composition

Abstract

The present invention provides an anti-block and / or slip composition comprising particles of mercerised and / or regenerated cellulose.

Description

[0001] COMPOSITION

[0002] The present invention concerns an anti-block and / or slip composition comprising particles of mercerised and / or regenerated cellulose, uses of said composition and a method of making said composition.

[0003] Anti-block and / or slip compositions are well known in the art to control the adhesion properties of a surface, for example, to prevent blocking (unwanted adhesion between two surfaces) and / or to increase slip between two surfaces (reduce the coefficient of friction (CoF)). Increasing the amount of anti-blocking or slip agents can improve the anti-block or slip properties, but this is often accompanied by a decrease in the optical properties, which is undesirable.

[0004] Many anti-block and slip compositions include small particles that increase the roughness of the film. This decreases the contact area between adjacent film layers, thereby reducing the potential for blocking, but also decreasing friction. Thus, a composition can act as both an antiblock and a slip agent. However, different compositions can have more of an effect on one than the other.

[0005] Many of the known anti-block and slip particulates are synthetic, non-biodegradable materials. For example, poly(methyl methacrylate) (PM MA) is widely used in the art as an anti-block and / or slip material. PMMA is versatile, highly biocompatible and has good optical properties. However, PMMA is non-biodegradable and so remains as a microplastic, which is particularly problematic when it is used in biodegradable materials such as cellulose films. There is therefore a growing need to replace PMMA with an environmentally friendly alternative that can still provide the desired anti-block and slip properties.

[0006] This is part of a wider drive to provide compositions which are fully compostable and biodegradable, as well as to reduce reliance on microplastic materials.

[0007] Therefore, there remains a need for the provision of an anti-block and / or slip composition which is fully compostable and provides comparable performance to anti-block and slip materials in the art, such as PMMA.

[0008] According to a first aspect of the present invention, there is provided an anti-block and / or slip composition comprising particles of mercerised and / or regenerated cellulose. The inventors have surprisingly found that the composition of the invention has comparable anti-block and slip properties to known anti-block and slip materials in the art, such as PMMA. The inclusion of the mercerised or regenerated cellulose particles also does not negatively impact the optical properties of the film.

[0009] However, the composition according to the invention is entirely biodegradable and compostable and therefore provides a more environmentally friendly alternative to existing compositions in the art. Thus, the use of the composition of the invention allows for an entirely biodegradable resulting product, for example an ink, coating or film. The inventors have also surprisingly found that the composition of the present invention has good stability.

[0010] The cellulose in the anti-block and / or slip composition may be predominantly crystalline cellulose. Thus, the cellulose may be more than 40% crystalline cellulose, preferably more than 50% crystalline cellulose and even more preferably more than 60% crystalline cellulose. The crystal type of cellulose particles may be type II. The cellulose is preferably not a cellulose derivative. Thus, the majority of the particles is formed from cellulose, not a cellulose derivative.

[0011] The cellulose particles may have an average particle size of between about 1 and 10 microns, between about 2 and 10 microns, or between about 3 and 9 microns. The particle sizes are comparable to known anti-block or slip components in the art, for example PMMA.

[0012] The average particle size in this context is to be understood as the D50 measurement (i.e. the particle size at which 50% of the particles in the sample are larger and 50% are smaller).

[0013] The inventors have found that an average particle size of between 1 and 10 microns advantageously provides particles with excellent anti-block and slip properties. For example, when the particles are present in a film, the average particle size of between 1 and 10 microns has been found to ensure that the cellulose particles protrude from the film, thereby providing a surface that is not too smooth and so limiting the contact area between surfaces. This decreases the tendency towards blocking (i.e., the adhesion developed between two smooth layers) and improves the slip properties.

[0014] An average particle size of above about 10 microns may result in particles that are larger than the thickness of a film, which would detrimentally influence the film’s properties, for example printability. An average particle size of below about 1 micron may result in particles that are not large enough to protrude from the film, so may have little effect on blocking and slip. However, the particles may be easily varied, for example the particle size may be changed depending on the intended use.

[0015] Furthermore, the inventors have found that the particles of the invention are well-dispersed and distributed when used as part of a composition, i.e. in a coating, a film or an ink.

[0016] The D10 measurement (i.e. the particle size at which 10% of the particles in the sample are smaller and 90% are larger) may be between 0.5 microns and 5 microns. The D90 measurement (i.e. the particle size at which 90% of the particles in the sample are smaller and 10% are larger) may be between 8 microns and 25 microns. The standard deviation of the particles may be between 1 and 10 microns, preferably between 2 and 8 microns.

[0017] The cellulose particles may be substantially spherical. This helps in providing the necessary anti-block and slip properties.

[0018] The particles of cellulose may be formed from a dispersion of cellulose. This may be a dispersion of cellulose in water. Said dispersion may have undergone homogenisation, preferably high-pressure homogenisation. The particles may have been formed by drying or emulsifying the cellulose dispersion to create particles.

[0019] This ensures that particles that are sufficiently small to function as an anti-block or slip agent are created, as the resulting cellulose particles are small in size and dispersed throughout a liquid. This also ensures that the addition of the particles is not overly detrimental to the optical properties of a material to which it is added.

[0020] The cellulose may be regenerated cellulose. Methods of manufacturing regenerated cellulose are known in the art. The regenerated cellulose may be formed from an aqueous alkali cellulose solution. This regeneration method involves combining an aqueous alkali cellulose solution with an acid in order to regenerate the cellulose. The use of a cellulose material that has been regenerated from an aqueous alkali cellulose solution according to the invention does not require an acid hydrolysis step.

[0021] The aqueous alkali cellulose solution may be created by dissolving a cellulose-containing material in an alkali. There are various methods known in the art for creating an aqueous alkali cellulose solution, all of which can be used in the present invention. The cellulose may also be mercerised on contact with an alkali, before it is dissolved. Thus, the regenerated cellulose may also have been previously mercerised. Homogenisation may be used to aid dissolution of cellulose in the alkali, preferably high- pressure homogenisation. High-pressure homogenisation is used herein to refer to homogenisation that occurs at a pressure of 100 bar or more. More than one homogenisation step may be used during dissolution of the cellulose in the alkali.

[0022] The alkali may be a hydroxide, preferably an alkali metal hydroxide and more preferably sodium hydroxide. The alkali may have a concentration between 5% w / w and 25% w / w, or between 10% w / w and 25% w / w. The concentration of alkali in the aqueous alkali cellulose solution may be between 2% w / w and 17.5% w / w.

[0023] However, mercerised cellulose may also be used without the regeneration step. A standard mercerisation step may be used, involving contacting the cellulose with an alkali. The cellulose may undergo oxidative degradation during or after the mercerisation step, such that the degree of polymerisation of mercerised cellulose is decreased to below 760, thereby forming a depolymerised cellulose.

[0024] Alkali as above can then be added to the mercerised cellulose. A total concentration of 2.5 to 17.5% of alkali in the composition may be achieved. The composition may then be homogenised, preferably high-pressure homogenised, in order to form cellulose microfibres. These microfibres can then be neutralised with an acid.

[0025] Thus, the high-pressure homogenisation can create either a cellulose solution or cellulose microfibres. At least part of the high pressure homogenisation may occur at temperatures of - 10°C or more, preferably at least 0°C or more. The high pressure homogenisation may preferably occur at temperatures of 50°C or less, preferably 40°C or less. The conditions of the high pressure homogenisation will determine whether a solution or microfibres are created, with lower temperatures in the above range being more likely to create a solution and higher temperatures in the above range being more likely to create microfibres. A mixture of a solution and microfibres may also be created, as the cellulose may only partially dissolve.

[0026] Thus, the dispersion of cellulose has preferably undergone homogenisation at least twice, firstly to aid dissolution of the cellulose in an alkali or to create cellulose microfibres and secondly after the cellulose has been dispersed in water. This is thought to reduce the particle size sufficiently to improve optical properties. There may be more than one homogenisation step at each point of the process. There may be two or more homogenisation steps to aid dissolution of the cellulose in an alkali or to create cellulose microfibres, and one or two homogenisation steps after the cellulose has been dispersed in water.

[0027] The cellulose composition may then be contacted with an acid. In the case of microfibers, this neutralises the cellulose microfibres. In the case of a cellulose solution, this regenerates the cellulose into solid regenerated cellulose.

[0028] The aqueous alkali cellulose solution may be regenerated in a liquid phase. This can be achieved by combining the aqueous alkali cellulose solution with an excess of acid under agitation, such as stirring. The aqueous alkali cellulose solution may be added to the acid, or the acid may be added to the aqueous alkali cellulose solution.

[0029] Similarly, when neutralising the cellulose microfibres, the acid can be added to the microfibres or the microfibres added to the acid.

[0030] Once the cellulose has contacted the acid, it may be washed to achieve a cellulose dispersion in water. The cellulose dispersion in water may be substantially free of the salts created by the acid.

[0031] The washing may comprise separating the cellulose from the acid, washing the cellulose with water and resuspending the cellulose in water to form a dispersion. The separation can be done by any conventional means, including filtering, centrifuging or using a vacuum. Alternatively, the washing may comprise continuous washing to remove the acid and create a dispersion of cellulose in water.

[0032] The cellulose dispersion in water may then be homogenised, preferably high-pressure homogenised.

[0033] Thus, the homogenised dispersion of cellulose in water may be obtained using a method comprising the steps of:

[0034] (a) mercerising a cellulose to form a mercerised cellulose;

[0035] (b) adding an aqueous alkali to the mercerised cellulose;

[0036] (c) homogenizing the cellulose to form cellulose microfibers or a cellulose solution;

[0037] (d) contacting the cellulose microfibers or solution with acid to form neutralized or regenerated cellulose; (e) washing the neutralized or regenerated cellulose with water to form a cellulose dispersion in water;

[0038] (f) homogenising the cellulose dispersion in water; and

[0039] (g) emulsifying or drying the cellulose dispersion to create cellulose particles.

[0040] If a cellulose solution is created on homogenisation, then contact with the acid creates a regenerated cellulose. If cellulose microfibres are created on homogenisation, then contact with the acid neutralises the mercerised cellulose

[0041] The cellulose dispersion in water may comprise between 1 and 20% w / w cellulose, preferably between 2 and 10% w / w cellulose.

[0042] The cellulose-containing material that is dissolved in an alkali to create the aqueous alkali cellulose solution may be at least partly purified so as to remove some non-cellulose components compared to the starting material. The aqueous alkali cellulose solution may be produced using the steps of:

[0043] (a) neutralising an alkaline cellulose-containing precursor material with an acid and obtaining a neutralised solid cellulose-containing material;

[0044] (b) mixing the neutralised solid cellulose-containing material with bleach to create a mixture;

[0045] (c) separating a solid cellulose-containing product from the mixture; and

[0046] (d) dissolving the solid purified cellulose-containing product in an aqueous alkali.

[0047] Alternatively, the cellulose particles may be obtained using a method comprising the steps of:

[0048] (h) crushing a regenerated cellulose material;

[0049] (i) decreasing the degree of polymerization of the crushed material to form a depolymerized cellulose;

[0050] (j) washing the depolymerized cellulose with water to form a cellulose dispersion in water;

[0051] (k) homogenising the cellulose dispersion in water; and

[0052] (l) drying or emulsifying the cellulose dispersion to create cellulose particles.

[0053] The degree of depolymerisation may be decreased to below 350 in step (i). This can be achieved using any known process to decrease the degree of polymerisation in cellulose. A lower degree of polymerisation decreases the resulting particle size. The antiblock and / or slip composition can comprise a blend of cellulose particles obtained from different methods. The cellulose particles can each contain cellulose obtained via different methods. For example, the cellulose dispersion in water created using steps (a) to (f) above can be mixed with the cellulose dispersion in water created using steps (h) to (k) above, either before or after homogenisation. This blend can then be dried or emulsified to create cellulose particles.

[0054] The emulsification or drying step (step (g) or step (I) above) has advantageously been found to create cellulose particles with the even size distribution, bulk density and particle shape required to provide anti-block or slip properties. For example, it is desirable to create cellulose particles with a low size distribution.

[0055] Furthermore, the inventors have found that the parameters in the emulsification or drying step can be used to influence the properties of the resulting cellulose, for example, the size of the particles created. Therefore, the desired particle size for the cellulose may easily be obtained and altered as necessary without the inclusion of additional steps.

[0056] The cellulose particles may be obtained by a variety of different drying processes. For example, the drying process may include spray drying or freeze drying. The inventors have found that spray drying or freeze drying the cellulose dispersion results in particles that are consistent and substantially spherical, with an even size distribution.

[0057] In some embodiments, the drying process is spray drying. The cellulose dispersion may be atomised into droplets, with the water being rapidly evaporated by hot air or gas in a drying chamber to form cellulose particles with the desired characteristics. The temperature and airflow conditions can be modified to obtain the desired particle size.

[0058] The size of the particles formed may be influenced by other conditions used in step (g) or (I), for example, the solids content of the cellulose dispersion and the settings on the spray dryer, for example air flow, temperature, speed and diffuser nozzle tip size.

[0059] In another embodiment, the drying process is freeze drying, in which the temperature is lowered to below freezing at a low pressure.

[0060] In another embodiment, step (g) or step (I) may involve emulsifying the cellulose dispersion. This step may include emulsifying the cellulose dispersion into an oil, passing the oil through an antisolvent or crosslinker, followed by washing, drying and filtering to form cellulose particles. There may be more than one washing, drying and / or filtration step to form the desired cellulose particles. The drying step may be in a fluid bed dryer. The skilled person would be aware of methods known in the art for emulsification.

[0061] The use of different filter sizes may have an effect on the size of the cellulose particles produced. In embodiments where there is more than one filtration stage, the filters used may be of different sizes.

[0062] The inventors have advantageously found that emulsifying the cellulose dispersion creates homogenous cellulose particles with the desired particle size.

[0063] The antisolvent or crosslinker may be selected from at least one of calcium chloride, citric acid, butane tetracarboxylic acid, epichlorohydrin, or an amino-acid based crosslinker (e.g. TAHT).

[0064] The degree of polymerization in the regenerated cellulose in step (h) may be less than 600. This makes it easier to reduce the degree of polymerization to the level needed to create the desired particle size.

[0065] Step (i) may comprise reducing the degree of polymerization of regenerated cellulose using sodium hypochlorite. The sodium hypochlorite may have an effective chlorine concentration of 0.13% or higher, preferably 3% or higher.

[0066] Step (j) may comprise separating the cellulose from sodium hypochlorite, washing and resuspending in water to form a dispersion in water. Alternatively, step (j) may comprise continuous washing to remove sodium hypochlorite and create a dispersion in water.

[0067] According to a second aspect of the present invention, there is provided an anti-block and / or slip dispersion comprising the composition discussed above and a carrier material.

[0068] Anti-block and / or slip dispersions are known in the art as a means for adding anti-block / slip components into a final product. The carrier material of the dispersion is used as a carrier for the cellulose particles. Thus, the dispersion can be added directly to the material that needs improved anti-block or slip properties.

[0069] The anti-block / slip dispersion may be used in known methods in the art, for example, in the production of films. The carrier material may be water or another inert carrier liquid. Alternatively, the carrier material may be a polymeric material. The polymeric material may be the same as the polymeric material in the final product.

[0070] The polymeric material may comprise at least one of polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoates (PHA), polyamide (e.g. nylon), polyethylene terephthalate (PET), or a polyolefin such as polypropylene (PP) or polyethylene (PE). The polymeric material may include more than one of these components.

[0071] The dispersion may contain between 1 and 90%, preferably 1 and 50% and more preferably 1 and 30% of the cellulose particles in a polymeric material. If the dispersion is an aqueous dispersion, it may comprise between 1 and 80%, preferably 1 and 50% and more preferably 1 and 30% cellulose particles in water or another carrier. The dispersion preferably has as high an amount of cellulose particles as possible, while still retaining good particle dispersion and flow rate.

[0072] The dispersion may contain other components. For example, the dispersion may contain a rheology modifier to aid in the suspension of the particles, such as carboxymethylcellulose. The dispersion may contain other additives, either to aid dispersion of the particles or to add other functionality to the product.

[0073] The dispersion has been found to impart good slip and anti-blocking properties to a resulting product when used, for example in an ink, coating or film.

[0074] According to a third aspect of the present invention, there is provided a method of making the anti-block and / or slip dispersion comprising manufacturing the cellulose particles using some or all of the steps outlined above and subsequently dispersing the cellulose particles in a carrier material. The carrier material may be any of the carrier materials discussed above.

[0075] For example, the steps may include:

[0076] (a) mercerising a cellulose to form a mercerised cellulose;

[0077] (b) adding an aqueous alkali to the mercerised cellulose;

[0078] (c) homogenizing the cellulose to form cellulose microfibers or a cellulose solution;

[0079] (d) contacting the cellulose microfibers or solution with acid to form neutralized or regenerated cellulose;

[0080] (e) washing the neutralized or regenerated cellulose to form a cellulose dispersion in water;

[0081] (f) homogenising the cellulose dispersion in water; and (g) emulsifying or drying the cellulose dispersion to create cellulose particles, or the steps of:

[0082] (h) crushing a regenerated cellulose material;

[0083] (i) decreasing the degree of polymerization of the crushed material to form a depolymerized cellulose;

[0084] (j) washing the depolymerized cellulose to form a cellulose dispersion in water;

[0085] (k) homogenising the cellulose dispersion in water; and

[0086] (l) drying or emulsifying the cellulose dispersion to create cellulose particles, and subsequently dispersing the cellulose particles in a carrier material.

[0087] According to a fourth aspect of the present invention, there is provided an ink comprising the anti-block and / or slip composition discussed above. The anti-block and / or slip composition can be added itself, or as part of a dispersion, as discussed above.

[0088] Thus, the resulting ink can be biodegradable with good anti-block / slip properties and no microplastics. The ink can be printed onto an article such as a film in order to create an anti- block / slip article.

[0089] According to a fifth aspect of the present invention, there is provided a coating composition comprising the anti-block and / or slip composition discussed above. The anti-block and / or slip composition can be added itself, or as part of a dispersion, as discussed above.

[0090] The coating composition can be used to form a coating. The coating composition may be coated onto an article, for example a film such as a cellulose-based film. The resulting coating provides a thin, biodegradable coating on an article, with good anti-block / slip and optical properties.

[0091] According to a sixth aspect of the present invention, there is provided a film comprising the anti-block and / or slip composition discussed above. The anti-block and / or slip composition can be added itself, or as part of a dispersion, as discussed above.

[0092] It has surprisingly been found that a film comprising the composition discussed herein demonstrates excellent anti-block / slip and optical properties, such as transparency. Furthermore, the cellulose particles present in the composition of the invention have been found to be well-dispersed and distributed when present in a film, thereby providing a film with improved properties that are consistent over the whole length or width of the film. The film may be a cellulose, polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polyamide (e.g. nylon), polyethylene terephthalate (PET), or a polyolefin film such as polypropylene (PP) film or a polyethylene (PE) film. The film may contain the same polymeric material as in the dispersion, if the particles are applied as part of a dispersion having a polymeric material.

[0093] The film may have one or more layers. The particles of cellulose may be added to one or both of the outer layers of the film. The film may further comprise a coating, such as an adhesive layer or a barrier coating, on one or both sides thereof.

[0094] The cellulose particles function as a replacement for conventional anti-block / slip particles, such as PMMA. As such, they may be included in the film, coating or ink in comparable amounts to those conventionally used for PMMA. For example, a film may contain between 0.01 and 5% cellulose particles, preferably between 0.02 and 2%.

[0095] According to a seventh aspect of the present invention, there is provided the use of mercerised or regenerated cellulose particles as an anti-block and / or slip component in a polymeric composition. The use of cellulose particles to provide anti-block and / or slip has been found to provide comparable properties to known anti-block and / or slip components, such as PMMA. However, as the cellulose particles are biodegradable, no microplastics are needed and so entirely biodegradable articles can be created.

[0096] According to a eighth aspect of the present invention, there is provided a method of making an anti-blocking and / or slip article comprising the steps of adding the anti-block and / or slip composition or the dispersion discussed above to said article.

[0097] The article may be a film. The anti-block and / or slip composition or the dispersion discussed above may be added to one or more layers thereof.

[0098] The film may be a cellulose, polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polyamide (e.g. nylon), polyethylene terephthalate (PET), or a polyolefin film such as polypropylene (PP) film or a polyethylene (PE) film. The film may contain the same polymeric material as in the dispersion.

[0099] The film may have one or more layers. The particles of cellulose may be added to one or both of the outer layers of the film. The film may further comprise a coating, such as an adhesive layer or a barrier coating, on one or both sides thereof. Any of the aspects disclosed herein can include the features of any of the earlier aspects.

[0100] The invention is further discussed in the examples and figures outlined below, which are not intended to be limiting to the scope of protection.

[0101] Figure 1 illustrates a particle size distribution graph comparing different anti-block / slip dispersions;

[0102] Figures 2 and 3 illustrate microscopic images of cellulose films comprising PMMA anti-block particles at 4x zoom (left) and 10x zoom (right);

[0103] Figures 4 and 5 illustrate microscopic images of cellulose films comprising compositions according to the present invention at 4x zoom (left) and 10x zoom (right);

[0104] Figure 6 illustrates a scanning electron microscope (SEM) image of the cellulose particles according to a first embodiment described herein; and

[0105] Figure 7 illustrates a scanning electron microscope (SEM) image of the cellulose particles according to a second embodiment described herein.

[0106] Example 1

[0107] The particle size distributions of three dispersions were measured on a MasterSizer (RTM) at room temperature.

[0108] The first sample (Sample 1) was a comparative sample of a dispersion comprising commercially available anti-block PMMA spheres dispersed in water with carboxymethyl cellulose. Samples 2 and 3 were dispersions of regenerated cellulose particles in water with carboxymethyl cellulose, comprising approximately 8 micron and 5 micron regenerated cellulose particle sizes respectively. The cellulose particles in Samples 2 and 3 were made according to Method 1 , namely:

[0109] (a) mercerising a cellulose to form a mercerised cellulose;

[0110] (b) adding aqueous sodium hydroxide to the mercerised cellulose;

[0111] (c) homogenizing the cellulose to form a cellulose solution;

[0112] (d) contacting the cellulose solution with acid to form neutralized and regenerated cellulose; (e) washing the neutralized or regenerated cellulose with water to form a cellulose dispersion in water;

[0113] (f) homogenising the cellulose dispersion in water; and

[0114] (g) spray drying the cellulose dispersion to create cellulose particles.

[0115] As can be seen from Figure 1 , Sample 3 shows a narrower distribution profile compared to Sample 2, which is desirable. However, the distribution curve of Sample 2 is more comparable to Sample 1 , with the average particle size being in an analogous region. Therefore, in use, the particles of Sample 2 are likely to be comparable to those of Sample 1 when utilised as an anti-block or slip agent.

[0116] Additionally, it was advantageously found that the spheres of Samples 2 and 3 remained stable and inert over time and did not show signs of swelling or agglomerating behaviour in the water. Therefore, Samples 2 and 3 provide an alternative biodegradable dispersion that exhibits good stability.

[0117] Example 2

[0118] In order to test the properties of the regenerated cellulose particle anti-block / slip composition of the present invention, cellulose films containing these particles were compared to cellulose films containing PMMA anti-block particles.

[0119] Anti-block / slip dispersions were prepared by adding 500 g of water and 1.25 g of carboxymethylcellulose to a vessel. 4.5 g of the relevant anti-block / slip particles were added (i.e. , regenerated cellulose particles or PMMA) to another 500 g of water and the composition then poured through a 25 micron bag filter and into the vessel containing the water and carboxymethylcellulose. If necessary, the dispersion was filtered at least once more through a second filter. The average particle size of the PMMA and the regenerated cellulose used in the following examples was approximately 8 microns. The resulting dispersion was continuously stirred at a slow speed and the dispersions were continuously agitated prior to use.

[0120] Each dispersion was injected into viscose at 0.045 wt% or 0.09 wt%, which was then used to create a regenerated cellulose film using conventional methods. The resulting regenerated cellulose film was tested for various properties. The target dosages and injection flowrates are shown in Table 1 below. Table 1

[0121] The resulting films were visually assessed under a microscope and can be seen in Figures 2 - 5.

[0122] Figure 2 (Comparative A) and Figure 3 (Comparative B) show microscopic images of a film comprising PMMA anti-block particles. Comparing these images to Figures 4 (Film 1) and 5 (Film 2), it can be seen that the particles present in both the comparative films and the films according to the present invention are well dispersed within the film. The number of particles that can be seen in the Figures is greater in the films comprising 0.09% of dispersion dosage compared to 0.045%. The particles according to the present invention are substantially spherical.

[0123] Figures 4 and 5 therefore show that the composition according to the invention is comparable to compositions in the art.

[0124] Coefficient of Friction

[0125] The slip of the samples of Table 1 was tested on an Instron (RTM) in accordance with a static 10N load cell, sledge dimensions of 6.3 x 6.3 x 0.6 cm, a sledge weight of 194.00g and a drawing rate of 20 cm / min. A 15cm width (transverse direction) and a 35cm length (machine direction) was placed on the slip bed, ensuring as few creases as possible. A strip approximately 10cm wide (to cover the sledge weight) was cut from the bottom of the sample and placed on top of the film on the slip bed such that side A of the film on the slip bed contacts side B of the strip. The strip was wrapped around the sledge weight. A standard coefficient of friction measurement using the Instron (RTM) was taken 6 times with new film on the slip bed and sledge weight each time and an average calculated.

[0126] The average coefficients of friction recorded are set out in Table 2 for both static and dynamic measurements. Table 2

[0127] As will be recognized by those skilled in the art, lower CoF values indicate lower friction and therefore greater slip. As shown in Table 2, the coefficients of friction are relatively low in the films according to the invention. Furthermore, the different dosage levels provide similar CoF results.

[0128] Additionally, films according to the present invention have comparable CoF values to the comparative films containing PMMA, thereby providing a more environmentally friendly alternative that provides effective slip properties, while being fully biodegradable and compostable.

[0129] Example 3

[0130] The dispersions of PMMA or regenerated cellulose particles in Example 2 were used to produce more regenerated cellulose films. PMMA particles were added to viscose at 0.06% in Comparative C, and regenerated cellulose particles were added to viscose at 0.06% in Film 3. The viscose was then used to create a regenerated cellulose film using conventional methods.

[0131] The CoF was measured using the test method outlined above in Example 2 and the results are shown in Table 3.

[0132] Table 3

[0133] As shown by the CoF values, films according to the present invention are comparable with the comparative PMMA-containing film, thereby providing effective slip properties, while being more environmentally friendly.

[0134] Pressure Block

[0135] A pressure block test was carried out for the same samples tabulated in Table 3. 50 sheets of the film were stacked A to B and cardboard sheets positioned at either end of the stack. Another 50 sheets of the film were stacked A to B on one side of a carboard sheet, with another cardboard sheet positioned at the end of the stack to form a structure of cardboard / 50 sheets of film / cardboard / 50 sheets of film / cardboard.

[0136] This structure was then placed between metal plates and compressed under 3 tonnes of pressure for 15 minutes. The stacks of film were then removed and the blocking between the sheets of film assessed.

[0137] The resulting pressure blocking values are summarized in Table 4. The degree of blocking is rated subjectively between a value of 1 and 50, wherein 50 represents the best result. For example, if the films cannot be pulled apart from one another (i.e., are fully adhered) the value would be 0.

[0138] Table 4

[0139] The films according to the invention provide excellent anti-blocking properties and are comparable with films comprising PMMA, thereby providing an environmentally friendly alternative to known anti-block compositions. Therefore, the films according to the present invention will have sufficient anti-blocking that they will not stick together when stored, for example, in reels.

[0140] Example 4

[0141] Scanning electron microscopy was used to image the cellulose particles according to the present invention. The particles shown in Figure 6 were created by mercerising a cellulose to form a mercerised cellulose, adding an aqueous sodium hydroxide to the mercerised cellulose, high-pressure homogenizing the cellulose at around 25°C to form cellulose microfibers, neutralising the cellulose microfibers with acid, washing the neutralized cellulose with water to form a cellulose dispersion in water, homogenising the cellulose dispersion in water using high-pressure homogenisation and drying the cellulose dispersion to create cellulose particles.

[0142] The particles shown in Figure 7 were created by crushing a regenerated cellulose film, decreasing the degree of polymerization of the crushed cellulose film using sodium hypochlorite to form a depolymerized cellulose having a degree of polymerization of below 350, washing the depolymerized cellulose with water to form a cellulose dispersion in water, homogenising the cellulose dispersion in water using high-pressure homogenisation and drying the cellulose dispersion to create cellulose particles.

[0143] As shown in both figures, the cellulose particles of the present invention are substantially spherical.

[0144] Example 5

[0145] Cellulose particles were created according to Method 1 , as outlined above, or according to Method 2, namely:

[0146] (a) crushing a regenerated cellulose material;

[0147] (b) decreasing the degree of polymerization of the crushed material to form a depolymerized cellulose using sodium hypochlorite;

[0148] (c) washing the depolymerized cellulose with water to form a cellulose dispersion in water;

[0149] (d) homogenising the cellulose dispersion in water; and

[0150] (e) spray drying the cellulose dispersion to create cellulose particles.

[0151] However, in Film 9, the homogenised cellulose dispersion in water resulting from step (f) of Method 1 is mixed with the homogenised cellulose dispersion in water resulting from step (d) of Method 2. The resulting cellulose dispersion is then spray dried to create cellulose particles. The average particle size of the PMMA used was approximately 8 microns, the average particle size of the particles from Methods 1 and 2 was between 6 and 7 microns and the average particle size of the particles in Film 9 was between 8 and 9 microns.

[0152] Anti-block / slip dispersions were prepared by combining 2800 kg of water, 7 kg of carboxymethylcellulose and 12.6 kg of the relevant anti-block / slip particles (i.e., cellulose particles or PMMA). If necessary, the dispersion was filtered once or more. The resulting dispersion was continuously stirred at a slow speed and the dispersions were continuously agitated prior to use.

[0153] Each dispersion was injected into viscose at the injection rates outlined in Table 5 below and said viscose was then used to create a regenerated cellulose film using conventional methods.

[0154] The static and dynamic coefficients of friction were then measured in the same manner as outlined above in Example 2.

[0155] Table 5

[0156] These results demonstrate that both Methods 1 and 2 generate regenerated / mercerised cellulose particles that can create comparable coefficient of friction values to traditional antiblock and / or slip material PMMA. These particles can therefore provide effective slip properties while being more environmentally friendly.

[0157] Film 5, Comparative Film 5, Film 6 and Comparative Film 6 were then tested via a pressure block test as outlined above in Example 3.

[0158] Table 6

[0159] The films according to the invention provide excellent anti-blocking properties and are comparable with films comprising PMMA, thereby providing an environmentally friendly alternative to known anti-block compositions. Therefore, the films according to the present invention will have sufficient anti-blocking that they will not stick together when stored, for example, in reels.

Claims

CLAIMS1. An anti-block and / or slip composition comprising particles of mercerised and / or regenerated cellulose.

2. The composition of Claim 1 wherein the particles of cellulose are more than 40% crystalline, preferably more than 50% crystalline, more preferably more than 60% crystalline.

3. The composition according to Claim 1 or Claim 2 wherein the crystal type of the cellulose particles is type II.

4. The composition according to any one of Claims 1 to 3 wherein the cellulose particles have an average particle size of between about 1 and 10 microns, between about 2 and 10 microns, or between about 3 and 9 microns.

5. The composition according to any one of Claims 1 to 4 wherein the cellulose particles are substantially spherical.

6. The composition according to any one of Claims 1 to 5 wherein the particles of cellulose are formed from a dispersion of cellulose, preferably a dispersion of cellulose in water.

7. The composition according to Claim 6 wherein the cellulose dispersion has undergone homogenisation, preferably high-pressure homogenisation.

8. The composition according to any one of Claims 1 to 7 wherein the cellulose particles are obtained using a method comprising the steps of:(a) mercerising a cellulose to form a mercerised cellulose;(b) adding an aqueous alkali to the mercerised cellulose;(c) homogenizing the cellulose to form cellulose microfibers or a cellulose solution;(d) contacting the cellulose microfibers or solution with acid to form neutralized or regenerated cellulose;(e) washing the neutralized or regenerated cellulose to form a cellulose dispersion in water;(f) homogenising the cellulose dispersion in water; and(g) emulsifying or drying the cellulose dispersion to create cellulose particles.

9. The composition according to Claim 8 wherein the aqueous alkali in step (b) is a hydroxide, preferably an alkali metal hydroxide and more preferably sodium hydroxide.

10. The composition according to Claim 8 or 9 wherein step (c) comprises high-pressure homogenisation.

11. The composition according to any one of Claims 8 to 10 wherein step (e) comprises separating the cellulose from the acid, washing and resuspending in water to form a dispersion in water, or wherein step (e) comprises continuous washing to remove the acid and create a dispersion in water.

12. The composition according to any one of Claims 1 to 7 wherein the cellulose particles are obtained using a method comprising the steps of:(h) crushing a regenerated cellulose material;(i) decreasing the degree of polymerization of the crushed material to form a depolymerized cellulose;(j) washing the depolymerized cellulose to form a cellulose dispersion in water;(k) homogenising the cellulose dispersion in water; and(l) drying or emulsifying the cellulose dispersion to create cellulose particles.

13. The composition according to any one of Claims 8 to 12 wherein the drying step in step (I) or (g) includes spray drying or freeze drying.

14. The composition according to any one of Claims 8 to 12 wherein the emulsifying step in step (I) or (g) involves emulsifying the cellulose dispersion into an oil, passing the oil through an antisolvent and / or crosslinker and washing, drying and filtering to form cellulose particles.

15. The composition according to any one of Claims 12 to 14 wherein the degree of polymerization in the regenerated cellulose material in step (h) is less than 600.

16. The composition according to any one of Claims 12 to 15 wherein step (i) comprises reducing the degree of polymerization of regenerated cellulose using sodium hypochlorite with an effective chlorine concentration of 0.13% or higher, preferably 3% or higher.

17. The composition according to Claim 16 wherein step (j) comprises separating the cellulose from sodium hypochlorite, washing and resuspending in water to form a dispersion in water, or wherein step (j) comprises continuous washing to remove sodium hypochlorite and create a dispersion in water.

18. The composition according to any one of Claims 6 to 17 wherein the cellulose dispersion comprises between 1 and 20% w / w cellulose, preferably between 2 and 10% w / w cellulose.

19. An anti-block and / or slip dispersion comprising the composition according to any one of Claims 1 to 18 and a carrier material.

20. The dispersion according to Claim 19 wherein the carrier material is water, or a polymeric material, preferably comprising at least one of polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polyamide (e.g. nylon), polyethylene terephthalate (PET), or a polyolefin such as polypropylene (PP) or a polyethylene (PE).

21. A method of making the anti-block and / or slip dispersion of Claim 19 or 20 comprising the steps of:(a) mercerising a cellulose to form a mercerised cellulose;(b) adding an aqueous alkali to the mercerised cellulose;(c) homogenizing the cellulose to form cellulose microfibers or a cellulose solution;(d) contacting the cellulose microfibers or solution with acid to form neutralized or regenerated cellulose;(e) washing the neutralized or regenerated cellulose to form a cellulose dispersion in water;(f) homogenising the cellulose dispersion in water; and(g) emulsifying or drying the cellulose dispersion to create cellulose particles, or the steps of:(h) crushing a regenerated cellulose material;(i) decreasing the degree of polymerization of the crushed material to form a depolymerized cellulose;(j) washing the depolymerized cellulose to form a cellulose dispersion in water;(k) homogenising the cellulose dispersion in water; and(l) drying or emulsifying the cellulose dispersion to create cellulose particles, and subsequently dispersing the cellulose particles in a carrier material.

22. An ink comprising an anti-block and / or slip composition according to any one of Claims 1 to 18, or a dispersion according to Claims 19 or 20.

23. A coating composition comprising an anti-block and / or slip composition according to any one of Claims 1 to 18, or a dispersion according to Claims 19 or 20.

24. A film comprising an anti-block and / or slip composition according to any one of Claims 1 to 18, or a dispersion according to Claims 19 or 20.

25. The film according to Claim 24 wherein the film is a cellulose, polylactic acid (PLA), polybutylene succinate (PBS), polyhydroxyalkanoate (PHA), polyamide (e.g. nylon), polyethylene terephthalate (PET), or a polyolefin film such as polypropylene (PP) film or a polyethylene (PE) film.

26. Use of mercerised or regenerated cellulose particles as an anti-block and / or slip component in a polymeric composition.

27. A method of making an anti-blocking and / or slip article comprising adding the anti-block and / or slip composition according to any one of Claims 1 to 18 or a dispersion according to Claims 19 or 20 to one or more layers thereof.

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