US 3264054 A
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United States Patent A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant .sublicenses for such purposes, is hereby granted to the Government of the United States of America.
This invention relates to treatments which impart Wrinkle resistance to cellulosic textile materials. More particularly, it provides a process by which cellulosic textile materials may be treated with gaseous formaldehyde to yield products modified by chemical reaction such that there I are crosslinks between cellulosic chains, said products exhibiting markedly improved wrinkle-resistance properties.
The treatment of cellulosic materials with formaldehyde has been the subject of research for at least sixty years. A successful treatment for cellulosic textile materials using formaldehyde is particularly desirable because of the low cost of formaldehyde. Operative processes for finishing cellulosic textiles with formaldehyde are known in which cotton or other cellulosic material: (a) is impregnated with formaldehyde and a suitable catalyst, then dried and cured to effect reaction with the fibrous material in a non-swollen, collapsed, dry state; or (b) is treated with a solution containing formaldehyde and catalyst in a suitable solvent system to effect reaction with the fibrous material in either a swollen or non-swollen state. Both of these processes have some disadvantages.
The products of process (a) have poorer strength than is usually associated with a given degree of wrinkle resistance when other common crosslinking finishing agents are used. Furthermore, these products have moisture regain properties significantly decreased from those of the untreated textile material used in the process.
The products of process (b) exhibit practically no improvement in dry (conditioned) crease recovery angle if the solvent employed in the process is water. To obtain a useful level of dry wrinkle resistance, a large amount of the water employed as solvent must be replaced by a relatively low swelling, inert, water miscible solvent. Acetic acid, acetone, and dioxane are examples of such solvent. Their use, however, changes the process from inexpensive to relatively high in cost because of the economic necessity of reclaiming the solvent and because of higher insurance rates applying to operations employing flammable reagents.
A third type of process for the reaction of cellulosic textile materials with formaldehyde is that of gaseous treatment. However, no operative, economically attractive process has heretofore been developed for the gaseous treatment of cellulosic textile materials with formaldehyde to produce wrinkle-resistant fabrics. Known proc esses for carrying out gaseous treatment-s include: (c) reaction of the catalyst impregnated cellulosic material with paraformaldehyde in sealed tubes at elevated temperatures and presumably elevated pressures; and (d) reaction of the cellulosic material with the vapors of a hydrogen chloride-paraformaldehyde product in closed containers at room temperature and atmospheric pressure.
Neither of these gaseous processes has achieved commercial adoption. Degradation in process (0) is proice nounced. Process (d) requires excessively :long treatment times 15 hours) to produce a degree of wrinkle resistance considered adequate for the present demands of industry and the consumer.
It is an object of the present invention to provide a process for the treatment of cellulosic textile materials with gaseous formaldehyde to produce fabrics with increased resiliency, wrinkle resistance, muss resistance, shape-holding ability, and dimensional stability. By the process of this invention, this object is achieved through economical operating conditions which involve the use of only inexpensive reagents, at relatively low temperatures, without the need of pressure equipment. Furthermore, this object is achieved in reaction times markedly shorter than those necessary in previously known processes for gaseous formaldehyde treatments.
A further object of the present invention is to provide a process for producing chemically modified cotton fabrics with novel wrinkle resistance characteristicshigh dry (conditioned) crease recovery angles with low wet crease recovery angles. Heretofore, such a combination of wrinkle-resistance characteristics has been unknown in durably crosslinked cotton fabrics. Regenerated cellulose fabrics when crosslinked usually exhibit higher dry than wet wrin kle resistance, but crosslinkage of cotton generally results in essentially equivalent degrees of dry and wet wrinkle resistance.
Conversely, cotton fabrics may be treated by the process of this invention to yield products with high wet crease recovery angles and low dry crease recovery angles. By adjustment of the variables of the process of this invention, cotton fabrics with wet/dry crease recovery angle relationships of 1, 1, or 1 can be prepared. This versatility permits the operator to produce fabrics with wrinkle-resistance characteristics tailored to the desire of the consumer and the use intended for theend-product.
For example, fabrics with a wet/dry crease recovery angle relationship of about 1 at a level of about 260 (sum of the crease recovery angles in the warp and filling directions) will exhibit good wash-and-wear appearance after laundering. That is, garments made from these fabrics will be essentially free of wrinkles and mussiness and will be ready for Wearing without ironing or with a minimum of touch-up ironing when tumble-dried, line-dried, or drip-dried after laundering, and will be muss and wrinkle resistant during wearing.
Fabrics with wet/dry crease recovery angle relationship of 1 at a level of about 260 wet crease recovery angle will exhibit better wash-and-wear appearance when dripor line-dried after laundering than when tumbledried after laundering, While fabrics with wet/ dry crease recovery angle relationship of 1 at this level of wrinkle resistance will exhibit better wash-and-wear appearance after tumble-drying and will be muss and wrinkle resistant during wearing.
At other levels of wrinkle resistance, this same correlation of the effects of the wet/dry crease recovery angle relationship is evident. The actual crease recovery angle at hand determines the quality of the appearance after a certain type of drying, but the wet/dry crease recovery angle relationship determines which type of drying results in the best wash-and-wear appearance.
The reaction of gaseous formaldehyde with cellulosic textile materials is believed to proceed by a mechanism in which the cellulosic chains are crosslinked through methylene linkages. This reaction may be depicted as taking place in two steps:
1) ZOH+HCHO Z-OCHzOH 2) Z-OCHaOH+Z-OH zooHtoZ'+Hz0 Z and Z represent cellulosic chains. I represents the intermediate reaction product, a cellulose hemiformal. The final reaction product (II) is produced by reaction of the hemiformal (I) with the OH group of another cellulosic chain; this product (II) is extremely stable. Any hemiformal groups present at the end of the treatment time are attached through labile linkages which are readily hydrolyzed in the afterwash. It is possible, also, that more formaldehyde will react with product II to give longer crosslinks. The above mechanism is merely sug .gested and not to be considered as limiting this invention.
Crosslinkage of the cellulosic chains brings about a number of important changes in properties. Evidence for crosslinkage in the products of the gaseous formaldehyde treatment include: (i) Formaldehyde content by analysis. If not bound as methylene crosslinks between cellulosic chains, the formaldehyde would be removed on washing; hemiformals are unstable, and formaldehyde monomer or low-molecular weight polymers merely sorbed by the fiber are water-soluble. (ii) Insolubility in cupraethylenediamine solution. Crosslinked cellulosics are insoluble in this reagent. (iii) Increased resiliency. (iv) Improved dimensional stability. (v) Improved wrinkle resistance. (vi) Improved rot resistance. (vii) Reduced water absorption. (viii) Reduced affinity for direct cellulosic dyes. (ix) Reduced strength.
Any of these phenomena alone could not be considered proof of crosslinkage, but when considered together they present overwhelming inference of crosslinkage. However, the products of gaseous formaldehyde treatment are unique in that some of the effects of crosslinkage are less pronounced than in the products of many other crosslinking treatments. That is, by proper selection of operating conditions, the process of this invention can be carried out such that the products have the desired combination of dry and wet wrinkle resistance, have moisture absorption capacities only slightly less than that of the unmodified starting material, and a high strength to crease recovery angle relationship.
Briefly, the process of this invention provides for the treatment of cellulosic textile materials in an atmosphere of gaseous formaldehyde employing hydrogen chloride in catalyst for the reaction. This treatment may be carried out in a single chamber in the presence of both gaseous formaldehyde and hydrogen chloride, in a single chamber in which gaseous formaldehyde is furnished first, followed by addition of hydrogen chloride, or in a two-chamber treatment in which fabric is treated with gaseous formaldehyde in one chamber and with hydrogen chloride in the other. The process may be conducted on a batch scale or continuously.
Adjustment of the variables of the process determines the properties of the finished fabrics. Among the variables which affect the properties of the product are: nature of the cellulosic textile starting material, pretreatments, fabric structure, moisture content of fabric, concentration of formaldehyde and hydrogen chloride catalyst, time of treatment, and temperature of treatment. The variables are interrelated such that products with almost any desired properties within an extremely broad range can be prepared by the process of the invention.
More particularly, the process of this invention provides for the treatment of cellulosic textile materials, such as cot-ton, regenerated cellulose, paper, and chemically modified celluloses, in an atmosphere of gaseous formaldehyde, hydrogen chloride, and air, or alternatively in separate atmospheres of gaseous formaldehyde and air and in hydrogen chloride and air. The process is operative over a broad range of conditions.
Fiber yarn, or fabric may be treated; preferred treatment is carried out on fabric. The fabric treated may be composed of cotton, regenerated cellulose fiber, or chemically modified cellulosic fiber, such as etherified cellulosic fiber, esterified cellulosic fiber, oxidized celfibers which may be employed in the process of this invention are cotton fibers chemically modified so as to bear an ether substituent selected from the group consisting of methyl, ethyl, carboxymethyl, carboxyethyl, alpha-methyl carboxymethyl, phosphonomethyl, aminoethyl, hydroxyethyl, carbamoylethyl, and sulfoethyl to a degree of substitution (D.S.) of about from 0.01 to about 0.25 ether radical per anhydroglucose unit of the cellulose vchain. Esterified cellulosic fibers which may be employed include ace-tylated cotton, phthalated cotton, and the like. Oxidized cellulosic fibers which may be employed include both the acidic type oxycellulose, such as is produced by the treatment of cotton With nitrogen dioxide, and the reducing type oxycellulose, such as is produced by treatment of cot-ton with periodic acid.
Fabrics composed of blends of any of the cellulosic fibers, and fabrics composed of blends of these fibers with other fibers also may be treated by the process of this invention. When cotton fabric is used as the starting material, the fabric may be treated with the fibers in the native state or in a prepared state, that is, the fabric may be scoured, kier-boiled, desized, bleached, mercerized, or dyed, or may be subjected to any combination of these pretreatment operations. Furthermore, cellulosic fibers which previously have been subjected to any treatment stable to acid hydrolysis and which still have sites available for further reaction may be treated by the process of this invention.
Paper also may be treated by the process of this invention to produce improved wrinkle resistance and improvement in other properties. That is, the cellulosic chains of the paper fibers are crosslinked to produce improvements, especially in the wet properties of the paper. Wet strength, wet abrasion resistance, and wet rub resistance are increased, water swellability of the treated paper is decreased as is the moisture regain. Paper to 'be treated by the process of the invention may be purified and bleached or may be unbleached kraft.
Treatment of the cellulosic textile material with softeners, hand modifiers, and other additives prior to treatment with gaseous formaldehyde is often beneficial. Application of emulsified polyethylene to cotton fabric prior to gaseous formaldehyde treatment, for example, results in a finished fabric with higher tearing strength and higher wet and dry (conditioned) crease recovery angles than cotton fabric similarly treated without prior application of polyethylene.
Moisture content of the cellulosic fibers at the time of reaction affects the rate and extent of reaction in the gaseous formaldehyde treatment. Best results are obtained when the fibers contain from about their normal moisture regain, about 6%, to about 10% moisture. When the fibers contain less than normal regain, the rate and extent of reaction are decreased. When completely dry, little or no reaction of formaldehyde takes place with the fibers. With moisture contents above about 10%, the rate and extent of reaction are less than when the fibers contain from about 6% to about 10% moisture.
The treatment is carried out in an atmosphere to which from about 0.004 to about 0.016 mole/liter of gaseous formaldehyde has been added and is constantly furnished during treatment at the rate of about 0.008 to about 0.033 mole/liter/hour. Maintenance of gaseous formaldehyde concentration at a precise level is not critical as long as sufficient concentration is present to provide the reagent in excess of the amount to be fixed to the cellulosic material.
a The concentration of hydrogen chloride employed to catalyze the reaction may be varied from about 0.25% OWF (percent by weight of catalyst based on weight of fabric treated) to about 10% OWF. higher the catalyst concentration employed, the faster the reaction of the formaldehyde with the cellulosic material and the shorter the treatment time necessary to achieve a given degree of wrinkle resistance.
In general, the
The treatment time necessary to carry out the process of this invention varies from about one minute to about three hours. The treatment time employed in any given case is a function of the fabric properties desired and of the temperature of the treatment and of the concentration of catalyst used. In general, treatment time is adjusted inversely with temperature of treatment and catalyst concentration. In the present invention, treatment times markedly shorter than those operative to produce equivalent results by other gaseous formaldehyde treatment processes may be employed. Treatment times of one-half hour or less, in fact, of one to fifteen minutes can be utilized to produce high degrees of wrinkle resistance in cotton fabrics, with less strength loss than previous processes which required unduly long treatment times-often of the order of magnitude of 15-24 hours or longer.
A wide range of temperatures may be employed in carrying out the process of this invention. Temperatures of from about 20 C. (68 F.) to about 80 C. (176 F.) may be used. It is preferable to operate the process in the range of from about 20 C. (68 F.) to about 40 C. (104 F.), however, because above about 40 0, loss of strength of the product may become a problem if other variables of the treatment are not carefully adjusted to compensate for the higher operating temperature. In general, the temperature of the treatment is adjusted inversely to the time of treatment and the concentration of catalyst employed.
The treatment is carried out at normal atmospheric pressure.
The preferred conditions for carrying out the process of the present invention thus include treatment of a cellulosic textile material in the form of fabric, yarn, or fiber, such as cotton, regenerated cellulose, and chemically modified cellulose under the following conditions:
(i) With the cellulosic fibers containing from about 6% to about moisture,
(ii) In an atmosphere containing about 0.004 to about 0.016 mole of gaseous formaldehyde per liter, to which additional gaseous formaldehyde is furnished at a rate of about 0.008 to about 0.033 mole of gaseous formaldehyde per liter per hour,
(iii) Said atmosphere also containing from about 0.25% OWF to about 8% OWF of hydrogen chloride, (or alternatively, the treatment with hydrogen chloride catalyst may be carried out in a separate chamber),
(iv) At a temperature of from about 20 C. to about 80 C.,
(v) Under normal atmospheric pressure,
(vi) For a period of time of from about one minute to about three hours. I
After treatment, the product should be thoroughly washed immediately to remove residual catalyst, unused reactant, and byproducts. To facilitate washing,
often desirable to first neutralize residual catalyst and acidic byproducts by immersing the treated fabric in a dilute solution containing sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium phosphate, or the like.
The process of the invention may be further illustrated 'by the following examples.
Properties reported in the examples were determined by the following test procedures:
Crease recovery angles.Determinations of conditioned crease recovery angles were carried out on samples equilibrated at 70 F. and 65% relative humidity by the test procedure of the American Association of Textile Chemists and Colorists, tentative test method 66-1959T. This procedure is described on pages 155-156 of the 1961 Technical Manual of the AATCC.
Wet crease recovery angles were determined using this same procedure on samples which had been soaked for five minutes at 150 F. in water containing a nonionic wetting agent and blot-ted to remove excess water.
Breaking strength and el0ngati0n.-These properties were determined by the procedure of ASTM test method D168259T as given in ASTM Standards on Textile Materials, published by Committee D-13 of the American Society for Testing Materials.
Tearing strength.'1 he falling pendulum method as described in ASTM test method Dl424-59 was used for the determination of tearing strength.
Moisture regain.-ASTM test method D62959T wa used for the determination of moisture regain.
EXAMPLE 1 Samples of an 80 x 80 cotton print cloth which had been scoured, bleached, and desized were treated in a glass reaction chamber charged with gaseous formaldehyde to a concentration of 0.008 mole of formaldehyde per liter. The time and temperature of the treatments, and the concentrations of hydrogen chloride catalyst employed are given in Table I. Additional gaseous formaldehyde was charged into the reaction vessel at the rate of 0.0167 mole/liter/hour during the treatment. Moisture content of the fabric used in the treatment was about 6.5%. After treatment, samples were soaked briefly in 1% sodium carbonate solution, washed, and dried. Properties imparted to the fabric by the various treatments and those of the it is cottons. Samples number 5, 6, 7, 8, l0, l1, l2, and 13 Table I Treatment Properties T Igglirogen F 1d Crease 1:85??? Angle emp. on e orma e- Breakin E] n t Sample Number Time (min.) (deg. C.) (C(at.) 0021c. hy(de Congent Strength iv Br ak a v) gg i r i pereen percen lb. e e OWF) Cond. (deg) Wet (deg) (p m Ht) (percent) 2. 5 40 3.0 0. 38 271 244 29. 9 5. 3 I 1 4o 4. a 0. a1 261 234 29. 6 5. 3 7 so so 1. o 0. 50 276 247 23. 4 6.3 "6. 1 14- 15 0.25 0.38 272 268 21. 9 4. 3 6. 1 Untreated 7 169 42. 7 6. 8 6. 9
have conditioned crease recovery angles at least 25 degrees higher than their wet crease recovery angles. Sample number is a striking example of this novel effect; conditioned crease recovery angle is 50 degrees higher than th wet crease recovery angle. 1 I
' EXAMPLE 2 Samples of an 80 x 80 cotton print cloth which had been scoured, bleached, desized, and mercerized were treated as in Example 1. Concentration of catalyst, and time and temperature of treatment used on each sample and the properties imparted 'are listed in Table II. Moisture content of the mercerized fabric was about 7% at the time of treatment.
It can be noted that when mercerized cotton is used as a starting material, products with approximately equivalent wet and dry (conditioned) crease recovery angles or with wet crease recovery angles considerably higher than the conditioned angles can be prepared.
EXAMPLE 3 A sample of mercerized cotton print cloth was pretreated with polyethylene before reaction with gaseous formaldehyde. The pretreatment consisted of padding the fabric with emulsified polyethylene (1.7% solids), drying at 60 C. for seven minutes, and baking at 160 C. for three minutes. The sample was allowed to equilibrate to normal moisture regain at room conditions. This and a mercerized cotton sample which had not been pretreated were then treated for one hour at 40 C. with gaseous formaldehyde as in Example 1, using 1% OWF of hydrogen chloride as catalyst, washed, and dried. Properties of the treated samples are given in Table III.
respectively, corresponding to the moisture contents ranging from lowest to highest.
EXAMPLE 5 Table IV Untreated Treated Cr. Rec. Angle Formal- Or. Rec. Angle (W+F) dehyde (W+F) Cotton Fabric Treated Content,
(percent) Cond. Wet Cond. Wet
(d g) (d g) (d g) 80 x 80 Print Cloth. N. 166 184 0. 64 280 276 80 x 80 Print Cloth,
Mercerized 157 227 0. 54 238 262 144 x 62 Broadcloth.-- 181 203 0. 44 279 270 144 x 62 Broadcloth,
Mercerized 160 234 0. 35 231 260 48 x 48 Sheeting 171 189 0. 51 258 250 62 x 59 Slack Mercerized Stretch Cloth- 200 240 0.21 262 252 EXAMPLE 6 The following samples were pretreated as indicated below and then treated with gaseous formaldehyde. Con- T able II Treatment Properties Sample Hydrogen Crease Recovery Number Chloride Formalde- Angel (W+F) Breaking Time Temp. (Cat.) Cone. hyde Content Strength (min.) (deg. 0.) (percent (percent) (W) (1b.)
OWF) Cond. Wet
( g-l (deg.)
150 20 2. 0 0. 26 214 267 30. 5 120 30 1. 0 0. 231 270 29. 0 90 30 2. 0 0. 83 291 294 23. 5 10 30 4. 0 0. 54 238 262 30 1. o 0. 36 231 266 29. 8 6O 40 1. 0 0. 90 283 288 24. 7 90 1. 0 0. 53 256 251 21. 9 22 15 80 0. 25 0.30 243 255 24. 9 Mercerized 143 202 47. 0
Table III 50 centration of formaldehyde in the reactor was 0.016 mole/liter at the beginning of treatment, and gaseous Cotton formaldehyde was constantly added during the treatment at the rate of about 0.033 mole/liter/hour. Treatments Treated with Gaseous were carried out at 40 C. for five minutes with 3% OWF Fabm Property Mercerized Formaldehyde 55 hydrogen chloride catalyst. P-retreatments were:
Only Sample 23.Scoured, bleached, and desized 80 x 80 Pretr-eated Not I cotton print cloth I: P t t a poifitfitiene m Sample 24.Cotton print cloth hydroxyethylated to a D.S. of 0.11 with ethylene oxide by the method of Crease Recovery Angle, Lawrie as disclosed in the Journal of the Society of Dyers d Colour'ists volume 56 pages 617 (1940).
Cond. w+r 143 268 251 an 3 Wet W+F) 202 260 258 Sample 25.-Cotton print cloth hydroxyethylated elm- Tearing Strength, g.: to a D S of 0 Warp 910 653 513 Filling--- 593 367 253 Sample 26.Cotton pl'lnt cloth carboxymethylated to g a D.S. of 0.07 with monoohloroacetic acid by the method EXAMPLE 4 of Daul as disclosed in Textile Research Journal, volume Five samples of scoured, bleached, and desized contents w-hich were 0.10, 0.30, 041,090,, and 046%,...
22, pages 787-792 (1952) Sample 27.Cotton print cloth aminoethylated to a D.S. of 0.05 with 2-aminoethylsulfuric acid by the method of Guthrie as disclosed in Textile Research Journal, volume 17, pages 625629 (1947).
Sample 28.Cotton print cloth phosphonomethylated to a D.S. of 0.04 with chloromethyl phosphonic acid by the method of Drake as disclosed in Textile Research Journal, volume .29, pages 270275 (1959).
Sample 29.-Cotton print cloth acetylated to a D5. of 0.60 with acetic anhydride by the method of Cooper as dis-closed in Textile Industries, volume 116, pages 97- 102, 194-195 (January 1952).
Sample 30.-C otton print cloth oxidized to a D.S. of 0.11 by treatment with gaseous nitrogen dioxide at 25 C. for one hour.
Sample 31 .Viscose rayon fabric, structure 58 x 54, 8 oz./ sq. yd.
Sample 32.Cotton (35%)-Dacron polyester (65%) blended fabric, structure 118 x 80.
Sample 33.-Whatman No. 1 filter paper (W. & R. Balston, Ltd.)
Sample 34.Unbleached kraft paper.
After treatment, samples were soaked in 1% sodium carbonate solution, washed, and dried. Table V lists the crease recovery angles of the samples before and after treatment and for the formaldehyde contents of the treated samples.
In addition to the properties listed in the table, it was noted that the wet strength and wet abrasion resistance of the treated paper samples (Nos. 33 and 34) were greatly increased, and the water swellability of these samples was decreased. 1
Table V Untreated Treated Crease Recovery Crease Recovery Sample Number Angle (W-l-F) Formal- Angle (W+F) dehyde Content Cond. Wet (percent) nd. Wet g) g) e g) 180 179 0. 56 280 263 183 195 0. 50 290 287 151 217 0. 70 299 293 195 225 0. 26 233 273 230 249 0. 40 231 261 180 211 0.35 242 287 180 173 0. 26 183 186 119 247 0. 22 229 219 286 197 O. 48 285 262 279 282 0. 24 301 302 e 35 l 100 0. 62 91 B 145 B 31 e 116 0. 55 e 67 i 140 Crease recovery angles of paper samples determined in one direction on y.
The wash-wear ratings of the treated-hydroxyethylated cotton samples (Nos. 24 and 25) after washing and tumble-drying (by comparison with AATCC plastic replica standards, Tentative test method 88-1960T) were particularly good. Apparently, the combination of hydroxyethylation and gaseous formaldehyde treatment is particularly efiicacious in producing a high quality wash-Wear appearance.
1. A process for crosslinking a cellulose textile or a cellulosic paper material with formaldehyde which process consists of exposing at atmospheric pressure a cellulosic textile or a cellulosic paper material that contains about from 6% to 10% by weight of moisture to an atmosphere containing about from 0.004 to 0.016 mole of gaseous formaldehyde per liter and about from 0. 25% to 8% by weight, based on the Weight of the material being treated, of gaseous hydrogen chloride at a temperature of about from 20 C. to C. for a period of from about one minute to three hours with the concomitant proviso that during exposure of the said cellulosic material to the gaseous formaldehyde atmosphere, additional gaseous formaldehyde be furnished at the rate of about from 0.008 to 0.003 mole per liter per hour.
2. The process of claim 1 wherein the cellulosic material is paper.
3. The process of claim 1 wherein the cellulosic material is a cellulosic textile material.
4. The process of claim 1 wherein the cellulosic material is a chemically modified cellulosic textile material.
5. The process of claim 1 wherein the cellulosic material is a blend of textile fibers wherein cotton fibers predominate.
References Cited by the Examiner UNITED STATES PATENTS 3,154,373 10/1964 Guthrie 8-1164 NORMAN G. TORCHIN, Primary Examiner.
H. WOLMAN, Assistant Examiner.