Lignin acrylation

Figure 6. Relationship between gel fraction and vinyl equivalent weight of several acrylated lignin derivatives. (40 wt. % lignin acrylate and 60 wt. % MMA).

Internal treatment-related problems may take the form of organic material present in deposits of iron oxide corrosion debris and salt scales. The material typically is present as carbonized organic components and may originate from water treatment chemicals such as quebracho, wattle, pymgallol, or other tannin derivatives. Also, acrylates, starches, sulfonated lignins, and other sludge dispersants may be present. 

Synthetic examples include the poly(meth)acrylates used as flocculating agents for water purification. Biological examples are the proteins, nucleic acids, and pectins. Chemically modified biopolymers of this class are carboxymethyl cellulose and the lignin sulfonates. Polyelectrolytes with cationic and anionic substituents in the same macromolecule are called polyampholytes. 

A polymeric composition for reducing fluid loss in drilling muds and well cement compositions is obtained by the free radical-initiated polymerization of a water-soluble vinyl monomer in an aqueous suspension of lignin, modified lignins, lignite, brown coal, and modified brown coal [705,1847]. The vinyl monomers can be methacrylic acid, methacrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, vinylacetate, methyl vinyl ether, ethyl vinyl ether, N-methylmethacrylamide, N,N-dimethylmethacrylamide, vinyl sulfonate, and additional AMPS. In this process a grafting process to the coals by chain transfer may occur. 

In a large number of oxide flotation plants, sodium silicate (Na2Si03) is used as a gangue depressant. In the past two decades, a new line of depressants has been developed and introduced into a number of operating plants. Some of these depressants include (a) a mixture of sodium phosphate and lignin sulphonate (i.e. depressant 3XD), (b) a mixture of a low-molecular-weight acrylic acid and sodium silicate (depressant 2D) and (c) hydrosol based on the reaction of sodium silicate with alumina sulphate (depressant SD). These depressants were extensively examined on copper oxide ores from the Nchanga mine in Zambia. 

Derivatives of Lignin and Ligninlike Models with Acrylate Functionality... 

Although most previous research on the use of lignin in structural polymers has dealt with its contribution to polyphenolics and polyurethanes (8), alternatives for crosslinking it with other polymer systems exist as well. These have been summarized recently (9). Among these alternatives are lignin derivatives with acrylate functionality. 

Acrylation of lignin has been reported by Naveau (10), who employed... 

This study examines the synthesis of acrylated lignin derivatives using IEM, and the copolymerization characteristics of these derivatives with methylmethacrylate (MMA) and styrene (S). 

Acrylated lignin derivatives were copolymerized with MMA and S in dry methylene chloride with benzoyl peroxide and N,N-dimethyl anyline as catalyst. Reaction mixtures were poured onto Teflon molds, the solvent was evaporated at room temperature in the fume hood, and films were cured in an oven at 105°C for 6 hrs. Experimental details and results are given elsewhere (15). 

Figure 2. Acrylated lignin-like model compounds, GA and HPGA.

Reactivity ratios between acrylated lignin model compound (Fig. 2), defined as Mi, with either MM A or S, defined as M2, were determined experimentally in accordance with standard procedures (15). These involve mixing two different vinyl monomers in various molar ratios with catalyst (i.e., benzoyl peroxide) and solvent, heating the mixture to achieve polymerization, and recovering the polymer by the addition of non-solvent, and centrifugation. The respective molar monomer fractions of the copolymer were determined by UV-spectroscopy in the cases where MMA served as M2, and by methoxyl content analysis in those cases in which S was the M2-species. The results were subjected to numerical treatments according to the established relationships of Kelen-Tiidos (17) and Yezrielev-Brokhina-Roskin (YBR) (18), and this is described elsewhere (15). 

Solvent soluble and liquid (i.e., tars with Tg below ambient) acrylated lignin derivatives have been formulated by reaction of hydroxyalkyl lignin derivatives with isocyanotoethyl methacrylate (IEM). 

Copoiymerization behavior of acrylated lignin-like model compounds with MMA and styrene indicated a preference for the formation of alternating copolymers. 

Table I. Experimental Reactivity Ratios between Acrylated Lignin Model Compounds and MMA and S...

Acrylated lignin derivatives were copolymerized with vinyl monomers to yield network materials (gels) with gel fraction declining as vinyl equivalent weight increased. 

Acrylated lignin derivatives are viewed as a new and promising class of functional macromers from lignin useful for the formulation of block and segmented copolymers. 

Grafting in Presence of Added Lignin. Ceric ammonium sulfate is an effective initiator for grafting polyethyl acrylate and polyacrylonitrile onto pure celluloses (8), while sodium... 

Figure 5. Grafting rate of two monomers. Conditions initiator, ceric ammonium sulfate (0.08 g/100 mL, 1% HtSOu). Lignin (g%) using ethyl acrylate (40°C) ...

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