PROCESS FOR DYEING ANIMAL TEXTILE FIBERS COMPRISING THE USE OF PURIFIED SYNTHETIC FOOD DYES

Abstract

A textile dyeing process is described for dyeing a textile material, product or article consisting of animal fibers, comprising the steps of dipping said textile material, product or article into a dyeing bath comprising at least one detergent substance, a wetting substance, a leveling substance and an acidity regulator; adding to the dyeing bath a coloring substance approved for food use; subjecting the dyed textile material, product or article to washes; and finally subjecting the dyed textile material, product or article to a color fixing treatment.

Claims

1. A textile dyeing process for dyeing a textile material, product or article of fibers and fabrics consisting of animal hair, comprising the following steps, wherein steps 1) to 5) take place under stirring: 1) dipping the textile material, product or article for a period between 5 and 15 minutes into a water-based dyeing bath having a temperature between 20 and 30° C., said bath comprising at least: 2,2-dimethyl-1,3-propanediol (CAS no. 126-30-7) as a detergent substance; a wetting substance selected from polyethylene glycol-10 propyl ether ((C.sub.2H.sub.4O).sub.nC.sub.10H.sub.22O, CAS no. 160875-66-1), petroleum distillate (CAS No. 64742-47-8), undecyl alcohol ethoxylates (CAS No. 127036-24-2) and a mixture of 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone (CAS no. 55965-84-9); a leveling substance selected from 5-sulfosalicylic acid (CAS no. 97-05-2), polyethoxylated tallow amines (CAS no. 61791-26-2), quaternary salts of polyethoxylated tallow amines with diethylsulphate (CAS no. 68071-95-4) and a mixture of C16-C18 ethoxylated unsaturated alcohols (CAS no. 68920-66-1); an acidity regulator consisting of a mixture of citric acid (CAS no. 77-92-2) and 5-sulfosalicylic acid (CAS no. 97-05-2), in a weight ratio between citric acid and 5-sulfosalicylic acid between 4:1 and 9:1; 2) adding to the dyeing bath of step 1 one or more synthetic coloring substances approved for use in the food industry, bringing the bath to a temperature between 80 and 120° C. in a time between 50 and 80 minutes, leaving it at this temperature for a time between 30 and 90 minutes, and finally cooling the bath to a temperature between 60 and 80° C. in a time between 10 and 30 minutes; 3) draining the bath and subjecting the textile material, product or article dyed in the previous passages to a first wash in the same machine at a temperature between 35 and 55° C. for a time between 5 and 15 minutes; 4) draining the bath of the first wash and subjecting the textile material, product or article to a second wash in the same machine at a temperature between 20 and 35° C. for a time between 2 and 10 minutes in water, or at 50° C. for a time between 2 and 10 minutes in a solution of sodium acetate in water; 5) draining the bath of the second wash and subjecting the textile material, product or article to a color fixing treatment in a bath containing a fixing substance with a percentage between 1% and 6% with respect to the initial weight of the textile material, product or article at a temperature between 20 and 60° C., for a time between 5 and 30 minutes, and at a pH between 4.5 and 6.5 obtained with a pH regulator consisting of a mixture of citric acid and 5-sulfosalicylic acid in a weight ratio between 4:1 and 9:1, and said fixing substance is selected among diethylene glycol, a 5% suspension of silica in water, or a mixture thereof; 6) draining the bath and subjecting the textile material, product or article to drying.

2. The process according to claim 1, further comprising a preliminary step 0 carried out under stirring, wherein said textile material, product or article to be colored is dipped into water at a temperature between 20 and 30° C. for a time between 5 and 10 minutes, and wherein all or part of the quantity of wetting substance necessary for carrying out step 1 is optionally added to water.

3. The process according to claim 1, wherein the quantities are used, in percentage by weight with respect to the weight of said textile material, product or article, 1% of said detergent substance, 1% of said wetting substance, between 1% and 2% of said leveling substance and between 10 and 30% of said acidity regulator.

4. The process according to claim 1, wherein said one or more synthetic coloring substances approved for use in the food industry are selected from the substances of the following table: TABLE-US-00005 Commercial name CAS No. Code Color Tartrazine - Acid yellow 23 1934-21-0 E102 Yellow Quinoline yellow 8004-92-0 E104 Yellow Sunset yellow 2783-94-0 E110 Yellow-orange Food red 3 3567-69-9 E122 Carmine Acid red 18 2611-82-7 E124 Red Erythrosine B - Acid red 51 16423-68-0 E127 Red Food red 17 25956-17-6 E129 Scarlet red Amaranth red - Acid red 27 915-67-3 E123 Amaranth red Food blue 5:2 20262-76-4 E131 Blue Acid blue 74 860-22-0 E132 Blue Erioglaucine disodium salt - 3844-45-9 E133 Blue Food blue 2 Lissamine green B - Acid green 50 3087-16-9 E142 Green Food black 1 2519-30-4 E151 Black Chocolate brown HT 4553-89-3 E155 Brown

5. The process according to claim 1, wherein said one or more synthetic coloring substances approved for use in the food industry are used in a quantity between 0.001% and 6% of the weight of the textile product.

6. The process according to claim 1, wherein said step 5 is carried out by dipping said textile material, product or article into the bath containing the fixing substance, or with the “foulard” technique when said textile material, product or article is a fabric, or with a spray technique when said textile material, product or article is a finished item of clothing.

7. The process according to claim 1, wherein said textile material, product or article is made of wool.

8. A textile material, product or article consisting of animal hair textile fibers, dyed with the textile process according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 reproduces a time diagram which schematically represents a characteristic textile dyeing process of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] In the following description of the textile dyeing process of the invention, the reference to a respective and specific embodiment and/or application does not exclude that a particular configuration, structure or characteristic described in relation to this embodiment and application can be included also in other embodiments and applications of the process, in which for reasons of brevity it has not been described. This implies that particular configurations and/or characteristics of the dyeing process of the invention can be combined in any suitable and coherent way in one or more embodiments and applications.

[0039] The process of the invention is applied to textile fibers formed from animal fibers. Studies carried out by the inventors have shown that the process of the invention is not effective, for example, for dyeing silk, even if this yarn is in turn of animal origin. This observation confirms what has been said previously, namely that not all processes and not all substances are suitable for coloring all fibers, and that dyes known and used with some fibers (for example, on vegetable fibers such as cotton) are not necessarily usable for coloring fibers derived from animal hair, in particular wool.

[0040] In the rest of the text and claims, the following conventions and definitions are adopted: [0041] “synthetic food color” means a dye made through chemical synthesis, and normally used in the food industry to color foodstuffs and beverages; [0042] “textile product” means an animal textile fiber, in particular wool, or any article made with said fiber, therefore the loose fiber, the fiber in yarn, a fabric made with the yarn, or a finished item of clothing made with said yarn or fabric; [0043] all the percentages of the various components used in the process are to be understood by weight relative to the initial weight of the textile product to be colored; [0044] finally, the exact chemical and/or commercial name will be given of all the substances used in the process of the invention; in addition, in order to provide information that is as complete and accurate as possible, the CAS (Chemical Abstract Service) register number is also indicated for the used substances.

[0045] The textile dyeing process of the invention comprises a first part, indicated hereinafter also as BT part, in which the textile product to be dyed is dipped and treated in a dyeing bath, and a second part, indicated hereinafter also as TF part, in which the textile product is subjected to a finishing treatment. The bath of the process is water based, i.e. the liquid phase into which the textile product is dipped and the compounds that perform the functions of the various steps (detergents, wetting agents, dyes, . . . ) are dissolved, is water.

[0046] All steps of the process of the invention are carried out under stirring. The products used in the process are generally dissolved in water in a separate tank and sent to the dyeing machine by means of a circulation pump which keeps the bath under stirring throughout the process.

[0047] All steps of the process take place in water, with a weight ratio between water and the textile product to be dyed which can vary between 10:1 and 40:1; these quantities of water are sufficient to completely solubilize all the chemical compounds (detergents, wetting agents, dyes, . . . ) used in the process.

[0048] The process of the invention comprises a preliminary step (also referred to hereinafter as step 0), which consists in leaving the textile product to be colored dipped into water at a temperature between 20 and 30° C. for a time between 5 and 10 minutes. This preliminary step has the purpose of completely impregnating the fibers with water, so that the components of the bath added subsequently can effectively and quickly contact the textile fibers.

[0049] The actual process (BT part) begins with step 1 in which, maintaining the temperature between 20 and 30° C., at least one detergent substance, a wetting substance, a leveling substance and an acidity regulator are added to the bath. Said substances essentially have the function of preparing the bath for dyeing the textile product; said substances are known to those skilled in the art, as well as their effects on fibers, and comprise at least: [0050] a detergent substance (which also acts as an emulsifier) having the function of cleaning the textile product so as to prepare it to be dyed in the same dyeing bath; the detergent substance can be for example 2,2-dimethyl-1,3-propanediol (CAS no. 126-30-7); [0051] a wetting substance having the function of deaerating the textile product; the wetting substance can be, for example, polyethylene glycol-10 propyl ether (general formula ((C.sub.2H.sub.4O).sub.nC.sub.10H.sub.22O, CAS no. 160875-66-1), petroleum distillate (CAS No. 64742-47-8), undecyl alcohol ethoxylates (CAS No. 127036-24-2) or a mixture of 2-methyl-3(2H)-isothiazolone and 5-chloro-2-methyl-3(2H)-isothiazolone (CAS no. 55965-84-9); [0052] a leveling substance having the function of leveling the characteristics of the textile product so as to prepare it to be dyed homogeneously; the leveling substance can be for example 5-sulfosalicylic acid (CAS no. 97-05-2), polyethoxylated tallow amines (CAS no. 61791-26-2), quaternary salts of polyethoxylated tallow amines with diethylsulphate (CAS no. 68071-95-4) or a mixture of C16-C18 ethoxylated unsaturated alcohols (CAS no. 68920-66-1); and [0053] an acidity regulator, which consists of a mixture of citric acid (CAS no. 77-92-2) and 5-sulfosalicylic acid (CAS no. 97-05-2), which has the function of maintaining the pH constant during the treatment; the weight ratio between citric acid and 5-sulfosalicylic acid can vary between 4:1 and 9:1.

[0054] The following table summarizes the substances that are added in step 1 in the dyeing bath and shows the indicative percentages of said substances in the bath with respect to the weight of the textile product to be dyed.

TABLE-US-00001 SUBSTANCE Percentage (%) Detergent 1 Wetting agent 1 Leveling agent 1-2 pH regulator 10-30

[0055] Step 1 of the process lasts between 5 and 15 minutes.

[0056] In a variant of the process, the wetting substance can be added in step 0 described above, or in part in step 0 and the remaining part in step 1.

[0057] Subsequently, at the beginning of step 2 of the process, a purified synthetic food color is added to the dyeing bath, according to a salient feature of the dyeing process of the invention. The synthetic coloring substances for food use that can be used in the invention are shown in the following table, in which a chemical or commercial name, the GAS number, the code with which this is designated in the European Union (when available) and the color that the substance gives to the textile product, are indicated for each substance:

TABLE-US-00002 Commercial name CAS No. Code Color Tartrazine - Acid yellow 23 1934-21-0 E102 Yellow Quinoline yellow 8004-92-0 E104 Yellow Sunset yellow 2783-94-0 E110 Yellow-orange Food red 3 3567-69-9 E122 Carmine Amaranth red - Acid red 27 915-67-3 E123 Amaranth red Acid red 18 2611-82-7 E124 Red Erythrosine B - Acid red 51 16423-68-0 E127 Red Food red 17 25956-17-6 E129 Scarlet red Food blue 5:2 20262-76-4 E131 Blue Acid blue 74 860-22-0 E132 Blue Erioglaucine disodium salt - Food 3844-45-9 E133 Blue blue 2 Lissamine green B - Acid green 50 3087-16-9 E142 Green Food black 1 2519-30-4 E151 Black Chocolate brown HT 4553-89-3 E155 Brown

[0058] Each of said coloring substances can be used alone, or it is possible to use a mixture of two or more of these substances to obtain particular shades of color; both in the case of a single substance and in the case of a mixture of two or more of these coloring substances, the percentage in the dyeing bath of this component can vary between 0.001% and 6%. Within this range, the actual quantity to be used can be determined using methods and techniques known to the experts in the sector, according to the desired result (for example, the intensity of color or the tone to be obtained).

[0059] For example, it is possible, through a common laboratory textile dyeing machine, to prepare a plurality of recipes, that is a plurality of dyeing baths having different percentages, even slightly, of said synthetic food color and then test them to verify their real effect on the textile product to be dyed, in order to select the recipe or the dyeing bath with the percentage of synthetic food coloring substance that provides the best result as regards the dyeing of the textile product.

[0060] Simultaneously with the introduction of the synthetic food color in the desired percentage into the dyeing bath, the temperature of the latter is gradually increased, in a time between 50 and 80 minutes, preferably 70 minutes, from the initial temperature, for example 30° C., to a temperature between 80 and 120° C., preferably of about 100° C. After reaching the desired temperature, the bath is left at this temperature for a time between 30 and 90 minutes, preferably 60 minutes, and finally it is cooled to a temperature between 60 and 80° C., preferably to 70° C.; cooling generally requires a time between 10 and 30 minutes, typically about 15 minutes.

[0061] After being treated and dyed in the dyeing bath, the textile product is subjected to a finishing treatment, indicated as a whole with TF, comprising various steps and interventions. This part can be started immediately after the conclusion of the BT part or later.

[0062] In particular, after having reached 70° C. of the dyeing bath with cooling, the bath is drained to perform a first wash in water of the dyed textile product, corresponding to step 3 of the process of the invention. Said first wash is preferably carried out in the same machine in which the dyeing took place, at a temperature between 35 and 55° C., preferably 40° C., for a time between 5 and 15 minutes, preferably for 10 minutes, after which the bath of the first wash is drained from the machine.

[0063] Then, the textile product is subjected, preferably in the same machine of the first wash, to a second wash, corresponding to step 4 of the process of the invention; said wash can take place in water at a temperature between 20 and 35° C., preferably at 30° C., for a time between 2 and 10 minutes, preferably for 5 minutes; alternatively, the second wash can be done at a temperature of 50° C. for a time between 2 and 10 minutes, preferably for 5 minutes, in an aqueous solution containing 5% by weight (with respect to the textile product) of sodium acetate. After the conclusion of this step, the bath of the second wash is drained from the machine.

[0064] In step 5 of the process of the invention, the dyed textile product is subjected to a color fixing treatment. Said treatment consists in dipping the textile product (in the same machine of the washing baths or in another machine) into a bath containing a fixing substance in a percentage between 1% and 6% by weight with respect to the initial textile product, at a temperature between 20 and 60° C., preferably at 40° C., for a time between 5 and 30 minutes, preferably 20 minutes, at a pH between 4.5 and 6.5, preferably 5.5. This treatment has the function of increasing wet fastness, the resistance of the textile product to pilling, and also conferring water repellency to the final textile product. Alternatively, the fixing substance can be applied in “foulard mode” (impregnation followed by squeezing and drying) if the textile product is a fabric; or by spraying distribution, particularly suitable when the textile product to be treated is an already finished item of clothing. The fixing substance is diethylene glycol, a 5% suspension of silica in water, or a mixture thereof. The silica gel having the desired concentrations can be produced by suspending in water the product known as “nanometric silica”, “colloidal silica” or “fumed silica”; said form of silica is widely available commercially and is sold for example by the company Evonik Resource Efficiency GmbH of Essen (Germany) under the name AEROSIL®, or by the company Cabot Corporation of Boston, Mass. (USA) under the name Cab-O-Sil®.

[0065] At the end of the fixing treatment, in step 6 of the process the bath is drained, and the textile product is sent for drying in view of any subsequent treatments.

[0066] FIG. 1 represents a time diagram which schematically shows the time/temperature profile of a typical dyeing process according to the invention, which is reported by way of example. As shown in the FIGURE, the process consists of a first BT part (in which the textile product is colored) and a second TF part (finishing treatments, in which the color is fixed). Each of the steps of the process (including the preliminary step 0) is indicated with the corresponding number in the lower part of the diagram (near the time axis).

[0067] In the process of the example in FIG. 1, the preliminary step 0 (impregnation of the textile product with water) and step 1 (addition of detergent, wetting agent, leveling agent and acidity regulator) are both carried out at 30° C., each with a duration of 5 minutes. The actual dyeing step, 2, which begins with the addition of the chosen dye to the bath, comprises a first part of increasing the temperature from 30° C. to 100° C. in 70 minutes, holding the bath containing the textile product at 100° C. for 60 minutes, cooling from 100° C. to 70° C. in 15 minutes and subsequent cooling to temperatures around room temperature.

[0068] There is no fixed temporal relationship between the end of the BT part and the beginning of the TF part of the process: this condition is represented by the broken axis of times between these two parts of the process.

[0069] The TF part of the process starts at the minute zero of this part, with step 3 (first wash) which is carried out at 40° C. for a time of 10 minutes, followed by a step 4 (second wash) carried out at 30° C. for 5 minutes, and subsequently by the color fixing step 5, which is carried out at 40° C. for 20 minutes. Step 6 (drain of the finished textile product from the last bath and subsequent operations) has no precise temperature and duration.

[0070] As said, the one represented in FIG. 1 is only one possible example of the process of the invention; as will be evident to the person skilled in the art, each of the steps represented in the FIGURE and described in detail below could be carried out at a temperature or for a duration of time different from those indicated in the FIGURE, provided that these temperatures and durations fall within the ranges previously reported; in particular, remaining within said intervals, the duration of each of the steps of the process will generally be the shorter, the higher the temperature at which it is carried out, and vice versa.

[0071] The process of the invention can also admit other variations, modifications and improvements with respect to what has been described and illustrated so far.

[0072] For example, without prejudice to the use, for preparing the BT dyeing bath, of a purified synthetic dye already used in the food sector, which use corresponds to the salient feature of the invention, the other conventional substances, included in the BT dyeing bath and used in the TF finishing treatment of the textile product, may vary with respect to those previously described and illustrated with reference to the dyeing process, in particular as a function of the specific characteristics that the textile product, once dyed, must satisfy.

[0073] The invention will be further described by the following examples.

Example 1

[0074] Six samples of wool fabric are colored according to processes of the invention and according to processes not of the invention. The samples obtained in preparations 1A, 1B, 2A and 2B have been produced with processes that do not satisfy the conditions of the invention, and are therefore comparative samples; the samples 1C and 2C are instead samples obtained according to the process of the invention.

[0075] To allow the comparison of the results, the thermal profile (temperature/time) adopted in the preparation process is the same for all six samples and corresponds to the thermal profile described above with reference to FIG. 1. The components adopted in the various steps of the process for the six samples are shown in Table 1. The components used in each of the tests are identified with the CAS number apart from silica which is indicated by its formula SiO.sub.2. Sodium sulphate and formic acid are used in the comparison tests as they are typical components of dyeing baths of the prior art. For each of the components used, the table shows the quantity used (in % by weight on the weight of the sample of the colored wool fabric).

TABLE-US-00003 TABLE 1 Preparation or sample Component 1A 1B 1C 2A 2B 2C CAS 1934-21-0 non-food dye   0.3 / /   0.25 / / CAS 2611-82-7 non-food dye   0.3 / /   0.2 / / CAS 3844-45-9 non-food dye   0.3 / / / / / 2519-30-4 non-food dye / / /   0.6 / / CAS 1934-21-0 food dye /   0.3   0.3 /   0.25   0.25 CAS 2611-82-7 food dye /   0.3   0.3 /   0.2   0.2 CAS 3844-45-9 2 food dye /   0.3   0.3 / / / 2519-30-4 food dye / / / /   0.6   0.6 Wetting agent (CAS 1 1 1 1 1 1 55965-84-9) Detergent (CAS 126-30-7) / / 1 / / 1 Leveling agent (CAS 61791-26-2) 1 1 / 1 1 / Leveling agent (CAS 61791-26-2 + / / 1 / / 1 CAS 97-05-2) Sodium sulphate (CAS 5 5 / 5 5 / 14808-79-8) Formic acid (CAS 64-18-6) 4 4 / 4 4 / PH regulator (CAS 77-92-9 + / / 20  / / 20  CAS 97-05-2 + CAS 64-18-6) Fixing agent (CAS 111-46-6 + / / 5 / / 5 SiO.sub.2)

Example 2

[0076] The six samples obtained in Example 1 are subjected to a color release test according to the UNI EN ISO 105-E04 standard test, which is the most severe and selective test to pass the GB 18401 standard; according to this standard, the test simulates the release of color by a fabric in the presence of alkaline perspiration (alkaline perspiration is simulated with a basic solution sold specifically for carrying out said test).

[0077] The test is carried out by impregnating each sample with the diluted soda solution and then placing the sample in contact with a “witness fabric”, that is, a strip of fabric made with six different materials (acetate, cotton, polyamide, polyester, acrylic and wool), and by evaluating the intensity of the color acquired by the various parts of the witness through release from the sample under examination; the more intense the staining of the witness, the greater the release from the examined tissue and therefore the worse the result is considered. The values are reported to a grey scale with values varying between 1 and 5, in which the lower the value, the poorer the fastness. GB 18401 accepts 3-4 as a minimum dye-fading value.

[0078] The results of the tests carried out on the six samples 1A, 1B, 1C, 2A, 2B and 2C are shown in Table 2.

TABLE-US-00004 TABLE 2 Witness fabric 1A 1B 1C 2A 2B 2C Acetate 4-5 4-5 5 4-5 4-5 5 Cotton 2 2 5 1-2 1-2 5 Polyamide 2 2 4 2-3 2-3 4-5 Polyester 4 4 5 4 4 5 Acrylic 4 4 5 4 4 5 Wool 2 2 3-4 2 2 4

[0079] From the results of the tests reported in Table 2 it can be deduced that purified synthetic dyes for food use applied in the textile field to dye the protein fibers, if used with the known process (samples 1B and 2B) would only have the advantage of being eco-sustainable compared to the same not purified dyes (samples 1A and 2A); on the other hand, if applied with the process of the invention (samples 1C and 2C) in addition to eco-sustainability, the purified synthetic dyes for food use also allow excellent wet color fastness to be obtained.

[0080] Comments

[0081] The new textile dyeing process of the invention, which uses purified synthetic dyes approved for the food industry, allows to fully achieve the set objectives and in particular provides both a new innovative textile dyeing process capable of eliminating all the negative effects connected to the use, in conventional textile dyeing, of synthetic and natural dyes, and also a new and innovative use of purified dyes of synthetic origin which are usually and currently used in the food industry.

[0082] This process offers a series of relevant and unique advantages, some of which have already been illustrated above, among which the following ones can be mentioned: [0083] the dyes used in the textile dyeing process, being synthetic but purified, do not feature any toxicity or harmfulness to the operators and workers who manage the textile dyeing processes and plants in which said dyes are used; [0084] in particular, the purified synthetic dyes used are metal-free, do not contain allergenic substances, are not mutagenic, and the respective powders do not contain any type of free amines or other substances harmful to the health of the operators who must handle said dyes; [0085] the process allows a significant reduction of the costs for treating and disposing of the residues and waste produced by the textile dyeing, since the dyes used are free of polluting substances; [0086] there are better and healthier working conditions in textile dyeing plants; [0087] the dyeing costs of textile products and/or articles are competitive with those of the conventional textile dyeing processes, that is, using conventional dyes; [0088] the textile products colored with the process of the invention meet the GB18401, GOTS 5.0 standards and the requirements of the ZDHC programme.