US3386193A - Dry shaping of cellulosic fabrics at temperatures greater than 400 u deg. f. and pressures greater than 300 p. s. i. - Google Patents

Description

United States Patent Ofice Patented June 4, 1968 3,386,193 DRY SHAPING F CELLULQSIC FABRICS AT TEMPERATURES GREATER THAN 4tftl F. AND PRESSURES GREATER THAN 300 P.S.l. Charles G. Tewksbury, Siiver Spring, Md, and Bernard G. Kidda, Washington, l).C., assignors to The Cotton Producers Institute of the National Gotten Council of America, Memphis, Tenn, a non-profit corporation of Tennessee No Drawing. Filed July 24, 1964, Ser. No. 385,089 11 Claims. (Cl. 38144) This invention relates to a process for imparting a durable configuration such as a durable crease to cotton, other cellulosics, and cellulosic-containing blends through a combination of high temperature and high physical pressure, without requiring the use of resin finishes, crosslinking systems, added chemical swelling agents or other chemicals. By this process, durable creases and shape retention can be imparted to textile articles made of untreated cotton or other cellulosics as well as to fabrics made of cotton and other cellulosics which have been previously set, e.g., in the flat state, by chemical finishes.

It is known that fabrics of cotton or other cellulosics or cellulosics-containing blends can be set in the fiat, smooth state, with an embossed effect, or in a creased configuration, through the use of various chemical systems in conjunction with ironing or other mechanical treatment for shaping or holding the fabric in a desired form during setting. For example, it is common commercial practice to impregnate a cotton fabric with a solution of a prepolymer of a thermosetting resin such as urea formaldehyde, or of a cross-linking agent such as divinyl sulfone, or with other extraneous reactive chemicals, and then to dry and to cure the fabric while it is maintained in the flat or in a creased state, so as to impart a durable configuration to the fabric. Although such chemical finishing processes do indeed confer durable flat setting or crease setting to cotton fabrics, the amount of chemical finishing agent required for effective setting generally lowers the strength of the fabric, in some cases to as little as one half the strength of the original untreated fabric. Another disadvantage of such chemical finishing processes is that they are essentially irreversible in the sense that once the finished fabric has been set in a given configuration, shape, or form, it is extremely difiicult to alter the fabric configuration, shape or form by methods now available. Thus, once a fabric has been flat set with a wash-wear finish, such as a cyclic ethylene urea compound, it is impossible to produce a durable crease in a garment manufactured from such a fabric by conventional means, as for example by the pressing of a completed garment. This disadvantage of such chemical finishing processes is of practical importance because in usual garment manufacture creases are introduced only,

after the garment has been fabricated.

As a means of eliminating or reducing the strength loss resulting from chemical treatments of the type described above, recent Work has been directed toward setting -with chemical systems which swell or plasticize the cotton, allowing it to be molded to the desired state. Examples of such efforts have been the work of Reeves and Mack with alkaline systems (Am. Dyestufi Reptr., 48, No. 21, 43-6 (1959)) and Loeb and Segal utilizing amines (Textile Research 1., 25, 516-19 (1955)). Setting techniques such as these, incorporating various swelling systems, have been developed for use with existing equipment, such as hand irons, steam presses, and other more or less conventional apparatus. Although successful to some degree in imparting durable creases to cotton, setting by means of swelling agents involves handling problems in applying the necessary chemicals as well as extra finishing steps to insure that all of the swelling agent has been removed from the finished fabric after setting. Other work has also recently been conducted on processes wherein the chemical bonds formed in durablefinished fabrics are reversed or split to permit creasing or otherwise shaping or molding a fabric after a chemical finish has been applied and set. In such processes, the chemical bonds or cross-links are reformed after the fabric is shaped in the desired configuration, to set the material in its final shape. This particular approach, however, also involves the use of acid chemicals and therefore presents handling problems, increased costs, etc.

It is an object of the present invention to provide an improved, effective and economical process for setting cellulosic textile articles durably in any desired configuration. It is a more specific object to provide a setting process for cotton and similar textiles which does not depend on any pretreatment with costly chemicals or additives. It is a still further object to provide a process for imparting durable creases and shape retention to cotton and similar textiles by the application thereto of a controlled amount of thermal energy and pressure, rather than by reaction with added chemicals. Still another object is to provide an economical process for imparting durable creases to cotton-containing fabrics which were previously made wrinkle resistant by chemical treatment in the flat state.

These and other objects, as Well as the nature, scope and operation of this invention will become more clearly apparent from the following general description and specific examples, as well as from the appended claims. It should be understood that all proportions of materials are expressed herein on a weight basis unless indicated otherwise.

It has now been discovered that these objects can be effectively achieved by a new, high-energy process which involves the controlled application of high temperature combined with high mechanical pressure to a fabric for a suitably short time. The process can be applied either to untreated or to durably finished, fiatet wash-wear cotton or other fabrics containing at least and preferably at least of cotton or related cellulosic fiber such as linen or rayon. By this process, durable creases may be imparted to untreated cotton fabric without the use of extraneous swelling agents, resin systems, cross-linking agents, or other chemicals. In addition, this process also makes it possible to insert durable creases in cotton or cellulosic fabrics which have been previously set in the flat state with a durable chemical wash-wear finish. Further, in conjunction with chemical finishing, this process may permit reducing the amount of chemical finishing agent required to attain the desired level of durable shape retention in a fabric.

In practicing the present invention, its desired effects can be accomplished by pressing a folded or otherwiseshaped fabric between the platens of a heated press for a brief period at a high temperature and under a high pressure which correspond to a considerably more severe treatment than is produced by the combination of pressure and temperature conditions used in prior cotton finishing processes. For instance, the Hoffmann press, a steam-heated press in wide use for pressing and finishing garments, operates at mechanical pressures up to about 5 p.s.i. against the pre-moistened or steamed fabric and at nominal steam temperatures up to about 380 F. However, the temperature of the fabric itself in such processes does not exceed 212 F. because of the moisture present and the short duration of the pressing step. The hot head press, also a steam-heated press used in garment finish ing, has been used in the past to produce fabric surface temperatures up to about 380 F. but operates against the fabric at relatively low mechanical pressures. Similarly, the common hand iron is normally applied to pre-mc-istened fabrics at iron surface temperature up to about 450 F but the maximum pressure applied against the moist fabric in such an operation is less than about 5 psi. and the fabric temperature is normaliy, of course, considerably lower than the iron temperature.

In contrast, the process of the present invention requires platen surface temperatures ranging from about 380 F. to about 600 F, preferably from 450 F. to 525 F., combined with pressures against the fabric of about 100 to about 1200 p.s.i., preferably between about 300 and 950 p.s.i., and still more preferably between 600 and 900 psi. Since the pressing treatment according to this invention is applied to a fabric from which any moisture present evaporates rapidly after the hot pressing surface is applied to it, the temperature of the fabric is essentially the same as the temperature of the pressing surface. Pressing temperatures below about 450 F., and particularly below about 400 F. are not effective for setting by this process except at impractically slow rates even when very high pressures are used, and temperatures in excess of 600 F. result in rapid degradation of most fabrics. Pressures below about 300 psi, and particularly those below 100 p.s.i. generally do not provide durable creases, and pressures higher than about 950 psi. do not provide additional improvement in crease setting and, especially when in excess of about 1200 p.s.i., may actually cause crushing of the fabric. At the temperatures and pressures utilized in this process, the duration of pressing or dwell time may extend from only a second or less at the higher temperatures and pressures, to about 5 minutes at the lower temperatures and pressures. Within the limits stated, the effectiveness of the process for a given fabric is determined by the particular temperature-pressure-time relationship employed, it being understood that a decrease in any of the variables can generally be compensated for by a suitable increase in either or both of the other two. Optimum conditions for a specific case are of course best determined by preliminary'empirical testing. In most instances, the severity of treatment should be controlled such that fabric strength is degraded by less than preferably less than 10% with reference to the strength of untreated fabric. Combinations of temperature and pressure requiring a dwell time of between about 2 and seconds are particularly preferred.

The pressing conditions required for durable crease setting in dry cotton may be attained with any heavy duty press capable of producing the combination of temperature and pressure previously described. Typical of such presses are the Carver and Pasadena laboratory presses, which are hydraulically-loaded, electrically-heated, platen presses widely used in plastics and textile research. Tests described in this sepcification were performed using a Pasadena laboratory press equipped with steel platens. However, the process of this invention can be performed by other on-and-off presses capable of exerting the required high pressures at elevated temperatures, or on a continuous basis within the nip of suitable slow-moving, heated calender rolls which can produce the required timetemperature-pressure relationship.

In addition to the variables of time, temperature, and pressure, the amount of moisture present in the cotton fabric prior to pressing also can affect the process. Any such effect, however, can be readily compensated for by changes in procedure based on simple preliminary tests. The process is particularly effective with initial moisture l regains in the normal range, preferably between about 0.5% and about 10%, and most preferably between about 2% and 5% (based on bone-dry fabric weight). The presence of small initial amounts of moisture appears to be beneficial in minimizing injury to the fibers, perhaps by plasticizing them during the initial stages of the process wherein the fibers are bent to form the intended crease or other non-fiat configuration. The pressing of a fabric which is initially bone-dry tends to result in a poorer set as well as poorer fabric strength under the conditions of the present invention than when some small amount of moisture is initially present.

Higher than normal initial moisture regains, i.e., regains as high as 25% or even higher, are permissible and can be compensated for by longer treating times. While it is not intended that this invention be limited by any particular theory, it is suggested that most of the essential action on which the present invention is based takes place in the iast stages of the high energy treatment after all but a relatively small trace of the initially present moisture has been evaporated in the hot press which com municates with the atmosphere. When a substantial amount of water is initially present, it will of course prevent the temperature of the fabric from reaching the desired level and the setting or cross-linking mechanism from taking effect until all but a very small amount of the moisture has evaporated from the fabric and escaped from the press. Thus, when a higher than normal moisture regain is initially present in a fabric being creased by the present process, the initial hot pressing of such a fabric is largely the equivalent of an ordinary drying step. The time consumed in reducing the moisture content of such a high-moisture containing fabric in the hot press to the normal regain level consequently may be considered as ordinary drying time and the treating cycle proper can be considered as beginning only after the moisture regain of the fabric has dropped below 10%, and especially after it has dropped below 5%. The present treatment, being essentially independent of moisture, is of course clearly distinguishable from certain previously described attempts to crease fabrics by pressing them at high temperature in an autoclave under conditions of artificially high humidity, the maintenance of such high humidity throughout the entire course of the pressing treatment having been an essential condition of such treatment.

The presence of chemical finishes, as well as the presence of other fibers such as polyester, nylon, wool or rayon with which the cotton may be blended, also may have some effect on the optimum treating conditions required for a given case. Generally, however, as long as the fabric contains at least preferably at least cotton, the desired durable effect is obtained when operating within the time-ternperature-pressure relationship described above. The size and weight of the fabric being treated also have some effect on the treating conditions required, small fabric articles showing the desired effect more readily than articles of larger size.

In a typical method of practicing the present invention, a cotton fabric is dried or conditioned to a moisture regain of between about C and 7%, Le, to a moisture condition which cotton will attain under a wide range of atmospheric conditions, and particularly after a drying operation. The substantially dry fabric is then folded into the desired crease and subjected to the pressing conditions as specified below and the creased fabric is finally removed from the press and cooled, or cooled in the press and then removed from it.

In evaluating the fabric specimens treated in accordance with this invention, the effectiveness of crease setting was determined by a panel of observers who judged the level of crease of the crease-set specimens by comparing each specimen against a set of photographic standards supplied by the Eastman Chemical Products Company. These standards depict fabric specimens having a range of crease level from no crease through to a very sharp crease and assigned crease rating levels of 1 through 5, respectively.

The strength of the specimens was determined by the raveled strip method (ASTM D3949), with the test specimens cut across the direction of the crease. In this manner, the tensile strength across the crease was determined.

Crease durability was determined by subjecting the creased specimens (8 in. x 8 in.) to five consecutive home laundering and tumble drying cycles and then measuring crease level as described, after allowing the dried specimens to condition at 65% relative humidity (RH) and at 70 F. while hanging open with the crease in a vertical position. The laundering was conducted in an automatic home washer at a cotton setting using a commercial detergent and a wash cycle of 45 minutes. Drying was done in an automatic home drier at a hot setting (about 180 F.) and a drying time of 35 minutes.

The following examples further illustrate the mode of practice as well as the elfectiveness of this invention.

Example 1 Four specimens of an 80 x 80, unmercerized, bleached cotton print-cloth were creased by four methods. A fifth specimen was used as a control, without creating. (1) One specimen was folded and then pressed in a Holfmann press for two minutes using live steam at a temperature of 295 F. and a press loading of approximately 3 p.s.i. Immediately following steaming, the pressed specimen was hand ironed with an electric iron for two minutes at the temperature setting for cotton. (2) A second specimen was wet out with Water at room temperature, folded into a crease, and hand ironed. (3) A third specimen was folded while dry into a crease, and pressed between the platens of a Pasadena laboratory press under a pressure of 900 p.s.i. for ten seconds at a temperature of 380 F. (4) A fourth specimen was folded into a crease and pressed while dry at 900 p.s.i. for minutes at room temperature. After five home laundering cycles, the crease and strength values of the specimens were as follows:

Crease Breaking Level Strength (lbs.)

Treatment:

(1) Steamed 2 min, hand ironed l 31. 9

(2) Wet out, hand ironed. 2- 33.8

(3) Pressed dry at 380 F., 10 sec 3 31. 5

(4) Pressed dry at room temp., 10 min 2 32. 3

(5) Untreated control 34. 4

Example 2 Crease Level Breaking Strength (lbs.)

Press Loading (p.s.i.):

used; and the four specimens were pressed for 3, 6, 15, and 60 seconds, respectively. After laundering the creased specimens exhibited the following properties:

Crease Level Breaking Strength (lbs.)

Press Loading (see):

Specimens of the same fabric used in Example 1 were creased dry for 15 seconds under a press loading of 900 p.s.i. and at setting temperatures of 425, 450, 475, 500, 550, and 600 F. (6 seconds), respectively. After five laundering cycles, the specimens exhibited the following properties:

Creasc Level Breaking Strength (lbs.)

25 3 26. 5 450 3+ 24. 4 475 3+ 29. 0 500 4- 24. G 550 4 18. 4 600 (6 seconds) 4+ 8. 1

These data show that increasing intensity of treatment, in this case due to increased temperature, results in progressively better crease levels but beyond a certain point also causes loss of strength. Optimum results are obtained in the range between about 450 and 525 F.

Example 5 Creasing experiments were performed on a yarn-dyed cotton poplin fabric, having a weight of 5.0 oz./ sq. yd. This fabric had been treated with a dimethylol ethylene urea type setting agent and had been set in the flat state to a wash-wear rating of about 5, i.e., the fiat fabric exhibited excellent resistance to creasing or wrinkling as well as excellent crease recovery. One specimen was wet out with water at room temperature, folded, and hand ironed for 2 minutes at a cotton setting. A second specimen was folded dry and creased for 15 seconds in the Pasadena laboratory press at a platen temperature of 400 F. under a press loading of 900 p.s.i. A third specimen was folded dry and creased for 15 seconds at a temperature of 475 F. and at 900 p.s.i. A fourth specimen was creased for 15 seconds at a temperature of 525 F. and at 900 p.s.i. After five laundering cycles, the specimens exhibited the following properties:

These results show that the treatment for 15 seconds at 400 F. and at pressures of 600 p.s.i. or higher produced a good durable crease. At pressures in excess of about 1000 p.s.i., however, a significant reduction in breaking strength resulted.

creased as in Example 2, except that a setting temperature of 500 F. and a press loading of 900 p.s.i. were The wash and wear ratings for the above creased laundered samples ranged from 4+ to 5, i.e., about the same as prior to creasing. This demonstrates that the high energy process of this invention does not have any adverse eifect on the basic flat-setting characteristics of the chemical finish, but rather superimposes an improved creasability on the inherently excellent wash-wear characteristics of resin-finished fabrics, i.e., fabrics pretreated with conventional hardenable aminoplasts such as the various known precondensates of formaldehyde with 7 urea, melamine, cyclic ethylene urea, formamide, etc., or with wrinkle-proofing resins of still other kinds.

These crease ratings tabulated above show that a good durable crease is obtained with this fabric when it is creased for 15 seconds at 900 p.s.i. and at a temperature above 450 F. At temperatures below 450 F. dwell times substantially longer than 30 seconds are required in order to produce a durable crease capable of withstanding repeated laundering.

Example 6 Two specimens of a white cotton broadcloth, treated and set in the flat state with an epoxy resin to a washwear rating of 5, were creased. One specimen was wet out in water, folded, and hand ironed 2 minutes at a cotton setting. A second specimen was pressed dry in the Pasadena laboratory press for 15 seconds under 900 p.s.i. pressure and 'at 500 F. After five laundering cycles, there was no evidence of a crease in the hand ironed specimen, whereas the dry pressed specimen had a good crease, corresponding to a residual crease rating of about 3.

Example 7 Specimens of (1) a uniform twill fabric woven from yarns composed of a fiber blend of 85% cotton fibers and 15% nylon fibers, (2) a broadcloth woven from a blend comprising 35% cotton fibers and 65% polyester fibers, and (3) a denim fabric comprising 75% cotton fibers and 25% nylon fibers, were creased dry in the Pasadena press for 15 seconds at a platen pressure of 900 p.s.i. and a temperature of 450 F. The laundered specimens exhibited the following residual crease ratings:

Fabric specimen: High energy dry crease Twill, 85 cotton/15 nylon 4- Denim, 75 cotton/25 nylon 5- Broadcloth, 35 cotton/ 65 polyester 5 It can be seen that a very good durable crease has resulted in treating each of these blends according to the present invention. Excellent, durable creases have been imparted to low synthetic-content, cotton blended fabrics, in which durable creases are ditficult to impart by conventional means. 1

Example 8 Specimens of (1) a crash toweling fabric comprising a fiber blend of 70% cotton and 30% viscose rayon, (2) an untreated, all-linen fiat-woven toweling fabric, and (3) an all-linen dress goods fabric that had been fiat set with a durable resin finish, were creased dry in the Pasadena press for 30 seconds under a platen pressure of 900 p.s.i. and at a temperature of 500 F. Duplicate specimens of the same fabric were wet out with tap water at room temperature, folded, and hand ironed in a creased configuration for two minutes at a cotton temperature setting. The laundered specimens exhibited the following residual crease levels:

Creasing Treatment Fabric Specimen High Energy Hand Ironed Dry Crease Cotton/rayon toweling 3 1 Untreated linen toweliug 3+ 1+ Resin treated linen dress goods 4 1+ scribed in the foregoing specification and preferred modes of carrying it out having been set forth therein, the subject matter claimed to be novel is particularly pointed out in the appended claims.

What is claimed is:

1. A dry process for imparting a durable configuration to a fabric possessing a cellulosic fiber content of at least 35%, which comprises shaping said fabric into the desired configuration, and mechanically dry pressing it while in said configuration at a pressure above 300 p.s.i. and below 1200 p.s.i. and at a temperature above 400 F. and below 600 F. for a period in the range of from about 1 second to about 5 minutes until said fabric is durably set in the desired configuration.

2. A process according to claim 1 wherein the pressing is done in a compression zone which is in open communication with the atmosphere.

3. A dry process for imparting a durable configuration to a fabric made predominantly of cellulosic fibers which comprises shaping said fabric into the desired configuration, conditioning it to a moisture regain of between about 0.5% and about 10% based on bone-dry fabric weight, and thereafter mechanically dry pressing it while in said configuration at a pressure above 300 p.s.i. and below 1000 p.s.i. and at a temperature between 450 F. and 600 F. for a period in the range from about 1 second to about 30 seconds until said fabric is durably set in the desired configuration.

4. A dry process for imparting a durable configuration to a fabric characterized by a cotton content of at least 35 without application of extraneous chemicals thereto, which process comprises shaping said fabric into the desired configuration, and mechanically pressing the shaped fabric at a pressure between 600 p.s.i. and 900 p.s.i. and at a temperature between about 450 F. and 525 F. for a treating time in the range of from about 5 to 30 seconds after the moisture regain of the fabric has been reduced to about 7% based on bone-dry fabric weight or less, a relatively short treatment time being required when the pressing step is conducted at a pressure and a temperature in the upper portions of the recited pressure and temperature ranges and a relatively longer treatment time being required when the pressing step is conducted at a pressure and a temperature in the lower portions of the recited pressure and temperature ranges.

5. A process according to claim 3 wherein the fabric is an all-cotton fabric.

6. A process according to claim 3 wherein the fabric comprises a blend of at least 35% cotton and not more than 65 of a member selected from the class consisting of synthetic thermoplastic fibers and wool fibers.

7. A dry process for imparting a durable configuration including at least one crease to a cell-ulosic fabric pretreated with a wash-and-wear resin finish, which process comprises shaping said pretreated fabric into the desired configuration, and mechanically pressing the shaped fabric at a mechanical pressure of about 600 p.s.i. to about 900 p.s.i. and at a temperature between about 450 F. and 525 F. for a period of about 5 to 30 seconds while said fabric is in the range of moisture regain of 10% or less, said pressing being carried out in a compression zone which is in open communication with the atmosphere.

8. A process according to claim 7 wherein the cell-ulosic fabric is predominantly composed of cotton.

9. A process according to claim 7 wherein the cellulosic fabric is a linen fabric.

10. A process according to claim 7 wherein the cellulosic fabric is a rayon fabric.

11. A process according to claim 7 wherein the cellulosic fabric is a blend comprising at least 35% cotton and not more than 65% of a fiber selected from the class consisting of synthetic thermoplastic fibers and wool fibers.

(References on following page) References Cited UNITED STATES PATENTS 10 OTHER REFERENCES Overman et a1. 10093 23*28 (1964)' Meyer 3816 NORMAN G. TORCHIN, Primary Examiner. z ir 100-93 5 JORDAN FRANKLIN E Bridwell 100-93 Pyke el; al. 38144 G. V. LARKIN, Assistant Examiner.

Lindberg et 21.: Textile Research Journal, v01. 34, pp.

Claims (1)

1. A DRY PROCESS FOR IMPARTING A DURABLE CONFIGURATION TO A FABRIC POSSESSING A CELLULOSIC FIBER CONTENT OF AT LEAST 35%, WHICH COMPRISES SHAPING SAID FABRIC INTO THE DESIRED CONFIGURATION, AND MECHANICALLY DRY PRESSING IT WHILE IN SAID CONFIGURATION AT A PRESSURE ABOVE 300 P.S.I. AND BELOW 1200 P.S.I. AND AT A TEMPERATURE ABOVE 400* F. AND BELOW 600*F. FOR A PERIOD IN THE RANGE OF FROM ABOUT 1 SECOND TO ABOUT 5 MINUTES UNTIL SAID FABRIC IS DURABLY SET IN THE DESIRED CONFIGURATION.