Method for improving the colour fastness of textile material made of plastics

Abstract

The invention relates to a method for improving the colour fastness of textile material made of plastics, whereby one or more vat dyes are applied to the textile material which undergoes heat treatment on its own or combined with other dyes/pigments. The material undergoes at least one additional heat treatment in connection with the colour thereof.

Description

[0001] The present invention relates to a method of improving the colorfastness of textile materials made of synthetics.

BACKGROUND INFORMATION

[0002] Synthetic materials are not adequately dyed by the traditional dyeing methods. Problems occur with polyesters (PES), polyamides (PA), polyurethanes (PU) and other synthetics in particular when the textile material is composed of a blend of different synthetics, e.g., PA and PES. Additional problems occur when dealing with microfibers. Therefore, there has been a search for possibilities which yield good dyeing of individual synthetics and blends and also have high use fastness values such as washfastness and lightfastness.

[0003] European Patent 0 772 709 B1 describes a method of dyeing materials made of synthetics using vat dyestuffs, which yields greatly improved washfastness and lightfastness in comparison with older methods (Thomas Vickerstaff, The Physical Chemistry of Dyeing (1968), 2nd edition, page 479), and the method described there includes the following steps:

[0004] a) Selecting a vat dyestuff

[0005] b) Treating the material with the dyestuff in the presence of a reducing agent and an alkali, where the alkali has a concentration of more than 0.2 mol/L and

[0006] c) Oxidizing the treated material produced in step b).

[0007] The disadvantage of this method is that the large quantities of alkali required result in a substantial wastewater load and high process costs. In the case of fiber materials containing PES, e.g., PA/PES blends, the large amounts of alkali used may also result in damage to the PES fiber and thus a considerable loss of tensile strength.

EXPLANATION OF THE INVENTION

[0008] The object of the present invention is to provide a method which yields good colorfastness results—in particular lightfastness—as well as causing only a minor loss of tensile strength by working with smaller quantities of alkali, in particular in the case of material made of PES and/or PA.

[0009] According to the present invention, this object is achieved by a method as defined in the preamble in which the material is exposed to at least one additional heat treatment following its dyeing.

[0010] This method preferably involves the heat treatment being performed in a dry atmosphere for a period of 0.1 sec to 60 min at temperatures between 50° C. and 300° C.

[0011] As an alternative, the process may be carried out by performing the heat treatment in the presence of moisture for 0.1 sec to 60 min, at temperatures between 50° C. and 300° C.

[0012] The heat treatment is performed for a period of time from 0.1 sec to 2 min at temperatures between 100° C. and 250° C.

[0013] The additional heat treatment is preferably performed during treatment steps such as embossing, finishing or make-up of the material.

[0014] The additional heat treatment is preferably applied to a material containing microfibers or made entirely of microfibers.

[0015] The additional heat treatment is preferably applied to a material made of a nonwoven, in particular a material made of PA and/or a mixture of PA and PES fibers and/or microfibers.

[0016] In this way the colorfastness, in particular the lightfastness of the dyeings is greatly increased, as shown by the following examples. At the same time, in comparison with the known dyeing method, samples obtained in dyeing polyester fibers show only a comparatively minor loss of tensile strength.

[0017] Microfibers or microfilaments in the sense of this patent application are understood to be those having a titer of <1 dtex.

[0018] The present invention is explained below on the basis of five examples. The results of the evaluation of colorfastness are subsequently summarized.

EXAMPLE 1

[0019] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES is dyed in a one-step exhaust method using the vat dyestuff indicated in Table 1 (3% dyestuff used, based on the fiber weight). For this purpose, the vat dyestuff is dispersed together with 1 g/L of the dispersant Dekol® SN and 0.5 g/L of Trilon® TA, a chelating agent. The bath ratio is 1:20. It is first heated to 80° C., then pigmented for 20 minutes at this temperature. Vatting is performed with 20 mL/L NaOH (32 wt %) and 8 g/L hydrosulfite. After vatting, dyeing is continued for 30 minutes at 80° C., then it is cooled to 50° C. and rinsed. Oxidation is performed at a bath ratio of 1:20 using 5 mL/L hydrogen peroxide (30 wt %) for 15 minutes at 60° C. followed by saponification at 70° C. with 2 g/L soda and 1 g/L Kieralon® B. After drying, heat treatment is performed for 1 minute at 180° C. on the tenter frame.

EXAMPLE 2

[0020] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES is dyed in a one-step exhaust dyeing process using a mixture of the dispersed dyes and vat dyes listed in Table 2. Both the disperse dye and the vat dye are dispersed together with 1 g/L of the dispersant Dekol® SN and 0.5 g/L of the chelating agent Trilon® TA and then the pH is adjusted to 4.5 to 5 using acetic acid. The bath ratio is 1:20. Dyeing is performed at 130° C. for 45 minutes. Then the bath is cooled to 80° C. and vatting is performed using 12 mL/L NaOH (32 wt %) and 6 g/L hydrosulfite with the addition of 20 g/L of Glauber's salt. After vatting, dyeing is continued for 30 minutes at 80° C., then cooling to 50° C. and rinsing. Oxidation is performed at a bath ratio of 1:20 using 5 mL/L hydrogen peroxide (30 wt %) for 15 minutes at 60° C. followed by saponification at 40° C. with 2 g/L soda and 1 g/L Kieralon® B. After drying, heat treatment is performed for 1 minute at 150° C.

EXAMPLE 3

[0021] A printing paste containing 800 g/L of a stock paste of 600 g/L starch ether thickener, 50 g/L Glyezin® A, 100 g/L potash and 100 g/L Rongalit C+20 g/L of the vat dyestuff Indanthrene® Yellow T-5GF and 180 g/L water is applied with a doctor blade to a microfilament nonwoven of 35 wt % PA and 65 wt % PES, dried at 98° C., fixed for 10 minutes at 102° C. with saturated steam. The dyeing is then rinsed and oxidized for 15 minutes at 60° C. with 5 mL/L hydrogen peroxide (30 wt %) and saponified at 70° C. with 2 g/L soda and 1 g/L Kieralon® B. After drying, embossing is performed at 240° C. using a calender.

EXAMPLE 4

[0022] A microfilament nonwoven having a weight of 100 g/m2 containing 35 wt % PA and 65 wt % PES is pad dyed at room temperature using a vat containing 100 g/L of the vat dyestuff Indanthrene Direct Black RB, dried at 120° C. and then developed by a saturated steam treatment for 1 minute at 103° C. using 60 g/L NaOH (50 wt %) and 80 g/L hydrosulfite (bath uptake 100%). Oxidation is performed using 10 mL/L hydrogen peroxide (50 wt %) at a bath ratio of 1:20. At the same time 3 mL/L acetic acid (60 wt %) is used for neutralization. Then saponification is performed at 70° C. using 2 g/L soda and 1 g/L Kieralon® B. After drying, heat treatment is performed for 1 minute at 200° C.

EXAMPLE 5

[0023] A microfilament nonwoven made of 35 wt % PA and 65 wt % PES is dyed in a one-step exhaust dyeing method with 6.6% (based on the fiber weight) of the vat dyestuff C.I. Vat Black 27 at a bath ratio of 1:57.

[0024] First it is heated to 95° C., then pigmenting is performed at this temperature for 20 minutes.

[0025] Vatting is performed with 25 mL/L NaOH (32 wt %) and 9 g/L hydrosulfite.

[0026] After vatting, dyeing is continued for 45 minutes at 95° C., then cooling to 50° C. and rinsing and oxidizing and saponifying as described in Example 1.

[0027] After drying, heat treatment is performed for 1 minute at 180° C. in a tenter frame.

COMPARATIVE EXAMPLE

[0028] According to Example 3 of European Patent 0772709 B1, the microfilament nonwoven described in Example 5, containing 35 wt % PA and 65 wt % PES, was dyed with C.I. Vat Black 27. A sample of nonwoven (1.5 g) was treated for 45 minutes at 95° C. in an aqueous solution of C.I. Vat Black 27 (2 mL of a 5% aqueous solution), sodium hydroxide (10 mL of a 4M aqueous solution), Rongal HT (3 g) and water (60 mL). The treated sample was rinsed, oxidized by treating it with 75 mL of an aqueous solution of potassium dichromate (1.5 g) and acetic acid (15 g) for 30 minutes at 65° C., then rinsed and washed with 75 mL of an aqueous solution containing soap flakes (3.75 g) in boiling water for 10 minutes.

[0029] After the process described here without a heat aftertreatment, the lightfastness and tensile strength values listed in Table 5 are obtained.

[0030] The results obtained for the lightfastness are summarized in the following tables: 1 TABLE 1 Indanthrene ® Ruby R Indanthrene ® Orange GR With heat With heat treatment treatment No heat 1 min at No heat 1 min at treatment 180° C. after treatment 180° C. after Example 1 after dyeing dyeing after dyeing dyeing Lightfastness 5 6 5-6 7-8 EN ISO 105 B02

[0031] 2 TABLE 2 1% Dianix Red AM-B 3% Indanthrene ® Red FFB No heat With heat treatment after treatment 1 min at Example 2 dyeing 150° C. after dyeing Lightfastness 5 6 EN ISO 105 B02

[0032] 3 TABLE 3 Indanthrene ® Yellow T-5GF No heat With heat treatment treatment after (embossing) at Example 3 dyeing 240° C. after dyeing Lightfastness 6 6-7 EN ISO 105 B02

[0033] 4 TABLE 4 Indanthrene ® Direct Black RB No heat With heat treatment after treatment 1 min at Example 4 dyeing 200° C. after dyeing Lightfastness 4 5 EN ISO 105 B02

[0034] 5 TABLE 5 C.I. Vat Black 27 With heat treatment 1 min at 180° C. after Comparative Example 5 dyeing Example Lightfastness 5-6 5-6 EN ISO 105 B02 Maximum tensile 229.5 N 95.3 N strength EN20073, part 3

[0035] Lightfastness according to EN ISO 105b02: score 1=very bad, 8=very good

Claims

1. A method of improving the colorfastness of textile material manufactured from synthetics in which the textile material is exposed to a heat treatment when applying one or more vat dyestuffs alone or in combination with other dyestuffs/pigments,

wherein the material is exposed to at least one additional heat treatment following its dyeing.

2. The method as recited in claim 1,

wherein the heat treatment is performed in a dry atmosphere for a period of time from 0.1 second to 60 minutes at temperatures between 50° C. and 300° C.

3. The method as recited in claim 1,

wherein the heat treatment is performed in the presence of moisture for 0.1 second to 60 minutes at temperatures between 50° C. and 300° C.

4. The method as recited in one of claims 2 or 3,

wherein the heat treatment is performed for a period of time from 0.1 second to 2 minutes.

5. The method as recited in one of claims 2 or 3,

wherein the heat treatment is performed between 100° C. and 250° C.

6. The method as recited in one of claims 1 through 5,

wherein the additional heat treatment is performed in treatment steps such as embossing, finishing or make-up of the material.

7. The method as recited in one of claims 1 through 6,

wherein the additional heat treatment is applied to a material containing microfibers.

8. The method as recited in one of claims 1 through 6,

wherein the additional heat treatment is applied to a material made entirely of microfibers.

9. The method as recited in one of claims 7 through 8,

wherein the additional heat treatment is applied to a material made of a nonwoven.

10. The method as recited in one of claims 1 through 9,

wherein the additional heat treatment is applied to a material made of PA and/or a blend of PA and PES fibers and/or microfibers.