Cellulose material plasticization and viscosity controlled cellulosic material

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

• means for forming a cellulose-water mixture (15),
• a continuous reactor (101) for treating the cellulose-water mixture in a plasticization step (100) at a temperature between 130° C. and 200° C.,
• mixing means for mixing the cellulose-water mixture during the plasticization step,
• heating means for increasing temperature of the cellulose-water mixture in the continuous reactor, such as a feeder to feed water steam to the continuous reactor,
• means for depressurizing the treated mixture (18) in a controlled manner without a steam explosion after the plasticization step (100), and
• optionally, means for conveying at least part of a filtrate (102) obtained from the plasticization step to the continuous reactor (101).

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

• i) forming a cellulose-water mixture (15) comprising
• water and
• 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 formed cellulose-water mixture (15) in a plasticization step (100) at
• a temperature between 130° C. and 200° C., and
• a pressure between 3 bars and 15 bars,
• at least 5 minutes and 120 minutes at the most,
• while
• mixing the cellulose-water mixture (15), and
• feeding hot water and/or water steam to the cellulose-water mixture,
• thereby obtaining a treated mixture (18),
• and
• iii) depressurizing the treated mixture (18) after the plasticization step (100) in a depressurizing step (105) in a controlled manner without a steam explosion to maintain fiber integrity,
• thereby obtaining the viscosity controlled cellulosic material (20).