Low-VOC Ionic Solvents as Dye Carriers for Aramid Fibers

Abstract

Compositions and methods for dyeing aramid are one or more dye carriers selected from dialkylimidazolium salts having a cation of the following general formula: JPEG2025523891000012.jpg10128 wherein R1 and R2 are independently selected from C1-C8 alkyl and bisquaternary amine salts having a cation of the following formula: JPEG2025523891000013.jpg19128 wherein R1 is independently C1-C6 alkyl in each case, R2 and R3 are independently C1-C6 alkyl or substituted C1-C6 alkyl in each case, and X is independently halogen in each case, and one or more cationic dyes.

Description

Technical Field

[0001] Embodiments relate to non-volatile dye carriers for dyeing and processing aromatic polyamides, and methods for dyeing aramid fibers and fabrics.

[0002] (Introduction) Fibrous forms of aromatic polyamides (aramids) produce textile materials and articles that are durable, highly resistant to chemicals, and stable at high temperatures (fire-resistant). Compared to typical textiles, aramids are hydrophobic, making them difficult to dye because standard aqueous dye formulations cannot penetrate the material. In typical aramid fiber dyeing operations, aramid fabrics and fibers are treated in a pressured dyeing apparatus using an aqueous dye solution containing a dye carrier that swells the constituent fibers. The dye carrier facilitates the penetration of the dye throughout the aramid fiber and improves color and color retention. Solvents such as acetophenone were once ubiquitous as dye carriers in industrial processes, but concerns regarding high vapor pressure and odor and toxicity have led to interest in alternatives with reduced volatile organic compound (VOC) emissions.

Summary of the Invention

[0003] A composition for dyeing aramid is one or more dye carriers selected from dialkylimidazolium salts having cations of the following general formula:

[0004]

Chem.

[0005]

Chem.

Embodiments for Carrying Out the Invention

[0006] Embodiments relate to a dyeing composition containing a dye carrier composition, and a method for dyeing aramid fibers and articles, particularly meta - aramid. The dye carrier composition disclosed herein is non - volatile, has a low or negligible vapor pressure at room temperature, and accordingly has a negligible VOC emission, and may contain one or more ionic liquids and / or bis - quaternary ammonium salts. The method for dyeing aramid fibers and articles may include contacting the fiber or article with a dye formulation containing one or more dye carriers.

[0007] As used herein, "aramid" means an aromatic polyamide having at least 85% amide bonds formed between aromatic rings, particularly aromatic polyamides such as poly - meta - phenylene isophthalamide and poly - para - phenylene terephthalamide. Examples of aramids may include commercially available materials formed by the reaction of meta - phenylenediamine and isophthaloyl chloride, such as NOMEX (trademark) and CONEX (trademark) manufactured by DuPont and Teijin, respectively.

[0008] Examples of the dye complex may include one or more of a cationic dye, a solvent, a dye carrier, and various additives. Examples of the cationic dye include any dye suitable for application to aramid, including phenoxazinium dyes such as phenoxazine-5-ium, 3,7-bis(diethylamino)-chloride, azo dyes, triarylmethane dyes, anthraquinone dyes, azamethine dyes, triazole azo dyes, thiazole azo dyes, benzothiazole azo dyes, triphenylmethane dyes, and the like. Examples of the solvent used in the dye complex include an aqueous fluid, a salt or brine solution, a buffer solution, an alcohol-water mixture, and the like. The dye complex may contain one or more cationic dyes at any suitable concentration, for example, in the range of 1 wt% to 10 wt%, 2 wt% to 10 wt%, or 2 wt% to 8 wt% by weight percent (wt%).

[0009] The dye complex disclosed herein may contain one or more dye carriers such as a dialkylimidazolium salt or a bisquaternary ammonium salt. Examples of the dialkylimidazolium salt include salts having a cation of the following general formula:

[0010] [Chemical formula] In the formula, R1 and R2 are each independently selected from C1-C8 alkyl. Examples of the imidazolium salts disclosed in this specification include 1,3-dialkylimidazolium salts having a dialkylimidazolium cation, such as 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1-octyl-3-methylimidazolium salt, 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, and the like. The anion moiety of the imidazolium salt can be a halide, such as chloride, bromide, iodide, etc., or a C1-C6 carboxylate, such as formate, acetate, propionate, etc. Examples of the dialkylimidazolium salt include 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium propionate, 1-methyl-3-methylimidazolium formate, 1-propyl-3-methylimidazolium formate, and 1-allyl-3-methylimidazolium chloride.

[0011] Examples of the dye carrier include bisquaternary ammonium salts having a cation of the following formula:

[0012] [Chemical formula] In the formula, R1 is independently C1-C6 alkyl in each case, R2 and R3 are independently C1-C6 alkyl or substituted C1-C6 alkyl in each case, and X is independently a halogen such as Cl, Br, or I in each case. Suitable bisquaternary salts include, for example, N,N''-(oxybis(ethane-2,1-diyl))-bis(3-chloro-2-hydroxy-N,N-dimethylpropan-1-aminium) chloride.

[0013] The dye complex may contain one or more dye carriers in a weight percentage (wt%) in the range of 1 wt% to 10 wt%, 2 wt% to 8 wt%, or 2 wt% to 6 wt%. The one or more dye carriers may also be combined with 1-phenoxy-2-propanol (PPh) in a weight percentage (wt%) in the range of 1 wt% to 10 wt%, 2 wt% to 8 wt%, or 2 wt% to 5 wt%, or in a weight ratio of 2:1 to 1:2, or 1.5:1 to 1:1.5. The dye complex may have a pH in the range of pH 5 to pH 13, pH 6 to pH 12.5, or pH 6.5 to pH 12. If the dye complex contains PPh, the pH may be lower, for example, in the range of pH 2.5 to pH 5, pH 2.5 to pH 4, or pH 3 to pH 4. In one example, the dye complex may contain 3 wt% to 6 wt% of one or more dye carriers, 0 wt% to 6 wt% of PPh, and a pH in the range of 2.5 to 12.5.

[0014] The dye complex may contain one or more additives, such as organic acids, mineral acids, pH-adjusting materials including inorganic salts (such as sodium nitrate or sodium chloride), surfactants such as emulsifiers and anionic surfactants, UV light absorbers, buffers, pH adjusters such as acids or bases, and processing aids.

[0015] A method of applying a dye to an aramid fiber may include preparing a dye solution using a dye carrier, quantifying and adjusting the pH, contacting an aramid fiber sample with the dye solution, dyeing the aramid fiber at a selected temperature, rinsing excess dye from the dyed aramid fiber, and drying the fiber sample.

[0016] During the application of the dye complex (e.g., when in contact with aramid fibers or an article), the temperature of the mixture may be in the range of 120 °C to 170 °C, 130 °C to 160 °C, or 130 °C to 150 °C. The contact can occur in any suitable dyeing apparatus including a pressurized or non-pressurized vessel. Optionally, the aramid fibers and the article may be wound through an internal rotating assembly and circulated through the dye complex during the dyeing operation. The dyeing time can vary depending on many factors such as the size of the sample, temperature, dye or dye carrier concentration, etc., but generally can vary from 30 minutes to 1 hour or more. The color values can be quantified using a Hunterlab™ colorimeter and include L, A, and B color values.

Examples

[0017] The following examples are presented to illustrate embodiments of the invention and are not intended to limit its scope. Table 1 provides the materials used in the following examples.

[0018]

Table 1

[0019] Example 1: Dyeing Process of Aramid Fabric In this example, various dye complexes were used to evaluate aramid fabric samples. A 2 wt% solution of Basic Blue #3 was prepared by dissolving 2 g of the dye in 98 g of deionized water.

[0020] Dyeing Apparatus and Loading Procedure Dyeing was performed in a Datacolor Ahiba™ IR Pro Exhaust Dyeing chamber. The chamber could accommodate up to 15 stainless steel, 250 mL capacity dyeing vessels within a rotating assembly and operate at a maximum of 130 °C.

[0021] Samples were prepared using 2-inch × 2-inch Nomex® switches and placed into numbered dyeing containers. 2.5 g of an aqueous blue dye solution was placed into the containers, followed by the various individual components of the desired weight of the test dye bath (e.g., dye carrier and water), and adjusted to 50.0 g with water. The pH of each bath was adjusted with acid or base as needed. The dyeing containers were then sealed and placed into the numbered holders of the rotary assembly. The Ahiba™ IR chamber was then heated at the desired temperature for 50 minutes. After the dye formulation treatment, the samples were cooled and washed with water to remove excess dye. The rinsed switches were dried in an oven at 45 °C.

[0022] The L and b color values of the switches were then measured with a Hunterlab® colorimeter. The colorimeter was calibrated with a D65-10 Diffuse 8° white tile provided by the manufacturer. As a control sample, an undyed NOMEX® switch was placed at the center of a 4.25 × 4.25-inch black ceramic tile equipped with a mask designed to assist in positioning and holding the switch on the tile. Readings were taken several times and the results averaged. An undyed switch was exchanged with one of the dyed switches to enable color readings. This procedure was repeated for all switches. The sample formulations and color results are shown in Table 2.

[0023]

Table 2

[0024] Samples in the chart are indicated as "Nomex" for control samples not exposed to the dye solution, "B" for blank samples containing a solution of dye and water without a dye carrier, "CS" for comparative samples containing only PPh, or "IS" for samples of the present invention containing a dialkylimidazolium or bisquaternary amine dye carrier alone or in combination with PPh. The target performance values for the samples are the minimum values of L or b relative to the Nomex and blank samples.

[0025] Samples were evaluated at pH values ranging from low pH (3.5, typical pH for dyes for PPh) to high pH (about 6.7 - 12.5), and at low dyeing temperatures (70 °C) and high dyeing temperatures (130 °C). The samples of the present invention typically functioned equivalently or better than comparative formulations containing only PPh. Example 1 shows that the dye formulations (IS) of the present invention were generally found to have superior performance to PPh at higher pH (6 - 12). Notably, when 2 wt% of PPh was combined with 2 wt% of bis-quaternary ammonium salt (IS8), an L value of 39.7 and a b value of -16.7 were obtained, which was superior to CS4 containing 4 wt% of PPh. In contrast, L values of 43.4 - 46.2 were achieved by adding 3, 4, or 6 wt% of dialkylimidazolium salt to the dye bath in the pH range of 6.2 - 6.5 (IS10 - IS12). Additionally, an L value of 46.6 was obtained using 4% dialkylimidazolium salt at pH 12.5 (IS13, b value of -14.1). When 4 wt% of bis-quaternary ammonium salt was added to the dye bath with a pH value of 9.6 (IS14) or 6.7 (IS15), an L value of about 55 was obtained, but when increased to 6 wt%, an L value of 29.3 and a b value of about -19.7 were obtained (IS16).

[0026] The foregoing is directed to exemplary embodiments, but other further embodiments may be devised without departing from the basic scope thereof, which is determined by the following claims.

Claims

1. A composition for dyeing aramid, comprising: One or more dye carriers selected from dialkylimidazolium salts having cations of the following general formula: And one or more cationic dyes. 【Chemical 1】 wherein R １ and R ２ are each independently selected from C1-C8 alkyl and bisquaternary amine salts having a cation of the following formula: [Chemical 2] In the formula, R １ is, independently in each case, C1-C6 alkyl, R ２ and R ３ are, independently in each case, C1-C6 alkyl or substituted C1-C6 alkyl, and X is, independently in each case, halogen, one or more dye carriers, A composition for dyeing aramid.

2. The composition according to claim 1, wherein the one or more dye carriers are present in a weight percentage in the range of 3% to 6% by weight.

3. The composition according to claim 1, wherein the composition has a pH in the range of pH 6 to pH 12.

5.

4. The composition according to claim 1, further comprising 1-phenoxy-2-propanol in a weight percentage in the range of 2% to 6% by weight.

5. The composition according to claim 4, wherein the pH is in the range of pH 2.5 to pH 4.

6. The composition according to claim 1, wherein the one or more dye carriers contain a bis-quaternary amine salt in a weight percentage (% by weight) of the composition in the range of 2% to 6%, and the composition has a pH of 6 to 7.

7. A method comprising: Contacting aramid with a dye formulation at a temperature in the range of 120°C to 160°C, the dye formulation comprising: One or more dye carriers selected from dialkylimidazolium salts having cations of the following general formula: 【Chemical 3】 wherein R １ and R ２ are each independently selected from C1-C8 alkyl and a bisquaternary amine salt having a cation of the following formula: [Chemical Formula 4] In the formula, R １ is, independently in each case, C1-C6 alkyl, R ２ and R ３ are, independently in each case, C1-C6 alkyl or substituted C1-C6 alkyl, and X is, independently in each case, halogen, one or more dye carriers, And one or more cationic dyes.

8. The method according to claim 7, wherein the temperature is in the range of 130°C to 140°C.

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