Method for manufacturing intermediate product for conversion into microfibrillated cellulose
AssigneeStora Enso OYJ
InventorsKaj Backfolk, Isto Heiskanen, Esa Saukkonen, Katja Lyytikäinen, Heidi Saxell
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Abstract
The present invention relates to a method for manufacturing an intermediate product that can be stored and transported and efficiently converted into microfibrillated cellulose with limited energy input at the time of conversion. More specifically, the invention involves the use of dewatered carboxymethylcellulose or carboxylated cellulose fiber having a low degree of substitution and a high amount of additives.
Claims9
A process for preparing an intermediate product suitable for subsequent conversion into microfibrillated cellulose comprising the steps of
- a) providing an aqueous suspension comprising carboxymethylcellulose or carboxylated cellulose fiber having a degree of substitution less than 0.4;
- and
- b) dewatering the suspension of step a) on a wire to achieve an intermediate B product in the form of a sheet or web having at least 30% dry content,
- wherein the additive is a salt or a salt with a retention aid or a dewatering aid or a combination thereof, and
- wherein an additive is added to the suspension in step b) by spraying,
- wherein the concentration of additive in the suspension that is being dewatered in step b) is at least 5% by weight of the solids of the suspension,
- wherein neither the dewatering aid, nor the retention aid, nor the salt comprise a calcium salt, and
- wherein the salt is a monovalent or divalent metal salt selected from sodium chloride, lithium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, potassium nitride, sodium acetate, potassium hydroxide, sodium citrate, zinc phosphate and iron phosphate.
A process for preparing a microfibrillated cellulose comprising the steps of
- a) providing an aqueous suspension comprising carboxymethylcellulose or carboxylated cellulose fiber having a degree of substitution less than 0.4;
- and
- b) dewatering the suspension of step a) on a wire to achieve an intermediate product in the form of a sheet or web having at least 30% dry content,
- c) dispersing the intermediate product obtained in step b) in water to obtain a dispersion, optionally with addition of additives and/or fibers and/or minerals;
- and
- d) mechanically fibrillating the dispersion of step c) to obtain microfibrillated cellulose
- wherein an additive is selected from a retention aid, a dewatering aid and a salt or a combination thereof, and
- wherein the additive is added to the suspension in step b) by spraying,
- wherein the concentration of additive in the suspension that is being dewatered in step b) is at least 5% by weight of the solids of the suspension, and
- wherein neither the dewatering aid, nor the retention aid, nor the salt comprise a calcium salt.
Dependencies are inferred from the claim text.