EP3377693A1

EP3377693A1 - Composition for the treatment of a cellulosic substrate and method for colouring the cellulosic substrate

Info

Publication number: EP3377693A1
Application number: EP16733690.8A
Authority: EP
Inventors: Ambrogio Caccia Dominioni
Original assignee: ICS Tech SRL
Current assignee: ICS Tech SRL
Priority date: 2015-11-20
Filing date: 2016-05-16
Publication date: 2018-09-26
Anticipated expiration: 2036-05-16
Also published as: ITUB20155790A1; EP3377693B1; WO2017085567A1

Abstract

The composition for the treatment of a cellulosic substrate in order to colour it by means of monochlorotriazine dyes comprises nicotinamide as activator, polydimethylsiloxane, and urea.

Description

COMPOSITION FOR THE TREATMENT OF A CELLULOSIC SUBSTRATE AND METHOD FOR COLOURING THE CELLULOSIC SUBSTRATE

This invention relates to a composition for the treatment of a cellulosic substrate with a view to colouring it by printing, and a kit for that treatment, a method for colouring the cellulosic substrate and use associated with that method.

More particularly it relates to a composition and kit for the treatment of cellulosic fibres in order to colour them by means of printing, and a method and a use for the colouring of cellulosic fibres using monochlorotriazine dyes.

It has been known for a long time that fabrics can be coloured using any digital printing method to apply the dye to the fabric, such as for example by ink-jet or rotary printing.

When a printing method is used to colour the fabrics, the quality of the coloured fabric also depends on the fixing method used after the colouring stage.

Excellent results are obtained through fixing by means of steaming, although it is known that steaming gives rise to a number of disadvantages, such for example great consumption of water, time and logistics; an increased risk of defects associated with the repeatability of tones and migration of the dyes which takes place during the steaming stage; also the repeatability of the percentage of dye fixed varies on the basis of the settings; steaming gives rise to different kinetics in the dye fixing reaction, subsequently causing migration of the unreacted dye during subsequent washing, with consequent contamination of the printed areas and unprinted white areas.

A known alternative method of fixing is thermofixing, which consists in fixing the dyes through the application of dry heat. This process proves more advantageous in terms of water consumption, application times, washing efficiency and reduced plant size. It has also been found that after thermofixing the quantity of dye lost during the washing stage is less than in comparison with steaming.

However it is known that thermofixing has an adverse effect on the final appearance of the dyed fabric. In particular the colours obtained are visibly less intense, and the fabric has a slightly rough feel to the touch.

The object of this invention is therefore that of providing a composition and a kit for the treatment of a cellulosic substrate which allows the latter to be coloured by means of printing and which makes it possible to obtain an optimum final product even after thermofixing.

Another object of the invention is that of providing a method for colouring a cellulosic substrate in which colouring of the cellulosic substrate can be performed by ink-jet printing or rotary printing.

This and other objects will be accomplished by means of a composition, a kit, a use and a method performed in accordance with the technical teachings in the appended claims.

This invention relates to a composition for the treatment of a cellulosic substrate for colouring it through printing. In the present context printing is to be understood to mean any type of printing suitable for the application of a dye onto a cellulosic substrate using digital printing methods such as for example ink-jet printing, rotary printing, screen printing or others.

In the context of this invention cellulosic substrate means cellulosic fibres in the form of fabrics and yarns in general.

In accordance with the invention the composition comprises nicotinamide, a polydimethylsiloxane and urea.

The nicotinamide acts as an activator or catalyst of the colouring reaction with the cellulosic substrate. This activator function is more efficient with monochlorotriazine dyes.

The polydimethylsiloxane on the other hand has a corrective function in that it closes off much of the porosity in the cellulosic substrate, rendering it smoother.

This brings about various advantages, such as better optical density of the inks. It has also been found that using polydimethylsiloxane together with nicotinamide it is possible to obtain a better colour yield on the fabric, with more intense tones and brighter colours, even in the situation where a printing process combined with thermofixing is used. In addition to this, the fabric obtained is softer to the touch in comparison with fabric which has only been treated with nicotinamide. This reactive polydimethylsiloxane is permanent and can therefore not be washed out in subsequent washes and does not in any way affect the final fastness of the applied dyes.

Urea acts as a hydrating agent for the thermofixing stage. More specifically, during the application of heat associated with fixing, the urea creates a network on the cellulosic substrate which contains the dye in a non-aggregated form and maintains it in that state until temperatures are high, in addition to the function of retaining the water which is necessary for the reaction between the dye and the cellulosic substrate at the abovementioned high temperatures.

Preferably the polydimethylsiloxane is of the hydrophilic type, is reactive with the substrate, is permanent and has a low refractive index. By permanent is meant that the polydimethylsiloxane remains on the cellulosic substrate even after washing. By low refractive index is meant a refractive index of less than 1 .4, so that the dye has greater intensity and brightness. For this purpose it is useful also to add an oil to the polydimethylsiloxane in order to have a second refractive index which is different from that of the polydimethylsiloxane, and thus further improve the brilliance and intensity of the dye.

Even more preferably the polydimethylsiloxane is of the amine type, that is it comprises at least one amine functional group.

It is particularly advantageous to provide that the polydimethylsiloxane should be in a macroemulsion, so as to render the cellulosic substrate less porous, with the result of achieving a better optical density for the inks.

Preferably the nicotinamide is present in a concentration of between 5 and 25 g/kg, the polydimethylsiloxane between 30 and 90 g/kg, and the urea between 50 and 400 g/kg with respect to the total weight of the composition. Even more preferably the composition comprises between 10 and 20 g/kg of nicotinamide, between 40 and 80 g/kg of polydimethylsiloxane, and between 200 and 300 g/kg of urea with respect to the total weight of the composition.

Preferably the composition also comprises a thickener, which may be of natural or synthetic origin. In accordance with a preferred embodiment of the invention the thickener is selected from alginates, polyacrylates or carboxymethylcellulose. These compounds have the advantage that they do not contain OH groups which are likely to react with the dye, and therefore enter into competition with the OH groups in the cellulosic substrate, which would result in less dye being available for reaction with the cellulosic substrate.

The alginates may be of the high, medium or low viscosity type, and the carboxymethylcellulose may have various degrees of substitution.

In a preferred manner the thickener comprises medium/high viscosity alginates which have the advantage of giving rise to a porous structure on the cellulosic substrate which is more regular than acrylates and carboxymethylcellulose, with regard to their thermal stability, that is they maintain a suitable viscosity and a suitably porous structure, above all in the temperature range required for thermofixing.

As is known, regularity of the porous structure is an advantage for the regularity of the optical density of the ink deposited on the substrate. Correct pore size at the high temperatures in use makes the ink pass through correctly without creating steric hindrance interferences because of the dimensions of the dye molecules, but not pore sizes which are sufficiently high to sufficiently impede migration of the ink. It is furthermore obvious that an increase in the surface area of the porous structure will result in an increase in its porosity, and greater porosity results in less coalescence of the drops of ink on the substrate, and therefore a more regular optical density. Furthermore it has been observed that thickening agents based on alginates make optimum control of dye migration possible even at high temperatures, in that their cross-linked structure, and therefore their viscosity, also persists as temperature rises, and therefore, by not decomposing their porous structure and reducing only their viscosity, they favour migration of dye from the thickener to the cellulose, maintaining the desired definition of the printing, thanks to the residual viscosity, as well as the necessary contact with the cellulosic substrate, thanks to the reduced migration, so that the dye-fibre reaction can take place.

Among the alginates, medium/high viscosity alginates give the best results in terms of the optical density of printing and colour yield. It will also be noted that medium/high viscosity alginates maintain a regular porous network, above all even under alkaline conditions, in particular at pH 8 - 9.

Preferably the composition according to the invention also comprises at least one rheological stabiliser selected from the terpenes. Even more preferably the terpene is pinene. Advantageously it is possible for the pinene to be provided in the form of pine oil, and incorporated in the composition through an aqueous emulsion of nicotinamide in the pine oil; this terpene has the ability to modify the rheology of the printing paste, rendering it less pseudoplastic, and therefore more newtonian, and increasing the transfer capacity of the printing paste onto the substrate during the stage of preparation for ink-jet printing or direct printing using rolls and silk screen.

In accordance with a preferred aspect of the invention the composition also comprises a hydrophilic polydimethylsiloxane having a low refractive index. As already mentioned, by a low refractive index is meant a refractive index of less than 1 .4.

The presence of the polydimethylsiloxane having a low refractive index makes it possible to reduce the refractive index of the substrate, thus increasing the optical path of the light incident within the fibre on which the ink is deposited. This results in a decrease in the white reflection of the substrate, and therefore in a relative increase in the optical density of the printed colour.

Preferably the composition comprises nicotinamide, the hydrophilic and reactive polydimethylsiloxane having a low refractive index, an increased quantity of urea, a thickener selected from alginates, carboxymethylcellulose and polyacrylates, sodium bicarbonate and an anti-reducing agent based on meta- nitrobenzene-sulfonate.

The composition may also form part of a kit for preparation of the cellulosic substrate. This kit is to be intended as being part of this invention.

The above composition may be applied directly to the cellulosic substrate before the printing stage and that stage of the process is described as "preparation" in the case where ink-jet printing is intended.

If instead rotary printing is used, the composition should be provided in the form of a paste which also comprises at least one dye. This paste for colouring a cellulosic substrate is also intended to be protected by this application.

In the paste the dye is preferably a monochlorotriazine dye and even more preferably a monofunctional monochlorotriazine dye. It has been found that when undergoing thermofixing monofunctional monochlorotriazine dyes are fixed to a greater extent than bifunctional monochlorotriazine dyes.

This invention also relates to a method for dyeing a cellulosic substrate, comprising, but not necessarily in the order indicated, the stages of:

a) applying a composition according to the invention to the cellulosic substrate;

b) drying the cellulosic substrate;

c) applying at least one dye by means of printing; d) fixing the dye by thermofixing; and

e) washing the cellulosic substrate.

Through using a composition comprising nicotinamide, polydimethylsiloxane and urea it is possible to avoid fixing stage d) being performed by steaming, and to maintain a high quality of the dyed cellulosic substrate in both colour yield, maintenance of the white (unprinted parts) and the softness of the fabric.

Preferably the dye is a monochlorotriazine dye. Even more preferably the dye is a monofunctional monochlorotriazine dye. It has been found that when they undergo thermofixing monofunctional monochlorotriazine dyes are fixed more quickly than in the steaming process, resulting in an improvement in production times and energy expenditure, but comparable as regards the quantity of reacted dye. Bifunctional monochlorotriazine dyes on the other hand are fixed less effectively by thermofixing.

In accordance with a first variant of the method, stage c) of applying the dye is carried out by ink-jet printing of the dye onto the cellulosic substrate.

In this case stages a), b) and c) are performed in succession, and in the order indicated, that is after the substrate has been treated with the composition according to the invention the treated substrate is dried and then coloured by ink- jet printing.

In accordance with a second variant of the method, stage c) of applying the dye is carried out by rotary printing.

In this case however the paste mentioned above, which comprises both the composition according to the invention and the dye, has to be used. It is pointed out that the stages a) of applying the composition and c) of applying the dye are simultaneous, and that these take place before stage b) of drying the cellulose substrate.

In accordance with a preferred aspect of the invention, stage a) of treating the cellulosic substrate takes place through a procedure of impregnating the substrate, in particular through a pad batch or rotary printing process.

Washing stage e) is preferably carried out using at least one fatty amine, preferably ethoxylated. This surfactant has a dye inhibitor function during the stage of washing the dyed cellulosic substrate.

According to a preferred aspect of the invention washing is also carried out using sodium dodecylbenzene sulfonate, mixed with the fatty amine. It has in fact been found that in the presence of the ethoxylated fatty amine this compound produces a synergistic effect in washing efficiency and inhibition of dye redeposition, thus resulting in better efficiency in washing the unfixed dyes and optimum maintenance of the white and the original printed tones due to contamination of the unfixed dye. It has been found that this washing kit reduces the washing tanks in continuous washing to only three in comparison with the six normally used, thus improving water consumption.

Advantageously the ethoxylated fatty amine or the mixture of fatty amine with sodium dodecylbenzene sulfonate is sold in the form of a kit for washing a cellulosic substrate following printing and thermofixing.

Claims

1 . Composition for the treatment of a cellulosic substrate for colouring it with monochlorotriazine dyes, comprising

nicotinamide as activator,

polydimethylsiloxane, and

urea.

2. Composition according to claim 1 , wherein the polydimethylsiloxane is of the permanent reactive hydrophilic type and has a low refractive index.

3. Composition according to claim 1 or 2, wherein the polydimethylsiloxane is of the amine type.

4. Composition according to any one of the preceding claims, wherein the polydimethylsiloxane is provided as a macroemulsion.

5. Composition according to one or more of the preceding claims, comprising between 5 and 25 g/kg of nicotinamide, between 30 and 90 g/kg of polydimethylsiloxane, and between 50 and 400 g/kg of urea in relation to the total weight of the composition.

6. Composition according to one or more of the preceding claims, comprising between 10 and 20 g/kg of nicotinamide, between 40 and 80 g/kg of polydimethylsiloxane, and between 200 and 300 g/kg of urea in relation to the total weight of the composition.

7. Composition according to one or more of the preceding claims, comprising at least one thickener selected from an alginate, a polyacrylate or a carboxymethylcellulose.

8. Composition according to the preceding claim, comprising a rheological stabiliser based on pinene.

9. Paste for colouring a cellulosic substrate by printing, comprising the composition according to one or more of the preceding claims, and at least one dye.

10. Kit for the treatment of a cellulosic substrate in order to colour it by means of monochlorotriazine dyes, comprising the composition according to one or more of claims 1 to 9.

1 1 . Use of a polydimethylsiloxane together with nicotinamide to treat a cellulosic substrate in order to colour it by printing.

12. Method for colouring a cellulosic substrate, comprising, not necessarily in the following order, the stages of:

a) applying a composition according to one of claims 1 to 8 to said cellulosic substrate;

b) drying said cellulosic substrate;

c) applying at least one dye to said cellulosic substrate by printing;

d) fixing said dye by thermofixing; and

e) washing said cellulosic substrate.

13. Method according to the preceding claim, wherein stage c) of applying the dye is carried out by ink-jet printing, stages a) and c) being performed one after the other.

14. Method according to claim 12, wherein stage c) of applying the dye is carried out by rotary printing, stages a) and c) being carried out simultaneously, and before stage b) of drying the cellulosic substrate.

15. Method according to one of claims 12 to 14, wherein the dye is a monochlorotriazine dye.

16. Method according to the preceding claim, wherein the dye is a monofunctional monochlorotriazine dye.

17. Method according to one or more of claims 12 to 16, wherein the dye is applied by ink-jet printing.

18. Method according to one or more of claims 12 to 17, wherein stage a) of treating the cellulosic substrate is performed using an impregnation or rotary printing process.

19. Method according to one or more of claims 12 to 17, wherein washing stage e) is performed with an ethoxylated fatty amine.

20. Method according to the preceding claim, wherein washing stage e) is carried out with sodium dodecylbenzene sulfonate mixed with the ethoxylated fatty amine.