Process for providing dyed nylon fibers with resistance to staining and fading
Dyed nylon fibers are provided with resistance to (a) staining from neutral colorants and anionic colorants and (b) fading from chemical agents.
This application is a continuation-in-part of, and claims the benefit of, U.S. patent application Ser. No. 10/128,733, filed Apr. 23, 2002, which is a continuation of, and claims the benefit of, U.S. Provisional Patent Application Ser. No. 60/286,246, filed Apr. 26, 2001.
TECHNICAL FIELDThis invention relates to a process for providing nylon fibers with resistance to staining from neutral colorants and anionic colorants. This invention also relates to a process for providing dyed nylon fibers with resistance to fading from chemical agents.
By the term “colorants”, we mean materials such as iodine which may be found in betadine solutions and turmeric which may be found in mustard products.
By the term “chemical agents”, we mean materials such as sodium hypochlorite which may be found in bleach products and benzoyl peroxide which may be found in acne care products.
BACKGROUND OF THE INVENTIONIn 1985, the carpet industry began using anionic (negatively charged) polymers on acid dyeable nylon fibers to impart stain resistance (stainblocking) to carpets and rugs to protect these items from colorant type stains. Colorant stains are caused by dyes in food and drink products that come into contact with nylon fibers. Colorants have the ability to permanently dye the nylon fibers with the severity of the stain being dependent on the type and polymer structure of the fibers. Because acid dyeable nylon fibers are cationic (positively charged), these fibers tend to stain easily when in contact with anionic (negatively charged) colorants such as those in Kool-Aid, brand beverages, wine and coffee. Cationic dyeable nylon fibers, however, are anionic (negatively charged) fibers and have natural resistance to anionic colorant stains. Although cationic dyeable and stainblocked acid dyeable nylon fibers have negative charges, these fibers contain similar polymer structures (i.e., morphologies).
As a result of the natural stain resistance of cationic dyeable nylon fibers, there has been an increase in their use over the years, particularly in commercial carpets used for schools, offices, healthcare facilities and in the food service industry. The method for coloration of the cationic dyeable nylon fibers has mostly involved the use of solution dyed nylon fibers, which are dyed nylon fibers where the color (shade) is introduced as a pigment in the manufacturing process of the fibers. The advantage is that the dye pigments in the solution dyed fibers are resistant to fading from chemical agents; whereas, dyestuffs in acid dyed nylon fibers will fade.
A carpet mill dye process to impart coloration to cationic dyeable nylon fibers is disclosed in U.S. Pat. No. 5,058,667. Although the dyes are not resistant to chemical agents by this method, color combinations beyond that of solution dyed nylon can be achieved. Regardless of the method of coloration, carpet products from both methods are stain resistant to anionic colorant type stain.
Similar stain resistance (stainblocking) properties can be achieved using acid dyeable nylon fibers treated with sulfonated aromatic aldehyde condensation polymers (also referred to as SAC polymers or simply SAC) and methacrylate type anionic polymers to impart an anionic charge on the fibers similar to that of the cationic dyeable nylon type fibers. These polymers are disclosed in patents such as U.S. Pat. Nos. 4,822,373; 4,875,901 and 4,937,123. But whether the nylon fibers are naturally or chemically stain resistant, these fibers are not protected against stains from iodine and turmeric (mustard); nor are the dyes on dyed nylon fibers protected against fading from reactive chemical agents contained, for example, in bleach and acne care products.
When nylon fibers have a negative charge, either naturally or from stainblocker treatments, there is a charge/charge repulsion between the colorant and the fiber surface. Therefore, an ionic charge repulsion mechanism prevents negatively charged colorants from diffusing to available free amine end groups (dye sites) that are contained in the nylon fibers. As a consequence, a colorant containing product that is spilled on a carpet can be removed by rinsing or extracting with water without leaving a stain.
The mechanism by which dyestuffs on dyed nylon are faded by reactive chemical agents is somewhat more complex. Chemicals such as sodium hypochlorite and benzoyl peroxide, form highly reactive chemical species such as chlorine and benzoyl radicals. These species react with surrounding organic molecules, especially organic molecules that contain highly unsaturated chemical bonds. Dyestuffs are organic molecules that contain highly conjugated unsaturated molecular arrays. The structure of these arrays is observed as color. The reaction of dyes on nylon fibers with the reactive species in chemical agents destroys the chemical bonds which give color to dyes. This decolorizing effect can visually appear as a shade loss, a bleaching effect or sometimes as a different looking stain. Reactive chemical agents permanently damage dyes on carpet in those areas where the agents are located.
Although cationic dyeable nylon fibers and stainblocked acid dyeable nylon fibers prevent staining from most colorant stains, these fibers do not prevent stains from iodine or turmeric. The reason is that colorants contained in betadine and mustard are neutrally charged and are unaffected by a charge/charge repulsion mechanism. As a consequence, these colorants readily diffuse into the nylon polymer structure causing a stain. There are, however, stain removal methods such as disclosed in U.S. Pat. No. 6,300,299 for mustard and betadine.
Ironically, recommended methods and cleaning agents for removing iodine and mustard stains can themselves damage dyes on acid dyed nylon fibers, thereby causing dye fading. Colorant pigments in solution dyed fibers are not effected by cleaning chemical products or benzoyl peroxide in acne care products. Many multicolored commercial carpet styles contain both acid dyed nylon fibers and solution dyed nylon fibers for color effects and styling, which tends to compound the problem when deciding which cleaning method and cleaner to use.
Although stainblocked acid dyeable nylon fibers and cationic dyeable nylon fibers are stain resistant to food grade acid dyes, which are anionic colorants contained in food and drink products, these fibers are not stain resistant to all anionic colorants contained in consumer products. For example, colorants contained in certain fabric dyes will severely stain carpet products regardless of whether these fibers were conventionally stainblocked in the carpet mill or cationic dyeable nylon produced at the fiber producer. Fabric dyes sold in stores for consumer use are generally composed of anionic colorants used to dye cotton. These would be anionic colorants that are part of the same group of dyes as acid colorants.
The reason that certain anionic colorants have a tendency to stain anionic nylon fibers may lie in the degree of the ionic charge density of the colorant, or the reason may lie in the chemical structure of the colorant or the reason may lie in a combination of both. Regardless of why staining occurs between nylon fibers and certain colorants of like ionic charges, there exists a need to impart stain resistance to these types of colorants.
Because of mobility, nylon fabrics in garments are generally exposed to a greater number of staining materials and/or chemical agents than would be expected for carpets. In addition, many stains are more visually apparent on a flat fabric such as a woven or knit garment than would be apparent on a piled fabric such as a carpet. The reason for this is partly due to the differences in light reflective properties between piled goods and flat goods, and partly due to colors and styles. Carpets, especially commercial carpets, contain dark shades and/or multicolors which hide lighter stains, soils and oils. Garments generally are light to medium colors in solid shades or solid shaded panels. Light stains are often visible on fabrics. Chemical agent exposure between carpets and garments is also different. With carpets, exposure to chemical agents, for example bleach, is unintended and usually is caused by a spill or misuse of a household cleaning product. Garments, however, are exposed to low levels of chemicals such as chlorines or bromines used in water, pools, hot tubes, etc., as well as chemical additives (bleach, per-borate, etc.) in home laundering.
To fully appreciate the staining mechanism of nylon fibers, the chemical properties of colorants, especially those contained in nature, must be understood. Unlike synthetic colorants, which may be food grade acid dyes added to food and drink products, natural colorants are very diverse and can impart stains appearing as a colorant stain, an oil stain or combinations of both types of stains.
In general, colorants occurring in nature are neutrally charged organic molecules (neutral colorants). As a consequence they have the ability to migrate into the nylon fiber structure and cause staining regardless of whether the fiber is acid dyeable nylon or cationic dyeable nylon. Unlike acid colorants, they do not need to attach to amine end groups (dye sites) to impart a stain. A notorious natural colorant pigment is curcumin which is a part of the curcuminoid family. Curcumin is the yellow pigment contained in turmeric and accounts for the bright yellow stains caused by mustard products, as well as the yellow color of curry. As shown in earlier experiments, this pigment imparts a heavy stain to nylon carpets and has been used in hair dying. Curcumin is a fat soluble (lipid soluble) colorant pigment, but the intense yellow color stain obscures any oily appearance that may be present.
The carotenoid pigments, for which there are over 700 naturally occurring, are widely distributed in nature and account for the red, yellow and orange colors in fruits, vegetables, leaves, grasses, etc. For example, beta-carotene is one of the orange pigments found in most green leaves and in carrots. Beta-carotene is used to provide color to margarine and other foods. When leaves lose their chlorophyll in the Fall season, carotene and xanthophyll account for the colors left in the leaf. Saffron is another carotenoid used to color rice and other foods. Lycopene is the red pigment that gives ripe tomatoes their color as well all tomato based red sauces.
The carotenoids are fat soluble pigments. Due to their lower color yield, they can impart stains that appear as colorant stains, oily stains or both. Interestingly, grass stains that remain on nylon fabrics after washing are primarily due to the carotenoid pigments in the grass, not the highly colored green chlorophyll pigments.
The natural colorant that enjoys the most attention is the anthocyanins. These colorants are widely distributed in plants and are responsible for the pink, red and purple seen in many fruits and vegetables such as grapes, cranberries, blueberries, red cabbage, etc. Unlike the curcuminoids and carotenoids which are fat soluble, the anthocyanins are water soluble natural dyes that account for the colors observed in red wines, grape juice, grape color extract and other food products.
Accordingly, a need has remained for a process for providing dyed nylon fibers with resistance to staining from neutral colorants and anionic colorants and with resistance to fading from chemical agents.
DETAILED DESCRIPTION OF THE INVENTIONIn the present invention, acid dyeable and cationic dyeable nylon fibers colored by either acid dyed (mill) processes, solution dyed (fiber) processes, or combinations thereof, are treated with a high level of a sulfonated aromatic aldehyde condensation polymer and then fixed by a wet heat method. By high level is meant at least 2% wt/wt (dry weight SAC/dry weight nylon fibers). So treated, the nylon fibers in dyed nylon are protected from staining by neutrally charged colorants, and the dyes in the dyed nylon are protected from fading by chemical agents.
We have also discovered that when nylon fibers are treated as described in the preceding paragraph, carpet products made from these fibers are stain resistant to acid colorants and anionic colorants such as those used in fabric dyes sold to individual consumers or those used to dye cotton fabrics in textile manufacturing, and these fibers are resistant to fading from chemical agents.
The reason for this phenomenon is not clear. We know that high levels of methacrylate type stainblockers are totally ineffective in blocking neutrally charged colorants, anionic colorants and chemical agents. The application of high levels of SAC polymers is also ineffective if fixed by a dry heat method. Apparently, the new two step process of the present invention closes the crystalline structure of the nylon fibers, a phenomenon previously observed in U.S. Pat. No. 5,350,426 which utilized a dry heat set method. In any event, the process of the present invention renders the dyed nylon fibers resistant to staining and fading. Examples of effective SAC anionic polymers are described in Textile Chemist & Colorist, November 1989, Vol. 21, No. 11.
There are two well known fixation methods used to achieve stain resistance from colorant type stains in the industry. These are the dry heat method and the wet heat method. In the dry heat method, a SAC polymer is applied using either spray or foam onto a carpet. The treated carpet is then heated and dried in a dryer range or oven. The heat fixes the SAC polymer to the nylon fibers.
The wet heat method is done in either of two ways. The first way, referred to as the wet heat steam method, involves applying the SAC polymer as an aqueous mix to either carpet, carpet yarns or nylon sock and then steaming the goods for several minutes to fix the SAC polymer to the fibers. The second way, referred to as the wet heat batch method, involves applying the SAC polymer to a treatment bath and then submerging the carpet, carpet yarns or carpet fibers into the bath. The bath is heated to elevated temperatures and held for several minutes to fix the SAC polymer to the nylon fibers.
Both the dry and wet heat application methods are predominately done in the carpet industry for stainblocking on acid dyeable nylon fibers. As cationic dyeable nylon fibers are naturally stain resistant, this treatment is not required. Since colorants contained in betadine, mustard, red sauces, grass stains, fabric dyes, etc., stain by different mechanisms both types of nylon fibers must be treated to provide resistance to staining and fading. In addition, they must be treated by a wet heat fixation as the dry heat process is not effective. Conventional methods of stainblocking with SAC polymers and methacrylates are sufficient for preventing colorant type stains from acid colorants such as Kool-Aid brand beverages, etc., but they do little to prevent staining from neutrally charged and anionically charged colorants or to prevent fading from chemical agents.
The present invention is further illustrated by the following examples which are illustrative of certain embodiments designed to teach those of ordinary skill in the art how to practice this invention and to represent the best mode contemplated for practicing this invention.
EXAMPLE 1Carpet samples: Four nylon sample sets were treated. Sample set 1 was an acid dyed cationic dyeable T-66 nylon sock. Sample set 2 was a solution dyed cationic dyeable T-66 nylon carpet. Sample set 3 was an acid dyeable T-6 nylon carpet. Sample set 4 was a blend of acid dyed T-66 and solution dyed T-6 acid dyeable nylon carpet. The SAC used was the numerically available product Simcofix N-201A, which is a 30% solids product sold by SIMCO Products Inc. of P.O. Box 17903, Greenville, S.C. This SAC is also referred to as a sulfonated novolac type anionic polymer. The SAC chemistry is used for both stainblocking and colorfastness.
The method for testing iodine stain resistance was a modified version of the American Association of Textile Chemists and Colorists (AATCC) Test Method 175. The only difference was that betadine solution, which contains about 1% iodine, was used to replace the red dye 40 test solution. Approximately 20 ml was used.
Both the dry heat and wet heat methods were used to fix the SAC to the nylon fibers. In the dry heat method, samples were treated with an aqueous solution of N-201A (pH=4.5) using a sprayer at a level of 100% wet add-on. The samples were then dried in a small drying oven to fix the SAC. In the wet heat method one sample group from the sets was treated with N-201A (pH=4.5) at a 200% wet add-on level by padding on the finish. These samples were then steamed in a small steamer for five minutes to fix the SAC. Another sample Group from the sets was submerged in a water bath that contained the N-201A (pH 4.5) product. The bath was heated to 180° F. and held for 20 minutes to fix the SAC.
Although all treatment solutions were adjusted to a pH of 4.5, the pH range that could be used in this experiment is between 1-7. The optimum treatment level based on the weight of the fiber (% OWF) can vary depending on the fiber type. The optimum range is from 8-16% OWF of N-201A (30%) for most nylon fibers. This amounts to about 2-4% wt/wt (weight dry SAC/weight dry nylon fibers. The results are shown in TABLE 1.
In AATCC Test Method 175, 1 is severe staining and 10 is no staining. 7 or above is acceptable. All test samples were treated at 12% OWF with N-201A.
This test was to determine if methacrylate type stainblockers could also impart iodine resistance to nylon fibers. Sample sets 1 and 2 above were used for testing. Methacrylate stainblockers, 668F from the 3M Company and Eronial NYB from Ciba Specialty Chemical Co. and Simcofix N-201A (pH=4.5) from Simco Products were tested as the SAC product. All test samples were treated at a level of 12% OWF and fixed by the wet heat batch method. The results are shown in TABLE 2 where the numbers indicate the same as in TABLE 1.
Fourteen carpet samples from eight manufacturers were obtained to test for betadine resistance using the wet heat batch method to fix the SAC. All test samples were treated at 15% OWF using Simcofix-201A (pH 4.5) as the SAC. In addition, two of the acid dyed samples were tested for bleach resistance. The following describes nylon type and manufacturer.
The results for betadine resistance are shown in TABLE 3 and bleach resistance in TABLE 4.
The test method was the same as AATCC Test Method 175 except household bleach at 100% strength was used instead of red dye 40 solution. The bleach resistance of the dyes to fading were rated poor, fair, good or excellent.
EXAMPLE 4 Samples from a, b and c from TABLE 3 were tested for betadine resistance using the following SAC polymers: N-201 A from Simco Products, TN-16 from Nicca USA, Erional NW from Ciba Nylan Fixan P from Clariant, and Mesitol NBS from Mobay. All samples were treated at 15% OWF and fixed by wet heat batch method. All samples were adjusted to pH 4.5. The results are shown in TABLE 5.
Four sample sets of a multi-colored carpet were studied for stain resistance to iodine found in betadine, turmeric found in mustard, chlorine found in household bleach solutions and benzoyl peroxide found in acne treatment products. The multicolored carpet contained both solution dyed cationic dyeable nylon fibers and acid dyed acid dyeable nylon fibers. Both types of fiber were type 66 nylon from DuPont.
The test samples in the sets were treated by a wet heat batch method at 9, 12 and 15% OWF with N-201A (pH=4.5). The treatment chemicals were placed on the carpet. About 20 ml of betadine and household bleach were added into a 2 inch diameter ring. About 20 grams of mustard and a maximum strength acne wash (OXY-10, 10% benzoyl peroxide) were placed on the carpet samples and massaged into the carpet pile. All treated samples were left for 24 hours, then rinsed with water, dried and evaluated for results. All test products were used without dilution.
Two methods were used to obtain the results. Since betadine and mustard impart color to carpet, they were rated by the AATCC Test method 175. Since household bleach and benzoyl peroxide destroy dyes to cause fading, these samples were rated by the AATCC grey scale for dye fade.
TM 175: 1 = severe stain; 10 = no stain. 8 or above is acceptable
Grey scale: 1 = severe fade; 5 = no fade. 3-4 or above is acceptable
In this multicolored carpet, especially the untreated control samples, those fibers that were dyed with acid dyestuffs were affected by the test product and showed fading. Colorant pigments contained in the solution dyed yarns of the carpet showed no fading. The grey scale evaluation centered only on fading in the acid dyed yarns.
EXAMPLE 6 Treated and untreated samples from Example 3 were tested for stain resistance against colorants contained in mustard. Samples were a, b, c, d, f, k, l and n. The method of application and the chemical and mustard resistance testing were the same as in Example 5. The results are shown in TABLE 7.
Six sets of carpets (samples 1a and 1b-6a and 6b) were evaluated for stain resistance to anionic colorants contained in unsweetened cherry-flavored Kool-Aid brand drink, Rite brand red dye, and a dye mix of red and blue direct dyes used to dye cotton fabrics. The carpet samples were the following:
Sample
- 1. Solution dyed acid dyeable type 6 nylon: stainblocked with methacrylate polymer
- 2. Solution dyed acid dyeable type 6 nylon: stainblocked with methacrylate/SAC polymers
- 3. Acid dyed acid dyeable type 66 nylon: stainblocked with methacrylate polymer
- 4. Acid dyed acid dyeable type 66 nylon: stainblocked with methacrylate/SAC polymers
- 5. Solution dyed cationic dyeable nylon type 66: No stainblocker treatment
- 6. Acid dyed cationic dyeable nylon type 66: No stainblocker treatment
Samples 1a-6a were used as control samples, whereas samples 1b-6b were treated with N-201 A (30% solids) at 15% OWF (4.5% wt/wt; dry weight SAC/dry weight nylon fiber) by a wet heat batch method.
All samples were evaluated for stain resistance using the AATCC Test Method 175, wherein the staining solutions were substituted for Red Dye 40. One percent solutions of the Rite dye and dye mix were prepared as the test solutions. TABLE 8 shows the rating results of stain resistance wherein 1=heavy stain and 10=no stain.
In samples 1a-6a, the results show that the stain resistance of stainblocked acid dyeable nylon fibers or naturally stain resistant cationic dyeable nylon fibers is limited to acid dye type anionic colorants contained in foods and drinks. They are not stain resistant to anionic dyes outside of the acid dye class of dyestuffs in particular anionic dyes used to impart colors to fabrics and perhaps inks, paints and other products. Samples 1a-6b, which are treated by this invention, have stain resistance to acid and non-acid type anionic colorants.
Two sets of acid dyeable T-66 nylon knit fabrics comprising three panels each were evaluated for stain resistance and dye fading. Two of the panels in each set were dyed. One was dyed a medium blue and the other panel a turquoise color, with the remaining panel a bleach white shade.
One set of fabrics (test samples) was treated by the wet heat batch method with the SAC polymer Simcofix N-201A at 10% OWF (3.3% wt/wt) at 200 F for 40 minutes, pH=4.5. The other set of fabrics was untreated (control samples). Each panel was designed for multiple stain application and measured 72″ long and 8 inches wide. A number of staining products or chemical agents were applied along the length of each panel, left for 24 hours, washed warm in a washing machine using a liquid soap detergent, air dried and then evaluated for stain resistance to colorant stains or dye fade resistance to chemical agents (on colors only).
Due to the differences in the appearance of staining from the various materials, three rating methods were used to evaluate the results with two methods being AATCC standards. The following staining materials and rating methods are shown in TABLE 9 wherein AATCC Test Method 175 uses a 10 point rating with 1=severe stain and 10=no stain. The AATCC Grey Scale for dye fade uses a 5 point rating with 1=severe fade and 5=no fade. Staining materials that imparted an oily appearance, a colorant appearance or some combination of both were rated as A=acceptable wherein no stain appeared or U=unacceptable wherein stains of either or both types were visually apparent.
* made by grinding green grass and leaves in blender with water
TABLE 10 shows the rating results on the blue, turquoise and white test panels treated by the method of the present invention.
TABLE 11 shows the rating on the blue, turquoise and white untreated control panels.
The results show that when nylon fibers are treated by the method of this invention they are stain resistant to synthetic and natural colorants and oils. In addition dye fade from chemical agents is eliminated or significantly reduced.
Furthermore, the results demonstrate that the treated fabrics are stain resistant to the different groups of naturally occurring colorant dyes and pigments found in vegetables, fruits, leaves, grasses, etc. Olive oil was the only oil in the experiments that was visually observed on the dyed untreated control fabrics, and olive oil appeared more as a dark spot as opposed to an oily spot.
This new process thus provides two general types of protection to dyed nylon fiber products. The first type of protection involves preventing colorants such as betadine, turmeric (mustard), red sauces, grass stains, fabric dyes, etc., from permanently staining the nylon fibers. The second type of protection involves preventing reactive chemical agents such as those contained in chlorine bleach products or acne care products from reacting with, therefore permanently fading, dyestuffs on nylon fibers dyed with acid dyes.
We believe that the SAC polymers chemically reduce the permeability of the nylon surface structure (surface morphology) to penetration from neutrally charged colorants and reactive chemical agents by a cross-linking mechanism. Since the polymer structure of nylon fibers for carpet products must be open (porous) for dyes to penetrate or diffuse into the fibers in the dyeing processes, then we believe that colorants and chemical agents also penetrate the fibers in the same manner. Apparently, SAC polymers under wet heat conditions have the ability to form a cross-linked polymer matrix (spider web) over the openings of the porous structures of the fibers. As a consequence, the fibers and dyes are protected from entry to colorants and reactive chemical agents. As to why methacrylate stainblocker polymers do not exhibit the same behavior as SAC polymers, we believe this is due to differences in charge density, molecular weight and chemical structure between the two classes of polymers.
This invention has been described in detail with particular reference to certain embodiments, but variations and modifications can be made without departing from the spirit and scope of the invention as defined in the following claims:
Claims
1. A process for providing nylon fibers with resistence to staining from neutral colorants and anionic colorants, wherein the process comprises the steps of:
- (a) treating the nylon fibers with at least 2% weight/weight (weight dry sulfonated aromatic aldehyde condensation polymer/weight dry nylon fibers) of sulfonated aromatic aldehyde condensation polymer and
- (b) fixing the treated nylon fibers by a wet heat method.
2. A process as defined by claim 1 wherein the nylon fibers are selected from the group consisting of acid dyeable nylon fibers and cationic dyeable nylon fibers.
3. A process as defined by claim 1 wherein the nylon fibers are selected from the group consisting of acid dyed acid dyeable nylon fibers, acid dyed cationic dyeable nylon fibers, solution dyed acid dyeable nylon fibers and solution dyed cationic dyeable nylon fibers.
4. A process for providing dyed nylon fibers with resistence to fading from chemical agents, wherein the process comprises the steps of:
- (a) treating the dyed nylon fibers with at least 2% weight/weight (weight dry sulfonated aromatic aldehyde condensation polymer/weight dry nylon fibers) of sulfonated aromatic aldchyde condensation polymer and
- (b) fixing the treated nylon fibers by a wet heat method.
5. A process as defined by claim 4 wherein the dyed nylon fibers are selected from the group consisting of acid dyed acid dyeable nylon fibers and acid dyed cationic dyeable nylon fibers.
Type: Application
Filed: Nov 4, 2004
Publication Date: Jul 7, 2005
Inventors: Joseph Pacifici (Anderson, SC), Daniel Sims (Greenville, SC)
Application Number: 10/981,094
