Alkaline paper product comprising calcium silicate mixture

Abstract

The present invention relates to a paper filler comprising a mixture of three calcium silicate minerals, namely akermanite, gehlenite and wollastonite A, a paper product comprising the paper filler and the use of the paper filler as an alkaline paper filler in a paper product.

Description

Alkaline paper products containing calcium silicate mixture Technical Field

[0001] This invention relates to a paper filler comprising a mixture of three calcium silicate minerals, namely magnesium feldspar, calcium aluminum feldspar and alpha-wollastonite, a paper product comprising the paper filler, and the use of the paper filler as an alkaline paper filler in a paper product. Background Technology

[0002] Paper production consumes millions of tons of wood fiber raw materials annually. However, sensitivity to protecting forest resources, mitigating global warming, and reducing energy consumption is rapidly increasing. Consequently, the market for the large quantities of paper-based waste generated is growing. Typically, waste paper recycling involves separating pulp fibers from other components of the paper (especially mineral fillers, printing inks, etc.) through a series of different steps (depending on the recycling process used). This recycling produces pulp fibers that can be used as recycled raw materials in paper production, as well as a mixture of components removed as part of the deinking process, typically referred to as deinking sludge. However, this deinking sludge is typically incinerated and landfilled as fly ash.

[0003] Furthermore, it is well known that the pH of pulp suspensions derived from recycling processes typically decreases over time. During repulping, starch (added as an additive to improve paper properties) is hydrolyzed into glucose, providing a rich nutrient base for bacteria. Bacterial metabolism produces fatty acids such as acetic acid, which leads to acidification (pH decrease) of the process water, thereby generating calcium ions (Ca). 2+ Furthermore, it increases water hardness. These cations interact with the anionic surface charge of the fibers, leading to charge neutralization and the accumulation of sticky deposits. This reduces the effectiveness of cationic wet-end additives such as internal sizing agents and retention aids. Consequently, product specifications may not be met, larger quantities of additives may be required, and machine downtime may increase. In light of this, pH reduction in paper production is typically controlled through the addition of sodium hydroxide, biocides, and / or CaO / Ca(OH)2-based concepts. However, due to the safety risks associated with using these additives and the additional materials used in the preparation of recycled materials, a safe and economically viable pH control concept is desired.

[0004] Calcium silicate, due to its high alkalinity, possesses antimicrobial activity and can be used as a paper filler. Its highly porous surface structure and large specific surface area result in paper products with high opacity and whiteness. This calcium silicate can exist in varying compositions in the fly ash of incinerated deinking sludge. Therefore, maximizing resource utilization and waste recycling is crucial for process efficiency and circularity in paper production.

[0005] Several methods for using calcium silicate or fly ash have been proposed in this art, including the use of calcium silicate or fly ash in the production of paper products. For example, WO9628517A1 relates to a paper comprising cellulose fibers and a composite granular material comprising an internal portion of ash from an inorganic mineral material and an external portion of calcium carbonate. The inorganic mineral material may comprise ash obtained from the incineration of waste paper deinking residues. JP2008025088A relates to a neutral paper, which is a bulky paper. The neutral paper contains 0.3-20% by weight of calcium silicate particles as filler, comprising aggregates in the form of petal-like flakes, and the mercury porosimetry method in the neutral paper. US5660900A relates to an article comprising a starch-bonded honeycomb matrix of starch and inorganic aggregates, the starch-bonded honeycomb matrix comprising: a starch-based binder that has been substantially gelled by water and then hardened by evaporation to remove most of the water; and inorganic aggregates dispersed throughout the starch-bonded honeycomb matrix at a concentration of about 20% to about 90% by weight of total solids, wherein the starch-bonded honeycomb matrix has a thickness of less than about 1 cm and degrades upon prolonged exposure to water. CN102433795A relates to a papermaking filler, characterized in that the filler is activated calcium silicate. The activated calcium silicate can be made from fly ash as a raw material and prepared by a pretreatment method comprising adding the activated calcium silicate to hot water at a temperature of 50-100°C, stirring thoroughly, and dissolving it into an emulsion. US6139960A relates to a mineral filler comprising: dry-processed fly ash containing about 5-60 wt% alumina, about 0.5-60 wt% calcium oxide, about 5-30 wt% silica, about 0.5-15 wt% magnesium oxide, and about 0.1-10 wt% titanium dioxide. KR20130017453A relates to a method for enhancing the optical properties of waste paper, achieved by simultaneously synthesizing PCC and waste paper using an in-situ method of high-loading PCC synthesis from paper sludge ash.

[0006] In view of the above, there remains a need in the art for an effective and efficient paper filler that can be used in the production of paper products, especially recycled paper products. More specifically, there is a need for a paper filler obtained from the incineration of deinking sludge that provides alkalinity to the paper products prepared therefrom, especially recycled paper products, and thus provides adequate pH control. Summary of the Invention

[0007] Therefore, one object of the present invention is to provide a paper filler for use in paper products. Another object of the present invention is to provide a paper filler for use in paper products that provides alkaline properties. Preferably, the paper filler is obtained from the incineration of deinking sludge, and is thus derived from a paper recycling process. Another object of the present invention is that the paper filler is preferably used in combination with recycled pulp fibers, and is thus derived from a paper recycling process.

[0008] These and other objects of the present invention can be achieved by the paper filler of the present invention, paper products containing the paper filler, and the use of the paper filler as an alkaline paper filler in paper products.

[0009]

[0010] According to one aspect of the invention, a paper filler is provided. The paper filler comprises a mixture of three calcium silicate minerals: magnesium feldspar, calcium aluminum feldspar, and morphomorphic wollastonite, wherein the paper filler comprises 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of morphomorphic wollastonite, and 0.1-15% by weight of magnesium feldspar, based on the total weight of the filler.

[0011] A second aspect of the invention relates to paper products prepared from paper fillers and furnishes as defined herein, the furnishes comprising pulp, preferably virgin pulp and / or recycled pulp obtained from paper and / or paperboard recycling.

[0012] A third aspect of the invention relates to the use of paper fillers as defined herein as alkaline paper fillers in paper products, preferably recycled paper products, more preferably carton board such as coated or uncoated carton board, or container board such as linerboards, flutings, and dual papers.

[0013] The inventors have surprisingly discovered that this paper filler provides alkaline properties to the paper products prepared therefrom. Furthermore, the use of additives (such as sodium hydroxide, biocides, and / or CaO / Ca(OH)2-based concepts) used in paper production to control pH reduction can be reduced or avoided. Moreover, this paper filler can be obtained from the fly ash of incinerated deinking sludge and can also be used in combination with recycled pulp obtained from paper and / or paperboard recycling. Therefore, the paper filler and / or paper products of the present invention maximize resource utilization and thus improve process efficiency and circularity in paper production.

[0014] Advantageous embodiments of the invention can be found in the corresponding dependent claims.

[0015] In one embodiment of any aspect of the invention, the paper filler comprises a mixture of three calcium silicate minerals, as determined by X-ray diffraction, wherein the total amount of the mixture is ≥0.3 wt%, preferably 0.3-60 wt%, based on the total weight of the filler.

[0016] In another embodiment of any aspect of the invention, the mixture of the three calcium silicate minerals comprises, as determined by X-ray diffraction:

[0017] i) A weight ratio of wollastonite to calcium aluminum feldspar of 30:1 to 1:2, preferably 20:1 to 1.2, and / or

[0018] ii) A weight ratio of wollastonite to magnesia of 10:1 to 2:1, preferably 8:1 to 2:1, and / or wollastonite of 10:1 to 2:1.

[0019] iii) The weight ratio of calcium aluminum feldspar to magnesium feldspar is 5:1 to 1:5, preferably 3:1 to 1:3.

[0020] In another embodiment of any aspect of the invention, the paper filler has a Ca content of ≥50% by weight, preferably 20-70% by weight, as determined by CaO in X-ray fluorescence measurements, based on the total weight of the filler.

[0021] In one embodiment of any aspect of the invention, the paper filler has a volumetric median particle size d measured using a laser diffraction system. 50 The thickness ranges from 0.8 to 6.0 μm, with 1.0 to 3.0 μm being preferred.

[0022] In another embodiment of any aspect of the invention, the paper filler further comprises one or more components selected from the group consisting of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel, and mixtures thereof.

[0023] In another embodiment of any aspect of the invention, the paper filler comprises lime, determined by X-ray diffraction, in an amount of >3 to 30% by weight, preferably 4 to 30% by weight, based on the total weight of the filler.

[0024] In one embodiment of any aspect of the invention, the paper filler is obtained by incinerating deinked sludge, preferably from white recycled paper made from tissue, supercalendered paper, or newsprint, at a temperature of at least 800°C, preferably at least 850°C.

[0025] In another embodiment of any aspect of the invention, the paper filler is an alkaline paper filler.

[0026] In one embodiment of the paper product of the present invention, the paper filler is present in an amount of 0.3-10% by weight, based on the total weight of the paper product.

[0027] In another embodiment of the paper product of the present invention, the paper product contains lime, the amount of which, as determined by X-ray diffraction, is ≤10% by weight, preferably ≤5% by weight, based on the total weight of the paper product.

[0028] In another embodiment of the paper product of the present invention, the paper product...

[0029] i) Having a surface pH of 7.9 or higher, preferably 8.0 or higher, most preferably 8.1 or higher, and / or

[0030] ii) When slushed in water, it results in a water pH of 9.4 or higher, preferably 9.5 or higher.

[0031] In one embodiment of the paper product of the present invention, the paper product is a recycled paper product, preferably a boxboard such as coated or uncoated boxboard, or a containerboard such as linerboard, corrugated board and double-sided paper.

[0032] In another embodiment of the paper product of the present invention, the paper product, when incinerated in a microwave muffle furnace at 850°C ± 10°C, has a lime content determined by X-ray diffraction of >3 to 40% by weight, preferably 4 to 40% by weight, based on the total weight of the paper product.

[0033] For the purposes of this invention, the term "recycled pulp" is understood to refer to pulp derived from paper and / or paperboard recycling, i.e., pulp derived from paper and / or paperboard waste that has already undergone recycling processes. Therefore, this recycled pulp is preferably obtained from "post-consumer paper and / or paperboard waste" generated by consumers. Alternatively, this recycled pulp may be obtained from "post-industrial paper and / or paperboard waste" generated in industry or during the manufacture of paper products. Recycled pulp can be a mixture of fibers, but may also contain only one type of fiber. Furthermore, recycled pulp may contain further additives, such as mineral fillers, printing inks, etc.

[0034] For the purposes of this invention, the term "virgin pulp" is understood to refer to pulp derived from renewable resources, i.e., pulp not obtained by recycling methods.

[0035] When referring to a singular noun, the use of an indefinite article or a definite article such as "a", "an" or "the" includes the plural form of that noun, unless otherwise specifically stated otherwise.

[0036] When the term "comprising" is used in this specification and claims, it does not exclude other elements. For the purposes of this invention, the term "consisting of" is considered a preferred embodiment of the term "comprising". If a group is defined below to include at least a certain number of embodiments, this is also understood to disclose a group that preferably consists only of these embodiments.

[0037] Wherever the terms “including” or “having” are used, they are considered equivalent to “comprising” as defined above.

[0038] Terms such as “obtainable” or “definable” and “obtained” or “defined” are used interchangeably. This means, for example, that unless the context explicitly indicates otherwise, the term “obtainable” does not imply that an embodiment must be obtained through, for example, a sequence of steps following the term “obtainable”, although the terms “obtainable” or “defined” always include such limiting understanding as a preferred embodiment.

[0039] When embodiments or technical details of the paper filler of the present invention are mentioned below, it should be understood that these embodiments or technical details also relate to the paper products of the present invention and the uses of the present invention.

[0040] Paper filler

[0041] The paper filler of this invention comprises a mixture of three calcium silicate minerals. Specifically, these three calcium silicate minerals include magnesium feldspar, calcium aluminum feldspar, and alpha-wollastonite, thereby obtaining a paper product with alkaline properties.

[0042] In the context of this invention, magnesian feldspar is considered to be a calcium silicate mineral, particularly a calcium magnesium silicate mineral, having the formula Ca2Mg[Si2O7].

[0043] In the context of this invention, calcium aluminum feldspar is considered to be a calcium silicate mineral, particularly a calcium aluminum silicate mineral, having the formula Ca2Al[AlSiO7].

[0044] In the context of this invention, alpha-wollastonite is considered to be a calcium silicate mineral, particularly a dicalcium silicate mineral, having the formula β-Ca2[SiO4].

[0045] Further requirement: The paper filler comprises 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of morpho-wollastonite, and 0.1-15% by weight of magnesium feldspar, based on the total weight of the filler. In one embodiment, the paper filler comprises 1-15% by weight of calcium aluminum feldspar, 1-50% by weight of morpho-wollastonite, and 1-15% by weight of magnesium feldspar, based on the total weight of the filler; or the paper filler comprises 2-15% by weight of calcium aluminum feldspar, 5-50% by weight of morpho-wollastonite, and 1.5-15% by weight of magnesium feldspar, based on the total weight of the filler.

[0046] In a preferred embodiment, the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of wollastonite, and 2-15% by weight of magnesium feldspar, based on the total weight of the filler.

[0047] It should be noted that, unless otherwise specified, the amount and composition of minerals in paper fillers and in incinerated paper products are determined throughout this invention by X-ray diffraction. This method is further described in the Examples section of this document.

[0048] For example, the paper filler contains 3-12% by weight, preferably 3-10% by weight, and most preferably 3-8% by weight of calcium aluminum feldspar based on the total weight of the filler.

[0049] Additionally or alternatively, the paper filler contains 12-45% by weight, preferably 14-40% by weight, and most preferably 15-38% by weight, of wollastonite based on the total weight of the filler.

[0050] Additionally or alternatively, the paper filler contains 2-12% by weight, preferably 2-10% by weight, and most preferably 2-8% by weight of magnesia feldspar based on the total weight of the filler.

[0051] In one embodiment, the paper filler thus comprises

[0052] i) Calcium aluminum feldspar in an amount of 3-12% by weight, preferably 3-10% by weight, and most preferably 3-8% by weight, based on the total weight of the filler.

[0053] ii) A quantity of 12-50% by weight of type A wollastonite based on the total weight of the filler, and

[0054] iii) A quantity of 2-15% by weight of magnesium feldspar based on the total weight of the filler.

[0055] Alternatively, the paper filler therefore contains

[0056] i) Based on the total weight of the filler, a quantity of calcium aluminum feldspar of 3-15% by weight,

[0057] ii) Based on the total weight of the filler, 12-45% by weight, preferably 14-40% by weight, and most preferably 15-38% by weight of wollastonite, and

[0058] iii) A quantity of 2-15% by weight of magnesium feldspar based on the total weight of the filler.

[0059] Alternatively, the paper filler therefore contains

[0060] i) Based on the total weight of the filler, a quantity of calcium aluminum feldspar of 3-15% by weight,

[0061] ii) A quantity of 12-50% by weight of type A wollastonite based on the total weight of the filler, and

[0062] iii) Amount of 2-12% by weight, preferably 2-10% by weight, and most preferably 2-8% by weight, of the total weight of the filler.

[0063] In another embodiment, the paper filler contains

[0064] i) Calcium aluminum feldspar in an amount of 3-12% by weight, preferably 3-10% by weight, and most preferably 3-8% by weight, based on the total weight of the filler.

[0065] ii) Based on the total weight of the filler, 12-45% by weight, preferably 14-40% by weight, and most preferably 15-38% by weight of wollastonite, and

[0066] iii) A quantity of 2-15% by weight of magnesium feldspar based on the total weight of the filler.

[0067] Alternatively, the paper filler contains

[0068] i) Calcium aluminum feldspar in an amount of 3-12% by weight, preferably 3-10% by weight, and most preferably 3-8% by weight, based on the total weight of the filler.

[0069] ii) A quantity of 12-50% by weight of type A wollastonite based on the total weight of the filler, and

[0070] iii) Amount of 2-12% by weight, preferably 2-10% by weight, and most preferably 2-8% by weight, of the total weight of the filler.

[0071] Alternatively, the paper filler contains

[0072] i) Based on the total weight of the filler, a quantity of calcium aluminum feldspar of 3-15% by weight,

[0073] ii) Based on the total weight of the filler, 12-45% by weight, preferably 14-40% by weight, and most preferably 15-38% by weight of wollastonite, and

[0074] iii) Amount of 2-12% by weight, preferably 2-10% by weight, and most preferably 2-8% by weight, of the total weight of the filler.

[0075] In a preferred embodiment, the paper filler thus comprises

[0076] i) Based on the total weight of the filler, 3-12% by weight, preferably 3-10% by weight, and most preferably 3-8% by weight of calcium aluminum feldspar, and

[0077] ii) Based on the total weight of the filler, 12-45% by weight, preferably 14-40% by weight, and most preferably 15-38% by weight of wollastonite, and

[0078] iii) Amount of 2-12% by weight, preferably 2-10% by weight, and most preferably 2-8% by weight, of the total weight of the filler.

[0079] Regarding the mixture of three calcium silicate minerals, it should be understood that the silicate minerals are preferably present in a specific weight ratio.

[0080] For example, the mixture of the three calcium silicate minerals preferably contains wollastonite and calcium aluminum feldspar in a weight ratio of 30:1 to 1:2, preferably 20:1 to 1.2.

[0081] Alternatively or additionally, the mixture of the three calcium silicate minerals preferably comprises wollastonite and magnesia in a weight ratio of 10:1 to 2:1, preferably 8:1 to 2:1 [wollastonite / magnesia feldspar].

[0082] Alternatively or additionally, the mixture of the three calcium silicate minerals preferably comprises calcium aluminum feldspar and magnesium feldspar in a weight ratio of 5:1 to 1:5, preferably 3:1 to 1:3.

[0083] In a preferred embodiment, the mixture of the three calcium silicate minerals thus comprises

[0084] i) A weight ratio of wollastonite to calcium aluminum feldspar of 30:1 to 1:2, preferably 20:1 to 1.2, and

[0085] ii) The weight ratio of wollastonite to magnesia is 10:1 to 2:1, preferably 8:1 to 2:1.

[0086] In another embodiment, the mixture of the three calcium silicate minerals thus contains

[0087] i) A weight ratio of wollastonite to calcium aluminum feldspar of 30:1 to 1:2, preferably 20:1 to 1.2, and

[0088] ii) The weight ratio of calcium aluminum feldspar / magnesia feldspar is 5:1 to 1:5, preferably 3:1 to 1:3.

[0089] Preferably, the mixture of the three calcium silicate minerals thus contains

[0090] i) A weight ratio of wollastonite to calcium aluminum feldspar of 30:1 to 1:2, preferably 20:1 to 1.2, and

[0091] ii) A weight ratio of wollastonite / magnesia feldspar of 10:1 to 2:1, preferably 8:1 to 2:1, of wollastonite and magnesium feldspar.

[0092] iii) The weight ratio of calcium aluminum feldspar / magnesia feldspar is 5:1 to 1:5, preferably 3:1 to 1:3.

[0093] In one embodiment, the mixture of the three calcium silicate minerals preferably comprises wollastonite and calcium aluminum feldspar in a weight ratio of 10:1 to 1:1, preferably 8:1 to 2:1.

[0094] Alternatively or additionally, the mixture of the three calcium silicate minerals preferably comprises wollastonite and magnesia in a weight ratio of 10:1 to 2:1, preferably 8:1 to 4:1 [wollastonite / magnesia].

[0095] Alternatively or additionally, the mixture of the three calcium silicate minerals preferably comprises calcium aluminum feldspar and magnesium feldspar in a weight ratio of 5:1 to 1:2, preferably 3:1 to 1:1.

[0096] In a preferred embodiment, the mixture of the three calcium silicate minerals thus comprises

[0097] i) A weight ratio of wollastonite / calcium aluminum feldspar of 10:1 to 1:1, preferably 8:1 to 2:1, of wollastonite and calcium aluminum feldspar.

[0098] ii) A weight ratio of 10:1 to 2:1, preferably 8:1 to 4:1, of wollastonite and magnesia.

[0099] In another embodiment, the mixture of the three calcium silicate minerals thus contains

[0100] i) A weight ratio of wollastonite / calcium aluminum feldspar of 10:1 to 1:1, preferably 8:1 to 2:1, of wollastonite and calcium aluminum feldspar.

[0101] ii) The weight ratio of calcium aluminum feldspar to magnesium feldspar is 5:1 to 1:2, preferably 3:1 to 1:1.

[0102] Preferably, the mixture of the three calcium silicate minerals thus contains

[0103] i) A weight ratio of wollastonite / calcium aluminum feldspar of 10:1 to 1:1, preferably 8:1 to 2:1, of wollastonite and calcium aluminum feldspar.

[0104] ii) A weight ratio of wollastonite / magnesia feldspar of 10:1 to 2:1, preferably 8:1 to 4:1, of wollastonite and magnesium feldspar.

[0105] iii) The weight ratio of calcium aluminum feldspar / magnesia feldspar is 5:1 to 1:2, preferably 3:1 to 1:1.

[0106] Very typically, the paper filler comprises a mixture of the three calcium silicate minerals within a specific range. More precisely, the paper filler preferably comprises a mixture of the three calcium silicate minerals in a total amount of ≥0.3% by weight based on the total weight of the filler. In particular, the paper filler comprises a mixture of the three calcium silicate minerals in a total amount of 0.3-60% by weight, more preferably 0.3-55% by weight, and most preferably 0.3-50% by weight based on the total weight of the filler.

[0107] In one embodiment, the total amount of the mixture of the three calcium silicate minerals contained in the paper filler is preferably ≥1% by weight, for example 1-60% by weight, more preferably 5-55% by weight, and most preferably 10-50% by weight, based on the total weight of the filler.

[0108] For example, the total amount of the mixture of the three calcium silicate minerals contained in the paper filler is preferably ≥20% by weight based on the total weight of the filler. In particular, the total amount of the mixture of the three calcium silicate minerals contained in the paper filler is 20-60% by weight based on the total weight of the filler, more preferably 24-55% by weight, and most preferably 25-50% by weight.

[0109] Since the paper filler comprises a mixture of three calcium silicate minerals, it should be understood that the paper filler has a Ca content within a certain range, which is determined as CaO in X-ray fluorescence measurements. Particularly preferably, the paper filler has a Ca content of ≥50% by weight, determined as CaO in X-ray fluorescence measurements, based on the total weight of the filler. In one embodiment, the paper filler has a Ca content of 20-70% by weight, determined as CaO in X-ray fluorescence measurements, based on the total weight of the filler.

[0110] Furthermore, it should be understood that the paper filler has a relatively low median particle size (d) that supports the alkaline properties of the paper product. 50 Therefore, the paper filler preferably has a volume median particle size d as measured using a laser diffraction system. 50 The particle size is 0.8-6.0 μm. It should be noted that if the volumetric median particle size (d) of this paper filler... 50 The value is at the median particle size d in this volume. 50 In the lower range, the alkalinity of the paper product is even further increased. Therefore, the paper filler preferably has a median particle size d measured using a laser diffraction system. 50 The range is 1.0-3.0 μm.

[0111] The paper filler of the present invention comprises a mixture of three calcium silicate minerals: magnesium feldspar, calcium aluminum feldspar, and alpha-wollastonite.

[0112] In one embodiment, the paper filler of the present invention is composed of a mixture of three calcium silicate minerals: magnesium feldspar, calcium aluminum feldspar, and diatomaceous wollastonite.

[0113] However, it should be understood that the paper filler is preferably obtained by a recycling process and, in particular, by the incineration of deinking sludge. In view of this, the paper filler of the present invention preferably comprises further components typically contained in such sludge.

[0114] For example, the paper filler further comprises one or more components selected from the group consisting of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel, and mixtures thereof.

[0115] The term "one or more" components indicates that the further component may comprise one further component or a mixture of two or more components. Preferably, the further component comprises a mixture of two or more components.

[0116] For example, the further component is a mixture comprising calcite, calcium hydride, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, siliceous silica, clay, and spinel. In this embodiment, it should be understood that the paper filler may contain further components other than calcite, calcium hydride, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, siliceous silica, clay, and spinel, present in low amounts, for example, less than 1% by weight based on the total weight of the filler.

[0117] Alternatively, the further component is a mixture of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, and spinel.

[0118] In one embodiment, the paper filler thus comprises

[0119] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and alpha-wollastonite, wherein the paper filler comprises, based on the total weight of the filler, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of alpha-wollastonite, and 0.1-15% by weight of magnesia feldspar, and

[0120] (b) One or more components selected from the group consisting of: calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel and mixtures thereof.

[0121] For example, the paper filler contains

[0122] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and alpha-wollastonite, wherein the paper filler comprises, based on the total weight of the filler, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of alpha-wollastonite, and 0.1-15% by weight of magnesia feldspar, and

[0123] b) As a component of a mixture comprising calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0124] In a preferred embodiment, the paper filler comprises the following:

[0125] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and alpha-wollastonite, wherein the paper filler comprises, based on the total weight of the filler, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of alpha-wollastonite, and 0.1-15% by weight of magnesia feldspar, and

[0126] (b) One or more components selected from the group consisting of: calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel and mixtures thereof.

[0127] Preferably, the paper filler consists of the following:

[0128] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and alpha-wollastonite, wherein the paper filler comprises, based on the total weight of the filler, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of alpha-wollastonite, and 0.1-15% by weight of magnesia feldspar, and

[0129] b) As a component of a mixture comprising calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0130] For example, the paper filler consists of the following items

[0131] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and alpha-wollastonite, wherein the paper filler comprises, based on the total weight of the filler, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of alpha-wollastonite, and 0.1-15% by weight of magnesia feldspar, and

[0132] b) As a component of a mixture consisting of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0133] In another embodiment, the paper filler thus contains

[0134] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of diatomaceous earth, and 2-15% by weight of magnesia feldspar, based on the total weight of the filler.

[0135] (b) One or more components selected from the group consisting of: calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel and mixtures thereof.

[0136] For example, the paper filler contains

[0137] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of diatomaceous earth, and 2-15% by weight of magnesia feldspar, based on the total weight of the filler.

[0138] b) As a component of a mixture comprising calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0139] In a preferred embodiment, the paper filler comprises the following:

[0140] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of diatomaceous earth, and 2-15% by weight of magnesia feldspar, based on the total weight of the filler.

[0141] (b) One or more components selected from the group consisting of: calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel and mixtures thereof.

[0142] Preferably, the paper filler consists of the following:

[0143] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of diatomaceous earth, and 2-15% by weight of magnesia feldspar, based on the total weight of the filler.

[0144] b) As a component of a mixture comprising calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0145] For example, the paper filler consists of the following items

[0146] a) A mixture of three calcium silicate minerals, namely, magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises 3-15% by weight of calcium aluminum feldspar, 12-50% by weight of diatomaceous earth, and 2-15% by weight of magnesia feldspar, based on the total weight of the filler.

[0147] b) As a component of a mixture consisting of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay and spinel.

[0148] Therefore, it can be understood that the mixture of the three calcium silicate minerals in the paper filler, namely magnesium feldspar, calcium aluminum feldspar and diatomaceous earth, together with one or more components selected from the group including calcite, calcium hydroxide, lime, quartz, calcium aluminum, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel and mixtures thereof, is 100 by weight.

[0149] Preferably, the paper filler contains lime. To obtain the alkaline properties of the paper product, preferably, the paper filler contains >3 to 30% by weight of lime based on the total weight of the filler. Preferably, the paper filler contains 4 to 30% by weight of lime based on the total weight of the filler.

[0150] In one embodiment, the paper filler comprises >3 to 20% by weight of lime based on the total weight of the filler. Preferably, the paper filler comprises 4 to 20% by weight of lime based on the total weight of the filler.

[0151] As mentioned above, the paper filler is preferably obtained from a paper recycling process. Specifically, the paper filler is obtained by incinerating deinked sludge, particularly white recycled paper. It should be understood that the deinked sludge from white recycled paper is preferably obtained from tissue paper, supercalendered paper, and / or newsprint. In one embodiment, the deinked sludge is obtained from only one type of paper source to be recycled. Therefore, the deinked sludge from white recycled paper can preferably be obtained from tissue paper, supercalendered paper, or newsprint. Alternatively, the deinked sludge can be obtained from a mixture of paper sources to be recycled. Therefore, the deinked sludge from white recycled paper can preferably be obtained from tissue paper, supercalendered paper, and newsprint.

[0152] To obtain the paper filler of the present invention, it is required that the paper filler be obtained by incinerating deinking sludge from white recycled paper at a temperature of at least 800°C, preferably at least 850°C. For example, the paper filler is obtained by incinerating deinking sludge from white recycled paper at a temperature of 800-1000°C, preferably 850-900°C.

[0153] In view of the above, the paper filler of the present invention is preferably an alkaline paper filler.

[0154] Paper products

[0155] In a second aspect of the invention, a paper product is provided. This paper product is prepared from paper fillers as defined herein and papermaking ingredients comprising pulp.

[0156] It should be noted that this paper product can be obtained by any methods and equipment known in the art for preparing paper products. These methods and equipment are well known and do not need to be described in more detail here.

[0157] The papermaking ingredients include pulp. The pulp used to prepare the paper product can be any pulp known to those skilled in the art that is suitable for making a paper product.

[0158] The pulp can therefore be virgin pulp and / or recycled pulp obtained from paper and / or paperboard recycling. Preferably, the pulp is recycled pulp obtained from paper and / or paperboard recycling. In one embodiment, it may be advantageous to change the composition of the recycled pulp by adding virgin pulp. Thus, the pulp can be a mixture of recycled pulp obtained from paper and / or paperboard recycling and virgin pulp.

[0159] The pulp, whether virgin or recycled, is preferably in the form of an aqueous suspension containing fibers.

[0160] It should be understood that the amount of fiber in the aqueous suspension of the pulp can vary within a wide range. However, preferably, the amount of fiber in the aqueous suspension is such that the fibers can be easily deposited on the papermaking equipment. Furthermore, preferably, the amount of solvent in the aqueous suspension is such that the energy required for water removal and water consumption are as low as possible.

[0161] Typically, the aqueous suspension contains 0.1-30% by weight of fibers based on the total weight of the aqueous suspension. Preferably, the aqueous suspension contains 0.2-20% by weight, more preferably 0.4-10% by weight, and most preferably 0.5-5% by weight of fibers based on the total weight of the aqueous suspension. For example, the aqueous suspension contains 0.5-10% by weight of fibers based on the total weight of the aqueous suspension.

[0162] The fibers in this aqueous suspension are not limited to a specific type of fiber. Generally, any type of fiber suitable for preparing paper products can be used in this invention. More precisely, any fiber suitable for the desired paper product and its corresponding use can be used in this aqueous suspension.

[0163] Preferably, the fibers in the aqueous suspension comprise cellulose.

[0164] Preferably, the fibers contained in the pulp (whether virgin or recycled pulp) are selected from the group consisting of: eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, cotton pulp (including lint), wheat pulp, oat pulp, rye pulp, barley pulp, rice straw pulp, bamboo pulp, bagasse pulp, miscanthus pulp, sisal pulp, jute pulp, acacia pulp, birch pulp, fir pulp, lyocell pulp, and mixtures thereof. In one embodiment, the fiber is contained in recycled or virgin eucalyptus pulp or recycled or virgin cotton pulp.

[0165] In one embodiment, the pulp (whether virgin or recycled) is a mixture of pulps comprising two or more types of pulp selected from the group consisting of: eucalyptus pulp, spruce pulp, pine pulp, beech pulp, hemp pulp, cotton pulp, wheat pulp, oat pulp, rye pulp, barley pulp, rice straw pulp, bamboo pulp, bagasse pulp, miscanthus pulp, sisal pulp, jute pulp, acacia pulp, birch pulp, fir pulp, and lyocell pulp.

[0166] In view of this, the fibers in the aqueous suspension of the pulp (whether virgin pulp or recycled pulp) are selected from the group consisting of: eucalyptus fiber, spruce fiber, pine fiber, beech fiber, hemp fiber, cotton fiber, cotton linter, wheat fiber, oat fiber, rye fiber, barley fiber, rice straw fiber, bamboo fiber, bagasse fiber, miscanthus fiber, sisal fiber, jute fiber, acacia fiber, birch fiber, fir fiber, lyocell fiber, viscose fiber, and mixtures thereof. In one embodiment, the fibers in the aqueous suspension of the pulp are eucalyptus fiber, cotton fiber, or cotton linter.

[0167] In one embodiment, the fibers in the aqueous suspension of the pulp (whether virgin pulp or recycled pulp) are a mixture of fibers comprising two or more types of fibers, preferably biocompatible fibers selected from the group consisting of: eucalyptus fiber, spruce fiber, pine fiber, beech fiber, hemp fiber, cotton fiber, cotton linter, wheat fiber, oat fiber, rye fiber, barley fiber, rice straw fiber, bamboo fiber, bagasse fiber, miscanthus fiber, sisal fiber, jute fiber, acacia fiber, birch fiber, fir fiber, viscose fiber, and lyocell fiber.

[0168] It should be understood that the fiber has dimensions that are typically required to be followed for the paper products to be produced.

[0169] Therefore, the fibers in the aqueous suspension of the pulp preferably have an average diameter of 1-35 μm, more preferably 2-30 μm, and most preferably 3-25 μm.

[0170] Additionally or alternatively, the fibers in the aqueous suspension of the virgin pulp preferably have an average length of 0.7-250 mm, more preferably 0.8-230 mm, and most preferably 0.9-200 mm.

[0171] Additionally or alternatively, the fibers in the aqueous suspension of the recycled pulp preferably have an average length of 0.5-200 mm, more preferably 0.6-150 mm, and most preferably 0.7-100 mm.

[0172] For example, the fibers in the aqueous suspension of the virgin pulp have an average diameter of 1-35 μm, preferably 2-30 μm, and most preferably 3-25 μm, or an average length of 0.7-250 mm, preferably 0.8-230 mm, and most preferably 0.9-200 mm. In another embodiment, the fibers in the aqueous suspension of the virgin pulp have an average diameter of 1-35 μm, preferably 2-30 μm, and most preferably 3-25 μm, and an average length of 0.7-250 mm, preferably 0.8-230 mm, and most preferably 0.9-200 mm.

[0173] In the case of recycled pulp, the fibers in the aqueous suspension of the recycled pulp have an average diameter of 1-35 μm, preferably 2-30 μm, and most preferably 3-25 μm, or an average length of 0.5-200 mm, preferably 0.6-150 mm, and most preferably 0.7-100 mm. In another embodiment, the fibers in the aqueous suspension of the recycled pulp have an average diameter of 1-35 μm, preferably 2-30 μm, and most preferably 3-25 μm, and an average length of 0.5-200 mm, preferably 0.6-150 mm, and most preferably 0.7-100 mm.

[0174] The solvent of this aqueous suspension comprises water, which is optionally mixed with an organic solvent, such as methanol, ethanol, n-butanol, isopropanol, n-propanol, acetone, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and mixtures thereof. Preferably, the solvent is water, methanol, ethanol, and / or acetone. More preferably, the solvent comprises water, and most preferably consists of water.

[0175] It should be noted that the papermaking ingredients may further include typical additives used in the papermaking process. For example, the papermaking ingredients may further include retention aids, fillers such as calcium carbonate, clay, resin control agents such as talc, defoaming agents, sizing agents, starch, etc., as additives.

[0176] Preferably, the paper product contains the paper filler in an amount typically used in the product to be prepared. Therefore, the paper filler is preferably present in an amount of 0.3-10% by weight based on the total weight of the paper product. For example, the paper filler is present in an amount of 0.4-7% by weight, most preferably 0.5-5% by weight, based on the total weight of the paper product.

[0177] It should be understood that the paper product contains a low amount of lime. Preferably, the paper product contains ≤40% by weight, more preferably ≤30% by weight, and most preferably ≤20% by weight, based on the total weight of the paper product. For example, the paper product contains ≤10% by weight, more preferably ≤5% by weight, based on the total weight of the paper product.

[0178] Because of the paper filler of the present invention, it is understood that the paper product has alkaline properties. Specifically, the paper product has a surface pH of 7.9 or higher. For example, the paper product has a surface pH of 8.0 or higher, and most preferably 8.1 or higher. Preferably, the paper product has a surface pH in the range of 7.9-9.0, more preferably in the range of 8.0-8.8, and most preferably in the range of 8.1-8.6.

[0179] Additionally or alternatively, the paper product, when pulped in water, results in a water pH of 9.4 or higher, preferably 9.5 or higher. For example, the paper product, when pulped in water, results in a water pH in the range of 9.4-10.0, and preferably in the range of 9.5-9.9.

[0180] In a preferred embodiment, the paper product

[0181] i) Having a surface pH of 7.9 or higher, preferably 8.0 or higher, and most preferably 8.1 or higher.

[0182] ii) When pulping in water, it results in a water pH of 9.4 or higher, and preferably 9.5 or higher.

[0183] It should be understood that the lime content increases when the paper product is incinerated at 850℃±10℃. For example, the paper product has a lime content of >3 to 40% by weight based on the total weight of the paper product when incinerated in a microwave muffle furnace at 850℃±10℃. Preferably, the paper product has a lime content in the range of 4-40% by weight based on the total weight of the paper product when incinerated in a microwave muffle furnace at 850℃±10℃. For example, the paper product has a lime content in the range of >3 to 30% by weight, preferably >3 to 20% by weight, and most preferably >3 to 10% by weight based on the total weight of the paper product when incinerated in a microwave muffle furnace at 850℃±10℃. Alternatively, the paper product has a lime content in the range of 4-30% by weight, preferably 4-20% by weight, and most preferably 4-10% by weight based on the total weight of the paper product when incinerated in a microwave muffle furnace at 850℃±10℃.

[0184] As mentioned above, the paper product is preferably a recycled paper product. In a preferred embodiment, the paper product is boxboard such as coated or uncoated boxboard, or containerboard such as linerboard, corrugated board, and double-sided paper.

[0185] It should be understood that examples of (recycled) coated boxboard include coated recycled board (CRB), greyback duplex (GBD), bleached pulp facing board (WLC), and whiteback duplex (WBD). Examples of (non-recycled) coated boxboard include boxboard, paper tube board, duplex, gypsum backing board, gypsum facing board, and uncoated recycled board. Examples of facing board include brown testliner, brown high-performance recycled facing board, brown kraft paper top liner, white top testliner, and mottled testliner. Examples of corrugated board include recycled corrugated board (medium) and lightweight recycled corrugated board (core). Examples of double-layered paper include recycled double-layered paper.

[0186] In view of the very good results achieved by the paper filler of the present invention, the present invention relates in another aspect to the use of the paper filler as defined herein as an alkaline paper filler in paper products, preferably recycled paper products, more preferably boxboard such as coated or uncoated boxboard, or containerboard such as linerboard, corrugated board and double-sided paper.

[0187] For the definition of the paper product, the use of the paper filler and its preferred embodiments, refer to the statements provided above in the discussion of the technical details of the paper filler and the paper product. Attached Figure Description

[0188] Figure 1 illustrates the effect of filler 1 particle size on pulp pH over time. Detailed Implementation

[0189] The scope and benefits of the invention will be better understood based on the following embodiments, which are intended to illustrate certain implementations of the invention and are not limiting.

[0190] Example

[0191] Material

[0192]

[0193]

[0194] X-ray diffraction (XRD) measurement of filler

[0195] XRD is a versatile non-destructive analytical technique sensitive to the atomic structure of substances. XRD enables phase identification and quantification. The sample is split using a rifle splitter to reduce it to a suitable analytical volume. The sample is then dried overnight at 105°C. Afterward, the sample is ground for 90 seconds at 1100 rpm using a Retsch RS200 mill. Five drops of isopropanol are used as a grinding aid. The sample is then homogenized in a glass vial.

[0196] All samples were analyzed using a Bruker D8 Advance powder diffractometer that obeys Bragg's law. This diffractometer consists of a 1kW X-ray tube, a sample holder, and... - It consists of a goniometer and a LYNXEYE XE-T detector. It operates at 0.02° / second (2 The scanning velocity profiles were collected. Qualitative analysis of the obtained powder diffraction patterns was performed using the DIFFRACsuite EVA software package, based on reference patterns from the International Center for Diffraction Data (ICDD) database.

[0197] Quantitative analysis of diffraction data refers to determining the amount of different phases (minerals) in a multiphase sample and is performed using the DIFFRACsuite software package TOPAS. Specifically, quantitative analysis allows for the determination of structural properties and phase (mineral) proportions using quantifiable numerical precision derived from the experimental data itself. This involves modeling the entire diffraction pattern (Rietveld method), enabling the calculated pattern to replicate the experimental pattern. The Rietveld method requires knowledge of the approximate crystal structures of all phases (minerals) of interest in the pattern.

[0198] Table 1: X-ray diffraction analysis of different fillers.

[0199]

[0200] The total amounts of calcium silicate minerals, magnesian feldspar, calcium aluminum feldspar, and diatomaceous wollastonite, were significantly higher in fillers 1 and 2 (28% and 44%, respectively) and fillers 6, 7, and 8 (15%, 20%, and 27%) derived from deinking sludge incineration than in filler 3 (12%) derived from oil shale incineration. Specifically, fillers 1 and 2 showed higher concentrations of calcium aluminum feldspar and diatomaceous wollastonite compared to filler 3, while filler 6 showed a higher concentration of calcium aluminum feldspar compared to filler 3, and fillers 7 and 8 showed a higher concentration of diatomaceous wollastonite compared to filler 3. The amount of lime (wt%) was significantly higher in fillers 1 and 2 and in fillers 6, 7, and 8 than in filler 3.

[0201] X-ray fluorescence (XRF) measurement of packing material

[0202] XRF is a non-destructive analytical technique used to determine the elemental composition of materials. Filler samples were prepared as molten beads with a flux:sample ratio of 9:0.9 (g flux / g sample) excluding loss on ignition (LOI). Lithium tetraborate (66:34%):lithium metaborate (99.98%) + 0.20% lithium bromide was used as the flux. The LOI was obtained by annealing the samples in a furnace at 700°C. The prepared molten beads were measured by XRF using a Perform'X sequential X-ray fluorescence spectrometer from Thermo Fisher Scientific. Results are expressed as the average of two measurements. A single measurement is valid if its relative standard deviation is not greater than 10%.

[0203] Table 2: X-ray fluorescence analysis of different packing materials.

[0204]

[0205] Compared with filler 4 obtained by incinerating industrial waste, filler 1 obtained by incinerating deinking sludge has a much higher Ca content determined by CaO (see Table 2).

[0206] Particle size distribution measurement

[0207] The "particle size" of granular materials is determined by the distribution of their particle size. x To describe, where the value d x This represents a diameter such that, relative to this diameter, particles with a volume of x% have a density smaller than d. x The diameter. This means, for example, d. 20 The value refers to a particle size in which 20% of the volume of all particles is smaller than that particle size. d 50The value is therefore the volumetric median particle size, meaning that 50% of the volume of all particles is larger than this particle size. The particle size distribution of the filler material used was measured using a Malvern Mastersizer 3000 laser diffraction system with a dry dispersion unit (Malvern Instruments Plc., UK). The methods and instruments are known to those skilled in the art and are commonly used to determine the particle size of fillers and other particulate materials. The following parameters from Table 3 were used:

[0208] Table 3: Measurement parameters of particle size distribution

[0209]

[0210] Filler grinding

[0211] The filler samples were ground using a Hosokawa Alpine jet mill. The grinding conditions are shown in Table 4. A dm of 2.45 μm was obtained. 50 The packing sample 1 (see Table 5).

[0212] Table 4: Grinding conditions for fillers.

[0213]

[0214] Table 5: Particle size distribution of filler 1 before and after jet milling.

[0215]

[0216] Preparation of handmade paper

[0217] 100g (dry) used corrugated cardboard pulp at 10dm 3 The solution was added to tap water (20°C), followed by a certain amount of the filler to be tested to obtain the total filler content based on the final paper weight. The suspension was stirred for 30 minutes. Subsequently, 0.06% (based on dry weight) of poly(amide) (Percol 1540) was added as a retention aid and a Rapid-Köthen hand-made paper forming machine was used to form 80 g / m³ paper. 2 The sheets were dried using a Rapid-Köthen dryer. The composition of the handmade paper is given in Table 6 below.

[0218] Paper surface pH

[0219] The pH value on the paper surface was measured after the sample surface was wetted with water. The pH measurement lasted for 60 seconds.

[0220] Table 6: Composition of the produced handmade paper.

[0221]

[0222] Table 7: pH measurement of the surface pH of different types of handmade paper.

[0223]

[0224] The addition of fillers 1 and 2, with a total amount of calcium silicate minerals (magnesia feldspar, calcium aluminum feldspar, and diatomaceous wollastonite) of ≥20% by weight based on the total weight of fillers, resulted in an increase in the surface pH of the paper sheet. Conversely, fillers with a total amount of calcium silicate minerals (magnesia feldspar, calcium aluminum feldspar, and diatomaceous wollastonite) of <20% by weight based on the total weight of fillers, such as filler 3 derived from oil shale combustion, did not result in an increase in surface pH. The addition of filler 5 (naturally ground calcium carbonate) as a standard filler or filler 4 derived from industrial waste combustion also did not result in an increase in pH.

[0225] Analysis of fillers produced by burning paper sheets at 850°C

[0226] Handmade paper produced by incinerating paper in a microwave muffle furnace at 850℃±10℃. Ash content of the obtained samples was analyzed by X-ray diffraction (see Table 8).

[0227] Table 8: Calcium silicate minerals and lime identified by X-ray diffraction analysis of ash from the burning of handmade paper.

[0228]

[0229] Compared to the addition of fillers obtained from deinking sludge incineration (fillers 1 and 2, S1 and S2 respectively) and the absence of filler (S0), the addition of standard fillers such as filler 5 (naturally ground calcium carbonate) resulted in lower levels of calcium silicate minerals. The addition of fillers 1 and 2 (obtained from deinking sludge incineration) (S1 and S2) resulted in higher levels of lime compared to the absence of filler. The addition of filler 3 did not affect the lime content.

[0230] T60 Reactivity Test

[0231] This method assesses the reactivity of the filler. The ash sample is calcined at 950°C for 1 hour to ensure that only CaO is present in the material. The required amount of sample is added to a selected amount of water at 20°C. The mixture is stirred at 300 rpm with a mechanical stirrer, and the temperature rise is monitored using a standard thermometer and stopwatch. Then, it is processed according to European standards. 2 (European Norm) 2 The method for calculating R as specified in the text. DIN value.

[0232] The effect of fillers on pulp pH

[0233] 0.8 liters of used corrugated box pulp (4% solids content) was added to a 1-liter bottle. Then, 1.8% of filler 1 with different particle size distributions (2.45 μm and 4.83 μm) was added to the bottle. A bottle containing only pulp was also added as a control. The pH of the mixture over time was recorded. The results are presented in Figure 1.

Claims

1. A paper filler comprising a mixture of three calcium silicate minerals: magnesia feldspar, calcium aluminum feldspar, and diatomaceous earth, wherein the paper filler comprises, by X-ray diffraction, 0.1-15% by weight of calcium aluminum feldspar, 0.1-50% by weight of diatomaceous earth, and 0.1-15% by weight of magnesia feldspar, based on the total weight of the filler.

2. The paper filler according to claim 1, wherein the paper filler comprises a mixture of the three calcium silicate minerals, as determined by X-ray diffraction, and the total amount of the mixture is ≥0.3% by weight, preferably 0.3-60% by weight, based on the total weight of the filler.

3. The paper filler according to claim 1 or 2, wherein the mixture of the three calcium silicate minerals comprises, as determined by X-ray diffraction: i) wollastonite and calcium aluminum feldspar in a weight ratio of 30:1 to 1:2, preferably 20:1 to 1.2, and / or ii) wollastonite and magnesium feldspar in a weight ratio of 10:1 to 2:1, preferably 8:1 to 2:1, and / or iii) calcium aluminum feldspar and magnesium feldspar in a weight ratio of 5:1 to 1:5, preferably 3:1 to 1:

3.

4. The paper filler according to any one of claims 1-3, wherein the paper filler has a Ca content determined by CaO in X-ray fluorescence measurements of ≥50% by weight, preferably 20-70% by weight, based on the total weight of the filler.

5. The paper filler according to any one of claims 1-4, wherein the paper filler has a volumetric median particle size d as measured by using a laser diffraction system. 50 The thickness ranges from 0.8 to 6 μm, with 1.0 to 3.0 μm being preferred.

6. The paper filler according to any one of claims 1-5, wherein the paper filler further comprises one or more components selected from the group consisting of calcite, calcium hydroxide, lime, quartz, calcium aluminate, tricalcium aluminate, feldspar, anhydrous calcium sulfate, serpentine, white silica, clay, spinel, and mixtures thereof.

7. The paper filler according to any one of claims 1-6, wherein the paper filler comprises lime, as determined by X-ray diffraction, wherein the amount of lime is >3 to 30% by weight, preferably 4 to 30% by weight, based on the total weight of the filler.

8. The paper filler according to any one of claims 1-7, wherein the paper filler is obtained by incinerating deinking sludge, preferably from white recycled paper made of tissue paper, supercalendered paper or newsprint, at a temperature of at least 800°C, preferably at least 850°C.

9. The paper filler according to any one of claims 1-8, wherein the paper filler is an alkaline paper filler.

10. A paper product prepared from paper fillers and papermaking ingredients according to any one of claims 1-9, wherein the papermaking ingredients comprise pulp, preferably virgin pulp and / or recycled pulp obtained from paper and / or paperboard recycling.

11. The paper product of claim 10, wherein the paper filler is present in an amount of 0.3-10% by weight, based on the total weight of the paper product.

12. The paper product according to any one of claims 10 or 11, wherein the paper product i) has a surface pH of 7.9 or higher, preferably 8.0 or higher, most preferably 8.1 or higher, and / or ii) when pulped in water, results in a water pH of 9.4 or higher, preferably 9.5 or higher.

13. The paper product according to any one of claims 10-12, wherein the paper product is a recycled paper product, preferably a boxboard such as coated or uncoated boxboard, or a container board such as linerboard, corrugated board and double-sided paper.

14. The paper product according to any one of claims 10-13, wherein the paper product, when incinerated in a microwave muffle furnace at 850°C ± 10°C, has a lime content determined by X-ray diffraction of >3 to 40% by weight, preferably 4 to 40% by weight, based on the total weight of the paper product.

15. Use of the paper filler according to any one of claims 1-9 as an alkaline paper filler in a paper product, wherein the paper product is preferably a recycled paper product, more preferably a boxboard such as coated or uncoated boxboard, or a container board such as linerboard, corrugated board and double-sided paper.

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