US 3138802 A
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United States Patent 3,138,802 PROCESS FOR IMPARTING DURABLE CREASES,
WRINKLE RESISTANCE AND SHAPE RETEN- TI'DN T0 CELLULOSIC TEXTILE ARTICLES Nelson F. Getchell, Great Falls, Va., assignor to The Cotton Producers Institute of the National Cotton Council of America, Memphis, Tenn., a non-profit corporation of Tennessee No Drawing. Filed May 25, 1962, Ser. No. 197,617 6 Claims. (Cl. 2243) This invention relates to an improvement in cellulosic fibrous textile products. More particularly, it relates to a process wherein cellulosic fibers are chemically pretreated in a first stage to impart to them a latent ability to become more resilient and this latent ability is then developed by simple heat treatment at a preselected later stage, for instance, after the pretreated fibrous material has been finished into a garment or other finished article. Still more particularly it relates to a novel process which comprises impregnating cellulosic fibers, yarns, fabrics or other products with a curable resin-containing solution before they are made into a more finished article, wet curing the impregnated product so as to render the resin therein water insoluble but without materially affecting the strength or resilience thereof, and finally developing improved shape retention or resilience therein only after it has been made into an article of the desired shape or form by sewing, tufting, laminating, pressing, or other conventional procedures.
Various methods have been developed for treating fabrics to impart durable wrinkle resistance or better resilience thereto. Generally, such methods have involved impregnating a fabric with a suitable thermosetting resin in aqueous solution and thereafter dry curing the fabric by heat. However, such prior practices have had numerous disadvantages, due mainly to the decreased mobility of the cross-linked structural elements. Thus, when such fabrics were cured in the flat condition, they tended to resist any kind of subsequent deformation. This has made fabrication of textile articles therefrom more difficult. For instance, it has been difiicult to press durable creases into such garments and at least some careful touchup pressing has been necessary after each Washing or cleaning for the purpose of resetting creases. In addition, garments made of the fiat-cured fabrics of the prior art have tended to exhibit unsightly puckering at seams and the like. Moreover, such prior treated fabrics have had substantially impaired tensile and tear strength such that, for instance, conventional methods have been found unsuited for the treatment of sheer fabrics having low tensile strength to begin with.
Various expedients have been proposed previously to overcome the aforementioned difliculties. Thus, it has been proposed to impregnate and cure finished garments rather than flat fabrics so as to permit setting the garment only after it has been shaped and creased as desired. It has also been proposed to treat garments made of crease resistant, cured fabrics by localized treatment with acid or acid-containing resin solutions which would temporarily remove the crease resistance in the area where a crease was to be imparted and then cause it to reappear after the crease has been formed. All of these expedients have, however, found only limited application because manufacturers and commercial cleaners of garments or other textile articles are rarely equipped to carry out such relatively cumbersome and delicate chemical resin treatments.
Alternately it has been proposed to impregnate fabric with an aqueous melamine-formaldehyde resin solution, dry it under conditions carefully controlled to avoid polymerization, convert the fabric containing the unset or unpolymerized resin into a garment, and then only cure the resin in the garment to a water insoluble state. This, however, has also proved impractical because the fabric containing the unset water soluble resin is excessively water sensitive and also gives off an offensive and hygienically objectionable formaldehyde odor. Moreover, even under careful control, premature setting of the thus impregnated resin is practically unavoidable in normal garment manufacturing procedures and schedules.
It is an object of this invention to provide resilient, shape holding, crease-retentive textile articles by a process requiring no wet chemical resin-treatment of the articles themselves.
A more specific object of this invention is to provide a process of manufacturing wrinkle resistant and crease retentive garments or other articles made from cellulosic fabrics, threads or other fibrous materials which have been pretreated with a curable thermosetting resin so that the resin is set on the cellulosic material in a Water insoluble form but without significantly affecting the deformation recovery or tensile strength of the material and which can be dry cured into a wrinkle resistant and shape retentive form at any desired stage of subsequent manufacture without subjecting the finished article itself to any separate resin impregnation treatment.
Another object is to provide shape holding Wash-andwear garments which will not pucker at the seams and will withstand numerous washings without loss of creases or pleats.
A still further object is to provide a process for making deformation resistant and shape-retentive textile articles such as garments, draperies or carpets from curable resincontaining fibrous cotton materials which can be readily cured after they have been manufactured into the desired articles but which can be processed, stored and handled by the manufacturer and others in their relatively non-resilient form over extended periods of time under normal conditions without undergoing premature curing.
Still another object is to improve the shape retentiveness and wrinkle resistance of cellulosic materials, even of sheer fabrics, without impairing the tensile strength thereof except perhaps to a marginal extent, much less so than in the case of conventional crease proofing treatments.
Other objects and advantages of the invention, as well as modes of using it, will become apparent from the following description. It will be understood, of course, that the invention is not to be limited to the particular embodiments described.
The present invention is based on the discovery that cellulosic materials which have had an aminoplast wet fixed therein can be subsequently dry cured to give improved resilience with no serious strength loss. More particularly it has been found that it is possible to im pregnate cellulosic fibrous materials such as cotton or viscose fibers, filaments, yarns, threads, fabrics, nonwovens or other textile products with a hardenable aminoplast; insolubilize the aminoplast therein by wet fixation without importantly increasing the wet or dry crease resistance or resilience thereof; treat such fibrous material with a latent curing catalyst which will remain inactive over extended periods at room temperature but can be readily activated; and finally dry curing the present resin in the fibrous material when desired so as to impart improved crease resistance, shape retention and generally improved resilience thereto. The serious strength loss that otherwise attends conventional treatments wherein cellulosic materials are impregnated with an aminoplast and dry cured directly is reduced. The dry curing step is preferably performed only after the treated material has been manufactured into a textile article of the desired =3 final shape, for instance, after it has been cut, sewn and pressed into a garment, or tufted to make a carpet, or molded into batting or the like.
The expression hardenable aminoplasts as used with respect to the present invention is to be understood as including hardenable amineformaldehyde precondensates which are either freely soluble in water or soluble therein to a limited but substantial extent. They are well known materials obtained by condensation of formaldehyde with compounds such as melamine, urea, thiourea, cyanamide, dicyandiamide, cyclic ethylene urea, formamide, ethyl carbamate, triazones, acetoguanarnide, mixtures of such compounds and their alkyl and acyl derivatives. Subsequent methylation or other modification of the resulting N-methylol compounds or triazines is often beneficial. Particularly convenient are the triazines obtained by condensing melamine and formaldehyde and the precondensates of urea-formaldehyde. Especially good results are obtained with dimethylol melamine or trimethylol melamine precondensates, i.e., products obtained by condensing one mol of melamine with about two or preferably three moles of formaldehyde.
Precondensates of limited but substantial water solubility in the sense of the present invention are those colloidal intermediates which occur by continuing the condensation beyond the crystalline methylol stage. characteristically, they are precipitated from their concentrated aqueous solutions by the addition of water. The condensation products of unlimited water solubility are used in the form of aqueous solutions while those of limited water solubility are used either in the form of solutions of the condensation products which have been rendered soluble with the aid of acids or in the form of dispersions. Suitable commercial products of this type have been heretofore made and sold for use as rot proofing agents. Examples of such products are the Arigal C textile finish made by Ciba Company, Inc., and Aerotex Sta-Tuff Resin A made by the American Cyanamid Company.
In applying the aminoplast solutions or dispersions to the fibrous material, it is advantageous to include in the former customary catalysts or fixation agents, e.g., formic, hydrochloric or sulfuric acid, maleic anhydride or the like. Formic acid is particularly preferred. However, other organic or inorganic acids or salts of strong acids with weak bases such as ammonium salts of hydrochloric, sulfuric, nitric, oxalic, lactic, or other strong inorganic or organic acids, various amine hydrochlorides, or still other acid forming salts such as zinc fluoborate, zinc nitrate, magnesium chloride as well as Lewis acids such as aluminum chloride can also be used. The fixation catalyst can usefully be added in an amount between about 1 and 10%, preferably between about 2 and 5% based on the weight of aminoplast present. Instead of or in addition to the acid or acid-forming catalysts, minor amounts of oxidizing agents such as hydrogen peroxide can also be used in the bath. The catalytic action of such oxidizing agents is believed to be attributable to their ability to convert some of the formaldehyde content of the resin to formic acid. Actually, the use of hydrogen peroxide without any other fixation catalyst has been found especially advantageous to effect the wet fixation required as part of this invention. The addition of non-ionic wetting agents, though not usually necessary, can be helpful when the condition of the fibrous material does not permit the impregnating bath to penetrate with the desired degree of readiness or evenness. When the fixation catalyst is added to the aminoplast solution, it is desirable to keep the pH of the bath high enough to prevent premature condensation, e.g., between about 7.5 and 9 when melamine formaldehyde precondensates are used. This is particularly advisable if the catalyst containing bath is to be kept usable for an extended period.
The aqueous bath for the impregnation according to this invention may contain about 3 to 20 weight percent of hardenable aminoplast, either in solution or emulsion. Depending on the requirements of the finished fabrics, the impregnation is carried out in such a manner that the add-on of aminoplast deposited on the material is between about 3 and 25 percent, preferably between about 8 and 20 percent, based on the weight of fibrous material. The optimum add-on is determined mainly by factors such as the type of aminoplast and catalyst used, the effectiveness of the final curing technique employed and the amount of strength loss one can afford. A relatively high add-on will impart good resilience to the material even when a relatively mild curing technique is employed but will also result in a greater strength loss than is caused by a lower add-on.
The impregnation with the aminoplast can be done by conventional padding using customary equipment, or by spraying and other known processes.
The essential feature of this part of the process is that the deposited resin is fixed in the fibrous material while the latter is wet and the fibers are distended or swollen with water, so that the resin becomes insolubilized in the fibrous cellulosic material without converting the latter to a shape holding, crease resistant form at this stage. Without wishing to be bound by any particular theory, it is believed by way of possible explanation that wet fixing may achieve this result because the wet swollen state of the fibers either prevents extensive cross-linking of the cellulose by the resin or, even if such cross-linking takes place, the fibers are greatly distended when so treated and hence the treated structure still retains a high degree of mobility when dried. For instance, when melamine-formaldehyde precondensates or similar aminoplasts are used, the desired degree of resin insolubilization with the fibrous material is conveniently obtained by the wet fixing method described in US. Patent 2,763,574, the pertinent disclosure of which is hereby incorporated herein by reference. This method, heretofore used for rot proofing, involves impregnation of the fibrous material at about 10 to 30 C., e.g., on a padding mangle, followed by drying the material to a moisture content between about 20 and about preferably between about 30% and 40%, by passage though a tenter frame or the like, and then subjecting the partially dried material to wet fixation while maintaining its moisture content within the aforesaid limits.
Such wet fixation can be accomplished in various known ways, continuously or batchwise. Thus, the material can be steamed for about 5 to 15 minutes with saturated steam (at 100 C.) by passage through a Mather- Platt high speed steamer or similar equipment. Alternately, the partially dried material can be steamed batchwise with saturated steam in a Star steamer or similar equipment for any desired period. Prolonged exposure to saturated steam has no deleterious effect. However, to assure uniformity of treatment, the material should be protected during fixation from contact with liquid condensate, water drops and splashes. If steaming facilities are not available, satisfactory fixation can be obtained, for instance, by rolling up the partially dried fabric, wrapping the roll air-tight with a polyethylene film or the like and then storing at 20 to 30 C. for several days until the desired degree of resin insolubilization is reached. In contrast to the usual dry curing process which imparts shape holding and Wrinkle resistant properties to the treated cellulosic material, with attendant losses of tensile and tear strength, the wet fixation employed in this invention insolubilizes the resin in the fibrous material while producing therein neither significant wrinkle resistance nor tensile losses. The mechanical properties of the treated material are thus hardly changed. Of course, when the fixation step has been completed, the material can be washed without removing the resin or causing any other harm.
When the aminoplast has been wet fixed on the cellu- J losic material in a suitable manner and thereby made water insoluble, the material is preferably washed with water to rinse out any residual fixation agent or hardener, and dried. Drying conditions after wet fixation and removal of the hardener are not especially critical but temperatures in excess of about 90 C. are preferably avoided.
The pretreated dried material is next padded or otherwise treated with a solution of a latent catalyst, or the latent catalyst can be applied to the pretreated material without intervening drying. In fact, even the above mentioned rinsing step may be omitted if the kind of catalyst remaining after the wet fixing step is not harmful to the textile material and the amount of such residual catalyst is known so that it can be taken into account in providing the required amount of latent catalyst for the final curing step. If desired, the pretreated dried material can be stored for any desired length of time prior to applying the latent catalyst. The latent catalyst may again be any of the relatively non-volatile compounds known to promote curing of the resin, such as those mentioned previously herein. Particularly suitable here are salts of suitable polyvalent metals such as magnesium chloride or nitrate or zinc chloride or nitrate; various amine hydrochlorides such as Z-amino-Z-methyl-l-propanol hydrochloride, or triethanolamine hydrochloride; and ammonium salts such as ammonium tartarate, citrate, formate, oxalate, nitrate or ammonium ethyl phosphate or ammonium dihydrogen phosphate or the like. Organic acids, particularly those having a high melting point, e.g., above about 120 C., such as malonic or succinic acid are similarly useful.
Obviously, if the cellulosic material is not to be subjected to the final dry curing step for some time after impregnation with the latent catalyst, it is desirable to use as a catalyst a compound which does not volatilize in the interim and is not deleterious to the cellulosic material during storage or intervening handling. The use of toxic compounds as latent catalysts is also preferably avoided if the material is to undergo considerable further handling by garment workers or other workmen prior to the final cure. Of course, any catalyst remaining after the final cure can be removed by simple washing.
The latent catalyst solution containing the catalyst in any convenient concentration is desirably used in a quantity such that about 0.25 to preferably about 0.5 to 2%, of the salt, is added on to the cellulosic material based on the weight of the latter. The material is then dried at room temperature or at an elevated temperature but below about 90 C. to avoid permature dry curing, and is then ready for conversion into garments or other desired textile articles.
Finally, when the desired textile article, such as garments or shaped draperies, is sewn and finished and all desired creases, curves and pleats are pressed into it, with or without prior moistening, the article is cured at an elevated temperature, above about 100 C. and below charring temperature, preferably between about 120 and 180 C. For instance, exposure of the finished article in a forced air oven at 150 C. for about 2 to 5 minutes usually gives a satisfactory cure. Somewhat longer times may be necessary at lower curing temperatures, and shorter times may be sufiicient at higher curing temperatures, as can be readily determined by any person skilled in the art. Thus, the preferred embodiment of the present invention provides a process for improving the shape holding properties of cellulosic textile articles which does not require any wet treatment of the finished fabric. Wet resin impregnation of the finished article can also be avoided and improved resiliency Without much strength loss achieved by making the wet-fixed fibrous material into the desired textile article and then treating the latter with any of a Wide range of catalysts commonly used for heat curing aminoplast resins in textile materials, and finally curing the article. In this case the catalyst can be applied by spraying, exposure to vapor, or other known methods.
a 6 The process of the present invention can be used on all cellulosic materials but is especially useful for the treatment of natural cellulose materials, as for example cotton or linen. The impregnation can be applied to loose fibers, filaments, non-woven fabrics or bats and other material, to yarns and materials in an intermediate stage.
of conversion into yarn such as condensed sliver, or to woven, knitted or tufted goods. It can be applied to mercerized as well as unmercerized materials, either before or after dyeing, printing or other finishing treatments as long as the material is receptive to uniform wetting by the required treating solutions. Sized material is therefore preferably desized prior to treatment with the resin solution. It will also be understood that the pad bath containing the aminoplastmay contain diverse conventional agents such as wetting agents, softeners, Water repellents, anti-microbial agents and the like.
The following examples are illustrative of the process of the invention and of the results obtained thereby, but are not to be considered as limiting. On the contrary, it will be understood that persons skilled in the textile treating art will be able to make many variations and modifications of this invention not specifically described herein Without departing from the spirit of this invention or from the scope of the appended claims.
Unless otherwise indicated, all percentages and ratios of materials are expressed on a weight basis therein.
Example I A desized, bleached, and mercerized cotton print cloth was padded to a wet pickup of approximately in a solution prepared by adding grams of a methylolmelamine precondensate (Arigal C resin) to 360 grams of Water at 80 C., cooling, diluting to a total volume of one liter, and adding 10 ml. of a 30% hydrogen peroxide solution as fixation catalyst, so as to give a nominal dry add-on of about 12%. After padding, the fabric was dried for 3%. minutes at 40 C. to 30-40% moisture content in a forced air textile oven. The partially dried fabric was rolled onto a plastic cylinder, wrapped and sealed in polyethylene film, and the resin wet-fixed therein by curing at 37 C. for 24 hours. After machine washing and tumble drying, the treated farbic was padded with a solution containing 2.7% of MgC1 -6H O to an 80% wet pickup, so as to give an approximately 1% nominal dry add-on of MgCl and dried at 40 C. The treated, latent catalyst containing fabric was then dry cured for 3 minutes in a forced air oven at C. without any further treatment.
The Wrinkle recovery, wash-and-wear index and strength retention of the fabric, in its untreated, wetfixed and dry cured state were determined by standard methods. In particular, American Society for Testing Materials Method D1295-60T was used to determine wrinkle recovery, American Association of Textile Chemists and Colorists Method 88-1960 was used to determine the wash-and-wear index, and American Society for Testing Materials Method D39-49 was used to determine breaking strength.
The treated fabric had a total dry add-on of 15.3%; its dry wrinkle recovery was 68%, and wet Wrinkle recovery 65%, its wash-and-wear index after one cycle including hot Water laundering and tumble drying was 4; and its breaking strength retention, as compared with the original untreated fabric, was 90%.
The corresponding figures for the untreated mercerized cotton fabric were 35% and 50% for the dry and wet Wrinkle recovery respectively, and 1- for the Wash-andwear index.
The corresponding figures for the resin-treated wetfixed fabric before dry cure were 15.6% add-on; 47%
A wash-and-wear index rating of 5 means excellent wrinkle recovery; a rating of 1 means very poor wrinkle recovery.
7 dry, and 53% wet wrinkle recovery; 2- wash-and-wear index; and 107% tensile strength.
It can be seen that the fabric treated according to this invention had excellent wrinkle recovery and crease retention and only slightly lower tensile strength than the untreated fabric. The fabric which had the resin wet-fixed thereon Without the final dry curing step had only slightly better wrinkle recovery than the untreated fabric. A fabric which is dry cured directly according to conventional techniques, without the intervening wetfixing step, has good wrinkle recovery but is dilficult to crease by pressing and has greatly impaired strength; a loss of 50% or more of the original fabric strength has not been uncommon.
Example II The fabric was treated and tested as in Example 1, except that the resin-treated latent catalyst-containing fabric was permitted to age at 65 relative humidity and 21 C. for one day, after which it was dry cured as in Example I without any further treatment. Add-on was 15.7%; wrinkle recovery was 62% dry and 63% wet; wash-and-wear index was 3+; and breaking strength retention was 87%.
Example Ill The fabric was treated and tested as in Example I, except that the resin-treated latent catalyst-containing fabric was permitted to age at 65% relative humidity and 21 C. for eight days, after which it was dry cured as in Example I without any further treatment. Add-on was 15.8%; wrinkle recovery was 60% dry and 68% wet; wash-and-wear index was 3+; and breaking strength retention was 89%.
Examples II and III show that the latent catalyst-containing fabric can be aged, i.e., stored or subjected to manufacturing operations such as cutting and sewing, over extended periods without curing prematurely and without impairment of the desired end results.
Example IV The fabric was treated and tested as in Example I, except that the resin-treated fabric was permitted to age for eight days at 65 relative humidity and 21 C. before the catalyst solution was applied. The fabric was then treated with a MgCl solution, dried, and dry cured as described in Example I. Add-on was 15.6%; wrinkle recovery was 63% dry and 70% wet; wash-and-wear index was 3+; and breaking strength retention was 85%.
Example V The fabric was treated and tested as in Example II, except that the resin-treated latent catalyst-containing aged fabric was not subjected to dry cure. The add-on was 16.1%; wrinkle recovery was 49% dry and 53% wet; wash-and-wear index was 2+; and breaking strength retention was 103 Example VI Example VII The fabric was treated and tested as in Example II, except that it was not subjected to dry cure. The resintreated, latent catalyst-containing, one day aged fabric was then creased on a tailors press for 5 minutes with dry heat, and subsequently cured in an air oven at 150 C.
for 3 minutes. The crease retention rating of the fabric (measured on a scale where a rating of 1 means no crease retention and a rating of 5 means excellent crease retention) was 5 after one laundering cycle involving one hot water laundering and one tumble drying. The rating was 5- after five hot water laundering cycles. The untreated cotton fabric creased in the same manner had a rating of 2 after the first, and 2 after five launderings.
Example VIII The fabric was treated as in Example VII, except that the resin-treated, one-day aged, latent catalyst-containing fabric was sprayed with water to an weight gain and then immediately creased for 5 minutes on a tailors press with dry heat. The crease retention rating after the laundering cycle was 3+, and after five laundering cycles was 3-. A comparison between Examples VII and VIII shows that even without a separate curing step hot pressing alone of the catalyst-containing treated fabric results in a significant improvement in crease retention.
Example IX The treatment described in Example VIII was repeated except that after creasing for 5 minutes on the tailors press the fabric was cured at 150 C. for 3 minutes. The crease retention rating after the first laundering was 4+, and after five laundering cycles was 4. A comparison between Examples VII and IX shows that dry pressing followed by a dry cure gives better crease retention than wet pressing followed by a dry cure.
Example X Fabrics were treated as in Examples LIX, except that the concentration of resin in the bath was 5%. The addon on the dry-cured fabrics was about 7.5%, the dry and wet wrinkle recovery and the wash-and-wear index of the fabrics were similar to, but somewhat lower than, those of fabrics treated as in Examples I-IX, while their strength retention was a few percentage points higher.
Having described the general nature of the invention and having illustrated its operation and advantages by specific examples, the invention is particularly pointed out and claimed in the appended claims.
1. A process of forming a resilient, crease resistant, shape-retentive textile article from a cellulosic fibrous material which comprises treating said material with a water-soluble aminoplast precondensate, wet fixing said precondensate in said fibrous material into a water insoluble condensation product in the presence of a wet fixation agent while maintaining a moisture con-tent of at least 20% in said material, applying a latent curing catalyst to the wet fixed material, manufacturing a textile article from said treated material, and curing the manufactured textile article to increase its resilience.
2. A process of forming a shaped cloth article which is wrinkle resistant and shape retentive after repeated laundering, which comprises the steps of impregnating cloth made of cellulosic fibers with an aqueous solution of a resin selected from the group consisting of melamineformaldehyde, urea-formaldehyde, and cyclic ethylene urea-formaldehyde precondensates, and with a catalytic amount of a wet fixation agent, maintaining the impregnated cloth at a moisture content of at least about 20% under conditions of temperature and time such that the resin is wet fixed in said cloth into a water insoluble condensation product without causing any significant strength loss in the cloth, drying the cloth, impregnating it with an aqueous solution of a latent curing catalyst, drying the thus impregnated cloth at a temperature not above about C., forming the thus dried cloth into a finished article of the desired shape, and dry curing the said article at an elevated temperature until it is rendered wrinkle resistant and shape retentive.
3. A process according to claim 2 wherein said resin is a precondensate of about 2 to 3 moles of formaldehyde and 1 mole of melamine, said curing catalyst is magnesium chloride and said curing temperature is between about 120 C and 180 C.
4. A process for making a shape-retentive garment from a cotton fabric which comprises impregnating said fabric with an aqueous solution of a melamine-formaldehyde precondensate which contains a catalytic amount of an acidic hardening accelerator, mechanically removing the excess of impregnating liquid, wet fixing the melamine-formaldehyde precondensate in the cotton fabric in the presence of between about 20% to about 40% of water (calculated on the weight of the fabric) and said hardening accelerator into a water insoluble condensation product, rinsing the wet fixed fabric, impregnating the wet fixed fabric with an aqueous solution of a latent hardening catalyst, drying the resulting catalyst-containing fabric at a temperature below about 90 0., cutting, sewing and pressing the said fabric to form a garment of desired size and shape, and dry curing the resulting catalyst-containing garment at a temperature above about 120 C. and below the charring temperature of the fabric, whereby improved crease retention and deformation resistance are imparted to the garment.
5. A process according to claim 4 wherein said hardening accelerator is hydrogen peroxide.
6. A process according to claim 4 wherein said hardening accelerator is formic acid.
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