Dimerization of rosin

Dimerization of rosin (Figure 3B.24) increases its molecular weight and softening point, induces higher viscosity (molten and in solution), and improves stabihty. 

Liu S, Xie C, Yu S, Liu F. Dimerization of rosin using Bronsted-Lewk acidic ionic liquid as catalyst. Catal Cammun June 2008 9(10) 2030-4. 

The trend towards increased calcium carbonate usage and therefore neutral pH paper making has meant that there has been a steady decline in the use of rosin and alum and a concomitant increase in the use of sizes which are effective at higher pH. Commercially the most important in this group are the alkenyl succinic anhydrides (ASA) and the alkyl ketene dimers (AKD). These are able to esterify fibre surfaces directly and are more effective at neutral to high pH. 

Important reactions of rosin are summarized in Figure 8. Dimerization is generally carried out by a Lewis acid catalyst such as sulfuric acid, boron fluoride, or zinc chloride (14-16). A rosin dimer finds uses in resin preparation because it allows quick buildup of molecular weight through a polyfunctional alcohol or amine. 

Chem. Descrip. Resin of dimeric adds derived trom rosin with lesser amounts of monomeric resin acids, and neutral material of rosin origin Uses Thermoplastic resin used in mtg. of protective coatings, spirit varnishes, epoxy ester resin vehicles, adhesives, and printing inks as a soldering flux tackitier tor NR, SBR, NBR, PS, PVC reinforcement for specialty adhesive prods. 

Dehnition Hexaester of 6-hydroxystearic acid, stearic acid, the acids derived from rosin, and a dimer of pentaerythritol... 

Figure 7.18. Chemical structures of (a) abietic acid, which is one of the more common constituents of rosin (b) alkyl ketene dimer (AKD), with R = C14-C18 (saturated or unsaturated) (c) alkenyl succinic anhydride (ASA) with R = C14-C18 (unsaturated)...

Parkin B.A., SchiiUer W.H., Catalyst-solvent systems for dimerization of abietic acid and rosin, Ind. Eng. Chem. Prod. Res. Develop., 11(2), 1972, 156-158. 

Disproportionation/dehydrogenation of rosin is also a process that decreases the ability of colophony to oxidize, since the amount of resin acids with conjugated double bonds is diminished in favour of dehydroabietic acid. Polymerization dimerization of colophony decreases its tendency to crystallize. Major products formed are dimers of resin acids, but the degree of polymerisation varies with the conditions (time, temperature) under which the modification is performed. Formaldehyde modification of colophony includes several different reactions performed under various conditions where formaldehyde reacts with resin acids. Colophony can also be modified by reacting metal salts, e.g. sodium, potassium, or barium, calcium, cobalt and zinc, with resin acids to form salts resinates) (McSweeney et al. 1987 Soltes and Zinkel 1989). 

Besides hydrogenation, dimerization of abietic acid using sulfuric acid as a catalyst is a way to make rosin less susceptible to oxidation. ... 

Glycerol ester of rosin Pentaerythritol ester of rosin Dimerized rosin Esters of hydrogenated rosin... 

The rosin column spHt is controUed by the fatty acid content specified for rosin. This is usuaUy set at 2% fatty acids. At the high temperature near the bottom of the column and the reboUer, rosin dimerizes to some extent. By taking rosin from the column as a sidestream above the bottom, its rosin dimer content is minimized. Because of its high purity, sidestream rosin product is prone to crystallization. 

Internal Sizing. The most widely used internal sizes are alkyl ketene dimers (AKD), alkenylsuccinic anhydrides (ASA), and rosin-based sizes that are used with papermaker s alum (aluminum sulfate with 14 waters of hydration), polyaluminum chloride (PAG), or polyaluminum siUcosulfate (PAS) (61). The rosin-based sizes are used under acidic conditions. Since the mid 1980 s there has been a steady conversion from acid to alkaline paper production, resulting in static to declining demand for the rosin-based sizing systems. Rosin is a complex mixture of compounds and consists primarily of monocarboxyhc acids with alkylated hydrophenan threne stmctures (62). A main constituent of wood rosin, gum rosin and taH-oil rosin is abietic acid. 

Dimerization is mediated by the phosphotyrosine residue and the SH2 domain. Highly resolved structural investigation show that the phosphotyrosine residue of one Stat protein binds to the SH2 domain of the partner and vice versa, so that the phosphoty-rosine-SH2 bonds fimction as a double clasp (structure in complex with DNA Becker et al., 1998 Chen et al., 1998). The binding to DNA is in the form of a dimer, with the Stat-DNA complex showing a large similarity to the structure of the NFxB-DNA complex (see Fig. 1.10). 

During the last several decades, naturally derived masticatory substances have been displaced to a considerable degree by synthetic materials — for reasons of availability, economics, and. frequently, better control over purity. These developments essentially paralleled the development of Ihe synthetic rubbers for industrial uses. Some of the synthetic substances now used and listed in the "Food Chemicals Codex, published by the National Academy of Sciences (Washington. DC) include- butadiene-styrene 75/25 rubber butadiene-styrene 50/50 rubber glycerol ester of partially dimerized rosin glycerol ester of partially hydrogenated wood... 

Glycerol Ester of Partially Dimerized Rosin / Monographs... 

Glycerol Ester of Partially Dimerized Rosin occurs as a hard, pale, amber-colored resin (color M or paler as determined by ASTM Designation D 509) produced by the esterification of partially dimerized rosin with food-grade glycerin, and purified by steam stripping. It is soluble in acetone, but is insoluble in water. 

Alternative types of size quickly filled the void, rosin was reformulated to enable sizing up to pH 6.5, whilst alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA) provided non-rosin solutions. 

Chem. Descrip. Glycerol ester of a partially dimerized rosin CAS 8050-31-5 EINECS/ELINCS 232-482-5 Uses Softener or plasticizer for elastomeric masticatory agents in chewing gums modifier for rubbers, film-formers, and waxes in adhesives and protective coatings Features Thermoplastic resin... 

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