A 0 0 13 51 185 159 60 152 50% B 0 0 13 49 113 111 23 114 100% C 0 0 6 21 56 80 17 121

[0051] The reduction of ammonia emissions was consistent across multiple test scenarios, indicating that the unique configuration of short fibers effectively limits the volatilization of ammonia and other odor-causing compounds.Example 2

[0052] in this example the odor control test was measured trough 5 mL of synthetic urine and 1 pL urease were mixed using an Eppendorf pipette. The samples were fluff pulp discs or pads manually produced at Suzano’s lab.

[0053] The pH mixture was around 5, indicating a mild acidity. The mixture was applied to each sample. Urease was used to simulate bacterial activity responsible for ammonia generation. Each Nalophan® bag was closed and filled with neutral air. Samples were stored for 24h at 36°C in a climate chamber, and ammonia concentrations were measured in duplicate at four time points: after 1, 3, 5, 8 and 24 hours. Ammonia (NH₃) levels were determined by using a ERA multigas sensor from ICO Data. All samples were prepared and evaluated in duplicate for the ammonia test. The reference sample was also prepared twice. The main difference between samples could be identified at the 24h time stamp, as seen in Table 2, and figure 2.Table 2% reduction in % reduction vs reference | ppm measurementSample i Sample relation to long fiber | at 24 h - 5 Pad | at 24h - 5 Padsfiber Long Fiber (Pine) i A 91,1 | 22,5Short Fiber |93,2 | 17,0 24,4% (Eucalyptus) i BShort Fiber |(Eucalyptus) with acid | C 96,6 | 8,0 64,4%PH I

[0054] According to the results obtained on this example, the use of the short fiber fluff pulp of the present invention promotes significant reduction on ammonia levels.Example 3

[0055] In this example, the odor control test for menstrual fluids was measured through trimethylamine (TMA) test, measured by GC-MS. The results can be seen in Table 3 and figure 3.Table 3% reduction of volatilized Sample Sample Volatilized TMA (%)TMA in relation to long fiber Long Fiber (Pine) A 45,1 -Short Fiber (Eucalyptus) B 45,2 0,0%Short Fiber Eucalyptus „C 2,1 95,3%|with acid pH | ’

[0056] According to the results obtained on this example, the use of the short fiber fluff pulp with acid pH promotes significant reduction on quantity of volatilized TMA.Example 4

[0057] In this example, fiber width and cell wall thickness are determined in accordance with ISO 16065-2. Determination of fiber length and fiber coarseness was done using an automated optical analyzer. From these, it was possible to determine the Runkel index, as demonstrated by Table 4 below.Table 4Wall thickness Fiber width Lumen Diameter Runkel index (pm) (pm) (pm)3,8 15,58 7,98 0,953,25 14,64 8,14 0,803,72 15,67 8,23 0,903,56 14,87 7,75 0,92 Minimum 3,25 14,64 6,62 0,80 Maximum 4,48 15,67 8,23 0,95Median 3,76 15,27 7,74 0,91

[0058] After measurements and the Runkel Index calculation, it was possible to demonstrate values below 1.0, which promotes optimized properties for the pulp and the absorbent product in which it is used.Example 5

[0059] The percentage of pentosan (dry-mass basis) was determined according to TAPPI Standard T 223 - Pentosans in Wood and Pulp. The results are shown in Table 5 below.Table 5Pentosans (%)Minimum 12.70 |Maximum 18.41 |Median 15.57 |

[0060] By means of the present examples, it is possible to confirm the improved characteristics of the short fiber fluff pulp and its increased performance on reducing urine and menstrual fluids odor perception on absorbent products.

Claims

CLAIMS1. Short fiber fluff pulp, wherein the fibers comprise a Runkel index below around 1.6 and promote reduction on odor perception.

2. Short fiber fluff pulp according to claim 1, wherein the pentosan content in the fibers is from about 10% to about 20% of the total weight of the fibers.

3. Short fiber fluff pulp according to claim 1, wherein the fibers comprise a Runkel index preferably from about 0.6 to about 1.1.

4. Short fiber fluff pulp according to claim 1, wherein the odor is menstrual fluids odor and / or urine odor.

5. A fluff pulp panel, wherein it comprises at least 10% by weight of the short fiber fluff pulp defined in claim 1.

6. A fluff pulp panel according to claim 5, wherein it optionally comprises a superabsorbent additive, preferably a superabsorbent polymer or a superabsorbent fiber.

7. An absorbent article, wherein it comprises at least 10% by weight of the short fiber fluff pulp defined in claim 1.

8. An absorbent article according to claim 7, wherein it optionally comprises a superabsorbent additive, preferably a superabsorbent polymer or a superabsorbent fiber.

9. Use of the short fiber fluff pulp defined in claim 1, wherein it is applicable on sanitary napkins, diapers, pet pads, underpads and / or urinary incontinence products.

10. Use of the fluff pulp panel defined in claim 5, wherein it is applicable on sanitary napkins, diapers, pet pads, underpads and / or urinary incontinence products.

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