Introduction of a temporary stiffness into knitted cotton for stability during patterning
United States Patent Frick et al.  
 INTRODUCTION OF A TEMPORARY STIFFNESS INTO KNITTED COTTON FOR STABILITY DURING PATTERNING lnventors: John G. Frick; Bethlehem K.  
 Andrews, both of New Orleans; Gloria A. Gautreaux, Metairie. all of La.  
 The United States of America as represented by the Secretary of Agriculture, Washington, DC.  
 Filed: Apr. 17, 1973 Appl. No.: 351,935  
 Assignee:  
 US. Cl. 8/ll5.6; 138/144; 112/262; 117/4; 28/77 Int. Cl D07m 13/12 Field of Search 117/4; 8/1 15.6; 138/144; 112/262 51 Apr. 22, 1975 [56] References Cited UNITED STATES PATENTS 2.974.432 3/1961 Wamock et a1. 38/144 3.036.537 5/1962 Breicr 28/77 UX 3.329.116 7/1967 Attwood et a1. 28/77 UX Primary E.\&#39;aminerDona1d Levy Attorney, Agent, or FirmM. Howard Silverstein; Max D. Hensley [57] ABSTRACT 3 Claims, No Drawings INTRODUCTION OF A TEMPORARY STIFFNESS INTO KNITTED COTTON FOR STABILITY DURING PATTERNING FIELD TO WHICH THIS INVENTION RELATES This invention relates to a method for making knitted cotton fabric intended for post-cured durable-press textile items easier to cut or otherwise shape into patterned parts of the final item without adversely affecting the final properties of the fabric. Specifically. this invention provides a method of making the knitted cotton firm and stable enough to allow easy patterning or tailoring which method does not greatly increase the stiffness of the final durable-press product after it has been washed.  
 Definitions:  
  By the stability of a fabric we mean the resistance the fabric offers to undesired deformations. A stable knitted fabric can be handled and cut without changing the number of stitches for unit length in any direction. This stability is related to the firmness of the fabric and is accompanied by a stiffness or rigidity.  
  A stabilizing or firming agent is a material that can be applied to a fabric and give the stability or firmness described in the preceding paragraph.  
  Durable press refers to the ability of a fabric to resist wrinkling in wear and laundering. This property is obtained to a noticeable and important extent on cotton by finishing or treating with a crosslinking agent.  
  Post-cure durable press refers to durable-press finishing of cotton textiles in which a crosslinking agent is applied to a length of fabric, but curing to promote reaction of the agent with the cotton is postponed or deferred until the fabric has been fashioned into the final textile item.  
  Spray application means the deposition of a material on fabric by dispersing the material as fine particles and carrying these particles to the fabric in a stream of gas. The particles are small enough to travel easily in a stream of gas moving through the atmosphere but are not small enough to remain suspended indefinitely in an ordinary atmosphere without a propelling stream of gas.  
 The Problem Knitted cotton fabric often lacks body and firmness and, therefore, lacks a stability in handling. As a consequence, it is difficult to avoid accidental stretching, skewing, or other distortion in cutting or otherwise shaping the fabric to fit a pattern for part of a textile article. The parts then are misshapen or missized, and the final shape of the article is distorted. This problem can be avoided by the application of agents that give a stability and a stiffness to the fabric. Unfortunately, the properties introduced by these stabilizing agents when they are applied in the usual wet application are sometimes persistent. They remain through tailoring or other fabrication into the final textile product. This is often objectionable because it detracts from the softness and suppleness usually desired in articles of knitted fabric. The persistence of these properties is a particularly serious problem in durable-press articles treated by a post-cure process. In such treatments, the durable-press finishing agents are applied before the fabric is cut to patterns, but the fabric is not cured until the final textile article is formed. The stiffening agent is present, therefore, when the durable-press finishing agent is cured or set on the fabric. The stiffening agent tends to be bound by the finishing agent as a consequence. This tendency to bind the stiffening agent is aggravated by the fact that many of the stiffening agents can react chemically with the durable-press finishing agent.  
  The problem of misshaped fabric is also more serious in durable-press items because the shape and dimensions of the fabric cannot be changed by stretching or pressing after the durable-press treatment.  
 THE PRIOR ART No method of solving the problem is known in the prior art. Where it arises the problem is tolerated. The best compromise is usually employed where the stability of the fabric is less than ideal and some stiffness. less than would be obtained with a fully stabilized fabric. is allowed to persist in the final product. Otherwise. the use of knitted cotton is avoided.  
 OBJECT OF THE INVENTION The object of the instant invention is to apply a stabilizing or firming agent to knitted cotton fabric being treated for post-cure durable-press textile items in such a manner that the fabric is stable enough to allow easy shaping to patterns but the fabric does not retain objectionable stiffness after the fabric is completely treated and washed.  
 How the Objective is Achieved The objective of this invention is achieved by spraying a temporary stabilizing or firming agent on a knitted cotton fabric to which a durable-press finishing agent has been applied but which fabric has not been cured. Curing is then performed after spray application of the stabilizing agent to promote reaction of the finishing agent.  
  The stabilizing or firmingagent can be any polymeric material that will adhere to the fabric and that has a modulus high enough to hold the yarns in place. These agents are commonly sold under the name of sizes or sizing agents. Spraying consists of blowing a fine dispersion of solution or dispersion of stabilizing agent onto the fabric. The solvent or dispersing medium may be water or organic liquid. If the medium is a liquid of low volatility it must not be in such quantity that it saturates any part of the fabric and causes movement of the durable-press finishing agent as it flows on the fabric. With highly volatile liquids the problem is minimized because only a small quantity of liquid reaches the fabric.  
  After spraying the fabric with the firming agent of this invention the fabric is stable and firm enough for easy handling and shaping without causing stretch or other distortion. After the fabric is cut and sewn into a garment or other textile item, it is cured by heating to impart durable-press properties, that is, wrinkle resistance and the ability to dry smooth. When the item is washed after curing, the stabilizing agent is removed. The fabric then has a stiffness no more than slightly greater than a similar durable-press fabric that has not been treated with a stabilizing agent before curing for ease of shaping and cutting.  
  The ability to remove readily the stabilizing and stiffening agent in laundering comes from the nature of the application. The stabilizing agent is only on the surface of the fabric and is not subject to binding by the durable-press finishing agent, either through physical entrapment or chemical attachment, when that agent reacts on curing. With application by spraying, even those stabilizing agents that are capable of reacting with the durable-press finishing agent may be used. For instance, a starch product may be applied to the fabric containing the durable-press finishing agent, and the fabric can be washed free of noticeable starch after curing.  
 SUMMARY OF THE lNVENTlON The instant invention can be described as a method for providing knitted cotton fabric that is stable and firm enough to be cut easily into patterns without distortion, that can be cured by heat to introduce durablepress properties, and that can be restored to near its original soft hand by washing after it has been cured.  
  1n the practice of this invention, a formulation commonly used in the durable-press finishing of cottoncontaining fabric is applied to the knitted cotton fabric. This formulation contains 315% of a durable-press finishing agent that is a water-soluble crosslinking agent for cellulose. The preferred type of crosslinking agent for the process of this invention is a methylol amide, such as dimethylol dihydroxyethyleneurea, dimethylol ethyleneurea, dimethylol propyleneurea, and dimethylol methyl carbamate. In addition, the formulation will contain a catalyst to promote reaction of the crosslinking agent. Common catalysts are zinc nitrate, zinc&#39;chloride, and magnesium chloride. Both agent and catalyst are dissolved in water. The aqueous formulation also may contain other substances such as hand modifiers for the fabric, wetting agent, or odor control agent.  
  The knitted cotton fabric is impregnated with the formulation by padding. The wet, impregnated fabric is dried at 50-l00C until the fabric contains less than of fabric weight in residual water but is not heated long enough to cause extensive crosslinking by the durable-press finishing agent. Crosslinking at this stage of the process would make it difficult to shape from the fabric garments or other textile items that require sharp folds or creases.  
  After it is dried, the fabric is sprayed with the stabilizing agent. This is most conveniently a modified starch or other sizing material dispersed in volatile liquid and under pressure. On release of pressure at a nozzle, a spray is formed, and the liquid rapidly evaporates. The spray should be applied long enough to give the fabric a 1 to 3% increase in weight, distributed as uniformly as possible across the surface. The fabric is then firm, stable, and moderately stiff. It can be handled and smoothed easily when it is being prepared for cutting and while it is being cut to a pattern, without excessive stretching or other distortion of shape. After the patterned pieces are cut and sewn to form the desired garment or other textile item, the fabric is cured in its final form by heating 2-20 minutes at l40-180C. When the textile item is washed following this treatment, the sprayed-on stabilzing and stiffening agent is removed. The fabric is then nearly as soft, pliable, and unwrinkled as a similar durable-press fabric that was treated without using the stabilizing agent.  
  Note: With some sprays the fabric is dry after spraying without further attention. The solvent or dispersing media is volatile enough to evaporate during the operation. With a dilute water dispersion, more than one drying step may be necessary.  
  The detailed description and specific examples that follow are provided merely to illustrate the invention as well as preferred embodiments. These illustrations should not be construed as limiting the scope of the instant invention in any manner whatever. Numerous changes and modifications within the spirit of the invention will become apparent to those skilled in the art. 1n the examples. components of the finishing formulations are listed with quantities designated as percentage of the weight of the total formulation. Weight gains of fabric samples are noted as percentage of the weight of the original,- untreated fabric. Physical properties of the fabric samples were determined by test methods described by the American Association of Textile Chemists and Colorists and in Federal Test Methods. An increase in stiffness or bending moment, determined by the Tinius Olsen method, is taken as an indication of increased stability and firmness as well as a loss in softness.  
 EXAMPLE 1 Samples of a cotton jersey were padded with a durable-press formulation composed of 6% dimethylol dihydroxyethyleneurea, 1.8% magnesium chloride hexahydrate, and 0.5% polyethylene in water. The samples were dried by heating them in a mechanical convection oven at C for 10 minutes. Some samples of the fabric then were sprayed with a non-starch fabric sizing, sold commercially as Niagara Fabric Finish and Sizing, by means of pressure from a volatile propellant to give 1.0-1.5% additional weight add-on to the fabric. Some samples, with and without the sizing were cured by heating at C for 3 minutes. The samples left uncured were used to demonstrate the properties of the fabric at this stage of the treatment. This stage is the one where the fabric will be cut to patterned pieces for making durable-press textile items. Cured samples were washed by the usual home laundry procedure. The stiffness and hand of the fabric samples are indicated by the bending moment in the following table.  
 The data show that the sizing imparted stiffness at the stage of the treatment where the textile item would be fabricated in a post-cure durable&#39;press finishing procedure. Also, it is shown that after completion of the treatment and washing the stiffness of the fabric approached that in fabric treated without sizing. Actual feel of the fabric confirmed the test results.  
  Durable-press rating was unaffected by the temporary sizing; both fabric samples that were cured and washed had a durable-press rating of 3.7.  
 EXAMPLE 2 A sample of cotton jersey was padded with an aqueous durable-press formulation containing 6% dimethylol dihydroxyethyleneurea, 1.8% magnesium chloride hexahydrate, and 0.5% emulsified polyethylene. The fabric sample was dried at 70C for minutes and then sprayed with a modified starch dispersed in a volatile liquid under pressure sold commercially as Easy-on Speed Starch. An add-on of l.32.3% modified starch was obtained. At this stage of the treatment the fabric had bending moments of 7.2 X 10&#34; and 5.5 X 10&#34; in lb in length and width directions respectively. The fabric was then cured at 160C for 3 minutes. After washing, the fabric dried smoothly and had bending moments of 2.0 X 10&#39; and 1.8 X 10&#39; in lb in length and width directions. Bending moments of the untreated fabric were 1.8 X 10 in lb in each direction.  
 EXAMPLE 3 Samples of a cotton jersey were padded with a durable-press formulation composed of 6% dimethylol dihydroxyethyleneurea, 1.8% magnesium chloride hexahydrate, and 0.5% emulsified polyethylene in water. The padded samples of fabric were dried at 70C for 10 minutes. Two samples of the padded and dried fabric were sprayed with a 10% aqueous solution of hydroxyethylated starch to give 1.0-l.5% weight gain after drying. The spray was formed by an atomizer with compressed air. Two samples, one with the hydroxyethylated starch sizing and one without were cured by heating at 160C for 3 minutes. The cured samples were then washed by a laundry procedure commonly used in the home. The procedure used a home-type laundry machine and a tumble dryer. Stiffness of the fabric samples are shown in the following table.  
  Bending moment, in lb X l0 Fabric sample lengthwise widthwise lllill Durable-press treated fabric with hydroxyethylated starch before curing after curing and washing The fabric sprayed with the hydroxyethylated starch shows an increased stiffness or firmness before curing the point in the process at which durable-press textile items are made from the fabric. After curing and washing, little of this increased stiffness persists. Durable-press ratings on both cured fabrics were between 3.5 and 4.0 indicating that smooth-drying ability was about equal in both samples.  
 We claim:  
  1. A method of imparting temporary firmness and stability to knittedcellulosic fabrics intended for postcured durable-press goods, said temporary firmness and stability facilitating the cutting and shaping or forming of patterned knitted fabric during the stage of processing between initial impregnation and the curing step, said curing step occurring post-fabrication, without affecting the desired degree of final stiffness, the method comprising impregnating the cellulosic knitted fabric with an aqueous solution containing a crosslinking agent and its catalyst, drying the wet impregnated fabric, spraying a temporary sizing solution to a dryweight pickup of about from I to 3% without saturating said fabric, submitting the treated knitted cellulosic fabric to fabrication, and curing the fabricated material.  
  2. A method of imparting temporary firmness and stability to knitted cellulosic fabrics intended for postcured durable-press goods in order to facilitate the cutting and shaping or forming of patterned knitted fabric during the stage of processing, specifically between initial impregnation and curing, wherein the curing step is postponed to post-fabrication, the method not affecting the desired degree of final stiffness of the knitted fabric, the method comprising:  
 a. impregnating a cellulosic knitted fabric to a wet pickup of about 50 to with a methylol amide crosslinking agent and catalyst,  
 b. drying the wet impregnated knitted fabric,  
 c. spraying a temporary sizing solution selected from the group consisting of modified starch, hydroxyethyl starch, and non-starch sizing without saturating said fabric,  
 d. submitting the impregnated knitted fabric to fabrication, and  
 e. curing the impregnated and fabricated goods.  
  3. A method of imparting temporary firmness and stability to knitted cellulosic fabrics intended for postcured durable-press goods in order to facilitate the cut ting and shaping or forming of patterned knitted fabric during the stage of processing, specifically between initial impregnation and curing, wherein the curing step is postponed to post-fabrication, the method without affecting the desired degree of final stiffness, the method comprising:  
 a. impregnating a cellulosic knitted fabric to a wet pickup of about 50 to 100% with an aqueous solution containing a methylol amide crosslinking agent selected from the group consisting of dimethylol dihydroxyethyleneurea, dimethylol ethyleneurea, dimethylol propyleneurea, and dimethylol methyl carbamate, and a catalyst selected from the group consisting of zinc nitrate, zinc chloride, and magnesium chloride,  
 b. drying the wet impregnated knitted cellulosic fabric for about from 2 to 15 minutes at about from 60 to 100C,  
 c. spraying a temporary sizing solution selected from the group consisting of modified starch, hydroxyethyl starch, and non-starch sizing to a dry weight pickup of about from 1 to 3% without saturating said fabric,  
 d. submitting the dry impregnated knitted cellulosic fabric to cutting, shaping, molding, or other fabrication desired, and  
 e. curing the fabricated goods for about from 2 to 20 minutes at about from to C, and washing the temporary sizing off and drying the crosslinked goods.