Biodegradable scale inhibitors

A depol5nnerized carboxyl alkyl guar with a degree of substitution of up to 3 carboxylic groups per sugar unit can be used as a scale inhibitor in oilfield applications (40 This is a biodegradable scale inhibitor which is effective under severe scaling conditions. 

These amino acid anhydrides are usuaiiy made with phosgene. The use of dimethyi carbonate shouid be tested in the preparation of the monomers. Poiyaspartic acid can be made by heating aspartic acid without soivent to form a polysuccinimide which is then hydrolyzed (12.34).186 It can also be made directly from maleic anhydride and ammonia. It promises to be useful as a scale inhibitor in water, an antiredeposition agent in detergents, and such. Gamma-irradiation converts it to a biodegradable superabsorbent material that takes up 3400 g water per gram of dry polymer.187 (Most superabsorbent polymers are based on acrylamide, a neurotoxin.)... 

In the area of water treatment, polyacrylate scale inhibitors and dispersants, based on homopolymers of polyacrylic acid, are commonly used. Although generally of low toxicity, these polymers are not biodegradable. In some sensitive areas, such as the North Sea Oil fields, this has led to the search for biodegradable alternative to polyacrylates. 

Polyaspartates, as exemplified by the parent polymer, polyaspartic add, offer an attractive biodegradable alternative to polyacrylates [21]. In addition to thdr activity as scale inhibitors and dispersants, polyaspartates have also been shown to have corrosion inhibition activity, particularly for the corrosion environments frequently found in oil-field applications. Polyaspartates have very high biodegradability as indicated by OECD guidelines for aquatic biodegradability. 

Ross, R. J., Low, K. C., and Shannon, J. E. 1996. Polyaspartate Scale Inhibitors—Biodegradable Alternatives to Polyacrylates, CORROSION 96, Paper No. 162, NACE International, Conferences Div., Houston, Texas. 

To get scale inhibitors with improved biodegradability, during the radical polymerization, chain transfer agents have been used. Conventional chain transfer agents are halogen compoimds and thiols. 

However, the use of chain transfer agents containing at least one P-H bond, allows to produce polymers which combine excellent activity as oilfield scale inhibitors with good biodegradability, often in excess of that required by the OECD 306B standard (11). 

Polymers which contain phosphorus end capping groups can have a desirably high biodegradability as weU as being effective as oilfield scale inhibitors (9). 

Miscellaneous recent acetal polymer chemistry to produce biodegradable water-soluble polymers includes superabsorbents [159], the use of hydroxycarboxylic acid to produce lubricants [160], scale inhibitors [161], and water-soluble packaging materials [162]. 

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