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FAIR-CT97-3521
VALOIR: Value added lignins as renewable raw materials dedicated to the end-users requirements out of black liquor of existing pulp mills |
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Contract No: | FAIR-CT97-3521 |
| Date Prepared: | July 2000 | |
| Source: | Second Annual Progress Report |
Objectives
This project aims to develop methods to prepare sulphur-free lignins of controlled grades from black liquors in order to provide the European chemical industry with a new renewable resource at a competing price level, which can be adapted to the requirements for different specific end-uses. To achieve this goal, the following objectives, divided in three main tasks, have been set:
Activities
During the second project year black liquors from alkaline pulping of different raw materials, such as flax, hemp, sisal, abaca and jute were used, as well as black liquors from various stages in a flax pulping campaign. Straw black liquor was obtained from a Turkish mill. These materials were extensively characterised and evaluated for different applications, like wood adhesives, (bio) polymer additives and surfactants. Some sample of black liquor were used to isolate primary lignins at laboratory and pilot scale (up to 80 kg). In addition an off-line process optimisation was carried out.
Several analytical protocols for characterisation of lignin were developed, optimised and validated by means of a round robin test involving five of the participants. The effects of the precipitation process used, on the chemical composition and purity of the lignins isolated, was investigated. Isolated lignins were evaluated for the three end-uses stated in the Technical Annex by determination of structure-function relationships. Precipitated lignins were chemically modified and the effects of modification on the properties of lignins were determined by wet chemical and spectroscopic methods according to the developed and established protocols.
Potential lignins from different raw materials, such as flax, hemp and straw, were tested for the different applications. Development of lignin based bio-polymers and polymer additives were studied, as were wood adhesives (with special attention to use in plywood). These were investigated on both laboratory scale and on a larger scale. Further work investigated the development of lignin-based surfactants for cement application.
Progress
During the second year of the project a large amount of lignin has been precipitated at laboratory and pilot scale (up to 80 kg product) from black liquors from alkaline straw, hemp, flax, abaca, sisal and jute pulping. The laboratory scale precipitation has been optimised in order to get a better comparison with the pilot plant. Removal of rejects and impurities from the isolated lignin as well as grinding and screening could be performed on large scale. Black liquors from different raw materials showed variation in dry matter and composition, which will effect the isolated lignin purity and yield. Consistent quality of several black liquors could be obtained, but not for all. Several month storage of black liquor did not really change the quality of the isolated lignin. The feasibility of an industrial process for the isolation of lignin from black liquor has been shown and the lignin prices are at a competing level. First attempts at correlating processing conditions and lignin properties have been completed, but this must be extended in the next period.
Soda lignins from straw, hemp and flax contained a lignin content above 80 %, a sugar content up to 2.2 % and substantial contents of proteins up to 15 %. Flax and Alcell lignins have much lower softening temperatures (90 °C) than straw (140 - 180 °C) or hemp lignins (160 °C).
Several protocols for characterisation of lignin have been developed, optimised and established as a result of round robin tests performed by several project partners. In addition several application-derived protocols have been developed.
Laboratory scale modification of lignin has been performed by several partners. These modifications can be easily scaled up to industrial scale. Modified lignins have been characterised and tested for various end-use applications. Wet chemical and spectroscopic methods proved that the modifications were successful, but lignin structure-properties will be further evaluated in the third year.
Results obtained thus far indicated that lignin shows potential as a polymer additive. Similar product properties have been obtained for (bio) polymers filled with flax and Alcell lignin. Lignin can be used as a stabiliser against biodegradation for biodegradable polymers and as a stabiliser for thermal oxidation of rubbers. Flax lignin plastised with ethylene glycol resulted in an injection mouldable product, which was reinforced with relatively high amounts of wood and showed good properties.
Positive results have been obtained for the application of lignin in a wood adhesive for plywood. 30% replacement of phenol formaldehyde resin by soda lignin resulted in comparable adhesive properties compared to the PF-resin without lignin addition. However, the cold tack properties were very poor and need to be enhanced for industrial application. Further improvement of the adhesive properties, by optimising processing conditions and modification of lignin, will be performed in the next period. Difficulties found in mixing lignin with the glue have been solved by screening of the lignin.
For application of lignin in concrete, lignin should contain less than 2% sugar impurities. Soda lignin showed improved flow behaviour in mortar and satisfactory or good product performance of the mortar. Flax lignins performed best in this application compared to other lignin types. Sulfonation did not change the performance of lignin in this application. In contrast, carboxy-methylated lignin had an increased performance. For cement application, addition of anti-foaming agents to the lignin is necessary. First tests with flax lignin on larger scale have been successful and these tests will be continued in the third year. Several alkaline sulphur-free lignins can be used as an emulsion stabiliser. Addition of lignin resulted in a stable emulsion, which is resistant against change of pH.
Achievements
After 2 years the following deliverables were achieved.
Evaluating the project progress and the deliverables and milestones achieved as described in the consolidated progress report after year 2 and in the Technical Annex, it can be concluded that after 2 years the project is well on schedule. No major changes or delays are observed nor expected for the third project year.
Future actions
During the final year the work performed should enable the following deliverables to be realised:
Task A
Task B
Task C
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