DESCRIPTION

The present invention relates to a new method of preparing a colouring mixture, to the colouring mixture obtainable by this method and to the uses thereof. The method and the products of the invention are used in the natural dyeing of animal fibres, plant fibres, hides, paper and other products.

PRIOR ART

Since ancient times until approximately the mid 19 ^th century only natural colouring substances were available for dyes. With the discovery in 1853 of the first synthetic colourant, mauveine, and, above all, with the discovery in 1868 of the chemical synthesis of alizarin, which is the main pigment of madder and was already being marketed in 1 871 , there was an extremely rapid substitution of natural colourants with synthetic colourants due to the lower cost, the greater reproducibility of the colour and standardization of the process. By the end of the 19 ^th century synthetic colourants had almost completely replaced many natural colourants.

Currently however, colourants from natural sources have regained a high level of interest both as a result of reports of carcinogenic effects of synthetic colourants and as a result of the growing need for products and processes which have a low environmental impact. In particular within the textiles industry the use of technologies and chemical products of which the transformation and finishing processes are not optimised from an environmental point of view has a significant effect both on the environment and on the health of workers, and a growing number of people experiencing problems of contact dermatitis caused by synthetic colourants has been observed.

A series of tests have been carried out in various countries in order to identify new plants from which colourants can be obtained. In I ndia the use of different dyeing plants including Arnebia hispidissima, Euphorbia cotinifolia, litchi, apricot and tulsi basil has been reported. More recently and again in India, the flowers of Rhododendron arboreum have been used in combination with different mordants (chromium, copper, iron, alum and tin) for the dyeing of natural fibres.

In Turkey the dyeing of natural fibres in different pH conditions using leaves of walnut trees, Quercus infectoria gall oak and Hypericum scabrum L. has been studied. In Iran the optimization of the process of extraction and dyeing using the roots of Rubia tinctoria has been studied.

In various studies in China the process of dyeing natural fibres using Lotus flowers, the roots of madder, the fruits of Gardenia jasminoides and using chrysanthemum has been reported. He et al. (2008) reported a study on the process of yellow dyeing using natural colourants applied to cotton fabrics and soybean fibre (a new plant fibre). Chinese patent application CN 101307569A describes a method for dyeing natural fibres using extracts of plants belonging to the chrysanthemum genus.

In recent years in Italy, research has focused primarily on the cultivation and use of "blue plants" (Angelini and Bertolacci, 2008). In Sardinia the tradition of using natural colourants is preserved above all in carpet weaving; again in Sardinia a study has also been carried out in order to identify and quantify the anthocyanins in Pistacia lentiscus L, Phillyrea latifoglia L. and Rubia peregrina L, which are three plants which are widely distributed within the Mediterranean regions.

Although it is possible to obtain natural colourants from different plants, there are many unresolved problems which mean their use is limited.

During the phase of production , the acquisition of colourants from plants which are not very widespread over the region results in a high end cost of the colourant itself.

Despite the numerous studies carried out in order to identify new dyeing plants, they are still insufficient in n umber. I n particular it may be beneficial to increase the n u m ber of species wh ich are typical, even spontaneous to the Mediterranean area by rediscovering tradition and by studying new species. In fact, in contrast with what has happened in the past, use is currently limited to a few dyeing plants which originate, for the most part, from oriental countries and from South America. The cultivation of such plants may have negative consequences on biodiversity, may create problems of adaptation to the pedoclimatic conditions, and has a greater envi ronmental im pact i n terms of landscape. Fu rthermore, the avai labi l ity of a h igher n u m ber of species makes it possible to i ncrease the harvesting interval, thus making different vegetal materials available throughout the year. The use of species which are typical, even spontaneous to the region makes it possible to recover degraded areas in terms of productivity and environment.

The cultivation of species which are typical to the Mediterranean area makes it possible to tweak eco-compatible cultivation processes and to obtain a controlled colouring vegetal material.

Many of the extraction methods for obtaining colourants from plants are not very ecological and in some cases, in particular when obtaining blue from indigotin, they use mordants and chemical solvents wh ich can on ly be d isposed of with difficulty.

Many colourants obtained from plants do not make it possible to obtain dyes which have increased saturation of the colour and which exhibit light fastness. Some colourings, such as orange, can be obtained predominantly by combining the colouring mixture of yellow and red.

The need to provide eco-sensitive methods for the preparation of colouring mixtures with a high dyeing capability was therefore particularly evident in the prior art.

SUMMARY OF THE INVENTION

The present invention relates to a method for obtaining a colouring mixture within the yellow shades characterised by the use of fresh and/or dried flower heads of plants belonging to the genus Anacyclus. The inventors have succeeded in identifying, among the many plant genera belonging to the family of Compositeae, a specific genus of plant from which it is possible to obtain, according to the method of the present invention, a colouring mixture with an increased dyeing power within the yellow shades. No plant belonging to this genus had been used previously to prepare natural colourants. It was not obvious to select plants of the gen us anacyclus to extract different shades of yellow, both because the colour yellow present in the flowers or inflorescences is not sign of suitability of dyeing power and because many species from which yellow is extracted do not exhibit yellow colouration (mallow, white iris, cistus, lentisk, reseda of which the entire plant is used , olive, etc.). I n particular many species, although they exhibit a yellow colouration which may be deep, do not enable extraction of a colouring mixture. In other cases the colouring mixture has a very low level of saturation of the colour, a very low level of dyeing power and is hardly, or not at all, light stable, for example as is the case for a very large number of species of mimosa, coronilla, sonchus, picris and yellow autumn crocus which do not provide effective dyes.

The inventors have surprisingly found that the use as vegetal material of just the flower heads of Anacyclus plants makes it possible to obtain colouring mixtures with a dyeing power which is greater than those obtained using flower heads with stems and leaves as vegetal material.

The present invention therefore relates to a method of preparing a colouring mixture comprising a step wherein the colouring mixture is extracted from flower heads of a plant belonging to the genus Anacyclus with water or aqueous solution at a temperature comprised between 50 and 80 °C for a time of about 30-90 min.

The present invention secondly relates to a colouring mixture which is obtainable by the method disclosed herein and the compositions comprising said colouring mixture.

The invention thirdly relates to the use of the colouring mixture obtainable by the method disclosed herein and of the compositions comprising said colouring mixture in colouring procedures of a material such as, for example, natural fibres, synthetic fibres, hides, paper, paperboard, ceramics and cosmetics.

The invention fourthly relates to a method for the dyeing of a material as described above, which uses the colouri ng mixture obtainable by the method disclosed herein or compositions comprising said colouring mixture.

The present invention affords the following advantages over the known prior art:

The method uses a spontaneous plant originating from Europe and very widespread over the entire Mediterranean area and, in particular, the South of Italy, and therefore it is a readily available starting vegetal material to be used for dyeing purposes which is economical and of which the exploitation may provide a valid contribution to the safeguarding of biodiversity. Furthermore, its use makes it possible to attribute to the products obtained a strong link with the region.

The increased dyeing power of the colouring obtained by the method disclosed herein makes it possible to use the natural colourants obtained in many industries and to use a very low ratio between vegetal material used to extract the colourant and material to be dyed.

From an agronomic point of view, the use in the method of merely flower heads prolongs the period of use, ensures a better coverage of the ground, above all in areas which are vulnerable in terms of erosion, and improves the supply of organic substance, thus promoting the sustainable management of the agricultural system.

The method also exhibits an increased level of eco-compatibility since organic solvents are not necessary for the preparation of the colourant, but instead only water is used.

All the colourants obtained on fibre with Anacyclus flower heads have a very high index of saturation (greater than 80 %), with values between 8 and 12 of the Munsell Colour Atlas with light stability greater than 5 in accordance with the blue scale.

The advantages, features and uses of the present invention will become clear upon reading the detailed description given hereinafter of some exemplary and non-limiting embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 image A is in colour; image B is in black and white; The figure shows yarns of new wool dyed with the colourant obtained as described in the examples. Fig. 1 a shows the natural fibre, Fig. 1 b shows a yarn of wool dyed as described in Example 3, and Fig. 1 c shows a yarn of wool dyed as described in Example 4. DETAILED DESCRIPTION OF THE INVENTION

Glossary

Within the scope of the present invention the following definitions are used with the following meanings:

Vegetal material In the present invention the expression 'vegetal material' means a part of the plant, for example leaves, flowers, fruits, berries, branches, roots.

Colouring mixture For the purposes of the present invention the expression 'colouring mixture' means all pigments responsible for the colour of a natural extract.

Mordanting The term 'mordanting' generally means the subjection of one or more fibres to be dyed to the action of a substance which fixes the colour.

Dyeing plant Dyeing plants are all those plants from which it is possible to obtain a mixture of substances which can be used as colourants.

Flower head A flower head is an inflorescence, i.e. a group of small flowers arranged at the end of the receptacle.

Colour bath A colour bath is the solution in which the material to be dyed is dipped.

Yellow shade In the present description yellow shades are the colours which range from a straw-coloured yellow to orange.

The present invention provides, for the first time, a method of preparing a colouring mixture comprising a step wherein the colouring mixture is extracted from flower heads of a plant belonging to the genus Anacyclus by heating in water or aqueous solution at a temperature comprised between 50 and 80 °C for a time of about 30-90 min.

The plants of the genus Anacyclus belong to the family of Compositae. Suitable species of this genus which can be used in the method disclosed herein include, for example, A. radiatus Loisel, A. tomentosus (AIL), sin. A. clavatus (Desf.) (present in Italy) and A. valentinus L.

In one embodiment of the present invention the plant belonging to the genus

Anacyclus, used for the preparation of the colouring mixture according to the method disclosed herein, advantageously belongs to the species Anacyclus radiatus Loisel. This species is an annual plant with assurgent, branched, splined, smooth or virtually smooth stems, with more or less irregular pinnate leaves and flower heads with a diameter of 1 .5 to 4 cm.

The extraction of the colouring mixture from a plant belonging to the genus Anacyclus in accordance with the method disclosed herein provides the use of the flower heads of these plants. The flower heads can be obtained directly by harvesting during the flowering period which runs from May to August, or can be bought. The flower heads can be used in the method of the invention either fresh or after having been dried or else by mixing fresh flower heads with dried ones. There are various drying methods in the known prior art, such as air drying or vacuum drying. The person skilled in the art will be able to identify, without any inventive activity, the most suitable method for drying the flower heads of Anacyclus plants based on the known prior art.

According to the method disclosed herein, a colouring mixture is extracted from fresh and/or dried flower heads by heating in water or aqueous solution, such as solutions containing citric acid or acetic acid, in an amount sufficient to ensure full extraction of the pigments. In one embodiment of the invention the amount of water in which the flower heads are placed is present in a ratio of 160 ml for each gram of fresh flower heads or 140 ml for each gram of dried flower heads. Said flower heads are left in water at a temperature comprised substantially between 50 and 80 °C for a time comprised substantially between 30 and 90 minutes. More specifically, this temperature may be a temperature of approximately 50 °C, 55 °C, 60 °C, 65 °C, 70 ° C , 75 ° C , 80 ° C . I n on e embodiment a temperature of 70 °C will be used, constituting an energy saving of the entire process.

The heating should be carried out for a time sufficient to obtain extraction of a colouring mixture from the vegetal material. In particular, in accordance with the method described herein , the heating in water can be carried out for a time of approximately 30-90 minutes. The extraction process preferably lasts for approximately 60 minutes. A shorter period obviously defines a reduced extraction of the colour; less than 30 minutes the mixture has a very weak colouring power. Periods longer than 120 minutes are not economically suitable. They also lead to an alteration of the colouring mixture which brings about a darkening of the colourations of the dyed fibres and a loss of brightness.

In one embodiment of the invention the method may comprise a further step in wh ich the colouring mixture obtainable by the method disclosed herein is subsequently separated from the residual solid vegetal material by any solid/liquid separation method and is then recovered. Non-limiting examples of separation methods which may be used are filtration and centrifugation. These methods are routinely used in practice and are described in detail in any laboratory manual and therefore do not require further study in this description. Purely by way of example, the obtainable colouring mixture may be filtered using a filter with a suitable cut off. The person skilled in the art will be able to select the filter with the cut off which is most suitable for filtration based on the amount of material to be separated present in the colouring mixture without being provided with any specific teaching. The colouring mixture can preferably be filtered using a first filter of porosity equal to approximately 1 .25 mm to separate coarser vegetal material, and using a second filter of porosity of approximately 1 .18 mm to separate finer material.

The colouring mixture obtainable using the method disclosed herein is characterised by an increased power of colouration in the shades of yellow and greater light stability compared with that which can be observed for the mixtures obtainable by the methods reported in the known prior art.

In one embodiment the colouring mixture obtainable as disclosed herein may be i n th e form of powder, solution, suspension, granulate, paste, tablet, or lyophilised product.

These specific embodiments are developed by methods known to the person skilled in the art.

The present invention also relates to compositions comprising the colouring mixture obtainable as disclosed herein and one or more thickeners, adjuvants, oxidizing or preserving agents, etc.

Said compositions may be in the form of powder, solution, suspension, granulate, paste, tablet or spray. The colouring mixture obtainable as described above may be used in processes of colouring carried out on an industrial scale in industries such as textiles, cosmetics, clothing, furnishings and construction.

Taking into account all the possible embodiments indicated above, the person skilled in the art will be able to use the colouring mixture of the invention to dye the following materials within shades of yellow: natural fibres of animal or plant origin such as wool, cotton , flax and silk, synthetic fibres, hides, paper articles, paperboard articles, ceramics, wood, plastics, glass, cosmetics, etc.

In the case in which the colouring mixture is used to dye natural fibres, it will be necessary to prepare said colouring mixture in accordance with the method first described, taking into account the weight of the fibre to be coloured. In particular, for effective colouration the ratio between the weight of the fibre and the weight of the fresh vegetal material is comprised between 1 :0.5 and 1 :2. For dried flower heads the ratio between the weight of the material to be dyed and the weight of the flower heads is comprised in the range of 1 :0.25 and 1 :1 . The ratio of fresh and/or dried flower heads to the water or aqueous solution is instead comprised between 40 and 200 ml per gram of flower heads. It is obvious that the selection within the ranges described above of a greater or lesser quantity of flower heads or water will lead to the acquisition of a colouring mixture which is able to dye the natural fibres in a darker or lighter shade of yellow. The selection of a greater quantity of flower heads in a smaller volume of water will lead to the acquisition of a colouring mixture in the darker shades of yellow until turning to orange if extraction and dyeing are carried out together, and vice versa a lesser quantity of flower heads in a greater volume of water will lead to the acquisition of a colouring mixture in the lighter shades of yellow.

As is known to the person skilled in the art, fibres are coloured efficiently once the fibres to be coloured have been mordanted. The term 'mordanting' generally means to subject one or more fibres to be coloured to the action of a substance which fixes the colour. Although this step is not part of the invention, the person skilled in the art will be aware of the fact that an effective process of colouration requires an initial phase of mordanting of the material to be coloured. For this reason, when colouring natural fibres, the optional phase of mordanting can be carried out in accordance with any method known to the person skilled in the art. For example, in accordance with the protocol reported below:

· washing the fibres in water with Marseille soap at temperatures comprised between 30 °C and 50 °C

• preparation of the mordant with potassium alum (20 %) and cream of tartar (5 %) in water in an amount sufficient to completely cover the material to be mordanted

• mordanting by heating for a period of time comprised between 30 and 90 minutes in a temperature range comprised between 50 °C and 80 °C.

In a specific embodiment of the invention the dyeing method comprises a step of adding the material to be dyed in a colour bath comprising said colouring mixture or said composition, holding a temperature comprised in the range of 50-80 °C, extremes included. More specifically, the temperature may be a temperature of approximately 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C. The dyeing should be carried out for a time sufficient to obtain complete colouration of the material to be dyed. In particular, in accordance with the method described herein, dyeing in water will be carried out for a period of approximately 30-120 minutes.

The dyeing method can also comprise a step of eliminating excess colour by one or more washings in water at a temperature comprised in the range 30-50 °C, extremes included. In particular, this temperature is a temperature of approximately 30 °C, 32.5 °C, 35 °C, 37.5 °C, 40 °C, 42.5 °C, 45 °C, 47.5 °C, 50 °C.

A step of adding water or aqueous solution to the colour bath or to the colouring mixture as defined above may also optionally be provided. The water or aqueous solution is added in order to ensure the complete dipping of the material to be dyed in the colour bath and is also dependent on the type of shade which it is sought to achieve. It will be obvious to the person skilled in the art that the greater the volume of material to be dyed , the more water will have to be added to the colour bath, taking into account however the variation in shade which an addition of this type could cause.

In a further embodiment of the invention natural fibres can be dyed in orange tones by adding the fibres to be dyed directly to the means of extraction of the colouring mixture in accordance with one of the methods described above.

In this embodiment in particular, the method makes it possible to carry out the extraction of the colouring mixture and concomitantly the dyeing orange of natural fibres in a single step. Said method is carried out by dipping, simultaneously, in a suitable volume of water the natural fibres to be dyed and the flower heads, placed in an appropriate filter, of plants of Anacyclus. 'Suitable volume of water' means a volume sufficient for the complete dipping both of the vegetal material and of the fibre to be dyed in the aqueous solvent. In a specific embodiment said natural fibres of natural origin are wool fibres.

The method of extraction and simultaneous dyeing is carried out by heating in water to a temperature comprised in the range of 50-80 °C, extremes included, for a time of approximately 30-120 minutes.

Once the process of extraction and simultaneous dyeing is complete, the vegetal material will be separated (either by separation of the filter containing said material or by the optional step of filtration as already described above) and the excess colour from the fibre will be removed by washing in tap water or distilled water at temperatures comprised in the range of 30 °C and 50 °C.

The invention also relates to the material coloured in accordance with the dyeing methods disclosed herein.

The invention is described hereinafter in detail in the following examples which are purely illustrative and do not limit the scope of protection afforded.

EXAMPLES

Example 1. Method for preparing yellow colour baths from flower heads of Anacyclus

Preparation of the colour bath comprising the following steps:

Preparation of the vegetal material weighing 25 g of dried flower heads

Dipping of the flower heads in 3 litres of water (ratio 1 : 120 between flower heads expressed in g and water expressed in ml)

Heating in water to a temperature of 70 °C for 60 minutes; double filtration of the colour bath with a 1 .25 mm sieve to separate the coarser vegetal material and then with a 1.18 mm sieve to separate the finer material.

Example 2. Characterisation of the natural colourant

The UV spectrum of the mixture obtained registered peaks corresponding to the wavelengths 260 - 290 - 31 0 and 340, which can be considered to be characteristic of ye l l ow ; fo r th e o ra n g e colouring mixture further peaks corresponding to 360 - 400 - 440 - 480 were also recorded.

Example 3. Yellow dyeing of new wool yarn

A) Process of mordanting comprising the following steps:

washing of 50 g of new wool with Marseille soap at a temperature of 40 °C and rinsing in water;

preparation of the mordant with potassium alum (10 g) and cream of tartar

(0.25 g) in 3 litres of water;

Mordanting by heating at 70 °C for 60 minutes

B) Preparation of the colour bath comprising the following steps:

Preparation of the vegetal material weighing 25 g of dried flower heads; Dipping of the flower heads in 1.5 litres of water (ratio 1 :0.5 between fibre and vegetal material);

Heating in water to a temperature of 70 °C for 60 minutes; double filtration of the colour bath with a 1 .25 mm sieve to separate the coarser vegetal material and then with a 1 .18 mm sieve to separate the finer material.

C) Process of dyeing comprising the following steps:

Bringing the colour bath to a volume of 3 litres by adding water

Dipping of the mordanted fibres in the colour bath

Heating in the colour bath, holding the temperature at 70 °C for 60 minutes. Removal of the excess colour by washing in water at a temperature of 30 °C. Example 4 Orange dyeing of new wool yarn

A) Process of mordanting comprising the following steps:

washing of the fibres with Marseille soap at ambient temperatures;

preparation of the mordant with potassium alum (25 %) and cream of tartar (5 %) in water in an amount sufficient to ensure complete covering of the material to be mordanted

- mordanting by heating for a period comprised between 30 and 90 minutes at a temperature of 70 °C;

B) Preparation of extraction and dyeing comprising the following steps: Dipping of the flower heads in 3 litres of water (ratio 1 :120 between flower heads expressed in g and water expressed in ml) placed in a suitable filter.

Addition of water in an amount sufficient to ensure complete dipping of the mordanted fibres and complete extraction of the colour;

Heating at a temperature of 70 °C for 60 minutes;

Separation of the dyed fibres from the vegetal material by separation of the filter;

Removal of the excess colour from the fibres by washing in water at ambient temperature.

BIBLIOGRAPHY

Angelini L.G., Bertolacci M. 2008. Vegetative production and indigo yield of woad (Isatis tinctoria L.) and dyer's knotweed (Polygonum tinctorium Ait.) under irrigation in central Italy. Ital.J.Agron., 3 Suppl., 427-428;

He Z. 2008. Dyeing cotton fabrics containing functional maifanite fiber with high colour fixation properties. Faming Zhuanli Shenqing Gongkai Shuomingshu, CN 101314921 ;

Jia L. 2008. Research on dyeing of henna and other Arab vegetable dyes. Maofang Keji, 1 1 , 21 -24;

Yuan H. 2008d. Method for dyeing chrysanthemum on natural fibres. Faming Zhuanli Shenqing Gongkai Shuomingshu, CN 101307569.