Method for preparing a compound comprising at least one imine function by a specific condensation reaction, and particular application of said method in the field of dyeing

Abstract

A method for manufacturing a compound comprising at least one imine group, the method comprising a step of reaction between a first compound comprising at least one amine group and a second compound comprising at least one carbonyl group, the reaction step being carried out in the presence of at least one supercritical fluid.

Claims

1. A method for manufacturing a compound comprising at least one imine group, said method comprising a step of reaction between a first compound comprising at least one amine group and a second compound comprising at least one carbonyl group, said reaction step being carried out in the presence of at least one supercritical fluid.

2. The method according to claim 1, wherein the reaction step is carried out in the presence of a single supercritical fluid, which is supercritical CO.sub.2.

3. The method according to claim 1, wherein, for the first compound, the amine group(s) are primary amine groups and, for the second compound, the carbonyl group(s) are aldehyde groups.

4. The method according to claim 1, wherein, for the first compound and the second compound, at least one of said compounds is capable of being solubilised in the supercritical fluid.

5. The method according to claim 1, wherein the reaction step is implemented in a reactor by the following sequence of operations: an operation of contacting the first compound, the second compound and the fluid under non-supercritical conditions; an operation of bringing the mixture comprising the fluid, the first compound and the second compound under supercritical conditions, the supercritical conditions once established being maintained until completion of the reaction step.

6. The method according to claim 1, wherein the reaction step is implemented in a reactor by the following sequence of operations: an operation of introducing a fluid into the reactor under non-supercritical conditions; an operation of bringing the fluid under supercritical conditions; an operation of introducing the first compound and the second compound into the reactor, the supercritical conditions being maintained until completion of the reaction step.

7. The method according to claim 1, wherein one of the compounds, namely the first compound or the second compound, is a dye compound and the other compound is a compound intended to be dyed, said method thus being a dyeing method.

8. The method according to claim 1, wherein the first compound is a compound intended to be dyed and the second compound is a dye compound, said method thus being a dyeing method.

9. The method according to claim 1, wherein the first compound is a polymer comprising, at all or part of the repeating units thereof, at least one amine group.

10. The method according to claim 1, wherein the first compound is a polymer belonging to the chitosan family.

11. The method according to claim 10, wherein the first compound is integrated into a sheet of paper.

12. The method according to claim 1, wherein the second compound is a compound comprising one or more aromatic rings, the or all or part of said aromatic rings comprising at least one carbonyl group and optionally at least one other group different from a carbonyl group and comprising at least one atom bearing a lone pair.

13. The method according to claim 1, wherein the second compound is an aromatic compound comprising a single aromatic ring, which aromatic ring is bearing at least one carbonyl group and at least one other group different from a carbonyl group and comprising at least one atom bearing a lone pair.

14. The method according to claim 1, wherein the second compound is a monocyclic aromatic carbon compound.

15. The method according to claim 1, wherein the second compound is a monocyclic aromatic carbon compound bearing a single carbonyl group and a single other group different from a carbonyl group and comprising at least one atom bearing a lone pair, such as an electron withdrawing group and with a donor mesomeric effect, for example comprising an oxygen atom, such as a hydroxyl group, said carbonyl group and the other group being in the ortho position to each other on the aromatic carbon ring.

16. The method according to claim 1, wherein the second compound is a compound having the following formula (I): ##STR00012## wherein: —R.sup.1 represents a hydrogen atom or an alkyl group; —R.sup.2 represents a group different from a carbonyl group and comprising an electron withdrawing oxygen atom and with a donor mesomeric effect, such as a hydroxyl group; —R.sup.3 to R.sup.6 represent, independently of each other, a hydrogen atom, an alkyl group, an alkoxy group, an ester group.

17. The method according to claim 1, wherein the second compound is a compound of the following formula (II): ##STR00013## wherein R.sup.7 represents an alkyl group.

18. The method according to claim 1, wherein the second compound is an aromatic compound comprising several aromatic rings, said aromatic rings being fused, at least one of said rings comprising at least one carbonyl group and at least one of said rings comprising at least one other group different from a carbonyl group and comprising at least one atom bearing a lone pair.

19. The method according to claim 1, wherein the second compound is a bicyclic aromatic compound, whose rings are fused, one of the rings being a heteroaromatic ring, while the other ring is an aromatic carbon ring, one of the rings is bearing at least one carbonyl group and one of the rings is bearing at least one other group different from a carbonyl group and comprising at least one atom bearing a lone pair, such as an electron withdrawing group and with a donor mesomeric effect, for example comprising an oxygen atom, such as a hydroxyl group.

20. The method according to claim 1, wherein the second compound is a bicyclic aromatic compound, whose rings are fused, one of the rings being a heteroaromatic ring, while the other ring is an aromatic carbon ring, the heteroaromatic ring is bearing at least one carbonyl group and the aromatic carbon ring is bearing at least one other group different from a carbonyl group and comprising at least one atom bearing a lone pair, such as an electron withdrawing group and with a donor mesomeric effect, such as a hydroxyl group.

21. The method according to claim 1, wherein the second compound has the following formula (III): ##STR00014## wherein: —R.sup.8 represents a hydrogen atom or an alkyl group, preferably, a hydrogen atom; —R.sup.14 represents a group different from a carbonyl group and comprising an electron withdrawing oxygen atom and with a donor mesomeric effect; —R.sup.9 to R.sup.13 represent, independently of each other, a hydrogen atom, an alkyl group, an alkoxy group, an ester group.

22. The method according to claim 1, wherein the second compound has the following formula (IV): ##STR00015##

23. The method according to claim 1, wherein at least one of the first or second compounds has a melting temperature less than the operating temperature of the reaction step.

24. The method according to claim 1, wherein at least one of the first or second compounds has a melting temperature less than 120° C., preferably less than or equal to 100° C.

25. A compound capable of being obtained by the method as defined in claim 1, which is a compound of the chitosan family functionalised by groups, called groups A, comprising one or more aromatic rings, the or all or part of said aromatic rings comprising at least one imine group and the or all or part of said rings comprising at least one other group different from an imine group and comprising at least one atom bearing a lone pair.

26. The compound according to claim 25, wherein the groups A consist of aromatic groups comprising a single aromatic ring, which aromatic ring is bearing at least one imine group and at least one other group different from an imine group and comprising at least one atom bearing a lone pair.

27. The compound according to claim 25 or 26, wherein the groups A consist of monocyclic aromatic carbon groups, the ring of the groups is bearing both at least one imine group and at least one other group different from an imine group and comprising at least one atom bearing a lone pair, such as an electron withdrawing group and with a donor mesomeric effect.

28. The compound according to claim 25, wherein the groups A consist of monocyclic aromatic carbon groups bearing a single imine group and a single other group different from an imine group and comprising at least one atom bearing a lone pair, said imine group and the other group being in the ortho position to each other on the aromatic ring.

29. The compound according to claim 25, wherein the groups A have the following formula (V): ##STR00016## wherein: —R.sup.1 represents a hydrogen atom or an alkyl group; —R.sup.2 represents a group comprising an electron withdrawing oxygen atom and with a donor mesomeric effect; —R.sup.3 to R.sup.6 represent, independently of each other, a hydrogen atom, an alkyl group, an alkoxy group, an ester group, the brace indicating where the group A is bound to the chitosan radical either directly or via an organic spacer group.

30. The compound according to claim 25, wherein the groups A have the following formula (VI): ##STR00017## wherein R.sup.7 represents an alkyl group and the brace indicating where the group A is bound to the chitosan radical either directly or via an organic spacer group.

31. The compound according to claim 25, wherein the groups A consist of aromatic groups comprising several aromatic rings, said aromatic rings being fused, at least one of said rings comprising at least one imine group and at least one of said rings comprising at least one other group different from an imine group and comprising at least one atom bearing a lone pair.

32. The compound according to claim 25, wherein the groups A consist of bicyclic aromatic groups, whose rings are fused, one of the rings being a heteroaromatic ring, while the other ring is an aromatic carbon ring, one of the rings is bearing at least one imine group and one of the rings is bearing at least one other group different from an imine group and comprising at least one atom bearing a lone pair.

33. The compound according to claim 25, wherein the groups A consist of bicyclic aromatic groups, whose rings are fused, one of the rings being a heteroaromatic ring, while the other ring is an aromatic carbon ring, the heteroaromatic ring is bearing at least one imine group and the aromatic carbon ring is bearing at least one other group different from an imine group and comprising at least one atom bearing a lone pair.

34. The compound according to claim 25, wherein the groups A has the following formula (VII): ##STR00018## wherein: —R.sup.8 represents a hydrogen atom or an alkyl group; —R.sup.14 represents a group comprising an electron withdrawing oxygen atom and with a donor mesomeric effect; —R.sup.9 to R.sup.13 represent, independently of each other, a hydrogen atom, an alkyl group, an alkoxy group, an ester group, the brace indicating where the group A is bound to the chitosan radical either directly or via an organic spacer group.

35. A paper comprising at least one compound belonging to the chitosan family as defined according to claim 25.

Description

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

Example 1

[0103] This example illustrates a method in accordance with the invention and, more specifically, a method for dyeing a paper.

[0104] The concerned paper is a specific paper comprising a chitosan up to 20% by weight, which is a natural polymer having pendant primary amine groups, which groups are very reactive to react with aldehyde groups and form imine groups.

[0105] The aforementioned paper is placed in a reactor filled with supercritical CO.sub.2 and a compound of formula (II) in which R.sup.7 is an ethyl group.

##STR00010##

[0106] this compound corresponding to ethyl 3-formyl-4-hydroxybenzoate.

[0107] The pressure is set at 280 bars and the temperature is set at 105° C., whereby the CO.sub.2 is in the supercritical state. Under these conditions, ethyl 3-formyl-4-hydroxybenzoate is in liquid form knowing that its melting point is 67-73° C. and is soluble in supercritical CO.sub.2 given its lipophilic nature due to the presence of an ethyl benzoate group. The aforementioned pressure and temperature are maintained for 1 hour.

[0108] At the end of this period, the resulting paper displays an intense yellow colour.

[0109] In order to confirm the efficiency of the method, in parallel, the same reaction was carried out with an identical paper sample and the same aldehyde but in ethanol. It took 2 weeks using a wet process to bring this dyeing reaction to completion, thus highlighting the considerable time saving to reproduce this reaction under supercritical CO.sub.2.

[0110] Standardized (ISO 105-B02) light-fastness and colour fastness tests have been conducted in order to assess the colorimetric performance of the dyed sample obtained under supercritical CO.sub.2. Thus the light-fastness under UV of the sample was assessed at 3. For paper manufacturers, the cellulosic substrates are considered as having a suitable light-fastness from 3. The colour fastness, for its part, was assessed at 3-4, which is satisfactory.

[0111] Finally, in order to confirm the covalent attachment of the dye to the paper, the dyed sample was subjected to cleaning then to leaching with acetone and ethanol. After drying at ambient temperature, the sample retains a good yellow tint. The confirmation of the covalent attachment of the dye via the formation of an imine function (C═N) was validated by IR spectroscopy, with observation of the stretching band of the C═N function at 1635 cm.sup.−1, a band which is absent on the original paper.

Example 2

[0112] This example illustrates a method in accordance with the invention and a compound obtained in accordance with the method of the invention and in accordance with the invention, this compound resulting from the condensation of a chitosan polymer with a compound of the following formula (IV):

##STR00011##

[0113] These two reagents are placed in a reactor filled with CO.sub.2, the pressure being set at 260 bars and the temperature is set at 105° C., whereby the CO.sub.2 is in the supercritical state. Under these conditions, 8-hydroxy-2-quinolinecarboxaldehyde is in liquid form knowing that its melting point is 87-100° C. The aforementioned pressure and temperature are maintained for 3 hours

[0114] At the end of this period, the initially colourless chitosan displays an orange tint, typical of the increase in the conjugated system and proof that the chitosan and 8-hydroxy-2-quinolinecarboxaldehyde have reacted together covalently.