Modified methods for producing a paper pulp or paper product

Abstract

A method of producing a paper pulp or paper product, wherein the method comprises obtaining de-oiled spent coffee grounds; combining the de-oiled spent coffee grounds with cellulose-containing fibers to obtain a mixture comprising de-oiled spent coffee grounds and cellulose-containing fibers; and processing the mixture into the paper pulp; wherein the method further comprises one or more of modification, grinding and dispersing the obtained de-oiled, spent coffee grounds and / or the mixture comprising de-oiled spent coffee grounds and cellulose-containing fibers, and optionally processing the paper pulp into the paper product.

Description

Modified methods for producing a paper pulp or paper productField of the Invention

[0001] The present invention relates to methods of producing a paper pulp or paper product using de-oiled, spent coffee grounds and also to a paper pulp or paper product comprising the de-oiled, spent coffee grounds.Background of the Invention

[0002] It is estimated that over 2.25 billion cups of coffee are consumed in the world each day. Given that the population of the world continues to increase, the amount of coffee consumed is also expected to increase. Much has been publicized about reducing the amount of disposable coffee cups that are associated with this coffee consumption - mainly in terms of developing more environmentally-friendly disposable coffee cups and encouraging the use of reusable coffee cups. However, there have been very few developments or publicity surrounding coffee waste that is produced in the coffee-making process. Brewing coffee produces used or spent coffee grounds as the final product after preparation of coffee. In fact, 1 kg of soluble coffee produces more than 2 kg of wet coffee grounds. Despite having several highly-desirable chemical components, used (or spent) coffee grounds are generally regarded as waste, and they are mostly used in energetic utilization, composted or deposited in a landfill. This can be problematic as spent coffee grounds are known to generate methane when dumped in landfill. As of 2019, it was estimated that over 15 million tonnes of spent coffee grounds are generated annually. Due to this quantity of waste and the chemical properties of used coffee grounds, it would be highly beneficial to develop further uses for spent coffee grounds in order to reduce the amount of waste thrown away.

[0003] Most used coffee grounds are similar in chemical composition, although coffee grounds used to make instant coffee have fewer chemicals in them due to a more extensive extraction process. De-oiled coffee grounds are rich in sugars, which typically comprise about half of their weight. A further 20% is usually made up of proteins, and about 20% is usually lignin content, although this depends on where the bean is cultivated and with which process the coffee is made. The dry coffee grounds often contain significant amounts of potassium (about 11.7 g / kg), nitrogen (about 2.8 g / kg), magnesium (about 1.9 g / kg), and phosphorus (about 1.8 g / kg). The quantity of caffeine remaining in used coffee grounds is around about 48% of that in fresh coffee grounds. There are significantly less tannins in used coffee grounds than fresh coffee grounds.

[0004] Due to the demands on the paper industry, there is a continual search for alternative ways of replacing the fibre raw material with alternative, inexpensive materials. Commonly used are inexpensive minerals such as calcium carbonate or kaolin in paper or cardboard product. These, however, have the disadvantage of reducing various properties of the paper such as reducing the paper thickness, volume, strength and stiffness. These can be important parameters for processing of, for example, corrugated base paper and cartons. There exists a need for more sustainable alternatives which do not have such a detrimental effect on various properties of the final paper product and are more environmentally friendly.

[0005] Methods have been developed in the art to use spent coffee grounds in various different ways. It has been identified in the art that coffee can be used in the manufacture of paper, which can be additionally advantageous in reducing the amount of raw materials required to produce the paper which can, amongst other things, lower the production cost and also improve the sustainability of paper manufacturing. The following have identified ways in which spent coffee grounds can be used in the manufacture of paper: WO 2014 / 081093 A, KR 102280322 B and KR 101904854 B. However, all of these methods have disadvantages associated with them such as producing a paper product having certain poor characteristics (e.g., low tensile strength) or difficulties in actually carrying out the process, such that it cannot be carried out on an industrial scale.

[0006] The inventors of the present invention have surprisingly found that sufficiently deoiled, spent coffee grounds (SCGs), that have been processed in a particular way, most preferably having been subject to a grinding or dispersing step, can be used in place of conventional fillers in order to produce high quality paper, in particular packaging paper with high tensile strength properties, without significantly impairing the stiffness of the paper product, and in a process which is economical, easy to carry out and scalable for industry. In certain aspects, the use of such spent coffee grounds in place of conventional fillers has been found to actually improve certain stock suspension and paper properties. Furthermore, spent coffee grounds can be considerably cheaper than conventional fillers and so their incorporation into paper products in a convenient way could lead to considerable cost savings.Summary of the Invention

[0007] In a first aspect of the invention there is provided a method of producing paper pulp, wherein the method comprises: obtaining de-oiled, spent coffee grounds;combining the de-oiled, spent coffee grounds with cellulose-containing fibers to obtain a mixture comprising de-oiled, spent coffee grounds and cellulose-containing fibers; and processing the mixture into the paper pulp; wherein the method comprises grinding or dispersing the obtained de-oiled, spent coffee grounds and / or the mixture comprising de-oiled, spent coffee grounds and cellulose- containing fibers.

[0008] In a second aspect of the invention there is provided a method of producing a paper product, wherein the method comprises: carrying out the steps according to the first aspect of the invention, and processing the paper pulp into the paper product.

[0009] In a third aspect of the invention there is provided a paper pulp obtainable or obtained by the method of the first aspect of the invention.

[0010] In a fourth aspect of the invention there is provided a paper product obtainable or obtained by the method of the second aspect of the invention.

[0011] Further embodiments of the aspects of the invention are as defined in the appended claims.

[0012] Also described herein is the use of de-oiled spent coffee grounds in a paper product or a paper-making process to increase the opacity and / or the air permeability (porosity) of the paper product and / or to increase the volume and stiffness of the paper product. Also described herein is the use of de-oiled spent coffee grounds in a pulp suspension for a paper-making process to stabilize the charge and enhance the zeta-potential of the suspension.Brief Description of the Drawings

[0013] Certain embodiments of the present invention are shown in the accompanying drawings and hereinafter described in detail.

[0014] Figure 1 shows a general schematic route of the present invention.

[0015] Figure 2 is a prediction plot showing the influence of the amount of de-oiled SCGs on the air permeability of a paper product.

[0016] Figure 3 is a prediction plot showing the influence of the amount of de-oiled SCGs on the specific volume of a paper product.

[0017] Figure 4 is a prediction plot showing the influence of the amount of de-oiled SCGs on the bending stiffness of a paper product.

[0018] Figure 5 is a prediction plot showing the influence of the amount of de-oiled SCGs on the internal strength (i.e., splitting resistance) of a paper product.

[0019] Figure 6 shows a graph demonstrating the influence of the amount of (comparative) conventional filler on the specific volume of a paper product.

[0020] Figure 7 shows a graph demonstrating the influence of the amount of de-oiled SCGs on the specific volume of a paper product.

[0021] Figure 8 shows a graph comparing the influence of the amount of de-oiled SCGs, acetosolv modified de-oiled SCGs and conventional filler on the burst strength of a paper product.

[0022] Figure 9 shows a graph comparing the influence of the amount of de-oiled SCGs, acetosolv modified de-oiled SCGs and conventional filler on the air permeability of a paper product.

[0023] Figure 10 shows a side-by-side comparison of the effect of the amount of de-oiled SCGs on the conductivity and zeta potential properties of a pulp suspension.

[0024] Figure 11 shows a bar chart demonstrating the effect of co-refining / co-grinding on the zeta potential (anionic charge) of a pulp suspension.Detailed Description

[0025] Provided herein are methods and processes for producing paper pulp and paper products.

[0026] In a first step of the process, de-oiled spent coffee grounds are obtained. Spent coffee grounds (SCGs) is a term that can be used interchangeably with used coffee grounds. SCGs are the leftover, waste product produced in a coffee-making process i.e., from coffee beans that have been roasted and ground and then had water-soluble compounds removed from them in order to prepare a coffee-based beverage. Preferably, the SCGs are obtained from industry or industrial processes. Industry means, for example, significant size coffee shops or other businesses which produce coffee waste on a large scale. SCGs from industry are preferred because they usually have similar properties, due to being from a similar type or ratio of coffee bean and having been processed in a coffeemaking process in a similar manner. SCGs from various households can, in contrast, have vastly different properties due to the different coffee beans used and the different coffeemaking processes. With household SCGs, transporting them to a central facility is alsomore challenging. From households, the transportation would also usually take longer and not drying the SCGs quickly enough can cause the SCG properties to degrade. Therefore, prompt treatment of the SCGs to ensure that they are dried quickly enough is easier when using SCGs from industry.

[0027] SCGs that are de-oiled means that the SCGs have undergone a process to reduce the oil content present in the SCGs and thus have a lower residual oil content than previously. Typically, untreated SCGs contain more than 20 wt% oil content. In certain embodiments herein, oil content and fatty acid methyl ester (FAME) content are used interchangeably. FAMEs are the typical oils found in unprocessed SCGs. However, it has been identified that de-oiling the SCGs, i.e., reducing the oil content / FAME content, helps to enable the SCGs to be used in a paper pulp or paper product in place of conventional fillers without reducing the quality of pulp / paper and, in certain embodiments, surprisingly improves the properties of the pulp / paper. For example, it has been found that replacing additives such as Carboxymethyl Cellulose (CMC) with de-oiled SCGs can improve the charge stability and zeta-potential of the pulp suspension (e.g., when replacing Carboxymethyl Cellulose (CMC)). This is particularly advantageous since CMC and the like are typically very expensive. Further surprisingly it has been found that paper with improved volume properties, air permeability, burst strength, stiffness etc. can be prepared by the present method while avoiding / reducing the reliance on more expensive fillers etc.

[0028] The SCGs may be de-oiled by any known process of de-oiling spent coffee grounds. In certain embodiments, this may be via a chemical de-oiling process. An example of such a suitable chemical de-oiling process is provided in "Gewinnung von Fettsauremethylestern aus industriellem Kaffeesatz", Chem. Ing. Tech. 2024, 96, No. 3, 347-354 (Extraction of fatty acid methyl esters from industrial coffee grounds). In alternative embodiments, the de-oiling can be achieved by a mechanical de-oiling process. However, a chemical deoiling process is particularly preferred since it can usually reduce the residual oil content to lower levels than a mechanical de-oiling process. Furthermore, chemically de-oiled SCGs have been found to produce a paper product having improved strength, such as tensile strength and bursting pressure, compared to when mechanically de-oiled SCGs are used. In this respect, it has been surprisingly found that chemically de-oiled SCGs generates approximately 40 % more tensile strength when added to paper compared to if the same amount of mechanically de-oiled SCG is added to the paper. Furthermore, the burst strength of the paper has been found to decrease by up to 47 % if chemically deoiled SCGs are replaced by mechanically de-oiled in the paper. In certain embodiments, the method of the invention further comprises a step of chemically and / or mechanically de-oiling the SCGs in order to obtain the de-oiled SCGs. It is possible that a combination of chemical and mechanical de-oiling takes place.

[0029] Preferably, the de-oiled SCGs have a residual oil content (or FAME content in certain embodiments) of less than about 20 wt%, preferably less than about 16 wt%, preferably less than about 15 wt%, preferably less than about 10 wt%, preferably less than about 8 wt%, preferably less than about 7 wt%, or less than about 6 or 5 or 4 or 3 or 2 or 1 wt%. The residual oil content is typically measured by gas chromatography with a flame ionization detector and a mass spectrometer, such methods being known to a person in the relevant technical field, and preferably according to "Gewinnung von Fettsauremethylestern aus industriellem Kaffeesatz", Gran-Heedfeld, J., A. Kraft, A. Fastabend and F. Kahl (2024), Chemie Ingenieur Technik: 347-354 (Extraction of fatty acid methyl esters from industrial coffee grounds). Typically de-oiled SCGs, that have undergone a mechanical de-oiling process, will have a residual oil content of up to about 15 or 20 wt%, and is usually about 15 wt%. De-oiled SCGs, that have undergone a chemical de-oiling process, will usually have a lower residual oil content of up to about 5 or 10 wt%, and is usually about 5 wt%. In certain embodiments, when the de-oiled SCGs have been chemically de-oiled, there is a residual content of de-oiling chemicals (i.e., chemicals used to de-oil of the SCGs) of less than about 10 wt%, preferably less than about 5 wt%, preferably less than about 3 wt%, most preferably less than about 1 wt%. Such de-oiling chemicals comprise one or more of methanol, sulphuric acid, sodium sulphate, n-heptane, n-hexane, and potassium hydrogen carbonate, preferably wherein the de-oiling chemicals comprise n-heptane.

[0030] Preferably the de-oiled SCGs are analyzed in order to determine various parameters and / or properties in order to determine the most suitable way to process them into a paper pulp. Preferably one or more of the following parameters and / or properties are analyzed:(a) bulk density;(b) refractive index;(c) lignin content;(d) zeta potential;(e) native surface charge;(f) surface energy;(g) dry content; and(h) residual oil content.

[0031] Typically, the properties of the SCGs are analyzed before and / or after de-oiling. By extensively characterizing the SCGs it is possible to know how to process, in particular grind or disperse, the SCGs so that they can be processed in a manner suitable for incorporation into a paper pulp and paper product. Once the properties of particular batches of SCGs from commercial use have been determined, it is generally not necessaryto analyze the properties each time thereafter since the properties of the SCGs generally remain consistent across batches.

[0032] Preferably the above parameters and / or properties of the de-oiled SCGs satisfy predetermined, preferred criteria. In the event that the properties and / or properties do not satisfy the pre-determined, preferred criteria, either a late aspect of the process will be modified or that specific parameter and / or property of the de-oiled SCGs will be modified such that it does satisfy the pre-determined, preferred criteria in accordance with preferred processes described herein.

[0033] In preferred embodiments, particles of the obtained de-oiled, SCGs have one or more of the following characterizing properties:(a) a bulk density in the range of about 1.18 - 1.68 g / cm3, preferably between about 1.40 - 1.42 ± 0.001 g / cm3(measured according to DIN 9277-2014-01);(b) a refractive index in the range of about 1.27-1.57; preferably between about 1.46-1.48 ± 0.001 (measured according to ISO 13320 and ISO 13322-2 with MIE Theory);(c) a lignin content of below about 50 wt%, preferably below about 40 wt%, further preferably between about 2-9 wt% (measured according to Klason Lignin Savard - TM 222 om-02);(d) a zeta potential in the range of about -22 to about -60 mV, preferably between about -30 to about -50 mV (measured using 3P Instruments: Device DT-310. The SCGs were added to desalinated water at 10 % concentration. For one measurement two runs were necessary. In the first run KOH (1 mol) was added until pH 14. The pH was controlled by a pH-measuring device. In the second run HCI (1 mol) was added into the solution until pH 2);(e) a native surface character that is anionically charged and in the range of about 20 to 60 peq / g, preferably between about 31.26 - 50.001 peq / g (measured according to PTS-RH-102 / 2009 polyelectrolyte titration with a P-DADMAC 0.00250 N);(f) a surface energy in the range of about 40 to 80 mJ / m2, preferably in the range of about 50 to 70 mJ / m2(measured according to the Inverse Gas Chromatography method according to Surface Measurement System Ltd. London);(g) a dry content of at least about 50%, preferably at least about 85%, most preferably at least about 90% (measured according to DIN EN ISO 287-2018-3); and(h) a residual oil content of less than about 20 wt%, preferably less than about 5 wt%, preferably wherein the residual oil content is the content of fatty acid methyl esters (FAME) (measured according to the method in Gran-Heedfeld).

[0034] In certain embodiments the obtained de-oiled SCGs have undergone a drying process in order for the dry content to be at a satisfactory level. A higher dry content is preferred because it reduces the energy required in the overall process to incorporate the de-oiled SCGs into a paper pulp, in particular when grinding or dispersing the de-oiled SCGs before mixing with the cellulose-containing fibers.

[0035] Preferably, the surface energy of the particles is heterogeneously distributed and the particles exhibit reversible sorption behaviour. The following table shows a comparison between the surface energy of the de-oiled SCGs and raw or auxiliary materials already commonly used for paper production.

[0036] Should the obtained de-oiled SCGs not satisfy one or more of the desired characterizing properties, then the process may further include a modification step. Any modification step is envisaged that modifies one or more of the characterizing properties of the de-oiled SCGs so that it falls within the desired range. Such modification can be desirable in order to improve mixing with the cellulose-containing fibers to form a paper pulp and / or to optimize or improve the properties of a final paper product. The de-oiled SCGs may be modified before being combined with the cellulose-containing fibers or together with the cellulose-containing fibers after having been combined with them i.e., mixed. In certain embodiments, the modification takes place through the grinding or dispersing step described in more detail later herein.

[0037] In certain embodiments the de-oiled SCGs composition may also be modified in an acetosolv process, as described in DE 3445132 A (or Das Papier (Darmstadt), 1993, Vol 47, Num 10A, pp V16-V24, ref: 9). Preferably, in this process the lignin content is reduced to less than about 10 wt%, preferably less than about 5 wt%, preferably between about 1 to 5 wt%. In addition to, or instead of, or as a part of, the lignin reduction, the composition may also be subject to a bleaching modification step. The lignin reduction step itself may also bleach the de-oiled SCGs to sufficient levels, or a separate bleaching process may be carried out in order to ensure that the pulp and final paper product is of a suitable whiteness. Preferably, the modified product has a degree of whiteness of greater than about 50, preferably greater than about 80. A separate bleaching process may comprise oxidative or reductive processes. The bleachability of coffee residues was proven and described in Li, S., et al., "From brown to coloured: Polylactic acid composite withmicro / nano-structured white spent coffee grounds for three-dimensional printing", International Journal of Biological Macromolecules, 2021. 174: p. 300-308. In addition to, or instead of, the above modification steps, the composition may also be subject to a charge modification step, which is any process step which specifically adjusts the particle charge. This can be done, for example, by introducing functional groups, such as hydrophilic cationisation with 3-chloro-2-hydroxypropyl trimethylammonium chloride (QUAB) according to the principles of direct reaction, grafting, or binding of oligomers / polymers, preferably according to the principle of direct reaction.

[0038] In the process, the obtained de-oiled SCGs are combined with (a composition comprising) cellulose-containing fibers, preferably by mixing them together. The components are preferably mixed together using high shear forces. High shear forces can be advantageous in order for the de-oiled SCGs and cellulose-containing fibers to sufficiently mix. Preferably the difference in flow velocities is greater than about 0.5 m / s, preferably greater than about 2 m / s if mixed in a pipe. Typically, the cellulose-containing fibers are part of a composition which is a paper pulp composition i.e., a pulp in water composition. In certain embodiments, the cellulose is microfibrillated cellulose (MFC). Herein, paper pulp takes its usual meaning in the art.

[0039] The amount of de-oiled SCGs dosed together with the composition comprising cellulose-containing fibers will depend on the properties of the de-oiled SCGs and the desired end paper product and the properties required by this paper product. However, in certain embodiments the amount of de-oiled SCGs can be between about 2 to 90 wt% based on the total weight of the de-oiled SCG and composition comprising cellulose- containing fibers, such as about 5 to 80 wt% or 10 to 70 wt% or 20 to 60 wt% or 30 to 50 wt%, or between about 1 to 50 wt%, or between about 1 to 20 wt%, or between about 1 to 15 wt%, or between about 2 to 10 wt% or 3 to 7 wt% or as high as about 50 to 90 wt% or 60 to 80 wt% (or up to any of the wt% amounts listed here i.e., from zero to the wt% amount).

[0040] Either before, or after, combining the de-oiled SCGs with cellulose-containing fibers, there is a grinding or co-grinding step. In certain embodiments, the de-oiled SCGs are first subject to a grinding process and then subsequently combined with the composition comprising cellulose-containing fibers. In alternative embodiments, the de-oiled SCGs are first combined (i.e., mixed) with the composition comprising cellulose-containing fibers and then subject to a co-grinding process.

[0041] Herein, grinding is understood to be the mechanical modification of the de-oiled SCGs alone or together with the paper fibres. Typically the material is squeezed, shortened and additionally roughened or enlarged on its surface. Herein, grinding does not merelyrefer to cutting grinding, which is a process in which the material is essentially shortened but its other dimensions are not changed. Grinding herein is intended to refer to a grinding process in which the material is crushed and / or fibrillated such that the material is shortened and the shape of the material (i.e., its other dimensions) is changed, as will be understood by a person skilled in the art. This squeezing (fibrillating) allows more connections to form between the macromolecules and increases the surface area. Similar considerations apply to the dispersing process referred to below. Processing the de-oiled SCGs in this way helps to improve the SCG retention in the paper pulp by enhancing the attractive bonding forces between the paper fibers and the de-oiled SCGs.

[0042] Alternatively to the grinding processes described above, a dispersing step may be performed on the de-oiled SCGs alone or after mixing with the paper fibers. A dispersion step is similar to a grinding / refining step in that it subjects the composition and / or fibers to high-shear forces. Conventionally, a disperser is used in recycled fiber lines, to reduce the size of dirt specks below the limit of visibility, reduce the size of any sticky particles, break down particles, distribute wax finely, detach ink or toner particle from fibers, disintegrate fiber bundles, treat fibers mechanically and thermally and mix in bleaching agents. More information on dispersing and how this may be performed is described in "Unit operations and equipment in recycled fiber processing", Holik, H. (1999), "Recycled Fiber and Deinking" L. Gdttsching and H. Pakarinen, Helsinki, Finnish Paper Engineers' Association / Paperi ja Puu Oy. 7 and "Handbook of Paper and Board", Holik, H. (2013), Weinheim, Wiley-VCH.

[0043] The grinding / dispersing step may be carried out in accordance with known dispersing / grinding / refining processes in paper-making processes. By performing a grinding or dispersing step the properties of the material and thus ultimately the material properties are specifically influenced. It has been found that grinding or dispersing in a particular way results in de-oiled SCGs that can be readily incorporated into a paper pulp to produce a paper product and can also have a positive impact on the properties of the paper product relative to the use of conventional fillers. It has been found that co-grinding or co-dispersing (i.e., mechanically treating the de-oiled SCGs and cellulose-containing fiber mixture) in a particular way also has a similar effect.

[0044] Any suitable grinding / dispersing apparatus or process known in the art that would reduce the particle size distribution of the SCGs can be adapted for use. However, for grinding particularly preferred is using hammer, centrifuge or ball mills, most preferably a ball mill. Dry grinding is possible, as is a wet grinding process. As will be understood in the art, the degree of grinding will be dependent on the desired particle size distributions that are necessitated by the planned final paper product. Thus, no particular limitationson particle size or degree of grinding are to be put in place, since this will depend on the desired final paper product, and particularly the required thickness of this product.

[0045] Most preferred is a ball mill using a ball size of 1 mm - 20 mm, a rotation speed of 100 - 550 min1and / or for a duration of between 1 minute to 3 hours. Preferably the ball size in the ball mill is between 10 to 20mm, preferably 14 to 16 mm, most preferably about 15 mm. Preferably the rotation speed is 300 to 500 min-1, preferably 400 to 500 min-1, most preferably about 450 min-1. Most preferably, the ball mill operates for between 10 mins to 1 hour, preferably 20 mins to 40 mins, most preferably about 3 x 10 mins with about 5 minute pauses in between. It has been found that grinding in this way enables the de-oiled SCGs to be ground to have a desired pre-determined specific surface area and / or particle size distribution that can be advantageous. Exemplary preferred conditions using a ball mill are provided in Table 1 below.Table 1

[0046] For dispersing, particularly preferred is a disc disperser, in particular a fast-running disc disperser, preferably having intermeshing teeth or refiner-type bars. Preferably the gap between the rotor and stator is about 1 mm or less and the peripheral speed is between about 30 to 100 m / s. The specific energy demand is around 30 to 150 kWh / t at consistencies of about 25 to 35 % and temperatures between about 60 to 130 °C.

[0047] It has been found to be particularly advantageous to grind or disperse the de-oiled SCGs to a pre-determined specific surface area and / or particle size distribution. In particular, it has been found that grinding or dispersing the de-oiled, spent coffee grounds to have a specific surface area in the range of 4.15 - 7.96 m2 / g and / or a particle size distribution (cumulative volume distribution - Dv) of one or more of: a DvlO of 2-30 pm, a Dv50 of 12-100 pm and a Dv90 of 30-250 pm (as measured according to DIN EN 9277:2014-01) results in de-oiled SCGs that are particularly useful in a papermaking process. In grinding, a wet grinding process typically results in larger particle sizes overall than a dry grinding process. Before the grinding or dispersing, typically the de-oiled SCGs have a particle size of greater than 250 pm. It has also been found that grinding or dispersing the de-oiled SCGs to have an aspect ratio (longest diameter / shortest diameter) of 1.03-1.21, with exceptions up to 3 is desirable and to have a ISO circularity (Form factor C) of 0.87 to 0.93 with the exceptions up to 0.69 is desirable (measured according to ISO 13320 and ISO 13322-2 respectively).

[0048] In certain embodiments, it is preferred to co-grind / co-disperse the de-oiled SCGs with the composition comprising cellulose-containing fibers. This is because it has been surprisingly identified that co-grinding / co-dispersing the two components, instead of just grinding / dispersing the de-oiled SCGs alone, can increase of the surface charge and the zeta potential of the composition (zeta potential and conductivity referred to herein refers to the pulp suspension or composition of de-oiled SCGs and paper pulp). In this respect, the zeta potential becomes increasingly negative when co-grinding / co-dispersing is performed as opposed to single grinding, which is advantageous because it allows more efficient application of other necessary additives like retention aids or wet strength aids. Zeta potential referred to herein is as described in Israelachvili, J. N. (2006), "Repulsive Forces, Total Intermolecular Pair Potentials and Liquid Structure. Intermolecular and surface forces.", Academic Press: 109-121).

[0049] In certain embodiments, the co-grinding / co-dispersing step advantageously leads to a higher intrinsic retention i.e., an increase in retention of the de-oiled SCGs in the paper pulp. In certain embodiments, this step can improve initial retention by up to 70% compared to a process not comprising a refining step. Preferably, the co-grinding / co- dispersing step is carried out with a low specific edge load down to 5 Ws / m, preferably less than 2 Ws / m. When co-grinding / co-dispersing, a disc grinder / disperser is preferred, preferably at a rotation speed of 710-1490 min1or a disc refiner / disperser at a rotation speed of 500-2500 min1and / or at a specific edge load of 0.1 to 5 Ws / m. The consistency during this process is between 1 and 40 wt%, preferably between 2 - 6 wt% for low consistency refining / dispersing and for high consistency 25 to 35 wt%.

[0050] Such grinding / dispersing advantageously results in de-oiled SCGs that are particularly useful for incorporation into paper in a papermaking process. As already explained, said grinding / dispersing step can also be used to modify the characterizing properties of the de-oiled SCGs so that they satisfy pre-determined parameters and are made more suitable for mixing with a paper pulp and inclusion into a paper product.

[0051] Under given conditions, the grinding / dispersing process can be described with the pure specific grinding / dispersing work (kWh / t) and the specific grinding load (J / m). The specific refining energy [kWh / t dry stock] is calculated as follows:With :Wspez: specific refining EnergyPRM : pure refining energy (PRM = Ptotai - Pidie )Ptotai : total refining energyPidie : idle powerQv: Volumeflow StockStDcon: Consistency of the StockThe specific Edge load (BS) [Ws / m] is calculated as follows:With:PRM= Refining energy [kWh / t]Ls= Cutting length per second [m / s]The cutting length per second is calculated as follows:LS = ZR* Zst* IM* nWith:ZR: Number of knifes on rotorZst: Number of knifes at statorIm: Knifelength (average)[m] n : Rotation of Rotor [U / Sec]

[0052] Subsequent to the above steps, the pulp comprising cellulose-containing fibers and the de-oiled SCGs, as well as preferably water, is then further processed into a paper pulp suitable for preparation into a paper product (i.e., processing the mixture into the paper pulp). Said paper pulp is then processed in accordance with conventional paper-making methods in order to process the pulp into a final paper product. These conventional papermaking steps are known in the art and are not particularly limited due to the presence of the de-oiled, SCGs. Examples of such a method can be found in, for example, Paulapuro, H. Karlsson, M., Jokio, M. (1999), "Papermaking Part 1 to 3, Stockpreparation and Wet End", Helsinki, Finnish Paper Engineers' Association / Paperi ja Puu Oy and Holik, H. (2013), "Handbook of Paper and Board", Vol. 1 and 2, Weinheim, Wiley-VCH and Smook, G. A. (1992), "Handbook for pulp & paper technologists", Angus Wilde Publications.

[0053] The type of paper product is not particularly limited and would include paper products such as paper, tissue, paperboard etc. including packaging paper, hygiene paper, speciality paper etc. In certain embodiments, the paper product is a functional paper. In particular, paper product includes moulded paper products e.g., egg cartons.

[0054] In the final paper product the amount of de-oiled, SCGs that is present is preferably up to about 60 wt% based on the total weight of the paper product, preferably up to about 50 wt% based on the total weight of the paper product. Preferably, the amount of SCGs present is adjusted depending on the type of paper product. For paper having between about 15 to 40 gsm, preferably the amount of SCGs present is up to about 5 wt% based on the total weight of the paper product. For paper having between about 70 to 140 gsm, preferably the amount of SCGs present is up to about 25 wt% based on the total weight of the paper product. For paper board and moulding products, preferably the amount of SCGs present is up to about 80 wt% based on the total weight of the paper product.

[0055] In certain embodiments, the paper pulp or paper product may comprise other components such as (conventional) filler e.g., calcium carbonate or kaolin.

[0056] Surprisingly, it has been found that incorporating de-oiled SCGs according to the present method produces a paper pulp that can be more easily processed into a final paper product and produces a final paper product having at least satisfactory properties, and in many instances having improved properties, as demonstrated in the following specific examples.

[0057] The order of the steps of the processes described herein is exemplary (unless a certain order is necessitated through the explicit wording of the steps), but the steps may be carried out in any suitable order, or simultaneously where appropriate. Additionally, steps may be added or substituted in, or individual steps may be deleted from any of the processes without departing from the scope of the subject matter described herein.

[0058] It will be understood that the description of preferred embodiments herein is given by way of example only and that various modifications may be made by those skilled in the art. What has been described above includes examples of one or more embodiments. It is, of course, not possible to describe every conceivable modification and alteration of the above process and apparatus for purposes of describing the aforementioned aspects, but one of ordinary skill in the art can recognize that many further modifications and permutations of various aspects are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the scope of the appended claims.ExamplesExample 1 - Board product based recycled fibers

[0059] In this example, the effect of de-oiled SCGs dosage amount on various properties of a paper board product was investigated.

[0060] In this example, 87.5 g of oven dry material was prepared. The material consisted of 75 wt% paper for recycling i.e., waste paper (paper grade 4.01) and 25 wt% of de-oiled SCGs. The de-oiled SCGs were subject to a grinding process using 1000 kWh / t using a centrifugal mill (Retsch: ZM300, Stainless Steel) according to the following: Number of rotors: 12Grinding time: 3 times at 10000 rpmSpecific surface area before grinding: <4 m2 / gSpecific surface area after grinding: 7,96 m2 / gParticle size before grinding: > 250 pmParticle size after grinding: Dv90: 94.7, Dv50: 24.7, DvlO: 3.76.

[0061] Both materials were placed in a standard lab disintegrator (Estanit, Model AG 04) and two liters of tap water was added (DIN EN ISO 5263). After 30,000 revolutions the disintegrated pulp was transferred to a mixing chest (chest 1) and diluted to 0.35 % stock consistency. The process was then repeated with 100 % paper for recycling (paper grade 4.01) in an amount of 35 g oven dry. This was diluted to 0.35 % stock consistency in a separate mixing chest (chest 2). After 10 minutes of mixing, to maintain a proper distribution in the chest, various stock amounts were taken from the chests (1 and 2) to create a lab sheet on a rapid-kdthen lab sheet former with a desired grammage of 100 g / m2(DIN EN ISO 5269). Each final paper consists of four layers. Two layers from chest 1 (the two inner layers) which also comprise the de-oiled SCGs and two layers from chest 2 (outer layers) without any de-oiled SCG additive. The sheet buildup was carried out by producing the top layer first using pulp from chest 2, followed by forming the second layer from chest 1 and placing it on top of the first layer. Next, another sheet was produced from chest 1 and placed onto the two other layers. The final layer was produced with the pulp from chest 2 and placed onto the three other layers. The final paper with the four layers was dried in a rapid kdthen sheet dryer at 95 °C ± 5 °C at 800 mbar1vacuum for 20 minutes. After that the paper sheets were stored under controlled conditions (DIN EN 20187: 23 °C and 50 % rel. humidity).

[0062] This experimental procedure was repeated with different amounts of de-oiled SCG additive in the two inner layers. The following amounts were additionally tested:• 0 wt% de-oiled SCGs, 100 wt% paper for recycling;• 12.5 wt% de-oiled SCGs, 87.5 wt% paper for recycling;• 37.5 wt% de-oiled SCGs, 63.5 wt% paper for recycling; and• 50 wt% de-oiled SCGs, 50 wt% paper for recycling.

[0063] The following properties of each paper board product were then analyzed and compared. The following properties were evaluated:• air permeability (r2adj : 0.988) (DIN EN ISO 53120-1 : 1998-06);• specific volume (r2adj : 0.977) (DIN EN ISO 534);• bending stiffness (r2adj : 0.957) (DIN 53121); and• splitting resistance (r2adj : 0.878) (DIN ISO 16260:2016).

[0064] The results of the analysis of these properties are shown in Figures 2 (air permeability), 3 (specific volume), 4 (bending stiffness) and 5 (splitting resistance). The data points in between those physically measured were predicted using an appropriate software program. As can be seen from these graphs, the dosage amount of de-oiled SCGsimpacts the properties of the paper product and the inclusion of de-oiled SCGs can surprisingly improve a wide range of properties of the paper product.Example 2 - Further analysis of the effect of de-oiled SCGs

[0065] In this example the effect of de-oiled SCGs, compared to conventional filler, on the specific volume of the paper was assessed. De-oiled SCGs, modified by a ball mill, were mixed with bleached virgin pulp in amounts of 0 wt%, 5 wt%, 10 wt% and 15 wt%. The pulp and de-oiled SCGs were mixed with Munich tap water in a standard lab disintegrator (Estanit, Model AG 04; DIN EN ISO 5263). After 30,000 revolutions the mixture was transferred into a lab mixing chest and diluted to a stock consistency of 0.35 %. After 10 minutes of mixing time, stock was taken out to produce 100 g / m2lab sheets on a Rapid Kothen sheet former device (DIN EN ISO 5269). The lab sheets were dried and measured under controlled climate conditions (DIN EN 20187: 23 °C and 50 % rel. humidity). The specific volume (DIN EN ISO 534) of the paper was then measured. This protocol was then repeated using calcium carbonate conventional filler instead of the de-oiled SCGs.

[0066] The effect of the use of calcium carbonate conventional filler on specific volume are shown in Figure 6 and the results of the use of de-oiled SCGs on specific volume are shown in Figure 7. Surprisingly, it can be seen that dosing the spent coffee grounds into the virgin pulp mix increases the specific volume, while the dosage of conventional filler, decreases the specific volume of the paper.

[0067] The above experimental procedure was repeated by instead using acetosolv modified de-oiled SCGs prepared following the acetosolv protocol referenced herein. The influence of the three additives (de-oiled SCGs ("SCGs"), acetosolv modified de-oiled SCGs ("Acetosolv") and conventional calcium carbonate filler ("Filler")) on burst-strength [EN ISO 2758:2014] and Porosity [DIN 53108:2011-01] is shown in Figures 8 and 9. As can be seen, de-oiled SCGs and particularly acetosolv modified de-oiled SCGs improved the burst strength of the paper (i.e., the smallest reduction in burst strength). Both of these additives also outperform the conventional calcium carbonate filler in air permeability.Example 3 - Analysis of the effect of de-oiled SCGs on conductivity and zeta potential

[0068] In this example the effect of de-oiled, refined SCGs on the conductivity and zeta potential was analyzed, based on a dosage amount of 0 to 20 wt% of de-oiled SCGs. The varying amounts of de-oiled SCGs were added to virgin pulp and disintegrated in a standard lab disintegrator with 2 liters of Munich tap water (Estanit, Model AG 04; DIN EN ISO 5263). After 30,000 revolutions the stock consistency was set to 10 % and it was co-refined in a PFI-Mill (ISO 5264-2:2011) with 200, 400, 600, 800, 1000, 1200 and 1400 revolutions. The conductivity and zeta-potential of the pulp suspension was then analyzed. The results are shown in Figure 10. Surprisingly the de-oiled SCGS advantageously have a decreasingeffect on the zeta potential, as well a reduction of the conductivity of the pulp suspension. Reducing both of these properties is good for paper production. For the avoidance of doubt, in Figure 10 0.2 on the wt% x axis of Figure 10 refers to 0.2 / 1 i.e., 20 wt% of de-oiled SCGs.

[0069] The same procedure was followed, except the raw material was changed from virgin pulp to paper for recycling. The paper for recycling (grade 4.01) pulp has an initial zeta potential of -11.3 mV ("Reference", i.e., without any de-oiled SCGs). When the paper for recycling pulp was refined with 200 revolutions within the PFI-mill the zeta potential was reduced to -19.5 mV ("Pulp Refining"). By adding 10 wt% of de-oiled SCGs and using the same revolutions, the zeta potential was reduced to -21.35 mV ("Co- Refining"). These results are shown in Figure 11. Therefore, the de-oiled SCGs have a positive impact on the pulp zeta potential.

[0070] In the Examples, zeta potential is as described according to Israelachvili, J. N. (2006). "Repulsive Forces, Total Intermolecular Pair Potentials and Liquid Structure", Intermolecular and surface forces, Amsterdam, Academic Press: 109-121. The zeta potential was measured using devices from BTG Instruments GmbH or emtec GmbH to measure the streaming potential in mV according to the manual of the relevant device.

Claims

Claims1. A method of producing a paper pulp, wherein the method comprises: obtaining de-oiled, spent coffee grounds; combining the de-oiled, spent coffee grounds with cellulose-containing fibers to obtain a mixture comprising de-oiled, spent coffee grounds and cellulose-containing fibers; and processing the mixture into the paper pulp; wherein the method comprises grinding or dispersing the obtained de-oiled, spent coffee grounds and / or the mixture comprising de-oiled, spent coffee grounds and cellulose-containing fibers.

2. The method of claim 1, wherein the de-oiled spent coffee grounds have been chemically and / or mechanically de-oiled.

3. The method of claim 2, wherein the de-oiled spent coffee grounds have been chemically de-oiled, preferably wherein the content of de-oiling chemicals remaining in the de-oiled spent coffee grounds is less than about 10 wt%, further preferably less than about 5 wt%, most preferably less than about 1 wt%.

4. The method of any preceding claim, wherein the method further comprises analyzing one or more of the following properties of the de-oiled, spent coffee grounds before being combined with the cellulose-containing fibers:(a) bulk density;(b) refractive index;(c) lignin content;(d) zeta potential;(e) native surface charge;(f) surface energy;(g) dry content; and(h) residual oil content.

5. The method of any preceding claim, wherein the de-oiled, spent coffee grounds have one or more of the following characterizing properties:(a) a bulk density in the range of about 1.18 - 1.68 g / cm3, preferably between about 1.40 - 1.42 ± 0.001 g / cm3;(b) a refractive index in the range of about 1.27-1.57; preferably between about 1.46-1.48 ± 0.001;(c) a lignin content of below about 50 wt%, preferably below about 40 wt%, further preferably between about 2-9 wt%;(d) a zeta potential in the range of about -22 to about -60 mV, preferably between about -30 to about -50 mV;(e) a native surface character that is anionically charged and in the range of about 20 to 60 peq / g, preferably between about 31.26 - 50.001 peq / g);(f) a surface energy in the range of about 40 to 80 mJ / m2, preferably in the range of about 50 to 70 mJ / m2;(g) a dry content of at least about 50%, preferably at least about 85%, most preferably at least about 90%; and(h) a residual oil content of less than about 20 wt%, preferably less than about 5 wt%, preferably wherein the residual oil content is the content of fatty acid methyl esters (FAME).

6. The method of claim 5, wherein the method further comprises modifying the obtained de-oiled spent coffee grounds before or after being combined with the cellulose- containing fibers, such that the de-oiled spent coffee grounds have one or more or all of the characterizing properties, preferably wherein the modification takes place through the grinding or dispersing step.

7. The method of any preceding claim, further comprising bleaching the de-oiled, spent coffee grounds so that the de-oiled, spent coffee grounds have a degree of whiteness of greater than about 50.

8. The method of any preceding claim, wherein grinding or dispersing the de-oiled, spent coffee grounds comprises grinding or dispersing the de-oiled, spent coffee grounds to have a pre-determined specific surface area and / or particle size distribution.

9. The method of claim 8, further comprising grinding or dispersing the de-oiled, spent coffee grounds to have a specific surface area in the range of about 4.15-7.96 m2 / g and / or one or more of a DvlO of about 2-30 pm, a Dv50 of about 12-100 pm and a Dv90 of about 30-250 pm.

10. The method of any preceding claim, wherein grinding the de-oiled, spent coffee grounds comprises wet or dry grinding, preferably using a ball mill, further preferably using a ball mill and one or more of a ball size of about 1 mm - 20 mm, a rotation speed of about 100 - 550 min1and for a duration of between about 1 minute to 3 hours.

11. The method of any preceding claim, wherein grinding or dispersing the mixture comprises grinding using a disc grinder, preferably at a rotation speed of about 710-1490 min1or using a disc refiner, preferably at a rotation speed of about 500-2500 min1and / or at a specific edge load of about 0.2 to 5 Ws / m, further preferably at a consistency of about 1 to 40 wt %, such as between about 3 to 6 wt% for low consistency grinding and between about 25 to 35 wt% for high consistency grinding.

12. The method of any preceding claim, wherein combining the de-oiled, spent coffee grounds with cellulose-containing fibers comprises mixing them together, preferably mixing in a pipe at different flow velocities of greater than about 0.5 m / s, preferably greater than about 2 m / s.

13. A method of producing a paper product, wherein the method comprises: carrying out the steps of any of claims 1 to 12, and processing the paper pulp into the paper product.

14. A paper pulp obtainable or obtained by the method of any of claims 1 to 12.

15. A paper product obtainable or obtained by the method of claim 13.

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