Patent Application
20180044856
Embodiments of the present invention relate to the manufacture of dermatological treatment products, and pertain particularly to methods and systems for forming hydrated, nonwoven nanocellulose sheets for use as a dermatological treatment.
Nanocellulose, or nano-structured cellulose, comprises cellulose particles or fibers which have been exfoliated from cellulose fibrils using either mechanical or chemical means. The “nano” portion indicates that at least one dimension is measured in nanometers. This is in contrast with other fibers having similar geometry that are formed by dissolving the cellulose and regenerating it. Nanocellulose materials can be derived from wood, algae, plant or bacterial sources.
Due to its relative strength, especially in terms of strength/weight ratio, viscosity, and other mechanical properties, nanocellulose can be used for many applications. Some of the applications for nanocellulose include fillers for food products, paper towels or other paper products that benefit from increased absorbency, reinforcing plastics, medical and pharmaceutical applications, as well as multiple other applications.
Similar to nanocellulose, hydrogels of alginate, starch, polymers or cellulose can hold a significant amount of water. Hydrogels are cross-linked polymers which are well known in the art to hold large amount of water. For this reason, hydrogels are often used in situations where it is important to maintain a certain level of saturation and/or absorption. One application of hydrogels is for a dermatological mask, where hydrogels' water retention capacity, coupled with or without the inclusion of dermatological agents, enables the application of a saturated hydrogel mask to a user's skin. Unfortunately, such masks have a low degree of conformability to the skin and are not porous. The lack of porosity limits the absorption of dermatologically active ingredients by the skin.
In addition to cross-linked alginates, nonwoven sheets with dermatologically active ingredients may be used for dermatological masks as well. Such nonwoven sheets are usually made from long fibers bonded together using chemical, mechanical, heat, or solvent treatments. A flat, porous sheet is typically formed using this method. Nonetheless, conventional systems are not optimized for efficient production of nonwoven sheets with even dispersion of active ingredients or controlled formation of porous sites.
Therefore, in view of the aforementioned difficulties, there is an unsolved need for methods and systems for efficient production of hydrated, nonwoven dermatological sheets capable of transpiring or evaporating water through, thereby causing a dynamic fluid system between the skin beneath the sheet and the sheet itself. In addition, it would be an advancement in the state of the art to incorporate particulates and solution-based active ingredients for even dispersion throughout the formed sheets.
It is against this background that various embodiments of the present invention were developed.
A method is provided for manufacturing hydrated, nonwoven nanocellulose sheets, using a high pressure or vacuum filtration process from a diluted nanocellulose suspension.
More specifically, in one aspect, one embodiment of the present invention is a method of manufacture for forming a hydrated, nonwoven nanocellulose sheet, the method comprising the steps of: providing a purified nanocellulose slurry; forming a colloidal nanocellulose suspension by diluting the nanocellulose slurry with a suspension medium; dispersing pure nanocellulose crystals into the nanocellulose suspension in a nanocellulose crystal to total nanocellulose ratio below 50%, weight per weight (w/w); placing the nanocellulose suspension over a filter sheet in a dispensing device; and forming the hydrated, nonwoven nanocellulose sheet by filtering the nanocellulose suspension with a pressure difference across the filter sheet.
In some embodiments, the nanocellulose slurry comprises at least one of nanocellulose fibrils or nanocellulose crystals. In some embodiments, the nanocellulose suspension has a nanocellulose concentration between 0.010% to 1% by weight;
In some embodiments, the method further comprises drying the nanocellulose sheet to a water content between 300% to 700% of nanocellulose weight, wherein the nanocellulose crystal to total nanocellulose ratio is between 0.001 to 10%.
In some embodiments, the method further comprises adding a pure nanocellulose crystal suspension in crystal weight percent composition between 0.001% and 10% to a surface of the hydrated, nonwoven nanocellulose sheet.
In some embodiments, the suspension medium is oil-based. In some embodiments, the method further comprises adding a polyelectrolyte to the suspension in a polyelectrolyte to total nanocellulose ratio between 0.01% to 84% weight per weight (w/w) as a flocculation agent.
In another aspect, one embodiment of the present invention is a method of manufacture for forming a hydrated, nonwoven nanocellulose sheet, the method comprising the steps of: providing a purified nanocellulose slurry; forming a colloidal nanocellulose suspension by diluting the nanocellulose slurry with a suspension medium; adjusting a pH value of the nanocellulose suspension to above 12.4; dissolving a polyelectrolyte in the pH-adjusted suspension, wherein an ionic charge of the polyelectrolyte is an integer multiple of a nanocellulose backbone charge of the suspension; placing the nanocellulose suspension over a filter sheet in a dispensing device; and forming the hydrated, nonwoven nanocellulose sheet by filtering the nanocellulose suspension with a pressure difference across the filter sheet.
In some embodiments, the adjusting of the pH value is by adding 1.0M NaOH to increase the pH value, or adding 1.0M HCl to decrease the pH value. In some embodiments, the integer multiple is between 1 and 6 inclusive.
In some embodiments, the method further comprises stirring the suspension after the dissolving of the polyelectrolyte to form polyelectrolyte complex networks, wherein a viscosity of the suspension is between 0.890 centipoise (cP) inclusive and 500,000 centipoise (cP) inclusive. In some embodiments, the viscosity of the suspension is between 1 centipoise (cP) and 500 cP.
In some embodiments, the method further comprises adding a polyelectrolyte to a surface of the nanocellulose sheet in a total polyelectrolyte to total nanocellulose ratio between 0.01% to 84% weight per weight (w/w).
In some embodiments, the method further comprises adding an amount of a dermatologically active ingredient to the nanocellulose suspension, after the dissolving of the polyelectrolyte.
In a third aspect, one embodiment of the present invention is a method of manufacture for forming a hydrated, nonwoven nanocellulose sheet, the method comprising the steps of: providing a purified nanocellulose slurry; forming a colloidal nanocellulose suspension by diluting the nanocellulose slurry with a suspension medium; adding a first binding agent into the nanocellulose suspension; adding a cross-linking agent into the nanocellulose suspension; placing the nanocellulose suspension over a filter sheet in a dispensing device; and forming the hydrated, nonwoven nanocellulose sheet by filtering the nanocellulose suspension with a pressure difference across the filter sheet.
In some embodiments, a mass concentration of the binding agent in the nanocellulose suspension is between 0.001 grams per liter to 10 grams per liter. In some embodiments, a mass concentration of the cross-linking agent in the nanocellulose suspension is between 0.001 grams per liter to 20 grams per liter.
In some embodiments, the method further comprises adding a second binding agent to a surface of the nanocellulose sheet in a second binding agent to total nanocellulose ratio between 0.001% to 10% weight per weight (w/w).
In some embodiments, the method further comprises adding a hydrophilic pore former to the nanocellulose suspension, wherein a pore former to total nanocellulose ratio is between 5% and 75% weight per weight (w/w).
In some embodiments, the method further comprises adding a hydrophilic pore former to a surface of the hydrated, nonwoven nanocellulose sheet, wherein a pore former to total nanocellulose ratio is between 5% and 75% weight per weight (w/w).
Yet other aspects of the present invention include methods, processes, and algorithms comprising the steps described herein, and also include the processes and modes of operation of the systems and devices described herein. Other aspects and embodiments of the present invention will become apparent from the detailed description of the invention when read in conjunction with the attached drawings.
Embodiments of the present invention described herein are exemplary, and not restrictive. Embodiments will now be described, by way of examples, with reference to the accompanying drawings. For purposes of clarity, not every component is labeled in every drawing. The drawings are not drawn to scale, with emphasis instead being placed on illustrating various aspects of the techniques and devices described herein.
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the invention can be practiced without these specific details. In other instances, structures, devices, activities, methods, and processes are shown using schematics, use cases, and/or diagrams in order to avoid obscuring the invention. Although the following description contains many specifics for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to suggested details are within the scope of the present invention. Similarly, although many of the features of the present invention are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the invention is set forth without any loss of generality to, and without imposing limitations upon, the invention.
Broadly, embodiments of the present invention relate to a hydrated, nonwoven nanocellulose sheet, and methods and systems for manufacturing the nanocellulose sheet. The hydrated, nanocellulose sheet is formed through a pressured filtration process from a diluted nanocellulose suspension. Various additives may be dissolved or dispensed into the diluted nanocellulose suspension in controlled steps or sequences. Such additives include, but are not limited to, binding agents, cross-linking agents, dermatologically active ingredients, morphology-altering particles, base material modifiers, pure nanocellulose crystals, polyelectrolytes, and pH modifying solutions. Binding agents added to the nanocellulose suspension improve the strength of the nonwoven nanocellulose sheet. Such binding agents may alternatively be “activated” or cross-linked after the formation of the sheet by applying other chemical agents or treating the sheet after formation. Similarly, additive ingredients as listed above may be applied to the sheet after formation of the nanocellulose sheet, via mechanisms such as spraying, dipping, soaking, and the like.
The elements and process of manufacturing the hydrated, nonwoven nanocellulose sheet produce several advantageous properties, include high conformability, drape-ability, large surface area, good levels of adhesion to the skin of a user, ability to contain and effectively deliver nano and micro particles, high porosity, and high rate of evaporation of water from the sheet. These properties make the nanocellulose sheet ideal for resting against the skin of a user and delivering dermatological agents which are generally difficult to do or which require multi-step processes to be delivered to the skin.
Furthermore, some embodiments of the present invention introduce pure nanocellulose crystals into the nanocellulose sheet production process, which increases the overall strength of the sheet produced, making it less likely to tear, while reducing the sheet drying time. Conventionally, high levels of hydration are desirable and crystals are not used in nanocellulose sheet production because they do not swell in the presence of an aqueous solution. Embodiments of the present invention carefully balances the use of nanocellulose crystals and nanocellulose fibers to achieve desired hydration levels while enhancing sheet durability and tensile strength, and reducing overall processing times.
Moreover, a novel polyelectrolyte addition process during nanocellulose sheet production is disclosed herein to allow the porosity and extrinsic charge sites within the formed sheets to be tuned by varying a ratio of the polyelectrolyte to the nanocellulose. Polyelectrolytes have been frequently used to form multilayers and free standing thin films. Unlike traditional polyelectrolyte complexes where a solid precipitate is formed, such as between Polystyrene Sulfonate (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC), in embodiments of the present invention, polyelectrolytes act as a scaffold and ion exchange sites, bind to the nanocellulose upon filtration without forming any solid precipitates.
In some embodiments, sheet 110 may be cut into different forms, including different shapes, sizes or configurations that facilitate direct application to the skin. The different shapes and sizes may be used for different skin-contact applications on different parts of a user's body. Exemplary applications include, but are not limited to, wound healing, dermatology, and cosmetology.
As disclosed herein, hydrated, nonwoven nanocellulose sheets produced according to embodiments of the present invention may incorporate dermatologically active ingredients to enhance the effects of applying a hydrated sheet mask. To produce a nanocellulose sheet such as 110, a series of steps may be carried out.
At step 316, the nanocellulose is diluted into a suspension medium to form a nanocellulose suspension. In some embodiments, the nanocellulose is diluted to a mass concentration between 0.01 gram per liter to 10 grams per liter. In some embodiments, the nanocellulose is diluted to a mass concentration between 0.1 gram per liter to 10 grams per liter. In some embodiments, the nanocellulose is diluted with a suspension medium capable of being combined with the cellulose to form a stable suspension. Exemplary suspension media include, but are not limited to, water, alcohols, or oil. In some embodiments, an oil-based suspension medium may further comprise a surfactant.
The dilution of nanocellulose into a suspension and subsequent usage of such a nanocellulose suspension in sheet production is beneficial as they allow nanocellulose material to be accepted from multiple sources. For example, grown pellicles of nanocellulose are commonly obtained in bacterially grown cellulose. In some embodiments, the nanocellulose material may be pre-treated before nanocellulose formation from cellulose fibers. Such pre-treatments may include mechanical or enzymatic treatment of a cellulose containing material. For example, cellulose containing material may be oxidized using 2,2,6,6-tetramethylpiperidin-1-oxyl radical (“TEMPO”), which introduces charged groups. Carboxymethylation may also be used to pre-treat the cellulose containing material. Finally, acid hydrolysis may be used to treat the cellulose containing material.
Next, at step 327, the nanocellulose suspension is placed into a dispensing device for a filtering or micro-filtration process, where the suspension is filtered at step 328 to form a nanocellulose sheet. The dispensing device may be a device capable of micro-filtration and/or fabricating sheets of nanomaterials, using positive pressure or vacuum across a filter medium such as a filter paper or filter membrane, to produce large, uniform-thickness sheets of nanomaterials of variable sizes, shapes, and thicknesses. An exemplary device that may be used in embodiments of the present invention and is discussed in more detail with reference to FIG. 8 is disclosed in U.S. application Ser. No. 14/186,795, the entire disclosure of which is incorporated by reference in its entireties herein. During the filtration process, the dispensing device may remove water from the suspension, leaving a hydrated but solid sheet. The solid sheet may be, in one example, 10-50% solids.
Other optional steps shown in
In some embodiments, each of the binding and cross-linking solution may be prepared by diluting a binding agent or a cross-linking agent to suitable mass concentrations. For example, between 0.001 grams per liter to 100 grams per liter, 0.001 grams per liter to 10 grams per liter, 0.01 grams per liter to 10 grams per liter, or 0.01 grams per liter to 20 grams per liter. The nanocellulose sheet may be dipped into the binding solution only, the cross-linking solution only, or one solution after the other. Exemplary wet binding agent or gelling agents include sodium alginate, agar, any polycationic, such as polyamidoamine-epichlorohydrin or KYMENE, and any anionic such as carboxymethylcellulose or Hyaluronic acid. Sodium alginate is a negatively charged polymer that forms a hydrogel. Addition of sodium alginate helps retain water well against outside forces. Exemplary cross-linking agents include calcium lactate, calcium chloride, calcium stearate or oil, which may be capable of cross-linking or “setting” the binding agent, where relevant. Moreover, although a “dipping” action is referred to in steps 330 and 322, in some embodiments, similar operations such as spraying, soaking, and the like may be performed instead.
In this embodiment and other embodiments disclosed herein, the term “ingredient” or “additive ingredient” collectively refers to one or more of the following materials: particulate or solution-based dermatologically active ingredients, base material modifiers including pure nanocellulose crystals, morphology-altering particles, and other similar additives. One or more additive ingredients may be added to the nanocellulose suspension before the micro-filtration process, or may be added to the formed sheet after the micro-filtration process such as shown by step 332 in
Many known particulate or solution-based materials may be used as additive ingredients. Exemplary dermatologically active ingredients include, but are not limited to, silver, collagen, proteins, fragrances or antioxidants such as blended green tea. Exemplary base material modifiers include, but are not limited to, other forms of cellulose fibers, other forms of nanofibers such as cellulose nanocrystals (CNC), nanoclay, extended release particles, micro-encapsulates, polyelectrolytes such as poly(diallyldimethylammonium chloride) (PDADMAC), and polyether such as Polyethylene glycol (PEG).
In general, when only nanocellulose fiber or 100% cellulose nanofibers (CNF) are diluted into a nanocellulose suspension, without additive ingredients, a hydrogen-bonded network of polymer chains is formed during sheet formation, capable of holding several times its mass in water. When this network interacts with external additives, the external additives inhibit the hydrogen bonding capabilities of the 100% CNF network, which causes a decrease in an extent of hydration (EOH). A decrease in EOH may be beneficial for a variety of applications that require shorter processing times and lower EOH values, such as cosmetic applications that need specific amounts of water with good durability.
As mentioned above, one additive ingredient may be CNC, which are crystalline regions of CNF. When added, CNC neither swell significantly, nor exhibits ⅔ of the available H-bonding sites, thus causing the manufactured nanocellulose sheet to hold less water.
Another additive ingredient may be a polyelectrolyte such as PDADMAC, which is a positively charged polymer that directly binds with negatively charged CNF, and significantly reduces EOH. By varying the proportion of PDADMAC to CNF, an extent of intrinsic ionic compensation may be tuned, reflecting how many charged groups from each chain interact with one another.
In
Although not shown explicitly in
A hydrated, nonwoven nanocellulose sheet manufactured according to embodiments of the present invention have high conformability and drape-ability, a high surface area, a good level of adhesion to the skin, the ability to trap nano and micro particles, high porosity, and a high rate of evaporation of water from the sheet. Conformability, drape-ability, high surface area and adhesion to the skin are characteristics that make the nanocellulose sheet ideal for lying against the skin. The ability to contain nano and micro particles, as well as absorbing aqueous solutions, make the material ideal as a delivery mechanism for dermatological agents that are known to be difficult to deliver, or require multi-step processes to deliver to the skin. Thus, a hydrated, nonwoven nanocellulose sheets such as 110, 200, 220, 240, or 260 are capable of delivering dermatological agents or other ingredients more effectively and for a longer period of time than conventional sheet masks.
More specifically, similar to the process shown in
An optional step 417 may then be performed to add an amount of ingredients to the nanocellulose suspension. Different types of ingredients are previously discussed with reference
Next, at step 418, a binding agent is added to the nanocellulose suspension. At step 420, a cross-linking agent is diluted in a solvent, such as water, to form a cross-linking solution. At step 422, the nanocellulose suspension is dispensed into the cross-linking solution to form a gel.
Similar to the embodiment illustrated by
At step 424, the formed gel is collected from the mixture of the nanocellulose suspension and the cross-linking solution, and re-dispensed at step 426 into a solution to form a second nanocellulose suspension. The second nanocellulose suspension is then filtered at step 428 to form a nanocellulose sheet via positive or vacuum pressure.
Optionally, the sheet is collected at step 430, dipped into an ingredient slurry of liquid or solid additive ingredients at step 432, and cut into a desirable form and packaged at step 434.
In some embodiments, including when both steps 417 and 432 are performed in the process shown in
The suspension medium may be any suspension medium capable of being combined with the nanocellulose to form a stable suspension. Exemplary suspension media include, but are not limited to, water, alcohols or oil, which may further comprise a surfactant. In some embodiments, when the suspension medium is oil based, a polyelectrolyte may be further added to the suspension in a polyelectrolyte to total nanocellulose ratio between 0.01% to 84% weight per weight (w/w) as a flocculation agent.
Once a nanocellulose suspension is formed, one or more of a binding agent, a cross-linking agent, or one or more additive ingredients may be added to the nanocellulose suspension. As discussed previously, an additive ingredient may be a base modifier such as cellulose nanocrystals (CNC), polymers, polyelectrolytes, pore formers, or dermatologically active ingredients. These additives may be added, mixed, dispensed, dispersed, or dissolved into the nanocellulose suspension in any desired order and proportions, in different embodiments of the present invention. For example, dermatologically active ingredients may be added after a polyelectrolyte dissolution into the nanocellulose suspension.
In the embodiment shown in
At step 527, the nanocellulose suspension is placed over a filter sheet in a dispensing device, and a hydrated, nonwoven nanocellulose sheet is fully formed at step 528 by filtering the nanocellulose suspension with a pressure difference across the filter sheet. The nanocellulose manufacture process terminates at step 540. Similar to the processes shown in
More specifically, polyelectrolytes are a base modifier material capable of tuning the porosity and extrinsic charge sites within the formed nanocellulose sheet, and helping avoid the use of cross-linking chemicals during sheet production. In this embodiment, at step 617, a pH value of an aqueous nanocellulose suspension may first be adjusted by the addition of acids or bases, to deprotonate hydroxyl groups and induce negative surface charges to create electrostatic binding sites, before polyelectrolytes are added to the pH-adjusted suspension at step 618, wherein an ionic charge of the polyelectrolytes is an integer multiple of a nanocellulose backbone charge of the suspension. For instance, pH may be adjusted up using 1.0 M NaOH and down using 1.0 M HCl. Total deprotonation occurs at a pH level of 12.5, while partial deprotonation occurs at a pH level of 8.5, and a target pH level may be set at 8.4. High pH values may result in the degradation of cellulose through the production of isosaccharinic acid, but only for long time scales, such as weeks or months. In addition, hydrolysis may be performed at a pH less than 3 to cleave glycosidic linkages between cellulosic units, which results in shorter CNF chains that are unlikely to bind to a polycation. Further stirring of the suspension after the dissolving of the polyelectrolyte may help form polyelectrolyte complex networks, wherein a viscosity of the suspension may be in controlled ranges, such as between 0.890 centipoise (cP) inclusive and 500,000 cP inclusive, between 0.890 cP inclusive and 1,000 cP inclusive, or between 1 cP inclusive and 500 cP inclusive.
In some embodiments, polyelectrolytes may be further added to one or both surfaces of the formed nanocellulose sheet in a total polyelectrolyte to total nanocellulose ratio between 0.01% to 84% weight per weight (w/w).
In particular, at step 717, a first binding agent is added into the nanocellulose suspension. At step 718, a cross-linking agent is added into the nanocellulose suspension. These two steps are interchangeable in order. Similar to the embodiment illustrated by
While not shown explicitly in
In
In obtaining the graphs shown in
More specifically, filtration of the base nanocellulose suspension is performed to generate the 100% CNF graph 1030 according to
As discussed with reference to
When this hydrogen-bonded network interacts with external additives, the hydrogen bonding capabilities is inhibited, causing a decrease in an extent of hydration (EOH). Such a decrease in EOH is beneficial as it reduces overall processing time, especially when lower EOH is desired for particular applications that required specific amounts of water content with good sheet durability.
In
In
In what follows, three additional exemplary embodiments are described for nanocellulose sheet production. Although the following description contains many specifics for the purposes of illustration, and many of the features of the present invention are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the invention is set forth without any loss of generality to, and without imposing limitations upon, the invention.
One of ordinary skill in the art knows that the use cases, structures, schematics, and flow diagrams may be performed in other orders or combinations, but the inventive concept of the present invention remains without departing from the broader scope of the invention. Every embodiment may be unique, and methods/steps may be either shortened or lengthened, overlapped with the other activities, postponed, delayed, and continued after a time gap, such that every user is accommodated to practice the methods of the present invention.
Although the present invention has been described with reference to specific exemplary embodiments, it will be evident that the various modification and changes can be made to these embodiments without departing from the broader scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than in a restrictive sense. It will also be apparent to the skilled artisan that the embodiments described above are specific examples of a single broader invention which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the descriptions without departing from the scope of the present invention.
This application is a Continuation-In-Part (CIP) of and claims the benefit of priority to U.S. Ser. No. 14/986,578, filed on 31 Dec. 2015, entitled “Formation of Hydrated Nanocellulose Sheets With or Without a Binder for the Use as a Dermatological Treatment,” which itself a non-provisional of provisional U.S. Ser. No. 62/098,627, filed on 31 Dec. 2014, entitled “Formation of Hydrated Nanocellulose Sheets With or Without a Binder for the Use as a Dermatological Treatment,” the entire disclosures of both of which are incorporated by reference in their entireties herein.
| Number | Date | Country | |
|---|---|---|---|
| 62098627 | Dec 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14986578 | Dec 2015 | US |
| Child | 15791525 | US |
