Phosphate salts as mordants for dyeing

Abstract

The present disclosure relates to the use of a phosphate metal salt of the following formula: (Mz+)n(PO4 3-)m, wherein M is a metal provided that M is not nickel; z is 2 or 3; m is such that (n * z) – (m*3) = 0; as mordant. The invention also relates to a process for mordanting fibers using mordants of formula (Mz+)n(PO4 3-)m, wherein M is a metal, z is 2 or 3 and m is such that (n * z) – (m*3) = 0. The mordants are useful in fibers dyeing process.

Description

[0001] PHOSPHATE SALTS AS MORDANTS FOR DYEING

[0002] FIELD OF THE INVENTION

[0003] The invention belongs to the field of textile chemical industry, and particularly relates to improved green and ecological metal salt mordants suitable for dyeing fibers, such as wool.

[0004] BACKGROUND OF THE INVENTION

[0005] Dyes have been widely employed in human daily life since antiquity in a variety of fields, including the textile industry[1]. The latter has been under intense pressure to limit the use of hazardous compounds that are still connected with detrimental effects on the environment, particularly the allergic, mutagenic, and carcinogenic effects of chemicals and textile dyes[2]. In this context, academics have concentrated on more sustainable, cleaner, and cost- effective manufacturing processes and tactics[2].

[0006] Majority of fabrics are colored and printed with synthetic dyes. However, dyeing fabrics with natural dyes is gaining popularity as an environmentally benign and sustainable alternative to dyeing with synthetic dyes[3]. It is also viewed as a means of conserving local customs and cultural heritage, as well as helping rural livelihoods. In Morocco, the artisanal carpet plays a significant role in rural heritage, and the country is home to some of the most magnificent carpets in the world, noted for its quality as well as their vibrant colors[4]. Each big portion of the country is distinguished by distinct patterns, colors, weaving methods, or shapes. The creation of these carpets necessitates a multi-step procedure that begins with the collection of the wool and ends with knotting the carpets, which includes mordanting and vegetable dyeing.

[0007] Natural dyeing is associated with various technical challenges and disadvantages, including difficulty of color reproducibility, use of the same traditional chemicals (e.g., alum), no standard recipes and dyeing procedures and poor color stability and fastness.

[0008] Mordanting is a crucial step for good wool dyeing because it helps the molecules contained in plant extracts to bond with the fibers, allowing the color to be reinforced and sometimes modified. Mordants are consequently highly significant fixing agents since they make the wool resistant to washing, light, and abrasion[5]. These mordants can be natural substances such as urine, wood ash, plant galls, and tannins, or pure chemical compounds containing metal ions[6]. These chemical substances are typically salts of aluminum (potassium alum - potassium aluminum sulfate, ammonia alum - ammonium aluminum sulfate), iron (ferrous sulfate), chromium (potassium dichromate), copper (copper sulfate), and tin (stannous chloride). The mordant can be used before (pre-mordanting), during (meta-mordanting) or after (post-mordanting) the dyeing process. Nitrate and chloride metal salts used in mordanting process causes serious health and environmental problems[7].

[0009] The problem with the dyeing procedure described above is that the wastewater produced during fabric mordanting with metal salts containing nitrate, sulfate, ammonium, and chloride ions can create serious water pollution and potential toxic wastes.

[0010] Thus, there is an urgent need to develop new consistent and fast color fabrics in a green and sustainable manner.

[0011] SUMMARY OF THE INVENTION

[0012] The invention relates to the use of a phosphate metal salt of the following formula:

[0013] (Mz+)n(PO43')rri, wherein

[0014] M is a metal; z is 2 or 3; m is such that (n * z) - (m*3) = 0; as mordant.

[0015] The invention also relates to a process for mordanting fibers comprising the following steps:

[0016] (a) preparing an aqueous mordanting suspension comprising a phosphate metal salt of the following formula:

[0017] (Mz+)n(PO43')rri, wherein

[0018] M is a metal; z is 2 or 3; m is such that (n * z) - (m*3) = 0;

[0019] (b) sonication of the aqueous mordanting suspension,

[0020] (c) contacting the fibers with the aqueous mordanting suspension, (d) separating the fibers from the aqueous mordanting suspension,

[0021] (e) washing the fibers and collecting the mordanted fibers,

[0022] (f) filtering the aqueous mordanting suspension resulting from step (d) to recover the phosphate metal salts.

[0023] Finally, the invention relates to a fibers dyeing process comprising a fibers mordanting step in accordance with the process as disclosed herein and a dyeing step, wherein the fibers mordanting step is performed: before dyeing the fibers, or at the same time of dyeing the fibers, or after dyeing the fibers.

[0024] Further aspects of the invention are as disclosed herein.

[0025] DESCRIPTION OF THE INVENTION

[0026] The inventors have discovered that phosphate metal salts can be successfully employed for mordanting fibers and allow overcoming the problem of toxicity encountered in fibers dyeing processes. The proposed new mordants are safe and nontoxic.

[0027] Thus, the present invention relates to the use of phosphate metal salts of the following formula:

[0028] (Mz+)n(PO43')rri, wherein

[0029] M is a metal; z is 2 or 3; m is such that (n * z) - (m*3) = 0; as mordants.

[0030] The phosphate metal salts may be either in the pure form or can be derived from phosphate by-products such as phosphogypsum.

[0031] Preferred phosphate metal salts include AIPO4, FePO4, Ca3(PO4)2, Co3(P04)2, Cu3(PO4)2, Mg3(PO4)2, Ni3(PO4)2and Zn3(PO4)2, in particular AIPO4, FePO4, Ca3(PO4)2, Co3(P04)2, Cu3(PO4)2, Mg3(PO4)2, and Zn3(PO4)2. In some embodiments, the phosphate metal salt is not nickel phosphate.

[0032] The mordants may be used to prepare mordanting aqueous suspension and be used in a fibers mordanting process as described above.

[0033] The aqueous mordanting suspension typically comprises from 1 to 50 %, preferably from about 20%, by weight of mordants relative to the weight of the fibers. As phosphate metal salts are often insoluble in water, they tend to remain in solid form within the aqueous solution.

[0034] Subjecting the mordanting suspension to sonication in an ultrasonic bath or probe for 15 to 30 minutes significantly enhances the solubility of the developed mordants in water and improves dyeing performance, notably of natural dyeing.

[0035] The pH of the mordanting suspension can be adjusted depending on the nature of the fibers to be mordanted. For instance, the pH of the aqueous mordanting suspension may range from 3 to 9, preferably is about 7.

[0036] The fibers to be mordanted can be natural fibers, such as wool, cotton or silk fibers, or be synthetic fibers.

[0037] The fibers to be mordanted are contacted with the aqueous mordanting suspension. The fibers are typically immersed / introduced in a bath of the aqueous mordanting suspension. The contacting step may be performed at a temperature ranging from 60 to 90°C, typically for 30 min to 1 hour, to provide the mordanted fibers. The aqueous mordanting suspension may be heated by any conventional means. The heating can also be assisted by microwave.

[0038] To prepare the mordanting suspension, the quantity of mordant required is determined according to the weight of the fibers to be mordanted. This suspension is then typically applied in a 1 :100 ratio (mass of fibers / volume of mordanting solution).

[0039] Generally, 100 L of the aqueous mordanting suspension are used per kilograms of fibers. The mordanting suspension is typically acid-free. Hence, in preferred embodiments, no acidic additives is added to the mordanting suspension.

[0040] Then, the mordanted fibers are separated from the aqueous mordanting suspension and washed, typically with water. The collected mordanted fibers may then be squeezed and dried.

[0041] After use, the aqueous mordanting suspension is filtered to recover the phosphate metal salts. As the mordants are not completely soluble in the aqueous mordanting suspension, the insoluble fractions can be collected through simple filtration and can be re-used subsequently to prepare a novel aqueous mordanting suspension. By collecting the mordants post-use, the primary source of pollution in the dyeing process is eradicated.

[0042] The mordants of the invention can be used in dyeing and printing processes to improve the fastness and stability of the dyes and can be reused at the end without harming the environment.

[0043] The present invention also relates to a fibers dyeing process comprising a fibers mordanting step as disclosed herein and a dyeing step, wherein the fibers mordanting step is performed: before dyeing the fibers (pre-mordanting), or at the same time of dyeing the fibers (meta-mordanting), i.e. the dyes are present in the aqueous mordanting suspension, or after dyeing the fibers (post-mordanting).

[0044] The fibers mordanting is preferably performed before dyeing (pre-mordanting).

[0045] The mordants may be used with any natural dyes to cover the whole colors palette.

[0046] The color of the obtained mordanted and dyed fibers is stable and consistent.

[0047] The dyeing step, when performed after or before the mordanting step, may notably include a sub-step (i) of dye extraction followed by a sub-step (ii) of dyeing.

[0048] In some embodiments, the sub-step (i) of dye extraction comprises solubilizing a dye, preferably a natural dye, in aqueous solution, in particular in water, and then heating the solution to a temperature and for a time period enabling the dye extraction, depending of the nature of the dye. Typically, the temperature ranges from 40°C to 100°C, preferably from 60°C to 80"C, more preferably from 70°C to 80°C, and the time period is for example from 30 minutes to 1 hour. The solution is then filtrated to recover the dye extract.

[0049] In some embodiments, the sub-step (ii) comprises contacting the dye extract from step (i) to the mordanting fibers or the fibers to be mordanted, and heating to a temperature and for a time period enabling the dyeing, depending of the nature of the dye. Typically, the temperature ranges from 40°C to 100°C, preferably from 60°C to 80"C, more preferably from 70°C to 80°C, and the time period is for example from 30 minutes to 1 hour. The dyed fibers are then washed and dried.

[0050] Embodiments of the present invention will now be described by way of the following examples which are provided for illustrative purposes only, and not intended to limit the scope of the disclosure.

[0051] EXAMPLES

[0052] In the following examples, the advantages of the mordants of the invention are evidenced using two natural dye yielding plants: madder (Rubia tinctorum) a red dye source and Weld (Reseda Luteola) known for its vivid yellow dye.

[0053] The efficiency of the developed mordants in the dyeing process is compared to that of nonemordanted yarns and to a reference mordant which is alum.

[0054] To examine the efficiency of the mordants, exhaustion (%E) and fixation (%F) rates were determined. The exhaustion and fixation rates are calculated with formula (1) and (2) respectively:

[0055] Ea: absorbance of the initial dye solution

[0056] Eb: absorbance of the final dye solution

[0057] Ec: absorbance of the after washing solution Table 1 shows the depletion and fixation rates of dyed wool for the described examples.

[0058] Example 1 :

[0059] Wool yarns were mordanted with copper phosphate before dyeing with madder roots powder (Rubia tinctoria). The method includes the following steps:

[0060] Step 1 : Mordanting

[0061] 1 . Add 20 % by weight, relative to the weight of the fabric, of copper phosphate to water (bath ratio of 1 :100 mass of fibers / volume of mordanting solution; i.e. for 1 g of fabric, 100 mL of mordanting solution) and stir preferably in an ultrasonic bath.

[0062] 2. Add wool yarns and heat the suspension at 68°C for 1 hour.

[0063] 3. Wash wool yarns with cold water and allow them to dry.

[0064] 4. Filter the residual bath and recover the precipitating copper phosphate.

[0065] Step 2: Dye extraction

[0066] 1 . Add 1 g of madder roots powder to water (bath ratio 1 :200).

[0067] 2. Heat the solution at 76°C for 30 min with rigorous stirring.

[0068] 3. Filter the solution and recover the dye extract.

[0069] Step 3: Dyeing

[0070] 1 . Add 1 g of mordanted yarns to the extracted dye (M: L 1 : 100).

[0071] 2. Heat the dyeing bath at 76°C for 1 hour.

[0072] 3. Wash the dyed yarns with water and dry them at ambient air. Dyed yarns obtained are represented as D1 .

[0073] Example 2:

[0074] Example 2 is based on the same steps as example 1 , except the use of weld (Reseda Luteola) powder in step 2, the obtained yarns are described as D2.

[0075] Example 3:

[0076] Wool yarns were mordanted with zinc phosphate and dyed with madder (Rubia tinctorum) extract as following:

[0077] Step 1 : Mordanting

[0078] 1 . Add 20 % by weight, relative to the weight of the fabric, of zinc phosphate to water (bath ratio of 1 :100 mass / volume) and stir the suspension preferably in an ultrasonic bath. 2. Add wool yarns to the suspension and heat it at 68°C for 1 hour.

[0079] 3. Wash wool yarns with water and allow them to dry.

[0080] 4. Filter the residual bath and recover the precipitating zinc phosphate.

[0081] Step 2: Dye extraction

[0082] 1 . Add 1 g of madder roots powder to water (bath ratio 1 : 100).

[0083] 2. Heat the solution at 76°C for 30 min with rigorous stirring.

[0084] 3. Filter the solution and recover the dye extract.

[0085] Step 3: Dyeing

[0086] 1 . Add 1 g of mordanted yarns to the extracted dye (M: L 1 : 100).

[0087] 2. Heat the dyeing bath at 76°C for 1 hour.

[0088] 3. Wash the dyed yarns with water and dry them at ambient air. The obtained wool is represented as D3.

[0089] Example 4:

[0090] Example 4 was based on the same procedure as example 3 except the use of weld (Reseda Luteola) powder in step 2 to obtain wool yarns represented by D4.

[0091] Example 5:

[0092] The procedure was followed as described in example 3 except the use of calcium phosphate as mordant in step 1 . The resulting wool is represented as D5.

[0093] Example 6:

[0094] The same procedure of example 5 was followed except the use of weld (Reseda Luteola) in step 2, so dyed yarns D6 are obtained.

[0095] Example 7:

[0096] Wool fabric was dyed with madder (Rubia tinctorum) according to the same procedure as example 3, but using magnesium phosphate as mordant in step 1. The resulting wool is represented by D7.

[0097] Example 8:

[0098] The procedure was followed as described in example 7, except using weld (Reseda Luteola) in step 2. The obtained dyed wool is represented by D8. Example 9:

[0099] Wool yarns were dyed with madder extract (Rubia tinctorum) and mordanted with aluminum phosphate. The method includes the following steps:

[0100] Step 1 : Mordanting

[0101] 1. Add 10 % by weight, relative to the weight of the fabric, of aluminum phosphate to water (bath ratio of 1 :100 mass / volume) and stir the suspension preferably in an ultrasonic bath.

[0102] 2. Add wool yarns to the suspension and heat it at 68°C for 1 hour.

[0103] 3. Wash wool yarns with water and allow them to dry.

[0104] 4. Filter the residual bath and recover the precipitating aluminum phosphate.

[0105] Step 2: Dye extraction

[0106] 1 . Add 1 g of madder roots powder to water (bath ratio 1 :200).

[0107] 2. Heat the solution at 76°C for 30 min with rigorous stirring.

[0108] 3. Filter the solution and recover the dye extract.

[0109] Step 3: Dyeing

[0110] 1 . Add 1 g of mordanted yarns to the extracted dye (M: L 1 : 100).

[0111] 2. Heat the dyeing bath at 76°C for 1 hour.

[0112] 3. Wash the dyed yarns with water and dry them at ambient air. The obtained wool yarns are described as D9.

[0113] Example 10:

[0114] Carried out as described in example 9 except using weld (Reseda Luteola) in step 2. The obtained wool yarns are represented by D10.

[0115] Comparative example 10’:

[0116] Carried out as described in example 9 except that no stirring of the suspension is ultrasonic bath is achieved. The wool yarns obtained are represented by D10’.

[0117] Example 11 :

[0118] The procedure is as described in example 9, except that the mordant used was Nickel phosphate in step 1 . The resulting wool is described as D11 .

[0119] Example 12: Example 12 is based on Example 11 , except using weld (Reseda Luteola) in step 2. The resulting dyed wool is described as D12.

[0120] Example 13:

[0121] Wool fibers were mordanted with iron phosphate and dyed with madder extract (Rubia tinctorum) according to the following procedure:

[0122] Step 1 : Mordanting

[0123] 1 . Add 2% by weight, relative to the weight of the fabric, of iron phosphate to water (bath ratio of 1 :100 mass / volume) and stir the suspension preferably in an ultrasonic bath.

[0124] 2. Add wool yarns to the suspension and heat it at 68°C for 1 hour.

[0125] 3. Wash wool yarns with water and allow them to dry.

[0126] 4. Filter the residual bath and recover the precipitating iron phosphate.

[0127] Step 2: Dye extraction

[0128] 1 . Add 1 g of madder roots powder to water (bath ratio 1 : 100).

[0129] 2. Heat the solution at 76°C for 30 min with rigorous stirring.

[0130] 3. Filter the solution and recover the dye extract.

[0131] Step 3: Dyeing

[0132] 1 . Add 1g of mordanted yarns to the extracted dye (M: L 1 :100).

[0133] 2. Heat the dyeing bath at 76°C for 1 hour.

[0134] 3. Wash the dyed yarns with water and dry them at ambient air. The obtained yarns are described as D13.

[0135] Example 14:

[0136] The procedure was followed as described in example 13, except, the use of weld (Reseda Luteola) in step 2, so that the obtained wool is represented by D14.

[0137] Example 15:

[0138] Conducted as described in example 13, except that, cobalt phosphate was used as a mordant in step 1 , and the use of a bath ratio of 1 :200 in step 2. The resulting wool is described as D15.

[0139] Example 16: The procedure was followed as described in example 15, except that Weld (Reseda Luteola) was used in step 2, so that dyed wool D16 is obtained.

[0140] Comparative example 1 :

[0141] Wool yarns were mordanted with alum and dyed with madder extract (Rubia tinctorum) according to the following procedure:

[0142] Step 1 : Mordanting

[0143] 1. Add 2 % by weight, relative to the weight of the fabric, of alum to water (bath ratio of 1 : 100 mass / volume) and stir the solution manually or in an ultrasonic bath.

[0144] 2. Add wool yarns to the solution and heat it at 68°C for 1 hour.

[0145] 3. Wash wool yarns with cold water and allow them to dry.

[0146] Step 2: Dye extraction

[0147] 1 . Add 1g of madder roots powder to water (bath ratio 1 :200).

[0148] 2. Heat the solution at 76°C for 30 min with rigorous stirring.

[0149] 3. Filter the solution and recover the dye extract.

[0150] Step 3: Dyeing

[0151] 1 . Add 1 g of mordanted yarns to the extracted dye (M: L 1 : 100).

[0152] 2. Heat the dyeing bath at 76°C for 1 hour.

[0153] 3. Wash the dyed yarns with water and dry them at ambient air. The obtained wool yarns are described as D17.

[0154] Comparative example 2:

[0155] Carried out as described in comparative example 1 except using weld powder (Reseda Luteola) in step 2, so wool yarns D18 are obtained.

[0156] Comparative example 3:

[0157] The procedure was followed as described in comparative example 1 , except that the step 1 was skipped (no mordanting), and in step 3 raw wool were used in the dyeing process. The resulting wool is described as D19.

[0158] Comparative example 4: The procedure was followed as described in comparative example 1 except that step 1 was skipped (no mordanting), and in step 2, weld powder (Reseda Luteola) was used as dye yielding plant. In step 3, raw wool was dyed with dye extract, so the yarns D20 are obtained. Table i :

[0159] Example N° Exhaustion rate Fixation rate (%)

[0160] D19 29,16 25,84

[0161] D20 6,17 4,06

[0162] To judge the efficiency of the developed mordants, its exhaustion and fixation values were compared to un-mordanted and alum mordanted yarns as a standard reference. Hence, the results showed that all phosphate mordanted yarns showed better dye uptake than unmordanted yarns. The new mordants showed also comparable dye fixation rate to alum mordanted yarns which indicate the feasibility of the present invention. The reusing of these phosphate mordants has shown to be very successful in the mordanting and dyeing of wool fibers, despite their uncomplete solubility in aqueous media.

[0163] The solubility of the developed mordants is enhanced through the application of ultrasound which enables to improve the dyeing performances (see D10 and comparative D10’). The mordants developed in this invention are not restricted to the natural dyes mentioned herein but can also be employed with other dyes to cover the whole color palette. Moreover, the mordants are not limited to dyeing wool fibers, though it is exceptionally successful with these fibers, it may also be used on other natural fibers such as cotton, silk, and synthetic fibers. The mordants of the present invention can be also tested for antimicrobial and antifungal properties.

[0164] REFERENCES

[0165] [1] K. H. Prabhu and A. S. Bhute, “Plant based dyes and mordant: A Review Plant based natural dyes and mordants: A Review,” J. Nat. Prod. Plant Resour, vol. 2012, no. 6, pp. 649- 664, Accessed: Jan. 27, 2022. [Online], Available: http: / / scholarsresearchlibrary.com / archive.html.

[0166] [2] M. Shahid, Shahid-UI-lslam, and F. Mohammad, “Recent advancements in natural dye applications: A review,” J. Clean. Prod., vol. 53, pp. 310-331 , Aug. 2013.

[0167] [3] H. Kfizova, “Natural dyes: their past, present, future and sustainability,” 2016,

[0168] Accessed: Jan. 27, 2022. [Online], Available: https: / / www.researchgate.net / publication / 293885858.

[0169] [4] T. Maraini, “Some Observations on Traditional Popular Art in Morocco,” https: / / doi.org / 10.1080 / 17496772.2020.1735131 , vol. 13, no. 1 , pp. 107-114, Jan. 2020, doi: 10.1080 / 17496772.2020.1735131 .

[0170] [5] A. P. Manian, R. Paul, and T. Bechtold, “Metal mordanting in dyeing with natural colourants,” Color. Technol., vol. 132, no. 2, pp. 107-113, Apr. 2016, doi: 10.1111 / COTE.12199.

[0171] [6] O. E. I§mal and L. Yildirim, “Metal mordants and biomordants,” in The Impact and Prospects of Green Chemistry for Textile Technology, Elsevier, 2018, pp. 57-82.

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Claims

CLAIMS1 . Use of a phosphate metal salt of the following formula:(Mz+)n(PO43')rri, whereinM is a metal provided that M is not nickel; z is 2 or 3; m is such that (n * z) - (m*3) = 0; as mordant.

2. Use according to claim 1 , wherein M is aluminum, Iron, calcium, cobalt, copper, magnesium or zinc.

3. Use according to claim 1 or 2, wherein the phosphate metal salt is AIPO4, FePO4,Ca3(PO4)2, Co3(P04)2, Cu3(PO4)2, Mg3(PO4)2or Zn3(PO4)24. Process for mordanting fibers comprising the following steps:(a) preparing an aqueous mordanting suspension comprising a phosphate metal salt of the following formula:(Mz+)n(PO43')m, whereinM is a metal; z is 2 or 3; m is such that (n * z) - (m*3) = 0;(b) sonication of the aqueous mordanting suspension,(c) contacting the fibers with the aqueous mordanting suspension,(d) separating the fibers from the aqueous mordanting suspension,(e) washing the fibers and collecting the mordanted fibers,(f) filtering the aqueous mordanting suspension resulting from step (d) to recover the phosphate metal salts.

5. The process according to claim 4, wherein step (c) is performed at a temperature ranging from 60 to 90°C.

6. The process according to claim 4 or 5, wherein the aqueous mordanting suspension has a pH ranging from 3 to 9.

7. The process according to any one of claims 4 to 6, wherein step (c) is performed for 30 min to 1 hour.

8. The process according to any one of claims 4 to 7, wherein the recovered phosphate metal salts in step (f) are reused to prepare the aqueous mordanting suspension of step (a).

9. The process according to any one of claims 4 to 8, wherein the fibers are natural fibers, preferably wool, cotton and silk fibers.

10. The process according to any one of claims 4 to 8, wherein the fibers are synthetic fibers.

11. A fibers dyeing process comprising a fibers mordanting step in accordance with the process recited in any one of claims 4 to 9 and a dyeing step, wherein the fibers mordanting step is performed: before dyeing the fibers, at the same time of dyeing the fibers, or after dyeing the fibers.

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