Coating processes – Coating pavement or the earth
Patent
1994-04-05
1995-03-07
Beck, Shrive
Coating processes
Coating pavement or the earth
427154, 210925, C09K 332
Patent
active
053956460
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a process for the protection of solid surfaces, and most particularly of coastal areas and banks, against pollution by hydrocarbons.
The protection of coastal areas against the effects of accidental spillages of hydrocarbons is provided by mechanical or chemical means. Mechanical means consist of the deployment of dams or nets to prevent the hydrocarbon slick from reaching the banks. Chemical means are aimed at breaking up the slick of crude before it reaches the coast. Chemical processes make use of dispersants by themselves or of absorbents.
If the pollution due to hydrocarbons has already reached the coast, the processes used have only a curative effect. They consist in the cleaning of the banks using jets of cold or hot water, or in shovelling.
There are also physicochemical processes employing absorbents or else washing agents. This treatment may be supplemented by the addition of nutrient substances whose purpose is to promote the development of the microorganisms responsible for the biodegradation of hydrocarbons. This process is described in French Patents 2,490,672 and 2,512,057.
Protection of coastal areas before the arrival of the hydrocarbon slick has also been envisaged. This involves protecting rocks or shingle forming the beaches with a coating which prevents the adhesion of hydrocarbons. Among the products tested in this application we can mention sodium silicate, xanthan gum and polyvinyl acetate. Among these products, only polyvinyl acetate has been considered as being appropriate for such an application (C. L. Foget et al - Technical Report EPA-60012-84-085). At the same time, the use of a vinyl chloride polymer in a marine environment encounters fears concerning the harmful effect of the traces of monomer which the polymer unavoidably contains. The effect of the other recommended products has been too short-lived. Washing-out of the products by seawater reduces the effectiveness of the protection in practice to the duration of one tide.
We have now found a process which makes it possible to protect the coast durably against the deposition of hydrocarbons and does so without danger to the environment, by employing a natural and entirely biodegradable product. This process can also be employed for the protection of other solid surfaces, such as cement or plastic floors.
For this purpose, this invention relates to a process for the protection of solid surfaces against the deposition of oleophilic materials by application to the said surfaces of a protective layer, characterized in that the protective layer is made up of at least one polysaccharide containing free carboxyl groups, chosen from the group consisting of alginates and slightly methylated pectins taken by themselves or mixed.
The alginates are extracted from brown seaweed present on most rocky coasts. They are harvested chiefly in the North Atlantic, in France on the coasts of Brittany.
The alginates are obtained from this brown seaweed by demineralization in an acidic medium and extraction of the alginate in an alkaline medium followed by a precipitation of alginic acid.
It is also possible to employ alginates of bacterial origin.
Alginic acid is a polyuronide, consisting of a chain sequencing of two hexuronic acids, beta-D-mannuronic acid and alpha-L-guluronic acid.
Studies using partial hydrolysis and carbon-13 NMR have shown that these two monomers are distributed in blocks of about twenty units. The various seaweeds contain very variable proportions of mannuronic acid/guluronic acid. Alginates with a high content of guluronic acid are advantageously employed.
Since alginic acid is insoluble in water, use is made of water-soluble alginates obtained by neutralization of the acid with a basic compound, generally an alkaline base.
The pectins are extracted chiefly from apple marc or lemon peel by an acidic treatment followed by precipitation with alcohol. The pectin obtained consists essentially of alpha-D-galacturonic acids partially esterified with methanol. It also contains small quantities of beta-L
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Amoco Cadiz Oil Spill, Marine Pollution Bulletin, vol. 9, No. 11, Nov. 1978.
Biotechnology of Marine Polysaccarides, The Use of Water-Soluble Polymers in Oil Field Applications: Hydraulic Fracturing, pp. 250-280, Apr. 1984. Translation of JP 05-070796.
JP 05-070796A. Abstract Only.
Basseres Anne
Ladousse Alain
Beck Shrive
Cameron Erma
Societe Nationale Elf Aquitaine
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