"PROCESS FOR THE PRESERVATION OF ORGANIC PRODUCTS" It is well known that, for the preservation and storage of corrosive aqueous solutions, additives are used in order to avoid corrosion of the containers and to limit the preserved products becoming coloured due to the formation of salts or metal compounds at the expense of the material of which the container itself is made.

The problem of corrosion still however exists when organic products- in. a non-aqueous phase have to be stored. Storage of certain natural or synthetic organic products, such as, for example,oils and fatty acids of animal or vegetable origin monomers or polymers having free acid groups which can release acid groups by hydrolysis, gives rise to considerable problems of corrosion, that may be prejudicial to their quality, together with phenomena of polymerization or metal catalyzed oxydation due to the presence of oxygen in the air.

Subject invention removes the above drawbacks at the same time providing important advantages as will be described below.

Subject of the invention is a process for the preservation of organic products possessing corrosive properties, by the use of certain phosphonic compounds. In particular, compounds are used as anticorrosive agents, corresponding to the formula

where R is a linear or branched alkyl or aryl-alkyl radical having a number of carbon atoms from 8 to 22 and X 1 ,X2,χ3,

4 +

X , are equal or different: hydrogen NH substituted cyclo-

alkyl or alkyl-aryl, aryl, alkyl quaternary ammonium radi¬ cal, a metal belonging to group 1-4.

The above compounds inhibit corrosion of the metallic ma¬ terials of the containers by the organic products stored inside them in a non-aqueous phase. Further, while such compounds exercize a markedanticorrosion action if they are used in the storage of organic products having corrosive properties, actually they show no effect i'f used in the storage of acqueous solutions. They also show great ability to form complex ions of transition metal in the organic phases and,by a variation in oxido-reduction potential as well, they ensure a nota¬ ble degree of inhibition of phenomena of degradation re¬ lating to oxidation or polymerization due to the oxygen in the air.

In particular the compounds concerned can be diphosphonic hydroxy derivates of caprylic, lauric, palmitic, stearic, undecenoic, oleic, cyclohexanecarboxylic acids. The methods followed in preparing the compounds correspond- ing to the above formula have been well known for some time and are based on the reaction of anhydrous phosphorous acid with the anhydrides or chlorides of carboxylic acids or on the interaction of phosphorus trichloride with the organic acids. According to the process subject of the invention such com pounds are prepared to obtain the maximum concentration of diphosphonate products keeping the level of secondary com¬ pounds and,above all,of inorganic acids very low, in order to ensure the highest anticorrosion effect and the best binding ability on transition metal ions.

Reaction between the ^" organic component, namely the alipha¬ tic acid or its anhydride and the chloride, and the inor-

ganic component, namely the phosphorus trichloride or the phosphorous acid, takes place with an excess of the orga¬ nic component and under strictly controlled temperatures and time of reaction.

The reaction is carried out in such a way that all the i- norganic reagent reacts and the quantity of nonyolatile inorganic components is reduced to the minimum. The above compounds are used just as they are obtained and may be added directly to the product to be stored, since they are perfectly soluble in the organic phase, or else, even better, they are added in the form of a suitably con¬ centrated solution, using as a solvent the same organic substances to be treated or any other kind of suitable solvent for the purpose. Concentrations used depend to a great extent on the physi- cal and chemical characteristics of the organic products to be protected, and especially on the acidity of the com¬ pound, on storage temperature and, of course, on length of storage. Concentrations in active substance range from 100 to 1500 p.p.m. (parts per million) .

The above compounds can be used as filming agents in all operations connected with pickling and protection of iron metal surfaces, in such a way that they act as corrosion inhibitors. Further, for the purposes of stabilizing organic products, they also constitute an alternative as--preyiάusly _-- de.sc_-ibed provided they are modified depending on physico-chemical characteristics of organic products to be protected,tempe¬ rature and storage time. The protective film can be made through treatment of sur¬ faces with solution of the subject cαrpounds. in suitable solvents ⁽ whether volatile or not) in accordance w'ith the usual

procedures (immersion, spraying or some other) , especially using solutions at concentrations between 0.5 and 10%. The characteristics and purposes of the invention will be made even clearer by the following examples of its execu- tion assisted by charts and graphs. Example 1 In an inert atmosphere with three moles of caprylic acid,one mole of phosphorous trichloride is added gradually, keeping o the temperature at 60 C. The reaction mass is then raised to 70 C continually stir¬ ring the product for two hours.

The temperature is then slowly raised over a period of 4 hours up to 130 C, removing the HC1 which develops. The temperature is maintained for another 4 hours, after which the volatile components are distilled from the reaction mass under a 1 m Hg vacuum up to a temperature o ^* f 160 C. In this way a brown product is obtained which is dis¬ solved in 2 parts of toluene and purified, washing with a saturated aqueous solution of NaCl. The aqueous phase is analyzed in order to measure its con¬ tent of inorganic P. The organic phase is used as reported _^ in the following examples.

Analytic results show a content of inorganic phosphorus equivalent to 6.5% of the phosphorus added in the reaction. Example 2

3 moles of laurilchloride are added dropwise in 2 hours to 2 moles of H PO. kept at constant temperature of 130 C,which is rapidly stirred, and the temperature is then gradually raised to

150 C and kept at this level for 4 hours , removing the ga- ses developing under reduced pressure and thinned down . The mass is then cooled down to 80 C and 2 moles of H O are added dropwise keeping the temperature at 80/90 C .

The product is then cooled and a white mass obtained. A portion of said mass is subjected to purification as des cribed in Example 1.

Analytical analysis shows inorganic P content equal to 1.7 _% of the total phosphorus added in the reaction. Example 3

3 glass test tubes A, B, C are set up open, each containing 6 g. of fatty acids from mixed seeds.

Laurilhydroxydiphosphonic acid is added to two of said test tubes, F and C, so that they respectively contain 800 and 1600 p.p.m. of phosphonate.

2

A steel lamina, surface area 8.4 cm is completely immersed, after suitable pickling and drying, in each of the 3 test tubes and said test tubes are placed in a air-forced oven at 85°C.

Every 12 hours small quantities of fatty acids are drawn off and analysed to check Fe content.

The results, given in the following table, show Fe content in p.p.m. of test tubes A,B,C, after respectively 12,24 and 36 hours.

12 h. 24 h. 36 h.

A) (without phosphonate) 13.7 45 .2 1 04 .4

B) (800 p.p.m. of phosphonate) 6.5 7 . 0 21 . 1

C) (1600 " " " )7.9 1 0 . 7 1 2 .5

Example 4

Four 800 cc. beakers are filled with 500 g. of olive fatty acids originally containing 0.4 p.p.m. Fe.

2

3 steel laminas, surface area 80 cm , treated as in Exam- pie 3, are also prepared.

Suitable additions of diphosphonic oleilhydroxy acid are made to two beakers so as to obtain concentrations of 100

and 800 p. .m. of.phosphonate in the acid.

The 4 samples thus obtained called A) , B) , C) , D) , are the following:

A) (blank) without phosphonate or an Fe lamina in it; B) without phosphonate and with Fe lamina;

C) containing 100 p.p.m. of oleilphosphonate and with Fe lamina;

D) containing 800 p. .m. of oleilphosphonate and with Fe lamina. The samples are placed in an air-forced oven at 85 C for 96 hours. They are then analysed to check Fe content and lo- vibond colour grade.

Results are given in the following table. p.p.m. Fe Lovibond A 0.4 4

B 60.4 6

C 7.3 4/5

D 4.6 4

Example 5 Following the methodus used in the previous examples,and

2 using 2 steel laminas, surface area 50 cm , 3 samples called A, B, C of 200 g. of olive fatty acids are prepa¬ red as follows. A) (blank) olive acids without phosphonate and Fe lamina; B) olive acids, without phosphonate, with Fe lamina;

C) olive acids + 800 p.p.m. laurilhydroxydiphosphonic acid and Fe lamina. The samples are placed in an air-forced oven at 85°C. Over time small quantities of solution are drawn off and ana- lysed to check Fe content and colour.

The results of colori etric analyses on the three samples A, B, C are shown in the following graph with colour gra-

- 7 - dings on one axis and times on the o her,

• .- A

Concentrations of Fe ion p. .m. determined at the various times, are listed below.

96 h. 168 h. 264 h.

B) 73.5 144 249 C) 2.3 2.5 2.5 Example 6

An iron lamina, total surface area 50 cm , pickled as in Example 3, is immersed for half an hour in a toluene solu ^¬ tion at 1% of lauroildiphosphonic acid.

It is then dried at room conditions.

After drying the lamina is completely immersed in a bea¬ ker containing 200 g. of olive fatty acids. The beaker is placed in an air-forced oven at 85 C for

268 hours; at the end of the test, analysis shows Fe ion content of 1 p.p. Example 7

Two steel lamina are prepared with ground wires,and then pickled by the usual method.

With these larainas two tests, A and B, are set up with olive fatty acids as follows:

A) olive fatty acid, without phosphonate, with steel lamina

B) olive fatty acid, 800 p.p.m. of laurilhydroxydiphosphonic

2 acid, with lamina, lamina surface being 34 cm .

Grounding connections are set up and the beakers are placed o in an air-forced oven at 85 C.

After 268 hours/ sample A contains 213.5 p.p.m. of Fe,while sample B contains 7.3 p.p.m. As the applications of the invention have been described as examples only not limited to these, it is understood that any equivalent application of the ^"■' nventive concepts here explained, and any product executed and/or operating in accordance with the characteristics of the invention will be covered by its field of protection.