阅读说明：本技术 纤维素材料塑化和粘度受控的纤维素材料 (Cellulosic material plasticization and viscosity controlled cellulosic material ) 是由 P·维尔塔宁 M·里斯托莱南 H·科索宁 T·泊伽莱恩 S·莫地格 J·赛普科塔 于 2019-05-10 设计创作，主要内容包括：本发明涉及一种以连续工艺生产粘度值在150ml/g至500ml/g之间的粘度受控的纤维素材料的方法,所述方法包括以下步骤：i)形成纤维素-水混合物(15),其包含水和经过化学处理的木基纤维素材料,该纤维素-水混合物(15)的干物质含量在3％至20％之间,ii)在塑化步骤(100)中在130℃至200℃之间的温度和3巴至15巴之间的压力下对形成的纤维素-水混合物(15)进行处理,持续至少5分钟,并且最长120分钟,同时对纤维素-水混合物(15)进行混合,并将热水和/或水蒸气供给到纤维素-水混合物中,从而获得处理过的混合物(18),以及iii)在减压步骤(105)中以受控的方式对处理过的混合物(18)进行减压,从而获得粘度受控的纤维素材料(20)。本发明还涉及粘度受控的纤维素材料和用于生产粘度受控的纤维素材料的系统。(The present invention relates to a method for producing a viscosity controlled cellulosic material with a viscosity value between 150ml/g and 500ml/g in a continuous process, said method comprising the steps of: i) forming a cellulose-water mixture (15) comprising water and chemically treated wood-based cellulose material, the cellulose-water mixture (15) having a dry matter content of between 3% and 20%, ii) treating the formed cellulose-water mixture (15) in a plasticizing step (100) at a temperature of between 130 ℃ and 200 ℃ and a pressure of between 3 bar and 15 bar for at least 5 minutes and up to 120 minutes while mixing the cellulose-water mixture (15) and feeding hot water and/or water vapour into the cellulose-water mixture, thereby obtaining a treated mixture (18), and iii) depressurizing the treated mixture (18) in a controlled manner in a depressurizing step (105), thereby obtaining a cellulose material (20) having a controlled viscosity. The invention also relates to a viscosity-controlled cellulosic material and a system for producing the viscosity-controlled cellulosic material.)

1. A method of producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process, the method comprising the steps of:

i) forming a cellulose-water mixture (15) comprising:

-water and

-a chemically treated wood based cellulosic material comprising bleached kraft pulp, bleached sulfite pulp and/or bleached soda pulp, the cellulose-water mixture (15) having a dry matter content between 3% and 20%,

ii) treating the cellulose-water mixture (15) formed in a plasticizing step (100) under the following conditions:

-a temperature between 130 ℃ and 200 ℃, and

-a pressure between 3 bar and 15 bar,

lasting at least 5 minutes, and up to 120 minutes,

at the same time, the user can select the desired position,

-mixing a cellulose-water mixture (15), and

-feeding hot water and/or water vapour into the cellulose-water mixture,

thereby obtaining a treated mixture (18),

and

iii) the treated mixture (18) after the plasticizing step (100) is depressurized in a controlled manner in a depressurization step (105) without steam explosion to maintain fiber integrity,

thereby obtaining a viscosity controlled cellulosic material (20).

2. The method according to claim 1, wherein the plasticizing step (100) is carried out by treating the formed cellulose-water mixture (15) in a continuous screw reactor, such as a horizontal screw reactor.

3. The method as claimed in any of the preceding claims, wherein the plasticizing step (100) is carried out by treating the cellulose-water mixture (15) formed in a continuous kneading reactor.

4. A method according to any one of the preceding claims, wherein the depressurisation in the depressurisation step comprises the steps of:

-cooling the treated mixture (18) by adding water.

5. The method according to any of the preceding claims, wherein the depressurization of the depressurization step (105) is performed for at least 1 second, preferably at least 3 seconds, and for at most 30 minutes.

6. The method of any one of the preceding claims, wherein the method further comprises:

-adding an activating agent to the cellulose-water mixture (15) to plasticize the wood-based cellulosic material (10) during the plasticizing step (100) in the presence of the activating agent, wherein the activating agent comprises or consists of the filtrate (102) obtained from the plasticizing step.

7. The method according to claim 6, wherein the total amount of filtrate (102) obtained from the plasticizing step is at least 50%, more preferably at least 70%, calculated on the total amount of activating agent.

8. A method according to any of the preceding claims, wherein the total amount of chemicals used is less than 3%, preferably less than 1%, calculated on the dry weight of the chemically treated wood-based cellulosic material, excluding any filtrate or water obtained from the plasticizing step.

9. The method according to any one of the preceding claims, wherein the duration of the plasticizing step (100) is at most 50 minutes, preferably equal to or less than 20 minutes.

10. The method of any one of the preceding claims, wherein the pressure of the plasticizing step (100) is between 5 bar and 10 bar, more preferably between 6 bar and 8 bar.

11. The method according to any one of the preceding claims, wherein the chemically treated wood-based cellulosic material has a viscosity value of between 400ml/g and 1200ml/g measured from the cellulose-water mixture (15).

12. The method as claimed in any one of the preceding claims, wherein the cellulose-water mixture (15) has a dry matter content of between 5% and 17%.

13. The method according to any one of the preceding claims, wherein the hemicellulose content of the cellulose-water mixture (15) is at least 0.5%, preferably between 10 and 33%% based on the dry weight of the chemically treated wood based cellulosic material.

14. The method according to any of the preceding claims, wherein the chemically treated wood based cellulosic material (10) has an alpha cellulose content of between 65% and 99.5% measured before the plasticizing step (100).

15. A viscosity controlled cellulosic material having a viscosity value of between 150ml/g and 500ml/g and a R18 solubility of between 60% and 87%, wherein the viscosity controlled cellulosic material comprises a wood based cellulosic material.

16. The method or controlled viscosity cellulosic material of any of the preceding claims, wherein the ISO brightness of the controlled viscosity cellulosic material is between 75% and 90%.

17. The process or controlled viscosity cellulosic material of any of the preceding claims, wherein the controlled viscosity cellulosic material has a viscosity value of between 170ml/g and 350 ml/g.

18. The process or controlled viscosity cellulosic material of any of the preceding claims, wherein the controlled viscosity cellulosic material has a crystallinity index of at least 74%, preferably at least 76%.

19. The process or controlled viscosity cellulosic material of any of the preceding claims, wherein the content of fibers having a length of less than 0.6mm measured from the controlled viscosity cellulosic material is between 10% and 30%.

20. The process or controlled viscosity cellulosic material of any of the preceding claims, wherein the alpha cellulose content of the controlled viscosity cellulosic material is between 67% and 99.5%.

21. The method or the controlled viscosity cellulosic material of any of the preceding claims, wherein the hemicellulose content of the controlled viscosity cellulosic material is between 0.5 dry wt% and 30 dry wt%.

22. The process or controlled viscosity cellulosic material of any of the preceding claims, wherein the controlled viscosity cellulosic material has an R18 solubility of at least 70% and at most 87%.

23. A system for producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process, the system comprising:

-means for forming a cellulose-water mixture (15),

-a continuous reactor (101) for treating a cellulose-water mixture in a plasticizing step (100) at a temperature between 130 ℃ and 200 ℃,

-mixing means for mixing the cellulose-water mixture during the plasticizing step,

heating means for increasing the temperature of the cellulose-water mixture in the continuous reactor, such as a feeder supplying water vapour to the continuous reactor,

-means for depressurizing the treated mixture (18) in a controlled manner without steam explosion after the plasticizing step (100), and

-optionally means for conveying at least a portion of the filtrate (102) obtained from the plasticizing step to the continuous reactor (101).

Technical Field

The present invention relates to methods and systems for making viscosity controlled cellulosic materials. The invention also relates to a viscosity-controlled cellulosic material.

Background

Cellulose, an abundant natural raw material, is a polysaccharide consisting of linear chains of thousands to tens of thousands of linked D-glucose units. For example, cellulose may be modified to man-made fiber (MMF). Viscose filaments are currently the most commonly produced MMF filaments.

Disclosure of Invention

The present invention discloses a new solution for manufacturing a viscosity controlled cellulosic material. According to the new process, it is possible to use a wood-based cellulose material and treat the wood-based cellulose material in a continuous process to obtain a viscosity controlled cellulose material having a viscosity value between 150ml/g and 500 ml/g.

Aspects of the invention are characterized by what is stated in the independent claims. Various embodiments of the invention are disclosed in the dependent claims.

A method of producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process may comprise the steps of:

i) forming a cellulose-water mixture comprising water and chemically treated wood-based cellulosic material, such as bleached kraft pulp and/or bleached sulfite pulp and/or bleached soda pulp, the cellulose-water mixture having a dry matter content of between 3% and 20%,

ii) treating the cellulose-water mixture formed in the plasticizing step at a temperature of between 130 ℃ and 200 ℃ and a pressure of between 3 bar and 15 bar, preferably between 5 bar and 10 bar, for at least 5 minutes and at most 120 minutes, while

-mixing a cellulose-water mixture, and

-feeding hot water and/or water vapour into the cellulose-water mixture,

thereby obtaining a treated mixture, an

iii) the treated mixture after the plasticizing step is decompressed in a controlled manner in a decompression step and no steam explosion occurs to maintain fiber integrity,

thereby obtaining a viscosity-controlled cellulosic material having a viscosity value between 150ml/g and 500 ml/g.

A system for producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process may comprise the following apparatus:

-means for forming a cellulose-water mixture,

a continuous reactor, for example a continuous kneader reactor, for treating the cellulose-water mixture in a plasticizing step at a temperature between 130 ℃ and 200 ℃,

-mixing means for mixing the cellulose-water mixture in a plasticizing step,

heating means for increasing the temperature of the cellulose-water mixture in the continuous reactor, e.g. a feeder for supplying water vapour to the continuous reactor, and

means for depressurizing the treated mixture in a controlled manner without steam explosion after the plasticizing step,

thereby obtaining a viscosity-controlled cellulosic material having a viscosity value between 150ml/g and 500 ml/g.

The system may comprise means for recycling at least a portion of the filtrate obtained from the plasticizing step to the continuous reactor. This can reduce the chemical consumption of the process and speed up the plasticizing step, thereby reducing manufacturing costs. Therefore, the production efficiency can be improved.

A viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g can have an R18 solubility between 60% and 87%. Thus, a method of producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process may be a method of producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g and a solubility of R18 between 60% and 87% in a continuous process.

The plasticizing step may be carried out by treating the formed cellulose-water mixture in a continuous reactor, such as a continuous screw reactor. The continuous screw reactor may be, for example, a horizontal screw reactor or a vertical screw reactor. Advantageously, the continuous reactor is a kneader reactor. Thus, the material to be treated can be easily and efficiently conveyed forward. Alternatively, the plasticizing step can be carried out without a screw reactor, for example by treating the cellulose-water mixture formed in an apparatus comprising chambers separated from each other.

During the plasticizing step, steam may be continuously or substantially continuously fed into the continuous reactor.

Advantageously, the following parameter combinations are used in the method: the duration of the plasticizing step may be at least 5 minutes or at least 6 minutes. Furthermore, the duration of the plasticizing step may be at most 50 minutes, more preferably at most 25 minutes, most preferably at most 20 minutes. Further, the temperature of the plasticizing step may be at least 140 ℃. Furthermore, the temperature of the plasticizing step may be at most 180 ℃, more preferably at most 170 ℃. Furthermore, the pressure of the plasticizing step may be at least 5 bar. Furthermore, the pressure of the plasticizing step may be less than 10 bar. The technical effect of the combination of parameters is that production efficiency and the quality of the resulting viscosity-controlled cellulosic material can be improved.

To further improve the process, the pH of the cellulose-water mixture may be at least 1, preferably at least 2. Furthermore, the pH of the cellulose-water mixture may be at most 6, preferably at most 5. Most preferably, the pH of the cellulose-water mixture is between 2 and 5.

The viscosity value of the chemically treated wood-based cellulosic material determined from the cellulose-water mixture prior to the plasticizing step may be at least 400ml/g, preferably at least 450 ml/g. Furthermore, the viscosity value of the chemically treated wood-based cellulosic material determined from the cellulose-water mixture prior to the plasticizing step may be at most 1400ml/g, more preferably at most 1200 ml/g. The viscosity range may improve the reaction during the plasticizing step and thus reduce the reaction time. Thus, the viscosity range can improve the production efficiency of the process.

The dry matter content of the cellulose-water mixture may be at least 3%, more preferably at least 5%. Furthermore, the dry matter content of the cellulose-water mixture may be less than 20%, more preferably less than 17%, most preferably less than 14%. Due to this very low consistency, the influence of the mixing on the plasticizing step can be improved. Furthermore, the quality of the obtained viscosity-controlled cellulosic material can be improved.

The chemically treated wood-based cellulosic material may have an ISO brightness determined prior to the plasticizing step of at least 70%, more preferably at least 86%. Therefore, the brightness of the final product can be improved. Furthermore, due to said brightness of the raw material, chemical consumption may be reduced.

The hemicellulose content of the chemically treated wood-based cellulosic material in the cellulose-water mixture may be at least 0.5%, more preferably at least 3%, such as 3% to 10%, most preferably equal to or less than 33%, such as 10% to 33%, based on the dry weight of the chemically treated wood-based cellulosic material. Such hemicellulose content may improve the yield and material efficiency of the manufacturing process, and hemicellulose may act as an internal activator, resulting in a faster reaction.

The chemically treated wood-based cellulosic material may have an extract content of less than 0.4%, more preferably less than 0.2%, as measured from the cellulose-water mixture prior to the plasticizing step, based on the dry weight of the chemically treated wood-based cellulosic material in the cellulose-water mixture. The low content of extract may improve the quality of the obtained viscosity controlled cellulosic material and the runnability of the manufacturing process.

The ash content of the chemically treated wood-based cellulosic material as measured from the cellulose-water mixture may be less than 0.7%, more preferably less than 0.5%, based on the dry weight of the chemically treated wood-based cellulosic material in the cellulose-water mixture. The low ash content can improve the quality of the obtained viscosity controlled cellulosic material and the runnability of the manufacturing process.

The content of fibers having a length of less than 0.6mm, determined from the cellulose-water mixture, may be between 10% and 30% based on the total content of chemically treated wood-based cellulosic material fibers. The degree of crimp of the wood-based cellulosic material measured from the cellulose-water mixture before the plasticizing step may be, for example, between 7% and 40%, preferably between 20% and 40%. These values may improve the properties of the obtained viscosity controlled cellulosic material, such as the strength properties of the product.

The sodium (Na) content of the cellulose-water mixture may be at least 200mg/kg, preferably 200mg/kg to 1500mg/kg, based on the dry weight of the chemically treated wood-based cellulosic material fibers. Due to the sodium content, the efficiency of the manufacturing process can be improved. If the sodium content is too low, the swelling degree of the cellulose-based fibers is insufficient and the chemicals may be difficult to access. Furthermore, if the sodium content is too high, the pH will be lowered and thus the chemical consumption will increase. Furthermore, water may not penetrate the fiber walls.

Chemically treated wood-based cellulosic materials, such as kraft pulp, are preferably so-called "never-dried pulp". Never-dried pulp is easier to handle than dried pulp, and furthermore, never-dried chemically treated wood-based cellulosic material can be a very cost-effective raw material for the disclosed manufacturing process.

The WRV of the cellulose-water mixture may be between 1 and 2g/g for easy chemical access, thereby reducing reaction time.

The chemically treated wood-based cellulosic material may have an alpha cellulose content of at least 65%, more preferably at least 67%, measured before the plasticizing step. Furthermore, the alpha cellulose content of the chemically treated wood-based cellulosic material measured before the plasticizing step may be less than 99.5%, more preferably at most 90%. Such alpha cellulose content can exert technical effects by improving yield and material efficiency, causing a rapid reaction, and acting as an internal activator.

The lignin content of the chemically treated wood-based cellulosic material measured before the plasticizing step may be less than 3%, more preferably less than 1.0%, most preferably less than 0.5%, based on the dry weight of the chemically treated wood-based cellulosic material. The low lignin content can improve the brightness of the product.

The chemically treated wood-based cellulosic material may have a softwood content of at least 70%, more preferably at least 85%, most preferably greater than 95%, e.g. 100%, measured prior to the plasticizing step, based on the dry weight of the chemically treated wood-based cellulosic material. Softwood has a lower total hemicellulose content, but a higher glucomannan content, and therefore, has better solubility and faster reaction than hardwood.

The mixing efficiency in the plasticizing step may be between 10kWh/ADt and 150 kWh/ADt. More preferably from 15kWh/ADt to 80kWh/ADt and most preferably from 20kWh/ADt to 50 kWh/ADt. The technical effect of the mixing efficiency is to obtain improved uniform quality, better solubility and faster reaction.

During the depressurization step, i.e. the depressurization step without steam explosion, (the rate of) the pressure drop may be lower than 15 bar/s, more preferably lower than 10 bar/s, e.g. equal to or lower than 5 bar/s, most preferably equal to or lower than 2 bar/s. Thus, steam explosion can be avoided, and the integrity of the fibers can be improved. Generally, as the rate of the pressure drop is reduced, the integrity of the fibers is improved.

The depressurization step without steam explosion, wherein the treated mixture 18 is depressurized, may take at least 1 second, more preferably at least 3 seconds, and most preferably at least 10 seconds. Furthermore, the pressure reduction step without steam explosion takes at most 30 minutes, more preferably less than 20 minutes, such as at most 10 minutes, most preferably equal to or less than 5 minutes. This has the technical effect of improving the process and maintaining the integrity of the fibers.

In order to depressurize the treated mixture in a controlled manner,

-water, and/or

-a mechanical arrangement

Can be used for obviously slowing down the pressure reduction step. Thus, an uncontrolled way of depressurizing the treated mixture, i.e. "steam explosion", can be avoided, wherein steam can escape very quickly. The mechanical arrangement for the depressurization step may comprise, for example, a chamber and at least one valve, preferably at least one chamber and at least two valves.

Additionally or alternatively, the mechanical arrangement may have separate chambers, each chamber having a reduced pressure compared to the previous chamber. In this case, the mechanical arrangement may have, for example, at least three chambers, for example 3 to 6 chambers. Furthermore, there is preferably at least one valve or similar solution between two adjacent chambers.

The depressurizing step may include the steps of:

-cooling the treated mixture by adding water.

Additionally or alternatively, the depressurizing step may include the steps of:

mechanically reducing the water vapor, for example by using:

-a screw, and/or

A chamber with a valve, and/or

-a compartment valve.

Most preferably, the depressurisation step has two means, water and mechanical solutions.

The method may further comprise the following:

-metering an activating agent into the cellulose-water mixture in order to plasticize the chemically treated wood-based cellulosic material in the presence of the activating agent during the plasticizing step.

The activator may comprise the filtrate obtained from the plasticizing step. The filtrate may comprise hydrolysate from the plasticizing step. The amount of filtrate may be more than 50%, more preferably more than 90%, most preferably at least 99% of the total amount of activating agent. Due to the filtrate, the total amount of chemicals added to the manufacturing process can be reduced, so that the manufacturing cost can be reduced, and the production efficiency can be improved. Furthermore, this may be an environmentally friendly way of manufacturing cellulose material with controlled viscosity.

Alternatively or additionally, the activator may comprise an acid solution, preferably an acid filtrate, from a chemical pulp mill. The amount of said acid filtrate from the chemical pulp may be at least 30%, more preferably at least 40%, most preferably at least 50%, calculated on the total amount of activating agent. Therefore, the manufacturing cost can be reduced, and the production efficiency can be improved.

Alternatively or additionally, the activating agent may comprise sulfuric acid or acetic acid, and the total amount of sulfuric acid and acetic acid is preferably less than 5%, such as at most 2%, more preferably less than 1.5%, such as at most 1.0%, most preferably less than 0.5%, calculated on the dry weight of the chemically treated wood based cellulosic material.

The total amount of added chemicals of the disclosed method may be less than 5%, such as at most 3%, more preferably less than 2%, such as at most 1%, most preferably less than 0.5%, such as at most 0.2%, or just 0%, excluding any recycled filtrate or water from the plasticizing step, calculated on the basis of the dry weight of the chemically treated wood-based cellulosic material. Thus, viscosity controlled cellulosic materials having viscosity values in the range of 150 to 500ml/g can be produced in a chemical-free or substantially chemical-free process. This can have a significant impact on production costs. Furthermore, the process may be an environmentally friendly way of manufacturing cellulose material with controlled viscosity.

The viscosity controlled cellulosic material may have a viscosity value of at least 170ml/g, preferably at least 180 ml/g. Furthermore, the viscosity controlled cellulosic material may have a viscosity value of at most 350ml/g, more preferably at most 300ml/g, most preferably at most 250 ml/g. Such viscosity values may result in improved and faster solubility of the resulting viscosity-controlled cellulosic material.

The obtained cellulose material with controlled viscosity may be washed with water in a washing step. Preferably, the temperature of the water used in the washing step is higher than 50 ℃, such as at least 70 ℃ and most preferably at least 85 ℃. Furthermore, advantageously, the temperature of the water is at most 100 ℃. The washing step can be used to wash at least a portion of the unwanted residue from the controlled viscosity cellulosic material. Therefore, the quality of the product can be improved.

Advantageously, at least a portion of the water used in the washing step is delivered to the cellulose-water mixture to increase the temperature of the cellulose-water mixture.

Optionally, the pH of the obtained viscosity-controlled cellulosic material may be adjusted in a pH adjustment step. Preferably, the target pH value in the pH adjustment step is between 4 and 9. By using water in the adjusting step, at least a portion of the unwanted residue can be washed from the viscosity controlled cellulosic material while adjusting the pH. The pH adjustment may increase the effectiveness of a dissolution step of the viscosity controlled cellulosic material, which may be subsequent to the pH adjustment step.

The obtained cellulose material with controlled viscosity can be dried to a dry matter content of at least 60% if desired, e.g. for transport.

Due to the novel process, the obtained viscosity controlled cellulosic material may have a crystallinity index of at least 74%, more preferably at least 75%, most preferably at least 76%.

Due to the novel process, the viscosity controlled cellulosic material produced according to the process may have an ISO brightness of at least 70%, typically between 75% and 90%. Therefore, the optical characteristics of the final product can be improved.

Furthermore, due to the novel process, the length weighted fiber length lc (l) of the viscosity controlled cellulosic material measured according to ISO16065-N may be at least 0.9mm, more preferably at least 1.0mm, most preferably at least 1.2 mm. Furthermore, the fiber content measured from the viscosity controlled cellulosic material with a length below 0.6mm may be between 10% and 30%. Such fiber content and length may improve the ease of use of the product, i.e. the product may be more easily handled and cleaned. In addition, the yield can be improved.

The viscosity controlled cellulosic material may have an alpha cellulose content of at least 67%, preferably at least 69%. Furthermore, the alpha cellulose content of the viscosity controlled cellulosic material is less than 99.5%, more preferably at most 90%. This content of alpha cellulose may improve reactivity and yield due to improved material efficiency. Furthermore, it may have an improved environmental impact.

The hemicellulose content of the viscosity controlled cellulosic material may be at least 0.5 dry weight%, more preferably at least 3 dry weight%, for example between 3 and 10 dry weight%. Such hemicellulose content may improve reactivity and further improve yield due to improved material efficiency. Furthermore, it may have an improved environmental impact.

As a result of the novel process, the R18 solubility of the viscosity-controlled cellulosic material may be at least 60%, more preferably at least 70%. Furthermore, the viscosity controlled cellulosic material may have an R18 solubility of up to 87%, more preferably up to 84%, for example between 70% and 84%. The R18 solubility describes the solubility of a material as measured by using an 18% NaOH solution. The value of R18 solubility discloses the insoluble portion of the material. The resulting viscosity-controlled cellulosic material may have good solubility due to the R18 solubility of the material. Therefore, the production efficiency of the regenerated cellulose material that can be produced from the cellulose material whose viscosity is controlled can be improved.

The sodium (Na) content of the viscosity-controlled cellulosic material may be at least 200mg/kg, for example between 200mg/kg and 1500mg/kg, based on the dry weight of the chemically treated wood-based cellulosic material fibers. The sodium content affects the solubility of the resulting viscosity-controlled cellulosic material, for example, by increasing the dissolution rate of the material. In addition, the viscosity can be improved.

The controlled viscosity cellulosic material may have a crimp level of at least 25%, more preferably at least 30%, for example at least 35%, most preferably at least 40%. Further, the controlled viscosity cellulosic material can have a crimp level of up to 90%, such as less than 85% or equal to or less than 80%. The degree of curl has an effect on the strength of the final product and the water removal properties of the product.

The viscosity controlled cellulosic material can have a Water Retention Value (WRV) of between 1g/g and 2 g/g. This may result in easier chemical entry and, therefore, faster reaction.

The lignin content of the viscosity controlled cellulosic material may be less than 1.5%, more preferably less than 1%, most preferably less than 0.5%. Such very low lignin content can increase the brightness of the product, with the effect on brightness increasing as the lignin content decreases.

The extract content of the viscosity controlled cellulosic material may be less than 0.2%, more preferably less than 0.1%. Such low extract content can improve the quality of the product.

The chemically treated wood-based cellulosic material may comprise bleached kraft pulp and/or bleached sulfite pulp and/or bleached soda pulp. Chemically treated wood-based cellulosic material may refer to bleached kraft pulp and/or bleached sulfite pulp and/or bleached soda pulp. Most preferably, the chemically treated wood-based cellulosic material is kraft pulp.

The invention does not relate to viscose, which can be manufactured from dissolving pulp. Viscose is an example of different kinds of cellulosic material obtained from different kinds of raw materials by using different kinds of processes. Viscose manufacture is generally an environmentally problematic and slow process. The new process may be an environmentally friendly solution to treat wood based cellulosic material to obtain a viscosity controlled cellulosic material with a specific viscosity value.

Thanks to the method, it is possible to manufacture a cellulose material with controlled viscosity by using a medium price material instead of an expensive organic solvent, and without the need to handle toxic products. Thanks to the new solution, the product can also be used as a raw material for cosmetic or food packaging products.

The yield of the manufacturing process depends on the raw materials and conditions of the process, such as the use of chemicals, temperature, dry matter content, pH level and duration of the plasticizing step. By using a novel manufacturing method, the yield of the method can be significantly increased. For example, rather than simply removing substantially all of the hemicellulose, the hemicellulose content of the manufactured product can be adjusted.

The new method can be quite simple. Furthermore, the new method can be easily operated. The new manufacturing process may also be environmentally friendly. By the new process, very small amounts of chemicals can be consumed. Furthermore, by using chemically treated cellulose-based raw materials, such as kraft pulp, a cellulose material with controlled viscosity can be obtained without further dosing of chemicals, e.g. after kraft pulping.

The product obtained from the process, i.e. the viscosity-controlled cellulosic material, typically has cold alkali solubility. The manufactured viscosity controlled cellulosic material can be modified to produce several different types of end products. Typically, no additional chemical treatment is required to dissolve the viscosity-controlled cellulosic material. Thus, a viscosity controlled cellulosic material may be more economical than other cellulosic materials treated with known methods.

Furthermore, due to the new process, the novel viscosity controlled cellulosic material product can be manufactured in a continuous process with good production efficiency.

Brief description of the drawings

The invention is explained below by means of the attached drawings, in which:

figures 1-3 schematically illustrate some example steps,

figures 4a-c show some photographs of experimental tests,

FIGS. 5a-c show micrographs of some experimental tests, an

Fig. 6a-11 show the test results of the experimental tests.

Detailed Description

In the disclosure below, all percentages are by weight, if not otherwise stated. All percentages relating to cellulosic material are on a weight basis if not otherwise stated.

All embodiments in this application are presented as illustrative examples and should not be considered as limiting.

Unless otherwise indicated, the following criteria (effective at 01/2019) and measurement methods refer to methods that can be used to obtain the parameter values:

-R18 solubility: t235cm-00

-consistency: ISO 638 (dry matter content)

-degree of curling [% ]: ISO16065-N

Ash content [% ]: mod ISO 2144

-lignin content [% ]: KCl 115b82

-extract content [% ]: mod.iso 14453

By using a microscope, it is possible to analyze softwood and/or hardwood microscopically.

WRV (g/g) measured according to ISO 23714:2014, which specifies the procedure for determining the Water Retention Value (WRV) of the various pulps.

Luminance [% ISO ]: ISO 2470-1

The alpha-cellulose content [% ] can be determined by using R18 solubility measurements,

hemicellulose content [% ] can be determined by measuring the total sugar content of the sample according to the standard SCAN-CM 71:09 and determining the hemicellulose content from the total sugar content.

The glucose content [% ] in the total sugar content can be determined by determining the total sugar content using the standard SCAN-CM 71:09 and determining the glucose content from said total sugar content.

-measuring the fiber properties according to standard ISO16065-2:2014 by using a Valmet fiber image analyser (Valmet FS 5). The weight of the sample should be at least 0.1g, such as 0.1g to 0.2g for hardwood samples, and at least 0.3g, such as 0.3 to 0.5g for softwood samples. ISO16065-2:2014 specifies a method for determining the fiber length by automated optical analysis using unpolarized light. The method is applicable to various slurries. However, for the purpose of ISO16065-2:2014, fibrous particles shorter than 0.2mm are not considered fibers and are therefore not included in the results.

-sodium content of feedstock [ mg/kg dry pulp ] and sodium content of viscosity controlled cellulosic material [ mg/kg dry material ]: SFS-EN ISO 11885 using an ICP analyzer.

-measuring the viscosity [ ml/g ] according to ISO 5351: 2010. It involves determining the intrinsic viscosity number in Copper Ethylenediamine (CED) solutions. ISO 5351:2010 specifies a method that produces values that are estimates of specific viscosity numbers of slurries in dilute Copper Ethylenediamine (CED) solutions.

-measuring the crystallinity index [% ] according to the following method (RISE, Research of swedish):

WAXS (Wide-angle X-ray scattering) measurements were performed on an Anton Paar SAXSpoint 2.0 system (Anton Paar, Australia) equipped with a Microsource X-ray source (Cu Ka radiation, wavelength 0.15418nm) and a Dectiris 2D CMOS Eiger 1M detector (75 mm. times.75 mm pixel size). All measurements were performed at a beam size of about 500mm diameter, a stage temperature of 25 ℃ (using temperature control) and a beam path pressure of about 1-2 mbar. During the measurement, the sample-to-detector distance (SDD) was 111 mm. All samples were mounted on a Multi-Solid Sample Holder (Multi-Solid-Sample Holder, Anton Paar, Austria Graves). The sampler was then mounted on a VarioStage (Anton Paar, grizzly, austria). The sample was exposed to vacuum during the measurement. For 6 frames per sample, the duration of the detector reading per frame was 6 minutes, and the total measurement time per sample was 36 minutes. For all samples, the transmittance was determined and used to scale the intensity. The software used for instrument control was SAXSdrive version 2.01.224(Anton Paar, glaz austria) and post acquisition data processing was performed using software SAXSanalysis version 3.00.042(Anton Paar, glaz austria). The Crystallinity index (CrI) of the samples was determined according to Segal Signal height Method (Segal et al, 1959), reference Segal, L, Creely, J.J., Martin Jr., A.E., and Condrad, C.M. (1959), Empirical methods for Estimating the Crystallinity of natural Cellulose Using X-Ray diffraction instruments Using X-Ray diffractometers (An Empirical Method for Estimating the Degree of crystallization of natural Cellulose Using the X-Ray diffraction instrument), Textile Research Journal (Journal), 29, 786-794.

-measuring the Molar Mass Distribution (MMD) according to the following method:

tetrahydrofuran (THF) was used as the mobile phaseThe Molar Mass Distribution (MMD) of the cellulose derivative was determined by Size Exclusion Chromatography (SEC). The SEC system consisted of a Guard column, a PLgel 10 μm Guard 50X7.5mm and three PLgel 10 μm MIXED-B LS 300X 7.5mm columns (connected in series). Detection was performed using a refractive index detector (Waters 410). The sample was dissolved in THF (about 1.5mg/ml) and filtered (PTFE syringe filter 0.2 μm). The sample was not completely dissolved in THF. Replicate samples were analyzed. Calibration was performed using polystyrene standards with molecular weights of 3000 to 7270000. The calibration points are fitted to a linear function. MMD, Peak molar weight (Mp), weight average molar weight (M) were calculated by Polymer laboratories (Polymer laboratories, Agilent) using the Cirrus GPC software version 3.1_w) Number average molar weight (M)_n) And Polydispersity (PD) index (M)_w/M_n)。

The values measured/determined from the cellulose-water mixture 15 and/or the chemically treated wood-based cellulosic material 10 are values determined before the plasticizing step 100.

The value measured/determined from the viscosity controlled cellulosic material is the value determined after the plasticizing step 100.

The following reference numerals are used in this application:

10 a chemically treated wood-based cellulosic material,

15 of a cellulose-water mixture, the cellulose-water mixture,

18 of the mixture after the treatment, and,

20 a cellulose material having a controlled viscosity,

30 dissolved cellulose material of controlled viscosity,

40 of the regenerated cellulose material, and,

90 the pre-treatment step comprises for example a pulper,

95 to form a cellulose-water mixture 15,

96 for forming the cellulose-water mixture 15,

100 of a plasticizing step, and a plasticizing step,

101 of a continuous reactor, a reactor for the continuous reactor,

102 of the filtrate obtained from the plasticizing step,

105 a step of reducing the pressure of the mixture,

the washing step 110 includes, for example, a washing press,

120, a drying step of drying the mixture,

121 a drying means for drying the mixture of the components,

130 a dissolution step of a viscosity controlled cellulosic material, and

140 further processing of the dissolved viscosity controlled cellulosic material.

Native cellulose is a linear compound with a simple chemical functionality of 3 hydroxyl groups for the glucose unit.

In the present application, the term "chemically treated wood-based cellulosic material 10" refers to kraft pulp, sulfite pulp and soda pulp, which may contain any wood-based cellulosic material, i.e. the chemically treated wood-based cellulosic material 10 may be derived from any wood material.

Further, the term "chemically treated wood-based cellulosic material 10" refers to a material that does not contain dissolving pulp. The term "dissolving pulp" refers to so-called dissolving pulp, which is bleached pulp having a cellulose content of more than 90% by weight and a particularly low hemicellulose content. The dissolving pulp can be dissolved in a specific solvent. However, the yield and production efficiency of the manufacturing process may not be as good as kraft, soda or sulfite pulp.

Further, the term "chemically treated wood-based cellulosic material 10" refers to a material that does not contain mechanical pulp. The term "mechanical pulp" refers to cellulose fibers separated from any wood-based cellulosic material by a mechanical pulping process. Preferably, the controlled viscosity cellulosic material 20 does not comprise mechanical pulp.

Kraft, soda and/or sulfite pulps, which may be dried and/or never dried pulps, may be chemically, physically or enzymatically pretreated to enhance the plasticizing effect. Never-dried pulp can be handled more easily and the use of never-dried pulp can reduce the manufacturing costs of the obtained viscosity controlled cellulosic material, and therefore, preferably, the pulp comprises or consists of never-dried pulp.

In the present application, the term "cellulose material 20 with controlled viscosity" refers to a material that can be obtained from a chemically treated wood-based cellulose material 10 by using a plasticizing step and a pressure reduction step. Viscosity-controlled cellulosic materials typically have cold alkali solubility.

The term "cold alkali soluble" refers to plasticized cellulosic materials having cold alkali solubility, i.e., cellulosic materials with controlled viscosity that are soluble in an aqueous alkaline solution at a temperature of from-3 ℃ to-12 ℃, e.g., a temperature of from-5 ℃ to-8 ℃, and a NaOH content of between 5% and 10%, e.g., 7% to 8%.

The term "R18 solubility" refers to solubility in the case of no carbon sulfide treatment. The solubility of R18 was measured according to standard T235 cm-00.

The term "steam explosion" refers to a process in which the pressure is caused by superheated water and the pressure drop is faster than 15 bar/sec. This rapid pressure release can result in significant fiber structure changes.

Preferably, the amount of non-wood material in the controlled viscosity cellulosic material is less than 20%, more preferably less than 10%, most preferably less than 5%, e.g. at most 2%, calculated on the dry weight of the controlled viscosity cellulosic material. In an advantageous embodiment, the controlled viscosity cellulosic material does not comprise non-wood materials at all. The non-wood material may be agricultural residues, grasses or other plant matter, such as straw, coconut, leaves, bark, seeds, hulls, flowers, vegetables or fruits from cotton, corn, wheat, oats, rye, barley, rice, flax, hemp, abaca, sisal, jute, ramie, kenaf, sisal (bagass), bamboo or reed.

The chemically treated wood-based cellulosic material may be obtained from softwood trees such as spruce, pine, fir, larch, douglas fir or hemlock, or hardwood trees such as birch, poplar, alder, eucalyptus or acacia, or a mixture of softwood and hardwood.

The effectiveness of the plasticizing step 100 is generally dependent on the raw material, e.g., wood, used in the process. Thus, preferably the chemically treated wood based cellulose material comprises or consists of eucalyptus, birch, spruce and/or pine, the total amount of these woods preferably being more than 70%, more preferably at least 80%, most preferably at least 90%, calculated on the total amount of the chemically treated wood based cellulose material. This may improve the properties of the resulting product.

The chemically treated wood-based material preferably has a softwood content, measured from the cellulose-water mixture 15, of more than 30%, such as at least 50%, more preferably at least 70%, most preferably at least 90%, based on the dry weight of the chemically treated wood-based cellulosic material 10. The use of cork has an effect on the hemicellulose content. Cork has a high glucomannan content. In addition, cork can have better solubility and lower reaction time. Therefore, the production efficiency can be improved.

Most advantageously, the chemically treated wood based cellulosic material comprises at least 50%, more preferably at least 70% and most preferably at least 90% softwood kraft pulp, based on the dry weight of the chemically treated wood based cellulosic material, having:

-fibres having a length of more than 2mm,

-a lignin content of between 0 and 3%,

-a hemicellulose content between 0.5 and 33%, and

among these, advantageously, more than 70% of the fibres have a fibre length greater than 0.2mm and a width between 10 and 50 microns, when measured with a Valmet fibre image analyser (Valmet FS5) with the standard ISO16065-2: 2014. By using such materials, the properties and quality of the manufactured product can be improved.

The chemically treated wood-based cellulosic material 10 preferably has an alpha cellulose content of at least 65%, more preferably at least 67%, measured prior to the plasticizing step 100. Further, the chemically treated wood-based cellulosic material 10 preferably has an alpha cellulose content of less than 99.5%, more preferably equal to or less than 95%, most preferably equal to or less than 90%, measured before the plasticizing step 100. Due to said alpha cellulose content of the raw material, i.e. the chemically treated wood-based cellulose material 10, a high yield, i.e. a high material efficiency, can be obtained. Furthermore, the process can have short processing times (due to faster reaction).

The chemically treated wood-based cellulosic material 10 contains cellulosic material that may contain hemicellulose. Usually, lignin and wood extracts have been at least largely removed.

The chemically treated wood-based cellulosic material 10 can include cellulosic fibers that are separated from the cellulosic material by a chemical pulping process. Thus, lignin has been at least largely removed from the material. The chemically treated wood-based cellulosic material 10 can be unbleached or bleached. Preferably, the chemically treated wood-based cellulosic material 10 is bleached.

Since natural pulp fibers have a high crystallinity preventing chemicals from penetrating the fiber surface, it may be very difficult to treat them with chemicals. Due to the novel process disclosed in the present application, cellulose-based products can be produced with improved worker safety. For example, the highly toxic carbon disulphide used for the production of viscose can be replaced by safer raw materials.

The chemically treated wood based cellulosic material 10 is preferably kraft pulp and/or sulfite pulp and/or soda pulping to obtain a viscosity controlled cellulosic material 20 with good properties. Furthermore, by using these materials, a cellulose material with controlled viscosity can be produced in an environmentally friendly manner. Thus, the chemically treated wood-based cellulosic material 10 may comprise at least 70 wt.% or at least 80 wt.%, more preferably at least 90 wt.% or at least 95 wt.%, most preferably at least 98 wt.% or exactly 100 wt.% of bleached kraft pulp and/or sulfite pulp and/or soda pulp, based on the dry weight of the chemically treated wood-based cellulosic material 10. These raw materials may have the following advantages:

high yield, and

the reaction is accelerated during the plasticizing step 100 until the desired viscosity range is reached, due to the hemicellulose which tends to degrade to acids.

Most advantageously, the chemically treated wood-based cellulosic material 10 comprises kraft pulp, preferably bleached kraft pulp. The amount of bleached kraft pulp is preferably at least 50 wt.%, more preferably at least 80 wt.%, most preferably at least 90 wt.%, for example 100 wt.%, calculated on the total dry weight of the chemically treated wood-based cellulosic material 10. Bleached kraft pulp is an economical raw material with suitable properties for this new process. In addition, the use of kraft pulp can improve the properties of the resulting viscosity-controlled cellulosic material. Furthermore, kraft pulp may be an environmentally friendly raw material. Therefore, the yield and quality of the resulting product and the production efficiency of the manufacturing process can be increased.

The lignin content of the chemically treated wood-based cellulosic material 10 is preferably less than 3%, more preferably less than 1.0%, most preferably less than 0.5% based on the dry weight of the chemically treated wood-based cellulosic material. Thus, lignin, which may be detrimental to the process, does not reduce the efficiency of the process. Furthermore, a very low lignin content may increase the brightness value of the resulting product.

The chemically treated wood-based cellulosic material 10 may be pretreated for better manufacturing efficiency. Thus, the chemically treated wood-based cellulosic material 10 may have at least one pretreatment step 90 to pretreat the chemically treated wood-based cellulosic material 10 prior to the plasticizing step 100.

The pre-treatment step 90 may include, for example, a refining step. The refining step of the chemically treated lignocellulose material 10 may be performed with an apparatus capable of separating cellulose fibers and/or making cellulose fibers shorter. The pre-refining apparatus may be a refiner, such as a hammer mill, a tumbling mill, a rotary cutter, a conical refiner or a disc refiner.

In one embodiment, chemically treated wood-based cellulosic material 10 is preferably unrefined pulp due to increased cost and the impact of pre-refining on the properties of the manufactured product.

The mechanical energy used for refining is related to the resistance to drainage and can be measured by the Schopper Riegler (SR) freeness test. The Schopper Riegler (SR) freeness test provides an empirical measure of the drainage resistance of a slurry. The Schoerlerger (SR) freeness value can be determined using the SCAN-C19:65 test method. The chemically treated wood based cellulosic material 10, such as kraft pulp, preferably has a Schopper Riegler (SR) freeness of at most 35, more preferably at most 30, such as between 12 and 20, measured prior to the plasticizing step.

The pre-treatment step 90 may include the metered addition of a chemical, such as an acid. The pretreatment step may include, for example, the metered addition of acetic acid. The pre-treatment step including the metered addition of acid may reduce the time required for the plasticizing step 100. However, the addition of chemicals, such as acids, increases the manufacturing cost of the manufactured product. However, since the duration of the plasticizing step 100 is shortened, the production efficiency can be improved although the chemical cost is increased.

Due to the novel process, the properties of the resulting viscosity-controlled cellulosic material can be improved. Thus, the properties of the regenerated cellulose material 40 obtainable from the viscosity-controlled cellulose material 20 can also be improved. Further, since dissolving pulp is not required as a raw material, raw material cost can be reduced.

The hemicellulose content of the chemically treated wood-based cellulosic material 10 may be between 0 and 33 wt%. The hemicellulose content of the chemically treated wood based cellulosic material 10 is preferably at least 0.5 wt.%, more preferably at least 3 wt.%, or at least 5 wt.%, most preferably at least 10 wt.%. Further, the hemicellulose content of the chemically treated wood-based cellulosic material 10 is preferably at most 33 wt%, more preferably at most 20 wt%, most preferably at most 15 wt%. Higher hemicellulose content can be used to increase yield and achieve higher material efficiency. In addition, hemicellulose can act as an internal activator, improving the reaction and reducing the addition of other chemicals.

The chemically treated wood-based cellulosic material 10 can be processed in a continuous process to form a viscosity controlled cellulosic material 20. Due to the new continuous process, the production capacity can be increased and the production cost can be reduced, so that the production efficiency can be improved. Surprisingly, the brightness of the continuously manufactured product is also improved compared to the product obtained from a batch process.

A method of making a viscosity controlled cellulosic material 20 having a viscosity value between 150ml/g and 500ml/g in a continuous process can include the steps of:

i) forming a cellulose-water mixture 15 comprising chemically treated wood-based cellulosic material, the cellulose-water mixture having a dry matter content of between 3% and 20%,

ii) treating the cellulose-water mixture 15 formed in a plasticization step at a temperature between 130 ℃ and 200 ℃ and preferably at a pressure between 3 bar and 15 bar, more preferably between 5 bar and 10 bar, for at least 5 minutes and at most 120 minutes, while mixing the cellulose-water mixture 15 and supplying hot water and/or steam to the cellulose-water mixture, thereby obtaining a treated mixture 18, and

iii) the treated mixture 18 after the plasticizing step 100 is decompressed in a controlled manner in a decompression step 105 without steam explosion to maintain fiber integrity, thereby obtaining a cellulose material with controlled viscosity.

The step ii) of treating the cellulose-water mixture in the presence of hot water and/or water vapour in the plasticizing step 100 may activate the fibres.

The resulting viscosity controlled cellulosic material may have a polydispersity of less than 10, for example, up to 8, more preferably less than 7, most preferably less than 6, for example, up to 5. Further, the polydispersity may be at least 1. Due to the new continuous process, the polydispersity of the viscosity controlled cellulosic material 20 may be improved, i.e., the polydispersity value may be less than conventional. Thus, the properties and solubility of the viscosity-controlled cellulosic material 20 can also be improved.

A system for producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process may comprise the following means:

means for forming and/or feeding a cellulose-water mixture to a continuous reactor,

a continuous reactor, for example a continuous kneader reactor, for treating the cellulose-water mixture in a plasticizing step 100 at a pressure of between 5 bar and 10 bar,

mixing means, such as a mixing device, for mixing the cellulose-water mixture during the plasticizing step,

heating means for increasing the temperature of the cellulose-water mixture in the continuous reactor, e.g. a feeder for supplying water vapour to the continuous reactor, and

means for depressurizing the treated mixture 18 in a controlled manner without steam explosion after the plasticizing step, such as a feeder supplying water to the treated mixture.

Furthermore, the system for producing a viscosity controlled cellulosic material with a viscosity value between 150ml/g and 500ml/g in a continuous process may further comprise the following means:

washing devices, such as washing presses, for washing the resulting cellulose material of controlled viscosity, and/or

pH-adjusting devices, e.g. for adding water and/or metering chemicals, and/or

-a dryer for drying the resulting viscosity controlled cellulosic material.

The viscosity value of the chemically treated wood-based cellulosic material determined from the cellulose-water mixture 15 before the plasticizing step may be between 400ml/g and 1200 ml/g. The viscosity number of the chemically treated wood-based cellulosic material determined from the cellulose-water mixture 15 before the plasticizing step is preferably at least 400ml/g, more preferably at least 450ml/g, most preferably at least 500 ml/g. Furthermore, the viscosity number of the chemically treated wood-based cellulosic material determined from the cellulose-water mixture 15 before the plasticizing step is preferably at most 1200ml/g, more preferably at most 1000ml/g, most preferably at most 900 ml/g. The technical effect of the viscosity values is that the reaction can be improved, i.e. the reaction time during the plasticizing step can be shortened. In addition, in general, the alkali solubility of viscosity-controlled cellulosic materials improves as the viscosity decreases. However, too low a viscosity may cause several problems to the final product, for example, the average fiber length and brightness of the final product may be reduced, and the yield may also be reduced.

The ISO brightness of the chemically treated wood-based cellulosic material 15 determined before the plasticizing step is preferably at least 70%, more preferably at least 86%. Thus, the resulting viscosity-controlled cellulosic material can have desired optical properties. Furthermore, if the brightness of the raw material is sufficiently high, the chemical consumption of the process can be reduced. Thus, the chemically treated wood-based cellulosic material preferably consists of bleached pulp.

Further, the extract content of the chemically treated wood-based cellulosic material 15 determined before the plasticizing step is preferably less than 0.4%, more preferably less than 0.2%, based on the dry weight of the chemically treated wood-based cellulosic material. The quality of the resulting viscosity controlled cellulosic material can be improved and if the extract content is sufficiently small, the runnability of the final product can be increased.

The ash content of the chemically treated wood-based cellulosic material, as measured from the cellulose-water mixture, is preferably less than 0.7%, more preferably less than 0.5%, based on the dry weight of the chemically treated wood-based cellulosic material. The technical effect of the low ash content is that the quality of the viscosity-controlled cellulosic material and the operability of the process can be improved.

The content of fibers having a length of less than 0.6mm, determined by the fibers of the cellulose-water mixture 15, is preferably between 10% and 30% based on the total content of chemically treated wood-based cellulosic material fibers.

The degree of crimp of the chemically treated wood-based cellulosic material 10 determined from the cellulose-water mixture 15 before the plasticizing step is preferably between 7% and 40%, more preferably between 20% and 40%. This has the technical effect of improving the strength properties of the resulting product.

The sodium (Na) content of the cellulose-water mixture 15 is preferably at least 200mg/kg, for example 200mg/kg to 1500mg/kg, based on the dry weight of the chemically treated cellulose material fibres. If the sodium content is too low, the fibers may not swell sufficiently and, therefore, the chemicals may have difficulty entering the fibers. Furthermore, if the sodium content is too high, the consumption of chemicals may increase and water may not penetrate the fiber wall as effectively as the optimum sodium content.

The chemically treated wood-based cellulose material 10 may have a crystallinity index of 50% to 70%. The crystallinity index may improve the chemical access of the fibers of the chemically treated wood-based cellulosic material.

The WRV of the cellulose-water mixture 15 is preferably between 1g/g and 2 g/g. This WRV ratio may improve chemical access, thus shortening the reaction time.

At least one acid is preferably used as an activator to accelerate viscosity adjustment during the plasticizing step 100. The activator may be dosed prior to the plasticizing step 100 and/or at the beginning of the plasticizing step. Thus, the method may comprise the steps of:

-metering an activating agent into the cellulose-water mixture 15 in order to hydrolyze the chemically treated wood based cellulosic material 10 in the presence of the activating agent during said plasticizing step 100.

Advantageously, the activating agent comprises the filtrate 102 from the plasticizing step 100. The acid from the wood may release protons during the plasticizing step 100, and thus may create mildly acidic conditions in the absence of chemicals. However, this is often insufficient for the acidic conditions required. Thanks to the new method, a part of the acid solution can be separated and transferred as filtrate 102 and used again in the plasticizing step 100, whereby improved acidic conditions can be obtained without adding any chemicals (see fig. 1 b).

Thus, the activator may comprise the filtrate 102 obtained from the plasticizing step 100. The filtrate 102 is typically a reaction filtrate from the plasticizing step 100 that contains a hydrolysate. The filtrate 102 typically contains carboxylic acids, and therefore, can be used to improve the efficiency of the reaction during the plasticizing step 100. Thus, the activator comprising the filtrate 102 may be used to obtain suitable acidic conditions to obtain a predetermined viscosity adjustment during the plasticizing step 100.

The total amount of said filtrate 102 obtained from the plasticizing step 100 may be more than 50%, such as at least 80%, more preferably more than 90%, such as at least 95%, most preferably at least 99% or just 100%, calculated on the total amount of activating agent. This may be a very cost effective solution for the activator. Thus, the production efficiency of the new process can be increased. Furthermore, the separation of said filtrate 102 from the plasticizing step 100 and recycling to the plasticizing step 100, for example to the continuous reactor 101, can be a very environmentally friendly solution.

Additionally or alternatively, the activator may comprise an acid solution, preferably an acid filtrate, such as an acid bleaching filtrate from a chemical pulp mill.

If the activator comprises an added chemical, such as an added acid, and not just the filtrate, the added acid preferably comprises acetic acid and/or sulfuric acid. In this case, the added chemicals preferably comprise at least 80 wt.%, more preferably at least 90 wt.%, most preferably at least 97 wt.% of acetic acid and/or sulfuric acid. Advantageously, the chemical added comprises or consists of acetic acid. The amount of acetic acid may be at least 80 wt.%, more preferably at least 90 wt.%, most preferably at least 97 wt.%, based on the total weight of added chemicals of the plasticizing process. Acetic acid has good activator properties and is therefore a very cost effective chemical, and thus, manufacturing costs can be reduced and production efficiency can be improved by viscosity adjustment using acetic acid.

If the activator comprises sulfuric acid and/or acetic acid, the total amount of sulfuric acid and acetic acid may be less than 5%, such as at most 3%, more preferably less than 2%, such as at most 1.5%, most preferably less than 1%, such as at most 0.5%, calculated on the dry weight of the chemically treated wood-based cellulosic material. Thus, due to the new environmentally friendly solution, only small amounts of acid can be used if used.

The acid from the filtrate 102 may be separated by, for example, distillation, and/or at least a portion of the filtrate 102 may be recycled to the plasticizing step 100 without a separation stage. Advantageously, in order to obtain an improved production efficiency, the filtrate 102 or at least a portion of the filtrate 102 is recycled as such to the plasticizing step 100. Typically, these filtrates 102 obtained from the plasticizing step contain carboxylic acids formed from the wood-based cellulosic material during the plasticizing step 100.

The only chemical used in the method may be the filtrate 102 obtained from the plasticizing step 100. Thus, due to the new process, a cellulose material with controlled viscosity can be manufactured from the chemically treated wood-based cellulose material 10 without chemicals. Thus, the new process may be chemical-free.

Advantageously, the total dose of chemicals added to the system during the following steps is less than 5%, such as at most 3%, more preferably less than 2%, such as 1%, most preferably less than 0.5%, such as exactly 0%, calculated on the dry weight of the chemically treated wood-based cellulosic material 10:

i) a cellulose-water mixture is formed which,

ii) treating the cellulose-water mixture 15 formed in a plasticizing step, and

ii) the treated mixture 18 after the plasticizing step 100 is depressurized in a depressurization step 105.

Thus, due to this new method, the viscosity controlled cellulosic material 20 can be manufactured in an environmentally friendly manner and still have high yields and improved production efficiency.

Preferably, the plasticizing step 100 is enzyme free, as enzymes are expensive and difficult to use. In addition, the enzyme may not function under the conditions of the plasticizing step 100. Thus, if any enzyme is used, it is preferably dosed before the plastication step 100, and therefore the enzyme will be destroyed during the plastication step. Thus, any allergic reactions of the end user, as well as other problems caused by enzymes, can be avoided. The total dosage of enzymes is preferably less than 0.5%, more preferably less than 0.1%, most preferably just 0%, calculated on the dry weight of the chemically treated wood-based cellulosic material 10.

Step i), i.e. forming the cellulose-water mixture 15, may be achieved by any means known to the person skilled in the art.

The plasticizing step 100 may be performed in a continuous reactor 101. Thus, the plasticizing step 100 preferably comprises the steps of:

feeding the cellulose-water mixture 15 to the continuous reactor 101, and

continuous treatment of the cellulose-water mixture 15 formed in the reactor 101, so as to obtain a treated mixture 18.

Therefore, the apparatus for treating the cellulose-water mixture 15 during the plasticizing step preferably comprises a continuous reactor 101.

Advantageously, during the plasticizing step 100, the raw material is conveyed horizontally, or at least substantially horizontally. This can improve the effect of mixing, and thus can improve the reaction efficiency. Therefore, the production efficiency can be improved. Preferably, the angle between the horizontal and the length direction of the continuous reactor 101 may be less than 20 °.

The heating means in the plasticizing step 100 may comprise feeding means for feeding steam and/or hot water to the continuous reactor 101 to increase the temperature of the reactor 101.

The mixing means for mixing the cellulose-water mixture 15 during the plasticizing step may comprise, for example, a mixing device. The mixing device may comprise, for example, an extruder. Advantageously, the mixing device for mixing the cellulose-water mixture 15 may comprise, for example, a continuous kneading reactor (i.e. a kneader type of reactor), or another continuous screw reactor configured to mix the cellulose-water mixture during the plasticizing step 100. Due to the mixing during the plasticizing step 100, the reaction efficiency during the plasticizing step can be greatly improved, and therefore, the production time and energy required for the plasticizing step can be reduced. In addition, properties of the manufactured product, such as polydispersity and brightness of the viscosity controlled cellulosic material 20, can be improved.

Preferably, the mixing efficiency during the plasticizing step is between 10kWh/ADt and 150 kWh/ADt. More preferably, the mixing efficiency during the plasticizing step is at least 15kWh/ADt, most preferably at least 20 kWh/ADt. Furthermore, the mixing efficiency during the plasticizing step is more preferably equal to or less than 80kWh/ADt, most preferably equal to or less than 50 kWh/ADt. The technical effect of the mixing efficiency is a uniform quality, better solubility and faster reaction. Therefore, the reaction time can be shortened, and thus the production efficiency can be improved.

A continuous reactor may have multiple sections, where each section forms a chamber, so there may not be excessive material exchange between adjacent chambers over the length of the continuous reactor.

Advantageously, the plasticizing step 100 is carried out by treating the cellulose-water mixture 15 formed in a continuous horizontal reactor. The cellulose-water mixture 15 can be efficiently transported over the length of a continuous horizontal reactor, such as a continuous horizontal screw reactor. Most preferably, the continuous horizontal reactor is a kneader reactor. Thus, there may not be any or hardly any material exchange between adjacent components over the length of the continuous horizontal reactor. Therefore, the manufacturing process can be easily controlled. Thus, there may be a mild treatment which may improve the properties of the manufactured product.

The continuous reactor 101, such as a screw reactor, may have valves that open at different times to prevent mixing of the materials in the different chambers, and therefore, the valves may be used to control the transport process of the materials during the plasticizing step 100.

In one embodiment, if a screw reactor is used, it does not have a very high pressing effect on the wood-based cellulosic material during the plasticizing step 100 to avoid many fiber bundles affecting the properties of the manufactured product.

The system may further comprise means for dosing an activating agent into the cellulose-water mixture 15, so that the cellulose-water mixture is treated in the presence of the activating agent in the plasticizing step 100.

At least a portion of the filtrate 102 obtained from the plasticizing step 100 may be transferred from at least one chamber of the continuous reactor 101 and/or after the continuous reactor 101 to another chamber of the continuous reactor 101 and/or before the first chamber of the continuous reactor 101. Thus, at least a portion of the acid filtrate 102 may be separated and delivered as an acid filtrate and used again in the plasticizing step 100. Thus, when, for example, the continuous reactor 101 has a chamber, improved acidic conditions can be obtained without adding any chemicals.

The means for dosing the activating agent into the cellulose-water mixture may comprise means for conveying the filtrate 102 obtained from the second part 100b of the continuous reactor 101 and/or after the continuous reactor 101 to the first part 100a of the continuous reactor 101 and/or before the continuous reactor 101. The second section 100b of the continuous reactor 101 is located in front of the first section 100b of the continuous reactor 101. This is illustrated in fig. 1 b.

The temperature of the plasticizing step 100 may be increased and/or controlled by:

-a water vapour stream,

-a supply of hot water,

-electrical power (with resistance),

-a gas, and/or

-fuel oil.

Preferably, the temperature of the plasticizing step 100 is increased and/or controlled by using hot water and/or steam. Thus, the chemically treated wood-based cellulosic material 10 is preferably treated with hot water and/or steam during the plasticizing step 100. Accordingly, the plasticizing step 100 may further include:

supplying steam and/or hot water to continuous reactor 101 to increase the temperature of continuous reactor 101.

Due to the water vapor and/or hot water, the viscosity-controlled cellulosic material 20 can be efficiently and environmentally friendly manufactured. Furthermore, hot water and/or steam plasticization is economically feasible. Most preferably, water vapor is used to increase the temperature of the continuous reactor 101, since water vapor can effectively diffuse into the chemically treated wood-based cellulose material 10 and permeate onto the fiber walls of the chemically treated wood-based cellulose material 10.

The duration of the plasticizing step 100 is preferably less than 60 minutes, such as at most 50 minutes, more preferably less than 30 minutes, such as at most 25 minutes, most preferably less than 20 minutes, such as at most 15 minutes. Furthermore, the duration of the plasticizing step 100 is preferably at least 4 minutes, more preferably at least 5 minutes. Most advantageously, the duration of the plasticizing step is between 5 and 20 minutes. Due to the present invention having a continuous process, wherein the treated mixture is mixed during the plasticizing step, by using a short treatment time, a viscosity controlled cellulosic material 20 having good properties can be obtained while avoiding steam explosion. Thus, the manufacturing costs can be significantly reduced due to the rather fast viscosity adjustment and the lower energy consumption during the plasticizing step 100. In addition, the shorter reaction time increases the throughput. Thus, a cellulose material with controlled viscosity can be manufactured with improved production efficiency. In addition, properties of the viscosity-controlled cellulosic material, such as brightness and/or polydispersity, can be improved.

The plasticizing step 100 may be performed at a temperature of at least 130 ℃, more preferably at least 140 ℃, and most preferably at least 150 ℃. Furthermore, the temperature of the plasticizing step 100 may be up to 200 ℃, more preferably up to 180 ℃, most preferably up to 170 ℃ or 160 ℃. Such a relatively low temperature, particularly when used with a relatively short duration of the plasticizing step 100, may provide significant savings in manufacturing costs due to lower energy consumption. Furthermore, such a temperature range, especially if the temperature is at most 170 ℃ or at most 160 ℃, may improve the brightness of the resulting product. As the temperature of the process decreases, the brightness value of the resulting product generally increases (i.e., increases).

The pressure during the plasticizing step 100 may be at least 3 bar, more preferably at least 4 bar, most preferably at least 5 bar. Furthermore, the pressure of the steaming may be at most 15 bar, more preferably at most 10 bar, most preferably at most 8 bar. This relatively low pressure, particularly when used with the above-described duration of the plasticizing step 100, can result in significant manufacturing cost savings and improved properties of the viscosity controlled cellulosic material produced. Furthermore, this may improve the brightness of the resulting product.

The pH of the plasticizing step 100 may be at least 1, more preferably at least 2, and most preferably at least 3. In addition, the pH of the plasticizing step 100 may be at most 6, more preferably at most 5, most preferably at most 4, for example, between 2 and 5. By using said pH range, an efficient manufacturing process of cellulose material with controlled viscosity can be obtained, which pH effect increases when used together with the above mentioned pressure and duration of the plasticizing step.

During the plasticizing step 100, the cellulose-water mixture 15 may have a dry matter content (consistency) of 3% to 20%. The dry matter content during the plasticizing step 100 may be at least 5%, more preferably at least 7%, most preferably at least 10%. Furthermore, the dry matter content during the plasticizing step 100 may be at most 18%, more preferably at most 15%, most preferably at most 13%. Such a consistency range, in particular a consistency between 5% and 15% or between 5% and 13%, may improve the properties of the manufactured viscosity controlled cellulosic material.

During the plasticizing step 100, the degree of polymerization may be reduced by at least 50%, more preferably by at least 70%, and most preferably by at least 80%. This may improve the R18 solubility of the resulting product.

After the plasticizing step 100, the depressurization of the treated mixture 18 may be performed in a controlled manner to avoid steam explosion in a depressurization step 105. Thus, the treated mixture 18 may be non-explosively depressurized to atmospheric pressure after the plasticizing step 100. Therefore, the depressurization step 105 is preferably performed substantially slowly and controlled, i.e. without steam explosion. Therefore, the depressurization step 105 cannot be advantageously carried out simply, for example by opening the valve of the continuous reactor 101, and thus blowing off water vapor from the continuous reactor 101. Thus, the integrity of the fibers can be maintained due to the novel process.

The suitable depressurization time depends, for example, on the pressure at which the plasticizing step 100 is carried out.

The depressurizing step 105 can be accomplished, for example, by adding water to the treated mixture 18. For example, by using a chamber approach, water addition during the depressurization step may be applied, wherein water is added to the intermediate chamber to lower the temperature and pressure of the treated mixture 18. The intermediate chamber may comprise at least one valve for letting the wood based cellulose material into the chamber and at least one further valve for letting the wood based cellulose material out of the intermediate chamber after said depressurization.

Further, the intermediate chamber may comprise at least one valve, for example exactly one valve, for letting some water vapour out of the chamber while cold water is added.

Alternatively or additionally, the addition of water may be achieved, for example, by using a compartment valve.

Alternatively or additionally, the addition of water may be accomplished by using a continuous screw reactor, wherein cold water is added to the continuous screw reactor, for example to the last chamber of the screw reactor, to lower the temperature and pressure of the treated mixture 18.

Thus, the depressurizing step 105 may include the steps of:

cooling the treated mixture 18 by adding water.

The water used for cooling preferably has a temperature below 40 ℃, for example between 5 ℃ and 30 ℃. The temperature of the viscosity-controlled cellulosic material obtained after the depressurization step is preferably about 100 ℃, for example between 90 ℃ and 110 ℃. Thus, the effectiveness of possible post-processing may be increased.

This gentle pressure reduction step 105 may be used to maintain the integrity of the fibers.

Thus, the means for depressurizing the treated mixture 18 during the depressurizing step may include means for adding water (preferably cold water) to the treated mixture 18. Further, the means for depressurizing the treated mixture 18 may comprise an openable valve. Furthermore, the means for depressurizing the mixture may comprise an intermediate chamber. In this case, cold water is preferably added to the intermediate chamber.

During the depressurization step 105, the pressure can be reduced from the pressure of the plasticizing step to standard atmospheric pressure (i.e., standard pressure, 1atm) or to a pressure which is less than 1 bar different from atmospheric pressure, preferably less than 0.5 bar different from atmospheric pressure. Due to the non-explosive depressurization step 105, the properties of the manufactured viscosity-controlled cellulosic material 20 can be significantly improved. In particular, the strength properties can be significantly improved.

After the depressurizing step 105, the obtained controlled viscosity cellulosic material 20 can be further processed, for example, as follows:

washing the cellulosic material 20 in a washing step 110, and/or

-adjusting the pH of the obtained viscosity controlled cellulosic material 20 in a pH adjusting step.

The washing step 110 may include the steps of:

washing the obtained cellulose material 20 of controlled viscosity with water to remove excess acid.

Further, the washing step 110 may include the steps of:

-conveying at least a part of the water used in the washing step to the cellulose-water mixture 15.

Thus, in this embodiment, at least a portion of the water used in the washing step 110 of the viscosity-controlled cellulosic material 20 can be used to dilute the cellulose-water mixture 15 prior to the plasticizing step. Thus, the water may increase the temperature of the cellulose-water mixture 15 prior to the plasticizing step. In addition, at least some of the excess acid removed during the washing step 110 may be recycled to and reused in the plasticizing step.

Further, the washing step 110 may include the steps of:

-dewatering the washed controlled viscosity cellulosic material, for example by pressing the controlled viscosity cellulosic material 20 to reach a dry matter content of between 10% and 50%, preferably at least 15%, more preferably at least 20%, and preferably at most 45%, more preferably at most 40%.

The washing step 110 may be performed, for example, by using a washing press.

In one embodiment, the pH of the controlled viscosity cellulosic material can be adjusted, for example, by diluting the material with water, wherein the controlled viscosity cellulosic material 20 is diluted to a predetermined pH. Alternatively or additionally, suitable chemicals known to those skilled in the art may be used for the pH adjustment. The predetermined pH value may be, for example, between 4 and 7, more preferably between 4 and 6.

Furthermore, the method may comprise the following steps, preferably after the washing step 110 and/or the pH adjustment step:

drying the obtained viscosity controlled cellulosic material 20 in a drying step 120 to reach a dry matter content of at least 50%.

After the drying step 120, the dry matter content of the viscosity controlled cellulosic material 20 may be between 50% and 100%, preferably between 80% and 90%.

For example, for shipping, a drying step 120 is typically required.

The drying step 120 may be performed in a flash drying step using a flash dryer. However, flash dryers are not necessarily economical devices. Thus, it is more advantageous to carry out the drying step, for example by using a dryer of the pulp mill. Thus, the drying step 120 can be carried out without a large investment.

If the manufacturing process is an integrated process, for example, in a pulp mill, the drying step 120 of the obtained viscosity controlled cellulosic material may not be required before forming a regenerated cellulosic material, for example, from the viscosity controlled cellulosic material 20.

Due to the novel process, the obtained viscosity-controlled cellulosic material 20 may have a viscosity value between 150ml/g and 500 ml/g. Preferably, the viscosity controlled cellulosic material has a viscosity value of at least 160ml/g, more preferably at least 170ml/g, most preferably at least 180 ml/g. Furthermore, preferably, the viscosity controlled cellulosic material has a viscosity value of at most 350ml/g, more preferably at most 300ml/g, most preferably at most 250 ml/g.

Due to the novel process, the viscosity-controlled cellulosic material 20 can have a specific hemicellulose content. The hemicellulose content of the resulting viscosity-controlled cellulosic material 20 can be between 0.5% and 30% by weight. The hemicellulose content of the viscosity controlled cellulosic material 20 is preferably at least 1 wt%, more preferably at least 3 wt%, most preferably at least 5 wt%. Further, the hemicellulose content of the viscosity-controlled cellulosic material 20 is preferably at most 30 wt%, more preferably at most 25 wt%. The technical effects of the hemicellulose content include improved yield and material efficiency, improved environmental impact, and improved reactivity.

Due to the novel process, the viscosity-controlled cellulosic material 20 can have a specific glucose content. The glucose content of the obtained viscosity controlled cellulosic material 20 can be between 76 wt.% and 99.6 wt.% calculated from the total sugar content of the viscosity controlled cellulosic material. The glucose content of the controlled viscosity cellulosic material 20 is preferably at least 80 wt.%, more preferably at least 85 wt.%, most preferably at least 90 wt.%, calculated on the total sugar content of the controlled viscosity cellulosic material. Furthermore, the glucose content of the controlled viscosity cellulosic material 20 is preferably at most 99 wt.%, more preferably at most 95 wt.%, calculated on the total sugar content of the controlled viscosity cellulosic material. The technical effect of the glucose content includes improved material efficiency.

The alpha cellulose content of the viscosity controlled cellulosic material is preferably at least 67%, more preferably at least 69%. Furthermore, the alpha cellulose content of the viscosity controlled cellulosic material is preferably less than 99.5%, more preferably less than 95%, most preferably at most 90%. The technical effect is improved yield, improved reactivity and material efficiency, and better environmental impact.

The resulting viscosity-controlled cellulosic material 20 can have a degree of polymerization of 200 to 700. The degree of polymerization is preferably at least 220, more preferably at least 250, most preferably at least 300. Furthermore, the degree of polymerization is preferably at most 650, more preferably at most 620, most preferably at most 600.

Due to the novel process, the viscosity controlled cellulosic material 20 can have a specific fiber length. Advantageously, the content of fibres having a length lower than 0.6mm, measured from the cellulose material with controlled viscosity, is between 10% and 30%. The technical effect is that such a viscosity controlled material can be handled and cleaned very easily and, in addition, yield losses can be reduced.

Furthermore, due to the novel process, the length weighted fiber length lc (l) of the viscosity controlled cellulosic material measured according to ISO16065-N may be greater than 0.5mm, such as at least 0.7mm, more preferably at least 0.9mm or at least 1.0mm, most preferably at least 1.2 mm. Further, the viscosity-controlled cellulosic material 20 can have an average fiber length of up to 3.0 mm. The fiber length of the viscosity-controlled cellulosic material depends on the fiber length of the raw material, which is influenced by the amount of, for example, softwood and/or hardwood raw materials. Said length weighted fiber length of the viscosity controlled cellulosic material may improve the strength properties of the product. In particular, the burst strength of the final product can be improved.

Good optical properties may be important for the viscosity controlled cellulosic material 20. Using the novel process, the ISO brightness of the viscosity controlled cellulosic material may be at least 70%, for example between 75% and 90%. Therefore, the quality of the final product can be improved.

The controlled viscosity cellulosic material may have a crimp level of between 20% and 90%, more preferably between 25% and 85%, most preferably between 30% and 65%. This may improve the strength properties of the final product. In addition, the degree of curling can improve the water removal performance of the product.

Furthermore, the WRV of the controlled viscosity cellulosic material 20 is preferably between 1g/g and 2 g/g. The technical effect is improved chemical access and improved reaction efficiency, i.e. shortened reaction time.

To obtain good properties of the viscosity controlled cellulosic material, the lignin content of the viscosity controlled cellulosic material may be less than 1.5%, more preferably less than 1%, most preferably less than 0.5%. Furthermore, the extract content of the viscosity-controlled cellulosic material is preferably less than 0.2%, more preferably less than 0.1%. The reduction of the lignin and extract content in the product improves the brightness and quality of the product.

Due to the novel process, the viscosity controlled cellulosic material 20 can have a specific crystallinity index CrI. The resulting controlled viscosity cellulosic material 20 can have a crystallinity index of at least 74%, more preferably at least 75%, and most preferably at least 76%. Further, the crystallinity index of the resulting viscosity-controlled cellulosic material can be less than 85%, such as up to 80%. Thanks to the new process, the improved crystallinity index can be obtained, which can improve the properties of the product, such as strength properties.

The sodium (Na) content of the viscosity-controlled cellulosic material may be at least 200mg/kg, preferably from 200mg/kg to 1500mg/kg, based on the dry weight of the chemically treated cellulose material fibers. The sodium content has an influence on the viscosity number of the resulting product. Too high a sodium content of the viscosity controlled cellulosic material may result in a product with too high a viscosity value.

Due to the novel process, the new controlled viscosity cellulosic material can have a specific R18 solubility of the controlled viscosity cellulosic material 20. The viscosity controlled cellulosic material may have a R18 solubility of at least 60%, more preferably at least 65%, most preferably at least 70%. Furthermore, the viscosity controlled cellulosic material preferably has an R18 solubility of at most 87%, most preferably at most 84%. Due to this new R18 solubility of the viscosity controlled cellulosic material, an environmentally friendly product can be obtained. In addition, the yield and the production efficiency can be improved.

The viscosity controlled cellulosic material 20 can be dissolved in an aqueous alkali hydroxide solution at a temperature between-5 ℃ and 0 ℃, typically between-10 ℃ and 5 ℃ to form a homogeneous cellulosic solution. Most preferably, the controlled viscosity cellulosic material 20 is at least soluble in cold NaOH at temperatures within the above temperature ranges. NaOH can help to obtain a relatively cheap and environmentally friendly aqueous base solution.

The controlled viscosity cellulosic material 20 can be dissolved in an aqueous alkaline solution to form a dissolved controlled viscosity cellulosic material 30. Further, regenerated cellulosic material 40 can be obtained from dissolved viscosity-controlled cellulosic material 30. The reactivity of the fiber may be increased due to the activation of the fiber in the plasticizing step 100, and thus, the cellulose material having the controlled viscosity may be easily modified into the regenerated cellulose material 40. Furthermore, if water vapor is used during the plasticizing step, the water vapor may reduce the crystallinity of the viscosity-controlled cellulosic material.

The dissolved controlled viscosity cellulosic material 30, which may also be referred to as "dope," may be a raw material for other products, such as fibers. The dissolved controlled viscosity cellulosic material 30, i.e., dope, can be used, for example, in filaments, staple fibers, cellulose beads, and/or films.

A method of treating the resulting controlled viscosity cellulosic material 20 to form a regenerated cellulosic material 40 can comprise the steps of:

dissolving the controlled viscosity cellulosic material 20 in a dissolving step 130 by using an aqueous alkaline solution, thereby forming a dissolved controlled viscosity cellulosic material 30, and

forming regenerated cellulosic material 40 from dissolved viscosity-controlled cellulosic material 30.

The concentration of the viscosity controlled cellulosic material in the dissolving step 130 is preferably between 5% and 10%.

The basic aqueous solution may comprise:

-NaOH,

-LiOH, and/or

-KOH,

And/or mixtures of any of the above with zinc compounds.

Advantageously, at least NaOH is used for the dissolution step 130, since NaOH is a significantly cost-effective chemical that can be readily used in the process.

For example, adding a zinc compound to an alkali metal hydroxide solution can increase the stability of the solution. The stabilization time of the dissolved viscosity-controlled cellulosic material 30 can be, for example, 30 days at room temperature, 180 days in a refrigerator.

Optionally, additives such as colorants, surfactants, ultraviolet degradation inhibitors, antifungal ingredients, antimicrobial ingredients, inorganic fillers, or other ingredients may be mixed into the dissolved controlled viscosity cellulosic material 30.

The novel process can be technically simple and ecologically safe without the need for toxic substances. Furthermore, the new method can be cheap due to the small consumption of chemicals and the substantially simple technology.

Experimental testing, example 1

Three similar samples were processed by using different kinds of manufacturing methods. The results can be seen in fig. 4a-4 c. The treatment was as follows:

sample 1A: a viscosity controlled cellulosic material produced in the case of steam explosion using a batch process (figure 4a),

sample 2A: a viscosity controlled cellulosic material produced using a batch process without steam explosion (fig. 4b), and

sample 3A: a controlled viscosity cellulosic material produced using a continuous process without steam explosion (fig. 4 c).

As can be seen from the photographs, sample 3, which was produced using a continuous process without steam explosion, had improved optical properties, e.g., increased brightness values, as compared to sample 1. In addition, the fibers of sample 1 were damaged more than the fibers of sample 3.

Example 2

Three different samples were analyzed under an optical microscope. The results can be seen in fig. 5a-5 c. The samples were stained with Graff-C.

Sample 1B (fig. 5a) is kraft pulp, which was used as the raw material,

sample 2B (FIG. 5B) is a controlled viscosity cellulosic material, and

sample 3B (fig. 5c) is a steam exploded cellulose material.

The fibers of sample 1 were straight and intact with typical pores clearly visible. Some kraft fibers have a loose outer protofiber layer and the typical kinking of kraft fibers.

The fibers of sample 2 were significantly more fibrillated on the surface and they obtained a loose structure. The fibers have considerable crimp. The fibrous structure may be absorbent and readily disintegrate.

Sample 3 consisted of crystalline material and some elongated fibers.

As can be seen from fig. 5b and 5c, the continuous process without steam explosion maintained the integrity of the fibers, while the steam explosion process almost destroyed the fibers.

Example 3

During the experimental tests, several slurry samples were treated in a plasticizing step and the properties of the treated slurry were measured. These results are shown in FIGS. 6-11.

Sample a was never-dried conifer pulp, which was treated without steam explosion using a batch reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: 120 minutes, and

pH：3.3。

sample B was never dried conifer pulp, which was treated without steam explosion using a continuous reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: for 20 minutes, and

pH：3.3。

sample C was never dried conifer pulp, which was treated without steam explosion using a continuous reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: for 50 minutes, and

pH：3.3。

sample D was never dried conifer pulp, which was treated without steam explosion using a semi-continuous reactor with the following parameters:

temperature: at a temperature of 160 c,

pressure: at a pressure of 6 bar and, in particular,

time: for 25 minutes, and

pH：3.3。

sample E was never dried conifer pulp, which was treated without steam explosion using a semi-continuous reactor with the following parameters:

temperature: at a temperature of 160 c,

pressure: at a pressure of 6 bar and, in particular,

time: for 10 minutes, and

pH：3.3。

sample F was dry conifer pulp, treated without steam explosion using a semi-continuous reactor with the following parameters:

temperature: at a temperature of 160 c,

pressure: 6 bar, and

time: for 25 minutes.

Sample G was dry conifer pulp, treated without steam explosion using a batch reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: 120 minutes, and

pH：4.0。

sample H was dry conifer pulp, treated with a steam explosion method using a continuous reactor with the following parameters:

temperature: at the temperature of 190 ℃,

pressure: at a pressure of 10 bar and at a pressure of 10 bar,

time: for 5 minutes, and

pH：4.0。

samples I and J were processed from undried birch pulp using a continuous reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: for 50 minutes, and

pH：3.3。

samples K and L were processed from undried conifer pulp using a continuous reactor with the following parameters:

temperature: at the temperature of 170 ℃, the temperature of the mixture is adjusted,

pressure: at a pressure of 7 bar and at a pressure of,

time: for 50 minutes, and

pH：10.3。

reference samples Ref1 and Ref2 are never dried conifer pulp (untreated).

FIGS. 6a and 6b show the molar mass distribution, Mw [ g/mol ], determined by tricarbanilate (RI assay) for all samples. It can be seen that the sample obtained by using the continuous and semi-continuous processes (sample B, C, D, E, F) has improved characteristics compared to the samples obtained using the batch process (samples a and G).

The viscosity values of the samples are shown in FIG. 7. It can be seen that the pH has an effect on the viscosity value of the manufactured product. The high pH values (samples K and L) increase the viscosity values of the manufactured products. Furthermore, surprisingly, the batch process (samples a and G) is a very inefficient way to produce a cellulose material with controlled viscosity. Samples a and G obtained from the batch process had higher viscosity values than samples obtained from the continuous process. In contrast, a continuous process appears to be very efficient. The viscosity values of samples B-F and H obtained from the continuous process (reaction time between 10 and 50 minutes) were lower than the viscosity values of samples A and G obtained from the batch process (reaction time of about 120 minutes).

The viscosity value of the sample decreases with increasing reaction temperature and/or reaction time. It can be seen that a viscosity controlled cellulosic material can be obtained in an efficient manner by using the method. Thus, due to the new method, the production efficiency can be significantly improved. Furthermore, due to the shortened reaction time and/or the reduced reaction temperature, the properties of the obtained viscosity-controlled cellulosic material, such as the brightness value of the obtained product, may be significantly increased.

The length weighted fiber length of the sample is shown in fig. 8 a. It can be seen that sample H, which was made using the steam explosion process, had shorter fibers. The fibers of the sample H (made by using the steam explosion method) appeared to be so broken that the length weighted fiber length of the sample H had been reduced to the same level as the samples I and J starting from birch pulp. The length weighted fiber lengths of samples a-G and K-L made without steam explosion were at a very good level.

Furthermore, a continuous process appears to be very efficient. The fiber length of those samples made using the continuous process had decreased when the treatment time was 50 minutes. Thus, for a continuous process, a very short time, for example about 10 minutes, is also sufficient for the process. Batch processes require longer processing times than continuous processes. Therefore, the continuous process can improve the production efficiency, and the product quality is better than that of the product manufactured by the steam explosion method.

Fiber crimp [% ] is shown in fig. 8 b. It can be seen that the degree of fiber crimp in sample H is very small due to the steam explosion process. Furthermore, samples a and G obtained from a batch process, and sample C obtained from a continuous process with a relatively long treatment time and a relatively high temperature, have reduced curl values. In addition, the high pH (samples K and L) and birch pulp as the feedstock (samples I and J) appeared to reduce the crimp of the fibers. Samples B, D, E and F, obtained from a continuous process with treatment times between 10 and 25 minutes, had the most promising results.

The kink number [1/m ] is shown in FIG. 9 a. It can be seen that the kink values are minimal in samples a and G (batch process). In addition, the kink value of sample H (steam explosion process) was slightly lower. The samples produced using the continuous process without steam explosion had the highest kink values.

Fibrillation is shown in figure 9 b. It can be seen that the samples made using the continuous process without steam explosion had slightly higher levels of fibrillation than the samples made using the batch process. The steam explosion process (sample H) destroyed the fiber structure, resulting in a very high level of fibrillation.

The polydispersity is shown in figure 10. The polydispersity values of samples made using a continuous process are improved. A continuous process appears to be very efficient. Sample E, obtained from a continuous process with a very short treatment time (10 minutes), has the same level of polydispersity as samples a and G, obtained from a batch process with a long treatment time (120 minutes). Therefore, by using a continuous process, production efficiency can be improved.

The XRD-indicated crystallinity index [% ] is shown in fig. 11. The crystallinity index is generally increased by the plasticizing process.

The following numbered examples disclose some examples of preferred embodiments of the present invention.

Numbering example

1. A method of producing a viscosity controlled cellulosic material having a viscosity value between 150ml/g and 500ml/g in a continuous process, the method comprising the steps of:

i) forming a cellulose-water mixture 15 comprising:

-water and

-a chemically treated wood based cellulosic material comprising bleached kraft pulp and/or bleached sulfite pulp and/or bleached soda pulp,

the cellulose-water mixture has a dry matter content of between 3% and 20%,

ii) treating the cellulose-water mixture 15 formed in the plasticizing step (100) at a temperature between 130 ℃ and 200 ℃ and a pressure between 3 bar and 15 bar, preferably between 5 bar and 10 bar, for at least 5 minutes and at most 120 minutes, while simultaneously

Mixing the cellulose-water mixture 15, and

-feeding hot water and/or water vapour into the cellulose-water mixture,

so as to obtain a treated mixture 18 which,

and

iii) the treated mixture 18 after the plasticizing step 100 is depressurized in a controlled manner in a depressurization step 105 without steam explosion to maintain fiber integrity to obtain a viscosity controlled cellulosic material 20.

2. The method according to example 1, wherein the plasticizing step 100 is carried out by treating the cellulose-water mixture 15 formed in a continuous kneading reactor.

3. The method of any of the preceding examples, wherein the plasticizing step 100 is performed by treating the formed cellulose-water mixture 15 in a continuous screw reactor.

4. The process of example 3, wherein the continuous screw reactor is a horizontal screw reactor.

5. The method of any of the preceding examples, wherein the depressurizing step comprises the steps of:

cooling the treated mixture 18 by adding water.

6. The method of any of the preceding examples, wherein the depressurizing step 105 comprises:

mechanical reduction of water vapor, for example by using a screw or chamber method.

7. The method of any of the preceding examples, wherein the depressurizing step 105 is performed for at most 30 minutes, preferably at most 20 minutes.

8. The method of any of the preceding examples, wherein the depressurizing step 105 is performed for at least 1 second, preferably at least 3 seconds.

9. The method of any of the preceding examples, wherein the method further comprises:

-metering an activating agent into the cellulose-water mixture 15 to plasticize the wood based cellulosic material in the presence of the activating agent during the plasticizing step 100.

10. The method according to example 9, wherein the activating agent comprises a filtrate obtained from the plasticizing step, wherein the filtrate preferably comprises a hydrolysate from the plasticizing step.

11. The method according to example 10, wherein the amount of filtrate obtained from the plasticizing step is at least 90%, more preferably at least 95%, most preferably at least 99% or exactly 100%, calculated on the total amount of activating agent.

12. The method of examples 9, 10 or 11, wherein the activator comprises sulfuric acid or acetic acid, the total amount of sulfuric acid and acetic acid being less than 5%, more preferably less than 3%, most preferably less than 2% calculated on the dry weight of the chemically treated wood-based cellulosic material 10.

13. The method of any of preceding examples 9-12, wherein the activator comprises an acid solution, preferably an acid filtrate from a chemical pulp mill.

14. The method according to any of the preceding examples, wherein the total amount of chemicals used is less than 5%, such as less than 2%, excluding filtrate obtained from the plasticizing step, calculated on the basis of the dry weight of the chemically treated wood-based cellulosic material 10.

15. The method according to any one of the preceding examples, wherein in the depressurizing step 105 the treated mixture 18 is depressurized to a pressure that differs from atmospheric pressure by less than 1 bar, preferably by less than 0.5 bar.

16. The method of any of the preceding examples, wherein the duration of the plasticizing step 100 is at most 50 minutes, preferably at most 20 minutes, most preferably at most 15 minutes.

17. The method of any of the preceding examples, wherein the duration of the plasticizing step 100 is at least 6 minutes.

18. The method of any of the preceding examples, wherein the temperature of the plasticizing step 100 is at least 140 ℃, preferably at least 150 ℃.

19. The method of any of the preceding examples, wherein the pressure of the plasticizing step 100 is at least 5 bar, preferably at least 6 bar.

20. The method of any of the preceding examples, wherein the pressure of the plasticizing step 100 is less than 10 bar, preferably at most 8 bar.

21. The method of any of the preceding examples, wherein the temperature of the plasticizing step 100 is at most 180 ℃, preferably at most 170 ℃.

22. The method of any of the preceding examples, wherein the cellulose-water mixture has a pH of at most 6, preferably at most 5.

23. The method of any of the preceding examples, wherein the cellulose-water mixture has a pH of at least 1, preferably at least 2.

24. The method of any of the preceding examples, wherein the viscosity of the wood-based cellulosic material determined from the cellulose-water mixture prior to the plasticizing step is at least 400ml/g, preferably at least 450 ml/g.

25. The method of any of the preceding examples, wherein the viscosity of the wood-based cellulosic material determined from the cellulose-water mixture prior to the plasticizing step is at most 1,200ml/g, preferably at most 900 ml/g.

26. The method of any of the preceding examples, wherein the dry matter content of cellulose-water mixture 15 is at least 5%, more preferably at least 10%.

27. The method of any of the preceding examples, wherein the dry matter content of cellulose-water mixture 15 is less than 17%, more preferably less than 14%.

28. The method of any of the preceding examples, wherein the mixing efficiency during the plasticizing step is between 15 and 80 kWh/ADt.

29. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a viscosity value of at least 170ml/g, preferably at least 180 ml/g.

30. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a viscosity value of at most 350ml/g, preferably at most 300ml/g, most preferably at most 250 ml/g.

31. The method of any of the preceding examples, wherein the method further comprises:

washing the obtained viscosity-controlled cellulosic material 20 in a washing step, preferably with water, and/or

-adjusting the pH of the resulting viscosity-controlled cellulosic material in a pH adjustment step.

32. The method of any of the preceding examples, wherein the method further comprises:

-drying the obtained viscosity controlled cellulosic material 20 to obtain a dry matter content of at least 60%.

33. The method of any of the preceding examples, wherein the chemically treated wood-based cellulosic material has an ISO brightness determined prior to the plasticizing step of at least 70%, preferably at least 86%.

34. The method of any of the preceding examples, wherein the hemicellulose content of the cellulose-water mixture is at least 0.5%, preferably between 10% and 33%, based on the dry weight of the chemically treated wood-based cellulosic material.

35. The method of any of the preceding examples, wherein the controlled viscosity cellulosic material has a crystallinity index of at least 74%, preferably at least 76%.

36. The method of any of the preceding examples, wherein the chemically treated wood-based cellulosic material has an extract content of less than 0.4%, more preferably less than 0.2%, as measured from the cellulose-water mixture prior to the plasticizing step 100, based on the dry weight of the chemically treated wood-based cellulosic material in the mixture.

37. The method of any of the preceding examples, wherein the ash content of the chemically treated wood-based cellulosic material measured from the cellulose-water mixture is less than 0.7%, more preferably less than 0.5%, based on the dry weight of the chemically treated wood-based cellulosic material in the mixture.

38. The method of any of the preceding examples, wherein the content of fibers having a length of less than 0.6mm determined from the cellulose-water mixture prior to the plasticizing step 100 is between 10% and 30% based on the total content of chemically treated wood-based cellulosic material fibers.

39. The method of any of the preceding examples, wherein the degree of crimp of the wood-based cellulosic material measured prior to the plasticizing step 100 is between 7% and 40%.

40. The method of any of the preceding examples, wherein the cellulose-water mixture 15 has a sodium (Na) content of at least 200mg/kg, preferably between 200mg/kg and 1500mg/kg, based on the dry weight of the chemically treated wood-based cellulosic material fibers.

41. The method of any of the preceding examples, wherein the cellulose-water mixture has a WRV value between 1g/g and 2 g/g.

42. The method of any of the preceding examples, wherein the chemically treated wood-based material has a softwood content of at least 70%, more preferably at least 85%, based on the dry weight of the chemically treated wood-based cellulosic material.

43. The method of any of the preceding examples, wherein the chemically treated wood-based cellulosic material 10 has an alpha cellulose content of at least 65%, preferably at least 67%, measured prior to the plasticizing step 100.

44. The method according to any of the preceding examples, wherein the chemically treated wood-based cellulosic material 10 has an alpha cellulose content of less than 99.5%, more preferably at most 90%, measured before the plasticizing step 100.

45. The method of any of the preceding examples, wherein the chemically treated wood-based cellulosic material 10 has a lignin content of less than 3%, more preferably less than 1.0%, most preferably less than 0.5%, measured prior to the plasticizing step 100.

46. The method of any of the preceding examples, wherein the length weighted fiber length lc (l) of the viscosity controlled cellulosic material 20 measured according to ISO16065-N is at least 0.9mm, more preferably at least 1.0mm, most preferably at least 1.2 mm.

47. The method of any of the preceding examples, wherein the controlled viscosity cellulosic material 20 has an alpha cellulose content of at least 67%, preferably at least 69%.

48. The method of any of the preceding examples, wherein the controlled viscosity cellulosic material 20 has an alpha cellulose content of less than 99.5%, preferably at most 90%.

49. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a hemicellulose content of at least 0.5 dry weight percent, more preferably at least 5 dry weight percent.

50. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a hemicellulose content of between 10 and 30 dry weight percent.

51. The method of any of the preceding examples, wherein the controlled viscosity cellulosic material 20 has an R18 solubility of at least 60%, preferably at least 70%.

52. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has an R18 solubility of at most 87%, preferably at most 84%.

53. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a sodium (Na) content of at least 200mg/kg, preferably in the range of 200mg/kg to 1500mg/kg, based on the dry weight of the chemically treated wood based cellulosic material fibers.

54. The method of any of the preceding examples, wherein the content of fibers having a length of less than 0.6mm, as measured from the controlled viscosity cellulosic material 20, is between 10% and 30%.

55. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has an ISO brightness of at least 70%, preferably between 75% and 90%.

56. The method of any of the preceding examples, wherein the controlled viscosity cellulosic material 20 has a crimp level of between 25% and 90%, preferably between 35% and 80%.

57. The method of any of the preceding examples, wherein the viscosity controlled cellulosic material 20 has a WRV between 1g/g and 2 g/g.

58. The method of any of the preceding examples, wherein the lignin content of the controlled viscosity cellulosic material 20 is less than 1.5%, more preferably less than 1%, and most preferably less than 0.5%.

59. The method of any of the preceding examples, wherein the extract content of the controlled viscosity cellulosic material 20 is less than 0.2%, more preferably less than 0.1%.

60. A controlled viscosity cellulosic material obtainable by using the method of any one of the preceding examples 1-59.

61. A system for producing a viscosity controlled cellulosic material 20 having a viscosity value between 150ml/g and 500ml/g in a continuous process, the system comprising:

-means for forming a cellulose-water mixture,

a continuous reactor 101, for example a continuous kneader, for treating the cellulose-water mixture in a plasticizing step 100 at a temperature between 130 ℃ and 200 ℃,

-mixing means for mixing the cellulose-water mixture during the plasticizing step,

heating means for increasing the temperature of the cellulose-water mixture in the continuous reactor, e.g. a feeder for supplying water vapour to the continuous reactor, and

means for depressurizing the treated mixture 18 in a controlled manner without steam explosion after the plasticizing step 100.

62. The system of example 61, wherein the continuous reactor 101 is a horizontal screw reactor.

63. The system of claim 61 or 62, further comprising:

means for dosing the activating agent to the cellulose-water mixture for treating the cellulose-water mixture in the presence of the activating agent in the plasticization step 100, for example means for conveying at least a portion of the filtrate 102 obtained from the plasticization step to the continuous reactor.

64. A viscosity controlled cellulose material having a viscosity value between 150ml/g and 500ml/g, wherein the viscosity controlled cellulose material 20 has an R18 solubility between 60% and 87%.

65. The controlled viscosity cellulosic material of example 64 wherein the controlled viscosity cellulosic material 20 is made from a chemically treated wood-based cellulosic material 10, the chemically treated wood-based cellulosic material 10 comprising bleached kraft pulp, bleached sulfite pulp, and/or bleached soda pulp.

66. The controlled viscosity cellulosic material of example 64 or 65 wherein the length weighted fiber length lc (l) of the controlled viscosity cellulosic material 20 measured according to ISO16065-N is at least 0.9mm, more preferably at least 1.0mm, most preferably at least 1.2 mm.

67. The controlled viscosity cellulosic material of any of the preceding examples 64-66, wherein the controlled viscosity cellulosic material has an alpha cellulose content of at least 67%, preferably at least 69%.

68. The controlled viscosity cellulosic material of any of the preceding examples 64-67, wherein the controlled viscosity cellulosic material has an alpha cellulose content of less than 99.5%, preferably at most 90%.

69. The controlled viscosity cellulosic material of any of the preceding examples 64-68, wherein the hemicellulose content of the controlled viscosity cellulosic material is at least 0.5 dry weight percent, more preferably at least 5 dry weight percent.

70. The controlled viscosity cellulosic material of any of the preceding examples 64-69, wherein the hemicellulose content of the controlled viscosity cellulosic material is between 10 dry weight% and 30 dry weight%.

71. The controlled viscosity cellulosic material of any of the preceding examples 64-70, wherein the R18 solubility is at least 70%.

72. The controlled viscosity cellulosic material of any of the preceding examples 64-71, wherein the R18 solubility is at most 84%.

73. The controlled viscosity cellulosic material of any of the preceding examples 64-72, wherein the sodium (Na) content of the controlled viscosity cellulosic material 20 is at least 200mg/kg, preferably in the range of 200mg/kg to 1500mg/kg, based on the dry weight of the chemically treated wood-based cellulosic material fibers.

74. The controlled viscosity cellulosic material of any of the preceding examples 64-73, wherein the controlled viscosity cellulosic material 20 comprises between 10% and 30% fibers having a length of less than 0.6 mm.

75. The controlled viscosity cellulosic material of any of the preceding examples 64-74, wherein the controlled viscosity cellulosic material has an ISO brightness of at least 70%, preferably between 75% and 90%.

76. The controlled viscosity cellulosic material of any of the preceding examples 64-75, wherein the controlled viscosity cellulosic material 20 has a crimp level of between 25% and 90%, preferably between 30% and 85%.

77. The controlled viscosity cellulosic material of any of the preceding examples 64-76, wherein the controlled viscosity cellulosic material 20 has a WRV of between 1g/g and 2 g/g.

78. The controlled viscosity cellulosic material of any of the preceding examples 64-77, wherein the lignin content of the controlled viscosity cellulosic material 20 is less than 1.5%, more preferably less than 1%, and most preferably less than 0.5%.

79. The controlled viscosity cellulosic material of any of the preceding examples 64-78, wherein the controlled viscosity cellulosic material 20 has an extract content of less than 0.2%, more preferably less than 0.1%.

80. The controlled viscosity cellulosic material of any of the preceding examples 64-79, wherein the controlled viscosity cellulosic material has a viscosity value of at least 170ml/g, preferably at least 180 ml/g.

81. The controlled viscosity cellulosic material of any of the preceding examples 64-80, wherein the controlled viscosity cellulosic material 20 has a viscosity value of at most 350ml/g, preferably at most 320 ml/g.

82. A regenerated cellulosic material comprising the controlled viscosity cellulosic material 20 according to any one of the preceding examples 60 or 64 to 81.