Device and process for indigo dyeing

1. A dyeing device ( 100 ) in continuous with indigo for warp yarn chains ( 3 ) and/or fabrics, equipped with a first hermetically sealed dyeing compartment ( 1 ), suitable for containing the dye bath and at least one squeezing element ( 11 ) capable of exerting a strong pressure on the yarn chain ( 3 ), and a second hermetically sealed fixing/dehydration compartment ( 2 ) of said yarn ( 3 ), wherein said first ( 1 ) and second ( 2 ) compartments comprise an inert environment and are functionally and hermetically connected with each other wherein in said first ( 1 ) and second ( 2 ) compartments, there are means ( 4 ) for introducing nitrogen and/or deoxygenated air inside the first ( 1 ) and second ( 2 ) compartments wherein said second compartment ( 2 ) is provide with at least one means for directly heating and/or dehydrating the yarn ( 3 ) consisting of a plurality of heatable cylinders ( 5 ) on which the yarn ( 3 ) passes, to increase the diffusion and fixing of the dye in the yarn ( 3 ) and to dehydrate said yarn ( 3 ) so as to increase the absorption of the dye in the subsequent yarn ( 3 ) processing phases, and wherein at least one of said cylinders ( 5 ) can also be cooled.

2. The device ( 100 ) according to claim 1 , further comprising, downstream of said squeezing element ( 11 ), means for directly heating and/or dehydrating the yarn ( 3 ) consisting of at least one infrared source suitable for heating said yarn ( 3 ) by direct irradiation.

3. The device ( 100 ) according to claim 1 , further comprising, downstream of said squeezing element ( 11 ), means for directly heating and/or dehydrating the yarn ( 3 ) consisting of at least one microwave or radiofrequency source suitable for directly heating the yarn ( 3 ) downstream of said squeezing element ( 11 ).

4. The device according to claim 1 , further comprising, downstream of said squeezing element ( 11 ), means for directly heating and/or dehydrating the yarn ( 3 ) at least one source for at least a flow of warm fluid suitable for heating the yarn ( 3 ) by convection.

5. The device ( 100 ) according to claim 1 , characterized in that said means ( 4 ) for the introduction of deoxygenated air/nitrogen inside said first ( 1 ) and second ( 2 ) compartments comprise at least one inlet nozzle ( 8 ) connected to a deoxygenated air or nitrogen source under pressure.

6. The device ( 100 ) according to claim 5 , characterized in that said indirect heating means ( 12 ) comprise a tile ( 13 ) with sloping brims and a coil ( 14 ) in which hot fluid circulates.

7. The device ( 100 ) according to claim 1 , characterized in that it comprises means ( 6 ) and ( 7 ) for the expulsion of the air from compartments 1 and 2 equipped with at least one discharge valve ( 9 ) and ( 10 ).

8. The device ( 100 ) according to claim 1 , characterized in that said fixing/dehydration compartment ( 2 ) comprises at least one indirect heating means ( 12 ).

9. The device according to claim 8 , characterized in that said fixing/dehydration compartment ( 2 ) comprises at least one condensate collection point ( 22 ) comprising at least one discharge valve ( 23 ) driven by specific control means ( 24 ).

10. The device ( 100 ) according to claim 9 , characterized in that said device ( 30 ) for the heating or cooling of the bath forms an interspace close to the bottom of said compartment ( 1 ) and comprises at least one coil ( 31 ) in which a heating or cooling fluid circulates.

11. The device ( 100 ) according to claim 1 , characterized in that said inert environment fixing/dehydration compartment ( 2 ) also comprises, on the side walls and on the bottom, cooling means ( 17 ) of the walls to condense the water which evaporates from said yarn ( 3 ) following the passage on said direct heating means ( 5 ).

12. The device ( 100 ) according to claim 1 , characterized in that said inert environment fixing/dehydration compartment ( 2 ) also comprises at least one suction means ( 102 ) suitable for sucking the nitrogen mixed with vapour from said inert environment fixing/dehydration compartment ( 2 ) and at least one heat exchanger ( 104 ) suitable for condensing the water vapour and returning dehumidified nitrogen to said inert fixing/dehydration compartment ( 2 ).

13. The device ( 100 ) according to claim 1 , characterized in that said dyeing compartment ( 1 ) comprises, on the bottom, at least one device ( 30 ) for the heating or cooling, indirect and without contact, of the dye bath contained in said compartment ( 1 ).

14. The device ( 100 ) according to claim 13 , characterized in that said hermetically sealed dyeing compartment ( 1 ) comprises airtight sealing means ( 28 ).

15. The device ( 100 ) according to claim 1 , characterized in that said hermetically sealed compartment ( 1 ) comprises at least one tank ( 26 ) and at least one hood ( 27 ) which is liftable with respect to said tank ( 26 ) for cleaning and maintenance interventions and hermetically reclosable on said tank ( 26 ).

16. The device ( 100 ) according to claim 1 , characterized in that said dyeing compartment ( 1 ) comprises at least an intermediate squeezing group ( 33 ) suitable for exerting a squeezing on said yarn ( 3 ).

17. The device ( 100 ) according to claim 1 , characterized in that it comprises a series of guide rolls ( 36 , 37 ) of the yarn ( 3 ) placed in the hermetically sealed connection area between said dyeing compartment ( 1 ) and said fixing/dehydration compartment ( 2 ).

18. The device ( 100 ) according to claim 1 , characterized in that said dyeing compartment ( 1 ) comprises at least one inlet ( 34 a , 34 b ) and at least one outlet ( 35 a , 35 b ) of the overflow type.

19. The device ( 100 ) according to claim 1 , characterized in that said dyeing compartment ( 1 ) can operate with different bath levels.

20. A continuous dyeing process with indigo for yarn chains ( 3 ) with the device ( 100 ) according to claim 1 , characterized in that it comprises the following phases:

a) introducing a flow of nitrogen and/or deoxygenated air into said first dyeing compartment ( 1 ) and said fixing/dehydration compartment ( 2 ) for a time sufficient for obtaining an inert environment inside said compartments ( 1 , 2 );

b) immersing the yarn ( 3 ) in said compartment ( 1 ) containing the dye bath;

c) exerting a squeezing on said yarn ( 3 ) at the outlet of the bath of said compartment ( 1 );

d) directly heating the yarn ( 3 ) in the compartment ( 2 ) to increase the diffusion and fixing of the dye in the fibre and to dehydrate it so as to increase the absorption of the dye in the subsequent phases; and

e) subjecting the yarn oxidation outside the device ( 100 ).

21. A dyeing plant characterized in that it comprises at least one dyeing device ( 100 ) according to claim 1 .