Chapter 15
Commercial Use of Lignin-Based Materials J. D. Gargulak and S. E . Lebo
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LignoTech U S A , 100 Highway 51 South, Rothschild, W I 54474
The usefulness of industrial lignins has been demonstrated by the profitability of the lignin chemicals business operated worldwide. The total sales in 1980 amounted to 180 million dollars. By 1996 that number had grown to 600 million dollars. This growth is fueled by demand in the traditional industries: oil well drilling additives, concrete additives, dyestuff dispersants, agricultural chemicals, animal feed and other industrial binders. Within the past few years new potential uses for modified commercial lignins have appeared that will continue to fuel this growth. Specialty polymers for the paper industry, enzyme protection, neutralization of biocides, precious metal recovery aids and wood preservation are some examples of these advanced uses.
Historically, lignosulfonates and other lignin based products have been viewed as waste materials of limited industrial usefulness. Advances in lignin technology, however, have led to the development of specialty products that can compete with higher cost synthetics. The improved performance of these products together with the fact that they are essentially non-toxic and derived from a renewable resource make them versatile, cost-effective chemicals for today's environmentally conscious consumer. In this chapter, we will attempt to summarize the mature markets for lignin materials, as well as look at some promising future technologies. Definitions Commercial lignosulfonates are complex anionic polymers obtained as co-products of wood pulping. They are obtained from spent sulfite pulping liquors (Figure 1) or from postsulfonation of kraft (i.e. sulfate) lignins (Figure 2). Lignosulfonates derived from spent pulping liquors are actually mixtures of sulfonated lignins and other wood
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© 2000 American Chemical Society Glasser et al.; Lignin: Historical, Biological, and Materials Perspectives ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
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CHO
Figure 1. Structural representation of Spruce Lignosulfonate.
Glasser et al.; Lignin: Historical, Biological, and Materials Perspectives ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
Glasser et al.; Lignin: Historical, Biological, and Materials Perspectives ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
Figure 2. Proposed structure of Kraft Pine Lignin.
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307 derivatives that may be used with little or no modification, or they may be modified to produce specialty materials with chemical and physical properties specific to certain end-use markets. A number of specialty uses also exist for kraft lignins isolated from sulfate pulping liquors.
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Producers Excluding the former Soviet Union, lignosulfonate capacity worldwide is estimated to be about 975M solid tons/year (Table 1). Production is concentrated among a few well-established companies and is dominated by lignosulfonate derived from spent sulfite liquor. Only Westvaco and LignoTech Sweden produce lignosulfonates by postsulfonation of kraft lignin. Not listed on Table 1 is the recently announced lignosulfonate producer LignoTech South Africa. Slated to start up in 1999, production at this facility will add 200,000 solid tons/yr capacity by 2003.
Table I; Major Lignosulfonate Producers
Producer
Country
Borregaard LignoTech
Norway
160,000
LignoTech Sweden
Sweden
60,000
Borregaard Germany
Germany
50,000
LignoTech Iberica
Spain
30,000
LignoTech Finland
Finland
20,000
LignoTech U S A
United States
60,000
Georgia Pacicfic
United States
200,000
Westvaco
United States
35,000
Flambeau Paper
United States
60,000
Tembec
Canada
20,000
Avebene
France
40,000
Tolmezzo
Italy
30,000
Sanyo Kokusaka
Japan
50,000
Others
Annual Capacity (solid tons/year)
150.000 975,000
Glasser et al.; Lignin: Historical, Biological, and Materials Perspectives ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
308 Production Chemistries
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For some applications, spent sulfite liquors containing crude lignosulfonate are used without further modification. For most specialty applications, however, impurities negatively impact performance and purification and/or modification is required. Purification methods include sugar removal by fermentation or chemical destruction. Ultrafiltration and chemical precipitation are also used commercially to produce high purity lignosulfonates. Chemical modifications include: sulfonation, sulfoalkylation, desulfonation, formulation, oxidation, carboxylation, amination, crosslinking, depolymerization, graft polymerization, and combinations of the above. Chemical modifications are generally performed to enhance the dispersing, completing or binding properties of the finished product. Chemical And Physical Properties As stated earlier, lignosulfonates are complex polymers. As such, detailed characterization of their chemical and physical properties is often difficult. Analytical techniques for determining gross properties such as purity, degree of sulfonation and degree of carboxylation are fairly well established (1). Analysis of minor functional groups is more difficult and often yields ambiguous results. Even more difficult is the analysis of physical properties, particularly molecular weight. From an industrial standpoint, it is not always critical that properties of a given lignosulfonate are known in detail. While not belittling the advances lignosulfonate producers have made in this area, semi-quantitative characterizations are often sufficient to provide information for determining the usefulness of a given product in a particular application. In fact, it is there wide variety of physical properties that make industrial lignosulfonates useful in a wide variety of applications. Toxicological Properties Extensive testing has shown that lignosulfonates are non-toxic at typical use levels (Table Π). Their use in a wide variety of food and food packaging applications has been approved under the following U.S. Food and Drug Administration regulations (2). Markets Several, more detailed, reviews have been done on this subject (2,3). However, a breif mention of the commercial markets is appropriate for this tutorial. The markets for lignosulfonates can, in general, be divided into two classes, commodity and specialty. Many, but not all, of the large volume markets use lignosulfonates from spent pulping liquors without further processing. Most, but not all, of the specialty markets use modified or highly modified lignosulfonates or lignosulfonates derived by postsulfonation of kraft lignin.
Glasser et al.; Lignin: Historical, Biological, and Materials Perspectives ACS Symposium Series; American Chemical Society: Washington, DC, 1999.
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Properly
Ammonium Lignosulfonate
Acute Toxicity"
> 2,000
> 10,000
>10,000
Eye Irritant
No
No
No
Skin Irritant
No
No
No
Fish Toxicity*
> 1,000
> 1,000
> 1,000
Bacteria Toxicity*
5,000
5,000
343
fl
(LD
50
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Table Π. Toxicity of Lignosulfonates. Sodium Calcium Lignosulfonate Lignosulfonate
- mg/kg). *(LC - mg/1),
