Process for preparing a solution of lignin in an aqueous medium
AssigneeStora Enso OYJ
InventorsBen Nasli Bakir, Ashar Zafar, Jesper Ekström
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Abstract
The present invention relates to a process for lignin dissolution in which partial methylolation of lignin is carried out during the step of preparing a solution of lignin in an aqueous medium comprising alkali and phenol. The lignin prepared according to the process of the present invention can be used to manufacture lignin-based phenolic resins, which are particularly useful in the manufacture of laminates.
Claims16
A method for dissolving lignin in an aqueous medium comprising the steps of
- a) mixing lignin, alkali, phenol and formaldehyde in an aqueous medium;
- b) mixing until a solution of the lignin in the aqueous medium has been obtained;
- wherein a molar ratio between the formaldehyde and a total amount of the phenol and lignin monomer, based on an average lignin monomer molecular weight, is 0.4 or less.
A method for preparing a resin comprising the steps of
- a) mixing lignin, alkali, phenol and formaldehyde in an aqueous medium;
- b) mixing until a solution of the lignin in the aqueous medium has been obtained;
- c) keeping the mixture obtained in step b) at a temperature in a range of from 30° C. to 95° C. and;
- d) adding additional formaldehyde and optionally additional phenol and maintaining the mixture at a temperature of from 30° C. to 95° C. for at least 30 minutes;
- wherein a molar ratio between the formaldehyde and a total amount of the phenol and lignin monomer, based on an average lignin monomer molecular weight, in step a) is 0.4 or less.
A method for increasing the solubility of lignin in an aqueous medium comprising the steps of
- a) mixing lignin, alkali, phenol and formaldehyde in an aqueous medium;
- b) mixing until a solution of the lignin in the aqueous medium has been obtained;
- wherein a molar ratio between the formaldehyde and a total amount of the phenol and lignin monomer, based on an average lignin monomer molecular weight, is 0.4 or less.
Dependencies are inferred from the claim text.