Method for producing bleached pulp, bleached pulp and use thereof

Abstract

The invention relates to a method for obtaining bleached pulp, to bleached pulp, and to the use thereof. The one-stage method for obtaining bleached pulp is based on the Acetosolv method using phosphoric acid as a catalyst.

Description

[0001] Process for the production of bleached pulp, bleached pulp, and their use

[0002] The invention relates to a process for producing bleached pulp, bleached pulp, and their use.

[0003] Pulp is an important raw material, including for paper production. Pulp production varies regionally from a variety of raw materials, mostly from wood chips.

[0004] The wood chips are digested using various processes. The dominant process is the so-called sulfate process, in which the raw material is digested using caustic soda and sodium sulfide at pressures of 0.8 MPa to 1.0 MPa and temperatures of around 160 °C to 180 °C. The resulting pulp must then be bleached, a complex process. The regeneration of the digestion chemicals contained in the resulting black liquor is also complex in terms of energy consumption and the necessary, multi-stage plant technology. The sulfite process, which also represents the state of the art, includes some embodiments at temperatures around 140 °C and increased pressures, primarily due to the base used and the pH value applied. These lead to more easily bleachable pulp, but also require very complex and expensive chemical regeneration.

[0005] The Acetosolv process has been known since the 1920s. The pulping process uses acetic acid catalyzed by hydrochloric or sulfuric acid at pressures of 0.8 MPa to 1.5 MPa and temperatures of 180 °C. It yields partially acetylated pulp, which is subsequently bleached. Due to the aggressive conditions, defects such as corrosion in the equipment and product damage due to severe cellulose degradation occur. Therefore, the process has not yet been scaled up to industrial scale.

[0006] EP 0 325 890 A1 discloses a process for separating lignin from cellulosic masses or lignocelluloses which are exposed to ozone in the presence of a C 1-3 fatty acid and acetic acid, so that the solubility of the lignin in acetic acid is improved by an oxidative conversion.

[0007] DE 10 2016 225 827 B4 describes a two-stage pulping process for the chemical fractionation of lignocellulose, in which the lignocellulose is treated with steam or water in the first stage at a pressure of more than 1 bar and temperatures above 100°C. Subsequently, it is treated with an extraction solution consisting of water and at least one lignin-dissolving organic solvent, such as aliphatic alcohols, and a catalyst, such as inorganic acids, in particular sulfuric acid, at more than 1 bar and temperatures above 80°C. DE 3445 132 C2 discloses a process for pulping comminuted wood and annual plants in acetic acid with small amounts of hydrochloric acid, the resulting pulp having a kappa number of approximately 30. The resulting pulp can then be further extracted with acetic acid and hydrogen peroxide and bleached in a further step.

[0008] WO 2011 / 073284 A1 discloses a process for extracting hemicelluloses and lignin from lignocellulose-containing biomass. In a first pre-hydrolysis step, the biomass is contacted with a digestion solution comprising 5 to 95 wt.% acetic acid at a temperature of 80-195°C. In a further step, the thus pretreated biomass is subjected to an intermediate wash with acetic acid and, in a subsequent digestion step, is contacted with a digestion solution comprising 5 to 95 wt.% peracetic acid at 50-95°C. The resulting pulp has a kappa number in the range of 16-40 and a brightness according to ISO 2470-1 in the range of 31-43.

[0009] The aim is therefore to provide a simplified, less complex process for the production of bleached pulp, which overcomes the above-mentioned disadvantages of the state of the art and, in particular, enables the production of bleached pulp in an industrially scalable process with improved properties.

[0010] According to the invention, this object is achieved by a method and a bleached pulp according to the independent claims. Advantageous embodiments of the invention are specified in the dependent claims. Furthermore, this object is achieved by the use of the method and the bleached pulp.

[0011] The main claim of the invention relates to a process for producing bleached pulp comprising a modified Acetosolv process. The modified Acetosolv process is characterized in that the at least one catalyst is selected from oxygen acids of phosphorus with an oxidation number of +5, phosphates, and mixtures thereof; and that at least one oxidizing bleaching agent comprising hydrogen peroxide is added to the pulping solution; and that the process takes place at atmospheric pressure.

[0012] This advantageously avoids the deficiencies, such as corrosion phenomena, associated with previously known catalysts such as hydrochloric or sulfuric acid, and enables the industrial production of bleached pulp based on an acetosolve process. Furthermore, the process according to the invention advantageously enables pulping and bleaching in a single process step, in a single-stage process that can be carried out under atmospheric pressure.

[0013] Phosphates refer to the salts and esters of orthophosphoric acid H3PO4, such as primary, secondary, and tertiary phosphates. Primary phosphates are also called dihydrogen phosphates, e.g., sodium dihydrogen phosphate NaH2PO4. Secondary phosphates are also called hydrogen phosphates, e.g., disodium hydrogen phosphate Na2HPO4. A tertiary phosphate, for example, is sodium phosphate NasPO4.

[0014] The digestion solution in the Acetosolv process comprises an aqueous acetic acid to which at least one catalyst and at least one oxidizing bleaching agent are added.

[0015] Atmospheric pressure refers to the prevailing air pressure at any location on Earth where the procedure is carried out, e.g. the mean air pressure of the atmosphere at sea level, which is 101,325 Pa by default.

[0016] In preferred embodiments, the process for producing bleached pulp comprises the following steps: a) providing mechanically comminuted cellulose-containing plant components, b) adding the mechanically comminuted cellulose-containing plant components to a digestion solution comprising aqueous acetic acid, c) adding at least one catalyst and at least one oxidizing bleaching agent comprising hydrogen peroxide, d) heating the digestion solution with the mechanically comminuted cellulose-containing plant components, characterized in that the at least one catalyst is selected from oxygen acids of phosphorus with the oxidation number +5, phosphates, and mixtures thereof, and that the process takes place at atmospheric pressure.

[0017] This advantageously achieves pulping and bleaching in a single process step – step d) – and provides a single-step process for the production of bleached pulp that does not require complex plant technology, operates at atmospheric pressure, and thus offers improvements in terms of energy consumption and the hazard potential of the chemicals used. Furthermore, it enables the production of in-situ functionalized pulp, which, as a cellulose monomaterial, opens up further application possibilities. Furthermore, the pulping solution, catalyst, and bleaching agent used enable universal delignification capabilities.Furthermore, the process advantageously achieves yields of bleached pulp in the range of 40% to 60% based on wood as the cellulose-containing plant components used and 50% to 80% based on non-wood plants as the cellulose-containing plant components used, whereby the yield refers to the percentage of the mass of the pulping material, i.e. the bleached pulp, of the mass of the cellulose-containing plant components used, in each case based on the dry mass. Furthermore, such a process can be used for a variety of possible cellulose-containing plant components as starting material. Furthermore, energy can be saved by means of the process according to the invention due to the low process temperatures.An in-situ functionalized pulp within the meaning of the invention refers to a pulp that undergoes esterification of the hydroxyl groups during delignification, resulting in a degree of substitution (abbreviated DS value) or degree of acetylation in the range of 0.1 to 0.9. Such pulps can advantageously be adapted to the subsequent function / application of the pulp through partial derivatization during production. A cellulose monomaterial within the meaning of the invention means that, in the application case, the product consists of only one cellulose-based material and contains no foreign components, e.g., plastics.

[0018] In embodiments, steps b) and c) can be performed sequentially or simultaneously. In further embodiments, step d) occurs after step c) or simultaneously with step c).

[0019] Preferably, steps b), c) and d) are carried out simultaneously.

[0020] This advantageously enables the production of bleached pulp in a single-step process. Furthermore, the pulp produced in this way advantageously has a kappa number in the range of 1 - 15 according to DIN 54357 and a whiteness of 45 - 95% according to DIN 3145-1. Likewise advantageously, the pulp produced in this way can be used directly - i.e. without further process steps - for example in the production of paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives and / or barrier films. In further embodiments, it is advantageous if the cellulose-containing plant components are comminuted such that they have a homogeneous size distribution. A homogeneous size distribution means that 80% of the comminuted cellulose-containing plant components have a size in the range of 15 mm x 10 mm x 3 mm to 40 mm x 30 mm x 4 mm (length x width x thickness).

[0021] Cellulose-containing plant components include wood, annual plants, grasses, biogenic residues and / or waste wood.

[0022] Wood refers to hardwoods, such as beech or aspen, and softwoods, such as spruce or pine. Annual plants refer to plants that require a growing season from seed germination to the development of the entire plant, flower formation, and fertilization, all the way to the ripening of the new seed, such as hemp. Grasses refer to sweet grasses, such as miscanthus.

[0023] Biogenic residues refer to wood residues that arise during the felling of wood, during the treatment and processing of wood, but also to other plant, harvest and processing residues that arise as residues in agriculture, such as straw, harvest residues from root crops such as potatoes or beets.

[0024] Waste wood refers to used wood of waste wood classes A1 and A2 according to the German Waste Wood Ordinance (AltholzV), which has already been put to a specific use and is available as waste or secondary raw material, such as beams from roof trusses.

[0025] In embodiments, it is advantageous if the weight ratio of the cellulose-containing plant components to the digestion solution is in the range of 1:1 to 1:14.

[0026] In embodiments, the reaction temperature of the digestion solution is 80 °C to 120 °C.

[0027] In preferred embodiments, heating in step d) is carried out with constant mixing until the boiling point of the pulping solution is reached. This can advantageously improve pulping and bleaching, making the recovery of the bleached pulp more efficient.

[0028] In further preferred embodiments, the oxygen acids of phosphorus with the oxidation number +5 are H3PO4 and / or polyphosphoric acids of the formula H n +2PnO3n+i with n = 3 to 8.

[0029] This advantageously avoids known deficiencies of previous catalysts, such as corrosion phenomena. Furthermore, the catalysts according to the invention enable the economical production of bleached pulp in an atmospheric pressure process. Furthermore, the aforementioned oxygen acids of phosphorus enable stabilization of the peroxides and minimize hydrolysis of the carbohydrates.

[0030] In preferred embodiments, the digestion solution is an aqueous acetic acid with a concentration in the range of 50 wt% to 95 wt%.

[0031] This advantageously results in savings in the use of chemicals, digestion solution, catalyst, and bleaching agents, as well as energy costs. Furthermore, it can minimize corrosion on the equipment.

[0032] It is advantageous to select the concentration of aqueous acetic acid depending on the lignification of the cellulose-containing plant components used and the further processing of the resulting pulp. In principle, it is advantageous to select a higher concentration of aqueous acetic acid for more lignified cellulose-containing plant components used.

[0033] In further embodiments, the digestion solution is an aqueous acetic acid with a concentration in the range of 70 wt% to 75 wt%. This is advantageous when biogenic residues are used as cellulose-containing plant components.

[0034] In further preferred embodiments, 0.05 wt.% to 1 wt.% of the at least one catalyst and 1 wt.% to 10 wt.% of the at least one bleaching agent are added, in each case based on the amount of the digestion solution in step c).

[0035] This advantageously allows for efficient pulping and bleaching in a single process step (step c) in a single-stage process. Furthermore, economical processing times are achieved.

[0036] In further embodiments, the digestion solution has a pH in the range of 1 to 4, preferably in the range of 2 to 3.

[0037] In further preferred embodiments, the mechanically comminuted cellulose-containing plant components are impregnated with the digestion solution, the at least one catalyst and / or the at least one oxidizing bleaching agent after step a) and before step b).

[0038] This advantageously improves the digestion and bleaching, so that the process times can be reduced.

[0039] Impregnation, in the sense of the invention, means that the mechanically comminuted cellulose-containing plant components are brought into contact with the digestion solution, the at least one catalyst, and / or the at least one bleaching agent. In embodiments, impregnation is carried out by dipping, soaking, or spraying.

[0040] In preferred embodiments, the process comprises at least one further step, wherein the at least one further step is washing the obtained bleached pulp, sorting the washed bleached pulp, and / or circulating the obtained mixture.

[0041] Advantageously, the washing process removes the digestion solution, the at least one catalyst, and the bleaching agent. In some embodiments, washing is carried out with water or an alkaline wash. Alkaline wash refers to washing with an alkaline solution with a pH value greater than 7. Furthermore, sorting advantageously separates the coarse material and classifies the obtained pulp for various downstream processes. In some embodiments, the obtained pulp is sorted based on particle size. This advantageously allows for the removal of insufficiently digested components, so-called coarse materials, which can then be subjected to a further digestion step if necessary.

[0042] Circulating the resulting mixture of mechanically comminuted cellulose-containing plant components, pulping solution, at least one catalyst, and at least one bleaching agent intensifies pulping and bleaching. In further embodiments, the circulation is achieved by stirring.

[0043] In further preferred embodiments, the resulting mixture is circulated for a period of 1.5 to 8 hours.

[0044] This advantageously improves the duration and uniformity of the digestion and bleaching.

[0045] If the mechanically comminuted cellulose-containing plant components are impregnated with the digestion solution, the at least one catalyst, and / or the at least one bleaching agent after step a) and before step b), the circulation times can be in the lower range, e.g., 1 to 4 hours. If no impregnation occurs, the circulation times can be in the upper range, e.g., 4 to 8 hours.

[0046] In preferred embodiments, the bleached pulp obtained is washed with a sodium hydroxide solution.

[0047] This advantageously achieves a neutralization of the cooking acid.

[0048] A further aspect of the invention relates to a product obtainable by the process according to the invention.

[0049] Advantageously, the product obtained by the process according to the invention can be used as a starting material for the production of paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives and / or barrier films.

[0050] A further aspect of the invention relates to a bleached pulp having a kappa number according to DIN 54357 in the range from 1 to 15, a whiteness in the range from 45% to 95% according to DIN 3145-1, a hemicellulose content in the range from 3% to 25%, and a degree of acetylation of 0.1 to 0.9. Such a pulp is advantageously suitable for further processing into paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives, and / or barrier films. Furthermore, such a pulp is advantageously functionalized in situ, e.g., partially acetylated.

[0051] A bleached pulp according to the invention comprises a fibrous mass containing cellulose, cellulose derivatives, hemicelluloses and residual lignin.

[0052] Chemical pulp means high-purity cellulose with a cellulose content of at least 90% a-cellulose, which serves as a starting material for cellulose forming and derivatization and for the production of regenerated cellulose, also known as regenerated cellulose fibers.

[0053] Regenerated cellulose fibers are fibers made from natural, renewable raw materials that are produced through chemical processes, such as viscose, modal, or lyocell fibers.

[0054] Cellulose derivatives refer to chemical derivatives of cellulose obtained by modifying or substituting the hydroxy groups of anhydroglucose units (AGU), e.g., by methylation, ethylation, acetylation, or nitration. Well-known cellulose derivatives include cellulose ethers and cellulose esters.

[0055] Barrier films are dense papers that form a barrier against air, oxygen, aromas and fats, which can be in the form of individual transparent barrier films or as barrier coatings.

[0056] The kappa number indicates the residual lignin content of the pulp obtained, which is determined according to DIN 54357.

[0057] The degree of whiteness refers to the spectral reflection factor at a wavelength of 457 nm and is determined according to DIN 53145-1.

[0058] Hemicelluloses are polysaccharides composed of a variety of possible monomers, such as hexoses and pentoses. Examples of hemicelluloses are xylan and mannan, whose content can be determined from the mass difference between holocellulose and cellulose.

[0059] The degree of acetylation refers to the degree of substitution (DS) of the bleached pulp. The degree of substitution is defined as the average number of hydroxyl groups esterified with acetyl groups per anhydroglucose unit (AGU) of cellulose.

[0060] In preferred embodiments, the bleached pulp has a drainage resistance of 85 SR after 6,000 revolutions of PFI refining according to DIN EN ISO 5264-2.

[0061] SR means the freeness of the bleached pulp, which is determined as the Schopper-Riegler degree (SR) according to DIN EN ISO 5267-1. In further preferred embodiments, the bleached pulp has a DP range of 300 to 1,200, preferably from 450 to 1,000 and particularly preferably from 550 to 800, an α-cellulose content in the range of > 80 wt.%, preferably > 90 wt.% and particularly preferably ≤ 95 wt.%, a hemicellulose content in the range of < 20%, preferably ≤ 10 wt.% and particularly preferably a maximum of 5 wt.%, and a kappa number below 5, preferably below 3 and particularly preferably below 1.5.

[0062] Such pulp is advantageously suitable for the production of the above-mentioned types of regenerated cellulose fibres and cellulose derivatives.

[0063] DP range means the average degree of polymerization of the pulp, which is usually determined using aqueous copper(II) ammonium hydroxide (Cuoxam) solutions according to, for example, TS 3852 - Method for determining the viscosity of cotton and regenerated cellulose fibers / fibers in copper ammonium hydroxide (Cuoxam) solution or using aqueous copper(II) ethylenediamine hydroxide (Cuen) solution according to DIN EN 60450.

[0064] A bleached pulp with a DP of around 1,000 can be used advantageously as a raw material for the production of cellulose triacetate or textile CA fibers (acetate fibers), with a DP of around 800 as a raw material for the production of sustainable viscose or modal fibers, and with a DP of around 600 as a raw material for the production of lyocell fibers.

[0065] In further preferred embodiments, the bleached pulp has metal contents of <10 ppm for the sum of all heavy metals from the group consisting of iron, copper, manganese, chromium, and / or nickel, <200 ppm for the alkaline earth metals magnesium and / or calcium, and <100 ppm for the alkali metals sodium and / or potassium. Such a pulp is advantageously suitable as a chemical pulp for the production of regenerated cellulose or cellulose derivatives.

[0066] A further aspect of the invention relates to barrier films produced from a product of the process according to the invention or from a bleached pulp according to the invention, characterized in that the barrier films are slightly permeable to air according to Bendtsen in accordance with ISO 5636-3 and / or have a barrier to fat and flavors with a Kit value > 12 according to TAPPI T-559.

[0067] Such barrier films are advantageously suitable as impermeable papers, with the barrier to grease being determined according to TAPPI T-559. Furthermore, such barrier films are advantageously low in air permeability according to Bendtsen in accordance with ISO 5636-3. Low in air permeability, as defined by the invention, means values ​​below 0.38 pm / Pa s according to Bendtsen in accordance with ISO 5636-3. Greaseproof, as defined by the invention, means a Kit value > 12 according to TAPPI T-559.

[0068] A further aspect of the invention relates to the use of the product of the process according to the invention and / or the bleached pulp according to the invention for the production of paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives and / or barrier films.

[0069] Advantageously, a large number of products can thus be produced from the product of the process according to the invention and / or the bleached pulp according to the invention.

[0070] A further aspect of the invention relates to the use of oxygen acids of phosphorus with the oxidation number +5, phosphates and mixtures thereof as catalyst in a process for producing bleached pulp from cellulose-containing plant components, preferably wood, annual plants, grasses, biogenic residues and / or waste wood.

[0071] This advantageously overcomes the shortcomings of known catalysts, such as corrosion phenomena, and enables the industrial production of bleached pulp using acetic acid as the digestion solution.

[0072] For the realization of the invention, it is also expedient to combine the above-described inventive embodiments, embodiments and features of the claims.

[0073] Examples of implementation

[0074] The invention will be explained in more detail below using an exemplary embodiment. This exemplary embodiment is intended to describe the invention without limiting it.

[0075] The invention is explained in more detail with the aid of drawings.

[0076] Fig. 1 is a flow diagram of an embodiment of the process according to the invention for obtaining bleached pulp, and

[0077] Fig. 2 shows a flow diagram of a further embodiment of the process according to the invention. Figure 1 shows an embodiment of a process for obtaining bleached pulp, wherein the entire process takes place at atmospheric pressure and the pulping and bleaching occur in a single process step. According to Figure 1, in step a), mechanically comminuted cellulose-containing plant components, e.g. wood, annual plants, grasses, agricultural residues and / or waste wood, are provided. It is advantageous if the cellulose-containing plant components are in the form of wood chips. These are added in step b) to a pulping solution, an acetic acid with a concentration of 70 wt.%. It can also be advantageous if the comminuted cellulose-containing plant components are impregnated with the pulping solution before step b), e.g. by spraying.In embodiments, impregnation of the cellulose-containing plant components with the catalyst and the bleaching agent may also be advantageous, for example, before step b) and / or c). This improves the digestion and bleaching, which can lead to a reduction in the overall process time. In step c), phosphoric acid H3PO4 is added as a catalyst and hydrogen peroxide as a bleaching agent, with 0.5 wt.% phosphoric acid and 5 wt.% hydrogen peroxide being added, each based on the mass of the digestion solution. In step d), the resulting mixture of cellulose-containing plant components, digestion solution, catalyst, and bleaching agent is heated to boiling point, in this example up to 104°C, and constantly mixed. In embodiments, a phosphate, for example, sodium hydrogen phosphate, can be added as a catalyst in step c), which forms phosphoric acid in the acetic acid digestion solution.Steps b), c) and d) can be carried out sequentially or simultaneously.

[0078] The bleached pulp thus obtained can be subjected to further, known process steps for further processing into paper or fibers.

[0079] Figure 2 shows a further embodiment of the process according to the invention, wherein steps a) to d) are carried out according to Figure 1. The heating of the digestion solution (step d)) is followed by circulation of the resulting mixture or is carried out simultaneously for a duration of 1.5 h to 8 h. The bleached pulp thus obtained can be washed in a subsequent step in order to remove the residues of the digestion solution, the catalyst and the bleaching agent. The washing can be carried out with water or an alkaline wash with a sodium hydroxide solution. The washed, bleached pulp is then sorted. The sorting can be carried out on the basis of particle size so that any insufficiently digested pulp can be subjected to further digestion.The thus sorted, washed, and bleached pulp can be used in known processes for the production of paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives, and / or barrier films.

[0080] In a further embodiment, the process according to the invention is carried out in such a way that the steps b) adding the mechanically comminuted cellulose-containing plant components to a digestion solution comprising aqueous acetic acid, c) adding at least one catalyst and at least one bleaching agent comprising hydrogen peroxide, and d) heating the digestion solution with the mechanically comminuted cellulose-containing plant components are carried out simultaneously. Table 1 below shows the parameters of the individual process steps of WO 2011 / 073284 A1 and the properties of the resulting pulp in comparison to the process according to the invention.

[0081] Table 1:

Claims

Patent claims 1. A process for producing bleached pulp comprising a modified Acetosolv process, characterized in that the at least one catalyst is selected from oxygen acids of phosphorus with an oxidation number of +5, phosphates, and mixtures thereof; and that at least one oxidizing bleaching agent, comprising hydrogen peroxide, is added to the pulping solution, and that the process takes place at atmospheric pressure.

2. A process for producing bleached pulp, comprising the following steps: a) providing mechanically comminuted cellulose-containing plant components, b) adding the mechanically comminuted cellulose-containing plant components to a digestion solution comprising aqueous acetic acid, c) adding at least one catalyst and at least one bleaching agent comprising hydrogen peroxide, d) heating the digestion solution with the mechanically comminuted cellulose-containing plant components, characterized in that the at least one catalyst is selected from oxygen acids of phosphorus with the oxidation number +5, phosphates and mixtures thereof, and that the process takes place at atmospheric pressure.

3. Process according to claim 1 or 2, characterized in that the heating in step d) is carried out with constant mixing until the boiling point of the digestion solution.

4. Method according to one of claims 1 to 3, characterized in that the Oxygen acids of phosphorus with the oxidation number +5 H3PO4 and / or Polyphosphoric acids of the formula H n +2PnO3n+i with n = 3 to 8.

5. Method according to one of claims 1 to 4, characterized in that the The digestion solution is an aqueous acetic acid with a concentration in the range of 50 wt% to 95 wt%.

6. Process according to one of claims 1 to 5, characterized in that 0.05 wt.% to 1 wt.% of the at least one catalyst and 1 wt.% to 10 wt.% of the at least one oxidizing bleaching agent, in each case based on the amount of the digestion solution in step c).

7. The method according to any one of claims 1 to 6, characterized in that the mechanically comminuted cellulose-containing plant components are impregnated with the digestion solution, the at least one catalyst and / or the at least one oxidizing bleaching agent after step a) and before step b).

8. The method according to any one of claims 1 to 7, characterized in that the method comprises at least one further step, wherein the at least one further step is washing the obtained bleached pulp, sorting the washed bleached pulp, and / or circulating the obtained mixture.

9. Process according to claim 8, characterized in that the circulation of the resulting mixture takes place for a period of 1.5 to 8 hours.

10. A process according to claim 8, characterized in that the bleached pulp obtained is washed with a sodium hydroxide solution.

11. Product obtainable by the process according to any one of claims 1 to 10.

12. Bleached pulp having a kappa number according to DIN 54357 in the range of 1 to 15, a whiteness in the range of 45% to 95% according to DIN 3145-1, a hemicellulose content in the range of 3% to 25% and a degree of acetylation of 0.1 to 0.

9.

13. Bleached pulp according to claim 12, characterized in that the pulp has a drainage resistance of 85 SR after 6,000 revolutions of PFI refining according to DIN EN ISO 5264-2.

14. Bleached pulp according to one of claims 12 or 13, characterized in that the pulp has a DP range of 300 to 1,200, preferably from 450 to 1,000 and particularly preferably from 550 to 800, a content of α-cellulose in the range of >80 wt.%, preferably >90 wt.% and particularly preferably >95 wt.%, a hemicellulose content in the range of <20%, preferably <10 wt.% and particularly preferably of at most 5 wt.%, and a kappa number below 5, preferably below 3 and particularly preferably below 1.

5.

15. Barrier films made from a product according to claim 11 or from a bleached pulp according to one of claims 12 or 13, characterized in that they have low are permeable to air according to Bendtsen in accordance with ISO 5636-3 and / or have a barrier against fat and flavors with a Kit value > 12 according to TAPPI T-559.

16. Use of the product according to claim 11 and / or the bleached pulp according to claim 12 or 13 for the production of paper, chemical pulp, regenerated cellulose fibers, cellulose derivatives and / or barrier films.

17. Use of oxygen acids of phosphorus with the oxidation number +5, phosphates and mixtures thereof as catalyst in a process for producing bleached pulp from cellulose-containing plant components, preferably wood, annual plants, grasses, biogenic residues and / or waste wood.

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