Abstract:
The present invention relates to methods for dyeing fibers which comprises adding to the fibers an effective amount for the purpose of a composition including an alkyl lactate and additional components. The present invention further relates to a dyeing composition, comprising (a) a cationic monomer, (b) an alkyl lactate and (c) a zeolite.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation of U.S. Ser. No. 11/168,095, filed Jun. 28, 2005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to compositions and methods for the improved dyeing of textiles and fabrics, resulting in enhancements in efficiency, as well as associated environmental advantages.  
       BACKGROUND OF THE INVENTION  
       [0003]     Cellulose dyeing requires large quantities of common salts, e.g. sodium or potassium salts of mineral acids such as sodium chloride or sodium sulfate, as an aid in dyeing the fiber. The amount of salt may range from 5 up to 125% on weight of goods (OWG). It has been determined that the sodium and the chloride and/or sulfate content of textile wastewater can be a primary source of pass-through aquatic toxicity in industrial and municipal discharge of treated wastewater. This is because there is no known commercially viable process to remove the dissolved salts from the treated water prior to returning the treated wastewater to the natural waterway. In North Carolina alone, approximately 40% of all wastewater is from textile mills. As a result the amount of salt water being continually discharged into the natural, fresh water receiving streams is increasing. Unfortunately, most fresh water organisms find salt toxic over certain concentrations.  
         [0004]     Cotton is one of the most significant fibers being processed today. It is appreciated that a system to dye cotton that offered significant environmental benefit would be desired. There are currently two types of dyes are utilized to dye cotton, namely direct and reactive dyes. Direct dyes are the most widely used. Reactive dyes are used where light and wash fastness are paramount. The current state of the art by which cellulosic fiber is dyed requires the use of high percentages of a reducing agent, typically salt to overcome the zeta potential of cellulosic fiber in water and alkaline solution. Direct dyes require a post dyeing fixing agent to provide minimum standards of wash fastness. Both reactive and direct dyes require an extensive post dye clean up to remove hydrolyzed and unfixed dyes.  
         [0005]     Research using a Dow Chemical Co. product, CR-2000 (CHTAC), a quaternary ammonium compound containing 3-chloro-2-hydroxypropyl-trimethylammonium chloride, 1, 3-Bis (trimethylammonium)-2-hydroxypropane dichloride and water has been conducted. CHTAC is a reagent chemical that when applied to cotton creates cationic dye sites within the fiber. These sites have a high affinity for anionic dyes such as direct or reactive.  
         [0006]     There remains a need for a low toxicity composition for use in dyeing of cotton and cotton blended fabrics which is efficacious in the dyeing of cellulose fiber, and non-toxic in the aquatic environment. It would be beneficial to use chemical treatments that are non-toxic, derived from renewable resources and that function in an effective process. In addition, improved treatments for use in the dyeing of nylon and wool fibers are needed. Such compositions and methods are further described below.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention relates to methods for dyeing fibers which comprises adding to the fibers an effective amount for the purpose of a composition including an alkyl lactate and additional components. The present invention further relates to a dyeing composition, comprising (a) a cationic monomer, (b) an alkyl lactate and (c) a zeolite.  
         [0008]     Additionally, the present invention relates to a method for dyeing various fibers, including cotton, as well as acrylic and polyester fibers, which comprises adding to the fibers an effective amount for the purpose of a composition comprising (a) a cationic monomer, (b) an alkyl lactate and (c) a zeolite.  
         [0009]     The treatments of the present invention significantly reduce process time, resulting in less energy and water consumption, as well as higher throughputs. Enhanced product performance is a result, e.g., brighter colors in fabric, yarn, and fibers, as well as greater wash fastness. In addition, the present invention is an environmentally friendly treatment due to, e.g., lower volumes of wastewater and little or no salt or dye in effluent as a result of such treatment.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     The present invention provides compositions that are appropriate for use across a range of dyestuffs on various fibers, including cotton, acrylic and polyester fibers.  
         [0011]     The present invention represents an enhancement in the exhaustion method of cationizing cotton, thereby making exhaustion dyeing possible. Noted advantages include reductions in processing time, water and energy use. Amounts of dye required to achieve a desired shade are reduced, thereby reducing discharge to wastewater treatment. No salts or dye fixes are required. Fibers treated by the compositions of the present invention possess superior wash fastness, and provide higher outputs of dyed cotton, e.g., a more than doubling of dyed cotton output is possible.  
         [0012]     In a preferred embodiment of the present invention, amounts of cationic monomer (e.g., CHTAC) and alkyl lactate (e.g., ethyl lactate) of from about 75-95 weight % cationic monomer and about 5-25 weight % alkyl lactate are effective in providing optimum exhaustion and fastness for both direct and fiber reactive dyes.  
         [0000]     Experimental  
         [0013]     In developing the compositions that are the subject of the present invention, polyamide (e.g., nylon) fiber testing initially revealed that in pure form, ethyl lactate did not provide adequate performance on metal complex dyes, particularly 2:1 chrome complex dyes. Many manufacturers prefer the use of metal complex dyes, because they provide superior wash and light fastness, as well as a desirable depth of shade on dark colors such as black and navy blue. Traditional dyeing systems utilize conventional dye levelers with extended durations at atmospheric boiling temperature. Exhaustion of the dyestuff under these traditional systems is incomplete, causing high levels of dye to be emitted to the effluent system. The unexhausted dye contains chromium; processors are often under guidelines to reduce chromium output. Secondly, wastewater treatment costs are significantly increased due to the high chemical oxygen demand/biological oxygen demand (COD/BOD) levels caused by the high level of unexhausted dye in the effluent.  
         [0014]     Preliminary testing indicated that metal complex dyes, particularly 2:1 complexes, possessed a high degree of insolubility at lower temperatures. It was found that ethyl lactate, formulated with lactic acid, provided solubility of the dyes at low temperatures. Additionally, the inclusion of an amount of methyl bis (canola amidoethyl)-2-hydroxyethyl ammonium methyl sulfate provided enhanced performance as a buffering and wetting agent.  
         [0015]     In further testing on polyamide fibers, it was found that by using between 1 and 5 grams per liter of ethyl lactate in the dyeing process, dye solubility was achieved early in the process (at lower temperatures), and consequently, traditional amounts of dye could be significantly reduced. It was also found that on average, the traditional metal complex dye formula could be cut by about 20 to 55% with the ethyl lactate treatment, and shade could be achieved. Furthermore, by reducing the amount of dye in the dye bath, the treatment achieved nearly total exhaustion, thereby virtually eliminating chrome and dye discharge to the effluent stream.  
         [0016]     Additional testing was conducted on nylon as well as wool fiber using standard nylanthrene dyes. It was found that process time could be significantly reduced using a mixture of an ethyl lactate formulation noted above. Additionally, by varying the percentage of wetting agent, blended nylon and wool could be dyed with optimum union between nylon and wool. Traditionally, significant buffering would be required to prevent all the dye from going to the nylon, which has a higher affinity for the dye.  
         [0017]     Further testing was conducted with machinery used throughout the textile industry. The machines in which the ethyl lactate was tested were beam, Beck, jet, paddle tub, rotary skein, and package. Results were superior in each type of machine. Note that procedural differences exist between the different types of machines.  
         [0018]     Note that the above-described enhancements to prior treatment methods were limited to the dyeing of nylon or wool fibers. Thus, there still remained the need to develop improved compositions and treatments for the dyeing of cotton and other fibers. Such developments are described below.  
         [0019]     Noting that ethyl lactate provided a mechanism for hydrolyzing to lactic acid in aqueous solution and heat, the solvent was blended with CHTAC at a 1:3 ratio, and laboratory experiments were conducted where varying grams per liter were applied to cellulosic fiber using 2 g/l of NaOH. The same grams per liter of pure CHTAC to identical cotton using 2 g/l NaOH were used as a control. The sequence was as follows: Drop water; Add cellulosic fiber; Drop CHTAC; Drop NaOH; Circulate 10 minutes; Ramp temperature of bath to atmospheric boil at 2-3° F. per minute; Hold at boil for 30 minutes. This sequence was followed by the dyeing sequence as follows: Drop out CHTAC/ethyl lactate solution, Refill with fresh water; Drop direct dye black; Circulate 5 minutes; Ramp temperature to boil; Hold 30 minutes; Drop dye bath; Refill; Fill with rinse water; Rinse 5 minute; Drop and extract. The results demonstrated that the mixture of CHTAC and ethyl lactate provided better exhaustion of the dyestuff than CHTAC as a “stand alone.” However, fixation to the fiber was inadequate, hence, the need for the compositions and treatments of the present invention.  
         [0020]     Zeolites are crystalline oxides of aluminum and silicon. Synthetic zeolites offer a uniform pore system, resulting in an open structure with a high surface area. This open structure gives zeolites unusual reactive properties and molecular filtering abilities.  
         [0021]     Valfor® 100 Zeolite A by PQ Corporation, with a median particle size (3-5 μm) and nominal pore size (4.2 Å) was tested. Since the zeolite donates alkalinity and possesses a small particle size, it was anticipated to be a superior alternative to NaOH. In addition, the alkaline crystalline structure in conjunction with anionic dyestuffs was anticipated to be attracted to the cationic dye sites in the CHTAC processed cotton.  
         [0022]     The following composition was tested: Zeolite in the form of Valfor 100; CHTAC; ethyl lactate from American Natural Bio-Solvents LLC (ANBS); and methyl bis (canola amidoethyl)-2-hydroxethyl ammonium methyl sulfate (optional). CHTAC was blended with ethyl lactate at a percentage of 75:23 CHTAC: ethyl lactate. Methyl bis (canola amidoethyl)-2-hydroxyethyl ammonium methyl sulfate (hereinafter, canola amidoethyl) was then added at 2% and blended. Valfor 100 was kept in pure powder form.  
         [0023]     The following experiments were conducted and repeated three times: Add water to test container; Drop 1-5 g/l zeolite Valfor 100 and blend; Drop 3-7 g/l blended mixture of CHTAC, ethyl lactate, and canola amidoethyl; Ramp temperature to boil at 6° F. per minute; Hold 15 minutes; Drop; Add water; Drop direct dyes or reactive dyes; Circulate 5 minutes; Ramp to boil at 3° F. per minute; Hold at boil 15-30 minutes; Drop; Refill; Add ANBS WrinkleGuard™-100 at 1.5 g/l; Ramp temperature to 140° F.; Hold 5 minutes; Drop; Rinse. Both direct and reactive dyes responded with nearly 100% exhaustion, and no salt was required to achieve dyeing. Both dyes also passed crocking and wash fastness testing. Thus, a significant improvement in the dyeing of cotton is achieved, by eliminating salt and fixes, reducing the use of water and energy, and shortening the cycle times to dye. Also the amount of CHTAC required is significantly reduced.  
         [0024]     The advantages achieved by the treatment of the present invention (exemplified by Composition A, below), e.g., lower effluent discharge and effluent volume are further shown in Table I, below. Note that in Table I, the liquor ratio is recognized as the amount of water (in liters) versus the amount of goods, while the effluent volume is the amount of water used per kilogram of cotton to accomplish dyeing.  
                                           TABLE I                           Effluent Comparison in the Dyeing of Cotton                Composition A   Control (including salt)                        Liquor Ratio   10:1   10:1       Chemical Discharge   15 g/kg   263 g/kg       Effluent Volume   10 L/kg    40 L/kg                  
 
         [0025]     Thus, the above results indicate that in accordance with the composition and method of the present invention, the dyeing of cotton will generate significantly less chemical to the waste stream. For instance, for every 1 kg of cotton dye under current technology, 263 grams of chemicals were discharged to waste water. In contrast, in the composition and method of the present invention, only 15 g were discharged. Conventional treatment approaches require multiple rinses; therefore, approximately 40 L per kg of cotton is required. However, for the composition and method of the present invention only 10 L is needed.  
         [0026]     These descriptions and examples are intended to be illustrative and are not to be taken as limiting. Still other variations within the spirit and scope of this invention are possible and will readily present themselves to those skilled in the art.