Description:FIELD OF INVENTION
[001] The present invention relates to a biodegradable absorbent core for menstruation and hygiene products and a method of preparation thereof. Particularly, the present invention relates to preparation of biodegradable tri-layered absorbent core comprising primarily of biodegradable super-absorbent polymer with self-adhesive properties.

BACKGROUND OF THE INVENTION

[002] Sanitary pad making industry is one of the major sector that uses single-use plastics. Every year tones of used sanitary pads reach India’s landfills, adding to the prevailing plastic pollution in the country. Further, improper disposal of menstrual waste and non-segregation of menstrual waste from domestic waste leads to unhealthy working conditions for waste workers and poses hazard of contagious diseases among them.

[003] The Super-Absorbent Polymers (SAP) and Holt-Melt Adhesives are the chief raw materials used in fabrication of menstruation pad’s absorbent core region. Such products are non-biodegradable in nature and thus difficult to recover from the core. The single-use plastics used in the absorbent core region are root cause of environmental pollution as it is difficult to sort and contributes to more than 40% of total single use plastics wastes.

[004] Presently, sanitary pad fabricators procure synthetic SAP and Hot-melt adhesive from various industries and machines with exceeding process steps, which are then used to construct absorbent core, resulting in fabrication of non-biodegradable and unsustainable sanitary pads. In order to avoid hazards associated with non-biodegradable and unsustainable absorbent core, there exists a need to develop sanitary pads having biodegradable absorbent core.

[005] There are several patent applications that disclose sanitary pads with biodegradable absorbent core/absorber. One such Patent Application WO2019093700A1 discloses a biodegradable sanitary pad comprising an absorber containing seaweed, as a natural material, which contains a large amount of water-soluble fibers. The sanitary pad of the invention has no harmful chemical components and can rather provide beneficial effects to the human body by replacing a super absorbent polymer (SAP), as a synthetic compound, which is a conventional absorber.

[006] Another Patent Application KR102288713B discloses a detachable female pad, which includes a fixed part fixed to a base sheet and a separation part detachably attached to the base sheet, such that in order to reuse the pad, a user can remove a portion with a lot of menstrual blood only without a need to replace the entire pad, and thus can help prevent waste of resources and environmental pollution. To this end, the detachable female pad according to the invention comprises: a base sheet attached to underwear; and an absorption pad attached to the base sheet. The absorption pad includes: a fixed part permanently fixed to the base sheet; and a separation part detachably attached to the base sheet.

[007] Another Patent Application WO2021067769A1 discloses absorbent article with biocompostable properties, such as a feminine hygiene pad. Particularly, the invention is directed to an absorbent sanitary article with a high degree of biocompostability. The sanitary article comprises, in one embodiment, at least a top layer, a back layer, and absorbent core, wherein the absorbent core includes a superabsorbent polymer, and wherein at least the superabsorbent polymer is bio-compostable. The absorbent article exhibits improved biocompostable properties and performance comparable to non-biodegradable absorbent articles which include non-biodegradable superabsorbent polymers.

[008] Conventional absorbent pad makers provide biodegradable alternatives for top and bottom layers but fail to provide a solution to reduce usage of single-use plastics in absorbent region of the sanitary pads and other products such as diapers and wipes.

[009] Therefore, keeping in view the problems associated with the above state of the art, there is a need for reduction of single-use plastics in pads and preparation of economic, biodegradable, disposable, and reusable products including sanitary pads, diapers, wipes etc. with biodegradable absorbent core.

SUMMARY OF THE INVENTION

[0010] The present invention relates to a biodegradable absorbent core and a method of preparation thereof. The absorbent core comprises of a top layer, middle layer, and a bottom layer. The top layer and the bottom layer are made up of cellulose microfibers, or regenerated cellulose microfibers, or regenerated cellulose fibres. The middle layer is made up of biodegradable super absorbent polymer based composition coated on open woven fabric impregnated with the oils. The biodegradable super absorbent polymer based composition comprises of a plurality of natural oils, plurality of inorganic acids, and a plurality of biopolymers, or a combination thereof. The present invention also provides a method for preparation of absorbent core using infusion process.

OBJECTIVES OF THE INVENTION

[0011] A primary objective of the present invention is to provide a biodegradable absorbent core and a method of preparation thereof.

[0012] Another objective of the present invention is an absorbent core having superabsorbent properties.

[0013] Another objective of the present invention is to provide a biodegradable absorbent cloth for fabrication of economical, sustainable and biodegradable products including sanitary pads, diapers and wipes.

[0014] Other objects and advantages of the present invention will become apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 shows biodegradable absorbent core according to the present invention.

[0016] Figure 2 shows C-folded biodegradable absorbent core according to the present invention.
[0017] Figure 3 shows C-folded biodegradable absorbent cloth with self-adhesive tape as bottom layer.
SOURCE OF BIOLOGICAL MATERIAL USED IN THE INVENTION

[0018] The plurality of commercially available natural oils used in the composition such as soybean oil, palm oil, coconut oil and vegetable glycerin were procured (marketed products); commercially available biopolymers such as almond gum and arabic gum and cellulose microfibers or regenerated cellulose fibres used for preparing the top layer and the bottom layer were procured from vendors in Chennai.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Before the present composition and method are described, it is to be understood that this disclosure is not limited to a particular composition and method as described, as there can be multiple possible embodiments that are not expressly illustrated in the present disclosure but may still be practicable within the scope of the present disclosure.

[0020] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0021] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0022] The terms and words used in the following description are not limited to the bibliographical meanings, but, are merely used to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustrative purpose only and not for the purpose of limiting the invention.
[0023] It is to be understood that the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0024] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, steps or components but does not preclude the presence or addition of one or more other features, steps, components or groups thereof.

[0025] Accordingly, the present invention relates to a biodegradable absorbent core and a method of preparation thereof. Particularly, the present invention relates to preparation of biodegradable tri-layered absorbent core comprising primarily of biodegradable super-absorbent polymer with self-adhesive properties.

[0026] In another embodiment, figure 1 shows biodegradable absorbent core according to the present invention. The absorbent core comprises of a top layer, a core layer, and a bottom layer. The layers of the absorbent core are described herein detail:

[0027] (a) Top Layer – The top layer used in the present invention aids in absorption of the body fluids such as menstrual flow. The top layer is made up of cellulose microfibers or regenerated cellulose fibres. The cellulose microfibers are extracted from such as, but not limited to, wood pulp or banana. The regenerated cellulose fibres are produced from such as, but not limited to, bamboo and wood pulp. The amount of cellulose microfibers or regenerated cellulose fibres is in a range of 15 to 80 g/m2.

[0028] (b) Middle layer – The middle layer induces anti-leakage property and aids in conversion of the absorbed fluid into hydrogel. The middle layer is made up of biodegradable super absorbent polymer based composition coated on a fabric. The composition is in powdered form which is further coated on open woven fabric impregnated with the oils, forming a middle layer. In an exemplary embodiment, the open woven fabric is made up of material selected from a group, consisting of, such as, but not limited to, cotton fabric, jute fabric, and the like. In another exemplary embodiment, the amount of composition in the open fabric is in a range of 15 to 40 g/m2. In yet another exemplary embodiment, the oil may be selected from a group, consisting of, such as, but not limited to, glycerine, polyethylene glycol, vegetable oil, or a combination thereof. The vegetable oil may include, such as, but not limited to, coconut oil, palm oil, or a combination thereof. In an embodiment, the biodegradable super absorbent polymer based composition for preparing the middle layer comprises a plurality of natural oils, plurality of inorganic acids, and a plurality of biopolymers, or a combination thereof. The composition is described herein detail:

[0029] (a) Natural oils: The natural oils used in the composition is selected from, but not limited to, soybean oil, palm oil, coconut oil and vegetable glycerin. Each natural oil is present in different amount based on their absorption and swelling ratios. For instance, glycerin is present in a range of 5-10% by total weight of the composition. In an exemplary embodiment, amount of natural oils used in the composition is in a range of 5%-15% by total weight of the composition.

[0030] (b) Inorganic acid: The inorganic acids used in the composition may be selected from a group consisting of, such as, but not limited to, boric acid and citric acid. In an exemplary embodiment, amount of inorganic acid used in the composition is in a range of 5%-10% by total weight of the composition.

[0031] (c) Biopolymer: The biopolymers used in the present invention includes such as, but not limited to, almond gum, arabic gum, starch, or a combination thereof. In an exemplary embodiment, amount of biopolymers used in the composition is in a range of 5%-85% by total weight of the composition. Each biopolymer is present in different amount. For instance, almond gum is present in a range of 50-80% by total weight of the composition; Arabic gum is present in a range of 5-20% by total weight of the composition; and starch is present in a range of 5-20% by total weight of the composition.

[0032] (c) Bottom Layer – The bottom layer aids in absorption of the menstrual flow that reaches the bottom layer from the top layer. The bottom layer is made up of cellulose microfibers or regenerated cellulose fibres. The cellulose microfiber is extracted from such as, but not limited to, wood, banana stem, and jute stem. The regenerated cellulosic fibres are produced from such as, but not limited to, wood and bamboo. In an exemplary embodiment, the amount of cellulose microfibers or regenerated cellulose fibres is in a range of 15 to 80 g/m2.

[0033] In an embodiment, natural oils used in the middle layer plasticizes and swells biopolymer. In swelled state, the biopolymer absorbs fluids faster as compared to its original state; exhibit tackiness property and is used to bound cellulosic layers. This combined effect further accelerates the formation of hydrogel to achieve anti-leakage properties.

[0034] In an embodiment, biopolymers increases the gel strength thereby, inducing the synergistic effect.

[0035] In a specific embodiment, Table 1 illustrates different components of the biodegradable super absorbent polymer based composition and quantity of each component of the composition.

Sr. No. Components Quantity (%)
1. Biopolymer 5%-85%
2. Inorganic Acids 5%-10%
3. Natural Oils 5%-15%
Table 1
[0036] The following exemplary embodiments of the present invention is provided by way of illustration and should not be constructed to be limiting the scope of the present invention.

[0037] In an exemplary embodiment, biodegradable absorbent core of the present invention (EXAMPLE 1) comprises:

Sr. No. Components Quantity (%)
1. Polysaccharides 80%
2. Corn Starch 10%
3. Glycerol 5%
4. Critic Acid 5%
Table 2

[0038] In another exemplary embodiment, biodegradable absorbent core of the present invention (EXAMPLE 2) comprises:

Sr. No. Components Quantity (%)
1. Polysaccharides 60%
2. Tapioca Starch 25%
3. Glycerol 15%
Table 3

[0039] In another exemplary embodiment, biodegradable absorbent core of the present invention (EXAMPLE 3) comprises:

Sr. No. Components Quantity (%)
1. Polysaccharides 25%
2. Tapioca Starch 60%
3. Glycerol 10%
4. Boric Acid 5%
Table 4

[0040] In an embodiment, the present invention also provides a method for preparing the absorbent core. The method employs infusion process wherein the middle layer is infused between the top layer and the bottom layer. The method of preparation of middle layer comprises the following steps:

a) grinding of biopolymers using pulverizer;
b) blending the grinded biopolymers obtained in step (a) using a blender at a speed of 40 RPM, forming biodegradable super absorbent polymer-based composition;
c) coating the composition prepared in step (b) in a range of 70-80% by weight at a temperature range between 30°-40°C on open woven fabric impregnated with the oils, forming a middle layer;
d) infusing the middle layer obtained in step (c) in between top and bottom layers using infusion process; forming an absorbent core.

[0041] In an embodiment, the infusion process comprises the following steps:
a) applying heat on the middle layer within a temperature range of 30°-120°C for plasticization of the middle layer;
b) applying lamination pressure on the middle layer ranging from 0.5-5 KN for infusing the middle layer between top and bottom layers forming an absorbent core.

[0042] In an embodiment, as shown in figure 1, the infusion process of the present invention is the green process, free from any solvent and synthetic adhesives materials. In this process, middle layer with self-adhesive properties is coated on oil impregnated cotton gauge and it is infused with cellulosic layers on both sides to produce bio-sheets /absorbent core with super-absorbent property.

[0043] In another embodiment, salts may be added to the biodegradable super absorbent polymer based composition to regulate the pH of the composition.

[0044] In an exemplary embodiment, the absorbent core encloses all the primary raw material needed to construct superabsorbent core of sanitary pad. The use of absorbent core simplifies the preparation process of entire sanitary pad by reducing number of process steps and layers in the process. This is feasible for batch, semi-automatic and fully automatic production line. The absorbent core in the roll form can be fed into sanitary pad machine where it is covered/ thermally laminated by top and bottom plastic film sheets. The top layer is made up of PLA sheet/ non-woven PLA sheet with perforated structure to allow the fluid to penetrate. The bottom layer is made up of PLA based film which form the protective layer. The top and bottom layer made of same polymer is thermally sealed to form a disposable sanitary pad.

[0045] In another exemplary embodiment, figure 2 shows C-folded biodegradable absorbent core according to the present invention. The absorbent core of 6-inch width is produced and it is C-folded into specific width of 70-75 mm and cut into specific length of 20-25 cm. The absorbent core with excellent wet strength is being used as Super-Absorbent/Disposable cloth and this will be used along with pad fixtures to reduce single-use plastics.

[0046] The bio-absorbent pad may be made in different configurations and shapes and may also be supplemented with additional pads by means of a sticky tape provided on at least one side of the bio-absorbent pad. In an exemplary embodiment, figure 3 shows C-folded biodegradable absorbent cloth with self-adhesive tape as bottom layer. The self-adhesive layer acts as pad fixture to use C-folded biodegradable absorbent cloth directly without any additional support.

[0047] In an embodiment, biodegradable absorbent core prepared in the present invention is used for the preparation of menstruation and hygiene products such as but not limited to sanitary pads, diapers, baby wipes and similar hygiene supplies.

[0048] In another embodiment, biodegradable absorbent core may be used as a baby wipe when loaded with disinfected liquids.

[0049] In yet another embodiment, biodegradable absorbent core may be used as an open woven cloth to be used as sandwich with open woven fabrics for production of menstruation and hygiene products.

[0050] In yet another embodiment, the biodegradable super absorbent polymer based composition may be stored in an air tight container/bottle in a dry and cool place.

[0051] The following illustrates the experimental data of the present invention and should not be construed to limit the scope of the present invention.

EXPERIMENTAL DATA

1. Centrifuge Retention Capacity

[0052] Centrifuge Retention Capacity (CRC) of core layer was evaluated in accordance with EDNA (European Disposables and Nonwovens Association) recommended test WSP 241.3-2011. About 0.2 g of superabsorbent core was uniformly put in a nonwoven fabric-made bag followed by sealing. The bag was immersed in a physiological saline solution composed of 0.9 wt.% aqueous sodium chloride solution at room temperature. After 30 minutes water was removed from the bag by centrifugation at 250 G for 3 minutes and the weight of the bag was again measured. Further, similar procedure was carried out without using the super absorbent core and the resultant weight was measured.

[0053] Using the respective weights obtained, CRC (g/g) was evaluated according to the following Calculation:
CRC (g/g) = {[W2 (g) - W1 (g) -W0 (g)]/W0 (g)} [Equation 1]
Wherein,
W0 (g) is the initial weight of the core;
W1 (g) is the weight without the core, which was measured after immersing and absorbing the polymer into a physiological saline solution for 30 minutes and then dehydrating using a centrifuge at 250 G for 3 minutes; and
W2 (g) is the weight including the core, which was measured after immersing and absorbing the polymer into a physiological saline solution at room temperature for 30 minutes and then dehydrating by using a centrifuge at 250G for 3 minutes.

[0054] The centrifuge retention capacity of the absorbent core is evaluated to be 1.5 in case of wood pulp, 4 in case of cotton, and 10.2 in case of Absorbent core as provided below:
Material/Product Wood Pulp Cotton Wood Pulp infused with Biodegradable Absorbent Core Biodegradable Absorbent Core
CRC (g/g) 1.5 4 11 10.2

Table 5

[0055] In an exemplary embodiment, Table 6 illustrates the experimental results for different tests performed on the absorbent core.

S. No Name of Test Testing Standards Remarks Specification Required
1. Aerobic Biodegradation

ISO 17088-2008
92.41 after 135 days > 90%
(Within 180 days)
2. Disintegration 7.36 % Not more than 10%
3. Plant growth study
(Composting) 94.5 to 95 % >90
4. Heavy Metal Conc. (Toxicity) No toxic metals Well below the specified ppm level.
3. Centrifuge Retention Capacity (CRC)
WSP 241.3-2011
10.25 g/g Superior to Cotton (2x) and Wood pulp (7x)
Anti-leakage Property
4. pH of Extract IS 5405:2019
5.0 to 6.5 Weak Acid Range inhibits Bad bacteria, Safe to skin
5. Ability of Pads to withstand pressure after absorption
IS 5405: 2019 Absorbed 30ml of colored liquid within 6 min. The mean blood loss per menstrual period is 30 ml.

Table 6
pH of Extract
[0056] The pH of the extract of cloth samples loaded with biodegradable super-absorbent polymer was measured. Extract was prepared in triplicate at the temperature of 23o C by taking a test specimen weighing 2 ± 0*05 g and 100 ml of the distilled/deionized water into a stoppered glass flask. The flask was manually agitated for 20-30 minutes in order to ensure wetting of the specimen. The flask was further shaken mechanically for 20-30 minutes.
Ability of Pads to withstand pressure after absorption
[0057] Ability of Pads to withstand pressure after absorption was measured. The sanitary pad was laid on a flat and transparent surface in order to observe the underside of the pad. Test fluid was dropped on the pad at the rate of 15 mL/l and 30 mL/l. The temperature of the fluid was maintained at 27° ± 2°C. After the absorption of the fluid and the back and sides of the sanitary napkins were observed for leakage.

[0058] The test fluid was prepared by taking 6 L of boiling water in a stainless steel/glass vessel. 4 g of methyl paraben was dissolved in the water. Further, 740 g of Arabic gum/acacia gum was dissolved. Water was added in order to make 8 L of solution and the solution was allowed to settle for 24 hours. The solution was filtered through a layer of glass wool. 9.2 L of solution was prepared by adding 9 g of methylene blue; 470 ml of glycerin ad 840 ml of water was added to the solution and stirred thoroughly. The solution was again allowed to settle for 24 hours and shaken well before use.

[0059] The absorbent core prepared in the present invention possess a number of advantages:

• The absorbent core reduces use of single-use plastics in and preparation of economic, biodegradable, disposable, and reusable menstruation and hygiene products including sanitary pads, diapers, baby wipes and similar hygiene supplies.
• The use of absorbent core simplifies the preparation process of entire sanitary pad by reducing no. of process steps and layers in the process.

[0060] While the present invention has been described with reference to one or more preferred aspects, which have been set forth in considerable detail for the purposes of making a disclosure of the invention, such aspects are merely exemplary and are not intended to be limiting or represent an exhaustive enumeration of all aspects of the invention. The scope of the invention, therefore, shall be defined solely by the claims which will be followed in the complete specification to be filed at a later stage. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the principles of the invention.
, Claims:WE CLAIM:

1. A biodegradable absorbent core, comprising:
• a top layer facilitating absorption of body fluids;
• a middle layer infused between the top and bottom layers; the middle layer converts absorbed fluid into hydrogel to induce anti-leakage property; and
• the bottom layer facilitating absorption that reaches the bottom layer from top layer;
wherein,
(I) the top layer and the bottom layer are made up of cellulosic microfibers, or regenerated cellulose fibres; and
(II) the middle layer is made up of biodegradable super absorbent polymer based composition coated on an open woven fabric impregnated with natural oils.

2. A process for preparation of biodegradable absorbent core as claimed in claim 1, comprising:
• grinding of biopolymers using pulverizer;
• blending the grinded biopolymers obtained in step (a) using a blender at a speed of 40 RPM, forming biodegradable super absorbent polymer-based composition;
• coating the composition prepared in step (b) in a range of 70-80% by weight at a temperature range between 30°-40°C on open woven fabric impregnated with the oils, forming a middle layer; and
• infusing the middle layer obtained in step (c) in between top and bottom layers using infusion process; forming an absorbent core.

3. A process for preparation of biodegradable absorbent core as claimed in claim 2, wherein the infusion process comprising the steps of:
• applying heat on the middle layer within a temperature range of 30°-120°C for plasticization of the middle layer; and
• applying lamination pressure on the middle layer ranging from 0.5-5 KN for infusing the middle layer between top and bottom layers forming an absorbent core.

4. The process as claimed in claim 2, wherein the natural oils are selected from a group comprising of soybean oil, palm oil, coconut oil and vegetable glycerin.

5. The process as claimed in claim 2, wherein the inorganic acids are selected from a group comprising of boric acid and critic acid.

6. The process as claimed in claim 2, wherein the biopolymers are selected from a group comprising of almond gum, arabic gum, starch, or a combination thereof.

7. The process as claimed in claim 5, wherein the natural oils are in a range of 5%-15% by total weight of the composition.

8. The process as claimed in claim 6, wherein the inorganic acids are in a range of 5%-10% by total weight of the composition.

9. The process as claimed in claim 7, wherein the biopolymers are in a range of 5%-85% by total weight of the composition.

10. A product comprising a biodegradable absorbent core as claimed in claim 1 and open woven fabrics wherein the biodegradable absorbent core is sandwiched between at least two woven fabrics.

11. The product as claimed in claim 10, wherein the product is selected from menstruation and hygiene products including sanitary pads, diapers, baby wipes and similar hygiene supplies.