Coating Composition

Abstract

The present invention provides a coating composition comprising a homogenized dispersion of regenerated cellulose in water, where regenerated cellulose includes both amorphous and crystalline cellulose.

Description

[Technical Field]

[0001] The present invention relates to a cellulose coating composition and a method for making the composition.

[0002] Cellulose-based coating compositions are known in the art and are used as barrier coatings or to improve the hydrophobicity or scratch resistance of articles. The coatings are compostable and biodegradable and can therefore be used to create environmentally friendly articles.

[0003] The formation of cellulose-based coatings typically involves applying a cellulose dispersion to a surface and then drying the dispersion to create a coating layer. Conventionally, the cellulose in the dispersion is microcrystalline cellulose. For example, Canadian Patent Application Publication No. A668443(A) discloses boiling cellulose material with hydrochloric acid to create crystalline cellulose, which is then washed and dispersed in water to form a coating composition. Similarly, U.S. Patent No. 6,541,627 discloses the use of acid hydrolysis to increase the crystallinity of cellulose-based coating compositions.

[0004] Crystalline cellulose has been considered important for its optical properties, such as transparency. Therefore, methods for creating cellulose coating materials often involve a process such as acid hydrolysis to remove the amorphous cellulose, leaving only crystalline cellulose in the coating. However, this process can be expensive and complicated, and is also uneconomical because it removes some of the cellulose.

[0005] Cellulosic coatings in the art also often contain non-biodegradable components or use cellulose derivatives such as nitrocellulose, thereby reducing the biodegradability of the coating itself and increasing the complexity of the manufacturing process.

[0006] Dusting is also a problem with coatings in the art, so coatings with improved adhesion are also desirable.

[0007] It is therefore desirable to create a simpler and cheaper cellulosic coating composition that maintains the necessary optical properties and adhesion, and is biodegradable.

[0008] According to a first aspect of the present invention, there is provided a coating composition comprising a homogenized dispersion of regenerated cellulose in water, the regenerated cellulose including both amorphous and crystalline cellulose.

[0009] The regenerated cellulose in the coating composition can be predominantly amorphous cellulose, and thus can be greater than 50% amorphous cellulose, preferably greater than 75% amorphous cellulose, and more preferably greater than 90% amorphous cellulose.

[0010] It has surprisingly been found that homogenized dispersions of regenerated cellulose in water exhibit good optical properties, such as transparency, without the need to remove the amorphous cellulose regions, as is done in prior art coatings. Furthermore, the coatings of the present invention have good adhesion to surfaces and are completely biodegradable. The present invention therefore results in simpler, less expensive cellulose coatings with excellent optical properties and adhesion.

[0011] Thus, the coating compositions of the present invention have not been subjected to an acid hydrolysis treatment.

[0012] Regenerated cellulose may be regenerated from an aqueous alkaline cellulose solution. This regeneration method is well known in the art and involves combining an aqueous alkaline cellulose solution with an acid to regenerate the cellulose. The use of cellulose material regenerated from an aqueous alkaline cellulose solution is believed to help improve the transparency of the coating even in the presence of amorphous regions, thereby eliminating the need for an acid hydrolysis step.

[0013] The aqueous alkaline cellulose solution may be created by dissolving a cellulose-containing material in alkali. There are various methods known in the art for creating aqueous alkaline cellulose solutions, all of which can be used in the present invention.

[0014] The alkali may be a hydroxide, preferably an alkali metal hydroxide, more preferably sodium hydroxide. The alkali may have a concentration of 5% w / w to 25% w / w, or 10% w / w to 25% w / w. The alkali concentration in the aqueous alkali cellulose solution may be 2% w / w to 15% w / w.

[0015] Dissolving cellulose in alkali may include homogenization, preferably high-pressure homogenization, to aid dissolution. As used herein, high-pressure homogenization refers to homogenization occurring at a pressure of 100 bar or greater. Multiple homogenization steps may be used during dissolving cellulose in alkali.

[0016] High pressure homogenization may be carried out at a temperature above 0°C to ensure dissolution.

[0017] Therefore, the regenerated cellulose dispersion is preferably homogenized at least twice: first to aid in dissolving the cellulose in the alkali, and then after the regenerated cellulose has been dispersed in water. This is believed to reduce the particle size sufficiently to improve optical properties. Multiple homogenization steps may be performed at each point in the process. There may be two or more homogenization steps to aid in dissolving the cellulose in the alkali, and one or two homogenization steps after the cellulose has been regenerated.

[0018] Alternatively, the cellulose may be dissolved in alkali using any other known method, or in any other known cellulose solvent, such as ionic liquids, NMMO, and deep eutectic solvents.

[0019] The cellulose particles preferably have an average radius of less than 1 micron, more preferably less than 0.75 microns. The largest particles may have a radius of less than 2 microns, preferably less than 1.5 microns.

[0020] The aqueous alkali cellulose solution may be regenerated in the liquid phase. This may be achieved by carrying out the regeneration process under agitation, such as stirring. The regeneration process may involve combining the aqueous alkali cellulose solution with an excess of acid. The aqueous alkali cellulose solution may be added to the acid, or the acid may be added to the aqueous alkali cellulose solution.

[0021] Dissolving cellulose in alkali is well known to allow further processing, such as creating regenerated cellulose products in the form of films, fibers, or molded articles. Regeneration of alkaline cellulose solutions, for example by extruding the solution into acid, is also well known in the art. However, this creates a cellulose film with the smallest possible thickness, which is too thick to be used as a coating in many applications. In contrast, the use of liquid-phase regeneration, in which cellulose is regenerated under agitation, results in a dispersion of regenerated cellulose particles. This dispersion can then be used to create coatings that are much thinner than the regenerated cellulose films known in the art.

[0022] Once the cellulose is regenerated, it may be washed to obtain a cellulose dispersion in water, which may be substantially free of salts created by the acid.

[0023] Washing may include separating the regenerated cellulose from the acid, washing the regenerated cellulose with water, and resuspending the regenerated cellulose in water to form a dispersion. Separation may be accomplished by any conventional method, including filtration, centrifugation, or the use of a vacuum. Alternatively, washing may include successive washes to remove the acid and create a regenerated cellulose dispersion in water.

[0024] The cellulose dispersion in water may then be homogenized, preferably high pressure homogenized. The inventors have discovered that homogenizing a dispersion of regenerated cellulose creates cellulose particles that are small enough that the resulting coating composition has good optical properties without the need for further processing steps such as acid hydrolysis.

[0025] Thus, a homogenized dispersion of regenerated cellulose in water may have the following properties: (a) dissolving a cellulose-containing material in aqueous alkali to form an aqueous alkali cellulose solution; (b) regenerating the cellulose in the liquid phase by combining the aqueous alkaline cellulose solution with an excess of acid under agitation; (c) washing the resulting regenerated cellulose to obtain a cellulose dispersion in water that is substantially free of salts created by the acid; (d) homogenizing the cellulose dispersion in water can be obtained using a method including

[0026] These steps, when combined, can have any of the functions described above.

[0027] The cellulose dispersion in water may contain 1 to 10% w / w cellulose, preferably 2 to 7% w / w cellulose.

[0028] The cellulose-containing material dissolved in the alkali to create the aqueous alkaline cellulose solution may be at least partially purified to remove some non-cellulose components compared to the starting material. The at least partially purified cellulose-containing material may be one of the following: (a) neutralizing an alkaline cellulose-containing precursor material with an acid and obtaining a neutralized solid cellulose-containing material; (b) mixing the neutralized solid cellulose-containing material with a bleaching agent to create a mixture; (c) separating the solid cellulose-containing product from the mixture; can be produced using

[0029] The method may further include step (d) dissolving the solid purified cellulose-containing product in aqueous alkali to create an aqueous alkaline cellulose solution. One or more steps of the method may be carried out at a temperature of about 2 to about 90°C, preferably about 20 to about 60°C.

[0030] The acid may comprise a weak acid, which may be a carboxylic acid such as acetic acid. The concentration of the acid may be about 1 to about 20% w / w. The polysaccharide-containing material may be left in the acid for about 10 minutes to about 3 hours, preferably about 0.5 to about 1 hour. This may ensure that all of the solid material is neutralized. The resulting pH of the neutralized solid polysaccharide-containing material may be 6 to 8, preferably about 7.

[0031] The bleaching agent may include a chlorine-containing bleaching agent. For example, the bleaching agent may include sodium hypochlorite. The bleaching agent may include a chlorine-free bleaching agent. For example, the bleaching agent may include hydrogen peroxide. The bleaching agent may be at a concentration of 0.1 to 10% w / w, preferably 0.1 to 2% w / w.

[0032] One or more washing steps using hot and / or cold water may also be included. The solid cellulose-containing product may be separated from the mixture by any conventional means, including filtration, vacuum, or centrifugation.

[0033] The alkaline cellulose-containing precursor material can be created by combining the cellulose-containing precursor material with an alkaline solution to produce an alkaline mixture. The alkaline mixture can be agitated. The solid alkaline cellulose-containing precursor material can then be separated from the alkaline mixture and used in the process described above. The alkaline solution can include a hydroxide. The alkaline solution can be sodium hydroxide. The hydroxide can be present in a concentration of about 0.1 to about 30% by weight of the alkaline solution.

[0034] These pretreatment steps have been found to improve the solubility of cellulose-containing materials in alkali, creating stable aqueous alkaline cellulose solutions that can then be used to create dispersions of regenerated cellulose, as described above.

[0035] The coating composition may further comprise one or more additives selected from waxes, biopolymers, pigments, active ingredients, reference particles, or dye-incorporating dopants. The total amount of additives in the coating composition is preferably less than 40% by weight, with each additive preferably being present at less than 20% by weight.

[0036] The wax is preferably a bio-based wax such as carnauba wax and / or candelilla wax. The wax is preferably biodegradable. The wax may be included in the coating composition to improve hydrophobicity, gloss, and scratch resistance.

[0037] Biopolymers are natural polymers that are biodegradable. These include, for example, PHAs and bioplastics. Depending on the properties of the biopolymer itself, biopolymers can be added to the coating composition to modify the properties of the resulting coating. For example, biopolymers can be added to create a seal.

[0038] Pigments or other colorants may be added to the coating composition to modify the color of the resulting coating.

[0039] An active ingredient is a component that exhibits a chemical or biological effect on the surrounding environment. For example, the active ingredient may be a zeolite that can absorb ethylene from the environment. Alternatively, the active ingredient may be an antimicrobial component, such as a component with antibacterial or antiviral activity. These components may thus be used to impart a chemical or biological effect on the surrounding environment to the resulting coating.

[0040] The coating composition may also include one or more reference particles. These may be inert particles, often used as visual reference points for size or staining comparison. Reference particles may include PMMA or silica particles, cellulose fibers, air bubbles, and / or proteins. The reference particles may be of known size, orientation, and / or concentration within the cellulose film. The reference particles may be randomly distributed to generate a unique pattern that can be used to identify and / or track the coated article.

[0041] The coating compositions of the present invention can also be stained using conventional histological stains, including, for example, hematoxylin and eosin (H&E) or diaminobenzidine (DAB) and horseradish peroxide (HRP). Accordingly, the coating compositions may include dopants that affect the staining characteristics of the coating composition, such as chitosan, gelatin, and / or keratin.

[0042] For example, staining variability decreases with increasing chitosan levels in the coating. The coating composition may contain 1-10%, preferably 3-10%, and most preferably 5-10% chitosan. Furthermore, both keratin and gelatin have been found to increase dye uptake. Dopants can be added in amounts such that the dye uptake of the coating matches that of the target tissue sample. Thus, the coating can be tailored to the target tissue sample.

[0043] When the coating composition of the present invention is used in applications related to histological staining, it may contain both reference particles and dopants. The reference particles can also be used to visually represent the tissue itself to assist the pathologist in examining the sample.

[0044] According to a second aspect of the present invention, there is provided a coating comprising the above-mentioned cellulose coating composition. The coating can be formed by applying the coating composition or a composition comprising the coating composition to a surface and then drying the coating. This can be done by any conventional method, such as gravure, spray, or print coating.

[0045] The coating may have a thickness of 0.1 to 50 microns, preferably 0.5 to 8 microns, and therefore can be significantly thinner than films made from regenerated cellulose known in the art.

[0046] The coating may have a coat weight of 0.1 to 20 gsm, preferably 1 to 10 gsm, which therefore creates a thin coating on the surface, especially compared to cellulose films known in the art.

[0047] The coating may have a wide-angle haze of less than 75%, preferably less than 70%. Thus, the coatings formed from the coating compositions of the present invention have good optical properties.

[0048] Coating: 1000~1250g / m 2 / 24 hours, preferably 1050-1200g / m 2 The water vapor permeability can be varied beyond these ranges by including additives in the coating in a conventional manner.

[0049] The coating has good adhesion when dried above room temperature, with less than 10%, preferably less than 5%, of the area of ​​the coating being removed by a tape test, and little or no visible coating being removed by a scratch test. The tape test involves applying Scotch Tape 600 to the coating so that the end of the tape extends beyond the coating. One end of the tape is held at a 180 degree angle and quickly removed, and the area of ​​coating removal is calculated.

[0050] The coating may comprise more than 60% w / w, preferably more than 80% w / w, of the cellulose coating composition. The additives described above may make up the remainder of the coating. In this embodiment, the cellulose coating composition, optionally with some further additives, is used to create the coating.

[0051] Alternatively, the coating may comprise less than 50% w / w, preferably less than 20% w / w, of the above-described cellulose coating composition. The coating may further comprise an additional coating composition, optionally with further additives. In this embodiment, the cellulose coating composition is used as an additive in another coating composition. This can be used to impart advantageous properties, such as print receptivity or adhesion, to known coating compositions using the above-described cellulose coating composition.

[0052] The coating may be dried at or near room temperature (above 20° C.), for example, 15-25° C. Drying the coating composition at room temperature has been found to create a coating containing a higher amount of amorphous cellulose, which is softer and swells on contact with water.

[0053] Alternatively, the coating may be dried at temperatures above room temperature (eg above 25°C), preferably above 35°C, more preferably above 50°C or 60°C or above.

[0054] It has been surprisingly found that drying the coating composition at a temperature higher than room temperature can produce a hard coating with good adhesion to the substrate.Without being bound by theory, it is believed that the heat of the drying process effectively crosslinks the cellulose particles through hydroxyl functional groups, creating a crystalline structure.Therefore, the particles can form hydrogen bonds with both other cellulose particles and the substrate, thereby forming a hard coating with good adhesion to the substrate, especially to glass substrates.

[0055] Coatings dried at elevated temperatures can have a crystallinity of greater than 60%, preferably greater than 75%. This is much greater than the typical amount of crystallinity found in conventional cellulose coatings, which can be about 30%. This is also much greater than the amount of crystallinity found in coatings dried at or near room temperature, which are primarily amorphous.

[0056] The regenerated cellulose may be predominantly cellulose II. The regenerated cellulose may be greater than 75% cellulose, preferably greater than 85% cellulose II.

[0057] According to a third aspect of the present invention, there is provided a coated article comprising the coating described above, which provides a thin, biodegradable coating on the article having good adhesion and optical properties, as well as good water vapor permeability.

[0058] The coating may be applied using any conventional method, including gravure, spray, or print coating. The coating may have any of the characteristics described above.

[0059] The coated article may be coated on one side or both sides, in other words, a planar article such as a film may be coated on one side or both sides.

[0060] The coated article can be any article, for example, a film, such as a cellulosic film.

[0061] The coated article can be a histological quality control device, such as a reference slide. As explained above, the coating composition of the present invention can be stained using conventional histological stains. Thus, the coating composition can be used to create a quality control device for histological staining procedures, which allows the staining of various tissue samples to be standardized.

[0062] Specifically, the quality control device can be stained along with the tissue sample. Because the staining characteristics of the cellulose coating are known, variations in tissue staining due to slight changes in timing, component concentration, camera used, or light intensity can be identified and standardized based on the staining seen on the cellulose coating. Thus, the quality control device can be used to correct for image variations in the histopathological staining and imaging process.

[0063] The quality control device of the present invention is an improvement over prior art devices that use cellulose films that are subject to dimensional changes due to different hydration states. Size changes are not observed with the cellulose coating of the present invention, and no additional attachment means are required to attach it to a surface such as a slide to create the quality control device.

[0064] The coating does not have to cover the entire surface of the quality control device. A tissue sample can then be positioned on the surface of the quality control device and stained simultaneously with the coating, ensuring that the tissue sample and coating are subjected to identical staining conditions. This is an improvement over prior art arrangements because the coating of the present invention is thinner than conventionally used films. This allows a coverslip to be positioned over the tissue sample and coating, which is not possible when using cellulose film, because the film is thicker than the tissue sample and therefore holds the coverslip away from the tissue sample.

[0065] The coated article may include additional layers, such as an adhesion layer or a barrier coating. The barrier coating may include ethylene acrylic acid, polyvinylidene chloride, acrylic, or other barrier coating material.

[0066] According to a fourth aspect of the present invention there is provided a method of forming a coating composition comprising the step of homogenising a dispersion of regenerated cellulose in water. The method of the fourth aspect of the present invention may have the features of any of the previous aspects.

[0067] Thus, the homogenization may be high-pressure homogenization. The regenerated cellulose may be regenerated from an aqueous alkaline cellulose solution, preferably in the liquid phase. The regenerated cellulose may then be washed to remove salts created by the acid. The method for forming the coating composition includes the following: (a) dissolving a cellulose-containing material in an alkali to form an aqueous alkaline cellulose solution; (b) regenerating the cellulose in the liquid phase by combining the aqueous alkaline cellulose solution with an excess of acid under agitation; (c) washing the resulting regenerated cellulose to obtain a cellulose dispersion in water that is substantially free of salts created by the acid; (d) homogenizing the cellulose dispersion in water to create a coating composition may include:

[0068] Any of the embodiments disclosed herein may include features of any of the embodiments described above.

[0069] The present invention is further illustrated in the examples and figures outlined below, which are not intended to limit the scope of protection. [Brief explanation of the drawings]

[0070] [Figure 1]1 shows an X-ray diffraction (XRD) image of a coating material according to the present invention dried at a temperature above 100° C. [Figure 2] 1 shows an XRD image of a coating composition according to the present invention that has been slightly dried.

[0071] Example 1 Wood pulp was dissolved in sodium hydroxide using high-pressure homogenization to form an aqueous sodium hydroxide cellulose solution. This solution was then added to an excess of hydrochloric acid under constant agitation. This allowed the cellulose to be regenerated in the liquid phase, creating a dispersion of regenerated cellulose in the acid.

[0072] The regenerated cellulose was filtered, washed with water, and then resuspended in water to create an aqueous dispersion free of acid-created salts. The aqueous dispersion was then subjected to high-pressure homogenization to form the coating composition.

[0073] The coating compositions were coated onto regenerated cellulose film (Natureflex™ NP) by coating one or both sides of the film with the coat weights shown in Table 1 below. [Table 1]

[0074] The coating was dried at a temperature above 60° C. The water vapor permeability and wide angle haze were then measured. Wide angle haze was measured at 2.5° and conforms to ASTM D1003.

[0075] To measure WVP, a sufficient amount of silica gel was placed into a cup so that the bottom was covered to a depth of approximately 0.8 cm. A circular film sample with a diameter of approximately 10 cm was then cut out. A thin layer of paraffin wax was wiped onto the surface of the cup. The circular sample was placed so that its edge was in contact with and pressed against the surface, ensuring there were no creases. The coated side of the film was positioned toward the outside of the cup. The cup was then placed in an oven at the desired temperature and relative humidity (RH). After 24 hours, the cup was removed and immediately weighed. The cup was returned to the oven and weighed every 24 hours until a consistent increase was observed (usually after 72 hours).

[0076] The results are shown in Tables 2 and 3 below. [Table 2]

[0077] [Table 3]

[0078] Example 2 A solution of the present invention was prepared with a solids content of 2%. Two glass plates, 11.5 cm long and 7.5 cm wide, were placed on the drawdown bed and a coating of the solution was applied at a rate of 6.75 g / m 2 A coat weight of 1000 ppm was applied to each of the plates using a standard red K bar (12 μm wet film deposition). The glass plates were then removed from the drawdown bed and dried in an oven at 60° C. for 45 minutes. After the coating was completely dry, the plates were removed from the oven and allowed to cool to room temperature, which took approximately 5 minutes.

[0079] A glass plate was placed on a hard, flat surface and the coating was scratched along its entire length with a penny in a continuous motion, with no visible removal of the coating observed.

[0080] The other glass plate was placed on a hard, flat surface, and a piece of Scotch tape 600 was firmly adhered across the entire width of the coated plate, with the edge of the tape extending beyond the width of the plate. One edge of the tape was then held at a 180-degree angle and quickly removed. The area from which the coating had been removed was then calculated and compared to the total area where the tape had been applied to the coated plate. Less than 5% of the coating area was removed, demonstrating that the coating showed good adhesion.

[0081] Example 3 A solution of the present invention was prepared with a solids content of 2%. Two glass plates, 11.5 cm long and 7.5 cm wide, were placed on the drawdown bed and a coating of the solution was applied at a rate of 6.75 g / m 2 was applied to each of the plates using a standard red K bar (12 μm wet film deposition) at a coat weight of 1. The glass plates were then removed from the drawdown bed and allowed to dry at room temperature for 24 hours.

[0082] A glass plate was placed on a hard, flat surface and the coating was scratched along its entire length with a penny in a continuous motion. Portions of the coating were removed, revealing the glass underneath. This demonstrates that the coating of the present invention is much softer and less adhesive when dried at room temperature compared to when dried at elevated temperatures.

[0083] The other glass plate was placed on a hard, flat surface, and a piece of Scotch tape 600 was firmly adhered across the entire width of the coated plate, with the edge of the tape extending beyond the width of the plate. One edge of the tape was then held at a 180-degree angle and quickly removed. The area from which the coating was removed was then calculated and compared to the total area where the tape had been applied to the coated plate. More than 5% of the coating area was removed, demonstrating that this coating exhibited less good adhesion than coatings dried at higher temperatures.

[0084] Example 4 Figure 1 shows X-ray diffraction (XRD) images of coating materials according to the invention dried at temperatures above 100°C. In the XRD, Cellulose I is characterized by two peaks in the center of the scan and a broad peak further along the scan, while Cellulose II is characterized by one peak near the center beam at the beginning of the scan and two peaks further along the scan.

[0085] Figure 1 shows that the coating of the present invention is almost entirely cellulose II. From the line scan of Figure 1, the coating material was found to have a crystallinity of about 80%.

[0086] In contrast, Figure 2 shows an XRD image of a coating composition according to the present invention that has been only lightly dried, showing that the coating composition has almost no diffraction, suggesting a very low level of crystallinity.

[0087] Figures 1 and 2 therefore show that the coating composition according to the invention is predominantly amorphous before it is dried, but is then predominantly crystalline cellulose II after drying at temperatures above room temperature.

Claims

1. A coating composition comprising a homogenized dispersion of regenerated cellulose in water, wherein the regenerated cellulose comprises both amorphous cellulose and crystalline cellulose.

2. 10. The coating composition of claim 1, wherein the regenerated cellulose is regenerated in the liquid phase from an aqueous alkaline cellulose solution.

3. The homogenized dispersion of regenerated cellulose in water is (a) dissolving a cellulose-containing material in aqueous alkali to form an aqueous alkaline cellulose solution; (b) regenerating the cellulose in a liquid phase by combining the aqueous alkaline cellulose solution with an excess of acid under agitation; (c) washing the resulting regenerated cellulose to achieve a cellulose dispersion in water that is substantially free of the salt created by the acid; (d) homogenizing the cellulose dispersion in water; The coating composition of claim 2 obtained using a process comprising:

4. 4. The coating composition of claim 3, wherein the aqueous alkali in step (a) is a hydroxide, preferably an alkali metal hydroxide, and more preferably sodium hydroxide.

5. 5. The coating composition of claim 3 or claim 4, wherein step (a) comprises homogenization, preferably high pressure homogenization, to aid dissolution.

6. 6. The coating composition of claim 3, wherein step (b) comprises adding an aqueous alkaline cellulose solution to the acid or adding the acid to the aqueous alkaline cellulose solution.

7. 7. The coating composition of claim 3, wherein step (c) comprises separating the regenerated cellulose from the acid, washing and resuspending in water to form a dispersion in water, or wherein step (c) comprises successive washings to remove the acid and create a dispersion in water.

8. The coating composition of any one of claims 1 to 7, wherein the cellulose dispersion in water has been subjected to high pressure homogenization.

9. Coating composition according to any one of claims 1 to 8, wherein the cellulose dispersion in water comprises 1 to 10% w / w of cellulose, preferably 2 to 7% w / w of cellulose.

10. The aqueous alkaline cellulose solution (a) neutralizing an alkaline cellulose-containing precursor material with an acid and obtaining a neutralized solid cellulose-containing material; (b) mixing the neutralized solid cellulose-containing material with a bleaching agent to create a mixture; (c) separating a solid purified cellulose-containing product from the mixture; (d) dissolving the solid purified cellulose-containing product in aqueous alkali; The coating composition of any one of claims 2 to 9, produced using

11. The coating composition of any one of claims 1 to 10, further comprising one or more additives selected from waxes, biopolymers, pigments, active ingredients, reference particles or dopants for dye incorporation.

12. A coating composition according to any preceding claim, wherein the cellulose particles have an average radius of less than 1 micron, more preferably less than 0.75 micron.

13. A coating comprising the cellulose coating composition of any one of claims 1 to 12.

14. The coating of claim 13 having a thickness of 0.1 to 50 microns, preferably 0.5 to 8 microns.

15. 15. The coating of claim 13 or 14, having a coat weight of 0.1 to 20 gsm, preferably 1 to 10 gsm.

16. 16. The coating of any one of claims 13 to 15, having a wide angle haze of 50 to 75%, preferably 55 to 70%.

17. 1000~1250g / m ２ / 24 hours, preferably 1050 to 1200 g / m ２ The coating according to any one of claims 13 to 16, having a water vapor permeability of 24 hours.

18. 18. The coating of any one of claims 13 to 17, wherein the coating comprises less than 50% w / w of the cellulosic coating composition, or wherein the coating comprises more than 60% w / w of the cellulosic coating composition.

19. The coating of any one of claims 13 to 18, which has been dried at a temperature above 25°C, preferably above 35°C and more preferably above 50°C.

20. 20. The coating of claim 19, having a crystallinity of more than 60%, preferably more than 75%.

21. A coated article comprising the coating of any one of claims 13 to 20.

22. 22. The coated article of claim 21, wherein the coating is applied by gravure, spray or print coating.

23. 23. The coated article of claim 21 or claim 22, wherein the article is a film or a histological quality control device.

24. (a) dissolving a cellulose-containing material in an alkali to form an aqueous alkaline cellulose solution; (b) regenerating the cellulose in a liquid phase by combining the aqueous alkaline cellulose solution with an excess of acid under agitation; (c) washing the resulting regenerated cellulose to achieve a cellulose dispersion in water substantially free of the salt created by the acid; (d) homogenizing the cellulose dispersion in water to create a coating composition. A method of forming a coating composition comprising:

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