Food or edible material: processes – compositions – and products – Inhibiting chemical or physical change of food by contact...
Reexamination Certificate
1999-08-27
2001-04-24
Pratt, Helen (Department: 1761)
Food or edible material: processes, compositions, and products
Inhibiting chemical or physical change of food by contact...
C426S102000, C426S615000, C564S307000, C564S433000, C564S435000, C564S437000
Reexamination Certificate
active
06221414
ABSTRACT:
The present invention relates to a simplified process for purifying plant-protection products contaminated with impurities of aromatic primary amine type.
Many plant-protection products commonly used in the treatment of fruit and vegetables are contaminated, in their commercial form, with undesirable toxic substances. This is the case especially for diphenylamine, which is widely used on account of its antioxidant properties, which is contaminated with various manufacturing side products, in particular primary aromatic amines such as aniline, 4-aminobiphenyl and 2-aminobiphenyl.
This is also the case for ethoxyquine, an antioxidant product, which is contaminated with p-phenetidine. Mention may also be made of chlorprofam which is a potato anti-germinating agent and which contains appreciable amounts of meta-chloroaniline.
FR 2,689,506 describes a process for selectively eliminating primary amines contaminating diphenylamine, by placing a solution of contaminated diphenylamine in contact with a cationic ion-exchange resin in the presence of water. Although effective, this process is complex and laborious. It requires either the use of columns packed with ion-exchange resin or the separation of the ion-exchange resin from the reaction medium before treatment of the fruit and vegetables.
The process of the invention does not have these drawbacks. Specifically, according to the invention, the reaction medium recovered after the process can be used directly for the preparation of a plant-protection composition intended for the treatment of fruit and vegetables. The use of the process of the invention is also particularly simple and requires no sophisticated or expensive apparatus.
The process claimed is directed towards freeing a given plant-protection product of its impurities of aromatic primary amine type. The process of the invention is effective irrespective of the exact nature and the amount of the said impurities of aromatic type. It is particularly suitable for the elimination of the impurities of formula I:
Ar—NH
2
I
in which Ar represents a monocyclic or polycyclic aromatic nucleus optionally substituted with one or more radicals chosen from a halogen atom; a (C
1
-C
8
)alkyl or (C
1
-C
8
)alkoxy group; and amino.
The term “alkyl group” means a linear or branched hydrocarbon chain. Preferably, the said alkyl group comprises from 1 to 5 carbon atoms.
The alkyl part of the alkoxy group is defined similarly.
In a particularly advantageous manner, the aromatic nucleus Ar is mono- or bicyclic. Examples which may be mentioned are phenyl, naphthyl, anthryl and phenanthryl groups, phenyl and naphthyl groups being preferred.
The process of the invention is particularly suitable for the purification of plant-protection products comprising up to 10,000 ppm by weight of impurities of aromatic primary amine type, preferably up to 1000 ppm.
The process of the invention consists in treating, in acid medium, the plant-protection product with an alkali metal nitrite, such as sodium nitrite or potassium nitrite.
More specifically, the process of the invention comprises:
a) the placing in contact with stirring, at a temperature between 15 and 25° C., of an aqueous solution of the said alkali metal nitrite with an organic solution prepared by dissolving the said plant-protection product to be purified in a solvent chosen from a nonionic surfactant, a C
2
-C
12
glycol and mixtures thereof;
b) the addition of a strong inorganic acid to the resulting reaction medium, while stirring at the said temperature;
c) followed by heating of the reaction medium to a temperature of between 30 and 70° C.
The first and second steps of the process claimed are generally performed in the order indicated. However, it is possible, in the context of the invention, to acidify the aqueous alkali metal nitrite solution in a first step, and then place the said acidified aqueous solution in contact with the organic solution of the plant-protection product, with stirring, before heating the reaction medium to a temperature of between 30 and 70° C.
It should be understood, however, that the embodiment which consists in carrying out steps a) and b) in the order indicated (step a) and then step b)) is preferred.
The aqueous alkali metal nitrite solution is preferably an aqueous solution containing 0.5 to 3 mol/liter of alkali metal nitrite, better still from 0.5 to 1.5 mol/liter, for example a molar solution.
The amount of the said aqueous solution used in step a) depends on the amount of impurities of primary aromatic amine type contained in the organic solution of the plant-protection product.
Strictly speaking, a stoichiometric amount of the alkali metal nitrite relative to the total number of moles of aromatic primary amino groups present in the organic solution is sufficient for total removal of the impurities. It will be noted that a given impurity can contain more than one aromatic primary amino group. This is the case in particular for the impurities of formula Ar—NH
2
, in which Ar represents an aromatic nucleus substituted with more than one amino group.
However, it is desirable to use an excess of alkali metal nitrite. An amount ranging between 1 and 5 molar equivalents of the alkali metal nitrite relative to the total number of moles of aromatic primary amino groups, for example between 1 and 3 molar equivalents, is appropriate.
The organic solution of the plant-protection product is prepared by dissolving the plant-protection product in a solvent which is chosen from a nonionic surfactant, a C
2
-C
12
glycol and mixtures thereof in any proportion.
According to the invention, it is nevertheless preferred for the said solvent to consist:
of one or more nonionic surfactants;
or of a mixture of one or more nonionic surfactants with one or more C
2
-C
12
-glycols.
Advantageously, the said solvent consists of one or more nonionic surfactants.
In the context of the invention, the term “glycols” means dihydroxylated alcohols derived from aliphatic hydrocarbons by replacement of two hydrogen atoms with two hydroxyl groups.
According to the invention, C
2
-C
6
glycols are preferred, and in particular ethylene glycol and propylene glycol. Examples of nonionic surfactants which can be used according to the invention are, in particular:
the product of condensation of an aliphatic fatty alcohol, preferably a C
8
-C
22
aliphatic fatty alcohol, with a C
2
-C
3
alkylene oxide. The C
2
-C
3
alkylene oxide can be ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion. An example of such surfactants is the product of condensation of lauryl alcohol (or n-dodecyl alcohol) with 30 mol of ethylene oxide;
the product of condensation of an alkylphenol in which the alkyl chain is C
8
-C
22
with a C
2
-C
3
alkylene oxide. Here also, the products of condensation with ethylene oxide, propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion are again advantageous. As examples of such surfactants, mention may be made of the product of condensation of n-nonylphenol with 10 mol of ethylene oxide;
the product of condensation of a fatty acid, preferably a C
8
-C
22
fatty acid, with a C
2
-C
3
alkylene oxide, for example ethylene oxide or propylene oxide or a mixture of ethylene oxide and propylene oxide in any proportion. These condensation products have an alkoxylated chain on the hydroxyl function of the carboxylic group. Preferred surfactants of this group are the condensation products obtained from oleic acid, palmitic acid and stearic acid.
Usually, the surfactants used result from the condensation of a fatty alcohol, a fatty acid or an alkylphenol with 3 to 50 mol of C
2
-C
3
alkylene oxide.
Among the surfactants mentioned above, those with an HLB (hydrophilic-lipophilic balance) constant of between 6 and 18 are particularly preferred.
The organic solution used in step a) preferably comprises from 5 to 50% by weight of the said plant-protection product, better still from 10 to 30% by weight.
The aqueous solution is placed in contact with the
Pratt Helen
Wenderoth , Lind & Ponack, L.L.P.
Xeda International
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